JP6648707B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus and an image forming method.

  In an electrophotographic image forming apparatus, after an electrostatic latent image is formed on a charged photoreceptor, a toner image on the photoreceptor developed with toner is transferred to a sheet, and charges remaining on the photoreceptor are removed. It is removed by the static eliminator. As an example of the static eliminator, a configuration is known in which a grounded static elimination member is brought into contact with a photoconductor to remove electric charges from the photoconductor (for example, see Patent Document 1).

JP-A-01-154186

  Incidentally, in an image forming apparatus, an applied voltage applied to a charging member for charging a photoconductor may be changed. Here, in a configuration in which the static eliminator contacts the photoconductor, if the static elimination performance of the static eliminator is set in accordance with the maximum value of the applied voltage, the wear of the photoconductor is promoted and the life of the photoconductor is shortened. May be changed.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus and an image forming method capable of suppressing abrasion of a photoreceptor while securing required static elimination performance.

  An image forming apparatus according to one aspect of the present invention includes a photosensitive member, a charge removing member, a charging member, a voltage changing unit, and a speed changing unit. The charge removing member is electrically grounded, and is rotatably disposed in contact with the surface of the photoconductor. The charging member charges the photoconductor. The voltage changing unit changes an applied voltage applied to the charging member. The speed changing unit increases the difference between the linear speed of the photoconductor and the linear speed of the charge removing member as the applied voltage applied to the charging member increases.

  An image forming apparatus according to another aspect of the present invention includes a photoconductor, a charge removing member, a charging member, a voltage changing unit, and a movement processing unit. The static elimination member is electrically grounded, is rotatably disposed in contact with the surface of the photoconductor, and moves in a first direction approaching the photoconductor and in a second direction opposite to the first direction. It is possible. The charging member charges the photoconductor. The voltage changing unit changes an applied voltage applied to the charging member. The movement processing unit increases a separation distance between the photoconductor and the charge removing member as the applied voltage applied to the charging member increases.

  According to another aspect of the present invention, there is provided an image forming method, comprising: a photoconductor; a static elimination member electrically grounded and rotatably disposed in contact with a surface of the photoconductor; and a charging device for charging the photoconductor. , And includes the following voltage changing step and speed changing step. In the voltage changing step, an applied voltage applied to the charging member is changed. In the speed changing step, a difference between a linear speed of the photoconductor and a linear speed of the charge removing member increases as the applied voltage applied to the charging member increases.

  According to the present invention, there is provided an image forming apparatus and an image forming method capable of suppressing abrasion of a photoreceptor while securing required static elimination performance.

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a diagram for explaining a main part of an image forming unit of the image forming apparatus according to the first embodiment of the present invention. FIG. 3 is a diagram illustrating an equivalent circuit for describing electrical characteristics between a photoconductor and a charge removing member of an image forming unit of the image forming apparatus according to the first embodiment of the present invention. FIG. 5 is a diagram illustrating an example of a result of a Cole-Cole plot of the static elimination member of the image forming apparatus according to the first embodiment of the present invention. FIG. 4 is a diagram illustrating an example of an experimental apparatus used to obtain a Cole-Cole plot result of the static elimination member of the image forming apparatus according to the first embodiment of the present invention. FIG. 4 is a diagram illustrating an example of an experimental apparatus used to obtain a Cole-Cole plot result of the static elimination member of the image forming apparatus according to the first embodiment of the present invention. It is a figure showing an example and a comparative example. FIG. 3 is a diagram illustrating a relationship between a ratio of a linear speed of a charge removing member to a linear speed of a photoconductor of the image forming apparatus according to the first embodiment of the present invention and a potential after charge removal. FIG. 3 is a diagram illustrating a configuration of brush bristles of the charge removing member of the image forming apparatus according to the first embodiment of the present disclosure. FIG. 2 is a block diagram illustrating a system configuration of the image forming apparatus according to the first embodiment of the present invention. 6 is a flowchart illustrating an example of a first speed change process performed by the image forming apparatus according to the first embodiment of the present disclosure. FIG. 3 is a diagram illustrating a relationship between a ratio of a linear speed of a charge removing member to a linear speed of a photoconductor of the image forming apparatus according to the first embodiment of the present invention and a potential after charge removal. FIG. 7 is a diagram for explaining a main part of an image forming unit of an image forming apparatus according to a second embodiment of the present invention. FIG. 9 is a block diagram illustrating a system configuration of an image forming apparatus according to a second embodiment of the present invention. 9 is a flowchart illustrating an example of a contact pressure changing process performed by an image forming apparatus according to a second embodiment of the present disclosure. FIG. 11 is a block diagram illustrating a system configuration of an image forming apparatus according to a third embodiment of the present invention. 13 is a flowchart illustrating an example of a second speed change process performed by the image forming apparatus according to the third embodiment of the present disclosure. FIG. 13 is a diagram illustrating a relationship between a cumulative printing ratio of the image forming apparatus according to the third embodiment of the present invention and a contact resistance component in a contact impedance of the charge removing member. FIG. 13 is a diagram for describing a main part of an image forming unit of an image forming apparatus according to a modification of the third embodiment of the present disclosure. It is a block diagram showing a system configuration of an image forming apparatus according to a fourth embodiment of the present invention. 15 is a flowchart illustrating an example of a third speed change process performed by the image forming apparatus according to the fourth embodiment of the present disclosure. FIG. 13 is a diagram illustrating a relationship between an accumulated number of printed sheets and an outer diameter of a charge removing member of the image forming apparatus according to a fourth embodiment of the present invention. FIG. 13 is a block diagram illustrating a system configuration of an image forming apparatus according to a modification of the fourth embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the following embodiments are examples embodying the present invention, and do not have characteristics that limit the technical scope of the present invention.

[First Embodiment]
As shown in FIG. 1, an image forming apparatus 10 according to the first embodiment of the present invention includes an electrophotographic monochromatic type including a control unit 1, an image forming unit 2, a paper feeding unit 3, a paper discharging unit 4, and the like. It is a printer. Other examples of the image forming apparatus according to the present invention include a facsimile, a copier, and a multifunction peripheral. Further, the image forming apparatus according to the present invention is not limited to the monochrome-compatible image forming apparatus 10 as described in the first embodiment, but can be a tandem-type electrophotographic apparatus having an image forming unit corresponding to each color. An image forming apparatus of a system may be used.

  The control unit 1 includes a CPU, a RAM, a ROM, an EEPROM (registered trademark), and the like, and controls the image forming apparatus 10 by executing various processes by the CPU according to a control program stored in the ROM.

  The image forming unit 2 includes an electrophotographic image forming unit including a photosensitive drum 21, a charging device 22, an optical scanning device 23, a developing device 24, a transfer roller 25, a cleaning member 26, a charge removing member 27, and a fixing device 28. It is. The photoconductor drum 21 is an example of a photoconductor, and for example, a photoconductor belt may be used as the photoconductor instead of the photoconductor drum 21.

  In the image forming apparatus 10, the image forming unit 2 is controlled by the control unit 1, so that an image is formed on a sheet such as a sheet supplied from the sheet feeding cassette 31 of the sheet feeding unit 3. The printing process is executed, and the sheet after the image forming process is discharged to the paper discharge unit 4.

  Specifically, in the printing process, an electrostatic latent image based on image data is formed on the surface of the photosensitive drum 21 charged by the charging device 22 by scanning of the light beam by the optical scanning device 23. Then, the electrostatic latent image formed on the surface of the photosensitive drum 21 is developed with toner by the developing device 24 and then transferred to the sheet by the transfer roller 25.

  Thereafter, the toner transferred to the sheet is fused and fixed to the sheet by the fixing device 28. The toner remaining on the surface of the photosensitive drum 21 is cleaned by the cleaning member 26. Further, the charge remaining on the photosensitive drum 21 is removed by a charge removing member 27 disposed downstream of the cleaning member 26.

  The photoconductor drum 21 is, for example, an organic photoconductor (OPC) having a single-layer structure in which a photosensitive layer containing a charge generation material and a charge transport material is formed around an aluminum tube. For example, the charge generation material is a perylene pigment, a thalocyanine pigment, or the like, and the charge transport material is a hydrazone compound, a fluorenone compound, an arylamine compound, or the like.

  In particular, the photoconductor drum 21 is a positively-charged single-layer organic photoconductor (PSLP: Positive-charged Single Layer Photoconductor) drum having a positively-charged single-layer structure. It is to be noted that the photoconductor drum 21 may be an organic photoconductor having a multilayer structure as another embodiment.

  As shown in FIG. 2, the charging device 22 includes a charging roller 220 (an example of a charging member) that comes into contact with the photosensitive drum 21. A positive DC voltage is applied to the charging roller 220 from the power supply 221. As a result, a positive DC voltage is applied from the charging roller 220 to the photoconductor drum 21, and the photoconductor drum 21 is charged to a predetermined charging potential. That is, the charging device 22 according to the present embodiment is not an AC superposition type charging device that superimposes an AC voltage on a DC voltage, and a non-contact type that charges the photosensitive drum 21 in a non-contact type such as scorotron charging. It is not a charging device. As another embodiment, the charging device 22 may be an AC superimposition type charging device or a non-contact type charging device.

  The neutralization member 27 is electrically grounded. Further, the charge removing member 27 is rotatably supported in contact with the surface of the photosensitive drum 21. Specifically, the charge removing member 27 is a brush-like roller member formed of a conductive metal material or a resin material. As shown in FIG. 2, the charge removing member 27 includes a cylindrical base 270 and brush bristles 271 having one end fixed to the base 270 and the other end in contact with the surface of the photosensitive drum 21. The charge removing member 27 is not limited to a brush shape, and may be a cylindrical (roll-shaped) roller member formed of a conductive metal material or a resin material. The resin material is, for example, rubber or sponge.

  By the way, in the configuration in which the charge removing member 27 contacts the photosensitive drum 21 as in the image forming apparatus 10, the electrical characteristics such as the internal capacitance of the charge removing member 27 depend on the potential stability and the memory image on the photosensitive drum 21. May be affected. However, not only the internal capacitance of the charge removing member 27 but also the contact capacitance of the charge removing member 27 may affect the potential stability and the presence or absence of a memory image.

  Further, in the image forming apparatus 10, electric characteristics such as the internal resistance of the charge removing member 27 may affect the charge removing performance. However, not only the internal resistance of the static elimination member 27 but also the contact resistance of the static elimination member 27 may affect the static elimination performance. Specifically, since the photoconductor drum 21 has a high surface resistance value, no lateral flow of charges occurs on the surface of the photoconductor drum 21. Therefore, even if the internal resistance of the charge removing member 27 is small, if the contact resistance with the photosensitive drum 21 is large, the charge on the photosensitive drum 21 cannot be effectively removed.

  In particular, when a contact-type charging device 22 that contacts the photosensitive drum 21 is used as in the first embodiment, a VOC (Volatile Organic) is used as compared with a non-contact charging device such as scorotron charging. Compounds) are suppressed. However, the charging performance of the contact charging device 22 may be inferior to that of the non-contact charging device. Further, the fact that the charging device 22 is a DC voltage application type charging device can also be a factor that impairs the charging performance.

  On the other hand, in the image forming apparatus 10, as described below, since the electrical characteristics of the charge removing member 27 are configured to satisfy the first specific condition set in advance, the contact capacitance is also considered. Thus, the potential stability can be improved and the occurrence of a memory image can be suppressed. In addition, as described below, since the electrical characteristics of the static elimination member 27 are configured to satisfy the second specific condition set in advance, the static elimination performance is improved in consideration of the contact resistance of the static elimination member 27. It is possible.

  First, as shown in FIG. 3, in the equivalent circuit 5 showing the electrical characteristics between the photosensitive drum 21 and the charge removing member 27 of the image forming unit 2, the resistance 51 corresponding to the DC resistance R1 of the photosensitive drum 21 A capacitor 52 corresponding to the capacitance C1 of the photosensitive drum 21 and a resistor 53 corresponding to the DC resistance value R2 of the charge removing member 27 are connected in parallel.

  Generally, in the equivalent circuit 5, it is considered that the lower the DC resistance value R2 of the charge removing member 27, the higher the charge removal performance of the photosensitive drum 21 by the charge removing member 27. However, in fact, it was found that not only the DC resistance value R2 of the charge removing member 27 but also the contact resistance of the charge removing member 27 with the photosensitive drum 21 affects the charge removal performance.

  On the other hand, as shown in FIG. 4, the internal impedance Z1 and the contact impedance Z2 of the static eliminator 27 in the preset frequency range of, for example, 0.05 Hz to 100 kHz by the AC impedance method. Is measured, a Cole-Cole plot is obtained. Thereby, the internal resistance component Ra and the internal capacitance component Ca in the internal impedance Z1 and the contact resistance component Rb and the contact capacitance component Cb in the contact impedance Z2 can be calculated. Here, as shown in FIG. 4, in the Cole-Cole plot, the plots corresponding to the internal impedance Z1 and the contact impedance Z2 respectively depict a semicircle, but may have an arc shape such as a semielliptical shape. .

  In the first embodiment, the resistance between the metal core of the photosensitive drum 21 and the photosensitive layer is assumed to be negligible. The DC resistance R1 of the photosensitive drum 21 is much larger than the DC resistance R2 of the charge removing member 27. Therefore, the combined resistance R3 of the photosensitive drum 21 and the charge removing member 27 can be considered to be the same as the DC resistance value R2 of the charge removing member 27.

  Here, the charge elimination time in which each area of the photosensitive drum 21 is in contact with the charge elimination member 27 is t, and the potential after charge elimination predetermined as the target value of the surface potential of the photosensitive drum 21 after the lapse of the charge elimination time t is V1, the potential before static elimination of the photosensitive drum 21 at the start of static elimination by the static elimination member 27 is V0, and the capacitance of the photosensitive drum 21 is C. In this case, the value of the theoretical DC resistance value R2 of the static elimination member 27 (hereinafter referred to as “calculated resistance”) capable of eliminating the surface potential of the photosensitive drum 21 from the potential V0 before static elimination to the potential V1 after static elimination in the neutralization time t. The value R21 is calculated based on the following equation (1). When the linear speed (surface speed) of the photosensitive drum 21 is S and the contact width between the photosensitive drum 21 and the charge removing member 27 in the rotation direction of the photosensitive drum 21 is L, the charge removal time t is L / S. It can be calculated.

  However, as described above, the contact impedance of the charge removing member 27 with the photosensitive drum 21 also affects the charge removal performance of the charge removing member 27. Therefore, in the image forming apparatus 10, the charge removing member 27 is configured so as to satisfy the conditions of the following expressions (2) and (3) (the second specific condition).

  That is, in the image forming apparatus 10, as shown in the above equation (2), the internal resistance component Ra of the static elimination member 27 is calculated by adding the calculated resistance value R 21 of the static elimination member 27 to the static elimination member 27 with respect to the linear speed of the photosensitive drum 21. Is less than or equal to a value obtained by multiplying the first specific value calculated based on the linear velocity ratio Sr of the above. Further, in the image forming apparatus 10, as shown in the above equation (3), the contact resistance component Rb of the charge eliminating member 27 is calculated based on the calculated resistance value R21 of the charge eliminating member 27 based on the ratio Sr. It is less than or equal to the product of the values.

  As described above, in the image forming apparatus 10, since the electrical characteristics of the charge removing member 27 are determined in consideration of not only the DC resistance value R2 of the charge removing member 27 but also the internal resistance component Ra and the contact resistance component Rb, the charge removal is performed. The static elimination performance of the member 27 can be improved. On the other hand, the actual DC resistance value R2 of the static elimination member 27 may be equal to or smaller than the calculated resistance value R21 or larger than the calculated resistance value R21.

  Specifically, the internal resistance component Ra and the contact resistance component Rb of the static elimination member 27 are calculated according to the calculated resistance value R21 capable of static elimination to the potential V1 after static elimination at the static elimination time t and the line of the static elimination member 27 with respect to the linear velocity of the photosensitive drum 21 By being equal to or less than the values respectively defined based on the speed ratio Sr, the static elimination performance by the static elimination member 27 is improved. Note that the first specific value and the second specific value are not limited to the above-described values as long as a similar effect is obtained.

  For example, in the image forming apparatus 10, as shown in FIG. 9, the brush bristles 271 of the charge removing member 27 have a core 271A and a surface layer 271B. Here, FIG. 9 is a cross-sectional view of one brush hair 271. The core 271A is made of resin. The surface portion 271B is made of carbon and covers the surface of the core portion 271A. For example, the surface portion 271B is formed together with the core 271A when the brush bristles 271 are manufactured. Further, the surface portion 271B may be formed by spraying carbon onto the surface of the core 271A after the core 271A is formed. Thus, the internal resistance component Ra and the contact resistance component Rb of the charge removing member 27 are reduced while maintaining the strength of the brush bristles 271 as compared with a configuration in which the brush bristles 271 are formed only of the resin layer containing carbon. Is possible. The surface portion 271B may include a component other than carbon as long as the charge eliminating member 27 satisfies the above formulas (2) and (3). Further, the core 271A may contain carbon. Further, the brush bristles 271 may be formed only of the resin layer containing carbon.

  In the image forming apparatus 10, the charge removing member 27 rotates by receiving a rotational driving force supplied from a first driving unit 272 (see FIG. 10) such as a motor. For example, the charge removing member 27 rotates at a linear velocity higher than the photosensitive drum 21. The charge removing member 27 may be rotated at the same speed as the photosensitive drum 21 or at a lower linear velocity than the photosensitive drum 21. Further, the charge removing member 27 may be driven to rotate at a speed obtained by multiplying the linear speed of the photosensitive drum 21 by a predetermined ratio.

  As described above, the contact stability of the charge removing member 27 with the photosensitive drum 21 also affects the potential stability of the photosensitive drum 21 and the presence or absence of an image memory. In the image forming apparatus 10, the static elimination member 27 is configured to satisfy the following expressions (4) and (5) (the first specific condition).

  Ca ≦ 1.0E + 05 (4)

  0 ≦ Cb / Ca ≦ 0.4 (5)

  That is, in the image forming apparatus 10, as shown in the above equation (4), the internal capacitance component Ca of the charge removing member 27 is equal to or less than 1.0E + 05, which is an example of a predetermined fourth specific value. Further, in the image forming apparatus 10, as shown in the above equation (5), the capacitance ratio (Cb / Ca) which is a value obtained by dividing the contact capacitance component Cb of the charge removing member 27 by the internal capacitance component Ca. ) Is 0.4 or less, which is an example of a predetermined third specific value.

  As described above, in the image forming apparatus 10, since the electric characteristics of the charge removing member 27 are determined in consideration of the internal capacitance component Ca and the contact capacitance component Cb of the charge removing member 27, the photosensitive drum 21 Can be improved, and the occurrence of image memory can be suppressed. Specifically, the internal capacitance component Ca is determined so that the electric charge accumulated in the static elimination member 27 is small, and the ratio of the contact capacitance component Cb to the internal capacitance component Ca is small. Since the electric charge is easily released from 27, the potential stability is improved and the occurrence of image memory is suppressed. Note that the third specific value and the fourth specific value are not limited to the above-described values as long as a similar effect is obtained.

[Example]
Hereinafter, measurement results in the image forming apparatus 10 will be described with reference to FIGS.

  FIGS. 5 and 6 are diagrams illustrating an experimental device 90 for measuring the internal resistance component Ra, the contact resistance component Rb, the internal capacitance component Ca, and the contact capacitance component Cb of the static elimination member 27. The experimental apparatus 90 includes two stainless steel SUS rollers 91 and 92 each having a diameter of 18 mm and arranged at a distance of 4 mm in the horizontal direction. An aluminum film electrode 93 (horizontal length 150 mm) is suspended between the SUS roller 91 and the SUS roller 92. Then, the static elimination members 27 according to Comparative Examples 1 to 15 and Examples 1 to 5 to be tested are arranged so as to be in contact with the upper surface of the film electrode 93.

  Further, the experimental apparatus 90 includes a SUS roller 95 having a diameter of 30 mm disposed above the neutralizing member 27. A load is applied to the SUS roller 95 downward by a 1 kg weight 96, and the load is applied to the charge removing member 27 via the SUS roller 95. The experiment is performed in a state where the charge removing member 27 and the SUS rollers 91, 92, and 95 are not rotated. The two SUS rollers 91 and 92 are connected to one electrode of an impedance measuring device 97 (LCR height tester 3522 manufactured by Hioki Electric Co., Ltd.), and the base portion 270 of the static elimination member 27 is connected to the other of the impedance measuring device 97. In this state, impedance measurement by the impedance measuring device 97 is performed. In this experiment, a sine waveform AC voltage having a voltage value of 5.0 V is applied to both ends of the electrode of the impedance measuring instrument 97. Then, while changing the frequency of the applied AC voltage in the range of 0.05 Hz to 100 kHz, the internal resistance component Ra, the contact resistance component Rb, the internal capacitance component Ca, and the contact capacitance component of the charge removing member 27 are changed. Measure Cb. The measurement was performed a plurality of times (2 to 16 times), and the experimental results are shown in the table of FIG. 7 based on the average value of the measured values.

  7, the printing process is executed by the image forming apparatus 10 equipped with the static elimination member 27 of each example illustrated in FIG. 7, and the static elimination performance of the photosensitive drum 21 by the static elimination member 27, potential stability, and image The results of the evaluation of the presence or absence of the memory are shown.

  Here, regarding the charge removal performance, it was evaluated whether or not the potential of the photosensitive drum 21 was removed to a desired post-discharge potential V1 after the charge removal of the photosensitive drum 21 by the charge removal member 27 in the image forming apparatus 10. . In FIG. 7, “○” indicates that the charge has been removed to the desired post-discharge potential V1, and “x” indicates that the charge has not been removed to the desired post-discharge potential V1 or less.

  Regarding the potential stability, after performing continuous printing for 60 minutes in the image forming apparatus 10, the surface potential of the photosensitive drum 21 after being charged by the charging device 22 was measured. As a result, before the start of the continuous printing. It was evaluated whether or not the initial surface potential after being charged by the charging device 22 decreased by 10% or more. FIG. 7 shows the evaluation results of the potential stability as “O” when the initial surface potential has not decreased by 10% or more, and “X” when the initial surface potential has decreased by 10% or more. When the initial surface potential is lowered by 10% or more, a problem such as fogging may occur. Therefore, the value of 10% is adopted here.

  Regarding the presence or absence of the image memory, the image forming apparatus 10 forms a black patch of a predetermined shape on the leading edge of the printing paper by the printing process, and then prints a half image (gray image) in another area. The occurrence of image memory was visually evaluated. Specifically, when the shape of the black patch appears in the area of the half image, it is determined that an image memory has occurred. In FIG. 7, “○” indicates that no image memory has occurred, and “×” indicates that an image memory has occurred.

  More specifically, the image forming apparatus 10 used in the experiment is a remodeled version of a printer “FS-1320DN” manufactured by Kyocera Document Solutions. Further, in the image forming apparatus 10, the potential V0 before static elimination of the photoconductor drum 21 is 500 [V], the surface speed (linear speed) S of the photoconductor drum 21 is 0.15 [m / s], and the contact width L is 0. .005 [m]. The vacuum permittivity ε0 is 8.9E-12 [F / m], the relative permittivity εr of the photoconductor drum 21 is 3.5, and the film thickness d of the photoconductor drum 21 is 3.5E-05 [m]. It is. In this case, the capacitance value C of the photosensitive drum 21 is 8.85E-07 [F] from “ε0 × εr / d”.

  Then, the potential V1 after static elimination, which is a desired potential after static elimination of the photosensitive drum 21 by the static elimination member 27, is set to 100V. In this case, the calculated resistance value R21 of the charge removing member 27 is calculated to be 2.34E + 04 [Ω] according to the above equation (1). The potential V1 after static elimination may be, for example, a value calculated by an operation formula such as V1 = V0 × 0.2, or an operation such as V1 = V0 × 0.22 + 80 in order to provide a margin. It may be a value calculated by an equation.

  Here, in Comparative Examples 1 to 13 and Examples 1 to 3, the surface speed (linear speed) of the charge eliminating member 27 was set to 0.15 [m / s], which is the same as the linear speed S of the photosensitive drum 21. Therefore, in Comparative Examples 1 to 13 and Examples 1 to 3, when the internal resistance component Ra of the charge removing member 27 is equal to or less than 7.02E + 04 [Ω], which is three times the calculated resistance value R21, the above equation (2) is used. Will be satisfied. When the contact resistance component Rb of the charge removing member 27 is equal to or less than 2.81E + 04 [Ω], which is 1.2 times the calculated resistance value R21, the above expression (3) is satisfied.

  On the other hand, in Comparative Examples 14 and 15 and Examples 4 and 5, the linear speed of the charge eliminating member 27 was set to a speed higher than the linear speed S of the photosensitive drum 21.

  Specifically, in Comparative Example 14, the linear velocity of the charge removing member 27 was set to 0.24 [m / s], which is 1.6 times the linear velocity S of the photosensitive drum 21. Therefore, in Comparative Example 14, when the internal resistance component Ra of the charge removing member 27 is equal to or less than 1.502E + 05 [Ω], which is 6.42 times the calculated resistance value R21, the above expression (2) is satisfied. When the contact resistance component Rb of the charge removing member 27 is equal to or less than 6.01E + 04 [Ω], which is 2.57 times the calculated resistance value R21, the above expression (3) is satisfied.

  In Comparative Example 15, the linear velocity of the charge removing member 27 was set to 0.165 [m / s], which is 1.1 times the linear velocity S of the photosensitive drum 21. Therefore, in Comparative Example 15, when the internal resistance component Ra of the charge removing member 27 is equal to or less than 8.35E + 04 [Ω], which is 3.57 times the calculated resistance value R21, the above expression (2) is satisfied. When the contact resistance component Rb of the charge removing member 27 is equal to or less than 3.35E + 04 [Ω], which is 1.43 times the calculated resistance value R21, the above expression (3) is satisfied.

  In the fourth embodiment, the linear velocity of the charge removing member 27 is set to 0.24 [m / s], which is 1.6 times the linear velocity S of the photosensitive drum 21. Therefore, in the fourth embodiment, when the internal resistance component Ra of the charge removing member 27 is equal to or less than 1.502E + 05 [Ω], which is 6.42 times the calculated resistance value R21, the above expression (2) is satisfied. When the contact resistance component Rb of the charge removing member 27 is equal to or less than 6.01E + 04 [Ω], which is 2.57 times the calculated resistance value R21, the above expression (3) is satisfied.

  In the fifth embodiment, the linear velocity of the charge removing member 27 is set to 0.255 [m / s], which is 1.7 times the linear velocity S of the photosensitive drum 21. Therefore, in the fifth embodiment, when the internal resistance component Ra of the charge removing member 27 is equal to or less than 1.64E + 05 [Ω], which is 6.99 times the calculated resistance value R21, the above expression (2) is satisfied. When the contact resistance component Rb of the charge removing member 27 is equal to or less than 6.55E + 04 [Ω], which is 2.80 times the calculated resistance value R21, the above expression (3) is satisfied.

In Comparative Example 1, the charge removing member 27 in which the bristle 271 is a raw yarn obtained by subjecting a conductive acrylic fiber of SA7 manufactured by Toray Co., Ltd. to a cleavage treatment was used. In the static elimination member 27 according to Comparative Example 1, the yarn resistance is 1.00E + 07 [Ω], the brush fineness is 30 [μm], which is high (the fiber is thick), and the brush density is 100 [kF / inch ² ]. And low density. Comparative Examples 1 to 9 are all-dispersed systems in which the state of carbon in the fiber is dispersed in the entire area of the original yarn. That is, in the static elimination member 27 according to Comparative Examples 1 to 9, the brush bristles 271 are formed only of the resin layer containing carbon.

In Comparative Example 2, as in Comparative Example 1, a brush neutralizing member 27 was used, in which the bristle 271 was a raw yarn obtained by subjecting a conductive acrylic fiber of SA7 manufactured by Toray Industries, Inc. to a cleavage treatment. In the static elimination member 27 according to Comparative Example 2, the yarn resistance was 1.00E + 06 [Ω], the brush fineness was 7 [μm], which was low (the fiber was fine), and the brush density was 500 [kF / inch ² ]. High density.

In Comparative Example 3, the brush bristles 271 used the static elimination member 27 which is a raw yarn of conductive nylon manufactured by Unitika Co., Ltd. In the static elimination member 27 according to Comparative Example 3, the yarn resistance was 1.00E + 06 [Ω], the brush fineness was 7 [μm], which was low (the fiber was fine), and the brush density was 500 [kF / inch ² ]. High density. The neutralizing members 27 according to Comparative Examples 3 to 13 and Examples 1 to 3 have a circular fiber cross-sectional shape.

In Comparative Examples 4 to 6, in the same manner as in Comparative Example 3, the charge removing member 27 in which the brush bristles 271 are the raw yarns of UUN conductive nylon manufactured by Unitika Ltd. was used. In the static elimination member 27 according to Comparative Examples 4 to 6, the original yarn resistance is 1.00E + 05 [Ω], 1.04E + 05 [Ω], and 1.00E + 05 [Ω], respectively. In the static elimination members 27 according to Comparative Examples 4 to 6, the finenesses are 7 μm, 6 μm, and 6 μm, respectively. Furthermore, in the static elimination member 27 according to Comparative Examples 4 to 6, the densities are 500 [kF / inch ² ], 550 [kF / inch ² ], and 500 [kF / inch ² ], respectively.

In Comparative Examples 7 to 9, similarly to Comparative Example 3, the charge removing member 27 in which the brush bristles 271 were the raw yarn of the conductive nylon manufactured by Unitika Ltd. was used. On the other hand, in the static elimination member 27 according to Comparative Examples 7 to 9, the carbon amount of the fiber is increased as compared with Comparative Example 3 so that the values of the internal resistance component Ra and the contact resistance component Rb are reduced. In the static elimination member 27 according to Comparative Examples 7 to 9, the original yarn resistance was 1.00E + 05 [Ω], 1.00E + 04 [Ω], 1.00E + 05 [Ω], and the brush fineness was 6 [μm], 7 [μm]. ], 6 [μm] and low (the fibers are fine), and the brush density is 550 [kF / inch ² ], 500 [kF / inch ² ], 580 [kF / inch ² ] and high density.

In Example 1, the charge removing member 27 in which the brush bristles 271 are GBN fiber original yarns manufactured by KB Seiren Co., Ltd. was used. In the neutralizing member 27 according to the first embodiment, the yarn resistance is 1.00E + 04 [Ω], the brush fineness is 7 [μm], which is low (the fiber is thin), and the brush density is 500 [kF / inch ² ]. High density. In addition, in the static elimination member 27 according to Examples 1 to 3 and Comparative Examples 10 to 13, the presence state of carbon in the fiber is not a fully dispersed system, but has a two-layer structure in which carbon exists outside the fiber. Rb is decreasing. That is, in the static elimination member 27 according to Examples 1 to 3 and Comparative Examples 10 to 13, the brush bristles 271 have a core 271A and a surface layer 271B.

  In Comparative Example 10, as in Example 1, the brush bristles 271 used the static elimination member 27 which is a raw yarn of GBN fiber manufactured by KB Seiren Co., Ltd. However, the difference is that the raw yarn resistance is higher by two digits.

  In Comparative Examples 11 to 13, the charge removing member 27 in which the brush bristles 271 were yarns obtained by spraying carbon on the polyester yarn was used. In the static elimination member 27 according to Comparative Examples 11 to 13, carbon is sprayed on the polyester yarn so that the values of the internal resistance component Ra and the contact resistance component Rb are reduced. The amount of carbon sprayed in Comparative Examples 11 to 13 was the same as in Example 3, and the fineness and density of the polyester yarn were different from those in Example 3.

In Example 2, the charge removing member 27 in which the brush bristles 271 were made of polyester yarn was used. In the static elimination member 27 according to the second embodiment, the yarn resistance is 5.80E + 03 [Ω], the brush fineness is 7 [μm], which is low (the fibers are fine), and the brush density is 300 [kF / inch ² ]. High density. Further, the static elimination member 27 according to the second embodiment has a two-layer structure in which carbon exists outside the fiber as in the first embodiment, but in a state where carbon particles are directly sprayed outside the fiber. As a result, the same electrical characteristics as those of the first embodiment are realized with a brush density lower than that of the first embodiment.

In Example 3, the static elimination member 27 in which the brush bristles 271 were made of polyester yarn was used. In the neutralizing member 27 according to the third embodiment, the yarn resistance is 6.40E + 03 [Ω], the brush fineness is 7 [μm], which is low (the fibers are thin), and the brush density is 300 [kF / inch ² ]. High density. Further, the static elimination member 27 according to the third embodiment has a two-layer structure in which carbon exists outside the fiber as in the first embodiment, but in a state where carbon particles are directly sprayed outside the fiber. The amount of carbon sprayed in the third embodiment is smaller than that in the second embodiment.

  In Comparative Example 14, the same static elimination member 27 as in Comparative Example 10 was used. In Comparative Example 15, the same static elimination member 27 as in Comparative Example 13 was used. In Example 4, the same static elimination member 27 as in Comparative Example 5 was used. In Example 5, the same static elimination member 27 as in Comparative Example 6 was used.

  As shown in FIG. 7, in Comparative Examples 1 to 6 and Comparative Example 10, since the internal resistance component Ra exceeds 7.02E + 04 [Ω], which is three times the calculated resistance value R21, the above equation (2) is used. Condition is not satisfied. On the other hand, in Comparative Examples 7 to 9 and Comparative Examples 11 to 13, since the internal resistance component Ra is equal to or less than 7.02E + 04 [Ω], which is three times the calculated resistance value R21, the condition of the above expression (2) is satisfied. ing. In Comparative Example 14, since the internal resistance component Ra is equal to or less than 1.502E + 05 [Ω], which is 6.42 times the calculated resistance value R21, the condition of Expression (2) is satisfied. In Comparative Example 15, since the internal resistance component Ra is equal to or less than 8.35E + 04 [Ω], which is 3.57 times the calculated resistance value R21, the condition of the above expression (2) is satisfied. However, in Comparative Examples 1 to 6, Comparative Example 10, and Comparative Example 13, the contact resistance component Rb exceeds 2.81E + 04 [Ω], which is 1.2 times the calculated resistance value R21. Expression condition is not satisfied. In Comparative Examples 1 to 6, Comparative Example 10, and Comparative Example 13, the evaluation result of the static elimination performance was “x”.

  On the other hand, in the first to third embodiments, the condition of the above expression (2) that the internal resistance component Ra of the charge removing member 27 is equal to or less than 7.02E + 04 [Ω], which is three times the calculated resistance value R21, is satisfied. In addition, the condition of the above expression (3) that the contact resistance component Rb is equal to or less than 2.81E + 04 [Ω] which is 1.2 times the calculated resistance value R21 is satisfied. Further, in the fourth embodiment, the condition of the above expression (2) that the internal resistance component Ra of the charge removing member 27 is equal to or less than 1.502E + 05 [Ω], which is 6.42 times the calculated resistance value R21, is satisfied. In addition, the condition of the above expression (3) that the contact resistance component Rb is equal to or less than 6.01E + 04 [Ω] which is 2.57 times the calculated resistance value R21 is satisfied. In the fifth embodiment, the condition of the above equation (2) that the internal resistance component Ra of the charge removing member 27 is equal to or less than 1.64E + 05 [Ω], which is 6.99 times the calculated resistance value R21, is satisfied. In addition, the condition of the above expression (3) that the contact resistance component Rb is equal to or less than 6.55E + 04 [Ω], which is 2.80 times the calculated resistance value R21, is satisfied. In Examples 1 to 5, the evaluation result of the static elimination performance was “で”.

  Here, in Comparative Example 5, the evaluation result of the static elimination performance is “×”, whereas in Example 4 in which the same static elimination member 27 is used, the evaluation result of the static elimination performance is improved to “○”. . Further, in Comparative Example 6, the evaluation result of the static elimination performance is “×”, whereas in Example 5 in which the same static elimination member 27 is used, the evaluation result of the static elimination performance is improved to “○”. Similarly, in Comparative Examples 10 and 13, the evaluation result of the static elimination performance is “×”, whereas in Comparative Examples 14 and 15 in which the same static elimination member 27 is used, the evaluation result of the static elimination performance is “X”. It has improved to "○". From these results, it is understood that the static elimination performance can be improved by setting the linear velocity of the static elimination member 27 to a speed higher than the linear velocity S of the photosensitive drum 21. FIG. 8 illustrates the relationship between the linear velocity of the charge removing member 27 and the potential V1 after charge removal in the image forming apparatus 10 in which the charge removing members 27 according to Comparative Examples 5 to 6, 6, and 13 are mounted.

  As described above, in the image forming apparatus 10, it was found that a desired static elimination performance can be obtained by considering not only the DC resistance value R2 of the static elimination member 27 but also the internal impedance Z1 and the contact impedance Z2. . More specifically, the desired static elimination performance was obtained when the conditions of the above equations (2) and (3) were satisfied.

  As shown in FIG. 7, the internal capacitance of the contact capacitance component Cb in the Cole-Cole plot measured using the experimental device 90 for the static elimination members 27 according to Comparative Examples 1 to 15 and Examples 1 to 5 The capacitance ratio (Cb / Ca) to the capacitance component Ca was calculated. Here, in Comparative Examples 1 to 4, Comparative Examples 8 to 9, Comparative Examples 12 to 13, and Comparative Example 15, since the capacitance ratio (Cb / Ca) exceeds 0.4, the capacitance ratio The condition of the above expression (5) that (Cb / Ca) is 0 or more and 0.4 or less is not satisfied. On the other hand, in Comparative Examples 5 to 7, Comparative Examples 10 to 11, and Comparative Example 14, since the capacitance ratio (Cb / Ca) is 0.4 or less, the capacitance ratio (Cb / Ca) is 0 or more. The condition of the above expression (5) of not more than 0.4 is satisfied. However, in Comparative Examples 1 to 3, Comparative Examples 7 to 8, and Comparative Examples 10 to 15, since the internal capacitance component Ca of the static elimination member 27 exceeds 1.0E + 5.0, the internal capacitance component Ca Is not more than 1.0E + 5.0, the condition of the above equation (4) is not satisfied. The potential stability and the presence / absence of an image memory were evaluated only for the case where the evaluation result of the static elimination performance was “○”. Specifically, in Comparative Examples 7 to 9, Comparative Examples 11 to 12, and Comparative Examples 14 to 15 in which the evaluation result of the static elimination performance was “O”, the evaluation results of the potential stability and the presence or absence of the image memory were “X”. "Met.

  On the other hand, in Examples 1 to 5, the condition of the above equation (4) that the internal capacitance component Ca of the charge removing member 27 is 1.0E + 5.0 or less is satisfied, and the capacitance ratio (Cb) is satisfied. / Ca) is not less than 0 and not more than 0.4, which satisfies the condition of the above equation (5). In Examples 1 to 5, the evaluation results of the potential stability and the presence or absence of the image memory were “で”.

  As described above, in the image forming apparatus 10, not only the DC resistance of the charge removing member 27 but also the internal impedance Z1 and the contact impedance Z2 are taken into consideration, whereby the potential stability is improved and the occurrence of image memory is suppressed. all right. More specifically, when the conditions of the above equations (4) and (5) were satisfied, the potential stability was improved and the occurrence of image memory was suppressed.

  Incidentally, in the image forming apparatus 10, the applied voltage applied to the charging roller 220 that charges the photosensitive drum 21 is changed. Here, in a configuration in which the charge removing member 27 is in contact with the photosensitive drum 21, when the charge removing performance of the charge removing member 27 is set in accordance with the maximum value of the applied voltage, the wear of the photosensitive drum 21 is promoted. The life of the photosensitive drum 21 may be shortened. On the other hand, in the image forming apparatus 10 according to the first embodiment of the present invention, as described below, it is possible to suppress the abrasion of the photosensitive drum 21 while securing the required static elimination performance.

  Specifically, a first speed change program for causing the CPU to execute a later-described first speed change process (see a flowchart of FIG. 11) is stored in the ROM of the control unit 1 in advance. The first speed change program is recorded on a computer-readable recording medium such as a CD, a DVD, and a flash memory, and is read from the recording medium and installed in a storage unit such as the EEPROM of the control unit 1. May be used.

  And the control part 1 contains the density detection part 11, the voltage change part 12, and the 1st speed change part 13A as shown in FIG. Specifically, the control unit 1 executes the first speed change program stored in the ROM using the CPU. Thereby, the control unit 1 functions as the density detecting unit 11, the voltage changing unit 12, and the first speed changing unit 13A.

  The density detection unit 11 executes a density detection process for detecting the density of a patch image based on predetermined image data formed on the surface of the photosensitive drum 21.

  Specifically, in the image forming apparatus 10, as shown in FIG. 2, on the downstream side in the rotation direction of the photosensitive drum 21 from the developing device 24, and on the upstream side in the rotation direction from the transfer roller 25, A density sensor 29 is provided. For example, the density sensor 29 is an optical sensor having a light emitting unit and a light receiving unit. In the density sensor 29, the light emitted from the light emitting unit and reflected on the surface of the photosensitive drum 21 is received by the light receiving unit. Then, an electric signal corresponding to the amount of received light is output from the light receiving unit.

  For example, when a predetermined first timing has arrived, the density detection unit 11 controls the operation of each unit of the image forming unit 2 to form the patch image on the surface of the photosensitive drum 21. Then, the density detector 11 detects the density of the patch image using the density sensor 29. For example, the first timing is when the image forming apparatus 10 is powered on, when returning from a sleep state in which some functions of the image forming apparatus 10 are stopped to a normal state, and when executing the print processing.

  The voltage changing unit 12 changes the applied voltage applied from the power supply 221 to the charging roller 220.

  Specifically, the voltage changing unit 12 changes the applied voltage based on the density of the patch image detected by the density detecting unit 11. The voltage changing unit 12 changes a developing bias voltage applied to a developing roller provided in the developing device 24 together with the applied voltage.

  For example, in the image forming apparatus 10, the initial setting value of the applied voltage is set to 500V. The voltage changing unit 12 changes the applied voltage from 500 V to 800 V when the density of the patch image detected by the density detecting unit 11 is lower than a predetermined specific range. The voltage changing unit 12 changes the applied voltage from 500 V to 300 V when the density of the patch image is higher than the specific range.

  Note that the image forming apparatus 10 may be provided with a temperature and humidity sensor for detecting the temperature and humidity inside the apparatus. In this case, the voltage changing unit 12 may change the applied voltage based on the detection result of the temperature and humidity inside the device by the temperature and humidity sensor.

  The first speed changing unit 13 </ b> A increases the difference between the linear speed of the photosensitive drum 21 and the linear speed of the charge removing member 27 as the applied voltage applied to the charging roller 220 increases. Here, the first speed changing unit 13A is an example of the speed changing unit in the present invention.

  Specifically, when the calculated resistance value after the change of the applied voltage by the voltage changing unit 12 calculated based on the above equation (1) is R22, the first speed changing unit 13A sets the linear velocity of the charge removing member 27 to R22. , The ratio Sr satisfies the following formulas (6) and (7), and is changed to the first specific speed at which the difference from the linear speed of the photosensitive drum 21 is minimized. The potential V0 before static elimination in the above equation (1) is obtained by multiplying the applied voltage after change by the voltage changing unit 12 or by multiplying the applied voltage after change by a predetermined coefficient.

  For example, in the image forming apparatus 10, as described above, the charge removing member 27 rotates at a linear velocity higher than that of the photosensitive drum 21. Therefore, the first speed changing unit 13A increases the linear speed of the charge removing member 27 to increase the difference between the linear speed of the photosensitive drum 21 and the linear speed of the charge removing member 27. When the charge removing member 27 rotates at a linear speed lower than that of the photosensitive drum 21, the first speed changing unit 13A reduces the linear speed of the charge removing member 27 to reduce the linear speed of the photosensitive drum 21 and the charge removing member 27. The difference from the linear velocity may be increased.

  For example, in the image forming apparatus 10, the internal resistance component Ra, the contact resistance component Rb, and the calculated resistance value R22 corresponding to each of the applied voltages that can be set in the image forming apparatus 10 are stored in the ROM of the control unit 1 in advance. I have. When the voltage change unit 12 changes the applied voltage, the first speed change unit 13A uses the internal resistance component Ra, the contact resistance component Rb, and the calculated resistance value R22 stored in the ROM to perform the above-described operation. The linear velocity of the static elimination member 27 that satisfies the above condition is calculated. Then, the first speed changing unit 13A changes the linear speed of the charge removing member 27 based on the calculation result.

  Note that the first speed changing unit 13A may change the linear speed of the charge removing member 27 to a speed at which the difference from the first specific speed is equal to or less than a preset allowable value. Further, the first speed changing unit 13A may change the linear speed of the charge removing member 27 to a speed at which the ratio Sr satisfies the above formulas (6) and (7).

  In the image forming apparatus 10, first table data indicating the linear velocity of the charge removing member 27 corresponding to each of the applied voltages that can be set in the image forming apparatus 10 may be stored in the ROM of the control unit 1 in advance. . In this case, the first speed changing unit 13A may change the linear speed of the charge removing member 27 using the first table data when the applied voltage is changed by the voltage changing unit 12. For example, the first table data is created based on experimental data obtained by an experiment using the image forming apparatus 10 to investigate the relationship between the ratio Sr corresponding to each of the pre-discharge potentials V0 and the post-discharge potential V1. Here, FIG. 12 shows an example of experimental data obtained by the experiment. Here, the difference between the linear velocity of the charge removing member 27 and the linear velocity of the photosensitive drum 21 corresponding to the minimum value of the applied voltage in the first table data is an example of a preset lower limit value in the present invention. . The difference between the linear velocity of the charge removing member 27 and the linear velocity of the photosensitive drum 21 corresponding to the maximum value of the applied voltage in the first table data is an example of a preset upper limit value in the present invention.

  Further, the first speed changing unit 13 </ b> A may change the linear speed of the photosensitive drum 21 to increase the difference between the linear speed of the photosensitive drum 21 and the linear speed of the charge removing member 27.

[First speed change processing]
Hereinafter, an example of a procedure of the first speed changing process executed by the control unit 1 in the image forming apparatus 10 will be described with reference to FIG. Here, steps S11, S12,... Represent the numbers of the processing procedures (steps) executed by the control unit 1.

<Step S11>
First, in step S11, the control unit 1 determines whether the first timing has arrived.

  Here, when determining that the first timing has come (Yes in S11), the control unit 1 shifts the processing to step S12. If the first timing has not arrived (No in S11), the control unit 1 waits for the arrival of the first timing in step S11.

<Step S12>
In step S12, the control unit 1 executes the density detection processing. Here, the processing of step S11 and step S12 is executed by the density detection unit 11 of the control unit 1.

  For example, the control unit 1 controls the operation of each unit of the image forming unit 2 to form the patch image on the surface of the photosensitive drum 21. Then, the control unit 1 detects the density of the patch image using the density sensor 29. In step S12, the control unit 1 may detect the temperature and the humidity inside the image forming apparatus 10.

<Step S13>
In step S13, the control unit 1 changes the applied voltage based on the density of the patch image detected in step S12. Here, the process of step S13 is an example of the voltage changing step in the present invention, and is executed by the voltage changing unit 12 of the control unit 1.

  For example, when the density of the patch image detected in step S12 is lighter than the specific range, the controller 1 sets the applied voltage stored in a predetermined first storage area of the RAM. The applied voltage is changed to 800 V by rewriting the data indicating the value. Further, when the density of the patch image is higher than the specific range, the control unit 1 rewrites the data in the first storage area to change the applied voltage to 300V. Further, when the density of the patch image is within the specific range, the control unit 1 rewrites data in the first storage area to change the applied voltage to 500V.

<Step S14>
In step S14, the control unit 1 changes the linear velocity of the charge removing member 27 according to the applied voltage after the change in step S13. Here, the process of step S14 is an example of the speed changing step in the present invention, and is executed by the first speed changing unit 13A of the control unit 1.

  Specifically, the control unit 1 determines that the linear velocity of the charge removing member 27 is such that the ratio Sr satisfies the above formulas (6) and (7), and the difference between the linear speed of the photosensitive drum 21 and the linear speed is minimum. Change to the first specific speed. For example, the control unit 1 changes the linear velocity of the charge eliminating member 27 by rewriting data indicating a set value of the linear velocity of the charge eliminating member 27 stored in a predetermined second storage area of the RAM.

  As described above, in the image forming apparatus 10 according to the first embodiment, the difference between the linear velocity of the photosensitive drum 21 and the linear velocity of the charge removing member 27 increases as the applied voltage applied to the charging roller 220 increases. . This makes it possible to suppress the abrasion of the photosensitive drum 21 while securing the required static elimination performance, as compared with a configuration in which the linear velocity of the static elimination member 27 is set according to the maximum value of the applied voltage. .

  In the image forming apparatus 10 according to the first embodiment, the linear velocity of the charge eliminating member 27 is such that the ratio Sr satisfies the above formulas (6) and (7), and the linear speed of the photosensitive drum 21 is different. Is changed to the first specific speed that minimizes the speed. Thereby, the difference between the linear velocity of the photosensitive drum 21 and the linear velocity of the charge removing member 27 is minimized within a range where the required charge removing performance can be secured. Therefore, abrasion of the photosensitive drum 21 can be more effectively suppressed.

  Note that the first speed changing unit 13A reduces the difference between the linear speed of the photosensitive drum 21 and the linear speed of the charge removing member 27 according to a decrease in the surface potential of the photosensitive drum 21 due to aging or the like. It is considered as a modification of the first embodiment. For example, a configuration in which the first speed changing unit 13A decreases the linear speed of the charge removing member 27 every time a predetermined period elapses is considered. According to this configuration, it is possible to more effectively suppress the wear of the photosensitive drum 21.

[Second embodiment]
Hereinafter, an image forming apparatus 10 according to the second embodiment of the present invention will be described with reference to FIGS. In the image forming apparatus 10 according to the second embodiment, the configurations of the charge removing member 27 and the control unit 1 are different from those of the first embodiment. Other configurations are common to the first embodiment and the second embodiment.

  Specifically, in the image forming apparatus 10 according to the second embodiment, as illustrated in FIG. 13, the charge removing member 27 includes a first direction D1 approaching the photosensitive drum 21 and a first direction D1 opposite to the first direction D1. It is movable in two directions D2. For example, in the image forming apparatus 10 according to the second embodiment, the bearing that supports the rotating shaft of the charge removing member 27 is supported by the housing of the image forming apparatus 10 so as to be able to move in the first direction D1 and the second direction D2. I have.

  Further, as shown in FIG. 14, the control unit 1 includes a movement processing unit 14 instead of the first speed changing unit 13A.

  Specifically, the ROM of the control unit 1 stores in advance a contact pressure change program for causing the CPU to execute a later-described contact pressure change process (see a flowchart in FIG. 15). The control unit 1 executes the contact pressure changing program stored in the ROM using the CPU, thereby functioning as a concentration detecting unit 11, a voltage changing unit 12, and a movement processing unit 14. Note that the density detector 11 and the voltage changer 12 are not different from those of the first embodiment, and thus description thereof is omitted.

  The movement processing unit 14 decreases the separation distance between the photosensitive drum 21 and the charge removing member 27 as the applied voltage applied to the charging roller 220 increases. That is, the movement processing unit 14 increases the contact pressure between the photosensitive drum 21 and the charge removing member 27 as the applied voltage applied to the charging roller 220 increases. Thereby, the contact resistance component Rb between the photosensitive drum 21 and the charge removing member 27 decreases.

  Specifically, when the voltage changing unit 12 increases the applied voltage, the movement processing unit 14 moves the charge removing member 27 in the first direction D1 to reduce the distance between the photosensitive drum 21 and the charge removing member 27. . Further, when the applied voltage is reduced by the voltage changing unit 12, the movement processing unit 14 moves the charge removing member 27 in the second direction D2 to increase the distance between the photosensitive drum 21 and the charge removing member 27.

  For example, in the image forming apparatus 10, as shown in FIG. 14, a second driving unit 273 such as a motor for moving the charge removing member 27 is provided. Further, in the image forming apparatus 10, the second table data indicating the position within the movable range of the charge removing member 27 corresponding to each of the applied voltages that can be set in the image forming apparatus 10 is stored in advance in the ROM of the control unit 1. I have. The movement processing unit 14 moves the static elimination member 27 using the second table data when the voltage change unit 12 changes the applied voltage.

[Contact pressure change processing]
Hereinafter, an example of a procedure of a contact pressure changing process performed by the control unit 1 in the image forming apparatus 10 will be described with reference to FIG. In addition, among the steps included in the contact pressure change processing, steps having the same processing content as the steps included in the first speed change processing are denoted by the same reference numerals as those in the first speed change processing. The description thereof will be omitted.

<Step S15>
In step S15, the control unit 1 moves the static elimination member 27 in the first direction D1 or the second direction D2 according to the applied voltage after the change in step S13, and separates the photosensitive drum 21 and the static elimination member 27 from each other. Is increased or decreased. Here, the process of step S15 is executed by the movement processing unit 14 of the control unit 1.

  For example, when the applied voltage increases, the control unit 1 moves the charge removing member 27 in the first direction D1 based on the second table data to decrease the distance between the photosensitive drum 21 and the charge removing member 27. . Further, when the applied voltage decreases, the control unit 1 moves the charge removing member 27 in the second direction D2 based on the second table data to increase the separation distance between the photosensitive drum 21 and the charge removing member 27. .

  As described above, in the image forming apparatus 10 according to the second embodiment, as the applied voltage applied to the charging roller 220 increases, the separation distance between the photosensitive drum 21 and the charge removing member 27 decreases. Thus, compared to a configuration in which the separation distance between the photosensitive drum 21 and the charge removing member 27 is set in accordance with the maximum value of the applied voltage, the wear of the photosensitive drum 21 is suppressed while the necessary charge removing performance is secured. It is possible.

  Note that the control unit 1 of the image forming apparatus 10 according to the second embodiment may include a first speed changing unit 13A. Specifically, in the image forming apparatus 10 according to the second embodiment, as the applied voltage applied to the charging roller 220 increases, the separation distance between the photosensitive drum 21 and the charge removing member 27 decreases, and the photosensitive drum 21 The difference between the linear velocity of the static elimination member 27 and the linear velocity may increase.

  By the way, in a configuration in which the charge removing member 27 contacts the photosensitive drum 21, an external additive such as silica contained in the toner may adhere to the charge removing member 27. Here, when the amount of the external additive attached to the charge removing member 27 increases, the contact resistance between the photosensitive drum 21 and the charge removing member 27 increases, and the charge removing performance of the charge removing member 27 decreases.

[Third embodiment]
Hereinafter, an image forming apparatus 10 according to a third embodiment of the present invention will be described with reference to FIGS. In the image forming apparatus 10 according to the third embodiment, the configurations of the control unit 1 and the image forming unit 2 are different from those of the first embodiment. Other configurations are common to the first embodiment and the third embodiment.

  Specifically, in the image forming apparatus 10 according to the third embodiment, the image forming unit 2 is not provided with the density sensor 29.

  Further, as shown in FIG. 16, the control unit 1 replaces the density detection unit 11, the voltage change unit 12, and the first speed change unit 13A with a first acquisition processing unit 15A and a first change amount acquisition unit 16A. , And a second speed changing unit 13B.

  Specifically, a second speed change program for causing the CPU to execute a later-described second speed change process (see the flowchart of FIG. 17) is stored in the ROM of the control unit 1 in advance. Then, the control unit 1 executes the second speed change program stored in the ROM by using the CPU, so that the first acquisition processing unit 15A, the first change amount acquisition unit 16A, and the second speed change It functions as the changing unit 13B.

  The first acquisition processing unit 15A acquires the accumulated value of the toner (developer) consumption based on a first acquisition condition set in advance.

  For example, the first acquisition processing unit 15A acquires the accumulated value of the toner consumption when a predetermined second timing has come. For example, similarly to the first timing, the second timing is when the power of the image forming apparatus 10 is turned on, when returning from the sleep state in which some functions of the image forming apparatus 10 are stopped to the normal state, and when the printing is performed. For example, when a process is executed.

  For example, in the image forming apparatus 10, the cumulative printing rate which is the cumulative value of the printing rate of each printed matter output by the image forming apparatus 10 is stored in a predetermined third storage area of the EEPROM. For example, when the printing process is executed, the control unit 1 calculates a printing rate of each printed matter output in the printing process based on image data printed in the printing process. When the size of a sheet on which an image is printed in the printing process is different from a predetermined reference size, the control unit 1 converts each of the calculated printing rates into a printing rate of a sheet of the reference size. I do. Then, the control unit 1 updates the cumulative printing rate stored in the third storage area based on the calculated or converted total value of the printing rates.

  Then, the first acquisition processing unit 15A acquires the accumulated value of the toner consumption based on the accumulated printing rate (an example of the first acquisition condition) stored in the third storage area. For example, the first acquisition processing unit 15A acquires the cumulative value of the toner consumption by multiplying the cumulative printing rate read from the third storage area by a predetermined coefficient.

  The first acquisition processing unit 15A accumulates the toner consumption based on the accumulated number of printed sheets (another example of the first acquisition condition), which is the accumulated value of the number of printed matter output by the image forming apparatus 10. You may get the value.

  The first change amount acquisition unit 16A acquires the change amount ΔRb of the contact resistance component Rb of the contact impedance Z2 of the charge removing member 27 based on the accumulated value of the toner consumption acquired by the first acquisition processing unit 15A.

  For example, in the image forming apparatus 10, the third table data indicating the change amount ΔRb of the contact resistance component Rb of the charge removing member 27 corresponding to each of the predetermined cumulative values of the toner consumption is stored in the ROM of the control unit 1 in advance. Is stored. The first change amount acquisition unit 16A acquires the change amount ΔRb of the contact resistance component Rb of the charge removing member 27 based on the accumulated value of the toner consumption amount acquired by the first acquisition processing unit 15A and the third table data. I do. For example, the third table data is created based on experimental data obtained by an experiment for examining the relationship between the accumulated value of toner consumption and the contact resistance component Rb in the image forming apparatus 10 using the image forming apparatus 10. You. Here, FIG. 18 shows an example of experimental data obtained by the experiment. FIG. 18 shows the relationship between the cumulative printing ratio P and the contact resistance component Rb used for calculating the cumulative value of the toner consumption.

  The following equation (8) showing the relationship between the cumulative printing ratio P derived from the experimental data shown in FIG. 18 and the variation ΔRb of the contact resistance component Rb may be stored in the ROM of the control unit 1 in advance. . In this case, the first change amount acquisition unit 16A may acquire the change amount ΔRb of the contact resistance component Rb based on the cumulative printing rate P read from the third storage area and the following equation (8). Further, the control unit 1 may not include the first acquisition processing unit 15A. In the following equation (8), F, G, and H are constants derived from the experimental data shown in FIG.

  The second speed changing unit 13B calculates the difference between the linear speed of the photosensitive drum 21 and the linear speed of the charge removing member 27 in accordance with the increase in the accumulated value of the toner consumption obtained based on the first obtaining condition. increase.

  More specifically, the second speed changing unit 13B sets the linear velocity of the charge removing member 27 such that the ratio Sr satisfies the above equation (2) and the following equation (9), and the difference between the linear velocity of the photosensitive drum 21 and the linear velocity is the smallest. Is changed to the second specific speed.

  For example, in the image forming apparatus 10, as described above, the charge removing member 27 rotates at a linear velocity higher than that of the photosensitive drum 21. Therefore, the second speed changing unit 13B increases the linear speed of the charge removing member 27 to increase the difference between the linear speed of the photosensitive drum 21 and the linear speed of the charge removing member 27. When the charge removing member 27 rotates at a linear velocity lower than that of the photosensitive drum 21, the second speed changing unit 13B reduces the linear speed of the charge removing member 27 and the linear speed of the photosensitive drum 21 and the linear velocity of the charge removing member 27. The difference from the linear velocity may be increased.

  For example, in the image forming apparatus 10, the internal resistance component Ra, the contact resistance component Rb, and the calculated resistance value R21 are stored in the ROM of the control unit 1 in advance. When the first change amount acquisition unit 16A acquires the change amount ΔRb of the contact resistance component Rb, the second speed change unit 13B calculates the internal resistance component Ra, the contact resistance component Rb stored in the ROM, and calculates The linear velocity of the charge removing member 27 that satisfies the above-described condition is calculated using the resistance value R21. Then, the second speed changing unit 13B changes the linear speed of the charge removing member 27 based on the calculation result.

  The second speed changing unit 13B may change the linear speed of the charge removing member 27 to a speed at which the difference from the second specific speed is equal to or less than the allowable value. Further, the second speed changing unit 13B may change the linear speed of the charge removing member 27 to a speed at which the ratio Sr satisfies the above formulas (2) and (9).

  Further, in the image forming apparatus 10, fourth table data indicating the linear velocity of the charge removing member 27 corresponding to each of the predetermined cumulative values of the toner consumption may be stored in the ROM of the control unit 1 in advance. . In this case, the second speed change unit 13B may change the linear speed of the charge removing member 27 using the accumulated value of the toner consumption acquired by the first acquisition processing unit 15A and the fourth table data. In this case, the control unit 1 does not need to include the first change amount acquisition unit 16A. For example, the fourth table data includes experimental data obtained by an experiment for investigating the relationship between the accumulated value of toner consumption and the potential V1 after static elimination using the image forming apparatus 10, and the ratio using the image forming apparatus 10. It is created based on experimental data obtained by an experiment for investigating the relationship between Sr and the potential V1 after static elimination.

  Further, the second speed changing unit 13 </ b> B may change the linear speed of the photosensitive drum 21 to increase the difference between the linear speed of the photosensitive drum 21 and the linear speed of the charge removing member 27. The second speed changing unit 13B may increase the difference between the linear speed of the photosensitive drum 21 and the linear speed of the charge removing member 27 within a range equal to or less than a preset upper limit.

[Second speed change process]
Hereinafter, an example of a procedure of the second speed changing process executed by the control unit 1 in the image forming apparatus 10 will be described with reference to FIG.

<Step S21>
First, in step S21, the control unit 1 determines whether or not the second timing has arrived.

  When determining that the second timing has come (Yes in S21), the control unit 1 shifts the processing to step S22. If the second timing has not arrived (No in S21), the control unit 1 waits for the arrival of the second timing in step S21.

<Step S22>
In step S22, the control unit 1 acquires the accumulated value of the toner consumption in the image forming apparatus 10. Here, the processing of step S21 and step S22 is executed by the first acquisition processing unit 15A of the control unit 1.

  Specifically, the control unit 1 obtains a cumulative value of toner consumption by multiplying the cumulative print rate read from the third storage area by the coefficient.

<Step S23>
In step S23, the control unit 1 acquires a change amount ΔRb of the contact resistance component Rb of the charge removing member 27 based on the accumulated value of the toner consumption acquired in step S22. Here, the process of step S23 is executed by the first change amount acquisition unit 16A of the control unit 1. Note that the processing in step S23 may be omitted.

  Specifically, the control unit 1 acquires a change amount ΔRb of the contact resistance component Rb of the charge removing member 27 based on the accumulated value of the toner consumption acquired in step S22 and the third table data.

<Step S24>
In step S24, the control unit 1 changes the linear velocity of the charge removing member 27 based on the variation ΔRb of the contact resistance component Rb of the charge removing member 27 acquired in step S23. Here, the process of step S24 is executed by the second speed changing unit 13B of the control unit 1.

  Specifically, the control unit 1 determines that the linear velocity of the charge removing member 27 is such that the ratio Sr satisfies the above formulas (2) and (9), and the difference between the linear speed of the photosensitive drum 21 and the linear speed is minimum. Change to the second specific speed. For example, the control unit 1 changes the linear speed of the charge eliminating member 27 by rewriting data indicating the set value of the linear velocity of the charge eliminating member 27 stored in the second storage area of the RAM.

  As described above, in the image forming apparatus 10 according to the third embodiment, the linear velocity of the photosensitive drum 21 and the static elimination member are increased in accordance with the increase in the cumulative value of the toner consumption acquired based on the first acquisition condition. The difference from the linear velocity of 27 increases. Accordingly, it is possible to suppress a decrease in the static elimination performance of the static elimination member 27 due to an increase in the amount of the external additive attached to the static elimination member 27.

  In the image forming apparatus 10 according to the third embodiment, the linear velocity of the charge eliminating member 27 is such that the ratio Sr satisfies the above formulas (2) and (9), and the linear velocity of the photosensitive drum 21 is different. Is changed to the second specific speed that minimizes the speed. Thereby, the difference between the linear velocity of the photosensitive drum 21 and the linear velocity of the charge removing member 27 is minimized within a range where the required charge removing performance can be secured. Therefore, it is possible to suppress abrasion of the photosensitive drum 21.

  Note that the second speed changing unit 13 </ b> B determines, from among the predetermined divided areas in the main scanning direction orthogonal to the sheet conveyance direction on which an image is to be formed, the cumulative printing rate acquired for each of the divided areas is the largest. A configuration is provided in which the difference between the linear speed of the photosensitive drum 21 and the linear speed of the charge removing member 27 is increased in accordance with an increase in the cumulative value of the toner consumption obtained based on the cumulative printing rate corresponding to the divided area. It is considered as a modification of the third embodiment. For example, it is conceivable that the EEPROM of the control unit 1 is provided with a plurality of storage areas for storing the cumulative printing rate for each of the divided areas. It is also conceivable that the first acquisition processing unit 15A acquires the cumulative value of toner consumption by multiplying the cumulative print rate corresponding to the specific divided area by the number of the divided areas and the coefficient. Can be According to this configuration, it is possible to set the linear velocity of the charge eliminating member 27 based on a position on the charge eliminating member 27 where the amount of the external additive attached is the largest in the main scanning direction.

  As another modified example of the third embodiment, a configuration in which the image forming apparatus 10 includes a cleaning member 274 that cleans the surface of the charge removing member 27 as illustrated in FIG. For example, the cleaning member 274 is a blade-shaped member that is long in the axial direction of the rotation axis of the photosensitive drum 21, and is provided in contact with the brush bristles 271 of the charge removing member 27. For example, the cleaning member 274 is provided at a position where the cleaning member 274 digs into the outer diameter of the charge removing member 27 by 0.1 mm to 1.1 mm. According to this configuration, it is possible to prevent the external additive from adhering to the charge eliminating member 27. When the cleaning member 274 is provided in the image forming apparatus 10, it is conceivable to correct the contents of the third table data, the expression (8), and the fourth table data.

  By the way, in the configuration in which the charge removing member 27 is in contact with the photosensitive drum 21, the tip of the brush bristles 271 that contact the photosensitive drum 21 is curved in accordance with an increase in the number of executions of the printing processing, and the outer diameter of the charge removing member 27 May decrease. Here, when the outer diameter of the charge removing member 27 decreases, the contact area between the photosensitive drum 21 and the charge removing member 27 decreases, and the contact resistance between the photosensitive drum 21 and the charge removing member 27 increases. The static elimination performance decreases.

[Fourth embodiment]
Hereinafter, an image forming apparatus 10 according to a fourth embodiment of the present invention will be described with reference to FIGS. In the image forming apparatus 10 according to the fourth embodiment, the configurations of the control unit 1 and the image forming unit 2 are different from those of the first embodiment. Other configurations are common to the first embodiment and the fourth embodiment.

  Specifically, in the image forming apparatus 10 according to the fourth embodiment, the image forming unit 2 is not provided with the density sensor 29.

  Also, as shown in FIG. 20, the control unit 1 replaces the density detection unit 11, the voltage change unit 12, and the first speed change unit 13A with a second acquisition processing unit 15B and a second change amount acquisition unit 16B. , And a third speed changing unit 13C.

  Specifically, a third speed change program for causing the CPU to execute a third speed change process (see a flowchart in FIG. 21) described later is stored in the ROM of the control unit 1 in advance. Then, the control unit 1 executes the third speed change program stored in the ROM using the CPU, thereby obtaining the second acquisition processing unit 15B, the second change amount acquisition unit 16B, and the third speed change unit. It functions as the changing unit 13C.

  The second acquisition processing unit 15B acquires the outer diameter of the charge removing member 27 based on a preset second acquisition condition.

  For example, the second acquisition processing unit 15B acquires the outer diameter of the charge removing member 27 when a predetermined third timing has arrived. For example, the third timing is, similarly to the first timing, when the image forming apparatus 10 is powered on, when returning from a sleep state in which some functions of the image forming apparatus 10 are stopped to a normal state, and when the printing is performed. For example, when a process is executed.

  For example, the second acquisition processing unit 15B acquires the outer diameter of the charge removing member 27 based on the accumulated number of printed sheets in the image forming apparatus 10 (an example of the second acquisition condition).

  For example, in the image forming apparatus 10, the accumulated number of printed sheets in the image forming apparatus 10 is stored in a predetermined fourth storage area of the EEPROM. For example, the control unit 1 updates the cumulative number of printed sheets stored in the fourth storage area every time the print processing is executed.

  In the image forming apparatus 10, fifth table data indicating the outer diameter of the charge removing member 27 corresponding to each of the predetermined cumulative number of printed sheets is stored in the ROM of the control unit 1 in advance. The second acquisition processing unit 15B acquires the outer diameter of the charge removing member 27 based on the accumulated number of printed sheets read from the fourth storage area and the fifth table data. For example, the fifth table data is created based on experimental data obtained by an experiment for examining the relationship between the cumulative number of printed sheets and the outer diameter of the charge removing member 27 in the image forming apparatus 10 using the image forming apparatus 10. . Here, FIG. 22 shows an example of experimental data obtained by the experiment.

  Note that the second acquisition processing unit 15B may acquire the outer diameter of the charge removing member 27 based on the cumulative number of rotations of the charge removing member 27 (another example of the second acquisition condition). Further, the second acquisition processing unit 15B acquires the outer diameter of the static elimination member 27 based on the current value (another example of the second acquisition condition) flowing through the first drive unit 272 that drives the static elimination member 27. Is also good. The second acquisition processing unit 15 </ b> B acquires the outer diameter of the charge removing member 27 based on any one of the cumulative number of printed sheets, the cumulative number of rotations, and the current value flowing through the first driving unit 272. Is also good. For example, the second acquisition processing unit 15B calculates the average value of the outer diameter of the static elimination member 27 acquired based on the cumulative number of printed sheets and the outer diameter of the static elimination member 27 acquired based on the cumulative number of rotations. It may be obtained as the outer diameter of the charge removing member 27.

  The second change amount acquisition unit 16B acquires the change amount ΔRb of the contact resistance component Rb of the contact impedance Z2 of the charge removal member 27 based on the decrease amount of the outer diameter of the charge removal member 27 acquired by the second acquisition processing unit 15B. I do.

  For example, in the image forming apparatus 10, the sixth table data indicating the change amount ΔRb of the contact resistance component Rb of the static elimination member 27 corresponding to each of the predetermined reduction amounts of the outer diameter of the static elimination member 27 is stored in the control unit 1 in advance. It is stored in ROM. The second change amount acquisition unit 16B is configured based on the outer diameter of the charge eliminating member 27 acquired by the second acquisition processing unit 15B and the outer diameter of the charge eliminating member 27 stored in the ROM before manufacturing the image forming apparatus 10. Thus, the reduction amount of the outer diameter of the charge removing member 27 is calculated. Then, the second change amount acquiring unit 16B acquires the change amount ΔRb of the contact resistance component Rb of the charge eliminating member 27 based on the calculated outer diameter reduction amount of the charge eliminating member 27 and the sixth table data. For example, the sixth table data is created based on experimental data obtained by an experiment for examining the relationship between the outer diameter reduction amount of the charge eliminating member 27 and the contact resistance component Rb using the image forming apparatus 10.

  The third speed changing unit 13C increases the difference between the linear speed of the photosensitive drum 21 and the linear speed of the charge removing member 27 according to the decrease in the outer diameter of the charge removing member 27 acquired based on the second acquisition condition. Let it.

  More specifically, the third speed changing unit 13C sets the linear velocity of the charge eliminating member 27 such that the ratio Sr satisfies the expression (2) and the expression (9) and the difference between the linear velocity of the photosensitive drum 21 and the linear velocity is the smallest. Is changed to the third specific speed.

  For example, in the image forming apparatus 10, as described above, the charge removing member 27 rotates at a linear velocity higher than that of the photosensitive drum 21. Therefore, the third speed changing unit 13C increases the linear speed of the charge removing member 27 to increase the difference between the linear speed of the photosensitive drum 21 and the linear speed of the charge removing member 27. When the charge removing member 27 rotates at a linear speed lower than that of the photosensitive drum 21, the third speed changing unit 13C reduces the linear speed of the charge removing member 27 to reduce the linear speed of the photosensitive drum 21 and the linear speed of the charge removing member 27. The difference from the linear velocity may be increased.

  For example, when the change amount ΔRb of the contact resistance component Rb is acquired by the second change amount acquisition unit 16B, the third speed changing unit 13C may use the internal resistance component Ra, the contact resistance component Rb, Using the calculated resistance value R21, the linear velocity of the charge removing member 27 that satisfies the above condition is calculated. Then, the third speed changing unit 13C changes the linear speed of the charge removing member 27 based on the calculation result.

  Note that the third speed changing unit 13C may change the linear speed of the charge removing member 27 to a speed at which the difference from the third specific speed is equal to or less than the allowable value. Further, the third speed changing unit 13C may change the linear speed of the charge removing member 27 to a speed at which the ratio Sr satisfies the above formulas (2) and (9).

  In the image forming apparatus 10, seventh table data indicating the linear velocity of the charge removing member 27 corresponding to each of the predetermined reduction amounts of the outer diameter of the charge removing member 27 is stored in the ROM of the control unit 1 in advance. Is also good. In this case, the third speed changing unit 13C changes the linear velocity of the charge eliminating member 27 using the amount of decrease in the outer diameter of the charge eliminating member 27 acquired by the second acquisition processing unit 15B and the seventh table data. Good. In this case, the control unit 1 does not need to include the second change amount acquisition unit 16B. For example, the seventh table data is obtained by using experimental data obtained by an experiment for investigating the relationship between the reduction amount of the outer diameter of the charge removing member 27 using the image forming apparatus 10 and the potential V1 after charge removal, and using the image forming apparatus 10. It is created based on experimental data obtained by an experiment for examining the relationship between the ratio Sr and the potential V1 after static elimination.

  Further, the third speed changing unit 13C may change the linear speed of the photosensitive drum 21 to increase the difference between the linear speed of the photosensitive drum 21 and the linear speed of the charge removing member 27. Further, the third speed changing unit 13C may increase the difference between the linear speed of the photosensitive drum 21 and the linear speed of the charge removing member 27 within a range equal to or less than a preset upper limit value.

[3rd speed change process]
Hereinafter, an example of a procedure of the third speed change process executed by the control unit 1 in the image forming apparatus 10 will be described with reference to FIG.

<Step S31>
First, in step S31, the control unit 1 determines whether the third timing has arrived.

  Here, when determining that the third timing has come (Yes in S31), the control unit 1 shifts the processing to step S32. If the third timing has not arrived (No in S31), the control unit 1 waits for the arrival of the third timing in step S31.

<Step S32>
In step S32, the control unit 1 acquires the outer diameter of the charge removing member 27. Here, the processing of step S31 and step S32 is executed by the second acquisition processing unit 15B of the control unit 1.

  Specifically, the control unit 1 acquires the outer diameter of the charge removing member 27 based on the accumulated number of printed sheets read from the fourth storage area and the fifth table data.

<Step S33>
In step S33, the control unit 1 acquires a change amount ΔRb of the contact resistance component Rb of the charge eliminating member 27 based on the decrease amount of the outer diameter of the charge eliminating member 27 acquired in step S32. Here, the process of step S33 is executed by the second variation obtaining unit 16B of the control unit 1. Note that the processing in step S33 may be omitted.

  More specifically, the control unit 1 determines whether or not the static elimination member 27 is obtained based on the outer diameter of the static elimination member 27 obtained in step S32 and the outer diameter of the static elimination member 27 stored in the ROM before manufacturing the image forming apparatus 10. The amount of decrease in the outer diameter of 27 is calculated. Then, the control unit 1 acquires a change amount ΔRb of the contact resistance component Rb of the charge eliminating member 27 based on the calculated decrease amount of the outer diameter of the charge eliminating member 27 and the sixth table data.

<Step S34>
In step S34, the control unit 1 changes the linear velocity of the charge removing member 27 based on the variation ΔRb of the contact resistance component Rb of the charge removing member 27 acquired in step S33. Here, the process of step S34 is executed by the third speed changing unit 13C of the control unit 1.

  Specifically, the control unit 1 determines that the linear velocity of the charge removing member 27 is such that the ratio Sr satisfies the above formulas (2) and (9), and the difference between the linear speed of the photosensitive drum 21 and the linear speed is minimum. Change to the third specific speed. For example, the control unit 1 changes the linear speed of the charge eliminating member 27 by rewriting data indicating the set value of the linear velocity of the charge eliminating member 27 stored in the second storage area of the RAM.

  As described above, in the image forming apparatus 10 according to the fourth embodiment, the linear velocity of the photosensitive drum 21 and the static elimination member 27 are reduced in accordance with the decrease in the outer diameter of the static elimination member 27 acquired based on the second acquisition condition. The difference with the linear velocity of the line increases. Thereby, it is possible to suppress a decrease in the static elimination performance of the static elimination member 27 due to a decrease in the outer diameter of the static elimination member 27.

  Further, in the image forming apparatus 10 according to the fourth embodiment, the linear velocity of the charge eliminating member 27 is such that the ratio Sr satisfies the formulas (2) and (9) and the linear velocity of the photosensitive drum 21 is different. Is changed to the third specific speed that minimizes the speed. Thereby, the difference between the linear velocity of the photosensitive drum 21 and the linear velocity of the charge removing member 27 is minimized within a range where the required charge removing performance can be secured. Therefore, wear of the photosensitive drum 21 can be suppressed.

  Note that a configuration in which the image forming apparatus 10 includes the rotation control unit 17 as shown in FIG. 23 is considered as a modification of the fourth embodiment. Specifically, every time the cumulative number of prints or the cumulative number of rotations increases by a predetermined reference value, the rotation control unit 17 performs a predetermined fourth timing different from the time of execution of the print processing, The static elimination member 27 is rotated in a direction opposite to the rotation direction when the printing process is performed. For example, the rotation control unit 17 rotates the charge removing member 27 in a direction opposite to the rotation direction at the time of executing the printing process for a predetermined time or the number of rotations. According to this configuration, since the curvature of the tip of the brush bristles 271 is regularly corrected, a decrease in the outer diameter of the charge removing member 27 can be suppressed. When the rotation control unit 17 is provided in the image forming apparatus 10, the contents of the fifth table data may be corrected.

REFERENCE SIGNS LIST 1 control unit 2 image forming unit 3 paper feeding unit 4 paper discharging unit 10 image forming apparatus 11 density detecting unit 12 voltage changing unit 13A first speed changing unit 13B second speed changing unit 13C third speed changing unit 14 movement processing unit 15A First acquisition processing unit 15B Second acquisition processing unit 16A First variation acquisition unit 16B Second variation acquisition unit 17 Rotation control unit 21 Photoconductor drum 22 Charging device 23 Optical scanning device 24 Developing device 25 Transfer roller 26 Cleaning member 27 Static elimination member 270 Base part 271 Brush bristles 272 First driving part 273 Second driving part 274 Cleaning member 28 Fixing device 29 Density sensor

Claims (5)

A photoreceptor,
A static elimination member that is electrically grounded, is rotatably disposed in contact with the surface of the photoconductor, and is movable in a first direction approaching the photoconductor and in a second direction opposite to the first direction ; ,
A charging member for charging the photoconductor,
A voltage changing unit that changes an applied voltage applied to the charging member,
As the applied voltage applied to the charging member is higher, a speed changing unit that increases a difference between a linear speed of the photoconductor and a linear speed of the charge removing member,
As the applied voltage applied to the charging member is higher, a movement processing unit that reduces a separation distance between the photoconductor and the charge removing member,
An image forming apparatus comprising: The speed changing unit increases or decreases the difference between the linear speed of the photoconductor and the linear speed of the charge removing member within a range equal to or greater than a preset lower limit and equal to or less than an upper limit.
The image forming apparatus according to claim 1. The speed changing unit increases a linear velocity of the charge eliminating member, and increases a difference between a linear velocity of the photoconductor and a linear velocity of the charge eliminating member.
The image forming apparatus according to claim 1. The speed changing unit decreases the linear velocity of the charge eliminating member, and increases the difference between the linear speed of the photoconductor and the linear velocity of the charge eliminating member.
The image forming apparatus according to claim 1. A photoconductor, electrically grounded, rotatably disposed in contact with the surface of the photoconductor, and movable in a first direction approaching the photoconductor and in a second direction opposite to the first direction; A static elimination member, and a charging member for charging the photoreceptor, an image forming method executed by an image forming apparatus including:
A voltage changing step of changing an applied voltage applied to the charging member,
As the applied voltage applied to the charging member is higher, a speed changing step of increasing a difference between a linear speed of the photoconductor and a linear speed of the charge removing member,
As the applied voltage applied to the charging member is higher, a moving step of reducing a separation distance between the photoconductor and the charge removing member,
And an image forming method.

Images