JP6601195B2 - Image forming apparatus, control method, and control program - Google Patents

Description

  The present disclosure relates to control of an image forming apparatus, and more particularly to control of an electrophotographic image forming apparatus.

  An electrophotographic image forming apparatus is widely used. An electrophotographic image forming apparatus forms a toner image corresponding to an input image on an image carrier such as a photosensitive member or an intermediate transfer member in a printing process, and transfers the toner image on the image carrier onto a sheet. Performing a step and a step of fixing the toner image on the paper.

  An AC (Alternating Current) transfer technique is known as a transfer technique of a toner image from an image carrier to a sheet. In the AC transfer process, an AC voltage having a polarity different from that of the toner image and superimposed with a DC component and an AC component is applied to the toner image by the transfer member. Hereinafter, the AC voltage applied in the AC transfer process is also referred to as “transfer voltage”. By applying the transfer voltage, the toner reciprocates, and a physical and electrical interaction occurs between the toners. As a result, the adhesion force of the toner is reduced, and the transferability of the toner image from the image carrier to the paper is improved. Further, the occurrence of uneven density in the toner image is also suppressed.

  However, the sheet may be charged by applying a transfer voltage, and the sheet may be attracted to the image carrier. As a technique for preventing this, an AC static elimination technique for separating a sheet from an image carrier is known. In the AC discharging step, an AC voltage having a polarity different from that of the transfer voltage and having a DC component and an AC component superimposed thereon is applied to the sheet by the discharging member. As a result, the sheet is neutralized. Hereinafter, the AC voltage applied in the AC static elimination step is also referred to as “static elimination voltage”.

  Regarding a technique combining an AC transfer technique and an AC charge eliminating technique, Japanese Patent Application Laid-Open No. 61-87179 (Patent Document 1) discloses a copying apparatus that is capable of stable transfer / separation without causing retransfer. Yes. Japanese Patent Laid-Open No. 11-38783 (Patent Document 2) discloses an image forming apparatus that “smoothly removes charges accumulated in an intermediate transfer member”. Japanese Patent Laying-Open No. 2013-83951 (Patent Document 3) discloses an image forming apparatus that “prevents leakage between members to which alternating current is applied”.

JP-A-61-87179 Japanese Patent Laid-Open No. 11-38783 JP2013-83951A

  The copying apparatus disclosed in Patent Document 1 detects an image area from a document and lowers the DC component voltage of the AC voltage applied to the image area lower than the DC component voltage of the AC voltage applied to the non-layer area. To do. However, when the voltage of the DC component is low, the sheet is not effectively neutralized.

  The image forming apparatus disclosed in Patent Document 2 applies a neutralization voltage having a phase opposite to the transfer voltage to the intermediate transfer member in the AC neutralization step. As a result, the image forming apparatus neutralizes the intermediate transfer member. However, when the conveyance of the paper is not stable, the phase of the transfer voltage or the neutralization voltage may be shifted more than intended. In this case, the image forming apparatus disclosed in Patent Document 2 cannot effectively neutralize the intermediate transfer member.

  When the AC transfer technique and the AC charge removal technique are combined, the potential difference between the transfer member and the charge removal member increases, and thus there is a possibility that discharge (leakage) occurs between the transfer member and the charge removal member. In order to prevent such discharge, the image forming apparatus disclosed in Patent Document 3 sets the transfer voltage and the neutralization voltage in the same phase. As a result, the potential difference between the transfer member and the charge removal member is reduced, and discharge that occurs between the transfer member and the charge removal member is prevented. However, if the transfer voltage and the charge removal voltage are set in the same phase, the potential difference between the sheet and the charge removal member becomes constant, and the sheet is not discharged efficiently. As a result, the potential unevenness of the sheet is not eliminated, and the conveyance failure of the sheet occurs, or the noise accompanying the conveyance defect occurs. In addition, potential unevenness affects the toner image, and print quality may be deteriorated.

  The present disclosure has been made in order to solve the above-described problems, and an object in one aspect is to provide an image forming apparatus capable of more effectively discharging the paper after transferring the toner image than before. Is to provide. Another object of the present invention is to provide a control method capable of discharging the paper after transferring the toner image more effectively than before. Still another object of the present invention is to provide a control program capable of discharging the paper after transferring the toner image more effectively than before.

According to a certain aspect, an image forming apparatus for transferring a toner image formed in accordance with an input image onto a transferred transfer medium, an image carrier for carrying the toner image, the toner image, a different polarity is applied to the DC component and the transfer target medium being transported a first AC voltage AC component is superimposed, a transfer member for transferring the toner image on the transfer medium, the upper Symbol first A neutralizing member for applying a second AC voltage having a polarity different from that of the one AC voltage and having a DC component and an AC component superimposed thereon, to the transfer medium being transferred ; the first AC voltage and the second AC voltage; And a control unit for controlling . The control unit sets the frequency and phase of the second AC voltage to the frequency and phase of the first AC voltage when the distance between the transfer medium and the charge removal member is longer than a predetermined distance. When the distance between the transfer medium and the charge removal member is shorter than the predetermined distance, the frequency of the second AC voltage is set to be the same as that of the first AC voltage. Control to be higher than the frequency .

  Preferably, the frequency of the second AC voltage is an integer multiple of the frequency of the first AC voltage.

Preferably, the transfer medium is a sheet. The control unit obtains a control value corresponding to the characteristic of the paper being conveyed based on paper information defining the control value of the first AC voltage for each characteristic of the paper, and according to the control value Te that controls the first AC voltage.

Preferably, the transfer medium is a sheet. The control unit obtains a control value corresponding to the characteristic of the paper being conveyed based on the paper information that defines the control value of the second AC voltage for each characteristic of the paper, and according to the control value Te that controls the second alternating voltage.

Preferably, an insulating member is provided between the transfer member and the charge removal member.
According to another aspect, a method for controlling an image forming apparatus is provided. The control method includes a step of forming a toner image corresponding to an input image, a step of conveying a transfer medium, and a first AC voltage having a polarity different from that of the toner image and having a DC component and an AC component superimposed thereon. It is applied to the transfer medium being transported, step a, a second alternating voltage DC and AC components comprising: a first AC voltage on SL and opposite polarity are superimposed to transfer the toner image to the transfer medium Is applied to the transfer medium by a charge eliminating member provided on the transfer path of the transfer medium. In the applying step , the frequency and phase of the second AC voltage are set to the frequency and phase of the first AC voltage when the distance between the transfer medium and the charge removal member is longer than a predetermined distance. And when the distance between the transfer medium and the charge removal member is shorter than the predetermined distance, the frequency of the second AC voltage is set to the first AC voltage. And a step of controlling the frequency so as to be higher than the frequency .

According to still another aspect, a control program for an image forming apparatus is provided. The control program includes a step of forming a toner image corresponding to an input image on the image forming apparatus, a step of transporting a transfer medium, and a DC component and an AC component that are different in polarity from the toner image and superimposed. and the first AC voltage is applied to the transfer medium being transported, and transferring the toner image to the transfer medium, the DC and AC components comprising: a first AC voltage on SL and opposite polarity are superimposed Applying the applied second AC voltage to the transfer medium by a charge eliminating member provided on the transfer path of the transfer medium. In the applying step , the frequency and phase of the second AC voltage are set to the frequency and phase of the first AC voltage when the distance between the transfer medium and the charge removal member is longer than a predetermined distance. And when the distance between the transfer medium and the charge removal member is shorter than the predetermined distance, the frequency of the second AC voltage is set to the first AC voltage. And a step of controlling the frequency so as to be higher than the frequency of .

  In one aspect, the paper after transferring the toner image can be discharged more effectively than before.

  The above and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the present invention taken in conjunction with the accompanying drawings.

It is a figure which shows an example of the apparatus structure of the image forming apparatus according to 1st Embodiment. It is a figure showing the timing which changes the frequency of a transfer voltage, and the frequency of a static elimination voltage. FIG. 6 is a diagram illustrating a potential of a sheet, a potential of a charge removal member, and a potential difference between the sheet and the charge removal member when the sheet does not reach the charge removal region indicating the vicinity of the charge removal member. FIG. 6 is a diagram illustrating a sheet potential, a potential of a charge removal member, and a potential difference between the sheet and the charge removal member when the sheet reaches a charge removal region. It is a figure which shows the voltage control according to a comparative example. It is a figure which shows an example of the circuit structure for controlling a transfer voltage and a static elimination voltage. It is a figure which shows an example of a static elimination area. It is a figure which shows the other example of a static elimination area. It is a figure which shows the further another example of a static elimination area. It is a figure which shows the content of the paper information referred when determining a transfer voltage and a static elimination voltage. 5 is a flowchart showing a part of processing executed by the image forming apparatus according to the first embodiment. 2 is a block diagram showing an example of a hardware configuration of the image forming apparatus according to the first embodiment. FIG. It is a figure which shows the structure of the static elimination member periphery of the image forming apparatus according to 2nd Embodiment.

  Embodiments according to the present invention will be described below with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated. Each embodiment and each modified example described below may be selectively combined as appropriate.

<First Embodiment>
[Internal structure of image forming apparatus 100]
With reference to FIG. 1, an image forming apparatus 100 according to the embodiment will be described. FIG. 1 is a diagram illustrating an example of an apparatus configuration of the image forming apparatus 100.

  FIG. 1 shows an image forming apparatus 100 as a color printer. Hereinafter, the image forming apparatus 100 as a color printer will be described, but the image forming apparatus 100 is not limited to a color printer. For example, the image forming apparatus 100 may be a monochrome printer, may be a FAX, or may be a monochrome printer, a color printer, and a multifunction machine (MFP: Multi-Functional Peripheral).

  The image forming apparatus 100 includes image forming units 1Y, 1M, 1C, and 1K, an intermediate transfer belt 30 (image carrier), a primary transfer member 31, an optical sensor 32, a secondary transfer member 33, and a cassette 37. The driven roller 38, the driving roller 39, the timing roller 40, the charge eliminating member 41, the fixing device 50, the cleaning blade 36, and the control device 101 are provided.

  The image forming unit 1Y receives toner from the toner bottle 15Y and forms a yellow (Y) toner image. The image forming unit 1M receives the supply of toner from the toner bottle 15M and forms a magenta (M) toner image. The image forming unit 1C receives toner from the toner bottle 15C and forms a cyan (C) toner image. The image forming unit 1K receives toner from the toner bottle 15K and forms a black (BK) toner image.

  The image forming units 1Y, 1M, 1C, and 1K are arranged along the intermediate transfer belt 30 in the rotation direction of the intermediate transfer belt 30, respectively. Each of the image forming units 1Y, 1M, 1C, and 1K includes a photoreceptor 10 (image carrier), a charger 11, an exposure unit 12, a developing unit 13, and a cleaning blade 17.

  The charger 11 uniformly charges the surface of the photoconductor 10. The exposure unit 12 irradiates the photoconductor 10 with laser light in accordance with a control signal from the control device 101, and exposes the surface of the photoconductor 10 according to a designated image pattern. As a result, an electrostatic latent image corresponding to the input image is formed on the photoreceptor 10.

  The developing device 13 applies a developing bias to the developing roller 14 while rotating the developing roller 14, and causes the toner to adhere to the surface of the developing roller 14. As a result, the toner is transferred from the developing roller 14 to the photoreceptor 10, and a toner image corresponding to the electrostatic latent image is developed on the surface of the photoreceptor 10.

  The photoreceptor 10 and the intermediate transfer belt 30 are in contact with each other at a portion where the primary transfer member 31 is provided. The toner image developed on the photoreceptor 10 is transferred to the intermediate transfer belt 30 by the transfer bias applied to the contact portion. At this time, a yellow (Y) toner image, a magenta (M) toner image, a cyan (C) toner image, and a black (BK) toner image are sequentially superimposed and transferred to the intermediate transfer belt 30. As a result, a color toner image is formed on the intermediate transfer belt 30.

  The intermediate transfer belt 30 is stretched around a driven roller 38 and a driving roller 39. The drive roller 39 is connected to a motor (not shown). The motor is controlled by the control device 101, for example. As a method for controlling the motor, for example, PWM (Pulse Width Modulation) control is employed. When the control device 101 controls the motor, the intermediate transfer belt 30 and the driven roller 38 rotate in conjunction with the driving roller 39. As a result, the toner image on the intermediate transfer belt 30 is conveyed to the secondary transfer member 33.

  The cleaning blade 17 is in pressure contact with the photoreceptor 10. The cleaning blade 17 collects toner remaining on the surface of the photoconductor 10 after the transfer of the toner image from the photoconductor 10 to the intermediate transfer belt 30.

  The optical sensor 32 captures a toner image on the intermediate transfer belt 30 and generates a toner image. The image is output to the control device 101. The control device 101 calculates the density of the toner image from the image, and adjusts the degree of exposure of the photoconductor 10 so that the density of the toner image becomes a target value.

  In the cassette 37, a sheet S (medium to be transferred) is set. The sheets S are sent one by one from the cassette 37 to the secondary transfer member 33 by the timing roller 40. The control device 101 controls the transfer voltage applied to the paper S from the secondary transfer member 33 and the static elimination voltage applied to the paper S from the static elimination member 41 in synchronization with the timing at which the paper S is sent out by the timing roller 40.

  The secondary transfer member 33 applies a transfer voltage (first AC voltage) having a polarity different from that of the toner image and superimposed with a DC component and an AC component to the sheet S being conveyed. The toner image is transferred to an appropriate position on the sheet S by synchronizing the timing of feeding and conveying the sheet S with the position of the toner image on the intermediate transfer belt 30.

  The static elimination member 41 applies a static elimination voltage (second AC voltage) having a polarity different from that of the transfer voltage and having a DC component and an AC component superimposed on the sheet S being conveyed. Thereby, potential unevenness of the sheet S caused by application of the transfer voltage is suppressed. The neutralizing member 41 is, for example, a saw blade electrode. The plate | board thickness of the static elimination member 41 is 0.05 mm, for example. The needle pitch of the static elimination member 41 is 3 mm, for example.

  The fixing device 50 includes a heating roller 51 and a pressure roller 52. The fixing device 50 passes between the heating roller 51 and the pressure roller 52 through the sheet S, and pressurizes and heats the sheet S. As a result, the toner image transferred onto the paper S is fixed on the paper S. Thereafter, the sheet S is discharged to the tray 48.

  In FIG. 1, the conveyance path of the paper S from the cassette 37 to the tray 48 is indicated by a one-dot chain line.

  The cleaning blade 36 is in pressure contact with the intermediate transfer belt 30. The cleaning blade 36 collects the toner remaining on the surface of the intermediate transfer belt 30 after the transfer of the toner image from the intermediate transfer belt 30 to the paper S. The collected toner is conveyed by a conveying screw (not shown) and stored in a waste toner container (not shown).

[Control of transfer voltage and static elimination voltage]
As described above, the secondary transfer member 33 applies a transfer voltage (first AC voltage), which is different in polarity from the toner image and on which the DC component and the AC component are superimposed, to the sheet S being conveyed. The toner image on the transfer belt 30 is transferred to the paper S. The neutralization member 41 applies a neutralization voltage having a polarity different from that of the transfer voltage to which a direct current component and an alternating current component are superimposed on the paper S, thereby causing potential unevenness of the paper S caused by application of the transfer voltage (second alternating voltage). Is solved.

  A method for controlling the transfer voltage applied to the secondary transfer member 33 and the charge removal voltage applied to the charge removal member 41 will be described with reference to FIGS. FIG. 2 is a diagram illustrating the timing of changing the frequency of the transfer voltage and the frequency of the static elimination voltage.

  The image forming apparatus 100 sets the frequency of the static elimination voltage to be higher than the frequency of the transfer voltage based on the fact that the sheet S has reached the static elimination region C1 indicating the vicinity of the static elimination member 41. As a result, the potential difference between the sheet S and the charge removal member 41 increases, and a discharge occurs between the sheet S and the charge removal member 41. Thus, by setting the frequency of the static elimination voltage higher than the frequency of the transfer voltage, it is possible to eliminate the paper S without depending on the phase of the static elimination voltage or the transfer voltage. Therefore, even if the phase of the static elimination voltage and the transfer voltage changes due to a conveyance failure of the paper S, the image forming apparatus 100 can effectively neutralize the paper S. As a result, conveyance failure of the paper S due to potential unevenness, generation of noise due to conveyance failure, and deterioration of image quality due to potential unevenness are prevented.

  As a more specific voltage control process, the image forming apparatus 100 executes the voltage control process of steps S1 to S7 shown in FIG. Below, the process of step S1-S7 is demonstrated in order.

  As shown in step S <b> 1, the image forming apparatus 100 does not apply a transfer voltage to the secondary transfer member 33 before receiving a printing operation from the user. Further, the image forming apparatus 100 does not apply a static elimination voltage to the static elimination member 41.

  In step S2, it is assumed that the image forming apparatus 100 receives a print operation from the user. As a result, the image forming apparatus 100 starts preprocessing for printing the paper S. As an example of preprocessing, the image forming apparatus 100 stabilizes the potential on the surface of the photoconductor 10, stabilizes the high voltage output from each component, or adjusts the amount of toner attached to the photoconductor 10. Or At the time of pre-processing, the image forming apparatus 100 sets the frequency of the transfer voltage and the static elimination voltage to zero, and outputs only the DC component of the transfer voltage and the static elimination voltage.

  In step S3, the conveyance of the paper S is started. The sheet S is conveyed to the secondary transfer member 33. 3 shows the potential 71 of the paper S, the potential 72 of the static elimination member 41, and the potential difference 73 of the paper S and the static elimination member 41 when the paper S has not reached the static elimination area C1 indicating the vicinity of the static elimination member 41. FIG. The potential 71 of the sheet S corresponds to the potential of the secondary transfer member 33.

  As shown in FIGS. 2 and 3, when the sheet S has not reached the charge removal region C1, the image forming apparatus 100 sets the transfer voltage and the charge removal frequency to “f1”, the transfer voltage and the charge removal. Set the voltage to the same phase. By setting the transfer voltage and the charge removal voltage in the same phase, the potential difference 73 between the sheet S and the charge removal member 41 becomes constant, and the potential difference compared to the case where the phase between the transfer voltage and the charge removal voltage is shifted. 73 becomes smaller. As a result, the discharge that can occur between the secondary transfer member 33 and the charge removal member 41 is suppressed.

  The voltage of the DC component of the transfer voltage applied in step S3 is +3 kV, for example. The amplitude of the AC component of the transfer voltage is, for example, ± 1.0 kV. The frequency of the transfer voltage is 0.2 kHz, for example. The waveform of the transfer voltage is, for example, a sin wave. The voltage of the DC component of the static elimination voltage is, for example, -3 kV. The amplitude of the AC component of the static elimination voltage is, for example, ± 1.0 kV. The frequency of the static elimination voltage is 0.2 kHz, for example. The waveform of the static elimination voltage is, for example, a sine wave.

  In step S4, it is assumed that the sheet S has reached the charge removal area C1. At this time, potential unevenness occurs on the back surface of the paper S due to the application of the transfer voltage in step S3. The back surface means a surface on the opposite side of the surface onto which the toner image is transferred. FIG. 4 is a diagram illustrating the potential 71 of the paper S, the potential 72 of the static elimination member 41, and the potential difference 73 of the paper S and the static elimination member 41 when the paper S reaches the static elimination area C1.

  As shown in FIGS. 2 and 4, the image forming apparatus 100 changes the frequency of the static elimination voltage when the paper S reaches the static elimination region C1. For example, the image forming apparatus 100 increases the frequency of the static elimination voltage from “f1” to “f2” when the paper S reaches the static elimination region C1. The frequency of the transfer voltage is maintained at “f1”.

  As described above, the image forming apparatus 100 sets the frequency of the static elimination voltage from the frequency of the transfer voltage based on the fact that the distance between the sheet S being conveyed and the static elimination member 41 is shorter than the predetermined distance. Set too high. As a result, the voltage difference between the charge removal voltage and the transfer voltage increases at the timing when the sheet S approaches the charge removal member 41. As a result, a discharge occurs between the sheet S and the charge removal member 41, and the sheet S can be effectively discharged.

  Preferably, the frequency of the static elimination voltage is set to an integral multiple (for example, 3 times or more) of the frequency of the transfer voltage. The frequency of the static elimination voltage is preferably set to 100 Hz to 10 kHz, for example. Thereby, the temperature rise of the board | substrate accompanying a high frequency, etc. are prevented. Further, since the potential difference 73 follows the potential 72 on the back surface of the sheet S, the image forming apparatus 100 can discharge the sheet S more efficiently and uniformly.

  The voltage of the DC component of the transfer voltage applied in step S4 is +3 kV, for example. The amplitude of the AC component of the transfer voltage is, for example, ± 1.0 kV. The frequency of the transfer voltage is 0.2 kHz, for example. The waveform of the transfer voltage is, for example, a sin wave. The voltage of the DC component of the static elimination voltage is, for example, -3 kV. The amplitude of the AC component of the static elimination voltage is, for example, ± 1.0 kV. The frequency of the static elimination voltage is 1.0 kHz, for example. That is, the frequency of the static elimination voltage is set to 5 times the frequency of the transfer voltage. The waveform of the static elimination voltage is, for example, a sine wave.

  In step S5, it is assumed that the sheet S passes through the charge removal area C1. At this time, the image forming apparatus 100 restores the frequency of the static elimination voltage and sets the static elimination voltage and the transfer voltage to the same phase. More specifically, the image forming apparatus 100 decreases the frequency of the static elimination voltage from “f2” to “f1” while maintaining the frequency of the transfer voltage at “f1”.

  In step S6, it is assumed that the printing process is finished. At this time, the image forming apparatus 100 stops applying the transfer voltage and the charge removal voltage as post-processing.

  In step S <b> 7, the image forming apparatus 100 again shifts to a state where a printing operation is accepted from the user.

[Comparison result]
Referring again to FIG. 5 with reference to FIG. 4 again, the advantage of making the frequency of the static elimination voltage higher than the frequency of the transfer voltage when the paper S reaches the static elimination region C1 will be described. FIG. 5 is a diagram illustrating voltage control according to the comparative example.

  In the image forming apparatus 100 according to the comparative example, when the sheet S reaches the static elimination region C1, the frequency of the static elimination voltage remains equal to the frequency of the transfer voltage without setting the frequency of the static elimination voltage higher than the frequency of the transfer voltage. To do. As a result, the relationship between the potential 71 of the sheet S generated by applying the transfer voltage, the potential 72 of the charge removal member 41, and the potential difference 73 between the sheet S and the charge removal member 41 is as shown in FIG. In the comparative example, the peak of the potential 71 is shifted from the valley of the potential 72, or the valley of the potential 71 is shifted from the peak of the potential 72, and the potential difference 73 does not increase.

  On the other hand, as shown in FIG. 4, the image forming apparatus 100 according to the first embodiment sets the frequency of the static elimination voltage higher than the frequency of the transfer voltage when the paper S reaches the static elimination region C1. . Accordingly, the amount of deviation between the peak of the potential 71 and the valley of the potential 72 is reduced, or the amount of deviation between the valley of the potential 71 and the peak of the potential 72 is reduced, and the potential difference 73 is increased. Thereby, the image forming apparatus 100 according to the first embodiment can increase the potential difference 73 between the sheet S and the charge removal member 41 without depending on the phase of the transfer voltage and the charge removal voltage. As a result, a discharge occurs between the sheet S and the charge removal member 41, and the sheet S can be discharged. Further, since the potential difference 73 follows the potential 72 of the paper S, the image forming apparatus 100 can efficiently and uniformly remove the paper S.

[Circuit structure]
With reference to FIG. 6, a circuit configuration for controlling the transfer voltage and the static elimination voltage will be described. FIG. 6 is a diagram illustrating an example of a circuit configuration for controlling the transfer voltage and the static elimination voltage.

  As shown in FIG. 6, a power supply 34 is connected to the secondary transfer member 33 in series. The power source 34 includes a constant voltage source or a constant current source and an AC voltage source or an AC current source. As a result, a transfer voltage in which the DC component and the AC component are superimposed is applied to the secondary transfer member 33. The control device 101 sends a control signal to the power supply 34 to control the frequency and phase of the transfer voltage.

  A power source 42 is connected in series to the charge removal member 41. The power source 42 includes a constant voltage source or a constant current source and an AC voltage source or an AC current source. Thereby, the static elimination voltage on which the direct current component and the alternating current component are superimposed is applied to the static elimination member 41. The DC component of the static elimination voltage is different in polarity from the DC component of the transfer voltage. The transfer voltage applied to the sheet S is canceled out by the charge removal voltage, and the sheet S is discharged. The control device 101 sends a control signal to the power supply 34 to control the frequency and phase of the static elimination voltage.

[Static elimination area]
With reference to FIGS. 7 to 9, the above-described charge removal region C <b> 1 will be described. FIG. 7 is a diagram illustrating an example of the charge removal area. FIG. 8 is a diagram illustrating another example of the charge removal region. FIG. 9 is a diagram illustrating still another example of the charge removal region.

  As shown in FIG. 7, the secondary transfer member 33 and the charge removal member 41 are provided along the transport path of the paper S. More specifically, the charge removal member 41 is provided on the transport direction side (that is, the downstream side) of the sheet S from the secondary transfer member 33.

  In one aspect, the charge removal region C1 is determined in advance according to the distance L2 between the secondary transfer member 33 and the charge removal member 41. As an example, the charge removal region C1 represents a range in which the charge removal member 41 is the center and the distance L2 is a radius. That is, the radius of the charge removal region C1 is shorter than the distance L2 between the secondary transfer member 33 and the charge removal member 41.

  The image forming apparatus 100 is set so that the frequency of the neutralization voltage is higher than the frequency of the transfer voltage based on the fact that the sheet S has reached the neutralization region C1. That is, the image forming apparatus 100 eliminates the charge removal based on the fact that the distance L1 between the sheet S being conveyed and the charge removal member 41 is shorter than the distance L2 between the charge removal member 41 and the secondary transfer member 33. The voltage frequency is set higher than the transfer voltage frequency. As an example, the distance L1 is represented by the shortest distance between the sheet S being conveyed and the charge removal member 41.

  When the distance L1 becomes shorter than the distance L2, the frequency of the static elimination voltage is set to be higher than the frequency of the transfer voltage, so that the static elimination member 41 is discharged more than between the static elimination member 41 and the secondary transfer member 33. And the sheet S. As a result, the discharge between the charge eliminating member 41 and the secondary transfer member 33 is prevented, and the sheet S is effectively discharged.

  In another aspect, as shown in FIG. 8, the charge removal region C2 is determined in advance according to the distance L3 between the charge removal member 41 and the intermediate transfer belt 30 as the image carrier. The intermediate transfer belt 30 and the charge removal member 41 are provided with the conveyance path of the paper S interposed therebetween. The distance L3 corresponds to, for example, the distance between the tip of the static elimination member 41 and the surface of the intermediate transfer belt 30 or the outer peripheral surface of the drive roller 39. The static elimination region C2 represents a range in which the static elimination member 41 is the center and the distance L3 is a radius. That is, the radius of the charge removal region C2 is shorter than the distance L2 between the charge removal member 41 and the intermediate transfer belt 30.

  The image forming apparatus 100 is set so that the frequency of the charge removal voltage is higher than the frequency of the transfer voltage based on the fact that the sheet S has reached the charge removal region C2. In other words, the image forming apparatus 100 determines whether the distance L1 between the sheet S being conveyed and the charge removal member 41 is shorter than the distance L3 between the intermediate transfer belt 30 and the charge removal member 41. Is made higher than the frequency of the transfer voltage.

  When the distance L1 becomes shorter than the distance L3, the frequency of the static elimination voltage is set to be higher than the frequency of the transfer voltage, so that the discharge is performed between the static elimination member 41 and the intermediate transfer belt 30 rather than between the static elimination member 41 and the intermediate transfer belt 30. It tends to occur between the sheet S and the sheet S. As a result, discharge between the charge eliminating member 41 and the intermediate transfer belt 30 is prevented, and the sheet S is effectively discharged.

  In still another aspect, as shown in FIG. 9, the charge removal region C1 in FIG. 7 and the charge removal region C2 in FIG. 8 may be combined. As an example, the narrower one of the static elimination area C1 and the static elimination area C2 is adopted as the static elimination area. Or the wider one of the static elimination area C1 and the static elimination area C2 may be employ | adopted as a static elimination area. Alternatively, an overlapping area between the static elimination area C1 and the static elimination area C2 may be adopted as the static elimination area.

[Method for Detecting that Paper S has Reached the Static Elimination Area]
Hereinafter, a method for detecting that the sheet S has reached the charge removal area C1 (see FIG. 7) will be described.

  The image forming apparatus 100 includes a detection unit that detects the position of the sheet S on the conveyance path. For example, the detection means is a timing roller 40 (see FIG. 1). The timing roller 40 is provided on the upstream side of the conveyance path of the paper S with respect to the static elimination member 41. The timing roller 40 sends out the paper S at a predetermined timing. As shown in the following formula (1), the control device 101 determines that the paper S reaches the static elimination area C1 from the distance La between the timing roller 40 and the static elimination area C1 and the conveyance speed V of the paper S. The required time Ta is calculated.

Ta (s) = V (mm / s) / La (mm) (1)
The control device 101 determines that the paper S has reached the static elimination region C1 when the time Ta has elapsed from the timing when the paper S is sent out by the timing roller 40, and makes the frequency of the static elimination voltage higher than the frequency of the transfer voltage. To do. That is, the timing for changing the frequency of the transfer voltage includes the timing at which a predetermined time Ta has elapsed after the timing roller 40 detects the paper S.

  As another detection unit of the sheet S, the control device 101 detects the sheet S passing through the nip portion between the intermediate transfer belt 30 and the secondary transfer member 33. When the sheet S passes through the nip portion, the voltage value or current value in the secondary transfer member 33 changes. Focusing on this point, the control device 101 determines that the sheet S is moved between the intermediate transfer belt 30 and the secondary transfer member 33 when the voltage value or current value in the secondary transfer member 33 changes by a predetermined value or more. Detects reaching the nip. As shown in the following formula (2), the control device 101 determines that the paper S reaches the static elimination region C1 from the distance Lb between the nip portion and the static elimination region C1 and the conveyance speed V of the paper S. The required time Tb is calculated.

Tb (s) = V (mm / s) / Lb (mm) (2)
The control device 101 determines that the paper S has reached the static elimination region C1 when the time Tb has elapsed from the timing when the intermediate transfer belt 30 and the paper S have reached the nip portion between the secondary transfer member 33, and the static elimination voltage. Is made higher than the frequency of the transfer voltage. That is, the timing for changing the frequency of the transfer voltage includes the timing at which a predetermined time Tb has elapsed since the sheet S was detected at the nip portion between the intermediate transfer belt 30 and the secondary transfer member 33.

[Paper information 124]
With reference to FIG. 10, a method for determining the transfer voltage and the charge removal voltage will be described. FIG. 10 is a diagram showing the contents of the sheet information 124 that is referred to when determining the transfer voltage and the charge removal voltage.

  The optimum transfer voltage varies depending on the type of paper. For example, in the case of a paper having an uneven surface such as embossed paper, the transfer efficiency is improved by increasing the DC component and AC component of the transfer voltage. On the other hand, in thin paper, even if the direct current component and the alternating current component of the transfer voltage are small, the transfer efficiency does not decrease so much.

  Similarly, the optimum static elimination voltage varies depending on the type of paper. For example, for a sheet having a small sheet resistance such as a thin sheet, it is preferable to reduce the DC component and the AC component of the static elimination voltage so that the sheet is not excessively neutralized. On the other hand, in a sheet having a high sheet resistance, it is preferable to increase the DC component and the AC component of the discharge voltage in order to increase the discharge efficiency of the sheet.

  As shown in FIG. 10, the sheet information 124 defines voltage control values for the transfer voltage and the charge removal voltage in accordance with the characteristics of the sheet. More specifically, in the sheet information 124, a voltage control value of the transfer voltage is defined for each sheet characteristic. The image forming apparatus 100 refers to the paper information 124, acquires a voltage control value corresponding to the characteristics of the paper to be printed, and controls the transfer voltage applied to the secondary transfer member 33 according to the voltage control value. . As a result, the image forming apparatus 100 can apply a transfer voltage that matches the characteristics of the paper, and can increase the transfer efficiency of the toner image.

  Further, in the paper information 124, a voltage control value for the static elimination voltage is defined for each characteristic of the paper. The image forming apparatus 100 refers to the paper information 124, acquires a voltage control value corresponding to the characteristics of the paper to be printed, and controls the static elimination voltage applied to the static elimination member 41 according to the voltage control value. As a result, the image forming apparatus 100 can effectively neutralize the sheet according to the characteristics of the sheet.

  The sheet characteristics defined in the sheet information 124 include, for example, the sheet thickness. As an example, the paper characteristics are acquired from the print setting information. The voltage control value of the secondary transfer member 33 defined in the paper information 124 includes, for example, the magnitude of the DC component of the transfer voltage, the frequency of the AC component of the transfer voltage, and the like. The voltage control value of the static elimination member 41 defined in the paper information 124 includes the magnitude of the DC component of the static elimination voltage, the frequency of the AC component of the static elimination voltage, and the like.

  Preferably, in the paper information 124, environmental conditions around the image forming apparatus 100 are further defined for each voltage control value. The environmental conditions include, for example, temperature information and humidity information. The image forming apparatus 100 detects the temperature and humidity inside the apparatus and acquires a voltage control value associated with the temperature and humidity from the sheet information 124. The image forming apparatus 100 controls the transfer voltage and the charge removal voltage according to the acquired voltage control value. As a result, the image forming apparatus 100 can apply a transfer voltage and a static elimination voltage suitable for the environment to the sheet.

[Control structure]
A control structure of the image forming apparatus 100 will be described with reference to FIG. FIG. 11 is a flowchart showing a part of processing executed by image forming apparatus 100. The processing in FIG. 11 is realized by the control device 101 of the image forming apparatus 100 executing a program. In other aspects, some or all of the processing may be performed by circuit elements or other hardware.

  In step S10, the control apparatus 101 determines whether a printing operation has been accepted. When control device 101 determines that a printing operation has been accepted (YES in step S10), control is switched to step S12. When that is not right (in step S10 NO), the control apparatus 101 performs the process of step S10 again.

  In step S12, the control apparatus 101 causes the image forming apparatus 100A to execute a process of forming a toner image according to the input image. More specifically, the control device 101 sends a control signal to the exposure unit 12 (see FIG. 1). Thereby, the exposure unit 12 exposes the surface of the photoreceptor 10 (see FIG. 1) according to the input image. As a result, an electrostatic latent image corresponding to the input image is formed on the photoreceptor 10. Thereafter, the control device 101 applies a developing bias to the developing roller 14 (see FIG. 1). As a result, the toner is transferred from the developing roller 14 to the photoconductor 10, and a toner image corresponding to the electrostatic latent image is formed on the surface of the photoconductor 10.

  In step S <b> 14, the control apparatus 101 causes the image forming apparatus 100 to execute a process for conveying paper. At this time, the control device 101 controls the sheet conveyance timing in accordance with the position of the toner image on the intermediate transfer belt 30 (see FIG. 1).

  In step S <b> 20, the control device 101 functions as a paper position detection unit, and determines whether or not the paper has reached a predetermined position on the transport path. The predetermined position is a position on the sheet conveyance path that is upstream of the static elimination region C1 (see FIG. 3). Since the method for detecting the position of the sheet is as described above, description thereof will not be repeated. When it is determined that the sheet has reached a predetermined position on the transport path (YES in step S20), control device 101 switches control to step S22. Otherwise (NO in step S20), control device 101 executes step S20 again.

  In step S <b> 22, the control device 101 applies a transfer voltage having a polarity different from that of the toner image and on which the direct current component and the alternating current component are superimposed to the paper being transported, and performs a process of transferring the toner image onto the paper. To run. More specifically, the control device 101 acquires the characteristics of the paper to be printed (for example, the thickness of the paper) from the print setting information. The control device 101 refers to the sheet information 124 (see FIG. 10) and acquires a voltage control value of the transfer voltage corresponding to the acquired sheet characteristic. The control device 101 applies a transfer voltage corresponding to the acquired voltage control value to the secondary transfer member 33.

  In step S24, after applying the transfer voltage to the sheet, the control device 101 removes the charge removal voltage provided on the sheet conveyance path with a charge removal voltage that is different in polarity from the transfer voltage and on which the DC component and the AC component are superimposed. The image forming apparatus 100 is caused to execute processing to be applied to the sheet by the member 41 (see FIG. 1). More specifically, the control device 101 refers to the paper information 124 and acquires the voltage control value of the static elimination voltage corresponding to the characteristics of the paper to be printed. The control device 101 applies a static elimination voltage corresponding to the acquired voltage control value to the static elimination member 41.

  In step S30, the control device 101 determines whether or not a predetermined time has elapsed since the sheet was detected in step S20. The control device 101 determines that the sheet has reached the charge removal area C1 when the predetermined time has elapsed. When it is determined that a predetermined time has elapsed since the sheet was detected in step S20 (YES in step S30), control device 101 switches control to step S32. If not (NO in step S30), control device 101 executes step S30 again.

  In step S <b> 32, the control device 101 makes the frequency of the static elimination voltage applied to the static elimination member 41 higher than the frequency of the transfer voltage applied to the secondary transfer member 33. Thus, the frequency of the static elimination voltage becomes higher than the frequency of the transfer voltage at the timing when the sheet approaches the static elimination member 41 by steps S30 and S32. That is, the control device 101 executes a process for changing the frequency of the static elimination voltage on the image forming apparatus 100 based on the fact that the distance between the sheet being conveyed and the static elimination member 41 is shorter than a predetermined distance. Let

  In step S40, the control device 101 determines whether or not a predetermined time has elapsed since the paper S reached the static elimination area C1. The control device 101 determines that the sheet has passed through the charge removal area C1 when the predetermined time has elapsed. When the control device 101 determines that a predetermined time has elapsed after the paper S reaches the static elimination region C1 (YES in step S40), the control device 101 switches the control to step S42. If not (NO in step S40), control device 101 executes step S40 again.

  In step S <b> 42, the control device 101 restores the frequency of the static elimination voltage applied to the static elimination member 41. As an example, the control device 101 sets the static elimination voltage to be the same as the frequency of the transfer voltage. Preferably, the control device 101 sets the static elimination voltage and the transfer voltage in the same phase.

  In step S50, the control apparatus 101 determines whether printing of all sheets for which a print instruction has been received has been completed. When control device 101 determines that printing of all sheets has been completed (YES in step S50), control device 101 switches control to step S52. If not (NO in step S50), control device 101 returns control to step S20.

  In step S52, the control device 101 stops the application of the transfer voltage and the application of the static elimination voltage.

[Hardware Configuration of Image Forming Apparatus 100]
An example of the hardware configuration of the image forming apparatus 100 will be described with reference to FIG. FIG. 12 is a block diagram illustrating an example of a hardware configuration of the image forming apparatus 100.

  As illustrated in FIG. 12, the image forming apparatus 100 includes a control device 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, a network interface 104, an operation panel 107, and a storage device 120. With.

  The control device 101 is configured by at least one integrated circuit, for example. The integrated circuit includes, for example, at least one CPU (Central Processing Unit), at least one ASIC (Application Specific Integrated Circuit), at least one FPGA (Field Programmable Gate Array), or a combination thereof.

  The control apparatus 101 controls the operation of the image forming apparatus 100 by executing various programs such as the control program 122 according to the present embodiment. The control device 101 reads the control program 122 from the storage device 120 to the ROM 102 based on receiving the execution instruction of the control program 122. The RAM 103 functions as a working memory and temporarily stores various data necessary for executing the control program 122.

  An antenna (not shown) or the like is connected to the network interface 104. The image forming apparatus 100 exchanges data with an external communication device via the antenna. The external communication device includes, for example, a mobile communication terminal such as a smartphone, a server, and the like. Image forming apparatus 100 may be configured to download control program 122 according to the present embodiment from a server via an antenna.

  The operation panel 107 includes a display unit and a touch panel. The display unit and the touch panel are overlapped with each other, and the operation panel 107 receives a touch operation on the display unit. The operation panel 107 receives, for example, a printing operation or a scanning operation for the image forming apparatus 100.

  The storage device 120 is a storage medium such as a hard disk or an external storage device. Storage device 120 stores control program 122, paper information 124 (see FIG. 10), and the like according to the present embodiment. The storage location of the paper information 124 is not limited to the storage device 120, and the paper information 124 is stored in a storage area (for example, a cache) of the control device 101, a ROM 102, a RAM 103, an external device (for example, a server), or the like. Also good.

  The control program 122 may be provided by being incorporated in a part of an arbitrary program, not as a single program. In this case, the processing according to the present embodiment is realized in cooperation with an arbitrary program. Even such a program that does not include some modules does not depart from the spirit of the control program 122 according to the present embodiment. Furthermore, some or all of the functions provided by the control program 122 may be realized by dedicated hardware. Furthermore, the image forming apparatus 100 may be configured in the form of a so-called cloud service in which at least one server executes a part of the processing of the control program 122.

[Summary of First Embodiment]
As described above, the image forming apparatus 100 according to the first embodiment sets the frequency of the static elimination voltage higher than the frequency of the transfer voltage based on the fact that the sheet has reached the static elimination region representing the vicinity of the static elimination member. To do. By setting the frequency of the static elimination voltage higher than the frequency of the transfer voltage at the timing when the sheet approaches the static elimination member 41, the voltage difference between the static elimination voltage and the transfer voltage becomes large. As a result, a discharge occurs between the sheet S and the charge removal member 41, and the sheet S can be effectively discharged.

<Second Embodiment>
With reference to FIG. 13, an image forming apparatus 100 according to the second embodiment will be described. FIG. 13 is a diagram showing a structure around the charge removal member 41 of the image forming apparatus 100 according to the second embodiment.

  In the second embodiment, an insulating member 55 is further provided between the secondary transfer member 33 and the charge removal member 41. As a result, when the static elimination member 41 is provided in the vicinity of the secondary transfer member 33, even if the potential difference between the static elimination member 41 and the secondary transfer member 33 increases, the static elimination member 41 and the secondary transfer member No discharge occurs between the member 33 and the member 33.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1C, 1K, 1M, 1Y Image forming unit, 10 photoconductor, 11 charger, 12 exposure unit, 13 developing unit, 14 developing roller, 15C, 15K, 15M, 15Y toner bottle, 17, 36 cleaning blade, 30 intermediate transfer Belt, 31 Primary transfer member, 32 Optical sensor, 33 Secondary transfer member, 34, 42 Power supply, 37 Cassette, 38 Drive roller, 39 Drive roller, 40 Timing roller, 41 Static elimination member, 48 tray, 50 Fixing device, 51 Heating Roller, 52 Pressure roller, 55 Insulating member, 61 JP, 71,72 Potential, 73 Potential difference, 100 Image forming device, 101 Control device, 102 ROM, 103 RAM, 104 Network interface, 107 Operation panel, 120 Storage device 122 control program, 1 4 paper information.

Claims (7)

An image forming apparatus for transferring a toner image formed according to an input image to a transfer medium being conveyed,
An image carrier for carrying the toner image;
A transfer member for applying a first AC voltage having a polarity different from that of the toner image and having a DC component and an AC component superimposed thereon to the transfer medium being transferred, and transferring the toner image to the transfer medium; ,
And neutralizing member of the order to be applied to the transfer medium being transported a second alternating voltage direct current component and an AC component is superimposed a pre Symbol first AC voltage of a polarity opposite,
A controller that controls the first AC voltage and the second AC voltage ;
The controller is
When the distance between the transfer medium and the charge removal member is longer than a predetermined distance, the frequency and phase of the second AC voltage are made the same as the frequency and phase of the first AC voltage. Control to
When the distance between the transfer medium and the charge removal member is shorter than the predetermined distance, the frequency of the second AC voltage is controlled to be higher than the frequency of the first AC voltage. , Image forming apparatus.   The image forming apparatus according to claim 1, wherein the frequency of the second AC voltage is an integer multiple of the frequency of the first AC voltage. The transfer medium is paper,
The control unit obtains a control value corresponding to the characteristic of the paper being transported based on the paper information defining the control value of the first AC voltage for each characteristic of the paper, and according to the control value that controls the first AC voltage Te, the image forming apparatus according to claim 1 or 2. The transfer medium is paper,
The control unit obtains a control value corresponding to the characteristic of the paper being transported based on the paper information defining the control value of the second AC voltage for each characteristic of the paper, and according to the control value that controls the second alternating voltage Te, the image forming apparatus according to claim 1 or 2.   The image forming apparatus according to claim 1, wherein an insulating member is provided between the transfer member and the charge removal member. An image forming apparatus control method comprising:
Forming a toner image according to the input image;
Conveying the transfer medium;
Applying a first AC voltage having a polarity different from that of the toner image and having a direct current component and an alternating current component superimposed thereon to transfer the toner image to the transfer medium;
The pre-Symbol second alternating voltage DC and AC components and a first AC voltage and opposite polarity is superimposed, is applied to the transfer medium the by neutralizing member provided on the conveying path of the transfer medium With steps,
The applying step includes:
When the distance between the transfer medium and the charge removal member is longer than a predetermined distance, the frequency and phase of the second AC voltage are made the same as the frequency and phase of the first AC voltage. Controlling step;
Controlling the frequency of the second AC voltage to be higher than the frequency of the first AC voltage when the distance between the transfer medium and the charge removal member is shorter than the predetermined distance. And a control method. A control program for an image forming apparatus,
The control program is stored in the image forming apparatus.
Forming a toner image according to the input image;
Conveying the transfer medium;
Applying a first AC voltage having a polarity different from that of the toner image and having a direct current component and an alternating current component superimposed thereon to transfer the toner image to the transfer medium;
The pre-Symbol second alternating voltage DC and AC components and a first AC voltage and opposite polarity is superimposed, is applied to the transfer medium the by neutralizing member provided on the conveying path of the transfer medium Step and
The applying step includes:
When the distance between the transfer medium and the charge removal member is longer than a predetermined distance, the frequency and phase of the second AC voltage are made the same as the frequency and phase of the first AC voltage. Controlling step;
Controlling the frequency of the second AC voltage to be higher than the frequency of the first AC voltage when the distance between the transfer medium and the charge removal member is shorter than the predetermined distance. And a control program.