JP2005010809A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To electrostatically and uniformly charge a photoreceptor for a long period and to make its reliability higher in an image forming apparatus which uses a cleaning and charging blade. <P>SOLUTION: The image forming apparatus is equipped with a conductive blade (3a) which comes into contact with the surface of a movable image carrier (1) to remove residual toner on the image carrier and also electrostatically charges the image carrier for image formation, an electrostatic charging power source (4a) which applies a voltage for electrostatic charging for image formation to the conductive blade, and potential switching means (4b to 4d, 64, and 60) of switching the potential of the conductive blade to a potential for separating sticking matter, i.e. a cleaning potential. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus using an electrophotographic process such as an electrostatic copying machine or a laser printer, and more particularly to cleaning and charging of an image carrier.

FIG. 6 shows an outline of a conventional image forming apparatus using an electrophotographic process. The photosensitive drum 1 as an image carrier is formed by applying the photosensitive member 1a to the surface of the conductor 1b, and rotates in the direction of the arrow in FIG. In this image forming apparatus, an image is formed in the following procedure:
1) The surface of the photoreceptor 1a is charged to a desired potential by the charging roller 2.
2) The exposure device 7 exposes the photoconductor 1a to generate an electrostatic latent image corresponding to a desired image.
Formed on the photoreceptor 1a,
3) The developing device 8 develops the electrostatic latent image with toner to form a toner image on the photoreceptor 1a.
4) The transfer roller 13 transfers the toner image on the photoconductor 1a onto a transfer paper 15 such as a paper transported by a transport means (not shown).
5) Clean the toner remaining on the photoreceptor 1a without being transferred to the transfer paper 15 with a cleaning device.
6) The transfer paper 15 to which the toner image has been transferred is conveyed to a fixing device (not shown), and the fixing device heats and presses the transfer paper, whereby the toner on the transfer paper 15 is fixed to the transfer paper.

  Since the photosensitive drum 1 rotates in the direction of the arrow in FIG. 6, a desired image (toner image) is formed on the photosensitive member 1a by repeating the above steps 1) to 6). Transferred onto the transfer paper 15.

  In general, in a conventional image forming apparatus, a cleaning device and a charger are separately arranged to have a single function. As a conventional cleaning device, a method of bringing an elastic blade into contact with a photosensitive member is common.

  FIG. 7 shows an example of a conventional blade type cleaning device 3. The blade 3a has a thickness of 2 [mm], a length of 300 [mm], is supported by the support member 3b, and is adjusted so that the protruding amount from the front end of the support member is 8 [mm]. The support angle of the blade 3a (the angle of the blade with respect to the tangential direction of the photosensitive drum 1) is 20 °, and the amount of biting is 1.2 [mm]. The material constituting the blade 3a is urethane rubber.

  As a charging device, a so-called contact charging device is widely used in addition to a conventional corona charging device such as a scorotron. The contact charging device charges a photosensitive member by bringing a charging member into contact with the photosensitive member and applying a voltage to the charging member.

FIG. 8 is an example of a conventional contact charging device, and shows a cross-sectional view thereof. The charging roller 2 has a diameter of 5 to 20 [mm] and a length of about 300 [mm], and an elastic layer 2a is formed on the conductor 2b. The photosensitive drum 1 has a diameter of 30 to 80 [mm] and a length of about 300 [mm], and the photosensitive member 1a is formed on the conductor 1b. The charging roller 2 is in contact with the rotating photosensitive drum 1 and is driven to rotate. The elastic layer 2a of the charging roller 2 is made of a material having a resistivity of 10 ⁷ to 10 ⁹ [Ωcm]. Further, a surface protective layer having a film thickness of about 10 to 20 [μmm] may be formed on the surface of the charging roller 2 (surface of the elastic layer 2a). A charging voltage is applied to the charging roller 2 by a charging power source 4 to charge the photoreceptor 1a. The charging voltage is −1.0 to −1.5 [kV] in direct current.

However, the conventional image forming apparatus in which the cleaning device and the charging device are separately provided has the following problems:
1: Since both a cleaning space and a charging space are required, this is a bottleneck in reducing the overall size of the image forming apparatus.
2: Since the cleaning device and the charging device are separate parts, an increase in the number of parts and an increase in the materials constituting the parts lead to an increase in the cost of the entire image forming apparatus.

JP 56-165166, Japanese Patent Application Laid-Open No. 07-92767, Japanese Patent Application Laid-Open No. 07-325459.

  As a method for solving such a problem, there has been proposed a cleaning / charging combined device that combines the functions of both the cleaning device and the charging device. For example, in Patent Document 1, a fur brush or blade that contacts and cleans a photoconductor is formed of a conductive material such as carbon fiber, and a voltage necessary for charging the photoconductor is applied to the fur brush or blade. The structure which performs is disclosed. Since it is not necessary to equip the charging device itself as a separate body, it is possible to reduce the size and the cost.

In Patent Document 2, a conductive blade is used for charging and cleaning, the range of electrical resistance of the blade (10 ⁶ to 10 ⁹ [Ωcm]), and the range of contact pressure to the photoreceptor (1.5 [g / mm]. ], And a cleaning / charging combined device in which the particle diameter range of the developer (number ratio of 5 [μm] or less is 20% or less) and the blade edge angle (5 ° to 13 °) have been proposed. .

  In the cleaning / charging apparatus, it is possible to simultaneously solve the problem of the space that has become a bottleneck in downsizing the image forming apparatus as described above and the problem of the cost increase accompanying the increase in the number of parts.

FIG. 9 shows an example of a conventional cleaning / charging device. The blade 3 a is formed of a conductive elastic body and is in contact with the photoreceptor 1. The thickness of this blade is 2 [mm], the length is 300 [mm], the protruding amount from the tip of the support member is 8 [mm], the support angle of the blade is 20 °, and the biting amount is 1.2 [mm]. It is arranged to become. Further, the blade is adjusted to have a resistivity of 10 ⁶ to 10 ⁹ by dispersing carbon or an ion conductive material based on urethane rubber. A charging voltage is applied to the blade 3 a by a charging power source 4 to charge the photosensitive member 1. The charging voltage is −1.5 to −2.0 [kV] in direct current.

  The conventional cleaning / charging apparatus has the following problems when used for a long period of time. Originally, the transfer residual toner adhering to the photoreceptor after the transfer should be removed by the cleaning blade. In practice, however, there is toner that passes through the cleaning blade, although only a little at a time. This is considered to be caused by slight vibration of the blade itself or vibration applied to the blade at the start or stop of rotation of the photosensitive member. Even in the cleaning / charging apparatus, there is also toner that passes through the blade. In the cleaning / charging apparatus, toner that passes through the blade is particularly problematic. Part of the toner that has passed through the blade adheres to the surface of the blade that faces the photoreceptor. When toner is laminated and adhered to the blade over a long period of use, the discharge that occurs between the blade and the photoconductor becomes an abnormal discharge through the toner, and the photoconductor cannot be uniformly charged. . Therefore, there is a problem that an abnormal image occurs due to the adhered toner.

  The reason why the toner adheres to the blade is considered as follows. In a so-called negative-positive development image forming apparatus, toner that is positively charged (reverse to the charged polarity of the photoconductor) is present in the residual toner on the photoconductor after transfer due to discharge during transfer. To do. Even when the blade passes, positively charged toner is present due to friction with the blade. When such a positively charged toner passes through the cleaning / charging blade, the toner adheres to the surface of the cleaning / charging blade to which the negative high voltage is applied facing the photoreceptor. To do. In so-called positive / positive development, since the toner itself is originally positively charged, the toner passing through the cleaning / charging blade adheres to the blade. Since the toner adhered to the blade is laminated on the surface of the blade over a long period of use, the discharge generated between the blade and the photoconductor is not uniform, and the photoconductor cannot be uniformly charged.

  To solve this problem, the toner remaining on the blade is reduced by charging the transfer residual toner to the same polarity as the voltage applied to the blade in advance before passing through the cleaning / charging device. A method has also been proposed (Patent Document 3). Patent Document 3 discloses that a sheet for charging the residual toner with the same polarity as the charging polarity is provided on the upstream side of the charging cleaning blade. Since the residual toner is charged to the same polarity as the charging polarity, even if it passes through the charging / cleaning blade (tip edge), the surface of the blade facing the photoconductor (the surface on which discharge for charging the photoconductor occurs) ). As a result, uniform charging of the photoreceptor is ensured over a long period of time.

  SUMMARY OF THE INVENTION An object of the present invention is to make it possible to uniformly charge a photosensitive member over a long period of time in an image forming apparatus using a cleaning / charging blade, and to increase this reliability.

(1) An image carrier (1a) and a conductive blade (3a) in contact with the image carrier are provided.
The conductive blade (3a) is in a state where the tip of the conductive blade (3a) from the downstream side to the upstream side in the moving direction of the image carrier (1a) is in contact with the image carrier (1a). Is switched between a charging potential for charging the image carrier (1a) for image formation and a cleaning potential for cleaning the toner adhering to the conductive blade (3a) (4, 64). , 60). An image forming apparatus comprising: In addition, in order to make an understanding easy, the code | symbol or corresponding matter of the corresponding element of the Example shown in drawing and mentioned later in parentheses is added for reference.

  According to this, since the conductive blade (3a) is commonly used for cleaning and charging of the image carrier, it is possible to reduce the size of the entire image forming apparatus, reducing the number of components and component materials, and reducing costs. Is possible. Since there is provided a potential switching means (4, 64, 60) for switching the potential of the conductive blade (3a) to a potential for releasing the deposit, that is, a cleaning potential, the potential of the conductive blade (3a) is changed by this potential switching means. When the charging potential (−1.8 kV) is switched to the cleaning potential (0, +0.5 kV or AC 1.0 kV), the image carrier (3a) side becomes a negative high potential, and it is positively attached to the blade (3a). The charged toner is attracted to the image carrier (1a) (imaginary line in FIG. 2). As a result, the toner attached to the surface of the blade (3a) facing the image carrier (1a) is removed (blade cleaning process).

  As described above, it is possible to positively clean the toner attached to the surface of the blade (3a) facing the image carrier (1a) by the potential switching means (4b to 4d, 64, 60). . The residual toner is prevented from being positively charged by friction with the blade (3a), the residual toner is not attracted to the blade by frictional charging, and the cleaning effect is high. By appropriately performing this blade cleaning process, toner is not stacked on the surface of the blade (3a) facing the photoconductor, and the photoconductor can be uniformly charged over a long period of time.

(1a) A conductive blade (3a) for contacting the surface of the movable image carrier (1a) to remove residual toner on the image carrier and charging the image carrier for image formation And a charging power source (4a) for applying a voltage for performing charging for image formation to the conductive blade,
In the state where the tip of the conductive blade (3a) from the downstream side to the upstream side in the moving direction of the image carrier is in contact with the image carrier (1a), the potential of the conductive blade is set to An image forming apparatus comprising means (4b-4d, 64, 60) for switching to a cleaning potential for cleaning toner adhering to the conductive blade.

(1b) A conductive blade (3a) for contacting the surface of the movable image carrier (1a) to remove residual toner on the image carrier and charging the image carrier for image formation And a charging power source (4a) for applying a voltage for performing charging for image formation to the conductive blade,
The conductive blade (3a) is in a state where the tip of the conductive blade (3a) from the downstream side to the upstream side in the moving direction of the image carrier (1a) is in contact with the image carrier (1a). Means (4b-4d, 64, 60) for switching the potential of the toner to a cleaning potential for returning the toner adhering to the surface of the conductive blade facing the image carrier to the image carrier. Image forming apparatus.

  (2) A conductive entrance seal (5) provided upstream of the conductive blade (3a) in the moving direction of the image carrier (1a) is provided, and a voltage having the same polarity as the charging potential is applied. The image forming apparatus as described in any one of (1) to (1b) above.

  Since the entrance seal (5) charges the residual toner to the same polarity as the charging polarity, the residual toner is pulled by the image carrier (1) and hardly adheres to the blade (3a), and the toner adheres less to the blade (3a). Yes. In addition, since potential switching means (4b to 4d, 64, 60) for switching the potential of the conductive blade (3a) to the potential for separating the attached matter, that is, the cleaning potential, is provided, the conductive blade ( When the potential of 3a) is switched from the charging potential (-1.8 kV) to the cleaning potential (0, +0.5 kV or AC 1.0 kV), the image carrier (1a) charged (negatively charged) by the entrance seal (5). ) Enters the blade (3a), but by the switching, the image carrier (3a) side becomes a negative high potential, and the positively charged toner attached to the blade (3a) is transferred to the image carrier (1a). ) (Virtual line in FIG. 2). As a result, the toner attached to the surface of the blade (3a) facing the image carrier (1a) is removed (blade cleaning process).

  As described above, it is possible to positively clean the toner attached to the surface of the blade (3a) facing the image carrier (1a) by the potential switching means (4b to 4d, 64, 60). . The positive charging of the residual toner due to friction with the blade (3a) is suppressed by applying a charging voltage (-1.2 kV) to the image carrier (3a) by the entrance seal (5), and residual toner due to frictional charging On the contrary, the toner adhering to the surface of the blade (3a) by the application of the cleaning voltage is attracted to the image carrier (3a) and transferred to the image carrier (3a), and the cleaning effect is high. By appropriately performing this blade cleaning process, toner is not stacked on the surface of the blade (3a) facing the photoconductor, and the photoconductor can be uniformly charged over a long period of time.

  (2a) The conductive entrance seal (5) has a tip abutted against the image carrier (1a) from the upstream side to the downstream side in the moving direction of the image carrier (1a). The image forming apparatus described in 1.

  (3) The image forming apparatus according to any one of (1) to (2a), wherein the cleaning potential is substantially the same as the potential (earth) of the image carrier (1a). According to this, since the cleaning potential for cleaning the toner adhering to the blade (3a) is set to the potential (ground) of the image carrier, it is not necessary to prepare a special power source. For this reason, it is possible to clean the toner adhering to the blade (3a) with a simple configuration and without increasing the cost, and it is possible to uniformly charge the photosensitive member over a long period of time.

  (4) The cleaning potential of the above (1) to (2a) is a potential (+0.5 kV) having a polarity opposite to a polarity (−1.8 kV) for charging the image carrier for image formation. The image forming apparatus according to any one of the above. According to this, since the cleaning potential is opposite in polarity to the potential for charging the image carrier, the electric field formed between the blade (3a) and the image carrier becomes larger in the blade cleaning process. For this reason, the toner adhering to the surface of the blade (3a) is cleaned with a stronger electric field, and the photosensitive member can be uniformly charged over a long period of time.

  (5) The image forming apparatus according to any one of (1) to (2a), wherein the cleaning potential is an AC potential (AC 1.0 kV). According to this, since an AC potential (AC 1.0 kV) is applied to the blade (3a), the toner attached to the blade (3a) is electrically vibrated and easily separated from the blade (3a). Becomes larger. As a result, the photosensitive member can be uniformly charged over a long period of time.

  (6) The potential switching means (4, 64, 60) applies a cleaning potential to an outer region of the image carrier (1) where the image formation scheduled region is at the position of the conductive blade (3a). To do. According to this, blade cleaning is performed in a non-image forming area during repeated image formation, and the effect of keeping the blade (3a) clean is high.

  (7) The potential switching means (4, 64, 60) switches to the cleaning potential every time the image is formed a set number of times (10 sheets) or more. According to this, the blade (3a) is kept clean. Further, since the blade is cleaned every time the set number of times of image formation, the number of cleaning operations can be set to the minimum necessary.

  (8) The potential switching means (4, 64, 60) switches to the cleaning potential in response to an image formation start instruction (start signal). According to this, at the time of image formation, charging for image formation is always performed in a state where the toner is not attached to the surface of the blade (3a) facing the photoreceptor, and the toner of the blade (3a) There is a low possibility of producing an abnormal image due to dirt.

  (9) The potential switching means (4, 64, 60) switches to the cleaning potential at the end of image formation (during the end cycle). According to this, the toner does not adhere to the blade (3a) due to the stop of image formation for a long period of time, and there is a low possibility that an abnormal image is generated due to the contamination of the toner on the blade (3a).

  (10) The potential switching means (4, 64, 60) is configured such that when the outer area of the image carrier (1) outside the transfer paper contact planned area is at the position of the conductive blade (3a), a cleaning potential is applied thereto. Is applied. According to this, the blade cleaning process is performed at a portion corresponding to a so-called paper gap. For this reason, even when the toner (cleaned toner) moved from the blade (3a) to the image carrier passes through the developing device and reaches the transfer device, it is not transferred onto the transfer paper. That is, the cleaned toner does not stain the transfer paper.

  Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

  FIG. 1 shows an outline of a main part of a mechanism according to an embodiment of the present invention. A photosensitive drum 1 as an image bearing member is formed by applying the photosensitive member 1a to the surface of the conductor 1b, and rotates in the direction of the arrow in FIG. In this embodiment, the peripheral speed of the photosensitive drum 1 is 180 [mm / sec]. The cleaning / charging device 2 includes a cleaning / charging blade 3 formed of a conductive elastic body, a power source 4 for selectively applying a charging voltage and a cleaning voltage thereto, an entrance seal 5, and a sheath. And a power source 6 for applying a voltage. A voltage is applied to the blade 3 by a power source 4 to charge the photoreceptor. The power source 4 supplies a charging voltage (-1.8 [kV]) for charging the photosensitive member 1a on the photosensitive drum 1 for image formation and toner attached to the surface of the blade 3 facing the photosensitive member 1a. A cleaning voltage to be cleaned (0 [kV]: ground potential) can be switched and applied to the blade 3. The switching timing will be described later.

  An inlet seal 5 formed of a conductive member is disposed on the upstream side of the blade 3 with respect to the photosensitive member moving direction. A seal voltage is applied to the entrance seal 5 by a power source 6. The seal voltage is −1.2 [kV].

  The exposure device 7 forms an electrostatic latent image by irradiating light corresponding to a target image on the surface of the photosensitive member uniformly charged by the blade 3. The light source of the exposure device 7 is a laser diode, and scans while irradiating the photosensitive member with a laser beam by a polygon mirror.

  The developing device 8 includes a developing roller 9, a developer 10, and a power source 11. By applying a developing voltage (−0.6 [kV]) to the developing roller 9, the electrostatic latent image on the photoreceptor 1a is developed, and a toner image is formed on the photoreceptor 1a (so-called reverse development). . The developer 10 is a two-component developer composed of a carrier and toner. In this embodiment, the developer 10 is a two-component developer, but may be a one-component developer.

  The transfer device 12 transfers the toner image on the photoconductor 1a onto a transfer paper 15 conveyed from a paper supply device (not shown). The transfer device 12 includes a transfer roller 13 and a power source 14, and applies a voltage from the power source 14 to the transfer roller. The applied voltage is constant current control and is 20 [μA]. The transfer paper 15 is conveyed to a fixing device (not shown), and the toner image on the transfer paper 5 is fixed to the transfer paper 15.

  FIG. 2 shows the configuration of the blade 3 and the power supply 4 shown in FIG. The blade 3 is obtained by mounting an elastic conductor blade 3a on a metal support member 3b. The blade 3a has a thickness of 2 [mm] and a length of 300 [mm], is supported by the support member 3b, and is adjusted so that the protruding amount from the front end of the support member is 8 [mm]. The support angle of the blade is 20 °, and the biting amount is 1.2 [mm]. The material constituting the blade 3a is a urethane rubber-based conductive elastic body. This is one in which conductivity is imparted by adding an ionic compound such as a halide or an alkali metal salt to urethane rubber. The material constituting the blade 3a may be other than those described above. For example, rubber or resin may be provided with conductivity. Further, an electronic conductive material to which carbon or the like is added may be used.

  The power source 4 includes a charging power source 4a, a cleaning power source 4b, and a switching relay (contact piece 4c and relay coil 4d). The switching relay contact piece 4c is an input / output interface, which will be described later. 64 and the relay driver are switched to the charging power source 4a side or the cleaning power source 4b side in accordance with an instruction from the CPU 60. In the first embodiment, the cleaning voltage is the equipment ground potential, and the cleaning power supply 4b is a simple equipment ground connection line. When the CPU 60 switches the contact piece 4c to the charging power source 4a side, a charging voltage (-1.8 [kV]) is applied to the blade 3a, but when the CPU 60 switches the contact piece 4c to the cleaning power source 4b side, A cleaning voltage (0 [kV]: ground potential) is applied to the blade 3a.

  The entrance seal 5 has a thickness of 0.2 [mm] and a length of 300 [mm], and is supported by a support member (not shown). The support method of the inlet seal 5 does not have to be as strict as the blade 3a. The amount of protrusion of the entrance seal 5 from the support member, the support angle, the amount of biting, etc. may be appropriate, and the toner separated from the photoreceptor drum 1 by the blade 3a is upstream (upstream with respect to the photoreceptor rotation direction). It does not matter if it can be prevented from scattering. The material constituting the entrance seal 5 is a conductive material. Any material such as an ion conductive material based on plastic, resin, rubber or the like or an electronic conductive material dispersed in carbon may be used. A seal voltage (−1.2 [kV]) is applied to the entrance seal 5 while the photosensitive drum 1 is rotating.

  FIG. 3 shows a schematic configuration of a control system of the image forming apparatus shown in FIG. First, a control unit using a microcomputer including a CPU 60, a RAM 61, a ROM 62, an EEPROM 67 (nonvolatile memory), an input / output port buffer amplifier 63, 64, etc. is provided, and the T × D, R × D, CP2 terminals of the CPU 60 are provided. The ADF 80 and the exposure apparatus 7 are controlled by serial communication between them. This serial communication is configured such that when the output of the PC 2 is at the H level, the ADF 80 communicates with the control unit, and when the output of the PC 2 is at the L level, the exposure apparatus 7 communicates with the control unit. ing. Here, the microcomputer of the ADF 80 performs document feeding / discharging processing and jam detection based on data transmitted from the control unit of the copying machine. On the other hand, the microcomputer of the exposure apparatus 7 drives and controls the scanner and the mirror based on the data transmitted from the control unit. Note that the CPU 60 is formed with firmware or the like, such as paper sorting means, paper reuse means, defective printing prevention means, and transport resumption means.

  In synchronization with the rotation of the photosensitive drum 1, the pulse generator 65 generates one synchronization pulse per minute rotation, and the control unit here is a pulse generated by the synchronization pulse generator 65. Based on the count value, transfer paper feed control, document feed control, and image formation processing (particularly timing control) are performed. The synchronization pulse is generated by the pulse generator 65 in synchronization with the rotation of the photosensitive drum 1 and is given to the CPU 60. The CPU 60 executes an interrupt process every time one pulse arrives, counts up the number of incoming pulses, and compares the count value with the count value of the timing table (the table storing the relationship between the count value and the event). If the count value matches one count value of the table, an event (image forming element on / off) addressed to the count value is executed.

  FIG. 4 shows an outline of the control operation of the CPU 60. When the power is turned on, the CPU 60 sets internal registers, counters, timers, and the like to standby state values, and sets standby signal levels to the input and output ports for the mechanism unit (step 1). Hereinafter, in parentheses, the word “step” is omitted and only the step number is written.

  When the initialization (1) is completed, the CPU 60 reads the state of the mechanism unit, checks whether there is an abnormality (a state where image formation cannot be started) (2, 3), and if there is an abnormality, the operation button (4). If there is no abnormality, the heater of the fixing device is energized, the target temperature is set to a standby value, warming up to the target temperature is started, and “charging charge voltage setting” (Vac1 ). During and after that, it is checked whether the fixing temperature is the standby temperature. If it is not at the standby temperature, it waits for the standby temperature to be reached. When the standby temperature is reached, “ready” (image formation is possible) is displayed on the operation display section, and if an operator operation is performed on the operation board 66, it is read (5). Here, the input such as recording number input, recording magnification input, recording density input, etc. is written in the register. The register is an internal memory of the CPU 60 or a memory area allocated to the RAM 61 or the EEPROM 67.

  When there is a start input in the input reading (5), the fact is displayed on the operation board 66, and the CPU 60 updates the target temperature of the fixing device 8 to a high temperature for fixing processing (accordingly, A driver for controlling the fixing temperature switches the energizing current of the fixing heater to a high level), starts rotating the photosensitive drum 1 and turns on the discharging lamp (static discharge exposure), and forms one image (recording one image) The start and end timings for charging, exposure, erasing, paper feeding, development, transfer, etc., correspond to the recording mode that has already been input (the standard mode when there is no input). The timing table is set, one copy cycle (one image forming process) is executed (6, 7), and the recorded number counter is incremented by one (6, 7).

  In this "1 copy cycle" (7), the CPU 60 executes process control of charging (by the blade 3), exposure, development and transfer. In the charging process in the first “1 copy cycle” (7), the CPU 60 turns on the charging power source 4a, connects the relay contact piece 4c to the charging power source 4a side, and applies a charging voltage to the blade 3a. However, when the charging process is completed, the relay contact piece 4c is connected to the cleaning power source 4b side and a cleaning voltage is applied to the blade 3a. In the subsequent "1 copy cycle" (7), the relay contact piece 4c is switched to the charging power source 4a side at the charging process start timing, and the relay contact piece 4c is switched to the cleaning power source 4b side at the charging process end timing.

  When the “one copy cycle” (7) is completed, the CPU 60 increments the accumulation counter Cn for determining the execution timing of the “blade cleaning” by one (Bp1). Then, the count data of the accumulation counter Cn is checked (Bp2). If it indicates a number of 10 or more, the accumulation counter Cn is cleared (Bp3), and “blade cleaning” ( Bp4) is executed.

  When the data of the accumulation counter Cn does not reach 10 or when “Blade Cleaning” (Bp4) is executed, the value of the recorded number counter is equal to or greater than the set number (continuous copy set value). Is checked (8). If the set number has not been reached, the process proceeds to "1 copy cycle" (7). When the set number of sheets is reached, the target temperature of the fixing device is returned to the standby value, and post-processing (end cycle) such as cleaning of the photosensitive member, transfer roller, and blade 3a is set (9), Wait for an input to the operation board 66 (5). When there is no start input from the operation board 66 and the end cycle is completed, the rotation of the photosensitive drum 1 is stopped and the static elimination lamp is turned off, and the end cycle is stopped (10, 11). That is, the mechanism unit is set in a standby state (stopped).

  When the process proceeds to the “blade cleaning” (Bp4), the relay contact piece 4c is switched to the cleaning power source 4b side at the charging process end timing in the “1 copy cycle” (7). Therefore, the blade 3a is connected to the cleaning power source 4b by the relay contact piece 4c. That is, the cleaning process of the blade 3a is performed. In “Blade Cleaning” (Bp4), the drum rotation synchronization pulse (output of 65 in FIG. 3) starts counting up, and when the count value becomes equal to or greater than a set value corresponding to several rotations of the drum 1, The “cleaning” (Bp4) is terminated. That is, the process proceeds to step 8.

  Although the charging power source 4a is turned off in the above-described end cycle setting (9), the relay contact piece 4c is connected to the cleaning power source 4b, so that the cleaning process of the blade 3a is not performed even during the end cycle. continue. The seal power source 6 takes time for the photosensitive member 1a to move around the circumference of the inlet seal 5 / blade 3 of the photosensitive member 1a rather than the timing of connecting the relay contact piece 4c to the cleaning power source 4b side. It is turned on at an earlier timing, and in order to charge the photoreceptor 1a for image formation, the entrance seal 5 / blade of the photoreceptor 1a is earlier than the timing at which the relay contact piece 4c is connected to the charging power supply 4a side. The peripheral length between the three is turned off at an earlier timing by the time the photosensitive member 1a moves. That is, the seal voltage is applied to the entrance seal 5 only while the surface of the photoreceptor passing under the blade 3 a during the cleaning process of the blade 3 a passes the entrance seal 5.

  As described above, in the first embodiment, in “1 copy cycle” (7), after charging of the photoconductor 1a for forming one image is completed, the photoconductor 1a is charged for forming the next image. A blade cleaning process is performed in the non-image forming area until immediately before the image forming operation, and every 10 image formations, the “blade cleaning” (Bp4) is performed over several rotations of the photosensitive drum 1. -A blade cleaning process (Bp4) is performed, and a blade cleaning process is also performed during the end cycle.

  During the blade cleaning process, a voltage of -1.2 [kV] is applied to the inlet seal 5 and 0 [kV] (equipment ground potential) is applied to the blade 3a. However, the voltage for cleaning the toner adhering to the surface of the blade 3a may not be the above-mentioned value, and any voltage can be used as long as the toner adhering to the blade 3a can be cleaned. May be. Further, the voltage of the above-mentioned value (−1.2 [kV]) is applied to the inlet seal 5 only while the blade 3a is being cleaned, but the inlet seal 5 is not used even while the blade 3a is being cleaned. The voltage may be applied to the inlet seal 5 or a voltage may be applied to the inlet seal 5 at all times. That is, the voltage may be applied continuously during the rotation of the photosensitive drum 1.

  The configuration of the image forming apparatus of the second embodiment is the same as that of the first embodiment in the configuration of the image forming apparatus, the configuration of the cleaning / charging combined device, the configuration of the cleaning / charging combined blade. The difference between the image forming apparatus of the second embodiment and the image forming apparatus of the first embodiment is that the cleaning voltage is opposite in polarity to the charging voltage for charging the photoreceptor 1a. Specifically, the cleaning power supply 4b applies a voltage of +0.5 [kV] to the blade 3a via the relay contact piece 4c. The charging voltage is −1.8 [kV] as in the first embodiment.

  Also in the image forming apparatus of the second embodiment, a seal voltage (-1.2 [kV]) is applied to the entrance seal 5. Further, in the image forming apparatus of the second embodiment, the timing of switching the voltage application of the cleaning / charging device 2 and the timing of switching the voltage application of the entrance seal 5 are the same as in the first embodiment. In other words, the cleaning voltage is applied to the blade 3a while the photosensitive member 1a charged by the entrance seal 5 passes through the blade 3a.

  The image forming apparatus of the third embodiment is the same as that of the first embodiment in the configuration of the image forming apparatus, the configuration and materials of the cleaning / charging device 2. The difference between the image forming apparatus of the third embodiment and the first embodiment is that the cleaning power source generates an AC voltage and applies it to the blade 3a via the relay contact piece 4c. Specifically, the cleaning voltage is a sin wave having an amplitude of 1.0 [kV] (so-called peak-to-peak value) and a frequency of 1 [kHz]. Also in the image forming apparatus of the third embodiment, a seal voltage (-1.2 [kV]) is applied to the entrance seal 5. In the image forming apparatus according to the third embodiment, the timing for switching the voltage application to the cleaning / charging blade 3a and the timing for switching the voltage application to the entrance seal 5 are the same as those in the first embodiment.

  The image forming apparatus of the fourth embodiment is the same as that of the first embodiment in the configuration of the image forming apparatus, the configuration and materials of the cleaning / charging device 2. The difference of the fourth embodiment from the first embodiment is that the voltage applied to the blade 3a is switched (switching to the cleaning voltage) at the start of image formation and between sheets.

  The start of image formation means immediately before the first first image is formed when the image forming apparatus starts one or more image forming operations. In other words, in the image forming apparatus of the fourth embodiment, immediately before the start signal is generated and a series of image forming operations are started, the voltage applied to the blade 3a is switched to the cleaning voltage, and the blade 3a serving as both cleaning and charging is used. Clean.

  Further, the paper interval is a portion corresponding to a space between the paper on the photosensitive member 1a when the image forming apparatus forms one or more images, and is a part of the non-image forming region. Also in the image forming apparatus of Example 4, a voltage (−1.2 [kV]) is applied to the entrance seal 5. The charging voltage applied to the cleaning / charging blade 3a is -1.8 [kV], and the cleaning voltage of the blade 3a is 0 [kV].

  FIG. 5 shows an outline of the control operation of the CPU 60 of the fourth embodiment. When the CPU 60 of the fourth embodiment reads the start input, it drives the photosensitive drum 1, connects the relay contact piece 4c to the cleaning power supply 4b side, turns on the seal power supply 6, and turns on the seal power supply 6. "Blade cleaning" (Bp4) is executed. This content is the same as that of the first embodiment. In the "1 copy cycle" (7) of the fourth embodiment, from the end of charging of the photoconductor 1a for forming one image to just before charging of the photoconductor 1a for forming the next image. In this non-image forming area, the blade cleaning process is performed outside the area where the transfer paper 15 contacts, that is, between the paper. The other processes are the same as those in the first embodiment shown in FIG. 5, and in this embodiment, the blade cleaning process is also performed during the end cycle.

FIG. 2 is a cross-sectional view illustrating an outline of a main part of the image forming mechanism according to the first embodiment of the present invention. It is a block diagram which shows the structure of the power supply 4 and the brate 3a shown in FIG. FIG. 2 is a block diagram illustrating a system configuration of an electrical component of the image forming apparatus illustrated in FIG. 1. It is a flowchart which shows the outline | summary of control operation of CPU60 shown in FIG. It is a flowchart which shows the outline | summary of control operation of CPU60 of 4th Example of this invention. It is a cross-sectional view showing one outline of a conventional contact charging type image forming apparatus. It is a cross-sectional view of a conventional cleaning / charging blade 3. 2 is a cross-sectional view of a conventional charging roller 2. FIG. It is a block diagram which shows the structure of the conventional cleaning and charging combined use apparatus.

Explanation of symbols

4a: Charging power source 4b: Cleaning power source

Claims (5)

An image carrier, and a conductive blade in contact with the image carrier,
In the state where the tip of the conductive blade from the downstream side to the upstream side in the moving direction of the image carrier is in contact with the image carrier, the potential of the conductive blade is applied to the image carrier for image formation. An image forming apparatus comprising: a potential switching unit that switches between a charging potential for charging the toner and a cleaning potential for cleaning toner adhering to the conductive blade.   2. A conductive entrance seal provided upstream of the conductive blade in the moving direction of the image carrier is provided, and a voltage having the same polarity as the charging potential is applied. Image forming apparatus.   The image forming apparatus according to claim 1, wherein the cleaning potential is substantially the same as the potential of the image carrier.   The image forming apparatus according to claim 1, wherein the cleaning potential is a potential having a polarity opposite to a polarity for charging the image carrier for image formation. The image forming apparatus according to claim 1, wherein the cleaning potential is an AC potential.

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