JPH09211935A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the shortening of the life of a photoreceptor caused by the contact/separate operations of a charge member with the photoreceptor by providing a control means for driving the charge member from a second position away from the photoreceptor to a first position in contact with the photoreceptor, via a contact/separate means, when the photoreceptor is stopped. SOLUTION: At the time of forming an image, a charge roller 2 is rotated with the photoreceptor 1 in a press-contact state with the surface of the photoreceptor 1 by a tension spring 25. Then, a releasing projection part 21a in the bearing 21 of the charge roller 2 is pushed by the movement of a releasing cam 50a, to separate the roller 2 from the photoreceptor 1. In other words, while a power supply switch is opened, the roller 2 is separated from the photoreceptor 1, so that the roller 2 is not deformed by press-contact with the photoreceptor 1. On the other hand, the roller 2 is moved from the second position to the first position, to come into contact with the photoreceptor 1, when it is stopped. Further, the roller 2 is moved from the first position to the second position, to be separated from the photoreceptor 1, when it is stopped, as well. Thus, rubbing due to the relative movement of the roller 2 with respect to the photoreceptor 1 never occurs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus provided with a charging member for charging a photosensitive member or for transferring an image, the member being in contact with the photosensitive member, and is used in, for example, a copying machine, a facsimile or a printer. .

[0002]

2. Description of the Related Art Image forming apparatuses having a contact charging member are known. One of the typical contact charging members is a conductive roller, which is composed of a cored bar and a conductive rubber layer formed on the outer periphery of the cored bar, and is driven to rotate as the photosensitive member rotates. The conductive roller is pressed against the surface of the photosensitive member with a predetermined pressing force by a conductive spring. A predetermined charging voltage is applied to the conductive rubber layer from the charging power supply circuit via the spring and the cored bar. Electric charges are injected from the conductive rubber layer to the photoconductor, and the outer peripheral surface of the photoconductor is charged. Such a contact charging device is
Compared with a corona discharge device that has been widely used as an effective means for uniformly charging the surface of a photoconductor, it has advantages such as a low charging voltage and an extremely small amount of ozone. There is.

Actually, in order to stably charge the photosensitive member, a rubber material having a small humidity fluctuation is used and a DC voltage is applied; a material which does not fluctuate over time (current fatigue of resin) is used; toner adhesion is prevented. Therefore, various measures such as using a fluorine-based resin material for the surface layer; mixing an abrasive with the surface layer to prevent image deterioration (bleeding etc.) due to long-term contact between the photoconductor and the charging member; Has been.

Nevertheless, (1) if the apparatus is left for a long period of time, the photoconductor may be contaminated by the plasticizer oozing out from the charging member side. The charging member is constantly pressed against the surface of the photoconductor by a spring or the like.If the device is left for a long time without the photosensitive member being driven, the charging member is pressed against the conductive rubber or high The plasticizer that oozes out from the resistance layer or the like adheres to a partially contaminated state. The contaminated area becomes streaky and causes streaks on the image. Although the streak-like contamination on the photosensitive surface is hardly visible to the naked eye, a large amount of the developer adheres to it during development, resulting in the appearance of a black streak image corresponding to the contaminated part, resulting in an image defect. Becomes The phenomenon that the plasticizer oozes and adheres to the surface of the photoconductor from the charging member side, and the resulting output image defect occurs when the surface of the charging member is not contaminated (used). This is most noticeable when the product is shipped from the factory and left unused for a long time as is. Conversely, after using the device to some extent, even if it is left for a long period of time, the above-mentioned phenomenon becomes almost no problem. In addition to the plasticizer, it has been found that when the charging member is pressed against the photosensitive member for a long time, the difference in surface resin material causes a temporary decrease in the charged object as a pressing trace, and it is not possible to press for a long time on different surfaces. There's a problem.

(2) There is a local deformation of the charging member when the device is left for a long period of time.
The charging member is constantly pressed against the surface of the photoconductor by a spring or the like, and if the device is left for a long period of time (for example, one year or more) without being driven to move the surface of the photoconductor, the charging member is pressed against the surface of the photoconductor. Parts may undergo irreversible deformation (depression deformation). Once such deformation occurs, a charging failure occurs at that portion, and a normal image cannot be obtained.

In order to solve the above-mentioned problems, there are proposals for contacting and separating the charging member with respect to the photosensitive member and various contacting and separating mechanisms. For example, in Japanese Patent Laid-Open No. 1-207768, the apparatus is in standby mode. There is a proposal to keep the charging member away from the photoreceptor when in the state. Japanese Unexamined Patent Publication No. 2-039169 discloses a pressure contact releasing means for bringing a charging member into pressure contact and non-pressure contact with a photoreceptor. Japanese Unexamined Patent Publication No. 2-134670 proposes to provide a separating member that prevents the charging member from coming into contact with the photoconductor when the image forming apparatus is not used (when shipped from the factory).
Japanese Unexamined Patent Publication No. 3-048870 proposes that the charging member be in non-contact or in contact with a small pressure except the time period in which the photoreceptor is charged. In addition to these, Japanese Patent Application Laid-Open Nos. 4-019674, 4-076569, 4-076571 and 4-076571
140770, JP 4-157485, and JP 5-03
Japanese Patent No. 3670 proposes a similar or various contact / separation mechanism or contact / separation mode.

[0007]

In order to uniformly press the charging member against the photosensitive member, a pressure of, for example, about 1 kgf / 210 mm is applied, but when the charging member starts contact with the surface of the moving photosensitive member, charging is performed. Relative rubbing occurs between the member and the photoconductor surface, causing scratches on the photoconductor surface. That is,
Microscopically, there are irregularities and deformations on the surface of the photoconductor and the charging member (typically eccentricity), and the contact / separation mechanism has mechanical backlash.
When the charging member is brought into contact with the photoconductor, the entire tangent line (the axial connection of the two contact points) does not come into contact at the same time point, but comes into partial contact. At this time, a pressure contact force acts on the previously contacted portion, but since the moving speed of the charging member is not the same as the moving speed of the photoconductor, the charging member rubs the photoconductor surface, causing scratches (scratches). When the charging member comes into contact with the photoconductor, the rubbing appears significantly because the static inertia of the charging member delays the speed increase of the charging member. There is a similar problem when the charging member is separated from the photoconductor.

In the state where there are few scratches, there is no particular problem, but as the number increases (accumulation of repeated contact / separation operations: the use of the image forming apparatus), the cleaning property of the photosensitive member deteriorates and the image on the photosensitive member decreases. The forming characteristics deteriorate. That is, the photoconductor life is shortened. It is an object of the present invention to prevent the life of the photoconductor from being shortened due to the contacting / separating operation of the charging member with respect to the photoconductor.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to a charging member for charging a photosensitive member, a first position for contacting the charging member with the photosensitive member, and a contact for selectively driving the charging member to a second position separated from the photosensitive member. An image forming apparatus comprising: a separating means, a means for exposing a photoconductor, and a means for developing an electrostatic latent image formed on the photoreceptor by the exposure, wherein the charging member is provided via the contacting / separating means when the photoconductor is stopped. Is provided with a control means for driving from the second position to the first position.

According to this, since the charging member comes into contact with the photosensitive member when the photosensitive member is stopped, the charging member does not cause the above-mentioned scratches on the photosensitive member. Therefore, the life of the photoconductor is prevented from being shortened.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In order to prevent the above-mentioned scratches from occurring when the charging member is separated from the photoconductor, the charging member is placed in a first position (contact with the photoconductor when the photoconductor is stopped). The charging operation position) is driven to the second position (retraction position away from the photoconductor).

Further, in order to suppress the deformation of the photosensitive member and the charging member and the contamination of the photosensitive member due to the charging member being pressed against the photosensitive member for a long period of time, the charging member is set to the second position () when the image forming apparatus is not used. Retreat position). In order to do this automatically, in the first aspect, the charging member is driven to the first position (charging action position) immediately after the power switch of the image forming apparatus is closed, and then the photoconductor is driven to supply the power. The charging member is driven to the second position (retracted position) when the switch is opened.

In the second aspect, when the fixing temperature of the fixing device reaches the preheating temperature after the power switch is closed, the charging member is driven to the first position (charging operation position), and then the photoconductor is driven. Then, when the apparatus returns to the standby state, the charging member is driven to the second position (retracted position). Then, when the apparatus enters the image forming step, the charging member is driven to the first position (charging operation position), and then the photoconductor is driven.

In the third aspect, immediately after the power switch of the image forming apparatus is closed, the charging member is driven to the first position (charging position), the photosensitive member is driven thereafter, and the apparatus returns to the standby state. And the charging member is driven to the second position (retracted position). Then, when the apparatus enters the image forming step, the charging member is driven to the first position (charging operation position), and then the photoconductor is driven.

In the fourth aspect, when the fixing temperature of the fixing device reaches the preheating temperature after the power switch is closed, the charging member is driven to the first position (charging operation position), and then the photoconductor is driven. Then, the charging member is driven to the second position (retracted position) when the power switch is opened.

[0016]

【Example】

-First Embodiment- Fig. 1 shows an outline of a mechanical portion according to an embodiment of the present invention. The photoconductor 1 is rotationally driven clockwise by a main power system (not shown). The photoconductor 1 is charged by the charging roller 2, and the erase lamp 14 irradiates the charged surface of the photoconductor 1 with light to a region where image formation is not necessary to eliminate the charge. An image forming area on the charged surface of the photoconductor 1 is irradiated with image light from an exposing device (not shown) through a reflection mirror 40, and an electrostatic latent image is formed on the image forming area. A toner is applied to the electrostatic latent image from the developing roller 16 of the developing device 15, so that a toner image (visual image) appears on the electrostatic latent image. The toner image is transferred onto the recording paper 19 on the transfer belt 3. The recording paper on which the toner image is placed is transferred by a transfer belt 3 to a fixing device (not shown). When the charging roller 2 is in contact with the surface of the photoconductor 1 as shown in FIG. 1, the photoconductor 1 rotates in the counterclockwise direction as the photoconductor 1 rotates in the clockwise direction.

FIG. 2 is an enlarged view of the charging roller 2 shown in FIG. 1 and the mechanism for supporting it. 2 shows the charging roller.
This is a view showing one end portion of the la 2 divided. The charging roller 2 has one end supported by a bearing 21 that is rotatable about a support shaft 23 supported by the bracket 8 as a rotation center. A contact member 27 fixed to a leaf spring 26 made of a conductor comes into contact with one end of the charging roller 2, and the contact member 27,
A charging voltage is applied from a charging power supply circuit 29 via the leaf spring 26, the support shaft 23, and the leaf spring 28. At the time of image formation, that is, when the charging roller 2 and the photoconductor 1 are in contact with each other (FIG. 1), the charging roller 2 moves at the peripheral speed Vo of the photoconductor 1.
And rotate with the same peripheral speed. Charging roller 2
Is selectively moved between a first position ((a) in FIGS. 1 and 3) in contact with the photosensitive member 1 and a second position ((b) in FIG. 3) separated from the photosensitive member 1 by the contact / separation mechanism. Positioned.

FIG. 4 shows the appearance of the contact / separation mechanism, FIG. 5 shows the contact / separation driver in the contact / separation mechanism, and FIG. 6 shows an exploded view of the contact / separation motion transmission system of the contact / separation mechanism. As described above, the charging roller 2 is supported by the bearing 21 which is rotatable around the support shaft 23 as a fulcrum, and the tension spring 25 is provided at one end of the bearing 21 so that the charging roller 2 is charged with a predetermined pressing force during image formation. The roller 2 is rotated by contacting and pressing the surface of the photoconductor (FIG. 3B). When the releasing cam 50a moves from left to right and pushes the releasing projection 21a on the bearing 21 of the charging roller 2 as shown in FIGS. 3A and 3B, the charging roller 2 is pushed.
Moves away from the photoconductor 1. Release cams 50a and 50b
With regard to the above, since it is necessary to drive those two at the same phase at the same time, the mechanism shown in FIGS. 4 and 6 is adopted in this embodiment.

Referring to FIGS. 4 and 6, the releasing cams 50a and 50b are integrally formed by the releasing rail 50, and an L-shaped lever 51 is provided in the vicinity of each cam.
When the lever 51 is engaged, the rotational movement of the lever 51 is converted into the reciprocating movement of the release rail 50. The lever 51 is engaged at one end with a link 52 via a tension spring 53, and further the link 5
2 is connected to a lever 57 by a drive wire 55. The lever 57 abuts on a cam 59 that rotates while being position-controlled so that the other end thereof can take a predetermined stop position, and reciprocates in the direction of the arrow shown in FIG.

Reference numeral 56 is a pulley for changing the extending direction of the drive wire 55 by 90 degrees. The tension spring 54 is for causing the lever 57 to follow the operation of the cam 59, that is, the release rail 50 (and the cam 50).
a, 50b) is returned to the position (position (a) in FIG. 3) escaped from the charging roller bearing 21. As shown in FIG. 5, the cam 59 is fixed to the output rotary shaft of the 90-degree rotary rotary solenoid 59RL. The rotary solenoid 59RL has a mechanism for the rotation range of about 90 degrees of the stepping motor, and the cam 59 is shown in FIG.
From the solid line position (second position) to the dotted line position (first position)
On the contrary, it is driven to rotate.

The cam 59 is moved from the solid line position to the dotted line position by approximately 90.
When the reverse rotation is performed for a certain degree, as shown in FIG. 3A, the cams 50a and 50b retract, and the charging roller 2 is pressed against the photoconductor 1 by the tensile force of the spring 25. When the cam 59 is driven in the forward direction by about 90 degrees from the dotted line position to the solid line position, the cam 50 moves.
a and 50b are projected as shown in FIG. 3 (b),
The charging roller 2 is at the second position away from the photoconductor 1. As described above, by driving the cam 59 in the reverse direction by the solenoid 59RL, the charging roller 2 is shown in FIG.
From the second position (retracted position) separated from the photoconductor 1 to the first position (charging action position) in pressure contact with the photoconductor 1 shown in FIG. 3A, the cam 59 is normally rotated by the solenoid 59RL. When driven, the charging roller 2 returns to the second position (retracted position).

FIG. 7 shows the relationship between the link 52 and the lever 51 when the charging roller and the photosensitive member are in contact with each other and when they are separated from each other.
The arrows in the figure represent the direction of the force acting on the spring locking shaft 51a of the lever 51 in each state.

FIG. 8 shows a schematic structure of a control system of the copying machine shown in FIG. First, CPU 60, RAM 61, ROM 6
2, a control section using a microcomputer including an EEPROM 67 (nonvolatile memory), input / output port buffer amplifiers 63, 64, etc. is provided.
By serial communication between RxD and CP2 terminals,
The ADF 80 and the exposure device 70 are controlled. In this serial communication, when the output of PC2 is at the H level, the ADF 80 and the control unit of the copying machine communicate with each other, and the output of PC2 becomes L.
When the level is reached, the exposure device 70 and the control unit of the copying machine communicate with each other. 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 70 uses the data transmitted from the control unit of the copying machine to
Drive and control scanners and mirrors. In this copying machine, the CPU 60 is provided with a sheet selecting means, a sheet reusing means, a defective printing preventing means, a conveyance resuming means, and the like by firmware or the like.

Incidentally, in synchronization with the rotation of the photosensitive member 1, the pulse generator 65 generates a synchronization pulse of one pulse for each rotation of the minute angle, and the control unit of the copying machine is the synchronization pulse generator here. Based on the count value of the pulse generated by 65, the transfer paper feed control, the document feed control, and the image forming process (especially timing control) are performed. The synchronization pulse is generated by the pulse generator 65 in synchronization with the rotation of the photoconductor 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 (table storing the relationship between the count value and the event). If the count value matches one count value of the table, an event (on / off of the image forming element) addressed to the count value is executed.

FIG. 9 shows an outline of the control operation of the CPU 60. Equipped with a mechanical closing latch mechanism and a latch release mechanism, when the operator presses the operation button, the switch contacts (closes) and the closing latch mechanism latches the switch to the contact, and the operator operates the operation button in the closed position. When is pressed again, the latch is released and the switch returns to open. When the release solenoid is energized when the operation button is in the closed position, the latch is released and the switch contact and the operation button are returned to the open position. -When the switch is closed by pressing the operation button,
A self-holding circuit of a power supply circuit (not shown) is inserted between the power supply and the receiving wire (the contact point is the power switch S).
(Parallel connection to W) is turned on (self-holding), whereby the power supply circuit supplies a constant voltage for control to the CPU 60.
Is applied. In response to this, the CPU 60 sets the internal register, the counter, the timer, etc. to the values in the stand-by state, and sets the signal levels in the stand-by state to the input / output ports of the mechanical unit (step 1). Below, in parentheses,
The word "step" is omitted and only the step number is shown.

Upon completion of the initialization (1), the CPU 60 reads the state of the mechanical unit and checks whether or not there is an abnormality (a state in which image formation cannot be started) (2, 3). It is displayed on the operation board 66 (4). If there is no abnormality, the solenoid 59RL is biased in the reverse direction by 90 degrees to bias the cam 59 from the solid line position (second position) shown in FIG. 5 to the dotted line position (first position) (R
D1). As a result, the charging roller 2 rotates from the second position (retracted position) shown in FIG. 3B to the first position (contact position; charging action position).

Next, the CPU 60 starts energizing the heater of the fixing device 8 to set the target temperature to the standby value (preheating temperature) and starts the warm-up to the target temperature ( 5). And the fixing temperature (the temperature of the fixing roller of the fixing device)
Check whether the temperature has reached the preheat temperature (6). If it is not at the preheat temperature, wait until it reaches the preheat temperature.

When the preheat temperature is reached, the operation display section displays "ready" (image formation is possible), and when the operation board 66 has an operator operation, it is read (7). Here, the input, such as the input of the number of recording sheets, the input of the recording magnification, the input of the recording density, etc., is written in the register. The register means the CPU 6
It is an internal memory of 0 or a memory area allocated to the RAM 61 or the EEPROM 67.

If there is a start input, an operation button to that effect is displayed.
Then, the CPU 60 updates the target temperature of the fixing device to a high temperature for the fixing process (the driver that controls the fixing temperature switches the energizing current of the fixing heater to a high level), as displayed on the screen 66. The rotation driving of the photosensitive drum 1 is started, and the start and end timings of charging, exposure, erase, paper feeding, developing, transfer, etc. for one image formation (recording one image) are already input. The recording table (standard mode when there is no input, standard value for parameters that do not have input) and set the timing table to 1
A copy cycle (1 image forming process) is executed, and the recorded number counter (register) is incremented by 1 (8,
9). In this 1 copy cycle (9), the CPU 60
Performs process control of charging (by the charging roller 2), exposure, development and transfer.

Next, it is checked whether the number of copies (the number of times an image has been formed: the number of continuous copies) has reached the set number (1
0), when the set number has not been reached, one copy
Execute cycle (9). When the set number of sheets is reached, the target temperature of the fixing device is returned to the preheat temperature, and the shutoff timer T
Start w (timer for Tw time period), set post-processing (end cycle) such as cleaning (duration time) of photoconductor and transfer belt (11), and input to operation board 66. Wait for it (7). When there is no start input from the operation board 66 and the end cycle ends, the photosensitive drum 1
Rotation drive is stopped, the static elimination lamp is turned off, and the end cycle is stopped there (12, 13). That is,
Put the mechanical unit in the standby state (stop).

When the power switch SW changes from closed to open before the end cycle ends, the end cycle described above is waited for, and when the power switch SW changes from closed to open after the end cycle ends, immediately. ,
The solenoid 59RL is biased in the forward direction to move the cam 59 from the dotted line position (first position) shown in FIG. 5 to the solid line position (second position) (RD2), and the self-holding of the power supply circuit is released (16). The charging roller 2 returns from the first position shown in FIG. 3 (a) to the second position shown in FIG. 3 (b), and when the self-holding of the power supply circuit is released, the power supply circuit is separated from the receiving wire ( Power is cut off, and power supply to each part of the circuit shown in FIG. 8 is interrupted. If the power switch SW remains closed even after the end cycle ends, the CPU 60 causes the shutoff timer T
It is checked whether w has time-over, and when it has time-over, the solenoid 59RL is biased in the forward forward direction to move the cam 59 from the dotted line position (first position) to the solid line position (second position) shown in FIG. And (RD2), power switch SW
The release solenoid is energized to release the closing latch of the power switch SW (which causes the power switch SW to mechanically return to the open state) and release the self-holding of the power circuit (16).

When the start key is turned on, the photosensitive drum 1 is rotationally driven in the clockwise direction in FIG. 1 at a predetermined peripheral speed Vo and is in contact with the surface of the photosensitive drum 1 with a predetermined contact pressure. The charging roller 2 is driven to rotate in a counterclockwise direction as the photosensitive drum 1 rotates. A predetermined charging bias voltage is applied to the charging roller 2 from the charging power supply circuit,
As a result, the peripheral surface of the photoconductor is charged by the charging roller 2 to a predetermined surface potential. The exposure device projects image light onto the charged surface via the mirror 40 to form an electrostatic latent image. The electrostatic latent image is developed by the developing roller 16 of the developing device 15, whereby a toner image is formed on the photosensitive drum 1.
Formed on the surface. On the other hand, recording paper is fed from a paper feed unit (not shown), and is fed to the transfer unit between the photoconductor drum 1 and the transfer belt 3 with appropriate timing by the registration roller, and the recording paper is fed. The toner images on the surface of the photoconductor are sequentially transferred. The recording paper on which the toner image has been transferred is separated from the surface of the photoconductor and is conveyed by the transfer belt 3 to a fixing device (not shown) for image fixing. The surface of the photoconductor after the image transfer is subjected to removal and cleaning of adhering contaminants such as transfer residual toner by the cleaning blade 10 and is charged again by the charging roller 2.

In the first embodiment described above, while the power switch SW is open, the charging roller 2 is separated from the photoconductor 1 as shown in FIG. There is no deformation due to the pressure contact of, and the surface shape is not substantially deformed. The charging roller 2 moves from the second position to the first position when the photoconductor 1 is stopped and contacts the photoconductor 1, and when the photoconductor 1 is stopped, the charging roller 2 moves from the first position to the first position. Since it moves to the 2 position and separates from the photoconductor 1, when the charge roller is driven in contact with or separated from the photoconductor while it is rotating, no friction occurs due to the relative movement of the charge roller with respect to the photoconductor. . That is, the surface of the photoconductor is not scratched.

Second Embodiment The structure of the mechanical portion and the electrical equipment portion of the second embodiment is the same as that of the first embodiment described above, but the first position / second position of the charging roller 2 of the CPU 60. The driving timing is different from that in the first embodiment. FIG. 10 shows an outline of the control operation of the CPU 60 of the second embodiment. The CPU 60 of the second embodiment starts the heat-up to the preheat temperature of the fixing device, and when the fixing temperature warms up to the preheat temperature (lower than that at the time of image formation), the solenoid 59RL is energized in step rotation. Due to 9
The cam 59 is biased in the reverse direction by 0 degrees to move the cam 59 to the position shown by the solid line in FIG.
Drive from the position) to the dotted line position (first position) (RD
1). As a result, the charging roller 2 rotates from the second position (retracted position) shown in FIG. 3B to the first position (contact position; charging action position). When there is no start input from the operation board 66 and the end cycle ends, the CPU 60 of the second embodiment energizes the solenoid 59RL in the forward forward direction to move the cam 59 to the position shown by the dotted line in FIG. From the position) to the solid line position (second position) (RD2). As a result, the charging roller 2 returns from the first position shown in FIG. 3 (a) to the second position shown in FIG. 3 (b). After that, if there is a start input, it is checked whether the roller 2 is in the first position (RD12a), and if it is not in the first position, the roller 2 is driven to the first position (RD12b). . As a result, the charging roller 2
Also rotates from the second position (retracted position) shown in FIG. 3B to the first position (charging position) shown in FIG. 3A. The other control operations of the CPU 60 of the second embodiment are similar to those of the above-mentioned first embodiment.

According to the second embodiment, immediately after the power is turned on, the charging roller 2 is set to (a) in FIG. 3 from the time when the fixing device rises to the preheating temperature to the end of the first end cycle. ) Is driven to the first position, after that, there is a copy start input until the end of the end cycle thereafter.
The charging roller 2 is driven to the first position. Roughly speaking,
The charging roller 2 is in contact with the photoconductor 1 only from the copy start to the end of the end cycle, and the charging roller 2 is separated from the photoconductor 1 in the other time intervals. Therefore, even when the power is turned on, the time during which the charging roller 2 is away from the photoconductor 1 (the time during which image formation is not performed) is long, and the deformation due to the pressure contact with the photoconductor 1 is correspondingly small. The first
Similarly to the embodiment, the charging roller 2 moves from the second position to the first position when the photoconductor 1 is stopped and comes into contact with the photoconductor 1, and when the photoconductor 1 is stopped. In the case where the charging roller is driven in and out of contact with the charging roller while the photosensitive member is rotating, since it moves from the first position to the second position and separates from the photosensitive member 1,
Rubbing due to relative movement of the charging roller with respect to the photoconductor does not occur. That is, the surface of the photoconductor is not scratched.

-Third Embodiment- The structure of the mechanical portion and the electrical equipment portion of the third embodiment is the same as that of the above-mentioned first embodiment, but the first position / second position of the charging roller 2 of the CPU 60. Driving timing is 1st and 2nd
Different from the embodiment. FIG. 11 shows the CPU 60 of the third embodiment.
The outline of the control operation of FIG. The CPU 60 of the third embodiment is
As in the first embodiment, immediately after the power is turned on, the charging roller 2 is driven from the second position to the first position (RD1). Then, similarly to the second embodiment, when the end cycle is completed, the charging roller 2 is returned to the second position (RD2). After that, the star
Then, the charging roller 2 is driven to the first position again (RD12b). The other control operations of the CPU 60 of the third embodiment are similar to those of the above-mentioned first embodiment.

Fourth Embodiment The structure of the mechanical portion and the electrical equipment portion of the fourth embodiment is the same as that of the first embodiment described above, but the first position / second position of the charging roller 2 of the CPU 60. The driving timing is different from that of the first to third embodiments. FIG. 12 shows an outline of the control operation of the CPU 60 of the fourth embodiment. Similar to the second embodiment, the CPU 60 of the fourth embodiment starts the heat-up to the preheating temperature of the fixing device, and when the fixing temperature warms up to the preheating temperature, the charging roller 2 is turned on. Driving from the second position to the first position (RD1). As in the first embodiment, when the power switch SW changes from closed to open, the charging roller 2 is moved to the second position.
Return to position (RD2).

In any of the first to fourth embodiments described above, the charging roller 2 as a charging member is made of stainless steel or iron and has a core metal of 8 mm in diameter, epichlorohydrin rubber 3 mm, hydrin rubber, fluororesin, Elastic rubber coated with a surface layer consisting of a mixture of silica (length 30
0 mm) is attached. The photoconductor 1 is an organic photoconductor of a three-layer laminated type and has a drum diameter of 60.
mm. A force of about 1 kg is applied to the charging roller 2 with respect to the photoconductor 1 in the direction toward the photoconductor 1.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a main part of a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of one end of the charging roller 2 shown in FIG.

3A is a side view of the charging roller 2 shown in FIG. 1 in a first position, and FIG. 3B is a side view in a second position.

FIG. 4 is a perspective view showing a part of a mechanism for bringing the charging roller 2 shown in FIG. 1 into and out of contact with the photoconductor 1.

5 is a side view of a mechanism that drives the lever 57 shown in FIG. 4 to drive the charging roller 2 to contact and separate from the charging roller 2. FIG.

FIG. 6 is an exploded perspective view of the mechanism shown in FIG.

FIG. 7 is an enlarged plan view showing a part of the L-shaped lever 51 and the link 52 shown in FIGS. 4 and 6;
(A) shows the state when the charging roller 2 is at the first position,
(B) shows the state when in the second position.

8 is a block diagram showing a system configuration of an electric device coupled to the mechanism shown in FIG.

9 is a flowchart showing an outline of an image forming control operation of the CPU 60 shown in FIG.

FIG. 10 is a flowchart showing an outline of an image forming control operation of the CPU 60 according to the second embodiment of the present invention.

FIG. 11 is a flowchart showing an outline of an image forming control operation of the CPU 60 according to the third embodiment of the present invention.

FIG. 12 is a flowchart showing an outline of an image forming control operation of the CPU 60 according to the fourth embodiment of the present invention.

[Explanation of symbols]

1: Photoconductor 2: Charging roller 3: Transfer belt 8: Bracket 10: Cleaning blade 14: Erasing lamp 15: Developing device 16: Developing roller 19: Recording paper 21: Charging roller bearing 21a: Protrusion for Release 23: Support Shaft 24: Bushing 25: Spring for Pressure Roller Pressure Contact 26: Leaf Spring for Feeding Terminal 26a: Leaf Spring Cutout Piece 27: Contact Member 28: Leaf Spring (Feeding Contact) 29: Charging Power Supply Circuit 50: Release rail 50a, 50b: Release cam 51: L-shaped lever 51a: Spring diameter stop shaft 52: Link 53, 54: Tension spring 55: Drive wire 56: Pulley 57: Lever 58 : Frame 59RL: Solenoid 59: Cam 60: CPU 61: RAM 62: ROM 63, 64: I / O port buffer amplifier 65: Synchronous pulse generator 66: Operation board 67: EEPROM (nonvolatile memory) 70: exposure device 80: ADF

Claims (6)

[Claims] 1. A charging member for charging a photosensitive member, a first position for contacting the charging member with the photosensitive member, and a second position separated from the photosensitive member.
An image forming apparatus comprising: a contacting / separating unit that selectively drives to a position; a unit that exposes a photoconductor; and a unit that develops an electrostatic latent image on the photoconductor caused by the exposure. An image forming apparatus comprising: a control unit that drives the charging member from a second position to a first position via a separating unit. 2. The image forming apparatus according to claim 1, wherein the control means drives the charging member from the second position to the first position via the contacting / separating means in response to power-on of the image forming apparatus. 3. The apparatus further comprises means for transferring a visible image developed by development to a recording medium, a fixing device for thermally fixing the transferred visible image on the recording medium, and a preheating temperature of the fixing device in response to power-on. A fixing device temperature control means for heating up the charging member as a target value, and the control means moves the charging member from the second position to the first position via the contacting / separating means when the fixing device reaches a preheating temperature. The image forming apparatus according to claim 1, which is driven. 4. The image forming apparatus according to claim 1, wherein the control means drives the charging member from the first position to the second position via the contacting / separating means when the photoconductor is stopped. apparatus. 5. The control means, in response to the opening of the power switch, moves the charging member from the first position to the second position via the contacting / separating means.
The image forming apparatus according to claim 4, which is driven to a position. 6. A fixing device temperature control means, in response to an image forming start instruction, heats up the fixing device with a fixing temperature as a target value, and sets a preheating temperature as a target when a predetermined condition is satisfied after completion of fixing. 4. The image forming apparatus according to claim 3, wherein the control unit drives the charging member from the first position to the second position via the contacting / separating unit when returning to the standby with a value.