JPH07210034A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain a high-quality image by averaging the load of a photoreceptor and preventing the fluctuation of carrying speed. CONSTITUTION:The time for the transer of a 1st sheet and the start and the finish of cleaning actuation is set to about the time of process for forming the first image of the image of a 2nd sheet, for example, yellow(Y) latent image forming process, so that switching is avoided in the midst of exposing the image. Furthermore, when image transfer and the cleaning actuation are not performed, a press-contact member is brought into press-contact with the photoreceptor so as to impress the load equivalent to the transfer and the cleaning actuation on the photoreceptor by actuating a load device, so that the load imposed on the photoreceptor is averaged and rotating speed is stabilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotating body of an image output device for digitally forming an image by an electrophotographic method and a peripheral process unit, and more particularly, to a driving device and cleaning of the rotating body for rotating a photosensitive body. The present invention relates to a device or a transfer device.

Further, the present invention relates to a color image forming apparatus for forming a color toner image by arranging a plurality of developing devices on the peripheral surface of an image forming body and superposing monochromatic toner images.

[0003]

2. Description of the Related Art In electrophotographic copying machines, printers, etc., an electrostatic latent image is formed on a surface of a rotating cylindrical photosensitive member or a belt-shaped photosensitive member to form an electrostatic latent image on the surface. Toner is attached to the latent image for development, and the toner image is transferred and fixed on a recording paper to obtain an image.

Here, the cylindrical photosensitive member of the image output device,
That is, the photoconductor drum and the drive roller that drives the belt-shaped photoconductor are referred to as a rotating body.

If the speed of the rotating photosensitive member fluctuates due to some influence, jitter or image unevenness occurs in the output image. This is particularly noticeable in the digital electrophotographic technology in which writing on the photoconductor is performed by scanning with a semiconductor laser, and the speed fluctuation of the rotation of the photoconductor becomes the speed fluctuation of the writing system in the sub-scanning direction. This causes a slight deviation in the interval between the two and causes a significant deterioration in image quality.

Particularly, in a color image forming apparatus for forming a color toner image by arranging a plurality of developing devices on the peripheral surface of an image forming body and superposing monochromatic toner images,
Since the color tone of the secondary color formed by two or more toner layers is determined by the appropriate adhesion amount of the toner of each color of each layer, the accuracy of the position of each layer is strictly required. That is, the first mechanism for changing the color tone is that, in the image forming process for the second and subsequent layers, the semiconductor layer or the like exposes the toner layer already formed on the photoconductor,
When the position of what is to be exposed on the toner layer is displaced due to the fluctuation of the speed of the photoconductor, the surface of the photoconductor without the toner layer is exposed. At this time, the surface potential of the photoconductor is lower than that when the toner layer is already present.
The amount of adhered toner after development is larger than that when considered on the toner layer. As a result, the color tone of this portion deviates from the target value. Further, as a second mechanism for changing the color tone, in a digital image output device, an image is often composed of a line that is a continuous body of dots,
In this case, since there is a difference in the density of lines or dots between the portion where the exposure interval is narrowed and the portion where the exposure interval is widened due to the speed fluctuation of the photoconductor, this causes color unevenness in the rotational direction of the photoconductor as an image. appear. This significantly deteriorates the quality of the color image.

Various fluctuations that occur in the drive system of the photosensitive member, such as those that give the above-mentioned fluctuations in the speed of the photosensitive member,
There are fluctuations of one rotation of the motor and fluctuations that occur for each tooth of the gear. These are fluctuations that occur constantly during the operation of the drive system. On the other hand, when the cleaning device, the transfer device, or the like starts or ends the operation in the middle of the process operation, the load of the photosensitive member temporarily changes, and the speed changes. When the absolute value of these unsteady speed fluctuations is large compared to the steady speed fluctuations,
The above mechanism causes image deterioration. In particular, the biggest problem with load fluctuations is that due to the magnitude of the load on the photoconductor, the elasticity of the photoconductor drive system causes a slight difference in the twist angle, which is a few microns to tens of microns on the photoconductor surface. The size becomes micron, which causes the laser writing position to be displaced. As a result, a slight deviation occurs in an image where a plurality of colors should originally overlap, which significantly deteriorates the image quality that should be obtained.

On the other hand, in the conventional design of a drive system such as a copying machine or a printer, the drive target is suitable in relation to the allowable space while satisfying the numerical values such as the line speed and the rotation speed derived from the product specifications. Emphasis was placed on exploring the placement. In other words, how to transmit the power from the power source to the drive target and what to use as a mechanical element for power transmission were of great interest. Therefore, if the unevenness or uneven rotation occurs in the finished product, search for the cause and change the bearing of the drive shaft of the photoconductor to a sintered product, or connect the flywheel to the drive shaft of the photoconductor.
Measures have been taken such as mounting a brake that combines a spring and a friction member on the rotating shaft of the photoconductor, improving gear accuracy, and using helical gears having various torsion angles.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the unsteady load fluctuation caused by the operation of the cleaning device or the transfer device which occurs during the image forming process.

That is, it is possible to prevent speed fluctuations due to load fluctuations generated on a rotating photoconductor of an image output device that digitally forms an image by an electrophotographic method, and to prevent a jitter, an image unevenness, and a positional deviation of an image with high image quality. An object of the present invention is to provide an image forming apparatus capable of forming an image.

A further object of the present invention is to provide an image forming apparatus for forming a high-quality image in a digital color image without density unevenness or color unevenness occurring in the rotation direction of the photoconductor.

[0012]

According to the present invention, in order to solve the above problems, a load or a load is applied to a cleaning device or a transfer device in a non-image area in a latent image forming process by laser writing. At the same time, the pseudo load corresponding to the load of these devices is released or applied so that the load becomes substantially constant during latent image formation by laser writing. The object is to solve the above-mentioned problems, and a driving device of a rotating body for rotating a photosensitive body which forms an image by an electrophotographic method in a digital manner, and an image exposure for forming a latent image on the surface of the photosensitive body. Means, a transfer means for transferring an image to a transfer body, and a cleaning means for cleaning the residual toner on the surface of the photoconductor. In the non-image area of the rotating body, a pressure contact member that enables pressure contact and release of the pressure contact is provided, and the transfer means and the cleaning means in a state in which an image writing process by the image exposure means is in a non-image area between images. Image forming apparatus (first invention), wherein the pressure contact of the pressure contact member is released or pressure contact is performed at substantially the same time and in response to the operation or stop of the cleaning means. An image forming body, a charging means for charging the image forming body, an image exposing means for forming a latent image on the image forming body,
A plurality of developing means for developing the latent image to obtain a toner image, a transfer means for transferring the toner image to a transfer body,
In a color image forming apparatus including a cleaning unit for cleaning residual toner on the surface of the image forming body, a pressure contact member that enables pressure contact and release of pressure contact is provided in a non-image area of the image forming body, and the image exposing unit is used. The transfer means and the cleaning means are operated or stopped in a state where the image writing process is in the non-image area between the images, and the pressure contact of the pressure contact member is performed substantially at the same time and corresponding to the operation or the stop of the operation of the cleaning means. This is achieved by an image forming apparatus (second invention) characterized by releasing or pressing.

[0013]

When the above pseudo load is made to correspond to the activation or deactivation of the cleaning device or the transfer device, and at the same time as these actions, the releasing or loading action is applied at the timing corresponding to the non-image area of laser writing. In the latent image forming process, the magnitude of the load on the photoconductor can be made constant, and the twist angle of the photoconductor can be made almost constant. Therefore, even if the cleaning device or the transfer device is operated, the image to be formed can be of high quality without any color misregistration, color unevenness, or density unevenness.

As a result, even if the load varies, the variation in the rotation angle of the rotating body is reduced, and the quality of the output image can be greatly improved. Further, the device can be downsized, the cost can be reduced, and the reliability of the entire system can be improved.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of the embodiments of the present invention, the construction and operation of the color image forming apparatus of the present invention will be described with reference to FIGS.
Explained by.

In the figure, reference numeral 10 denotes a photosensitive drum which is an image bearing member, which is applied on the OPC photosensitive drum and is grounded and driven and rotated clockwise. Reference numeral 12 denotes a scorotron charger, which applies a uniform charge of V _{H to} the peripheral surface of the photosensitive drum 10 by corona discharge by a grid and a corona discharge wire whose potential is held at V _G. This scorotron charger 12
Prior to the charging by (1), the peripheral surface of the photoconductor is neutralized by performing exposure by the PCL 11 using a light emitting diode or the like in order to eliminate the history of the photoconductor until the previous printing.

After the photosensitive member is uniformly charged, the image exposure means 13 performs image exposure based on the image signal. Image exposure means
Reference numeral 13 is a reflection mirror 1 via a polygon mirror 131 that rotates using a laser diode (not shown) as a light emitting source, an fθ lens
The operation is performed by bending the optical path by 32, and the latent image is formed by the rotation (sub-operation) of the photoconductor drum 10.
In this embodiment, the character portion is exposed to form an inverted latent image in which the character portion has a lower transition V _L.

Yellow (Y) on the periphery of the photosensitive drum 10,
Developers each containing a developer composed of toner such as magenta (M), cyan (C), black (K), and a carrier.
14 is provided, and first, the development of the first color is performed by the developing sleeve 141 which contains a magnet and holds the developer and rotates. The developer is a carrier in which a ferrite core is coated with an insulating resin around it, a polyester as a main material, a pigment according to the color, and a charge control agent,
The toner is composed of toner to which silica, titanium oxide, etc. are added.
The layer is regulated to a layer thickness (developer) of 600 μm and transported to the development area.

The gap between the developing sleeve 141 and the photosensitive drum 10 in the developing area is 0.2 mm, which is larger than the layer thickness (developer).
As 1.0 mm, DC bias of AC bias and V _DC of V _AC is applied to overlap therebetween. Since V _DC and V _H and the toner are charged with the same polarity, the toner that is given the opportunity to be separated from the carrier by V _AC does not adhere to the V _H portion, which has a higher potential than V _{DC, and} has a potential higher than V _DC. attached to a lower V _L portion of visualized (reversal development) is carried out.

After the visualization of the first color is completed, the process proceeds to the image forming step of the second color, the uniform charging is performed again by the scorotron charger 12, and the latent image by the image data of the second color is formed by the image exposing means 13. To be done. At this time, the charge elimination by the PCL 11 performed in the image forming process for the first color is not performed because the toner adhered to the image portion for the first color scatters due to the sudden decrease in the potential around the image.

Again, V is applied over the entire surface of the photosensitive drum 10.
A latent image similar to that of the first color is formed on the portion of the photoconductor having the _H potential and the image of the first color is not developed, but development is performed again on the portion having the image of the first color. In the portion to be performed, the latent image of V _M ′ is formed by the toner attached to the first color due to the light blocking and the charge of the toner itself, and the development is performed according to the potential difference between V _DC and V _M ′. When the first color image is formed by forming a VL latent image in the overlapping portion of the first color image and the second color image, the balance between the first color and the second color is lost, so that the exposure amount of the first color is reduced and V _H > It may be set to an intermediate potential such that V _M > V _L.

An image forming process similar to that for the second color is performed for the third and fourth colors, and a visible image of four colors is formed on the peripheral surface of the photosensitive drum 10.

On the other hand, the recording paper P carried out from the paper feed cassette 15 via the half-moon roller 16 is temporarily stopped, and when the transfer timing is adjusted, it is fed to the transfer area by the rotation operation of the paper feed roller 17.

In the transfer area, the transfer roller 18 is pressed against the peripheral surface of the photoconductor drum 10 in synchronization with the transfer timing, and the recording paper P that has been fed is sandwiched and a multicolor image is collectively transferred. .

Then, the recording paper P is discharged at almost the same time by a separating brush 19 which is brought into a pressure contact state, separated by the peripheral surface of the photosensitive drum 10 and conveyed by a fixing device 20, and a heat roller 20.
The toner is melted by heating and pressurizing the pressure roller 1 and the pressure-bonding roller 202, and then the toner is discharged to the outside of the apparatus through the paper discharge roller 21. The transfer roller 18 and the separation brush 19 are withdrawn from the peripheral surface of the photosensitive drum 10 after the recording paper P has passed and are ready for the next toner image formation.

On the other hand, the photosensitive drum 10 in which the recording paper P is separated
Removes and cleans the residual toner by pressing the blade 221 of the cleaning device 22, and again receives the charge removal by the PCL 11 and the charge by the charger 12 to start the next image forming process. The blade 221 moves immediately after cleaning the surface of the photoconductor and retracts from the peripheral surface of the photoconductor drum 10.

FIG. 2 shows a layout on a plane of each unit constituting the apparatus, and the side indicated by an arrow A corresponds to the front surface of the apparatus, that is, the side surface on the operating side.

The main body of the apparatus is composed of two upright side panels 1.
And a side panel 2, and a writing unit which is the image exposing means 13 between these side panels, a photosensitive drum 10, a developing unit for accommodating a plurality of developing devices 14, and a fixing device. Twenty units and a DC power supply unit are incorporated, while on the outside of the side panel 1, a drive system, a formatter for decoding printer commands, and control boards for sequence control of machine operation are housed. A toner box connected to each developing unit 14 in the developing unit is housed outside.

Since the photosensitive drum 10 and the developing unit are located near the operation side surface of the apparatus, it is possible to have a structure in which they can be pulled out to the front of the operation by a simple operation, and the upper part of the main body is opened. By making it possible, it is possible to perform the jam processing at the transfer position by pulling out the drum base to the pull-out position without taking out the photosensitive drum 10 and the developing unit from the main body.

Further, the jam processing in the paper feeding section is performed by the paper feeding cassette loaded below the photosensitive drum 10 and the developing unit.
This can be done by taking 15 out of the apparatus, and jam processing at the paper discharge section can also be realized by making the back side of the apparatus open.

The features of the functions and performances of the respective equipments constituting the image forming section of the above apparatus will be described below.

(Photoreceptor) FIG. 3 shows a method of transmitting rotational power to the photoconductor drum 10. Both flanges 101 and 102 for supporting the peripheral surface of the drum are made rotatable with the drive shaft 103, and the drive shaft 103 is rotated. A spring member 105 is provided between a fixing member 104 fixed to 103 and one of the flanges 101, and is connected to each other. In this way, the photosensitive drum 10 and the drive shaft 10
It is possible to obtain the same effect as reducing the rigidity of the drive system including 3 and reduce the natural frequency so as not to resonate with the fluctuation of the vibration from the drive gear G. Then, the fluctuation of the rotation speed input to the drive shaft 103 can be absorbed by the low-rigidity member, and the photosensitive drum 10 can be rotated without causing the fluctuation of the rotation speed.

The photosensitive drum 10 is stably rotated so that the peripheral OPC photosensitive member is uniformly charged by the scorotron charger 12. During charging, the grid potential is controlled to stabilize the charging potential. The specifications of the photoconductor and the charging conditions thereof are set as follows as an example.

Photoconductor: OPC φ120 Linear velocity 100 mm / sec Negative charging Charging condition: Charging wire: Platinum wire (clad or alloy)
Is preferably used. _VH- 850V, _VL- 50V (Image exposure) FIG. 4A shows the plane and side surfaces of the layout of the image exposure means 13, and FIG. 4B shows the semiconductor laser unit used for the image exposure means 13. It is explanatory drawing of 135.

The OPC photosensitive member on the peripheral surface of the photosensitive drum 10 is negatively charged by the charger 12 and then exposed by the light emission of the semiconductor laser unit 135 of the image exposing means 13 to form an electrostatic latent image.

The image data from the formatter is sent to the laser diode (LD) modulation circuit, and when the LD of the semiconductor laser unit 135 emits light by the modulated image signal, the beam light is beam indexed via the mirror 132. The scanning lines are synchronized by 136 and projected onto the polygon mirror 131.

The polygon mirror 131 reflects the beam light on its polyhedron and scans it. The beam shape of the scanning light is corrected by the fθ lens 133 and the cylindrical lens 134, and then the photoconductor is exposed through the reflecting mirror 132. Main scanning is performed to form an electrostatic image.

The beam system of the laser light is narrowed down by the optical system to the equivalent of 600 DPI. Therefore, in order to obtain a high quality image, it is necessary to reduce the particle size of the toner. In this embodiment, toner of 8 μm size is used for each color. However, what is most important to the user is the black character quality, and small particle size toner (7 μm to 11 μm) is suitable for the black toner.

As the image exposure optical system, for example, one having the following construction is used.

Polygon mirror: 6 surfaces, rotation speed 23600 rpm, air bearing adopted Lens focal length: f = 140 mm Dot clock: 20 MHz Beam diameter: about 60 × 80 μm (Development) FIG. 5 shows the construction of the developing device 14, The toner supplied from the toner box is dropped to the right end of the developing unit, and is agitated and mixed with the carrier by a pair of agitating screws 142 rotating in opposite directions to set a predetermined charge amount (Q / M). .

On the other hand, the toner concentration is detected by a magnetic detection method, and the toner supply amount is controlled based on the output frequency to set and control the toner concentration value to about 5 to 7%.

The agitated two-component developer is supplied to the supply roller 143.
Is conveyed to the developing sleeve 141 via the layer thickness regulating member 144.
Is transferred to the developing area of the photosensitive drum 10 as a thin layer, and reversal development of the electrostatic latent image is performed under the developing conditions described below.

Development gap: 0.5 mm Toner conveying amount: 20 to 30 mg / cm ² Development bias (AC): 2 KV, 8 KHZ (DC): -750 V Rotation direction of developing sleeve: Normal rotation with respect to photosensitive drum Image density adjustment: Development Sleeve speed control or development bias control (a standard plate is formed on the photoconductor by a laser beam, and the image density is adjusted by measuring the reflection density after development) Toner density control: Magnetic detection method By using the toner bolt loaded in the box as it is as a toner hopper, the toner supply device can be made smaller and simpler, and at the same time, the toner bottle can be made of a translucent material so that the remaining amount can be easily viewed. Is.

(Paper Feeding) FIG. 6 shows a paper feeding portion for the recording paper P. The recording paper P is stored in the paper feeding cassette 15 on a one-sided basis. The half-moon roller 16 is provided only on the reference surface side, and the half-moon roller 16 has a cantilever structure, and is positioned on the reference surface side of the recording paper P.

The paper feeding section has a dedicated motor, and the half-moon roller 16 rotates in the direction of the arrow to move the recording paper P stacked on the push-up plate 152 by the action of the separating claw 151 to the uppermost layer. Carry out only one.

The recording paper P carried out from the paper feed cassette 15 enters the conveyance path and makes a U-turn, and immediately after the leading edge passes the paper feed roller 17, the motor is temporarily stopped by the detection of a paper feed sensor (not shown). When the transfer timing is adjusted, the motor starts rotating again, and the paper is fed to the transfer area while maintaining a predetermined angle with respect to the surface of the photoconductor.

On the other hand, the manual feeding is performed by rotating the manual feeding table M located on the front surface of the apparatus main body from the position shown by the alternate long and short dash line in FIG. 1 to the position shown by the solid line.

The manually fed paper is picked up by a pickup roller 153.
Is conveyed by the rotation of, and is fed to the transfer area through the same process as the above-mentioned paper feeding from the paper feeding cassette 15.

Papers to be fed manually are not only ordinary recording papers P of 16 lbs to 24 lbs, but also 36 lbs of thick paper and transparency for OHP. It is also possible to feed envelopes by removing the manual feed tray M and installing a dedicated feeder as an option.

(Transfer) The transfer roller 18 has a variable position with respect to the peripheral surface of the photosensitive drum 10, and is always placed in a pressure contact state as shown in FIG. 7 when a monochromatic image is printed, but during the formation of a color image. It is retracted and kept in a separated position, and is pressed into contact only during transfer. On the other hand, the separation brush 19 also transfers the transfer roller 18.
The pressure contact and separation operations are performed on the peripheral surface of the photosensitive drum 10 almost in synchronism with the position variation of the.

In the apparatus of this embodiment, a transfer roller 18 of a type in which an applied voltage is +3 to 4 KVDC and a roller surface is cleaned by a blade is used, and a separating brush is used.
A bias voltage in which DC and AC are superposed is applied to 19 for use.

(Fixing) Fixing device provided in the apparatus of this embodiment
Reference numeral 20 denotes a so-called heat roller type fixing device including a pair of rollers as shown in FIG. 8, which includes an upper roller 201 having a built-in heater H and driven and rotated clockwise, and a lower roller which is pressed against the upper roller 201 and driven to rotate. The recording paper P is heated and conveyed by the nip portion formed between the roller 202 and the roller 202 to fuse the toner image.

The upper and lower rollers are both covered with a heat-resistant tube, and the nip portion is formed in a straight line by pressure contact, so that wrinkles on the paper surface which are likely to occur when an envelope or the like is conveyed are prevented.

The peripheral surface temperature of the upper roller 201 is controlled by being detected by the temperature sensor S to be kept within a predetermined temperature range, and the dirt adhered by the welding of the toner is removed and cleaned by the pressure contact of the cleaning roller 203. To be done. The cleaning roller 203 is replaced with a new one when the number of printed sheets is about 40,000. If the fixing heater is not used for a predetermined period of time, the fixing heater enters the SLEEP mode and energy saving control is performed.

Further, when the transparency used for OHP is used as a transfer material, the peripheral surface of the upper roller 201 is smoothed for the purpose of smoothing the toner image surface to prevent irregular reflection in order to improve the transmittance of the color toner image. Oil pad 2
Silicon oil is applied to the roller surface by 04.

Therefore, in the apparatus of this embodiment, the transfer speed of the transfer material can be switched among three levels of 100 mm / sec, 50 mm / sec and 12.5 mm / sec, and three types of plain paper, envelope and transparency can be selected. It has a mode in which a transfer material can be used and is used in a wide range of applications.

The set temperature of the upper roller 201 can be lowered to about 180 ° C. by using a toner that melts at a low temperature, and the oil pad 204 is sponge material (porous PTFE coating). By using, the uneven pressure is eliminated and uniform oil application is realized.

The transfer roller 18 for the peripheral surface of the photosensitive drum 10 and the partial blade 221 of the cleaning device 22.
The operation of pressing and releasing the pressing is performed by detecting that the image writing process is in a non-image area between images in order to avoid the speed movement of the photosensitive drum 10 during image exposure, or according to a preset program, For example, as shown in FIG. 9, the pressure contact (ON) is activated at a time after the formation of the black (K) latent image of the first image until the start of the formation of the yellow (Y) latent image of the second image. The pressure contact release (OFF) is activated during the period from the formation of the yellow (Y) latent image of the first image to the start of the formation of the magenta (M) latent image.

On the other hand, the load device for the photosensitive drum 10 shown in FIG. 10 is provided as a means for suppressing the speed fluctuation of the drum due to the load fluctuation when the pressure contact of the transfer roller 18 and the blade 221 of the cleaning device 22 is released (OFF). To be

The load device shown in FIG. 9 (a) is of a type in which the photosensitive drum 10 is braked by the pressure contact of a roller member, and a bell crank 301A having a rotating roller R attached to one end thereof has a shaft 302.
It is supported by the drum mount 300 while being urged counterclockwise by a tension spring 303A with A as a fulcrum.

A plunger of a solenoid SOL is connected to the other end of the bell crank 301A via a link member. When the solenoid SOL is ON, the bell crank 301A is attached with a tension spring 303A by the operation of the plunger. The rotation roller R is rotated in the clockwise direction against the force and is kept at the position retracted from the peripheral surface of the photosensitive drum 10 as shown in the figure. However, when the solenoid SOL is OFF, The crank 301A has a tension spring 303 when the plunger is released.
It is rotated counterclockwise by the urging force of A, and the rotating roller R presses against the non-image area provided in the end surface direction of the photosensitive drum 10 to brake the rotation of the drum.

The pressure contact load of the rotating roller R against the drum peripheral surface is adjusted by the urging force of the tension spring 303A so as to be substantially equivalent to the pressure contact load of the transfer roller 18 and the blade 221 of the cleaning device 22 against the drum peripheral surface. It

ON / OFF of the solenoid SOL, that is, ON / OFF of the load device is performed in synchronization with OFF / ON of the transfer roller 18 and the blade 221 of the cleaning device 22 as shown in the timing chart of FIG. As a result, the photosensitive drum 10 receives a uniform load and is rotated at a stable speed throughout the entire rotation operation.

As the pressure contact member, a pad-like brake member as shown in FIGS. 9B and 9C can be used in addition to the roller member.

The above-mentioned brake member B1 or B2 is fixed to the tip of each bell crank 301B or 301C by means such as adhesion, and the same tension spring 303B or 303C as the device using the above-mentioned roller member.
Is pressed against the photosensitive drum 10 by the urging force of the solenoid SOL, and released by the operation of the solenoid SOL.

Since the pad-shaped brake member has a large friction coefficient, a large braking effect can be obtained by the urging force of the weak tension spring, and therefore, the solenoid SOL used for releasing the pressure contact can also have a small power.

Further, in the apparatus shown in FIG. 10 (b), the brake member B1 is pressed against the non-image area provided in the end face direction of the drum peripheral surface like the roller member, but in the apparatus shown in FIG. 10 (c). Since the brake member B2 is pressed against the side surface of the drum, it is not necessary to provide a non-image area in the end surface direction of the photoconductor, and therefore the photoconductive surface of the photoconductor drum 10 can be effectively used.

In the embodiment, the object to which a load is applied is limited to the drum-shaped photosensitive member, but the first invention of the present invention is also applicable to the belt-shaped photosensitive member and the rotating member so-called rotating roller. include.

FIG. 11 shows this embodiment, in which a charger 412 and a plurality of developing devices 41 containing different color toners are provided at the peripheral portion of a belt photosensitive member 410 having a photosensitive member provided on a belt.
4, a transfer unit 418 and a cleaning unit 422 are provided.
The belt photoconductor 410 includes a driving roller 420A and a driven roller 420B.
It is stretched between and and rotated clockwise in the figure, after charging by the charger 412 on the belt photoreceptor 410, scanning is performed by the exposure means 413 using a laser to form a latent image. The developing device 414 develops the toner image. By repeating the image forming process a plurality of times, multicolor toner images are superposed on the belt photoreceptor 410. The superposed toner images are transferred onto the recording paper fed separately by the transfer unit 418,
The recording paper is separated and then fixed.

The belt photoconductor 410 that has completed the transfer is cleaned by the cleaning unit 422. Also in a color image forming apparatus using such a belt-shaped photoconductor, a load device as shown in FIG. 10 is provided, and a non-image of the end surface of the belt photoconductor 410 is substantially synchronized with the pressing or releasing of the blade of the cleaning unit 422. Area or drive roller 4
By releasing pressure contact or performing pressure contact with the side edge of 20A, the same effect as in the previous embodiment can be obtained.

[0071]

According to the image forming apparatus of the present invention, in the latent image forming process by laser writing, the magnitude of the load on the photoconductor can be made constant, and the magnitude of the twist angle of the photoconductor can be made substantially constant. You can Therefore, even if the cleaning device or the transfer device is operated, the image to be formed can be of high quality without any color misregistration, color unevenness, density unevenness, or the like.

As a result, even if the load varies, the variation in the rotation angle of the rotating body is reduced, and the quality of the output image can be greatly improved. Further, the device can be downsized, the cost can be reduced, and the reliability of the entire system can be improved.

Further, a device having a complicated and large size in the prior art can be realized by a simple and compact structure.
Moreover, the cost can be reduced by this. Furthermore, the simplification of the mechanism has significantly improved the reliability of the entire system.

Further, in a color image forming apparatus in which a plurality of developing devices are arranged on the peripheral surface of the photoconductor and a toner image of a single color is superposed, a color shift and a color are generated in the rotational direction of the photoconductor. The phenomena of unevenness and uneven density could be remarkably improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus of the present invention.

FIG. 2 is an explanatory diagram showing a layout of each device in the apparatus.

FIG. 3 is a main part diagram showing a driving method of a photosensitive drum.

FIG. 4 is an explanatory diagram showing an optical system of an image exposure unit.

FIG. 5 is a cross-sectional configuration diagram of a developing device.

FIG. 6 is a main part diagram of a paper feeding unit.

FIG. 7 is a main part view of a transfer unit.

FIG. 8 is a main part diagram of a fixing device.

FIG. 9 is a timing chart of a load on the photosensitive drum.

FIG. 10 is a configuration diagram of a load device.

FIG. 11 is a sectional configuration diagram of a color image forming apparatus showing another embodiment.

[Explanation of symbols]

 10 Photosensitive drum 12 Charging device 13 Image exposure means 14 Developing device 15 Paper cassette 18 Transfer roller 22 Cleaning device 221 Blade 300 Drum stand 301A, 301B, 301C Bell crank 303A, 303B, 303C Tension spring R Rotating roller B1, B2 Brake member SOL solenoid

Claims (2)

[Claims] 1. A driving device of a rotating body for rotating a photosensitive body which forms an image by digital method by electrophotography, an image exposing means for forming a latent image on the surface of the photosensitive body, and an image In an image forming apparatus equipped with a transfer unit for transferring to a transfer member and a cleaning unit for cleaning the residual toner on the surface of the photosensitive member, a pressure contact member that enables pressure contact and release of pressure contact to a non-image area of the rotating member is provided. The transfer means and the cleaning means are activated or deactivated in a state where the image writing process by the image exposure means is in the non-image area between the images, and the cleaning means is activated or deactivated almost simultaneously. An image forming apparatus, wherein the pressure contact of the pressure contact member is released or pressure contact is performed correspondingly. 2. An image forming body, charging means for charging the image forming body, image exposing means for forming a latent image on the image forming body, and for developing the latent image to obtain a toner image. A plurality of developing means, a transfer means for transferring the toner image to a transfer body, and a cleaning means for cleaning the residual toner on the surface of the image forming body. A pressure contact member that enables pressure contact and pressure contact release is provided in the region, and the transfer unit and the cleaning unit are operated or stopped in a state where the image writing process by the image exposure unit is in the non-image region between images, and At the same time, the image forming apparatus is characterized in that the pressure contact of the pressure contact member is released or pressure contact is performed in response to the activation or deactivation of the cleaning means.