JPH0329985A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain a uniform image by providing a cleaning means in a holding means for holding an image-formed medium to which a developer image is transferred and allowing the cleaning member to work to clean the holding means when the image-formed medium is not held by the holding means. CONSTITUTION:An image forming means 3 forms an electrostatic latent image on an image carrier 5 and developing means 9A-9D develop the electrostatic latent image formed by the image forming means 3, then the holding means 11 holds the image-formed medium P to which the developer image which is developed by the means 9A-9D is transferred. The cleaning means 100 cleans the holding means 11 when the image-formed medium P is not held by the holding means 11. Therefore, the stain on the back side of the image-formed medium P is prevented even when dust, etc., adheres to the holding means 11. The unevenness of transfer caused by the ruggedness of the image-formed medium P held by the holding means 11 is prevented from occurring. Thus, the uniform image is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an image forming apparatus that forms a plurality of images on an image forming medium, which is used in, for example, a color copying machine.

(Prior Art) Conventionally, as this type of image forming apparatus, there is one that performs color printing by superimposing and transferring developer images of a plurality of colors onto an image forming medium. In such an image forming apparatus, a developer image is formed for each color and transferred to an image forming medium in multiple times for each color, and the image forming medium or image forming medium to which the plurality of types of developer images are transferred is transferred. By fixing the images, a color image can be printed.

In such an apparatus, when transferring a plurality of developer images to an image forming medium, the image forming medium is held on a rotating body, and this rotating body is rotated a number of times according to the color to be used. In this way, the image is transferred to the image forming medium.

Then, after the transfer of the plurality of developer images is completed, the image forming medium is removed from the rotating body and fixing is performed, thereby completing one sheet of color printing. When performing color printing on a plurality of sheets, the image forming media are sequentially held on a rotating body, and color printing is performed one after another in the same manner as described above.

In the image forming apparatus configured as described above, when dust or dirt adheres to the rotating body that holds the image forming medium,
There have been problems in that the back side of the image forming medium is stained, and the image forming medium held by the rotating body is uneven, resulting in uneven transfer and making it impossible to obtain a uniform image.

(Problems to be Solved by the Invention) Conventionally, as described above, when dust or the like adheres to the rotating body of an image forming apparatus, the back side of the imaged form or medium may become stained, or the rotating body may become dirty. This was done to solve the problem that unevenness occurs on the held image forming medium, causing uneven transfer and making it impossible to obtain a uniform image. An image forming apparatus that can prevent staining on the back side of a forming medium, and can also prevent irregularities in transfer caused by unevenness on an image forming medium held by a rotating body, thereby obtaining a uniform image. The purpose is to provide

[Structure of the Invention] (Means for Solving the Problems) The image forming apparatus of the present invention includes an image forming means for forming an electrostatic latent image on an image bearing member, and an electrostatic latent image formed by the image forming means. A developing means for developing an electrostatic latent image, a holding means for holding an image forming medium to which a developer image developed by the developing means is transferred, and a holding means for holding an image forming medium when the holding means does not hold an image forming medium. It is characterized by comprising a cleaning means for cleaning the holding means.

(Function) The present invention provides a cleaning means in the holding means that holds the image forming medium to which the developer image is transferred, and operates the cleaning means at a timing when the holding means does not hold the image forming medium or the medium. It is designed to remove dust, dirt, etc. on the holding means. As a result, it is possible to prevent the back side of the image forming medium from becoming dirty, and also to prevent unevenness from occurring on the image forming medium, thereby making it possible to obtain a uniform image.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view schematically showing the internal structure of a color copying machine as an image forming apparatus of the present invention.

This image forming apparatus includes a document reading device (not shown) and a recording device 1. The document reading device separates the image information of the read document into dots and sequentially outputs the image information obtained for each color component to the recording device 1.

A recording device 1 sequentially records image information for each color component using a laser beam 2.
The photoreceptor drum 5 is
to form a latent image. The photosensitive drum 5 is a developing device 9
The first color toner from A is attracted and the latent image formed by the laser beam 2 is visualized to form a toner image. On the other hand, the gripper 13 provided on the transfer drum 11 as a rotating body supports the transfer paper (image forming medium) P stored in the paper feed cassette 17, and this supported transfer paper P is transferred It is attached to the outer peripheral surface of the drum 11 by electrostatic action, which will be described later. The photosensitive drum 5 and the transfer drum 11 face each other while maintaining contact at a point 51C, and rotate at a constant speed in the directions of arrows E and F, respectively, to transfer the first color on the photosensitive drum 5. Transfer the toner image onto transfer paper P. When the transfer of the first color onto the transfer paper P is completed, the photosensitive drum 5 and the transfer drum 11 are separated from each other by a distance of 2 to 3 mm from the contact state, and the transfer drum 11
1. Rotate by a predetermined amount (the length of the toner image) in a direction opposite to the direction F in which the toner image was rotated when transferred. When the transfer drum 11 is reversely rotated by a predetermined amount, the initial position of the transfer paper P is opposite to the photosensitive drum 5 at a point 5IC. Also, while rotating the photosensitive drum 5 in the E direction,
Similarly, the position is set so that the transfer can be restarted when the initial position reaches the point 51C. In this way, the second, third, and fourth color toner images are sequentially transferred onto the transfer paper P. When the transfer is completed, the transfer paper P is peeled off from the transfer drum 11, fixed by a fixing device 21, and discharged to a collection tray 23.

The exposure optical system 3 is provided at the top of the recording device 1 and includes a high-speed rotation motor 27, a polyhedral rotation mirror 29, and an fθ lens 3.
1. Reflection mirror 3B. 35, an aspherical lens 37, and three protective glasses. This exposure optical system 3 includes
Laser light 2 oscillated from a semiconductor laser oscillator (not shown) is shaped by a beam shaping optical system (not shown) including, for example, a cylindrical drill lens, and inputted. Further, the laser beam 2 is transmitted by a polyhedral rotating mirror 29 that is rotationally driven by a high-speed rotating motor 27 using an air bearing that is drive-controlled by a drive controller 41 adjacent to the exposure optical system 3 in the upper part of the recording apparatus 1. Deflected. The deflected laser beam 2 passes through an fθ lens 31 to a mirror 3.
3 and reflected by mirror 35, a spot image is formed at an exposure position 51A on photoreceptor drum 5 through an aspherical lens 37 and a protective glass 39, and scanned exposure is performed.

Around the photosensitive drum 5, along the rotation direction E,
A charger 43 for charging the drum surface, a developing device support 7 equipped with developing devices for each color, a transfer drum 11 that rotates with transfer paper P attached to the drum surface, a cleaner 53, and an erasing and neutralizing lamp 55 are provided. There is. The photosensitive drum 5 is constantly driven to rotate at an outer circumferential speed of Vo by a pulse motor 79, which will be described later, and the drum surface is charged by a charger 43 having a grid electrode 45 and provided facing the drum surface. be done. The laser beam 2 is spot-imaged at the exposure position 51A on the drum surface of the charged photoconductor drum 5 via the protective mirror 39, and the electrostatic charge is removed in accordance with the laser beam 2. A latent image is formed. The photosensitive drum 5 on which this electrostatic latent image is formed is
V in the direction of arrow E to the point of development position 51B. When it rotates at a speed of , it comes into contact with the developing device 9A of the developing device support 7, and yellow 1.toner is supplied from the developing sleeve 49A of the developing device 9A to the photosensitive drum 5 and is attracted thereto.

A cylindrical developing device support body 7 housing this developing device 9A
In addition to the developing device 9A, the developing device 9B has a developing sleeve 49B containing magenta 1.toner, the developing device 9C has a developing sleeve 49C containing cyan toner, and
Developing units 9D each having a developing sleeve 49D containing black toner are provided adjacent to each other. The developing device support 7 is rotated in the direction of arrow G around the central axis 47 by the drive of a process drive system 81 to be described later, and the transfer of each color to the transfer paper P attached to the transfer drum 11 is completed. Each time, the developing units 9A to 9D are sequentially moved to the developing position 51B of the photosensitive drum 5. For example, a developer image formed by the first yellow toner is transferred to the transfer paper P attached to the transfer drum 11 at the transfer position 51C of the photoreceptor drum 5, but the transfer is completed. The developing device support 7 rotates in the direction of arrow G until the transfer of the second color starts, and moves the second color magenta developing device 9B to the developing position 51B of the photosensitive drum 5.

The photosensitive drum 5, on which a developer image is formed by adsorbing toner of one color in the developing device, continues to rotate, and the transfer paper P adhering to the transfer drum 11 at the transfer position 51C.
The visualized toner image is transferred to the toner 9. After the transfer at the transfer position 51C, the photosensitive drum 5 has a constant velocity V. The cleaner 5, which is provided opposite the photosensitive drum 5, continues to rotate further in the direction of the arrow E.
3 removes the residual toner adhering to the surface of the photoreceptor drum 5, and furthermore, the erasing and neutralizing lamp 55 removes the residual potential on the surface of the photoreceptor drum 5.

The transfer drum 11 as a holding means is fixedly provided on a part of the drum surface, and includes a gripper 13 for supporting the transfer paper P, and this gripper 13 holds the transfer paper P fed by the paper feed roller 19. Sensor 15 that detects holding
It is equipped with The transfer drum 11 is rotated at a speed V of the photoreceptor drum 5 while transferring the toner image formed on the photoreceptor drum 5 onto the transfer paper P by rotational driving of a pulse motor 79 which will be described later. When the transfer is completed, the outer peripheral speed v is faster than the photosensitive drum 5.
1, the toner image is rotated in the opposite direction to the arrow F direction by the distance of the toner image. Further, in addition to the photosensitive drum 5, paper feed rollers 19, 10, a charger 59, a movable guide plate 61, and a cleaner 100 as a cleaning means are arranged around the transfer drum 1.

The surface of the transfer drum 11 is charged by a charger 59 provided opposite to the transfer drum 11, and the paper feed cassette 17 is rotated by the rotation of the paper feed roller 19.
When the transfer paper P stored in the transfer drum 11 is fed one by one, the gripper 13 provided at the end of the transfer drum 11
holds the leading edge of the transfer paper P, and the transfer paper P is attached to the transfer drum 11 by the electrostatic force generated by the charger 59 . Further, when the transfer paper P is held by the gripper 13, the sensor 15 provided at the end of the drum detects the transfer paper P.
is detected and outputs a detection signal to a control device 75, which will be described later. Transfer drum 11 with transfer paper P attached
is the arrow F to the transfer position 51C of the photoreceptor drum 5.
When the leading edge of the transfer paper P reaches a transfer position 51C where a toner image is formed on the photoreceptor drum 5, a controller 75 (to be described later) controls the pulse motor 7.
By changing the rotational speed of the pulse motor 11-7 in response to the pulse signal outputted to the pulse motor 9, the speed V1 changes from the speed V1 to the same speed as the photosensitive drum 5. It rotates with attenuation.

The transfer drum 11 has a speed V that is the same as that of the photosensitive drum 5. The 1.color image formed on the photoreceptor drum 5 is transferred onto the transfer paper P while rotating. When the transfer paper P passes the rear end of the transfer paper P or the transfer position 51C of the photosensitive drum 5 and the transfer is completed, the control device 75 excites the eccentric cam solenoid 83, which will be described later, to drive the eccentric cam 73a. The photosensitive drum 5 and the transfer drum 11 are spaced apart from each other by 2 to 3 mm. When this separation is completed, the control device 75 outputs a pulse signal to the pulse motor 79 to rotate the transfer drum 11 by the size of the transfer paper P in the direction opposite to the direction of the arrow F. This series of operations is repeated until full-color transfer, in which four colors are superimposed and transferred, is completed. When the transfer is completed, a movable guide plate 61 provided at one end is rotatably supported and the other end is moved toward and away from the surface of the transfer drum 11 by a signal from the control device 75. For example, the transfer paper P attached to the transfer drum 11 is peeled off by the movable guide plate 61, and the movable guide The transfer paper P is guided to the fixing device 21 provided near the plate 61 and is conveyed between the heat roller 63 and the pressure roller 65 in the fixing device 21. After the toner image is heated and fixed on the transfer paper P, it is further conveyed by paper discharge rollers 67 and 69 and discharged onto the collection tray 23.

The cooling fan 71 cools waste heat discharged from the heat roller 63 and the like of the fixing device 21 to prevent the temperature inside the recording apparatus 1 from becoming high.

The eccentric cam 73a controls the contact between the photosensitive drum 5 and the transfer drum 11 or the separation of about 2 to B+nm. This eccentric cam 73a is provided on one side of the recording apparatus 1 between the cooling fan 71 and the fixing device 2, and a solenoid (not shown) is excited by a control signal from a control device 75, which will be described later. Therefore, a point (indicated by a dashed line in the figure) connecting the cooling fan 71 and the fixing device 21, the photosensitive drum 5 and the transfer drum 11, and the developing device support 7 and the control circuit 25 from the point of the eccentric cam 73a is 73b. They are separated by rotating around the point. The trowel separates the photosensitive drum 5 from the transfer drum 11 so that there is a distance of about 2 to 3 mm.

Also, a transfer drum 11 provided at the bottom of the recording device 1
A cleaner (cleaning means) 100 is composed of a box 101 for storing dirt, dust, etc., and a blade 102. This blade 102 is provided to be swingable about a support shaft. This blade 102 is
Due to the driving force of the press solenoid 103 (see FIG. 2), which is excited by a control signal from the control device 75, the transfer paper P comes into contact with the transfer drum 11 when it is not attached to the transfer drum 11, and The transfer paper P is controlled to be separated from the transfer drum 1 when it is attached to the transfer drum 11. The blade 102 is made of a resilient material such as hard rubber, and is biased against the transfer drum 11 when it comes into contact with the transfer drum 14. Below this blade 102 is a box 10.
1 is provided to store dust, dust, etc. on the transfer drum 11 that is scraped off by the blade 102.

FIG. 2 is a block diagram of main parts of the control circuit 25 that controls the image forming apparatus described in FIG. 1.

In the figure, a control device 75 includes a CPU (central processing unit), and performs various controls and calculations. The sensor 15 is provided at the end of the transfer drum 11 and detects when the gripper 13 holds the leading edge of the transfer paper P and outputs a detection signal to the control device 75.

The laser oscillator 76 outputs laser light 2 according to image information from a page memory 85, which will be described later. The paper feed cassette detector 77 detects that a paper feed cassette 17, which will be described later, is inserted into the cassette holding section, and the control device 75
It outputs a detection signal. The pulse motor 79 rotates in response to the number of pulses output from the control device 75, and rotates the photosensitive drum 5 and the transfer drum 11, respectively. For example, if the timing for writing one color of toner from the developer onto the transfer paper P is 5000/< pulses, the writing timing for the first color is 0th square, and the timing for writing the second color is 5000/< pulses. The timing of writing the third color on the pulse is controlled to be the 10,000th pulse. In this way, since the writing timing is controlled according to the number of pulses, color shift during transfer can be prevented. Also, the speed of the transfer drum 11 is set to ■. From v1 or from V1■. The rotational speed of the pulse motor 79 is also controlled in accordance with the pulses output from the control device 75 when changing the rotation speed to . Note that this pulse motor 79 is controlled by the control device 7.
Any rotational drive can be performed by the pulse outputted from 5. The process drive system 81 outputs a drive signal to the charging charge 43, the developing device support 7, etc. in response to a control signal output from the control device 75, thereby controlling the drive thereof.

The eccentric cam solenoid 83 drives the eccentric cam 73a by exciting the solenoid 1 6 in response to a control signal from the control device 75, and the photosensitive drum 5 and the transfer drum 11 are moved between 2 and 3 depending on the amount of eccentricity e. The transfer drum 11 is made to be able to be reversed by being spaced apart from each other by a distance of approximately 1 mm.

When an image signal obtained by reading an image written on an object to be read is input to the control device 75 from a document reading section (not shown), the page memo sensor 85 sends it to a predetermined address under the control of the control device 75. It stores image signals for each color component.

The control device 75 reads the image signal stored at a predetermined address in the page memory 85, forms a toner image on the photoreceptor drum 5, and the toner image formed on the photoreceptor drum 5 is transferred to the photoreceptor. When the photosensitive drum 5 reaches the transfer position 51C and the transfer paper P attached to the transfer drum 11 reaches the transfer position 51C, the transfer drum 11 moves at the speed V of the photosensitive drum 5. A pulse signal that rotates at a constant speed is output to the pulse motor 79.

The control device 75 also outputs a signal to the blade solenoid 10B. This blade solenoid 1 7 id 103 is connected to the blade 1 as described above. When a signal is output from the control device 75, the blade solenoid 103 is turned on, the blade 102 comes into contact with the transfer drum 11, and the control device 7
When the signal output is stopped from 5, the plaid solenoid 10
3 is in the off state, and the blade 102 is in the transfer drum 1
1.

Figures 3(a) and (b) show the paper feed cassette shown in Figure 1.
FIG. 3 is a diagram showing the dimensions of transfer paper stored in the soto 17.

Figure 3 (a) is A3 size transfer paper P, D, = 420
The dimensions are m+n, ρ2=297 mm. Also, Fig. 4(b) shows A4 size transfer paper P, (1 3 = 297
mm,. 1) 4 = 21.0 degrees.

FIG. 4 is a diagram showing the shapes of the photosensitive drum 5 and the transfer drum 11 explained in FIG. 2. This transfer drum 1
] If the diameter D7 of the transfer drum 11 is set to 1.50 mm, for example, the circumference (circumferential length) of the transfer drum 11 becomes 471++++n, and the circumferential length including the toner image of the A4 size transfer paper P is ρ.
When +o=100 mm, the circumference excluding the toner 1 8 image becomes ρ6=371+n+n. Here, for example, the outer peripheral speed V of the photoreceptor drum 5. 100 per second
(2), and while the toner image on the photosensitive drum 5 is being transferred to the transfer paper P attached to the transfer drum 11, the transfer drum 11 is
The outer peripheral speed V. The photosensitive drum 5 and the transfer drum 11 face each other while maintaining contact with each other at a constant speed of 100 nm per second, and transfer the toner image onto the transfer paper P while rotating at a speed of 100+ nm per second. On the other hand, when the transfer from the photoreceptor drum 5 is completed, the drive of the transfer drum 11 is stopped and the solenoid (not shown) of the eccentric cam 73a is energized, thereby increasing the distance between the photoreceptor drum 5 and the transfer drum 11 by 2 to 3 mm, the outer peripheral speed V1 of the transfer drum 11 is 400 mm per second, and the direction of rotation F during transfer is
Rotate in the opposite direction by the length of the toner image. The transfer time when printing four colors on the transfer paper P by these series of operations is such that the transfer drum 11 is always at the speed V. 10 per second
The speed can be increased by about 3 times compared to when transferring at 0 mm. Furthermore, if the length of the toner image is reduced, the speed can be further increased19.

Note that speeding up the transfer time is not affected by the diameter of the photosensitive drum 5.

FIGS. 5(a) to 5(e) are diagrams showing the transfer process by the photosensitive drum 5 and the transfer drum 11. FIG. Figure 5(a)
is a diagram showing a process before transferring the transfer paper P attached to the transfer drum 11. In the figure, the photoreceptor drum 5 is exposed to the laser beam 2 guided from the protective glass 39 at the exposure position 51A on the surface of the drum. The outer peripheral velocity is V while the point is irradiated. Rotate with. This photosensitive drum 5 has a speed of V. to transfer position 5
While rotating by a distance ρ8 to the point 1C, the transfer drum 11 moves at the speed V of the photosensitive drum 5 explained in FIG. 4, for example. 5 from point 57A at outer peripheral speed V1, which is four times faster than
Rotate by distance ρ to point 7B.

Note that the speed V1 of the transfer drum 11 can be arbitrarily set by the number of pulses output to the pulse motor 79. In this manner, in the transfer drum 1120, the transfer paper P is supplied to the transfer drum 11 by the paper feed roller 19, and the leading edge of the transfer paper P is held by the gripper 13. When the leading edge of the transfer paper P is held, the sensor 15 detects the transfer paper P and outputs a detection signal to the control device 75. At the same time, the transfer drum 11 moves at the speed V of the photosensitive drum 5. It rotates by a distance ρ9 to point 57B at a faster speed V1.

FIG. 5(b) is a diagram showing a process in which the toner image on the photosensitive drum 5 is transferred to the transfer paper P attached to the transfer drum 11. The process of transferring onto the transfer paper P is performed using the transfer drum 11.
holds the leading edge of the transfer paper P with the gripper 13 and rotates at an outer circumferential speed V1, and the transfer paper P held by the gripper 13 passes the transfer position 51C of the photoreceptor drum 5 and is transferred to the photoreceptor. When the toner image on the photosensitive drum 5 is transferred to the transfer paper P, the speed of the transfer drum 11 is determined by the speed of the photosensitive drum 5.
It rotates at a constant speed of 0 while maintaining contact with the photoreceptor drum 5.

FIG. 5(e) shows that after the first color of the toner image on the photosensitive drum 215 is applied to the transfer paper P attached to the transfer drum 11 in FIG. 5(b), the transfer drum 11
FIG. 3 is a diagram illustrating a process of rotating in a direction opposite to the direction during transfer. After the transfer of the first color of the toner image on the photoreceptor drum 5 to the transfer paper P is completed, the transfer paper P is moved to the transfer position 51 of the photoreceptor drum 5.
After passing point C, the control device 75 controls the pulse motor 7
The pulse motor 79 stops outputting the pulse signal to the pulse motor 79.
By stopping the driving of the transfer drum 11, the transfer drum 11 is stopped. After this, the control device 75 controls the eccentric cam solenoid 8.
By energizing the solenoid No. 3, the eccentric cam 73a
Due to the eccentricity e, the photosensitive drum 5 and the transfer drum 11 are separated from each other by about 2 to 3 mm. and,
The control device 75 outputs a pulse signal to the pulse motor 79 to cause the transfer drum 11 to rotate at an outer circumferential speed V1 in a direction opposite to the rotation direction in which the toner image on the photoreceptor drum 5 was transferred, so that the transfer drum 11 rotates to the length of the toner image. It just rotates backwards. and,
The control device 75 stops outputting the control signal to the eccentric cam solenoid 83 and de-energizes the solenoid, thereby bringing the photosensitive drum 5 and the transfer drums 11 and 22 into contact, and further sends a pulse signal to the pulse motor 79. When output, the photoreceptor drum 5 and transfer drum 11 have an outer peripheral speed V. to rotate to the second, third, and fourth colors respectively.
The color is transferred.

6(a) and 6(b) are schematic diagrams of the structure of the paper feed cassette 17. For example, FIG. 6(a) shows an A3 size paper feed cassette 17, and FIG. 6(b) shows an A4 size paper feed cassette.

The A3 size paper feed cassette shown in FIG. 6(a) has a display panel (not shown) with transfer paper on the surface facing the insertion direction (in the direction of arrow H) into the cassette holder that holds the paper feed cassette 17 in the recording apparatus 1. A coupling section 87 is provided which generates a signal for displaying the size of the transfer paper P or informing the control device 75 of the size of the transfer paper P that can be used. This joint 87
has four square steps on the surface to be inserted into the cassette holder of the recording device 1, and the size of the transfer paper P stored in the paper feed cassette 17 can be measured between these square steps. A rectangular member 89a shown is placed at the left end of the step. The A423 size paper feed cassette 17 in FIG. 6(b) has the same structure as that in FIG. 6(a) except for the joining part 87, and the member indicating the size of the transfer paper P in the joining part 87 is the member 39a from the left end of the step.
, 89b are inserted.

FIG. 6(c) is a configuration diagram of a detection unit 91 that detects the size of transfer paper stored in the paper feed cassette 17 provided in the cassette 1/holding part of the recording apparatus 1. When inserted into the cassette holder, the paper feed cassette 17
A rectangular member 8 fitted between the steps of the joint portion 87 of
Four switches 93a to 93d are provided to detect which member is fitted by contacting the switches 9a. These switches 93a to 93d are each switch 93a to 93d.
A rectangular parallelepiped claw 95 is provided on the paper feed cassette 17 side of each paper feed cassette 17. When the paper feed cassette 17 is inserted, this claw 95 is inserted into the square member 89a of the joint portion 87 of the paper feed cassette 17.
, 89b and is provided in the recording device 1.
7 detects the claw 95 and outputs a detection signal to the control device 75 to detect the size of the transfer paper stored in the paper feed cassette 17 based on the number of eight members that come into contact with the claw 95. Become.

Next, the operation of this image forming apparatus with the above configuration will be explained.

First, turn on the power switch of the device to start the system. When the copy start key is pressed after setting the paper cassette 17 and specifying the size and transfer density of the transfer paper P, the device starts reading the original placed in the original reading section (not shown). Start. The image information of the document read by the document reading section is separated into each color component.
It is sent to the control device 75. The control device 75 temporarily stores image information of the document for each color component in the page memory 85. The control device 75 sequentially reads the image information stored in the page memory 85 for each color and sends it to the semiconductor laser oscillator 76, which is an oscillator using a conductor laser. Laser light 2 oscillated from this semiconductor laser oscillator 76 is shaped by a shaping optical system and deflected by a polyhedral rotating mirror 29.

The deflected laser beam 2 passes through the fθ lens 31 25, is reflected by the mirrors 33 and 35, passes through the aspherical lens 37 and the protective glass 39, and is directed to the necessary point 51A on the drum surface of the photoreceptor drum 5. Scanning exposure is performed by spot imaging with high resolution. The photosensitive drum 5 is charged in advance by a charger 43, and is neutralized by the laser beam 2 irradiated through the three protective glasses to form an electrostatic latent image corresponding to the image of the document.

The photosensitive drum 5 on which this electrostatic latent image is formed rotates at an outer peripheral speed vo, and at a developing position 51B, a developing sleeve 49 carrying the yellow toner contained in the developing device 9A
Contact A. Due to this contact, the yellow toner is attracted to the electrostatic latent image on the photoreceptor drum 5, and a toner image is formed.

The photoreceptor drum 5 on which the toner image has been formed continues to rotate while maintaining contact with the transfer drum 11 at a speed VO.

While this photosensitive drum 5 continues to rotate, the transfer drum 1
1, the surface of the drum is charged by the charger 59, the paper feed roller 19 is driven, and the leading edge of the transfer paper P stored in the paper feed cassette 1/17 is fed to the gripper 13.

The supplied transfer paper P electrostatically adheres to the charged surface of the drum and is gripped by the gripper 1 of the transfer drum 11.
3. When the transfer paper P is held by the gripper 13, the sensor 15 detects that the transfer paper P is held and outputs a detection signal to the control device 75. Transfer drum 1
1 is an outer circumferential speed v1 while maintaining contact with the photosensitive drum 5 in the direction of arrow F with the transfer paper P held by the gripper 13 up to the toner image at the transfer position 51C of the photosensitive drum 5. Continue to rotate. This transfer drum 11
continues to rotate at speed V1, the control device 75:
The timing for transferring the toner image formed on the photosensitive drum 5 onto the transfer paper P is calculated from the image signal stored at a predetermined address in the page memory 85. When the transfer paper P held by the gripper 13 of the transfer drum 11 approaches the transfer position 51C of the photosensitive drum 5, the control device 75
outputs a pulse signal to the pulse motor 79. The pulse motor 79 rotates in response to a pulse signal from the control device 75, thereby moving the transfer drum 11 to a speed V constant to the speed of the photoreceptor drum 5. It rotates at the peripheral speed of . V while the photosensitive drum 5 and the transfer drum 11 maintain contact with each other. By rotating at a speed of , the toner image on the photosensitive drum 5 is transferred onto the transfer paper P of the transfer drum 11. In this manner, when the first color transfer to the transfer paper P is completed, the control device 75 stops outputting the pulse signal to the pulse motor 79. By stopping the driving of the pulse motor 79, the transfer drum 11 is also stopped.

Thereafter, the control device 75 energizes the solenoid of the eccentric cam solenoid 83 so that the distance between the photosensitive drum 5 and the transfer drum 11 becomes approximately 2 to 3 mm according to the eccentricity e of the eccentric cam 73a. Separate. Then, the control device 75 causes the pulse motor 79 to control the photoreceptor drum 5.
1. The outer peripheral speed in the direction opposite to the direction of rotation in which the toner image was transferred.■
1 outputs a pulse signal that causes the transfer drum 11 to rotate.

By driving the pulse motor 79, the transfer drum 11 is rotated by the length of the toner image, 1lto. On the other hand, after the photosensitive drum 5 is transferred to the transfer drum 11, a cleaner 5
3, the toner adhering to the drum surface is removed, and the erase static electricity lamp 55 removes static electricity from the surface of the drum. By repeating these operations for each color, control is performed when full-color transfer is completed by overlapping transfer using toner of each of the four colors from the yellow developing sleeve 49A of the developing device 9A to the black developing sleeve 49D of the developing device 9D. The device 75 outputs a drive signal to the process drive system 81 to turn on the pred solenoid 103, and moves the movable guide plate 61 from a point 61a about 2 to 3 cm away from the transfer drum 11.
It is rotated to the lb point and brought into contact with the transfer drum 11.

With this blade 103 in contact with the transfer drum 11, the transfer drum 11 rotates one rotation or more, and the transfer drum 11
The dust and dirt adhering to the box 101 are scraped off and stored in the box 101.

Then, when the gripper 13 faces the paper feeding position, it stops rotating. Next, the control device 75 stops outputting the signal to the blade solenoid 103. As a result, the blade solenoid 103 is turned off 2 9 , and the blade 102 is separated from the transfer drum 11 .

On the other hand, the transferred transfer paper P is peeled off from the transfer drum 11 by the movable guide plate 61 and guided between the heat roller 63 and the pressure roller 65 of the fixing device 21 to have the toner image fixed thereon. is transported and discharged onto the collection tray 23.

As described above, the cleaner 100 is provided on the transfer drum 11 that holds the transfer paper P to which the toner image is transferred, and the blade 101 of the cleaner 100 is moved to the transfer drum 11 at a timing when the transfer drum 11 is not holding the transfer paper P. Since dust and dirt on the transfer drum 11 are removed by contact with the transfer drum 11, it is possible to prevent stains on the back of the transfer paper P, and also to prevent unevenness from occurring on the transfer paper P, thereby obtaining a uniform image. It is possible to do this.

Further, when transferring 1.color from the photoreceptor drum 5 to the transfer paper P placed on the transfer drum 11, the outer peripheral speed of the photoreceptor drum 5 and the transfer drum 11 is set to a constant speed of 30 Vo, and the transfer of each color is performed. When the process is completed, the transfer drum 1
Since the photosensitive drum 1 is rotated by the length of the toner image in a direction opposite to that during transfer at a faster speed than the photosensitive drum 5, it is possible to speed up the transfer time.

Further, in this embodiment, since there is no need to add a special circuit or the like to control the speed of the transfer drum 11, the apparatus does not become complicated.

Furthermore, this embodiment is not limited to application to color copying machines, but can also be applied to, for example, facsimile machines, monochrome copying machines, etc. that read and transfer documents.

[Effects of the Invention] As explained above, according to the present invention, even if dust or the like adheres to the rotating body, the back side of the image forming medium can be prevented from being stained, and the image forming medium held on the rotating body can be To provide an image forming apparatus that can prevent unevenness in transfer caused by unevenness on a medium and obtain a uniform image.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, in which Fig. 1 is a sectional view schematically showing the internal structure of a color copying machine, Fig. 2 is a block diagram showing the schematic structure of the control circuit, and Fig. 3 ( a) ,
(b) is a diagram for explaining the dimensions of the transfer paper, FIG. 4 is a diagram showing the dimensions of the photosensitive drum and the transfer drum, and FIG.
) to 6(c) are diagrams for explaining the transfer process of the photosensitive drum and the transfer drum, and FIGS. 6(a) to 6(c) are perspective views showing the schematic configuration of the paper feed cassette and the cassette holding section. 3... Exposure optical system (image forming means), 5... Photosensitive drum (image carrier), 9A, 9B, 9C, 9D... Developing device (developing means), 11... Transfer drum ( holding means)
, 13...Gripper 5...Charger, 10
0...Cleaner (cleaning means), 101...Box, 10
2... Blade, 103... Blade solenoid,
P...Transfer paper (image forming medium).

Claims (1)

[Scope of Claims] An image forming means for forming an electrostatic latent image on an image carrier, a developing means for developing the electrostatic latent image formed by this image forming means, and a developed image developed by this developing means. An image characterized by comprising a holding means for holding an image forming medium to which a dye image is transferred, and a cleaning means for cleaning the holding means when no image forming medium is held on the holding means. Forming device.