JPH0540390A - Multicolor image formation device - Google Patents

Abstract

PURPOSE:To obtain an image which has small color difference from an input image by preventing speed variation due to the vibration of a photosensitive body belt itself. CONSTITUTION:An electrostatic charger 21 and plural image recording parts consisting of image writing devices 22, 26... and development devices 24, 28... be arranged in order along the surface of the beltlike photosensitive body 3 and the photosensitive body 3 is passed once to form plural different-color toner images. This multicolor image formation device is provided with backup members 22a, 24b, 26a, 28b... for the photosensitive body at positions opposite the respective image writing devices and development devices, and at least two of the image writing devices 22, 26... are equalized in photosensitive body peripheral length. Consequently, vibration is caused, but they vibrates all synchronously to almost the same extent, and relative variation between respective colors is reduced to obtain the excellent image which is free from color slurring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a plurality of recording sections each comprising a charging device, an exposure system (image writing device) and a developing device, which are arranged around a belt-shaped photoconductor so that each color can be obtained during one rotation of the photoconductor. The present invention relates to a multi-color image forming apparatus for forming a toner image of 1) on a photoconductor and transferring the toner image of each color onto recording paper in one transfer process.

[0002]

2. Description of the Related Art The present applicant has already filed Japanese Patent Application No. 3-2107.
In No. 2, a plurality of recording portions including a charging device, an exposure system and a developing device are arranged around a belt-shaped photoconductor, and a toner image of each color is formed on the photoconductor during one rotation of the photoconductor. A multicolor image forming apparatus has been proposed in which toner images of respective colors are transferred onto recording paper in a single transfer process. A problem in such a multi-color image forming apparatus is color misregistration of each toner image. Regarding this color shift, it is separated into the photoconductor advancing direction and the direction orthogonal thereto, but what is discussed in the present invention is the color misregistration in the photoconductor advancing direction.

For example, C (cyan), M (magenta),
When forming a full-color image with four colors of Y (yellow) and K (black), when the recorded toner image causes a slight misalignment in the moving direction of the photoconductor, a difference in hue occurs on the recording paper. , Causes a color difference from the original (input image) and deteriorates the image quality.

This effect is particularly great at the image writing position and greatly affects the color misregistration. Writing is normally performed by irradiating the photosensitive member with light by electrical timing control, and accurate writing is performed. However, when speed fluctuation occurs in the photosensitive member facing the exposure system, the position to be originally written on the photosensitive member. Occurs, and the position of the toner image shifts.

Further, even at the developing position, it is affected by minute speed fluctuations of the photosensitive member, which affects color shift (density shift).

The cause of these color misregistrations is speed fluctuation of the photoconductor (displacement fluctuation is obtained by integrating the speed fluctuation). Therefore, by improving the rotation accuracy of the photoconductor driving member such as a motor. In some cases, improvement can be expected.

[0007]

However, in the belt-shaped photoconductor, the rigidity of the belt itself is small, so even if the rotation accuracy of the photoconductor drive member is improved, it is not transmitted to the photoconductor side. I can't hold back.

Further, the belt itself vibrates due to load fluctuations of the constituent members (cleaning device, etc.) arranged around the photosensitive member. The vibration caused by the belt gives a stretching motion to the belt, and gives a displacement variation in the belt traveling direction.

As a result, vibrations of different modes (frequency, displacement) occur at each image writing position and developing position,
The deterioration of image quality as described above becomes a problem.

The present invention has been made in view of such a situation, and an object thereof is to prevent the speed fluctuation due to the vibration of the photosensitive belt itself as described above and obtain an image with a small color difference from the input image. It is to provide a multicolor image forming apparatus capable of performing the same.

[0011]

In the present invention, a backup member for the photoconductor is provided at a position facing the image writing device and the developing device for the belt-shaped photoconductor, and the peripheral length of the photoconductor between the image writing devices is reduced. The photoconductor peripheral length between the developing devices and the photoconductor peripheral length between the image writing device and the developing device are the same, and the vibration mode (frequency, displacement) generated between them
Is made uniform and the vibration modes at each image writing position are synchronized, and as a result, the influence of speed fluctuation is suppressed.

That is, the multicolor image forming apparatus of the present invention is
A plurality of image recording units including a charging device, an image writing device, and a developing device are sequentially arranged along the surface of the belt-shaped photoconductor, and a plurality of toner images of different colors can be obtained by one pass of the photoconductor. In a multicolor image forming apparatus in which the image recording section of the image forming unit sequentially forms the same or different positions of the photoconductor, a backup member for the photoconductor is provided at a position facing each image writing device and the developing device, and It is characterized in that at least two photoconductors have the same circumference.

In this case, it is desirable that at least two photoconductor peripheries between the developing devices are the same, and at least two photoconductor peripheries between the image writing device and the developing device are the same. Further, it is more preferable that at least two photoconductor peripheral lengths between the image writing devices and at least two photoconductor peripheral lengths between the developing devices are all the same.

As the backup member, either a backup roll or a fixed member can be used.

[0015]

According to the present invention, a plurality of image recording portions including a charging device, an image writing device, and a developing device are sequentially arranged along the surface of a belt-shaped photosensitive member, and a plurality of image recording portions are formed by one passage of the photosensitive member. In a multicolor image forming apparatus that sequentially forms toner images of different colors by the plurality of image recording units at the same position or different positions of the photoconductor, a backup member for the photoconductor at a position facing each image writing device and the developing device. Since the peripheral lengths of at least two photoconductors between the image writing devices are made the same, the minute speed fluctuation state of the belt-shaped photoconductor becomes the same at least at the image writing position, and vibration occurs, but all are synchronized. In addition, the same degree of occurrence occurs, and as a result, the relative variation between the colors is reduced, and it becomes possible to obtain a good image with no color shift.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The principle and embodiments of the multicolor image forming apparatus of the present invention will be described below with reference to the drawings. FIG. 2 schematically shows a part of an image writing device and a developing device around a belt-shaped photosensitive member of a conventional multicolor image forming apparatus. The belt-shaped photosensitive member 3 is stretched between the driving roller 4a and the idler roller 4c by applying tension so as to rotate in the arrow direction. Around it, the first charger 21 and the first exposure device 2
2, first developing device 24, second charging device 25, second exposure device 2
6, the second developing device 28 and the like are arranged. The state of the belt-shaped photoconductor 3 is originally designed by assuming a straight line shown by a solid line, but when it is rotationally driven by the drive roller 4a, a vibrating state shown by a dotted line in FIG. 2 is obtained. This vibration mode is determined by the peripheral speed of the belt 3, the tension on the belt 3, the load state of the cleaning device on the belt 3, and the like.

In such a vibrating state, the belt 3 expands and contracts, and different vibration modes occur at the positions of the image writing devices 22, 26, ... For the respective colors, so that the written image is relatively displaced. Color shift occurs after development.

In order to prevent this, even if a backup roll is provided to obtain a predetermined set position accuracy at each image writing position, the vibration cannot be made uniform,
Vibrations of different frequencies and different displacements are generated, which also affects the traveling direction of the photoconductor 3. As a result, different displacement fluctuations occur in the advancing direction of the photoconductor 3, causing color shifts due to relative fluctuations between the colors. Also, the developing device 2 for each color
Similarly, the vibration modes are different at positions 4, 28, ... As a result, a color shift (density shift) occurs due to a relative speed change between the photoconductor 3 and the developing roll.

Therefore, in the present invention, as schematically shown in FIG. 1 a part of the image writing device and the developing device around the belt-shaped photosensitive member, the image writing devices 22 and 2 of each color are shown.
6 ... Positions and developing devices 24, 28 .... Backup rolls 22a, 26a ... 24b, 28b facing the positions
・ Place. Arranged in this way is for each element 2
This is for the purpose of obtaining a predetermined set position accuracy of the belt 3 with respect to 2, 26 ,. Here, the image writing devices 22, 26 ... And the developing devices 24, 28 ... Are brought into contact with the backup rolls 22a, 26a ... 24b, 28b.

By the way, the natural frequency of the belt 3 is defined by the spring constant and the mass, and the frequency is defined by the natural frequency, (natural frequency) ∝ (spring constant / mass) ^1/2
Have a relationship. The spring constant of the belt 3 is the rigidity of the belt,
It is determined by the tension of the belt and the shape of the belt.

Further, the backup rolls 22a, 26a
.. 24b, 28b ... are approximated by a vibration system with free ends, and the natural frequency is defined by the backup roll spacing, belt rigidity (elastic coefficient, moment of inertia), and belt mass. If they are the same, the natural frequencies are also the same (see Chapter 8 of "Mechanical Design Handbook" published by Maruzen Co., Ltd.).

In the present invention, as shown in FIG.
Backup roll spacing S ₁ between the image writing device 22, 26 ... position of each color, each color developing devices 24, 28 ...
The backup roll interval S ₂ between the positions and the backup roll interval S ₃ between the image writing devices 22, 26 ... Positions and the developing devices 24, 28 .. Since the tension applied to 3 has almost the same value, the natural frequencies of the backup rolls 22a, 26a ... 24b, 28b ...
(Between the image writing devices 22, 26 ... Positions of each color, between the developing devices 24, 28 ... Position of each color, between the image writing devices 22, 26 ... Position and developing devices 24, 28.
Will be the same. As a result, the backup roll 22a,
The vibrations generated between 26a ... 24b and 28b ... are synchronized, and the vibration mode of the belt 3 becomes constant.

This is for each backup roll 22a, 2
Since the conditions between 6a ... 24b, 28b ... (backup roll interval, belt rigidity (elastic coefficient, moment of inertia), belt mass) are constant, the belt 3 at the image writing position and the developing position is Although the minute speed fluctuation state is the same and vibration occurs, they all occur in synchronization and at the same level. As a result, the relative variation between the colors is reduced, and as a result, it is possible to obtain a good image with no color shift.

In the above, the intervals S ₁ , S ₂ , and S ₃ must be the same in at least two places (that is, the case where three or more image writing devices and developing devices are arranged). ). The intervals S ₂ , S ₃
Even if is not constant, it is necessary for the minimum interval S _{1 to} have the same value in at least two places in order to eliminate color misregistration,
Desirably, the spacing S ₂ also has the same value in at least two places, and further, it is desirable that the spacing S ₃ also has the same value in at least two places. Furthermore, it is more preferable that S ₁ = S ₂ = S ₃ , but it is generally difficult to arrange such members due to the arrangement of the members, so it is preferable that S ₁ = S ₂ . Further, as the backup member, a fixed member may be used instead of the backup roll that is driven to rotate. In the former case, since there is no friction, the belt-shaped photosensitive member 3 can be rotated by a weak driving force, but on the other hand, vibration may occur due to eccentricity. On the other hand, when the fixed member constitutes the backup member, a large driving force is required to cope with friction, but the possibility of vibration is low.

Next, FIG. 3 shows a side view of an embodiment of a multicolor image forming apparatus in which a backup roll is provided in contact with the back surface of a belt-shaped photosensitive member, satisfying the above conditions. The multi-color image forming apparatus 50 includes an image forming section 1 above the apparatus and a sheet feeding section 2 below. In the image forming unit 1, the translucent belt-shaped photosensitive member 3 is vertically arranged around the driving roller 4a, the idler rollers 4b to 4d, and the like. The belt-shaped photoconductor 3 is moved by the drive roller 4a so that the arrow A
Driven to rotate. Around the belt-shaped photoreceptor 3, the first image recording unit 5, the second image recording unit 6, the third image recording unit 7, the fourth image recording unit 8, the pre-transfer corotron 9, the developing density sensor 10b, A light guide unit 11, a transfer unit 12, a pre-cleaning corotron 13, a cleaning device 14, and a ground strip 15 are arranged. The components forming each of these image recording units and the like are arranged along a substantially vertical surface of the belt-shaped photoconductor 3. Further, inside the lower end portion of the belt-shaped photosensitive member 3, there are disposed static elimination lamps 16 that irradiate the belt-shaped photosensitive member 3 from the inside before and after the transfer section 12.

The transfer section 12 is a transfer corotron 12a.
Also, the peeling corotron 12b is provided, and is arranged at the lowermost end of the vertically long belt-shaped photoconductor 3 so that the paper conveyance direction is substantially horizontal. Further, adjacent to the transfer unit 12, a sheet conveying device 17 and a conveying roller 18 are provided on the sheet introducing side, and a conveying belt 20 for conveying the recording sheet after transfer to the fixing device 19 is provided on the sheet discharging side. ..

The first image recording section 5 includes the first charger 2
1. Laser light source (not shown), rotary polygon mirror 22b irradiated with laser light, motor 22c for rotating and driving this rotary polygon mirror 22b, lenses 22d and 22e, mirrors 22f and 22.
A first exposure device 22, a first potential sensor 23, a first developing device 24, and the like, which are configured by g and the like, are provided. In addition, the second image recording unit 6 includes a second charger 25, a second exposure device 26 including a light emitting diode array (LED array), a second potential sensor 27, a second developing device 28, and the like. Similarly, the third and fourth image recording units 7 and 8 are also provided with the third and fourth chargers 2.
9, 33, 3rd, 4th exposure apparatus 30, 34, 3rd, 4th
Potential sensors 31, 35, third and fourth developing devices 32, 36, etc. are provided. Then, each exposure device 22, 26, 30,
At the position 34, the backup rolls 22a, 26a, 30a, 34a are provided on the back surface of the photoconductor 3 and the intervals S between them are equal.

The first, second, third and fourth image recording units 5, 6, 7 and 8 are, for example, black and red, respectively.
An image of each color is formed on the belt-shaped photoconductor 3 by using toners of each color of green and blue. In addition, each potential sensor 23,
Reference numerals 27, 31, 35 detect the surface potential of the belt-shaped photoconductor 3 in each of the image recording units 5, 6, 7, 8 and are controlled by a control circuit (not shown) so that the surface potential is set to a predetermined potential. The chargers 21, 25, 29, 33 are controlled. Further, the final development density is detected by the development density sensor 10b,
In order to obtain an appropriate density, each image recording unit 5, 6,
The development conditions in 7 and 8 are adjusted. The developing density sensor 10b has color sensor elements corresponding to the respective colors.
The photoconductors 3 are arranged in a direction perpendicular to the moving direction. Each of the developing devices 24, 28, 32, 36 includes developing rolls 24a, 28a, 32a, 36a and backup rolls 24b, 28b, 32b, 36b. These backup rolls 24b, 28b, 32
The intervals between b and 36b are arranged at the same distance S. Also, the backup rolls 22a, 24b and 26a
And 28b, 30a and 32b, and 34a and 36b have the same spacing and are held at S '. The second, third and fourth
Since the developing devices 28, 32, and 36 must not disturb the toner image formed on the photoconductor 3 by the preceding developing device, a non-contact type developing device is adopted.

Further, the sheet feeding section 2 includes an intermediate tray 41 having sheet feeding devices 37, 38, 39 and 40, sheet feeding trays 42 and 43, a large capacity tray 44, and a sheet reversing section 4.
5 etc. are arranged. The intermediate tray 41 is provided with a switching claw device 46 having a plurality of switching claws 46a, 46b, 46c. Incidentally, 47 and 48 are conveying rolls, and 49 is a reversing roll.

Next, a circuit configuration for forming an image in the above-described multicolor image forming apparatus 50 will be described with reference to FIG. Image signals from the image input device 51, the computer 52, the communication device 54 that performs communication via the communication line 53, and the like are supplied to the multicolor image forming device 50 through the image processing device 55. The image signal supplied to the image processing device 55 is first to
The fourth color component signal is separated into, for example, four color component signals of black, red, green, and blue, and the first color component signal is substantially not delayed and the first exposure device 22 of the first recording unit 5 is separated. And the second to fourth color component signals are supplied to the second to fourth recording units 6 to 8 via the first to third delay circuits 57 to 59, respectively.
~ It is supplied to the fourth exposure device 26, 30, 34. In addition,
Delay time T ₁ in the first to third delay circuits 57 to 59,
T ₂ and T ₃ correspond to the distances of the exposure positions of the belt-shaped photoconductor 3 by the second to fourth exposure devices 26, 30, and 34 from the exposure position of the first exposure device 22. However, each of the delay circuits 57 to 59 is a variable delay circuit,
The delay time can be slightly changed based on an instruction from the microcomputer 60. As the delay circuit, for example, a delay circuit using a BBD (bucket relay type charge transfer device) can be adopted, and the delay is performed by changing the frequency of the transfer clock for the BBD according to the control data from the microcomputer 60. The time can be changed continuously. Further, switching circuits 61 to 64 controlled by the microcomputer 60 are provided in the paths of the respective color component signals, and these switching circuits 61 to 64 are connected to the pattern generation circuit 65 controlled by the microcomputer 60. Test pattern signal is supplied.

The first to fourth chargers 21, 25, 29, 33 of the recording units 5 to 8 and the first to fourth exposure devices 22, 2 are also provided.
6, 30, 34, first to fourth developing devices 24, 28, 32,
The operation of 36 is controlled by the control device 66 that operates based on an instruction from the microcomputer 60. Further, an operation panel 67 for inputting various instructions to the copying machine and a non-volatile memory 68 for storing control data for the delay circuits 57 to 59 are connected to the microcomputer 60.

First, regarding the image forming mode, red and black 2
A case of forming a color image will be described as an example. In this case, when the operation panel 67 is instructed to operate the apparatus in the image forming mode and further an image is formed in two colors of red and black, the microcomputer 60 causes the switching circuits 61 to 64 to perform color separation. While being switched to the circuit 56 side, the control device 66 enables only the first and second image recording units 5 and 6, and disables the third and fourth image recording units 7 and 8. This operation / non-operation switching is performed by, for example, the first and second chargers 21, 2
5, by applying a predetermined operating voltage or bias voltage only to the first and second exposure devices 22 and 26 and the first and second developing devices 24 and 28. ..

The belt-shaped photosensitive member 3, which is rotationally driven in the direction of arrow A by the driving roller 4a, firstly includes the first image recording unit 5
In FIG. 5, the first charger 21 uniformly charges the toner as shown in FIG. As a result, the surface potential of the photoconductor 3 becomes, for example, V _P (where V _P is a negative value). Next, in the first exposure device 22, the surface of the photoconductor 3 is exposed by the light L _k from the laser modulated by the signal corresponding to the black of the image, and the potential of the exposed portion is, for example, V _R (however,
V _R decreases to a negative value (see (b) in the figure). Next, this exposed portion advances to the first developing portion 24, where it is developed with the black toner T _k (see FIG. 7C). Even after this development, the surface potential of the black image portion remains lowered.

Next, the black developing portion advances to the second image recording portion 6, is charged again by the second charger 25, and the photoconductor 3
Surface potential rises to near V _P (see FIG. 7D). Next, in the second exposure device 26, the surface of the photoconductor 3 is exposed by the light L _R from the light emitting diode array modulated by the signal corresponding to the red color of the image, and the potential of the exposed portion drops to V _R. .. (Refer to the same figure (e)). Next, this exposed portion advances to the second developing portion 28 where it is developed with the red toner T _R (see FIG. 7F). After this red development, the surface potential of the red image portion remains low.

The belt-shaped photosensitive member 3 further advances and passes through the third and fourth image recording portions 7 and 8, but since these image recording portions 7 and 8 are inoperative, toner images of respective colors are not formed. Not affected.

Then, the charge of the toner image is adjusted by the pre-transfer corotron 9 and the charge eliminating lamp 16 to be in a state suitable for transfer.

When the toner image of each color reaches the transfer unit 12, in synchronization therewith, the recording paper is conveyed from any of the trays 41 to 44 of the paper feeding unit 2 by any of the paper feeding devices 37 to 40. The sheet is fed to the image forming unit 1 side along B, is further conveyed by the sheet conveying device 17 and the conveying roller 18, and comes into contact with the surface of the belt-shaped photoreceptor 3.

In the transfer section 12, the toner image of each color is transferred from the surface of the belt-shaped photoconductor 3 to the recording paper by the electric field from the transfer corotron 12a. The recording paper after the transfer is separated from the belt-shaped photoconductor 3 by the separating corotron 12b and is conveyed to the fixing device 19 by the conveying belt 20 to fix the toner image on the recording paper. The recording paper after fixing advances in the direction of arrow C, for example, and is directly discharged out of the apparatus by the conveying roller 47 with the image surface facing upward. When the image surface is to be ejected downward, the sheet is once conveyed by the conveying rollers 48 and 49 in the directions of arrows D and E, and then the conveying rollers 48 and 49.
The rotation of 9 is reversed, and it is carried out of the machine by the carrying roller 47.

The toner remaining on the belt photosensitive member 3 after the transfer is removed by the cleaning device 14 after the charge state is adjusted by the charge eliminating lamp 16 and the bri-cleaning corotron 13. Further, the electric charge remaining on the photoconductor 3 is discharged through the ground strip 15 to prepare for the next image forming cycle.

In the case of double-sided copying, the recording sheet after fixing advances in the direction of arrow D, is conveyed to the sheet reversing section 45 of the sheet feeding section 2 by the conveying roller 48, and is once in the direction of arrow E by the reversing roller 49. After being conveyed, the rotation of the reversing roller 49 is reversed, the conveying direction of the recording paper is reversed in the arrow F direction, and the recording paper is stored in the intermediate tray 41 with the image surface facing upward. At this time, by changing the postures of the switching claws 46a, 46b, 46c of the switching claw device 46 according to the size of the recording paper,
The recording paper is stored in the intermediate tray 41 from an appropriate position. This recording paper is sent to the transfer unit 12 of the image forming unit 1 again by the paper feeding device 37, and the image on the back surface of the recording paper is formed this time. In the case of double-sided printing, it goes without saying that a toner image is formed by the image forming unit 1 on each side.

Further, in the case of making two copies by overlapping on one side, the recording paper is directly fed from the transport roller 48 to the intermediate tray 4.
It may be transported to 1.

The above is a description of the case of forming a two-color image of red and black, but the image forming operation is clear from the above description even when the image recording sections 7 and 8 are also operated to form an image in full color. Let's see

As described above, each exposure device 22, 26, 3
The intervals between the backup rolls 22a, 26a, 30a, 34a provided on the back surface of the belt-shaped photoconductor 3 at the 0, 34 positions are kept equal to each other and kept at a constant value S.
Backup rolls 24b, 28b, 32b, 36b provided opposite to the developing rolls 4, 28, 32, 36.
The distances between the backup rolls 22a and 24b, 26a and 28b, 30a and 3 are also kept at the same distance S.
The distances 2b, 34a and 36b are also equal, and by holding at S ', the image writing position (exposure device 22, 26,
30 and 34 positions) and developing position (developing devices 24, 28, 3)
The minute speed fluctuation state of the belt-shaped photosensitive member 3 at the positions (2, 36) becomes the same, and vibrations occur, but they all occur in synchronization and at the same degree. As a result, relative fluctuations between the colors are generated. Is reduced, and a good image without color shift can be obtained.

The multicolor image forming apparatus of the present invention has been described above based on the embodiments, but the present invention is not limited to these embodiments and various modifications can be made.

[0045]

As described above, according to the multicolor image forming apparatus of the present invention, a plurality of image recording units including a charger, an image writing device, and a developing device are provided along the surface of a belt-shaped photoconductor. In a multicolor image forming apparatus that sequentially arranges toner images of a plurality of different colors by one pass of the photoconductor at the same position or different positions of the photoconductor by the plurality of image recording units, writing each image Since a backup member for the photoconductor is provided at a position facing the developing device and the developing device, and at least two photoconductor peripheral lengths between the image writing devices are made the same, a minute speed fluctuation state of the belt-shaped photoconductor at least at the image writing position. , But the vibrations occur, but they all occur at the same time and at the same level, and as a result, the relative variation between each color is reduced and a good image without color misregistration can be obtained. So that it is.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a part of an image writing device and a developing device around a belt-shaped photoconductor for explaining the principle of a multicolor image forming apparatus of the present invention.

FIG. 2 is a view similar to FIG. 1 of a conventional example.

FIG. 3 is a side view of one embodiment of the multicolor image forming apparatus of the present invention.

FIG. 4 is a diagram showing a circuit configuration for forming an image of the apparatus of FIG.

5 is a diagram showing the relationship between each process and the surface potential in the apparatus of FIG.

[Explanation of symbols]

1 ... Image forming unit, 2 ... Paper feeding unit, 3 ... Belt-shaped photoconductor, 4
a ... driving roller, 4b to 4d ... idler roller, 5 ... first image recording section, 6 ... second image recording section, 7 ... third image recording section, 8 ... fourth image recording section, 9 ... pre-transfer corotron 10b ... Development density sensor, 11 ... Light guide part, 1
2 ... Transfer part, 12a ... Transfer corotron, 12b ... Peeling corotron, 13 ... Pre-cleaning corotron, 14 ...
Cleaning device, 15 ... Ground strip, 16 ... Static elimination lamp, 17 ... Paper transport device, 18 ... Transport roller, 19
... fixing device, 20 ... transport belt, 21 ... first charger, 2
2 ... First exposure device, 22a, 26a, 30a, 34a,
24b, 28b, 32b, 36b ... Backup roll, 22b ... Rotating polygon mirror, 22c ... Motor, 22d, 2
2e ... Lens, 22f, 22g ... Mirror, 23 ... First potential sensor, 24 ... First developing device, 25 ... Second charger, 26 ... Second exposure device, 27 ... Second potential sensor, 28 ... Second developing Container, 29 ... Third charger, 30 ... Third exposure device, 31 ... Third potential sensor, 32 ... Third developing device, 33 ... Fourth charger,
34 ... 4th exposure device, 35 ... 4th electric potential sensor, 36 ... 4th developing device, 24a, 28a, 32a, 36a ... Developing roll, 37, 38, 39, 40 ... Paper feeder, 41 ... Intermediate tray, 42 , 43 ... paper feed tray, 44 ... large capacity tray,
45 ... Paper reversing section, 46 ... Switching claw device, 46a, 46
b, 46c ... Switching claws, 47, 48 ... Conveying rolls, 49 ...
Inversion roll, 50 ... Multicolor image forming apparatus, 51 ... Image input apparatus, 52 ... Computer, 53 ... Communication line, 54 ... Communication apparatus, 55 ... Image processing apparatus, 56 ... Color separation circuit, 57
-59 ... First to third delay circuits, 60 ... Microcomputer, 61-64 ... Switching circuit, 65 ... Pattern generating circuit, 66 ... Control device, 67 ... Operation panel, 68 ... Nonvolatile memory

Claims (6)

[Claims] 1. A plurality of image recording units including a charger, an image writing device, and a developing device are sequentially arranged along the surface of a belt-shaped photoconductor, and a plurality of different colors are formed by one pass of the photoconductor. In a multicolor image forming apparatus that sequentially forms a toner image at the same location or different locations of the photoconductor by the plurality of image recording units, a backup member for the photoconductor is provided at a position facing each image writing device and the developing device. A multicolor image forming apparatus, wherein at least two photoconductor peripheral lengths between the image writing devices are made the same. 2. A multicolor image forming apparatus according to claim 1, wherein at least two photoconductor peripheral lengths between the developing devices are made the same. 3. The multicolor image forming apparatus according to claim 1, wherein at least two photoconductor peripheral lengths between the image writing device and the developing device are the same. 4. The peripheral length of at least two photoconductors between the image writing devices and the peripheral length of at least two photoconductors between the developing devices are all the same. The multicolor image forming apparatus according to the item. 5. The multicolor image forming apparatus according to claim 1, wherein the backup member is a backup roll. 6. The multicolor image forming apparatus according to claim 1, wherein the backup member is a fixed member.