JPH08110669A - Color image forming device - Google Patents

Abstract

PURPOSE: To provide a color image forming device capable of preventing color slurring without enhancing the dimensional accuracy and the attaching accuracy of an image carrier belt and a driving roll, preventing it even when thermal expansion and contraction is caused based on temperature change and preventing it without causing the rise of cost. CONSTITUTION: This color image forming device is provided with an intermediate transfer belt device 16 constituted of an inner belt 17A frictionally contact with an intermediate transfer belt 15, an inner belt driving roll 17B driving the inner belt 17A through a driving transmission system from a motor, a tensioner 17C giving specified tensile force to the inner belt 17A by a spring 27 stretched between the main body of the color image forming device and the tensioner 17C, and a guide 17D fixed so that the inner belt 17A may be brought into contact with the outer peripheral surface of the driving roll 17B. The radius of the driving roll 17B is made fixed by correcting eccentricity by the pressing of the guide 17D.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus, and more particularly to a color misregistration by compensating for the deviation of the circumference of an image carrying belt on which a color toner image is formed and the rotation circumference of a roll for driving the belt. The present invention relates to a color image forming apparatus that prevents the above.

[0002]

2. Description of the Related Art As a conventional color image forming apparatus, there is a color image forming apparatus which uses a belt as an image bearing member such as a photoconductor or an intermediate transfer member, or a sheet conveying device. In this color image forming apparatus, for example, as shown in JP-A-2-12271, the ratio of the peripheral length of the intermediate transfer belt to the peripheral length of the driving roll is set to an integral multiple, and each color is overlapped three times. I try not to cause color misregistration.

In such a color image forming apparatus, if an eccentricity occurs in the rotating shaft of the drive roll that drives the belt, the drive roll rotates to cause a velocity error on the roll surface as shown in FIG. This speed error is the eccentricity a of the drive roll with respect to the average speed V ₀ of the drive roll.
Is represented by an amplitude based on the product of the angular velocity ω and the velocity error, which causes a circumferential length difference b (positional error) between the circumferential length of the rotation of the drive roll and the circumferential length of the belt. Here, r is the radius of the drive roll.

FIG. 9 shows a belt position error at a time t at a peripheral length difference b between the rotation length of the drive roll and the belt peripheral length, which occurs based on the speed error shown in FIG.
1) In the color registration in which the leading ends of the images of the color image and the image of the color n are matched,
A belt position error D (n) is generated between the color image and the color image. In FIG. 9, the belt surface position I (n) of the nth color is expressed by the following equation. I (n) = rωt Therefore, the position error D (n) on the belt surface is I (n) -I
From (n-1), it is represented by the following equation. D (n) = (ab ÷ r)

The belt position error D (n) is a color shift amount. As shown in FIG. 10, this color shift amount changes with an amplitude corresponding to a value obtained by dividing the product of the eccentricity amount a of the drive roll and the circumferential length difference b by the radius r of the drive roll, and the maximum value thereof is shown in FIG. As shown, it is approximated by 2ab / r.

Normally, it can be recognized that the color shift is about 0.1 mm, and therefore, the color shift due to this phase shift needs to be 0.05 mm or less in order to obtain high image quality.

The position error D (n) on the belt surface is a = 2
mm, r = 15 mm, b = 2 mm, and when a color image is formed by four rotations of the belt, accumulated error D at the fourth rotation
(3) has the following values. D (3) = 3 × 0.2 × 2 ÷ 15 = 0.08 mm Therefore, in the conventional color image forming apparatus, 0.08
In order to reduce the color misregistration of mm to 0.05 mm or less, it is necessary to increase the dimensional accuracy of the peripheral length of the intermediate transfer belt, the outer diameter of the drive roll and the roundness, and the mounting accuracy when assembling these. .

[0008]

However, according to the conventional color image forming apparatus, there is a limit to increase the above-described dimensional accuracy and mounting accuracy, and even if the accuracy is increased, thermal expansion based on temperature change is caused. It is difficult to compensate for the reduction in accuracy due to contraction. Naturally, the higher the precision, the higher the cost. These problems are common to other color image forming apparatuses, such as an apparatus that superimposes color toner images on a photosensitive belt without using an intermediate transfer belt. Therefore, an object of the present invention is to provide a color image forming apparatus that prevents color misregistration without increasing the dimensional accuracy and mounting accuracy of the image bearing belt and the drive roll.

Another object of the present invention is to provide a color image forming apparatus capable of preventing color misregistration even if there is thermal expansion and contraction due to temperature change.

Still another object of the present invention is to provide a color image forming apparatus capable of preventing color misregistration without increasing cost.

[0011]

SUMMARY OF THE INVENTION The present invention prevents color misregistration without increasing the dimensional accuracy and mounting accuracy of the image bearing belt and the driving roll, and prevents color misregistration even if there is thermal expansion and contraction due to temperature changes. In order to prevent color misregistration without causing rise, a driving force transmission belt that transmits driving force by frictionally contacting the image bearing belt and an image bearing belt that receives driving force from a driving source and is transmitted through the driving force transmission belt. Provided is a color image forming apparatus having a belt drive roll to be driven and a belt guide means for correcting the eccentricity of the belt drive roll by pressing the drive force transmission belt onto the belt drive roll to make the radius constant.

[0012]

According to the color image forming apparatus of the present invention, the driving force transmission belt driving roll drives the driving force transmission belt based on the driving force generated by the driving source. At this time, the driving force transmission belt guide means brings the driving force transmission belt into contact with the outer circumferential surface of the driving force transmission belt driving roll so that the rotation shaft of the driving force transmission belt driving roll and the outer circumferential surface have a constant distance. By transmitting the driving force to the driving force transmission belt in this manner, speed fluctuation due to eccentricity of the driving force transmission belt drive roll is prevented. The driving force transmission belt transmits the driving force to the image bearing belt by making frictional contact with the image bearing belt.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A color image forming apparatus of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of a color image forming apparatus using an intermediate transfer belt. As shown in FIG. 1, this color image forming apparatus prints on a sheet based on an image input device 1 for scanning an original image and an image signal scanned by the image input device 1 and processed by an image processing device (not shown). The image output device 8 is used for printing.

The image input device 1 includes a lamp 3 for irradiating a document (not shown) placed on a transparent document table 2 with light.
And the reflection mirrors 4 and 5 that reflect the reflected light from the original,
A lens 6 that focuses the reflected light from the mirror 5, and a lens 6
And a charge-coupled device (CCD) 7 on which the light focused by the above is incident. The charge-coupled device 7 passes the incident light through R, G, and B filters to Y (yellow), M (magenta), and C.
(Cyan) signal is separated and read.

The image output device 8 complements the Y, M, and C signals obtained by the image input device 1 into Y, M, C, and BK (black), and saves them by IPS (Image (not shown)).
Image writing device 9 which has a processing system) and which emits laser light modulated based on image data obtained by the laser light source 9A performing image processing by IPS and deflects the emitted light by the polygon mirror 9B.
A mirror 10 for reflecting the laser light emitted from the image writing device 9 in the scanning direction, a photosensitive drum 11 for emitting the laser light reflected by the mirror 10, Y, M,
The developing units for the C and BK toners are arranged at intervals of 90 degrees in the circumferential direction, and are rotated at the time of development to supply the toner corresponding to each color to the surface of the photoconductor drum 11. A charger 1 is provided around the photosensitive drum 11.
3 and a photoconductor cleaner 14 for removing the toner remaining on the photoconductor drum 11 are arranged.

Below the photosensitive drum 11, there is provided an intermediate transfer belt device 16 having a polyimide intermediate transfer belt 15 having a thickness of 0.1 mm and a peripheral length of 567 mm to which the toner image formed on the surface of the drum is transferred. The intermediate transfer belt 15 is driven by a roll 17 having a diameter of 30 mm (not necessarily a drive roll in this embodiment), and is supported by a tension roll 18 and a secondary transfer backup roll 19.

A driving force is transmitted to the roll 17 from an inner belt drive roll 17B whose surface is made of a material having a low hardness via an inner belt 17A described later, and the inner belt 17A is given a predetermined tension by a tensioner 17C. It is supported by the guide 17D so as to come into contact with the outer circumference of the inner belt drive roll 17B.

The tension roller 18 is provided with an intermediate transfer belt tension adjusting mechanism (not shown), and applies a predetermined tension to the intermediate transfer belt 15.

The intermediate transfer belt 15 is configured to rotate once when the roll 17 rotates 6 times.

The intermediate transfer belt device 16 includes a primary transfer corotron 20 provided at a primary transfer point of the intermediate transfer belt 15, a belt cleaner 21 provided adjacent to the roll 17, and a reference position of the intermediate transfer belt 15. The sheet conveying device (tray) 23 is provided at the secondary transfer point where the secondary transfer backup roll 19 is located, which has the belt reference position detection sensor 22 for detecting the mark 28 provided.
By sandwiching a sheet (not shown) supplied from the sheet supply roller 24 by the secondary transfer roller 25, the toner image transferred to the intermediate transfer belt 15 is transferred to the sheet. The sheet on which the toner image is transferred is conveyed to the fixing device 26 and the toner image is fixed.

FIG. 2 shows a drive system of the roll 17 in the intermediate transfer belt device 16. An inner belt 17A for transmitting a driving force to the roll 17 is inserted so as to run between the intermediate transfer belt 15 and the roll 17. And a tensioner 1 that applies a predetermined tension to the inner belt 17A.
7C has a spring 27 stretched between the main body (not shown) of the image forming apparatus.

The operation of the color image forming apparatus of the present invention having the above construction will be described below.

When the start of image formation is instructed, the laser light source 9A of the image writing device 9 outputs laser light corresponding to the color image of the first color. This laser light is deflected in the scanning direction by the polygon mirror 9B, then reflected by the mirror 10 and irradiated onto the photosensitive drum 11 charged by the charger 13 to form an electrostatic latent image. This electrostatic latent image is developed with the corresponding color toner in the developing device unit 12 located in the rotation direction of the photosensitive drum 11.

The developed color toner image is transferred from the photosensitive drum 11 to the intermediate transfer belt at the primary transfer position where the primary transfer corotron 20 is provided when the mark 28 provided on the intermediate transfer belt 15 is detected by the sensor 22. Transferred to 15.

The intermediate transfer belt 15 is a photosensitive drum 11.
It is driven by the roll 17 so as to rotate in synchronization with the roll 17, and the driving force of the inner belt drive roll 17B is transmitted to the roll 17 via the inner belt 17A inserted between the roll 17 and the intermediate transfer belt 15. A driving force is transmitted to the inner belt drive roll 17B from a motor (not shown) via a reduction gear or a drive transmission system such as a timing belt.

A guide 17D provided in the vicinity of the inner belt driving roll 17B guides the inner belt 17A so as to contact the surface of the inner belt driving roll 17B. The inner belt drive roll 17B holds the inner belt 17A with the guide 17D while rotating.

At this time, the inner belt driving roll 17
The surface of B presses the inner belt 17A against the guide 17D and elastically deforms to transmit the driving force. The guide 17D is the inner belt driving roll 1 when the driving force is transmitted.
It is fixed so that the distance between the rotating shaft of 7B and the guide 17D is kept constant. The inner belt 17A driven in this way moves on the roll 17 to the intermediate transfer belt 1
By making frictional contact with 5, the driving force of the inner belt driving roll 17B is transmitted to the intermediate transfer belt 15.

The full-color image formed by repeating the above-described operation for each color and transferring the color toner images in a multiplex manner is transferred from the paper tray 23 at the secondary transfer point where the support roll 19 and the secondary transfer roll 25 are located. The image is transferred onto a sheet (not shown) supplied through the sheet supply roll 24.

According to the above structure, it is possible to improve the rotational accuracy of the intermediate transfer belt 15 by suppressing the occurrence of speed fluctuation due to roll eccentricity or the like when the driving force is transmitted from the inner belt driving roll 17B to the inner belt 17A.

FIG. 3 shows a modified example of the drive system in the intermediate transfer belt device 16, which is an inner belt drive roll 17.
The inner belt 17A driven by B is inserted between the intermediate transfer belt guide 17E that supports the intermediate transfer belt 15 and the intermediate transfer belt 15. Other configurations and functions are the same as those of the drive system shown in FIG. The intermediate transfer belt guide 17E is, for example, the roll 1
It is provided between 7 and 18.

According to the above-mentioned structure, since the positional change of the intermediate transfer belt 15 due to the eccentricity of the inner belt driving roll does not occur, the rotation accuracy of the intermediate transfer belt 15 can be improved.

FIG. 4 shows another modification of the drive system in the intermediate transfer belt device 16, in which the guide 17D is fixed to the inner peripheral side of the inner belt 17A and the inner belt 17A guided by the guide 17D is driven by a motor (see FIG. The inner belt driving roll 17B is directly driven by a not shown). Other configurations and functions are the same as those of the drive system shown in FIGS. 2 and 3, and therefore their explanations are omitted.

According to the above construction, since the inner belt driving roll 17B is arranged on the outer peripheral side of the inner belt 17A, the circumferential length of the inner belt 17A can be shortened, so that the driving system can be made compact.

FIG. 5 shows another modification of the drive system in the intermediate transfer belt device 16, which is an intermediate transfer belt guide 17.
The spring 27 is attached to E, and the guide 17D is fixed to the inner peripheral side of the inner belt 17A.
The inner belt 17A guided to 7D is driven by the inner belt driving roll 17B directly driven by a motor (not shown). The other configurations and functions are the same as those of the drive system shown in FIGS. 2, 3 and 4, and the description thereof is omitted.

According to the above construction, since the position of the intermediate transfer belt 15 does not fluctuate due to the eccentricity of the inner belt driving roll, the rotational accuracy of the intermediate transfer belt 15 can be improved and the structure of the tensioner can be simplified. Since the circumference of 17A can be shortened, the drive system can be made compact.

FIG. 6 shows an image forming apparatus in which a photoconductor belt 29 is driven by a drive roll 30 instead of the photoconductor drum 11. Overlapping description of parts having the same configurations and functions as those of the first embodiment will be omitted. In this image forming apparatus, an inner belt 31 inserted between a drive roll 30 and a photoconductor belt 29, an inner belt drive roll 32 for driving the inner belt 31, and an inner belt drive roll for guiding the inner belt 31. A guide 33 that comes into contact with 32 and a tensioner 34 that applies a predetermined tension to the inner belt 31 are provided.

According to the color image forming apparatus having the above structure, when the toner image is formed on the photosensitive belt 29, it is possible to prevent the speed variation of the photosensitive belt 29. Further, the toner of each color is formed on the photoconductor belt of the image forming apparatus using a transfer drum that holds the paper and transfers the toner image, or on the photoconductor belt 29 driven by the drive roll 30 as shown in FIG. The same effect can be obtained by applying the present invention to a color image forming apparatus in which multicolor toner images are formed by superimposing images and are collectively transferred onto a recording sheet, or a color image forming apparatus in which a belt is reciprocally driven. be able to.

[0039]

As described above, according to the color image forming apparatus of the present invention, the driving force transmission belt is driven by the driving force transmission belt drive roll which is driven by receiving the driving force from the driving source. Since the image bearing belt and the image bearing belt are brought into frictional contact with each other on the roll, color shift is prevented without increasing the dimensional accuracy and mounting precision of the image bearing belt and the roll, and color shift is prevented even if there is thermal expansion and contraction due to temperature change. Therefore, it is possible to prevent the color shift without increasing the cost.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a color image forming apparatus of the present invention.

FIG. 2 is an explanatory diagram showing an example of a drive system of an intermediate transfer belt device.

FIG. 3 is an explanatory diagram showing a modified example of the drive system of the intermediate transfer belt device.

FIG. 4 is an explanatory diagram showing a modified example of the drive system of the intermediate transfer belt device.

FIG. 5 is an explanatory diagram showing a modified example of the drive system of the intermediate transfer belt device.

FIG. 6 is an explanatory diagram showing a color image forming apparatus of the present invention.

FIG. 7 is an explanatory diagram showing a color image forming apparatus of the present invention.

FIG. 8 is an explanatory diagram showing a speed variation of a drive roll.

FIG. 9 is an explanatory diagram showing a belt position error due to a speed error.

FIG. 10 is an explanatory diagram showing a color shift due to a speed error.

FIG. 11 is an explanatory diagram showing a color shift due to a speed error.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image input device 2 Original plate 3 Lamp 4, 5 Reflection mirror 6 Lens 7 Charge coupled device 8 Image output device 9 Image writing device 9A Laser light source 9B Polygon mirror 10 Reflection mirror 11 Photoreceptor drum 12 Developer unit 13 Charger 14 Photoconductor cleaner 15 Intermediate transfer belt 15A Mark 16 Intermediate transfer belt device 17 Roll 17A Inner belt 17B Inner belt drive roll 17C Tensioner 17D guide 17E Intermediate transfer belt guide 18 Tension roll 19 Secondary transfer backup roll 20 Primary transfer Corotron 21 Belt cleaner 22 Belt Reference Position Detection Sensor 23 Paper Tray 24 Paper Supply Roll 25 Secondary Transfer Roll 26 Fixing Device 27 Spring 28 Mark 29 Photosensitive Belt 30 Drive Roll 31 N'naberuto 32 Inner belt drive rolls 33 guide 34 tensioner

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kimito Omori 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd.Ebina Works (72) Inventor Susumu Kibayashi 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd.Ebina Co., Ltd. On-site (72) Inventor Junichi Murakami 2274 Hongo, Ebina-shi, Kanagawa Fuji Xerox Co., Ltd.

Claims (1)

[Claims] 1. A color image forming apparatus for forming a color image by superposing a plurality of color toner images on an image bearing belt which is supported and rotated by a plurality of rolls, by frictionally contacting the image bearing belt. A driving force transmitting belt for transmitting a driving force; a belt driving roll for receiving the driving force from a driving source to drive the image carrying belt via the driving force transmitting belt; and a driving force transmitting belt for the belt driving roll. And a belt guide unit for correcting the eccentricity of the belt drive roll by pressing it upward to make the radius constant.