JPS63249163A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent transfer deviation, multiple transfer deviation in color images, or the like by detecting the moving speed of a freely moving band- shaped member with a high precision and accurately controlling the moving speed. CONSTITUTION:A freely rotatable speed detecting roll 11 is pressed to an area other than the area, on which a transfer material 3 is placed, of a transfer material carrying belt 4 and is rotated in accordance with movement of the carrying belt 4, and a rotary encoder 12 outputs a signal of pulses corresponding to the rotation number of the speed detecting roll 11. A control circuit 13 receives this pulse signal to perform PLL (phase locked loop) control of the driving speed of a motor 7. Thus, transfer deviation, multiple transfer deviation in color images, or the like is prevented, and transferred images are free from distortion to form images high in quality.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to an image forming apparatus, and in particular, for example, a plurality of latent image bearing members such as electrophotographic photoreceptors are arranged side by side, and an electrophotographic image forming process is performed on these photoreceptors to form images of each color. The present invention relates to a multicolor electrophotographic image forming apparatus that obtains a color image by obtaining a visible image and transferring or retransferring the visible image to a transfer material such as a transfer paper supplied from the outside. Although the present invention can be implemented not only in an electrophotographic color copying device but also in various color printers, the present specification will be described in relation to a color electrophotographic copying device. In addition, the image carrier used in the present invention may be in any form, such as a belt or a drum, as long as it moves endlessly; however, in this specification, it is described as being drum-shaped. do.

A secondary "LL" E type image forming apparatus, in particular, includes a plurality of image forming units arranged in parallel corresponding to the number of colors of developer stored therein, and an image forming apparatus provided in each of the plurality of image forming units. An image forming apparatus that transfers a developed image of each color formed on a carrier, that is, a photosensitive drum, to an externally supplied image carrier sheet, that is, a transfer material such as transfer paper, transfers the image in just one transfer process. There are two types of methods: those in which the image is completely transferred and those in which the image is transferred once from the image carrier to an intermediate transfer medium and then transferred again to a transfer material such as transfer paper.

The first type of image formation mentioned above? , M, as is already well known, has a plurality of image forming processes equipped with image bearing members (i.e. photosensitive drums), developing means, etc. arranged in parallel according to the number of developer colors, and a transfer material supply mechanism. A supplied transfer material such as a transfer paper is sequentially conveyed by a transfer material conveying member such as a belt, and the visible images formed in each of the image forming processes are sequentially transferred to the conveyed transfer material. This is how it is. By the way, regarding such a first type of image forming apparatus, the applicant has the following:
Already published in JP-A-59-155871 and JP-A-59-1
A number of proposals have been made, such as those disclosed in Japanese Patent Application Laid-open No. 6847, Japanese Patent Application Laid-open No. 59-182139, and Japanese Patent Application Laid-Open No. 59-204089. When the transfer material conveyance belt (material conveyance belt) conveys the transfer material to each image forming process, torque fluctuations occurring in the drive roller that transmits the driving force from the driving means (for example, an electric motor, etc.) to the transfer material conveyance belt, and the The moving speed of the transfer material conveyance belt tends to fluctuate due to fluctuations in friction and the like occurring between the transfer material conveyance belt and the transfer material conveyance belt. Therefore, when the color-specific visible images formed in each of the image forming processes are transferred onto a single transfer material conveyed by the transfer material conveyance belt, transfer misalignment may occur or the visible images may overlap each other. Problems such as misalignment of the relative positions between the images (that is, misalignment of multiple transfers in color images) or distortion of transferred images tend to occur. Therefore.

In order to prevent the occurrence of such problems, the applicant has proposed the following. That is, the outline of the proposal is as follows.

A guide rib is attached as a meandering regulating member to the inner circumferential side of the transfer material conveying belt in a region outside the transfer material mounting area on one side in the moving direction of the transfer material conveying belt, and the transfer material conveying belt is wound. A guide groove for guiding the guide rib is formed in a portion of the transfer material conveying belt that corresponds to a portion of the transfer material conveying belt to which the guide rib of the driving roller and the driven roller is attached, and cooperation between the guide rib and the guide groove is formed. A speed detecting means such as a pulse encoder for detecting the moving speed of the transfer material conveying belt is provided on the side of the transfer material conveying belt where the guide ribs are arranged. The apparatus is equipped with a feedback control system that presses a speed detection roller and performs feedback control of the moving speed of the transfer material conveyance belt based on a speed detection signal output from the speed detection means. In the image forming apparatus according to the proposal, the reason why the speed detection roller is brought into pressure contact with an area outside the transfer material placement area of the transfer material conveyance belt is that the speed detection roller This is to prevent the transferred image from being disturbed by being pressed against the material placement area.

゛μ However, in the image forming apparatus configured as described above, the rigidity of the portion of the transfer material conveying belt where the guide rib is attached and its vicinity is reduced due to the attachment of the guide rib. To avoid wrinkles on the transfer material conveyance belt because the guide ribs are higher than other parts of the transfer material conveyance belt and it is technically difficult to adhere the guide ribs to the transfer material conveyance belt in an orderly manner. Moreover, in addition to the above-mentioned factors, there are also unstable factors such as load fluctuations occurring on the transfer material conveying belt due to the contact state between the guide ribs and the guide grooves. Even if the moving speed of the transfer material conveying belt is detected in such a manner, it is not possible to perform highly accurate speed detection, and therefore it is difficult to accurately feedback control the moving speed of the transfer material conveying belt. . A similar problem arises when all visible images of different colors formed in each image forming process are once transferred to the second type of image forming apparatus, that is, an intermediate transfer body such as a belt, and then transferred to an external transfer body. This problem has also occurred in image forming apparatuses in which the visible image on the intermediate transfer belt means is transferred again to the transfer material when the transfer material is supplied from the intermediate transfer belt.

SUMMARY OF THE INVENTION Therefore, the present invention has been devised to solve the above-mentioned problems, and its purpose is to improve the transfer material conveying belt and intermediate transfer belt means for placing and conveying the transfer material. By accurately detecting the moving speed of a movable band-like member such as a belt-like member and controlling the moving speed of the band-like member appropriately, it is possible to prevent transfer misalignment or multiple transfer misalignment in color images. An object of the present invention is to provide an image forming apparatus capable of forming a high-quality image without causing distortion in a transferred image.

The above objects are achieved by an image forming apparatus according to the present invention. In summary, the present invention comprises an image carrier and a band-like member that is movable through a transfer area set near the image carrier to transfer a visible image formed on the image carrier. At the same time, a meandering regulating member for regulating meandering of the strip-shaped member is provided in an area on the image carrier on one side in the moving direction of the strip-shaped member that corresponds to an area where the visible image is not formed. An image forming apparatus comprising:
The image forming apparatus is characterized in that a moving speed detecting means for detecting a moving speed of the band-like member is provided on the other side in the moving direction of the band-like member.

Support 11 An image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an image forming apparatus according to an embodiment of the present invention.

As is clear from FIG. 1, an outline of an image forming apparatus according to an embodiment of the present invention includes a plurality of image forming processes, that is, image forming units! , ■, and ■ are arranged in parallel, each of the above-mentioned image forming units)1. Drive roller 5 in close proximity to ff and IIr.
A movable belt-shaped member, that is, a transfer material conveying belt 4, which is wound around a driven roller 6 and a movable belt member, is provided, and a moving speed detecting means that detects the moving speed of the transfer material conveying belt 4 and outputs a speed detection signal. The rotary encoder 12 is provided, and a control circuit 13 is provided for feedback controlling the rotational speed of the motor 7 connected to the drive roller 5 based on a speed detection signal outputted from the rotary encoder 12.

The above-mentioned image forming units I, ■, ■ have substantially the same configuration, and each image forming unit) I, ■, ■ has a first
Latent image carriers, that is, electrophotographic photoreceptor drums 2Y, 2M, and 2C in this embodiment, which are rotationally driven in the direction of the arrow in the figure, and charging devices provided sequentially in the drum rotation direction around the respective photoreceptor drums. The apparatus includes a developing device, a transfer corona charger, a cleaning device (none of which are shown), and laser beam scanners IY, IM, and IC provided above the photosensitive drums 2Y, 2M, and 2C, respectively. . The developing device of image forming unit (I) contains yellow toner, the developing device of image forming unit H contains magenta toner, and the developing device of image forming unit M contains cyan toner. ing. The laser beam scanner IY, IM, and IC include a semiconductor laser, a polygon mirror,
It consists of an f0 lens, etc., receives an input of an electric digital pixel signal, and scans a laser beam modulated in accordance with the signal in the generatrix direction of each photoreceptor drum between the charger and the developer. The drum surface is exposed.

The aforementioned laser beam scanner IY receives a pixel signal corresponding to the yellow component image of the color image, the laser beam scanner IM receives a signal corresponding to the magenta component image, and the laser beam scanner IC receives a pixel signal corresponding to the cyan component image. The respective signals are input. The above-mentioned transfer material conveying belt 4 is connected to each of the above-mentioned image forming units! , ■, ■ are respectively wound around the driving roller 5 and the driven roller 6 so as to be able to come into contact with the outer circumferential surfaces of the photosensitive drums 2Y, 2M, and 2C provided at the photosensitive drums 2Y, 2M, and 2C, respectively.

To describe the transfer material conveyance belt 4, the driving roller 5, and the driven roller 6 in more detail, the transfer material conveyance belt 4 in the area where the transfer material 3 is not placed on one side in the moving direction of the transfer material conveyance belt 4. On the inner circumferential side, the transfer material conveying belt 4
The transfer material conveying belt 4 is provided with a guide rib 9, which is a meandering regulating member for regulating meandering during movement, and the guide ribs 9 of the driving roller 5 and the driven roller 6 are attached. Guide grooves 10 for guiding the guide ribs 9 are formed at positions corresponding to the respective positions. The guide rib 9 and the guide groove 10 are
They are configured to cooperate with each other to prevent the transfer material conveying belt 4 from twisting or meandering while conveying the transfer material 3.

According to the present invention, the rotary encoder 12 described above is
As shown in FIG. 1, the other side in the moving direction of the transfer material conveyance belt 4, that is, the side opposite to the side where the guide ribs 9 are attached across the transfer material 3 placement area of the transfer material conveyance belt 4. The rotary encoder 1 is arranged in
A rotatable speed detection roller 11 connected to the rotating shaft of No. 2
is pressed against an area of the transfer material transport belt 4 outside the transfer material 3 mounting area from the outer peripheral side of the transfer material transport belt 4 . The speed detection roller 11 rotates according to the moving speed of the transfer material conveyance belt 4, and the rotary encoder 12 outputs a number of pulse signals according to the rotation speed of the speed detection roller 11. There is.

The control circuit 13 described above is connected to the rotary encoder 12.
The drive speed of the motor 7 is controlled by PLL (phase locked loop control) in response to a pulse signal output from the
It is configured to do this.

In the image forming apparatus configured as described above, when a start signal is output from a control unit (not shown) provided in the image forming apparatus, the photosensitive drums 2Y, 2M of each image forming unit) I, ①, ② are activated. ,
2C starts rotating. The driving roller 5 is also driven at the same time, and the transfer material conveying belt 4 starts driving in the direction of the arrow in FIG. With the start of rotation of the photoreceptor drums 2Y, 2M, and 2C of each of the image forming units) I, (1), and (4), image formation on each of the photoreceptor drums 2Y, 2M, and 2C is sequentially started. That is, the yellow image is on the photoreceptor drum 2Y of the image forming unit IT.
A magenta image is formed in the image forming unit m, and a cyan image is formed in the image forming unit m. The principle of image formation in each of the above-mentioned image forming units) I, ①, and ② is already well known as the Carlson process, so its explanation will be omitted.

Due to the movement of the transfer material conveyance belt 4, a specific portion of the transfer material 3 fed from the left side in FIG. When it comes into contact with the photoreceptor drums 2Y, 2M, and 2C (2), each color of yellow, magenta, and cyan is superimposed and transferred in the order of yellow, magenta, and cyan by the transfer corona charger of each unit, and a color visible image is synthesized. Then, when the transfer material 3 on which the color visible image has been combined is sent out in the direction of the arrow on the right side of FIG. 1, the transfer material 3 is sent into a fixing device (not shown), and Niso transfer material 3
The color visible image is fixed on the transfer material 3 by applying appropriate pressure or heat to the transfer material 3.

By the way, as described above, the present inventors disposed the rotary encoder 12 on the side opposite to the side where the guide rib 9 is attached across the transfer material 3 placement area of the transfer material conveying belt 4, and An image forming apparatus has been proposed in which a rotatable speed detection roller 11 connected to the rotating shaft of an encoder 12 is brought into pressure contact with an area of the transfer material conveying belt 4 outside the area where the transfer material 3 is placed. The reason is as follows. That is, as a result of experiments conducted by the present inventors using a device in which a movable belt-like member such as the transfer material conveying belt 4 is attached with a guide rib 9, which is a meandering regulating member for regulating the meandering of the belt-like member, As mentioned above, the rigidity of the portion of the transfer material conveyance belt 4 to which the guide rib 9 is attached and its vicinity is higher than that of the transfer material conveyance belt 4 due to the attachment of the guide rib 9. It turned out that the price was higher than the other parts. Moreover, it is technically impossible to adhere the guiding ribs 9 to the transfer material conveying belt 4 in an orderly manner! Due to the difficulty, it is impossible to avoid the occurrence of wrinkles in the portions of the transfer material conveyance belt 4. Various vibrations such as slight speed fluctuations and torque fluctuations that occur in the transfer material conveyance system consisting of the driving roller 5, driven roller 6, etc., and mechanical noise cannot be absorbed, and unstable running conditions are eliminated. The experimental result was that it did not. Furthermore, in addition to these problems, the guide rib 9
It is said that the running state of the transfer material conveying belt 4 is disturbed due to the contact state between the transfer material conveying belt 4 and the guide groove 10, and that this disturbance in the running state is difficult to eliminate at the above-mentioned portion of the transfer material conveying belt 4. The facts were also revealed. Therefore, based on the results of such research, the inventors of the present invention determined that the speed detection roller 11 of the O-tary encoder 12 is attached to the guide rib 9 of the transfer material conveyance belt 4, as in conventional image forming apparatuses. It was determined that the speed of the conveyor belt 4 could not be accurately detected if the part and its vicinity were pressed against each other, and therefore, the moving speed of the conveyor belt 4 could not be accurately controlled, so as in this embodiment, The speed detection roller 1
An image forming apparatus has been devised in which a pressure contact area with respect to the conveyor belt 4 of No. 1 is set on the opposite side of the area where the guide rib 9 is attached, with the transfer material 3 placement area in between.

The inventors of the present invention tried an image forming apparatus having the above-mentioned configuration, and found that an image forming apparatus of a type in which the drive motor 7 itself is simply servo-controlled without using the speed detection roller 11 was used, and speed detection according to the prior art. A comparison was made with any of the cases using an image forming apparatus of the type in which the speed of the conveying belt 4 is controlled by pressing a roller against the portion of the transfer material conveying belt 4 where the guide rib 9 is attached and its vicinity. However, the device according to the present invention was able to realize a much more stable drive of the conveyor belt, thereby reducing the occurrence of defects such as transfer misalignment and obtaining higher quality images. . Note that the method of detecting the moving speed of the transfer material conveyance belt described above is not limited to using a speed detection roller. Any method may be used as long as the moving state of the transfer material conveying belt can be directly detected.

FIG. 2 shows an image forming apparatus according to another embodiment of the present invention. Visible images of different colors formed in the image forming units are sequentially transferred to an intermediate transfer body such as an endless belt to form a visible image with composite colors on the intermediate transfer body. The image forming apparatus according to this embodiment is configured to retransfer the synthesized color visible image at once to the transfer material supplied to the intermediate transfer body. A rotatably supported backup roller 13 is attached almost directly below the driven roller 6 of the image forming apparatus according to the embodiment shown in the figure, and an appropriate size is provided between the backup roller 13 and the driven roller 6. By applying pressure or heat, the transfer material 4 is supplied from the right side in Figure 2 and is conveyed to the left side in Figure 2 in close contact with the intermediate transfer belt 40 moving in the direction of the arrow in Figure 2. This is to fix the visible image that has been retransferred to the image. Although not shown in FIG. 2, guide grooves 10 as shown in FIG. 1 are formed in the driving roller 5 and the driven roller 6.
The image forming apparatus according to this embodiment can shorten the conveyance distance of the transfer material compared to an apparatus in which the transfer material is moved using a conveyance belt as shown in FIG. Although it is possible to reduce the occurrence of defects such as bending or staining of the transfer paper, the present inventors also believe that the image forming apparatus according to this embodiment can achieve stable intermediate transfer as in the above embodiment. belt 40
It was confirmed that this drive was able to achieve high-quality images with almost no transfer misalignment.

Although the above description describes the case where the present invention is applied to an electrophotographic copying apparatus, the scope of application of the present invention is not limited only to electrophotographic copying apparatuses. It can be applied to any image forming process, such as printing plates.

As explained above, according to the present invention, by highly accurately detecting the moving speed of a movable band-like member and appropriately controlling the moving speed of the band-like member, transfer misalignment can be prevented. It is possible to provide an image forming apparatus capable of forming high-quality images without causing multiple transfer deviations in color images or distortion in transferred images.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a perspective view showing the configuration of an image forming apparatus according to another embodiment of the present invention. 2Y, 2M, 2C: Photosensitive drum 4: Transfer material conveyance belt 5: Drive roller 6: Followed roller 9: M guiding pulley: Guide groove 11: Speed detection roller 12: Rotary encoder 40: Intermediate transfer belt FIG. r

Claims (1)

[Scope of Claims] 1) An image carrier, and a band-like member that is movable through a transfer area set near the image carrier to transfer a visible image formed on the image carrier. At the same time, a meandering regulating member for regulating meandering of the strip-shaped member is provided in an area on the image carrier on one side in the moving direction of the strip-shaped member that corresponds to an area where the visible image is not formed. What is claimed is: 1. An image forming apparatus comprising: a moving speed detecting means for detecting a moving speed of the strip-like member; provided on the other side in the moving direction of the strip-like member. 2) The image carrier is a plurality of rotatable photosensitive drums arranged in parallel, and the belt-like member receives a transfer material supplied from the outside and has a transfer area set near the image carrier. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is an endless transfer material conveying belt. 3) The image carrier is a plurality of rotatable photoreceptor drums arranged in parallel, and the band-shaped member sequentially transfers the visible images formed on each of the image carriers, and 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is an endless intermediate transfer belt for retransferring a visible image onto a transfer material supplied from the outside.