JP2002006640A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease speed fluctuations by detecting the moving speed of a transfer body of an image forming device with high accuracy. SOLUTION: This image forming device is constituted to have a photoreceptor, an electrostatic charging means which uniformly electrostatically charges the surface of the photoreceptor, an exposure means which forms an electrostatic latent image by irradiating the surface of the electrostatically charged photoreceptor with the light corresponding to image data, a developing means which develops the electrostatic latent image formed on the photoreceptor by toners, the transfer body 6 which is transferred with the toner image formed on the photoreceptor, plural detecting pattern images which are formed apart prescribed intervals along the moving direction of the transfer body 6 on the transfer body 6, first and second image reading means 1 and 2 which read the detecting pattern images and a moving speed detecting means 3 which detects the moving speed of the transfer body 6 from the time lag of the detection timing of the respective image reading means 1 and 2 reading the same detected pattern images.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming a composite image by transferring a toner image formed on a photosensitive member onto an intermediate transfer member by transfer means, and more particularly, to increasing the moving speed of the intermediate transfer member. The present invention relates to technology for detecting with high accuracy.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus employing an electrophotographic technique, a photosensitive member as an image carrier is charged by a charger, and the photosensitive member is irradiated with light according to image information to form a latent image. Is formed, the latent image is developed by a developing device, and then transferred to a sheet material or the like to form an image.

On the other hand, with the colorization of images, a plurality of image forming stations for performing the above-described image forming processes are provided, and a cyan image, a magenta image, a yellow image,
And a tandem-type image forming apparatus for forming a full-color image by forming each color image of a black image on each image carrier, and superimposing and transferring each color image onto a sheet material at a transfer position of each image carrier. Has also been proposed. Such a tandem-type image forming apparatus has an image forming unit for each color, and is therefore advantageous for speeding up.

Hereinafter, a conventional image forming apparatus will be described.

FIG. 6 is an explanatory view showing the structure of a conventional image forming apparatus.

As shown in FIG. 6, an image forming apparatus according to the present embodiment has four image forming stations Pa, Pb, P
c and Pd are arranged. Each of the image forming stations Pa, Pb, Pc, and Pd has photoconductors 100a, 100b, 100c, and 100d as image carriers.

The photosensitive members 100a, 100b, 100c, 1
00d, each photoconductor 100a, 100b, 10
Charging means 101a, 101b, 101c, 101d for uniformly charging the surfaces of Oc, 100d to a predetermined potential; charged photoconductors 100a, 100b, 100c, 100
a laser beam 102 corresponding to image data of a specific color
a, 102b, 102c, and 102d, an exposure unit 102 that is a scanning optical system that forms an electrostatic latent image by irradiating the photosensitive member 1;
Developing means 103a, 103b, 1 for visualizing the electrostatic latent images formed on 00a, 100b, 100c, 100d
03c, 103d, photoconductors 100a, 100b, 100
c, 100d, the toner image developed on the drive roller 1
Transfer devices (transfer means) 104 a, 104 b, 104 c, which transfer to an intermediate transfer member (transfer member) 106 in the form of an endless belt which is wound around and looped between the roller 12 and the driven roller 113.
104d, photoconductors 100a, 100b, 100c, 10
Cleaning means 105a for removing the residual toner remaining on the photoconductors 100a, 100b, 100c, and 100d after transferring the toner image from 0d to the intermediate transfer body 106;
105b, 105c and 105d are arranged respectively.

Here, in the case shown, the intermediate transfer member 106 rotates in the direction of arrow A. In the image forming stations Pa, Pb, Pc, and Pd, a black image, a cyan image, a magenta image, and a yellow image are formed, respectively. Then, the photoconductors 100a, 100b,
The single-color images of the respective colors formed on 100c and 100d are sequentially superimposed and transferred onto the intermediate transfer body 106 to form a full-color image.

At the lower part of the apparatus, there is provided a paper feed cassette 108 in which a sheet material 109 such as printing paper is stored. Then, the sheet material 109 is sent out one sheet at a time from the sheet feeding cassette 108 to the sheet conveying path by the sheet feeding roller 107.

The intermediate transfer body 106 contacts the outer peripheral surface of the intermediate transfer body 106 for a predetermined amount on the paper transport path.
A sheet material transfer roller 110 for transferring the color image formed thereon to the sheet material 109, and heating for fixing the color image transferred on the sheet material 109 to the sheet material 109 by the pressure and heat accompanying the pinching rotation of the roller. A fixing device 111 having a roller 111a is provided.

In the image forming apparatus having such a configuration,
First, a latent image of a black component color of image information is formed on the photoreceptor 100a by the charging unit 101a and the exposing unit 102 of the image forming station Pa. This latent image is visualized as a black toner image by a developing unit 103a having black toner, and is transferred as a black toner image onto the intermediate transfer body 106 by a transfer unit 104a.

On the other hand, the black toner image is
6, a latent image of a cyan component color is formed in the image forming station Pb.
At 3b, the cyan toner image by the cyan toner is visualized. Then, the cyan toner image is transferred by the transfer unit 104b of the image forming station Pb to the intermediate transfer body 106 where the transfer of the black toner image has been completed in the previous image forming station Pa, and is superimposed on the black toner image.

Hereinafter, image formation is performed in the same manner for the magenta toner image and the yellow toner image, and when the superposition of the four color toner images on the intermediate transfer member 106 is completed,
Sheet material transfer rollers 110 collectively transfer toner images of four colors onto sheet material 109 fed from sheet cassette 108 by sheet feed roller 107. Then, the transferred toner image is heated and fixed to the sheet material 109 by the fixing device 111, and a full-color image is formed on the sheet material 109.

Each of the photosensitive members 1 whose transfer has been completed
The remaining toners 00a, 100b, 100c, and 100d are removed by the cleaning units 105a, 105b, 105c, and 105d, and are prepared for the subsequent image formation.

However, in such a tandem type image forming apparatus, the respective photoconductors 100a, 100
b, 100c, and 100d have a problem in how to properly align the images formed thereon. This is because the shift of the image forming positions of the four colors transferred to the sheet material 109 finally appears as a color shift or a change in color tone.

Here, as one of the factors that cause the shift of the image forming position, the eccentricity of the driving roller 112 for rotationally driving the intermediate transfer member 106 and the intermediate thickness caused by the unevenness of the belt thickness of the intermediate transfer member 106, and the like. The fluctuation of the moving speed of the transfer body 106 is mentioned.

In order to reduce this, Japanese Patent Laid-Open No.
In Japanese Patent Application Laid-Open No. 0-186787 and the like, a predetermined detection pattern is formed on the intermediate transfer body 106, and the moving speed of the intermediate transfer body 106 is detected by detecting and calculating the interval between the detection patterns. There is disclosed a technique for forming a good image by controlling.

[0018]

However, in the above-described technique for detecting the moving speed of the surface of the intermediate transfer member, the detected moving speed data is affected by fluctuations both during the formation of the detection pattern and during the detection. In order to adjust this, a complicated correction operation is performed, and a mechanical restriction such as disposing the detection position along the intermediate transfer member at a position apart from the image forming unit by half the length of the intermediate transfer member is involved. become.

Therefore, the present invention provides a method for controlling the moving speed of a transfer member.
It is an object of the present invention to provide an image forming apparatus capable of detecting with high accuracy and reducing speed fluctuation without performing complicated correction calculation processing and without being subjected to mechanical restrictions on a detection position.

[0020]

In order to solve this problem, an image forming apparatus according to the present invention comprises a photosensitive member, charging means for uniformly charging the surface of the photosensitive member, and Exposure means for irradiating light corresponding to image data to form an electrostatic latent image, developing means for visualizing the electrostatic latent image formed on the photoreceptor with toner, and a developing means formed on the photoreceptor A transfer member on which the toner image is transferred, a plurality of detection pattern images formed on the transfer member at predetermined intervals along the movement direction of the transfer member, and a predetermined interval along the movement direction of the transfer member A plurality of image reading means for reading the detection pattern image, and a movement speed detection means for detecting a movement speed of the transfer body from a time difference between detection timings of the respective image reading means for reading the same detection pattern image; With the configuration That.

Thus, the moving speed of the transfer body is detected from the time difference between the detection timings of the same detection pattern image by a plurality of image reading means, and the moving speed of the transfer body is obtained. It is possible to detect the moving speed of the transfer body with high accuracy and reduce fluctuations in the speed without being subject to mechanical restrictions on the detection position.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a photosensitive member, a charging means for uniformly charging the surface of the photosensitive member, and a light corresponding to image data on the charged photosensitive member. Exposure means for forming an electrostatic latent image by irradiating the toner, developing means for visualizing the electrostatic latent image formed on the photoconductor with toner, and transferring the toner image formed on the photoconductor A transfer body, and a plurality of detection pattern images formed on the transfer body at predetermined intervals along the moving direction of the transfer body,
A plurality of image reading means arranged at predetermined intervals along the moving direction of the transfer body to read the detection pattern image, and the transfer body Moving speed detecting means for detecting the moving speed of the image forming apparatus,
Since the moving speed of the transfer body is determined by detecting the moving speed of the transfer body from the time difference between the detection timings of the same detection pattern image by a plurality of image reading means, complicated correction arithmetic processing is performed, and There is an effect that it is possible to detect the moving speed of the transfer body with high accuracy and reduce the speed fluctuation without being restricted.

According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the detection pattern image is a hole formed at a predetermined interval at an end of the opening of the transfer member. There is an effect that it is possible to reduce the cost by sharing the detection pattern image and the transfer body.

According to a third aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the detection pattern image is formed on a reinforcing member provided at an opening end of the transfer body. In addition, the transfer pattern and the reinforcing member can be shared so that the cost can be reduced.

According to a fourth aspect of the present invention, there is provided the image forming apparatus according to the third aspect, wherein the linear expansion coefficient of the reinforcing member is the same as the linear expansion coefficient of the transfer member.
This has an effect that distortion of linear expansion between the reinforcing member and the transfer member caused by expansion is reduced, and deterioration of detection accuracy can be prevented.

According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the transfer speed is detected by the transfer driving means for rotatingly driving the transfer body and the moving speed detecting means. An image forming apparatus provided with a transfer drive control unit that controls the rotation speed of the transfer drive unit based on the moving speed, wherein the fluctuation of the transfer speed of the transfer body is reduced, and a good image can be formed. Has the effect of becoming

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In the present embodiment, illustration and description of the same configuration and operation as those of the conventional image forming apparatus described above are omitted.

FIG. 1 is a block diagram showing the configuration of a detection control system for detecting the moving speed of a transfer member and controlling the speed in an image forming apparatus according to an embodiment of the present invention, and FIG.
FIG. 3 is an explanatory diagram showing an arrangement relationship between a detection pattern image on a transfer body and an image reading means in the detection control system of FIG. 3, FIG. 3 is an explanatory diagram showing an arrangement relationship between the detection pattern image of FIG. 2 and a reinforcing member, and FIG. FIG. 5 is a timing chart showing detection signals of the first image reading means and the second image reading means in the detection control system of FIG. 1, and FIG. 5 shows the moving speed of the transfer body detected by the moving speed detecting means in the detection control system of FIG. 6 is a timing chart showing a moving speed when correction control is performed by a transfer drive control unit.

The transfer member 6 shown in FIG.
Corresponds to the intermediate transfer member (transfer member) 106 in FIG. A first image reading means 1 and a second image reading means 2 for reading a plurality of detection pattern images 7 (FIG. 2) formed on the transfer body 6 are attached along the moving direction of the transfer body 6. Have been. Here, as the detection pattern image 7, for example, a pattern of a toner image formed at any one of the four image stations and transferred onto the transfer body 6, or a detection pattern formed on the transfer body 6 in advance. A slit (not shown) or the like can be applied.

It is sufficient that a plurality of image reading means are provided, and the invention is not limited to the two shown in the present embodiment.

Further, the image forming apparatus detects the moving speed of the transfer member 6 from a detection signal corresponding to the pattern image 7 for detection detected by the first image reading means 1 and the second image reading means 2. Moving speed detecting means 3 is provided. For this moving speed detecting means 3, a central processing unit such as a CPU is used.

Further, in order to rotationally drive the transfer body 6,
For example, a transfer driving unit 5 configured using a motor or the like is provided. Further, a transfer drive control means 4 for controlling the rotation speed of the transfer drive means 5 based on the movement speed of the transfer body 6 detected by the movement speed detection means 3 is provided.

The detection of the moving speed of the transfer body 6 and the drive control in the present embodiment configured as described above will be described with reference to FIGS.

First, the detection of the moving speed of the transfer body 6 will be described with reference to FIGS. 2, 3 and 4.

In FIG. 2, the transfer member 6 is driven to rotate in the direction of arrow A. In addition, the first image reading unit 1 and the second image reading unit
Image reading means 2 are arranged at a distance l along the moving direction A of the transfer body 6. For example, the detection pattern image 7 on the transfer body 6 is located at a position that can be detected by the first image reading unit 1 and the second image reading unit 2 along the moving direction A of the transfer body 6 at a predetermined interval r. It is formed by making a hole in the transfer body 6.

As shown in FIG. 3, when a reinforcing member 8 such as a tape is attached to the end of the opening of the transfer body 6, the first image reading means 1 and the second The detection pattern images 7 are formed at predetermined intervals r by printing or the like at positions where the second image reading means 2 can detect them, so that the detection pattern images 7 can be shared with the reinforcing member 8. Here, by using a material such that the linear expansion coefficient of the reinforcing member 8 is the same as the linear expansion coefficient of the transfer body 6, distortion of the linear expansion caused by expansion due to heat or the like is reduced and detection is performed. Accuracy can be prevented from deteriorating.

Here, when the detection pattern image 7 is formed by a toner image, each of the photosensitive members 100a, 100b, 1
The interval r fluctuates due to an image forming state such as a speed fluctuation of 00c and 100d (FIG. 6) and a moving speed fluctuation of the transfer body 6 generated at the time of transfer.

Assuming that the average moving speed of the transfer body 6 is Vm, the average frequency fs of the detection pattern image 7 detected by either the first image reading means 1 or the second image reading means 2
Is fs = Vm / r.

On the other hand, the fluctuation component of the moving speed of the transfer body 6 includes frequency components corresponding to fluctuation factors such as the eccentricity of the driving roller 112 for driving the transfer body 6 to rotate and the unevenness of the belt thickness of the transfer body 6. It is. For example, the eccentricity of the driving roller 112 includes a moving speed variation of a frequency component corresponding to one cycle of the driving roller 112, and the non-uniformity of the belt thickness of the transfer body 6 includes a moving speed of a frequency component corresponding to one cycle of the belt. Fluctuations are included. When detecting a periodic fluctuation component of the moving speed of the transfer body 6 generated due to these various factors, among various frequency components included,
Set the maximum frequency component to be detected in advance,
An interval r between the detection pattern images 7 is set for the frequency fmax based on a known sampling theorem so as to satisfy a relationship of fs ≧ 2fmax.

The distance l between the first image reading means 1 and the second image reading means 2 is arranged so as to satisfy the following condition: l <r.

Thus, after the first image reading means 1 has detected one detection pattern image 7 and before the second image reading means has detected the same detection pattern image 7, the first image reading means 1 Means 1 can be prevented from detecting the next detection pattern.

That is, as shown in FIG. 4, the respective detection signals for the detection pattern image 7 detected by the first image reading means 1 and the second image reading means 2 are the same as those of the first image reading means 1 and the second image reading means 1. The interval 1 between the first and second image reading means 2 is shifted by the time required for the detection pattern image 7 to pass, and this time difference is the time required for the same detection pattern image 7 to pass. The moving speed detecting means 3 sequentially determines a time difference between the time when the first image reading means 1 detects the detection pattern image 7 and the time when the second image reading means 2 detects the detection pattern image, at t1 and t2.
are measured as t2, t3,... In this way, the time during which the same pattern passes between the first image reading means 1 and the second image reading means 2 can be measured. From the times t1, t2, t3,... Detected by the moving speed detecting means 3, the moving speed Vn of the transfer body 6 is given by: Vn = 1 / tn (where n = 1, 2, 3,...) It can be obtained by calculation.

Thus, the moving speed Vn of the transfer member 6
Can be detected without performing a complicated correction operation or the like.

FIG. 5 is a timing chart showing the moving speed Vn of the transfer member 6 detected by the moving speed detecting means 3 and the moving speed when the transfer control means 4 performs the correction control.

FIG. 5A shows a fluctuation component of the moving speed Vn of the transfer body 6 obtained by the moving speed detecting means 3.
And a plurality of frequency components corresponding to fluctuation factors such as eccentricity of the drive roller 112 for rotationally driving the roller and unevenness of the belt thickness of the transfer body 6. In order to reduce the fluctuation component indicated by a, the transfer driving control unit 4 performs feedforward control of the transfer driving unit 5 such as a motor so that the transfer body 6 rotates at a speed fluctuation indicated by b. As a result, the fluctuation component of a having a relatively large period is canceled out, and the fluctuation component can be reduced as shown in c.

[0046]

As described above, according to the present invention, the moving speed of the transfer body is detected from the time difference between the detection timings of the same detection pattern image by a plurality of image reading means to determine the moving speed of the transfer body. Therefore, there is an effective effect that it is possible to detect the moving speed of the transfer body with high accuracy and reduce the speed fluctuation without performing complicated correction calculation processing and mechanical restrictions on the detection position. can get.

If the detection pattern image is a hole formed at the end of the opening of the transfer member, it is possible to use the detection pattern image and the transfer member in common, thereby reducing the cost. Is obtained.

If the detection pattern image is formed on the reinforcing member provided at the end of the opening of the transfer body, the transfer pattern and the reinforcing member can be shared, and the cost can be reduced. Effects can be obtained.

If the linear expansion coefficient of the reinforcing member is the same as the linear expansion coefficient of the transfer member, the distortion of the linear expansion of the reinforcing member and the transfer member caused by expansion is reduced, and deterioration of the detection accuracy can be prevented. Is obtained.

The provision of the transfer drive means and the transfer drive control means has an effective effect that fluctuations in the moving speed of the transfer body are reduced and a good image can be formed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a detection control system for detecting a moving speed of a transfer body and controlling the speed in an image forming apparatus according to an embodiment of the present invention;

FIG. 2 is an explanatory diagram showing an arrangement relationship between a detection pattern image on a transfer body and an image reading unit in the detection control system of FIG. 1;

FIG. 3 is an explanatory diagram showing an arrangement relationship between a detection pattern image and a reinforcing member in FIG. 2;

FIG. 4 is a timing chart showing detection signals of a first image reading unit and a second image reading unit in the detection control system of FIG. 1;

5 is a timing chart showing the moving speed of the transfer body detected by the moving speed detecting means in the detection control system of FIG. 1 and the moving speed when correction control is performed by the transfer drive control means;

FIG. 6 is an explanatory diagram illustrating a configuration of a conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st image reading means (image reading means) 2 2nd image reading means (image reading means) 3 moving speed detection means 4 transfer drive control means 5 transfer drive means 6 transfer body 7 detection pattern image 8 reinforcing member

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tomoyuki Noguchi 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. (Reference) 2H027 DA16 EC03 EC07 ED16 ED24 EE03 2H032 AA05 BA01 BA03 BA09 BA23 CA02 CA13

Claims (5)

[Claims] A photosensitive member; a charging means for uniformly charging the surface of the photosensitive member; and an exposure device for irradiating the charged photosensitive member with light corresponding to image data to form an electrostatic latent image. Means, developing means for visualizing the electrostatic latent image formed on the photoconductor with toner, an endless belt-shaped transfer body onto which the toner image formed on the photoconductor is transferred, A plurality of detection pattern images formed on the transfer body at predetermined intervals along the direction of movement of the transfer body; and the detection patterns arranged at predetermined intervals along the direction of movement of the transfer body. A plurality of image reading means for reading an image; and a moving speed detecting means for detecting a moving speed of the transfer body from a time difference between detection timings of the respective image reading means for reading the same detection pattern image. Image shape Equipment. 2. The image forming apparatus according to claim 1, wherein the detection pattern image is a hole formed at a predetermined interval at an end of an opening of the transfer body. 3. The image forming apparatus according to claim 1, wherein the detection pattern image is formed on a reinforcing member provided at an end of an opening of the transfer body. 4. The image forming apparatus according to claim 3, wherein a linear expansion coefficient of the reinforcing member is equal to a linear expansion coefficient of the transfer body. 5. A transfer driving means for driving the transfer body to rotate, and a transfer drive control means for controlling a rotation speed of the transfer driving means based on the moving speed detected by the moving speed detecting means. Claim 1 characterized by the fact that
The image forming apparatus according to claim 4.