JPH10133517A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a toner image with proper image magnification, even if temp. in an image forming device body is changed. SOLUTION: When a temperature sensor 9 detects the fact that the temp. in a transfer belt 5a is raised for instance, the circumferential speed of the transfer belt 5a is slowdown so that a printer controller 10 executes control for reducing the scanning speed of a polygon mirror 3b or the processing speed of a photoreceptor drum 1 and the scanning speed of the polygon mirror 3b, or increasing the moving speed of the transfer belt 5a. Thus, the fluctuation of image magnification caused by the change in the temp. can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus, and more particularly to an image forming apparatus using a second image carrier for collectively transferring toner images.

[0002]

2. Description of the Related Art Some conventional image forming apparatuses have a structure as shown in FIG. In FIG. 1, a drum type electrophotographic photosensitive member (hereinafter, referred to as a “photosensitive drum”) 1 as a first image carrier has an organic photosensitive member (OPC), A-Si, CdS, S
e is coated with a photoconductor.

The photosensitive drum 1 is driven in a direction indicated by an arrow R1 by driving means (not shown). Around the photosensitive drum 1, a roller charger 2 for uniformly charging the photosensitive drum 1 to a predetermined potential, a light source 3a such as a laser, a polygon mirror 3b for performing raster scan, and a lens 3 for forming an image are provided.
c, an exposing device 3 having a folding mirror 3d and the like, and forming an electrostatic latent image on the photosensitive drum 1 by exposure light, and yellow for turning the electrostatic latent image formed on the photosensitive drum 1 into a visible image.
A developing device 4 in which developing devices 4Y, 4M, 4C, and 4Bk containing toners such as magenta, cyan, and black are supported by a support 4a, and a toner image formed on the photosensitive drum 1 that has been visualized is transferred. Transfer member 5 serving as a second image carrier to be transferred, and photosensitive drum 1 transferred to intermediate transfer member 5
And a cleaning device 6 for removing the toner remaining in the toner cartridge.

The intermediate transfer member 5 is pressed against a transfer belt 5a made of ethylene propylene rubber (EPDM), nitrile rubber (NBR), urethane, silicone rubber or the like by a driving roller 5b, a driven roller 5c, and a spring 5d. 1 that is stretched on the tension roller 5e and contacts the photosensitive drum 1 with the transfer belt 5a interposed therebetween.
The secondary transfer roller 5g is configured to contact the driven roller 5c with the next transfer roller 5f and the transfer belt 5a interposed therebetween.

A fixing device 7 for fixing the toner image transferred from the intermediate transfer member 5 to a transfer sheet P as a recording material is disposed downstream of the transfer sheet in the transport direction. The transfer belt 5a is provided with a cleaning device 8 such as a fur brush or a web for removing the toner remaining on the transfer belt 5a so as to be able to contact and separate from the transfer belt 5a.

The primary transfer roller 5f and the secondary transfer roller 5g have a structure in which a conductive sponge layer is provided on a shaft.
A bias is applied from a high-voltage power supply (not shown) to transfer the toner image on the photosensitive drum 1 onto the transfer belt 5a,
Alternatively, the toner image on the transfer belt 5a is transferred onto the transfer paper P. Then, the transfer belt 5a is driven in the direction of the arrow R5 in the figure by rotating the drive roller 5b in the direction of the arrow in the figure by a motor (not shown).

The photosensitive drum 1 is driven by a driving means in the direction of arrow R1 in the figure, and is uniformly charged to a predetermined potential by a roller charger 2. Next, the photosensitive drum 1 is scanned with exposure light according to yellow image information from the exposure device 3 to form an electrostatic latent image. Next, the supporter 4a is rotated to select the developing device 4Y to be opposed to the photosensitive drum 1 to visualize the electrostatic latent image, and then transfer the toner image to the transfer belt 5a by the primary transfer roller 5f.

[0008] Similarly, by repeating the above steps, magenta,
The cyan and black toner images are multiple-transferred onto the transfer belt 5a to form a color toner image on the transfer belt 5a. When the color toner image is formed on the transfer belt 5a, when the transfer paper P conveyed in synchronization with the movement of the transfer belt 5a arrives at the transfer portion between the transfer belt 5a and the secondary transfer roller 5g, the color image is formed. The toner images are collectively transferred to the transfer paper P.

The color toner image transferred to the transfer paper P is heated and pressurized by the fixing device 7 so as to be fused and fixed to the transfer paper P. Further, the transfer residual toner on the photosensitive drum 1 is removed by the cleaning device 6, and the transfer residual toner on the transfer belt 5a is also removed by the cleaning device 8.

[0010]

However, in the above-described conventional image forming apparatus, if the temperature in the image forming apparatus main body changes or the number of image formations overlaps,
The circumference and thickness of the transfer belt 5a change. For example,
As a result of the change in the thickness of the transfer belt 5a, the transfer belt 5a
Of the toner image formed on the transfer paper P, the desired image magnification cannot be obtained.

That is, the distance L to the surface of the transfer belt 5a is represented by the sum of the radius R of the drive roller 5b and the thickness t of the transfer belt 5a as shown in FIG. The peripheral speed v of the transfer belt 5a is determined by the product of the rotation speed ω of the drive roller 5b and the distance L from the center of the drive roller 5b to the surface of the transfer belt 5a. Therefore, if the thickness t of the transfer belt 5a changes due to temperature change or durability,
The distance L to the surface of the transfer belt 5a changes,
Eventually, the peripheral speed v of the transfer belt 5a changes.

When the peripheral speed v of the transfer belt 5a changes, the relative speed between the transfer belt 5a and the photosensitive drum 1 changes, so that a toner image of a predetermined magnification cannot be obtained on the transfer paper P. In other words, as shown in FIG. 7A, the transfer belt 5a is transferred to the toner image on the transfer paper P when the relative speed between the transfer belt 5a and the photosensitive drum 1 is appropriate.
When the peripheral speed v of the transfer belt 5a is low, the toner image on the transfer paper P becomes an overall contracted image as shown in FIG. 7B. As shown in FIG. 7C, the toner image on the paper P is an image which is entirely extended.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has an appropriate image magnification even when the temperature in the second image carrier changes and the number of formed images increases. It is an object to provide an image forming apparatus capable of obtaining a toner image.

[0014]

In order to achieve the above object, an image forming apparatus according to the present invention forms an electrostatic latent image by irradiating a first image carrier with scanning light. An exposure device; and a second image carrier to which a toner image formed on the first image carrier is repeatedly transferred. The toner image multiplex-transferred onto the second image carrier is recorded on a recording material. A temperature detecting means for detecting the temperature in the second image carrier, and a temperature in the second image carrier detected by the temperature detecting means. A control unit for controlling at least one of a scanning speed of the exposure device, a moving speed of the first image carrier, and a moving speed of the second image carrier.

According to a second aspect of the present invention, there is provided an exposure apparatus for irradiating a scanning light to a first image carrier to form an electrostatic latent image, and wherein a toner image formed on the first image carrier is repeatedly formed. A second image carrier to be transferred, wherein the toner images multiplex-transferred to the second image carrier are collectively transferred to a homecomer. Counting means for counting, based on the number of image forming sheets of the recording material counted by the counting means, a scanning speed of the exposure device, a moving speed of the first image carrier,
Control means for controlling at least one of the moving speeds of the second image carrier.

According to the third aspect of the present invention, when the peripheral speed of the second image carrier decreases, the control means reduces the rotational speed of the polygon mirror provided in the exposure device. To control.

According to a fourth aspect of the present invention, when the peripheral speed of the second image carrier decreases, the control means determines the number of rotations of the polygon mirror provided in the exposure device and the first number. And the rotation speed of the image carrier is controlled to decrease.

According to the fifth aspect of the present invention, the control means increases the rotation speed of the second image carrier when the peripheral speed of the second image carrier decreases. Control.

According to the invention, the second image carrier is constituted by a transfer belt or a transfer drum.

[Operation] Based on the above configuration, a first aspect is provided.
According to the invention described above, the scanning speed of the exposure device, the moving speed of the first image carrier, and the movement of the second image carrier are based on the temperature inside the second image carrier detected by the temperature detecting means. By controlling at least one of the speeds, a change in image magnification due to a temperature change is prevented.
For example, when the temperature of the second image carrier rises,
In order to reduce the peripheral speed of the image carrier, the scanning speed of the exposure device is decreased by the control means, the moving speed of the first image carrier is decreased, or the second speed is decreased.
The moving speed of the image carrier is increased.

According to the second aspect of the present invention, the scanning speed of the exposure device, the moving speed of the first image carrier, and the moving speed of the second image carrier are based on the number of image formations counted by the counting means. By controlling at least one of the speeds, a change in image magnification due to durability is prevented. For example, when the number of formed images exceeds a predetermined number, it is determined that the peripheral speed of the second image carrier is increased, and the control unit increases the scanning speed of the exposure device,
Increasing the moving speed of the first image carrier,
Alternatively, the moving speed of the second image carrier is reduced.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings. <First Embodiment> FIG. 1 is a schematic structural view showing an image forming apparatus according to a first embodiment of the present invention. In FIG. 1, the same components as those in FIG. And a duplicate description is omitted. In the figure, reference numeral 9 denotes a temperature sensor as a temperature detecting means using a thermocouple, a thermistor, or the like for detecting the temperature inside the image forming apparatus main body. This temperature sensor 9 accurately detects the temperature of the transfer belt 5a. For this purpose, as shown in the vicinity of the intermediate transfer member 5 and in the present embodiment,
It is more preferable to arrange inside the intermediate transfer member 5. 10 is
It is a printer controller as control means for controlling the number of rotations of the drive roller 5b based on the temperature of the transfer belt 5a detected by the temperature sensor 9.

Next, a change in the thickness of the transfer belt 5a with respect to a change in the temperature in the intermediate transfer member 5 shown in FIG. 2 will be described. It should be noted that urethane rubber having a circumference of 400 mm and a thickness of 1 mm was used as the transfer belt 5a. A tension of 5 kg was applied to the tension roller 5e by the spring 5d. As is apparent from FIG. 2, when the temperature of the transfer belt 5a when the temperature in the intermediate transfer body 5 is 20 ° C. is set as a reference, the change in the thickness of the transfer belt 5a at a temperature of 10 ° C. is +0.1 mm. Therefore, the thickness of the transfer belt 5a is 1.1 mm, and the temperature of the transfer belt 5a is 30 mm.
At ° C., the amount of change in the thickness of the transfer belt 5a is -0.1 mm, and therefore, the thickness of the transfer belt 5a is changed to 0.9 mm. In the present embodiment, the radius of the driving roller 5b is 10 mm, and if the peripheral speed when the thickness of the transfer belt 5a is 1.0 mm is 100%, the thickness of the transfer belt 5a is 1.1 mm.
The peripheral speeds for mm and 0.9 mm are as follows, respectively.

First, when the thickness of the transfer belt 5a is 1.1 mm (10 + 1.1) ÷ (10 + 1) × 100 ≒ 101% Next, when the thickness of the transfer belt 5a is 0.9 mm, (10 + 0.9) ) ÷ (10 + 1) × 100 ≒ 99% That is, in a low-temperature environment at a temperature of 10 ° C., the transfer belt 5a
Moves about 1% faster, and conversely, in a high temperature environment of 30 ° C,
The transfer belt 5a moves about 1% slower. Therefore, in a low-temperature environment of 10 ° C., the toner image
The image expands as shown in (c), and in a high temperature environment of 30 ° C., the image becomes in a contracted state as shown in FIG.
In each case, the image magnification fluctuates.

For this reason, in the embodiment of the present invention, the temperature inside the intermediate transfer member 5 is detected by the temperature sensor 9, and the rotation speed of the drive roller 5 b is controlled by the printer controller 10 based on the detected temperature. Thus, the image magnification is prevented from changing due to the temperature change.

Specifically, when the temperature of the transfer belt 5a is low and the thickness of the transfer belt 5a changes greatly, the number of rotations of the drive roller 5b is reduced, and conversely, the transfer belt 5a
Is high and the thickness of the transfer belt 5a changes thinly, the rotational speed of the drive roller 5b may be increased.
The method of changing the rotation speed of the driving roller 5b may be any of a conventionally known electric method and a mechanical method.
The method of changing the frequency for controlling the number of rotations is the most accurate, and does not require a mechanism for changing the speed, so that the method can be downsized and economical.

The rotation speed ω of the driving roller 5b is obtained as follows.

Ω = v / {R + t ₀ −k ₁ (T−20)} (1) v: peripheral speed of the transfer belt 5 a R: radius of the drive roller 5 b t ₀ : thickness of the transfer belt 5 a at a reference temperature of 20 ° C. K ₁ : transfer belt thickness temperature change coefficient T: temperature The above conditions are substituted into the above equation (1), and the rotational speed ω with respect to the temperature T when the rotational speed ω at 20 ° C. is 100%. Is as follows.

Ω = (11 × 100) / (11.2-0.
01T) (%) This relational expression may be stored in the printer controller 10, the desired rotation speed ω may be obtained from the temperature of the transfer belt 5a detected by the temperature sensor 9, and the rotation speed of the drive roller 5b may be controlled.

In the first embodiment, the case where the rotation speed of the drive roller 5b is controlled by the temperature in the transfer belt 5a has been described. However, the rotation speed of the photosensitive drum 1 and the polygons are controlled by the temperature in the transfer belt 5a. The number of rotations of the mirror 3b may be controlled to adjust the image magnification set at the time of image formation. In this case, when the temperature in the transfer belt 5a rises above the reference temperature, the rotation speed of the polygon mirror 3b is reduced or the rotation speed of the photosensitive drum 1 and the rotation speed of the polygon mirror 3b are reduced. In particular, the latter enables the relative speed between the photosensitive drum 1 and the transfer belt 5a to be kept constant, which is preferable from the viewpoint of transfer efficiency.

The intermediate transfer member 5 includes a transfer belt 5
Although the case where b is used has been described, the invention is not limited to this, and an intermediate transfer member using a transfer drum may be used. <Second Embodiment> Next, a second embodiment will be described with reference to FIG.

FIG. 3 is a schematic configuration diagram showing an image forming apparatus according to a second embodiment of the present invention. In FIG. 3, the same components as those in FIG. Omitted.

In the figure, reference numeral 11 denotes a counter as counting means for counting the number of image formations. The feature of the present embodiment is that, by controlling at least one of the rotation speeds of the driving roller 5b, the photosensitive drum 1, and the polygon mirror 3b according to the number of images to be formed, a change in image magnification due to durability as a result of overlapping the number of images to be formed Is to prevent.

FIG. 4 is a diagram showing the relationship between the number of formed images and the amount of change in the thickness of the transfer belt 5a. In this embodiment, the transfer belt 5a and the driving roller 5b are the first
The same one as that of the embodiment is used.

As is apparent from FIG. 4, as the number of formed images increases and the durability increases, the thickness of the transfer belt 5a gradually decreases, and therefore the peripheral speed of the transfer belt 5a gradually decreases. Therefore, based on the number of image formation counted by the counter 11, the printer controller 10
Thus, the number of rotations of the driving roller 5b is controlled to be gradually increased. When the thickness of the transfer belt 5a shows the characteristic shown in FIG. 4, the rotation speed ω of the drive roller 5b is as follows.

Ω = v / (R + t ₀ −k ₂ log N) (2) v: peripheral speed of transfer belt 5 a R: radius of drive roller 5 b t ₀ : thickness of transfer belt 5 a at the first image formation number k ₂ : Thickness of transfer belt 5a Image formation number change coefficient N: Image formation number The above conditions are substituted into the above equation (2), and the rotational speed ω at the initial stage of the image formation number is 100%. , The number of rotations ω with respect to the number N of formed images is as follows.

Ω = 11 × 100 / (11−0.05 log N) (%) This relational expression is held in the printer controller 10,
A desired rotational speed ω may be obtained from the number of image formation counted by the counter 11 and controlled.

In the second embodiment, the case where the number of rotations of the drive roller 5b is controlled by the number of images to be formed, but the number of rotations of the photosensitive drum 1 and the number of rotations of the polygon mirror 3b by the number of images to be formed. The image magnification may be controlled and adjusted to the image magnification set at the time of image formation. In this case, control is performed such that the rotation speed of the polygon mirror 36 is reduced or the rotation speed of the photosensitive drum 1 and the rotation speed of the polygon mirror 3b are reduced in accordance with the increase in the number N of formed images.

Further, the control based on the temperature in the image forming apparatus main body of the first embodiment and the control based on the number of images to be formed may be combined.

[0040]

As described above, according to the first aspect of the present invention, the scanning speed of the exposure device and the first image carrier based on the temperature inside the second image carrier detected by the temperature detecting means. Since at least one of the moving speed of the body and the moving speed of the second image carrier is controlled, a change in image magnification due to a temperature change can be prevented.

According to the second aspect of the present invention, the scanning speed of the exposure device, the moving speed of the first image carrier, and the moving speed of the second image carrier are based on the number of formed images counted by the counting means. Since at least one of the speeds is controlled, it is possible to prevent a change in the image magnification due to the durability as a result of stacking the number of formed images.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram illustrating a relationship between a change in a thickness of a transfer belt and a temperature according to the first embodiment.

FIG. 3 is a schematic configuration diagram illustrating an image forming apparatus according to a second embodiment of the present invention.

FIG. 4 is a diagram illustrating a relationship between the number of formed images and a change amount of a thickness of a transfer belt according to the second embodiment.

FIG. 5 is a schematic configuration diagram illustrating an example of a conventional image forming apparatus.

FIG. 6 is an enlarged view illustrating a transfer belt and a driving roller of the image forming apparatus.

FIG. 7 is a diagram illustrating a change in image magnification during image formation based on a change in peripheral speed of the transfer belt.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st image carrier (photosensitive drum) 3 Exposure apparatus 3b Polygon mirror 5 2nd image carrier (intermediate transfer body) 5a Transfer belt 9 Temperature detection means (temperature sensor) 10 Control means (printer controller) 11 Counting means (counter)

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takaaki Tsuruya 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (6)

[Claims] An exposure device configured to irradiate a first image carrier with scanning light to form an electrostatic latent image; and a second device configured to repeatedly transfer a toner image formed on the first image carrier. An image forming apparatus, comprising: an image carrier, wherein the toner images multiplex-transferred onto the second image carrier are collectively transferred onto a recording material; and a temperature for detecting a temperature inside the second image carrier. Detecting means, a scanning speed of the exposure device, a moving speed of the first image carrier, and a movement of the second image carrier based on the temperature inside the second image carrier detected by the temperature detecting means. Control means for controlling at least one of the speeds. 2. An exposure apparatus for irradiating a scanning light to a first image carrier to form an electrostatic latent image, and a second apparatus for repeatedly transferring a toner image formed on the first image carrier. An image forming apparatus comprising: an image carrier, wherein the toner images multiplex-transferred onto the second image carrier are collectively transferred onto a recording material, wherein a counting means for counting the number of images formed on the recording material; At least one of a scanning speed of the exposure device, a moving speed of the first image carrier, and a moving speed of the second image carrier, based on the number of image formed sheets of the recording material counted by the counting unit. An image forming apparatus, comprising: control means for controlling one of the speeds. 3. The control means controls the rotation speed of a polygon mirror provided in the exposure device to decrease when the peripheral speed of the second image carrier decreases. The image forming apparatus according to claim 1 or 2, wherein 4. The control device according to claim 1, wherein when the peripheral speed of the second image carrier decreases, the rotation speed of the polygon mirror provided in the exposure device and the rotation speed of the first image carrier are adjusted. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled to lower the image forming apparatus. 5. The control device according to claim 1, wherein when the peripheral speed of the second image carrier decreases, the control unit controls to increase the rotation speed of the second image carrier. The image forming apparatus according to claim 1. 6. The image forming apparatus according to claim 5, wherein the second image carrier is configured by a transfer belt or a transfer drum.