JP2915699B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanism for pressing a transfer roller against a photosensitive member via an intermediate transfer member in an image forming apparatus such as a full-color copying machine having an intermediate transfer member.

[0002]

2. Description of the Related Art A conventional color copying machine will be described with reference to FIGS. In the drawing, reference numeral 1 denotes a document table, 2 denotes an exposure optical system, 2a denotes a light source lamp, 2b denotes a reflection mirror, 2c denotes an image forming lens, 2d denotes a color separation filter, 3 denotes a belt-shaped organic photoreceptor (OPC), Denotes a paper feed cassette, 5 denotes a paper feed roller, 6 denotes a timing roller, and 7 denotes a belt-shaped intermediate transfer member.

The intermediate transfer member 7 includes first to third rollers 8a,
8b, 8c, and is wrapped in a U-shape.
The photoconductor 3 is pressed against a photoconductor drive roller 9 that drives the photoconductor 3.

A pair of first transfer rollers 10 for transferring a toner image on the photosensitive member 3 to the intermediate transfer member 7 by applying a high voltage is provided on the back side of the intermediate transfer member 7 which is pressed against the photosensitive member 3. The transfer charger 11 is provided.

[0005] A second transfer roller 12 is disposed on the surface of the intermediate transfer member 7 at the position where the third roller 8c is disposed. On the delivery side of the second transfer roller 12, a peeling plate 13, a transport belt 14, and a fixing device 15 are arranged in this order.

In the drawing, reference numeral 16 denotes a charging charger;
Denotes a neutralization lamp, 18 denotes a cleaning device, 19 denotes a black and white developing tank, and 20 to 22 denote color developing tanks.

[0007]

However, in the above-mentioned conventional copying machine, as shown in FIG. 14, the intermediate transfer member 7 includes rollers 8a, 8b and 8c and a photosensitive member driving roller 9 for driving the photosensitive member 3. It is attached in a U-shape by applying tension to it by press-contacting to it.

In this structure, a large amount of stress is applied to the surface of the intermediate transfer member 7 near the rollers 8a, 8b, and 8c due to the tension applied to the intermediate transfer member 7, and the intermediate portion near the drive roller 9 The back side of the transfer body 7 is apt to receive much stress, and the belt is easily damaged.

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide an image forming apparatus which reduces stress caused by tension of an intermediate transfer member and suppresses damage to the intermediate transfer member.

[0010]

SUMMARY in accordance with the present onset bright Means for Solving the Problems] are as shown in FIG. 1, the intermediate transfer member 29 of the rotatable endless toner image formed on the photoconductor 23 is transferred, A transfer unit 35 for transferring a toner image from the photoconductor 23 to the intermediate transfer body 29, and the transfer unit 35 is pressed against and separated from the photoconductor 23 via the intermediate transfer body 29, thereby transferring the intermediate transfer body 29 to the photoconductor 23. The intermediate transfer member 29 includes a plurality of rollers 31.
a, 31b, and 31c, and held in a substantially elliptical shape.
The transfer unit 35 and the pressure
The contact / separation means 36 is provided.

[0011] Then, the transfer Yunitsuto 35 includes a transfer roller 34 for transferring the toner image on the photosensitive member 23 by applying a voltage to the intermediate transfer member 29, the intermediate transfer member 29 disposed in parallel with the transfer roller 34 And a pressing roller 48 for pressing the photosensitive member 23 through the photosensitive member 23. The transfer roller 34 is configured to prevent the photosensitive member 23 from being damaged when the pressing roller 48 is pressed.
3 with a gap.

Further, a pressure contact variable portion 59 for gradually changing the pressure force of the pressure roller 48 of the transfer unit 35 constantly pressed against the photosensitive member 23, and when the power is turned on, the pressure force of the pressure roller 48 is increased, and the power is turned off. In some cases, a control unit 66 that drives the pressure contact variable unit 59 so as to reduce the pressure contact force of the pressure roller 48 is provided.

[0013]

[0014]

In the above-mentioned means for solving the above problems, the pressing roller 48
Is in pressure contact with the intermediate transfer member 29, and the transfer roller 34 is in contact with the intermediate transfer member 29 but is separated from the photosensitive member 23. When a voltage is applied to the transfer roller 34, a toner image is transferred to the intermediate transfer body 29. Since the transfer roller 34 is not in direct contact with the photoconductor 23, it does not damage the photoconductor 23 when a voltage is applied.

When the power is turned off, the intermediate transfer member 2 is turned off.
9 rotates idly, and the pressure contact variable portion 59 is driven to reduce the pressure applied to the pressure contact roller 48. Therefore, when not in use, the intermediate transfer member 29 is in pressure contact with the photoconductor 23.
Is pressed with a small pressing force, so that the stress applied to the intermediate transfer body 29 can be reduced.

When the intermediate transfer member 29 is exchanged, first, the pressing roller 48 is pressed against the photosensitive member 23 through the intermediate transfer member 29 with a certain pressure by operating the pressing / separating means 36, and then the intermediate transfer member is moved. During the idle rotation of the body 29, the pressure is gradually increased by the rotation of the cam 60, so that the photoreceptor 23, the intermediate transfer body 29, and the transfer unit
5 can be reduced, and damage can be suppressed.

Further, even when the intermediate transfer member 29 is mounted obliquely, the intermediate transfer member 29 is gradually pressurized while idling, so that tension is applied to the intermediate transfer member 29 so that the intermediate transfer member 29 can be moved to a natural position. Then, the wobble can be corrected during rotation, and the wander can be suppressed.

[0018]

【Example】

<First Embodiment> FIG. 1 is a perspective view of a press-contact portion of an intermediate transfer member of a copying machine to a photosensitive member according to a first embodiment of the present invention, FIG. 2 is a front view of a transfer roller and a press roller, and FIG. FIG. 4 is a view showing a pressure distribution when the intermediate transfer member is pressed against the photosensitive member, and FIG. 4A is a diagram showing a pressure contact force of the pressing roller of 2 kg.
/ Cm ² , (B) shows that the pressing force of the pressing roller is 5 kg
/ Cm ² , FIG. 5 is a diagram showing the relationship between the applied voltage and the image density when the pressing force of the pressing roller is changed, FIG. 6 is a configuration diagram showing the intermediate transfer member separated from the photoreceptor, FIG. 7 is a configuration diagram showing the intermediate transfer member in a state of being pressed against the photosensitive member.

As shown in FIG. 3, the color copying machine of the first embodiment has a transparent document table 20 on the upper surface of the machine frame. An exposure optical system 21 is provided below the document table 20. The exposure optical system 21 emits light to a document 22 placed on the document table 20 with a light source lamp 21a. And a plurality of reflecting mirrors 21b for guiding the reflected light from the document 22 onto the photoreceptor 23 as indicated by a dashed line, for example.
And an imaging lens 21c disposed on the optical path, and red, green,
And a color separation filter 21d having three primary color filters of blue.

On the optical axis of the exposure optical system 21, there is provided a drum-shaped photoconductor 23 made of an organic photoconductor (OPC) to which an optical image subjected to exposure scanning is irradiated. Paper feed cassettes 25 and 26 accommodating transfer paper 24 are disposed on the paper feed direction side of the paper feeder 23. Paper feed rollers 27 and 28 are provided on the upper surfaces of these paper feed cassettes 25 and 26, respectively. These paper feed rollers 27 and 28 transfer the transfer paper 24 from the paper feed cassettes 25 and 26. The sheet is ejected and sent toward the intermediate transfer member 29.

A timing roller 30 is provided on the side from the paper feed rollers 27 and 28 toward the intermediate transfer member 29. The timing roller 30 is rotated in synchronization with the intermediate transfer member 29. It has become so. Also,
The intermediate transfer member 29 is a belt-shaped first to third roller 31.
a, 31b, and 31c, are held in a substantially elliptical shape, and are rotationally driven by the intermediate transfer body driving unit 32. The intermediate transfer body driving unit 32 includes first to third rollers 31a and 31a.
b, 31c and the first roller 31a via a gear and a belt.
And a drive motor 33 for driving the motor.

A transfer unit 35 having a first transfer roller 34 for transferring the toner image on the photosensitive member 23 to the intermediate transfer member 29 is disposed on the back side of the intermediate transfer member 29 which is pressed against the photosensitive member 23. I have. The transfer unit 35 can be pressed and separated from the photoreceptor 23 via the intermediate transfer member 29 by pressing and separating means (pressing unit) 36.

A second transfer roller 37 is disposed on the surface of the intermediate transfer member 29 at the position where the third roller 31c is disposed. Then, on the sending side of the second transfer roller 37,
Release plate 38, transport belt 39, and fixing device 40
Are arranged in this order.

A charger 41 for charging the photosensitive member 23 and a discharge lamp 42 for removing the charge from the photosensitive member 23 are provided around the outer periphery of the photosensitive member 23. A cleaning device 43 as cleaning means for removing toner remaining on the body 23 is provided. Above that,
A developing tank 44 for black and white and developing tanks 45 to 47 for color are provided independently of each other in a state of not contacting the photoreceptor 23, and yellow and magenta are provided in the developing tanks 45 to 47 for color. , And cyan color developers are individually accommodated.

The transfer unit 35 is, as shown in FIGS. 1 and 2, a pressure roller 48 for pressing the photosensitive member 23 through an intermediate transfer member 29, and an intermediate transfer of the toner image on the photosensitive member 23 by applying a high voltage. The unit comprises a first transfer roller 34 for transferring the image onto the body 29, and a unit body 35a which rotatably supports the pressure roller 48 and the first transfer roller 34 via shafts 48a and 34a, respectively.

Both ends of the first transfer roller 34 have diameters slightly larger than the diameter of the first transfer roller 34 so that the first transfer roller 34 is not directly pressed against the photosensitive member 23 via the intermediate transfer member 29. A flange 34b for preventing pressure contact is provided. The flange 34b is in contact with the photoconductor 23.

As shown in FIG. 2, the distance between the pressing roller 48 and the first transfer roller 34 is 10 mm or more, and the contact portion of the first transfer roller 34 with the intermediate transfer member 29 is It is inclined at least 3.0 degrees with respect to the contact portion with the photoconductor. Accordingly, when the first transfer roller 34 does not directly contact the photoconductor 23 and a high voltage is applied to the first transfer roller 34, it is possible to prevent the surface of the photoconductor 23 from being damaged.

The unit body 35a is rotatably supported at both axial ends thereof by a frame of the copying machine body H via a shaft 35b.

The pressurizing unit 36 is connected to the transfer unit 3
5, a pair of push-up bodies 49 for pushing up the unit body 35a in the direction of the photoreceptor 23, a connecting rod 50 rotatably supported by the copier body H and connecting the lower portions of both push-up bodies 49, and a front side of the copier body H. And a lever 51 fixed to the end of the connecting rod 50.

The lifting body 49 is connected to the unit body 35.
a rolling roller 52 that presses while rolling the lower surface of a, a rolling roller supporting member 53 that rotatably supports the rolling roller 52, and a rectangular parallelepiped in which the rolling roller supporting member 53 is slidably mounted. And a compression spring 54 that urges the rolling roller support member 53 upward.

When the pressure roller 48 of the transfer unit 35 is pressed against the photosensitive member 23 via the intermediate transfer member 29, the biasing force of the compression spring 54 presses the photosensitive member 23 with an optimum pressing force. It is set as follows. This pressing force is set based on experiments.

FIG. 4 shows the pressure distribution when the intermediate transfer member 29 is pressed against the photosensitive member 23 by the pressing roller 48. The dots in the figure indicate the photosensitive member 23 and the pressing roller 4.
8 shows a state in which they are in pressure contact with each other. FIG. 4A shows a state where the pressing force of the pressing roller 48 is 2 kg / cm ² , and FIG. 4B shows a pressing state when the pressing force is 5 kg / cm ² . As described above, when the pressing force is as low as about 2 kg / cm ² , the photosensitive member 23 and the pressing roller 48 are not completely pressed against each other, and when a high voltage is applied to the first transfer roller 34 in this state, the transfer failure of the copied image occurs. Will cause. In an experiment using a change in pressure, it was possible to completely press-contact the photosensitive member 23 and the pressing roller 48 with a pressing force of 3 kg / cm ² or more.

FIG. 5 shows the relationship between the applied voltage and the image density obtained by changing the pressing force of the pressing roller 48. The voltage required to obtain an image density of 1.4 or more that can obtain a good image from the experimental results shown in FIG.
It can be seen that the lower the voltage, the higher the pressing force. However, when pressure is applied at 5 kg / cm ² or more, the image density becomes high or low and is not stable. In this case, characters are missing in the copied image, and it is impossible to actually use the copied image.
Further, even if the pressing force is 5 kg / cm ² or less, 100
If it exceeds 0 V, the image is retransferred.

Therefore, the pressing force of the pressing roller 48 is
3 kg / cm ² or more and 5 kg / cm ² or less, and the voltage applied to the first transfer roller 34 is 700 V or more and 1000 V or more.
It is set to less than V.

The operation of the full-color copying machine having the above configuration will be described below. First, when a copy start switch (not shown) is pressed, a copy mode is executed.
This copy mode has a copy cycle in which yellow, magenta, and cyan are developed and transferred to the intermediate transfer body 29, respectively. When the copy mode is executed,
First, a yellow copy cycle is executed.

That is, the original 22 placed on the original placing table 20 is irradiated with light from the light source lamp 21a to perform exposure scanning. The reflected light from the original 22 is reflected by the reflecting mirror 21.
b and the color separation filter 21 via the imaging lens 21c
d, and is separated for each color component by the color separation filter 21d.

The light for each color component transmitted through each color filter of the color separation filter 21d in the above-described exposure scan is irradiated onto the photoreceptor 23 uniformly charged by the charging charger 41.
The photoreceptor 23 is exposed at the portion A. On the photoreceptor 23, a yellow electrostatic latent image corresponding to the image of the document 22 is formed.

Thereafter, each of the above-described electrostatic latent images is developed with a developer supplied from a developing magnet roller at a portion opposite to a developing tank 45 having a yellow developer which is a complementary color of the color separation filter 21d. It is visualized and becomes a toner image. Then, this toner image is applied to the first transfer roller 34 by the
By applying a voltage of 00 V or more and less than 1000 V, the image is transferred to the intermediate transfer body 29 pressed against the photoconductor 23.

When the yellow copy cycle is completed, the photosensitive member 23 is cleaned by the cleaning device 43 and is discharged by the discharge lamp 42. Then, the magenta and cyan toner images are transferred to the intermediate transfer member 29 in the same copy cycle as described above.

When each copy cycle described above is executed,
The toner image for each color component is transferred to the same position on the intermediate transfer member 29 by the first transfer roller 34, and a single toner image is formed by superimposing the toner images for each color component. become.

On the other hand, the transfer paper 24 stored in the paper feed cassettes 25 and 26 is fed one by one to the timing roller 30 by the paper feed rollers 27 and 28,
A value of 0 conveys the transfer paper 24 between the intermediate transfer member 29 and the second transfer roller 37 in synchronization with the intermediate transfer member 29. After the toner image on the intermediate transfer body 29 is transferred by the second transfer roller 37, the transfer paper 24 conveyed is separated from the intermediate transfer body 29 by the peeling plate 38, and is introduced into the fixing device 40 by the conveyance belt 39. . Then, after the color toner image is fixed on the transfer paper 24, it is discharged to the outside, thereby completing one copy mode.

Each member is periodically inspected by a service person, and the intermediate transfer member must be replaced due to deterioration due to aging or the like.

As shown in FIG. 6, when the lever 51 of the pressure unit 36 is pushed down around the connecting rod 50, the transfer unit 35 is rotated downward by its own weight around the shaft 35b, as shown in FIG. The pressing by the pressing roller 48 is released,
After removing the tension of the intermediate transfer member 29, the intermediate transfer member 29
Replace.

Then, a new intermediate transfer member is added to each roller 31.
a, 31b, and 31c, and manually raising the lever 51 in the direction B of FIG.
2 rolls on the lower surface of the unit body 35a of the transfer unit 35. The transfer unit 35 is rotated in the direction of the photoconductor 23, and lifts the pressing roller 48 and the first transfer roller 34. The pressure contact roller 48 is pressed by a compression spring 54 in the push-up body 49a, and stretches the intermediate transfer member 29 to a substantially elliptical shape while maximally applying the pressure to the photosensitive member 23 by 3 kg / cm ² or more.
It is brought into pressure contact with a pressure of not more than kg / cm ² , as shown in FIG.

As described above, the intermediate transfer member 29 has an elliptical shape and is pressed against the photosensitive member 23 by the pressure roller 48 of the transfer unit 35 at a pressure suitable for transfer of 3 kg / cm ² or more and 5 kg / cm ² or less. ing. For this reason, in the intermediate transfer body 21, stress applied to the intermediate transfer body due to tension as in the related art is reduced, and damage to the intermediate transfer body can be prevented.

<Second Embodiment> FIG. 8 is a flow chart of a press-contact mechanism for an intermediate transfer member of a copying machine according to a second embodiment of the present invention, and FIG. 10 is a perspective view, FIG. 10 is a partial cross-sectional view of the push-up body and the cam when fixed by the lever, FIG. 11 is a partial cross-sectional view of the push-up body and the cam when the power is on, and FIG. 12 is a partial cross-section of the push-up body and the cam when the power is off. FIG.

Members having the same functions as in the first embodiment are denoted by the same reference numerals.

As shown in FIG. 9, the intermediate transfer member 29 in the full-color copying machine of the second embodiment is connected to the pressing / separating means (pressing unit) 36 of the first embodiment and to the photosensitive member via the pressing unit 36. A pressure contact variable portion 59 for varying the pressure force of the pressed pressure roller 48 ; and a pressure contact variable portion 59 for increasing the pressure force of the pressure roller 48 when the power is on, and reducing the pressure force of the pressure roller 48 when the power is off. And a control unit 66 for driving the unit 59.

The pressure-contact variable section 59 is provided for the transfer unit 35.
A rotatable cam 60 for contacting the pressurizing unit 36 at the time of pressing and varying the pressing force, and a cam driving means 61 for driving the cam 60 are provided.

The cams 60 are arranged below the push-up bodies 49 and are fixed to a cam shaft 60a rotatably supported by a frame of the copying machine main body H. The upper portion of the cam 60 abuts on a bottom plate 53a slidably mounted on the push-up body body 49a, and between the bottom plate 53a and the rolling roller support member 53,
A compression spring 54 is interposed. A connecting rod 50 is rotatably fitted on the cam shaft 60a, and one end on the rear side of the copying machine main body H is connected to the cam driving means 61.

The cam driving means 61 uses a driving force of the driving motor 33 of the intermediate transfer member driving section 32 to reduce the driving force from the driving motor 33 and transmit the reduced driving force to the cam shaft 60a. Switching means 63 for separating the driving force from the driving motor 33.

As shown in FIG. 9, the speed reduction mechanism 62 includes a driving gear 33b for transmitting the driving force from the driving motor 33 via a driving belt 33a, and a driving gear 64 meshed with the driving gear 33b. The gear ratio is set to 1: 2, and the rotation speed from the drive motor 33 is reduced to 1/2 and transmitted to the camshaft 60a.

The switching means 63 is an electromagnetic clutch interposed between the driving gear 64 and a driven gear 65 fixed to one end of the camshaft 60a.
And the driven gear 65 are separated from each other.
Driven by the control unit 66 so as to connect the driven gear 65 and the driven gear 65.

The control unit 66 is a microcomputer built in the copying machine main body H. The control unit 66 has a rotation drive function for idling the intermediate transfer member 29 when the power is turned on and off, and a control unit for turning on the power when the transfer unit 35 is pressed. The rotation of the cam 60 pushes up the transfer unit 35 to drive the cam driving means 61 so that the pressing force of the pressing roller 48 becomes 3 kg / cm ² to 5 kg / cm ² , and the rotation of the cam 60 when the power is turned off. pressure low by lowering the transfer Yunitsuto 35 by
And a pressure reducing function for driving the cam driving means 61 so that the pressing force of the roller 48 becomes 5 kg / cm ² to 3 kg / cm ² .

The copier main body H is provided with a timer for turning off all power after a lapse of a predetermined time after the power switch is turned off. After the power switch is turned off, the intermediate transfer member 29 idles for a certain time. After that, turn off all power.

In the above configuration, as shown in FIG. 8, when the replacement of the intermediate transfer member 29 is completed, the pressing roller 48 is pressed against the photosensitive member 23 via the intermediate transfer member 29 with a pressing force of 3 kg / cm ² . At this time, the cam 42 is at the position shown in FIG.

Here, when the power is turned on, the intermediate transfer member 29 is idled by a simulation function for simulating a part of the machine before the copying operation. At this time, the electromagnetic clutch 63 is operated by the control unit 66 to bring the main driving gear 64 and the driven gear 65 into a connected state, and the driving force of the driving motor 33 of the intermediate transfer body driving unit 32 is transmitted to the cam shaft 60a. Therefore, at the same time as the intermediate transfer body 29 rotates,
The cam 60 rotates slowly at half the rotation speed of the drive motor 33.

By the rotation of the cam 60, the rolling roller supporting member 53 is pushed up via the bottom plate 53a, and as shown in FIG. 11, the rolling roller 52 gradually presses the transfer unit 35 upward, and the pressing roller 48 is moved to the intermediate position. The transfer member 29 is pressed against the photosensitive member 23 at a pressure of 5 kg / cm ² while maximally stretching the transfer member 29. Then, the electromagnetic clutch 63 is turned off, and the driving gear 64 and the driven gear 65 are separated from each other, so that a normal transfer is possible.

When the power is turned off, the intermediate transfer body driving section 32 is driven, and the intermediate transfer body 29 is idled for a certain period of time. Then, the cam 60 is rotated again to lower the pressure of the transfer unit 35 as shown in FIG. 12, and the pressing force of the pressing roller 48 is set to 3 kg / cm ² .

As described above, when the intermediate transfer member 29 is pressed against the photosensitive member 23 at the time of replacement of the intermediate transfer member 29, first, the pressing roller 48 is operated by operating the lever 51 to move the intermediate transfer member 2.
9 to press the photosensitive member 23 at a pressure of 3 kg / cm ² , and then, when the intermediate transfer member 29 is idle, gradually pressurized to a pressure of 5 kg / cm ² by the rotation of the cam 60. Compared to the case of pressing and fixing at a stretch, the photoconductor 23,
Shock to the intermediate transfer member 29, the transfer unit 35, and the like can be reduced, and damage to the photoconductor 23 can be suppressed.

Even when the intermediate transfer member 29 is mounted obliquely, since the intermediate transfer member 29 is gradually pressurized while idling, the tension is applied to the intermediate transfer member 29 so that the intermediate transfer member 29 can be moved to a natural position. Then, the wobble can be corrected during rotation, and the wander can be suppressed.

Further, when the power is turned on, the pressing roller 48
The contact pressure and optimum pressure contact state to transfer pressurized to 5 kg / cm ^2, when the power is turned off, 3 the pressing force of the pressure roller 48
kg / cm ² to reduce the intermediate transfer member 29 when not in use.
Relieve stress on Therefore, the intermediate transfer body 2
9 can be extended.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that many modifications and changes can be made to the above-described embodiment within the scope of the present invention.

For example, a unit in which the transfer unit 35 and the pressure unit 41 are integrated may be provided, and this unit may be pressed against the photosensitive member by a cam or the like.

As a method for varying the pressing force of the pressing roller 48 , a solenoid, a cylinder, or the like may be used.

[0066]

As apparent from the above description, according <br/> to the onset bright, since the transfer roller and the photosensitive member does not directly contact,
When a voltage is applied to the transfer roller, the photoconductor is not destroyed.

The transfer unit is separated from the photosensitive member when the intermediate transfer body is replaced , or the transfer unit is depressurized when the power is turned off to reduce the pressing force of the pressing roller to reduce the stress applied to the intermediate transfer body. can do. For this reason, the life of the intermediate transfer member can be extended. When the power is turned on, the pressing roller is gradually applied.
Pressing, photoconductor, intermediate compared to pressing at once
Shock to transfer body, transfer unit, etc. can be reduced, preventing damage
Can be obtained.

The intermediate transfer member is held in a substantially elliptical shape.
So that stress due to tension is less likely to be applied.
Can be in a state. In addition, this allows intermediate transfer
Since there is a space inside the body, here the transfer unit
Space and pressure contact / separation means
Can be effectively used, and the size of the device can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view of a portion of a copying machine in which an intermediate transfer member is pressed against a photosensitive member according to a first embodiment of the present invention.

FIG. 2 is a front view of a transfer roller and a pressing roller;

FIG. 3 is an overall configuration diagram of a copying machine.

[Figure 4] a diagram showing a pressure distribution during pressing of the intermediate transfer member to the photosensitive member, (A) is pressing force of the press roller 2 kg / cm ²
(B) shows that the pressing force of the pressing roller is 5 kg / cm ²
When

FIG. 5 is a diagram illustrating a relationship between an applied voltage and an image density when a pressing force of a pressing roller is changed.

FIG. 6 is a configuration diagram illustrating an intermediate transfer member separated from a photoconductor;

FIG. 7 is a configuration diagram showing an intermediate transfer member in a state in which the intermediate transfer member is pressed against a photoconductor;

FIG. 8 is a flowchart of a pressing mechanism of an intermediate transfer member of the copying machine according to the second embodiment.

FIG. 9 is a perspective view of a transfer unit, a pressure contact / separation unit, and a pressure contact variable portion of the copying machine.

FIG. 10 is a partial cross-sectional view of the push-up body and the cam when the lever is fixed.

FIG. 11 is a partial cross-sectional view of the push-up body and the cam when the power is turned on.

FIG. 12 is a partial cross-sectional view of the push-up body and the cam when the power is off.

FIG. 13 is an overall configuration diagram of a conventional copying machine.

FIG. 14 is a perspective view showing a state in which a conventional intermediate transfer member is mounted.

[Explanation of symbols]

 Reference Signs List 23 photoconductor 32 intermediate transfer member drive unit 29 intermediate transfer member 34 transfer roller 35 transfer unit 36 pressure contact / separation means 48 pressure contact roller 59 pressure contact variable unit 66 control unit

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Kawamoto 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Katsuhiro Nagayama 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (56) References JP-A-5-72840 (JP, A) JP-A-56-164372 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/16

Claims (3)

(57) [Claims] A rotatable endless intermediate transfer member onto which a toner image formed on a photoconductor is transferred; a transfer unit for transferring a toner image from the photoconductor to the intermediate transfer member; and the transfer unit. the a pressure separating means for pressing away the photosensitive member via an intermediate transfer member, the transfer Yunitsuto the toner on the photosensitive member by applying a voltage
A transfer roller for transferring an image to an intermediate transfer member, and a photoreceptor arranged in parallel with the transfer roller via the intermediate transfer member
The transfer roller has a pressing roller that presses against the photosensitive member.
An image forming apparatus , wherein a photoconductor is disposed with a gap between the photoconductor and the photoconductor . 2. An endless rotatable intermediate transfer member onto which a toner image formed on a photosensitive member is transferred, a transfer unit for transferring a toner image from the photosensitive member to the intermediate transfer member, and an intermediate transfer member. a pressure separating means for pressing away the transfer Yunitsuto the photoconductor via the intermediate transfer member when exchanging a pressure variable portion of gradually variable pressure contact force of the pressure roller always pressed transcription Yunitsuto the photoreceptor, An image forming apparatus comprising: a control unit that drives a press-contact variable unit so as to increase the press-contact force of the press-contact roller when the power is turned on and to decrease the press-contact force of the press-contact roller when the power is off. 3. The intermediate transfer member is wound around a plurality of rollers.
And a transfer unit and a pressure contact / separation unit are provided inside the intermediate transfer member.
The image forming apparatus according to claim 1, wherein the image forming apparatus is arranged .