JPH09325552A - Pressurizing mechanism for unit device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressurizing mechanism capable of mitigating vibration or a shock occurring when a unit device is pressed and facilitating the attachment and the detachment of the unit device to/from a device main body. SOLUTION: A developing unit (unit device) 4C executing an approaching and a separating actions to/from a photosensitive drum (the other unit) 1 is set to that it can be moved to a pressing position where it is positioned by approaching the drum 1, a standby position separated from the pressing position by a required distance and a retreat position separated from the standby position. Besides, the moving distance to the pressing position from the standby position of the unit 4C is set to be shorter than the moving distance to the retreat position from the pressing position of an action finish time. Thus, the speed of the pressing time of the unit 4C is reduced and the vibration and the shock are softened when the unit 4C is pressed. Besides, the sufficiently long distance can be secured between the unit 4C and the drum 1, and the attachment and the detachment of the unit 4C to/from the device main body are facilitated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressurizing mechanism for a unit device such as a developing device and a suction roller for performing an approaching operation and a separating operation with respect to an image carrier and a recording material carrier in an image forming apparatus or the like.

[0002]

2. Description of the Related Art A developing device of an image forming apparatus is a unit device that can be moved closer to and away from another unit and is positioned under pressure with respect to another unit. This will be explained as an example.

In a developing device of an image forming apparatus, a developing roller, which is a developer carrying member, is arranged with a predetermined gap between it and a photosensitive drum, which is an image carrying member, and the developing roller has a predetermined alternating pattern. By applying a voltage to form an alternating electric field with the photosensitive drum, the toner on the developing roller is caused to fly to an electrostatic latent image on the photosensitive drum, and the electrostatic latent image is visualized as a toner image. The non-contact developing method is often used.

In the developing device adopting such a non-contact developing system, the abutting member provided on the developing roller side is abutted against the abutted member provided on the non-image area of the photosensitive drum surface or on the photosensitive drum side, In many cases, the gap between the developing roller and the photosensitive drum is maintained with high accuracy by pressing the developing device itself toward the photosensitive drum.

Incidentally, for example, in a multicolor image forming apparatus having a plurality of developing devices around the photosensitive drum, only the developing device having a desired toner is moved from the predetermined standby position to the developing position to the photosensitive drum side. In this case, the photosensitive drum and the developing device are positioned by abutting members provided at the front and rear two positions on the developing roller side against corresponding abutted members provided at the front and rear two positions on the photosensitive drum side. After that, this developing device is pressed to the photosensitive drum side.

[0006]

However, in the developing device in which the gap between the photosensitive drum and the developing roller is held constant via the abutting member and the abutted member as described above, the developing device is a photosensitive member. Vibration is generated by the impact of two abutting operations at the front and rear when abutting against the drum side, and this vibration propagates not only to the developing device itself but also to the photosensitive drum and the like, causing disturbance of the image.

That is, when the latent image is formed on the photosensitive drum by the optical means, if the vibration is transmitted to the photosensitive drum or the optical means, the latent image is disturbed and the photosensitive drum or the developing device is vibrated during the development. Is left, development failure will occur. Further, if the vibration is transmitted when the image is transferred onto the recording material, the transfer is disturbed. Such image disturbance generally appears as "blurring", which is a major cause of image quality deterioration.

In order to eliminate such inconvenience, a method of suppressing the pressing speed of the developing device to reduce the impact at the time of abutting may be considered. According to this method, the moving time becomes long and the pressing time is limited. This method is unacceptable for some high-speed type image forming apparatuses.

A method of lowering the mass of the developing device itself to suppress the impact at the time of abutting may be considered, but since the developing device has parts having a relatively large mass such as a developing roller, image blurring can be prevented. It has been practically difficult to reduce the weight of the developing device to a certain degree. In this case, there is also a method of making the developing container small and reducing the amount of developer held in the developing device. However, if the amount of developer held is reduced, the number of times of supplying the developer to the developing device increases, and the operation is That's not valid.

Further, there is also a method of reducing the pressing speed of the developing device by shortening the moving stroke of the developing device by shortening the pressing stroke of the developing device (the distance from the standby position to the developing position). When removing the developing device from the main unit at the standby position during service maintenance, it is not easy to take out and install the developing device because the photosensitive drum and the developing device are close to each other.
There is a possibility of damaging important parts such as the photosensitive drum and the developing sleeve.

The present invention has been made in view of the above problems, and an object of the present invention is to alleviate vibrations and shocks when pressurizing a unit device and to improve the take-out and mounting of the unit device with respect to the main body of the device. It is to provide a pressurizing mechanism of a unit device capable of performing.

[0012]

In order to achieve the above object, the invention according to claim 1 is a pressurizing position at which a unit device for performing a proximity operation and a separation operation with respect to another unit is positioned in proximity to the other unit. And a retracted position separated from the pressurizing position by a required distance and a retracted position separated from the standby position, and a movement distance of the unit device from the standby position to the pressurizing position is determined when the operation is completed. It is characterized in that it is set shorter than the moving distance from the pressurizing position to the retracted position.

A second aspect of the invention is characterized in that, in the first aspect of the invention, the unit device can be attached to and detached from the device body only at the retracted position.

According to a third aspect of the present invention, in the first aspect of the present invention, the unit device is a developing device for performing an approaching operation and a separating operation with respect to the image carrier.

A fourth aspect of the invention is characterized in that, in the first aspect of the invention, the unit device is a suction roller means for performing an approaching operation and a spacing operation with respect to the recording material carrier.

A fifth aspect of the present invention is characterized in that, in the first aspect of the invention, the unit device is a recording material carrier cleaning means for performing an approaching operation and a separating operation with respect to the recording material carrier.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the unit device is a transfer material peeling unit that performs a proximity operation and a separation operation with respect to the recording material carrier.

According to a seventh aspect of the present invention, in the first aspect of the present invention, the unit device is close to or away from the other unit in a state where a separation distance from the other unit at the retracted position is maintained. It is characterized in that it can be attached to and detached from the apparatus main body in a direction substantially orthogonal to the movement direction of the operation.

According to an eighth aspect of the invention, in the invention of the third aspect, a plurality of developing devices are integrally moved between the standby position and the retreat position, and a required development is performed between the pressing position and the standby position. The feature is that the vessel can be selectively moved.

Therefore, according to the present invention, the moving distance from the standby position to the pressing position of the unit device is set shorter than the moving distance from the pressing position to the retracted position when the operation is completed. It is possible to reduce the speed at the time, and to alleviate vibration and shock when pressurizing the unit device.

Further, according to the present invention, since the unit device can be attached to and detached from the device main body only at the retracted position, a sufficiently large distance is secured between the unit device and other units at the retracted position. It is possible to improve the take-out and attachment of the unit device with respect to the device body, and prevent damage and the like due to collision of the unit device.

[0022]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1> FIG. 1 is a schematic sectional view of a color image forming apparatus. The color image forming apparatus has a digital color image reader section in an upper part and a digital color image printer section in a lower part.

In the digital color image reader section, the original 30 is placed on the original table glass 31, and the original 30 is exposed and scanned by the exposure lamp 32, so that the reflected light image from the original 30 is reflected by the lens 33 by the full color sensor 34. And the color separation image signal is obtained. The color-separated image signal is processed by a video processing unit (not shown) through an amplifier circuit (not shown), and then sent to the digital color image printer section.

In the digital color image printer unit, the photosensitive drum 1 as an image carrier is rotatably supported in the direction of the arrow in the figure, and a pre-exposure lamp 11, a corona charger 2 are provided around the photosensitive drum 1. Laser exposure optical system 3,
Potential sensor 12, four developing devices 4Y, 4C of different colors,
4M, 4BK, on-drum light amount detection means 13, transfer device 5
And a cleaning device 6 are arranged.

In the laser exposure optical system 3, the image signal from the reader section is converted into an optical signal by a laser output section (not shown), and the converted laser beam is polygon mirror 3a.
Is reflected on the surface of the photosensitive drum 1 through the lens 3b and the mirror 3c.

When forming an image on the printer section, the photosensitive drum 1
Is rotated in the direction of the arrow shown in the figure, and the photosensitive drum 1 after having been neutralized by the pre-exposure lamp 11 is uniformly charged by the corona charger 2, and the photosensitive drum 1 is irradiated with the light image E for each separation color. A latent image is formed on the photosensitive drum 1.

Next, desired developing devices (4Y, 4C, 4M,
4BK) to develop the latent image on the photosensitive drum 1,
A toner image based on a resin is formed on the photosensitive drum 1. The developing units 4Y, 4C, 4M, and 4BK are configured to selectively approach the photosensitive drum 1 in accordance with each separated color by the operation of the eccentric cams 24Y, 24C, 24M, and 24BK.

On the other hand, the recording material housed in the recording material cassette 7 is supplied to a position facing the photosensitive drum 1 via the conveying system and the transfer device 5, and the toner image on the photosensitive drum 1 is transferred to the recording material. To be done. In the present embodiment, the transfer device 5 includes a transfer drum 5a, a transfer charger 5b, an attraction charger 5c for electrostatically attracting a recording material, and an attraction charger 5c.
The recording material carrying sheet 5f made of a dielectric material in the peripheral opening area of the transfer drum 5a which has a suction roller 5g, an inner charging device 5d and an outer charging device 5e facing each other. Is integrally stretched in a cylindrical shape. still,
A dielectric sheet such as a polycarbonate film is used as the recording material carrying sheet 5f.

With the rotation of the transfer drum 5a, the toner image on the photosensitive drum 1 is transferred onto the recording material carried on the recording material carrying sheet 5f by the transfer charger 5b.

In this way, a desired number of color images are transferred to the recording material that is sucked and conveyed to the recording material carrying sheet 5f, and a full color image is formed.

In the case of full-color image formation, when the transfer of the four color toner images onto the recording material is completed as described above,
Separation claw 8a, separation push-up roller 8b, and separation charger 5h
The recording material is separated from the transfer drum 5a by the action of, and the recording material is sent to the heat roller fixing device 9 to fix the toner image on the recording material, and the recording material on which the toner image is fixed is placed on the tray 10 outside the machine. Is discharged.

When the transfer is completed, the photosensitive drum 1 is
The residual toner on the surface is cleaned by the cleaning device 6 and is again provided for image formation.

By the way, when images are formed on both sides of the recording material, after the recording material exits the heat roller fixing device 9, the conveying path switching guide 19 is immediately driven to convey the recording material through the conveying vertical path 20. After being guided to the reversing path 21a once, the reversing roller 21b is rotated in the reverse direction so that the trailing end of the recording material when fed is withdrawn to the opposite side to the feeding direction, and is stored in the intermediate tray 22. Thereafter, an image is formed again on the other surface of the recording material by the image forming step.

Further, the recording material carrying sheet 5 of the transfer drum 5a
f and the recording material supporting sheet 5 in order to prevent scattering of powder on f, adhesion of oil on the recording material, and the like.
The cleaning is performed by using a backup brush 15 facing the fur brush 14 via the f, and a backup brush 17 facing the roller 16 via the oil removing roller 16 and the recording material carrying sheet 5f. Such cleaning is performed before or after image formation, and at any time when a jam (paper jam) occurs.

Further, in the present embodiment, the eccentric cam 25 is driven at a desired timing, and the cam follower 5i integrated with the transfer drum 5f is driven, so that the gap between the transfer drum 5a and the photosensitive drum 1 is reduced. The configuration can be set arbitrarily. For example, during standby or power supply OF
At the time of F, the interval between the transfer drum 5a and the photosensitive drum 1 is increased.

Next, the developing device 4Y,
The pressurizing operation of 4C, 4M and 4BK will be described in detail. 2 is a cross-sectional view showing the pressure mechanism around the developing device, FIG. 3 is a cross-sectional view taken along line XX of FIG. 2, FIGS. 4 to 6 are explanatory views of the action of the pressure cam, and FIG. FIG. 8 is a side view of the part of FIG.
5 is a sectional view taken along line YY of FIG.

FIG. 2 shows the pressing mechanism of the cyan developing device 4C as an example, but the pressing mechanisms of the developing devices 4Y, 4M and 4BK of other colors are also configured in the same manner.

The cyan developing device 4C includes a developing sleeve 401,
It is composed of screws 403 and 404, a blade 405, and the like, which is inserted into the cyan pressure rail 101C from the front side and fixed with screws from the front side. Details of the fixing structure will be described later.

As shown in FIG. 3, the pressure rail 101C has slide pins 103C projecting from the front and rear of the pressure rail 101C, slide holes 91a and 9 formed in front and rear side plates 91 and 92, respectively.
It is slidably supported by engaging with 2a.

Further, pressure leaf springs 102C are attached to two positions on the front and back of the pressure rail 101C. Then, at a position corresponding to the pressing leaf spring 102C, the cam shaft 104C rotatably supported by the body side plates 91, 92.
A pressure cam 24C attached to the photosensitive drum 1. The rotation of these pressure cams 24C presses the pressing leaf spring 102C, and the cyan developing device 4C presses the photosensitive drum 1 by the pressing leaf spring 102C. Is pressed. Then, the pressurizing cam 24C makes a half rotation, and these follower 1
When 05 is pressed, the pressure rail 101C slides along with the cyan developing device 4C along the side plates 91 and 92, whereby the cyan developing device 4C is separated from the photosensitive drum 1.

By the way, as shown in FIG. 3, the cam shaft 104C is connected to a stepping motor 56C via gears 54C and 55C.
Is driven to rotate. A flag 51C for position detection is fixed to the rear end of the cam shaft 104C, and the pressure cam 24 is detected by detecting the flag 51C by sensors 52C and 53C provided on the main body side.
The position of C is controlled. As a result, the cyan developing device 4C
Of the pressurization / development position shown in FIG. 2 or FIG. 6A, the standby position shown in FIG. 5A which is slightly separated from this pressurization / development position, and the retracted position shown in FIG. You can stop at 3 places.

Further, as shown in FIG. 3, the cyan developing device 4C and the photosensitive drum 1 are positioned by the abutting piece 93 having the same radius as the photosensitive drum 1 fixed to the front and rear side plates 91 and 92.
This is done by bringing abutting rollers 402f and 402b provided coaxially with the developing sleeve 401 into contact with f and 93b. Here, the abutting rollers 402f, 402
The radius of b is set to be larger than the radius of the developing sleeve 401 by a predetermined gap (a gap between the photosensitive drum 1 and the developing sleeve 401), whereby the predetermined gap between the photosensitive drum 1 and the developing sleeve 401. Is secured.

Next, the operation of the pressing mechanism according to this embodiment will be described with reference to FIGS. 4 to 6. 4 to 6
In each figure, (a) is a cross-sectional view showing the pressure mechanism around the developing device, and (b) is a view showing the relationship between the pressure cam, the flag, and the sensor.

A power source (not shown) provided in the apparatus body is turned on.
Then, the home position of each developing device 4Y, 4C, 4M, 4BK is checked. Here, the cyan developing device 4
Describing C, the cyan developing device 4C is at the home position (retracted position) and the pressure cam 24C is in the state shown in FIG. 4, one sensor 52C detects the flag 51C, and the other sensor 53C detects the flag 51C. 4 is not detected, the pressure cam 24C is held at the position shown in FIG. 4 as it is, the cyan developing device 4C is not in the home position, and the pressure cam 24C is in the state shown in FIGS. 5 and 6 (sensor 52C, When both 53C are in the detection state and one sensor 52C is in the non-detection state, the other sensor 53C
Is detected), the stepping motor 56C
Is driven to rotate the pressure cam 24C until the state shown in FIG. 4 is reached. When the cyan developing device 4C is at the home position shown in FIG. 4A, the distance between the photosensitive drum 1 and the developing sleeve 401 is set to about 5 to 20 mm.

Next, when a copy start button (not shown) provided on the apparatus main body is turned on, the developing devices 4C (4Y, 4M, 4BK) required for image formation are moved to the standby position shown in FIG. 5 (a). To move. When the full color mode is designated, the developing devices 4Y, 4C, 4M and 4BK are sequentially moved to the standby position, and when the cyan single color mode is designated, only the cyan developing device 4C is moved to the standby position. To be The distance between the developing sleeve 401 and the photosensitive drum 1 at the standby position is set to about 2 to 5 mm.

At this time, when the stepping motor 56C is driven and the pressure cam 24C and the flag 51C rotate in the direction of the arrow in FIG. 5B and the sensor 53C detects the flag 51C, the rotation of the pressure cam 24C is stopped. And prepare for the timing of image formation.

After that, when the stepping motor 56C is driven at the timing of the latent image of each color on the photosensitive drum 1 and the sensor 52C of the cyan developing device 4C stops detecting the flag 51C, the pressure cam 24C is rotated. When stopped in the state shown in FIG. 6, the cyan developing device 4C is
It is moved to the pressurizing / developing position shown in FIG.

When the latent image on the photosensitive drum 1 passes through the cyan developing device 4C, the stepping motor 56C is again activated.
Is driven to start the separation operation of the cyan developing device 4C. That is, the pressure cam 24C rotates 180 ° to rotate the cyan developing device 4
Although C returns to the home position shown in FIG. 4A, during the same job, the stepping motor 56C is driven to rotate the pressure cam 24C until the sensor 53C detects the flag 51C while passing through the home position. Then, the cyan developing device 4C is stopped at the standby position shown in FIG. 5A, and the timing of the next latent image is awaited.

When one job is completed by repeating the above operation for a predetermined number of sheets, all developing units 4Y, 4C, 4M,
4BK from the pressing / developing position shown in FIG.
The operation is completed by moving to the home position (withdrawal position) shown in (a).

As described above, in the present embodiment, the pressing operation of the developing device 4C (4Y, 4M, 4BK) during image formation is as shown in FIG.
Since the movement is performed only by a short distance from the standby position shown in (a) to the pressing / developing position shown in FIG. 6 (a), the pressing speed can be reduced and the shock at the time of pressing can be reduced. It At the home position (retracted position) shown in FIG. 4A, the distance between the developing device 4C (4Y, 4M, 4BK) and the photosensitive drum 1 is sufficiently secured.
Workability when removing (4Y, 4M, 4BK) from the device main body or attaching it does not deteriorate.

Although only the operation of the cyan developing device 4C has been described above, when the full color mode is designated, the four developing devices 4Y, 4C, 4M and 4BK are used to form latent images corresponding to the respective colors. The same operation can be performed for.

Further, in this embodiment, the developing device 4C is used.
6 passes through the home position when moving from the pressing / developing position shown in FIG. 6 (a) to the standby position shown in FIG. 5 (a). The stepping motor 56C may be reversely rotated and the pressure cam 24C may be reversely rotated to move the developing device 4C to the standby position shown in FIG. 5A. By doing this, the developing device 4
The pressing / developing position of C can be moved from the developing position to the standby position in a shorter time, the preparation for the next latent image can be completed quickly, and higher-speed image formation can be performed.

It is desirable to excite the stepping motor 56C at the time of stopping at each position to apply a braking force to the cam shaft 104C.

Further, when the developing device 4C is detached from the apparatus main body at the home position shown in FIG. 4A, the moving direction of the developing device 4C is the axial direction of the photosensitive drum 1 (the arrow direction in FIG. 3). Therefore, the detaching operation of the developing device 4C is performed at a home position while maintaining a relatively large distance between the developing device 4C and the photosensitive drum 1, so that the photosensitive drum 1 and the developing sleeve 401 are damaged. Disappears.

Here, a mechanism that allows the developing device 4C to be attached to and removed from the apparatus main body only at the home position shown in FIG. 4A will be described with reference to FIGS.

The developing device 4C can be inserted into the pressure rail 101C from the front side of FIG. 7 (the direction of the arrow in FIG. 8), and the fixing portion 4Ca provided on the developing device 4C is attached to the pressure rail 101C. The developing device 4C is fixed to the pressure rail 101C by abutting and fixing it with the fixing screw 100.

Further, a notch 91b is formed in the front plate 91 of the main body, and the fixing portion 4Ca of the developing device 4C can pass through the notch 91b only when the developing device 4C is at the home position.

Then, the developing device 4C operates and this is shown in FIG.
The standby position shown in (a) or the pressurization shown in FIG. 6 (a)
When moved to the developing position, the fixed portion 4Ca interferes with the front side plate 91 and cannot be pulled out forward. Also, the fixing screw 100 cannot be loosened with a screwdriver. As a result, the developing device 4C and the photosensitive drum 1 cannot be pulled out at a position close to each other, so that troubles during service maintenance such as damage to the photosensitive drum 1 and the developing sleeve 401 can be eliminated.

By the way, in the above-described embodiment, each of the developing devices 4Y, 4C, 4 for each color is moved between the standby position and the pressing / developing position, and between the retracted position and the standby position.
Although it can be performed every M and 4BK, the movement between the standby position and the pressurizing / developing position can be performed by a plurality of developing devices 4Y, 4C, and
4M and 4BK may be simultaneously performed integrally, and the movement between the first and second positions may be selectively performed for each of the developing devices 4Y, 4C, 4M, and 4BK of each color. Examples thereof are shown in FIGS.
Shown in

9 to 11 are partial sectional views of the photosensitive drum and the developing device portion of the image forming apparatus showing a modified example of the pressing mechanism,
FIG. 12 is a view in the direction of arrow A in FIG. 9, and in these drawings, the same elements as those shown in FIGS. 2 to 6 are designated by the same reference numerals, and the description thereof will be omitted below.

The pressing subunit 600 having a mechanism for selectively pressing the four-color developing devices 4Y, 4C, 4M, and 4BK against the photosensitive drum 1 is the front and rear side plates 91 and 9 of the main body.
It is provided inside 2.

As shown in FIG. 12, slide pins 602 are fixed to the pressure subunit side plates 611 and 612, respectively.
The pressurizing subunit 600 is slidably supported with respect to the main body of the apparatus by engaging with the slide holes 91a and 92a formed in the terminals 1, 92.

On the other hand, a pressure set arm 604 is fixed to a position corresponding to the subunit side plates 611 and 612 of the rotary shaft 603 which is rotatably supported by penetrating between the front and rear side plates 91 and 92 of the main body. A roller 605 is rotatably supported by a shaft 606 at the tip of each pressure setting arm 604.

Further, a set arm 607 is fixed to the outside of the front plate 91 of the main body of the rotary shaft 603. When the set arm 607 is rotated in the arrow direction (counterclockwise direction) of FIG. 605 is the subunit side plates 611, 61
When the set arm 607 is further rotated by contacting the pressing arm 2, the pressing subunit 600 is pushed up toward the photosensitive drum 1 as shown in FIG.

The pressurizing subunit 600 has the pin 602.
Are slide holes 91a, 92a of the front and rear side plates 91, 92
It slides along and moves in the direction of the photosensitive drum 1, and stops when the pin 602 hits the ends of the slide holes 91a, 92a. At this time, roller 605
Is the engaging recess 611 of the subunit side plates 611, 612.
It is held by engaging b and 612b.

By the above operation, the four color developing devices 4Y, 4
C, 4M and 4BK are integrally moved and set from the retracted position shown in FIG. 9 to the standby position shown in FIG.

Then, the developing devices 4Y, 4C, 4M, 4B
The pressure of K is applied to the rails 101M and 10 that slide between the subunit side plates 611 and 612 of the pressure subunit 600.
1C, 101Y, 101BK.

A mechanism for pressing the yellow developing device 4Y will be described with reference to FIG.

As shown in FIG. 12, the pressure rail 101Y slides by engaging the slide pins 103Y protruding in front of and behind it with the slide holes 611a and 612a formed in the subunit side plates 611 and 612, respectively. Supported as possible.

Pressurizing leaf springs 102Y are attached to the back and front of the pressing rail 101Y at two positions. A pressure cam 24Y rotatably attached to the subunit side plates 611, 612 by a cam shaft 104Y is provided at a position corresponding to the pressure leaf spring 102Y, and these pressure cams 24Y rotate. As a result, the pressing leaf spring 102Y is pressed, and the yellow developing device 4Y is pressed.
Is pressed against the photosensitive drum 1 by the pressing leaf spring 102Y. When the pressure cam 24Y makes a half rotation and presses the follower portion 105, the pressure rail 101Y moves together with the yellow developing device 4Y and the subunit side plates 611, 61.
Slide along 2 and thereby yellow developer 4
Y separates from the photosensitive drum 1.

The cam shaft 104Y is connected to a stepping motor 56Y fixed to the subunit rear side plate 612 via gears 54Y and 55Y.
It is rotationally driven by 6Y.

A flag 51Y for position detection is fixed to the rear end of the camshaft 104Y, and the subunit 6
The position of the pressure cam 24Y is detected and controlled by the sensor 52Y on the 00 side. As a result, the yellow developing device 4Y can be stopped at the pressurizing / developing position shown in FIG. 11 and the standby position shown in FIG. 10 slightly separated from the pressurizing / developing position. In FIG. 11, all the developing devices 4Y, 4C,
4M and 4BK are under pressure, but in actual operation, the required developing devices (4Y, 4C, 4M, 4B) are selectively used.
K) is sequentially pressurized.

By the way, in the embodiment shown in FIGS. 4 to 6, two sensors are provided to control three positions, but here, since the movement is between the pressing / developing position and the standby position, Two position control is enough, and only one sensor is needed. A spring clutch or the like may be used as the pressing means for the developing device to the photosensitive drum. In this case, the positioning of the developing device to the photosensitive drum is the same as described above.

As described above, by performing the movement of the developing device between the standby position and the retreat position and the movement between the pressing / developing position and the standby position by different mechanisms, the control process is simplified and The movement distance between the standby position and the retreat position can be set to be further large, and the unit can be mounted at a position sufficiently separated from the photosensitive drum, and the workability can be further improved.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIGS. 13 to 17. FIG.
3 is a sectional view of a transfer drum and a suction roller portion of the image forming apparatus showing the pressure mechanism according to the second embodiment, and FIG.
15 is a sectional view taken along line ZZ of FIG.

In the first embodiment described above, the reduction of the vibration due to the collision of the developing device positioned with respect to the photosensitive drum has been described, but the present invention is positioned and rotated with respect to the image carrier and the recording material carrier. It can also be applied to a unit device that generates load fluctuations.

Here, as an example, a suction roller 5g which comes into contact with and separates from the transfer drum 5a which is a recording material carrier.
Will be described.

The suction roller 5g is a suction roller arm 503.
The suction roller arm 503 is rotatably supported with respect to the suction roller arm 503. The suction roller arm 503 is swingably supported about a pin 504, and this is pressed by a pressure spring 507 toward the transfer drum 5a.

The other end of the suction roller arm 503 is engaged with the front and rear separation cams 505, and the suction roller arm 503 is rotated by the separation cam 505 to transfer the drum 5a.
Abut or separate from. The separation cam 505 is fixed to the cam shaft 506.

The cam shaft 506 is connected to a stepping motor 556 via gears 554 and 555, and is rotationally driven by the stepping motor 556.

A flag 551 for position detection is fixed to the rear end of the cam shaft 506, and the position of the separation cam 505 is detected and controlled by sensors 552 and 553 provided on the apparatus main body side. As a result, the suction roller 5g
Is the pressurization / suction position shown in FIG. 13 (or FIG. 17A), the standby position shown in FIG. 16 (a) slightly separated from this pressurization / suction position, and the retracted position shown in FIG.
You can stop at any point.

When the recording material is attracted to the transfer drum 5a, the attraction roller 5g contacts the transfer drum 5a as shown by the solid line in FIG. 13, and when the attraction of the recording material is completed, the attraction roller 5g moves to the position shown in FIG. To the position indicated by the broken line and separated from the transfer drum 5a. When the suction roller 5g comes into contact with the transfer drum 5a, rollers 502 provided at both ends of the suction roller 5g come into contact with the transfer drum ring 501, whereby the suction roller 5g receives a rotational driving force from the transfer drum 5a. Rotate. It should be noted that the roller 502 is formed with a flange 502a for preventing displacement in the thrust direction, and the flange 502a is formed in the groove portion 50 of the transfer drum ring 501.
It has entered 1a.

Here, the suction roller 5g is the transfer drum 5a.
When it comes into contact with the transfer drum 5a, a load for rotating the suction roller 5g acts on the outer periphery of the transfer drum 5a.
Is engaged with the photosensitive drum 1, the rotation of the photosensitive drum 1 is easily disturbed. In particular, when the transfer drum 5a is suddenly subjected to a rotational load change, the image is disturbed when the latent image is formed on the photosensitive drum 1 or when the developing device develops the latent image.

Thus, in the present embodiment as well, as in the first embodiment, the pressing operation of the suction roller 5g is only a short distance movement from the standby position to the pressure / suction position, so that It is possible to reduce the speed at the time of pressure and reduce the shock at the time of pressurization. As a result, the image disturbance is suppressed to the minimum, and a good image can be stably obtained.

The operation of the pressurizing mechanism according to this embodiment will be described with reference to FIGS. 15 to 17. Note that FIG.
17A to 17A are sectional views, and FIG. 17B is a view showing the relationship between the separation cam, the flag, and the sensor.

A power source (not shown) provided in the apparatus body is turned on.
Then, the home position of the suction roller 5g is checked. Here, the suction roller 5g is at the home position (retracted position), the separation cam 505 is in the state shown in FIG. 15, one sensor 552 detects the flag 551, and the other sensor 553 does not detect the flag 551. If so, the separation cam 505 is held at the position shown in FIG. 15 as it is, the suction roller 5g is not in the home position, and the separation cam 505 is in the state shown in FIGS. 16 and 17 (both the sensors 552 and 553 are in the detection state). When and when one sensor 552 is undetected, the other sensor 553
Is detected), the stepping motor 556
15 to drive the separation cam 505 until the state shown in FIG. 15 is reached.
To rotate. When the suction roller 5g is at the home position shown in FIG. 15, the distance between the transfer drum 5a and the suction roller 5g is set to about 5 to 20 mm.

Next, when a copy start button (not shown) provided on the apparatus main body is turned on, the suction roller 5g is moved to the standby position shown in FIG. The distance between the transfer drum 5a and the suction roller 5g at the standby position is set to about 2 to 5 mm.

At this time, the stepping motor 556 is driven so that the separation cam 505 and the flag 551c are set as shown in FIG. 16 (b).
When the sensor 553 detects the flag 551 by rotating in the direction of arrow, the rotation of the separation cam 505 is stopped to prepare for the timing of suction of the recording material to the transfer drum 5a.

After that, when the stepping motor 556 is driven at the timing when the recording material is attracted to the transfer drum 5a and the sensor 552 no longer detects the flag 551, the rotation of the separation cam 505 is stopped in the state shown in FIG. The suction roller 5g moves to the pressure / suction position shown in FIG. 17A to perform the suction operation.

Then, the suction of the recording material onto the transfer drum 5a is completed, the stepping motor 556 is driven again, and the separation operation of the suction roller 5g starts. That is, the separation cam 50
5 rotates 180 ° and the suction roller 5g returns to the home position shown in FIG. 15, but during the same job, the sensor 553 passes the home position and the sensor 553 sets the flag 551.
The stepping motor 556 is driven and the separation cam 505 is rotated until c is detected, and the suction roller 5g is stopped at the standby position shown in FIG. 16 to wait for the next recording material suction timing.

When one job is completed by repeating the above operation for a predetermined number of sheets, the suction roller 5g is moved from the pressurization / suction position shown in FIG. 17 (a) to the home position (retracted position) shown in FIG. 15 (a). Move to complete the operation.

The present invention is not limited to the suction roller 5g,
It is also applicable to the separating claw 8a which is a peeling means for peeling and separating the recording material from the recording material carrier, and the fur brush 14 (see FIG. 1) for cleaning the recording material carrier.

[0094]

As is apparent from the above description, according to the present invention, the moving distance from the standby position to the pressurizing position of the unit device is more than the moving distance from the pressurizing position to the retracted position when the operation is completed. Since the length is set to be short, the speed at the time of pressurizing the unit device can be reduced, and an effect that vibration and shock at the time of pressurizing the unit device can be mitigated can be obtained.

Further, according to the present invention, since the unit device can be attached to and detached from the device main body only in the retracted position, a sufficiently large distance is secured between the unit device and other devices in the retracted position. Therefore, it is possible to obtain the effect that the unit device can be taken out and attached to the device body, and the unit device can be prevented from being damaged by collision.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a color image forming apparatus.

FIG. 2 is a cross-sectional view of a developing device portion of the photosensitive drum showing the pressing mechanism according to the first exemplary embodiment of the present invention.

FIG. 3 is a sectional view taken along line XX of FIG. 2;

FIG. 4 is an operation explanatory view of the pressure cam of the pressure mechanism according to the first embodiment of the present invention.

FIG. 5 is an operation explanatory view of the pressure cam of the pressure mechanism according to the first embodiment of the present invention.

FIG. 6 is an operation explanatory view of the pressure cam of the pressure mechanism according to the first embodiment of the present invention.

FIG. 7 is a side view of a developing device mounting portion showing a modified example of the pressure mechanism according to the first embodiment of the present invention.

FIG. 8 is a sectional view taken along line YY of FIG. 7;

FIG. 9 is a cross-sectional view of the developing device portion of the photosensitive drum of the image forming apparatus showing another modified example of the pressure mechanism according to the first embodiment of the present invention.

FIG. 10 is a cross-sectional view of the developing device portion of the photosensitive drum of the image forming apparatus showing another modification of the pressure mechanism according to the first embodiment of the invention.

FIG. 11 is a cross-sectional view of the developing device portion of the photosensitive drum of the image forming apparatus showing another modification of the pressing mechanism according to the first embodiment of the present invention.

12 is a view in the direction of arrow A in FIG.

FIG. 13 is a cross-sectional view of a transfer drum and a suction roller portion of an image forming apparatus showing a pressure mechanism according to a second embodiment of the present invention.

14 is a sectional view taken along line ZZ in FIG.

FIG. 15 is an operation explanatory view of the separation cam of the pressure mechanism according to the second embodiment of the present invention.

FIG. 16 is an operation explanatory view of the spacing cam of the pressure mechanism according to the second embodiment of the present invention.

FIG. 17 is an operation explanatory view of the spacing cam of the pressurizing mechanism according to the second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photosensitive drum (image bearing member; other unit) 4 Developing device (unit device) 5a Transfer drum (recording material bearing member; other unit) 5g Adsorption roller (unit device) 8a Separation claw (recording material peeling unit; unit device) ) 14 fur brush (cleaning member for recording material; unit device) 24C pressure cam 51C flag 52C, 53C sensor 505 separation cam 551 flag 552, 553 sensor

Claims (8)

[Claims] 1. A pressurizing mechanism of a unit device for performing approaching and separating operations with respect to another unit, the pressurizing position at which the unit device is positioned close to another unit, and a required distance from the pressurizing position. And a retracted position separated from the standby position can be set, and the moving distance of the unit device from the standby position to the pressurizing position can be set from the pressurizing position to the retracted position when the operation is completed. A pressurizing mechanism for a unit device, which is set to be shorter than a moving distance. 2. The pressing mechanism for a unit device according to claim 1, wherein the unit device is configured such that the unit device can be attached to and detached from the device body only in the retracted position. 3. The pressing mechanism for a unit device according to claim 1, wherein the unit device is a developing device that performs a proximity operation and a separation operation with respect to the image carrier. 4. The pressurizing mechanism of the unit device according to claim 1, wherein the unit device is a suction roller unit that performs an approaching operation and a spacing operation with respect to the recording material carrier. 5. The pressurizing mechanism of the unit device according to claim 1, wherein the unit device is a recording material carrier cleaning unit that performs a moving operation toward and away from the recording material carrier. 6. The pressurizing mechanism of the unit device according to claim 1, wherein the unit device is a transfer material peeling unit that performs a moving operation toward and away from a recording material carrier. 7. The unit device moves to the main body of the device in a direction substantially orthogonal to the moving direction of the approaching and separating operation with respect to the other unit in a state where the separating distance from the other unit at the retracted position is maintained. The pressurizing mechanism of the unit device according to claim 1, wherein the pressurizing mechanism is attachable and detachable. 8. A plurality of developing devices are integrally moved between the standby position and the retreat position, and a required developing device is selectively moved between the pressing position and the standby position. The pressurizing mechanism of the unit device according to the third aspect.