JP2001337511A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To bring a developing roll into contact with a photoreceptor drum only when a toner image is formed on the photoreceptor drum. SOLUTION: The device has a first housing 10a in which the photoreceptor drum 1a is provided. The device also has a second housing 4a in which the developing roll 7a and a thin layer formation blade are provided. The second housing 4a is swinguable about a support shaft 9a to bring the developing roll 7a into contact with the photoreceptor drum 1a and separate the roll 7a from the drum 1a and is urged in the direction of the first housing 10a. The device further has a developing roll control means. When printing is not carried out, the control means separates the developing roll 7a from the photoreceptor drum 1a and stops their rotations. When printing is carried out, the control means brings the developing roll 7a into contact with the photoreceptor drum 1a by swinging the second housing 4a towards the first housing 10a while rotating the developing roll 7a and the photoreceptor drum 1a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus for forming a composite image by superimposing image information on a transfer material using electrophotographic technology.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic technique, the surface of a photosensitive drum serving as an image carrier is uniformly charged to a predetermined potential by a charging means, and an image is formed on the photosensitive drum. 2. Description of the Related Art An electrostatic latent image is formed by irradiating light according to information, and an image is formed by transferring a toner image developed from the electrostatic latent image by a developing device to a sheet material or the like.

On the other hand, with the colorization of images, a plurality of image carriers for executing these image forming processes are provided.
A full-color image is formed by forming each color image of a cyan image, a magenta image, a yellow image, and preferably a black image on each image carrier, and superimposing and transferring each color toner image onto a sheet material at a transfer position of each image carrier. A tandem image forming apparatus for forming an image has also been proposed.

[0004] Such a tandem type multiplex image forming apparatus has an image forming section for each color, which is advantageous for speeding up.

Here, a conventional tandem type color image forming apparatus will be described.

FIG. 7 is a sectional view showing a conventional image forming apparatus.

As shown in FIG. 7, four image forming units Pa, Pb, Pc, and Pd are provided in the main body of the image forming apparatus.
Are arranged in a line at predetermined intervals, and each image forming unit Pa, Pb, Pc, Pd has a photosensitive drum 1a, 1b, 1c, 1d as an image carrier.

Further, the photosensitive drums 1a, 1b, 1c, 1
d, each photosensitive drum 1a, 1b, 1c, 1d
Charging means 2a, which uniformly charges the surface of the
2b, 2c, 2d, the respective photosensitive drums 1a, 1b, 1c,
Exposure units 3a and 3 that are provided corresponding to 1d and irradiate laser beams corresponding to image information in the main scanning direction of the respective photosensitive drums 1a, 1b, 1c and 1d to form electrostatic latent images.
b, 3c, 3d, photosensitive drums 1a, 1b, 1c, 1d
A developing roller 7a for visualizing the electrostatic latent image formed thereon;
7b, 7c, 7d, photosensitive drums 1a, 1b, 1c, 1
transfer means 20a, 20b, 20c, and 20d for transferring the toner image visualized on the intermediate transfer belt 19 to the intermediate transfer belt 19, and cleaning means 6a and 6b for removing residual toner on the photosensitive drums 1a, 1b, 1c, and 1d. , 6c and 6d are arranged respectively.

The transfer means 20a, 20b, 20c,
Reference numeral 20d is installed on the apparatus main body side, and units made of other members are detachably attached to the apparatus main body, and the convenience of replacement work when a predetermined life is reached as a consumable is considered.

Here, the image forming units Pa, Pb, P
For c and Pd, a black image, a yellow image,
A magenta image and a cyan image are formed.

Each image forming unit Pa, Pb, Pc, P
d, the photosensitive drums 1a, 1b, 1c,
1d, an endless intermediate transfer belt 19 which is stretched around a driving roller 18 and a driven roller 17 which is driven to rotate by a driving means (not shown) and rotates in the direction of arrow T.
Is arranged.

At the lower part of the apparatus, there is provided a paper cassette 11 containing sheet materials 14 such as printing paper.
Then, the sheet material 14 is sent out from the paper cassette 11 to the paper transport path one by one by the paper feed roller 12.

A sheet material transfer roller 13 that contacts the outer peripheral surface of the intermediate transfer belt 19 for a predetermined amount and transfers a color image formed on the intermediate transfer belt 19 to a sheet material 14, A fixing device 15 having a heating roller for fixing the color image transferred onto the sheet material 14 to the sheet material 14 by pressure and heat due to the holding rotation of the roller is disposed.

Further, at the rear of the conveyance path of the fixing device 15, a paper discharge roller (not shown) for discharging the sheet material 14 on which the color image is fixed, and the sheet material 14 discharged from the paper discharge roller
A paper discharge tray (not shown) in which is stored is provided.

Next, the operation of the image forming apparatus configured as described above will be described.

First, the charging means 2 of the image forming unit Pa
The latent image of the black component color of the image information is formed on the photosensitive drum 1a by the exposure device 3a and the exposure device 3a. This latent image is visualized as a black toner image by a developing roller 7a having black toner, and is transferred as a black toner image onto the intermediate transfer belt 19 by a transfer unit 20a.

On the other hand, while the black toner image is being transferred to the intermediate transfer belt 19, a latent image of a yellow component color is formed in the image forming unit Pb.
At b, the yellow toner image is visualized by the yellow toner. Then, the yellow toner image is transferred by the transfer means 20b of the image forming unit Pb to the intermediate transfer belt 19 where the transfer of the black toner image has been completed in the previous image forming unit Pa, and is superimposed on the black toner image.

Hereinafter, image formation is performed in the same manner for the magenta toner image and the cyan toner image, and when the superposition of the four color toner images on the intermediate transfer belt 19 is completed,
Paper is fed from the paper cassette 11 by the paper feed roller 12,
A sheet material 14 adjusted to the printing timing is introduced into the nip area by a registration roller (not shown), and is transferred onto the sheet material 14 by a sheet material transfer roller 13.
The color toner images are collectively transferred.

The transferred toner image is supplied to the fixing device 15.
Is heated and fixed to the sheet material 14, and a full-color image is formed on the sheet material 14.

Each of the photosensitive drums 1a, 1b, 1c and 1d after the transfer is completed is connected to a cleaning means 6a,
At 6b, 6c and 6d, the residual toner is removed, and is prepared for the next image formation to be performed subsequently.

As described above, the plurality of image forming units P
In a color image forming apparatus having a, Pb, Pc, and Pd, the photosensitive drums 1a, 1b, 1c, and 3d are irradiated by laser beams emitted from exposure units 3a, 3b, 3c, and 3d.
1d, the image information is exposed, and the intermediate transfer belt 19 is conveyed in the direction of arrow T in the figure through a known image forming process.
, Toner images of different colors are sequentially superimposed and transferred.
Then, the toner image is collectively transferred to the sheet material 14.

Here, each image forming unit Pa, Pb,
At the same time as the photoconductor drums 1a, 1b, 1c and 1d of Pc and Pd are driven to rotate, the intermediate transfer belt 19 is driven to run. At this time, the photosensitive drums 1a, 1b, 1c, 1
In order to prevent friction due to a speed difference between the peripheral speed d and the traveling speed of the intermediate transfer belt 19, the photosensitive drums 1a, 1b, 1
c, 1d and the intermediate transfer belt 19 are brought into contact with each other when the operation is completed, and image formation is performed at an operation timing at which the operation is completed after the separation.

That is, each image forming unit Pa, P
b, Pc, Pd are the photosensitive drums 1a, 1b, 1c,
Rotation driving is started before 1d contacts the intermediate transfer belt 19, and the photosensitive drums 1a, 1b, 1c and 1d are brought into contact after the intermediate transfer belt 19 is driven. Then, laser is applied to the photosensitive drum 1 by the exposure units 3a, 3b, 3c, and 3d.
a, 1b, 1c, 1d to form an electrostatic latent image, form a toner image by developing rollers 7a, 7b, 7c, 7d, and transfer the formed toner image to the intermediate transfer belt 19. .

The sheet material 14 in the paper cassette 11 is picked up one by one by the paper feed roller 12, and the timing is adjusted by the cooperation of the conveying roller and the registration roller to adjust the timing of the intermediate transfer belt 19 and the sheet material transfer roller 13. Paper is fed to the nip area. The sheet material 14 on which the toner images of the respective colors on the intermediate transfer belt 19 are collectively transferred to the nip area with the sheet material transfer roller 13 is discharged outside the apparatus main body through the fixing device 15.

[0025]

As described above, in the conventional color image forming apparatus, in any of the image forming units, when the photosensitive drum is rotating, the photosensitive drum contacts the peripheral surface thereof. The developing roller is always rotating at the same time.

On the other hand, in the case of the tandem system, since the printing operation is performed in order from the black image forming unit to the cyan image forming unit, the respective printing timings are slightly shifted.

That is, in the operation of each image forming unit, printing is not always performed, but an image signal is input to each unit, and the printing operation mode is set only for a predetermined period. Therefore, if the developing roller rotates at the same time as the rotation of the photosensitive drum, the developing roller remains in contact with the photosensitive drum during periods other than the printing period, and a reduction in life due to wear is inevitable.

The surface of the developing roller is made of conductive silicone rubber, and is in contact with a thinning blade for controlling the amount of toner supplied from the supply roller. Since the thinning blade comes into contact with the developing roller from the same direction as the photosensitive drum, the developing roller is also worn.

As described above, in the conventional color image forming apparatus, the photosensitive drum and the developing roller, which are rotated or driven in contact with or separated from the intermediate transfer belt in a timely manner, always operate. For this reason, even during the non-printing period, the developing roller is subjected to friction by the photosensitive drum, and the life is shortened due to abrasion.

Accordingly, the present invention provides a color image forming apparatus capable of bringing a developing roller into contact with a photosensitive drum only when a toner image is formed on the photosensitive drum.

[0031]

To solve this problem, a color image forming apparatus according to the present invention comprises a first housing provided with a photosensitive drum on which an electrostatic latent image is formed, and a photosensitive drum. A developing roller for supplying toner to the developing roller to visualize the electrostatic latent image, and a thinning blade for uniformly thinning the toner on the developing roller and charging the toner to an electric potential. A second housing biased in the direction of the first housing, and the developing roller is moved from the photosensitive drum during a non-printing period. During the printing period, the second housing is swung toward the first housing while rotating the developing roller and the photosensitive drum, and the developing roller is brought into contact with the photosensitive drum. It is obtained by a structure having a developing roller control means.

As a result, the developing roller can be brought into contact with the photosensitive drum only at the time of forming the toner image, and the life can be prevented from being shortened due to the contact wear between the photosensitive drum and the developing roller.

Further, since the rotation of the developing roller is stopped when the developing roller is separated from the photosensitive drum, it is possible to prevent abrasion due to sliding friction with the thinning blade.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, there is provided a first housing provided with a photosensitive drum on which an electrostatic latent image is formed, and a toner supply to the photosensitive drum by statically supplying the toner. A developing roller for visualizing the latent image and a thinning blade for uniformly thinning the toner on the developing roller and charging the toner to an electric potential are provided, and are provided so as to be swingable around a support shaft. And the second housing urged in the direction of the first housing, and the developing roller is separated from the photosensitive drum during a non-printing period to stop the rotation. And a developing roller control means for causing the second housing to swing toward the first housing while rotating the developing roller and the photosensitive drum during the printing period to bring the developing roller into contact with the photosensitive drum. An over the image forming apparatus has an effect that it is possible to contact the developing roller only when the toner image formed on the photosensitive drum. Also, since the rotation of the developing roller is stopped at the time of separation from the photosensitive drum,
This has the effect that it is possible to prevent wear due to sliding friction with the thinning blade.

According to a second aspect of the present invention, in the color image forming apparatus according to the first aspect, an electrostatic latent image is formed on the photosensitive drum after the developing roller contacts the photosensitive drum. In addition, since the vibration due to the contact of the developing roller does not occur during the formation of the electrostatic latent image on the photosensitive drum, it has an effect that a stable latent image can be formed.

According to a third aspect of the present invention, there is provided a color image forming apparatus according to the first or second aspect, wherein the developing roller is separated from the photosensitive drum after the toner image is transferred by the photosensitive drum. In addition, since there is no disturbance due to separation of the developing roller at the time of transferring the toner image from the photosensitive drum, the transfer accuracy can be improved.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In these drawings, the same members are denoted by the same reference numerals, and duplicate description is omitted.

FIG. 1 is an explanatory view showing a color image forming apparatus according to an embodiment of the present invention, FIG. 2 is an explanatory view showing an image forming unit of the color image forming apparatus of FIG. 1 and its periphery, and FIG. FIG. 4 is a perspective view showing an image forming unit of the color image forming apparatus and its periphery, FIG. 4 is an explanatory view showing a control mechanism of a developing roller in the image forming unit of FIG. 3,
FIG. 5 is a cross-sectional view showing a spring clutch attached to an end of a developing roller in the image forming unit of FIG. 3, and FIG. 6 shows an image forming unit of a color image forming apparatus according to another embodiment of the present invention and its periphery. FIG.

As shown in FIG. 1, the image forming apparatus
Image forming units Pa, Pb, Pc, and Pd are arranged in a line at a predetermined interval, and each image forming unit P
a, Pb, Pc, and Pd respectively have photosensitive drums 1a, 1b, 1c, and 1d as image carriers.

The photosensitive drums 1a, 1b, 1c, 1
d, each photosensitive drum 1a, 1b, 1c, 1d
Charging means 2a, which uniformly charges the surface of the
2b, 2c, 2d, the respective photosensitive drums 1a, 1b, 1c,
Exposure units 3a and 3 that are provided corresponding to 1d and irradiate laser beams corresponding to image information in the main scanning direction of the respective photosensitive drums 1a, 1b, 1c and 1d to form electrostatic latent images.
b, 3c, 3d, photosensitive drums 1a, 1b, 1c, 1d
A developing roller 7a for visualizing the electrostatic latent image formed thereon;
7b, 7c, 7d, developing rollers 7a, 7b, 7c, 7d
Supply rollers 44a, 44b, 44c, and 44d for supplying toner from a toner tank (not shown) to the surface of the developing roller 7a, 7b, 7c, and 7d to press the toner on the developing rollers 7a, 7b, 7c, and 7d. Thinning blade 8 that uniformly thins the toner and charges the toner to a potential.
a, 8b, 8c, 8d, photosensitive drums 1a, 1b, 1
c, 1d to the intermediate transfer belt 1
9, transfer means 20a, 20b, 20c, 20
d, cleaning means 6a, 6b, 6c, 6 for removing residual toner on the photosensitive drums 1a, 1b, 1c, 1d
d, static eliminators 5a, 5b, 5c, 5d for removing residual potentials of the photosensitive drums 1a, 1b, 1c, 1d after the transfer are arranged, respectively.

The photosensitive drums 1a, 1b, 1c,
1d, charging means 2a, 2b, 2c, 2d and cleaning means 6a, 6b, 6c, 6d
a, 10b, 10c, 10d to form a photoreceptor unit, and developing rollers 7a, 7b, 7c, 7d,
The supply rollers 44a, 44b, 44c, 44d and the thinning blades 8a, 8b, 8c, 8d are incorporated in the second housings 4a, 4b, 4c, 4d to form a developing unit.

Then, the second housings 4a, 4b, 4
2c, 4d are urged in the directions of the first housings 10a, 10b, 10c, 10d so as to be swingable in the direction of arrow T in FIG. 2A with the support shafts 9a, 9b, 9c, 9d as fulcrums. Thereby, the developing rollers 7a, 7b, 7c,
Reference numeral 7d allows the photosensitive drums 1a, 1b, 1c, 1d to come and go.

The transfer means 20a, 20b, 20c,
Reference numeral 20d is installed on the apparatus main body side, and units made of other members are detachable from the apparatus main body, and the convenience of replacement work when a predetermined life is reached as a consumable is considered.

Here, the image forming units Pa, Pb, P
For c and Pd, a black image, a yellow image,
A magenta image and a cyan image are formed.

Each image forming unit Pa, Pb, Pc, P
d, the photosensitive drums 1a, 1b, 1c,
1d, an endless intermediate transfer belt 19 which is stretched around a driving roller 18 and a driven roller 17 which is driven to rotate by a driving means (not shown) and rotates in the X direction.
Is arranged. Further, a cleaner 16 which is in contact with the intermediate transfer belt 19 and removes residual toner on the intermediate transfer belt 19 is provided.

At the lower part of the apparatus, there is provided a paper cassette 11 containing sheet materials 14 such as printing paper.
Then, the sheet material 14 is sent out from the paper cassette 11 to the paper transport path one by one by the paper feed roller 12.

A sheet material transfer roller 13 that contacts the outer peripheral surface of the intermediate transfer belt 19 for a predetermined amount and transfers the color image formed on the intermediate transfer belt 19 to the sheet material 14, A fixing device 15 having a heating roller for fixing the color image transferred onto the sheet material 14 to the sheet material 14 by pressure and heat due to the holding rotation of the roller is disposed.

Further, a paper discharge roller (not shown) for discharging the sheet material 14 on which the color image is fixed, and the sheet material 14 discharged from the paper discharge roller
A paper discharge tray (not shown) in which is stored is provided.

Next, the operation of the image forming apparatus configured as described above will be described.

First, the charging means 2 of the image forming unit Pa
The latent image of the black component color of the image information is formed on the photosensitive drum 1a by the exposure device 3a and the exposure device 3a. This latent image is visualized as a black toner image by a developing roller 7a having black toner, and is transferred as a black toner image onto the intermediate transfer belt 19 by a transfer unit 20a.

On the other hand, while the black toner image is being transferred to the intermediate transfer belt 19, a latent image of a yellow component color is formed in the image forming unit Pb.
At b, the yellow toner image is visualized by the yellow toner. Then, the yellow toner image is transferred by the transfer means 20b of the image forming unit Pb to the intermediate transfer belt 19 where the transfer of the black toner image has been completed in the previous image forming unit Pa, and is superimposed on the black toner image.

Hereinafter, image formation is performed in the same manner for the magenta toner image and the cyan toner image, and when the superposition of the four color toner images on the intermediate transfer belt 19 is completed,
Paper is fed from the paper cassette 11 by the paper feed roller 12,
A sheet material 14 adjusted to the printing timing is introduced into the nip area by a registration roller (not shown), and is transferred onto the sheet material 14 by a sheet material transfer roller 13.
The color toner images are collectively transferred.

Then, the transferred toner image is transferred to the fixing device 15.
Is heated and fixed to the sheet material 14, and a full-color image is formed on the sheet material 14.

Each of the photosensitive drums 1a, 1b, 1c, 1d after the transfer is completed is connected to a cleaning unit 6a,
The residual toner is removed by 6b, 6c, 6d, and the surfaces of the photosensitive drums 1a, 1b, 1c, 1d are electrically initialized by the static eliminators 5a, 5b, 5c, 5d provided on the apparatus body side. In preparation for the subsequent image formation.

As described above, the plurality of image forming units P
In a color image forming apparatus having a, Pb, Pc, and Pd, the photosensitive drums 1a, 1b, 1c, and 3d are irradiated by laser beams emitted from exposure units 3a, 3b, 3c, and 3d.
1d, the image information is exposed, and the intermediate transfer belt 19 is conveyed in a direction indicated by an arrow X in FIG.
, Toner images of different colors are sequentially superimposed and transferred.
Then, the toner image is collectively transferred to the sheet material 14.

Next, details of such a color image forming apparatus will be described. Note that all the image forming units P
Since a, Pb, Pc, and Pd have the same configuration as each other, a yellow image forming unit P will be described below.
a will be described.

As shown in FIG. 2, the second housing 4a
A trigger 23a rotatably attached to a pin 24a fixed to the apparatus main body and engaged with a lower end of the second housing 4a is disposed below the lower side. The trigger 23a has a substantially L-shape,
A guide pin 25a is provided at a position separated by a predetermined distance from a. The trigger 23a has a long groove 22 for rotating the trigger 23a by the movement of the guide pin 25a to swing the second housing 4a about the support shaft 9a.
The guide 21a formed with a is attached.

That is, the long groove 22a of the guide 21a is
A part of the groove 22a-1 is formed as a concave part 22a-1 which is lowered, and when the guide pin 25a moves left and right in such a long groove 22a, as shown in FIG.
, The trigger 23a is rotated counterclockwise in the drawing to move the second housing 4a to the first housing 10a.
Side, and the developing roller 7a comes into contact with the photosensitive drum 1a. Further, as shown in FIG.
a is not in the recess 22a-1, the trigger 23a is rotated clockwise in the drawing and the second housing 4a
Is displaced in the direction of arrow U away from the first housing 10a, and the developing roller 7a is separated from the photosensitive drum 1a.

As described above, by connecting the guide pin 25a of the trigger 23a to the guide 21a having the concave portion 22a-1, the second housing 4a is swung by the lateral movement of the guide 21a, and the photosensitive drum 1a is moved. , The developing roller 7a can be brought into contact or separated therefrom.

Here, in the color image forming apparatus of the present embodiment, the developing rollers 7a, 7b, 7c, and 7d are used only during the period in which the photosensitive drums 1a, 1b, 1c, and 1d rotate and print while rotating the intermediate transfer belt 19. 7d is the photosensitive drum 1
a, 1b, 1c, and 1d, and is driven to rotate so as to be separated from each other during the non-printing period, and to the developing rollers 7a, 7d.
The rotation of b, 7c, 7d is stopped.

The developing rollers 7a, 7b, 7c,
The operation of 7d will be described with reference to FIGS.

As shown, an Oldham gear 31a having a spring clutch mechanism is provided at an end of the developing roller 7a (FIG. 5). The Oldham gear 31a includes a driven hub 38a fixed to the shaft 40a of the developing roller 7a by a parallel pin 39a, a driving hub 31a-1 receiving drive transmission from an external driving means (not shown), and a driven hub 3a.
An engaging portion 43a that engages with the guide hole on the side of the drive hub 3a;
The clutch spring 41a includes a clutch spring 41a covering up to 1a-1, and a collar member 36a that engages with the cut-and-raised portion 42a at the other end of the clutch spring 41a. Further, a convex portion 37a is formed on the collar member 36a.

According to such a structure, the clutch spring 41a receives power transmitted from an external driving means (not shown).
4A and 4B showing the rotational force in the same direction as the drawing direction of FIG.
When the drive hub 31a-1 receives the rotational force in the direction of the arrow X shown in FIG. 7, the driven hub 38a also rotates in the same direction by the winding torque of the clutch spring 41a, so that the developing roller 7a is rotated.

Next, the drive control of the developing roller will be described. The spring clutch control means (developing roller control means)
A hinge 30a rotatably mounted around the pivot pin 32a, a control plate 34a fixed to the hinge 30a, and a control pin 33a below the pivot pin 32a of the hinge 30a. One end is movably connected and the other end is a fixing pin 3 on the side surface of the first housing 10a.
It comprises a connecting plate 29a connected to 5a.

According to this, the developing roller 7 shown in FIG.
a from the state where a is in contact with the photosensitive drum 1a, FIG.
As shown in (b), the trigger 23a rotates around the pin 24a in the direction of the arrow Z by the movement of the guide 21a, and engages with the projection 26a at the lower portion of the second housing 4a to move the developing roller 7a around the support shaft 9a. When pivoting counterclockwise to separate the photosensitive drum 1a from the photosensitive drum 1a, the hinge portion 30a of the spring clutch control means is connected to the pivot pin 3 by the connecting plate 29a.
It is rotated in the direction of arrow Y around 2a. Accordingly, the control plate 34a moves in the direction of the Oldham gear 31a. The convex portion 37a of the Oldham gear 31a is indicated by an arrow X.
And stopped by the end of the control plate 34a.

At this time, a force in the direction opposite to the winding direction of the clutch spring 41a acts to release the throttle force of the clutch spring 41a, and the rotational force of the drive hub 31a-1 is not transmitted to the driven hub 38a, so that the developing roller The rotation of 7a stops.

Next, the printing operation of the above configuration will be described.

In the non-printing period, all the developing rollers 7a, 7
b, 7c, 7d are photosensitive drums 1a, 1b, 1c, 1d
Away from and not driven to rotate. When the printing operation starts, a latent image is first written on the photosensitive drum 1a of the yellow (Y) image forming unit Pa by the laser from the exposure device 3a. Immediately before this writing, the photosensitive drum 1a starts rotating, and the intermediate transfer belt 19 starts running. At this time, the movement of the guide member 21 causes the second
Of the housing 4a rotates clockwise around the support shaft 9a,
The developing roller 7a contacts the photosensitive drum 1a. During this contact, the developing roller 7a, the photosensitive drum 1a, and the supply roller 44a are all driven to rotate.

As described above, after the developing roller 7a comes into contact with the photosensitive drum 1a, the laser is irradiated from the exposure unit 3a to write an electrostatic latent image on the surface of the photosensitive drum 1a. The electrostatic latent image is visualized. Then, by the rotation of the photosensitive drum 1a, the toner image on the peripheral surface is transferred to the surface of the intermediate transfer belt 19 as a yellow toner image.

According to such an operation, the developing roller 7a
The image writing is performed by the exposure device 3a after the light comes into contact with the photosensitive drum 1a. In the other image forming units Pb, Pc, Pd, since the spring clutch control means is in the activated state, the developing rollers 7b, 7
Both c and 7d are stopped and the photosensitive drums 1b and 1d are stopped.
There is no contact with c and 1d.

Subsequently, the magenta image forming unit Pb
Immediately before the transfer operation by the developing device 7, as in the case of the yellow image forming unit Pa, the developing roller 7 b comes into contact with the photosensitive drum 1 b, the image is written by the exposure device 3 b, and the written electrostatic latent image is written. The image is developed by the developing roller 7b. Then, the magenta toner image is superimposedly transferred on the yellow toner image on the intermediate transfer belt 19 which has been previously transferred. Subsequently, similarly, the transfer of the cyan toner to the intermediate transfer belt 19 by the cyan image forming unit Pc is started, and the intermediate transfer belt 19 of the black toner by the black image forming unit Pd.
The transfer to the transfer is sequentially performed. Thereafter, in all the image forming units Pa, Pb, Pc, and Pd, the developing roller 7
a, 7b, 7c, 7d are photosensitive drums 1a, 1b, 1
c, 1d, and yellow, magenta, cyan, and black toners are simultaneously transferred to the intermediate transfer belt 19.

Subsequently, immediately before the transfer of the yellow toner is completed, the guide member 21a is further moved, and the upper end of the trigger 23a of the yellow image forming unit Pa is in an upright position, and the second housing 4a is supported by the support shaft 9a. Swing around counterclockwise. As a result, the hinge portion 30a of the spring clutch control means is rotated in the direction of the arrow Y around the pivot pin 32a by the connecting plate 29a. Accordingly, the control plate 34a moves in the direction of the Oldham gear 31a, and the protrusion 37a of the Oldham gear 31a rotates in the direction of the arrow X, so that the control plate 34a is stopped by the end of the control plate 34a. At this time, a force in the direction opposite to the winding direction of the clutch spring 41a acts to release the throttle force of the clutch spring 41a, and the rotational force of the drive hub 31a-1 is reduced by the driven hub 38a.
And the rotation of the developing roller 7a stops. The photoreceptor drum 1a is connected to the intermediate transfer belt 19 thereafter.
Continue to rotate while the vehicle is traveling.

Here, the developing roller 7a is connected to the photosensitive drum 1
The timing to move away from a is set after the transfer process from the photosensitive drum 1a to the intermediate transfer belt 19 is completed. By doing so, disturbance due to reaction vibration or the like when the developing roller 7a separates is eliminated, so that transfer accuracy to the intermediate transfer belt 19 is not reduced.

Thereafter, as the guide member 21 moves, the developing roller 7b of the magenta image forming unit Pb separates from the photosensitive drum 1b and stops rotating, and then the cyan image forming unit Pc operates in the same manner and 7c
Stops rotating after moving away from the photosensitive drum 1c. Further, the black image forming unit Pd operates in the same manner, and the developing roller 7d separates from the photosensitive drum 1d and stops rotating. Then, at this point, the toner image transfer process on each of the image forming units Pa, Pb, Pc, and Pd on the intermediate transfer belt 19 is completed.

After the step of transferring the toner image to the intermediate transfer belt 19 is completed, the intermediate transfer belt 19 continues to run, and the photosensitive drums 1a, 1b, 1c, and 1d also avoid abrasion due to a speed difference from the intermediate transfer belt 19. Continue spinning. Then, the color image is transferred to the paper while the intermediate transfer belt 19 travels and nips the paper from the paper cassette 11 with the transfer roller 13. After the transfer is completed, the intermediate transfer belt 19 stops, and each image forming unit Pa,
Pb, Pc, Pd photosensitive drums 1a, 1b, 1c, 1
d also stops rotating, the guide member 21 moves to the initial position and waits for the next operation.

In this embodiment, as the developing roller rotation control means, the hinge means linked to the vertical rotation operation of the second housing 4a is exemplified. However, the developing roller rotation control means is the first housing 4a. The member fixed to 10a may have an engaging portion that engages with the convex portion of the spring clutch collar of the developing roller. Further, the first housing 10a may be provided with an actuator such as an electromagnetic solenoid.

FIG. 6 shows the first and second housings 10.
An electromagnetic solenoid is provided as control means for controlling the spring clutch mechanism (color member) of the drive connection means at the end of the developing roller 7a on the main body of the apparatus other than a and 4a.

In FIG. 6, when the developing roller 7a is in contact with the photosensitive drum 1a, the trigger 23a rotates around the pin 24a by the movement of the guide 21a, and engages with the lower convex portion 26a of the second housing 4a. When the developing roller 7a is rotated counterclockwise around the support shaft 9a to separate the developing roller 7a from the photosensitive drum 1a, the electromagnetic solenoid 45a
, The flapper 45a-1 moves upward, and the end of the flapper 45a-1 stops the rotation of the convex portion 37a.

At this time, a force in a direction opposite to the direction in which the clutch spring 41a is wound acts to release the throttle force of the clutch spring 41a, and the rotational force of the drive hub 31a-1 is not transmitted to the driven hub 38a. The rotation of 7a stops.

As described above, in this embodiment, in each of the image forming units Pa, Pb, Pc and Pd, the developing rollers 7a, 7b,
7c, 7d are brought into contact with the photosensitive drums 1a, 1b, 1c, 1d, the electrostatic latent images on the photosensitive drums 1a, 1b, 1c, 1d are developed and the toner images are transferred to the intermediate transfer belt 19 and then separated again. Let me. As a result, toner images are formed on the photosensitive drums 1a, 1b, 1c, 1d instead of causing the developing rollers 7a, 7b, 7c, 7d to contact the photosensitive drums 1a, 1b, 1c, 1d throughout the printing period. The developing rollers 7a, 7b, 7c, and 7d are stopped at intervals except during this period. Therefore, the contact time between the developing rollers 7a, 7b, 7c, 7d and the photosensitive drums 1a, 1b, 1c, 1d is shortened, and the degree of wear can be suppressed.

Further, at the time of separation, the developing rollers 7a, 7b,
Since the rotation of 7c and 7d is stopped, the thinning blade 8
The sliding friction with a, 8b, 8c, 8d is also eliminated, and the degree of wear is similarly suppressed. Therefore, even with the developing rollers 7a, 7b, 7c, 7d whose surfaces are formed of conductive silicon rubber, the generation and wear of contact friction flaws and the like can be suppressed and the durability can be improved.

[0082]

As described above, according to the present invention, it is possible to obtain an effective effect that the developing roller can be brought into contact with the photosensitive drum only when a toner image is formed.

As a result, there is obtained an effective effect that it is possible to prevent the life from being shortened due to the contact wear between the photosensitive drum and the developing roller.

Further, according to the present invention, since the rotation of the developing roller is stopped when the photosensitive drum is separated from the photosensitive drum, it is possible to effectively prevent abrasion due to sliding friction with the thinning blade. The effect is obtained.

If the electrostatic latent image is formed on the photosensitive drum after the developing roller comes into contact with the photosensitive drum, vibration due to the contact of the developing roller occurs during the formation of the electrostatic latent image on the photosensitive drum. Therefore, an effective effect of stably forming a latent image can be obtained.

If the developing roller is separated from the photosensitive drum after the transfer of the toner image by the photosensitive drum, disturbance due to separation of the developing roller during transfer of the toner image from the photosensitive drum is eliminated. An effective effect that the accuracy can be improved can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a color image forming apparatus according to an embodiment of the present invention;

FIG. 2 is an explanatory diagram showing an image forming unit of the color image forming apparatus of FIG. 1 and its periphery;

FIG. 3 is a perspective view showing an image forming unit of the color image forming apparatus of FIG. 1 and its periphery;

FIG. 4 is an explanatory diagram illustrating a control mechanism of a developing roller in the image forming unit in FIG. 3;

5 is a cross-sectional view showing a spring clutch attached to an end of a developing roller in the image forming unit in FIG.

FIG. 6 is a perspective view showing an image forming unit of a color image forming apparatus according to another embodiment of the present invention and the periphery thereof;

FIG. 7 is a sectional view showing a conventional image forming apparatus.

[Explanation of symbols]

 1a, 1b, 1c, 1d Photoconductor drum 4a, 4b, 4c, 4d Second housing 7a, 7b, 7c, 7d Developing roller 9a, 9b, 9c, 9d Support shaft 10a, 10b, 10c, 10d First housing

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tosumi Hattori 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Naoki Yamaguchi 1006 Odaka Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. 72) Inventor Yuzo Kawano 1006 Kadoma, Kazuma, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. (reference) 2H027 DA22 ED02 ED08 EE02 EF06 EF09 EF13 2H030 AB02 AD17 BB21 BB33 BB71

Claims (3)

[Claims] A first housing provided with a photosensitive drum on which an electrostatic latent image is formed; a developing roller for supplying toner to the photosensitive drum to visualize the electrostatic latent image; A thinning blade for uniformly thinning the toner on the developing roller and charging the toner to an electric potential is provided. The thinning blade is provided so as to be swingable around a support shaft, and the developing roller contacts the photosensitive drum. A second housing that is detachable and urged in the direction of the first housing; and the developing roller is separated from the photosensitive drum to stop rotation during a non-printing period, and during the printing period, A developing roller control unit that swings the second housing toward the first housing while rotating the developing roller and the photosensitive drum to contact the developing roller with the photosensitive drum; Color image forming apparatus characterized by a means. 2. The color image forming apparatus according to claim 1, wherein an electrostatic latent image is formed on said photosensitive drum after said developing roller contacts said photosensitive drum. 3. The color image forming apparatus according to claim 1, wherein the developing roller moves away from the photosensitive drum after the transfer of the toner image by the photosensitive drum.