JP2001249519A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact color image forming device capable of freely forming both of a monochrome image and a color image at low cost. SOLUTION: By providing primary transfer roll supporting devices 6 and 7 with a primary transfer roll moving device 8 for freely switching and parallel displacing primary transfer rolls 5Y, 5M and 5C other than a primary transfer roll 5K to a transfer position where the rolls 5Y, 5M and 5C are brought into contact with corresponding photoreceptors through a transfer belt 15 and a retreat position where they are separated from the corresponding photoreceptors through the belt 15 while one roll 5K of the four rolls 5Y, 5M, 5C and 5K is supported in a state where it is brought into contact with the corresponding photoreceptor 1K through the belt 15, the remaining rolls 5Y, 5M and 5C are supported at any position whether it is the transfer position or the retreat position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a plurality of photosensitive members used for a color copying machine, a color printer, and the like.

[0002]

2. Description of the Related Art In an image forming apparatus provided with a plurality of photoconductors used in a color copying machine, a color printer, or the like, a single color image may be formed using only an arbitrary photoconductor, for example, only a black photoconductor. . In this case, if the photoconductor other than black is driven as it is, power is wasted, and the life of the photoconductor and its related components is shortened.

[0003] As a solution to this problem, for example, Japanese Patent Application Laid-Open No. 9-6088 discloses an image in which four photoconductors are arranged in contact with a transfer belt along a transfer paper conveyance direction. There is disclosed an image forming apparatus including a photoconductor displacement driving unit for displacing a photoconductor other than black among the four photoconductors above the transfer belt when forming a monochromatic image of only black in the forming apparatus. ing.

Japanese Patent Application Laid-Open No. 11-84799 discloses an image forming apparatus in which four photosensitive members are arranged in parallel so as to be in contact with a transport belt for transporting a transfer material. When the monochrome photosensitive member is set to a black monochromatic image mode, the photosensitive members other than black are rotated around the rotating shaft. There is disclosed an image forming apparatus including a photoconductor moving unit configured to rotate a frame in a direction away from a conveyor belt.

Japanese Patent Application Laid-Open No. 9-146383 discloses that a transfer belt is held at a transferable position so as to always contact the black photosensitive member in the same posture, and the transfer belt is moved to three photosensitive members other than black. In order to move the transfer material to any one of a transferable position where the transfer material is brought into contact with the photoreceptor and a non-transferable position separated from the photoreceptor so that the transfer material is not brought into contact with the photoreceptor, 3 A transport belt support roller corresponding to each of the photoconductors is attached to a movable arm that can rotate up and down around a rotation axis provided at a position near the black photoconductor,
In the black single-color image mode, the movable arm is rotated downward to separate the three photoconductors other than black from the conveyor belt.

[0006]

However, Japanese Patent Application Laid-Open No. 9-6 / 1994
In the methods disclosed in Japanese Patent Application Laid-Open No. 088 and Japanese Patent Application Laid-Open No. H11-84799, the photosensitive member requiring high mounting accuracy must have a movable structure. However, there is a problem that the cost increases.

In the system disclosed in Japanese Patent Application Laid-Open No. Hei 9-146383, the above problem can be avoided, but since the transport belt and the belt support structure are rotated about a rotation axis, the image is not displayed. A large space is required in the forming apparatus. Therefore, it is inevitable that this is contrary to the recent demand for downsizing of the image forming apparatus.

The present invention has been made in view of the above circumstances, and has as its object to provide a small-sized color image forming apparatus capable of freely forming both a monochrome image and a color image at low cost.

[0009]

In order to achieve the above object, an image forming apparatus according to the present invention comprises a plurality of photoconductors arranged in parallel and rotating in a predetermined direction, and a surface of each of the plurality of photoconductors having different colors. A plurality of image forming units for forming an image, contacting each of the photoconductors at a predetermined primary transfer position, transferring the image formed on each photoconductor, carrying the transferred image, and transporting the image in a predetermined direction Endless belt, and a primary transfer for transferring an image formed on each photoconductor to the endless belt by contacting a back side with respect to a front side of the endless belt which comes into contact with each photoconductor at each primary transfer position. Rolls, and primary transfer roll supporting means for supporting the plurality of primary transfer rolls at predetermined positions, respectively, and the image transferred to the endless belt is finally secondarily transferred to a predetermined recording medium. In the image forming apparatus for fixing and forming a fixed image on the recording medium, the primary transfer roll supporting unit may be configured to transfer a predetermined one of the plurality of primary transfer rolls via the endless belt. While remaining supported in contact with the photoconductor corresponding to the primary transfer roll, the remaining primary transfer rolls other than the predetermined primary transfer roll are brought into contact with the photoconductor corresponding to the primary transfer roll via the endless belt. A transfer position, and a primary transfer roll moving means for switchably moving in parallel to a retreat position for separating from the photoreceptor corresponding to the primary transfer roll via the endless belt, and any one of the transfer position or the retreat position Is also characterized by supporting the remaining primary transfer roll.

Here, the contact surface between the photosensitive member corresponding to the predetermined one primary transfer roll and the endless belt is moved to each of the transfer positions, and the photosensitive member corresponding to the remaining primary transfer roll is moved to the transfer position. Preferably, it is on a plane different from the contact surface with the endless belt.

The contact surface between the photoconductor corresponding to the predetermined one primary transfer roll and the endless belt and the contact surface between the photoconductor corresponding to the remaining primary transfer roll and the endless belt are formed. It is also preferable that the angle is an angle of 180 degrees or less that is open inside the ring formed by the endless belt both when moving to the transfer position and when moving to the retreat position.

Further, it is a preferable embodiment that the photosensitive member corresponding to the predetermined one primary transfer roll has a larger diameter than the photosensitive member corresponding to the remaining primary transfer roll.

It is preferable that the photosensitive member corresponding to the one predetermined primary transfer roll has a surface on which a black image is formed.

[0014]

Embodiments of the present invention will be described below.

FIG. 1 is a schematic configuration diagram showing an embodiment of the image forming apparatus of the present invention.

The image forming apparatus shown in FIG.
(Yellow), M (magenta), C (cyan), K
Four photoconductors 1Y, 1M, and 4 corresponding to the color (black) and rotating in the direction of arrow A, respectively, are arranged in parallel.
1C and 1K, and image forming units 10Y and 10 corresponding to the four colors arranged around the respective photoconductors.
M, 10C, and 10K. Each image forming unit includes a developing unit 2Y, 2M, 2C, 2K, a cleaner 3Y,
3M, 3C, 3K, and ROS (exposure device) 4Y, 4
M, 4C and 4K. Further, the image forming apparatus contacts each of the photoconductors at a predetermined primary transfer position to receive a transfer of an image formed on each photoconductor, and carries the transferred image and transports the image in the direction of arrow B. An image formed on each photoconductor is transferred to the transfer belt 15 by contacting the transfer belt 15 in the form of an endless belt and the back side of the transfer belt 15 at the primary transfer position with respect to the front side of the transfer belt 15 that comes into contact with each photoconductor. Primary transfer rolls 5Y, 5M, 5C, 5K
And primary transfer roll supporting devices 6 and 7 for supporting the plurality of primary transfer rolls at predetermined positions, respectively, and secondary transferring the image transferred to the transfer belt 15 to the recording medium P.
Transfer roll 11 composed of two rolls 11a and 11b
And a fixing device 13 for fixing the image secondary-transferred to the recording medium P onto the recording medium P, so that a fixed image is finally formed on the recording medium P.

The transfer belt 15 includes a drive roll 9a,
Tension rolls 9b, 9c, 9d and roll 11
a and circulates in the direction of arrow B. The recording medium P supplied from the paper tray 14 receives the transfer of the image on the transfer belt 15 on the secondary transfer roll 11,
After the image is fixed by the fixing device 13, the sheet is discharged outside the apparatus.

The primary transfer roll supporting devices 6 and 7 in the present embodiment correspond to the primary transfer roll supporting means in the present invention, and the primary transfer roll moving device 8 in the present embodiment is It corresponds to the primary transfer roll moving means according to the invention.

As shown in FIG. 1, the primary transfer roll supporting devices 6 and 7 of this embodiment are divided into two parts. On the other hand, the primary transfer roll supporting device 6 transfers the primary transfer roll 5K of the fourth color among the four primary transfer rolls 5Y, 5M, 5C, 5K via the transfer belt 15 to the photosensitive transfer corresponding to the primary transfer roll 5K. It is supported in contact with the body 1K.

On the other hand, the primary transfer roll supporting device 7
Is a transfer position where the remaining three primary transfer rolls 5Y, 5M and 5C other than the primary transfer roll 5K are brought into contact with the corresponding photoconductors 1Y, 1M and 1C via the transfer belt 15, and via the transfer belt 15. And a primary transfer roll moving device 8 for switching and moving in parallel to a retreat position to be separated from the corresponding photoconductors 1Y, 1M, 1C, respectively, in each of the transfer position or the retreat position. In addition to supporting the primary transfer rolls 5Y, 5M, 5C, it also supports the drive roll 9a and the tension roll 9b.

The primary transfer roll moving device 8 includes a retract frame 7a to which bearings for supporting the primary transfer rolls 5Y, 5M, 5C, a drive roll 9a, a tension roll 9b, and the like are fixed, and two retractable frames fixed to the retract frame 7a. The guide pins 7b and 7c contact the retract frame 7a and rotate in the direction of arrow C to move the retract frame 7a up and down. The cam 8a guides the vertical movement of the retract frame 7a due to the rotation of the cam 8a. And guide pin guide grooves 8b and 8c fixed to the image forming apparatus main body. The two guide pin guide grooves 8b and 8c are provided so as to form predetermined inclination angles with respect to the contact surfaces 16Y, 16M and 16C between the photoconductors 1Y, 1M and 1C and the transfer belt 15, respectively. When the two guide pins 7b and 7c are guided by the two guide pin guide grooves 8b and 8c and slide in an oblique direction, the retract frame 7a moves in a vertical direction.

Further, in this embodiment, when the contact surface 16K between the photoreceptor 1K and the transfer belt 15 corresponding to the primary transfer roll 5K of the fourth color is moved to each transfer position, the remaining primary transfer rolls 5Y, 5Y are moved. Photoconductor 1Y corresponding to 5M, 5C
Contact surfaces 16Y, 16 between 1M, 1C and transfer belt 15
It is configured to be on a different plane from M and 16C. That is, in the present embodiment, since the diameters of the respective photoconductors of the four image forming units are all the same, the fourth
The center of the photoconductor 1K of the color image forming unit 10K is
Distance from the center of photoconductor 1Y of image forming unit 10Y of the first color to the center of photoconductor 1C of image forming unit 10C of the third color via the center of photoconductor 1M of image forming unit 10M of the second color It is arranged at a position shifted by x.

FIG. 2 is an explanatory view of the operation of the primary transfer roll moving device in the image forming apparatus of the embodiment shown in FIG.

FIG. 2A shows three primary transfer operations by rotating the cam 8a of the primary transfer roll moving device 8 in the image forming apparatus shown in FIG. 1 to move the retract frame 7a upward in parallel. Rolls 5Y, 5M, 5C
The corresponding photoconductors 1Y, 1Y,
The state set at the transfer position that comes into contact with 1M and 1C is shown. The full-color image is formed by the four image forming units 10Y, 10M, 10C, and 10K in the state set at the transfer position, and a full-color image is formed on the recording medium P.

FIG. 2B shows the three primary transfer operations by rotating the cam 8a of the primary transfer roll moving device 8 in the image forming apparatus shown in FIG. 1 to move the retract frame 7a downward in parallel. Rolls 5Y, 5M, 5C
The drawing shows a state in which each of the photosensitive members 1Y, 1M, and 1C is set to a retracted position to be separated from the corresponding photosensitive member. The image forming unit 1 for the fourth color is set in the retracted position.
0K, a black monochrome image is formed, and the recording medium P
A black image is formed on the top. Therefore, at the time of forming a black single-color image, the remaining three image forming units 10Y, 10M, and 10C other than the image forming unit 10K do not operate, so that power consumption is reduced, noise is reduced, and the photosensitive member 1 is reduced.
Wear of Y, 1M, 1C and its related parts is prevented.

As described above, in the image forming apparatus according to the present embodiment, the primary transfer roll moving device 8 controls the remaining primary transfer rolls 5Y, 5M, 5C other than the predetermined primary transfer roll 5K.
Is moved in parallel to a transfer position where it comes into contact with each corresponding photoconductor via the transfer belt 15 and a retracted position where it is separated from each corresponding photoconductor via the transfer belt 15. The space occupied by the primary transfer roll moving device as compared with a method in which a photoconductor or a primary transfer roll is moved between a transfer position and a retreat position by a rotation motion about a rotation axis as seen in the prior art. Can be greatly reduced, which is extremely advantageous in reducing the size of the image forming apparatus.

That is, in the conventional method in which the photosensitive member or the primary transfer roll is rotationally moved about the rotational axis, the photosensitive member closest to the rotational axis and the transfer belt are separated by a necessary distance during monochromatic image formation. If separated, the distance between the photosensitive member closest to the rotation axis and the transfer belt must be considerably large. However, in the image forming apparatus of this embodiment, each photosensitive member and the transfer belt This is because if all the minimum intervals are secured, each photosensitive member and the transfer belt can be sufficiently separated.

In the image forming apparatus of this embodiment, the contact surface 16K between the photosensitive member 1K corresponding to the primary transfer roll 5K of the fourth color and the transfer belt 15, and the remaining primary transfer roll 5K
When the angles between the photoconductors 1Y, 1M, 1C corresponding to Y, 5M, 5C and the contact surfaces 16Y, 16M, 16C of the transfer belt 15 move to the above-described transfer position and to the retreat position. In both cases, the transfer belt 15 is configured to have an angle of 180 degrees or less that is open inside the ring formed by the transfer belt 15.

Without such a configuration, the angle formed between the contact surface 16K and the contact surfaces 16Y, 16M, and 16C when the retract frame 7a is moved to the transfer position or the retracted position. When the image forming apparatus is configured to have an angle of 180 degrees or more, the transfer belt 15 separates from the tension roll 9b when the retract frame 7a is moved to the retracted position, and the transfer belt 15 is stretched. There is a danger of becoming unstable.
In order to prevent this, instead of the tension roll 9b, the transfer belt 1
5 is required to regulate the running of the transfer belt 1.
The transferred toner image is formed on the surface of the photosensitive member 5 on the photoconductor side, and cannot be easily realized.

Next, a second embodiment of the image forming apparatus of the present invention will be described.

FIG. 3 is a diagram for explaining the operation of the primary transfer roll moving device in the image forming apparatus according to the second embodiment.

The image forming apparatus shown in FIGS. 3A and 3B is similar to the image forming apparatus shown in FIG. 1 in that Y (yellow), M (magenta), C (cyan), and K ( Four image forming units 10Y, 10M, and 10 incorporating photoconductors 1Y, 1M, 1C, and 1K corresponding to the respective colors (black).
C, 10K, and each image forming unit includes a developing unit 2Y, 2M, 2C, 2K, and a cleaner 3Y, 3K.
M, 3C, 3K, and ROS (exposure device) 4Y, 4
M, 4C, and 4K. Of the four photoconductors, the photoconductor 1K corresponding to black is replaced with the remaining three photoconductors 1K.
It is configured to have a diameter larger than Y, 1M, and 1C.

Further, this image forming apparatus has the same transfer belt 15, primary transfer rolls 5Y, 5M, 5C, 5K, primary transfer roll supporting devices 6, 7 and primary transfer roll movement as in the image forming apparatus shown in FIG. Apparatus 8, secondary transfer roll 1
1 so that a fixed image is finally formed on the recording medium P. The primary transfer roll supporting devices 6 and 7 of the present embodiment also support the primary transfer roll 5K and the primary transfer rolls 5Y, 5M and 5C of the fourth color similarly to the image forming apparatus shown in FIG. The configuration and operation of the primary transfer roll supporting device 7 by the transfer roll moving device 8 are the same.

FIG. 3A shows a primary transfer roll moving device 8.
By rotating the cam 8a, the retract frame 7a is moved upward in parallel, and the three primary transfer rolls 5 are moved.
5 shows a state in which Y, 5M, and 5C are set at transfer positions where they contact the corresponding photoconductors 1Y, 1M, and 1C via the transfer belt 15. With the four image forming units 10Y, 10M, 10
A full-color image is formed by C and 10K, and a full-color image is formed on the recording medium P.

FIG. 3B shows a primary transfer roll moving device 8.
By rotating the cam 8a, the retract frame 7a is moved downward in parallel, and the three primary transfer rolls 5 are moved.
Y, 5M, and 5C correspond to the corresponding photoconductors 1Y, 1
It shows a state in which it is set to a retreat position to be separated from M and 1C. In this state, the black single-color image is formed only by the fourth color image forming unit 10K, and a black image is formed on the recording medium P.

As described above, in this image forming apparatus, 4
Of the three photoconductors, photoconductor 1K corresponding to black is the remaining three photoconductors.
Although the photoconductors 1Y, 1M, and 1C have diameters larger than those of the photoconductors 1Y, 1M, and 1C, these four photoconductors are different from the image forming apparatus shown in FIG.
It is arranged in line with the center of M, 1C. Therefore,
Also in this embodiment, the primary transfer roll 5K of the fourth color is used.
Contact surface 16 between photoreceptor 1K and transfer belt 15 corresponding to
K is on a different plane from the contact surfaces 16Y, 16M, 16C of the photoreceptors 1Y, 1M, 1C and the transfer belt 15 corresponding to the remaining primary transfer rolls 5Y, 5M, 5C when moved to each transfer position. It is configured to be.

As described above, in the second embodiment, as in the first embodiment, the remaining three image forming units 10Y, 10M, and 10C other than the image forming unit 10K do not operate at the time of forming a black single-color image. Therefore, power consumption is reduced, noise is reduced, and wear of the photoconductors 1Y, 1M, 1C and related parts is prevented. However, the frequency of use is usually lower than that of the other photoconductors 1Y, 1M, 1C. The life of the black photoconductor can be made closer to the other photoconductors by making the diameter of the black photoconductor that is likely to shorten the life of the photoconductor higher than that of the other photoconductors. Replacement intervals can be matched, and maintenance man-hours can be reduced. However, on the other hand, there is a disadvantage that the number of component types increases.

In each of the above embodiments, only an example of an image forming apparatus having four photosensitive members has been described.
Image forming units other than the K color image forming unit are combined into one unit, for example, Y, M, C image forming units, and can be expanded from a single color copying machine or a single color printer to a full color copying machine or a full color printer as needed. The present invention can also be applied to such an image forming apparatus.

[0039]

As described above, according to the present invention, a predetermined primary transfer roll of a plurality of primary transfer rolls is supported while being in contact with a corresponding photosensitive member via an endless belt. A switchable parallel position that allows the remaining primary transfer rolls other than the predetermined primary transfer roll to come into contact with the corresponding photoconductor via an endless belt, and a retracted position where the primary transfer roll is separated from the corresponding photoconductor via the endless belt. Having a primary transfer roll moving means for moving, and having a primary transfer roll supporting means configured to support the remaining primary transfer roll at any of the transfer position and the retreat position, so as to provide a monochrome image and a color image. An image forming apparatus capable of freely forming both images can be reduced in size. That is, in comparison with the conventional method in which the photosensitive member or the primary transfer roll is rotated and moved, the method of the present invention employs a method in which the primary transfer roll is simply moved in parallel. The distance from the belt can be made much smaller than in the conventional method.

Accordingly, the power consumption of the image forming units other than black is reduced during the formation of a black single-color image, the noise is reduced, and a low-cost and small-sized device capable of preventing abrasion of the photoreceptor and its related parts can be prevented. A color image forming apparatus can be realized.

Further, in the case where the diameter of the black photosensitive member which is used more frequently than the color photosensitive member and whose life tends to be shorter is made larger than that of the color photosensitive member, the black photosensitive member has The service life can be made closer to other photoconductors,
The replacement intervals of the four photoconductors can be matched, and the number of maintenance steps can be reduced.

[Brief description of the drawings]

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

FIG. 2 is an operation explanatory view of a primary transfer roll moving device in the image forming apparatus of the embodiment shown in FIG.

FIG. 3 is an operation explanatory view of a primary transfer roll moving device in an image forming apparatus according to a second embodiment.

[Explanation of symbols]

 1Y, 1M, 1C, 1K Photoconductor 2Y, 2M, 2C, 2K Developing unit 3Y, 3M, 3C, 3K Cleaner 4Y, 4M, 4C, 4K ROS (exposure device) 5Y, 5M, 5C, 5K Primary transfer roll 6, 7 Primary transfer roll supporting device 7a Retract frame 7b, 7c Guide pin 8 Primary transfer roll moving device 8a Cam 8b, 8c Guide pin guide groove 9a Drive roll 9b, 9c, 9d Tension roll 10Y, 10M, 10C, 10K Image forming unit 11 Secondary transfer roll 11a, 11b Roll 13 Fixing unit 14 Paper tray 15 Transfer belt 16K, 16Y, 16M, 16C Contact surface A, B, C direction P Recording medium

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/16 103 G03G 15/16 103

Claims (5)

[Claims] A plurality of photoconductors arranged in parallel and rotating in a predetermined direction; a plurality of image forming units for forming images of different colors on the surfaces of the plurality of photoconductors; An endless belt that receives a transfer of an image formed on each photoconductor in contact at a primary transfer position, carries the transferred image and conveys the image in a predetermined direction, and the endless belt at each of the primary transfer positions. A primary transfer roll for transferring an image formed on each of the photoconductors to the endless belt by contacting a back side with respect to a front side of the photoconductor, and supporting the plurality of primary transfer rolls at predetermined positions, respectively; An image forming apparatus comprising: a primary transfer roll supporting means; and an image transferred to the endless belt is secondarily transferred and fixed to a predetermined recording medium to form a fixed image on the recording medium. The primary transfer roll supporting means keeps supporting a predetermined one of the plurality of primary transfer rolls in a state where the primary transfer roll is in contact with the photoconductor corresponding to the primary transfer roll via the endless belt. A transfer position where the remaining primary transfer rolls other than the predetermined primary transfer roll are brought into contact with a photoconductor corresponding to the primary transfer roll via the endless belt, and corresponding to the primary transfer roll via the endless belt. A primary transfer roll moving means for switchably moving in parallel to a retracted position separated from the photosensitive member to be moved, and supporting the remaining primary transfer roll at any of the transfer position and the retracted position. An image forming apparatus comprising: 2. A photoconductor corresponding to the remaining primary transfer roll when a contact surface between the photoconductor corresponding to the predetermined one primary transfer roll and the endless belt is moved to each of the transfer positions. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is on a plane different from a contact surface with the endless belt. 3. A contact surface between the photoconductor corresponding to the predetermined one primary transfer roll and the endless belt and a contact surface between the photoconductor corresponding to the remaining primary transfer roll and the endless belt. 2. The angle formed by the endless belt and being 180 ° or less opened inside a ring formed by the endless belt both when moving to the transfer position and when moving to the retreat position. Image forming apparatus. 4. The photoconductor according to claim 1, wherein the photoconductor corresponding to the predetermined primary transfer roll has a larger diameter than the photoconductor corresponding to the remaining primary transfer roll. Image forming device. 5. The photoconductor according to claim 1, wherein a black image is formed on a surface of the photoconductor corresponding to the predetermined one primary transfer roll. Image forming device.