JP2001166602A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a separation mechanism for separating a transfer part constituted of a transfer roller and a transfer belt from an image carrier, and also a mechanism for releasing the tension of the transfer belt, on a tandem type image forming device with an inexpensive and simple mechanism. SOLUTION: A slider 20 with opening parts 20a to 20d which are engaged with rotary arms 7a to 7d for supporting respective transfer rollers 2a to 2d is attached so as to slide in a horizontal direction in the figure. Here, the width of the opening part 20a is made larger than the width of each opening part 20b to 20d. Besides, an engagement projection 20e which is engaged with the supporting shaft 4a of a driven roller 4 is arranged at the end part of the slider 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plurality of image carriers which are arranged in series, a plurality of transfer rollers which are arranged in a state of being urged against the image carriers, and a plurality of the transfer rollers. And a transfer belt wound around a transfer roller of the so-called tandem type.

[0002]

2. Description of the Related Art Conventionally, a plurality of sets of an image carrier such as a photoreceptor drum and transfer means such as a transfer roller arranged in opposition thereto are arranged in series, and a transfer is wound around the plurality of transfer rollers. 2. Description of the Related Art A tandem-type color image forming apparatus that sequentially transfers toner images of different colors onto the transfer sheet while conveying the transfer sheet by a belt is known. Among such tandem-type color image forming apparatuses, in a quadruple tandem-type image forming apparatus using four color toners in which black is added to three colors of yellow, magenta, and cyan, a black toner is used for a monochrome image. The image formation using only the image is performed. When forming an image using only black toner, if the transfer belt is kept in close contact with the image carrier that is in charge of the toner other than black, the transfer belt becomes dirty, and the image formed with the black toner is disturbed. Problem occurs. Therefore, for example, Japanese Patent Laid-Open No.
For example, Japanese Patent Application Laid-Open No. 1927/1998 and Japanese Patent Application Laid-Open No. Hei 10-198121 propose a four-tandem type image forming apparatus in which a transfer belt is separated from an image carrier that is in charge of a toner other than black when forming a monochrome image. I have.

First, the configuration of an image forming apparatus Z0 proposed in Japanese Patent Application Laid-Open No. 10-181927 will be briefly described with reference to FIG. The image forming apparatus Z0 includes four photoconductor drums 51a to 51m for forming images using magenta, cyan, yellow, and black toners.
51d, and four image forming units including transfer brushes 52a to 52d facing the four photosensitive drums, respectively. Transfer paper is sequentially conveyed to the four image forming units by a transfer belt 65 rotated counterclockwise. The transfer belt 65 includes a driving roller 58, a driven roller 59, an auxiliary roller 60, a tension roller 61,
And four backup rollers 53a to 53d. The backup rollers 53a to 53d
Are provided on the upstream side of the transfer brushes 52a to 52d, respectively, and bring the transfer belt 65 into close contact with the photosensitive drums 51a to 51d, respectively. Further, the tension roller 61 is attached to one end of a key-shaped member 62 that is swingably supported at a fulcrum 62a. A spring 63 is connected to the other end of the key-shaped member 62, and the tension roller 61 is urged by the spring 63 so as to apply tension to the transfer belt 65. Reference numeral 64 denotes a regulating member that regulates the swing of the key member 62 at a predetermined position. The backup rollers 53a to 53c and the transfer brush 52a
52c are mounted on an arm 54 supported coaxially and swingably with the rotation axis of the backup roller 53d. Further, an end of an intermediate connecting rod 55 is rotatably connected near the upstream end of the arm 54, and the other end of the intermediate connecting rod 55 is connected to a driving source (not shown). It is rotatably connected to a turning arm 56 connected to the drive shaft of the gear 57.

[0004] Image forming apparatus Z having the above configuration
0, when four-color full-color image formation is performed, as shown in FIG. 3A, the driving gear 57 is driven counterclockwise, whereby the arm 54 is pushed upward and the transfer belt 65 is moved. And transfer brushes 52a to 52
d is in a state of being in contact with the photosensitive drum. On the other hand, when performing monochrome image formation using only black toner, as shown in FIG.
Is driven clockwise by a predetermined amount, and the arm 54 is tilted downward. As a result, the transfer belt 65 and the transfer brushes 52a to 52c are separated from the photosensitive drums 51a to 51c for magenta, cyan, and yellow, and the transfer brush 52d and the transfer belt 65 are separated only to the photosensitive drum 51d for black. It is in a state of being pressed. This makes it possible to form a monochrome image without problems such as contamination of the transfer belt and disturbance of the formed image. At this time, the key-shaped member 62 comes into contact with the regulating member 64 or is in a state immediately before the contact. Further, when the image forming operation is not performed, as shown in FIG.
Is further driven clockwise by a predetermined amount than the state shown in FIG. 3B, and the arm 54 is further tilted downward. At this point, the swing of the key-shaped member 62 is already regulated by the regulating member 64, so that the tension of the transfer belt 65 is relaxed by the amount of the inclination of the arm 54. Thus, when the image forming operation is not performed, the transfer belt 6
By loosening the tension of No. 5, it is possible to prevent the transfer belt 65 from being bent or sagged.

However, in the image forming apparatus Z0, even when the image forming operation is not performed, the transfer belt 65 and the transfer brush 52d are always in pressure contact with the photosensitive drum 51d in charge of black. However, when JAM occurs, there is a problem that the processing becomes difficult. In contrast, Japanese Patent Laid-Open No. 10-198
In a tandem type image forming apparatus Z0 '(not shown) proposed in Japanese Patent Publication No. 121, a transfer unit separating mechanism is also provided for an image forming unit for black, in addition to an image forming unit for magenta, cyan, and yellow. Are provided, and respective driving sources are connected. Thus, when the image forming operation is not performed, the transfer units can be separated from all the photosensitive drums, and the JAM process and the like can be easily performed.

[0006]

However, in the image forming apparatus Z0 'proposed in Japanese Patent Application Laid-Open No. HEI 10-198121, the separation mechanism for the image forming section in charge of black and the other image forming sections is driven by different systems. Therefore, the mechanism becomes complicated and causes a cost increase. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a separation mechanism for separating a transfer unit including a transfer roller and a transfer belt from an image carrier on a so-called tandem type image forming apparatus. Another object of the present invention is to realize a mechanism for releasing the tension of the transfer belt by a low-cost simple mechanism.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a plurality of image carriers arranged in series, and a plurality of image carriers arranged in a state of being pressed against the image carriers. And an image forming apparatus comprising a plurality of transfer rollers, the transfer roller being provided so as to be movable in a predetermined direction. A moving member having a plurality of transfer roller action parts for separating from the body,
An image forming apparatus, wherein the timing at which at least one of the transfer roller operating portions of the moving member is pressed against the transfer roller or the supporting member thereof and the timing at which the transfer member is pressed by another transfer roller operating portion are made different. It is configured as a device. Accordingly, it is possible to separate two or more sets of transfer rollers from the image carrier at different timings only by moving the moving member by one drive source, thereby simplifying the mechanism and reducing the cost. The transfer belt further includes a transfer belt wound around the plurality of transfer rollers and a tension roller for applying tension to the transfer belt. By providing a tension roller acting portion for moving the tension roller in a direction to loosen the tension of the transfer belt, in addition to the operation of separating the transfer roller from the image carrier, the operation of relaxing the transfer belt during non-image formation. This can be achieved only by moving the moving member by one driving source. The image forming apparatus is suitable, for example, when the plurality of image carriers respectively carry out image formation using a plurality of color toners including a black toner.
In this case, the timing of pressing the transfer roller working portion against the transfer roller facing the image carrier for the black toner or the supporting member thereof and the timing of pressing the other transfer roller working portion are different from each other, so that the color and monochrome can be used. Switching between the pressure contact and separation of each transfer roller from the image carrier can be realized by a simple mechanism using one drive source.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and examples of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention. The following embodiments and examples are examples embodying the present invention, and do not limit the technical scope of the present invention. Here, FIG. 1 is an explanatory view of a state change of the tandem type image forming apparatus Z1 according to the embodiment of the present invention in full-color, monochrome, and non-image forming, and FIG. 2 is a tandem type image forming apparatus. Partial plane (partial cross section) showing a schematic configuration of the transfer unit 30 of Z1
It is a figure and a side view. As shown in FIG. 1, a tandem type image forming apparatus Z1 according to the present embodiment includes four photosensitive drums 1a to 1d (image carriers) which are in charge of image formation using respective toners of black, cyan, magenta, and yellow. ) And transfer rollers 2a to 2d facing the four photosensitive drums, respectively. Further, the transfer rollers 2a to 2d,
The driving roller 3, the driven roller 4, and the auxiliary roller 5 include:
An endless transfer belt 6 is wound. The transfer belt 6 is rotated counterclockwise in FIG. 1 by the driving of the drive roller 3 to sequentially pass the transfer paper through the four image forming units.

Next, the configuration of a characteristic portion of the present embodiment will be described with reference to FIG. FIG. 2 is a partial plan view and a side view of a transfer unit 30 in which the transfer rollers 2a to 2d, the drive roller 3, the driven roller 4, the auxiliary roller 5, and the transfer belt 6 wound around them are integrated. It is. A slider 20 (an example of a moving member) is slidably attached to the side plate 14 of the transfer unit 30 in the left-right direction in FIG. The slider 20 is slid left and right by driving a cam 11 rotating about a support shaft 11a. The slider 20 has four openings 20a to 20d (an example of a transfer roller operating portion). The transfer rollers 2a to 2d are attached to one ends of key-shaped rotary arms 7a to 7d (one example of a support member for the transfer roller), respectively.
a to 7d are fulcrums 8a to 8
At 8d, it is swingably supported. Further, the other end sides of the rotating arms 7a to 7d are provided with projecting rods 9a to 9a, respectively.
9d are integrally formed, and the protruding rods 9a to 9d penetrate through the openings 20a to 20d of the slider 20, respectively. The tips of the projecting rods 9a to 9d penetrating the openings 20a to 20d and the slider 20 are connected by spring members 10a to 10d, respectively. The transfer rollers 2a to 2d are photosensitive drums 1a to 1
d (see FIG. 1).

When the slider 20 is at the rightmost position in FIG. 2, the projecting rods 9a to 9d do not come into contact with the openings 20a to 20d and the transfer rollers 2a to 2d do not come into contact with the openings 20a to 20d.
d are pressed against the photosensitive drums 1a to 1d by the urging of the spring members 10a to 10d. In the process of sliding the slider 20 to the left in FIG. The edge portion abuts on the protruding rods 9a to 9d and pushes the same, whereby the transfer rollers 2a to 9d are moved.
2d is separated from the photosensitive drums 1a to 1d. However,
The width of the opening 20a is larger than that of the openings 20b to 20d, so that when the slider 20 is slid to the left in FIG.
d comes into contact with the protruding rods 9b to 9d so that the transfer rollers 2b to 2d are separated from the photosensitive drums 1b to 1d. , And the transfer roller 2a is separated from the photosensitive drum 1a.

The driving roller 3 and the auxiliary roller 5 are directly supported by the side plate 14, and the driven roller 4 (an example of a tension roller) slides in the horizontal direction of FIG. It is supported by a support member 12 that is freely attached. Above driven roller 4
Is biased rightward in FIG. 2 by a spring member 13 attached between the support member 12 and the side plate 14, thereby applying tension to the transfer belt 6. The support member 12 and the slider 2
0 is provided with engaging projections 12a and 20e (an example of a tension roller operating portion) that engage with each other while the slider 20 slides leftward in FIG. As the slider 20 is slid to the left in FIG.
The engagement projection 20e of the slider 20 is
2 to move the support member 12 to the left in FIG. 2 against the bias of the spring member 13. Thus, the tension applied to the transfer belt 6 by the driven roller 4 is relaxed. The timing of the engagement between the engagement projections 12a and 20e is determined by the opening 2
The timing of the contact between the edge of Oa and the protruding rod 9a is adjusted.

Next, the operation of the image forming apparatus Z1 during full-color, monochrome, and non-image formation of the four colors of the image forming apparatus Z1 will be described with reference to FIG. In FIG. 1, FIG.
The structure near the driven roller 4 shown in FIG. 3 is schematically shown, in which the engaging projection 12e of the slider 20 abuts on the support shaft 4a of the driven roller 4 instead of the engaging projection 12a of the support member 12. When four full-color images are formed in the image forming apparatus Z1, as shown in FIG. 1A, the slider 20 is held at the rightmost position in FIG. In this state, none of the protruding rods 9a to 9d comes into contact with the openings 20a to 20d, and all of the transfer rollers 2a to 2d
The photosensitive drums 1a to 1d are urged by 0a to 10d.
Is pressed against. In this state, the engagement protrusion 12e of the slider 20 does not abut on the support shaft 4a of the driven roller 4, so that the transfer belt 6 is tensioned by the driven roller 4 urged by the spring member 13. Becomes

On the other hand, when performing monochrome image formation using only black toner, as shown in FIG. 1B, the cam 11 is rotated by 90 ° from the full-color state, whereby the slider 20 is rotated. 1 is moved to the left by a predetermined amount. In this process, the edges of the openings 20b to 20d come into contact with the projecting rods 9b to 9d, and the transfer rollers 2b to 2d
d is separated from the photosensitive drums 1b to 1d that are in charge of cyan, magenta, and yellow image formation. However, at this time, the opening 20a does not come into contact with the protruding rod 9a, and the transfer roller 2a is in contact with the photosensitive drum 1 for forming a black image.
It is held in a state of being pressed against a. At this time, the engagement projection 12e of the slider 20 has not yet come into contact with the support shaft 4a of the driven roller 4, and the transfer belt 6 is maintained in a tensioned state. Accordingly, it is possible to form a monochrome image without problems such as contamination of the transfer belt 6 and disturbance of a formed image.

Further, when the image forming operation is not performed,
As shown in FIG. 1 (c), the cam 11 is further rotated by 90 °, whereby the slider 20 is further moved to the left in FIG. 1 by a predetermined amount. In this process, the opening 20a contacts the projecting rod 9a, and the transfer roller 2a is also separated from the photosensitive drum 1a. That is, at this point, all the transfer rollers 2a to
2d is separated from the photosensitive drums 1a to 1d. Furthermore,
Simultaneously with the contact of the opening 20a with the protruding rod 9a, the engagement projection 12e of the slider 20 contacts the support shaft 4a of the driven roller 4 to push the driven roller 4 against the urging of the spring member 13. The tension of the transfer belt 6 is also loosened. As described above, when the image forming operation is not performed, the tension of the transfer belt 6 is relaxed,
The transfer belt 6 can be prevented from being bent or set.

As described above, in the tandem type image forming apparatus Z1 according to the present embodiment, cyan, magenta,
A mechanism for pressing / separating a transfer roller in charge of yellow image formation from / to the photosensitive drum, a mechanism for pressing / separating a transfer roller in charge of black image formation to / from the photosensitive drum, and a mechanism for tensioning / releasing the transfer belt. Can be operated by one cam rotation, that is, by one drive source, so that the mechanism is simplified and the cost can be reduced as compared with the related art.

[0016]

In the above embodiment, the engagement timing between the engagement projections 12a and 20e in FIG. 2 (the contact timing between the support shaft 4a of the driven roller 4 and the engagement projection 12e of the slider 20 in FIG. 1) is determined. Edge of opening 20a and protruding rod 9a
The tension of the transfer belt 6 is relaxed at the same time as the transfer roller 2a is separated from the photosensitive drum 1a in accordance with the contact timing of the transfer roller 2. However, the timing of loosening the tension of the transfer belt 6 may be slightly delayed.
The mechanism for interlocking the operation of the slider 20 and the transfer rollers 2a to 2d is such that the projecting rods 9a to 9d of the rotating arms 7a to 7d supporting the transfer rollers 2a to 2d are connected to the openings 20a to 20d of the slider 20. It is not limited to the one that penetrates through the 20d, but may be one that simply engages the engagement protrusions.

[0017]

As described above, according to the present invention, a plurality of image carriers are arranged in series, and a plurality of transfer rollers are respectively arranged in a state of being pressed against the image carriers. In the image forming apparatus, a plurality of transfer rollers are provided so as to be movable in a predetermined direction, and at the time of the movement, are pressed against the plurality of transfer rollers or their support members to separate the transfer rollers from the image carrier. A moving member having a transfer roller operating portion, wherein at least one of the transfer member operating portions of the moving member is pressed against the transfer roller or the supporting member thereof and pressed by another transfer roller operating portion; And an image forming apparatus characterized in that the moving member is moved by one driving source, and two sets are formed. It is possible to separate the transfer roller of the upper from the image carrier at different times, simplifying the mechanism, cost reduction can be achieved. If this is applied to, for example, an image forming apparatus that forms an image with a plurality of colors of toners including black toner using a plurality of image carriers, a transfer roller facing the image carrier for black toner or a transfer roller for a supporting member thereof. By making the pressure contact timing of the action portion different from the pressure contact timing of the other transfer roller action portions, the switching between the pressure contact / separation of each transfer roller with respect to the image carrier in color and monochrome can be simplified by one drive source. This can be realized by a mechanism. Furthermore,
A transfer belt wound around the plurality of transfer rollers,
A tension roller for applying tension to the transfer belt, wherein the moving member presses the tension roller or its support member during the movement to move the tension roller in a direction to loosen the tension of the transfer belt. With the action section, in addition to the operation of separating the transfer roller from the image carrier,
The loosening operation of the transfer belt during non-image formation can be performed only by moving the moving member by one driving source.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a state change of a tandem-type image forming apparatus Z1 according to an embodiment of the present invention during full-color, monochrome, and non-image formation.

FIG. 2 is a partial plan view (partially sectional view) and a side view showing a schematic configuration of a transfer unit 30 of the tandem image forming apparatus Z1.

FIG. 3 shows a tandem image forming apparatus Z0 according to the related art.
FIG. 7 is an explanatory diagram of a state change during full-color, monochrome, and non-image formation of four colors.

[Explanation of symbols]

1a to 1d: photosensitive drum (an example of an image carrier) 2a to 2d: a transfer roller 3 ... a drive roller 4 ... a driven roller (an example of a tension roller) 4a: a support shaft of a driven roller 5 ... an auxiliary roller 6 ... a transfer belt 7a 9a to 9d: Protruding rods 10a to 10d: Spring member 11: Cam 11a: Cam support shaft 12: Support member 12a: Engagement projection 20a to 20d Opening (an example of a transfer roller operating portion) 20e ... engagement projection

Claims (3)

[Claims] 1. An image forming apparatus comprising: a plurality of image carriers which are arranged in series; and a plurality of transfer rollers which are arranged in a state of being pressed against the image carriers, respectively. A moving member having a plurality of transfer roller action portions which are provided so as to be movable in a predetermined direction and which presses the plurality of transfer rollers or their support members during the movement to separate the transfer roller from the image carrier. And a timing at which at least one of the transfer roller working portions of the moving member is pressed against the transfer roller or the supporting member thereof and a time at which the transfer member is pressed by another transfer roller working portion. Image forming apparatus. 2. A transfer belt, comprising: a transfer belt wound around the plurality of transfer rollers; and a tension roller for applying tension to the transfer belt, wherein the moving member is pressed against the tension roller or its support member during the movement. 2. The image forming apparatus according to claim 1, further comprising a tension roller operating section for moving the tension roller in a direction to loosen the tension of the transfer belt. 3. The image forming apparatus according to claim 1, wherein the plurality of image carriers are each responsible for forming an image using a plurality of color toners including black toner, and a transfer roller facing the black toner image carrier or a transfer roller for supporting the transfer roller. 3. The image forming apparatus according to claim 1, wherein the pressure contact timing of the action portion and the pressure contact timing of the other transfer roller action portions are different.