JP3434155B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device used in an image forming apparatus or the like, and more particularly to an apparatus for favorably transferring an image formed on a recording medium to a sheet or the like which is a transfer material being conveyed. , sheets provided with a plurality of transfer portions in the direction that will be conveyed to an image forming apparatus having a conveying device for conveying the sheet to these transfer portion.

[0002]

2. Description of the Related Art In an image forming apparatus using an electrophotographic system or the like, a desired image is formed on a photosensitive member, which is a recording medium, with a toner, which is a coloring agent, and the image is appropriately transferred. It is designed to be transferred to a sheet that is a material.
Therefore, a color image can be obtained by using a plurality of colors of toner.

In recent years, the color orientation of offices has become stronger,
Color image forming apparatuses have come into wide use. As one method of forming this color image, there is a method of forming a toner image for each color on a photoconductor and sequentially superposing the toner image on a sheet to obtain a color image of a desired color. In this case, the sheet is repeatedly conveyed a plurality of times to the position where it comes into contact with the photosensitive member. Therefore, in forming a color image, it takes 3 or 4 times as much as in forming a color image because an image is formed by using toners of 3 or 4 colors.

Therefore, a photosensitive member corresponding to each color is provided, and a toner image formed on the photosensitive member is sequentially conveyed along a conveying path to a sheet, so that a color is formed at the same speed as a monochromatic image forming speed. There are three or four tandem photosensitive drum systems that can obtain an image. For example, four photoconductor drums are arranged side by side at regular intervals, and a toner image is formed on each photoconductor drum by using yellow, magenta, cyan, and black toners, and one sheet is formed. The toner images sequentially formed in the above are transferred at each transfer position to obtain a color image.

For example, in a four-tandem tandem system, a sheet is held on a conveyor belt, and the sheet is fed to the transfer position of each photoconductor drum so as to be in contact with the photoconductor, and the toner image is transferred.

In addition to the formation of color images, image formation using black toner is desired. In other words, in the case of a monochromatic image, an image with black toner is desired because it is much easier to recognize the image in terms of contrast as compared with images with toners of other colors. Therefore, when forming an image in such a single color, toner images are not formed on the other three photosensitive drums of yellow, magenta, and cyan, but a black toner image is formed and transferred onto the sheet, and a black toner image is formed. I'm getting an image.

Even in the formation of the image in the single color, the sheet is conveyed while being held on the conveyor belt so as to face the transfer positions of the four photosensitive drums. Therefore, there remains a problem that the surface of the conveyor belt is always soiled with toner or the like.

[0008] The stains on the conveyor belt may cause contamination of the back side of the sheet opposite to the image forming side, or may cause transfer efficiency deterioration when transferring a toner image from the surface of the photosensitive drum to the surface of the sheet, resulting in transfer unevenness. is there. Dirt of the conveyor belt surface is mostly toner adhesion, the photosensitive drum and disposed opposite the developing means onto a conveyor belt and roughly, falling toner scattered from the developing device containing a means that the developer The toner adhered to the photosensitive drum and the toner transferred to the surface of the photosensitive drum from the transfer belt are separated.

When the toner adheres to the surface of the conveyor belt, the most stain is left on the surface of the photosensitive drum after the sheet having the poor conveyance on the conveyor belt is removed when the sheet conveyance failure occurs. That is, the untransferred toner image is attached in contact with the surface of the conveyor belt.

Therefore, in the image forming apparatus described in Japanese Patent Application Laid-Open No. 3-288173, at the time of forming a black image, the conveying belt is separated from the photosensitive drum of the remaining image forming portion not involved in the image formation, and the toner is I try to prevent dirt. The configuration described in this publication will be described with reference to FIG.

FIG. 7 shows a color image forming apparatus using a laser beam printer, which adopts a 4-tandem tandem photosensitive body system. This image forming apparatus is provided with four image forming sections around which a developing device and the like are opposed to each other around a photosensitive drum, and the toner image formed on each of the image forming sections is transferred to each photosensitive member. It is configured to be transferred onto a sheet that is held and conveyed on an endless conveyor belt that moves and passes while contacting the body drum.

In the figure, each image forming portion P for forming an image of each color of magenta, cyan, yellow and black.
m, Pc, Py, and Pk are the photosensitive drums 1 respectively.
01M, 101C, 101Y and 101K are arranged, and each photoconductor drum is rotatable in the arrow direction. Further, the photosensitive drums 101M, 101C, 101
Chargers 102M, 102 are provided around Y and 101K.
C, 102Y and 102K, scanning optical device 103M, 1
03C, 103Y and 103K, and developing device 104
M, 104C, 104Y and 104K, and cleaners 105M, 105C, 105Y and 105K are sequentially arranged along the rotation direction of the photosensitive drum. Further, below the photoconductor drums 101M, 101C, 101Y and 101K, transfer units 106M, 106C, 10C are provided.
6Y and 106K are arranged to face each other.

[0013] As the conveyor belt 107 of endless Between each photoconductor drum and each of the transfer unit is moved passes, that are arranged at intervals that cover the placement distance 101K from the photosensitive drum 101M drive It is stretched between the roller 108 and the driven roller 109. The conveyor belt 107 is
The driving roller 108 is rotationally driven to be driven in the direction of the arrow.

On the right side of the conveyor belt 107, a paper feed cassette 1 for feeding the sheet P to the conveyor belt 107.
Ten are arranged. Therefore, when the image forming operation is started, when the color image is formed, the image forming operation is executed by the first magenta image forming portion Pm, and the magenta toner image formed on the photosensitive drum 101M is transferred to the transfer position. The sheet P fed from the sheet feeding cassette 110 is transferred to the conveyance belt 10 at the timing when it reaches.
The transfer unit 106, which is the first transfer position, is held on the transfer unit 106.
Sent to M.

The sheet P is conveyed by the conveyor belt 107.
The toner images that are sequentially conveyed by the image forming units Pc, Py, and Pk are sequentially superposed on the sheet every time they pass the transfer position. The sheet P that has passed all of these transfer steps is separated from the conveyor belt 107 and is sent to the fixing device 111 via the guide belt 112. In this fixing device 111, the toner images superposed on the sheet P are simultaneously heat-fixed, and a desired color image is formed on the sheet.

The above is the image forming operation with a full-color image. To explain the case of forming an image with a single color, especially black toner, the conveyor belt 107 is provided on the support 112, and the support 113. Is a rotating eccentric cam 11
It is supported by 4a and 114b. Especially the support 11
3 is provided so as to be rotatable around a rotation shaft of a drive roller 108 for driving the transport belt 107 or a rotation shaft of a driven roller 109.

Therefore, when an image is formed using the image forming portion Pk, the eccentric cam 11 on the side opposite to the drive roller 108 is formed.
By rotating 4b in the Q direction, the support base 112 is rotated in the R direction, and an image is formed with black toner while the photosensitive drums other than the image forming portion Pk are separated from the conveyor belt 107. That is, the photosensitive drum 101K is brought into contact with the conveyor belt 107, the formed toner image is transferred onto the conveyed sheet P held by the conveyor belt 107, and an image with black toner can be obtained.

[0018]

As described above, the conveyance for conveying the sheet, which is the transfer material having the structure described in JP-A-3-288273, provided in the conventional image forming apparatus to each transfer position. By providing the belt, the dirt of the belt due to the toner can be reduced.

However, since it is not possible to separate all the photoconductor drums of the image forming section from the conveyor belt, the image forming section is in standby during copying or during correction.
It is not possible to prevent toner stains on the conveyor belt.

In the processing of the sheet having the conveyance failure by the conveyance belt, when the sheet having the conveyance failure is removed from the inside of the apparatus, the sheet is partially sandwiched between the photosensitive drum and the transfer belt. It becomes difficult to remove the sheet, and if the sheet is forcibly removed, there is a possibility that the transport belt or the surface of the photoconductor may be damaged. Also, the sheet is torn,
A part of the torn sheet remains, which hinders the conveyance of the sheet during the next image formation.

Further, if the support base 113 is configured to be rotatable in any direction so that the conveyor belt can be separated from the photosensitive belt, it is possible to improve the sheet removing process and the like, but the conveyor belt is supported. The position of the support base 113 cannot be accurately positioned. That is, it is not possible to rotatably support the drive belt 108 and the driven roller 109 side of the conveyor belt 107 as a fulcrum, the position of the support base is not stable, and the transfer conditions and the like are different each time they are separated to form a stable image. become unable. Moreover, the supporting mechanism becomes very complicated.

In view of the above-mentioned problems, the present invention has a plurality of image forming units arranged in parallel by a simple means, and a conveyor belt for sequentially conveying sheets to these positions is provided from a recording medium for image formation. The purpose is to enable separation.

Further, an object of the present invention is to provide a mechanism capable of bringing the recording medium into contact with and separating from the conveying belt so that the transfer condition to the sheet conveyed by each image forming section and the conveying belt does not change. It is in.

[0024]

An apparatus for achieving the above-mentioned object according to the present invention is provided with a plurality of image forming portions for forming a toner image side by side, and the toner of each formed image forming portion is formed. In an image forming apparatus equipped with a conveyor belt that sequentially conveys the transfer material to each transfer position in order to transfer the image onto the transfer material, at least one transfer portion provided at the transfer position is supported and unidirectionally supported. A first rotating member rotatably provided and a second rotating member rotatably unidirectionally supporting the other transfer portion provided at the transfer position . Rotate each of the first and second rotating members.
The rotation axis for rotation is opposite to the transfer material loading and unloading sides.
Positions on opposite sides and facing each other
It is characterized in that the first and second rotating members are arranged so as to be capable of contacting and separating the conveying belt with respect to the image forming units.

According to this structure, since the conveyor belt is brought into and out of contact with the recording medium of the image forming section individually, it is not necessary to provide a mechanism for moving the entire conveyor belt. Simple to configure. Further, since the conveyor belt can be separated from all the image forming units, the operation for removing the jammed transfer material can be simplified,
There is no risk of scratching the conveyor belt.

Therefore, in the image forming apparatus having the above-described structure, the conveying belt is stretched between the driving roller and the driven roller provided between the image forming portions arranged in parallel, and the rollers are called. Separately, by providing a tension roller so that a constant tension state is applied regardless of the contact state and separation state of the conveyor belt with respect to the image forming section, the conveyor belt is separated from one image forming section and the other image forming section is separated. Even in the contacted state, the tension state of the conveyor belt can be maintained constant. Therefore, the transfer conditions do not differ, and the image formation can always be performed under the fixed conditions.

In the image forming apparatus having the above-mentioned structure, the image forming section can be selected for color image formation or black image formation of a single color, and the color image formation is set as the first rotating portion. If the black image forming portion is provided corresponding to the second rotating member, and the other transfer portion is selectively separated from the image forming portion in accordance with selection of color image formation or black image formation, Image formation in color or black can be selected. In addition, it is possible to obtain a combined color image of color and black.
In this case, as described above, the tension state can be constantly maintained in the contacting / separating state of the conveyor belt, so that a stable image can be expected.

Further, it the first and second rotating members
Use the rotating shafts for rotating the transfer material and the transfer material.
On the opposite side to the output side, and so that they face each other
If the transfer belt is placed in such a positional relationship , the transfer belt loading and unloading side is opened in a state where the conveyor belt is completely separated from the image forming section, so that a large space is formed between the transfer sheet and the image forming section, and the transfer sheet is contaminated by toner. At the same time, the effect of eliminating the transfer is facilitated, and at the same time, the operation for removing the jammed transfer material is simplified. here
To rotate the first and second rotating members respectively.
The rotation axis can be the same axis.

In the image forming apparatus having the above structure , the tension roller is moved toward the conveyor belt.
A compression spring that is movably installed and has one end locked to the fixed part.
Apply the urging force of the
The fixing portion is interlocked with the rotation of the first rotation member to move the pressure.
The structure is such that it can be moved in the biasing direction of the compression spring.
For example, the tension roller is interlocked with the rotation of the first rotation member.
The tension state of the conveyor belt due to can be maintained constant.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view showing the configuration of the entire image forming apparatus according to the present invention.

First, referring to FIG. 1, an image forming apparatus according to the present invention will be described. Although the image forming apparatus is a laser beam printer in FIG. 1, the present invention is not limited to these. For example, it can be applied to a digital color copying machine and a normal analog color copying machine.

In the figure, in the image forming apparatus 1, image forming units Pa, Pb, Pc, P corresponding to at least four colors are provided.
d is provided. Although the number of the image forming portions is four in the following embodiments of the present invention, the image forming portions can be applied when at least two or more are arranged in parallel.

A paper feeding device 2 is provided on one side surface of the image forming apparatus 1, that is, on the right side, and a discharge portion 3 for discharging a sheet as a transfer material is provided on the opposite side thereof. A fixing device 4 for heating and fixing the unfixed toner image transferred onto the sheet is provided adjacent to the discharge portion 3, particularly on the upstream side in the sheet conveying direction.

Between the sheet feeding device 2 and the fixing device 4, the sheet P fed by the sheet feeding device 2 is transferred to each of the above-mentioned image forming portions Pa, Pb, Pc and Pd. A conveyance unit 5 that holds and conveys the sheet P is arranged so as to pass through the sheet.

The sheet feeding device 2 has a conventionally well-known structure, and if one example is shown, a large number of sheets P are accommodated in a sheet feeding cassette 20 detachably provided in the main body of the image forming apparatus 1. The sheets in the paper feed cassette 20 are fed one by one by the paper feed rollers 21 arranged opposite to each other.
The fed sheet P is stopped at the position of the registration roller 22 arranged between the sheet feeding roller and the conveying means 5, and the first image is conveyed through the conveying means 5 so as to be synchronized with the image forming operation. It is sent to the transfer position of the forming section Pa.

Further, the discharging section 3 is a discharging roller 30 provided at a discharging port corresponding to a pair of rollers constituting the fixing device 4.
And a discharge tray 31 for receiving the sheet P sent through the discharge roller 30.

The fixing device 4 is well known in the prior art. To briefly describe the structure of the fixing device 4, a heat roller 41 whose surface is maintained at a temperature at which the surface can be fixed by a heater (not shown) and the heat roller 41 The pressure roller 42 is brought into pressure contact with a suitable pressure.

On the other hand, the image forming portions Pa, Pb, Pc and Pd have substantially the same structure, and only the colors of the images formed are different. The image forming portions Pa, Pb, Pc
And Pd are means for forming toner images of magenta, cyan, yellow and black, for example. In the figure, the same parts are designated by the same reference numerals, and the difference due to the color is a,
Differentiated by b, c and d.

The structure of the image forming portion Pa will be described as a representative. The image forming portion Pa includes the photosensitive drums 10a which are driven to rotate in the direction of arrow F, and the periphery of each photosensitive drum is provided. A charger 11a for uniformly charging the photosensitive surface of the photosensitive drum, a developing device 12a for developing the electrostatic latent image formed on the photosensitive surface, and a transfer for transferring the developed toner image to the cyan P described above. Part 13a, cleaning device 1 for removing toner remaining on the surface of the photoconductor after transfer
4a are sequentially arranged to face each other in the rotation direction of the photosensitive drum.

An imaging lens 15a and a laser beam scanner 16a are provided above the photosensitive drum 10a. The laser beam scanner 16a has a conventionally well-known structure. Especially laser beam scanner 1
6a is for forming a magenta image,
The semiconductor laser is ON / OFF driven and controlled according to the image data corresponding to the magenta, is deflected through a rotating mirror (polygon mirror), etc., and is further rotated on the photosensitive drum 10a through the fθ lens and the like on the photosensitive drum 10a. It is designed to scan.

The image forming portions Pa and P having the above-mentioned configuration
b, Pc, Pd, the developing devices 12a, 12b,
Reference numerals 12c and 12d contain magenta, cyan, yellow, and black toners, respectively, and the laser beam scanners 16a, 16b, 16c, and 16d form images of respective color components, particularly latent images on the photoconductor. And is developed.

On the other hand, the image forming portions Pa, Pb, P
The sheet conveying means 5 for transferring the toner image formed by c and Pd onto the sheet is a driving roller provided so as to correspond to the sheet feeding device 2, particularly the registration roller 22 and the fixing device 4. An endless sheet conveying belt 52 stretched between 50 and a driven roller 51 is provided. Inside the sheet conveying belt 52, a driven roller 53 for further stabilizing the conveyance of the belt and a movable member in the direction of the arrow X are provided so as to be further urged in that direction to give an appropriate tension to the belt 52. It has a tension roller 54 with a compression spring 55 that acts to cause it.

Further, in order to hold and convey the sheet P fed on the surface of the sheet conveyance belt 52, the sheet fed via the registration roller 22 is moved to the driven roller 51 facing the sheet. A sheet adsorption charger 56 is provided at a corresponding position. Therefore, the conveyed sheet P is electrostatically adsorbed and conveyed by the sheet conveying belt 52 by the action of the adsorption charger 56.

Further, transfer portions 13a, 13b, 13c and 13d constituting the above-mentioned image forming portions Pa, Pb, Pc and Pd are arranged in the sheet conveying belt 52, and these are arranged. The transfer unit includes a support 57 which is a first rotating member and a support 5 which is a second rotating member.
8 is provided. The first support 57 particularly supports the transfer portions 13a, 13b, 13c, and the second support 58 supports the transfer portion 13d.

The first support 57 is rotatable by a rotation shaft 59 provided on the side corresponding to the image forming portion Pc, particularly on the side opposite to the sheet P feeding side. The second support body 58 is axially supported, and the side corresponding to the image forming portion Pd, particularly the side discharged from the sheet image forming portion Pd, is rotatably supported by the rotating shaft 60. . Further, the first support 57 is supported by the peripheral surface (cam surface) of the eccentric cam 61 at the position opposite to the supported transfer portion at the position opposite to the rotating shaft 59 side. Further, also in the second support body 58, the surface opposite to the similarly supported transfer portion is supported by the peripheral surface (cam surface) of the eccentric cam 62 at a position opposite to the rotating shaft 60.

The above-mentioned eccentric cams 61 and 62 are arranged such that the transfer portions 13 have the longest distance from the rotary shaft to the cam surface.
a, 13b, 13c and 13d are the image forming portions Pa and P
b, Pc, Pd photosensitive drums 10a, 10b, 10c
The sheet conveying belt 52 is in contact with 10 and 10d with a constant width, and is positioned in a transferable state.

Transfer parts 13a, 13b, 13c and 13d
In the above, it may be configured by two cylindrical rollers, and a transfer voltage is applied to the two rollers to perform transfer. Further, the roller may be provided simply to bring the belt into contact with the photosensitive drum, and a transfer device (not shown) for performing corona discharge may be separately provided therebetween.

(Description of Image Forming Operation) The image forming apparatus according to the present invention is configured as described above, and the image forming operation will be described below. When forming a full-color image including black toner, the eccentric cams 61 and 62 are maintained in the state of FIG. 1, and the first and second support members 5 are
The transfer portions 13a, 13b, 13c, and 13d supported by 7, 58 are positioned at the transfer position.

In this state, when the image forming operation is started, the sheet P is rotated by the rotation of the sheet feeding roller 21, and one sheet is fed from the sheet feeding cassette 20. If the leading edge of the fed sheet is detected by the sheet leading edge detection means (not shown),
The signal causes the photosensitive drums 10a, 10b, 10c, and 10d of the image forming units Pa, Pb, Pc, and Pd to start rotating. Sheet P fed is Ru is stopped at once the standby state the leading end to the position of the registration rollers 22.

In response to the above detection signal, the drive roller 50 in the sheet conveying means 5 also rotates and the sheet conveying belt 52.
Is driven in the direction of arrow Z. As a result, the sheet conveying belt 52 sequentially passes through the image forming portions Pa, Pb, Pc and Pd. Then, the registration roller 2
At a predetermined timing as the driving base point of 2, that is, the conveyance start base point of the sheet P, the photosensitive drums 10a, 10b, 10
The image forming operation for c and 10d is sequentially started.
First, the photosensitive drum 10a which is the first image forming portion Pa
On the photosensitive drum 10b of the second image forming portion Pb, an image of cyan toner is formed on the photosensitive drum 10c of the third image forming portion Pc. Image with yellow toner,
Finally, on the photosensitive drum 10d of the fourth image forming unit Pd,
Images of black toner are shared and formed at different times.

Here, the deviation of the timing of forming the image of each color is set equal to the time for the sheet conveying belt 52 to move from the transfer portion 13a to the next transfer portion 13b. In this case, the transfer portions 13a, 13b, 13c and 13d are arranged at equal intervals.

The sheet P is conveyed by the sheet conveying belt 52.
It is adsorbed on the surface by the action of the adsorption charger 56 and is sent to the first image forming unit Pa. At the timing when the leading edge of the sheet is fed to the transfer position facing the transfer section 13a, the leading edge of the magenta toner image formed on the photosensitive drum 10a reaches and the transfer of the toner image is started. Thereafter, similarly, the sheets P conveyed by the sheet conveying belt 52 are sequentially arranged in the second, third and fourth image forming portions P.
By passing through the transfer portions b, Pc, and Pd, the toner images of respective colors are sequentially transferred and superimposed. Then, when the sheet P passes through the transfer portion of the final fourth image forming portion Pd, the electrostatic attraction state is released from the sheet / sheet conveying belt 52 by an AC static eliminator (not shown) and separated from the belt. Then, it is sent to the fixing device 4.

Sheet P fed into the fixing device 4
The toner images of the respective colors are sequentially superposed and transferred on the upper surface of the sheet, and the toner images are heated and fixed to combine the color images. The sheet P after the fixing is sent to the discharge tray 31 via the discharge roller 30 at the discharge port.

(Description According to One Embodiment of the Present Invention)
In the image forming apparatus having the above-described configuration according to the present invention, the image forming units Pa and P formed by the sheet conveying belt 52 are used.
Operation in one embodiment of a mechanism for bringing the photoconductors b, Pc, and Pd into and out of contact with each other, that is, a mechanism for bringing the photoconductor drums 10a, 10b, 10c, and 10d of each image forming unit into and out of the mechanism, and its operation Will be explained.

The sheet conveying belt 52 constituting the sheet conveying means 5 is stretched between the driving roller 50 and the driven roller 51 arranged on both sides. Further, the driven roller 53 and the tension roller 54 exert an appropriate tension, and the driving roller 50 carries out normal conveyance in the arrow Z direction, that is, traveling drive.

Although not shown, the drive roller 50 and the driven rollers 51 and 53 are support bases (not shown in FIG. 1) that can be pulled out from the main body of the image forming apparatus 1.
Is rotatably supported, and only the driving roller 50 is provided so as to be connectable to the driving unit on the main body side of the image forming apparatus 1. Then, the tension roller 54 is movably supported in the direction of the arrow X relative to the support base, Ru <br/> is interposed between a fixed portion 55-1 of the supporting base (not shown) side rollers 54 compress The spring 55 constantly applies a biasing force in the Y direction. As a result, an appropriate tension is applied to the sheet conveying belt 52, and the close contact state with the drive roller 50 is kept good.

On the other hand, the image forming portions Pa, Pb, Pc, P
The transfer portions 13a, 13b, 13c and 13d of d are divided into those for color transfer and those for black transfer, and are divided and held by a first support 57 and a second support 58, respectively. . That first held on the support 57 have <br/> Ru transfer unit 13a, 13b, 13c is configured as a color transfer unit, black transfer unit at the transfer portion 13d which is held by the second support 58 Is configured.

The first support 57 which is the color transfer unit and the second support 5 which is the black transfer unit.
8, the sheet conveying belt 52 is provided on the surface opposite to the transfer portion holding surface.
There are provided eccentric cams 61 and 62 which are rotationally driven for contact and separation. Therefore, the first and second supports 57, 58
Is rotatably supported by the shaft portions 59 and 60, so that the rotation of the eccentric cams 61 and 62 causes the eccentric cams 61 and 62 to rotate due to the difference in the distance from the rotation shaft to the cam surface.

In the full-color image forming mode including the normal black toner, the eccentric cam 6 is in the state shown in FIG.
It is maintained in the rotational position of 1 and 62. That is, the first and second support bodies 57 and 58 are supported and positioned by the cam surface having the longest distance from the rotation shafts of the eccentric cams 61 and 62. Thereby, the transfer parts 13a, 13b, 13c
And 13d, the sheet conveying belt 52 has a constant width, and the photoconductor drum 10 of each of the image forming portions Pa, Pb, Pc, and Pd.
Contact a, 10b, 10c and 10d. In this state, the full-color image forming operation is performed.

When the color image forming mode described above is selected to the monochromatic image forming mode, that is, the image forming mode using black, the eccentric cam 61 is rotationally driven in the direction of the arrow S, and the cam surface that is the smallest from the rotating shaft. Is rotated to a position supporting the first support 57. That is, the eccentric cam 61 is driven to rotate by 180 ° and stops. As a result, as shown in FIG. 1, the first support 57 is rotated about the rotation shaft 59 in the direction of arrow T, and the transfer portions 13a, 13b, 13c, which are color transfer units, are moved as shown in FIG. It is separated from the photoconductor drums 10a, 10b, 10c. For this reason, the sheet conveying belt 52 is not limited to the photosensitive drums 10a, 10
It is separated from b and 10c.

[0061] At this time, the tension roller 5 4 is moved by the rear mark X direction to the action of the compression spring 55, the biasing force of the Y-direction Grant to the sheet conveying belt 52, to maintain good tension state To do.

In this case, the fixed portion 55-1 which fixes (locks) one end of the compression spring 55 is provided on the side of the first support 57 without being fixedly provided on a support base (not shown). Accordingly, the fixing portion 55-1 is rotated at the same time, whereby the sheet conveying belt 52 by the tension roller 54 can be maintained in a better tension state, especially in the color image forming mode.

By the above operation, an image forming operation for a single color, that is, black is performed in the state where the color transfer unit is separated. In this case, the sheet P is adsorbed and conveyed by the sheet conveying belt 52 by the adsorption charger 56 facing the constant driven roller 51 under exactly the same conditions as the color image forming operation. Further, in the image forming section Pd with the black, since the transfer unit 13d are contacted to maintain constant conditions in the photosensitive drum 10d, enables a stable image formation in a state that at all conditions do not change.

Next, a description will be given of a color image forming mode using color toners, which is different from the monochromatic image forming mode using black and different from the full color image forming mode including black. In this case, magenta as color 1, cyan, although you are so formed by three colors of yellow, not limited to this, when performing single color image formation by color, an image by color toners corresponding to color Any one of the forming portions Pa, Pb, Pc is provided.

Therefore, in forming a color image including a single color image with color toner in FIG. 1, the eccentric cam 62 is driven to rotate by 180 ° in the direction of arrow Q, and the second support is provided by the shortest cam surface from the rotating shaft. Supports body 58. As a result, the second support body 58 is rotated in the arrow R direction,
The sheet conveying belt 52 is separated from the photosensitive drum 10d of the image forming portion Pd as shown in FIG. The slack of the sheet conveying belt 52 in this separation is caused by the tension roller 5
Relaxed in 4.

Therefore, the sheet conveying belt 52 is stretched with an appropriate tension by the action of the tension roller 54,
Photosensitive drums 10a, 1 of the image forming portions Pa, Pb, Pc
By contacting 0b and 10c, an image of a required color can be formed. Even in this case, the sheet conveying belt 52
The photosensitive drum 10a, 10b, the contact state between 10c or the like is kept constant and does not transfer conditions are changed.

In the tension roller 54, the fixed portion 55-1 at one end of the compression spring 55 has the first support member 5.
When it is provided on the 7 side, the fixed portion cannot be moved to the X direction and a constant tension state cannot always be applied to the sheet conveying belt 52. However, the sheet conveying belt 52 is moved from the photosensitive drum 10d of the image forming portion Pd using black toner to the sheet conveying belt 52.
In the case where only the color unit is separated, it is smaller than in the case where the previous color unit is separated, and the tension state of the belt does not change much. Therefore, even if the position of the spring 55 is rotated in the Q direction of the rotary cam 62 and does not change, the sheet conveying belt 52 is in a constant tension state within a predetermined range.

The tension state of the sheet conveying belt 52 will be described in detail in the section of description of another embodiment.

As described above, by setting the image forming mode with the color toner, only the image forming portion Pd with the black toner is set to the non-image forming state, and the single color image formation with any one color and the two colors are performed. Single color image formation, for example, magenta and yellow red image formation, cyan and yellow green image formation, and the like. Further, it is also possible to form a color image without black toner, if necessary.

Finally, the operation of the image forming apparatus during standby, during aging, or when a sheet jam trouble occurs, particularly the state where the sheet conveying belt 52 is separated from the photosensitive drum, will be described.

In this case, the rotary cam 61 and the rotary cam 62
Are respectively rotated in the directions of arrows S and Q in FIG. That is, the sheet conveying belt 52 is connected to each image forming portion P.
It is rotated so as to be separated from a, Pb, Pc and Pd. As a result, the first and second supports 57 and 58 are rotated as shown in FIG.
The photosensitive drums 10a, 10b, 10c and 10d are separated from each other.

[0072] In this state, the correction Ejin grayed is performed, toner contamination from the photosensitive drum of the sheet conveying belt 52 is prevented. Further, in the case of a sheet jam trouble, since the belt 25 is entirely separated from the photosensitive drum, the removal process is simplified, and there is no risk of damage to the sheet or damage to the sheet conveying belt or the surface of the photosensitive drum.

(Another Embodiment) Next, another embodiment according to the present invention will be described below. In this embodiment, the tension state of the sheet conveying belt 52 can be kept constant in each image forming mode.

[0074] In cases described in an embodiment target is to reduce the slack in the sheet conveying belt 52 Ri by the action <br/> the spring 55 of the tension roller 54, applies a constant tension state to the belt 52 Or the fixing portion at one end of the spring 55 is provided on the side of the first support body 57, and the fixing portion 55-1 is similarly moved in the X direction in association with the rotation of the first support body 57. And the length of the spring 55 is made constant, and the tension state is kept constant.

Separately from this, as shown in FIG. 4, a fixing portion 55-1 having one end of the spring 55 fixed is mounted on a support base (not shown in FIG. 4) for supporting the sheet conveying belt 52. On the other hand, the fixed portion 5 is provided so as to be movable in the X direction.
5-1 by interlocking with the rotation of the rotary eccentric cam 61, as shown in FIG.
As shown in (b), the cam surface of the rotary eccentric cam 61 is used to move in the X direction. As a result, the sheet conveying belt 52 moves the image forming portions Pa, Pb, P
The length of the compression spring 55 between the tension roller 54 and the fixed portion 55-1 is kept constant in the state of being separated from the c and in the state of being in contact with each other, so that the tension state acting on the sheet conveying belt 52 is maintained. Can be kept constant.

Further, although the fixed portion 55-1 of the spring 55 is interlocked and moved by utilizing the cam surface of the rotary eccentric cam 61, the first part which is interlocked with the rotary shaft 63 of the rotary cam 61 is rotated. A rotary eccentric cam or the like is provided for the second
The fixed portion 55-1 may be moved in the X direction on the surface of the rotational eccentric cam.

In such a structure, the second support 5
It is also possible to provide a third rotary eccentric cam that interlocks with the rotation of the rotary eccentric cam 62 that supports 8 and to move the fixing portion 55-1 in the X direction also in the third rotary eccentric cam.

In this case, since the distance by which the sheet conveying belt 52 is separated from the photosensitive drum 10d of the image forming portion Pd is short when rotated by the rotating cam 62, the third cam that interlocks with the rotation of the rotating cam 62 is used. The cam surface of the third rotary eccentric cam is formed such that the distance by which the fixed portion 55-1 is moved in the X direction is shortened. With such a configuration, the tension state of the sheet conveying belt 52 can be maintained constant even in the color image forming mode.

Here, when the single color unit and the color unit are separated from the image forming portions Pa, Pb, Pc and Pd, the fixing portion 55-1 is naturally moved by the second rotary eccentric cam. That is, the second rotary eccentric cam and the third rotary eccentric cam rotate together, but the distance by which the fixed portion 55-1 is substantially moved by the second rotary cam is larger. In this case, since it is not directly related to image formation, there is no problem even if the tension state of the sheet conveying belt 52 is slightly changed, and the sheet conveying belt 52 maintains a proper tension action.

(Other Embodiments) Next, another embodiment according to the present invention, that is, a mechanism for pulling out a support base for supporting the sheet conveying belt 52 will be described. In particular, when the entire sheet transport belt 52 is pulled out, the sheet transport belt 52 is used by the image forming portions Pa, Pb, Pc and Pd.
It is configured such that it can be pulled out only when it is further separated, and cannot be pulled out in the contact state.

Therefore, as shown in FIG.
Locking members 65 and 66 for pulling out locks are attached to one end of the rotary shafts 63 and 64 on the inner side of the rotary shafts 63 and 64.
So as to correspond to the locking member 65 and 66, the fixed plate 67 and 68 provided in the image forming apparatus 1 main body is provided, it has been configured locking mechanism in the locking member and the fixed plate .

The locking members 65 and 66 and the fixing plate 67.
6 and 68, the positional relationship is provided on the far side in the drawing direction W as shown in FIG. FIG. 6 is a top view in which unnecessary portions in FIG. 5 are omitted, and the support base 69 is schematically illustrated.

In this figure, the rotary eccentric cams 61 and 6 are shown.
Rotary shaft 63 and 64 of 2 is rotatably supported on the support base 69, that has the locking member 65 and 66 Ritsuke be taken to one end of the rotary shaft 63 and 64. The fixing plates 67 and 68 are fixed to the main body side of the image forming apparatus 1. Further, the locking members 65 and 66 and the fixing plate 67.
And 68 mean that the sheet conveying belt 52 is the image forming portion P.
a, Pb, Pc, and Pd photosensitive drums 10a, 10
b, the state in contact with 10c and 10d, i.e. in the state in which the longest distance to the cam surface of the rotating eccentric cam 61 and 62 in contact with the first and second supports 57 and 58,
Their Re respectively are located opposite locking (lock) state.

Therefore, when the sheet conveying belt 52 is in contact with the photosensitive drums 10a, 10b, 10c and in the state where it is in contact with the photosensitive drum 10d, both and / or either of the locking members 65 and 66 are provided. One is fixed plate 67
6 and 68, and the locked state is maintained as shown in FIGS. 6 (a) and 6 (b). Therefore, a support base 69 that supports the entire conveyance unit including the sheet conveyance belt 52.
Cannot be pulled out in the direction of arrow W.

That is, as shown in FIG. 3, when the sheet conveying belt 52 is separated from the photosensitive drums 10a, 10b, 10c and 10d, the locking members 65 and 66 are fixed plates 67 and 68. Not facing
Thereby, the support base 69 can be pulled out in the arrow W direction. In this case, since the sheet conveying belt 52 is separated from the photosensitive drums 10a, 10b, 10c and 10d, there is no hindrance to the pulling-out operation, and there is no risk of damage to the photosensitive drums or the sheet conveying belt. Absent.

[0086] Incidentally, on the support base 69 that is supported all members constituting the transfer means 5. That is, the drive roller 50 for stretching the sheet conveying belt 52, the driven rollers 51 and 53, the tension roller 54, and the spring 5.
5, fixed part 55-1, first and second supports 57 and 5
8. The rotary cams 61 and 62 are rotatably and movable, and are supported in a fixed state.

As described above, according to the present invention, the sheet conveying belt 52 is provided in the image forming portions Pa, Pb, Pc and Pd so as to be able to come into contact with and separate from the sheet conveying belt 52 at will. Since it is not necessary to provide the supporting base 69 including the supporting base 69 so that the supporting base 69 can be brought into contact with and separated from the supporting base 69, its mechanism and configuration are very simple. Moreover, although the sheet conveying belt 52 is provided so as to be contactable and separable, a tension roller 54 is provided so that the tension state at that time can be maintained constant, and the distance of the compression spring 55 for applying tension to the tension roller 54 is set. It is made invariable, so that it can always be maintained in a constant state regardless of the image forming mode, and in particular, the transfer conditions do not change.

In particular, in the embodiment according to the present invention, the rotating shafts 59 and 60 of the first and second supports 57 and 58 are opposed to each other in order to separate the sheet conveying belt 52 from the photosensitive drum. It is provided in. That is, the rotating shafts 59 and 60 are provided so as to be opposite to the driven roller 51 or the drive roller 50 side. By doing so, a large space is formed on the carry-in side or the carry-out side of the sheet, as shown in FIG. 3, so that the removal of the sheet or the like becomes easier. That is, if the rotation shaft 59 is provided on the driven roller 51 side, a large space cannot be secured on the sheet loading side, and removal of the jammed sheet becomes troublesome. Further, when the rotating shaft 60 is provided on the drive roller 50 side, the distance between the photosensitive drums 10a, 10b, 10c and 10d and the sheet conveying belt 52 becomes very short, and the sheet removing operation is troublesome. In addition, it is not possible to completely separate the contact state with the photosensitive drum, and it becomes impossible to prevent the stain and the like from being caused by the toner.

Such an inconvenience can be eliminated in the structure of the present invention. For example, as shown in FIG. 3, the sheet conveying belt 52 is largely opened to the sheet carrying-in side and the sheet carrying-out side, so that the sheet is extremely removed. To be easy.

Here, the first and second supports 57 and 5
Although the rotating shafts 59 and 60 of 8 are provided separately, they are made to be the same shaft, and the first and second supports 57 and 58 are provided on the shafts so as to be rotatable in opposite directions, respectively. You can This can be said to be a unique configuration of the present invention which is adopted by providing the rotating shafts 59 and 60 on the side opposite to the driven roller 51 or the drive roller 50 side.

[0091]

According to the image forming apparatus of the present invention, when a plurality of image forming units are arranged in parallel, when the toner image is transferred onto the transfer material, the individual image forming units are used to form an image. In this case, the transfer belt for transferring the transfer material can be easily brought into contact with and separated from the image forming portion, so that the dirt of the toner can be eliminated and the jammed transfer material can be easily removed.

Further, since the conveying belt is separated from the image forming portion, the structure is very simple, the separating space can be increased, and the jam sheet can be removed.
Will be easier.

Furthermore, since a constant tension can always be applied to the conveyor belt even in the separated state, the transfer conditions do not change and simple image formation can be performed under the constant conditions.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the overall structure of an image forming apparatus provided with a sheet conveying unit provided with a sheet conveying belt according to the present invention so that it can be arbitrarily contacted and separated from a plurality of image forming units.

FIG. 2 is an explanatory diagram showing a state in which a conveyance belt is separated from one image forming unit in FIG.

FIG. 3 is an explanatory diagram illustrating a state in which the image forming unit is separated from all the image forming units in FIG.

FIG. 4 is a diagram for explaining the structure and operation of the portion of the transporting means for explaining another embodiment according to the present invention.

FIG. 5 is a diagram for explaining a structure and an operation for enabling the carrying means to be pulled out for explaining another embodiment according to the present invention.

FIG. 6 is a top view showing a state in which unnecessary portions of FIG. 5 are omitted.

FIG. 7 is a cross-sectional view showing the structure of a conventional sheet conveying belt provided with a plurality of image forming portions so that the entire sheet can be brought into contact with and separated from the image forming portions.

[Explanation of symbols]

1 Image forming device body 2 Paper feeder 5 Sheet transport means 10 photoconductor 11 charger 12 Development device 13 Transfer part 14 Cleaning device Image forming unit for each color of Pa, Pb, Pc, Pd 22 Registration roller 50 drive roller 51 Driven roller 52 Sheet Conveyor Belt 54 Tension roller (tension means) 55 Compression spring (tensioning means) 57 first support (first rotating member) 58 Second Support (Second Rotating Member) 59 rotation axis 60 rotation axis 61 Eccentric cam (contact / separation member) 62 Eccentric cam (contact / separation member) 63 Cam rotation axis 64 cam rotation axis 65 Locking member 66 Locking member 67 Fixed plate 68 Fixed plate 69 Support

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-160328 (JP, A) JP-A-5-19641 (JP, A) JP-A-8-22198 (JP, A) JP-A-6- 102776 (JP, A) JP 5-142954 (JP, A) JP 6-258914 (JP, A) JP 59-111653 (JP, A) JP 7-261504 (JP, A) JP-A-7-64362 (JP, A) JP-A-3-106736 (JP, A) JP-A-5-88501 (JP, A) Actually developed JP-A-3-77940 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/01-15/01 117 G03G 15/16

Claims (3)

(57) [Claims] 1. A transfer material is provided to each transfer position so that a plurality of image forming portions for forming a toner image are provided side by side and the toner image of each formed image forming portion is transferred onto the transfer material. An image forming apparatus provided with a conveyor belt that sequentially conveys, a first rotating member that supports at least one transfer portion provided at the transfer position and is rotatable in one direction,
A second rotation member that supports another transfer portion provided at the transfer position and is rotatably provided in one direction, for rotating each of the first and second rotation members. The rotating shaft is arranged on the opposite side of the transfer material carrying-in side and the carrying-out side, and in a positional relationship such that they face each other, and the first and second rotating members are the above-mentioned respective ones. An image forming apparatus characterized in that the above-mentioned conveying belt can be brought into contact with and separated from an image forming portion. 2. A transfer material is provided to each transfer position so that a plurality of image forming parts for forming a toner image are provided side by side and the toner image of each formed image forming part is transferred onto the transfer material. In an image forming apparatus having a conveyor belt for sequentially transporting the sheet, a first rotating member that is rotatably provided to support at least one transfer portion provided at the transfer position, and provided at the transfer position. And a second rotating member that is rotatably provided and supports the other transfer unit, and the first and second rotating members contact and separate the conveyor belt with respect to the image forming units. The transfer belt is provided so as to be capable of being stretched between a driving roller and a driven roller provided between the image forming units arranged in parallel, and the transfer material is transferred to the driven roller so as to face the driven roller. A member for electrostatically adsorbing the material to the conveyor belt is provided, Serial such that a constant tension state regardless contact to the image forming section of the conveyor belt acts on the conveyor belt, a tension roller on the opposite side provided with the image forming unit, the tension roller, said conveyor belt Can be moved to the side
It is provided with a compression sleeve with one end locked to the fixed part.
A biasing force of pulling so granted to the tension roller
And the fixed portion is interlocked with the rotation of the first rotation member.
An image forming apparatus, wherein the image forming apparatus is provided so as to be movable in a biasing direction of a compression spring . 3. The image forming section is selectable for color image formation and for black image formation of a single color, wherein the color image formation is a first rotating member and the black image formation is a second. 3. The image forming apparatus according to claim 1, wherein the image forming unit is provided so as to correspond to the rotating member, and the other transfer unit is selectively separated from the image forming unit according to selection of color image formation or black image formation. apparatus.