JP3522534B2 - Intermediate transfer device for image forming apparatus - 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 of an image forming apparatus, and more particularly to an image forming apparatus for temporarily transferring a toner image formed on the peripheral surface of a photosensitive drum and further transferring the toner image onto a sheet. The present invention relates to a transfer device.

[0002]

2. Description of the Related Art There is an image forming apparatus such as a copying machine or a printer that forms a color image on a sheet by superposing plural kinds of color toners. For example, in a full-color copying machine, an image reading unit that reads a document image, an image processing unit that separates the read document image into four color components of cyan, magenta, yellow, and black, and an electrostatic latent image is formed on the peripheral surface. The photosensitive drum, the exposure means for forming an electrostatic latent image for each color component on the peripheral surface of the photosensitive drum, and the electrostatic latent image formed on the photosensitive drum are visualized by corresponding color toners. Four developing devices, a transfer belt on which the toner images formed on the photosensitive drum are sequentially transferred to form a laminated color toner image, and the color toner image transferred on the transfer belt is transferred onto a sheet 2 Some include a secondary transfer roller and a fixing device that heats and fixes a color toner image on a sheet.

The read original image is cyan, magenta,
The electrostatic latent image corresponding to cyan is first formed on the peripheral surface of the photosensitive drum by being decomposed into yellow and black color components. The electrostatic latent image formed on the peripheral surface of the photosensitive drum is visualized by a developing device that stores cyan toner, and the cyan toner image is transferred to the surface of the transfer belt. After that, toner images of magenta, yellow, and black are similarly formed on the peripheral surface of the photosensitive drum and transferred to the transfer belt. As a result, the color toner images are formed by laminating the toner images of the respective colors on the surface of the transfer belt.

After that, the paper is conveyed between the transfer belt and the secondary transfer roller, and the color toner image on the surface of the transfer belt is transferred onto the paper by the secondary transfer roller. The paper on which the color toner image is transferred is further conveyed to the fixing device. The fixing device is provided with a heating roller having a built-in heater and a pressure roller that is in pressure contact with the heating roller. The paper is sandwiched between the heating roller and the pressure roller to melt and fix the color toner image and the paper. Are conveyed in the discharge direction.

In the image forming apparatus having the above-mentioned structure, the transfer belt is stretched between the driving roller driven by the motor and the driven roller rotatably supported by the apparatus and the photosensitive drum. It is constructed so as to face each other and go around a predetermined orbit. On the inner peripheral surface of the transfer belt, the transfer belt surface is pressed against the peripheral surface of the photosensitive drum to transfer the toner image formed on the peripheral surface of the photosensitive drum to the transfer belt surface, and the tension of the transfer belt is adjusted. A tension roller and the like for arranging are arranged. Further, at a secondary transfer position where the toner image on the transfer belt is transferred onto the surface of the conveyed paper, a pair of secondary transfer rollers which are pressed against the inner and outer circumferences of the transfer belt via the transfer belt are arranged. Further, a cleaning device for collecting the toner remaining on the surface of the transfer belt is provided on the downstream side of the secondary transfer position in the circumferential direction of the transfer belt. This cleaning device is provided with a cleaning blade that comes into pressure contact with the transfer belt surface, and a transfer cleaning roller is provided on the inner peripheral surface side of the transfer belt so as to face the cleaning blade.

As described above, the transfer belt includes a driving roller, a driven roller, a tension roller, a primary transfer roller,
It is stretched around a plurality of rollers such as a secondary transfer roller and a transfer cleaning roller, and orbits a predetermined orbit. The transfer belt which is stretched around a plurality of rollers and circulates is made of an elastic material such as a fluorine resin.
There is a risk that the track will meander due to a shift in the width direction during orbit.

For this reason, protrusions protruding toward the inner peripheral surface are provided at both ends in the width direction of the transfer belt, and grooves for receiving the protrusions are provided at both ends in the width direction of each roller to prevent the transfer belt from meandering. It is possible to do it.

[0008]

When the transfer belt is provided with a ridge to prevent meandering, the inner peripheral surface of the ridge provided on the transfer belt contacts the outer peripheral surfaces of the grooves provided at both ends in the width direction of the roller. If they are not in contact with each other, a difference in tension may occur between the intermediate portion of the transfer belt supported by the intermediate portion of the roller and the widthwise both ends where the protrusions are provided, and the transfer belt surface may be uneven.

In particular, as the primary transfer roller, two transfer rollers are provided side by side on the orbit of the transfer belt, and the transfer belt is pressed against the peripheral surface of the photosensitive drum between the positions where the two transfer rollers respectively support the transfer belt. In this case, the transfer belt is dented in the vicinity of both ends in the width direction between the transfer rollers, and a toner image is omitted in the primary transfer from the photosensitive drum to the transfer belt. There is a risk.

An object of the present invention is to provide a transfer device of an image forming apparatus capable of preventing meandering of the transfer belt and preventing unevenness on the surface of the transfer belt to prevent missing of a transferred toner image. To provide.

[0011]

A transfer device of an image forming apparatus according to the present invention comprises a transfer belt, a plurality of rollers, a support roller, and a primary transfer means. The transfer belt is
It is arranged so as to face the photoconductor drum so that the toner image formed on the peripheral surface of the photoconductor drum can be transferred, and to be rotatable along a predetermined track, and to prevent meandering protruding to the inner peripheral surface at a predetermined height. The projecting ridges extend in the length direction of both side edges. The plurality of rollers support the intermediate portion in the width direction excluding the meandering-preventing ridge portion of the transfer belt in a tensioned state to orbit the transfer belt. The support rollers are rotatably attached to the rotary shafts of the rollers at both ends in the width direction of the rollers, and have a diameter smaller than the diameter of each roller corresponding to the height of the meandering-preventing ridge. And supports the inner peripheral surface of the meandering-preventing ridge. The primary transfer means transfers the toner image formed on the peripheral surface of the photosensitive drum to the surface of the transfer belt.

In this case, in the transfer belt, the intermediate portion in the width direction is supported by the rollers, and the both end edges in the width direction where the meandering preventing ridges are provided are supported by the support rollers and are rotated. Since the support roller is rotatably supported coaxially with the roller, the inner peripheral surface of the meandering-preventing ridge provided on the edge portion of the transfer belt abuts and integrally rotates. Therefore, it is possible to solve the problems of poor rotation and wear of the transfer belt and the rollers due to the peripheral speed difference between the widthwise intermediate portion and the widthwise end portion of the transfer belt.

In this case as well, as in the case of the above-mentioned invention, it is possible to further comprise a secondary transfer means for transferring the toner image transferred on the surface of the transfer belt onto the paper, and a plurality of rollers are provided. Can be configured to include a drive roller that is rotationally driven by a motor and a driven roller that is rotatably supported.

Further, the primary transfer means includes two primary transfer rollers which are arranged along a predetermined orbit around which the transfer belt circulates and which support a widthwise intermediate portion of the transfer belt excluding meandering preventing ridges, The transfer belt is in pressure contact with the peripheral surface of the photoconductor drum between the positions where the two primary transfer rollers support the transfer belt. The meandering prevention ridge has a diameter smaller than that of each primary transfer roller that is rotatably attached to the rotation axis of the roller and is coaxially attached corresponding to the height of the meandering prevention ridge. It can be configured to have a support roller that supports the inner peripheral surface of the.

Further, at least one of the two primary transfer rollers can be moved to a separated position where it is separated from the photosensitive drum and the surface of the transfer belt is separated from the peripheral surface of the photosensitive drum.

Further, a plurality of developing devices for accommodating toners of different color components are provided, and the toner image by the toners of the respective color components is laminated to be used in an image forming apparatus for forming a full color image on a sheet. be able to.

[0017]

1 is a cross-sectional view of a full-color copying machine to which an embodiment of the present invention is applied. The copying machine 1 has a main body 10 and a document holder 11 mounted on the top of the main body 10 so as to be openable and closable.

A document table 15 on which a document is placed is arranged at the upper part of the main body 10. Inside the main body 10, an image forming unit 16 is provided at an end portion on the left side when viewed from the front and substantially at the center in the vertical direction. Further, at the lower part, a paper feeding unit 17 for feeding a document to the image forming unit 16 is provided.
Is provided.

The paper feed unit 17 is removably attached to the main body 10 and holds paper feed cassettes 18, 19,
20 and 21, and a bypass tray 22 provided on the right side thereof. Below the document table 15, the document table 1
An optical system 23 for reading the image information of the document placed on the sheet 5 is provided. The optical system 23 is a light source 24 for irradiating the surface of a document placed on the document table 15 with light.
And a mirror 2 for deflecting the light reflected from the document surface.
5, 26, 27, a lens 28 for converging the light from the mirror 27, a color image pickup device such as a CCD sensor for receiving the light converged by the lens 28 and generating an image data signal corresponding to an original image. 29 and 29.

The image forming section 16 has a photosensitive drum 30 on the surface of which an electrostatic latent image is formed, and further the photosensitive drum 3
0, the main charging device 31, the developing device 33,
It has 34, 35, 36, a transfer device 37 and a cleaning device 38. The main charging device 31 is a device for charging the surface of the photosensitive drum 30, and is arranged above the photosensitive drum 30. Developing devices 33, 34, 35, 36 for forming a toner image on the photoconductor drum 30 are arranged from the left side to the bottom of the photoconductor drum 30 with a predetermined gap from the main charging device 31. Each of the developing devices 33, 34, 35, and 36 stores cyan, magenta, yellow, and black toners, respectively, and visualizes the electrostatic latent image formed on the photosensitive drum 30 with each color toner. . The transfer device 37 is a device for transferring the toner image on the photoconductor drum 30 onto a sheet, and is arranged diagonally below and to the right of the photoconductor drum 30.
The cleaning device 38 is a device for removing residual toner and the like on the surface of the photoconductor drum 30, and is arranged obliquely above and to the right of the photoconductor drum 30.

An exposure device 39 for forming an electrostatic latent image on the peripheral surface of the photosensitive drum 30 is provided diagonally above and to the left of the photosensitive drum 30. The exposure device 39 includes a laser unit 40 and a mirror 41 that deflects the laser light from the laser unit 40 to the peripheral surface of the photosensitive drum 30, and the peripheral portion of the photosensitive drum 30 is rotated based on an image data signal obtained from the color image pickup device 29. An electrostatic latent image is formed on the surface. The laser light emitted from the exposure device 39 passes between the main charging device 31 and the developing device 33 and is applied to the peripheral surface of the photosensitive drum 30.

[Transfer Device] As shown in FIG. 2, the transfer device 37 includes a drive roller 44 to which the drive force of the drive motor 42 is transmitted via the drive belt 43, a secondary transfer upper roller 45, and a drive roller. The transfer belt 4 stretched between the upper transfer roller 44 and the secondary transfer upper roller 45.
6, a primary transfer upper roller 47 that presses the outer peripheral surface of the transfer belt 46 against the peripheral surface of the photosensitive drum 30, a primary transfer lower roller 48, and a tension roller 49 that is disposed on the inner peripheral surface side of the transfer belt 46. It has and.

The primary transfer upper roller 47 and the primary transfer lower roller 48 are located between the driving roller 44 and the secondary transfer upper roller 45, and the photosensitive drum 30 is provided via the transfer belt 46.
It is located at a position facing. Primary transfer upper roller 4
7 is movable between the primary transfer lower roller 48 and the pressing position where the transfer belt 46 is pressed against the peripheral surface of the photosensitive drum 30 and the separated position where the transfer belt 46 is separated from the peripheral surface of the photosensitive drum 30. ing.

For example, as shown in FIG. 3, the primary transfer roller 47 is rotatably mounted on a mounting plate 50.
The mounting plate 50 is rotatably mounted on the transfer device 37 via a support shaft 51. The mounting plate 50 has a projecting piece 52 projecting downward, and the projecting piece 52 has a primary pressing roller 53 provided in parallel with the rotation axis of the primary transfer upper roller 47.
Is provided. Also. The mounting plate 50 is biased by a spring 54 'in a direction away from the peripheral surface of the photosensitive drum 30.

On the transfer device 37 side, the primary pressing cam 5 having a cam surface capable of contacting the primary pressing roller 53 of the mounting plate 50.
4 is movably supported and provided. The driving force of the primary pressing cam drive motor 56 is transmitted to the primary pressing cam 54 by the driving belt 55, and the primary pressing cam 54 is rotatable.

A light-shielding plate 57 that rotates integrally with the primary pressing cam 54 is provided on the rotating shaft of the primary pressing cam 54.
The light shielding plate 57 has a fan shape in which a part of a circular plate is cut out, and is arranged so as to be able to block the optical path of the transfer belt pressing sensor 58 composed of a photo interrupter.

For example, when the distance for pressing the primary pressing roller 53 on the cam surface of the primary pressing cam 54 is maximum, the primary transfer upper roller 47 presses the transfer belt 46 against the peripheral surface of the photosensitive drum 30. At the same time, the transfer belt pressing sensor 58 is shielded from light by the light shielding plate 57 and is turned on. Further, when the distance for pressing the primary pressing roller 53 on the cam surface of the primary pressing cam 54 is the minimum, the primary transfer upper roller 47 is located at the separated position for separating the transfer belt 46 from the peripheral surface of the photosensitive drum 30. At the same time,
The transfer belt pressing sensor 58 is released by the light shielding plate 57 and is turned off.

The transfer device 37 is provided with a zinc stearate coating device 59 for coating the transfer belt 46 with zinc stearate. The zinc stearate coating device 59 includes a zinc stearate coating brush 60 that is in pressure contact with the driving roller 44 via the transfer belt 46, and a zinc stearate storage unit 61 for supplying zinc stearate to the zinc stearate coating brush 60. It consists of and. The zinc stearate applying device 59 is used for the transfer belt 46.
When the toner attached to the paper is transferred to the surface of the paper, the binding force of the toner to the transfer belt 46 is weakened, and zinc stearate for preventing the hollowing of the toner image formed on the paper is transferred at regular intervals. 46 is applied to the surface. For this reason, the zinc stearate coating brush 60 is capable of projecting and retracting with respect to the transfer belt 46, and is pressed against the drive roller 44 as necessary to apply zinc stearate to the transfer belt 46. ing.

Further, the transfer belt 37 is attached to the transfer device 37.
Cleaning device 6 for cleaning the surface of 6
Two are provided. This cleaning device 62 is
The cleaning roller 63, which is disposed between the lower secondary transfer roller 48 and the upper secondary transfer roller 45, is in contact with the inner peripheral surface of the transfer belt 46, the cleaning blade 64 is in pressure contact with the cleaning roller 63, and the cleaning blade 6.
4 is provided with a toner collecting section 66 having a spiral 65 for sending the scraped toner to a collecting tank.

The transfer device 37 includes a transfer belt 46.
A secondary transfer lower roller 67, which is disposed at a position facing the secondary transfer upper roller 45 via the transfer belt 46, applies a voltage having a polarity opposite to that of the toner on the surface of the transfer belt 46 to transfer the toner image onto the sheet. There is.

The secondary transfer lower roller 67 is rotatably supported by a mounting plate 68, as shown in FIG. Also, 2
The secondary transfer lower roller 67 is provided with secondary pressing rollers 69 having a slightly larger outer diameter and rotating integrally with each other at both ends in the width direction. The secondary pressing roller 69 is positioned such that the outer peripheral surface of the secondary pressing roller 69 contacts the side plate of the transfer device 37 so that the peripheral surface of the secondary transfer lower roller 67 and the surface of the transfer belt 46 are at a constant distance. Is. The distance between the peripheral surface of the secondary transfer lower roller 67 and the surface of the transfer belt 46 is
It is preferable to set the thickness of one sheet of paper.

The mounting plate 68 is movable in the vertical direction in FIG. 4, and is urged downward by an urging member (not shown) such as a spring. Further, the mounting plate 68 has a protruding piece 70 protruding downward. The projecting piece 70 is provided with a contact piece 71 that is projected in parallel with the rotation axis of the secondary transfer lower roller 67. The contact piece 71 can come into contact with the cam surface of the secondary pressing cam 72 rotatably supported by the side plate of the transfer device 37. The secondary pressing cam 72 is rotatable by a drive motor (not shown) and includes a light shielding plate 73 that rotates integrally. The light shielding plate 73 is configured so as to be capable of taking a position where the optical path of the transfer roller pressing sensor 74 constituted by a photo interrupter is blocked and a position where it is opened by rotating.

For example, when the contact piece 71 moved by the cam surface of the secondary pressing cam 72 is located at the uppermost position,
The mounting plate 68 is pushed up to the highest. At this time, 2
The next pressing roller 69 comes into contact with the side plate of the transfer device 37 to position the secondary transfer lower roller 67 at a predetermined position, and the light blocking plate 73 blocks the optical path of the transfer roller pressing sensor 74 to turn it on. When the contact piece 71 moved by the cam surface of the secondary pressing cam 72 is located at the lowest position,
The mounting plate 68 is positioned at the lowest position by the urging of the urging member. At this time, the secondary transfer lower roller 67 is separated from the surface of the transfer belt 46, and at the same time, the light shielding plate 73 opens the optical path of the transfer roller pressing sensor 74 to turn it off.

Further, the secondary transfer lower roller 67 is provided with a cleaning blade 75 for peeling off the toner adhering to the peripheral surface in a state of being pressed against the peripheral surface. further,
A separation needle 7 for separating a sheet from the transfer belt 46 by applying a predetermined voltage in the vicinity of the secondary transfer lower roller 67.
6 is provided.

[Paper Feed Unit] The paper feed unit 17 includes the paper feed cassettes 18, 19, 20, 2
A vertical transport path 81 for transporting a sheet from 1 to the image forming section 16 and a bypass transport path 82 for transporting a sheet from the bypass tray 22 to the image forming section 16 are provided. Pickup rollers 83, 84, 85, 86, 8 for taking out the stored sheets are provided in each of the sheet feeding cassettes 18, 19, 20, 21 and the bypass tray 22.
7 and a pair of paper feed rollers 88, 89, 90, 91, 92 for feeding the papers one by one to the transport path. The vertical transport path 81 has a pair of transport rollers 93, 94, 9
5, 96 are provided. The vertical conveyance path 81 and the bypass conveyance path 82 are joined at the right side of the secondary transfer upper roller 45 and the second transfer lower roller 67 of the transfer device 37,
It is continuous with a paper feed conveyance path 97 that supplies paper to the transfer device 37. The sheet feeding / transporting path 97 is provided with registration rollers 98 for holding the sheet transported from the sheet feeding section 17 at a predetermined position.

[Fixing Device] On the left side of the secondary transfer upper roller 45 and the secondary transfer lower roller 67 of the transfer device 37, a paper discharge transport path 99 for transporting the paper on which the toner image is transferred is formed. The fixing device 100 is arranged on the left side of the fixing device 100. The fixing device 100 is provided with a heating roller 101 having a built-in heater and a pressure roller 102 that is in pressure contact with the heating roller 101. The sheet is sandwiched between both rollers to be conveyed and formed on the surface of the sheet. The toner image is heated and fixed.

A paper discharge roller pair 103 is provided on the further left side of the fixing device 100, and is configured to discharge the paper to a paper discharge tray 104.

[Transfer Belt] The transfer belt 46, which is a reference example, is made of a fluororesin or the like. As shown in FIG. 5, the transfer belt 46 has an outer peripheral surface 111 to which a toner image is transferred and an outer peripheral surface of each roller. It has an intermediate inner peripheral surface 112 that is supported. At both edges of the transfer belt 46 in the width direction, meandering prevention ridges 11 protruding toward the inner peripheral surface side are formed.
3,113 are provided. This meandering prevention ridge 11
Reference numerals 3 and 113 have end inner peripheral surfaces 114 and 114 that contact the outer peripheral surfaces of the end edges of the rollers.

Each roller on which the transfer belt 46 is stretched has a structure as shown in FIG. 5, and here the primary transfer upper roller 47 is shown as an example.

The primary transfer upper roller 47 is a transfer belt 46.
The intermediate support portion 115 that supports the intermediate inner peripheral surface 112, and the edge support portion 116 that has a diameter smaller than that of the intermediate support portion 115 by the height of the meandering prevention protrusion 113. The outer peripheral surface of the intermediate support portion 115 has a width substantially the same as the width of the intermediate inner peripheral surface 112 of the transfer belt 46, and contacts the intermediate inner peripheral surface 112 to support the intermediate inner peripheral surface 112 of the transfer belt 46. Intermediate support surface 117. The end edge support portions 116 are provided at both end edges of the intermediate support portion 115, and the outer peripheral surfaces thereof have a width substantially the same as the width of the meandering prevention ridges 113 of the transfer belt 46. End support surface 1 that supports the end inner peripheral surface 114 of the strip 113
18 is composed.

As a result, as shown in FIG. 6, the intermediate inner peripheral surface 112 of the transfer belt 46 has the primary transfer upper roller 47.
Of the primary transfer roller 47 by contacting the inner peripheral surface 114 of the end portion of the meandering prevention protrusion 113 with the end support surface 118 of the primary transfer upper roller 47. It is supported on the outer peripheral surface.

Primary transfer lower roller 48, cleaning roller 63, secondary transfer upper roller 45, tension roller 4
9, each roller of the drive roller 44 is configured to have an intermediate support portion and an edge support portion, like the primary transfer upper roller 47 described above. As a result, the transfer belt 46
Is abutted against and uniformly supported on the outer peripheral surface of each roller at the widthwise intermediate portion and the widthwise end portion, so that no irregularity is generated on the outer peripheral surface. Particularly, in the primary transfer portion, the primary transfer upper roller 47 and the primary transfer lower roller 4
Since 8 are arranged relatively close to each other, when the inner peripheral surface of the meandering preventing protrusion 113 is separated from the outer peripheral surface of the roller, a dent is likely to occur at the end edge portion between both rollers. In the above-described embodiment, such a problem is improved, and it is possible to prevent the toner image to be transferred from being missing.

A detection hole 120 penetrating through the front and back is provided at the widthwise edge of the transfer belt 46. The detection holes 120 are provided at six locations at equal intervals in the rotation direction of the transfer belt 46, and are used to position the tip of the toner image formed on the outer peripheral surface 111.

As shown in FIG. 2, the frame of the transfer device 37 is provided with a photo interrupter 12 via a mounting plate 121.
2 is attached. This photo interrupter 12
As shown in FIG. 7, reference numeral 2 denotes a light emitting unit 12 including LEDs.
3 and a light receiving portion 124 formed of a phototransistor are arranged to face each other with a predetermined distance therebetween.
23 and the light receiving portion 124 are arranged so as to sandwich the end portion in the width direction of the transfer belt 46. Photo interrupter 12
The light emitted from the second light emitting portion 123 is transferred to the transfer belt 46.
When the light is blocked by and does not reach the light receiving unit 124,
The photo interrupter 122 does not output a detection signal. When the detection hole 120 reaches the position of the photo interrupter 122 as the transfer belt 46 rotates, the light emitting unit 1
The light from the light receiving unit 23 is received by the light receiving unit 124, and the photo interrupter 122 generates a detection signal. Based on the detection signal output from the photo interrupter 122, a timing signal for performing the transfer operation is generated to perform the primary transfer of the toner image from the photosensitive drum 30 to the transfer belt 46 or the toner image from the transfer belt 46 to the paper. Second transfer is performed.

At this time, the detection holes 120 provided at the widthwise edge of the transfer belt 46 are provided at six positions at equal intervals in the rotation direction, and the photo interrupter 122 detects which detection hole 120. A transfer timing signal can be generated even at the timing, and the standby time can be shortened and the processing time can be shortened.

[Control System] Inside the copying machine 1, as shown in FIG.
Is provided. The control unit 201 includes a CPU, a RAM,
It is composed of a microcomputer system including a ROM and various drivers. An operation panel 202 for issuing various operation instructions is connected to the control unit 201. The operation panel 202 includes an input key unit including a ten-key pad and other command keys, a display unit including a liquid crystal display element and an LED, and a start key for instructing the start of a copying operation and a special paper mode setting. It also includes a switch.

The control unit 201 further includes an image reading unit 2
03 is connected. The image reading unit 203 includes the above-described optical system 23 and the like, irradiates a document placed on the document table 15 with light, and reflects light reflected from the document on the color image pickup device 2.
It is read at 9 and converted into an image data signal. The control unit 201 also receives an image data signal output from the color image sensor 29 and performs image processing on the image data.
4 is connected. In the image processing unit 204, a two-dimensional color image is restored by the image data signal output from the color image pickup device 29, and this is further converted into cyan,
Decomposes into images of magenta, yellow, and black color components.

An exposure section 205 including a laser unit 40 is connected to the control section 201. In the exposure unit 205, laser light is emitted from the laser unit 40 based on the image information decomposed into each color component by the image processing unit 204, and an electrostatic latent image is formed on the peripheral surface of the photosensitive drum 30.

Further, the control section 201 is connected to a photosensitive drum driving section 206 for rotating the photosensitive drum 30. The photoconductor drum drive unit 206 rotationally drives the photoconductor drum 30 in synchronization with the laser light emitted from the exposure unit 205.

Further, the control unit 201 includes a paper transport system 20.
7 is connected. The paper transport system 207 includes a paper feed transport system including a drive motor 42 for rotationally driving the transfer belt 46, a paper discharge transport path 99, a fixing device 100, and a discharge motor including drive motors such as a pair of paper discharge rollers 103. It is composed of the system. The paper carrying system 207 can be set to at least one of the normal carrying speed and the special paper carrying speed which is slower than the normal carrying speed, and performs speed control according to the set mode. Is possible.

The control unit 201 includes a primary transfer upper roller 47.
A primary transfer roller control unit 208 for moving the pressure roller between the pressure contact position and the separation position is connected. The primary transfer roller control unit 208 drives and controls the primary pressing cam drive motor 56 to bring the primary transfer upper roller 47 into pressure contact with and away from the photosensitive drum 30.
In normal operation, the primary transfer upper roller 47 moves the transfer belt 46 together with the primary transfer lower roller 48 to the photosensitive drum 30.
The primary transfer upper roller 47 is moved to the press contact position so as to be pressed against the peripheral surface, and in the special paper mode, the primary transfer upper roller 47 separates the transfer belt 46 from the peripheral surface of the photosensitive drum 30. The next transfer upper roller 47 is moved to the separated position.

The control unit 201 includes a secondary transfer lower roller 67.
Secondary transfer roller control unit 2 for moving the sheet between a predetermined position at the time of transfer and a separated position separated from the transfer belt 46.
09 is connected. This secondary transfer roller control unit 20
Reference numeral 9 indicates that the secondary transfer lower roller 67 is moved toward and away from the transfer belt 46 by driving and controlling a motor that drives the secondary pressing cam. Photoconductor drum 30
During the primary transfer of the toner image from the transfer belt 46 to the transfer belt 46, the secondary transfer lower roller 67 is separated from the transfer belt 46, and the secondary transfer of the toner image from the transfer belt 46 to the sheet is performed.
When performing the secondary transfer, the secondary transfer lower roller 67 is moved so that the gap between the peripheral surface of the secondary transfer lower roller 67 and the surface of the transfer belt 46 becomes a predetermined distance.

Further, a secondary transfer voltage controller 210 for controlling the voltage applied to the secondary transfer lower roller 67 is connected to the controller 201. Secondary transfer voltage controller 2
Reference numeral 10 denotes a transfer belt 46 for attracting toner from the back surface of the paper onto the paper and transferring the toner image to the front surface of the paper.
A voltage having a polarity opposite to that of the surface toner is applied to the secondary transfer lower roller 67. When the toner is negatively charged, the voltage applied to the secondary transfer lower roller is a DC bias voltage of about +1 kV to 2.5 kV. Immediately after the apparatus returns from the stopped state, there is a possibility that toner is attached to the secondary transfer lower roller 67, and the secondary transfer voltage controller 210 applies a predetermined voltage to the secondary transfer lower roller 67 for a certain period of time. Both applied 2
The transfer belt 46 and the secondary transfer roller 67 are rotationally driven at a position where the lower secondary transfer roller 67 is close to the transfer belt 46. At this time, the voltage applied to the secondary transfer lower roller 67 has the same polarity as that at the time of transfer and is a DC bias voltage of about +300 to 400V. However, when the cleaning blade 75 is not in contact with the secondary transfer lower roller 67, the voltage at this time is preferably reverse polarity.
Another input / output unit is further connected to the control unit 201.

[General Operation] The operation of the copying machine 1 thus configured will be described with reference to the flowchart shown in FIG. When the power of the copying machine 1 is turned on, various parameters and the entire apparatus are initialized in step S1 shown in FIG. During this initialization operation, a toner peeling voltage is applied to the secondary transfer lower roller 67 to rotationally drive the transfer belt 46 and the secondary transfer lower roller 67 for a predetermined time, and the toner is attached to the secondary transfer lower roller 67. The operation includes retransferring the remaining toner to the transfer belt 46 and collecting the toner in the cleaning device 62 provided on the transfer belt 46. Two
When the cleaning blade 75 is in contact with the peripheral surface of the secondary transfer lower roller 67, the toner separation voltage applied to the secondary transfer lower roller 67 is a DC voltage of +300 to 400V. After that, the photosensitive drum 30, the transfer belt 46, etc. are set to the initial positions.

In step S2, it is determined whether or not the special paper mode is set. Here, the operation panel 20
When the special paper mode is selected by the mode setting button No. 2, it is determined that the special paper mode has been set, and the process proceeds to step S3. In step S3, an image forming process in the special paper mode is executed.

If it is determined in step S2 that the special paper mode is not set, the process proceeds to step S4. In step S4, the apparatus is set to the normal image forming mode. In step S5, it is determined whether or not there is an instruction to start image formation. When the start key provided on the operation panel 202 is operated, it is determined that an instruction to start image formation has been given, and the process proceeds to step S6.

In step S6, an image is formed on the sheet based on the normal image forming mode. Here, a document placed on the document table 15 is irradiated with light by the optical system 23, and the reflected light is converted into an image data signal by the color image pickup device 29. The image data signal is decomposed into an image of each color component by the image processing unit 204, and first, an electrostatic latent image based on the cyan color component is formed on the photoconductor drum 30. This electrostatic latent image is visualized by the developing device 33 containing cyan toner.

The primary transfer upper roller 47 is the photosensitive drum 3
It is located at a pressure contact position close to the 0 side, and the transfer belt 46 together with the primary transfer lower roller 48 is in pressure contact with the peripheral surface of the photosensitive drum 30. As a result, the toner image of cyan color toner formed on the photosensitive drum 30 is transferred onto the surface of the transfer belt 46 by the primary transfer upper roller 47 and the primary transfer lower roller 48.

When the toner image of cyan color toner is transferred to the transfer belt 46, an electrostatic latent image corresponding to magenta is formed on the photosensitive drum 30, and similarly, the toner of color toner is developed by the developing device 34. The image is visualized. This toner image is similarly transferred onto the transfer belt 46. Thereafter, in the same manner, the toner images of the respective color components of yellow and black are transferred onto the transfer belt 46 in a laminated state. When transferring the toner image of each color component,
The images are synchronized so that the images are not displaced.
At the same time, the paper feed cassettes 18, 19, 20, 21,
The sheet is conveyed from one of the bypass trays 22 and is made to stand by the registration rollers 98 in the sheet feeding passage 97.

When the transfer of the color toner image onto the transfer belt 46 is completed, a sheet is supplied from the registration roller 98 between the secondary transfer upper roller 45 and the secondary transfer lower roller 67, and is stacked on the surface of the transfer belt 46. The color toner image formed in this state is transferred onto the sheet by the secondary transfer lower roller 67. After that, the paper on which the color toner image is transferred is conveyed to the fixing device 100 through the paper discharge conveyance path 99, and the color toner image transferred on the paper surface is heated and melted and fixed, and then discharged onto the paper discharge tray 104. To do. During this time, 1
The next transfer upper roller 47 is located at the pressure contact position,
The surface of the transfer belt 46 is pressed against the peripheral surface of the photosensitive drum 30 by a primary transfer upper roller 47 and a primary transfer lower roller 48. Further, the paper transport system 207 is set to a normal transport speed in synchronization with the photosensitive drum drive unit 206.

In step S7, it is determined whether or not a predetermined image forming operation has been completed. Here, the operation panel 20
When the copying operation for the number of sheets instructed from 2 is completed, it is determined that the predetermined image forming operation is completed, and step S8 is performed.
Move to. In step S8, other processing is executed.

[Special Paper Mode] In the special paper mode in step S3, the operation as shown in FIG. 10 is executed. In step S11, it is determined whether or not there is an instruction to start image formation. Here, special paper for image formation is set in advance in any of the paper feed cassettes 18, 19, 20, 21, and the bypass tray 22 of the paper feed unit 17, and paper is fed from the place where the special paper is set. The operation panel 202 is instructed to perform the setting. The special paper is a thick paper, an OHP sheet, or a surface-coated paper with a surface coating, and is often set in the bypass tray 22 in most cases. In this case, the setting for feeding from the bypass tray 22 is operated. It may be indicated from the panel 202. After that, when the start key provided on the operation panel 202 is operated, it is determined that there is an instruction to start image formation, and the process proceeds to step S12.

In step S12, a step of reading the original image placed on the original table 15 and transferring the color toner image onto the transfer belt 46 is executed. In this case, similarly to the case of forming an image on plain paper, the original placed on the original table 15 is irradiated with light by the optical system 23, and the reflected light is imaged by the color image pickup device 29. Convert to signal. The image data signal from the color image pickup device 29 is decomposed into an image of each color component by the image processing unit 204, and an electrostatic latent image is formed on the peripheral surface of the photosensitive drum 30 in the order of cyan, magenta, yellow, and black. The developing devices 33, 34, 35, and 36 visualize the images, and the images are sequentially transferred to the transfer belt 46. At the same time, the paper feed unit 1
The paper is taken out from a position designated in advance in 7 and conveyed to the transfer device 37 side, and is made to stand by by the registration roller 98.

At this time, the primary transfer upper roller 47 is positioned at a pressure contact position which is close to the photosensitive drum 30 side, and the paper transport system 207 operates normally in synchronization with the photosensitive drum driving section 206. Driving each part at speed.

In step S13, it is determined whether or not the primary transfer operation is completed. Here, cyan, magenta,
When the transfer of the yellow and black toner images onto the transfer belt 46 is completed, it is determined that the primary transfer operation is completed, and the process proceeds to step S14.

In step S14, the primary transfer upper roller 4
7 is moved to the separated position to separate the surface of the transfer belt 46 from the peripheral surface of the photoconductor drum 30, and the paper transport speed of the paper transport system 207 is set to a special paper transport speed slower than the transport speed in the normal operation. To do. This special paper conveyance speed is set to such a speed that the color toner image transferred in a stacked state on the surface of material paper such as thick paper, OHP sheet, and surface coated paper is sufficiently melted and fixed in the fixing device 100.

In step S15, the registration roller 98
The sheet of paper that has been made to stand by is conveyed to the transfer device 37, and the secondary transfer operation for this paper is started. Here, the secondary transfer upper roller 45 is driven by the special paper transport speed, and the paper is transported by this special paper transport speed, and the color toner image formed on the transfer belt 46 is transferred onto the paper. . After that, the paper on which the color toner image is transferred is conveyed to the fixing device 100, the color toner on the paper surface is melted and fixed, and the paper discharge roller pair 1
The sheet is discharged to the sheet discharge tray 104 by 03.

In step S16, it is determined whether or not a predetermined image forming operation has been completed. Here, the operation panel 2
When the copying operation for the number of sheets instructed from 02 is completed,
When it is determined that the predetermined image forming operation is completed, the process returns to the main routine.

In this case, when the image formation is performed on the material paper such as the thick paper, the OHP sheet and the surface coated paper, the primary transfer is performed when the transfer of the toner image onto the transfer belt 46 is completed. The upper roller 47 is moved to the separating position to separate the surface of the transfer belt 46 from the peripheral surface of the photoconductor drum 30, and the sheet is conveyed at a special sheet conveying speed which is lower than the ordinary conveying speed of the sheet conveying system 207. Since this is performed, the color toner image transferred onto the paper can be sufficiently fused and fixed, and the photosensitive drum 30
It is possible to prevent the peripheral surface of the sheet from being rubbed against the transfer belt 46 and damaged.

[Secondary Transfer Voltage Control] Transfer the toner image on the surface of the transfer belt 46 onto the paper 2
At the time of the next transfer, the voltage applied to the secondary transfer lower roller 67 by the secondary transfer voltage control unit 210 is set to +1 kV to 2.5 kV, which has a polarity opposite to that of the toner on the transfer belt 46.

At the time of initial setting immediately after the power is turned on, as described above, the toner separation voltage is applied to the secondary transfer lower roller 67 to transfer the transfer belt 46 and the secondary transfer lower roller 67.
Is rotationally driven for a certain period of time, the toner adhering to the secondary transfer lower roller 67 is retransferred to the transfer belt 46, and a roller initialization operation is performed to collect the toner on a cleaning device 62 provided on the transfer belt 46. In this case, the cleaning blade 75 is provided in pressure contact with the secondary transfer lower roller 67, and the toner separation voltage applied to the secondary transfer lower roller 67 by the secondary transfer voltage controller 210 is the toner on the surface of the transfer belt 46. And +300 to 400V, which is the opposite polarity.

When the paper jam or the device cover is opened, the device is stopped. The operation at this time is shown in a flowchart in FIG.

In step S21, it is determined whether or not a paper jam has occurred. Here, it is provided at various places such as the vertical conveyance path 81 of the paper feed section 17, the bypass conveyance path 82, the paper feed conveyance path 97, the paper ejection conveyance path 99, and the path from the fixing device 100 to the paper ejection roller pair 103. It is determined based on the detection signal of the paper detection sensor whether the paper is normally conveyed.
For example, when one of the paper detection sensors does not detect the paper even after the lapse of a predetermined time, it is determined that a paper jam has occurred, and the process proceeds to step S23.

In step S22, it is determined whether the device cover is open. For example, a sensor that turns off when the device cover is in the closed position at a predetermined position and turns on when the device cover is in the open state is provided, and the device cover opens based on the detection signal of this sensor. It is possible to determine whether or not there is. If the device cover is open, the process proceeds to step S23.

In step S23, the apparatus is stopped, the operation instruction input from the operation panel 202 is prohibited, and the location of the paper jam on the liquid crystal display of the operation panel 202, the opened apparatus cover position, etc. Is displayed in correspondence with the current situation.

In step S24, it is determined whether or not the return work has been completed. For example, when a paper jam occurs, it is determined that the restoration work is completed when the paper is removed from the location where the jam occurs and the reset switch is operated. Further, when the device cover is opened and the sensor is turned off and the device cover is in the closed state, it is determined that the restoration work is completed. However, in order to remove the paper from the location where the paper jam occurred, it is necessary to open the device cover and perform the paper removal work.If the device is stopped due to the paper jam, the device cover is closed. Things are included in the return work. Therefore, here, the case where the apparatus cover is opened is, for example, a case where an operation inside the apparatus is performed due to toner replenishment or other maintenance, or when the apparatus cover is accidentally opened. If it is determined in step S24 that the restoration work is completed, the process proceeds to step S25.

In step S25, the same roller initialization work as that performed immediately after the power is turned on is performed. Here, the secondary transfer lower roller 67 has a polarity of +30 opposite to that of the toner on the surface of the transfer belt 46.
By applying a toner peeling voltage of 0 to 400 V, the transfer belt 46 and the secondary transfer lower roller 67 are rotationally driven for a fixed time (here, 3 seconds). As a result, the toner attached to the secondary transfer lower roller 67 is retransferred to the transfer belt 46, and the cleaning device 6 provided on the transfer belt 46.
Collect to 2.

For example, when the transfer of the toner image onto the transfer belt 46 is completed and a paper jam occurs in the registration roller 98 when the secondary transfer is started, the paper is not conveyed to the transfer site. Nevertheless, the voltage application to the secondary transfer lower roller 67 is started, and the toner on the transfer belt 46 is transferred to the secondary transfer lower roller 67. Since the distance between the registration roller 98 and the transfer portion (the position where the transfer belt 46 and the secondary transfer lower roller 67 are close to each other) is short, when the occurrence of a paper jam is detected, the voltage application to the secondary transfer lower roller 67 is already started. The toner is transferred to the secondary transfer lower roller 67. When the jammed paper is removed and the apparatus returns from the stopped state, the secondary transfer lower roller 67
If the toner adhered to is left as it is, the toner adheres to the back surface side of the paper at the time of the next image formation, and the paper is contaminated. Therefore, when the apparatus returns from the stopped state, a predetermined toner peeling voltage is applied to the secondary transfer lower roller 67 to retransfer to the transfer belt 46 side, and the cleaning apparatus 62 collects the toner.

Even when the apparatus is stopped other than a paper jam in the registration roller 98, there is a possibility that toner is attached to the secondary transfer lower roller 67, and when the apparatus returns from the stopped state. The secondary transfer lower roller 6 is always applied for a predetermined time by applying the toner peeling voltage as described above.
7 and the transfer belt 46 are rotationally driven.

The toner peeling voltage is the secondary transfer lower roller 67.
Of the cleaning blade 75 that is pressed against the surface of No. 1 differs from that of No. In the case of the above-described embodiment, since the cleaning blade 75 is pressed against the surface of the secondary transfer lower roller 67, it is preferable to apply a voltage having a polarity opposite to that of the toner on the surface of the transfer belt 46.

Toner is forcibly attached to the secondary transfer lower roller 67, and the voltage applied to the secondary transfer lower roller 67 is set to −20.
0V, -150V, -100V, -50V, 0V, +5
Table 1 shows the cleaning performance when 0V, + 100V, and + 200V are set, and the voltage application time is 3 seconds.
Shown in column (1) . From this, when the applied voltage is a negative voltage of the same polarity as the toner, the effect of peeling off the toner adhering to the secondary transfer lower roller 67 becomes poor, and when the applied voltage is a positive voltage of the opposite polarity to the toner, the secondary transfer It was found that the effect of removing the toner adhering to the roller 67 was good.

Further, when there is no cleaning blade 75 pressed against the peripheral surface of the secondary transfer lower roller 67, it is preferable to apply a voltage having the same polarity as the toner. When the cleaning blade 75 is not provided, the toner is forcibly attached to the secondary transfer lower roller 67, and the voltage applied to the secondary transfer lower roller 67 is -500V, -400V, -300V, -20.
0V, -150V, -100V, -50V, 0V, +5
Set to 0V and + 100V, and set the voltage application time to 3
The cleaning performance in seconds is shown in Table 1 (2) .
From now on, if there is no cleaning blade 75,
When the applied voltage is a negative voltage having the same polarity as the toner, the effect of removing the toner adhering to the secondary transfer lower roller 67 is good, and when the applied voltage is a positive voltage having the opposite polarity to the toner, the secondary transfer lower roller 67 is provided. It was found that the peeling effect of the toner attached to the toner deteriorates.

[0083]

[Table 1] As described above, when the apparatus returns from the stopped state, the toner peeling voltage is applied to the secondary transfer lower roller 67 to re-transfer the adhered toner to the secondary transfer lower roller 67 for cleaning. Therefore, it is possible to prevent the toner from adhering to the back surface of the paper and causing it to be contaminated.

[Copy Control for Multiple Copies] When the copy process for multiple copies is selected by an instruction from the operation panel 202, the operation is performed based on the flowchart shown in FIG.

In step S31, the copy number n designated by the operation panel 202 is substituted into the variable k. In step S32, the optical system 2 is added to the original placed on the original table 15.
3 is used to irradiate light, the reflected light is converted into an image data signal by the color image pickup device 29, and the original image is read. In step S33, the color image sensor 2
The image data signal converted by the image processing unit 2
By 04, it is decomposed into images of each color component.

In step S34, it is determined whether or not the size of the original set on the original table 15 or the paper size instructed from the operation panel 202 is A4 landscape or smaller.
The size of the paper to be copied exceeds A4 landscape, eg A3
If it is the size, the process proceeds to step S35. In step S35, a normal image forming operation is performed in which a toner image based on the original image is formed on the peripheral surface of the photoconductor drum 30, and the toner image is transferred onto the surface of the transfer belt 46 and further transferred onto a sheet. In this case, the toner image based on each color component of the original image is laminated on the surface of the transfer belt 46 with the leading edge positioned based on the detection signal detected by the photo interrupter 122 in the detection hole 120 of the transfer belt 46. . As described above, the widthwise end portion of the transfer belt 46 is provided with the six detection holes 120 at equal intervals in the rotation direction, and cyan toner from the photosensitive drum 30 is generated based on the first detection signal. The transfer of the image to the surface of the transfer belt 46 is started. After this, the photo interrupter 1
The counting of the detection signal output by 22 is started, and the transfer of the toner image by magenta is started based on the sixth detection signal. Similarly, the yellow and black toner images are transferred based on the sixth detection signal, and a full-color image in which the toner images of the respective color components are stacked is formed on the transfer belt 46. Further, the secondary transfer is started based on the predetermined number of detection signals. This ensures the positioning of the front end of the transferred toner image, and can start image formation based on the detection signal by the earliest one of the six detection holes 120 at the start of transfer. The waiting time at the start of image formation is reduced, and the processing time can be shortened.

When the copying operation for one sheet is completed, the value of the variable k is decremented and the above operation is repeated until the value of the variable k reaches 0.

When it is determined in step S34 that the size of the paper to be copied is A4 landscape or smaller, the process proceeds to step S36. In step S36, it is determined whether or not the photo interrupter 122 has output a predetermined detection signal. Here, the process proceeds to step S37 based on the detection signal when the photo interrupter 122 first detects the detection hole 120.

In step S37, the transfer of the toner image by the color component of the first color of the first image onto the transfer belt 46 is started. Here, the color component of the first color is cyan. At this time, counting of the detection signal output from the photo interrupter 122 is started. In step S38, it is determined whether or not the detection signal of the photo interrupter 122 has reached a predetermined number. Here, when the count number of the detection signal of the photo interrupter 122 reaches "3", it is determined that the count has reached a predetermined number, and the process proceeds to step S39. At this time, the transfer belt 46 has made 1/2 rotation after the transfer of the toner image by the first color component of the first image is started, and the size of the paper to be copied is A4 landscape or smaller. The transfer operation of the toner image of the first image onto the transfer belt 46 is completed.

In step S39, transfer of the toner image by the color component of the first color of the second image onto the transfer belt 46 is started. At this time, the count of the detection signal output from the photo interrupter 122 is reset and a new count is started. In step S40, it is determined whether or not the detection signal of the photo interrupter 122 has reached a predetermined number. Here, when the count number of the detection signal of the photo interrupter 122 becomes “3”, it is determined that the count has reached the predetermined number, and the process proceeds to step S41. At this time, the transfer belt 46 has rotated once since the transfer of the toner image by the first color component of the first image was started. Therefore, the transfer of the toner image onto the transfer belt 46 by the second color component of the first image is started. Here, the color component of the second color is magenta. Further, the count number of the detection signal of the photo interrupter 122 is reset. In step S42, it is determined whether or not the detection signal of the photo interrupter 122 has reached a predetermined number. Similarly to the above, when the count number of the detection signal of the photo interrupter 122 becomes “3”, it is determined that the count has reached the predetermined number, and the process proceeds to step S43.

In step S43, the transfer of the toner image by the second color component of the second image onto the transfer belt 46 is started. At this time, the count of the detection signal output from the photo interrupter 122 is reset and a new count is started. In step S44, it is determined whether or not the detection signal count number of the photo interrupter 122 is "3". When the count number of the detection signal of the photo interrupter 122 becomes "3", the process proceeds to step S45.

In step S45, transfer of the toner image by the color component of the third color of the first image onto the transfer belt 46 is started. Here, the third color component is yellow. Further, the count number of the detection signal of the photo interrupter 122 is reset. In step S46, it is determined whether or not the count number of the detection signal of the photo interrupter 122 has reached "3". When the number of detection signals of the photo interrupter 122 reaches "3", the process proceeds to step S47.

In step S47, transfer of the toner image by the color component of the third color of the second image onto the transfer belt 46 is started. At this time, the count of the detection signal output from the photo interrupter 122 is reset and a new count is started. In step S48, it is determined whether or not the detection signal count number of the photo interrupter 122 has become "3". When the count number of the detection signal of the photo interrupter 122 becomes "3", the process proceeds to step S49.

In step S49, transfer of the toner image by the color component of the fourth color of the first image onto the transfer belt 46 is started. Here, the fourth color component is black. Further, the count number of the detection signal of the photo interrupter 122 is reset. In step S50, it is determined whether or not the count number of the detection signal of the photo interrupter 122 has reached "3". When the count number of the detection signal of the photo interrupter 122 becomes “3”, the process proceeds to step S51.

In step S51, transfer of the toner image by the color component of the fourth color of the second image onto the transfer belt 46 is started. At this time, the count of the detection signal output from the photo interrupter 122 is reset and a new count is started. In step S52, it is determined whether or not the count number of the detection signal of the photo interrupter 122 has reached a predetermined number. Here, when the count number of the detection signal of the photo interrupter 122 reaches a predetermined number, the front end position of the first image is set to reach a predetermined position near the secondary transfer position, and the detection of the photo interrupter 122 is performed. When the signal count reaches the predetermined number, the count is reset to newly start the detection signal count, and the process proceeds to step S53.

In step S53, the sheet which has already been put on standby by the registration rollers 98 is conveyed to the transfer device 37 side, a predetermined voltage is applied to the secondary transfer lower roller 67, and the secondary transfer operation for the sheet is started. . At this time, at the same time, the next sheet is conveyed from the sheet feeding unit 17 and the registration roller 98
To wait. As a result, the first image formed on the transfer belt 46 is transferred to the paper. When the count number of the photo interrupter 122 reaches “3”, the secondary transfer operation of the first image has already been completed,
The leading end position of the second image has reached a predetermined position near the secondary transfer position. Therefore, the sheet of paper which is kept waiting by the registration roller 98 is conveyed to the transfer device 37 side, a predetermined voltage is applied to the secondary transfer lower roller 67, and the secondary transfer operation for the sheet is started. When the secondary transfer operation of the two images is completed, the process proceeds to step S54. Step S54
Then, "2" is subtracted from the variable k indicating the number of copies remaining. In step S55, the value of the variable k is compared with "1". When the value of the variable k is larger than “1”, the process proceeds to step S36 and the same image forming operation is repeated. If the value of the variable k is "1", step S3
Go to 5. This corresponds to the final copy when an odd number is selected as the number of copies, and in this case, only one image needs to be formed on the transfer belt 46, so that normal image formation in step S35 is performed. It suffices to perform processing. If the value of the variable k is smaller than 1, it is determined that all the instructed copy numbers have been processed, and the step S
Move to 56. In step S56, end processing is performed.

In the embodiment configured as described above, the detection hole 12 provided at the widthwise edge of the transfer belt 46.
0 is provided at six positions at equal intervals in the rotation direction, and a transfer timing signal can be generated at the timing at which any of the detection holes 120 is detected by the photo interrupter 122, and the waiting time is shortened and the processing time is also reduced. It can be shortened.

[ Embodiment] In the above-described reference example, the intermediate support surface and the edge support of each roller are supported.
There is a difference in peripheral speed between the surface and the surface. On the other hand, the transcription bell
End of the intermediate inner peripheral surface 112 of the gutter 46 and the meandering-preventing ridge 113
The inner peripheral edge surface 114 is moving at the same speed in the straight portion.
It Therefore, the intermediate inner peripheral surface 112 of the transfer belt 46
The inner peripheral surface 114 of the edge of the meandering-preventing ridge 113 is
Be careful not to contact the intermediate support surface and the edge support surface at all points.
This causes problems such as wear of parts.

In order to solve such a problem, each
FIG. 14 shows an embodiment in which the ruler is configured as shown in FIG. here
However, the primary transfer upper roller 47 is shown as an example. Primary transfer
The transfer roller 47 is provided with the intermediate inner peripheral surface 112 of the transfer belt 46.
It has a roller body 131 for supporting the. This roller
The main body 131 is substantially the same as the intermediate inner peripheral surface 112 of the transfer belt 46.
They have almost the same width, and the outer peripheral surface is the middle of the transfer belt 46.
An intermediate support surface 132 that abuts and supports the inner peripheral surface 112 is constructed.
Is made.

At both ends of the roller body 131,
Is rotatably supported by a rotary shaft (not shown) of the main body 131
The supporting roller 133 is provided. Supporting roller 133
Is larger than the diameter of the roller body 131 and is a protrusion 113 for preventing meandering.
The diameter is set to be smaller by the height of the
Is almost equal to the width of the meandering-preventing protrusion 113 of the transfer belt 46.
The inner circumference of the end of the meandering-preventing ridge 113, which has the same width
It constitutes an end support surface 134 which supports the surface 114.
This support roller 133 rotates independently of the roller body 131.
It is movably supported.

As a result, in the middle of the transfer belt 46
The peripheral surface 112 contacts the intermediate support surface 132 of the roller body 131.
The inner peripheral surface 114 of the end portion of the protrusion 113 for preventing meandering is supported
By contacting the end supporting surface 134 of the roller 133,
The transfer belt 46 is supported on the outer peripheral surface of the primary transfer roller 47.
I have it.

Primary transfer lower roller 48, cleaning low
LA 63, secondary transfer upper roller 45, tension roller 4
9. Each roller of the drive roller 44 is on the primary transfer described above.
Like the roller 47, it has a roller body and a support roller.
It is composed. As a result, the transfer belt 46
At the widthwise middle portion and the widthwise end edge, respectively.
Roller body and the outer peripheral surface of the support roller to evenly support
As a result, unevenness is not generated on the outer peripheral surface.
Become The support roller 133 rotates the roller body 131 and
It is possible to rotate independently regardless of the roller book.
Even if the diameters of the body 131 and the support roller 133 are different, the peripheral speed difference
Does not occur. Therefore, within the transfer belt 46
No wear between the peripheral surface and each roller, resulting in wear
This can prevent the life of each component from being shortened.

[Other Embodiments] (A) Reflecting members such as aluminum foils are provided at six positions in the widthwise end portion of the transfer belt 46 at equal intervals in the rotation direction,
A light emitting portion such as an LED that irradiates the reflecting member with light and a light receiving portion such as a phototransistor that receives the light reflected from the reflecting member are arranged and used as a transfer timing signal based on the output signal of the phototransistor It is also possible.

(B) In the above example , the six detection holes 120
However, the number is not limited to this, and it is also possible to provide an even number of 4 or 6 or more.

(C) In the above example , the secondary transfer timing signal is generated based on the detection signal of the photo interrupter 122. However, the detection signal of the photo interrupter 122 and the timer are used. Thus, it is possible to generate a signal for the timing of secondary transfer, and it is also possible to separately provide a photo interrupter for generating a timing signal for secondary transfer.

(D) An automatic document feeder (ADF) is provided so that two toner images can be formed on the transfer belt 46 when performing a copying operation based on a plurality of documents inserted in the ADF. When images are formed on various sizes of paper, the two original images are read and the transfer belt 4
It is possible to form two toner images in parallel on the image forming device 6 and to secondarily transfer the toner images continuously onto two sheets of paper. In this case, similarly to the case of the above-described embodiment, the transfer timing signal is generated based on the detection signal of the photo interrupter 122, and the toner image based on the two originals is formed on the transfer belt 46. After the toner images based on the respective color components are formed in a laminated state, the secondary transfer is continuously performed on two sheets of paper. When the number of originals is an odd number, normal transfer processing is performed only on the final original.

With this configuration, the ADF
It is possible to perform the copying process using the high speed .

[0108]

According to the transfer device of an image forming apparatus according to the present invention, a plurality of rollers for rolling support in the width direction intermediate portion except the meandering preventing ridge portion of the shooting belt tension, the plurality of rollers rotatably attached to the rotation shaft of each roller to a width direction end, since a structure and a supporting roller for supporting the inner peripheral surface of the meandering prevention protrusion, the ends of the rollers and their roller There is no difference in peripheral speed between the support roller provided and slippage does not occur between the inner peripheral surface of the transfer belt and each roller. Therefore, it is possible to prevent the life of each component such as the transfer belt and the roller from being shortened due to abrasion.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of a copying machine adopting an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part thereof.

FIG. 3 is a perspective view for explaining a main part.

FIG. 4 is a partial vertical sectional view thereof.

FIG. 5 is a perspective view showing a relationship between a transfer belt and rollers as a reference example .

FIG. 6 is a vertical sectional view thereof.

FIG. 7 is a vertical cross-sectional view showing an edge portion of a transfer belt.

FIG. 8 is a control block diagram.

FIG. 9 is a control flowchart of one embodiment.

FIG. 10 is a control flowchart of one embodiment.

FIG. 11 is a control flowchart of one embodiment.

FIG. 12 is a control flowchart of one embodiment.

FIG. 13 is a vertical cross-sectional view showing the relationship between the transfer belt and the rollers according to the embodiment of the present invention .

[Explanation of symbols]

1 Copier 10 body 15 Platen 16 Image forming section 17 Paper feeder 22 Bypass tray 23 Optical system 30 photoconductor drum 33 Developing device 34 Developing device 35 developing device 36 Developing device 37 Transfer device 39 Exposure equipment 43 Secondary transfer upper roller 46 transfer belt 47 Primary transfer upper roller 48 Primary transfer lower roller 67 Secondary transfer lower roller 111 outer peripheral surface 112 Middle inner surface 113 Meandering prevention ridges 114 Inner peripheral surface 115 Intermediate support 116 Edge support part 117 Intermediate support surface 118 End support surface 120 detection holes 122 Photointerrupter 123 Light emitting part 124 Light receiving part 131 Roller body 132 Intermediate support surface 133 support roller 134 End support surface

Continuation of the front page (56) Reference JP-A-10-104995 (JP, A) JP-A-10-39576 (JP, A) JP-A-62-235146 (JP, A) JP-A-9-301565 (JP , A) JP-A-9-114266 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/16 G03G 21/00

Claims (6)

(57) [Claims] 1. A toner image formed on the peripheral surface of a photoconductor drum is disposed so as to face the photoconductor drum so that the toner image can be transferred, and can be rotated along a predetermined track, and has a predetermined height on the inner peripheral surface side. And a transfer belt in which the meandering-preventing ridges projecting in the lengthwise direction extend in the lengthwise direction of both side edges, and the widthwise intermediate portion of the transfer belt excluding the meandering-preventing ridges is supported in a tensioned state. A plurality of rollers that circulate the transfer belt, and rotatably attached to the rotation shafts of the rollers at both ends in the width direction of the plurality of rollers and corresponding to the heights of the meandering prevention ridges. A support roller having a diameter smaller than that of the roller and supporting the inner peripheral surface of the meandering preventing protrusion, and a primary roller for transferring the toner image formed on the peripheral surface of the photosensitive drum to the transfer belt surface. An image forming apparatus including a transfer unit; Transfer device. Wherein further comprising a secondary transfer means for transferring the toner image transferred to the transfer belt surface onto the sheet, a transfer device of an image forming apparatus according to claim 1. Wherein said plurality of rollers includes a drive roller that is driven to rotate by the motor, a driven roller that is rotatably supported, a transfer device of an image forming apparatus according to claim 1 or 2. 4. The two primary transfer rollers, wherein the primary transfer means are arranged along a predetermined orbit around which the transfer belt circulates and support an intermediate portion in the width direction of the transfer belt excluding meandering preventing ridges. And a configuration in which the transfer belt is pressed against the peripheral surface of the photoconductor drum between the positions where the two primary transfer rollers support the transfer belt, respectively, in the width direction of each of the primary transfer rollers. It has a diameter smaller than the diameter of each primary transfer roller which is rotatably attached to the rotation shaft of each roller at both ends and is coaxially attached corresponding to the height of the meandering preventing ridge. The transfer device of the image forming apparatus according to claim 1 , further comprising a support roller that supports an inner peripheral surface of the meandering prevention ridge. 5. At least one of the two primary transfer rollers is movable to a separated position where it is separated from the photosensitive drum and the surface of the transfer belt is separated from the peripheral surface of the photosensitive drum. The transfer device of the image forming apparatus according to claim 4 . 6. An image forming apparatus, comprising a plurality of developing devices for storing toners of different color components, wherein the toner images of the toners of the respective color components are laminated to form a full color image on a sheet. The transfer device of the image forming apparatus according to any one of 1 to 5 .