JP4481026B2 - Belt drive device and image forming apparatus having the same - Google Patents

Description

  The present invention includes a belt drive device including a belt that is stretched between a plurality of rollers and that rotates, and a mark for detecting the belt position is formed on the belt along a circumferential direction of the belt. The present invention relates to an image forming apparatus provided.

For example, in a belt driving device used in an image forming apparatus, the surface of a belt that is rotatably provided between a plurality of rollers is charged, a sheet is adsorbed to the charging surface by static electricity, and the color on the sheet surface is different. In the case where the toner images are sequentially transferred to the superimposed state, if the moving speed of the belt is not accurately controlled, color misregistration or the like occurs in the toner images of the respective colors.
Therefore, such a belt drive device requires a mechanism for always detecting the position of the belt in the rotational direction.

Therefore, for example, in the image forming apparatus described in Patent Document 1, an intermediate transfer belt (transfer belt) is rotatably stretched between five support rollers including one drive roller, and the intermediate transfer belt A scale formed with fine and precise scales is provided on the inner surface, and the scale is read by an optical detector to accurately detect the moving speed of the intermediate transfer belt, and the detected moving speed is fed back by a feedback control system. The intermediate transfer belt is controlled so as to have an accurate moving speed.
Further, in the image forming apparatus described in Patent Document 2, a detection body (mark) for detecting the position of the belt is provided on the front surface or the back surface of the belt, and this is detected by the sensor to detect the belt rotation direction. The position is detected.

Japanese Patent Laid-Open No. 11-24507 (pages 3-4, FIG. 1) Japanese Patent No. 3413035 (page 4)

However, in the case of the image forming apparatus described in Patent Document 1, since detection bodies such as marks formed on the belt surface are always exposed to the environment in the apparatus, they deteriorate over time (in the case of sticking). If the mark is peeled off, the accuracy of reading the mark by the sensor may be lowered, or in the worst case, the mark may become unreadable.
Further, as in the image forming apparatus described in Patent Document 2, a belt is provided with a rib and a notch, and light is irradiated in a direction parallel to the belt surface to detect the belt position by a TOP sensor. With the configuration described above, there is a risk of erroneous detection when the belt vibrates in a direction perpendicular to the belt surface.
The present invention has been made in view of the above-described problems, and prevents deterioration of the mark even over time so that the mark can be read reliably, thereby stably detecting the position of the belt in the rotational direction. The purpose is to be able to do.

In order to achieve the above object, the present invention includes a belt that is stretched and rotated between a plurality of rollers, and a mark for detecting the position of the belt is provided on the belt at an end in the width direction of the belt. In the belt driving device formed along the circumferential direction of the belt, the mark is formed on the outer surface of the belt, and guide members are arranged on the outer surfaces of both ends in the width direction of the belt so as to cover the outer surface of the mark. And a support roller functioning as a guide contact member for preventing meandering of the belt so as to be able to come into contact with each inner side edge of the guide member in the width direction of the belt. At least the belt among the belts is formed of a light transmitting member, and the belt made of the light transmitting member is transmitted through the belt to a position corresponding to the mark inside the belt. It is provided with a light sensor that can detect.

The belt may be a belt that adsorbs a sheet to the belt surface and conveys the sheet on which toner images are sequentially transferred in a superimposed state.
Alternatively, the belt may be an intermediate transfer body in which the toner images are sequentially transferred onto the belt surface in a superimposed state.
The region where the mark is provided on the belt may be a non-image region .

Alternatively, the photosensor may be a reflective photosensor that detects reflected light, and at least a surface of the mark facing the sensor may be formed of a material that reflects light.
The surface of the mark facing the sensor may be formed by aluminum vapor deposition.
The optical sensor may be a sensor that uses infrared light.
The mark is used for detecting the moving speed of the belt, and may be used for correcting the inherent circumferential speed fluctuation of the belt that occurs when the belt rotates.
An image forming apparatus including any one of the belt driving devices described above is also provided.
Also provided is an image forming apparatus provided with a quadruple tandem mechanism in which four photosensitive members are arranged at intervals along the moving direction of the belt.

According to this invention, the outer surface of the mark formed at the end portion in the width direction on the outer surface of the belt is covered with the guide member, the belt is formed of the light transmitting member, and the optical sensor is provided on the inner side of the belt. Since the mark is detected through the belt formed of the transmissive member, the deterioration of the mark can be prevented over time. Accordingly, the mark can be reliably read over time, and the position detection in the belt rotation direction can be stably performed.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing a main part of a belt driving device as a basis of the present invention, FIG. 2 is a block diagram showing the overall configuration of the belt driving device, and FIG. 3 is an image forming system also including the belt driving device. 1 is an overall configuration diagram showing a color laser printer as an apparatus.
The color laser printer shown in FIG. 3 is an image forming apparatus that forms an image using an electrophotographic method, and images of each color of yellow (Y), magenta (M), cyan (C), and black (K) are displayed. The photosensitive drums 11Y, 11M, 11C, and 11K (hereinafter simply referred to as the photosensitive drum 11 if not specified) that are image carriers to be formed are indicated by arrows indicating the moving direction of the transfer conveyance belt 60 of the belt driving device 6. It is a direct transfer type image forming apparatus provided with a quadruple tandem mechanism arranged at intervals along the A direction.

The four photosensitive drums 11 have toner image forming units 1Y, 1M, 1C, and 1K (images for forming colors of yellow (Y), magenta (M), cyan (C), and black (K)). Hereinafter, when not specified, it is simply provided in the toner image forming unit 1).
The toner image forming units 1Y, 1M, 1C, and 1K are each provided with a developing unit 12 corresponding to each photosensitive drum 11. The positions of the toner image forming portions 1 are such that the rotation axes of the photosensitive drums 11 are parallel to each other and have a predetermined equal pitch in the paper movement direction (arrow A direction).

In addition, this color laser printer has the optical writing unit 2, the paper feed cassettes 3 and 4, the registration roller pair 5, and the transfer paper (paper) P in a state where the transfer paper P is carried on each toner image forming unit. 1 and a belt driving device 6 that sequentially conveys the toner to the fixing unit 7. In this example, the belt driving device 6 also functions as a transfer unit.
The color laser printer further includes a paper discharge tray 8, a manual feed tray 14, a toner supply container 22, and the like. In addition, although not shown, a waste toner bottle, a duplex / reversing unit, a power supply unit, and the like are provided in the space S indicated by phantom lines in FIG.

The optical writing unit 2 includes a light source, a polygon mirror, an fθ lens, a reflection mirror, and the like, and irradiates the surface of each photosensitive drum 11 with laser light corresponding to each color image based on the image data. And each latent image is formed there.
The fixing unit 7 is a fixing device using a belt fixing method.
As shown in FIG. 2, the belt driving device 6 includes a transfer conveyance belt 60 that is stretched between a plurality of support rollers 61 to 66 and rotates in the direction indicated by the arrow A. The belt conveys the sheet on which the sheet is adsorbed on the surface and the toner images are sequentially transferred onto the sheet in a superimposed state.

As shown in FIG. 1, a mark 15 is formed on the transfer / conveying belt 60 on the outer surface of one end side in the width direction of the transfer / conveying belt 60 along the circumferential direction of the belt.
The mark 15 is used for detecting the circumferential position and moving speed of the transfer / conveying belt 60 and corrects the inherent circumferential speed fluctuation of the belt that occurs when the transfer / conveying belt 60 rotates. Used for.

In the belt driving device 6, the guide member 16 is provided along the circumferential direction on the outer surface of one end in the width direction of the transfer conveyance belt 60 so as to cover the outer surface of the mark 15, and the transfer conveyance in the guide member 16 is performed. A support roller 64 (in addition to this, a roller may be provided) functioning as a guide contact member for preventing meandering of the transfer conveyance belt 60 so as to be able to come into contact with the inner side edge in the width direction of the belt 60 is provided. The member 16 is formed of a transparent transmitting member, and an optical sensor 17 that allows the mark 15 to be detected by transmitting the guide member 16 (light transmitting member) at a position corresponding to the mark 15 is provided.
The optical sensor 17 is, for example, a reflective photosensor that detects reflected light, and at least the surface of the mark 15 that faces the sensor 17 is formed of a material that reflects light.

Further, as shown in FIG. 1, also the end portion outer surface of the other end side in the width direction of the transfer conveyance belt 60, are formed along the guide member 16 in the circumferential direction of the transfer conveyance belt 60, the guide member 16 A support roller 64 functioning as a guide contact member for preventing meandering of the transfer / conveyance belt 60 is also provided so as to be able to contact the inner side edge of the transfer / conveyance belt 60 in the width direction .
Then, based on the information detected by the optical sensor 17 on the mark 15 on the transfer / conveying belt 60, the position of the transfer / conveying belt 60 in the rotational direction is detected, thereby detecting the belt position and the moving speed at the time of detection. Correction control is performed to achieve the basic speed.
A detailed description of the mark 15 detection system will be described later.

The transfer conveyance belt 60 of the belt driving device 6 is a high-resistance endless single-layer belt having a volume resistivity of 10 ⁹ to 10 ¹¹ Ωcm, for example, and its material is, for example, PVDF (polyvinylidene fluoride).
As shown in FIG. 2, the transfer conveyance belt 60 is stretched between a plurality of support rollers 61 to 66. Among the support rollers, the transfer conveyance belt 60 is connected to the support roller 61 at the inlet portion on the upstream side in the transfer paper moving direction. Are arranged on the outer peripheral surface of the transfer conveyance belt 60 so that the electrostatic adsorption roller 80 to which a predetermined voltage is applied from the power source 18 faces each other.
The transfer paper fed between the support roller 61 and the electrostatic attraction roller 80 is electrostatically adsorbed on the transfer transfer belt 60 in a charged state, which is respectively photosensitive drums 11Y, 11M, 11C, 11K. The toner images of the respective colors are sequentially transferred in a superimposed state at the respective transfer positions that are in contact with each other.

The support roller 63 is a driving roller that drives the transfer conveyance belt 60 by frictional force and rotates it in the direction of arrow A, and is rotated in the direction of the arrow in FIG. 2 by a drive source (not shown).
At each transfer position corresponding to each of the photosensitive drums 11Y, 11M, 11C, and 11K, roller-shaped transfer bias applying members 27Y, 27M, 27C, and 27K are respectively provided as transfer electric field forming units that form transfer electric fields. It is provided so as to be in contact with the back surface of the transfer conveyance belt 60.

The transfer bias applying members 27Y, 27M, 27C, and 27K are bias rollers each provided with a sponge or the like on the outer periphery, and there are transfer biases from the transfer bias power supplies 9Y, 9M, 9C, and 9K to the core metal of the roller. Applied. The transfer bias is applied to the transfer conveyance belt 60 by the applied transfer bias, and a transfer electric field having a predetermined strength is generated between the transfer conveyance belt 60 and the surface of each photosensitive drum 11 at each of the four transfer positions. Is formed.
At each transfer position, a backup roller 68 is provided in the vicinity of each transfer position in order to keep the contact between the transfer paper and each photosensitive drum 11 in an optimal state in order to obtain the best transfer nip.

The transfer bias applying members 27Y, 27M, and 27C and the three backup rollers 68 corresponding to the transfer bias applying members 27Y, 27M, and 27C are rotatably held by the swing bracket 93, respectively. The swing bracket 93 is centered on the rotation shaft 94. It can be turned.
The swing bracket 93 is rotated by rotating a cam 96 fixed to the cam shaft 97 in the direction of the arrow in FIG.
Further, both the support roller 61 on the entrance side and the electrostatic attraction roller 80 are rotatably supported by a roller bracket 90, and the roller bracket 90 rotates around the shaft 91 in the clockwise direction from the state of FIG. It can be moved.

A pin 92 is fixed to the roller bracket 90, and the pin 92 is engaged with a hole 95 formed in the swing bracket 93. As a result, the roller bracket 90 also rotates in conjunction with the rotation of the swing bracket 93.
By rotating the swing bracket 93 and the roller bracket 90 in the clockwise direction in FIG. 2, the transfer bias applying members 27Y, 27M, and 27C and the backup rollers 68 disposed in the vicinity thereof are photoreceptors 11Y, 11M, and 11C. The support roller 61 and the electrostatic attraction roller 80 are also moved downward. Therefore, when an image of only one black color is formed, the transfer conveyance belt 60 can be separated from the photosensitive drums 11Y, 11M, and 11C.

On the other hand, the transfer bias applying member 27K and the backup roller 68 corresponding to the transfer bias applying member 27K are supported by the outlet bracket 98 so as to be rotatable about the shaft 99.
The outlet bracket 98 is rotated in the clockwise direction in FIG. 2 by operating a handle (not shown) when the belt driving device 6 is attached to or detached from the main body, whereby the transfer bias applying member 27K and the corresponding backup are supported. The roller 68 is separated from the photosensitive drum 11K for black image.

As shown in FIG. 3, a cleaning device 85 including a brush roller and a cleaning blade is arranged in contact with the outer peripheral surface of a portion wound around the driving support roller 63 of the transfer conveyance belt 60. ing. The cleaning device 85 removes foreign matters such as toner adhering to the transfer / conveying belt 60.
A support roller 64 for pressing the outer peripheral surface of the transfer conveyance belt 60 is provided on the downstream side in the movement direction of the transfer conveyance belt 60 with respect to the support roller 63, and the transfer conveyance belt 60 wound around the drive support roller 63 is wound around the support roller 63. The corner is set to the optimum angle.
At a further downstream side of the support roller 64, a tension support roller 65 pressed and urged by a spring 69 is provided in contact with the inner surface of the transfer conveyance belt 60, thereby applying a predetermined tension to the transfer conveyance belt 60. I am doing so.

In this color laser printer, the transfer paper P is transported along a transport path indicated by a one-dot chain line in FIG. 3, and an image is formed on the transfer paper P and discharged onto the paper discharge tray 8.
That is, when the image forming operation is started, the transfer paper P fed from the paper feed cassettes 3 and 4 or the manual feed tray 14 is conveyed to the registration roller pair 5 by the conveyance rollers while being guided by the conveyance guide plate. Stopped.
Then, the registration roller pair 5 rotates at a predetermined timing, and the transfer paper P is conveyed onto the transfer conveyance belt 60 and is adsorbed onto the belt surface by static electricity. Then, the toner is sequentially conveyed to the toner image forming units 1Y, 1M, 1C, and 1K by the transfer conveyance belt 60 that rotates in the direction indicated by the arrow A in FIG.

When the transfer paper P passes through the transfer nips of the toner image forming portions 1Y, 1M, 1C, and 1K, the toner images of the respective colors formed on the photosensitive drums 11Y, 11M, 11C, and 11K are The images are sequentially transferred to the superimposed state by the action of the transfer electric field and nip pressure. Thereby, a full-color toner image is formed on the transfer paper P.
After the toner image is transferred to the transfer paper P, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11K are cleaned and discharged by each cleaning device, and are prepared for the next formation of an electrostatic latent image.

After the toner image is fixed by the fixing unit 7 on the transfer paper P on which the full-color toner image is formed, the first paper discharge direction indicated by the arrow B or the arrow indicated by the arrow in accordance with the switching position of the switching guide 21. Heading in C second paper discharge direction.
When the transfer paper is discharged from the first paper discharge direction onto the paper discharge tray 8, it is discharged and stacked in a so-called face-down state with the image surface down. Further, when the paper is discharged in the second paper discharge direction, it is conveyed toward a post-processing device (sorter, binding device, etc.) (not shown), or again through the switchback unit for double-sided printing. Or is transported to

  By the way, as described in FIG. 1, the belt driving device 6 of the color laser printer has a belt driving device 6 that rotates at the end of one end in the width direction of the transfer conveyance belt 60 along the circumferential direction of the belt. A mark 15 for detecting the belt position in the moving direction is formed, and a guide member 16 is provided along the circumferential direction of the transfer conveyance belt 60 so as to cover the outer surface of the mark 15. The guide member 16 is formed of a transparent transmitting member, and an optical sensor 17 that allows the mark 15 to be detected by transmitting the guide member 16 (light transmitting member) at a position corresponding to the mark 15 is provided.

Therefore, since the belt driving device 6 is provided in the apparatus main body as shown in FIG. 3, when the transfer conveying belt 60 is exposed to the environment in the apparatus, the non-removal of one end on the transfer conveying belt 60 is not performed. The mark 15 formed along the circumferential direction of the belt using the outer surface of the end of the image area may deteriorate over time (may be peeled off in the case of sticking). In this example, since the outer surface of the mark 15 is entirely covered with the guide member 16, the deterioration of the mark 15 can be prevented.

Since the guide member 16 covering the outer surface of the mark 15 is formed of a transparent transmission member, the light emitted from the optical sensor 17 passes through the guide member 16 and hits the mark 15, and the reflected light is light. The mark 17 can be reliably detected by being received by the sensor 17.
Therefore, the mark 15 can be reliably read while preventing the reading accuracy of the mark 15 from being read by the optical sensor 17 over time. Thereby, the position detection of the transfer conveyance belt 60 in the rotation direction can be stably performed.
The surface of the mark 15 facing the optical sensor 17 (mark surface) may be formed by aluminum vapor deposition. By doing so, the reflectance of the reflected light reflected by the mark 15 is increased, so that more reliable mark detection is possible.

In addition, since the belt driving device 6 uses a reflection type optical sensor as the optical sensor 17, mark detection with little reading error is possible even with respect to a vibration in a direction perpendicular to the belt surface of the transfer conveyance belt 60. it can.
That is, as shown in FIG. 4 which compares the sensor output sensitivities of the reflective and transmissive photosensors, in the case of the transmissive photosensor, the sensor output sensitivities are almost the same from the optimum detection distance to the predetermined distance Lb. However, when the distance Lb is exceeded, the sensor output sensitivity is abruptly reduced, which causes a reading error.

  On the other hand, in the case of a reflection type optical sensor, as shown in FIG. 4, the sensor output sensitivity does not drop suddenly and gradually decreases even when the distance Lb exceeds the optimum detection distance. Therefore, even if the position of the mark 15 exceeds the predetermined distance Lb due to the transfer / conveying belt 60 being swung in a direction perpendicular to the belt surface during traveling, no reading error occurs.

Further, in the belt driving device 6 shown in FIG. 1, the position where the guide member 16 is provided is a place where the transfer bias applying members 27Y, 27M, 27C, and 27K (see FIG. 2) cannot be arranged, so that area is a non-image area. Although the, in this example since a guide member 16 on the one end portion outer surface of the transfer conveyance belt 60, it is possible to effectively use the non-image area.
Since the guide member 16 is provided at the above position, the transfer bias applying members 27Y, 27M, 27C, and 27K and the belt stretching support rollers 61 to 66 are not in contact with the upper surface of the guide member 16. The deterioration of the upper surface of the guide member 16 is small. Furthermore, since the upper surface of the guide member 16 in the non-image area is not easily contaminated with toner, the decrease in the sensor detection sensitivity of the optical sensor 17 is small.

FIG. 5 is a longitudinal sectional view similar to FIG. 1 showing an embodiment of the belt driving device according to the present invention, and the same reference numerals are given to portions corresponding to FIG.
In the belt driving device according to this embodiment, the transfer conveying belt 60 'side is formed of a light transmitting member with respect to the belt driving device 6 described in FIG. 1, and the light transmitting member is disposed at a position corresponding to the mark 15 inside the belt. The difference is that an optical sensor 17 that allows the mark 15 to be detected through the transfer conveyance belt 60 'is provided. In this embodiment , the guide member 16 ' covering the outer surface of the mark 15 provided on the outer surface of the end portion in the width direction of the transfer conveyance belt 60' does not necessarily need to be transparent.

In this belt driving device, the light emitted from the optical sensor 17 strikes the mark 15 provided on the outer surface through the transparent transfer conveyance belt 60 ′, and the reflected light is received by the optical sensor 17 to detect the mark 15. In this way, the light from the optical sensor 17 strikes the mark 15 through the inner surface of the transfer / conveying belt 60 ′ that is not easily contaminated with scattered toner or the like, so that the reading accuracy of the optical sensor 17 is prevented from being lowered over time. The mark 15 can be read reliably. Thereby, the position detection of the transfer conveyance belt 60 ′ in the rotation direction can be stably performed.
The color laser printer, which is an image forming apparatus provided with the belt driving device, is different from the color laser printer described in FIG. 3 only in the belt driving device, and the other components are the same as those in the color laser printer in FIG. Therefore, illustration and description thereof are omitted.

Having described embodiments of the application of the belt driving device according to the present invention in an image forming apparatus of the direct transfer type, the invention belt, directly toner image on the belt surface is transferred to the state sequentially superimposed The present invention can be similarly applied to an intermediate transfer body (indirect transfer type). In this case, a high-quality image forming apparatus can be configured by accurately detecting the mark position on the belt and accurately controlling the belt position and speed.
Note that the optical sensor 17 shown in FIG. 1 or the like may be a sensor that uses infrared light. That is, in general, in an optical sensor that emits infrared light and reads the amount of reflection, a strong response is obtained when the color of the mark to be detected is silver.
Therefore, if the optical sensor 17 is a sensor that uses infrared light, the difference in sensor output between the portion with the mark 15 and the non-mark portion becomes larger, and the effect of reducing error detection can be obtained.

  The present invention is widely applied to a belt driving device in which a guide member for preventing meandering of a belt stretched between a plurality of rollers and rotating is provided at an end portion of the belt, and an image forming apparatus including the belt driving device. be able to.

It is a longitudinal cross- section which shows the principal part of the belt drive device used as the foundation of this invention. It is a block diagram which similarly shows the whole structure of the belt drive device. It is the whole block diagram which shows the color laser printer which is an image forming apparatus provided with the belt drive device similarly. It is a diagram which shows the comparison of the sensor output sensitivity of a reflection type and a transmission type optical sensor. 2 is a longitudinal sectional view similar to FIG. 1 showing an embodiment of a belt driving device according to the present invention .

Explanation of symbols

6: Belt drive device, 11Y, 11M, 11C, 11K: Photoconductor drum, 15: Mark, 16, 16 ': Guide member, 17: Optical sensor, 60, 60': Transfer conveyance belt, 61, 62, 63, 64, 65, 66: support rollers

Claims (10)

A belt provided with a belt that is stretched and rotated between a plurality of rollers, and a mark for detecting the position of the belt is formed on the belt at an end portion in the width direction of the belt along the circumferential direction of the belt In the drive device,
The mark is formed on the outer surface of the belt, and guide members are provided at both ends in the width direction of the belt along the circumferential direction of the belt so as to cover the outer surface of the belt, and the width of the belt of the guide member the support roller that serves as a guide contact member for preventing the meandering of the respective contactable with said belt on each inner side of the side edge direction is provided, forming the belt at least one of the belt and the guide member in the light transmission member And a belt driving device provided with an optical sensor that allows the mark to be detected by passing through the belt made of the light transmitting member at a position corresponding to the mark inside the belt.   2. The belt driving apparatus according to claim 1, wherein the belt is a belt that conveys a sheet on which a sheet is adsorbed on a belt surface and toner images are sequentially transferred onto the sheet in a superimposed state.   2. The belt driving device according to claim 1, wherein the belt is an intermediate transfer member in which toner images are directly transferred onto the belt surface in an overlapping state.   4. The belt driving device according to claim 3, wherein an area of the belt where the mark is provided is a non-image area.   5. The optical sensor according to claim 1, wherein the optical sensor is a reflective photosensor that detects reflected light, and at least a surface of the mark that faces the sensor is formed of a material that reflects light. A belt driving device according to claim 1.   6. The belt driving device according to claim 5, wherein a surface of the mark facing the sensor is formed by aluminum vapor deposition.   The belt driving device according to claim 1, wherein the optical sensor is a sensor that uses infrared light.   2. The mark is used to detect a moving speed of the belt, and is used to correct an inherent circumferential speed variation of the belt that occurs when the belt rotates. The belt drive device as described in any one of thru | or 7.   An image forming apparatus comprising the belt driving device according to claim 1.   The image forming apparatus according to claim 9, further comprising a quadruple tandem mechanism in which four photosensitive members are arranged at intervals along the moving direction of the belt.

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