JP2004145004A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce deviation in the position of an image formed on a belt body more by highly accurately detecting the moving amount of the belt body used in image forming. <P>SOLUTION: An image forming apparatus is provided with a plurality of photoreceptors 40, an intermediate transfer belt 10 laid over a plurality of supporting rollers 14, 15 and 16, the driving means 78 of the belt, a plurality of transfer devices 62 to transfer the images on the photoreceptors 40 to the intermediate transfer belt 10, a scale 71 to detect the moving amount of the intermediate transfer belt, a sensor 75 to read the scale and a controlling means to perform feed-back control based on a read result, and a scale reading means is arranged on the upstream side of the supporting roller 15 on the upstream side of a first transfer device 62Y and on a downstream side from the supporting roller 14 on the downstream side of a last transfer device 62K in the rotating direction of the intermediate transfer belt. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine and a printer. More specifically, the present invention relates to an image forming apparatus for sequentially transferring and superimposing images on a plurality of image carriers on a belt body wound around a plurality of support members or a transfer body conveyed to the belt body to obtain an image. It is.
[0002]
[Prior art]
In recent years, in the electrophotographic apparatus, demands for higher image quality, higher durability, lower cost, full color, and the like have been increasing from the market. In particular, recently, with the spread of color printers and color copiers, offices have become full-colored, and there has been an increasing demand for devices that output full-color images at the same speed as monochrome. In order to satisfy this demand, a so-called tandem type image forming apparatus has attracted attention. A tandem image forming apparatus is provided with a plurality of photoconductors arranged side by side, individually provided with a developing device, forms a single-color toner image on each photoconductor, transfers the single-color toner images, and sequentially transfers the single-color toner images. A composite color image is recorded on a superimposed recording material. This tandem type image forming apparatus has a much higher print speed than a so-called one-drum type image forming apparatus that forms a combined full-color image by repeating image formation a plurality of times (usually four times) using one photoconductor. It is possible to save time.
[0003]
As a transfer device used in this tandem image forming apparatus, there are a direct transfer type and an indirect transfer type. In the direct transfer method, as shown in FIG. 3, images on the respective photoconductors 40Y, 40C, 40M, 50K are sequentially transferred to a transfer material conveyed by a transfer belt 75 by transfer devices 62Y, 62C, 62K, 62K. Things. In addition, the indirect transfer method is, as shown in FIG. 4, after the images on the respective photoconductors 40Y, C, M, and K are sequentially transferred to the intermediate transfer belt 10 by the primary transfer devices 62Y, C, M, and K once. This is an indirect transfer type in which images on the intermediate transfer belt 10 are collectively transferred to a transfer material by a secondary transfer device 23.
[0004]
In an image forming apparatus including a belt body for image formation such as a transfer belt and a transport belt, the amount of movement of the belt body is required to be high in order to accurately align an image formed on the belt body. Control is required. Therefore, a fine and precise scale for detecting the amount of movement on the belt body and scale reading means for electrically reading the scale on the belt body are provided, and the driving means for the belt body is fed back based on the detection result of the reading means. An image forming apparatus to be controlled has been proposed (for example, Patent Document 1). This image forming apparatus detects the amount of movement even when the moving speed of the belt member fluctuates, and performs feedback control on the driving means of the belt member based on the detection result. The resulting image displacement can be reduced. Further, a change in the moving speed of the belt body is detected, and feedback control is performed to a latent image forming unit that forms an electrostatic latent image on each photoconductor, and the position of the electrostatic latent image is adjusted to form the electrostatic latent image. An image forming apparatus that performs high-accuracy image alignment is also known.
[0005]
[Patent Document 1]
JP 11-24507 A
[Problems to be solved by the invention]
However, in the image forming apparatus using the scale reading means, depending on the arrangement of the scale reading means, the detected amount of movement of the belt body is likely to include an error. It was found that the reduction of was not satisfactorily performed. Specifically, in the vicinity of the transfer section where a high voltage is applied to the belt member to transfer the toner, the scale reading means may be electrically malfunctioned under the influence of the high voltage.
[0007]
In the case of the indirect transfer method, the linear velocity of the recording material conveying device conveyed so as to be in contact with the intermediate transfer belt at the secondary transfer position is set so that the linear velocity with the intermediate transfer belt is substantially the same. I have. However, in practice, the linear speed between the intermediate transfer belt and the recording material conveying device has a slight speed difference due to dimensional tolerance or the like. For this reason, the intermediate transfer belt is affected by the speed difference at the secondary transfer position, and fluctuates in speed. Also, the sheet starts to contact the intermediate transfer belt near the secondary transfer position, but the speed of the intermediate transfer belt fluctuates due to the impact when the sheet hits the intermediate transfer belt. From these facts, the intermediate transfer belt is likely to undergo large speed fluctuations near the secondary transfer device, and the movement amount of the intermediate transfer belt read near the secondary transfer device is the movement amount of the intermediate transfer belt at the primary transfer position. There is a possibility that there will be a large difference between
[0008]
Further, a pressure member such as a tension roller as a means for applying tension to the intermediate transfer belt is disposed on the intermediate transfer belt. Here, the tension of the intermediate transfer belt fluctuates due to an impact when the sheet hits the intermediate transfer belt. Due to this tension change, the intermediate transfer belt causes a position change. The position change is largest at the tension roller portion for adjusting the tension, and becomes almost zero at the contact portion between the tension roller and the support roller adjacent to the tension roller. If the scale is read in the vicinity of the tension roller portion where the position of the intermediate transfer belt greatly fluctuates, chattering or the like occurs in the read data, an error is detected, and the speed cannot be accurately detected.
[0009]
The present invention has been made in view of the above background, and an object of the present invention is to detect a movement amount of a belt used for image formation with high accuracy to thereby reduce a positional shift of an image formed on the belt. An object of the present invention is to provide an image forming apparatus capable of further reducing the number of images.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 includes a plurality of image carriers, a latent image forming means for forming an electrostatic latent image on the image carrier, and an electrostatic latent image on the image carrier. A plurality of developing devices for developing an image, a belt member wrapped around a plurality of support members, a driving unit for rotating the belt member, and a plurality of members for transferring an image on the image carrier onto the belt member A transfer device, a secondary transfer device that transfers an image superimposed on the belt member to a transfer-receiving member, a scale provided on the belt member for detecting an amount of movement of the belt member, An image forming apparatus comprising: scale reading means for reading a scale; and control means for controlling the driving means or the latent image forming means based on a reading result of the scale reading means. For the direction of body rotation, Upstream in than the first belt support member disposed upstream of the transfer device, the belt support member which is disposed downstream of the final transfer device is characterized in that arranged downstream.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the scale reading unit is disposed near a support member connected to the driving unit.
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the image forming apparatus further includes a pressing member that applies tension to the belt body, and the scale reading unit presses the scale reading unit with respect to a rotation direction of the belt body. It is characterized by being arranged upstream of the belt support member upstream of the member and downstream of the belt support member downstream of the pressure member.
The invention according to claim 4, wherein a plurality of image carriers, latent image forming means for forming an electrostatic latent image on the image carrier, and a plurality of developing devices for developing the electrostatic latent image on the image carrier A belt member wrapped around a plurality of support members, driving means connected to one of the plurality of support members for rotating the belt member, and transferring the image on the image carrier to the belt member. A plurality of transfer devices for transferring onto a transfer object conveyed by a body, a scale provided on the belt body for detecting an amount of movement of the belt body, scale reading means for reading the scale, and the scale An image forming apparatus comprising: a driving unit or a control unit that controls the latent image forming unit based on a reading result of the reading unit. Located upstream of the second transfer device Upstream in than is the belt support member, it is characterized in that the belt support member which is disposed downstream of the final transfer device positioned downstream.
In these image forming apparatuses, the scale reading unit is disposed upstream of the belt supporting member disposed upstream of the first transfer device and downstream of the belt supporting member disposed downstream of the final transfer device. I do. That is, the scale reading means is installed at a place other than the area including the transfer portion for transferring the image on the image carrier onto the belt body. Therefore, the scale reading unit is less susceptible to the high voltage than the case where the scale reading unit is arranged in the area including the transfer section. Therefore, the possibility that the scale reading means malfunctions electrically is reduced, and the movement amount of the belt body can be detected with high accuracy. Since the driving means or the latent image forming means of the belt member is feedback-controlled based on the detection result, the image displacement caused by the fluctuation of the moving speed of the belt member can be favorably reduced.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a color printer which is an image forming apparatus of a tandem type intermediate transfer system will be described.
FIG. 1 is a schematic configuration diagram of a color printer to which the present invention can be applied. This color printer comprises a copying apparatus main body 100, a paper feed table 200 on which the copying machine main body 100 is mounted, a scanner 300 mounted on the copying apparatus main body 100, and an automatic document feeder (ADF) 400 mounted thereon. Is done. The copying apparatus main body 100 is provided with an intermediate transfer belt 10 as an endless belt in the center.
[0012]
The intermediate transfer belt 10 is wound around three supporting rollers (a driving roller 14, a driven roller 15, and a secondary transfer opposing roller 16) as shown in FIG. A drive motor (not shown) as a drive source is connected. A driving unit that rotationally drives the intermediate transfer belt 10 is configured using the driving roller 14 and a driving motor. When the drive motor is driven, the intermediate transfer belt 10 rotates clockwise in the drawing, and the support rollers 15 and 16 that can be driven rotate. Further, an intermediate transfer body cleaning device 17 for removing residual toner remaining on the intermediate transfer belt 10 after image transfer is provided to the left of the second support roller 15. Further, on the intermediate transfer belt 10 stretched between the driving roller 14 and the driven rollers 15 and 16, four image forming units 18 Y, C, M, and 18 of yellow, cyan, magenta, and black are arranged along the conveying direction. The tandem image forming unit 20 is configured by arranging K side by side. In the tandem image forming unit 20, the image forming units 18Y, 18C, 18M, and 18K as individual toner image forming units are arranged around photosensitive drums 40Y, 40C, 40M, and 40K as drum-shaped latent image carriers. It includes a charging device, a developing unit, a primary transfer device 62, a photoconductor cleaning device, a static elimination device, and the like. However, the order of these four colors is an example, and the present invention is not limited to this.
[0013]
An exposure device 21 is provided on the tandem image forming section 20, as shown in FIG. On the other hand, on the opposite side of the intermediate transfer belt 10 from the tandem image forming unit 20, a secondary transfer device 22 as a secondary transfer unit is provided. In the illustrated example, the secondary transfer device 22 is configured by extending a secondary transfer belt 24, which is an endless belt, between two rollers 23, and is disposed by pressing against the driven roller 16 via the intermediate transfer belt 10. Then, the image on the intermediate transfer belt 10 is secondarily transferred to a sheet S as a transfer material. A fixing device 25 for fixing a transferred image on the sheet S is provided beside the secondary transfer device 22. The fixing device 25 is configured by pressing a pressure roller 27 against a fixing belt 26 which is an endless belt.
[0014]
The secondary transfer device 22 also has a sheet conveying function of conveying the sheet S after the image transfer to the fixing device 25. Of course, a transfer roller or a non-contact charger may be provided as the secondary transfer device 22, and in such a case, it is difficult to additionally provide the sheet conveying function. In the illustrated example, under the secondary transfer device 22 and the fixing device 25, the sheet reversing is performed in parallel with the above-described tandem image forming unit 20 to reverse the sheet S so as to record images on both sides of the sheet S. An apparatus 28 is provided.
[0015]
Now, when making a copy using this color electrophotographic apparatus, an original is set on the original table 30 of the automatic original transport apparatus 400. Alternatively, the automatic document feeder 400 is opened, a document is set on the contact glass 32 of the scanner 300, and the automatic document feeder 400 is closed and pressed.
When a start switch (not shown) is pressed, when the original is set on the automatic document feeder 400, the original is conveyed and moved onto the contact glass 32, and then the original is set on the other contact glass 32. Immediately drives the scanner 300 to travel on the first traveling body 33 and the second traveling body 34. Then, the first traveling body 33 emits light from the light source and further reflects the reflected light from the document surface to the second traveling body 34, is reflected by the mirror of the second traveling body 34, and passes through the imaging lens 35. The original is read by the reading sensor 36 and read.
[0016]
Then, the photosensitive drums 40Y, C, M, and K are rotated by the individual image forming units 18Y, 18C, 18M, and 18K. The surfaces of the drums 40Y, C, M, and K are uniformly charged, and then the exposure device 21 irradiates writing light such as a laser or an LED according to the contents read by the scanner 300 to irradiate the photosensitive drums 40Y, C, and K. An electrostatic latent image is formed on M and K.
Thereafter, a toner is adhered by the developing unit to visualize the electrostatic latent image, thereby forming a single color image of yellow, cyan, magenta, and black on each of the photosensitive drums 40Y, 40C, 40M, and 40K. The drive roller 14 is driven to rotate by a drive motor (not shown), the other two driven rollers 15 and 16 are driven to rotate, the intermediate transfer belt 10 is rotated and conveyed, and the visible image is intermediate-transferred by the primary transfer device 62. The images are sequentially transferred onto the belt 10. Thereby, a composite color image is formed on the intermediate transfer belt 10. The surface of the photoconductor drums 40Y, 40Y, 40C, 40M, and 40K after the image transfer is cleaned by removing the residual toner by the photoconductor cleaning device, and the charge is removed by the discharge device to prepare for the image formation again.
[0017]
On the other hand, when a start switch (not shown) is pressed, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotated to feed out the sheet S from one of the paper feed cassettes 44 provided in the paper bank 43 in multiple stages. The sheets are separated one by one at 45 and fed into a paper feed path 46, transported by a transport roller 47, guided to a paper feed path 48 in the copier main body 100, and stopped against a registration roller 49. Alternatively, the sheet S on the manual feed tray 51 is fed out by rotating the sheet feeding roller 50, separated one by one by the separation roller 52, put into the manual sheet feeding path 53, and similarly stopped against the registration roller 49. Then, the registration roller 49 is rotated in synchronization with the composite color image on the intermediate transfer belt 10, and the sheet S is sent between the intermediate transfer belt 10 and the secondary transfer device 22, and is transferred by the secondary transfer device 22. To record a color image on the sheet S.
[0018]
The sheet S after the image transfer is conveyed by the secondary transfer device 22 and sent to the fixing device 25, where the transfer image is fixed by applying heat and pressure by the fixing device 25, and then switched and discharged by the switching claw 55. The sheet is discharged by rollers 56 and stacked on a sheet discharge tray 57. Alternatively, the sheet is switched into the sheet reversing device 28 by the switching claw 55, reversed and guided again to the transfer position, the image is recorded on the back surface, and then discharged onto the discharge tray 57 by the discharge roller 56. On the other hand, the intermediate transfer belt 10 after the image transfer is cleaned by the intermediate transfer body cleaning device 17 to remove the residual toner remaining on the intermediate transfer belt 10 after the image transfer, so that the tandem image forming unit 20 prepares for the second image formation.
[0019]
In the above-described image process, if the rotational movement speed of the intermediate transfer belt 10 fluctuates, a color image on the intermediate transfer belt 10 or on the sheet S is disturbed. . The rotational movement of the intermediate transfer belt 10 is affected by the deformation and eccentricity of the drive roller 14 and the driven rollers 15 and 16, the eccentricity of the rotation shaft of each support roller, the speed fluctuation of the drive motor, and the like. The movement amount in the rotation direction fluctuates.
[0020]
Therefore, in the color printer according to the present embodiment, in order to accurately detect the amount of movement of the intermediate transfer belt 10, a scale 70 with a fine precision scale is provided on the inner peripheral surface of the intermediate transfer belt 10, and a scale for reading the scale 70. A sensor 71 as reading means was provided. Further, a feedback control system is provided to precisely perform feedback control of the moving position and the moving speed of the intermediate transfer belt 10.
[0021]
FIG. 2 is a perspective view illustrating the positions of the scale 70 and the sensor 71 provided on the intermediate transfer belt 10. FIG. 4 is a cross-sectional view illustrating the positions of the scale 70 and the sensor 71 provided on the intermediate transfer belt 10. The scale 70 is adhered over one circumference in the rotation direction of the intermediate transfer belt 10. The sensor 71 is provided on the intermediate transfer belt 10 below the drive roller 14 on the upstream side of the drive roller 14 upstream of the first color transfer device and on the downstream side of the driven roller 15 downstream of the final color transfer device. Inside, it is arranged so as to face the scale 70. Here, since the scale 70 is provided on the inner peripheral surface of the intermediate transfer belt 10, the sensor 71 for reading the scale 70 is relatively clean and is a space of the intermediate transfer belt 10 which is a space that does not affect the layout of other members. It can be provided inside.
[0022]
The intermediate transfer belt 10 and the scale 70 are integrated, and are rotated by a drive motor unit 86. Therefore, the rotational movement of the intermediate transfer belt 10 and the scale 70 is accompanied by the deformation and eccentricity of the driving roller 14 and the driven rollers 15 and 16, the eccentricity of the shaft, the speed fluctuation of the driving motor, and the like. All the slippage caused by the friction with the intermediate transfer belt is transmitted to the intermediate transfer belt 10 and the scale 70, so that the sensor 71 can accurately detect the amount of movement of the intermediate transfer belt.
[0023]
Here, the arrangement of the sensor 71 will be described in detail. The intermediate transfer belt 10 applies a high voltage to the primary transfer devices 62Y, C, M, and K while being pressed against the respective photosensitive drums 40Y, C, M, and K by the primary transfer devices 62Y, C, M, and K. By applying the voltage, the toner images of the respective colors on the photosensitive drums 40Y, 40C, 40M, 40K are transferred to the intermediate transfer belt 10. The transfer current flowing from the primary transfer devices 62Y, C, M, and K flows along the back surface of the intermediate transfer belt 10 and flows into the drive roller 14 and the driven roller 15 that are close to the primary transfer devices 62Y, C, M, and K. When the sensor 71 is disposed between the primary transfer devices 62Y, C, M, and K and the adjacent support rollers 14, 15, the sensor 71 is erroneously affected by the high voltage of the primary transfer devices 62Y, C, M, and K. Operation may occur. In order to prevent this, a position other than between the driven roller 15 upstream of the first color transfer device 62Y and the drive roller 14 downstream of the final color transfer device 62K, that is, the driven It is arranged upstream of the roller 15 and downstream of the drive roller 14. In this embodiment, it is arranged below the drive roller 14.
[0024]
Further, the linear speed between the secondary transfer device 22 and the intermediate transfer belt 10 is set to be substantially the same. However, since the linear speed cannot be made exactly the same due to the dimensional tolerance of the roller diameter, etc. Is generated. Further, in the vicinity of the secondary transfer device 22, a large speed fluctuation is given to the intermediate transfer belt 10 due to an impact when the sheet collides with the intermediate transfer belt 10. Therefore, if the reading is arranged in the vicinity of the secondary transfer device 22 with respect to the rotation direction of the intermediate transfer belt 10, the sensor 71 reads the speed of the intermediate transfer belt 10 which has received the above-mentioned speed fluctuation. In FIG. 5, a sensor 71 is disposed immediately downstream of the secondary transfer device 22, and based on the sensor 71, a belt body speed Va near the drive roller 14 when fed back to the drive unit of the intermediate transfer belt 10, and the secondary transfer device 22 shows the belt body speed Vb read immediately downstream of FIG. With such control, the belt speed Vb downstream of the secondary transfer device 22 is constant, but the belt speed Va near the drive roller 14 has a large fluctuation. For this reason, the speed of the intermediate transfer belt 10 in each primary transfer unit fluctuates, causing a position shift.
[0025]
Therefore, in the printer according to the present embodiment, the sensor 71 is disposed near the driving roller 14 in order to read the speed of the intermediate transfer belt 10 at a position that is not affected by such speed fluctuation. The belt body speed excluding the influence of the speed fluctuation is detected. 6, a sensor 71 is disposed near the drive roller 14, and based on the sensor 71, a belt body speed Va near the drive roller 14 when feedback is provided to the drive unit of the intermediate transfer member, and a belt speed downstream of the secondary transfer device 22. This shows the body speed Vb. With such control, the fluctuation of the belt speed Va in the vicinity of the drive roller 14 can be reduced. That is, the fluctuation of the speed of the intermediate transfer belt in each primary transfer unit can be reduced, and the displacement can be reduced.
[0026]
Further, a tension roller 76 as a means for applying tension to the intermediate transfer belt 10 is disposed on the intermediate transfer belt 10. The tension of the intermediate transfer belt 10 changes due to the impact when the sheet enters. Due to the change in the tension, the position fluctuation in the vertical direction near the tension roller 76 increases. Further, the position fluctuation of the intermediate transfer belt 10 is largest at the tension roller portion, and becomes almost zero at the contact point with the driven rollers 15 and 16 adjacent to the tension roller. The amount of displacement of the intermediate transfer belt 10 is large, and the gap between the scale 70 and the sensor 71 fluctuates. If the scale 70 is read in such a place where the gap between the scale 70 and the sensor 71 fluctuates greatly, chattering occurs in the read data and an error is detected, and the speed cannot be detected accurately. For this reason, it is preferable to dispose the sensor 71 in a position where the position fluctuation of the intermediate belt 10 due to such a change in tension is small.
[0027]
Therefore, in the printer according to the present embodiment, the sensor 71 determines that the driven roller 16 upstream of the tension roller 76 is also upstream and the downstream of the driven roller 15 downstream of the tension roller 76 with respect to the rotation direction of the intermediate transfer belt 10. It is arranged at the position where With such an arrangement, it is possible to prevent the sensor 71 from being arranged at a position where the position fluctuation due to the tension roller 76 is large. Therefore, the belt speed can be detected with high accuracy.
[0028]
In this embodiment, an example in which the present invention is applied to a so-called tandem-type indirect transfer type color printer has been described, but the printer to which the present invention can be applied is not limited to this type of printer. For example, the present invention may be applied to a tandem type direct transfer type color printer as shown in FIG. In this printer, four photosensitive drums 40Y, 40C, 40M, 40K are individually provided with image forming means 18Y, 18C, 18K, and 18K, respectively, and an image formed on the photosensitive drum 40 is transferred to a primary transfer device. The image is sequentially transferred to the sheet S conveyed to the conveyance belt 75 by 62. In the drawings, the same reference numerals are given to the same functional members, and the description is omitted. Then, a scale 70 is provided on the inner peripheral surface of the transport belt 75, and a sensor 71 for reading the movement amount is provided. The position of the sensor 71 is such that, with respect to the rotation direction of the transport belt 75, a driven roller disposed upstream of the drive roller 14 disposed upstream of the first transfer device 2Y and downstream of the final transfer device 2K. It is arranged downstream from 15. With this arrangement, the transfer devices 62Y, C, M, and K can be sufficiently separated from each other, and high-accuracy detection with little influence of a high voltage of the transfer device can be performed.
[0029]
In the present embodiment, the apparatus that controls the driving unit of the belt body is described. However, feedback control is performed on the exposure apparatus that is the optical writing unit for each photoconductor, and the position of the latent image on each photoconductor is determined. The adjustment can also reduce the displacement of the image.
[0030]
As described above, according to the present embodiment, the scale reading unit is less likely to be affected by the high voltage than when the scale reading unit is arranged in the area including the primary transfer unit. Therefore, the possibility that the scale reading means malfunctions electrically is reduced, and the movement amount of the belt body can be detected with high accuracy. Since the driving means or the latent image forming means of the belt member is feedback-controlled based on the detection result, the image displacement caused by the fluctuation of the moving speed of the belt member can be favorably reduced.
Further, the sensor 71 is arranged near the drive roller 14. As a result, the amount of movement of the intermediate transfer belt 10 is read at a position where the influence of the speed fluctuation of the intermediate transfer belt 10 occurring near the secondary transfer device 22 is small. Therefore, it is possible to eliminate the possibility that the detected movement amount of the intermediate transfer belt 10 has a large difference from the movement amount of the intermediate transfer belt 10 at the primary transfer position.
Further, the sensor 71 is disposed at a position where the support roller 16 upstream of the tension roller 76 is also upstream and downstream of the support roller 15 downstream of the tension roller 76 with respect to the rotation direction of the intermediate transfer belt 10. Accordingly, the position fluctuation of the intermediate transfer belt 10 is small, and the sensor 71 can detect the movement amount of the intermediate transfer belt 10 with high accuracy.
[0031]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, there exists the outstanding effect that the displacement of the image formed in a belt body can be reduced by detecting the moving amount of the belt body used for image formation with high precision.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a color printer to which the present invention is applied.
FIG. 2 is a perspective view illustrating the position of a scale and a sensor provided on an intermediate transfer belt of the color printer.
FIG. 3 is a cross-sectional view of a tandem type direct transfer type color printer applied to a color printer.
FIG. 4 is a cross-sectional view of a tandem-type indirect transfer type color printer applied to a color printer.
FIG. 5 is a diagram illustrating a belt speed V near the driving roller and a belt speed Vb downstream of the secondary transfer device when a sensor is disposed downstream of the secondary transfer device.
FIG. 6 is a diagram illustrating a belt body speed Va near a driving roller and a belt body speed Vb downstream of the secondary transfer device when a sensor is disposed upstream of the secondary transfer device.
[Explanation of symbols]
Reference Signs List 10 intermediate transfer belt 14 drive roller 15 driven roller 16 driven roller (secondary transfer opposing roller)
Reference Signs List 17 Intermediate transfer body cleaning device 18Y, C, M, K Image forming means 20 Tandem image forming unit 21 Exposure device 22 Secondary transfer device 24 Secondary transfer belt 25 Fixing device 26 Fixing belt 28 Sheet reversing device 30 Document table 32 Contact glass 40Y, C, M, K Photoreceptor drums 62Y, C, M, K Primary transfer device 70 Scale 71 Sensor 75 Conveyor belt 78 Drive motor unit 100 Copier main body 200 Feed table 300 Scanner 400 Automatic document feeder (ADF)

Claims (4)

A plurality of image carriers, a latent image forming means for forming an electrostatic latent image on the image carrier, a plurality of developing devices for developing the electrostatic latent image on the image carrier, and a plurality of support members A looped belt body, driving means coupled to one of the plurality of support members for rotationally driving the belt body, and a plurality of images for transferring an image on the image carrier onto the belt body. A transfer device, a secondary transfer device for transferring an image superimposed on the belt member to a transfer-receiving member, a scale provided on the belt member for detecting an amount of movement of the belt member, and a scale provided on the belt member. An image forming apparatus comprising: a scale reading unit that reads the image data; and a control unit that controls the driving unit or the latent image forming unit based on a reading result of the scale reading unit.
The scale reading unit is arranged such that, with respect to the rotation direction of the belt body, a belt supporting member disposed upstream of the first transfer device and a belt supporting member disposed downstream of the final transfer device. An image forming apparatus, which is disposed downstream. 2. The image forming apparatus according to claim 1, wherein the scale reading unit is disposed near a support member connected to the driving unit. 3. The image forming apparatus according to claim 1, further comprising a pressing member that applies tension to the belt member, wherein the scale reading unit is configured to support the belt upstream of the pressing member with respect to a rotation direction of the belt member. 4. An image forming apparatus, wherein the image forming apparatus is disposed upstream of a member and downstream of a belt supporting member downstream of the pressing member. A plurality of image carriers, a latent image forming means for forming an electrostatic latent image on the image carrier, a plurality of developing devices for developing the electrostatic latent image on the image carrier, and a plurality of support members A looped belt body, driving means connected to one of the plurality of support members for rotationally driving the belt body, and an image transferred on the image carrier by the belt body. A plurality of transfer devices for transferring onto the body, a scale provided on the belt body for detecting the amount of movement of the belt body, scale reading means for reading the scale, and a reading result of the scale reading means. A control means for controlling the driving means or the latent image forming means,
The scale reading unit is arranged such that, with respect to the rotation direction of the belt body, a belt supporting member disposed upstream of the first transfer device and a belt supporting member disposed downstream of the final transfer device. An image forming apparatus, which is disposed downstream.

Images