JP2004226867A - Image transfer device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that the occurrence of color slippage tends not to be suppressed due to the lowering of measuring accuracy because the vicinity of the side edge part of an endless belt where tension is applied is corrugated with time even though feed-back is applied to a driving source by providing a linear scale at the side edge part of the back side of the endless transfer belt so as to overlap and transfer the image of each color without causing the color slippage and measuring the surface speed of the belt in a color image forming apparatus. <P>SOLUTION: A sensor 71 is provided at either of specified ranges 75a and 75b to a position where the reading distance of the sensor is kept within an allowable error range even though a transfer belt is separated from a photoreceptor drum 40 or a transfer roller 62 before or after a transfer nip part formed by the drum 40 and the roller 62, and a scale 70 provided at the side edge part of the transfer belt 10 is read, and the feed-back is applied to the drive source, so that the highly accurate drive control of the transfer belt is attained. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
[Industrial applications]
The present invention relates to a color image forming apparatus requiring color matching, such as a color copying machine and a color printer.
[0002]
[Prior art]
2. Description of the Related Art In recent years, color image output apparatuses such as color copiers and color printers have been increasingly used in accordance with market requirements.
2. Description of the Related Art A color electrophotographic apparatus includes a plurality of color developing devices around a single photosensitive drum. The developing devices apply toner to form a composite toner image on a photosensitive member, and transfer the toner image. A color image is recorded on a sheet-like transfer material, that is, a so-called one-drum type, and a plurality of photoreceptor drums provided side by side are provided with developing devices individually, and a single-color toner image is formed on each photoreceptor, There is a so-called tandem type in which these single-color toner images are sequentially transferred to record a composite color image on a sheet.
[0003]
Comparing the one-drum type and the tandem type, the former has a single photoconductor drum, and thus has the advantage of being relatively small in size and cost. Since a full-color image is formed by repeating image formation (usually four times), it is difficult to speed up image formation. The latter, on the other hand, has the disadvantage of increasing the size and increasing the cost, but has the advantage that it is easy to speed up image formation.
Recently, tandem type has been attracting attention because full-color is desired to be as fast as monochrome.
[0004]
FIG. 5 is a diagram for explaining a tandem image forming apparatus of a direct transfer system.
FIG. 6 is a view for explaining a tandem image forming apparatus of the indirect transfer type.
As shown in FIG. 5, a tandem type electrophotographic apparatus includes a direct transfer type in which an image on each photosensitive drum 40 is sequentially transferred to a sheet s conveyed by a sheet conveying belt 10 by a transfer device 62; As shown in FIG. 6, the images on the respective photosensitive drums 40 are sequentially transferred to the intermediate transfer belt 10 by the primary transfer device 62 once, and then the images on the intermediate transfer belt 10 are sheet-transferred by the secondary transfer device 24. and s.
In the direct transfer method, the sheet transport belt indirectly contacts the photosensitive drum via the sheet s, and in the indirect transfer method, the intermediate transfer belt directly contacts the photosensitive drum. Although the secondary transfer device 24 is shown in the form of a belt in the figure, a roller-type system is also available.
[0005]
In any method, a function of transferring images of respective colors in a superimposed manner without color shift is a major problem, and various devices have been devised to drive the images at a stable and constant speed.
As one of measures against the problem, there is measurement of a surface speed using a linear encoder at a side edge portion of the intermediate transfer belt (for example, see Patent Document 1). The output is a means that can be used as feedback to a drive source, correction of write timing, and the like, and can be a source of alignment technology.
[0006]
[Patent Document 1]
JP-A-11-24507 (Page 3, paragraph 0020, FIG. 2)
[0007]
[Problems to be solved by the invention]
A further problem here is the disturbance of the side edges of the belt. Generally, when an endless belt is used for a long time, unevenness of the belt causes unevenness near the side edges even if tension is applied. This often causes a problem of lowering the measurement accuracy of the linear scale provided on the side edge of the belt. Furthermore, the presence of the scale itself to be read and the thickness thereof have an electrostatic effect on the image and transfer paper transportability, which often causes a problem of a decrease in accuracy.
[0008]
With respect to waving, if the area in contact with the drum etc. is used, it can be said that the waving is also corrected and it can be read stably. There is a case where the reflection of the sensor light of the mold is diffused and the reading is not stable.
These problems are unavoidable not only for the tandem type but also for the one-drum type color image forming apparatus in order to further improve the image quality.
SUMMARY OF THE INVENTION An object of the present invention is to provide a linear scale reading mechanism that does not affect the image and does not impair the reading accuracy, and a high-quality color image forming apparatus capable of performing feedback control and the like of the transfer apparatus using the mechanism. To provide.
[0009]
[Means for Solving the Problems]
According to the first aspect of the present invention, at least a part of the transfer belt is pressed by the transfer roller and comes into direct or indirect contact with the photosensitive drum, and is transferred to the endless transfer belt supported by the plurality of support rollers and to the back surface of the transfer belt. In the image transfer apparatus having a linear scale formed over one circumference in the direction and a belt drive control unit including a sensor for reading the linear scale, the installation position of the sensor is located immediately before the position where the transfer belt contacts the photosensitive drum. It is a predetermined range.
[0010]
According to the second aspect of the present invention, at least a part of the transfer belt is pressed by the transfer roller and comes into direct or indirect contact with the photosensitive drum, and is transferred to the endless transfer belt supported by the plurality of support rollers and to the back surface of the transfer belt. In an image transfer apparatus having a belt drive control means including a linear scale formed over one circumference in a direction and a sensor for reading the linear scale, the installation position of the sensor is a predetermined position immediately after a position at which the transfer belt separates from the transfer roller. It is characterized by being a range.
[0011]
According to the third aspect of the present invention, at least a part of the endless transfer belt is in direct or indirect contact with the photosensitive drum and is supported by the plurality of support rollers, and is formed on the back surface of the transfer belt over the entire circumference in the feed direction. In the image transfer apparatus having a belt drive control unit including a linear scale and a sensor that reads the linear scale, the installation position of the sensor is set immediately before the transfer belt comes into contact with any one of the plurality of support rollers or the position of the sensor. It is a predetermined range immediately after the position away from the roller.
[0012]
According to the fourth aspect of the present invention, at least a part of the transfer belt is in direct or indirect contact with the photosensitive drum and is supported by a plurality of support rollers. In the image transfer apparatus having the linear drive and the belt drive control means including a plurality of sensors for reading the linear scale, the installation position of the plurality of sensors is within a predetermined range immediately before the position where the transfer belt contacts the photosensitive drum. A predetermined range immediately after the transfer belt is separated from the transfer roller, and a predetermined range immediately before the transfer belt is in contact with any one of the plurality of support rollers or immediately after the position separated from the roller. It is characterized by two or more locations.
[0013]
According to a fifth aspect of the present invention, in the image transfer device according to any one of the first to fourth aspects, the installation position of the linear scale on the back surface of the transfer belt is related to a depth direction of a transfer voltage applying unit with respect to the transfer belt. It is characterized by being outside the transfer voltage application region.
According to a sixth aspect of the present invention, in the image transfer apparatus according to any one of the first to fifth aspects, a part of all or a part of the rollers supporting the transfer belt facing the linear scale is a relief. It has a stepped portion, and is configured not to contact the linear scale.
[0014]
According to a seventh aspect of the present invention, there is provided the image transfer apparatus according to any one of the first to sixth aspects, a single photosensitive drum, and an optical writing apparatus for repeatedly forming a latent image on the photosensitive drum based on color-specific information. And a plurality of developing devices for visualizing the latent image into a toner image of a color corresponding to the write information, and a secondary transfer device, wherein the image transfer device is configured to transfer the toner image to the transfer belt. A color image forming apparatus is sequentially transferred, and the toner image is transferred to a sheet-like transfer material by the secondary transfer device.
[0015]
According to an eighth aspect of the present invention, there is provided the image transfer apparatus according to any one of the first to sixth aspects, a single photosensitive drum, and an optical writing apparatus for repeatedly forming a latent image on the photosensitive drum based on color-specific information. And a plurality of developing devices for visualizing the latent image into a toner image of a color corresponding to the write information, wherein the image transfer device temporarily fixes a sheet-shaped transfer material on the transfer belt. A color image forming apparatus which carries and transfers the toner image to the transfer material sequentially is characterized.
[0016]
According to a ninth aspect of the present invention, there is provided the image transfer device according to any one of the first to sixth aspects, a plurality of photosensitive drums provided for each color, and a light for forming a latent image on each of the plurality of photosensitive drums. A writing device, a plurality of developing devices for visualizing each of the latent images into a toner image, and a secondary transfer device, wherein the image transfer device transfers the toner image sequentially to the transfer belt, The color image forming apparatus is characterized in that the toner image is transferred to a sheet-like transfer material by the secondary transfer device.
[0017]
According to a tenth aspect of the present invention, there is provided the image transfer apparatus according to any one of the first to sixth aspects, a plurality of photosensitive drums provided for each color, and a light for forming a latent image on each of the plurality of photosensitive drums. A writing device, a plurality of developing devices for visualizing each latent image as a toner image, and a secondary transfer device, wherein the image transfer device is configured such that the transfer belt conveys a sheet-like transfer material. A color image forming apparatus for sequentially transferring the toner image to the transfer material is characterized.
[0018]
According to an eleventh aspect of the present invention, in the color image forming apparatus according to the seventh or ninth aspect, the sensors are provided at least at two locations near the photosensitive drum and near the secondary transfer device. Controlling the drive of the transfer belt using a sensor provided near the photosensitive drum, and controlling the drive of the transfer belt using a sensor provided near the secondary transfer device at a secondary transfer timing. Features.
According to a twelfth aspect of the present invention, in the color image forming apparatus according to any one of the ninth to eleventh aspects, when the sensor is installed near any one of a plurality of photosensitive drums, Are photosensitive drums for black.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described according to embodiments.
FIG. 7 is a diagram illustrating an example of an image forming apparatus to which the present invention is applied.
In the figure, reference numeral 100 denotes a copying apparatus main body, 200 denotes a paper feeding table on which the copying machine is mounted, 300 denotes a scanner mounted on the copying apparatus main body 100, and 400 denotes an automatic document feeder (ADF) further mounted thereon. Other symbols are referenced directly in the detailed description.
The image forming apparatus shown in FIG. 1 is a tandem type indirect transfer type electrophotographic apparatus.
[0020]
An endless intermediate transfer belt 10 as an intermediate transfer member is provided at the center of the copying apparatus main body 100.
In the illustrated example, the intermediate transfer belt 10 is wrapped around three support rollers 14, 15, 16 so as to be rotatable clockwise in FIG. Hereinafter, when the rotational movement of the belt is partially viewed, it is simply referred to as movement.
An intermediate transfer belt 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 among the three support rollers.
[0021]
In addition, on the intermediate transfer belt 10 stretched between the first support roller 14 and the second support roller 15 among the three support rollers, yellow (Y), cyan (C) ), Magenta (M), and black (K) are arranged side by side to constitute a tandem image forming apparatus 20.
An exposure device 21 is further provided on the tandem image forming device 20.
[0022]
On the other hand, a secondary transfer device 22 is provided on the side opposite to the tandem image forming device 20 with the intermediate transfer belt 10 therebetween. 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 presses the secondary transfer belt 24 against the third support roller 16 via the intermediate transfer belt 10. The image on the intermediate transfer belt 10 is transferred to a sheet.
A fixing device 25 for fixing a transferred image on a sheet 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.
[0023]
The above-described secondary transfer device 22 also has a sheet conveying function of conveying the sheet after image transfer to the fixing device 25. Of course, a transfer roller or a non-contact charger may be disposed 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, a sheet reversing device that reverses the sheet so as to record an image on both sides of the sheet in parallel with the above-described tandem image forming device 20 under the secondary transfer device 22 and the fixing device 25. 28.
[0024]
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.
[0025]
When a start switch (not shown) is pressed, when a document is set in the automatic document feeder 400, the document is fed and moved onto the contact glass 32. On the other hand, when an original is set on the contact glass 32, the scanner 300 is immediately driven. Next, the vehicle travels 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 a reading sensor 36 and read.
[0026]
In parallel with the reading of the document, one of the support rollers 14, 15, 16 is rotationally driven by a drive motor (not shown), and the other two support rollers are driven to rotate, thereby rotating the intermediate transfer belt 10. At the same time, the photoreceptor drums 40 are rotated in the individual image forming means 18 and are exposed and developed on the respective photoreceptor drums 40 using color-specific information of black, yellow, magenta, and cyan to form a single-color toner image. I do. Then, as the intermediate transfer belt 10 moves, those single-color toner images are sequentially transferred to form a composite color image on the intermediate transfer belt 10.
[0027]
On the other hand, in parallel with the image formation, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotated, and the sheet-like transfer material s is fed out from one of the paper feed cassettes 44 provided in the paper bank 43 in multiple stages. The sheet is separated one by one by a separation roller 45 and put into a sheet feeding path 46, conveyed by a conveying roller 47, guided to a sheet feeding 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.
[0028]
Then, the registration roller 49 is rotated in synchronization with the composite color image on the intermediate transfer belt 10, the sheet s is fed 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. At this time, the support roller 16 plays the role of the secondary transfer opposing roller, and will be referred to as necessary thereafter.
[0029]
The sheet s to which the image has been transferred is conveyed by the belt 24 and sent to the fixing device 25. The fixing device 25 applies heat and pressure to fix the transferred image. The sheet is discharged and stacked on the 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.
[0030]
On the other hand, the intermediate transfer belt 10 after the image transfer is removed by an intermediate transfer belt cleaning device 17 to remove the residual toner remaining on the intermediate transfer belt 10 after the image transfer, and the tandem image forming device 20 prepares for another image formation.
Here, the registration roller 49 is generally used with being grounded, but it is also possible to apply a bias for removing paper dust of the sheet s.
[0031]
Using this electrophotographic apparatus, black monochrome copies are often made. In this case, the intermediate transfer belt 10 is separated from the photosensitive drums 40Y, 40C, and 40M by means not shown. The driving of these photosensitive drums is temporarily stopped. Only the black photosensitive drum 40K contacts the intermediate transfer belt 10 to form and transfer an image.
[0032]
FIG. 1 is a partial perspective view of an intermediate transfer belt according to an embodiment of the present invention.
In the figure, reference numeral 65 denotes a tension roller, 70 denotes a linear scale, 71 denotes a sensor, 73 denotes a stopper for a convex roller provided on a side edge portion of the intermediate transfer belt 10, 74 denotes an image transfer area, and 75 denotes a sensor installation range. Are respectively shown.
The detailed configuration and operation around the intermediate transfer belt will be described with reference to FIG. In the following description, since only the intermediate transfer belt 10 is used as the belt, it is simply referred to as the belt 10.
[0033]
The linear scale 70 (hereinafter simply referred to as the scale 70) is provided on the surface of the belt 10 opposite to the image transfer surface (this surface is called the back surface for convenience) over the entire circumference in the rotational movement direction. The sensor 71 is a light-emitting / light-receiving sensor that is generally used. The sensor 71 is arranged in a predetermined range described below as far as the structurally closest position in the vicinity of the secondary transfer opposing roller 16. And the control device constitute a belt drive control means. Although the position of the sensor 71 is arranged on the upstream side in the belt moving direction with respect to the secondary transfer roller 23 in the figure, it may be arranged on the downstream side. In this way, when the upstream side and the downstream side are collectively referred to, for example, they are expressed as “near the secondary transfer roller”. Also, when one of the upstream side and the downstream side is specified without specifying the same, it is similarly expressed as “near”.
[0034]
FIG. 2 is a partially enlarged view and a sectional view of an intermediate transfer member according to another embodiment.
When viewed from the front of the image forming apparatus, the sensor 71 is installed in a predetermined range of a front 75a of the nip between the photosensitive drum 40 and the belt 10 or a rear 75b of the nip as shown in FIG. Is done. The predetermined ranges 75a and 75b are determined by the degree of waving of the belt side edge. The condition of the waving changes depending on the material and thickness of the belt used, the tension applied constantly, the curvature of the photosensitive drum or the support roller, the period of use, and the like, but when these conditions are determined, almost the same result is obtained.
[0035]
The undulation of the side edge of the belt varies between large and small in the same belt, and is fixed or movable with respect to the belt. Although it changes, it is almost fixed to the roller near the roller. The present invention takes advantage of this situation. Since the belt is affected by the curvature of the transfer roller 62 in a range where the belt 10 is in contact with the transfer roller 62, the belt is not suitable as a position where the sensor is installed. Immediately after the position where the belt 10 separates from the transfer roller 62, the effect of the regulation by the roller acts, so that the side edge of the belt 10 is stable and suitable as a position to be read by the sensor.
[0036]
Therefore, when the design conditions of the mechanism and the service period to be guaranteed are determined, it is practical to determine the predetermined range 75b by actually measuring the waving of the belt side edge under the conditions. Since the reading distance of the sensor 71, that is, the distance between the scale 70 and the sensor 71, has an allowable error that can guarantee the accuracy, even if the belt side edge away from the roller starts waving, the fluctuation width of the fluctuation is The predetermined range 75b is determined so that the distance does not exceed the allowable error even at the upper limit. The installation position of the sensor shown in FIG. 1 also defines a predetermined range by the same method. By doing so, even if the belt side edge is extended with time and starts to undulate, the reading distance of the sensor is always within the allowable error range, so that there is an effect that highly accurate belt drive control can be performed. is there.
[0037]
Immediately before the belt 10 contacts the transfer roller 62, the belt contacts the photosensitive drum 40. From the position where the belt 10 comes into contact with the drum to the position where it comes into contact with the transfer roller 62, the side edge of the belt is a very stable position. However, as described above, since the belt surface follows the curvature of the drum, It is not suitable as a scale reading position. However, in a certain range immediately before the belt 10 comes into contact with the photosensitive drum 40, the stable state of the side edge of the belt is almost the same as the above-mentioned predetermined range 75b, and the predetermined range 75a can be determined by the same method. . Since the photosensitive drum is configured to contact the side edge of the belt, the predetermined range 75a can be expected to be larger than the predetermined range 75b. Therefore, in addition to the above-described effects, the predetermined range 75a can have more room for the sensor installation position than the predetermined range 75b.
[0038]
As shown in FIG. 2B, a non-stop 73 is attached to the side edge of the belt 10 so that the belt does not come off the roller. A scale 70 is provided over the entire periphery of the belt at a position on the side edge that does not overlap with the non-stop 73.
At a distance a from the inner end 73a of the shift stopper 73 and at a distance b from the end of the image transfer area 74 which is a transfer voltage application area, that is, an end 62a of the transfer roller 62 as a transfer voltage application unit. The scale 70 is attached so as to be centered at a distance b from the sensor 70, and a sensor 71 is installed at a distance of a reading distance p. If the distances a and b are larger than one half of the width of the sensor 71, the sensor can be installed. However, in order to provide a margin, it is preferable that the distances are equal to the width of the sensor 71. The relationship between the distances a and b is not particularly limited, but may be the same. With such a configuration, the presence of the scale does not directly affect the image transfer, so that the image quality does not deteriorate.
[0039]
The secondary transfer opposing roller 16 is formed with a stepped portion 16 a for escape having a relation of thickness t of the scale 70 <end step c, and rotates inside the stopper 73. Although not shown, this configuration is common to the configuration shown in FIG. Similarly, some or all of the rollers that may come into contact with the scale 70 may be provided with a stepped portion for escape so that the scale 70 does not come into contact with the roller surface. By doing so, it is possible to prevent uneven stress from being applied to the belt at the time of roller contact due to the thickness of the scale 70.
[0040]
The clearance may be provided with a slight margin only at the position facing the scale 70, and the roller end may have the same diameter as the center. By doing so, when the belt 10 passes through the position of the secondary transfer opposing roller 16, the belt side edge is regulated to the roller end, so that the waving before and after the passage is reduced. Similarly, the non-stop 73 has the effect of suppressing the waving of the side edge of the belt 10.
The linear speed of the belt 10 is measured by the scale and the sensor, and the belt drive control means performs feedback or the like on the drive system of the drive roller 14 of the belt 10 to drive the belt with high positional accuracy. Since a specific control method is publicly known, a detailed description is omitted.
[0041]
FIG. 3 is a diagram for explaining another embodiment.
This embodiment is an overall configuration of a transfer apparatus according to an embodiment in which a tandem-type direct transfer type is used for a sheet-like transfer material such as paper, that is, a transfer conveyance belt is used instead of an intermediate transfer belt. The transfer conveyor belt must also ensure stable running, and the undulation of the side edges tends to reduce the scale reading accuracy. This is the same as the intermediate transfer belt. To When both the intermediate transfer belt and the transfer conveyance belt are collectively referred to as a transfer belt.
[0042]
A scale 70 is attached to the belt 10 and a sensor 71 is installed. The configuration in the depth direction is the same as that in FIG.
The installation position of the sensor 71 may be near any photosensitive drum. However, in the case of a configuration in which the intermediate transfer belt is separated from the photosensitive drums of the other three colors in order to form a black monochrome image, the sensor 71 is preferably installed near the photosensitive drum for black. . By doing so, stable belt drive control can always be performed in any image formation.
In addition to the vicinity of the photosensitive drum, the vicinity of the support rollers 14 and 15 can also be used as the installation position of the sensor 71.
[0043]
FIG. 4 is a diagram for explaining still another embodiment.
In the figure, reference numeral 80 denotes a belt driving roller, 81 denotes a driving motor, and 83, 84, 85, 86 denote supporting rollers.
This embodiment is an example of an intermediate transfer type having a one-drum configuration. Similarly, the configuration of the sensor / scale unit is the same as that of FIG. A transfer nip portion is provided between the support rollers 84 and 85.
The sensor 71 may be installed at any position before and after the transfer nip, that is, near the support rollers 84 and 85, near the support rollers 83 and 86, and near the belt drive roller 80.
Although not shown, if necessary, a one-drum direct transfer type image forming apparatus can be easily configured.
[0044]
In the description so far, the case where the sensor 71 is installed at only one position has been described. However, the sensor 71 can be provided at a plurality of positions as needed. For example, at the timing of primary transfer at which an image is transferred from the photosensitive drum to the intermediate transfer belt, belt driving is controlled by a sensor provided near the primary transfer device, that is, near the photosensitive drum, and at the timing of secondary transfer. The belt drive control is shifted to a secondary transfer device, that is, a sensor provided near the secondary transfer roller. By doing so, control can be performed at a position very close to the position where the most stable running is required, so that more precise control can be performed.
[0045]
【The invention's effect】
According to the present invention, the reading distance of the sensor for reading the scale falls within the allowable error range even if the side edge of the transfer belt undulates due to a change over time, so that the belt driving speed can be adjusted with high accuracy. By controlling, it is possible to reduce speed unevenness.
[Brief description of the drawings]
FIG. 1 is a partial perspective view of an intermediate transfer member according to an embodiment of the present invention.
FIG. 2 is a partially enlarged view and a cross-sectional view of an intermediate transfer member according to an embodiment of the present invention.
FIG. 3 is a diagram for explaining another embodiment.
FIG. 4 is a diagram for explaining still another embodiment.
FIG. 5 is a diagram illustrating a tandem image forming apparatus of a direct transfer type.
FIG. 6 is a diagram illustrating a tandem image forming apparatus of an indirect transfer type.
FIG. 7 is a diagram illustrating an example of an image forming apparatus to which the present invention is applied.
[Explanation of symbols]
10 transfer belt 14 support roller 15 support roller 16 support roller (secondary transfer opposing roller)
62 Transfer roller 70 Scale 71 Sensor 73 Non-stop 74 Image transfer area

Claims (12)

At least a part thereof is pressed by the transfer roller and is in direct or indirect contact with the photosensitive drum, and is formed on an endless transfer belt supported by a plurality of support rollers, and is formed over the entire back surface of the transfer belt in the feeding direction. An image transfer apparatus having a belt drive control means including a linear scale and a sensor for reading the linear scale, wherein the installation position of the sensor is a predetermined range immediately before a position where the transfer belt contacts the photosensitive drum. Image transfer device. At least a part thereof is pressed by the transfer roller and is in direct or indirect contact with the photosensitive drum, and is formed on an endless transfer belt supported by a plurality of support rollers, and is formed over the entire back surface of the transfer belt in the feeding direction. In the image transfer apparatus having a linear scale and a belt drive control unit including a sensor for reading the linear scale, the installation position of the sensor is a predetermined range immediately after the transfer belt is separated from the transfer roller. Image transfer device. An endless transfer belt at least part of which is in direct or indirect contact with the photosensitive drum and is supported by a plurality of support rollers; a linear scale formed over the back surface of the transfer belt over the entire circumference in the feed direction; In the image transfer apparatus having a belt drive control unit including a sensor for reading the image, the sensor is installed at a position immediately before the transfer belt comes into contact with any one of the plurality of support rollers or immediately after a position at which the transfer belt separates from the roller. An image transfer device characterized by being within a predetermined range. An endless transfer belt at least part of which is in direct or indirect contact with the photosensitive drum and is supported by a plurality of support rollers; a linear scale formed over the back surface of the transfer belt over the entire circumference in the feed direction; In the image transfer apparatus having a belt drive control unit including a plurality of sensors for reading the image, the installation position of the plurality of sensors is a predetermined range immediately before a position where the transfer belt comes into contact with the photoconductor drum, and the transfer belt is A predetermined range immediately after the position away from the roller, and a predetermined range immediately before the transfer belt comes into contact with any one of the plurality of support rollers or immediately after the position away from the roller. An image transfer device, comprising: 5. The image transfer device according to claim 1, wherein an installation position of the linear scale on a back surface of the transfer belt is outside a transfer voltage application region in a depth direction of the transfer voltage application unit with respect to the transfer belt. An image transfer device, comprising: The image transfer apparatus according to claim 1, wherein a part of a roller supporting the transfer belt or a part of all rollers facing the linear scale has a recessed step, and An image transfer device, which is configured so as not to contact a linear scale. An image transfer device according to any one of claims 1 to 6, one photoconductor drum, an optical writing device that repeatedly forms a latent image on the photoconductor drum based on color-specific information, and writes the latent image. A plurality of developing devices for visualizing a toner image of a color corresponding to information; and a secondary transfer device, wherein the image transfer device sequentially transfers the toner images to the transfer belt, A color image forming apparatus, wherein the toner image is transferred to a sheet-like transfer material by a transfer device. An image transfer device according to any one of claims 1 to 6, one photoconductor drum, an optical writing device that repeatedly forms a latent image on the photoconductor drum based on color-specific information, and writes the latent image. A plurality of developing devices for visualizing a toner image of a color corresponding to information, wherein the image transfer device temporarily fixes and supports a sheet-shaped transfer material on the transfer belt; Is sequentially transferred to the transfer material. An image transfer device according to claim 1, a plurality of photosensitive drums provided for each color, an optical writing device for forming a latent image on each of the plurality of photosensitive drums, and each of the latent images. The image transfer device includes a plurality of developing devices for visualizing the image as a toner image and a secondary transfer device. The image transfer device sequentially transfers the toner image to the transfer belt, and the secondary transfer device A color image forming apparatus wherein a toner image is transferred onto a sheet-like transfer material. An image transfer device according to claim 1, a plurality of photosensitive drums provided for each color, an optical writing device for forming a latent image on each of the plurality of photosensitive drums, and each of the latent images. A plurality of developing devices for visualizing the image as a toner image, and a secondary transfer device, wherein the image transfer device transfers the toner image while the transfer belt conveys a sheet-like transfer material. A color image forming apparatus, which is sequentially transferred to a material. 10. The color image forming apparatus according to claim 7, wherein the sensors are provided at least at two positions near the photosensitive drum and near the secondary transfer device, and are provided near the photosensitive drum at a primary transfer timing. A driving device for controlling the driving of the transfer belt by using a sensor provided in the vicinity of the secondary transfer device at a secondary transfer timing. . 12. The color image forming apparatus according to claim 9, wherein when the sensor is installed near any one of the plurality of photosensitive drums, the photosensitive drum is a black photosensitive drum. A color image forming apparatus.

Images