JP2004035200A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently adjust deviation of a belt with minimum number of rollers. <P>SOLUTION: The image forming device has an image carrier and an endless shape belt body suspended between the plurality of rollers. The outside roller suspending the belt body from the outside of the belt body is provided on the more upstream position than the upstream roller positioned upstream in the moving direction of the belt body of the roller forming the face opposed to the image carrier, and the alignment of the outside roller is adjustable. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus employing an electrostatic recording method, an electrophotographic recording method, or the like, and more particularly to an image forming apparatus having a plurality of image forming units and an intermediate transfer member.
[0002]
[Prior art]
Conventionally, various types of color image forming apparatuses have been proposed. One of them is provided with an image forming section for each color developer, and in the image forming section, a visible image of each color is formed on a photosensitive drum as an image carrier by a known image forming process. There is an electrophotographic color image forming apparatus that sequentially transfers a developed image onto a conveyer, which is an endless circulating motion, a so-called intermediate transfer belt, and collectively transfers the image onto a transfer material supplied from the outside and then fixes the image to obtain a color image. .
[0003]
In such an intermediate transfer type image forming apparatus, the intermediate transfer belt is generally suspended from inside by a plurality of rollers. However, these intermediate transfer belts have a problem in that the intermediate transfer belt shifts due to a change in the alignment of rollers due to a distortion of the apparatus main body, that is, a so-called misalignment.
[0004]
As a means for correcting the belt deviation, for example, there is a method of detecting the amount of deviation of the belt by detecting the position of the belt end, and correcting the alignment of one of the rollers described above based on this information. Be taken. According to this method, the mechanical stress is reduced and the life of the belt is reduced as compared with a method in which the rib-shaped rubber portion attached to the belt edge is regulated, or the belt edge is regulated by directly abutting the flange or the like. It can be greatly improved.
[0005]
On the other hand, there has been proposed a configuration in which an outer roller for suspending the belt body from the outer peripheral side of the belt body is provided for the purpose of improving the degree of freedom of unit arrangement in the apparatus and reducing the belt biasing force (JP-A-2001-2001). -117374).
[0006]
FIG. 7 is a cross-sectional view illustrating an intermediate transfer unit using the above-described conventional example. The intermediate transfer belt 31 is suspended from the inside by a drive roller 32, a secondary transfer inner roller 34, a steering roller 133, and a tension roller 137, and is suspended from the outside by an outer roller 180. By providing the outer roller 180, the intermediate transfer belt can be formed with a smaller cross section than a cross section of the intermediate transfer belt formed by a tangent line (dashed line in the drawing) connecting the secondary transfer inner roller 34 and the steering roller 133. The effect of being able to form is obtained, the degree of freedom for arranging other units can be increased, and as a result, there is an advantage that the apparatus main body can be made small.
[0007]
[Problems to be solved by the invention]
The tension roller 137 is configured to be movable only in the horizontal direction because it is necessary to maintain the primary transfer plane A facing the photosensitive drum of each color in parallel with the drum surface. It is biased to the left. Therefore, a steering roller 133 is separately provided, and the alignment of the belt is adjusted in the direction of arrow D in the drawing to adjust the deviation of the belt.
[0008]
However, in the above-described configuration, since the steering roller 133 needs to be separately provided in addition to the tension roller 137, the number of rollers increases, the cost increases, and the configuration is complicated.
[0009]
Another problem is that there is a difficulty in designing the arrangement of the cleaning device for the intermediate transfer belt. In other words, if the cleaning device is to be disposed at the opposite portion of the tension roller 137, a sufficient space cannot be obtained, and the steering roller 133 needs to be further disposed to the right in the drawing. On the other hand, if the steering roller 133 is arranged in the right direction in the figure, the amount of engagement with the intermediate transfer belt 31 decreases, and the response to alignment adjustment decreases.
[0010]
Therefore, an object of the present invention is to efficiently adjust the deviation of the belt with a minimum number of rollers.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a typical configuration of the present invention is an image forming apparatus having an image carrier and an endless belt suspended between a plurality of rollers, wherein the image carrier is opposed to the image carrier. An outer roller for suspending the belt body from outside the belt body is provided at a further upstream position of an upstream roller positioned upstream of the roller forming the surface to be moved in the belt body moving direction, and the alignment of the outer roller can be adjusted. It is characterized by doing.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
The image forming apparatus of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view of a main part of the image forming apparatus. The illustrated image forming apparatus is a color image forming apparatus in which a plurality of image forming units are arranged in parallel. The illustrated color image forming apparatus is provided with an image output unit 1P. The image output unit 1P is roughly divided into an image forming unit 10 (four stations a, b, c, and d are arranged side by side. The configuration is the same), and the control unit includes a feeding unit 20, an intermediate transfer unit 30, a fixing unit 40, and a control board 70.
[0013]
Here, each unit will be described in detail. In the image forming section 10, photosensitive drums 11a, 11b, 11c and 11d as image carriers rotatably driven in the direction of the arrow shown in the figure are supported at their centers and opposed to the outer peripheral surfaces of the photosensitive drums 11a to 11d. The primary charger 12 (12a, 12b, 12c, 12d), the optical system 13 (13a, 13b, 13c, 13d), and the developing device 14 (14a, 14b, 14c, 14d) are arranged in the rotation direction. .
[0014]
In the primary chargers 12a to 12d, charges of a uniform charge amount are applied to the surfaces of the photosensitive drums 11a to 11d, and light beams such as laser beams modulated by optical systems 13a to 13d according to recording image signals are exposed. The photosensitive drums 11a to 11d are exposed to light to form electrostatic latent images on the respective photosensitive drums 11a to 11d. Then, each electrostatic latent image is visualized as a toner image by the developing devices 14a to 14d storing the developers (toners) of four colors of yellow, cyan, magenta, and black, respectively. Note that, on the downstream side of the image primary transfer areas Ta, Tb, Tc, and Td for transferring the visualized toner image to the intermediate transfer belt 31 as a belt body, the photosensitive drums 11a to 11d are not transferred to the recording material P and are not transferred. The toner remaining above is scraped off by the cleaning device 15 (15a, 15b, 15c, 15d), and the surfaces of the photosensitive drums 11a to 11d are cleaned. Through the processes described above, image formation by each toner is sequentially performed.
[0015]
On the other hand, the feeding unit 20 includes a cassette 21 (21a, 21b) for storing the recording material P and a manual tray 27, and a pickup for feeding the recording material P one by one from the cassettes 21a, 21b or the manual tray 27. The rollers 22a, 22b, 26, the feed roller pair 23 for feeding the recording material P sent from each of the pickup rollers 22a, 22b, 26 to the registration rollers 25a, 25b, the feed guide 24, and the image forming unit 10 It is composed of registration rollers 25a and 25b for sending the recording material P to the secondary transfer area Te at the timing of image formation.
[0016]
The intermediate transfer unit 30 has an intermediate transfer belt 31 as an intermediate transfer body. The intermediate transfer belt 31 has a drive roller (downstream roller) 32 for transmitting a driving force to the intermediate transfer belt 31, and a spring (not shown). A tension roller (upstream roller) 33 that applies an appropriate tension to the intermediate transfer belt 31 by the urging force of the elastic member), a secondary transfer inner roller 34 that faces the secondary transfer area Te with the intermediate transfer belt 31 interposed therebetween, and It is wound around an outer roller 80 provided outside the intermediate transfer belt 31 between the secondary transfer area Te and the primary transfer area Td in the direction (arrow B direction). As a material of the intermediate transfer belt 31, for example, PET (polyethylene terephthalate), PVdF (polyvinylidene fluoride), or the like is selected.
[0017]
A primary transfer plane A is formed between the drive roller 32 and the tension roller 33. The drive roller 32 is coated with a rubber (urethane or chloroprene) having a thickness of several mm on the surface of a metal roller, and is formed with the intermediate transfer belt 31. Slip is prevented. The drive roller 32 is driven to rotate by a pulse motor (not shown).
[0018]
In the primary transfer areas Ta to Td where the respective photoconductor drums 11a to 11d and the intermediate transfer belt 31 face each other, primary transfer devices 35a to 35d as primary transfer means are arranged behind the intermediate transfer belt 31. Then, the secondary transfer device 36 is disposed so as to face the secondary transfer inner roller 34, and a secondary transfer area Te is formed.
[0019]
A cleaning device 50 for cleaning the image forming surface of the intermediate transfer belt 31 is disposed downstream of the secondary transfer area Te on the intermediate transfer belt 31. The cleaning device 50 cleans the cleaning blade 51 and the waste toner. It comprises a waste toner box 52 to be stored. The material of the cleaner blade 51 is polyurethane rubber or the like.
[0020]
The fixing unit 40 includes a fixing roller 41a having a heat source such as a halogen heater therein, a pressing roller 41b pressed against the fixing roller 41a (the pressing roller 41b may also include a heat source), a fixing roller. A guide 43 for guiding the recording material P to the nip portion between the pressure roller 41a and the pressure roller 41b, an inner discharge roller 44 for further guiding the recording material P discharged from the fixing roller 41a and the pressure roller 41b outside the apparatus, It is composed of a discharge roller 45 and the like. The control device includes a control board 70 for controlling the operation of the mechanism in each unit, a motor drive board (not shown), and the like.
[0021]
Next, the operation of the present color image forming apparatus will be described. When the image forming operation start signal is issued, first, the recording materials P are sent out one by one from the cassette 21a by the pickup roller 22a. Then, the recording material P is guided between the feeding guides 24 by the feeding roller pair 23 and is conveyed to the registration rollers 25a and 25b. At this time, the registration rollers 25a and 25b are stopped, and the leading end of the recording material P strikes the nip. Thereafter, the registration rollers 25a and 25b start rotating at the timing when the image forming unit 10 starts forming an image. The rotation timing of the registration rollers 25a and 25b is set such that the recording material P and the toner image primarily transferred from the image forming unit 10 onto the intermediate transfer belt 31 exactly coincide with each other in the secondary transfer area Te. ing.
[0022]
On the other hand, in the image forming section 10, when the image forming operation start signal is issued, the toner image formed on the photosensitive drum 11d, which is the most upstream in the rotation direction of the intermediate transfer belt 31 through the above-described process, becomes high. The primary transfer is performed on the intermediate transfer belt 31 in the primary transfer area Td by the primary transfer device 35d to which the voltage is applied. Then, the toner image primarily transferred onto the intermediate transfer belt 31 is transported to the next primary transfer area Tc, where image formation is performed with a delay of the toner image transport time between the image forming units 10. Thus, the next toner image is transferred by aligning the resist on the previous image. Hereinafter, the same steps are repeated, so that the four color toner images are primarily transferred onto the intermediate transfer belt 31.
[0023]
Thereafter, when the recording material P enters the secondary transfer area Te and comes into contact with the intermediate transfer belt 31, a high voltage is applied to the secondary transfer device 36 in synchronization with the passage timing of the recording material P. Then, the four-color toner images formed on the intermediate transfer belt 31 by the above-described process are transferred onto the surface of the recording material P, and the recording material P on which the toner images have been transferred is fixed by the conveyance guide 43 to the fixing roller of the fixing unit 40. It is accurately guided to the nip portion between the pressure roller 41a and the pressure roller 41b. Then, the toner image is fixed on the surface of the recording material P by the heat of the roller pair 41 a and 41 b of the fixing unit 40 and the pressure of the nip, and the recording material P on which the toner image is fixed is an inner discharge roller 44 and an outer discharge roller 45. And discharged out of the machine.
[0024]
Next, a characteristic configuration of the present embodiment will be described. FIG. 2 is a diagram showing a configuration of the intermediate transfer unit 30 employing the outer roller 80. As described above, the intermediate transfer belt 31 is suspended from the inside by the drive roller 32, the secondary transfer inner roller 34 and the tension roller 33 as the secondary transfer means, and from the outside by the outer roller 80. Here, the tension roller 33 is urged leftward in the figure by a spring member (not shown) to apply an appropriate tension to the intermediate transfer belt 31. The outer roller 80 has a rear end portion supported by a bearing (not shown) in the drawing, and is configured so that alignment can be adjusted by moving a front end portion in the direction of arrow C.
[0025]
FIG. 3 is a perspective view illustrating an alignment adjustment mechanism. A front shaft end 80a of the outer roller 80 is rotatably supported by a long bearing 83 fixed to a side plate (not shown). The long bearing 83 is provided with a long hole that fits in only one direction with respect to the shaft end portion 80a and allows movement only in the direction of arrow C in FIG. More outside, bearing 82 is fitted movably in an arrow R ₁ and R ₂ direction (arrow C direction parallel). On the other hand, a steering motor 81 is fixed to a side plate (not shown). An output shaft 81 a provided with a lead is attached to a distal end of the steering motor 81, and the distal end of the output shaft 81 a contacts a bearing 82. A spring member (not shown) is provided on the opposite side of the bearing 82, and presses the bearing 82 against the output shaft 81a.
[0026]
Therefore, when the steering motor 81 is rotated in the arrow M ₁ direction by a predetermined number of steps, the output shaft tip end portion of 81a is moved in the arrow L ₁ direction by a predetermined amount, also by a predetermined amount the bearing 82 at the same time the arrow L ₁ direction Go to Conversely, when the steering motor 81 is rotated in the arrow M ₂ direction by a predetermined number of steps, the output shaft tip end portion of 81a is moved in the arrow L ₂ direction by a predetermined amount, at the same time bearing 82 by a predetermined amount arrow L ₂ Move in the direction. In this way, it is possible to move the front shaft end portion 80a of the outer roller 80 in the direction of the arrow R ₁ or R _2, as a result, it is possible to adjust the alignment of the outer roller 80.
[0027]
In order to control the direction in which the intermediate transfer belt 31 shifts, the alignment of the outer roller 80 may be adjusted. Moving the front shaft end portion 80a of the outer roller 80 in the direction of the arrow R _1, the intermediate transfer belt 31 causes a force close to the direction of the arrow S _1, arrows a front shaft end portion 80a of the outer roller 80 R ₂ moving of the direction, the intermediate transfer belt 31 results in a force close to the direction of the arrow S _2. If the alignment of the outer roller 80 is adjusted using this characteristic, a biasing force is positively generated in a direction to offset the biasing force generated on the intermediate transfer belt 31 due to the distortion of the apparatus main body or the like. it is possible to travel without departing from the transfer belt 31 from the predetermined position X _0.
[0028]
A belt edge sensor 92 as a detecting unit including a light emitting unit 90 and a light receiving unit 91 is provided on the inner side of the primary transfer plane A that receives the transfer from the photosensitive drum 11 in the drawing. FIG. 4 is a top view illustrating the operation of the belt edge sensor 92. The light receiving section 91 is provided with a slit 91a. A predetermined voltage is output by detecting the amount of light that has passed through the slit 91a among the light emitted from the light emitting unit 90 (not shown in FIG. 4, see FIG. 2).
[0029]
FIG. 6A is a diagram illustrating the relationship between the amount of displacement of the edge 31 a of the intermediate transfer belt 31 and the output voltage of the belt edge sensor 92. Now, considering the case where the edge portion 31a is moved to X ₁ by shifting from the predetermined position X _0, the amount of the edge portion 31a blocks the slit 91a is reduced, so that the amount of light detected by the light receiving unit 91 is increased I do. At this time, the belt edge sensor 92, the voltages V ₁ is output. Based on the information of the output voltage V _1, the control device 95 shown in FIG. 5, the number of drive pulses of the steering motor 81 is determined.
[0030]
FIG. 6B is a diagram showing the relationship between the output voltage of the belt edge sensor 92 and the number of drive pulses of the steering motor 81. When voltage V ₁ is output from belt edge sensor 92, control device 95 determines P ₁ as the number of driving pulses for steering motor 81. The drive pulse signal _{P 1} is transmitted to the steering motor 81, steering motor 81 is rotated in the direction of the arrow _{M 1} pulse number _{P 1.} Accordingly, as described above, the tip portion of the output shaft 81a of the steering motor 81 is moved in the arrow L ₁ direction by a predetermined amount, as a result, the front side of the alignment of the outer roller 80 is displaced in the direction of R ₁ and the intermediate transfer belt 31 moves in the direction of the arrow S _1. Thus, the intermediate transfer belt 31 is returned to the predetermined position _{X 0.}
[0031]
As described above, in the present invention, since the alignment of the outer roller 80 is configured to be adjustable, an intermediate transfer belt having a small cross-sectional area can be configured with a minimum number of rollers, and the deviation of the belt can be corrected. It is. Further, since the outer roller 80 is provided between the tension roller 33 as the upstream roller and the inner secondary transfer roller 34 as the secondary transfer means, the degree of design freedom for other components is increased, and as a result Can be made smaller. Further, by having a control device 95 as a control means for operating a steering motor 81 as an alignment changing means of the outer roller 80 based on information of the belt end detecting means, the deviation of the intermediate transfer belt 31 is automatically adjusted. It is possible to make corrections.
[0032]
(Other embodiments)
The alignment adjustment mechanism and the belt edge detection means described in the above-described embodiment are merely examples, and do not limit the present invention. For example, the alignment adjusting mechanism may use a cam follower to shift the shaft end position, or the belt detecting means may detect a shift amount of an arm abutting on a belt edge. It may be.
[0033]
Further, in the above-described embodiment, the configuration in which the downstream roller is driven to apply tension to the upstream roller has been described. However, even in the configuration in which the upstream roller is driven to apply tension to the downstream roller, the effects of the present invention can be obtained. Is similarly obtained.
[0034]
【The invention's effect】
As described above, according to the present invention, in an image forming apparatus having an image carrier and an endless belt suspended between a plurality of rollers, a roller forming a surface opposed to the image carrier is provided. An outer roller for suspending the belt body from outside the belt body is provided at a further upstream position of an upstream roller located upstream in the belt body moving direction, and the outer roller is configured to be capable of adjusting the alignment of the outer roller. With the minimum number of rollers, the deviation of the belt can be adjusted efficiently. In addition, since the number of rollers for suspending the belt body can be configured with a minimum number, the degree of freedom in designing the arrangement of the cleaning device for the intermediate transfer belt can be increased.
[Brief description of the drawings]
FIG. 1 is a sectional view of a main part of an image forming apparatus.
FIG. 2 is a diagram showing a configuration of an intermediate transfer unit employing an outer roller.
FIG. 3 is a perspective view illustrating an alignment adjustment mechanism.
FIG. 4 is a top view illustrating the operation of the belt edge sensor.
FIG. 5 is a diagram illustrating the operation of the control device.
FIG. 6A is a diagram illustrating a relationship between a positional displacement amount of an edge portion of an intermediate transfer belt and an output voltage of a belt edge sensor.
FIG. 3B is a diagram illustrating a relationship between an output voltage of the belt edge sensor and the number of driving pulses of the steering motor.
FIG. 7 is a cross-sectional view illustrating an intermediate transfer unit in a conventional example.
[Explanation of symbols]
A: Primary transfer plane, P: Recording material, Ta to Td: Image primary transfer area,
Te: secondary transfer area,
1P: Image output unit, 10: Image forming unit, 11: Photoconductor drum,
12: primary charger, 13: optical system, 14: developing device,
15 ... cleaning device, 20 ... feeding unit, 21 ... cassette,
22a: Pickup roller, 22b: Pickup roller,
23: feed roller pair, 24: feed guide,
25a: a registration roller; 25b: a registration roller;
26: pickup roller 27: manual feed tray,
30: Intermediate transfer unit, 31: Intermediate transfer belt,
31a: edge portion 32: drive roller 33: tension roller
34: secondary transfer inner roller 35: primary transfer device
36: secondary transfer device, 40: fixing unit, 41a: fixing roller,
41b: pressure roller, 43: conveyance guide, 44: internal discharge roller,
45: outside discharge roller, 50: cleaning device,
51 ... cleaner blade, 52 ... waste toner box,
70: control board 80: outer roller 80a: shaft end
81: steering motor, 81a: output shaft, 82: bearing,
83 ... long bearing, 90 ... light emitting part, 91 ... light receiving part,
91a: slit, 92: belt edge sensor, 95: control device

Claims (5)

In an image forming apparatus having an image carrier and an endless belt suspended between a plurality of rollers,
An outer roller for suspending the belt body from outside the belt body is provided at a further upstream position of an upstream roller located upstream of the roller forming the surface facing the image carrier in the belt body moving direction, and An image forming apparatus, wherein the alignment is adjustable. The belt body is an intermediate transfer belt,
Primary transfer means for transferring the toner image on the image carrier to the intermediate transfer belt,
Secondary transfer means for transferring the toner image on the intermediate transfer belt to a recording material,
The image forming apparatus according to claim 1, wherein the outer roller is provided between the upstream roller and the secondary transfer unit. Detecting means for detecting an end of the belt body,
Alignment changing means for changing the alignment of the outer roller,
The image forming apparatus according to claim 1, further comprising: a control unit that operates the alignment changing unit based on information of the detection unit. The image forming apparatus according to claim 1, wherein a cleaning device that cleans the belt body is attached to a portion facing the upstream roller. At least one of the upstream roller or the downstream roller located downstream of the roller forming the surface facing the image carrier in the belt body moving direction can be moved in parallel with the surface of the belt body facing the image carrier. The image forming apparatus according to claim 1, further comprising an elastic member configured to urge the belt body in a direction in which tension is applied to the belt body.

Images