JP4590215B2 - Belt device - Google Patents

Description

  The present invention relates to a belt device, and more particularly to a belt device having a meandering prevention function in a transfer belt of an image forming apparatus.

  In image forming apparatuses, particularly color image forming apparatuses such as color copiers and color printers, a multi-stage drum type (tandem type) capable of high-speed processing is becoming more popular than a single drum type. In this tandem type color image forming apparatus, image forming units are arranged side by side in, for example, magenta, yellow, cyan, and black colors in the paper transport direction.

  The image forming portions for each color are arranged to face the transfer belt, which is an image carrier, and the toner images sequentially formed by the image forming portions for each color are transferred to the transfer belt by the primary transfer means. The transfer belt is wound endlessly on a plurality of rollers, and a toner image on the transfer belt is transferred to a transfer material by a secondary transfer unit. On the other hand, the transfer material is conveyed from the paper feed unit to the transfer position via the registration roller pair.

  In such an image forming process, the transfer belt wound endlessly on a plurality of rollers may be wavy or meandering in the running direction. When meandering occurs on the transfer belt, image distortion, transfer deviation of each color, and the like occur, such as an essentially perpendicular image becoming a parallelogram image. Further, when the transfer belt is wavy, image deformation, transfer omission, and the like occur.

In order to accurately superimpose the images of the respective colors and obtain a high-quality image with no image distortion, it is necessary to prevent the transfer belt from meandering and undulation and to stably drive and convey the transfer belt. Therefore, a technique for correcting the meandering by tilting the steering roll in conjunction with the meandering of the belt has been proposed. There has also been proposed a technique in which a plurality of meandering correction rollers are provided and meandering correction is performed by changing the meandering correction roll according to the meandering direction of the belt.
Japanese Patent Laid-Open No. 9-60693

  However, in the structure described in Japanese Patent Laid-Open No. 9-60693, it is necessary to add a meandering correction roll, which not only complicates the mechanical structure but also leads to an increase in the cost of the entire apparatus.

  Therefore, an object of the present invention is to provide a belt device that can prevent the meandering of the belt with a simple structure.

In order to achieve the above object, the present invention provides:
An endless belt stretched between a driving roller and a driven roller ;
A tension roller that extends along the width direction of the endless belt and adjusts the tension of the endless belt ;
Meander detection means for detecting meandering in the running direction of the endless belt ;
Tension adjusting means for adjusting the pressure contact force with respect to the endless belt at both axial ends of the tension roller ;
Control means for operating the tension adjustment means to correct the meandering of the endless belt based on the detection result of the meander detection means ;
The belt apparatus provided with,
The tension adjusting means is supported in parallel with the pair of bearings that support both ends of the tension roller in the axial direction and the axial direction of the tension roller so that the central portion in the axial direction can swing around a fulcrum. A pressure adjusting plate, a spring provided between the axial ends of the pressure adjusting plate and the bearing, and for urging the bearing in a direction in which the tension roller is pressed against the endless belt, and an attachment of the spring It includes a pressure adjustment mechanism that adjusts the power,
The pressure adjusting mechanism includes a pair of moving bodies having inclined surfaces that contact both axial ends of the pressure adjusting plate, and a moving mechanism that moves the moving body in the axial direction of the tension roller,
The control means controls the tension adjusting means so as to increase a pressure contact force with respect to the endless belt on a side opposite to the side where the endless belt is biased, in both axial ends of the tension roller. Features.

  In this apparatus, when the endless belt stretched between the driving roller and the driven roller is driven by the driving roller, the tension of the belt is maintained by the tension roller. If the belt meanders for some reason, such as the belt processing accuracy or the deviation of the cylindricity of the roller, the meandering occurrence of the belt and the amount of meandering are detected by the meander detection means. Based on the detection result, the belt tension adjusting means is operated by the control means, and the belt meander is corrected by adjusting the tension of the belt on the side where the meandering occurs.

  Therefore, it is possible to correct the meandering of the belt with a simple structure without separately providing a meandering correction roll or the like, and it is possible to maintain the belt running stability.

  This apparatus employs a line sensor as meander detection means, and can detect the meandering accurately by proportionally continuously detecting the edges of the transfer belt.

  In this device, the tension roller adjusts the pressure contact force of the belt at both ends of the belt by adjusting the spring biasing force that biases the bearings at both ends of the tension roller as a tension adjusting means. It has become. Therefore, the tension at both ends of the tension roller can be adjusted with a simple mechanism.

  In this apparatus, when it is necessary to adjust the tension at both ends of the tension roller, the vertical position of the both ends of the pressure adjusting plate provided below the tension roller is changed by a turning mechanism. The pressure adjusting plate swings up and down at both ends corresponding to the pair of bearings around a fulcrum provided at the axial center of the tension roller, so that the pressure adjusting plate and the bearings at both ends of the tension roller The distance is changed. In addition, since a spring is provided between the pressure adjustment plate and the pair of bearings, if the distance between the pressure adjustment plate and the bearings at both ends of the tension roller is changed, the springs at both ends of the tension roller are changed. The biasing force can be adjusted.

  In this apparatus, when the moving body is moved in the axial direction of the tension roller by the moving mechanism, the inclined surface of the moving body is brought into contact with the lower surfaces of the both ends of the pressure adjusting plate, and the vertical positions of the both ends of the pressure adjusting plate are Can be changed.

  In this device, meandering occurs while the belt is running. For example, if the belt runs with a bias toward the right side of the running direction, the tension adjusting means is controlled by the control means so that the pressure contact force of the tension roller to the left belt is increased. To do. Then, the tension on the left side of the tension roller is increased, the belt is moved to the left side where the tension is higher, and the meandering of the belt is corrected.

  In an image forming apparatus employing a transfer belt, the toner image formed by the image forming unit is transferred to the transfer belt, and the toner image on the transfer belt is transferred to a transfer material. If meandering occurs in the transfer belt in the process of transferring the toner image to the transfer belt or the process of transferring the toner image on the transfer belt to the transfer material, image distortion or transfer deviation occurs. Therefore, by adopting the present invention for the transfer belt of the image forming apparatus, a high-quality formed image can be obtained.

  In the present invention, the meandering of the belt can be prevented with a simple structure by adjusting the tension at both ends of the tension roller of the endless belt.

  FIG. 1 is a diagram showing a configuration of a main part of a main body of a tandem type color printer 1 in which an embodiment of the present invention is adopted. The color printer 1 includes an image forming unit 2 for forming a color image, a transfer unit 3 that transfers a toner image formed by the image forming unit 2 to a transfer material, a paper feeding unit 4 that supplies the transfer material, A registration roller unit 5 for synchronizing transfer material conveyance and image formation, a transfer material conveyance guide mechanism 6 for guiding the transfer material reaching the registration roller unit 5 to a transfer position, and a toner image transferred to the transfer material A fixing unit 7 for fixing and a paper discharge unit 8 for discharging the transfer material are provided.

  The image forming unit 2 is located almost in the center of the color printer, and is provided with four process units 21a, 21b, 21c, and 21d corresponding to four colors of black, yellow, cyan, and magenta. Primary drums that transfer the toner images formed on the surfaces of the photosensitive drums 22a, 22b, 22c, and 22d on which the electrostatic latent images are formed, and the photosensitive drums 22a, 22b, 22c, and 22d. It includes transfer rollers 23a, 23b, 23c, and 23d, and a transfer belt 24 as an image carrier.

  Here, since the internal configurations of the four process units corresponding to the four colors of black, yellow, cyan, and magenta are the same, the configuration will be described using the black process unit 21a as an example. As shown in FIG. 2, a charging device 101a, an exposure device 102a, a developing device 103a, a cleaning device 104a, and a charge eliminating device 105a are arranged around the photosensitive drum 22a of the black process unit 21a.

  The transfer belt 24 is disposed above the photosensitive drums 22a, 22b, 22c, and 22d, and is disposed apart from the driving roller 25a and a driving roller 25a that is rotationally driven by driving means such as a motor (not shown). Between the driven roller 25c and the driven roller 25c. A tension roller 28 is provided between the driving roller 25a and the driven roller 25c. The primary transfer rollers 23a, 23b, 23c, and 23d are urged so as to be in pressure contact with the photosensitive drums 22a, 22b, 22c, and 22d via the transfer belt 24, respectively. 22a, 22b, 22c and 22d are in pressure contact. Further, an intermediate transfer cleaning device 26 for cleaning toner and the like attached to the transfer belt 24 is provided at a position facing the driven roller 25c.

  The paper feed unit 4 is provided below the image forming unit 2, and includes a cassette 41 for storing a transfer material, pickup rollers 42 and 43 for taking out the stored paper, and a conveyance path for the paper one by one. A pair of paper feed rollers 44 and 45 are provided for feeding to the printer. The transfer material conveyed from the paper supply unit 4 is conveyed to the transfer position through the vertical conveyance path 46. A pair of registration rollers 5a and 5b is provided on the downstream side of the vertical conveyance path 46 in the conveyance direction. The pair of resist rollers 5a and 5b waits for the transfer material conveyed from the paper feeding unit 4 and is placed on the transfer belt 24. The image is sent to the transfer position A in synchronization with image formation.

  The fixing device 7 is provided above the transfer unit 3 and melts and fixes the toner transferred onto the transfer material. The fixing device 7 includes a heating roller 7a having a built-in heater and a pressure roller 7b that is in pressure contact with the heating roller 7a. The toner image is heat-fixed. Discharge rollers 81a and 81b are provided above the fixing device 7, and a transfer material on which a toner image is formed is disposed on the top of the color printer via the discharge rollers 81a and 81b. To be discharged.

  As shown in FIGS. 1 and 3, the tension roller 28 extends in a direction (belt width direction) orthogonal to the traveling direction of the transfer belt 24, and is formed to have substantially the same length as the width of the transfer belt 24. A shaft protrudes from both ends of the tension roller 28, and each shaft is rotatably supported by bearings 28a and 28b. A pressure adjusting plate 29 is provided below the tension roller 28 in parallel with the tension roller 28. Further, a spring 30 a is provided between the left bearing 28 a that supports the tension roller 28 and the corresponding left end portion 29 a of the pressure adjustment plate 29, and similarly, the right bearing 28 b that supports the tension roller 28 and the pressure adjustment plate 29. A spring 30b is provided between the corresponding right end portion 29b. The tension roller 8 is urged upward with respect to the pressure adjusting plate 29 by these springs 30a and 30b. The bottom portions of both end portions 29a and 29b of the pressure adjusting plate 29 are in contact with a turning mechanism, which will be described later, provided below them. The both ends of the pressure adjustment plate 29 can swing up and down around a fulcrum 29 c provided at the center of the pressure adjustment plate 29.

  As shown in FIG. 4A, the left end portion 29a of the pressure adjustment plate 29 is provided with a turning mechanism 31a for changing the position of the left end portion 29a of the pressure adjustment plate 29 in the vertical direction. The turning mechanism 31a includes a moving body 32a, a moving mechanism 33a, and a stopper 35a. The moving body 32 a has a sloped surface that comes into contact with the bottom of the pressure adjustment plate left end portion 29 a, and is movable in the left-right direction with respect to the pressure adjustment plate 29. The moving mechanism 33a is for moving the moving body 32a left and right. In this embodiment, the moving mechanism 33a includes a bolt 34a connected to the moving body 32a and a motor 36a that moves the bolt 34a in the direction of the moving body 32a. It is configured. The stopper 35a is a plate provided at the left limit position of the moving body 32a. When the moving body 32a is moved left and right by the moving mechanism 33a, the left end portion 29a of the pressure adjusting plate 29 is moved up and down, and the urging force by the spring 30a can be adjusted. The right end portion 29b of the pressure adjusting plate 29 is also provided with a turning mechanism having the same structure (not shown).

  FIG. 5 shows a control block of the image forming apparatus. The control unit 90 includes a microcomputer having a CPU, a RAM, a ROM, and the like. The control unit 90 includes an image forming unit 2, a paper feeding unit 4, a paper discharging unit 8, an image data input unit 60, an input operation unit 70, and a meander detection unit. 80, tension adjusting means 91, and the like are connected. Here, the image data input unit 60 is for receiving image data from a personal computer connected via a network or the like. The image data received here is sent to the image forming unit 2 or the control unit 90. The input operation unit 70 has a key group and a display panel (not shown). The key group includes a numeric keypad and a start key. The start key is a key for instructing image formation by the image forming unit 10. The meander detection sensor 80 is for detecting whether or not meandering has occurred while the belt is running. In this embodiment, as shown in FIG. 4B, the meandering sensor 80 is orthogonal to the running direction of the transfer belt 24. A line sensor 80a is disposed on the left side edge in the direction. Similarly, a line sensor 80b (not shown) is also disposed at the right edge in the direction orthogonal to the running direction of the transfer belt 24. The control unit 90 controls operations such as image formation in the image forming unit 2, or corrects the meandering by controlling the tension adjusting unit 91 when the meandering detection unit 80 detects the meandering of the belt. It is.

Next, an image forming operation will be described. First, when the color printer is turned on, various parameters are initialized, and initial settings such as setting the temperature of the fixing unit 7 are executed. Image data from such a personal computer connected by such a network is received by the image data input unit 60 shown in FIG. The image data received here is sent to the image forming unit 2.

  In each process unit 21a, 21b, 21c, 21d of the image forming unit 2, a toner image is formed based on the received image data. Here, the image forming operation will be described by taking the black process unit 21a as an example. First, the photosensitive drum 22a is charged by the charging device 101a, the exposure device 102a performs exposure corresponding to the black image data, and an electrostatic latent image corresponding to the black image data is formed on the surface of the photosensitive drum 22a. Is done. The electrostatic latent image is converted into a toner image by the black developing device 103a and transferred onto the transfer belt 24 by a transfer bias applied to the primary transfer roller 23a. The residual developer remaining on the photosensitive drum 22a is cleaned by the cleaning device 104a and discarded in a waste toner container (not shown). Further, the static elimination device 105a neutralizes the photosensitive drum 22a. Such an operation is also performed for the other colors, the magenta process unit 21b, the cyan process unit 21c, and the yellow process unit 21d, and a full-color toner image is formed on the transfer belt 24.

  At the same time, in the paper feed unit 4, the transfer material is taken out from the paper feed cassette 41 by the pickup rollers 42 and 43, and sent out to the vertical conveyance path 46 through the paper feed roller pair 44 and 45. Thereafter, the transfer material conveyed from the pair of registration rollers 5 a and 5 b in time with the image formation on the transfer belt 24 is guided to the transfer unit 3 by the transfer material conveyance guide mechanism 6. In the transfer unit 3, the secondary transfer roller 31 contacts the transfer belt 24, and the full-color toner image formed on the transfer belt 24 is transferred to the transfer material by the secondary transfer bias applied to the secondary transfer roller 31. Is done. Further, the full color toner image transferred to the transfer material is fixed to the transfer material by heating and pressurization by the fixing unit 7, and the transfer material on which the full color toner image is formed is discharged to the paper discharge unit 8. Further, the toner remaining on the transfer belt 24 is cleaned by the intermediate transfer cleaning device 26 and discarded in a waste toner container (not shown).

Next, the meandering correction operation in the image forming process will be described with reference to the flowchart of FIG. When the color printer 1 is turned on, in step S1, various parameters are initialized, and initial settings such as setting the temperature of the fixing unit 7 are executed. In step S2, data on the running state of the transfer belt 24 is taken in by the line sensors 80a and 80b . In step S <b> 3, it is determined whether or not meandering in which the transfer belt 24 is biased to the right has occurred. Transfer the right side of the belt 24 line sensor 80b (not shown) is provided, by converting the light hits the photodiode array aligned in a row in an electrical signal, proportional to detect the right end portion of the transfer belt 24 To do. When the position of the end of the transfer belt 24 meanders to the right from the reference detection position, the process proceeds to step S4, and when meandering biased to the right does not occur, the process proceeds to step S5. In step S4, the motor 36a is rotated by the controller 90, and the moving body 32a is moved in the right direction via the bolt 34a. Then, when the pressure adjusting plate 29 moves upward and compresses the spring 30a to increase the left pressure contact force of the tension roller 28 to the transfer belt 24, the transfer belt 24 tilts to the left and the bias to the right is corrected. The Here, based on the amount of meandering of the transfer belt 24, the controller 90 controls the rotation speed of the motor 36a. The amount of vertical movement of the left side of the pressure adjustment plate 29 is controlled by the rotational speed of the motor 36a, and the value of the tension on the left side of the tension roller 28 is controlled.

  On the other hand, in step S5, it is determined whether or not meandering on the left side of the transfer belt traveling direction has occurred. Here, a line sensor 80a is provided on the left side of the belt, and the method for determining whether or not a meander to the left side has occurred is the same as in step S3. If the meandering to the left side has occurred, the process proceeds to step S6. If the meandering to the left side has not occurred, the process proceeds to step S7, and normal image formation is performed. The meandering correction method in step S6 is the same as in step S4.

[Effect of this embodiment]
In the present embodiment, a line sensor 80a and an unshown 80b are provided at both side edges in a direction orthogonal to the running direction of the transfer belt 24, and the occurrence of meandering on the left side of the transfer belt 24 is detected by the laline sensor 80a. In this case, the control unit 90 activates the tension adjustment on the right side of the tension roller 28 to increase the tension on the right side of the tension roller 28. When the tension on the right side of the tension roller 28 increases, the transfer belt 24 tilts to the right, and the meandering of the transfer belt 24 to the left is corrected. Accordingly, without increasing the new parts, a simple structure, Ru can correct the meandering of the transfer belt 24.

[Other Embodiments]
In the above-described embodiment, the springs 30a and 30b, the pressure adjustment plate 29, and the diverting mechanisms 31a and 31b provided on the bearings at both ends of the tension roller 28 are employed as the tension adjusting means. Although the direction mechanism is operated, at the time of shipment, the tension on the left and right sides of the tension roller 28 can be adjusted by manually rotating the bolts 34a and 34b without rotating the motors 36a and 36b.

  Further, by providing solenoids to the bearings at both ends of the tension roller 28 as tension adjusting means, the tension at both ends of the tension roller can be adjusted.

  In this embodiment, a tandem type color printer is used as the image forming apparatus and the belt is a transfer belt. However, a monochrome printer is used as the image forming apparatus, and the belt is a photosensitive belt and a document. Needless to say, the present invention can be applied to a belt for conveyance. The present invention can also be applied to image forming apparatuses such as copying machines, printers, and facsimiles.

The block diagram of the principal part of a color printer. Enlarged view of the black process unit. The perspective view of a tension roller. The block diagram of a tension adjustment mechanism. Control block diagram. The meandering correction operation flowchart.

Explanation of symbols

24 Transfer belt 28 Tension roller 29 Pressure adjustment plate 30 Spring 31 Tension adjustment means 32 Moving body 33 Pressure adjustment mechanism 80 Meander detection means 80a Line sensor 90 Control means

Claims (1)

An endless belt stretched between a driving roller and a driven roller;
Extending along the width direction of the endless belt, and a tension roller for adjusting the tension of the endless belt,
Meander detection means for detecting meandering in the running direction of the endless belt;
Tension adjusting means for adjusting the pressure contact force with respect to the endless belt at both axial ends of the tension roller;
Control means for operating the tension adjustment means to correct the meandering of the endless belt based on the detection result of the meander detection means;
The belt apparatus provided with,
The tension adjusting means is supported in parallel with the pair of bearings that support both ends of the tension roller in the axial direction and the axial direction of the tension roller so that the central portion in the axial direction can swing around a fulcrum. A pressure adjusting plate, a spring provided between the axial ends of the pressure adjusting plate and the bearing, and for urging the bearing in a direction in which the tension roller is pressed against the endless belt, and an attachment of the spring It includes a pressure adjustment mechanism that adjusts the power,
The pressure adjusting mechanism includes a pair of moving bodies having inclined surfaces that contact both axial ends of the pressure adjusting plate, and a moving mechanism that moves the moving body in the axial direction of the tension roller,
The control means controls the tension adjusting means so as to increase a pressure contact force with respect to the endless belt on a side opposite to the side where the endless belt is biased, in both axial ends of the tension roller. A belt device characterized.

Images