JP2016009161A - Belt driving device, and image forming apparatus and belt conveyor including the belt driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt driving device that is capable of accurately correcting the meander of a belt and is flexible in design.SOLUTION: A belt driving device 100 comprises: an endless belt 30 supported by a prescribed number of rollers including a driving roller; a drive motor 110 for driving the driving roller to make the belt 30 travel; a meander control device 300 for correcting the meander that is a positional variation in the width direction of the belt 30, generated during traveling of the belt 30 driven by the drive motor 110; an optical sensor 200 for detecting the amount of the meander of the belt 30 without contacting with the belt 30; and a belt control section for controlling the meander control device 300 in accordance with the amount of the meander detected by the optical sensor 200. The optical sensor 200 receives reflection light of light radiated on the belt 30 and thereby detects the movement amount of the belt 30 in a two-dimensional direction to detect the amount of the meander of the belt 30.

Description

  The present invention relates to a belt drive device, an image forming apparatus, and a belt conveyor, and more particularly to a technique for correcting belt meandering.

  As one type of information processing apparatus, an image forming apparatus (typically a copier) is installed in many offices (company, office, etc.). Many MFPs (Multifunction Peripheral (MFP)), which is one of such image forming apparatuses, have a plurality of modes such as a copy mode, a network-compatible print mode, and a scanner mode. Yes.

  Some of these image forming apparatuses use an endless belt to form an image on a sheet. As an image forming apparatus using an endless belt, conventionally, an image forming unit corresponding to each color of yellow, magenta, cyan, and black is provided on an endless belt such as a primary transfer belt (also referred to as an “intermediate transfer belt”). An individually provided tandem color image forming apparatus is known. In such an image forming apparatus, a belt driving device for running an endless belt is incorporated. The belt driving device includes an endless belt and a plurality of rollers that support the endless belt. The plurality of rollers include drive rollers. The belt driving device drives an endless belt by driving the driving roller.

  In general, in a belt driving device, a so-called meandering of the belt is generated in which the belt moves in the width direction (a direction orthogonal to the belt traveling direction) while the belt is traveling. In the tandem color image forming apparatus, images of the respective colors are transferred onto the primary transfer belt so that when the belt meanders in the tandem color image forming apparatus, the relative position shift of the images of the respective colors occurs. A relative positional shift of each color image causes a color shift, color unevenness, and the like, and degrades the print image quality. For this reason, in order to obtain a high-quality image while suppressing a decrease in print image quality, it is necessary to appropriately correct (correct) the meandering of the belt.

  Patent Document 1 described later discloses a belt driving device that can correct meandering of an endless belt. The belt driving device includes an edge sensor that detects an edge position of the belt and a steering roller that controls meandering of the belt. The belt driving device detects position variation (meandering) in the width direction of the belt by an edge sensor, and corrects the meandering of the belt by changing the inclination of the steering roller based on the detection result. The detection data of the edge sensor includes a position variation component (error component) caused by the belt edge shape. In Patent Document 1, an error component due to an edge shape is removed by taking a difference between detection data detected by an edge sensor and edge shape data. The edge shape of the belt is measured by an edge sensor at the time of manufacturing the apparatus, replacing the belt, and during regular maintenance, and the measured data is stored in advance as edge shape data. As the edge sensor, one having a configuration in which a displacement sensor detects a displacement of a contact held in a pressure contact state on an edge portion of the belt is used. Patent Document 1 further describes an edge sensor (transmission type optical sensor) in which an LED (Light Emitting Diode) and a light amount sensor are arranged in an opposed state via an edge portion of a belt.

  Japanese Patent Application Laid-Open No. 2004-133620 discloses an image forming apparatus that can correct meandering of an endless belt. This image forming apparatus detects a positional variation (meandering) of a belt edge using a transmission type optical sensor. The optical sensor includes a light emitting unit composed of an LED and a light receiving unit that receives light from the light emitting unit. The light emitting part and the light receiving part are arranged in an opposed state via the edge of the belt. In Patent Document 2, the light receiving unit of the optical sensor includes a plurality of light receiving elements.

Japanese Patent Laid-Open No. 11-295948 JP 2013-97313 A

  In the configuration in which the meandering of the belt is detected by the edge sensor including the contact, the contact is pressed against the edge of the belt, so that the belt may be damaged. On the other hand, since the transmission type optical sensor can detect the positional variation of the edge of the belt without contact, by using such a transmission type optical sensor as an edge sensor, damage to the belt due to contact between the sensor and the belt can be suppressed. .

  However, as described in Patent Document 1 and Patent Document 2, when correcting the meandering of the belt based on the output from the transmission type optical sensor, the optical sensor changes the amount of light received with the positional variation of the edge of the belt. Therefore, an optical sensor having a size that can always detect the edge of the belt is required. That is, an optical sensor including a light receiving portion that is larger than the maximum fluctuation amount due to meandering (variation quantity in the belt width direction) is required. Therefore, there is a disadvantage that the sensor itself is increased in size.

  By configuring the light receiving unit to include a plurality of light receiving elements as described in Patent Document 2, it is possible to reduce the size of each light receiving element. However, when the area of the light receiving element (the area of the light receiving surface) is reduced, the amount of light received is reduced, so that it is easily affected by noise. In this case, detection accuracy decreases. In order to accurately detect the amount of belt position variation based on the amount of light received by the light receiving element (light quantity sensor), the area of the light receiving element needs to be increased. As the area of the light receiving element increases, the sensor itself increases in size.

  Since the edge sensor that detects the edge of the belt needs to be mounted at a position where the edge can be detected, the mounting position is limited. When the size of the sensor increases, the mounting position is further restricted, and design restrictions are imposed. Therefore, the configurations described in Patent Document 1 and Patent Document 2 have a problem that it is difficult to give design freedom. In addition, the accuracy of the optical sensor is greatly reduced due to contamination. Therefore, it is preferable that the optical sensor is installed at a position where it is difficult to get dirty. However, in the configurations described in Patent Document 1 and Patent Document 2, it is difficult to provide a degree of freedom in the mounting position of the optical sensor (edge sensor), and thus it is possible to suppress a decrease in detection accuracy due to dirt. It becomes difficult.

  Further, in Patent Document 1 and Patent Document 2, since the position variation of the edge of the belt is detected by the edge sensor, the detection data of the edge sensor includes an error component due to the edge shape of the belt as described above. . Although it is possible to improve the detection accuracy by taking the difference between the detection data and the edge shape data as described in Patent Document 1, for that purpose, the edge shape data is acquired and stored in advance. There is a need. Therefore, complicated operations are required.

  The present invention has been made to solve the above-described problems, and one object of the present invention is to correct belt meandering with high accuracy and to have a high degree of design freedom. To provide a driving device, an image forming apparatus, and a belt conveyor.

  Another object of the present invention is to provide a belt driving device, an image forming apparatus, and a belt conveyor capable of accurately correcting the meandering of the belt without requiring a complicated operation.

  A belt driving device according to a first aspect of the present invention includes an endless belt supported by a predetermined number of rollers including a driving roller, and roller driving means for driving the driving roller to run the belt. A meandering correction means for correcting meandering, which is a position variation in the width direction of the belt, generated when the belt is driven by the roller driving means, and a meandering amount detection means for detecting the meandering amount of the belt in a non-contact manner. Meandering control means for controlling the meandering correction means in accordance with the meandering amount detected by the meandering amount detection means. The meandering amount detecting means includes an optical sensor that detects the amount of movement in the two-dimensional direction of the belt by receiving reflected light of the light irradiated to the belt, and using the optical sensor, the meandering amount of the belt is detected. To detect.

  The endless belt is supported by a predetermined number of rollers including a driving roller. When the driving roller is driven by the roller driving means, the endless belt runs. The meandering amount detecting means detects the meandering amount of the belt in a non-contact manner. The meandering correction means is controlled according to the detected meandering amount, and the meandering correction of the belt is corrected by the meandering correction means. The meandering amount detection means includes an optical sensor that detects the amount of movement of the belt in the two-dimensional direction by receiving reflected light of the light applied to the belt. The meandering amount detection means detects the meandering amount using this optical sensor.

  Since the optical sensor is configured to receive the reflected light from the belt and detect the amount of movement in the two-dimensional direction, the optical sensor only needs to be large enough to receive the reflected light. Therefore, it can suppress that sensor itself enlarges. Furthermore, the optical sensor can detect the meandering amount of the belt at a desired position other than the edge of the belt. Thereby, the freedom degree of design is raised. If the optical sensor is installed at a position where it is difficult to get dirty, it is possible to suppress a decrease in detection accuracy due to the dirt. Furthermore, since the detection data detected by the optical sensor does not include an error component due to the edge shape of the belt, the amount of meandering can be detected with high accuracy by using such an optical sensor. In addition, since it is not necessary to acquire and store the edge shape data in advance, it is not necessary to perform such a complicated operation. Therefore, by controlling the meandering correction unit according to the meandering amount detected by the meandering amount detection unit, the meandering of the belt can be accurately corrected without requiring a complicated operation.

  Preferably, the optical sensor continuously obtains an image of an irradiation unit that irradiates light to the belt and a portion of the belt irradiated with light by receiving reflected light from the belt of light irradiated by the irradiation unit. And a movement amount detector that detects a movement amount of the belt in the two-dimensional direction.

  More preferably, the belt driving device determines whether or not the meandering amount of the belt detected by the meandering amount detecting means is larger than a predetermined value, and stops the belt driving device in response to the determination result being affirmative. Means for further comprising:

  More preferably, the belt driving device includes a speed detecting unit for detecting the speed of the belt in the traveling direction, and a roller so that the belt speed becomes a predetermined speed according to the speed detected by the speed detecting unit. Speed control means for controlling the drive means, the optical sensor is capable of detecting the movement speed based on the detected movement amount, and the speed detection means uses the optical sensor to detect the belt. Detect the speed in the direction of travel.

  More preferably, the belt driving device determines whether or not the belt speed detected by the speed detecting means has changed to a predetermined speed different from a predetermined speed, and responds that the determination result is affirmative. And further includes means for stopping the belt drive.

  More preferably, the belt driving device includes a speed storage unit for storing the belt speed detected by the speed detection unit, and a reading unit for reading the speed stored in the speed storage unit in response to a user instruction. Further included.

  More preferably, the belt driving device reads the meandering amount storage means for storing the meandering amount of the belt detected by the meandering amount detection means, and the meandering amount stored in the meandering amount storage means according to a user instruction. And further reading means.

  An image forming apparatus according to a second aspect of the present invention is an image forming apparatus including the belt driving device according to the first aspect.

  The belt conveyor which concerns on the 3rd aspect of this invention is a belt conveyor containing the belt drive device which concerns on the said 1st aspect.

  As described above, according to the present invention, it is possible to obtain a belt driving device, an image forming apparatus, and a belt conveyor that can accurately correct the meandering of the belt and have a high degree of design freedom.

  Furthermore, according to the present invention, it is possible to obtain a belt driving device, an image forming apparatus, and a belt conveyor that can accurately correct the meandering of the belt without requiring a complicated operation.

1 is a diagram schematically showing an internal configuration of an image forming apparatus according to a first embodiment of the present invention. It is a figure which shows the structure of an image forming unit typically. It is a figure which shows the structure of the belt drive device of the image forming apparatus shown in FIG. It is a top view which shows the structure of an optical sensor. It is sectional drawing which shows the structure of an optical sensor. It is a top view which shows the structure of a meandering control apparatus. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus shown in FIG. 1 together with some hardware. It is a block diagram which shows the electric constitution of a belt drive device. 2 is a flowchart showing a control structure of a program executed by the image forming apparatus shown in FIG. 2 is a flowchart showing a control structure of a program executed by the image forming apparatus shown in FIG. It is a figure for demonstrating the meander control operation of a meander control apparatus. It is a figure for demonstrating the operation | movement which correct | amends the meandering of a primary transfer belt. It is a figure for demonstrating the operation | movement for keeping the traveling speed of a primary transfer belt constant. It is a figure which shows the structure of the belt drive device which concerns on the 2nd Embodiment of this invention. FIG. 6 is a diagram illustrating a configuration of a fixing unit according to a third embodiment of the present invention. It is a figure which shows the structure of the belt conveyor which concerns on the 5th Embodiment of this invention.

  In the following embodiments, the same parts are denoted by the same reference numerals. Their functions and names are also the same. Therefore, detailed description thereof will not be repeated.

(First embodiment)
[Hardware configuration]
"overall structure"
Referring to FIG. 1, an image forming apparatus 20 according to the present embodiment is a tandem full-color image forming apparatus. In the tandem full-color image forming apparatus, images of respective colors are transferred on a primary transfer belt 30 described later. Therefore, the image forming apparatus 20 includes a belt driving device 100 that drives the primary transfer belt 30.

  The image forming apparatus 20 includes image forming units 22K, 22C, 22M, and 22Y for forming a black toner image, a cyan toner image, a magenta toner image, and a yellow toner image, respectively. In the following description, the image forming units 22K, 22C, 22M, and 22Y may be collectively referred to as “image forming unit 22”.

  Below the image forming unit 22, a laser scanner unit (hereinafter referred to as “LSU”) 24 for exposing the image forming unit 22 by laser scanning is provided. The LSU 24 converts image data (hereinafter referred to as “output image data”) output from the laser oscillation unit 26 for oscillating laser light and the image processing device 38 into a laser emission signal, and converts the laser emission signal into the laser emission signal. An LSU control device 28 for controlling the operation of the laser oscillation unit 26 based on the above is included.

  Above the image forming unit 22, a primary transfer belt 30 for transferring a single color toner image formed by each of the image forming units 22 on a recording sheet as a recording medium and a primary transfer belt 30 are supported. Support rollers 32a and 32b are provided. The primary transfer belt 30 is an endless belt-like member wound around the support rollers 32a and 32b. The constituent material of the primary transfer belt 30 is not particularly limited as long as it is generally used in the field. For example, a material containing an appropriate amount of an electron conductive conductive material in a resin such as polyimide or polyamide, etc. Can be used. The support rollers 32a and 32b are provided inside the primary transfer belt 30 with an interval in the left-right direction on the paper surface.

  The belt driving device 100 includes such a primary transfer belt 30 and support rollers 32a and 32b. The support roller 32a (on the right side in FIG. 1) is provided so as to be rotationally driven around the axis by the drive motor of the belt drive device 100, and by the rotational drive, the primary transfer belt 30 is rotated in the direction indicated by the arrow R, that is, counterclockwise. Rotate around (run). The support roller 32b (left side in FIG. 1) is provided so as to be able to be driven to rotate by the rotation of the support roller 32a, and applies a certain tension to the primary transfer belt 30 so that the primary transfer belt 30 does not loosen. The detailed configuration of the belt driving device 100 will be described later.

  A secondary transfer belt 34 is provided on the opposite side of the support roller 32a across the primary transfer belt 30 so as to face the support roller 32a. In the following description, upstream and downstream are expressed with reference to a secondary transfer position (transfer nip portion) where the support roller 32a and the secondary transfer belt 34 are in pressure contact with the rotation direction of the primary transfer belt 30. . The image forming units 22K, 22C, 22M and 22Y are arranged in this order from the upstream side to the downstream side in the rotation direction of the primary transfer belt 30 indicated by the arrow R.

  The image forming apparatus 20 is further provided inside the primary transfer belt 30 so as to face the image forming units 22K, 22C, 22M, and 22Y, and each single color formed by the image forming units 22K, 22C, 22M, and 22Y. Four primary transfer rollers 40 for transferring the toner image onto the primary transfer belt 30 are included. When a transfer bias having a polarity opposite to the charging polarity of the toner is applied from the primary transfer roller 40, the single color toner images formed by the image forming units 22K, 22C, 22M, and 22Y are sequentially superimposed on the primary transfer belt 30. Are transferred to form a full-color toner image.

  The secondary transfer belt 34 described above for transferring the full-color toner image formed on the primary transfer belt 30 onto a recording sheet is provided downstream of the image forming unit 22Y in the rotation direction of the primary transfer belt 30. . A belt cleaning unit 42 for cleaning the surface of the primary transfer belt 30 is provided downstream of the secondary transfer belt 34 in the rotation direction of the primary transfer belt 30. The belt cleaning unit 42 includes a belt cleaning brush 44 and a belt cleaning blade 46 that contact the surface of the primary transfer belt 30 in order to remove toner remaining on the surface of the primary transfer belt 30. The belt cleaning blade 46 is disposed downstream of the belt cleaning brush 44 in the rotation direction of the primary transfer belt 30.

  The image forming apparatus 20 further includes a tray 48 provided below the LSU 24 for accommodating recording paper therein and a plurality of sets (four sets in the present embodiment) for transporting the recording paper inside the tray 48. And a pair of paper feed rollers 54. The recording paper stored in the tray 48 is conveyed to the secondary transfer position (transfer nip portion) by the pair of paper feed rollers 54. The conveyance direction of the recording paper (hereinafter referred to as “paper conveyance direction”) is indicated by an arrow F.

  A fixing unit 50 for fixing the full-color toner image transferred onto the recording paper onto the recording paper is provided downstream of the secondary transfer belt 34 in the paper conveying direction indicated by an arrow F. A discharge roller 52 for discharging a recording sheet on which a full-color image is formed from the image forming apparatus 20 is provided further downstream of the fixing unit 50 in the sheet conveyance direction. Above the primary transfer belt 30, a control device 36 for controlling the entire image forming apparatus 20 and screen processing (gradation processing) for input image data (hereinafter referred to as “input image data”). ) And the like are generated to generate output image data of a predetermined gradation and output to the LSU control device 28.

  The image forming apparatus 20 further includes an operation panel in which a display device such as a liquid crystal display and an input device such as a touch panel are stacked. The image forming apparatus 20 receives a user instruction for the operation of the entire image forming apparatus 20 and displays the contents of the instruction. In addition, an operation unit 58 (see FIG. 7) for outputting a control signal corresponding to the instruction to the control device 36 and the like to be described later is included.

  According to the image forming apparatus 20, the single color toner images formed by the image forming units 22K, 22C, 22M, and 22Y are sequentially superimposed on the primary transfer belt 30 and primarily transferred to form a full color toner image. The full-color toner image formed on the primary transfer belt 30 is secondarily transferred onto the recording paper conveyed by the paper feed roller pair 54 at the secondary transfer position (transfer nip portion), and then recorded by the fixing unit 50. Fixed on paper. The recording paper on which the full color image is formed by the fixing unit 50 is discharged from the image forming apparatus 20 by the paper discharge roller 52. Further, after the secondary transfer, toner remaining on the surface of the primary transfer belt 30 without being transferred to the recording paper is removed by the belt cleaning unit 42.

<< Configuration of Image Forming Unit 22 >>
The image forming units 22K, 22C, 22M, and 22Y have the same configuration except that the color of toner stored in a developing tank 68 described later is different. Therefore, hereinafter, the configuration of the image forming unit 22K will be described on behalf of these.

  Referring to FIG. 2, the image forming unit 22K includes a photosensitive drum 60, a charger 62 for uniformly charging the surface of the photosensitive drum 60, and an electrostatic latent image formed on the surface of the photosensitive drum 60. A developing device 64 for visualizing the toner and a photosensitive drum cleaner 66 for removing a residue including toner remaining on the surface of the photosensitive drum 60. The photosensitive drum 60 is provided so as to be rotatable around an axis by a drive unit (not shown). The photosensitive drum 60 is rotated in the direction indicated by the arrow Rd, that is, in the clockwise direction by the rotational driving thereof. The charger 62, the developing device 64, and the photosensitive drum cleaner 66 are provided around the photosensitive drum 60 in this order along the rotation direction of the photosensitive drum 60 indicated by an arrow Rd. The developing device 64 is provided below the charger 62, and the photosensitive drum cleaner 66 is provided above the charger 62.

  The charger 62 is a scorotron charger and performs corona discharge on the photosensitive drum 60 to charge the surface of the photosensitive drum 60 to a predetermined potential. The charger 62 is not limited to the scorotron charger and may be any one that is generally used in this field. For example, a corotron charger, a charging roller, or a contact charger using a charging brush can be used. The surface of the photosensitive drum 60 charged to a predetermined potential by the charger 62 is exposed by laser scanning of the laser oscillation unit 26 shown in FIG. 1, so that an electrostatic latent image based on output image data is generated. It is formed on the surface of the photosensitive drum 60.

  The developing device 64 includes a developing tank 68 for storing therein a two-component developer containing toner and a carrier, and an opening 70 is provided at a position facing the surface of the photosensitive drum 60 on the side surface of the developing tank 68. It is formed. The two-component developer is not particularly limited as long as it is generally used in the field. The developing device 64 further includes a developing roller 72, a regulating blade 74, and an agitator 76. The developing roller 72 is provided in the developing tank 68 at a position facing the photosensitive drum 60 through the opening 70 so as to be rotatable around an axis by a driving unit (not shown). The developing roller 72 is provided so as to be separated from the surface of the photosensitive drum 60 by a predetermined gap, and the rotation direction of the developing roller 72 at the closest part to the photosensitive drum 60 is the same as the rotational direction of the photosensitive drum 60. Rotate in the direction. The developing roller 72 carries and conveys a two-component developer on the outer peripheral surface thereof, and supplies toner to the electrostatic latent image formed on the surface of the photosensitive drum 60 at the closest part to the photosensitive drum 60. The electrostatic latent image is developed (visualized). When supplying the toner, a potential having a polarity opposite to the charging potential of the toner is applied to the surface of the developing roller 72 as a developing bias voltage. As a result, the toner on the surface of the developing roller 72 is smoothly supplied to the electrostatic latent image. The regulating blade 74 is a plate-like member provided in the vicinity of the opening 70 in the developing tank 68 so that its longitudinal direction extends along the axial direction of the developing roller 72. The regulating blade 74 is provided so that one end in the short direction is spaced from the surface of the developing roller 72 by a predetermined gap, and regulates the layer thickness of the two-component developer carried and conveyed on the surface of the developing roller 72. The agitator 76 is a roller-like member that is rotatably provided by a driving unit (not shown) at a position facing the developing roller 72 inside the developing tank 68, and is accommodated in the developing tank 68 by the rotational driving. Stir the resulting two-component developer.

  The photoconductive drum cleaner 66 holds the cleaning blade 78 for scraping off the residue including toner remaining on the surface of the photoconductive drum 60, and holds the residue scraped off by the cleaning blade 78 to prevent the scattering. A cleaner housing 80 and a seal 82 are included. The cleaning blade 78 is a plate-like member that is provided so that its longitudinal direction extends along the axial direction of the photosensitive drum 60, and one end portion 84 in the short side direction faces the rotational direction of the photosensitive drum 60 downward. At the position, it is arranged in the cleaner housing 80 so as to be bent and pressed in the counter direction (the direction opposite to the rotation direction of the photosensitive drum 60) with respect to the rotation direction of the photosensitive drum 60. By disposing in this way, the residue can be scraped off more easily at the one end portion 84 in the short direction.

  According to the image forming unit 22K, the surface of the photosensitive drum 60 that has been uniformly charged by the charger 62 is irradiated with laser light based on the output image data from the LSU 24 to form an electrostatic latent image. To the formed electrostatic latent image, toner is supplied from the developing device 64 to form a monochromatic toner image, and the formed toner image is primarily transferred to the primary transfer belt 30. After the primary transfer, the residue remaining on the surface of the photosensitive drum 60 is removed by the photosensitive drum cleaner 66. This series of toner image forming operations is repeatedly executed in the image forming units 22K, 22C, 22M and 22Y.

<< Configuration of Belt Drive Device 100 >>
Referring to FIG. 3, a belt driving device 100 includes a primary transfer belt 30 that is an endless belt, a predetermined number of rollers that support the primary transfer belt 30, and a drive motor 110 that drives the primary transfer belt 30. An optical sensor 200 for detecting the meandering (meandering amount) of the primary transfer belt 30 in a non-contact manner, and a meandering control device 300 for correcting the meandering of the primary transfer belt 30 based on the meandering amount detected by the optical sensor 200. Including. The meandering control device 300 includes a steering roller 310. The predetermined number of rollers that support the primary transfer belt 30 include support rollers 32 a and 32 b and a steering roller 310. The drive motor 110 is a motor that rotationally drives the support roller 32a. The belt driving device 100 causes the primary transfer belt 30 to travel in the direction indicated by the arrow R by rotating the support roller 32 a via the drive motor 110.

  As the primary transfer belt 30 travels, each single color toner image formed by the image forming units 22K, 22C, 22M and 22Y is sequentially superimposed on the primary transfer belt 30 to be primary transferred to form a full color toner image. The The full-color toner image primarily transferred onto the primary transfer belt 30 is carried to the secondary transfer position (transfer nip portion) by the travel of the primary transfer belt 30. The full color toner image formed on the primary transfer belt 30 is secondarily transferred onto the recording paper P at the secondary transfer position.

  In the present embodiment, an optical finger mouse (OFM), which is a small optical pointing device, is used for the optical sensor 200 that detects the meandering (meandering amount) of the primary transfer belt 30. Referring to FIG. 4, optical sensor 200 includes a sensor unit 200A and a flexible printed board 200B for outputting information sensed by sensor unit 200A to the outside. The sensor unit 200A has a rectangular planar shape. The length a1 in the vertical direction and the length a2 in the horizontal direction of the sensor unit 200A are each about 8.0 mm, for example. The thickness of the sensor unit 200A is, for example, about 1.56 mm to about 3.1 mm.

  Referring to FIG. 5, the optical sensor 200 receives a light emitting unit 210 that irradiates light to a measurement object (primary transfer belt 30 in the present embodiment), and reflected light from the measurement object, And a sensor IC 220 that detects a movement amount, a movement speed, and the like of the measurement object in a two-dimensional direction. The light emitting unit 210 includes, for example, an infrared LED that irradiates a measurement object with infrared light. The sensor IC 220 calculates an amount of movement, a moving speed, and the like of the measurement object in a two-dimensional direction by calculating (image processing) an image sensor described later and image data acquired by the image sensor. including. The sensor unit 200 </ b> A further includes a substrate 230, a light shielding member 232, and an optical cover 234. The light emitting unit 210 and the sensor IC 220 are mounted on the substrate 230. The optical cover 234 is a member that covers the light emitting unit 210 and the sensor IC 220 mounted on the substrate 230. On the upper surface of the optical cover 234, a detection window (not shown) is provided for detecting the amount of movement of the primary transfer belt 30 (measurement object). The size of the detection window is, for example, about 1 mm × 1 mm. The light shielding member 232 is provided inside the sensor unit 200A so as to suppress light other than the reflected light from the primary transfer belt 30 from entering the image sensor (sensor IC 220). The detection accuracy of the optical sensor 200 is, for example, 1400 dpi.

  Referring to FIG. 3 again, the optical sensor 200 is disposed on the surface side of the primary transfer belt 30 and between the belt cleaning unit 42 and the image forming unit 22K. By disposing the optical sensor 200 at such a position, it is possible to avoid the sensor from becoming dirty due to toner scattering or the like. Note that the optical sensor 200 is preferably disposed in the center portion of the primary transfer belt 30 in the width direction. The meandering control device 300 is disposed, for example, between the support roller 32b and the image forming unit 22K.

  Referring to FIG. 6, meander control device 300 includes a steering roller 310, a swing arm 320, an eccentric cam 330, and an eccentric cam drive motor 340. The steering roller 310 is a driven roller that supports the primary transfer belt 30. One end of the steering roller 310 is rotatably supported by the swing arm 320, and the other end on the opposite side is rotatably supported by the fulcrum 312. The swing arm 320, the eccentric cam 330, and the eccentric cam drive motor 340 are mechanism members that control the tilt of the steering roller 310. The meandering control device 300 controls (corrects) the meandering of the primary transfer belt 30 by controlling the tilt of the steering roller 310.

  The middle part of the swing arm 320 is supported by a support shaft 322 so as to be rotatable (swingable). One end portion of the steering roller 310 is rotatably connected to one side surface of the swing arm 320, and the lower surface on the other end side of the opposite arm is in pressure contact with the outer peripheral surface (cam surface) of the eccentric cam 330. ing. A fulcrum 312 that supports the other end of the steering roller 310 is fixed. The eccentric cam drive motor 340 rotates the eccentric cam 330 by driving. For example, a stepping motor is used as the eccentric cam drive motor 340. When the eccentric cam 330 rotates by driving the eccentric cam drive motor 340, the swing arm 320 swings up and down. As the swing arm 320 swings, one end of the steering roller 310 connected to the swing arm 320 moves up and down. Thereby, the inclination of the steering roller 310 is changed. In the following description, in the steering roller 310, one end side (D1 side) to which the swing arm 320 is connected is referred to as “swing arm side”, and the other end side (D2 side) that is one end on the opposite side. Is called the “fulcrum side”.

[Electrical configuration]
Referring to FIG. 7, control device 36 is substantially a computer, and includes a CPU (Central Processing Unit) 36a, a ROM (Read-Only Memory) 36b, a RAM (Random Access Memory) 36c, and an HDD (Hard Disk Drive). 36d. In the control device 36, a BUS line 90 is connected to the CPU 36a, and the ROM 36b, RAM 36c, and HDD 36d are electrically connected to the CPU 36a via the BUS line 90.

  The CPU 36 a further includes the image forming units 20 </ b> K, 22 </ b> C, 22 </ b> M and 22 </ b> Y, the LSU control device 28, the image processing device 38, the operation unit 58, and the belt driving device 100 via the BUS line 90. And an NIC (Network Interface Card) 96 that interfaces with a network 92 using a LAN (Local Area Network) line. The image forming apparatus 20 can communicate with an external device such as a personal computer on the network 92 via the NIC 96.

  The ROM 36 b in the control device 36 is a read-only memory that stores a computer program (hereinafter simply referred to as “program”) for executing and controlling the operation of each component of the image forming apparatus 20. The RAM 36c is a temporary storage memory in which the program in the ROM 36b is expanded or used as a working memory when the CPU 36a executes various programs. The HDD 36d is an auxiliary storage device that stores various data such as programs and image data. In the present embodiment, the ROM 36b or the HDD 36d stores a program for realizing a process for correcting the meandering of the belt, which will be described later, together with a program for realizing a general operation of the image forming apparatus 20. This program is provided from an external device via the network 92 and the NIC 96. This program may be provided by a recording medium such as a DVD (Digital Versatile Disk) on which the program is recorded.

  The CPU 36a executes various computer programs to execute a desired process such as an image forming process in the image forming apparatus 20 and a communication with an external apparatus. The various programs are stored in advance in the ROM 36b or the HDD 36d, and are read from the ROM 36b or the HDD 36d and transferred to the RAM 36c when desired processing is executed. The CPU 36a reads and interprets a program instruction from an address in the RAM 36c designated by a value stored in a register called a program counter (not shown) in the CPU 36a. The CPU 36a also reads data necessary for the operation from the address specified by the read instruction, and executes an operation corresponding to the instruction on the data. The execution result is also stored at an address specified by the instruction, such as a register in the RAM 36c, HDD 36d, and CPU 36a.

  The control device 36 operates the image forming units 22K, 22C, 22M and 22Y, the LSU control device 28, the image processing device 38, the operation unit 58, the belt driving device 100, and the operation of each component of the image forming device 20 including the NIC 96. And controlling the entire image forming apparatus 20 as a sequence, thereby executing desired processes such as an image forming process in the image forming apparatus 20 and communication with an external apparatus.

  Referring to FIG. 8, belt driving device 100 includes a belt control unit 120 that controls the travel of primary transfer belt 30 under the control of control device 36. The belt control unit 120 is electrically connected to the optical sensor 200, the drive motor 110, and the eccentric cam drive motor 340. The optical sensor 200 includes a light emitting unit 210, an image sensor 222, and a calculation unit 224. The image sensor 222 is composed of, for example, a CMOS image sensor. The optical sensor 200 irradiates the primary transfer belt 30 with light from the light emitting unit 210 through a detection window, and the image sensor 222 that receives the reflected light reads the pattern on the surface of the primary transfer belt 30 as an image. The optical sensor 200 continues to acquire (continuously acquires) the pattern of the surface of the primary transfer belt 30 with respect to the movement of the primary transfer belt 30 due to running and meandering, and the image sensor 222 outputs the pattern. The calculation unit 224 performs calculation processing on the image data to calculate the moving direction, moving amount, and moving speed of the primary transfer belt 30. That is, the optical sensor 200 reads the movement of the pattern to calculate the movement amount and movement speed of the primary transfer belt 30 in the two-dimensional direction.

  A sensor signal from the optical sensor 200 is input to the belt control unit 120. The belt control unit 120 detects the belt traveling speed, the meandering amount, and the meandering speed (moving speed in a direction orthogonal to the traveling direction (rotating direction)) in real time based on the sensor signal from the optical sensor 200. The belt controller 120 further corrects the meandering of the primary transfer belt 30 by driving the eccentric cam drive motor 340 according to the detected meandering amount. Further, the belt control unit 120 drives the drive motor 110 in accordance with the detected traveling speed, thereby performing feedback control so that the traveling speed of the primary transfer belt 30 becomes constant. Thereby, the traveling speed of the primary transfer belt 30 is kept constant. When the running speed of the primary transfer belt 30 changes, the image transferred onto the primary transfer belt 30 extends or shrinks in the belt running direction, and the print image quality deteriorates. In the present embodiment, since the traveling speed of the primary transfer belt 30 is feedback-controlled, deterioration in image quality due to a change in the traveling speed of the primary transfer belt 30 is also suppressed.

  In the present embodiment, the upper limit value and the lower limit value of the traveling speed are further stored in advance in the HDD 36d or the like. It is preferable that the upper limit value and the lower limit value are set to a speed at which the primary transfer belt 30 is damaged due to some trouble or is considered to be possibly damaged. Regarding the meandering amount of the primary transfer belt 30, the upper limit value and the lower limit value are stored in advance in the HDD 36d or the like. When the position of the primary transfer belt 30 where no meandering occurs (position where the meandering amount is 0) is the Ref position, the upper limit value is the meandering amount to the fulcrum side (+ side) of the steering roller 310, and the lower limit value is swinging. The amount of meandering to the arm side (-side) can be set. The upper limit value and the lower limit value are preferably set to values that may damage or break the primary transfer belt 30 when the amount of meandering is further increased. When the traveling speed or the meandering amount output from the optical sensor 200 exceeds the upper limit value or falls below the lower limit value, the image forming apparatus 20 is stopped.

Software configuration
With reference to FIG. 9, a control structure of a computer program executed by the image forming apparatus 20 in order to correct the meandering of the primary transfer belt 30 will be described. This program starts in response to a print instruction.

  This program is executed after step S1000 for detecting the meandering amount using the optical sensor 200 and after step S1000, and it is determined whether the detected meandering amount exceeds the upper limit value or falls below the lower limit value. In step S1010 for branching the control flow according to the determination result, and in step S1010, it is executed and detected when it is determined that the upper limit value is not exceeded or the lower limit value is not exceeded. Step S1020 which determines which side of the steering roller 310 the primary transfer belt 30 is approaching based on the meandering amount and branches the control flow according to the determination result.

  This program is further executed when it is determined in step S1020 that the primary transfer belt 30 is close to the swing arm side, and the primary transfer belt 30 is moved via the belt control unit 120 so that the primary transfer belt 30 moves to the fulcrum side. In Steps S1030 and S1020 for controlling the tilt of the steering roller 310, it is executed when it is determined that the primary transfer belt 30 is close to the fulcrum side so that the primary transfer belt 30 moves to the swing arm side. Then, after step S1040 for controlling the tilt of the steering roller 310 via the belt control unit 120, and after step S1030, or step S1040, or in step S1020, the primary transfer belt 30 approaches either side of the steering roller 310. Not meandering, ie There is executed if it is determined (weight meander 0), it is determined whether or not all printing has been completed, and a step S1050 for branching control flow depending on the result of determination. If it is determined in step S1050 that all printing has not been completed, control returns to step S1000. On the other hand, if it is determined in step S1050 that all printing has been completed, the program ends.

  This program is further executed when it is determined in step S1010 that the detected meandering amount exceeds the upper limit value or falls below the lower limit value, and the operation of the image forming apparatus 20 is stopped to execute this program. Step S1060 is ended.

  A control structure of a computer program executed by the image forming apparatus 20 in order to keep the traveling speed of the primary transfer belt 30 constant will be described with reference to FIG. This program starts in response to a print instruction.

  This program is executed after step S2000 for detecting the traveling speed of the primary transfer belt 30 using the optical sensor 200 and after step S2000, and the detected traveling speed exceeds the upper limit value or falls below the lower limit value. Executed when it is determined in step S2010 that branches whether the flow of control depends on the determination result and in step S2010 that the upper limit value is not exceeded or the lower limit value is not exceeded. It is determined whether the detected traveling speed is the same as a preset traveling speed (hereinafter referred to as “Ref speed”), and if not, it is determined whether the detected traveling speed is slow or fast. Step S2020 for branching the flow of control.

  This program is further executed when it is determined in step S2020 that the detected traveling speed is slower than the Ref speed, and the speed of the drive motor 110 is controlled to be faster via the belt control unit 120 so as to match the Ref speed. This is executed when it is determined in step S2030 and step S2020 that the detected traveling speed is faster than the Ref speed, and the speed of the drive motor 110 is controlled to be slower via the belt control unit 120 so as to match the Ref speed. This is executed after step S2040, step S2030, or step S2040, or when it is determined in step S2020 that the detected traveling speed is the same as the Ref speed, and whether or not all printing has been completed. Step of branching the control flow according to the determination result And a 2050. If it is determined in step S2050 that all printing has not been completed, control returns to step S2000. On the other hand, if it is determined in step S2050 that all printing has been completed, the program ends.

  This program is further executed when it is determined in step S2010 that the detected traveling speed exceeds the upper limit value or falls below the lower limit value, and the operation of the image forming apparatus 20 is stopped and this program is executed. Step S2060 is included.

[Operation]
The image forming apparatus 20 according to the present embodiment operates as follows. In the following description, only the part related to the present invention in the operation of the image forming apparatus 20 will be described. Other operations are the same as those of the conventional image forming apparatus.

  The operation of the meander control apparatus 300 will be described with reference to FIG. As shown in FIG. 11A, when the eccentric cam 330 stops at a predetermined angle and the steering roller 310 is held substantially horizontal (inclination is almost 0) corresponding to the stop angle, It is assumed that the primary transfer belt 30 does not move in the width direction D. That is, in this state, the primary transfer belt 30 does not meander. From this state, as shown in FIG. 11B, when the eccentric cam 330 is rotated counterclockwise by driving the eccentric cam drive motor 340, the swing arm 320 is rotated according to the amount of eccentricity of the eccentric cam 330. Swings in the θ1 direction. Accordingly, one end of the steering roller 310 is lifted by the swing arm 320, and the steering roller 310 is inclined according to the lift amount. The primary transfer belt 30 moves to the swing arm side by running in this state. On the other hand, as shown in FIG. 11C, when the eccentric cam 330 is rotated clockwise by driving the eccentric cam drive motor 340, the swing arm 320 is moved in the θ2 direction according to the eccentric amount of the eccentric cam 330. Rocks. As a result, one end of the steering roller 310 is pushed down by the swing arm 320, and the steering roller 310 is inclined according to the amount of the push-down. When the primary transfer belt 30 runs in this state, the primary transfer belt 30 moves to the opposite side (fulcrum side) from the swing arm 320.

  The image forming apparatus 20 executes a printing process when a printing instruction is given. The image forming apparatus 20 controls the belt driving device 100 to cause the primary transfer belt 30 to travel. On the primary transfer belt 30, the single color toner images formed by the image forming units 22K, 22C, 22M, and 22Y are sequentially superimposed and primarily transferred to form a full color toner image. The belt driving device 100 detects the meandering amount of the primary transfer belt 30 using the optical sensor 200 (step S1000 shown in FIG. 9).

  The image forming apparatus 20 (belt driving apparatus 100) determines which side of the steering roller 310 the primary transfer belt 30 is based on the detected meandering amount. When it is determined that the vehicle does not approach either side, that is, meandering has not occurred (the meandering amount is 0), the steering roller 310 is held in this state without controlling the meandering control device 300. (See FIG. 11A). When it is determined that the primary transfer belt 30 is close to the swing arm side, the image forming apparatus 20 causes the primary transfer belt 30 to move to the fulcrum side of the steering roller 310 via the belt control unit 120. The inclination of the steering roller 310 is controlled (step S1030). Specifically, as shown in FIG. 11C, the eccentric cam drive motor 340 is driven to rotate the eccentric cam 330 clockwise in the drawing. As a result, one end of the steering roller 310 is pushed down by the swing arm 320, and the primary transfer belt 30 moves to the fulcrum side. On the other hand, when it is determined that the primary transfer belt 30 is close to the fulcrum side, the image forming apparatus 20 causes the primary transfer belt 30 to move to the swing arm side of the steering roller 310 via the belt control unit 120. Then, the tilt of the steering roller 310 is controlled (step S1040). Specifically, as shown in FIG. 11B, the eccentric cam drive motor 340 is driven to rotate the eccentric cam 330 counterclockwise in the drawing. Thus, one end of the steering roller 310 is lifted by the swing arm 320, and the primary transfer belt 30 moves to the swing arm side. In this manner, the meandering of the primary transfer belt 30 is corrected (corrected) by feedback controlling the meandering control device 300 according to the meandering amount detected by the optical sensor 200.

  If the detected meandering amount exceeds the upper limit value or falls below the lower limit value (YES in step S1010 shown in FIG. 9), image forming apparatus 20 stops its own operation (step S1060). The apparatus can be stopped before the primary transfer belt 30 is damaged or broken by detecting the abnormality of the apparatus. Thereby, it is possible to suppress the primary transfer belt 30 from being damaged or broken by meandering.

  The belt driving device 100 also monitors the traveling speed of the primary transfer belt 30 using the optical sensor 200 that detects the amount of meandering (step S2000 shown in FIG. 10). The primary transfer belt 30 normally travels at a predetermined traveling speed (Ref speed). When the image forming apparatus 20 (belt driving device 100) detects that the traveling speed of the primary transfer belt 30 is lower than the Ref speed, the traveling speed of the primary transfer belt 30 is set to the Ref speed via the belt control unit 120. Thus, the speed of the drive motor 110 is controlled to be high (step S2030). When the image forming apparatus 20 detects that the traveling speed of the primary transfer belt 30 is higher than the Ref speed, the drive motor is configured so that the traveling speed of the primary transfer belt 30 becomes the Ref speed via the belt control unit 120. The speed of 110 is controlled to be slow (step S2040). As described above, the driving speed of the primary transfer belt 30 is controlled to be the Ref speed by performing feedback control of the drive motor 110 according to the traveling speed detected by the optical sensor 200.

  If the detected traveling speed exceeds the upper limit value or falls below the lower limit value (YES in step S2010 shown in FIG. 10), image forming apparatus 20 stops its own operation (step S2060). Also by this, it is possible to stop the apparatus before the abnormality of the apparatus is detected and the primary transfer belt 30 is damaged or broken.

  A more specific control operation of the primary transfer belt will be described with reference to FIGS. FIG. 12 shows an example of the meandering amount of the primary transfer belt detected by the optical sensor 200. FIG. 13 shows an example of the traveling speed of the primary transfer belt detected by the optical sensor 200. 12 and 13 are graphs in a state where correction control is not performed.

  Referring to FIG. 12, an upper limit value is set on the fulcrum side of steering roller 310 and a lower limit value is set on the swing arm side with respect to the Ref position (position where the meandering amount is 0). The broken line in the figure shows an example when the amount of meandering exceeds the upper limit value. In the sections AB and CD, the image forming apparatus 20 determines that the belt is close to the swing arm side with respect to the Ref position, and the steering roller 310 moves so that the primary transfer belt moves to the fulcrum side. Control the tilt. In the section B-C, the image forming apparatus 20 determines that the belt is close to the fulcrum side with respect to the Ref position, and controls the tilt of the steering roller 310 so that the primary transfer belt moves to the swing arm side. In the section D-E, since the detected meandering amount exceeds a set value (lower limit value or upper limit value), the image forming apparatus 20 performs an emergency stop of the own apparatus, for example.

  Referring to FIG. 13, in section ab, since the actual traveling speed is slower than the Ref speed, image forming apparatus 20 performs control to increase the rotation of drive motor 110. In the section bc, since the actual traveling speed is faster than the Ref speed, the image forming apparatus 20 performs control to reduce the rotation of the drive motor 110. In the section cd or the section ce, the speed of the primary transfer belt suddenly decreases and the belt traveling speed exceeds the lower limit value. Judging that the belt is caught, stop the aircraft urgently. In the section ef, since the belt speed is rapidly increased and the belt traveling speed exceeds the upper limit value, the image forming apparatus 20 determines that the belt is broken, for example. Emergency stop.

[Action / Effect]
As is clear from the above description, the following effects can be obtained by using the image forming apparatus 20 according to the present embodiment.

  Referring to FIG. 1, the primary transfer belt 30 is supported by a predetermined number of rollers including a driving roller (supporting roller 32a). When the support roller 32a is driven by the drive motor 110, the primary transfer belt 30 travels in the arrow R direction. With reference to FIG. 3, the optical sensor 200 detects the meandering amount of the primary transfer belt 30 in a non-contact manner. The optical sensor 200 detects the amount of movement of the primary transfer belt 30 in the two-dimensional direction by receiving reflected light of the light irradiated on the primary transfer belt 30. The inclination of the steering roller 310 in the meandering control device 300 is controlled according to the detected meandering amount, and the meandering of the primary transfer belt 30 is corrected by the meandering control device 300.

  Since the optical sensor 200 is configured to receive the reflected light from the primary transfer belt 30 and detect the amount of movement in the two-dimensional direction, the size of the optical sensor 200 should be such that the reflected light can be received. It's enough. Therefore, it can suppress that sensor itself enlarges. Furthermore, the optical sensor 200 can detect the meandering amount of the primary transfer belt 30 even at a desired position other than the edge of the primary transfer belt 30. Of course, the meandering amount of the primary transfer belt 30 can also be detected at the edge position of the primary transfer belt 30. Thereby, the freedom degree of design is raised. By installing the optical sensor 200 at a position where it is difficult to become dirty, it is possible to suppress a decrease in detection accuracy due to the dirt. Furthermore, since the detection data detected by the optical sensor 200 does not include an error component due to the edge shape of the belt, the amount of meandering can be accurately detected by using such an optical sensor. In addition, since it is not necessary to acquire and store the edge shape data in advance, it is not necessary to perform such a complicated operation. Therefore, by controlling the meandering control device 300 according to the meandering amount detected by the optical sensor 200, the meandering of the primary transfer belt 30 can be accurately corrected without requiring a complicated operation.

  Further, by using the optical sensor 200, not only the meandering amount but also the traveling speed of the primary transfer belt 30 can be detected in real time. The traveling speed can be kept constant by feedback control of the traveling speed of the primary transfer belt 30 in accordance with the detected traveling speed. For example, when meandering occurs in the primary transfer belt 30, the traveling speed of the primary transfer belt 30 may change. In the present embodiment, by performing such feedback control, the traveling speed can be kept constant even when meandering occurs in the primary transfer belt 30. Accordingly, since the travel of the primary transfer belt 30 can be appropriately controlled, it is possible to effectively suppress a decrease in print quality (image quality).

  By disposing the optical sensor 200 in the central portion of the primary transfer belt 30 in the width direction, the meandering amount and the traveling speed of the primary transfer belt 30 can be detected at a position closer to the area where the toner image is transferred. By controlling the primary transfer belt 30 based on the detected meandering amount and traveling speed, the meandering of the primary transfer belt 30 can be corrected more accurately and the traveling speed of the primary transfer belt 30 can be kept constant more accurately. it can. Thereby, since the positional deviation in the width direction of the area where the toner image is transferred can be effectively suppressed, it is possible to more effectively suppress the decrease in print quality (image quality).

(Second Embodiment)
Referring to FIG. 14, in the image forming apparatus according to the present embodiment, optical sensor 200 and meandering control device 300 are arranged between image forming unit 22Y and support roller 32a (secondary transfer belt 34). This is different from the image forming apparatus 20 according to the first embodiment. In other respects, the image forming apparatuses have the same configuration.

  The meandering of the primary transfer belt 30 and the change in the running speed need to be suppressed before the toner image on the primary transfer belt 30 is transferred to the recording paper P. In the present embodiment, the optical sensor 200 is disposed between the image forming unit 22Y and the support roller 32a in order to effectively suppress changes in the meandering and running speed of the primary transfer belt 30. However, when the optical sensor 200 is provided on the surface side of the primary transfer belt 30 at such a position, there is a possibility that the sensor becomes dirty due to toner scattering or the like and cannot be sensed. Therefore, in the present embodiment, the optical sensor 200 is disposed on the back side of the primary transfer belt 30. That is, the optical sensor 200 detects the amount of meandering of the primary transfer belt 30 by irradiating the back surface of the primary transfer belt 30 with light. When detecting the amount of meandering, the running speed, etc. on the back side of the primary transfer belt 30, a reading error corresponding to the thickness of the belt may occur. Therefore, it is preferable that such an error be corrected as necessary.

  In the present embodiment, the meandering control device 300 is also disposed between the image forming unit 22Y and the support roller 32a in accordance with the change in the arrangement position of the optical sensor 200.

(Third embodiment)
In the present embodiment, the present invention is applied to a fixing unit for fixing a full-color toner image transferred onto a recording sheet onto the recording sheet. In this respect, the image forming apparatus according to the present embodiment is different from the image forming apparatus 20 according to the first embodiment. In other respects, the image forming apparatuses have the same configuration.

  Referring to FIG. 15, fixing unit 400 includes a belt driving device 410. The belt driving device 410 includes a fixing belt 412, a fixing roller 414, a fixing belt driving motor 416, a heating roller 418, an optical sensor 420, and a meandering control device 430. The fixing unit 400 further includes a pressure roller 440 and a belt cleaning unit 450. The fixing unit 400 may not include the belt cleaning unit 450.

  The fixing belt 412 is an endless belt member that is stretched between the fixing roller 414 and the heating roller 418 to form a loop-shaped movement path. The fixing belt 412 is provided so as to come into contact with the pressure roller 440 through a pressure contact between the fixing roller 414 and the pressure roller 440, and each color toner constituting an unfixed multicolor toner image carried on the recording paper P. Is heated and melted and fixed on the recording paper P. The fixing belt 412 rotates (runs) at a predetermined speed in the direction of the arrow Ra by the rotation driving of the fixing roller 414.

  The fixing roller 414 is a roller-like member (drive roller) that is rotatably supported by a support member (not shown) and is driven to rotate by a fixing belt drive motor 416. The heating roller 418 is a roller-like member (driven roller) that is rotatably supported and is provided so as to apply tension to the fixing belt 412. The heating roller 418 has a heating member (not shown) therein. As a result, the fixing belt 412 is heated.

  The pressure roller 440 is pressed against the fixing roller 414 via the fixing belt 412 by a pressure mechanism (not shown) to form a fixing nip portion. The pressure roller 440 presses each color toner in a molten state against the recording paper P when the fixing roller 414 heats and fixes the unfixed multicolor toner image onto the recording paper P, thereby unfixed multicolor toner images. The fixing of the color toner image to the recording paper P is promoted.

  The optical sensor 420 and the meandering control device 430 have the same configurations as the optical sensor 200 and the meandering control device 300 shown in the first embodiment, respectively. The optical sensor 420 detects the amount of meandering and traveling speed of the fixing belt 412. The meandering control device 430 corrects the meandering of the fixing belt 412 according to the meandering amount detected by the optical sensor 420. In the present embodiment, the meandering of the fixing belt 412 is corrected and the running speed of the fixing belt 412 is kept constant by the same control as the belt driving device 100 in the first embodiment.

  When meandering occurs on the fixing belt 412, fixing unevenness or the like occurs and print quality (image quality) decreases. Even when the traveling speed of the fixing belt 412 changes, the print quality (image quality) is lowered. Therefore, it is possible to suppress a decrease in print quality (image quality) by appropriately correcting the meandering of the fixing belt 412 and the like.

  The meandering and speed changes of the fixing belt 412 need to be suppressed before the toner image is fixed on the recording paper P. Therefore, it is preferable that the optical sensor 420 and the meandering control device 430 are disposed at a position before the toner image is fixed on the recording paper P. In the case where the belt cleaning unit 450 is provided, the optical sensor 420 is more preferably disposed at a position downstream of the belt cleaning unit 450. Since the dirt on the fixing belt 412 is removed by the belt cleaning unit 450 before reaching the position of the optical sensor 420, the dirt on the fixing belt 412 can prevent the optical sensor 420 from becoming dirty. Thereby, the fall of the detection accuracy resulting from the optical sensor 420 becoming dirty can be suppressed.

(Fourth embodiment)
The image forming apparatus according to the present embodiment is the image forming apparatus according to the first embodiment in that the meandering amount of the belt and the traveling speed detected by the optical sensor are stored in the HDD as a history of the belt movement locus. Different from 20. In other respects, the image forming apparatuses have the same configuration.

  In the present embodiment, the information detected by the optical sensor is stored in the HDD together with the detected date / time information. The image forming apparatus stores all the history of the belt movement locus detected by the optical sensor in the HDD. Information stored in the HDD can be read by the user operating the operation unit. This makes it possible to confirm in detail how the primary transfer belt or the fixing belt has moved in the event of a trouble such as a decrease in print image quality, thereby facilitating analysis of the cause of the trouble.

  Information detected by the optical sensor may be stored (stored) in a storage device other than the HDD (for example, an external storage device such as a USB memory). Instead of storing all the information detected by the optical sensor, a part of the information may be stored. For example, information detected by the optical sensor may be stored in response to a predetermined trigger. Specifically, for example, a threshold value may be set for the meandering amount or traveling speed, and information may be stored when the detected meandering amount or traveling speed exceeds a set threshold value. Further, when the stored information passes a certain period, the information may be deleted. Furthermore, information newly detected in predetermined time units may be overwritten and stored.

(Fifth embodiment)
Referring to FIG. 16, belt conveyor 500 according to the present embodiment places manufactured product 610 below lot number printing device 600 when printing a lot number or the like on manufactured product 610 using lot number printing device 600. It is the conveying apparatus which conveys to. The belt conveyor 500 includes a belt driving device 510. The belt driving device 510 includes a conveying belt 512 that is an endless belt-like member, a predetermined number of rollers that support the conveying belt 512, and a belt driving motor 524 that rotates (runs) the conveying belt 512. The belt driving device 510 further includes an optical sensor 530 that detects the meandering amount and traveling speed of the transport belt 512 and a meander control device 540 that corrects the meandering of the transport belt 512.

  The optical sensor 530 and the meandering control device 540 have the same configurations as the optical sensor 200 and the meandering control device 300 according to the first embodiment, respectively. The meandering control device 540 corrects the meandering of the conveyor belt 512 by the tilting operation of the steering roller. The predetermined number of rollers that support the conveyance belt 512 include a driving roller 514, driven rollers 516 to 522, and a steering roller. The driving roller 514 is rotationally driven by a belt driving motor 524. The conveyance belt 512 rotates (runs) at a predetermined speed in the direction of the arrow Rb by the rotational driving of the driving roller 514. The belt driving device 510 includes a control device (not shown), and corrects meandering of the conveying belt 512 and makes the traveling speed of the conveying belt 512 constant by the same control as the belt driving device 100 in the first embodiment. Perform feedback control.

  In the belt conveyor 500 according to the present embodiment, since the meandering of the transport belt 512 can be corrected appropriately, the printing accuracy of the lot number and the like by the lot number printing device 600 can be improved. It is preferable that the optical sensor 530 and the meandering control device 540 are arranged in front of the lot number printing device 600 (on the upstream side in the belt traveling direction). By arranging the optical sensor 530 and the meandering control device 540 at such a position, it is possible to improve the printing accuracy and increase the speed of the conveying belt 512. FIG. 16 shows an example in which the optical sensor 530 is arranged on the back side of the conveyor belt 512. However, the optical sensor 530 can also be disposed on the surface side of the conveyor belt 512.

(Modification)
In the above-described embodiment, an example in which the present invention is applied to a tandem full-color image forming apparatus has been described. However, the present invention is not limited to such an embodiment. The present invention can be applied to any image forming apparatus other than the tandem type as long as the image forming apparatus includes a belt driving device that travels an endless belt. Furthermore, the present invention can also be applied to apparatuses other than the image forming apparatus and the belt conveyor. The image forming apparatus may be a multifunction peripheral (MFP) having a plurality of operation modes such as a copy mode and a print mode, or may be an image forming apparatus such as a copier, a printer, or a facsimile.

  In the above-described embodiment, an example in which an optical finger mouse, which is a small optical pointing device, is used as an optical sensor that detects the amount of meandering is shown, but the present invention is not limited to such an embodiment. The optical sensor may be a sensor other than the optical finger mouse as long as it can detect the amount of movement of the belt by receiving the reflected light from the belt.

  In the said embodiment, although the light emitting part of the optical sensor showed about the structural example containing LED which irradiates infrared light, this invention is not limited to such embodiment. The light emitting unit of the optical sensor may include a light emitting element that emits light other than infrared light. For example, the light emitting element which irradiates light (for example, blue light) whose wavelength is shorter than infrared light may be included. Further, the light emitting unit may include a laser diode (Laser Diode) that emits invisible laser light, for example, instead of the LED. Since the laser light travels in a uniform direction, irregular reflection is unlikely to occur, so the image sensor can accurately capture the image (pattern) on the irradiated surface. Therefore, the amount of belt meandering can be detected with higher accuracy.

  In the above embodiment, in addition to the detection of the meandering amount, the moving speed in the belt width direction (direction perpendicular to the running direction) may be detected by an optical sensor. In this case, it is preferable to be configured to warn the user or stop the device in response to detecting a sudden fluctuation in the width direction.

  In the said embodiment, the example which stops an apparatus when the amount of meandering detected by the optical sensor or the running speed of a belt exceeded an upper limit or a lower limit was shown. In this case, a message screen may be displayed on the operation unit to notify the user of the reason for stopping the apparatus.

  In the fourth embodiment, an example in which the amount of meandering is detected using the same optical sensor as the optical sensor shown in the first embodiment has been described. However, the present invention includes such an embodiment. It is not limited. Data such as the meandering amount of the belt may be acquired using a sensor having a configuration different from that of the optical sensor, and the acquired data may be stored in the storage device such as the HDD as history data of the belt movement locus. For example, instead of the optical sensor, data such as the amount of meandering of the belt may be acquired by a transmission type optical sensor or the like, and the acquired data may be stored in a storage device such as an HDD.

  The embodiment disclosed herein is merely an example, and the present invention is not limited to the embodiment described above. The scope of the present invention is indicated by each claim of the claims after taking into account the description of the detailed description of the invention, and all modifications within the meaning and scope equivalent to the wording described therein are included. Including.

20 Image forming device 22K, 22C, 22M, 22Y Image forming unit 30 Primary transfer belt 32a, 32b Support roller 36 Control device 50, 400 Fixing unit 100, 410, 510 Belt drive device 110 Drive motor 120 Belt control unit 200, 420, 530 Optical sensor 210 Light emitting unit 222 Image sensor 224 Arithmetic unit 300, 430, 540 Meander control device 310 Steering roller 320 Oscillating arm 330 Eccentric cam 340 Eccentric cam drive motor 412 Fixing belt 414 Fixing roller 416 Fixing belt driving motor 418 Heating roller 500 Belt conveyor 512 Conveyor belt 514 Drive roller 524 Belt drive motor

Claims (9)

An endless belt supported by a predetermined number of rollers including a drive roller;
Roller driving means for driving the drive roller to run the belt;
Meandering correction means for correcting meandering, which is a position variation in the width direction of the belt, generated when the belt is driven by the roller driving means;
Meandering amount detection means for detecting the meandering amount of the belt in a non-contact manner;
Meandering control means for controlling the meandering correction means according to the meandering amount detected by the meandering amount detection means,
The meandering amount detection means includes an optical sensor that detects the amount of movement in the two-dimensional direction of the belt by receiving reflected light of the light irradiated to the belt, and using the optical sensor, A belt drive that detects the amount of meandering. The optical sensor is
An irradiation unit for irradiating the belt with light;
Movement that detects the amount of movement in the two-dimensional direction of the belt by continuously acquiring images of the portion irradiated with light on the belt by receiving reflected light from the belt of light irradiated by the irradiation unit The belt drive device according to claim 1, further comprising a quantity detection unit.   Means for determining whether the meandering amount of the belt detected by the meandering amount detection means is greater than a predetermined value, and for stopping the belt driving device in response to a positive determination result; The belt drive device according to claim 1, comprising: a belt drive device according to claim 1. Speed detecting means for detecting the speed of the belt in the running direction;
A speed control means for controlling the roller driving means so that the belt speed becomes a predetermined speed according to the speed detected by the speed detection means;
The optical sensor is capable of detecting a moving speed based on the detected moving amount,
The belt driving device according to any one of claims 1 to 3, wherein the speed detection unit detects a speed of the belt in a traveling direction using the optical sensor.   It is determined whether the speed of the belt detected by the speed detection means has changed to a predetermined speed different from the predetermined speed, and in response to the determination result being affirmative, the belt drive device is The belt drive of claim 4, further comprising means for stopping. Speed storage means for storing the speed of the belt detected by the speed detection means;
The belt driving device according to claim 4 or 5, further comprising a reading unit for reading the speed stored in the speed storage unit in response to a user instruction. Meandering amount storage means for storing the meandering amount of the belt detected by the meandering amount detection means;
The belt driving device according to claim 1, further comprising: a reading unit configured to read the meandering amount stored in the meandering amount storage unit according to a user instruction.   An image forming apparatus comprising the belt driving device according to claim 1. A belt conveyor including the belt driving device according to claim 1.

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