JP2009258281A - Belt position detecting mechanism and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a position of the end in a width direction of a circulating endless belt while preventing drastic rise of cost. <P>SOLUTION: The belt position detecting mechanism for detecting the position of the end in the width direction of an endless intermediate transfer belt 1 provided in an image forming apparatus main body and circulating at constant speed with respect to the image forming apparatus main body is equipped with: a part to be detected 2 provided at a part of one periphery 1a of the intermediate transfer belt 1, extending in the width direction B of the intermediate transfer belt 1 and having a pair of detection ends 2a and 2b which are non-parallel with each other and located front and rear in a circulating direction; an optical sensor 3 fixed in the image forming apparatus main body to face the one periphery 1a of the intermediate transfer belt 1 and optically detecting the pair of detection ends 2a and 2b of the circulating part to be detected 2; and an arithmetic means 4 measuring passing time T1 between both detection ends 2a and 2b based on a detection signal from the optical sensor 3 and obtaining the position of the end in the width direction based on previously stored reference passing time and the measured passing time T1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a belt position detection mechanism and an image forming apparatus that detect the end position in the width direction of an endless belt that circulates in an image forming apparatus such as a facsimile, a copying machine, and a printer.

  In the image forming apparatus described above, various endless belts are incorporated. For example, an intermediate transfer belt or a conveyance belt used to transfer an electrostatic latent image formed on a photosensitive member to a transfer sheet after being visualized with toner is incorporated. ing.

In such an endless belt used for various purposes, a sensor for detecting an end position in the width direction of the belt is attached. The sensor includes a photoelectric sensor provided with an LED and a photodetector, a shutter attached to a shaft that rotates in the optical path between the LED and the photodetector, and one end mechanically connected to the shaft. And an elongated arm that is fixed to the other end of the elongated arm that engages the movable photoreceptor surface, thereby rotating the shutter in the optical path between the LED and the photodetector when the edge position of the photoreceptor surface is misaligned Mechanically coupled to the contact member to be driven, and the surface of the photoconductor and a steering motor connected to the steering roll, whereby the edge position of the surface of the photoconductor is adjusted according to the position of the shutter with respect to the optical path between the LED and the photodetector. One having a steering roll to be changed is known (for example, see Patent Document 1).
JP-A-8-106237

  By the way, the sensor for detecting the position in the width direction of the belt according to Patent Document 1 is expensive and has a drawback that the cost is significantly increased.

  The present invention has been made to solve the above-described problems of the prior art, and is a belt position detection mechanism that can detect the end position in the width direction of an endless belt that circulates while preventing a significant increase in cost. It is another object of the present invention to provide an image forming apparatus including the same.

  A belt position detection mechanism according to a first aspect of the present invention is a belt position detection mechanism for detecting an end position in a width direction of an endless belt provided in an image forming apparatus main body and rotating at a constant speed with respect to the image forming apparatus main body. A detected portion having a pair of detection end portions provided in a part of one peripheral edge of the endless belt and extending in the width direction of the endless belt, which are non-parallel to each other and back and forth in the circumferential direction; and the endless belt An optical sensor that is fixed to the image forming apparatus main body so as to face one of the peripheral edges and optically detects the pair of detection end portions of the detected portion that circulates, and a detection signal from the optical sensor. Computation means for measuring the passage time between the two detection ends and calculating the end position in the width direction based on the reference passage time stored in advance and the measured passage time are provided.

  The belt position detection mechanism according to claim 2 of the present invention is characterized in that the pair of detection end portions of the detected portion are inclined in opposite directions.

  The belt position detection mechanism according to claim 3 of the present invention is characterized in that each of the pair of detection end portions has an inclination angle of 45 degrees or less with respect to the belt peripheral edge.

  The belt position detecting mechanism according to claim 4 of the present invention is characterized in that the detected portion is formed of a light shielding piece projecting outward from a peripheral edge of the endless belt.

  In the belt position detection mechanism according to claim 5 of the present invention, the detected portion includes a translucent base material protruding outward from a peripheral edge of the endless belt, and a light shielding pattern formed on the base material. It is characterized by comprising.

  An image forming apparatus according to the present invention includes an endless rotating intermediate transfer belt to which an image formed by each color image forming unit provided in an image forming apparatus main body is transferred, and the end position in the width direction of the intermediate transfer belt is set. A belt position detection mechanism according to any one of claims 1 to 5 is provided.

  In the case of the belt position detection mechanism of the present invention, the passage time between the detection ends by the calculation means based on the detection of the front detection end and the rear detection end of the detected portion by the optical sensor. Is required. At this time, when the endless belt meanders, the detection position in the belt width direction of the detected portion by the optical sensor arranged at a fixed position changes. And since a pair of detection edge part of a to-be-detected part is mutually non-parallel, the passage time between both detection edge parts changes according to the position change of the detection edge part in the said belt width direction. Based on the reference passage time as a reference value of the passage time and the measured passage time, for example, the relationship between the difference between the reference passage time and the measured passage time and the change in the end position in the width direction of the endless belt, or The end position of the endless belt in the width direction is obtained by calculation based on the relationship between the difference between the reference passing time and the measured passing time and the position change of the detection end in the belt width direction. Therefore, since detection using a normal optical sensor is possible, a significant increase in cost can be prevented.

  In the case of the belt position detection mechanism according to the second aspect, both the detection end on the downstream side in the circumferential direction and the detection end on the upstream side in the circumferential direction of the detected part are inclined in opposite directions. The change in the passage time between the end portions can be increased, and the end position in the width direction of the endless belt is obtained with high accuracy.

  In the case of the belt position detection mechanism according to claim 3, each detection end inclined in the opposite direction has an inclination angle of 45 degrees or less with respect to the belt peripheral edge, and between the two detection ends with respect to a change in the belt width direction. Therefore, the detection accuracy of the end position in the width direction of the endless belt based on the passage time between the two detection end portions is improved.

  As the detected part of the present invention, for example, a light shielding piece as in claim 4 or a light-shielding pattern formed on a translucent substrate as in claim 5 is used. In the case of a light shielding piece, the detection end portion corresponds to a part of the outer peripheral edge, and in the case where the light shielding pattern is formed on the base material, a part of the outer peripheral edge of the light shielding pattern corresponds. .

  Further, in the case of the image forming apparatus of the present invention, the same effect as the belt position detection mechanism described above can be obtained with the intermediate transfer belt as the detection target.

  The present invention will be specifically described below.

  FIG. 1 is a front sectional view for explaining an embodiment of an internal structure of an image forming apparatus including a belt position detecting mechanism according to the present invention. An image forming apparatus 10 shown in FIG. 1 is used as a printer dedicated to printing processing, and forms an image in an apparatus body 11 having a box shape based on image information transmitted from an external device such as a computer. An image forming unit 12, a fixing unit 13 that fixes the image formed by the image forming unit 12 and transferred to the paper P, and a paper storage unit 14 that stores the transfer paper P are provided. At the same time, a basic structure is formed by forming a paper discharge portion 15 for discharging the paper P after the fixing process at the upper portion of the apparatus main body 11.

  At an appropriate position on the upper surface of the apparatus main body 11, an operation panel (not shown) for inputting the output conditions of the paper P and the like is provided. This operation panel is provided with a power key, a start button (not shown), various keys for inputting output conditions, and the like.

  The image forming unit 12 forms a toner image on the paper P fed from the paper storage unit 14, and in the present embodiment, the image forming unit 12 is directed from the upstream side (the right side of the paper surface in FIG. 1) to the downstream side. Sequentially arranged magenta unit 12M using magenta toner (developer), cyan unit 12C using cyan toner, yellow unit 12Y using yellow toner, and black toner And a black unit 12K using the above. These units 12M, 12C, 12Y, and 12K constitute an image forming unit for each color.

  Each of the units 12M, 12C, 12Y, and 12K is provided with a photosensitive drum (image carrier) 20 and a developing device 121, respectively. The photosensitive drum 20 is for forming an electrostatic latent image and a toner image (visible image) along the electrostatic latent image on the peripheral surface. Each photoconductor drum 20 receives supply of toner from the corresponding developing device 121 while rotating counterclockwise in FIG. Each developing device 121 is replenished with toner from an unillustrated toner cartridge disposed on the front side of the apparatus main body 11 (the front side of the paper surface of FIG. 1).

In the present embodiment, a so-called two-component system composed of toner and carrier is used as the developer. The toner is a fine powder having a particle diameter of 6 to 12 μm in which additives such as a colorant, a charge control agent and wax are dispersed in a binder resin. On the other hand, the carrier is magnetic particles having a particle size of 60 to 200 μm such as magnetite (Fe ₃ O ₄ ), and is used for charging the toner. The toner is a consumable that is appropriately replenished to the developing device 121 from a toner cartridge (not shown), whereas a predetermined amount of the carrier is loaded in the developing device 121 in advance, and is used without being consumed. It is common to be done.

  A charging device 122 is provided immediately below each of the photosensitive drums 20, and an exposure device 123 is provided further below each charging device 122. Each photosensitive drum 20 is charged uniformly by the charging device 122, and laser light corresponding to each color based on image data input from a computer or the like is charged from each exposure device 123 after being charged. By irradiating the peripheral surface of the photoconductive drum 20, an electrostatic latent image is formed on the peripheral surface of each photoconductive drum 20. By supplying toner from the developing device 121 to the electrostatic latent image, a toner image is formed on the peripheral surface of the photosensitive drum 20.

  An intermediate transfer belt (transfer object) 1 is disposed above each of the photosensitive drums 20. The intermediate transfer belt 1 is stretched between a left driving roller 36 and a right driven roller 37 in FIG. 1, and a forward belt (lower belt) on the side performing its function is a photosensitive drum. 20 is in contact with the peripheral surface. The intermediate transfer belt 1 is synchronized with each photoconductive drum 20 while being pressed against the peripheral surface of the photoconductive drum 20 by a primary transfer roller (transfer member) 40 provided corresponding to each photoconductive drum 20. It circulates between the driving roller 36 and the driven roller 37.

  A tension roller 38 is provided between the drive roller 36 and the driven roller 37 and at a position close to the driven roller 37 side. The tension roller 38 applies tension to the intermediate transfer belt 1 and is biased upward by a biasing force of a biasing member (not shown). Accordingly, the return belt on the upper side of the intermediate transfer belt 1 (the belt on the side not in contact with the photosensitive drum 20 but in contact with the tension roller 38) is pushed upward by the tension roller 38, thereby The portion supported by the tension roller 38 has a mountain shape with a peak.

  As the intermediate transfer belt 1 circulates, the toner image of the magenta toner is transferred onto the surface of the intermediate transfer belt 1 by the photosensitive drum 20 of the magenta unit 12M, and then the cyan unit 12C is transferred to the same position on the intermediate transfer belt 1. The transfer of the cyan toner toner image by the photosensitive drum 20 is performed in an overcoating state, and then the transfer of the yellow toner toner image by the photoconductor drum 20 of the yellow unit 12Y to the same position of the intermediate transfer belt 1 is performed. Then, the transfer of the black toner image by the photosensitive drum 20 of the last black unit 12K is performed in an overcoating state, whereby a color toner image is formed on the surface of the intermediate transfer belt 1. The color toner image formed on the surface of the intermediate transfer belt 1 is transferred to the paper P conveyed from the paper storage unit 14.

  Further, a drum cleaning device 124 that removes and cleans residual toner on the peripheral surface of the photosensitive drum 20 is provided at the left position of each photosensitive drum 20 in FIG. The peripheral surface of the photosensitive drum 20 cleaned by the drum cleaning device 124 is directed to the charging device 122 for a new charging process.

  Waste toner removed from the peripheral surface of the photosensitive drum 20 by the drum cleaning device 124 is collected in a toner collection bottle (not shown) through a predetermined path.

  A sheet conveyance path 111 extending in the vertical direction is formed at the left position of the image forming unit 12 in FIG. The sheet conveying path 111 is provided with a pair of conveying rollers 112 at appropriate positions, and the sheet P from the sheet storage unit 14 is directed to the intermediate transfer belt 1 that is wound around the driving roller 36 by the driving of the conveying roller pair 112. Are transported. In the sheet conveyance path 111, a secondary transfer roller 113 that is in contact with the surface of the intermediate transfer belt 1 is provided at a position facing the driving roller 36. Then, the sheet P being conveyed through the sheet conveyance path 111 is pressed and sandwiched between the intermediate transfer belt 1 and the secondary transfer roller 113, whereby the toner image on the intermediate transfer belt 1 is transferred to the sheet P.

  The fixing unit 13 performs a fixing process on the toner image on the paper transferred by the image forming unit 12, and includes a heating roller 131 including an energization heating element serving as a heating source therein, and a left side in FIG. The fixing roller 132 disposed opposite to the heating roller 131, the fixing belt 133 stretched between the fixing roller 132 and the heating roller 131, and disposed opposite to the fixing roller 132 via the fixing belt 133. The pressure roller 134 is provided.

  The sheet P supplied to the fixing unit 13 in a state where the toner image on the intermediate transfer belt 1 is transferred by passing through the nip portion between the intermediate transfer belt 1 and the secondary transfer roller 113 is pressurized. While passing between the roller 134 and the high-temperature fixing belt 133, heat from the fixing belt 133 is obtained and fixing processing is performed.

  The color-printed paper P that has been subjected to the fixing process passes through a paper discharge conveyance path 114 extending from the upper part of the fixing unit 13 to a paper discharge tray 151 of a paper discharge unit 15 provided at the top of the apparatus main body 11. It is discharged towards.

  The sheet storage unit 14 includes a manual feed tray 141 that can be freely opened and closed on the right side wall in FIG. 1 of the apparatus main body 11, and a paper tray 142 that is removably mounted at a position below the exposure device 123 in the apparatus main body 11. And. A sheet bundle in which a plurality of sheets P are stacked is stored in the sheet tray 142.

  The manual feed tray 141 is for manually feeding the paper P one by one toward the image forming unit 12 by manual feed operation, and is usually stored on the right wall surface of the apparatus main body 11, but manually fed. Only when this is done, as shown in FIG. 1, it is pulled out from the wall surface and used for manual paper feeding.

  The paper tray 142 includes a box body whose upper surface is open on the entire surface, and can store a sheet bundle P1 formed by stacking a plurality of sheets P. The uppermost sheet P of the sheet bundle P1 stored in the sheet tray 142 is fed from the sheet bundle P1 toward the sheet conveyance path 111 by driving the pickup roller 143 from the upper surface of the downstream end (left end in FIG. 1). Then, the sheet P fed out one by one from the sheet tray 142 passes through the sheet conveyance path 111 by driving the conveyance roller pair 112, and the nip between the secondary transfer roller 113 and the intermediate transfer belt 1 in the image forming unit 12. It is sent to the department.

  In the illustrated example, secondary transfer (the color image on the forward belt of the intermediate transfer belt 1 is transferred onto the paper P at the nip portion between the intermediate transfer belt 1 and the secondary transfer roller 113 at the position of the drive roller 36). A belt cleaning device 125 is provided at a position corresponding to the driven roller 37 to remove and clean the residual toner remaining on the return belt of the intermediate transfer belt 1 after the above.

  FIG. 2 is a perspective view schematically showing an intermediate transfer belt as a detection target to be detected by a belt position detection mechanism according to an embodiment of the present invention, and FIG. 3 is a belt position detection according to the embodiment. It is a block diagram which shows a mechanism.

  The intermediate transfer belt 1 shown in FIG. 2 is an endless belt that circulates between the driving roller 36 and the driven roller 37 in synchronization with the respective photosensitive drums 20 as described above, and is attached upward by the tension roller 38. It is energized.

  The circumferential direction A of the intermediate transfer belt 1 is clockwise in FIGS. 1 and 2. A detected portion 2 is provided at one peripheral edge of the intermediate transfer belt 1, and an optical sensor 3 is provided at a position downstream of the driving roller 36 of the intermediate transfer belt 1.

  The to-be-detected part 2 is formed in a trapezoidal shape by cutting both longitudinal ends of a belt-shaped material made of a resin film such as a PET (polyethylene terephthalate) film. This PET film has a light shielding property due to coloring or the like. The attachment base 2c of the detected portion 2 is attached to a part of one peripheral edge 1a of the intermediate transfer belt 1. The detection part 2 is attached in such a manner that the height direction of the trapezoidal detection part 2 (the direction perpendicular to the longitudinal direction of the belt-like resin film) coincides with the width direction B of the intermediate transfer belt 1 and from the peripheral edge 1a. The height dimension (dimension in the direction coinciding with the width direction B) of the detected portion 2 protruding outward is set to, for example, 5 mm to 10 mm.

  Further, the portion of the detected portion 2 that protrudes outward from the peripheral edge 1a is detected in the circumferential direction downstream side (hereinafter simply referred to as the front side) that is oblique to the circumferential direction and is linearly cut in opposite directions. It has an end 2a and a detection end 2b on the upstream side in the circumferential direction (hereinafter simply referred to as the rear side). The inclinations of the detection end 2a on the front side and the detection end 2b on the rear side are set to 45 ° with respect to the circumferential direction, for example. The detection end 2a on the front side is positioned closer to the circumferential direction A side than the side far from the intermediate transfer belt 1, and the detection end 2b on the rear side is opposite to the detection end 2a on the front side. The far side is located closer to the circumferential direction A than the near side. In addition, since it is not a location used for a measurement regarding the base 2c, it may have an arbitrary shape suitable for attachment, for example, a rectangular shape indicated by a broken line in FIG.

  As the optical sensor 3, for example, a transmission type having a light emitting element 3a and a light receiving element 3b is used, and is fixed so that the detected portion 2 passes between the light emitting element 3a and the light receiving element 3b. Yes. The light emitting element 3a has a light emitting part 3c that emits light, and the light emitted from the light emitting part 3c is transmitted by the detected part 2 when the detected part 2 passes between the light emitting element 3a and the light receiving element 3b. Shaded. On the other hand, before and after the detected portion 2 passes between the light emitting element 3a and the light receiving element 3b, the light emitted from the light emitting portion 3c is captured by the light receiving portion 3d of the light receiving element 3b. . In addition, when using what has a light reflection function for the to-be-detected part 2 as the optical sensor 3, you may use the reflective type which catches the reflected light from the to-be-detected part 2. FIG.

  The optical sensor 3 outputs a Hi signal to the arithmetic unit 4 as a detection signal when the level of light captured by the light receiving unit 3d is equal to or higher than a predetermined value, and a Lo signal when the level is lower than the predetermined value.

  The calculation device 4 includes a width direction end position calculation unit 5. The width direction end position calculation unit 5 is configured to detect both detection end portions 2a and 2b based on the detection signal from the detection end 2a on the front side of the detection target portion 2 and the detection signal from the detection end portion 2b on the rear side from the optical sensor 3. And the end position in the width direction is obtained based on the reference passage time stored in advance and the measured passage time (T).

  That is, since the detection end 2a on the front side and the detection end 2b on the rear side of the detected part 2 are oblique to the circumferential direction A and are linearly cut in opposite directions, The length dimension in the circumferential direction A is changed in the width direction B of the intermediate transfer belt 1. Therefore, when the intermediate transfer belt 1 meanders and the detection position of the detected portion 2 by the fixed optical sensor 3 changes in the width direction B of the intermediate transfer belt 1, both detection end portions detected by the optical sensor 3 are detected. The transit time (T) between 2a and 2b changes. For example, when the optical sensor 3 measures a location C1 far from the peripheral edge 1a, the passing time (T) is T1, and when the optical sensor 3 measures a location C2 close to the peripheral edge 1a, the passing time (T) is T2. (> T1).

Here, when the inclination angle θa of the detection end 2a relative to the peripheral edge 1a is equal to the inclination angle θb of the detection end 2b, the change ΔW in the width direction position (width direction end position) of the intermediate transfer belt 1 is a triangle. It can be easily calculated using a function. That is, when ½ of the distance obtained from the time difference ΔT between T1 and T2 is ΔT _dis , ΔW can be calculated by the following equation.

ΔW = ΔT _dis × tan θ (where θ = θa = θb)
In this case, the width direction end position calculation unit 5 calculates ΔW using the above calculation formula based on the time difference ΔT, and adds or subtracts ΔW with respect to the reference position, whereby the width direction end position of the intermediate transfer belt 1 is calculated. Find the position.

  Even if the above calculation formula is not used, or even when the inclination angle θa and the inclination angle θb are not equal, the end position in the width direction of the intermediate transfer belt 1 can be obtained by the following method.

  When the position in the width direction (end position in the width direction) of the peripheral edge 1a of the intermediate transfer belt 1 is located at a desired reference position, that is, when there is no meandering, the optical sensor 3 is at the center in the width direction B of the detected portion 2. Assuming that the reference detection point C0 is detected at the reference passage time T0 (<T2,> T1), the time difference (ΔT) between the reference passage time T0 and the measured passage time (T1 or T2) and the intermediate transfer belt 1 Between the change amount (ΔW) of the width direction position (width direction end position), since the front and rear detection end portions 2a and 2b are diagonal and linear as described above, a certain amount corresponding to the inclination angle is set. There is a relationship. Therefore, when the time difference (ΔT) when measuring the distant place C1 is ΔT1 (ΔT1 ′ + ΔT1 ″), the position in the width direction (end position in the width direction) of the peripheral edge 1a in the intermediate transfer belt 1 is the reference detection position C0. 3 becomes ΔW1, which is the end position in the width direction toward the left side of FIG. On the other hand, when the time difference (ΔT) when measuring the near portion C2 is ΔT2 (ΔT2 ′ + ΔT2 ″), the position in the width direction (end position in the width direction) of the peripheral edge 1a in the intermediate transfer belt 1 is the reference detection position C0. 3 becomes ΔW2, which is the width direction end position on the right side of FIG.

  Therefore, a relational expression between such time difference (ΔT) and position change (ΔW) is stored in advance in the width direction end position calculation unit 5, and this relational expression, the reference passage time T0, and the measured passage time are measured. The width direction end position of the intermediate transfer belt 1 is obtained based on the time (T1 or T2). The reference passage time and the measured passage time both correspond to a time difference from when the optical sensor 3 detects the front detection end 2a until it detects the rear detection end 2b.

  The meandering direction and meandering amount of the intermediate transfer belt 1 can be calculated based on the end position in the width direction. Then, by adjusting the axial direction of at least one of the driving roller 36 and the driven roller 37 on which the intermediate transfer belt 1 is stretched, the meandering amount is controlled to be within a range of, for example, ± 1 mm. It becomes possible. As described above, the timing for obtaining the width direction end position by the width direction end position calculation unit 5 is set when the intermediate transfer belt 1 rotates at a constant speed.

  Therefore, in the case of the belt position detection mechanism of the present embodiment, since the normal optical sensor 3 is used for detecting the width direction end position of the intermediate transfer belt 1, a significant increase in cost can be prevented. .

  In the above-described embodiment, a relational expression between the time difference (ΔT) between the reference passage time and the measured passage time and the change (ΔW) in the width direction position (width direction end position) of the intermediate transfer belt 1 is expressed as follows. A width direction end position of the intermediate transfer belt 1 is obtained based on the relational expression, the reference passage time T0, and the measured passage time (T1 and T2). However, the present invention is not limited to this. For example, instead of the relational expression between the time difference (ΔT) and the change (ΔW), the time difference (ΔT) between the reference passage time and the measurement passage time and the belt width direction B of the detection end portions 2a and 2b. The position in the width direction of the intermediate transfer belt 1 may be obtained based on this relational expression, the reference passage time T0, and the measured passage time (T1 or T2). Alternatively, the inclination angle θa of the detection end 2a and the inclination angle θb of the detection end 2b are stored in advance in the width direction end position calculation unit 5, and two non-parallel ones are based on the inclination angles θa and θb. The position of the intersection of the detection ends 2a and 2b is obtained, the obtained intersection position, the length across the detection ends 2a and 2b at the reference passage time T0, and the detection end 2a at the measured passage time (T1 and T2). The widthwise end position of the intermediate transfer belt 1 may be calculated by determining the height difference between two similar triangles having the intersection position as a vertex based on the length across 2b.

  In the above-described embodiment, the detected portion 2 is used in which the detection end 2a on the front side and the detection end 2b on the rear side are cut in a straight line obliquely with respect to the circumferential direction. However, the present invention is not limited to this. Alternatively, the detection can be performed in the same manner by using a detected portion in which only one of the front detection end 2a and the rear detection end 2b is linearly cut obliquely with respect to the circumferential direction. In short, it is sufficient that the front detection end 2a and the rear detection end 2b are not parallel to each other. However, in the case of using a detection part in which both the front detection end part and the rear detection end part are cut obliquely with respect to the circulation direction and linearly in the opposite direction as in the embodiment described above, The change in the length dimension of the detection unit can be increased, and the end position in the width direction of the intermediate transfer belt 1 can be obtained with high accuracy.

  Furthermore, in the above-described embodiment, an example in which the detection end 2a on the front side and the detection end 2b on the rear side of the detected portion 2 are detected by the optical sensor 3 is described, but the present invention is not limited to this. In addition, a pattern film made of a light shielding material or a reflective material may be formed on the translucent film, and a front detection end and a rear detection end that can be optically detected may be provided. An example thereof is the configuration shown in FIG.

  FIG. 4A shows a light-transmitting film 7 as a base material on which a pattern film 8 made of a light shielding material is formed to provide a trapezoidal light-transmitting portion 9, and the boundary between the light-transmitting portion 9 and the pattern film 8. Thus, a detection base portion 8a and a detection end portion 8b on the rear side are formed to be detected, and a mounting base portion 8c that functions as the base portion 2c is attached to the belt. In FIG. 6B, a trapezoidal pattern film 18 made of a light shielding material is formed on the translucent film 7, and the detection end 18 a on the front side is separated from the boundary between the translucent part 19 without the pattern film 18 and the pattern film 18. A detection base portion 18b is formed on the rear side, and a mounting base portion 18c that functions as the base portion 2c is attached to the belt. In (c), a pattern film 8 ′ is formed on the translucent film 7 so that the trapezoidal translucent part 9 ′ is opposite to the translucent part 9 of (a), and the translucent part 9 ′ is formed. And a detection end 8a ′ on the front side and a detection end 8b ′ on the rear side formed by a boundary between the pattern film 8 ′ and the mounting base 8c ′ functioning as the base 2c. Mounted. (D) shows that a trapezoidal pattern film 18 ′ is formed on the translucent film 7 so as to be opposite to the pattern film 18 of (b), and a translucent portion 19 ′ without the pattern film 18 ′ and the pattern film are formed. A detection base portion 18a ′ and a detection end portion 18b ′ on the rear side are formed by a boundary with 18 ′, and a mounting base portion 18c ′ functioning as the base portion 2c is attached to the belt.

  The pattern film shown in FIG. 4 uses a light-shielding material because it is detected by a transmissive optical sensor. When detecting by a reflective optical sensor, a reflective material is used instead of the light-shielding material. In other words, a detection target having the same form may be used.

  In the above-described embodiment, the case of obtaining the end position in the width direction of the color intermediate transfer belt 1 is described as an example, but the present invention is not limited to this. For example, the present invention can be similarly applied to the case where the end position in the width direction of the endless transfer belt for black and white is obtained, or the case where the end position in the width direction of the endless transport belt for transporting the paper P is obtained.

1 is an explanatory diagram of a front sectional view for explaining an embodiment of an internal structure of an image forming apparatus according to the present invention. FIG. 4 is a perspective view schematically showing an intermediate transfer belt that is a detection target to be detected by a belt position detection mechanism according to an embodiment of the present invention. It is a block diagram which shows the belt position detection mechanism which concerns on one Embodiment of this invention. It is a figure which shows the other structural example of the to-be-detected part used for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS A Circumferential direction B Width direction 1 Intermediate transfer belt 1a One peripheral edge 2 Detected part 2a Front detection end 2b Rear detection end 3 Optical sensor 4 Computing device 5 Width direction end position computing unit 10 Image forming apparatus 8a, 18a, 8a ′, 18a ′ front detection end 8b, 18b, 8b ′, 18b ′ rear detection end

Claims (6)

A belt position detection mechanism for detecting an end position in a width direction with respect to the image forming apparatus main body of an endless belt that circulates at a constant speed provided in the image forming apparatus main body,
A part to be detected which is provided on a part of one peripheral edge of the endless belt and has a pair of detection end parts extending in the width direction of the endless belt and being non-parallel to each other and back and forth in the circumferential direction;
An optical sensor that optically detects the pair of detection end portions of the detected portion that is fixedly mounted on the image forming apparatus main body so as to face one peripheral edge of the endless belt;
Calculation means for measuring the passage time between both detection ends based on the detection signal from the optical sensor, and obtaining the end position in the width direction based on the reference passage time stored in advance and the measured passage time A belt position detecting mechanism.   The belt position detection mechanism according to claim 1, wherein the pair of detection end portions of the detected portion are inclined in directions opposite to each other.   The belt position detection mechanism according to claim 2, wherein each of the pair of detection end portions has an inclination angle of 45 degrees or less with respect to the belt peripheral edge.   The belt position detection mechanism according to claim 1, wherein the detected portion is a light shielding piece projecting outward from a peripheral edge of the endless belt.   The said to-be-detected part consists of the translucent base material projected outward from the periphery of the said endless belt, and the light-shielding pattern formed on this base material, The any one of Claim 1 thru | or 3 characterized by the above-mentioned. A belt position detection mechanism according to claim 1. 6. The image forming apparatus according to claim 1, further comprising an endless rotating intermediate transfer belt to which an image formed by each color image forming unit provided in the image forming apparatus main body is transferred, and detecting an end position in the width direction of the intermediate transfer belt. An image forming apparatus comprising the belt position detection mechanism according to any one of the above.

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