Abstract: An image forming apparatus includes a developing unit which develops toner to form an image, a transfer unit which transfers the image onto a printing medium, and a fusing unit to fuse the image transferred onto the printing medium, wherein the transfer unit includes a belt, a plurality of rollers which rotatably supports the belt, and a belt tension applying unit which moves a first roller of the plurality of rollers between a belt tension release position at which a tension of the belt releases and a belt tension applying position at which the tension of the belt applies by the interlocking motion between the belt tension applying unit and a second roller of the plurality of rollers.

Abstract: According to aspects of the embodiments, there is provided methods of optimizing contact forces between transfer and photoreceptor belts in image forming devices. The method acquires initial and operational set point data for the photoreceptor and transfer belt at different stages of engagement. Yaw motion is applied to reduce any misalignment between the belts based on the acquired data. A processor is used to determine misalignment between the photoreceptor belt and the transfer belt, and an actuator can be used to apply yaw motion. The yaw motion can return the transfer belt and the photoreceptor belt to their initial set position, or return a steering subsystem actuator to its setting prior to engagement of the belts. Set point data can be from the respective transfer steering subsystem for the photoreceptor and the transfer belts.

Abstract: A control unit calculates a difference between a displacement of a belt detected by an encoder and a predetermined target value, calculates a pulse frequency of a driving pulse signal based on a feedback control based on the difference and a feed-forward control based on a reference driving pulse frequency, sets a control range of the feedback control to be equal to or smaller than a frequency of one rotation of a driven roller, and controls driving of a pulse motor such that the belt moves at a constant speed.

Abstract: To enable not only releasing pressurization by a pressurization mechanism for pressurizing a belt thereby preventing a deformation therein but also easily and securely releasing the pressurization mechanism held in the pressure release state, thereby facilitating the installation operation of an apparatus. A pressurization mechanism for pressurizing a belt is in a released state prior to the use of the main body of the apparatus. Prior to the initial use of the main body, the pressurization of the pressurizing mechanism for the belt is exerted in linkage with a user operation of placing a recording material in a feed tray.

Abstract: An image forming apparatus includes a plurality of rotors, and an endless belt that is supported with tension by the plurality of rotors and rotated by the rotors. Herein, at least one of the plurality of rotors is provided, at a first end, with a belt restraining member that has a restraining face for restraining displacement of the endless belt toward the first end and that is rotatable with respect to the rotor; and the belt restraining member is arranged such that an angle between the restraining face of the belt restraining member and a rotation shaft of the rotor is greater at a contact start point at which the endless belt begins contact with the belt restraining member during rotation than at a contact end point at which the endless belt ends contact with the belt restraining member during rotation.

Abstract: According to aspects of the embodiments, there is provided methods of optimizing contact forces between transfer and photoreceptor belts in image forming devices. The method acquires initial and operational set point data for the photoreceptor and transfer belt at different stages of engagement. Yaw motion is applied to reduce any misalignment between the belts based on the acquired data. A processor is used to determine misalignment between the photoreceptor belt and the transfer belt, and an actuator can be used to apply yaw motion. The yaw motion can return the transfer belt and the photoreceptor belt to their initial set position, or return a steering subsystem actuator to its setting prior to engagement of the belts. Set point data can be from the respective transfer steering subsystem for the photoreceptor and the transfer belts.

Abstract: A color laser printer includes a plurality of photosensitive drums and a paper-conveying belt disposed in confrontation with the photosensitive drums. The paper-conveying belt conveys a sheet of paper as the photosensitive drums sequentially transfer toner images thereon. This printer also includes a tension-adjusting mechanism capable of adjusting the tension state produced in the paper-conveying belt, and a controller for controlling the tension-adjusting mechanism. Through the control of the controller, the tension-adjusting mechanism is capable of adjusting the tension state of the paper-conveying belt between a first tension state used for transferring toner images from the photosensitive drum, and a second tension state producing a tension greater than that produced by the first tension state for performing a cleaning operation.

Abstract: A belt rotating apparatus according to an exemplary embodiment of the invention includes a circular belt; plural rollers about which the belt is entrained, the plural rollers including a drive roller which rotates the belt and an inclination change roller which can change an inclination thereof; a belt side edge sensor which measures a position of a belt side edge in a belt width direction of the belt; and a cutter which can trim the belt side edge.

Abstract: A belt is looped around a plurality of rollers including a drive roller and a follow roller. The belt has an inner peripheral surface facing inside of a loop of the belt and an outer peripheral surface opposite the inner peripheral surface. The belt has a first widthwise edge and a second widthwise edge. A widthwise-movement restricting member is disposed on the inner peripheral surface on a first widthwise edge side. The widthwise-movement restricting member restricts widthwise movement of the belt in a direction toward a second widthwise edge side. An expansion-contraction restricting member is disposed on the second widthwise edge side on at least one of the inner peripheral surface and the outer peripheral surface. The expansion-contraction restricting member is less expandable in a peripheral direction of the belt than the widthwise-movement restricting member is. An urging member applies tension to the belt in the peripheral direction.

Abstract: A belt member is supported by a plurality of rollers and moves in a predetermined moving direction. A detecting unit detects a displacement of the belt member in its width direction. A correcting unit moves a second end of a first roller from among the rollers in either one of a forward direction and a backward direction while fixing its first end based on a result of detecting the displacement of the belt member such that a tilt of a rotating shaft of the first roller is changed to correct a meandering of the belt member. An adjusting unit adjusts a fixing position of the first end.

Abstract: A steering mechanism moves an intermediary transfer belt in its width direction by moving an inclination angle of two steering rollers with respect to a rotational direction of the intermediary transfer belt. The two steering rollers changes the inclination angle while maintaining a rectangle defined by the steering rollers and bearing arms to ensure a thrust movement distance in a period from start of winding of one of the steering rollers and end of winding of the other steering roller.

Abstract: A belt tension mechanism includes a tension roller disposed on a side of a photoconductive belt for pressing the photoconductive belt, a first elastic component connected to the tension roller for providing the elastic force to the tension roller, and a releasing device disposed on the other side of the photoconductive belt. The releasing device includes a actuating component for moving in a first direction and separating from the tension roller when being electrified so that the first elastic component can drive the tension roller to a position where the tension roller can press the photoconductive belt, and a second elastic component connected to the actuating component for driving the actuating component to a second direction opposite to the first direction when the actuating component is not electrified so that the actuating component can drive the tension roller to a position where the tension roller cannot press the photoconductive belt.

Abstract: An image forming apparatus for forming an image on a recording medium includes a belt configured to travel rotationally and looped around at least two rotary support members, a driven rotary member disposed facing at least one of the rotary support members via the belt and configured to rotate with the belt, and a controller. The controller is configured to minimize fluctuation in one of a travel velocity and a travel distance of the belt by controlling the travel of the belt based on one of a rotational angular displacement and a rotational angular velocity of each of the rotary support member and the driven rotary member.

Abstract: An endless belt member is suspended in a tensioned manner by a plurality of roller members including a drive roller and a drive motor drives the drive roller member so as to move the belt member in a predetermined direction of travel. A detecting unit detects an amount of displacement of the belt member in a widthwise direction of the belt member, and a correction unit that corrects displacement of the belt member in the widthwise direction. The correction unit corrects the displacement of the belt member in a widthwise direction based on data sampled by the detecting unit every time a drive signal is input to the drive motor a prescribed number of times.

Abstract: A multi-function peripheral includes an image forming unit having an image forming device, and an image reading unit having an image reading device and located above the image forming unit. The image forming device forms an image on a recording sheet with moving a carriage reciprocally in a predetermined horizontal direction. The image reading device reads an image of an object by moving an image capturing element in the predetermined horizontal direction when the image forming unit operates. Spring elements are provided between the image forming unit and the image reading unit to apply an urging force therebetween in a direction parallel to the predetermined horizontal direction. The spring elements satisfy the following condition: f f n > 2 , where, f and fn are characteristic frequencies of the image forming unit and the image reading unit, respectively, in the predetermined horizontal direction.

Abstract: This is a specifically configured roller used in a belt transport system that minimizes ripples or wrinkles in the belt. Based upon a roller having a cylindrical configuration and a one inch diameter, the roller has a concave shape having a 0.005 to 0.1 inch smaller diameter in the center compared to the end portion diameters.

Abstract: An image forming apparatus includes a belt unit detachably installed in a main body, a first positioning mechanism provided in the main body to rotatably support a first support roller, a second positioning mechanism provided in the main body to rotatably support a second support roller, an urging mechanism that urges the second support roller in a direction to move the second support roller away from the first support roller, a reference protrusion provided in the belt unit in a predetermined positional relationship with the first support roller, and a reference wall disposed to face the reference protrusion in the main body at a position closer to the second support roller than the reference protrusion.

Abstract: The invention provides a film driving apparatus in which no adverse effect is caused by a change in the circumferential length of a film even if there arises the change in circumferential length of the film due to environmental fluctuation. In the film driving apparatus, an endless film 1 supported by a driving roller 2, a film support roller 4 and a skew correction roller 3 is rotated in a predetermined direction by the rotation of a driving roller 2. The skew correction roller 3 has a structure in which one end thereof is movable with the other end as a fulcrum. The movement trajectory of the movable end portion of the skew correction roller 3 is an elliptic trajectory not causing any change in the circumferential length of the film 1.

Abstract: A belt conveying device includes: at least three rollers, about which an endless belt to convey an object, is entrained, including an oscillation roller having a rotation shaft, whose one end is fixed and another end is oscillatably supported; a belt detection sensor provided adjacent to a side edge of the belt, which detects presence of the belt; and a belt skew controller which controls the oscillator to oscillate the oscillation roller according to a preset control value in a predetermined range to correct skew. The oscillator moves a rotation center of a movable edge of the oscillation roller along a tangential line of an ellipse having elliptical focuses corresponding to rotation centers of rotation shafts of the two rollers, other than the oscillation roller, positioned respectively in upstream and downstream of and adjacent to the oscillation roller in a belt conveyance direction.

Abstract: A docking system may repeatedly dock a movable sensor module relative to another module with high precision. The docking system may move with minimal constraints and several degrees of freedom. The docking system may be particularly useful for precisely locating a movable sensor module relative to another module, such as a full width array sensor relative to a photoreceptor module within an image forming apparatus. A high degree of freedom may be achieved through use of a series of at least three spherical bearing connections that enable freedom of movement about X, Y and Z axes.

Abstract: A plurality of supporting rollers over which the endless belt member is supported includes at least a driving roller that drives the endless belt member and a driven roller that is driven by a rotation of the endless belt member. A detecting unit detects a plurality of marks provided on the driven roller at a predetermined position. A control unit controls a speed at which a driving unit drives the endless belt member based on a result of detecting the marks. The driven roller functions as a tension roller that applies a tension to the endless belt member. The detecting unit is held by the tension roller.

Abstract: The image forming apparatus includes a belt member having a convex portion, effecting a circular movement, a first support member and a second support member for supporting the belt member, and a drive receiving unit for receiving force from circular movement of the belt member. An angle of the second support member to the first support member is affected by inputting the force arising from the circular movement into the drive receiving unit, and the force arising from the circular movement is input by contacting convex portion to the drive receiving unit.

Abstract: Disclosed is an image forming apparatus, which comprises an intermediate transfer belt (15), and a plurality of image-forming units (11) to (14) disposed along the intermediate transfer belt (15) and adapted to form toner images of different colors and sequentially transfer the toner images onto the intermediate transfer belt (15) in a superimposed manner so as to form a color toner image. The intermediate transfer belt (15) is laid across a drive roller (16), a driven roller (17) and a tension roller (18), in a tensioned condition. A rotation speed of the tension roller (18) adapted to apply a tension to the intermediate transfer belt (15) is detected to obtain a linear speed of the intermediate transfer belt (15). In a process of color-misregistration correction, a write-start timing for each toner image of the colors is adjusted based on the linear speed of the intermediate transfer belt (15).

Abstract: The image forming apparatus includes a belt member having a convex portion, effecting a circular movement, a first support member and a second support member for supporting the belt member, and a drive receiving unit for receiving force from circular movement of the belt member. An angle of the second support member to the first support member is affected by inputting the force arising from the circular movement into the drive receiving unit, and the force arising from the circular movement is input by contacting the convex portion to the drive receiving unit.

Abstract: A tension adjuster for a belt of image forming apparatus is provided. The tension adjuster of the belt includes a tension roller which rotates in contact with an inner surface of the belt. A fixed shaft is disposed a predetermined distance away from the tension roller. A pair of swing arms connect the fixed shaft to a shaft of the tension roller. A tension unit rotates the swing arm on a circumference of the fixed shaft in a first direction so that the tension roller produces a tension on the belt. A tension releasing unit applies torque to the swing arm on the circumference of the fixed shaft in a second direction opposite to the first direction. When the belt rotates, torque generated by the tension unit is greater than the torque generated by the tension releasing unit. When the belt is stopped, the belt is released by the torque of the tension releasing unit.

Abstract: A belt member of the present invention includes ribs that prevent the belt member from being shifted to either side. A plurality of cuts are formed in each rib at preselected intervals in the circumferential direction of the belt member, and each extends from the top toward the bottom of the rib. The cuts may be replaced with projections and recesses alternating with each other in the cicumferential direction of the belt member or bores formed at preselected intervals in the above direction. Such ribs allow, without being subject to a heavy load, the belt member to be wrapped around a support roller with a large curvature or bent in the inverse direction. This reduces deterioration and slippage ascribable to the position of the belt member desirable for the size reduction of an apparatus on which the belt member is mounted.

Abstract: A belt traveling unit includes an endless belt, a drive roller and a correction roller, a driving unit, a correction unit, a contact member, a position detector and a regulating member. The endless belt is spanned between a plurality of rollers. The driving unit rotates the drive roller to drive the belt. The correction unit adjusts a tilt angle of the correction roller to correct drifting of the belt in the width direction thereof. The contact member is rotatable in conjunction with traveling of the belt in the width direction thereof. The position detector detects a position of the contact member to detect a position of the belt in the width direction thereof. The regulating member is located at a position where the position detector does not misdetect the position of the belt when the contact member rotates.

Abstract: An image forming apparatus includes a first roller; a second roller; a belt tensely provided between the first roller and the second roller; and a guiding member for guiding an edge of the belt. Further, the belt has an edge surface having a step portion of equal to or smaller than 0.05 mm and a ten-point mean roughness (Rz) of equal to or smaller than 5.0 ?m.

Abstract: A belt unit of an electrophotographic printing apparatus, includes: two rollers for supporting a belt so as to be substantially in parallel with each other; two frames for supporting the rollers and attached to opposite ends of one of the rollers respectively so as to be perpendicular to the rollers; two support members attached to opposite ends of the other roller so as to be perpendicular to the rollers; two elastic members interposed between the two support members and the two frames respectively; and a belt mounting guide provided between the two frames. The belt mounting guide includes a rotating shaft disposed in parallel with the rollers, and an edge portion inclined relative to an axial direction of the rotating shaft.

Abstract: A scale is provided on a back side edge of an intermediate transfer belt for detecting an amount of movement of the belt. In a tandem type image forming apparatus, a sensor is provided as a scale-reading unit that reads the scale. Materials used for the intermediate transfer belt and the scale satisfy a relation that the Young's modulus of the intermediate transfer belt is greater than the Young's modulus of the scale.

Abstract: A belt driving apparatus for driving a belt has the belt hung around and between rollers, and has a meandering prevention member provided in each end part of each roller to restrict the meandering of the belt in the roller axial direction. A cut is formed to be open toward the roller end face and to extend in the roller axial direction, and a boss that fits into the cut is formed on the inner circumference of the meandering prevention member.

Abstract: The image forming apparatus includes a belt member having a convex portion, effecting a circular movement, a first support member and a second support member for supporting the belt member, and a drive receiving unit for receiving force from circular movement of the belt member. An angle of the second support member to the first support member is affected by inputting the force arising from the circular movement into the drive receiving unit, and the force arising from the circular movement is input by contacting the convex portion to the drive receiving unit.

Abstract: In an image forming apparatus such as a color laser printer wherein a toner image is transferred onto a continuous paper, one or more of a exposure timing of each exposure device, a rotation speed of each image carrier device, a transfer bias voltage applied to each transfer device, and a wrap amount of each wrap device are controlled based on a coverage of a toner image formed on each image carrier device, thereby preventing a color-to-color registration state which tends to be caused due to a variation in the transport speed of the continuous paper in a transfer process.

Abstract: Disclosed are various embodiments of a belt support module design for use in an imaging forming apparatus or machine. The belt support module is utilized in association with an electrostatographic imaging belt. The belt support module has at least one flexible spreader roller to suppress, or effect the elimination of, belt ripple or wrinkle development during machine belt cycling operation.

Abstract: An apparatus for providing tension to a photoreceptor belt mounted for rotation about a plurality of fixed rollers mounted to a frame of an imaging device comprises a tensioning roller having a longitudinal axis and a convex contact surface for forcing a wrap angle with an inner surface of the photoreceptor belt, a moment arm mounted at a first end to the frame for pivotal movement relative to the frame about a pivot axis fixed relative to the frame and mounted at a second end to the tensioning roller; and a force exerting mechanism mounted to the frame and coupled through the moment arm to the tensioning roller to provide a force perpendicular to the longitudinal axis of the tensioning roller, the force exerting mechanism being configured to increase the force exerted thereby as the length of the photoreceptor belt increases.

Abstract: The present invention relates to an image forming apparatus comprising: an image bearing member; toner image forming means for forming a plurality of toner images on the image bearing member; primary transfer means for superimposing the plurality of toner images on the image bearing member on one another in succession to primary transfer the same to a moving intermediate transfer belt in a primary transfer region; a driving source for moving the intermediate transfer belt through a driving transmitting member with respect to a driving roller which supports the intermediate transfer belt and which moves the intermediate transfer belt; a secondary transfer means for collectively secondary transferring the toner images on the intermediate transfer belt to a recording material; removing means which can abut against and separate from the intermediate transfer belt in a approaching and separating region on the intermediate transfer member and which removes toner on the intermediate transfer belt; and locus varying

Abstract: Pulleys 29a, 29b are provided on both ends of the driven roller 28 as separate components from the driven roller 28, and on both edges in the width direction of the transfer belt 24, ribs 24a, 24b that can be engaged with the outer sides in the axial direction of the pulleys 29a, 29b are provided. If the transfer belt 24 becomes inclined to the left side during movement, the rib 24a on the right edge of the transfer belt 24 will be restricted by the outer side in the axial direction of the pulley 29a provided on the right side end of the driven roller 28, thereby correcting meandering to the left at the position of the driven roller 28.

Abstract: A transfer belt unit and image forming apparatus that achieves the reduction in size and cost of a transfer belt unit and can prevent fluctuation of the cleaning performance. The unit has a transfer belt, and a plurality of rollers around which the transfer belt 14 is laid with certain tension, wherein at least one of the rollers is a tension roller 13 for tensioning to the transfer belt; frames supporting the plurality of rollers; tensioning mechanisms which are disposed on the side faces of the frames to bias the tension roller in a belt tensioning direction; a cleaning device in contact with the transfer belt at a position opposing the tension roller; rotation preventing members which prevent the rotational torque from being transmitted to the cleaning device; and position restricting members which restrict the relative position between the cleaning device and the tension roller.

Abstract: An endless belt including an endless body having opposite side edges and an interior surface, and a pair of spaced apart parallel guides bonded to the interior surface of the endless body at positions adjacent to the side edges thereof and extending longitudinally along the side edges, wherein each of the guides is made of an elastic material and has inside and/or outside surfaces having specific roughness.

Abstract: An apparatus and method for extending the lifetime of belts, especially photoreceptor belts inside of a printing device, which includes detensioning the belt during periods where the belt is not in use, such as where a printing device is in an idle state.

Abstract: A belt transporting device for circulatingly transporting an endless belt, which is in use with an image forming apparatus, such as copying machine or a printer. The belt transporting device includes a plurality of tension rolls, an endless belt laid on the tension rolls, the endless belt having a belt-end edge part protruding from an end of one of the tension roll and a guide member provided in the vicinity of the endless belt. The guide member comes in contact with the belt-end edge part so as to bend the belt-end edge part in a tapering-off direction. The guide member regulates the shape of the belt-end edge part so that a rotary peripheral length of the belt-end edge part becomes smaller than that of an area where a rear side of the endless belt is in contact with the tension roll.

Abstract: An image forming apparatus having therein an image carrier, an intermediate transfer belt is trained about plural rollers and is located at a position where it comes in contact with the image carrier, a primary transfer roller that is arranged to face the image carrier through the intermediate belt for the purpose of transferring toner on the image carrier onto the intermediate transfer belt, wherein the following expression holds when Ft (kgf) represents tension of the intermediate transfer belt, Fr (kgf) represents pressing force of primary transfer roller and d (mm) represents a shift amount for the image carrier and the primary transfer roller, Fr?(0.05×Ft+0.11)×d?0.3.

Abstract: An endless power transmission belt having (1) a tension section; (2) a cushion section; and (3) a load-carrying section disposed between said tension section and cushion section; and the belt containing an elastomeric composition comprising (a) 100 parts by weight of a rubber; and (b) from about 1 to about 175 parts by weight of wood flour.

Abstract: An image formation apparatus is provided with a photosensitive drum, an optical writing device which writes an image on the outer surface of the photosensitive drum, a developing device which develops the image using toner an intermediate transfer belt onto which the toner image on the photosensitive drum is transferred, a rotation angle detection unit which detects the rotation angle of the photosensitive drum, an eccentric detection unit which detects the amount eccentricity of the photosensitive drum from the rotary axis of the photosensitive drum, and a correction unit which, obtains eccentricity of the photosensitive drum based on the amount eccentricity, the rotation angle and the radius of the photosensitive drum, and corrects a distortion and a color offset in the toner image based on the obtained eccentricity.

Abstract: An electrophotographic endless belt has a beltlike substrate and a meandering-preventive member attached to the inner peripheral surface of the beltlike substrate via a pressure-sensitive adhesive, double-coated tape. The pressure-sensitive adhesive, double-coated tape is a pressure-sensitive adhesive, double-coated tape having i) a reinforcing base material and ii) pressure-sensitive adhesive layers on both sides of the reinforcing base material. The reinforcing base material has a thickness of from 25 ?m or more to 200 ?m or less, and the pressure-sensitive adhesive layers on both sides each have a thickness of 200 ?m or less and at least one of the pressure-sensitive adhesive layers has a thickness of from more than 100 ?m to 200 ?m or less, and the meandering-preventive member has a hardness of from 15° or more to 70° or less. Also disclosed are a process cartridge and an electrophotographic apparatus which have the electrophotographic endless belt as an intermediate transfer belt.

Abstract: Ensuring proper compass and register positioning during printing. Marks are imprinted on a carrying element and at least one sensor is present to detect the marks on the carrying element and a second sensor detects a seam on the carrying element. A control mechanism receives mark values from the first sensor and seam values from the second sensor, and discarding mark values when the seam is detected.

Abstract: A belt driving apparatus which inhibits a belt meandering so as to improve a printing quality and rapidly starts a printing motion at a time of starting the apparatus such as a time of turning on power or the like, and an image forming apparatus using the same. The belt driving apparatus has an endless belt, a plurality of belt tension supports for supporting the belt in a tension manner, and a steering roller supported in a tiltable manner and compensating a meandering of the belt, and the belt driving apparatus is provided with a meandering compensation sensitivity adjuster for adjusting a belt meandering compensation sensitivity of the steering roller per an angle of incline.

Abstract: A method and apparatus for driving a belt is provided. Included is a method and apparatus for searching for a home position of a steering roller for adjusting a position of the belt in a widthwise direction of the belt and placing the steering roller in the home position. The steering roller is moved from the home position to a balance point, in which an amount of variation of the belt in the widthwise direction is less than a predetermined value, or moved to a position of the steering roller that corresponds to a previously driven final position of the belt. The belt is driven in this state such that the amount of initial weaving of the belt is reduced. Thus, an amount of initial weaving of the belt when the belt is driven can be minimized such that a time to obtain images with suitable registration can be greatly reduced.

Abstract: In an electrophotographic endless belt having a beltlike substrate, a meandering-preventive member and a position detection member, the meandering-preventive member is disposed on the inner-periphery side of one end portion of the beltlike substrate, the position detection member is disposed on the outer-periphery side of the other end portion of the beltlike substrate, and the meandering-preventive member and the position detection member are 200 mm to 250 mm away from each other in the width direction of the electrophotographic endless belt. The beltlike substrate contains a thermoplastic resin as a binder resin, and the beltlike substrate has a 25 ?m×25 ?m surface total current value of from 300 nA to 2,000 nA at the time of application of 100 V as measured by SPM.

Abstract: In this invention, the relationship between the attachment position of a sensor and the formation positional shift of a color image is checked by moving a color misregistration detection sensor along an attachment position candidate line that is defined in advance in a direction perpendicular to the rotational direction of an endless-belt-shaped transfer body. A specific attachment position on the sensor attachment position candidate line, at which color misregistration of the color image at a side edge portion of the transfer body becomes equal to the maximum value of color misregistration at a portion except the side edge portion, is found. The sensor is fixed at a position that satisfies the specific attachment position and opposes the color image formation surface of the transfer body. Accordingly, the image forming apparatus is controlled to correct color overlay on the basis of the detection signal of the color image by the sensor.