JP2013257472A - Transfer device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transfer device and an image forming apparatus, which are capable of reducing abrasion of a belt member while securing the accuracy of positions between detection means used for detecting a toner pattern formed on a surface of the belt member and an opposite member facing the detection means with intervention of the belt member, thereby suppressing occurrence of abnormal noise associated with chattering.SOLUTION: A transfer device 9 includes: a belt member 8 circularly stretched by plural stretching-members; transfer means 16 for transferring a toner image formed on a surface of the belt member onto a transfer material P; detection means 120, disposed at a position opposite to the surface, for detecting a detecting-toner pattern formed on the surface; and an opposite member 110 disposed oppositely to the detection means with the belt member intervening in-between. Further, the device includes: a contact member 14 disposed nearby the opposite member of the belt member and in contact with the belt member; and shifting-means 45 for shifting the contact member. Further, the device causes the shifting-means to shift the contact member, thereby changing states of contact between the opposite member and belt member.

Description

  The present invention relates to a transfer device used in an image forming apparatus such as a printer, a facsimile machine, and a copying machine, and an image forming apparatus including the transfer device.

  Conventionally, a toner image on a photoconductor as an image carrier is temporarily transferred onto an intermediate transfer belt as a belt member by a primary transfer unit, and the toner image on the intermediate transfer belt is transferred onto a recording sheet by a secondary transfer unit. An image forming apparatus provided with a transfer device is known. In this image forming apparatus, the primary transfer by the primary transfer unit is performed a plurality of times for each different color, thereby forming a superimposed image on the intermediate transfer belt. The superimposed images are collectively transferred from the intermediate transfer belt to the recording paper by secondary transfer means to obtain a color image.

  Further, in such an image forming apparatus, an image adjustment mode for performing positional deviation correction and image density control of each color toner image is executed, and the primary transfer position of each color toner image on the intermediate transfer belt is prevented from being shifted. In addition, there is known one that suppresses image density unevenness of each color. For example, first, a toner pattern for detecting misalignment or detecting image density is formed on the intermediate transfer belt. Next, the toner pattern is detected by an optical sensor provided at a position facing the front surface which is the outer peripheral surface of the intermediate transfer belt in the toner pattern passage region. Then, based on the detection result of the optical sensor, positional deviation correction control and image density control are performed.

  However, an error may occur in the detection of the toner pattern by the optical sensor. The cause of such an optical sensor detection error is that the intermediate transfer belt is wavy. For example, unevenness due to distortion at the time of molding the intermediate transfer belt, or the drive of the intermediate transfer belt is stopped for a long time, and the portion of the intermediate transfer belt that has been in contact with the tension member for a long time may be along the contact surface shape of the tension member. As a result, the intermediate transfer belt is wavy. When the intermediate transfer belt is wavy, the intermediate transfer belt moves up and down at a position facing the optical sensor, and the interval between the optical sensor and the intermediate transfer belt varies. For this reason, the reflection angle and position of the beam irradiated from the optical sensor and reflected by the intermediate transfer belt, the toner pattern, and the like fluctuate, resulting in a detection error of the optical sensor and a detection failure.

  In the image forming apparatus described in Patent Document 1, a backing member, which is a facing member that faces the optical sensor via the intermediate transfer belt, is always provided in contact with the back surface of the intermediate transfer belt. As described above, by contacting the backing member to the back surface of the belt, even if the intermediate transfer belt is wavy, the movement of the intermediate transfer belt, the width direction, and the unevenness in both directions are detected at the detection position of the optical sensor. Can be reduced or eliminated. Therefore, the detection error of the optical sensor can be suppressed. Further, as the amount of biting on the back surface of the backing member increases, the waviness of the intermediate transfer belt is corrected at the detection position of the optical sensor. Therefore, increasing the amount of biting is effective for improving sensor detection. .

  However, as the amount of biting increases, the frictional force generated between the intermediate transfer belt and the backing member increases, so that the intermediate transfer belt is easily worn by friction between the intermediate transfer belt and the backing member. As a result, the frictional resistance between the intermediate transfer belt and the backing member increases with time, so if the backing member is in contact with the intermediate transfer belt, the chatter that causes the intermediate transfer belt to vibrate finely occurs. , The accompanying noise will occur.

  In the image forming apparatus described in Patent Document 2, a backing member is provided so as to be displaceable with respect to the apparatus main body, and the backing member is configured to be able to contact and separate with respect to the intermediate transfer belt by contact and separation means. When the toner pattern is not detected by the optical sensor, it is not necessary to bring the backing member into contact with the intermediate transfer belt. Therefore, the backing member is separated from the intermediate transfer belt by the contacting / separating means. Accordingly, since the amount of biting is not always large, the wear of the intermediate transfer belt due to friction between the intermediate transfer belt and the backing member can be reduced. Accordingly, it is possible to suppress the frictional resistance between the intermediate transfer belt and the backing member from increasing with time, and to suppress the generation of noise due to chatter.

  However, if the backing member is provided so as to be displaceable with respect to the apparatus main body, rattling of the backing member is likely to occur, and the optical sensor is more effective than the case where the backing member is fixed to the apparatus main body. It is difficult to ensure the positional accuracy between the cover member and the backing member. For this reason, when the backing member is brought into contact with the back surface of the intermediate transfer belt, the distance between the intermediate transfer belt on the backing member and the optical sensor is deviated from an appropriate distance, resulting in detection failure of the optical sensor. Problem arises.

  The present invention has been made in view of the above problems, and an object of the present invention is to detect a toner pattern formed on the surface of the belt member, and an opposing member that faces the detection device via the belt member. It is possible to provide a transfer device and an image forming apparatus including the transfer device that can reduce the wear of the belt member and suppress the generation of noise due to chatter while ensuring the positional accuracy of the belt.

  In order to achieve the above object, a first aspect of the present invention provides a belt member that is rotatably supported by a plurality of tension members, and a transfer that transfers a toner image formed on the surface of the belt member to a transfer material. A detecting means for detecting a toner pattern for detection formed on the surface, and facing the detecting means via the belt member. In the transfer device including the opposing member, the transfer device includes a contact member provided in contact with the vicinity of the opposing member of the belt member, and a displacement unit that displaces the contact member, and the contact member is configured to displace the contact member. The contact state between the opposing member and the belt member is changed by displacing the belt.

In the present invention, by displacing the contact member by the displacing means, the tension posture in the region in the vicinity of the opposing member of the belt member is changed, the contact state between the opposing member and the belt member is changed, and the opposing member The amount of biting into the belt member can be increased or decreased. As a result, when the toner pattern is detected by the detecting means, the biting amount can be increased by pressing the belt member against the opposing member without displacing the opposing member. Therefore, the opposing member can be fixedly provided with respect to the apparatus main body, and unlike the configuration in which the opposing member is provided so as to be displaceable with respect to the apparatus main body, it is possible to ensure the positional accuracy between the detection means and the opposing member. it can.
When the toner pattern is not detected by the detecting means, the contact member is displaced by the displacing means to reduce the amount of biting. As a result, the amount of biting is not always large, so that the wear of the belt member due to friction between the belt member and the opposing member can be reduced, and the generation of noise due to chatter is suppressed. can do.

  As described above, according to the present invention, the position accuracy of the belt member is ensured while ensuring the positional accuracy between the detection unit that detects the toner pattern formed on the surface of the belt member and the opposing member that faces the detection unit via the belt member. There is an excellent effect that it is possible to reduce wear and to suppress the generation of abnormal noise due to chatter.

(A) The figure which shows the state which the intermediate transfer belt spaced apart with respect to the backing member, (b) The figure which shows the state which the intermediate transfer belt contacted with respect to the backing member. 1 is a schematic configuration diagram of an image forming apparatus according to Embodiment 1. FIG. FIG. 2 is a schematic configuration diagram of a transfer device using a secondary transfer roller instead of a secondary transfer belt. 6 is a graph showing the relationship between the amount of biting of the backing member into the intermediate transfer belt and the sensor detection fluctuation amount. FIG. 3 is a schematic configuration diagram of an image forming apparatus according to a second embodiment. The schematic diagram which looked at the density sensor at the time of image adjustment mode, and its vicinity from the apparatus side. FIG. 3 is a schematic view of the density sensor and its vicinity when the printing operation and the apparatus are stopped as viewed from the side of the apparatus. The figure which shows a state when changing inclination (theta) of the reflection member made into the planar shape with respect to the detection surface of a density sensor. The graph which shows the relationship between inclination (theta) and a sensor output. FIG. 6 is a schematic diagram when viewed from the side of the density sensor in the image adjustment mode and the vicinity of the density sensor. The schematic diagram which looked at the density sensor and shutter at the time of image adjustment mode from the apparatus upper direction. FIG. 6 is a schematic view of the density sensor when printing is performed and when the apparatus is stopped, as viewed from the side of the apparatus in the vicinity thereof. FIG. 3 is a schematic view of a density sensor and a shutter when the printing operation is performed and when the apparatus is stopped as viewed from above the apparatus.

[Embodiment 1]
Hereinafter, a first embodiment of an electrophotographic printer (hereinafter simply referred to as a printer) will be described as an image forming apparatus to which the present invention is applied.

  First, the basic configuration of the printer will be described. FIG. 2 is a schematic configuration diagram showing the printer from the front. In the figure, the printer includes four process cartridges 6Y, 6M, 6C, and 6Bk for forming yellow (Y), magenta (M), cyan (C), and black (Bk) toner images. These use Y, M, C, and Bk toners of different colors as the image forming material, but the other configurations are the same and are replaced when the lifetime is reached. For example, a process cartridge 6Y for generating a Y toner image includes a drum-shaped photosensitive member 1Y as an image carrier, a cleaning device 2Y, a charge eliminating device 3Y, a charging device 4Y, a developing device 5Y, and the like. As the developing device 5Y, a two-component developer containing toner and a magnetic carrier may be used, or only a toner powder may be used.

  In the photoreceptor 1Y, a surface layer of an organic semiconductor, which is a photoconductive substance, is coated on an aluminum cylinder. An amorphous silicon surface layer may be coated. Further, it may be a belt shape instead of a drum shape.

The charging device 4Y uniformly charges the surface of the photoreceptor 1Y that is rotated clockwise in the drawing by a driving unit (not shown). The uniformly charged surface of the photoreceptor 1Y is exposed and scanned by the laser beam L _y carries an electrostatic latent image for Y. The electrostatic latent image for Y is developed into a Y toner image by the developing device 5Y using Y toner, and is primarily transferred from the photoreceptor 1Y to the intermediate transfer belt 8.

  The cleaning device 2Y removes the toner remaining on the surface of the photoreceptor 1Y after the Y toner image is transferred onto the intermediate transfer belt 8. Further, the charge removal device 3Y removes the residual charge of the photoreceptor 1Y after the cleaning by the cleaning device 2Y. By this charge removal, the surface of the photoreceptor 1Y is initialized and prepared for the next image formation.

  In the other process cartridges 6M, 6C, and 6Bk, M, C, and Bk toner images are similarly formed on the photoreceptors 1M, 1C, and 1Bk, and are primarily transferred onto the intermediate transfer belt 8 in a superimposed manner.

  An optical writing unit 7 is disposed below the process cartridges 6Y, 6M, 6C, and 6Bk in the drawing. An image data processing device (not shown) generates an exposure scanning control signal based on an image information signal sent from a personal computer or the like and sends it to the optical writing unit 7. The optical writing unit 7 serving as a latent image forming unit irradiates the photoconductors 1Y, 1M, 1C, and 1Bk of the process cartridges 6Y, 6M, 6C, and 6Bk with the laser light L generated based on the exposure scanning control signal. Electrostatic latent images for Y, M, C, and Bk are formed on the photoreceptors 1Y, 1M, 1C, and 1Bk exposed by the irradiation.

  The optical writing unit 7 scans the laser light L emitted from the light source with a polygon mirror that is rotationally driven by a motor, and onto the photoreceptors 1Y, 1M, 1C, and 1Bk via a plurality of optical lenses and mirrors. Irradiation. Instead of the optical writing unit 7 having such a configuration, one that irradiates LED light from the LED array may be employed.

  The electrostatic latent images for Y, M, C, and Bk formed on the photoreceptors 1Y, 1M, 1C, and 1Bk are developed by the developing devices 5Y, 5M, 5C, and 5Bk in the process cartridges 6Y, 6M, 6C, and 6Bk. Are developed into Y, M, C, and Bk toner images, and then a transfer process by the transfer device 10 is performed. The transfer device 10 includes a first transfer unit 15 and a second transfer unit 24.

  Below the optical writing unit 7, a first paper cassette 25 and a second paper cassette 26 are disposed so as to overlap in the vertical direction. The first paper cassette 25 and the second paper cassette 26 accommodate a recording paper bundle in which a plurality of recording papers P as transfer materials are stacked.

  On the right side of the first paper cassette 25 and the second paper cassette 26 in the drawing, paper feeding means is provided. The sheet feeding means includes a first sheet feeding roller 28, a second sheet feeding roller 29, a registration roller pair 31, a sheet feeding path 32, and the like. The first paper feed roller 28 and the second paper feed roller 29 are in contact with the top recording paper P of the recording paper bundle accommodated in the first paper cassette 25 and the second paper cassette 26. Then, the uppermost recording paper P is sent out toward the paper feed path 32 by being driven to rotate by a driving means (not shown). The recording paper P delivered to the paper feed path 32 is sandwiched between rollers of a registration roller pair 31 disposed near the end of the paper feed path 32 in the recording conveyance direction.

  The registration roller pair 31 rotates both rollers in the forward direction so as to sandwich the recording paper P, but once the recording paper P is sandwiched, the rotation of both rollers is temporarily stopped. Then, rotation of both rollers is resumed at an appropriate timing, and the recording paper P is sent out toward a secondary transfer nip described later.

  The first transfer unit 15 of the transfer apparatus 10 is disposed above the four process cartridges 6Y, 6M, 6C, and 6Bk that are arranged in the horizontal direction. Further, the intermediate transfer belt 8, which is a belt member, four primary transfer rollers 22Y, 22M, 22C, and 22Bk, a belt cleaning device 23, a cleaning counter roller 23a, a driving roller 11, a secondary transfer backup roller 12, a tension roller 13, and a support roller 14 and so on. The intermediate transfer belt 8 is endlessly moved counterclockwise in the figure by the rotational driving of the driving roller 11 while being stretched around these rollers. The space inside the loop of the intermediate transfer belt 8 in the apparatus can be reduced by bringing the support roller 14 into contact with the intermediate transfer belt 8 from the front surface side and pushing the intermediate transfer belt 8 into the loop. Therefore, it is possible to reduce the size of the apparatus.

  The four primary transfer rollers 22Y, 22M, 22C, and 22Bk sandwich the intermediate transfer belt 8 that is moved endlessly in this manner between the photoreceptors 1Y, 1M, 1C, and 1Bk. By this sandwiching, primary transfer nips for Y, M, C, and Bk where the front surface of the intermediate transfer belt 8 and the photoreceptors 1Y, 1M, 1C, and 1Bk abut are formed. The primary transfer rollers 22Y, 22M, 22C, and 22Bk are applied with a primary transfer bias having a polarity (for example, plus polarity) opposite to that of the toner by a power source (not shown). By this application, primary transfer electric fields for electrostatically moving the toner images on the photoreceptors 1Y, 1M, 1C, and 1Bk toward the intermediate transfer belt 8 are formed in the primary transfer nips for Y, M, C, and Bk, respectively. Has been. Instead of the four primary transfer rollers 22Y, 22M, 22C, and 22Bk of the bias application method, a charger method that discharges from the electrode may be used.

  The intermediate transfer belt 8 is a base layer made of fluorine resin, polyvinylidene fluoride, polyimide resin or the like with little elongation, and a coat layer having excellent surface smoothness made of a fluorine-based resin coated on the front surface side thereof, It has a multi-layer structure. Then, along the endless movement, it sequentially passes through the primary transfer nips for Y, M, C, and Bk. In each primary transfer nip, Y, M, C, and Bk toner images on the photoreceptors 1Y, 1M, 1C, and 1Bk are primarily transferred to the intermediate transfer belt 8 by the action of the nip pressure and the primary transfer electric field. As a result, a four-color superimposed toner image (hereinafter referred to as a four-color toner image) is formed on the intermediate transfer belt 8.

  The secondary transfer backup roller 12 that stretches the intermediate transfer belt 8 is disposed at a position that bites into a secondary transfer belt 16 that is an endless belt member described later. With such a biting arrangement, a secondary transfer nip is formed in which the front surface of the intermediate transfer belt 8 and the front surface of the secondary transfer belt 16 come into contact with each other.

  The visible four-color toner image formed on the intermediate transfer belt 8 enters the secondary transfer nip as the intermediate transfer belt 8 moves endlessly. Then, secondary transfer is performed on the recording paper P at the secondary transfer nip.

  Untransferred toner that has not been secondarily transferred to the recording paper P adheres to the front surface of the intermediate transfer belt 8 after passing through the secondary transfer nip. This is removed from the front surface of the intermediate transfer belt 8 by the belt cleaning device 23. Specifically, the intermediate transfer belt 8 after passing through the secondary transfer nip has a belt cleaning device 23 disposed so as to come into contact with the outer surface of the loop and the inner surface of the loop. It is sandwiched between the disposed cleaning facing roller 23a. The transfer residual toner on the front surface of the intermediate transfer belt 8 is mechanically collected and cleaned by the belt cleaning device 23.

  The second transfer unit 24 of the transfer device 10 is disposed on the right side of the first transfer unit 15 in the drawing, and includes a secondary transfer belt 16 that is an endless belt member, a belt cleaning device 18, and the like. Yes. A secondary transfer roller 17, a nip expansion roller 19, a tension roller 20, and a driving roller 21 are also provided. The secondary transfer belt 16 is endlessly moved clockwise in the figure by the rotational driving of the driving roller 21 while being stretched around these four rollers.

  A secondary transfer bias having a polarity (for example, plus polarity) opposite to that of the toner is applied to the secondary transfer roller 17 of the second transfer unit 24 by a power source (not shown). By this application, a secondary transfer electric field for electrostatically moving the four-color toner image on the intermediate transfer belt 8 toward the secondary transfer belt 16 is formed in the secondary transfer nip.

  The registration roller pair 31 of the paper feeding means feeds the recording paper P sandwiched between the rollers at a timing at which the recording paper P can be brought into close contact with the four-color toner image on the intermediate transfer belt 8 in the secondary transfer nip. As a result, the four-color toner image on the intermediate transfer belt 8 is secondarily transferred onto the recording paper P in the secondary transfer nip, and becomes a full-color image combined with the white color of the recording paper P.

  At the exit of the secondary transfer nip, the intermediate transfer belt 8 is separated from the recording paper P, and the recording paper P is carried and conveyed only on the surface of the secondary transfer belt 16. Then, as the secondary transfer belt 16 moves endlessly, it is sent to a fixing device 35 described later.

  Further, the secondary transfer belt 16 is sandwiched between the driving roller 21 and the belt cleaning device 18 so that the transfer residual toner on the surface is mechanically or electrostatically cleaned.

  Above the second transfer unit 24 in the figure, a fixing device 35 serving as fixing means is disposed. The fixing device 35 has two fixing rollers 35a and a pressure roller 35b that contact each other while rotating in the forward direction to form a fixing nip. The fixing roller 35a has heat generating means such as a halogen lamp, and heats the recording paper P sandwiched in the fixing nip. Then, the full color image formed on the recording paper P is fixed on the recording paper P by heating and pressure at the fixing nip. The recording sheet P after fixing is discharged out of the apparatus through a pair of discharge rollers 37. And it is stacked on the stack part 38 formed on the upper surface of the housing of the printer main body.

  A bottle container 54 is disposed above the first transfer unit 15 in the drawing. In the bottle container 54, toner bottles BY, BM, BC, BBk containing toner to be supplied to the developing devices 5Y, 5M, 5C, 5Bk in the process cartridges 6Y, 6M, 6C, 6Bk are stored. It has been.

  In this printer, the combination of the process cartridges 6Y, 6M, 6C, 6K, the optical writing unit 7, and the transfer device 10 is visible on the front surface of the intermediate transfer belt 8 or the secondary transfer belt 16. It functions as a visible image forming means for forming a toner image.

  A backing member 110 is disposed inside the loop of the intermediate transfer belt 8 of the first transfer unit 15 and in the vicinity of the drive roller 11. The backing member 110 is fixed to the inner side of the belt loop so as to be slidable over the entire area in the width direction with respect to the back surface of the intermediate transfer belt 8 immediately after passing the stretched position by the driving roller 11. .

  Outside the loop of the intermediate transfer belt 8, an optical sensor 120 that detects the image density and positional relationship of a toner pattern that is a toner image for detecting each color on the intermediate transfer belt 8 is provided on the front surface of the intermediate transfer belt 8. Are arranged to face each other with a predetermined interval.

  Of the entire region of the front surface of the intermediate transfer belt 8, the region backed by the backing member 110 is a region to be detected by the optical sensor 120. Specifically, the optical sensor 120 has a light emitting element (not shown) and a light receiving element (not shown), and the light emitted from the light emitting element is backed by the backing member 110 on the front surface of the intermediate transfer belt 8. Irradiate the detected area that is the area. The light reflected by the detection region is received by the light receiving element of the optical sensor 120, and the light receiving element outputs a voltage having a value corresponding to the amount of received light to a control unit (not shown). The amount of reflected light in the detection area of the intermediate transfer belt 8 has a correlation with the toner adhesion amount per unit area in the detection area. Therefore, the amount of light received by the light receiving element represents the toner adhesion amount in the detection area.

  The printer performs an image adjustment mode called process control immediately after a power switch (not shown) is turned on, immediately after rising from the energy saving mode, and whenever a predetermined number of printouts are performed. The energy saving mode refers to image formation in a state where power supply to the heat generating means of the fixing device 35 is stopped when an image formation command such as a print command signal sent from a personal computer (not shown) is not given for a predetermined time or longer. This is a mode to wait for an instruction. In the image adjustment mode, an image density adjustment process for each color toner image and a position adjustment process for detecting the position shift of each color toner image are performed.

  In the process control, first, the optical sensor 120 is calibrated. Specifically, an output voltage value from the light receiving element in a state where light emission by the light emitting element of the optical sensor 120 is turned off is detected as Vsg. A ROM of a control unit (not shown) stores in advance Vs0 that is a saturation output voltage value from the light receiving element when a high-density black solid toner image is detected. The light emission amount of the light emitting element is adjusted so that a value obtained by subtracting Vs0 from Vsg described above becomes a predetermined value (for example, 1.5 [V]). By this adjustment, the optical sensor 120 is calibrated.

  When the calibration of the sensor is completed, the plotter startup operation is performed next. In this plotter start-up operation, predetermined drive bias, development bias, and transfer bias are started after each drive motor is started.

  When the plotter startup operation is performed, gradation pattern detection processing is performed next. In this gradation pattern detection process, first, a Bk gradation pattern image composed of 17 toner patterns having different toner adhesion amounts is formed on the Y photoreceptor 1Bk, and then transferred onto the intermediate transfer belt 8. The At this time, the toner adhesion amount for each toner pattern in the Bk gradation pattern image is adjusted by the difference in development potential. The development potential is a potential difference between the electrostatic latent image on the photoreceptor 1Bk and the surface potential (development bias VB) of the development roller of the development device 5Bk. The development potential is adjusted by the difference in the optical writing intensity with respect to the photoreceptor 1Bk.

  The electrostatic latent image for each toner pattern in the Bk tone pattern image is detected by a potential sensor (not shown) prior to development, and the detection result is output to the control unit. In addition, the toner adhesion amount per unit area for each toner pattern in the Bk gradation pattern image is detected by the optical sensor 120.

  The control unit calculates the development potential when developing each toner pattern based on the output signal from the potential sensor and the development bias VB. Further, the toner adhesion amount for each toner pattern is calculated based on the output signal from the optical sensor 120. Then, an approximate linear equation indicating the relationship between the toner adhesion amount for each toner pattern and the development potential corresponding to each toner pattern is calculated. This approximate linear expression indicates the image forming ability of the visible image forming means. Therefore, the control unit measures the image forming performance by performing the gradation pattern detection process.

  When the control unit obtains the above approximate linear equation, the control unit specifies an optimum development potential for obtaining the target toner adhesion amount based on the approximate linear equation. Then, after the identification, the photosensitive member uniform charging potential VL, the developing bias VB, and the optical writing intensity VD that match the developing potential are specified based on the data table stored in advance in the ROM. And a specific result is memorize | stored in NVRAM which is a non-volatile information storage means. Such gradation pattern detection processing is also performed for M, C, and Bk.

  After performing the process control, when performing a print job based on the image information signal, the photosensitive member uniform charging potential VL, the developing bias VB, and the optical writing intensity VD for each color are stored in the NVRAM during the process control. Set to the same value as the stored data. This suppresses fluctuations in image density and gradation reproducibility caused by fluctuations in the environment (temperature and humidity) and toner characteristics (fluidity, bulk density, etc.), and stably forms high-quality images over a long period of time. be able to.

  Further, the optical writing position with respect to the photoconductors 1Bk, 1Y, 1M, and 1C is shifted due to subtle expansion and contraction of the optical system components, and the photoconductors 1Bk, 1Y, 1M, and 1C are transferred from the photoconductors 1Bk, 1Y, 1M, and 1C to the recording paper when the image forming unit is replaced. If the transfer position of the toner image is shifted, color misregistration will occur. For this reason, a toner pattern for detecting misregistration composed of toner images of the respective colors formed by the process cartridges 6Y, 6M, 6C, and 6K is formed on the intermediate transfer belt 8 at a predetermined timing, and based on the detection result by the optical sensor 120. Thus, the relative positional deviation of the toner patterns of the respective colors is detected. Then, by adjusting the optical writing timing of each color to the photoreceptors 1Bk, 1Y, 1M, and 1C based on the detection result, it is possible to suppress the color shift due to the relative positional shift of each color toner image.

  In the case where the process control is performed in the image adjustment mode as in the present printer, if the detected area in the intermediate transfer belt 8 undulates with the endless movement of the intermediate transfer belt 8, the amount of light received by the light receiving element due to the undulations. It will change. As a result, the detection accuracy of the toner adhesion amount with respect to each toner pattern deteriorates, and it becomes difficult to accurately detect the image forming performance of the visible image forming means. Therefore, in the present printer, when the process control is executed, the detected area is tensioned by sliding the backing member 110 on the back side of the detected area on the intermediate transfer belt 8 to suppress the undulation of the detected area. ing.

  Note that, instead of the secondary transfer belt 16 provided in the second transfer unit 24, a configuration using a secondary transfer roller 36 as shown in FIG. 3 may be employed.

  Here, usually, the detection by the optical sensor 120 is generally performed in a state where the backing member 110 is about 1 mm in the intermediate transfer belt 8. As the amount of biting of the backing member 110 with respect to the intermediate transfer belt 8 is increased, even if the waviness of the intermediate transfer belt 8 is large or the intermediate transfer belt 8 is deformed, the fluctuation amount of sensor detection becomes smaller. Has been confirmed (FIG. 4). However, if the amount of biting of the backing member 110 with respect to the intermediate transfer belt 8 is increased, the sliding load of the backing member 110 increases, which may cause chattering noise or wear of the intermediate transfer belt 8.

[Configuration example 1]
In the present configuration example, the intermediate transfer belt 8 is one of a plurality of stretching members that are rotatably stretched, and is provided on the front surface of the intermediate transfer belt 8 near the backing member 110 (near the optical sensor 120). The contacting support roller 14 is held by an arm 46 that can swing around a fulcrum. Further, the support roller 14 is provided to be displaceable with the swing of the arm 46. Then, the amount of biting of the backing member 110 with respect to the intermediate transfer belt 8 is increased only in the image adjustment mode in which the toner is detected by the optical sensor 120 by displacing the support roller 14.

FIG. 1 shows the contacting / separating state of the backing member 110 with respect to the intermediate transfer belt 8.
FIG. 1A shows a state in which detection by the optical sensor 120 is not performed, and shows a state in which the intermediate transfer belt 8 is separated from the backing member 110. In this state, the cam 45 is in contact with the arm 46 holding the support roller 14 on the short diameter side, and the arm 46 is pulled in a direction away from the backing member 110 by the tension spring 47. At this time, the pressing of the intermediate transfer belt 8 by the support roller 14 is small, and the amount of biting of the backing member 110 into the intermediate transfer belt 8 is small, or the intermediate transfer belt 8 is completely separated from the backing member 110. It is in the state.

  Accordingly, the intermediate transfer belt 8 does not always remain in a state where the amount of biting is large or in contact with the backing member 110. Therefore, the wear of the intermediate transfer belt 8 due to friction between the intermediate transfer belt 8 and the backing member 110 can be reduced, and the life can be extended. Further, since the wear of the intermediate transfer belt 8 can be reduced, the frictional resistance between the intermediate transfer belt 8 and the backing member 110 can be prevented from increasing with time, and abnormal noise accompanying chatter of the intermediate transfer belt 8 can be prevented. Generation | occurrence | production can be suppressed. Further, since the intermediate transfer belt 8 and the backing member 110 do not remain in contact with each other when the apparatus is stopped, the intermediate transfer belt 8 and the backing member 110 can be prevented from sticking to each other, and the intermediate transfer belt is started at the next belt rotation start. It can suppress that 8 breaks.

  FIG. 1B shows a state in which detection by the optical sensor 120 is performed, and shows a state in which the intermediate transfer belt 8 is in contact with the backing member 110. Before the detection by the optical sensor 120 is started, the cam 45 rotates counterclockwise in the drawing, so that the long diameter side of the cam 45 hits the arm 46 holding the support roller 14, and the tensile force of the tension spring 47 is applied. Against this, the arm 46 swings toward the backing member 110. As a result, the support roller 14 is displaced and the intermediate transfer belt 8 is greatly pushed inward from the outside of the loop by the support roller 14, and the amount of biting of the backing member 110 with respect to the intermediate transfer belt 8 increases. As described above, the toner is detected by the optical sensor 120 in a state where the amount of biting of the backing member 110 into the intermediate transfer belt 8 is increased, so that the intermediate transfer belt 8 is not wavy or fluttered. The toner pattern on the belt 8 can be read accurately.

  The optical sensor 120 and the backing member 110 are fixed to the apparatus main body, and neither is displaced in the operation of increasing the amount of biting of the backing member 110 into the intermediate transfer belt 8. The positional relationship between the optical sensor 120 and the backing member 110 affects sensor detection unless it is installed particularly accurately. Therefore, as in this printer, by providing the optical sensor 120 and the backing member 110 fixed to the apparatus main body, it is easy to ensure the positional accuracy of the optical sensor 120 and the backing member 110, and the mechanism is Simplification is possible.

[Configuration example 2]
If the intermediate transfer belt 8 is left standing for a long time, the intermediate transfer belt 8 is deformed by the bending of each stretching roller, and immediately returns to the original state even when the rotation operation of the intermediate transfer belt 8 is started. Absent. Due to the deformation of the intermediate transfer belt 8 when left in a stationary state for a long time, a sensor detection failure may occur.

  In this configuration example, a timer is provided in the control unit, and this timer is used as a stationary time measuring unit that measures the stationary time of the intermediate transfer belt 8. Then, based on the measurement result of the timer, the intermediate transfer belt 8 of the backing member 110 is displaced by displacing the support roller 14 only in the image adjustment mode for a fixed number of times after the intermediate transfer belt 8 is left stationary for a fixed time. The amount of biting into 8 was increased to improve the sensor detection margin. Thereby, it is possible to suppress the occurrence of sensor detection failure due to the deformation of the intermediate transfer belt 8 when left in a stationary state for a long time. Further, the amount of biting of the backing member 110 into the intermediate transfer belt 8 is increased only for a limited time until the deformation of the intermediate transfer belt 8 is recovered, thereby suppressing an increase in driving load, chatter noise, and belt wear. Is also effective.

[Configuration example 3]
In the present configuration example, the length of the belt portion wound around the cleaning facing roller 23a and the driving roller 11 on both sides adjacent to the support roller 14 is not changed by the displacement of the support roller 14.

  In FIG. 1A, the distance between the cleaning opposing roller 23a and the support roller 14 when the sensor is not detected is L, and the distance between the support roller 14 and the drive roller 11 is M. In FIG. 1B, the distance between the cleaning facing roller 23a and the support roller 14 at the time of sensor detection is L ', and the distance between the support roller 14 and the drive roller 11 is M'. Then, the support roller 14 is displaced so as to satisfy the relationship L + M = L ′ + M ′. Thereby, the tension of the intermediate transfer belt 8 does not change with the displacement of the support roller 14. Therefore, it is possible to suppress the occurrence of color shift due to the displacement of the support roller 14 and the occurrence of sensor detection failure.

[Embodiment 2]
FIG. 5 is a schematic configuration diagram of the image forming apparatus according to the present embodiment. This image forming apparatus is an image forming apparatus employing a so-called tandem type intermediate transfer system.

  As shown in FIG. 5, image forming units corresponding to yellow (Y), magenta (M), cyan (C), and black (Bk) colors are arranged in parallel, and each image forming unit carries a latent image. Four drum-shaped photoconductors 71Y, 71M, 71C, 71Bk are arranged as the body. Around the photoconductors 71Y, 71M, 71C, 71Bk, developing devices for developing the latent images formed on the photoconductor surfaces using charging devices 74Y, 74M, 74C, 74Bk for charging the surfaces of the photoconductors. Devices 76Y, 76M, 76C, and 76M are sequentially arranged. Further, a cleaning device 72 including a cleaning blade 73 for cleaning the surface of the photoreceptor after the toner image is transferred is disposed.

Below each image forming unit, optical writing is performed with laser light L _Y , L _M , L _C , and L _Bk to form a latent image on the surface of each photoconductor 71Y, 71M, 71C, 71Bk. Is provided.

  A transfer device 9 having an intermediate transfer belt 90 as an intermediate transfer member is disposed above each image forming unit. In the transfer device 9, the intermediate transfer belt 90 is a plurality of stretching rollers, a driving roller 92, a tension roller 93 that is biased by a spring 94 and applies tension to the intermediate transfer belt 90, a stretching roller 95, and a stretching roller 96. The belt is rotatably stretched by a tension roller 98 or the like. By driving the driving roller 92 by a driving motor (not shown), the intermediate transfer belt 90 is driven counterclockwise in the drawing. Further, the tension roller 93 is driven to rotate as the intermediate transfer belt 90 rotates.

  In the present embodiment, the drive speed (process speed) of the intermediate transfer belt 90 is adjusted to 200 [mm / sec]. In order to transfer the toner images formed on the photoreceptors 71Y, 71M, 71C, 71Bk onto the intermediate transfer belt 90 at positions facing the photoreceptors 71Y, 71M, 71C, 71Bk with the intermediate transfer belt 90 interposed therebetween. Primary transfer rollers 91Y, 91M, 91C, 91Bk are disposed. The primary transfer rollers 91Y, 91M, 91C, and 91Bk are respectively pressed by springs 99Y, 99M, 99C, and 99Bk so as to contact the intermediate transfer belt 90. In this embodiment, the load is set to 1 [N] on one side. A predetermined transfer bias is applied to the primary transfer rollers 91Y, 91M, 91C, and 91Bk by power supplies 100Y, 100M, 100C, and 100Bk. In the present embodiment, +1800 [V] is set as the transfer bias.

  Further, the intermediate transfer belt 90 faces the drive roller 92 downstream of the primary transfer rollers 91Y, 91M, 91C, 91Bk in the intermediate transfer belt rotation direction via the intermediate transfer belt 90, and is brought into contact with the front surface of the intermediate transfer belt 90. A secondary transfer roller 81 is provided. The drive roller 92 that stretches the intermediate transfer belt 90 has a function as a secondary transfer counter roller, and the secondary transfer roller 81 and the drive roller 92 pass the secondary transfer roller 90 via the intermediate transfer belt 90. A transfer nip is formed.

  A belt cleaning device 51 that removes residual toner remaining on the intermediate transfer belt 90 after the transfer is opposed to the tension roller 93 via the intermediate transfer belt 90 on the downstream side of the secondary transfer roller 81 in the rotation direction of the intermediate transfer belt. It is provided to do. The belt cleaning device 51 is configured to press a cleaning blade 52 made of urethane rubber against the surface of the intermediate transfer belt to block the toner and clean it.

  In the transfer device 9, the belt cleaning device 51 is disposed below the tension roller 93 to reduce the size of the transfer device 9 in the horizontal direction. The tension roller 93 has a function as a belt cleaning counter roller, and improves the adhesion between the cleaning blade 52 and the intermediate transfer belt 90.

The material of the intermediate transfer belt 90 will be described.
The intermediate transfer belt 90 is composed of polyvinylidene fluoride, ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate) or the like in a single layer or a plurality of layers, and is made of a conductive material such as carbon black. The volume resistivity is 10 ⁸ [Ω · cm] to 10 ¹² [Ω · cm], and the surface resistivity is in the range of 10 ⁹ [Ω · cm] to 10 ¹³ [Ω · cm]. It has been adjusted.

  Note that a release layer may be coated on the surface of the intermediate transfer belt 90 as necessary. Materials used for the coating include ETFE (ethylene-tetrafluoroethylene copolymer), PTFE (polytetrafluoroethylene), polyvinylidene fluoride, PEA (perfluoroalkoxy fluororesin), FEP (ethylene tetrafluoride- A fluororesin such as hexafluoropropylene copolymer) or PVF (vinyl fluoride) can be used, but is not limited thereto. The method of manufacturing the intermediate transfer belt 90 includes a casting method, a centrifugal molding method, and the like, and the surface thereof may be polished as necessary.

  If the volume resistivity of the intermediate transfer belt 90 exceeds the above range, the bias required for transfer increases, which increases the power supply cost, which is not preferable. In addition, since the charging potential of the intermediate transfer belt 90 becomes high and the self-discharge becomes difficult in the transfer process, the transfer paper peeling process, etc., it is necessary to provide a static elimination means. Also, if the volume resistivity and surface resistivity are below the above ranges, the charge potential decays quickly, which is advantageous for static elimination by self-discharge, but toner scatter occurs because the current during transfer flows in the surface direction. End up. Therefore, the volume resistivity and the surface resistivity of the intermediate transfer belt 90 in this embodiment are preferably within the above ranges.

  The volume resistivity and the surface resistivity were measured using a high resistivity meter (Mitsubishi Chemical Corporation: Hiresta IP) with an HRS probe (inner electrode diameter 5.9 [mm], ring electrode inner diameter 11 [mm]). A voltage of 100 [V] (surface resistivity is 500 [V]) was applied to the front and back of the intermediate transfer belt 90, and the measured value after 10 seconds was used.

Next, the secondary transfer roller 81 will be described.
The secondary transfer roller 81 covers a metal core such as stainless steel with an elastic body such as urethane adjusted to a resistance value in a range of 10 ⁶ [Ω] to 10 ¹⁰ [Ω] with a conductive material. It is composed of that.

  Here, since the current hardly flows when the resistance value of the secondary transfer roller 81 exceeds the above range, it is necessary to apply a higher voltage in order to obtain a required transfer property, which increases the power supply cost. Invite. In addition, since a high voltage is applied, a discharge occurs in the gap before and after the secondary transfer nip, so that white spots are lost due to the discharge on the halftone image. On the contrary, if the resistance value of the secondary transfer roller 81 is below the above range, the transferability between the multi-color image portion (for example, three-color superimposed image) and the single-color image portion existing on the same image cannot be achieved. This is because the resistance value of the secondary transfer roller 81 is low, so that a sufficient current flows to transfer the monochrome image portion at a relatively low voltage. However, it is optimal for the monochrome image portion to transfer the multiple color image portion. A voltage value higher than the voltage is required. For this reason, if the voltage is set so that the multi-color image portion can be transferred, the transfer current becomes excessive in a single-color image, and the transfer efficiency is reduced.

  The resistance value of the secondary transfer roller 81 is measured by installing the secondary transfer roller 81 on a conductive metal plate and 4.9 [N] on one side at both ends of the core metal (total of 9.8 [N] on both sides). It calculated from the value of the electric current which flows when the voltage of 1000 [V] is applied between a metal core and a metal plate in the state which applied the load of. Further, the secondary transfer roller 81 is brought into contact with the drive roller 92 with a load of 50 [N] via an intermediate transfer belt 90 by a spring (not shown), and rotates with the drive roller 92 via the intermediate transfer belt 90. It is the composition to do.

  A transfer bias is applied to the drive roller 92 by the power supply 101 in order to transfer the toner image on the intermediate transfer belt 90 onto the recording paper P as a transfer material. In this embodiment, constant current control is performed on the power supply 101 to apply a transfer bias to the driving roller 92, and the current setting value in this constant current control is set to −30 [μA].

  In the transfer device 9 having such a configuration, the recording paper P is fed in accordance with the timing when the leading end of the four-color superimposed image formed by being sequentially transferred onto the intermediate transfer belt 90 reaches the secondary transfer nip. The paper is fed by a roller 82, a recording paper conveyance roller 83, and a registration roller pair 84. The four-color superimposed image transferred from the intermediate transfer belt 90 to the recording paper P by the secondary transfer roller 81 is conveyed to the fixing device 30, fixed by the fixing device 30, and then discharged by the paper discharge roller pair 85.

  Reference numeral 55 in the figure denotes a density sensor that reads the density of the toner pattern formed on the intermediate transfer belt 90. The density sensor 55 is an optical density sensor including a light emitting element and a light receiving element, and a total of three density sensors 55 are arranged along the width direction of the intermediate transfer belt 90. The detection surface of the density sensor 55 is located at a position of 5 [mm] from the surface of the intermediate transfer belt 90.

  In the image forming apparatus of the present embodiment, the image adjustment mode is executed at a predetermined timing, and each color image forming unit forms a density detection toner pattern and transfers it onto the intermediate transfer belt 90. Based on the detection result of the density sensor 55, the amount of toner attached to each toner image of the toner pattern is grasped, and the development conditions such as the development bias are adjusted based on the result. As a result, the density of each color toner image can be stabilized over time, and color tone disturbance can be suppressed.

  Reference numeral 56 in the figure denotes a shutter for preventing the detection surface of the density sensor 55 from becoming dirty. By moving the shutter 56 in parallel with the detection surface, the detection surface of the density sensor 55 is opened and closed. It can be performed. The density sensor 55 and the shutter 56 are fixed to a pair of side plates (not shown) that are stationary members of the apparatus main body.

  A backing member 97 is installed at a position opposite to the density sensor 55 across the intermediate transfer belt 90. The backing member 97 is a sheet metal having a thickness of 1.6 [mm], and, for example, nylon having good slidability is planted in a portion that contacts the back surface of the intermediate transfer belt 90.

[Configuration Example 4]
Next, the concentration sensor and the vicinity of the backing member, which are the features of the present invention, will be described with reference to FIGS. FIG. 6 is a schematic view of the density sensor 55 and its vicinity when viewed from the side of the apparatus in the image adjustment mode.

  When density detection is performed by the density sensor 55, the eccentric cam 62 is rotated so that the short diameter side of the eccentric cam 62 is brought into contact with the shutter 56, whereby the shutter 56 is urged and moved in the left direction in the drawing by the compression spring 64. The detection surface of the density sensor 55 is opened.

  In order to accurately read the toner pattern on the intermediate transfer belt 90 by the density sensor 55, the intermediate transfer belt 90 is required to be in a state where there is no undulation or fluttering. Therefore, a highly rigid backing member 97 is disposed at a position facing the density sensor 55 via the intermediate transfer belt 90. The contact portion of the backing member 97 with the back surface of the intermediate transfer belt 90 has a planar shape and is fixed with high perpendicularity to the optical axis of the density sensor 55.

  Here, as shown in FIG. 8, the output voltage measurement result of the density sensor 55 when the inclination θ of the reflection member 57 having a planar shape with respect to the detection surface of the density sensor 55 is changed is shown in FIG.

  The higher the output voltage of the density sensor 55, the more accurate density detection can be performed, but as can be seen from FIG. 9, the output voltage is the highest in the vicinity of the gradient θ = 0 [°]. If the reflecting member 57 has a cylindrical surface instead of a planar shape, the inclination θ of the reflecting member 57 with respect to the detection surface of the density sensor 55 increases at an accelerated rate when the cylindrical position is shifted in the left-right direction in FIG. Therefore, accurate density detection cannot be performed. Therefore, it is desirable that the surface of the backing member 97 that faces the detection surface of the density sensor 55 via the intermediate transfer belt 90 is a flat surface or a surface having the smallest possible curvature.

  In this configuration example, in order to firmly attach the backing member 97 and the intermediate transfer belt 90, the intermediate transfer belt 90 is backed by the stretching roller 96 from the front surface side that is the outer peripheral surface of the intermediate transfer belt 90. The pressure is applied toward the contact member 97. Both ends of the tension roller 96 are held by a roller support member 63, and the eccentric cam 61 is rotated so that the roller support member 63 is moved downward so that the short diameter side is in an upward position. As the roller support member 63 moves, the stretching roller 96 also moves downward, and the intermediate transfer belt 90 can be pressed toward the backing member 97. By detecting the density with the density sensor 55 in this state, the density of the toner pattern on the intermediate transfer belt 90 can be accurately read in a state where the intermediate transfer belt 90 is not wavy or fluttered.

  FIG. 7 is a schematic view of the density sensor 55 and its vicinity when the printing operation is performed and when the apparatus is stopped as viewed from the side of the apparatus.

  If the intermediate transfer belt 90 continues to rotate while the backing member 97 and the back surface of the intermediate transfer belt 90 are in contact with each other, the back surface of the intermediate transfer belt 90 is worn and the life of the intermediate transfer belt 90 is shortened. Further, if the intermediate transfer belt 90 and the backing member 97 are kept in contact with each other when the apparatus is stopped during standby or when the power is turned off, the intermediate transfer belt 90 and the backing member 97 adhere to each other, and the next belt. The intermediate transfer belt 90 may be damaged at the start of rotation.

  Therefore, at the time of a normal printing operation in which density detection by the density sensor 55 is not performed or when the apparatus is stopped, as shown in FIG. 7, the eccentric cam 61 is rotated so as to take a posture in which the long diameter side is upward, and the roller support member 63 Is moved upward from the position of FIG. As the roller support member 63 moves, the stretching roller 96 also moves upward from the position shown in FIG. 6, and the intermediate transfer belt 90 is not pressed against the backing member 97 by the stretching roller 96. As a result, the intermediate transfer belt 90 is separated from the backing member 97 by the tension of the intermediate transfer belt 90.

  As described above, in this configuration example, the intermediate transfer belt 90 is not always in contact with the backing member 97, so that the intermediate transfer belt 90 is caused by friction between the intermediate transfer belt 90 and the backing member 97. Wear can be reduced, and the life can be extended. Furthermore, the frictional resistance between the intermediate transfer belt 90 and the backing member 97 can be prevented from increasing over time by reducing the wear of the intermediate transfer belt 90, and abnormal noise accompanying chatter of the intermediate transfer belt 90 can be prevented. Generation | occurrence | production can be suppressed. Further, since the intermediate transfer belt 90 and the backing member 97 do not remain in contact with each other when the apparatus is stopped, the intermediate transfer belt 90 and the backing member 97 can be prevented from sticking, and the intermediate transfer belt is started at the next belt rotation start. 90 can be prevented from being damaged.

  Further, at the time of a normal printing operation in which density detection by the density sensor 55 is not performed or when the apparatus is stopped, the shutter 56 is moved to the right side of the position of FIG. 6 by the eccentric cam 62 as shown in FIG. The detection surface is blocked by the shutter 56. In this way, by blocking the detection surface of the density sensor 55 with the shutter 56, it is possible to suppress the toner adhering to the intermediate transfer belt 90 during the printing operation from scattering and adhering to the detection surface.

  There is another reason for separating the intermediate transfer belt 90 and the backing member 97 when the apparatus is stopped. If the intermediate transfer belt 90 is left standing for a while, the winding rollers 92, 93, 95, 96, and 98 may be wound around the intermediate transfer belt 90. If there is a winding wrinkle on the intermediate transfer belt 90, accurate transfer is not performed at the primary transfer portion or the secondary transfer portion of each color, resulting in a horizontal band image. Further, the winding wrinkle of the intermediate transfer belt 90 also affects the density detection by the density sensor 55 and reduces the adhesion between the intermediate transfer belt 90 and the backing member 97. For this reason, the intermediate transfer belt 90 and the backing member 97 are separated from each other to reduce the tension of the intermediate transfer belt 90 and make it difficult to cause a winding wrinkle.

[Configuration Example 5]
In this configuration example, the shutter 56 and the stretching roller 96 are operated by the same drive source.

  FIG. 10 is a schematic view of the density sensor 55 in the image adjustment mode viewed from the side of the apparatus in the vicinity thereof, and FIG. 11 is a schematic view of the density sensor 55 and the shutter 56 in the image adjustment mode viewed from above the apparatus. is there.

  Drive is transmitted from a motor 130 as a drive source provided in the apparatus main body to a gear 65 held in a unit including the intermediate transfer belt 90. The gear 42 is rotated by the gear 65 to which the drive is transmitted in this manner, and the eccentric cam 61 provided coaxially with the gear 42 is rotated so that the short diameter side is in an upward position, whereby the roller support member 63 is rotated. Move down. By the movement of the roller support member 63, the stretching roller 96 is also moved downward, and the intermediate transfer belt 90 can be pressed toward the backing member 97 by the stretching roller 96. By detecting the density with the density sensor 55 in this state, the density of the toner pattern on the intermediate transfer belt 90 can be accurately read in a state where the intermediate transfer belt 90 is not wavy or fluttered.

  On the other hand, when driving is transmitted from the motor 130 to the gear 65, the gear 41 provided with the side cam 43 rotates from the gear 65 via the gear 40, and the side cam 43 moves as the gear 41 rotates. Thus, the shutter 56 moves to the front in the direction perpendicular to the sheet of FIG. As shown in FIG. 11, the shutter 56 has three exposure holes 56F, 56C, and 56R in the longitudinal direction. The exposure holes 56F, 56C, and 56R and the detection surfaces of the density sensors 55F, 55C, and 55R face each other, so that the detection surfaces of the density sensors 55F, 55C, and 55R are exposed from the exposure holes 56F, 56C, and 56R and opened. The

  FIG. 12 is a schematic view of the density sensor 55 at the time of printing operation and when the apparatus is stopped and a side view of the vicinity of the density sensor 55. FIG. 13 shows the density sensor 55 and the shutter 56 at the time of printing operation and when the apparatus is stopped. It is the schematic diagram seen from.

  At the time of printing operation and when the apparatus is stopped, the gear 42 is rotated by the gear 65 to which the drive is transmitted from the motor 130 provided in the apparatus main body, and the eccentric cam 61 provided coaxially with the gear 42 is positioned so that the longer diameter side is upward. The roller support member 63 is moved upward from the position shown in FIG. Due to the movement of the roller support member 63, the stretching roller 96 moves upward from the position of FIG. 10, so that the intermediate transfer belt 90 is not pressed against the backing member 97 by the stretching roller 96. As a result, the intermediate transfer belt 90 is separated from the backing member 97 by the tension of the intermediate transfer belt 90.

  As described above, in this configuration example, the intermediate transfer belt 90 is not always in contact with the backing member 97, so that the intermediate transfer belt 90 is caused by friction between the intermediate transfer belt 90 and the backing member 97. Wear can be reduced, and the life can be extended. Further, since the wear of the intermediate transfer belt 90 can be reduced, the frictional resistance between the intermediate transfer belt 90 and the backing member 07 is prevented from increasing with time, and abnormal noise due to chattering of the intermediate transfer belt 90 is reduced. Generation | occurrence | production can be suppressed. Further, since the intermediate transfer belt 90 and the backing member 97 do not remain in contact with each other when the apparatus is stopped, the intermediate transfer belt 90 and the backing member 97 can be prevented from sticking, and the intermediate transfer belt is started at the next belt rotation start. 90 can be prevented from being damaged.

  On the other hand, when the drive is transmitted from the motor 130 to the gear 65, the gear 41 having the side cam 43 rotates from the gear 65 through the gear 40, and the side cam 43 moves as the gear 41 rotates. Then, the shutter 56 moves to the back side in the vertical direction in FIG. As a result, the exposure holes 56F, 56C, and 56R of the shutter 56 and the detection surfaces of the density sensors 55F, 55C, and 55R do not face each other, and the detection surfaces of the density sensors 55F, 55C, and 55R are blocked.

  In this configuration example, the number of teeth of the gear 40 and the gear 65 is set to 40, and the number of teeth of the gear 41 and the gear 42 is set to 50 in order to synchronize the operations of the stretching roller 96 and the shutter 56.

  By using the same drive source for the shutter 56 and the stretching roller 96 as in this configuration example, the apparatus can be reduced in size and cost.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
A belt member such as an intermediate transfer belt 8 that is rotatably supported by a plurality of tension members, and a secondary transfer belt 16 that transfers a toner image formed on the surface of the belt member to a transfer material such as a recording paper P. Such as an optical sensor 120 that is provided at a position facing the surface of the belt member and detects a detection toner pattern formed on the surface, and the detection means via the belt member. In the transfer device such as the transfer device 10 provided with the opposing member such as the backing member 110 provided as a contact member, the contact member such as the support roller 14 provided in contact with the vicinity of the opposing member of the belt member, and the contact member Displacement means such as a cam 45 for displacing the contact member, and the contact member is displaced by the displacement means to change the contact state between the opposing member and the belt member. According to this, as described in the above-described embodiment, it is possible to reduce the wear of the belt member while suppressing the positional accuracy between the detection means and the backing member, and to suppress the generation of noise due to chatter.
(Aspect B)
In (Aspect A), as a change in the contact state between the facing member and the belt member, the belt member is brought into contact with and separated from the facing member. According to this, as described in the above embodiment, the belt member can be brought into contact with and separated from the facing member while ensuring the positional accuracy between the detection means and the facing member.
(Aspect C)
In (Aspect A), the amount of biting of the facing member into the belt member is changed as a change in the contact state between the facing member and the belt member. According to this, as described in the above embodiment, the amount of biting into the belt member of the backing member can be changed while ensuring the positional accuracy between the detection means and the facing member.
(Aspect D)
In (Aspect A), (Aspect B), or (Aspect C), the contact member is provided in contact with a front surface that is an outer peripheral surface of the belt member. According to this, as described in the above embodiment, the space inside the loop of the belt member can be reduced in the apparatus, and the apparatus can be reduced in size.
(Aspect E)
In (Aspect A), (Aspect B), (Aspect C) or (Aspect D), due to the displacement of the contact member, the contact member and the driving roller 11 adjacent to both the upstream side and the downstream side in the rotational direction of the belt member are cleaned. The length of the belt member at the portion hung around two stretching members such as the opposing roller 23a does not change. According to this, as described in the above embodiment, it is possible to suppress the occurrence of color shift due to the displacement of the contact member and the occurrence of sensor detection failure.
(Aspect F)
In (Aspect A), (Aspect B), (Aspect C), (Aspect D), or (Aspect E), the contact portion of the facing member with the belt member has a planar shape or a substantially planar shape. According to this, as described in the above embodiment, the perpendicularity between the sensor optical axis and the belt surface is increased, and accurate density detection can be performed.
(Aspect G)
In (Aspect A), (Aspect B), (Aspect C), (Aspect D), (Aspect E) or (Aspect F), a position where the detection surface of the detection means is opened and a position where the detection surface is blocked A shutter member such as a shutter 56 that can be displaced between the two is provided. According to this, as described in the above embodiment, it is possible to suppress the toner adhering to the belt member during the printing operation from scattering and adhering to the detection surface.
(Aspect H)
(Aspect G) includes a driving roller such as a driving roller 11 that is one of the plurality of stretching members and rotationally drives the belt member, and a motor 130 that drives the driving roller and the shutter member. The drive source is the same. According to this, as described in the above embodiment, it is possible to reduce the size and cost of the apparatus.
(Aspect I)
In (Aspect A), (Aspect B), (Aspect C), (Aspect D), (Aspect E), (Aspect F), (Aspect G) or (Aspect H), the contact member is a roller member. Thus, wear of the belt member due to the contact member can be suppressed.
(Aspect J)
In (Aspect A), (Aspect B), (Aspect C), (Aspect D), (Aspect E), (Aspect F), (Aspect G), (Aspect H) or (Aspect I), the contact member is One of the plurality of stretching members. According to this, since it is not necessary to provide a dedicated member for changing the contact member, cost reduction and space saving can be achieved.
(Aspect K)
Image bearing members such as a plurality of photoconductors 1, developing means such as a plurality of developing devices 5 that form toner images of different colors composed of different color toners on each image bearing member, and each image bearing member In the image forming apparatus provided with a transfer device such as the transfer device 10 that is finally provided to transfer the toner image onto a transfer material such as the recording paper P, the transfer device (Aspect A) , (Aspect B), (Aspect C), (Aspect D), (Aspect E), (Aspect F), (Aspect G), (Aspect H), (Aspect I) or (Aspect J) are provided. It was. According to this, as described in the above embodiment, the belt member can be brought into and out of contact with the opposing member while ensuring the positional accuracy between the detection means and the opposing member, and abnormal noise caused by chatter is generated. Can be suppressed, and good image formation can be performed.
(Aspect L)
In (Aspect K), in the image adjustment mode in which an image adjustment process is performed based on the detection result of the detection means, the contact member is displaced by the displacement means so that the belt member is brought into contact with the opposing member, Otherwise, the contact member is displaced by the displacing means to separate the belt member from the opposing member. According to this, as described in the above embodiment, since the belt member is brought into contact with the opposing member only in the image adjustment mode in which toner detection is performed by the detection unit, an increase in driving load, chatter noise, belt Effective in suppressing wear.
(Aspect M)
(Aspect K) In the image adjustment mode in which image adjustment processing is performed based on the detection result of the detection means, the contact member is displaced by the displacement means to increase the amount of biting of the counter member into the belt member. Otherwise, the contact member is displaced by the displacing means to reduce the amount of biting of the opposing member into the belt member. According to this, as described in the above embodiment, the amount of biting into the belt member of the opposing member is increased only in the image adjustment mode in which toner detection is performed by the detection unit. Effective in suppressing noise and belt wear.
(Aspect N)
In (Aspect K), (Aspect L) or (Aspect M), it has a stationary time measuring means such as a timer for measuring the stationary time of the belt member, and based on the measurement result of the stationary time measuring means, The contact member is displaced by the displacing means to bring the belt member into contact with the opposing member only when the image adjustment mode is executed a certain number of times after the belt member has been left stationary for a certain time. According to this, as described in the above embodiment, it is possible to improve the margin of sensor detection, and it is effective for increasing the driving load, suppressing chatter noise, and belt wear.
(Aspect O)
In (Aspect K), (Aspect L), (Aspect M) or (Aspect N), the belt member is an intermediate transfer belt such as the intermediate transfer belt 8, and the plurality of image carriers are placed on the intermediate transfer belt. A secondary transfer unit such as a second transfer unit 24 that collectively transfers the transferred toner image to the recording medium is provided. According to this, as described in the above-described embodiment, it is possible to suppress the occurrence of detection failure, and to suppress color unevenness due to density unevenness of each color toner image and relative positional shift.

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Cleaning apparatus 3 Static elimination apparatus 4 Charging apparatus 5 Developing apparatus 6 Process cartridge 7 Optical writing unit 8 Intermediate transfer belt 9 Transfer apparatus 10 Transfer apparatus 11 Drive roller 12 Secondary transfer backup roller 13 Tension roller 14 Support roller 15 First roller Primary transfer unit 16 Secondary transfer belt 17 Secondary transfer roller 18 Belt cleaning device 19 Nip expansion roller 20 Tension roller 21 Drive roller 22 Primary transfer roller 23 Belt cleaning device 23a Cleaning counter roller 24 Second transfer unit 25 First paper cassette 26 Second paper cassette 28 First paper feed roller 29 Second paper feed roller 30 Fixing device 31 Registration roller pair 32 Paper feed path 35 Fixing device 35a Fixing roller 35b Pressure roller 36 Secondary transfer roller 37 Paper discharge roller pair 38 Stack portion 40 Gear 41 Gear 42 Gear 43 Side cam 45 Cam 46 Arm 47 Spring 50 Exposure device 51 Belt cleaning device 52 Cleaning blade 54 Bottle container 55 Concentration sensor 56 Shutter 56F Exposure hole 56C Exposure hole 56R Exposure hole 57 Reflecting member 61 Eccentric cam 62 Eccentric cam 63 Roller support member 64 Compression spring 65 Gear 71 Photoconductor 72 Cleaning device 73 Cleaning blade 74 Charging device 76 Developing device 81 Secondary transfer roller 82 Paper feed roller 83 Recording paper conveyance roller 84 Registration roller Pair 85 Discharge roller pair 90 Intermediate transfer belt 91 Primary transfer roller 92 Drive roller 93 Tension roller 94 Spring 95 Tension roller 96 Tension roller 97 Backing member 98 Tension roller 9 9 Spring 100 Power supply 101 Power supply 110 Backing member 120 Optical sensor 130 Motor

JP 2001-5247 A JP 2011-59190 A

Claims (15)

A belt member rotatably stretched by a plurality of tension members;
Transfer means for transferring a toner image formed on the surface of the belt member to a transfer material;
A detecting means provided at a position facing the surface of the belt member and detecting a detection toner pattern formed on the surface;
In a transfer device provided with a facing member provided to face the detection means via the belt member,
A contact member provided in contact with the vicinity of the opposing member of the belt member, and a displacement means for displacing the contact member;
A transfer device, wherein the contact member is displaced by the displacing means to change a contact state between the facing member and the belt member. The transfer device according to claim 1.
A transfer apparatus, wherein the belt member is brought into contact with or separated from the facing member as a change in the contact state between the facing member and the belt member. The transfer device according to claim 1.
A transfer device, wherein the amount of biting of the opposing member into the belt member is changed as a change in the contact state between the opposing member and the belt member. The transfer device according to claim 1, 2 or 3,
An image forming apparatus, wherein the contact member is provided in contact with a front surface which is an outer peripheral surface of the belt member. The transfer apparatus according to claim 1, 2, 3 or 4.
Due to the displacement of the contact member, the length of the belt member at the portion of the contact member that is hung around two adjacent stretching members on both the upstream side and the downstream side in the rotation direction of the belt member does not change. The transfer device. The transfer apparatus according to claim 1, 2, 3, 4 or 5.
The transfer device, wherein a contact portion of the facing member with the belt member has a planar shape or a substantially planar shape. The transfer device according to claim 1, 2, 3, 4, 5 or 6.
A transfer device comprising a shutter member displaceable between a position where the detection surface of the detection means is opened and a position where the detection surface is blocked. The transfer device according to claim 7.
A driving roller that is one of the plurality of stretching members and rotationally drives the belt member;
2. A transfer apparatus according to claim 1, wherein the drive source for driving the drive roller and the shutter member is the same. The transfer apparatus according to claim 1, 2, 3, 4, 5, 6, 7 or 8.
The transfer device, wherein the contact member is a roller member. The transfer apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, or 9.
The transfer device, wherein the contact member is one of the plurality of stretching members. A plurality of image carriers;
A plurality of developing means for forming a plurality of color toner images made of different color toners on each image carrier;
In an image forming apparatus provided with a transfer device provided at a position facing each image carrier and finally transferring the toner image onto a transfer material,
11. An image forming apparatus comprising the transfer device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 as the transfer device. The image forming apparatus according to claim 11.
In the image adjustment mode in which image adjustment processing is performed based on the detection result of the detection means, the displacement member displaces the contact member to bring the belt member into contact with the opposing member, otherwise the displacement means An image forming apparatus, wherein the contact member is displaced to separate the belt member from the opposing member. The image forming apparatus according to claim 11.
In the image adjustment mode in which the image adjustment process is performed based on the detection result of the detection means, the displacement member displaces the contact member to increase the amount of biting of the counter member into the belt member. An image forming apparatus, wherein the contact member is displaced by a displacement means to reduce the amount of biting of the opposing member into the belt member. The image forming apparatus according to claim 11, 12 or 13.
Having a stationary time measuring means for measuring the stationary time of the belt member,
Based on the measurement result of the stationary time measuring means, the contact member is displaced by the displacing means only when the image adjustment mode is executed a certain number of times after the belt member is left in a stationary state for a certain time. An image forming apparatus, wherein a belt member is brought into contact with the facing member. The image forming apparatus according to claim 11, 12, 13 or 14.
The belt member is an intermediate transfer belt;
An image forming apparatus comprising: a secondary transfer unit that collectively transfers the toner images transferred from the plurality of image carriers onto the intermediate transfer belt to the recording body.

Images