JP2010019964A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid cost rise resulting from using an expensive drive source accurately worked as a drive source for contacting/separating a secondary transfer roller 19 with/from an intermediate transfer belt 8 and accurately positioning the drive source, while holding pressure of a transfer nip within a desired range. <P>SOLUTION: The image forming apparatus includes an biasing coil spring 61 for biasing and abutting the secondary transfer roller 19 toward the intermediate transfer belt 8, and an eccentric cam 64 disposed on a shaft member 12a of a driving roller 12 so as to idly rotate. As the eccentric cam 64 is rotated with the shaft member 12a as center and stopped at a predetermined rotational angle position, the eccentric cam 64 is pressed on the secondary transfer roller 19 against biasing force by the biasing coil spring 61, and the secondary transfer roller 19 is separated from the belt. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer having a function of contacting and separating a transfer nip forming member that forms a transfer nip by contacting an image carrier with a predetermined timing. It is.

  2. Description of the Related Art Conventionally, there has been known an image forming apparatus provided with a contact / separation unit that contacts and separates a transfer roller as a transfer nip forming member with respect to an image carrier such as a photosensitive member or an intermediate transfer member. There are various reasons why the transfer roller is brought into contact with and separated from the image carrier. For example, when the operation is resumed after the jammed paper jammed at or near the transfer nip due to the contact between the image carrier and the transfer roller is removed, the toner image remaining on the surface of the image carrier is removed. The transfer roller may be soiled by direct contact with the transfer roller. In order to avoid such contamination of the transfer roller, an image forming apparatus is known in which the transfer roller is separated from the image carrier for a predetermined time when the operation is resumed after removing jammed paper. Further, in an image forming apparatus that adjusts the image forming performance of the image forming means based on the result of detection by a sensor of a predetermined reference toner image formed on the surface of the intermediate transfer body without passing paper, the reference on the intermediate transfer body The toner image may be transferred to the transfer roller. In order to avoid such transfer of the reference toner image, an image forming apparatus is also known in which the transfer roller is separated from the intermediate transfer member when the reference toner image is formed. If the apparatus is stopped for a long time while the transfer roller is in pressure contact with the image carrier, a dent may be formed on the contact portion of the transfer roller with the image carrier. An image forming apparatus is also known that stops the printing operation in a state where the transfer roller is separated from the image carrier in order to avoid the generation of the dent wrinkles.

In these image forming apparatuses, as a contact / separation means for contacting / separating the transfer roller to / from the image carrier, a swing arm type as described in Patent Document 1 is generally used. In the swing arm type contact / separation means, a transfer roller is rotatably held at one end of a swing arm that swings about a swing shaft. The transfer roller is brought into contact with and separated from the image carrier by swinging the swing arm by turning on and off the solenoid.
JP 7-234595 A

  However, such contact / separation means has a problem of high cost because high-precision positioning is required for the telescopic shaft of the solenoid. Specifically, when a transfer nip is formed by bringing the transfer roller into contact with the image carrier, it is necessary to keep the nip pressure within a predetermined range in order to obtain a desired transfer performance. In order to keep the nip pressure within a predetermined range, it is necessary to keep the amount of biting of the transfer roller with respect to the image carrier within the predetermined range. In the swing arm system, the amount of biting is determined by the position of the distal end of the telescopic shaft in the solenoid that is driven or stopped. In order to keep the biting amount within a predetermined range, it is necessary to position the tip position to a predetermined position. To that end, an expensive swing arm or solenoid with little dimensional error and operation amount error is required. It is necessary to use it. Furthermore, it is necessary to assemble the swing arm and solenoid with high accuracy and to position the tip of the telescopic shaft of the solenoid with high accuracy. Such high-precision positioning causes high costs.

  Even if a configuration is adopted in which the transfer roller is slid instead of oscillating, in order to keep the transfer nip pressure within a desired range, the expansion / contraction shaft of the solenoid is highly accurate with respect to the image carrier. Need to be positioned.

  The present invention has been made in view of the above background, and an object thereof is to provide the following image forming apparatus. In other words, a high-precision machined drive source is used as a drive source for bringing the transfer nip forming member into and out of contact with the image carrier while keeping the transfer nip pressure within a desired range, or the drive source is positioned with high accuracy. This is an image forming apparatus capable of avoiding an increase in cost due to.

In order to achieve the above object, the invention of claim 1 is directed to an image carrier that carries a visible image while rotating about a rotation axis, and a transfer nip that forms a transfer nip in contact with the image carrier. A transfer member for transferring a visible image on the image carrier to the transfer nip member or a recording member sandwiched in the transfer nip, and the transfer nip member to the image carrier. An image forming apparatus comprising a contact / separation unit for contacting / separating the image to / from the image forming apparatus, wherein the contact / separation unit includes the transfer nip forming member or the holding member for holding the transfer nip forming member by an urging unit. An urging means for urging the transfer nip forming member against the image carrier and an on-axis member disposed on the rotation shaft so as to be able to idle. A predetermined rotation after rotating the on-axis member around the axis The axial member is pressed against the transfer nip forming member or the holding member against the urging force of the urging means with the stop at the position, and the transfer nip forming member is separated from the image carrier. On the other hand, as the axial member is moved to another rotational angle position around the rotational axis, the axial member is moved away from the transfer nip forming member or the holding member, and the transfer nip is moved. The forming member is brought into contact with the image carrier.
According to a second aspect of the present invention, there is provided a belt-like image carrier that is endlessly moved while being wound around a tension member that can rotate about a rotation shaft, and a transfer nip formed by contacting the image carrier. A transfer nip forming member, a transfer means for transferring a visible image on the image carrier to the transfer nip forming member or a recording member sandwiched in the transfer nip, and the transfer nip forming member to the image An image forming apparatus comprising a contact / separation unit for contacting / separating the carrier, wherein the contact / separation unit is configured to bias the transfer nip forming member or the holding member holding the transfer nip forming member by an urging unit. An urging means for urging the transfer nip forming member against the image carrier by urging the image carrier, and an on-axis member disposed on the rotation shaft so as to be idled. A predetermined rotation of the on-axis member about the rotation axis The axial member is pressed against the transfer nip forming member or the holding member against the urging force of the urging means, and the transfer nip forming member is removed from the image carrier. As the axial member is rotationally driven to another rotational angle position, the axial member is separated from the transfer nip forming member or the holding member, and the transfer nip forming member is moved to the image. It is a thing made to contact | abut to a support body, It is characterized by the above-mentioned.
According to a third aspect of the present invention, in the image forming apparatus according to the second aspect of the present invention, the tension member in which the on-axis member is rotatably disposed is driven to rotate by a driving force transmitted from a driving source. Accordingly, the belt-like image carrier is configured as a driving stretch member that moves the image endlessly.
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, an eccentric cam is used as the axial member.
According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, when the rotary shaft rotates in the positive direction, which is the rotational direction for the image forming operation, the rotational driving force of the rotary shaft is decentered. When the rotating shaft rotates idly with respect to the eccentric cam without being connected to the cam, the rotational driving force of the rotating shaft is connected to the eccentric cam when the rotating shaft rotates in the direction opposite to the forward direction. A one-way clutch that rotationally drives the eccentric cam in the reverse direction is provided between the rotary shaft and the eccentric cam, and the cam surface of the eccentric cam is held or held by the transfer nip forming member when the rotary shaft rotates in the reverse direction. The transfer nip forming member is separated from the image carrier by being pressed against the member.
According to a sixth aspect of the present invention, in the image forming apparatus of the fifth aspect, when the rotating shaft is rotated in the reverse direction, the torque applied to the rotating shaft is higher than that when the rotating shaft is rotated in the forward direction. The drive means for rotationally driving the rotary shaft so as to supply the rotational drive force is configured.
According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, when the rotation shaft is rotated in the reverse direction, the gear ratio from the drive source is larger than when the rotation shaft is rotated in the forward direction. The drive transmission means, which is a part of the drive means, is configured to transmit the rotational drive force.
According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the transfer nip forming member is a transfer roller that is rotatable about a rotation shaft, and the axial member is The transfer roller is directly abutted against the rotation shaft of the transfer roller so as to be separated from the image carrier.

  In these inventions, the on-axis member provided on the rotation shaft is pressed against the transfer nip forming member or the holding member according to the rotation angle position to separate the transfer nip forming member from the image carrier, It is separated from the transfer nip forming member or the holding member. When the axial member is separated from the transfer nip forming member or the holding member, the transfer nip forming member urged toward the image carrier by the urging means contacts the image carrier to form a transfer nip. . The transfer nip pressure at this time is determined by the urging force of the urging means. In such a configuration, the transfer nip pressure can be kept within a desired range only by using an urging means such as a spring that exhibits an appropriate urging force. The on-axis member has a shape capable of being separated from the transfer nip forming member or the holding member at another rotation angle position while being pressed against the transfer nip forming member or the holding member at a predetermined rotation angle position. If so, it may be processed with a relatively low dimensional accuracy. In addition, the drive source of the on-axis member has dimensions within a range that does not hinder stopping the on-axis member at the above-described predetermined rotation angle position or stopping at the above-described another rotation angle position. It is possible to use one having a relatively low processing accuracy or to assemble with a relatively low assembling accuracy. Therefore, it is possible to keep the transfer nip pressure within a desired range without using an expensive machined with high accuracy as a drive source or positioning the drive source with high accuracy.

Hereinafter, as an image forming apparatus to which the present invention is applied, an embodiment of an electrophotographic printer (hereinafter simply referred to as a printer) will be described.
First, the basic configuration of the printer will be described. FIG. 1 is a schematic configuration diagram showing the printer. In this figure, this printer includes four process cartridges 6Y, 6M, 6C, and 6K for generating toner images of yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K). Yes. These use Y, M, C, and K toners of different colors as the image forming material, but the other configurations are the same and are replaced when the lifetime is reached. Taking a process cartridge 6Y for generating a Y toner image as an example, as shown in FIG. 2, a drum-shaped photoreceptor 1Y, a drum cleaning device 2Y, a charge eliminating device (not shown), a charging device 4Y, a developing device 5Y, and the like. It has. The process cartridge 6Y is detachable from the printer main body, so that consumable parts can be replaced at a time.

  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 1 </ b> Y is exposed and scanned by the laser beam L to carry a Y electrostatic latent image. The electrostatic latent image of Y is developed into a Y toner image by a developing device 5Y using a Y developer containing Y toner and a magnetic carrier. Then, intermediate transfer is performed on an intermediate transfer belt 8 described later.

  The drum cleaning device 2Y removes the toner remaining on the surface of the photoreceptor 1Y after the intermediate transfer process. The static eliminator neutralizes residual charges on the photoreceptor 1Y after cleaning. By this charge removal, the surface of the photoreceptor 1Y as a latent image carrier is initialized and prepared for the next image formation. Similarly, in the process cartridges (6M, C, K) of other colors, (M, C, K) toner images are formed on the photoreceptors (1M, C, K) and are superimposed on the intermediate transfer belt 8. In addition, intermediate transfer is performed.

  The developing device 5Y has a developing roll 51Y disposed so as to be partially exposed from the opening of the casing. Further, it also includes two conveying screws 55Y, a doctor blade 52Y, a toner density sensor (hereinafter referred to as T sensor) 56Y, and the like that are arranged in parallel to each other.

  In the casing of the developing device 5Y, a Y developer (not shown) including a magnetic carrier and Y toner is accommodated. The Y developer is frictionally charged while being agitated and conveyed by the two conveying screws 55Y, and is then carried on the surface of the developing roll 51Y. Then, after the layer thickness is regulated by the doctor blade 52Y, the layer is transported to the developing region facing the Y photoreceptor 1Y, where Y toner is attached to the electrostatic latent image on the photoreceptor 1Y. This adhesion forms a Y toner image on the photoreceptor 1Y. In the developing unit 5Y, the Y developer that has consumed Y toner by the development is returned into the casing as the developing roll 51Y rotates.

  A partition wall is provided between the two transport screws 55Y. By this partition wall, the first supply unit 53Y that accommodates the developing roll 51Y, the right conveyance screw 55Y in the drawing, and the like, and the second supply unit 54Y that accommodates the left conveyance screw 55Y in the drawing are separated in the casing. . The right conveying screw 55Y in the drawing is driven to rotate by a driving means (not shown), and supplies the Y developer in the first supply unit 53Y to the developing roll 51Y while being conveyed from the near side to the far side in the drawing. The Y developer conveyed to the vicinity of the end of the first supply unit 53Y by the right conveyance screw 55Y in the drawing enters the second supply unit 54Y through an opening (not shown) provided in the partition wall. In the second supply unit 54Y, the left conveyance screw 55Y in the drawing is driven to rotate by a driving means (not shown), and the Y developer sent from the first supply unit 53Y is the right conveyance screw 55Y in the drawing. Transport in the reverse direction. The Y developer transported to the vicinity of the end of the second supply unit 54Y by the transport screw 55Y on the left side in the drawing passes through the other opening (not shown) provided in the partition wall, and the first supply unit. Return to 53Y.

  The above-described T sensor 56Y composed of a magnetic permeability sensor is provided on the bottom wall of the second supply unit 54Y and outputs a voltage having a value corresponding to the magnetic permeability of the Y developer passing therethrough. Since the magnetic permeability of the developer containing toner and magnetic carrier shows a good correlation with the toner concentration, the T sensor 56Y outputs a voltage corresponding to the Y toner concentration. This output voltage value is sent to a control unit (not shown). This control unit includes a RAM that stores a Vtref for Y that is a target value of an output voltage from the T sensor 56Y. The RAM also stores M Vtref, C Vtref, and K Vtref data, which are target values of output voltages from a T sensor (not shown) mounted in another developing device. The Y Vtref is used for driving control of a Y toner conveying device to be described later. Specifically, the control unit drives and controls a Y toner conveying device (not shown) so that the value of the output voltage from the T sensor 56Y is close to the Y Vtref, and the Y toner in the second supply unit 54Y. To replenish. By this replenishment, the Y toner concentration in the Y developer in the developing device 5Y is maintained within a predetermined range. The same toner replenishment control using the M, C, and K toner conveying devices is performed for the developing units of the other process units.

  In FIG. 1 described above, an exposure device 7 is disposed below the process cartridges 6Y, 6M, 6C, and 6K in the drawing. The exposure device 7 serving as a latent image forming unit irradiates the respective photosensitive members in the process cartridges 6Y, 6M, 6C, and 6K with a laser beam L emitted based on the image information. By this exposure, electrostatic latent images for Y, M, C, and K are formed on the photoreceptors 1Y, 1M, 1C, and 1K. The exposure device 7 irradiates the photosensitive member through a plurality of optical lenses and mirrors while scanning laser light (L) emitted from a light source with a polygon mirror rotated by a motor.

  On the lower side of the exposure apparatus 7 in the figure, paper storage means having a paper storage cassette 26, a paper feed roller 27 incorporated therein, and the like are disposed. The paper storage cassette 26 stores a plurality of recording papers P, which are sheet-like recording media, and a paper feed roller 27 is brought into contact with each uppermost recording paper P. When the paper feed roller 27 is rotated counterclockwise in the drawing by a driving means (not shown), the uppermost recording paper P is sent out toward the paper feed path 170.

  Near the end of the paper feed path 170, a registration roller pair 28 is disposed. The registration roller pair 28 rotates both rollers so as to sandwich the recording paper P, but temporarily stops the rotation as soon as it is sandwiched. Then, the recording paper P is sent out toward a later-described secondary transfer nip at an appropriate timing.

  Above the process cartridges 6Y, 6M, 6C, and 6K, an intermediate transfer unit 15 that moves the intermediate transfer belt 8 that is an intermediate transfer member endlessly while stretching is disposed. The intermediate transfer unit 15 includes a secondary transfer roller 19 and a cleaning device 10 in addition to the intermediate transfer belt 8. Also provided are four primary transfer rollers 9Y, 9M, 9C, 9K, a driving roller 12, a cleaning backup roller 13, a tension roller 14, and the like. The intermediate transfer belt 8 is endlessly moved counterclockwise in the figure by the rotation of the driving roller 12 that is rotated by driving means (not shown) while being stretched around these seven rollers.

  The primary transfer rollers 9Y, 9M, 9C, and 9K hold the intermediate transfer belt 8 that is moved endlessly in this manner between the photoreceptors 1Y, 1M, 1C, and 1K, thereby forming primary transfer nips. . In these methods, a transfer bias having a polarity opposite to that of toner (for example, plus) is applied to the back surface (loop inner peripheral surface) of the intermediate transfer belt 8. All the rollers except the primary transfer rollers 9Y, 9M, 9C, and 9K are electrically grounded.

  The intermediate transfer belt 8 sequentially passes through the primary transfer nips for Y, M, C, and K along with the endless movement thereof, and Y, M, and C on the photoreceptors 1Y, M, C, and K are sequentially transferred. , K toner images are superimposed and primarily transferred. 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 drive roller 12 that stretches the belt inside the loop of the intermediate transfer belt 8 sandwiches the intermediate transfer belt 8 with the secondary transfer roller 19. As a result, a secondary transfer nip is formed in which the secondary transfer roller 19 disposed outside the loop of the intermediate transfer belt 8 and the portion where the intermediate transfer belt 8 is wound around the drive roller 12 abuts.

  A secondary transfer bias having the same polarity as the toner is applied to the drive roller 12 disposed in the loop of the intermediate transfer belt 8 by a power source (not shown). On the other hand, the secondary transfer roller 19 disposed outside the loop of the intermediate transfer belt 8 is grounded. Thereby, a secondary transfer electric field for electrostatically moving the toner from the drive roller 12 side to the secondary transfer roller 19 side is formed in the secondary transfer nip. The driving roller 12 may be installed while applying a secondary transfer bias having a polarity opposite to that of the toner to the secondary transfer roller 19.

  The visible four-color toner image formed on the intermediate transfer belt 8 is transferred onto the recording paper P at the secondary transfer nip. Then, combined with the white color of the recording paper P, a full color toner image is obtained. Untransferred toner that has not been transferred to the recording paper P adheres to the intermediate transfer belt 8 after passing through the secondary transfer nip. This is cleaned by the cleaning device 10. The recording paper P on which the four-color toner images are collectively transferred at the secondary transfer nip is sent to the fixing device 20 via the post-transfer conveyance path 171.

  The fixing device 20 forms a fixing nip by a fixing roller 20a having a heat source such as a halogen lamp inside, and a pressure roller 20b that rotates while contacting the roller with a predetermined pressure. The recording paper P fed into the fixing device 20 is sandwiched between the fixing nips so that the unfixed toner image carrying surface is in close contact with the fixing roller 20a. Then, the toner in the toner image is softened by the influence of heating and pressurization, and the full color image is fixed.

  The recording paper P on which the full-color image is fixed in the fixing device 20 exits the fixing device 20 and then reaches a branch point between the paper discharge path 172 and the pre-reversal conveyance path 173. At this branch point, a first switching claw 175 is swingably disposed, and the path of the recording paper P is switched by the swing. Specifically, by moving the tip of the claw in a direction approaching the pre-reverse feed path 173, the path of the recording paper P is set in a direction toward the paper discharge path 172. Further, by moving the tip of the claw in a direction away from the pre-reversal conveyance path 173, the path of the recording paper P is changed to the direction toward the pre-reversal conveyance path 173.

  When the path to the paper discharge path 172 is selected by the first switching claw 175, the recording paper P is disposed outside the apparatus after passing through the paper discharge roller pair 100 from the paper discharge path 172. Are stacked on a stack unit 150a provided on the upper surface of the printer housing. On the other hand, when the first switching claw 175 selects the course toward the conveyance path 173 before reversal, the recording paper P enters the nip of the reversing roller pair 21 via the conveyance path 173 before reversal. The reversing roller pair 21 conveys the recording paper P sandwiched between the rollers toward the stack portion 150a, but reversely rotates the rollers immediately before the trailing edge of the recording paper P enters the nip. Due to this reverse rotation, the recording paper P is transported in the opposite direction, and the rear end side of the recording paper P enters the reverse transport path 174.

  The reverse conveyance path 174 has a shape extending while curving from the upper side to the lower side in the vertical direction, and the first reverse conveyance roller pair 22, the second reverse conveyance roller pair 23, and the third reverse conveyance in the path. A roller pair 24 is provided. The recording paper P is conveyed while sequentially passing through the nips of these roller pairs, so that the recording paper P is turned upside down. The recording paper P that has been turned upside down is returned to the paper feed path 170 and then reaches the secondary transfer nip again. Then, this time, the image transfer surface enters the secondary transfer nip while bringing the non-image carrying surface into close contact with the intermediate transfer belt 8, and the second four-color toner image of the intermediate transfer belt is collectively transferred to the non-image carrying surface. The Thereafter, the sheet is stacked on the stack unit 150 a outside the apparatus via the post-transfer conveyance path 171, the fixing device 20, the paper discharge path 172, and the paper discharge roller pair 100. A full color image is formed on both sides of the recording paper P by such reverse conveyance.

  A bottle support portion 31 is disposed between the intermediate transfer unit 15 and the stack portion 150a located above the intermediate transfer unit 15. The bottle support portion 31 has toner bottles 32Y, 32M, 32C, 32K serving as toner storage portions for storing Y, M, C, and K toners. The toner bottles 32Y, 32M, 32C, and 32K are arranged so as to be arranged at an angle slightly inclined from the horizontal, and the arrangement positions are higher in the order of Y, M, C, and K. The Y, M, C, and K toners in the toner bottles 32Y, 32M, 32C, and 32K are appropriately supplied to the developing units of the process cartridges 6Y, 6M, 6C, and 6K, respectively, by a toner transport device that will be described later. These toner bottles 32Y, 32M, 32C, and 32K are detachable from the printer main body independently of the process cartridges 6Y, 6M, 6C, and 6K.

  The above-described reverse conveyance path 174 is formed in the reverse conveyance unit 160, and the reverse conveyance unit 160 includes a side cover 161 and a swinging body 162. Specifically, the side cover 161 of the reverse conveyance unit 160 is supported by the casing 150 so as to swing around a first swing shaft 159 provided in the casing 150 of the printer main body. By this swinging, the side cover 161 opens and closes with respect to the housing 150. Further, as shown in FIG. 3, the swinging body 162 of the reverse transport unit 160 is exposed to the outside when the side cover 161 is opened with respect to the housing 150, and the second swinging shaft 163 provided on the side cover 161. Is supported by the side cover 161 so as to swing around the center. By this swinging, the swinging body 162 swings with respect to the side cover 161 opened from the housing 150.

  In FIG. 1 described above, the swinging body 162 is locked at the first position where it hits the fixing device 20 in the housing 150 with the side cover 161 closed with respect to the housing 150. . The reversing conveyance unit 160 in such a state forms a paper feed path 170, a post-transfer conveyance path 171 and the like between the swinging body 162 and the housing 150. When the side cover 161 is rotated clockwise in the drawing around the first swing shaft 159 and opened, the housing 150 and the swing body 162 are greatly separated. By this separation, as shown in FIG. 3, the paper feed path 170, the post-transfer conveyance path 171 and the like are exposed to the outside, and the jammed paper in these paths is easily removed.

  Further, when the side cover 161 is opened, one end portion of the fixing device 20 remaining on the housing 150 side is exposed as illustrated. The fixing device 20 can be attached to and detached from the housing 150, and can be attached to and detached from the housing 150 as shown in FIG. 4 by being exposed to the outside as the side cover 161 is opened. Become.

  In the reverse conveyance unit 160, a reverse conveyance path 174 is formed between the side cover 161 and the swinging body 162. As shown in FIG. 3, the reverse conveying path 174 is exposed to the outside when the swinging body 162 swings away from the side cover 162 in a state where the side cover 161 is opened. By this exposure, the jammed paper in the reverse conveyance path 174 is easily removed.

  Even if the side cover 161 is opened, most of the transfer unit 15 remains in the casing 150, but only the secondary transfer roller 19 supported by the swinging body 162 moves to the reverse conveyance unit 160 side.

  In the printer having the above-described configuration, a visible image in which a toner image, which is a visible image, is formed on the recording paper P by the four process cartridges 6Y, 6M, 6C, 6K, the exposure device 7, the intermediate transfer unit 15 serving as transfer means, and the like. Forming means are configured. Further, around the secondary transfer nip, there is configured a recording member transport mechanism that transports the recording paper P while sandwiching the recording paper P between the driving roller 12 as the first rotating body and the secondary transfer roller 19 as the second rotating body. ing.

Next, a printer according to a comparative example will be described.
FIG. 5 is an enlarged configuration diagram showing the secondary transfer nip and its surrounding configuration in the printer of the comparative example. In the figure, a secondary transfer roller 19 as a transfer nip forming member has shaft portions protruding from both end faces in the longitudinal direction of the roller portion, and are rotatably supported by bearings (not shown). These bearings are slidably held by holding means (not shown), and are urged toward an intermediate transfer belt 8 as an image carrier by an urging coil spring 61 as urging means. By this biasing, the secondary transfer roller 19 is indirectly biased toward the intermediate transfer belt 8.

  An arm member 62 that can swing about the swing shaft 62a abuts against the shaft portion of the secondary transfer roller 19 that is biased in this way. The swing shaft 62 a is provided at one end of the arm member 62 in the longitudinal direction, and an eccentric cam 63 as a butting member abuts against the other end of the arm member 62. The eccentric cam is driven to rotate by a drive motor (not shown), thereby changing the abutting position with the arm member 62. Then, the arm member 62 swings and the secondary transfer roller 19 is pushed back against the biasing force of the biasing coil spring 61 to be separated from the intermediate transfer belt 8 or away from the shaft member of the secondary transfer roller 19. The secondary transfer roller 19 is brought into contact with the intermediate transfer belt 8. Thus, in this printer, the secondary transfer roller 19 urged toward the intermediate transfer belt 8 by the urging coil spring 61 is pushed back or released by the swing of the arm member 62. Then, the secondary transfer roller 19 is brought into contact with and separated from the intermediate transfer belt 8. In this printer, a holding means for holding a bearing (not shown) that rotatably supports the rotation shaft of the secondary transfer roller 19 so as to be slidable in a direction to move closer to or away from the intermediate transfer belt 8, and a biasing coil spring 61. The secondary transfer roller 19 as a transfer nip forming member is brought into contact with and separated from the intermediate transfer belt 8 by an arm member 62, an eccentric cam 63, a drive unit for the eccentric cam 63, a control unit (not shown) for controlling the drive of the drive unit, and the like. The contacting / separating means to be configured is configured.

  The secondary transfer nip pressure when the secondary transfer roller 19 is in contact with the intermediate transfer belt 8 is the urging force of the urging means that urges the secondary transfer roller 19 toward the intermediate transfer belt 8. That is, it is determined by the spring constant of the urging coil spring 61. In such a configuration, an expensive spring processed with high accuracy as a driving source that exerts a driving force to bring the secondary transfer roller 19 into and out of contact with the belt can be obtained simply by using an urging coil spring 61 having an appropriate spring constant. It is possible to keep the secondary transfer nip pressure within a desired range without using a special one or positioning the drive source with high accuracy.

  However, since a space for swinging the arm member 62a and a space for disposing the eccentric cam 63 are required, the apparatus becomes large.

Next, a characteristic configuration of the printer according to the embodiment will be described.
FIG. 6 is an enlarged configuration diagram showing a secondary transfer nip and its surrounding configuration in a print job in the printer according to the embodiment. In the figure, a driving roller 12 as a stretching member around which the intermediate transfer belt 8 is wound is driven to rotate counterclockwise in the drawing by a driving means (not shown). By this rotational drive, the intermediate transfer belt 8 is moved endlessly in the counterclockwise direction in the figure. During the print job, the intermediate transfer belt 8 is thus moved endlessly in the counterclockwise direction in the figure.

  A shaft member 12a as a rotation shaft of the drive roller 12 is rotatably supported by a bearing (not shown). An eccentric cam 65 as an abutting member is fixed to the shaft member 12a via a one-way clutch 64. The one-way clutch 64 cuts off the rotational driving force of the shaft member 12a so as to prevent the eccentric cam 65 from rotating when the shaft member 12a of the drive roller 12 rotates in the counterclockwise direction in the drawing as shown in the figure. Thus, the shaft member 12 a is idled with respect to the eccentric cam 65. However, when the shaft member 12a rotates in the clockwise direction in the drawing, that is, when it rotates in the reverse direction, the rotational driving force is connected to the eccentric cam 65, and the eccentric cam 65 is rotated around the shaft member 12a. In the state shown in the drawing, the shaft member 12a rotates in the positive direction. The eccentric cam 65 on the shaft member 12 a rotating in the forward direction is locked at a position where it abuts against the shaft portion of the secondary transfer roller 19.

  When the secondary transfer roller 19 is moved away from the intermediate transfer belt 8, a control unit including a CPU (not shown) rotates a drive motor (not shown) serving as a drive source of the drive roller 12 for a predetermined time. Then, as shown in FIG. 7, the eccentric cam 64 reversely rotates about 350 [°] together with the shaft member 12 a of the drive roller 12, and the cam surface abuts against the shaft portion of the secondary transfer roller 19. Accordingly, the secondary transfer roller 19 is separated from the intermediate transfer belt 8 by pushing back the secondary transfer roller 19 against the urging force of the urging coil spring 61.

  In such a configuration, the secondary transfer nip pressure can be kept within a desired range by simply using an urging coil spring 61 having an appropriate spring constant. The eccentric cam 64 as an on-axis member is pressed against the shaft member of the secondary transfer roller 19 at a predetermined rotation angle position, and is separated from the shaft member of the secondary transfer roller 19 at another rotation angle position. As long as it has a shape capable of being processed, it may be processed with a relatively low dimensional accuracy. Further, the drive motor that is the drive source of the eccentric cam 64 is a range that does not hinder the eccentric cam 64 from being stopped at the predetermined rotational angle position described above or stopped at another rotational angle position described above. Among them, it is possible to use one having a relatively low dimensional processing accuracy or to assemble with a relatively low assembling accuracy. Therefore, the secondary transfer nip pressure can be kept within a desired range without using an expensive one processed with high accuracy as the drive motor or positioning the drive motor with high accuracy. Further, since the secondary transfer roller 19 is brought into contact with and separated from the intermediate transfer belt 19 without using an arm member, it is possible to avoid an increase in size of the apparatus due to securing a swinging space for the arm member.

  A control unit (not shown) that controls the driving of the eccentric cam 64 performs a process of bringing the secondary transfer roller 19 into and out of contact with the intermediate transfer belt 8 as follows. That is, the paper feed path 70 and the post-transfer conveyance path 71 are provided with well-known jam detection means (not shown) for detecting a jam of the recording paper P in those paths. Further, a well-known paper detecting means (not shown) for detecting the recording paper P in the path is also provided. It is assumed that the user opens the reverse conveyance unit 60 to remove the jammed paper and then closes the reverse conveyance unit 60 based on the detection of the jam by the jam detection unit. At this time, the control unit determines whether or not the jammed paper has been removed based on the output from the paper detection means. If it has not been removed, a message prompting the user to re-execute the jam paper removal operation is displayed. On the other hand, when the shaft member 12a is removed, the eccentric cam 64 is moved to the rotational angle position where it abuts against the shaft member of the secondary transfer roller 19 by the reverse rotation of the shaft member 12a. The secondary transfer roller 19 that has been in contact with the secondary transfer nip is separated from the intermediate transfer belt 8. Thereafter, the intermediate transfer belt 8 is moved endlessly for a predetermined time by forward rotation of the shaft member 12. At this time, due to the function of the one-way clutch, the eccentric cam 64 remains in a position where it abuts against the shaft member of the secondary transfer roller 19. By moving the intermediate transfer belt 8 endlessly, even if a toner image remains on the surface of the intermediate transfer belt 8 at the time of occurrence of a jam, the toner image is not transferred to the secondary transfer roller 19 and cleaned. It can be removed from the belt surface by the device 10. Therefore, it is possible to avoid the occurrence of the backside contamination of the recording paper P in the subsequent print job by transferring the toner image remaining on the surface of the intermediate transfer belt 8 to the secondary transfer roller 19 when the jam occurs. Can do.

  After the secondary transfer roller 19 is moved away from the intermediate transfer belt 8 and the intermediate transfer belt 8 is moved endlessly in the positive direction for a predetermined time and the belt surface is cleaned, the control unit By the reverse rotation, the eccentric cam 64 is moved to a rotation angle position where it does not abut against the shaft member of the secondary transfer roller 19. Accordingly, the secondary transfer roller 19 that has been separated from the intermediate transfer belt 8 until then is brought into contact with the intermediate transfer belt 8.

  The following contact / separation operation may be executed in addition to or instead of such contact / separation operation when a jam occurs. That is, a predetermined reference toner image is formed on the intermediate transfer belt 8 at a predetermined timing such as immediately after the power is turned on or every predetermined number of prints, and the development performance is based on the result of detection of this reference toner image by a photo sensor or the like. In addition, when executing a process of detecting a positional deviation of each color toner image, the secondary transfer roller 19 is separated from the belt. Thereby, the transfer of the reference toner image to the secondary transfer roller 19 due to the reference toner image entering the secondary transfer nip where the recording paper P is not fed is avoided. After all the reference toner images are removed by the cleaning device 10, the secondary transfer roller 19 is brought into contact with the intermediate transfer belt 8.

  In addition, the following contact / separation operation may be executed. That is, the secondary transfer roller 19 is separated from the intermediate transfer belt 8 before the print job is completed and the driving of each driving member in the apparatus is stopped. Then, the print command from the user is put on standby in such a separated state. When a print command is received and a print job is started, the secondary transfer roller 19 that has been separated until then is brought into contact with the intermediate transfer belt 8.

  Further, instead of abutting the eccentric cam 64 against the shaft member of the secondary transfer roller 19, it abuts against a bearing as a holding member that receives the shaft member of the secondary transfer roller 19 to transfer the secondary transfer roller 19 to the intermediate transfer. It may be separated from the belt 8.

  FIG. 8 is an enlarged perspective view showing a part of the intermediate transfer belt 8 together with the driving means of the driving roller 12. The drive means for driving the drive roller 12 to rotate includes a drive motor 66 as a drive source and drive transmission means for transmitting the rotational drive force of the drive motor 12 to the drive roller 12. The drive transmission means includes a first motor gear 67 fixed to the motor shaft of the drive motor 66, a second motor gear 67 fixed to the motor shaft, a first relay gear 69, a second relay gear 70, and a third relay gear. 71, a fourth relay gear 72, a first roller gear 73, a second roller gear 74 held by the first relay gear 73, and the like.

The first motor gear 67 is fixed to the motor shaft of the drive motor 66 through a one-way clutch (not shown), and as the motor shaft rotates in the reverse rotation direction as shown by the solid line arrow, When the motor shaft rotates in the positive direction, it rotates idle. When the first motor gear 67 rotates in the direction of the solid arrow in the figure due to the reverse rotation of the motor shaft, the rotational driving force is the first relay gear 69, the second relay gear 70, the third relay gear 71, the fourth relay gear 72. The first roller gear 73 is sequentially transmitted to the first roller gear 73 and rotates in the direction of the solid line arrow in the figure. The first roller gear 73 is fixed to the shaft member 12a of the drive roller 12 via a one-way clutch (not shown). The one-way clutch connects the rotational driving force to the shaft member 12a when the first roller gear 73 rotates in the direction of the solid arrow in the figure. As a result, the shaft member 12a rotates in the reverse direction in the direction of the solid arrow in the figure. The eccentric cam 65 is also rotated in reverse with this reverse rotation, and a secondary transfer roller (not shown) is pushed back to be separated from the intermediate transfer belt 8.

  On the other hand, the second motor gear 68 is fixed to the motor shaft of the drive motor 66 via a not-shown one-way clutch, and as shown by the solid line arrow in the figure, the second motor gear 68 idles when the motor shaft rotates in the reverse rotation direction. On the other hand, when the motor shaft rotates in the positive direction as indicated by the dotted line arrow in the figure, it rotates with it. At this time, as described above, since the first motor gear 67 runs idle, the first relay gear 96 and the like do not rotate. The rotational driving force of the second motor gear 68 is transmitted to the second roller gear 74 meshing therewith. The second roller gear 74 is fixed to the shaft member 12a of the drive roller 12 via a one-way clutch (not shown). The one-way clutch connects the rotational driving force to the shaft member 12a when the second roller gear 74 receives the rotational driving force of the second motor gear 68 and rotates in the direction of the dotted arrow in the figure. Thereby, the shaft member 12a rotates in the forward direction. The shaft member 12a idles in a state where the eccentric cam is abutted against the shaft portion of the secondary transfer roller (not shown).

  The diameter of the first roller gear 73 is larger than the diameter of the second roller gear 74. This means that the driving force from the drive motor 66 is transmitted to the shaft member 12a with a larger gear ratio when the shaft member 12a is rotated in the reverse direction than when the shaft member 12a is rotated in the forward direction. . When the driving force is transmitted with a larger gear ratio, a higher torque driving force is supplied to the rotating shaft 12a. In other words, not only the intermediate transfer belt 8 is moved endlessly by the reverse rotation of the drive motor 66, but also the intermediate transfer belt 8 is moved endlessly during the separation operation in which the secondary transfer roller needs to be pushed back by the eccentric cam 65. The shaft member 12a is driven at a higher torque than during the job. Thereby, the secondary transfer roller can be reliably separated from the intermediate transfer belt.

  Examples in which the present invention has been applied to contact / separation means for contacting / separating the secondary transfer roller 19 to / from a belt as an image carrier in a secondary transfer nip where the secondary transfer roller 19 is in contact with the intermediate transfer belt 8 so far However, it is also possible to apply the present invention to the following contact / separation means. In other words, in a primary transfer nip where a drum-shaped photoconductor as an image carrier and a transfer nip forming member such as a transfer roller or a belt are in contact with each other, the contacting / separating means for bringing the transfer nip forming member into and out of contact with the photoconductor It is. In this case, an eccentric cam may be provided on the rotating shaft of the photoconductor so as to be idled.

  As described above, in the printer according to the embodiment, as the image carrier, the intermediate transfer belt 8 that is moved endlessly while being wound around the driving roller 12 that is a tension member that can rotate around the rotation axis is used. Then, an eccentric cam 65 as an abutting member is disposed on the rotation shaft of the drive roller 12 so as to be idled, and the eccentric cam 65 is rotated about the rotation shaft, thereby being a transfer nip forming member 2. The contact / separation means is configured to bring the next transfer roller 19 into and out of contact with the intermediate transfer belt 8. In this configuration, as described above, the secondary transfer roller 19 is brought into contact with and separated from the intermediate transfer belt 19 without using an arm member, so that the cost can be reduced compared to the printer of the embodiment using the arm member (62). And space saving. Furthermore, it is possible to avoid the occurrence of variations in the secondary transfer nip pressure due to the deflection or inclination of the arm member.

  In the printer according to the embodiment, the drive tension member that moves the intermediate transfer belt 8 endlessly as the drive roller 12 is rotationally driven by the drive force transmitted from the drive motor 66 as a drive source. It is configured as. In such a configuration, the rotating shaft of the drive roller 12 can be used as a holding unit that holds the eccentric cam 65.

  In the printer according to the embodiment, the eccentric cam 65 is used as the pushing member. In such a configuration, the secondary transfer roller 19 can be separated from the intermediate transfer belt 8 by pressing the cam surface of the eccentric cam 65 against the rotation shaft (or bearing) of the drive roller 12.

  In the printer according to the embodiment, a one-way clutch is provided between the shaft member 12a that is the rotation shaft of the drive roller 12 and the eccentric cam 65, and the shaft member 12a is rotated in the direction opposite to the rotation direction of the print job. Accordingly, the secondary transfer roller 19 is separated from the intermediate transfer belt 8 by pressing the cam surface of the eccentric cam 65 against the secondary transfer roller 19. In such a configuration, the eccentric cam 65 is subjected to the secondary transfer only at the timing when the secondary transfer roller 19 is desired to be separated from the belt while the drive motor 66 that is the drive source of the drive roller 12 is also used as the drive source of the eccentric cam 65. It can be pressed against the roller 19.

  In the printer according to the embodiment, a higher driving force is supplied to the shaft member 12a when the shaft member 12a of the drive roller 12 is rotated in the reverse direction than when the shaft member 12a is rotated in the forward direction. As described above, a driving means for rotationally driving the shaft member 12a is configured. In such a configuration, for the convenience of pushing back the secondary transfer roller 19 against the biasing force of the biasing coil spring 61 by the eccentric cam 65, during reverse rotation that requires higher torque than during forward rotation, during forward rotation, By exhibiting higher torque than that, the secondary transfer roller 19 can be reliably separated from the belt.

  In the printer according to the embodiment, the driving force from the driving source is transmitted with a larger gear ratio when the shaft member 12a of the driving roller 12 is rotated in the reverse direction than when the shaft member 12a is rotated in the forward direction. Thus, the drive transmission means which is a part of the drive means is configured. In such a configuration, the torque can be increased by increasing the gear ratio.

  In the printer according to the embodiment, as the transfer nip forming member, the secondary transfer roller 19 as a transfer roller that can rotate around the rotation shaft is used, and the eccentric cam 65 is used as the rotation shaft of the secondary transfer roller 19. The secondary transfer transfer roller 19 is separated from the intermediate transfer belt 8 by directly abutting. In such a configuration, the configuration can be simplified as compared with the case where the eccentric cam 65 is abutted against the rotation shaft of the secondary transfer roller 19 via the intermediate member.

1 is a schematic configuration diagram illustrating a printer according to an embodiment. FIG. 2 is an enlarged configuration diagram illustrating a process cartridge for Y of the printer. FIG. 2 is an enlarged configuration diagram showing one end portion of the printer. FIG. 3 is an enlarged configuration diagram for explaining an attaching / detaching operation of a fixing device at the same end. FIG. 3 is an enlarged configuration diagram illustrating a secondary transfer nip and its surrounding configuration in a printer according to a comparative example. FIG. 3 is an enlarged configuration diagram illustrating a secondary transfer nip and its surrounding configuration during a print job in the printer according to the embodiment. The expanded block diagram which shows the same surrounding structure at the time of separation | spacing operation | movement. FIG. 3 is an enlarged perspective view showing a part of an intermediate transfer belt of the printer together with a driving unit of a driving roller.

Explanation of symbols

8: Intermediate transfer belt (image carrier)
12: Drive roller (stretching member)
15: Intermediate transfer unit (transfer means)
19: Secondary transfer roller (transfer nip forming member)
61: Energizing coil spring (urging means)
63: Eccentric cam (abutting member)
65: Eccentric cam (butting member)

Claims (8)

An image carrier that carries a visible image while rotating about a rotation axis, a transfer nip forming member that forms a transfer nip in contact with the image carrier, and a visible image on the image carrier, An image forming apparatus comprising: transfer means for transferring to the transfer nip forming member or a recording member sandwiched in the transfer nip; and contact / separation means for bringing the transfer nip forming member into and out of contact with the image carrier. There,
The contact / separation means urges the transfer nip forming member or the holding member that holds the transfer nip forming member toward the image carrier by an urging means to cause the transfer nip forming member to move to the image carrier. An urging means that abuts on the rotating shaft, and an axial member disposed on the rotating shaft so as to be idled, and after the axial member is driven to rotate about the rotating shaft, a predetermined rotation angle The axial member is pressed against the transfer nip forming member or the holding member against the urging force of the urging means, and the transfer nip forming member is separated from the image carrier as it stops at the position. On the other hand, as the axial member is moved to another rotational angle position around the rotational axis, the axial member is moved away from the transfer nip forming member or the holding member to form the transfer nip. The member is brought into contact with the image carrier. An image forming apparatus comprising. A belt-like image carrier that is endlessly moved while being wound around a tension member that can rotate around a rotation axis, a transfer nip forming member that forms a transfer nip in contact with the image carrier, and the image Transfer means for transferring a visible image on the carrier to the transfer nip forming member or a recording member sandwiched in the transfer nip, and contact for bringing the transfer nip forming member into contact with and separating from the image carrier. An image forming apparatus comprising a separating unit,
The contact / separation means urges the transfer nip forming member or the holding member that holds the transfer nip forming member toward the image carrier by an urging means to cause the transfer nip forming member to move to the image carrier. And an axial member disposed on the rotating shaft so as to be idled, and the axial member is driven to rotate to a predetermined rotational angle position about the rotating shaft. Accordingly, the axial member is pressed against the transfer nip forming member or the holding member against the urging force of the urging means to separate the transfer nip forming member from the image carrier, As the axial member is rotated to another rotational angle position, the axial member is moved away from the transfer nip forming member or the holding member, and the transfer nip forming member is brought into contact with the image carrier. What is claimed is: 1. An image forming apparatus comprising: The image forming apparatus according to claim 2.
A drive stretcher that moves the belt-like image carrier endlessly as the stretch member on which the axial member is rotatably mounted is driven to rotate by the drive force transmitted from the drive source. An image forming apparatus configured as a member. The image forming apparatus according to any one of claims 1 to 3,
An image forming apparatus using an eccentric cam as the axial member. The image forming apparatus according to claim 4.
When the rotation shaft rotates in the positive direction, which is the rotation direction for image forming operation, the rotation drive force of the rotation shaft is not connected to the eccentric cam, and the rotation shaft is idled with respect to the eccentric cam. When the rotating shaft rotates in the direction opposite to the forward direction, the one-way clutch that rotates the eccentric cam in the opposite direction by connecting the rotational driving force of the rotating shaft to the eccentric cam is rotated. The cam is provided between the shaft and the eccentric cam, and the cam surface of the eccentric cam is pressed against the transfer nip forming member or the holding member when the rotary shaft rotates in the reverse direction so that the transfer nip forming member is separated from the image carrier. An image forming apparatus characterized in that the image forming apparatus comprises: The image forming apparatus according to claim 5.
Driving means for rotationally driving the rotating shaft so that a rotational driving force having a higher torque is supplied to the rotating shaft when rotating in the reverse direction than when rotating the rotating shaft in the forward direction. An image forming apparatus comprising: The image forming apparatus according to claim 6.
Drive that is part of the drive means so that the rotational drive force from the drive source is transmitted with a larger gear ratio when rotating in the reverse direction than when rotating the rotary shaft in the forward direction. An image forming apparatus comprising a transmission unit. The image forming apparatus according to claim 1,
As the transfer nip forming member, a transfer roller that can rotate around a rotation axis is used,
An image forming apparatus, wherein the axial member is directly abutted against a rotation shaft of the transfer roller to separate the transfer roller from the image carrier.

Images