JP2006151620A - Roller pair unit, carrying device, and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roller pair unit, capable of securely carrying a sheet member S while finely regulating pressure of a driven roller 102 by a coil spring 103 inserted to a through hole 102a in the driven roller 102, and preventing the sheet member S from being caught by the coil spring 103. <P>SOLUTION: As the coil spring 103, the one formed in such a way that the center of a hook 103a in a pressurizing direction to pressurize the driven roller 102 toward a drive roller is deflected from the center of the coil spring 103 in the pressurizing direction at a part positioned in the through hole 102a in a natural state when it is not elongated is used. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a roller pair unit having a driving roller that is rotationally driven, a driven roller that is driven to rotate while being in contact with the roller, and a support member that rotatably supports both rollers, and a conveyance device and image forming apparatus using the roller pair unit. It relates to the device.

  2. Description of the Related Art Conventionally, a roller pair unit that conveys a sheet member such as recording paper while being sandwiched between rollers of a pair of rollers composed of a driving roller and a driven roller that abuts the recording roller has been used in various devices such as an image forming apparatus. . In this type of roller pair unit, the end of the shaft member of the driven roller is urged toward the drive roller by a biasing means such as a spring in order to bring the driven roller into contact with the drive roller with a predetermined pressure. It was general. However, in the configuration in which the driven roller is pressed in this way, a large space is taken up by extending a coil spring or a leaf spring in a direction perpendicular to the axial direction near the end of the shaft member of the driven roller. It was.

  On the other hand, a roller in which a coil spring is passed through a through hole provided so as to extend over the entire axial direction at the center of rotation of the driven roller, and the driven roller is pressed toward the drive roller by the coil spring. Pairs are known (for example, those described in Patent Document 1). In this roller pair, the driven roller is pressurized toward the drive roller by stretching the coil spring so that both ends of the coil spring are pulled toward the drive roller. In such a configuration, it is not necessary to provide an urging means such as a spring extending in the surface direction perpendicular to the axial direction in the vicinity of both ends of the driven roller, so that space can be saved.

JP-A-8-25738

  However, in this roller pair, if the sheet member is to be reliably conveyed while finely adjusting the applied pressure, the sheet member may be caught on the coil spring. Specifically, as shown in FIG. 1, in the roller pair 100, both end portions of the coil spring 103 inserted into the through hole 102 a of the driven roller 102 are protruded from both ends of the driven roller 102 in the axial direction. In order to exert a biasing force toward the driving roller 101 against the coil spring 103, as shown in FIG. 2, the hook 103a at the end of the coil spring 103 is positioned closer to the driving roller 101 than the center of the through hole 102a. Fix it. In such fixing, if a desired pressure is to be obtained with the coil spring 103 having a relatively small spring constant, it is necessary to fix the end of the spring fairly close to the driving roller 101. As a result, as shown in the drawing, the coil spring 103 may protrude from the roller surface of the driven roller 102 toward the driving roller 101 and be caught by the sheet member S sandwiched between both rollers. If a coil spring having a larger spring constant is used as the coil spring 103, the hook 103a is fixed at a position where it does not protrude from the surface of the driven roller 102, and a desired pressure can be obtained while avoiding such a catch. . However, in such a coil spring 103, since the tensile strength per unit deformation amount increases, there is a risk that it may be difficult to finely adjust the pressing force.

  So far, the problem in the case of using the coil spring as the elastic body inserted into the through hole of the driven roller has been described, but the same problem may occur even if another elastic body such as a leaf spring is used.

  The present invention has been made in view of the above background, and an object of the present invention is to provide the following roller pair unit, conveying apparatus, and image forming apparatus. That is, a roller that can reliably convey the sheet member while finely adjusting the pressure applied to the driven roller by the elastic body that has passed through the through hole of the driven roller, and can prevent the sheet member from being caught by the elastic body. For example, a unit.

In order to achieve the above object, a first aspect of the present invention is a drive roller that is driven to rotate, a driven roller that rotates while being in contact with the roller, a support that rotatably supports both rollers, and the driven roller. A through hole provided so as to extend over the entire axial direction of the driven roller at the rotation center, and an elastic body inserted into the through hole, and the elastic body is connected to the through hole. A roller pair unit that pressurizes the driven roller toward the driving roller by its own restoring force in a state where the engaging portions provided at both ends in the insertion direction are extended while being engaged with the support. The center of the engaging portion in the pressurizing direction in which the elastic body presses the driven roller toward the driving roller, and a position located in the through hole in the elastic body in a natural state that does not expand and contract. In the same pressure direction It is characterized in that it is shaped to shift the heart.
The invention according to claim 2 is the roller pair unit according to claim 1, wherein the elastic body is a coil spring, and has a hook that is hooked on a protrusion of the support as the engagement portion. It is a feature.
According to a third aspect of the present invention, in the roller pair unit according to the second aspect, the hook has a ring shape without a break.
The invention according to claim 4 is the roller pair unit according to claim 3, wherein the hook has a non-circular ring shape having a space in the insertion direction rather than the pressing direction. To do.
The invention according to claim 5 is the roller pair unit according to any one of claims 1 to 4, wherein the portion is positioned in the through hole, and the two engaging portions are opposite to each other through the through hole. The elastic body that is positioned on the side and is in a natural state that does not expand and contract has a shape in which the end of the projected image in the axial direction of the engagement portion is positioned outside the through hole. It is what.
The invention according to claim 6 provides a drive roller that is rotationally driven, a driven roller that is driven to rotate while abutting against the drive roller, a support that rotatably supports both rollers, and a driving force applied to the drive roller. A roller pair unit having a drive source, and a conveying device that conveys a sheet member sandwiched between both rollers, wherein the roller pair unit according to claim 1 is used as the roller pair unit. It is what.
According to a seventh aspect of the present invention, there is provided a recording means for recording an image on a recording sheet as a sheet member, and a conveying device for conveying the recording sheet before or after the image is recorded by the recording means. In the image forming apparatus having the above, the transport device according to claim 6 is used as the transport device.
According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect, the roller pair unit is used as a pair of discharge rollers for discharging the recording sheet from the inside to the outside of the housing of the image forming apparatus main body. A roller pair is used.

  In these inventions, as an elastic body, in a natural state where the elastic body is not expanded and contracted, the center in the pressurizing direction of the portion located in the through hole of the driven roller and the pressurization of the engaging portion such as the hook 103a shown in FIG. The center in the direction is not at the same position as each other, but the centers are shifted from each other in the pressing direction. This elastic body drives the engaging portions at both ends by the amount that the both centers are displaced compared to the conventional elastic body in which both the centers are in the same position in a natural state in which they are not expanded and contracted. Position it away from the rollers. In the elastic body having such a configuration, it is possible to exert the same pressure as that of the conventional elastic body in a state where the engaging portions at both ends thereof are fixed at positions farther from the driving roller than the conventional elastic body. . As a result, while using an elastic body having a relatively low spring constant as in the prior art, it is possible to suppress a situation in which both ends of the elastic body protrude toward the driving roller rather than the roller surface of the driven roller. While the pressure force is finely adjusted, it is possible to reliably convey the sheet member, and to prevent the sheet member from being caught by the elastic body.

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. 3 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. 4, 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 as an image forming unit can be attached to and detached from the main body of the printer 100 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 the intermediate transfer belt 8. 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 is initialized and prepared for the next image formation. In the other process cartridges 6M, 6C, and 6K, M, C, and K toner images are similarly formed on the photoreceptors 1M, 6C, and 6K, and are intermediately transferred onto the intermediate transfer belt 8.

  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, Y developer containing 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 conveyed to the developing area facing the Y photoreceptor 1Y, where Y toner is attached to the electrostatic latent image on the photoreceptor 1Y. By this adhesion, a Y toner image is formed 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 near the center 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 two-component developer containing toner and magnetic carrier shows a certain degree of 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. 3 shown above, an exposure device 7 is disposed below the process cartridges 6Y, 6M, 6C, and 6K. 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 photoconductor with a laser beam (L) emitted from a light source through a plurality of optical lenses and mirrors while scanning with a polygon mirror rotated by a motor. The exposure device 7, together with the process process cartridges 6Y, 6M, 6C, 6K, etc., constitutes a toner image forming means for forming a toner image on a photosensitive member as a latent image carrier.

  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 transfer papers P as sheet members, and a paper feed roller 27 is brought into contact with the uppermost transfer paper P. When the paper feeding roller 27 is rotated counterclockwise in the drawing by a driving means (not shown), the uppermost transfer paper P is sent out toward the paper feeding path 70.

  A registration roller pair 28 is disposed near the end of the paper feed path 70. The registration roller pair 28 rotates both rollers so as to sandwich the transfer paper P that is a recording sheet. Then, the transfer 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 cleaning device 10 in addition to the intermediate transfer belt 8. Also provided are four primary transfer bias rollers 9Y, 9M, 9C, 9K, a secondary transfer backup roller 12, a cleaning backup roller 13, a tension roller 14, and the like. The intermediate transfer belt 8 is endlessly moved in the counterclockwise direction in the figure by the rotational drive of at least one of the rollers while being stretched around these seven rollers. The primary transfer bias 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 to form primary transfer nips. Yes. 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 of the rollers except the primary transfer bias 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 secondary transfer backup roller 12 sandwiches the intermediate transfer belt 8 between the secondary transfer roller 19 and forms a secondary transfer nip. The visible four-color toner image formed on the intermediate transfer belt 8 is transferred to the transfer paper P at the secondary transfer nip. Then, combined with the white color of the transfer paper P, a full color toner image is obtained. Untransferred toner that has not been transferred onto the transfer paper P adheres to the intermediate transfer belt 8 after passing through the secondary transfer nip. This is cleaned by the cleaning device 10.

  In the secondary transfer nip, the transfer paper P is nipped and conveyed between the intermediate transfer belt 8 and the secondary transfer roller 19 whose surfaces move in the forward direction. The transfer 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 71.

  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 transfer 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 transfer sheet 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 72 and the pre-reversal conveyance path 73. At this branch point, a first switching claw 75 is swingably disposed, and the path of the transfer paper P is switched by the swing. More specifically, the path of the transfer paper P is set to the direction toward the paper discharge path 72 by moving the tip of the claw in a direction approaching the pre-reverse feed path 73. Further, by moving the tip of the claw away from the conveyance path 73 before reversal, the path of the transfer paper P is changed to the direction toward the conveyance path 73 before reversal.

  When the path to the paper discharge path 72 is selected by the first switching claw 75, the transfer paper P passes through the nip of the paper discharge roller pair 100 described later from the paper discharge path 72 and then goes out of the apparatus. Arranged and stacked on a stack 50a provided on the upper surface of the printer housing. On the other hand, when the path toward the conveyance path 73 before reversal is selected by the first switching claw 75, the transfer paper P enters the nip of the reversing roller pair 21 via the conveyance path 73 before reversal. The reversing roller pair 21 conveys the transfer paper P sandwiched between the rollers toward the stack portion 50a, but reversely rotates the rollers immediately before the rear end of the transfer paper P enters the nip. Due to this reverse rotation, the transfer paper P is conveyed in the opposite direction, and the rear end of the transfer paper P immediately approaches the branch path.

  A second switching claw 76 is swingably disposed on the branch path. When the sheet is fed from the fixing device 20 side toward the reversing roller pair 21 side in the pre-reversing conveyance path 73, the swing position where the second switching claw 76 brings the tip of the claw closer to the reversing conveyance path 76 described later. Has stopped at. Since the second switching claw 76 is stopped at such a swinging position, the transfer paper P in the pre-reverse conveyance path 73 is conveyed toward the reverse roller pair 21.

  On the other hand, almost simultaneously with the reverse transfer of the pair of reverse rollers 21, the transfer paper P is transported in the reverse direction starting from the rear end side, and the second switching claw 76 moves the front end of the claw to the pre-reverse transport path 73. Swing so that it approaches. As a result, the rear end side of the transfer paper P that is transported in the reverse direction is guided toward the reverse transport path 74.

  The reverse conveyance path 74 has a shape that greatly curves the conveyance path 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 transfer paper P is conveyed while sequentially passing through the nips of these roller pairs, so that the upper and lower sides thereof are reversed. After the transfer paper P is turned upside down, it is returned to the paper feed path 70 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 50a outside the apparatus via the post-transfer conveyance path 71, the fixing device 20, the paper discharge path 72, and the paper discharge roller pair 100. A full color image is formed on both sides of the transfer paper P by such reverse conveyance.

  A bottle support portion 31 is disposed between the intermediate transfer unit 15 and the stack portion 50a located above the intermediate transfer unit 15. The bottle support portion 31 is equipped with 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 replenished to the developing units of the process cartridges 6Y, 6M, 6C, and 6K, respectively, by a toner conveyance device that will be described later. These toner bottles 32Y, 32M, 32C, and 32K are detachable from the main body of the printer 100 independently of the process cartridges 6Y, 6M, 6C, and 6K.

  In the printer having the above-described configuration, the four process cartridges 6Y, 6M, 6C, and 6K, the exposure device 7, the intermediate transfer unit 15, and the like constitute recording means for recording an image on the transfer paper P that is a recording sheet. . Further, the paper feed path 70, the post-transfer conveyance path 71, the paper discharge path 72, the pre-reversal conveyance path 73, the reverse conveyance path 74, each roller pair disposed in these paths, the first separation claw 75, the second separation. Conveying means for conveying the transfer paper P is constituted by the claws 76 and the like.

Next, a characteristic configuration of the printer will be described.
FIG. 5 is an enlarged perspective view showing a paper discharge roller pair unit as a roller pair unit in the printer. In the figure, the paper discharge roller pair unit includes a driving roller 101 that is driven to rotate by receiving a driving force from a driving motor (not shown), a plurality of driven rollers 102 that rotate while abutting against the driving roller 101, a coil spring (not shown), And a support 105.

  The driving roller 101 includes a plurality of roller portions 101a arranged in a straight line in the rotation axis direction, and a round bar-shaped shaft member 101b made of metal to which the plurality of roller portions 101a are fixed so as to penetrate the respective rotation centers. have. Each of the plurality of roller portions 101a is made of an elastic material such as rubber, and is rotated together with the shaft member 101a. One driven roller 102 is in contact with each of the roller portions 101a, and the roller portions 101a are driven to rotate by contact with the roller portions 101a. The plurality of driven rollers 102 are supported by a support body 105 made of resin or the like. The support body 105 rotatably supports both end portions of the shaft member 101b of the drive roller 101 in a region not shown.

  Each of the plurality of driven rollers 102 is provided with a through hole 102a (not shown) extending in the axial direction at the center of rotation, and a coil spring is inserted therein. The coil spring is tensioned by hooks (not shown) at both ends of the coil spring being hooked on a pin 105 a which is a protrusion provided on the support body 105, and the driven roller 102 is directed toward the driving roller 101 by the restoring force. Energize. By this urging, the driven roller 102 is pressed toward the driving roller 101.

  FIG. 6 is an enlarged sectional view showing the driven roller 102. The through hole 102a of the driven roller 102 is provided so as to extend over the entire region in the roller axial direction at the rotation center of the roller main body made of resin or the like. A coil spring 103 that is an elastic body is inserted into the through hole 102a, and both end portions of the coil spring 103 protrude from the end surface of the driven roller 102 in the axial direction. Hooks 103a, which are engaging portions, are provided at the ends of the protruding portions. In the drawing, reference numeral A indicates a biasing direction of the coil spring 103 with respect to the driven roller 102, that is, a pressing direction of the driven roller 102. Moreover, the dashed-dotted line shown with the code | symbol B has shown the centerline in the said pressurization direction of the location which exists in the through-hole 102a among the whole area | regions of the axial direction (extension direction of the through-hole 102a) of the coil spring 103. FIG. . Also, the alternate long and short dash line indicated by the symbol C indicates the center line of the hook 103 a in the pressurizing direction in the entire region of the coil spring 103 in the axial direction. In the figure, the coil spring 103 is in a natural state where it does not expand and contract.

  As shown in the drawing, the coil spring 103 is positioned in the center of the hook 103a in the pressurizing direction in which the driven roller 102 is pressed toward the driving roller (101) and in the through hole 102a in a natural state without being expanded or contracted. The center in the pressurizing direction of the location to be performed (hereinafter referred to as the hole location) is deviated. More specifically, a driving roller (not shown) exists above the illustrated driven roller 102 in the drawing. In the pressurizing direction, the center of the hook 103a is shifted in a direction away from the drive roller from the center of the hole. Such a coil spring 103 has both centers compared to a conventional coil spring (for example, the one shown in FIG. 1) in which the center of the hook 103a is in the same position as the center of the hole in a natural state where the coil spring 103 does not expand and contract. The hook 103a is positioned away from the drive roller by the amount of deviation (distance L1 in FIG. 6). In such a configuration, it is possible to exert the same applied pressure as that of the conventional elastic body in a state where the hooks 103a at both ends are fixed at positions farther from the driving roller than the conventional coil spring. As a result, even when the spring constant is relatively low as in the prior art, the situation where the hooks 103a at both ends of the hooks 103a protrude toward the drive roller rather than the roller surface of the driven roller 103 is suppressed. Therefore, it is possible to reliably transfer the transfer paper P as the sheet member while finely adjusting the pressing force of the driven roller 102 and to prevent the transfer paper P from being caught by the coil spring 103.

  As the material of the roller body of the driven roller 102, it is desirable to use polyacetal resin having a very small surface friction coefficient. This is because by using the polyacetal resin, the frictional force between the coil spring 103 and the driven roller 102 can be suppressed and the driven roller 102 can be favorably rotated on the coil spring 103.

  The hooks 103a at both ends of the coil spring 103 each have an unbroken ring shape as shown in the figure. In this ring shape with no breaks, unlike the hooks with cuts, even if a large amount of coil springs 103 are put in the same container and stocked at the assembly factory of this printer, the coil springs 103 are mutually hooked like wisdom rings. There is no such situation as being hooked on 103a and connected. This eliminates the time-consuming work of uncoupling the coil spring 103, and improves the manufacturing efficiency of the printer.

  FIG. 7 is a schematic diagram showing a modification of the coil spring of the printer. In the same figure, the modified coil spring 203 has a horizontally long ring shape in which the unbroken hook 203a takes a space in the axial direction (extending direction of the through hole) rather than the pressurizing direction. The reason why such a ring shape is used is as follows. That is, the larger the hook 203a is in the pressing direction, the closer the center of the pressing direction is to the driving roller, and thus the hook 203a is easily caught on the transfer paper P. For this reason, it is desirable to make the dimension of the hook 203a in the pressing direction as small as possible. On the other hand, it is desirable to make the pin of the support member that hooks the hook 203a as thick as possible in order to suppress breakage and breakage, but it is necessary to make the outer shape smaller than the inner diameter of the hook 203a. If the hook 203a is not enlarged as much as possible in the pressurizing direction and its ring shape is a perfect circle, the pin 105a becomes very thin and fragile as shown in FIG. Therefore, in addition to making the size of the hook 203a in the pressurizing direction as small as possible, the hook 203a has a horizontally long ring shape as described above. By doing so, it is possible to increase the opening area of the hook 203a without increasing the dimension of the hook 203a in the pressing direction. As shown in FIG. 9, a thick and sturdy pin 105a for supporting the hook 203 can be used. In addition, by increasing the thickness of the pin 105a, the operability with the finger can be improved as compared with the small-diameter one shown in FIG.

  FIG. 10 is an enlarged cross-sectional view showing the modified coil spring 203 together with the driven roller 102. In the same figure, the modified coil spring 203 is expanded and contracted while the above-mentioned holes are located in the through holes 102a of the driven roller 102 and the two hooks 203a are positioned on the opposite sides via the through holes 102a. There is no natural state. In this state, the end of the projected image in the spring axis direction of the hook 203a is located outside the through hole 102a as indicated by the arrow in the figure. In such a configuration, even when the driven roller 102 and the modified coil spring 203 inserted into the modified coil spring 203 are mounted on a support (not shown) and the driven roller 102 is slid on the modified coil spring 203, the following is possible. It becomes possible. In other words, the axial end of the driven roller 102 can be hooked on the hook 203 a of the modified coil spring 203. By hooking in this way, the driven roller 102 can be prevented from falling off from the modified coil spring 203, and the assembling operability can be improved.

  In order to position the end portion of the projection image of the hook 203a in the spring axis direction outside the through hole 102a, a dimension design as shown in FIG. 11 may be used. That is, the length L2 from the driving roller side (upper side in the figure) end of the modified coil spring 203 in the pressurizing direction to the opposite end is set to the length L2 of the through hole 102a of the driven roller 102 in the pressurizing direction. What is necessary is just to make it larger than length L3.

  In FIG. 1 described above, the printer uses the paper discharge roller pair 100 as a roller pair according to the roller pair unit of the present invention. In each conveyance path, all other roller pairs employ a system in which the shaft member of the driven roller is urged toward the drive roller. This is for the reason explained below. That is, in general, each roller pair in the conveyance path is required to have a relatively high sheet conveyance accuracy in order to suppress image recording position deviation, as represented by a registration roller pair. In the configuration in which the driven roller is urged by the coil spring that is passed through the through hole of the driven roller, it is difficult to satisfy such sheet conveyance accuracy. Become. However, the pair of paper discharge rollers only serves to discharge the recording sheet on which an image has already been recorded to the outside of the apparatus, so that a high sheet conveyance accuracy is not required. By employing the roller pair according to the present invention for such a pair of conveying rollers, it is possible to reduce the size of the apparatus without encouraging image recording positional deviation.

  So far, an example using a coil spring as an elastic body has been described. However, the present invention can also be applied to a roller pair unit using another elastic body such as a leaf spring. For reference, a driven roller in a roller pair using a leaf spring is shown in FIG. 12 together with the leaf spring. In the leaf spring 303, the portions protruding from both ends of the through hole 102a of the driven roller 102 are bent in the opposite direction to the driving roller, respectively. As a result, the driven roller 102 is urged in the direction of the arrow in the figure where there is a drive roller (not shown). However, in the plate spring 203 having such a configuration, the inside of the driven roller 102 is easily worn by the edge.

  Further, the example in which the present invention is applied to an electrophotographic printer has been described so far. However, the present invention can also be applied to an image forming apparatus that forms an image by other methods such as a direct recording method and an inkjet recording method. Is possible. This direct recording method is not related to the latent image carrier, but forms a pixel image by directly adhering a toner group that has been ejected in a dot shape from a toner flying device to a recording medium or an intermediate recording medium. In this method, a toner image is directly formed on an intermediate recording medium.

  As described above, in the printer according to the embodiment, since the elastic body inserted into the through hole 102a of the driven roller 102 is a coil spring, wear of the driven roller 102 can be suppressed compared to the case of a leaf spring. Further, since the engaging portion is the hook 103a that is hooked on the pin 105a that is a protrusion of the support, the coil spring 103 can be easily fixed without using a bolt, a nut, or the like.

  Further, in the printer according to the embodiment, since the hook 103a has a continuous ring shape, for the reasons described above, the laborious work of releasing the connection of the coil spring 103 is unnecessary, and the manufacturing efficiency of the printer is improved. Can be made.

  Further, in the modified coil 203, the hook 203a without a break has a non-circular ring shape that takes a space in the coil insertion direction rather than the pressurizing direction, so that the hook 203 is hooked for the reason described above. As the support pin 105a for this purpose, a thick and sturdy pin can be used. In addition, it is possible to improve the operability with a finger when the hook 203 is hooked.

  Further, in the modified coil 203, the above-described hole location is positioned in the through hole 102a, the two hooks 203a are positioned on the opposite sides of each other through the through hole 102a, and in a natural state in which they are not expanded and contracted. Since the end of the projected image in the axial direction is positioned outside the through hole 102a, for the reasons described above, the driven roller 102 is prevented from falling off from the modified coil spring 203, and the assembly operability is improved. Can be made.

  In the printer according to the embodiment, the roller pair of the roller pair unit according to the present invention is used as the discharge roller pair 100 for discharging the transfer paper P as a recording sheet from the inside of the housing of the printer body to the outside. Therefore, for the reason described above, the apparatus can be reduced in size without promoting the image recording position shift.

The expanded sectional view which shows the conventional driven roller with a coil spring. The expanded sectional view which shows the conventional driven roller and a coil spring with a drive roller. 1 is a schematic configuration diagram illustrating a printer according to an embodiment. FIG. 3 is an enlarged configuration diagram showing a process cartridge for Y of the printer and its surroundings. FIG. 3 is an enlarged perspective view showing a paper discharge roller pair unit as a roller pair unit in the printer. The expanded sectional view which shows the driven roller of the discharge roller pair unit. FIG. 3 is a perspective view showing a bottle support portion and four toner bottles in the printer. The schematic diagram which shows the 1st modification of the same coil spring. The side view which shows the coil spring which made the hook the ring shape of perfect circle shape with a pin. The side view which shows the coil spring of the 1st modification with a pin. The expanded sectional view which shows the coil spring of the 1st modification with a driven roller. The expanded sectional view which shows the relationship of the dimension of the coil spring and the follower roller of the said 1st modification. The expanded sectional view which shows the leaf | plate spring which is a 2nd modification with a driven roller.

Explanation of symbols

6Y, M, C, K Process cartridge (part of recording means)
7 Exposure equipment (part of recording means)
15 Transfer unit (part of recording means)
100 Paper discharge roller pair (part of roller pair unit)
101 driving roller 101a shaft member 102 driven roller 102a through hole 103 coil spring (elastic body)
103a Hook (engagement part)
105 Support 105a Pin 203 Modified Example Coil Spring (Elastic Body)
203a Hook (engagement part)

Claims (8)

A driving roller that is driven to rotate, a driven roller that rotates while being in contact with the roller, a support that rotatably supports both rollers, and the axial direction of the driven roller at the rotational center of the driven roller. A through hole provided so as to extend, and an elastic body inserted into the through hole, and the elastic body includes engaging portions respectively provided at both ends in the insertion direction of the through hole. A roller pair unit that pressurizes the driven roller toward the driving roller by its own restoring force in a state of being stretched while being engaged with the support,
Addition of the center of the engaging portion in the pressurizing direction in which the elastic body presses the driven roller toward the driving roller, and the location of the elastic body in the natural state that is not expanded or contracted. A roller pair unit characterized by having a shape that deviates from the center in the pressure direction. The roller pair unit of claim 1,
The roller pair unit, wherein the elastic body is a coil spring, and the engaging portion has a hook that is hooked on a protrusion of the support. The roller pair unit of claim 2,
The roller pair unit, wherein the hook has an unbroken ring shape. The roller pair unit of claim 3,
The roller pair unit, wherein the hook has a non-circular ring shape that takes a space in the insertion direction rather than the pressing direction. The roller pair unit according to any one of claims 1 to 4,
The elastic body in a natural state in which the portion is positioned in the through hole, the two engaging portions are positioned on opposite sides of the through hole, and is not expanded or contracted, is the engaging portion. A roller pair unit having a shape in which an end portion of the projected image in the axial direction is positioned outside the through hole. A roller pair unit having a drive roller that is rotationally driven, a driven roller that is driven to rotate while being in contact with the roller, a support that rotatably supports both rollers, and a drive source that applies a drive force to the drive roller. A conveying device that sandwiches and conveys a sheet member between both rollers,
6. A conveying apparatus using the roller pair unit according to claim 1 as the roller pair unit. In an image forming apparatus comprising: a recording unit that records an image on a recording sheet that is a sheet member; and a conveyance device that conveys the recording sheet before or after the image is recorded by the recording unit.
An image forming apparatus using the transport device according to claim 6 as the transport device. The image forming apparatus according to claim 7.
An image forming apparatus comprising: a roller pair of the roller pair unit as a pair of paper discharge rollers for discharging the recording sheet from the inside to the outside of a housing of the image forming apparatus main body.

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