JP2006011044A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which disordering of a toner image and noise in transfer of a toner image to a recording sheet are suppressed while a rise in production cost is suppressed. <P>SOLUTION: The image forming apparatus is equipped with an intermediate transfer belt 151 which conveys a toner image to a transfer area by carrying the toner image on a cyclically moving surface, an intermediate transfer unit 115 having a frame 158 supporting the intermediate transfer belt 151 in a housing 101, a movable guide 121 which is provided on the conveyance path of a recording sheet upstream of the transfer area and guides a conveyed recording medium to the side of the transfer area, a biasing spring 122 which biases a transfer-area side end of the movable guide 121 toward the intermediate transfer belt 151, and a restricting member 130 which is fitted to the frame 158 and restricts the gap between the end of the movable guide 121 biased toward an image conveyance path and the intermediate belt 151. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a printer, a facsimile machine, a copier, and a multifunction machine having the functions of these apparatuses.

  Conventionally, as an example of the image forming apparatus as described above, a toner image is formed on the surface of a photoconductor, and after the toner image is transferred to the intermediate transfer belt, the toner image is finally recorded from the intermediate transfer belt. 2. Description of the Related Art A so-called electrophotographic image forming apparatus is known in which the image is transferred to an image (for example, see Patent Document 1). In such an image forming apparatus, in order to reliably guide the recording sheet to the transfer area where the toner image is finally transferred from the intermediate transfer belt, a guide as described below is provided in the vicinity of the transfer area in the apparatus. Are often provided.

  FIG. 3 is a diagram illustrating an example of a configuration in the vicinity of a transfer region in an image forming apparatus including an intermediate transfer belt.

  FIG. 3 shows an intermediate transfer belt 21, two rollers 22 and 23 for circulating and moving the intermediate transfer belt 21, a transfer roller 31, a registration roller 32, an upper guide 33, and a lower guide 34. Has been.

  The intermediate transfer belt 21 constitutes an intermediate transfer unit 20 together with a plurality of rollers including the two rollers 22 and 23 shown in FIG.

  The intermediate transfer belt 21 is stretched by the plurality of rollers described above, and is further circulated and moved in the direction of the arrow X as these rollers rotate. Further, one of the plurality of rollers 23 faces the transfer roller 31 with the intermediate transfer belt 21 interposed therebetween, and the nip portion sandwiches the intermediate transfer belt 21 with the two rollers 23 and 31. N is formed. When the toner image is transferred from the photoreceptor (not shown) to the intermediate transfer belt 21, the toner image is conveyed to the nip portion N as the intermediate transfer belt 21 is circulated. Then, the registration roll 32 feeds the recording sheet P toward the nip portion N at a timing when the toner image on the intermediate transfer belt 21 reaches the nip portion N. Then, at the nip portion N, the recording sheet P and the intermediate transfer belt 21 on which the toner image is placed are pressed against each other by the transfer roller 31 and the roller 23, and the toner image is transferred from the intermediate transfer belt 21 to the recording sheet P. Is done. That is, in the example of FIG. 3, the nip portion N corresponds to the transfer region.

  In addition, between the registration roll 32 and the nip portion N, two guides 33 and 34 are disposed in order to reliably guide the recording sheet P to the nip portion N. The upper guide 33 plays a role of regulating the movement of the recording sheet P in the direction away from the intermediate transfer belt 21, and the lower guide 34 moves the recording sheet P along the surface on the upper guide 33 side to the nip portion N. I have a role to guide.

Here, the shape of the leading end portion P1 of the recording sheet P inserted into the nip portion N often varies depending on the curl of the recording sheet P or the like, and the leading end portion P1 is accurately inserted into the nip portion N. It is very difficult. Therefore, in order to smoothly guide the leading end portion P1 of the recording sheet P to the nip portion N, the leading end portion P1 of the recording sheet P is brought into contact with the intermediate transfer belt 21 before the nip portion N, and the leading end portion P1 is moved to the intermediate portion. There has been proposed a method of guiding the transfer belt 21 to the nip portion N while being attracted to the transfer belt 21 by electrostatic force. Here, in the example of this method shown in FIG. 3, the leading end portion P <b> 1 attracted to the intermediate transfer belt 21 decreases before the nip portion N reaches the nip portion N and peels off from the intermediate transfer belt 21. In order to avoid such a problem that the intermediate transfer belt 21 vibrates due to the leading end portion P1 coming into contact with the intermediate transfer belt 21 at a steep angle, the lower guide 34 is provided with the leading end portion P1 of the recording sheet P. Are arranged so as to be in contact with the intermediate transfer belt 21 at a shallow angle C of 10 ° to 20 ° with respect to the intermediate transfer belt 21 in an area A several mm to several tens of mm before the nip portion N.
JP-A-6-289686 (page 3-6, FIG. 1)

  In the example of FIG. 3, the end 34 a on the nip portion N side of the lower guide 34 is separated from the intermediate transfer belt 21 by a predetermined distance B so as not to touch the toner image conveyed to the nip portion N. It is fixed. The recording sheet P guided to the nip portion N along the lower guide 34 and passing through the nip portion N has a rear end portion P2 of the recording sheet P passing through the end portion 34a on the nip portion N side of the lower guide 34. When passing, there is a possibility that the recording sheet P itself may collide with the intermediate transfer belt 21 vigorously due to the elasticity of the recording sheet P itself. When such a collision occurs, there arises a problem that abnormal noise occurs or the toner image on the intermediate transfer belt 21 is disturbed by the vibration of the collision.

  At first glance, such a problem seems to be suppressed by bringing the end 34a on the nip N side of the lower guide 34 as close as possible to the intermediate transfer belt 21, that is, by reducing the predetermined distance B shown in FIG. However, in consideration of various factors such as processing errors and mounting errors of the lower guide 34 fixed to the housing and peripheral parts, a highly accurate processing is required to reduce the predetermined distance B shown in FIG. 3 with high accuracy. There is a problem that assembly is required and the production cost is significantly increased.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an image forming apparatus in which the disturbance of a toner image and the generation of abnormal noise when a toner image is transferred to a recording sheet are suppressed while suppressing an increase in production cost. And

The image forming apparatus of the present invention that achieves the above object has a medium transport path for transporting a recording medium and an image transport path for transporting a toner image that join at a confluence before a predetermined transfer area. In an image forming apparatus which is provided inside and forms an image composed of a fixed toner image on a recording medium by transferring and fixing the toner image to the recording medium in the transfer region,
An image carrying body that carries a toner image on a surface that moves along the image carrying path and carries the toner image to the transfer region, and an image carrying unit that supports the image carrying body in the housing;
A guide member provided on the upstream side of the transfer region on the medium transport path and guiding the recording medium along the transported recording medium to the merging point on the medium transport path;
An urging means for urging the transfer region side end of the guide member toward the image conveying path;
The guide member is provided with a regulating member that regulates a distance between an end portion of the guide member that is biased toward the image conveyance path and the image conveyance path.

  According to the image forming apparatus of the present invention, the distance between the transfer region side end of the guide member and the image transport path, that is, the transfer region side end of the guide member and the image transport of the image transport unit. The distance from the body surface can be regulated, for example, so that they are as close as possible. Thus, when the rear end portion of the recording medium passes the end portion on the transfer area side of the guide member, the toner caused by the rear end portion of the recording medium colliding with the surface of the image carrier vigorously. Image distortion and abnormal noise are suppressed. In the image forming apparatus of the present invention, the restriction on the distance between the transfer region side end of the guide member and the surface of the image carrier is performed only by the restriction member. In other words, the only increase in production cost necessary to suppress problems such as toner image disturbance and abnormal noise when the toner image is transferred to the recording medium is only the production cost related to the above-mentioned regulating member. According to the image forming apparatus of the invention, the above-described problems can be suppressed while suppressing an increase in production cost.

  Here, in the image forming apparatus of the present invention, the regulating member protrudes a predetermined length from the image conveying path side toward the medium conveying path side, and is biased toward the image conveying path of the guide member. It may be a protruding member with which the end abuts.

  According to such a regulating member, for example, by setting the predetermined length to an appropriate length, the distance between the transfer region side end of the guide member and the surface of the image carrier can be as much as possible. It can be easily regulated to be close.

Further, in the image forming apparatus of the present invention, “the image transport unit is arranged to be freely pulled out from the housing,
The guide member can move an end portion of the guide member biased toward the image transport path in a direction away from the image transport path against the biasing force of the biasing means. The form “is” is a preferred form.

  According to this preferred embodiment of the image forming apparatus, the image transport unit can be detached from the casing, for example, during maintenance. Furthermore, when the image transport unit is pulled out from the housing, the end of the guide member that is biased toward the image transport path is against the biasing force of the biasing means from the image transport path. By moving in the direction away from each other, it is possible to easily avoid problems such as the guide member and the surface of the image transport body of the image transport unit coming into contact with each other and being damaged.

  Further, the image forming apparatus according to the preferred embodiment maintains the posture of the guide member in a state where the end of the guide member urged toward the image transport path moves away from the image transport path. A form in which the holding mechanism is provided is a more preferable form.

  According to this further preferred embodiment of the image forming apparatus, for example, when maintenance is performed, the end of the guide member biased toward the image transport path is moved away from the image transport path. In addition, the holding mechanism maintains the posture of the guide member in the state where the end portion is moved, thereby further reliably avoiding contact between the guide member and the surface of the image carrier of the image carrying unit. Can do.

  As described above, according to the present invention, it is possible to provide an image forming apparatus in which the toner image is prevented from being disturbed and abnormal noise is suppressed when the toner image is transferred to a recording sheet, while suppressing an increase in production cost. can do.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram illustrating a printer according to an embodiment of the present invention.

  The printer 100 shown in FIG. 1 includes a so-called tandem type electrophotographic apparatus in which a photoreceptor, a developing device, and the like are provided for each color of yellow (Y), magenta (M), cyan (C), and black (K). It is a printer.

  The printer 100 includes a housing 101, a sheet tray 110, a pickup roller 111, a paper feed roller 112, a registration roller 113, and four types of image forming units 114Y, 114M, 114C corresponding to each color of YMCK. 114K, an intermediate transfer unit 115, a transfer roller 116, a fixing device 117, a discharge roller 118, a fixed guide 120, a movable guide 121, a biasing spring 122, and a regulating member 130. Here, the intermediate transfer unit 115, the movable guide 121, the urging spring 122, and the regulating member 130 correspond to examples of the image transport unit, the guide member, the urging means, and the regulating member, respectively, according to the present invention.

  A plurality of recording sheets P are stored in the sheet tray 110 and are picked up one by one by the pickup roller 111. In the housing 101 of the printer 100, a plurality of fixed guides 120 are arranged between a plurality of rollers that convey the recording sheet P. The recording sheet P basically has a fixed guide 120 between the rollers. It is designed to flow along. Each fixed guide 120 is formed in a thin plate shape that is gently curved into a shape in which the recording sheet P flows smoothly between the rollers. In the present embodiment, the plurality of fixed guides 120 and the plurality of rollers in the housing 101 form a conveyance path for the recording sheet P from the pickup roller 111 to the discharge roller 118. The recording sheet P taken out by the pickup roller 111 is sent out to the transport path by the paper feed roller 112 and further sent by a registration roller 113 to a transfer area described later at a predetermined timing.

  Each of the image forming units 114Y, 114M, 114C, and 114K includes photosensitive drums 141Y, 141M, 141C, and 141K, exposure chargers 142Y, 142M, 142C, and 142K, exposure devices 143Y, 143M, 143C, and 143K, and development. 144Y, 144M, 144C, 144K, transfer chargers 145Y, 145M, 145C, 145K, cleaners 146Y, 146M, 146C, 146K, and static eliminators 147Y, 147M, 147C, 147K.

  Each of the image forming units 114Y, 114M, 114C, and 114K is supplied with image data representing a color separation image obtained by separating the color image to be printed into yellow, magenta, cyan, and black by a control unit (not shown). Each color toner image is formed in the image forming units 114Y, 114M, 114C, and 114K. Then, the formed toner images of the respective colors are transferred to the intermediate transfer belt 151 provided in the intermediate transfer unit 115. Here, a series of processes from the toner image formation in the image forming unit to the transfer to the intermediate transfer belt 151 will be described below, but the processes of the respective colors are equivalent to each other, and here, the process corresponds to yellow (Y). The image forming unit 114Y will be described as an example.

  First, the photosensitive drum 141Y is rotated, and the surface of the photosensitive drum 141Y is charged by the exposure charger 142Y. Next, the surface of the charged photosensitive drum 141Y is exposed by the exposure unit 143Y based on the image data representing the color separation image. As a result, an electrostatic latent image corresponding to the color separation image is formed on the surface of the photosensitive drum 141Y. The electrostatic latent image formed on the surface of the photoreceptor drum 141Y is developed with toner by the developing device 144Y, and a toner image corresponding to the color separation image is formed on the surface of the photoreceptor drum 141Y. Further, the surface of the photosensitive drum 141Y on which the toner image is formed is charged by the transfer charger 145Y, and the toner image on the surface is transferred to the intermediate transfer belt 151 provided in the intermediate transfer unit 115. When this transfer is completed, the surface of the photosensitive drum 141Y is neutralized by the static eliminator 147Y, and the waste toner remaining on the surface is removed by the cleaner 146Y.

  The intermediate transfer unit 115 includes the intermediate transfer belt 151, the driving roller 152, two stretching rollers 153, a tension adjusting roller 154, a frame 158, and a rail 159. Here, the intermediate transfer belt 151 and the frame 158 correspond to examples of the image carrier and the support member according to the present invention.

  A driving roller 152, two stretching rollers 153, and a tension adjusting roller 154 are attached to the frame 158, and the intermediate transfer belt 151 is stretched by these rollers. The frame 158 is detachably attached to the housing 101 via a rail 159. As a result, the intermediate transfer unit 115 can be removed from the housing 101 or remounted during maintenance or the like.

  Here, the four types of image forming units 114Y, 114M, 114C, and 114K are arranged such that the photosensitive drums 141Y, 141M, 141C, and 141K of the image forming units are in contact with the intermediate transfer belt 151. Therefore, in the present embodiment, when the intermediate transfer unit 115 is attached or detached for maintenance or the like, the image forming units 114Y, 114M, 114C, and 114K are moved away from the intermediate transfer unit 115 by a predetermined moving mechanism. Moved to position.

  The drive roller 152 serves to circulate and move the intermediate transfer belt 151 in the arrow Y direction by rotating. The drive roller 152 faces the transfer roller 116 with the intermediate transfer belt 151 interposed therebetween, and a nip portion N is formed by the drive roller 152 and the transfer roller 116 with the intermediate transfer belt 151 interposed therebetween. As will be described later, the nip portion N corresponds to a transfer region where the toner image is finally transferred to the recording sheet P in this embodiment. Further, the tension adjusting roller 154 plays a role of adjusting the tension of the intermediate transfer belt 151 by being moved in the push-pull direction with respect to the intermediate transfer belt 151.

  When the yellow toner image is transferred onto the intermediate transfer belt 151 that is circulated in the direction of the arrow Y by the yellow image forming unit 114Y, the yellow toner image reaches the magenta image forming unit 114M. The toner image is formed by the magenta image forming unit 114M in accordance with the timing. The formed magenta toner image is transferred onto the yellow toner image on the intermediate transfer belt 151 in an overlapping manner. Such toner image formation and transfer is also performed in the cyan and black image forming portions 114C and 114K, and a color toner image is formed on the intermediate transfer belt 151.

  The color toner image transferred onto the intermediate transfer belt 151 is conveyed to the nip portion N as the intermediate transfer belt 151 is circulated and moved in the arrow Y direction. The registration roller 113 sends the recording sheet P taken out from the sheet tray 110 toward the nip portion N in synchronization with the timing at which the color toner image is conveyed to the nip portion N.

  Between the registration roller 113 and the nip portion N, a fixed guide 120 and a movable guide 121 are disposed so as to face each other. Here, the movable guide 121 has a thin plate shape that is gently curved like the fixed guide 120, and the end on the registration roller 113 side is the housing so that the convexity of the curve faces the intermediate transfer belt 151. 101 is supported to be rotatable. A biasing spring 122 is attached to the support position, and the biasing spring 122 biases the end of the movable guide 121 on the nip portion N side toward the intermediate transfer belt 151. The leading end of the movable guide 121 is brought into contact with the biased end of the movable guide 121 before the nip portion N, and the leading end of the movable guide 121 protrudes from the intermediate transfer belt 151 toward the movable guide 121 by a predetermined length. 130 is fixed to the frame 158 of the intermediate transfer unit 115. The movable guide 121 and the regulating member 130 will be described again with reference to other drawings.

  The recording sheet P sent out by the registration roller 113 flows along the movable guide 121, and its leading end comes into contact with the intermediate transfer belt 151 before the nip portion N. The leading end of the recording sheet P is attracted to the surface of the intermediate transfer belt 151 by electrostatic force, and is guided to the nip portion N while being attracted.

  The recording sheet P guided to the nip portion N is pressed against the color toner image on the intermediate transfer belt 151 by the transfer roller 116 and the driving roller 152 when passing through the nip portion N. As a result, a color toner image is transferred onto the recording sheet P. The recording sheet P to which the toner image has been transferred is conveyed to the fixing device 117, and the unfixed toner image is fixed to the recording sheet P by the fixing device 117. As a result, a color image composed of a fixed toner image is formed on the recording sheet P. Thereafter, the recording sheet P on which the color image is formed is discharged to the outside of the housing 101 by the discharge roller 118.

  Above, the outline | summary description about the structure and operation | movement of the printer 100 of this embodiment is complete | finished. Here, the feature of the printer 100 as the present invention is the structure around the movable guide 121 described above. Hereinafter, the structure around the movable guide 121 will be described in detail.

  FIG. 2 is an enlarged view showing the periphery of the movable guide 121.

  As described above, the end of the movable guide 121 on the side of the registration roller 113 is rotatably supported, and the end 121a on the side of the nip N is attached to the intermediate transfer belt by the biasing spring 122 attached to the support position. 151 is energized. The urged end 121 a is in contact with the tip of the regulating member 130 fixed to the frame 158 of the intermediate transfer unit 115. Here, in the present embodiment, the position of the front end portion of the regulating member 130 is highly accurate so that the distance B between the end portion 121a on the nip portion N side of the movable guide 121 and the intermediate transfer belt 151 is very short. Is positioned. When the recording sheet P flows along the movable guide 121 and the trailing end portion P2 of the recording sheet P passes through the end portion 34a on the nip portion N side of the movable guide 121, the trailing end portion P2 is the intermediate transfer belt. Stay on a very short distance to 151. As a result, the collision force between the rear end portion P2 of the recording sheet P and the intermediate transfer belt 151 is very small, and the intermediate transfer belt 151 vibrates very little. As a result, the occurrence of abnormal noise and the disturbance of the toner image due to the vibration of the intermediate transfer belt 151 are suppressed. Further, the main cost required to suppress the generation of abnormal noise and the disturbance of the toner image is only the cost related to the positioning of the regulating member 130 described above. In other words, according to the printer 100 of the present embodiment, it is possible to suppress the distortion of the toner image and the generation of abnormal noise when the toner image is transferred to the recording sheet, while suppressing an increase in production cost.

  Further, when the intermediate transfer unit 115 is attached or detached during maintenance, the intermediate transfer unit 115 is pulled out while the regulating member 130 fixed to the frame 158 pushes back the movable guide 121. Therefore, the movable guide 121 is removed. Contact with the intermediate transfer belt 151 is avoided. Furthermore, in this embodiment, the movable guide 121 is attached to the end portion 34a on the nip portion N side by a hook 123 attached to the movable guide 121 and a fastener 124 on which the hook 123 provided on the housing 101 is hooked. Can be fixed to the housing 101 in a state 121 ′ sufficiently separated from the intermediate transfer belt 151. Here, a combination of the hook 123 and the fastener 124 corresponds to an example of a holding mechanism according to the present invention. In this embodiment, the user moves the movable guide 121 and hangs the hook 123 on the fastener 124 before attaching and detaching the intermediate transfer unit 115, so that the movable guide 121 and the intermediate transfer belt 151 at the time of attachment and detachment are attached. Can be reliably avoided.

  In the above description, as an example of the restricting member according to the present invention, the end of the movable guide 121 urged toward the intermediate transfer belt 151 comes into contact with the intermediate transfer unit 115 protruding from the intermediate transfer belt 151 by a predetermined amount. Although the restricting member 130 fixed to the frame 158 has been described, the present invention is not limited to this. The regulating member referred to in the present invention may be, for example, a member that hooks and supports the end of the movable guide 121 that is biased toward the intermediate transfer belt 151 at a predetermined distance above the intermediate transfer belt 151.

  In the above description, the hook 123 attached to the movable guide 121 and the fastener 124 on which the hook 123 is hung are described as an example of the holding mechanism according to the present invention, but the present invention is not limited to this. The regulating member referred to in the present invention may be any member as long as it holds the position of the movable guide in a state where the end urged toward the intermediate transfer belt moves away from the intermediate transfer belt.

1 shows a printer according to an embodiment of the present invention. FIG. 6 is an enlarged view showing the periphery of a movable guide 121. FIG. 4 is a diagram illustrating an example of a configuration in the vicinity of a transfer region in an image forming apparatus including an intermediate transfer belt.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Printer 101 Case 110 Sheet tray 111 Pickup roller 112 Paper feed roller 113 Registration roller 114Y, 114M, 114C, 114K Image forming unit 115 Intermediate transfer unit 116 Transfer roller 117 Fixing device 118 Discharge roller 120 Fixed guide 121 Movable guide 121a End 121 'Fully separated from the intermediate transfer belt 151 122 Biasing spring 123 Hook 124 Fastener 130 Restriction member 141Y, 141M, 141C, 141K Photosensitive drum 142Y, 142M, 142C, 142K Exposure chargers 143Y, 143M, 143C , 143K Exposure unit 144Y, 144M, 144C, 144K Developer 145Y, 145M, 145C, 145K Transfer charger 146Y, 146M, 146C, 146K LINA 147Y, 147M, 147C, 147K Static eliminator 151 Intermediate transfer belt 152 Drive roller 153 Tension roller 154 Tension adjustment roller 158 Frame 159 Rail 20 Intermediate transfer unit 21 Intermediate transfer belt 22, 23 Roller 31 Transfer roller 32 Registration roller 33 Upper guide 34 Lower guide 34a End

Claims (4)

A medium transport path for transporting the recording medium and an image transport path for transporting the toner image, which join at a confluence before the predetermined transfer area, are provided inside the housing, and the toner image is recorded in the transfer area. In an image forming apparatus for forming an image composed of a fixed toner image on a recording medium by transferring and fixing the medium on the medium,
An image carrying body that carries a toner image on a surface that moves along the image carrying path and carries the toner image to the transfer region, and an image carrying unit that has a support member that supports the image carrying body in the housing;
A guide member provided on the upstream side of the transfer area on the medium transport path and guiding the recording medium along the transported recording medium to the junction on the medium transport path;
An urging means for urging the transfer region side end of the guide member toward the image conveying path;
An image forming apparatus comprising: a regulating member that is attached to the support member and that regulates a distance between an end portion of the guide member biased toward the image conveyance path and the image conveyance path. .   The regulating member is a protruding member that protrudes a predetermined length from the image conveying path side toward the medium conveying path side, and an end portion of the guide member that is urged toward the image conveying path contacts. The image forming apparatus according to claim 1. The image transport unit is provided so as to be freely pulled out from the housing,
The guide member can move an end portion of the guide member urged toward the image conveyance path in a direction away from the image conveyance path against the urging force of the urging means. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   A holding mechanism for holding the posture of the guide member in a state in which an end portion of the guide member urged toward the image transport path is moved in a direction away from the image transport path is provided. The image forming apparatus according to claim 3.

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