JP2010066391A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of suppressing a center precedence of a recording medium. <P>SOLUTION: In a body casing 2 of a printer 1, a carrier belt 9 for carrying a sheet 100 and the first guide member 24 arranged on an upstream side in a carrying direction of the sheet 100 with respect to the carrier belt 9 are provided. In a process unit 50, a pressing member 31 arranged on the upstream side in the carrying direction with respect to the carrier belt 9 is provided. The pressing member 31 presses only a center area 100A of the sheet 100 in a width direction orthogonal to the carrying direction, so that the pressed center area 100A is pushed to the first guide member 24 arranged to be opposed to the pressing member 31. Thus, resistance occurs in only the center area 100A in the sheet 100 carried toward the carrier belt 9, so that the center area 100A is not carried prior to both end parts 100B in the width direction and the center precedence of the sheet 100 can be suppressed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as an electrophotographic system.

  An endless transfer material conveyance belt that conveys a transfer material onto which a toner image is transferred, a plurality of rotating rolls that are arranged inside the transfer material conveyance belt and move around the transfer material conveyance belt, and form a toner image A color image forming apparatus including a plurality of image forming units is known (see, for example, Patent Document 1). In the color image forming apparatus of Patent Document 1, the toner image formed by each image forming unit is sequentially transferred onto a transfer material conveyed on a transfer material conveyance belt that moves in a circular manner. An image is formed.

The color image forming apparatus disclosed in Patent Document 1 includes a transfer material suction roll on the upstream side of the transfer material conveyance belt in the transfer material conveyance direction. The transfer material adsorbing roll faces the rotating roll located at the most upstream position in the transfer material transport direction with the transfer material transport belt interposed therebetween. The transfer material conveyed toward the transfer material conveyance belt is sandwiched between the transfer material adsorption roll and the rotating roll (strictly, the transfer material conveyance belt) on the upstream side of the transfer material conveyance belt, thereby being transferred to the transfer material conveyance belt. Adsorbed. Thereby, the adhesiveness of a transfer material and a transfer material conveyance belt can be improved.
Japanese Patent Laid-Open No. 5-270686

A phenomenon of central leading may occur with respect to the transfer material transfer. The center leading means that when the transfer material is conveyed, the central region of the transfer material in the direction orthogonal to the transfer material conveyance direction (so-called paper width direction) precedes both ends in the orthogonal direction (conveyed first). That is.
Here, for example, when a large number of transfer materials are left in a stacked state under high temperature and high humidity, the transfer material in a position excluding the upper part in the stacking direction exposes only the peripheral edge to the atmosphere. While the region remains dry, both end portions absorb moisture in the atmosphere and get wet. That is, in this transfer material, the wetness differs in the orthogonal direction. Further, in this transfer material, the central region is dry while the both end portions are moistened, so that the central region is hard and the both end portions are soft.

  When the central leading occurs during the transfer of the transfer material, a force from the both ends to the central region is generated in the transfer material where the central leading occurs. At this time, if the transfer material in which the central leading has occurred is a transfer material having a uniform wetness (in other words, hardness) in the orthogonal direction, like the upper transfer material in the laminating direction described above, from both ends. Each force toward the central area is offset and does not adversely affect the transfer material.

  However, in the transfer material in which the central leading occurs, if the central region is hard as described above and both ends are soft, the forces from the both ends to the central region are concentrated in the central region without being canceled, Therefore, wrinkles can occur in the central region of this transfer material. When the transfer material in which the wrinkles are generated in the central area is conveyed to the transfer material conveying belt without the wrinkles being eliminated, and the toner image is transferred to the transfer material, in the central area in which the wrinkles are generated in the transfer material, Transfer defects occur. In addition, if there are wrinkles on the transfer material, there is a risk of poor conveyance.

Therefore, it is necessary to suppress the central leading of the transfer material.
Here, in the color image forming apparatus of Patent Document 1, the transfer material suction roll extends in the orthogonal direction, and both ends of the transfer material suction roll are supported on the color image forming apparatus main body side. That is, in the transfer material suction roll, the rigidity at both ends is higher than the rigidity at the center in the orthogonal direction. Therefore, when the transfer material is sandwiched between the transfer material suction roll and the rotating roll on the upstream side of the transfer material conveyance belt, both ends of the transfer material are sandwiched more strongly than the center region in the orthogonal direction. The part side is conveyed to the central area with a delay. For this reason, in the color image forming apparatus of Patent Document 1, the center leading is promoted rather than being suppressed.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of suppressing the central leading of a recording medium.

  In order to achieve the above object, an invention according to claim 1 is an image forming apparatus, wherein the apparatus main body and a photosensitive member that is detachably attached to the apparatus main body and forms an electrostatic latent image. A photosensitive member unit that holds the recording medium, a conveyance member that is provided in the apparatus main body and conveys a recording medium, and is provided on the photosensitive member unit, and is disposed on the upstream side in the conveyance direction of the recording medium with respect to the conveyance member, A pressing member that presses only a central area of the recording medium in a direction orthogonal to the transport direction, and provided in the apparatus main body, disposed on the upstream side in the transport direction with respect to the transport member, and opposed to the press member And a first guide member that guides the recording medium toward the transport member.

According to a second aspect of the present invention, in the first aspect of the present invention, the pressing member is a roller that can rotate by contacting a recording medium to be conveyed.
The invention described in claim 3 is characterized in that, in the invention described in claim 1 or 2, the pressing member can be brought into contact with or separated from the first guide member.

The invention according to claim 4 is characterized in that, in the invention according to claim 3, the pressing member is capable of contacting the downstream end of the first guide member in the transport direction. .
According to a fifth aspect of the present invention, in the fourth aspect of the present invention, a portion of the downstream end portion of the first guide member in the transport direction that is in contact with the pressing member is downstream in the transport direction. It is the inclined surface which approaches the said conveyance member as it goes to the side.

According to a sixth aspect of the present invention, in the invention according to any one of the third to fifth aspects, the photosensitive member unit has a recording medium facing the first guide member and facing the conveying member. A second guide member for guiding is provided, and the pressing member is supported by the second guide member.
According to a seventh aspect of the invention, in the sixth aspect of the invention, the second guide member is provided with a swingable support member that supports the pressing member. Yes.

The invention according to claim 8 is the invention according to claim 7, wherein the support member includes one end and the other end arranged so as to sandwich the swing center, and the pressing member is supported by the one end. And a pressing member that biases the other end so that the pressing member faces the first guide member.
The invention according to claim 9 is the invention according to claim 8, wherein the support member is arranged such that the one end is disposed downstream of the other end in the transport direction, and the transport direction is downstream. The one end side is inclined so as to approach the recording medium as it goes to.

According to a tenth aspect of the present invention, in the invention according to any one of the seventh to ninth aspects, the photosensitive member unit includes the support member when the photosensitive member unit is detached from the apparatus main body. It is characterized in that a regulating member for regulating the swing is provided.
The invention according to claim 11 is the invention according to any one of claims 1 to 10, which is arranged on the upstream side in the transport direction with respect to the pressing member and contacts at least the central region of the recording medium. Accordingly, a registration roller for feeding the recording medium downstream in the transport direction at a predetermined timing is provided.

According to the first aspect of the present invention, in this image forming apparatus, the photosensitive unit holding the photosensitive member on which the electrostatic latent image is formed is detachably attached to the apparatus main body.
The apparatus main body includes a conveying member that conveys the recording medium, and a first guide that is disposed upstream of the conveying member in the conveying direction of the recording medium (hereinafter, simply referred to as “conveying direction”). And a member.

The photoreceptor unit is provided with a pressing member disposed on the upstream side in the transport direction with respect to the transport member.
Since the pressing member presses only the central area of the recording medium in a direction orthogonal to the transport direction (hereinafter, also referred to as “orthogonal direction”), the pressed central area is disposed to face the pressing member. Pressed against the first guide member.

Thereby, in the recording medium conveyed toward the conveying member, resistance is generated only in the central area, so that the central area is not conveyed before other areas (both ends in the orthogonal direction), and the recording medium Can suppress the center leading.
Here, the photoconductor unit holds the photoconductor on which the electrostatic latent image is formed, and is thus positioned with a relatively high accuracy with respect to the apparatus main body. Accordingly, the pressing member is also positioned with relatively high accuracy, so that the pressing member can accurately press only the central area of the recording medium.

According to the second aspect of the present invention, since the pressing member is a roller that can rotate by contacting the recording medium to be conveyed, the pressing member rotates while pressing the central area of the recording medium. As a result, the resistance of the recording medium is not generated more than necessary. Therefore, the recording medium can be smoothly conveyed toward the conveying member while suppressing the central leading.
According to the third aspect of the present invention, the pressing member can be brought into and out of contact with the first guide member, so that the pressing member has an appropriate strength that does not cause the recording medium to generate more resistance than necessary. Now, the central area of the recording medium can be pressed.

According to invention of Claim 4, a press member can contact | abut to the downstream end part (part nearest to a conveyance member) of the 1st guide member in a conveyance direction.
Thereby, it is possible to suppress the central leading of the recording medium immediately before the conveying member. Therefore, there is no center leading in the recording medium that passes the pressing member toward the conveying member, and the recording medium is quickly transferred to the conveying member while maintaining the state without the central leading, and continues to be conveyed in that state. Is done.

That is, by suppressing the central leading of the recording medium immediately before the conveying member, it is possible to effectively suppress the recording medium from being conveyed to the conveying member in a state where the central leading occurs.
According to the fifth aspect of the present invention, the portion in contact with the pressing member at the downstream end of the first guide member in the transport direction is an inclined surface that approaches the transport member as it goes downstream in the transport direction. As a result, the recording medium passing the pressing member toward the conveying member is smoothly transferred to the conveying member by being guided by the inclined surface. Therefore, smooth conveyance of the recording medium can be achieved.

According to the sixth aspect of the present invention, the photosensitive unit is provided with the second guide member that faces the first guide member and guides the recording medium toward the transport member. Therefore, the recording medium is smoothly guided toward the transport member by being guided not only by the first guide member but also by the second guide member.
Since the pressing member is supported by the second guide member, the second guide member has both the role of guiding the recording medium and the role of supporting the pressing member, so that the number of parts can be reduced. .

According to the invention described in claim 7, since the second guide member is provided with a support member that supports the pressing member and is swingable, the pressing member swings together with the support member. The first guide member can be easily contacted and separated.
According to the eighth aspect of the present invention, in the support member, the pressing member is supported at one end at the one end and the other end disposed so as to sandwich the swing center, and the pressing member on the one end side is the first pressing member. The other end is urged by the urging member so as to face one guide member. Therefore, the pressing member is urged by the urging member, thereby reliably approaching the first guide member and strongly pressing the central area of the recording medium.

According to the ninth aspect of the present invention, the support member is inclined such that one end thereof is disposed downstream of the other end in the transport direction and the one end side approaches the recording medium toward the downstream side in the transport direction. ing.
Accordingly, when the other end of the support member is urged by the urging member and the pressing member on one end approaches the first guide member, the pressing member passes between the pressing member and the first guide member. When the central area of the recording medium to be pressed is pressed, a part of the urging force of the urging member can be applied to the central area on the upstream side in the transport direction. For this reason, resistance is generated only in the central region of the recording medium, and the central leading of the recording medium can be reliably suppressed.

If the support member is inclined as described above, the pressing member can be separated from the first guide member by the reaction force from the recording medium while pressing the recording medium. And the first guide member can pass smoothly.
On the other hand, when the support member is inclined such that the other end is disposed downstream of the one end in the transport direction and the one end approaches the recording medium toward the upstream in the transport direction, the pressing member is Instead of pressing the conveyed recording medium, the recording medium is pressed against the first guide member side to close the gap with the first guide member. In this case, the recording medium cannot pass between the pressing member and the first guide member, and a jam may occur.

According to the tenth aspect of the present invention, the photoconductor unit is provided with the regulating member that regulates the swinging of the support member when the photoconductor unit is detached from the apparatus main body. It is possible to prevent the support member from unnecessarily swinging when it is detached from the apparatus main body.
According to the eleventh aspect of the present invention, the registration roller disposed on the upstream side in the transport direction with respect to the pressing member contacts at least the central region of the recording medium, thereby moving the recording medium downstream in the transport direction at a predetermined timing. Send out. As a result, in the recording medium, the central region is apt to be conveyed before the both ends in the orthogonal direction, so that the central leading is likely to occur after passing through the registration rollers. The central leading of the recording medium can be suppressed by the pressing member on the downstream side in the conveyance direction of the roller.

1. Printer FIG. 1A is a side sectional view showing an embodiment of a printer as an example of an image forming apparatus of the present invention. FIG. 1B is a perspective view of the printer as viewed from the right front side, and shows a state in which a process unit as an example of a photoconductor unit is attached to and detached from a main body casing as an example of an apparatus main body. In addition, when referring to a direction, the illustrated direction arrow is referred to (the same applies to other drawings). Here, the left-right direction and the width direction are the same, and the horizontal direction includes the width direction and the front-rear direction.

  The printer 1 is a color printer. As shown in FIG. 1A, the printer 1 includes a substantially box-shaped main body casing 2 that is long in the front-rear direction. In the main casing 2, four photosensitive drums 3 as an example of photosensitive members are arranged in parallel along the front-rear direction in a rotatable state. In the following, the four photosensitive drums 3 are divided into photosensitive drums 3K (black) and photosensitive drums 3C (depending on the color (black, cyan, magenta or yellow) of a toner image (described later) formed on each photosensitive drum 3. Cyan), photosensitive drum 3M (magenta), and photosensitive drum 3Y (yellow). Each photosensitive drum 3 is mainly provided with a scorotron charger 4 and a developing roller 6 facing each other.

  The surface of the photosensitive drum 3 is uniformly charged by the scorotron charger 4 and then exposed to a laser beam (see the broken arrow in the drawing) emitted from the scanner unit 17 provided on the upper portion of the main casing 2. . Thereby, an electrostatic latent image based on the image data is formed on the surface of each photosensitive drum 3. Each electrostatic latent image is visualized by toner (developer) carried on the developing roller 6 corresponding to each photosensitive drum 3, and a toner image is formed on the surface of the photosensitive drum 3.

  Sheets 100 as an example of a recording medium are accommodated in a vertically stacked state in a sheet feed cassette 7 disposed at the bottom of the main casing 2. Among the sheets 100 stored in the sheet cassette 7, the uppermost sheet 100 is raised while changing the direction from the front side to the rear side by various rollers of the sheet feeding unit 8 provided around the front end of the sheet cassette 7. Then, it is transported to a transport belt 9 as an example of a transport member. Here, the various rollers include a pair of registration rollers 18, and the registration rollers 18 convey the paper 100 from the paper feed cassette 7 toward the conveyance belt 9 at a predetermined timing. The recording medium includes an OHP sheet and the like in addition to the paper 100.

The conveyor belt 9 is disposed between the photosensitive drums 3K, 3C, 3M, and 3Y and the transfer roller 10 facing each photosensitive drum 3. The toner image on the surface of each photosensitive drum 3 is transferred onto the paper 100 conveyed to the conveyor belt 9 by the transfer bias applied to the transfer roller 10 and is sequentially superimposed.
The paper 100 on which the four color toner images have been transferred is conveyed to the fixing unit 11 on the rear side by the conveying belt 9. The toner image transferred onto the paper 100 is thermally fixed by the fixing unit 11. Thereafter, the sheet 100 is raised by various rollers while changing the direction from the rear side to the front side, and is discharged to the discharge tray 12 at the upper part of the main body casing 2.

In this way, the paper 100 is transported between the paper feed cassette 7 and the discharge tray 12 along the vertical direction and / or the front-back direction.
Here, the printer 1 includes four process cartridges 13 corresponding to the respective colors. Hereinafter, the four process cartridges 13 are distinguished from the process cartridge 13K (black), the process cartridge 13C (cyan), the process cartridge 13M (magenta), and the process cartridge 13Y (yellow) corresponding to each color.

The process cartridges 13 are arranged in parallel along the front-rear direction in the main casing 2.
In the casing (process casing 14) of each process cartridge 13, the corresponding photosensitive drum 3, scorotron charger 4, developing roller 6, supply roller 15, and toner hopper 16 are mainly disposed. The central axes (rotating shafts) of the photosensitive drum 3, the developing roller 6, and the supply roller 15 extend along the width direction. In each process cartridge 13, the toner stored in the toner hopper 16 is supplied to the developing roller 6 by the supply roller 15 and is carried on the developing roller 6 as described above.

These process cartridges 13 are unitized and collectively constitute a process unit 50 (see FIG. 1B). A handle 55 is provided at the front end of the process unit 50. The process unit 50 holds the photosensitive drum 3 in each process cartridge 13 and is detachably attached to the main casing 2.
Here, a plate-like cover 51 having a substantially rectangular shape when viewed from the front is provided on the front wall of the main casing 2. The cover 51 is supported on the front wall of the main casing 2 so as to be swingable about a swing shaft 52 provided at the lower end of the front wall of the main casing 2. The swinging shaft 52 extends along the width direction, and the cover 51 swings, as shown in FIG. 1A, extends to a substantially vertical direction and rises up to the front position to the approximately horizontal position. It is possible to move to a separation position (see FIG. 1B) that tilts to the right.

The cover 51 in the approach position approaches the main casing 2 and closes the inside of the main casing 2 from the front side. Specifically, an attachment / detachment port 42 communicating with the inside of the main body casing 2 is formed on the front wall of the main body casing 2, and the cover 51 in the approach position closes the attachment / detachment port 42 from the front side.
As shown in FIG. 1B, the cover 51 in the separated position is separated from the main body casing 2 to the front side, and opens the inside of the main body casing 2 and the attachment / detachment port 42 to the front side. When the cover 51 is in the separated position, the front end portion (the vicinity of the handle 55) of the process unit 50 that is mounted on the main body casing 2 is exposed to the front side from the front wall of the main body casing 2 through the attachment / detachment port 42. .

  Normally, the cover 51 is in the approach position (see FIG. 1A). However, by moving the cover 51 from the approach position to the separation position, the above-described process unit 50 is moved from the front side through the opened opening 42. It can be pushed into the body casing 2 from the drawer or from the front side. That is, when the cover 51 is in the separated position, the process unit 50 can be attached to and detached from the main casing 2. The attachment / detachment direction of the process unit 50 is the front-rear direction. Further, the handle 55 is held when the process unit 50 is attached or detached.

  Here, in addition to the process cartridge 13, the process unit 50 described above includes a frame (process frame 43) that holds the four process cartridges 13 in the front-rear direction. The process frame 43 has a substantially rectangular frame shape with an internal space 44 formed in the center in plan view, and the four process cartridges 13 are inserted into the internal space 44 of the process frame 43, whereby the process frame 43. Retained. The handle 55 described above is attached to an upper portion of the front wall 43A of the process frame 43.

A reference shaft 45 that protrudes outward in the width direction is integrally provided at the front end of the process frame 43, and a recess 46 that is recessed forward is formed at the rear end edge of the process frame 43. . When the process unit 50 is mounted on the main casing 2, the reference shaft 45 engages with the main casing 2 in the process frame 43, and the reference shaft (not shown) on the main casing 2 side engages with the recess 46. . As a result, the process unit 50 is positioned at a predetermined position while being mounted on the main casing 2.
2. Paper Transport Unit As shown in FIG. 1A, the printer 1 includes a paper transport unit 20 for transporting the paper 100 transported from the paper feed cassette 7 to the fixing unit 11. In the following, it is assumed that the process unit 50 is mounted on the main casing 2 and the cover 51 is in the approach position unless otherwise specified.

FIG. 2 is a perspective view of the periphery of the front wall of the process frame of the process unit as viewed from the left rear side. FIG. 3 is an enlarged view of a main part of FIG. 1A around the paper transport unit. In FIG. 3, the process cartridge 13 (see FIG. 1A) is not shown.
In the main casing 2, the paper transport unit 20 is disposed above the paper feed cassette 7 and below each process cartridge 13 (process unit 50). The paper transport unit 20 includes the transport belt 9 and the transfer roller 10 described above, and further includes a frame (transport frame 21), a driving roller 22, and a driven roller 23.

As shown in FIG. 2, the transport frame 21 is formed in a frame shape that is thin in the vertical direction and has a substantially rectangular shape in plan view. In FIG. 2, only the front portion of the transport frame 21 is shown.
The driving roller 22 and the driven roller 23 are opposed to each other with a space in the front-rear direction with the central axes extending in the width direction (see also FIG. 1A). Specifically, the drive roller 22 is supported on the rear end portion of the transport frame 21 (not shown in FIG. 2), and the driven roller 23 is supported on the front end portion of the transport frame 21.

  The conveyor belt 9 is an endless belt made of a resin such as polycarbonate that is wider than the paper 100, and is wound between the driving roller 22 and the driven roller 23 in a state where a predetermined tension is applied (FIG. 1A). See also). That is, the transport belt 9 is supported by the transport frame 21 via the driving roller 22 and the driven roller 23. In the transport belt 9 in this state, at least the upper surface (upper portion 9A) is substantially in the horizontal direction (see also FIGS. 1A and 3). Here, the left end portion 21 </ b> A and the right end portion 21 </ b> B of the conveyance frame 21 protrude outward from the conveyance belt 9 in the width direction over the entire range in the front-rear direction between the driving roller 22 and the driven roller 23.

  Four transfer rollers 10 are provided according to the number of the photosensitive drums 3, and are supported on the upper portion of the transport frame 21. As shown in FIG. 1A, the four transfer rollers 10 are provided with a corresponding photosensitive drum 3 and an upper portion 9 </ b> A of the conveyor belt 9 in the conveyor belt 9 wound between the driving roller 22 and the driven roller 23. They are lined up at an interval in the front-rear direction while facing each other from below.

  During image formation, a driving force from a motor (not shown) provided in the main body casing 2 is transmitted to the driving roller 22 and the driving roller 22 is rotated. Along with this, the conveyor belt 9 rotates in the counterclockwise direction when viewed from the left side, and the driven roller 23 is driven. Thereby, in the conveyor belt 9, the upper portion 9A moves from the front side to the rear side along the substantially horizontal direction.

  Here, when the paper 100 transported from the paper feed cassette 7 and delivered to the transport belt 9 is placed on the upper portion 9A of the transport belt 9, it is transported from the front side toward the rear side, and in the middle Thus, the contact position (transfer position) between each photosensitive drum 3 and the upper portion 9A is sequentially passed. At this time, as described above, the toner images on the surface of each photosensitive drum 3 are sequentially transferred onto the paper 100 and superimposed. Then, the sheet 100 on which the toner image is transferred is further conveyed toward the rear side by the conveyance belt 9 and delivered to the fixing unit 11.

The paper transport unit 20 that transports the paper 100 as described above includes a first guide member 24 and a second guide member 25, as shown in FIG.
The first guide member 24 has a plate shape that is long in the width direction and is wider than the transport belt 9. Although not shown, the first guide member 24 is installed between the front end portion of the left end portion 21A (see FIG. 2) of the transport frame 21 and the front end portion of the right end portion 21B (see FIG. 2). 21 is supported. In this state, the first guide member 24 faces the vicinity of the portion of the transport belt 9 that coincides with the upper end portion of the driven roller 23 from above with a predetermined interval. None of the portions are in contact with the conveyor belt 9. At least the rear side portion of the upper surface of the first guide member 24 is inclined obliquely rearward and downward to form a first guide surface 24A. The first guide surface 24 that inclines in this way is an inclined surface that approaches the upper portion 9A of the transport belt 9 from above as it goes rearward.

A guard 26 is integrally attached to the first guide member 24. The guard 26 extends downward along the curved portion 9B that curves along the outer peripheral surface of the driven roller 23 at the front end portion of the transport belt 9, and faces the curved portion 9B from the front with a predetermined interval. is doing. Thereby, the guard 26 is protecting the curved part 9B from the front side.
The second guide member 25 has a plate shape that is long in the width direction and has substantially the same width direction dimensions as the first guide member 24. As shown in FIG. 2, the second guide member 25 is integrally provided on the rear side surface of the front wall 43 </ b> A of the process frame 43 of the process unit 50, not the transfer frame 21. The rear side surface of the front wall 43A is a surface facing the internal space 44 (see also FIG. 1B) of the process frame 43 from the front side. The second guide member 25 forms the lower end of the front wall 43A and protrudes rearward from the rear side surface of the front wall 43A.

  As shown in FIG. 3, in a state in which the process unit 50 is mounted on the main casing 2, the second guide member 25 is spaced from the first guide member 24 without contacting the transport belt 9. Opposite from. The entire second guide member 25 is inclined obliquely rearward and downward, as is the case with the first guide surface 24A (see also FIG. 2). Specifically, the inclination angle of the second guide member 25 with respect to the horizontal plane (see the upper portion 9A of the conveyor belt 9) is larger than the inclination angle of the first guide surface 24A with respect to the horizontal plane.

  Further, the lower surface of the inclined second guide member 25 is opposed to the upper surface of the first guide member 24 (including the first guide surface 24A) from above, and is defined as the second guide surface 25A. The The second guide surface 25A is curved so as to protrude smoothly upward from the front side to the rear side, and then inclined downward and obliquely rearward so as to approach the first guide surface 24A toward the rear side. is doing.

  Here, the space 40 sandwiched from above and below by the upper surface of the first guide member 24 and the second guide surface 25 </ b> A has a substantially triangular shape that narrows toward the rear side in the left side view, and is wider than the paper 100. It is. The rear end of the space 40 faces the upper portion 9A of the conveyor belt 9 from the front upper side. The pair of registration rollers 18 described above are arranged in contact with each other at a position facing the space 40 from the front side. These registration rollers 18 are rotatably supported by the rear side of the cover 51, not the transport frame 21, and form a part of the paper transport unit 20.

As shown in FIG. 2, a support member 30 and a pressing member 31 are provided below the center of the upper surface of the second guide member 25 in the width direction.
The support member 30 is slightly longer in the width direction and has a substantially rectangular plate shape in plan view (see the portion indicated by dots, and the same applies to FIGS. 1A and 3).
The support member 30 is swingably supported by the second guide member 25 in a state where the support member 30 is inclined obliquely rearward and downward along the second guide member 25. As shown in FIG. 3, the swing center 30A of the support member 30 is substantially at the center in the vertical (front-rear) direction of the support member 30 in the left side view, and the swing axis of the support member 30 is the swing center 30A. And extends in the width direction. Here, the lower end (rear end) of the support member 30 is one end 30B, and the upper end (front end) of the support member 30 is the other end 30C. The swing center 30A is sandwiched by the one end 30B and the other end 30C from the up and down direction. When the support member 30 swings, the one end 30B and the other end 30C move up and down. Specifically, when one end 30B is raised, the other end 30C is lowered, and when one end 30B is lowered, the other end 30C is raised.

  Here, as shown in FIG. 2, protrusions 53 that protrude outward in the width direction as an example of a regulating member are integrally provided on each of the left and right edges in the vicinity of one end 30 </ b> B of the support member 30. In other words, these protrusions 53 are provided on the process frame 43 (process unit 50) via the support member 30 and the second guide member 25. As shown by dotted lines, these protrusions 53 are arranged so as to sink under a portion (referred to as an engaged portion 54) adjacent to the one end 30 </ b> B of the support member 30 from the left and right in the second guide member 25. . Therefore, if one end 30B tries to rise more than necessary due to the swing of the support member 30, each projection 53 engages with the corresponding engaged portion 54 from below, so that the one end 30B cannot rise any further. Accordingly, the swinging of the support member 30 stops. Of course, when the process unit 50 is attached to the main casing 2, and even when the process unit 50 is detached from the main casing 2, the protrusion 53 is engaged with the engaged portion 54, The swinging of the support member 30 in the clockwise direction in the left side view is restricted.

  As shown in FIG. 3, a boss 32 protruding downward is integrally provided on the lower surface of the other end 30 </ b> C of the support member 30, and the upper surface of the second guide member 25 is opposed to the boss 32 of the support member 30. A boss 33 that protrudes upward is integrally provided at a portion facing from below. A spring 34 as an example of an urging member included in the printer 1 is interposed between the boss 32 and the boss 33. Therefore, the other end 30 </ b> C provided with the boss 32 is urged upward by a spring 34 that tries to extend upward (strictly, obliquely rearwardly upward). Accordingly, the entire support member 30 is urged so as to swing counterclockwise as viewed from the left side, and therefore, the one end 30B is directed downward (strictly, obliquely downward on the front side, solid line) (See the biasing force A indicated by the arrow).

  The pressing member 31 is a roller that is long in the width direction and has a central axis extending in the width direction. The pressing member 31 is rotatably supported by one end 30 </ b> B of the support member 30. In other words, the pressing member 31 is provided in the process unit 50 and supported by the second guide member 25 via the support member 30. In a state where the support member 30 is supported by the second guide member 25, the pressing member 31 is arranged on the rear side (specifically, the rear end of the space 40 described above) with respect to the second guide member 25, The lower portion of the outer peripheral surface of the member 31 faces the rear end portion of the upper surface (first guide surface 24A) of the first guide member 24 from above.

  In this state, since the support member 30 is swingable as described above, the pressing member 31 moves up and down as the support member 30 swings, thereby contacting the rear end portion of the first guide surface 24A. Can be separated. In the normal state, as described above, the other end 30C of the support member 30 is urged by the spring 34, so that the one end 30B is urged downward, so that the pressing member 31 supported by the one end 30B is the first guide. It is urged downward to face the rear end of the surface 24A. Therefore, when there is nothing between the pressing member 31 and the first guide surface 24A, the pressing member 31 is in contact with the rear end portion of the first guide surface 24A from above.

Here, as described above, when the protrusion 53 of the support member 30 is engaged with the engaged portion 54 of the second guide member 25, the support member 30 is swung in the clockwise direction in the left side view. It is regulated (see Fig. 2). Therefore, in a state where the process unit 50 is mounted on the main casing 2, the pressing member 31 is lifted and separated from the first guide member 24 by the support member 30 swinging more than necessary in the clockwise direction. Can be prevented.
3. Paper Transport Here, the flow of transporting the paper 100 of the paper feed cassette 7 shown in FIG. 1A to the transport belt 9 will be described in detail. In the following, it is assumed that the process unit 50 is continuously mounted on the main casing 2.

As described above, the uppermost sheet 100 among the sheets 100 stored in a stacked state in the sheet feeding cassette 7 is distinguished from the various rollers (registration rollers 18 provided around the front end of the sheet feeding cassette 7. , The conveying roller 19) is first conveyed between the pair of registration rollers 18.
The pair of registration rollers 18 sandwich the leading end of the conveyed paper 100 (the downstream end in the transport direction, the same applies hereinafter), and rotate at a predetermined timing, thereby causing the paper 100 to move downstream in the transport direction. It sends out toward the conveyor belt 9. At this time, the pair of registration rollers 18 feeds the paper 100 by contacting at least the central region 100A (see FIG. 2) in the width direction (direction orthogonal to the conveyance direction of the paper 100) of the paper 100. In FIG. 3, the leading end X of the sheet 100 immediately after being sent out by the registration roller 18 is shown.

  The sheet 100 sent out by the registration roller 18 is conveyed rearward and enters the space 40 (a space sandwiched from above and below by the upper surface of the first guide member 24 and the second guide surface 25A) from the front side. The sheet 100 is continuously conveyed rearward (specifically, obliquely rearward and upward) and contacts the front end portion of the second guide surface 25A. Here, as described above, the second guide surface 25A is curved so as to protrude smoothly upward from the front side toward the rear side, and then approaches the first guide surface 24A toward the rear side. As shown in FIG. Therefore, the sheet 100 that has contacted the front end portion of the second guide surface 25A does not bend at the curved portion of the first guide surface 24A, and then in the space 40 along the rear portion of the second guide surface 25A. Is conveyed obliquely rearward and downward. At this time, the front end of the paper 100 is marked with a symbol Y.

Thereafter, the sheet 100 continues to be conveyed obliquely rearward and downward along the second guide surface 25A, and reaches a contact portion between the pressing member 31 and the rear end portion of the first guide surface 24A. At this time, the leading end of the paper 100 is marked with a symbol Z. Thus, the second guide 25 guides the paper 100 toward the transport belt 9 on the downstream side in the transport direction on the second guide surface 25A.
Here, in the paper 100, the above-described central region 100A and the pressing member 31 coincide with each other in the width direction (see FIG. 2). Therefore, in the paper 100, only the central region 100A reaches the contact portion between the pressing member 31 and the rear end portion of the first guide surface 24A. Since the sheet 100 is conveyed rearward from the registration roller 18, the rear end portion of the first guide surface 24 </ b> A is a downstream end portion of the first guide member member 24 in the conveyance direction of the sheet 100.

When the central region 100A (see FIG. 2) of the paper 100 (specifically, the leading end Z of the paper 100) reaches the contact portion between the pressing member 31 and the rear end portion of the first guide surface 24A, the paper 100 is upstream in the transport direction. Since the side portion is sandwiched between the pair of registration rollers 18, the paper 100 is continuously conveyed backward by the rotating registration rollers 18.
Therefore, the central region 100A at the leading end Z of the paper 100 pushes the pressing member 31 upward against the urging force of the spring 34 and separates it from the rear end portion of the first guide surface 24A. It advances to the rear side through a gap formed between the guide surface 24A. Accordingly, the leading end Z of the paper 100 passes through the pressing member 31 to the rear side in the left side view over the entire region in the width direction. As a result, the entire sheet 100 is continuously conveyed backward.

  While the sheet 100 passes through the pressing member 31, only the central region 100A of the sheet 100 is moved to the first guide by the pressing member 31 that is directed toward the rear end portion of the first guide surface 24A by the biasing force of the spring 34. It is pressed from above toward the surface 24A and is pressed against the first guide surface 24A. Accordingly, an area other than the central area 100A in the width direction on the paper 100 is not pressed against the first guide surface 24A, but approaches the first guide surface 24A. Here, as described above, the first guide surface 24A is inclined so as to approach the upper portion 9A of the transport belt 9 from above as it goes to the rear side (downstream in the transport direction). Therefore, the sheet 100 conveyed to the rear side while approaching the first guide surface 24A is guided to the upper portion 9A of the conveyance belt 9 by the first guide surface 24A. In this way, the first guide 24 guides the paper 100 toward the transport belt 9 on the downstream side in the transport direction on the first guide surface 24A. Further, since the pressing member 31 is rotatable, it comes into contact with the upper surface of the central region 100A of the paper 100 passing between the pressing member 31 and the rear end portion of the first guide surface 24A, so that the paper 100 rotates while rotating. The central area 100A is pressed.

Thus, the sheet 100 guided to the upper portion 9A of the transport belt 9 is placed (passed) on the upper portion 9A and is transported to the rear side as described above.
As described above, the paper 100 of the paper feed cassette 7 passes through the registration roller 18, the second guide member 25, the pressing member 31, and the first guide member 24 in order from the upstream side in the transport direction, and then the transport belt 9. Is passed on. Therefore, the pressing member 31 and the first guide member 24 are arranged on the upstream side in the conveyance direction of the paper 100 with respect to the conveyance belt 9, and the registration roller 18 is arranged on the upstream side in the conveyance direction with respect to the pressing member 31. I understand.

  Further, as shown in FIG. 1A, in the paper transport unit 20, the transport belt 9, the transfer roller 10, the transport frame 21, the drive roller 22, the driven roller 23, and the first guide member 24 are provided in the main body casing 2. However, the registration roller 18 is provided on the cover 51, and the second guide member 25, the support member 30, and the pressing member 31 are provided on the process unit 50 (process frame 43).

The transport belt 9, the transfer roller 10, the transport frame 21, the drive roller 22, the driven roller 23, and the first guide member 24 are unitized to form a belt unit 56. Like the process unit 50, the belt unit 56 can be attached to and detached from the main casing 2 from the front side after the cover 51 is moved to the separated position (see FIG. 1B). Here, the process unit 50 can be moved in a state where the lower end portions of the second guide member 25 on the process unit 50 side, the support member 30 and the pressing member 31 are spaced upward from the first guide member 24 on the belt unit 56 side. For example, only the process unit 50 can be attached to and detached from the main casing 2 without the belt unit 56 interfering with the process unit 50.
4). As described above, in this printer 1, as shown in FIG. 1A, the process unit 50 holding the photosensitive drum 3 on which the electrostatic latent image is formed is detachably attached to the main body casing 2. Has been.

As shown in FIG. 3, the main casing 2 includes a conveyance belt 9 that conveys the paper 100 and a first guide member 24 that is disposed on the upstream side of the conveyance belt 9 in the conveyance direction of the paper 100. Is provided.
Further, the process unit 50 is provided with a pressing member 31 disposed on the upstream side in the transport direction with respect to the transport belt 9.

Since the pressing member 31 presses only the central region 100A of the paper 100 in the orthogonal direction (width direction) orthogonal to the transport direction (see also FIG. 2), the pressed central region 100A faces the pressing member 31. It is pressed against the arranged first guide member 24.
2, in the paper 100 conveyed toward the conveyance belt 9, resistance is generated only in the central region 100A, so that the central region 100A is more than the other regions (both end portions 100B in the width direction). It is not transported first, and the central leading of the paper 100 can be suppressed.

  Here, since the process unit 50 holds the photosensitive drum 3 on which the electrostatic latent image is formed, the process unit 50 is positioned with a relatively high accuracy with respect to the main body casing 2 at the reference shaft 45 and the recess 46 (see FIG. 1B). The As a result, the pressing member 31 provided in the process unit 50 is also positioned with relatively high accuracy, so that the pressing member 31 can accurately press only the central region 100A of the paper 100.

In addition, as shown in FIG. 3, if the pressing member 31 presses at least the front end (see the front end Z) in the central region 100 </ b> A, not only the center leading of the front end Z but also the front end Z on and after the front end Z in the paper 100. Since the central leading in the upstream region in the transport direction is also suppressed, the central leading in the entire transport direction of the paper 100 can be reliably suppressed as a result.
In addition, referring to FIG. 2, when the sheet 100 tries to be in the center, a force is generated in the width direction from both end portions 100B toward the center region 100A, but the pressing member 31 presses only the center region 100A. Since a force from the central region 100A toward both ends 100B is applied to the sheet 100, the force in the width direction is canceled in the sheet 100.
(2) As shown in FIG. 2, the pressing member 31 is a roller that can rotate by contacting the conveyed paper 100 without receiving a driving force such as a motor. In the middle of pressing, the sheet 100 does not cause more resistance than necessary by rotating. Therefore, it is possible to smoothly convey the sheet 100 toward the conveyance belt 9 while suppressing the central leading.
(3) As shown in FIG. 3, the pressing member 31 can be brought into contact with and separated from the first guide member 24. The central region 100A of the paper 100 can be pressed with strength.

Here, since the pressing member 31 does not contact the conveying belt 9, the conveying belt 9 is not worn due to the pressing member 31.
(4) The pressing member 31 can come into contact with the downstream end of the first guide member 24 in the transport direction (the rear end of the first guide surface 24A and the portion closest to the transport belt 9).
Accordingly, it is possible to suppress the central leading of the paper 100 immediately before the conveyance belt 9. Therefore, there is no central leading of the paper 100 passing the pressing member 31 toward the transport belt 9, and the paper 100 is quickly transferred to the transport belt 9 while maintaining the state without the central leading. Will continue to be transported.

That is, by suppressing the central leading of the paper 100 immediately before the transport belt 9, it is possible to effectively suppress the transport of the paper 100 to the transport belt 9 in the state where the central leading occurs.
(5) The rear end portion of the first guide surface 24A, which is a portion in contact with the pressing member 31 at the downstream end portion of the first guide member 24 in the transport direction, is directed toward the downstream side (rear side) in the transport direction. It is an inclined surface that approaches the conveyor belt 9. As a result, the paper 100 that passes the pressing member 31 toward the conveyance belt 9 is smoothly transferred to the conveyance belt 9 by being guided by the first guide surface 24A. Therefore, smooth conveyance of the paper 100 can be achieved.
(6) As shown in FIG. 3, the process unit 50 includes a second guide member 25 that faces the first guide member 24 and guides the paper 100 toward the conveyance belt 9. Therefore, the paper 100 is smoothly guided toward the transport belt 9 by being guided not only by the first guide member 24 but also by the second guide member 25.

Since the pressing member 31 is supported by the second guide member 25, the second guide member 25 has both the role of guiding the paper 100 and the role of supporting the pressing member 31, so the number of parts can be reduced. Can be planned.
Conversely, if the second guide member 25 does not support the pressing member 31, an iron shaft or the like extending in the width direction is provided on the front wall 43A of the process frame 43, and the pressing member 31 is not supported by this iron shaft. In this case, the cost is higher than when the second guide member 25 supports the pressing member 31.
(7) Since the second guide member 25 is provided with the support member 30 that supports the pressing member 31 and is swingable, the pressing member 31 swings together with the support member 30, thereby the first guide. The member 24 can be easily contacted and separated.
(8) In the support member 30, the pressing member 31 is supported by the one end 30B at the one end 30B and the other end 30C arranged so as to sandwich the swing center 30A, and the pressing member 31 on the one end 30B side is the first The other end 30 </ b> C is biased by the spring 34 so as to face the one guide member 24. Therefore, the pressing member 31 is surely approached to the first guide member 24 by being biased by the spring 34, and can strongly press the central region 100 </ b> A of the paper 100.
(9) The support member 30 is obliquely rearward so that the one end 30B is disposed on the downstream side (rear side) with respect to the other end 30C in the transport direction, and the one end 30B side approaches the sheet 100 toward the downstream side in the transport direction. It is inclined downward on the side.

  Thereby, in the support member 30, when the other end 30 </ b> C is urged by the spring 34 and the pressing member 31 on the one end 30 </ b> B side is lowered and approaches the first guide member 24, the pressing member 31 is separated from the pressing member 31. When the central region 100A of the paper 100 passing between the first guide member 24 is pressed, the urging force of the spring 34 (the urging force toward the diagonally downward front shown by the solid line arrow in the figure) is applied to the central region 100A. A part of (see A) (refer to the forward component force C indicated by the dotted arrow in the figure. Note that another component force orthogonal to the component force C is denoted by B) upstream in the transport direction. Can act on the side (ie, the front side). Therefore, resistance is generated only in the central region 100A of the paper 100, and the central leading of the paper 100 can be reliably suppressed.

If the support member 30 is inclined as described above, the pressing member 31 can be separated from the first guide member 24 by the reaction force from the paper 100 while pressing the paper 100, so that the paper 100 is The pressure member 31 and the first guide member 24 can pass smoothly.
On the other hand, the other end 30C is disposed downstream of the one end 30B in the transport direction, and the support member 30 moves from the other end 30C to the one end 30B so that the one end 30B side approaches the sheet 100 as it goes upstream in the transport direction. In the case where the pressing member 31 is inclined obliquely downward toward the front side, the pressing member 31 is pressed against the first guide member 24 side by the sheet 100 instead of pressing the conveyed sheet 100. It closes the gap. In this case, the paper 100 cannot pass between the pressing member 31 and the first guide member 24, and a jam may occur.
(10) As shown in FIG. 2, the process unit 50 is provided with a protrusion 53 that restricts the swinging of the support member 30 when the process unit 50 is detached from the main casing 2. It is possible to prevent the support member 30 from unnecessarily swinging when it is detached from the main casing 2.
(11) As shown in FIG. 3, the registration roller 18 disposed on the upstream side in the transport direction with respect to the pressing member 31 contacts at least the central region 100 </ b> A of the paper 100 to the downstream side in the transport direction at a predetermined timing. The paper 100 is sent out. As a result, in the paper 100, the central region 100A is inevitably easily conveyed before both end portions 100B (see FIG. 2) in the width direction, so that the central leading is likely to occur after passing through the registration roller 18. Even in such a case, the central leading of the paper 100 can be suppressed by the pressing member 31 on the downstream side in the conveyance direction of the registration roller 18.
5). In the above embodiment, as shown in FIG. 3, the pressing member 31 provided at one end 30 </ b> B of the support member 30 is urged toward the paper 100 using the spring 34, but the support member 30, Instead of the spring 34 and the pressing member 31, for example, an elastic film may be used. In that case, the film is attached to the process frame 43 (specifically, the second guide member 25) in a bent state in advance, and when the bent film is restored to its original shape, the tip of the film is The pressing member 31 is used to press the central area of the paper 100.

  In the above embodiment, the printer configured to expose the photosensitive drum 3 with a laser to form an electrostatic latent image is illustrated, but the present invention can also be applied to a printer configured to expose the photosensitive drum 3 with an LED. Furthermore, the present invention can be applied to all types of image forming apparatuses that transport the paper 100 using the transport belt 9.

1 is a side sectional view showing an embodiment of a printer as an example of an image forming apparatus of the present invention. FIG. 2 is a perspective view of the printer as viewed from the right front side, and shows a state where a process unit as an example of a photosensitive unit is attached to and detached from a main body casing as an example of an apparatus main body. It is the perspective view which looked at the front wall periphery of the process frame of a process unit from the left rear side. FIG. 1B is an enlarged view of a main part of FIG. 1A around a paper transport unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 2 Main body casing 3 Photosensitive drum 9 Conveyance belt 18 Registration roller 24 1st guide member 24A 1st guide surface 25 2nd guide member 30 Support member 30A Swing center 30B One end 30C The other end 31 Press member 34 Spring 50 Process unit 53 Protrusion 100 Paper 100A Central area

Claims (11)

The device body;
A photoreceptor unit that is detachably attached to the apparatus main body and holds a photoreceptor on which an electrostatic latent image is formed;
A conveying member provided in the apparatus main body for conveying a recording medium;
A pressing member that is provided in the photosensitive unit, is disposed upstream of the transport member in the transport direction of the recording medium, and presses only a central region of the recording medium in a direction orthogonal to the transport direction;
A first guide member provided on the apparatus main body, disposed on the upstream side in the transport direction with respect to the transport member, facing the pressing member, and guiding a recording medium toward the transport member. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the pressing member is a roller that can be rotated by contacting a recording medium to be conveyed.   The image forming apparatus according to claim 1, wherein the pressing member is capable of contacting and separating from the first guide member.   The image forming apparatus according to claim 3, wherein the pressing member is capable of contacting a downstream end portion of the first guide member in the transport direction.   The portion of the downstream end portion of the first guide member in the transport direction that is in contact with the pressing member is an inclined surface that approaches the transport member toward the downstream side in the transport direction. Item 5. The image forming apparatus according to Item 4. The photoreceptor unit includes a second guide member that opposes the first guide member and guides the recording medium toward the transport member,
The image forming apparatus according to claim 3, wherein the pressing member is supported by the second guide member.   The image forming apparatus according to claim 6, wherein the second guide member is provided with a swingable support member that supports the pressing member. The support member includes one end and the other end arranged so as to sandwich the swing center, and supports the pressing member at the one end.
The image forming apparatus according to claim 7, further comprising an urging member that urges the other end so that the pressing member faces the first guide member.   The support member is inclined such that the one end is disposed downstream of the other end in the transport direction and the one end approaches the recording medium toward the downstream in the transport direction. The image forming apparatus according to claim 8.   10. The photoconductor unit is provided with a regulating member for regulating rocking of the support member when the photoconductor unit is detached from the apparatus main body. An image forming apparatus according to claim 1.   A registration roller is provided on the upstream side in the conveyance direction with respect to the pressing member, and includes a registration roller that sends the recording medium downstream in the conveyance direction at a predetermined timing by contacting at least the central region of the recording medium. The image forming apparatus according to claim 1.

Images