JP2017009904A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can satisfy rigidity in attaching a separation member for separating a sheet material to a transfer part and a request for accuracy of position with respect to a transfer body.SOLUTION: In an image forming apparatus comprising: a transfer part 30 that transfers a toner image carried on an intermediate transfer belt 32 being a transfer body to a sheet material S; and a fixing part 60 that is arranged on the downstream side of the transfer part 30 in a direction of conveyance of the sheet material S and fixes the toner image transferred to the sheet material S by the transfer part 30 to the sheet material S, a separation guide 50 separating the sheet material S from the intermediate transfer belt 32 for guidance is swingably supported by a fixing frame 63 constituting the fixing part 60 and arranged in proximity with and opposite to the intermediate transfer belt 32 at a free end on the upstream side in the conveyance direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus including a transfer unit that transfers a toner image onto a sheet material and a fixing unit that fixes the toner image, and more particularly, to a support structure for a separation member for improving the separation of the sheet material at the transfer unit. .

In recent years, the environment surrounding image forming devices is also growing in demand for ecology, and one of them is support for eco-friendly media, such as thin paper that uses less forest resources and recycled paper that uses a high percentage of recycled materials. There is. These eco-friendly media are weak as a sheet material, and tend to curl when heat is applied at the fixing unit, which causes various problems in realizing stable sheet conveyance. Yes.
One of the problems caused by thin paper and recycled paper is jamming of a sheet material around a transfer body on which a toner image to be transferred is formed, such as a photosensitive drum or an intermediate transfer belt.

In other words, the image forming apparatus includes a transfer unit that transfers a toner image formed on a transfer body to a sheet material, and a toner that is disposed on the downstream side of the transfer unit in the conveyance direction of the sheet material and is transferred to the sheet material by the transfer unit. A fixing unit that fixes the image on the sheet material.
In the transfer unit, the toner image on the image carrier is transferred to the sheet material using a transfer bias, and thus the sheet material that has passed through the transfer unit is attracted to the surface of the transfer member. It is separated from the transfer body without following the curvature. At this time, if the stiffness of the sheet material is weak, the traveling direction of the leading edge of the sheet material is greatly bent toward the transfer body, and if the leading edge of the sheet material is bent so much that the leading edge of the sheet material is not properly guided to the fixing portion located downstream of the transfer portion, Occur.

  Therefore, it is conceivable to use a separation member in order to reliably separate the sheet material that has passed through the transfer portion from the transfer body. That is, it is a method in which the leading end of the separating member is inserted into the leading end of the sheet material that slightly floats from the transfer body, and the sheet material is forcibly separated from the transfer body. Such a separating member for separating the sheet material is described in Patent Documents 1 and 2, for example.

JP 2013-57886 A JP 2013-41070 A

However, when the separation member is provided, it is necessary to position the separation member with respect to the transfer body with high accuracy, and the separation member damages the surface of the transfer body even when vibration or impact is applied during distribution. There is also a need for mounting rigidity.
However, in recent years, with the progress of miniaturization of image forming apparatuses, the transfer unit and the fixing unit have a layout that is very close to each other in the sheet material conveyance direction. Therefore, it is difficult to arrange a frame structure having sufficient strength and dimensional accuracy for attaching a separating member between the transfer portion and the fixing portion, and there is a problem that it is very difficult to dispose the separating member. .
The present invention has been made to solve the above-described problems of the prior art, and includes a separating member that can satisfy the requirements of mounting rigidity and positional accuracy with respect to the transfer body even when the space between the transfer section and the fixing section is narrow. Another object of the present invention is to provide an image forming apparatus.

In order to achieve the above object, the present invention provides:
A transfer unit for transferring the toner image carried on the transfer body to a sheet material;
An image forming apparatus comprising: a fixing unit that is disposed downstream of the transfer unit in a sheet conveyance direction and fixes a toner image transferred to the sheet material in the transfer unit to the sheet material;
A separation member for separating the sheet material from the transfer body is disposed between the transfer portion and the fixing portion, and the separation member is supported by a fixing frame constituting the fixing portion.

  According to the present invention, even in an image forming apparatus pursuing miniaturization, it is possible to stably guarantee the mounting rigidity of the separation member of the transfer portion and the positional accuracy with respect to the image carrier. Due to this effect, good transfer and separation properties are realized even for sheet materials such as thin paper and recycled paper, which are weak and easily curl.

(A), (b) is operation | movement explanatory drawing of the separation guide interlock | cooperated with opening / closing of the conveyance path door of the image forming apparatus which concerns on Embodiment 1 of this invention. (A) thru | or (c) is operation | movement explanatory drawing of operation | movement of the separation guide of FIG. 1, and a positioning method, (d) is a fragmentary perspective view of a separation guide. (A) thru | or (c) is explanatory drawing which shows the behavior of the sheet | seat material when the separation guide of FIG. 1 is provided, and when there is no separation guide. FIG. 2 is a schematic cross-sectional view illustrating an overall configuration of the image forming apparatus in FIG. 1. (A), (b) is operation | movement explanatory drawing of the separation guide interlock | cooperated with the position of the process cartridge of the image forming apparatus which concerns on Embodiment 2 of this invention. (A) thru | or (c) is operation | movement explanatory drawing of operation | movement of the separation guide of FIG. 5, and the positioning method, (d) is a figure of the elongate hole vicinity where a separation guide is supported. (A) is a schematic sectional drawing which shows the whole structure of the image forming apparatus which concerns on Embodiment 2 of this invention, (b) is a figure which shows an example of positioning of a photosensitive drum.

Hereinafter, the present invention will be described in detail based on illustrated embodiments.
Embodiment 1
1 to 4 show an image forming apparatus according to Embodiment 1 of the present invention.
First, the overall configuration of the image forming apparatus will be described with reference to FIG.
This image forming apparatus is a color laser printer, and a transfer unit 30 that transfers a toner image formed on an intermediate transfer belt 32 as a transfer member to a sheet material S, and a downstream side of the transfer unit 30 in the conveyance direction of the sheet material S. And a fixing device 60 as a fixing unit disposed in the.

That is, in the printer main body 1 as an image forming apparatus main body, a sheet feeding tray 21 as a sheet stacking unit, an optical unit 10, an image forming station 11 as an image forming unit, and an intermediate transfer unit 34 are sequentially arranged from bottom to top. They are arranged so as to overlap. The transfer unit 30 is provided at one end in the horizontal direction of the intermediate transfer unit 34, that is, at the right end in the illustrated example, and the fixing device 60 is disposed above the transfer unit 30.
The conveyance path of the sheet material S passes from one end of the paper feed tray 21 (right end in the drawing) to one side of the optical unit 10 and the image forming station 11, passes through the transfer unit 30, the fixing device 60, and the upper surface of the printer main body 1. This is a so-called C-path transport path that reaches the paper discharge tray 27 serving as a paper discharge unit.

The image forming station 11 includes yellow (Y), magenta (M), cyan (C), and black (K
), A plurality of process cartridges 6 (indicated by 6Y, 6M, 6C, and 6K in the figure) that are image forming units for forming a primary image are arranged in parallel. The process cartridge 6 includes a photosensitive drum 12, a charger 13 that uniformly charges the surface of the photosensitive drum 12, a developing device 14 that develops an electrostatic latent image formed on the photosensitive drum 12 into a toner image, and a photosensitive drum. The cleaner 15 is configured to remove residual toner remaining on the body drum 12. Between the charger 13 and the developing unit 14, the surface of the uniformly charged photosensitive drum 12 is irradiated with the laser light from the optical unit 10 to form an electrostatic latent image.

  The optical unit 10 irradiates a laser beam on the photosensitive drum 12 based on the image data, and draws an optical image according to the image data. The image forming apparatus according to the present embodiment employs a configuration in which a single optical unit 10 performs laser irradiation on the photosensitive drum 12 of each process cartridge 6. The image data is print data transmitted from an external device such as a PC, for example, and is received by a controller (not shown) that controls the printer body 1 and output from the controller to the optical unit 10. Further, a primary transfer roller 33 for primarily transferring a toner image developed on the surface of the photosensitive drum 12 to the intermediate transfer belt 32 of the intermediate transfer unit 34 at a position opposite to the photosensitive drum 12 of each process cartridge 6. Is arranged.

In the intermediate transfer unit 34, an intermediate transfer belt 32 as a transfer body is wound around a driving roller 31 and a driven roller 37 incorporated in a transfer frame 34a. The transfer unit 30 is a secondary transfer unit, and includes a nip portion where the driving roller 31 and the transfer roller 24 are pressed against each other via the intermediate transfer belt 32. The toner image carried on the intermediate transfer belt 32 is a sheet material. Secondary transfer onto S, ie retransfer. The toner remaining on the intermediate transfer belt 32 without being transferred to the sheet material S in the transfer unit 30 is collected by the belt cleaner 18 disposed on the driven roller 37 side opposite to the drive roller 31.
The fixing device 60 includes a heating rotator 61, a pressure roller 62 pressed against the heating rotator 61, a first fixing frame 63 that supports the heating rotator 61, and a second fixing frame that supports the pressing roller 62. 64.

  When the sheet material S stacked and stored in the paper feed tray 21 is fed by the paper feed conveyance unit 20, it is conveyed upward along the conveyance path 22. In the conveyance path 22, a registration roller pair 23, a transfer unit 30, and a fixing device 60 are disposed. In the registration roller pair 23, the final skew correction of the sheet material, the timing of image writing in the transfer unit 30 and the conveyance of the sheet material are performed, sent to the transfer unit 30, and after transfer, to the fixing device 60. The toner image on the sheet material S is fixed as a permanent image.

On the downstream side of the fixing device 60, a discharge path 38 that continues to the discharge roller 26 for discharging the sheet material S from the printer main body 1, and a reverse roller 35 for reversing the conveyance direction of the sheet material S during double-sided printing. And an inversion path 39 having. Which path the sheet material S is guided to can be selected by switching the reverse flapper 36.
With respect to the second side of single-sided printing and double-sided printing, the sheet material S is guided to the discharge path 38 and discharged outside the apparatus by the paper discharge roller 26. The discharged sheet material S is stacked on a paper discharge tray 27 provided at the top of the printer main body 1.
On the other hand, the first sheet of double-sided printing is guided to the reversing path 39, and then the conveying direction is reversed by the reversing roller 35 and conveyed to the double-sided conveying path 28 for returning to the image forming path. The double-sided conveyance path 28 is provided with a double-sided conveyance roller 29 for refeeding the sheet material S that has been reversely conveyed by the reverse roller 35 to the transfer unit 30.

The image forming apparatus according to the present embodiment includes a transport path door 40 as an opening / closing body that can open and close the entire transport path 22 including the transfer unit 30. The lower end of the transport path door 40 is rotatably supported by the printer main body 1 via a hinge portion, and the transport path 22 is indicated by a dotted line in the drawing.
The part extending from the fixing device 60 to the upper end surface of the printer main body 1 is divided and opened and closed.

FIG. 1A partially shows a state before the conveyance path door 40 is opened, and FIG. 1B partially shows a state after the conveyance path door 40 is opened.
As shown in FIG. 1B, the intermediate transfer unit 34 can be attached to and detached from the printer body 1 with the conveyance path door 40 opened. In FIG. 1B, the alternate long and short dash line indicates the attachment / detachment locus range X of the intermediate transfer unit 34, with the upper edge being the upper locus and the lower edge being the lower locus. The intermediate transfer unit 34 is disposed so as to be inclined downward toward the conveyance path 22 with respect to the horizontal. From the beginning to the middle of the drawing, the intermediate transfer unit 34 is drawn obliquely downward, and is drawn almost horizontally from the middle.

Next, the separation structure of the sheet material S in the transfer unit 30 that is a feature of the present invention will be described with reference to FIGS.
In the present invention, for the purpose of assisting the separation of the sheet material S, which is a medium such as thin paper, separation as a separation member for separating and guiding the sheet material S from the intermediate transfer belt 32 between the transfer unit 30 and the fixing device 60. A guide 50 is arranged. The separation guide 50 is supported by the first fixing frame 63 of the fixing device 60, and the free end, which is the upstream end portion in the transport direction, faces the surface of the intermediate transfer belt 32 so as to face the front end of the sheet material S. The transfer belt 32 is surely separated. The separation guide 50 also functions as a guide member that guides the side surface of the sheet material on the image surface side in the conveyance path between the transfer unit 30 and the fixing device 60.
In this embodiment, in order to guarantee the relative positional relationship between the free end of the separation guide 50 and the intermediate transfer belt 32, the end on the downstream side in the transport direction, which is one end of the separation guide 50, constitutes the fixing device 60. The first fixing frame 63 that is a frame is swingably supported. The swinging direction is a direction in which the free end of the separation guide 50 approaches and separates from the intermediate transfer belt 32, and the interval between the free end of the separation guide 50 and the intermediate transfer belt 32 is controlled by restricting the swing at a predetermined position. Is positioned to a predetermined dimension. The detailed configuration of the separation guide 50 and the configuration of the positioning means will be described later.

Next, the operation of the separation guide 50 when the intermediate transfer unit 34 is attached / detached will be described with reference to FIG.
When the intermediate transfer unit 34 is taken out from the printer main body 1, the transport path door 40 is opened. Then, in conjunction with the opening operation of the conveyance path door 40, the separation guide 50 swings and rotates in a direction away from the intermediate transfer belt 32 and retracts to the outside of the attachment / detachment locus range X of the intermediate transfer unit 34. If the intermediate transfer unit 34 is pulled out in this state, it can be taken out of the apparatus without contacting the separation guide 50.
The retraction position of the separation guide 50 is a position where the free end of the separation guide 50 contacts the second fixing frame 64 and closes the entrance of the fixing device 60. By closing the inlet of the fixing device 60, there is an advantage that the temperature of the fixing device 60 is prevented from lowering and the rise time of the fixing device 60 after the intermediate transfer unit 34 is mounted can be shortened.

Next, the basic operation of the separation guide 50 will be described with reference to FIG. 3 in comparison with the case where no separation guide is provided. FIG. 3A shows the vicinity of the separation guide of the present invention, and FIGS. 3B and 3C show the case where there is no separation guide.
In the transfer unit 30, the transfer roller 24 is pressed against the intermediate transfer belt 32 to form a transfer nip, and the toner image on the intermediate transfer belt 32 is applied to the sheet material S using a transfer bias applied to the transfer roller 24. Transcript. Since the intermediate transfer belt 32 is wound around the drive roller 31 and the wound portion is curved in an arc shape that follows the curvature of the drive roller 31, the sheet material conveyed by the electrostatic force generated during the transfer S is attracted to the intermediate transfer belt 32. Normally, the sheet material S that has passed through the transfer unit 30 is separated from the intermediate transfer belt 32 by the stiffness. However, if the stiffness of the sheet material S is weak, the restoring force of the sheet material leading edge S1 to be separated from the surface of the intermediate transfer belt 32 is weak, so that the traveling direction of the sheet material leading edge S1 is greatly bent toward the intermediate transfer belt 32 ( (Refer FIG.3 (b)).
This phenomenon is more likely to occur if the sheet material front end S1 is curled toward the intermediate transfer belt 3 on the second side of double-sided printing (see FIG. 3C). In addition to the tendency of the sheet material leading edge S1 to deviate from the ideal conveyance path due to the original curl shape, the distance between the sheet material S and the intermediate transfer belt 32 in the natural state is short, and thus the sheet material S against the electrostatic attraction force. This is because its own resilience is weak. In any case, a conveyance jam occurs when the traveling direction of the leading edge of the sheet material is bent so much that the leading edge of the sheet material cannot be correctly guided to the fixing device 60 positioned downstream in the conveying direction of the transfer unit 30.

On the other hand, according to the present invention, as shown in FIG. 3A, even if the sheet material S that has passed through the transfer portion 30 is greatly bent toward the intermediate transfer belt 32, the leading edge of the sheet material S is separated. The guide 50 can reliably separate from the intermediate transfer belt 32. Then, the separated sheet material S is guided by the separation guide 50 on the side of the image surface side, and is stably conveyed to the entrance of the fixing device 60. In particular, since the separation guide 50 is attached to the fixing first frame 63 having high rigidity, the attachment rigidity is high, the guide main body 54 can be arranged with high accuracy, and the sheet material S can be reliably separated and guided.

Next, with reference to FIG. 2, the specific configuration, operation, and positioning method of the separation guide 50 will be described in more detail following the movement in the process of closing the conveyance path door 40.
First, the basic configuration of the separation guide 50 will be described.
The separation guide 50 is a long plate extending in a direction orthogonal to the conveyance direction of the sheet material S, and serves as a rotation axis of the separation guide 50 at one end in the short direction, that is, the downstream end in the conveyance direction of the sheet material S. The support shaft 53 protrudes (see FIG. 2D). The support shaft 53 is rotatably supported by frame side surface parts 63 a located at both ends of the fixing first frame 63 of the fixing device 60 in the longitudinal direction (rotation axis direction of the heating rotator 61). The support shaft 53 is parallel to the rotation shaft of the drive roller 31 of the intermediate transfer belt 32 of the transfer unit 30, and the free end of the separation guide 50 on the upstream side in the transport direction of the sheet material S is in relation to the intermediate transfer belt 32. It is possible to approach and separate.
The guide body 54 is thick at the base end portion on the downstream side in the transport direction fixed to the support shaft 53 and gradually decreases toward the free end on the upstream side in the transport direction. The end surface of the free end has a predetermined thickness. Now it is cut diagonally. The guide body 54 is cut with respect to the circumferential surface of the arc-shaped intermediate transfer belt 32 that follows the drive roller 31 and has an acute angle with the surface facing the sheet material S. The free ends are closer. The guide body 54 need not be a long plate, and may be configured such that a plurality of flappers are fixed in the longitudinal direction with respect to a support shaft extending in the longitudinal direction.

In order to ensure the relative positional relationship between the intermediate transfer belt 32 and the free end of the guide main body 54, a positioning portion 34b is provided on the transfer frame 34a of the intermediate transfer unit 34. On the other hand, the separation guide 50 is provided with an engagement lever 51 having an engagement protrusion 51a pressed against the positioning portion 34b, and the conveyance path door 40 is used to press the engagement protrusion 51a against the positioning portion 34b. A pressing spring 43 and a pressing member 42 are provided. The pressing spring 43 and the pressing member 42 constitute the first urging means of the present invention.
Here, the transfer frame 34a provided with the positioning portion 34b is a rectangular frame body in which a pair of side plate portions that support both shaft end portions such as the driving roller 31 and the driven roller 37 are rigidly connected by a connecting member, The illustrated portion shows the vicinity of the end portion of the side plate portion on the drive roller 31 side. That is, the end shape of the transfer frame 34a is an arc shape that follows the arc shape of the intermediate transfer belt 32 wound around the drive roller 31, and the upper edge portion extends linearly toward the driven roller 37 side. . The positioning portion 34b partially protrudes upward in a quadrangular shape from the end region on the arc portion side of the upper edge portion, and the engaging projection 51a of the engaging lever 51 contacts the end portion on the transport path 22 side. It is the contact surface 34c.
The engaging lever 51 extends from the support shaft 53 at the longitudinal end portion of the separation guide 50 in a direction orthogonal to the support shaft 53 in parallel with the guide body 54, and the distal end side of the engagement guide 51 is halfway with respect to the rotation shaft of the separation guide 50. It is bent at a predetermined angle within an orthogonal plane, and an engagement protrusion 51a is provided at the tip. By pressing the engagement protrusion 51 a against the contact surface 34 c of the positioning portion 34 b of the transfer frame 34, the relative position between the free end of the guide main body 54 of the separation guide 50 and the intermediate transfer belt 32 via the engagement lever 51. Is positioned. In this specification, the free end position of the separation guide 50 is the free end position of the guide body 54.
In other words, the rotational movement of the guide body 54 in the direction in contact with the intermediate transfer belt 32 is restricted by the engagement protrusion 51 a of the engagement lever 51 coming into contact with the positioning portion 34 b of the intermediate transfer unit 34. As a result, a certain gap is formed between the free end of the guide body 54, that is, the free end of the separation guide 50 and the arc-shaped curved surface of the intermediate transfer belt 32 that is wound around the drive roller 31. become.

The pressing member 42 is elastically supported by the conveying frame 40 a of the conveying path door 40 by a pressing spring 43, and the pressing member 42 is engaged with and disengaged from the engaging protrusion 51 a of the separation guide 50 by opening and closing the conveying path door 40. It is like that. The conveyance frame 40 a of the conveyance path door 40 is a pair of highly rigid frames that support both shaft end portions of each roller such as the transfer roller 24 disposed in parallel with the driving roller 31 of the intermediate transfer unit 34. The unit 34 is substantially at the same position as the transfer frame 34a. Therefore, in the process of closing the conveyance path door 40, the pressing member 42 engages with the engaging protrusion 51a of the engaging lever 51 provided on the support shaft 53 of the separation guide 50, and pushes it toward the positioning portion 34b. It abuts on the contact surface 34c. On the other hand, when the transport path door 40 is opened, the pressing member 42 is detached from the engaging protrusion 51a in the process of opening.
A torsion coil spring 56 is attached to the support shaft 53 of the separation guide 50 as second urging means that constantly urges the free end of the separation guide 50 in a direction away from the intermediate transfer belt 32. The torsion coil spring 56 has one engagement end portion 56 a engaged with the engagement lever 51, the other engagement end portion 56 b engaged with the fixing first frame 63, and the separation guide via the engagement lever 51. The rotation is energized.
When the conveyance path door 40 is closed, the separation guide 50 is configured to abut against the positioning portion 34 b by the biasing force of the pressing spring 43 against the rotational biasing force of the torsion coil spring 56. When the conveyance path door 40 is opened, the pressing spring 43 is released, so that the free end of the separation guide 50 is rotated away from the intermediate transfer belt 32 by the urging force of the torsion coil spring 56.

Next, the movement of the separation guide 50 will be described along the process of closing the transport path door 40.
In the state where the conveyance path door 40 is opened, as shown in FIG. 2A, the separation guide 50 is urged to rotate away from the intermediate transfer belt 32 by the torsion coil spring 56 and retracts to the retracted position. ing. In this example, the free end portion of the guide main body 54 of the separation guide 50 is in contact with the fixing second frame 64 across the entrance of the fixing device 60.

When the conveyance path door 40 is closed, in the process, as shown in FIG. 2B, the pressing protrusion 51a of the engagement lever 51 of the separation guide 50 is provided on the conveyance path door 40 side. 42, and starts swinging toward the intermediate transfer belt 32 as the conveyance path door 40 is closed.
Further, when the conveyance path door 40 is closed, the engagement protrusion 51a of the engagement lever 51 provided near the both longitudinal ends of the separation guide 50 eventually pushes the positioning portion 34b provided on the transfer frame 34a of the intermediate transfer unit 34. (FIG. 2C) The pressing member 42 is biased by the pressing spring 43 so as to push back the separation guide 50 with a force larger than the biasing force of the torsion coil spring 56, and the conveyance path door 40 is completely closed. Then, the separation guide 50 is pressed and fixed to the positioning portion 34b.
As described above, according to the present embodiment, the separation guide 50 required for separating the sheet material from the transfer unit 30 is supported by supporting the separation guide 50 on the fixing first frame 63 of the fixing device 60 having high rigidity. The position accuracy and mounting rigidity can be satisfied. Therefore, even if the fixing device 60 is disposed immediately above the intermediate transfer unit 34 and the space between the transfer unit 30 and the fixing device 60 is narrow, good sheet separation performance is realized.
In this embodiment, since the intermediate transfer unit 34 is configured to be attached / detached, the relative positional relationship between the intermediate transfer unit 34 and the fixing device 60 is likely to be unstable due to the attaching / detaching operation. However, in this embodiment, since the engagement lever 51 and the transfer frame 34a are positioned by engagement, positioning accuracy of the relative position of the free end portion of the guide body 54 with respect to the intermediate transfer belt 32 regardless of the attachment / detachment operation. Can be set with high accuracy. Therefore, the gap dimension between the free end of the guide main body 54 and the intermediate transfer belt 32 is stabilized, and the effect that the positional accuracy can be guaranteed is obtained.

Here, the advantages of the present invention will be described in comparison with the case where the separation guide 50 is disposed on the intermediate transfer unit 34.
When the separation guide 50 is attached to the intermediate transfer unit 34, it is necessary to assume that the user directly touches the separation guide 50 when the intermediate transfer unit 34 is removed. However, it is difficult to realize such a strength that the separation guide 50 is not deformed to damage the surface of the intermediate transfer belt 32 when an external force acting on the separation guide 50 is applied.
In the present invention, since the fixing first frame 63 is used for attachment, the position accuracy of the attachment position can be set high regardless of whether the intermediate transfer unit 34 is attached or detached. In this embodiment, since the separation guide 50 is swung to the retracted position where it does not interfere with the intermediate transfer unit 34, both the detachability of the intermediate transfer unit 34 and the separation of the sheet material S can be achieved. it can.

  In this embodiment, in order to avoid interference with the intermediate transfer unit 34, the separation guide 50 is retracted when the conveyance path door 40 is opened. However, the intermediate transfer unit 34 is detached from the conveyance door side. If not, the separation guide 50 does not need to be retracted. In that case, the torsion coil spring 56 is unnecessary, and only the pressing member 42 and the pressing spring 43 are required. When the conveyance path door 40 is opened, the separation guide 50 swings around the support shaft 53 by its own weight. It is held in a freely suspended state. Further, the pressing member 42 and the pressing spring 43 are eliminated, and the urging force of the torsion coil spring 56 is always urged not in the retracting direction but in the direction in which the engaging protrusion 51a of the engaging lever 51 is pressed against the positioning portion 34b of the transfer frame 34a. The first urging means may be used.

Next, a second embodiment of the present invention will be described with reference to FIGS.
FIG. 7 is a schematic cross section of an image forming apparatus according to Embodiment 2 of the present invention. The image forming apparatus according to the second embodiment is an example of a monochrome printer. In the following description, the same reference numerals are given to portions common to the first embodiment, and description thereof is omitted. Also, the description of parts not directly related to the present invention will be omitted.
That is, in the printer main body 1, the optical unit 10 and one process cartridge 206 are arranged in parallel in the horizontal direction on a sheet feeding tray 21 as a lowermost sheet stacking unit. The transfer unit 230 is provided at one end of the process cartridge 206 in the horizontal direction, that is, the right end in the illustrated example, and the fixing device 60 is disposed above the transfer unit 330. An optical unit 10 is disposed on the other horizontal end of the process cartridge 6.
In the second embodiment, the transfer unit 230 includes a photosensitive drum 12 as a transfer body on which a toner image to be transferred is formed, and a transfer roller 24 that contacts the photosensitive drum 12 and forms a transfer nip. Is done. A fixing device 60 for fixing the transferred toner image to the sheet material is disposed on the downstream side of the transfer unit 230 in the transport direction, in this embodiment, immediately above the transfer unit 230.

The process cartridge 206 is configured to be attached / detached from the front surface of the printer main body 1 by inserting / removing the process cartridge 206 in a direction perpendicular to the paper surface of FIG. The process cartridge 206 is between an image forming position (FIG. 5A) where the photosensitive drum 12 is pressed against the transfer roller 24 and a spaced position (FIG. 5B) spaced from the transfer roller 24. , Configured to be movable. In the separation position, the process cartridge 206 can be attached and detached. In this embodiment, the movement of the process cartridge 206 between the image forming position and the separation position is interlocked with the opening / closing operation of the front door 4 of the printer body 1. Composed.
As shown in FIG. 7A, the process cartridge 206 is mounted by engaging the guide rail 71 on the process cartridge 06 side with the guide rail 70 for attachment / detachment provided on the printer body 1, and It is inserted toward. In this state, the photosensitive drum 12 is separated from the transfer roller 24, the process cartridge 206 is moved toward the transfer roller 24 by the pressure lock lever 72, and the photosensitive drum 12 is added to the transfer roller 24. Press to complete installation.

The process cartridge 206 is provided with a pressure engagement convex portion 73 that engages with the concave portion 72a of the pressure lock lever 72, and the position of the process cartridge 206 on the pressure lock lever 72 side is positioned. On the other hand, for positioning on the photosensitive drum 12 side, a flange portion 74 (a part of the frame of the process cartridge) provided coaxially with the photosensitive drum 12 on the end surface of the process cartridge 206 is provided on the side plate of the printer main body 1. Positioned against the edge of the groove 75 formed (see FIG. 7B).
As an interlocking mechanism for interlocking the opening / closing operation of the pressure lock lever 72 and the front door 4, although not shown in particular, a motion conversion that converts the opening / closing motion of the front door 4 in the front-rear direction into a swinging motion of the pressure lock lever 72. A mechanism may be used. For example, if a bell crank that swings about a vertical axis is used and one end is engaged with the pressure lock lever 72 and the other end is engaged with the front door 4, the closing operation of the front door 4 is performed. Can be converted into a pressing movement of the pressure lock lever. However, the interlocking mechanism is not limited to the bell crank, and other configurations can be adopted, and not the configuration that interlocks with the front door 4 but the configuration in which the pressure lock lever 72 is manually operated. But you can.
Further, in the second embodiment, the process cartridge 206 is attached and detached from the front surface by opening the front door 4 of the printer main body 1. However, an openable and closable upper door is provided to attach and detach the process cartridge 206 from above. It may be configured. Even in this case, the process cartridge is located at the separation position before pressurization and the pressurization position, and therefore, the configuration of the separation guide can be applied in exactly the same manner.

  In the present embodiment, the separation guide 250 according to the present invention is disposed on the image surface side of the transfer path of the transfer unit 230 and the fixing device 60 to assist the separation of the sheet from the photosensitive drum 12 at the image forming position. Has been. The separation guide 250 is supported by the fixing device 60 so that the downstream end in the transport direction is swingable. That is, the upper end portion of the separation guide 250 is swingably supported by the fixing first frame 63 of the fixing device 60, and the free end portion, which is the upstream end portion in the transport direction, is disposed in close proximity to the surface of the photosensitive drum 12. It is positioned in the state.

Next, with reference to FIG. 6, the operation | movement of the separation guide 250 and the detail of the positioning method are demonstrated later on the operation | movement in the process in which the front door 4 is closed. 6A shows a separated position state, FIG. 6B shows a moving state, and FIG. 6C shows an image forming position state.
The separation guide 250 includes a guide main body 54 and a support shaft 53, and is the same as the first embodiment in that the engagement lever 51 is provided at the shaft end of the support shaft 53. In this embodiment, the support shaft 250a on the separation guide side is engaged with the elongated hole 225a provided in the first fixing frame 63 of the fixing device 60, and the separation guide 250 is swung. In addition to the operation, it is supported so as to be movable within the range of the long hole 225a (see FIG. 6D).

In this embodiment, the first engagement portion 256 a that is one end portion of the torsion coil spring 256 is inserted into the engagement hole 64 a provided in the end plate of the fixing second frame 64, and the first engagement portion 256 a is the other end portion. The two engaging portions 256 b are engaged with the engaging lever 51. By this torsion coil spring 256, the separation guide 250 is urged in the direction approaching the process cartridge 6 with respect to the swinging direction and the region of the elongated hole 225a. On the other hand, the support shaft 53 is provided with a stopper lever 57 that protrudes in the opposite direction to the engagement lever 51 with respect to the support shaft 53.
On the other hand, the frame 6a of the process cartridge 6 is provided with a positioning groove 6b as a positioning portion, and the torsion coil spring 256 as the first urging means has the engagement protrusion 251a of the separation guide 250 at the image forming position. Positioning is performed by pressing against the positioning groove 6b.
In the separation position, the positioning groove 6 b of the process cartridge 6 is separated from the engagement protrusion 251 a of the separation guide 250. Then, the free end of the separation guide 250 waits in the biasing direction of the torsion coil spring 256, in the clockwise direction in the drawing, from the position of the normal posture positioned by the engagement of the positioning groove 6b and the engagement protrusion 251a. It is configured to be held in position

Hereinafter, the operation of the separation guide will be described with reference to FIGS. 6A and 6B, step by step from the separation position of the process cartridge 6 to the image forming position.
In the state where the front door 4 is opened, as shown in FIG. 6A, the process cartridge 6 is located at the separation position, and the separation guide 50 and the photosensitive drum 12 are largely separated from each other. That is, in this separated position, the engagement lever 51 is moved in the direction in contact with the photosensitive drum 12 and in the clockwise direction in the figure by the force of the torsion coil spring 256, and is held at the standby position by the stopper lever 57. That is, the stopper lever 57 is positioned and held against the first engagement portion 256a of the torsion coil spring 256. At this time, the support shaft 53 is positioned at the lower end of the long hole 225a by the weight of the separation guide 250 (see FIG. 6D).
In the standby position, the free end of the separation guide 50 is relatively far away from the photosensitive drum 12 than the image forming position by the amount that the photosensitive drum 12 is separated from the transfer roller. It waits in a state closer to the process cartridge 6 side than the position in the position.

When the front door 4 starts to close, the process cartridge 6 starts to move from the separation position toward the image forming position (see FIG. 6B). In this process, first, against the spring force of the torsion coil spring 256, the engagement lever 51 is pushed by the front end portion of the frame 6a of the process cartridge 6 and starts rotating in the clockwise direction. Then, the engagement protrusion 252 of the separation guide 250 is inserted into the positioning groove 6b provided in the frame 6a. As the engagement lever 51 rotates, the torsion coil spring 256 is compressed in the twisting direction between the first engagement portion 256a and the second engagement portion 256b.
Further, when the process cartridge 6 moves to reach the image forming position, the engaging protrusion 252 of the separation guide 250 swings while being pushed into the positioning groove 206b, and reaches the normal position during image forming. (FIG. 6C). That is, the free end of the separation guide 250 is positioned at a position close to and opposite to the photosensitive drum 12.

[Other embodiments]
In the first and second embodiments, different configuration examples of the positioning means have been shown as the position assurance method of the separation guide 50 with respect to the intermediate transfer belt, which is a transfer body carrying a toner image, and the photosensitive drum. It is not limited to these structures. As long as the relative positional relationship between the free end of the separation guide and the transfer body necessary for separating the sheet material can be satisfied by other means, the positioning may not be performed directly with respect to the frame that supports the transfer body. The “other means” mentioned here may be, for example, a method of positioning with respect to the frame of the image forming apparatus or a method of guaranteeing with the component dimensional accuracy of the fixing device itself.
For example, in the first embodiment, a positioning unit may be provided on a frame (not shown) on the printer body 1 side instead of the positioning unit 34b of the transfer frame 34a in FIG. Since only the engaging protrusion 51a of the engaging lever 51 of the separation guide 50 abuts against the frame on the printer body 1 side, there is no problem in space.
Further, in the second embodiment, instead of the positioning portion 6b of the frame 6a of the process cartridge 6 in FIG. 6, a positioning portion is provided on a frame (not shown) on the printer body 1 side, and the positioning is made by abutting against the positioning portion. It can also be configured. Further, if the configuration of holding the standby position in FIG. 6A is configured so as to be close to and opposed to the photosensitive drum 12, the dimensional accuracy of the fixing device 60 itself is ensured. Further, in order to ensure the dimensional accuracy of the fixing device 60 itself, the separation guide 50 does not have to be supported in a swingable manner.

  In addition, the swinging operation of the separation guide 50 has been described in the first embodiment with respect to the configuration interlocked with the opening / closing of the conveyance path door 40, and the configuration according to the second embodiment interlocked with the opening / closing of the front door 4 has been described. It is not limited. For example, in the first embodiment, it may be configured to be appropriately retracted by being pushed by the detachable intermediate transfer unit. In the second embodiment, similarly to the first embodiment, the opening and closing of the conveyance path door 40 may be performed. It may be configured to work together. Further, it may be interlocked with other movable parts such as the intermediate transfer unit 34, the process cartridge 6, and a mounting lever for other replacement units. Further, the separation guide 50 may be swung in conjunction with the image forming operation of the image forming apparatus. For example, as shown in the first embodiment except at the time of image formation, the entrance of the fixing unit is closed, and at the time of image formation, the free end is moved to a position close to and opposed to the transfer body. The temperature drop of the container can be reduced, and the power consumption can be reduced.

DESCRIPTION OF SYMBOLS 1 Printer main body (image forming apparatus main body) 4 Front door 6 Process cartridge, 6a frame, 6b Positioning groove part 11 Image forming station (image forming part), 12 Photosensitive drum 30 Transfer part, 24 Transfer roller 34 Intermediate transfer unit,
32 intermediate transfer belt (transfer body), 34a transfer frame, 34c frame side surface,
34b Positioning part 40 Transport path door (opening / closing body), 40a Frame side face part 42 Pressing member (first biasing means), 43 Pressing spring (first biasing means)
50 Separation guide (separation member)
51 engaging lever, 51a engaging protrusion, 53 support shaft, 54 guide body,
56 Torsion coil spring (second biasing means)
60 Fixing device (fixing part)
63 fixing first frame (fixing frame), 63a frame side surface portion, 64a engagement hole 74 flange portion, 75 groove 225a long hole 230 transfer portion 250 separation guide 252 engagement protrusion 256 torsion coil spring (first urging means),
256a 1st engaging part, 256b 2nd engaging part 330 Transfer part S Sheet material, S1 Sheet material front-end | tip X Attachment / detachment locus | trajectory range

Claims (13)

A transfer unit for transferring the toner image carried on the transfer body to a sheet material;
An image forming apparatus comprising: a fixing unit that is disposed downstream of the transfer unit in a sheet conveyance direction and fixes a toner image transferred to the sheet material in the transfer unit to the sheet material;
An image forming apparatus, wherein a separating member for separating a sheet material from the transfer member is disposed between the transfer unit and the fixing unit, and the separating member is supported by a fixing frame constituting the fixing unit.   The image forming apparatus according to claim 1, wherein the separation member is a guide member that guides an image surface side surface of a sheet material between a transfer portion and a fixing portion. The separation member is supported so as to be swingable with respect to the fixing frame,
The image forming apparatus according to claim 1, further comprising a positioning unit that positions the free end of the separation member at a position that is close to and faces the transfer body.   The image forming apparatus according to claim 3, wherein the positioning unit includes a positioning unit provided on a frame to which the transfer body is assembled, and a first urging unit that presses the separation member against the positioning unit. An opening / closing body capable of opening / closing a sheet material conveyance path passing through the transfer section;
The image forming apparatus according to claim 4, wherein the first urging unit is provided on the opening / closing body, and the first urging unit is engaged with the separation member in a process of closing the opening / closing body.   A second urging means for urging the separating member in a direction away from the transfer body; and when the opening / closing body is closed, the separating member resists the urging force of the second urging means; A structure that abuts against the positioning portion by the urging force of the first urging means, and moves to a standby position that is separated from the positioning portion by the second urging means when the opening / closing body is opened; The image forming apparatus according to claim 5.   The image forming apparatus according to claim 1, wherein the transfer body is an intermediate transfer belt on which a toner image formed on a photosensitive drum is primarily transferred in an image forming unit. The transfer body is an intermediate transfer belt to which a toner image formed on a photosensitive drum is primarily transferred in an image forming unit, and the intermediate transfer belt is configured as an intermediate transfer unit assembled to a transfer frame. The transfer unit is removable from the conveyance path opened by the opening / closing body,
The image forming apparatus according to claim 5, wherein a standby position of the separating member when the opening / closing body is opened is outside a range of the attachment / detachment locus of the intermediate transfer unit.   The image forming apparatus according to claim 5, wherein a standby position of the separation member is disposed so as to close an entrance of the fixing unit.   The image forming apparatus according to claim 1, wherein the transfer body in the transfer unit is a photosensitive drum.   The image forming apparatus according to claim 10, wherein a process cartridge to which the photosensitive drum is assembled is detachable from the main body of the image forming apparatus. The process cartridge is configured to move between an image forming position in which the photosensitive drum is pressed against a transfer roller disposed in the image forming apparatus main body, and a separated position separated from the transfer roller.
The positioning portion is provided on a frame of the process cartridge, and the first urging means presses the separating member against the positioning portion of the process cartridge at the image forming position, and positions the positioning member.
In the separation position, the positioning portion of the process cartridge is separated from the separation member, and the separation member is in a standby position advanced in the biasing direction of the first biasing means from the position positioned by the positioning portion. The image forming apparatus according to claim 11, wherein the image forming apparatus is held.   The image forming apparatus according to claim 12, wherein the movement of the image forming position and the separation position of the process cartridge is interlocked with opening / closing of a door of the image forming apparatus main body.

Images