JP5157688B2 - Transfer unit and image forming apparatus - Google Patents

Description

  The present invention relates to a transfer unit that transfers an image on an image carrier to a recording medium, a copier having the transfer unit, a printer, a facsimile machine, a plotter, and an image forming apparatus such as a multi-function machine including at least one of them. .

2. Description of the Related Art Conventionally, as a transfer device or transfer unit used in an image forming apparatus, there is known a configuration that includes a transfer roller and presses and contacts the transfer roller against a drum-like or endless belt-like image carrier.
In this type of transfer device, with a bias voltage applied to the transfer roller or the opposite roller of the transfer roller, the transfer paper is passed between the image carrier and the toner image formed on the image carrier is pressurized. It is transferred to transfer paper by electrostatic force.

FIG. 15 shows a general secondary transfer unit 90. The transfer unit main body 91 rotatably supports the secondary transfer roller 5 and moves (displaces) in a direction in which the image forming apparatus main body (not shown) contacts and separates from the image carrier under the biasing force of the spring 93. ) Is possible.
At the lower end portion of the transfer unit main body 91, a rotation fulcrum 94 for pivotally supporting the image forming apparatus main body or a double-side unit (not shown) is provided. When mounted on the image forming apparatus main body, the secondary transfer unit 90 is pressurized by, for example, a leaf spring 95 by a double-side unit (not shown), and the protrusion 96 hits a fixing unit frame (not shown) on the image forming apparatus main body side. As a result, positioning with respect to the main body of the image forming apparatus is performed.
Prior to the protrusion 96, the secondary transfer roller 5 contacts the image carrier on the image forming apparatus main body, and the spring 93 is compressed to obtain a predetermined transfer nip pressure.

In Patent Document 1, a secondary transfer unit is rotatably supported on the inner surface side of a double-sided unit, and an L-shaped lock member protruding from the inside of the upper end of the double-sided unit is associated with a bar member of the image forming apparatus main body. In addition, the secondary transfer unit and the duplex unit are positioned with respect to the image forming apparatus main body, and the color portions on both sides of the secondary transfer roller are engaged with the vertical positioning members of the image forming apparatus main body to move the upper and lower sides of the secondary transfer roller. A configuration for directional positioning is described.
As shown in FIG. 6 of Cited Document 1, the entire positioning of the secondary transfer unit with respect to the image forming apparatus main body is performed by the projections 116 formed at both inner ends of the duplex unit being arranged on the back surface of the secondary transfer unit (secondary transfer unit). This is done by pressing the contact portion 104 on the surface opposite to the roller.

JP 2007-148196 A

In the method described in Patent Document 1, positioning of the entire secondary transfer unit with respect to the image forming apparatus main body is performed by pressing by a protrusion accompanying the engagement of the lock member of the double-sided unit with the bar member on the image forming apparatus main body side as described above. Because of this method, a large force was required when closing the duplex unit, and the operability was not reduced.
That is, the members act in series both in the engagement of the lock member and the bar member and in the contact between the contact portion and the protrusion, in other words, the direction of the force for positioning is linear. Therefore, although the operability can be improved from the viewpoint that the secondary transfer unit can be positioned only by rotating the duplex unit, the reaction force of the spring for pressing the secondary transfer roller is directly received. It was inevitable that the operating force would increase.
Since the force from the duplex unit increases in proportion to the pressure applied to the secondary transfer roller to the image carrier, for example, in the case of an image forming apparatus using toner that requires a large pressure for transfer, the duplex unit is closed. In this case, a large force is required, and the operability is lowered.

Further, in this type of transfer device, if the transfer roller is pressed against the image carrier even during non-transfer, particularly when the transfer roller is made of a soft material such as sponge rubber or urethane foam, Deformation due to press contact appears remarkably, causing a transfer failure.
In order to solve this problem, control is performed to forcibly separate the transfer roller from the image carrier when non-transfer other than during image formation or when a jam occurs at the transfer site.
For example, when a predetermined time elapses after the last job ends, or when a predetermined time elapses after a jam occurs, a transfer roller or a transfer roller support member is driven by driving a cam provided on the image forming apparatus main body side. Is pressed to separate the transfer roller from the image carrier.
When the double-sided unit and the transfer unit are opened and then closed when the transfer roller is separated from the image carrier, the set force is larger than the closing operation when the transfer roller is in contact with the image carrier. Is required.
That is, an extra force that is pressed by the cam and separated is required, and the setting force increases.

  The present invention has been made in view of the above-described conventional situation, and can reduce the setting force for positioning the transfer unit with respect to the image forming apparatus main body, thereby contributing to improvement in operability and thus improvement in usability. An object of the present invention is to provide a transfer unit and an image forming apparatus having the transfer unit.

In order to achieve the above object, according to the present invention, the setting force (operation force) for positioning the transfer unit is expressed by the lever principle (the difference in distance from the rotation fulcrum) of the lever member. It was decided to reduce by using.
In addition, the present invention is to lower the setting force acting position for positioning to be lower than the operating position of the opening / closing body (double-sided unit), thereby causing the lever principle to be combined and further reducing the setting force. did.
Specifically, in the first aspect of the present invention, the transfer unit main body provided rotatably, a transfer member that forms a transfer nip by contacting an image carrier provided in the image forming apparatus main body, and the image carrier A transfer unit having a pressurizing unit that pressurizes the transfer member on a body, the transfer unit main body having a lever member rotatably provided, the lever member being a positioning unit provided in the image forming apparatus main body And an abutting portion that abuts an opening / closing body provided in the image forming apparatus main body so as to be openable and closable, and the lever member interlocks with the closing operation of the opening / closing body to rotate the image. can der positioned with respect to forming apparatus main body is, in a state that is not positioned relative to the image forming apparatus main body, the lever member in the rotational position where the engagement portion does not reach the engagement position with respect to the positioning portion It has biasing means for lifting and wherein Rukoto.

According to a second aspect of the present invention, in the transfer unit according to the first aspect, the engagement portion and the positioning portion are disengaged in conjunction with the opening operation of the opening and closing body, and the transfer unit body is the image carrier. The biasing force of the biasing means is set so as to be automatically movable in a direction away from the body .
According to a third aspect of the present invention, in the transfer unit according to the first or second aspect of the present invention, the transfer unit has a buffer member that reduces an impact when the engaging portion is engaged with the positioning portion .

According to a fourth aspect of the present invention, in the transfer unit according to any one of the first to third aspects, the position of the contact portion of the lever member is provided below the operation position of the opening / closing body. To do.
According to a fifth aspect of the present invention, an image forming apparatus includes the transfer unit according to any one of the first to fourth aspects.

According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, a protrusion guided by a guide portion provided in an image forming apparatus main body is provided on the engaging portion side of the lever member, and the guide The portion has a shape capable of preventing the lever member from rotating and reaching the engagement position before the engagement portion engages with the positioning portion. To do.
According to a seventh aspect of the invention, in the image forming apparatus according to the fifth or sixth aspect , the image forming apparatus further includes a stopper portion that holds the opening angle of the transfer unit at a predetermined angle when the opening / closing body is opened. It is characterized by.

According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect , the opening / closing body is opened, the engaging portion is disengaged from the positioning portion, the lever member is rotated, and the protrusion is the stopper portion. By being engaged, the predetermined angle is maintained .
According to a ninth aspect of the present invention, in the image forming apparatus according to the eighth aspect, the predetermined angle includes a portion of the transfer nip and a portion of a registration roller pair that conveys the recording medium to the transfer nip at a predetermined timing. Both are in a range that can be visually recognized from the outside of the apparatus .

According to a tenth aspect of the present invention, in the image forming apparatus according to the eighth or ninth aspect , the image forming apparatus further includes a release unit that releases the engagement of the protrusion with the stopper portion .
According to an eleventh aspect of the present invention, in the image forming apparatus according to any one of the fifth to tenth aspects , the opening / closing body is a double-sided unit .

According to a twelfth aspect of the present invention, in the image forming apparatus according to any one of the fifth to eleventh aspects, the image carrier is an intermediate transfer belt of an intermediate transfer unit .

According to the present invention, the setting force (operating force) for positioning the transfer unit with respect to the image forming apparatus main body can be greatly reduced, which can contribute to the improvement of operability and consequently the usability.
By reducing the setting force, it is possible to reduce the weight and size of the open / close body such as the double-sided unit, and to realize cost reduction.

Embodiments of the present invention will be described below with reference to the drawings. First, a first embodiment will be described with reference to FIGS. The same parts as those in the conventional example are denoted by the same reference numerals.
FIG. 1 shows a color printer as an image forming apparatus. As shown in FIG. 1, a color printer 100 includes a transfer belt unit 10 having an intermediate transfer belt 11 as an image carrier and four image stations. Each image station is provided with photosensitive drums 20Y, 20C, 20M, and 20Bk, around which are dedicated charging devices 30Y, 30C, 30M, and 30Bk, developing devices 50Y, 50C, 50M, and 50Bk, and cleaning devices 40Y and 40C. , 40M, and 40Bk are arranged.
The intermediate transfer belt 11 is supported by support rollers 16, 17, and 18. The support roller 16 is a secondary transfer counter roller, and the support roller 18 is also a cleaning counter roller.

Reference numeral 9 denotes a toner bottle that replenishes toner, and is filled with yellow (Y), cyan (C), magenta (M), and black (Bk) toners from the left in the drawing. Thus, the developing devices 50Y, 50C, 50M, and 50Bk of the respective colors are replenished by a predetermined replenishment amount.
In terms of operation, the transfer sheet 2 as a recording medium is fed from the sheet feeding cassette 1 by the sheet feeding roller 3 and is conveyed toward the registration roller pair 4 by the conveying roller pair 19.
When the leading edge of the transfer paper 2 reaches the registration roller pair 4, it is detected by a sensor (not shown). (Transfer nip).
The photosensitive drums 20Y, 20C, 20M, and 20Bk uniformly charged in advance by the charging devices 30Y, 30C, 30M, and 30Bk are exposed and scanned with laser light by the optical writing device 8, and the photosensitive drums 20Y, 20C, and 20M are scanned. , An electrostatic latent image is formed on 20 Bk. The electrostatic latent images are developed by the developing devices 50Y, 50C, 50M, and 50Bk for the respective colors, and yellow, cyan, magenta, and black toner images are formed on the surfaces of the photosensitive drums 20Y, 20C, 20M, and 20Bk.
Next, a voltage is applied to the primary transfer rollers 12Y, 12C, 12M, and 12Bk, and the toner on the photosensitive drums 20Y, 20C, 20M, and 20Bk is sequentially transferred onto the intermediate transfer belt 11. At this time, the image forming operation for each color is executed while shifting the timing from the upstream side toward the downstream side so that the toner image is transferred to the same position on the intermediate transfer belt 11.

The image formed on the intermediate transfer belt 11 is conveyed to the position of the secondary transfer roller 5 and is secondarily transferred to the transfer paper 2 at once. The transfer paper 2 onto which the toner images of the respective colors are transferred is conveyed to the fixing device 6 and thermally fixed, and is discharged onto a tray 21 as an upper surface of the apparatus main body by a pair of paper discharge rollers 7.
In other words, the image forming apparatus according to the present embodiment is a vertical conveyance type image forming apparatus that conveys a sheet feeding cassette positioned below the apparatus main body toward a transfer nip positioned above.
Residual toner on the photoconductive drums 20Y, 20C, 20M, and 20Bk is cleaned by the respective cleaning devices 40Y, 40C, 40M, and 40Bk, and then the charging devices 30Y, 30C, and 30C, in which the bias of the AC component is superimposed and applied to the direct current. 30M and 30Bk are charged simultaneously with static elimination to prepare for the next image formation.
The residual toner on the intermediate transfer belt 11 is cleaned by the intermediate transfer belt cleaning device 13 to prepare for the next image forming process.
In the case of duplex printing, the transfer paper 2 is guided to the duplex unit 15, reversed, and conveyed to the registration roller pair 4. In FIG. 1, reference numeral 55 denotes an image forming apparatus main body, and reference numeral 14 denotes a waste toner collecting container for collecting waste toner generated after transferring a toner image.
The duplex unit 15 has a configuration including at least a duplex conveyance path, and is provided in the image forming apparatus main body 55 so as to be openable and closable. Here, “provided to be openable and closable” means to include both those that are provided so as to be rotatable and those that are provided so as to be slidable.
The duplex unit 15 is a roller for transporting the transfer paper 2 in between, a manual feed tray, a paper feed roller for feeding the transfer paper 2 from the manual feed tray to the secondary transfer unit, a transport roller, and a paper feed roller for rotating the feed roller. Drive means such as a motor may be provided.

FIG. 2 shows a secondary transfer unit as a transfer unit. The secondary transfer unit 60 (not shown in FIG. 1) is pivotally supported on the image forming apparatus main body 55 by a pivot fulcrum 94. The secondary transfer roller 5 as a transfer member is rotatably supported by a bearing 63 fixed to a slider 62 guided and slid by guide portions 61 a and 61 b provided in the transfer unit main body 91. A spring 93 as a pressurizing unit is set between a spring receiver 64 provided in the transfer unit main body 91 and the slider 62.
A shaft (hereinafter also referred to as “rotation fulcrum”) 65 extending substantially parallel to the secondary transfer roller 5 is provided on the upper portion of the transfer unit main body 91, and a lever member 66 is rotatably supported on the shaft 65. Has been.

The lever member 66 includes a first lever 67 that is located on the outer side and extends obliquely downward to the right, and a second lever 68 that is located on the inner side. These levers are regulated by the E-ring 69 to be displaced and removed in the axial direction. The first lever 67 and the second lever 68 are spaced apart from each other in the rotational direction. In this embodiment, there is an angular difference of approximately 90 ° between the two levers.
The lower end side of the first lever 67 is provided with an abutting portion 67b that abuts on a double-sided unit 15 as an opening / closing body, which will be described later. It is fixed with a nut. In the present embodiment, the first lever body 67a is made of metal, and the contact portion 67b is made of synthetic resin in order to reduce the contact impact with the duplex unit 15. Of course, the entire first lever 67 may be formed of a single material such as metal or resin.
As shown in FIG. 4, the second lever 68 is integrally formed of, for example, synthetic resin, has an L-shaped engaging portion 68a on the front end side, and a spring locking portion 68b on the rear end side. A cylindrical projection 68c is provided on the inner side in the direction. Reference numeral 68d denotes an insertion hole into the shaft 65.

As shown in FIGS. 2 and 3 (rear view of the transfer unit main body as viewed from the direction A in FIG. 2), the second lever 68 is engaged between the first lever 67 and the second lever 68. A tension spring 71 for biasing in the direction of arrow B is provided, and the upper limit position of rotation of the second lever 68 is restricted by a locking piece 67c formed on the first lever body 67a. Thereby, the first lever 67 and the second lever 68 can be integrally rotated.
The tension spring 71 also has a function as a buffer member when the engaging portion 68a is engaged with a positioning portion on the image forming apparatus main body 55 side described later.
Instead of the tension spring 71, both levers may be connected by a link node (connecting member), and a buffer function may be obtained by connecting play. The link node may be an elastic body such as rubber.
In place of the tension spring 71, a torsion spring may be set on the shaft 65 to urge the second lever 68 in the B direction and obtain a buffer function.
Between the transfer unit main body 91 and the first lever 67, the lever member 66 is engaged with the positioning portion 68a in the state where the secondary transfer unit 60 is not positioned with respect to the image forming apparatus main body 55. A tension spring 72 is provided as an urging means for holding at a rotation position that does not reach (rotation position shown in FIG. 2; hereinafter referred to as “initial position”).

FIG. 5 shows a state where the duplex unit 15 and the secondary transfer unit 60 are fully opened. The spring force of the tension spring 72 is set to a magnitude that balances the applied pressure of the double-sided unit 15, and when the lever member 66 is opened, the pivot position of the lever member 66 is maintained at the initial position shown in FIG.
The frame of the intermediate transfer unit 73 of the image forming apparatus main body 55 is provided with a cylindrical stud 74 as a positioning portion for positioning the secondary transfer unit 60. Positioning is performed by engaging the engaging portion 68 a of the second lever 68 with the stud 74.
When positioning the secondary transfer unit 60 with respect to the image forming apparatus main body 55, the operator does not need to touch the first lever 67 of the lever member 66 and moves the duplex unit 15 in the direction of arrow C. Just do it. That is, the positioning operation of the secondary transfer unit 60 is performed in conjunction with the closing operation of the duplex unit 15.
The stud 74 may be provided in a portion other than the intermediate transfer unit 73 of the image forming apparatus main body 55. However, since errors in positioning accuracy are accumulated, the stud 74 is attached to the intermediate transfer unit 73 that is a direct positioning target of the secondary transfer unit 60. The positioning accuracy is improved by providing it.

In the closing operation of the duplex unit 15, as shown in FIG. 6, the initial position of the lever member 66 is maintained until the secondary transfer roller 5 comes into contact with the intermediate transfer belt 11 as an image carrier.
When the secondary transfer roller 5 comes into contact with the intermediate transfer belt 11, it receives the pressure of the spring 93 as a pressure means, and the spring force (spring constant) of the tension spring 72 is set to be smaller than the spring force of the spring 93. As a result, as the closing operation of the duplex unit 15 proceeds, the lever member 66 starts to rotate in the engagement direction (direction B).
Finally, as shown in FIG. 7, the engaging portion 68 a of the second lever 68 is engaged with the stud 74, and the secondary transfer unit 60 is positioned with respect to the image forming apparatus main body 55. The duplex unit 15 is also locked to the image forming apparatus main body 55 by engagement means (not shown).

When the secondary transfer roller 5 comes into contact with the intermediate transfer belt 11, as shown in FIG. 8A, the engaging portion 68a has a distance t between the stud 74 and the secondary transfer unit. When the 60 side further moves the distance t, as shown in FIG. 8B, the positioning of the secondary transfer unit 60 with respect to the image forming apparatus main body 55 is completed.
The distance t is a moving distance at which a predetermined nip pressure is obtained between the secondary transfer roller 5 and the intermediate transfer belt 11 by contracting the spring 93. Conventionally, the distance t is directly opposite to the reaction force of the spring 93 here. A large setting force was required for pressing.
In this embodiment, as shown in FIG. 2, the distance R1 from the rotation fulcrum 65 to the contact portion 67b is different from the distance R2 from the rotation fulcrum to the engagement portion 68a (here, about 2: 1). ) Due to the lever ratio between the first lever 67 and the second lever 68, the lever 93 reduces the force of the lever 93 as compared with the conventional method that directly receives and counteracts the reaction force of the spring 93. Thus, the pressure applied to the abutting portion 67b can be reduced, and the engaging portion 68a can be engaged with the stud 74 with a force smaller than that in the prior art. In other words, the pressing force (setting force) of the contact portion 67b by the duplex unit 15 at the time of engagement is small.
By reducing the setting force, the duplex unit 15 (opening / closing body) can be reduced in weight and size.
The spring force of the tension spring 71 is set to such an extent that the lever member 66 can overcome the reaction force of the spring 93 at the time of engagement with the stud 74 and can be rigidly engaged with the lever member 66 as a whole and a buffer function can be obtained. .

Further, as shown in FIG. 7, the position S of the contact portion 67 b of the lever member 66 is provided below the operation position 15 a of the duplex unit 15. In the present embodiment, the contact position S is further below the intermediate position 15 b of the duplex unit 15.
As a result, the set force F is applied by the lever principle based on the difference between the distance from the rotation fulcrum of the double-sided unit 15 to the pressure position S with respect to the contact portion 67b and the distance from the rotation fulcrum to the operation position 15a. The position S and the operation position 15a are smaller than the case where the position is the same, and the setting force can be greatly reduced as compared with the conventional case, coupled with the reduction of the setting force using the lever principle by the lever ratio.
When the setting force when the general secondary transfer unit shown in FIG. 15 was used was measured with a force gauge, it was 76.6 N, but in the configuration of this embodiment, it was 54.6 N.
The operation position 15a of the duplex unit 15 means the position when there is a mark conforming to the standard, and the upper end or the vicinity thereof when there is no mark.
When the engagement of the duplex unit 15 with the image forming apparatus main body 55 is released and opened, the lever member 66 is rotated to disengage the engagement portion 68a from the stud 74, and the secondary transfer unit 60 is also automatically activated. The spring force of the tension spring 72 is set so as to be released.
The tension spring 72 automatically rotates the secondary transfer unit 60 when the double-side unit 15 is opened. Therefore, the tension spring 72 only needs to have an urging force that can be disengaged from the stud 74, and preferably smaller. . This is because the biasing force of the tension spring 72 acts in the direction of increasing the operating force.

As shown in FIG. 9, the intermediate transfer unit 73 is integrally formed with a stopper portion 75 that holds the opening angle of the secondary transfer unit 60 at a predetermined angle when the duplex unit 15 is opened.
When the double-sided unit 15 is opened, the engagement between the engaging portion 68a and the stud 74 is automatically released as described above, and the lever member 66 is rotated to the initial rotation position. The protrusion 68 c of the lever 68 moves along a locus indicated by a two-dot chain line, hits the stopper portion 75, and the secondary transfer unit 60 is held in a state where it is opened at a predetermined angle with respect to the image forming apparatus main body 55.
As shown in FIG. 10, the predetermined angle θ is a range in which both the transfer nip portion and the registration roller pair 4 portion are visible from the outside of the apparatus. As a result, the operator can simultaneously see a plurality of sites where jamming is likely to occur, and it is easy to specify the jammed site.
When the jam processing is performed, the engagement between the protrusion 68c and the stopper portion 75 is released, and the secondary transfer unit 60 is released to the maximum as shown in FIG.

The engagement with the stopper portion 75 is released by a release means 76 provided on the back surface of the transfer unit main body 91 as shown in FIG.
The release means 76 includes a release lever 78, a rotation shaft member 79 that supports the release lever, and a bracket 80 that is fixed to the rotation shaft member 79 and rotates in synchronization with the release lever 78. A part of the bracket 80 faces a part of the release bracket 81 provided integrally with the first lever 67, and when the release lever 78 is raised, the first lever 67 engages with the stud 74. The protrusion 68c and the stopper portion 75 are disengaged by rotating in the direction, and the lever member 66 is rotated to the initial position.

As shown in FIG. 11, in the color printer 100 according to the present embodiment, when a predetermined time has elapsed since the last job ended, or when a jam occurs in the transfer nip, the apparatus stops and the predetermined time elapses. In this case, the secondary transfer roller 5 is forcibly separated from the intermediate transfer belt 11 in order to prevent transfer failure due to the pressure contact deformation of the secondary transfer roller 5.
The image forming apparatus main body 55 is provided with an eccentric cam 82 and presses a bracket 83 supporting the secondary transfer roller 5 to separate the secondary transfer roller 5. Here, for easy understanding, the position of the eccentric cam 82, the shape of the bracket 83, and the like are displayed differently from the actual ones.
In the state where the secondary transfer roller 5 is separated by the distance w, the lever member 66 is used to perform the jam processing or when the operator opens the secondary transfer unit 60 and closes it carelessly regardless of the jam processing. Since the rotation in the engagement direction starts earlier by the distance w, the engagement portion 68a of the second lever 68 reaches the engagement position before engaging with the stopper portion 75 and cannot be engaged.

In the present embodiment, in order to prevent this, as shown in FIG. 12, a guide portion 84 that guides the protrusion 68 c of the second lever 68 is integrally formed in the intermediate transfer unit 73.
The guide portion 84 has an inclined surface 84 a that spreads outward on the entry side of the protrusion 68 c and a parallel surface 84 b that presses the protrusion 68 c until it can be engaged with the stud 74.
Since the protrusion 68c is forcibly suppressed from moving upward by the guide portion 84, the protrusion 68c can be reliably engaged with the stud 74 while suppressing the early rise of the engaging portion 68a. Therefore, even if the operator carelessly opens the duplex unit 15 with the secondary transfer roller 5 being separated, subsequent setting failure of the secondary transfer unit 60 can be prevented.

FIG. 13 shows a second embodiment. Note that the same parts as those in the above embodiment are denoted by the same reference numerals, and unless otherwise specified, description of the configuration and functions already described is omitted, and only the main part will be described (the same applies to other embodiments below).
The present embodiment is characterized in that the lever member 85 is an integral member, and is provided with a compression spring 86 as an elastic member provided in the contact portion 85b. In FIG. 13, the duplex unit 15 is actually substantially vertical.
Reference numeral 85a denotes the engaging portion 68a in the above embodiment, and 85c denotes the protrusion 68c.
Also in the first embodiment, the lever member 66 may be integrated as with the lever member 85.

FIG. 14 shows a third embodiment.
The present embodiment is characterized in that the contact position of the contact portion 67b of the lever member 66 with respect to the duplex unit 15 can be adjusted.
A long hole 67a-1 extending in the longitudinal direction of the first lever main body 67a is formed at the lower end of the first lever main body 67a. After adjusting the position of the contact portion 67b, the bolt 70 and the unillustrated Secure with nuts.
Thereby, the contact position with respect to the double-sided unit 15 can be changed, the setting force can be adjusted, and the case where adjustment of the contact position with the double-sided unit 15 is necessary depending on the model can be arbitrarily handled.
Of course, the long hole may be provided in the contact portion 67b. Alternatively, the contact portion 67b may be screwed into the first lever main body 67a and the position may be adjusted by changing the screwing amount.
In the above embodiments, the secondary transfer unit 60 is provided on the image forming apparatus main body 55 so as to be rotatable. However, the secondary transfer unit 60 is also provided on the duplex unit 15 so as to be rotatable. A similar setting force reduction function can be obtained.

In each of the embodiments described above, the configuration using the intermediate transfer belt as an example of the image carrier has been described. However, the image carrier is not limited to the intermediate transfer belt, and the photosensitive drum, the photosensitive belt, and the intermediate transfer drum. Any image carrier such as can be used. Regarding the transfer member, the transfer roller has been described as an example in each of the above embodiments, but any transfer member such as a transfer brush or a transfer blade can be used.
The opening / closing body may be a simple cover member other than the duplex unit.

1 is a schematic configuration diagram of a color printer as an image forming apparatus according to a first embodiment of the present invention. It is a schematic side view of a secondary transfer unit as a transfer unit. It is a general | schematic rear view of a secondary transfer unit. It is a perspective view of a 2nd lever. FIG. 4 is a schematic side view of a state where a duplex unit and a secondary transfer unit are opened. FIG. 6 is a schematic side view showing a state in the middle of rotating the duplex unit to position the secondary transfer unit. FIG. 2 is a schematic side view of a state where a secondary transfer unit is positioned on an image forming apparatus main body. It is a principal part enlarged view which shows the engagement operation | movement of the engaging part with respect to a stud, (a) is a figure which shows the state just before engagement, (b) is a figure which shows the engaged state. FIG. 4 is a diagram illustrating a stopper portion formed in an intermediate transfer unit. FIG. 6 is a schematic side view showing a state where the secondary transfer unit is opened at a predetermined angle by a stopper portion. 2A and 2B are diagrams illustrating a separation operation of a secondary transfer roller, in which FIG. 3A illustrates a state before separation, and FIG. 3B illustrates a state of separation. FIG. 4 is a diagram illustrating a guide portion formed in an intermediate transfer unit. FIG. 10 is a schematic side view of a state where a secondary transfer unit according to a second embodiment is positioned on a main body of an image forming apparatus. It is a figure which shows the position adjustment structure of the contact part in 3rd Embodiment. It is a general | schematic side view which shows the conventional secondary transfer unit.

Explanation of symbols

4 Registration roller pair 5 Secondary transfer roller as transfer member 11 Intermediate transfer belt as image carrier 15 Double-sided unit as opening / closing body 15a operation position 55 Image forming apparatus main body 66 Lever member 67b Abutting portion 68a Engaging portion 68c Projection 71 Tension spring as buffer member 72 Tension spring as biasing means 73 Intermediate transfer unit 74 Stud as positioning part 75 Stopper part 76 Release means 84 Guide part 86 Compression spring as elastic member 91 Transfer unit main body 93 As pressure means Spring

Claims (12)

A transfer unit main body provided rotatably; a transfer member that forms a transfer nip in contact with an image carrier provided in the image forming apparatus main body; and a pressurizing unit that pressurizes the transfer member against the image carrier. A transfer unit having:
A lever member rotatably provided on the transfer unit main body, the lever member engaging with a positioning portion provided on the image forming apparatus main body;
An abutting portion that abuts on an opening / closing body provided in the image forming apparatus main body so as to be openable and closable,
By the rotation of the lever member interlocked with the closing operation of the opening-Ri can der positioned with respect to the image forming apparatus main body,
While not so positioned relative to the image forming apparatus main body, characterized that you have a biasing means for retaining said lever member in the rotational position where the engagement portion does not reach the engagement position with respect to the positioning portion Transcription unit. The transfer unit according to claim 1, wherein
The urging means is configured to disengage the engagement portion and the positioning portion in conjunction with the opening operation of the opening / closing body and automatically move the transfer unit main body in a direction away from the image carrier. A transfer unit characterized in that an urging force is set . The transfer unit according to claim 1 or 2 ,
A transfer unit comprising a buffer member for reducing an impact when the engaging portion is engaged with the positioning portion . In the transfer unit according to any one of claims 1 to 3,
The transfer unit , wherein a position of the contact portion of the lever member is provided below an operation position of the opening / closing body . An image forming apparatus comprising the transfer unit according to claim 1. The image forming apparatus according to claim 5 .
A protrusion guided by a guide portion provided in the image forming apparatus main body is provided on the engagement portion side of the lever member, and the guide portion is arranged before the engagement portion engages with the positioning portion. An image forming apparatus having a shape capable of preventing a lever member from rotating and the engagement portion from reaching an engagement position . The image forming apparatus according to claim 5 or 6 ,
An image forming apparatus comprising: a stopper portion that holds an opening angle of the transfer unit at a predetermined angle when the opening / closing body is opened . The image forming apparatus according to claim 7 .
The opening / closing body is opened, the engaging portion is disengaged from the positioning portion, the lever member is rotated, and the protrusion is held at the predetermined angle by being engaged with the stopper portion. An image forming apparatus. The image forming apparatus according to claim 8.
The predetermined angle is a range in which both the transfer nip portion and the registration roller pair portion that conveys the recording medium to the transfer nip at a predetermined timing are visible from the outside of the apparatus. . The image forming apparatus according to claim 8 or 9 ,
An image forming apparatus comprising release means for releasing the engagement of the protrusion with the stopper portion . The image forming apparatus according to claim 5 ,
An image forming apparatus, wherein the opening / closing body is a duplex unit . The image forming apparatus according to claim 5, wherein:
An image forming apparatus, wherein the image carrier is an intermediate transfer belt of an intermediate transfer unit .

Images