JP2009288808A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To satisfactorily maintain transfer performance by a transfer unit in an embodiment of an image forming apparatus of an intermediate transfer system having a transfer unit provided in an opening/closing door unit. <P>SOLUTION: The image forming apparatus including a photoreceptor drum 31, an intermediate transfer belt 230, and a secondary transfer roll 522 includes the door unit 70 provided to freely turn relative to an image forming apparatus body and opening/closing the image forming apparatus body, and a secondary transfer unit 52 provided inside the door unit 70 and having the secondary transfer roll 522. The secondary transfer unit 52 has a turning fulcrum 524 on an upper side than a position of the secondary transfer roll 522, and allows the secondary transfer roll 522 to rotate along in a conveying direction of recording material which advances from below to above in a transfer nip area between the secondary transfer roll 522 and the intermediate transfer belt 230. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer, and particularly includes a rotating body that is movable between a first position that is an operation position during image formation and a second position that is different from the first position. The present invention relates to an improvement of an image forming apparatus including a transfer unit as a subunit.

As an example of a conventional image forming apparatus, an intermediate transfer type image forming apparatus will be described as an example. A predetermined color component image (a toner image in the case of an electrophotographic system) is formed on a latent image carrier such as a photosensitive drum. After forming and primary-transferring the color component image on the latent image carrier to an intermediate transfer member such as an intermediate transfer belt, the color component image on the intermediate transfer member is batch-recorded on the recording material by a transfer unit for secondary transfer ( A secondary transfer is already provided.
As this type of transfer unit, for example, a unit in which a transfer roll is rotatably supported on a unit case and this unit case is supported by a door unit (provided to be openable and closable on the apparatus main body) is known. (For example, refer to Patent Document 1).
By the way, a member such as a door unit of the apparatus body is often a low-rigidity module with poor positional accuracy from the viewpoint of weight reduction, and the transfer unit is not positioned with respect to the module. In addition, a state in which the intermediate transfer member is in contact with a backup roll (opposing roll) in a predetermined nip region is set as an operation position for image formation, and is positioned.
If the image forming process of the image forming apparatus is four cycles, or if there is a concern that a long-term contact state may lead to deformation of the transfer roll depending on the material of the transfer roll, a cycle other than the cycle for transferring to the recording material. In many cases, when the power is turned off, the transfer roll is made to stand by at a retract position separated from the set position.

JP 2000-264492 A (Embodiment of the Invention, FIG. 2)

  The technical problem of the present invention is an aspect of an intermediate transfer type image forming apparatus in which a transfer unit is provided in a door unit that opens and closes, and provides an image forming apparatus capable of maintaining good transfer performance by the transfer unit. It is.

The invention according to claim 1 is a latent image carrier for carrying a latent image, an intermediate transfer belt on which an image obtained by visualizing the latent image on the latent image carrier is transferred and carried, An image forming apparatus comprising a transfer member that transfers an image on the intermediate transfer belt to a recording material conveyed from the bottom to the top with a transfer nip area formed between A door unit that is rotatably provided to open and close the image forming apparatus main body, and a transfer unit that is provided inside the door unit and includes the transfer member. And a rotation shaft on the upper side, and the transfer member is rotated in the transfer nip region between the transfer member and the intermediate transfer belt so as to follow the recording material conveyance direction from the bottom to the top. Image forming equipment It is.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the door unit has a rotation shaft below the transfer member position.
According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, a recording material supply cassette in which the recording material is accommodated so as to be supplied, and a vertical direction from the recording material supply cassette toward the transfer nip region. An image forming apparatus comprising: a recording material conveyance path that extends and serves as a conveyance path for the recording material.
According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, the transfer unit supports the unit case so as to be relatively movable with respect to the door unit and to be rotatable about the rotation shaft, An image forming apparatus characterized in that the transfer member is rotatably supported on a unit case.

Here, examples of the subunit driving method applicable to the transfer unit of the present invention include the following modes.
As shown in FIG. 1, this mode is a door unit that can be opened and closed with respect to the apparatus main body, and is provided in the door unit. Of the sub-unit 1 including the rotating body 2 movable between the position P1 and the second position P2 different from the above-mentioned position, and the drive source 3m fixed to the apparatus main body and the sub-unit 1 of the door unit A drive source 3m for rotating the rotator 2 and a rotation driving force from the drive source 3m when the door unit is opened are not transmitted to the rotator 2, and the sub-units at the first position P1 and the second position P2 when the door unit is closed. A drive transmission means 3 capable of transmitting a rotational drive force from a drive source 3m to one rotary body 2 is provided.
In this embodiment, the rotating body 2 is rotated before the rotating body 2 of the sub unit 1 provided in the door unit reaches the first position P1 when the door unit is closed without hindering the opening / closing operation of the door unit. Even when image formation is started, the rotary body 2 can be set to move to the operation position during image formation with the rotary body 2 of the subunit 1 rotated in advance.
For this reason, since the rotating body 2 is already in a state of stable rotation when the rotating body 2 reaches the operation position at the time of image formation, an image forming operation can be performed immediately in the subunit 1 including the rotating body 2. Thus, it is possible to easily shorten the image forming time.

In such technical means, the subunit 1 includes various units such as a transfer unit used in image formation (a unit including a transfer roll that can be brought into contact with and separated from the image carrier 5). The rotating body 2 includes a roll, a belt, and the like.
Here, in order to move the rotating body 2 between the first position P1 and the second position P2, the subunit 1 may be moved by the normal retract mechanism 4.
The second position P2 is a retract position at which the rotating body 2 normally stands by, but may be other than the retract position. For example, a temporary set position close to the set position may be selected as the second position P2. .

Further, the drive transmission means 3 includes a drive transmission member that is drivingly connected to the normal drive source 3m, and a driven transmission member that is drivingly connected to the rotating body 2 side and engages with the drive transmission member.
The layout of the drive transmission member only needs to be directly or indirectly connected to the drive source 3m. The layout of the drive transmission member is directly connected with the driven transmission member coaxially with the rotating body 2. Alternatively, the sub-unit 1 may be provided with a link mechanism as a retract mechanism 4 in which the rotating body 2 is moved between the first position P1 and the second position P2. May employ an indirect coupling method in which a driven transmission member is disposed at the center of rotation of the link mechanism and the drive transmission is transmitted to the rotating body 2 via the driven transmission member.
Here, when the direct connection method is adopted, the driven transmission member is also accurately positioned when the rotating body 2 is positioned, which is preferable in that stable driving is possible.
On the other hand, in the mode employing the indirect coupling method, the rotation center position of the link mechanism is less fluctuated with respect to the movement of the rotating body 2 between the first position P1 and the second position P2. If the driven transmission member is disposed at the position P1, the rotating body 2 can be stably driven at the positions P1 and P2.

In addition, the drive transmission member and the driven transmission member are not limited to gears, and may be appropriately selected as long as they can transmit a driving force. However, from the viewpoint of ensuring reliable drive transmission. For example, the drive transmission means 3 has a drive transmission gear coupled to the drive source 3m, and the driven transmission gear and the drive transmission gear that are coupled to the rotating body 2 at the first position P1 are brought into a normal state. And the meshing state between the driven transmission gear on the rotating body 2 side and the drive transmission gear may be maintained at the second position P2.
That is, when the meshing state of the drive transmission gear and the driven transmission gear is set to the normal position at the first position P1, the position of the driven transmission gear changes at the second position P2, so both The meshing state of the gear can be shifted from the normal position.
In this case, in the second position P2, if one drive transmission gear and one driven transmission gear are taken as an example, if the distance between the centers of the gears is arranged below the sum of the tooth tip radii of both gears, Good.
Furthermore, from the viewpoint of effectively preventing the deformation of the rotating body 2, it is preferable to employ a method of moving the rotating body 2 from the first position P1 to the second position P2 when the power is turned off.
More specifically, for example, a delay circuit may be provided in the retract mechanism 4 for setting the rotating body 2 to the second position P2, and the retract mechanism may be operated even when the power is turned off.

According to the first aspect of the present invention, the transfer performance of the transfer unit can be kept good in the intermediate transfer type image forming apparatus in which the transfer unit is provided in the door unit that opens and closes.
According to the second aspect of the present invention, the door unit can be easily opened and closed in the intermediate transfer type image forming apparatus in which the transfer unit is provided in the door unit that opens and closes. The performance can be kept good.
According to the third aspect of the invention, the recording material from the recording material supply cassette can be accurately guided to the transfer portion between the transfer member and the intermediate transfer belt through the recording material conveyance path extending in the vertical direction. The transfer performance by the transfer unit can be kept good.
According to the fourth aspect of the present invention, in the mode of the intermediate transfer type image forming apparatus in which the door unit that opens and closes is provided with the transfer unit, the transfer member of the transfer unit and the intermediate transfer belt are easily positioned when the door unit is closed. Can be done.

FIG. 3 is an explanatory diagram showing an outline of a subunit driving method applicable to the image forming apparatus according to the present invention. 1 is an explanatory diagram illustrating an overall configuration of an image forming apparatus according to a first embodiment. (A) is explanatory drawing which shows the state in which the door unit is closed in the image forming apparatus which concerns on this Embodiment, (b) is explanatory drawing which shows the state in which the door unit was opened in the image forming apparatus. It is explanatory drawing which shows the detail of the transfer unit used by this Embodiment. (A) is explanatory drawing which shows the state of the transfer unit when a transfer roll is located in a set position, (b) is explanatory drawing which shows the state of a transfer unit when a transfer roll is located in a retract position. It is explanatory drawing which shows the drive system of the transfer unit which concerns on this Embodiment. (A) is explanatory drawing which shows the state of a drive system when a transfer roll is located in a set position, (b) is explanatory drawing which shows the state of a drive system when a transfer roll is located in a retract position. FIG. 6 shows a modified form of the drive system of the transfer unit according to the present embodiment, (a) is an explanatory diagram showing the state of the drive system when the transfer roll is located at the set position, and (b) is the transfer roll at the retract position It is explanatory drawing which shows the state of the drive system when located.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Embodiment 1
FIG. 2 is an explanatory view showing Embodiment 1 of a tandem type image forming apparatus to which the present invention is applied.
In the same figure, the tandem type image forming apparatus is arranged in a horizontal direction with an image forming unit 22 (specifically, 22a to 22d) of four colors (black, yellow, magenta, cyan) in the main body housing 21. A belt unit (belt conveying device) 23 including an intermediate transfer belt 230 that is circulated and conveyed along the arrangement direction of the image forming units 22 is disposed above the image forming unit 22, and below the main body housing 21. Is provided with a recording material supply cassette (not shown) in which a recording material (not shown) such as paper is accommodated, and a recording material conveyance path serving as a recording material conveyance path from the recording material supply cassette is vertically arranged. It is arranged in the direction.

In the present embodiment, each of the image forming units 22 (22a to 22d) is, for example, for black, yellow, magenta, and cyan in order from the upstream side in the circulation direction of the intermediate transfer belt 230. (Not limited) toner image, each photosensitive unit 30, each developing unit 33, and one common exposure unit 40.
Here, the photoconductor unit 30 includes, for example, a photoconductor drum 31, a charger (charging roll in this example) 32 that charges the photoconductor drum 31 in advance, and a cleaner 34 that removes residual toner on the photoconductor drum 31. Are integrated into a cartridge.
The developing unit 33 develops the electrostatic latent image exposed and formed by the exposure unit 40 on the charged photosensitive drum 31 with a corresponding color toner (for example, negative polarity in the present embodiment). is there.
On the other hand, the exposure unit 40 corresponds to, for example, four semiconductor lasers (not shown), one polygon mirror (not shown), an imaging lens (not shown), and each photoconductor unit 30 in the unit case. A mirror (not shown) is stored, light from a semiconductor laser for each color component is deflected and scanned by a polygon mirror, and an optical image is guided to an exposure point on the corresponding photosensitive drum 31 via an imaging lens and mirror. It is what I did.

Further, in the present embodiment, the belt unit 23 is a belt in which an intermediate transfer belt 230 is stretched between a plurality of stretching rolls 231 to 236, and an intermediate transfer corresponding to the photosensitive drum 31 of each photosensitive unit 30. A primary transfer device (primary transfer roll in this example) 51 is disposed on the back surface of the belt 230, and a voltage having a polarity opposite to the charging polarity of the toner is applied to the primary transfer device 51, so The toner image is electrostatically transferred to the intermediate transfer belt 230 side.
Here, the intermediate transfer belt 230 uses a resin such as polyimide, polycarbonate, polyester, polypropylene, or various rubbers containing an appropriate amount of an antistatic agent such as carbon black, and has a volume resistivity of 10 ⁶ to 10 ¹⁴ Ω. The thickness is set to about 0.1 mm, for example.
On the other hand, the tension roll 231 is a steering drive roll that tilts to control the meandering in the lateral direction orthogonal to the traveling direction of the intermediate transfer belt 230 and drives the intermediate transfer belt 230. Reference numerals 232 and 233 denote surface-developing rolls (both driven rolls) for exposing the primary transfer surface of the intermediate transfer belt 230 to each image forming unit 22 (22a to 22d) to a predetermined position. Reference numeral 234 denotes a tension roll that is pressed against the intermediate transfer belt 230 with a predetermined tension by a biasing spring (not shown) to adjust the deflection of the intermediate transfer belt 230. Further, the tension roll 235 is a secondary transfer described later. It is a recording material posture adjusting roll that regulates the posture of the recording material entering the transfer nip area of the unit 52, and also a tension roller 236 is a roll (driven roll) which also serves as a backup roll below secondary transfer unit 52.

Further, a secondary transfer unit 52 is disposed at a portion corresponding to the tension roll 236 on the downstream side of the most downstream image forming unit 22d of the intermediate transfer belt 230, and a primary transfer image on the intermediate transfer belt 230 is recorded. Secondary transfer (collective transfer) is performed on the material.
In the present embodiment, the secondary transfer unit 52 is provided with a secondary transfer roll 522 in the opening of the unit case 521, and this secondary transfer roll is used as a backup roll (in this example, the tension roll 236 is also used). For example, the secondary transfer roll 522 is grounded and a bias having the same polarity as the charging polarity of the toner is applied to the backup roll (stretching roll 236).
Here, the secondary transfer roll 522 is made of urethane rubber tube with carbon dispersed on the surface, the inside is made of foamed urethane rubber with carbon dispersed, and further, the roll surface is coated with fluorine, and its volume resistivity is 10 ³ to 10 ^10. The roll diameter is Ω · cm, for example, φ28 mm, and the hardness is set to 30 ° (Asuka C), for example.
The backup roll 236 includes a tube of EPDM and NBR blend rubber in which carbon is dispersed on the surface, and the inside is formed of EPDM rubber, and its surface resistivity is 10 ⁷ to 10 ¹⁰ Ω / □. The roll diameter is, for example, 28 mm, and the hardness is set to 70 ° (Asuka C), for example.
In particular, in the present embodiment, the secondary transfer unit 52 includes a cleaning brush 523 that cleans the surface of the secondary transfer roll 522 in the unit case 521.
The mounting structure and drive system of the secondary transfer unit 52 will be described later.

Furthermore, a belt cleaner 53 is disposed on the upstream side of the most upstream image forming unit 22a of the intermediate transfer belt 230 so as to remove residual toner on the intermediate transfer belt 230.
A recording material supply cassette (not shown) is provided with a feed roll (not shown) for picking up the recording material, and a takeaway roll for sending the recording material is disposed immediately after the feed roll, and recording is performed. A suitable number of transport rolls 61 are disposed in the material transport path, and a registration roll that supplies the recording material to the secondary transfer site at a predetermined timing in the recording material transport path positioned immediately before the secondary transfer site. (Registration roll) 62 is disposed.
On the other hand, a fixing device 66 is provided in the recording material conveyance path located downstream of the secondary transfer site, and a discharge roll (not shown) for discharging the recording material is provided downstream of the fixing device 66. The recording material is accommodated in an accommodation tray 68 formed in the upper part of the main body housing 21.

Next, the mounting structure of the secondary transfer unit 52 will be described.
In the present embodiment, as shown in FIGS. 2 to 4, a door unit 70 is supported on the side of the main body housing 21 so as to be openable and closable around a rotation fulcrum 71. Further, the secondary transfer unit 52 is attached via a retract mechanism 80.
Here, the secondary transfer unit 52 has a pivot fulcrum (configured with pins in this example) 524 on both sides of the unit case 521, and a bracket 73 (an imaginary line in FIG. 4) attached to the frame 72 of the door unit 70. A long hole 74 (indicated by a phantom line in FIG. 4) is formed, and the rotation fulcrum 524 is locked in the long hole 74 so as to be pivotally supported.

  In this embodiment, as shown in FIGS. 4 and 5, the retract mechanism 80 is provided with an eccentric cam 81 that is rotated by a lifting motor (not shown), and a slide lever 82 is provided above the eccentric cam 81. Is held by a guide roller 83 (see FIG. 6), and a bent portion 82a facing the surface of the eccentric cam 81 is formed at the lower end of the slide lever 82, and the tip of the lower bent portion 82a is attached. While the spring 84 is biased downward, a bent portion 82b that is inclined obliquely downward from the horizontal direction is formed at the upper end of the slide lever 82, and the upper end bent portion 82b and the secondary transfer unit are formed. A part of the unit case 521 spaced from the rotation fulcrum 524 (in this example, the upper part of the unit case 521) is connected and fixed by a connecting rod 85.

On the other hand, on the belt unit 23 side, as shown in FIGS. 2 to 4, a positioning plate 90 (indicated by phantom lines in the figure) for positioning the secondary transfer roll 522 at the set position is disposed. A V-shaped positioning groove 91 for positioning the secondary transfer roll 522 is formed in the positioning plate 90, and a support shaft portion of the secondary transfer roll 522 is brought into contact with any edge portion of the positioning groove 91. The secondary transfer roll 522 is positioned in the positioning groove 91 by being guided and moved to the back of the positioning groove 91 (corresponding to the set position).
2 to 4, reference numeral 63 denotes a conveyance chute provided on the downstream side of the registration roll 62. When the door unit 70 is opened, one conveyance chute is opened together with the one registration roll 62 together with the door unit 70. Reference numerals 64 and 65 are conveyance guides provided on the downstream side of the secondary transfer portion and guiding and conveying the recording material toward the fixing device 66. In this example, the conveyance guides are opened together with the door unit 70. It is like that.

A drive system 100 of the secondary transfer unit 52 used in this embodiment is shown in FIGS.
In the figure, the drive system 100 of the secondary transfer unit 52 has a drive motor 101 fixedly disposed on a main body housing 21 (see FIG. 2), and a drive transmission gear 102 is coaxially fixed to the drive shaft of the drive motor 101. On the other hand, the driven transmission gear 103 is coaxially fixed to one end of the secondary transfer roll 522, and the secondary transfer roll 522 is set to the set position (see FIG. 7A) or retracted position (FIG. 7B). The drive transmission gear 102 and the driven transmission gear 103 are engaged with each other under any of the situations located in the reference).
7A and 7B, the same components as those in FIGS. 2 to 5 are denoted by the same reference numerals, and detailed description thereof is omitted here.

Next, an image forming process of the image forming apparatus according to the present embodiment will be described.
Each image forming unit 22 (22 a to 22 d) forms each color component image (toner image) on the photosensitive drum 31, and sequentially transfers each color component image onto the intermediate transfer belt 230 by the primary transfer device 51.
On the other hand, a recording material is supplied from a recording material supply cassette from outside the figure, and is conveyed to a secondary transfer portion through a registration roll 62 at a predetermined timing.
Then, the multiple transfer image primarily transferred onto the intermediate transfer belt 230 is conveyed to the secondary transfer portion and is collectively transferred to the recording material by the secondary transfer unit 52.
At this time, the secondary transfer unit 52 has a rotation fulcrum 524 above the position of the secondary transfer roll 522, and from above in the transfer nip region between the secondary transfer roll 522 and the intermediate transfer belt 230. Since the secondary transfer roll 522 is rotated along the recording material conveyance direction toward the recording medium, a rotational load is applied to the secondary transfer roll 522 when the recording material enters the transfer nip area from bottom to top. This rotational load acts in the direction of pressing the secondary transfer unit 52 toward the intermediate transfer belt 230 around the rotation fulcrum 524. As a result, the secondary transfer roll 522 and the intermediate transfer belt 230 are pressed. The positional relationship with is maintained.
Thereafter, the recording material fixes the images transferred in a batch via the fixing device 66 and then is discharged to the storage tray 68 through a discharge roll (not shown).
In each image forming unit 22, the residual toner on the photosensitive drum 31 is cleaned by the cleaner 34, while the residual toner on the intermediate transfer belt 230 is cleaned by the belt cleaner 53.

In such an image forming process, the secondary transfer unit 52 moves the secondary transfer roll 522 from the retract position (see FIG. 5B) to the set position (see FIG. 5A) immediately before performing the secondary transfer operation. When the secondary transfer operation is completed, or when the power is turned off, the set position is retracted to the retract position.
Here, the operation state of the retract mechanism 80 when the secondary transfer roll 522 is located at the set position will be described. In the retract mechanism 80, the cam surface of the eccentric cam 81 is in the lowest position (see FIG. 5A). It is in.
At this time, the lower end bent portion 82 a of the slide lever 82 is not in contact with the cam surface of the eccentric cam 81, and the slide lever 82 is pushed downward by the biasing spring 84.
Then, the unit case 521 rotates about the rotation fulcrum 524 in the direction of the arrow, and the secondary transfer unit 522 in the unit case 521 approaches the backup roll 236 side, and enters the positioning groove 91 of the positioning plate 90. Engaged and positioned.

On the other hand, the operation state of the retract mechanism 80 when the secondary transfer roll 522 is located at the retract position will be described. In the retract mechanism 80, the cam surface of the eccentric cam 81 is in the highest position (see FIG. 5B). is there.
At this time, the lower bent portion 82 a of the slide lever 82 is pushed up by the eccentric cam 81, and the slide lever 82 is pushed up against the biasing force of the biasing spring 84.
Then, the unit case 521 rotates about the rotation fulcrum 524, the secondary transfer roll 522 in the unit case 521 moves away from the backup roll 236, and reaches a retract position separated from the set position. .

In this example, the retract mechanism 80 includes a delay circuit that works when the power is turned off, and can move the secondary transfer roll 522 to the retract position when the power is turned off.
For this reason, in this embodiment, when the power is turned off, the retract mechanism 80 operates to set the secondary transfer roll 522 to the retract position at all times. Therefore, when the power is turned on, the secondary transfer unit 52 starts to operate from a state where the secondary transfer roll 522 is held at the retract position.

In the present embodiment, the drive system 100 of the secondary transfer unit 52 is driven by the drive motor 101 even when the secondary transfer roll 522 is located at the retract position, as shown in FIG. 7B. Since the coupled drive transmission gear 102 and the driven transmission gear 103 mesh with each other, the secondary transfer roll 522 is immediately driven to rotate.
Therefore, when the secondary transfer roll 522 is moved from the retract position (see FIG. 7B) to the set position (see FIG. 7A), the secondary transfer roll 522 is set to the set position while rotating. can do.
Therefore, even if the intermediate transfer belt 230 is rotated in advance before the secondary transfer roll 522 reaches the set position and the image forming process of each image forming unit 22 is started, the secondary transfer roll 522 reaches the set position. Thus, at the moment of contact with the intermediate transfer belt 230, a speed fluctuation is caused in the intermediate transfer belt 230, and there is no adverse effect on image positional deviation and motion quality of the intermediate transfer belt 230.

In this embodiment, the position of the drive transmission gear 102 is uniquely determined based on the positional relationship with the drive motor 101, but the position of the driven transmission gear 103 depends on the position change of the secondary transfer roll 522. Move with it.
Therefore, in the present embodiment, when the secondary transfer roll 522 is positioned at the set position (see FIG. 7A), the drive transmission gear 102 and the driven transmission gear 103 are meshed at the normal position, and the secondary transfer roll 522 is engaged with the secondary transfer roll 522 at the normal position. A stable rotational drive is applied to the transfer roll 522.
However, when the secondary transfer roll 522 is positioned at the retracted position (see FIG. 7B), the meshing state of both the gears 102 and 103 is deviated from the normal position, but the tooth tip radius of both the gears 102 and 103 is the same. If the distance between the centers of the two gears 102 and 103 is entered below the total, the meshing state of the two gears 102 and 103 is maintained.

Further, in the present embodiment, when a jam occurs in the recording material during the transfer operation by the secondary transfer unit 52, the door unit 70 is opened as shown in FIGS. Can be jammed.
In this case, the secondary transfer unit 52 is opened together with the door unit 70. The secondary transfer unit 52 is constructed by incorporating the secondary transfer roll 522 and the cleaning brush 523 into the unit case 521. 80, the secondary transfer unit 52 moves together with the unit case. Therefore, the opening of the unit case 521 only needs to be secured by a size corresponding to the secondary transfer roll 522, and the unit case 521 and the secondary transfer roll 522 are secured. There is no unnecessary gap between them.
Therefore, even if the secondary transfer unit 52 rotates together with the door unit 70, there is no possibility that the toner cloud is unnecessarily blown out from the opening of the unit case 521.

In the present embodiment, the drive system 100 of the secondary transfer unit 52 fixes the driven transmission gear 103 coaxially with the secondary transfer roll 522. However, the present invention is not limited to this. Instead, for example, a drive system 100 as shown in FIGS. 8A and 8B may be adopted.
In the drive system 100 of the secondary transfer unit 52 in the figure, a drive motor 111 is fixedly disposed on a main body housing 21 (see FIG. 2), and a drive transmission gear 112 is coaxially fixed to a drive shaft of the drive motor 111. The driven transmission gear 113 is coaxially fixed to the rotation fulcrum 524 of the unit case 521 of the secondary transfer unit 52, and the driven transmission is transmitted to the driven transmission gear 114 fixed coaxially to the secondary transfer roll 522. The drive transmission gear 112 is engaged under any situation where the gear 113 is engaged and the secondary transfer roll 522 is located at the set position (see FIG. 8A) or the retract position (see FIG. 8B). And the driven transmission gear 113 are meshed with each other.

Here, the retraction mechanism 80 causes the unit case 521 to rotate about the rotation fulcrum 524, and this rotation fulcrum 524 is a link that engages with the elongated hole 74 of the bracket 73 of the door unit 70. Since it is a mechanism, there is little variation in the position of the rotation fulcrum 524 that is the center of rotation of the link mechanism.
For this reason, in this example, the driven transmission gear 113 is fixed to the rotation fulcrum 524 of the unit case 521 with little position fluctuation, and the meshing state with the drive transmission gear 112 at each position can be maintained. It is.
In this example as well, when the secondary transfer roll 522 is positioned at the set position (see FIG. 8A), the drive transmission gear 112 and the driven transmission gear 113 are meshed at the regular position, and the secondary transfer roll 522 is engaged. Is provided with a stable rotational drive.
However, when the secondary transfer roll 522 is positioned at the retracted position (see FIG. 8B), the meshing state of both the gears 112 and 113 is deviated from the normal position, but the tooth tip radius of both the gears 112 and 113 is the same. If the distance between the centers of both gears 112 and 113 is set below the total, the meshing state of both gears 112 and 113 is maintained.

  DESCRIPTION OF SYMBOLS 1 ... Sub unit, 2 ... Rotating body, 3 ... Drive transmission means, 3m ... Drive source, 4 ... Retract mechanism, 5 ... Image carrier

Claims (4)

A latent image carrier that carries a latent image, an intermediate transfer belt on which an image obtained by visualizing the latent image on the latent image carrier is transferred, and a transfer nip area is formed between the intermediate transfer belt and the intermediate transfer belt. In this state, an image forming apparatus including a transfer member that transfers an image on the intermediate transfer belt to a recording material conveyed from below to above,
A door unit that is rotatably provided with respect to the image forming apparatus main body and opens and closes the image forming apparatus main body;
A transfer unit provided inside the door unit and having the transfer member;
The transfer unit has a rotation shaft above the transfer member position, and is along the conveying direction of the recording material from the bottom to the top in the transfer nip region between the transfer member and the intermediate transfer belt. An image forming apparatus, wherein the transfer member is rotated. The image forming apparatus according to claim 1.
The image forming apparatus according to claim 1, wherein the door unit has a rotation shaft below the transfer member position. The image forming apparatus according to claim 1.
A recording material supply cassette in which the recording material can be supplied;
An image forming apparatus comprising: a recording material conveyance path that extends in a vertical direction from the recording material supply cassette toward the transfer nip region and serves as a conveyance path for the recording material. The image forming apparatus according to claim 1.
The transfer unit is configured to support the unit case so as to be relatively movable with respect to the door unit and to be rotatable about the rotation shaft, and to support the transfer member on the unit case so as to be rotatable. An image forming apparatus.

Images