JP2023026990A - Image forming apparatus - Google Patents

Abstract

To improve the exchangeability of a pressing member in a configuration in which the amount of pressing of the pressing member against a belt is variable.SOLUTION: In an image forming apparatus 100 having a belt unit 3 including a pressing member 70 for a belt 31 and a moving mechanism 2 for the pressing member 70, the moving mechanism 2 includes a support part 71 for the pressing member 70, contact parts 80c for moving the support part 71, and a driving part 81, and an upstream side moving mechanism 2a including the contact parts 80c and the driving part 81 and a downstream side moving mechanism 2b including the support part 71 are separable from each other. The belt unit 3 is detachably attached with a pressing member unit 7 including the pressing member 70 and the downstream side moving mechanism 2b. The image forming apparatus 100 has a separation mechanism 3b for separating the support part 71 and the contact parts 80c from each other. The pressing member unit 7 is configured to be moved along the rotation axis direction of an inner roller 32 and removed from the belt unit 3 with the support part 71 separated from the contact parts 80c by the separation mechanism 3b.SELECTED DRAWING: Figure 6

Description

The present invention relates to an image forming apparatus such as a printer, a printing machine, a copying machine, a facsimile machine, or a multifunction machine having a plurality of functions among these using an electrophotographic system or an electrostatic recording system.

2. Description of the Related Art Conventionally, an image forming apparatus using an electrophotographic method or the like has a rotatable endless belt (hereinafter also simply referred to as "belt") as an image bearing member for carrying and conveying a toner image. be. As such a belt, for example, a second image that is conveyed to secondarily transfer a toner image that has been primarily transferred from a photosensitive member or the like as a first image carrier onto a sheet-like recording material such as paper. There is an intermediate transfer belt as a carrier. An image forming apparatus employing an intermediate transfer system having an intermediate transfer belt will be mainly described below as an example.

2. Description of the Related Art In an image forming apparatus using an intermediate transfer belt, a toner image formed on a photosensitive member or the like in an image forming section is primarily transferred onto the intermediate transfer belt in a primary transfer section. Further, the toner image primarily transferred to the intermediate transfer belt is secondarily transferred to the recording material at the secondary transfer portion. A secondary transfer portion is formed by an inner member (secondary transfer inner member) provided on the inner peripheral surface side of the intermediate transfer belt and an outer member (secondary transfer outer member) provided on the outer peripheral surface side of the intermediate transfer belt. is formed. As the inner member, a secondary transfer inner roller, which is one of a plurality of tension rollers for tensioning the intermediate transfer belt, is used. As the external member, a secondary transfer outer roller, which is arranged at a position facing the secondary transfer inner roller with the intermediate transfer belt interposed therebetween and is pressed toward the secondary transfer inner roller, is often used. Then, a voltage having a polarity opposite to the charging polarity of the toner is applied to the secondary transfer outer roller (or a voltage having the same polarity as the charging polarity of the toner is applied to the secondary transfer inner roller), thereby The toner image on the intermediate transfer belt is secondarily transferred onto the recording material. Regarding the recording material, the terms "leading edge" and "trailing edge" refer to the leading edge and the trailing edge in the conveying direction of the recording material, respectively. Further, the upstream of the secondary transfer portion with respect to the rotation direction (surface movement direction) of the intermediate transfer belt is also simply referred to as “upstream of the secondary transfer portion”.

In order to transfer the toner image formed on the intermediate transfer belt to the recording material with high accuracy, the contact length between the intermediate transfer belt and the recording material with respect to the rotation direction of the intermediate transfer belt upstream of the secondary transfer portion is required. becomes important. If the contact length is long, there is a possibility that the toner and the recording material rub against each other due to the speed difference between the intermediate transfer belt and the recording material, resulting in image defects. On the other hand, if the contact length is short, there is a possibility that an image defect or the like may occur due to discharge generated in the gap between the recording material and the intermediate transfer belt. Therefore, the conveying posture of the recording material and the tension layout of the intermediate transfer belt are determined in consideration of the contact position of the leading edge of the recording material with respect to the intermediate transfer belt upstream of the secondary transfer portion.

On the other hand, in recent years, with the diversification of recording materials in the commercial printing market, for example, there is a demand for good transfer on a wide variety of recording materials from high-rigidity thick paper to low-rigidity thin paper. In particular, when a recording material having high rigidity such as thick paper is used, the intermediate transfer belt tends to be deformed when the recording material enters the contact position. As a result, a minute gap is formed between the intermediate transfer belt and the recording material upstream of the secondary transfer portion, and an image defect or the like may occur due to discharge in the gap. Therefore, it is required to suppress the deformation of the intermediate transfer belt upstream of the secondary transfer portion and form a desired shape (orientation) of the intermediate transfer belt upstream of the secondary transfer portion with high accuracy.

In Japanese Patent Application Laid-Open No. 2002-100000, a plane that contacts the inner peripheral surface of the intermediate transfer belt and presses the intermediate transfer belt is located upstream of the contact position (tacking position) of the leading edge of the recording material with respect to the intermediate transfer belt in the rotation direction of the intermediate transfer belt. A configuration in which a sex correction member is provided has been proposed. In Patent Document 1, a flexible baffle plate and an elastic roll are used as flatness correcting members.

Further, Japanese Patent Application Laid-Open No. 2002-200000 proposes a configuration in which the pressing amount of a pressing member that presses the intermediate transfer belt by contacting the inner peripheral surface of the intermediate transfer belt is changed according to the type of recording material.

JP-A-9-80926 JP 2015-215594 A

As described above, by providing the pressing member that contacts the inner peripheral surface of the intermediate transfer belt and presses the intermediate transfer belt upstream of the secondary transfer portion, the shape (orientation) of the intermediate transfer belt upstream of the secondary transfer portion can be changed. ) can be made into a desired shape (orientation).

Since the pressing member may deteriorate due to wear, for example, its life is generally shorter than the life of the main body of the image forming apparatus. Therefore, when operating the image forming apparatus, it is necessary to periodically replace the pressing member, for example. In the image forming apparatus, the pressing member is included in an intermediate transfer belt unit (hereinafter also simply referred to as "belt unit") including an intermediate transfer belt and its tension roller. Since the life of the pressing member may differ from that of the intermediate transfer belt and its tension roller, the unit including the pressing member (here, also referred to as the "pressing member unit") in the belt unit is replaceable. It is desirable that Further, for example, in an image forming apparatus for commercial printing, the belt unit is large in size and weight due to its characteristics, and it is difficult for an operator to remove the belt unit from the main body of the image forming apparatus. Therefore, it is desired that the pressing member unit can be replaced while the belt unit is mounted on the main body of the image forming apparatus.

At this time, if a mechanism for varying the pressing amount of the pressing member against the intermediate transfer belt is attached to the belt unit, the workability of exchanging the pressing member unit with respect to the belt unit deteriorates. Then, there is a risk that the mechanism may be damaged.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to improve the replaceability of a pressing member in a configuration in which the pressing amount of the pressing member to the belt is variable.

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides a rotatable endless belt carrying a toner image, a plurality of tension rollers for stretching the belt, the inner roller and the inner roller in the direction of rotation of the belt. a plurality of tension rollers including an upstream roller disposed adjacent to the inner roller upstream of the inner roller; a tension applying unit that applies tension to the belt; a pressing member capable of contacting the inner peripheral surface of the belt upstream and downstream of the upstream roller; and a moving mechanism capable of moving the pressing member so as to change the amount of pressing of the pressing member against the belt. and an outer member disposed opposite the inner roller and forming a transfer portion that contacts the outer peripheral surface of the belt and transfers the toner image from the belt to the recording material. In the forming apparatus, the moving mechanism includes a movable support portion that supports the pressing member, a movable contact portion that contacts the support portion and moves the support portion, and a drive portion that moves the contact portion. and an upstream moving mechanism including the contact portion and the driving portion and a downstream moving mechanism including the support portion are separable, and the belt unit includes the pressing member and the moving mechanism. Only the downstream movement mechanism of the upstream movement mechanism and the downstream movement mechanism of is detachable, and the image forming apparatus separates the support portion and the contact portion from each other. The pressing member unit is removed from the belt unit by being moved along the rotation axis direction of the inner roller in a state in which the support portion is separated from the contact portion by the separation mechanism. The image forming apparatus is characterized by comprising:

According to the present invention, it is possible to improve the replaceability of the pressing member in a configuration in which the pressing amount of the pressing member to the belt is variable.

1 is a schematic cross-sectional view of an image forming apparatus; FIG. FIG. 4 is a schematic perspective view for explaining the support structure of the belt unit; 4 is a schematic cross-sectional view of the periphery of the secondary transfer portion when a pressing member is provided; FIG. 4 is a perspective view of a pressing member and a moving mechanism in Example 1. FIG. 4 is a cross-sectional side view of the periphery of the secondary transfer portion in Embodiment 1. FIG. 2 is a perspective view of an internal secondary transfer unit in Embodiment 1. FIG. 4 is a cross-sectional side view for explaining the operation of the moving mechanism in Embodiment 1; FIG. FIG. 11 is a cross-sectional side view for explaining the operation of the moving mechanism in Example 2; FIG. 11 is a perspective view of a pressing member and a moving mechanism in Example 3; FIG. 11 is a cross-sectional side view of the surroundings of a secondary transfer portion in Example 3; FIG. 11 is a perspective view of a pressing member and a moving mechanism in a modified example of Example 3; FIG. 11 is a perspective view of a pressing member and a moving mechanism in another modified example of the third embodiment; FIG. 2 is a schematic block diagram showing a control mode of main parts of the image forming apparatus; 4 is a schematic cross-sectional view of the periphery of the secondary transfer portion when no pressing member is provided; FIG.

Hereinafter, the image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

[Example 1]
1. 1. Overall Configuration and Operation of Image Forming Apparatus FIG. 1 is a schematic cross-sectional view of an image forming apparatus 100 of this embodiment (a cross section substantially orthogonal to the rotation axis direction of a photosensitive drum 11 and a tension roller of an intermediate transfer belt 31, which will be described later). ). The image forming apparatus 100 of this embodiment is a tandem printer that employs an intermediate transfer method. The image forming apparatus 100 prints a full-color image on a sheet-like recording material P formed of paper, plastic, or the like using an electrophotographic method in accordance with an image signal (image information) transmitted from an external device such as a personal computer. An image can be formed.

Image forming apparatus 100 includes four image forming units 1Y, 1M, 1Y, 1M, 1Y, 1M, 1Y, 1M, 1Y, 1M, 1Y, 1M, 1Y, 1M, 1M, 1Y, 1M, and 1M as a plurality of image forming units (stations). It has 1C, 1K. These image forming units 1Y, 1M, 1C, and 1K are arranged in a line along the direction of movement of an image transfer surface of an intermediate transfer belt 31 (to be described later) that is arranged substantially horizontally. Elements having the same or corresponding functions or configurations in the image forming units 1Y, 1M, 1C, and 1K are omitted from the symbols indicating that they are elements for one of the colors. may be described in a comprehensive manner. In this embodiment, the image forming unit 1 includes photosensitive drums 11 (11Y, 11M, 11C, 11K), chargers 12 (12Y, 12M, 12C, 12K), exposure devices 13 (13Y, 13M, 13C, 13K), which will be described later. ), developing device 14 (14Y, 14M, 14C, 14K), primary transfer roller 37 (37Y, 37M, 37C, 37K), cleaning device 15 (15Y, 15M, 15C, 15K), etc. .

The image forming apparatus 100 has a photosensitive drum 11 that is a rotatable drum-shaped (cylindrical) photosensitive member (electrophotographic photosensitive member) as a first image carrier that carries a toner image. A driving force is transmitted from a drum driving motor (not shown) as a driving source to the photosensitive drum 11, and the photosensitive drum 11 rotates in the direction of arrow R1 (counterclockwise direction) in FIG. 1 at a predetermined peripheral speed (process speed). driven. The surface of the rotating photosensitive drum 11 is uniformly charged to a predetermined potential with a predetermined polarity (negative polarity in this embodiment) by a charger 12 as charging means. During the charging process, a predetermined charging voltage (charging bias) is applied to the charger 12 by a charging power source (not shown). The charged surface of the photosensitive drum 11 is scanned and exposed according to an image signal by an exposure device 13 as an exposure unit, and an electrostatic image (electrostatic latent image) is formed on the photosensitive drum 11 . In this embodiment, the exposure device 13 is a laser scanner device that irradiates the photosensitive drum 11 with laser light modulated according to an image signal. The electrostatic image formed on the photosensitive drum 11 is developed (visualized) by supplying toner as developer by the developing device 14 as developing means, and a toner image (toner image, developer image) is formed on the photosensitive drum 11 . ) is formed. In this embodiment, an exposed portion (image portion) on the photosensitive drum 11, where the absolute value of the potential is lowered by being exposed after being uniformly charged, is provided with the same polarity as the charging polarity of the photosensitive drum 11 (this embodiment). In the example, negatively charged toner adheres (reversal development method). During development, a predetermined development voltage (development bias) is applied from a development power supply (not shown) to the development roller as a developer bearing member of the development device 14 . In this embodiment, the normal charge polarity of the toner, which is the charge polarity of the toner during development, is negative.

An intermediate transfer belt that is a rotatable intermediate transfer member composed of an endless belt as a second image carrier that carries a toner image so as to face the four photosensitive drums 11Y, 11M, 11C, and 11K. 31 are arranged. The intermediate transfer belt 31 is stretched around a driving roller 33, a tension roller 34, a secondary transfer pre-roller 35, and a secondary transfer inner roller 32 as a plurality of tension rollers (support rollers), and is applied with a predetermined tension (tensile force). ). The driving roller 33 transmits driving force to the intermediate transfer belt 31 . The driving roller 33 is rotationally driven by a driving force transmitted from a belt driving motor (not shown) as a driving source. As a result, the intermediate transfer belt 31 is driven by the driving roller 33 and rotates in the direction of arrow R2 (clockwise direction) in FIG. 1 at a peripheral speed (process speed) corresponding to the peripheral speed of the photosensitive drum 11. (move around). The tension roller 34 applies a predetermined tension to the intermediate transfer belt 31 and controls the tension of the intermediate transfer belt 31 to be constant. At both ends of the tension roller 34 in the rotation axis direction, tension springs 36, which are urging members (elastic members) as urging means, and which are configured by compression coil springs, are applied to the intermediate transfer belt 31 from the inner peripheral surface to the outer peripheral surface. It is biased toward the face side. The tension spring 36 constitutes tension applying means (tension applying section) that applies tension to the intermediate transfer belt 31 . The pre-secondary transfer roller 35 as an upstream roller forms the surface of the intermediate transfer belt 31 in the vicinity of the upstream of the secondary transfer portion N2, which will be described later, in relation to the rotation direction of the intermediate transfer belt 31 (moving direction of the surface). The secondary transfer inner roller (inner member) 32 functions as a secondary transfer member as a secondary transfer means in this embodiment. Among the plurality of tension rollers, the tension rollers other than the drive roller 33 are driven to rotate as the intermediate transfer belt 31 rotates. Further, on the inner peripheral surface side of the intermediate transfer belt 31, primary transfer rollers 37Y, which are roller-shaped primary transfer members as primary transfer means, corresponding to the respective photosensitive drums 11Y, 11M, 11C, and 11K, 37M, 37C and 37K are arranged. In this embodiment, each primary transfer roller 37 is arranged at a position facing each photosensitive drum 11 . The primary transfer roller 37 is pressed toward the photosensitive drum 11 and comes into contact with the photosensitive drum 11 via the intermediate transfer belt 31. A primary transfer portion (primary transfer roller 37) is formed where the photosensitive drum 11 and the intermediate transfer belt 31 are in contact with each other. nip) N1. The primary transfer roller 37 rotates following the rotation of the intermediate transfer belt 31 . Further, on the inner peripheral surface side of the intermediate transfer belt 31, a pressing member 70 is provided upstream of the inner secondary transfer roller 32 and downstream of the pre-secondary transfer roller 35 in the rotational direction of the intermediate transfer belt 31. there is The pressing member 70 and the moving mechanism 2 (FIG. 4) for changing the position of the pressing member 70 will be described later in more detail.

The toner image formed on the photosensitive drum 11 is transferred (primary transfer) onto the rotating intermediate transfer belt 31 by the action of the primary transfer roller 37 at the primary transfer portion N1. During the primary transfer, the primary transfer roller 37 is supplied with a DC voltage having a polarity (in this embodiment, a positive polarity) opposite to the normal charging polarity of the toner by a primary transfer power source (not shown). A voltage (primary transfer bias) is applied. For example, when forming a full-color image, the yellow, magenta, cyan, and black toner images formed on the photosensitive drums 11 are superimposed on the same image position (image area) on the intermediate transfer belt 31 . primary transfer sequentially. In this embodiment, the primary transfer portion N1 is an image forming position where a toner image is formed on the intermediate transfer belt 31. FIG. The intermediate transfer belt 31 is an example of a rotatable endless belt that conveys the toner image borne at the image forming position.

A secondary transfer outer roller (outer member) 41 is arranged at a position facing the secondary transfer inner roller 32 on the outer peripheral surface side of the intermediate transfer belt 31 . The secondary transfer outer roller 41 functions as a facing member (opposing electrode) of the secondary transfer inner roller 32 in this embodiment. The secondary transfer outer roller 41 is pressed toward the secondary transfer inner roller 32 and comes into contact with the secondary transfer inner roller 32 via the intermediate transfer belt 31, so that the intermediate transfer belt 31 and the secondary transfer outer roller 41 A contacting secondary transfer portion (secondary transfer nip) N2 is formed. The toner image formed on the intermediate transfer belt 31 is transferred (secondary transfer ) is done. In this embodiment, during the secondary transfer, a secondary transfer power supply (not shown) applies a DC voltage having the same polarity as the normal charging polarity of the toner (negative polarity in this embodiment) to the inner secondary transfer roller 32 . is applied (secondary transfer bias). In this embodiment, the secondary transfer outer roller 41 is electrically grounded (connected to the ground). The secondary transfer outer roller 41 is used as a secondary transfer member to which a secondary transfer voltage having a polarity opposite to the normal charging polarity of the toner is applied, and the secondary transfer inner roller 32 is used as a counter electrode. may be electrically grounded.

Recording materials (transfer materials, sheets, recording media, media) P are stored in recording material cassettes 61a to 61c as recording material storage units. The recording material P stored in the recording material cassettes 61a to 61c is sent out to the feeding and conveying path 63 by rotating any one of the feeding rollers 62a to 62c, which are feeding members as feeding means. be The recording material P is conveyed to a registration roller pair 65, which is a conveying member, by a conveying roller pair 64, which is a conveying member, and temporarily stopped. The recording material P is sent to the secondary transfer portion N2 in synchronization with the toner image on the intermediate transfer belt 31 by the registration roller pair 65 being rotationally driven.

A transport guide (pre-transfer guide) for guiding the recording material P to the secondary transfer portion N2 is provided downstream of the pair of registration rollers 65 and upstream of the secondary transfer portion N2 in the transport direction of the recording material P. ing. The conveying guide 66 includes a first guide member 66a that can come into contact with the front surface of the recording material P (the surface onto which the toner image is transferred immediately after passing the conveying guide 66), and the back surface of the recording material P (the front surface). and a second guide member 66b capable of contacting the surface on the opposite side). The first guide member 66a and the second guide member 66b are arranged to face each other, and the recording material P passes between these members. The first guide member 66 a regulates the movement of the recording material P in the direction toward the intermediate transfer belt 31 . The second guide member 66 b regulates the movement of the recording material P in the direction away from the intermediate transfer belt 31 .

The recording material P onto which the toner image has been transferred is conveyed to the fixing device 5 as fixing means by a conveying belt (pre-fixing conveying device) 67 or the like. The fixing device 5 heats and presses (heats and presses) the recording material P carrying an unfixed toner image on the surface of the recording material P by sandwiching and conveying the recording material P between the pair of fixing rotating bodies. Fix (melt, fix). The recording material P on which the toner image has been fixed is discharged (output) through a discharge conveying path 68 to a discharge tray 69 provided outside (outside) the apparatus main body 110 of the image forming apparatus 100 .

On the other hand, adherents such as toner remaining on the photosensitive drum 11 after the primary transfer (primary transfer residual toner) are removed and collected from the photosensitive drum 11 by a cleaning device 15 as cleaning means. Adhered matter such as toner remaining on the intermediate transfer belt 31 after the secondary transfer (secondary transfer residual toner) is removed from the intermediate transfer belt 31 by a belt cleaning device 38 as intermediate transfer body cleaning means and collected. be done.

In this embodiment, the intermediate transfer belt 31, the tension rollers 32 to 35, the primary transfer rollers 37, the belt cleaning device 38, a support frame 39 (FIG. 2), which will be described later, and the like are included. A unit (“belt unit”) 3 is configured. In this embodiment, the belt unit 3 is further provided with a pressing member 70 and a moving mechanism 2 ( FIG. 4 ) for changing the position of the pressing member 70 . In this embodiment, the belt unit 3 can be pulled out from the apparatus main body 110 of the image forming apparatus 100 for maintenance, as described later in detail. Further, in this embodiment, the secondary transfer unit 7 (FIG. 6) including the pressing member 70 is detachable from the belt unit 3 in order to replace the pressing member 70, etc., as will be described later in detail. It's becoming

Here, as the intermediate transfer belt 31, one made of a single-layer or multi-layered resin-based material, or a multi-layered belt having a resin layer made of a resin material and an elastic layer made of an elastic material. etc. can be used. Further, in this embodiment, the inner secondary transfer roller 32 is configured by providing an elastic layer of electronically conductive rubber on the outer circumference of a metal core (core material). In this embodiment, the pre-secondary transfer roller 35 is composed of a metal roller. Further, in this embodiment, the secondary transfer outer roller 41 is configured by providing an elastic layer of ion conductive foamed rubber on the outer periphery of a metal core (core material). In this embodiment, the bearing members (not shown) that support both ends of the secondary transfer outer roller 41 in the rotation axis direction are slidable in the direction toward the secondary transfer inner roller 32 and in the opposite direction. It has become. This bearing member is pressed toward the secondary transfer inner roller 32 by a pressing spring 42 (FIG. 3) constituted by a compression coil spring, which is a biasing member (elastic member) as biasing means. As a result, the secondary transfer outer roller 41 contacts the secondary transfer inner roller 32 with a predetermined pressure across the intermediate transfer belt 31 to form the secondary transfer portion N2. The rotation axis directions of the tension roller of the intermediate transfer belt 31 including the secondary transfer inner roller 32 and the secondary transfer outer roller 41 are substantially parallel to each other.

2. Belt Unit and its Support Structure Next, the belt unit 3 and the support structure of the belt unit 3 in this embodiment will be described. In this embodiment, regarding the image forming apparatus 100 and its elements, the front side of FIG. 1 is the front side, and the back side of FIG. 1 is the rear side. The front-rear direction connecting the front side and the rear side is assumed to be substantially parallel to the rotation axis direction of the photosensitive drum 11 and the tension roller of the intermediate transfer belt 31 . Regarding the image forming apparatus 100 and its elements, up and down means up and down in the gravitational direction (vertical direction). It includes an upper side and a lower side.

FIG. 2 is a schematic perspective view of the image forming apparatus 100 seen from the front side, showing the support structure of the belt unit 3 and the intermediate transfer belt 3. As shown in FIG. As shown in FIG. 2A, in this embodiment, the apparatus body 110 of the image forming apparatus 100 is provided with a support unit 120 as a holding member. The support unit 120 can hold the belt unit 3 at a first position where the toner image can be transferred from the photosensitive drum 11 to the intermediate transfer belt 31 . At the first position, the directions of the rotation axes of the tension rollers 32 to 35 and the primary transfer rollers 37 of the intermediate transfer belt 31 are substantially horizontal. The belt unit 3 has front side plates 39a disposed on both sides of the width direction (direction of the rotation axis of each of the tension rollers 32 to 35) substantially perpendicular to the moving direction of the surface of the intermediate transfer belt 31, that is, on the front side and the rear side. , a support frame 39 with a rear side plate 39b. Both ends of the tension rollers 32 to 35 and the primary transfer roller 37 in the rotation axis direction are rotatably supported by the front side plate 39a and the rear side plate 39b of the support frame 39 via bearing members. The belt unit 3 can be pulled forward from the housing 110a of the apparatus main body 110 of the image forming apparatus 100 when performing maintenance work such as replacing the intermediate transfer belt 31 or the pressing member 70, for example. Further, in this embodiment, the belt unit 3 is pulled out from the apparatus main body 110 and held with respect to the support unit 120 so as to be tiltable in the direction of arrow f (upward) in FIG. 2(b). . In addition, the support unit 120 can be pulled forward with respect to the apparatus main body 110 and can be inserted into the apparatus main body 110 . That is, the support unit 120 is held by the slide rails 111 provided in the apparatus main body 110 and can be inserted into and pulled out of the apparatus main body 110 along the slide rails 111 .

The support unit 120 includes a front support portion 120a provided on the front side, a rear support portion 120b provided on the rear side, and a pair of connection portions 120c that connect the front support portion 120a and the rear support portion 120b, 120c. The belt unit 3 is arranged in a space surrounded by the front support portion 120a, the rear support portion 120b, and the pair of connecting portions 120c, 120c. During maintenance of the belt unit 3, the support unit 120 holding the belt unit 3 is pulled forward from the apparatus main body 110 by an operator such as a user or a service person, as shown in FIG. 2(a). Then, the operator tilts the belt unit 3 in the direction of arrow f (upward) with respect to the support unit 120 to move it to the second position, as shown in FIG. 2(b). That is, as shown in FIG. 2A, the belt unit 3 is supported by the support unit 120 so as to be rotatable about one end (rear side) in the width direction of the intermediate transfer belt 31 by means of the hinge 3a. . Then, as shown in FIG. 2B , the belt unit 3 has a second belt in which the other end (front side) of the intermediate transfer belt 31 in the width direction is exposed above the front support portion 120 a of the support unit 120 . It is possible to tilt to the position of

With the belt unit 3 tilted to the second position, the operator operates the releasing mechanism 3b to release (loosen) the tension applied to the intermediate transfer belt 31 . As a result, the intermediate transfer belt 31 can be pulled out from the other end side (front side) in the width direction. Further, in this embodiment, in the state in which the tension of the intermediate transfer belt 31 is released as described above, the secondary transfer internal unit 7 (FIG. 6) including the pressing member 70 is moved to the other end of the intermediate transfer belt 31 in the width direction. It can be pulled out from the side (front side). The release mechanism 3b acts on, for example, a bearing member of the tension roller 34 to move the tension roller 34 from the outer peripheral surface side to the inner peripheral surface side of the intermediate transfer belt 31 against the biasing force of the tension spring 36 (FIG. 1). It is configured to be held in a state of being directed and moved. As described above, in this embodiment, maintenance work such as replacement of the intermediate transfer belt 31 and replacement of the pressing member 70 can be performed while the belt unit 3 is mounted in the apparatus main body 110 of the image forming apparatus 100 . Therefore, maintenance work such as replacement of the intermediate transfer belt 31 and replacement of the pressing member 70 can be easily performed.

In this embodiment, as described above, the rear side plate 39b of the support frame 39 arranged on the one end side (rear side) in the width direction of the intermediate transfer belt 31 and the rear side support portion 120b of the support unit 120 are connected. A hinge 3a with a built-in damper is provided between them. The hinge 3a dampens the moving speed when the belt unit 3 moves from the tilted second position toward the first position by gravity. Further, a lock mechanism may be provided to hold the belt unit 3 at the second position. In this embodiment, the hinge 3a and the lock mechanism constitute a rotating holding portion capable of holding the belt unit 3 at the second position. Projections (not shown) provided on the front side plate 39a and the rear side plate 39b of the support frame 39 are placed on mounting portions (not shown) provided on the front side support portion 120a and the rear side support portion 120b. By being placed, the belt unit 3 is supported by the support unit 120 at the first position.

3. Shape of Intermediate Transfer Belt Upstream of Secondary Transfer Portion Next, the shape (orientation) of the intermediate transfer belt 31 upstream of the secondary transfer portion N2 will be described. FIG. 3 is a schematic cross-sectional view for explaining the shape of the intermediate transfer belt 31 upstream of the secondary transfer portion N2 in the image forming apparatus 100 of the present embodiment (approximately in the rotation axis direction of the inner secondary transfer roller 32). perpendicular cross section). FIG. 14 is a schematic cross-sectional view for explaining the shape of the intermediate transfer belt 31 upstream of the secondary transfer portion N2 in the configuration of the comparative example in which the pressing member 70 is not provided (the inner secondary transfer roller 32). cross section substantially perpendicular to the direction of the rotation axis). In the comparative example, the same reference numerals are given to the elements corresponding to those of the present embodiment. 3A shows the state before the recording material P moves to the secondary transfer portion N2, and FIG. 3B shows the state after the recording material P moves to the secondary transfer portion N2. FIG. 3(c) shows an enlarged view of the vicinity of the secondary transfer portion N2 in FIG. 3(b). 14A, 14B, and 14C are diagrams corresponding to FIGS. 3A, 3B, and 3C, respectively, for the comparative example.

As shown in FIG. 3, in this embodiment, the shape of the intermediate transfer belt 31 formed by being stretched between the inner secondary transfer roller 32 and the pre-secondary transfer roller 35 (FIG. 1) is different from that of the secondary transfer belt. The outer transfer roller 41 is elastically biased by the pressure spring 42 toward the inner secondary transfer roller 32 . As a result, the intermediate transfer belt 31 is nipped between the inner secondary transfer roller 32 and the outer secondary transfer roller 41 to form the secondary transfer portion N2.

Further, in this embodiment, as will be described later in detail, a pressing member 70 is provided upstream of the secondary transfer portion N2 in proximity to the inner secondary transfer roller 32. As shown in FIG. In this embodiment, in the image forming apparatus 100, the tip of the pressing member 70 and the inner peripheral surface of the intermediate transfer belt 31 are in contact with each other during image formation in at least one predetermined mode (during secondary transfer). state. The pressing member 70 can contact the inner peripheral surface of the intermediate transfer belt 31 and press the intermediate transfer belt 31 from the inner peripheral surface side to the outer peripheral surface side. As a result, the pressing member 70 moves the stretched surface of the intermediate transfer belt 31 formed between the inner secondary transfer roller 32 and the pre-secondary transfer roller 35 from the inner peripheral surface side of the intermediate transfer belt 31 to the outer peripheral surface side. can be extended to In this embodiment, the pressing member 70 is formed of a plate-like member made of resin, and the pressing member 70 elastically urges the intermediate transfer belt 31 using bending elasticity. Therefore, the shape (amount of deflection, amount of deformation) of the pressing member 70 is such that the biasing force of the pressing member 70 biasing the intermediate transfer belt 31 and the resistance generated by the tension of the intermediate transfer belt 31 are balanced (here, " (also referred to as "statically determined shape"). The stationary shape of the pressing member 70 forms the shape of the intermediate transfer belt 31 upstream of the secondary transfer portion N2.

Further, in this embodiment, as will be described later in detail, the image forming apparatus 100 is configured such that the position of the pressing member 70 can be changed by the action of the moving mechanism 2 (FIG. 4). Thus, in this embodiment, the image forming apparatus 100 is configured to be able to control the static shape of the pressing member 70, that is, the shape of the intermediate transfer belt 31 upstream of the secondary transfer portion N2. .

In this embodiment, the secondary transfer inner roller 32 is applied with a bias having the same polarity as the charging polarity of the toner forming the toner image on the intermediate transfer belt 31, and the secondary transfer outer roller 41 is grounded. be. Thereby, a transfer electric field is formed at the secondary transfer portion N2. The recording material P is fed while being guided by a transport guide 66 to the secondary transfer portion N2 where the transfer electric field is formed. As shown in FIG. 3A, the leading edge of the recording material P abuts (contacts) the intermediate transfer belt 31 upstream of the secondary transfer portion N2, and is formed on the surface of the intermediate transfer belt 31. The toner image is conveyed toward the secondary transfer portion N2 while being in contact with the toner image. Then, as shown in FIG. 3B, when the recording material P is conveyed to the secondary transfer portion N2, the pressure action between the inner secondary transfer roller 32 and the outer secondary transfer roller 41, A toner image is transferred from the intermediate transfer belt 31 to the recording material P by the electric action of the transfer electric field.

Here, for high-precision secondary transfer, the intermediate transfer belt 31 upstream of the secondary transfer portion N2 when the recording material P is conveyed to the secondary transfer portion N2, in the rotational direction of the intermediate transfer belt 31 The length of contact between the recording material 31 and the recording material P (here, also referred to as "contact length") is important. If the contact length is long, there is a possibility that the toner image formed on the surface of the intermediate transfer belt 31 and the recording material P rub against each other, resulting in an image defect or the like. On the other hand, when the contact length is short, the gap (gap) G (FIG. 3(c)) between the intermediate transfer belt 31 and the recording material P becomes large, and the discharge phenomenon generated in the gap G causes an image. Defects may occur. In particular, when a recording material P having high rigidity such as thick paper or coated paper is used, the recording material P enters the contact position of the leading edge of the recording material P against the intermediate transfer belt 31 upstream of the secondary transfer portion N2. At this time, the intermediate transfer belt 31 is easily deformed. As a result, the air gap G is likely to occur, and image defects due to discharge in the air gap G may easily occur.

By providing the pressing member 70 as in this embodiment, it becomes easier to appropriately set the contact length between the intermediate transfer belt 31 and the recording material P upstream of the secondary transfer portion N2. In particular, in this embodiment, the shape of the intermediate transfer belt 31 upstream of the secondary transfer portion N2 can be controlled by variably controlling the position of the pressing member 70 using a moving mechanism 2 (FIG. 4), which will be described later. By optimizing the contact length between the intermediate transfer belt 31 and the recording material P upstream of the secondary transfer portion N2, the toner image can be stably secondarily transferred onto the recording material P. FIG. Furthermore, even when a recording material P with high rigidity such as thick paper or coated paper is used, the effect of elastic biasing of the pressing member 70 is as follows. That is, deformation of the intermediate transfer belt 31 when the recording material P and the intermediate transfer belt 31 come into contact with each other can be suppressed, and an increase in the gap G between the intermediate transfer belt 31 and the recording material P can be suppressed. .

On the other hand, as shown in FIGS. 14A to 14C, in the absence of the pressing member 70, when the recording material P is conveyed to the secondary transfer portion N2, the intermediate transfer portion is located upstream of the secondary transfer portion N2. The transfer belt 31 may be deformed and the gap G between the intermediate transfer belt 31 and the recording material P may become larger. As a result, the contact length between the recording material P and the intermediate transfer belt 31 may vary. As the gap G becomes larger, an image defect or the like may occur due to discharge. As described above, this tends to occur particularly when the recording material P having high rigidity such as thick paper or coated paper is used.

Thus, the image forming apparatus 100 of this embodiment can provide a product with stable image quality by the action of the pressing member 70 . In particular, the image forming apparatus 100 of the present embodiment can provide a high-quality product due to the action of the pressing member 70 even when a recording material P with high rigidity such as thick paper or coated paper is used.

Note that the image forming apparatus 100 of this embodiment is an apparatus that achieves high productivity, and the intermediate transfer belt 31 is conveyed at a speed of 600 mm/s. Further, in the image forming apparatus 100 of this embodiment, the toner has a negative polarity. In the image forming apparatus 100 of the present embodiment, a high voltage bias of −10 kV is applied to the inner secondary transfer roller 32 in order to ensure appropriate transfer performance even at the conveying speed of the intermediate transfer belt 31 . However, the conveying speed of the intermediate transfer belt 31, the polarity of the toner, and the value of the secondary transfer voltage are not limited to these.

4. Pressing Member and Moving Mechanism Next, the pressing member 70 and the moving mechanism 2 for changing the position of the pressing member 70 in this embodiment will be described. FIG. 4 is a rear perspective view of the pressing member 70 and the moving mechanism 2 in this embodiment. FIG. 5(a) is a cross-sectional side view of the periphery of the pressing member 70 and the moving mechanism 2 in this embodiment, viewed from the front side along the rotation axis direction of the secondary transfer inner roller 32. FIG. FIG. 5B is a cross-sectional side view of the surroundings of the pressing member 70 and the moving mechanism 2 of the belt unit 3 in this embodiment as seen from the rear side along the rotation axis direction of the inner secondary transfer roller 32. As shown in FIG. .

<Pressing member>
In this embodiment, the image forming apparatus 100 has a pressing member (backup member) 70 near the upstream side of the secondary transfer portion N2 on the inner circumferential surface side of the intermediate transfer belt 31 . The pressing member 70 can press the inner peripheral surface of the intermediate transfer belt 31 near the entrance of the secondary transfer portion N2 to project the intermediate transfer belt 31 toward the outer peripheral surface side. The pressing member 70 is upstream of the inner secondary transfer roller 32 and downstream of the pre-secondary transfer roller 35 with respect to the rotation direction of the intermediate transfer belt 31 so as to be able to contact the inner circumferential surface of the intermediate transfer belt 31 . are placed in In particular, in this embodiment, the pressing member 70 is positioned upstream of the secondary transfer inner roller 32 and downstream of the leading end of the transport guide 66 (first guide member 66a) with respect to the transport direction of the recording material P. It is arranged downstream so that it can come into contact with the inner peripheral surface of the intermediate transfer belt 31 .

In this embodiment, the pressing member 70 has predetermined lengths in the longitudinal direction arranged substantially parallel to the width direction of the intermediate transfer belt 31 and in the lateral direction substantially orthogonal to the longitudinal direction, It is composed of a plate-like (sheet-like) member that has a predetermined thickness and is approximately rectangular in plan view. The width direction of the intermediate transfer belt 31 is a direction substantially orthogonal to the movement direction of the surface of the intermediate transfer belt 31 and a direction substantially parallel to the rotation axis direction of the inner secondary transfer roller 32 . The length of the pressing member 70 in the longitudinal direction is the same as the length of the intermediate transfer belt 31 in the width direction. The pressing member 70 has a free end (tip) 70a, which is one end in the short direction (the end on the downstream side in the rotational direction of the intermediate transfer belt 31), over substantially the entire width of the intermediate transfer belt 31, and 31 and can press the intermediate transfer belt 31 . Further, in this embodiment, the pressing member 70 has a fixed end (base end) 70b side part thereof, which is the other end portion in the width direction (the end portion on the upstream side in the rotation direction of the intermediate transfer belt 31). , and is fixed to the mounting portion 70c by adhesion or the like. In this embodiment, the mounting portion 70c is made of sheet metal having a plate-shaped portion arranged along the width direction of the intermediate transfer belt 31 (longitudinal direction of the pressing member 70). It is used to attach the member 70 .

In this embodiment, the pressing member 70 is formed using a resin material. In particular, in this embodiment, the pressing member 70 is made of PPS (polyphenylene sulfide) with a thickness of 0.5 mm. In this embodiment, the pressing member 70 elastically urges the intermediate transfer belt 31 by using bending elasticity. In this embodiment, the pressing member 70 may be any member that can elastically urge the intermediate transfer belt 31 . For example, the thickness of the pressing member 70 is not limited to 0.5 mm, but is preferably about 0.4 to 1.5 mm, and may be 1.0 mm, for example. Further, the material of the pressing member 70 is not limited to PPS, and may be PEEK (polyetheretherketone), PET (polyethylene terephthalate), or the like.

Here, the pressing member 70, more specifically, the end (here, simply referred to as “tip”) on the side of the free end (tip) 70a in the short direction of the pressing member 70 is the inner secondary transfer roller. It is desirable to be placed as close to 32 as possible. However, the pressing member 70 is arranged so as not to contact the inner secondary transfer roller 32 . The pressing member 70 is positioned, for example, about 2 mm or more, typically about 10 mm or more, away from the position where the secondary transfer inner roller 32 and the intermediate transfer belt 31 contact to the upstream side in the rotation direction of the intermediate transfer belt 31 . It is arranged so as to be in contact with the inner peripheral surface of the intermediate transfer belt 31 . Further, the pressing member 70 is located at a position separated by, for example, about 40 mm or less, typically about 25 mm or less, toward the upstream side in the rotation direction of the intermediate transfer belt 31 from the position where the secondary transfer inner roller 32 and the intermediate transfer belt 31 contact each other. is arranged so as to be in contact with the inner peripheral surface of the intermediate transfer belt 31 .

<Movement Mechanism>
In this embodiment, the image forming apparatus 100 has a moving mechanism 2 that changes the position of the pressing member 70 . By changing the position of the pressing member 70, the moving mechanism 2 can control the static shape of the pressing member 70, that is, the shape of the intermediate transfer belt 31 upstream of the secondary transfer portion N2. In other words, the moving mechanism 2 can control the pressing amount of the pressing member 70 against the intermediate transfer belt 31 by changing the position of the pressing member 70 . Thereby, the moving mechanism 2 can optimize the contact length between the intermediate transfer belt 31 and the recording material P upstream of the secondary transfer portion N2.

The moving mechanism 2 has a support member 71 as a support portion arranged along the width direction of the intermediate transfer belt 31 . The pressing member 70 is supported by a supporting member 71 . In this embodiment, a portion of the pressing member 70 on the fixed end portion 70b side in the lateral direction is fixed over substantially the entire width in the longitudinal direction to the mounting portion 70c by adhesion or the like. It is fixed to the support member 71 . Note that the pressing member 70 may be directly fixed to the support member 71 . Rotating shafts 73 are provided at both ends of the support member 71 in the longitudinal direction. As will be described later in detail, the support member 71 is rotatable around the rotation shaft 73 about a rotation axis substantially parallel to the width direction of the intermediate transfer belt 31 via the rotation shaft 73 . are supported by a front frame 74 and a rear frame 75 (FIG. 6) of the secondary transfer internal unit 7 . By rotating the support member 71 about the rotation axis substantially parallel to the width direction of the intermediate transfer belt 31 in this manner, the pressing member 70 is rotated about the rotation axis, and the pressing member 70 position can be changed.

Further, the moving mechanism 2 has a cam shaft 80 formed of a cylindrical member extending along the width direction of the intermediate transfer belt 31 . As will be described later in detail, the cam shaft 80 is supported by the support frame 39 of the belt unit 3 so as to be rotatable around a rotation axis substantially parallel to the width direction of the intermediate transfer belt 31 . Further, the moving mechanism 2 has a cam 80c, a driving gear 80a and a flag 80b. These cam 80c, driving gear 80a and flag 80b are fixed to the cam shaft 80, respectively. The cams 80c are provided at both ends of the cam shaft 80 in the rotation axis direction. The drive gear 80a is provided at the rear end of the camshaft 80 in the rotational axis direction. The moving mechanism 2 also has a driving motor 81 configured by a stepping motor as a driving source that constitutes a driving section, and first and second transmission gears 82 and 83 . The drive motor 81 and the first and second transmission gears 82 and 83 are provided on the rear side of the cam shaft 80 in the rotational axis direction. The driving gear 80a is drivingly connected to a driving motor 81 via first and second transmission gears 82,83. That is, the output gear 81a fixed to the output shaft of the drive motor 81 meshes with the first transmission gear 82, the first transmission gear 82 meshes with the second transmission gear 83, and the second transmission gear 83 engages the camshaft. It meshes with a drive gear 80a fixed to 80. As will be described later in detail, the drive motor 81 and the first and second transmission gears 82 are supported by the support frame 39 of the belt unit 3 . When the drive motor 81 rotates, the drive is transmitted to the cam shaft 80 via the first and second transmission gears 82 and 83 and the drive gear 80a, and the cam 80c and the flag 80b are integrated with the cam shaft 80 to perform the intermediate transfer. It rotates around a rotation axis substantially parallel to the width direction of the belt 31 .

The cam 80c as the contact portion contacts the cam follower 71a as the contacted portion provided on the support member 71. As shown in FIG. The cam 80c forms a stepless surface in which the radius from the rotation center changes uniformly according to the rotation angle. The stepless surface as the contact surface contacts the contact surface of the cam follower 71 a of the support member 71 . The cam followers 71a are provided at both ends of the support member 71 in the longitudinal direction. Cams 80c provided at both ends of the cam shaft 80 in the direction of the rotational axis contact the cam followers 71a. Therefore, when the drive motor 81 rotates to rotate the cam 80c, the rotation of the cam 80c causes the support member 71 to rotate about the rotation shaft 73. As shown in FIG. That is, the rotational drive of the drive motor 81 is transmitted to the cam 80c through the first and second transmission gears 82 and 83 and the drive gear 80a, and the rotation is transmitted through the stepless surface of the cam 80c with the rotation shaft 73 as the rotation center. The support member 71 is rotated. Thereby, the moving mechanism 2 can move the pressing member 70 to change the position of the pressing member 70 . Here, in this embodiment, changing the position of the pressing member 70 means, more specifically, the position of the tip of the pressing member 70 when it is assumed that the intermediate transfer belt 31 does not exist (hereinafter, simply referred to as the "tip position"). ) is to be changed. Specifically, in the present embodiment, changing the position of the pressing member 70 means changing the position of the supporting member 71 as a movable moving part of the moving mechanism 2 .

The moving mechanism 2 also includes a position sensor (HP sensor) as position detection means for detecting the position (phase) of the cam 80c in the rotational direction, particularly the home position (HP) in the rotational direction of the cam 80c in this embodiment. ) 89. The position sensor 89 is supported by the support frame 39 of the belt unit 3. As shown in FIG. The position sensor 89 and the flag 80b fixed to the camshaft 80 constitute a photointerrupter. The movement mechanism 2 can set the attitude of the movement mechanism 2 to a preset neutral position by the action of the position sensor 89 and the flag 80b.

The operation of the moving mechanism 2 will be further described with reference to FIG. 5(a). For example, when the pressing member 70 is moved in the direction of pressing the intermediate transfer belt 31, the cam 80c is driven by the drive motor 81 to rotate clockwise in the figure. As a result, the support member 71 rotates about the rotation shaft 73 in the counterclockwise direction in the drawing, and the position of the pressing member 70 (more specifically, the tip position) moves toward the outer peripheral surface of the intermediate transfer belt 31 . and move. Further, for example, when the pressing member 70 is moved in the direction opposite to the direction of pressing the intermediate transfer belt 31, the cam 80c is driven by the drive motor 81 to rotate counterclockwise in the figure. As a result, the support member 71 rotates in the clockwise direction in the drawing about the rotation shaft 73 , and the position of the pressing member 70 (more specifically, the tip position) moves toward the inner peripheral surface of the intermediate transfer belt 31 . and move.

In this embodiment, the image forming apparatus 100 can control the rotation angle of the cam 80c by controlling the amount of rotation of the drive motor 81 by means of the control section 50 (FIG. 13), which will be described later. Accordingly, it is possible to control the position of the pressing member 70 (more specifically, the tip position) by controlling the position of the support member 71 in the rotational direction. In this embodiment, the control unit 50 controls the driving motor 81 according to the number of input pulses to the driving motor (stepping motor) 81 from the neutral position (the home position of the cam 80c) of the moving mechanism 2 detected by the position sensor 89. to control the amount of drive. This makes it possible to control the position of the support member 71 in the rotation direction by controlling the rotation angle of the cam 80c. In this embodiment, the control unit 50 sets the moving mechanism 2 to the neutral position, for example, in a power-off state of the image forming apparatus 100 or a standby state in which a job input is awaited while the power is on.

A specific support structure of each element in the moving mechanism 2 will be described later in more detail.

5. Control Mode FIG. 13 is a schematic block diagram showing a control mode of the main part of the image forming apparatus 100 of this embodiment. An apparatus body 110 of the image forming apparatus 100 is provided with a control section 50 as a control means. The control unit 50 includes a CPU 51 as arithmetic control means, which is a central element for arithmetic processing, a ROM 52 and a RAM 53 as storage means, an interface (input/output circuit), and the like. The CPU 51 can perform integrated control of each unit of the image forming apparatus 100 according to a control program stored in the ROM 52 and using the RAM 53 as a work area based on input signals from various sensors included in the image forming apparatus 100 . can. In this embodiment, in particular, the control unit 50 controls the operation of the driving motor 81 of the moving mechanism 2 based on the input signal from the position sensor 89 of the moving mechanism 2 to change the rotation direction of the cam 80c of the moving mechanism 2. to control the position (phase) of An operation unit (operation panel) 130 provided in the apparatus main body 110 of the image forming apparatus 100 is connected to the control unit 50 . The operation unit 130 includes a display unit (display means) that displays information under control of the control unit 50, and an input unit ( input means). The operation unit 130 may be configured with a touch panel having functions of display means and input means. Further, the controller 50 may be connected to an open/close sensor 140 for detecting opening/closing of a door provided in the apparatus main body 110 of the image forming apparatus 100 . Further, the image forming apparatus 100 may be connected to an external device such as a personal computer, an image reading device, and the like.

Here, the image forming apparatus 100 executes a job (print job), which is a series of operations for forming and outputting an image on a single or a plurality of recording materials P, which is started by one start instruction. . A job generally includes an image forming process (image forming operation), a pre-rotation process, an inter-paper process when forming images on a plurality of recording materials P, and a post-rotation process. The image forming process is a period in which electrostatic image formation of an image to be actually formed and output on the recording material P, formation of a toner image, primary transfer, and secondary transfer of the toner image are performed. formation period) refers to this period. More specifically, the timing of image formation differs depending on the position where each step of electrostatic image formation, toner image formation, primary transfer, and secondary transfer of the toner image is performed. The pre-rotation process is a period from when the start instruction is input to when the image formation is actually started, during which preparatory operations are performed before the image forming process. The paper interval process is a period corresponding to the interval between recording materials P when image formation is continuously performed on a plurality of recording materials P (continuous image formation). The post-rotation process is a period during which an arrangement operation (preparation operation) is performed after the image forming process. The non-image forming period (non-image forming period) is a period other than the image forming period, and includes the following periods. That is, a standby state, a pre-rotation process, a paper-to-paper process, a post-rotation process, a pre-multi-rotation process which is a preparatory operation when the power of the image forming apparatus 100 is turned on or when returning from a sleep state, and a pre-rotation process from the standby state. It is a period before starting a process or a pre-multi-rotation process. In this embodiment, the image forming apparatus 100 sets the amount of pressing of the pressing member 70 against the intermediate transfer belt 31, that is, the position of the pressing member 70, in accordance with the setting of the image forming to be executed after that, when the image is not formed. adjustment) can be performed.

The control unit 50 can control, for example, to change the amount of pressing of the pressing member 70 against the intermediate transfer belt 31, that is, the position of the pressing member 70, according to information about the recording material P used in the job. . In this case, information (table data, etc.) indicating the relationship between the information of the recording material P and the amount of pressing of the pressing member 70 against the intermediate transfer belt 31 , that is, the position of the pressing member 70 is stored in advance in the ROM 52 . Based on this information, the control unit 50 can perform control to change the amount of pressing of the pressing member 70 against the intermediate transfer belt 31, that is, the position of the pressing member 70, for the subsequent image formation when the image is not formed. can. The information of the recording material P includes attributes (so-called paper type category) based on general characteristics such as plain paper, thick paper, and thin paper, numerical values and numerical ranges such as basis weight, thickness, size, and rigidity, or It includes arbitrary information that can distinguish the recording material P, such as brand (including manufacturer, product name, product number, etc.). It can be considered that each recording material P distinguished by information on the recording material P constitutes the type of the recording material P. FIG. Further, the information of the recording material P may be included in information specifying operation settings of the image forming apparatus 100, such as "plain paper mode" and "thick paper mode", or may be replaced by the information. For example, when forming an image on thick paper, the pressure amount of the pressing member 70 against the intermediate transfer belt 31 may be larger than when forming an image on thin paper. Alternatively, the amount of pressing of the pressing member 70 against the intermediate transfer belt 31 can be arbitrarily changed in accordance with an instruction from the operating unit 130 or the like by an operator (operator) such as a user or a service person. . Further, in this embodiment, the neutral position of the moving mechanism 2 is set so that the pressure amount of the pressure member 70 against the intermediate transfer belt 31 is a predetermined pressure amount, that is, the position of the pressure member 70 is at a predetermined position. is set to

The amount of pressing of the intermediate transfer belt 31 by the pressing member 70 can be represented by, for example, the amount of penetration of the pressing member 70 into the intermediate transfer belt 31 . This amount of penetration is approximately the stretched surface of the intermediate transfer belt 31 formed by stretching the pressing member 70 between the inner secondary transfer roller 32 or the outer secondary transfer roller 41 and the pre-secondary transfer roller 35 . This is the amount by which the intermediate transfer belt 31 protrudes outward with respect to (stretching surface). The pre-secondary transfer roller 35 is an example of an upstream roller arranged adjacent to the inner secondary transfer roller 32 upstream of the inner secondary transfer roller 32 in the rotation direction of the intermediate transfer belt 31 among the plurality of tension rollers. is.

6. Unit in Secondary Transfer As described above, the life of the pressing member may differ from that of the intermediate transfer belt and its tension roller. ”) should be exchangeable. Further, for example, in an image forming apparatus for commercial printing, the belt unit is large in size and weight due to its characteristics, and it is difficult for an operator to remove the belt unit from the main body of the image forming apparatus. For this reason, it is desired that the regularly replaced parts in the belt unit, for example, the pressing member unit, can be replaced while the belt unit is mounted on the main body of the image forming apparatus. The state in which the belt unit is pulled out from the apparatus main body as in this embodiment is also included in the state in which the belt unit is mounted on the apparatus main body. Here, in order to realize a configuration in which the pressing amount of the pressing member against the intermediate transfer belt is variable, a configuration in which a mechanism for changing the pressing amount is attached to the belt unit is conceivable. At this time, for example, in an image forming apparatus for commercial printing, in a configuration in which the secondary transfer section is provided on the lower side of the apparatus main body of the image forming apparatus, when replacing the pressing member, it is possible to look from the lower side of the belt unit. In some cases, it may be necessary to perform the replacement work while being busy. In this case, the workability of exchanging the pressing member is very poor. In this way, when a mechanism for varying the pressing amount of the pressing member against the intermediate transfer belt is attached to the belt unit, the workability of exchanging the pressing member unit with respect to the belt unit deteriorates. Then, a risk such as damage to the mechanism may occur.

Therefore, in this embodiment, the moving mechanism 2 includes an upstream moving mechanism 2a (FIG. 4) including a drive motor 81, a downstream moving mechanism 2b (FIG. 4) including a support member 71 that supports the pressing member 70, The upstream moving mechanism 2a and the downstream moving mechanism 2b are driven and connected. Then, in the belt unit 2, the upstream side moving mechanism 2a is attached, and the stationary side unit 8 (FIG. 5), which is a unit fixed to the support frame 39 of the belt unit 3, and the downstream side moving mechanism 2b are attached and pressed. The secondary transfer internal unit 7 (FIG. 5), which is a unit ("pressing member unit") including the member 70, is separable. In particular, in this embodiment, the secondary transfer internal unit 7 can be moved to the front side of the image forming apparatus 100 and separated from the fixed unit 8 . Further, the inner secondary transfer unit 7 including the pressing member 70 can be moved to the front side of the image forming apparatus 100 and removed from the belt unit 3 . As a result, in this embodiment, the image forming apparatus 100 can realize high replaceability of the pressing member 70 while having a mechanism for varying the pressing amount of the pressing member 70 against the intermediate transfer belt 31 . A more detailed description will be given below.

5(a) and 5(b) are cross-sectional side views of the periphery of the pressing member 70 and the moving mechanism 2 in this embodiment as viewed from the front and rear sides, respectively, as described above. FIG. 6 is a perspective view of the internal secondary transfer unit 7, which is the pressing member unit in this embodiment, viewed from the rear side.

In this embodiment, the internal secondary transfer unit 7 includes an upper frame 72 arranged along the width direction of the intermediate transfer belt 31, front frames 74 arranged at both ends of the upper frame 72 in the longitudinal direction, and rear frames. 75 and . Note that the front frame 74 is not shown in FIG. 5(a). The front frame 74 is arranged on the front side of the image forming apparatus 100, the rear frame 75 is arranged on the rear side of the image forming apparatus 100, and the upper frame 72 connects the front frame 74 and the rear frame 75 above the pressing member 70 and the like. are arranged to In this embodiment, the secondary transfer inner unit 7 includes a secondary transfer inner roller 32 and a support member 71 to which a pressing member 70 is attached. That is, both ends of the inner secondary transfer roller 32 in the rotation axis direction are rotatably supported by the front frame 74 and the rear frame 75 via bearing members. Rotating shafts 73 provided at both ends of the support member 71 in the longitudinal direction are rotatably supported by the front frame 74 and the rear frame 75, respectively.

On the other hand, in this embodiment, a drive support plate 86 is fixed to a stay 85 provided on the support frame 39 of the belt unit 3 . In this embodiment, the drive support plate 86 is fixed to each of the front side plate 39a and the rear side plate 39b of the support frame 39, but the front side drive support plate 86 is not shown in FIG. 5(a). The drive motor 81 is fixed to the drive support plate 86 (rear side). Also, the first and second transmission gears 82 and 83 are rotatably supported by the drive support plate 86 (rear side). Also, the cam shaft 80 is rotatably supported by the drive support plate 86 (front side and rear side). In this embodiment, the drive support plate 86, the drive motor 81, the first and second transmission gears 82 and 83, the cam shaft 80, the drive gear 80a, the cam 80c, the flag 80b and the like are used to support the support frame 39 of the belt unit 3. A fixed unit 8 is configured as a fixed unit.

In this embodiment, the guide portions 72a and 72b provided on the upper frame 72 of the internal secondary transfer unit 7 are slidable along the rail portions 84a and 84b fixed to the support frame 39 of the belt unit 3. to engage. The guide portions 72a and 72b as first engaging portions are provided along the longitudinal direction of the upper frame 72 at both ends in the width direction of the upper frame 72 substantially orthogonal to the longitudinal direction. The rail portions 84a and 84b as second engaging portions are provided along the width direction of the intermediate transfer belt 31 so as to connect the front side plate 39a and the rear side plate 39b of the support frame 39 of the belt unit 3. It is As a result, the tension of the intermediate transfer belt 31 is released by the release mechanism 3b (FIG. 2) as described above, and the secondary transfer internal unit 7 is moved along the width direction of the intermediate transfer belt 31 relative to the belt unit 3. It is possible to insert and remove.

For example, when the pressing member 70 is replaced, the secondary transfer inner unit 7 is pulled out to the front side of the image forming apparatus 100 along the width direction of the intermediate transfer belt 31 and removed from the belt unit 3 . In this embodiment, at this time, the belt unit 3 is pulled out to the front side of the image forming apparatus 100 and tilted upward as described above, and the tension of the intermediate transfer belt 31 is released. At this time, the secondary transfer outer roller 41 is separated from the intermediate transfer belt 31 . For example, the pressing member 70 can be removed from the supporting member 71 together with the mounting portion 70c and replaced. Further, the attachment and detachment of the secondary transfer internal unit 7 with respect to the belt unit 3 may be performed for maintenance such as cleaning of the pressing member 70 . Further, the attachment and detachment of the inner secondary transfer unit 7 to and from the belt unit 3 may be performed for maintenance such as replacement or cleaning of the inner secondary transfer roller 32 in addition to or instead of replacement of the pressing member 70 or maintenance. good. Furthermore, for example, when the pressing member 70 reaches the end of its life, the entire secondary transfer unit 7 may be replaced.

In this embodiment, the rear side surface of the front frame 74 is provided with positioning projections 74a (two in this embodiment), and the rear side surface of the rear frame 75 is provided with positioning projections 75a (in this embodiment, two) are provided. When the internal secondary transfer unit 7 is inserted behind the image forming apparatus 100 with respect to the belt unit 3 along the width direction of the intermediate transfer belt 31, the following occurs. That is, the front and rear positioning protrusions 74a and 75a are fitted with positioning holes (not shown) provided in the front side plate 39a and the rear side plate 39b of the support frame 39 of the belt unit 3, respectively. As a result, the position of the in-secondary transfer unit 7 relative to the belt unit 3 is determined. Further, the internal secondary transfer unit 7 may be fixed to the belt unit 3 by any fixing means such as screws.

Thus, in this embodiment, the upstream moving mechanism 2a of the moving mechanism 2 includes the drive motor 81, the first and second transmission gears 82 and 83, the drive gear 80a, the cam shaft 80, the flag 80b, and the cam 80c. is configured with In this embodiment, the downstream moving mechanism 2b of the moving mechanism 2 includes a support member 71 to which the pressing member 70 is fixed and which has a cam follower 71a with which the cam 80c can abut. The moving mechanism 2 is divided into an upstream moving mechanism 2a and a downstream moving mechanism 2b, and the upstream moving mechanism 2a and the downstream moving mechanism 2b are drivingly connected. In this embodiment, in the belt unit 2, the fixed side unit 8 to which the upstream side moving mechanism 2a is attached and the secondary transfer internal unit 7 to which the downstream side moving mechanism 2b is attached are separable. there is In particular, in this embodiment, the secondary transfer internal unit 7 can be moved to the front side of the image forming apparatus 100 and separated from the fixed unit 8 .

Here, in this embodiment, as described above, the position of the pressing member 70 is made variable, and the risk of collision between the support member 71 and the cam 80c when the secondary transfer internal unit 7 is inserted into or removed from the belt unit 3 is reduced. In addition, the moving mechanism 2 has the following configuration. That is, during image formation (during image formation), the cam 80c and the cam follower 71a of the support member 71 are brought into contact to determine the position of the pressing member . On the other hand, when the secondary transfer internal unit 7 is inserted into or removed from the belt unit 3, the cam follower 71a of the support member 71 and the cam 80c are separated. In relation to the operation of the moving mechanism 2 , the time of image formation (during image formation) includes a period during which the image to be transferred to the recording material P and output from the image forming apparatus 100 is secondary transferred.

FIG. 7 is a cross-sectional side view of the inner secondary transfer unit 7 and the cam 80c in this embodiment as seen from the front side along the rotation axis direction of the inner secondary transfer roller 32. As shown in FIG. 7A shows an example of the attitude of the cam 80c and the support member 71 during image formation, and FIG. The posture of the support member 71 is shown.

In this embodiment, the support member 71 is configured such that a moment due to its own weight is generated in the counterclockwise direction in the figure, ie, in the direction in which the cam follower 71a of the support member 71 is separated from the cam 80c in the free state. That is, in the present embodiment, in FIG. 7A, the support member 71 is arranged so that the rotation axis is positioned to the right (cam shaft 80 side) in the horizontal direction with respect to the center of gravity 71G of the support member 71 to which the pressing member 70 is fixed. 73 is provided. In this embodiment, in FIG. 7A, the cam shaft 80 is arranged above the position where it overlaps the rotation shaft 73 in the horizontal direction. Therefore, in the free state, the support member 73 generates a moment due to its own weight in the counterclockwise direction in the figure, that is, in the direction in which the cam follower 71a of the support member 71 moves away from the cam 80c.

At the time of image formation shown in FIG. 7A, the support member 71 receives a moment clockwise from the intermediate transfer belt 31 via the pressing member 70 due to the tension of the intermediate transfer belt 31 . Then, the cam follower 71a of the support member 71 and the cam 80c contact each other to determine the position of the pressing member 70. As shown in FIG.

On the other hand, when the internal secondary transfer unit 7 shown in FIG. receives a counterclockwise moment in the figure due to its own weight. Then, the cam follower 71a of the support member 71 is separated from the cam 80c. In the present embodiment, when the tension of the intermediate transfer belt 31 is released, the belt unit 3, as shown in FIG. The configuration is such that the intermediate transfer belt 31 and the pressing member 70 do not come into contact with each other. As described above, in this embodiment, the release mechanism 3b for the intermediate transfer belt 31 that sets the support member 71 in the free state constitutes a separation mechanism that separates the support member 71 from the cam 80c.

The operation for attaching the secondary transfer unit 7 to the belt unit 3 is the reverse of the operation for removing it. In other words, in the state where the tension of the intermediate transfer belt 31 is released, as shown in FIG. It is attached to the belt unit 3. By tensioning the intermediate transfer belt 31, the cam follower 71a comes into contact with the cam 80c and the position of the pressing member 70 is determined as shown in FIG. 7A.

As described above, in this embodiment, when the inner secondary transfer unit 7 is removed from the belt unit 3, the front side of the belt unit 3 is rotated upward and tilted. operates as described above.

Also in the configuration of the present embodiment, as in the case of the second embodiment described later, when the secondary transfer internal unit 7 is inserted into or removed from the belt unit 3, the cam 80c is rotated to a position (phase) where it does not come into contact with the support member 71. (Evacuate). Specifically, for example, as shown in FIG. 7B, the cam 80c is rotated (retracted) to a position (phase) where the contact surface of the cam 80c that can contact the cam follower 71a faces the side opposite to the cam follower 71a. Let it be. This can further reduce the risk of collision between the support member 71 and the cam 80c.

As described above, the image forming apparatus 100 of this embodiment includes a rotatable endless belt 31 that carries a toner image, and a plurality of tension rollers that stretch the belt 31. The inner roller 32 and the belt A plurality of tension rollers 35 arranged adjacent to the inner roller 32 upstream of the inner roller 32 in the rotational direction of the belt 31; A pressing member 70 that can contact the inner peripheral surface of the belt 31 upstream of the inner roller 32 and downstream of the upstream roller 35 with respect to the rotation direction of the belt 31, and a pressing member that changes the amount of pressing of the pressing member 70 against the belt 31. A belt unit 3 provided with a moving mechanism 2 capable of moving a roller 70 , and an inner roller 32 , which is arranged to face the outer peripheral surface of the belt 31 and transfers a toner image from the belt 31 to the recording material P. and an external member 41 forming a transfer portion N2 for transfer. In this embodiment, the moving mechanism 2 includes a movable support portion 71 that supports the pressing member 70, a movable contact portion 80c that contacts the support portion 71 and moves the support portion 71, and a movable contact portion 80c. The upstream moving mechanism 2a including the contact portion 80c and the driving portion 81 and the downstream moving mechanism 2b including the support portion 71 are separable. In addition, in the present embodiment, the belt unit 3 has a detachable pressing member unit 7 that includes only the pressing member 70 and only the downstream moving mechanism 2b of the upstream moving mechanism 2a and the downstream moving mechanism 2b of the moving mechanism 2. is. Further, in this embodiment, the image forming apparatus 100 has a separation mechanism (release mechanism 3b) that separates the support portion 71 and the contact portion 80c. In this embodiment, the pressing member unit 7 is removed from the belt unit 3 by being moved along the rotation axis direction of the inner roller 32 while the support portion 71 is separated from the contact portion 80c by the separation mechanism 3b. configured to be

In this embodiment, the image forming apparatus 100 has a release mechanism 3b for releasing the tension, and the support portion 71 is rotatable around a rotation axis substantially parallel to the direction of the rotation axis of the inner roller 32. When the tension is released by the release mechanism 3b, the support portion 71 is placed in a free state, and the rotation axis is positioned so that the support portion 71 in the free state rotates in a direction away from the contact portion 80c. , and the release mechanism 3b constitutes the spacing mechanism. In addition, in this embodiment, the pressing member unit 7 has first engaging portions 72a and 72b extending along the rotation axis direction of the inner roller 32, and the belt unit 3 has the first engaging portions 72a and 72b. 72a has second engaging portions 84a, 84b with which it is slidably engaged. Further, in this embodiment, the pressing member unit 7 is pulled out from the housing 110a of the image forming apparatus 100 and removed from the belt unit 3 held in the housing 110a. Also, in this embodiment, the pressing member unit 7 includes an inner roller 32 . Further, in this embodiment, the pressing member 70 is arranged such that its longitudinal direction is substantially parallel to the width direction of the belt 31, and the upstream end of the belt 31 in its lateral direction is fixed to the supporting portion 71. The downstream end portion in the rotation direction of the belt 31 in the lateral direction is composed of a plate-like member that can come into contact with the inner peripheral surface of the belt 31 . Further, in this embodiment, the belt 31 is an intermediate transfer member that conveys the toner image that has been primarily transferred from the image carrier 11 so as to secondarily transfer it onto the recording material P at the transfer portion N2.

As described above, according to this embodiment, while the position of the pressing member 70 is variable, the risk of the support member 71 hitting the cam 80c when the secondary transfer unit 7 is inserted into or removed from the belt unit 3 is reduced. can be done. Further, according to this embodiment, it is possible to improve the replaceability of the pressing member 70 in a configuration in which the pressing amount of the pressing member 70 against the intermediate transfer belt 31 is variable.

[Example 2]
Another embodiment of the present invention will now be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of the first embodiment. Accordingly, in the image forming apparatus of the present embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof will be omitted. .

According to the configuration of the first embodiment, it is possible to reduce the risk of collision between the support member 71 and the cam 80c when the secondary transfer inner unit 7 is inserted into or removed from the belt unit 3 with a simple configuration. However, in the configuration of the first embodiment, since the distance from the rotation shaft 73 of the support member 71 to the tip position of the pressing member 70 is long, it is difficult to ensure the arm ratio with respect to the contact surface with the cam 80c. It is conceivable that In this case, it is conceivable that variations in the positional relationship between the cam 80c and the support member 71 have a greater influence on variations in the tip position of the pressing member . Therefore, it is conceivable that the position of the tip of the pressing member 70 tends to vary depending on the accuracy of parts. Therefore, in this embodiment, the moving mechanism 2 is configured as follows.

FIG. 8 is a cross-sectional side view of the inner secondary transfer unit 7 and the cam 80c in this embodiment as seen from the front side along the rotation axis direction of the inner secondary transfer roller 32. As shown in FIG. 8A shows an example of the posture of the cam 80c and the support member 71 during image formation, and FIG. The posture of the support member 71 is shown.

In this embodiment, the supporting member 71 is configured such that a moment due to its own weight is generated in the clockwise direction in the figure, ie, in the direction in which the cam follower 71a of the supporting member 71 abuts the cam 80c in the free state. That is, in this embodiment, in FIG. 8A, the support member 71 is positioned horizontally to the left (opposite side to the cam shaft 80) with respect to the center of gravity 71G of the support member 71 to which the pressing member 70 is fixed. It has a configuration in which a rotating shaft 73 is provided. In this embodiment, in FIG. 8A, the cam shaft 80 is arranged above the rotating shaft 73 at a position shifted to the right in the horizontal direction. In this embodiment, the front frame 74 and the rear frame 75 of the internal secondary transfer unit 7 are each provided with projections 76 as regulation portions. The projecting portion 76 abuts on the support member 71 and restricts the support member 71 from rotating in the clockwise direction in the figure by a predetermined angle or more. The protrusion 76 only needs to restrict the rotation of the support member 71 as described above, and may abut on the mounting portion 70 c of the pressing member 70 fixed to the support member 71 . The mounting portion 70 c of the pressing member 70 can be regarded as constituting a supporting portion that supports the pressing member 70 together with the supporting member 71 .

At the time of image formation shown in FIG. 8( a ), the support member 71 is subjected to a clockwise moment due to its own weight and tension of the intermediate transfer belt 31 . receives a moment in the clockwise direction in the figure. Then, the cam follower 71a of the support member 71 and the cam 80c contact each other to determine the position of the pressing member 70. As shown in FIG.

On the other hand, when the internal secondary transfer unit 7 shown in FIG. position is determined. At this time, in this embodiment, the cam 80c rotates (retracts) to a position (phase) where it does not contact the support member 71, which has rotated to a position where it abuts against the protrusion 76. As shown in FIG. Specifically, the cam 80c is rotated (retracted) to a retracted position (phase) where the contact surface of the cam 80c that can contact the cam follower 71a faces the opposite side of the cam follower 71a. Therefore, the cam follower 71a of the support member 71 is separated from the cam 80c when the support member 71 is rotated to the position where it abuts against the protrusion 76. As shown in FIG. Also in this embodiment, as in the first embodiment, when the secondary transfer internal unit 7 is removed from the belt unit 3, the tension of the intermediate transfer belt 31 is released. As described above, in this embodiment, a separation mechanism for separating the support member 71 from the cam 80c is configured by the protrusion 76, the driving motor 81 and the control section 50 that constitute a retraction mechanism for retracting the cam 80c.

In this embodiment, the neutral position of the moving mechanism 2 is set to a state in which the cam 80c rotates (retracts) to a position (phase) where the support member 71 does not contact as shown in FIG. 8(b). Therefore, in this embodiment, when the secondary transfer internal unit 7 is removed from the belt unit 3 , the cam 80 c is rotated (retracted) to a position (phase) where it does not contact the support member 71 . However, the present invention is not limited to such an aspect, and when the operator removes the inner secondary transfer unit 7 from the belt unit 3, the controller 50 retracts the cam 80c as described above. state. For example, the control section 50 can acquire a signal indicating that the secondary transfer internal unit 7 is to be removed from the belt unit 3 in accordance with the operator's operation on the operation section 130 (FIG. 13). Upon receiving this signal, the control unit 50 can bring the cam 80c into the retracted state as described above. Alternatively, the image forming apparatus 100 may be provided with an open/close sensor 140 ( FIG. 13 ) that detects opening/closing of a door provided in the apparatus main body 110 that allows the operator to access the belt unit 3 . The control unit 50 can acquire a signal indicating that the door is opened from the open/close sensor 140 . Upon receiving this signal, the control unit 50 can bring the cam 80c into the retracted state as described above. On the other hand, when the secondary transfer internal unit 7 is properly attached to the belt unit 3 and the belt unit 3 is properly attached to the apparatus main body 110, the control unit 50 controls the cam operation before the first image formation thereafter. 80 c can be rotated to a position where it can contact the support member 71 .

The operation for attaching the secondary transfer unit 7 to the belt unit 3 is the reverse of the operation for removing it. That is, in a state in which the tension of the intermediate transfer belt 31 is released, the support member 71 receives a clockwise moment due to its own weight as shown in FIG. The in-transfer unit 7 is attached to the belt unit 3 . At this time, the cam 80 c is rotated (retracted) to a position (phase) where it does not contact the support member 71 . By tensioning the intermediate transfer belt 31 and rotating the cam 80c to a position (phase) where it can contact the support member 71, the cam follower 71a contacts and presses the cam 80c as shown in FIG. The position of member 70 is determined.

As described above, in this embodiment, when the inner secondary transfer unit 7 is removed from the belt unit 3, the front side of the belt unit 3 is rotated upward and tilted. operates as described above.

Here, in this embodiment, the moving mechanism 2 can change the contact or separation state of the pressing member 70 with respect to the intermediate transfer belt 31 by changing the position of the pressing member 70 . . That is, as described above, by rotating (retracting) the cam 80 c to the position (phase) where it does not contact the support member 71 , the support member 71 abuts against the protrusion 76 . In this embodiment, the protrusion 76 is provided so that the tip of the pressing member 70 is separated from the inner circumferential surface of the intermediate transfer belt 31 which is tensioned at this time. In this embodiment, as described above, the support member 71 rotates clockwise by its own weight, so that the pressing member 70 is separated from the intermediate transfer belt 31 without providing a special biasing means such as a spring. be able to. The image forming apparatus 100 is configured so that the leading end of the pressing member 70 is separated from the inner peripheral surface of the intermediate transfer belt 31 during image formation in at least one predetermined mode (during secondary transfer). may be

Thus, in this embodiment, the image forming apparatus 100 has a retraction mechanism (drive motor 81, control section 50) that moves the contact portion 80c to the retracted position where it does not come into contact with the support portion 71, and the support portion 71 is It is rotatable around a rotation axis substantially parallel to the direction of the rotation axis of the inner roller 32. When the contact portion 80c is moved to the retracted position, it enters a free state. The supporting portion 71 is positioned so as to rotate in the direction toward the contact portion 80c. A regulating portion 76 that regulates rotation and holds the support portion 71 away from the contact portion 80c is provided. A spacing mechanism for spacing is configured.

As described above, according to this embodiment, the same effects as those of the first embodiment can be obtained, and the distance from the rotating shaft 73 to the tip position of the pressing member 70 can be shortened. The position can be determined with higher precision.

[Example 3]
Another embodiment of the present invention will now be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of the first embodiment. Accordingly, in the image forming apparatus of the present embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof will be omitted. .

The present embodiment differs from the first embodiment mainly in the configuration of an upstream moving mechanism 2a (fixed side unit 8) including a drive motor 81 in the moving mechanism 2. FIG.

FIG. 9 is a front perspective view of the pressing member 70 and the moving mechanism 2 in this embodiment. FIG. 10 is a cross-sectional side view of the periphery of the pressing member 70 and the moving mechanism 2 in this embodiment as seen from the front side along the rotation axis direction of the secondary transfer inner roller 32 .

As in the first embodiment, the pressing member 70 is fixed to a support member 71, and the support member 71 is rotatably attached to a front frame 74 and a rear frame 75 (FIG. 6) of the secondary transfer internal unit 7 around a rotation shaft 73. ).

Further, in this embodiment, the moving mechanism 2 has a driven pressurizing link shaft 80 d formed of a cylindrical member extending along the width direction of the intermediate transfer belt 31 . The driven pressure link shaft 80 d is supported by the support frame 39 of the belt unit 3 so as to be rotatable around a rotation axis substantially parallel to the width direction of the intermediate transfer belt 31 . Further, the moving mechanism 2 has a driven pressure link 80e. The driven pressure link 80e is fixed to the driven pressure link shaft 80d. The driven pressure links 80e are provided at both ends of the driven pressure link shaft 80d in the rotational axis direction. Further, the moving mechanism 2 includes a drive motor 81 configured by a stepping motor as a drive source, a drive pressure link 81b, a flag 81c provided on the drive pressure link 81b, and an urging member (elasticity) as urging means. member). The drive motor 81, the drive pressure link 81b, the flag 81c, and the pressure spring 87 are provided behind the driven pressure link shaft 80d in the rotational axis direction. A drive pressure link 81 b having a flag 81 c is fixed to the output shaft of the drive motor 81 . A pressure spring 87 connects the driven pressure link 80 e and the driving pressure link 81 b on the rear side. In this embodiment, the pressure spring 87 is composed of a tension coil spring, which is a biasing member made of piano wire. The drive motor 81 is supported by the support frame 39 of the belt unit 3 .

The driven pressure link 80 e has a contact portion 80 f that contacts the contacted portion 71 a of the support member 71 . The driven pressure link 80e transmits the force of the pressure spring 87 to the pressing member 70 via the contact portion 80f and the contacted portion 71a. Then, the support member 71 rotates until the force of the pressure spring 87 and the reaction force that the pressure member 70 receives from the intermediate transfer belt 31 are balanced, and the posture of the support member 71, that is, the position of the pressure member 70 is determined. . In this embodiment, when the drive motor 81 is rotationally driven, the angle of the drive pressure link 81b changes, and furthermore, the amount of deformation of the pressure spring 87 changes, thereby changing the spring force. The posture, that is, the position of the pressing member 70 also changes.

Further, as in the first embodiment, the belt unit 3 is provided with a position sensor 89 (not shown in FIGS. 9 and 10). A preset neutral position can be set.

The configuration of the internal secondary transfer unit 7 in this embodiment is substantially the same as that in the first embodiment, and is configured to be insertable/removable with respect to the belt unit 3 in the same manner as in the first embodiment. Further, in this embodiment, a drive support plate 86 is fixed to a stay 85 provided on the support frame 39 of the belt unit 3 . In this embodiment, the drive support plate 86 is fixed to each of the front side plate 39a and the rear side plate 39b of the support frame 39, but the front side drive support plate 86 is not shown in FIG. The drive motor 81 is fixed to the drive support plate 86 (rear side). A driven pressure link shaft 80d is rotatably supported by the drive support plate 86 (front side and rear side). In this embodiment, it is fixed to the support frame 39 by the drive support plate 86, the drive motor 81, the drive pressure link 81b, the flag 81c, the pressure spring 87, the driven pressure link shaft 80d and the driven pressure link 80e. A fixed-side unit 8, which is a unit, is configured.

In this embodiment, the pressing member 70 is made of a plastic material that does not easily damage the intermediate transfer belt 31 and ensures insulation (the same applies to the first embodiment). However, the elastic modulus of the pressing member 70 made of a plastic material tends to change over time due to environmental temperature and creep deformation. Therefore, with the configuration of the moving mechanism 2 according to the first embodiment, although the posture of the support member 71 can be maintained at a desired posture, the tip position of the pressing member 70 may change as the elastic modulus changes.

On the other hand, in the structure of the moving mechanism 2 in the present embodiment, the pressure spring 87 is made of piano wire, which changes little over time. Contact pressure can be realized. Further, by making the elastic modulus of the pressure spring 87 smaller than the elastic modulus of the pressing member 70, even if the elastic modulus of the pressing member 70 changes with time, the spring force of the pressure spring 87 hardly changes. , the change in the tip position of the pressing member 70 can be kept small.

According to the urging mechanism of the pressing member 70 in the present embodiment, the pressing member 70 may be made of a metal plate member (sheet metal) having relatively high rigidity. By biasing the pressing member 70 by the biasing member, the intermediate transfer belt 31 can be elastically biased by the pressing member 70 .

Thus, in this embodiment, the moving mechanism 2 has the elastically deformable elastically deformable portion 87 between the contact portion 80f and the driving portion 81, and the driving portion 81 adjusts the amount of deformation of the elastically deforming portion 87 to It is possible to change. Further, in this embodiment, the pressing member 70 is elastically deformable, and the elastic modulus of the pressing member 70 is greater than the elastic modulus of the elastic deformation member 87 .

As described above, according to the present embodiment, the same effects as those of the first embodiment can be obtained, and the influence of changes in the pressing member 70 over time can be reduced, so that the tip position of the pressing member 70 can be stabilized at a desired position. It can be kept in position.

It should be noted that the configuration of the internal secondary transfer unit 7, which is substantially the same as that in the second embodiment, may be combined with the present embodiment.

[Example 4]
Another embodiment of the present invention will now be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of the first embodiment. Accordingly, in the image forming apparatus of the present embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof will be omitted. .

Also, this embodiment is a modification of the third embodiment. In the present embodiment, elements having the same or corresponding functions or configurations as those of the third embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. FIG. 11 is a front perspective view of the pressing member 70 and the moving mechanism 2 in this embodiment.

According to the configuration of the moving mechanism 2 according to the third embodiment, it is possible to reduce the influence of aging of the pressing member 70 and stably maintain the tip position of the pressing member 70 at a desired position. However, in the configuration of the third embodiment, the contact pressure between the intermediate transfer belt 31 and the pressing member 70 depends on the spring force of the pressing spring 87 . Therefore, when the pressing member 70 receives an external force when the recording material P rushes into the secondary transfer portion N<b>2 , the pressing member 70 may deform depending on the elastic modulus of the pressure spring 87 . As a result, there is a possibility that the tip position of the pressing member 70 cannot be maintained properly.

Therefore, in this embodiment, as shown in FIG. 11, the driven pressure link shaft 80d is connected to the output shaft 88a of the electromagnetic clutch 88 via a coupling 88b. The driven pressure link shaft 80d constitutes a moving portion that moves integrally with the contact portion 80f. An input shaft 88c of the electromagnetic clutch 88 is fixed to the rear side plate 39b of the support frame 39 of the belt unit 3. As shown in FIG. In this embodiment, a closed type electromagnetic clutch 88 is used. In the electromagnetic clutch 88, the input shaft 88c and the output shaft 88a are connected when the voltage is cut off, and when the voltage is applied, the built-in spring (not shown) is released and the input shaft 88c and the output shaft 88a are disconnected. It is configured. In this embodiment, the control unit 50 is connected to a power supply (not shown) that applies voltage to the electromagnetic clutch 88, and the control unit 50 can control ON/OFF of the output of this power supply. there is In this embodiment, an electromagnetic clutch 88 as a clutch mechanism constitutes fixing means for fixing the position of the pressing member 70 .

In this embodiment, when the drive motor 81 rotates the drive pressure link 81b, the control unit 50 energizes the electromagnetic clutch 88 to make the driven pressure link shaft 80d rotatable. On the other hand, the control unit 50 fixes the position of the driven pressure link shaft 80d by interrupting the voltage input to the electromagnetic clutch 88 after the rotation of the drive motor 81 is completed. As a result, the posture of the support member 71 is fixed even when the recording material P enters the secondary transfer portion N2, and the leading end position of the pressing member 70 can be maintained as in the first embodiment.

As described above, according to the present embodiment, by using the pressure spring 87 and the electromagnetic clutch 88, it is possible to reduce the influence of aging of the pressing member 70 and to reduce the influence of the external force of the recording material P. It is possible to keep the tip position of the pressing member 70 at a desired position when receiving.

It should be noted that the fixing means for fixing the position of the pressing member 70 is not limited to the embodiment described above.

For example, the clutch mechanism connected to the driven pressurizing link mechanism is not limited to the electromagnetic clutch 88. For example, a one-way clutch (not shown) may be arranged between the driven pressure link shaft 80d and the driven pressure link 80e. In this case, the driven pressure link 80e constitutes a moving portion that moves integrally with the contact portion 80f. The one-way clutch is arranged to lock the driven pressurizing link 80e clockwise in FIG. 10 and to lock it counterclockwise in FIG. 10 with respect to the driven pressurizing link shaft 80d. As a result, the posture of the support member 71 can be maintained even when the recording material P enters the secondary transfer portion N2. When reducing the amount of deformation of the pressure spring 87, the drive motor 81 rotates the drive pressure link 81b clockwise in FIG. At the same time, by rotating the driven pressure link shaft 80d counterclockwise via a transmission gear (not shown), the driven pressure link 80e is also rotated counterclockwise.

Further, since the external force generated when the recording material P rushes into the secondary transfer portion N2 is temporary, a similar effect can be obtained by using a damper mechanism instead of the clutch mechanism, as shown in FIG. is also possible. FIG. 11 is a front perspective view of the pressing member 70 and the moving mechanism 2 in a modification of this embodiment using a damper mechanism. In this example, a driven pressure link shaft 80d and an output shaft 90a of a rotary damper 90 as a damper mechanism fixed to the rear side plate 39b of the support frame 39 of the belt unit 3 are connected via a coupling 90b. there is

Further, the above-described clutch mechanism (electromagnetic clutch 88, one-way clutch) and damper mechanism 90 may be connected to the rotation shaft 73 of the support member 71 instead of the driven pressure link shaft 80d. This also provides the same effect as described above. In this case, the rotating shaft 73 constitutes a moving portion that moves integrally with the support member 71 as a support portion for the pressing member 70 .

Thus, the moving mechanism 2 may have the clutch mechanism 88 connected to the moving portions (80d, 80e, 73) that move integrally with the contact portion 80f or the support portion 71. FIG. The clutch mechanism 88 permits movement of the moving portion when the support portion 71 is moved by the driving portion 81, and restricts the movement when performing transfer (at the time of image formation). Further, the moving mechanism 2 may have a damper mechanism 90 connected to the moving portions (80d, 80e, 73) that move together with the contact portion 80f or the support portion 71. FIG. The damper mechanism 90 allows the movement of the moving portion 71 when the driving portion 81 moves the supporting portion 71, and restricts the movement when performing transfer (at the time of image formation).

As described above, according to this embodiment, the same effects as those of Embodiments 1 and 3 can be obtained, and the support member 71 of the pressing member 70 is displaced by the external force when the recording material P enters the secondary transfer portion N2. change in posture can be suppressed.

It should be noted that the configuration of the internal secondary transfer unit 7, which is substantially the same as that in the second embodiment, may be combined with the present embodiment.

[others]
Although the present invention has been described with reference to specific examples, the present invention is not limited to the above-described examples.

In the above-described embodiments, rails and rail guides are provided to allow the secondary transfer internal unit to be inserted and removed, but the present invention is not limited to such an aspect. It is sufficient that the pressing member unit can be removed along the width direction of the belt, typically from the front side of the image forming apparatus. For example, the rail and the rail guide are not provided, and after releasing the engagement between the positioning protrusion and the positioning hole described in the first embodiment, the operator moves the pressing member unit along the width direction of the belt and removes it. It can be like this.

Further, in the above-described embodiment, the pressing member unit is provided with the secondary transfer inner roller, but the present invention is not limited to such an aspect. It may also be a unit having only a support member to which is fixed. However, when the pressing member unit includes the inner secondary transfer roller, it is possible to improve the positional accuracy between the inner secondary transfer roller and the pressing member. Further, a guide member (conveyance guide, secondary transfer entrance guide) for guiding the recording material conveyed to the transfer section may be fixed to the pressing member unit. In this case, for example, it is possible to first remove the conveying guide from the pressing member unit and then remove the unit. When the conveying guide is fixed to the pressing member unit, it is possible to improve the positional accuracy between the pressing member and the conveying guide.

Alternatively, the pressing member may be arranged so as to simply contact the inner circumferential surface of the intermediate transfer belt. In this case also, the effect of suppressing deformation of the intermediate transfer belt upstream of the secondary transfer portion can be obtained to some extent.

Further, the belt unit is not limited to a structure that can be pulled out from the main body of the image forming apparatus and tilted. Even if the pressing member is replaced while the belt unit is substantially accommodated in the apparatus main body of the image forming apparatus, according to the present invention, it is possible to improve the replaceability of the pressing member unit. Further, the belt unit may be detachable from the main body of the image forming apparatus for replacement or the like while the pressing member unit is still attached or with the pressing member unit removed.

Further, as the pressing member, for example, it is conceivable to use a roller formed of an elastic body such as sponge or rubber, or a roller formed of a rigid body such as resin or metal. However, from the viewpoint of arranging the pressing member sufficiently close to the secondary transfer portion, it is preferable that the pressing member is a plate-like member as in the above embodiment.

Further, in the above-described embodiments, an outer roller that directly contacts the outer peripheral surface of the intermediate transfer belt is used as an outer member that forms the secondary transfer portion together with the inner roller as the inner member. Alternatively, an outer roller and a secondary transfer belt stretched between the outer roller and another roller may be used as the outer member. Then, the outer roller can be brought into contact with the outer peripheral surface of the intermediate transfer belt via the secondary transfer belt. In such a configuration, the intermediate transfer belt and the secondary transfer belt are sandwiched between the inner roller that contacts the inner peripheral surface of the intermediate transfer belt and the outer roller that contacts the inner peripheral surface of the secondary transfer belt. A secondary transfer portion is formed.

In the above-described embodiments, the belt-shaped image carrier is an intermediate transfer belt. If so, the present invention can be applied. Examples of such a belt-like image carrier include the intermediate transfer belt in the above-described embodiments, as well as a photoreceptor belt and an electrostatic recording dielectric belt.

The present invention can also be implemented in other embodiments in which some or all of the configurations of the above-described embodiments are replaced with alternative configurations. Therefore, an image forming apparatus using a belt-like image bearing member can be used without distinguishing between the tandem type/single drum type, charging method, electrostatic image forming method, developing method, transfer method, and fixing method. In the above-described embodiments, the main parts related to the formation/transfer of toner images have been mainly described, but the present invention can be applied to printers, various printing machines, copying machines, , MFPs, etc.

1 Image Forming Section 2 Moving Mechanism 3 Belt Unit 7 Inner Secondary Transfer Unit 8 Fixed Unit 31 Intermediate Transfer Belt 32 Inner Secondary Transfer Roller 70 Pressing Member 71 Supporting Member 71a Cam Follower 80 Cam Shaft 80c Cam 81 Drive Motor

Claims (15)

a rotatable endless belt carrying a toner image;
A plurality of tension rollers for stretching the belt, the plurality of tension rollers including an inner roller and an upstream roller disposed adjacent to the inner roller upstream of the inner roller in the rotation direction of the belt. a tension roller;
a tension applying unit that applies tension to the belt;
a pressing member capable of contacting the inner peripheral surface of the belt upstream of the inner roller and downstream of the upstream roller in the rotational direction of the belt;
a moving mechanism capable of moving the pressing member so as to change the amount of pressing of the pressing member against the belt;
a belt unit with
an outer member disposed facing the inner roller and forming a transfer portion that abuts on the outer peripheral surface of the belt and transfers the toner image from the belt to the recording material;
In an image forming apparatus having
The moving mechanism includes a movable support portion that supports the pressing member, a movable contact portion that contacts the support portion and moves the support portion, and a drive portion that moves the contact portion. , an upstream moving mechanism including the contact portion and the driving portion, and a downstream moving mechanism including the support portion are separable,
The belt unit has a detachable pressing member unit including the pressing member and only the downstream moving mechanism of the upstream moving mechanism and the downstream moving mechanism of the moving mechanism,
The image forming apparatus has a separation mechanism for separating the support portion and the contact portion,
The pressing member unit is configured to be removed from the belt unit by being moved along the rotation axis direction of the inner roller in a state in which the support portion is separated from the contact portion by the separation mechanism. An image forming apparatus characterized by: Having a release mechanism for releasing the tension,
The support portion is rotatable around a rotation axis substantially parallel to the rotation axis direction of the inner roller, and is in a free state when the tension is released by the release mechanism,
The rotation axis is positioned so that the support portion in the free state rotates in a direction away from the contact portion,
the release mechanism constitutes the spacing mechanism;
2. The image forming apparatus according to claim 1, wherein: a retraction mechanism for moving the contact portion to a retraction position where the contact portion does not contact the support portion;
The support portion is rotatable around a rotation axis substantially parallel to the rotation axis direction of the inner roller, and is in a free state when the contact portion is moved to the retracted position,
The rotation axis is positioned so that the support portion in the free state rotates in a direction toward the contact portion,
The pressing member unit includes a restricting portion that abuts against the rotating support portion in the free state to restrict the rotation of the supporting portion and holds the supporting portion in a state separated from the contact portion. is provided,
The retracting mechanism and the restricting portion constitute the spacing mechanism,
2. The image forming apparatus according to claim 1, wherein: The pressing member unit has a first engaging portion extending along the direction of the rotation axis of the inner roller, and the belt unit has a first engaging portion that is slidably engaged with the first engaging portion. 4. The image forming apparatus according to claim 1, comprising two engaging portions. 5. The pressing member unit according to claim 1, wherein the pressing member unit is pulled out from a housing of the image forming apparatus and removed from the belt unit held in the housing. Image forming device. 6. The image forming apparatus according to claim 1, wherein the pressing member unit includes the inner roller. 7. The image forming apparatus according to claim 1, wherein a guide member that guides the recording material conveyed to the transfer section is fixed to the pressing member unit. The moving mechanism has an elastically deformable elastically deformable portion between the contact portion and the driving portion, and the driving portion is capable of changing the amount of deformation of the elastically deforming portion. The image forming apparatus according to any one of claims 1 to 7. 9. The image forming apparatus according to claim 8, wherein the pressing member is elastically deformable, and the elastic modulus of the pressing member is larger than the elastic modulus of the elastic deformation member. 10. The image forming apparatus according to claim 8, wherein the moving mechanism has a clutch mechanism connected to a moving portion that moves integrally with the contact portion or the support portion. 11. The image according to claim 10, wherein the clutch mechanism permits movement of the moving portion when the driving portion moves the supporting portion, and regulates the movement when performing the transfer. forming device. 10. The image forming apparatus according to claim 8, wherein the moving mechanism has a damper mechanism connected to a moving portion that moves integrally with the contact portion or the support portion. 13. The image according to claim 12, wherein the damper mechanism permits the movement of the moving part when the supporting part is moved by the driving part, and regulates the movement when the transfer is performed. forming device. The pressing member has a longitudinal direction substantially parallel to the width direction of the belt, an upstream end portion in the lateral direction of the belt in the rotational direction of the belt is fixed to the support portion, and a widthwise direction of the belt in the lateral direction. 14. The image forming apparatus according to any one of claims 1 to 13, wherein a downstream end portion of the belt in the rotational direction is composed of a plate-like member capable of coming into contact with an inner peripheral surface of the belt. 15. The belt according to any one of claims 1 to 14, wherein the belt is an intermediate transfer member that conveys the toner image that has been primarily transferred from the image carrier so that the toner image is secondarily transferred onto the recording material at the transfer unit. 10. The image forming apparatus according to claim 1.

Images