JP2020160192A - Image formation apparatus - Google Patents

Abstract

To provide an image formation apparatus which can form a high quality image regardless of the basis weight of a recording material in a configuration that has a support member pressing a belt from the inner peripheral surface side to the outer peripheral surface side in the vicinity of the upstream side of a secondary transfer unit.SOLUTION: A support member 3 can be arranged at a first position and a second position. For the movement from the first position to the second position, a movement distance in the direction orthogonal to a reference line L is longer than a movement distance in the direction in parallel with the reference line L. A second intrusion amount X2 being an intrusion amount X in a case where the support member 3 is arranged at the second position is larger than a first intrusion amount X1 being the intrusion amount X in a case where the support member 3 is arranged at the first position. Control means 50 performs control such that the support member 3 is arranged at the first position when performing transfer to a recording material P whose basis weight is the first basis weight and the support member 3 is arranged at the second position when performing transfer to the recording material P whose basis weight is the second basis weight smaller than the first basis weight.SELECTED DRAWING: Figure 1

Description

The present invention relates to an image forming apparatus such as a copier, a printer, or a facsimile using an electrophotographic method or an electrostatic recording method.

In recent years, in an image forming apparatus using an electrophotographic method or the like, it is required to form a high-quality image on a wide variety of recording materials. An intermediate transfer type image forming apparatus having an intermediate transfer belt, which is an intermediate transfer body composed of an endless belt, will be described as an example.

Recording materials with low surface smoothness generally have difficulty transferring the toner image on the intermediate transfer belt. When the surface of the recording material has irregularities of several tens of μm or more, for example, even if the secondary transfer bias is applied while pressing with a secondary transfer member composed of a conductive rubber roller or the like, the intermediate transfer belt is formed in the recessed portion of the recording material. And the recording material cannot be sufficiently contacted with each other, and voids are likely to be formed. Then, when a secondary transfer bias is applied, a discharge may occur in the portion where the void is formed. When the toner image on the intermediate transfer belt receives a discharge in the vicinity of the secondary transfer portion (secondary transfer nip) formed by the intermediate transfer belt and the secondary transfer member, the toner in the toner image is statically eliminated or charged. , The charge amount distribution of the toner becomes broad, and as a result, the transferability is impaired. As a result, a part of the toner image on the intermediate transfer belt may not be transferred properly (“transfer omission”). Further, the same phenomenon as described above occurs when the rotating intermediate transfer belt vibrates or undulates in the vicinity of the secondary transfer portion and the posture is not stable. The same applies even if the posture of the recording material is unstable in the vicinity of the secondary transfer portion. That is, when the adhesion between the recording material and the intermediate transfer belt is impaired, the charge distribution of the toner on the intermediate transfer belt is disrupted by the electric discharge received in the vicinity of the secondary transfer portion, and the electrostatic force acting on the secondary transfer portion is followed. The amount of toner that is not used increases, and the transferability to the recording material is impaired.

To solve such a problem, it is effective to provide a support member for holding the intermediate transfer belt from the inner peripheral surface side to the outer peripheral surface side of the intermediate transfer belt in the vicinity of the upstream side of the secondary transfer portion in the rotation direction of the intermediate transfer belt. (Patent Document 1). By suppressing the intermediate transfer belt by the support member, vibration and waviness of the intermediate transfer belt are suppressed, and discharge in the vicinity of the upstream side of the secondary transfer portion is suppressed.

JP-A-2007-57715

However, when the intermediate transfer belt is suppressed by the support member in the vicinity of the upstream side of the secondary transfer portion as described above, the recording material and the intermediate transfer belt are formed at a position where the support member is in contact with the inner peripheral surface of the intermediate transfer belt. The toner image may be disturbed by strong rubbing.

That is, the toner image is supported on the intermediate transfer belt at the position where the support member is in contact with the inner peripheral surface of the intermediate transfer belt. Since this toner image is supported on the intermediate transfer belt with a relatively weak force, it is easily disturbed when a force is applied. If the recording material and the intermediate transfer belt are strongly rubbed at the position where the toner image in such a state is supported, the toner image on the intermediate transfer belt is disturbed, and the toner image on the recording material after transfer is disturbed. "Image distortion" occurs. This image distortion tends to occur more easily as the contact pressure between the recording material and the intermediate transfer belt near the upstream side of the secondary transfer portion increases. When the intermediate transfer belt is suppressed by the support member, the contact pressure between the recording material and the intermediate transfer belt in the vicinity of the upstream side of the secondary transfer portion becomes larger than when the intermediate transfer belt is not provided. Therefore, this image distortion is likely to occur when the intermediate transfer belt is suppressed by the support member.

Further, the larger the basis weight of the recording material, the larger the contact pressure tends to be. This is because the larger the basis weight of the recording material, the higher the rigidity of the recording material. Therefore, the above-mentioned image distortion tends to be remarkable when an image is formed on thick paper having a large basis weight.

In the above, the conventional problem has been described by taking the secondary transfer portion, which is the transfer portion of the toner image from the intermediate transfer belt to the recording material, as an example, but from another belt-shaped image carrier such as a photoconductor to the recording material. There is a similar problem with the transfer portion of the toner image of.

Therefore, an object of the present invention is to obtain a high-quality image regardless of the basis weight of the recording material in a configuration having a support member that holds the belt from the inner peripheral surface side to the outer peripheral surface side in the vicinity of the upstream side of the secondary transfer portion. It is to provide an image forming apparatus which can form.

The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention is a transfer of a rotatable endless belt that carries a toner image carried at an image forming position and a transfer that contacts the outer peripheral surface of the belt and transfers the toner image from the belt to a recording material. An outer roller that forms a portion, a plurality of tension rollers that stretch the belt, and an inner roller that is arranged corresponding to the transfer portion, and downstream of the image forming position in the rotation direction of the belt. A plurality of tension rollers including an upstream roller arranged upstream of the inner roller, and an inner peripheral surface of the belt upstream of the inner roller and downstream of the upstream roller in the direction of rotation of the belt. The support member has a support member in contact with the support member, a moving means for moving the support member, and a control means for controlling the moving means, and the support member has a cross section substantially orthogonal to the rotation axis direction of the inner roller. It can be arranged at the first position in contact with the belt and the second position in contact with the belt, and the common tangent line between the inner roller and the upstream roller on the side on which the belt is hung is defined as the reference line L, The tangent line of the belt substantially parallel to the reference line L in the region where the support member contacts the belt is defined as the support portion tangent line Ld, and the distance between the reference line L and the support portion tangent line Ld is defined as the penetration amount X. At that time, in the movement from the first position to the second position, the movement distance in the direction orthogonal to the reference line L is larger than the movement distance in the direction parallel to the reference line L, and the support member The second intrusion amount, which is the intrusion amount X when the support member is arranged in the second position, rather than the first intrusion amount X1, which is the intrusion amount X when is arranged in the first position. X2 is larger, and the control means arranges the support member at the first position when performing the transfer to the recording material having the first basis weight, and the basis weight is larger than the first basis weight. The image forming apparatus is characterized in that when the transfer is performed on a recording material having a small second basis weight, the support member is controlled to be arranged at the second position.

According to the present invention, in a configuration having a support member that holds the belt from the inner peripheral surface side to the outer peripheral surface side in the vicinity of the upstream side of the secondary transfer portion, a high-quality image is formed regardless of the basis weight of the recording material. It becomes possible.

It is a schematic sectional view of an image forming apparatus. It is a schematic sectional view in the vicinity of the secondary transfer part. It is a schematic block diagram which shows the control mode of the main part of an image forming apparatus. It is a schematic cross-sectional view for demonstrating image distortion. It is a graph for demonstrating the difference in contact pressure between a recording material and an intermediate transfer belt due to the difference in the position of a backup roller. It is a flowchart of the control of Example 1. FIG. It is a schematic diagram for demonstrating an example of the input method of the information about a recording material. It is a schematic diagram for demonstrating another example of the input method of the information about a recording material. It is the schematic sectional drawing in the vicinity of the secondary transfer part for demonstrating the separability of a recording material. It is a graph for demonstrating the difference in the separation distance of a recording material due to the difference in the position of a backup roller. It is a schematic diagram and a block diagram of another example of an image forming apparatus. It is a flowchart of the control of Example 2. FIG. It is a schematic diagram of still another example of an image forming apparatus. It is a schematic cross-sectional view for demonstrating the moving mode of a backup roller. It is a schematic cross-sectional view of the vicinity of the secondary transfer part when the backup sheet is used.

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 the Image Forming Device FIG. 1 is a schematic cross-sectional view of the image forming device 100 of this embodiment. The image forming apparatus 100 of this embodiment has the functions of a tandem type multifunction device (copier, printer, facsimile apparatus) adopting an intermediate transfer method capable of forming a full-color image by using an electrophotographic method. ).

The image forming apparatus 100 forms the first, second, third, and fourth images of yellow (Y), magenta (M), cyan (C), and black (K) as a plurality of image forming units, respectively. It has image forming units UY, UM, UC, and UK. For elements having the same or corresponding functions or configurations in each image forming unit UY, UM, UC, UK, Y, M, C, K at the end of the code indicating that the elements are for any color is omitted. And there is a general explanation. The image forming unit U includes a photosensitive drum 101, a charging roller 102, an exposure device 103, a developing device 104, a primary transfer roller 105, a drum cleaning device 106, and the like, which will be described later.

The image forming unit U has a photosensitive drum 101 which is a rotatable drum-shaped (cylindrical) photoconductor (electrophotographic photosensitive member) as a first image carrier. The photosensitive drum 101 is rotationally driven in the direction of arrow R1 in the drawing at a predetermined peripheral speed. The surface of the rotating photosensitive drum 101 is uniformly charged to a predetermined potential of a predetermined polarity (negative electrode property in this embodiment) by a charging roller 102, which is a roller-type charging member as a charging means. The surface of the charged photosensitive drum 101 is scanned and exposed by an exposure device (laser scanner) 103 as an exposure means, and an electrostatic image (electrostatic latent image) is formed on the photosensitive drum 101. The electrostatic image formed on the photosensitive drum 101 is developed (visualized) by supplying toner as a developer by a developing device 104 as a developing means, and a toner image (developer image) is formed on the photosensitive drum 101. Will be done. In this embodiment, the exposed portion (image portion) on the photosensitive drum 101 whose absolute potential value is lowered by being exposed after being uniformly charged has the same polarity as the charging polarity of the photosensitive drum 101 (this embodiment). In the example, the negative electrode property) is charged with the toner.

An intermediate transfer belt 1 which is a rotatable intermediate transfer body composed of an endless belt is arranged as a second image carrier so as to face the four photosensitive drums 101. The intermediate transfer belt 1 is stretched over a drive roller 11, a tension roller 12, an idler roller 13, and a secondary transfer inner roller 14 as a plurality of tension rollers. The driving force of the intermediate transfer belt 1 is transmitted by the driving roller 11, and the intermediate transfer belt 1 rotates (circulates) at a predetermined peripheral speed in the direction of arrow R2 in the figure. On the inner peripheral surface side of the intermediate transfer belt 1, a primary transfer roller 105, which is a roller-type primary transfer member as a primary transfer means, is arranged corresponding to each photosensitive drum 101. The primary transfer roller 105 is urged toward the photosensitive drum 101 via the intermediate transfer belt 1 to form a primary transfer portion (primary transfer nip) T1 in which the photosensitive drum 101 and the intermediate transfer belt 1 come into contact with each other. The toner image formed on the photosensitive drum 101 as described above is primarily transferred on the rotating intermediate transfer belt 1 by the action of the primary transfer roller 105 in the primary transfer unit T1. During the primary transfer step, the primary transfer roller 105 has a polarity opposite to the normal charging polarity of the toner (charging polarity of the toner during development) due to the primary transfer power supply (high voltage power supply circuit) (not shown) (this embodiment). Then, a primary transfer bias (primary transfer voltage), which is a DC voltage of positive polarity), is applied. For example, when forming a full-color image, the toner images of each color of Y, M, C, and K formed on each photosensitive drum 101 are superposed on the intermediate transfer belt 1 in each primary transfer unit T1. The primary transfer is performed sequentially.

On the outer peripheral surface side of the intermediate transfer belt 1, at a position facing the secondary transfer inner roller 14, a secondary transfer outer roller 2 which is a roller type secondary transfer member as a secondary transfer means is arranged. The secondary transfer outer roller 2 is urged toward the secondary transfer inner roller 14 via the intermediate transfer belt 1, and the secondary transfer portion (secondary transfer portion) in which the intermediate transfer belt 1 and the secondary transfer outer roller 2 come into contact with each other. Transfer nip) T2 is formed. The toner image formed on the intermediate transfer belt 1 as described above is sandwiched between the intermediate transfer belt 1 and the secondary transfer outer roller 2 by the action of the secondary transfer outer roller 2 in the secondary transfer unit T2. It is secondarily transferred to a recording material (recording medium, sheet) P such as paper to be conveyed. In this embodiment, during the secondary transfer step, the secondary transfer outer roller 2 has a polarity opposite to the normal charging polarity of the toner due to the secondary transfer power supply (high voltage power supply circuit) 20 (positive electrode property in this embodiment). The secondary transfer bias (secondary transfer voltage), which is the DC voltage of the above, is applied.

The recording material P is sent out one by one from the cassettes 7a to 7c as the recording material storage unit by the pickup rollers 8a to 8c or the like as the feeding member, and is fed by a transport roller (conveying roller pair) or the like (not shown) as the transport member. Be transported. After that, the recording material P is conveyed to the secondary transfer unit T2 by the resist roller (resist roller pair) 5 as a transfer member at the same timing as the toner image on the intermediate transfer belt 1. In the transport direction of the recording material P, a transport guide 6 for guiding the recording material P to the secondary transfer section T2 is provided downstream of the resist roller 5 and upstream of the secondary transfer section T2. The transport guide 6 includes a first guide member 61 capable of contacting the front surface of the recording material P (the surface on which the toner image is transferred immediately after passing through the transport guide 6) and the back surface (front surface) of the recording material P. It is configured to have a second guide member 62 that can come into contact with the surface on the opposite side). The first guide member 61 and the second guide member 62 are arranged so as to face each other, and the recording material P passes between the two members. The first guide member 61 regulates the movement of the recording material P in the direction approaching the intermediate transfer belt 1. The second guide member 62 regulates the movement of the recording material P in the direction away from the intermediate transfer belt 1.

The recording material P to which the toner image is transferred is conveyed to the fixing device 108 as the fixing means. The fixing device 108 fixes (melts, fixes) the toner image to the recording material P by heating and pressurizing the recording material P carrying the unfixed toner image. The recording material P on which the toner image is fixed is discharged (output) to the outside of the main body of the image forming apparatus 100 by a discharge roller (a pair of discharge rollers) (not shown) or the like.

Further, the toner (primary transfer residual toner) remaining on the photosensitive drum 101 without being transferred onto the intermediate transfer belt 1 during the primary transfer step is removed from the photosensitive drum 101 by the drum cleaning device 106 as a photoconductor cleaning means. Will be collected. Further, on the outer peripheral surface side of the intermediate transfer belt 1, a belt cleaning device 107 as an intermediate transfer body cleaning means is arranged at a position facing the drive roller 11. Toner (secondary transfer residual toner) and paper dust remaining on the intermediate transfer belt 1 without being transferred to the recording material P during the secondary transfer step are removed from the intermediate transfer belt 1 by the belt cleaning device 107 and recovered. Toner.

Here, as the intermediate transfer belt 1, a resin such as polyimide or polyamide or an alloy thereof, or various rubbers containing an appropriate amount of an antistatic agent such as carbon black is preferably used. In this embodiment, the intermediate transfer belt 1 is formed so that its surface resistivity is 1 × 10 ^{9 to} 5 × 10 ¹³ Ω / □. Further, in this embodiment, the intermediate transfer belt 1 is formed so as to be a film-like endless belt having a thickness of, for example, about 0.04 to 0.5 mm. In this embodiment, the intermediate transfer belt 1 is stretched on the drive roller 11, the tension roller 12, the idler roller 13, and the secondary transfer inner roller 14 as described above. The drive roller 11 is driven by a motor having excellent constant speed to circulate (rotate) the intermediate transfer belt 1. The tension roller 12 applies a constant tension to the intermediate transfer belt 1. At both ends of the tension roller 12 in the direction of the rotation axis, a pressing spring (not shown), which is an urging member (elastic member) as an urging means, causes the intermediate transfer belt 1 from the inner peripheral surface side to the outer peripheral surface side. Is being urged towards. The idler roller 13 forms a surface of the intermediate transfer belt 1 near the upstream side of the secondary transfer unit T2. The secondary transfer inner roller 14 functions as an opposing member (opposing electrode) of the secondary transfer outer roller 2. In this embodiment, the image forming apparatus 100 is configured such that the tension of the intermediate transfer belt 1 with respect to the tension roller 12 is about 3 to 12 kgf.

As the intermediate transfer belt 1, a belt made of a resin-based material having a single-layer or multi-layer structure can be used. Further, as the intermediate transfer belt 1, a belt having a thickness of 40 μm or more, a Young's modulus of 1.0 GPa or more, and a surface resistivity of 1.0 × 10 ^{9 to} 5.0 × 10 ¹³ Ω / □ is preferably used. it can.

Further, in this embodiment, the primary transfer roller 105 is composed of a metal roller made of a metal material such as SUM or SUS. In this embodiment, the primary transfer roller 105 has a straight shape in the thrust direction (the outer diameter is substantially the same over substantially the entire rotation axis direction). Further, in this embodiment, the outer diameter of the primary transfer roller 105 is about 6 to 10 mm.

Further, in this embodiment, the secondary transfer inner roller 14 is configured by providing an elastic layer (rubber layer) made of EPDM rubber on the outer periphery of a metal core metal (base material). In this embodiment, the secondary transfer inner roller 14 is formed so that its outer diameter is 20 mm and the thickness of the elastic layer is 0.5 mm. Further, in this embodiment, the hardness of the elastic layer of the secondary transfer inner roller 14 is set to, for example, 70 ° (JIS-A). The secondary transfer inner roller 14 may be composed of a metal roller made of a metal material such as SUM or SUS.

Further, in this embodiment, the secondary transfer outer roller 2 has elasticity formed on the outer periphery of a metal core metal (base material) by NBR rubber or EPDM rubber containing a conductive agent such as a metal complex or carbon. A layer (rubber layer) is provided and configured. In this embodiment, the secondary transfer outer roller 2 is formed so that the outer diameter of the core metal is 12 mm, the thickness of the elastic layer is 6 mm, and the outer diameter of the secondary transfer outer roller 2 is 24 mm. .. Further, in this embodiment, the hardness of the elastic layer of the secondary transfer outer roller 2 is set to, for example, 28 ° (Asker C). Further, in the present embodiment, the secondary transfer outer roller 2 sandwiches the intermediate transfer belt 1 by a pressing spring 21 (FIG. 2) which is an urging member (elastic member) as an urging means. It is spring-urged so as to come into contact with 14 at a predetermined pressure.

Here, from the viewpoint of appropriately forming the secondary transfer portion T2, the secondary transfer outer roller 2 is urged toward the secondary transfer inner roller 14 via the intermediate transfer belt 1 by the urging member. It is preferable to have. Further, from the viewpoint of appropriately forming the secondary transfer portion T2, the hardness of the secondary transfer outer roller 2 (more specifically, the elastic layer constituting the surface layer thereof) is determined by the secondary transfer inner roller 14 (more specifically). Is preferably smaller than the hardness of the elastic layer constituting the surface layer). As an example, when the hardness of the secondary transfer inner roller 14 is 50 ° or more and 90 ° or less in JIS-A hardness, the hardness of the secondary transfer outer roller 2 is 15 ° or more and 50 ° or less in Asker C hardness. Is preferable.

The image forming apparatus 100 of this embodiment rotates and drives the intermediate transfer belt 1 so that the peripheral speed becomes 400 mm / sec, regardless of the type of the recording material P, to form an image.

2. 2. Configuration of Secondary Transfer Section FIG. 2 is a schematic cross-sectional view (cross section substantially orthogonal to the rotation axis direction of the secondary transfer inner roller 14) in the vicinity of the secondary transfer section T2 in this embodiment. Here, regarding the arrangement of the tension rollers 11 to 14, the secondary transfer outer roller 2, and the backup roller 3 described later, the terms upstream and downstream of the intermediate transfer belt 1 are the rotational directions of the intermediate transfer belt 1 unless otherwise specified. It means upstream and downstream in. Further, with respect to the recording material P, the front end and the rear end mean the front end and the rear end of the recording material P in the transport direction unless otherwise specified. In this embodiment, the rotation axis directions of the tension rollers 11 to 14, the secondary transfer outer roller 2, and the backup roller 3, which will be described later, of the intermediate transfer belt 1 are substantially parallel.

In this embodiment, the secondary transfer power source 20 is connected to the core metal of the secondary transfer outer roller 2. In this embodiment, the secondary transfer power supply 20 is a high-voltage power supply capable of switching between constant voltage and constant current. Further, in this embodiment, the core metal of the secondary transfer inner roller 14 is electrically grounded (connected to the ground potential). In this embodiment, the secondary transfer inner roller 14 and the secondary transfer outer roller 2 form an electric field for transferring the toner image from the intermediate transfer belt 1 to the recording material P in the secondary transfer unit T2. In this embodiment, a secondary transfer bias having a polarity opposite to the normal charging polarity of the toner is applied to the secondary transfer outer roller 2, and the secondary transfer inner roller 14 is electrically grounded. Alternatively, a secondary transfer bias having the same polarity as the normal charging polarity of the toner may be applied to the secondary transfer inner roller 14, and the secondary transfer outer roller 2 may be electrically grounded.

Further, in the vicinity of the upstream side of the secondary transfer inner roller 14, a backup roller 3 composed of a roller type member as a support member that contacts the inner peripheral surface of the intermediate transfer belt 1 and supports the intermediate transfer belt 1 is provided. Have been placed. More specifically, the backup roller 3 is arranged so as to come into contact with the inner peripheral surface of the intermediate transfer belt 1 upstream of the secondary transfer inner roller 14 and downstream of the idler roller 13. The backup roller 3 is arranged adjacent to the secondary transfer inner roller 14 upstream of the secondary transfer inner roller 14, and is arranged adjacent to the idler roller 13 downstream of the idler roller (upstream roller) 13. There is. In this embodiment, the backup roller 3 is a roller (metal roller) made of metal (made of SUS in this embodiment). The length of the backup roller 3 in the rotation axis direction is equivalent to the length in the width direction of the intermediate transfer belt 1 (direction substantially orthogonal to the moving direction of the surface), and the backup roller 3 hits the intermediate transfer belt 1 over substantially the entire width. Get in touch. The backup roller 3 is driven and rotated as the intermediate transfer belt 1 rotates in contact with the intermediate transfer belt 1. In this embodiment, the outer diameter of the backup roller 3 is 8 mm.

Further, in the present embodiment, the image forming apparatus 100 has a moving mechanism (position variable mechanism) 4 as a moving means (position variable means) for moving the backup roller 3 to change its position. The moving mechanism 4 includes an eccentric cam, a solenoid, and the like, as will be described later. Then, as will be described later, the backup roller 3 can be moved in the out-of-plane direction of the intermediate transfer belt 1 by the moving mechanism 4. In this embodiment, the backup roller 3 is slidable (reciprocally movable) in the above direction.

Here, in the present embodiment, the backup roller 3 presses the intermediate transfer belt 1 from the inner peripheral surface side toward the outer peripheral surface side so that the intermediate transfer belt 1 can be projected toward the outer peripheral surface side. It is configured. That is, in this embodiment, the backup roller 3 is configured to have a predetermined penetration amount with respect to the intermediate transfer belt 1 so that it can come into contact with the intermediate transfer belt 1. This penetration amount is roughly the penetration amount of the backup roller 3 with respect to the surface (tensioning surface) of the intermediate transfer belt 1 formed when the secondary transfer inner roller 14 and the idler roller 13 are stretched. More specifically, in FIG. 2, the common tangent line between the secondary transfer inner roller 14 and the idler roller 13 on the side on which the intermediate transfer belt 1 is hung is defined as the reference line L. Further, the tangent line of the intermediate transfer belt 1 in the region where the backup roller 3 comes into contact with the intermediate transfer belt 1 which is substantially parallel to the reference line L is defined as the support portion tangent line Ld. At this time, the distance X between the reference line L and the pressing portion tangent line Ld is set to the amount of penetration of the backup roller 3 into the intermediate transfer belt 1 (however, the support portion tangent line Ld is outside the intermediate transfer belt 1 from the reference line L. At some point, it is a positive value). In this embodiment, the backup roller 3 is configured so that the intrusion amount X is larger than 0 mm when it is arranged at any position described later, but it can be arranged at a position where the intrusion amount X is 0 mm. It may be configured as such. Further, although not limited to this, the penetration amount X is typically about 3.5 mm or less. When the penetration amount X is larger than 3.5 mm, the load applied to the contact surface between the backup roller 3 and the intermediate transfer belt 1 increases, so that the intermediate transfer belt 1 may not rotate smoothly.

The movement of the intermediate transfer belt 1 in the out-of-plane direction means that the movement distance in the direction orthogonal to the reference line L is larger than the movement distance in the direction parallel to the reference line L. That is, the backup roller 3 may be movable so as to change the intrusion amount X (see FIG. 14). However, from the viewpoint of miniaturization of the apparatus, the movement of the intermediate transfer belt 1 in the out-of-plane direction is preferably 5 in the direction in which the movement distance in the direction orthogonal to the reference line L is parallel to the reference line L. It is twice or more, more preferably 10 times or more. In this embodiment, the backup roller 3 can move in a direction substantially orthogonal to the reference line L. It should be noted that the fact that the movement is possible in a direction substantially orthogonal to the reference line L means that the movement is possible in a direction completely orthogonal to the reference line L and a direction deviated from the direction orthogonal to the error range (for example, about ± 10 °). Including the case where it can be moved to.

In this embodiment, the backup roller 3 is rotatably supported by bearing members (not shown) at both ends in the direction of the rotation axis. In this embodiment, the moving mechanism 4 has an eccentric cam 41 as a switching member, an arm 42 as an operating member, and an urging member (elasticity) as an urging means at both ends of the backup roller 3 in the rotation axis direction, respectively. It has a tension spring 43 which is a member). Further, the moving mechanism 4 has a driving unit 44 for driving the eccentric cams 41 at both ends in the rotation axis direction of the backup roller 3. The bearing member of the backup roller 3 is held in the main body of the image forming apparatus 100 or the housing of the unit including the intermediate transfer belt 1 so that the bearing member can be slid and moved in a direction substantially orthogonal to the reference line L. The eccentric cam 41 is held in the apparatus main body of the image forming apparatus 100, the housing of the unit including the intermediate transfer belt 1, and the like so as to be rotatable. The arm 42 is held in the apparatus main body of the image forming apparatus 100, the housing of the unit including the intermediate transfer belt 1, and the like so as to be rotatable (swingable) about the rotation center 42a. One end of the arm 42 engages the bearing member of the backup roller 3 and the other end engages the eccentric cam 41. Further, the tension spring 43 urges the arm 42 to rotate in the direction of engaging with the eccentric cam 41. Then, the moving mechanism 4 rotates the eccentric cam 41 by the drive unit 44 and rotates the arm 42 to slide the backup roller 3 as shown by the solid line and the chain line in FIG. In this embodiment, the moving mechanism 4 is configured so that the backup roller 3 can be arranged at positions where the penetration amounts X are 0.5 mm, 1.0 mm, 1.8 mm, and 2.5 mm, respectively.

In FIG. 2, a straight line passing through the rotation center of the secondary transfer inner roller 14 and substantially orthogonal to the reference line L is defined as the inner roller center line La. Further, a straight line passing through the rotation center of the backup roller 3 and substantially orthogonal to the reference line L is defined as the backup roller center line Lb. The backup roller center line Lb is an example of a straight line passing through substantially the center in the rotation direction of the belt in the contact region between the support member and the belt and substantially orthogonal to the reference line L. At this time, the distance between the inner roller center line La and the backup roller center line Lb is set to the distance between the backup roller 3 and the secondary transfer inner roller 14 (however, the backup roller center line Lb is larger than the inner roller center line La. Positive value when it is upstream) D. In this embodiment, the separation distance D is 16 mm. Typically, but not limited to this, the backup roller 3 is the inner circumference of the intermediate transfer belt 1 within 25 mm upstream from the region where the intermediate transfer belt 1 and the secondary transfer inner roller 15 come into contact with each other. Arranged so that it can contact the surface.

Further, in this embodiment, the secondary transfer outer roller 2 is arranged so as to be shifted (offset) to the upstream side with respect to the secondary transfer inner roller 14. Further, in this embodiment, the secondary transfer outer roller 2 comes into contact with the secondary transfer inner roller 14 via the intermediate transfer belt 1. With such a configuration, in this embodiment, the width of the secondary transfer portion T2, which is the contact region between the secondary transfer outer roller 2 and the intermediate transfer belt 1, is the contact between the secondary transfer inner roller 14 and the intermediate transfer belt 1. It extends upstream of the width of the area. That is, the upstream end of the contact area between the secondary transfer outer roller 2 and the intermediate transfer belt 1 is larger than the upstream end of the contact region between the secondary transfer inner roller 14 and the intermediate transfer belt 1. Located upstream. By arranging the secondary transfer outer roller 2 shifted to the upstream side with respect to the secondary transfer inner roller 14, the adhesion between the recording material P and the intermediate transfer belt 1 in the vicinity of the upstream side of the secondary transfer unit T2 can be improved. It can be improved and the transferability can be improved. In FIG. 2, a straight line passing through the rotation center of the secondary transfer inner roller 14 and substantially orthogonal to the reference line L is defined as the inner roller center line La. Further, a straight line passing through the rotation center of the secondary transfer outer roller 2 and substantially orthogonal to the reference line L is defined as the outer roller center line Lc. At this time, the distance between the inner roller center line La and the outer roller center line Lc is the shift amount Z of the secondary transfer outer roller 2 with respect to the secondary transfer inner roller 14 (however, the outer roller center line Lc is the inner roller center line). It is a positive value when it is upstream from La). In this embodiment, this shift amount Z is larger than 0 mm.

Further, in this embodiment, the backup roller 3 is formed of SUS, which is a conductive material (metal material in this embodiment) as described above. The backup roller 3 can be electrically grounded (connected to the ground potential) via a resistor such as a varistor. By electrically grounding the backup roller 3 via the resistor, the transfer current is suppressed by suppressing the current from flowing into the backup roller 3 when the secondary transfer bias is applied to the secondary transfer outer roller 2. It is possible to suppress the shortage. When a varistor is used as the resistor, for example, the voltage applied to the secondary transfer outer roller 2 is 0.5 to 8 kV, and the surface resistivity of the intermediate transfer belt 1 is 1.0 × 10 ^{9 to} 5.0 × 10 ¹³ Ω. If it is / □, it is preferable that the varistor has a varistor voltage of 1.0 kV or more. For example, in the configuration of this embodiment, the backup roller 3 can be electrically grounded via the varistor 32 having a varistor voltage of 1.5 kV.

3. 3. Control mode FIG. 3 is a schematic block showing a control mode of a main part of the image forming apparatus 100 of this embodiment. The control unit 50 as a control means controls communication with a CPU 51 as an arithmetic control means which is a central element for performing arithmetic processing, a memory (storage medium) 52 such as a ROM and a RAM as a storage means, and an external device. It is configured to include an interface unit 53 and the like. The RAM, which is a rewritable memory, stores the information input to the control unit 50, the detected information, the calculation result, and the like, and the ROM stores the control program, the data table obtained in advance, and the like. Data can be transferred and read from each other between the CPU 51 and the memory 52.

Each part of the mechanism (engine) that forms an image on the recording material P by the above-mentioned image forming process is connected to the control unit 50. In relation to this embodiment, for example, a secondary transfer power supply 20, a moving mechanism 4, and the like are connected to the control unit 50. The control unit 50 controls the voltage output by the secondary transfer power supply 20 so that the current value detected by the current detection unit included in the secondary transfer power supply 20 becomes a predetermined current value, thereby controlling the secondary transfer power supply 20. The bias applied to the secondary transfer outer roller 2 can be controlled by a constant current. Further, the control unit 50 controls the voltage output by the secondary transfer power supply 20 so that the voltage value detected by the voltage detection unit included in the secondary transfer power supply 20 becomes a predetermined voltage value, thereby performing secondary transfer. The bias applied from the power supply 20 to the secondary transfer outer roller 2 can be controlled by a constant voltage. In this embodiment, the secondary transfer voltage determined by applying a constant current-controlled bias to the secondary transfer outer roller 2 when there is no recording material P in the secondary transfer unit T2 is applied during image formation (during secondary transfer). ) Is applied to the secondary transfer outer roller 2 by constant voltage control.

Further, an operation unit (operation panel) 70 provided in the image forming apparatus 100 is connected to the control unit 50. The operation unit 70 has a display unit as a display unit for displaying information under the control of the control unit 50, and an input unit as an input unit for inputting information to the control unit 50. In this embodiment, the operation unit 70 is configured to have a touch panel having the functions of a display unit and an input unit. Further, the control unit 50 includes an image reading device (not shown) provided in the image forming device 100 or connected to the image forming device 100, a personal computer communicably connected to the image forming device 100, and the like. The external device 200 may be connected.

The control unit 50 is based on image data input from an image reading device (not shown) or an external device, and information on image forming conditions such as the type of recording material P input from the operation unit 70 or the external device. Each part of the image forming apparatus 100 can be controlled to form an image. The type of recording material P includes attributes, manufacturers, brands, product numbers, basis weights, thicknesses, sizes, etc. based on general characteristics such as plain paper, thick paper, thin paper, glossy paper, coated paper, and embossed paper. It includes arbitrary information that can distinguish the material P.

4. Position of backup roller In this embodiment, the transfer speed of the recording material P transferred to the secondary transfer unit T2 is set to be faster than the transfer speed of the intermediate transfer belt 1. This is to prevent the transfer speed of the recording material P from becoming slower than that of the intermediate transfer belt 1 due to wear of the resist roller 5 and changes in the outer diameter due to the usage environment. As a result, after the tip of the recording material P reaches the secondary transfer unit T2, the recording material P takes a transport path such that a loop is formed between the secondary transfer unit T2 and the resist roller 5. Therefore, as shown in FIG. 4, the recording material P and the intermediate transfer belt 1 may come into contact with each other at a position where the backup roller 3 is in contact with the inner peripheral surface of the intermediate transfer belt 1. At this time, the recording material P and the intermediate transfer belt 1 are strongly rubbed, and the toner image supported on the intermediate transfer belt 1 is disturbed, so that the toner image on the recording material P after transfer is disturbed and "image distortion" occurs. appear. FIG. 4 is a schematic cross-sectional view showing how the recording material P and the intermediate transfer belt 1 rub against each other in the vicinity of the upstream side of the secondary transfer unit T2 (cross section substantially orthogonal to the rotation axis direction of the secondary transfer inner roller 14). Is.

FIG. 5 is a graph showing the relationship between the position of the backup roller 3 and the contact pressure between the recording material P and the intermediate transfer belt 1 at the position where the backup roller 3 is in contact with the inner peripheral surface of the intermediate transfer belt 1. It is a figure. Here, the above relationship was obtained by a simulation by structural calculation assuming the case where a thick paper having a thickness of 0.3 mm was used as the recording material P. Further, here, the positions of the backup rollers 3 are the positions where the penetration amounts X are 1.8 mm, 1.0 mm, and 0.5 mm, respectively. From FIG. 5, the contact pressure is in the order of the position of the backup roller 3 at the position of the penetration amount X = 1.8 mm, the position of the penetration amount X = 1.0 mm, and the position of the penetration amount X = 0.5 mm. Can be seen to be decreasing. Further, it is known that the larger the contact pressure between the recording material P and the intermediate transfer belt 1, the more likely the image distortion is to occur. That is, from FIG. 5, it can be seen that the susceptibility to image distortion changes depending on the position of the backup roller 3.

Further, the contact pressure between the recording material P and the intermediate transfer belt 1 at the position where the backup roller 3 contacts the inner peripheral surface of the intermediate transfer belt 1 decreases as the basis weight of the recording material P decreases, and the recording material P becomes smaller. The larger the basis weight, the larger the tendency. This is because when the basis weight of the recording material P becomes small, the rigidity of the recording material P becomes low because the thickness of the recording material P becomes small, and when the basis weight of the recording material P becomes large, the thickness of the recording material P becomes small. This is because the rigidity of the recording material P increases as the size increases. Therefore, the larger the basis weight of the recording material P, the larger the contact pressure, which tends to cause image distortion. Therefore, it is desired that the backup roller 3 is arranged at a position where the penetration amount X is small so that the contact pressure is reduced as the basis weight of the recording material P is larger.

On the other hand, in the case of the recording material P having a small basis weight, image distortion is unlikely to occur as described above, so that transferability to various recording materials P including the recording material P having low surface smoothness as described above, for example. It is possible to arrange the backup roller 3 at a position where the intrusion amount X is large in order to increase the amount of penetration. As a result, the adhesion between the recording material P and the intermediate transfer belt 1 in the vicinity of the upstream side of the secondary transfer unit T2 can be improved, and the transferability can be improved. That is, it is desired that the backup roller 3 is arranged at a position where the penetration amount X is larger as the basis weight of the recording material P is smaller.

Table 1 shows the results of examining the transferability and the degree of image distortion using recording materials (paper) P of various brands. Recording materials P include "OFFICE70" from Canon Marketing Japan Co., Ltd., "Multi Paper Super Select" from Ascle Co., Ltd., "Rezac 66 115g" from Tokushu Tokai Paper Industries Co., Ltd., and New NPI High Quality (T) from Nippon Paper Industries Co., Ltd. ), Ose's "Top Color", Canon Marketing Japan Co., Ltd. "Image Coat Gross", Tokushu Tokai Paper Industries Co., Ltd. "Rezac 66 151g", Oji Paper Industries Co., Ltd. "OK Embossed Cloth", Canon Marketing Japan Co., Ltd. "GF-C157" and "OK Top Coat Dal" from Oji Paper Industries Co., Ltd. were used. The basis weight and surface smoothness of the recording material P of each of these brands are as shown in Table 1. Basis weight (g / m ² ) is the manufacturer's nominal value, and surface smoothness is Beck smoothness (sec) measured with a Beck smoothness tester (Beck smoothness tester HS type manufactured by Kumagai Riki Kogyo Co., Ltd.). Shown. The Beck smoothness means that the smaller the value, the lower the smoothness, and the larger the value, the higher the smoothness. Further, the same experiment was conducted by changing the position of the backup roller 3 to the positions where the penetration amount X was 0.5 mm, 1.0 mm, 1.8 mm, and 2.5 mm with respect to the recording material P of each brand. For "transferability", a predetermined chart including the secondary color solid images of cyan and magenta is output, and the transferability (secondary color loss) level of the output image is visually evaluated, and the secondary color loss occurs. The case where there was no color was evaluated as "○ (good)", and the case where secondary color loss was observed was evaluated as "x (bad)". For "image distortion", a predetermined chart including a halftone image is output, the output image is visually evaluated, and when there is no image distortion, "○ (good)" is obtained, and slight image distortion is observed. However, the case where there is no problem in practical use is evaluated as "Δ (generally good: acceptable in practical use)", and the case where image distortion at a level that may cause a problem in practical use is regarded as "x (defective)".

Looking at the cases where the Beck smoothness is 35 sec or more (No. 2, 4, 5, 6, 9 and 10) from Table 1, the larger the basis weight, the more likely it is that image distortion will occur when the penetration amount X is large. It turns out that The smoothness of the recording material P will be described later.

Therefore, in this embodiment, the backup roller 3 is arranged at the first position where the penetration amount X is the first penetration amount X1 when transferring to the recording material P having the first basis weight. Then, when transferring to the recording material P whose basis weight is smaller than the first basis weight, the backup roller 3 is subjected to the second penetration amount X2 in which the penetration amount X is larger than the first penetration amount X1. Place it in a second position.

As an example, based on the results shown in Table 1, the position of the backup roller 3 can be changed according to the basis weight of the recording material P as shown in Table 2.

5. Control Flow FIG. 6 is a flowchart showing an outline of a job control procedure in this embodiment. The job is a series of operations of forming an image on a single or a plurality of recording materials P and outputting the image. Here, a case where an operator such as a user causes the image forming apparatus 100 to execute a job by an operation in the operation unit 70 will be described as an example. Further, here, it is assumed that the types of recording materials P used for image formation in one job are the same. Note that FIG. 6 shows an outline of the control procedure focusing on the change of the position of the backup roller 3, and many other operations normally required for executing the job and outputting the image are omitted. ing.

The control unit 50 acquires information regarding the recording material P used for image formation specified by the operator in the operation unit 70 when starting the job (S101). FIG. 7 is a schematic view of a setting screen (paper setting screen) 71 for information regarding the recording material P used for image formation displayed on the display unit of the operation unit 70. FIG. 7A shows a selection of cassettes 7a to 7c (also referred to as “cassettes (1) to (3)” here) provided in the image forming apparatus 100 to supply the recording material P in the job. An example of inputting information about the recording material P used for image formation is shown. In this case, the memory 52 of the control unit 50 stores information about the recording material P, which is associated with each of the cassettes (1) to (3) in advance and is stored in each of the cassettes (1) to (3). There is. In this embodiment, the information regarding the recording material P includes at least the information regarding the basis weight of the recording material P. For example, it is registered in advance that the recording material P stored in the cassette (1) is "plain paper" having a basis weight of less than 105 g / m ² . Further, for example, the recording material P stored in the cassette (2) is registered in advance as "thick paper (1)" having a basis weight of 105 g / m ² or more and less than 150 g / m ² . Further, for example, the recording material P stored in the cassette (3) is registered in advance as "thick paper (2)" having a basis weight of 150 g / m ² or more. On the paper setting screen 71, the operator selects (presses) any of the cassettes (1) to (3) (that is, the recording material P stored in each cassette) by the selection unit (selection button) 71a, and confirms. Select (press) the part (OK button) 71b. As a result, information corresponding to the basis weight of the recording material P can be input to the control unit 50 from the operation unit 70 as the input means. In this case, the information corresponding to the basis weight of the recording material P is the information that specifies the type of the recording material P that correlates with the basis weight of the recording material P. When the operator registers the type of the recording material P stored in each cassette, the list of the types of the recording material P displayed in the display unit of the operation unit 70 and stored in the memory 52 in advance (at least). It may be selected from (classified according to basis weight). Further, on the paper setting screen 71 as shown in FIG. 7A, instead of selecting the type of recording material P by selecting a cassette, the type of recording material P associated with the cassette is selected. It may be.

The control unit 50 determines the position of the backup roller 3 based on the information regarding the recording material P acquired in S101 (S102). In the memory 52 of the control unit 50, information on the position (intrusion amount X) of the backup roller 3 according to the basis weight of the recording material P as shown in Table 2 described above is stored in advance. Therefore, for example, in the case of the above example, when the operator selects the cassette (1) (that is, "plain paper"), the control unit 50 sets the position of the backup roller 3 and the penetration amount X = 1.8 mm. Determine the position of. Further, for example, when the operator selects the cassette (2) (that is, "thick paper (1)"), the control unit 50 determines the position of the backup roller 3 at the position where the penetration amount X = 1.0 mm. To do. Further, for example, when the operator selects the cassette (3) (that is, "thick paper (2)"), the control unit 50 determines the position of the backup roller 3 at the position where the penetration amount X = 0.5 mm. To do.

When the start button (not shown) is pressed by the operator in the operation unit 70 and a job start instruction is input (S103), the control unit 50 moves the backup roller 3 to the position determined in S102 (S104). ). If the backup roller 3 is already arranged at a desired position, the position of the backup roller 3 may not be changed and the position may be maintained. Next, the control unit 50 starts feeding the recording material P from any of the cassettes (1) to (3) selected in S101 (S105) and starts image formation (S106). After that, the control unit 50 determines whether or not the formation of all the images of the job is completed (S107), returns the process to S105 if it is not completed, and ends the job if it is completed. Let me.

Here, the position of the backup roller 3 was changed before the feeding of the recording material P was started, but the tip of the recording material P was the secondary transfer unit T2 (more specifically, upstream of the secondary transfer unit T2). The backup roller 3 may be arranged at a desired position before reaching (near the side). That is, the position of the backup roller 3 may be changed when there is no recording material P in the secondary transfer unit T2 (more specifically, the secondary transfer unit T2 and the vicinity of the upstream side thereof). Therefore, the position of the backup roller 3 may be changed after the feeding of the recording material P is started. Further, for example, when a plurality of types of recording materials P are mixed in one job, the position of the backup roller 3 can be changed between the papers. More specifically, the vicinity of the upstream side of the secondary transfer unit T2 is the intermediate transfer belt 1 from the contact region between the backup roller 3 and the intermediate transfer belt 1 in the rotation direction of the intermediate transfer belt 1 to the secondary transfer unit T2. It is an area opposite to. Further, the space between papers is a period corresponding to the space between the recording materials P and the recording materials P when the images are continuously formed on the plurality of recording materials P (continuous image formation).

Further, for example, the information on the type of recording material P selected by the operator on the paper setting screen 71 shown in FIG. 7A is information on the brand (manufacturer, product number, etc.) of recording material P registered in advance. You may. In this case, the control unit 50 is stored in the memory 52 in advance, or information regarding the basis weight of the recording material P of each brand based on the information acquired from an external storage means, for example, via a network at an arbitrary timing. Can be obtained. Further, for example, as shown in FIG. 7B, the operator can input the information of the index value that correlates with the basis weight of the recording material P stored in each cassette in the numerical value input field 71c of the paper setting screen 71. It may be. In this case, the index value that correlates with the basis weight is not limited to the basis weight itself, and may be a thickness corresponding to the basis weight. Further, instead of the basis weight and thickness, information indicating the classification of basis weight and thickness such as thin paper, plain paper, and thick paper may be input.

Further, the information about the recording material P used for image formation may be input via an external device 200 such as a personal computer communicatively connected to the image forming device 100. In this case, the operator displays the recording material from the same paper setting screen as shown in FIGS. 7A and 7B displayed on the display unit of the external device 200 by the printer driver installed in the external device 100. Information about P can be entered. In this case, the interface unit 53 of the control unit 50 functions as an input means for inputting information corresponding to the basis weight of the recording material P from the external device 200 and the smoothness of the surface of the recording material P to the control unit 50.

6. Setting the position of the backup roller by the smoothness of the recording material As described above, the recording material P having a low surface smoothness generally makes it difficult to transfer the toner image on the intermediate transfer belt 1. For example, in the case of the example showing the results in Table 1, it can be seen that when the Beck smoothness of the surface of the recording material P is 35 sec or less, the transferability decreases as the penetration amount X decreases.

Therefore, when transferring to a recording material P whose surface smoothness is lower than a predetermined smoothness, the backup roller 3 can be arranged at the third position regardless of the basis weight of the recording material P. That is, the backup roller 3 can be arranged at the third position in the moving direction from the first position to the second position (in this embodiment, the direction substantially orthogonal to the reference line L). The third intrusion amount X3, which is the intrusion amount X when the backup roller 3 is arranged at the third position, is equal to or greater than the second intrusion amount X2 when the backup roller 3 is arranged at the second position. It shall be. When the third intrusion amount X3 is the same as the second intrusion amount X2, the third position is the same as the second position. On the other hand, when transferring to a recording material P having a surface smoothness equal to or higher than the predetermined smoothness, the position of the backup roller 3 is set to the above-mentioned first position according to the basis weight of the recording material P as described above. And change to the second position. The predetermined smoothness (for example, a predetermined Beck smoothness) can be appropriately set through experiments or the like in advance, and as an example, the Beck smoothness is 35 sec. Then, for example, when transferring to a recording material P having a Beck smoothness of less than 35 sec based on the results shown in Table 1, the position of the backup roller 3 is set to 1.8 mm (or 2.5 mm). be able to. As a result, high transferability can be exhibited even in the recessed portion on the surface of the recording material P. Here, in order to more reliably improve the transferability to the recording material P having low surface smoothness, the third position is the position where the penetration amount X is the largest among the positions where the backup roller 3 can be arranged ( In the configuration of this example, it is preferably 2.5 mm).

With such control, for example, when a recording material P (such as thick paper having a relatively high smoothness) having a relatively large basis weight and a relatively high surface smoothness is used, the penetration amount X can be made relatively small. it can. On the other hand, by such control, for example, when a recording material P (relatively thin embossed paper or the like) having a relatively small basis weight and a relatively low surface smoothness is used, the penetration amount X is relatively large. Can be done.

From Table 1, for example, No. 3, No. It can be seen that when the Beck smoothness is particularly small, less than 25 sec, as in No. 7, the transferability is significantly reduced by reducing the penetration amount X. Therefore, the penetration amount X may be changed in a plurality of steps by setting a plurality of threshold values for the smoothness of the surface. For example, two thresholds of Beck smoothness of 35 sec and 25 sec are set as thresholds, and when the Beck smoothness is less than 35 sec and 25 sec or more, the penetration amount X is set to 1.8 mm, and when the Beck smoothness is less than 25 sec, the penetration amount is set. X may be 2.5 mm and the like. Further, the recording material P having a relatively low surface smoothness is not limited to the above-mentioned examples, and is typically a so-called embossed paper, textured paper, matte coated paper, or the like.

As described above, the operation when the position of the backup roller 3 is changed based on the information on the smoothness of the surface of the recording material P in addition to the information on the basis weight of the recording material P is also described with reference to FIG. 6, for example. It is the same as the one that was done. However, in this case, the information regarding the recording material P previously associated with the cassettes (1) to (3) and stored in the memory 52 of the control unit 50 relates to at least the basis weight and surface smoothness of the recording material P. It shall contain information. Further, in this case, the memory 52 of the control unit 50 contains information on the position (intrusion amount X) of the backup roller 3 according to the basis weight of the recording material P as shown in Table 2 described above, and the surface of the recording material P. Information on the position (intrusion amount X) when the smoothness of the above is lower than the predetermined smoothness is stored in advance.

For example, the cassettes (1) and (2) contain the same "plain paper" and "thick paper (2)" as in the above example, respectively, and the Beck smoothness of these recording materials P is 35 sec or more. It shall be. Further, in the cassette (3), instead of the "thick paper (2)" in the above example, "embossed paper" having a basis weight of 150 g / m ² or more and a Beck smoothness of less than 35 sec is stored. To do. In this case, in S102, the control unit 50 determines the position of the backup roller 3 at the position where the penetration amount X = 1.8 mm when the cassette (1) (that is, "plain paper") is selected. .. Further, for example, when the cassette (2) (that is, "thick paper (2)") is selected, the control unit 50 determines the position of the backup roller 3 at a position where the penetration amount X = 0.5 mm. To do. Further, for example, when the cassette (3) (that is, "embossed paper") is selected, the control unit 50 sets the position of the backup roller 3 at the penetration amount X = 1.8 mm (or 2.5 mm). Determine the position of.

As in the case of the basis weight of the recording material P, the information corresponding to the smoothness of the surface of the recording material P can be input to the control unit 50 by the operation unit 70 as an input means. Further, as in the case of the basis weight of the recording material P, the information corresponding to the smoothness of the surface of the recording material P may be input via the external device 200. The information corresponding to the smoothness of the recording material P is information that specifies the type of the recording material P (an attribute such as embossed paper or a brand) that correlates with the smoothness of the surface of the recording material P. (See FIG. 8 (a)). Further, the information corresponding to the smoothness of the recording material P may be the information of the index value that correlates with the smoothness of the surface of the recording material P (see FIG. 8B). The index value that correlates with the surface smoothness is, for example, the value of Beck smoothness, but is not limited thereto. Further, instead of the value such as Beck smoothness, information indicating the classification of surface smoothness such as coat, fine quality, matte, and embossing may be input.

7. Separability Next, an example of another effect of arranging the backup roller 3 at a position where the penetration amount X is relatively large when the basis weight of the recording material P is relatively small will be described. It should be noted that the effects described below are effects that may be obtained depending on the type of recording material P and the like, and are not intended to be limited to the configuration that produces the effects according to the present invention.

As described above, in the present embodiment, the secondary transfer outer roller 2 is urged by the urging member toward the secondary transfer inner roller 14 via the intermediate transfer belt 1. Further, in this embodiment, the hardness of the secondary transfer outer roller 2 is smaller than the hardness of the secondary transfer inner roller 14. Further, regarding the length (wrapping amount) of the region where the intermediate transfer belt 1 and the secondary transfer outer roller 2 come into contact with each other in the circumferential direction of the secondary transfer outer roller 2, the backup roller 3 is arranged at the above-mentioned first position. It is larger when it is arranged at the above-mentioned second position than when it is.

FIG. 9A is a schematic cross-sectional view (inside the secondary transfer) for explaining the contact state between the secondary transfer inner roller 14, the intermediate transfer belt 1, and the secondary transfer outer roller 2 in the secondary transfer unit T2. A cross section substantially orthogonal to the direction of the rotation axis of the roller 14). Further, FIG. 9B is a schematic cross section for explaining the discharge angle of the recording material P and the separation distance between the tip of the recording material P and the intermediate transfer belt 1 in the vicinity of the downstream side of the secondary transfer unit T2. It is a figure (cross section substantially orthogonal to the rotation axis direction of the secondary transfer inner roller 14.

When the penetration amount X of the backup roller 3 is reduced, the discharge angle of the recording material P (θp in FIG. 9B) decreases as the deformation amount of the secondary transfer outer roller 2 increases, so that the recording material P becomes The separability from the intermediate transfer belt 1 is reduced. Further, as described above, when the penetration amount X of the backup roller 3 is reduced, the winding amount of the intermediate transfer belt 1 with respect to the secondary transfer outer roller 2 is reduced. As a result, of the intermediate transfer belt 1 of the secondary transfer unit T2, the outer peripheral surface is in contact with the secondary transfer outer roller 2 and the inner peripheral surface is not in contact with the secondary transfer inner roller 14 (a). ), The width of the portion indicated by Nt (also referred to as “tension nip region” here) becomes smaller. At this time, when the secondary transfer outer roller 2 is spring-loaded so as to abut against the secondary transfer inner roller 14 with a predetermined pressure across the intermediate transfer belt 1, the result is as follows. That is, of the intermediate transfer belt 1 of the secondary transfer unit T2, the portion indicated by Np in FIG. 9A sandwiched between the secondary transfer outer roller 2 and the secondary transfer inner roller 14 (here, "physical"). The load applied to the "nip area") increases. At this time, if the hardness of the secondary transfer outer roller 2 is smaller than the hardness of the secondary transfer inner roller 14, the secondary transfer outer roller 2 has a shape that follows the outer diameter of the secondary transfer inner roller 14. Transforms into. The widths of the tension nip region Nt and the physical nip region Np are the lengths in the moving direction of the surface of the intermediate transfer belt 1, respectively.

Here, the discharge angle of the recording material P in the vicinity of the downstream side of the secondary transfer unit T2 is affected by the surface of the physical nip region of the secondary transfer unit T2. The larger the deformation amount of the secondary transfer outer roller 2, the smaller the discharge angle of the recording material P in the vicinity of the downstream side of the secondary transfer portion T2, and the smaller the discharge angle of the recording material P in the vicinity of the downstream side of the secondary transfer portion T2. The separation distance between the and the intermediate transfer belt 1 becomes smaller. As a result, the separability of the recording material P from the intermediate transfer belt 1 is reduced. Further, the smaller the basis weight of the recording material P, the more easily it is affected by the surface of the physical nip region of the secondary transfer unit T2. Therefore, as the basis weight of the recording material P becomes smaller, the discharge angle of the recording material P in the vicinity of the downstream side of the secondary transfer portion T2 becomes smaller, and the separability of the recording material P from the intermediate transfer belt 1 tends to decrease. ..

FIG. 10 is a graph showing the relationship between the position of the backup roller 3 and the separation distance L1 between the tip of the recording material P and the intermediate transfer belt 1 in the vicinity of the downstream side of the secondary transfer unit T2. In FIG. 9B, the separation distance L1 is a vertical line passing through a point moved by 5.0 mm in the horizontal direction from the center of the secondary transfer inner roller 14 to the opposite side of the backup roller 8 and the tip of the recording material P. The distance between the intersection and the horizontal line passing through the center of the secondary transfer inner roller 14. This separation distance L1 indicates the separability of the recording material P from the intermediate transfer belt 1 in the vicinity of the downstream side of the secondary transfer unit T2. The larger the separation distance L1, the more difficult it is for the surface of the recording material P and the intermediate transfer belt 1 to be electrostatically adsorbed in the vicinity of the downstream side of the secondary transfer portion T2, so that the recording material P is separated from the intermediate transfer belt 1. The sex becomes high. Here, the above relationship was obtained by a simulation by structural calculation assuming the case where a thin paper having a thickness of 0.06 mm was used as the recording material P. Further, here, the positions of the backup rollers 3 are the positions where the penetration amounts X are 1.8 mm, 1.0 mm, and 0.5 mm, respectively. From FIG. 10, the separation distances are in the order of the position of the backup roller 3 at the position of the penetration amount X = 1.8 mm, the position of the penetration amount X = 1.0 mm, and the position of the penetration amount X = 0.5 mm. It can be seen that L1 is decreasing.

That is, by arranging the backup roller 3 at a position where the penetration amount X is relatively large when the basis weight of the recording material P is relatively small, the intermediate transfer belt 1 of the recording material P in the vicinity of the downstream side of the secondary transfer unit T2 It can be seen that the separability from can be improved.

As an example, the position of the backup roller 3 can be changed according to the basis weight of the recording material P as shown in Table 3 based on the result of the above simulation.

As described above, when the basis weight of the recording material P is relatively large, the image distortion can be suppressed by arranging the backup roller 3 at a position where the penetration amount X is relatively small. Then, when the basis weight of the recording material P is relatively small, the backup roller 3 is arranged at a position where the penetration amount X is relatively large to improve the transferability and from the intermediate transfer belt 1 of the recording material P. Separability can be improved. As described above, the separability of the recording material P from the intermediate transfer belt 1 tends to decrease as the basis weight of the recording material P decreases. Therefore, as shown in Table 3, when the basis weight of the recording material P such as, in particular, small and less than 60 g / m ^2, intrusion than the basis weight of the recording material P is 60 g / m ² or more plain paper or thick paper It is preferable to increase the amount X. Further, at this time, it is preferable to arrange the backup roller 3 at a position (2.5 mm in the configuration of this embodiment) where the intrusion amount X is maximum in the movable range.

[Example 2]
Next, other examples of the present invention will 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 Example 1. Therefore, 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 designated by the same reference numerals as those of the first embodiment, and detailed description thereof will be omitted.

In this embodiment, as described in the first embodiment, a case where the position of the backup roller 3 is changed based on the basis weight of the recording material P and the smoothness of the surface will be described as an example.

FIG. 11A is a schematic cross-sectional view of the image forming apparatus 100 of this embodiment. Further, FIG. 11B is a schematic block diagram showing a control mode of a main part of the image forming apparatus 100 of this embodiment.

The image forming apparatus 100 of this embodiment has a basis weight sensor 110 as a basis weight detecting means for detecting an index value that correlates with the basis weight of the recording material P. In this embodiment, the basis weight sensor 110 is arranged adjacent to the transport path of the recording material P upstream of the resist roller 5 in the transport direction of the recording material P. In this embodiment, the basis weight sensor 110 utilizes the attenuation of ultrasonic waves. That is, the basis weight sensor 110 has an ultrasonic wave generating unit 111 and an ultrasonic wave receiving unit 112 arranged so as to sandwich the transport path of the recording material P. Then, the basis weight sensor 80 receives the ultrasonic waves generated from the ultrasonic wave generating unit 111 and attenuated by passing through the recording material P by the ultrasonic wave receiving unit 112, and records based on the attenuation amount of the ultrasonic waves. An index value that correlates with the basis weight of the material P is detected. The basis weight detecting means may be any as long as it can detect an index value that correlates with the basis weight of the recording material P, and is not limited to the one using ultrasonic waves, for example, the one using light. You may. The index value that correlates with the basis weight of the recording material P is not limited to the basis weight itself, and may be a thickness corresponding to the basis weight. Information (signal) indicating the detection result of the basis weight sensor 110 is input to the control unit 50.

Further, the image forming apparatus 100 of this embodiment has a surface sensor 120 as a smoothness detecting means for detecting an index value that correlates with the smoothness of the surface of the recording material P. In this embodiment, the surface sensor 120 is arranged adjacent to the transport path of the recording material P upstream of the resist roller 5 in the transport direction of the recording material P. In this embodiment, the surface sensor 120 is composed of a specular reflected light sensor that irradiates the recording material P with light and reads the intensity of the specular reflected light and the diffusely reflected light with a light amount sensor. When the surface of the recording material P is smooth, the specular reflected light becomes strong, and when it is rough, the diffusely reflected light becomes strong. Therefore, the surface sensor 120 can detect an index value that correlates with the smoothness of the surface of the recording material P by measuring the amount of specularly reflected light and the amount of diffusely reflected light. The smoothness detecting means may be any as long as it can detect an index value that correlates with the smoothness of the surface of the recording material S, and is not limited to the one using the above-mentioned light amount sensor, for example, an image sensor. It may be the one used. The index value that correlates with the smoothness of the surface of the recording material P is not limited to the value converted into a value according to a predetermined standard such as Beck smoothness, but correlates with the smoothness of the surface of the recording material P. Any value may be used. Information (signal) indicating the detection result of the surface sensor 120 is input to the control unit 50.

The basis weight sensor 110 and the surface sensor 120 may be configured as one unit.

FIG. 12 is a flowchart showing an outline of a job control procedure in this embodiment. Here, a case where an operator such as a user causes the image forming apparatus 100 to execute a job by an operation in the operation unit 70 will be described as an example. Note that FIG. 12 shows an outline of the control procedure focusing on the change of the position of the backup roller 3, and many other operations normally required for executing the job and outputting the image are omitted. ing.

When the start button (not shown) is pressed by the operator in the operation unit 70 and a job start instruction is input (S201), the control unit 50 supplies the recording material P from any of the cassettes 7a to 7b. Sending is started (S202). Then, the control unit 50 acquires the detection result of each sensor when the recording material P is at the respective detection positions of the basis weight sensor 110 and the surface sensor 120 (S203). The basis weight sensor 110 and the surface sensor 120 can detect, for example, information on the basis weight of the recording material P temporarily stopped by the resist roller 5 and information on the smoothness of the surface.

Next, the control unit 50 determines the position of the backup roller 3 based on the information on the basis weight of the recording material P and the information on the smoothness of the surface acquired in S203 (S204). The memory 52 of the control unit 50 stores in advance information on the position (intrusion amount X) of the backup roller 3 according to the basis weight of the recording material P and the smoothness of the surface, which is the same as that described in the first embodiment. ing. Therefore, for example, when it is detected that the paper has a basis weight of less than 105 g / m ² and a Beck smoothness of 35 sec or more, the control unit 50 sets the position of the backup roller 3 and the penetration amount X =. Determine the position of 1.8 mm. Further, for example, when it is detected that the "thick paper (1)" has a basis weight of 105 g / m ² or more, less than 150 g / m ² , and a Beck smoothness of 35 sec or more, the control unit 50 uses the backup roller 3 The position of is determined at the position where the intrusion amount X = 1.0 mm. Further, for example, when it is detected that the "embossed paper" has a basis weight of 150 g / m ² or more and a Beck smoothness of less than 35 sec, the control unit 50 determines the position of the backup roller 3 and the penetration amount X = 1. Determine the position to be 0.8 mm (or 2.5 mm).

Next, the control unit 50 moves the backup roller 3 to the position determined in S204 (S205). If the backup roller 3 is already arranged at a desired position, the position of the backup roller 3 may not be changed and the position may be maintained. Further, the control unit 50 starts image formation at a predetermined timing, for example, in parallel with the above operation (S206). After that, the control unit 50 determines whether or not the formation of all the images of the job is completed (S207), returns the process to S202 if it is not completed, and ends the job if it is completed. Let me.

As described in the first embodiment, the backup roller 3 is desired before the tip of the recording material P reaches the secondary transfer unit T2 (more specifically, near the upstream side of the secondary transfer unit T2). It may be placed in a position. For example, when a plurality of types of recording materials P are mixed in one job, the position of the backup roller 3 can be changed between the papers.

Further, in this embodiment, an index value that correlates with the basis weight of the recording material P and an index that correlates with the smoothness of the surface of the recording material P by the basis weight detecting means and the smoothness detecting means provided in the image forming apparatus 100. The value was detected. On the other hand, the image forming apparatus 100 transmits information on the basis weight of the recording material P detected by the external basis weight detecting means, the smoothness detecting means, and information on the surface smoothness to the control unit 50 of the image forming apparatus 100. It may be configured so that it can be input. That is, as shown in the schematic diagram of FIG. 13, the image forming apparatus 100 may be an external basis weight sensor 110 and a surface sensor 120 (these may be one measuring apparatus) directly or via a network. ) May be configured to be communicable. In this case, for example, before starting the job, the operator uses the basis weight sensor 110 and the surface surface sensor 120 to provide information on the basis weight of the recording material P used for image formation in the job and information on the smoothness of the surface. And input to the control unit 50 of the image forming apparatus 100. Further, the information acquired by using the basis weight sensor 110 and the surface sensor 120 may be temporarily written in the storage medium 130 having an electronic memory built-in. In this case, the operator connects the storage medium 130 to the control unit 50 via a predetermined connection unit provided in the image forming apparatus 100, and the control unit 50 reads the above information from the storage medium. Then, when the job is started, the control unit 50 uses the information acquired by using the external basis weight sensor 110 and the surface sensor 120 to position the backup roller 3 in the same manner as in the present embodiment. You can control the changes in.

Further, in this embodiment, in addition to the basis weight of the recording material P, the smoothness of the surface of the recording material P was also detected, but the backup was performed based only on the basis weight of the basis weight and the smoothness of the surface of the recording material P. When determining the position of the roller 3, the above-mentioned smoothness detecting means may not be provided.

As described above, according to the present embodiment, the same effect as that of the first embodiment can be obtained, and the burden of setting the information regarding the recording material P of the operator can be reduced.

[Example 3]
Next, other examples of the present invention will 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 Example 1. Therefore, 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 designated by the same reference numerals as those of the first embodiment, and detailed description thereof will be omitted.

FIG. 15 is a schematic cross-sectional view (cross section substantially orthogonal to the rotation axis direction of the secondary transfer inner roller 14) in the vicinity of the secondary transfer unit T in this embodiment. In this embodiment, a backup sheet composed of a sheet-like member as a support member that contacts the inner peripheral surface of the intermediate transfer belt 1 and supports the intermediate transfer belt 1 in the vicinity of the upstream side of the secondary transfer inner roller 14. 9 is arranged. Further, the backup sheet 9 can be moved in the same direction as the backup roller 3 in the first embodiment by the moving mechanism (position variable mechanism) (not shown) as the moving means (position variable means) similar to the first embodiment. It is said that.

The backup sheet 9 can be formed by using a resin material. As the resin material for forming the backup sheet 9, for example, a polyester resin such as PET resin can be preferably used. In this embodiment, the backup sheet 9 has a longitudinal direction arranged substantially parallel to the width direction of the intermediate transfer belt 1 (a direction substantially orthogonal to the moving direction of the surface) and a lateral direction substantially orthogonal to the longitudinal direction. , Each of which has a predetermined length and is composed of a plate-shaped member having a predetermined thickness. The length of the backup sheet 9 in the longitudinal direction is equivalent to the length of the intermediate transfer belt 1 in the width direction, and the backup sheet 9 abuts over substantially the entire width of the intermediate transfer belt 1. Further, as an example, the thickness of the backup sheet 9 is 0.4 mm to 0.6 mm.

For example, when a PET resin sheet is used as the backup sheet 9, if a PET resin sheet having an electric resistance too low is used, a current flows through the backup sheet 9 as the secondary transfer voltage is applied to the secondary transfer outer roller 2. It may cause transfer defects. On the other hand, if a PET resin sheet having too high electrical resistance is used, static electricity (triboelectric charging) is generated due to friction between the backup sheet 9 and the intermediate transfer belt 1, and the intermediate transfer belt 1 is attracted to the backup sheet 9 to attract the intermediate transfer belt 1. It may interfere with the rotation of 1. Therefore, as the backup sheet 9, it is preferable to use a PET resin sheet adjusted to a medium resistance electrical resistance (for example, a volume resistivity of 1 × 10 ⁵ to 1 × 10 ⁹ Ω · cm).

As described above, according to the present embodiment, by using the backup sheet 9 as the support member, it is possible to reduce the size of the device and the initial cost as compared with the case where the backup roller 3 is used as the support member. Is possible.

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

In the above-described embodiment, the case where the position of the support member is changed in four stages has been described, but the position is changed in stages with a smaller number of stages or a larger number of stages, or is changed substantially continuously. It may be done.

In the above-described embodiment, the case where the support member is a roller-shaped member or a sheet-shaped (film-shaped) member has been described, but the support member has an arbitrary form such as a pad-shaped member or a brush-shaped member. It may be a member.

In the above-described embodiment, the case where the belt-shaped image carrier is an intermediate transfer belt has been described, but any image carrier composed of an endless belt that conveys the toner image supported at the image forming position can be used. , The present invention can be applied. Examples of such a belt-shaped image carrier include a photoconductor belt and an electrostatic recording dielectric belt, in addition to the intermediate transfer belt in the above-described embodiment.

In the above-described embodiment, the support member moves linearly, but the support member may rotate as long as it moves so as to change the intrusion amount X. For example, the support member can be moved by supporting the support member with a rotatable (swingable) support portion and rotating the support portion.

The present invention can also be implemented in another embodiment in which a part or all of the configuration of the above-described embodiment is replaced with an alternative configuration thereof. Therefore, any image forming apparatus using a belt-shaped image carrier can be implemented without distinction between a tandem type / 1 drum type, a charging method, an electrostatic image forming method, a developing method, a transfer method, and a fixing method. In the above-described embodiment, the main parts related to the formation / transfer of the toner image have been mainly described, but the present invention includes a printer, various printing machines, a copying machine, and a fax machine by adding necessary equipment, equipment, and a housing structure. , Multifunction machine, etc., can be implemented in various applications.

1 Intermediate transfer belt 2 Secondary transfer outer roller (outer roller)
3 Backup roller (support member)
4 Moving mechanism (means of moving)
13 Idler roller (upstream roller)
14 Secondary transfer inner roller (inner roller)

Claims (15)

A rotatable endless belt that conveys the toner image supported at the image formation position,
An outer roller that comes into contact with the outer peripheral surface of the belt and forms a transfer portion that transfers a toner image from the belt to the recording material.
A plurality of tensioning rollers for tensioning the belt, the inner rollers arranged corresponding to the transfer portion, and downstream of the image forming position and upstream of the inner roller in the rotation direction of the belt. Arranged upstream rollers, including multiple tension rollers,
A support member that contacts the inner peripheral surface of the belt upstream of the inner roller and downstream of the upstream roller in the direction of rotation of the belt.
A moving means for moving the support member and
A control means for controlling the moving means and
Have,
In a cross section substantially orthogonal to the rotation axis direction of the inner roller, the support member can be arranged at a first position in contact with the belt and a second position in contact with the belt, and the belt is hung around. The common tangent line between the inner roller and the upstream roller on the side is the reference line L, and the tangent line of the belt substantially parallel to the reference line L in the region where the support member contacts the belt is the support portion tangent line Ld, the reference. When the distance between the line L and the tangent line Ld of the support portion is defined as the intrusion amount X, the movement distance from the first position to the second position is greater in the direction orthogonal to the reference line L. The support member is larger than the first penetration amount X1 which is larger than the movement distance in the direction parallel to the reference line L and is the penetration amount X when the support member is arranged at the first position. The second intrusion amount X2, which is the intrusion amount X when arranged at two positions, is larger.
In the control means, the support member is arranged at the first position when the transfer is performed on a recording material having a basis weight of the first basis weight, and the basis weight is a second basis weight smaller than the first basis weight. An image forming apparatus characterized in that control is performed so that the support member is arranged at the second position when the transfer is performed on a recording material. The control means has an input means for inputting information corresponding to the basis weight of the recording material, and the control means controls a change in the position of the support member based on the information corresponding to the basis weight input by the input means. The image forming apparatus according to claim 1, wherein the image forming apparatus is performed. The image forming apparatus according to claim 2, wherein the information corresponding to the basis weight of the recording material is information for designating the type of recording material that correlates with the basis weight of the recording material. The image forming apparatus according to claim 2, wherein the information corresponding to the basis weight of the recording material is information of an index value that correlates with the basis weight of the recording material. It has a basis weight detecting means for detecting an index value that correlates with the basis weight of the recording material, and the control means controls a change in the position of the support member based on the detection result of the basis weight detecting means. The image forming apparatus according to claim 1. The support member can be arranged at a third position in the moving direction from the first position to the second position, and is the intrusion amount X when the support member is arranged at the third position. The 3 intrusion amount X3 is equal to or greater than the second intrusion amount X2.
In the control means, when the transfer is performed on a recording material whose surface smoothness is lower than a predetermined smoothness, the support member is arranged at the third position regardless of the basis weight of the recording material to be transferred. The image forming apparatus according to any one of claims 1 to 5, wherein the image forming apparatus is controlled so as to perform the above. The control means has an input means for inputting information corresponding to the smoothness of the surface of the recording material, and the control means of the support member is based on the information corresponding to the smoothness of the recording material input by the input means. The image forming apparatus according to claim 6, wherein the position change is controlled. The image forming apparatus according to claim 7, wherein the information corresponding to the smoothness of the recording material is information that specifies a type of recording material that correlates with the smoothness of the surface of the recording material. The image forming apparatus according to claim 7, wherein the information corresponding to the smoothness of the recording material is information of an index value that correlates with the smoothness of the surface of the recording material. It has a smoothness detecting means for detecting an index value corresponding to the smoothness of the surface of the recording material, and the control means controls a change in the position of the support member based on the detection result of the smoothness detecting means. The image forming apparatus according to claim 6, wherein the image forming apparatus is performed. The image forming apparatus according to any one of claims 1 to 10, wherein the outer roller is urged toward the inner roller via the belt by an urging member. The image forming apparatus according to any one of claims 1 to 11, wherein the hardness of the outer roller is smaller than the hardness of the inner roller. The length of the region where the belt and the outer roller contact in the circumferential direction of the outer roller is the case where the support member is arranged at the second position rather than the case where the support member is arranged at the first position. The image forming apparatus according to any one of claims 1 to 12, wherein the image forming apparatus is larger. The image forming apparatus according to any one of claims 1 to 13, wherein the support member is a roller. The image forming apparatus according to any one of claims 1 to 13, wherein the support member is a sheet-shaped member.

Images