JP2018146851A - Carrier unit, fixation unit, and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a domain which forms a nip part of a pressure member from being deformed, as compared with a configuration in which slits are at equal intervals along a length of the pressure member, in a configuration in which a nip part is formed by providing the pressure member having the slits formed inside a belt and pressing the belt against a rotary body.SOLUTION: A conveyance part 32 has a fixation roll 36, a belt 38, a pressure member 42, and a limitation part 44. The fixation roll 36 rotates on an axial direction orthogonal to a conveying direction of a sheet P. The belt 38 is endless, and forms a nip part N together with the fixation roll 36. The pressure member 42 is provided inside the belt 38, and has slits 72 formed at both Z-directional end parts and in a region where the nip part N is formed, and presses the belt 38 against the fixation roll 36. The limitation part 44 is provided between opposite surfaces 73, 75 of the slits 72 and restricts the interval between the opposite surfaces 73, 75 from becoming narrow.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a conveyance device, a fixing device, and an image forming apparatus.

  In the image heating apparatus of Patent Document 1, a pressure roller and a pressure roller that can be raised and lowered are pressed against a fixing belt supported on an inner surface by a heating member to form a heating nip portion of a recording material. On the lower surface of the heating member, an arc-shaped correction shape is formed in which the central portion protrudes from the both end portions toward the fixing belt. In addition, an arc-shaped correction shape in which the center portion is recessed upward from both end portions is formed on the lower surface of the pressure member.

JP 2010-181840 A

  There is a configuration in which a pressure member in which a slit is formed is provided on the inner side of the belt, and the belt is pressed toward a rotating body to form a nip portion. In this configuration, a reaction force from the nip portion acts on a portion that forms the nip portion of the pressure member and that is a peripheral portion of the slit, so that the portion may be deformed.

  According to the present invention, in a configuration in which a pressure member having slits is provided on the inner side of the belt and the belt is pressed toward the rotating body to form a nip portion, the slit interval is the same in the longitudinal direction of the pressure member. It aims at suppressing that the site | part which forms the nip part of a pressurization member deform | transforms compared with a structure.

  According to a first aspect of the present invention, there is provided a conveyance device that rotates around a direction orthogonal to the conveyance direction of the recording medium as an axial direction, and an endless belt that forms a nip portion that sandwiches the recording medium together with the rotation body. A pressure member provided on the inner side of the belt, in which slits recessed in the axial direction are formed at both end portions in the axial direction and in the portion forming the nip portion, and pressurizes the belt toward the rotating body And when the slit is viewed from the pressurizing direction in which the pressurizing member pressurizes, the limiting portion is provided between the pair of opposed surfaces of the slit, and restricts the interval between the opposed surfaces from being narrowed, Have

  The pressure member of the conveying device according to claim 2 of the present invention is such that one side with respect to the slit is a nip forming portion that forms the nip portion, the other side with respect to the slit is a main body portion, and the limiting portion is the It protrudes from the opposite surface on the other side.

  The pressure member of the conveying device according to claim 3 of the present invention is configured such that one side with respect to the slit is a nip forming portion that forms the nip portion, the other side with respect to the slit is a main body portion, and the nip forming portion includes A lower portion having a lower height in the pressurizing direction than the height in the pressurizing direction at the central portion in the axial direction of the nip forming portion is formed.

  According to a fourth aspect of the present invention, there is provided a fixing device comprising: a heating source; and a fixing rotating body as the rotating body that is heated by the heating source and melts the developer at the nip portion and pressurizes and fixes the recording medium. It has a conveyance device given in any 1 paragraph of Claims 1-3.

  According to a fifth aspect of the present invention, there is provided the image forming apparatus according to the fourth aspect, wherein a developer image forming unit for forming a developer image and a developer image formed by the developer image forming unit are fixed to the recording medium. And the fixing device described.

  According to the first aspect of the present invention, a pressure member having slits is provided inside the belt, and the belt is pressed toward the rotating body to form a nip portion. Compared to the same configuration in the direction, it is possible to suppress the deformation of the portion forming the nip portion of the pressure member.

  According to the second aspect of the present invention, it is possible to suppress the bending rigidity of the nip forming portion from increasing compared to the configuration in which the limiting portion is formed on the nip forming portion side.

  According to the invention of claim 3, it is possible to suppress the bending rigidity of the nip forming portion from increasing compared to a configuration in which the height in the pressing direction is the same at the center portion and the end portion of the nip forming portion.

  The invention of claim 4 can suppress the offset of the developer to the fixing rotator as compared with the configuration in which the slit interval is the same in the longitudinal direction of the pressure member.

  According to the fifth aspect of the present invention, it is possible to suppress defects in the output image after fixing as compared with the configuration in which the slit interval is the same in the longitudinal direction of the pressure member.

1 is a configuration diagram illustrating an image forming apparatus according to an exemplary embodiment. FIG. 4 is a longitudinal sectional view illustrating a state in which the fixing device according to the exemplary embodiment is viewed in the axial direction of the fixing roll. It is a perspective view of the pressurization member concerning this embodiment. It is the elements on larger scale of the site | part in which the slit of the pressurization member which concerns on this embodiment was formed. It is a longitudinal cross-sectional view (5-5 sectional view of FIG. 4) of the pressurization member which concerns on this embodiment. It is the elements on larger scale which show the low rank part of the pressurization member concerning this embodiment. It is the elements on larger scale which show the low rank part and slit of the pressurization member concerning this embodiment. (A) It is the elements on larger scale of the site | part in which the slit of the pressurization member which concerns on this embodiment was formed, (B) The part of the site | part in which the slit of the pressurization member which concerns on the 1st modification of this embodiment was formed It is an enlarged view. (A) It is a schematic diagram which shows the non-pressurization state of the site | part in which the slit of the pressurization member which concerns on this embodiment was formed, (B) The addition of the site | part in which the slit of the pressurization member which concerns on this embodiment was formed It is a schematic diagram which shows a pressure state. It is a graph which shows the relationship between the axial direction position and surface pressure of the belt which concerns on this embodiment. (A) It is the elements on larger scale of the part in which the slit of the pressurization member concerning the 2nd modification of this embodiment was formed, (B) The slit of the pressurization member concerning the 3rd modification of this embodiment is formed. It is the elements on larger scale of the made part.

  An example of a conveyance device, a fixing device, and an image forming apparatus according to the present embodiment will be described.

[overall structure]
FIG. 1 shows an image forming apparatus 10 of the present embodiment. In the following description, the direction indicated by the arrow Y in FIG. 1 is the apparatus height direction, and the direction indicated by the arrow X is the apparatus width direction. In addition, a direction (indicated by Z) orthogonal to each of the apparatus height direction and the apparatus width direction is defined as an apparatus depth direction. Then, when the image forming apparatus 10 is viewed from the front, the apparatus height direction, the apparatus width direction, and the apparatus depth direction are described as a Y direction, an X direction, and a Z direction. Further, when it is necessary to distinguish one side and the other side in the X direction, the Y direction, and the Z direction, when the image forming apparatus 10 is viewed from the front, the upper side is the Y side, the lower side is the -Y side, and the right side is X side, left side is described as -X side, back side is described as Z side, and front side is described as -Z side.

  The image forming apparatus 10 includes a transport unit 12 including a roll pair 13 that transports the paper P, an image forming unit 14 that forms a toner image G using toner T on the paper P transported by the transport unit 12, and a toner. And a fixing device 30 that fixes the image G on the paper P by heating and pressing. A line indicated by a symbol K shown in FIG. The paper P is an example of a recording medium. The toner T is an example of a developer. The toner image G is an example of a developer image. The image forming unit 14 is an example of a developer image forming unit.

  The image forming unit 14 includes an image forming unit 20 and a control unit 22 that controls the operation of each unit of the image forming unit 20 to form a toner image G on the paper P. For example, the image forming unit 20 is configured to perform each process of charging, exposure, development, and transfer, which are known electrophotographic methods.

[Main part configuration]
Next, the fixing device 30 will be described.

  The fixing device 30 illustrated in FIG. 2 includes a conveyance unit 32 as an example of a conveyance device and a heating unit 34 as an example of a heating source. The conveyance unit 32 and the heating unit 34 are housed in a rectangular parallelepiped housing (not shown) that is the main body of the fixing device 30.

[Transport section]
The conveyance unit 32 includes a fixing roll 36, a belt 38 that sandwiches the paper P together with the fixing roll 36, a pressure member 42 that is provided inside the belt 38 and presses the belt 38 toward the fixing roll 36, and an opposing surface that will be described later. And a restricting portion 44 that restricts the interval between 73 and 75 from being narrowed. The fixing roll 36 is an example of a rotating body and a fixing rotating body. Further, as an example, the conveying unit 32 includes support members 46 and 47 that support the pressure member 42, a coil spring 48 that presses the support members 46 and 47 toward the pressure member 42, and a plate spring that pressurizes the belt 38. 52 and a felt 54 in contact with the inner peripheral surface of the belt 38 is provided. In FIG. 2, members at the end on the −Z side in the width direction (Z direction) of the belt 38 are shown. A sliding sheet (not shown) is provided between the pressure member 42 and the plate spring 52 and the belt 38 to reduce frictional resistance.

<Fixing roll>
As an example, the fixing roll 36 has a configuration in which a covering portion 36B including an elastic body layer made of silicon rubber and a release layer made of fluororesin is formed on the outer peripheral surface of a cylindrical metal core 36A made of aluminum. . Further, the fixing roll 36 is disposed on the toner image G side with respect to the conveyance path K of the paper P so as to be rotatable about the axis with the Z direction as an axial direction. That is, the fixing roll 36 rotates with the Z direction orthogonal to the transport direction of the paper P as an axial direction. A heating unit 34 described later is provided inside the cored bar 36A.

  Further, a gear (not shown) is provided at the Z side end of the core metal 36 </ b> A of the fixing roll 36. This gear is rotated by a motor which is a driving means (not shown). The fixing roll 36 is heated by the heating unit 34 and melts and pressurizes the toner T (see FIG. 1) at a nip N (to be described later) while rotating together with the belt 38, and the toner image G on the paper P is transferred to the paper. It is fixed to P.

<Belt>
For example, the belt 38 is formed in an endless shape having a base layer made of polyimide and a release layer made of fluororesin laminated on the base layer. The belt 38 is disposed on the opposite side to the toner image G side with respect to the conveyance path K of the paper P so as to be able to rotate (circulate) around the axis with the Z direction as an axial direction. Specifically, the pressure member 42 and the leaf spring 52 described later come into contact with the inner peripheral surface of the belt 38, and the belt 38 is pressed (pressed) against the outer peripheral surface of the fixing roll 36. However, it moves around in synchronism with the rotation of the fixing roll 36.

  A portion where the outer peripheral surface of the fixing roll 36 and the outer peripheral surface of the belt 38 sandwich the paper P, and a portion where the toner image G on the paper P is heated and pressed is referred to as a nip portion N. That is, the belt 38 forms a nip portion N that sandwiches the paper P together with the fixing roll 36. In the nip portion N, the fixing roll 36 and the belt 38 are in contact with each other when paper is not passed.

  In the present embodiment, the transport path KA upstream of the nip portion N in the transport direction of the paper P is slightly in the Y direction so that the Y side is closer to the −X side (fixing roll 36 side) than the −Y side. It is arranged along the slanting direction inclined. In the present embodiment, the transport path KB on the downstream side of the nip portion N in the transport direction of the paper P is in the Y direction so that the Y side is closer to the −X side (fixing roll 36 side) than the −Y side. It is arranged along an oblique direction that is greatly inclined. The transport path KA and the transport path KB are included in the transport path K.

<Supporting member and coil spring>
The support members 46 and 47 are made of metal (for example, stainless steel), and are long members each having an L-shaped cross section when viewed from the Z direction and having the Z direction as an axial direction. Further, the support members 46 and 47 are arranged inside the belt 38 so as to have an inverted U shape that opens toward the nip portion N when viewed from the Z direction. The width of the support members 46 and 47 in the Z direction is longer than the width of the pressurizing member 42 described later in the Z direction.

  Both ends in the Z direction of the support members 46 and 47 are guided toward the fixing roll 36 by guide members (not shown). Furthermore, one end of each coil spring 48 is in contact with both ends of the support members 46 and 47 in the Z direction. The two coil springs 48 are compressed by contacting a plate (not shown), and urge the support members 46 and 47 and the pressure member 42 toward the fixing roll 36.

  The plate (not shown) that contacts the coil spring 48 can be moved by a retract mechanism (not shown) using a cam. That is, the pressurizing member 42 is switched between a pressurizing state in which the belt 38 is pressed and a non-pressurizing state in which the belt 38 is not pressed by driving a retracting mechanism (not shown).

<Felt>
The felt 54 is soaked with oil as a lubricant. The felt 54 is fixed to the surface of the support member 46 opposite to the pressure member 42 side. Further, the felt 54 is in contact with the inner peripheral surface of the belt 38, and oil is applied to the inner peripheral surface of the belt 38.

<Pressurizing member>
The pressure member 42 shown in FIG. 3 is made of polyimide resin as an example. The pressing member 42 is a long member extending with the Z direction as an axial direction. Furthermore, the pressurizing member 42 has a shape in which the Z side and the −Z side are symmetrical with respect to the center in the Z direction. For this reason, in the following description, when describing the end portion in the Z direction, the -Z side will be described, and the description on the Z side will be omitted.

  The width in the Z direction of the pressure member 42 is set longer than the width in the Z direction of the maximum paper P used in the image forming apparatus 10 (see FIG. 1) and longer than the width in the Z direction of the belt 38. . The pressing member 42 includes a main body portion 56, a vertical wall portion 58, a stepped portion 62, a nip forming portion 64, a first attached portion 66, and a second attached portion 68 (see FIG. 2). It is set as the structure formed integrally including. Further, a slit 72 is formed in the pressure member 42.

  In the following description, the longitudinal direction of the pressure member 42 is the Z direction, the direction orthogonal to the Z direction and the direction in which the vertical wall portion 58 extends is referred to as the A direction, and the direction orthogonal to the A direction and the Z direction is referred to as the B direction. . As shown in FIG. 2, the A direction is a direction that forms an angle θ with the X direction. The B direction is a direction that forms an angle θ with the Y direction. That is, the pressurizing member 42 is disposed on the inner side of the belt 38 so that the vertical wall portion 58 is along a direction inclined at an angle θ with respect to the Y direction. Further, the A direction is a pressing direction in which the pressing member 42 presses the belt 38 toward the fixing roll 36.

  FIG. 5 shows a longitudinal section of the pressure member 42 with the A direction as the vertical direction in the figure. Here, the side on which the vertical wall portion 58 in the B direction is disposed with respect to the main body portion 56 is referred to as a B side, and the side on which the nip forming portion 64 is disposed is referred to as a −B side. In addition, with respect to the main body portion 56, the side on which the vertical wall portion 58 extends in the A direction is referred to as the -A side, and the opposite side to the -A side is referred to as the A side.

(Main body)
When viewed from the A direction, the main body 56 is formed in a rectangular shape with the Z direction as the long direction and the B direction as the short direction. Moreover, the main-body part 56 is extended in the diagonal direction so that the -B side may be located in the A side rather than the B side. A rib 56A is formed on the A-side (upper) surface of the main body 56 so as to protrude in a plate shape toward the A-side when viewed from the Z direction. A surface on the −A side (lower side) of the main body portion 56 is an attached surface 56B to which a leaf spring 52 described later is attached.

(Vertical wall)
The vertical wall portion 58 extends from the end on the B side in the main body portion 56 toward the −A side. Further, when viewed from the B direction, the vertical wall portion 58 is formed in a rectangular shape in which the Z direction is the longitudinal direction and the A direction is the short direction. Further, the vertical wall portion 58 is formed with ribs 58A, ribs 58B, and ribs 58C.

(Step part)
As shown in FIG. 3, the stepped portion 62 has a main body portion so that a −A side plane 65 </ b> A of a nip forming portion 64, which will be described later, is located on the −A side with respect to the attachment surface 56 </ b> B of the main body portion 56. 56 and the nip forming portion 64 are connected.

(Nip forming part)
As shown in FIG. 5, the nip forming portion 64 is disposed on the −B side with respect to the main body portion 56 and is located on the −A side with respect to the end portion on the −B side of the main body portion 56. The nip forming portion 64 has an L-shaped cross section when viewed from the Z direction. Specifically, the nip forming portion 64 includes a bottom wall 65 extending in the B direction and a vertical wall 67 extending from the −B side of the bottom wall 65 to the A side along the A direction. A flat surface 65 </ b> A is formed in a portion that is on the −A side of the bottom wall 65 and on the B side from the center in the B direction. A surface between the bottom wall 65 and the vertical wall 67 is an arcuate curved surface 65B that is convex outward. The curved surface 65B is a surface that contacts the inner peripheral surface of the belt 38 (see FIG. 2) to form a nip portion N (see FIG. 2).

  Here, the nip portion N shown in FIG. 2 is a portion where the belt 38 sandwiches the paper P together with the fixing roll 36. The nip portion N is a portion from the entry position to the discharge position of the paper P. A portion where the nip forming portion 64 presses the paper P in the A direction and a leaf spring 52 described later defines the paper P in the A direction. And a portion that pressurizes in a different direction. Further, the nip portion N is formed from the Z side end of the belt 38 to the −Z side end.

  As shown in FIG. 6, the height in the A direction is set to H <b> 1 at the center of the vertical wall 67 in the Z direction. In addition, at both ends in the Z direction of the vertical wall 67, the height in the A direction is set to H2 (<H1). That is, at both ends in the Z direction of the nip forming portion 64, lower portions 74 having a height H2 in the A direction lower than the height H1 in the A direction at the center in the Z direction are formed.

  The low-order part 74 is comprised in the both-ends part of the Z direction of the vertical wall 67 by the part notched by the rectangular shape which makes Z direction a longitudinal direction and A direction is a transversal direction when it sees from B direction. . Note that the length of the lower portion 74 in the Z direction is L2. As an example, the length L2 is set in accordance with a length L1 (see FIG. 4) in a Z direction of a slit 72 described later.

(First mounted part)
As shown in FIG. 5, the first attached portion 66 includes a wall 66A standing upright from the A-side surface of the main body portion 56 toward the A-side (upper side), and an A-side end portion of the wall 66A that is formed on the wall 66A. And a concave portion 66B recessed toward the -A side. The wall 66A is disposed along the AB plane with the Z direction as the thickness direction. The shape and size of the recess 66B are set such that the end portion on the −A side of the support member 47 (see FIG. 2) is fitted (attached) in the A direction.

(Second mounted part)
The second attached portion 68 includes a wall 68A that stands upright from the A-side surface of the nip forming portion 64 toward the A-side (upper side), and a wall 68A that is formed on the wall 68A from the A-side end portion toward the -A-side. And a recessed portion 68B that is recessed. The wall 68A is disposed along the AB plane with the Z direction as the thickness direction. The shape and size of the recess 68B are set so that the end portion on the −A side of the support member 46 (see FIG. 2) is fitted (attached) in the A direction.

(slit)
The slits 72 shown in FIG. 4 are formed in both end portions in the Z direction of the pressure member 42 so as to be recessed toward the inside (center side) along the Z direction. In other words, in the pressure member 42, one side (−B side) with respect to the slit 72 is the nip forming portion 64, and the other side (B side) with respect to the slit 72 is the main body portion 56.

  Further, the slit 72 is formed in a rectangular shape with the Z direction as the long direction and the B direction as the short direction when viewed from the A direction. Here, the length of the slit 72 in the Z direction is L1. The length L1 is such that the position in the Z direction of the end surface on the Z side (back side) of the slit 72 is closer to the center side in the Z direction than the position in the Z direction of the Z direction outer side end of the maximum width paper P. Is set.

  Furthermore, as an example, the slit 72 is aligned with the stepped portion 62 in the Z direction. In other words, the slits 72 are formed on the −Z side with respect to the −Z side end of the stepped portion 62 and on the Z side with respect to the Z side end of the stepped portion 62. Moreover, the slit 72 has a pair of opposing surfaces 73 and 75 which oppose in B direction and X direction (refer FIG. 2).

  As shown in FIG. 7, the facing surface 73 is formed at the −Z side end portion and the −B side end portion of the main body portion 56. Further, the facing surface 73 is formed in a rectangular shape that is long in the Z direction when viewed in the B direction from the −B side. Furthermore, the facing surface 73 is along the AZ plane.

  As shown in FIG. 4, the facing surface 75 is formed at the −Z side end portion and the B side end portion of the nip forming portion 64. Further, the facing surface 75 is formed in a rectangular shape that is long in the Z direction when viewed from the B direction. Furthermore, the opposing surface 75 is along the AZ plane. Here, as shown in FIG. 5, the distance between the facing surface 73 and the facing surface 75 in the B direction is d1.

<Restriction section>
As shown in FIG. 8A, the restricting portion 44 is provided between the facing surface 73 and the facing surface 75 when the slit 72 is viewed from the A direction. Specifically, the restricting portion 44 protrudes from the facing surface 73 toward the facing surface 75. Further, as an example, the limiting portion 44 includes an outer limiting portion 44 </ b> A formed on the −Z side from the center in the Z direction on the facing surface 73 and an inner side formed on the Z side from the center in the Z direction on the facing surface 73. And a limiting portion 44B. The protruding length in the B direction from the facing surface 73 of the outer restricting portion 44A and the protruding length in the B direction from the facing surface 73 of the inner restricting portion 44B are, for example, substantially the same length.

  As shown in FIGS. 4 and 7, the outer restricting portion 44 </ b> A and the inner restricting portion 44 </ b> B are, for example, formed in a rectangular parallelepiped shape in which the shape of the surface along the BZ plane is a rectangle that is long in the Z direction. . In other words, the outer limiting portion 44A and the inner limiting portion 44B are each formed in a plate shape whose thickness direction is the B direction.

  The outer restriction portion 44A and the inner restriction portion 44B extend from the facing surface 73 beyond the end point (lower end) on the −A side of the facing surface 73 along the A direction from the main body portion 56 to the −A side. Yes. Thereby, as shown in FIG. 5, the restricting portion 44 faces the facing surface 75 in the B direction. Then, when the nip forming portion 64 is displaced to the main body portion 56 side by the reaction force from the nip portion N (see FIG. 2), the limiting portion 44 comes into contact with the facing surface 75 and faces the facing surface 73 and the facing surface 75. The space d1 is limited to be narrowed.

<Leaf spring>
The leaf spring 52 shown in FIG. 2 is disposed inside the nip portion N of the belt 38 and between the belt 38 and the pressure member 42 and extends in the Z direction. Further, as an example, the plate spring 52 is formed in a U shape when viewed from the Z direction by bending a stainless steel plate. Specifically, the leaf spring 52 includes an attachment portion 52A that is attached to the attachment surface 56B of the pressure member 42 by adhesion, and an elastic portion 52B that is elastically deformed with respect to the attachment portion 52A. The leaf spring 52 presses the belt 38 toward the fixing roll 36 when the elastic portion 52B contacts the inner peripheral surface of the belt 38 in a state where the attachment portion 52A is attached to the attachment surface 56B. . The leaf spring 52 is in contact with the belt 38 on the upstream side of the center position of the nip portion N in the circumferential direction of the belt 38 (on the inlet side of the paper P in the nip portion N).

[Heating section]
The heating unit 34 illustrated in FIG. 2 includes, as an example, halogen heaters 34A and 34B and a power source (not illustrated) of the image forming apparatus 10 (see FIG. 1). The halogen heaters 34A and 34B generate heat when energized from a power source (not shown), and heat the core metal 36A of the fixing roll 36 to heat the entire fixing roll 36. Whether the halogen heaters 34A and 34B are energized is determined by the control unit 22 (see FIG. 1) based on a detection result of a temperature sensor (not shown) that detects the temperature of the outer peripheral surface of the fixing roll 36.

[Action]
Next, the operation of this embodiment will be described.

  In the conveyance unit 32 and the fixing device 30 illustrated in FIG. 2, in a non-pressurized state where the nip portion N is not formed, the limiting unit 44 and the facing surface 75 are separated as illustrated in FIG. 9A. In this non-pressurized state, when the retract mechanism (not shown) is driven, the coil spring 48 is compressed as shown in FIG. Then, the pressing member 42 receiving the elastic force of the coil spring 48 via the support members 46 and 47 presses the belt 38 toward the fixing roll 36 in the A direction. The fixing roll 36 does not move in the A direction. Thereby, the nip portion N is formed. A pressing force is applied to the paper P passing through the nip portion N. In the transport unit 32, a slit 72 is formed in the pressure member 42. For this reason, when the pressing member 42 receives a reaction force from the nip portion N, the nip forming portion 64 is deformed to reduce the reaction force.

  10, the relationship between the axial direction (Z direction) position in the nip portion N (see FIG. 2) and the surface pressure in the nip portion N is shown by graphs G1 and G2. The graph G1 represents the relationship between the axial position and the surface pressure when the configuration of the present embodiment is used. Graph G2 represents the relationship between the axial position and the surface pressure when a configuration in which slits 72 (see FIG. 2) are not formed is used as a comparative example. Note that the center position in the Z direction of the fixing roll 36 (see FIG. 2) is Zc, the positions at both ends in the Z direction of the paper P are Za and Ze, and the position at which the slit 72 is the inner end in the Z direction is Zb, Zd. Comparing the graphs G1 and G2, it can be seen that in the graph G1, the position where the surface pressure is maximized is the center side in the axial direction and the surface pressure where the surface pressure is maximized is lower than in the graph G2. This is because the surface pressure acting on both ends of the paper P is reduced due to the formation of the slits 72.

  In the conveyance unit 32 and the fixing device 30 illustrated in FIG. 2, the fixing roll 36 is rotated and the belt 38 is driven and rotated in a pressurized state (a state where the nip portion N is formed). At this time, as shown in FIG. 9B, the nip forming portion 64 may be deformed to the facing surface 73 side in response to the reaction force F from the nip portion N (see FIG. 2).

  Here, in the conveyance unit 32, when the nip forming unit 64 is deformed to the facing surface 73 side, the restriction portion 44 comes into contact with the facing surface 75, so that the interval between the slits 72 is limited. Accordingly, the nip forming portion 64 is prevented from being deformed to the facing surface 73 side as compared with the configuration in which the restriction portion 44 is not provided and the interval d1 (see FIG. 5) of the slit 72 is the same in the longitudinal direction of the pressure member 42. The Further, since the deformation of the nip forming portion 64 toward the facing surface 73 is suppressed, the width of the nip portion N in the transport direction of the paper P is suppressed from changing between the central portion and both end portions in the Z direction. The

  As shown in FIG. 2, in the conveyance unit 32, the limiting unit 44 protrudes from the opposing surface 73 on the main body unit 56 side. For this reason, compared with the structure (refer FIG. 8 (B)) which formed the limiting part 44 in the opposing surface 75 by the side of the nip formation part 64, the bending rigidity of the nip formation part 64 with respect to the reaction force from the nip part N becomes high. It is suppressed.

  Furthermore, as shown in FIG. 6, in the transport section 32, a low-order section 74 is formed in the nip forming section 64. Therefore, the nip forming portion against the reaction force from the nip portion N is compared with the configuration in which the height H1 in the A direction at the center portion in the Z direction of the nip forming portion 64 and the height H2 in the A direction at the end portion are the same. It is suppressed that the bending rigidity of 64 becomes high.

  In the fixing device 30 shown in FIG. 2, the deformation of the width of the nip portion N in the rotation direction of the belt 38 is suppressed by suppressing the nip forming portion 64 from being deformed to the facing surface 73 side (B side). . Accordingly, the offset of the toner T (see FIG. 1) to the fixing roll 36 is suppressed as compared with the configuration in which the restriction portion 44 is not provided and the interval d1 of the slit 72 is the same in the longitudinal direction of the pressure member 42.

  In the image forming apparatus 10 shown in FIG. 1, the offset of the toner T to the fixing roll 36 in the fixing device 30 is suppressed, so that there is no limiting portion 44 and the interval d1 of the slit 72 is in the longitudinal direction of the pressure member 42. As compared with the same configuration, the defect of the output image after fixing is suppressed. Examples of defective output images include stains on the background other than the image on the paper P, image color unevenness, and image misregistration.

  In addition, this invention is not limited to said embodiment.

  Hereinafter, a first modification, a second modification, a third modification, and other modifications of the present embodiment will be described. Note that members and portions that are basically the same as those of the above-described embodiment are denoted by the same reference numerals as those of the embodiment, and description thereof is omitted.

<First Modification>
FIG. 8B shows a transport unit 80 according to a first modification. The conveyance unit 80 is configured such that, in the conveyance unit 32 (see FIG. 2), the limiting unit 44 is formed on the opposed surface 75 on the nip forming unit 64 side, not on the opposed surface 73 on the main body 56 side. The configuration other than the formation part of the restriction unit 44 is the same as that of the conveyance unit 32. When there is no possibility that the bending rigidity of the nip forming portion 64 with respect to the reaction force becomes excessively high, the limiting portion 44 may be formed on the facing surface 75 in this way. The deformation of the nip forming portion 64 is suppressed by the limiting portion 44 coming into contact with the facing surface 73.

<Second Modification>
FIG. 11A shows a transport unit 90 according to a second modification. The transport unit 90 includes a pressurizing member 92 and a restricting unit 94 in place of the pressurizing member 42 and the restricting unit 44 (see FIG. 2) in the transporting unit 32 (see FIG. 2). The pressurizing member 92 is configured such that a slit 96 is formed in the pressurizing member 42 instead of the slit 72 (see FIG. 8A). The configuration of the pressure member 92 other than the slit 96 is the same as that of the pressure member 42.

  The slits 96 are formed so as to be recessed inward along the Z direction at both ends of the pressing member 92 in the Z direction and at portions where the nip portion N (see FIG. 2) is formed. In other words, in the pressure member 92, one side with respect to the slit 96 is a nip forming portion 64, and the other side with respect to the slit 96 is a main body portion 56. Further, the slit 96 is formed in a triangular shape so that, when viewed from the A direction, the interval in the B direction at the end in the Z direction is wider than the interval in the B direction on the center side in the Z direction. Yes.

  For example, the slit 96 includes a facing surface 97 on the main body 56 side and a facing surface 98 on the nip forming portion 64 side. The facing surface 98 is a plane along the AZ plane. The facing surface 97 is an inclined surface that is inclined in a direction intersecting the Z direction when viewed from the A direction. The positions corresponding to the apexes of the triangles in the slit 96 are located inside the Z direction with respect to the positions of both ends of the paper P (not shown) in the Z direction.

  The restricting portion 94 is formed in a prismatic shape. Further, the restricting portion 94 includes an outer restricting portion 94A disposed on the outer side in the Z direction and an inner restricting portion 94B disposed on the inner side in the Z direction with respect to the outer restricting portion 94A. The outer restricting portion 94A and the inner restricting portion 94B protrude from the facing surface 97 toward the facing surface 98 along the B direction. Further, the −B side end surface 95A of the outer restricting portion 94A and the −B side end surface 95B of the outer restricting portion 94A are disposed substantially parallel to the facing surface 98 as an example. As described above, the limiting portion 94 may be provided in the slit 96 having a short interval on the center side in the Z direction and a long interval on the outside. The deformation of the nip forming portion 64 is suppressed by the limiting portion 94 coming into contact with the facing surface 98.

<Third Modification>
FIG. 11B shows a transport unit 100 according to a third modification. The conveyance unit 100 is configured such that a restriction unit 102 is provided in the conveyance unit 90 (see FIG. 11A) instead of the restriction unit 94 (see FIG. 11A). The configuration other than the limiting unit 102 is the same as that of the transport unit 90. The restricting portion 102 includes an outer restricting portion 102A disposed outside the Z direction, and an inner restricting portion 102B disposed inside the outer restricting portion 102A. Further, the restricting portion 102 protrudes from the facing surface 98 of the slit 96 toward the facing surface 97.

  The end surface on the B side of the outer restriction portion 102A is an inclined surface 103A that is disposed substantially parallel to the facing surface 97. An end surface on the B side of the inner restricting portion 102B is an inclined surface 103B that is disposed substantially parallel to the facing surface 97. The interval in the B direction between the inclined surface 103A and the opposing surface 97 and the interval in the B direction between the inclined surface 103B and the opposing surface 97 are substantially the same size. In the case where the bending rigidity of the nip forming portion 64 against the reaction force at the nip portion N is not likely to be excessively high, the limiting portion 102 may be formed on the facing surface 98 in this way. The deformation of the nip forming portion 64 is suppressed by the limiting portion 102 coming into contact with the facing surface 97.

<Other variations>
In the conveyance unit 32, when there is no possibility that the bending rigidity of the nip forming unit 64 with respect to the reaction force becomes excessively high, the height of the nip forming unit 64 may be aligned in the Z direction without forming the low-order portion 74. . Moreover, in the conveyance part 80 of the first modification, when there is no possibility that the bending rigidity of the nip forming part 64 against the reaction force becomes excessively high, the lower part 74 is not formed, and the height of the nip forming part 64 is increased. You may align in a Z direction.

  The restricting portions 44 and 94 are not limited to those formed integrally with the pressing member 42, and may be configured separately from the pressing member 42. For example, a restricting portion that is fixed to a housing (not shown) of the fixing device 30 and disposed between the facing surface 73 and the facing surface 75 of the slit 72 may be used.

  The rotating body is not limited to the fixing roll 36 but may be a transport roll that is not heated. Further, the rotating body may be formed of a solid member. Furthermore, the rotating body may be configured by a combination of a fixing belt and a pad that contacts the inside of the fixing belt. The outer circumferential surface of the fixing roll 36 may be linear, crowned, or reverse crowned when viewed from the X direction.

  The width of the pressure members 42 and 92 in the Z direction may be the same as the width of the support members 46 and 47 in the Z direction.

  The pair of opposed surfaces is not limited to the opposed surfaces 73 and 75 that are arranged substantially in parallel, and the opposed surfaces 97 and 98 that are inclined in an oblique direction with respect to the other. The configuration may be a trapezoidal shape when viewed from the direction. Further, the pair of opposed surfaces is not limited to a planar shape, and may be curved surfaces.

  The conveyance device is not limited to the one provided in the fixing device 30 as in the conveyance units 32, 80, 90, and 100, and may be provided in a conveyance path K other than the fixing device 30 of the image forming apparatus 10. . In addition to the image forming apparatus 10, a recording medium such as a sheet P or a film may be conveyed.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 14 Image formation part (an example of a developer image formation means)
30 Fixing device 32 Conveying section (an example of a conveying device)
34 Heating unit (an example of a heating source)
36 Fixing roll (an example of a rotating body and a fixing rotating body)
38 Belt 42 Pressure member 44 Restriction part 56 Main body part 64 Nip forming part 72 Slit 73 Opposing surface 74 Lower part 75 Opposing surface 80 Conveying part 90 Conveying part 92 Pressing member 94 Restricting part 96 Slit 97 Confronting face 98 Confronting face 100 Conveying Part 102 Restriction part N Nip part

Claims (5)

A rotating body that rotates about a direction orthogonal to the conveyance direction of the recording medium as an axial direction;
An endless belt that forms a nip portion that sandwiches the recording medium together with the rotating body;
A pressure member provided on the inner side of the belt, wherein slits recessed in the axial direction are formed at both ends of the axial direction and forming the nip portion, and pressurizes the belt toward the rotating body; ,
When the slit is viewed from the pressurizing direction in which the pressurizing member pressurizes, the limiting portion is provided between a pair of opposed surfaces of the slit and restricts the interval between the opposed surfaces from being narrowed;
Conveying device having The pressure member has a nip forming portion that forms the nip portion on one side with respect to the slit, and a main body portion on the other side with respect to the slit,
The transport device according to claim 1, wherein the restricting portion protrudes from the facing surface on the other side. The pressure member has a nip forming portion that forms the nip portion on one side with respect to the slit, and a main body portion on the other side with respect to the slit,
2. The lower part having a lower height in the pressurizing direction than the height in the pressurizing direction at the central part in the axial direction of the nip forming part is formed in the nip forming part. Item 3. The transfer device according to Item 2. A heating source;
4. The fixing rotating body according to claim 1, further comprising a fixing rotating body as the rotating body that is heated by the heat source and melts the developer at the nip portion and pressurizes and fixes the recording medium. A transport device;
A fixing device. Developer image forming means for forming a developer image;
The fixing device according to claim 4, wherein the developer image formed by the developer image forming unit is fixed on the recording medium.
An image forming apparatus.