JP2016166942A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device that can suppress a variation in width of a nip of pressing parts located on the most downstream in a direction of conveyance of a recording medium, compared with a configuration in which a pressing direction of pressing parts located on the most downstream in a direction of conveyance of a recording medium is inclined on the downstream side in the direction of conveyance of the recording medium with respect to a virtual straight line passing through a pressing point and the center of rotation of a first rotating body.SOLUTION: A fixing device 60 comprises: a first rotating body (for example, heating roll 62); a cylindrical second rotating body (for example, pressure belt 64) that is in contact with the first rotating body and rotates together with the first rotating body to convey a recording medium held with the first rotating body; pressing parts (for example, pressing parts 72 and 73) that are arranged on the upstream side and the downstream side in a direction of conveyance of the recording medium inside the second rotating body to press the second rotating body against the first rotating body; and a support member 78 that supports such that a direction to press the first rotating body by the pressing member 73 located on the most downstream in the direction of conveyance of the recording medium is inclined on the upstream side in the direction of conveyance of the recording medium with respect to a straight line L1 passing through a pressing point X and the center of rotation of the first rotating body.SELECTED DRAWING: Figure 3

Description

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

  Patent Document 1 discloses a fixing device that includes a fixing roller and an endless belt that contacts the outer surface of the fixing roller and rotates together with the fixing roller. In this fixing device, the endless belt is pressed against the fixing roller by a pre-nip member and a peeling nip member that constitute a pressure pad disposed inside the endless belt.

Japanese Patent Laid-Open No. 2002-148979

  By the way, in the case of a fixing device that presses the second rotating body against the first rotating body using a plurality of pressing portions, the nip width of the pressing portion depends on the pressing direction of the pressing portion located on the most downstream side in the conveyance direction of the recording medium. Is likely to fluctuate.

  The present invention is compared with a configuration in which the pressing direction of the pressing portion located on the most downstream side in the conveyance direction of the recording medium is inclined downstream in the conveyance direction of the recording medium with respect to a virtual straight line passing through the pressing point and the rotation center of the first rotating body. An object of the present invention is to obtain a fixing device capable of suppressing fluctuations in the nip width of the pressing portion located on the most downstream side in the conveyance direction of the recording medium, and an image forming apparatus using the fixing device.

  According to a first aspect of the present invention, the fixing device is disposed between the first rotating body and the outer surface of the first rotating body, and rotates between the first rotating body and the first rotating body. A cylindrical second rotating body that conveys the recording medium sandwiched between them, and an upstream side and a downstream side in the conveying direction of the recording medium inside the second rotating body, and the second rotating body is disposed on the first rotating body. A plurality of pressing portions that press against the rotating body, and a pressing direction of the first rotating body by the pressing portion that is disposed inside the second rotating body and is located on the most downstream side in the conveyance direction of the recording medium is a pressing point and the A support member that supports the virtual straight line passing through the rotation center of the first rotating body so as to be inclined toward the upstream side in the conveyance direction of the recording medium.

  The fixing device according to a second aspect of the present invention is the fixing device according to the first aspect, wherein the pressing portion located on the most downstream side in the conveyance direction of the recording medium is configured such that the rotation center of the first rotating body and the first An angle with respect to the center-to-center line in the pressing direction of the first rotating body by the pressing portion is arranged on the downstream side in the conveyance direction of the recording medium with respect to the center-to-center line passing through the rotation center of the two-rotating body. Is greater than the angle with respect to the straight line between the centers.

  The fixing device according to a third aspect of the present invention is the fixing device according to the first or second aspect, wherein the plurality of pressing portions are held by a holding member, and the support member is interposed via the holding member. The plurality of pressing portions are supported.

According to a fourth aspect of the present invention, there is provided an image forming apparatus for forming an image on a recording medium;
The fixing device according to any one of claims 1 to 3, wherein an image formed on the recording medium by the image forming unit is fixed to the recording medium.

  According to the fixing device of the first aspect of the present invention, the recording medium has a pressing direction of the pressing portion located on the most downstream side in the conveyance direction of the recording medium with respect to a virtual straight line passing through the pressing point and the rotation center of the first rotating body. As compared with the configuration inclined to the downstream side in the transport direction, fluctuations in the nip width of the pressing portion located on the most downstream side in the transport direction of the recording medium can be suppressed.

  According to the fixing device of the second aspect of the present invention, compared to the configuration in which the angle with respect to the center line in the pressing direction of the first rotating body by the pressing portion is smaller than the angle with respect to the center line of the virtual line, the conveyance direction. Variation in the nip width of the pressing portion located on the most downstream side can be suppressed.

  According to the fixing device of the third aspect of the present invention, the number of parts can be reduced as compared with the configuration in which the support member is provided for each of the plurality of pressing portions.

  According to the image forming apparatus described in claim 4 of the present invention, fixability can be improved as compared with the configuration not including the fixing device described in any one of claims 1 to 3.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic cross-sectional view illustrating a configuration of a fixing device according to an embodiment of the present invention. FIG. 3 is a schematic diagram showing an inclination of a support member used in the fixing device of FIG. 2 with respect to a virtual straight line.

  Hereinafter, a fixing device 60 and an image forming apparatus 10 according to an embodiment of the present disclosure will be described with reference to the drawings.

(Configuration of image forming apparatus 10)
First, the configuration of the image forming apparatus 10 will be described. FIG. 1 is a schematic diagram illustrating a configuration of the image forming apparatus 10.

  As shown in FIG. 1, the image forming apparatus 10 includes an apparatus main body 11 in which each component is housed. Inside the apparatus main body 11, a storage unit 12 that stores a sheet member P as a recording medium, a transport unit 16 that transports the sheet member P stored in the storage unit 12, and a toner on the transported sheet member P An image forming unit 14 that forms an image, a fixing unit 18 that fixes a toner image formed on the sheet member P by the image forming unit 14 to the sheet member P, and a control unit 20 that controls the operation of each unit of the image forming apparatus 10. And are provided. A discharge unit 22 for discharging the sheet member P on which the image is fixed by the fixing unit 18 is provided at the upper part of the apparatus main body 11.

  The image forming unit 14 includes a photosensitive drum 24 as an example of an image holding body that holds an image. The photosensitive drum 24 is configured to rotate in one direction (for example, counterclockwise in FIG. 1). Around the photosensitive drum 24, a charging roll 26 as an example of a charging device for charging the photosensitive drum 24 and a photosensitive drum 24 charged by the charging roll 26 in order from the upstream side in the rotation direction of the photosensitive drum 24. An exposure device 30 that exposes the photosensitive drum 24 to form an electrostatic latent image, and a developing device 32 that develops the electrostatic latent image formed on the photosensitive drum 24 by the exposure device 30 to form a black toner image. And a transfer roll 34 as an example of a transfer member that transfers a black toner image formed on the photosensitive drum 24 by the developing device 32 to the sheet member P.

  The transfer roll 34 is opposed to the photosensitive drum 24 and rotates with the sheet member P sandwiched between the photosensitive drum 24 and thereby conveys the sheet member P upward. Between the transfer roll 34 and the photosensitive drum 24 is a transfer position T at which the toner image formed on the photosensitive drum 24 is transferred to the sheet member P.

  Further, a toner cartridge 38 as a toner container that contains toner is disposed above the exposure device 30. Further, the image forming unit 14 is provided with a transport pipe (not shown) for transporting the toner contained in the toner cartridge 38 toward the developing device 32.

  The accommodating portion 12 is disposed below the image forming portion 14. And the accommodating part 12 is equipped with stacking member 12A, 12B, 12C on which the sheet | seat member P is stacked | stacked while arranging in the up-down direction.

  The transport unit 16 is disposed on the side of the storage unit 12 and the image forming unit 14. Then, the transport unit 16 feeds the uppermost sheet member P stacked on the respective stacking members 12A, 12B, and 12C, and the sheet member P fed by the feed roll 46 to the transport path of the sheet member P. And a plurality of transport rolls 50 transported along 48.

The fixing unit 18 is disposed above the image forming unit 14. The fixing unit 18 includes a fixing device 60. The fixing device 60 includes a heating roll 62 as an example of a first rotating body that heats the toner image transferred to the sheet member P while rotating by a rotational force transmitted from a motor (not shown), and a heating roll 62. A pressure belt 64 as an example of a second rotating body that contacts and rotates (circulates) together with the heating roll 62 while conveying the sheet member P between the heating roll 62 and the heating roll 62 is provided. Details of the fixing device 60 will be described later.
On the upper side of the fixing unit 18 (downstream in the transport direction), a discharge roll 52 that discharges the sheet member P on which the toner image is fixed to the fixing unit 18 is provided.

  Further, the reverse conveyance path 56 for reversing the sheet member P on which the toner image is fixed on one side and returning it to the transfer position T again is on the side opposite to the photosensitive drum 24 with respect to the transfer roll 34 (the right side in FIG. ). When images are formed on both sides of the sheet member P, the sheet member P with the toner image fixed on one side is switched back by the discharge roll 52 and guided to the reverse conveyance path 56 and sent back to the transfer position T. It is like that.

  Next, an image forming operation for forming an image on the sheet member P using the image forming apparatus 10 will be described.

  In the image forming apparatus 10, the sheet member P sent out from any one of the stacking members 12 </ b> A, 12 </ b> B, 12 </ b> C by the sending roll 46 is sent to the transfer position T by the plurality of conveying rolls 50.

  On the other hand, in the image forming unit 14, the photosensitive drum 24 is charged by the charging roll 26 and then exposed by the exposure device 30, so that an electrostatic latent image is formed on the photosensitive drum 24. The electrostatic latent image is developed by the developing device 32 to form a black toner image on the photosensitive drum 24. The black toner image is transferred to the sheet member P at the transfer position T by the transfer roll 34.

  The sheet member P to which the toner image has been transferred is conveyed to the fixing device 60, and the toner image is fixed by the fixing device 60. When an image is formed only on one side of the sheet member P, the sheet member P is discharged to the discharge unit 22 by the discharge roll 52 after the toner image is fixed.

  When images are formed on both sides of the sheet member P, after the image is formed on one side, the sheet member P is switched back by the discharge roll 52, reversed, and sent to the reverse conveyance path 56. Further, the sheet member P is sent again from the reverse conveyance path 56 to the transfer position T, and an image is formed on the opposite surface where no image is recorded in the same manner as described above, and is discharged to the fixing unit 18 by the discharge roll 52. . As described above, a series of image forming operations are performed.

Next, the fixing device 60 will be described.
The fixing device 60 of this embodiment includes the heating roll 62 and the pressure belt 64 described above.

  As shown in FIG. 2, the heating roll 62 is a cylindrical roll member, and includes a cylindrical base 62A and an elastic layer 62B that covers the outer periphery of the base 62A. A heating source 66 such as a halogen lamp for heating the heating roll 62 is provided in the internal space of the heating roll 62.

  The base 62A is a thin cylindrical body. Further, the base 62A is formed of a material having high thermal conductivity. Specifically, the base 62A is made of a metal material such as iron, nickel, nickel steel, stainless steel (SUS), aluminum, or the like.

  The elastic layer 62B covers the intermediate portion in the axial direction of the base body 62A. That is, both ends in the axial direction of the base body 62A are exposed without being covered with the elastic layer 62B. The elastic layer 62B is formed of an elastic body having heat resistance. Specifically, the elastic layer 62B is formed of a rubber material such as silicone rubber or fluorine rubber, for example.

As shown in FIG. 2, the heating roll 62 fixes the toner image with the sheet member P sandwiched between the elastic layer 62B and the pressure belt 64. A release layer (not shown) for facilitating peeling of the sheet member P is formed on the outer peripheral surface of the elastic layer 62B.
In the present embodiment, the heating roll 62 includes the base body 62A and the elastic layer 62B. However, the present invention is not limited to this configuration, and the heating roll 62 does not include the elastic layer 62B. It is good. For example, the heating roll 62 is composed of the base 62A, and the toner image is fixed by sandwiching the sheet member P between the base 62A and the pressure belt 64. In this case, a release layer (not shown) for facilitating peeling of the sheet member P is formed on the outer peripheral surface of the base 62A.

  The heating roll 62 is rotatably supported by a bearing portion provided in a casing (not shown) of the fixing device 60, and a driving force (rotational force) is supplied from a driving device (for example, a motor) (not shown) attached to the casing. It is designed to rotate by being transmitted. The housing is detachable from the apparatus main body 11.

  As shown in FIG. 2, the pressure belt 64 is an endless belt that rotates following the heating roll 62. Specifically, the pressure belt 64 is made of a polymer such as polyimide, polyamide, or polyimideamide, or a metal such as SUS, nickel, or copper. A release layer (not shown) for facilitating peeling of the sheet member P is formed on the outer peripheral surface of the pressure belt 64.

  A belt support member 70 is disposed inside the pressure belt 64. The pressure belt 64 is supported from the inside by the belt support member 70. The belt support member 70 is attached to the casing of the fixing device 60.

  As shown in FIG. 2, the belt support member 70 contacts the inner surface 64 </ b> A of the pressure belt 64 and presses the pressure belt 64 against the heating roll 62, and against the pressure members 72 and 73. A belt guide member 74 provided on the upstream side and the downstream side in the rotational direction of the pressure belt 64, a holder 76 as an example of a holding member that holds the pressing members 72 and 73, and a support member 78 that supports the holder 76 It is equipped with.

  The pressing member 72 is arranged on the upstream side of the pressing member 73 in the conveying direction of the sheet member P with a gap in the conveying direction of the sheet member P with respect to the pressing member 73. The pressing member 72 is an elastic body formed in a rectangular parallelepiped shape (see FIG. 2), and is held by a holder 76 so that the rotation axis direction of the pressure belt 64 is the longitudinal direction. The pressing member 72 is made of a rubber material such as silicone rubber or fluorine rubber, for example. In addition, the pressing member 72 of this embodiment is an example of the pressing part of this invention.

  The pressing member 73 is an elastic body formed in a rectangular parallelepiped shape (see FIG. 2), and is held by a holder 76 so that the rotation axis direction of the pressure belt 64 is the longitudinal direction. The pressing member 73 is made of a rubber material such as silicone rubber or fluorine rubber, for example. Note that the pressing member 73 of the present embodiment is an example of a pressing portion located on the most downstream side in the conveyance direction of the recording medium of the present invention.

  The holder 76 is a long member, and is supported by a support member 78 so that the rotation axis direction of the pressure belt 64 is the longitudinal direction. On the heating roll 62 side of the holder 76, groove-like recesses 76A and 76B extending along the longitudinal direction are formed. A pressing member 72 is inserted into the recess 76A from the back surface 72A side. When the pressing member 72 is inserted into the recess 76A, both side surfaces 72B of the pressing member 72 come into contact with the recessed wall surface of the recess 76A, and the pressing member 72 is held in the recess 76A. A pressing member 73 is inserted into the recess 76B from the back surface 73A side. When the pressing member 73 is inserted into the recess 76B, both side surfaces 73B of the pressing member 73 come into contact with the recessed wall surface of the recess 76B, and the pressing member 73 is held in the recess 76B.

  As shown in FIG. 2, the support member 78 is a long member that is bent so that the cross-sectional shape is L-shaped. It is attached to the casing. The support member 78 supports the pressing member 72 on the heating roll 62 side via the holder 76 on one end 78A side with the bent portion interposed therebetween, and supports the impregnation member 84 on the other end portion 78B side across the bent portion. ing.

Further, as shown in FIG. 3, the support member 78 has a pressing direction of the heating roll 62 by the pressing member 73 with respect to a straight line L1 as an example of an imaginary straight line passing through the pressing point X and the rotation center Y1 of the heating roll 62. Thus, the pressing member 73 is supported via the holder 76 so as to be inclined toward the upstream side in the conveying direction of the sheet member P. Here, the “pressing direction” refers to the extending direction of the linear plate portion 78 </ b> C including the one end portion 78 </ b> A of the support member 78. Further, a straight line extending along the extending direction of the plate portion 78C is indicated by a symbol L3 in FIG. Further, the “pressing point” here refers to a point located in the center of the conveying direction of the sheet member P on the surface that contacts the inner surface of the pressing belt 64 of the pressing member 73.
Further, in the present embodiment, the pressing member 73 is on the downstream side in the conveyance direction of the sheet member P with respect to the straight line L2 as an example of a straight line between the centers passing through the rotation center Y1 of the heating roll 62 and the rotation center Y2 of the pressure belt 64. The angle θ1 of the straight line L3 with respect to the straight line L2 extending along the pressing direction of the heating roll 62 by the pressing member 63 is larger than the angle θ2 of the straight line L1 with respect to the straight line L2.
In FIG. 3, some members of the heating roll 62 and some members of the pressure belt 64 are not shown.

  The impregnation member 84 is disposed between the other end 78B side and the pressure belt 64 with the bent portion of the support member 78 interposed therebetween, and is in contact with the inner surface 64A of the pressure belt 64. The impregnation member 84 is impregnated with lubricating oil, and the lubricating oil is supplied to the inner surface 64A from the contact portion with the inner surface 64A of the pressure belt 64. The impregnating member 84 is made of, for example, sponge or felt.

  The belt guide member 74 is a long member having an arcuate outer peripheral surface, and is attached to the casing of the fixing device 60 so that the rotation axis direction of the pressure belt 64 is the longitudinal direction. The belt guide member 74 is provided on both sides with the support member 78 interposed therebetween. The belt guide member 74 guides the inner surface 64A of the pressure belt 64 so as to be slidable by an outer peripheral surface 74A having an arc shape. A part of the outer peripheral surface 74 </ b> A may be formed in a rib shape along the rotation direction of the pressure belt 64.

  Next, the operation of the fixing device 60 will be described.

  When a rotational force is transmitted from a motor (not shown), the heating roll 62 of the fixing device 60 rotates in the direction of arrow R as shown in FIG. At this time, the pressure belt 64 pressed against the outer peripheral surface of the heating roll 62 rotates (circulates) in the direction opposite to the arrow R direction following the heating roll 62. The sheet member P to which the toner image is transferred is sandwiched between the rotating heating roll 62 and the pressure belt 64 and conveyed while being pressed, so that the toner image transferred to the sheet member P is transferred to the sheet member P. To be established.

Here, in the fixing device 60 of the present embodiment, the support member 78 is interposed via the holder 76 so that the straight line L3 extending along the pressing direction of the heating roll 62 by the pressing member 73 is inclined upstream in the transport direction with respect to the straight line L1. The pressing member 73 is supported. For this reason, for example, the pressing member 73 is dragged by the rotation of the pressure belt 64 that rotates following the rotation of the heating roll 62 as compared with the configuration in which the straight line L3 is inclined to the downstream side in the conveyance direction of the sheet member P with respect to the straight line L1. It is suppressed that the center part of the longitudinal direction of this is bent to the downstream side of the conveyance direction of the sheet member P rather than both ends. Thereby, the fluctuation | variation of the nip width of the longitudinal direction of the press member 73 is suppressed. In this way, by suppressing the variation in the nip width of the pressing member 73, the fixability of the toner image transferred to the sheet member P is stabilized. In addition, since the fluctuation of the nip width of the pressing member 73 is suppressed, the sheet member P is prevented from wrinkling.
In particular, the variation in the nip width of the pressing member 73 is suppressed as compared with the configuration in which the angle θ1 of the straight line L3 with respect to the straight line L2 is smaller than the angle θ2 of the straight line L1 with respect to the straight line L2.

  In the fixing device 60, the pressing members 72 and 73 are held by the holder 76, and the pressing members 72 and 73 are supported by the support member 78 via the holder 76. For example, a supporting member is provided for each pressing member. Compared to what is supported, the number of parts is reduced.

  Since the image forming apparatus 10 includes the fixing device 60, for example, as compared with a configuration that does not include the fixing device 60, fluctuations in the nip width of the pressing member 73 are suppressed, so that the fixing property is improved.

  In the above-described embodiment, the pressing force for pressing the pressure belt 64 by the pressing members 72 and 73 is not particularly defined. However, the pressing force of the pressing member 72 located on the downstream side in the conveyance direction of the sheet member P is the pressing member 73. It is good also as a structure made larger than pressing force of. In this case, the fixability of the toner image transferred to the sheet member P is improved.

  In the above-described embodiment, the pressing member 72 is arranged on the upstream side of the pressing member 73 in the conveying direction of the sheet member P with an interval in the conveying direction of the sheet member P with respect to the pressing member 73. The invention is not limited to this configuration, and the pressing member 72 and the pressing member 73 may be in contact with each other.

  Furthermore, in the above-described embodiment, the pressing members 72 and 73 are held by the holder 76. However, the present invention is not limited to this configuration, and three or more pressing members may be held by the holder. Further, the pressing members 72 and 73 may be integrally formed.

  The embodiments of the present invention have been described above with reference to the embodiments. However, these embodiments are merely examples, and various modifications can be made without departing from the scope of the invention. It goes without saying that the scope of rights of the present invention is not limited to these embodiments.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 14 Image forming part 60 Fixing apparatus 62 Heating roll (1st rotary body)
64 Pressure belt (second rotating body)
72 Pressing member (pressing part)
73 Pressing member (pressing portion located on the most downstream side in the conveyance direction of the recording medium)
76 Holder (holding member)
78 Support member L1 Straight line (virtual straight line)
L2 straight line (straight line between centers)
P sheet member (recording medium)
X Pressing point Y1 The rotation center of the heating roll (the rotation center of the first rotating body)
Y2 Center of rotation of the pressure belt (Rotation center of the second rotating body)
θ1 angle θ2 angle

Claims (4)

A first rotating body;
A cylindrical second rotating body that is disposed in contact with the outer surface of the first rotating body and that conveys the recording medium sandwiched between the first rotating body by rotating together with the first rotating body;
A plurality of pressing portions that are arranged inside the second rotating body on the upstream side and the downstream side in the conveyance direction of the recording medium, and press the second rotating body to the first rotating body;
An imaginary direction in which the pressing direction of the first rotating body by the pressing portion disposed inside the second rotating body and located on the most downstream side in the conveyance direction of the recording medium passes through the pressing point and the rotation center of the first rotating body. A support member that supports the recording medium so as to be inclined upstream in the conveyance direction of the recording medium;
A fixing device. The pressing portion located on the most downstream side in the conveyance direction of the recording medium is further downstream in the conveyance direction of the recording medium than a straight line between the centers passing through the rotation center of the first rotation body and the rotation center of the second rotation body. Arranged,
2. The fixing device according to claim 1, wherein an angle of the pressing direction of the first rotating body by the pressing portion with respect to the straight line between the centers is larger than an angle of the virtual straight line with respect to the straight line between the centers. The plurality of pressing portions are held by a holding member,
The fixing device according to claim 1, wherein the support member supports the plurality of pressing portions via the holding member. An image forming unit for forming an image on a recording medium;
The fixing device according to claim 1, wherein the image formed on the recording medium by the image forming unit is fixed on the recording medium.
An image forming apparatus comprising:

Images