JP5325801B2 - Fixing apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of stably giving nip pressure in a fixing nip when fixing images on a cylindrical object such as an envelope and a normal transferred material which is not a cylindrical object. <P>SOLUTION: The fixing device has a first rotating body 9a, a second rotating body 9b, a support member 524 for supporting the second rotating body 9b and capable of changing the position of the second rotating body 9b for the first rotating body 9a, a first biasing member 522 capable of being biased so as to be first nip pressure, a second biasing member 525 capable of being biased so as to be second nip pressure smaller than the first nip pressure; and a change member 521 capable of being changed into a state where any one biasing force of the first biasing member 522 or the second biasing member 525 is transmitted to the second rotating body 9b. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

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

  Conventionally, as an apparatus for forming (printing) an image on a sheet, an image forming apparatus such as a copier, a printer, a facsimile, or a complex machine of these is known. In the image forming apparatus, a charging step for charging the surface of the photosensitive drum, an exposure step for irradiating the charged photosensitive drum with laser light to form an electrostatic latent image on the surface of the photosensitive drum, and the surface of the photosensitive drum A developing process for developing the toner by attaching toner to the electrostatic latent image formed thereon, a transferring process for transferring the toner image formed from the toner attached to the surface of the photosensitive drum to the paper, and the toner transferred to the paper An image is formed on the paper by sequentially performing each of the fixing steps for fixing the image on the paper.

  Of the above steps, in the fixing step, it is necessary to melt the toner in order to fix the toner image transferred to the paper to the paper. Conventionally, a fixing device including a heating roller (first rotating body) and a pressure roller (second rotating body) that forms a fixing nip together with the heating roller is used as a fixing device that performs a fixing process. In such a fixing device, a pressure nip is pressed against the heating roller to form a fixing nip therebetween, and a predetermined nip pressure is secured in the fixing nip. In such a fixing device, when the paper is conveyed to the fixing nip, the toner transferred onto the paper is melted and pressurized, and is fixed to the paper.

  By the way, depending on the image forming apparatus, an image can be formed (printed) on a cylindrical object such as an envelope. A cylindrical object such as an envelope is formed into a cylindrical shape by folding paper and partially bonding the paper. Therefore, when the cylindrical object is passed through the fixing nip of the fixing device, distortion and wrinkles (wrinkles) associated with the cylindrical object are likely to occur. Thus, when a cylindrical object is passed through the fixing nip, the fixing nip pressure is generally reduced as much as possible.

  Patent Document 1 describes a fixing device in which a fixing nip pressure is reduced when an image is fixed on a cylindrical object. The fixing device described in Patent Document 1 includes a biasing member that biases the heating roller toward the pressure roller, and a cam member that rotates so as to press the biasing member against the biasing force. Therefore, the fixing nip pressure applied to the cylindrical object can be reduced, and the generation of wrinkles generated on the cylindrical object can be suppressed.

JP 2007-79160 A

  However, the fixing device described in Patent Document 1 applies one urging member for fixing an image on a normal transfer target and for fixing an image on a cylindrical object such as an envelope. By rotating the cam member so as to press against the force, the fixing nip pressure is adjusted by changing the degree of expansion and contraction of the biasing member.

The fixing device described in Patent Document 1 is configured to change the degree of expansion and contraction of the urging member by rotating the cam member. Therefore, when the outer shape of the urging member changes due to deformation or wear, the urging force is applied. There was a possibility that the member could not be pressed stably against the urging force. Therefore, there is a possibility that a stable fixing nip pressure is not applied.
Further, since one urging member is pressed against the urging force, there is a possibility that a stable fixing nip pressure may not be applied due to deterioration of the urging member.
Therefore, it is possible to stably apply the nip pressure at the fixing nip when fixing an image on a cylindrical object such as an envelope and when fixing an image on a normal transfer material that is not a cylindrical object. A fixing device that can be used has been desired.

Accordingly, the present invention provides a fixing device that can stably apply a nip pressure at a fixing nip when fixing an image on a cylindrical object such as an envelope and a normal transfer material that is not a cylindrical object. The purpose is to do.
Another object of the present invention is to provide an image forming apparatus including the fixing device.

  The present invention relates to a fixing device that melts toner constituting a toner image transferred to a transfer material while being provided in the image forming apparatus and fixes the toner image on the transfer material, and has a first rotation shaft as a center. A first rotating body that is rotatable and a fixing nip through which the transfer material is transported and parallel to the first rotating shaft. A second rotating body rotatable around a second rotating shaft, wherein the second rotating body is biased in a direction away from the first rotating body in a state where the fixing nip is formed, and the second rotating body. A support member that supports the rotating body and can change the position of the second rotating body relative to the first rotating body by swinging, and the support so that the nip pressure at the fixing nip is the first nip pressure. The second rotating body is moved through the member to the first A first urging member capable of urging in a direction toward the rolling element, and the second rotation via the support member so that a nip pressure in the fixing nip is a second nip pressure smaller than the first nip pressure. A second urging member capable of urging the body in a direction toward the first rotator, and an urging force of either the first urging member or the second urging member is transmitted to the second rotator. The present invention relates to a fixing device including a switching member that can be switched to a state in which it is performed.

  The switching member is disposed between the support member and the first urging member, and is engaged with the support member so that the urging force of the first urging member is applied to the second rotating body. It is movable between an engagement position, which is a transmitted position, and a non-engagement position, which is a position where the urging force of the first urging member is not transmitted to the second rotating body without being engaged with the support member. The second rotating body is biased by the first biasing member via the switching member and the support member when the switching member is in the engagement position, and the switching member is not engaged. When in the position, it is preferable that the second urging member is urged through the support member.

  The first cam state where the position of the switching member is located at the engagement position without pressing the switching member, and the state where the switching member is pressed against the biasing force of the first biasing member. It is preferable to further include a cam member that is rotated to a second cam state where the position of the switching member is located at the non-engagement position.

  The present invention also provides one or more image carriers on which electrostatic latent images are formed on the surface, and a developer for developing a toner image on the electrostatic latent images formed on the one or more image carriers. The present invention relates to an image forming apparatus including: a transfer unit that directly or indirectly transfers a toner image formed on the image carrier to the transfer material; and the fixing device.

According to the present invention, there is provided a fixing device capable of stably applying a nip pressure at a fixing nip when an image is fixed to a cylindrical object such as an envelope and a normal transfer material that is not a cylindrical object. can do.
In addition, the present invention can provide an image forming apparatus including the fixing device.

It is a front view for demonstrating arrangement | positioning of each component in the printer 1 of one Embodiment of this invention. FIG. 3 is a perspective view of the fixing device 9 at a normal fixing position as viewed from the center in the Y direction. It is the perspective view which looked at the fixing device 9 in the cylindrical object fixing position from the Y direction center side. FIG. 6 is a front view showing the fixing device 9 in a normal fixing position. It is a front view shown to the fixing device 9 in a cylindrical article fixing position.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
With reference to FIG. 1, the overall structure of a printer 1 as an image forming apparatus in the present embodiment will be described. FIG. 1 is a diagram for explaining the arrangement of each component of the printer 1.

As shown in FIG. 1, a printer 1 as an image forming apparatus includes an apparatus main body M and an image forming unit GK that forms a predetermined toner image on a transfer material (paper, envelope, etc.) T based on predetermined image information. And a paper supply / discharge unit KH that supplies the transfer material T to the image forming unit GK and discharges the transfer material T on which the toner image is formed.
The outer shape of the apparatus main body M is configured by a case body BD as a casing.

  As shown in FIG. 1, the image forming unit GK includes a photosensitive drum 2 as an image carrier (photosensitive member), a charging unit 10, a laser scanner unit 4 as an exposure unit, a developing device 16, and a toner cartridge. 5, a toner supply unit 6, a drum cleaning unit 11, a static eliminator 12, a transfer roller 8, and a fixing device 9.

  As shown in FIG. 1, the paper feed / discharge unit KH includes a paper feed cassette 52, a manual paper feed unit 64, a transfer path L for the transfer material T, a registration roller pair 80, and a paper discharge unit 50. .

Hereinafter, each configuration of the image forming unit GK and the paper supply / discharge unit KH will be described in detail.
First, the image forming unit GK will be described.
In the image forming unit GK, in order from the upstream side to the downstream side along the surface of the photosensitive drum 2, charging by the charging unit 10, exposure by the laser scanner unit 4, development by the developing device 16, transfer by the transfer roller 8. Then, static elimination by the static eliminator 12 and cleaning by the drum cleaning unit 11 are performed.

  The photosensitive drum 2 is made of a cylindrical member and functions as a photosensitive member or an image carrier. The photosensitive drum 2 is disposed so as to be rotatable in the direction of the arrow about an axis extending in a direction orthogonal to the conveyance direction of the transfer material T in the conveyance path L. An electrostatic latent image can be formed on the surface of the photosensitive drum 2.

  The charging unit 10 is disposed to face the surface of the photosensitive drum 2. The charging unit 10 uniformly charges the surface of the photosensitive drum 2 to be negative (minus polarity) or positive (plus polarity).

  The laser scanner unit 4 functions as an exposure unit, and is disposed away from the surface of the photosensitive drum 2. The laser scanner unit 4 includes a laser light source (not shown), a polygon mirror, a polygon mirror driving motor, and the like.

  The laser scanner unit 4 scans and exposes the surface of the photosensitive drum 2 based on image information input from an external device such as a PC (personal computer). By scanning exposure with the laser scanner unit 4, the charge on the exposed portion of the surface of the photosensitive drum 2 is removed. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 2.

  The developing device 16 is provided corresponding to the photosensitive drum 2 and is disposed to face the surface of the photosensitive drum 2. The developing device 16 attaches a single color (usually black) toner to the electrostatic latent image formed on the photoconductive drum 2 to form a single color toner image on the surface of the photoconductive drum 2. The developing device 16 includes a developing roller 17 disposed opposite to the surface of the photosensitive drum 2, a stirring roller 18 for stirring the toner, and the like.

  The toner cartridge 5 is provided corresponding to the developing device 16 and stores toner supplied to the developing device 16.

  The toner supply unit 6 is provided corresponding to the toner cartridge 5 and the developing device 16, and supplies the toner contained in the toner cartridge 5 to the developing device 16. The toner supply unit 6 and the developing device 16 are connected by a toner supply path (not shown).

  The transfer roller 8 transfers the toner image developed on the surface of the photosensitive drum 2 to the transfer material T. A transfer bias for transferring the toner image formed on the photosensitive drum 2 to the transfer material T is applied to the transfer roller 8 by a transfer bias applying unit (not shown). The transfer roller 8 is configured to be rotatable while being in contact with the photosensitive drum 2.

  Between the photosensitive drum 2 and the transfer roller 8, the transfer material T conveyed through the conveyance path L is sandwiched. The transferred material T sandwiched between them is pressed against the surface of the photosensitive drum 2. A transfer nip N is formed between the photosensitive drum 2 and the transfer roller 8. In the transfer nip N, the toner image developed on the photosensitive drum 2 is transferred to the transfer material T.

  The static eliminator 12 is disposed to face the surface of the photosensitive drum 2. The static eliminator 12 irradiates the surface of the photosensitive drum 2 with light, thereby neutralizing the surface of the photosensitive drum 2 after the transfer is performed (removing the electric charge).

  The drum cleaning unit 11 is disposed to face the surface of the photosensitive drum 2. The drum cleaning unit 11 removes toner and deposits remaining on the surface of the photosensitive drum 2, and transports the removed toner and the like to a predetermined recovery mechanism for recovery.

The fixing device 9 melts and presses the toner constituting the toner image transferred onto the transfer material T and fixes the toner on the transfer material T. The fixing device 9 includes a heating rotator (heating roller) 9a as a first rotator that is heated by a heater (not shown), and a pressure rotator (pressurization) as a second rotator that is pressed against the heating rotator 9a. Roller) 9b. The heating rotator 9a and the pressure rotator 9b sandwich and pressurize and transfer the transfer material T onto which the toner image has been transferred. When the transfer material T is conveyed while being sandwiched between the heating rotator 9a and the pressure rotator 9b, the toner transferred to the transfer material T is melted and pressurized, and the transfer material T Fixed to T.
Details of the configuration of the fixing device 9 will be described later.

Next, the paper supply / discharge unit KH will be described.
As shown in FIG. 1, in the lower part of the apparatus main body M, one sheet feeding cassette 52 that accommodates the transfer material T is disposed. The paper feed cassette 52 is configured to be drawable in the horizontal direction from the right side (the right side in FIG. 1) of the apparatus main body M. A placement plate 60 on which the transfer material T is placed is disposed in the paper feed cassette 52. In the paper feed cassette 52, the transfer material T is accommodated in a state of being stacked on the mounting plate 60. The transfer material T placed on the placement plate 60 is sent out to the transport path L by the cassette paper feed unit 51 disposed at the end of the paper feed cassette 52 on the paper feed side (the right end in FIG. 1). It is. The cassette paper feeding unit 51 includes a forward feed roller 61 for taking out the transfer material T on the mounting plate 60 and a feed roller pair 63 for feeding the transfer material T one by one to the transport path L. A double feed prevention mechanism is provided.

  On the right side (right side in FIG. 1) of the apparatus main body M, a manual paper feed unit 64 is provided. The manual paper feed unit 64 is provided mainly for supplying a transfer material T having a size and type different from that of the transfer material T set in the paper feed cassette 52 to the apparatus main body M. The manual paper feed unit 64 includes a manual feed tray 65 that forms a part of the front surface of the apparatus main body M in the closed state, and a paper feed roller 66. The lower end of the manual feed tray 65 is attached to the vicinity of the paper feed roller 66 so as to be rotatable (openable and closable). The transfer material T is placed on the open manual feed tray 65. The paper feed roller 66 feeds the transfer material T placed on the open manual feed tray 65 to the manual feed path La.

  A paper discharge unit 50 is provided on the upper side of the apparatus main body M. The paper discharge unit 50 discharges the transfer material T to the outside of the apparatus main body M by the third roller pair 53. Details of the paper discharge unit 50 will be described later.

  The conveyance path L for conveying the transfer material T includes a first conveyance path L1 from the cassette paper feeding unit 51 to the transfer nip N, a second conveyance path L2 from the transfer nip N to the fixing device 9, and a fixing device 9. The third conveyance path L3 to the paper discharge section 50, the manual conveyance path La that joins the paper supplied from the manual sheet feeding section 64 to the first conveyance path L1, and the third conveyance path L3 from the downstream side to the upstream side. A return conveyance path Lb that reverses the sheet to be conveyed and returns it to the first conveyance path L1 is provided.

Moreover, the 1st junction part P1 and the 2nd junction part P2 are provided in the middle of the 1st conveyance path L1. A first branch portion Q1 is provided in the middle of the third transport path L3.
The first joining part P1 is a joining part where the manual feed path La joins the first transport path L1. The second junction P2 is a junction where the return conveyance path Lb merges with the first conveyance path L1.
The first branch portion Q1 is a branch portion where the return transport path Lb branches from the third transport path L3, and includes a first roller pair 54a and a second roller pair 54b. One roller of the first roller pair 54a and one roller of the second roller pair 54b are combined.

  In the middle of the first transport path L1 (specifically, between the second joining portion P2 and the transfer roller 8), a sensor for detecting the transfer material T and a skew (oblique paper feed) of the transfer material T. ) A registration roller pair 80 is arranged for matching the timing of correction and toner image formation in the image forming unit GK. The sensor is disposed immediately before the registration roller pair 80 in the transport direction of the transfer material T (upstream in the transport direction). The registration roller pair 80 conveys the transfer material T by performing the above-described correction and timing adjustment based on detection signal information from the sensor.

The return conveyance path Lb is a conveyance path that is provided in order to make the opposite surface (unprinted surface) opposite to the surface that has already been printed face the photosensitive drum 2 when performing double-sided printing on the transfer material T.
According to the return conveyance path Lb, the transfer material T conveyed from the first branching section Q1 to the sheet discharge section 50 side by the first roller pair 54a is reversed, and the second roller pair 54b enters the first conveyance path L1. It can be returned to the upstream side of the registration roller pair 80 disposed on the upstream side of the transfer roller 8. A predetermined toner image is transferred onto the unprinted surface at the transfer nip N on the transfer material T that is reversed by the return conveyance path Lb.

  A paper discharge unit 50 is formed at the end of the third transport path L3. The paper discharge unit 50 is disposed on the upper side of the apparatus main body M. The paper discharge unit 50 opens toward the right side of the apparatus main body M (the right side in FIG. 1, the manual paper feed unit 64 side). The paper discharge unit 50 discharges the transfer material T conveyed on the third conveyance path L <b> 3 to the outside of the apparatus main body M by the third roller pair 53.

On the opening side of the paper discharge unit 50, a paper discharge stacking unit M1 is formed. The paper discharge stacking unit M1 is formed on the upper surface (outer surface) of the apparatus body M. The paper discharge stacking unit M1 is a part formed by the upper surface of the apparatus main body M being depressed downward. The bottom surface of the paper discharge stacking unit M1 constitutes a part of the top surface of the apparatus main body M. In the paper discharge stacking unit M1, a transfer material T on which a predetermined toner image is formed and discharged from the paper discharge unit 50 is stacked and stacked.
A paper detection sensor is disposed at a predetermined position on each conveyance path.

  Next, a configuration related to the fixing device 9 which is a characteristic part of the printer 1 of the present embodiment will be described in detail. FIG. 2A is a perspective view of the fixing device 9 at the normal fixing position as viewed from the center in the Y direction. FIG. 2B is a perspective view of the fixing device 9 at the cylindrical object fixing position viewed from the center in the Y direction. FIG. 3A is a front view showing the fixing device 9 in the normal fixing position. FIG. 3B is a front view showing the fixing device 9 at the cylindrical object fixing position.

  In the description of the printer 1 of the present embodiment, the rotation axis direction of various rotating bodies (rollers and the like) in the photosensitive drum 2, the fixing device 9 and the like is “Y direction” (direction passing through FIG. 1, see FIG. 2A and the like). That's it. The Y direction is also a direction orthogonal to the transport direction of the transfer material T. In the Y direction, the front side is also referred to as “+ (plus) side”, and the rear side is also referred to as “− (minus) side”. The direction that is horizontal and orthogonal to the Y direction is referred to as the “X direction”. In the X direction, the right side is also referred to as the “+ side” and the left side is also referred to as the “− (minus) side”. The vertical direction is referred to as the Z direction (also a direction orthogonal to the X direction and the Y direction). In the Z direction, the upper side is also referred to as “+ side” and the lower side is also referred to as “− (minus) side”. Further, as shown in FIGS. 2A to 3B, the specific description of the fixing device 9 and the like will be made with reference to the view from the “− (minus) side” in the Y direction in FIG.

  As shown in FIGS. 2A to 3B, the fixing device 9 according to the present embodiment has a transfer material (paper) on which a non-fixed toner image (toner) is transferred (formed) on the peripheral surface of a heated heating roller 9a. The envelope T) is conveyed in the conveying direction while being pressed by the pressure roller 9b. Accordingly, the fixing device 9 melts the toner image while heating and pressing to fix (fix) the toner image on the surface of the transfer material T.

  Further, the fixing device 9 includes a normal fixing position (see FIGS. 2A and 3A) for performing a fixing operation on a normal transfer material (transfer material other than a cylindrical material, for example, paper) T, and a cylindrical shape such as an envelope. It is possible to switch between two fixing positions: a cylindrical object fixing position (see FIGS. 2B and 3B) that performs a fixing operation on an object. The switching of the fixing position is performed, for example, by controlling the driving of a fixing nip pressure changing unit 511 (described later) by a fixing nip pressure changing control unit (not shown).

As shown in FIGS. 2A to 3B, the fixing device 9 includes a fixing frame 500, a heating roller 9a, a pressure roller 9b, and a fixing nip pressure changing unit 511.
The fixing nip pressure changing section 511 moves the pressure roller 9b relative to the heating roller 9a to change the nip pressure of the fixing nip N9 shown in FIG.

Each component constituting the fixing device 9 will be described in detail.
The fixing frame 500 will be described. As shown in FIGS. 2A to 3B, the fixing frame 500 constitutes a casing of the fixing device 9, and includes a pair of side plates 501 and a connecting member 502 that connects the pair of side plates 501 in the Y direction. Prepare. The pair of side plates 501 are spaced apart on both sides in the Y direction in the second transport path L2.

To the fixing frame 500, a heating roller 9a, a pressure roller 9b, and some constituent members of the fixing nip pressure changing unit 511 are rotatably connected. The side plate 501 includes a bearing (not shown) for supporting the heating roller 9a and an engagement hole 503 for supporting the pressure roller 9b via a support member 524 (described later) (see FIGS. 3A and 3B). And have.
The fixing device 9 constitutes one assembly from these components. The fixing device 9 is mounted on the case body BD (see FIG. 1) in the printer 1 (see FIG. 1) in the assembled state.

  The heating roller 9a will be described. As shown in FIGS. 2A to 3B, the heating roller 9a is configured to be rotatable about a first rotation axis J1 extending in the Y direction. The heating roller 9a includes a heating roller main body 911 and a first shaft member 912 that is coaxial with the first rotation axis J1. The heating roller main body 911 includes a cylindrical metal member and a release layer formed on the outer peripheral surface of the metal member. For example, the heating roller body 911 is provided with a magnetic metal layer plated with nickel or the like on the outer peripheral surface of a metal tube such as aluminum or iron having a diameter of about 40 mm, and a PFA having a thickness of about 20 μm on the outer peripheral surface of the magnetic metal layer. It is formed by providing a release layer made of a fluororesin such as (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer).

  The first shaft member 912 is formed so as to protrude outward from the both ends of the heating roller body 911 in the Y direction. The first shaft member 912 is rotatably supported via the bearing (not shown) in the side plate 501 of the fixing frame 500. Thereby, the heating roller 9a can rotate around the first rotation axis J1 extending in the Y direction. The heating roller 9a does not move relative to the case body BD (fixing frame 500).

  A heater (not shown) is disposed inside the heating roller 9a. The heater is disposed in a state where the axial direction thereof is parallel to the first rotation axis J1 (Y direction) of the heating roller 9a. The heater generates heat when energized, and heats the heating roller 9a from the inside. The heater is composed of, for example, a halogen heater or a ceramic heater. The heater heats the fixing nip N9 via the heating roller 9a.

  The pressure roller 9b will be described. The pressure roller 9b is configured to be rotatable around a second rotation axis J2 that is parallel to the first rotation axis J1 and extends in the Y direction. The pressure roller 9b includes a pressure roller body 921 and a second shaft member 922 that is coaxial with the second rotation axis J2. The pressure roller main body 921 has an elastic layer having a predetermined thickness made of silicon rubber or the like on the outer periphery of a metal columnar member, and is formed in a columnar shape having a predetermined outer diameter. A fluorine-based release layer is formed on the surface of the elastic layer.

  The second shaft member 922 is formed so as to protrude outward from the both ends of the pressure roller main body 921 in the Y direction. A drive source (not shown) such as a motor is connected to the second rotating shaft J2. The pressure roller 9b is configured to be rotationally driven by this drive source via the second rotation shaft J2. Further, the pressure roller 9 b is rotatably supported by a support member 524 (described later) in the fixing nip pressure changing unit 511 via the second shaft member 922. The pressure roller 9b is disposed on the opposite side of the heating roller 9a with the fixing nip N9 interposed therebetween. Accordingly, the pressure roller 9b is disposed to be rotatable about the second rotation axis J2 and opposed to the heating roller 9a.

  The pressure roller 9b forms a fixing nip N9 (see FIG. 1) through which the transfer material T is conveyed by the heating roller 9a. The pressure roller 9b is disposed so as to press the heating roller 9a in a state where the fixing nip N9 is formed. Therefore, the pressure roller 9b is elastically deformed along the surface shape of the heating roller 9a at a portion facing the heating roller 9a. Thus, the pressure roller 9b is urged away from the heating roller 9a by a repulsive force generated by the nip pressure of the fixing nip N9 in a state where the fixing nip N9 is formed.

  Although details will be described later, the support member 524 in the fixing nip pressure changing portion 511 swings with respect to the side plate 501 of the fixing frame 500. By the swinging of the support member 524, the pressure roller 9b approaches or is separated from the heating roller 9a (see FIGS. 2A and 3A) (see FIGS. 2B and 3B).

Specifically, the pressure roller 9b can take two different positions with respect to the heating roller 9a. The two-stage position of the pressure roller 9b is such that the "normal fixing position" (see FIGS. 2A and 3A) where the outer peripheral surface of the pressure roller 9b most interferes with the outer peripheral surface of the heating roller 9a is referred to. The “cylinder fixing position” (FIGS. 2B and 3B) is that the interference amount of the pressure roller 9b with respect to is smaller than the interference amount at the normal fixing position.
The position of the pressure roller 9b is changed by a fixing nip pressure changing unit 511.

  The heating roller 9a rotates as follows. Specifically, when the pressure roller 9b rotates, the heating roller 9a that contacts the outer peripheral surface of the pressure roller 9b is driven to rotate.

The fixing nip pressure changing unit 511 will be described.
As shown in FIGS. 2A to 3B, the fixing nip pressure changing unit 511 can support the supporting member 524 that supports the pressure roller 9b, the switching member 521 that can be engaged with the supporting member 524, and the switching member 521. The pressing member 523, the nip pressure changing cam 515 as a cam member for pressing the switching member 521 via the pressing member 523, and the switching member 521 are biased toward the support member 524 (to the plus side in the Z direction). A first urging member 522, a second urging member 525 capable of urging the pressure roller 9b toward the heating roller 9a via the support member 524, the first urging member 522, and the second urging member 525. A regulating member 528 that regulates the movement in the negative direction in the Z direction, a gear 513 coupled to the nip pressure changing cam 515, and the nip pressure changing cam 515 via the gear 513. To comprise a gear drive mechanism (not shown), the cam shaft member 514 for connecting the nip pressure changing cam 515 and the gear 513, the.

  Each component in the fixing nip pressure changing portion 511 is provided in a pair in the Y direction except for the gear 513 and the gear driving mechanism. Only one of the pair of components in the Y direction will be described unless otherwise required. The gear 513 and the gear drive mechanism are provided only on the negative side in the Y direction.

  The support member 524 will be described. As shown in FIGS. 2A to 3B, the support member 524 is an arm-shaped member, and is formed of a plate material having a predetermined thickness such as a steel plate. The support member 524 includes a roller support portion 524A, an engagement fulcrum portion 524B, a first extension portion 524C, an operation arm 524D, a second extension portion 524E, a second spring locking portion 524F, and a convex shape. Part 524G.

  The roller support portion 524A has a bearing, and the second shaft member 922 of the pressure roller 9b is rotatably supported by the bearing. The engagement fulcrum portion 524B extends from the outer peripheral edge of the roller support portion 524A so as to be bent at a substantially right angle outward in the Y direction, and is formed in a hook shape. The engagement fulcrum part 524B is engaged with an engagement hole 503 provided in the side plate 501. Accordingly, the support member 524 can swing with respect to the side plate 501 in the XZ plane with the engagement hole 503 as a fulcrum. When the support member 524 swings around the engagement hole 503, the pressure roller 9b approaches or separates from the heating roller 9a. That is, the support member 524 supports the pressure roller 9b so as to be movable by its swinging.

  Further, since the pressure roller 9b is urged away from the heat roller 9a in a state where the fixing nip N9 is formed, the support member 524 is heated by using the engagement hole 503 as a fulcrum via the pressure roller 9b. It is energized in the direction away from 9a.

The first extending portion 524C is a portion extending a predetermined length obliquely upward from the roller support portion 524A.
The operation arm 524D is formed to extend from the upper end portion of the first extending portion 524C to the plus side in the X direction. The operation arm 524D is inserted into a long hole 521D (described later) in the first vertical arm 521B of the switching member 521.

  The operation arm 524D can be engaged with the lower end of the long hole 521D in the first vertical arm 521B of the switching member 521. Specifically, the operation arm 524D is engaged with the lower end of the long hole 521D when the switching member 521 moves in the Z direction (see FIGS. 2A and 3A) and the lower end of the long hole 521D. It is changed to a state that does not (see FIG. 2B and FIG. 3B).

  In a state where the operation arm 524D is engaged with the lower end of the long hole 521D of the switching member 521 (see FIGS. 2A and 3A), the urging force of the first urging member 522 described later is interposed via the switching member 521 and the support member 524. Is transmitted to the pressure roller 9b.

  Further, in a state where the operation arm 524D is not engaged with the long hole 521D of the switching member 521 (see FIGS. 2B and 3B), the operation arm 524D swings due to the urging force in the direction away from the heating roller 9a in the support member 524, which will be described later. The urging force of the second urging member 525 is transmitted to the pressure roller 9b via the support member 524.

The second extending portion 524E is formed so as to extend from the upper end portion side of the first extending portion 524C to the minus side in the Z direction.
The convex portion 524G is formed so as to extend from the end portion on the minus side in the Z direction of the second extending portion 524E to the minus side in the Z direction. The width of the convex portion 524G in the X direction is narrower than that of the second extending portion 524E. The convex portion 524G is inserted into a second urging member 525 described later.

The second spring locking portion 524F is formed along the X direction across the convex portion 524G at the end in the Z direction of the second extending portion 524E. The second spring locking portion 524F is configured to be able to lock an end portion on the plus side in the Z direction of a second biasing member 525 described later.
Specifically, the second spring locking portion 524F is in a state where the upper end of the second urging member 525 is locked by the support member 524 swinging (see FIGS. 2A and 3A), The biasing member 525 is changed to a state where the upper end of the biasing member 525 is not locked (see FIGS. 2B and 3B).

The switching member 521 will be described. The switching member 521 is a member that can be switched to a state in which the urging force of either the first urging member 522 or the second urging member 525 is transmitted to the pressure roller 9b. The switching member 521 is a member that can move to an engagement position (see FIGS. 2A and 3A) that engages with the support member 524 and a non-engagement position (see FIGS. 2B and 3B) that does not engage with the support member 524. is there. The switching member 521 is formed from a plate material having a predetermined thickness such as a steel plate.
As shown in FIGS. 2A to 3B, the switching member 521 includes a horizontal arm 521A extending in the X direction, a first vertical arm 521B extending from the horizontal arm 521A to the negative side in the Z direction, and a Z direction from the first vertical arm 521B. A second vertical arm 521C extending to the negative side of the first and a protruding portion 521F protruding from the horizontal arm 521A to the positive side in the Z direction.

  The switching member 521 has a shape in which the horizontal arm 521A and the first vertical arm 521B are bent in an L shape. That is, the horizontal arm 521A and the first vertical arm 521B are substantially orthogonal to each other. Further, the protruding portion 521F, the first vertical arm 521B, and the second vertical arm 521C are formed linearly along the Z direction.

  The first vertical arm 521B is formed in a rectangular plate shape having a predetermined width in the Y direction. The first vertical arm 521B has a long hole 521D and a first spring locking portion 521E. The long hole 521D is formed so as to extend in the Z direction at substantially the center of the first vertical arm 521B, and penetrates in the X direction.

  The first spring locking portions 521E are formed at both ends of the end surface of the first vertical arm 521B facing the negative side in the Z direction. The first spring locking portion 521E is formed along the Y direction across the second vertical arm 521C. The first spring locking portion 521E locks the positive end of the first urging member 522, which will be described later, in the Z direction.

  The second vertical arm 521C has a narrower width in the Y direction than the first vertical arm 521B, and is formed so as to extend from the negative end side in the Z direction of the first vertical arm 521B to the negative side in the Z direction. The

The switching member 521 has an engagement position (see FIGS. 2A and 3A) where the end of the elongated hole 521D in the Z direction is engaged with the operation arm 524D of the support member 524, and a non-engagement that does not engage the support member 524. It is configured to be movable to the engagement position (see FIGS. 2B and 3B).
When the switching member 521 is located at the engagement position, the urging force of the first urging member 522 is transmitted to the pressure roller 9b via the switching member 521 and the support member 524 (see FIGS. 2A and 2B). . In this case, the switching member 521 is urged by the first urging member 522 toward the support member 524 (toward the positive side in the Z direction). Accordingly, the urging force of the first urging member 522 is transmitted to the pressure roller 9b via the switching member 521 and the support member 524.

  On the other hand, when the switching member 521 is located at the non-engagement position, the urging force of the first urging member 522 is not transmitted to the pressure roller 9b (see FIGS. 3A and 3B). In this case, the support member 524 is swung by a biasing force in a direction away from the heating roller 9a generated by a repulsive force of the pressure roller 9b with respect to the heating roller 9a. Thereby, the second urging member 525 is locked to the second spring locking portion 524F of the support member 524. As a result, the urging force of the second urging member 525 is transmitted to the pressure roller 9b via the support member 524.

  The pressing member 523 will be described. The pressing member 523 is configured to be pressed by the rotation of the nip pressure changing cam 515. The pressing member 523 is a member that presses the switching member 521 to the minus side in the Z direction by being pressed by the nip pressure changing cam 515. The switching member 521 is formed from a plate material having a predetermined thickness such as a steel plate.

  The pressing member 523 includes a pressing fulcrum 523A that is rotatably supported by the side plate 501, a pressing support plate 523B that is arranged along the side plate 501, and a positive side (inside) in the Y direction from the pressing support plate 523B. And a pressing lateral arm 523C extending.

  The pressing member 523 has a shape in which the pressing support plate 523B and the pressing lateral arm 523C are bent in an L shape. That is, the pressing support plate 523B and the pressing lateral arm 523C are orthogonal to each other.

  The pressing fulcrum portion 523A is slidably engaged with the side plate 501. Thus, the pressing member 523 can swing with respect to the side plate 501 in the XZ plane with the pressing fulcrum portion 523A as a fulcrum.

  The pressing lateral arm 523C is disposed between the switching member 521 and a nip pressure changing cam 515 (described later). The lower surface on the positive side end portion in the X direction of the pressing lateral arm 523C faces the upper surface of the lateral arm 521A of the switching member 521. When the pressing member 523 swings around the pressing fulcrum portion 523A, the lower surface of the pressing lateral arm 523C presses the upper surface of the lateral arm 521A of the switching member 521, and the switching member 521 moves to the negative side in the Z direction.

  A slide through hole 523D that extends long in the X direction and penetrates in the Z direction is formed in the pressing lateral arm 523C. The protrusion 521F of the switching member 521 is inserted through the slide through hole 523D.

  The pressing member 523 swings around the pressing fulcrum portion 523A when the upper surface of the pressing lateral arm 523C is pressed by the nip pressure changing cam 515. Then, the pressing horizontal arm 523C of the pressing member 523 has the protruding portion 521F inserted through the slide through hole 523D slidable through the slide through hole 523D, and the horizontal arm 521A of the switching member 521 is directed to the negative side in the Z direction. Move with or without pressing.

  The nip pressure changing cam 515 will be described. As shown in FIGS. 2A to 3B, the nip pressure changing cam 515 is disposed on the plus side in the Z direction with respect to the pressing lateral arm 523C of the pressing member 523. The nip pressure changing cam 515 is formed in a shape in which a part of the outer periphery of the cylindrical member is cut. The outer peripheral surface of the nip pressure changing cam 515 includes an arc-shaped portion 515A as a cam surface and a notch 515B.

  The cam shaft member 514 extends in the Y direction and connects the pair of nip pressure changing cams 515. The cam shaft member 514 is rotationally driven by a gear drive mechanism (not shown) via a gear 513. By the rotation of the cam shaft member 514, the nip pressure changing cam 515 is in the first cam state in which the notch 515B is located on the negative side in the Z direction and the nip pressure changing cam 515 as shown in FIGS. 2A and 3A. Does not press the switching member 521 via the pressing member 523, and as shown in FIGS. 2B and 3B, the arc-shaped portion 515A is in the second cam state positioned on the negative side in the Z direction, and the arc-shaped portion 515A is the pressing member. It rotates between the state where the switching member 521 is pressed via the pressing lateral arm 523C of 523.

When the nip pressure changing cam 515 is in the first cam state, the nip pressure changing cam 515 does not press the switching member 521, and the switching member 521 is located at the engagement position.
When the nip pressure changing cam 515 is in the second cam state, the switching member 521 presses the first urging member 522 against the urging force of the first urging member 522, and the switching member 521 , Located in the disengaged position.

The first urging member 522 will be described. As shown in FIGS. 2A to 3B, the first urging member 522 is formed of a coil spring having a predetermined length, and is disposed in a state where the second vertical arm 521C of the switching member 521 is disposed inside. That is, the second vertical arm 521C of the switching member 521 is inserted inside the first biasing member 522. Further, the positive end of the first biasing member 522 in the Z direction is locked to the first spring locking portion 521E.
The first urging member 522 is expanded and contracted while the switching member 521 moves in the Z direction and is locked to the first spring locking portion 521E.

  The first urging member 522 causes the switching member 521 to face the support member 524 (Z direction) in a state where the operation arm 524D of the support member 524 is engaged with the long hole 521D of the switching member 521 by the elastic return force. (Toward the positive side of). Thereby, the first urging member 522 can urge the pressure roller 9b toward the heating roller 9a via the support member 524 so that the nip pressure at the fixing nip N9 becomes the first nip pressure.

  The second urging member 525 will be described. As shown in FIGS. 2A to 3B, the second urging member 525 is formed of a coil spring having a predetermined length, and is disposed in a state where the convex portion 524G of the switching member 521 is disposed inside. That is, the convex portion 524G of the switching member 521 is inserted inside the second urging member 525. Further, the positive end of the second urging member 525 in the Z direction can be locked to the second spring locking portion 524F.

  The second biasing member 525 is not locked by the second spring locking portion 524F due to the swinging of the support member 524 (see FIGS. 2A and 3A) and the second biasing member 525 is elastically restored by the elastic return force of the second biasing member 525. It is expanded and contracted to a state (see FIGS. 2B and 3B) that is locked to the two spring locking portion 524F.

  The second urging member 525 has a natural length and does not urge the support member 524 when the second urging member 525 is not locked to the second spring locking portion 524F. Further, the second urging member 525 urges the support member 524 to press toward the plus side in the Z direction in a state where the second urging member 525 is locked to the second spring locking portion 524F by the elastic return force. Thus, the second biasing member 525 moves the pressure roller 9b toward the heating roller 9a via the support member 524 so that the nip pressure at the fixing nip N9 is a second nip pressure smaller than the first nip pressure. Can be energized.

  The regulating member 528 will be described. The regulating member 528 is attached to the side plate 501. The regulating member 528 is formed from a plate material having a predetermined thickness such as a steel plate. The restricting member 528 includes a base plate 528A disposed along the side plate 501 and a restricting plate 528B extending from the base plate 528A to the plus side (inward) in the Y direction. The regulating member 528 has a shape in which the base plate 528A and the regulating plate 528B are bent in an L shape.

The restriction plate 528B is formed to extend in the X direction on the negative side of the first biasing member 522 and the second biasing member 525 in the Z direction.
The negative end portion in the Z direction of the first biasing member 522 and the negative end portion in the Z direction of the second biasing member 525 are in contact with the upper surface of the regulating plate 528B. Thereby, the restricting plate 528B restricts the movement of the first urging member 522 and the second urging member 525 to the minus side in the Z direction.

  The restriction plate 528B is formed with a through hole 528C penetrating in the Z direction. The through hole 528 </ b> C is inserted with the negative end side in the Z direction of the second vertical arm 521 </ b> C of the switching member 521. The second vertical arm 521C is movable in the Z direction while being inserted through the through hole 528C. Therefore, the switching member 521 is movable in the Z direction in a state where the second vertical arm 521C is inserted through the through hole 528C.

  The gear drive mechanism is configured to rotationally drive a pair of nip pressure changing cams 515 connected to the cam shaft member 514 via the gear 513.

  Although details will be described later, the fixing nip pressure changing unit 511 rotates the nip pressure changing cam 515 to move the pressure roller 9b in a direction toward the heating roller 9a or away from the heating roller 9a, thereby fixing. The nip pressure of the nip N9 is changed.

  In brief, the switching member 521 moves in the Z direction by being pressed by the pressing member 523 corresponding to the displacement of the cam surface of the nip pressure changing cam 515 due to the rotation of the nip pressure changing cam 515. As the switching member 521 moves in the Z direction, the support member 524 swings. Therefore, the urging force of either the first urging member 522 or the second urging member 525 can be applied to the pressure roller 9b via the support member 524.

  Thereby, the position of the pressure roller 9b supported by the support member 524 is different when the urging force of either the first urging member 522 or the second urging member 525 is applied. Therefore, the position of the pressure roller 9b with respect to the heating roller 9a can be changed. As a result, the nip pressure of the fixing nip N9 can be changed.

Next, the fixing position in the fixing device 9 of this embodiment will be described in detail.
As described above, the nip pressure changing cam 515 is rotationally driven by the fixing nip pressure changing portion 511, and the arc-shaped portion 515A does not press the switching member 521 via the pressing member 523 (see FIGS. 2A and 3A). ) And the second cam state in which the arcuate portion 515A presses the switching member 521 against the urging force of the first urging member 522 via the pressing member 523 after rotating 180 degrees from the first cam state (FIG. 4B and FIG. 4B). The state can be changed to that shown in FIG. 5B.

When the nip pressure changing cam 515 is in the first cam state, it is the normal fixing position. When the nip pressure changing cam 515 is in the first cam state, it is also said that the nip pressure changing cam 515 is in the “normal posture”.
Further, when the nip pressure changing cam 515 is in the second cam state, it becomes the cylindrical object fixing position. When the nip pressure changing cam 515 is in the second cam state, it is also said that the nip pressure changing cam 515 is in the “pressure-reducing posture”.

More specifically, as shown in FIGS. 2A and 2A, when the nip pressure changing cam 515 is in the first cam state (normal fixing position), the nip pressure changing cam 515 and the pressing member 523 are separated from each other. The notch 515B of the nip pressure changing cam 515 is opposed to the upper surface (the surface on the plus side in the Z direction) of the pressing lateral arm 523C of the pressing member 523. In this state, the support member 524 is urged toward the heating roller 9 a by the first urging member 522 via the switching member 521. In this case, the switching member 521 is positioned at an engagement position where the operation arm 524D of the support member 524 engages with the negative end of the elongated hole 521D in the switching member 521 in the Z direction.
The pressure roller 9b supported by the support member 524 is positioned at a normal fixing position where the outer peripheral surface of the pressure roller 9b interferes with the outer peripheral surface of the heating roller 9a most greatly.

The nip pressure at the fixing nip N9 at the normal fixing position is also referred to as “first nip pressure”.
When the fixing device 9 is in the normal fixing position, the urging force of the first urging member 522 acts on the pressure roller 9b via the switching member 521 and the support member 524. Note that the urging force of the second urging member 525 does not act on the pressure roller 9b because the support member 524 is not in contact with the second urging member 525.

  In the normal fixing position, the pressure roller 9b interferes with the outer peripheral surface of the heating roller 9a and elastically deforms. The pressure roller 9b is urged away from the heating roller 9a by the elastic restoring force of the elastic layer of the pressure roller 9b. The first urging member 522 urges the pressure roller 9b toward the heating roller 9a so as to resist the urging force caused by the elastic return force of the elastic layer of the pressure roller 9b, whereby the nip pressure in the fixing nip N9 is obtained. Is the first nip pressure.

  On the other hand, as shown in FIGS. 2B and 3B, when the nip pressure changing cam 515 is in the second cam state (cylindrical object fixing position) rotated from the first cam state, the pressing member 523 has the nip pressure changing cam. It is pressed by the arcuate portion 515A of 515 and swings. The switching member 521 is pressed to the negative side in the Z direction by being pressed by the pressing member 523. Thereby, the switching member 521 is positioned at a non-engagement position where the operation arm 524D does not engage with the end portion on the minus side in the Z direction in the long hole 521D.

  The support member 524 swings in the direction away from the heating roller 9a in order to support the pressure roller 9b biased in the direction away from the heating roller 9a. Accordingly, the second spring locking portion 524F of the support member 524 is locked to the second biasing member 525. As a result, the pressure roller 9b supported by the support member 524 is positioned at the cylindrical object fixing position where the outer peripheral surface of the pressure roller 9b interferes with the outer peripheral surface of the heating roller 9a with a smaller amount of interference than at the normal fixing position. become. That is, in the case of the cylindrical object fixing position, the outer peripheral surface of the pressure roller 920 is further away from the outer peripheral surface of the heating roller 9a than in the normal fixing position.

The nip pressure of the fixing nip N9 at the cylindrical object fixing position is also referred to as “second nip pressure”. The second nip pressure is smaller than the first nip pressure at the normal fixing position.
When the fixing device 9 is in the cylindrical object fixing position, the urging force of the second urging member 525 acts on the pressure roller 9b via the support member 524. Note that the urging force of the first urging member 522 does not act on the pressure roller 9b because the support member 524 does not transmit the urging force from the first urging member 522.

  At the cylindrical object fixing position, the pressure roller 9b interferes with the outer peripheral surface of the heating roller 9a with a smaller amount of interference than that at the normal fixing position, and is elastically deformed. The pressure roller 9b is urged away from the heating roller 9a by the elastic restoring force of the elastic layer of the pressure roller 9b. The second urging member 525 urges the pressure roller 9b toward the heating roller 9a so as to resist the urging force caused by the elastic return force of the elastic layer of the pressure roller 9b. Is the second nip pressure.

According to the fixing device 9 of the present embodiment, for example, the following effects are exhibited.
The fixing device 9 in the present embodiment supports the heating roller 9a, the pressure roller 9b, and the pressure roller 9b, and supports the support member 524 that can change the position of the heating roller 9a with respect to the heating roller 9a by swinging. A first biasing member 522 that can be biased so that the nip pressure is the first nip pressure, and a second bias that can be biased so that the nip pressure is a second nip pressure that is smaller than the first nip pressure. A biasing member 525, and a switching member 521 that can be switched to a state in which the biasing force of either the first biasing member 522 or the second biasing member 525 is transmitted to the pressure roller 9b.

Therefore, in the fixing device 9 of the present embodiment, the urging force of either the first urging member 522 or the second urging member 525 can be applied to the pressure roller 9b by the switching member 521. Specifically, when fixing an image on a normal transfer material that is not a cylindrical object, the first urging member 522 urges the pressure roller 9b in a direction toward the heating roller 9a. In this case, the first urging member 522 urges the nip pressure of the fixing nip N9 to be the first nip pressure.
Further, when fixing an image on a cylindrical object such as an envelope, the second urging member 525 urges the pressure roller 9b in a direction toward the heating roller 9a. In this case, the second urging member 525 urges the nip pressure of the fixing nip N9 to be the second nip pressure.
Thereby, when fixing an image on a cylindrical object such as an envelope and a normal transfer material that is not a cylindrical object, the nip pressure in the fixing nip N9 can be stably applied.

  Further, in the fixing device 9 of the present embodiment, the switching member 521 is disposed between the support member 524 and the first biasing member 522, an engagement position that engages with the support member 524, and the support member The pressure roller 9b is urged by the first urging member 522 when the switching member 521 is in the engaged position, and the switching member 521 is non-engaged. When in the engaged position, it is urged by the second urging member 525. Therefore, the urging force of either the first urging member 522 or the second urging member 525 can be transmitted to the pressure roller 9b with a simple configuration. As a result, when fixing an image to a cylindrical object such as an envelope and a normal transfer material that is not a cylindrical object, the nip pressure at the fixing nip N9 can be more stably applied.

Further, in the fixing device 9 of the present embodiment, the first cam state in which the position of the switching member 521 is located at the engagement position without pressing the switching member 521, and the biasing force of the first biasing member 522. A nip pressure changing cam 515 that is rotated to a second cam state in which the position of the switching member 521 is positioned at the non-engagement position in a state where the switch member 521 is pressed against the above is further provided.
Therefore, the nip pressure changing cam 515 is in a state in which the switching member 521 is not pressed when the pressure roller 9b is urged by the first urging member 522. Further, when the pressure roller 9b is urged by the second urging member 525, the nip pressure changing cam 515 is in a state where the switching member 521 is pressed against the urging force of the first urging member 522. is there.

As a result, the switching member 521 transmits the urging force of the first urging member 522 to the pressure roller 9b or the urging force of the second urging member 525 by the rotation of the nip pressure changing cam 515. The state is switched to 9b. As a result, since the nip pressure changing cam 515 is used only when the switching member 521 is switched, the nip pressure can be stably applied even when the outer shape of the nip pressure changing cam 515 changes due to wear or the like. Can do.
Further, the nip pressure of the fixing nip N9 can be changed with a simple configuration.

As mentioned above, although preferred embodiment of this invention was described, this invention can be implemented with a various form, without being limited to embodiment mentioned above.
For example, in the above-described embodiment, the pressure roller 9b is driven to rotate and the heating roller 9a is driven to rotate. However, the present invention is not limited to this, and the heating roller 9a is driven to rotate and the pressure roller 9b is driven to rotate. You may let them.

  In the embodiment, the heating roller 9a is used as the first rotating body and the pressure roller 9b is used as the second rotating body. However, the present invention is not limited to this. While using the pressure roller 9b as the first rotating body, the heating roller 9a may be used as the second rotating body.

  In the above embodiment, the heating roller 9a is used as the first rotating body. However, instead of this, a heating rotating body formed of an endless belt may be used. Similarly, the pressure roller 9b is used as the second rotator, but instead, a pressure rotator formed of an endless belt may be used.

  In the embodiment, the nip pressure in the fixing nip N9 is changed by changing the position of the pressure roller 9b. However, the present invention is not limited to this. Fixing by changing the position of only the heating roller 9a (first rotating body) or by changing the position of both the heating roller 9a (first rotating body) and the pressure roller 9b (second rotating body). The nip pressure at the nip N9 may be changed.

  In the above-described embodiment, the first urging member 522 having the nip pressure at the fixing nip N9 as the first nip pressure and the second urging member 525 having the nip pressure at the fixing nip N9 as the second nip pressure are provided. However, it is not limited to this. For example, the pressure roller 9b can be biased in the direction toward the heating roller 9a via the support member 524 so that the nip pressure at the fixing nip N9 is a nip pressure different from the first nip pressure and the second nip pressure. The urging member may be further provided. Thereby, a nip pressure different from the first nip pressure and the second nip pressure can be stably applied.

  In the above-described embodiment, the nip pressure changing cam 515 has the cam surface (arc-shaped portion) 515A so that the nip pressure changing cam 515 is switched to two nip pressures. For example, the nip pressure changing cam 515 may be configured to change to three or more nip pressures by having a plurality of cam surfaces.

  Moreover, in the said embodiment, although the nip pressure change cam 515 which can be pressed against the urging | biasing force of the 1st urging | biasing member 522 is provided, it is not restrict | limited to this. For example, a first cam member that can be pressed against the biasing force of the first biasing member 522 and a second cam member that can be pressed against the biasing force of the second biasing member 525 are provided at the same time. Also good.

The type of the image forming apparatus of the present invention is not particularly limited, and may be a color copier, a printer, a facsimile, or a complex machine thereof.
Further, the transfer material T is not limited to a sheet or a cylindrical object, and may be a film sheet, for example.

  DESCRIPTION OF SYMBOLS 1 ... Printer (image forming apparatus), 2 ... Photosensitive drum (image carrier), 9 ... Fixing device, 9a ... Heating roller (first rotating body), 9b ... Pressure roller (second rotation) Body), 511... Fixing nip pressure changing portion, 521... Switching member, 522... First urging member, 524... Supporting member, 525 ... second urging member, J1. J2: Second rotation axis, N9: Fixing nip, T: Transfer material (paper, cylindrical)

Claims (3)

A fixing device that melts toner constituting a toner image transferred to a transfer material and fixes the toner on the transfer material while being provided in the image forming apparatus,
A first rotating body rotatable about a first rotation axis;
The first rotating body is disposed opposite to the first rotating body, forms a fixing nip through which the transfer material is transported by the first rotating body, and is rotatable about a second rotating shaft parallel to the first rotating shaft. A second rotating body that is biased in a direction away from the first rotating body in a state where the fixing nip is formed,
A support member that supports the second rotating body and can change the position of the second rotating body with respect to the first rotating body by swinging;
A first urging member capable of urging the second rotator in a direction toward the first rotator via the support member so that a nip pressure at the fixing nip is a first nip pressure;
A second capable of urging the second rotating body toward the first rotating body via the support member so that the nip pressure at the fixing nip is a second nip pressure smaller than the first nip pressure; A biasing member;
Said first biasing member and the second biasing switching member capable of switching either to a state where one biasing forces are transmitted to the second rotor member, Bei give a,
The switching member is disposed between the support member and the first biasing member, and engages with the support member to transmit the biasing force of the first biasing member to the second rotating body. And an engagement position that is a position where the urging force of the first urging member is not transmitted to the second rotating body without being engaged with the support member,
The second rotating body is biased by the first biasing member via the switching member and the support member when the switching member is in the engagement position, and the switching member is in the non-engagement position. The fixing device is urged by the second urging member via the support member . The first switching state in which the position of the switching member is located at the engagement position without pressing the switching member, and the switching in the state in which the switching member is pressed against the biasing force of the first biasing member. The fixing device according to claim 1 , further comprising a cam member that is rotated to a second cam state in which the position of the member is located at the non-engagement position. One or more image carriers on which electrostatic latent images are formed; and
A developer for developing a toner image on the electrostatic latent image formed on the one or more image carriers;
A transfer unit that directly or indirectly transfers the toner image formed on the image carrier to the transfer material;
Image forming apparatus and a fixing device according to claim 1 or 2.

Images