JP2018010120A - Image heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image heating device that is designed to prevent plastic deformation of an elastic layer of a heating rotating body or pressure contact rotation, while improving workability in replacing the heating rotating body or a pressure contact rotating body.SOLUTION: An image heating device is provided with a rotation regulating member 900 that performs a contact/separation operation with respect to a drive train M1 accompanying a rotation operation of a pressure support member 700. When replacing a heating rotating body 100 or a pressure contact rotating body 200, the image heating device rotates the pressure support member 700 to bring the rotation regulating member 900 into contact with the drive train M1 and lock the rotation of the drive train M1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image heating apparatus that heats a toner image on a recording material. This image heating apparatus can be used in an image forming apparatus such as an electrophotographic copying machine, a printer, a fax machine, or a multi-function machine thereof.

  A toner image formed on an image carrier such as a photoreceptor is transferred to a recording material directly or via an intermediate transfer member, and the recording material is heated while being nipped and conveyed by a nip portion of a fixing device which is an example of an image heating device. An image forming apparatus that pressurizes and fixes an image on a recording material is widely used.

  In the image heating apparatus, a nip portion of a recording material is formed by press-contacting a pressure rotator (belt member or roller member) having an elastic layer to a heating rotator (belt member or roller member). In the image heating apparatus, in order to prevent plastic deformation of the elastic layer, it is desirable that the heating rotating body and the pressure rotating body be separated from each other when the apparatus is stopped (Patent Document 1).

  Patent Document 1 discloses a mechanism for releasing the pressurization of the nip portion pressed by the spring member by rotating the cam member using a motor. During the period when the recording material is not heated, the pressurization of the nip portion is reduced or released.

JP 2005-114959 A

  In such an image heating apparatus, it is required to take out the heating rotator and the press-contact rotator from the apparatus so that they can be replaced with new ones. However, there is a possibility that the cam member releasing the pressurization of the nip portion rotates during the work of exchanging the heating rotator or the press-contact rotator, and the apparatus is in a pressurized state when the exchange work is completed. there were. Then, there is a possibility that the heating rotator or the pressure-rotating elastic layer may be plastically deformed by being left in a pressurized state for a long time.

  An object of the present invention is to provide an image heating apparatus capable of preventing plastic deformation of the heating rotator and the elastic layer of the press-rotating rotation while improving the workability of replacing the heating rotator and the press-rotating rotator. It is to provide.

In order to achieve the above object, a typical configuration of the image heating apparatus according to the present invention is as follows.
First and second rotating bodies for heating a toner image on a recording material at a nip portion therebetween;
A pressing member for pressing at least one of the first and second rotating bodies toward the other; and
A pressing force changing mechanism capable of changing the pressing force of the nip portion by the pressing member into a first pressing force and a second pressing force lower than the first pressing force;
A drive train for transmitting a drive force to the pressure change mechanism;
A first position that supports the pressure member and is fixed to the apparatus to enable the apparatus to operate, and the fixed state is released and the first and second rotating bodies are removed from at least one of the apparatuses. A pressure support member movable to a second position different from the first position;
A regulating member that performs a contact / separation operation with the drive train in accordance with the movement of the position of the pressure support member,
The regulating member is separated from the drive train when the pressure support member is located at the first position, and is in contact with the drive train when located at the second position. The operation of the drive train is locked.

  ADVANTAGE OF THE INVENTION According to this invention, the elastic layer of a 1st rotary body or a 2nd rotary body is improved, improving the exchange workability | operativity of a 1st rotary body (heating rotary body) or a 2nd rotary body (pressure contact rotary body). It is possible to provide an image heating apparatus that can prevent plastic deformation of the image.

Structure explanatory drawing of the gear lock mechanism in Example 1 Configuration schematic diagram of an example of an image forming apparatus The perspective view which looked at the fixing device in Example 1 from the front side. Front view of the device Enlarged perspective view on the drive side of the device and block diagram of the control system Expanded cross-sectional schematic diagram of the main part of the device A perspective schematic view of the main part of the internal structure of the device (A) is a schematic diagram of the layer structure of the fixing belt, (b) is a perspective view of the coil unit viewed with the cover plate removed, and (c) is a perspective view of the internal assembly of the belt unit. State diagram of pressure switching mechanism in normal pressurization mode (cross section AA in FIG. 4) State diagram of pressurizing force switching mechanism in normal pressurizing mode (cross section BB in FIG. 4) Cam phase diagram of pressure release cam State diagram of pressurizing force switching mechanism in low pressure mode (cross section BB in FIG. 4) State diagram of pressure switching mechanism in pressure release mode (cross section BB in FIG. 4) Explanation of drive unit Explanatory drawing of replacement procedure of belt unit (and pressure roller) (Part 1) Explanatory diagram of the replacement procedure (2) Explanatory diagram of the replacement procedure (part 3) Explanatory drawing when the pressure release cam has been turned to the pressure plate Diagram for explaining the force applied to the pressure release cam The figure for demonstrating the torque holding a pressure release cam Diagram when pressure is applied when replacing belt unit Illustration when the rotation restricting member is away from the gear Illustration when the rotation restricting member is in contact with the gear Configuration of Gear Lock Mechanism in Embodiment 2 Illustration when the rotation restricting member is away from the gear Illustration when the rotation restricting member is in contact with the gear

  Hereinafter, the present invention will be described more specifically with reference to examples. Although these examples are examples of the best mode of the present invention, the present invention is not limited to these examples.

Example 1
[Image forming apparatus]
FIG. 2 is a schematic configuration diagram of an example of the image forming apparatus. The image forming apparatus 1 is a tandem-intermediate transfer full-color electrophotographic copying machine equipped with an automatic document feeder 2.

  UY, UM, UC, and UK are four image forming units that form toner images of yellow (Y), magenta (M), cyan (C), and black (K), respectively. Each image forming unit includes a photosensitive drum 3, a charger 4, a laser scanner 5, a developing device 6, a primary transfer charger 7, and a drum cleaner 8. In order to avoid complication of the drawing, the reference numerals for these devices in the image forming units UM, UC, UK other than the image forming unit UY are omitted. Further, since the electrophotographic process and image forming operation of these image forming units are known, the description thereof will be omitted.

  The toner images of the respective colors are primarily transferred onto the intermediate transfer belt 9 that is rotated from the drum 3 of each image forming unit in a predetermined manner. As a result, a four-color superimposed toner image is formed on the belt 9. On the other hand, a recording material (sheet: hereinafter referred to as paper or paper) S is fed from the cassette 10 or 11 or the manual feed tray 12 to one sheet. The sheet S passes through the conveyance path 13 and is introduced into the secondary transfer nip portion which is a pressure contact portion between the belt 9 and the secondary transfer roll 15 at a predetermined control timing by the resist roll pair 14. As a result, the four color superimposed toner images on the belt 9 are secondarily transferred onto the sheet S at once.

  In the image forming apparatus 1 according to the present exemplary embodiment, the mechanism unit is an image forming unit that forms an unfixed toner image on the paper S. The sheet S is introduced into a fixing device (fixing device) F, which is an image heating device, and heated and pressurized, whereby an unfixed toner image is melted and softened and fixed as a fixed image. In the single-sided image forming mode, the sheet S exiting the fixing device F is introduced to the conveyance path 16 side by the path control and is discharged onto the discharge tray 17.

  In the double-sided image forming mode, the sheet S on which the single-sided image has been formed exiting the fixing device F is introduced to the reverse conveyance path 18 side by route control, then switched back and introduced into the double-side conveyance path 19. Then, in a state where the front and back sides are reversed, the toner image is again formed through the conveyance path 13 and introduced into the secondary transfer nip portion to form a toner image on the back surface. Thereafter, it is introduced into the fixing device F as in the case of single-sided image formation, and is discharged as a double-sided image formed product onto the discharge tray 17. In the image forming apparatus 1 according to the first exemplary embodiment, the conveyance of the large and small width sheets S is performed based on a so-called central reference at the center of the sheet width. An apparatus configuration that performs sheet conveyance on a so-called one-side basis may also be used.

  As described above, a series of image forming processes from charging, exposure, development, transfer, and fixing are executed, and an image is recorded and formed on the paper S. In a monochrome image forming apparatus, only a black image forming unit exists. The arrangement order and configuration of the image forming units for Y, M, C, and K are not limited to this.

[Fixing device]
Regarding the fixing device F described below, the front side is the entrance side of the sheet S and the back side is the exit side of the sheet S. Left and right are left or right when the device F is viewed from the front side. In this embodiment, the left side is defined as one end side (driving side) and the right side is defined as the other end side (non-driving side). Up and down are up or down in the direction of gravity. The upstream side and the downstream side are the upstream side and the downstream side in the conveyance direction (recording material conveyance direction) of the sheet S.

  3 is a perspective view of the fixing device F as viewed from the front side, FIG. 4 is a front view of the device F, FIG. 5 is an enlarged perspective view of the driving side of the device F and a block diagram of a control system, and FIG. FIG. 7 is a schematic perspective view of the essential part of the internal structure of the apparatus F. FIG.

  The fixing device F of the present embodiment is an IH (induction heating) type-belt type image heating device, and mainly includes the following members and mechanisms, mainly referring to FIG.

a: a flexible endless belt (hereinafter referred to as a fixing belt or a belt) as a first rotating body (heating rotating body: fixing member) that heats the toner image t formed on the paper S at the nip portion N; ) Belt unit 110 including 100
b: a pressure roller 200 having elasticity as a second rotating body (pressure contact rotating body: pressure member) that forms the nip portion N with the belt 100
c: Coil unit (induction heating device, magnetic flux generation means) 300 as a heater for heating the belt 100
d: A pressure mechanism 710L on one end side and the other end side that forms a nip portion N that heats an image on a sheet (on a recording material) by pressing the belt 100 and the pressure roller 200 (image heating processing: fixing).・ 710R (FIGS. 3 to 5)
e: Pressure changing mechanism 720L / 720R (FIGS. 3 to 5) capable of changing the pressure applied to the nip N by the pressure member of the pressure mechanisms 710L / 710R.
f: an apparatus frame having a bottom plate 601 and one side and other side plates 602L and 602R fixedly opposed to the bottom plate 601 and containing the above-described members and mechanisms ( Chassis, housing) 600 (FIGS. 3-5, 7)
(2-1) Belt Unit The belt unit 110 includes an endless belt 100 having a metal layer. Further, as a belt internal assembly, a fixing pad (hereinafter referred to as a pad) 103, a pad member 101 that holds the pad 103, a stay 102 that holds the pad member 101, and an inner core (inner magnetic core) 104 that covers the stay 102. And so on. FIG. 8C is a perspective view of the belt inner assembly.

  The pad 103, the pad member 101, and the stay 102 are all members that are long in the longitudinal direction (width direction) of the belt 100. One end and the other end of the stay 102 protrude outward from both ends of the belt 100, and flange members 105 </ b> L and 105 </ b> R (FIG. 7) on one end and the other end are fitted to the protrusion. Has been. The belt 100 is loosely fitted on the outside of the belt inner assemblies 101 to 104 between the opposing surfaces of the flange members 105L and 105R.

  On the inner side of the pad member 101 (on the side opposite to the pad 103 side), a temperature sensor mounting portion (not shown) is disposed at the longitudinal center of the pad member 101. A temperature sensor (temperature detection element) TH1 such as a thermistor is provided at the mounting portion via an elastic support member 109, for example.

  The elastic support member 109 protrudes to the outside of the inner core 104 through the through hole 102a provided in the longitudinal center portion of the upper surface of the stay 102 and the through hole 104a provided at the inner core position corresponding to the through hole. Yes. The temperature sensor TH1 supported at the tip of the elastic support member 109 is in elastic contact with the inner surface of the longitudinal central portion of the belt 100. As a result, even if a position variation such as the sensor contact surface of the rotating belt 100 undulates, the temperature sensor TH1 follows this and maintains a good contact state with the inner surface of the belt 100.

  FIG. 8A is a layer configuration model diagram of the belt 100. The belt 100 has a metal base layer 100a having an inner diameter of about 20 to 40 mm. A heat resistant rubber layer is provided as an elastic layer 100b on the outer periphery of the base layer 100a. The thickness of the rubber layer is preferably set within a range of 100 to 800 μm. In the present embodiment, the thickness of the rubber layer is set to 200 μm in consideration of reducing the heat capacity of the belt 100 to shorten the warm-up time and obtaining a suitable fixed image when fixing a color image. Further, a fluororesin layer (for example, PFA or PTFE) is provided on the outer periphery of the elastic layer 100b as the surface release layer 100c.

  In order to reduce the sliding friction between the inner surface of the belt and the temperature sensor TH1, a sliding layer 100d having a high sliding property may be provided on the inner surface side of the base layer 100a. In this embodiment, a 30 μm polyimide layer is provided, and heat resistant grease as a lubricant is applied to the surface of the polyimide layer to maintain the lubricity of the inner surface of the belt 100. For the metal layer 100a of the belt 100, an iron alloy, nickel alloy, copper, silver, or the like can be selected as appropriate.

  The pad member 101 holding the pad 103 applies a pressing force between the belt 100 and the pressure roller 200 to form the nip portion N. The pad 22 is made of a material having high hardness such as a metal such as stainless steel or ceramics, and has a shape extending in the longitudinal direction with a thickness of about 1 mm. The material of the pad member 101 is made of a heat resistant resin such as PPS or LCP.

  The stay 102 that holds the pad member 101 is a rigid member made of metal because it needs rigidity to apply pressure to the nip portion N. As a material of the stay 102, it is desirable that only the belt 100 generates heat by the coil unit 300 as a heater, and a non-magnetic material such as stainless steel which is not easily affected by induction heating is desirable.

  An inner core 104 is provided on the stay 102 on the coil unit 300 side in order to perform induction heating more effectively. As shown in FIG. 8C, the inner core 104 is divided into a plurality of parts in the longitudinal direction, and is arranged so as to gradually change the distance between the coil unit 300 and an exciting coil 301 described later. The inner core 104 is made of a material having high permeability such as ferrite that shields the magnetic flux so that the magnetic flux generated by applying a high-frequency current to the exciting coil 301 can be used more efficiently for heating the belt 100.

  As shown in FIG. 7, the belt unit 110 includes longitudinal members 105 </ b> L and 105 </ b> R on the one end side and the other end side formed in the side plates 602 </ b> L and 602 </ b> R on the one end side and the other end side of the device frame 600, respectively. The guide slit portion 602a is disposed so as to be engaged therewith. Therefore, the belt unit 110 as a whole has a degree of freedom to move vertically between the side plates 602L and 602R along the slit portion 602a.

(2-2) Pressure roller The pressure roller 200 is an elastic roller having an outer diameter of 30 mm, in which a metal cored bar 200a is provided with a rubber layer as an elastic layer 200b and a release layer 200c is provided on the surface. The pressure roller 200 is disposed on the lower side of the belt unit 110 so that its axial direction is substantially parallel to the longitudinal direction of the belt unit 110 and is rotatable between the side plates 602L and 602R via bearings 603, respectively (see FIG. FIG. 7).

  A pressure roller gear 801 (FIG. 5) is disposed concentrically and integrally at the end of one end of the cored bar 200a. A driving force of a fixing motor (drive source) 800 controlled by a control unit (CPU) 1000 is transmitted to the gear 801 through a fixing drive train (gear train) M2 serving as a drive transmission means. As a result, the pressure roller 200 is driven to rotate at a predetermined speed in the counterclockwise direction indicated by arrow R200 in FIG.

(2-3) Coil Unit The coil unit 300 is a heater for induction heating the belt 100, and is disposed on the upper side of the belt unit 110. The coil unit 300 is obtained by assembling an excitation coil (coil that generates magnetic flux) 301, an outer core (outer magnetic core) 302, and the like inside a housing 303 that is long along the longitudinal direction of the belt 100.

  The housing 303 is a horizontally long box-shaped molded product made of a heat-resistant resin (a molded member having an electric insulating resin thickness of about 2 mm). The side of the bottom plate 303 a of the housing 303 is a surface facing the belt 100. The bottom plate 303a is curved inward of the housing 303 so as to follow a substantially half-circumferential range of the outer peripheral surface of the belt 100 in the cross section.

  In the coil unit 300, both end portions of the housing 303 are received by one end side and the other end side flange members 105 </ b> L and 105 </ b> R of the belt unit 110. Accordingly, the bottom plate 303a of the housing 303 faces the upper surface of the belt 100 with a predetermined gap (gap) α. In the coil unit 110, side plates on one end side and the other end side of the housing 303 are tied to flange members 105L and 105R on the respective sides by wire springs (not shown). That is, the coil unit 300 is integrated with the belt unit 110.

  Therefore, when the flange members 105L and 105R of the belt unit 110 are pressed by the pressurizing mechanisms 710L and 710R and sink as described later, the coil unit 300 also sinks together with the belt unit 110 while maintaining the gap α. Further, when the flange members 105L and 105R are lifted by being depressurized or released, the coil unit 300 is also lifted together with the belt unit 110 while maintaining the gap α.

  The coil 301 is formed by using, for example, a litz wire as an electric wire, which is horizontally long and shaped like a ship bottom and is opposed to a part of the peripheral surface and side surface of the belt 100. And it is applied to the inner surface of the bottom plate 303a that is curved inside the housing and is housed inside the housing. A high frequency current of 20 to 60 kHz is applied to the coil 301 from a power supply device (excitation circuit) 1001 controlled by the control unit 1000. The metal layer (conductive layer) 100a of the belt 100 is inductively heated by the magnetic field generated by the coil 301 by applying this current.

  The outer core 302 is an outer magnetic core that covers the coil 301 so that the magnetic field generated by the coil 301 does not substantially leak outside the metal layer (conductive layer) of the belt 100. And the outer core 302 is divided | segmented into plurality along the longitudinal direction, and is arrange | positioned along with the longitudinal direction like (b) of FIG. FIG. 8B is a view of the inside of the housing with the cover plate of the housing 303 removed from the coil unit 300.

(2-4) Fixing Operation When the image forming apparatus 1 is in a standby state (standby state), the fixing device F causes the pressure applied to the nip portion N by pressure mechanisms 710L and 710R described later to be applied by the pressure changing mechanisms 710L and 710R. The pressure release mode (pressure release state) that is substantially released is maintained. The fixing motor 800 is turned off, and the rotation of the pressure roller 200 is stopped. Power supply to the coil 301 of the coil unit 300 is turned off.

  Based on the input of the print job start signal (image formation job start signal), the control unit 1000 performs a pre-rotation operation (preparation operation prior to the image formation operation) of the apparatus for raising the fixing device F to a predetermined temperature. Run.

  That is, the control unit 1000 controls the pressurizing force changing mechanisms 720L and 720R at a predetermined control timing to place the pressurizing mechanisms 710L and 710R in a predetermined pressurizing mode (pressurized state). As a result, the stay 104 of the belt unit 110 is pressed to a predetermined pressure via the flange members 105L and 105R, and the in-belt assembly resists the elasticity of the elastic layer 200b against the pressure roller 200 via the belt 100. Pressurized. As a result, the pad 103 is pressed against the pressure roller 200 via the belt 100, and a nip portion N having a predetermined width is formed between the belt 100 and the pressure roller 200 in the sheet conveyance direction a.

  In addition, the control unit 1000 turns on the fixing motor 800. As a result, the driving force of the fixing motor 800 is transmitted to the pressure roller gear 801 via the fixing drive train M2, and the pressure roller 200 is rotationally driven in the counterclockwise direction indicated by the arrow R200 in FIG.

  By the rotation of the pressure roller 200, a rotational force acts on the belt 100 by the frictional force between the surface of the pressure roller 200 and the surface of the belt 100 in the nip portion N. While the inner surface of the belt 100 slides in close contact with the pad 103, the outer periphery of the belt inner assemblies 101 to 104 is driven to rotate in the clockwise direction indicated by an arrow R100 in FIG. Movement in the thrust direction accompanying the rotation of the belt 100 is restricted by the flange portions of the flange members 105L and 105R.

  The control unit 1000 applies a high frequency current (alternating current) of 20 kHz to 60 kHz to the coil 301 from the power supply device (excitation circuit) 1001. The coil 301 generates an alternating magnetic flux (magnetic field) by supplying a high frequency current. The alternating magnetic flux is guided to the metal layer 100 a of the belt 100 on the upper surface side of the belt 100 rotating by the core 302. Then, an eddy current is generated in the metal layer 100a, the metal layer 100a is self-heated (electromagnetic induction heat) by Joule heat due to the eddy current, and the belt 100 is heated.

  That is, when the rotating belt 100 passes through the region where the magnetic field generated from the coil unit 300 is present, the metal layer 100a generates heat by electromagnetic induction and is heated all around. The temperature of the belt 100 is detected by the temperature sensor TH1. The temperature sensor TH <b> 1 detects the temperature of the portion of the belt 100 that becomes the paper passing area, and the detected temperature information is fed back to the control unit 1000. The control unit 1000 applies power to the coil 301 from the power supply device 1001 so that the detected temperature (information on the detected temperature) input from the sensor TH1 is maintained at a predetermined target temperature (fixing temperature: information corresponding to the predetermined temperature). The power supply is controlled.

  In the present embodiment, the temperature adjustment is performed by controlling the power input to the coil 301 by changing the frequency of the high-frequency current based on the detected value of the temperature sensor TH1 so that the belt 100 becomes constant at the target temperature of 180 ° C. It is carried out.

  In the above pre-rotation operation, the pressure roller 200 is driven, and the belt 100 rises to a predetermined fixing temperature and is in a temperature-controlled state. In this state, the sheet S carrying the unfixed toner image t in the nip portion N of the fixing device F is introduced from the image forming unit side while being guided by the guide member 106 with the toner image carrying surface side facing the belt 100 side. The The sheet S is in close contact with the outer peripheral surface of the belt 100 at the nip portion N, and is nipped and conveyed through the nip portion N together with the belt 100.

  As a result, the heat of the belt 100 is mainly applied, and the unfixed toner image t is fixed to the surface of the paper S by heat pressure under the pressure of the nip portion N. The sheet S that has passed through the nip portion N is self-separated (curvature separation) from the outer peripheral surface of the belt 100 due to deformation of the exit portion of the nip portion N, and further receives separation assistance by the separation guide 107, The paper is discharged and conveyed from the fixing device F by the guide member 108.

  The separation guide 107 has a certain gap (gap between the belt 100 and the belt 100 so that the paper S coming out from the exit portion of the nip portion N does not wrap around the belt 100 and does not touch the belt 100 and damage the belt 100. ) Is arranged. The separation guide 107 is engaged with a part of the flange members 105L and 105R and is fixed by a biasing means such as a spring.

  When the print job (print job) is completed, the control unit 1000 stops the image forming apparatus after a predetermined post-rotation operation and shifts to the standby state. For the fixing device F, the pressure mechanisms 710L and 710R are returned to the pressure release mode. The fixing motor 800 is turned off. The power supply to the coil 301 of the coil unit 300 is also turned off.

(2-5) Pressurizing Mechanism / Pressurizing Change Mechanism In this embodiment, the pressurizing mechanisms 710L and 710R pressurize (press) the flange members (pressing members) 105L and 105R of the belt unit 110, respectively. And a pressure roller 200 to form a nip portion N having a predetermined width in the paper transport direction a. The pressurizing force changing mechanisms (pressure releasing mechanisms) 720L and 720R are mechanisms for changing the pressurizing force of the pressurizing mechanisms 710L and 710R, respectively.

  In the present embodiment, the pressurizing mechanisms 710L and 710R and the pressurizing force changing mechanisms 720L and 720R are synchronized with the same configuration symmetrically to the outside of the side plates 602L and 602R on one end side and the other end side of the apparatus frame 600, respectively. It is provided as a mechanism that operates. Therefore, the following description will be mainly given of the pressurizing mechanism 710L and the pressing force changing mechanism 720L on one end side.

(A) Pressurization mechanism The pressurization mechanism 710L (R) includes a pressure support plate (pressure support member) 700, a pressure plate 1 (701: pressure member), a pressure plate 2 (702: pressure member), and a rotation. A central shaft 703, a pressure spring 1 (704), a pressure spring 2 (705), and a pressure adjustment screw 709 are included.

  The pressure support plate 700 of the pressure mechanism 710L on the one end side and the pressure mechanism 710R on the other end side is a pressure release shaft 708 with respect to the side plate 602L on one end side and the side plate 602R on the other end side of the apparatus frame 600, respectively. Is supported by penetrating. At the tip of the pressure support plate 700, the side plate 602L on one end side and the side plate 602R on the other end side are fixed with screws 403.

  The pressure plate 1 (701) and the pressure plate 2 (702) are pivotally supported by a rotation center shaft 703, and the pressure plates 1, 2 (701, 702) move freely with respect to the pressure support plate 700. I can do it. The pressure plate 1 (701) is attached to the pressure spring 1 (704), the pressure plate 2 (702) is pressed to the pressure spring 2 (705), and the flange member 105L (R) is pressed against the pressure roller 200 side with a spring. It is fast. However, the pressure plate 1 (701) pressurizes the flange 105 member 105L (R) via the pressure plate 2 (702).

  A pressure adjustment screw 709 is fastened to the pressure support plate 700, and the spring length of the pressure spring 1 (704) is adjusted by the amount by which the pressure adjustment screw 709 is tightened. The spring load applied to the flange 105 member L (R) can be adjusted.

9 is a cross-sectional view taken along line AA in FIG. 4, and FIG. 10 is a cross-sectional view taken along line BB in FIG.
The pressure plate 2 (702) has a protrusion 702a on a part of the surface for pressing the flange member 105L, and the pressure plate 1 (701) and the pressure plate are pressed by the pressure plate 1 (701) pressing the protrusion 702a. 2 (702) simultaneously pressurizes the flange member 105L. A nip portion N is formed between the pressure roller 200 and the belt 100.

  The pressure spring 1 (704) is set so as to generate a higher urging force than the pressure spring 2 (705). For example, when a pressing force of 550 N is applied to the nip portion N, the pressure spring 1 (704) is set to bias 520 N, and the pressure spring 2 (705) is set to bias the remaining 30 N. The nip force of 550 N is used for media such as plain paper, glossy paper, and cardboard. Hereinafter, this pressure state is referred to as a normal pressurizing mode. By appropriately controlling the pressure in the normal pressurization mode and the paper feeding speed and temperature control temperature, it becomes possible to satisfy not only plain paper but also fixing properties and glossiness of thick paper and glossy paper.

(B) Pressure change mechanism The pressure change mechanism 720L (R) includes a pressure release cam 706, a pressure release gear 707, and a pressure release shaft 708.

  A pressure release cam 706 as a pressure release mechanism and a pressure release gear 707 and a pressure release shaft 708 outside the space containing the pressure plate of the pressure support plate on the opposite side of the rotation center shaft 703 across the flange member 105L. Is arranged. The gear 707 is not disposed in the pressure change mechanism 720R on the other end side. The pressure release gear 707 and the pressure release cam 706 are arranged coaxially with the pressure release shaft 708, and are engaged so that the pressure release cam 706 is rotated by the rotation of the pressure release gear 707.

  The pressure release cam 706 has a shape in which two cams are arranged in the longitudinal direction, and has two cam profiles. Specifically, the small cam portion 706b of the pressure release cam rotates the pressure plate 2 (702) around the rotation center axis, and the large cam portion 706a of the pressure release cam rotates the pressure plate 1 (701) around the rotation center axis. Can be rotated.

  FIG. 11 shows the amount of rotation about the rotation center axis of each of the pressure plates 1 (701) and 2 (702) by the small cam portion 706b and the large cam portion 706a when the pressure release cam 706 rotates. In FIG. 11, the pressure state corresponds to 0 ° on the vertical axis, and in FIGS. 5, 9, and 10, the pressure plates 1 (701) and 2 (702) are counterclockwise about the rotation shaft 70. The time of rotation is positive.

(B-1) Low Pressurization Mode Next, a state where the nip pressure is low (hereinafter, low pressurization mode) will be described with reference to FIG. When a print job (JOB) for passing a sheet in the low pressure mode, for example, an envelope sheet passing job (a print job using an envelope as paper) is input, the control unit 100 shifts to the low pressure mode. To do.

  Driving is transmitted from the fixing motor 800 (FIG. 5) to the pressure release gear 707 via the detachable drive train M1, and the pressure release gear 707 is rotated clockwise. As a result, the pressure release shaft 708 and the pressure release cam 706 that are engaged with the pressure release gear 707 by a parallel pin, D-cut, or the like are rotated. FIG. 12 shows a state where the pressure release cam 706 has stopped in the low pressure mode and the fixing device F has shifted to the low pressure mode. The pressurizing force changing mechanism 720R on the other end side also performs the same operation in conjunction with it.

  In FIG. 12, the large cam portion 706a of the pressure release cam 706 pushes up the pressure plate 1 (701), and the pressure plate 1 (701) is in a pressure release state. On the other hand, the small cam portion 706b does not touch the pressure plate 2 (702), and the pressure plate 1 (701) and the pressure plate 2 (702) are not in contact with each other. Therefore, the pressure applied by the pressure spring 1 (704) can be sufficiently received by the pressure release cam 706, and the pressure applied by the pressure spring 1 (704) does not act on the flange member 105L (R).

  Since the pressure spring 2 (705) is disposed on the pressure plate 2 (702), only the pressure spring 2 (705) acts on the flange member 105L (R) in the state of FIG. As described in the description of the normal pressure mode, the biasing force of the pressure spring 2 (705) is about 1/18 compared to the biasing force of the pressure spring 1 (704). Thus, the pressurizing force in the low pressurization mode can be greatly reduced.

(B-2) Pressure Release Mode When the image forming apparatus 1 is not operating and the main power switch (not shown) is turned off or when a paper jam occurs, the fixing device F shifts to the pressure release mode. To do. In this case, the normal pressure mode or the low pressure mode is shifted to the pressure release mode shown in FIG.

  In the pressure release mode, unlike the low pressure mode, the pressure plate 1 (701) and the pressure plate 2 (702) are both lifted by the large cam portion 706a and the small cam portion 706b of the pressure release cam 706, respectively. As a result, the pressure release cam 706 receives the urging force of both the pressure spring 1 (704) and the pressure spring 2 (705), thereby releasing the pressure applied to the nip portion N. Enter mode. Thereby, the plastic deformation of the belt 100 and the pressure roller 200 and the paper removability at the time of paper jamming are improved.

(2-6) Drive Configuration FIG. 14 is an explanatory diagram of a drive unit in the fixing device F of this embodiment. This drive unit is disposed outside the side plate 602L on one end side of the fixing device F so as to face the side plate 602L and is assembled to the unit frame 404, and includes a fixing motor 800 and a gear train.

  In the fixing device F of the present embodiment, the fixing operation and the attaching / detaching operation are performed by switching the rotation direction with one fixing motor 800 provided in the drive unit. The drive configuration is roughly divided into the following two drive trains (gear trains) (see FIG. 14).

1. Removable drive train (M1): drive train of the fixing motor 800 to the pressure release gear 707 Fixing drive train (M2): Drive train of the fixing motor 800 to the pressure roller gear 801 A peristaltic gear 806 is provided in the attach / detach drive train (M1) so that the attach / detach operation is not performed during the fixing operation. The oscillating gear 806 is a gear that is oscillated by the tangential force of the gear, and the oscillating gear 806 is configured to be disengaged from the removable drive train (M1) during the fixing operation.

  A one-way clutch 802a is incorporated in the one-way gear 802 so that the pressure roller 200 does not rotate during the attachment / detachment operation. At the time of attachment / detachment driving, the one-way clutch 802a is idled with respect to the drive shaft 808 so that the pressure roller 200 does not rotate.

(2-7) Belt Unit and Pressure Roller Replacement Operation The procedure for replacing the belt unit 110 and the pressure roller 200 (or one of them) will be described with reference to FIGS. 15 (a) to 15 (c). To do. This replacement operation is generally performed in a state in which the fixing device F is sufficiently pulled out from the inside of the image forming apparatus main body to the outside by a predetermined procedure and exposed, or removed from the image forming apparatus main body. Alternatively, the fixing device F is exposed by opening the inside of the image forming apparatus main body while being mounted on the image forming apparatus 1.

  When the opening / closing part of the image forming apparatus 1 is opened for maintenance of the image forming apparatus 1 or the like, the power of the image forming apparatus main body is turned off by the turning-off operation of the kill switch. As described above, when the image forming apparatus 1 is not in operation and the power is turned off, the mounted fixing device F is in the pressure release mode.

  That is, as shown in FIG. 15A, the pressure release cam 706 lifts the pressure plates 1 and 2 (701 and 702) to release the pressure applied to the belt unit 110. Accordingly, when the belt unit 110 and the pressure roller 200 are replaced, the pressure is applied to the fixing device F as shown in FIG. 15A.

  Here, in the pressure mechanisms 710L and 710R on the one end side and the other end side, the pressure support plate 700 is always fixed to the side plate 602L on one end side and the side plate 602R on the other end side by screws 403, respectively. The position of the pressure support plate 700 fixed to the device is defined as a first position Z1. The first position Z1 fixed to the apparatus of the pressure support plate 700 is a position that enables the apparatus operation.

  When replacing the belt unit and the pressure roller, first, the screws 403 that fasten the pressure support plate 700 and the side plates 602L and 602R are removed from the pressure mechanisms 710L and 710R on the one end side and the other end side. .

  Next, the pressure support plate 700 is caused to rotate from the side plates 602L and 602R around the pressure release shaft 708 (FIG. 15B). In this embodiment, the pressure support plate 700 is rotated by 90 °. The rotation position of the pressure support plate 700 caused by 90 ° is a second position Z2 different from the first position Z1 that enables the belt unit 110 and the pressure roller 200 to be taken out from at least one of the devices. . At this time, the posture of the pressure release cam 706 does not change, and the pressure plates 1 and 2 (701, 702) rotate while sliding on the surface of the pressure release cam 706 around the pressure release shaft 708.

  Then, the belt unit 110 and the pressure roller 200 are removed from the side plates 602L and 602R on one end side and the other end side of the apparatus frame 600. Then, the new belt unit 106 and the pressure roller 200 are set on the side plates 602L and 602R on the one end side and the other end side of the apparatus frame 600 (FIG. 15C). The case where only one of the belt unit 110 and the pressure roller 200 is replaced is also included.

  Finally, the pressure support plate 700 is rotated about the pressure release shaft 708 in the opposite direction to return to the first position Z1 from the second position Z2, and the screw 403 removed earlier is tightened to complete the replacement operation. It becomes.

(2-8) Defect Phenomenon and its Mechanism However, the pressure release cam 706 may rotate unexpectedly during this replacement work, and a situation may occur in which the pressure is applied at the end of the replacement work. . If the pressure is applied at the end of the replacement operation and left as it is, plastic deformation (C set) may occur in the elastic layer of the belt 100 or the pressure roller 200.

  This phenomenon is likely to occur when the friction coefficient between the pressure plates 1 and 2 (701 and 702) and the pressure release cam 706 increases due to durability and the like. When the friction coefficient between the pressure plates 1 and 2 (701 and 702) and the pressure release cam 706 increases, the pressure release cam 706 is rotated by the rotation of the pressure plates 1 and 2 (701 and 702) during the replacement operation. (FIG. 16). The detailed mechanism is described below.

(A) Torque for the pressure plate to rotate the pressure release cam In the pressure release mode, the pressure release cam 706 is forced from the pressure plates 1 and 2 (701 and 702) by the pressure springs 1 and 2 (701 and 702). Only P is pressed (FIG. 17).

  When the pressure support plate 700 is rotated around the pressure release shaft 708 in this state, a frictional force F is generated between the pressure plates 1 and 2 (701 and 702) and the pressure release cam 706. Then, the friction force F generates a torque T that tries to rotate the pressure release cam 706.

F = P · μ (N) μ: friction coefficient between pressure plate and pressure release cam T = F · r (N · m) r: radius of pressure release cam (b) Torque holding pressure release cam Pressure support plate When opening 700, the pressure release cam 706 receives torque T in the clockwise direction in FIG. At this time, the pressure release cam 706 is held by the attachment / detachment drive torque T1.

  On the other hand, when the pressure support plate 700 is closed, the pressure release cam 706 receives the torque T in the counterclockwise direction. At this time, the pressure release cam 706 is held by the sum (T1 + T2) of the attachment / detachment drive torque T1 and the fixing drive torque T2. This is because when the pressure release cam 706 is rotated in this direction, the one-way clutch 802a is locked to the drive shaft 808, and the drive train is connected to the pressure roller gear.

(C) Torque relationship Here, the torque T at which the pressure plates 1 and 2 (701, 702) rotate the pressure release cam 706, the drive torque T1 of the detachable drive train, the detachable drive torque T1, and the fixing drive torque. The magnitude relationship with the sum of T2 (T1 + T2) will be described.

  In this embodiment, the initial torque relationship of the fixing device is T <T1 <(T1 + T2). However, when the attaching / detaching operation is repeated, the surfaces of the pressure plates 1 and 2 (701 and 702) and the pressure release cam 706 are scraped, and the pressure that the pressure plates 1 and 2 (701 and 702) try to rotate the pressure release cam 706 is removed. T increases. As a result, a relationship of T1 <T <(T1 + T2) is established.

  In the relationship of T1 <T, when the pressure support plate 700 is opened, the pressure release cam 706 is rotated by the pressure plates 1 and 2 (701 and 702), and the state shown in FIG. 16 is obtained. However, when the pressure support plate 700 is closed, the holding torque (T1 + T2) of the pressure release cam 706 is larger than the torque T for turning the pressure release cam 706. Therefore, the pressure release cam 706 is maintained in the posture shown in FIG. 16, and only the pressure plates 1 and 2 (701 and 702) rotate so as to slide on the surface of the pressure release cam 706.

  Then, the following event occurs at the timing when the pressure plates 1 and 2 (701 and 702) exceed the inflection point 706c of the pressure release cam 706. In other words, the pressure release cam 706 is rotated in the clockwise direction by the force P ′ to be applied to the pressure springs 1 and 2 (704, 705) that has been compressed by the pressure release cam 706 until now (FIG. 19). Then, at the end of the replacement work, it will be in a pressurized state.

  In the initial setting, if T> T1> (T1 + T2), the pressure release cam 706 always rotates with the pressure plates 1 and 2 (701 and 702) by the opening and closing operation of the pressure support plate 700. . In this state, the above situation (pressurized state) does not occur during the replacement work.

  However, the relationship T> T1> (T1 + T2) means that the attachment / detachment torque is increased. When the attachment / detachment torque is increased, the surface of the pressure plate or the pressure release cam becomes noticeable, and problems such as torque increase in attachment / detachment operation and scattering of shaving powder occur. For this reason, it is not preferable to set the relationship T> T1> (T1 + T2).

(9) Gear lock mechanism A gear lock mechanism 910, which is a countermeasure against the above-described defects, will be described with reference to FIGS.

  The gear lock mechanism 910 includes a rotation regulating member (regulating member) 900 and a rotation shaft 902. The rotation restricting member 900 can be rotated about the center of the rotation shaft 902 (FIG. 1). Normally, one end 900a of the rotation restricting member 900 is in contact with the abutting portion 700a of the pressure support plate 700, and the other end 900b of the rotation restricting member is separated from the pressure release idler gear 2 (804) (FIG. 1).

  When the pressure support plate 700 is opened when replacing the belt unit 110 or the pressure roller 200, the abutting portion 700a of the pressure support plate 700 and the one end 900a of the rotation regulating member 900 are separated. The rotation regulating member 900 rotates toward the pressure release idler gear 2 (804) by its own weight (FIG. 21). Then, the other end 900b of the rotation restricting member enters between the teeth of the pressure release idler gear 2 (804) to restrict the rotation of the pressure release idler gear 2 (804). In this way, the rotation restricting member 900 is in contact with the drive train M1 to lock the operation in only one direction.

  The rotation direction of the pressure release idler gear 2 (804) will be described with reference to FIG. When the pressure support plate 700 is opened, that is, when the pressure release cam 706 is about to rotate in the clockwise direction, the pressure release idler gear 2 (804) attempts to rotate in the clockwise direction.

  When the pressure release idler gear 2 (804) rotates in the clockwise direction, the other end 900b of the rotation restricting member 900 bites into the tooth surface of the pressure release idler gear 2 (804) and receives force. Therefore, the rotation restricting member 900 is not separated from the pressure release idler gear 2 (804) by the rotational torque of the pressure release idler gear 2 (804).

  When the pressure support plate 700 is closed, that is, when the pressure release cam 706 is going to rotate in the counterclockwise direction, the pressure release idler gear 2 (804) tends to rotate in the counterclockwise direction. At this time, the other end 900b of the rotation restricting member receives a force away from the pressure release idler gear 2 (804) by the rotational torque of the pressure release idler gear 2 (804). However, when the pressure support plate 700 is closed, the pressure release cam 706 is held at the sum (T1 + T2) of the attachment / detachment drive torque T1 and the fixing drive torque T2, and the holding torque is sufficiently large. Since (804) does not rotate, there is no problem.

  As described above, the rotation regulating member 900 regulates the rotation of the pressure release idler gear 2 (804), so that the pressure release cam 706 can be reliably prevented from being rotated by the pressure plates 1 and 2 (701, 702). . As a result, it is possible to prevent the fixing device F from being pressed during the replacement operation of the belt unit 106 and the pressure roller 200.

  The characteristic configuration of the fixing device F according to the first embodiment is summarized as follows. A belt 100 and a pressure roller 200 are provided to heat the toner image t on the paper at the nip portion N therebetween. There are pressure members 701 and 702 for pressing at least one of them toward the other. A pressing force changing mechanism 720 (L, R) that can change the pressing force of the nip portion N by the pressing members 701 and 702 to a first pressing force and a second pressing force lower than the first pressing force. . A driving train M1 for transmitting a driving force to the pressure changing mechanism is provided.

  Further, the pressure support plate 700 that supports the pressure members 701 and 702 is provided. The pressure support plate 700 is fixed to the device to enable the device operation, and the fixing is released to enable the belt 100 and the pressure roller 200 to be taken out from at least one device. It can move to a second position Z2 different from the first position Z1.

  A rotation restricting member 900 that performs a contact / separation operation with respect to the drive train M <b> 1 as the pressure support plate 700 moves is provided. The rotation regulating member 900 is separated from the drive train M1 when the pressure support plate 700 is located at the first position Z1, and contacts the drive train M1 when located at the second position Z2. Thus, the operation of the drive train M1 is locked.

Example 2
The second embodiment is different from the first embodiment only in the configuration of the gear lock mechanism.

(10) Gear Lock Mechanism A gear lock mechanism 910 according to the second embodiment will be described with reference to FIGS. The gear lock mechanism 910 includes a rotation restricting member 900, an urging member 901, and a rotating shaft 902. The rotation restricting member 900 is rotatable about a rotation shaft 902 and is urged clockwise by the urging member 901 (FIG. 22).

  Normally, one end 900a of the rotation restricting member 900 abuts against the abutting portion 700a of the pressure support plate 700, and the other end 900b of the rotation restricting member 900 is separated from the pressure release idler gear 2 (804) ( FIG. 23).

  When replacing the belt unit 110 or the pressure roller 200, the pressure support plate 700 is opened. Then, the abutting portion 700a of the pressure support plate 700 and the one end 700a of the rotation restricting member 900 are separated, and the rotation restricting member 900 is rotated toward the pressure release idler gear 2 (804) by the biasing member 901. Then, the other end 900b of the rotation restricting member enters between the teeth of the pressure release idler gear 2 (804) to restrict the rotation of the pressure release idler gear 2 (804) (FIG. 24).

  Regardless of the rotation direction of the pressure release idler gear 2 (804), the rotation restricting member 900 can restrict the rotation of the pressure release idler gear 2 (804) by the biasing force of the biasing member 901.

  As described above, the rotation regulating member 900 regulates the rotation of the pressure release idler gear 2 (804), so that the pressure release cam 706 can be reliably prevented from being rotated by the pressure plates 1 and 2 (701, 702). . As a result, it is possible to prevent the fixing device from being pressed during the replacement operation.

<< Other Examples >>
(1) In the embodiment, the image heating apparatus has been described by taking as an example a fixing apparatus that heats and fixes an unfixed toner image formed on a sheet (on a recording material), but is not limited thereto. The present invention can also be applied to an apparatus (gloss enhancement apparatus) that increases the gloss (glossiness) of an image by reheating a toner image fixed or assumed on the paper P.

  (2) The image heating apparatus may have a device configuration in which the first rotating body and the second rotating body are both roller bodies, or may be an apparatus configuration in which both are endless belts. An apparatus configuration in which a roller body and the other is an endless belt may be employed.

  (3) The pressurizing mechanism of the image heating apparatus may be configured to pressurize at least one of the first rotating body and the second rotating body toward the other.

  (4) The image heating device may be any device configuration in which at least one of the first rotating body and the second rotating body is externally heated or internally heated by a heater, and the heater is not limited to the induction heating in the embodiment. . It may be a contact type heater or heat ray irradiation heating.

  (5) The image forming apparatus is not limited to an image forming apparatus that forms a full-color image as in the embodiment, and may be an image forming apparatus that forms a monochrome image. In addition, the image forming apparatus can be implemented in various applications such as a copying machine, a FAX, and a multifunction machine having a plurality of these functions in addition to necessary equipment, equipment, and housing structure.

  F..Image heating device (fixing device), 100..First rotating body, 200..Second rotating body, 701.702..Pressure member, 720..Pressure changing mechanism, M1..Drive Row, 700 ... Pressure support member, 900) ... Control member

Claims (7)

First and second rotating bodies for heating a toner image on a recording material at a nip portion therebetween;
A pressing member for pressing at least one of the first and second rotating bodies toward the other; and
A pressing force changing mechanism capable of changing the pressing force of the nip portion by the pressing member into a first pressing force and a second pressing force lower than the first pressing force;
A drive train for transmitting a drive force to the pressure change mechanism;
A first position that supports the pressure member and is fixed to the apparatus to enable the apparatus to operate, and the fixed state is released and the first and second rotating bodies are removed from at least one of the apparatuses. A pressure support member movable to a second position different from the first position;
A regulating member that performs a contact / separation operation with the drive train in accordance with the movement of the position of the pressure support member,
The regulating member is separated from the drive train when the pressure support member is located at the first position, and is in contact with the drive train when located at the second position. An image heating apparatus that locks an operation of the drive train.   The image heating apparatus according to claim 1, wherein the regulating member is in contact with the drive train to lock the operation in only one direction.   The image heating apparatus according to claim 1, further comprising an urging member that urges the restricting member so as to come into contact with the drive train.   The image heating apparatus according to claim 1, wherein the pressing force changing mechanism can substantially cancel the pressing force of the nip portion.   The image heating apparatus according to any one of claims 1 to 4, wherein both the first and second rotating bodies are rollers.   The image heating apparatus according to claim 1, wherein one of the first and second rotating bodies is an endless belt and the other is a roller.   2. The endless belt, wherein the first rotating body corresponds to a side of a recording material carrying an unfixed toner image and is driven by the second rotating body to rotate. The image heating apparatus according to any one of 1 to 4.