JP2016148759A - Image heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image heating device that alleviates deterioration of a heating rotary due to excessive heating of the heating rotary arising from overheating of a radiant heat source upon occurrence of jamming and the like.SOLUTION: An image heating device includes: a heating rotary 202 that heats a developer image t on a recording material; a radiant heat source 201 that emits radiant heat; a reflection member 203 that reflects the radiant heat to be emitted by the radiant heat source toward a heated part 208 serving as one part area in a peripheral direction of the heating rotary; a heat absorption member 207 in which a heat capacity is equal to or more than 6(J/°C), and a face opposing the radiant heat source has a radiation factor equal to or more than 0.7, and of which a length is longer than that of the radiant heat source; a movement mechanism of the heat absorption member; and a control unit 300 that controls the movement mechanism in such a way that, when rotating the heating rotary, the heat absorption member is located at a first position A where the heating rotary and a reflection surface of the reflection member do not oppose each other, and, when stopping the rotation of the heating rotary, a power supply to the radiant heat source is stopped and the heat absorption member is located at a second position B where the heating rotary and the reflection surface of the reflection member oppose each other.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image heating apparatus suitable for use as a fixing device mounted on an image forming apparatus such as a multifunction machine, a copier, a printer, or a fax machine.

  The image forming apparatus forms an image on a recording material using an image forming process such as an electrophotographic system, an electrostatic recording system, a magnetic recording system, or the like. The recording material is an image on which an image is formed by an image forming apparatus, and includes, for example, paper, an OHT sheet (resin sheet), and the like.

  As an image heating device, a fixing device that heats and fixes an unfixed toner image formed on a recording material as a fixed image on the recording material, a toner image that is assumed to be fixed on the recording material, or a toner image that has been heat-fixed once is heated again. Examples thereof include an image quality reforming device that improves the glossiness by applying pressure. The following will be described as a fixing device.

  A fixing device used in an image forming apparatus is known which includes a thin endless belt (fixing film) made of a metal base material and an elastic rubber layer as a heating rotator. Thus, by providing a thin belt with a reduced heat capacity, the energy required for heating the belt can be greatly reduced. Therefore, warm-up time (time required from normal temperature condition such as power supply to printable temperature (reload temperature)) and first print time (after receiving print request, printing operation is performed through print preparation. (Time until paper discharge is completed) can be shortened.

  In addition, a radiation heat source capable of directly heating the belt is used as a heat source for further energy saving and shortening of the first print time, and a halogen heater is used as the heat source.

  However, a radiant heat source represented by a halogen heater does not stop generating heat immediately after the power supply to the heater is cut, and continues to generate heat for several seconds (hereinafter referred to as overshoot) while being attenuated. Therefore, when a situation where the belt does not rotate occurs, such as when a jam occurs, the heated portion of the belt may be excessively heated even if the power supply is cut, and the belt may be damaged.

  In Patent Documents 1 and 2, in order to prevent the heated air in the belt from locally heating the belt, the heat of high-temperature air is prevented from being transferred to the belt by using a shielding member having low thermal conductivity. A configuration has been proposed.

JP2013-242383A JP 2013-174785 A

  However, when heating is cut off, heating by radiation is dominant, and the above-described technique cannot reduce damage caused by excessive heating to the belt that has stopped rotating when a jam occurs.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image heating apparatus that reduces deterioration of a heating rotator due to excessive heating due to overshoot of a radiant heat source with respect to the heating rotator that has stopped rotating when a jam occurs.

  A typical configuration of an image heating apparatus according to the present invention for solving the above-described problems is an image heating apparatus that thermally fixes a developer image on a recording material, and includes a cylindrical heating rotator and the heating unit. A radiant heat source that emits radiant heat disposed inside the rotator, a sliding contact member that is disposed so as to slidably contact the inner surface of the heating rotator, and a radiant heat generated by the radiant heat source around the inner surface of the heating rotator. Pressurization that forms a nip portion between the heating rotator by sandwiching the heating rotator between the reflective member that reflects toward the heated part that is a partial region in the direction and the sliding contact member A member, and a heat capacity of 6 (J / ° C.) or more, and a surface facing the radiant heat source has a radiation rate of 0.7 or more, and a heat absorbing member having a length equal to or greater than a length of the radiant heat source; A rotating mechanism for rotating and moving the heat absorbing member, and the heat absorbing portion when the heating rotating body rotates. When the rotation of the heating rotator is stopped, power supply to the radiant heat source is stopped and the heat absorbing member is heated and rotated so that the heating rotator and the reflecting surface of the reflecting member are not opposed to each other. And a control unit that controls the rotation mechanism so that the body and the reflecting surface of the reflecting member are located at a second position facing each other.

  In addition, another representative configuration of the image heating apparatus according to the present invention for solving the above-described problems includes a heating rotator for heating a developer image on a recording material, a radiant heat source for generating radiant heat, and the radiant heat. A reflecting member that reflects the radiant heat generated by the source toward a heated portion that is a partial region in the circumferential direction of the heating rotator, and a surface that has a heat capacity of 6 or more and that faces the radiant heat source has an emissivity of 0. 7 or more, the heat absorbing member having a length longer than the length of the radiant heat source, the moving mechanism of the heat absorbing member, and the heat absorbing member reflecting the heating rotator and the reflecting member during rotation of the heating rotator. The moving mechanism is controlled so as to be positioned at a first position where the surfaces do not face each other, and when the rotation of the heating rotator is stopped, power supply to the radiant heat source is stopped and the heat absorbing member is connected to the heating rotator and the reflecting member. At the second position where the reflective surfaces of And having a control unit which controls the moving mechanism so as to location.

  ADVANTAGE OF THE INVENTION According to this invention, deterioration of the heating rotary body by the excessive heating by the overshoot of a radiation heat source with respect to the heating rotary body which stopped rotation at the time of jam generation etc. can be reduced.

FIG. 3 is an enlarged cross-sectional model view of the main part of the fixing device according to the first embodiment. Similarly, a cross-sectional view of the image forming apparatus Expanded cross-sectional model view of the main part of the fixing device Longitudinal front view of the main part of the fixing device. External perspective view of reflector External perspective view of endothermic assembly Block diagram of the fixing device control system Cross section of heat absorbing member Graph of correlation between emissivity of radiant heat absorption layer and rising temperature of belt Graph of correlation between heat capacity of endothermic member and rising temperature of endothermic member Operation control flow chart of fixing device Graph of effect confirmation experiment result of heat absorbing member Configuration diagram of fixing device in embodiment 2

Embodiment 1
(1) Image Forming Unit FIG. 2 is a cross-sectional view along the sheet conveying direction of an example of an image forming apparatus 100 in which the image heating apparatus according to the present invention is mounted as a fixing device (fixing device) 200. The image forming apparatus 100 is an intermediate transfer type, tandem four-color full-color electrophotographic laser printer, which can form a full-color toner image (developer image) on a sheet P and print it out.

  The sheet P is a recording material (recording medium) on which a toner image can be formed, and examples thereof include plain paper, resin sheets that are substitutes for plain paper, cardboard, overhead projector sheets, glossy paper, postcards, and envelopes. Hereinafter referred to as paper.

  Since the printer configuration other than the fixing device 200 belongs to the public knowledge, the following description of the printer configuration will be simplified. An image forming unit 10 includes four image forming units U (UY, UM, UC, UBk), a laser scanner unit 12 as an exposure unit, and an intermediate transfer belt unit 13. Each image forming unit U includes a rotating drum type photoreceptor 11 and a charger, a developing device, a primary transfer device, a cleaning device, etc. (all not shown) as image forming process means acting on the photosensitive drum 11.

  Then, a yellow (Y) toner image is formed on the photoconductor 11 of the image forming unit UY, and a magenta (M) toner image is formed on the photoconductor 11 of the image forming unit UM. Further, a cyan (C) toner image is formed on the photoconductor 11 of the image forming unit UC, and a black (Bk) toner image is formed on the photoconductor 11 of the image forming unit UBk. The four color toner images are sequentially superimposed and preliminarily transferred onto the intermediate transfer belt 14 that circulates and moves from the photoreceptor 11 of each image forming unit U to form a full-color toner image on the intermediate transfer belt 14. Is done.

  The full-color toner image is secondarily transferred onto the paper P at a secondary transfer nip portion that is a pressure contact portion between the intermediate transfer belt 14 and the secondary transfer roller 15. The sheets P are fed one by one from the sheet feeding cassette 17 of the sheet feeding unit 16 or the sheet feeding unit 16 or the multi sheet feeding tray 19 and fed to the registration roller pair 20. The registration roller pair 20 receives the paper P once, and straightens it when the paper P is skewed. Then, the registration roller pair 20 sends the paper P to the secondary transfer unit in synchronization with the toner image on the intermediate transfer belt 14.

  The sheet P is subjected to secondary transfer of the full-color toner image on the intermediate transfer belt 14 side at the secondary transfer portion, and then conveyed to the fixing device 200 and subjected to toner image fixing processing. The sheet P exiting the fixing device 200 is discharged out of the apparatus by the discharge roller 21 as an image formation (single-sided print). In the duplex mode, the sheet P on which the first-side image has been formed exiting the fixing device 200 is introduced into the recirculation conveyance unit 22 of the sheet feeding unit 16, reversed, and fed into the registration roller pair 20 again. Then, the paper is transported along the path of the secondary transfer unit and the fixing device 200 and is discharged out of the apparatus by the discharge roller 21 as a double-sided image formed product (double-sided print).

  In the image forming apparatus 100 of this example, the conveyance of the paper P in the apparatus is performed by central reference conveyance. In this paper conveyance, the center line in the width direction of the paper P is centered in the width direction of the paper conveyance path for any of the papers P that can be used (passable) in the apparatus (paper of any size). It is a form that passes the paper together.

(2) Fixing Device (2-1) Overall Schematic Configuration The fixing device 200 of this example is a belt heating type and pressure roller driving type (tensionless type) image heating device. FIGS. 1 and 3 are enlarged cross-sectional schematic views of the main part of the fixing device 200. FIG. 1 shows a state where the heat absorbing member 207 is located at the first position (standby position) A, and FIG. A state 207 is in a second position (operating position) B is shown. FIG. 4 is a longitudinal front view of the main part of the fixing device 200 with the middle portion omitted, and shows a state where the heat absorbing member 207 is located at the second position B. FIG.

  Here, in this example, regarding the fixing device 200 or its constituent members, the front side is the surface viewed from the paper inlet side, the back surface is the opposite side (paper outlet side), and the left and right sides are the front side of the device. When viewed from the left (one end side) or right (the other end 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 paper transport direction a. The longitudinal direction (or the width direction) and the paper width direction are directions substantially parallel to the direction orthogonal to the paper transport direction a on the paper transport path surface. The short direction is a direction substantially parallel to the paper transport direction a on the paper transport path.

  The fixing device 200 includes a fixing belt (hereinafter referred to as a belt) 202 as a cylindrical (endless) first rotating body (a heating rotating body that heats (heat-fixes) a developer image on a recording material). . The pressure pad 204 is disposed inside the belt 202 and serves as a sliding contact member that is in sliding contact with the inner surface of the belt. A halogen heater (hereinafter referred to as a heater) 201 as a radiant heat source (heating element) that emits radiant heat disposed inside the belt 202 is included. A reflection plate 203 is provided as a reflection member that is disposed inside the belt 202 and reflects radiant heat from the heater 201 toward the belt 202.

  A heat absorbing member 207 is provided inside the belt 202 and is movable between a first position A and a second position B, which will be described later. Further, a pressure roller 205 is provided as a second rotating body (opposing rotating body, pressure member) that forms a nip portion N in contact with the pressure pad 204 via the belt 202.

  The belt 202 is a heating member that transfers heat. The belt 202 in this example is a thin and flexible belt having a four-layer composite structure of a release layer, an elastic layer, a base layer, and an inner surface coating layer, which is a surface layer in order from the outer side to the inner side. Exhibits a substantially cylindrical shape due to its elasticity.

  As the release layer, a fluororesin material having a thickness of 100 μm or less, preferably 20 to 70 μm can be used. Examples of the fluororesin layer include PTFE, FEP, and PFA. In this example, a 30 μm thick PFA tube was used.

  The elastic layer can be made of a rubber material having a thickness of 1000 μm or less, preferably 500 μm or less in order to reduce the heat capacity and improve the quick start. For example, silicone rubber, fluorine rubber and the like can be mentioned. Silicone rubber having a rubber hardness of 10 degrees (JIS-A), a thermal conductivity of 1.3 W / m · K, and a thickness of 300 μm was used.

  Similarly to the elastic layer, the base material can be made of a heat-resistant material (resin material or metal material) having a thickness of 100 μm or less, preferably 50 μm or less and 20 μm or more in order to improve the quick start property. For example, a metal belt such as SUS or nickel can be used. In this example, a cylindrical nickel metal belt having a thickness of 30 μm and a diameter of 30 mm was used.

  Since the inner surface coating layer is in contact with the pressure pad 204, a heat-resistant resin layer, ceramics, metal, or the like can be used. Also, engineering plastics can be mentioned. For example, polyimide, polyimide amide, PEEK, polytetrafluoroethylene resin (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer resin (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin ( PFA). Moreover, diamond like carbon (DLC) etc. are mentioned.

  The pressure pad 204 is made of a highly rigid member such as an aluminum material or a steel material. If necessary, the pressure pad 204 is slid on the sliding contact surface with the inner surface of the belt 202 via a heat insulating member, a sliding member, or a heat insulating member. A sex member or the like can also be provided. The pressure pad 204 is a member that is long in the left-right direction, and is disposed between the opposing side plates 210L and 210R on the left and right (one end side and the other end side) of the fixing device casing.

  The belt 202 is loosely fitted to the pressure pad 204. The width dimension (length dimension) of the belt 202 is substantially the same as the separation dimension of the side plates 210L and 210R. Arc-shaped guide members 211L and 211R that are respectively fitted into the left and right ends of the belt 202 are disposed on the inner surfaces of the side plates 210L and 210R in a mirror-symmetric manner.

  The heater 201 is supported between the side plates 210 </ b> L and 210 </ b> R by fitting the bases at both left and right ends into sockets 212 </ b> L and 212 </ b> R disposed on the side plates 210 </ b> L and 210 </ b> R, respectively. The heater 201 may be another heating element (heating body) such as a carbon heater.

  In this example, the reflecting plate 203 is a metal groove member (channel member) in a form in which the side wall plate portions 203b and 203b on both sides in the cross section are opened outward by a predetermined angle with respect to the bottom plate portion 203a. The inner surface is mirror-finished as a reflective surface. The reflection plate 203 has a length that is equal to or greater than the length of the effective heat generation area of the heater 201. FIG. 5 is an external perspective view of the reflection plate 203.

  The reflection plate 203 is arranged substantially parallel to the heater 201 on the inner side of the belt 202 with the radiant heat reflection side facing upward, and the left and right ends are respectively attached to the side plates 210L and 210R. -It is supported between 210R.

  The reflecting plate 203 reflects the radiant heat of the heater 201 toward the inner surface of the belt 202. In this example, the reflecting plate 203 reflects the radiant heat of the heater 201 upward. As a result, the belt 202 is heated by the direct radiant heat from the heater 201 and the radiant heat reflected by the reflecting plate 203 with the range region 208 of FIG. The heating region 208 is a heated portion that is a partial region in the circumferential direction of the belt 202.

  The pressure roller 205 is a heat-resistant elastic roller having a cored bar 205a and an elastic layer 205b on the outer periphery thereof. The elastic layer 205b is, for example, a heat-resistant rubber such as silicone rubber or fluorine rubber, or a foam of silicone rubber. The pressure roller 205 is arranged substantially parallel to the pressure pad 204 on the lower side of the belt 202, and the left and right shaft portions 205c are rotatable between the side plates 210L and 210R via bearing members 213L and 213R, respectively. It is supported by. A first drive gear G1 is disposed substantially concentrically and integrally at the end of the right shaft 205c.

  The pressure pad 204 is inserted into the vertical guide slots 214L and 214R formed in the side plates 210L and 210R at the left and right ends, respectively, and has a degree of freedom of parallel movement in the vertical direction along the guide slots. is there. The pressure pad 204 is pressed and biased downward by biasing members (not shown) at both left and right ends, and resists the elasticity of the elastic layer 205b against the pressure roller 205 via the belt 202. Are pressed with a predetermined pressure. By this pressure contact, a nip portion N having a predetermined width is formed between the belt 202 and the pressure roller 205 in the short side direction (paper conveyance direction).

  The driving force of the first motor M1 controlled by the control unit 300 (FIG. 7) is transmitted to the first driving gear G1 via a drive transmission mechanism (not shown). As a result, the pressure roller 205 is driven to rotate at a predetermined peripheral speed in the counterclockwise direction of the arrow R205 in FIG.

  A rotational force (rotational torque) acts on the belt 202 by a frictional force at the nip portion N between the pressure roller 205 and the outer surface of the belt 202 due to the rotation of the pressure roller 205. As a result, the belt 202 slides in close contact with the surface (downward surface) of the pressure pad 204 at the nip portion N at the inner surface of the belt 202, and the rotation peripheral speed of the pressure roller 205 in the clockwise direction indicated by the arrow R202 in FIG. It is driven and rotated at the corresponding peripheral speed.

  The heater 201 generates heat by receiving power supply from the power supply unit 301 controlled by the control unit 300 via the sockets 212L and 212R. Radiant heat of the heater 201 reaches the inner surface of the belt 202 directly and is reflected by the reflecting plate 203, and the belt 41 is heated from the inside in the heating region 208.

  TH is a temperature sensor (contact thermometer: thermistor) disposed in contact with the inner surface of the belt at the central portion in the width direction of the belt 202, and a belt passing area through which large and small width sheets usable in the apparatus pass. Detect (measure) the temperature of The temperature sensor TH is supported by the pressure pad 204 via the elastic support member 215 and elastically contacts the inner surface of the belt by the elasticity of the elastic support member 215. Electrical information related to the temperature detected by the temperature sensor TH is input to the control unit 300 via wiring (not shown).

(2-2) Fixing Operation The control unit 300 activates the first motor M1 based on the image formation start signal and starts to rotate the pressure roller 205. In addition, power supply from the power supply unit 301 to the heater 201 is started. As a result, the belt 202 is driven and rotated from the inside by the radiant heat of the heater 201. That is, the direct radiant heat from the heater 201 and the radiant heat reflected by the reflector 203 reach the heating area 208 of the belt 202, and the belt 202 rotates to pass through the heating area 208, and the entire belt 202 is heated. The

  The pressure pad 204 also functions as a rotation guide member for the belt 202. The width dimension of the belt 202 is substantially the same as the separation dimension of the side plates 210L and 210R. Therefore, the left and right ends of the belt 202 are restricted by the inner surfaces of the side plates 210L and 210R on the side, respectively, and the lateral movement of the belt 202 during belt rotation is restricted.

  Further, the guide members 211L and 211R guide the inner peripheral surfaces of both ends of the belt 202 so that the shapes in the circumferential direction of both the left and right ends of the belt 202 when the belt 202 rotates are regulated. In order to make the driven rotation of the belt 202 smooth, a lubricant may be interposed (applied) at the sliding contact portion between the belt 202 and the pressure pad 204.

  The control unit 300 controls the power supplied to the heater 201 so that the temperature of the belt 202 is raised to a predetermined fixing temperature based on the temperature information detected by the temperature sensor TH, and the fixing temperature is maintained. Adjust the temperature.

  In this fixing device state, the paper P carrying the unfixed toner image t from the image forming unit 10 side is introduced into the fixing device 200 and is nipped and conveyed by the nip portion N. As a result, the toner image t and the paper P are heated and pressed by the heat of the belt 202 and the nip pressure, whereby the toner image t is fixed to the paper P as a fixed image. The sheet P that is nipped and conveyed by the nip portion N is separated from the surface of the belt 202 by the curvature at the sheet exit portion of the nip portion N and is discharged and conveyed from the fixing device 200.

(2-3) Heat-absorbing member The heat-absorbing member 207 has a first position A (FIG. 1) where the inner surface of the belt 202 and the reflecting surface of the reflecting plate 203 do not face each other inside the belt 202, and the inner surface of the belt 202 and the reflecting plate. It is possible to move between the second position B (FIG. 3) where the reflecting surface 203 faces. Hereinafter, the position A in FIG. 1 of the heat absorbing member 207 is referred to as a standby position, and the position B in FIG. 3 is referred to as an operating position.

  The standby position A of the heat absorbing member 207 is retracted from the position corresponding to the heating region 208 of the belt 202, and the heat input from the heater 202 and the reflector 203 to the heating region 208 of the belt 202 (the arrival of radiant heat). ). That is, the standby position A of the heat absorbing member 207 is a position where the belt 202 can be heated. Further, the operation position B of the heat absorbing member 207 is a position where the heat input from the heater 202 and the reflection plate 203 to the heating area 208 of the belt 202 is interrupted by intervening at a position corresponding to the heating area 208.

  The heat absorbing member 207 is a plate-like member that has a length equal to or greater than the length of the effective heat generation area of the heater 201 and has a short dimension that can sufficiently cover the upper side of the heater 201 in the left-right direction. The endothermic member 207 of this example has an inner and outer two-layer structure with a circular cross section as shown in the cross section model diagram of FIG. The outer layer (second layer) facing the inner peripheral surface of the belt 202 is a heat storage layer 207a, and the inner layer (first layer) facing the heater 202 is a radiation heat absorption layer 207b. The heat absorbing member 207 has a heat capacity of 6 (J / ° C.) or more, and the surface (the inner surface of the heat absorbing member) facing the heater 202 at the operating position B has a radiation rate (absorption rate) of 0.7 or more. This will be described later.

  In this example, the heat absorbing member 207 is disposed by fitting the left and right ends into semicircular arc shaped slit guide holes 216R and 216L formed on the side plates 210L and 210R in mirror symmetry. The semicircular arc-shaped slit guide holes 216R and 216L are substantially concentric with the center of rotation of the cylindrical belt 202. The heat absorbing member 207 is slidably moved between the standby position A and the operating position B by being guided by the semicircular arc-shaped slit guide holes 216R and 216L.

  The left and right end portions of the heat absorbing member 207 protrude from the slit guide holes 216R and 216L to the outside of the side plates 210L and 210R, respectively, and arm plates 207La and 207Ra are attached symmetrically to the left and right protruding ends, respectively. The shafts 207Lb and 207Rb are coaxially planted on the end portions of the arm plates 207La and 207Ra so as to protrude outward.

  The left shaft portion 207Lb is rotatably supported via a bearing member 218L on a support plate 217L that is fixedly disposed outside the left side plate 210L. Further, the right shaft portion 207Rb is rotatably supported via a bearing member 218R on a support plate 217R that is fixedly disposed outside the right side plate 210R. A second drive gear G2 is disposed substantially concentrically and integrally at the end of the right shaft portion 207Rb.

  FIG. 6 is an external perspective view of the assembly of the heat absorbing member 207, the arm plates 207La and 207Ra, the shaft portions 207Lb and 207Rb, and the second drive gear G2. The forward / reverse driving force of the second motor M2 controlled by the control unit 300 is transmitted to the second driving gear G2 via a drive transmission mechanism (not shown). In a state where the heat absorbing member 207 is positioned at the standby position A, the positive driving force of the second motor M2 is transmitted to the second driving gear G2, and thus the heat absorbing member 207 is moved to the operating position B and held. In the state where the heat absorbing member 207 is located at the operating position B, the reverse driving force of the second motor M2 is transmitted to the second driving gear G2, so that the heat absorbing member 207 is moved to the standby position A and held.

  In this example, the slit guide hole 216, the arm plates 207La and 207Ra, the shaft portions 207Lb and 207Rb, the support plate 217, the bearing member 218, the drive gear G2, the motor M2, and the like move (rotate) the heat absorbing member 207. This constitutes a mechanism (rotating mechanism).

  The time over which the heater 202 is energized from the stop is several seconds, and the upper limit of the heat generation amount does not exceed 2000 W. Therefore, in this example, the heat absorbing member 207 is configured so as not to exceed the upper limit temperature 250 ° C. of the belt 202 when the heat generation amount upper limit due to overshoot is 2000 W.

  Further, since the heat absorbing member 207 is in the belt 202, it is necessary to prevent the heat resistant temperature of the belt 202 from exceeding 300 ° C. when the overshoot of the heater 201 has a heat generation upper limit of 2000 W.

  9 shows a state where the heat absorption member 207 is moved to the operating position B as shown in FIG. 3 to block heat input to the heating region 208 of the belt 202, and the temperature of the belt 202 rises when the heating value of the heater is 2000W. It is the graph which showed. The emissivity on the horizontal axis is the emissivity of the radiation endothermic layer 207b of the endothermic member 207. When the emissivity decreases, the temperature of the belt 202 rises due to the amount of heat leaked by the heat absorbing member 207. The upper limit temperature of use of the belt 202 is 250 ° C., and it is necessary to configure the heat absorbing member 207 so as not to exceed this. Therefore, in this example, the radiation rate of the radiation endothermic layer 207b is set to 0.7 or more.

  FIG. 10 shows the temperature rise of the heat absorbing member 207 when the heat generation amount of the heater is 2000 W in the state where the heat absorbing member 207 is moved to the operating position B as shown in FIG. It is the graph which showed. The heat capacity of the heat absorbing member 207 is plotted on the horizontal axis, and the temperature of the heat absorbing member 207 is plotted on the vertical axis. When the heat capacity increases, the temperature increase of the heat absorbing member 207 is suppressed. In this example, the heat capacity of the heat absorbing member 207 is set to 6 J / ° C. or higher so that the heat absorbing member 207 has a heat resistant temperature of 300 ° C. or lower of the belt 202.

  The configuration of the heat absorbing member 207 is summarized as follows. The heat absorbing member 207 includes at least one of a first layer (radiant heat absorbing layer) 207b on the side facing the heater 201 in the operating position (second position) B and a second layer (heat storage layer) 207a facing the inner surface of the belt 202. It is a two-layer structure. The first layer 207b has an emissivity of 0.7 or more, the second layer 207a has a higher heat capacity than the first layer 207b, and the combined heat capacity of the first layer 207b and the second layer 207a is 6 (J / ° C.). That's it.

  FIG. 11 is an operation control flowchart of the fixing device 200 performed by the control unit 300. In this example, when the fixing device 200 is on standby (S1), the control unit 300 stops the driving of the first motor M1. That is, the rotation of the pressure roller 205 and the belt 202 is stopped. Power supply to the heater 201 is stopped. The heat absorbing member 207 is held at the operating position B in FIG.

  The control unit 300 starts driving the first motor M1 and supplying power to the heater 202 based on a predetermined control signal of the image forming sequence of the image forming apparatus 100. Further, the second motor M2 is reversely driven to move the heat absorbing member 207 from the operating position B of FIG. 3 to the standby position A of FIG. 1 and hold it at the standby position A (S2). As a result, the radiant heat directly from the heater 201 and the radiant heat reflected by the reflector 203 reach the heating area 208 of the belt 202 and pass through the heating area 208 as the belt 202 rotates, and the entire belt 202 is heated. Is done.

  Then, the control unit 300 controls the power supplied to the heater 201 so that the temperature of the belt 202 is raised to a predetermined fixing temperature based on the temperature information detected by the temperature sensor TH and the fixing temperature is maintained. The temperature of the belt 202 is adjusted (S3).

  In this state, the sheet P carrying the unfixed toner image t from the image forming unit 10 is introduced into the fixing device 200, and is nipped and conveyed by the nip N (S4). As a result, the toner image t and the paper P are heated and pressed by the heat of the belt 202 and the nip pressure, whereby the toner image t is fixed to the paper P as a fixed image.

  The control unit 300 stops power supply to the heater 202 based on a predetermined control signal at the end of the image forming sequence or a jam detection signal from the paper jam detecting unit 302 during the execution of the image forming sequence. Further, the second motor M2 is driven forward to move the heat absorbing member 207 from the standby position A in FIG. 1 to the operating position B in FIG. Further, the driving of the first motor M1 is stopped. That is, the rotation of the pressure roller 205 and the belt 202 is stopped (S5 to S7).

  Since the heat absorbing member 207 is moved to the operating position B and held, excessive heating of the belt 202 due to overshoot of the heater 201 is suppressed even when the belt 202 stops rotating.

The control unit 300 displays an error on the display unit 303 when the drive stop of the first motor M1, that is, the rotation stop of the belt 202 is based on the jam detection signal from the jam detection unit 302 (S8).
The paper jam detection unit 302 detects the occurrence and location of a jam based on the input timing of the paper arrival detection signal and the passage detection signal from the paper sensors arranged at various points in the paper conveyance path. The control unit 300 urgently stops the image forming operation of the image forming apparatus based on the jam detection signal from the paper jam detection unit 302.

  The control of the control unit 300 is summarized as follows. When the belt (heating rotator) 202 rotates, the moving mechanism of the heat absorbing member 207 is controlled so that the heat absorbing member 207 is positioned at a standby position (first position) A where the belt 202 and the reflecting surface of the reflecting plate 203 do not face each other. When the rotation of the belt 202 is stopped, power supply to the heater (radiant heat source) 201 is stopped, and the heat absorbing member 207 absorbs heat so that the belt 202 and the reflecting surface of the reflecting plate 203 face each other at an operating position (second position) B. The moving mechanism of the member 207 is controlled.

  The following are examples of the heat absorbing member 207 and comparative examples.

[Example 1]
The heat storage layer 207a was an iron plate having a thickness of 1 mm. The radiation endothermic layer 207b is a graphite sheet with high radiation rate and good thermal conductivity (for example, SPREADERSHIELD (registered trademark) manufactured by GRAF TECH) in order to convert heat rays to heat with high efficiency and to uniformly transfer heat to the heat storage layer 207a. ) To give a radiation rate of 0.7.

[Example 2]
The heat storage layer 207a is an iron plate having a thickness of 1 mm, and the radiation heat absorption layer 207b is black body spray (for example, OP-96929 manufactured by KEYENCE) and the radiation rate is set to 0.94.

[Comparative Example 1]
No endothermic member. The heat quantity overshooted by the heater 201 enters the belt 202 as it is.

[Comparative Example 2]
An aluminum plate having a thickness of 1 mm was used as the heat absorbing member 207.

[Comparative Example 3]
A quartz glass plate having a thickness of 1 mm is used as the heat storage layer 207a of the heat absorbing member 207, and the radiation rate is set to 0.94 using a black body spray (for example, OP-96929 manufactured by KEYENCE Corp.) for the radiation heat absorbing layer 207b.

[Conventional example]
Quartz glass having a thickness of 1 mm and an emissivity of 0.4 was used as the shielding member.

[Confirmation of effect of endothermic member]
As a confirmation experiment, the heater 201 generates heat while idling the fixing device, and when the belt 202 is heated to 200 ° C., the rotation of the pressure roller 205 and the belt 202 is stopped. Then, the heat absorbing member 207 is moved from the standby position A to the operating position B to block heat input to the heating region 208. The temperature of the belt portion corresponding to the heating region 208 at this time was measured with a radiation thermometer (manufactured by KEYENCE, FT-H30).

  FIG. 12 is a graph comparing belt temperatures in the case of the conventional example, Examples 1 and 2 and Comparative Examples 1 and 2 in the confirmation experiment.

  Table 1 shows the endothermic member temperature and belt temperature in the confirmation experiment and the determination results. When the belt temperature was 250 ° C. or less, the endothermic effect was obtained (◯), and when the belt temperature exceeded, the endothermic effect was small (×).

  In the conventional example, the endothermic member temperature is 190 ° C., which is less than the upper limit of 300 ° C., but since the amount of leaked heat enters the belt 202, the belt temperature becomes 300 ° C. Since the heat resistance temperature of the belt 202 exceeds 300 ° C., the belt 202 is damaged.

  In Comparative Example 1, since all of the overshooted heat is used to heat the belt 202, the belt temperature reaches a maximum of 350 ° C., and the belt 202 is damaged.

  In Comparative Example 2, the upper end temperature of the heat absorbing member 207 reaches 300 ° C. and the endothermic effect is small, and the upper limit temperature of the belt 202 exceeds 250 ° C., so that the endothermic member 207 is insufficient.

  In Comparative Example 3, the temperature of the endothermic member reaches 476 ° C. and exceeds the upper limit temperature of the endothermic member 207, so that the condition for the endothermic member is insufficient.

  In the first embodiment, the endothermic member temperature is 147 ° C., which is lower than the upper limit temperature of the endothermic member 207, and the temperature rise of the belt 202 can be suppressed to 250 ° C. or lower, which is effective in suppressing an excessive temperature increase due to overshoot. I understand that there is.

  In the second embodiment, the endothermic member temperature is 196 ° C., which is equal to or lower than the upper limit temperature of the endothermic member 207, the temperature rise of the belt 202 is suppressed to 217 ° C. I know that there is.

  From the above, by setting the radiation rate of the heat absorbing member 207 radiation heat absorbing layer 207b to 0.7 or more and the heat capacity of the heat absorbing member 207 to 6 J / ° C. or more, thermal damage to the belt 202 due to overshoot of the heater 201 is caused. Can be suppressed.

<< Embodiment 2 >>
The fixing device is not limited to an internal heating type device configuration like the fixing device 200 of the first embodiment. As in the example of FIG. 13, an external heating system configuration may be used. That is, a cylindrical belt or roller is used as the heating rotator 202. Then, the heater 201, the reflection plate 203, and the heat absorbing member 207 are disposed outside the heating rotator 202, and the heated portion 208, which is a partial region in the circumferential direction of the outer surface of the heating rotator 202, is externally heated. .

  Also in the case of this apparatus, the control unit 300 causes the heat absorbing member 207 to be positioned at the standby position (first position) A where the heating rotator 202 and the reflecting surface of the reflection plate 203 do not face each other when the heating rotator 202 rotates. The moving mechanism of the heat absorbing member 207 is controlled ((a) of FIG. 13). When the rotation of the heating rotator 202 is stopped, power supply to the heater 201 is stopped and the heat absorbing member 207 absorbs heat so that the heating rotator 202 and the reflecting surface of the reflecting plate 203 face each other at an operating position (second position) B. The movement mechanism of the member 207 is controlled ((b) of FIG. 13).

  As a result, the heat absorbing member 207 is moved to and held at the operating position B, so that excessive heating of the heating rotator 202 due to overshoot of the heater 201 is suppressed even when the heating rotator 202 stops rotating.

  In the case where the heating rotator 202 is a belt, an apparatus configuration in which the belt is suspended and rotated between a plurality of members may be employed.

《Other matters》
(1) The image heating apparatus according to the present invention is not limited to use as the fixing device 200 of the embodiment. It can also be effectively used as a glossiness increasing device (image modifying device) that increases the glossiness of an image by heating the image fixed on the recording material.

  (2) The image forming apparatus is not limited to the electrophotographic system of the embodiment. An apparatus such as an electrostatic recording system or a magnetic recording system may be used. A monochromatic image forming apparatus may be used. The apparatus is not limited to the transfer method, and may be a device that forms a toner image (developer image) directly on a sheet.

  (3) The control unit 300 may be a control unit (a CPU provided in the image forming apparatus) that combines control relating to image formation and control relating to fixing, or may be a control unit that exclusively performs control relating to fixing.

  (4) The fixing device (image heating device) is not limited to one fixed inside the image forming apparatus, but may be a unit that can be removed and replaced outside the image forming apparatus. In this case, the controller 300 may be removed and replaced, or the controller 300 may be removed and replaced. In addition, the fixing device may be used independently of the image forming apparatus and independently of the fixing device.

  200 .. Fixing device (image heating device), P .. Recording material, t .. Developer image, 202 .. Heating rotary member, 201 .. Heater (radiant heat source), 203 .. Reflecting member, 208. Heating, 207 ... Heat absorbing member, A ... First position, B ... Second position, 300 ... Control section

Claims (10)

An image heating apparatus for thermally fixing a developer image on a recording material,
A cylindrical heating rotor,
A radiant heat source that emits radiant heat, disposed inside the heating rotator,
A sliding contact member disposed so as to be in sliding contact with the inner surface of the heating rotating body;
A reflecting member that reflects radiant heat generated by the radiant heat source toward a heated portion that is a partial region in the circumferential direction of the inner surface of the heating rotator;
A pressure member that forms a nip portion with the heating rotator by sandwiching the heating rotator with the sliding contact member;
A heat absorption member having a heat capacity of 6 (J / ° C.) or more and a surface facing the radiant heat source having a radiation rate of 0.7 or more, and a length greater than or equal to the length of the radiant heat source;
A rotating mechanism for rotating the heat absorbing member;
When the rotation of the heating rotator is stopped, power is supplied to the radiant heat source when the rotation of the heating rotator is stopped so that the heat absorbing member is positioned at a first position where the reflecting surface of the heating rotator and the reflecting member does not face each other. A control unit that controls the rotating mechanism so that the heat absorbing member is positioned at a second position where the heating rotating body and the reflecting surface of the reflecting member face each other while stopping.
An image heating apparatus comprising:   The endothermic member has a structure of at least two layers of a first layer facing the radiation heat source at the second position and a second layer facing the heating rotating body, and the first layer has a radiation rate. The second layer has a higher heat capacity than the first layer, and the combined heat capacity of the first layer and the second layer is 6 (J / ° C.) or more. The image heating apparatus according to claim 1. A heating rotator for heating the developer image on the recording material;
A radiant heat source that emits radiant heat;
A reflective member that reflects radiant heat generated by the radiant heat source toward a heated portion that is a partial region in the circumferential direction of the heating rotator; and
The heat capacity is 6 (J / ° C.) or more, the surface facing the radiant heat source has an emissivity of 0.7 or more, and the endothermic member has a length greater than or equal to the length of the radiant heat source. A moving mechanism
When the heating rotator rotates, the moving mechanism is controlled so that the heat absorbing member is positioned at a first position where the heating rotator and the reflecting surface of the reflecting member do not face each other. When the heating rotator stops rotating, A controller that stops the power supply to the radiant heat source and controls the moving mechanism so that the heat absorbing member is positioned at a second position where the heating rotating body and the reflecting surface of the reflecting member face each other;
An image heating apparatus comprising:   The image heating apparatus according to claim 3, wherein the heating rotator has a cylindrical shape, and the radiant heat source, the reflection member, and the heat absorbing member are disposed inside the cylindrical heating rotator. .   The image heating apparatus according to claim 3, wherein the radiant heat source, the reflection member, and the heat absorption member are disposed outside the heating rotator.   The endothermic member has a structure of at least two layers of a first layer facing the radiation heat source at the second position and a second layer facing the heating rotating body, and the first layer has a radiation rate. The second layer has a higher heat capacity than the first layer, and the combined heat capacity of the first layer and the second layer is 6 (J / ° C.) or more. The image heating apparatus according to any one of claims 3 to 5.   7. The heating rotating body and an opposing rotating body that forms a nip portion, and the developer image on the recording material is heated by nipping and conveying the recording material at the nip portion. An image heating apparatus according to claim 1.   The image heating apparatus according to claim 3, wherein the heating rotator is an endless belt.   Opposing rotation that forms a nip portion that sandwiches and conveys the recording material between the belt and the sliding contact member disposed so as to be in sliding contact with the inner surface of the belt. The image heating apparatus according to claim 8, further comprising: a body.   The image heating apparatus according to claim 3, wherein the heating rotator is a roller.