JP2005142023A - Heating arrangement, image forming device equipped with the same, and heating method of heating arrangement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating arrangement capable of speedily reducing unevenness of temperatures on the surface of a heating member when moving from a standby state to an operating state, an image forming device equipped with the heating arrangement, and a heating method of the heating arrangement. <P>SOLUTION: This heating arrangement 12 is provided with a heating roller 31, an induction heating means 37, and a pressurizing member 32 heated by a heating member 33. The induction heating means 37 and the pressurizing member 32 form three heating regions on the surface of the heating roller 31 by partially heating the peripheral surface of the heating roller. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heating device, an image forming apparatus including the same, and a heating method of the heating device, and more specifically, a heating device with reduced temperature unevenness during standby, an image forming apparatus including the heating device, and heating. The present invention relates to a method for heating an apparatus.

  2. Description of the Related Art In electrophotographic image forming apparatuses such as copying machines and printers, a heating apparatus having a heating roller having a hollow core metal such as aluminum and a heating means such as a halogen heater inside the heating roller is widely used as a fixing device. It is used. The heating device heats the heating roller to a predetermined temperature (fixing temperature) by the halogen heater.

  The heating device having the above-described configuration has a large heat capacity of the heating roller and transfers heat generated in the halogen heater to the heating roller, so that the heating roller reaches the fixing temperature from the start of heating and performs a heating operation (fixing operation). It takes a long time to perform (hereinafter referred to as warm-up time). In view of this, for example, Patent Document 1 proposes a dielectric heating type heating apparatus in which a heating layer is provided with a conductive layer having a small heat capacity and the conductive layer generates heat to improve heating efficiency. That is, in the heating device of Patent Document 1, magnetic field generating means is arranged so as to face the heating roller, and the magnetic field is applied to the conductive layer by the magnetic field generating means. Thereby, an eddy current is generated in the conductive layer, and the conductive layer having a small heat capacity is heated by the Joule heat generated by the eddy current. Therefore, the warm-up time of the heating roller can be shortened.

  However, in the above-described induction heating type heating apparatus, the magnetic field from the magnetic field generating unit mainly acts on the conductive layer facing the magnetic field generating unit due to the skin effect. For this reason, in a standby state where the heating roller stops rotating, the heat generating area of the heating roller becomes a local area facing the magnetic field generating means. As described above, when the heating roller generates heat locally, the temperature distribution in the circumferential direction of the heating roller becomes non-uniform, and when the fixing operation is performed in this state, unevenness in the gloss of the image occurs.

Japanese Patent Application Laid-Open No. 2004-260688 discloses a heating device for suppressing uneven temperature distribution of the heating roller during the fixing process as described above. In the heating device described in Patent Document 2, the heating roller is heated by the magnetic field generating means while the rotation of the heating roller is stopped during standby. Thereafter, before starting the fixing operation, the temperature of the heating roller is made uniform by rotating the heating roller.
JP 2001-188427 A (publication date: July 10, 2001) JP 2001-194947 A (publication date: July 19, 2001)

  However, the heating device in Patent Document 2 requires time for rotating the heating roller in order to make the temperature distribution uniform. In particular, when the standby state lasts for a long period of time or when the ambient temperature of the heating device is low, the temperature variation on the surface of the heating roller tends to increase. Therefore, in order to make the surface temperature of the heating roller uniform, the time for rotating the heating roller becomes longer, and the warm-up time until the fixing operation becomes possible becomes longer.

  The present invention has been made in view of the above-described problems, and its purpose is to quickly eliminate temperature unevenness of the heating member and the pressure member during the transition from the standby state to the operation state, and to return to the operation state. It is an object of the present invention to provide a heating apparatus capable of performing a transition quickly, an image forming apparatus including the same, and a heating method for the heating apparatus.

  In order to solve the above-described problems, a heating device according to the present invention includes a pressure member that presses against a heating member and rotates with the rotation of the heating member, and locally heats the peripheral surface of the heating member by a heating source. Thus, in the heating device in which the heating region extending between both ends in the rotation axis direction of the heating member is formed in parallel to the rotation axis direction, when the rotation of the heating member is stopped, the heating member is The peripheral surface of the heating member has at least three heating regions.

  Further, in the heating device according to the present invention, in the above heating device, when the rotation of the heating member is stopped, the heating source is disposed on the peripheral surface of the heating member along the rotation direction of the heating member. It is preferable that the non-heated area which is not heated by the heat treatment and the heating area are alternately formed.

  In the heating device according to the present invention, in the above heating device, the heating regions are preferably formed at equal intervals.

  In the heating device according to the present invention, it is preferable that the outer peripheral length of the heating member and the outer peripheral length of the pressure member are different from each other in the heating device.

  Further, the heating device according to the present invention is the above heating device, wherein the outer peripheral length of one member having a relatively long outer peripheral length among the heating member and the pressure member is the other outer peripheral length being relatively short. It is preferable to have a length that is not an integral multiple of the outer peripheral length of the member.

  The heating device according to the present invention is the above heating device, wherein the heating member has a heat generating layer that generates heat by the heating source, and at least one of the heating sources heats the heat generating layer by induction heating. Induction heating means may be used.

  Moreover, in the heating device according to the present invention, in the heating device, the induction heating unit may be disposed so as to face an outer periphery of the heating member.

  In the heating device according to the present invention, the pressure member is preferably at least one of the heating sources.

  In the heating device according to the present invention, in the above heating device, the pressurizing member may have an internal heat source that uniformly heats the entire pressurizing member inside the pressurizing member.

  In addition, an image forming apparatus according to the present invention includes any one of the above heating devices in order to solve the above problems.

  In order to solve the above-described problem, the heating method of the heating device according to the present invention includes a pressing member that presses the heating member to form a pressing portion, and the peripheral surface of the heating member is locally applied by a heating source. The heating member and the pressure member rotate in an operating state in a heating device in which a heating region extending between both ends in the rotation axis direction of the heating member is formed in parallel with the rotation axis direction. By heating the heated material at the pressure-contacting portion, in the standby state, the rotation of the heating member and the pressure member is stopped, and the heating device that preheats the heating member with the heating source is heated. In the method, the return state in which the operation of returning from the standby state to the operation state is performed, the first step of rotating the heating member and the pressure member, and the rotation of the heating member and the pressure member at a predetermined position. , Predetermined time A second step of stopping, is characterized in that a third step resumes rotation of the heating member and the pressure member.

  Further, the heating method of the heating device according to the present invention is the heating method of the heating device described above, in the standby state, on the peripheral surface of the heating member along the rotation direction of the heating member. In the second step of the return state, the non-heated area that is not heated by the heating region is alternately formed, and the heating member is rotated at a position where the non-heated area in the standby state is heated by the heating source. Is preferably stopped.

  Moreover, the heating method of the heating device according to the present invention is the above heating method of the heating device, wherein at least two heating regions are formed on the peripheral surface of the heating member in the standby state, and the heating device It is preferable that the regions are formed at equal intervals along the rotation direction of the heating member.

  Further, the heating method of the heating device according to the present invention is the heating method of the heating device described above, wherein the entire pressure member is uniformly heated as the heating source and at the position of the pressure contact portion in the standby state. While using a pressurizing member provided with an internal heat source for heating the heating member, and using a local heating source that heats the heating member at a position other than the press contact portion in the standby state, in the return state, The power source of the internal heat source may be turned off, and a larger amount of power may be input to the local heating source than the amount of power input to the local heating source during the operation state.

  Further, in the heating method of the heating device according to the present invention, in the heating method of the heating device, the set temperature in the standby state of the pressure member may be set to a temperature higher than the set temperature in the operating state. .

  Further, the heating method of the heating device according to the present invention is the heating method of the heating device described above, in the standby state, in which the peripheral surface of the heating member has at least two heating regions, and in the standby state. The set temperature in the first heating area where the length of the heating area in the rotation direction of the heating member is relatively narrow is higher than the set temperature in the second heating area where the length of the heating area is relatively wide May be set.

  The heating method of the heating device according to the present invention is the heating method of the heating device described above, wherein, in the first step, the heating member is rotated at least once and the temperature distribution on the peripheral surface of the heating member is stored. In the second step, the rotation of the heating member may be stopped at a position where a relatively low temperature region is heated by the heating source based on the temperature distribution.

  Moreover, the heating method of the heating device according to the present invention may be performed by repeating the second step and the third step in the heating method of the heating device.

  As described above, the heating device of the present invention includes a pressure member that is pressed against the heating member and rotates with the rotation of the heating member, and the peripheral surface of the heating member is locally heated by a heating source. In a heating device in which a heating region extending between both ends in the rotation axis direction of the heating member is formed parallel to the rotation axis direction, when the rotation of the heating member is stopped, the heating member is The peripheral surface has at least three heating regions. Here, the peripheral surface of the heating member refers to the inner periphery or the outer periphery of the heating member. In addition, the rotation axis refers to the rotation center of the heating member, and “parallel to the rotation axis direction” includes substantially parallel to the rotation axis.

  According to said structure, the temperature nonuniformity of a heating member can be suppressed in the standby state which the heating apparatus has pre-heated and has stopped operation | movement. Therefore, the uneven temperature on the surface of the heating member can be quickly eliminated in the return state in which the heating device returns to the operation state in which the heating device performs a predetermined heating operation from the standby state.

  Further, in the heating device of the present invention, when the rotation of the heating member is stopped, the peripheral surface of the heating member is not heated by the heating source along the rotation direction of the heating member. Since the heating regions and the heating regions are alternately formed, it is possible to reduce uneven temperature in the circumferential direction of the heating member in the standby state. Therefore, the surface temperature can be quickly made uniform by heating the heating member in the return state.

  Further, in the heating device of the present invention, since the heating regions are formed at equal intervals, the temperature unevenness on the surface of the heating member in the standby state can be further reduced. Thereby, the temperature irregularity on the surface of the heating member can be eliminated in a short time in the return state.

  Further, in the heating device of the present invention, the outer peripheral length of the heating member and the outer peripheral length of the pressure member are different from each other, and preferably the outer peripheral length of the heating member and the pressure member is The outer peripheral length of one member that is relatively long has a length that is not an integral multiple of the outer peripheral length of the other member that has a relatively short outer peripheral length. According to said structure, whenever a heating member or a pressurization member rotates 1 time, the heating member surface and the pressurization member surface in the position where a heating member and a pressurization member press-contact can be varied. Therefore, the unevenness of the surface temperature of the heating member generated in the standby state can be reduced by rotating the heating member and the pressure member in the return state, thereby reducing the temperature unevenness on the surface of the heating member.

  In the heating device of the present invention, the heating member further includes a heat generating layer that generates heat by the heating source, and at least one of the heating sources is induction heating means that heats the heat generating layer by induction heating. There may be. Here, the induction heating means may be arranged so as to face the outer periphery of the heating member. According to the above configuration, the heat generating layer is provided on the heating member, and the heat generating layer is heated using the induction heating means having excellent heating efficiency, so that the heating member can be efficiently heated.

  In the heating device of the present invention, it is preferable that the pressure member is at least one of the heating sources. As described above, the pressure member has a function as a heating source, so that the structure of the heating device can be simplified. Moreover, since the pressure member is provided in pressure contact with the heating member, the heating member can be efficiently heated by using the pressure member as a heating source.

  In the heating device of the present invention, the pressurizing member may further include an internal heat source that uniformly heats the entire pressurizing member inside the pressurizing member. According to the above configuration, since the entire pressure member is heated uniformly, even if the pressure member rotates in the return state and the pressure contact position between the heating member and the pressure member changes, the pressure member is pressed. The heating member can always be heated by the member. Thereby, a heating member can be heated efficiently.

  In addition, since the image forming apparatus of the present invention includes any one of the above-described heating devices, image formation that can quickly eliminate uneven temperature on the surface of the heating member when returning from the standby state to the operating state. An apparatus can be provided.

  Further, as described above, the heating method of the heating device of the present invention includes a pressurizing member that press-contacts the heating member to form a press-contact portion, and locally heats the peripheral surface of the heating member by a heating source. By the heating device in which the heating region extending between both end portions in the rotation axis direction of the heating member is formed in parallel to the rotation axis direction, the heating member and the pressure member rotate in the operating state, thereby heating the heating member. The material to be heated is heated at the pressure contact portion formed by pressure contact between the member and the pressure member, and in the standby state, the rotation of the heating member and the pressure member is stopped, and the heating member is heated by the heating source. In the heating method of the heating apparatus that performs preheating, the return state in which the operation of returning from the standby state to the operation state is performed in the first step of rotating the heating member and the pressure member, and the heating member and the pressure member. Rotate into place Has a second step of stopping the predetermined time, and a third step resumes rotation of the heating member and the pressure member.

  According to the above method, in the return state, the heating member and the pressure member can be rotated by a predetermined rotation angle, the rotation can be stopped, and the heating member can be heated. Therefore, by adjusting the rotation angle of the heating member, it is possible to intensively heat a low temperature region (hereinafter referred to as a low temperature region) on the surface of the heating member in the standby state. In addition, since the heating member and the pressure member are rotated after the low temperature region of the heating member is intensively heated, the entire heating member can be uniformly heated to reduce temperature unevenness on the surface of the heating member. it can.

  Further, as described above, in the return state, by stopping the rotation of the heating member and intermittently rotating the heating member, the return time for the heating member to reach a predetermined temperature can be shortened. it can.

  Moreover, the heating method of the heating device of the present invention further includes, in the standby state, a non-heated region that is not heated by the heating source along the rotation direction of the heating member on the peripheral surface of the heating member, and The heating region may be alternately formed, and the rotation of the heating member may be stopped at a position where the non-heating region in the standby state is heated by the heating source in the second step of the return state. . Alternatively, in the standby state, at least two heating regions are formed on the peripheral surface of the heating member, and the heating regions are formed at equal intervals along the rotation direction of the heating member. May be.

  According to the above method, the heating region and the non-heating region are alternately formed, or the heating regions are formed at equal intervals, so that the temperature in the circumferential direction of the heating member in the standby state is increased. Nonuniformity can be reduced. Therefore, the temperature unevenness of the surface temperature can be quickly eliminated by heating the heating member in the return state.

  Further, the heating method of the heating device of the present invention further includes an inside for heating the entire pressure member uniformly as the heating source and heating the heating member at the position of the pressure contact portion in the standby state. While using a pressure member having a heat source therein, and using a local heating source that heats the heating member at a position other than the pressure contact portion in the standby state, the power source of the internal heat source is turned off in the return state. In addition, it is preferable to input a larger amount of power to the local heating source than the amount of power input to the local heating source in the operation state.

  According to the above method, since the pressure member includes the internal heat source, the entire pressure member is heated in the standby state. Therefore, even if heating of the pressure member is stopped in the return state, the heating member can be heated at the pressure contact portion that is in pressure contact with the heating member. Even when there is a limit to the amount of power that can be used for the heating device, if the power supply to the internal heat source is stopped, a larger amount of power can be supplied to the local heating source. Therefore, the heating member can be efficiently heated by the local heating source. Therefore, the temperature unevenness on the surface of the heating member can be quickly reduced in the return state.

  In the heating method of the heating device of the present invention, the set temperature in the standby state of the pressurizing member may be set higher than the set temperature in the operating state. According to this method, the pressure member can be heated so that the pressure member can maintain a sufficient amount of heat in the standby state. Therefore, even if heating of the pressure member is stopped in the return state, the heating member can be sufficiently heated at the pressure contact portion.

  Moreover, the heating method of the heating device of the present invention further includes at least two heating regions on the peripheral surface of the heating member in the standby state, and in the standby state in the rotation direction of the heating member. It is preferable that the set temperature in the first heating region having a relatively narrow heating region length is set to be higher than the setting temperature in the second heating region having a relatively large heating region length. .

  According to said method, compared with the case where the preset temperature of a 1st heating area is lower than the preset temperature of a 2nd heating area, the temperature nonuniformity of the heating member surface in a standby state can be suppressed. Therefore, the non-uniformity of the temperature of the heating member surface can be quickly eliminated in the return state.

  In the heating method of the heating device of the present invention, the heating member is further rotated at least once in the first step, the temperature distribution on the peripheral surface of the heating member is stored, and the heating step is performed in the second step. Based on the temperature distribution, rotation of the heating member may be stopped at a position where a relatively low temperature region is heated by the heating source.

  According to the above method, since the temperature distribution on the surface of the heating member at the stage of transition to the return state can be detected, the low temperature region of the heating member can be intensively heated based on the detection result. . Therefore, the temperature unevenness on the surface of the heating member can be eliminated in a short time in the return state.

  Further, the heating method of the heating device of the present invention may be performed by repeating the second step and the third step. According to this method, since the heating member is repeatedly rotated and stopped, the low temperature region of the heating member can be effectively heated even when the temperature unevenness of the surface of the heating member is not uniform. it can. Therefore, uneven temperature on the surface of the heating member can be efficiently eliminated in the return state.

[Embodiment 1]
An embodiment of the present invention will be described below with reference to FIGS.

  FIG. 2 is a schematic cross-sectional view of the heating device according to the present invention. A heating device 12 shown in FIG. 2 is provided in, for example, an electrophotographic image forming apparatus, and melts an unfixed toner image T made of unfixed toner on a recording paper (material to be heated) P to record the recording paper P. The toner image is heated and pressed and fixed on the top. Specifically, the heating device 12 heats the heating roller (heating member) 31 having the heat generating layer 31b by the induction heating means (heating source) 37 disposed outside thereof. Thereafter, the recording paper P having the unfixed toner image T is passed through the pressure contact portion between the heating roller 31 heated to a certain temperature and the pressure roller (pressing member / heating source) 32, whereby the recording paper P Fix the image on Therefore, as shown in FIG. 2, the heating device 12 includes a heating roller 31, a pressure roller 32, an induction heating unit 37, a heating unit (internal heat source) 33, a heating roller thermistor 35, and a control unit. 36, a pressure roller thermistor 38, and an excitation circuit 34.

  The heating roller 31 melts the toner on the recording paper P and fixes the toner image on the recording paper P by the pressure applied by the heating roller 31 and the pressure roller 32. The heating roller 31 receives a driving force from the driving means 43 and is rotationally driven in the direction of the arrow R1 in FIG. The heating roller 31 includes a cored bar 31d, an elastic layer 31c, a heat generating layer 31b, and a release layer 31a. On the cored bar 31d, the elastic layer 31c, the heat generating layer 31b, and the release layer 31a are provided. It is formed sequentially.

  The cored bar 31d is made of a metal such as aluminum, iron, or stainless steel. Of these, aluminum is more desirable to prevent heat generation by induction heating.

  The elastic layer 31c is provided between the heat generating layer 31b and the cored bar 31d in order to fix and support a thin heat generating layer 31b described later. By providing the elastic layer 31c, sufficient mechanical strength of the heat generating layer 31b can be ensured. The elastic layer 31c has a heat insulating property to prevent the heat generated in the heat generating layer 31b from escaping to the cored bar 31d as much as possible. Furthermore, the elastic layer 31c has heat resistance that is unlikely to deteriorate due to heat generated by the heat generating layer 31b. Therefore, the elastic layer 31c is preferably formed of a material excellent in heat insulation and heat resistance such as foamed silicon rubber.

  The heating layer 31b is a heating element that generates heat by induction heating. In order to shorten the rise time of the surface temperature of the heating roller 31, the thickness of the heat generating layer 31b is preferably thinned to about 40 μm to 50 μm. Since the material of the heat generating layer 31b is heated by induction heating, it may be any conductive member having magnetism, such as iron or SUS430 stainless steel. In particular, a material having a high relative permeability is preferable, and a silicon steel plate, an electromagnetic steel plate, nickel steel, or the like can be used. Moreover, even if it is a nonmagnetic material, if it is a material with high resistance value, it will generate | occur | produce heat | fever by induction heating, Therefore You may use SUS304 stainless steel material etc. Furthermore, as the heat generating layer 31b, a nonmagnetic base member such as ceramic may be used as long as a material having a high relative magnetic permeability is disposed so as to have conductivity. In order to increase the amount of heat generated, a plurality of heat generating layers 31b may be formed.

  The release layer 31a covers the surface (outer peripheral surface) of the heat generating layer 31b and prevents the toner having a lowered viscosity from adhering to the surface of the heating roller 31 due to heating at the nip portion (pressure contact portion). The release layer 31a is made of a fluororesin such as PTFE (polytetrafluoroethylene) or PFA (a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether), or an elastic body such as silicon rubber, fluororubber or fluorosilicone rubber, Alternatively, a plurality of these are stacked. In particular, when the heating device 12 performs fixing processing of toner for color printing, it is preferable to use a rubber-based material having elasticity as the release layer 31a.

  The induction heating means 37 causes the heat generating layer 31b to generate heat by applying an alternating magnetic field to the heat generating layer 31b of the heating roller 31. As shown in FIG. 2, the induction heating means 37 has an induction coil 37a and a resin holder 37b for holding the induction coil 37a, and is arranged so as to face the outer peripheral surface of the heating roller 31. . More specifically, the induction heating means 37 is disposed so as to locally cover the outer peripheral surface of the heating roller 31 with a predetermined curvature along the outer peripheral surface of the heat generating layer 31 b of the heating roller 31.

  FIG. 3 shows a top view of the induction heating means 37. As shown in FIGS. 2 and 3, the induction coil 37 a is formed by winding a conducting wire a plurality of times with an air core. In other words, the induction coil 37a is wound around the central portion of the induction coil 37a so as to form a gap having a distance L along the rotation direction of the heating roller 31. For the conductive wire forming the induction coil 37a, for example, an aluminum single wire having an oxide film as a surface insulating layer may be used in consideration of heat resistance. Or you may use the litz wire which makes a copper wire or a copper-based composite member wire, an enameled wire, etc. a stranded wire. Whichever lead is used, in order to suppress Joule loss in the induction coil 37a, the total resistance value of the induction coil 37a is preferably 0.5Ω or less, and preferably 0.1Ω or less. Is more preferable.

  The heating roller 31 is induction-heated by an alternating magnetic field generated by flowing a high-frequency current from the excitation circuit 34 shown in FIG. As described above, since the induction heating unit 37 has a predetermined curvature, the conductive wire is wound so that the induction coil 37 a also has a predetermined curvature along the outer peripheral surface of the heating roller 31. Therefore, when a high frequency current is passed through the induction coil 37a, the magnetic flux concentrates on the center side of the induction coil 37a, and the amount of eddy current generated increases. As a result, the surface temperature of the heating roller can be quickly raised. Note that a plurality of the induction heating means 37 may be arranged in the direction of the rotation axis of the heating roller according to the size of the recording paper P passing through the nip portion.

  Further, as shown in FIG. 2, the pressure roller 32 is in pressure contact with the heating roller 31, and the recording paper P carrying the unfixed toner image T between the pressure roller 32 and the heating roller 31. The toner image is fixed on the recording paper P. The pressure roller 32 is pressed against the heating roller 31 with a predetermined pressing force (contact pressure) by an urging means such as a pressure spring (not shown). As the heating roller 31 rotates, the pressure roller 32 is driven to rotate in the direction of the arrow R2 in FIG.

  The pressure roller 32 includes a pressure roller side core metal 32b, a pressure roller side release layer 32a, and a heating means 33, and the pressure roller side release layer 32a is provided on the pressure roller side core metal 32b. Is formed. The pressure roller side metal core 32b is made of iron, stainless steel, or aluminum and is formed in a hollow shape. The pressure roller side release layer 32a is formed to prevent adhesion of toner and paper powder. As the material of the pressure roller side release layer 32a, it is preferable to use a fluorine resin material such as PFA or PTFE, or a rubber material such as silicon rubber, fluorine rubber, or fluorosilicon rubber.

  The heating means 33 is disposed inside a hollow cored bar 32 b of the pressure roller 32 in order to heat the pressure roller 32. As the heating means 33, for example, a lamp heater such as a halogen lamp or a ceramic heater may be used. The entire pressure roller 32 is uniformly heated by the infrared rays emitted from the heating means 33.

  The heating roller thermistor 35 is provided to detect the surface temperature of the heating roller 31. The heating roller thermistor 35 is provided near the surface of the heating roller 31 in the vicinity of the downstream side in the conveyance direction of the recording paper P at the nip portion.

  The pressure roller thermistor 38 is provided to detect the surface temperature of the pressure roller 32. The pressure roller thermistor 38 is provided so as to face the surface of the pressure roller 32 in the vicinity of the downstream side in the conveyance direction of the recording paper P at the nip portion.

  The excitation circuit 34 is connected to the induction coil 37a and supplies a high-frequency current to the induction coil 37a.

  The said control means 36 is CPU (Central Processing Unit), for example, and controls operation | movement of the heating apparatus 12 whole. That is, the control means 36 controls the drive means 43 having a motor and a motor driver to drive the heating roller 31 to rotate. The driver circuit 42 and the excitation circuit 34 are controlled based on the detection signals of the heating roller thermistor 35 and the pressure roller thermistor 38 to control the temperatures of the heating roller and the pressure roller, respectively.

  In the heating apparatus shown in FIG. 2 having the above-described configurations, the pressure roller 32 is disposed in pressure contact with the heat roller 31 with a predetermined pressure by an urging means such as a pressure spring (not shown). Thereby, a nip portion which is a contact portion between the heating roller 31 and the pressure roller 32 is formed. As described above, since the pressure roller 32 includes the heating means 33 inside, the entire pressure roller 32 is heated. Therefore, the heating roller 31 is heated by the pressure roller 32 at the nip portion.

  In addition, an induction heating unit 37 is provided so as to face a region other than the formation position of the nip portion on the outer surface of the heating roller 31. As described above, the induction coil 37 a of the induction heating unit 37 extends in a direction parallel to the rotation axis of the heating roller 31, and is folded at both ends of the heating roller 31 in the rotation axis direction. A conducting wire is wound with a predetermined curvature along the surface.

  As shown in FIGS. 2 and 3, a portion (heating source, hereinafter referred to as a parallel portion) 37c of the induction coil 37a extending in parallel with the rotation axis of the heating roller 31 is folded at both ends. Winding direction is different before and after. As will be described later, since the current is supplied from the excitation circuit 34 to the induction coil 37a, an alternating magnetic field generated in the induction coil 37a when the winding direction in the parallel portion 37c, that is, the current flowing direction is different. The direction of will be different. Therefore, as shown in FIG. 3, the induction coil 37a is formed with a parallel portion 37c at a distance L in the rotational direction of the heating roller 31 so that the parallel portions 37c do not contact each other. Yes. Therefore, as shown in FIG. 2, the parallel portion 37 c of the induction coil 37 a is disposed so as to face the surface of the heating roller 31 with a distance L in the rotation direction of the heating roller 31.

  In the heating device 12 having the above-described configuration, the following operation is performed when the unfixed toner image T is fixed on the recording paper P. That is, when energization to the heating device 12 is started from a power source (not shown), the driving unit 43 rotates the heating roller 31 under the control of the control unit 36. As a result, the pressure roller 32 is driven to rotate, and a state in which the heating device 12 can be fixed, that is, warm-up for raising the heating roller 31 and the pressure roller 32 to a predetermined control temperature is started.

  During the warm-up, the excitation circuit 34 connected to the induction coil 37a is turned on by the control of the control means 36, and a high-frequency current is supplied to the induction coil 37a. Thereby, the induction coil 37a is excited, and an alternating magnetic field is generated in the induction coil 37a. When this alternating magnetic field acts on the heat generating layer 31b of the heating roller 31, an eddy current is induced in the heat generating layer 31b and Joule heat is generated. As a result, the heating roller 31 generates heat. At the same time, the control means 36 controls the driver circuit 42 to supply power to the heating means 33. As a result, the entire pressure roller 32 is uniformly heated by the infrared rays emitted from the heating means 33, and the heating roller 31 is heated at the nip portion. At this time, the control means 36 detects the surface temperatures of the heating roller 31 and the pressure roller 32 based on detection signals from the heating roller thermistor 35 and the pressure roller thermistor 38, respectively.

  When the heating roller 31 and the pressure roller 32 rise to a predetermined control temperature, the warm-up is completed, and when the fixing process is requested, the operation mode (operating state) for executing the fixing process is entered. In the operation mode, the total amount of power supplied to each of the induction coil 37a and the heating means 33 via the excitation circuit 34 and the driver circuit 42 is made smaller than the total amount of power during warm-up. Set to. Specifically, for example, the amount of power supplied to the induction coil 37a is switched to be smaller than the amount of power supplied during warm-up.

  This is because, when the heating device 12 is provided in the image forming apparatus, only the heating device 12 operates at the time of warm-up performed after turning on the power to the image forming apparatus, and the entire image forming apparatus is operated in the operation mode. It is to work. That is, at the time of warm-up, each part other than the heating device 12 provided in the image forming apparatus does not operate. Therefore, it is only necessary to supply power to the heating device 12 during warm-up. On the other hand, in an operation mode in which image processing including fixing processing is performed, each unit other than the heating device 12 also starts to operate, so that the amount of power that can be input to the heating device 12 is limited. Therefore, the amount of power supplied to the induction coil 37a is switched when shifting from the warm-up time to the operation mode.

  Then, with the heating roller 31 and the pressure roller 32 maintained at the control temperature, as shown in FIG. 2, the recording paper P on which the unfixed toner image T is held is conveyed to the nip portion. When the recording paper P is conveyed between the heating roller 31 and the pressure roller 32 at the nip portion, the toner on the recording paper P is melted and pressed. Thereby, the fixing processing operation is completed.

  When the fixing process is completed as described above, or when the fixing process is not requested after the warm-up, the heating device 12 performs a preheating in preparation for the next fixing process request (standby state). ). In the standby mode, the driving unit 43 stops the rotation of the heating roller 31 under the control of the control unit 36. As a result, the rotation of the pressure roller 32 is also stopped. At the same time, the control temperature of the heating roller 31 and the pressure roller 32 during the warm-up or operation mode is switched to the control temperature in the standby mode.

  In the standby mode, since the rotation of the heating roller 31 and the pressure roller 32 is stopped, the surface of the heating roller 31 is locally heated. That is, the surface of the heating roller 31 that generates heat by the alternating magnetic field supplied from the induction heating unit 37 is present in a region facing the induction coil 37a. Therefore, the heating region heated by the parallel portion 37c of the induction coil 37a on the surface of the heating roller 31 is parallel to the rotation axis direction of the heating roller 31 and one end of the heating roller 31 in the rotation axis direction. To the other end (hereinafter, between both ends).

  When the surface of the heating roller 31 is heated using the induction coil 37a while the heating roller 31 is stopped, heat distribution characteristic data representing the temperature distribution on the surface of the heating roller 31 is obtained as shown in FIG. Here, in FIG. 4, the horizontal axis represents the central position of the heating roller 31 in the rotation direction of the heating roller 31, that is, the midpoint of the distance L shown in FIG. The position of the surface of the heating roller 31 is represented by an angle θ up to ± 180 °, where 0 ° is the rotation direction of the heating roller 31 is positive and the opposite direction to the rotation direction is negative. The vertical axis indicates the percentage obtained by dividing the temperature at each position of the heating roller 31 by the highest temperature of the heat generation distribution of the heating roller 31.

  It can be seen from the heat distribution characteristic data shown in FIG. 4 that the surface of the heating roller 31 in the region facing the induction coil 37a tends to generate heat. That is, by heating the heating roller 31 by the induction coil 37a, two heating regions are formed in the entire region between both ends of the heating roller 31 in the rotation axis direction, in parallel with the rotation axis direction.

  Further, as described above, since the pressure roller 32 generates heat, the heating roller 31 forms a heating region between both ends in the rotation axis direction of the heating roller 31 also in the nip portion. Therefore, by providing the pressure roller 31 incorporating the induction heating unit 37 and the heating unit 33, when the rotation of the heating roller 31 is stopped, three heating regions are formed in the heating roller 31.

  As described above, when the heating device 12 is used, even when the rotation of the heating roller 31 is stopped, the heating roller 31 is heated in three locally existing heating regions. Therefore, even in the standby mode in which the heating roller is not rotating, the temperature variation on the surface of the heating roller 31 can be reduced and the heating roller 31 can be preheated. Thereby, even when the heating roller 31 is heated again in the return mode described later, the temperature unevenness on the surface of the heating roller 31 can be eliminated in a short time.

  In particular, when three heating regions are arranged evenly in the circumferential direction of the heating roller 31 on the peripheral surface of the heating roller 31, the heating roller when heating is performed in a state where the rotation of the heating roller 31 is stopped. The temperature unevenness of the 31 surface can be further reduced. That is, a heating area (P1, P2, P3 in FIG. 2) heated by the induction coil 37a and the pressure roller 32 and a non-heating area (P4.P in FIG. 2) not heated by the induction coil 37a and the pressure roller 32. P5 and P6) are alternately arranged, and the length in the circumferential direction of the non-heating area on the surface of the heating roller 31, which is the distance between the heating areas, is made substantially constant. Thereby, since a non-heating area | region is arrange | positioned between heating areas, the heat of a heating area | region becomes easy to transfer to a non-heating area | region, and the temperature nonuniformity of the heating roller 31 surface is reduced. Further, if the distance between the heating regions is made constant, the temperature distribution in each non-heating region shows almost the same tendency. Therefore, the temperature of the surface of the heating roller 31 varies within a predetermined range, and the temperature unevenness of the entire surface of the heating roller 31 is suppressed.

  As described above, in order to uniformly arrange the heating region on the surface of the heating roller 31, the center position P3 of the nip portion and the heat generation peak positions P1 and P2 on the surface of the heating roller 31 that generate the heat most by the induction coil 37a are obtained. The arrangement positions of the induction heating means 37 and the pressure roller 32 may be set so as to form an angle of about 120 ° about the rotation axis of the heating roller 31. That is, by heating the heating roller 31 by the induction coil 37a, the heat generation peak positions P1 and P2 of the surface of the heating roller 31 facing the parallel portion 37c of the induction coil 37a, as shown in FIG. It can be seen near the center in the direction of rotation. Therefore, the induction coil 37a is formed so that the heat generation peak positions P1 and P2 form an angle of 120 ° with each other on the peripheral surface of the heating roller 31. In other words, on the surface of the heating roller 31, the induction coil 37a is formed by setting the distance L between the parallel portions 37c so that the heat generation peak positions P1 and P2 are 120 ° to each other.

  In addition, induction heating is performed on the peripheral surface of the heating roller 31 so that the heat generation peak positions P1 and P2 and the center position P3 of the nip portion form about 120 ° about the rotation axis of the heating roller 31, respectively. A means 37 is arranged. Thus, the heat generation peak positions P1 and P2 and the center position P3 of the nip portion are arranged at equal intervals from each other. As a result, the three heating regions can be formed with the distance between the heating regions in the circumferential direction of the surface of the heating roller 31 being substantially constant.

  When a request for fixing processing is made in the standby mode, a transition is made to a return mode (return state). In the return mode, the driving unit 43 rotates the heating roller 31 under the control of the control unit 36. As a result, the pressure roller 32 is driven to rotate, and the heating device 12 can be fixed, that is, the return operation for raising the heating roller 31 and the pressure roller 32 to a predetermined control temperature is started. At this time, the total amount of power supplied to each of the induction coil 37a and the heating means 33 is set to be larger than the total amount of power in the standby mode. Specifically, for example, the amount of power supplied to the induction coil 37a is switched to be larger than the amount of power supplied in the standby mode.

  As described above, since the heating roller 31 is heated in the three heating regions in the standby mode, the temperature unevenness on the surface of the heating roller 31 generated in the standby mode can be quickly eliminated in the return mode. Therefore, the temperature variation on the surface of the heating roller 31 during the fixing process is reduced, and the toner image is well fixed on the recording paper P without causing image quality deterioration such as uneven glossiness. Can be obtained.

  Here, the outer diameter of the heating roller 31 and the outer diameter of the pressure roller 32 are preferably different. In particular, of the outer diameter of the heating roller 31 and the outer diameter of the pressure roller 32, the outer diameter of the roller having the larger outer diameter (the heating roller 31 or the pressure roller 32) is smaller (the heating roller). It is preferably not an integral multiple of the outer diameter of the roller 31 or the pressure roller 32).

  In this way, by setting the outer diameter of the heating roller 31 and the outer diameter of the pressure roller 32 so that the outer diameter ratio does not become an integral multiple, the larger one of the outer diameter of the heating roller 31 and the pressure roller 32. The surface of the heating roller 31 and the surface of the pressure roller 32 that are in contact with each other at the nip portion can be made different each time the roller of the roller rotates once. That is, in the heating device 12, since the outer diameter of the heating roller 31 is larger than the outer diameter of the pressure roller 32, the surface of the pressure roller 32 that contacts the surface of the heating roller 31 is rotated every time the heating roller 31 makes one rotation. Different. Thereby, temperature unevenness on the surface of the heating roller 31 when the heating roller 31 and the pressure roller 32 are rotated can be reduced.

  When shifting from the standby mode to the return mode, the power supply to the heating means 33 may be stopped and a large amount of power may be supplied to the induction coil 37a. That is, when the heating means 33 is provided inside the pressure roller 32, the entire pressure roller 32 is heated in the standby mode. Therefore, even when the pressure roller 32 rotates in the return mode, the heating roller 31 can be heated at the nip portion that is in pressure contact with the heating roller 31. That is, the pressure roller 32 can be a heating source for heating the heating roller 31. Further, in order to quickly heat the heating roller 31 in the return mode, it is preferable to supply a large amount of power to the induction heating means 37 having higher heating efficiency.

  Therefore, even if the power supply to the heating means 33 is stopped, the temperature unevenness of the surface of the heating roller 31 in the return mode is caused by the current supplied to the induction coil 37a without causing a significant temperature drop of the pressure roller 32. It can be resolved quickly. In addition, since the heating roller 31 can be efficiently heated, the recovery time during which the heating roller 31 rises to a temperature at which the fixing process can be performed can be shortened.

  Further, the control temperature of the pressure roller 32 in the standby mode may be higher than the control temperature of the pressure roller 32 in the operation mode and the return mode. As a result, the pressure roller 32 can maintain a sufficient amount of heat in the standby mode. Therefore, when shifting from the standby mode to the return mode, the power supply to the heating means 33 is stopped and the pressure roller 32 Even when the heating is stopped, the pressure roller 32 can heat the heating roller 31 at the nip portion.

  Further, when the heating roller 32 has heating regions formed by different heating sources as in the heating device 12, the set temperature of each heating region can be made different. That is, the circumferential length of the heating roller 32 in the at least two heating regions is made different, and the set temperature of the heating region in which the circumferential length is relatively short is relatively increased, so that the circumferential length is increased. The set temperature of the heating region having a relatively long length is relatively lowered. Specifically, in the heating device 12, the circumferential length of the heating region is usually formed in the nip portion rather than the heating region (hereinafter referred to as the coil side heating region) formed by heating by the induction coil 37a. The heating region (nip portion side heating region) is shorter. Therefore, the surface temperature of the heating roller 31 by the induction heating unit 37 and the pressure roller 32 is controlled so that the set temperature of the nip portion side heating region is higher than the set temperature of the coil side heating region.

  As described above, even if the set temperature of the nip portion side heating region is relatively high, the circumferential length of the nip portion side heating region is shorter than the coil side heating region. The influence on the temperature unevenness of the heating roller 31 in the standby mode is smaller than when the set temperature of the region is relatively high. Therefore, as described above, by setting the control temperature of the pressure roller 32 in the standby mode higher than the control temperature of the pressure roller 32 in the operation mode and the return mode, the temperature of the nip side heating region in the standby mode. However, even if the temperature is higher than the temperature of the coil side heating region, the temperature unevenness of the heating roller 31 is not increased.

  In the above description, the case where the heating roller 31 is always rotated in the return mode has been described as an example. However, the heating roller 31 may be intermittently rotated. That is, in the standby mode, since the rotation of the heating roller 31 is stopped, a heating region and a non-heating region exist. Therefore, temperature unevenness occurs on the surface of the heating roller 31 due to a temperature difference generated between the heating region and the non-heating region.

  Therefore, in the return mode, the heating roller 31 is intermittently rotated by repeating the rotation and the stop so that the non-heating region in the standby mode is heated intensively. That is, after the heating roller 31 is rotated so that the non-heating region in the standby mode is located at a heating position such as the induction coil 37a and the nip portion, the rotation is stopped. Thereby, since the non-heating area | region in standby mode is fully heated, the temperature nonuniformity of the heating roller 31 can be reduced efficiently. The intermittent rotation of the heating roller 31 is performed immediately after the transition to the return mode, and after the temperature unevenness of the heating roller 31 is reduced by the intermittent rotation, the heating roller 31 may be rotated at a predetermined speed.

  In the standby mode, when there are three heating regions and three non-heating regions on the surface of the heating roller 31 as in the heating device 12, there are three heating positions. Therefore, it is preferable to repeat the rotation of the heating roller 31 and the stop of the rotation so that the three non-heating regions are sequentially arranged at the three heating positions. Thereby, even when there is a difference in heating performance at each heating position, the surface of the heating roller 31 can be uniformly heated by eliminating the variation in the heating performance.

  Alternatively, when shifting from the standby mode to the return mode, the temperature distribution in the circumferential direction of the surface of the heating roller 31 may be detected, and the rotation angle of the heating roller 31 may be determined based on the detected temperature distribution. That is, the temperature distribution on the surface of the heating roller 31 is actually detected, and the rotation angle of the heating roller 31 is set so that heating can be performed at a position where the temperature unevenness on the surface of the heating roller 31 can be reduced most. Also good.

  Specifically, the heat generation distribution (hereinafter referred to as the following) at each position on the peripheral surface of the heating roller 31 when the control unit 36 is previously heated by the induction heating unit 37 and heated by the pressure roller 32 at the nip portion. (Heat generation distribution characteristic data) is stored. Then, after shifting to the return mode, first, the heating roller 31 is rotated once (360 ° rotation), and the temperature distribution (hereinafter, detected temperature data) at each position on the peripheral surface of the heating roller 31 detected by the thermistor 35 is detected. Then, the detected temperature data is stored in the control means 36.

  The control means 36 compares the detected temperature data with the heat distribution characteristic data stored in advance, and determines the optimum rotation angle of the heating roller 31. That is, using the detected temperature data and the heat generation distribution characteristic data, the temperature unevenness on the surface of the heating roller 31 when the heating roller 31 is rotated at an arbitrary rotation angle and heated at each heating position is evaluated. Based on this evaluation result, an optimal rotation angle of the heating roller 31 may be determined. The evaluation of the temperature unevenness on the surface of the heating roller 31 assumes that when the heating roller 31 is rotated at an arbitrary rotation angle, the surface of the heating roller 31 is heated by the heat generation distribution of the heat generation distribution characteristic data. The assumed temperature distribution on the surface of the heating roller 31 is represented by the sum of the temperature distribution of the temperature distribution data and the heat generation distribution of the heat generation distribution characteristic data at each position of the heating roller 31. Thereafter, a standard deviation which is a variation of the sum at each position of the heating roller 31 is obtained.

  The above operation is performed by sequentially changing the rotation angle of the heating roller 31, and the standard deviation at each rotation angle is compared. By this comparison, the rotation angle at which the smallest standard deviation is obtained may be determined as the optimum rotation angle for heating the heating roller 31. Thereby, in the return mode, it is possible to detect a low temperature region on the surface of the heating roller 31 and to intensively heat the detected low temperature region.

  In the present embodiment, the heating device in which the induction coil is arranged outside the heating roller has been described as an example. However, the present invention is not limited to this, and the induction coil may be arranged inside the heating roller. Good. Alternatively, a belt-shaped heating member may be used in place of the heating roller, and instead of the induction coil, the infrared rays from the halogen heater are reflected to the heating roller side by the reflecting plate, and the surface of the heating roller is localized. Heating may be used. That is, the present invention can be applied to a heating device configured to locally heat the heating member. Furthermore, the heating area provided in the heating roller is not limited to three, and may be four or more.

  Next, an image forming apparatus including the above-described heating device will be described with reference to FIG. FIG. 1 is a cross-sectional configuration diagram illustrating a system example of an image forming apparatus 100 using an electrophotographic process to which a heating apparatus of the present invention is applied.

  The image forming apparatus 100 is a printer capable of forming an image with multicolor and single color toners on a predetermined recording sheet based on, for example, image data transmitted from each terminal device on a network (not shown). As shown in FIG. 1, the image forming apparatus 100 includes the image forming station W (Wa / Wb / Wc / Wd), the transfer / conveying belt unit 8 and the sheet conveying path S / S ′ (along with the heating device 12 described above. In the drawing, a one-dot chain line), a paper feed tray 10 and paper discharge trays 15 and 81 are provided.

  Since the image forming apparatus 100 is capable of full-color printing and monochrome printing, four image stations Wa corresponding to each color of black (K), cyan (C), magenta (M), and yellow (Y).・ Wb, Wc, Wd are arranged side by side. That is, the image forming station Wa forms an image using black (K) toner, the image forming station Wb forms an image using cyan (C) toner, and the image forming station Wc uses magenta ( The image formation is performed using the toner M), and the image forming station Wd performs the image formation using the yellow (Y) toner.

  The image forming stations W (Wa to Wd) have substantially the same configuration, and each includes an exposure unit 1 (1a, 1b, 1c, 1d), a developing device 2 (2a, 2b, 2c, 2d), A photosensitive drum 3 (3a, 3b, 3c, 3d), a charger 5 (5a, 5b, 5c, 5d), and a cleaner unit 4 (4a, 4b, 4c, 4d) are provided. In the above and below, “a” to “d” assigned to each member number correspond to “a” to “d” assigned to each image forming station W.

  As the exposure unit 1 (1a to 1d), for example, an EL writing head or LED writing head in which light emitting elements are arranged in an array, a laser scanning unit (LSU) provided with a laser irradiation unit and a reflection mirror, or the like is used. The exposure unit 1 (1a to 1d) exposes the charged photosensitive drum 3 (3a to 3d) in accordance with input image data, whereby the surface of the photosensitive drum 3 (3a to 3d) is exposed. Then, an electrostatic latent image corresponding to the image data is formed.

  The developing unit 2 (2a to 2d) develops the electrostatic latent image formed on the surface of each photosensitive drum 3 (3a to 3d) using a toner of each color (K, C, M, Y). It is to become.

  The photosensitive drum 3 (3a to 3d) is an image carrier that forms an electrostatic latent image or a toner image corresponding to image data input on the surface of the photosensitive drum 3 (3a to 3d). The forming apparatus 100 is mounted almost at the center.

  The charger 5 (5a to 5d) uniformly charges the surface of the photosensitive drum 3 (3a to 3d) to a predetermined potential. The charger 5 (5a to 5d) may be, for example, a contact roller charger or a brush charger, or may be a non-contact charger charger.

  The cleaner unit 4 (4a to 4d) transfers a developing process in the developing device 2 (2a to 2d) and a toner image formed on the photosensitive drum 3 (3a to 3d) to a transfer belt 7 described later. Thereafter, the toner remaining on the surface of the photosensitive drum 3 (3a to 3d) is removed and collected.

  The transfer / conveying belt unit 8 is disposed below the photosensitive drum 3, and includes a transfer belt 7, a transfer belt driving roller 71, a transfer belt tension roller 72, a transfer belt driven roller 73, a transfer belt support roller 74, and a transfer roller. 6 (6a, 6b, 6c, 6d) and a transfer belt cleaning unit 9. The transfer belt drive roller 71, the transfer belt tension roller 72, the transfer roller 6 (6 a to 6 d), the transfer belt driven roller 73, and the transfer belt support roller 74 stretch the transfer belt 7 and transfer belt 7. Is driven to rotate in the direction of arrow B.

  The transfer roller 6 is rotatably supported by a frame (not shown) inside the transfer belt unit, and a toner image formed on the photosensitive drum 3 is attracted onto the transfer belt 7 and conveyed. It is to be transferred to paper. The transfer roller 6 (6a to 6d) is applied with a high voltage (a high voltage having a polarity (+) opposite to the toner charging polarity (-)) in order to transfer the toner image. The transfer roller 6 (6a to 6d) is based on a metal shaft such as stainless steel having a diameter of 8 to 10 mm, and the surface thereof is a conductive elastic material such as EPDM (ethylene-propylene-methylene copolymer) or urethane foam. Become covered by. By providing this conductive elastic material, a high voltage can be uniformly applied to the recording paper. In the image forming apparatus 100, a transfer electrode is used as the transfer roller 6 (6a to 6d), but a brush-like transfer electrode or the like can also be used.

  The transfer belt 7 is provided so as to be in contact with each photosensitive drum 3. The transfer belt 7 is endlessly formed using a film having a thickness of about 100 μm. The transfer belt cleaning unit 9 is set to remove and collect toner that adheres to the transfer belt 7 due to contact with the photosensitive drum 3 and causes the back surface of the recording paper to become dirty. The transfer belt cleaning unit 9 is provided with a cleaning blade, for example, as a cleaning member that contacts the transfer belt 7, and the transfer belt 7 that contacts the cleaning blade is supported by a transfer belt support roller 74 from the back side.

  The paper feed tray 10 is a tray for storing recording paper used for image formation, and is provided below the image forming stations W (Wa to Wd) of the image forming apparatus 100. Further, a paper discharge tray 15 provided on the upper portion of the image forming apparatus 100 is a tray for placing printed sheets face down. A paper discharge tray 81 provided on the side portion of the image forming apparatus 100 is a tray on which the image-formed sheet is placed face up.

  Further, in the image forming apparatus 100, the S-shaped paper transport path S • for feeding the recording paper in the paper feed tray 10 to the paper discharge tray 15 via the transfer transport unit 8 and the heating device 12. S ′ is provided. Further, along the paper transport path S · S ′ from the paper feed tray 10 to the paper discharge tray 15 and paper discharge tray 81, the pickup roller 16, the registration roller 14, the heating device 12, the transport direction switching gate 44, and the recording paper. A conveying roller 25 and the like are disposed.

  The transport roller 25 is a small roller for promoting and assisting the transport of the recording paper, and a plurality of the transport rollers 25 are provided along the paper transport path S. The pickup roller 16 is a pull-in roller that is provided at the end of the paper feed tray 10 and separates the recording paper one by one from the paper feed tray 10 and supplies it to the paper transport path S. The transport direction switching gate 44 is rotatably provided on the side cover 45. The conveyance direction switching gate 44 rotates from the state indicated by the solid line to the state indicated by the broken line, thereby switching the paper conveyance path S and discharging the recording paper to the paper discharge tray 81. When the transport direction switching gate 44 is in the state indicated by the solid line, the recording paper passes through the paper transport path S ′ formed between the heating device 12, the side cover 45, and the transport direction switching guide 44, and is discharged. It is discharged to the paper tray 15.

  The registration roller 14 temporarily holds the recording paper conveyed through the paper conveyance path S. Then, the recording paper is conveyed at a predetermined timing in accordance with the rotation of the photosensitive drum 3 so that the toner image on the photosensitive drum 3 can be satisfactorily transferred onto the recording paper. That is, the registration roller 14 adjusts the leading edge of the toner image on each of the photosensitive drums 3a to 3d to the leading edge of the image forming range on the recording paper based on a detection signal output from a pre-registration detection switch (not shown). The recording paper is set to be conveyed.

  In the image forming apparatus 100 configured as described above, the print processing operation is performed as follows. That is, when image data is input to the image forming apparatus 100 from the outside, the recording sheets stored in the paper feed tray 10 are separated one by one by the pickup roller 16 provided at the end of the paper feed tray 10. Then, the sheet is sent to the sheet conveyance path S. Thereafter, the recording sheet is conveyed to the registration roller 14, and the conveyance of the recording sheet is temporarily stopped with the leading edge of the recording sheet reaching the registration roller 14.

  In parallel with the feeding of the recording paper from the paper feed tray 10, the image forming stations Wa to Wd start forming a toner image based on the input image data. That is, when image data is input to the image forming apparatus 100, the surface of the photosensitive drum 3 (3a to 3d) is charged by the charger 5 (5a to 5d). Thereafter, an electrostatic latent image is formed on the surface of the photosensitive drum 3 (3a to 3d) by the exposure unit 1 (1a to 1d) according to the input image data. In order to develop the electrostatic latent image, toner is supplied from the developing device 2 (2a to 2d) to form a toner image.

  When the toner image is formed on the transfer belt 7 in this way, the recording paper is conveyed from the registration roller 14 at the timing when the leading edge of the toner image and the leading edge of the image forming range of the recording paper P are aligned. Be started. When the recording paper passes between the transfer roller 6 and the transfer belt 7, the toner image formed on the photosensitive drum 3 (3a to 3d) by the transfer roller 6 (6a to 6d) is placed on the recording paper. Transfer sequentially. By sequentially superimposing the toner images of the respective colors, a multicolor toner image is formed on the recording paper. Thereafter, after the toner image on the recording paper is melted and fixed by the heating device 12 and printed, it passes through the paper transport path S or S ′ by the transport roller 25 and onto the paper discharge tray 15 or the paper discharge tray 81. Discharged.

  Although the image forming apparatus provided with a plurality of image forming stations has been described above, the heating device 12 can be used for an image forming apparatus provided with a single image forming station. In the present embodiment, the image forming apparatus 100 has been described as a printer. However, the present invention is not limited to this, and a copier, a fax machine, or a digital composite having a printer function, a copy function, a fax function, etc. The heating device 12 can be applied to various image forming apparatuses that perform electrophotographic image formation, such as a printer.

[Embodiment 2]
Another embodiment of the present invention will be described below with reference to FIG. In this embodiment, in order to explain the difference from the first embodiment, for the sake of convenience of explanation, members having the same functions as those described in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. Is omitted.

  FIG. 16 is a schematic cross-sectional view of a heating device according to another embodiment of the present invention. The heating device shown in FIG. 16 replaces the pressure roller 32, the heating means 33, and the driver circuit 42 provided in the heating device 12 (FIG. 2) described in the first embodiment, respectively. (Pressure member / heating source) 40, heating means 41, and heating means side excitation circuit 34 '.

  The pressure roller 40 includes a pressure roller side metal core 40d, a pressure roller side elastic layer 40c, a pressure roller side heat generating layer 40b, and a pressure roller side release layer 40a. A pressure roller side elastic layer 40c, a pressure roller side heat generating layer 40b, and a pressure roller side release layer 40a are formed in this order on the side metal core 40d. The pressure roller side metal core 40d is formed of a metal such as aluminum, iron or stainless steel. The pressure roller side metal core 40d is preferably made of aluminum in order to prevent heat generation by induction heating.

  The pressure roller side elastic layer 40c is provided between the pressure roller side heat generation layer 40b and the pressure roller side cored bar 40d in order to fix and support the thinned pressure roller side heat generation layer 40b. It is done. By providing the pressure roller side elastic layer 40c, sufficient mechanical strength of the pressure roller side heat generating layer 40b can be ensured. The pressure roller side elastic layer 40c has heat insulation properties to prevent heat generated in the pressure roller side heat generating layer 40b from escaping to the pressure roller side cored bar 40d. Further, the pressure roller side elastic layer 40c has heat resistance that is not easily deteriorated by the heat generated by the pressure roller side heat generating layer 40b. Therefore, the pressure roller side elastic layer 40c is preferably formed of a material having excellent heat insulation and heat resistance such as foamed silicon rubber.

  The pressure roller side heating layer 40b is a heating element that generates heat by induction heating. In order to shorten the rise time of the surface temperature of the pressure roller 40, the thickness of the pressure roller side heat generating layer 40b is preferably thinned to about 40 μm, for example. Since the material of the pressure roller side heat generating layer 40b is heated by induction heating, it may be any conductive member having magnetism such as iron or SUS430 stainless steel. In particular, a material having a high relative permeability is preferable, and a silicon steel plate, an electromagnetic steel plate, nickel steel, or the like can be used. Moreover, even if it is a nonmagnetic material, if it is a material with high resistance value, it will generate | occur | produce heat | fever by induction heating, Therefore You may use SUS304 stainless steel material etc. Furthermore, as the pressure roller side heat generating layer 40b, a non-magnetic base member such as ceramic may be used as long as a material having a high relative permeability is disposed so as to have conductivity.

  The pressure roller side release layer 40a covers the surface (outer peripheral surface) of the pressure roller side heat generating layer 40b, and the toner whose viscosity is lowered by heating at the nip (pressure contact) portion adheres to the surface of the heating roller. To prevent. The pressure roller side release layer 40a is made of a fluororesin such as PTFE or PFA, an elastic body such as silicon rubber, fluororubber or fluorosilicone rubber, or a plurality of these laminated.

  The heating means 41 is an induction heating type heating source that causes an alternating magnetic field to act on the pressure roller side heat generating layer 40b of the pressure roller 40 to generate heat in the pressure roller side heat generating layer 40b. As shown in FIG. 16, the heating means 41 has an induction heating coil (heating source) 41a and a resin holder 41b for holding the induction heating coil 41a, and faces the outer peripheral surface of the pressure roller 40. Are arranged to be. More specifically, the heating means 41 locally covers the outer peripheral surface of the pressure roller 40 with a predetermined curvature along the outer peripheral surface of the pressure roller side heat generating layer 40b of the pressure roller 40. Has been placed.

  The induction heating coil 41a is formed by winding a conducting wire a plurality of times with an air core. That is, it is wound in a spiral shape along the rotational direction of the pressure roller 40 so that a gap is formed in the central portion of the induction heating coil 41a. For the conductive wire forming the induction heating coil 41a, for example, an aluminum single wire having an oxide film as a surface insulating layer may be used in consideration of heat resistance. Or you may use the litz wire which makes a copper wire or a copper-based composite member wire, an enameled wire, etc. a stranded wire. In any case, in order to suppress the Joule loss in the induction heating coil 41a, the total resistance value of the induction heating coil 41a is preferably 0.5Ω or less, preferably 0.1Ω or less. More preferably.

  The heating means side excitation circuit 34 'is connected to the induction heating coil 41a and supplies a high frequency current to the induction heating coil 41a.

  The pressure roller 40 is induction-heated by an alternating magnetic field generated by flowing a high-frequency current from the heating means side excitation circuit 34 'shown in FIG. The heat generation distribution of the pressure roller 40 at this time is the same as the heat generation distribution of the heating roller 31 as described in the first embodiment with reference to FIG.

  The operation when the unfixed toner image is fixed on the recording paper P by the heating apparatus having the above configuration is different from that of the first embodiment in the following points. That is, in the first embodiment, the entire pressure roller 32 is heated by supplying power to the heating means 33 by controlling the driver circuit 42 shown in FIG. In contrast, in the present embodiment, the heating means side excitation circuit 34 'connected to the induction heating coil 41a is turned on by the control of the control means 36, and a high frequency current is supplied to the induction heating coil 41a. Thereby, the induction heating coil 41a is excited, and an alternating magnetic field is generated in the induction heating coil 41a. When this alternating magnetic field acts on the pressure roller side heat generating layer 40b of the pressure roller 40, an eddy current is induced in the pressure roller side heat generating layer 40b and Joule heat is generated. As a result, the pressure roller 40 generates heat, and the heating roller 31 is heated at the nip portion.

  Like the heating device, the pressure roller 40 may have a heating region that is locally heated, like the heating roller 31.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. Embodiments are also included in the technical scope of the present invention.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example and a comparative example, this invention is not limited to this.

  As the heating device 12 having the configuration shown in FIG. 2, a heating roller 31, a pressure roller 32, an induction heating unit 37, and a heating unit 33 having the following configurations were used. That is, as the heating roller 31, an elastic layer 31c formed of a foamed silicon sponge having a thickness of 6 mm on the outer surface of an aluminum core 31d having a diameter of 28 mm, and nickel having a thickness of 40 μm manufactured by electroforming. A heat release layer 31b and a release layer 31a in which a PFA tube layer having a thickness of 30 μm is provided on a silicon rubber (LTV) layer having a thickness of 150 μm are used in this order.

  As the pressure roller 32, a roller having a pressure roller side release layer 32 a formed by coating a hollow pressure roller side core metal 32 a made of aluminum with a diameter of 30 mm with PTFE having a thickness of 30 μm was used. The pressure roller 32 was set to be in pressure contact with the heating roller 31 at 280 N by an elastic member (not shown), and the width of the nip portion formed by the pressure contact was about 6 mm. Further, a halogen lamp was used as the heating means 33.

  In order to form the induction coil 37a of the induction heating means 37, an aluminum single wire whose surface was covered with an oxide film was used. As shown in FIG. 2, the aluminum single wire extends along the outer peripheral surface of the heating roller 31 so that the heat generation peak positions P1 and P2 on the surface of the heating roller 31 form an angle of 120 ° with respect to the rotation axis of the heating coil 31. The induction coil 37a was wound. Further, the exothermic peak positions P1 and P2 were set to be about 120 ° in terms of the rotation axis of the heating coil 31 from the center P3 of the nip portion between the heating roller 31 and the pressure roller 32, respectively. As a result, the two heating regions on the surface of the heating roller 31 formed by heating the induction coil 37a are each about 130 ° around the rotation axis and about 45 mm in the circumferential direction of the heating roller 31. Further, as the resin holder 37b, a holder made of G-PET (polyethylene terephthalate containing glass reinforced fibers) was used, and the induction coil 37a was held by the resin holder 37b.

  Using the heating device 12, operation control was performed in the temperature control sequence shown in Table 1. In Table 1, the war-up is a period from when the power to the heating device 12 is turned on until the operation mode is shifted to, and the operation mode is a period during which the unfixed toner image T is fixed to the recording paper P. The standby mode is a period from the end of the operation mode until the next fixing process is performed, and the return mode is a period from the standby mode to the transition to the operation mode. The above description applies similarly to the table shown below.

  After turning on the power to the heating device 12, under the control of the control means 36, the excitation circuit 34 and the driver circuit 42 generate electric power of the magnitude shown in the column of warm-up in Table 1 from the induction heating means 37 and the heating means. 33. The total amount of power at this time is 1200W. Simultaneously with the supply of electric power, the heating roller 31 was rotated by the driving unit 43 and the pressure roller 32 was driven and rotated under the control of the control unit 36. Thereafter, the heating roller 31 and the pressure roller 32 are heated until the control temperature shown in the warm-up column in Table 1 is reached, and the control means 36 detects the detection signals of the heating roller side thermistor 35 and the pressure roller side thermistor 38. When it is determined that the heating roller 31 and the pressure roller 32 have reached the control temperature, the operation mode is entered.

  After shifting to the operation mode, the amount of electric power supplied to the induction heating means 37 was switched to the magnitude shown in the column of the operation mode in Table 1. The total amount of power at this time is 950 W. Subsequently, the recording paper P on which the unfixed toner image T was formed was passed through the nip portion, and the unfixed toner image T was fixed on the recording paper P. When the passing of the recording paper P is completed, the mode is changed to the standby mode, and the rotation of the heating roller 31 and the pressure roller 32 is stopped. Thereafter, the amount of electric power supplied to the induction heating unit 37 and the heating unit 33 was controlled so that the control temperature shown in the column of standby mode in Table 1 was reached, and the standby mode was set for 15 minutes.

  Subsequently, when a fixing process request is made to the heating device, the process shifts to the return mode, and electric power having a magnitude shown in the column of the return mode in Table 1 is supplied to the induction heating unit 37 and the heating unit 33. The total amount of power at this time is 1200W. Simultaneously with the supply of electric power, the heating roller 31 is rotated by the driving unit 43 under the control of the control unit 36 until the control temperature shown in the column of the return mode in Table 1 is reached. 32 was heated.

  FIG. 5 shows the surface temperature of the heating roller 31, the surface temperature of the pressure roller 32, and the power consumption of the induction heating means 37 in the return mode. In FIG. 5, the horizontal axis indicates the elapsed time when the time point when the standby mode is switched to the return mode is set to 0 second, and the vertical axis indicates the surface temperatures of the heating roller 31 and the pressure roller 32 (in the drawing, Roller temperature) and the amount of induction heating power supplied to the induction heating means 37.

  Using the heating device 12 having the configuration described in Example 1, operation control was performed according to the temperature control sequence shown in Table 2. The temperature control sequence of the first embodiment and the temperature sequence of the present embodiment are different in control temperature of the heating roller 31 and the pressure roller 32 in the standby mode, and are supplied to the induction heating unit 37 and the heating unit 33 in the return mode. The same procedure as in Example 1 was performed except that the amount of power was different. That is, in the present embodiment, in the return mode, the power supply to the heating unit 33 is stopped, and the power supplied to the heating unit 33 is supplied to the induction heating unit 37.

  FIG. 6 shows the surface temperature of the heating roller 31, the surface temperature of the pressure roller 32, and the power consumption of the induction heating means 37 in the return mode. The horizontal and vertical axes in FIG. 6 are the same as those in FIG.

  As shown in FIGS. 5 and 6, it can be seen that in Example 1 (FIG. 5) and 2 (FIG. 6), the temperature unevenness on the surface of the heating roller 31 can be quickly eliminated in the return mode. In particular, in the second embodiment, as shown in FIG. 6, the temperature unevenness on the surface of the heating roller 31 in the return mode is further reduced as compared with the first embodiment. Therefore, in the second embodiment, the temperature difference between the control temperature of the heating roller 31 and the control temperature of the pressure roller 32 in the standby mode is smaller than that in the first embodiment, so that the heating region on the surface of the heating roller 31 is increased. It can be seen that the temperature difference between the unheated region and the non-heated region can be reduced.

  The circumferential length of the surface of the heating roller 31 heated by the induction coil 37a is about 45 mm, whereas the width of the nip portion is about 6 mm. The length is different. Therefore, in the standby mode, even if the control temperature of the pressure roller 32 is higher than the control temperature of the heating roller 31 as in the second embodiment, the width of the nip portion is narrowed. Further, as compared with the case where the control temperature of the heating roller 31 is higher than the control temperature of the pressure roller 32, the temperature unevenness on the surface of the heating roller 31 can be suppressed. Therefore, compared with Example 1, it is thought that Example 2 can further reduce the temperature unevenness of the surface of the heating roller 31 in the return mode.

  Further, in the second embodiment, compared with the first embodiment, the return time until the surface temperature of the heating roller 31 reaches the control temperature at which the fixing process can be performed in the return mode is shorter. This suggests that the return time can be shortened by stopping the power supply to the heating means 33 in the return mode and increasing the amount of power supplied to the induction heating means 37. That is, the entire pressure roller 32 is uniformly heated by the heating means 33 disposed inside the pressure roller 32 in the standby mode. Therefore, even when the pressure roller 32 rotates in the return mode, the heating roller 31 can be heated at the nip portion, so that the temperature of the heating roller 31 is not lowered. Therefore, by increasing the power supply amount to the induction heating means 37 with higher heating efficiency, the return time can be shortened compared to the first embodiment.

  In the second embodiment, the temperature drop of the pressure roller 32 immediately after the return mode is shifted is very small although the pressure roller 32 is not heated in the return mode. This is considered because the heat capacity of the pressure roller 32 is larger than that of the heat roller 31 and the pressure roller 32 holds a sufficient amount of heat in the standby mode.

[Comparative example]
Instead of the heating device 12 having the configuration described in Example 1, a heating device shown in FIG. 17 was used. That is, instead of the pressure roller 32 described in the first embodiment, the configuration described in the first embodiment is provided except that the pressure roller 39 shown in FIG. 17 is used and the heating unit 33 and the driver circuit 42 are not provided. A heating device was used. As the pressure roller 39, a silicon rubber layer 39b having a thickness of 5 mm is provided on an iron pressure roller side metal core 39c having a diameter of 20 mm, and a pressure roller side separation made of a PFA tube having a thickness of 50 μm is further provided. What has the type | mold layer 39a was used. The pressure roller 39 was set so as to be in pressure contact with the heating roller 31 at 280 N by an elastic member (not shown), and the width of the nip portion formed by the pressure contact was about 7 mm.

  Operation control was performed by the temperature control sequence shown in Table 3 using the heating apparatus having the above configuration. In this comparative example, since a heating device that does not include the heating unit 33 is used, it is not necessary to supply power to the heating unit 33 and it is not necessary to control the temperature of the pressure roller 39. Therefore, the same amount of power as the total amount of power supplied to the heating roller 31 and the pressure roller in Example 1 was supplied to the heating roller of this comparative example. The control temperature of the heating roller 31 is the same as in the first embodiment.

  FIG. 7 shows the surface temperature of the heating roller 31, the surface temperature of the pressure roller 39, and the power consumption of the induction heating means 37 in the return mode. The horizontal and vertical axes in FIG. 7 are the same as those in FIG.

  As shown in FIGS. 5 and 7, it can be seen that in Example 1 (FIG. 5), the temperature unevenness of the heating roller 31 at the time of return is much smaller than in the comparative example (FIG. 7). From this, it can be understood that, in the standby mode, the heating roller 31 is heated in three locally existing heating regions, so that the temperature unevenness on the surface of the heating roller 31 can be quickly eliminated in the return mode. .

  That is, in Example 1, as shown in FIG. 2, the heating roller 31 is heated by the induction heating unit 37 and the pressure roller 32, and in the comparative example 1, the heating roller 31 is heated by the induction heating unit 37. That is, in Example 1, the heating roller 31 is heated in three heating regions, whereas in Comparative Example 1, the heating roller 31 is heated in two heating regions. Therefore, the size of the temperature unevenness generated on the surface of the heating roller 31 in the standby mode varies depending on the number of heating regions existing on the surface of the heating roller 31, and the temperature unevenness on the surface of the heating roller 31 in the standby mode decreases as the heating region decreases. It seems that it is getting bigger. Therefore, in the return mode, the temperature unevenness on the surface of the heating roller 31 can be eliminated more quickly in Example 1 where the temperature unevenness of the heating roller 31 is smaller in the standby mode than in Comparative Example 1. In particular, in the first embodiment, since the three heating regions are arranged so that the heating regions are equally spaced, the temperature unevenness on the surface of the heating roller 31 is reduced more quickly in the return mode. It is considered possible.

  Further, as shown in FIGS. 5 and 7, in the return mode, the amount of electric power by induction heating consumed in Example 1 and the comparative example was substantially the same. Therefore, in the first embodiment, in the return mode, it is possible to efficiently reduce the temperature unevenness on the surface of the heating roller 31 with the same power consumption as in the comparative example.

  Using the heating apparatus having the configuration described in Example 1, operation control was performed according to the temperature control sequence shown in Table 4. The temperature control sequence of the present embodiment is the same as that of the second embodiment except that the heating roller 31 and the pressure roller 32 are rotated and the rotation operation is stopped in the return mode. Specifically, in the present embodiment, in the return mode, the heating roller 31 is first rotated by 180 °, stopped in this state and held for 0.5 seconds, and then the heating roller 31 is rotated again, In Table 4, heating was performed until the control temperature shown in the column of return mode was reached. By the rotation of the heating roller 31, the non-heating region of the heating roller 31 in the standby mode is moved to the heating position where the heating source is arranged, and the non-heating region is heated intensively.

  FIG. 8 shows the surface temperature of the heating roller 31, the surface temperature of the pressure roller 32, and the power consumption of the induction heating unit 37 in the return mode. The horizontal and vertical axes in FIG. 8 are the same as those in FIG.

  As shown in FIGS. 6 and 8, in Example 3 (FIG. 8), it is understood that the temperature unevenness of the heating roller in the return mode is further reduced compared to Example 2 (FIG. 6). Therefore, by unevenly heating the non-heating area in the standby mode in the return mode, the temperature unevenness on the surface of the heating roller 31 can be efficiently eliminated.

  The same operation as in Example 3 was performed except that the operation control of the heating device was performed in the temperature control sequence shown in Table 5. The temperature control sequence of this embodiment is the same as that of Embodiment 3 except for the return mode. That is, in the return mode of the present embodiment, the heating roller 31 was first rotated by 60 °, stopped in this state, and held for 0.33 seconds. Thereafter, the heating roller 31 is further rotated by 120 °, the rotation is stopped in this state, the operation of holding for 0.33 seconds is repeated twice, and then the heating roller 31 is rotated again to return in Table 5 Heating was performed until the control temperature indicated in the mode column was reached. By rotating the heating roller 31, the non-heating area of the heating roller 31 in the standby mode is sequentially moved to each heating position where the heating source is arranged, and the heating of each non-heating area is performed at all the heating positions. The effect of the difference in heating performance at the heating position was reduced.

  FIG. 9 shows the surface temperature of the heating roller 31, the surface temperature of the pressure roller 32, and the power consumption of the induction heating means 37 in the return mode. The horizontal and vertical axes in FIG. 9 are the same as those in FIG.

  As shown in FIGS. 8 and 9, it can be seen that in Example 4 (FIG. 9), the temperature unevenness of the heating roller in the return mode is further reduced compared to Example 3 (FIG. 8). Accordingly, in the return mode, the non-heating area in the standby mode is heated intensively and evenly, so that the difference in heating performance at the heating position is reduced, and the temperature unevenness on the surface of the heating roller 31 is more efficiently eliminated. can do.

  The same operation as in Example 1 was performed except that the operation control of the heating device was performed in the temperature control sequence shown in Table 6. The temperature control sequence of this embodiment is the same as that of the first embodiment except for the return mode. That is, in the return mode of this embodiment, the heating roller 31 is rotated once (360 ° rotation), and at this time, the temperature distribution at each position on the peripheral surface of the heating roller 31 detected by the thermistor 35 (hereinafter, detected temperature data). ) And the heat generation distribution at each position on the peripheral surface of the heating roller 31 (hereinafter referred to as heat generation distribution characteristic data) when the heating roller 31 whose rotation has been stopped is heated by the induction heating unit 37, the control unit 36 heats The rotation angle of the roller 31 was determined.

  The detected temperature data is shown in FIG. 10, and the heat generation distribution characteristic data 2 is shown in FIG. Here, in FIG. 10, the horizontal axis represents the rotation angle of the heating roller 31, and the arrangement position of the thermistor 35 on the surface of the heating roller 31 before the rotation of the heating roller 31 is 0 °. The vertical axis indicates the detected temperature as a percentage obtained by dividing the detected temperature by the highest temperature among the detected temperatures.

  Thereafter, the heating roller 31 is rotated to the determined rotation angle, stopped in this state, held for a predetermined time, and then the heating roller 31 is rotated again, as shown in the return mode column in Table 6. Heating was performed until a controlled temperature was reached.

  The control means 36 determined the rotation angle of the heating roller 31 as follows. That is, the heating roller 31 is efficiently heated by rotating the heating roller 31 so that the low temperature region of the heating roller 31 is the region that generates the most heat by the heating by the induction heating unit 37. Can do. The temperature unevenness of the heating roller 31 when the heating roller 31 is rotated by the respective rotation angles and heated by the induction heating means 37 can be evaluated using the detected temperature data and the heat generation distribution data. That is, when the heat generation distribution characteristic data shown in FIG. 4 and the temperature detection data shown in FIG. 10 are overlapped, the value of the heat generation distribution (vertical axis in FIG. 4) and the temperature distribution at each position of the heating roller 31. A sum with the value (vertical axis in FIG. 10) is obtained, and a standard deviation σ which is a variation of the sum at each obtained position is calculated. The superposition is performed by sequentially changing the rotation angle of the heating roller 31, the standard deviation σ of the sum at each rotation angle is calculated, and the rotation angle at which the standard deviation σ is the smallest is the heating roller most efficiently. It will be in the state which can heat 31. That is, by rotating the heating roller 31 to the rotation angle at which the standard deviation σ is minimized and performing the heating by the induction heating unit 37, the temperature unevenness on the surface of the heating roller 31 can be suppressed by the heating in the return mode. it is conceivable that.

  Accordingly, the heat distribution characteristic data (FIG. 4) of the induction heating means 37 measured in advance and the detected temperature data (FIG. 10) at each position of the heating roller 31 obtained by rotating the heating roller 31 once after returning to the return mode. ) To obtain the standard deviation σ when the heating roller 31 is rotated at each rotation angle. The result is shown in FIG. 11, the horizontal axis is the same as the horizontal axis in FIG. 10, and the vertical axis is the standard deviation σ. As shown in FIG. 11, the standard deviation σ is minimized when the heating roller 31 is rotated by 155 °.

  Therefore, after shifting to the return mode, the control unit 36 first rotates the heating roller 31 and then further rotates the heating roller 31 by 155 ° to stop the rotation in this state for 0.33 seconds. After being held, the heating roller 31 was rotated again, and heating was performed until the control temperature shown in the column of the return mode in Table 6 was reached.

  FIG. 12 shows the surface temperature of the heating roller 31, the surface temperature of the pressure roller 32, and the power consumption of the induction heating means 37 in the return mode. The horizontal and vertical axes in FIG. 12 are the same as those in FIG.

  As shown in FIGS. 5 and 12, in Example 5 (FIG. 12), it is understood that the temperature unevenness of the heating roller 31 in the return mode is further reduced as compared with Example 1 (FIG. 5). Therefore, it can be seen that the temperature unevenness on the surface of the heating roller 31 in the return mode can be efficiently eliminated by rotating the heating roller 31 and stopping the rotation in the return mode.

  The heating apparatus shown in FIG. 16 was used in place of the heating apparatus having the configuration described in Example 1, and the operation was performed in the same manner as in Example 1 except that the operation control of the heating apparatus was performed in the temperature control sequence shown in Table 7. It was. That is, instead of the pressure roller 32, the heating means 33, and the driver circuit 42 described in the first embodiment as the heating device, the pressure roller 40, the heating means 41, and the heating means side excitation circuit 34 ′ shown in FIG. The heating apparatus provided with the structure demonstrated in Example 1 was used except having used. The temperature control sequence is the same as the temperature control sequence of the first embodiment. However, in the first embodiment, since the heating means 41 is used instead of the heating means 33, the heating means 33 in the second embodiment is used. The input power is input to the heating means 41.

  As the pressure roller 40, a pressure roller side elastic layer 40c formed of foamed silicon sponge having a thickness of 6 mm on a pressure roller side metal core 40d made of aluminum having a diameter of 18 mm, nickel having a thickness of 40 μm. A pressure roller side release layer 40a in which a PFA tube layer having a thickness of 30 μm is provided on a 150 μm thick silicon rubber (LTV) layer is formed in this order. Was used. The pressure roller 40 was set so as to be in pressure contact with the heating roller 31 at 280 N by an elastic member (not shown), and the width of the nip portion formed by the pressure contact was about 7 mm.

  In order to form the induction coil 41a of the heating means 41, an aluminum single wire whose surface was covered with an oxide film was used. As shown in FIG. 2, the heat generation peak positions at two locations on the surface of the pressure roller 40 on the surface of the pressure roller 40 are 120 ° at an angle with respect to the rotation axis of the pressure coil 40. The coil was wound along the outer peripheral surface of the pressure roller 40 to obtain an induction coil 41a. In addition, the two heat generation peak positions were set to be about 120 ° in terms of the rotation axis of the pressure coil 40 from the center of the nip portion between the heating roller 31 and the pressure roller 40, respectively. Further, a G-PET holder was used as the resin holder 41b, and the induction coil 41a was held by the resin holder 41b.

  FIG. 13 shows the surface temperature of the heating roller 31, the surface temperature of the pressure roller 40, and the power consumption of the induction heating means 37 in the return mode. The horizontal and vertical axes in FIG. 13 are the same as those in FIG. Table 8 shows the temperature unevenness of each of the heating roller 31 and the pressure roller 40 when the return is completed after the return mode transition.

  A configuration similar to that of Example 6 except that a pressure roller having a pressure roller side metal core 40d having a diameter of 40 mm is used in place of the pressure roller 40 provided in the heating device having the configuration described in Example 6. The operation control of the heating device was performed in the same temperature control sequence as in Example 6. FIG. 14 shows the surface temperature of the heating roller 31, the surface temperature of the pressure roller, and the power consumption of the induction heating means 37 in the return mode. The horizontal and vertical axes in FIG. 14 are the same as those in FIG. Table 8 shows the temperature unevenness of each of the heating roller 31 and the pressure roller 40 when the return is completed after the return mode transition.

  Heating of the same configuration as that of Example 6 except that a pressure roller side cored bar 40d pressure roller having a diameter of 20 mm was used instead of the pressure roller 40 provided in the heating device having the configuration described in Example 6. Using the apparatus, the operation control of the heating apparatus was performed in the same temperature control sequence as in Example 6. FIG. 15 shows the surface temperature of the heating roller 31, the surface temperature of the pressure roller, and the power consumption of the induction heating means 37 in the return mode. The horizontal and vertical axes in FIG. 15 are the same as those in FIG. Table 8 shows the temperature unevenness of each of the heating roller 31 and the pressure roller 40 when the return is completed after the return mode transition.

  As shown in FIGS. 13 to 15 and Table 8, the outer diameter of the heating roller 31 is an integral multiple of the outer diameter of the pressure roller 40 (Examples 7 and 8). It can be seen that the temperature unevenness of the heating roller 31 in the return mode can be suppressed when it is not (Example 6). In other words, when the heating roller 31 and the pressure roller 40 are rotated in the return mode, the heating roller 31 is configured so that the region in contact with the pressure roller 40 at the nip portion is different every time the heating roller 31 rotates once. It can be seen that the temperature unevenness of the heating roller 31 and the pressure roller 40 is reduced by setting the outer diameters of the pressure roller 31 and the pressure roller 40.

  In the comparative example, the heating apparatus having the configuration shown in FIG. 17 has been described. However, the temperature control sequence for rotating the heating roller 31 and stopping the rotation in the return mode described in the third to fifth embodiments. Can also be applied to the heating device shown in FIG.

  The heating device of the present invention can quickly eliminate the uneven temperature of the heating roller when returning from the standby mode. Therefore, in the image forming apparatus such as a printer, a copier, a fax machine, or a digital multifunction machine having these functions, the fixing process is performed by using the heating roller having a small temperature unevenness by using the heating device as a fixing device. Therefore, it is possible to provide an image forming apparatus capable of performing the above.

  Furthermore, the heating device is suitably used as a fixing device in dry electrophotographic equipment, a drying device in wet electrophotographic equipment, a drying device in an inkjet printer, an erasing device for rewritable media, and the like.

1 is a schematic configuration diagram of an image forming apparatus including a heating device of the present invention. It is a schematic block diagram of the heating apparatus concerning one Embodiment of this invention. It is a top view of the induction heating means with which the said heating apparatus is equipped. It is a graph which shows the heat-generation distribution characteristic of the circumferential direction of the heating roller heated by the said induction heating means. It is a graph which shows the surface temperature of the heating roller and pressure roller at the time of the return of a heating apparatus performed in Example 1, and the induction heating electric energy consumed by the induction heating means. It is a graph which shows the surface temperature of the heating roller and pressure roller at the time of return of a heating apparatus performed in Example 2, and the induction heating electric energy consumed by the induction heating means. It is a graph which shows the surface temperature of the heating roller and pressure roller at the time of return of a heating apparatus performed in the comparative example, and the induction heating electric energy consumed by the induction heating means. It is a graph which shows the surface temperature of the heating roller and pressurization roller at the time of the return of a heating apparatus performed in Example 3, and the induction heating electric energy consumed by the induction heating means. It is a graph which shows the surface temperature of the heating roller and pressure roller at the time of the return of a heating apparatus performed in Example 4, and the induction heating electric energy consumed by the induction heating means. 10 is a graph showing the temperature distribution on the surface of the heating roller when the heating roller is rotated once at the time of return, as detected in Example 5. 10 is a graph showing the standard deviation of the surface temperature of the heating roller calculated based on detected temperature data and heat generation distribution data in Example 5. It is a graph which shows the surface temperature of the heating roller and pressure roller at the time of the return of a heating apparatus performed in Example 5, and the induction heating electric energy consumed by the induction heating means. It is a graph which shows the surface temperature of the heating roller and pressure roller at the time of the return of a heating apparatus performed in Example 6, and the induction heating electric energy consumed by the induction heating means. It is a graph which shows the surface temperature of the heating roller and pressure roller at the time of the return of a heating apparatus performed in Example 7, and the induction heating electric energy consumed by the induction heating means. It is a graph which shows the surface temperature of the heating roller and pressure roller at the time of the return of a heating apparatus performed in Example 8, and the induction heating electric energy consumed by the induction heating means. It is a schematic block diagram of the heating apparatus concerning other embodiment of this invention. It is a schematic block diagram of the heating apparatus used in the comparative example.

Explanation of symbols

12 Heating device 31 Heating roller (heating member)
31a Release layer 31b Heat generation layer 31c Elastic layer 31d Core metal 32 Pressure roller (Pressure member / heating source)
33 Heating means (internal heat source)
34 Excitation circuit 34 'Heating means side excitation circuit 35 Thermistor for heating roller 36 Control means 37 Induction heating means (heating source / local heating source)
37c Parallel part (heating source)
38 Thermistor for pressure roller 40 Pressure roller (pressure member / heating source)
41 Heating means 42 Driver circuit 43 Driving means 100 Image forming apparatus P Recording paper (heated material)

Claims (18)

A pressure member that is in pressure contact with the heating member and rotates with the rotation of the heating member is provided, and the peripheral surface of the heating member is locally heated by a heating source, thereby extending between both ends in the rotation axis direction of the heating member. In the heating device in which the heating region is formed parallel to the rotation axis direction,
When the rotation of the heating member is stopped, the heating member has at least three heating regions on the peripheral surface of the heating member.   When the rotation of the heating member is stopped, non-heated regions and the heated regions that are not heated by the heating source are alternately formed on the peripheral surface of the heating member along the rotation direction of the heating member. The heating device according to claim 1, wherein   The heating apparatus according to claim 2, wherein the heating regions are formed at equal intervals.   4. The heating device according to claim 1, wherein an outer peripheral length of the heating member and an outer peripheral length of the pressure member are different from each other.   Of the heating member and the pressure member, the outer peripheral length of one member having a relatively long outer peripheral length is not an integral multiple of the outer peripheral length of the other member having a relatively shorter outer peripheral length. The heating apparatus according to claim 4. The heating member has a heat generating layer that generates heat by the heating source,
6. The heating apparatus according to claim 1, wherein at least one of the heating sources is induction heating means for heating the heat generating layer by induction heating.   The heating apparatus according to claim 6, wherein the induction heating unit is disposed so as to face an outer periphery of the heating member.   The heating device according to any one of claims 1 to 5, wherein the pressure member is at least one of the heat sources.   The heating apparatus according to claim 6, wherein the pressurizing member has an internal heat source that uniformly heats the entire pressurizing member inside the pressurizing member.   An image forming apparatus comprising the heating device according to claim 1. A pressure member that press-contacts the heating member to form a pressure-contact portion is provided, and a heating region extending between both end portions in the rotation axis direction of the heating member is obtained by locally heating the peripheral surface of the heating member with a heating source. The heating device formed in parallel with the rotation axis direction rotates the heating member and the pressure member in the operating state, thereby heating the material to be heated at the pressure contact portion and in the standby state. In the heating method of the heating device that stops the rotation of the heating member and the pressure member and preheats the heating member with the heating source,
The return state for performing the operation to return from the standby state to the operation state is
A first step of rotating the heating member and the pressure member;
A second step of stopping the rotation of the heating member and the pressure member at a predetermined position for a predetermined time;
And a third step of resuming the rotation of the heating member and the pressure member. In the standby state, on the peripheral surface of the heating member, non-heating regions that are not heated by the heating source and the heating regions are alternately formed along the rotation direction of the heating member,
The heating device according to claim 11, wherein, in the second step of the return state, rotation of the heating member is stopped at a position where the non-heating region in the standby state is heated by the heating source. Heating method.   In the standby state, at least two heating regions are formed on the peripheral surface of the heating member, and the heating regions are formed at equal intervals along the rotation direction of the heating member. The heating method of the heating device according to claim 12, wherein: As the heating source, a pressure member having an internal heat source for heating the entire pressure member uniformly and heating the heating member at the position of the pressure contact portion in the standby state is used. Using a local heating source that heats the heating member at a position other than the pressure contact portion in a standby state,
The power source of the internal heat source is turned off in the return state, and more electric energy is supplied to the local heating source than the electric energy supplied to the local heating source in the operation state. The heating method of the heating device according to any one of 11 to 13.   The heating method of the heating device according to claim 14, wherein the set temperature of the pressurizing member in the standby state is set to be higher than the set temperature in the operating state. In the standby state, the peripheral surface of the heating member has at least two heating regions,
In the standby state, the set temperature in the first heating region in which the length of the heating region in the rotation direction of the heating member is relatively narrow is set in the second heating region in which the length of the heating region is relatively wide. The heating method of the heating device according to any one of claims 11 to 15, wherein the heating device is set to a temperature higher than the temperature. In the first step, the heating member is rotated at least once, and the temperature distribution on the peripheral surface of the heating member is stored,
The rotation of the heating member is stopped in the second step at a position where a relatively low temperature region is heated by the heating source based on the temperature distribution. The heating method of the heating apparatus of any one of these.   The heating method of the heating device according to any one of claims 11 to 17, wherein the second step and the third step are repeated.

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