JP5639488B2 - Image heating device - Google Patents

Description

  The present invention relates to an image heating apparatus used in an image forming apparatus adopting an image forming process such as an electrophotographic system or an electrostatic recording system, such as a copying machine, a facsimile machine, or a printer. As an image heating device, a fixing device that heats and fixes an unfixed toner image formed on a recording material as a fixed image, or a glossiness increasing device that increases the glossiness of an image by heating the image fixed on the recording material Etc.

  In recent years, a fixing device having a small heat capacity has been proposed and put into practical use from the viewpoint of energy saving in an image forming apparatus using an electrophotographic system. As a specific measure for reducing the heat capacity of the fixing device, there is a belt fixing method using a belt-like endless belt (hereinafter referred to as a fixing belt) as a fixing member, and the following configurations have been proposed.

  In Patent Document 1, a ceramic heater as a heating element is disposed in a nip portion formed by a fixing member and a pressure member, and an unfixed toner image is applied by applying pressure in the fixing region while applying heat from the heater via a fixing belt. Describes a belt fixing method for fixing the toner image onto the recording material surface. In this fixing method, since the heat capacity of the heater and the fixing member is small, the waiting time from the power-on of the image forming apparatus to the image forming executable state is short (quick start property), and the power consumption during standby is also significantly small (power saving) ) Etc.

  However, since the belt fixing device of Patent Document 1 is configured to locally heat the nip portion with the pressure roller via the fixing belt (partial heating in the belt circumferential direction), it rotates to heat the entire circumference of the fixing belt. It is necessary to warm up while driving. For this reason, there is a problem that the warm-up time becomes longer than necessary. As a means for solving this problem, a fixing device in which a resistance heating layer is provided on a fixing belt has been proposed. That is, Patent Document 2 is configured such that a fixing belt having a resistance heating layer made of a substance that generates heat when energized is formed on the entire circumference is rotated. Since this type of fixing belt can heat the entire circumference, a very fast warm-up is possible.

JP 2006-293225 A JP 2009-92785 A

  However, since the fixing belt is as thin as about 0.5 mm, the heat capacity is very low. When there is a contact member (for example, a pressure roller that is in contact with the fixing belt to form a nip portion for pressurizing and heating an unfixed toner image) when the belt is stopped during warm-up, The temperature of the belt is difficult to rise only by the position of the contact member. For this reason, temperature unevenness occurs in the circumferential direction of the belt. This temperature unevenness leads to image defects such as uneven glossiness of the image and unfixed toner that cannot be fixed in severe cases. On the other hand, when the belt kept in contact with the pressure roller is idled in order to adjust the temperature unevenness, since the heat capacity of the pressure member is larger than that of the fixing belt, the warm-up time is greatly increased.

  An object of the present invention is to provide an image heating apparatus capable of uniformly heating the entire circumference and performing image heating through very fast warm-up.

  In order to achieve the above object, an invention according to the present application includes a first rotating body, a second rotating body that forms a nip portion with the first rotating body, and a part of the first rotating body. A heating source for heating; and a driving means for driving the second rotating body to rotate. The second rotating body forms the second nip when the first rotating body and the second rotating body form the nip portion. In the image heating apparatus for rotating the first rotating body to rotate the first rotating body and nipping and conveying the recording material carrying the image in the nip portion, the first rotating body and the second rotating body are heated. Conversion means for switching between a contact state in which the rotating body is contacted to form the nip portion and a separated state in which the first rotating body and the second rotating body are separated from each other, The first rotator generates heat by power supply and heats the first rotator all around. A heating layer, and during the warm-up, power is supplied to the resistance heating layer in a state where the first rotating body and the second rotating body are switched to a separated state by the switching means, and the first heating body is In the first heating mode in which the rotator is heated, and in the state where the first rotator and the second rotator are converted into a contact state by the converting means at the time of image heating. And a second heating mode in which the body is rotated by the driving means and the first rotating body is heated by the heating source.

  According to the present invention, by combining different heating means for heating the first rotating body locally and locally with the separation / contact of the second rotating body with respect to the first rotating body, Image heating can be performed through uniform heating and very fast warm-up.

FIG. 3 is a schematic cross-sectional view of the image heating apparatus according to the first embodiment of the present invention viewed from a direction orthogonal to the recording material conveyance direction. 1 is a diagram illustrating an image forming apparatus equipped with a fixing device as an image heating apparatus according to a first embodiment. FIG. FIG. 6 is a diagram illustrating a state in which a fixing belt and a pressure roller are in contact with each other during image heating. FIG. 4 is a diagram illustrating a state where a fixing belt and a pressure roller are separated during warm-up. (A) is a figure explaining the layer structure of the fixing belt provided with the resistance heat generating layer used for the whole circumference used at the time of warm-up, (b) is a figure which shows the modification of an electric power feeding part. 6 is a flowchart showing fixing start-up in the present embodiment. FIG. 6 is a diagram illustrating a temperature transition at the time of fixing start-up regarding the fixing belt and the heater in the present embodiment. It is a figure which shows the comparison of the starting time of the Example in this embodiment with respect to a comparative example, and fixing belt temperature nonuniformity. FIG. 2 is a block diagram of a fixing device in the present embodiment. FIGS. 2A and 2B show a second embodiment, in which FIG. 3A shows a state of being separated during warm-up, and FIG.

<< First Embodiment >>
(Image forming device)
FIG. 2 is a cross-sectional view of the color electrophotographic printer, which is an example of an image forming apparatus equipped with the image heating apparatus of this embodiment, along the recording material conveyance direction. Hereinafter, the color electrophotographic printer is simply referred to as “printer”. The recording material is a material on which a toner image is formed. Specific examples of the recording material include plain paper, a resin recording material that is a substitute for plain paper, cardboard, and overhead projector.

  The printer shown in FIG. 2 includes an image forming unit 10 for each color of Y (yellow), M (magenta), C (cyan), and Bk (black). The photosensitive drum 11 is charged in advance by a charger 12. Thereafter, a latent image is formed on the photosensitive drum 11 by the laser scanner 13. The latent image becomes a toner image by the developing device 14. The toner image on the photosensitive drum 11 is sequentially transferred by the primary transfer blade 17 to, for example, an intermediate transfer belt 31 that is an image carrier. After the transfer, the toner remaining on the photosensitive drum 11 is removed by the cleaner 15. As a result, the surface of the photosensitive drum 11 becomes clean and prepares for the next image formation.

  On the other hand, the recording material P is sent out one by one from the paper feed cassette 20 or the multi paper feed tray 25 and sent to the registration roller pair 23. The registration roller pair 23 once receives the recording material P and straightens it when the recording material P is skewed. The registration roller pair 23 feeds the recording material P between the intermediate transfer belt 31 and the secondary transfer roller 35 in synchronization with the toner image on the intermediate transfer belt 31. The color toner image on the intermediate transfer belt 31 is transferred to the recording material P by, for example, a secondary transfer roller 35 which is a transfer body. Thereafter, the unfixed toner image T of the recording material P is fixed to the recording material P when the recording material P is heated and pressurized by the fixing device 40.

  When the toner image T is formed only on one surface of the recording material P, the recording material P is disposed on the side surface of the image forming apparatus 1 via the paper ejection roller 63 by switching the switching flapper 61. To 64. Alternatively, the paper is discharged to a paper discharge tray 65 disposed on the upper surface of the image forming apparatus 1. When the switching flapper 61 is at the position of the broken line, the recording material P is discharged onto the paper discharge tray 64 face up (toner image T is on the upper side). When the switching flapper 61 is at the position of the solid line, the recording material P is discharged to the paper discharge tray 65 face down (the toner image T is on the lower side).

  When the unfixed toner image T is formed on both surfaces of the recording material P, the recording material P on which the unfixed toner image T is fixed by the fixing device 40 is guided upward by the flapper 61 located at the position of the solid line. When the rear end reaches the reversal point R, it is switched back and conveyed by the conveyance path 73 and reversed. Thereafter, the recording material P is conveyed through the double-sided conveyance path 70, and the unfixed toner image T is formed on the other side through the same process as the single-sided image formation. To be discharged. The portion constituted by the flapper 61, the switchback conveyance path 73, and the like is an example of a reversing unit.

(Image heating device)
Next, as an example of the image heating device, a fixing device 40 (FIG. 2) for fixing the recording material P to which the unfixed toner image T has been transferred will be described. 1 is a schematic configuration diagram viewed from a direction (longitudinal direction) orthogonal to the recording material conveyance direction of the fixing device 40, and FIG. 3 is a schematic configuration diagram of the fixing device 40 in the longitudinal direction of the recording material during image heating. Reference numeral 100 denotes a fixing belt (endless belt) including a resistance heating layer provided on the entire circumference, which will be described in detail later. The fixing belt 100 is pressed against the upper surface of the pressure roller 110 with a predetermined pressing force via a nip portion forming member 113 as a backup member, and a fixing nip portion N having a predetermined width is formed.

  Reference numeral 112 denotes a support stay disposed inside the fixing belt 100, and supports a backup member 113 that pressurizes and urges the fixing belt 100 toward the pressure roller 110. Reference numeral 116 denotes a ceramic heater (hereinafter referred to as a heater), which is a heating means for heating the image and is a heating source for heating a part of the circumferential direction of the rotatable fixing belt. The heater 116 is provided inside the fixing belt 100 at a position facing the pressure roller 110.

  When the pressure roller 110 is driven to rotate and the cylindrical fixing belt 100 is driven to rotate, energization is performed to the resistance heating layer of the heater 116. When the temperature of the fixing belt 100 rises to the set temperature, the recording material P carrying the unfixed toner image T is introduced into the fixing nip portion N. In the fixing nip portion N, the toner image carrying surface side of the recording material P comes into close contact with the outer surface of the fixing belt 100, and the recording material P moves together with the fixing belt 100. In the nipping and conveying process at the fixing nip N, heat generated in the resistance heating layer of the heater 116 is applied to the recording material P, and the unfixed toner image T is melted and fixed on the recording material P. The recording material P that has passed through the fixing nip N is separated from the fixing belt 100 by the curvature, and is discharged from the fixing device 40.

  The pressure roller 110 has a multilayer structure in which a silicone rubber layer having a thickness of about 3 mm and a PFA resin tube having a thickness of about 50 μm are sequentially laminated on a stainless steel core. As shown in FIG. 4, both end portions of the metal core of the pressure roller 110 are rotatably supported by bearings between the back side plate and the near side plate of the apparatus frame. The applied pressure in this embodiment is 156.8N at one end and the total applied pressure is 313.6N (32 kgf). The support stay 112 is preferably made of a material that is not easily bent even when a high pressure is applied. In the present embodiment, SUS304 is used.

  Reference numerals 111 (FIGS. 3 and 4) denote left and right fixing flanges as regulating members that regulate the longitudinal movement and the circumferential shape of the fixing belt 100. Then, with respect to contact / separation between the fixing belt and the pressure roller 110, which will be described later, the pressure spring 115 is contracted between the left and right fixing flanges 111 and the pressure arm 114 (displaced in the vertical direction by the rotation of the cam 119). Set up.

  On the surface of the support member of the heater 116, a thermistor for image heating (not shown) is provided as temperature detection means during image heating. Reference numeral 118 in FIG. 2 denotes a warm-up thermistor as temperature detection means during warm-up described later.

(A: Heating mode during image heating)
A-1) Heating means The heating mode at the time of image heating is set to the second heating mode with respect to the first heating mode at the time of warm-up before image heating. Regarding the second heating mode, reference numeral 116 denotes a heater that heats a part of the circumferential direction of the fixing belt 100 that can be rotated during image heating, and constitutes a heating unit during image heating. The heater 116 is basically composed of a thin plate-like ceramic substrate that is elongated in the longitudinal direction, which is perpendicular to the paper surface, and a resistance heating layer provided on the substrate surface. It is a heater with a low heat capacity that rises in temperature. In the present embodiment, a resistance heating layer for heating a part of the fixing belt 100 in the circumferential direction is formed on a ceramic substrate having a thickness of 600 μm.

  The nip portion forming member 113 on which the heater 116 is fixedly supported is a heat insulating member such as a heat resistant resin having a substantially semi-circular arc shape in cross section and having a longitudinal direction in the direction perpendicular to the paper surface. From the viewpoint of energy saving, it is desirable to use a material with low heat conduction to the support stay 112. For example, heat resistant glass, polycarbonate, liquid crystal polymer, or other heat resistant resin is used. In this embodiment, Sumika Super E5204L manufactured by Sumitomo Chemical Co., Ltd. was used. The heater 116 is disposed in a groove formed along the longitudinal direction on the lower surface of the nip portion forming member 113 so that the heater surface is exposed downward and fixed with a heat resistant adhesive or the like.

A-2) Power Supply Unit of Heating Unit Power supply units are provided at both ends of the heater 116 in the longitudinal direction (perpendicular to the plane of FIG. 1), and the heater 116 is heated by energizing the resistance heating layer of the heater 116 (image) A portion of the circumferential direction of the fixing belt 100 that can be rotated during heating is heated).

A-3) Contact with Pressure Roller During image heating, as shown in FIG. 3, the fixing device 40 causes the cam 119 to contact the pressure arm 114 due to the rotation of the cam 119, and the pressure arm 114 adds the pressure. The fixing flange 112 supported via the pressure spring 115 is lowered. As a result, the fixing belt 100 comes into contact with the pressure roller 110. These members constitute conversion means for switching between the separated state and the contact state with respect to the fixing belt 100 as the first rotating body and the pressure roller 110 as the second rotating body.

  In FIG. 1, when the image is heated, the pressure roller 110 is rotationally driven in the direction of the arrow at a predetermined peripheral speed, and the fixing belt 100 in contact with the pressure roller 110 is driven to rotate by the pressure roller 110 and rotates at a predetermined speed. . Grease is applied to the inner surface of the fixing belt 100 to reduce wear on the inner surface of the fixing belt 100 caused by friction between the nip forming member 113 as a backup member and the inner surface of the fixing belt 100.

A-4) Heating Control As described above, an unillustrated thermistor for image heating as temperature detecting means during image heating is provided directly above the fixing nip portion N on the surface of the support member of the heater 116. This image heating thermistor is connected to a control circuit section (CPU) as a control means via an A / D converter (not shown). This control circuit section samples the output from the thermistor at a predetermined cycle, and reflects the obtained temperature information in the energization control to the heater 116. That is, the control circuit unit determines the energization control content to the heater 116 based on the output of the thermistor for image heating, and controls the energization supplied from the power source unit to the heater 116 via the power supply member.

(B: Heating mode during warm-up before image heating)
Here, warm-up means that the fixing device 40 can be printed by heating the temperature of the fixing belt 110 to the set temperature when the fixing belt 110 is less than the set temperature when the printer is in a standby state or in a power-off state. It is to be in a state.

B-1) Heating Means The configuration of the fixing belt 100 provided with a resistance heating layer that is heated all around during warm-up before image heating will be described in detail with reference to FIG. FIG. 5A is a schematic diagram of a layer configuration laminated in the radial direction of the fixing belt provided on the entire circumference, and the arrow A direction is the direction from the outer side to the inner side in the radial direction. The fixing belt 100 in the present embodiment has a four-layer composite structure of a base layer 101, a resistance heating layer 102, an elastic layer 103, and a release layer 104 in order from the inner peripheral side to the outer peripheral side.

  For the base layer 101, a heat-resistant material having a thickness of 100 μm or less, preferably 50 μm or less and 20 μm or more can be used in order to reduce the heat capacity and improve the quick start property. For example, resin belts such as polyimide, polyimide amide, PEEK, PTFE, PFA, and FEP, and metal belts such as SUS and nickel can be used. In this embodiment, a cylindrical polyimide belt having a thickness of 30 μm and a diameter of 25 mm was used. In the case where a conductive material is used for the base layer 20a, it is necessary to provide an insulating layer such as polyimide between the base layer 101 and the resistance heating layer 102.

  As the elastic layer 103, silicone rubber having a rubber hardness of 10 degrees (JIS-A), a thermal conductivity of 1.3 W / m · K, and a thickness of 300 μm was used. The release layer 104 was a PFA tube having a thickness of 20 μm. A PFA coat may be used as the release layer, and the PFA tube and the PFA coat can be used properly according to the required thickness, mechanical and electrical strength. The release layer 104 is bonded to the elastic layer 103 with an adhesive made of silicone resin.

  The resistance heating layer 102 is a resistance heating element that heats the fixing belt 100 over the entire circumference, in which a polyimide resin containing carbon as conductive particles is applied on the base layer 101 with a uniform thickness. The total resistance value of the heat generating layer is 10.0Ω. Therefore, the electric power generated when energizing an AC power supply with a voltage of 100 V is 1000 W. The resistance value may be determined as appropriate according to the amount of heat generated as a fixing device, and can be adjusted as appropriate according to the mixing ratio of carbon.

  In this embodiment, the fixing belt 100 is separated from the heater 116 by its own weight during warming up, and the fixing belt 100 is also separated from the pressure roller 100. For this reason, when there is a contact member, the fixing belt 100 does not lose heat to the contact member, and can be rapidly started up.

B-2) Power Supply Section of Heating Unit As shown in FIG. 5A, power supply electrode sections 105 are formed at both ends in the longitudinal direction of the fixing belt 100, and the power supply electrode section 105 is formed of the resistance heating layer 102. Electrically connected to both ends. The power supply electrode unit 105 is made of a material having conductive characteristics including silver and palladium, and power is appropriately supplied from a power source (not shown).

  In general, in the method of heating the resistance heating layer arranged on the belt member, when the belt itself is a rotating body, the friction with the power feeding unit 105 at both ends in the longitudinal direction shown in FIG. Occur. In particular, when the belt is driven at high speed, it is difficult to stably supply power to the resistance heating layer of the rotating belt. For this reason, power is supplied to the resistance heating layer only when the fixing belt does not rotate. However, as shown in FIG. 5B, when the power feeding portion 105 extends to the rotation shaft portion of the fixing flange and is fed by the rotation shaft portion, the resistance heating layer 102 is used even when the fixing belt is rotating. Power can be supplied to

B-3) Relative separation from the pressure roller As shown in FIG. 4, during the warm-up, the fixing device 40 releases the contact between the cam 119 and the pressure arm 114 by the rotational operation of the cam 119. The fixing flange 112 supported by the pressure arm 114 via the pressure spring 115 is lifted against its own weight. As a result, the fixing belt 100 is relatively separated from the pressure roller 110. In the present embodiment, the fixing belt 100 is separated upward from the pressure roller 110 against the gravitational direction. However, the pressure roller 110 is separated from the fixing belt 100 in the gravitational direction to form a separated state. May be.

  In the initial state, power is not supplied to the feeding electrode portion 105 and the heater 116 of the fixing belt 100, and the pressure roller 110 is also stopped.

B-4) Heating control The operation of the fixing device 40 during warm-up is shown in the flowchart of FIG. The warm-up operation is sequentially controlled by the control unit shown in the block diagram of FIG. When the printer receives a print start command from an input device such as an operation unit in the standby state (STEP 1), power is supplied to the fixing belt 110 from the power supply unit (STEP 2). That is, the fixing belt 100 as the first rotating body and the pressure roller 110 as the second rotating body supply power to the resistance heating layer 102 of the fixing belt 100 in a separated state.

  As the next step, after a predetermined time has elapsed (STEP 3), power supply to the heater 116 is started and heating by the heater 116 is started (STEP 4). The predetermined time in STEP 3 can be appropriately determined so that the temperature of the heater 116 falls within about ± 10 ° C. with respect to the temperature of the fixing belt 100 when the fixing belt 100 and the heater 116 contact each other in STEP 6 described later. desirable. As a result, since the temperature of the heater 116 is different from the temperature of the fixing belt 100, it is possible to suppress temperature unevenness in the circumferential direction of the fixing belt 100 that occurs when the fixing belt 100 and the heater 116 come into contact in STEP6.

  When the temperature of the fixing belt 100 detected by the thermistor 118 reaches the rising target temperature (STEP 5), power supply from the power supply unit to the fixing belt 100 is stopped (STEP 6).

  As the next third step, the fixing flange 112 is brought into contact with the fixing belt 100 as the first rotating body and the pressure roller 110 as the second rotating body by the pressing spring 115 by the rotating operation of the cam 119. Conversion (release of separation of the fixing belt 100: STEP 6). Then, the pressure driving unit starts driving the pressure roller 110 (STEP 7). With the above steps, the warm-up of the fixing device 40 is completed, and the state shifts to a state in which the fixing operation to the recording material carrying the unfixed toner image can be performed.

  The graph shown in FIG. 7 shows the temperature transition of the fixing belt 100 and the heater 116 when the fixing device 40 is warmed up in the above-described flowchart. In FIG. 7, the heater temperature adjustment temperature and the fixing belt temperature adjustment temperature are different because the phases of the nip portion N and the thermistor 118 are different as shown in FIG. 116 and the temperature of the fixing belt 100 are substantially equal. In the configuration of the present embodiment, the time required to shift from the standby state to the fixable state can be shifted to 3 seconds as long as sufficient power supply is possible. Does not occur.

  However, as Comparative Example 1 (FIG. 8), the same configuration as that of the present embodiment is used, the heater 116 is used as a heating means during warm-up, the fixing belt does not generate heat, and the fixing belt and the pressure roller are not separated. When the pressure roller is driven, the start-up time takes 20 seconds. Further, as Comparative Example 2 (FIG. 8), the same configuration as that of the present embodiment is used, the belt and the heater 116 are used as heating means during warm-up, and the pressure roller is driven without separating the fixing belt and the pressure roller. If not, the following problems occur. That is, the thermistor detection temperature reaches the target temperature in 3 seconds or less, but the fixing belt temperature at the nip portion N cannot be guaranteed, and temperature unevenness occurs in the circumferential direction of the fixing belt or the pressure roller. A defect or a paper conveyance defect occurs (FIG. 8).

  For temperature control, the thermistor 118 is connected to a control circuit section (CPU) as control means via an A / D converter (not shown). This control circuit section samples the output from the thermistor 118 at a predetermined cycle, and reflects the obtained temperature information in the energization control to the heating element.

  That is, the control circuit unit determines the energization control content to the heating element based on the output of the thermistor 118, and controls the energization supplied from the power source unit to the heating element via the power supply member. Note that the above control in the fixing device of the present embodiment is controlled so that the temperature detected by the thermistor 118 is constant at 160 ° C. in consideration of the temperature for fixing the toner image on the recording material P.

  As described above, according to this embodiment, when the fixing belt is stopped, the resistance heating layer provided on the fixing belt having a low heat capacity is used, so that the warm-up time is shortened from 20 seconds to 3 seconds as compared with the case of heating only. The Furthermore, by not contacting a pressure roller having a larger heat capacity than that of the fixing belt during warm-up, it is possible to stably suppress the temperature unevenness in the circumferential direction of the fixing belt within 10 ° C. even when the fixing belt is stopped. A fixing device can be provided. Further, the fixing belt 100 can be configured not to contact the heater 116 as well.

  Note that the image heating apparatus described in the above embodiment relates to a fixing apparatus that fixes a recording material on which an unfixed image has been transferred. However, the gloss that increases the glossiness by reheating a recording material that has already been fixed. Needless to say, the present invention can also be applied to a degree increasing device.

<< Second Embodiment >>
A second embodiment will be described with reference to FIG. The fixing belt 100 is suspended from the rollers R1 and R2, and is rotated by the pressure roller 110 rotatingly driven in contact with the pressure roller 110 and the heater 116 as shown in FIG. At the time of warm-up, as shown in FIG. 10A, the pressure roller 110 is separated downward, and the fixing belt 100 is supplied with power to the resistance heating layer of the fixing belt that is heated all around without rotating the fixing belt 100. 100 itself is heated to the fixing target temperature at high speed.

  In this embodiment, since there are members (rollers R1, R2 and heater 116) that come into contact with the fixing belt during warm-up, high-speed startup is slower than in the first embodiment.

(Modification)
In the above-described embodiment, the fixing belt 100 is separated from the pressure roller 110 at the time of warm-up, and is further separated from the heater 116 so that there is no abutting member, so that the apparatus can be started up at a higher speed. However, the fixing belt 100 may be separated from the pressure roller 110 during warm-up due to the large heat capacity, and may be configured to contact the heater 116 having a small heat capacity.

100 ... Fusing belt 101 ... Base layer 102 ... Resistance heating element layer 104 ... Release layer 105 ... Power feeding part 110 ... Pressing roller 111 ... Fusing flange 112 ... Support stay , 113 ·· Nip forming member, 114 ·· Pressure arm, 115 ·· Pressure cam, 116 ·· Heater, 119 ·· Cam, N ·· Fixing nip, P ·· Recording material, T ··· Undetermined Toner image

Claims (6)

A first rotating body, a second rotating body that forms a nip with the first rotating body, a heating source that heats a part of the first rotating body, and the second rotating body. Driving means for driving the first rotating body by rotating the second rotating body in a state where the first rotating body and the second rotating body form the nip portion. In the image heating apparatus that heats the recording material that carries the image by being driven and rotated by nipping and conveying the recording material at the nip portion,
An abutting state in which the first rotating body and the second rotating body are brought into contact with each other to form the nip portion, and a separated state in which the first rotating body and the second rotating body are separated from each other. Have conversion means to convert each other,
The first rotating body includes a resistance heating layer that generates heat by power supply and heats the first rotating body around the entire circumference.
At the time of warm-up, power is supplied to the resistance heating layer in a state where the first rotating body and the second rotating body are converted into the separated state by the conversion means, and the first rotating body is heated. A first heating mode,
At the time of image heating, the second rotating body is rotationally driven by the driving means in a state where the first rotating body and the second rotating body are converted into a contact state by the converting means, and the heating A second heating mode in which the first rotating body is heated by a source;
An image heating apparatus comprising:   2. The image heating apparatus according to claim 1, wherein, in the first heating mode, heating by the heating source is started after a predetermined time has elapsed since power is supplied to the resistance heating layer.   In the first heating mode, as the first step, the first rotating body and the second rotating body supply power to the resistance heating layer in a separated state, and the second step after the predetermined time has elapsed Each step of starting the heating by the heating source, stopping the power supply to the resistance heating layer as the next third step, and converting the first rotating body and the second rotating body into a contact state. The image heating apparatus according to claim 2, further comprising:   4. The image heating apparatus according to claim 1, wherein in the second heating mode, power supply to the resistance heating layer is stopped. 5.   5. The image heating apparatus according to claim 1, wherein the heating source is provided at a position inside the first rotating body and facing the second rotating body. 6. 6. The image heating apparatus according to claim 1, wherein in the first heating mode, the first rotating body and the heating source are separated from each other.