JP4164408B2 - Image heating device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetic induction heating type heating device suitable for use as a fixing device for heating and pressure-fixing an unfixed toner image in an image forming apparatus such as a copying machine, a laser beam printer, or a facsimile, and the heating device. The present invention relates to an image forming apparatus provided.
[0002]
[Prior art]
In known image forming apparatuses such as copying machines, laser beam printers, and facsimiles, a toner image electrostatically formed on a transfer material as a recording material such as paper is transferred through a transfer process in an image forming process section. It is necessary to fix it to the material. As a means for this purpose, it has been widely used that a transfer material carrying a toner image is passed between a pair of heating rollers that are in pressure contact and fixed by applying heat and pressure to the toner. As is known. FIG. 10 shows a typical example of a known electromagnetic (magnetic) induction heating type fixing device.
[0003]
The induction heating method uses an electromagnetic induction phenomenon (Faraday's law) in which the magnetic flux changes when the metal crosses the magnetic field, and eddy currents flow in the metal in a direction that suppresses the movement of the metal due to the change in the magnetic flux. . When a current flows through the metal, heat is generated by the electric resistance of the metal. An induction heating type fixing device uses this heat for a fixing device (fixing device) of the image forming apparatus.
[0004]
As shown in FIG. 10, in the fixing device, a magnetic flux generating means 4 is arranged inside a fixing roller 1 as an induction heating element instead of a heat source such as a heater. The magnetic flux generating means 4 includes an exciting coil 5 and a core material (core) 6. As the material of the core 6, a material having a high magnetic permeability and a low residual magnetic flux density such as ferrite and permalloy may be used.
[0005]
The core 6 and the coil 5 are supported by a holder 9. Moreover, the heat-resistant heat-shrinkable tube 7 is used for the outer periphery so that the coil surface may be covered.
[0006]
When electric power is input to the coil 5 from a power source (not shown), a magnetic flux is generated. Actually, the magnetic field lines pass through the inside of the fixing roller 1 having a high magnetic permeability, but are shown as in FIG. 11 for easy understanding.
[0007]
FIG. 11 is a distribution diagram of magnetic flux generated in the fixing roller 1, and the magnetic field lines J of the magnetic flux distribution (magnetic circuit) pass through the vertical portion 6 a of the core 6, the fixing roller 1, and the horizontal portion 6 b of the core 6. The magnetic circuit is symmetrical on the left and right of the horizontal part with respect to the vertical part of the core. Further, the coil 5 has a substantially elliptical shape extending in the longitudinal direction of the fixing roller 1 as shown in FIG. 12, and is arranged along the inner surface of the fixing roller as shown in FIG.
[0008]
Heating 箇 plants by electromagnetic induction heating becomes particularly large at the coil facing portion of the fixing roller 1. The fixing roller 1 is also heated by a magnetic flux (not shown) generated by each coil. With only this, only about half of the fixing roller 1 generates heat, but the fixing roller 1 rotates and is heated without temperature unevenness.
[0009]
The magnetic flux is generated in such a direction as to alternately pass through the inside of the core 6. An AC power supply in which current flows alternately is suitable for input power from the power supply. There is a metal portion of the fixing roller 1 where the generated magnetic flux passes. Since the magnetic flux alternately passes through the metal portion, the effect is the same as when the metal crosses the magnetic flux, and heat is generated in the metal portion.
[0010]
A material having a ferromagnetic property, for example, iron, nickel, cobalt, or the like, is suitable for the metal serving as the heat generating portion. In the conventional example shown in FIG. 10, an iron-based alloy is used for the fixing roller 1.
[0011]
In the above fixing device, since the fixing roller 1 itself becomes a heating element, power efficiency is better than that of a fixing device using a known halogen heater as a heat generating means. Generally, compared with the life of the halogen heater, the life of the magnetic flux generating means 4 is long, so that it does not become a consumable part. Therefore, it also plays a role in improving serviceability.
[0012]
Furthermore, since the magnetic flux generating means can change the electric power smoothly, it is said that it is easy to take countermeasures against high frequency flicker countermeasures.
[0013]
In recent years, such merits have attracted attention as a heat generating means.
[0014]
A pressure roller 8 that forms a nip portion (heating nip portion) N in pressure contact with the fixing roller 1 is provided. The fixing roller 1 and the pressure roller 8 are in pressure contact with each other and are rotatably supported. The pressure roller 8 is pressed against the fixing roller 1 by a pressure unit (not shown). The pressurizing means generally uses a spring and is loaded with about 19.6 to 980.6 N (about 2 to 100 kgf). The width of the nip part is generally about 6 mm. The pressure load is a value set in consideration of the toner fixing property.
[0015]
In the fixing roller 1, a toner release layer (not shown) is provided on the outer surface of the roller. The toner release layer is generally composed of PTFE of 10 to 50 μm or PFA of 10 to 50 μm.
[0016]
In addition, a configuration in which a rubber layer is used inside the toner release layer is also known.
[0017]
The pressure roller 8 has a configuration in which a toner release layer is provided on the outer periphery of an iron cored bar like the silicone rubber layer and the fixing roller 1.
[0018]
The fixing roller 1 is rotated in the clockwise direction indicated by an arrow A by a gear (not shown) provided at the end of the fixing roller 1, and the pressure roller 8 is also driven and rotated in the counterclockwise direction indicated by an arrow B.
[0019]
In the fixing device having such a configuration, as shown in FIG. 10, a sheet-like transfer material P carrying a toner image t electrostatically formed at a transfer site in an image forming apparatus (not shown) After passing N, the heated toner image is fused and fixed to the transfer material and discharged outside the apparatus.
[0020]
In addition, a separation claw 10 that suppresses the transfer material from being wound around the fixing roller 1 and separates it from the fixing roller is disposed. Further, based on the temperature detected by the detection means (thermistor) 11 for detecting the surface temperature of the fixing roller, a temperature control unit (not shown) controls the temperature control so that the surface temperature of the fixing roller is kept constant. Is done.
[Patent Document 1]
Japanese Patent Laid-Open No. 09-061322 [Patent Document 2]
Japanese Patent Laid-Open No. 09-171889
[Problems to be solved by the invention]
In the fixing device as described above, a thermistor 11 that is a temperature detection unit of the fixing roller 1 and a thermo switch (not shown) that is an abnormal temperature detection unit that detects that the fixing roller 1 is at an abnormally high temperature are fixed. It is in contact with the roller surface.
[0022]
For this reason, an image defect occurs due to scraping or scratching of the roller surface at the contact portion with the thermistor or thermo switch in the fixing roller, and the accurate temperature of the fixing roller 1 cannot be measured.
[0023]
Further, when the toner image is fixed on the transfer material, the toner may slightly move to the surface of the fixing roller 1 and accumulate between the fixing roller 1 and the contact portion. In many cases, the accumulated toner leaks from the contact portion due to vibration in the image forming apparatus or the like and is sent to the sheet conveying portion, resulting in image contamination.
[0024]
The purpose of temperature control of the fixing roller 1 for fixing the toner on the transfer paper is to control the fixing temperature at the nip N between the fixing roller 1 and the pressure roller 8. However, conventionally, the fixing temperature of the nip portion N cannot be detected.
[0025]
Therefore, as a method for detecting the accurate fixing temperature of the fixing roller, a method for detecting the fixing temperature by bringing a thermistor (not shown) or a thermo switch (not shown) into contact with the inner surface of the fixing roller 1 can be considered.
[0026]
However, in the electromagnetic induction heating type fixing device, heat is generated from the inner surface of the fixing roller 1 and is transferred to the surface, so that the temperature detected by the thermistor and the surface temperature (fixing temperature) of the fixing roller 1 are different. Accurate temperature control was not possible.
[0027]
Further, since the inner surface of the fixing roller 1 is not coated like the surface and has a large surface roughness, if the thermistor is brought into contact, the detection portion of the thermistor is damaged and the accurate temperature cannot be measured. .
[0028]
The present invention relates to those that prevent the while detecting the temperature near the nip in an image heating equipment of an electromagnetic induction heating system, insufficient heat for heating the toner image on the recording material.
[0029]
[Means for Solving the Problems]
The present invention is an image heating equipment characterized by the following constructions.
[0030]
A coil that generates magnetic flux when energized, a coil holder that supports the coil, a cylindrical rotatable heat generating member that generates heat by the action of the magnetic flux generated by the coil , and press-contacts the heat generating member to sandwich the recording material A pressure member that forms a nip portion to be conveyed, a temperature detecting member that contacts the inside of the cylinder of the heat generating member, detects the temperature of the heat generating member, and energizes the coil based on the output of the temperature detecting member. and a control means for controlling the said heating member has a protective layer in contact with the temperature sensing member, and a metal layer provided on the protective layer, provided on the metal layer, the toner image on the recording material anda release layer in contact with, the coil holder is an inside of the heating member, the image heating apparatus is provided to face the nip portion,
The temperature detection member is supported by the coil holder, and the coil wire is provided on both sides of the temperature detection member in the circumferential direction of the heat generation member in a cross section of the heat generation member orthogonal to the rotation axis of the heat generation member. It is provided in contact with the inner surface of the heat generating member in a nip region at a certain position, and the thickness of the protective layer made of a fluororesin of the same material as the release layer is larger than the thickness of the release layer. An image heating apparatus.
[0041]
DETAILED DESCRIPTION OF THE INVENTION
[Example 1]
FIG. 1 is a cross-sectional view showing a schematic configuration in the radial direction of the fixing roller of the electromagnetic heating type fixing device of the first embodiment. FIG. 2 is a cross-sectional view showing a schematic configuration of the ID fixing device in the longitudinal direction of the fixing roller. FIG. 3 is an enlarged sectional view of the nip portion of the identification dressing device. FIG. 4 is a temperature gradient diagram around the nip portion of the identification apparatus.
[0042]
In this example, components having the same functions as those of the conventional example are designated by the same reference numerals in the drawings of the examples.
[0043]
1 and 2, the magnetic flux generation means 4 is held by a holder 12 as in the prior art. That is, the excitation coil 5 (hereinafter referred to as a coil) and the magnetic core 13 (hereinafter referred to as a core) are held by the holder 12. The fixing roller 14 is supported at both ends 14a and 14b , which are metal layers, by a bearing 15 so as to be rotatable on fixing side plates 16 and 17, respectively. One end portion 14a of the fixing roller 14 is a fixing drive gear 18 is fixedly arranged, driving the fixing roller from the gear 18 is input.
[0044]
Holder support bases 19 and 20 that support the holder 12 at both ends are fixedly supported by screws 21 on the fixing side plates 16 and 17.
[0045]
Further, the holder support base 19 is provided with a notch 19-a at a position corresponding to the fixing drive gear 18, and is driven by an image forming apparatus main body (for example, a copier main body) (not shown) through the notch. A gear (not shown) is engaged with the fixing drive gear 18.
[0046]
The holder 12 is made of a heat-resistant resin such as PPS, but a slight expansion phenomenon occurs when heat is applied. In particular, since the expansion in the direction of arrow A (holder longitudinal direction) shown in FIG. 2 is remarkable, there arises a problem that when the holder 12 is regulated and fixed in the direction of arrow A, the holder 9 is compressed and broken. Therefore, a restriction flange 12-a is provided at one end of the holder 12 (left end in the example in the figure), the restriction flange 12-a is abutted against the holder support base 19, and the end on the opposite side of the holder 12 (in the example in the figure). The position of the holder 12 is regulated by urging the right end part) to the holder support 19 on one end side by the leaf spring 22 and pressing the flange 12-a against the inner surface of the holder support 19. The leaf spring 22 is fixed to the holder support base 20 with screws 23. Thereby, even if the holder 12 expands in the direction of arrow A, it becomes possible to extend against the urging force of the leaf spring 19, and damage to the holder 12 can be prevented.
[0047]
Reference numeral 24 denotes a bearing that rotatably supports the pressure roller 8, reference numeral 25 denotes a pressure support arm that supports the bearing 24 , and reference numeral 26 denotes a pressure that urges the support arm 25 and urges the pressure roller 8 toward the fixing roller 14. It is a spring. The operating length of the pressure spring 26 is changed by rotating the screw 27, and the pressure applied to the pressure roller 8 is adjusted at the fixing nip N with the fixing roller 14.
[0048]
In this embodiment, the temperature of the fixing roller 14 is adjusted so that the thermocouple thermistor 28 contacts the inner peripheral surface of the fixing roller 14 at a position opposite to the fixing nip N between the fixing roller 14 and the pressure roller 8. Detect surface temperature.
[0049]
The thermistor 28 includes a temperature detecting portion (not shown) and an elastic portion such as a sponge, and is supported and fixed to the holder 12 at a position corresponding to a non-sheet passing region in the longitudinal direction of the fixing roller 14 in the fixing nip portion N. .
[0050]
Further, in this example, the contact surface of the thermistor 28 is formed along the curved surface of the inner peripheral surface of the fixing roller 14 in order to ensure contact with the inner peripheral surface of the fixing roller 14. In other words, by making the contact surface slightly convex, it is possible to reliably contact the inner peripheral surface of the fixing roller 14 without floating at the contact portion.
[0051]
Next, the configuration of the fixing roller 14 will be described in more detail with reference to FIGS.
[0052]
In the fixing roller 14 of this example, a material having ferromagnetic properties is used for the cored bar 14-a as a metal layer. On the outer periphery, there is a toner release layer 14-b as in the conventional case. The toner release layer 14-b is generally composed of PTFE 10 to 50 μm or PFA 10 to 50 μm.
[0053]
As a material of the ferromagnetic layer used as the core metal 14-a of the fixing roller 14, a metal such as iron, nickel, or cobalt is used. By using a ferromagnetic metal (a metal having a high magnetic permeability), the magnetic flux generated from the magnetic flux generating means 4 can be restrained more in the ferromagnetic metal. That is, the magnetic flux density can be increased. Thereby, an eddy current is efficiently generated on the surface of the ferromagnetic metal (core metal surface) to generate heat.
[0054]
On the other hand, in a metal having a low magnetic permeability such as aluminum, the magnetic flux cannot be constrained in the metal, so that the magnetic flux density becomes small and a little eddy current is generated.
[0055]
A protective layer 14-c is disposed on the inner surfaces of both end portions 14 a and 14 b of the fixing roller 14. The heating point due to electromagnetic induction heating is the inner surface of the cored bar 14-a, that is, the point B shown in FIG. 3, and the amount of heat is transferred from this portion into and out of the fixing roller 14. The temperatures at points A to D are determined by the cross-sectional area and thermal conductivity of each of the core metal 14-a, the toner release layer 14-b, and the protective layer 14-c.
[0056]
FIG. 4 shows a graph of the temperature gradient at points A to D. In FIG. 4, the position of each point A to D in the radial direction (radial direction) of the fixing roller is taken on the horizontal axis, and the temperature corresponding to each point is taken on the vertical axis.
[0057]
In this example, as shown in FIG. 4, the temperature at the point A (= detection point temperature Tb) which is the temperature detection point of the thermistor 28 is equal to the temperature T1 (= heating point temperature Ta) at the point D which is the fixing nip temperature. The cross-sectional area and thermal conductivity of the core metal 14-a, the toner release layer 14-b, and the protective layer 14-c are determined so that (Ta = Tb). Further, the temperature at the point A may not be equal to the temperature at the point D, but the temperature at the point A may be slightly higher than the temperature at the point D (Ta <Tb). This is to quickly detect an abnormal increase in fixing temperature.
[0058]
As shown in the figure, the relationship between the temperature T2 at point B, which is a heat generation point due to electromagnetic induction heating, the temperature T1 at points A and D, and the metal layer (core metal) surface temperature T3 at point C is T2>T3> T1.
[0059]
The material of the protective layer 14-c is a resin material that does not wear even when the thermistor 28 comes into sliding contact, specifically, a fluororesin material or an elastomer material having a lower thermal conductivity than the toner release layer 14-b. Has been. Further, the coating of the same material as that of the toner release layer 14-b may be used to increase the thickness of the protective layer 14-c to slow the heat transfer to the point A. Further, unlike the cored bar 14-a, the toner release layer 14-b and the protective layer 14-c are non-magnetic materials and therefore do not generate heat due to electromagnetic induction.
[0060]
In the fixing device of this example, in the fixing roller 14, the temperature detection point A of the thermistor 28 and the temperature T1 of the point D which is the fixing nip temperature, that is, the heating point temperature is equal, or the temperature of the temperature detection point A is the temperature of the point D. By determining the cross-sectional area and thermal conductivity of the core metal 14-a, the toner release layer 14-b, and the protective layer 14-c so as to be slightly higher than T1, the temperature of the temperature detection point A (= detection point temperature) Since Tb) can be regarded as the fixing nip temperature T1 (= heating point temperature Ta), the thermistor 28 can accurately detect the temperature Tb at the temperature detection point A as the heating point temperature Ta.
[0061]
As a result, by controlling the power applied to the coil based on the detection point temperature Tb detected by the thermistor 28, the fixing temperature can be accurately controlled according to the amount of heat generated by the electromagnetic induction of the fixing roller 14, and thus stable. Temperature control is performed so that the fixing temperature of the fixing roller 14 is kept constant.
[0062]
Accordingly, the fixing temperature can be accurately controlled even when the thermistor 28 is disposed on the inner surface of the fixing roller 14.
[0063]
[ Reference example ]
6 is a cross-sectional view showing a schematic configuration of the fixing roller radial direction of the electromagnetic heating type fixing device of the reference example , FIG. 7 is an enlarged cross-sectional view of the nip portion of the identification fixing device, and FIG. FIG.
[0064]
Also in this example, the same parts as those in the conventional example and Example 1 are not described and are denoted by the same reference numerals.
[0065]
In the reference example , the holder 12 of the first embodiment is slightly rotated counterclockwise to remove the position of the thermistor 28 from the periphery of the fixing nip N to the upstream side in the rotation direction. The fixing roller 30 has three layers as in the first embodiment, and the core metal 30-a and the toner release layer 30-b are made of the same material as in the first embodiment.
[0066]
FIG. 8 shows a graph of the temperature gradient at points A to D shown in FIG. In FIG. 8, the horizontal axis represents the position of each point A to D in the radial direction (radial direction) of the fixing roller, and the vertical axis represents the temperature corresponding to each point.
[0067]
In the fixing device of the reference example , the temperature T3 (see FIG. 8) of the outer peripheral point (heating point temperature) D corresponding to the position of the thermistor 28 of the fixing roller 30 shown in FIG. 7 is the fixing nip portion N (point E). The temperature becomes lower. The point D is in contact with the air layer, whereas the point E is in contact with the pressure roller 8 having a metal layer having a higher thermal conductivity than air on the surface. This is because the heat escapes. Accordingly, the thickness and thermal conductivity of the inner layer (protective layer) 30-c of the fixing roller 30 are set so that the temperature T1 shown in FIG. 8 of the temperature detection point A of the thermistor 28 is lower than the temperature T3 of the point D. The material and thickness are determined.
[0068]
That is, in the fixing device of the reference example , the relationship between the temperature T2 at the point B, which is a heat generation point by electromagnetic induction heating, the temperature T1 at the temperature detection point A, and the temperature T3 at the outer peripheral point D is T2> as shown in FIG. T3> T1. Further, the temperature at point A (= detection point temperature Tb) which is the temperature detection point of the thermistor 28 shown in FIG. 7 is equivalent to the temperature T1 (= heating point temperature Ta) at point D which is the fixing nip temperature (Ta = Tb). Alternatively, the thickness and thermal conductivity of the inner layer 30-c of the fixing roller 30 are determined so that the temperature at the point A is slightly higher than the temperature at the point D (Ta <Tb). Therefore, also in this reference example , the temperature and temperature detection point A (= detection point temperature Tb) can be regarded as the fixing nip temperature T1 (= heating point temperature Ta), and therefore, the same actions and effects as in the first embodiment are obtained. Obtainable.
[0069]
In the reference example , the thermistor 28 is disposed on the upstream side in the counterclockwise rotation direction with respect to the fixing nip portion N. However, it goes without saying that the thermistor 28 may be disposed on the downstream side in the clockwise rotation direction with respect to the nip portion. Yes. Also in this case, a temperature gradient as shown in FIG. 8 can be obtained.
[0070]
[Other thermistor examples]
As the thermistor used in the fixing device of Example 1 and the reference example , as shown in FIG. 5, the surface of the thermistor 29 is coated with a protective layer 29-a made of the same material as the protective layer 14-c described above as the protective layer protective layer. Processing may be performed. In this case, the temperature at point A (= detection point temperature Tb) which is the temperature detection point of the thermistor 28 shown in FIG. 3 or FIG. 7 is equivalent to the temperature T1 (= heating point temperature Ta) at point D which is the fixing nip temperature. (Ta = Tb) Alternatively, the cross-sectional area and thermal conductivity of the protective layer 29-a are determined so that the temperature at the point A is slightly higher than the temperature at the point D (Ta <Tb). Also in this reference example , since the temperature at the temperature detection point A (= the detection point temperature Tb) can be regarded as the fixing nip temperature T1 (= the heating point temperature Ta), the same operations and effects as those in the first embodiment can be obtained. Can do.
[0071]
[Example of image forming apparatus]
FIG. 9 is a cross-sectional view showing a schematic configuration of an electrophotographic image forming apparatus (copier) 32 equipped with the electromagnetic heating and fixing apparatus 31 of the first embodiment.
[0072]
The document placed on the document table 33 is read by the document reading unit 34 to form a latent image on the photosensitive drum 35. The latent image is formed into a toner image by the developing unit 36. The transfer paper P as a recording material placed on the cassettes 37 and 38 is conveyed to the transfer / separation unit 40 via the conveyance path 39. The toner image formed with the image is transferred onto the transfer paper P by the transfer / separation unit 40. Then, it is conveyed to the electromagnetic heating and fixing device 31 via the conveyance unit 41.
[0073]
In the fixing device 31, the transfer paper P onto which the toner image has been transferred is conveyed to the position of the fixing roller 1 by a predetermined conveying device, is pressed against the fixing roller 14 by the pressure roller 8, and is provided in the fixing roller. The toner on the transfer paper P is melted and fixed on the transfer paper P by electromagnetic induction heating by the magnetic flux generating means. Thereafter, the transfer paper P on which the toner image is fixed is discharged onto a tray 43 outside the apparatus main body by a paper discharge roller 42, and a series of image forming processes is completed.
[0074]
As described above, according to the fixing device shown in the present embodiment, the following effects can be obtained.
[0075]
1) Since the surface temperature of the fixing rollers 14 and 30 can be accurately detected, it becomes possible to quickly detect and control the overshoot of the fixing temperature when the power is turned on. As a result, it is possible to prevent image defects such as ignition due to abnormal temperature rise, fusing of the fixing roller surface, and high temperature offset.
[0076]
2) Since the thermistor 28 is provided in the holder 12 inside the fixing rollers 14 and 30, there is no need to provide a mounting member unlike the thermistor outside the fixing roller, and there is an effect of saving space and cost. In addition, ease of assembly has been improved.
[0077]
3) Since the thermistor 28 is disposed inside the fixing rollers 14 and 30, foreign matter such as toner and paper dust does not adhere to the thermistor 28, and problems such as image defects associated therewith are solved.
[0078]
4) In the thermistor 29, the frictional resistance with the protective layers 14-c and 30-c on the inner surface of the fixing roller is reduced by the protective layer 29-a provided on the thermistor surface, so that the life of the thermistor is dramatically improved. .
[0079]
[Others]
1) In this example, the thermistor 28 is used as the temperature detecting means, but a thermo switch (not shown) may be used instead of the thermistor 28 or in combination with the thermistor 28. In this case, a thermo switch that cuts off the power supply when the fixing roller reaches a predetermined temperature is preferable.
[0080]
2) Although a protective layer is provided on the inner surfaces of both ends (both sides) of the fixing rollers 14 and 30, a protective layer may be provided on the inner surface of one end (one side) of the fixing rollers 14 and 30 according to the mounting position of the thermistor 28. .
[0081]
3) The image heating apparatus of the present invention is not limited to the electromagnetic heating and fixing apparatus of the embodiment, but an image heating apparatus that heats a recording material carrying an image to improve surface properties such as gloss, and an image heating apparatus that is assumed Etc. can also be used.
[0082]
4) The image forming method of the image forming apparatus including the fixing device is not limited to the electrophotographic method, and may be an electrostatic recording method, a magnetic recording method, or the like, or may be a transfer method or a direct method.
[0083]
Although various examples and embodiments of the present invention have been shown and described above, those skilled in the art will not be limited to the specific description and drawings in the present specification, the spirit and scope of the present invention, It will be understood that various modifications and changes are set forth in all the claims that follow.
[0084]
【The invention's effect】
According to the present invention, since the temperature of the heat generating member is detected by the temperature detecting member provided in contact with the inner surface of the heat generating member in the nip region, the toner on the recording material can be detected while detecting the temperature close to the nip portion. Insufficient heat for heating the image can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a fixing roller radial direction of an electromagnetic heating fixing device according to a first embodiment.
FIG. 2 is a schematic cross-sectional view of the electromagnetic heating and fixing apparatus according to the first embodiment in the longitudinal direction of the fixing roller.
FIG. 3 is an enlarged sectional view of a nip portion of the electromagnetic heating fixing device according to the first embodiment.
FIG. 4 is a temperature gradient diagram around the nip portion of the electromagnetic heating fixing apparatus according to the first embodiment.
5 is a cross-sectional view showing another example of the thermistor used in the electromagnetic heating and fixing apparatus of Example 1 or Example 2. FIG.
FIG. 6 is a schematic cross-sectional view of a fixing roller radial direction of an electromagnetic heating fixing device according to a reference example .
FIG. 7 is an enlarged cross-sectional view around a nip portion of an electromagnetic induction heating fixing device according to a reference example .
FIG. 8 is a temperature gradient diagram around a nip portion of an electromagnetic heating fixing apparatus according to a reference example .
FIG. 9 is a schematic sectional view of an image forming apparatus equipped with the electromagnetic heating and fixing apparatus according to the first embodiment.
FIG. 10 is a schematic cross-sectional view of a conventional electromagnetic heat fixing apparatus.
FIG. 11 is a magnetic flux distribution diagram of a conventional electromagnetic heating and fixing apparatus.
FIG. 12 illustrates a coil in a fixing roller in an electromagnetic induction heating fixing apparatus according to a conventional example.
DESCRIPTION OF SYMBOLS 4 ... Magnetic flux generation means 5 ... Excitation coil 13 ... Magnetic body core 12 ... Holder 14, 30 ... Fixing roller ( heating member )
14-a, 30-a ... Metal core (metal layer)
14-b, 30-b ··· toner release layer 14-c, 30-c ··· protective layer 28, 29 ... thermistor (temperature detection knowledge member)
29-a ... detecting part protective layer 31 ... fixing device ( image heating device)
32. Image forming apparatus

Claims (2)

A coil that generates magnetic flux when energized, a coil holder that supports the coil, a cylindrical rotatable heat generating member that generates heat by the action of the magnetic flux generated by the coil , and press-contacts the heat generating member to sandwich the recording material A pressure member that forms a nip portion to be conveyed, a temperature detection member that contacts the inside of the cylinder of the heat generation member, detects the temperature of the heat generation member, and energizes the coil based on the output of the temperature detection member and a control means for controlling the said heating member has a protective layer in contact with the temperature sensing member, and a metal layer provided on the protective layer, provided on the metal layer, the toner image on the recording material anda release layer in contact with, the coil holder is an inside of the heating member, the image heating apparatus is provided to face the nip portion,
The temperature detection member is supported by the coil holder, and the coil wire is provided on both sides of the temperature detection member in the circumferential direction of the heat generation member in a cross section of the heat generation member orthogonal to the rotation axis of the heat generation member. It is provided in contact with the inner surface of the heat generating member in a nip region at a certain position, and the thickness of the protective layer made of a fluororesin of the same material as the release layer is larger than the thickness of the release layer A featured image heating apparatus.   2. The image heating apparatus according to claim 1, wherein a portion where the temperature detection member comes into contact with the protective layer is coated with the same material as the protective layer.