JPH08305191A - Heating device - Google Patents

Abstract

PURPOSE: To solve a problem of delayed response of an element, and the problem of placing accuracy with distance between a heating body and the element, in the case that the safety temp. detection element for emergency cut-off power to the heating body at the time of abnormal temp. rising in the heating body is arranged in non- contact with the heating body, with regard to the heating device imparting thermal energy from the heating body to a heat receiving material through a film, by holding the heat resisting film in sliding contact with the heating body heated by resistance, while keeping the heat receiving material in close contact with the surface of the side opposite to the heating body side of the film and allowing to pass the heating body position in company with the film. CONSTITUTION: The safety counter measure temp. detection element 10 is placed in non-contact with respect to the heating body 3, with the distanced (d) across a spacer member 13, at least, a part of the spacer member 13 is composed by the softening member which is provided with a softening point higher than the actuating temp. of the element 10, softened prior to the actuation of the element 10 at the time of abnormal temp. rising of the heating body 3, and allowed to make the spacer function of the spacer member 13 lost, and therefore to permit the element 10 coming in contact with respect to the heating body 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to heating a heat-resistant film in contact with a heating body which generates heat by energizing, and bringing a material to be heated into close contact with the surface of the film opposite to the heating body. The present invention relates to a film heating type heating device which passes a body position and applies heat energy from a heating body to a material to be heated through the film.

[0002]

2. Description of the Related Art A film heating type heating device as described above is known from Japanese Patent Application Laid-Open No. 63-313182 and Japanese Patent Application Laid-Open No. 2-157878 related to the applicant's earlier proposal. An image heat fixing device in an image forming apparatus such as a copying machine, a printer, or a fax machine, that is, a developer (toner) made of a heat-meltable resin is used by an image forming process means such as electrophotography, electrostatic recording, magnetic recording, etc. An unfixed image corresponding to the intended image information formed on the surface of the recording material (transfer material sheet, electrofax sheet, electrostatic recording sheet, printing paper, printing paper, etc.) by the indirect (transfer) method or the direct method. It can be utilized as a heat fixing device for performing a heat fixing process on a surface of a recording material carrying the image as a fixed image.

Further, it can be used, for example, as an apparatus for heating a recording material carrying an image to modify the surface properties of gloss and the like, an apparatus for post-treatment, etc.

FIG. 14 shows a schematic cross-sectional view of a main portion of an image heat fixing device as a film heating type heating device.

Reference numeral 1 is a stay, 11 is a heater support member having heat resistance, heat insulation and rigidity (hereinafter referred to as a heater holder), 3 is a heater, and in this example, a ceramic heater. The heating element 3 is fixedly held on the lower surface of the heater holder 11, and the heater holder 11 is fixedly held on the lower surface of the stay 1. Reference numeral 2 is a heat resistant film such as polyimide (hereinafter referred to as a fixing film), and 6 is an elastic pressure roller such as a silicon rubber roller as a pressure member. The heating body 3 and the pressure roller 6 are pressed against each other with a predetermined pressing force sandwiching the fixing film 2 to form a pressure contact nip portion N (hereinafter referred to as a fixing nip portion) having a predetermined width.

The fixing film 2 is brought into close contact with the lower surface of the heating body 3 by a driving means (not shown) or the pressure roller 6 being driven to rotate, and is slid and conveyed in a direction a at a predetermined speed.

The ceramic heater as the heating element 3 is energized to rise to a predetermined fixing temperature and temperature is adjusted.
In the state where the fixing film 2 is being conveyed, a recording material P to be image-fixed as a material to be heated is introduced between the fixing film 2 and the pressure roller 6 in the fixing nip portion N so that the recording material P together with the fixing film 2 is introduced. By nip-conveying the fixing nip portion N, the heat of the heating element 3 is applied to the recording material P via the fixing film 2 to form an unfixed visible image (toner image) formed and carried on the surface of the recording material P. ) T is thermally fixed. The recording material P passing through the fixing nip portion N is separated from the surface of the fixing film 2 and conveyed.

The ceramic heater as the heating element 3 is an elongated ceramic substrate 3 having electric insulation, heat resistance and low heat capacity.
a and an electric heating element 3b formed in a linear or strip shape along the length of the surface of the substrate as a basic constituent
The temperature is rapidly raised by energizing the energization heating element 3b.

The temperature of the heating element 3 is detected by a temperature detecting element (not shown), and the detected information is fed back to an energization control circuit (not shown) to control the energization from the power source to the energization heating element 3b to execute fixing. Temperature control is performed so that the temperature of the heating element 3 that is sometimes detected by the temperature detecting element reaches a predetermined temperature (fixing temperature).

Further, a temperature detecting element 10 for safety measures (a thermal protector, hereinafter referred to as a temperature fuse) which heats the heating element 3 by the heat of the heating element when the temperature of the heating element 3 abnormally rises and urgently cuts off the power supply to the heating element is heated. The heating element 3 is arranged in contact with the surface of the body 3 opposite to the fixing film contact surface side (the back surface of the heating element), and an uncontrollable state occurs in the energization of the energization heating element 3b, causing the heating element 3 to malfunction. When the temperature rises (runaway of the heating element, excessive temperature rise beyond the allowable level), the temperature fuse 10 operates at the abnormally elevated temperature of the heating element 3, and the energization of the energization heating element 3b is urgently cut off.

The film heating type apparatus as described above is
Since the heating element 3 having a low heat capacity can be used, the weight time can be shortened (quick start property) as compared with the conventional heating device such as the heat roller system, and the quick start can be performed. Preheating when not in use is not necessary, and power saving can be achieved in a comprehensive sense. In addition, it has an advantage that it can solve various drawbacks of other heating type devices, and is effective.

The thermal fuse 10 as a temperature detecting element for safety measures is generally classified into two types, a temperature sensitive pellet type and an alloy type.

15A and 15B show an example of a temperature-sensitive pellet type thermal fuse, wherein FIG. 15A is a vertical sectional view in a normal state and FIG. 15B is a vertical sectional view in operation.

Reference numeral 31 denotes an outer metal case of the thermal fuse, 3
Reference numeral 2 is a first lead wire, and an insulating ceramic cylindrical member 33 is attached to the tip of the first lead wire.
By being fitted into one end of the casing 1 and caulking the case, the case 31 is insulated and prevented from coming off.

Reference numeral 34 denotes a second lead wire, the tip end portion of which is inserted into the other end side of the case 31 and the case is caulked to electrically connect to the metal case 31 to prevent it from coming off.

35, 36, 37, 38, 39, and 40 are arranged in order from the first lead wire 32 side to the second lead wire 34 side in the case 31, respectively. , A second spring, a disc, and a temperature-sensitive pellet made of an organic material that is a temperature-sensitive member.

The first spring 35 is an insulating ceramic 33.
And the movable electrode 36, and the second spring 38 is compressed between the disk 37 and the disk 39.

The spring force of the second spring 38 is set to be larger than that of the first spring 35. In the normal state (A), the tension force between the discs 37 and 39 of the second spring 38 causes the first spring to move. 35 is compressed between the movable electrode 36 and the insulating ceramic cylindrical member 33,
6 is pressed against the tip portion of the first lead wire 32 to maintain electrical continuity with the first lead wire 32. Further, the temperature-sensitive pellet 40 abuts on and is received by the tip of the second lead wire 34, and is kept in a state of being interposed as a spacer member between the disc 39 and the tip of the second lead wire 34.

The movable electrode 36 has a metal case 3 at its outer peripheral edge.
It is in contact with the inner surface of No. 1 and keeps electrical connection with the case 31, and is freely movable in the axial direction in the case.

In this normal state, the electric current to the energization heating element 3b of the heating element 3 is the first lead wire 32, the movable electrode 36 which is in pressure contact with the tip of the first lead wire 32, and the metal case electrically connected to this. 31 and the second lead wire 34 flow.

In order to maintain the airtightness of the case 31, 41 in this example is a sealing (sealing) resin formed by coating between the end surface of the metal case 31 on the first lead wire mounting side and the first lead wire base. It is a department.

By disposing the thermal fuse 10 in contact with the heating element 3, the heat of the heating element 3 is transferred to the metal case 3.
It is transmitted to the temperature-sensitive pellet 40 inside via 1 etc. As long as the temperature of the temperature-sensitive pellet 40 is below a predetermined operating temperature, the thermal fuse 10 is kept in the normal state (A), and the energization heating element 3b of the heating element 3 is passed through the thermal fuse 10. Is supplied to.

On the other hand, when the heating element 3 overheats due to the runaway of the heating element due to the failure of the energization control system 15 and the temperature of the temperature sensitive pellet 40 becomes higher than a predetermined operating temperature, the temperature sensitive pellet 40 is heated.
Melts or sublimes to become liquid or disappear as in (B), and the temperature-sensitive pellet 40 as a spacer member between the disc 39 and the tip of the second lead wire 34 disappears. Therefore the first
The second spring 38 is pushed toward the second lead wire 34 side by the spring force of the spring 35 so that the movable electrode 36 is separated from the tip of the first lead wire 32, and the heating element 3 of Power is cut off.

FIGS. 16A and 16B show an example of an alloy type thermal fuse. FIG. 16A is a vertical sectional view in normal times, and FIG. 16B is a vertical sectional view in operation.

Reference numeral 43 denotes an exterior ceramic case of the thermal fuse 10, reference numeral 44 denotes an alloy serving as a temperature-sensitive member, which is located in the case and has first and second lead wires 32 and 34 connected to both ends by welding. It is a conductive soluble body. The outer periphery of the fusible body 44 is covered with the flux 45.

Numerals 41, 41 are sealing resin portions in which both end openings of the case 43 are closed in order to maintain the airtightness of the case 43.

By disposing the thermal fuse 10 in contact with the heating element 3, the heat of the heating element 3 is transferred to the fusible element 44 inside via the ceramic case 43 and the like. As long as the temperature of the fusible body 44 is equal to or lower than a predetermined operating temperature, the thermal fuse 10 is kept in the normal state (A), and the first lead wire 32, the fusible body 44, and the second lead wire 34.
Power is supplied to the energized heat generating element 3b of the heating element 3 through the path.

On the other hand, when the heating element 3 overheats due to runaway of the heating element and the fusible element 44 reaches a predetermined operating temperature or higher, the fusible element 44 melts. At this time, the fusible body 44 is melted by the action of the flux 45 that surrounds the fusible body 44 and the surface tension of the fusible body 44, and the fusible body 44 instantly melts the first and second lead wires 3.
As shown in (B), the tip ends of 2.34 are agglomerated, sphered, and melted, and the power supply circuit to the energization heating element 3b of the heating element 3 is reliably cut off.

As described above, both the temperature-sensitive pellet type thermal fuse and the alloy type thermal fuse are made airtight by the sealing resin 41 in the fuse cases 31 and 43. If the inside of the case is not kept airtight, the temperature sensitive pellets 40, the fusible body 44, and the flux 4 inside the case
This is because the quality of No. 5 deteriorates over time and operates at or below the original operating temperature, or conversely it does not operate even when the operating temperature is reached, resulting in reduced reliability.

Conventionally, as the sealing resin 41, even if a strong force is applied to the sealing resin portion when bending the lead wires 32 and 34, peeling, cracking, deformation, etc. are prevented so that the airtightness is not broken. A resin made of a heat-resistant non-elastic material having a certain strength such as an epoxy resin is used.

[0031]

[Problems to be Solved by the Invention]

(A) Unlike other heating devices such as a heating roller system, a film heating type heating device frequently repeats a heat cycle of rapid heating and rapid cooling of a heating element.

That is, the thermal fuse 10 provided in contact with the heating element 3 also undergoes such a heat cycle, so that the sealing resin portion 41 repeats thermal expansion and contraction, so that the sealing resin portion 41 is cracked. However, there is a possibility that the airtightness is broken and the thermal fuse 10 malfunctions.

(B) The temperature distribution in the longitudinal direction of the heating element 3 changes corresponding to the size of the recording material P between the paper passing portion and the non-paper passing portion.

Therefore, when the thermal fuse 10 is arranged in direct contact with the heating element 3 as in the conventional case, the temperature fuse having a temperature as low as possible is provided in the paper passing portion where the temperature of the heating element 3 is always stable during paper passing. It is necessary to dispose of and to speed up the response at the time of abnormal temperature rise.

Further, when a plurality of thermal fuses are arranged for the purpose of enhancing safety, the temperature may be increased even in a region which is a non-sheet passing portion in the longitudinal direction of the heating element 3 depending on the size of the recording material P. The fuse will come into contact. In such a case, when the thermal fuse 10 is placed in direct contact with the heating element 3, a thermal fuse having a high rated temperature is used to the extent that malfunction does not occur due to temperature rise in the non-sheet passing portion when passing small size paper. It will be. However, this would slow down the response during abnormal temperature rise.

(C) When the thermal fuse 10 is directly contacted with the heating element 3 as in the conventional case, heat is taken by the thermal fuse 10 even during normal paper passing, and the heating element 3 is contacted with the thermal fuse 3. The fixability of the part is reduced. In the first start-up in the morning (starting from a state where the temperature of the thermal fuse is low to about room temperature), the temperature of the heating body portion in contact with the thermal fuse 10 is about 20 deg lower than that of the other heating body portions. This reduces the fixability in the morning.

In order to prevent this, the energization heating element is constructed so that the heating value of the energization heating element 3b becomes higher in accordance with the temperature fuse contact portion. For example, the pattern of the energization heating element 3b is squeezed to lengthen the length of the energization heating element. The distribution of heat generation along the line had to be partially changed, and the pattern of the electric heating element was complicated.

(D) As a measure for solving the above problems, it is also considered to arrange the thermal fuse 10 in the vicinity of the heating body 3 in a non-contact manner.

However, when the thermal fuse 10 is provided on the heating element 3 in a non-contact manner, the heat conduction from the heating element 3 to the thermal fuse 10 is slow, and therefore the excessive heating of the heating element at the time of abnormality is detected and the thermal fuse is applied to the heating element. There was a possibility that it would be a problem that the current supply to the device would be cut off lately and smoke might be generated.

Further, in order to improve the detection accuracy, it is necessary to make the accuracy of the spacing between the heating element and the thermal fuse extremely high, but this is technically difficult and increases the cost.

The present invention relates to a film heating type heating device, in which the temperature detecting element for safety measures (temperature fuse) for urgently cutting off the power supply to the heating body when the temperature of the heating body is abnormally elevated is the same as in the case of the above (D). The non-contact arrangement with the heating element, but the problem of the response delay of the element, the problem of the disposition accuracy of the heating element and the temperature detecting element for safety measures as described above in the case of the non-contact arrangement. It is an object of the present invention to provide a heating device that has been eliminated to improve safety and reliability.

[0042]

The present invention is a heating device characterized by the following constitutions.

(1) A heat-resistant film is brought into contact with and slides on a heating body that generates heat when energized, and a material to be heated is brought into close contact with the surface of the film opposite to the heating body side so that the film and the film pass through the heating body position. In a heating device that applies heat energy to a material to be heated through the film from a heating element, temperature detection for safety measures that is activated by the heat of the heating element when the temperature of the heating element is abnormally high and that interrupts the power supply to the heating element The element is spaced apart from the heating element via a spacer member and arranged in a non-contact manner, and the softening point of at least a part of the spacer element is higher than the operating temperature of the temperature detecting element for safety measures, and the heating element When the temperature rises abnormally, the temperature sensing element for safety measures is softened before the operation to lose the spacer function of the spacer member, and it is configured with a softening member that allows the temperature sensing element for safety measures to contact the heating body. Heating device for the.

(2) The present invention is characterized in that a member for constantly urging the temperature detecting element for safety measures, which is arranged in a non-contact manner with being separated from the heating body via a spacer member, is constantly urged toward the heating body (1) ) The heating device described in.

(3) The temperature detecting element for safety measures is provided on the side of the heating body opposite to the heat-resistant film contacting side through the spacer member at the highest temperature portion of the temperature distribution along the direction of travel of the heated material. The heating device according to (1) or (2), characterized in that the heating device is separated from each other and disposed in a non-contact manner.

(4) In any one of (1) to (3), a space is provided in a portion of the heating member supporting member which is adjacent to a surface of the heating member opposite to the heat-resistant film contact surface side. Heating device.

(5) The heating device according to any one of (1) to (4), wherein a plurality of temperature detecting elements for safety measures are arranged in the longitudinal direction of the heating body.

(6) A temperature detecting element for safety measures is provided in the vicinity of an abutting portion formed on the side of the heating element opposite to the heat-resistant film contacting side, (1) to (). 5)
The heating device according to any one of 1.

[0049]

[Action]

a) A temperature detecting element for safety measures, which is activated by the heat of the heating body when the temperature of the heating body is abnormally elevated and is urgently cut off from power supply to the heating body, is arranged in a non-contact manner with a spacer member spaced from the heating body. However, at least a part of the spacer member has a softening point higher than the operating temperature of the temperature detecting element for safety measures and is softened before the operation of the temperature detecting element for safety measures when the temperature of the heating element is abnormally high. By using a softening member that eliminates the spacer function of the member and allows the temperature sensing element for safety measures to contact the heating body, in normal times, that is, as long as the heating body is heated and controlled at the normal temperature control temperature. Does not soften the spacer member of the temperature detecting element for safety measures, and therefore the temperature detecting element for safety measures is arranged in a non-contact manner with a predetermined spacing from the heating member via the spacer member. Be held in a state

As described above, during normal times, the temperature detecting element for safety measures is held in a non-contact state separated from the heating body, so that even if the heat cycle of rapid heating / cooling of the heating body is frequently repeated. , The thermal effect of the heating cycle of the heating element is greatly reduced compared to the case of contact arrangement, and therefore cracking and airtightness breakage due to repeated large thermal expansion and contraction of the sealing resin of the temperature sensing element for safety measures are prevented, and safety The predetermined performance of the temperature sensing element for countermeasures can be maintained for a long time without deterioration, and the temperature sensing element for safety countermeasures does not malfunction, thus improving the safety and reliability of the device.

B) During normal times, the temperature detecting element for safety measures is held in a non-contact state separated from the heating body, so that the temperature detecting element for safety measures of the heating body as in the case of contact arrangement. There is no local temperature drop due to heat removal by the temperature sensing element for safety measures at the contact part, the temperature distribution along the length of the heating element can be made uniform, and the pattern of the energization heating element of the heating element can be simplified. It will be possible.

C) By providing an air gap in the portion of the heating body supporting member which is close to the surface side of the heating body which is opposite to the heat resistant film contact surface side, this and the temperature detecting element for safety measures are arranged in non-contact with the heating body. Combined with the above, even if the amount of heat generated by the heating element was constant in the longitudinal direction, the temperature distribution along the longitudinal direction of the heating element could be made uniform to the extent that fixability was not affected. As a result, the structure of the electric heating element of the heating element can be simplified and the cost can be reduced. In addition, the presence of the above-mentioned gap in the heating body support member portion on the heating body rear surface side can prevent heat from escaping from the heating body back surface to the heating body support member, and also enables quick start and reduction in power consumption. became.

D) Depending on the size of the material to be heated that is passed through the apparatus, the temperature detecting element for safety measures can be arranged in the non-sheet passing area where the temperature rises in the non-sheet passing area. In addition, it is possible to dispose a plurality of temperature detecting elements for safety measures in the longitudinal direction of the heating body without causing a malfunction.

E) When an uncontrollable condition occurs in the energization of the heating element and the temperature of the heating element rises abnormally, when the temperature rise reaches the softening temperature of the spacer member, the spacer member softens and melts, resulting in safety. When the temperature sensing element for safety measures cannot be supported, and the temperature sensing element for safety measures is equipped with a pressing biasing member in the direction of the heating body, it is in contact with the heating body by the biasing force of the member or by its own weight. It changes automatically.

When the temperature detecting element for safety measures is brought into contact with the heating body, it is directly heated by the heating body having an abnormal temperature rise to operate, and the power to the heating body is cut off urgently. By setting the softening temperature of the spacer member to be higher than the operating temperature of the temperature sensor for safety measures, when the spacer member softens and the temperature sensor for safety measures comes into contact with a heating element with an abnormally high temperature, the time lag is substantially reduced. Immediately, the temperature sensing element for safety measures starts to operate, and the power supply to the heating element is urgently cut off before smoke or ignition occurs in the heating element. That is, there is no problem in the responsiveness of the temperature detecting element for safety measures at the time of abnormal temperature rise of the heating body.

F) The spacing between the heating element and the temperature detecting element for safety measures can be regulated by a spacer member with a predetermined variation, and the accuracy of the spacing is also taken as a safety measure in the present invention when the temperature of the heating element abnormally rises. Since the temperature detecting element is not operated while being separated from the heating body but is operated while being changed into a contact state with the heating body, strictness is not required and cost reduction can be achieved.

G) The temperature detecting element for safety measures is not provided on the side of the heating body opposite to the heat-resistant film contact surface side through the spacer member at the position where the temperature distribution has the highest temperature along the advancing direction of the heated material. By arranging them apart from the contact,
When the spacer member softens and the temperature sensor for safety measures comes into contact with the heater when the temperature of the heater rises abnormally, the temperature sensor for safety measures comes into contact with the high temperature portion of the heater and the response becomes quick.

H) By providing the temperature detecting element for safety measures in close proximity to the contact portion (recessed groove portion) formed on the side of the heating element opposite to the heat-resistant film contacting side, abnormal heating of the heating element occurs. When the temperature sensing element for safety measures comes into contact with the heating element due to softening of the spacer member when the temperature is high, the temperature sensing element for safety measures is received by the corresponding contact portion and the position corresponding to the center of the heating element on the surface side of the heating element. It does not easily come off. In addition, since the temperature sensing element for safety measures is received at the contact part, the contact area between the temperature sensing element for safety measures and the heating element increases, and the distance from the energized heating element of the heating element becomes shorter The temperature sensing element responds quickly.

[0059]

【Example】

<Example 1> (Figs. 1 to 8) (1) Heating device Fig. 1 is a cross-sectional view showing a schematic configuration of a heating device of this example. The heating device of this example is disclosed in JP-A-4-44075.
This is a so-called tensionless type film heating type image fixing device disclosed in JP-A-4-204980-204980-204984. Constituent members and parts common to those of the apparatus shown in FIG. 14 are designated by the same reference numerals, and repetitive description will be omitted.

Reference numeral 1 denotes a stay made of a heat-resistant resin having a substantially semi-circular cross-section gutter shape, and a fixing film 2 and a recording material P are conveyed in a conveying direction a.
It is a laterally elongated member having a longitudinal direction in a direction orthogonal to (the direction perpendicular to the drawing).

The heating element 3 is a ceramic heater, and the heating element 3 is fitted and held in a groove 11a having a width of the heating element provided along the longitudinal direction on the lower surface of the heater holder 11 which is a heating element supporting member.
The heater holder 11 is fitted and held in a groove portion 1a formed along the length of the lower surface of the stay 1 and having a heater holder width.

The fixing film 2 is a cylindrical (endless) heat resistant film, and is fitted onto the stay 1 holding the heating body 3 as described above. Regarding the inner peripheral length of the cylindrical fixing film 2 and the outer peripheral length of the stay 1 including the heating body 3, the film 2 is made larger by about 3 mm, for example.
Therefore, the film 2 is loosely fitted to the stay 1 including the heating element 3 with a sufficient circumferential length.

The pressure roller 6 is an elastic roller in which a heat-resistant rubber layer 6b having a good releasability, such as silicon rubber, is concentrically and integrally provided on the outer periphery of a core metal 6a. The pressure roller 6 and the heating body 3 on the stay 1 side are sandwiched by the fixing film 2 and pressed against the elasticity of the pressure roller to form a fixing nip portion N having a predetermined width.

The pressure roller 6 is rotationally driven in the counterclockwise direction indicated by the arrow at a predetermined peripheral speed by the drive system M, and the rotational drive of the pressure roller 6 causes the roller 6 and the film 2 in the fixing nip portion N to rotate. The rotational force acts directly on the film 2 due to the frictional force with the outer surface (when the recording material P is introduced into the fixing nip portion N, the rotational force is indirectly applied to the film 2 via the recording material P). Function), the film 2 is rotationally driven in the clockwise direction a as indicated by the arrow while sliding in pressure contact with the lower surface of the heating body 3. The stay 1 has both ends thereof fixedly supported by side members (not shown) of the apparatus, and functions as an inner surface guide member for the cylindrical fixing film 2 that rotates while holding the heating body 3 and facilitates rotation of the film 2. To In order to reduce the sliding resistance between the inner surface of the film 2 and the lower surface of the heating element 3, a small amount of lubricant such as heat resistant grease may be interposed between the two.

In a state where the rotation of the film 2 is stabilized by the rotation of the pressure roller 6 and the temperature of the heating body 3 rises to a predetermined value, the fixing formed by the heating body 3 and the pressure roller 6 with the film 2 sandwiched therebetween. A recording material P to be image-fixed as a material to be heated is introduced between the film 2 and the pressure roller 6 in the nip portion N, and the fixing nip portion N is nipped and conveyed together with the film 2 to heat the heating member. The heat of 3 is applied to the recording material P / unfixed visible image t via the film 2, and the unfixed visible image t on the recording material P is heated and fixed on the surface of the recording material P. The recording material P passing through the fixing nip portion N is separated from the surface of the film 2 and conveyed.

In the film heating type apparatus of this embodiment, the fixing nip portion N and the contact portion area between the outer surface portion of the stay upstream of the nip portion N in the film rotation direction and the inner surface of the film 1 in the film rotation driving state. The tension acts only on the film part of the above, and the tension does not act on the rest of the film part (tensionless, tension free). Therefore, the shift force of the film 2 along the length of the stay in the film rotational driving state is small, and the shift control means for the film 2 or the film shift control means can be simplified. For example, the film shift control means can be as simple as a flange member that receives the film end portion, and the film shift control means can be omitted to reduce the cost and size of the apparatus.

The fixing film 2 has a total thickness of 100 in order to reduce the heat capacity and improve the quick start property.
PTFE, PFA, F having heat resistance, releasability, strength, durability, etc. of not more than μm, preferably not more than 40 μm and not less than 20 μm
Single layer film of EP or P on the outer peripheral surface of polyimide, polyamide imide, PEEK, PES, PPS, etc.
A composite layer film coated with TFE, PFA, FEP, etc. can be used. In this example, a polyimide film having an outer peripheral surface coated with PTFE was used.

FIG. 2 is a plan view of a ceramic heater as the heating element 3 with the middle part omitted and partially cut away, and a block diagram of the energization control system.

Ceramic heater 3 as the heating element of this example
Has the following configuration.

A. Al ₂ O ₃ (alumina), Al whose longitudinal direction is substantially orthogonal to the transport direction a of the fixing film 2
Width 7 with electrical insulation, heat resistance, and low heat capacity of N, SiC, etc.
mm ceramic substrate 3a having a thickness of 1 mm, b. The width of the substrate 3a is reduced by screen printing or the like along the length of the substrate at the central portion in the substrate width direction on one surface side (front surface side).
linear or strip formed by coating and baking in mm, silver-palladium (Ag / Pd), energization heater 3b of the electrical resistance material such as _{RuO 2, Ta 2 N, c} . Power supply electrodes 3c and 3d formed on the surface of the substrate by electrically connecting both ends of the electric heating element 3b, d. An electrically insulating overcoat layer 3e such as glass or fluororesin as a surface protection layer covering the surface of the substrate 3a on which the electric heating element is formed, e. A temperature detecting element 3f such as a thermistor provided in contact with the other surface side (back surface side) of the substrate 3a, f. As will be described later, a temperature fuse 10, which is a temperature detecting element for safety measures, is arranged on the other surface side of the substrate 3a so as to be separated in a non-contact manner via a spacer member 13.

The overcoat layer 3e side of the heating element 3 is the film contact sliding surface side. This surface side is exposed to the outside so that the heating element 3 is held by the heater holder 11, and the heater holder 11 is held by the stay 1. .

A voltage is applied to the heating element 3 from the AC power source 20 between the power supply electrodes 3c and 3d at both ends of the energization heating element 3b, and the energization heating element 3b generates heat to raise the temperature.

The temperature of the heating element 3 is detected by the temperature detecting element 3f on the back surface of the substrate, the detected information is fed back to the energization control circuit 15, and the energization from the AC power source 20 to the energization heating element 3b is controlled to fix the fixing. Temperature detection element 3 during execution
Temperature control is performed so that the temperature of the heating element 3 detected at f reaches a predetermined temperature (fixing temperature).

The temperature control of the heating element 3 employs a method of controlling the applied voltage or current to the energization heating element 3b or the energization time. The method to control the energization time is to control the energization or non-energization for each half-wave of the power supply waveform.
There is a phase control that controls the phase angle of energization for each half-wave of the power supply waveform.

That is, the output of the temperature detecting element 3f is A / D exchanged and fetched in the CPU, and based on the information, the AC voltage applied to the energization heating element 3b is subjected to pulse width modulation such as phase control or wave number control by a triac. Applied temperature detection element 3
The energization of the energization heating element 3b is controlled so that the temperature detected by the heating element 3 by f is constant.

The thermal fuse 10 may be either the temperature sensitive pellet type shown in FIG. 13 or the alloy type shown in FIG. Other types may also be used. The thermal fuse 10 is connected in series to the energization path for the energization heating element 3b, and the energization control of the energization heating element 3b occurs in a situation in which the heating element 3 cannot be controlled.
When the temperature rises abnormally (runaway of the heating element), the thermal fuse 10 comes into contact with the heating element 3 due to the softening / melting of the spacer member 13 as described below.
Is activated, and the energization of the energization heat generating element 3b of the heating element 3 is urgently cut off.

(2) Thermal fuse 10 a) Arrangement configuration FIGS. 3 and 4 are an enlarged horizontal sectional model view and an enlarged vertical sectional model view of the portion where the thermal fuse of the heating element is disposed.

The thermal fuse 10 is provided on the rear surface of the heating body (rear surface of the ceramic substrate 3a) at the center in the width direction.
0 are arranged in a non-contact manner at a predetermined distance d via four downward facing spacer protrusions 13 as spacer members which are attached and attached to the left and right side of the front end side and the left and right side of the rear end side. In this example, the spacing d is 0.5 mm.

In the portion corresponding to the temperature fuse of the heater holder 11, a temperature fuse drop through hole 11b having a width substantially corresponding to the width of the temperature fuse 10 is formed in advance, and the heating element 3 is fitted in the groove portion 11a of the heater holder 11. After that, the temperature fuse 10 is dropped into the through hole 11b of the heater holder 11 with the spacer protrusion 13 side facing downward, and the spacer protrusion 13 is brought into contact with the rear surface of the heating element. The thermal fuse drop-through hole 11b ensures that the thermal fuse 10 is located at the center of the rear surface of the heating element in the width direction.

After the thermal fuse 10 is dropped into the through hole 11b, the first lead wire 32 and the second lead wire 34 of the thermal fuse 10 are respectively formed on the back surface of the ceramic substrate of the heating element 3 through unillustrated through holes. Electrically connect to the circuit pattern by brazing.

Further, the heater holder fitting groove portion 1 of the stay 1
A spring receiving hole 1b is provided at a position corresponding to the temperature fuse of a. When the heater holder 11 in which the heating element 3 and the temperature fuse 10 are assembled as described above is fitted into the heater holder fitting groove portion 1a of the stay 1. Insert one end side of a pressure spring (coil spring) 12 into the spring receiving hole 1b on the stay 1 side, and press the pressure spring 12 between the temperature fuse 10 and the spring receiving hole 1b to hold the heater holder 11 in place. The first heater holder fitting groove portion 1a is fitted and held.

As a result, the stay 1 and the heater holder 11 are
In the assembled state, the thermal fuse 10, which is spaced apart from the rear surface of the heating element 3 via the spacer member 13 in a non-contact manner, is constantly urged by the pressure spring 12 toward the heating element.

The thermal fuse 10 corresponds to the position of the highest temperature in the temperature distribution along the advancing direction of the material to be heated on the central portion in the width direction of the rear surface of the heating element, that is, on the surface of the heating element 3 opposite to the fixing film contact surface side. I am letting you.

FIG. 6 shows the temperature distribution along the width direction of the heating element (the direction in which the material to be heated advances) when the energization heating element 3b of the heating element 3 is energized. This temperature distribution diagram is the one when the temperature of the heating body is controlled to 180 ° C by the thermistor provided at the position Tm which is the widthwise central portion of the back surface of the heating body, and the horizontal axis is the position in the heating body width direction. The vertical axis is the temperature at that position. As can be seen from the figure, there is a temperature difference of 50 ° C. or more between the central portion and the end portion of the heating element 3 in the width direction.
The temperature difference may be further increased depending on the size, the width of the electric heating element 3b, and the position with respect to the substrate 3a. From the experiment by the present inventor, it is known that the temperature is highest at the position corresponding to the approximate center of the energization heating element 3b in the width direction on the back side of the heating element. Therefore, in the present embodiment, the thermal fuse 10 is arranged on the rear surface of the heating element at a substantially central portion in the width direction where the temperature is highest.

At least a part of the spacer member 13 has a softening point T1 higher than the operating temperature T2 of the thermal fuse 10 and the thermal fuse 1 when the heating element 3 is abnormally heated.
Before the operation of 0, the softening member is softened to lose the spacer function of the spacer member 13 and permit the contact of the thermal fuse 10 with the heating body 3. That is, the spacer member 13 is selected so that it does not soften at the temperature of the heating body 3 in the normal temperature control temperature state, but softens when the heating body 3 is in an excessive temperature rise state that is higher than the allowable temperature.

Specifically, the temperature of the heating element 3 during the passage of paper is
In order to prevent deterioration due to the heat of the heating device even when a small size paper is passed and the temperature of the non-sheet passing portion where the heat is not taken by the recording material P is raised, the temperature control temperature and the throughput are controlled. The temperature is controlled to be about 210 ° C at worst. Therefore, the spacer member 13 may be selected from a resin that softens when the temperature becomes higher than that.

For example, polyamide-imide (softening temperature 27
4 ° C.), glass fiber-containing polyether sulfone (softening temperature 216 ° C.), glass fiber-containing polyethylene terephthalate (softening temperature 235 ° C.), glass fiber-containing polyamide (softening temperature 228 ° C.), etc. Resin can be used as the spacer member 13. The softening temperature is according to JIS K2531 ring and ball method.

In this embodiment, all of the four spacer protrusions 13 serving as spacer members are the above-mentioned softening members.

B) Normal period In a normal state, that is, as long as the heating element 3 is heated and controlled at a normal temperature control temperature, the spacer member 13 of the thermal fuse 10 does not soften, and therefore the thermal fuse 10 has the structure shown in FIG.・
As shown in FIG. 4, a predetermined spacing d (0.5 mm) is provided in the widthwise central portion of the back surface of the heating element via the spacer member 13.
Existing in a non-contact manner.

As described above, during normal operation, the thermal fuse 10 is held in a non-contact state separated from the rear surface of the heating body,
Even if the heat cycle of rapid heating and rapid cooling of the heating element 3 is frequently repeated, the thermal effect (heat shock) of the heating element heat cycle is greatly reduced as compared with the case of contact arrangement, and therefore the thermal fuse 10 The sealing resin 41 is prevented from cracking and airtightness due to repeated large thermal expansion and contraction, and the predetermined performance of the thermal fuse 10 can be maintained for a long time without deterioration.

Further, under normal conditions, the thermal fuse 10 is held in a non-contact state separated from the back surface of the heating body, so that the thermal fuse of the thermal fuse contact portion of the heating body 3 absorbs heat as in the case of contact arrangement. There is no local temperature drop due to, the temperature distribution along the length of the heating element can be made uniform, and the pattern of the electric heating element 3b can be simplified.

C) Abnormal temperature rise of heating element When the heating element 3 has an abnormal temperature rise due to an uncontrollable condition of energization of the heating element 3 to the energization heating element 3b, the temperature rise is the softening temperature of the spacer member 13. When T1 is reached, the spacer member 13 is softened and melted so that the thermal fuse 10 cannot be supported, and the thermal fuse 10 is automatically brought into contact with the back surface of the heating element as shown in FIG. Changes to. In FIG. 5, 13 'is a softened / melted spacer member.

When the thermal fuse 10 comes into contact with the back surface of the heating element, the thermal fuse 10 is directly heated by the heating element 3 having an abnormal temperature rise and operates to urgently cut off energization to the energization heating element 3b. In this embodiment, the softening temperature T1 of the spacer member 13 is the thermal fuse 1
It is set higher than the operating temperature T2 of 0. Therefore, when the spacer member 13 is softened and melted and the thermal fuse 10 comes into contact with the back surface of the heating body 3 having an abnormal temperature rise, the thermal fuse 10 is immediately activated with substantially no time lag, and the heating body 3 is heated.
The electric power to the electric heating element 3b is urgently cut off before smoke or ignition occurs. That is, there is no problem in the responsiveness of the thermal fuse 10 at the time of abnormal heating of the heating element.

Further, the spacing d between the heating element 3 and the thermal fuse 10 can be regulated by the spacer member 13 with a predetermined variation, and the precision of the spacing is also defined in the present invention.
When the temperature of the heating element is abnormally increased, the temperature fuse 10 is not operated while being separated from the heating element 3, but is operated by changing the contact state with the heating element. Therefore, strictness is not required and cost reduction is achieved. Can be planned.

In this embodiment, as the spacer member 13,
A glass fiber-containing polyethylene terephthalate member having a softening temperature of 235 ° C. was used, and the temperature fuse 10 was arranged at a distance of 0.5 mm from the back surface of the heating body. The relationship between the operating temperature of the thermal fuse 10 and the overheated temperature of the heating body in this case is as shown by the solid line graph A in FIG. 7. As a result, the operating temperature 21
The thermal fuse 10 of 0 ° C. to 230 ° C. can be used, and the thermal fuse of 210 ° C., which has the lowest operating temperature, did not malfunction during printing.

With such a structure, in order to enhance safety, when a plurality of thermal fuses 10 are arranged in series in the longitudinal direction of the heating element as shown in FIG.
Even if the position of 0 became the non-sheet passing portion when the small size sheet was passed, it did not operate erroneously during printing.

As a comparative experiment, a thermal fuse was held 0.5 mm away from the heating element using a metal spacer. Temperature fuses with different operating temperatures were attached, and the temperature of the heating body when the temperature fuse was activated was measured by forcibly raising the temperature from room temperature of 20 ° C. The result is shown by a broken line graph B in FIG. 7.

In this case, when a thermal fuse having an operating temperature of 210 ° C. was used, the temperature of the heating element 3 rose to 420 ° C. and smoke was generated.

When a temperature fuse having an operating temperature of 200 ° C. is used, the temperature rise of the heating element drops to 380 ° C. However, the temperature fuse malfunctions during printing, and the printer cannot be operated.

<Embodiment 2> (FIG. 9) In this embodiment, in the heating apparatus of Embodiment 1, as shown in FIG. 9, a slit-like member having a width of 4 mm is formed in the central portion of the heater holder 11 in the width direction along the holder longitudinal direction. A void portion 11c is provided. The slit-shaped void portion 11a has a groove portion 1 in which the heater 3 is provided on the lower surface of the heater holder 11 along the longitudinal direction.
When it is fitted and held in 1a, the central portion in the width direction of the back surface of the heating body 3 is located at a corresponding position, and has a length dimension substantially corresponding to the length of the heating body 3. Then, the temperature fuse 10 is dropped at a predetermined position in the longitudinal direction of the slit-shaped void portion 11c of the heater holder 11 and separated from the rear surface of the heating body via the spacer member 13 so as to be arranged in a non-contact manner. In other words, in the apparatus of the first embodiment, the temperature fuse drop through hole 11b of the heater holder 11 is extended along the length of the heater holder 11 by a length substantially corresponding to the length of the heating body 3 so that the slit-like void portion 11c is provided. It is a thing. The other device configuration is the same as that of the first embodiment.

As described above, the heater holder 3 is attached to the heater holder 11.
Slit-like voids 11 having a length dimension substantially corresponding to the length of
By including c, the temperature distribution along the longitudinal direction of the heating body 3 can be made more uniform by the non-contact arrangement of the thermal fuse 10 with the heating body 3.

That is, the presence of the slit-like void 11c of the heater holder 11 and the non-contact temperature fuse 10 make the temperature distribution along the length of the heating element 3 constant even if the amount of heat generated by the electric heating element 3b is constant in the longitudinal direction. It could be made uniform to the extent that the fixability was not affected.

As a result, the structure of the electric heating element 3b of the heating element 3 can be simplified and the cost can be reduced.

Further, according to the heating element holder structure of this embodiment, since the slit-shaped void 11c is provided on the rear surface side of the heating element,
It is possible to prevent heat from escaping from the back surface of the heating element to the heater holder 11, and it is possible to perform quick start and reduce power consumption.

<Embodiment 3> (FIGS. 10 and 11) In this embodiment, in the heating device of Embodiment 1 or 2, the thermal fuses 10 are arranged in a non-contact manner with a spacer member 13 interposed therebetween. As shown in FIG. 10, a concave groove portion 3g (contact portion) into which the lower surface of the thermal fuse 10 is inserted is formed on the surface of the rear surface of the heating body corresponding to the thermal fuse.

The recessed groove portion 3g is located in the widthwise central portion of the rear surface of the heating element, and corresponds to the widthwise central portion of the electric heating element 3b on the heating element surface side. In the present embodiment, the concave groove portion 3g is a triangular groove having a triangular cross section and a triangular cross section in which the vertex corresponds to the central portion in the width direction of the electric heating element 3b on the heating body surface side. It can also be an arc groove or the like.

Therefore, as in the case of the above-mentioned first embodiment,
When an uncontrollable situation occurs in the energization of the heating element 3 to the energization heating element 3b and the heating element 3 has an abnormal temperature rise, when the temperature rise reaches the softening temperature T1 of the spacer member 13, the spacer member 13 is softened.・ The temperature fuse 10 cannot be supported by melting 13 ′ (FIG. 11), and the lower surface of the temperature fuse 10 is engaged with the concave groove portion 3g on the rear surface of the heating body as shown in FIG. 11 by the pressing force of the pressure spring 12. Then, it contacts the rear surface of the heating element in the state of being received, and is directly heated by the heating element 3 having an abnormal temperature rise to operate to urgently cut off the energization to the energization heating element 3b.

By providing the concave groove portion 3g in this way, the spacer member 13 is softened when the temperature rises excessively, and when the thermal fuse 10 contacts the rear surface of the heating body, the lower surface thereof is received by the concave groove portion 3g and heated. It does not easily deviate from the position corresponding to the central portion of the electric heating element on the body surface side.

Further, since the lower surface of the thermal fuse 10 is inserted in the concave groove portion 3g, the contact area between the thermal fuse 10 and the heating element 3 is increased, and the distance from the energization heating element 3b is further shortened, so that the response of the thermal fuse 10 is further improved. It has the advantage of being faster.

In each of the above-described embodiments, the temperature fuse 10 arranged in the non-contact manner on the rear surface of the heating element 3 via the spacer member 13 is pressed in the assembled state of the stay 1 and the heater holder 11. The spring 12 constantly urges the heating body toward the heating body, and when the spacer member 13 is softened when the heating body is abnormally heated, the thermal fuse 10 is brought into contact with the rear surface of the heating body by the urging force of the pressing spring 12. However, when the spacer member 13 is softened, the thermal fuse 10 may be brought into contact with the back surface of the heating body by its own weight, so that the pressing spring 12 may be omitted.

The configuration of the spacer member 13 is arbitrary, and it is not necessary to make all of it the softening member. At least a part of the softening point T1 is higher than the operating temperature T2 of the thermal fuse 10 and the heating element 3 is used. It suffices that the temperature fuse 10 is softened before the temperature fuse 10 is actuated at the time of abnormal temperature rise to lose the spacer function of the spacer member 13 to allow the temperature fuse 10 to contact the heating body 3.

<Embodiment 4> (FIG. 12) (a), (b), and (c) show other examples of the configuration of the film heating type heating device.

In the case of (a), the first film suspending roller 51, the second film suspending roller 52, and the heater holder 11 and the heating element 3 held by the stay 1 are arranged in parallel with each other by three members 51. An endless belt-shaped heat-resistant film 2 is stretched between 52 and 3, and the pressure roller 6 is arranged by pressing the heat-resistant film 2 against the heating body 3 with the film 2 interposed therebetween. The film suspension roller 51 or the pressure roller 6 is used as a film driving roller to be rotationally conveyed a. When the first film suspension roller 51 is used as a driving roller, the pressure roller 6 is driven to rotate.

In the case of (b), the endless belt-shaped heat-resistant film 2 is suspended between the heater holder 11 and the heating member 3 held by the stay 1 and the two members 3 and 53 of the film suspension roller 53. The heat-resistant film 2 is stretched, and the pressure roller 6 is arranged in pressure contact with the heating body 3 with the film 2 interposed therebetween.
Is used as the film suspension roller 53 or the pressure roller 6 as the film driving roller, and is rotationally conveyed a. When the film suspension roller 53 is used as a drive roller, the pressure roller 6 is driven to rotate.

In the case of (c), the heat-resistant film 2 is not an endless belt-shaped one, but a long end film wound in a roll is used.
From the side to the winding shaft 55 side via the heating body 3, the pressure roller 6 is brought into pressure contact with the heating body 3 with the film 2 sandwiched therebetween, and the film 2 is transported and conveyed to the winding shaft 55 side. It is a thing. The pressure roller 6 may be a film driving roller.

In any of the above devices (a), (b), and (c), the heat resistant film 2 and the pressure roller 6 in the pressure contact nip portion N are used.
The material P to be heated is introduced between the heat-resistant film 2 and the heat-resistant film 2 to pass through the pressure contact nip portion N, so that heat energy is applied from the heating body 3 to the material-to-be-heated via the heat-resistant film 2.

In any device, the same effect as in Examples 1 to 3 can be obtained by disposing the temperature detecting element (thermal fuse) 10 for safety measures in the heating body 3 according to the present invention.

<Fifth Embodiment> (FIG. 13) FIG. 13 shows an image heat fixing device A in which the film heating type heating device according to the present invention as shown in the first embodiment is used.
1 shows a schematic configuration of an example of an image forming apparatus incorporated as. The image forming apparatus of this embodiment is a reciprocating platen type, a rotary drum type, a transfer type, and a process cartridge attaching / detaching type electrophotographic copying apparatus.

Reference numeral 100 is an apparatus casing, 101 is a reciprocating type document placing table made of a transparent plate member such as a glass plate disposed on an upper surface plate 102 of the apparatus casing, and the apparatus casing upper plate 102
The upper part is driven to reciprocate to the right a and the left a'in the drawing at a predetermined speed.

Reference numeral G denotes an original document, which is placed on the upper surface of the original document table 101 according to a predetermined placement standard with the image surface side to be copied facing downward, and by pressing the original document pressure plate 103 onto the original document platen plate 103. Set.

Reference numeral 104 denotes a slit opening serving as a document illuminating section which is opened on the surface of the machine top plate 102 with the direction perpendicular to the reciprocating direction of the document placing table 101 (direction perpendicular to the paper surface) as the longitudinal direction.

The downward image surface of the document G placed and set on the document placing table 101 sequentially moves the positions of the slit openings 104 from the right side to the left side in the forward movement process of the document placing table 101 to the right a. The light L of the lamp 105 is passed through the slit opening 104 and the transparent original placing table 101 to be illuminated and scanned in the passing process, and the original surface reflected light of the illumination scanning light is reflected by the image element array 106 by the photosensitive drum. Image formation exposure is performed on the 107th surface.

The photosensitive drum 107 is coated with a photosensitive layer such as a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer, and is rotated in the clockwise direction indicated by the arrow b at a predetermined peripheral speed around the central support shaft 108. During the rotation process, the charging device 109 receives a uniform positive or negative charging process, and the uniformly charged surface is subjected to the image formation exposure (slit exposure) of the original image, so that the surface of the photosensitive drum 107 is formed. An electrostatic latent image corresponding to the image-exposed original image is sequentially formed.

This electrostatic latent image is sequentially visualized by the developing device 110 with toner made of resin or the like that is softened and melted by heating, and the toner image as the visualized image is provided with a transfer discharger 111 as a transfer portion. It moves to the part.

Reference numeral S denotes a cassette in which transfer material sheets P as recording materials are stacked and accommodated. The sheets in the cassette are fed out and fed one by one by the rotation of the feeding roller 112, and then the drum is moved by the registration rollers 113. When the leading edge of the toner image forming portion on 107 reaches the portion of the transfer discharger 111, the leading edge of the transfer material sheet P also arrives at the position between the transfer discharger 111 and the photosensitive drum 107 so that they both coincide with each other. It is returned and is synchronously fed.

Then, the transfer discharger 111 sequentially transfers the toner image on the photosensitive drum 107 side to the surface of the fed sheet.

The sheet to which the toner image has been transferred at the transfer portion is sequentially separated from the surface of the photosensitive drum 107 by separation means (not shown), and is guided to the above-mentioned thermal fixing device A by the conveying device 114 and is unfixed thereon. The toner image is heated and fixed, and is discharged as an image-formed product (copy) onto the discharge tray 117 outside the apparatus through the discharge roller 116.

The surface of the photosensitive drum 107 after the image transfer is subjected to removal of adhered contaminants such as transfer residual toner by the cleaning device 118, and is repeatedly used for image formation.

The PC is a process cartridge which is attached / detached to / from the cartridge attaching / detaching portion 120 in the apparatus main body 100.
In the case of the present example, the apparatus main body 10 including the four process devices of the photosensitive drum 107 as an image bearing member, the charging device 109, the developing device 110, and the cleaning device 118 together.
It is detachable and replaceable with respect to 0.

[0130]

As described above, according to the present invention, in the film heating type heating device, a temperature detecting element (temperature fuse) for safety measures for urgently cutting off the power supply to the heating body when the heating body is abnormally heated is provided. Although it is arranged in a non-contact manner with the heating element, the problem of response delay of the element and the problem of accuracy in disposing the heating element and the temperature sensing element for safety measures as described above, which was a problem in the non-contact arrangement. Can be solved, and a heating device with improved safety and reliability can be obtained, and the intended purpose is often achieved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a schematic configuration of a heating device according to a first embodiment.

FIG. 2 is a plan view of a ceramic heater serving as a heating element, with an intermediate part omitted and a part notched, and a block diagram of an electric control system

FIG. 3 is an enlarged cross-sectional model view of a portion where a thermal fuse of a heating element is arranged.

FIG. 4 is an enlarged vertical cross-sectional model view of a portion where a thermal fuse of a heating element is arranged.

FIG. 5 is a diagram showing a state where the spacer member is softened and the thermal fuse is in contact with the rear surface of the heating body when the temperature of the heating body is abnormally increased.

FIG. 6 is a temperature distribution diagram along the width direction (heated material advancing direction) of the heating element when the heating element is energized.

FIG. 7 is a correlation diagram between the operating temperature of the thermal fuse and the heating body temperature.

FIG. 8 is a partially enlarged vertical cross-sectional view of a heating body when a plurality of thermal fuses are arranged in series in the heating body longitudinal direction.

FIG. 9 is a perspective view of a heater holder of the heating device according to the second embodiment.

FIG. 10 is an enlarged cross-sectional model view of a portion where a thermal fuse of a heating device of Example 3 is provided.

FIG. 11 is a diagram showing a state where the spacer member is softened and the thermal fuse is in contact with the back surface of the heating body when the heating body is abnormally heated.

12 (a), (b), and (c) are schematic views of various configuration examples of a film heating type heating device, respectively.

FIG. 13 is a schematic diagram of an example of an image forming apparatus.

FIG. 14 is a schematic model diagram of a main part of a film heating type heating device.

15 (A) and (B) are vertical cross-sectional views showing the internal state of a temperature-sensitive pellet type thermal fuse in normal operation and during operation, respectively.

16 (A) and 16 (B) are vertical cross-sectional views showing the internal state of an alloy type thermal fuse during normal operation and during operation, respectively.

[Explanation of symbols]

 1 Stay 2 Heat Resistant Film (Fixing Film) 3 Heater (Ceramic Heater) 6 Pressure Roller 10 Temperature Detection Element for Safety Measures (Temperature Fuse) 11 Heater Support Member (Heater Holder) 12 Pressure Spring 13 Spacer Member N Pressure Nip Part (fixing nip part) P Heated material (recording material)

Claims (6)

[Claims] 1. A heat-resistant film is brought into contact with and slides on a heating body that generates heat when energized, and a material to be heated is brought into close contact with the surface of the film opposite to the heating body side and the film is passed through the heating body position together with the film for heating In a heating device that applies heat energy to a material to be heated from the body through the film, a temperature detection element for safety measures that is activated by the heat of the heating body when the temperature of the heating body is abnormally high and that interrupts power supply to the heating body Are spaced apart from the heating body via a spacer member in a non-contact manner, and the softening point of at least a part of the spacer member is higher than the operating temperature of the temperature detecting element for safety measures, and It is composed of a softening member that softens before operating the temperature sensor for safety measures during abnormal temperature rise and loses the spacer function of the spacer member to allow the temperature sensor for safety measures to contact the heating element. That the heating device. 2. A member for constantly urging a temperature detecting element for safety measures, which is arranged in a non-contact manner with being separated from a heating body via a spacer member, in a direction toward the heating body. The heating device according to. 3. A temperature detecting element for safety measures is separated by a spacer member at a position where the temperature distribution has the highest temperature along the advancing direction of the material to be heated on the side opposite to the heat resistant film contact surface side of the heating element. The heating device according to claim 1 or 2, wherein the heating device is arranged in a non-contact manner. 4. The heater according to claim 1, wherein a gap is provided in a portion of the heating member supporting member which is adjacent to a surface of the heating member opposite to the heat resistant film contact surface side. Heating device. 5. A plurality of temperature detecting elements for safety measures are arranged in the longitudinal direction of the heating element and provided.
The heating device according to claim 4. 6. The temperature detecting element for safety measures is provided in the vicinity of an abutting portion formed on the side of the heating element opposite to the heat-resistant film contacting side. 5
The heating device according to any one of 1.