JP2002270337A - Heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating device wherein a power supply to a heating body is quickly cut-off and safety and reliability of the heating device can be further enhanced at the time of abnormal temperature-rise of the heating body by arranging plural fuses at the heating body in a sure adhesion within a limited range where the heated body of the smallest width size passes. SOLUTION: This is the heating device equipped with the heating body 2 to generate heat by supply of a current and to be put into a fixed state to a base 100, thermal fuses 9a, 9b to cut-off supply of the current by detecting an abnormal temperature-rise of the heating body, an endless heat resistant film 1 guided and rotatably retained by a guide member 14 so that its inner peripheral face 1a will be crimped with the heating body 2, and a pressurizing roller 10. Plural thermal fuses are arranged and installed within a region of the smallest width size Smin of a recording sheet S.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a heating device,
In particular, an endless heat-resistant film is used for the heating element that generates heat when energized, and the sheet that is the material to be heated is brought into close contact with the surface of the heat-resistant film opposite to the heating element, and the film is removed from the heating element as it passes The present invention relates to an arrangement of a temperature fuse, which is one of safety devices, in a heating device that applies thermal energy to a material to be heated via the heating device.

[0002]

2. Description of the Related Art An endless heat-resistant film is used for a heating element, and a sheet as a material to be heated is brought into close contact with the surface of the heat-resistant film opposite to the heating element. Heating devices for applying thermal energy to a material to be heated via the heating device are known from JP-A-63-313182 and JP-A-2-157788.

[0003] These techniques include an image heating and fixing device in an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile, that is, a resin which is heated and melted by an image forming process means such as electrophotography, electrostatic recording, and magnetic recording. Recording material (electrofax sheet, electrostatic recording sheet, transfer material sheet, printing paper, etc.) using a developing agent (toner) composed of
An image heating and fixing device that forms an unfixed developer image corresponding to the target image information as a fixed image on a recording material carrying the image by forming the image directly or indirectly (transferring) on the surface of the image Can be used. Further, for example, it can be used as a device for heating a recording material carrying an image to improve the surface properties such as gloss, or a device for performing a temporary deposition process.

More specifically, a thin heat-resistant film (sheet), a driving means for moving the film, and a heater (heater) fixedly supported and arranged on one side of the film with the film inside. And a pressure member disposed on the other surface to face the heating element and closely contact the developer image carrying surface of the recording material to be image-fixed to the heating element via the film, wherein the film has at least an image. At the time of fixing, the recording material conveyed and introduced between the film and the pressing member is moved in the forward direction at the same speed as the recording material to be fixed. By passing through a fixing nip portion as a fixing portion formed by the above, the developer image carrying surface of the recording material is heated by a heating element via a film to form an unfixed developer image (unfixed toner image). Softening and melting by applying heat energy And then an image heating fixing apparatus of film heating type which is based on that to separate the recording material and the film after fixing portion passing through at the separation point.

FIG. 8 is a circuit diagram of a conventional image heating and fixing apparatus. In FIG. 8, a safety circuit including a temperature detecting element 8 such as a thermistor and a relay and a thermal fuse 9 are shown.
For example, when the temperature of the heating element 2 is abnormally increased, the power supply to the heating element 2 can be cut off.
A voltage is applied to the heating element 2 from the AC power supply 20 between the power supply electrodes 5 and 6 at both ends of the heating element 4, and the temperature of the heating element 2 rises as the heating element 4 generates heat.

The temperature of the heating element 2 is detected by a temperature detecting element 8 on the rear surface of the substrate, and the detected information is fed back to an energization control circuit 15 so that the energization from the AC power supply 20 to the energizing heating element 4 is controlled, thereby fixing the image. Temperature control is performed so that the temperature of the heating element 2 detected by the temperature detecting element 8 at the time of execution becomes a predetermined temperature (fixing temperature).

The heating element 2 includes an energizing heating element (resistance heating element) 4 as a heat source that generates heat by supplying power, and the temperature of the heating element 2 is increased by the heat generated by the energizing heating element 4. This heating element 2 has a longitudinal direction substantially perpendicular to the moving direction of the film 1,
₂ O ₃ (alumina), AIN, the ceramic substrate 3 of elongate electrical insulation, heat resistance and low heat capacity such as SiC, the substrate longitudinally of the substrate widthwise central portion of one surface of the substrate 3 (the surface side) Along with this, an electric heating element 4 such as silver palladium (Ag / Pd), RuO ₂ , Ta ₂ N, etc., as an exothermic source, formed in a linear or strip shape, and electrically connected to both ends of the electric heating element 4. Power supply electrodes 5 and 6 formed on the substrate surface;
And a temperature detecting element such as a thermistor provided in contact with the other surface side (back side) of the substrate 3, such as glass, as a surface protective layer covering the surface on which the electric heating element is formed. And a temperature fuse 9 as a temperature detecting element (thermal protector) for safety measures.

The overcoat layer 7 side of the heating element 2 is a film contact sliding surface side, and this surface side is exposed to the outside,
As described above, the heating element 2 is fixedly supported by the heating element accommodating recess formed at the center of the outer surface of the film guide member 14.

The temperature control of the heating element 2 is controlled by controlling the voltage or current applied to the energizing heating element 4 or by controlling the energizing time. Methods of controlling the energization time include zero-crossing wave number control for controlling energization and non-energization for each half-wave of the power supply waveform, and phase control for controlling the phase angle of energization for each half-wave of the power supply waveform.

That is, the output of the temperature detecting element (thermistor) 8 is A / D exchanged and taken into the CPU, and based on the information, the AC voltage applied to the energizing heating element 4 by the triac is controlled by a pulse such as phase control or wave number control. The temperature detected by the temperature detecting element 8 by applying the width modulation to the heating element is constant (for example, 19
0 ° C.). Although this heating device can fix an undefined image T printed on recording sheets S of various sizes, the temperature detecting element 8 detects that all of the recordable sheets S can pass through the heating element 2 while the sheet is passing. Is required to control the temperature of the recording sheet S, and the recording sheet S is arranged on the rear surface of the substrate inside the recording sheet S which can be fixed by the heating device and having the smallest width dimension. The recording sheet Smin having the smallest width among the passable recording materials differs depending on the device in which the heating device is used.
In many cases, printing of a 5 inch (76 mm x 127 mm) index card is required, and the temperature detecting element is arranged in a range where the short side (76 mm) of the recording material passes.

On the other hand, if the heating element 2 becomes uncontrollable due to a triac or a failure of the CPU and the temperature rises abnormally, information detected by the temperature detecting element 8 is detected by a detection circuit other than the CPU, and the relay is activated. As a result, the power supply to the heating element 2 is cut off. In that respect, the temperature detecting element 8 also has a function as a part of the safety circuit.

Further, one temperature fuse 9 as another temperature detecting element for safety measures is wired, and there are various types of this temperature fuse 9, but the heating device has a quick response. A thermosensitive pellet type is generally used.

As described above, the safety of the apparatus against abnormal temperature rise of the heating element 2 is further improved. However, it is required to secure further safety by providing multiple safety devices. The thermal fuse 9 only needs to be connected in series in the power supply circuit to the heating element 2 and does not require any other relay or the like, and functions independently as a safety device. Therefore, the circuit configuration is simple and the reliability is low. Since it is expensive and inexpensive, arranging a plurality of thermal fuses 9 in a circuit for supplying power to the heating element 2 is an effective means when attempting to further improve safety.

[0014]

However, when a plurality of thermal fuses 9 are arranged in series in a circuit for supplying power to the heating element 2 and arranged so as to be in contact with the heating element 2, the following restrictions are imposed. Therefore, it was difficult to arrange a safety device using a plurality of thermal fuses in the heating device.
In other words, (1) if the temperature fuse 9 is not used in close contact with the heating element 2, the response speed of the current cutoff at the time of abnormal temperature rise becomes slow. For reasons (2) and (1), it is desirable that the thermal fuse 9 be brought into contact with the heating element 2 having the highest temperature in the apparatus. Since none of the above exist, even during normal use, it cannot be used in contact with a region where the temperature of the heating element reaches 230 ° C. or higher.
(3) On the other hand, the heating element 2 is controlled based on the temperature detected by the temperature detecting element 8 so that the temperature of the heating element 2 becomes, for example, 190 ° C. Since the heat generated from the heating element 2 is not deprived by the recording sheet S, the temperature of the area (area) becomes higher than the temperature of the area (paper passing area) of the heating element 2 through which the recording sheet S passes.
It may reach about 0 ° C.

Therefore, the thermal fuse 9 cannot be arranged in the non-sheet passing area due to the restriction of (2), and the temperature of the heating element 2 is always lower than the temperature fuse operating temperature limit of 230 ° C. during normal use, that is, as described above. Must be arranged in the paper passing area of

Such an area is only an area through which a recording sheet Smin having a minimum width passes in a recording material that can be passed. Specifically, in the case of a printer, the area is 3 × 5 inches as described above. It is within the range where the short side (76 mm) of the index card passes. That is, the above-described temperature detecting element 8 and the plurality of thermal fuses 9 need to be arranged in an area (76 mm) through which the recording sheet S having the width dimension Smin passes. (4) When the pressing pressure for bringing the thermal fuse 9 into close contact with the heating element 2 is increased, the metal case 3 of the thermal fuse 9 is increased.
1 is deformed, the slidability between the disk 37 and the metal case 31 is deteriorated, and there is a possibility that the current cannot be cut off even if the temperature of the thermal fuse 9 reaches the operating temperature. The pressure cannot be increased unnecessarily in order to bring them into close contact with each other, and specifically, it is desirably 150 gf or less.

On the other hand, as a method of connecting a plurality of thermal fuses, there is a method using a caulking connecting member 13 as shown in FIGS. 9A to 9C. In FIG. 9, the pressing springs 21a and 21b are two thermal fuses 9a and 9b.
Is urged against the heating element 2. However, when the two thermal fuses 9a and 9b were connected using such a caulking connecting member 13, the thermal fuses 9a and 9b could be connected in a straight line as shown in FIG. 9A. In this case, there is no problem. However, as shown in FIGS. 9B and 9C, the two thermal fuses 9a and 9b are aligned in a straight line due to deformation of the leads of the thermal fuses 9a and 9b or displacement during crimping. When not connected, the rigidity of the caulking connection member 13 itself is high, and the lead of the thermal fuse has a linear shape of one.
mm, the rigidity is high, so that the rigidity is lost. When a fuse holding spring with a pressing force of about 150 gf is used, it is found that the thermal fuse cannot be brought into close contact with the heating element 2.

Further, it is not possible to make the thermal fuses 9a and 9b adhere to the heating body 2 by increasing the size so as to overcome the rigidity described above for the reason (4). Further, the two thermal fuses 9a and 9b are connected by using the caulking connecting member 13, and the lead wires which are sufficiently long so as not to be affected by the rigidity of the caulking connecting member 13 are used. Is not practicable due to the restriction shown in the above (3).

Therefore, the present invention has been made in view of the above-mentioned problems, and a plurality of thermal fuses can be securely connected to a heating element within a limited range in which an object having a minimum width passes. In order to provide a heating device capable of further improving the safety and reliability of the heating device by swiftly shutting off the power supply to the heating device when abnormal heating of the heating device occurs by disposing them in close contact with each other. I have.

In addition, it is another object of the present invention to provide a heating device that can be simplified and reduced in size by pressing a first thermal fuse and a second thermal fuse on a heating element by a common urging means. .

[0021]

Means for Solving the Problems The above-mentioned problems are solved,
In order to achieve the object, according to the present invention, a heating element that generates heat by energization and is fixed to a base, a temperature fuse that shuts off the energization by detecting an abnormal temperature rise of the heating element, An endless heat-resistant film guided by guide means such that the inner peripheral surface thereof comes into pressure contact with the heating body and held rotatably, and is brought into close contact with the outer peripheral surface of the heat-resistant film while being heated. A heating device comprising: a contact unit that applies heat energy from the heating body to the sheet body with passage of the body, wherein the plurality of temperature fuses are defined by a minimum width dimension of the body to be heated. It is characterized by being arranged in the area where

Further, the invention is characterized in that the thermal fuses are connected in series via a conductive thin plate.

Further, an urging means for bringing the thermal fuse connected in series into contact with the heating element is provided in the guide means.

Further, the series connection is performed by spot welding the lead portion of the thermal fuse and the thin plate.

The biasing means may include a compression coil spring or a leaf spring member for holding the one end of the guide means to individually contact the series-connected thermal fuses with the heating element. It is characterized by including.

[0026] The thermal fuse contains a sealed body (thermosensitive pellet) that melts when the heating element is abnormally heated, and is provided inside the case body so as to cut off the energization by the melting. It is characterized by having.

The contact means is a roller made of a heat-resistant rubber rotatably supported at the base.

[0028]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of a specific example of the image heat fixing device. In this figure, the endless heat-resistant film 1 (fixing film) has a total thickness of 100 μm or less, preferably 50 μm or less and 30 μm or more in order to reduce the heat capacity and improve the quick start property. Single-layer film of PTFE, PFA, etc., which has releasability, release property, strength, durability, etc., or polyimide, polyamideimide, PE
PTFE, EK, PES, PPS, etc.
A composite layer film coated with PFA, FEP or the like as a release layer.

As shown in the figure, the inner peripheral surface 1a of the film 1 is guided by a film guide member 14 having a semicircular arc shape, and the heating element 2 is fitted into a heating element accommodating recess formed at the center of the outer surface of the film guide 14. After being mounted immovably. Thus, the film guide member 14 is externally fitted so that the outer peripheral surface 1b of the cylindrical heat-resistant film 1 is on the outside. The roller 10 is configured to be pressed against the heating element 2.

The inner peripheral length of the endless film 1 and the outer peripheral length of the film guide member 14 including the heating element 2 are set to be larger than that of the film 1 by, for example, about 3 mm. As a result, as shown in the figure, the film 1 is loosely fitted to the film guide member 14 including the heating element 2 with a sufficient inner peripheral length.

A pressure roller 10 having a rubber elastic layer having good releasability, such as silicon rubber, which presses the film to the surface of the heater 2 with a total pressure of 4 to 15 kg with the film 1 interposed between the heater 2 and the film 1. Is supported by a bearing (not shown) at a base 100 shown by hatching, and is rotated counterclockwise in the direction of the arrow by power transmission by a drive motor (not shown). As a result, the cylindrical film 1 is configured to be rotationally driven while being in close contact with and sliding on the surface of the heating element 2 by the frictional force of the pressure roller 10.

The recording sheet S, which is a material to be heated, is introduced between the film 1 and the pressure roller 10 in the pressure contact nip portion N between the heating body 2 and the pressure roller 10, and is heated by passing in the direction of the arrow. Thermal energy is applied to the recording sheet S from the body 2 via the film 1 to heat and fix the unfixed toner image T on the recording sheet S. Further, the heating element 2 is provided so that the first thermal fuse 9a and the second thermal fuse 9b are in contact with each other.

Next, FIG. 2 is an external perspective view showing a state where the first temperature fuse and the second temperature fuse are connected in series via a thin plate. FIG. 3 is a center sectional view of the thermal fuse. In FIGS. 2 and 3, thermosensitive pellet type thermal fuses 9a and 9b are shown to absorb the misalignment of the first thermal fuse and the second thermal fuse and to make both thermal fuses adhere to the heating body with a small pressing force. It is provided as follows.

These thermal fuses 9a, 9b are
As shown in the center cross-sectional view of FIG. 1, a thermosensitive pellet 40 is sealed on one side in the external metal case 31 of the thermal fuse, and when the temperature exceeds a predetermined operating temperature, the thermosensitive pellet 40 melts or sublimes. The thermal fuses 9a and 9b are configured to cut off power supply to the heating element 2.
Then, the first thermal fuse 9a and the second thermal fuse 9b
Leads are protruded one by one from both ends of the first temperature fuse 9a and the second lead wire 34b of the second temperature fuse 9b (the lead wire containing the thermosensitive pellet). (Lead wire on the side containing the thermosensitive pellet) is spot-welded between the lead wire and the thin plate 11 via a highly conductive thin plate 11 such as phosphor bronze or copper.
The parts are mechanically and electrically connected by spot welding.

The first lead 32 of the first thermal fuse is provided.
a (lead wire without thermosensitive pellet) and 2nd
The first lead 32b of the thermal fuse (the lead wire on which the thermosensitive pellet is not inserted) is caulked by the caulking members 12a and 12b to the conductors of the covered bundles 16 and 17, respectively. The coated bundles 16 and 17 are formed from a wire that can be bent into a free shape, and are respectively connected in series in a power supply circuit to the heating body 2 shown in FIG. 31 is an outer metal case of a thermal fuse, 32
Is a first lead wire. An insulating ceramic cylindrical member 33 is attached to the end of the first lead wire, and the cylindrical member 33 is inserted into one end side of the case 31 and caulked the case to be insulated from the case 31 and removed. Stopped.

The second lead wire 34 is inserted into the other end side of the case 31 and the case is caulked and the metal case 3
It is electrically connected to 1 to prevent it from falling off. Also, 35
A first spring, a movable electrode, a disk, a second spring, and 36, 37, 38, 39, and 40 are sequentially arranged in the case 31 from the first lead wire 32 side to the second lead wire 34 side. It is a temperature-sensitive pellet made of a disc and an organic material that is a temperature-sensitive member.

The first spring 35 is made of an insulating ceramic 33.
The second spring 38 is contracted between the circular plate 37 and the circular plate 39.

The spring force of the second spring 38 is made larger than that of the first spring 35, and in the normal state shown in FIG. The first spring 35 is compressed between the movable electrode 36 and the insulating ceramic cylindrical member 33, and the movable electrode 36 is pressed against the tip of the first lead 32, so that electrical conduction with the first lead 32 is established. Will be kept. Further, the temperature-sensitive pellet 40 is received in contact with the tip of the second lead wire 34, and is kept in a state interposed as a spacer member between the disk 39 and the tip of the second lead wire 34.

The outer periphery of the movable electrode 36 is
The inner case 1 is in contact with the inner surface and maintains electrical continuity with the case 31, so that it is free to move in the axial direction in the case.

In the normal state, the electric current to the energizing heating element 4 of the heating element 2 is applied to the first lead wire 32, the movable electrode 36 which is in pressure contact with the end of the first lead wire 32, and the metal case which is electrically connected to this. 31, flows on the path of the second lead wire 34.

In this embodiment, reference numeral 41 denotes a sealing (sealing) resin formed by applying a coating between the end face of the metal case 31 on the first lead wire mounting side and the first lead wire base in order to maintain the airtightness in the case 31. Department. This thermal fuse 9 is connected to the heating element 2
The heat of the heating element 2 is transmitted to the internal temperature-sensitive pellet 40 via the metal case 31 or the like. As long as the temperature of the thermosensitive pellet 40 is equal to or lower than a predetermined operating temperature, the thermal fuse 9 is kept in a normal state shown in FIG. Power is supplied to the body 4.

On the other hand, when the temperature of the heat-sensitive pellet 40 becomes higher than a predetermined operating temperature due to excessive heating of the heater 2 due to runaway of the heater due to a failure of the power supply control system 15, the temperature-sensitive pellet 4
0 melts or sublimes, and becomes liquid or disappears as shown in FIG. 3B, and the temperature-sensitive pellet 40 as a spacer member between the disk 39 and the tip of the second lead wire 34 disappears. Therefore, the second spring 38 is driven by the spring force of the first spring 35.
Is pushed toward the second lead wire 34 so that the movable electrode 36 is separated from the tip of the first lead wire 32, and the heating element 2
Is turned off.

FIG. 4 is a three-dimensional exploded view showing how the thermal fuse wired as described above is assembled. In this drawing, the same reference numerals are given to the components already described and the description thereof is omitted.
And the minimum width Smin of the recording sheet S
Shape portion 14 for accommodating thermal fuses 9a and 9b in the range of
a, 14a are formed, and thermal fuses connected in series as shown in the figure are disposed as shown by the broken lines. Also,
Thereafter, the spring members 18 are set so that they can be individually pressed against the heating element 2.

FIG. 5 is a view taken along the line XX of FIG. 4 showing an example of dimensions when the first thermal fuse 9a and the second thermal fuse 9b are connected. In FIG. 5, the wire diameter of the lead wire is 1 mm, the thickness t of the thin plate is 0.2 mm, and the vertical and horizontal dimensions are 4 mm × 12 mm. Both ends of the thin plate 11 are lead wires 34a, 34b of the first and second thermal fuses.
Are connected by spot welding, but the spot welding portion 11a of the first thermal fuse 9a and the second thermal fuse 9
The distance between the spot welds 11a of b is 10 m in this embodiment.
m.

FIG. 6 (c) shows the temperature fuse 9a,
FIG. 5 is a view taken along line XX of FIG. 4, showing a state in which a pressure spring 18 for pressing 9b against the heating body 2 is provided. In FIG. 6C, the pressing spring 18 is pressed so as to have a shape as shown in the drawing, and the pressing portions 18a, 18b, 18
By c and 18d, the upper end is fixed to a guide member (not shown) so as to urge the heating element 2 with the pressing force P. Here, the case 31a of the thermal fuses 9a and 9b,
31b has electrical continuity regardless of whether the thermal fuse is active or inactive. Therefore, even if pressure is applied by a single metal spring across the thermal fuses 9a and 9b, it does not affect the thermal fuse operation. Absent.

The surfaces of the first thermal fuse 9a and the second thermal fuse 9b that are in close contact with the heating element 2 are not displaced during welding and lead to the thermal fuse when not pressed by the pressure spring 18 of the thermal fuse. Due to a positional shift at the time of attachment or the like, the surface contacting the heating element 2 does not become the same plane as shown in FIG. 6A, and the angle θ shifts as shown in FIG. 6B. .

However, since the first lead 9b of the first thermal fuse 9a and the second lead 9b of the second thermal fuse 9b are connected via the thin plate 11 as described above, the first thermal fuse 9a is pressed by the pressure spring 18 of the thermal fuse. Then the thin plate 11 bends first
And the metal cases 31a and 31b of the first thermal fuse 9a and the second thermal fuse 9b can be brought into close contact with the heater 2 without any gap. Become.

In FIG. 5, the distance from the load center of the thermal fuse to the welding point is L, the moment of inertia of section of the thin plate is I, and the longitudinal elastic modulus of the thin plate is E. Only the thin plate between the welds bends. The maximum deviation angle θm of the attachment of the thermal fuse that the thin plate 11 can absorb by bending.
ax is θmax = lLP / EI, and in this embodiment, l = 1
0 [mm], L = 12 [mm], P = 0.1 [kg]
f], t = 0.2 [mm], E = 13400 [kgf /
mm ² ] (phosphor bronze), θmax = 19 [d
eg].

That is, since the thin plate 11 can be flexed by θmax = 19 [deg] under the above conditions, the first plate
The deviation angle between the thermal fuse 9a and the second thermal fuse 9b is θ
If max = 19 [deg] or less, the first thermal fuse 9a and the second thermal fuse 9b are in close contact with the heater 2 without any gap.

As described above, the first thermal fuse 9
a second lead 34a of the second thermal fuse 9b and the second lead 34b of the second thermal fuse 9b are connected to each other via a thin conductive plate 11 made of phosphor bronze, copper, or the like.
By connecting by spot welding at a and 11b,
The displacement of the connection between the first thermal fuse 9a and the second thermal fuse 9b is absorbed, and the heating element 2 and the thermal fuses 9a and 9b are absorbed.
The adhesion of the metal case portion 31 between b is improved.

Further, for example, the recording sheet S having the smallest width dimension
The first thermal fuse 9a and the second thermal fuse 9a fall within a range of min = 76 mm.
The temperature fuse 9b and the temperature detecting element 8 can be arranged.

Further, by connecting the leads of the thermal fuse filled with the thermosensitive pellets via thin plates, it is possible to press the two thermal fuses with one spring.

In this embodiment, the spot welding is performed on one lead one by one. However, the same effect can be obtained even if the welding portion is divided into a plurality of pieces and welded on one lead wire. . FIGS. 7A and 7B are diagrams showing another configuration of the temperature-sensitive pellet type thermal fuse. In this drawing, the same reference numerals are given to the components already described and the description is omitted. In the above-described embodiment, an example is shown in which the thermal fuses are simultaneously pressed by the pressing springs 18.
As shown in FIG. 7, even if each of the thermal fuses is pressed by using two pressure springs 21a and 21b, the adhesion between the thermal fuses 9a and 9b and the heating element 2 can be similarly improved.

The number of thermal fuses is not limited to two but may be more. As described above, the first temperature fuse 9a and the second temperature fuse 9b are provided in the limited space of the guide member, and it is possible to dispose the heater 2 with good adhesion by the spring. The safety when the heating element 2 abnormally rises in temperature due to the failure of the control system 15 is further improved. In addition, by connecting the leads on the side of the thermal fuse filled with the thermosensitive pellet through a thin plate, it becomes possible to press two thermal fuses with one spring, thereby simplifying the device. Thus, miniaturization and cost reduction can be achieved.

[0055]

As described above, according to the present invention,
By placing a plurality of thermal fuses in close contact with the heating element within a limited range where the heating element with the smallest width passes, power to the heating element can be Disconnect supply quickly, safety of heating device,
A heating device that can further improve reliability can be provided.

In addition, it is possible to provide a heating device that can be simplified and reduced in size by pressing the first thermal fuse and the second thermal fuse with respect to the heating element by a common urging means.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image heat fixing device.

FIG. 2 is an external perspective view showing an installation state of a thermal fuse.

FIGS. 3A and 3B are center sectional views of a thermal fuse.

FIG. 4 is a three-dimensional exploded view of the image heating and fixing device.

FIG. 5 is a view taken along line XX of FIG. 4;

6 (a) is a normal view, FIG. 6 (b) is an abnormal state, and FIG. 6 (c) is a thermal fuse 9a, 9b.
FIG. 4 is a diagram showing a state in which a pressure spring 18 for pressing the heating member 2 is provided.

FIG. 7 is a diagram of a heating device according to another embodiment.

FIG. 8 is a circuit diagram of a conventional image heating and fixing apparatus.

FIGS. 9A to 9C are diagrams in which a plurality of thermal fuses are connected to each other by using a caulking connection member 13. FIGS.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat resistant film 2 Heating body 8 Thermistor (temperature detecting element) 9a 1st temperature fuse 9b 2nd temperature fuse 10 Pressure roller (adhesion means) 11 Thin plate 14 Guide member (guide means) 15 Current control circuit 18 Pressure spring S Recording sheet (heated object) T Toner image

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/20 109 G03G 15/20 109 H01H 37/76 H01H 37/76 K F Term (Reference) 2F056 UB02 UB05 2H033 AA42 BA25 BA38 BB29 BB30 BE03 CA06 CA17 CA34 CA45 3K058 AA12 BA18 CA12 CA22 CA78 CA91 5G502 AA02 BA03 BE09 CC20 CC24 CC32 CC51 FF10

Claims (7)

[Claims] 1. A heating element that generates heat when energized and is fixed to a base portion, a temperature fuse that interrupts the energization when an abnormal temperature rise of the heating element is detected, and an inner periphery of the heating element An endless heat-resistant film guided by guide means so that the surfaces are pressed against each other, and held rotatably; and the heat-resistant film is brought into close contact with the outer peripheral surface of the heat-resistant film and passes through the object to be heated. And a contact unit for applying heat energy from the body to the sheet body, wherein the plurality of thermal fuses are arranged in a region defined by a minimum width dimension of the body to be heated. A heating device, characterized in that: 2. The heating device according to claim 1, wherein the thermal fuses are connected in series via a conductive thin plate. 3. The heating device according to claim 2, wherein an urging means for contacting the thermal fuse connected in series with the heating element is provided in the guide means. 4. The heating device according to claim 2, wherein the series connection is performed by spot welding between a lead portion of the thermal fuse and the thin plate. 5. A compression coil spring or a leaf spring member for holding the one end of the urging means at the guide means to individually contact the temperature fuses connected in series with the heating element. The heating device according to claim 3, further comprising: 6. The thermal fuse contains a sealed body (thermosensitive pellet) that melts when the heating element abnormally rises in temperature, and is provided inside the case body so as to cut off the energization by the melting. The heating device according to any one of claims 1 to 5, wherein the heating device is provided. 7. The heating device according to claim 1, wherein the contact unit is a heat-resistant rubber roller rotatably supported at the base.