JPH07199697A - Heater - Google Patents

Abstract

PURPOSE:To facilitate temp. control, to impart an optimum heat quantity to a material to be heated even under any conditions and to solve problems, such as fixing defect and high-temp. offset by forming >=2 kinds of resistance heating elements varying in temp. characteristics of resistance on a heating body. CONSTITUTION:A heater 2 is constituted by forming a first PTC heating element having a phase transition temp. Tc 160 deg.C by screen printing etc., on an alumina substrate, then insulating the discrete electrodes on the side where a glass insulating layer 10 is divided from each other and coating the substrate in such a manner as not to insulate an electrode 9 on a common side. The PTC heating elements 8b, 8c of second and third layers respectively having the phase transition temps. Tc 170 deg.C and 180 deg.C are successively formed thereon. Further, the surface thereof is coated with a glass layer 11 which is a protective layer. The electrodes of the respective first and third heating elements 8a to 8c are, in such a case, made common (common electrode 9) on one side of the heater 2 and are respectively divided (discrete electrodes 9a to 9c) on the other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device of a system (film heating system) for applying heat energy to a material to be heated through a heat resistant film.

This device is an electrophotographic copying machine, printer,
An image heating device in an image forming apparatus such as a fax, that is, an image forming process means such as electrophotography, electrostatic recording, magnetic recording, etc., uses a recording material (electrofax sheet, electrostatic recording Unfixed toner image corresponding to the target image information formed directly or indirectly (transfer) on the surface of the sheet, transfer material sheet, printing paper, etc. is permanently fixed to the surface of the recording material carrying the image. It can be used as a fixing device that performs heat fixing processing as an image.

Further, the present invention is not limited to the image heating and fixing device, and can be widely used as a device and a device for heat-treating an image carrier, such as a device for heating a recording material carrying an image to modify the surface property.

[0004]

2. Description of the Related Art Conventionally, a recording material heating device for heating and fixing an image, for example, comprises a heating roller which is maintained at a predetermined temperature and a pressure roller which has an elastic layer and is pressed against the heating roller. A heat roller method is widely used in which a recording material is nipped and conveyed and heated. Various methods and configurations such as a flash heating method, an oven heating method, and a hot plate heating method are known and put to practical use. Further, as disclosed in US Pat. No. 3,578,797, a belt heating type is also known.

Recently, a heating element (thermal heater, hereinafter referred to as a heater) fixed and supported directly to a metal or resin holder, and a heat resistant film (fixing film) conveyed while being pressed against the heater, An unfixed image formed and carried on the surface of the recording material is formed on the surface of the recording material by applying heat of the heater to the recording material through the film. A fixing device of a film heating system / structure for heating and fixing to a device has been devised.

According to the applicant's previous proposal, for example, Japanese Patent Laid-Open No.
The system, device, etc. disclosed in Japanese Patent Laid-Open No. 3-313182 belong to this, and are arranged such that a thin heat-resistant film, a moving driving means for the film, and the film inside are fixedly supported on one side thereof. A heater and a pressurizing member which is disposed on the other surface side so as to face the heater and makes a visible image bearing surface of a recording material to be image-fixed through the film adhere to the heater, the film being at least the image. At the time of fixing, the recording material to be image-fixed, which is conveyed and introduced between the film and the pressure member, is moved in the forward direction at the same speed, and the running moving film is sandwiched between the heater and the pressure member by pressure contact. By passing through the fixing nip portion as a fixing point to be formed, the visible image bearing surface of the recording material is heated by the heater through the film to give thermal energy to the visible image (unfixed toner image). Soften and melt Because, then a heating means or apparatus which is based on that are spaced from each other by a separation point of the recording material and the film after fixing points pass.

In such a film heating type heating device, a low heat capacity heating element can be used as a heater. Therefore, it is possible to reduce the power consumption and shorten the wait time (quick start) as compared with a heating device such as a heat roller system or a belt heating system, which are conventional contact heating systems. In addition, it has an advantage that the drawbacks of the conventional heating type device can be solved, and is effective.

[0008]

Conventionally, however, such a film heating type heating device uses a heating body having a low heat capacity, so that a rapid temperature rise occurs even when a small amount of power is supplied, and power is supplied even for a short time. It is very difficult to control the temperature because the temperature drops suddenly when the supply is stopped. For this reason, control such as temperature control of a heat roller type device cannot be achieved by controlling only energization ON / OFF, and many methods such as wave number control and phase control have been proposed.

On the other hand, a method has also been proposed in which the heating element itself of the heating element has a temperature control function without using such complicated control. For example, a heating element having a PTC characteristic is used, and the resistance rapidly increases at a predetermined temperature (hereinafter referred to as a phase transition point Tc), and the power supply is stopped. After that, when the temperature decreases, the resistance decreases, the supply of electric power starts again, and the temperature is adjusted to a certain temperature if only a voltage is applied from the outside.

However, in the case of the film heating type apparatus, since the rising time is very short, the heating processing is carried out in a state where the temperature of the entire heating apparatus is low, and the continuous processing is carried out to warm the entire apparatus. In some cases, the heat treatment is performed in this state. In these cases, the material to be heated is also given heat from the portion other than the heating body, so that the optimum amount of heat given from the heating body to the heating material naturally changes.

For example, when a film heating type heating device is used as an image heating and fixing device of an image forming apparatus, if the temperature of the heating body is kept constant and the temperature of the entire heating device is low, the amount of heat received from other than the heating body is small. There is a problem that fixing failure is likely to occur, and if the entire device after continuous heat treatment warms up and the amount of heat received from other than the heating body is too large, a problem such as high temperature offset is likely to occur. . When a self-temperature control type heating element using a PTC-characteristic heating element or the like is used, it has been very difficult to change the set temperature for conventional temperature control.

The present invention has been proposed in view of the above,
A film heating type heating device using a heating element having a low heat capacity and having a PTC characteristic can easily control temperature and can provide an optimum amount of heat to a material to be heated under any condition. Therefore, it is an object of the present invention to provide an image heating and fixing device capable of solving the problems of defective fixing and high temperature offset.

[0013]

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

(1) In a heating device in which a heating element is adhered to one surface side of a heat resistant film and a material to be heated is adhered to the other surface side, and heat energy of the heating element is applied to the material to be heated through the heat resistant film. A heating device having at least two types of resistance heating elements having positive temperature characteristics of resistance and different temperature characteristics of resistance formed on the heating element.

(2) In the heating device of the above (1), it is possible to switch power supply to a plurality of resistance heating elements having a positive temperature characteristic of resistance on the heating element and different temperature characteristics of resistance. Characteristic heating device.

(3) In the heating device of the above (1), a plurality of resistance heating elements having different temperature characteristics of resistance on the heating body and having positive temperature characteristics of resistance have a laminated structure. Heating device.

(4) In the heating device of the above (1), a plurality of resistance heating elements having different temperature characteristics of resistance on the heating body and having positive temperature characteristics of resistance are adjacent to each other in the traveling direction of the material to be heated. A heating device characterized by having a different structure.

(5) In the heating device of the above (1), the switching of the power supply to the resistance heating element having a positive temperature characteristic of a plurality of resistors having different temperature characteristics of the resistor on the heating element is performed in the heating device. A heating device characterized by detecting the temperature of a member other than a heating body.

(6) In the heating device of the above (1), switching of power supply to a heating element having a positive temperature characteristic of a plurality of resistors having different temperature characteristics of the resistor on the heating element is performed in the heating device. A heating device, which is installed on a member other than the body and is made of a member having a characteristic that insulation or resistance increases due to temperature rise.

(7) The heating device according to any one of (1) to (6), wherein the heating device is an image heating device for heating a recording material supporting a toner image.

[0021]

That is, according to the present invention, in the film heating type heating device, the heating element on the heating element is a heating element having a PTC characteristic, so that temperature control can be simplified and PTC heat generation having different temperature characteristics can be performed. By providing a plurality of bodies on the heating body, multi-step temperature control is possible. That is, the present invention can have the advantages of both the simple control, which is an advantage of the self-temperature control type heating element, and the fine temperature control by power control.

[0022]

【Example】

<Embodiment 1> (Figs. 1 and 2) Fig. 1 shows a schematic configuration of a heating apparatus according to a first embodiment of the present invention. The heating device of this example is disclosed in JP-A-4-4407.
This is a tensionless type film heating type image heating and fixing device disclosed in Japanese Patent Laid-Open No. 5 and the like.

(1) Schematic configuration of the apparatus 1 is a resin-made lateral stay, which serves as an inner surface guide member of a film 3 described later and a support of a heater 2 as a heating body described later.

3 is an endless heat resistant film,
The stay 1 including the heater 2 is externally fitted. The inner peripheral length of the endless heat-resistant film 3 and the outer peripheral length of the stay 1 including the heater 2 are larger than those of the film 3 by, for example, about 3 mm. The length fits loosely with a margin.

The film 3 has a total thickness of 100 in order to reduce the heat capacity and improve the quick start property.
It is possible to use a single-layer or multi-layer film having heat resistance, releasability, strength, durability, etc., which is set to not more than μm, preferably not more than 60 μm and not less than 20 μm.

Reference numeral 4 designates a fixing nip portion N with the heater 2 sandwiching the film 3, and a pressure roller (pressure contact roller, backup roller) as a rotating body for driving the film.
The central shaft 5 and the roller portion 6 made of a rubber elastic body having a good releasability such as silicon rubber, which is sheathed on the central shaft 5, are provided at the left and right end portions of the central shaft 5, respectively, on the left side (not shown). The right bearing member is rotatably supported by the bearing.

The rotation of the pressure roller 4 causes the film 3 to rotate around the stay 1 while closely contacting the heater 2 with the inner peripheral surface thereof. The heater 2 is energized to the heating element 8 at a predetermined timing to be in a heat generating state at a predetermined temperature.

A recording material P, which is a material to be heated and carries an unfixed toner image T conveyed from an image forming mechanism (not shown) on its upper surface, is a fixing nip portion N between the heater 2 and the pressure roller 4.
, The toner image surface comes into close contact with the outer surface of the film 3 while passing between the film 3 and the pressure roller 4, and passes through the fixing nip portion N in an overlapping state with the film 3 in the passing process. The heat of the heater 2 is received through the film 3 to heat and fix the toner image T. A is the traveling direction of the recording material P as the material to be heated.

(2) Structure of Heater 2 As shown in the enlarged cross-sectional model view of FIG. 2A and the notched plane model view of the front side of FIG. An elongated substrate (ceramic substrate) having electrical insulation, heat resistance, and low heat capacity, such as Al ₂ O ₃ (alumina), AlN, and SiC, whose longitudinal direction is substantially orthogonal to the moving direction of the film 3.
7, and b. A first heat source is formed by laminating three layers in the order of lower phase transition temperature Tc from the substrate 7 in a strip shape along the length of the substrate at a substantially central portion in the substrate width direction on one surface side (front surface side) of the substrate 7. Second and third PTC heating elements 8a, 8b, 8c (the phase transition points Tc of the respective PTC heating elements 8a, 8b, 8c are 160 ° C, 170 ° C, and 180 ° C, respectively); and c. The first, second and third PTC heating elements 8a, 8b
An insulating layer 10 for insulating between 8c, and d. The first, second and third PTC heating elements 8a, 8b
The common electrode 9 and the first, second, and third individual electrodes formed along the lengths of the heating elements 8a, 8b, and 8c in order to supply power to the heating element 8c in the same direction as the traveling direction A of the heated material P. 9a
9b and 9c, e. On the laminated PTC heating element, a glass layer 11 having a thickness of about 20 to 60 μm as a protective layer formed for both insulation and protection of the heating element is formed.

The heater 2 is formed by first forming a first PTC heating element 8a having a phase transition temperature Tc of 160 ° C. on a substrate 7 made of alumina by screen printing or the like, and then forming a thickness 5 thereof.
Coating is performed so as to insulate the individual electrodes on the side where the glass insulating layer 10 having a thickness of up to 20 μm is divided and not to insulate the electrodes 9 on the common side. On top of that, the second and third PTC heating elements 8b and 8c having the phase transition points Tc temperatures of 170 ° C. and 180 ° C. are sequentially formed so as to be sandwiched therebetween. Further, a glass layer 11 as a protective layer is coated on it. In this case, the electrodes of the first to third heating elements 8a, 8b, 8c are shared (common electrode 9) on one side of the heater 2 (on the upstream side in the direction in which the material to be heated travels) and divided on the other side. (Individual electrodes 9a, 9b, 9c).
These electrodes 9, 9a, 9b, 9c extend the common electrode 9 to one end of the heater 2, and the other divided individual electrodes 9a, 9b, 9c extend to the opposite end so that both ends of the heater are It is configured to supply more power. S is a power supply, and 15 is a switching circuit.

.. In the case of a film heating type fixing device using such a heater 2, first, when the machine is not used for a while and the entire device is cold, the common electrode 9 and the third phase transition point Tc of 180 ° C. Power is supplied to the third individual electrode 9c of the PTC heating element 8c to heat the third PTC heating element 8c, and the temperature control temperature is set to 180 ° C.

.. Next, when continuous heating is performed and the temperature of the pressure roller 4 of the entire apparatus rises, and heat is applied to the heated material P from the pressure roller 4 side as well, the individual electrodes are moved to the third position. The individual electrode 9c is switched to the second individual electrode 9b to supply power to heat the second PTC heating element 8b and lower the temperature control temperature to 170 ° C.

.. Further heat treatment continues and the pressure roller 4
When the amount of heat applied to the material P to be heated from the side increases, the individual electrode is switched from the second individual electrode 9b to the first individual electrode 9a to supply power to heat the first PTC heating element 8b to control the temperature. To 160 ° C.

Thus, the temperature of the apparatus, especially the pressure roller 4
By gradually changing the temperature control temperature depending on the temperature, it was possible to solve both the fixing failure when insufficient heat was applied and the high temperature offset that occurs when excessive heat was applied.

At this time, it is preferable that a temperature detecting element is provided on the pressure roller 4 and the temperature is switched according to the temperature of the temperature control temperature. It is also possible to estimate and switch the pressure roller temperature.

Further, in order to further shorten the rise time, it is possible to reduce the start-up time by supplying power to all of the first to third heating elements 8a, 8b and 8c at the same time.

Further, as in the present embodiment, the electric current is applied to the heating element having the PTC characteristic in the traveling direction A of the heated material P in the non-sheet passing portion which occurs when a small-sized heated material is continuously processed. It is possible to prevent an abnormal temperature rise, that is, a so-called non-sheet passing portion temperature rise.

<Embodiment 2> (FIGS. 3 and 4) As shown in the enlarged cross-sectional model view of FIG. An elongated substrate (ceramic substrate) having electrical insulation, heat resistance, and low heat capacity, such as Al ₂ O ₃ (alumina), AlN, and SiC, whose longitudinal direction is substantially orthogonal to the moving direction of the film 3.
7, and b. The first, second, and second heat sources formed on one surface side (front surface side) of the substrate 7 in a strip shape along the substrate longitudinal direction from the upstream side in the film advancing direction in three rows in ascending order of the phase transition point Tc temperature.
Third PTC heating elements 8d, 8e, 8f (the phase transition points Tc of the respective PTC heating elements 8d, 8e, 8f are 155 ° C.
165 ° C / 180 ° C), and c. The first, second and third PTC heating elements 8d, 8e,
Electrodes 9.9d.9e formed along the length of the heating element for supplying power to 8f in the same direction as the traveling direction A of the heated material P.
9f, d. A glass layer 11 having a thickness of about 20 to 60 μm on the laminated PTC heating element as a protective layer that serves both as an insulation and a protection for the heating element.
Consists of.

The heater 2 is a fixing nip portion N formed by pressure contact with a pressure roller 4 on an alumina substrate 7.
An electrode 9, a first heating element 8d, an electrode 9f, a second heating element 8e, an electrode 9e, a third heating element 8f, and an electrode 9f are formed in this order from the upstream side in the recording material traveling direction.
At this time, the electrodes 9d, 9e, and 9f are formed to be extremely narrow in order to reduce the area where heat is not generated.

.. In the case of the film heating type fixing device using the heater 2 of the present embodiment, first, when the machine is not used for a while and the entire device is cold, the third electrode 9e and the phase transition point Tc of 180 ° C. are used. Power is supplied to the electrode 9f that supplies power to the PTC heating element 8f to cause the third PTC heating element 8f to generate heat, and the temperature control temperature is set to 180 ° C.

.. Next, when a continuous heat treatment is performed and the temperature of the pressure roller 4 of the entire apparatus rises and heat is applied to the material P to be heated from the pressure roller 4 side as well, the electrodes 9e to 9d Switch to. Electrode 9d is electrode 9f
And the third heating element 8f having a phase transition point Tc of 180 ° C. and the second heating element 8e having a phase transition point Tc of 165 ° C. are connected in series with each other. When the temperature of 2 reaches 165 ° C., the second heating element 8e acts so that almost no current flows between the electrodes 9 and 9e, and the third heating element 8f produces almost no heat.
Is controlled at 165 ° C. which is the phase transition point Tc of the lower second heating element 8e.

.. Further heat treatment continues and the pressure roller 4
When the amount of heat applied to the heated material P from the side increases, the electrode 9
The electrode 9 is switched from d to the controlled temperature, and the temperature is lowered to 155 ° C. which is the phase transition point Tc of the first PTC heating element 8d. The temperature is regulated to 155 ° C. by energization between the electrodes 9 and 9f for the same reason as above.

By using the heater 2 of the second embodiment in a film heating type fixing device similar to that of the first embodiment,
The same effect as in Example 1 can be obtained, and since the first to third PTC heating elements 8d, 8e, 8f are located close to the film 3, that is, close to the material to be heated, heat conduction is fast. When the other conditions are the same as in the first embodiment, the temperature control temperature can be suppressed low.

However, in the present embodiment, the plurality of heating elements 8d, 8e, 8f are not aligned unless the fixing nip N portion is enlarged. In such a case, the electrode 9 as shown in FIG.
The heating elements 8d, 8e, 8f are made to overlap each other by making d9e slanted, or the heat conducting member 12 is formed on the heating layers 8d, 8e, 8f and the protective layer as shown in FIG. 4B. It is possible to solve it by providing it between 11th.

<Embodiment 3> (FIG. 5) In this embodiment, a heater 2 similar to that of Embodiment 1 and a heating device using the heater 2 are used for the second and third heating elements 8b and 8c. The individual electrodes 9bn and 9c are connected to two thermostats 13b and 13c having different operating temperatures which are brought into contact with the pressure roller 4 as shown in FIG. This 2
The operating temperatures of the two thermostats 13b and 13c are 70 ° C. and 50 ° C., respectively, and they are brought into contact with the pressure roller 4 at substantially the same position.

In this way, each heating element 8a, 8b,
8c in parallel with the power source S, and the second and third heating elements 8b.
・ For 8c, thermostats 13b and 13 respectively
Connect c in series.

.. First, when the machine has not been used for a while and the entire device is cold, the common electrode 9 and the first to third
Power is supplied to the first to third individual electrodes 9a, 9b, 9c of all of the PTC heating elements 8a, 8b, 8c, and the temperature of the third PTC heating element 8c having the highest temperature is 180 ° C. The apparent controlled temperature of the heater 2 is reached.

.. Then, when the temperature of the pressure roller 4 of the entire apparatus rises to 50 ° C. by continuous heat treatment, the thermostat 13c becomes the open state, and the first and second
Electric power is supplied to the individual electrodes 9a and 9b. As a result,
Here, too, the temperature of the second PTC heating element 8b, which has a high temperature, is 17
0 ° C. is the apparent temperature control temperature of the heater 2.

.. Further heat treatment continues and the pressure roller 4
When the temperature reaches 70 ° C., the thermostat 13b is opened, power is supplied only to the first individual electrode 9a, and the temperature of the heater 2 is adjusted to 1 by the heat generated by the first PTC heating element 8a.
Reduce to 60 ° C.

As described above, when the present embodiment is used, the same effect as that of the first embodiment can be obtained, and the thermostats 13b and 13c detect the temperature of the apparatus, and the heating elements 8a, 8b and 8c are detected.
It is not necessary to control switching for switching the electrodes 9a, 9b, 9c of No. 1, and the device only needs to determine whether or not the heating process is being performed and only perform power feeding or power feeding stop.

Needless to say, a resistor having a PTC characteristic can be used instead of the thermostats 13b and 13c.

[0052]

As described above, according to the present invention, there is provided a film heating type heating device using a heating element having a PTC characteristic, and a plurality of PTC heating elements having different phase transition temperatures. By providing the heating element, it is possible to easily control the temperature of the heating device using the heating element with a low heat capacity, which has been considered difficult until now, and it becomes possible to switch the temperature control temperature according to the temperature of the device.
It has become possible to give the material to be heated an optimum amount of heat under any conditions.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an example of a film heating type heating device.

FIG. 2 (a) is an enlarged cross-sectional model view of the heating element (heater) of Example 1, and FIG. 2 (b) is a cutaway plan view model.

FIG. 3 is an enlarged cross-sectional model view of a heating body of the apparatus of Example 2.

4 (a) and 4 (b) are schematic cross-sectional views of modified examples of the heating body, respectively.

FIG. 5 is an energization circuit diagram of the device according to the third embodiment.

[Explanation of symbols]

 1 Stay 2 Heater 3 Heat Resistant Film 4 Pressure Roller 5 Pressure Roller Center Shaft 6 Pressure Roller Roller Part 7 Heater Substrate 8 (a to f) PTC Heating Element 9 (a to f) Electrode 10 Insulating Layer 11 Glass Layer 12 Heat conduction member 13 (b, c) Thermostat

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsunori Ishiyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (7)

[Claims] 1. A heating device for closely contacting a heating body on one surface side of a heat resistant film and a heating target material on the other surface side, and applying heat energy of the heating body to the heating target material through the heat resistant film, At least two resistance heating elements having positive temperature characteristics of resistance and different temperature characteristics of resistance are provided on the heating element.
A heating device characterized by being formed in more than one kind. 2. The heating device according to claim 1, wherein the temperature characteristics of the resistance on the heating element are positive and the power supply to a plurality of resistance heating elements having different temperature characteristics of the resistance is switched. Heating device. 3. The heating device according to claim 1, wherein a plurality of resistance heating elements having different temperature characteristics of resistance on the heating body and having positive temperature characteristics of resistance have a laminated structure. apparatus. 4. The heating device according to claim 1, wherein a plurality of resistance heating elements having different temperature characteristics of resistance on the heating body and having positive temperature characteristics of resistance are adjacent to each other in the traveling direction of the material to be heated. A heating device characterized by being. 5. The heating device according to claim 1, wherein switching of power supply to a resistance heating element having a positive temperature characteristic of a plurality of resistors having different temperature characteristics of resistance on the heating element is performed in the heating device. A heating device characterized by detecting the temperature of members other than the above. 6. The heating device according to claim 1, wherein the switching of power supply to a heating element having a positive temperature characteristic of a plurality of resistors having different temperature characteristics of the resistors other than the heating element in the heating device. The heating device is characterized in that the heating is performed by a member which is installed on the member of 1 above and has a characteristic that insulation or resistance increases due to temperature rise. 7. The heating device according to claim 1, wherein the heating device is an image heating device for heating a recording material supporting a toner image.