JPH11251042A - Heating element, fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable heating element in which a crack is not generated because an adhesive well matches with a substrate and/or a base material of a temperature sensor and peeling is not generated because initial adhesive strength is large enough, by regulating the most appropriate percentage content range of a filler, a fixing device using it and an image forming device. SOLUTION: A slender resistance heating element is adhered to an electrically insulated slender substrate along its longitudinal direction, a temperature sensor 5 mounted on a base material is connected to a conductive material pattern formed on the substrate at a position where heat from the resistance heating element can be sensed, and in addition, adhesive 9 in polyamide group having equivalent or higher thermal conductivity, smaller coefficient of thermal expansion, to the material used in the substrate 1 and/or the base material, or a filler containing the same material for 76±1 wt.%, is applied between the temperature sensor 5 and the substrate 1. If thermal conductivity of the adhesive approaches enough to the material used the substrate 1 and/or the base material, its coefficient of thermal expansion becomes equivalent to it, or a filler of the same material is used, a crack or peeling is not generated in the adhesive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating element having an elongated resistance heating element, a fixing device using the heating element, and an image forming apparatus.

[0002]

2. Description of the Related Art In a heating element of this kind, since a heat capacity of a resistance heating element is small, when a power supply voltage is applied, a working portion of the heating element contributing to fixing of toner immediately rises to a required temperature. Therefore, there is an advantage that no preheating time is required. For this reason, it is possible to control the heating element to generate heat to a required temperature only when the fixing operation is performed, thereby greatly reducing power consumption.

In order to control the heating temperature of the resistance heating element,
A temperature sensor such as a temperature detecting element is provided, and the control output signal is transmitted to the control device.

[0004] However, if the temperature sensor is not properly fixed so as to accurately detect the temperature of the resistance heating element, the temperature control is incorrect and thermal runaway occurs. Similarly, a malfunction of the temperature control device causes the heating element to run out of heat.

[0005] When a thermal runaway occurs, the temperature of the heating element rises excessively, and a resistance heating element crack occurs due to thermal stress. When a crack occurs, the resistance value of the crack portion increases, so the calorific value of the portion further increases, and the crack portion causes smoke or fire before a safety device such as a thermal fuse operates. There is a problem.

Therefore, it is necessary to appropriately fix the temperature sensor as a measure against the heat runaway on the heating element side. When the temperature sensor is in the form of a chip mounted on a base material such as ceramics, and fixed to a predetermined position of the base body while maintaining an electrical connection relationship, the base body and the temperature sensor are combined. Apply adhesive for mechanical fixation.

However, this type of heating element has a
Since the heat cycle due to turning off is frequently repeated and high-temperature operation is performed, it is not easy to maintain proper fixation for a long period of time, and various difficulties are involved.

[0008] The applicant of the present patent application is Japanese Patent Application No. 9-26719.
In the above item, the applicant has filed an application for the invention having the following summary. That is, a flat substrate having heat resistance and insulating properties;
A heating resistance pattern formed on the surface of the substrate; a power supply electrode pattern for the heating resistance pattern formed on the surface of the substrate; and a detection electrode pattern for a temperature detection element formed on the back surface of the substrate. And a filler made of the same material, a material having an approximate coefficient of thermal expansion, or a material having an equivalent or higher thermal conductivity with respect to the substrate or the base material of the temperature detecting element in a weight ratio of 70 to 90. %, Preferably about 74 to 78%, and an adhesive for reinforcing and fixing the temperature detecting element.

It is an object of the present invention to improve the durability of mounting a temperature detecting element on a substrate.

[0010]

However, from the subsequent studies by the present inventors, it was found that there was room for improvement, although part of the allowable range of the filler content in the invention of the earlier application. I understood. That is, there is too much difference in the coefficient of thermal expansion between the adhesive and the substrate within the allowable range, and cracks are generated between the adhesive and the substrate due to repeated use of the heating element, though at a slight rate of occurrence. Easy range is recognized.

On the other hand, the initial adhesive strength of the adhesive is not sufficiently large to a required degree, and there is a range in which, although the occurrence rate is small, the adhesive peels off during use.

As described above, it is necessary to understand that even if the occurrence rate of defects such as cracks and peeling is small, it causes a very large problem in the nature of the image forming apparatus to be incorporated.

According to the present invention, by defining the optimum content range of the filler, the adhesion of the adhesive to the base material and / or the base material of the temperature sensor is extremely good, and no cracks are generated. It is an object of the present invention to provide a heating element which is sufficiently large and does not cause peeling and has extremely high reliability, and a fixing device and an image forming apparatus using the same.

[0014]

According to the present invention, there is provided a heating element comprising: an elongate electrically insulating base; an elongate resistance heating element attached to a surface of the base along a longitudinal direction of the base; A pair of conductive patterns spaced apart from each other and formed on the substrate at a position where the heat of the resistance heating element can be sensed; and mounted on an electrically insulating base material and capable of sensing the heat of the resistance heating element. A chip-shaped temperature sensor disposed so as to be conductively connected across the conductor pattern at the position; and 76 ± 1% by weight of a fine powder filler having a thermal conductivity equal to or higher than that of the base and / or the base of the temperature sensor. And a polyimide-based adhesive applied so as to fix between the temperature sensor and the substrate.

In the present invention and each of the following inventions, definitions and technical meanings of terms are as follows unless otherwise specified.

About the Substrate The substrate only needs to have electrical insulation at least on the surface where the resistance heating element is formed. Specifically, the base can be obtained by forming ceramics into a plate shape using a doctor blade method or the like, or by forming a heat-resistant insulating layer such as glass on the surface of a metal plate such as glass or aluminum. it can. In addition, as ceramics,
Alumina, aluminum nitride, or the like can be used.

The planar shape of the substrate is not limited to a quadrangle, but may be any shape.

Further, needless to say, required heat resistance is required within the operating temperature range of the heating element. When the heating element is used for fixing a toner image, it is required to have heat resistance enough to withstand 190 ° C., which is the melting temperature of the toner.

Regarding the Resistance Heating Element The resistance heating element is not particularly limited in material, but is most preferably formed by printing a conductive paste containing a silver-palladium-based alloy as a main component by a screen printing method, drying and firing. It is a thick-film resistance heating element. According to this thick-film resistance heating element, the resistance value of the resistance heating element is increased to a required value in a long heating element capable of fixing toner satisfactorily on paper of mainly A4 size which is frequently used. And it is easy to set so that the amount of heat can be obtained. Of course, it is possible to obtain an effective resistance heating element not only for A4 paper but also for A3 paper.

Further, the number of resistance heating elements is not limited to one, and a plurality of resistance heating elements can be used if necessary. In that case, the resistance heating element can be connected in series or parallel to the power supply.

In order to supply power to the resistance heating element, an appropriate power supply terminal can be formed on the resistance heating element. The power supply terminal is preferably a silver-based thick film.

The power supply terminal can be easily formed on the surface of the base on which the resistance heating element is formed. However, the resistance heating element is not used due to the circumstances on the power supply side and the entire layout of the heating element. The power supply terminal may be formed on a surface opposite to the surface on which the power supply terminal is formed. In this case, wiring can be routed to the opposite surface side through the conductive through hole.

Accordingly, the power supply terminal is provided on the surface on which the resistance heating element is formed, on the opposite side, or on one side of the power supply terminal on the side of the resistance heating element and on the other side on the opposite side. It can be formed separately.

Regarding Conductor Pattern The conductor pattern provides the temperature sensor with a conductive path for connecting the temperature sensor to a temperature control circuit located outside the heating element. Therefore, the conductor pattern is
First, it functions to connect the temperature sensor to the terminal portion provided on the heating element. The terminal section is preferably arranged in a place that is not easily affected by the temperature of the heating element, and must be aligned with the entire layout of the heating element. The conductor pattern connects between the position of the temperature sensor and the terminal.

Further, any conductor may be used for the conductor pattern, but a conductor containing silver as a main component can be used. And a thick film can be formed like a resistance heating element.

The temperature sensor may be a thermistor, that is, a negative temperature sensitive resistor. However, the present invention is not limited to this. A temperature resistor or the like may be used.

The temperature sensor is mounted on a substrate made of an insulator such as ceramics.
Usually, a temperature sensor film is formed on a base material, and a pair of terminal portions is formed on the temperature sensor film so as to be spaced apart and opposed to each other to be a thick film or the like.

Further, the temperature sensor may be disposed at any position where the heat of the resistance heating element can be sensed, and may be located on the same surface as the surface on which the resistance heating element is formed, or adjacent to the resistance heating element, or On the surface opposite to the surface on which the resistance heating element is formed with the substrate interposed, the resistance heating element can be disposed facing the resistance heating element.

In order to connect the temperature sensor to the conductor pattern, the temperature sensor is placed on the conductor pattern with its terminals facing each other, and bonded by a conductive adhesive. Can be connected to

By the way, the content of the filler in the adhesive applied between the temperature sensor of the heating element and the substrate is analyzed by a heating gravimetric analysis method and an infrared spectrophotometry method. In the former analysis method, the sample is heated to burn off the organic synthetic resin component, and the content is calculated from the difference between the mass before and after that.

In the latter analysis method, a sample is irradiated with infrared rays, and the components are specified based on their light absorption characteristics.

Regarding the adhesive The adhesive is applied between the side surface of the temperature sensor and the surface of the base, and is used for mechanically fixing the temperature sensor to the base with a required strength.

As the adhesive in the present invention, a polyimide-based adhesive is used, and a filler is added.

As the filler, a fine powder of mainly inorganic material having a thermal conductivity equal to or higher than that of the substrate and / or the substrate of the temperature sensor is used. Since the thermal conductivity of the polyimide-based adhesive is generally lower than that of the base material and the base material of the temperature sensor, addition of the filler increases the synthesized thermal conductivity of the adhesive alone. For example, when the substrate is made of alumina ceramics, fine powder such as aluminum nitride or alumina can be used as the filler. Since the thermal conductivity of aluminum nitride is higher than that of alumina, the thermal conductivity of the entire adhesive containing the filler in the above-mentioned ratio is close to that of the substrate and / or the substrate of the temperature sensor.

Also, when alumina fine powder is used as the filler, if the content is within the above range, the thermal conductivity of the adhesive is practically the thermal conductivity of the base and / or the base of the temperature sensor. Approach.

The mode of applying the adhesive will be described below. That is, when the temperature sensor has a size of about 1.6 mm × 0.8 mm × 0.35 mm, the applied amount of the adhesive is set to 0.005 ± 0.002.
By regulating to g, good adhesion can be obtained. If the applied amount of the adhesive is too large, cracks are likely to occur.

If the longitudinal sectional shape of the adhesive after curing is concave, the adhesion becomes good.

Further, when the position of application of the adhesive is not more than half of the height direction of the temperature sensor, good adhesion can be obtained.

Further, if the position applied to the substrate side is within 1 mm from the side surface of the temperature sensor, more favorable adhesion can be obtained.

Furthermore, the adhesive may be applied to the entire periphery of the side surface of the temperature sensor, may be applied only to the corner, or may be applied to the side excluding the corner. You may.

Other Configurations In order to protect the resistance heating element electrically, an electrically insulating glass film can be formed on the resistance heating element and on the substrate surface around the resistance heating element.

When the heating element is used as a fixing heating element of a fixing device in an image forming apparatus of an electrophotographic process system, the resistance heating element is slidably brought into contact with a fixing member to which toner has adhered directly or via a conveyance sheet. However,
In order to provide resistance to abrasion due to sliding contact, the glass film can be formed using not only an electrically insulating glass but also a glass having abrasion resistance.

Further, if necessary, an abrasion-resistant glass film can be formed in addition to the electrically insulating glass film.
Still further, the substrate can be made of a material having a high thermal conductivity such as aluminum nitride, and the substrate can be slid on the body to be fixed.

Further, when a thin ceramic plate is used as the base, a laser scribe line is formed on the ceramic base plate in advance to form a large number of bases, and a resistance heating element and the like are simultaneously printed and fired. It is common to perform so-called multi-point picking after forming by performing such a process. In this case, a minute crack starting from the laser scribe line may be generated, which may cause undesirable breakage of the substrate.

On the other hand, by forming a glass reinforcing film containing an alumina filler on substantially the entire back surface of the substrate, minute cracks in the substrate can be filled with the glass reinforcing film to prevent breakage.

Operation of the present invention The temperature sensor is fixed at a predetermined position on the base with an adhesive, and the adhesive has a thermal conductivity equal to or higher than that of the base and / or the base of the temperature sensor. Contains 76 ± 1% by weight of the filler, so that the adhesion between the substrate, the temperature sensor and the adhesive is very good, the initial adhesive strength is large, and the adhesive cracks even after long-term use. No peeling or peeling.

Therefore, the reliability of adhesion of the temperature sensor to the base is improved, and a highly reliable heating element can be provided.

If the content of the filler is less than 75% by weight, the thermal conductivity of the adhesive as a whole is not sufficiently close to the thermal conductivity of the substrate and the substrate of the temperature sensor. On the other hand, if the content of the filler exceeds 77% by weight, it is difficult to obtain a sufficiently high adhesive strength, so that it is impossible.

It is desirable that the filler be a fine powder having an average particle diameter of 10 μm or less.
When the average particle size is in the above range, the adhesive before curing is given an appropriate fluidity, so that the adhesive applied to the side surface of the temperature sensor flows, and the temperature sensor and the facing surface thereof are opposed to each other. The temperature sensor can be firmly adhered to the substrate because it penetrates a small gap between the substrate and the temperature sensor.

The heating element of the present invention can be applied not only to fixing but also to any use requiring heating over a required length.

A heating element according to a second aspect of the present invention comprises an electrically insulating elongated base; an elongated resistive heating element attached to a surface of the base along a longitudinal direction of the base; A pair of spaced apart conductor patterns formed at positions where the heat of the heating element can be sensed; and a conductor pattern mounted on an electrically insulating base material at a position where the heat of the resistance heating element can be sensed. A chip-shaped temperature sensor disposed so as to be conductively connected across the substrate; and a coefficient of thermal expansion of the substrate and / or the temperature sensor substrate such that the coefficient of thermal expansion is close to that of the substrate and / or the substrate of the temperature sensor. Contains 76 ± 1% by weight of fine powder filler with low coefficient of thermal expansion,
A polyimide-based adhesive applied so as to fix between the temperature sensor and the substrate.

According to the present invention, by adding 76 ± 1% by weight of a filler having a thermal expansion coefficient equal to or more than that of the base material and / or the base material of the temperature sensor as a filler, for example, 76 ± 1% by weight, the thermal expansion coefficient of the adhesive as a whole And / or the coefficient of thermal expansion of the substrate of the temperature sensor can be approximated. For example:

Thermal expansion coefficient of alumina ceramics (substrate, substrate): 6p
pm / ° C Thermal expansion coefficient of polyimide adhesive: 60 ppm / ° C Thermal expansion coefficient of silica (filler): 0.6 ppm / ° C Thermal expansion coefficient of adhesive containing filler in the above range: about 6 p
pm / ° C. Since the heating element of the present invention has a large initial adhesive strength of the adhesive between the temperature sensor and the base, no peeling occurs, and even if the heating element is used for a long time, Since thermal expansion and contraction of the base (substrate) and the adhesive are performed in the same manner by turning on / off the energization, cracks do not occur between the adhesive and the base.

When the content is less than 75% by weight,
Due to the difference in the coefficient of thermal expansion, there is a slight occurrence of cracks between the substrate and the adhesive due to long-term use. On the other hand, if the content exceeds 77% by weight, the initial adhesive strength tends to be low, and there is a case where a slight peeling occurs between the substrate and the adhesive due to long-term use.

According to a third aspect of the present invention, there is provided a heating element, comprising: an elongated base having electrical insulation; an elongated resistance heating element attached to a surface of the base along a longitudinal direction of the base; A pair of spaced apart conductor patterns formed at positions where the heat of the heating element can be sensed; and a conductor pattern mounted on an electrically insulating base material at a position where the heat of the resistance heating element can be sensed. A chip-shaped temperature sensor disposed so as to be conductively connected across the substrate; and 76 ± 1% by weight of a fine powder filler made of the same material as the base and / or the base of the temperature sensor. A polyimide-based adhesive applied to fix the gap therebetween;
It is characterized by having.

Thus, in the present invention, since the adhesive contains 76 ± 1% by weight of a fine powder of the same material as the base material and / or the base material of the temperature sensing sensor as a filler, the adhesive and the base material are contained. And / or the thermal expansion difference between the temperature sensor and the base material is extremely small, and the thermal conductivity is the same. It is difficult to cause cracks, and the peeling does not occur because the initial adhesive strength of the adhesive is large.

According to a fourth aspect of the present invention, there is provided a fixing device comprising: the heating element according to any one of the first to third aspects; and a pressure roller disposed in pressure contact with the heating element. It is characterized by having.

A conveyance sheet made of a plastic sheet such as a thin polyimide resin may be interposed between the heating element of the fixing device and the object to be fixed to facilitate conveyance of the object to be fixed. Further, the conveying sheet can be formed into an endless belt shape.

Also in the present invention, the function of the heating element according to claims 1 to 3 is exerted.

According to a fifth aspect of the present invention, the image forming apparatus forms a reverse image by attaching toner to the formed electrostatic latent image.
5. An image forming means for forming an image by transferring an inverted image to a fixing member; and a fixing device according to claim 4, wherein the fixing device fixes the image by fusing toner adhered to the fixing member. It is characterized by.

In the present invention, the image forming apparatus includes all devices having a function of forming an image using toner. The image means a character, a figure, a code, a video, and the like. Specifically, for example, there are image forming apparatuses such as a copying machine, a printer, and a facsimile.

[0062]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a front view showing a first embodiment of the heating element of the present invention.

FIG. 2 is also a rear view.

In the figure, 1 is a base, 2 is a resistance heating element,
3a, 3b are power supply terminals, 4 is a power supply conductor pattern, 5
Is a temperature sensor, 6 is a control terminal, 7 is a control conductor pattern, and 8a and 8b are conductive through holes.

The base 1 is a thin and elongated plate made of alumina ceramics.

The resistance heating element 2 is disposed along the longitudinal direction of the base 1 at a position slightly deviated from the center on one surface of the base 1, and is made of a conductive material mainly composed of a silver / palladium alloy. The paste is screen-printed, dried and fired to form a thick-film resistance heating element.

The power supply terminal 3a is directly connected to one end of the resistance heating element 2 near one end of the base 1, and a conductive paste containing silver as a main component is formed in a thick film by the same manufacturing method as that of the resistance heating element 2. Things.

The power supply conductor pattern 4 includes the resistance heating element 2
Is connected to the other end of the resistance heating element 2 and is folded back along the resistance heating element 2 to provide another end in the middle of the resistance heating element 2, and a conductive through hole 8 a is provided at the other end. The other power supply terminal 3b connected to the power supply conductor pattern 4 via the conductive through hole 8a is provided on the back surface of the base 1.

The temperature sensor 5 is composed of a thermistor, and is disposed at a position where the heat of the resistance heating element 2 can be sensed, that is, at a position opposite to the resistance heating element 22 on the back surface of the base 1.
The configuration of the temperature sensor 5 and the fixation to the base 1 will be described later.

A pair of control terminals 6 are provided near the other end of the base 1, and conductive through holes 8b, 8b are provided respectively.

The control conductor pattern 7 includes a temperature sensor 5
And a conductive through hole 8b between the control terminals 6a and 6b.
Connected through.

Thus, the other power supply terminal 3b, power supply conductor pattern 4, control terminal 6, and control conductor pattern 7 are also formed of the same material and method as the main terminal 3a.

Although not shown, the main part of the resistance heating element 2 is covered with a glass protective film including the peripheral substrate surface.

FIG. 3 is an enlarged rear view of a main part of the heating element according to the first embodiment of the present invention.

FIG. 4 is an enlarged rear view of a main part showing a fixed state of the temperature sensor.

FIG. 5 is an enlarged sectional view of a main part in a direction crossing the base.

FIG. 6 is an enlarged cross-sectional view of a main part in a direction in which the base is similarly longitudinally cut.

In each of the figures, reference numeral 9 denotes an adhesive.

The adhesive 9 is applied between the pair of opposed longitudinal side surfaces of the temperature sensor 5 and the base 1, and mechanically firmly fixes the temperature sensor 5 to the base 1 in a cured state. . The temperature sensor 5 is configured as follows. That is, it is composed of the base material 5a, the temperature sensor film 5b, and the terminal portion 5c.

The substrate 5a is made of alumina ceramics.

The temperature sensor film 5b is a thermistor film formed on the substrate 5a by thick film printing or vapor deposition.

The terminal 5c is made of a conductive film formed on the temperature sensor film 5b by printing or vapor deposition.

Then, the temperature sensor 5 is 1.6 mm ×
It has a chip shape with a size of 0.8 mm x 0.25 mm. The temperature sensor 5 is bonded and electrically connected between the pair of control conductor patterns 6 by a conductive adhesive.

On the other hand, the adhesive 9 is a polyimide-based adhesive containing 76% by weight of a silica filler having an average particle diameter of 10 μm or less.

The applied amount of the adhesive 9 is 0.1 in the cured state.
005 g.

Further, as shown in FIG. 6, the adhesive 9
The surface is concave in the cured state. Thereby, the familiarity with the substrate 1 and the substrate 5a is further improved, and cracks are less likely to occur.

Since the average particle size of the filler is 10 μm or less, the adhesive 9 has good fluidity, and penetrates into a slight gap between the temperature sensor 5 and the base 1 facing the temperature sensor 5. And strong mechanical adhesion can be obtained.

FIG. 7 is a partially cut-away enlarged front view showing a second embodiment of the heating element of the present invention.

In the figure, the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment,
The arrangement position of the temperature sensor 5 is different.

That is, the temperature sensor 5 is disposed adjacent to the resistance heating element 2 on the same surface of the base 1 on which the resistance heating element 2 is formed.

In this embodiment, the power supply terminal 3
a, 3b and the control terminals 6, 6 and thus all the terminals are arranged on one side of the substrate 1.

FIG. 8 is a sectional view showing an embodiment of the fixing device of the present invention.

In the drawing, 10 is a heating element, 11 is a pressure roller, 12 is a conveying sheet, 13 is a guide roller, 14 is a machine frame, 15 is a fixed member, and 16 is a heating element supporter / conveying sheet guide. is there.

The heating element 10 has the structure shown in FIGS. 1 to 6 and is supported on the lower surface of a heating element support / conveyance sheet guide 16.

The pressure roller 11 is in pressure contact with the heating element 10 with the conveyance sheet 12 interposed therebetween.

The transport sheet 12 is made of, for example, a polyimide resin, and has an endless belt shape that gently makes a round around a heating element support / transport sheet guide 16 which also serves as a holder for the heating element 10.

The fixing member 15 is fixed to the guide roller 1.
The sheet 3 is fed between the conveying sheet 12 and the pressure roller 11. When the fixing member 15 is fed, the heating element 10 is energized by control means (not shown), and the heating element 10 instantaneously generates heat and rises to a temperature at which fixing can be performed. As a result of the heating element 10 heating the fixing member 15 via the transport sheet 12, the toner adhering to the fixing member 15 is melted and fused to the fixing member 15 by the pressure roller 11, so that fixing is performed. Will be

FIG. 9 is a conceptual diagram of a laser beam printer showing a first embodiment of the image forming apparatus of the present invention.

In the figure, reference numeral 17 denotes an image forming means which includes a laser scanner 17a, a photosensitive drum 17b, and the like. Reference numeral 18 denotes a fixing device having a structure shown in FIG. Reference numeral 19 denotes a printer main body, which includes components other than the above components, such as a paper feed tray, a power supply, a guide roller, an operation switch, a control circuit, a high voltage generation circuit, and a case.

When the laser beam printer receives the image signal, the laser beam is modulated by the image signal in the laser scanner 17a, and is scanned to partially expose the photosensitive drum 17b to form an inverted electrostatic latent image. To form Next, a reversal image is formed by attaching toner to the reversal electrostatic latent image, a fixing medium such as plain paper is fed from a tray by a guide roller, and the reversal image is transferred to the fixing medium to form an unfixed image. The obtained fixing member is obtained. Further, the fixing member is sent to the fixing device 18 by a guide roller. In the fixing device 18, fixing is performed by operating as described above, and a fixed image is obtained.

FIG. 10 is a conceptual diagram of a copying machine showing a second embodiment of the image forming apparatus of the present invention.

In the figure, 20 is an image reading means, 21 is an image forming means, 22 is a fixing device, and 23 is a copying machine main body.

The image reading means 20 includes a reading light source and an optical system such as a scanner.

The image forming means 21 forms a reversal electrostatic latent image on the photosensitive drum based on the image data read from the base paper by the image reading means 20, and then makes the toner adhere to the reversal electrostatic latent image to reverse the reversal electrostatic latent image. An image is formed, and the inverted image is transferred to a fixing medium such as plain paper to manufacture a fixing member on which the image is formed.

The fixing device 22 performs fixing by heating the member to be fixed and fusing the toner. Although the transport sheet is omitted in the figure, it is used as needed.

The copying machine main body 23 is provided with the image reading means 2.
0, a configuration other than the image forming unit 21 and the fixing unit 22 such as a main body case, a power supply, a control circuit, a high voltage generation circuit,
It is configured to include an operation switch, a paper feed tray, and the like.

[0108]

According to the first aspect of the present invention, an elongated resistive heating element is attached to an electrically insulating elongated base along its longitudinal direction, and the heat is sensed from the resistive heating element. A temperature sensor mounted on the substrate is connected across a pair of conductor patterns, and a fine powder filler having a thermal conductivity equal to or greater than that of the base and / or the base of the temperature sensor is added to the temperature sensor.
By fixing the temperature sensor to the substrate with a polyimide adhesive containing ± 1% by weight, the adhesion between the substrate and / or the substrate and the adhesive is very good, and the initial adhesive strength is large, so it can be used for a long time. Even if the adhesive does not crack or peel off,
A highly reliable heating element can be provided.

According to the second aspect of the present invention, an elongated resistive heating element is attached to an elongated electrically insulating base along its longitudinal direction, and mounted on the substrate at a position where the heat of the resistive heating element can be sensed. The temperature sensor is connected across a pair of conductor patterns, and the temperature sensor is expanded with a polyimide-based adhesive containing 76 ±% by weight of a fine powder filler having a smaller coefficient of thermal expansion than the base and / or the base of the temperature sensor. By fixing to the substrate, the initial adhesive strength is large and there is no peeling, and even when used for a long time, the thermal expansion and contraction of the substrate and the substrate and the adhesive by turning on and off the power supply are performed similarly. Therefore, it is possible to provide a highly reliable heating element without cracking between the adhesive and the base.

According to the third aspect of the present invention, an elongated resistive heating element is applied to an electrically insulating elongated base along its longitudinal direction, and mounted on the substrate at a position where the heat of the resistive heating element can be sensed. The temperature sensor is connected across a pair of conductor patterns, and the temperature sensor is connected to the base by a polyimide adhesive containing 76 ±% by weight of a fine powder filler made of the same material as the base and / or the base of the temperature sensor. By fixing to the base, the initial adhesive strength is large and no peeling occurs, and even when used for a long time, thermal expansion and contraction of the base material and the base material and the adhesive by turning on and off the current are performed similarly, Since the conductivity is also improved, it is possible to provide a highly reliable heating element without cracking between the adhesive and the substrate.

According to the fourth aspect of the invention, it is possible to provide a fixing device having the effects of the first to third aspects.

According to the fifth aspect of the present invention, it is possible to provide an image forming apparatus having the effects of the first to third aspects.

[Brief description of the drawings]

FIG. 1 is a front view showing a first embodiment of a heating element of the present invention.

FIG. 2 is a rear view of the same.

FIG. 3 is an enlarged rear view of a main part of the heating element according to the first embodiment of the present invention.

FIG. 4 is an enlarged rear view of a main part showing a fixed state of the temperature sensor.

FIG. 5 is an enlarged cross-sectional view of a main part in a direction crossing the base.

FIG. 6 is an enlarged cross-sectional view of a main part in a direction in which the base is similarly longitudinally cut;

FIG. 7 is a partially cutaway enlarged front view showing a second embodiment of the heating element of the present invention.

FIG. 8 is a conceptual sectional view showing an embodiment of the fixing device of the present invention.

FIG. 9 is a conceptual diagram of a laser beam printer showing a first embodiment of the image forming apparatus of the present invention.

FIG. 10 is a conceptual diagram of a copying machine showing a second embodiment of the image forming apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Base 5 ... Temperature sensor 6 ... Conductor pattern for control 8b ... Conductive through hole 9 ... Adhesive

Claims (5)

[Claims] 1. An electrically insulating elongated substrate; an elongated resistive heating element applied to a surface of the substrate along a longitudinal direction of the substrate;
A pair of spaced apart conductor patterns formed at least partially on the substrate at positions where the heat of the resistance heating element can be sensed; and mounted on an electrically insulating base material to sense the heat of the resistance heating element. A chip-shaped temperature sensor disposed so as to be conductively connected across the conductor pattern at a possible position; and 76 ± 1 fine powder filler having a thermal conductivity equal to or greater than that of the base and / or the base of the temperature sensor. And a polyimide-based adhesive applied to fix between the temperature sensor and the substrate. 2. An elongated electrically insulating substrate; an elongated resistive heating element applied to a surface of the substrate along a longitudinal direction of the substrate;
A pair of spaced apart conductor patterns formed at least partially on the substrate at positions where the heat of the resistance heating element can be sensed; and mounted on an electrically insulating base material to sense the heat of the resistance heating element. A temperature sensor in the form of a chip, which is electrically connected across the conductor pattern at a possible position; and a substrate and / or a temperature sensor such that the coefficient of thermal expansion is close to that of the substrate and / or the substrate of the temperature sensor. A polyimide-based adhesive containing 76 ± 1% by weight of a fine powder filler having a smaller coefficient of thermal expansion than that of the substrate, and applied so as to fix between the temperature sensor and the substrate. A heating element characterized in that: 3. An elongated electrically insulating substrate; an elongated resistive heating element applied to a surface of the substrate along a longitudinal direction of the substrate;
A pair of spaced apart conductor patterns formed at least partially on the substrate at positions where the heat of the resistance heating element can be sensed; and mounted on an electrically insulating base material to sense the heat of the resistance heating element. A chip-shaped temperature sensor disposed conductively connected across the conductor pattern at a possible position; and 76 ± 1% by weight of a fine powder filler made of the same material as the base and / or the base of the temperature sensor Contains
A heating element, comprising: a polyimide-based adhesive applied so as to fix the space between the temperature sensor and the base. 4. A fixing device comprising: the heating element according to claim 1; and a pressing roller disposed in pressure contact with the heating element. . 5. An image forming means for forming a reversal image by adhering toner to the formed electrostatic latent image and transferring the reversal image to a fixing member to form an image; toner adhering to the fixing member An image forming apparatus comprising: the fixing device according to claim 4, wherein the fixing device fixes the image by fusing.