JPH07272836A - Plate-form heater, fixation device, and image forming device - Google Patents

Abstract

PURPOSE:To provide a sheet-form heater which allows easy mounting of a thermistor on the base board of the heater and can sense the temperature accurately and quickly. CONSTITUTION:A resistance heat-emitting body 2 in band shape is attached to the front surface 1A of a base board 1 made of a heat-resistant, electrically insulative material, and to the rear surface 1B a chip-shaped thermistor 5 which senses the temp. of the heat emitting body 2 is attached. A temp. sensing part and a terminal are provided on one of the surfaces of the base 5a of the thermistor 5, and the other surface of the thermistor base 5a is positioned on the board side and connected with a wiring conductor 6 where the terminal is formed on the rear of the base board 1. This makes possible high precision adjustment of the temperature, facilitates mounting of the thermistor on the board, heightens the bonding strength because of a large joining area covering the whole surface, and precludes risk of thermistor separation which might cause thermal violet run in the heater.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin plate heater used for mounting on small equipment such as office automation equipment, household electric equipment and precision manufacturing equipment, and a copying machine equipped with the thin plate heater. The present invention relates to a fixing device used for fixing a toner such as a facsimile and an image forming apparatus using the fixing device.

[0002]

2. Description of the Related Art For example, in an electronic copying machine, a copy sheet on which a toner image is formed is passed while being pinched between a fixing plate heater and a pressure roller, and the heat of the heater causes the copy sheet to remain on the copy sheet. The toner is heated and melted to fix the toner.

FIG. 9 shows a cross section of the fixing plate heater. The heater H is a surface side 1 of an elongated heat-resistant / electrically insulating substrate 1 made of alumina (Al ₂ O ₃ ) ceramics or the like.
A strip-shaped thick film resistance heating element is formed by printing, coating and firing a paste prepared by kneading silver / palladium alloy (Ag / Pd) powder and the like with glass powder (inorganic binder) and organic binder. 2 is formed, and a film made of a good conductor such as silver (Ag) or a silver / platinum (Ag / Pt) alloy or a silver / palladium alloy (Ag / Pd) is formed on both ends of the resistance heating element 2. A power supply terminal (not shown) is formed, and the surface of the resistance heating element 2 is further covered with a glassy overcoat layer 4 to improve mechanical strength such as abrasion resistance and impact resistance, and sulfurization. It protects against corrosion and oxidation and electrically insulates the pressure roller of the copying machine.

On the rear surface side 1B of the heater H, which is opposite to the front surface side 1A on which the resistance heating element 2 is formed, a chip shape (having no lead wire) as a temperature detecting element of the resistance heating element 2 is provided. Therefore, a thermistor 5 of a disc type is also attached. Reference numerals 6 and 6 in the figure denote silver (Ag) or silver / platinum (Ag) formed on the back surface 1B of the substrate 1.
-A pair of wiring conductors made of a film of a good conductor such as a Pt) alloy or a silver-palladium (Ag-Pd) alloy.

The chip-shaped thermistor 5 is
A flat plate-shaped substrate 5a made of alumina (Al ₂ O ₃ ) ceramics, manganese (Mn), cobalt (Co), nickel (Ni) formed in the central portion on one surface of the substrate 5a.
Temperature sensing part 5 consisting of a thin film formed by mixing oxides such as
b, the temperature sensitive portion 5b has electrode portions 5c and 5c made of, for example, a platinum (Pt) layer formed continuously on both ends thereof. Further, 5d is a silicon oxide (Si
It is an overcoat layer composed of O ₂ ).

In such a thermistor 5, both electrode portions 5c and 5c are provided with the temperature sensing portion 5b facing the back surface 1B of the substrate 1.
c is bonded to the wiring conductors 6 and 6 via a conductive adhesive 7 in which silver (Ag) or an alloy powder of silver / palladium (Ag / Pd) is mixed with an organic adhesive.

In the fixing device of a copying machine, for example, the plate heater and the pressure roller are arranged in parallel to face each other.
A roller portion made of a heat-resistant elastic material on the surface of a pressure roller having a rotating shaft and the overcoat layer 4 of the plate-shaped heater are lightly contacted directly or indirectly. Then, when the copy sheet is supplied between the plate-shaped heater H and the pressure roller, the copy sheet is pressure-fed while sliding on the overcoat layer 4 of the heater H by the rotation of the pressure roller, and the heater H during this period. The toner on the copy paper is heated and fixed by the heat of.

In this fixing device, the plate-shaped heater H detects the temperature of the heating element 2 by the chip-shaped thermistor 5 attached to the back surface 1B of the substrate 1 opposite to the surface on which the resistance heating element 2 is formed. The detected signal is fed back to the temperature control circuit device to control the electric power applied to the plate-shaped heater H to keep the heater H at a constant temperature.

[0009]

However, as described above, both the electrode portions 5c and 5c are placed on the wiring conductors 6 and 6 with the temperature sensing portion 5b of the chip-shaped thermistor 5 facing the back surface side 1B of the substrate 1. However, the following problems may occur when the conductive adhesive 7 is used for bonding.

The chip-shaped thermistor 5 is extremely small (length about 1,6 mm × width about 0.8 mm, thickness about 0.25 mm), and the electrode portion 5c (length about 0.5 mm × width about 0, 8 mm) and the contact area between the wiring conductor 6 and the wiring conductor 6 are small, the joining strength is reduced if the pressure is weak at the time of joining, or if the joining position is slightly displaced.
The thermistor 5 may peel off from the substrate 1 when subjected to vibration or shock when the high temperature state continues for a long time or when the bonding force decreases due to deterioration over time.

The surface of the temperature sensing portion 5b of the thermistor 5 is covered with an overcoat layer 5d for preventing damage and corrosion and deterioration due to humidity and impure gas.
If the overcoat layer 5d rides on the wiring conductor 6 without contact with c (shown in FIG. 10A), and if the layer thickness of the overcoat layer 5d is thicker than the wiring conductors 6 and 6, the temperature sensing portion 5 is formed.
In some cases, the terminal portions 5c and 5c on both sides of b cannot contact the wiring conductors 6 and 6 (shown in FIG. 10 (b)), so that the electrical connection becomes unstable or cannot be connected.

When the thermistor 5 is not satisfactorily mounted on the substrate 1 and the connection with the wiring conductor 6 is insufficient as described above, the temperature control of the resistance heating element 2 by the thermistor 5 becomes impossible. A voltage is continuously applied to cause an overcurrent to flow, and the temperature of the substrate 1 becomes high enough to heat it red. If this high temperature state continues, the tray made of plastic on which the plate-shaped heater H is mounted, the casing of the fixing device and the copy paper that is sent by being pressed on the heater H may be burned or ignited. was there.

Further, in such a plate-shaped heater H,
The layer thickness of the overcoat layer 5d of the thermistor 5 is smaller than the film thickness of the wiring conductors 6 and 6, and the substrate 1 and the overcoat layer 5d
If the space 5e between the substrate 1 and the
There is also a problem that it is difficult to accurately and quickly detect the temperature of, and accurate temperature control cannot be performed.

According to the present invention, it is easy to mount a temperature detecting element on a heater substrate, and a plate-shaped heater capable of accurately and quickly detecting temperature with high accuracy at the time of heat generation, a fixing device having the heater mounted, and a fixing device having the heater. An object of the present invention is to provide an image forming apparatus using the.

[0015]

The plate heater of the present invention comprises:
A substrate made of a heat-resistant and electrically insulating material, a strip-shaped resistance heating element formed on the front surface side of the substrate, and a thermocouple formed on the back surface side of the substrate for detecting the temperature of the resistance heating element. It is characterized by doing.

Further, the thermocouple is characterized in that it is formed on a substrate by printing.

Further, the thermocouple is characterized in that it is formed by being attached to a substrate.

The thermocouple is characterized in that it is connected to a wiring conductor arranged on the substrate.

Further, the invention is characterized in that a protective coating layer made of a resin adhesive or a ceramic adhesive is formed so as to cover the contact portion of the thermocouple on the back surface side of the substrate.

Further, it is characterized in that a vitreous overcoat layer is formed to cover the resistance heating element on the surface side of the substrate.

Further, the fixing device of the present invention is characterized in that the pressure roller and the plate heater described above are arranged opposite to each other.

Furthermore, the image forming apparatus of the present invention is characterized by including the fixing device described above.

[0023]

[Function] A thermocouple is used as the temperature detecting element, and the thermocouple is formed by printing a thick film and baking, so that the detecting element can be formed in close contact with the substrate, so that the temperature of the substrate can be detected accurately and quickly with high accuracy. It is possible and does not peel off from the substrate.

Further, in the case where the thermocouple formed separately is attached, the area can be joined in a larger area as compared with the case where the thermistor is joined, the fixing strength is improved, and peeling and dropping from the substrate can be reduced.

[0025]

Embodiments of the plate heater of the present invention will be described below with reference to the drawings. 1 to 3 show a first embodiment of the present invention. FIG. 1 is a top view of a plate heater H used in a fixing device or the like, FIG. 2 is a bottom view, and FIG. 3 is a line XX of FIG. FIG. 4 is an enlarged cross-sectional view of a portion cut along the line. In the figure, 1 is a heat-resistant and electrically insulating material such as alumina (Al ₂ O ₃ ) ceramics, which is an elongated substrate having a length of about 300 mm, a width of about 6 mm, and a thickness of about 0.8 to about 1 mm. 2 is a silver / palladium (Ag / Pd) alloy or nickel / tin (Ni / Sn) having a length of about 230 mm, a width of about 2 mm, and a thickness of about 10 μm formed along the longitudinal direction on the front surface side 1A of the substrate 1.
A strip-shaped resistance heating element mainly made of an alloy or the like, and 3, 3 and 3 have a length of about 15 formed in layers at both ends of the resistance heating element
mm, wide silver (Ag) of about 6 mm, platinum (Pt),
The power supply terminal portion is made of a good conductor film mainly composed of gold (Au), silver / platinum (Ag / Pt) alloy, silver / palladium (Ag / Pd) alloy, or the like.

Further, 4 is the terminal portions 3 and 3 and the substrate 1.
1A on the front surface side of the substrate 1 including the resistance heating element 2 excluding a part of
Is a glassy overcoat layer having a layer thickness of 20 to 100 μm formed by melting glass powder or the like formed so as to cover almost the entire surface.

Further, 6A and 6B are the back side 1 of the substrate 1.
Copper (Cu) formed on B and nickel-copper (Ni-
A pair of thick film wiring conductors having a Cu) alloy width of about 0.5 mm and a film thickness of 10 to 30 μm, one end of which is layered and connected at a position corresponding to the resistance heating element 2 on the front surface side 1A of the substrate 1 The thermocouple 5 constitutes a contact point (temperature sensitive portion) 5a, and the other end constitutes terminal portions 6c and 6d of the wiring conductors 6A and 6B.

Reference numeral 8 is a heat-resistant and electric-resistant material such as an epoxy resin, a silicone resin, or a polyimide resin, which is formed by covering the back side including the connecting portion between the thermocouple 5 portion and the wiring conductors 6 and 7 around the thermocouple 5 portion. The protective coating layer is made of an insulating resin adhesive or a ceramic adhesive containing silica or alumina as a main component.

Next, the production of the plate heater H will be described. First, the resistance heating element 2 is formed on the front surface side 1A of an elongated substrate 1 made of alumina (Al ₂ O ₃ ) ceramics. To form the heating element 2, for example, a conductive paste prepared by kneading a powder of silver-palladium (Ag.Pd) alloy, a glass powder (inorganic binder), an organic adhesive and the like is prepared. Then, this paste is applied as a strip-shaped thick film on the elongated substrate 1, dried, and dried at about 850 ° C. for about 10 minutes.
It is performed by baking for a minute. By this firing, the binder contained in the coating material is thermally decomposed, gasified and scattered, and the resistance heating element 2 made of silver / varadium (Ag / Pd) is formed.

Next, a conductive paste of, for example, a silver-platinum (Ag.Pt) alloy is applied as a thick film on the surface side 1A of both ends of the resistance heating element 2 by applying a thick film, and after drying and baking, a power supply is provided. The terminal parts 3 and 3 are formed.

Then, copper (Cu) is formed on the back surface 1B of the substrate 1.
And a nickel-copper (Ni-Cu) alloy paste is prepared. First, copper (Cu) paste is thick-film-printed in the shape of a hook-shaped strip along the extension direction of the substrate 1 by moving the copper paste from the vicinity of the center line on the elongated substrate 1 toward the short side of the substrate 1 and removing it from the center of the substrate 1. And apply it, and then nickel / copper (N
The i.Cu) alloy paste is similarly applied on the opposite side of the center line of the substrate 1 in the shape of a hook-shaped strip by thick film printing, facing the application position of the copper (Cu) paste. At this time, the tip portions of both are layered on the center line of the substrate 1.

Then, these thick-film printed coating films are dried and then baked at about 850 ° C. for about 10 minutes, so that each coating film is baked on the substrate 1 to 10-30.
A pair of wiring conductors 6A, 6B having a film thickness of μm is formed, and one end portion of the laminated layers constitutes a contact (temperature sensitive portion) 5a of the thermocouple 5.

After that, a glassy overcoat layer 4 is formed so as to cover the portion of the resistance heating element 2 of the belt-shaped thick film and the surface of the substrate 1. This overcoat layer 4 is formed by kneading a PbO-based glass powder containing lead oxide (PbO) as a main component with a vehicle (organic binder) in an organic solvent to form a glass paste, which is thickened. The film is printed to form a continuous coating film without gaps. And
After drying, bake at about 850 ° C for about 10 minutes to obtain a thickness of 2
The glass layer has a thickness of 0 μm to 100 μm.

Finally, a heat-resistant / electrically-insulating resin adhesive made of epoxy resin, silicone resin, polyimide resin, or the like is used to cover the surface of the thermocouple 5, the wiring conductors 6A, 6B, and the back surface 1B around them. Smitherum "
A ceramics adhesive such as (Asahi Chemical Co., Ltd.) is applied and the adhesive is cured to form the protective coat layer 8.

In the above-mentioned embodiment, in forming various coatings, each coating was formed and fired before the next coating was formed. However, a plurality of coatings having the same firing temperature may be simultaneously formed. By doing so, productivity can be improved.

Such a plate-shaped heater H is incorporated in a device and is energized by a circuit configuration as shown in FIG. 4 to adjust the heat generation temperature. That is, when the commercial power source S is energized between the terminal portions 3 and 3 of the heater H via the SSR (solid state relay) connected to the control terminal of the temperature control circuit T, a current flows through the resistance heating element 2 to generate heat. The temperature of the substrate also rises due to the heat generated by the resistance heating element 2, and this heat is transmitted to the contact point (temperature-sensitive portion) 5a of the thermocouple 5 formed on the rear surface 1B of the substrate 1, and the thermocouple 5 is heated. Change the power.
The change in the thermoelectromotive force of the thermocouple 5 is output from the terminal portions 6c and 6d via the wiring conductors 6A and 6B formed on the substrate,
This is input to the temperature control circuit T and it is determined whether or not it is within an appropriate temperature range (= set temperature). When the temperature is lower than the set temperature, the ON signal is output to the SSR, and when the temperature is higher than the set temperature, the OFF signal is output to the SSR.

In this way, the temperature of the resistance heating element 2 is adjusted by controlling the electric power applied to the resistance heating element 2. The temperature control circuit T has been described for the ON / OFF control of the SSR, but other than that, the PWM (Pulse Width)
h Modulation: pulse width control method) or the like.

When the plate-shaped heater H is energized between the terminal portions 3 and 3 at both ends, a current flows through the resistance heating element 2 and the heating element 2 exhibits a substantially uniform heat generation temperature distribution in the longitudinal direction. This heater H is made of silver / palladium (A
g · Pd) serves as an electric resistance element, and the resistance value of the heating element 2 is adjusted by the ratio of silver / palladium (Ag · Pd) contained in the resistance paste. In this embodiment, about 2
It has a resistance value of 5 ohms [Ω], a current of about 4 A flows when a voltage of 100 V is applied, and the amount of heat generated is about 400 W.

Usually, as described above, the thermocouple 5 provided on the back surface 1B of the substrate 1 detects the temperature of the heater H, and the SSR is turned on / off through the temperature control circuit T to control the temperature to a predetermined temperature. is doing.

In the case of this embodiment, a pair of wiring conductors 6 and 7 made of copper (Cu) and nickel-copper (Ni-Cu) alloy constituting the thermocouple 5 formed on the substrate 1 of the heater H.
Is composed of a thick film directly printed and applied on the relatively flat surface of the substrate 1, and the entire formation surface comes into contact with the substrate 1. Therefore, the heat of the substrate 1 is applied to the contact point (temperature-sensitive portion) 5a of the thermocouple 5. The temperature of the substrate 1 can be detected accurately and quickly.

Further, the protective coat layer 8 made of an adhesive covering the entire thermocouple 5 prevents the thermocouple 5 from peeling off, so that the fixing strength thereof can be improved. Further, the protective coat layer 8 has a function of wrapping the thermocouple 5 and shielding external heat, and can perform highly accurate temperature detection without exerting thermal influence from the other.

Therefore, the temperature can be adjusted with high accuracy, and the bonding strength is improved because the thermocouple 5 is directly formed on the substrate 1, so that the thermocouple 5 can be removed from the substrate 1 during use.
Is not peeled off and thermal runaway occurs in the heater H, and temperature detection can be performed quickly with high accuracy.

When the response speeds of the plate heater H having the thermocouple according to the embodiment of the present invention and the plate heater having the conventional thermistor shown in FIG. 9 are compared, for example, 20
The conventional heater took about 100 seconds to detect the state of 0 ° C., but the heater H of the present invention took about 50 seconds, which was about half the time.

FIG. 5 shows another embodiment of the present invention.
FIG. 5 shows a state in which the thermocouple 5 is molded separately, and the thermocouple 5 is bonded to the back surface side 1B of the substrate 1 via an adhesive. In the figure, the same parts as those in FIGS. 2 and 3 are designated by the same reference numerals, and the description thereof will be omitted. That is, in this embodiment, copper (Cu) and nickel-copper (Ni-C) are used.
u) The wiring conductors 6A and 6B are formed by a foil or a wire (not shown) made of an alloy, and the tip ends of the wiring conductors are joined by means such as welding or brazing to form the contact point (temperature sensitive portion) 5a. It is a thermocouple 5.

The wiring conductors 6A and 6B and the thermocouple 5 are made of a conductive adhesive 7 (for example, Epotec) of polyimide, epoxy, silicone or the like with a filler of silver-palladium (Ag.Pd) alloy powder or the like. Epoxy resin adhesive product No. H35-175
It is completed by bonding to the substrate 1 through an adhesive 9 such as MP).

In this embodiment, the adhesive area in which the adhesive 9 is interposed is large as compared with a thermistor or the like, and the thermocouple 5 does not peel off from the surface of the substrate 1.

Therefore, since the bonding of the thermocouple 5 to the substrate 1 is almost the entire surface including the wiring conductors 6 and 7, the fixing strength is improved, and the thermocouple 5 is peeled from the substrate 1 during use and the thermocouple 5 is attached to the heater H. Problems such as thermal runaway will not occur. In addition, the adhesive 9 is an adhesive having good thermal conductivity (for example, epoxy resin adhesive product No. H manufactured by Epotek Co., Ltd.).
65-175MP), the heat transfer property is not impaired by the adhesive 9 filled between the members,
Very good heat transfer can be performed, the temperature of the substrate 1 can be transmitted to the thermocouple 5, and accurate and rapid high-precision temperature detection can be performed.

The bonding of the thermocouple 5 and the wiring conductors 6 and 7 to the substrate 1 is not limited to the one in which the adhesive 9 is interposed between the two as in the embodiment, and the thermocouple 5 and the wiring to the substrate 1 are not necessary. The conductors 6 and 7 may be pressed against each other, and the adhesive 9 may be joined to the upper surface by raising it, or the adhesive 9 may be supplied so as to rise between the two and the upper surface to join them.

FIG. 6 shows another embodiment of the present invention,
In the figure, the same parts as those in FIGS. 2, 3 and 5 are designated by the same reference numerals, and the description thereof will be omitted. The difference from the above embodiment is that the thermocouple 5 portion formed on the back surface 1B of the substrate 1 and the wiring conductor are made of different materials. That is, the contact (temperature sensitive portion) 5a portion of the thermocouple 5 is formed of a pair of thick film wiring conductors 6A and 6B made of copper (Cu) and nickel-copper (Ni-Cu) alloy as in the above-described embodiment. The tip portion is formed by stacking layers, and further, thick-film wiring conductors 6E, 6F mainly made of silver-palladium (Ag.Pd) alloy are formed separately from the wiring conductors 6A, 6B. Therefore, both ends are electrically connected by the connecting portions 6h and 6i formed in multiple layers.

Then, as in the above embodiment, the change in thermoelectromotive force of the thermocouple 5 is output from the terminal portions 6c and 6d via the wiring conductors 6A, 6B and 6E, 6F, and this is input to the temperature control circuit T. Then, it is determined whether the temperature is within the proper temperature range.

The wiring conductors 6A, 6B, 6E,
6F and 5 parts of thermocouples may be formed by printing and baking similarly to the above-described embodiment, or may be formed in advance with a foil-shaped body or a linear body via an adhesive. Since this embodiment also has the same effect as the above-mentioned embodiment, the description thereof will be omitted.

Next, the fixing device C in which the plate heater H of the above embodiment is mounted and the copying machine P in which the fixing device C is mounted will be described with reference to FIGS. 7 and 8.

FIG. 7 shows an example of a fixing device C such as a copying machine, a printer or a facsimile in which the plate-shaped heater H described in the above embodiment is mounted. The heater H portion in the drawing is the same as that of the above embodiment and is the same. The same reference numerals are given to the parts, and the description thereof will be omitted.

In the figure, C1 is a pressure roller, and a heat-resistant elastic material such as a silicone rubber layer C4 is fitted to the surface of a cylindrical roller body C3 having rotary shafts C2 protruding from both end surfaces. The plate-shaped heaters H are juxtaposed to the rotation shaft C2 of the pressure roller C1 and attached to the base C5. A heat resistant sheet C6 such as a polyimide resin is wound around the base C5 including the heater H, and the surface of the overcoat layer 4 directly above the resistance heating element 2 is covered with the heat resistant sheet C6. It is in elastic contact with the silicone rubber layer C4 of the pressure roller C1.

Then, in the fixing device C, the plate-shaped heater H
Is energized through a connector (not shown) made of phosphor bronze plate or the like which is in contact with the terminals 3 and 3 and which is provided with elasticity,
The copy paper PA on which the toner image PT is formed is pressed out between the surface of the heat-resistant sheet C6 provided on the overcoat layer 4 of the resistance heating element 2 that has generated heat and the silicone rubber layer C4 while being pressed in the direction of the arrow in the figure. The unfixed toner image PT is melted and fixed on the copy sheet PA by heating the copy sheet PA with the heater H at that time.

That is, on the paper input side of the pressure roller C1, the unfixed toner image PT on the copy paper PA is first heated and melted by the heater H via the heat-resistant sheet C6, and at least the surface portion thereof largely exceeds the melting point and is completely melted. It softens and melts. Thereafter, on the sheet discharge side of the pressure roller C1, the copy sheet PA separates from the heater H, the toner image PT naturally radiates heat, and is cooled and solidified again, and the heat-resistant sheet C6 is also separated from the copy sheet PA.

In this way, the toner image PT is once completely softened and melted, and then cooled and solidified again on the paper discharge side of the pressure roller C1, so that the toner image PT has a very large condensing force.

Next, a copying machine P incorporating the above-mentioned fixing device C will be described. In FIG. 8, P1 is a casing of the copying machine P, and P2 is an original placing table made of a transparent member such as glass provided on the upper surface of the casing P1 to reciprocate in the arrow Y direction to scan the original PA1. A lamp L for irradiation is provided above the inside of the casing P1, and the reflected light from the original PA1 irradiated by the lamp L is slit-exposed onto the photosensitive drum P4 by the short-focus small-diameter image forming element array P3. To be done. The photosensitive drum P4 rotates in the arrow direction.

Further, P5 is a charger which uniformly charges the photosensitive drum P4 coated with, for example, a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer. On the drum P4 charged by the charger P5, an electrostatic image subjected to image exposure by the imaging element array P3 is formed. This electrostatic image is visualized using a toner made of a resin or the like that softens and melts when heated by the developing device P6.

On the other hand, the copy paper PA stored in the cassette P7 is a pair of conveying rollers P9 which are rotated in pressure contact with each other in the vertical direction at a timing synchronized with the image on the feeding roller P8 and the photosensitive drum P4. Is sent onto the drum P4. The toner image formed on the photosensitive drum P4 by the transfer discharger P10 is the copy paper P.
Transcribed on A.

After this, the paper PA separated from the drum P4
Is guided to a fixing device C, which will be described later, by a transport guide P11, subjected to heat fixing processing, and then discharged onto a tray P12. After the toner image is transferred, the residual toner on the drum P4 is removed by the cleaner P13.

The fixing device C has an effective length in the direction perpendicular to the moving direction of the copy sheet PA, which corresponds to the width (length) of the maximum size sheet that can be copied by the copying machine P, that is, the width of the maximum size sheet (length). A plate-shaped heater H is arranged by extending a longer resistance heating element 2 and a feed roller C1 is provided opposite to the resistance heating element 2 so as to make a light elastic contact in the extending direction of the resistance heating element 2. Has been. Then, the unfixed toner image on the sheet PA fed between the heater H and the feed roller C1 is melted by receiving heat from the resistance heating element 2, and characters, alphanumeric characters, drawings, etc. are printed on the surface of the sheet PA. Make the duplicated image appear.

Such a copy image by the fixing device C is
The resistance heating element 2 is continuously formed in a slender shape over the length (width) of the maximum size sheet permitted by the copying machine P, a substantially uniform temperature distribution is obtained in the extending direction, and the sheet PA is entirely covered. A clear, high-quality copy with the same contrast without transfer unevenness can be obtained.

Therefore, the fixing device C and the copying machine P incorporating the fixing device C as described above can accurately and promptly detect the heat generation temperature of the heater H to adjust the temperature with high accuracy, and the substrate Since the thermocouple 5 is firmly fixed to the heater 1, the thermocouple 5 does not detach from the substrate 1 during the operation of the apparatus and the heater H does not run out of temperature, and the heater H itself or a holding member of the heater H or a copy sheet. Ignition of PA etc. can be prevented.

The present invention is not limited to the above embodiment,
For example, the material of the substrate of the plate heater is alumina (Al ₂ O
₃ ) Not limited to ceramics, other materials such as ceramics, glass, and synthetic resin members having high heat resistance such as polyimide resin may be used.

Further, the formation of the thermocouple is not limited to printing, coating a foil-shaped body or a linear body with an adhesive, and other coating means or means such as vapor deposition or sputtering. May be.

Further, the formation of the overcoat layer for covering the resistance heating element and the substrate is not essential, and the material of the glass when forming it is not limited to that of the embodiment, but may be changed depending on the heating temperature and the situation of use. It goes without saying that you can select it appropriately.

The metal material of the thermocouple constituting the temperature detecting element is not limited to copper (Cu) or nickel-copper (Ni-Cu) alloy, but platinum (Pt), constantan, alumel,
It may be silver (Ag), gold (Au), iron (Fe), chromel, or the like, and the combination of metals used for joining may be appropriately selected according to the heat generation temperature of the heater, the detection temperature, and the like.

Further, the conductive adhesive for joining the thermocouple and the wiring conductor to the substrate is not limited to the one described in the embodiment,
As the epoxy resin adhesive, product number XNR5310 manufactured by Nagase Ciba Co., Ltd., product number 8700E manufactured by Ablestech Co., Ltd., product number C manufactured by Toshiba Silicone Co., Ltd.
Silicone resin adhesives such as T262K are manufactured by Toshiba Silicone Co., Ltd., product number YE3452uB, TC
M5406, TCM5417u, TCM5418u, T
CM5428u, TCM5107, TCM5508, T
It may be CM5516u or the like.

Further, the electrically insulating and good heat conductive adhesive interposed between the substrate and the thermocouple is not limited to the adhesive described in the examples, and the product number CRM-11 manufactured by Sumitomo Bakelite Co., Ltd.
45 may be used, and its thermal conductivity is 1 × 10 ⁻⁴ to 1 ×.
If it was 10 ^-2 cal / cm · sec · ° C, there was no problem in practical use.

Further, the formation of the protective coat layer covering the thermocouple is not essential, but the material of the insulating material in the case of forming is not limited to the resin adhesive or the ceramic adhesive of the embodiment, but other adhesives may be used. The area to be covered may be broadly formed on the back surface side 1B of the thermocouple, the wiring conductor, and the periphery of the board 1 (excluding the terminal portion), but the present invention is not limited to this, and the thermocouple and this thermoelectric You may form only in the peripheral part of a pair.

Further, the configuration of the base, the pressure roller and the like to which the plate heater is mounted in the fixing device is not limited to the embodiment. Further, in the embodiment of the fixing device, the heat-resistant sheet is interposed around the base on which the plate heater is mounted for the purpose of protecting the heater and feeding the paper, but the plate heater is not limited to such indirect contact. The copying paper may directly contact the surface of the resistance heating element or the surface of the overcoat layer.

Furthermore, the fixing device of the present invention is not limited to a copying machine, but can be put into practical use by being incorporated in an image forming apparatus of various OA equipment such as a laser printer, another printer or a facsimile.

[0074]

According to the present invention having the above-mentioned structure, the temperature detecting element provided on the substrate is constituted by a thermocouple, and the thick film or foil-shaped or linear body directly printed and applied on the substrate is bonded. As a result, the heat of the board is well transmitted to the temperature sensing part of the thermocouple,
The temperature of the substrate can be detected accurately and quickly.
Further, since the protective coat layer made of an adhesive covering the entire thermocouple prevents the thermocouple from peeling off, the fixing strength can be improved. Therefore, the temperature can be adjusted with high accuracy, and the bonding strength is improved because the thermocouple is directly formed on the substrate, and the thermocouple peels off from the substrate during use, causing thermal runaway in the heater. It is possible to quickly and highly accurately detect temperature without causing problems such as the above.

[Brief description of drawings]

FIG. 1 is a top view of a plate heater of the present invention.

FIG. 2 is a bottom view of FIG.

FIG. 3 is an enlarged cross-sectional view showing the plate heater of the present invention taken along line XX in FIG.

FIG. 4 is a circuit diagram showing an embodiment of a temperature control circuit and a temperature control circuit for energizing the plate heater of the present invention to adjust the temperature.

FIG. 5 is an exploded perspective view of a thermocouple forming portion and a wiring conductor of another plate heater according to the present invention before assembly.

FIG. 6 is a perspective view showing a thermocouple forming portion and a wiring conductor of another plate heater of the present invention.

FIG. 7 is an enlarged cross-sectional view showing a fixing device according to an embodiment of the present invention.

FIG. 8 is a sectional view showing a schematic configuration of a copying machine according to an embodiment of the present invention.

FIG. 9 is an enlarged cross-sectional view showing a conventional plate heater.

10A and 10B are schematic enlarged transverse sectional views showing a conventional plate heater.

[Explanation of symbols]

 H: Plate heater 1: Substrate 1A: Front side 1B: Back side 2: Resistance heating element 3: Terminal part 4: Overcoat layer 5: Thermocouple 5a: Contact (temperature sensitive part) 6, 6A, 6B, 6E, 6F: Wiring conductor 8: Protective coating layer 9: Adhesive C: Fixing device C1: Pressure roller C5: Base P: Copy machine PA: Copy paper

Claims (8)

[Claims] 1. A substrate made of a heat-resistant and electrically insulating material;
A plate-like member comprising: a strip-shaped resistance heating element formed on the front surface side of the substrate; and a thermocouple for detecting the temperature of the resistance heating element formed on the back surface side of the substrate. heater. 2. The plate heater according to claim 1, wherein the thermocouple is formed on a substrate by printing. 3. The plate-shaped heater according to claim 1, wherein the thermocouple is formed by being attached to a substrate. 4. The plate heater according to claim 2, wherein the thermocouple is connected to a wiring conductor arranged on the substrate. 5. A protective coating layer made of a resin adhesive or a ceramic adhesive is formed so as to cover the contact portion of the thermocouple on the rear surface side of the substrate. The plate-shaped heater according to the item. 6. The plate-shaped heater according to claim 1, wherein a vitreous overcoat layer is formed to cover the resistance heating element on the surface side of the substrate. 7. A fixing device in which a pressure roller and the plate heater according to any one of claims 1 to 5 are arranged opposite to each other. 8. An image forming apparatus comprising the fixing device according to claim 6.