JPH0764418A - Heater, current-carrying method for heater, fixing device, and equipment having fixing device built in - Google Patents

Abstract

PURPOSE:To provide a heater designed to permit the appropriate temperature control, etc., without generating noise in conductor wiring. CONSTITUTION:In a heater H which comprises a longitudinal strip of resistance heating element 2 formed on one side of a substrate 1 and two streaks of wiring conductors 51, 52 on the other side of the substrate 1, for connection to a temperature detecting element 6 for detecting the temperature of the heating element 2, the two streaks of wiring conductors 51, 52 are formed in equally spaced positions on both sides of the resistance heating element 2 and in the direction of extension of the heating element 2; and a method for passing current to be carried by the heater H, a fixing device using the heater H, and equipment having the fixing device built in are described. A precise signal can be fed back to a control circuit using simple constitution without providing electrical noise to the connecting wire of the detecting element, and so precise control of temperature and the like can be made within a predetermined range, producing the effects of quality enhancement in any products that use the heater, and safety enhancement in the equipment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to one surface (front surface) of a substrate.
The present invention relates to a heater in which a resistance heating element is provided on one side and a wiring conductor for detecting temperature is provided on the other surface (back surface) side, a heater energization method, and a fixing device.

[0002]

2. Description of the Related Art In an electronic copying machine, for example, a copy sheet on which a toner image is formed is passed while being pinched between a heater and a pressure roller, and the heat of the heater heats the copy sheet to melt the toner. I am trying to fix it.

As a conventional fixing device, a heat roller in which a tubular infrared light bulb or a rod-shaped heater is arranged at the center of a hollow roller is used, and at least one of a pair of upper and lower rollers is pressed as this heat roller. There is a heat roller fixing method in which a toner image is melted and fixed by passing an unfixed copy paper between the roller and the roller.

This heat roller fixing method involves heating a copy sheet indirectly through a roller from a heater, and therefore it takes a long time to start, and it requires preheating and consumes a large amount of electric power. In addition, when the temperature of the toner is not fixed within a predetermined temperature range, the toner is not fused, and when the temperature is low, the toner may be peeled off and the image may be mottled.

Therefore, the fixing device detects the temperature of the heat roller and adjusts the electric power to the electric bulb and the heater.
However, in the case of this method, since the temperature is transmitted from the heat source to the heat roller through a plurality of steps, the reaction is slow and it takes a long time until the temperature is adjusted, so that good quality copying cannot be performed in some cases.

Therefore, instead of the heat roller fixing method, a plate heater fixing method has been developed and put into practical use. The heater H used for the fixing method of this plate heater
Is, for example, as shown in FIG. 1 and FIG.
1 ₂ O ₃ ) ceramics or the like has a flat surface, a curved surface, or an inclined surface, on one surface (surface) 11 of the heat-resistant and electrically insulating substrate 1 having an elongated shape, a silver-palladium alloy (Ag
/ Pd) A paste in which powder or the like is mixed with water glass (inorganic binder) and a water-soluble organic binder is applied by printing and fired to form an elongated strip-shaped resistance heating element 2. The both ends are made wide and a film made of a good conductor such as silver (Ag) is formed on this portion to form the electrode parts 3 and 3. Further, the surface of the resistance heating element 2 is covered with a vitreous overcoat layer 4. There is. In addition, the other surface (back surface) 12 of this substrate 1
A two-row wiring conductor 51, 52 formed by applying a material having a low electric resistance, for example, a metal paste such as silver (Ag) in a thick film form, drying and firing it is provided between the conductors 51, 52. Is provided with a temperature detecting element 6 such as a thermistor.

A pressure roller (not shown) is a roller having a rotary shaft parallel to the heater, and its surface is made of a heat-resistant elastic material so that it can be rotated while lightly contacting the overcoat layer of the heater. Has become. Then, when the copy sheet is supplied between the heater and the pressure roller, the copy sheet is conveyed while sliding on the surface of the overcoat layer of the heater by the rotation of the pressure roller, and the heat of the heater causes the copy sheet to move on the copy sheet. The toner is heated and melted and fixed.

The plate-shaped heater H having such a structure is used, for example, by connecting it to the circuit shown in FIG. 5, and the resistance heating element 2 receives a phase-controlled alternating current and the temperature detecting element 6 receives a direct current. It is energized. This heater H has both electrode parts 3,
When electricity is applied for 3 times, the resistance heating element 2 generates heat and the temperature rises. The temperature adjustment is performed by detecting the heat generation temperature of the resistance heating element 2 by a temperature detection element 6 such as a thermistor provided on the other surface (back surface) 12 of the substrate 1, and through the wiring conductors 51 and 52, the control circuit T. It is fed back to and checked whether it is within the predetermined temperature range.If the temperature is out of the set temperature, the power is adjusted by the phase control so that it is within the set temperature range. To The above thermistor uses a semiconductor having a large negative temperature coefficient of electric resistance. When the temperature of the thermistor absorbs infrared energy and the temperature rises, the resistance value changes greatly, and the heat of the infrared ray becomes the resistance of the conductor. It is a sensor that consists of a thermal type detection element that converts the magnitude of the value to measure the intensity of infrared rays.

The features of this thermal type detection element are that the detection sensitivity is substantially constant regardless of the wavelength of the incident light, that it can be used at room temperature during operation, that it is easy to make, and that it is inexpensive.

Further, since the thermistor must receive the heat radiation to raise the temperature of the element and reduce the resistance value, the thinner the film thickness and the smaller the heat capacity, the better the sensitivity and response. In such a configuration, the temperature often goes out of the set range recently, and various investigations have been made into the cause thereof. As a result, as shown in FIG. 10, electric force lines generated from the resistance heating element 2 to which phase-controlled AC is supplied. It was found that P causes electromotive force to be generated in the wiring conductors 51 and 52 on the back surface 12 side of the substrate 1.

This is because the wiring conductor connected to the thermistor is asymmetrical due to the arrangement relationship of the electrodes provided for connecting to the external control circuit T, so that one of the wiring conductors 51 is close to the resistance heating element 2. (Distance A), the other 52 is formed distant (distance B) and unequal distance (A ≠ B), the magnitude of the current induced in the wiring conductors 51 and 52 is different, and the current corresponding to this difference is the wiring conductor. The noise enters 51 and 52 to generate noise, which causes the control circuit T for temperature control to malfunction.

FIG. 6A shows the magnitude of noise,
(1) is a phase-controlled AC current waveform supplied to both ends of the resistance heating element 2, and (2) is a line of electric force P generated from the resistance heating element 2 on the wiring conductor 52 distant from the resistance heating element 2.
The alternating current waveform of the current generated by (3) is the alternating current waveform of the current generated by the electric force line P generated from the resistance heating element 2 in the wiring conductor 51 adjacent to the resistance heating element 2, and (4) is the above ( It is an alternating current waveform in the state where the currents generated in 2) and (3) are superimposed.

That is, as shown in FIG. 10, the wiring conductors 51 and 52 are centered on the resistance heating element 4 in which an alternating current is applied and the electric force lines P are generated. When formed, the wave height of the waveform due to the lines of electric force P generated in the resistance heating element 2 to which an alternating current is applied is increased like the current waveform shown in (4), and the wiring conductor 51 in which a direct current flows, There is a case where AC noise is input to 52 and a control circuit connected to the wiring conductors 51 and 52 malfunctions and a predetermined output adjustment is not performed.

[0014]

SUMMARY OF THE INVENTION The present invention eliminates the above problems and provides a wiring conductor for connecting a temperature detecting element such as a thermistor on the back side of a substrate on which a band-shaped resistance heating element through which an alternating current flows is formed. It is an object of the present invention to provide a heater having a structure capable of performing proper temperature adjustment and the like in the formed heater without generating noise in the conductor wiring.

[0015]

A heater according to claim 1 of the present invention is one in which a strip-shaped resistance heating element is formed in the longitudinal direction on one surface side of a substrate made of an electrically insulating material and the other surface side of this substrate is formed. In a heater comprising two wire conductors for energizing a temperature detecting element for detecting the temperature of the heating element, the two wire conductors are arranged along the extending direction of the resistance heating element and on both sides of the heating element as a center. It is characterized in that it is formed at positions at equal intervals.

According to a second aspect of the present invention, the heater energization method is characterized in that AC power is supplied to the resistance heating element.

A fixing device according to a third aspect of the present invention is characterized in that the heater and the pressure roller according to the first aspect are arranged to face each other.

A fixing device incorporating apparatus according to a fourth aspect of the present invention is characterized in that the fixing device according to the third aspect is incorporated.

[0019]

Since the pair of wiring conductors are arranged at substantially equal distances with respect to the strip-shaped resistance heating element, noise does not occur in the conductor wiring.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the heater of the present invention will be described below with reference to FIGS. 1 is a plan view in which a middle portion of the heater H is cut away, FIG. 2 is a rear view of the heater H in FIG. 1, and FIG. 3 is an enlarged cross-sectional side view of a portion cut along a line XX in FIG. FIG. 4 is an explanatory view of the action of the heater H, and FIG. 5 is the heater H.
6B is an explanatory diagram of the control circuit T, and FIG. 6B is an explanatory diagram of a current waveform of the heater H. In the figure, reference numeral 1 is an elongated substrate made of a heat-resistant and electrically insulating material such as alumina (Al ₂ O ₃ ) ceramics and having a length of about 300 mm, a width of about 10 mm and a thickness of about 1 mm. 2 is one surface (front surface) of the substrate 1
The resistance heating elements 3 and 3 mainly formed of a silver-palladium alloy having a length of about 230 mm, a width of about 2 mm, and a thickness of about 10 μm, which are formed along the longitudinal direction, are connected to both ends of the resistance heating element 2. Approximately 25 in length made of formed material such as silver (Ag)
A wide electrode portion having a width of 7 mm and a width of about 7 mm.

Reference numeral 4 is a vitreous overcoat layer which covers and protects the entire surface of the resistance heating element 2 and a part of the electrode portions 3, 3.

On the other surface (back surface) 12 side of the substrate 1, two wire conductors 51 and 52 made of a material such as silver (Ag) similar to the electrode portion 3 and having a width of about 1 mm and a length of about 50 mm are provided. Wide electrode portions 53 and 54 of about 3 mm × about 3 mm square are formed continuously with the conductors 51 and 52. The two wire conductors 51, 52 are arranged along the extending direction of the heating element 2 with the resistance heating element 2 formed on the one surface (front surface) 11 side of the substrate 1 as a center, and are spaced at equal intervals on both sides. It is formed with.

A temperature detecting element 6 such as a thermistor is provided on the wiring conductors 51 and 52 with silver / palladium (Ag /
Pd) alloy powder or the like is bonded via a conductive adhesive 7 in which water glass (inorganic binder) or a water-soluble organic binder is mixed. The thermistor that constitutes the temperature detecting element 6 is an oxide (MnO ₂ , Co ₃ O ₄ , NiO) of manganese, cobalt, nickel or the like on the central portion of a plate-shaped substrate 61 made of alumina (Al ₂ O ₃ ) ceramics. A temperature sensitive portion 62 formed of a thin film formed by mixing is formed, and an electrode portion 63 formed of a platinum (Pt) layer or the like is connected to the temperature sensitive portion 62 on the base 61 at both ends of the temperature sensitive portion 62. , 64 are formed. (Note that each of the above-mentioned films is a thin film, but is exaggeratedly drawn in the drawing.) Further, the heater H is manufactured as follows.
First, a powder of silver-palladium alloy (Ag / Pd) or a metal (Ag / Pd + RuO ₂ ) obtained by adding ruthenium oxide to this, water glass (inorganic binder), and a water-soluble organic binder are kneaded with water. Prepare the conductive paste paint. Then, this paste paint is applied by printing on one surface (front surface) 11 of the elongated substrate 1, dried, and then baked at about 850 ° C. for about 10 minutes. By this firing, the residual water contained in the paint is scattered, then the organic binder is decomposed and gasified and scattered, and finally the water glass is dehydrated and becomes vitreous, and as a result, the silver / baladium powder Becomes a thin film and becomes vitreous on one surface (front surface) 11 of the substrate 1 and is firmly bound to form the resistance heating element 2.

Next, the contact electric resistance is smaller than that of the resistance heating element 2 at the end portions of the resistance heating element 2 and the other surface (rear surface) 12 of the substrate 1 in a key shape. Materials such as silver (Ag), silver-platinum alloy (Ag)
/ Pt), gold (Au), platinum (Pt), or the like is applied in a thick film form, dried and baked to form the electrode parts 3, 3, 53, 54 and the wiring conductors 51, 52.

After this, the strip-shaped resistance heating element 2 portion,
A glassy overcoat layer 4 is formed on the electrode portions 3 and 3 and the surface 11 of the substrate 1 which are connected to the strip portion. This overcoat layer 4 is formed by using PbO (55-85 Wt%)-B ₂ O ₃ (5) containing lead oxide (PbO) as a main component.
〜15Wt%)-SiO ₂ (10-30Wt%) glass powder is kneaded with nitrocellulose (organic binder) in an organic solvent. To form a continuous coating film. Then, after drying, it is baked at about 700 ° C. for about 8 minutes to form a glass layer having a thickness of 15 μm to 30 μm.

This glass has a melting point of about 600 ° C. and is lower than the firing temperature of the paste-like coating material constituting the resistance heating element 2, and the glass paste is used to cover the surface 11 of the substrate 1 including the strip-shaped portion of the resistance heating element 2. It is applied to the part to be coated in the longitudinal direction, dried, and then baked.

The plate-shaped heater H having such a structure is used, for example, by connecting it to the circuit shown in FIG. 5 as described above, and the resistance heating element 2 receives a phase-controlled alternating current,
Direct current is supplied to the thermistor which is the temperature detecting element 6. When the heater H is energized between the electrode portions 3 and 3, the resistance heating element 2 generates heat and the temperature rises. This resistance heating element 2
Due to the heat generation of the substrate 1, the substrate 1 is also subjected to heat conduction and its temperature rises, and this heat is transmitted to the temperature sensing portion 62 at the center of the thermistor 6 attached to the back surface 12 side of the substrate 1 and the resistance value of the temperature sensing portion 62 is changed. Let The change in the resistance value of the temperature sensing portion 62 is controlled by the wiring conductor 51,
It is output from the electrode parts 53 and 54 via 52 and fed back to the temperature control circuit T to check whether it is within a predetermined temperature range. If the temperature is out of the set temperature, By adjusting the power by phase control,
Make sure that it is within the set temperature range.

Of course, also in such a structure, the magnetic field lines are generated in the resistance heating element 2 to which an alternating current is applied, and electric lines of force P are generated. Since the two wire conductors 51 and 52 are arranged substantially parallel to each other on the 12 side with an equalization distance (C = D), the direction of the magnetic force lines exerted between the two wire conductors 51 and 52 is as shown in FIG.
As shown in (2) and (3) shown in (b), they are in opposite directions,
The overlapping ones cancel each other out, and both wiring conductors 5
No noise is generated in Nos. 1 and 52 and no malfunction occurs in the temperature control circuit, and the temperature can be adjusted accurately within a predetermined range.

7 and 8 show an example of a fixing device such as a copying machine or a facsimile in which the heater H is incorporated. In FIG. 7 and FIG. 8, the heater H portion is the same as that of the above embodiment, so that the same portions are the same. And the description thereof will be omitted. R
Is a pressure roller, and a heat-resistant elastic material such as silicone rubber 83 is fitted on the surface of a cylindrical roller body 82 having rotary shafts 81 protruding from both ends. The fixing heater H is juxtaposed to face the rotary shaft 81 of the pressure roller R, and the silicone rubber 83 is used as the resistance heating element 2 of the heater H.
It is lightly in contact with the surface of the overcoat layer 4 directly above.
Reference numeral 9 is a connector made of phosphor bronze plate and the like, which is provided with elasticity, and contacts the electrode portions 3 and 3 of the heater H to supply power to the heater H. Further, PA indicates a copy sheet.

The copying machine is used, for example, at a commercial voltage of 100V, and the heater H is energized with the phase thereof controlled by the circuit shown in FIG. Similarly to the above, the heater H presses the copy paper PA between the silicone rubber 83 and the surface of the overcoat layer 4 of the resistance heating element 2 which is energized through the electrode parts 3 and 3 and heats up to a rated temperature of about 200 ° C. The rotation of the pressure roller R conveys the copy sheet PA in the direction of the arrow, and the toner adhering to the copy sheet PA is heated and melted and fixed. In such a fixing device, noise is not included in a signal from the thermistor 6 which is a temperature detecting element formed in the heater H, and electric power to the resistance heating element 2 can be accurately controlled, so that copying is performed within a predetermined temperature range. It is possible to fix the toner on the paper P, and it is possible to prevent uneven fixing on the copy image, peeling of the toner, and discoloration of the paper PA.

The present invention is not limited to the above embodiment. For example, the material of the substrate that forms the resistance heating element and the substrate that forms the thermistor that is the temperature detection element is not limited to alumina ceramics, but other ceramics, glass, synthetic resin members with high heat resistance such as polyimide resin, etc. Good. Further, the temperature detection element attached to the wiring conductor is not limited to the thermistor, and may be another detection element.

Further, the resistance heating element is not limited to the above-mentioned silver-palladium alloy (Ag / Pd) type, but may be a PTC (positive temperature characteristic element) or the like. Further, the material forming the wiring conductor and the wiring pattern are not limited to those in the embodiment. For example, the wiring conductor is not a linear pattern centered on the resistance heating element, but is symmetrically spaced about the resistance heating element. Even if the width becomes wider or narrower, it does not matter because it will electrically cancel. The formation of the electrode part is not limited to the part of the embodiment, but may be another part of the substrate.

Further, the supply of electric power to the resistance heating element may be controlled by changing the current or voltage in addition to the phase control, and the electricity supplied to the detecting element through the wiring conductor is not limited to direct current but may be alternating current. It is applicable and is possible because the power supplied to the heating element is higher than that of the detection element.

Further, in the above embodiment, the silver-palladium alloy (Ag / Pd) type conductive adhesive is described.
If the allowable temperature of a detection target such as a heater is low, a conductive adhesive made of another material may be used.

Further, in the above embodiment, the glassy overcoat layer is formed on the resistance heating element and the substrate, but the overcoat layer is not essential, and when it is formed, the material is the same as that of the embodiment. Not exclusively.

Further, in the above-mentioned embodiment, the power supply to the resistance heating element is performed by the elastic connector, but the present invention is not limited to this, and a lead wire may be directly connected to the electrode layer.

Furthermore, the heater of the present invention is not limited to fixing of office automation equipment such as copying machines and facsimiles, but also to equipment incorporating fixing devices of other fields such as various industrial manufacturing facilities and household equipment. Is also practical.

[0038]

According to the present invention having the above-mentioned structure, when controlling the resistance heating element by using the detecting element, an electric noise is not given to the connecting wiring of the detecting element, and an accurate signal can be obtained with a simple structure. Can be fed back to the control circuit,
The temperature and the like can be appropriately controlled within a predetermined range, and the product using the heater has an effect of improving quality and the device can improve safety.

[Brief description of drawings]

FIG. 1 is a plan view in which a middle portion of a heater showing an embodiment of the present invention is cut away.

FIG. 2 is a rear view of the heater H shown in FIG.

FIG. 3 is an enlarged cross-sectional side view of a portion cut along line XX in FIG.

FIG. 4 is an explanatory view of the operation of the heater according to the present invention.

FIG. 5 is an explanatory diagram of a heater and a control circuit.

FIG. 6 is an explanatory diagram of a current waveform of a heater.

FIG. 7 is a partially sectional front view showing an embodiment of the fixing device of the present invention.

FIG. 8 is a cross-sectional view of a portion cut along the line VV in FIG.

FIG. 9 is a rear view showing a notched intermediate portion of a conventional heater.

FIG. 10 is an explanatory view of the operation of a conventional heater.

[Explanation of symbols]

 H: Heater R: Pressure roller 1: Substrate 11: One surface (front surface) 12: Other surface (back surface) 2: Resistance heating element 3, 53, 54: Electrode portion 51, 52: Wiring conductor 6: Temperature detection element (thermistor) )

Claims (4)

[Claims] 1. A strip-shaped resistance heating element is formed on one surface of a substrate made of an electrically insulating material in the longitudinal direction, and a temperature detecting element for detecting the temperature of the heating element is energized on the other surface of the substrate. In the heater having the wiring conductor formed as described above, the two wiring conductors are formed along the extending direction of the resistance heating element and at equal intervals on both sides of the heating element. 2. A method of energizing a heater, characterized in that AC electric power is supplied to a resistance heating element of the heater. 3. A fixing device in which the heater and the pressure roller according to claim 1 are arranged opposite to each other. 4. An apparatus incorporating a fixing device, wherein the fixing device according to claim 3 is incorporated.