JPH10302934A - Heating element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating element capable of highly precise temperature control which is used for a plane paper copying machine, a laser beam printer or a toner fixing device by using a thick film NTC thermister as a thermister. SOLUTION: A thick film NTC thermister 26 is provided between a pair of thermister electrodes 25 and electrically connected to the thermister electrodes 25. The thermister 26 is formed by adding boro-silicate lead glass and metal component with a low specific resistance or metal oxide additive to either Mn, Co, Ni or Mn, Co, Cu. In this way, the thermister constant of the thick film NTC thermister 26 is no less than 3000 Kelvin and so a resistance value is greatly changed with a temperature change in operation. As a result, a well sensitive heating element can be obtained. Connection between the thermister electrodes is made by a wide connection to allow the heating element to be easily manufactured without projections.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating element used for a toner fixing device such as a plain paper copy machine and a laser beam printer.

[0002]

2. Description of the Related Art A conventional heating element is disclosed in JP-A-8-18096.
Japanese Unexamined Patent Application Publication No. 1 (KOKAI) No. 1 is known.

[0003] A conventional heating element will be described below with reference to the drawings. FIG. 10 is a sectional view of a conventional heating element. In FIG. 10, reference numeral 1 denotes an alumina substrate. A pair of electrodes (not shown) are provided at both ends of the upper surface of the substrate 1. Reference numeral 2 denotes a long resistive film provided between a pair of electrodes and electrically connected to the electrodes. 3
Is a protective layer made of a lead borosilicate-based material provided so as to cover the upper surface of the resistive film 2 of the substrate 1. Reference numeral 4 denotes a thick film P made of a RuO ₂ -Au material provided on the lower surface of the substrate 1 by a thick film.
It is a TC thermistor. Reference numeral 5 denotes a Pd-Ag-based thermistor electrode portion electrically connected to the thick-film PTC thermistor 4. Reference numeral 6 denotes a thermistor protective layer made of a lead borosilicate-based material provided so as to cover the upper surfaces of the thick-film PTC thermistor 4 and the thermistor electrode portion 5.

[0004] A method of manufacturing the conventional heating element configured as described above will be described below. First, a strip-shaped alumina substrate 1 is prepared, and a resistive film 2 is printed, fired, and fixed on the upper surface of the alumina substrate 1. Next, Pd
-Screen printing of an Ag-based electrode on the upper surface of the substrate 1;
Baking at 50 ° C. for 10 minutes, and baking on the substrate 1. next,
A thick film PT is formed on the lower surface of the substrate 1 facing the resistance film 2 of the substrate 1.
After printing the C thermistor 4 and the thermistor electrode portion 5, the film is baked at 850 ° C. for 10 minutes to form the thick-film PTC thermistor 4 and the thermistor electrode portion 5. Next, the lead borosilicate-based protective layer 3 and the thermistor protective layer 6 are baked at 550 ° C. for 5 minutes on the upper and lower surfaces of the substrate 1, respectively.

The operation of the conventional heating element configured as described above will be described below. The toner is heated and fixed on the recording material 7 fed by the feed roller 8. At this time, the temperature instantly detected by the thick-film PTC thermistor 4 is fed back to the resistance coating 2 by a control circuit, and the heating temperature is fixed. Will be controlled.

Here, the relationship between the resistance of the thermistor and the temperature is basically expressed by the following equation. _{R = R 0 expB (1 /} T-1 / T 0) R: absolute temperature T resistance of the thermistor in (K) R _0: resistance value of the thermistor at an absolute temperature T ₀ (K) B: Thermistor constant or, thermistors The larger the constant B is,
Since the change in the resistance value with respect to the temperature change of the thermistor increases, a heating element with high sensitivity can be provided.

[0007]

In the above-mentioned conventional structure, the change in the resistance value with respect to the temperature change is relatively small because the thermistor constant of the thick-film PTC thermistor is several hundred Kelvin or less. Therefore, there is a problem that high-precision temperature control cannot be performed.

An object of the present invention is to solve the above conventional problems and to provide a heating element capable of controlling the temperature with high accuracy.

[0009]

In order to achieve the above object, a heating element according to the present invention has a thermistor as a thick-film NTC thermistor. Here, the thermistor constant of the thick-film NTC thermistor is 3000 Kelvin or more.

According to the present invention, a heating element capable of controlling the temperature with high accuracy can be obtained.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a substrate, a pair of electrodes provided at both ends of an upper surface of the substrate, and a pair of electrodes provided between the pair of electrodes and electrically connected to the electrodes. A protective layer provided so as to cover the upper surface of the resistive film of the substrate, a pair of thermistor electrode portions having a connection portion provided on the lower surface of the substrate, and a pair of thermistor electrode portions. A thick-film NTC thermistor provided therebetween and electrically connected to the thermistor electrode portion; and a thermistor protection layer provided so as to cover the thick-film NTC thermistor. , Ni or any one of Mn, Co, and Cu to which a lead borosilicate glass and an additive of a metal component or metal oxide having a low specific resistance are added. Since the thermistor constant of the NTC thermistor is a 3000 Kelvin or more, as it has the effect that the change in resistance with respect to temperature change is large.

According to a second aspect of the present invention, a substrate, a pair of electrodes provided at both ends of an upper surface of the substrate, and a pair of electrodes provided between the pair of electrodes and electrically connected to the electrodes are provided. A resistance film, a pair of thermistor electrode portions having connection portions arranged in parallel with the resistance film on the upper surface of the substrate, and provided between the pair of thermistor electrode portions and electrically connected to the thermistor electrode portion. Thick-film NTC thermistor connected to the resistance film and thick-film NTC
A thick-film NTC thermistor, wherein one of Mn, Co, Ni or Mn, Co, Cu is provided with a lead borosilicate glass and a low resistivity metal. It is made of a material to which a component or an additive of a metal oxide is added, and has an effect that a change in resistance value with respect to a temperature change is large.

[0013] The invention according to claim 3 is the invention according to claim 1 or 2.
In the invention described in the above, the thick-film NTC thermistor is electrically connected between the wide connecting portions of the thermistor electrode portion. The film NTC thermistor is electrically connected to a pair of thermistor electrode portions by sandwiching it between opposing connection portions of the pair of thermistor electrode portions. A thermistor is electrically connected to opposing comb-shaped connecting portions of a pair of thermistor electrode portions, and these are made of a thick film NTC.
This has the effect that the resistance value of the thermistor can be reduced.

Hereinafter, a heating element according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1 is a cross-sectional view of a heating element according to Embodiment 1 of the present invention. In FIG.
Reference numeral 21 denotes a ceramic substrate formed of a rectangular parallelepiped thin plate. Reference numeral 22 denotes a pair of Ag-based electrodes provided at both ends of the upper surface of the substrate 21. Reference numeral 23 denotes a long resistive film made of a conductive material such as RuO ₂ and provided between the pair of electrodes 22 and electrically connected to the electrodes 22. 2
Reference numeral 4 denotes a glass or Teflon protective layer provided so as to cover at least the upper surface of the resistive film 23 of the substrate 21. 25
Are a pair of Ag-based thermistor electrode portions provided from both ends of the lower surface of the substrate 21 toward the center. Reference numeral 26 denotes a thick-film NTC thermistor provided between the pair of thermistor electrode portions and electrically connected to the thermistor electrode portion 25. One of Mn, Co, Ni or Mn, Co, Cu is provided with borosilicate. It is composed of a material to which a lead-based glass and an additive of a metal component or metal oxide having a low specific resistance are added. Reference numeral 27 denotes a glass or Teflon thermistor protection layer provided so as to cover at least the thick film NTC thermistor 26. The thick-film NTC thermistor 26 is made of a material obtained by adding an additive of lead borosilicate glass and a low specific resistance metal component or metal oxide to either Mn, Co, Ni or Mn, Co, Cu. Therefore, the effect of increasing the thermistor constant B is obtained.

FIG. 2 is a process chart showing a method of manufacturing a heating element according to Embodiment 1 of the present invention. First, a ceramic substrate 21 is prepared as shown in FIG. 2A, and a pair of electrodes 22 shown in FIG. 2B are printed on both ends of the upper surface of the substrate 21 by a screen printing method. Bake for 1 hour. Next, as shown in FIG. 2C, a pair of thermistor electrode portions 25 are printed on the lower surface of the substrate 21 by a screen printing method, and baked at about 850 ° C. for about 1 hour.

Next, as shown in FIG.
A resistive film 23 made of a thick film such as RuO ₂ is formed by screen printing so as to be electrically connected to the electrode 22 on the upper surface of the substrate, and then baked at about 850 ° C. for about 1 hour. Next, as shown in FIG. 2E, a thick-film NTC thermistor 26 is printed by a screen printing method so as to be electrically connected to the thermistor electrode portion 25 provided on the back surface of the substrate 21.
Bake for about 1 hour before and after.

Here, as shown in FIG. 3, the connection between the thermistor electrode section 25 and the thick-film NTC thermistor 26 is made by a wide connection section 28 of the thermistor electrode section 25. Therefore, even if the printing of the thick-film NTC thermistor 26 is shifted, the thick-film NTC thermistor 26 has an effect of significantly reducing the protrusion from the wide connecting portion 28 of the thermistor electrode portion 25.
Next, as shown in FIG. 2F, the thermistor protection layer 2 is formed so as to cover the thick NTC thermistor 26 on the lower surface of the substrate 21.
7 is printed by a screen printing method and baked at about 850 ° C. for about 1 hour. Finally, as shown in FIG.
The protective layer 24 covers the resistive film 23 on the upper surface of the substrate 21.
Is printed by a screen printing method and baked at about 850 ° C. for about 1 hour. And since the thick-film NTC thermistor 26 is printed by the screen printing method, it has the effect of not requiring expensive equipment such as sputtering.

The operation of the heating element constructed and assembled as described above will be described below. FIG. 4 is a diagram showing a state in which the heating element according to Embodiment 1 of the present invention is mounted on a fixing device of a copying machine. In FIG. 4, the electrode 2 of the substrate 21
2 (not shown), the resistive film 23 generates heat when supplied with electricity from the outside.

Next, heat generated by the resistive film 23 is transmitted to the protective layer 24. At this time, the temperature of the protective layer 24 is controlled by the thick-film NTC thermistor 2 provided on the back surface of the substrate 21 through the substrate 21.
6 and input as a voltage change by a temperature control unit or the like (not shown) separately provided in the copying machine body. On the other hand, the toner fixing device has a cylindrical insertion film 3.
1 and the pressure roller 32 are rotated, and the paper 33 sandwiched is moved onto the protective layer 24 of the heating element. Here, the toner 34 is previously applied on the upper surface of the paper 33.
Therefore, when the paper 33 passes over the upper surface of the protective layer 24 via the insertion film 31, the toner 34 on the paper 33 is melted by heat and fixed on the paper 33.

In the heating element according to the first embodiment of the present invention, the connection between the thermistor electrode portion 25 and the thick-film NTC thermistor 26 is made by a wide connection portion 28 of the thermistor electrode portion 25. However, as shown in FIGS. 5 and 6, a thick film N is provided between the pair of thermistor electrode portions 41.
The TC thermistor 42 may be sandwiched three-dimensionally. In such a case, the resistance value of the thick-film NTC thermistor 42 can be controlled by the film thickness, so that the resistance value of the thick-film NTC thermistor 42 can be easily reduced.

As shown in FIG. 7, the connecting portion between the thermistor electrode portion 51 and the thick-film NTC thermistor 52 may be a comb-shaped connecting portion 53. In such a case, since the thick-film NTC thermistor 52 is connected in parallel to the thermistor electrode 51, the resistance value of the thick-film NTC thermistor can be easily reduced.

Embodiment 2 Hereinafter, a heating element according to Embodiment 2 of the present invention will be described with reference to the drawings.

FIG. 8 is a top view of a heating element according to Embodiment 2 of the present invention, and FIG. 9 is a process chart showing a method of manufacturing the heating element.

In FIG. 8, reference numeral 71 denotes a ceramic substrate. Reference numeral 72 denotes a pair of Ag-based electrodes provided at both ends of the upper surface of the substrate 71. Reference numeral 73 denotes a long resistive film made of a conductive material such as RuO ₂ and provided between the pair of electrodes 72 and electrically connected to the electrodes 72. 74
And a pair of Ag-based thermistor electrode portions provided on the upper surface of the substrate 71 in a position close to the resistance film 73. A thick film NTC 75 is provided between the pair of thermistor electrode portions 74 and is electrically connected to the thermistor electrode portion 74.
A thermistor, Mn, Co, Ni or Mn, C
It is made of a material in which either one of o and Cu is added with a lead borosilicate glass and a low specific resistance metal component or metal oxide additive. Reference numeral 76 denotes a glass or Teflon protective layer provided so as to cover the resistance film 73 and the thick-film NTC thermistor 75 on the substrate 71. Then, the thick-film NTC thermistor 75 is formed by adding an additive of lead borosilicate glass and a metal component or metal oxide of low specific resistance to either Mn, Co, Ni or Mn, Co, Cu. Therefore, the thermistor constant B has an effect of increasing to 3000 or more.

The method of manufacturing the heating element according to the second embodiment of the present invention configured as described above will be described below with reference to the drawings.

FIG. 9 is a process chart showing a method of manufacturing a heating element according to Embodiment 2 of the present invention.

First, as shown in FIG. 9A, a plate-like ceramic substrate 71 is prepared. Next, as shown in FIG. 9B, a pair of electrodes 72 are printed on both ends of the upper surface of the substrate 71 by a screen printing method, and baked at about 850 ° C. for about 1 hour. Next, as shown in FIG. 9C, a pair of thermistor electrode portions 74 for the thermistor are printed on the upper surface of the substrate 71 by a screen printing method, and baked at about 850 ° C. for about 1 hour. Next, as shown in FIG.
Then, a thick resistive film 73 is formed by a screen printing method so as to be electrically connected to No. 2 and then baked at about 850 ° C. for about 1 hour. Next, as shown in FIG. 9E, a thick-film NTC thermistor 75 is printed by a screen printing method so as to be electrically connected to the thermistor electrode portion 74 provided on the upper surface of the substrate 71. Bake for hours. Finally, as shown in FIG. 9F, the thick resistive film 73 and the thick film N
The protective layer 76 is printed by a screen printing method so as to cover the TC thermistor 75, and baked at about 850 ° C. for about 1 hour.

The operation of the heating element according to the second embodiment is basically the same as that of the heating element according to the first embodiment, and a detailed description of the operation will be omitted.

[0030]

As described above, the material component of the thick-film NTC thermistor of the heating element according to the present invention is one of Mn, Co, Ni or Mn, Co, Cu, lead borosilicate glass and low resistivity. By adding a metal component or a metal oxide additive, the thermistor constant B becomes 30
Since it is not less than 00 Kelvin, there is an effect that a heating element with good sensitivity can be provided.

Further, the connection between the thermistor electrode portion and the thick-film NTC thermistor is made by a wide connection portion of the thermistor electrode portion. Since it does not protrude from a wide connection portion, it has an effect that a heating element that can be easily manufactured can be provided.

Further, by forming the thick-film NTC thermistor three-dimensionally between a pair of thermistor electrodes, the resistance value of the thick-film NTC thermistor can be controlled by the thickness of the thick-film NTC thermistor. In addition, a heating element having a low resistance value of the thick-film NTC thermistor can be provided.

Further, since the connection between the thermistor electrode portion and the thick-film NTC thermistor is a comb-shaped connection portion, the thick-film NTC thermistor is connected in parallel to the thermistor electrode portion. This has the effect of providing a heating element having a low resistance value of the NTC thermistor.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a heating element according to Embodiment 1 of the present invention.

FIG. 2 is a process chart showing a method for manufacturing the heating element.

FIG. 3 is a top view showing a connection state between a thermistor electrode portion and a thick-film NTC thermistor, which are the main components.

FIG. 4 is a diagram in which the heating element is mounted on a toner fixing device of a copying machine.

FIG. 5 is a cross-sectional view showing another example of the connection state between the thermistor electrode portion and the thick-film NTC thermistor, which are the main components.

FIG. 6 is a top view showing another example of the connection state between the thermistor electrode part and the thick-film NTC thermistor, which are the main parts.

FIG. 7 is a top view showing another example of the connection state between the thermistor electrode part and the thick-film NTC thermistor, which are the main parts.

FIG. 8 is a top view of a heating element according to Embodiment 2 of the present invention.

FIG. 9 is a process chart showing a method for manufacturing the heating element.

FIG. 10 is a sectional view of a conventional heating element.

[Explanation of symbols]

 21, 71 Substrate 22, 72 Electrode 23, 73 Resistive film 24, 76 Protective layer 25, 41, 51, 74 Thermistor electrode part 26, 42, 52, 75 Thick NTC thermistor 27 Thermistor protective layer 28 Wide connection part 53 Comb shape Connection

Claims (5)

[Claims] A substrate, a pair of electrodes provided at both ends of an upper surface of the substrate, a resistive film provided between the pair of electrodes and electrically connected to the electrodes, and a resistive film of the substrate. A protective layer provided to cover the upper surface, a pair of thermistor electrode portions having a connection portion provided on the lower surface of the substrate, and provided between the pair of thermistor electrode portions and electrically connected to the thermistor electrode portion; Thick film N
A TC thermistor; and a thermistor protection layer provided so as to cover the thick-film NTC thermistor.
The thermistor is Mn, Co, Ni or Mn, Co, C
A heating element comprising a material obtained by adding a lead borosilicate glass and an additive of a metal component or metal oxide having a low specific resistance to either one of u. 2. A substrate, a pair of electrodes provided at both ends of an upper surface of the substrate, a resistive film provided between the pair of electrodes and electrically connected to the electrodes, and A pair of thermistor electrode portions having a connection portion juxtaposed in parallel with the resistance film, a thick-film NTC thermistor provided between the pair of thermistor electrode portions and electrically connected to the thermistor electrode portion; A protective layer provided so as to cover the resistance film and the thick-film NTC thermistor;
A heating element made by adding any one of o, Ni or Mn, Co, and Cu to a lead borosilicate glass and a low specific resistance metal component or metal oxide additive. 3. The heating element according to claim 1, wherein the thick-film NTC thermistor is electrically connected between wide connecting portions of the pair of thermistor electrode portions. 4. The heating element according to claim 1, wherein said thick-film NTC thermistor is sandwiched between said connecting portions of said pair of said thermistor electrode portions and electrically connected thereto. 5. The heating element according to claim 1, wherein the thick-film NTC thermistor is electrically connected to opposing comb-shaped connecting portions of the pair of thermistor electrode portions.