JPH0521135A - Ceramic heater - Google Patents

Abstract

PURPOSE:To enhance sensitivity in temperature detection by providing a heat sensing member just on the back of a heater, and concurrently providing a circuit pattern for the back face of a substrate in such a way that the heat sensing member is being avoided. CONSTITUTION:Since a heat sensing member 5 is so specified in place that the member 5 is disposed in such a way that a circuit pattern 6 is being avoided, the member 5 becomes closest in temperature to a heater 2, and sensitivity in temperature detection is thereby enhanced, so that delay in the action of the member 5 and overshoot due to dislocation in detected temperature hardly take place. A terminal 8 is subjected to pressing force and twisting force due to the stiffness of wires at the time of wiring, and the terminal is thereby repeatedly expanded and contracted due to thermal condition from the heating body 2 at the time of flashing, but strain, twisting and expansion/contraction are absorbed as the deformation of a curved section which is formed at the halfway of a handle section 81, the terminal 8 with thereby neither be broken away nor separated from the wires. By this constitution, sensitivity in temperature detection is enhanced, and overshoot hardly takes place.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to improve the sensitivity of a heat sensitive member provided on the back surface of a substrate in a double-sided pattern type ceramics heater.

[0002]

2. Description of the Related Art In a double-sided pattern type ceramics heater, a film heating element is provided on the front surface of a ceramic substrate, and a circuit pattern made of a silver film connected to one end of the heating element is provided on the back surface of the substrate to form a circuit. Since both terminals are concentrated on both the front and back surfaces of the other end of the board, there are great advantages such as easy wiring when assembled in an OA device and a simple socket. In this case, it is general that the circuit pattern is brought to the back side of the heating element and both are three-dimensionally superposed at the center of the substrate.

[0003]

As described above, when the heating element and the circuit pattern are arranged so as to overlap with each other on the front and back surfaces of the central portion of the substrate, when the heat sensitive member such as the thermistor is provided, these members are formed into the circuit pattern. Must be placed in direct contact. In this case, the heat-sensitive member senses the temperature of the circuit pattern, but since the circuit pattern conducts current and conducts heat well, the starting temperature of the circuit pattern is higher than that of the board surface at the time of starting. Also tends to be low.

Therefore, if a heat-sensitive member is attached to the circuit pattern, an excessive current flows into the heat-generating body because the temperature detected by the heat-sensitive member at startup is lower than the actual temperature, resulting in overshoot. This is the toner fixing temperature of 2
If the temperature exceeds 00 ° C, the members arranged in the vicinity of the heater will be heated and deteriorated, and the life of the heater itself will be shortened. Further, the heater consumes a large amount of power during operation, and thus has a drawback that a large capacity power source is required.

Therefore, an object of the present invention is to improve the structure of a double-sided pattern type ceramics heater so that the temperature detected by the heat-sensitive member disposed on the back surface of the substrate can approach the actual temperature of the substrate surface.

[0006]

According to the present invention, a heat sensitive member is provided on a back surface of a ceramics substrate having a heating element disposed on the front surface, at a position directly behind the heating element, and a circuit is provided on the back surface of the substrate avoiding the heat sensitive member. By providing a pattern, the detected temperature of the heat-sensitive member is made to approach the actual temperature.

[0007]

In such a double-sided pattern type ceramics heater, the temperature rises fastest on the back surface of the substrate at the time of rising after energization is at the position directly behind the heating element. Therefore, if the heat-sensitive member is provided at this position and the circuit pattern is avoided from this position, the temperature of the heat-sensitive member approaches the true temperature, and the heat-sensitive accuracy can be improved.

[0008]

EXAMPLES The details of the present invention will be described below with reference to various examples.

Embodiment 1 In this embodiment, a circuit pattern is closed around a heat-sensitive member and circumvented, the details of which are shown in FIGS. 1 to 3.
In the figure, (1) is an elongated substrate made of alumina ceramics, (2) is an elongated heating element formed along the center line of the surface of the substrate (1) and extending over most of the length of the substrate (1). , (31) and (32) are electrodes formed at both ends of the heating element (2), (4) is a glassy protective film covering the surface of the heating element (2), and (5) is the substrate (1). A thermistor (6), which is an example of a heat-sensitive member disposed directly behind the center of the heating element (1) on the back surface, includes a thermistor (6) on the back surface of the substrate (1) while avoiding the heat-sensitive member (5). Circuit patterns for communicating both ends, (7) and (7) penetrate one end of the substrate (1) and one electrode (31) and the circuit pattern (6)
Through holes (8) and (8) for electrically connecting and are terminals provided on the other electrode (32) and the other end of the circuit pattern (6), respectively.

The heating element (2) is, for example, a printed wiring of silver-palladium alloy paste and baked, and both ends (22) of the elongated heating section (21) as the main body.
Is formed wide.

The electrodes (31) and (32) are formed by printing a silver paste and baking it. As shown in the figure, a part of the electrodes is layered on the surfaces of the end portions (22) and (22) of the heating element and the main body is a substrate. (1) It may be directly formed on the surface, or, although not shown, the end portion of the heating element (2) may be formed to be large and the entire electrode may be layered on the end surface of the heating element. There is.

The circuit pattern (6) is formed by printing wiring of silver paste and baking it. One electrode (3
1) A connection part (61) provided at a position corresponding to 1), a detour part (62) that forms a ring and surrounds the heat-sensitive member (5), and a position different from the other electrode (32) on the back surface of the substrate (1). And a wide power receiving portion (63) provided corresponding to the above.

The terminals (8), (8) are, for example, a metal plate such as a copper plate or a brass plate which is press-formed and nickel-plated or silver-plated. For example, a U-shaped bent portion (82) for relaxing
And the tip is wide and has a wire connecting hole (8)
It is formed in 3). Then, the base end of the handle portion (81) is soldered (84) to the other electrode (32) and the power receiving portion (63).
It is fixed by and is projected in parallel to the same side of the substrate (1).

Then, both terminals (8), (8) are connected to both ends of a power source (not shown), and the heat sensitive member (5), that is, the thermistor is connected to a current control device (not shown).
Then, when the power is turned on, the current will flow to both terminals (8),
It flows in from (8) and flows through the heat generating part (21) of the heat generating element (2) to generate heat. Then, the heat generated in the heat generating portion (21) is gradually accumulated while warming the surroundings and the temperature rises.
At this time, the temperature of the central part of the heat generating part (21) is the highest,
The farther from this, the lower the temperature is, and the backside of the substrate (1) has the highest temperature just behind the center of the heat generating part (21).
The farther from this, the lower the temperature. When the energization is continued, the overall temperature rises in this partial temperature relationship, and when the temperature detected by the heat sensitive member (thermistor) (5) reaches a predetermined temperature, the energization is cut off and the temperature of each part is increased. Are averaged, and as a result, the heat-sensitive member (thermistor)
The temperature of (5) falls and the power is turned on again. In this way, the temperature of each part of the heater is about 200 ° C while the power is turned on and off several times.
Becomes almost constant at and becomes a steady state. In such a ceramic heater, however, the closer the temperature of the heat sensitive member (thermistor) (5) is to the temperature of the highest temperature point of the heating element (2), the better the sensitivity and the higher the temperature adjustment accuracy. The present inventors have found that the temperature of the position directly behind the middle part of the heating element (2) is close to the maximum temperature of the heating element (2), and the heat-sensitive member (thermistor) (5) is attached to the heating element. It is arranged at the position directly behind.

The silver film, which is an example of the metal film forming the circuit pattern (6), has a property of transferring heat well. Therefore, in this embodiment, a part of the circuit pattern (6) is formed in a ring-shaped bypass (62) surrounding the thermistor (5) to avoid contact with the heat sensitive member (thermistor) (5). .. Therefore, the heat reaching the heat sensitive member (thermistor) (5) does not escape to the circuit pattern (6), and the temperature of the heat sensitive member (thermistor) (5) becomes close to the temperature of the central portion of the heating element (2). It was.

As described above, in the ceramic heater of this embodiment, the position of the heat sensitive member (5) such as a thermistor is limited, and the circuit pattern (6) is arranged so as to avoid the heat sensitive member (5). Therefore, the temperature of the heat sensitive member (5) becomes the closest to the temperature of the heating element (2), and the temperature detection sensitivity is high, so that there is almost no overshoot due to the operation delay of the heat sensitive member (5) or the deviation of the detected temperature. It was.

Further, the terminal (8) receives a pressing force or a twisting pressure due to the rigidity of the electric wire during wiring, and when blinking, the expansion and contraction are repeated by the heat transfer from the heating element (2).
However, in the ceramic heater of the first embodiment, since the bent portion (62) is formed in the intermediate portion of the handle portion (81) of the terminal (8), the above-mentioned distortion, twist, expansion or contraction causes the bent portion (62). And is absorbed as a deformation of the bent portion (62) and the terminal (8) is not peeled off or the electric wire is not detached.

Embodiment 2 As shown in FIGS. 4 to 6, the ceramic heater of Embodiment 2 is formed on the heating element (2) along the center line of the surface of the substrate (1), and the back surface of the substrate (1) is formed. The thermistor, which is an example of the heat sensitive member (5), is arranged directly behind the central portion of the heating element (2), that is, on the center line, and the heat sensitive member (5) is provided.
In order to avoid the above, the circuit pattern (6) is arranged close to one side of the back surface of the substrate (1), and both terminals (8) and (8) are axially parallel to each other at the other end of the substrate (1). The same parts are designated by the same reference numerals and the description thereof will be omitted.

Also in this ceramic heater, the heat-sensitive member (5) is arranged on the back surface of the substrate (1) at a position directly behind the heating element (2), and the circuit pattern (6) avoids the heat-sensitive member (5). Since the temperature of the heat sensitive member (5) is extremely close to the temperature of the heating element (2) at the time of rising after starting, the temperature sensing sensitivity of the heat sensitive member (5) is high, and therefore, Almost no overshoot due to the operation delay of the heat sensitive member (5) or the deviation of the detected temperature.

The terminals (8) and (8) are also provided with the handle (81).
Since the bent portions (82) and (82) are provided in the middle portion of the terminal, there is a possibility that the pressing force and the twisting force due to the rigidity of the wiring or the expansion and contraction of the terminal due to the blinking of the heater are absorbed and the terminal and the electric wire may come off. lost.

Example 3 As shown in FIGS. 7 to 9, the ceramic heater of Example 3 has a heating element (2) formed along the center line of the surface of the substrate (1) and the heating element (2) of the substrate (1) is formed. A thermistor, which is an example of the heat-sensitive member (5), is arranged directly behind the center of the heating element (2) on the back surface, that is, on the center line, and the center of the circuit pattern (6) is arranged so as to avoid the heat-sensitive member (5). (6
4) is bent in a U shape, and both terminals (8) and (8) are provided so as to project back to both sides at the other end of the substrate (1). Are denoted by the same reference numerals and description thereof is omitted.

Also in the ceramic heater of the third embodiment, the heat sensitive member (5) is arranged on the back surface of the substrate (1) at a position directly behind the heat generating element (2), and the circuit pattern (6) has the heat sensitive member (5). Since it is arranged avoiding 5), the temperature of the heat-sensitive member (5) is very close to the temperature of the heating element (2) at the time of rising after starting, and therefore the temperature detection sensitivity of the heat-sensitive member (5) is high. Therefore, the overshoot due to the operation delay of the heat sensitive member (5) and the deviation of the detected temperature was almost eliminated.

Further, since the terminal (8) is also provided with the bent portion (82) in the handle portion (81), the same effects as those of the above-described embodiments can be obtained.

Example 4 As shown in FIGS. 10 and 11, the ceramic heater of Example 4 has a heating element (2) which is biased to one side of the surface of the substrate (1) to form the substrate (1). A circuit pattern (6) is provided on the substrate (a) so that the thermistor, which is an example of the heat sensitive member (5), is disposed so as to be biased directly behind the central portion of the heating element on the back surface of the substrate, that is, to one side. 1) It is biased toward the other side and both terminals (8) and (8) are attached to the substrate (1).
At the other end thereof, the two parts are provided so as to project back to both sides, and the same parts are denoted by the same reference numerals and description thereof is omitted.

Also in the ceramic heater of the fourth embodiment, the heat sensitive member (5) is arranged on the back surface of the substrate (1) at a position directly behind the heating element (2), and the circuit pattern (6) is the heat sensitive member ( Since it is arranged avoiding 5), the temperature of the heat-sensitive member (5) is very close to the temperature of the heating element (2) at the time of rising after starting, and therefore the temperature detection sensitivity of the heat-sensitive member (5) is high. Therefore, the overshoot due to the operation delay of the heat sensitive member (5) and the deviation of the detected temperature was almost eliminated.

Further, since the terminal (8) is also provided with the bent portion (82) in the handle portion (81), the same effect as the above-mentioned three embodiments can be obtained.

In each of the above-mentioned embodiments, the heating element is made of a silver-palladium alloy film, but the present invention is not limited to this, and may be made of another metal, or may not be a film. The circuit pattern may also be made of a conductive material other than silver, other circuit elements such as resistors, capacitors, and transistors may be included in the circuit, and the pattern need not be a film. Further, the heat-sensitive member is not limited to the thermistor described above, but may be any member such as a fuse that acts in response to temperature. Further, the shape of the substrate and the type of ceramics are not limited, but if the thickness is too thick, heat transfer is deteriorated and the temperature difference between the heating element and the heat-sensitive member becomes large, which is against the object of the present invention.

[0028]

As described above, in the ceramic heater of the present invention, the heating element is provided on the front surface of the ceramic substrate, and the heat sensitive member is provided on the back surface of the substrate at a position directly behind the heating element. Since the circuit pattern is formed on the backside of the board avoiding the members, the temperature of the heating element and the temperature of the heat-sensitive member are very close to each other at the start-up after starting, the temperature detection sensitivity of the heat-sensitive member is high, and the operation of the heat-sensitive member is delayed. Almost no overshoot caused by the deviation of the sensed temperature.

[Brief description of drawings]

FIG. 1 is a plan view of a ceramic heater according to a first embodiment of the present invention.

FIG. 2 is a bottom view of the first embodiment.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a plan view of a ceramic heater according to a second embodiment of the present invention.

FIG. 5 is a bottom view of the second embodiment.

6 is a cross-sectional view taken along the line VI-VI of FIG.

FIG. 7 is a plan view of a ceramic heater according to a third embodiment of the present invention.

FIG. 8 is a bottom view of the third embodiment.

9 is a sectional view taken along line IX-IX in FIG.

FIG. 10 is a plan view of a ceramic heater according to a fourth embodiment of the present invention.

FIG. 11 is a bottom view of the fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Heating element 21 ... Heating part 22 ... End part 31, 32 ... Electrode 4 ... Protective film 5 ... Heat sensitive member 6 ... Circuit pattern 7 ... Through hole 8 ... Terminal 81 ... Handle part 82 ... Bent part

Claims (1)

Claim: What is claimed is: 1. A ceramic substrate, a heating element provided on the front surface of the substrate, and a heat-sensitive member provided on the back surface of the substrate directly behind the heating element. A ceramic heater comprising a circuit pattern provided on the back surface of the substrate while avoiding the heat sensitive member.