JPS6246242Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a positive temperature coefficient thermistor device.

A conventional device of this kind has a structure in which a positive temperature coefficient thermistor 2 is mounted on a metal substrate 1 and an electrode plate 4 is pressed against the thermistor 2 via a coil spring 5, as shown in FIG.

In such a conventional structure, as shown in FIG.
When the metal substrate 1 is subjected to an external force or is distorted during manufacturing, a minute gap is created between the metal substrate 1 and the PTC thermistor 2, and therefore the heat generated by the PTC thermistor 2 cannot be efficiently dissipated to the metal substrate 1. It has the disadvantage of causing a situation.

Therefore, the present invention attempts to eliminate the above-mentioned drawbacks by creating a structure in which the positive temperature coefficient thermistor can be deformed so that the positive temperature coefficient thermistor can follow the convex distortion of the metal substrate.

Hereinafter, an embodiment in which the present invention is applied to an engine intake air heating device will be described.

Figure 3 shows the installed state of the intake air heating device for the engine, where A is the intake pipe, and the intake air heating device B is made by drilling a hole in the intake pipe A directly below the carburetor and inserting a gasket (not shown) into the hole. It is fixed with bolt C through the

Figure 4 shows the main body of the intake air heating device. 1 is a case that also serves as a heat sink, and since it is electrically grounded to the intake pipe A, it is made of a metal material with good thermal and electrical conductivity. It is made up of 2 is a disc-shaped positive temperature coefficient thermistor made of ceramic (for example, BaTiO ₃ type) having a positive temperature coefficient of resistance. This thermistor is pressed against the case 1 by a spring 5 via a disk-shaped graphite sheet 3, a disk-shaped electrode plate 4, and a ring-shaped plate 7 made of an electrically insulating material. Note that Ni--Ag based electrodes are provided on both sides of the thermistor 2. Also,
The graphite sheet 3 protects the thermistor 2 from contact with the electrode plate 4 and serves as an electrical path, so it has appropriate elasticity and conductivity.

The electrode plate 4 is as shown in FIGS. 4 and 5.
Its approximately central portion is convex by a very small height (0.2 mm), forming a protrusion 4a. The electrode plate 4 is connected to the core wire 6a of the lead wire 6 by folding back its central portion. The metal cover 10 is fixed to the case 1 with rivets, screws, etc., and protects the inside of the case 1 from water, dust, etc., and also supports the entire case by holding the spring 5 and the ring-shaped wave spring 8. . 9 is a support ring made of electrically insulating material.

The operation of the present invention will be explained in the structure as described above. The performance of the above-mentioned intake air heating device is almost determined by the thermal conductivity between the thermistor 2 and the case 1, but the case 1 is constantly deformed under the influence of the negative pressure inside the intake pipe A. Therefore, a minute gap is created between the thermistor 2 and the case 1, and sufficient performance cannot be obtained.

However, according to the embodiment described above, the thermistor 2 is considered to be an elastic body within a certain limit, and the central part of the thermistor 2 is connected to the protrusion 4 at the central part of the electrode plate 4.
a, it is possible to push the thermistor 2 appropriately through the spring 5 and make the thermistor 2 follow the distortion of the case 1 (see FIGS. 5 and 6). Therefore, the thermal radiation property does not change and its variation is small.

Note that the presence of the graphite sheet 3 allows uniform contact between the thermistor 2 and the electrode plate 4.

FIG. 8 shows the variation in heat dissipation between the conventional example and the example of the present invention.

The present invention is not limited to the above-described embodiments, but can be modified in various ways as follows.

(1) The metal substrate in the present invention does not have to be in the so-called cup shape as in case 1, but may be in the shape of a flat plate.

(2) The metal plate in the present invention is not one to which the lead wire 6 is connected like the electrode plate 4, and may be a mere metal plate (it does not have to serve as an electric conductor path).

(3) The same function as the graphite sheet 3 can be achieved by using elastic rubber with metal powder added instead of the graphite sheet 3.

(4) A plate spring may be used instead of the coil spring 5.

(5) It goes without saying that the present invention is applicable not only to the intake air heating device for an engine as in the above-mentioned embodiments, but also to various other uses.

In summary, the present invention is capable of deforming a PTC thermistor to follow the distortion of the metal substrate on which the PTC thermistor is supported, thus improving the contact between the PTC thermistor and the metal substrate and improving heat radiation. can.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views for explaining a conventional example, and FIG. 3 is a cross-sectional view showing an embodiment of the present invention.
4 is a sectional view showing the main part of FIG. 3, FIGS. 5 and 6 are sectional views for explaining the operation of the present invention, FIG. 7 is a perspective view showing the electrode plate of FIG. 4, and FIG. The figure is a characteristic diagram for explaining the effects of the present invention. 1...Case, 2...Positive characteristic thermistor, 4...
...Electrode plate, 4a...Protrusion, 5...Spring.

Claims (1)

[Scope of utility model registration request] Comprising a metal substrate, a metal plate with a protrusion in the center, a positive temperature coefficient thermistor, and a spring member,
A positive temperature coefficient thermistor device, wherein the thermistor is mounted between the metal substrate and the metal plate, and a spring load of the spring member is applied to the metal plate so as to press the thermistor toward the metal substrate.