JPH0247082B2 - SEITOKUSEISAAMISUTASOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a positive temperature coefficient thermistor device used, for example, as a starting device for an electric motor.
By reliably positioning the positive temperature coefficient thermistor element in a case in which the positive temperature coefficient thermistor element is sandwiched between a pair of electrode plates set upright in the case,
By always maintaining a certain spatial distance between the element and the case, we prevent the case from becoming extremely hot due to high-temperature elements approaching the case, lowering the heat resistance grade of the case, making it possible to use cheaper resin, and reducing costs. The aim is to lower the heat resistance and improve the heat resistance reliability of the device, and to achieve this without making the assembly process difficult.

In general, a positive temperature coefficient thermistor element (hereinafter simply referred to as an element) has a typical characteristic curve shown in FIG.
For example, when applied to the starting circuit of a motor shown in Figure 2 (A is a starting switch, B is a motor, and C is a positive temperature coefficient thermistor device), the element temperature reaches 150 to 200°C, and compared to the conventional positive coefficient thermistor. In the device,
Because the element could come into direct contact with the outer case, it was necessary to use a resin material with a very high heat-resistant grade. Therefore, the total cost of the positive temperature coefficient thermistor device has increased. Another conventional example, as shown in FIG. 3, is one in which an element D is fitted into a hole provided in a heat insulating plate E such as a mica plate fixed in a case so that the element D does not come into direct contact with the case. However, in this case, although it is possible to position the element against deviation in the radial direction, it is possible to move freely against deviation in the thickness direction (axial direction) of the element, causing the element to approach or come into contact with the case. Not only is there a risk, but the heat insulating plate must be inserted into the case with the elements inserted, making assembly difficult.

The present invention aims to eliminate the above-mentioned drawbacks of the conventional example and provide a positive temperature coefficient thermistor device that is inexpensive, easy to assemble, and highly reliable.

Hereinafter, the configuration of an embodiment of the present invention will be explained with reference to FIG. 4 and the subsequent drawings. In the figure, numeral 1 is a case made of phenol resin or the like that serves as an outer case for the PTC thermistor device, and numeral 2 is a case cover that fits into the case 1 to semi-seal the inside. Reference numeral 3 denotes a tab terminal fixed to the case 1 for connection to an external circuit, and a spring terminal 4 for connection to a hermetic terminal of a motor is fixed by spot welding or the like, if necessary. 5 is the tab terminal 3
and the case 1 is fixed by spot welding or the like.
A pair of electrode plates protruding toward the center of the case 1 so as to sandwich a positive temperature coefficient thermistor element (hereinafter simply referred to as the element) 6 located approximately in the center of the case 1 from both sides, and are also electrically connected to the element 6. . Reference numeral 7 denotes a substantially C-shaped first heat insulating plate formed of a mica plate or the like, which is parallel to the element 6 and extends approximately half the circumference between the case 1 and the element 6, and is integrally provided with the case 1. It is supported within the first groove 1a.

A second heat insulating plate 8 having a steady rest recess 8a and interposed between the element 6 and the case cover 2 in a direction perpendicular to the first heat insulating plate 7 is formed integrally with the case 1. is supported within the groove 1b.

Next, the assembly procedure for the above embodiment will be explained.
After loading a pair of assemblies in which the tab terminal 3, electrode plate 5, and if necessary spring terminal 4 are fixed in advance by spot welding or the like into the case 1, first the first heat insulating plate 7 is attached to the case 1. First groove 1a provided in the inner wall
Fit it in. Next, the element 6 was inserted between a pair of electrode plates 5 set upright in the case 1 using a jig, and a second heat insulating plate 8 was installed on the inner wall of the case 1 through the opening of the case 1. This is completed by fitting the element 6 in the recess 8a into the second groove 1b, and then fitting and fixing the cover case 2 to the case 1 to cover the opening of the case 1.

As is clear from the above description, the present invention has a positive temperature coefficient thermistor element sandwiched between a pair of electrode plates set upright in a case, in which a positive temperature coefficient thermistor element is sandwiched between the case and the element in parallel with the element and over approximately half the circumference. and a second thermal insulating plate having a steady rest recess and interposed between the element and the case in a direction orthogonal to the first thermal insulating plate. As a result, the element can be positioned reliably in both the radial and thickness directions relative to the element, so the spatial distance between the element and the case is always kept above a certain level, and the case is prevented from being exposed to hot elements approaching the case. This prevents extremely high heat from occurring, lowers the heat resistance grade of the case, and allows the use of cheaper resin.
It is possible to reduce the cost and improve the heat resistance reliability of the device, and it can be achieved without making the assembly process difficult, and its practical effects are very large.

[Brief explanation of the drawing]

Figure 1 is a typical characteristic curve of a positive temperature coefficient thermistor element, Figure 2 is a circuit diagram showing an example of application of a positive coefficient thermistor device to a motor starting circuit, and Figure 3 is a conventional example of a positive coefficient thermistor using a thermal insulation board. 4 is a central sectional view showing an embodiment of the present invention, FIG. 5 is a view taken along the line -' in FIG. 4, and FIG. 6 is an exploded perspective view of the same. DESCRIPTION OF SYMBOLS 1... Case, 5... Electrode plate, 6... Positive temperature coefficient thermistor element, 7... First thermal insulation plate, 8a... Recessed part, 8...
Second thermal insulation board.

Claims (1)

[Claims] 1. A positive temperature coefficient thermistor element is sandwiched between a pair of electrode plates set upright in a case, and a first thermal insulating plate is parallel to the element and interposed between the case and the element over approximately half the circumference; A positive temperature coefficient thermistor device comprising: a second heat insulating plate having a steady rest recess and interposed between the element and the case in a direction perpendicular to the first heat insulating plate.