JPH0992504A - Selection of ptc ceramic element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a PTC ceramic element which does not abnormally rise in temperature and have uniform heating characteristics by a method wherein the inrush current and the steady-state current corresponding to the prescribed surface temperature is set at the upper limit value, and a PTC ceramic element, having the inrush current and the steady-state current exceeding the upper limit value and the lower limit value, is selected. SOLUTION: In the titled PTC ceramic element 1 on which a pair of electrodes 2a and 2b are formed on one surface leaving an interval or a pair of electrodes 2 and 2 are formed on the opposing surface, an inrush current and a steady-state current are adjusted by providing a cut groove 3 on both or one of the electrodes, and the PTC ceramic element, having the inrush current and the steady-state current within the range of preset value is selected and manufactured. Accordingly, the PTC ceramic element can be accurately selected as the selection is conducted on the basis of the inrush current, and a PTC ceramic element, which is abnormally heated up exceeding the pres cribed temperature, can be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PTC ceramic element, and more particularly to a method for selecting PTC ceramic elements having uniform heating characteristics that prevent abnormal temperature rise above a predetermined temperature and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in a PTC ceramic element containing barium titanate as a main component, the selection is made by a resistance value. However, the resistance value of the PTC ceramic element is determined by the firing temperature, firing time, atmosphere in the manufacturing process. Therefore, the resistance value may vary and the resistance value may deviate from the standard. The PTC ceramic element which is out of the standard is defective because the resistance value cannot be adjusted.

[0003] In order to solve this, the actual exploitation Sho 63-10
No. 502 and the like propose a method of adjusting the resistance value of a PTC ceramic element. FIG. 10 is an explanatory view of a conventional method of adjusting a resistance value, in which a pair of electrodes 2a and 2b are formed on one surface of the PTC ceramic element 1 at a distance and one electrode 2c is formed on the other surface. Formed, electrode 2c
Is deleted by the width of x, and the resistance value is adjusted by reducing the area of the electrode 2c.

[0004]

However, according to the above-mentioned conventional method, it is necessary to remove the electrode 2c in order to reduce the electrode area, so that the removing work is troublesome and, as a result, the PTC ceramic element is required. 1 becomes expensive, and there is a limit in reducing the cost.

Even if the PTC ceramic elements are selected by resistance value, the resistance value is measured at about several V at most, so that the characteristics may differ greatly from those when actually used at high voltage. Further, the surface temperature may differ even if the resistance values are almost the same.

FIG. 9 is a graph showing the effect of voltage on the resistance-temperature characteristic of a PTC ceramic element.
It can be seen that there is a difference in characteristics at each voltage of (3), the PTC ceramic element has varistor characteristics, and has voltage dependency.

Therefore, when the PTC ceramic element is used at an actual high voltage based on the characteristics measured at a low voltage, the PTC ceramic element may excessively rise from a predetermined temperature due to a difference in characteristics due to voltage dependence. Therefore, for example, when used for floor heating or the like, an accident such as a burn may occur.

Therefore, the present invention has a sufficient heating capacity,
PTC with uniform heating characteristics that does not abnormally raise temperature above a prescribed temperature
The present invention provides a method for accurately selecting and manufacturing ceramic elements.

[0009]

SUMMARY OF THE INVENTION According to the present invention, when an electric current is applied under a condition where a certain radiation coefficient is relatively small, an inrush current and a steady current corresponding to a predetermined surface temperature are set as upper limits, and the upper limits and A PTC ceramic element is selected and a manufacturing method thereof is characterized in that a PTC ceramic element having an inrush current and a steady current which do not exceed a lower limit value is selected.

In addition, a pair of electrodes formed with a space on one surface or a pair of electrodes facing each other are formed on the surface P.
In the TC ceramic element, in which a pair of electrodes are formed on one surface of the PTC ceramic element with a space therebetween and one electrode is formed on the other surface, the inrush currents are out of the predetermined ranges. In the case of the above, the desired PTC ceramic element is obtained by providing a cutting groove in the electrode formed on the other surface to adjust the inrush current and selecting a PTC ceramic element having an inrush current not exceeding the upper limit value. Can be selected and manufactured.

The cutting groove can be finely adjusted so that a triangle is formed by diagonally crossing two adjacent sides of the electrode on the other surface.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1, 2 and 3 are perspective views of a PTC ceramic element. A PTC ceramic element 1 shown in FIG. 1 has a pair of electrodes 2a, 2b formed on one surface thereof at a distance. One electrode 2c is formed on the other surface.

In the PTC ceramic element 1 shown in FIG. 2, a pair of electrodes 2a and 2b are formed on one surface with a space therebetween, but no electrodes are formed on the other surface.

The PTC ceramic element 1 shown in FIG. 3 has electrodes 2 formed on both sides.

FIG. 4 is an explanatory view of a panel heater measuring device incorporating the PTC ceramic element 1, in which the PTC ceramic element 1 having electrodes 2a and 2b formed on the heat radiating plate 6 is attached via an insulating plate 8 and AC 200V. Then, the resistance value, the inrush current, the steady current, and the surface temperature were measured.

FIG. 5 is a graph of the time-current characteristics of the PTC ceramic element. The current value rapidly increases after energization, reaches a peak corresponding to the inrush current, and then rapidly decreases.
Eventually the steady current settles down.

The surface temperature was measured by mounting a thermocouple 7 on the heat dissipation plate 6 and pressing the heat insulating material 5 to close the surface.

Next, the inrush current adjustment of the PTC ceramic element will be described. FIG. 6 is a perspective view of the PTC ceramic element in which a cutting groove is formed to adjust the inrush current, and FIG. 7 shows a rear end portion during the formation of the cutting groove. FIG. 8 is a perspective view of a damaged PTC ceramic element, and FIG. 8 is a perspective view of a PTC ceramic element in which a cutting groove is formed according to the present invention to finely adjust the inrush current. In order to adjust the inrush current of the PTC ceramic element shown in FIG. The cutting groove 3 is formed in the electrode 2c. The position x at which the cutting groove 3 is formed is the adjustment amount and the position x for each PTC ceramic element.
The relationship may be obtained in advance, and it may be performed based on that.
Further, when finely adjusting the current of the PTC ceramic element having an inrush current value close to the target value, the width of x becomes extremely small according to the method of forming the cutting groove shown in FIG. As shown in 7, the edge of the element 1 is damaged and the defect 4
May be possible. Therefore, as a result of various studies, we have found that the current can be adjusted only by forming a groove at a predetermined position without deleting the predetermined width x of the electrode. As shown in FIG. 8, the current can be adjusted by changing the width of y such that a triangle is formed by diagonally crossing two adjacent sides of the electrode. In the method according to the present invention, since the groove is simply formed and the width of y can be increased, the PTC ceramic element 1 is less likely to be damaged.

In addition, since the cutting groove is used to adjust the current value extremely minutely, it is better to provide the cutting groove on the other part immediately below the pair of electrodes formed on one surface with a space between the other part. Since the amount of change in the current value is smaller than that in forming the cutting groove, it is desirable for accurate adjustment.

Further, when the shape of the PTC ceramic element and the shape of the electrode are restricted in consideration of the shape of the entire heater unit, the electrode layer 2 is formed as shown in FIG. 11 or 12.
It is also possible to insert a cutting groove 3 into the groove and divide it into 2b and 2b ', 2 and 2', respectively. Also, regarding the form of the electrodes of the ceramic element shown in FIG. 1, as shown in FIG. 13, cutting grooves 3 are formed on both sides of the electrode layer 2 and divided as 2b and 2b ′ and 2 and 2c ′, respectively. It is also possible.

[0021]

【Example】

Example 1 Table 1 shows the results of measurement of PTC ceramic elements having various resistance values.

[0022]

[Table 1] In Table 1, the pass / fail judgment was passed when the surface temperature was 70 ° C. or lower.

If the surface temperature is lower than 60 ° C, the heating capacity becomes too small. Therefore, the surface temperature of 60 ° C or higher was passed.

As is clear from Table 1, No. 1 having an inrush current of 46 mA or less at a surface temperature of 70 ° C. 8
And No. No. 10 has a surface temperature of no more than 70 ° C, so unless the inrush current of the selected PTC ceramic element exceeds that of 70 ° C, the surface temperature does not exceed 70 ° C. I can have sex. The resistance value in Table 1 shows the value measured under a voltage of 1 V. However, if the resistance value is selected conventionally, an accurate correlation between the resistance value and the surface temperature is obtained. Therefore, there is a case where the temperature rises above a predetermined temperature in some cases, and it is understood that the selection of the PTC ceramic element based on the resistance value lacks reliability.

On the other hand, No. 11 and No. It can be seen that in No. 12, although the inrush current is within the range, the steady current is less than 13 mA, the surface temperature is 60 ° C. or less, there is no abnormal temperature rise, and there is no heating capacity.

Further, No. For those that seem to have different Curie points due to the effects of compositional variations such as No. 13, the steady-state current was large and the surface temperature was 79 ° C.
It is high. Although such a thing is small in number from the whole, it is excluded by judging from the steady current.

Example 2 When 200 V was applied to the 15 mm × 25 mm × 2.5 mm PTC ceramic element 1 shown in FIG. 1, the inrush current was 70 mA. This element is shown in FIG.
= 7 mm, a cutting groove was provided, and when energized, the inrush current was 4 mA below the inrush current of 46 mA at a surface temperature of 70 ° C.
5mA, surface temperature is 68 ° C, 70 ° C
Never exceeded.

Example 3 In the same manner as in Example 2, 20 PTC ceramic elements 1
When an electric current of 0 V was applied, the inrush current was 51 mA.
When this device was provided with an oblique cutting groove at a position of y = 9 mm as shown in FIG. 8 and energized, the inrush current was 43 mA, and the surface temperature was 65 ° C. and did not exceed 70 ° C.

[0029]

The effects of the present invention are as follows.

(1) In the present invention, the inrush current is used as a reference for selection instead of the conventional resistance value, so that the PTC ceramic element can be accurately selected, and the heating characteristics that prevent abnormal temperature rise are consistent with P.
A TC ceramic element is obtained, and there is no PTC ceramic element that abnormally rises in temperature to a predetermined temperature or higher, which occurs when the conventional resistance value is selected.

(2) In the present invention, the adjustment of the rush current only forms the cut groove in the electrode, and therefore, unlike the conventional resistance value adjustment in which the electrode is peeled off, no labor is required.
Also, in the case of fine adjustment, since an oblique cutting groove is formed, P
This can be easily done without damaging the end of the TC ceramic element.

[Brief description of drawings]

FIG. 1 is a perspective view of a PTC ceramic element.

FIG. 2 is a perspective view of a PTC ceramic element.

FIG. 3 is a perspective view of a PTC ceramic element.

FIG. 4 is an explanatory diagram of a panel heater measuring device incorporating a PTC ceramic element.

FIG. 5 is a graph of time-current characteristics of a PTC ceramic device.

6 is a perspective view of the PTC ceramic element shown in FIG. 1 in which a cut groove is formed according to the present invention to adjust an inrush current.

FIG. 7 is a perspective view of a PTC ceramic element whose end portion is damaged during formation of a cutting groove.

FIG. 8 is a perspective view of a PTC ceramic element in which a cutting groove is formed according to the present invention to finely adjust an inrush current.

FIG. 9 is a graph showing the effect of voltage on the resistance-temperature characteristics of a PTC ceramic element.

FIG. 10 is an explanatory diagram of a conventional resistance value adjusting method.

11 is a perspective view of the PTC ceramic element shown in FIG. 2 in which a cutting groove is formed according to the present invention to finely adjust the inrush current.

FIG. 12 is a perspective view of the PTC ceramic element shown in FIG. 3 in which a cutting groove is formed according to the present invention to finely adjust the inrush current.

13 is a perspective view of the PTC ceramic element shown in FIG. 1 in which cutting grooves are formed on both sides according to the present invention to finely adjust an inrush current.

[Explanation of symbols]

1 PTC ceramic element, 2, 2 ', 2a, 2b,
2b ', 2c electrodes, 3 cutting grooves, 4 missing parts, 5
Heat insulating material, 6 heat sink, 7 thermocouple, 8 insulating board

Claims (6)

[Claims] 1. A P having a rush current corresponding to a predetermined surface temperature and having a rush current which does not exceed the range of the set value.
A method of selecting and manufacturing PTC ceramic elements having substantially the same heating characteristics, which is characterized by selecting TC ceramic elements. 2. The P according to claim 1, wherein a PTC ceramic element within a predetermined steady current range is selected.
TC ceramic element selection method. 3. A PTC ceramic element having a pair of electrodes formed on one surface at a distance, or a pair of electrodes formed on opposite surfaces, with both or the other electrode provided with a cutting groove and protruding. The PTC ceramic element selection and the manufacturing method thereof according to claim 1 or 2, wherein the PTC ceramic element having an inrush current and a steady current within a set value range is selected by adjusting the current and the steady current. 4. A PTC ceramic element having a pair of electrodes formed on one surface at a distance and one electrode formed on the other surface, wherein a cut groove is provided in the electrode formed on the other surface. P has a rush current and a steady current that do not exceed the set value range by adjusting the rush current and the steady current.
The PTC ceramic element selection and manufacturing method thereof according to claim 1 or 2, wherein a TC ceramic element is selected. 5. The PTC according to claim 1, 2 or 4, wherein the cut groove is provided in an electrode formed on the other surface immediately below the pair of electrodes formed on one surface with a space therebetween. Ceramic element selection and manufacturing method thereof. 6. The cutting groove is provided so that a triangle is formed by diagonally crossing two adjacent sides of an electrode on the other surface. A method for selecting a PTC ceramic element described above and a method for manufacturing the same.