JPH07302729A - Metalized film capacitor - Google Patents

Abstract

PURPOSE:To restrain generation of cracks at the time of heat cycle in a capacitor, especially a metalized film capacitor which is used for high heat resistance. CONSTITUTION:A metalized film capacitor element 1 is accommodated in a case 2, which is filled with resin 3 whose glass transition temperature is higher than or equal to 90 deg.C. An elastic member 7 as a stress absorbing means is laid around the metalized film capacitor element 1. Thereby, when a plastic film as dielectric is expanded or contracted at the time of heat cycle, stress applied to the resin can be reduced since the elastic member 7 absorbs the stress, and generation of cracks of filling resin can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power capacitor for improving power factor, a capacitor for electric equipment, a capacitor for various power supply circuits, and a dry metallized film capacitor used for communication equipment and the like.

[0002]

2. Description of the Related Art In metallized film capacitors which are conventionally required to have heat resistance, a high heat resistance film has been used as a dielectric.

FIG. 7 is a diagram showing a conventional capacitor structure. In FIG. 7, reference numeral 1 is a capacitor element, which is formed by winding a plastic film on which metal is vapor-deposited. Reference numeral 2 denotes a case, which houses the capacitor element 1 therein and is further filled with resin 3. Reference numeral 4 denotes a lead terminal, which is provided on the terminal plate 6 and is connected to the capacitor element 1 by a lead wire 5.

In such a capacitor, cracks sometimes occur in the resin 3 portion filled between the capacitor element 1 and the case 2 during the heat cycle. As a countermeasure, the ambient temperature is the glass transition temperature (Temp) of the resin.
When the temperature rises above the normal glass (Tg), the Tg of the filling resin 3 is higher than the temperature at which the capacitor is used by taking advantage of the glass transition property in which the resin softens and the strength and rigidity decrease due to the decrease in the intermolecular bonding force of the resin. There is a means to absorb the stress to the filling resin 3 due to the shrinkage of the element during the heat cycle by using a considerably low material.

[0005]

However, when the above-mentioned means is used in the heat-resistant capacitor, even if the temperature difference between Tg and the actual use temperature is the same as in the normal use, the resin 3 in the actual use state is not used. However, there is a problem in that the degree of softening increases, the outside air (air) enters the capacitor through the resin 3, and corona discharge or SH (self-healing action) frequently occurs due to the air layer, so that the capacity tends to decrease.

Therefore, in order to prevent this capacity decrease, T
Measures are used in which g is higher than the maximum ambient temperature of the capacitor, or a resin having Tg as close as possible to the maximum ambient temperature of the capacitor is used, but conversely, Tg is higher than the actual operating temperature, or Tg If the temperature difference from the actual use temperature is small, the intermolecular force of the resin is less likely to decrease, so the resin 3 does not soften and the strength and rigidity remain strong. There is a problem that cracks occur when the strength of the resin 3 is exceeded without being able to absorb the stress.

In order to solve these problems, if Tg is equal to or lower than the maximum ambient temperature of the capacitor, the degree of softening of the resin is not too large, and if it coincides with the temperature point at which the stress due to the contraction of the capacitor film can be absorbed, both problems will be solved. Although it can be solved, in that case, it was very difficult to find the optimum value of Tg because various conditions had to be taken into consideration.

The present invention solves the above-mentioned problems, and in a capacitor, particularly in a heat-resistant capacitor used at high temperature, even when a filling resin having a high Tg is used, generation of cracks during heat cycle is prevented. An object is to provide a metallized film capacitor.

[0009]

In order to achieve the above object, the metallized film capacitor of the present invention has a metallized film capacitor element housed in a case, and the case is filled with resin and the metallized film capacitor A stress absorbing means is provided around the film capacitor element.

[0010]

According to the present invention, when the plastic film, which is a dielectric, expands and contracts during high temperature and low temperature cycles by the above means, the stress absorbing means absorbs the stress even if the filling resin cannot absorb the stress. The stress applied to the resin can be reduced, and the occurrence of cracks in the filling resin can be prevented.

[0011]

EXAMPLES The present invention will be described below based on examples.

The capacitor used in the examples is a capacitor with a safety mechanism made of a 7 μm thick aluminum vapor-deposited film using a polypropylene film as a dielectric and has a capacity of 12
μF and Tg of the filling resin 3 are 90 to 100 ° C. For comparison with this example, the following conventional product was also manufactured at the same time.

The test results using these capacitors are shown in (Table 1).

[0014]

[Table 1]

Each form in the "prototype form" of Table 1 is as shown in FIGS.

That is, FIG. 1 is a diagram showing a first capacitor structure in one embodiment of the present invention. In the figure, the same parts as those of the conventional capacitor are designated by the same reference numerals and the description thereof will be omitted (the same applies hereinafter), but the difference from the conventional capacitor is that the elastic body 7 as the stress absorbing means is provided over the entire element 1. That is the point.

FIG. 2 is a diagram showing a second capacitor structure in one embodiment of the present invention. In this capacitor, the elastic body 7 is not provided on the entire element 1, but the elastic body 7 as the stress absorbing means is provided on the end surface of the element 1 on the upper lead terminal 4 side.

Further, FIG. 3 is a diagram showing a third capacitor structure in one embodiment of the present invention. For this capacitor, instead of providing the elastic body 7 on the entire element 1,
Elastic elements 7 serving as stress absorbing means are provided on all end faces of the element 1.

In each prototype, an elastic body 7 as shown in the "Material" column of (Table 1) was used as a stress absorbing means.

In this embodiment, as an example, 100 ° C.
We have tested with the capacitors used above,
The present invention is not necessarily limited to use at 100 ° C or higher.

As shown in (Table 1), No. Simultaneous test conditions for 3 samples of each of 1-6 prototypes-25 ° C, 6 hours applied voltage OFF, 115 ° C, 6 hours applied voltage 1.3EON
When a heat cycle test was carried out with, the conventional example had cracks on the resin 3 surface in 2 out of 3
The sample of this example showed a clear difference of 0 out of 15 units. Further, a sample having a thickness of 8 μm was also manufactured and subjected to a heat cycle test in the same manner, but at a thickness of 8 μm, no crack was generated and no difference appeared. From this, it is understood that the thinner the dielectric film is, the larger the heat shrinkage of the film is, the larger the stress applied to the filling resin 3 is, and the cracking easily occurs in the resin 3. Further, the easiness of cracking is not determined only by the thickness of the dielectric film, but the Tg of the filling resin 3,
It is also greatly affected by the width of the capacitor element and the outer diameter of the winding. Table 2 shows the heat cycle test results for each element width and winding outer diameter.

[0022]

[Table 2]

In this test, capacitors of the types shown in FIGS. 2 and 7 are used, but in Table 2 the element width is the length of the cylindrical capacitor element 1.
The outer diameter of winding means the diameter of the bottom surface of the capacitor element 1.

It is known that the shrinkage ratio of a plastic film used for a capacitor is generally larger in the width direction (MD direction) than in the film longitudinal direction (TD direction). It can be seen that the narrower the winding outer diameter, the harder the cracks are, and conversely, the wider the element width is and the larger the winding outer shape is, the more the cracks are easily generated. Resulted in no cracking. From this, it is understood that the elastic body 7 absorbs the stress even when the dielectric plastic film expands and contracts, so that the stress applied to the resin 3 is reduced. A similar test was also performed on the element 1 in which the elastic body 7 is inserted only on the non-end surface side (side surface side) (not shown), but in this case, there is no difference from the case without the elastic body 7, and the element width direction It can be seen that it is effective to insert the elastic body 7 against the contraction to the.

Further, for comparison, a capacitor filled with resin 3 having a low Tg of 90 ° C. or lower was also prepared at the same time, and the same test was performed. As a result, the sample having a low Tg showed a large decrease in capacity. The result is shown in FIG. This is because the Tg is low and the intermolecular force of the filling resin 3 is extremely reduced, the softening degree of the resin 3 becomes large, and the outside air (air) enters the capacitor through the resin 3, and the air layer causes corona discharge or It is considered that the decrease in capacity became large due to the frequent occurrence of SH (this is a story at the time of high temperature use, and it means that the present invention does not hold when using resin 3 having a Tg of 90 ° C. or less during normal use. Not what you do). By the way, there was no problem caused by putting the elastic body 7 in the resin-filled capacitor having Tg of 90 ° C. or higher, and there was no difference in other characteristics from the conventional example.

With respect to the material of the elastic body 7, it is desirable that the heat-resistant capacitor of the present invention has a property that does not change as much as possible between -25 ° C. and 115 ° C., is excellent in withstand voltage, and has a large insulation resistance.

Further, the thickness of the elastic body 7 is preferably 0.5 mm or more. That is, when the distance between the end surface of the capacitor element 1 on the external electrode lead-out side (upper side) and the electrode lead-out terminal 4 of the case 2 in FIG.
Insulation cannot be maintained and short circuit may occur. Therefore, it is necessary to consider the thickness of the elastic body 7 and the withstand voltage of the elastic body 7 itself, but the minimum withstand voltage value is the rated voltage (230 V).
2.15 times (495 V) or higher is required, and the withstand voltage of the elastic body 7 is A.V. C. This is because at 1 kV / mm, the minimum thickness is 0.5 mm.

Although the winding type capacitor is described in this embodiment, it is needless to say that the same effect can be obtained in a laminated type capacitor as shown in FIGS. 4 and 5.

FIG. 4 is a diagram showing a fourth capacitor structure according to one embodiment of the present invention, and FIG. 5 is a diagram showing a fifth capacitor structure according to one embodiment of the present invention. In FIG. 4, the capacitor element 1 is a laminated type, and the elastic body 7 covers the entire element 1. In FIG. 5, the elastic body 7 covers all the end faces. Others are the same as the other embodiments.

Furthermore, in this embodiment, the heat-resistant capacitor has been described as an invention, but it goes without saying that it is also useful as a countermeasure against cracks during normal use.

[0031]

As is apparent from the above description, the metallized film capacitor element is housed in the case, the case is filled with resin, and the stress absorbing means is provided around the metallized film capacitor element. Therefore, in the heat cycle test where the difference between high temperature and low temperature is large,
Even if the plastic film, which is the dielectric, expands and contracts, the stress absorbing means absorbs the stress, so that the stress applied to the resin can be reduced, and the cracking of the filling resin can be prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing a first capacitor structure according to an embodiment of the present invention.

FIG. 2 is a diagram showing a second capacitor structure according to an embodiment of the present invention.

FIG. 3 is a diagram showing a third capacitor structure according to an embodiment of the present invention.

FIG. 4 is a diagram showing a fourth capacitor structure according to an embodiment of the present invention.

FIG. 5 is a diagram showing a fifth capacitor structure of one embodiment of the present invention.

FIG. 6 is a view showing a heat cycle test result based on a difference in Tg of filled resins.

FIG. 7 is a diagram showing a conventional capacitor structure.

[Explanation of symbols]

 1 Capacitor element 2 Case 3 Filling resin 4 Lead-out terminal 5 Lead wire 6 Terminal board 7 Elastic body

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Mitsumasa Oku 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. A metallized film capacitor in which a metallized film capacitor element is housed in a case, resin is filled in the case, and stress absorbing means is provided around the metallized film capacitor element. 2. A metallized film capacitor element is housed in a case, resin is filled in the case, and all the end surfaces of the metallized film capacitor element, or at least the end surface located on the upper lead terminal side, A metallized film capacitor provided with a stress absorbing means. 3. The metallized film capacitor according to claim 1, wherein the glass transition temperature of the resin is 90 ° C. or higher. 4. The metallized film capacitor according to claim 1, wherein the stress absorbing means is an elastic body. 5. The metallized film capacitor according to claim 4, wherein the elastic body is a rubber having a thickness of 0.5 mm or more and having elasticity.