JP7586064B2 - Resin cover mounting structure for electrical equipment - Google Patents

Description

The present invention relates to an attachment structure for a resin cover that houses heat-generating parts of electrical equipment.

For example, in electrical products (electrical equipment) such as inverters and switching power supplies, electrical components are housed in a resin cover, and as shown in Figure 1, electrical components (heat-generating components) 1 such as switching elements are joined to an aluminum heat sink 4 connected to the resin cover 2 with screws 3 for cooling.

At this time, an attachment portion 2a is formed on the outer periphery of the resin cover 2, which is bent into an L-shape. An attachment hole (not shown) is formed in the flange portion 2b of this attachment portion 2a, through which the shaft portion of the screw 3 is inserted. The shaft portion is fastened to the screw hole of the heat sink 4 through this attachment hole.

However, the flange portion 2b compresses and contracts due to thermal expansion in response to changes in the surrounding temperature, which can cause cracks and deformation around the mounting hole. The mounting structure in Patent Document 1 has been proposed as a technology to prevent this.

Japanese Utility Model Application Publication No. 02-93185

In the mounting structure of Patent Document 1, the mounting hole is formed as a long hole that can slide in the direction that is most susceptible to thermal deformation (expansion/contraction), and the long hole absorbs the thermal deformation of the resin part (corresponding to the flange portion 2b).

However, if the thickness of the flange portion 2b is large, expansion and contraction (compression, contraction, etc.) occurs not only in the planar direction indicated by the arrow P in FIG. 1, but also in the thickness direction indicated by the arrow Q. Also, the flange portion 2b in FIG. 1 has a waterproof structure sealed with a ring-shaped packing 5.

In this waterproof structure, the gasket 5 needs to be tightened with a certain pressure when fixing the flange portion 2b, so expansion and contraction in the thickness direction due to temperature changes and other factors becomes a problem. That is, at low temperatures, the restraining force of the gasket 5 is reduced by the expanded flange portion 2b, while at high temperatures there is a risk that the screw 3 will bite into the expanded flange portion 2b and become deformed.

The present invention was made to solve these problems in the past, and aims to reduce the effects of expansion and contraction in the thickness direction of a plastic cover caused by temperature changes in the mounting structure of the plastic cover of an electrical device that is used in a wide range of temperature environments.

(1) The present invention provides a mounting structure for a resin cover that houses a heat generating component of an electric device and is fastened to a heat sink that cools the heat generating component by a plurality of screws,
a cover ceiling portion covering the heat generating component; and a mounting portion having an L-shaped cross section formed on an outer periphery of the cover ceiling portion,
The mounting portion includes a flange portion having an elongated mounting hole through which a shank of the screw is inserted,
A gap between the flange portion and the heat sink is sealed by a packing,
The flange portion is characterized in that it is formed in a tapered shape, with a thickness thinner on the inner periphery side and thicker on the outer periphery side.

(2) One aspect of the present invention is characterized in that the upper surface of the flange portion is formed as an inclined surface that slopes upward from the inner periphery side to the outer periphery side, and the mounting hole is inclined at an angle corresponding to the slope angle of the upper surface.

According to the present invention, in the mounting structure of a plastic cover for electrical equipment that is used in a wide range of temperature environments, the effects of expansion and contraction in the thickness direction of the plastic cover due to temperature changes can be suppressed.

FIG. 11 is a partial cross-sectional view showing the outer periphery of a conventional resin cover. FIG. 4 is a partial view of a resin cover according to the embodiment of the present invention. FIG. 4 is a partial cross-sectional view showing the outer peripheral edge of the resin cover of the first embodiment.

The resin cover mounting structure for electrical equipment according to an embodiment of the present invention will be described with reference to Figures 2 and 3. Here, the same components as those in Figure 1 will be described using the same reference numerals.

In Figure 2, 10 indicates a resin cover according to this embodiment. This resin cover 10, like the conventional resin cover 2, houses an electrical component (heat-generating component) 1 such as an inverter or switching power supply. Here, the heat-generating component 1 is bonded to an aluminum heat sink 4 inside the resin cover 2 for cooling.

Specifically, as shown in Figures 2 and 3, the resin cover 10 has a cover ceiling 12a that covers the heat-generating component 1, and an attachment portion 12b that is bent and formed with an L-shaped cross section on the outer periphery of the cover ceiling 12a. This attachment portion 12b has a leg portion 12c that stands on the outer periphery, and a flange portion 12d that extends from the tip of the leg portion 12c in the outer periphery direction. The heat-generating component 1 is housed in the internal space of the resin cover 10 formed by the cover ceiling 12a and the attachment portion 12b.

The flange portion 12d has a plurality of mounting holes at a predetermined interval for screwing to the heat sink 4 (see FIG. 2). As shown in FIG. 3, a groove 13 is provided around the bottom surface of the flange portion 12d (the surface facing the heat sink 4), and a ring-shaped waterproof packing 5 is fitted inside the groove 13.

In this mounted state, the shank of the screw 3 inserted through the mounting hole 12e is fastened to a screw hole (not shown) in the heat sink 4, thereby fixing the flange portion 12d to the heat sink 4. Here, the flange portion 12d presses the packing 5 with a constant pressure, creating a waterproof structure that seals the gap between the two 4 and 12d.

The mounting hole 12e is formed as an elliptical long hole, as in Patent Document 1, and is structured so that the long axis is arranged along the direction in which thermal deformation is likely to occur, i.e., along a planar direction radially from the center of the cover ceiling portion 12a in FIG. 2, and is slidable in the planar direction in which thermal deformation is likely to occur.

Flange portion 12d is formed in a tapered structure in which the thickness is thin on the inner periphery side (P1 side) and thick on the outer periphery side (P2 side). Therefore, the upper surface 12f of flange portion 12d is formed as an inclined surface (tapered surface) that slopes upward from the inner periphery side to the outer periphery side.

However, in Figure 2, the angle of the gradient is exaggerated to make the tapered structure easier to understand, but in reality, the shape of the tapered structure is determined by factors such as the linear expansion coefficient of the resin, the operating temperature range, and the degree of thermal deformation (compression and expansion) according to the size of the resin cover 10 and the thickness of the mounting hole 12e portion (surrounding area).

For example, if the linear expansion coefficient of the resin is 9 x 10 ^-5 /°C, the operating temperature range is -40°C to 80°C, the longest distance between the mounting holes 12e of the resin cover 10 is 300 mm, and the thickness of the mounting hole 12e portion is 6 mm, then the following will be specified.

-Temperature change range: 80℃-(-40℃)=120℃
Dimensions of compression and expansion in the planar direction (direction of arrow P in FIG. 3): 9×10 ⁻⁵ ×120° C.×300 mm=3.24 mm
Dimensions of compression and expansion in the thickness direction (direction of the arrow Q): 9 x 10 ^-5 x 120°C x 6 mm = 0.0648 mm
- Length of the long hole (mounting hole 12e) in the long axis direction: Standard hole size + (3.24/2) or more - Thickness of the outermost (P2 side) part of the long hole (mounting hole 12e) - Thickness of the innermost (P1 side) part of the long hole = 0.0648 mm or more At this time, to facilitate the tightening engagement of the head by fastening the screw 3, the screw hole is given the same inclination angle as the tapered surface 12f of the flange portion 12d. With this mounting structure for the resin cover 10, the following effects can be obtained.

(1) In other words, when the surrounding temperature rises or falls due to the heat of the heat-generating component 1, the flange portion 12d tries to thermally deform in the planar direction indicated by the arrow P. At this time, the mounting hole 12e of the flange portion 12d is formed as an elongated hole that can slide in the planar direction, as in Patent Document 1, and is therefore able to absorb the thermal deformation in the same direction.

(2) Furthermore, if the thickness of the flange portion 12d is large, thermal deformation also occurs in the thickness direction, as indicated by the arrow Q. For example, when the flange portion 12d becomes hot and expands, the fixing portion of the screw 3 in the mounting hole 12e moves inward (toward P1).

At this time, the thickness of the inner circumference side of the flange portion 12d is already thinner than the outer circumference side according to the linear expansion coefficient, so the expansion is offset and no change occurs in the thickness. Therefore, the force of the screw 3 holding down the flange portion 12d does not change, and the compressive force of the packing 5 remains constant.

On the other hand, when the flange portion 12d becomes cold and shrinks, the fixing portion of the screw 3 in the mounting hole 12e moves outward (towards P2). At this time, the thickness of the outer periphery of the flange portion 12d is already thicker than the inner periphery according to the linear expansion coefficient, so the shrinkage is offset and the thickness does not change. Therefore, the force of the screw 3 holding down the flange portion 12d does not change, and the compressive force of the packing 5 remains constant.

In this way, with the structure of the resin cover 10, the thickness of the screw-fixed portion of the flange portion 12d does not change within the expected temperature change range (normal operating temperature) of the electrical device, so the force holding down the packing 5 does not change, making it possible to maintain a constant waterproof effect at any temperature.

It is also possible to prevent the head of the screw 3 from biting into the flange portion 12d, causing deformation. As a result, it is possible to prevent not only the effect on the screw fixing portion caused by expansion and contraction in the planar direction of the resin cover 10 in response to temperature changes, but also the effect of expansion and contraction in the thickness direction.

The present invention is not limited to the above-described embodiment, but may be modified and implemented within the scope of the claims.

1...Electrical parts (heat generating parts)
Description of the symbols 3: screw 4: aluminum heat sink 5: packing 10: resin cover 12a: cover ceiling 12b: mounting portion 12c: leg 12d: flange 12e: mounting hole 12f: upper surface of flange 13: groove

Claims (2)

A mounting structure for a resin cover that houses a heat generating component of an electric device and is fastened to a heat sink that cools the heat generating component by a plurality of screws,
a cover ceiling portion covering the heat generating component; and a mounting portion having an L-shaped cross section formed on an outer periphery of the cover ceiling portion,
The mounting portion includes a flange portion having an elongated mounting hole through which a shank of the screw is inserted,
A gap between the flange portion and the heat sink is sealed by a packing,
The mounting structure for a resin cover of an electrical device, wherein the flange portion is formed in a tapered shape in which the thickness is thin on the inner periphery side and thick on the outer periphery side. The upper surface of the flange portion is formed as an inclined surface having an upward gradient from the inner circumferential side to the outer circumferential side,
2. The structure for mounting a resin cover of an electrical device according to claim 1, wherein the mounting hole is inclined at an angle corresponding to the inclination angle of the upper surface.

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