Electric compressor

Abstract

[Problem] To provide an electric compressor capable of handling high voltage without increasing the size. [Solution] An electric compressor 1 has: an electric motor 2; a rotating shaft 3 that is rotated by the electric motor 2; a compression mechanism 4 that is driven by the rotating shaft 3; an inverter 6 that drives the electric motor 2; a housing 5 that houses the electric motor 2, the rotating shaft 3, and the compression mechanism 4; and an inverter housing section 7 that is provided integrally with the housing 5 and houses the inverter 6. The inverter 6 includes a plurality of power switching elements 21 arranged side by side on a flat heat dissipation surface 7a provided inside the inverter housing section 7 with an insulating sheet 11 interposed therebetween. At least a part of the heat dissipation surface 7a positioned between the plurality of power switching elements 21 is formed as a convex portion 7b extending in a direction perpendicular to the arrangement direction of the plurality of power switching elements 21.

Description

Electric compressor

[0001] The present invention relates to an inverter integrated type electric compressor.

[0002] The inverter integrated type electric compressor has a bridge circuit composed of a plurality of power switching elements such as IGBTs (Insulated Gate Bipolar Transistors) that drive an electric motor. As described in Japanese Patent Application Laid-Open No. 2011-82344 (Patent Document 1), the plurality of power switching elements constituting the bridge circuit are arranged side by side on a flat heat dissipation surface provided inside the housing with an insulating sheet interposed therebetween. Here, a part of the die pad to which the semiconductor chip (die) is fixed is exposed on the back surface of the power switching element that contacts the insulating sheet, and is configured to dissipate the heat generated by the semiconductor chip.

[0003] Japanese Patent Application Laid-Open No. 2011-82344

[0004] By the way, when increasing the voltage to improve the efficiency of the electric compressor, it is necessary to increase the creepage distance between the die pads exposed on the back surfaces of two adjacent power switching elements arranged adjacent to each other. In the conventional configuration in which a plurality of power switching elements are arranged side by side on a flat heat dissipation surface, the distance between the power switching elements must be increased with the increase in voltage, and the electric compressor also becomes larger as the inverter becomes larger. When the electric compressor becomes larger, it may become difficult to mount the electric compressor in the engine room of the vehicle due to space problems.

[0005] Therefore, an object of the present invention is to provide an electric compressor that can cope with an increase in voltage without accompanying an increase in size.

[0006] The electric compressor comprises an electric motor, a rotating shaft rotated by the electric motor, a compression mechanism driven by the rotating shaft, an inverter that drives the electric motor, a housing that houses the electric motor, the rotating shaft, and the compression mechanism, and an inverter housing integrated with the housing that houses the inverter. The inverter includes a plurality of power switching elements arranged in a line on a flat heat dissipation surface provided inside the inverter housing, with insulating sheets interposed between them. Furthermore, at least a portion of the heat dissipation surface located between the plurality of power switching elements is formed as a convex portion extending in a direction perpendicular to the arrangement direction of the plurality of power switching elements.

[0007] According to the present invention, an electric compressor can handle higher voltages without increasing its size.

[0008] This is a longitudinal cross-sectional view showing an example of an inverter-integrated electric compressor. This is a perspective view showing the main part of the first embodiment of an electric compressor that increases the creepage distance between power switching elements. This is a cross-sectional view showing the main part of the first embodiment of an electric compressor that increases the creepage distance between power switching elements. This is an explanatory diagram for the reason why the creepage distance is increased in the first embodiment. This is a cross-sectional view of the main part showing a modified example of the first embodiment. This is a perspective view showing the main part of the second embodiment of an electric compressor that increases the creepage distance between power switching elements. This is a cross-sectional view showing the main part of the second embodiment of an electric compressor that increases the creepage distance between power switching elements. This is an explanatory diagram for the reason why the creepage distance is increased in the second embodiment. This is a cross-sectional view showing an example of the arrangement of recesses and insulating sheets in the second embodiment. This is a cross-sectional view showing another example of the arrangement of recesses and insulating sheets in the second embodiment.

[0009] The embodiments for carrying out the present invention will be described in detail below with reference to the attached drawings. It should be noted that the embodiments described below are merely examples and should not be interpreted as limiting the scope to their configurations.

[0010] Figure 1 shows an example of an inverter-integrated electric compressor 1 to which the present invention can be applied. The electric compressor 1 is incorporated, for example, into the refrigerant circuit (not shown) of an air conditioning system mounted on a vehicle, and is configured to compress and discharge the refrigerant.

[0011] The electric compressor 1 includes an electric motor 2, a rotating shaft 3 that rotates with respect to the electric motor 2, a compression mechanism 4 driven by the rotating shaft 3, a housing 5, an inverter 6 that drives the electric motor 2, an inverter housing 7, and a cover member 8.

[0012] The electric motor 2 is, for example, a three-phase brushless motor such as a brushless DC motor, and is driven by power supplied from the inverter 6. The rotating shaft 3 is rotatably supported in the housing 5 by bearings (not shown) and is rotated by the electric motor 2. The compression mechanism 4 can be a well-known compression mechanism such as a reciprocating compression mechanism, a swash plate compression mechanism, a screw type compression mechanism, a scroll type compression mechanism, or a slide vane type compression mechanism. The housing 5 has a cylindrical cross-section and houses the electric motor 2, the rotating shaft 3, and the compression mechanism 4. The electric motor 2, the rotating shaft 3, and the compression mechanism 4 are arranged concentrically inside the housing 5.

[0013] The inverter 6 includes an inverter circuit section 20 for driving the electric motor 2 and a well-known noise filter circuit section 30 for reducing electromagnetic noise. The inverter housing section 7 is provided integrally with the housing 5 and houses the inverter 6 inside. Specifically, the inverter housing section 7 is provided on the electric motor 2 side of the housing 5. The inverter housing section 7 has a larger projected area than the housing 5. The inverter housing section 7 is formed by a bottom wall 71 and a peripheral wall 73 rising from the periphery of the bottom wall 71, and has an opening 75 facing the bottom wall 71. With the inverter circuit section 20 and the noise filter circuit section 30 constituting the inverter 6 housed in the inverter housing section 7, the opening 75 of the inverter housing section 7 is closed by a cover member 8. The cover member 8 is fixed to the peripheral wall 73 of the inverter housing section 7 (which is also part of the housing 5) by bolts (not shown) with a well-known sealing member interposed between them.

[0014] An HV connector (high-voltage connector) 9 is attached to the bottom wall 71 of the inverter housing 7 for supplying DC power from an on-board battery (not shown) to the inverter circuit 20 of the inverter 6. In addition, a portion of the bottom wall 71 of the inverter housing 7 forms a partition wall 77 that separates the inside of the housing 5 from the inside of the inverter housing 7.

[0015] The housing 5 has an inlet 5a for introducing refrigerant into the housing 5 and an outlet 5b for releasing refrigerant out of the housing 5. The inlet 5a is configured to introduce refrigerant between the internal partition wall 77 and the electric motor 2 inside the housing 5. The refrigerant that enters the housing 5 from the inlet 5a passes through the electric motor 2 to the compression mechanism 4, where it is compressed. The refrigerant compressed by the compression mechanism 4 then flows out to the outside through the outlet 5b.

[0016] The refrigerant flowing into the housing 5 from the inlet 5a is a low-temperature gaseous refrigerant that has passed through the expansion valve and evaporator in the refrigerant circuit of the air conditioning equipment installed in the vehicle. Therefore, the partition wall 77 and the electric motor 2 can be cooled by the refrigerant flowing into the housing 5 from the inlet 5a.

[0017] The inverter circuit section 20 of the inverter 6 is configured to convert DC power supplied from the vehicle battery via the HV connector 9 into three-phase AC power, and to supply the three-phase AC power to the stator coil 2a of the electric motor 2 via a power supply line 10 that extends through the partition wall 77. For this reason, the inverter circuit section 20 has six power switching elements 21 and an inverter control board 25 on which a control circuit 23 for controlling the six power switching elements 21 is mounted.

[0018] The six power switching elements 21 can be divided into three upper power switching elements 21a connected to the positive terminal of the vehicle battery, and three lower power switching elements 21b connected to the negative terminal of the vehicle battery. The three upper power switching elements 21a turn ON or OFF in response to a drive signal from a control circuit 23 mounted on the inverter control board 25, controlling the supply of power from the vehicle battery to the U-phase coil, V-phase coil, and W-phase coil of the electric motor 2. Similarly, the three lower power switching elements 21b turn ON or OFF in response to a drive signal from a control circuit 23 mounted on the inverter control board 25, controlling the supply of power from the U-phase coil, V-phase coil, and W-phase coil of the electric motor 2 to the vehicle battery. Here, the three upper power switching elements 21a and the three lower power switching elements 21b are arranged in parallel with a predetermined distance between them, as shown in Figure 2. In the following explanation, when it is not necessary to distinguish between the upper power switching element 21a and the lower power switching element 21b, they will simply be referred to as "power switching element 21".

[0019] The three power switching elements 21a on the upper side and the three power switching elements 21b on the lower side are arranged parallel to each other at a predetermined distance apart, with an insulating sheet 11 interposed between them and a flat heat dissipation surface 7a formed on the side of the partition wall 77 facing the inverter housing 7. Here, each power switching element 21 is arranged so that the die pad DP (details will be described later) exposed on its back surface is in direct contact with the insulating sheet 11. Furthermore, the three power switching elements 21a on the upper side and the three power switching elements 21b on the lower side are fixed in a state where they are pressed against the insulating sheet 11 by an arm member 12. The arm member 12 is fixed by bolts 13 to an arm mounting part 14 provided inside the inverter housing 7.

[0020] The inverter control board 25 has multiple mounting holes formed on its surface and is fixed to multiple board mounting sections 15 (see Figure 2) provided inside the inverter housing 7 by multiple bolts (not shown). The inverter control board 25 is positioned near the cover member 8, that is, spaced apart from the six power switching elements 21. Therefore, each of the six power switching elements 21 has multiple pins extending toward the inverter control board 25, or more precisely, multiple pins extending through the inverter control board 25. These pins are soldered to the inverter control board 25, thereby electrically connecting the six power switching elements 21 and the inverter control board 25.

[0021] The noise filter circuit 30 is positioned between the inverter circuit 20 and the HV connector 9. The noise filter circuit 30 is fixed to a filter mounting section 17 located inside the inverter housing 7 by a plurality of bolts 16 (only one is shown in Figure 1). The upper surface of the noise filter circuit 30 is in contact with the inner surface of the cover member 8 via a heat dissipation sheet 18, and the lower surface is in contact with the bottom surface of the inverter housing 7 via a heat dissipation sheet 19. As a result, the amount of heat transferred from the noise filter circuit 30 to the cover member 8 and the inverter housing 7 increases, ensuring their cooling performance.

[0022] By the way, if the DC power supplied to the inverter circuit section 20 of the inverter 6 via the HV connector 9 is increased in voltage for the purpose of improving the efficiency of the electric compressor 1, it becomes necessary to increase the creepage distance between the die pads DP exposed on the back surface of two adjacent power switching elements 21. In this case, if the power switching elements 21 are arranged side by side on the flat heat dissipation surface 7a provided in the inverter housing section 7, the spacing between adjacent power switching elements 21 must be increased, and the electric compressor 1 will also become larger as the inverter 6 becomes larger. Therefore, in this embodiment, by adopting the configuration described below, the electric compressor 1 can be made to accommodate higher voltage without increasing its size.

[0023] <First Embodiment> Figures 2 and 3 show a first embodiment of the electric compressor 1 that can handle high voltage without increasing size. In the following description, the above-mentioned general electric compressor 1 is assumed, and the differences from it are mainly described (the same applies hereafter).

[0024] In the inverter 6, as described above, a plurality of power switching elements 21 (six power switching elements 21 in this embodiment) are arranged in a row on a flat heat dissipation surface 7a provided inside the inverter housing 7, with an insulating sheet 11 interposed between them. Each power switching element 21 has a roughly rectangular parallelepiped shape, and a plurality of pins are provided on one side in the longitudinal direction (the same applies hereinafter). In addition, a part of the die pad DP is exposed on the back surface (i.e., the surface facing the insulating sheet 11) of each power switching element 21, and the front surface (back surface) of the die pad DP is in contact with the insulating sheet 11.

[0025] Furthermore, at least a portion of the heat dissipation surface 7a located between the multiple power switching elements 21 is formed as a convex portion 7b extending in a direction perpendicular to the arrangement direction of the multiple power switching elements 21. That is, at least a portion of the heat dissipation surface 7a located between two adjacent power switching elements 21 is formed as a convex portion 7b extending in the arrangement direction of the upper power switching element 21a and the lower power switching element 21b. It is desirable that the convex portion 7b is formed over a range that faces at least the side surface of the power switching element 21 in its extending direction. The height of the convex portion 7b can be appropriately determined, for example, according to the DC voltage supplied to the inverter circuit section 20 of the inverter 6. Furthermore, the cross-sectional shape of the convex portion 7b is not limited to a substantially rectangular shape with chamfered corners as shown in Figures 2 and 3, but can be any shape such as a triangular shape, a semicircular shape, or a semielliptical shape.

[0026] In this electric compressor 1, at least a portion of the heat dissipation surface 7a located between two adjacent power switching elements 21 is formed as a protrusion 7b extending in a direction perpendicular to the arrangement direction of the power switching elements 21. Therefore, as shown in Figure 4, the insulating sheet 11 placed on the heat dissipation surface 7a is also lifted upward (away from the heat dissipation surface 7a) by the protrusion 7b. Consequently, the creepage distance A between the die pads DP of the two adjacent power switching elements 21 is larger by bypassing the protrusion 7b, as shown in the figure, compared to an electric compressor 1 without the protrusion 7b. Since the creepage distance A is increased without changing the spacing between the two adjacent power switching elements 21, it is possible to handle higher voltages without increasing the size of the electric compressor 1.

[0027] Here, it is desirable that the insulating sheet 11 adheres closely to the entire outer surface of the protrusion 7b. In this way, the creepage distance A can be maximized compared to a configuration in which there is a gap between the insulating sheet 11 and the heat dissipation surface 7a and its protrusion 7b.

[0028] Furthermore, since the protrusion 7b is formed over an area that faces at least the sides of two adjacent power switching elements 21, it does not affect the insulation performance between the die pads DP of adjacent power switching elements 21.

[0029] Furthermore, the protrusion 7b may be configured to contact at least a portion of the side surface of the power switching element 21, as shown in Figure 5. In the illustrated example, the entire heat dissipation surface 7a located between two substantially rectangular parallelepiped power switching elements 21 is formed on the protrusion 7b, and both sides of the protrusion 7b are in contact with the side surfaces of the power switching elements 21. However, the protrusion 7b may be configured so that only one side of the protrusion 7b is in contact with the side surface of the power switching element 21. In this way, the heat generated by the power switching element 21 is transferred from its side surface to the heat dissipation surface 7a via the insulating sheet 11, thereby improving the heat dissipation performance of the power switching element 21. Also, since the side surface of the power switching element 21 is in contact with the protrusion 7b, the power switching element 21 can be positioned relative to the inverter housing 7.

[0030] <Second Embodiment> Figures 6 and 7 show a second embodiment of the electric compressor 1 that can handle higher voltages without increasing size.

[0031] In the inverter 6, similar to the first embodiment, a plurality of power switching elements 21 are arranged in a row on a flat heat dissipation surface 7a provided inside the inverter housing 7, with an insulating sheet 11 interposed between them. Furthermore, a portion of the die pad DP is exposed on the back surface of each power switching element 21, and the surface of the die pad DP is in contact with the insulating sheet 11.

[0032] Furthermore, at least a portion of the heat dissipation surface 7a located between the multiple power switching elements 21 is formed as a recess 7c having a V-shaped cross-section that extends in a direction perpendicular to the arrangement direction of the multiple power switching elements 21. That is, at least a portion of the heat dissipation surface 7a located between two adjacent power switching elements 21 is formed as a recess 7c that extends in the arrangement direction of the upper power switching element 21a and the lower power switching element 21b. It is desirable that the recess 7c is formed over a range that at least faces the side surface of the power switching element 21 in its extending direction. In addition, the cross-sectional shape (width and depth) of the recess 7c can be appropriately determined, for example, according to the DC voltage supplied to the inverter circuit section 20 of the inverter 6.

[0033] In this electric compressor 1, at least a portion of the heat dissipation surface 7a located between two adjacent power switching elements 21 is formed as a recess 7c extending in a direction perpendicular to the arrangement direction of the power switching elements 21. As a result, as shown in Figure 8, a portion of the insulating sheet 11 placed on the heat dissipation surface 7a fits into the recess 7c. Consequently, the creepage distance B between the die pads DP of the two adjacent power switching elements 21 is larger than that of an electric compressor 1 without a recess 7c, as shown in the figure, by bypassing the surface of the insulating sheet 11, of which at least a portion fits into the recess 7c. Since the creepage distance B is increased without changing the spacing between the two adjacent power switching elements 21, it is possible to handle higher voltages without increasing the size of the electric compressor 1.

[0034] The cross-sectional shape of the recess 7c is not limited to the V-shape shown in Figures 6 and 7, but can be any shape such as a rectangle, trapezoid, U-shape, semicircle, or semi-ellipse. When the recess 7c has a rectangular cross-sectional shape, it is desirable that the insulating sheet 11 adheres tightly to the entire inner surface of the recess 7c, as shown in Figure 9. However, as shown in Figure 10, the insulating sheet 11 may not adhere tightly to the entire inner surface of the recess 7c, and a part of it may be fitted into the recess 7c.

[0035] Here, if the insulating sheet 11 is in close contact with the entire inner surface of the rectangular recess 7c, the creepage distance B can be maximized compared to a configuration in which there is a gap between the insulating sheet 11 and the inner surface of the recess 7c. The same applies when the recess 7c has a different cross-sectional shape.

[0036] Furthermore, since the recess 7c is formed over an area that faces at least the sides of two adjacent power switching elements 21, it does not affect the insulation performance between the die pads DP of adjacent power switching elements 21.

[0037] Furthermore, those skilled in the art will readily understand that, provided that there are no technical inconsistencies, new embodiments can be created by omitting parts of the various embodiments described above, combining parts of them, or replacing parts of them with well-known technologies. Therefore, it should be noted that embodiments created in this way are included within the scope of the present invention.

[0038] 1...Electric compressor, 2...Electric motor, 3...Rotating shaft, 4...Compression mechanism, 5...Housing, 6...Inverter, 7...Inverter housing, 7a...Heat dissipation surface, 7b...Protrusion, 11...Insulating sheet, 21...Power switching element

Claims

1. An electric compressor comprising: an electric motor; a rotating shaft rotated by the electric motor; a compression mechanism driven by the rotating shaft; an inverter that drives the electric motor; a housing that houses the electric motor, the rotating shaft, and the compression mechanism; and an inverter housing section integrally provided with the housing and housing the inverter, wherein the inverter includes a plurality of power switching elements arranged in a line on a flat heat dissipation surface provided inside the inverter housing section with an insulating sheet interposed between them, and at least a portion of the heat dissipation surface located between the plurality of power switching elements is formed into a convex portion extending in a direction perpendicular to the arrangement direction of the plurality of power switching elements.

2. The electric compressor according to claim 1, wherein the protrusion contacts at least a portion of the side surface of the power switching element.

3. The electric compressor according to claim 1, wherein the protrusion is formed over an area that faces at least the side surface of the power switching element.

4. The electric compressor according to claim 1, wherein the insulating sheet adheres closely to the entire outer surface of the protrusion.

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