A motor-driven compressor includes a metal housing accommodating a compression unit and an electric motor and a cover coupled to the housing. The cover and the housing define an accommodation chamber that accommodates a motor driving circuit that drives the electric motor. The cover includes a metal shield that blocks electromagnetic noise, a resin outer insulator that is fixed to an outer side of the shield and includes an outer circumferential portion, and a resin inner insulator that is fixed to an inner side of the shield and includes an outer circumferential portion. The shield, the outer insulator, and the inner insulator are separate from one another and stacked together. The shield is held between the outer insulator and the inner insulator. The outer circumferential portion of the outer insulator is joined to the outer circumferential portion of the inner insulator.

BACKGROUND OF THE INVENTION

The present invention relates to a motor-driven compressor.

A motor-driven compressor includes a metal housing accommodating a compression unit, which compresses and discharges refrigerant, and an electric motor, which drives the compression unit. A cover that defines an accommodation chamber is coupled to the housing. The accommodation chamber accommodates a motor driving circuit that drives the electric motor.

When the cover is made of metal, the overall weight of the motor-driven compressor increases. The use of a resin cover allows the motor-driven compressor to be lighter. However, a resin cover would transmit electromagnetic noise from outside the compressor to the motor driving circuit. In addition, electromagnetic noise from the motor driving circuit may leak out of the compressor through the resin cover.

Accordingly, in Japanese Laid-Open Patent Publication No. 2008-215236, a metal conductor (shield) is stacked on and fixed to a resin insulator. Electromagnetic noise from the exterior is blocked by the conductor and transmitted to a housing. This limits the electromagnetic noise that enters an accommodation chamber, which accommodates a motor driving circuit, through the insulator. In addition, electromagnetic noise from the motor driving circuit is blocked by the conductor and transmitted to the housing. This limits the leakage of electromagnetic noise from the motor driving circuit to the exterior through the insulator.

When the outer surface of the conductor is exposed, the ambient air may erode the conductor. Thus, an insulator (outer insulator) may be fixed to the outer surface of the conductor. The insulator covers the outer surface of the conductor so that the conductor is not exposed to the ambient air. Further, to insulate the motor driving circuit from the conductor, an insulator (inner insulator) may be stacked on and fixed to the inner surface of the conductor so that the insulator is located between the motor driving circuit and the conductor.

Molding may be performed to form such a three-layered cover including insulators fixed to the outer and inner surfaces of the conductor. Specifically, when a conductor is arranged in a mold, the mold is filled with molten resin at the inner and outer sides of the conductor. The molten resin is then hardened to form resin insulators that are stacked on and fixed to the inner and outer surfaces of the conductor. This forms the three-layered cover including insulators fixed to the outer and inner surfaces of the conductor.

When the cover is returned to room temperature after being molded, the conductor, the outer insulator, and the inner insulator undergo thermal contraction. Since the linear expansion coefficient of the conductor differs from that of the insulators, the degree of thermal contraction of the conductor differs from that of the insulators. The adherence between the conductor and the insulators may hinder smooth contraction of each layer. This may deform the conductor and insulators during the thermal contraction. As a result, the desired shape and dimensional accuracy may not be obtained with the cover.

SUMMARY OF THE INVENTION

It is an object of the present disclosure to provide a motor-driven compressor that includes a cover having the desired shape and high dimensional accuracy.

To achieve the above object, one aspect of the present invention is a motor-driven compressor including a metal housing accommodating a compression unit and an electric motor and a cover coupled to the housing. The cover and the housing define an accommodation chamber that accommodates a motor driving circuit that drives the electric motor. The cover includes a metal shield that blocks electromagnetic noise, a resin outer insulator that is fixed to an outer side of the shield and includes an outer circumferential portion, and a resin inner insulator that is fixed to an inner side of the shield and includes an outer circumferential portion. The shield, the outer insulator, and the inner insulator are separate from one another and stacked together. The shield is held between the outer insulator and the inner insulator. The outer circumferential portion of the outer insulator is joined to the outer circumferential portion of the inner insulator.

DETAILED DESCRIPTION OF THE INVENTION

Referring toFIGS. 1A to 4B, a motor-driven compressor of one embodiment will now be described. The motor-driven compressor is installed in a vehicle and used with a vehicle air-conditioning device.

As shown inFIG. 1A, a motor-driven compressor10includes a housing H that includes a cylindrical discharge housing member11and a cylindrical suction housing member12coupled to the discharge housing member11. The discharge housing member11and the suction housing member12are made of a metal, preferably aluminum, and each includes an open end and a closed end. The suction housing member12has a circumferential wall including a suction port (not shown). The suction port is connected to an external refrigerant circuit (not shown). The discharge housing member11includes a discharge port14connected to the external refrigerant circuit. The suction housing member12accommodates a compression unit15(indicated by the broken lines inFIG. 1A), which compresses refrigerant, and an electric motor16, which drives the compression unit15. Although not shown in the drawings, the compression unit15of the present embodiment includes a fixed scroll, which is fixed in the suction housing member12, and a movable scroll, which faces the fixed scroll.

A stator17is fixed to the inner surface of the suction housing member12. The stator17includes a stator core17a, which is fixed to the inner surface of the suction housing member12, and coils17b, which are wound around teeth (not shown) of the stator core17a. A rotatable rotation shaft19extends through the stator17in the suction housing member12. A rotor18is fixed to the rotation shaft19.

The suction housing member12has an end wall12ato which a cover13is coupled. The cover13is cylindrical and includes an open end and a closed end. A planar coupling base21is arranged between the suction housing member12and the cover13. The coupling base21is made of a metal, preferably aluminum. The coupling base21is coupled to the end wall12aof the suction housing member12. The coupling base21is thermally coupled to the suction housing member12. The coupling base21forms a portion of the suction housing member12(housing H).

The cover13and the coupling base21define an accommodation chamber22. The accommodation chamber22accommodates a motor driving circuit20that drives the electric motor16. The motor driving circuit20includes a flat circuit board20aand a plurality of electric components20b,20cand20d, which are electrically connected to the circuit board20a.

The surface of the coupling base21opposite to the end wall12aof the suction housing member12includes a plurality of bosses21aextending in the axial direction of the rotation shaft19. The circuit board20ais coupled to the bosses21aby fastening coupling bolts21bto the bosses21a. The motor driving circuit20is connected to the electric motor16by wires (not shown). In the present embodiment, the compression unit15, the electric motor16, and the motor driving circuit20are arranged in this order along the axis L of the rotation shaft19(in the axial direction).

In the present embodiment, the circuit board20a, the electric components20b,20cand20d, and the coupling bolts21dserve as components of the motor driving circuit20.

The cover13includes a shield23, a planar outer insulator24, which is fixed to the outer side (outer surface) of the shield23, and a planar inner insulator25, which is fixed to the inner side (inner surface) of the shield23. The shield23is formed from a thin plate made of a metal, preferably aluminum, and blocks electromagnetic noise. The outer and inner insulators24and25are made of resin. The shield23and the insulators24and25are stacked together. The shield23includes a flat lid23a, which is held between the outer insulator24and the inner insulator25, and a tubular portion23b, which extends from the rim of the lid23ain the axial direction of the rotation shaft19.

As shown inFIG. 1B, the outer circumferential portion of the outer insulator24and the outer circumferential portion of the inner insulator25are joined to each other by an annular resin joint26. The joint26includes an inner joint portion26alocated at the inner side of the tubular portion23bof the shield23. The inner joint portion26ais continuous with the outer circumferential portion of the inner insulator25. The joint26also includes an outer joint portion26blocated at the outer side of the tubular portion23bof the shield23. The outer joint portion26bis continuous with the outer circumferential portion of the outer insulator24. Further, the joint26includes a connection portion26clocated at the distal end of the tubular portion23bof the shield23. The connection portion26cconnects the inner joint portion26ato the outer joint portion26b.

As shown inFIG. 2, the inner surface of the outer insulator24faces the motor driving circuit20(faces the shield23) and includes recesses24a, where the outer insulator24does not contact the shield23, and projections24t, where the outer insulator24contacts the shield23. The outer surface of the inner insulator25faces away from the motor driving circuit20(faces the shield23) and includes recesses25a, where the inner insulator25does not contact the shield23, and projections25t, where the inner insulator25contacts the shield23. Further, the inner surface of the inner insulator25faces toward the motor driving circuit20and includes recesses25bto25e. Due to the recesses25band25c, interference is avoided between the inner insulator25and the electric components20band20c. Due to the recess25d, interference is avoided between the inner insulator25and the distal end of a lead201dextending from the electric component20dtoward the inner insulator25. Due to the recess25e, interference is avoided between the inner insulator25and a coupling bolt21b. In addition, the inner surface of the inner insulator25includes projections25kextending between the electric components20band20c, the lead201dof the electric component20d, and the coupling bolt21b.

The outer surface of the lid23aof the shield23includes a tubular inner connector portion23cextending in the axial direction of the rotation shaft19. The outer surface of the outer insulator24that faces away from the motor driving circuit20(and the shield23) includes a tubular outer connector portion24cextending in the axial direction of the rotation shaft19. The inner connector portion23cis located at the inner side of the outer connector portion24c.

A connector28is fixed between the shield23and the inner insulator25. The connector28includes a metal terminal27electrically connected to an external power supply (vehicle battery). The metal terminal27includes a first end portion and a second end portion that is opposite to the first end portion. The connector28also includes a holding portion28aand a flange28b. The holding portion28ais located in the inner connector portion23cof the shield23and holds the first end portion of the metal terminal27. The flange28bextends from the proximal end of the holding portion28atoward the second end portion of the metal terminal27. The first end portion of the metal terminal27is extended through a recess in the distal end of the holding portion28aand exposed to the exterior so as to be connected to the external power supply.

The outer surface of the inner insulator25includes an accommodation recess25fthat accommodates the proximal end of the holding portion28aand the flange28b. The flange28bis held and positioned between the bottom of the accommodation recess25fand the lid23aof the shield23. The section of the inner insulator25defining the bottom of the accommodation recess25fincludes an insertion hole25hthat receives the second end portion of the metal terminal27. The second end portion of the metal terminal27is extended through the insertion hole25hand electrically connected to the circuit board20a.

As shown inFIG. 1B, the surface of the coupling base21opposite to the end wall12aof the suction housing member12includes a plurality of bosses21f(only one shown inFIG. 1B) extending in the axial direction of the rotation shaft19. Each boss21fincludes a flat distal end that is in contact with the inner surface of the lid23aof the shield23. The boss21fextends through a through hole25gformed in the inner insulator25. In addition, each boss21fincludes a through hole21h.

The cover13includes insertion holes29into which bolts B are insertable. Each insertion hole29includes a first insertion hole29a, which is formed in the outer insulator24, and a second insertion hole29b, which is formed in the shield23. The first insertion hole29ahas a larger diameter than the second insertion hole29b. The first insertion hole29ais aligned with the second insertion hole29b. Each bolt B includes a threaded rod B1and a head B2, which is located at the proximal end of the rod B1.

A spacer30is arranged between the head B2of each bolt B and the shield23. The spacer30is made of a metal, preferably aluminum, and forms a portion of the shield23. The spacer30includes a flat end portion30aand a tubular portion30bextending from the rim of the end portion30aperpendicular to the end portion30a. The end portion30aincludes an insertion hole30hinto which the rod B1of the bolt B is insertable. The rod B1is inserted through the first insertion hole29a, the insertion hole30h, the second insertion hole29b, and the through hole21h. Then, the rod B1is fastened to the end wall12aof the suction housing member12. This couples the cover13to the end wall12aof the suction housing member12. The coupling base21is arranged between the cover13and the end wall12a.

The inner surface of the outer insulator24includes annular grooves31. Accommodation recesses32are formed between the inner surface of the outer insulator24and the shield23. Each annular groove31receives the tubular portion30bof the corresponding spacer30, and each accommodation recess32accommodates the end portion30aof the corresponding spacer30.

The outer insulator24also includes a seal accommodation groove33located at the inner side of each annular groove31. The seal accommodation grooves33are annular and continuous with the corresponding ones of the annular grooves31and the accommodation recesses32. Each seal accommodation groove33accommodates an annular sealing member34surrounding the first insertion hole29a. The sealing member34is held between the inner surface of the tubular portion30bof the spacer30and the wall of the seal accommodation groove33that faces the inner surface of the tubular portion30b. Thus, the sealing member34is compressed in a direction perpendicular to the axis of the rod B1of the bolt B. The sealing member34seals the gap between the shield23and the outer insulator24.

The head B2of each bolt B is located in the corresponding first insertion hole29a. A washer35is arranged between the end portion30aof each spacer30and the head B2of the corresponding bolt B in the axial direction of the rod B1of the bolt B. The washer35, which is made of a metal, preferably aluminum, surrounds the rod B1. The washer35seals the gap between the end portion30aof the spacer30and the head B2of the bolt B. The section of the shield23surrounding the second insertion hole29bis held between the head B2of the bolt B and the boss21f. The axial force of the bolt B is applied to this section through the spacer30and the washer35without being applied to the outer insulator24or the inner insulator25.

The method for manufacturing the cover13will now be described.

Referring toFIG. 3, the outer insulator24and the inner insulator25are separately molded in advance. Then, the connector28is attached to the inner insulator25so that the insertion hole25hreceives the second end portion of the metal terminal27and the accommodation recess25faccommodates the proximal end of the holding portion28aand the flange28bof the connector28. Then, the shield23is attached to the outer surface of the inner insulator25. This positions the holding portion28ain the inner connector portion23c.

Then, the spacer30, which accommodates the sealing member34, is arranged in the annular groove31and the accommodation recess32of the outer insulator24. The outer insulator24is then attached to the outer surface of the lid23aof the shield23. This positions the inner connector portion23cin the outer connector portion24c. In addition, the shield23is held between the outer insulator24and the inner insulator25.

As shown inFIG. 4A, the shield23, the outer insulator24, and the inner insulator25are arranged in a mold40, which includes a first mold member40aand a second mold member40b. This forms a filling cavity41in the mold40. The filling cavity41extends from the outer circumferential portion of the outer insulator24, passes beside the distal end of the tubular portion23bof the shield23, and extends to the outer circumferential portion of the inner insulator25.

As shown inFIG. 4B, the filling cavity41is filled with molten resin, which is then hardened. This forms the joint26in the filling cavity41. The joint26joins the outer circumferential portion of the outer insulator24to the outer circumferential portion of the inner insulator25. This forms the three-layered cover13, in which the outer insulator24is fixed to the outer surface of the shield23, and the inner insulator25is fixed to the inner surface of the shield23. When the cover13is removed from the mold40and returned to room temperature, the joint26undergoes thermal contraction. This forms the cover13that has the desired shape and high dimensional accuracy.

The cover13is formed just by joining the outer circumferential portion of the outer insulator24to the outer circumferential portion of the inner insulator25with the joint26when the shield23is held between the outer insulator24and the inner insulator25. This limits overall thermal contraction of the shield23, the outer insulator24, and the inner insulator25that would be caused if molding were performed to form the three-layered cover13. If the three-layered cover13were formed by performing molding, the shield23, the outer insulator24, and the inner insulator25may deform if those portions do not contract smoothly. In this regard, the present embodiment limits such deformation. This allows the cover13to have the desired shape and high dimensional accuracy.

The motor-driven compressor10is installed in a vehicle. Thus, the heat from the vehicle engine and the heat of the ambient air may deform the cover13. However, the recesses24a,25a,25b,25c,25dand25eand the projections24t,25kand25tlimit deformation of the cover13caused by heat. This improves the durability of the cover13.

The sealing member34is located between the outer insulator24and the spacer30. The sealing member34seals the gap between the outer insulator24and the spacer30, that is, the sealing member34seals the gap between the shield23and the outer insulator24. Thus, the sealing member34ensures the sealing between the shield23and the outer insulator24. This blocks entry of foreign matter such as water and dust into the accommodation chamber22through the gap between the shield23and the outer insulator24.

Further, the sealing member34surrounds the first insertion hole29a. This blocks entry of foreign matter from the first insertion hole29ainto the accommodation chamber22through the gap between the shield23and the outer insulator24when coupling the cover13to the suction housing member12with the bolt B.

The section of the shield23surrounding the second insertion hole29bis held between the head B2of the bolt B and the boss21f. The axial force of the bolt B is applied to this section through the spacer30and not applied to the outer insulator24or the inner insulator25. When coupling the cover13to the suction housing member12with the bolt B, the outer insulator24and the inner insulator25are not held between the head B2and the boss21f. Thus, the axial force of the bolt B does not deform the outer insulator24or the inner insulator25. This avoids deterioration in the sealing of the suction housing member12with the cover13that would be caused when the outer insulator24or the inner insulator25deforms and loosens the bolt B.

The advantages of the present embodiment will now be described.

(1) The cover13, which includes the shield23, the outer insulator24, and the inner insulator25that are separate from one another, is formed by joining the outer circumferential portion of the outer insulator24to the outer circumferential portion of the inner insulator25with the joint26when the shield23is held between the outer insulator24and the inner insulator25. Thus, the three-layered cover13, in which the shield23, the outer insulator24, and the inner insulator25are integrated, can by formed by just joining the outer circumferential portion of the outer insulator24to the outer circumferential portion of the inner insulator25when the shield23is held between the outer insulator24and the inner insulator25. This limits overall thermal contraction of the shield23, the outer insulator24, and the inner insulator25that would be caused if the three-layered cover13were formed by molding. In the three-layered cover13that is formed by molding, the shield23, the outer insulator24, and the inner insulator25may deform if those portions do not contract smoothly. The present embodiment limits such deformation. This allows the cover13to have the desired shape and high dimensional accuracy.

(2) The outer insulator24and the inner insulator25include the recesses24aand25awhere contact with the shield23does not occur, and the projections24tand25t, where contact with the shield23occurs. Compared to a structure in which the entire surface of the outer insulator24that faces the shield23and the entire surface of the inner insulator25that faces the shield23are in close contact with the shield23, the recesses24aand25aand the projections24tand25tlimit deformation of the cover13that may be caused by heat. This improves the durability of the cover13.

(3) The inner insulator25includes the recesses25b,25c,25dand25eso that the inner insulator25does not interfere with the electric components20band20c, the lead201dof the electric component20d, and the coupling bolt21b. The inner insulator25also includes the projections25kextending between the electric components20band20c, the lead201dof the electric components20d, and the coupling bolt21b. The recesses25b,25c,25dand25eallow the distance to be minimized between the inner insulator25and the motor driving circuit20. This reduces the size of the motor-driven compressor10. In addition, the projections25kreinforce the inner insulator25.

(4) The joint26joins the outer circumferential portion of the outer insulator24and the outer circumferential portion of the inner insulator25. This allows for easy connection of the outer circumferential portion of the outer insulator24and the outer circumferential portion of the inner insulator25.

(5) The connector28, which is electrically connected to the external power supply, is fixed between the shield23and the inner insulator25. This allows the connector28to be fixed just by holding the connector28between the shield23and the inner insulator25.

(6) The sealing member34, which blocks entry of foreign matter into the accommodation chamber22, is located between the shield23and the outer insulator24. The sealing member34seals the gap between the shield23and the outer insulator24. Thus, the sealing member34ensures the sealing between the shield23and the outer insulator24. This blocks entry of foreign matter into the accommodation chamber22through the gap between the shield23and the outer insulator24.

(7) The sealing member34is compressed in a direction perpendicular to the axis of the bolt B. If the sealing member34were compressed in the axial direction of the bolt B, for example, the sealing member34would produce a resilient force that acts to restore the original shape of the sealing member34. This would create a gap between the shield23and the outer insulator24. The present embodiment avoids such a problem.

(8) The sealing member34surrounds the first insertion hole29a. This blocks entry of foreign matter from the first insertion hole29ainto the accommodation chamber22through the gap between the shield23and the outer insulator24when coupling the cover13to the suction housing member12with the bolt B.

(9) The section of the shield23surrounding the second insertion hole29bis held between the head B2of the bolt B and the boss21f. The axial force of the bolt B is applied to this section through the spacer30and not applied to the outer insulator24or the inner insulator25. When coupling the cover13to the suction housing member12with the bolt B, the outer insulator24and the inner insulator25are not held between the head B2and the boss21f. Thus, the axial force of the bolt B does not deform the outer insulator24or the inner insulator25. This avoids deterioration in the sealing between the suction housing member12and the cover13that would be caused when the outer insulator24or the inner insulator25deforms and loosens the bolt B.

(10) If the outer insulator24and the inner insulator25were formed by filling a mold with molten resin at the outer and inner sides of the shield23and then hardening the molten resin, a pin would have to be arranged in the mold to hold and fix the shield23in the mold. However, this would form an unnecessary hole in the molded outer insulator24or the inner insulator25at the position where the pin was located during the molding. In the present embodiment, the outer insulator24and the inner insulator25are separately molded in advance and thus do not include an unnecessary hole. This improves the quality of the cover13.

(11) In addition, if the outer insulator24and the inner insulator25were formed by filling a mold with molten resin at the outer and inner sides of the shield23as described above, limitations would be imposed to the shapes of the outer insulator24and the inner insulator25due to the limitation in the direction in which the molded cover is removed from the mold. However, in the present embodiment, the outer insulator24and the inner insulator25are molded in advance and have the desired shape and high dimensional accuracy. Thus, unnecessary portions may be omitted from the outer insulator24and the inner insulator25. This reduces the weight of the cover13.

The outer circumferential portion of the lid23aof the shield23may include a through hole, and the outer insulator24may include a projection extending through the through hole of the lid23aso that the joint26and the projection are joined to each other. In this case, in addition to the connection between the outer circumferential portion of the outer insulator24and the outer circumferential portion of the inner insulator25by the joint26, the connection between the joint26and the outer insulator24by the projection is achieved. This strengthens the assembly of the shield23, the outer insulator24, and the inner insulator25.

Each of the outer insulator24and the inner insulator25may include an outer circumferential portion that extends in the axial direction of the rotation shaft19beyond the distal end of the tubular portion23bof the shield23. In this case, the outer circumferential portions of the outer and inner insulators24and25may be joined to each other by melting and then hardening the distal ends of the outer circumferential portions together.

The number of recesses24aand25aof the insulators24and25is not limited as long as the strength of the insulators24and25is ensured.

The outer insulator24does not have to include the recesses24aor the projections24t.

The inner insulator25does not have to include the recesses25aor the projections25t.

The inner surface of the inner insulator25does not have to include the recesses25b,25c,25dand25eor the projections25k.

The connector28may be fixed between the shield23and the outer insulator24.

The sealing member34may be compressed in the axial direction of the bolt B.

The sealing member34may be compressed in a direction that intersects the axis of the bolt B.

The shield23may be made of a conductive material such as iron or copper.

The outer insulator24and the inner insulator25may be made of different materials. For example, the outer insulator24may be made of a resin that has a high corrosion resistance, and the inner insulator25may be made of a resin that has a high strength.

The coupling base21may be omitted.

The washer35may be omitted. In this case, the spacer30functions as a washer.

A sealing member may be arranged between the joint26of the cover13and the end wall12aof the suction housing member12.

The compression unit15, the electric motor16, and the motor driving circuit20do not have to be arranged in this order in the axial direction of the rotation shaft19. For example, the cover13may be fixed to the circumferential wall of the suction housing member12, and the motor driving circuit20may be accommodated in an accommodation chamber defined by the circumferential wall of the suction housing member12and the cover13.

The compression unit15may be of a piston type or a vane type, for example

The motor-driven compressor10is not limited to vehicle air-conditioning devices and is applicable to other air-conditioning devices.