Motor-driven compressor

Abstract

A compression mechanism is provided, in a casing, and operatively coupled via a drive shaft 17 to an electric motor 21 accommodated in a motor chamber 15 within the casing, so that power can be transmitted. An in-shaft bore 17A is formed in the drive shaft and a first bifurcated hole 17B is formed for communicating the in-shaft bore 17A to the motor chamber 15. The in-shaft bore 17A is communicated to the suction chamber 31 via a second collecting hole 13F, the collecting chamber 13D and a suction communication hole 13G formed in a cylinder block 13. Thereby, part of the refrigerant sucked in the casing is introduced to the compression mechanism through a gap between a stator 19 and a rotor 20, and the remainder of the refrigerant is introduced to the compression mechanism without being used for cooling the electric motor 21.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a motor-driven compressor and, more specifically, to a motor-driven compressor provided in a casing with a compression mechanism for compressing a refrigerant and an electric motor for driving the compression mechanism.

[0003] 2. Description of the Related Art

[0004] A motor-driven compressor has been known in the art as a compressor to be incorporated in a refrigerant circulation circuit of a heat exchanger for a car air-conditioner. Generally speaking, the motor-driven compressor includes an electric motor and a refrigerant compression mechanism in a casing constituting an outer casing thereof. Since it is desirable that the motor has a rotating power to provide a high rotating speed and a driving force over a high torque loaded thereto, the compressor must have a high-output motor. In a design wherein the high output motor is used for overcoming a high rotating load, however, the motor generates a large amount of heat to further accelerate the temperature rise in the ambient atmosphere around the motor. Since such a temperature rise of the ambient atmosphere naturally causes the temperature of the motor itself to be higher, there is a risk in that the rotational efficiency becomes lower due to the demagnetization of the motor caused by the temperature rise. To solve such a problem, an arrangement may be adopted, wherein refrigerant sucked into the casing is introduced into a motor chamber for accommodating the motor, and after the motor has been cooled with the refrigerant, the refrigerant is introduced into the refrigerant compression mechanism.

[0005] According to this arrangement, however, since the refrigerant introduced into the motor chamber is heated by the motor, the refrigerant is introduced into the refrigerant compression mechanism while a specific volume thereof increases, which decreases an amount of the refrigerant circulating the refrigerant circulation circuit to result in a problem in that the cooling capacity is lowered. Also, when the refrigerant cools the motor, the refrigerant is often forced to pass through a small gap between a stator and a rotor of the motor, during which a flow resistance of the refrigerant, due to a viscosity of mist of lubricant contained in the refrigerant, disturbs the smooth flow of the refrigerant.

[0006] In Japanese Unexamined Patent Publication (Kokai) No. 9-236092, an arrangement is disclosed wherein two suction openings are provided for taking refrigerant into the interior of the compressor casing; one of which is provided in a wall portion of the motor chamber (part of the casing) closer to the refrigerant compression mechanism and the other is provided opposite to the refrigerant compression mechanism while the motor is interposed. According to this arrangement, part of the refrigerant taken into the compressor casing is sucked through the former suction opening and the remaining is sucked through the latter suction opening. The refrigerant sucked through the former suction opening is introduced into the refrigerant compression mechanism while hardly cooling the motor. Also, the refrigerant sucked through the latter suction opening is introduced into the refrigerant compression mechanism after cooling the motor. Thereby, the above-mentioned two problems can be solved because all of the refrigerant introduced into the refrigerant compression mechanism does not pass by the motor.

[0007] According to this arrangement, however, it is necessary to provide a plurality of seal members for isolating pressures in correspondence to the plurality of suction openings in the compressor casing, resulting in a problem in production cost or in reliability.

SUMMARY OF THE INVENTION

[0008] An object of the present invention is to provide a motor-driven compressor capable, in an inexpensive and reliable manner, of cooling a motor, reducing the specific volume of refrigerant and preventing the refrigerant suction efficiency of a compressor mechanism from falling due to the flow resistance caused by the viscosity of a lubricant oil.

[0009] To solve the above-mentioned problems, according to the present invention, a motor-driven compressor is provided which comprises, in a casing, a compression mechanism for compressing refrigerant, an electric motor having a stator and a rotor and disposed in a motor chamber in the casing, and a drive shaft connected to the rotor and transmitting the torque of the electric motor to the compression mechanism, wherein the motor chamber and an in-shaft refrigerant passage formed in the drive shaft are provided in a suction passage for introducing the refrigerant sucked into the casing to the compression mechanism, wherein part of the sucked refrigerant is introduced to the compression mechanism while passing through a gap between the stator and the rotor, and the rest of the sucked refrigerant is introduced to the compression mechanism without passing through the gap between the stator and the rotor but passes through the in-shaft refrigerant passage.

[0010] According to the present invention, part of the refrigerant sucked into the casing is introduced into the compression mechanism through the gap between the stator and the rotor. That is to say, not all the sucked refrigerant passes through the gap having a high temperature. In other words, the refrigerant introduced to the compression mechanism is not heated as a whole, whereby the temperature rise of the refrigerant is restricted. Thus, the increase in specific volume of the refrigerant introduced to the compression mechanism is suppressed to prevent the compression efficiency of the compression mechanism from falling. In addition, if a mist of lubricant oil exists in the refrigerant for lubricating the interior of the casing, the present invention serves to reduce the flow resistance caused by the viscosity of the lubricant oil when the refrigerant passes through the small gap between the stator and the rotor. Also, since the flow rate of the refrigerant passing through the gap between the stator and the rotor is adjustable by providing the in-shaft refrigerant passage, it is unnecessary to provide a plurality of suction inlets for sucking the refrigerant into the casing to adjust the flow rate of the refrigerant.

[0011] The present invention may be more fully understood from the description of the preferred embodiments of the invention, as set forth below, together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In the drawings:

[0013] FIG. 1 is a schematic side sectional view of a first embodiment of a motor-driven compressor according to the present invention;

[0014] FIG. 2 is a schematic side sectional view of a second embodiment of a motor-driven compressor according to the present invention; and

[0015] FIG. 3 is a rear side view of a movable scroll of the motor-driven compressor shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] (First Embodiment)

[0017] One aspect of the present invention, embodied as a swash plate type motor-driven compressor, will be described below with reference to FIG. 1, wherein it is assumed that the right of FIG. 1 is the front side of the compressor and the left thereof is the rear side.

[0018] As shown in FIG. 1, the motor-driven swash plate type compressor C1 includes a motor housing 11, a front housing 12, a cylinder block 13 and a rear housing 14. These housings 11, 12, 14 and the cylinder block 13 are fixedly connected to each other by a plurality of through-bolts not shown to define a generally cylindrical casing of the compressor. A space encircled by the motor housing 11 and the front housing 12 defines a motor chamber 15, and a space enclosed by the front housing 12 and the cylinder block 13 defines a swash plate chamber 16.

[0019] A drive shaft 17 is rotatably supported by a pair of front and rear radial bearings 18A, 18B between the motor housing 11 and the cylinder block 13 while extending through the motor chamber 15 and the swash plate chamber 16. The drive shaft 17 is loosely fitted in a central hole 12B bored through a wall portion 12A formed in the front housing 12. In the wall portion 12A, communication holes 12C are also formed for communicating the swash plate chamber 16 with the motor chamber 15.

[0020] An electric motor 21, accommodated within the motor chamber 15, consists of a stator 19 and a rotor 20 fixedly secured to the drive shaft 17 to be rotatable therewith. The stator 19 and the rotor 20 are arranged so that a small gap exists between the inner circumference of the stator 19 and the outer circumference of the rotor 20.

[0021] A disk-shaped swash plate 22 is fixedly secured onto the drive shaft 17 in the swash plate chamber 16 to be rotatable therewith, and a thrust bearing 23 which is one of the bearings for the drive shaft is disposed between the swash plate 22 and the wall portion 12A. The drive shaft 17 and the swash plate 22 connected integrally with each other are located at a position in the thrust direction (the axial direction of the drive shaft) via a washer 25 biased forward by a spring 24 accommodated in an accommodation recess 13A centrally formed in the cylinder block 13 and the thrust bearing 23.

[0022] A plurality of cylinder bores 13B (only two are visible in FIG. 1) are formed in the cylinder block 13. In the respective cylinder bore, a single-head piston 26 is accommodated to be slidable in reciprocated manner forward and backward, so that a compression chamber 13C is defined in the respective bore 13B, which is variable in volume in accordance with the reciprocation of the piston 26. A pair of recesses 26A is provided in a front portion of the respective piston 26, for accommodating a pair of shoes 28 therein. The shoes 28 grippingly holds the periphery of the swash plate 22 in a slidable manner to operatively couple the piston 26 with the swash plate 22. Thus, when the drive shaft 17 is made to rotate by the electric motor 21, the swash plate 22 also rotates in synchronism with the drive shaft 17, whereby the rotational motion of the swash plate 22 is converted to a linear reciprocating motion of the piston 26 having a stroke corresponding to the inclination angle thereof.

[0023] A valve-forming body 30 is provided between the cylinder block 13 and the rear housing 14 while being sandwiched by the both. Between the valve-forming body 30 and the rear housing 14, a suction chamber 31 through which refrigerant introduced into the respective cylinder bore 13B passes and a discharge chamber 33 through which refrigerant discharged from the respective cylinder bore 13B passes are defined. In a rear side wall of the rear housing 14, a discharge opening 33A, in communication with the discharge chamber 33, is formed.

[0024] The valve-forming body 30 is formed of a suction valve-forming plate, a port-forming plate, a discharge valve-forming plate and a retainer-forming plate which are secured together by a pin 34 in a superposed manner. In this valve-forming body 30, a suction port 35 and a suction valve 36 for opening/closing the port 35, and a discharge port 37 and a discharge valve 38 for opening/closing the port 37 are formed corresponding to the respective cylinder bore 13B. The suction chamber 31 and the respective cylinder bore 13B are communicated with each other via the suction port 35, and the respective cylinder bore 13B and the discharge chamber 33 are communicated with each other via the discharge port 37.

[0025] In this regard, a compression mechanism for compressing refrigerant is constituted by the cylinder bore 13B, the swash plate 22, the piston 26, the shoe 28 and the valve-forming body 30.

[0026] A collecting chamber 13D is defined in a central area of a rear side of the cylinder block 13, and a plurality of collecting holes 13E (only two are visible in FIG. 1) are formed between the collecting chamber 13D and the swash plate chamber 16 for communicating the chambers with each other. Further, a second collecting hole 13F is formed between the collecting chamber 13D and the accommodation recess 13A for communicating the chambers with each other. A suction communication hole 13G is provided in the cylinder block 13, for always communicating the collecting chamber 13D with the suction chamber 31.

[0027] A bearing accommodating portion 11A is provided in the front side wall of the motor housing 11, for accommodating the radial bearing 18A therein. Also, in the front side wall, a suction opening 11B is arranged on the axis of the drive shaft 17 for communicating the bearing accommodating portion 11A with the exterior of the motor chamber 15.

[0028] The drive shaft 17 is disposed so that a front end and a rear end thereof are accommodated in the bearing accommodating portion 11A and the accommodation recess 13A, respectively. The drive shaft 17 is provided with an in-shaft bore 17A extending between opposite ends of the drive shaft. That is, the bearing accommodating portion 11A and the accommodation recess 13A are communicated with each other via the in-shaft bore 17A. The drive shaft 17 is also provided with a first bifurcated hole 17B for communicating a front space of the motor chamber 15 forward of the rotor 20 with the in-shaft bore 17 and a second bifurcated hole 17C for communicating the interior of the thrust bearing 23 with the in-shaft bore 17A. An in-shaft refrigerant passage is constituted by the in-shaft bore 17A, the first bifurcated hole 17B and the second bifurcated hole 17C.

[0029] A suction passage is constituted by the bearing accommodating portion 11A, the in-shaft bore 17A, the accommodation recess 13A, the second collecting hole 13F, the collecting chamber 13D, the suction communication hole 13G, the suction chamber 31, the first bifurcated hole 17B, the motor chamber 15, the communication hole 12C, the swash plate chamber 16, the first collecting hole 13E, the second bifurcated hole 17C and the thrust bearing 23, for introducing the refrigerant sucked into the casing of the compressor Cl via the suction opening 11B.

[0030] The suction opening 11B and the discharge opening 33A are connected with each other via an external refrigerant circuit not shown. In the refrigerant which circulates in the compressor C1 and the external refrigerant circuit, a mist of lubricant oil is mixed for the purpose of lubricating the compressor C1 to allow smooth operation of the latter.

[0031] Next, the operation of the compressor thus structured will be described.

[0032] When the drive shaft 17 is driven to rotate by the electric motor 21, the swash plate 22 is also made to rotate therewith. As the swash plate 22 rotates, piston 26 reciprocates via the shoe 28. By continuing such a motion, the refrigerant is repeatedly sucked into the compression chamber 13C, compressed therein and discharged therefrom.

[0033] The refrigerant sucked from the external refrigerant circuit into the suction opening 11B is introduced into the in-shaft bore 17A via the bearing accommodating portion 11A. Part of the refrigerant introduced into the in-shaft bore 17A is introduced to the collection chamber 13D via the accommodation recess 13A and the second collecting hole 13F.

[0034] After being introduced into a space of the motor chamber 15 forward of the rotor 20 via the first bifurcated hole 17B, part of the remainder of the refrigerant is introduced into a space rearward of the stator 19 and the rotor 20 through a gap between the both, during which the electric motor is cooled because the refrigerant removes heat from the electric motor 21. Thereafter, the refrigerant introduced into the space rearward of the stator 19 and the rotor 20 is introduced into the swash plate chamber 16 via the communication hole 12C and then introduced into the collecting chamber 13D through the first collecting hole 13E.

[0035] The rest of the refrigerant introduced from the bearing accommodating portion 11A to the in-shaft bore 17A described hereinbefore is introduced into a gap in the thrust bearing 23 via the second bifurcated hole 17C, and then into the collecting chamber 13D via the swash plate chamber 16 and the first collecting hole 13E. The thrust bearing 23 is cooled by the refrigerant passing through the gap thereof and also lubricated with the mist of lubricant oil contained in the refrigerant.

[0036] In this regard, part of the refrigerant introduced into the swash plate chamber 16 is introduced into the collecting chamber 13D via the accommodation recess 13A and the second collecting hole 13F.

[0037] The refrigerant introduced into the collecting chamber 13D is introduced into the suction chamber 31 via the suction communication hole 13G, and then sucked into the compression chamber 13C via the suction port 35, wherein the refrigerant is subjected to the compressive operation of the piston 26 and discharged to the discharge chamber 33 through the discharge port 37. The refrigerant thus discharged into the discharge chamber 33 is delivered to the external refrigerant circuit via the discharge opening 33A.

[0038] The following effects are obtainable according to this embodiment:

[0039] (1) Since part of the low temperature refrigerant sucked from the suction opening 11B is introduced into the motor chamber 15, the cooling of the electric motor 21 is enhanced. Also, due to lubricant oil contained in the refrigerant, the lubrication of the radial bearing 18A is facilitated.

[0040] (2) Since the refrigerant introduced to the motor chamber 15 in the space forward of the rotor 20 via the first bifurcated hole 17B is transferred to the space rearward of the stator 19 and the rotor 20 through the gap between the two, it is possible to cool a wide area of the surface of the electric motor 21 whereby the cooling of the electric motor 21 is facilitated.

[0041] (3) Since only part of the refrigerant introduced from the suction opening 11B into the collecting chamber 13D is allowed to be introduced into the motor chamber 15 while the rest is not introduced into the motor chamber 15, it is possible to suppress the temperature rise of the refrigerant introduced into the collecting chamber 13D in comparison with a case wherein all the refrigerant from the suction opening 11B is introduced into the motor chamber 15. That is, it is possible to suppress the increase in specific volume of the refrigerant sucked into the compression chamber 13C caused by the temperature rise, and to prevent the compression efficiency from lowering.

[0042] Also, since all the refrigerant sucked from the suction opening 11B does not necessarily pass through the small gap between the stator 19 and the rotor 20, it is possible to reduce the flow resistance of the refrigerant generated by passing through the gap due to the viscosity of a lubricant oil contained in the refrigerant. Accordingly, the suction efficiency of the refrigerant is improved throughout an overall area from the suction opening 11B to the compression chamber 13C.

[0043] (4) The in-shaft bore 17A and the first bifurcated hole 17B are provided in the drive shaft 17 so that the refrigerant sucked from the suction opening 11B is divided into a part to be introduced into the motor chamber 15 and the rest not introduced thereto. Accordingly, it is possible to suck the refrigerant into the casing of the compressor C1 via a single suction opening 11B alone, without adopting, for example, an arrangement wherein inlets for sucking the refrigerant from the exterior of the casing of the compressor C1 are provided at two positions in the motor housing 11 forward and rearward of the electric motor 21 to prevent part of the refrigerant from by passing the electric motor 21. That is to say, since the number of joints between the compressor C1 and the external refrigerant circuit can be reduced, the sealing process is simplified to save the manufacturing cost and the reliability is improved. Also, the production becomes easier in comparison with an arrangement wherein a bypass is formed in the circumferential wall of the motor housing 11 and the front housing 12 to introduce the refrigerant sucked from the suction opening 11B into the swash plate chamber 16 or the suction chamber 31 via the bypath, not via the motor chamber 15.

[0044] (5) The second bifurcated hole 17C is provided for introducing part of the refrigerant in the in-shaft bore 17A into the swash plate chamber 16. Thus, lubrication of components in the swash plate chamber 16 (for example, the radial bearing 18B, the swash plate 22, the thrust bearing 23, recess 26A and the shoe 28) is enhanced.

[0045] (6) Due to the second bifurcated hole 17C, the refrigerant introduced from the in-shaft bore 17A to the swash plate chamber 16 passes through a gap in the thrust bearing 23. Thus, the lubrication of the thrust bearing is enhanced.

[0046] (7) Since the suction opening 11B is provided in the motor chamber 15 on the axis of the drive shaft 17, it is possible to shorten a path between the suction opening 11B and the in-shaft bore 17A and make the same linear. Accordingly, the flow resistance, to the refrigerant, until it reaches the in-shaft bore 17A can be reduced in comparison with a case wherein the path is longer and curved. Also, since the suction opening 11B can be easily aligned with a center of the motor housing 11 and/or the bearing accommodating portion 11A, the suction opening 11B is easily machined.

[0047] (8) The in-shaft bore 17A is provided through the opposite ends of the drive shaft 17 to introduce the refrigerant sucked from the suction opening 11B into the collecting chamber 13D. Thereby, it is possible to make a refrigerant passage from the suction opening 11B to the collecting chamber 13D shorter and more linear, resulting in a reduction of flow resistance to the refrigerant. Further, since the refrigerant can be directly introduced from the suction opening 11B to the collecting chamber 13D, it is possible to suppress the temperature rise and therefore an increase in specific volume of the refrigerant.

[0048] (Second Embodiment)

[0049] A second aspect of the present invention embodied to a scroll type motor-driven compressor will be describe below with reference to FIG. 2, wherein it is assumed that the right of FIG. 2 is the front side of the compressor and the left thereof is the rear side.

[0050] As shown in FIG. 2, a center housing 52 is fixedly secured to a stationary scroll 51, and a motor housing 53 is fixedly secured to the center housing 52. A casing for a motor-driven scroll type compressor C2 is constituted by the stationary scroll 51, the center housing 52 and the motor housing 53. A shaft 54 is supported in a rotatable manner by the center housing 52 and the motor housing 53 via radial bearings 55, 56 used as drive shaft bearings, and has an eccentric shaft 57 integrally formed therewith. A motor chamber 58 is defined by a space enclosed by the inner circumference of the motor housing 53 and the center housing 52.

[0051] A bushing 60 is fitted over the eccentric shaft 57. Note that the shaft 54, the eccentric shaft 57 and the bushing 60 constitute a drive shaft. A movable scroll 61 is supported by the bushing 60 via a needle bearing 62 to be opposed to the stationary scroll 51 and rotatable relative thereto. A movable spiral wall 64 is formed on a movable base plate 63 in the movable scroll 61, while a stationary spiral wall 66 is formed on a stationary base plate 65 in the stationary scroll 61 to be meshed with the movable spiral wall 64. The needle bearing 62 is accommodated in an accommodating portion formed in a boss 67 projected forward (right in FIG. 1) from the movable base plate 63. A space enclosed by the stationary base plate 65, the stationary spiral wall 66, the movable base plate 63 and the movable spiral wall 64 defines closed chambers 68, i.e., compression chambers which volume is variable as the movable scroll 61 rotates. Generally at a center of the stationary base plate 65, there is a discharge opening 69 for communicating the exterior of the casing of the compressor C2 with the closed chamber 68.

[0052] In a wall of the center housing 52 closer to the movable scroll 61, a plurality of recesses 70 (only one is visible in FIG. 2) are formed along substantially the same circle. In the respective recess 70 are accommodated a stationary pin 71 fixed to the center housing 52 and a movable pin 72 fixed to the movable scroll 61. The movable scroll 61 is subjected to an orbital motion as the eccentric shaft 57 rotates, but is inhibited from rotating about its own axis by means of the stationary pin 71, the movable pin 72 and an annular ring 73.

[0053] Note a scroll type compression mechanism is constituted by the movable scroll 61, the needle bearing 62, the stationary base plate 65, the stationary spiral wall 66, the stationary pin 71, the movable pin 72 and the annular ring 73.

[0054] A movable base plate chamber 52A is formed, rearward of the center housing 52, for accommodating the movable base plate 63. An intermediate chamber 52B is provided between the movable base plate chamber 52A and the motor chamber 58, for communicating the chambers with each other. As shown in FIGS. 2 and 3, a plurality of base plate communication holes 63A (eight are shown in FIG. 3) of an arcuate shape are provided in the vicinity of the outer circumference of the movable base plate 63 while penetrating front and rear surfaces of the latter. The outermost one of the plurality of closed chambers 68 (hereinafter referred to a low pressure closed chamber) and the intermediate chamber 52B are communicated with each other through the base plate communication holes 63A.

[0055] Generally at a center of the center housing 52, a boss chamber 52C is formed for accommodating the boss 67 therein. In a region of the boss chamber 52C closer to the motor chamber 58, a bearing chamber 52D for accommodating the radial bearing 55 is formed and protrudes into the motor chamber 58. The boss chamber 52C is communicated with the bearing chamber 52D via a gap in the radial bearing 55. Also the boss chamber 52C and the intermediate chamber 52B communicate with each other through a communication hole 52E provided between both the chambers.

[0056] A stator 80 is fixedly secured to the inner circumference of the motor housing 53, and a rotor 81 is fixedly secured to the outer circumference of the shaft 54 at a position opposite to the stator 80. The stator 80 and the rotor 81 are disposed so that a small gap exists between the inner circumference of the stator 80 and the outer circumference of the rotor 81. The stator 80 and the rotor 81 constitutes an electric motor in that the rotor 81 and the shaft 54 rotate together when the stator 80 is supplied with electric current.

[0057] In the front side wall of the motor housing 53, a bearing accommodating portion 53A is provided for accommodating the radial bearing 56 and a front end of the shaft 54. Further, in this front side wall, a suction opening 53B is provided on the axis of the shaft 54, for communicating the bearing accommodating portion 53A with the exterior of the motor chamber 58 and for sucking the refrigerant into the casing of the compressor C2.

[0058] The shaft 54 has a shaft bore 54A penetrating the opposite ends thereof. Also, the shaft 54 has a first bifurcated hole 54B for communicating a space in the motor chamber 58 forward of the rotor 81 with the shaft bore 54A and a second bifurcated hole 54C for communicating a space in the bearing chamber 52D forward of the radial bearing 55 with the shaft bore 54A. A shaft bore 57A is provided in the eccentric shaft 57 while penetrating the opposite ends thereof, and communicated with the shaft bore 54A. An internal drive shaft refrigerant passage is constituted by the shaft bore 54A, the first bifurcated hole 54B, the second bifurcated hole 54C and the shaft bore 57A.

[0059] As illustrated in FIGS. 2 and 3, a connecting chamber 63B is formed at a center of a front side of the movable base plate 63. A plurality of connecting passages 63C (four in this embodiment) are formed in the interior of the movable base plate 63, for communicating the connecting chamber 63B with the base plate communication holes 63A. An internal scroll refrigerant passage is constituted by the connecting chamber 63B, the connecting passages 63C and the base plate communication holes 63A, which in turn communicates with the accommodating portion in the boss 67 and the intermediate chamber 52B.

[0060] Note that a suction passage for introducing the refrigerant sucked via the suction opening 53B into the casing of the compressor C2 and further, to the scroll type compressor is constituted by the bearing accommodating portion 53A, shaft bore 54A, shaft bore 57A, the first bifurcated hole 54B, the motor chamber 58, the intermediate chamber 52B, the second bifurcated hole 54C, the bearing chamber 52D, the radial bearing 55, the boss chamber 52C, the communication hole 52E, the base plate communication hole 63A, the connecting chamber 63B and the connecting passages 63C.

[0061] The suction opening 53B is communicated with the discharge opening 69 via an external refrigerant circuit not shown.

[0062] Next, the operation of the compressor of the above-mentioned arrangement will be described.

[0063] When the shaft 54 is rotated by the electric motor, the eccentric shaft 57 rotates together with the bushing 60. The eccentric shaft 57 and the bushing 60 eccentrically rotate relative to the rotational center of the shaft 54. Such rotation is transmitted via the needle bearing 62 to the movable scroll 61 which then is subjected to an orbital motion. In accordance with this orbital motion, the volume of the closed chamber 68 varies to sequentially repeat the cycle of suction, compression and discharge.

[0064] The refrigerant sucked into the suction opening 53B from the external refrigerant circuit is introduced into the shaft bore 54A via the bearing accommodating portion 53A. Part of the refrigerant introduced into the shaft bore 54A is introduced into the base plate communication holes 63A through the shaft bore 57A, the accommodating portion in the boss 67, the connecting chamber 63B and the connecting passage 63C, and sucked in the closed chamber 68 (the low pressure closed chamber).

[0065] Part of the remainder of the refrigerant is introduced into a space in the motor chamber 58 forward of the rotor 81 through the first bifurcated hole 54B, and then into a space rearward of the stator 80 and the rotor 81 via a gap between the both, during which the electric motor is cooled. Thereafter, the refrigerant introduced into the space rearward of the stator 80 and the rotor 81 is introduced into the base plate communication holes 63A via the intermediate chamber 52B.

[0066] Part of the refrigerant introduced to the shaft bore 54A other than the above-mentioned part is introduced to the bearing chamber 52D via the second bifurcated hole 54C and then to the boss chamber 52C via the gap in the radial bearing 55. Thereby, the radial bearing 55 is lubricated. Part of the refrigerant introduced into the boss chamber 52C is introduced into the base plate communication holes 63A via the communication hole 52E and the intermediate chamber 52B, while the remainder of the refrigerant is introduced into the connecting chamber 63B via the gap in the needle bearing 62 accommodated in the boss 67. The needle bearing 62 is lubricated with the mist of lubricant oil contained in the refrigerant passing through the gap in the needle bearing 62.

[0067] The refrigerant sucked in the closed chamber 68 (low pressure chamber) is compressed due to the orbital motion of the movable scroll 61 and delivered via the discharge opening 69 to the external refrigerant circuit.

[0068] According to this embodiment, the following effects are obtainable in addition to those similar to the items (1) to (4), (7) and (8) described in relation to the preceding embodiment:

[0069] (9) The second bifurcated hole 54C is provided for introducing part of the refrigerant in the shaft bore 54A to the bearing chamber 52D and further to the boss chamber 52C via the radial bearing 55. Thereby, it is possible to facilitate the lubrication of the radial bearing 55 and the interior the boss chamber 52C (such as the bushing 60 or the needle bearing 62).

[0070] (10) Part of the refrigerant introduced into the boss chamber 52C is further introduced to the connecting chamber 63B through the gap in the needle bearing 62. Thereby, lubrication of the needle bearing 62 is facilitated.

[0071] (11) The refrigerant introduced into the connecting chamber 63B at a center of the movable base plate 63 from the shaft bore 57A is further guided to the base plate communication holes 63A through the connecting passage 63C provided in the outer circumference of the movable base plate 63. Thereby, it is possible to shorten the refrigerant path from the shaft bore 57A to the closed chamber 68 (low pressure closed chamber), whereby the flow resistance to the refrigerant can be reduced until it reaches the closed chamber 68 (low pressure chamber).

[0072] (12) By the provision of the connecting chamber 63B and the connecting passages 63C, the movable scroll 61 can be lighter in weight.

[0073] (13) All of the connecting passages 63C are not connected to the eight base plate communication holes 63A but only to four of them are. Thereby, it is possible to reduce the necessity of providing the connecting passages 63C to prevent the production cost from increasing.

[0074] The present invention should not be limited to the above-mentioned embodiments but may include the following:

[0075] The second bifurcated hole 17C (corresponding to the second bifurcated hole 54C in the second embodiment) may be eliminated. That is, the refrigerant in the in-shaft bore 17A (shaft bore 54A) need not be introduced into the thrust bearing 23 (radial bearing 55).

[0076] The suction opening 11B (suction opening 53B in the second embodiment) may not be provided on the axis of the drive shaft 17 (shaft 54). For instance, the suction opening 11B (suction opening 53B) may be communicated with the motor chamber 15 (motor chamber 58) and not via the bearing accommodating portion 11A (bearing accommodating portion 53A). In this case, part of the refrigerant introduced from the suction opening 11B (suction opening 53B) into the motor chamber 15 (motor chamber 58) is further introduced to the compression chamber 13C (closed chamber 68) via a gap between the stator 19 (stator 80) and the rotor 20 (rotor 81). Part of the remainder of the refrigerant is introduced to the in-shaft bore 17A (shaft bore 54A) via the first bifurcated hole 17B (first bifurcated hole 54B), and then further to the compression chamber 13C (closed chamber 68).

[0077] The in-shaft bore 17A may be eliminated in a region rearward of the second bifurcated hole 17C. In such a case, the refrigerant in the in-shaft bore 17A is introduced to the collecting chamber 13D via the second bifurcated hole 17C, the swash plate chamber 16 and the first collecting hole 13E.

[0078] The in-shaft bore 17A (shaft bore 54A) may be eliminated in a region forward of the first bifurcated hole 17B (first bifurcated hole 54B), provided the suction opening 11B (suction opening 53B) is communicated to the motor chamber 15 (motor chamber 58). In such a case, part of the refrigerant in the motor chamber 15 (motor chamber 58) is introduced to the in-shaft bore 17A (shaft bore 54A) via the first bifurcated hole 17B (first bifurcated hole 54B).

[0079] The compression mechanism of the motor-driven swash plate type compressor C1 (the motor-driven scroll type compressor C2 in the second embodiment) may not be of a fixed volume type wherein a discharged volume of the refrigerant per one rotation of the drive shaft 17 is constant. For example, the compression mechanism of the motor-driven swash plate type compressor C1 may be of a type wherein a stroke of the piston 26 is variable. Also, the compression mechanism of the motor-driven scroll type compressor C2 may be of a type wherein part of the refrigerant sucked in the closed chamber 68 is discharged out of the closed chamber 68 while reaching the discharge opening 69 so that the volume of the refrigerant discharged through the discharge opening 69 is variable.

[0080] Although the motor-driven swash plate type compressor C1 in the above-mentioned embodiment is of a type wherein the swash plate 22 rotates integrally with the drive shaft 17, it may be of another type wherein the swash plate for reciprocating the piston does not rotate integrally with the drive shaft but is operatively connected to a rotary plate rotatable together with the drive shaft to cause the piston to reciprocate without the rotation of the swash plate. The motor-driven swash plate type compressor C1 may be of a type wherein the drive shaft is provided with a support surface intersecting the axis of the drive shaft at an angle and a support shaft formed vertically to the support surface, and wherein the swash plate for reciprocating the piston is held via a thrust bearing provided between the piston and the support surface to be rotatable relative to the support shaft via a rolling bearing.

[0081] The motor-driven swash plate type compressor C1 may be of a type as disclosed in Japanese Unexamined Patent Publication (Kokai) No. 10-184539 wherein the refrigerant once discharged from a compression chamber is further sucked into another compression chamber and compressed again before being discharge.

[0082] The motor-driven swash plate type compressor C1 may have any number of cylinders. For instance, the number of cylinders may be two, three, four, five, six or seven.

[0083] The shaft bore 54A may be eliminated in a region rearward of the second bifurcated hole 54C. In such a case, the refrigerant in the shaft bore 54A is introduced to the base plate communication holes 63A via the second bifurcated hole 54C, the bearing chamber 52D, the boss chamber 52C, the communication hole 52E and the intermediate chamber 52B. According to this arrangement, the shaft bore 57A becomes unnecessary.

[0084] In the motor driven scroll type compressor C2, a seal member may be interposed between the bushing 60 and front side of the movable base plate 63 to prevent the refrigerant from the shaft bore 57A from being introduced into a space on the outer circumference side of the bushing 60.

[0085] The connecting chamber 63B and the connecting passages 63C may be eliminated.

[0086] The number of base plate communication holes 63A is not limited to eight, but may be optional, provided no trouble occurs in the introduction of the refrigerant into the closed chamber 68.

[0087] The connecting passages 63C may be communicated to all the base plate communication holes 63A. Also, any number of the connecting passages 63C may be communicated to one base plate communication hole 63A. Similarly, any number of connecting passages 63C may be provided.

[0088] As described in detail above, according to the present invention, it is possible to achieve, in a motor-driven compressor, in a reliable manner and at a lower cost, improved cooling of the motor and a reduction in specific volume of the refrigerant and to suppress a lowering of the refrigerant suction efficiency of the compression mechanism due to an increase in flow resistance caused by the viscosity of a lubricating oil.

Claims

1. A motor-driven compressor comprising, in a casing, a compression mechanism for compressing refrigerant, an electric motor having a stator and a rotor and disposed in a motor chamber in the casing, and a drive shaft connected to the rotor and transmitting a drive force of the electric motor to the compression mechanism, wherein

the motor chamber and an in-shaft refrigerant passage formed in the drive shaft are provided in a suction passage for introducing the refrigerant sucked into the casing to the compression mechanism, and

wherein part of the sucked refrigerant is introduced to the compression mechanism while passing through a gap between the stator and the rotor, and the other of the sucked refrigerant is introduced to the compression mechanism without passing through the gap between the stator and the rotor but while passing through the in-shaft refrigerant passage.

2. A motor-driven compressor according to claim 1, wherein at least one of a drive shaft bearing for rotationally supporting the drive shaft in the casing and a bearing for supporting part or all of the compression mechanism is disposed in the suction passage.

3. A motor-driven compressor according to claim 1, wherein a suction opening for sucking the refrigerant into the casing is provided in the motor chamber on the axis of the drive shaft.

4. A motor-driven compressor according to claim 1, wherein the in-shaft refrigerant passage is formed through opposite ends of the drive shaft.

5. A motor-driven compressor according to claim 1, wherein the compression mechanism is of a scroll type in which a stationary spiral wall formed in a stationary scroll provided on a side of the casing is meshed with a movable spiral wall formed in a movable scroll operatively coupled to the drive shaft so that the movable scroll is subjected to an orbital motion as the drive shaft rotates to compress the refrigerant, wherein an in-scroll refrigerant passage is formed in the movable scroll so that at least part of the refrigerant introduced into the in-shaft refrigerant passage is introduced into a compression chamber defined between both the spiral walls through the in-scroll refrigerant passage.

6. A motor-driven compressor according to claim 1, wherein the compression mechanism is of a reciprocating piston type in which a piston accommodated for reciprocation in a cylinder bore formed in the casing is operatively coupled to the drive shaft to compress the refrigerant by the reciprocation of the piston as the drive shaft rotates.