Variable displacement compressor

Details Variable displacement compressor Variable displacement compressor

2001-06-22

2003-02-18

Walberg, Teresa (Department: 3742)

Pumps

Condition responsive control of drive transmission or pump...

Adjustable cam or linkage

C417S269000

Reexamination Certificate

active

06520748

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to variable displacement compressors of swash plate type provided with a single head piston for use in, for example, air-conditioning systems of vehicles or the like, particularly to variable displacement compressors having special features in the lubrication systems of shaft sealing structures provided between drive shafts (rotary shafts) for driving pistons and their housings.
In a general swash plate compressor of this type, as shown in
FIG. 6
, its housing is essentially composed of a front housing member
71
, a cylinder block
72
, and a rear housing member
73
joined and fixed to each other. A drive shaft
74
, the front end of which protrudes beyond the front housing member
71
, is rotatably supported by the housing through a pair of radial bearings
75
and
76
respectively provided at front and rear portions of the shaft. In the housing, a shaft sealing assembly
78
is provided at a portion nearer to the front end of the drive shaft
74
than the first radial bearing
75
. The shaft sealing assembly
78
prevents the leakage of refrigerant gas from a crank chamber
77
to the atmosphere.
In such a compressor, the lubrication for sliding parts such as bearings is effected by lubricating oil, which exists as a mist in the refrigerant gas. Therefore, where the flow of the refrigerant gas is stagnant, the lubrication may become insufficient. Recently, compressors have been proposed for use in refrigerant circuits in which carbon dioxide (CO
2
) is used in place of chlorofluorocarbon as the refrigerant, and the refrigerant may be cooled in a supercritical region beyond the critical temperature of the refrigerant. When such a refrigerant is used, the refrigerant pressure may become ten or more times higher than that of chlorofluorocarbon refrigerant. Thus, the load on the bearing portions and the shaft sealing assembly increases, and the lubrication must be highly effective.
Japanese Unexamined Patent Publication No. Hei 11-241681 discloses, as shown in
FIG. 6
, a structure in which a depressurization passage
79
is provided in the drive shaft
74
. The inlet
79
a
of the depressurization passage
79
is open at a position closer to the front end of the drive shaft
74
than the first radial bearing
75
and corresponding to an isolation chamber
80
in which the shaft sealing assembly
78
is accommodated. The outlet
79
b
of the depressurization passage
79
is open at the rear end of the drive shaft
74
. A fan
81
is firmly attached to the end portion of the drive shaft
74
on the outlet
79
b
side. The fan
81
rotates together with the drive shaft
74
, and the refrigerant in the depressurization passage
79
is forced toward the outlet
79
b
side by the fan
81
. The refrigerant discharged on the outlet
79
b
side then flows through gaps in the radial bearing
76
into the crank chamber
77
.
Japanese Unexamined Patent Publication No- Hei 11-107914 discloses a fixed displacement type swash plate compressor that can tolerate a high axial load. In the compressor, as shown in
FIG. 7
, a suction chamber
82
and a discharge chamber
83
are located on the spline
74
a
side of a drive shaft
74
. A second piston
86
is provided on the opposite side of the spline
74
a
from a first piston
85
and the first and second pistons sandwich a swash plate
84
. In this compressor, the front housing member
71
is provided with an inlet
88
communicating with a swash plate chamber
87
and a connecting passage
89
, which connects the swash plate chamber
87
with the suction chamber
82
. A shaft seal
90
is located in the suction chamber
82
.
In the above-mentioned compressor of Japanese Unexamined Patent Publication No. Hei 11-241681, the operation of the fan
81
creates a refrigerant flow such that some refrigerant from the crank chamber
77
flows through gaps in the first radial bearing
75
or a thrust bearing
91
into the depressurization passage
79
and then returns to the crank chamber
77
through gaps in the second radial bearing
76
. Thus, the lubrication of both radial bearings
75
and
76
and the shaft sealing assembly
78
is improved. In this structure, however, since the fan
81
must be provided to make such a refrigerant flow in the depressurization passage
79
, the structure is relatively complex.
In the compressor disclosed in Japanese Unexamined Patent Publication No. Hei 11-107914, the suction chamber
82
in which the shaft seal
90
is located is connected with the swash plate chamber
87
by the connecting passage
89
. This connecting passage
89
is provided for conducting refrigerant to the suction chamber
82
from the swash plate chamber
87
, and it is a typical passage found in fixed displacement type swash plate compressors. In variable displacement type swash plate compressors, however, since the inclination angle of the swash plate (cam plate) is changed to change the displacement by controlling the pressure in the crank chamber, in which the swash plate is located, there is no need to provide such a passage.
BRIEF SUMMARY OF THE INVENTION
The present invention has been achieved in view of the problems described above, and the object of the present invention is to provide variable displacement compressors wherein good lubrication for the shaft sealing assembly for the drive shaft can be effected by a simple structure.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a variable displacement compressor is provided. The compressor includes a housing, a crank chamber, a drive shaft, a cylinder bore, a single head piston, a cam plate, a shaft sealing assembly and a bleed passage. The housing includes a suction chamber and a discharge chamber. The crank chamber is defined in the housing. A first end of the drive shaft extends from a front end of the housing. The shaft is supported by the housing. The suction and discharge chambers are closer to the first end of the drive shaft than the crank chamber. The cylinder bore is located in the housing between the crank chamber and the front end of the housing. The single head piston is located in the cylinder bore. The cam plate is located in the crank chamber and connected with the piston to convert rotation of the drive shaft into reciprocation of the piston. The inclination angle of the cam plate is controlled by controlling the pressure in the crank chamber, to change the discharge displacement. The shaft sealing assembly seals the drive shaft and is located in the suction chamber. The bleed passage connects the crank chamber with the suction chamber. An outlet of the bleed passage is located above the shaft sealing assembly.


REFERENCES:
patent: 4231713 (1980-11-01), Widdowson et al.
patent: 6099276 (2000-08-01), Taguchi
patent: 6244159 (2001-06-01), Kimura et al.
patent: 6280152 (2001-08-01), Sugiura et al.
patent: 6283722 (2001-09-01), Takenaka et al.
patent: 6290468 (2001-09-01), Kato et al.
patent: 6290470 (2001-09-01), Okuno et al.
patent: 6318971 (2001-11-01), Ota et al.
patent: 6435848 (2002-08-01), Minami et al.
patent: 2001/0053328 (2001-12-01), Yamada et al.
patent: 0 926 342 (1999-06-01), None
patent: 11-107914 (1999-04-01), None
patent: 11-241681 (1999-09-01), None

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