Pumps – Condition responsive variable volumetric capacity expansible...
Reexamination Certificate
2002-12-24
2004-09-07
Yu, Justine R. (Department: 3746)
Pumps
Condition responsive variable volumetric capacity expansible...
C417S222200, C092S012200, C092S013000
Reexamination Certificate
active
06786705
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a variable displacement compressor used in a vehicular air conditioner.
Japanese Laid-Open Patent Publication No. 6-288347 discloses such a variable displacement compressor.
As shown in
FIG. 12
, the compressor of the publication includes a housing
101
, in which a crank chamber
102
is defined. A drive shaft
103
is rotatably arranged in the crank chamber
102
. A rotor
104
is coupled to the drive shaft
103
and is located in the crank chamber
102
. The rotor
104
rotates integrally with the drive shaft
103
. A drive plate, which is a swash plate
105
in this embodiment, is accommodated in the crank chamber
102
. A spherical sleeve
106
is slidably supported by the drive shaft
103
. The swash plate
105
is tiltably supported by the spherical sleeve
106
.
Cylinder bores
101
a
are defined in the housing
101
. Each cylinder bore
101
a
accommodates a piston
107
. Each piston
107
is coupled to the swash plate
105
with a couple of shoes
108
. A valve plate assembly
109
is provided in the housing
101
. In each cylinder bore
101
a
, a compression chamber
110
is defined by the associated piston
107
and the valve plate assembly
109
.
A hinge mechanism
111
is located between the rotor
104
and the swash plate
105
. The swash plate
105
is coupled to the rotor
104
with the hinge mechanism
111
and is supported by the drive shaft
103
with the spherical sleeve
106
. This permits the swash plate
105
to rotate integrally with the rotor
104
and the drive shaft
103
, and to slide along the axis L of the drive shaft
103
. While sliding, the swash plate
105
inclines relative to the drive shaft
103
about the spherical sleeve
106
.
As the pressure in the crank chamber
102
varies, the difference between the pressure in the crank chamber
102
and the pressure in the compression chambers
110
is changed. Accordingly, the inclination angle of the swash plate
105
is changed. As a result, the stroke of each piston
107
, or the compressor displacement, is varied.
The hinge mechanism
111
includes support arms
112
projecting from the rotor
104
and guide pins
113
projecting from the swash plate
105
. A guide hole
114
is formed in each support arm
112
, and a spherical portion
113
a
is formed at the distal end of each guide pin
113
. The spherical portion
113
a
of each guide pin
113
is fitted in the guide hole
114
of the corresponding support arm
112
and slides with respect to the guide hole
114
. Each guide hole
114
is parallel to an imaginary surface defined by the axis L of the drive shaft
103
and the top dead center corresponding position of the swash plate
105
(or the center of an imaginary sphere formed by the shoes
108
of the piston
107
located at the top dead center position). Each guide hole
114
is also formed straight toward the axis L of the drive shaft
103
.
Therefore, when the inclination angle of the swash plate
105
increases, the spherical portion
113
a
of each guide pin
113
is rotated clockwise as viewed in the drawing about an axis P, which extend through the center of the spherical portion
113
a
and is perpendicular to the imaginary surface, inside the corresponding guide hole
114
. The spherical portion
113
a
of each guide pin
113
linearly slides along an inner surface (cam surface)
114
a
of the guide hole
114
in a direction to separate from the drive shaft
103
. When the inclination angle of the swash plate
105
decreases, the spherical portion
113
a
of each guide pin
113
is rotated counterclockwise as viewed in the drawing about the axis P inside the guide hole
114
. The spherical portion
113
a
of each guide pin
113
linearly slides along the cam surfaces
114
a
of the guide hole
114
in a direction to approach the drive shaft
103
.
That is, the profile of each cam surface
114
a
is designed such that a path P′ of the rotary axis P of the corresponding spherical portion
113
a
is straight.
The graph of
FIG. 6
shows the result of an examination on the variable displacement compressor of the above publication performed by the present inventor. As shown by a chain double-dashed line, which is a characteristic line, the present inventor discovered that according to the hinge mechanism
111
, or the profile of the cam surface
114
a
, of the above publication, the top dead center position of each piston
107
fluctuates by a large amount when the displacement is varied.
If the top dead center position of each piston
107
fluctuates, the clearance (top clearance) TC between the piston
107
and the valve plate assembly
109
varies. Therefore, if, for example, the top clearance TC increases by the variation of the displacement, the dead volume of each compression chamber
110
increases. Accordingly, the expansion amount of refrigerant gas increases, which decreases the volumetric efficiency of the variable displacement compressor.
SUMMARY OF THE INVENTION
Accordingly, it is an objective of the present invention to provide a variable displacement compressor that includes a hinge mechanism that suppresses fluctuation of a top clearance although the displacement is varied.
To achieve the above objective, the present invention provides a variable displacement compressor, which includes a housing, a single-headed piston, a drive shaft, a rotor, a drive plate, and a hinge mechanism. The housing includes a cylinder bore. The single-headed piston is accommodated in the cylinder bore. The drive shaft is rotatably supported by the housing. The rotor is supported by the drive shaft and rotates integrally with the drive shaft. The drive plate is supported by the drive shaft and slides along and inclines with respect to the drive shaft. The hinge mechanism is located between the rotor and the drive plate. Rotation of the drive shaft is converted into reciprocation of the piston via the rotor, the hinge mechanism, and the drive plate. The hinge mechanism guides the drive plate such that the drive plate slides along and inclines with respect to the drive shaft. The inclination angle of the drive plate determines the displacement of the compressor. The hinge mechanism includes a cam, which is locatedon one of the rotor and the drive plate, and a guide portion, which is located on the other one of the rotor and the drive plate. The cam has a cam surface, which has a predetermined profile. The guide portion abuts against the cam surface. One of the cam surface and the guide portion slides against the other in accordance with inclination of the drive plate. The guide portion traces a path corresponding to the profile of the cam surface with respect to the cam. The path includes a first path corresponding to a small displacement region of the compressor and a second path corresponding to a large displacement region of the compressor. The profile of the cam surface is determined such that the first path and the second path bulge in a direction opposite to each other to compensate for fluctuation of a top dead center position of the piston with respect to the housing.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
REFERENCES:
patent: 2956501 (1960-10-01), Norlin
patent: 4886423 (1989-12-01), Iwanami et al.
patent: 5242274 (1993-09-01), Inoue
patent: 5540559 (1996-07-01), Kimura et al.
patent: 5647730 (1997-07-01), Woollatt
patent: 5785503 (1998-07-01), Ota et al.
patent: 6244159 (2001-06-01), Kimura et al.
patent: 6443707 (2002-09-01), Kimura et al.
patent: 2001/0031205 (2001-10-01), Ota et al.
patent: 1 323 923 (2002-12-01), None
patent: 62-74179 (1987-05-01), None
patent: 06-288347 (1994-10-01), None
patent: 08-334084 (1996-12-01), None
Fukanuma Tetsuhiko
Kayukawa Hiroaki
Koide Tatsuya
Kurita Hajime
Mochizuki Kenji
Kabushiki Kaisha Toyota Jidoshokki
Morgan & Finnegan , LLP
Sayoc Emmanuel
Yu Justine R.
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