Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
1999-09-02
2002-04-09
Freay, Charles G. (Department: 3746)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
C417S269000, C092S071000
Reexamination Certificate
active
06368069
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a variable displacement compressor for vehicle air-conditioning systems.
In a prior art compressor shown in
FIGS. 6 and 7
, a housing
102
includes a crank chamber
101
, and a drive shaft
103
is rotatably supported by the housing
102
. A rotor
104
is secured to the drive shaft
103
in the crank chamber
101
. A drive plate, or a swash plate
105
, is supported by the drive shaft
103
to slide axially and to incline with respect to the axis L. A hinge mechanism
106
couples the rotor
104
to the swash plate
105
. The swash plate
105
integrally rotates with the drive shaft
103
through the hinge mechanism
106
.
A cylinder block
108
constitutes part of the housing
102
. A plurality of cylinder bores
108
a
(six in the compressor of
FIG. 7
) are formed in the cylinder block
108
. The cylinder bores
108
a
are arranged on a circle about the axis L of the drive shaft
103
at equal intervals. A piston
107
is accommodated in each cylinder bore
108
a
. Each piston is coupled to the swash plate
105
through a pair of shoes
115
. When the drive shaft
103
is rotated, the swash plate
105
is rotated through the rotor
104
and the hinge mechanism
106
. The rotation of the swash plate
105
is converted into reciprocation of each piston
107
in the corresponding cylinder bore
108
a
through the shoes
115
.
A thrust bearing
109
is located between the rotor
104
and an inner wall
102
a
of the housing
102
. The thrust bearing
109
includes rollers
109
a
and a pair of ring-shaped races
109
b
. The rollers
109
a
are arranged about the axis L of the drive shaft
103
and are held between the pair of races
109
b
. Each roller extends radially. The thrust bearing
109
receives a compression force applied to the rotor
104
from the pistons
107
through the swash plate
105
and the hinge mechanism
106
.
A discharge chamber
120
is connected to the crank chamber
101
through a pressurizing passage
110
. A displacement control valve
111
is provided in the pressurizing passage
110
. The control valve
111
adjusts the opening size of the pressurizing passage
110
and controls the flow rate of refrigerant gas fed to the crank chamber
101
from the discharge chamber
120
. This varies the difference between the pressure in the crank chamber
101
and the pressure in the cylinder bores
108
a
. The inclination angle of the swash plate
105
is varied in accordance with the pressure difference through the hinge mechanism
106
, which controls the displacement of the compressor.
The control valve
111
includes a valve body
112
, a solenoid
113
, and a pressure sensitive mechanism
114
. The valve body
112
opens and closes the pressurizing passage
110
. The solenoid
113
urges the valve body
112
toward its closed position. The pressure sensitive mechanism
114
operates the valve body
112
in accordance with the pressure (suction pressure) in a suction chamber
121
. The valve body
112
is operated by the pressure sensitive mechanism
114
and the solenoid
113
to vary the opening size of the pressurizing passage
110
.
When the cooling load is great, the electric current supplied to the solenoid
113
is increased, which increases a force urging the valve body
112
to reduce the opening size of the pressurizing passage
110
. In this case, the pressure sensitive mechanism
114
operates the valve body
112
to lower a target value of the suction pressure. In other words, the control valve
111
adjusts the displacement of the compressor so that a lower suction pressure is maintained by increasing the current supply to the solenoid
113
.
When the cooling load is small, the supply of electric current to the solenoid
113
is decreased, which decreases the force urging the valve body toward its closed position. In this case, the pressure sensitive mechanism
114
operates the valve body
112
to raise the target value of the suction pressure. In other words, the control valve
111
adjusts the displacement of the compressor so that a higher suction pressure is maintained decreasing the electric current supplied to the solenoid
113
.
As shown in
FIG. 6
, the swash plate
105
includes a point D
1
corresponding to the top dead center position of each piston
107
and a point D
2
corresponding to the bottom dead center position of each piston
107
. In
FIG. 6
, the upper piston
107
is positioned at the top dead center by the swash plate
105
corresponding to point D
1
, and the lower piston
107
is positioned at the bottom dead center by the part of the swash plate
105
corresponding to point D
2
. The hinge mechanism
106
is axially aligned with point D
1
.
As shown in
FIG. 7
, each piston
107
located on the part of the swash plate
105
ranging from point D
1
to point D
2
in the rotational direction (clockwise) of the swash plate
105
is performing a compression stroke, in which the piston moves from the bottom dead center to the top dead center. In the compression stroke, a compression reaction force applied to each piston
107
pushes the swash plate
105
toward the rotor
104
. On the other hand, each piston located on the part of the swash plate
105
ranging clockwise from point D
2
to point D
1
in
FIG. 7
is performing a suction stroke, in which the piston
107
moves from the top dead center to the bottom dead center. During the suction stroke, the negative pressure in the cylinder bore
108
a
causes the piston to pull the swash plate
105
.
Thus, the direction of the forces applied to the part of the swash plate
105
corresponding to the pistons
107
performing compression strokes is opposite to that of the forces applied to the part of the swash plate
105
corresponding to the pistons
107
performing suction strokes. Therefore, as shown in
FIG. 7
, a resultant force F of the forces applied to the swash plate
105
from the pistons
107
is offset from the axis L of the drive shaft
103
. Accordingly, a moment based on the resultant force F is applied to the rotor
104
, and the moment inclines the rotor
104
with respect to a plane perpendicular to the axis L of the drive shaft
103
.
The control valve
111
operates the valve body
112
using the pressure sensitive mechanism
114
and the solenoid
113
to adjust the displacement of the compressor. The compressor shown in
FIG. 6
can vary the compression ratio, which is the ratio of the discharge pressure to the suction pressure. For example, when the supply of electric current to the solenoid
113
is increased, which lowers the target suction pressure, the displacement is maximized by the pressure sensitive mechanism
114
, and this increases the compression ratio. In contrast, when the supply of the electric current to the solenoid
113
is decreased, which raises the target suction pressure, an intermediate displacement is set by the pressure sensitive mechanism
114
, and this decreases the compression ratio.
The location of the resultant force F applied to the swash plate
105
from the pistons
107
varies radially. As shown in
FIG. 7
, the resultant force F can be located further from the axis L than an effective reception radius r
1
. The effective reception radius r
1
is the radius of a circle defined by the outer-most points of contact between the rollers
109
a
and the races
109
b
. A force applied at a location within the effective reception radius r
1
is directly transferred to the housing by the thrust bearing
109
.
The phenomenon that the position of the resultant force F varies radially from the effective reception radius r
1
was discovered through an experiment performed by the present inventors. In the experiment, when the compression ratio was lowest, the location of the force F extended to a radius r
2
, which is the radius of the axis S of the pistons
107
. Accordingly, the resultant force F applied to the swash plate
105
is not directly received by the thrust bearing
109
through the rotor
104
. Therefore, an inclination moment based on the resultant fo
Fukanuma Tetsuhiko
Ishigaki Yoshinobu
Kawaguchi Masahiro
Murase Masakazu
Sonobe Masanori
Freay Charles G.
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Morgan & Finnegan , LLP
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