Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
2000-03-10
2002-03-05
Walberg, Teresa (Department: 3742)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
Reexamination Certificate
active
06352416
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a variable displacement compressor used in vehicle air conditioners. Specifically, the present invention pertains to a device and a method for controlling the displacement of a variable displacement compressor.
FIG. 12
shows a prior art variable displacement compressor. The compressor includes a housing
101
. A crank chamber
102
is defined in the housing
101
. A drive shaft
103
is supported in the housing
101
. A lip seal
104
is located between the housing
101
and the drive shaft
103
to prevent gas leakage along the surface of the drive shaft
103
.
The drive shaft
103
is connected to a vehicle engine Eg, which serves as an external power source, through an electromagnetic friction clutch
105
. The friction clutch
105
includes a pulley
106
, an armature
107
and an electromagnetic coil
108
. The pulley
106
is coupled to the engine Eg, and the armature
107
is coupled to the drive shaft
103
. When the clutch
105
engages, that is, when the coil
108
is excited, the armature
107
is attracted to and is pressed against the pulley
106
. As a result, the clutch
105
transmits the driving force of the engine Eg to the drive shaft
103
.
When the clutch
105
disengages, that is, when the coil
108
is de-excited, the armature
107
is separated from the pulley
106
. In this state, the driving force of the engine Eg is not transmitted to the drive shaft
103
.
A rotor
109
is secured to the drive shaft
103
in the crank chamber
102
. A thrust bearing
122
is located between the rotor
109
and the inner wall of the housing
101
. A swash plate
110
is coupled to the rotor
109
by a hinge mechanism
111
. The hinge mechanism
111
permits the swash plate
110
to rotate integrally with the drive shaft
103
and to incline with respect to the axis L of the drive shaft
103
. A limit ring
112
is fitted about the drive shaft
103
. When the swash plate
110
abuts against the limit ring
112
as illustrated by broken lines in
FIG. 12
, the swash plate
110
is at the minimum inclination position.
Cylinder bores
113
, suction chamber
114
and a discharge chamber
115
are defined in the housing
101
. A piston
116
is reciprocally housed in each cylinder bore
113
. The pistons
116
are coupled to the swash plate
110
. The housing
101
includes a valve plate
117
. The valve plate
117
separates the cylinder bores
113
from the suction chamber
114
and the discharge chamber
115
.
Rotation of the drive shaft
103
is converted into reciprocation of each piston
116
by the rotor
109
, the hinge mechanism
111
and the swash plate
110
. Reciprocation of each piston
116
draws refrigerant gas from the suction chamber
114
to the corresponding cylinder bore
113
via a suction port
117
a
and a suction valve flap
117
b
, which are formed in the valve plate
117
. Refrigerant gas in each cylinder bore
113
is compressed to reach a predetermined pressure and is discharged to the discharge chamber
115
via a discharge port
117
c
and a discharge valve flap
117
d
, which are formed in the valve plate
117
.
A spring
118
urges the drive shaft
103
forward (to the left as viewed in
FIG. 12
) along the axis L through a thrust bearing
123
. The spring
118
prevents axial chattering of the drive shaft
103
.
The crank chamber
102
is connected to the suction chamber
114
by a bleeding passage
119
. The discharge chamber
115
is connected to the crank chamber
102
by a supply passage
120
. The opening of the supply passage
120
is regulated by an electromagnetic displacement control valve
121
.
The control valve
121
adjusts the opening of the supply passage
120
to regulate the amount of pressurized refrigerant gas drawn into the crank chamber
102
from the discharge chamber
115
. The pressure in the crank chamber
102
is changed, accordingly. Changes in the crank chamber pressure alter the gas pressure moment acting on the pistons
116
through the swash plate
110
, which changes the inclination of the swash plate
110
. Accordingly, the stroke of each piston
116
is changed and the compressor displacement is varied. The gas pressure moment depends on the crank chamber pressure and the pressure in the cylinder bore
113
, which act on the pistons
116
.
When the clutch
105
disengages or when the engine Eg is stopped, the control valve
121
fully opens the supply passage
120
, which increases the pressure in the crank chamber
102
. Accordingly, the gas pressure moment decreases the inclination of the swash plate
110
. The compressor stops operating with the swash plate
110
at the minimum inclination position. When the compressor is started again, the displacement of the compressor is minimum, which requires minimum torque. The shock caused by starting the compressor is thus reduced.
When there is a relatively great cooling demand on a refrigeration circuit that includes the compressor, for example, when the temperature in a passenger compartment of a vehicle is much higher than a target temperature set in advance, the control valve
121
closes the supply passage
120
and maximizes the compressor displacement.
When the clutch
105
disengages or when the engine Eg is stopped, the compressor is stopped. If the compressor is stopped when operating at the maximum displacement, the control valve
121
quickly and fully opens the supply passage
120
, which was fully closed. Accordingly, highly pressurized refrigerant gas in the discharge chamber
115
is quickly supplied to the crank chamber
102
. Refrigerant gas in the crank chamber
102
constantly flows to the suction chamber
114
through the bleeding passage
119
. However, since the amount of refrigerant gas that flows to the suction chamber
114
through the bleeding passage
119
is limited, the pressure in the crank chamber
102
is quickly and excessively increased by as the supply passage
120
is quickly and fully opened. Also, when the compressor is stopped, the pressure in each cylinder bore
113
approaches the pressure in the suction chamber
114
, which is relatively low. As a result, the gas pressure moment decreasing the swash plate inclination becomes excessive.
Accordingly, the swash plate
110
is moved from the maximum inclination position to the minimum inclination position and strongly presses the drive shaft
103
rearward (to the right as viewed in
FIG. 12
) through the limit ring
112
. The swash plate
110
also strongly pulls the drive shaft
103
rearward through the hinge mechanism
111
and the rotor
109
. The drive shaft
103
is thus moved rearward along its axis L against the force of the spring
118
.
When the drive shaft
103
moves rearward, the axial position of the drive shaft
103
relative to the lip seal
104
, which is retained in the housing
101
, changes. Normally, a predetermined annular area of the drive shaft
103
contacts the lip seal
104
. Foreign particles and sludge adhere to areas of the drive shaft
103
that are axially adjacent to the predetermined annular area. Therefore, if the axial position of the drive shaft
103
relative to the lip seal
104
changes, sludge enters between the lip seal
104
and the drive shaft
103
. This lowers the effectiveness of the lip seal
104
and results in gas leakage from the crank chamber
102
.
Particularly, when the drive shaft
103
moves rearward due to disengagement of the clutch
105
, the armature
107
, which is fixed to the drive shaft
103
, moves toward the pulley
106
. The clearance between the pulley
106
and the armature
107
is as small as 0.5 mm when the clutch
105
disengages. Rearward movement of the drive shaft
103
eliminates the clearance between the pulley
106
and the armature
107
, which may cause the armature
107
to contact the rotating pulley
106
. This produces noise and vibration. Also, even if the clutch
105
disengages, the driving force of the engine Eg may be transmitted to the drive shaft
103
.
When the drive shaft
103
moves rearward, the average position of t
Fukanuma Tetsuhiko
Hamasaki Masaru
Hidaka Shigeyuki
Koumura Satoshi
Murao Kazushige
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Morgan & Finnegan , LLP
Patel Vinod D
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