Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
2001-09-25
2003-12-09
Walberg, Teresa (Department: 3742)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
C042S012000
Reexamination Certificate
active
06659733
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a variable displacement compressor capable of changing its displacement by changing the crank chamber pressure.
FIG. 5
shows a swash plate compressor to be used in a vehicle air conditioner. A crank chamber
82
is defined between a front housing
80
and a cylinder block
81
. A drive shaft
83
, which is driven by a vehicle engine, is supported by the crank chamber
82
and the cylinder block
81
. The crank chamber
82
contains a lug plate
84
that rotates integrally with the drive shaft
83
. A swash plate
85
is connected to the lug plate
84
through a hinge mechanism
102
.
A plurality of cylinder bores
86
are defined in the cylinder block
81
. Each cylinder bore
86
contains a piston
87
. The drive shaft
83
rotates the swash plate
85
to make each piston
87
connected to the swash plate
85
reciprocate between a top dead center position and a bottom dead center position within the cylinder bores
86
. The stroke of each piston
87
is changed depending on the inclination angle of the swash plate
85
to change the displacement of the compressor.
A valve plate
88
is located between the cylinder block
81
and a rear housing
89
. The rear housing
89
contains a suction chamber
90
and a discharge chamber
91
. As each piston
87
reciprocates, a refrigerant gas in the suction chamber
90
is caused to flow into the cylinder bore
86
. After the refrigerant gas is compressed in the cylinder bore
86
, it flows into the discharge chamber
91
.
The inclination angle of the swash plate
85
is determined by controlling the internal pressure of the crank chamber
82
(crank chamber pressure) with an electromagnetic control valve
93
. A supply passage
92
connects the discharge chamber
91
and the crank chamber
82
to each other through the electromagnetic control valve
93
. The electromagnetic control valve
93
controls the quantity of refrigerant gas flowing into the crank chamber
82
through the supply passage
92
. A bleed passage
94
connects the crank chamber
82
and the suction chamber
90
to each other. The refrigerant gas in the crank chamber
82
is allowed to flow into the suction chamber
90
through the bleed passage
94
constantly at a predetermined flow rate.
When no electric current is supplied to the control valve
93
, the valve
93
opens fully. Thus, the refrigerant gas is introduced to the crank chamber
82
at the maximum flow rate through the supply passage
92
. This increases the crank chamber pressure to cause the swash plate
85
to assume the minimum inclination angle. The control valve
93
closes when an electric current is supplied thereto, and the refrigerant gas cannot flow from the discharge chamber
91
into the crank chamber
82
. This reduces the crank chamber pressure to cause the swash plate
85
to assume the maximum inclination angle.
The swash plate
85
assumes the maximum inclination angle and the minimum inclination angle when it abuts against the lug plate
84
and against a restriction ring
101
fixed to the drive shaft
83
, respectively.
The clearance between the drive shaft
83
and the front housing
80
is sealed with a lip seal
95
. The distal end of the drive shaft
83
protrudes outward through the housing. An electromagnetic clutch
96
is attached to that end of the drive shaft
83
. The electromagnetic clutch
96
includes a fixed clutch disc
96
c
supported by the front housing
80
, a movable clutch disc
96
a
fixed to the distal end of the drive shaft
83
to oppose the fixed clutch disc
96
c
, and an electromagnetic coil
96
b
for moving the movable clutch disc
96
a
. When an electric current is supplied to the electromagnetic coil
96
b
, the movable clutch disc
96
a
is brought into contact with the fixed clutch disc
96
c
to transmit the driving force of an engine E to the drive shaft
83
.
A thrust bearing
97
is located between the lug plate
84
and the front housing
80
. The inner end of the drive shaft
83
is inserted to an insertion hole
98
defined in the cylinder block
81
and is supported therein. The insertion hole
98
contains a support spring
100
, which is a compression spring. The support spring
100
is located between a snap ring
99
contained in the insertion hole
98
and a thrust bearing
103
attached to the inner end of the drive shaft
83
. The support spring
100
urges the drive shaft
83
axially forward with respect to the front housing
80
(leftward in FIG.
5
). The support spring
100
controls axial backlash of the drive shaft
83
.
When a power switch of the air conditioner is turned off or when the engine E is stopped, the supply of electric current to the electromagnetic clutch
96
and to the control valve
93
is interrupted. Thus, the control valve
93
opens fully to let the refrigerant gas flow through the supply passage
92
into the crank chamber
82
. Here, the crank chamber pressure increases temporarily to an excessively high degree due to the abrupt inflow of the gas. The swash plate
85
having moved to the minimum inclination angle position (indicated by the chain double-dashed line in
FIG. 5
) is then pressed against the restriction ring
101
with an excessive force. As a result, the drive shaft
83
retracts along its axis against the force of the support spring
100
.
The displacement of the compressor is sometimes minimized to reduce the load of the compressor applied to the engine E during acceleration of a vehicle. In this case, the refrigerant gas flows rapidly into the crank chamber
82
as soon as the control valve
93
opens fully, which increases the crank chamber pressure temporarily to an excessively high degree. Thus, the drive shaft
83
retracts axially.
The retraction of the drive shaft
83
moves the pistons
87
toward the valve plate
88
. Thus, each piston
87
impinges upon the valve plate
88
at the top dead center position and causes hammering or vibration.
The retraction of the drive shaft
83
also moves the movable clutch disc
96
a
of the electromagnetic clutch
96
backward. This brings the movable clutch disc
96
a
into contact with the fixed clutch disc
96
c
, although the electromagnetic coil
96
b
is demagnetized. As a result, the two clutch discs
96
a
and
96
c
generate friction, abnormal noise and heat.
Further, if the drive shaft
83
retracts, the axial position of the drive shaft
83
changes with respect to the lip seal
95
held in the front housing
80
. Normally, the drive shaft
83
is in contact with the lip seal
95
at a predetermined axial position. The drive shaft
83
has a foreign matter such as sludge deposited on its outer surface at a position spaced from the predetermined axial position. Therefore, if the axial position of the drive shaft
83
changes with respect to the lip seal
95
, the sludge is caught between the lip seal
95
and the drive shaft
83
. This lowers the sealing performance of the lip seal
95
and permits gas leakage from the crank chamber
82
.
To solve the problems described above, it is possible to use a support spring
100
having a greater force so that the drive shaft
83
is not retracted by an excessively increased crank chamber pressure. In this case, however, excessive loads are applied to the thrust bearings
97
and
103
, which causes power loss in the compressor.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a variable displacement compressor capable of preventing shifting of the drive shaft in the axial direction.
In order to attain the above object, the present invention provides a compressor capable of changing its displacement depending on the internal pressure of the crank chamber. The compressor has a housing. The housing contains a cylinder block and a valve plate to be connected to the cylinder block. The cylinder block contains cylinder bores and a supporting hole. A piston is housed in each cylinder bore to compress gas drawn into the cylinder bore through the valve plate. The compressed gas is discharged from the cylinder
Fukanuma Tetsuhiko
Kawaguchi Masahiro
Takenaka Kenji
Fastovsky Leonid
Kabushiki Kaisha Toyota Jidoshokki
Morgan & Finnegan , LLP
Walberg Teresa
LandOfFree
Variable displacement compressor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Variable displacement compressor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Variable displacement compressor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3121001