Pumps – Condition responsive control of drive transmission or pump... – Having condition responsive pumped fluid control
Reexamination Certificate
2001-02-02
2003-06-03
Freay, Charles G. (Department: 3746)
Pumps
Condition responsive control of drive transmission or pump...
Having condition responsive pumped fluid control
C417S270000, C251S129020, C251S129150
Reexamination Certificate
active
06572341
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a variable displacement type compressor. More particularly, the present invention relates to a variable displacement type compressor used for an air conditioner incorporated in a vehicle, for example.
2. Description of the Related Art
In general, a refrigerating circuit of an air conditioner for a vehicle includes a condenser, an expansion valve, an evaporator and a compressor. The compressor sucks refrigerant gas from the evaporator, compresses it and discharges the thus compressed refrigerant gas to the condenser. In the evaporator, heat exchange is conducted between the refrigerant flowing in the refrigerating circuit and the air flowing into the passenger compartment.
In general, the compressor mounted on the vehicle is driven by the power of the engine of the vehicle, and the power of the engine is used by the compressor when the air conditioner of the vehicle is operated. Accordingly, when the vehicle is accelerated or the vehicle is driven while it is climbing a hill and when a heavy load is required for the compressor, the power of the engine becomes insufficient and the acceleration performance or the driveability of the vehicle is deteriorated. In order to solve the above problems, there is provided a variable displacement type compressor which can be driven in a small-capacity condition when the vehicle requires a higher power for running.
The variable displacement swash plate type compressor, which is commonly used as a compressor mounted on the vehicle, includes a plurality of cylinder bores, a crank chamber, a suction chamber and a discharge chamber formed in the housing of the compressor, pistons being reciprocatingly arranged in the cylinder bores. A drive shaft to which the power is transmitted from the engine (external drive source) of the vehicle is provided through the crank chamber. A rotary support body (lug plate) fixed to the drive shaft is operatively connected to the swash plate (cam plate) via a hinge mechanism (connection guide mechanism). The swash plate, converting a rotary motion of the drive shaft into a reciprocating motion of the pistons, can rotate with the drive shaft and can tilt with respect to the drive shaft while the swash plate is slid in the axial direction of the drive shaft. A stroke of the reciprocation of the pistons, that is, a displacement or a discharge capacity is determined by the inclination angle of the swash plate. However, the inclination of the swash plate is mainly determined by a difference between the pressure in the crank chamber controlled by the capacity control valve and the pressure in the cylinder bore, which act on opposite sides of the pistons.
In the variable displacement type compressor, in the case where the compressor is continuously driven under the condition that the peripheral temperature is low, there is a possibility that the evaporator is frozen. In order to prevent the occurrence of freezing, it is necessary to stop the operation of the compressor. It is a conventional technique that the power of the engine is transmitted to the drive shaft (rotary shaft) of the compressor via an electromagnetic clutch and that the compressor is driven via the electromagnetic clutch in the case of cooling and dehumidifying. However, problems are caused in the compressor having the electromagnetic clutch, because the manufacturing cost of the compressor is high and further the weight of the compressor is heavy. In order to solve the above problems, Japanese Unexamined Patent Publication No. 9-145172 discloses a vapor compression type refrigerating machine into which a variable displacement swash plate type compressor is incorporated, wherein a flow control valve for shutting off the flow of refrigerant or reducing a flow rate of refrigerant is arranged in the middle of the refrigerant passage provided between the outlet of the evaporator and the suction chamber (low pressure chamber) of the compressor.
As shown in
FIG. 6
of the attached drawings, a flow control valve
70
is arranged in a valve holding hole
73
formed between a suction port
71
connected to an outlet of an evaporator (not shown) and a low pressure chamber (suction chamber)
72
. The flow control valve
70
includes a valve casing
74
, a valve element
75
and a compression spring
76
. The valve casing
74
is arranged perpendicular to a suction passage
77
and includes an inlet port
78
for communication with the suction port
71
, and an outlet port
79
for communication with the low pressure chamber
72
. The valve element
75
is urged to the open side by the compression spring
76
. When the pressure in the discharge chamber is supplied to the pressure chamber
80
, the valve element
75
is moved to a closed position. In the middle of the passage connecting the pressure chamber
80
to a discharge chamber, there is provided an electromagnetic opening and closing valve.
In the case where it is unnecessary to cool the evaporator, for example, in winter, the electromagnetic opening and closing valve is opened, so that the valve element
75
is kept at a closed position. In this connection, there is provided a small clearance between the inner circumferential surface of the valve casing
74
and the outer circumferential surface of the valve element
75
, and therefore, a small quantity of refrigerant vapor and lubricant flows through this clearance. Accordingly, the quantity of refrigerant sucked from the evaporator into the compressor becomes very small, and there is no possibility that the evaporator is frozen even if the operation of the compressor is not stopped. As a result, it is possible to omit the electromagnetic clutch.
However, in the above conventional device, when the suction passage
77
is closed, it is not completely closed but the small clearance is formed between the valve casing
74
and the valve element
75
so that a small quantity of refrigerant gas and lubricant can flow through it. However, in the case where a quantity of refrigerant gas is reduced to a value at which the evaporator is not frozen while the refrigerant gas discharged from the compressor is flowing in the circulating circuit from the external refrigerant circuit including the evaporator to the compressor, it is difficult for the lubricant, which is discharged from the compressor into the external refrigerant circuit together with the refrigerant, to return to the compressor together with the refrigerant. As a result, when the compressor is continuously operated over a long period of time in winter, the quantity of lubricant accommodated in the crank chamber becomes insufficient, and there is a possibility that the sliding sections in the crank chamber seize up and deteriorate early.
In the structure of the flow control valve
70
disclosed in the above patent publication, the valve element
75
is arranged to move between the open position and the closed position, crossing the suction passage
77
. Therefore, under the condition that the valve element
75
is located at the closed position, refrigerant gas flows from the suction port
71
to the low pressure chamber
72
via the clearance formed for the valve element
75
to slide in the valve casing
74
. As a result, even if the clearance is not positively provided, it is impossible to reduce the quantity of refrigerant gas returning to the compressor via the external refrigerant circuit to zero, that is, lubricant is gradually removed from the compressor. As a result, the quantity of lubricant in the compressor becomes insufficient.
SUMMARY OF THE INVENTION
The present invention is made to solve the above problems, and the object of the present invention is to provide a variable displacement type compressor, by which an evaporator in an external refrigerant circuit is not frozen even if the operation of the compressor is continuously conducted at a minimum displacement state, and it is possible to prevent the compressor from falling into an insufficiently lubricating condition.
According to the present inventio
Kawaguchi Masahiro
Kimura Kazuya
Freay Charles G.
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Liu Han L.
Woodcock & Washburn LLP
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