Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
1999-10-04
2001-07-31
Walberg, Teresa (Department: 3742)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
Reexamination Certificate
active
06267562
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a variable displacement compressor used for compressing refrigerant in a refrigeration cycle of an automobile air conditioner or the like, comprising an airtight crank chamber and a variable inclination angle swing body installed on an axis of rotation inside said crank chamber, comprising at least one piston reciprocally guided in a cylinder and connected to said swing body, said cylinder being selectively connectable to a suction chamber in turn connected to a low-pressure refrigerant pipe conduit or to a discharge chamber in turn connected to a low-pressure refrigerant pipe conduit, and means in said variable displacement compressor for varying the amount of discharge of said refrigerant into said discharge chamber between a minimum discharge amount in a minimum operation state of the compressor and a maximum discharge amount by varying the angle of inclination of said swing body corresponding to a change of a pressure within said crank chamber, and further comprising a main valve between said low-pressure refrigerant pipe conduit and said suction chamber, said main valve being actuable between a fully closed state and a fully opened state.
2. Description of the Related Art
As the compressor used in a refrigeration cycle of an automobile air conditioner has a belt directly connected to the engine by a transmission belt, the number of its rotations cannot be controlled independently from engine speed. So a variable displacement compressor is used which can change the amount of refrigerant (the amount of discharge) to obtain the appropriate cooling capacity without being restricted by the number of rotations of the engine. In such a variable displacement compressor, a swing plate is generally installed in an airtight crank chamber so as to be able to tilt over a variable angle of inclination. The swing plate is driven by rotational movement of the axis of rotation and executes swing movements. A piston executing reciprocal motions by the swing movements of the swing plate sucks refrigerant of a suction chamber connected to a low-pressure refrigerant pipe conduit into a cylinder, compresses it, and discharges it to a discharge chamber connected to a high-pressure refrigerant pipe conduit. The amount of discharge of the refrigerant is changed by changing the angle of inclination of the swing plate according to change of pressure of the crank chamber. The variable displacement compressor used for a refrigeration cycle of an automobile air conditioner generally continues to operate even when cooling capacity is not needed, with a minimum displacement which is about 5% of the maximum displacement. That is, the compressor then operates at the minimum operation state. However, if simply operated like that, the problem occurs that even at the minimum operation state fins of the evaporator freeze when the load is small as in winter, due to a flow of compressed refrigerant into the evaporator. So, a valve is installed to enable a passage between the low-pressure refrigerant pipe conduit and the suction chamber to be fully closed, thereby preventing the low-pressure refrigerant from being sucked into the compressor at the minimum operation state. The conventional variable displacement compressor used in a refrigeration cycle of an automobile air conditioner makes the passage between the low-pressure refrigerant pipe conduit and the suction chamber to be fully closed at the minimum operation, irrespective of the season. However, freezing of the fins of the evaporator is a problem which occurs only when the load is small, as in winter. The problem of freezing does not occur, when the load is higher, as in summer. The load of the compressor for the engine produced by having closed the inlet of the compressor leads to a disadvantageous result because fuel efficiency decreases.
OBJECTS AND SUMMARY OF THE INVENTION
Therefore, the present invention aims to provide a variable displacement compressor with improved fuel efficiency which does not generate freezing of the fins of the evaporator at the minimum operation state, when the load is small, as in winter, and which reduces the load to the engine when the load is large, as in summer.
Said task can be achieved with a variable displacement compressor according to claim
1
, claim
2
, claim
3
or claim
4
.
According to a first aspect of the invention a main valve actuating structure is provided, actuating the main valve by refrigerant pressure into its closed state, said main valve actuating means being responsive to a relative pressure condition or a relative temperature condition of the refrigerant in the low-pressure pipe conduit, said relative pressure condition or relative temperature condition representing during said minimum operation state of said compressor a small load condition.
Since said main valve actuating structure is responsive to a relative pressure condition or a relative temperature condition of the refrigerant in the low-pressure pipe conduit which condition is representing either a small load condition and simultaneously said minimum operation state of the compressor or a large load condition, the main valve automatically is brought into a fully closed state only in case of a small load condition and simultaneously with a minimum operation state of the compressor. This means that in case of higher load conditions as in summer and during a minimum operation state of the compressor with the not fully closed main valve the power consumption of the compressor is low, improving the fuel efficiency of the engine driving the compressor. This is based on the recognition that in a large load condition as in summer there is no danger of fin freezing even though the compressor supplies a small amount of refrigerant to the evaporator. Operation of the compressor with fully closed main valve occurs only in case of a small load condition during the minimum operation state of the compressor and to the benefit of the elimination of the danger of fin freezing, e.g. as in winter with low ambient temperature.
According to a further aspect of the invention as said main valve a differential-pressure sensing open and close valve is provided which opens and closes respectively when a differential pressure Pd minus Pe between the pressure Pd of the refrigerant in said discharge chamber and the pressure of the refrigerant in said low-pressure refrigerant pipe conduit is larger or smaller than a predetermined differential pressure value.
According to a further aspect of the invention as a main valve a temperature sensing open and close valve for low-pressure refrigerant is provided between said low-pressure refrigerant pipe conduit and said suction chamber which opens and closes respectively when the temperature of the refrigerant in said suction chamber and/or in said low-pressure pipe conduit is higher or lower than a predetermined temperature value.
According to a further aspect of the invention as a main valve a pressure sensing open and close valve for low-pressure refrigerant is provided between the low-pressure refrigerant pipe conduit and said suction chamber which opens and closes respectively when the pressure of the refrigerant in said low-pressure refrigerant pipe conduit is lower or higher than a predetermined pressure value.
The present invention enables the inlet of a variable displacement compressor used in a refrigeration cycle of an automobile air conditioner automatically to be closed when the load is small and opened when the load is large. So, freezing of fins of an evaporator can be avoided at the minimum operation state with a small load for the engine, as in winter, and the fuel efficiency can be improved by reducing the load for the engine when the load is large, as in summer.
A refrigerant reflux conduit connecting the discharge chamber and the low-pressure refrigerant pipe conduit with a small cross-sectional area and only when the main valve is closed allows by a backflow of refrigerant to keep the pressure in the low-pressure refr
Fastovsky Leonid
Nilles & Nilles S.C.
TGK Co. Ltd.
Walberg Teresa
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