Capacity controller of capacity variable compressor

A small sized and structurally simple capacity controller having a wide control range of a compressor with variable capacity adds a differential pressure to an inhalation pressure on an arbitrary level by a piston valve body actuated by a solenoid and by the inhalation pressure. The differential pressure is transmitted into a capacity variation mechanism of the compressor in order to change the capacity of the compressor.

BACKGROUND OF THE INVENTION

The present invention relates to a capacity controller of a compressor with variable capacity used for a refrigerating cycle of an automobile air conditioner or the like.

DESCRIPTION OF THE RELATED ART

As the compressor in a refrigerating cycle of an automobile air conditioner directly is driven by the engine of the automobile the speed of the compressor cannot be controlled individually. In order to obtain proper refrigerating abilities without being limited by the engine speed compressors with variable capacity are used allowing to vary their capacity (the amount of discharged refrigerant) upon cooling or heating demand independent from the speed of the engine. The compressor may be a rotary compressor, a scroll compressor or a swash plate compressor. The capacity is controlled by controlling the inhalation pressure with the help of an energisation force brought onto a diaphragm by an electromagnetic solenoid. Due to said diaphragm also the pressure of the ambient air is applied. A capacity variation mechanism is controlled by the inhalation pressure. A capacity control mechanism having said diaphragm is complicated to operate, because the structure of the control mechanism is complicated and large in size, and because the available control range of the inhalation pressure is restricted. As a consequence, it is difficult, to control the compressor properly within a wide range of conditions.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a capacity control apparatus of a compressor with variable capacity which can be of compact size and structurally simple and which allows to obtain wide control range, and to propose a method for controlling the capacity of the compressor properly within a broader control range compared with the useable control range of only the inhalation pressure.

According to the invention a wide control range is obtained with a compact and small sized control apparatus having a simple configuration. This is achieved by controlling the capacity of the compressor with the help of a differential pressure added to the differential pressure port28c. Differential pressure port28cof controller20is connected to said other part of cylinder31on the side of piston32opposite to spring33.

As a consequence, said control pressure Pc when controlled corresponds to the inhalation pressure Ps but is higher by an increment of pressure due to the thrust F caused by moveable iron core23(and the setting of springs26,27).

Discharge pressure duct is connected to a discharge pressure port28dof controller20. Discharge pressure port28d(discharge pressure Pd) opens in the vicinity of valve seat42at the circumferential side of piston valve body25, so that discharge pressure Pd does not affect the piston valve body25in axial direction, i.e., piston valve body25is pressure balanced for discharge pressure Pd.

Said valve closure jaw part25aformed at the front end of piston valve body25serves to open and close said valve seat42between discharge pressure port28dand differential pressure port28c. As soon as said valve jaw part25ais lifted from valve seat42during a movement of piston valve body25with thrust F pressure Pd from discharge pressure duct2is transmitted via the open valve seat42into differential pressure port28c, according to the initial control condition of the controller.

Whenever the value of the pressure at the differential pressure port28cbecomes lower than the fixed value of control pressure Pc, piston valve body25is moved towards its opening state such that a communication is established between the discharge pressure port28dand differential pressure port28c. As soon as then the value of the pressure at the differential pressure port28creaches the fixed value of the control pressure Pc, piston valve body25returns into its closing state and again separates said differential pressure port28cfrom said discharge pressure port28d.

Furthermore, e.g. outside of controller20, differential pressure port28cand inhalation pressure port28sare directly interconnected via a leak passage40having a small cross-sectional area, e.g. provided in a connection between inhalation duct1and a duct connecting differential pressure port28cwith mechanism30. As soon as valve closure jaw part25acloses valve seat42the value of the pressure at the differential pressure port28cis allowed to little by little relieve via leak passage40into inhalation duct1. As inhalation pressure on an arbitrary level with the help of a controlling piston valve body, loaded inter alia by a solenoid. Additionally, the inhalation pressure is applied to the piston valve body so that a value of the differential pressure can be maintained and set arbitrary for the transmission into the capacity variation mechanism to correspondingly adjust the capacity of the compressor. Basically, the differential pressure used in connection with the inhalation pressure is derived from a discharge pressure of the compressor allowing to broaden the pressure variation range for the capacity variation mechanism. The inhalation pressure remains the leading control parameter. However, not only the inhalation pressure and/or its pressure variations control the capacity variation mechanism, but in addition an assistant differential pressure is taken from the discharge pressure of the compressor and is added. The magnitude of the differential pressure may be adjusted and varied by a solenoid, e.g. a proportional solenoid.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 to 8show a rotary compressor10with variable capacity in conjunction with a capacity controller20and a capacity variation mechanism30, together employed in a refrigerating cycle of an automobile air conditioner or the like. The compressor10has (FIG. 2) a circular housing11receiving a somewhat smaller circular rotor12disposed on an eccentric axis13. Said rotor12is driven e.g. by the engine of the automobile (not shown). In the outer periphery of rotor12radially displaceable seal pieces14are biased outwardly by spring means such that they contact the inner surface of housing11. At the closest position between the inner surface of housing11and periphery of rotor12a discharge port19is provided discharging compressed high pressure refrigerant into a discharge pressure duct2. An inhalation duct1for low-pressure refrigerant supplied from an evaporator (not shown) communicates with an inhalation port15aof an inhalation port control board15. Port15aallows to supply the low-pressure refrigerant into a compression chamber18of compressor10. Board15has axial and oversized bore16for eccentric axis13.

The capacity of the compressor10can be varied by increasing or decreasing the volume, i.e. the angular extension, of compression chamber18, e.g. by rotating the inhalation control board15in order to displace the inhalation port15ain rotary direction. Control board15has a protruding driving pin17which can be adjusted about the axis of board15by capacity variation mechanism30.

Mechanism30inFIG. 4controls the position of the driving pin17in order to control the rotary orientation of the inhalation port15aof control board. In a cylinder31of mechanism30a piston32is moveable in axial direction. Driving pin17engages into a circumferential groove32aof piston32. An axial movement of piston32automatically displaces control board15about its axis. Piston32is loaded by a spring33in a direction adjusting the capacity of the compressor towards a minimum. Spring33is received within one part of cylinder31. Said part of cylinder31is also connected to inhalation duct1such that the pressure inside said part of the cylinder31correspond an inhalation pressure Ps of the compressor. The opposite part of cylinder31(at the other side of piston32) is connected to a differential pressure port28cof said capacity controller20which operates as a differential pressure controller. The pressure within the other part of cylinder31is a control pressure Pc the value of which is controlled by said controller20. The higher said control pressure Pc is, the further piston32is displaced counter to spring33and the more control board15is rotated towards its position for maximum capacity of the compressor. The lower said control pressure Pc is, the more control board15rotated by spring33and inhalation pressure Ps towards its position of minimum capacity of the compressor10.

Capacity controller20, e.g. ofFIG. 1, is a fixed differential pressure valve and includes a solenoid (coil21, fixed iron core22and moveable iron core23) for controlling said differential pressure also by the pressures at both ends of a piston valve body25. The driving source of said solenoid is electromagnetic coil21to which electric current can be supplied upon demand (proportional solenoid, the actuation force of which directly is proportional to the value of current supplied to coil21).

In addition springs26,27are provided which act in opposite directions onto said piston valve body25. The setting of both springs26,27determines in the embodiment ofFIG. 1a basic maximum value of the differential pressure (Pc–Ps). Said value, however, can arbitrarily be decreased by feeding current into coil21. The stronger the current is, the more moveable iron core23is attracted by fixed iron22. Moveable iron core23causes a thrust F which is transmitted to said piston valve body25via a rod24extending along the axis of fixed iron core20. Thrust F is acting in opening direction of said differential pressure valve of said controller20inFIG. 1.

Said inhalation duct1is connected to an inhalation pressure port28sprovided in a side of a housing of controller20and behind the back or rear effective pressure area of piston valve body25which can be loaded in the same direction by the thrust F of moveable iron core23.

Piston valve body25co-operates by a front end valve closure jaw part25awith a valve seat42provided between a space41housing piston valve body25and axially disposed a result, piston valve body25always axially and slightly moves and control pressure Pc is controlled to the fixed value, e.g. corresponding to the value of the electric current supplied to electromagnetic coil21.

As shown inFIG. 5the larger the value of the electric current in electromagnetic coil21is, the larger the pressure differential of (Pc–Ps) becomes, and the angular position of the inhalation port15ais displaced in a direction towards (max) by capacity variation mechanism30. As a result the capacity of the inhalation compression chamber18and consequently the discharge pressure Pd increase.

The smaller the value of the electric current in electromagnetic coil21is, the smaller is the differential pressure of (Pc–Ps), as shown inFIG. 6and the angular position of inhalation port15ais adjusted in the direction towards (min) by capacity variation mechanism30. As a result, the capacity of said inhalation compression chamber18and the discharge pressure Pb both decrease.

As can be seen inFIG. 7the capacity of compression chamber18of compressor10is varied corresponding to the differential pressure Pc–Ps by controlling the value of the electric current in electromagnetic coil21′.

The value of the electric current in electromagnetic coil21is controlled by inputting detected signals from an engine sensor, temperature sensors inside and outside of an automobile compartment, an evaporator sensor and a plurality of other sensors detecting specific kinds of conditions. Said signals are input into a control part3containing a CPU and the like. Said CPU processes the input signals and provides an output signal based on the respective operation results. The control signal is then output from control part3to electromagnetic coil21, e.g. via a not shown driving circuit. In a second embodiment of controller20shown inFIG. 8piston valve body25is co-operating with valve seat42′ such that said valve seat42′ is closed by the front end closure part25a′ in the direction of thrust F generated by solenoid21,22,23. In this embodiment discharge pressure port28dis omitted. At the very same location instead inhalation pressure port28sis provided. Discharge pressure duct2directly is connected via leak passage40to the duct connecting differential pressure port28cto the left part of cylinder31of mechanism30. Inhalation pressure port28sof the embodiment ofFIG. 1is omitted. Inhalation pressure Ps can act on piston valve body25in the same direction as thrust F, namely towards the closing state. The pressure in differential pressure port28cis acting in opening direction.

Springs26,27determine a basic value of differential pressure Pc–Ps. Said value can be increased arbitrarily by increasing the value of the current supplied to electromagnetic coil21.

As soon as due to pressure passing leak passage40the pressure at differential pressure port28crises beyond the fixed value of the control pressure Pc, piston valve body25is lifted from its valve seat42′. A flow communication is established between differential pressure port28cand inhalation pressure port28s. Control pressure Pc drops to the fixed value. As soon as the pressure at the differential pressure port28chas reached the fixed value of the control pressure Pc, piston valve body25returns again into its closed state. Again high pressure refrigerant passes through leak passage40to differential pressure port28cin order to maintain the fixed value of the differential pressure Pc–Ps as adjusted by the value of the current for the coil21.

In both embodiments high pressure refrigerant from the discharge pressure duct2is used to build up the fixed pressure value for the control pressure Pc, however, influenced by the initial value of the inhalation pressure Ps.

The invention instead may be applied to control the capacity of a scroll compressor or the like instead of a rotary compressor10as shown.