EP2784320A2

EP2784320A2 - Control valve for variable displacement compressor

Info

Publication number: EP2784320A2
Application number: EP14160650.9A
Authority: EP
Inventors: Masaaki Tonegawa; Hidekazu Sakakibara; Ryouta Sugamura; Shinji Saeki
Original assignee: TGK Co Ltd
Current assignee: TGK Co Ltd
Priority date: 2013-03-27
Filing date: 2014-03-19
Publication date: 2014-10-01
Anticipated expiration: 2034-03-19
Also published as: EP2784320A3; EP2784320B1; JP6103586B2; JP2014190247A; KR20140118808A; KR102129731B1

Abstract

A control valve according to one embodiment includes a body having a main passage communicating a discharge chamber with a crankcase and a sub-passage communicating the crankcase with a suction chamber, a main valve provided in the main valve passage, a sub-valve provided in the sub-passage, a power element for receiving the suction pressure of the suction chamber and generating a drive force exerted in an opening direction of the main valve in accordance with the magnitude of the suction pressure, and a solenoid for generating a drive force in a closing direction of the main valve in accordance with the amount of current supplied. The control valve is configured such that the sub-valve remains closed when the main valve is controlled and such that the sub-valve is opened after the main valve is closed. Also, a change in the area of opening of the sub-valve relative to the uplift amount of the sub-valve element from the sub-valve seat is larger than that of the main valve relative to the uplift amount of the main valve element from the main valve seat.

Description

The present invention relates to a control valve that is suitable for controlling the discharging capacity of a variable displacement compressor.
An automotive air conditioner generally includes a compressor, a condenser, an expander, an evaporator, and so forth. Here, the compressor discharges a high-temperature and high-pressure gaseous refrigerant produced by compressing a refrigerant flowing through a refrigeration cycle of a vehicle. The condenser condenses the gaseous refrigerant. The expander produces a low-temperature and low-pressure refrigerant by adiabatically expanding the condensed liquid refrigerant. The evaporator evaporates the refrigerant and thereby causes a heat exchange of the refrigerant with air inside a vehicle's compartment. The refrigerant evaporated by the evaporator is again brought back to the compressor and thus circulates through the refrigeration cycle.
The compressor is, for example, a variable displacement compressor (hereinafter referred to simply as "compressor" also) capable of varying the refrigerant discharging capacity in order to maintain a constant level of cooling capacity irrespective of the engine speed. This compressor has a piston for compression linked to a wobble plate that is mounted to a rotational shaft rotated and driven by an engine, and the compressor regulates the refrigerant discharge rate by changing the stroke of the piston through changes in the angle of the wobble plate. The angle of the wobble plate can be changed continuously by changing the balance of pressure working on both faces of the piston as part of the discharged refrigerant is introduced into an airtight crankcase. The pressure within this crankcase (hereinafter referred to as "crank pressure") Pc is controlled by a control valve for a variable displacement compressor (hereinafter referred to simply as "control valve" also), which is provided between the discharge chamber and the crankcase of the compressor.
Such a control valve regulates the valve opening degree by supplying the externally applied current to a solenoid, which functions as a driver part. Suppose that an air conditioning function needs to be quickly fulfilled at the startup or the like of the air conditioner. Then, a valve section is set to a closed state by supplying the maximum current to the solenoid, for instance. Also, the wobble plate is tilt relative to the rotational shaft for a large angle by lowering a crank pressure Pc. As a result, the compressor can be operated at the maximum capacity. When the engine load of a vehicle is high, the compressor can be operated at the minimum capacity by fully opening the valve section with the solenoid turned off and by setting the wobble plate substantially at a right angle to the rotational shaft with the crank pressure Pc set high.
The control valve like this is disclosed in Reference (1) in the following Related Art List, for instance. That is, the control valve is provided with a main valve in a main passage that communicates the discharge chamber with the crankcase and also a sub-valve in a sub-passage that communicates the crankcase with a suction chamber. And the main valve and the sub-valve are driven by a single solenoid. During a steady operation, this control valve regulates the opening degree of the main valve with the sub-valve closed. Thereby, the crank pressure Pc can be controlled and the discharging capacity can also be controlled as described above. On the other hand, at a power-on of the air conditioner, the sub-valve is open with the main valve closed. Thereby, the crank pressure Pc is quickly lowered. As a result, the compressor can relatively promptly shift its operation mode to a maximum-capacity operation. Also, a plurality of valves are opened and closed by the use of a single solenoid. Thus, the control valve can be of a reduced size as a whole.
In such a control valve as described above, the main valve and sub-valve are driven by the single solenoid. Thus, a main valve element and a sub-valve element are provided along the same axis line, and the control valve has a mechanism that transports the solenoidal force to the each valve element by way of an actuating rod provided along said axis line. The body of the control valve has a main valve hole, and the main valve element has a sub-valve hole. That is, the sub-passage runs through the main valve element. The main valve element touches and leaves a main valve seat, provided in an opening end of the main valve hole, so as to close and open the main valve, respectively. And the sub-valve element touches and leaves a sub-valve seat, provided in an opening end of the sub-valve hole, so as to close and open the sub-valve, respectively. However, the sub-valve is pressed against the sub-valve seat during a steady operation of the compressor and thereby the sub-valve is kept closed. At the startup of the compressor, the solenoidal force is at its maximum and the sub-valve element is further biased in a valve opening direction while the main valve element is seated on the main valve seat. This opens the sub-valve.

Related Art List

(1) Japanese Unexamined Patent Application Publication (Kokai) No. 2008-240580 .
In recent years, vehicle makers demand that the compressor be started more promptly. Providing more quick air condition performance is advantageous in pursuit of increased vehicle comfort and eventually achieves the sale promotions of such vehicles. In order to achieve this, the flow rate of refrigerant at the time the sub-valve is open needs to be made larger. Since, however, the aforementioned control valve is configured such that the sub-valve hole is formed in the main valve element, the size of the sub-valve is constrained by the size of the main valve and therefore it is not easy to obtain a desired flow rate thereof.
The present invention has been made in view of the foregoing problems, and a purpose thereof is to obtain a large flow rate of refrigerant, at the time the sub-valve is open, in a control valve where a main valve and a sub-valve are driven by a single solenoid.
In order to resolve the aforementioned problems, a control valve, for a variable displacement compressor, according to one embodiment of the present invention varies a discharging capacity of the compressor for compressing refrigerant led into a suction chamber and discharging the compressed refrigerant from a discharge chamber, by regulating a flow rate or pressure of at least one of the refrigerant led into a crankcase from the discharge chamber and the refrigerant led out to the suction chamber from the crankcase , and the control valve includes: a body having a main passage, which communicates between the discharge chamber and the crankcase, and a sub-passage, which communicates between the crankcase and the suction chamber; a main valve seat provided in the main passage; a main valve element for opening and closing a main valve by touching and leaving the main valve seat; a sub-valve seat provided in the sub-passage; a sub-valve element for opening and closing a sub-valve by touching and leaving the sub-valve seat; a pressure-sensing section for sensing a predetermined pressure-to-be-sensed and for generating a drive force exerted in an opening direction of the main valve in accordance with a magnitude of the pressure-to-be-sensed; and a solenoid for generating a drive force in a closing direction of the main valve in accordance with an amount of current supplied, wherein the control valve is configured such that the sub-valve remains closed when the main valve is controlled and such that the sub-valve is opened after the main valve is closed, and wherein a change in an area of opening of the sub-valve relative to an uplift amount of the sub-valve element from the sub-valve seat is larger than that of the main valve relative to an uplift amount of the main valve element from the main valve seat.
By employing this embodiment, the sub-valve has a larger inclination of the valve opening characteristics indicating the relation between the uplift amount and an area of valve opening. In other words, a large flow rate of refrigerant can be obtained at the time the sub-valve is open and therefore a starting property of the compressor can be improved. On the other hand, the area of opening of the main valve relative to the uplift amount of the main valve element can be relatively finely regulated and the valve opening characteristic of the main valve can be stably kept. Hence, the control of the discharging capacity of the compressor can be accurately maintained.
Embodiments will now be described by way of examples only, with reference to the accompanying drawings which are meant to be exemplary, not limiting, and wherein like elements are numbered alike in several Figures in which:

FIG.1: is a cross-sectional view showing a structure of a control valve according to a first embodiment;
FIG. 2: is a partially enlarged cross-sectional view of the upper half of FIG. 1;
FIG. 3: shows an operation of a control valve;
FIG. 4: shows an operation of a control valve;
FIG. 5: is a graph showing a valve opening characteristic of a control valve;
FIG. 6: is a cross-sectional view showing a structure of a control valve according to a second embodiment;
FIG. 7: is a partially enlarged cross-sectional view of the upper half of FIG. 6;
FIG. 8: is a partially enlarged cross-sectional view of the upper half of a control valve according to a third embodiment; and
FIG. 9: is a partially enlarged cross-sectional view of the upper half of a control valve according to a fourth embodiment.

The invention will now be described based on preferred embodiments which do not intend to limit the scope of the present invention but exemplify the invention. All of the features and the combinations thereof described in the embodiment are not necessarily essential to the invention.
The present invention will now be described in detail based on preferred embodiments with reference to the accompanying drawings. In the following description, for convenience of description, the positional relationship in each structure may be expressed as "vertical" or "up-down" with reference to how each structure is depicted in Figures.

[First Embodiment]

FIG. 1 is a cross-sectional view showing a structure of a control valve according to a first embodiment.
A control valve 1 is configured as an electromagnetic valve for controlling the discharging capacity of a not-shown variable displacement compressor (hereinafter referred to simply as "compressor") installed for a refrigeration cycle of an automotive air conditioner. This compressor discharges a high-temperature and high-pressure gaseous refrigerant produced by compressing a refrigerant flowing through the refrigeration cycle. The gaseous refrigerant is then condensed by a condenser (external heat exchanger) and further adiabatically expanded by an expander so as to become a misty, low-temperature and low-pressure refrigerant. This low-temperature and low-pressure refrigerant is evaporated by an evaporator, and the evaporative latent heat cools the air of an interior of a vehicle. The refrigerant evaporated by the evaporator is again brought back to the compressor and thus circulates through the refrigeration cycle. The compressor, which has a rotational shaft rotatingly driven by an engine of an automobile, is configured such that a piston for compression is linked to a wobble plate mounted to the rotational shaft. The compressor regulates a refrigerant discharge rate by changing the stroke of the piston through changes in the angle of the wobble plate. The control valve 1 changes the angle of the wobble plate and consequently changes the discharging capacity of the compressor by controlling a flow rate of the refrigerant to be introduced from a discharge chamber to a crankcase of the compressor.
The control valve 1 is cofigured as a so-called Ps sensing valve that controls the flow rate of refrigerant introduced from the discharge chamber to the crankcase so that a suction pressure Ps of the compressor can be maintained at a certain set pressure. Note here that the suction pressure Ps thereof corresponds to "pressure-to-be-sensed". The control valve 1 is configured by integrally assembling a valve unit 2 and a solenoid 3. The valve unit 2 includes a main valve for opening and closing a refrigerant passage used to lead a part of the discharged refrigerant to the crankcase, during an operation of the compressor, and a sub-valve that functions as a so-called bleed valve for releasing the refrigerant in the crankcase to a suction chamber, at a startup of the compressor. The solenoid 3 regulates the opening degree of the main valve by driving the main valve in a valve opening or closing direction, and controls the flow rate of refrigerant introduced into the crankcase. The valve unit 2 includes a body 5 of stepped cylindrical shape, a main valve and a sub-valve, which are provided inside the body 5, a power element 6, which generates a drive force against a solenoidal force to adjust the opening level of the main valve, and so forth. The power element 6 functions as a "pressure-sensing section".
The body 5 has ports 12, 14, 16, and 18 in this order from top down. Of these ports, the port 12 is provided in an upper-end opening of the body 5, and the ports 14, 16, and 18 are provided on a lateral side thereof. The ports 12 and 18 each functions as a "suction chamber communication port" that communicates with the suction chamber. The port 14 functions as a "discharge chamber communication port" that communicates with the discharge chamber. The port 16 functions as a "crankcase communication port" that communicates with the crankcase. An end member 13 is fixed to the upper-end opening of the body 5. A plurality of communicating grooves 15 used to form the port 12 are provided on the outer periphery of the end member 13. A lower end of the body 5 is coupled to an upper end of the solenoid 3.
A main passage, which communicates the port 14 with the port 16, and a sub-passage, which communicates the port 16 with the port 18 are formed inside the body 5. The main valve of small diameter is provided in the main passage, whereas the sub-valve of large diameter is provided in the sub-passage. The sub-valve is disposed coaxially with the main valve further downward from the main valve, namely, on a side closer to the solenoid 3 than the main valve. In other words, as shown in FIG. 1, the control valve 1 is configured such that the power element 6, the main valve, the sub-valve, and the solenoid 3 are arranged in this order starting from one end side of the body 5. A main valve hole 20 and a main valve seat 22 are provided in the main passage. A sub-valve hole 32 and a sub-valve seat 34 are provided in the sub-passage.
Through the port 12, a pressure chamber 23, partitioned in an upper portion of the body 5, and the suction chamber are communicated with each other. And the refrigerant at the suction pressure Ps is led into the pressure chamber 23 through the port 12. The power element 6 is disposed in the pressure chamber 23. Through the port 14, the refrigerant at a discharge pressure Pd is introduced from the discharge chamber. Through the port 16, the refrigerant at a crank pressure Pc having passed through the main valve is led out toward the crankcase during a steady operation of the compressor. Also, through the port 16, the refrigerant at the crank pressure Pc discharged from the crankcase is led in at a startup of the compressor. At this time, the thus led-in refrigerant is introduced to the sub-valve. Through the port 18, the refrigerant at the suction pressure Ps is led in during a steady operation of the compressor and, on the other hand, the refrigerant at the suction pressure Ps having passed through the sub-valve is led out toward the suction chamber at a startup of the compressor.
The main valve hole 20 and the sub-valve hole 32 are formed coaxially with each other, and a pressure chamber 24, which is disposed between the main valve hole 20 and the sub-valve hole 32, communicates with the port 16. A guiding passage 25 (functioning as a "first guiding passage") is provided between the port 14 and the pressure chamber 23. A guiding passage 26 (functioning as a "second guiding passage") is provided between the port 14 and the port 16. A guiding passage 27 (functioning as a "third guiding passage") is provided between the port 16 and the port 18. A sub-valve element 36 of stepped cylindrical shape is slidably inserted to these guiding passages. The guiding passage 26 is formed such that the size (diameter) thereof is slightly larger than that of the guiding passage 25. And the sub-valve element 36 is slidably supported by the guiding passages 25 and 27 at one end side of the sub-valve element 36 and at the other end thereof. That is, the sub-valve element 36 is supported by the body at two points. The sub-valve seat 34 is formed on an upper surface of the solenoid 3. The sub-valve element 36 closes and opens the sub-valve by touching and leaving the sub-valve seat 34, respectively.
The main valve hole 20 is provided in a reduced diameter portion in an upper portion of the sub-valve element 36, and the main valve seat 22 is formed in a lower end opening of the main valve hole 20. Also, an elongated actuating rod 38 is provided along an axis line of the body 5. An upper half of the actuating rod 38 is inserted to the sub-valve element 36, whereas a lower half thereof is inserted to the solenoid 3. An upper end of the actuating rod 38 is slidably supported by an upper end of the sub-valve element 36, and the actuating rod 38 and the power element 6 are connected at ends thereof such that the actuating rod 38 can be operatively coupled or linked to the power element 6. A lower end of the actuating rod 38 is connected to a plunger 50 (described later) of the solenoid 3. The diameter of a middle part of the actuating rod 38 is enlarged, thereby forming the main valve element 30. The main valve element 30 closes and opens the main valve by touching and leaving the main valve seat 22 in the pressure chamber 24, respectively. Thereby the main valve element 30 regulates the flow rate of refrigerant flowing from the discharge chamber to the crankcase. The actuating rod 38 directly transmits the solenoidal force to the main valve element 30 and the sub-valve element 36.
When the sub-valve element 36 is seated on the sub-valve seat 34 with the result that the sub-valve is closed, the communication state of the pressure chamber 24 and the port 18 is blocked and the relief of refrigerant from the crankcase to the suction chamber is blocked. Also, when the sub-valve is opened with the sub-valve element 36 spaced apart from the sub-valve seat 34, the pressure chamber 24 and the port 18 come to communicate with each other and the relief of refrigerant from the crankcase to the suction chamber is permitted. Communicating holes 35 and 37 that communicate the inside and the outside of the sub-valve element 36 are formed in a middle part of and an upper portion of the sub-valve element 36, respectively. The communicating hole 35 communicates between the port 14 and the main valve hole 20, whereas the communicating hole 37 communicates between the port 16 and the pressure chamber 24.
A spring 44 (functioning as a "biasing member") that biases the sub-valve element 36 in a closing direction of the sub-valve is set between the sub-valve element 36 and the body 5. The power element 6 includes a bellows 45 (functioning as a "pressure-sensing member") that develops a displacement by sensing the suction pressure Ps. And the power element 6 generates an opposing force to oppose the solenoidal force by the displacement of the bellows 45. This opposing force is also transmitted to the main valve element 30 by way of the actuating rod 38.
The solenoid 3 includes a stepped cylindrical core 46, a bottomed cylindrical sleeve 48, which is so assembled as to seal off a lower-end opening of the core 46, a cylindrical plunger 50, which is housed in the sleeve 48 and which is disposed in a position opposite to the core 46 in the direction of axis line, a cylindrical bobbin 52, which is inserted around the core 46 and the sleeve 48, an electromagnetic coil 54, wound around the bobbin 52, which generates a magnetic circuit when the solenoid 3 electrically conducts, a cylindrical casing 56, which is so provided as to cover the electromagnetic coil 54 from outside and which also functions as a yoke, and an end member 58, which is so provided as to seal off a lower-end opening of the casing 56. In the present embodiment, the body 5, the core 46, the casing 56 and the end member 58 form a body for the whole control valve 1. A spring 47 (functioning as a "biasing member") that biases the plunger 50 in a direction separating the plunger 50 away from the core 46 is set between the plunger 50 and the core 46.
The valve unit 2 and the solenoid 3 are secured such that a lower end of the body 5 is press-fitted to an upper-end opening of the core 46. The pressure chamber 24 is formed between the core 46 and the sub-valve element 36. The actuating rod 38 is inserted to the core 46 such that the actuating rod 38 penetrates a center of the core 46 in the direction of axis line. The lower end of the actuating rod 38 is press-fitted to an upper half of the plunger 50, and the actuating rod 38 and the plunger 50 are coaxially connected to each other.
The actuating rod 38 is supported by the plunger 50 from below and is configured such that actuating rod 38 can be operatively coupled or linked to the main valve element 30, the sub-valve element 36 and the power element 6. The actuating rod 38 appropriately transmits the solenoidal force, which is a suction force generated between the core 46 and the plunger 50, to the main valve element 30 or the sub-valve element 36. At the same time, a drive force, which is generated by an expansion/contraction movement of the power element 6, is so exerted on the actuating rod 38 as to oppose the solenoidal force. Hereinafter, this drive force to oppose the solenoidal force will be referred to as "pressure-sensing drive force" also. In other words, when the main valve is under control, the force adjusted by the solenoidal force and the pressure-sending drive force acts on the main valve element 30 and appropriately controls the opening degree of the main valve. While the main valve is being closed, the actuating rod 38 is displaced relative to the body 5 in accordance with the magnitude of the solenoidal force, pushes up the sub-valve element 36 and thereby opens the sub-valve. Thereby, a bleed function is achieved.
A ring-shaped shaft support member 60 is press-fitted on an upper end of the core 46, and the actuating rod 38 is slidably supported by the shaft support member 60 in the direction of axis line. A communicating groove in parallel with the direction of axis line is formed in a predetermined position of the outer periphery of the shaft support member 60. The crank pressure Pc of the pressure chamber 24 passes through the communicating groove and a communicating path 62, which is formed by the spacing between the actuating rod 38 and the core 46, and is then led into the sleeve 48 as well.
The communicating path 62 functions as a orifice by which the interior of the sleeve 48 functions as an oil damper chamber. In other words, in the present embodiment, the same type of oil as that contained in the refrigerant for lubrication of the compressor is introduced, in advance, into the sleeve 48 as part of a manufacturing process of the control valve 1. In the present embodiment, the communicating groove provided in the shaft support member 60 functions as a throttle passage, which gives resistance to the flow of oil into and out of the sleeve 48. Such a structure as this enables the sleeve 48 to function as the oil damper chamber and enables the micro-vibration and the like of the plunger 50 placed in the sleeve 48 to be suppressed. As a result, the occurrence of noise caused by such micro-vibration is prevented or suppressed. In a modification to the present embodiment, the arrangement may be such that the communicating path 62 functions as the throttle passage, which gives resistance to the flow of oil into and out of the sleeve 48. In other words, it is preferable that at least one of the communicating groove provided in the shaft support member 60 and the communicating path 62 functions as the throttle passage. Note that the spring 47 function as an off-spring that biases both the core 46 and the plunger 50 in a direction in which they get mutually separated apart from each other.
The sleeve 48 is made of a nonmagnetic material. A plurality of communicating grooves 66 are provided, in parallel with the axis line, on a side of the plunger 50. A plurality of communicating grooves 68, which extend radially and communicates the inside and the outside of the plunger 50, are provided at a lower end surface of the plunger 50. Such a structure as this enables the crank pressure Pc to be led to a back pressure chamber 70 through the spacing between the plunger 50 and the sleeve 48 even though the plunger 50 is positioned at a bottom dead point as shown in FIG. 1.
A pair of connection terminals 72 connected to the electromagnetic coil 54 extend from the bobbin 52 and are led outside by passing through the end member 58. Note that only one of the pair of connection terminals 72 is shown in FIG. 1 for convenience of explanation. The end member 58 is installed in such a manner as to seal the entire structure inside the solenoid 3 contained in the casing 56 from below. The end member 58 is molded (injection molding) of a corrosion-resistant resin, and the resin material is filled into gaps between the casing 56 and the electromagnetic coil 54 also. With the resin material filled into the gaps between the casing 56 and the electromagnetic coil 54, the heat release performance is improved because the heat generated by the electromagnetic coil 54 is easily conveyed to the casing 56. The ends of the connection terminals 72 are led out from the end member 58 and connected to a not-shown external power supply.
FIG. 2 is a partially enlarged cross-sectional view of the upper half of FIG. 1. The body 5 is constituted by integrally assembling a first body 81 and a second body 82. The first body 81 is of a stepped cylindrical shape such that the outside diameter thereof gets smaller in stages upwardly. Also, the first body 81 slidably supports a lower half of the sub-valve element 36 along the guiding passage 27 formed inside the first body 81. The second body 82, which is of a stepped cylindrical shape, is fixed such that a lower half thereof is inserted to an upper half of the first body 81. Since the body 5 is configured by coupling the first body 81 and second body 82 together as described above, the body 5 is configured such that the outside diameter thereof becomes smaller toward a power element 6 side from a solenoid 3 side. As a result, easiness to insert the body 5 into a mounting hole of the not-shown compressor is enhanced.
A communicating hole 83, which communicates the inside and outside of the second body 82, is provided in a lower lateral part of the second body 82. The port 14 is formed in an overlapped portion that is a region where the first body 81 and the second body 82 are overlapped with each other. The power element 6 is so provided as to be held inside the upper half of the second body 82. The inside diameter of the lower half of the second body 82 is slightly reduced and thereby the guiding passages 25 and 26 are formed. An O-ring 28 for sealing (functioning as a "sealing member") is provided in a sliding surface of the guiding passage 26. The O-ring 28 prevents the high-pressure refrigerant introduced through the port 14 from leaking into the port 16 by passing through a gap between the sub-valve element 36 and the guiding passage 26.
An upper surface 90 of the main valve element 30 functions not only as a "attaching/detaching portion" that closes and opens the main valve by touching and leaving the main valve seat 22, respectively, but also as an "engagement portion" that presses the sub-valve element 36 upward (in an opening direction of the sub-valve) with the main valve element 30 being seated on the main valve seat 22. On the other hand, an upper surface 92 of the middle part of the sub-valve element 36 functions as a "stopper" that restricts an upward movement of the sub-valve element 36 when the upper surface 92 thereof is stopped by an underside of the second body 82. An upper end portion 94 of the actuating rod 38 is slidably inserted to an upper end of the sub-valve element 36, and the upper end portion 94 thereof also functions as a partition wall that isolates the pressure chamber 23 from other pressure chambers.
By employing such a structure like this, the actuating rod 38 is pushed down by the biasing force of the spring 47 (see FIG. 1) while the solenoid 3 is not electrically conducting. As a result, as shown in FIG. 2, the main valve element 30 is spaced apart from the main valve seat 22, and the main valve is fully opened. Although the sub-valve element 36 maintains a closed state of the sub-valve by the biasing force of the spring 44, the displacement of the sub-valve element 36 in the downward direction is restricted when the sub-valve element 36 is seated on the sub-valve seat 34. In the present embodiment, the shape and the size of the sub-valve element 36 are set such that the upper surface 92 thereof is spaced apart from the underside of the second body 82 at a predetermined interval L1, while the sub-valve is in a closed state.
The power element 6 is so structured that an upper end opening of the bellows 45 is closed by a first stopper 84 ("base member") and an lower end opening thereof is closed by a second stopper 86 ("base member"). The first stopper 84 is of a stepped cylindrical shape, and extends in the direction of axis line inside the bellows 45. The second stopper 86 is of a disk shape, and a central part of the upper surface of the second stopper 86 is disposed counter to a lower end surface of the first stopper 84. The interior of the bellows 45 is an airtight reference pressure chamber S, and a spring 88 is interposed between the first stopper 84 and the second stopper 86 in such a manner as to bias the bellows 45 in an expanding direction. The reference pressure chamber S is in a vacuum state according to the present embodiment. The first stopper 84 is formed integrally with the end member 13. Thus, the first stopper 84 is fixed relative to the body 5. The bellows 45 expands or contracts in the direction of axis line (opening/closing direction of the main valve) according to a pressure difference between the suction pressure Ps of the pressure chamber 23 and the reference pressure of the reference pressure chamber S. However, if the pressure difference becomes large, the end surfaces of the first stopper 84 and the second stopper 86 will abut against each other and will be stopped thereby as a result of a predetermined contraction of the bellows 45, thus restricting the contraction.
In the above-described structure, the main valve element 30 and the main valve seat 22 constitute a main valve, and the opening degree of the main valve regulates the flow rate of refrigerant flowing from the discharge chamber to the crankcase. Also, the sub-valve element 36 and the sub-valve seat 34 constitute a sub-valve, and the opening/closing of the sub-valve permits or shuts off the delivery of refrigerant from the crankcase to the suction chamber. In other words, the control valve 1 functions as a three-way valve, too, by opening either the main valve or the sub-valve.
According to the present embodiment, an effective pressure-receiving diameter A (seal section diameter) of the sub-valve element 36 in the sub-valve and an effective pressure-receiving diameter B (seal section diameter) of the sliding portion of the sub-valve element 36 relative to the guiding passage 27 are set equal to each other. Thus, most of the effect of the crank pressure Pc acting on the sub-valve element 36 is cancelled. Also, an effective pressure-receiving diameter C (seal section diameter) of the sliding portion of the sub-valve element 36 relative to the guiding passage 25 and an effective pressure-receiving diameter D (seal section diameter) of the sliding portion of the sub-valve element 36 relative to the guiding passage 26 are set equal to each other. Thus, the effect of the discharge pressure Pd acting on the sub-valve element 36 is cancelled.
That is, the effects of the crank pressure Pc and the suction pressure Ps are canceled as to a portion of the sub-valve element 36 where a large portion thereof has been formed to occupy. Also, a pressure difference (Pc - Ps) between the crank pressure Pc and the suction pressure Ps acts on a smaller-diameter part, which is the upper half of the sub-valve element 36. However, this pressure difference is relatively small and therefore the force by this pressure difference will not be larger than the biasing force by the spring 44 in a closing direction of the sub-valve. Thus, the closed state of the sub-valve can be stably kept when the compressor is under control, even though the sub-valve element 36 is configured in a relatively large size. Hence, at the startup of the compressor, the sub-valve can be quickly opened by starting the solenoid 3. In other words, since the effects of the crank pressure Pc and the suction pressure Ps are canceled as to the portion where the sub-valve element 36 is formed in a large size, the load that the sub-valve element 36 receives on account of the pressure difference (Pc - Ps) will not be large even though the size of this portion is changed.
Accordingly, the size of the sub-valve element 36 can be set freely. Also, an effective pressure-receiving diameter E (seal section diameter) of the main valve element 30 in the main valve and an effective pressure-receiving diameter F (seal section diameter) of the sliding portion of the main valve element 30 are set equal to each other. Thereby, the effect of the discharge pressure Pd acting on the main valve element 30 is canceled and the behavior of the main valve element 30, while the main valve is being controlled, can be stably maintained. In a modification, the sub-valve element 36 may be configured such that the outside diameter of a lower end opening thereof is made small, for instance, and the sub-valve element 36 is constructed in a stepped form. And an effective pressure-receiving area by a difference (D - E) between the effective pressure-receiving diameter D and the pressure-receiving diameter E may be set equal to an effective pressure-receiving area by a difference (B - A) between the effective pressure-receiving diameter B and the pressure-receiving diameter A. Thereby, the effect on account of the pressure difference (Pc - Ps) acting on the sub-valve element 36 may be canceled. Alternatively, an effective pressure-receiving area by the effective pressure-receiving diameter C (i.e., an area of a solid portion, including its effective pressure-receiving area, by the effective pressure-receiving diameter F) may be set equal to the effective pressure-receiving area by the difference (B - A) between the effective pressure-receiving diameter B and the pressure-receiving diameter A. Thereby, the effect of the suction pressure Ps working when the main valve element 30 and the sub-valve element 36 become integrated with each other may be canceled.
In such a structure as described above, the main valve operates autonomously so that, in a stable controlled state of the control valve 1, the suction pressure Ps of the pressure chamber 23 becomes a predetermined set pressure Pset. The set pressure Pset is basically adjusted beforehand by the spring loads of the springs 44, 47 and 88 and the load of the bellows 45, and is set as a pressure value at which the freezing of the evaporator can be prevented in view of the relationship between the temperature inside the evaporator and the suction pressure Ps. The set pressure Pset can be changed by varying the supply current (set current) to the solenoid 3. In the present embodiment, the load setting of the springs can be fine-adjusted by readjusting a press-fitting amount of the end member 13 when the assembly of the control valve 1 is nearly completed. By employing this method, the set pressure Pset can be adjusted with accuracy.
When, at the startup of the control valve 1, the solenoid 3 electrically conducts and thereby the actuating rod 38 is displaced relative to the sub-valve element 36, the main valve element 30 is seated on the main valve seat 22 so as to close the main valve. As a result, the valve-opening-direction drive force can be supplied to the sub-valve element 36 via the main valve element 30. This can lift the sub-valve element 36 from the sub-valve seat 34 so as to open the sub-valve. In other words, the control valve 1 has a "forcible valve-opening mechanism" or "valve-opening mechanism" used to forcibly open the sub-valve using the drive force of the solenoid 3. If the sub-valve element 36 is locked as a result of the entanglement of foreign material in the sliding portions of the sub-valve element 36 relative to the guiding passages 25, 26 and 27, this forcible valve-opening mechanism will function as a lock release mechanism (interlocking mechanism, pressing mechanism, etc.) as well.
Now, an operation of the control valve will be explained. FIG. 3 and FIG. 4 are each a diagram to explain an operation of the control valve, and FIG. 3 and FIG. 4 correspond to FIG. 2. FIG. 2, already described above, shows a state where the control valve operates with the minimum capacity. FIG. 3 shows a state where a bleed function is in effect. FIG. 4 shows a relatively stable controlled state. A description is given hereinbelow based on FIG. 1 with reference to FIG. 2 to FIG. 4, as appropriate.
While the solenoid 3 of the control valve 1 is not electrically conducting, namely while the automotive air conditioner is not operating, no suction power between the core 46 and the plunger 50 is in effect. At the same time, the suction pressure Ps is relatively high. Thus, as shown in FIG. 2, bellows 45 contracts and the power element 6 is substantially disabled. Also, the actuating rod 38 is pushed down by the biasing force of the spring 47, and the main valve element 30 is separated apart from the main valve seat 22 and therefore the main valve is fully opened. On the other hand, the state, where the sub-valve element 36 is seated on the sub-valve seat 34 by the biasing force of the spring 44, is kept and therefore the sub-valve remains closed.
On the other hand, when a control current is supplied to the electromagnetic coil 54 of the solenoid 3 at the startup or the like of the automotive air conditioner, the actuating rod 38 is driven in an upward direction by the solenoidal force as shown in FIG. 3 with the result that the main valve is closed and the sub-valve is opened. In other words, displacing the actuating rod 38 relative to the sub-valve element 36 has the main valve element 30 seated on the main valve seat 22 and then closes the main valve. Subsequently, further displacing the actuating rod 38 relative to the body 5, while the main valve element 30 is being seated on the main valve seat 22, has the sub-valve element 36 separated away from the sub-valve seat 34 and then opens the sub-valve. However, stopping the upper surface 92 of the sub-valve element 36 by the body 5 restricts an uplift amount of the sub-valve element 36 (i.e., the opening degree of the sub-valve). Note also that the suction pressure Ps is relatively high normally at the startup and thus the bellows 45 maintains its contracted state so as to maintain the state where the sub-valve is being open.
In other words, supplying the starting current to the solenoid 3 causes the main valve to be closed and thereby restricts the delivery of discharged refrigerant into the crankcase. At the same time, supplying the starting current thereto opens the sub-valve so as to promptly relieve the refrigerant in the crankcase into the suction chamber. This can promptly start the compressor. Even when the suction pressure Ps is low and the bellows 45 has been expanded, such as when a vehicle is exposed to a low-temperature environment, supplying a large current to the solenoid 3 enables the sub-valve to be opened and therefore the compressor can be promptly started.
Even if, at the start of the control valve 1 like this, the entry of foreign material into the sliding portion of the sub-valve element 36 has caused the sub-valve element 36 to be locked in a valve opening direction, the locking can be released by pressing the sub-valve element 36 with the solenoidal force. Also, if the entry of foreign material into the sliding portion of the sub-valve element 36 has caused the sub-valve element 36 to be locked in a valve closing direction, the locking can be released when the suction pressure Ps drops and the bellows 45 expands, with the startup of the control valve 1, and then the second stopper 86 abuts against an upper end surface of the sub-valve element 36 and presses the sub-valve element 36 downward.
Then, in the controlled state where the value of current supplied to the solenoid 3 is set to a predetermined value, the suction pressure Ps is relatively low as shown in FIG. 4. Thus, the bellows 45 expands and is operatively coupled to the actuating rod 38. Thereby, the main valve element 30 moves so as to regulate the opening degree of the main valve. At this time, the main valve element 30 stops at a valve-lift position. This valve-lift position is a position where three forces are all balanced thereamong. Here, the three forces are the force by the spring 47 in the valve opening direction, the solenoidal force by the solenoid 3 in the valve closing direction, and the opposing force, to oppose the solenoidal force, generated by the power element 6 operated according to the suction pressure Ps. Since the state, where the sub-valve element 36 is seated on the sub-valve seat 34 by the biasing force of the spring 44, is kept in the controlled state of the main valve, the closed state of the sub-valve is maintained.
As, for example, the refrigeration load becomes large and the suction pressure Ps becomes higher than the set pressure Pset, the bellows 45 contracts and therefore the main valve element 30 is displaced relatively upward (in the valve closing direction). As a result, the opening degree of the main valve becomes small and therefore the compressor operates in such a manner as to increase the discharging capacity. As a result, a change is made in a direction where the suction pressure Ps drops. Conversely, as the refrigeration load becomes small and then the suction pressure Ps becomes lower than the set pressure Pset, the bellows 45 expands. As a result, the biasing force by the power element 6 works in such a direction as to oppose the solenoidal force. As a result, the force toward the main valve element 30 in the valve closing direction is reduced and the opening degree of the main valve becomes large. Thus, the compressor operates in such a manner as to reduce the discharging capacity. As a result, the suction pressure Ps is kept at the set pressure Pset.
If the engine load gets larger during such a steady control operation and therefore a reduction in the load to the air conditioner is desired, the conduction state (on/off) of the solenoid 3 is switched from on to off in the control valve 1. This means that no suction power is in effect between the core 46 and the plunger 50. Thus the main valve element 30 gets separated away from the main valve seat 22 by the biasing force of the spring 47, and the main valve is fully opened. At this time, the sub-valve element 36 is seated on the sub-valve seat 34 and therefore the sub-valve is closed. The refrigerant, at the discharge pressure Pd, introduced into the port 16 from the discharge chamber of the compressor passes through the fully opened main valve and flows into the crankcase from the port 14. Thus, the crank pressure Pc rises and then the compressor performs the minimum capacity operation.
FIG. 5 is a graph showing a valve characteristic of the control valve. The horizontal axis in FIG. 5 indicates the displacement of the actuating rod 38, and the vertical axis indicates the valve opening degrees (area of opening) of the main valve and the sub-valve. The displacement of the actuating rod 38 corresponds to the uplift amount of the main valve element 30 from the main valve seat 22 and the uplift amount of the sub-valve element 36 from the sub-valve seat 34. A solid line in FIG. 5 indicates the main valve, and a dashed line indicates the sub-valve.
When, as shown in FIG. 2, the solenoid 3 is turned off and the actuating rod 38 is positioned at the bottom dead point, the uplift amount of the main valve element 30 becomes the maximum. When, as shown in FIG. 3, the solenoid 3 is switched on from off and the actuating rod 38 is positioned at a top dead point, the uplift amount of the sub-valve element 36 becomes the maximum. At an intermediate point of displacement of the actuating rod 38, there is a fully-closed point where both the uplift amount of the main valve element 30 and the uplift amount of the sub-valve element 36 are zero, that is, both the main valve and the sub-valve are simultaneously are closed. As the actuating rod 38 is displaced downward relative to the fully-closed point, the opening degree of the main valve becomes larger gradually while the sub-valve is being closed. Conversely, as the actuating rod 38 is displaced upward relative to the fully-closed point, the opening degree of the sub-valve becomes larger gradually while the main valve is being closed. The sub-valve starts to open simultaneously when the main valve is closed during the course when the actuating rod 38 is displaced upward. Also, the main valve starts to open simultaneously when the sub-valve is closed during the course when the actuating rod 38 is displaced downward.
Since the seal section diameter of the sub-valve element 36 in the sub-valve is considerably larger than that of the main valve element 30 in the main valve, the sub-valve has a larger inclination of the valve opening characteristics indicating the relation between the uplift amount of a valve element and the valve opening degree (area of opening), as compared with that of the main valve. That is, the area of opening of the sub-vale can be varied more greatly as compared to the uplift amount of the sub-valve element 36 (the displacement of the actuating rod 38) and therefore a large flow rate of refrigerant can be obtained at the time the sub-valve is open. As a result, a starting property of the compressor can be improved. In particular, the liquid refrigerant has to outflow from the crankcase, at the startup of the compressor, under conditions of a small pressure difference (Pc - Ps). Thus it is desired that the opening degree of the sub-valve be larger, and therefore the structure employed in the present embodiment is advantageous in this respect. At the same time, the area of opening of the main valve relative to the uplift amount of the main valve element 30 (the displacement of the actuating rod 38) can be relatively finely regulated. Thus, the valve opening characteristic of the main valve can be stably kept and the control of the discharging capacity of the compressor can be accurately maintained.
As described so far, in the present embodiment, the sub-valve seat 34 is not formed in the main valve element 30 but is formed as a part of the body 5. Accordingly, the sizes of the sub-valve hole 32 and the sub-valve element 36 can be set regardless of the size of the main valve element 30. In other words, the size of the sub-valve can be set regardless of the size of the main valve. In particular, the sub-valve element 36 is provided on a side closer to the solenoid 3, namely, on the side where the outside diameter of the body 5 is larger, so that the sub-valve element 36 can be sufficiently made large. In the present embodiment, as discussed above, the inclination of the valve opening characteristic of the sub-valve is set sufficiently larger than that of the main valve. Thus, a large flow rate of refrigerant is obtained when the sub-valve is opened, and therefore the bleed function can be enhanced. Since the main valve seat 22 is formed integrally with the sub-valve element 36, the number of components used can be reduced. Furthermore, the main valve seat 22 (seat forming section) and the sub-valve element 36 are formed integrally with each other. Thus, the sub-valve element 36, which is formed integrally with the main valve seat 22, moves to open the sub-valve simultaneously with the movement of said main valve seat 22 after the closing of the main valve. It is therefore no longer required to adjust separately the timing with which the main valve is closed and the timing with which the sub-valve is opened. This can reduce the time otherwise spent for selecting the particular parts required and the positions to be adjusted, thereby markedly improving the assemblability.

[Second Embodiment]

FIG. 6 is a cross-sectional view showing a structure of a control valve according to a second embodiment. A description is hereinbelow given centering around different features from the first embodiment. Note that the structural components in FIG. 6 closely similar to those of the first embodiment are given the identical reference numerals.
A control valve 201 is configured by integrally assembling a valve unit 202 and a solenoid 203. A body 205 is formed of a single member, and an adjustment member 213 is screwed in an upper-end opening of the body 205. The port 12 is open to a lateral side of the body 205 at an upper part thereof. A ring-shaped strainer 17 is provided around the port 14. The strainer 17 includes a filter that suppresses foreign materials or the like from entering into the interior of the body 205. An upper end of an actuating rod 238 extends to the interior of a power element 206. An upper end of a sub-valve element 236 is not exposed to the pressure chamber 23, and the discharge pressure Pd is received by the upper end thereof.
On the other hand, the solenoid 203 is provided with a core 246, a sleeve 248, a plunger 250, a bobbin 52, an electromagnetic coil 54, a casing 256, and an end member 58. In the second embodiment, the body 205, the casing 256 and the end member 58 form a body for the whole control valve 201. A lower end of the actuating rod 238 is inserted to an upper portion of the plunger 250. No spring is provided between the plunger 250 and the core 246. On the other hand, a spring 247 (functioning as a "biasing member") that biases force in a direction separating the plunger 250 away from the core 246 is set between the sub-valve element 236 and the actuating rod 238.
The valve unit 202 and the solenoid 203 are secured such that a lower end of the body 205 is press-fitted to an upper-end of the casing 256. A valve seat member 260 is fitted on an upper surface of the core 246, and an upper surface of the valve seat member 260 forms the sub-valve seat 34. The valve seat member 260, which is a nonmagnetic annular member, is formed of PTFE (polytetrafluoroethylene) in the second embodiment, and may be an elastic body such as rubber. The valve seat member 260 may be fitted or baked on the core 246.
FIG. 7 is a partially enlarged cross-sectional view of the upper half of FIG. 6.
The guiding passage 25 of the body 205 slidably supports an upper portion 262 of the actuating rod 238. A spring support member 240 is provided below the main valve element 30 in the actuating rod 238. A spring 247 is set between the sub-valve element 236 and the spring support member 240. The spring 247 biases the sub-valve element 236 in a valve opening direction. Although, in the second embodiment, the actuating rod 238 and the plunger 250 are not fixed as in the first embodiment, the actuating rod 238 is biased, by a reaction force of the spring 247, toward the plunger 250. Thus, the contact state where the actuating rod 238 and the plunger 250 abut against each other can be constantly maintained. In other words, a structure according to the second embodiment is such that the actuating rod 238 does not need to be press-fitted to the plunger 250.
The sub-valve element 236 is slidably inserted along the guiding passage 26 and the guiding passage 27. In other words, the sub-valve element 236 is supported by the body at two points. An O-ring 228 for sealing (functioning as a "sealing member") is provided in a surface of the sub-valve element 236 opposite to the guiding passage 26. The O-ring 228 prevents the refrigerant introduced through the port 14 from leaking into the port 16 by passing through a gap between the sub-valve element 236 and the guiding passage 26.
The power element 206 is configured by including a base member 284 and a bellows 245. The base member 284, which is constructed in a bottomed cylindrical shape by press-forming a metal, has a flange 286 that extends radially outward at a lower end opening thereof. The bellows 245 is configured such that an upper end of the bellows-like body thereof is closed and such that a lower end opening part thereof is hermetically welded to an upper surface of the flange 286. The bellows 245 expands and contracts with a body of the base member 284 as an axial center. The bellows 245 is supported, by the adjustment member 213, at an end thereof opposite to the flange 286. A spring 290 (functioning as a "biasing member") that biases the bellows 245 in a contraction direction is set between the flange 286 and the body 205.
In other words, the power element 206 is elastically supported in between the adjustment member 213 and the body 205. The set load of the power element 206 (i.e., the set load of the spring 88) can be adjusted by a screwing amount of the adjustment member 213 into the body 205. In a radially inward space of the bellows 245, a body of the base member 284 extends to a location near a bottom portion of the bellows 245, and an upper end (a bottom of the base member 284) of the body of the base member 284 is located near the bottom portion of the bellows 245. The upper end of the actuating rod 238 is inserted inside the body of the base member 284.
In the second embodiment, too, an effective pressure-receiving diameter E (seal section diameter) of the main valve element 30 in the main valve and an effective pressure-receiving diameter F (seal section diameter) of the sliding portion of the actuating rod 238 are set equal to each other. Thereby, the effect of the discharge pressure Pd acting on the main valve element 30 is cancelled and the control of the main valve is stabilized. On the other hand, an upper end of the sub-valve element 236 is open to the port 14. Thus, a pressure difference (Pd - Pc) between the discharge pressure Pd and the crank pressure Pc acts on the sub-valve element 236 in a closing direction of the sub-valve. The sub-valve element 236 is pressured against the sub-valve seat 34 by this pressure difference (Pd - Pc) when the main valve is being controlled, and therefore the closed state of the sub-valve is stably maintained. In other words, the main valve is controlled in a stabilized manner.
On the other hand, at the startup of the compressor, the pressure difference (Pd - Pc) is small. Thus, the sub-valve can be quickly opened by the drive force of the solenoid 203. Once the sub-valve element 236 starts to be lifted, the area of opening of the sub-valve becomes large quickly as described above, so that the bleed function can be effectively achieved. The control valve 201 according to the second embodiment can also achieve the same valve opening characteristic as shown in FIG. 5.
In the second embodiment, the control valve 201 is configured such that the nonmagnetic valve seat member 260 is provided for the core 246, which is formed of a magnetic material, and such that the sub-valve element 236 touches and leaves the valve seat member 260. This configuration has an improved sealing property of the sub-valve over that of the sub-valve used in the first embodiment. In other words, the refrigerant introduced through the port 14 may contain foreign material such as metallic powders. This is because the metallic powders, which have come off as a result of friction of a piston or the like in the compressor, are discharged together with the refrigerant. Such foreign material is more likely to be attracted to the surface of components, such as the core, which constitute the magnetic circuit. Accordingly, the foreign material may adhere to and stay on the valve seat in the configuration like the first embodiment where the valve seat (the sub-valve seat) is formed in the core itself. This may possibly deteriorate the sealing property of the valve section.
In this regard, in the second embodiment, the nonmagnetic valve seat member 260 is provided in the core 246, and the sub-valve seat 34 is formed in the valve seat member 260. Thus, this configuration according to the second embodiment can prevent or suppress the adherence of such foreign substances. As a result, the sealing property in between the sub-valve element 236 and the sub-valve seat 34 can be satisfactorily maintained. The valve seat member 260 may be constituted by an elastic or flexible member. In this case, even though a small amount of foreign substances adheres to the valve seat, the sagging or deflection of the valve seat member 260 occurs when the sub-valve element 236 is seated. Hence, the sealing property can be maintained.
That is, in the configuration like the second embodiment where a valve seat is provided in a magnetic member that constitutes the magnetic circuit of the solenoid, a "nonmagnetic part" is provided such that a nonmagnetic material is mounted to a part of said magnetic member and then the valve seat is formed in this nonmagnetic part. As a result, the same operation and advantageous effects as those described above, where the adherence of foreign substances can be prevented and the like, can be achieved. The "nonmagnetic part" may preferably be an elastic member or a flexible member. Note that an attaching/detaching portion that touches and leaves such the valve seat may be configured by using an elastic member or a flexible member. Such a technical idea underlying the present embodiment is applicable to not only the sub-valve but also the main valve. Also, this technical idea is applicable to a control valve having a single valve.

[Third Embodiment]

FIG. 8 is a partially enlarged cross-sectional view of the upper half of a control valve according to a third embodiment. The control valve according to the third embodiment differs from the second embodiment in a positional relationship between the sub-valve and the main valve. Thus, a description is hereinbelow given centering around different features from the second embodiment. Note that the structural components in FIG. 8 closely similar to those of the second embodiment are given the identical reference numerals.
A control valve 301 is configured by integrally assembling a valve unit 302 and a solenoid 303. An adjustment member 313 is screwed in an upper-end opening of a body 305. The port 12 is so provided as to run through the adjustment member 313. The port 16 is provided between the port 12 and the port 14. A guiding passage 327 (functioning as a "third guiding passage") is provided in an upper portion of the body 305. The guiding passage 26 is formed such that the size (diameter) thereof is slightly larger than that of the guiding passage 25.
A sub-valve element 336, which is of a stepped cylindrical shape, is inserted along the guiding passages 327, 25 and 26. That is, the sub-valve element 336 is supported by the body at two points. The sub-valve seat 34 is formed on an upper surface of a partition wall, which isolates the port 14 from the port 16, in the body 305. The sub-valve element 336 partitioned the body 305 at below the guiding passage 327 into a pressure chamber 325, which is located inside the sub-valve element 336, and a pressure chamber 326, which is located outside the sub-valve element 336. The pressure chamber 325 communicates with the port 12 via the pressure chamber 23, whereas the pressure chamber 326 communicates with the port 16. Communicating holes 337 and 35 that communicate the inside and the outside of the sub-valve element 336 are formed in a middle part of and an upper portion of the sub-valve element 336, respectively. The communicating hole 337 communicates between the sub-valve hole 32 and the pressure chamber 23.
The main valve hole 20 is formed in a lower part of the sub-valve element 336, and the main valve seat 22 is formed in a lower end opening of the main valve hole 20. A upper half of the actuating rod 338 penetrates the sub-valve element 336, and the actuating rod 338 is operatively coupled or linked to the power element 206. The O-ring 228 is provided in a surface of the sub-valve element 336 opposite to the guiding passage 26.
An intermediate pressure chamber 328 is formed between the body 305 and the solenoid 303. A lower end (i.e., the main valve seat 22) of the sub-valve element 336 is exposed to the intermediate pressure chamber 328. The main valve element 30 closes and opens the main valve by touching and leaving the main valve seat 22 from an intermediate pressure chamber 328 side. A communicating path 350 that communicates between the intermediate pressure chamber 328 and the pressure chamber 326 is formed in the body 305. In other words, the discharge pressure Pd of the refrigerant introduced through the port 14 is reduced to the crank pressure Pc by having passing through the main valve and is then temporarily introduced into the intermediate pressure chamber 328. Then, the refrigerant temporarily introduced into the intermediate pressure chamber 328 is led to the port 16 by way of the communicating path 350 and the pressure chamber 326.
Though not shown in FIG. 8, the spring 47 that biases force in a direction separating the plunger 250 away from the core 346 is set between the core 346 and the plunger 250 (see FIG. 1 and FIG. 6). The spring 290 is set between the power element 206 and the sub-valve element 336. In the third embodiment, the body 305, the casing 256 and the end member 58 form a body for the whole control valve 301.
Such a structure as described above maintains a closed state of the sub-valve, as shown in FIG. 8, by the biasing force of the spring 290, while the solenoid 303 is not electrically conducting. Since the actuating rod 338 is pushed downward by the spring 47 (see FIG. 1), the main valve element 30 is spaced apart from the main valve seat 22 and then the main valve is fully opened.
In a stable controlled state of the control valve 301, the main valve element 30 is pushed upward by the solenoidal force but is not engaged with the sub-valve element 336; thus, the sub valve will not be opened. The main valve element 30 operates autonomously so that the suction pressure Ps of the pressure chamber 23 becomes a predetermined set pressure Pset.
When, at the startup of the control valve 301, the solenoid 303 electrically conducts and thereby the actuating rod 338 is displaced relative to the sub-valve element 336, the main valve element 30 is seated on the main valve seat 22 so as to close the main valve. At this time, further displacing the actuating rod 338 relative to the body 305 with the main valve kept closed can lift the sub-valve element 336 from the sub-valve seat 34 so as to open the sub-valve. In other words, the control valve 301, too, has the "forcible valve-opening mechanism" or "valve-opening mechanism" used to forcibly open the sub-valve using the drive force of the solenoid 303. If the sub-valve element 336 is locked as a result of the entanglement of foreign material in the sliding portions of the sub-valve element 336 relative to the guiding passages 25, 26 and 327, this forcible valve-opening mechanism will function as a lock release mechanism (interlocking mechanism, pressing mechanism, etc.) as well. The control valve 301 can also achieve the same valve opening characteristic as shown in FIG. 5.

[Fourth Embodiment]

FIG. 9 is a partially enlarged cross-sectional view of the upper half of a control valve according to a fourth embodiment. The control valve according to the fourth embodiment differs from the second embodiment in a pressure-receiving structure of the main valve. Thus, a description is hereinbelow given centering around different features from the second embodiment. Note that the structural components in FIG. 9 closely similar to those of the second embodiment are given the identical reference numerals.
A control valve 401 is configured by integrally assembling a valve unit 402 and a solenoid 403. The strainer 17 is provided around the port 16 of a body 405. An upper end of a core 446 slightly protrudes inside the body 405, and a ring-shaped guide member 460 is press-fitted to an upper-end opening of the upper end thereof. A sub-valve element 436 closes and opens the sub-valve by touching and leaving the upper end surface of the core 446. A pressure chamber 462, which is surrounded by the guide member 460 and the shaft support member 60, is formed in the core 446. Also, a communicating hole 448, which communicates between the pressure chamber 462 and the port 18, is formed.
An actuating rod 438 is divided into a first rod 440 and a second rod 442. The first rod 440 is coupled to the power element 206, whereas the second rod 442 is coupled to the plunger 250 (see FIG. 6). A lower end of the first rod 440 is slidably supported by the guide member 460. An upper end of the second rod 442 is slidably supported by the shaft support member 60, and the tip thereof is formed in a semispherical shape. The second rod 442 is operatively coupled to the first rod 440 in a manner such that the second rod 442 is in a point-contact with an underside of the first rod 440. Since the suction pressure Ps is introduced to the pressure chamber 462, the interior of the sleeve 248 (see FIG. 6) is filled with the refrigerant at the suction pressure Ps and then the suction pressure Ps acts on the underside of the first rod 440. Both the main valve element 30 and the spring support member 240 are provided in the first rod 440.
In such a structure as described above, an effective pressure-receiving diameter E (seal section diameter) of the main valve element 30 in the main valve, an effective pressure-receiving diameter F (seal section diameter) of an upper sliding portion of the first rod 440 and an effective pressure-receiving diameter G (seal section diameter) of a lower sliding portion of the first rod 440 are all set equal to each other. Thereby, the effects of the discharge pressure Pd, the crank pressure Pc and the suction pressure Ps acting on the main valve element 30 are canceled. Also, the pressure difference (Pc - Ps) no longer acts on the main valve element 30 and therefore the behavior of the main valve element 30, while the main valve is being controlled, can be further stably maintained. In a modification, the first rod 440 and the second rod 442 may be formed integrally with each other.
The description of the present invention given above is based upon illustrative embodiments. These embodiments are intended to be illustrative only and it will be obvious to those skilled in the art that various modifications could be further developed within the technical idea underlying the present invention.
In each of the above-described embodiments, the so-called Ps sensing valve, which is enabled upon sensing the suction pressure Ps as the pressure-to-be-sensed, is described as a control valve. Instead, the control valve may be configured as a so-called Pc sensing valve, which is enabled upon sensing the crank pressure Pc. In such a case, the structure is such that the port 12 communicates with the crankcase.
In the above-described embodiments, the description has been given of examples where the bellows 45 or 245 is used for a pressure-sensing member that constitutes the power element 6 or 206. A diaphragm may be used, instead of the bellows. In such a case, the structure may be such that a plurality of diaphragms are coupled in the direction of axis line in order to ensure a necessary running stroke required for the pressure-sensing member.
In each of the above-described embodiments, a description has been given of an example where a single port 16 is provided as the "crankcase communication port" (lead-in/out port) that communicates with the crankcase. In a modification, the crankcase communication port may be structured that it is divided into a first port (lead-out port), which is used to lead out the refrigerant, having passed through the main valve, to the crankcase, and a second port (lead-in port), which is used to introduce the refrigerant of the crankcase.
In the above-described embodiments, the description has been given of examples where a spring (coil spring) is used as the biasing member regarding the springs 44, 47, 247, 290 and the like. It goes without saying that an elastic material, such as rubber or resin, or an elastic mechanism, such as a plate spring, may be used instead.
In the above-described embodiments, a description has been given of a control valve of inflow type where the flow rate or pressure of refrigerant introduced into the crankcase from the discharge chamber of the variable displacement compressor is regulated. In a modification, it may be configured as a control valve of outflow type where the flow rate or pressure of refrigerant introduced into the suction chamber from the crankcase is regulated. In the case where a control valve of outflow type is used, it is conceivable, in any of the first to fourth embodiments, for example, that the solenoidal force may be regulated such that an opened region of the sub-valve is used as a region to be controlled (hereinafter referred to as "controlled region" also). In other words, since a control valve of inflow type is used in each of the above-described embodiments, a left side to the fully-closed point of FIG. 5, namely the opened region of the main valve, is used as the controlled region. Where the control valve of outflow type is used, a right side to the fully-closed point of FIG. 5, namely the opened region of the sub-valve, is used as the controlled region. Also, the fully-closed point of FIG. 5 may be moved toward the bottom dead point by adjusting the length of the actuating rod, the length of the plunger or the position of the main valve element in the actuating rod; thereby a control range of the sub-valve element relative to the displacement of the actuating rod may be enlarged. This may achieve the control valve of outflow type where the opened region of the sub-valve is used as the controlled region. Also, the structure according to each of the above-described embodiments is applicable to a composite valve, such as a three-way valve under other modes, as long as a main valve and a sub-valve are provided in a common body and it is driven by a single solenoid.
In each of the above-described embodiments, a description has been given of the case where the reference pressure chamber S inside the bellows 45 or 245 is in a vacuum state. Instead, the reference pressure chamber S may be filled with air or filled with a predetermined gas serving as a reference. Or alternatively, it may be so filled as to have any one of the discharge pressure Pd, the crank pressure PC, and the suction pressure Ps. In such a case, the power element 6 or 206 may be configured such that it is activated by sensing, as appropriate, the pressure difference between the interior and exterior of the bellows.
The present invention is not limited to the above-described embodiments and modifications only, and those components may be further modified to arrive at various other embodiments without departing from the scope of the invention. Also, various other embodiments may be further formed by combining, as appropriate, a plurality of structural components disclosed in the above-described embodiments and modification. Also, one or some of all of the components exemplified in the above-described embodiments and modifications may be left unused or removed.

Claims

A control valve (1, 201, 301, 401) for a variable displacement compressor for varying a discharging capacity of the compressor for compressing refrigerant led into a suction chamber and discharging the compressed refrigerant from a discharge chamber, by regulating a flow rate of the refrigerant led into a crankcase from the discharge chamber, the control valve (1, 201, 301, 401) comprising:
a body (5, 205, 305, 405) having a main passage, which communicates between the discharge chamber and the crankcase, and a sub-passage, which communicates between the crankcase and the suction chamber;

a main valve seat (22) provided in the main passage;

a main valve element (30) configured to open and close a main valve by touching and leaving the main valve seat (22);

a sub-valve seat (34) provided in the sub-passage;

a sub-valve element (36, 236, 336, 436) configured to open and close a sub-valve by touching and leaving the sub-valve seat (34);

a pressure-sensing section (6, 206) configured to sense a predetermined pressure-to-be-sensed (Ps) and configured to generate a drive force exerted in an opening direction of the main valve in accordance with a magnitude of the pressure-to-be-sensed (Ps); and

a solenoid (3, 203, 303, 403) configured to generate a drive force in a closing direction of the main valve in accordance with an amount of current supplied,

wherein the control valve is configured such that the sub-valve remains closed when the main valve is controlled and such that the sub-valve is opened after the main valve is closed, and

wherein a change in an area of opening of the sub-valve relative to an uplift amount of the sub-valve element (36, 236, 336, 436) from the sub-valve seat (34) is larger than that of the main valve relative to an uplift amount of the main valve element (30) from the main valve seat (22).
A control valve (1, 201, 301, 401), for a variable displacement compressor, according to claim 1, wherein the sub-valve is opened at the same time as the main valve seat (22) moves after the main valve has been closed.
A control valve (1, 201, 301, 401), for a variable displacement compressor, according to claim 2, further comprising an actuating rod (38, 238, 338, 438) disposed between the pressure-sensing section (6, 206) and the solenoid (3, 203, 303, 403),
wherein the actuating rod (38, 238, 338, 438) is inserted to the sub-valve element (36, 236, 336, 436) and is formed integrally with the main valve element (30),
wherein the main valve seat (22) is formed integrally with the sub-valve element (36, 236, 336, 436), and
wherein when, in a controlled state of the main valve, the actuating rod (38, 238, 338, 438) is displaced relative to the sub-valve element (36, 236, 336, 436), the uplift amount of the main valve element (30) changes while the sub-valve remains closed, and
wherein the actuating rod (38, 238, 338, 438) and the sub-valve element (36, 236, 336, 436) become integrated with each other at the same time as the main valve is closed, and the uplift amount of the sub-valve element (36, 236, 336, 436) changes while the main valve remains closed.
A control valve (201, 401), for a variable displacement compressor, according to any one of claim 1 to claim 3, wherein the control valve (201, 401) is configured such that at least one of a first pressure difference and a second pressure difference operates on the sub-valve element (236, 436) in a closing direction of the sub-valve, where the first pressure difference is a pressure difference between a pressure (Pd) of the discharge chamber and a pressure (Pc) of the crankcase, and the second pressure difference is a pressure difference between the pressure (Pd) of the discharge chamber and a pressure (Ps) of the suction chamber.