Control valve for variable displacement compressors

Information

  • Patent Grant
  • 6354811
  • Patent Number
    6,354,811
  • Date Filed
    Thursday, November 9, 2000
    24 years ago
  • Date Issued
    Tuesday, March 12, 2002
    22 years ago
Abstract
A control valve controls the displacement of a variable displacement type compressor. The compressor includes a crank chamber, suction chamber, a bleed passage, and a supply passage. The control valve has a supply side valve, a transmission rod, and a relief side valve. The transmission rod connects the relief side valve with the supply side valve. The relief side valve includes a passage chamber constituting part of the bleed passage. The passage chamber is separated into a first area, which is connected to the crank chamber, and a lower area, which is connected to the suction chamber. A pressure sensing member moves the relief side valve body in accordance with the pressure in the upper area. The effective pressure receiving area of the sensing member is substantially equal to the cross sectional area of the passage chamber that is sealed by the relief side valve body.
Description




BACKGROUND OF THE INVENTION




The present invention relates to a control valve for a variable displacement type compressor, and, more particularly, to a control valve for a variable displacement type compressor, which adjusts the displacement of the compressor in accordance with the pressure in a crank chamber.




Generally speaking, in a variable displacement type swash plate compressor for use in a vehicle air-conditioning system, the inclination angle of a swash plate, which is located in a crank chamber, is changed in accordance with the pressure in the crank chamber (crank pressure Pc). The crank chamber is connected to a suction chamber via a bleed passage. In the bleed passage is a displacement control valve, which performs feedback control of the displacement to keep the pressure in the vicinity of the outlet of an evaporator (suction pressure Ps), or the pressure of the refrigerant gas that is drawn in by the compressor (suction pressure Ps), at a target suction pressure even when the thermal load varies.




For example, Japanese Unexamined Patent Publication (KOKAI) No. Hei 6-26454 discloses a relief side control valve of a variable target suction pressure type compressor. The bleed passage connects the crank chamber of the compressor to a suction pressure area. Defined in the valve housing of the control valve is a valve chamber, which constitutes part of the bleed passage. Located in the valve chamber are a valve body and a bellows, which actuates the valve body in accordance with the suction pressure Ps. The degree of opening of the valve is adjusted in accordance with the expansion and constraction of the bellows. The control valve has a transmission rod and an electromagnetic actuator connected to the bellows via the valve body. The force of the electromagnetic actuator varies in accordance with the electric current supplied to the actuator. A target suction pressure Pset varies by controlling the magnitude of the electric urging force applied by the actuator.





FIG. 7

is a graph showing the relationship, which is simulated by a computer, between the suction pressure Ps and the crank pressure Pc when the displacement of the compressor is controlled by the aforementioned relief side control valve. Seven characteristic curves φ


1


to φ


7


indicate the characteristics of seven types of control valves, the conditions of which differ only in the aperture size of the valve hole. The characteristic curve φ


1


corresponds to the control valve that has the smallest aperture size, and the characteristic curve φ


7


corresponds to the control valve that has the largest aperture size. The aperture size increases as the number following φ increases. Each characteristic curve has a right portion rightward that extends from lower left to upper right. The asymptotic line of each curve is the diagonal line α of the graph (linear line of Pc=Ps). Each curve has left portion that extends from upper left to lower right and is continuous with the right portion, and a critical point (minimum point) occurs between the two portions of each curve.




The Pc/Ps gain is one index to evaluate the response characteristics of a control valve for a compressor. The Pc/Ps gain is scalar defined as the absolute value of the ratio of the amount of change ΔPc in the crank pressure Pc, which is a control output value, to the amount of change ΔPs in the suction pressure Ps, which is a control input value. In

FIG. 7

, the differential (dPc/dPs) of the left portion of each of the characteristic curves φ


1





7


, or the inclination of the associated tangential line, is equivalent to the Pc/Ps gain (ΔPc/ΔPs).




In general, the greater the gain is, the better the response characteristic of the control valve is. Therefore, a compressor that incorporates such a control valve can quickly and precisely respond to a change in the thermal load. The control valve that has a high gain causes the actual suction pressure Ps to quickly converge to near the target suction pressure Pset. The fluctuation of the actual suction pressure Ps is extremely small. In a control valve that has a small gain, by way of contrast, the actual suction pressure Ps does not converge to the target suction pressure Pset and significantly fluctuates up and down, which is commonly called hunting. Specifically, even if the actual suction pressure Ps is falling due to a decrease in the thermal load, for example, an increase in the crank pressure Pc is slow when the Pc/Ps gain is small. Therefore, the displacement does not fall rapidly, and the large-displacement continues. As a result, the actual suction pressure Ps continues falling and overshoots the target suction pressure Pset. The same is true of the case where the suction pressure Ps is increasing due to an increase in the thermal load. With a small Pc/Ps gain, hunting of the suction pressure Ps occurs, particularly when the rotational speed of the swash plate is relatively slow.




To increase the Pc/Ps gain, a difference ΔQ of the flow rate of the gas that passes through the valve hole should be increased at the time the valve body moves in response to a change ΔPs in the suction pressure Ps. That is, the flow rate of the gas should be increased at once when the valve body is moved away from the valve seat. There are two ways to accomplish it as follows.




First, the amount of the displacement of the valve body with respect to a change ΔPs in the suction pressure Ps may be increased. In other words, a bellows that produces a large displacement in response to a slight change in the suction pressure Ps can be used. The large displacement of the valve body increases the difference ΔQ of the flow rate of the gas. However, such a bellows is generally large. Further, the displacement control valve of a variable target suction pressure type compressor requires that the electromagnetic actuator be enlarged in accordance with an increase in the size of the bellows. This leads to a cost increase.




The second way is to enlarge the area of the aperture of the valve hole (the area to be sealed by the valve body). When the area of the aperture of the valve hole is large, the amount of gas that passes through the valve hole changes significantly even if the displacement of the valve body is slight with respect to a change ΔPs in the suction pressure Ps.




The larger the aperture of the valve hole is, however, the smaller the inclination of the left portion of the characteristic curve becomes as shown in FIG.


7


. In other words, the Pc/Ps gain becomes smaller when the aperture increases. When the aperture of the valve hole is very small (e.g., as in the case φ


1


), the characteristic curve has a steep left portion but the radius of the curve increases gentle in the vicinity of the minimum point, making the Pc/Ps gain smaller. To keep a stable and large Pc/Ps gain over a wide range, it is essential to select the characteristic curve φ


3


or φ


4


of the control valve.




The Pc/Ps gain is influenced by the force that act on the valve body, which is based on the differential pressure between the crank pressure Pc and suction pressure Ps. This force is expressed by (Pc−Ps)×S where S is the aperture area of the valve hole (i.e., S is the effective pressure receiving area of the valve body). The direction of the force is the direction in which the valve body is separated from the valve seat. The larger the aperture area S of the valve hole becomes, the more difficult it becomes for the valve body to be seated due to the force of the differential pressure. When the aperture area of the valve hole is large, therefore, the differential pressure (Pc−Ps) makes it hard for the control valve to be closed. This results in a slow increase in the crank pressure Pc so that the Pc/Ps gain drops.




SUMMARY OF THE INVENTION




Accordingly, it is an object of the present invention to provide a control valve for a variable displacement type compressor that can quickly change the crank pressure Pc.




To achieve the above object, the present invention provides a control valve. A control valve controls the displacement of a variable displacement type compressor. The compressor includes a crank chamber, a suction pressure zone, the pressure of which is suction pressure, a discharge pressure zone, the pressure of which is discharge pressure. A bleed passage releases gas from the crank chamber to the suction pressure zone. A supply passage supplies gas from the discharge pressure zone to the crank chamber. The control valve comprises a valve housing. A supply side valve controls the opening degree of the supply passage. A transmission rod extends in the valve housing. The transmission rod moves axially and has a distal end portion and a proximal end portion. A relief side valve control the opening degree of the bleed passage. The transmission rod connects the relief side valve with the supply valve. The relief side valve includes a passage chamber constituting part of the bleed passage. A valve seat defines part of the passage chamber. A relief side valve body contacts the valve seat. The relief side valve body is located in the passage chamber. When the relief side valve body contacts the valve seat, the passage chamber is separated into a first area, which is connected to the crank chamber via an upstream part of the bleed passage, and a second area, which is connected to the suction pressure zone via a downstream part of the bleed passage. A pressure sensing member is located in the first area and moving the relief side valve body in accordance with the pressure in the first area. When the relief side valve body contacts the valve seat, the effective pressure receiving area of the pressure sensing member is substantially equal to the cross sectional area of the passage chamber that is sealed by the relief side valve body.




Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.











BRIEF DESCRIPTION OF THE DRAWINGS




The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:





FIG. 1

is a cross-sectional view of a variable displacement type swash plate compressor according to a first embodiment of this invention;





FIG. 2

is a cross-sectional view of a displacement control valve of the compressor in

FIG. 1

;





FIG. 3

is a partly enlarged cross-sectional view of a portion around the relief side valve portion of the control valve in

FIG. 2

;





FIG. 4

is an enlarged cross-sectional view showing the relief side valve portion and supply side valve portion of the control valve in

FIG. 2

;





FIG. 5

is a force diagram including the dimensions of the main portions of the control valve along side of a diagram of the valve of

FIG. 4

;





FIG. 6

is a force diagram like

FIG. 5

according to a second embodiment; and





FIG. 7

is a graph illustrating the relationship between the crank pressure and the suction pressure for various valves.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS




With reference to

FIGS. 1 through 5

, a description will be given of a first embodiment of the present invention as embodied in a displacement control valve for a clutchless variable displacement type swash plate compressor.




As shown in

FIG. 1

, this swash plate compressor includes a cylinder block


1


, a front housing


2


connected to the front end of the cylinder block


1


, and a rear housing


4


connected via a valve plate


3


to the rear end of the cylinder block


1


. The cylinder block


1


, front housing


2


, valve plate


3


and rear housing


4


are securely connected together by a plurality of bolts (not shown) to form a housing assembly. In

FIG. 1

, the left-hand side is the front side of the compressor and the right-hand side is the rear side.




A crank chamber


5


is defined in the area surrounded by the cylinder block


1


and the front housing


2


. A drive shaft


6


is located in the crank chamber


5


and is supported on a plurality of radial bearings


6




a


and


6




b


, which are provided in the housing assembly. Located in a accommodation chamber formed nearly in the center of the cylinder block


1


are a coil spring


7


and a rear thrust bearing


8


. A rotary support


11


is fixed to the drive shaft


6


to rotate together with the drive shaft


6


. A front thrust bearing


9


is located between the rotary support


11


and the inner wall of the front housing


2


. The drive shaft


6


is supported in the thrust direction by both the rear thrust bearing


8


, which is urged forward by the coil spring


7


, and the front thrust bearing


9


.




A pulley


32


is supported on the front end portion of the front housing


2


by a bearing


31


. The pulley


32


is secured to the front end of the drive shaft


6


by a bolt


33


. The pulley


32


is connected to an engine E or an external drive source via a power transmission belt


34


. While the engine E is running, the pulley


32


and the drive shaft


6


are rotated together.




A swash plate


12


is accommodated in the crank chamber


5


. The drive shaft


6


is inserted in a hole that is bored through the center of the swash plate


12


. The swash plate


12


is egaged with the rotary support


11


and the drive shaft


6


by a hinge mechanism


13


. The hinge mechanism


13


includes support arms


14


, each of which has a guide hole and protrude from the rear face of the rotary support


11


, and guide pins


15


, each of which has a spherical head and protrude from the front face of the swash plate


12


. The linkage of the support arms


14


and the guide pins


15


causes the swash plate


12


to rotate synchronously with the rotary support


11


and the drive shaft


6


. The swash plate


12


slides along the drive shaft


6


and inclines with respect to the drive shaft


6


.




An inclination-angle reducing spring


16


(preferably a coil spring coiled around the drive shaft


6


) is located between the rotary support


11


and the swash plate


12


. The inclination-angle reducing spring


16


urges the swash plate


12


toward the cylinder block


1


(i.e., in a direction reducing the inclination angle of the swash plate


12


). A restriction ring (preferably a circlip)


17


is attached to the drive shaft


6


behind the swash plate


12


. The restriction ring


17


restricts the backward movement of the swash plate


12


. The restriction ring


17


determines a minimum inclination angle θmin (e.g., 3 to 5°) of the swash plate


12


. A maximum inclination angle θmax of the swash plate


12


is determined by a counter weight portion


12




a


of the swash plate


12


, which abuts against a restriction portion


11




a


of the rotary support


11


.




A plurality of cylinder bores


1




a


(only one shown) are formed in the cylinder block


1


at equal intervals around the axial center of the drive shaft


6


. A single-head piston


18


is retained in each cylinder bore


1




a


. The front end of each piston


18


is connected to the peripheral portion of the swash plate


12


by a pair of shoes


19


. Between the valve plate


3


and the rear housing


4


are a suction chamber


21


and a discharge chamber


22


, which surrounds the suction chamber


21


, as shown in FIG.


1


. The valve plate


3


is provided with a suction port


23


, a suction valve


24


for opening and closing the suction port


23


, a discharge port


25


and a discharge valve


26


for opening and closing the discharge port


25


in association with each cylinder bore


1




a


. The suction chamber


21


is connected to the individual cylinder bores


1




a


by the suction ports


23


, and the discharge chamber


22


is connected to the individual cylinder bores


1




a


by the discharge ports


25


.




When the drive shaft


6


is rotated by the power supplied from the engine E, the swash plate


12


, which is inclined at a predetermined angle θ, rotates accordingly. As a result, the individual pistons


18


reciprocate at the stroke corresponding to the inclination angle θ of the swash plate


12


. This causes the sequence of suction of the refrigerant gas from the suction chamber


21


(at the suction pressure Ps), compression of the refrigerant gas and discharge of the refrigerant gas to the discharge chamber


22


(at the discharge pressure Pd) that is repeated in each cylinder bore


1




a.






The inclination angle θ of the swash plate


12


is determined based on the balance of various moments, such as a rotational moment originated due to the centrifugal force generated when the swash plate


12


rotates, a moment due to the urging force of the inclination-angle reducing spring


16


, a moment caused by the force of inertia based on the reciprocation of the piston


18


, and a moment due to the gas pressure. The gas-pressure moment is generated based on the relationship between the inner pressure of the cylinder bore


1




a


and the crank pressure Pc. In this embodiment, the gas-pressure moment is changed by adjusting the crank pressure Pc with a displacement control valve


50


(discussed later). The inclination angle θ of the swash plate


12


is changed to an arbitrary angle between the minimum inclination angle θmin and the maximum inclination angle θmax in accordance with the adjustment of the crank pressure Pc. The inclination angle θ of the swash plate


12


is the angle defined by the swash plate


12


and an imaginary plane perpendicular to the drive shaft


6


. The maximum inclination angle θmax of the swash plate


12


occurs when the counter weight


12




a


of the swash plate


12


abuts against a restriction portion


11




a


of the rotary support


11


. As the inclination angle of the swash plate


12


is changed in accordance with the crank pressure Pc, the stroke of each piston


18


and the displacement of the compressor are variably adjusted.




The control mechanism that controls the crank pressure Pc includes a bleed passage


27


, a supply passage


28


and the displacement control valve


50


, which are accommodated in the housing of the compressor as shown in

FIGS. 1 and 2

. The bleed passage


27


connects the suction chamber


21


to the crank chamber


5


, and the supply passage


28


connects the discharge chamber


22


to the crank chamber


5


. The bleed passage


27


and the supply passage


28


share a common passage


29


between the control valve


50


and the crank chamber


5


. The displacement control valve


50


has a relief side valve V


1


, located midway in the bleed passage


27


, and an supply side valve V


2


located midway in the supply passage


28


.




The suction chamber


21


and the discharge chamber


22


are connected by an external refrigeration circuit


40


. The external refrigeration circuit


40


and the compressor constitute the cooling circuit of the vehicle air-conditioning system. The external refrigeration circuit


40


includes a condenser


41


, an expansion valve


42


and an evaporator


43


. The opening size of the expansion valve


42


is feedback controlled based on the temperature detected by a temperature sensing cylinder


42




a


at the outlet side of the evaporator


43


. The expansion valve


42


provides the evaporator


43


with an amount of refrigerant gas that matches the thermal load, thus regulating the flow rate of the refrigerant gas.




As shown in

FIG. 1

, a check valve mechanism


35


is located between the discharge chamber


22


and the condenser


41


. The check valve mechanism


35


inhibits the counter flow of refrigerant from the condenser


41


to the discharge chamber


22


. When the discharge pressure Pd is relatively low, the check valve mechanism


35


is closed such that the refrigerant gas circulates inside the compressor.




As shown in

FIG. 2

, a temperature sensor


44


is provided near the evaporator


43


. The temperature sensor


44


detects the temperature of the evaporator


43


and provides a controller C with the information of the detected temperature. The controller C performs the entire control procedure of the vehicle air-conditioning system. Connected to the input side of the controller C are the temperature sensor


44


and a passenger compartment temperature sensor


45


for detecting the temperature inside the vehicle, a temperature setting unit


46


for setting the compartment temperature, an activation switch


47


and an electronic control unit (ECU) for the engine E. The output side of the controller C is connected to a drive circuit


48


, which supplies an electric current to a solenoid V


3


of the control valve


50


. The controller C instructs the drive circuit


48


to feed the appropriate current to the solenoid V


3


based on external information, such as the temperature from the temperature sensor


44


, the temperature sensed by the passenger compartment temperature sensor


45


, the target temperature set by the temperature setting unit


46


, the ON/OFF state of the activation switch


47


, the activation or deactivation of the engine E and the engine speed, the last two pieces of information being given by the ECU. The controller C externally controls the degree of opening of the supply side valve V


2


and a target suction pressure Pset at the relief side valve V


1


.




As shown in

FIG. 2

, the displacement control valve


50


includes the relief side valve V


1


, the supply side valve V


2


and the solenoid V


3


. The relief side valve V


1


can adjust the degree of opening (the amount of restriction) of the bleed passage


27


. The supply side valve V


2


controls the degree of opening of the supply passage


28


. The solenoid V


3


is an electromagnetic actuator that controls an actuation rod


80


of the control valve


50


based on an externally supplied current. While one of the relief side valve V


1


and the supply-side valve V


2


is substantially closed via the actuation rod


80


, which is controlled by the solenoid portion V


3


, the other is opened. The control valve


50


which has those relief side valve V


1


and supply side valve V


2


, is a three-way control valve.




The displacement control valve


50


has a valve housing


51


, which has an upper portion


51




a


and a lower portion


51




b


. The upper portion


51




a


constitutes the relief side valve V


1


and the supply side valve V


2


. The lower portion


51




b


includes the solenoid V


3


. Formed in the center of the upper portion


51




a


of the valve housing


51


is a guide passage


52


, which extends in the axial direction of the upper half portion


51




a


. The actuation rod


80


is retained in the guide passage


52


and is movable in the axial direction.




As shown in

FIGS. 2

to


5


, the actuation rod


80


has a distal portion


81


, a first link portion


82


, an intermediate portion


83


, a second link portion


84


, a valve body


85


, which serves as the supply side valve body, and a third link portion (or proximal portion)


86


. The cross sections of the individual portions


81


-


86


are circular. The distal portion


81


, the intermediate portion


83


, the valve body


85


and the third link portion


86


have the same outside diameter d


1


and the same cross-sectional area S


1


. The first link portion


82


, which links the distal portion


81


and the intermediate portion


83


, and the second link portion


84


, which links the intermediate portion


83


and the valve body


85


, have an outside diameter d


2


(which is smaller than the outside diameter d


1


) and a cross-sectional area S


2


. The outside diameter of the valve body


85


can be slightly smaller than d


1


(by Δd


1


). That is, the outside diameter of the valve body


85


ranges from d


1


to d


1


-Δd


1


.




The guide passage


52


extends in the axial direction of the actuation rod


80


. The first link portion


82


, the intermediate portion


83


, the second link portion


84


and the valve body


85


are retained in the guide passage


52


. The inside diameter of the guide passage


52


is nearly equal to the outside diameter d


1


of the intermediate portion


83


. When the intermediate portion


83


is fitted in the guide passage


52


, the guide passage


52


is separated into an upper area on the relief-side valve V


1


side and a lower area on the supply-side valve V


2


side. The intermediate portion


83


separates the two areas from each other in terms of pressure, not to connect the two areas through the intermediate portion


83


.





FIG. 3

is an enlargement of the relief-side valve V


1


in FIG.


2


. An adjusting member


54


is threaded into the upper portion of the upper portion


51




a


. A relief-side valve chamber


53


, which also serves as a pressure sensitive chamber, is defined in the upper portion


51




a


. A relief-side valve body


61


is provided in the valve chamber


53


. The relief-side valve body


61


is seated on a conical valve seat


55


at the lower portion of the valve chamber


53


. As shown in

FIG. 3

, an annular contact area LC is formed where the valve body


61


is seated on the valve seat


55


. The valve chamber


53


can be separated into an upper area (crank-chamber side area)


53




a


and a lower area (suction-chamber side area)


53




b


with the annular contact area LC as a boundary.




As shown in

FIGS. 3 and 4

, an intermediate port


56


, which connects the lower area


53




b


to the upper part of the guide passage


52


is formed in the center of the bottom of the valve chamber


53


. The inside diameter of the intermediate port


56


is slightly larger than the outside diameter d


1


of the distal portion


81


(the inside diameter of the guide passage


52


). Therefore, the distal portion


81


of the actuation rod


80


can move into and out of the intermediate port


56


. When the distal portion


81


enters the intermediate port


56


, as shown in

FIG. 3

, a slight clearance Δd


2


is formed between them. Since the slight clearance


66


d


2


is very small, it is not shown in the diagram. The slight clearance Δd


2


serves as a restrictor.




As shown in

FIGS. 2 and 3

, a plurality of supply ports


57


are provided in the upper portion


51




a


. The valve chamber


53


is connected to the crank chamber


5


by the individual supply ports


57


and the upstream portion


27




a


of the bleed passage


27


. The upstream portion


27




a


of the bleed passage


27


and the supply ports


57


serve as a part of a pressure-detecting passage for applying the crank pressure Pc to the upper area


53




a


. Between the guide passage


52


and the intermediate port


56


are a plurality of outlet ports


58


, which extend in the radial direction. The suction chamber


21


is connected to the upper area of the guide passage


52


and the intermediate port


56


by the individual outlet ports


58


and the downstream portion of the bleed passage


27




b


. When the intermediate port


56


is opened, as shown in

FIG. 4

, the suction pressure Ps is applied to the lower area


53




b


of the valve chamber


53


. The supply ports


57


, the valve chamber


53


, the intermediate port


56


, a part of the guide passage


52


and the outlet ports


58


constitute a part of the bleed passage


27


that connects the crank chamber


5


to the suction chamber


21


in the relief-side valve V


1


.




As shown in

FIG. 3

, a bellows


60


is provided in the upper area


53




a


to serve as a pressure sensitive member that moves in response to the crank pressure Pc. One end of the bellows


60


is secured to an adjusting member


54


, and the other end is movable. The inner space of the bellows


60


is set to a vacuum state or a depressurized state. A set spring


60




a


is located in the bellows


60


. With the adjusting member


54


as a support seat, the set spring


60




a


urges the valve body


61


toward the seat


55


. The movable end of the bellows


60


is integrated with the relief-side valve body


61


. The relief-side valve body


61


, when seated on the valve seat


55


, shuts the bleed passage


27


.




As shown in

FIG. 3

, the relief-side valve body


61


has a recess


63


, which is open toward the intermediate port


56


. The distal portion


81


of the actuation rod


80


is fitted in the recess


63


in a relatively loose manner. The recess


63


has an end surface


64


, which faces the end of the distal portion


81


, and an inner wall


65


, which faces the circumferential surface of the distal portion


81


. The end surface


64


contacts the end face of the distal portion


81


when the disital portion


81


is located in its upper portion. The inner wall


65


of the recess


63


partially contacts and guides the outer surface of the distal portion


81


. The inside diameter of the recess


63


is slightly larger than the outside diameter d


1


of the distal end portion


81


(by Δd


3


), i.e., the inside diameter is d


1


+Δd


3


. In other words, a clearance (Δd


3


) is formed between the outer surface of the distal end portion


81


and the inner wall


65


of the recess


63


. The clearance Δd


3


is larger than the clearance Δd


2


that is formed between the distal portion


81


and the wall of the intermediate port


56


(Δd


2


<Δd


3


).




An inner passage


66


is formed in the relief-side valve body


61


. The inner passage


66


is formed through the valve body


61


in the diametrical direction and extends axially in the center of the valve body


61


to communicate with the recess


63


. The inner passage


66


connects the upper area


53




a


to the interior of the recess


63


. When the end surface


64


contacts with the end face of the distal portion


81


, communication between the upper area


53




a


and the interior of the recess


63


is blocked. That is, when seated on the valve seat


55


, the relief-side valve body


61


blocks communication between the upper area


53




a


and the lower area


53




b


through the clearance between the valve body


61


and the valve seat


55


. However, communication between the upper area


53




a


and the lower area


53




b


of the valve chamber


53


continues through the path in the valve body


61


(i.e., the inner passage


66


and the path along the end surface


64


and the inner wall


65


of the recess


63


) unless the distal portion


81


of the actuation rod


80


closes the central opening of the inner passage


66


. That is, there are two branches of the bleed passage


27


that extend between the upper area


53




a


and the lower area


53




b


, and they are selectively opened.




As shown in

FIGS. 2 and 4

, in the supply-side valve V


2


, the lower area of the guide passage


52


and an supply-side valve chamber


70


are defined in the upper portion


51




a


. The supply-side valve chamber


70


is connected to the guide passage


52


. The inside diameter of the supply-side valve chamber


70


is larger than the inside diameter d


1


of the guide passage


52


. The bottom wall of the supply-side valve chamber


70


is provided by the upper end face of a fixed iron core


72


. A plurality of supply ports


67


, which extend in the radial direction, are provided in the valve housing at the lower part of the guide passage


52


. The guide passage


52


communicates with the discharge chamber


22


through the individual supply ports


67


and the upstream portion of the supply passage


28




a


. A plurality of outlet ports


68


, which extend in the radial direction, are provided in the valve housing at the supply-side valve chamber


70


. The individual outlet ports


68


connect the supply-side valve chamber


70


to the crank chamber


5


through the downstream portion of the supply passage


28




b


. That is, the supply ports


67


, the lower area of the guide passage


52


, the supply-side valve chamber


70


and the outlet ports


68


constitute a part of the supply passage


28


that communicates the discharge chamber


22


and the crank chamber


5


in the supply valve V


2


. The crank pressure Pc acts on the supply-side valve chamber


70


through the outlet ports


68


.




As shown in

FIG. 2

, the valve body


85


of the actuation rod


80


is located in the supply-side valve chamber


70


. When the actuation rod


80


moves to the position shown in

FIG. 4

from the state shown in

FIG. 2

, the valve body


85


enters the guide passage


52


and closes the passage


52


. The valve body


85


of the actuation rod


80


serves as an supply-side valve body that selectively opens or closes the guide passage


52


and to thus to open or close (or to open and substantially close) the supply passage


28


. In the supply-side valve V


2


, the guide passage


52


serves as a valve hole that is closed by the valve body


85


.




When the outside diameter of the valve body


85


is substantially equal to the inside diameter of the guide passage


52


, the supply-side valve V


2


fully closes. When the outside diameter of the valve body


85


is slightly smaller than the inside diameter of the guide passage


52


(i.e., d


1


-Δd


1


), the valve body


85


does not fully close the guide passage


52


even if the valve body


85


enters the guide passage


52


as shown in FIG.


4


. When the valve body


85


enters the guide passage


52


, however, the cross-sectional area of the resulting passage is significantly small so that the supply-side valve V


2


is substantially closed. When the valve body


85


enters the guide passage


52


, a restriction defined by the difference Δd


1


between the inside diameter of the guide passage


52


and the outside diameter of the valve body


85


is formed in the air-supply passage


28


. This restriction serves as an auxiliary supply passage to supplement the blowby gas. The blowby gas is refrigerant gas that leaks into the crank chamber


5


from around the piston


18


as the piston


18


performs the compression stroke. Since the supply of the blowby gas is generally unstable, it is preferred that the supply-side valve portion V


2


serve as an auxiliary supply passage to supplement the blowby gas when the relief-side valve V


1


is active (i.e., when the supply-side valve V


2


is substantially closed).




As shown in

FIG. 2

, the solenoid V


3


has a cylindrical retainer cylinder


71


with a bottom. The fixed iron core


72


is fitted in the upper portion of the retainer cylinder


71


. A solenoid chamber


73


is defined in the retainer cylinder


71


. A movable iron core


74


, or a plunger, is retained in the solenoid chamber


73


in an axially movable manner. The third link portion


86


of the actuation rod


80


is located at the center of the fixed iron core


72


and is movable in the axial direction. The upper end of the third link portion


86


is the valve body


85


. The lower end of the third link portion


86


is fitted into a through hole formed in the center of the movable iron core


74


and is secured in the through hole by crimping. Therefore, the movable iron core


74


and the actuation rod


80


move together. There is a slight clearance (not shown) between the inner wall of a rod guide passage formed in the center of the fixed iron core


72


and the outer surface of the third link portion


86


of the actuation rod


80


. The supply-side valve chamber


70


is connected to the solenoid chamber


73


by this clearance. According to this embodiment, therefore, the crank pressure Pc also acts on the solenoid chamber


73


.




A return spring


75


is located between the fixed iron core


72


and the movable iron core


74


. The return spring


75


acts to urge the movable iron core


74


away from the fixed iron core


72


, which is downward in FIG.


2


. The return spring


75


therefore initially positions the movable iron core


74


and the actuation rod


80


to the lowest movable position (the initial position at the time of deenergization) shown in FIG.


2


.




A coil


76


is wound around the fixed iron core


72


and the movable iron core


74


to surround both cores


72


and


74


. The drive circuit


48


supplies a predetermined current to the coil


76


in response to an instruction from the controller C. The coil


76


generates the electromagnetic force, the magnitude of which corresponds to the level I of the supplied current. The electromagnetic force causes the movable iron core


74


to be attracted toward the fixed iron core


72


, which moves the actuation rod


80


upward. When no current is supplied to the coil


76


, the urging force of the return spring


75


places the actuation rod


80


at the lowest movable position (initial position) shown in FIG.


2


. Then, the distal portion


81


of the actuation rod


80


moves away from the end surface


64


, and the valve body


85


is separated from the lower end of the guide passage


52


, as shown in

FIGS. 2 and 3

. That is, the relief-side valve body


61


is seated on the valve seat


55


, closing the relief-side valve V


1


and opening the supply-side valve portion V


2


.




When the current is supplied to the coil


76


, the upward electromagnetic force generated by the current supply becomes greater than the downward force of the return spring


75


. As a result, the valve body


85


moves into the guide passage


52


and the end face of the distal portion


81


contacts the end surface


64


, which closes the supply-side valve V


2


. Accordingly, the bellows


60


(including the spring


60




a


), the relief-side valve body


61


, the actuation rod


80


and the solenoid V


3


are operating coupled together. Based on the dynamic relationship between the coupled members, the position of the relief-side valve body


61


in the relief-side valve chamber


53


(the distance between the valve body


61


and the valve seat


55


) is determined. The degree of opening of the relief-side valve V


1


is determined accordingly. That is, the electromagnetic force, which is adjusted by the solenoid V


3


, changes the target suction pressure Pset of the relief-side valve V


1


against the opposing force of the entire pressure sensitive mechanism (


60


,


60




a


). In other words, when the current is supplied to the coil


76


, the relief-side valve V


1


serves as a variable setting type relief-side control valve that can change the target suction pressure Pset based on the value of the externally supplied current.





FIG. 5

shows the situation when the current supply to the coil


76


couples the relief-side valve body


61


and the actuation rod


80


together and when the control valve


50


serves mainly as a relief-side control valve.





FIG. 5

shows a downward force f


1


, which is generated by the bellows


60


and the set spring


60




a


, a downward force f


2


of the return spring


75


and an upward electromagnetic force of the actuation rod


80


.

FIG. 5

further shows an effective area A of the bellows


60


and a substantial seal area B formed by the relief-side valve body


61


when the valve body


61


is seated. As far as the crank pressure Pc that acts on the top and bottom surfaces of the movable iron core


74


is concerned, the effective pressure receiving area of the lower end portion of the actuation rod


80


in the solenoid chamber


73


can be regarded as the cross-sectional area S


1


of the third link portion (proximal end portion)


86


of the actuation rod


80


.




The following considers the pressure that acts on the relief-side valve body


61


, the intermediate portion


83


, the valve body


85


and the lower end portion of the actuation rod


80


. First, the mechanical urging force f


1


produced by the bellows


60


acts on the relief-side valve body


61


. Since the movable end of the bellows


60


is secured to the valve body


61


, the effective pressure receiving area of the relief-side valve body


61


in association with the crank pressure Pc is obtained by subtracting the effective area A of the bellows


60


from the seal area B. Therefore, the force due to the crank pressure Pc(B−A) in the direction of closing the guide passage


52


and the force due to the suction-pressure Ps(B−S


2


) in the direction of opening the guide passage


52


act on the relief-side valve body


61


. A force (Pd−Ps)×(S


1


−S


2


) that pushes the actuation rod


80


based on the differential pressure between the discharge pressure Pd and the suction pressure Ps acts on the intermediate portion


83


. A force Pd(S


1


−S


2


) that urges the actuation rod


80


downward based on the discharge pressure Pd acts on the valve body


85


. A force PcS


1


, which urges the actuation rod


8


upward and which is based on the cross-sectional area S


1


in the solenoid chamber


73


and the crank pressure Pc, acts on the lower end portion of the actuation rod


80


. Further, the upward electromagnetic force F, from which the force f


2


is subtracted, acts on the actuation rod


80


. Based on the balance of the various forces, the position of the actuation rod


80


(or the degree of opening of the relief-side valve V


1


) is determined. With the downward direction is viewed as the positive direction, the forces that act on the individual members have the relationship represented in a first equation below:








f




1


+


Pc


(


B−A


)−


Ps


(


B−S




2


)−(


Pd−Ps


)(


S




1





S




2


)+


Pd


(


S




1





S




2


)−


Pc·S




1





F+f




2


=0






Rearranging the equation 1 yields an equation 2 below:








Pc


(


B−A−S




1


)−


Ps


(


B−S




1


)=


F−f




1





f




2








In the process of rearranging the first equation to yield the second equation, S


2


and Pd are canceled from the second equation. Thus the influence of the suction pressure Ps that acts on the first link portion


82


on the actuation rod


80


does not depend on the cross-sectional area S


2


of the first link portion


82


. The canceling of S


2


and Pd also indicates that the influence of the discharge pressure Pd that acts on the second link portion


84


on the actuation rod


80


is always canceled regardless of the cross-sectional area S


1


and the cross-sectional area S


2


of the second link portion


84


.




If the effective area A of the bellows


60


, the seal area B formed by the valve body


61


and the effective pressure receiving area S


1


of the lower end portion of the actuation rod


80


are set to satisfy the condition of A≈B and S


1


<B (most preferably A+S


1


=B), the term Pc(B−A−S


1


) in the second equation becomes zero or small enough to be negligible. Therefore, the following third equation is derived from the second equation.








Ps≈


(


f




1


+


f




2





F


)/(


B−S




1


)










Ps=


(


f




1


+


f




2




−F


)/


A










(


A+S




1





B


)








(


A+S




1


=


B


)






In the third equation, f


1


, f


2


, A, B and S


1


are constants because they could be determined in advance in designing steps. The electromagnetic force F is changed in accordance with the value I of the current supplied to the coil


76


. The suction pressure Ps is specifically determined only by those parameters and does not depend on the crank pressure Pc at all. That is, the target suction pressure Pset when the control valve


50


serves as the relief-side control valve can be set variably in accordance with the value I of the current supplied to the coil


76


. In other words, the control valve


50


serves as a variable target suction pressure type control valve that performs control based on the externally supplied current. When the current supply to the coil


76


is stopped (i.e., F=0), the value of the target suction pressure Pset becomes maximum. As the value I of the current supplied to the coil


76


increases, the value of the target suction pressure Pset decreases. Therefore, the solenoid V


3


and the controller C externally change the target suction pressure Pset.




Controlling the variable displacement type compressor will now be discussed.




With the engine E stopped, no current is supplied to the coil


76


. At this time, the relief-side valve body


61


and the actuation rod


80


are uncoupled as shown in

FIGS. 2 and 3

. Therefore, the relief-side valve body


61


is seated mainly by the downward force f


1


by the bellows


60


, thus closing the relief-side valve V


1


. The downward force f


2


of the return spring


75


moves the actuation rod


80


to the lowest position (initial position) as shown in

FIG. 2

, thus opening the supply-side valve V


2


. When the deactivation of the compressor continues over a long period of time, the pressures in the individual chambers


5


,


21


and


22


equalize. As a result, the swash plate


12


is held at the minimum inclination angle by the force of the inclination-angle reducing spring


16


.




When the engine E runs, the clutchless compressor starts operating. With the activation switch


47


of the air-conditioning system set off, no current is supplied to the coil


76


and the inclination angle of the swash plate


12


is minimum, thus minimizing the displacement of the compressor. During a predetermined time from the activation of the engine E, the discharge pressure Pd in the discharge chamber


22


does not become high enough to push the check valve mechanism


35


open. Therefore, the refrigerant gas in the discharge chamber


22


flows into the crank chamber


5


via the upstream portion


28




a


of the supply passage


28


, the supply-side valve V


2


and the downstream portion


28




b


of the supply passage


28


. The gas that has entered the crank chamber


5


flows out to the suction chamber


21


through the upstream portion


27




a


of the bleed passage


27


, the relief-side valve V


1


and the downstream portion


27




b


of the bleed passage


27


.




When no current is supplied to the coil


76


, the force f


1


of the bellows


60


causes the relief-side valve body


61


to contact the valve seat


55


, thus closing the bleed passage


27


between the valve body


61


and the valve seat


55


as shown in FIG.


3


. At this time, the distal portion


81


of the actuation rod


80


is separated from the end surface


64


of the recess


63


. Consequently, a communication passage extending from the inner passage


66


of the valve body


61


through the clearance Δd


3


along the end surface


64


and the inner wall


65


is formed between the upper area


53




a


and the lower area


53




b


. The distal portion


81


enters the intermediate port


56


, forming the clearance Δd


2


, through which the lower area


53




b


is connected to the outlet ports


58


. That is, when no current is supplied to the coil


76


(when the relief-side valve V


1


does not perform automatic opening adjustment), at least a new flow path extending through the clearance Δd


2


from the inner passage


66


is formed. When the activation switch


47


is off, therefore, a circulation passage, which circulates the refrigerant gas back to the suction chamber


21


through the route of the suction chamber


21


, the cylinder bore


1




a


, the discharge chamber


22


, the upstream portion


28




a


of the supply passage


28


, the opened supply-side valve V


2


, the downstream portion


28




b


of the supply passage


28


, the crank chamber


5


, the upstream portion


27




a


of the bleed passage


27


, the relief-side valve V


1


(through the clearance of the inner passage


66


), and the downstream portion


27




b


of the bleed passage


27


is formed in the compressor even when the compressor is always operated with the minimum discharge capacity.




The clearance Δd


2


is smaller than the clearance Δd


3


, and the communication passage extending from the inner passage


66


through the clearance Δd


2


serves as a fixed-restriction passage. The flow rate of the refrigerant gas flowing in the circulation passage is restricted by the clearance Δd


2


. When the crank pressure Pc increases and the valve body


61


moves upward suddenly, therefore, the distal portion


81


is held in the intermediate port


56


and the clearance Δd


2


serves as a fixed restriction unless the current is supplied to the coil


76


.




Lubrication oil is supplied to the crank chamber


5


for lubrication of the sliding parts. To always feed lubrication oil to the sliding parts, the lubrication oil should be carried in the form of a mist by using the flow of the gas. When gas does not flow in the compressor, therefore, the oil drops off the sliding portions, resulting in insufficient lubrication. This shortcoming does not however occur in the compressor of this embodiment.




When the activation switch


47


is on while the engine E is running, the controller C instructs that current be supplied the coil


76


. Then, the electromagnetic force of the coil


76


causes the actuation rod


80


to move upward against the downward force f


2


of the return spring


75


, thus closing the supply-side valve V


2


. Then, the degree of opening of the relief-side valve V


1


is adjusted with the relief-side valve V


1


, which is coupled to the solenoid V


3


as shown in FIG.


4


. The degree of opening of the relief-side valve V


1


(i.e., the position of the relief-side valve body


61


in the valve chamber


53


) is determined by the balance of the various parameters given in equation 3. The relief-side valve V


1


serves as an internal control valve, which performs automatic opening adjustment in accordance with the suction pressure Ps.




When the cooling load becomes large, the pressure in the vicinity of the outlet of the evaporator


43


(the suction pressure Ps) increases gradually, and the difference between the temperature detected by, for example, the room temperature sensor


45


and the temperature set by the room temperature setting unit


46


increases. Since the discharge performance of the compressor must match the cooling load, the controller C controls the value of the current supplied to the coil


76


to change the target suction pressure Pset based on the detected temperature and the set temperature. Specifically, as the detected temperature gets higher, the controller C increases the value of the supplied current supplied to increase the electromagnetic force F. Thus the target suction pressure Pset of the control valve


50


is set to a relatively low level. To make the target suction pressure Pset lower than the actual suction pressure Ps, therefore, the opening size of the relief-side valve V


1


increases. This increases the flow rate of the refrigerant gas that relieved from the crank chamber


5


. As the supply-side valve V


2


is closed, the flow of gas out of the crank chamber


5


reduces the crank pressure Pc. Under a large cooling load, the pressure of the gas to be fed into the cylinder bore


1




a


, or the suction pressure Ps, is relatively high, making the difference between the pressure in the cylinder bore


1




a


and the crank pressure Pc relatively small. This increases the inclination angle of the swash plate


12


, thus increasing the displacement of the compressor.




When the cooling load decreases, the pressure in the vicinity of the outlet of the evaporator


43


(the suction pressure Ps) decreases gradually, and the difference between the temperature detected by, for example, the room temperature sensor


45


and the temperature set by the room temperature setting unit


46


decreases. To match the discharge performance of the compressor to the cooling load, the controller C controls the value of the current supplied to the coil


76


to change the target suction pressure Pset. Specifically, as the detected temperature decreases, the controller C decreases the value of the supplied current to the coil


76


, thereby reducing the electromagnetic force F. This causes the target suction pressure Pset to be relatively high. To change the suction pressure Ps to the target suction pressure Pset, the opening size of the relief-side valve V


1


decreases. This decreases the flow rate of the refrigerant gas that relieved from the crank chamber


5


. As a result, the flow rate of gas relieved from the crank chamber


5


becomes smaller than the flow rate of blowby gas from the cylinder bore


1




a


(or the sum of the amount of the blowby gas and the amount of supplemental gas supplied into the crank chamber


5


via the auxiliary supply passage), thus increasing the crank pressure Pc. Under a small cooling load, the suction pressure Ps in the cylinder bore


1




a


is relatively low, and the difference between the pressure in the cylinder bore


1




a


and the crank pressure Pc increases. This decreases the inclination angle of the swash plate


12


, thus decreasing the displacement of the compressor.




Even when the current is supplied to the coil


76


, the internal circulation of refrigerant gas in the compressor continues. In this case, however, the discharge capacity of the compressor becomes large to some degree and the supply-side valve V


2


is substantially closed, so that the blowby gas plays an important role. That is, gas circulates along the path that includes the suction chamber


21


, the cylinder bore


1




a


, the crank chamber


5


, the upstream portion


27




a


of the bleed passage


27


, the relief-side valve V


1


(via the clearance between the valve body


61


and the valve seat


55


), the downstream portion


27




b


of the bleed passage


27


and the suction chamber


21


. Therefore, gas flows inside the compressor, thus ensuring the feeding of the lubrication oil mist.




The controller C stops supplying the current to the coil


76


when, for example, the temperature of the evaporator


43


approaches the frost-generating temperature, when the activation switch


47


of the air-conditioning system is off or when a displacement limiting control is selected. In the displacement limiting control, when the load on a vehicle engine E increases, for example, when a vehicle is abruputly accelerated, the controller C stops supplying the current to the coil


76


to limit the displacement. This causes the electromagnetic force F of the solenoid V


3


to vanish. Consequently, the actuation rod


80


is immediately moved to the lowest position (the initial position) by the force of the return spring


75


, thus closing the relief-side valve V


1


and opening the supply-side valve V


2


. As a result, a large amount of refrigerant gas flows into the crank chamber


5


from the discharge chamber


22


via the supply passage


28


, which raises the crank pressure Pc. Then, the swash plate


12


is set to the minimum inclination, which minimizes the displacement of the compressor. A similar operation takes place when the engine E stalls suddenly, which blocks the current supply to the air-conditioning system.












TABLE 1









below shows the operational characteristics of






the above-described control valve 50.

























Solenoid




Supply-side




Relief-side valve V1














V3




valve V2




Passage formed




Passage








by the




formed inside








clearance




the valve








between the




body








valve body and








valve seat






When no




Open




Closed




Restricted






current is






passage for






supplied






internal









circulation









is formed






When current




Closed




The opening




Closed






is supplied




(auxiliary




size of the







supply




valve is







passage is




adjusted







formed)




according to Ps














This embodiment has the following advantages.




The cooperation of the relief-side valve V


1


and the supply-side valve V


2


through the actuation rod


80


allows the control valve


50


to selectively serve as a relief-side control valve or an supply-side control valve. This overcomes the drawbacks of a single relief-side control valve or a single supply-side control valve and provides the advantages of both types of a control valves.




The crank pressure Pc is applied to the relief-side valve chamber


53


, where the bellows


60


, or the pressure sensitive member, is located, and the effective area A of the bellows


60


and the seal area B by the relief-side valve body


61


are approximately the same. Therefore, the control valve


50


serves as a variable target suction pressure type control valve, which has the control characteristics indicated by the third equation. That is, when the actuation rod


80


and the relief-side valve body


61


are coupled, the relief-side valve body


61


is automatically positioned in accordance with the suction pressure Ps without being influenced by the discharge pressure Pd or the crank pressure Pc. Further, the electromagnetic force F is adequately adjusted by the externally supplied current to change the target suction pressure Pset with high precision.




Incorporating a compressor having the control valve


50


of this embodiment into the cooling circuit of a vehicle air-conditioning system optimizes the displacement of the compressor in accordance with a change in the cooling load at the evaporator


43


. Further, the temperature of the passenger compartment can always be kept near the desired temperature by keeping the pressure in the vicinity of the outlet of the evaporator


43


, which is nearly equal to the suction pressure Ps, at or near a desired value (the target suction pressure Pset).




The relief-side valve body


61


operates in accordance only with a change ΔPs in the suction pressure Ps without being influenced by the differential pressure (Pc−Ps) or the crank pressure Pc (see the third equation). Therefore, no problems will arise even if the seal area B of the relief-side valve body


61


is increased. That is, the relief-side valve body


61


operates in response to the suction pressure Ps regardless of the level of the differential pressure (Pc−Ps) or the crank pressure Pc. As the relief-side valve body


61


displaces in the axial direction in fine response to a change ΔPs in the suction pressure Ps, therefore, the flow rate of the gas that passes between the valve body


61


and the valve seat


55


changes significantly. This significantly improves the Pc/Ps ratio of the relief-side valve V


1


of the control valve


50


, making it possible to control the displacement of the compressor quickly and precisely in accordance with a change in the thermal load (or the cooling load). It is therefore possible to limit or avoid hunting.




Even when the compressor is operated with the minimum displacement, a circulation passage is formed for the refrigerant gas through the relief-side valve body


61


. This maintains lubrication of the individual sliding parts of the compressor. The control valve


50


is therefore most suitable for use in a clutchless compressor that is directly coupled to the drive source.




The outside diameter of the valve body


85


of the actuation rod


80


is smaller than the inside diameter of the guide passage


52


(i.e., d


1


-Δd


1


). This allows the clearance between the circumferential surface of the valve body


85


and the inner surface of the guide passage


52


(circumferential clearance) to serve as an auxiliary supply passage. Even if the displacement of the compressor is relatively small and blowby gas becomes insufficient, gas is supplied to the crank chamber


5


via the auxiliary supply passage so that the crank pressure Pc can be increased promptly when performing relief-side control.




This invention may be alternatively embodied as follows.




The pressure supplied to the solenoid chamber


73


is not limited to the crank pressure Pc, but may be the suction pressure Ps. If the suction pressure Ps is supplied to the solenoid chamber


73


, a variable target suction pressure type control valve can be constructed with area conditions simpler and less restricted than those of the embodiment illustrated in

FIGS. 1

to


5


.

FIG. 6

shows a control valve according to a second embodiment. From the structure of the control valve in

FIG. 6

, a forth equation (corresponding to the first equation) is satisfied and rearranging the forth equation yields a fifth equation (corresponding to the second equation) below.








f




1


+


Pc


(


B−A


)−


Ps


(


B−S




2


)−(


Pd−Ps


)(


S




1





S




2


)+


Pd


(


S




1





S




2


)−


Pc·S




1





F+f




2


0










Pc


(


B−A


)−


Ps·B=F−f




1





f




2








The fifth equation does not contain Pd, S


1


and S


2


. That is, the operation of the control valve in

FIG. 6

is not affected by the discharge pressure Pd and the cross-sectional areas S


1


and S


2


of the individual members of the actuation rod


80


at all. When the effective area A of the bellows


60


and the seal area B by the valve body


61


satisfy the condition A=B, the term Pc(B−A) in the fifth equation becomes zero. If A=B, the sixth equation (corresponding to the third equation) is derived as follows.








Ps=


(


f




1


+


f




2





F


)/


B








In the sixth equation, f


1


, f


2


and B are predetermined in the designing steps. The electromagnetic force F is a function of the value I of the current supplied to the coil


76


. Like the control valve in

FIG. 5

, therefore, the control valve in

FIG. 6

serves as a variable target suction pressure type control valve that performs control based on the externally supplied current. If the suction pressure Ps is applied to the solenoid chamber


73


so that the suction pressure Ps acts on the lower end of the actuation rod


80


as shown in

FIG. 6

, A can be set equal to B. This eliminates the influence of the size relationship between the seal area B and the effective pressure receiving area S


1


.




In the relief-side valve V


1


of each of the control valves


50


shown in

FIGS. 2

to


5


and

FIG. 6

, the bellows


60


may be replaced with a diaphragm to serve as the pressure sensitive member.




This invention may be adapted to a wobble type swash plate compressor.




It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the invention may be embodied in the following forms.




Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.



Claims
  • 1. A control valve for controlling the displacement of a variable displacement type compressor, wherein the compressor includes a crank chamber, a suction pressure zone, the pressure of which is suction pressure, a discharge pressure zone, the pressure of which is discharge pressure, a bleed passage for releasing gas from the crank chamber to the suction pressure zone, and a supply passage for supplying gas from the discharge pressure zone to the crank chamber, the control valve comprising:a valve housing; a supply side valve for controlling the opening degree of the supply passage; a transmission rod extending in the valve housing, wherein the transmission rod moves axially and has a distal end portion and a proximal end portion; a relief side valve for controlling the opening degree of the bleed passage, wherein the transmission rod connects the relief side valve with the supply valve, the relief side valve including: a passage chamber constituting part of the bleed passage; a valve seat for defining part of the passage chamber; and a relief side valve body that contacts the valve seat, the relief side valve body being located in the passage chamber, wherein, when the relief side valve body contacts the valve seat, the passage chamber is separated into a first area, which is connected to the crank chamber via an upstream part of the bleed passage, and a second area, which is connected to the suction pressure zone via a downstream part of the bleed passage; and a pressure sensing member located in the first area and moving the relief side valve body in accordance with the pressure in the first area, wherein, when the relief side valve body contacts the valve seat, the effective pressure receiving area of the pressure sensing member is substantially equal to the cross sectional area of the passage chamber that is sealed by the relief side valve body.
  • 2. The control valve according to claim 1, wherein the distal end portion is located in the second area, wherein the control valve further includes a solenoid to urge the transmission rod in a direction to move the relief side valve body away from the valve seat with a force in accordance with an external signal.
  • 3. The control valve according to claim 2, wherein an inner passage is formed in the relief side valve body, wherein, when the relief side valve body contacts the valve seat, a through passage is defined in the relief side valve body, wherein the through passage includes the inner passage and permits gas flow from the crank chamber to the suction pressure zone.
  • 4. The control valve according to claim 3, wherein the valve housing has a port for receiving the distal end portion of the transmission rod, wherein, when the distal end portion enters the port, a clearance, is defined between the distal end portion and a wall defining the port.
  • 5. The control valve according to claim 2, wherein the distal end portion of the transmission rod is located in the relief side valve, wherein the proximal end portion of the transmission rod is located in the solenoid, wherein the supply side valve is located between the relief side valve and the solenoid, wherein the relief side valve includes a guide passage that forms part of the supply passage, the transmission rod extending through the guide passage, wherein the transmission rod has a supply side valve body, and the solenoid axially moves the transmission rod such that the supply side valve body regulates an opening degree of the guide passage.
  • 6. The control valve according to claim 5, wherein, when electric current is supplied to the solenoid, the supply side valve body restricts the guide passage, and the solenoid applies a force to the relief side valve body through the transmission rod, wherein the force corresponds to the level of a current supplied to the solenoid, and the level of the current determines a target value of the suction pressure, and wherein the pressure sensing member moves the relief side valve body such that the suction pressure is steered toward the target value.
  • 7. The control valve according to claim 6 further includes an urging member, wherein the urging member urges the transmission rod in a direction opposite to the direction of the force applied to the transmission rod by the solenoid, wherein, when no current is supplied to the solenoid, the urging member moves the transmission rod such that the supply side valve body fully opens the guide passage and such that the relief side valve body contacts the valve seat.
  • 8. The control valve according to claim 2, wherein the pressure in the crank chamber is applied to an area in which the proximal end portion of the transmission rod is accommodated.
  • 9. The control valve according to claim 2, wherein the suction pressure is applied to an area in which the proximal end portion of the transmission rod is accommodated.
  • 10. A control valve for controlling the displacement of a variable displacement type compressor, wherein the compressor includes a crank chamber, a suction pressure zone, the pressure of which is suction pressure, a discharge pressure zone, the pressure of which is discharge pressure, a bleed passage for releasing gas from the crank chamber to the suction pressure zone, and a supply passage for supplying gas from the discharge pressure zone to the crank chamber, the control valve comprising:a valve housing; a supply side valve for controlling the opening degree of the supply passage; a transmission rod extending in the valve housing, wherein the transmission rod moves axially and has a distal end portion and a proximal end portion; a relief side valve for controlling the opening degree of the bleed passage, wherein the transmission rod connects the relief side valve with the supply side valve, the relief side valve including: a passage chamber constituting part of the bleed passage; a valve seat for defining part of the passage chamber; and a relief side valve body that contacts the valve seat, the relief side valve body being located in the passage chamber, wherein, when the relief side valve body contacts the valve seat, the passage chamber is separated into a first area, which is connected to the crank chamber via an upstream part of the bleed passage, and a second area, which is connected to the suction pressure zone via a downstream part of the bleed passage, wherein the distal end portion of the transmission rod is accommodated in the second area; a solenoid for urging the transmission rod in a direction to move the relief side valve body away from the valve seat with a force in accordance with an external signal, wherein the solenoid has an area for accommodating the proximal end portion, and wherein the pressure in the crank chamber is applied to the area; and a pressure sensing member located in the first area and moving the relief side valve body in accordance with the pressure in the first area, wherein the cross sectional area of the passage chamber that is sealed by the relief side valve body is substantially equal to a sum of the effective pressure receiving area of the pressure sensing member and an effective pressure receiving area of the proximal end portion.
  • 11. A control valve for controlling the displacement of a variable displacement type compressor, wherein the compressor includes a crank chamber, a suction pressure zone, the pressure of which is suction pressure, a discharge pressure zone, the pressure of which is discharge pressure, a bleed passage for releasing gas from the crank chamber to the suction pressure zone, and a supply passage for supplying gas from the discharge pressure zone to the crank chamber, the control valve comprising:a valve housing; a transmission rod extending in the valve housing, wherein the transmission rod moves axially and has a distal end portion and a proximal end portion; a solenoid located nearby in the proximal end portion of the transmission rod, wherein the solenoid urges the transmission rod in axial direction with a force in accordance with the electric current supplied to the solenoid, wherein the solenoid has an area for accommodating the proximal end portion, and wherein the pressure in the crank chamber is applied to the area; a supply side valve for controlling the opening degree of the supply passage, wherein the supply side valve includes a guide passage that constitutes a part of the supply passage and a supply side valve body formed on the transmission rod to enter in the guide passage, wherein the solenoid moves the transmission rod such that the supply side valve body is selectively entered and moved away to the guide passage; a relief side valve for controlling the opening degree of the bleed passage, wherein the transmission rod connects the relief side valve portion with the supply side valve portion, the relief side valve portion including: a passage chamber constituting part of the bleed passage; a valve seat for defining part of the passage chamber; and a relief side valve body that contacts the valve seat, the relief side valve body being located in the passage chamber, wherein, when the relief side valve body contacts the valve seat, the passage chamber is separated into a first area, which is connected to the crank chamber via an upstream part of the bleed passage, and a second area, which is connected to the suction pressure zone via a downstream part of the bleed passage; and a pressure sensing member located in the first area and moving the relief side valve body in accordance with the pressure in the first area, wherein the cross sectional area of the passage chamber that is sealed by the relief side valve body is substantially equal to a sum of the effective pressure receiving area of the pressure sensing member and an effective pressure receiving area of the proximal end portion.
  • 12. The control valve according to claim 11, wherein an inner passage is formed in the relief side valve body, wherein, when the relief side valve body contacts the valve seat, a through passage is defined in the relief side valve body, wherein the through passage includes the inner passage and permits gas flow from the crank chamber to the suction pressure zone.
  • 13. The control valve according to claim 12, wherein the valve housing has a port for receiving the distal end portion of the transmission rod, wherein, when the distal end portion enters the port, a clearance is defined between the distal end portion and a wall defining the port.
  • 14. The control valve according to claim 11, wherein the distal end portion of the transmission rod is located in the relief side valve, wherein the supply side valve is located between the relief side valve and the solenoid.
  • 15. The control valve according to claim 14, wherein, when electric current is supplied to the solenoid, the supply side valve body restricts the guide passage, and the solenoid applies a force to the relief side valve body through the transmission rod, wherein the force corresponds to the level of a current supplied to the solenoid, and the level of the current determines a target value of the suction pressure, and wherein the pressure sensing member moves the relief side valve body such that the suction pressure is steered toward the target value.
  • 16. The control valve according to claim 15 further includes an urging member, wherein the urging member urges the transmission rod in a direction opposite to the direction of the force applied to the transmission rod by the solenoid, wherein, when no current is supplied to the solenoid, the urging member moves the transmission rod such that the supply side valve body fully opens the guide passage and such that the relief side valve body contacts the valve seat.
Priority Claims (1)
Number Date Country Kind
11-319466 Nov 1999 JP
Foreign Referenced Citations (3)
Number Date Country
0 985 823 Mar 2000 EP
6-26454 Feb 1994 JP
2000-87849 Mar 2000 JP