Patent Application
20060237552
The present invention relates to a displacement control valve for a clutchless type variable displacement compressor for use in a vehicle air conditioner which variably controls its displacement.
Generally, a variable displacement compressor (hereinafter merely referred to as “compressor”) is known as a compressor for use in a vehicle air conditioner, which variably controls its displacement. In this type of compressor, a swash plate is accommodated in a control pressure chamber and inclinable with respect to a drive shaft. As the pressure in the control pressure chamber rises, the swash plate is inclined so as to approach a state perpendicular to the axis of the drive shaft (inclination of the swash plate becomes small). On the other hand, as the pressure in the control pressure chamber falls, the swash plate is inclined so as to approach the axis of the drive shaft (the inclination of the swash plate becomes large). The compressor has a piston whose stroke is changeable in accordance with the inclination of the swash plate. For example, when the pressure in the control pressure chamber is high and the inclination of the swash plate is small, the stroke of the piston is small. On the other hand, when the pressure in the control pressure chamber is low and the inclination of the swash plate is large, the stroke of the piston is large. As the stroke of the piston decreases, the displacement of the compressor is decreased. As the stroke of the piston increases, the displacement of the compressor is increased.
Japanese Unexamined Patent Application Publication (KOKAI) No. 2000-18420 discloses a displacement control valve for a variable displacement compressor.
A solenoid 110 is provided in a part of the valve housing 101 which is the furthest from the pressure sensing chamber 106 (at the other end of the valve housing 101). The solenoid 110 has a fixed core 111 fixed to the valve housing 101, a movable core 112 movable with respect to the fixed core 111 and an electromagnetic coil 113 enclosing the fixed and movable cores 111 and 112. The fixed core 111 has a hole 111a formed therein, through which a rod 114 that serves as a reciprocation body is inserted. The rod 114 also extends through the valve hole 105. One end of the rod 114 is in contact with the movable core 112, and the other end thereof is connected to the pressure sensing mechanism 107 in the pressure chamber 106.
The rod 114 includes a first shaft portion 115 having a valve body 116 for closing the valve hole 105, a second shaft portion 117 inserted in a hole 101a through which the pressure sensing chamber 106 is in communication with the refrigerant passage, and a small-diameter portion 118 that connects the first shaft portion 115 to the second shaft portion 117. A projection portion 119 is formed between the first shaft portion 115 and the small-diameter portion 118 so as to be tapered toward the small-diameter portion 118. The projection portion 119 is substantially in the shape of truncated cone and has a tapered surface in accordance with the tapered shape. The smallest diameter of the projection portion 119 (the diameter of the part thereof connected to the small-diameter portion 118) corresponds to the diameter of the small-diameter portion 118. The valve body 116 of the first shaft portion 115 is a valve body for opening and closing the valve hole 105. When the valve body 116 opens the valve hole 105, the refrigerant flows from the discharge pressure region into the control pressure chamber through the first port 102, the refrigerant passage and the second port 103. When the valve body 116 closes the valve hole 105, flow of the refrigerant from the discharge pressure region into the control pressure chamber is prevented.
When the solenoid 110 of the above displacement control valve 100 is excited to move the rod 114 in the direction that causes the valve hole 105 to be closed as shown in
In a clutchless type compressor that constantly receives power from an external drive source (e.g. a vehicle engine) so as to operate even at minimum displacement, the sufficient amount of the refrigerant flowing from the discharge pressure region into the control pressure chamber through the displacement control valve is needed in order to ensure sufficient lubrication in the compressor at the minimum displacement. Thus, the clearance between the circumferential surface of the rod and the inner circumferential surface of the valve hole, which is a part of the refrigerant passage, needs to be increased at the minimum displacement of the compressor.
Meanwhile, in a control region in which displacement of the compressor is varied, if the flow rate of the refrigerant from the discharge pressure region into the control pressure chamber is large, the variation of the flow rate of the refrigerant is significantly large when the rod opens the valve hole. This causes rapid change of the pressure in the control pressure chamber, with the result that the displacement controllability deteriorates.
The rod of the conventional displacement control valve has the projection portion tapered toward the small-diameter portion. Thus, the cross-sectional area of the valve hole is gradually changed by the projection portion, thereby gradually changing the flow rate of the refrigerant in the valve hole. In this respect, the conventional displacement control valve is advantageous. However, in order to gradually change the flow rate of the refrigerant in the valve hole, the angle of the tapered surface of the projection portion with respect to the axis of the rod needs to be set in a certain range. The length of the projection portion in the axial direction of the rod is set in accordance with the angle of the tapered surface. For processing reason, the sufficient length of the projection portion in the axial direction of the rod is needed for forming the tapered surface in the projection portion. More specifically, since the projection portion is formed in the rod, the distance of movement of the rod, which is moved by exciting the solenoid, needs to be set larger than the length of the projection portion in the axial direction of the rod in order to ensure the sufficient amount of the refrigerant required for lubrication in the compressor at the minimum displacement. When the distance of movement of the rod that serves as a reciprocation body is set large, magnetic force of the solenoid needs to be large, which is opposed to reduction of the displacement control valve in size and electric power saving.
Incidentally, in order to shorten the distance of movement of the rod, the angle of the tapered surface with respect to the direction of movement needs to be increased. There is fear that as the angle of the tapered surface increases, the flow rate of the refrigerant may extremely rapidly change when the rod opens the valve hole. Thus, the pressure in the control pressure chamber may rapidly change, thereby deteriorating the displacement controllability. Although there is a way of increasing the diameter of the small-diameter portion, the increase of the diameter of the small-diameter portion decreases the clearance between the small-diameter portion and the valve hole, which makes impossible to ensure the sufficient flow rate of the refrigerant when the valve body opens the valve hole.
When the refrigerant of the compressor is carbon dioxide, the difference of elevation of the pressure of the refrigerant becomes remarkable compared to that of the other refrigerant. This enables a sufficient flow rate of the refrigerant for controlling the compressor to be flowed into the valve hole by slightly spacing the valve body away from the valve hole. That is, when the refrigerant is carbon dioxide, the distance of movement of the rod of the displacement control valve is set small. If the tapered projection portion is provided in the rod, however, the distance of movement of the rod is increased by the length in the axial direction of the projection portion. In addition, since inflow and interruption of the refrigerant from the discharge pressure region to the control pressure chamber through the valve hole is achieved by substantially slight distance of movement of the rod, the function that the flow rate of the refrigerant is gradually changed caused by the conventional projection portion may not be properly achieved when the refrigerant is carbon dioxide. Furthermore, when the refrigerant is carbon dioxide, in addition to the shortening of the distance of movement of the rod, the amount of the refrigerant flowing from the discharge pressure region to the control pressure chamber in moving the rod in the direction that causes the valve hole to be closed needs to be reliably decreased to reliably suppress the flow rate of the refrigerant which passes through the valve hole.
The present invention is directed to a displacement control valve capable of shortening distance of movement of a reciprocation body having a valve body, and of reliably suppressing flow rate of refrigerant which passes through a valve hole in a control region, and of sufficiently performing lubrication in a compressor by ensuring the flow rate of refrigerant which passes through the valve hole at the minimum displacement of the compressor.
The present invention provides a displacement control valve for a clutchless type variable displacement compressor connected to an external refrigerant circuit. The compressor has a control pressure chamber. The compressor and the external refrigerant circuit have a discharge pressure region. The displacement control valve includes a first port, a second port, a refrigerant passage, a valve hole, a reciprocation body, a pressure sensing mechanism and a solenoid. The first port is in communication with the discharge pressure region. The second port is in communication with the control pressure chamber. The refrigerant passage connects the first port to the second port. The valve hole is provided in the refrigerant passage. The reciprocation body has a valve body for opening and closing the valve hole. The reciprocation body includes a first shaft portion that has the valve body and a second shaft portion that is coaxial with the first shaft portion and inserted in the valve hole. The pressure sensing mechanism moves the reciprocation body in a direction that causes the valve hole to be opened in accordance with pressure in the discharge pressure region. The solenoid urges the reciprocation body in a direction that causes the valve hole to be closed. The first shaft portion is located adjacent to the solenoid. The second shaft portion is connected to the pressure sensing mechanism. The second shaft portion and the valve hole define a flow path in which refrigerant freely flows. A throttle portion is formed between the first and second shaft portions and coaxial with the first and second shaft portions. Diameter of an end of the throttle portion adjacent to the second shaft portion is set larger than that of the second shaft portion adjacent to the throttle. Flow rate of the refrigerant in the flow path is suppressed by the throttle portion.
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.
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:
The following will describe a displacement control valve for a clutchless type variable displacement compressor (hereinafter merely referred to as “displacement control valve”) according to a first embodiment of the present invention with reference to
The front housing 13 has a control pressure chamber 16 formed therein, whose rear end is closed by the cylinder block 12. A drive shaft 17 is freely rotatably supported by a radial bearing 18 provided in the front housing 13 and a radial bearing 19 provided in the cylinder block 12 so as to extend through the vicinity of the center of the control pressure chamber 16. A sealing mechanism 20 is provided in front of the radial bearing 18 which supports the front part of the drive shaft 17 so as to keep in slide contact with the circumferential surface of the drive shaft 17. The sealing mechanism 20 has a lip seal member and the like to prevent refrigerant in the control pressure chamber 16 from leaking through the clearance between the front housing 13 and the drive shaft 17.
The front end of the drive shaft 17 is connected to an external drive source (not shown) through a power transmission mechanism (not shown). The power transmission mechanism is a clutchless mechanism provided by a combination of a belt and a pulley, which enables power to be continuously transmitted.
A lug plate 21 is fixedly mounted on the drive shaft 17 in the control pressure chamber 16, which enables the lug plate 21 to be integrally rotated with the drive shaft 17. A swash plate 23 which forms a displacement changing mechanism 22 is supported by the drive shaft 17 in the rear of the lug plate 21 so as to be capable of sliding along and of inclining relative to the axial direction of the drive shaft 17. A hinge mechanism 24 is interposed between the swash plate 23 and the lug plate 21, through which the swash plate 23 is connected to the lug plate 21 and the drive shaft 17 so as to be capable of synchronously rotating with and of inclining relative to the lug plate 21 and the drive shaft 17.
A coil spring 25 is wound around a part of the drive shaft 17 between the lug plate 21 and the swash plate 23, and pushing force thereof urges a tubular body 26 freely slidably fitted on the drive shaft 17 rearward. The swash plate 23 is continuously pushed rearward, or in a direction of decrease of inclination of the swash plate 23, by the tubular body 26 urged by the coil spring 25. It is noted that inclination of the swash plate 23 means an angle made by a plane perpendicular to the drive shaft 17 and the plane of the swash plate 23. A stopper portion 23a projects from the front face of the swash plate 23. When the stopper portion 23a is in contact with the lug plate 21 as shown in
Each cylinder bore 12a of the cylinder block 12 has a single-headed piston 29 disposed therein so as to be capable of reciprocating therein. A neck portion of each piston 29 engages with the periphery of the swash plate 23 through a pair of shoes 30. As the swash plate is rotated with the rotation of the drive shaft 17, each piston 29 is reciprocated through the corresponding pair of shoes 30.
On the other hand, as shown in
The valve plate 32 forms the compression chambers 31 in the cylinder bores 12a together with the pistons 29, respectively. The valve plate 32 also has the suction ports 36 in communication with the suction chamber 38 in the rear housing 14 and the discharge ports 37 in communication with the discharge chamber 39 in the rear housing 14. The valve body forming plate 33 is a suction valve forming plate which forms suction valves (not shown) interposed between the compression chambers 31 and the suction chamber 38. On the other hand, the valve body forming plate 34 is a discharge valve forming plate which forms reed type discharge valves 34a interposed between the discharge ports 37 and the discharge chamber 39. The retainer 35 regulates maximum opening of each discharge valve 34a.
Incidentally, while the piston 29 is moved from its top dead center to its bottom dead center, the refrigerant in the suction chamber 38 is introduced into its compression chamber 31 through its suction port 36 and its suction valve. While the piston 29 is moved from its bottom dead center to its top dead center, the refrigerant introduced into the compression chamber 31 is compressed to a predetermined pressure and then discharged into the discharge chamber 39 through its discharge port 37 and its discharge valve 34a. The inclination of the swash plate 23 is determined on the basis of the balance between moments such as moment of rotational movement caused by centrifugal force of the swash plate 23, moment caused by inertia force of the reciprocation of each piston 29, moment caused by pressure of the refrigerant, and the like. The moment caused by pressure of the refrigerant is moment generated on the basis of the correlation between the pressure in each compression chamber 31 and the pressure in the control pressure chamber 16 which is applied to the back surface of each piston 29, and is applied to the swash plate 23 in the direction of increase or decrease of inclination in accordance with fluctuation of the pressure in the control pressure chamber 16.
An external refrigerant circuit will now be described. The suction chamber 38 is connected to an external refrigerant circuit 42 through an inlet 40 formed in the rear housing 14, and the refrigerant in the external refrigerant circuit 42 is supplied to the suction chamber 38 through the inlet 40. In the present embodiment, the suction chamber 38 and the inlet 40 are included in a suction pressure region. Also, the discharge chamber 39 is connected to the external refrigerant circuit 42 through an outlet 41 formed in the rear housing 14, and the refrigerant in the discharge chamber 39 is supplied to the external refrigerant circuit 42 through the outlet 41. The external refrigerant circuit 42 includes a condenser 43 which absorbs heat from the refrigerant, an expansion valve 44 and an evaporator 45 which transfers heat to the refrigerant.
The expansion valve 44 is a temperature sensing type automatic expansion valve for controlling flow rate of the refrigerant in accordance with temperature fluctuation of the refrigerant downstream from the evaporator 45. A throttle 46 is provided in a part of the external refrigerant circuit 42 downstream from the outlet 41 and upstream from the condenser 43. In the present embodiment, for the sake of convenience, a part of the external refrigerant circuit 42 between the outlet 41 and the throttle 46 is an upstream circuit 42a on the discharge side of the external refrigerant circuit 42, and a part of the external refrigerant circuit 42 between the throttle 46 and the condenser 43 is a downstream circuit 42b on the discharge side of the external refrigerant circuit 42. In the present embodiment, the discharge chamber 39, the upstream circuit 42a and the downstream circuit 42b are included in a discharge pressure region.
In the first embodiment, the compressor 10 uses a displacement control valve 50 to adjust the pressure in the control pressure chamber 16, thereby to appropriately change the moment caused by pressure of the refrigerant. This enables inclination of the swash plate 23 to be set at an optional angle between the minimum inclination and the maximum inclination.
As shown in
The valve housing 51 has a pressure sensing chamber 52 and a valve chamber 53 formed therein. The pressure sensing chamber 52 is located on one end of the valve housing 51, and the valve chamber 53 is located next to the pressure sensing chamber 52. A partition wall 51a which has a valve hole 54 formed therethrough is formed between the pressure sensing chamber 52 and the valve chamber 53 to separate the pressure sensing chamber 52 from the valve chamber 53. The valve housing 51 also has a first pressure sensing chamber port 55 that serves as a first port, and a valve chamber port 57 that serves as a second port formed therein. The pressure sensing chamber 52 is in communication with the downstream circuit 42b through the first pressure sensing chamber port 55. The valve chamber 53 is in communication with the 20 control pressure chamber 16 through the valve chamber port 57. In addition, as shown in
The valve housing 51 has a supply passage formed therein ranging from the first pressure sensing chamber port 55 to the valve chamber port 57 through the valve hole 54. The supply passage serves as a refrigerant passage. That is, the supply passage formed between the first pressure sensing chamber port 55 and the valve chamber port 57 includes a low-pressure chamber 52a which is a part of the pressure sensing chamber 52, the valve chamber 53 and the valve hole 54. The first pressure sensing chamber port 55 is in communication with the downstream circuit 42b through a passage 59 and is exposed to pressure PdL of the downstream circuit 42b. The second pressure sensing chamber port 56 is in communication with the upstream circuit 42a through a passage 60 and is exposed to pressure PdH of the upstream circuit 42a. The valve chamber port 57 is in communication with the control pressure chamber 16 through a passage 61 and is exposed to pressure Pc of the control pressure chamber 16. Incidentally, while the pressure of the refrigerant in the discharge chamber 39 and the upstream circuit 42a is high, the pressure of the refrigerant is decreased in order of the downstream circuit 42b, the control pressure chamber 16 and the suction chamber 38. It is noted that when the compressor 10 is operated at maximum displacement, the suction chamber 38 has the same pressure as the control pressure chamber 16.
The pressure sensing chamber 52 accommodates the pressure sensing mechanism 62 therein. The pressure sensing mechanism 62 has a bellows 63 which divides the pressure sensing chamber 52 into the low-pressure chamber 52a and a high-pressure chamber 52b. A fixed end of the bellows 63 is fixed to the end wall member 58. The pressure sensing chamber 52 has the high-pressure chamber 52b formed inside the bellows 63, and the high-pressure chamber 52b is in communication with the second pressure sensing chamber port 56. The pressure sensing chamber 52 also has the low-pressure chamber 52a formed outside the bellows 63, and the low-pressure chamber 52a is in communication with the first pressure sensing chamber port 55. A movable member 64 is mounted on a movable end of the bellows 63. The pressure differential between the high-pressure chamber 52b and the low-pressure chamber 52a gives force in a direction of extension of the bellows 63 to the movable member 64. Therefore, when the pressure differential between the high-pressure chamber 52b and the low-pressure chamber 52a exists, the force in a direction of extension of the bellows 63 is given to the movable member 64.
The solenoid 66 is connected to an end of the valve housing 51 adjacent to the valve chamber 53, or the other end of the valve housing 51. The solenoid 66 has a fixed core 67 which faces the valve chamber 53, and the fixed core 67 seals the other end of the valve housing 51. The solenoid 66 also has a movable core 68 which faces the fixed core 67, and an electromagnetic coil 69 which is formed so as to enclose the fixed core 67 and the movable core 68. The fixed core 67 has a hole 67a formed through the center thereof, and the hole 67a has a larger diameter than the valve hole 54. The axial center of the hole 67a is coaxial with that of the valve hole 54. The fixed core 67 attracts the movable core 68 by excitation by current supply to the electromagnetic coil 69. The solenoid 66 is controlled by a current supply control (a duty cycle control) based on a duty ratio of a control unit (not shown).
The rod 70 will now be described. In the first embodiment, the rod 70 mainly includes a first shaft portion 71 and a second shaft portion 72, and is disposed in the valve housing 51. The first shaft portion 71 is a round bar, and corresponds to a part of the rod 70 located from the solenoid 66 to the valve chamber 53. The first shaft portion 71 has a larger diameter than the valve hole 54. In the present embodiment, most of the first shaft portion 71 is located in the hole 67a of the fixed core 67 so as to slide along the hole 67a. An end of the first shaft portion 71 adjacent to the solenoid 66 is connected to the movable core 68. Since the diameter of the first shaft portion 71 is set larger than that of the valve hole 54, an end of the first shaft portion 71 adjacent to the valve hole 54 includes the valve body 72 that serves as a valve for opening and closing the valve hole 54. That is, when the first shaft portion 71 including the valve body 72 is in contact with the partition wall 51a which faces the valve chamber 53, the valve hole 54 is closed. Also, when the contact between the first shaft portion 71 and the partition wall 51a is released, the valve hole 54 is opened.
A spring acceptor 73 having a flanged shape is mounted on the first shaft portion 71 so as to locate in the valve chamber 53, and a coil spring 74 is interposed between the spring acceptor 73 of the first shaft portion 71 and the partition wall 51a. When the movable core 68 is not operated by excitation of the electromagnetic coil 69, the coil spring 74 is capable of moving the rod 70 toward the solenoid 66. That is, the coil spring 74 gives the first shaft portion 71 urging force in a direction that causes the movable core 68 to be spaced away from the fixed core 67 through the spring acceptor 73. The end of the first shaft portion 71 which faces the valve hole 54 is connected to the second shaft portion 75 through a throttle portion 76. The second shaft portion 75 is a round bar and is coaxial with the first shaft portion 71. The second shaft portion 75 has a much smaller diameter than the valve hole 54 and extends through the valve hole 54 to be connected to the pressure sensing mechanism 62. Therefore, a clearance between the valve hole 54 and the second shaft portion 75 having an annular cross section forms a flow path when the valve body 72 opens the valve hole 54. The flow path forms a part of the refrigerant passage.
The throttle portion 76 will now be described. As shown in
Meanwhile, as shown in
Operation of the displacement control valve of the present embodiment will now be described with reference to
On the other hand,
As shown in
The following will describe the case where the valve hole 54 is opened by the movement of the rod 70 from the state where the valve hole 54 is closed by the valve body 72. When the rod 70 is moved in the direction that causes the valve hole 54 to be opened, the valve body 72 is spaced away from the valve hole 54 thereby to gradually open the valve hole 54. When the valve body 72 begins to open the valve hole 54, since the throttle portion 76 is deeply inserted in the valve hole 54, the cross sectional area of the flow path is relatively in a small state. At this time, the flow rate of the refrigerant is sufficiently throttled by the throttle portion 76 and a small amount of the refrigerant passes through the flow path. The cross sectional area of the flow path provided by the valve hole 54 and the tapered surface 76a is gradually increased with the movement of the rod 70. Since the inclination of the tapered surface 76a which inclines relative to the direction of movement of the rod 70 is a gradual angle regardless of the diameter of the second shaft portion 75, the flow rate of the refrigerant is not rapidly changed in the process of increasing the cross sectional area of the flow path. When the throttle portion 76 is removed from the valve hole 54 by the additional movement of the rod 70, the cross sectional area of the flow path becomes the maximum value provided by the valve hole 54 and the second shaft portion 75 thereby to enable a sufficient amount of the refrigerant to flow through the valve hole 54. It is noted that an opening state or closing state of the valve hole 54 by the valve body 72 is mainly determined on the basis of the balance between the exciting force of the solenoid 66, the urging force of the coil spring 74 and the urging force of the pressure sensing mechanism 62.
The displacement control valve 50 of the present embodiment has the following advantageous effects.
(1) Since the throttle portion 76 has the tapered surface 76a that is tapered from the first shaft portion 71 toward the second shaft potion 75, when the rod 70 is moved in the direction that causes the valve hole 54 to be closed thereby to insert a part of the throttle portion 76 into the valve hole 54, a part of the cross sectional area of the flow path is gradually decreased by the throttle portion 76. Therefore, the flow rate of the refrigerant flowing from the first pressure sensing chamber port 55 toward the valve chamber port 57 through the valve hole 54 is throttled in accordance with the position of the tapered surface 76a in the valve hole 54 thereby to stably sufficiently suppress the flow rate of the refrigerant. Thus, even when the throttle portion 76 has the tapered surface 76a, the increase of the distance of movement of the rod 70 is suppressed and at the same time controllability in a control region in which displacement of the compressor 10 is varied is reliably maintained.
(2) Since the first shaft portion 71, the second shaft portion 75 and the throttle portion 76 are integrally manufactured as a unit to form the rod 70, the reciprocation body is more easily processed and manufactured compared to the case where they are separately manufactured to form the reciprocation body. In addition, the number of parts is decreased.
(3) Since the axial length of the throttle portion 76 is set to be shorter than the distance of movement of the rod 70, there is no need to set the distance of movement of the rod 70 in accordance with the axial length of the throttle portion 76. Therefore, the exciting force of the solenoid that causes the movement of the rod 70 is reduced thereby to enable saving of the electric power of the solenoid 66 and reduction of the size of the solenoid 66, for example.
(4) When the refrigerant is carbon dioxide, the difference of elevation of the pressure of the refrigerant becomes remarkable compared to that of the other refrigerant. This enables a sufficient flow rate of the refrigerant to be flowed into the valve hole 54 by slightly spacing the valve body 72 away from the valve hole 54. In the state where the valve body 72 closes the valve hole 54, when the valve body 72 is spaced away from the partition 51a to begin to open the valve hole 54, the clearance between the tapered surface 76a and the valve hole 54 is sufficiently reduced thereby to suppress the rapid change of the flow rate of the refrigerant. At the same time, as the valve body 72 opens the valve hole 54, the throttle portion 76 enables the flow rate of the refrigerant flowing from the discharge pressure region into the control pressure chamber 16 to be gradually increased in accordance with the position of the tapered surface 76a in the valve hole 54 thereby to stably change the flow rate of the refrigerant which passes through the valve hole 54.
(5) Since the throttle portion 76 is removed from the valve hole 54 while the compressor 10 is operated at its minimum displacement, the flow rate of the refrigerant is not suppressed. That is, since the flow rate of the refrigerant is ensured by the large clearance between the outer circumferential surface of the second shaft portion 75 and the inner circumferential surface of the valve hole 54, the lubrication in the compressor 10 is sufficiently performed.
A displacement control valve according to a second embodiment of the present invention will now be described with reference to
The diameter of the throttle portion 86 is set smaller than the inside diameter of the valve hole 54. As shown in
The displacement control valve of the present embodiment has the following effects in addition to the effects (3) and (5) of the first embodiment.
(6) When the rod 81 is moved in the direction that causes the valve hole 54 to be closed thereby to insert a part of the throttle portion 86 into the valve hole 54, a part of the cross sectional area of the flow path is immediately decreased by the throttle portion 86. Therefore, the flow rate of the refrigerant flowing from the first pressure sensing chamber port 55 toward the valve chamber port 57 through the valve hole 54 is throttled by the throttle portion 86 in the valve hole 54 thereby to sufficiently suppress the flow rate of the refrigerant. Thus, controllability in a control region in which displacement of the compressor 10 is varied is reliably maintained.
(7) Since the first shaft portion 82, the second shaft portion 85 and the throttle portion 86 are integrally manufactured as a unit to form the rod 81, the reciprocation body is more easily processed and manufactured compared to the case where the reciprocation body including a projection member which has the conventional tapered surface is manufactured.
(8) When the refrigerant is carbon dioxide, the difference of elevation of the pressure of the refrigerant becomes remarkable compared to that of the other refrigerant. This enables a sufficient flow rate of the refrigerant to be flowed into the valve hole 54 by slightly spacing the valve body 83 away from the valve hole 54. When the rod 81 is moved in the direction that causes the valve hole 54 to be closed thereby to insert a part of or the entirety of the throttle portion 86 into the valve hole 54, the amount of the refrigerant flowing from the discharge pressure region to the control pressure chamber 16 is reliably decreased by the throttle portion 86 thereby to reliably suppress the flow rate of the refrigerant which passes through the valve hole 54.
A displacement control valve according to a third embodiment of the present invention will now be described with reference to
The throttle portion 95 is coaxial with the first shaft portion 92 and the second shaft portion 94, and is interposed between the first shaft portion 92 and the second shaft portion 94. The first throttle portion 96 is tapered from the first shaft portion 92 toward the second shaft portion 94. Therefore, the first throttle portion 96 has the tapered surface 96a so as to be tapered from the first shaft portion 92 toward the second shaft portion 94. The second throttle portion 97 extends from the first throttle portion 96 toward the second shaft portion 94 with the same diameter. The diameter of the second throttle portion 97 is set larger than that of the second shaft portion 94. The throttle portion 95 is integrally formed with the first shaft portion 92 and the second shaft portion 94 to form a part of the rod 91.
In the displacement control valve 90 of the present embodiment, the control of the flow rate caused by the throttle portion 95 is a fixed control of the flow rate caused by the operation of the circumferential surface 97a of the second throttle portion 97 in the state where only the second throttle portion 97 is inserted in the valve hole 54. The control of the flow rate caused by the throttle portion 95 is a movable control of the flow rate caused by the operation of the tapered surface 96a of the first throttle portion 96 in the state where the first throttle portion 96 is inserted in the valve hole 54. That is, the operation of the control of the flow rate caused by the throttle portion 95 is switched in accordance with the position of the insertion of the first throttle portion 96 and the second throttle portion 97 into the valve hole 54. The present embodiment has a part of the effects (6), (8) of the second embodiment in addition to the effects (1), (3), (4) of the first embodiment.
The present invention is not limited to the first through third embodiments, but may be variously modified within the scope of the invention. For example, the above embodiments may be modified as follows.
In each of the embodiments, the displacement control valve has the pressure sensing mechanism caused by the pressure difference between the upstream circuit and the downstream circuit on the discharge side of the discharge pressure region. However, the present invention may be applicable to a displacement control valve which has a pressure sensing mechanism caused by the pressure difference between the discharge pressure region and the suction pressure region. Alternatively, the present invention may also be applicable to a displacement control valve which has a pressure sensing mechanism caused by the pressure difference between the discharge pressure region and a control pressure region. In these cases, it is preferable that a refrigerant passage or a necessary chamber is added to the displacement control valve in accordance with the arrangement of the pressure sensing chamber and the valve chamber.
In each of the embodiments, although the throttle is provided in the external refrigerant circuit to separate the upstream circuit from the downstream circuit, the throttle may be provided in the outlet to introduce the refrigerant upstream from the discharge chamber or the throttle in the outlet into the high-pressure chamber in the control valve and to introduce the refrigerant downstream from the throttle in the outlet or in the discharge pressure region in the external refrigerant circuit into the low-pressure chamber in the control valve.
In each of the embodiments, although the displacement control valve allows the refrigerant in the discharge pressure region to flow into the control pressure chamber or prevents the refrigerant in the discharge pressure region from flowing into the control pressure chamber, the present invention is applicable to the displacement control valve which includes at least a passage which enables the refrigerant in the discharge pressure region to flow into the control pressure chamber. For example, the displacement control valve may be a three-way valve which includes a passage which enables the refrigerant in the discharge pressure region to flow into the control pressure chamber.
In each of the embodiments, although the type of the refrigerant is not specified, the type of the refrigerant is not specifically required. For example, the use of fluorocarbon-based gas or carbon dioxide is preferable. The refrigerant may be gas or liquid.
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 of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| P2005-127236 | Apr 2005 | JP | national |
| P2005-200315 | Jul 2005 | JP | national |
