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(11) | EP 0 896 154 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Variable displacement compressor in which a communication passage between a crank chamber and a suction chamber is improved in relation to a mounting posture of the compressor |
| (57) In a variable displacement compressor designed to be set with a predetermined posture
and having, between a suction chamber (13) and a crank chamber (3), a first communication
passage (18) controlled in dependence on a pressure differential therebetween and
a second communication passage (20) with a particular portion therebetween at which
a control valve (19) is disposed, the particular portion is located higher than another
portion of the second communication passage in the predetermined posture. A displacing
arrangement is placed in the crank chamber and displaces gas from the suction chamber
to a discharge chamber (14) with a variable displacement. Another control valve (16)
is disposed in the first communication passage to control opening and closing of the
first communication passage in dependence on the pressure differential. |
Background of the Invention:
[0001] The present invention relates to a variable displacement compressor suitable for use in a vehicle air conditioner or the like.
[0002] Japanese Second (examined) Utility Model Publication No. 2-17186 discloses a wobble plate type variable displacement compressor as one of variable displacement compressors for use in vehicle air conditioners. The disclosed compressor includes two communication passages each extending from a crank chamber to a suction chamber. One of the communication passages is provided therein with a bellows valve sensitive to a crank pressure, while the other communication passage is provided therein with an electromagnetic valve or a solenoid valve. While the solenoid valve is closed, a displacement control is carried out by the bellows valve to change the crank pressure so as to keep a suction pressure essentially constant. On the other hand, while the solenoid valve is opened, since communication is established between the crank chamber and the suction chamber irrespective of the opening state of the bellows valve, there is approximately no pressure differential between the crank chamber and the suction chamber so that an inclination of a swash plate becomes maximum to enable an operation of the compressor with the maximum piston stroke. Accordingly, by opening the solenoid valve using an arbitrary external signal, the maximum displacement operation can be forcibly realized.
[0003] However, when the compressor is operated with the maximum displacement by opening the solenoid valve, gas and oil in the crank chamber flows out into the communication passage so that a portion of the oil stays in the communication passage and the solenoid valve. If the compressor and the solenoid valve are activated in this state after, for example, being stopped in the low ambient temperatures, it is possible that a plunger of the solenoid valve can not move instantaneously due to increased viscosity of the oil at the low temperatures so that the maximum displacement can not be obtained. It is further possible that a substantial passage open area is diminished due to the oil staying in the communication passage so that a pressure loss is caused even if the solenoid valve is opened. This may cause an increase in pressure differential between the crank chamber and the suction chamber to reduce the piston stroke so that the maximum displacement can not be obtained.
Summary of the Invention:
[0004] It is therefore an object of the present invention to provide variable displacement compressor having a structure wherein oil is not liable to stay in a communication passage extending between a crank chamber and a suction chamber and including a solenoid valve therein.
[0005] According to one aspect of the present invention, there is provided a variable displacement compressor comprising a discharge chamber, a suction chamber, a crank chamber, displacing means placed in the crank chamber for displacing gas from the suction chamber to the discharge chamber with a variable displacement which is dependent on a pressure differential between the suction chamber and the crank chamber, a first communication passage establishing communication between the crank chamber and the suction chamber, a first control valve disposed in the first communication passage to control opening and closing of the first communication passage in dependence on the pressure differential, a second communication passage establishing communication between the crank chamber and the suction chamber and having a particular portion between the crank chamber and the suction chamber, and a second control valve disposed in the second communication passage for controlling opening and closing of the second communication passage at the particular portion, the compressor being designed to be set with a predetermined posture, the particular portion being located higher than another portion of the second communication passage in the predetermined posture.
[0006] According to another aspect of the present invention, there is provided a variable displacement compressor comprising a compressor casing having a crank chamber and a plurality of cylinder bores which is connected to the crank chamber and arranged around an axis extending in a horizontal direction in a mounting posture of the compressor, a plurality of pistons inserted in the cylinder bores, respectively, to be movable in the horizontal direction, a rear housing placed at one end of the compressor casing in the horizontal direction to form a suction chamber and a discharge chamber, a valve plate placed between the compressor casing and the rear housing, a front housing placed at another end of the compressor casing in the horizontal direction to close the crank chamber, a drive shaft extending along the axis and rotated around the axis, a crank mechanism connected to the drive shaft and the pistons in the crank chamber for moving the pistons in dependence on the rotation of the drive shaft, a first communication passage establishing communication between the crank chamber and the suction chamber, a first control valve disposed in the first communication passage to control opening and closing of the first communication passage in dependence on the pressure differential, a second communication passage establishing communication between the crank chamber and the suction chamber and having a particular portion between the crank chamber and the suction chamber, and a second control valve disposed in the second communication passage for controlling opening and closing of the second communication passage at the particular portion, the particular portion being located higher than another portion of the second communication passage in the mounting posture of the compressor.
Brief Description of the Drawing:
[0007]
Fig. 1 is a sectional view of a variable displacement compressor according to a first preferred embodiment of the present invention;
Fig. 2 is a sectional view of a pressure control valve used in the variable displacement compressor shown in Fig. 1;
Fig. 3 is a graph showing a pressure control characteristic of the pressure control valve shown in Fig. 2;
Fig. 4 is a sectional view of a variable displacement compressor according to a second preferred embodiment of the present invention; and
Fig. 5 is a sectional view of a solenoid valve inserting portion of the variable displacement compressor shown in Fig. 4.
Description of the Preferred Embodiment:
[0008] Referring now to Fig. 1, a variable displacement compressor according to the first preferred embodiment of the present invention will be described hereinbelow, wherein the compressor is of a wobble plate type well known in the art.
[0009] The shown compressor is for use in compressing refrigerant gas in a vehicle air conditioner and comprises a compressor casing 1 having a through hole at the center thereof. A main shaft 2 is inserted into this through hole and rotatably supported by the casing 1 via bearings 1a and 1b.
[0010] The casing 1 defines therein a crank chamber 3 wherein a rotor 4 is mounted on the main shaft 2. A swash plate 5 is coupled to the rotor 4 via a hinge mechanism 41 and slidably mounted on the main shaft 2. An inclination of the swash plate 5 relative to the main shaft 2 can be changed by means of the hinge mechanism 41. A wobble plate 6 is attached to the swash plate 5 via a bearing 51, and a plurality of piston rods 7 are coupled to the wobble plate 6 through ball connection.
[0011] The casing 1 is formed with a plurality of cylinders 8 which are arranged at regular intervals so as to surround the main shaft 2. Each of the piston rods 7 is coupled through ball connection to corresponding one of pistons 9 disposed in the respective cylinders 8. In the crank chamber 3, a guide rod 10 is supported by the casing 1 so as to extend in parallel to the main shaft 2. The guide rod 10 is sandwiched by an end portion of the wobble plate 6 so that the end portion of the wobble plate 6 is capable of wobbling relative to the guide rod 10 in an axial direction of the main shaft 2.
[0012] To a right end surface of the casing 1, a cylinder head 12 is attached via a valve plate 11 interposed therebetween, so as to close a right-side open end of the casing 1. The cylinder head 12 is formed with a suction chamber 13 and a discharge chamber 14. The suction chamber 13 communicates with a suction port 13a, while the discharge chamber 14 communicates with a discharge port (not shown). The valve plate 11 is formed with suction holes 11a and discharge holes 11b. The suction chamber 13 and the discharge chamber 14 communicate with the cylinders 8 via the suction holes 11a and the discharge holes 11b, respectively. At the center of the valve plate 11, a suction valve (not shown), a discharge valve (not shown) and a valve retainer 15 are fixedly mounted by means of a pressure control valve 16 and a nut 17. The pressure control valve 16 is referred to as a first control valve and disposed in a first communication passage 18 extending from the crank chamber 3 to the suction chamber 13. When the pressure control valve 16 is opened, the crank chamber 3 and the suction chamber 13 communicate with each other.
[0013] When the main shaft 2 is rotated, the rotor 4 rotates together with the swash plate 5 with respect to an axis of the main shaft 2. In response to rotation of the swash plate 5, the wobble plate 6 reciprocates the pistons 9 within the cylinders 8 through the piston rods 7 to displace the refrigerant gas from the suction chamber 13 to the discharge chamber 14 with a variable displacement in the manner known in the art. A combination of the rotor 4, the swash plate 5, the wobble plate 6, and the piston rods 7 will be called a crank mechanism. A combination of the crank mechanism and the pistons 9 is referred to as a displacing arrangement.
[0014] The discharge chamber 14 and the crank chamber 3 are in constant communication with each other through a fixed restrictor (not shown) so as to utilize a portion of discharged gas, in addition to blowby gas, as an increasing element for a pressure in the crank chamber 3.
[0015] As shown in Fig. 2, the pressure control valve 16 comprises a valve member 161 for opening and closing the first communication passage 18, and a bellows 162 fixed to the valve member 161 and sensitive to a pressure in the crank chamber 3. The inside of the bellows 162 is under vacuum and provided with a spring. The pressure control valve 16 further comprises a transfer rod 164 which receives at one end surface thereof a pressure of the discharge chamber 14 and applies a resultant acting force to the valve member 161 via a spring 163, and a casing 165 forming a valve seat for the valve member 161. Since a pressure in the suction chamber 13 is applied to an upper portion of the valve member 161, the pressure control valve 16 controls the opening state of the valve member 161 in response to the pressure in the suction chamber 13 so as to substantially control the suction pressure. Further, in response also to the pressure in the discharge chamber 14, the pressure control valve 16 changes the suction pressure depending on the discharge pressure as shown in Fig. 3.
[0016] At an upper portion of the casing 1, a solenoid valve 19 is disposed to open and close a second communication passage 20 extending from the crank chamber 3 to the suction chamber 13. Specifically, while the solenoid valve 19 is closed, the discharge displacement is controlled based on the suction pressure control characteristic shown in Fig. 3. On the other hand, while the solenoid valve 19 is opened, since the crank chamber 3 and the suction chamber 13 are in constant communication with each other through the second communication passage 20, there is essentially no pressure differential between the crank chamber 3 and the suction chamber 13. As a result, the inclination of the swash plate 5 becomes maximum so that the compressor is operated with the maximum piston stroke. The solenoid valve 19 is referred to as a second control valve.
[0017] It is to be noted that the second communication passage 20 has a particular portion 21 at which the solenoid valve 19 is disposed, an inlet side portion 22 between the crank chamber 3 and the particular portion 21, and an outlet side portion 23 between the particular portion 21 and the suction chamber 13. Each of the inlet side and the outlet side portions 22 and 23 is located lower than the particular portion 21.
[0018] A mounting attitude of the foregoing compressor is regulated such that the main shaft 2 should be horizontal. In other words, the compressor is designed to be set with a predetermined posture. In this mounting attitude or posture, the inlet side portion 22 of the second communication passage 20, extending from a crank chamber side opening to a solenoid valve inlet side pressure chamber 20a, and the outlet side portion 23 of the second communication passage 20, extending from a solenoid valve outlet side pressure chamber 20b to a suction chamber side opening are positioned below a contact portion between the valve member 191 and the valve seat 192 of the solenoid valve 19. Thus, essentially no oil stays in the solenoid valve 19. Further, the crank chamber side opening of the inlet side portion 22 of the second communication passage 20 is opened at an upper portion of the inner periphery of the crank chamber 3. Thus, even while the compressor is stopped, the opening is positioned above the oil level in the crank chamber 3 so that the second communication passage 20 is not closed by the oil. Further, the foregoing two inlet side portion 22 and outlet side portion 23 of the second communication passage 20 are lowered in position toward the crank chamber 3 and the suction chamber 13, respectively. Thus, the oil remaining in the two inlet side portion 22 and outlet side portion 22 flows toward the crank chamber 3 and the suction chamber 13, respectively, so that essentially no oil stays in these portions. As seen from Fig. 1, the latter portion of the second communication passage 20, that is, the outlet side portion 23 extending from the solenoid valve outlet side pressure chamber 20b to the suction chamber side opening, has a tapered shape.
[0019] Since the solenoid valve 19 is positioned on the casing 1, the foregoing inlet side portion 22 of the second communication passage 20 can be set notably short.
[0020] With the foregoing structure, essentially no oil stays in the solenoid valve 19 and the second communication passage 20 while the compressor is stopped. Thus, upon restarting the compressor, the operation failure of the solenoid valve 19 or the pressure loss increase in the second communication passage 20 can be avoided.
[0021] Referring now to Figs. 4 and 5, a variable displacement compressor according to the second preferred embodiment of the present invention will be described hereinbelow. Since the second preferred embodiment differs from the first preferred embodiment only in arrangement of a solenoid valve 19 and a second communication passage 20, the following explanation will be given only thereto. Similar parts are designated by like reference numerals.
[0022] The solenoid valve 19 is arranged at an upper portion of the cylinder head 12, and opens and closes the second communication passage 20 extending from the crank chamber 3 to the suction chamber 13. The second communication passage 20 is positioned below a contact portion between a valve member (not shown) and a valve seat (not shown) of the solenoid valve 19. Further, a crank chamber side opening of the second communication passage 20 is opened at an upper portion of the inner periphery of the crank chamber 3. Moreover, a passage, of the second communication passage 20, extending from the crank chamber side opening to a solenoid valve inlet side pressure chamber 20a has a tapered shape such that the passage is lowered in position toward the crank chamber 3.
[0023] As appreciated, the second preferred embodiment can achieve effects similar to those achieved in the first preferred embodiment.
[0024] While the present invention has thus far been described in conjunction with a few preferred embodiments, it will readily be possible for those skilled in the art to put this invention into practice in various other manners. For example, although the description is made as regards the variable displacement compressor of the wobble plate type, the present invention is also applicable to a variable displacement compressor of a single swash plate type known in the art. It is preferable that the crank chamber side opening of the second communication passage is located above the axis of the main shaft in the foregoing mounting attitude and opened at the inner periphery of the crank chamber.
a discharge chamber (14);
a suction chamber (13);
a crank chamber (3)
displacing means (5, 6, 7, 9) placed in said crank chamber (3) for displacing gas from said suction chamber (13) to said discharge chamber (14) with a variable displacement which is dependent on a pressure differential between said suction chamber (13) and said crank chamber (3);
a first communication passage (18) establishing communication between said crank chamber (3) and said suction chamber (13);
a first control valve (16) disposed in said first communication passage (18) to control opening and closing of said first communication passage (18) in dependence on said pressure differential;
a second communication passage (20) establishing communication between said crank chamber (3) and said suction chamber (13) and having a particular portion (21) between said crank chamber (3) and said suction chamber (13); and
a second control valve (19) disposed in said second communication passage (20) for controlling opening and closing of said second communication passage (20) at said particular portion (21),
said compressor being designed to be set with a predetermined posture, said particular portion (21) being located higher than another portion of said second communication passage (20) in said predetermined posture.
wherein said first control valve (16) serves to adjust said pressure differential only when said second valve (19) closes said second communication passage.
a swash plate (5) rotatable with respect to an axis which is horizontal in said predetermined posture, said swash plate (5) having an inclined angle dependent on said pressure differential; and
a piston (9) connected to said swash plate (5) to reciprocate in response to a rotation of said swash plate (5) with a piston stroke which is dependent on said inclined angle; preferably making said variable displacement become greatest when said second valve (19) opens said second communication passage (20).
a valve seat (192) fixed to said particular portion (21); and
a valve member (191) cooperated with said valve seat (192) to control opening and closing said second communication passage (20), each of said inlet side and said outlet side portions (22, 23) being located lower than said valve seat (192).
a crank chamber periphery surface defining said crank chamber (3); and
a main shaft (2) connected to said displacing means and rotatable with respect to an axis which is horizontal in said predetermined posture, said inlet side portion (22) having an opening on said crank chamber periphery surface, said opening of the inlet side portion (22) being located higher than said axis of the main shaft (2) in said predetermined posture.
a compressor casing (1) having a crank chamber (3) and a plurality of cylinder bores (8) which are connected to said crank chamber (3) and arranged around an axis extending in a horizontal direction in a mounting posture of said compressor;
a plurality of pistons (9) inserted in said cylinder bores (8), respectively, to be movable in said horizontal direction;
a rear housing (12) placed at one end of said compressor casing (1) in said horizontal direction to form a suction chamber (13) and a discharge chamber (14);
a valve plate (11) placed between said compressor casing (1) and said rear housing (12);
a front housing placed at another end of said compressor casing (1) in said horizontal direction to close said crank chamber (3);
a drive shaft (2) extending along said axis and rotated around said axis;
a crank mechanism connected to said drive shaft (2) and said pistons (9) in said crank chamber (3) for moving said pistons (9) in dependence on the rotation of said drive shaft (2);
a first communication passage (18) establishing communication between said crank chamber (3) and said suction chamber (13);
a first control valve (16) dipsosed in said first communication passage (18) to control opening and closing of said first communication passage (18) in dependence on said pressure differential;
a second communication passage (20) establishing communication between said crank chamber (3) and said suction chamber (13) and having a particular portion (21) between said crank chamber (3) and said suction chamber (13); and
a second control valve (19) disposed in said second communication passage (20) for controlling opening and closing of said second communication passage (20) at said particular portion (21),
said particular portion (21) being located higher than another portion of said second communication passage (20) in said mounting posture of the compressor.