Patent Application
20050220631
This application claims priority of Japanese Application No. 2004-097964 filed on Mar. 30, 2004 and entitled “CONTROL VALVE FOR VARIABLE DISPLACEMENT COMPRESSOR”.
(1) Field of the Invention
The present invention relates to a control valve for a variable displacement compressor, and more particularly to a control valve for a variable displacement compressor which is suitable for controlling refrigerant displacement of a variable displacement compressor for an automotive air conditioner.
(2) Description of the Related Art
A compressor used in a refrigeration cycle of an automotive air conditioner is driven by an engine whose rotational speed varies depending on a traveling condition of the vehicle, and hence incapable of performing rotational speed control. To eliminate the inconvenience, a variable displacement compressor capable of changing the discharge amount of refrigerant is generally employed so as to obtain an adequate refrigerating capacity without being constrained by the rotational speed of the engine.
In a typical variable displacement compressor, a wobble plate is disposed within a gastightly-formed crankcase such that the inclination angle thereof can be changed, and driven by the rotational motion of a rotational shaft, for performing wobbling motion, and pistons caused to perform reciprocating motion in a direction parallel to the rotational shaft by the wobbling motion of the wobble plate draw refrigerant from a suction chamber into associated cylinders, compress the refrigerant, and then discharge the same into a discharge chamber. In doing this, the inclination angle of the wobble plate can be varied by changing the pressure in the crankcase, whereby the stroke of the pistons is changed for changing the discharge amount of the refrigerant. The control valve for a variable displacement compressor provides control to change the pressure in the crankcase.
In general, the control valve for variably controlling the displacement of the compressor introduces part of refrigerant discharged at discharge pressure Pd from the discharge chamber into the gastightly-formed crankcase, and controls pressure Pc in the crankcase through control of the amount of refrigerant thus introduced. The amount of introduced refrigerant is controlled according to suction pressure Ps in the suction chamber. That is, the control valve senses the suction pressure Ps, and controls the flow rate of refrigerant introduced at the discharge pressure Pd from the discharge chamber into the crankcase, so as to maintain the suction pressure Ps at a constant level.
To this end, the control valve is equipped with a pressure-sensing section for sensing the suction pressure Ps, and a valve section for causing a passage leading from the discharge chamber to the crankcase to open and close according to the suction pressure Ps sensed by the pressure-sensing section. Further, a type of control valve for a variable displacement compressor, which is capable of freely externally setting a value of suction pressure Ps to be assumed at the start of the variable displacement operation, is equipped with a solenoid that enables the set point of the pressure-sensing section to be varied by external electric current. The pressure-sensing section is generally implemented by a bellows, but there has also been proposed a control valve using a diaphragm.
In the control valve having a pressure-sensing section implemented by a diaphragm, the relative pressure between the suction pressure Ps and atmospheric pressure is sensed, and hence due to a change in atmospheric pressure between when the vehicle is running on a road at a high altitude and when the vehicle is running on a road at a low altitude, there occurs a control error. To solve this problem, a control valve has been proposed in which suction pressure is sensed as an absolute pressure and the control error due to the difference in altitude is thereby eliminated (see Japanese Unexamined Patent Publication (Kokai) No. 2004-36596).
This control valve is formed by arranging a vacuum chamber sealed by a diaphragm, a valve section for controlling the flow rate of refrigerant introduced from a discharge chamber into a crankcase, and a solenoid for setting a value of suction pressure Ps to be received by the diaphragm, in the mentioned order.
However, the conventional control valve is configured such that refrigerant flows through the valve section and the solenoid, and hence metal dust contained in the refrigerant circulating through a refrigeration cycle tends to affect the solenoid, particularly movable parts thereof.
The present invention has been made in view of this point, and an object thereof is to prevent the movable parts of a solenoid of a control valve for a variable displacement compressor, in which a diaphragm is used as a pressure-sensing section, from being adversely affected by metal dust contained in refrigerant.
To solve the above problem, the present invention provides a control valve for a variable displacement compressor, which is mounted on the variable displacement compressor for control of pressure in a gastightly-formed crankcase by sensing suction pressure by a diaphragm, wherein a core of a solenoid and a plunger urged in a direction away from the core are accommodated in a bottomed sleeve, and an open end of the bottomed sleeve is sealed by the diaphragm such that an inside of the bottomed sleeve is kept gastight.
The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.
This control valve for a variable displacement compressor has a valve section provided at an upper location, as viewed in
In the refrigerant passage via which the port 12 and the port 14 are communicated through the body 11, a valve seat 15 is formed integrally with the body 11. In opposed relation to a side of the valve seat 15, from which the pressure Pc is introduced, a valve element 16 is axially disposed in a manner movable to and away from the valve seat 15. The valve element 16 is integrally formed with a shaft 17 which extends downward as viewed in the figure, through a valve hole such that it is axially movably held by the body 11. The discharge pressure Pd from the discharge chamber is introduced into a small-diameter portion which connects between the valve element 16 and the shaft 17. The outer diameter of the shaft 17 is set to be equal to the inner diameter of the valve hole forming the valve seat 15 such that the pressure-receiving area of the valve element 16 is equal to that of the shaft 17. This causes a force of the discharge pressure Pd which acts on the valve element 16 in the upward direction as viewed in the figure to be cancelled out by a force acting on the shaft 17 in the downward direction as viewed in the figure, so as to prevent the control of the valve section from being adversely affected by the discharge pressure Pd which is high in pressure level.
The valve element 16 is urged by a spring 18 in the valve-closing direction, and load of the spring 18 is adjusted by an adjustment screw 19 screwed into the port 14.
Further, a port 20 communicating with a suction chamber of the variable displacement compressor to receive suction pressure Ps is formed in a lower portion of the body 11 as viewed in the figure.
A pressure-sensing section and a solenoid are arranged below the body 11, as viewed in the figure. More specifically, on the lower end of the body 11, there is disposed an assembly that is formed by accommodating a plunger 22, a core 23, and a spring 24, as component elements of the solenoid, in a bottomed sleeve 21 which forms a vacuum container, and sealing the opening of the bottomed sleeve 21 with a metal diaphragm 25, and outside the bottomed sleeve 21, there are arranged a coil 26, a ring 27, a case 28, and a handle 29, which are made of magnetic substances and constitute a yoke for establishing a magnetic circuit.
In the bottomed sleeve 21, the core 23 is rigidly press-fitted and the plunger 22 is axially movably disposed on a side of the core 23 toward the valve section. The plunger 22 is rigidly press-fitted on one end of a shaft 30 axially extending in the center of the core 23, and the other end of the shaft 30 is supported by a bearing 31 slidably disposed in the core 23. A stop ring 32 is fitted on an intermediate portion of the shaft 30, and a spring-receiving member 33 is formed such that the upward movement thereof as viewed in the figure is restricted by the stop ring 32. The spring 24 is interposed between the spring-receiving member 33 and the bearing 31. The plunger 22 is urged by the spring 24 via the shaft 30 in a direction away from the core 23. It should be noted that load of the spring 24 can be changed by externally adjusting the axial position of the bearing 31. More specifically, in final adjustment after assembly of the control valve for a variable displacement compressor, the bottom of the bottomed sleeve 21 is pushed to be deformed inward, whereby the axial position of the bearing 31 in abutment with the bottom is changed to adjust the load of the spring 24. Thus, the set point of the control valve is adjusted.
The bottomed sleeve 21 accommodating the plunger 22 and the core 23 as described above is sealed by welding the diaphragm 25 to a flange portion formed on the open end of the bottomed sleeve 21. For example, as shown in detail in
This assembly is fixed to the body 11 via a reinforcing ring 35 by positioning the flange portion of the bottomed sleeve 21 in a recess formed in the lower end of the body 11 and caulking the peripheral wall of the recess. Then, the case 28 accommodating the coil 26 is fixed to the body 11 by caulking an upper end 36 of the case 28.
Further, in mounting the assembly to the body 11, an O ring 37 is interposed between the patch 34 and the body 11 so as to seal between a chamber receiving the suction pressure Ps and the atmosphere, such that the center of the solid part of the O ring 37 is positioned at a location radially inward of a weld line 38. Thus, stress generated by the displacement of the diaphragm is prevented from reaching the weld line 38 which has become fragile due to a change in material caused by the welding.
The bottomed sleeve 21 is formed by deep-drawing of a stainless steel material, such as SUS304. The bottomed sleeve 21 is required to be formed of a non-magnetic material so as to prevent the bottomed sleeve 21 from attracting the plunger 22 during energization of the solenoid and thereby increasing sliding resistance. However, SUS304 is known to have a property that when subjected to strong cold working, it acquires magnetism due to a partial change in its metallic crystal structure. In such a case, the bottomed sleeve 21 is made non-magnetic again by subjecting the same to annealing.
On the other hand, the bottomed sleeve 21 also includes a portion which is desirably magnetic in view of the magnetic circuit. The portion is in an area in which is located the handle 29 magnetically connecting between the core 23 and the case 28. For this reason, a part of the bottom-side portion of the bottomed sleeve 21 which is formed by deep drawing to extend straight, is further drawn as shown in detail in
It should be noted that when the bottomed sleeve 21 is made of a stainless steel, the diaphragm 25 is also made of a stainless steel material for springs, called SUS304CSP, in view of welding. Of course, the materials of the bottomed sleeve 21 and the diaphragm 25 are not limited to the stainless steel materials, but it is also possible to use copper for the bottomed sleeve 21, and beryllium copper for the diaphragm 25.
In the arrangement described above, the ring 27, the case 28, and the handle 29 are formed of magnetic materials to serve as the yoke of the magnetic circuit of the solenoid. Magnetic lines of force generated by the coil 26 pass through the magnetic circuit formed by the case 28, the ring 27, the plunger 22, the core 23, and the handle 29.
Now, assuming that the automotive air conditioner is started and the variable displacement compressor is driven for rotation by an engine, the variable displacement compressor whose control valve is in its fully-closed state is operated with the maximum displacement.
When the variable displacement compressor continues to operate with the maximum displacement to make the suction pressure Ps from the suction chamber sufficiently low, the diaphragm 25, sensing the suction pressure Ps, moves upward as viewed in the figure. With this upward motion of the diaphragm 25, the plunger 22 moves away from the core 23 in a state abutted to the diaphragm 25. At this time, if control current supplied to the solenoid coil 26 is set to a value of cooling capacity corresponding to a temperature set for air conditioning, the plunger 22 stops in a position where the suction pressure Ps, the loads of the springs 18 and 24, and the attractive force of the solenoid are balanced. This causes the valve element 16 held in contact with the diaphragm 25 via the shaft 17 to be pushed upward by the diaphragm 25 to move away from the valve seat 15 so as to be set to a predetermined valve lift. Therefore, refrigerant at the discharge pressure Pd is introduced into the crankcase at a flow rate controlled to a value dependent on the valve lift, whereby the variable displacement compressor is controlled to perform operation with the displacement corresponding to the control current.
When the control current supplied to the coil 26 of the solenoid is constant, the diaphragm 25 senses the suction pressure Ps as an absolute pressure to thereby control the valve lift of the valve section. For example, when the refrigeration load increases to make the suction pressure Ps high, the diaphragm 25 is displaced downward as viewed in the figure, so that the valve element 16 is also moved downward to decrease the valve lift of the valve section, causing the variable displacement compressor to operate in a direction of increasing the displacement. On the other hand, when the refrigeration load decreases to make the suction pressure Ps low, the diaphragm 25 is displaced upward as viewed in the figure to increase the valve lift of the valve section, causing the variable displacement compressor to operate in a direction of decreasing the displacement. Thus, the control valve controls the displacement of the variable displacement compressor such that the suction pressure Ps becomes equal to a value set by the solenoid.
The control valve for a variable displacement compressor of the second embodiment is distinguished from the control valve for a variable displacement compressor of the first embodiment in that the shape of the diaphragm 25 is modified. As shown in detail in
This diaphragm 25 can have a larger stroke in the direction of displacement than that of the control valve of the first embodiment in which the pressure-sensing section is formed by a single thin metal plate, and hence the control range of the valve section can be expanded.
The control valve for a variable displacement compressor, according to the present invention, is configured such that an assembly is separately formed by sealing the bottomed sleeve containing the movable parts of the solenoid with the diaphragm such that the assembly has a vacuum inside, and the assembly is fixed to the body of the valve section. Further, the assembly is fixed to the body of the valve section with the solenoid coil arranged therearound. Therefore, the control valve is advantageous in its ease of construction.
The foregoing is considered as illustrative only of the principles of the present invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and applications shown and described, and accordingly, all suitable modifications and equivalents may be regarded as falling within the scope of the invention in the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-097964 | Mar 2004 | JP | national |
