Patent Application
20100143162
1. Field of the Invention
A suction shutoff valve for a variable displacement axial piston compressor to regulate gaseous fluid flow through an inlet suction passage in the compressor.
2. Description of the Prior Art
The control valves of the type to which the subject invention pertains are disposed in a suction passage of a variable displacement axial piston compressor for changing the open area of the suction passage in response to demand for fluid flow by the compressor. One such control valve is illustrated in U.S. Patent Application 2008/0107544 to Hibino wherein a control valve is disposed in a suction passage for regulating fluid flow through the compressor. The control valve includes a valve body, a valve piston slidably disposed in the valve body, and a chamber flange extending radially inward from the valve body to define a compression chamber between the valve piston and the chamber flange. The valve piston controls flow through valve holes and defines a valve orifice. The chamber flange defines a flange orifice and the two orifices restrict fluid flow through the valve piston and the chamber flange respectively. The valve piston responds to the change in crankcase pressure and suction pressure through the orifices to regulate fluid flow through the valve holes, but the orifices are fixed and therefore the response to pressure pulsations is directly proportional to the areas of the orifices.
Although the prior art control valves regulate gaseous fluid flow into a variable displacement compressor to reduce pressure pulsations, there remains a need for a control valve that is incrementally more precisely responsive to pressure pulsations.
The invention provides such a control valve including a modulating valve for variably and incrementally modifying fluid flow through the chamber flange from the compression chamber to the suction passage in response to a change in the pressure in the suction passage in relation to a predetermined pressure.
Accordingly, the subject invention provides a control valve which variably and incrementally more precisely responds to internal suction pressure and to pressure pulsations.
Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a variable displacement axial piston compressor 20 is shown in
The compressor 20 generally indicated includes a cylinder housing 24 defining piston cylinders 26. The compressor 20 also includes a valve plate 28 and a cylinder head 30. The cylinder head 30 defines an electronic control valve cavity 31 for receiving an electronic control valve (not shown) to adjust the crankcase pressure. The cylinder head 30 also defines a suction port 32, a valve chamber 34, a suction chamber 36, and discharge ports 38 all disposed serially for moving a gaseous fluid through the compressor 20. The valve chamber 34 and the suction chamber 36 together make up a suction passage 34, 36. The valve plate 28 is disposed between the cylinder head 30 and the cylinder housing 24 for controlling fluid flow into the piston cylinders 26 from the suction chamber 36 and out of the piston cylinders 26 into the discharge ports 38.
The suction port 32 has an entry diameter De followed axially by a middle diameter Dm, less or smaller than the entry diameter De, and an outlet diameter Do, less or smaller than the middle diameter Dm. The valve chamber 34 has a constant valve chamber diameter Dvc greater than the outlet diameter Do to define a shoulder 40 there between and the valve chamber 34 receives the gaseous fluid from the outlet diameter Do of the suction port 32.
The suction shutoff valve 22 is disposed in the valve chamber 34 and is aligned with the suction port 32 on an axis A for regulating gaseous fluid flow to the suction chamber 36. As best shown in
A valve piston 56 is slidably disposed in the inner diameter Di of the inlet end 44 of the valve body 42. The valve piston 56 has a base 58 and a skirt 60 extending axially from the base 58 and engaging the inner diameter Di of the valve body 42. The valve body 42 defines a chamber flange 62 extending radially inward from the inner diameter Di of the valve body 42 to define a compression chamber 64 which is closed between the valve piston 56 and the chamber flange 62. A piston spring 66 is disposed in the compression chamber 64 and interacts between the valve piston 56 and the chamber flange 62 for biasing the valve piston 56 axially into engagement with the valve retainer ring 52 to define a closed position covering the holes 54. The piston spring 66 is compressible for allowing the valve piston 56 to move axially from the closed position to a fully open position which uncovers the holes 54 to allow fluid communication through the valve retainer ring 52 and the inlet end 44 to the annular space 50. In the closed position, the required force of the piston spring 66 is proportional to the inner diameter of the valve retainer ring 52. The valve body 42 defines an annular stop 68 extending radially inward from the inner diameter Di of the valve body 42 for limiting movement of the valve piston 56 to the fully open position. The chamber flange 62 presents a spring seat 70 extending axially from the chamber flange 62 into the compression chamber 64 for combining with the chamber flange 62 to position one end of the piston spring 66. The valve piston 56 defines a mound 72 extending axially into the piston spring 66 for radially positioning the other end of the piston spring 66 in the compression chamber 64.
The chamber flange 62 defines a flange orifice 74 disposed radially from the axis A having a flange orifice diameter Dfo of 1.8 mm to present a flange orifice area for restricting fluid flow through the chamber flange 62. The base 58 of the valve piston 56 defines a valve orifice 76 disposed on the axis A having a valve orifice diameter Dvo of 2.4 mm to present a valve orifice area for restricting fluid flow through the valve piston 56. The relationship of the areas of the flange orifice 74 and valve orifice 76 establishes a pressure in the compression chamber 64 which is greater than the pressure in the suction port 32 in the closed position for biasing the valve piston 56 axially away or upward from the chamber flange 62 to define a closed position covering the holes 54.
The suction shutoff valve 22 includes a modulating valve 78 generally indicated for variably and incrementally increasing fluid flow through the chamber flange 62 from the compression chamber 64 to the suction passage 34, 36 in response to a decrease in the pressure in the suction passage 34, 36 below a predetermined pressure. The modulating valve 78 includes a bellows chamber 80 defined by the valve body 42 which is closed and extends from the chamber flange 62 to the egress end 46. The bellows chamber 80 is closed by a plug 82 disposed in the egress end 46 of the valve body 42 and engaging the inner diameter Di of the bellows chamber 80. The plug 82 includes a discharge orifice 84 which is radially offset from the axis A and has a discharge orifice diameter Ddo of 2.8 mm to present a discharge orifice area for restricting fluid flow from the bellows chamber 80 to the suction chamber 36 and establishing a bellows chamber pressure which responds to and approximately equals the suction chamber pressure.
The modulating valve 78 includes a valve aperture 86 defined by the chamber flange 62 and a valve disk 88 for covering the valve aperture 86 in the closed position. The modulating valve 78 includes an actuator mechanism 90, 92 including a bellows 90 and a bellows spring 92 for moving the valve disk 88 to open the valve disk 88 in response to a decrease in the pressure in the suction chamber 36 below the predetermined pressure. The bellows 90 is closed and in sealed engagement with a recession in the plug 82 to establish an internal bellows pressure of 0 psia. Alternatively, the bellows 90 may be an integral sealed casing secured to the plug 82 with or without a recess in the plug 82. The bellows 90 extends axially from the plug 82 at the egress end 46 of the valve body 42 to a bellows top 94 and has a bellows diameter Db less than the inner diameter Di of the valve body 42. A valve stem 96 extends axially from the valve disk 88 through the valve aperture 86 and connects to the bellows top 94 for opening and closing the valve aperture 86 in response to axial incremental movement of the bellows top 94 for variably and incrementally increasing fluid flow from the compression chamber 64 to the bellows chamber 80. The bellows spring 92 is disposed in the bellows 90 and interacts between the bellows top 94 and the plug 82 at the egress end 46 of the valve body 42 for biasing the valve disk 88 axially away or upward from the valve aperture 86 to open the valve aperture 86 in response to a decrease in the pressure in the bellows chamber 80 below the predetermined pressure.
In the operation of the suction shutoff valve 22, fluid flows through the valve orifice 76 and the flange orifice 74 and the discharge orifice 84 in the closed position when the pressure in the suction chamber 36 is above the predetermined pressure. When the pressure in the suction chamber 36 decreases below the predetermined pressure, the bellows spring 92 axially moves the bellows 90 and the valve disk 88 to open the valve aperture 86. Thus, fluid flow increases from the compression chamber 64 to the bellows chamber 80 and through the discharge port 38 to the suction chamber 36 and exposes the valve piston 56 to the decreased suction chamber pressure to overcome the force of the piston spring 66 and move the valve piston 56 axially to uncover the holes 54 of the valve body 42 and increase fluid flow through the suction shutoff valve 22 to the suction chamber 36. In other words, when the decrease in the suction chamber pressure reduces the difference between the bellows chamber 80 pressure and the internal bellows 90 pressure so that the difference is equal to or less than the force of the bellows spring 92, the bellows spring 92 will axially move the bellows 90 and the valve disk 88 to open the valve aperture 86 and subsequently increase fluid flow through the suction shutoff valve 22 to the suction chamber 36. On the other hand, when the difference between the bellows chamber 80 pressure and the internal bellows 90 pressure is greater than the force of the bellows spring 92, the valve disk 88 will be held closed.
While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
