Scroll machine with reverse rotation protection

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FIELD OF THE INVENTION

The present invention relates generally to scroll machines, and more particularly to the elimination of reverse rotation problems in scroll machines such as those used to compress refrigerant in refrigerating, air-conditioning and heat pump systems.

BACKGROUND AND SUMMARY OF THE INVENTION

Scroll machines are becoming more and more popular for use as compressors in both refrigeration as well as air conditioning and heat pump applications due primarily to their capability for extremely efficient operation. Generally, these machines incorporate a pair of intermeshed spiral wraps, one of which is caused to orbit relative to the other so as to define one or more moving chambers which progressively decrease in size as they travel from an outer suction port towards a center discharge port. An electric motor is normally provided which operates to drive the orbiting scroll member via a suitable drive shaft.

Because scroll compressors depend upon a seal created between opposed flank surfaces of the wraps to define successive chambers for compression, suction and discharge valves are generally not required. However, when such compressors are shut down, either intentionally as a result of the demand being satisfied, or unintentionally as a result of a power interruption, there is a strong tendency for the pressurized chambers and/or backflow of compressed gas from the discharge chamber to effect a reverse orbital movement of the orbiting scroll member and the associated drive shaft. This reverse movement often generates noise or rumble which may be considered objectionable and undesirable. Further, in machines employing a single phase drive motor, it is possible for the compressor to begin running in the reverse direction should a momentary power failure be experienced. This reverse operation may result in overheating of the compressor and/or other damage to the apparatus. Additionally, in some situations, such as a blocked condenser fan, it is possible for the discharge pressure to increase sufficiently to stall the drive motor and effect a reverse rotation thereof. As the orbiting scroll orbits in the reverse direction, the discharge pressure will decrease to a point where the motor again is able to overcome this pressure head and orbit the scroll member in the forward direction. However, the discharge pressure will again increase to a point where the drive motor is stalled and the cycle is repeated. Such cycling is undesirable in that it results in excessive stresses on various components within the compressor. These components must then be increased in size or complexity in order to withstand the excessive stresses caused by this undesirable cycling.

A primary object of the present invention resides, in one embodiment, in the provision of a very simple and unique solenoid valve which can be easily assembled into a conventional gas compressor of the scroll type without significant modification of the overall compressor design, and which functions at compressor shut-down to allow gas flow from an area of intermediate pressure to an area of suction pressure. With intermediate pressure and suction pressure equalized, a leak is created from the discharge side of the compressor to the suction side of the compressor. This leak will balance the discharge gas with the suction gas thereby preventing discharge gas from driving the compressor in the reverse direction which in turn eliminates the normal shut-down noise associated with such reverse rotation.

Another object of the present invention resides, in an alternate embodiment, in the provision of a very simple and unique mechanically operated valve which can also be easily assembled into a conventional scroll compressor without significant modification of the overall compressor design, and which also functions at compressor shut-down to allow gas flow from an area of intermediate pressure to an area of suction pressure. With intermediate pressure and suction pressure equalized, a leak is created from the discharge side of the compressor to the suction side of the compressor. This leak will balance the discharge gas with the suction gas, thereby preventing reverse rotation and the attendant shut-down noise associated therewith.

Both of the primary embodiments of the present invention achieve the desired results utilizing a very simple valve which is positioned between an area of intermediate pressure and an area of suction pressure. In the first set of embodiments, the valve is actuated by a solenoid and in the second set of embodiments, the valve is actuated by a mechanical device. Additional embodiments are disclosed which also facilitate starting of the compressor which is especially applicable to compressors having low-starting-torque motors.

These and other features of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings which illustrate the best mode presently contemplated for carrying out the present invention:

FIG. 1 is a vertical sectional view through the center of a scroll compressor which incorporates a first embodiment of the present invention;

FIG. 2 is a top elevational view of the compressor shown in FIG. 1 with the cap and partition removed;

FIG. 3 is a fragmentary enlarged view of a portion of the floating seal illustrated in FIG. 1;

FIG. 4 is a vertical section through the upper portion of a scroll compressor which incorporates another embodiment of the present invention;

FIG. 5 is a vertical section through the upper portion of a scroll compressor which incorporates another embodiment of the present invention;

FIG. 6 is a vertical section through the upper portion of a scroll compressor which incorporates another embodiment of the present invention;

FIG. 7 is a vertical section through the center of a scroll compressor which utilizes the compressor motor as a solenoid valve;

FIG. 8 is a vertical section through the upper portion of a scroll compressor which utilizes the compressor motor as a solenoid valve according to another embodiment of the present invention;

FIG. 9 is a schematic of a vertical section through the upper portion of a scroll compressor which utilizes a centrifugal valve for releasing intermediate pressure;

FIG. 10 is an enlarged sectional view of the centrifugal valve shown in FIG. 9 shown in the closed position;

FIG. 11 is a schematic view of a vertical section through the center of a scroll compressor which utilizes angular acceleration of a component of the compressor to activate a valve (shown in the closed position) which releases intermediate pressure;

FIG. 12 is a schematic view of a vertical section through the center of a scroll compressor which utilizes angular acceleration of a component of the compressor to activate a valve (shown in the open position) which releases intermediate pressure;

FIG. 13 is a schematic view of a vertical section through the center of a scroll compressor which utilizes viscous drag of a component of the compressor to activate a valve, shown in the closed position, which releases intermediate pressure;

FIG. 14 is a horizontal sectional view through the crankshaft and collar shown in FIG. 13;

FIG. 15 is a schematic view of a fail safe device for a solenoid valve shown in a first position;

FIG. 16 is a schematic view of a fail safe device for a solenoid valve shown in a second position;

FIG. 17 is a schematic view of a fail safe device for a solenoid valve shown in a third position;

FIG. 18 is a schematic of a thermal valve, shown in the closed position, for releasing intermediate pressure to the suction area of the compressor; and

FIG. 19 is a schematic of a thermal valve, shown in the open position, for releasing intermediate pressure to the suction area of the compressor.

FIG. 20 is a vertical sectional view through the center of a scroll compressor which incorporates an additional embodiment of the present invention;

FIG. 21 is a top elevational view of the compressor shown in FIG. 20 with the cap and partition removed;

FIG. 22 is a fragmentary enlarged view of a portion of the floating seal illustrated in FIG. 20;

FIG. 23 is a vertical section through the upper portion of a scroll compressor which incorporates another embodiment of the present invention;

FIG. 23A is an enlarged view of the area identified by circle 23A in FIG. 23;

FIG. 24 is a vertical section through the upper portion of a scroll compressor which incorporates another embodiment of the present invention; and

FIG. 25 is a vertical section through the center of a scroll compressor which utilizes the compressor motor as a solenoid valve.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the present invention is suitable for incorporation in many different types of scroll machines, for exemplary purposes it will be described herein incorporated in a scroll refrigerant compressor of the general structure illustrated in FIG. 1. Referring now the drawings and in particular to FIG. 1, a compressor 10 is shown which comprises a generally cylindrical hermetic shell 12 having welded at the upper end thereof a cap 14. Cap 14 is provided with a refrigerant discharge fitting 18 which may have the usual discharge valve therein (not shown). Other major elements affixed to the shell include an inlet fitting 20, a transversely extending partition 22 which is welded about its periphery at the same point that cap 14 is welded to shell 12, a two piece main bearing housing 24 and a lower bearing housing 26 having a plurality of radially outwardly extending legs each of which is suitably secured to shell 12. Lower bearing housing 26 locates and supports within shell 12 two piece main bearing housing 24 and a motor 28 which includes a motor stator 30. A drive shaft or crankshaft 32 having an eccentric crank pin 34 at the upper end thereof is rotatably journaled in a bearing 36 in main bearing housing 24 and a second bearing 38 in lower bearing housing 26. Crankshaft 32 has at the lower end a relatively large diameter concentric bore 40 which communicates with a radially outwardly inclined smaller diameter bore 42 extending upwardly therefrom to the top of crankshaft 32. Disposed within bore 40 is a stirrer 44. The lower portion of the interior shell 12 defines an oil sump 46 which is filled with lubricating oil. Bore 40 acts as a pump to pump lubricating fluid up the crankshaft 32 and into bore 42 and ultimately to all of the various portions of the compressor which require lubrication.

Crankshaft 32 is rotatively driven by electric motor 28 including motor stator 30, windings 48 passing therethrough and a motor rotor 50 press fitted on crankshaft 32 and having upper and lower counterweights 52 and 54, respectively.

The upper surface of two piece main bearing housing 24 is provided with a flat thrust bearing surface 56 on which is disposed an orbiting scroll 58 having the usual spiral vane or wrap 60 on the upper surface thereof. Projecting downwardly from the lower surface of orbiting scroll 58 is a cylindrical hub having a journal bearing 62 therein and in which is rotatively disposed a drive bushing 64 having an inner bore 66 in which crank pin 34 is drivingly disposed. Crank pin 34 has a flat on one surface which drivingly engages a flat surface (not shown) formed in a portion of bore 66 to provide a radially compliant driving arrangement, such as shown in assignee's U.S. Pat. No. 4,877,382, the disclosure of which is hereby incorporated herein by reference. An Oldham coupling 68 is also provided positioned between orbiting scroll 58 and bearing housing 24. Oldham coupling 68 is keyed to orbiting scroll 58 and a non-orbiting scroll 70 to prevent rotational movement of orbiting scroll member 58. Oldham coupling 68 is preferably of the type disclosed in assignee's copending application Ser. No. 591,443, entitled "Oldham Coupling For Scroll Compressor" filed Oct. 1, 1990, the disclosure of which is hereby incorporated herein by reference.

Non-orbiting scroll member 70 is also provided having a wrap 72 positioned in meshing engagement with wrap 60 of orbiting scroll 58. Non-orbiting scroll 70 has a centrally disposed discharge passage 74 which communicates with an upwardly open recess 76 which in turn is in fluid communication via an opening 78 in partition 22 with a discharge muffler chamber 80 defined by cap 14 and partition 22. The entrance to opening 78 has an annular seat portion 82 therearound. Non-orbiting scroll member 70 has in the upper surface thereof an annular recess 84 having parallel coaxial sidewalls in which is sealingly disposed for relative axial movement an annular floating seal 86 which serves to isolate the bottom of recess 84 from the presence of gas under suction pressure at 90 and discharge pressure at 88 so that it can be placed in fluid communication with a source of intermediate fluid pressure by means of a passageway 92. Non-orbiting scroll member 70 is thus axially biased against orbiting scroll member 58 to enhance wrap tip sealing by the forces created by discharge pressure acting on the central portion of scroll member 70 and those created by intermediate fluid pressure acting on the bottom of recess 84. Discharge gas in recess 76 and opening 78 is also sealed from gas at suction pressure in the shell by means of seal 86 acting against seat portion 82. This axial pressure biasing and the functioning of floating seal 86 are disclosed in greater detail in applicant's assignee's U.S. Pat. No. 5,156,539, the disclosure of which is hereby incorporated herein by reference. Non-orbiting scroll member 70 is designed to be mounted to bearing housing 24 in a suitable manner which will provide limited axial (and no rotational) movement of non-orbiting scroll member 70. Non-orbiting scroll member 70 may be mounted in the manner disclosed in the aforementioned U.S. Pat. No. 4,877,382 or U.S. Pat. No. 5,102,316, the disclosure of which is hereby incorporated herein by reference.

The compressor is preferably of the "low side" type in which suction gas entering via fitting 20 is allowed, in part, to escape into the shell and assist in cooling the motor. So long as there is an adequate flow of returning suction gas the motor will remain within desired temperature limits, When this flow ceases, however, the loss of cooling will cause a motor protector 94 to trip and shut the machine down.

The scroll compressor as thus far broadly described is either now known in the art or is the subject of other pending applications for patent or patents of applicant's assignee.

As noted, both of the primary embodiments of the present invention utilize a very simple valve which functions at compressor shut down to allow gas flow from an area of intermediate pressure to an area of suction pressure. The valve of the present invention operates to allow gas at intermediate pressure to flow to an area of suction pressure which then allows discharge pressure to dump to suction pressure. By working with gas at intermediate pressure rather than directly with gas at discharge temperature, the size, complexity and cost of the valve can be significantly reduced. In the first set of embodiments, the valve is operated by a solenoid, and in the second set of embodiments, the valve is run by a mechanical device. It is believed that all primary embodiments of the present invention are fully applicable to any type of scroll compressor.

The first embodiment of the present invention is shown in FIGS. 1 through 3. The first embodiment makes use of the dual pressure balancing scheme described above which is used to axially balance non-orbiting scroll member 70 with floating seal 86 being used to separate the discharge gas pressure from the suction gas pressure.

A solenoid valve 98 comprises a solenoid 100 and a valve 102. Solenoid valve 98 can be wired in parallel or in series with motor 28 such that solenoid 100 is activated and deactivated with motor 28 or solenoid valve 98 may be wired independently from motor 28. When solenoid valve 98 is wired independently from motor 28, valve 98 may be operated in a pulsed manner or a pulsed width modulated manner to modulate the capacity of compressor 10. Solenoid 100 is operable to open and close valve 102 which is in communication with a passageway 104 located within non-orbiting scroll 70. Passageway 104 extends from the bottom of recess 84 which is at intermediate pressure during operation of the compressor to the area of the compressor which contains suction gas at suction gas pressure.

Solenoid 100 and valve 102 are best shown in FIG. 2. Solenoid 100 includes a cylindrical wire coil 106 surrounding a plunger 108 in the usual manner. Solenoid 100 is secured to valve 102 by any method known well in the art. Valve 102 includes a valve body 110 having a passageway 112 which is in communication with passageway 104 in non-orbiting scroll 70. Valve body 112 is attached to non-orbiting scroll 70 by methods known well in the art. A ball 114 is disposed within passageway 112 and moveable between an open position and a closed position due to the movement of plunger 108. In its open position, fluid is allowed to flow from passageway 104 through passageway 112. In its closed position fluid is prohibited from flowing through passageways 104 and 112 due to ball 114 being forced against a valve seat 116 located within passageway 112 by plunger 108.

At compressor start-up, solenoid 100 is energized and valve 102 is closed to block any fluid flow through passageway 104. In this manner, compressor 10 makes a normal start-up. In some designs of compressors, compression within the scrolls builds rapidly at start-up. This build up of pressure can be so rapid in fact that the compressor may stall because of insufficient motor torque. Generally, this is only a problem when using single phase motors. When this build up of pressure occurs, the motor stalls and the motor protector repeatedly trips and the compressor has a difficult time starting again. An option in the present invention is to build in a time delay to the activation of solenoid 100 to prevent the closing of passageway 104 at start-up, thus keeping intermediate pressure from building up. This lack of intermediate pressure will allow the scrolls to separate axially and prevent compression build-up until sufficient motor torque has been generated.

At compressor shut-down, solenoid 100 is de-energized at the same instant that power to motor 28 is cut off. The de-energization of solenoid 100 causes valve 102 to open and allows fluid flow through passageways 104 and 112 from the bottom of recess 84 to the suction area of compressor 10. As the intermediate pressure and suction pressure become equalized, floating seal 86 has a net downward force due to the discharge gas pressure and floating seal 86 moves downward in recess 84 and creates a discharge gas to suction gas leak across the top of floating seal 86 at annular seat portion 82. By controlling the size of passageway 104 and/or passageway 112, reverse rotation can be minimized to any acceptable reverse RPM or it can be completely eliminated.

Solenoid valve 98 may be an AC (alternating current) or a DC (direct current) solenoid independent of the type of motor 28. If a DC solenoid is to be used with an AC motor, a rectifier needs to be wired between the AC power source and the DC solenoid.

FIG. 4 shows another embodiment of the present invention. In FIG. 4, elements which are the same as those in FIGS. 1 through 3 have been given the same reference numerals. The embodiment in FIGS. 1 through 3 purges intermediate pressure within recess 84 which holds non-orbiting scroll 70 down allowing floating seal 86 to drop. The embodiment shown in FIG. 4 is incorporated into a compressor which uses intermediate pressure to bias orbiting scroll 58 upward. The embodiment shown in FIG. 4 purges the intermediate pressure holding orbiting scroll 58 up which then creates sufficient tip clearance between the tips of scroll wraps 60 and 72 and their respective mating scroll to allow high pressure discharge gas to leak back through scrolls 58 and 70 before excessive reversals occur.

FIG. 4 shows the upper section of a compressor 130. Compressor 130 is similar to compressor 10 with the exception that partition 22 of compressor 10 has been eliminated along with floating seal 86. In order to separate the discharge gas from the suction gas area, non-orbiting, or in this case, stationary, scroll 70 extends completely across shell 12 and cap 14. Both shell 12 and cap 14 are secured to non-orbiting scroll 70 by welding or other means known well in the art.

Main bearing housing 24 is provided with an annular chamber 132 extending into flat thrust bearing surface 56. A first annular seal 134 is positioned radially outward from chamber 132 and a second annular seal 136 is positioned radially inward from chamber 132. Seals 134 and 136 operate to prohibit fluid flow from chamber 132 to the suction side of compressor 130. A passageway 138 extends through orbiting scroll 58 and fluidically connects chamber 132 to an area of intermediate pressure within compressor 130. During operation of compressor 130, fluid at an intermediate pressure is supplied to chamber 132 through passageway 138. Orbiting scroll 58 is thus forced axially upward due to the fluid pressure within chamber 132. The fluid pressure within chamber 32 is maintained by seals 134 and 136.

Compressor 130 further includes a passageway 140 extending through main bearing housing 24 and connecting chamber 132 to solenoid valve 98. The embodiment shown in FIG. 4 includes a fluid tube 142 extending from passageway 140 to solenoid valve 98 which will allow the placement of solenoid valve 98 anywhere within the suction area of compressor 130 as space will permit. It will be appreciated that the use of tube 142 or its equivalent may be used with any of the embodiments of the present invention to facilitate packaging and design requirements. It is also possible to have tube 142 extend through shell 12 and have solenoid 100 and valve 102 located externally to shell 12 if desired.

The operation of the embodiment shown in FIG. 4 is similar to the operation of the embodiment shown in FIGS. 1 through 3. At compressor start-up, solenoid 100 is energized and valve 102 is closed to block any fluid flow from passageway 140 through passageway 112. In this way compressor 130 makes a normal start-up. The time delay feature at compressor start-up described above may also be built into solenoid valve 98 for this embodiment. At compressor shut-down, solenoid 100 is de-energized causing valve 102 to open and allow fluid flow through passageways 140 and 112 from chamber 132 to the suction area of compressor 130. As the intermediate pressure and suction pressure are equalized, orbiting scroll 58 moves downward and creates a discharge gas to suction gas leak across the tips of scroll wraps 60 and 72. The amount of reverse rotation can be controlled by controlling the size of passageway 140 and/or passageway 112. The de-energization of valve 102 and the shut-down of motor 28 may also be tied in with a time delay to insure that sufficient leakage between chamber 132 and the suction area of the compressor has occurred before the motor is shut down. It is to be appreciated that this time delay feature at the shut down of the compressor can be applied to any of the embodiments of the present invention which incorporate solenoid valve 98.

FIGS. 5 and 6 show another embodiment of the present invention. The embodiment shown in FIGS. 1 through 3 and the embodiment shown in FIG. 4 utilize the purging of intermediate pressure from an existing chamber in the compressor which is being utilized to bias one of the scroll members towards the other. The effect of purging this intermediate pressure from a biasing chamber is to create a leak between existing compressor components which then allows the discharge gas pressure and suction gas pressure to equalize. In some cases, it may be desirable to create a direct path for the discharge pressure to equalize with the suction pressure rather than relying on the movement or separation of various components of the compressor.

The embodiment shown in FIGS. 5 and 6 include a pressure ratio sensitive valve which directly bypasses discharge pressure to suction pressure. FIG. 5 shows a compressor 150 having a pressure ratio sensitive valve 152 incorporated into orbiting scroll 58. The design of compressor 150 in FIG. 5 is similar to the design of compressor 130 shown in FIG. 4 in that non-orbiting scroll 70 is a fixed scroll attached to shell 12 and cap 14. Main bearing housing 24 is provided with annular chamber 132 extending into flat thrust bearing surface 56. Seals 134 and 136 operate to prohibit fluid flow from chamber 132 to the suction side of compressor 150. Passageway 138 extends through orbiting scroll 58 and connects chamber 132 to an area of intermediate pressure within compressor 150. During operation of compressor 130, fluid at an intermediate pressure is supplied to chamber 132 through passageway 138. Orbiting scroll 58 is thus biased axially upward due to the fluid pressure within chamber 132. The fluid pressure within chamber 132 is maintained by seals 134 and 136.

The embodiment shown in FIG. 5 includes a passageway 140 extending through main bearing housing 24 and connecting chamber 132 to solenoid valve 98. The embodiment shown in FIG. 5 includes fluid tube 142 extending from passageway 140 which will allow the placement of solenoid valve 98 anywhere within the suction area of compressor 150 as space will permit. Up to this point, compressor 150 shown in FIG. 5 is the same as compressor 130 shown in FIG. 4 and the operation of compressor 150 is the same as the operation of compressor 130 as described above.

Compressor 150 further includes pressure ratio sensitive valve 152 disposed within a pocket 154 located within orbiting scroll 58. A discharge pressure passageway 156 extends between discharge passageway 74 and pocket 154. A suction pressure passageway 158 extends between pocket 154 and the suction area of compressor 150. A valve body 160 is disposed within pocket 154 and is axially movable within pocket 154 to allow or prohibit fluid flow between passageway 156 and passageway 158. Valve body 160 and pocket 154 are designed such that valve body 160 is capable of axial movement within pocket 154 but fluid flow between valve body 160 and pocket 154 is prohibited. The upper surface of valve body 160 has an annular ring 162 which separates the area above valve body 160 into an annular chamber 164 and a cylindrical chamber 166.

The operation of the embodiment shown in FIG. 5 is similar to the operation of compressor 130 shown in FIG. 4. At compressor start-up, solenoid 100 is energized and valve 102 is closed to block any fluid flow from passageway 140 through passageway 112. In this way compressor 150 makes a normal start-up. The time delay feature for compressor start-up may also be built into solenoid valve 98 for this embodiment. While compressor 150 is in operation, the position of valve body 160 is determined by the various pressures operating against respective surface areas of valve body 160. Intermediate pressure within chamber 132 exerts an upward force on valve body 160 equal to the amount of intermediate pressure times the surface area of valve body 160 exposed to chamber 132. Discharge pressure is being supplied to annular chamber 164 and thus exerts a downward force on valve body 160 equal to the amount of discharge pressure times the surface area of valve body 160 exposed to chamber 164. In a similar manner, suction pressure is being supplied to cylindrical chamber 166 and thus exerts a downward force on valve body 160 equal to the amount of suction pressure times the surface area of valve body 160 exposed to chamber 166. Thus, the opening and closing of pressure ratio sensitive valve 152 can be controlled by selecting the size of valve body 160 and the size and diameter of annular ring 162 to control the various surface areas.

At compressor shut-down, solenoid 100 is de-energized causing valve 102 to open and allow fluid flow through passageway 140 and 112 from chamber 132 to the suction area of compressor 150. As the intermediate pressure and suction pressure are equalized, both orbiting scroll 58 and valve body 160 are moved downward. The movement of scroll 58 causes a discharge gas to suction gas leak across the tips of scroll wraps 60 and 72 as explained above for the embodiment shown in FIG. 4. In addition, the movement of valve body 160 within pocket 154 allows discharge gas to flow from passageway 156 through passageway 158 thus creating a direct fluid flow between the discharge gas and the suction gas. The various controls including the size of passageway 140 and/or passageway 112 and the time delay at compressor shut down described above for the embodiment shown in FIG. 4 are also applicable to this embodiment