Rotary expansible chamber devices – Working member has planetary or planetating movement – Helical working member – e.g. – scroll
Reexamination Certificate
2001-10-22
2003-04-08
Vrablik, John J. (Department: 3748)
Rotary expansible chamber devices
Working member has planetary or planetating movement
Helical working member, e.g., scroll
C418S001000, C418S069000
Reexamination Certificate
active
06544017
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to scroll compressors and more particularly to mechanisms provided to prevent reverse scroll rotation.
Scroll compressors include a compression mechanism having a fixed scroll member and an orbiting scroll member. The compression mechanism is operatively connected to a motor via a drive shaft. Upon energizing the motor, rotation of the drive shaft is induced which in turn causes “rotation” or orbiting motion of the orbiting scroll member. The orbiting scroll member revolves about the drive shaft axis of rotation, moving with respect to the fixed scroll member to compress refrigerant gas received between the scroll members. The compressed fluid is usually discharged from the scroll compression mechanism discharge port into the compressor housing and then from the compressor assembly to the remainder of the refrigerant system.
Upon compressor shut down or during a temporary interruption of power to the compressor, the orbiting scroll member is no longer driven by the motor via the drive shaft. The orbiting scroll member is free to move in response to pressure differentials existing between the suction and discharge ports of the compression mechanism as the compressed gas reexpands. If unimpeded, the reexpansion of already compressed fluid will act upon the orbiting scroll member, causing it to rotate in a reverse direction. If the reverse rotation is not stopped or prevented, objectionable noise and vibration may result. If power is restored to the motor while the drive shaft is rotating reversely, the motor may continue to drive the shaft and thus the orbiting scroll member in a reverse direction.
Previous methods are available which attempt to prevent prolonged reverse orbiting motion of the orbiting scroll member. One such method includes providing a discharge check valve over the outlet of the discharge port located in the fixed scroll member. The discharge check valve may prevent the back flow of compressed refrigerant fluid into the space between the orbiting and fixed scroll members, thereby reducing the opportunity for reverse rotation to occur. By preventing the return of compressed refrigerant fluid to the area between the scroll members, the oil entrained in the refrigerant fluid is not available to lubricate the scroll wraps should even temporary reverse rotation occur. If the scroll wraps are not lubricated, and reverse rotation is not prevented, wearing of abutting surfaces may occur. Further, continued reverse rotation of the compressor without lubrication may result in seizure of the compressor. The temperature within the compressor housing may also increase due to the fact that there is a lack of mass flow through the compressor. Prolonged reverse running is a particular concern where electrical power is temporarily interrupted, and restored while the drive shaft is still rotating in the reverse direction.
Alternatively, a one-way bearing may be provided about the drive shaft of the scroll compressor to prevent or arrest rotation in a direction other than the desired direction of the orbiting scroll member. Previous one-way bearings have rollers coupled to the drive shaft which are designed to be wedged between the drive shaft and the clutch or brake component when reverse rotation occurs. The reverse rotation of the drive shaft is stopped, as is the reverse orbiting motion of the orbiting scroll member. A problem with this type of device is that a load imparted to the drive shaft by the one-way bearing may contribute to energy losses, wearing of the drive shaft, and additional vibration during normal compressor operation. An additional problem is that existing one-way bearings may not be constructed to withstand both the loads created during compressor operation and the sudden load created upon compressor shut down.
It is desired to provide a reverse rotation brake for a scroll compressor which stops reverse rotation of the orbiting scroll member, which is able to withstand the sudden load created during compressor shut down, and which does not introduce additional loads to the drive shaft during normal compressor operation.
SUMMARY OF THE INVENTION
The present invention provides a reverse rotation brake which is operatively engaged with the compressor crankcase to arrest reverse rotation of the orbiting scroll member at the onset of reverse rotation, but which engage the crankcase with the orbiting scroll member or the drive shaft during normal compressor operation. In one embodiment, a brake element is located in a cavity provided in the crankcase, in surrounding relationship with the hub of the orbiting scroll member. Pockets are formed in the radially outer surface of the brake element to receive rollers. The pockets have flat portions along which the rollers roll when the orbiting scroll member rotates in a reverse direction to bindingly engage the brake element and the crankcase. The binding engagement of the rollers with both the crankcase cavity surface and the pocket flat portions thus arrests reverse rotation of the orbiting scroll member.
In a second embodiment, a brake element is secured to and supported by a compressor counterweight which is fixedly mounted to the drive shaft. The brake element is located in surrounding relationship with a radially outer surface of the crankcase. Pockets are formed in the outer surface of the crankcase to receive rollers which upon reverse rotation of the drive shaft, roll along the flat portions of the pockets to bindingly engage the brake element and the crankcase. Reverse rotation of the drive shaft, and thus the orbiting scroll member is arrested.
In a third embodiment, a brake element is cup-shaped and secured to one end of the drive shaft for rotation therewith. The end of the drive shaft is formed having a plurality of splines located about the periphery thereof which are engaged by a plurality of splines located about the periphery of a hole extending through the base of the brake element. Pockets having flat portions are formed in the outer surface of the brake element to receive rollers. The rollers roll along the flat portions when the orbiting scroll member rotates reversely to bindingly engage the brake element and the crankcase, and thus arrest the reverse rotation of the orbiting scroll member. With the brake element in binding engagement with the crankcase, reverse rotation of the drive shaft is thus arrested through the splined engagement between the brake element and the drive shaft.
In accordance with the present invention, the load opposing reverse rotation is borne by the brake element and the crankcase, but not the drive shaft. Nor is the shaft subjected to loading by the inventive brake during normal compressor operation. Further, the brake engages existing, robust portions of the compressor which are able to withstand both the operational loads and the sudden load thereon created upon compressor shut down.
Further, radial compliance of the scroll members is maintained even with the reverse rotation brake installed.
The present invention provides a scroll compressor having a housing and a compression mechanism including a fixed scroll member and an orbiting scroll member disposed therein. A motor is disposed in the housing and is operatively coupled to the compression mechanism via a drive shaft. A crankcase is disposed in the housing and is connected to the compression mechanism. A brake element is operatively engaged with the crankcase, with at least one roller located therebetween. The brake roller has a first position relative to one of the brake element and the crankcase when the compressor operates in a forward direction, in which forward rotation of the orbiting scroll member is unimpeded. At the onset of reverse orbiting scroll member motion, the roller assumes a second position relative to the brake element or crankcase in which the roller is in binding engagement with the brake element and the crankcase, whereby reverse motion of the orbiting scroll member is arrested.
The present invention also provides a scroll compressor
Baker & Daniels
Tecumseh Products Company
Vrablik John J.
LandOfFree
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