Oil utilized as motor protector trip for scroll compressor

This invention relates to a system which optimizes the flow of a lubricant over portions of a scroll compressor which become hot during reverse rotation or loss of charge, and then passing the heated lubricant onto a motor protector.

Scroll compressors are becoming widely utilized in refrigerant compression applications. In a scroll compressor a first scroll member has a base and a generally spiral wrap extending from the base. The wrap of the first scroll member interfits with the wrap from a second scroll member. The second scroll member is caused to orbit relative to the first, and refrigerant is entrapped between the scroll wraps. As the second scroll member orbits the size of the compression chambers which entrap the refrigerant are reduced, and the refrigerant is compressed.

There are certain design challenges with a scroll compressor. As an example, while the scroll compressor efficiently compresses refrigerant when rotated in a proper forward direction, there are undesirable side effects if the scroll compressor is driven to rotate in a reverse direction. Moreover, if the level of refrigerant or charge level, being passed through the compressor is lower than expected, there may also be undesirable side effects. Among the many undesirable side effects is an increased heat level at the scroll compressor members.

One safety feature incorporated into most sealed compressors is the use of a motor protector associated with the electric motor for driving the compressor. The same is true in a scroll compressor, wherein a motor protector is typically associated with the stator for the electric motor. The motor protector operates to stop rotation of the motor in the event there is an electrical anomaly, or if the motor protector senses an unusually high temperature. However, the problems mentioned above with regard to reverse rotation and loss of charge typically cause heat to increase at the compressor pump set, or the scrolls, which is relatively far from the motor. Thus, it may take an undue length of time for the additional heat being generated in the compressor pump set to pass to the motor protector.

In the disclosed embodiment of this invention, lubricant is caused to flow over a portion of the compressor pump set and be heated, at least when there are adverse conditions in the compressor pump set. This heated lubricant is then passed to a motor protector. This will cause the motor protector to trip the motor and stop further rotation.

In preferred embodiments, the heated portion of the compressor over which the lubricant is passed is the non-orbiting scroll. Alternatively, in some embodiments the heated lubricant can pass over the orbiting scroll.

In one general type of disclosed embodiment, the flow of lubricant back to the motor protector is selective, and will only occur if a particularly high temperature is reached. At other times, the lubricant is directed to a normal return path.

These and other features of the present invention can be best understood from the following specification and drawings, the following which is a brief description.

FIG. 1 is a cross-sectional view through a first embodiment compressor.

FIG. 2 is a cross-sectional view through a second embodiment scroll compressor.

FIG. 3 shows a modification to the FIG. 2 embodiment.

FIG. 4 is an enlarged view of a portion of the FIG. 3 embodiment.

FIG. 5 shows yet another embodiment.

FIG. 1 shows a scroll compressor 20 having a compressor pump set 22 which incorporates an orbiting scroll and a non-orbiting scroll 25 , as known. A compressor rotor 26 drives a shaft 27 to drive the orbiting scroll, as known. A motor protector 28 is associated with the motor stator 29 . A lubricant level 30 is positioned beneath the motor. An oil feed tube 32 extends upwardly from the lubricant sump 30 and a lubricant is driven through a pump 34 on the feed tube 32 . The pump 34 may be driven by any known means. As an example, a separate motor may be provided, or the motor could be driven by a power takeoff from the shaft 27 . This figure shows the pump 34 schematically, and a worker in this art would recognize how to drive the motor 34 . The tube 32 has downstream portions 36 and 38 downstream from the pump 34 . These portions pass over the non-orbiting scroll 25 . An outlet 40 is positioned above the motor protector 28 , such that heated lubricant 42 is returned onto the motor protector 28 .

In operation, should conditions within the compressor pump set 22 be as expected, the lubricant 42 will not be at a predetermined high temperature. That is, while the lubricant 42 may be heated, it will not be heated to a sufficient amount that it will trip the motor protector 28 . However, should there be an adverse condition in the compressor pump unit 22 , such as reverse rotation or a loss of charge situation, then the temperature of the lubricant 42 will be elevated. Once the temperature reaches a predetermined amount it will trip the motor protector 28 and cause the motor protector 28 to stop further rotation of the motor.

FIG. 2 shows another embodiment 50 . In embodiment 50 , the orbiting scroll 52 is associated with the non-orbiting scroll 54 . A crankcase 56 supports the orbiting scroll 52 and has a lubricant passage 58 communicating with a shaft 27 . The shaft 27 , shown schematically here, is configured to have a lubricant feed tube 59 supplying lubricant to the chamber 61 . This portion of the invention is as known in the scroll compressor art. The passage 58 communicates with a tube 60 having a tube end 62 received in an opening 64 which communicates with the passage 58 . The tube 60 further has a second end 66 inserted into a bore 68 in the non-orbiting scroll 54 . This passage 68 communicates with a further passage 70 which wraps around the body of the non-orbiting scroll 54 , and then communicates with an outlet 40 much like the outlet shown in FIG. 1 . This embodiment differs from the FIG. 1 embodiment largely in the fact the oil feed is obtained from the passage 58 , rather than directly from the sump. The pumping action of the passage 59 will drive the lubricant through its path in this embodiment.

FIGS. 3 and 4 shows a further embodiment 80 which is slightly modified from the FIG. 2 embodiment. In this embodiment the oil tube 82 includes a downwardly extending return opening 84 selectively closed by a plug 86 . The plug 86 is connected to a cord 88 which extends through a small passage 89 to an actuator mechanism 90 .

As shown in FIG. 4, the mechanism 90 incorporates a clip spring 92 having a clip end 94 positioned outwardly of a housing 104 . This holds a spring member 96 at a predetermined position. The member 92 is formed of a shape memory alloy tension spring. As this member increases in temperature, it will contract in length or size. A second spring 98 is applying a bias force through a spring end 102 sitting against a flange 100 which is part of the spring 92 .

During normal operation, the spring 98 holds the spring 92 and cord 88 in the position illustrated in FIGS. 3 and 4. The plug 86 is allowed to move downwardly to the position such as shown in FIG. 3 . However, should the temperature on the spring 92 increase beyond a predetermine level, it will begin to contract in size. As it contracts in size it overcomes the force from spring 98 and the cord 88 is pulled to the right in FIG. 4 . This pulls the plug 86 upwardly such that it will close the opening 84 . At that time, lubricant will flow upwardly and into the passage 68 - 70 , such as explained with reference to FIG. 2 . From the passage 70 the lubricant is returned such as through an outlet 40 directed above a motor protector 28 . This embodiment provides a system wherein the lubricant is only passed over the non-orbiting scroll in the event that a predetermined condition is likely to exist. The lubricant will thus be heated such that it will trigger the motor protector, and stop operation under adverse conditions.

FIG. 5 shows another embodiment 106 , wherein a passage 108 communicates with a normal oil return path tube 110 . Oil will return from passage 108 back downwardly through the tube 110 . A valve 112 selectively closes this path when a spring 114 force is overcome by a spring 116 . The spring 114 pulls the valve 112 upwardly. The spring 116 is a temperature sensitive spring and will increase in the length as its temperature increases. As the temperature surrounding the valve 112 increases, the spring 116 will force the valve 112 downwardly to close communication between passages 108 and 110 . At that time, lubricant within a chamber 118 will no longer move into the passage 108 . Instead, the lubricant will be forced upwardly into a passage 120 , and from passage 120 it will communicate with an alternative oil path 124 which is positioned above the motor protector 28 . The positioning of the passage 120 closer to the orbiting scroll 125 ensures that better heat transfer is achieved. That is, the passage 120 is closer to the orbiting scroll 125 than is passage 108 .

While the invention has been disclosed for reacting to a predetermined high temperature, it should be understood that other conditions could cause the actuation. As an example, high pressure ratios or low suction pressure.

Although preferred embodiments of this invention have been disclosed, a worker in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.