Optimized radial compliance for a scroll compressor

[0002] This invention relates to a scroll compressor wherein the main benefits of fixed throw and radially compliant compressors are both achieved.

[0003] 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 second scroll member has a base and a generally spiral wrap extending from its base. The wraps of the two scroll members interfit to define compression chambers. The shaft is driven by an electric motor to rotate, and causes the orbiting scroll to orbit relative to the non-orbiting scroll. As the two orbit relative to each other, the size of the compression chambers decrease, and an entrapped refrigerant is compressed. The compression chambers are partially defined by contact between the flanks of the wraps of the two scroll members. In one type of scroll compressor, the position of the two wraps relative to each other is relatively fixed through the orbit. Such a scroll compressor is known as a “fixed throw”.

[0004] While a fixed throw compressor does have some benefits, it also has downsides. In particular, fixed throw scroll compressors are usually quieter than a second type of scroll compressor known as “radially compliant”. However, tolerance control in a fixed throw scroll may result in significant leakage gaps between the scroll flanks. Moreover, if there is ever an entrapped contaminant, a fixed throw scroll member does not have all of the benefits of a radially compliant scroll.

[0005] In a radially compliant scroll, the connection between the driveshaft and the orbiting scroll is a through a slider block such that the orbiting scroll can move or “slide” into and away from engagement from the non-orbiting scroll wrap. A centrifugal force forces the scroll wraps into contact. A force between the two wraps will tend to move the scroll members out of the contact at their flank surfaces. Due to the centrifugal force acting between the two, there is thus a significant amount of sliding contact. Hence, the operational noise of a radially compliant scroll is greater than that of a fixed throw scroll.

[0006] In a disclosed embodiment of this invention, the scroll compressor has a radially compliant orbiting scroll wrap connected to the driveshaft through a slider block. However, structure is also incorporated into the connection to limit or dampen movement of the orbiting scroll relative to the non-orbiting scroll. It can also limit or eliminate the centrifugal force acting between the two scroll wraps. In a first embodiment, a damper piston extends from an eccentric drive pin on the shaft into contact with the inner bore of the slider block. The piston will resist the force from the centrifugal force tending to move the orbiting scroll into contact with the non-orbiting scroll. Thus, the damper piston, which is spring biased outwardly of the eccentric pin, acts in conjunction with a flank contact force to resist the centrifugal force. In this way, flank contact force is minimized. However, the goal of maintaining the scroll wrap flanks in close proximity to each other is achieved. The spring force should be designed to achieve a maximum orbit, with minimal flank contact during most of that orbit.

[0007] In a second embodiment, a normally flat drive surface between the eccentric pin and the inner bore of the slider block has a number of incremental positioning structures. As an example, saw-tooth shapes can be formed on the two surfaces. The relative position of the slider block and the eccentric pin indexes along the incremental surfaces such that a large contact force between the flanks will cause movement of the slider block relative to the pin through the positioning structures to allow the orbiting scroll to move away from the non-orbiting scroll. On the other hand, the incremental positioning surfaces also allow the position of the slider block to advance along the eccentric pin until a balanced position is reached for the particular scroll arrangement. In a sense, the structure will then approximate a fixed throw scroll compressor that is ideally designed for the particular manufacturing tolerances of the components in that scroll compressor.

[0008] In general, the application could be described as a scroll compressor having a relationship between a slider block and an eccentric pin wherein the two are structured to allow movement of the slider block relative to the pin, but to limit such movement during operation.

[0009] These and other features of the present invention can be best understood from the following specification and drawings. The following of which is a brief description.

[0010] FIG. 1 is a cross-sectional view through a first embodiment scroll compressor.

[0011] FIG. 2 shows the first embodiment compressor.

[0012] FIG. 3 shows a second embodiment.

[0013] FIG. 1 shows a scroll compressor 20 incorporating a non-orbiting scroll 22 having a wrap 23. The orbiting scroll 24 has its wrap 25 interfitting with the wrap 23, as known.

[0014] A driveshaft 26 is driven by an electric motor 28. The orbiting scroll 24 has downwardly extending boss 30 which receives a slider block 32. The slider block 32 surrounds the eccentric pin 34.

[0015] As shown in FIG. 2, the slider block 32 has a bore 33 which receives the eccentric pin 34. The two have sliding surfaces shown in engagement at 35 to permit movement between the eccentric pin 34 and the slider block 32, as is known. The present invention is directed to a damper piston 36 which is forced outwardly of a bore 38 in the pin 34 by a spring 40. During forward rotation a centrifugal force F is applied to the slider block 32 tending to move it upwardly as shown in FIG. 2, in the direction of the arrow F. With this movement, the wrap 25 is brought into contact with the wrap 23 at its flanks, as shown schematically at point C near the top of FIG. 2.

[0016] With this contact, an opposing contact force F_cis created. The force F_cacts between the sliding surfaces of wraps 25 and 23 and vibration from the sliding friction and from interference between imperfections in the two surfaces results. This vibration is transferred through the compressor structure and results in some unwanted noise. The vibration also results in the orbiting scroll 24 moving vertically as shown in FIG. 2, with the sliding surfaces of the slider block 32 and eccentric pin 34 accommodating the movement. The piston 36 tends to dampen or slow down the rate of that movement by providing a force that tends to resist movement. Since the downward motion of orbiting scroll 24 is driven by mechanical interactions, its movement is not appreciably slowed by piston 36. However, since its upward movement (as shown in FIG. 2) is driven only by centrifugal forces, its upward movement is slowed by the resisting force of piston 36 and for a time contact between the sliding surfaces of wraps 25 and 23 is reduced or eliminated. For a time, the force F_cis supplemented or replaced by the resisting force of piston 36 until the wraps 25 and 23 eventually come back into contact. At that time the next excursion downward (as shown in FIG. 2) of the orbiting scroll 24 restarts the cycle and the force F_cis again reduced or eliminated.

[0017] In addition to this, the force from spring 40 tends to also reduce F_c, but its influence diminishes as the wraps 25 and 23 separate and the orbiting scroll moves downwards as shown in FIG. 2. Thus, the spring provides its greatest effect when the wraps 25 and 23 are near or in contact, which is where it is most needed to reduce F_c. When the wraps 25 and 23 are greatly separated, which would induce undesired leakage, the influence of spring 40 is reduced and it does not resist the upward movement of the orbiting scroll 24 needed to re-establish the close clearance or contact between wraps 25 and 23 needed to assure sealing and low leakage.

[0018] FIG. 3 shows another embodiment 50 wherein the eccentric pin 52 is provided with a plurality of saw-tooth shaped irregular surface portions 54. The slider block 56 has its bore 57 formed with a plurality of mating surfaces 58. Although saw-tooth shaped portions are shown, any other incremental indexed surface structures can be utilized. As shown, the force F will be applied to the slider block during rotation as in the prior embodiment. The force F_cwill also be applied as the scroll wraps 23 and 25 are brought into contact. The force F_cincreases as the force F brings the wrap 25 into undue engagement with the wrap 23, or if a contaminant is trapped between the two. The incremental surface structures 54 and 58 will find a equilibrium position such that the amount of movement of the slider block 56 relative to the pin 52 will be limited. Only movement sufficient to cause a force to exceed an inertia or holding frictional force between the structures 54 and 58 will cause any movement of the slider block 56 relative to the pin 52, and hence allow movement between the wraps 23 and 25. Thus, in effect, this embodiment will approximate the drive arrangement of a fixed throw scroll compressor while still allowing movement of the wraps 23 and 25 should there be a contaminant captured between the two. Moreover, by utilizing the incremental index structure an optimum can be achieved between the wraps 23 and 25 for the particular manufacturing tolerances in the particular scroll compressor components.

[0019] The preferred embodiments of this invention have been disclosed, however, a worker in this art would recognize that many modifications would come within the scope of this invention. For that reasons the following claims should be studied to determine the true scope and content of this invention.