KR960004246B1 - Scroll compressor with dual pocket axial compliance - Google Patents

Abstract

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Description

Scroll Compressor with Improved Axial Compliance

1 is a schematic side elevational view of a scroll compressor according to the present invention.

FIG. 2 is a cross sectional plan view showing a state where these scroll wraps are engaged to form compression pockets between protruding scroll wraps of the scroll compressor shown in FIG.

3 is an enlarged partial sectional view of a portion of the scroll compressor of FIG.

* Explanation of symbols for main parts of the drawings

10: scroll compressor 11: fixed scroll

13: orbital scroll 15: motor

19: compression pocket 21,23: port

TECHNICAL FIELD The present invention relates to scroll compressors, and more particularly to improving axial compliance between scroll elements to achieve high efficiency in scroll compressors.

Scroll compressors are widely applied in the air conditioning and heat pump industries, especially when the compression ratio is to be adjusted low. This application is more efficient, has fewer parts, lower noise and lower vibration than competing compressors. Conventional scroll compressors include a motor for driving an axis with an eccentric crank and cause orbital movement of the orbiting scroll element. The orbiting scroll element has an oil-shaped protruding wrap on the mating fixed element and a scroll or helical protruding wrap that works with each other. Compression occurs when the flow rate is reduced while moving the gaseous fluid radially inward by the interengaging action between the two projecting wraps.

However, internal leakage of pressurized fluid reduces the efficiency of the scroll compressor. There are two types of leaks associated with scroll compressors: flank leaks and tip leaks. In both cases, the fluid exits from the higher pressure pocket through the gap into the lower pressure pocket. Lateral leakage occurs when fluid from a pocket formed between two protruding engagement wraps exits side surfaces that are in contact with each other. Tip leakage occurs when fluid exits between them as the end surface of the protruding wrap of each element contacts the base of another element. Typically, tip leak is more than doubled because the total effective leak path width for tip leak is several times larger than the width for side leak. Moreover, the compression process increases tip leakage by generating large axial loads that push the orbiting scroll elements axially away from the fixed scroll elements. In addition to the axial force driving the orbiting scroll element away from the fixed scroll, there is also a reversal moment that attempts to tilt the orbiting scroll element from a plane in contact with the fixed scroll element.

Since the manufacturing techniques of close tolerances were not suitable for preventing the loss of pressure due to tip leakage, other methods have been developed. One approach is described in US Pat. No. 4,395,205; No. 4,411,605; No. 4,415,317; As described in US Pat. No. 4,415,48, various types of tip seals are used. The end surface of the protruding wrap of either scroll element is provided with tip sealing means for reducing tip leakage. Although this method is effective for sealing, this method requires a complicated manufacturing process, increases friction, and increases cost.

Another approach to reduce tip leakage is to apply compensating back pressures to pressurize the coupling elements together. The high pressure fluid intentionally exits from the compression chamber through the exhaust port into the back chamber, a relatively large typical single chamber located behind the orbiting scroll. This provides a pressurized fluid that pushes the orbiting pivotal element against the stationary element, thereby reducing the gap between the tip of the protruding scroll and the base of the elements. Reducing the gap minimizes the leakage of fluid, which in turn increases the pressure in the compression chamber.

See, for example, US Pat. No. 4,384,831; No. 4,600,369; No. 4,645,437; No. 4,696,630; Each of 4,861,245 describes a scroll compressor with such a back pressure chamber. Co-assigned US Pat. Nos. 4,992,032 and 4,993,928 also describe scroll compressors using back pressure technology. As described herein, two sealed pressure chambers, not a single back chamber, ie one at medium pressure and another at discharge pressure, are disposed behind the orbiting scroll element, to counteract the gas compression force in the compression chamber and to the fixed scroll element. It is designed to bias the orbiting scroll element toward. However, prior art back pressure techniques are designed to overcome the highest reversal moment experienced during orbital turn cycles, resulting in excessive thrust over the remaining cycles. Large thrust creates excessive friction between the two coupling parts and reduces the scroll compressor's efficiency.

Additionally, US Pat. No. 4,557,675 describes a method of adjusting the pressure in the back chamber by placing a pressure equalization port such that the pressure exhausted into the back chamber changes with changes in operating conditions. However, the back pressure remains relatively constant during any given steady state, thus trying to overcome peak reversal moments and axial forces with pressure changes as operating conditions change, resulting in excessive thrust and excess friction during the remaining cycles. Thereby reducing the efficiency of the scroll compressor.

It is an object of the present invention to increase the efficiency of a scroll compressor by reducing the friction between the scrolls.

According to the invention, pressurized fluid is discharged from the compression chamber into the at least one dynamic back chamber through a port in the scroll element such that the back pressure changes on a sub-cycle basis. The dynamic rear chamber, which is characterized by a relatively small volume chamber and a port of a large flow area for supplying pressure fluid to the chamber, is located behind the orbiting pivot element. According to the present invention, an effective means of repelling the reversing moment without generating excessive friction force can be achieved by changing the back pressure on the basis of the sub cycle.

These and other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the best embodiments with reference to the accompanying drawings.

1 to 3, the scroll compressor 10 includes a fixed scroll 11 that engages the orbiting scroll 13. The orbital swing scroll 13 is driven to orbital swing movement with respect to the fixed scroll 11 by an axis 17 driven by a motor 15. When the scroll wraps 18 and 20 protruding from the orbiting scroll 13 and the fixed scroll 11, respectively, form a plurality of compression pockets 19 therebetween to engage to trap a large amount of fluid. Compression is done. This orbital rotation reduces the amount of fluid in the pocket and simultaneously compresses the captured fluid by moving the pocket of trapped fluid inward in a helical direction.

As shown in FIG. 3, pressurized fluid flows into the back chambers 25 and 27 through the ports 21 and 23, respectively. The fluid in these chambers causes back pressure that pushes the orbiting scroll 13 towards the fixed scroll 11 to reduce tip leakage and counteract the reversing moment. However, the generated back pressure is not constant over the entire cycle. Instead, the back pressure changes in response to the change in the inversion moment acting on the orbiting scroll 13 during the cycle and tilting the orbiting scroll relative to the fixed scroll 11. The back pressure thus generated is sufficient to repel the inversion moment. If the reversal moment is large, greater back pressure is required to keep the orbiting scroll in place and prevent leakage. If the reversal moment is small, the back pressure also decreases, thus not causing excessive friction losses. This effect is achieved by providing at least one dynamic chamber in which the pressure varies in proportion to the reversing moment.

In the illustrated embodiment there are two ports 21, 23 and two corresponding chambers 25, 27. The port 23 supplies pressurized fluid into the static chamber 27. The port 21 supplies pressurized fluid into the dynamic chamber 25. The difference between the two is that the static chamber has a relatively constant fluid pressure over the entire cycle, while the dynamic chamber has a fluid pressure that varies widely during the cycle. The static port / chamber combination has a small port diameter and a large chamber volume. The dimensions are chosen in such a way as to cause sufficient damping so that the pressure is nearly constant throughout the cycle.

The pressure change based on the sub cycle in the dynamic chamber is obtained by giving the parameters of the port diameter and the chamber volume to appropriate dimensions relative to each other. The dynamic port / chamber pair has a large diameter port 21 and a small volume collection 25. The dimensions are chosen in such a way that the pressure in the dynamic chamber causes a very small damping action to follow the compression process. This allows to achieve pressure changes on a subcycle basis.

It has been found that the ratio of the port diameter to the cubic root of the chamber volume must be relatively small in order to keep the pressure in the static chamber substantially constant. In order to provide a wide variety of pressures in the dynamic chamber, this ratio must be relatively large. For example, when tested with a compressor designed to have a static chamber with a ratio of 0.05 and a dynamic chamber with a ratio of 0.22, the net axial force was reduced by approximately 45%.

Although the illustrated embodiment has one dynamic and one static chamber / port combination, other combinations are possible. The present invention includes any number of dynamic chamber / port combinations with one or more with or without a certain number of static chambers. Since the total back pressure on the scroll is the sum of the forces generated by the constant pressure in the static chamber and the change pressure in the dynamic chamber, the total back pressure changes on the orbital turning cycle instead of being kept constant as in the prior art.

Also, as long as the proper ratios of the cube root of the effective port diameter / effective chamber volume are maintained, one port can be led to one or more chambers, and vice versa, one or more ports can be led to one chamber. Another change that can actually lead to similar results is that back pressure is applied to fixed scrolls rather than orbiting scrolls so that the fixed scrolls can move axially. Although the exact location of the ports is not critical to the present invention and depends on the characteristics of each compressor, the location of the ports should utilize the pressure variations inside the compression chamber to generate sufficient pressure in the back chamber.

Although the present invention has been illustrated and described in accordance with the best embodiments thereof, it is understood that various other changes, omissions, and additions described above in the form and details of the invention may be made without departing from the spirit and the spirit of the invention. Can be understood by those skilled in the art.

Claims (5)

A first scroll means having a base portion comprising a bottom portion and a spiral wrap portion extending perpendicularly from the bottom portion and a base comprising a bottom portion and a spiral wrap portion extending perpendicularly from the bottom portion; A second scroll means and means for moving said first scroll means relative to said second scroll means along an orbiting path such that fluid compression occurs within a compression pocket, said spiral wrap of said second scroll means Is similar in shape to the helical wrap of the first scroll means, wherein the second scroll means is positioned to be positioned by the first scroll means such that the helical wraps engage each other to form a compression pocket therebetween. A compressor, comprising: a first sieve positioned behind a base of one of the first and second scroll means And a dynamic back pressure chamber having a first effective flow diameter and having a first effective flow diameter, the dynamic pressure repulsing against a reversal moment generated during the compression process, such that the ratio of the first effective flow diameter to the cube root of the first volume is at least about 0.2. And means for discharging fluid from the first selected compression pocket of the compression pockets into the dynamic back pressure chamber at a selected position. 2. The static back pressure chamber as claimed in claim 1, wherein said static back pressure chamber is disposed on the back surface of at least one of said first and second scroll means and has a second volume, and from said second selected compression pocket of said compression pockets. And means having a second effective flow diameter for dispensing fluid into and for internally setting a static pressure that remains relatively constant over the orbiting cycle of said first scroll means. 3. The apparatus of claim 2, wherein the means for discharging fluid from the first selective compression pocket into the dynamic back pressure chamber passes through the bottom portion of at least one of the first and second scroll means, A first fluid passage having an open first end and a second end open to the dynamic back pressure chamber, wherein the means for discharging fluid from a second selective compression chamber into the static back pressure chamber comprises: A second fluid passing through the bottom portion of at least one of the two scroll means and having a first end open in a second selective compression pocket and a second end open in the static back pressure chamber and also having a second effective flow diameter Scroll compressor comprising a passageway. 4. The method of claim 3, wherein the ratio of the second effective flow diameter to the cube of the second volume of the static back pressure chamber is relative to the ratio of the first effective flow diameter to the cube root of the first volume of the dynamic back pressure chamber. Scroll compressor, characterized in that relatively small. A first scroll means having a base portion comprising a bottom portion and a spiral wrap portion extending perpendicularly from the bottom portion and a base comprising a bottom portion and a spiral wrap portion extending perpendicularly from the bottom portion; A second scroll means and means for moving said first scroll means relative to said second scroll means along an orbiting path such that fluid compression occurs within a compression pocket, said spiral wrap of said second scroll means Is similar to the shape of the helical wrap of the first scroll means, wherein the second scroll means is positioned to be positioned by the first scroll means such that the helical wraps engage each other to form a compression pocket therebetween. 10. A compressor, the compressor being located on a backside of the base of one of the first and second scroll means A dynamic back pressure chamber having an enemy, a static back pressure chamber having a second volume much larger than the first volume and located behind the base of at least one of the first and second scroll means, and a first selection of the compression pockets A first fluid passage means for discharging fluid from the compression pocket into the dynamic back pressure chamber, and a second fluid passage means for discharging fluid into the static back pressure chamber from a second selected compression pocket in the constant compression pocket; The first fluid passage means has a first effective flow diameter and occurs during the compression process because the first ratio of the first effective flow diameter of the first fluid passage means to the cube root of the first volume of the dynamic back pressure chamber is relatively large. Dynamic that changes over the orbiting cycle of the first scrolling means in proportion to the reversed moment of reversal A pressure is set in the dynamic back pressure chamber, the second fluid passage means having a second effective flow diameter, and the second effective flow diameter of the fluid passage means relative to the cube root of the second volume of the static back pressure chamber. And set a static pressure in said static back pressure chamber that is maintained relatively constant over the orbiting cycle of said first scroll means because said ratio is relatively small compared to said first ratio.