WO2006064988A1

WO2006064988A1 - Oil path for rotary compressor

Info

Publication number: WO2006064988A1
Application number: PCT/KR2004/003306
Authority: WO
Inventors: Young Hwan Ko; Jong Bong Kim; Ji Young Bae; Jin Kook Kim
Original assignee: Lg Electronics Inc.
Priority date: 2004-12-15
Filing date: 2004-12-15
Publication date: 2006-06-22

Abstract

Disclosed is a rotary compressor having an improved lubricating mechanism. The rotary compressor includes a driving shaft (13) and having an eccentric portion (19a) of a predetermined size; a cylinder (21)defining a predetermined inner volume; a roller (22) installed rotatably on an outer circumference of the eccentric portion (13a) so as to contact an inner circumference of the cylinder (21) and performing a rolling motion along the inner circumference; a vane (23) installed elastically in the cylinder (21) to contact the roller (22) continuously; upper and lower bearings (24,25) installed respectively in upper and lower portions of the cylinder(21) , for supporting the driving shaft (13) rotatably and sealing the inner volume hermetically; and an oil path (100) including a first path (110) extending within the driving shaft (13) and being configured to pump an oil, and a second path (120) formed at any one of bearings and configured to allow the pumped oil to uniformly flow between the bearings (24,25)and the driving shaft (13).

Description

ROTARY COMPRESSOR

Technical Field

The present invention relates to a rotary compressor, and more particularly to a mechanism for supplying a lubricant to driving parts in the rotary compressor.

Background Art

In general, compressors are machines that are supplied with power by a power generator such as electric motor, turbine or the like and apply compressive work to a working fluid, such as air or refrigerant to elevate the pressure of the working fluid. Such compressors are widely used in a variety of applications, from electric home appliances such as air conditioners, refrigerators and the like to industrial plants.

The compressors are classified into two types according to their compressing methods: a positive displacement compressor, and a dynamic compressor (a turbo compressor). The positive displacement compressor is widely used in industry fields and configured to increase pressure by reducing its volume. The positive displacement compressors can be further classified into a reciprocating compressor and a rotary compressor.

The reciprocating compressor is configured to compress the working fluid using a piston that linearly reciprocates in a cylinder. The reciprocating compressor has an advantage of providing high compression efficiency with a simple structure. However, the reciprocation compressor has a limitation in increasing its rotational speed due to the inertia of the piston and a disadvantage in that a considerable vibration occurs due to the inertial force. In contrast, the rotary compressor is configured to compress working fluid using a roller eccentrically revolving along an inner circumference of the cylinder, and has an advantage of obtaining high compression efficiency at a low speed compared with the reciprocating compressor. Accordingly, the rotary compressor additionally has the advantage of reducing noise and vibration, and thus has been used in the home appliance more widely than the reciprocating compressor.

In such rotary compressor, as mechanical elements such as a motor, a driving shaft and the like move in a high speed, they are under a severe operational environment Therefore, a proper lubricating is important for such mechanical elements, and a lubricating mechanism for the proper lubricating is required.

Disclosure of Invention

Accordingly, the present invention is contemplated to substantially obviate problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a rotary compressor having an improved lubricating mechanism.

To achieve such object, the present invention provides a rotary compressor which comprises a driving shaft and having an eccentric portion of a predetermined size; a cylinder defining a predetermined inner volume; a roller installed rotatably on an outer circumference of the eccentric portion so as to contact an inner circumference of the cylinder, and performing a rolling motion along the inner circumference; a vane installed elastically in the cylinder to contact the roller continuously; upper and lower bearings installed respectively in upper and lower portions of the cylinder, for supporting the driving shaft rotatably and sealing the inner volume hermetically; and an oil path including a first path extending within the driving shaft and being configured to pump an oil, and a second path formed at any one of bearings and configured to allow the pumped oil to uniformly flow between the bearings and the driving shaft.

The second path could be comprised of a single straight groove allowing the oil to flow therein regardless of rotational directions of the driving shaft. Alternatively, the second path could be comprised of at least one groove each configured to allow the oil to flow therein in corresponding rotation of the driving shaft, and in this case the second path extend in direction opposite to a rotation direction of the driving shaft.

The second path is preferably positioned where an eccentricity of the driving shaft is small, and is basically spaced apart from the vane in clockwise or counterclockwise direction. The second path is preferably spaced apart from the vane by a range of 170°-210° in clockwise or counterclockwise direction, and more preferably is spaced apart from the vane by 190° in clockwise or counterclockwise direction. Further, a width of the second path is 3.8mm, and a depth of the second path is 1.67mm.

The second path is formed at the upper bearing at least. The second path is formed on an inner circumferential surface of the bearing, and continuously extends from an upper end to a lower end of the bearing. In addition, the second path is provided with the oil from the first path, and more specifically communicates with the first path. For such a reason, the first path includes at least one hole formed at the driving shaft and connecting the first path with the second path.

The first path is configured to disperse the oil toward driving parts of the compressor. Preferably, the first path continuously extends from a lower end to an upper end of the driving shaft and passes through the driving shaft in an axial direction of the driving shaft.

The oil path further comprises an auxiliary path formed at any one of journals in the driving shaft. The auxiliary path is formed on an outer circumferential surface of the journal. Specifically, the auxiliary path comprises at least one straight groove or at least one helical groove.

By the invention described above, driving parts in the rotary compressor are appropriately lubricated during operation.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. - A -

Brief Description of Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated as a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:

FIG. 1 is a partial longitudinal sectional view of a rotary compressor to which an oil path according to the present invention is applied;

FIG. 2 is a cross-sectional view of a cylinder taken along a line I-I of FIG. 1 ;

FIG. 3 is a front view showing the oil path of the rotary compressor according to the present invention;

FIG. 4 is a sectional view taken along a line H-II of FIG. 3 and showing a second path of the oil path;

FIG. 5A and 5B are partial sectional views each showing an inner circumferential surface of a bearing which includes the embodiment of the second path; FIG. 6 is a graph showing an optimal setting angle of the second path; and

FIGS. 7 A and 7B are partial front views each showing an auxiliary path.

Best Mode for Carrying Out the Invention

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or similar parts.

FIG. 1 is a partial longitudinal sectional view of a rotary compressor to which an oil path according to the present invention is applied, and FIG. 2 is a cross-sectional view of a cylinder of taken along a line I-I of FIG. 1.

As shown in FIG. 1, a rotary compressor of the present invention includes a case 1 and a power generating unit 10 and a compressing unit 20 which are positioned in the case 1. Referring to FIG. 1, the power generating unit 10 is positioned on the upper portion of the rotary compressor and the compressing unit 20 is positioned on the lower portion of the rotary compressor. However, their positions may be changed if necessary. An upper cap 3 and a lower cap 5 are installed on the upper portion and the lower portion of the case 1 respectively to define a sealed inner space. A suction pipe 7 for sucking a working fluid is installed on a side of the case 1 and connected to an accumulator 8 for separating a lubricant from a refrigerant. A discharge pipe 9 for discharging the compressed fluid is installed on the center of the upper cap 3. A predetermined amount of the lubricant "O" is filled in the lower cap 5 so as to lubricate and cool members that are moving frictionally. An end of a driving shaft 13 is dipped in the lubricant O.

The power generating unit 10 includes a stator 11 fixed to the case 1, a rotor 12 rotatably supported in the stator 11, and the driving shaft 13 inserted forcibly into the rotor 12. The rotor 12 is rotated by an electromagnetic force, and the driving shaft 13 delivers the rotation force of the rotor to the compressing unit 20. To supply external power to the stator 11 , a terminal 4 is installed in the upper cap 3.

The compressing unit 20 includes a cylinder 21 fixed to the case 1, a roller 22 disposed in the cylinder 21 (see FIG. 2), and upper and lower bearings 24 and 25 respectively installed on upper and lower portions of the cylinder 21.

The cylinder 21 has a predetermined inner volume and strength enough to endure the pressure of the compressed fluid. As shown in FIG. 2, the cylinder 21 accommodates an eccentric portion 13a formed on the driving shaft 13 in the inner volume thereof. The eccentric portion 13a is a kind of an eccentric cam and has a center spaced by a predetermined distance from a rotation center of the driving shaft 13. The cylinder 21 has a groove 21a extending by a predetermined depth from its inner circumference. A vane 23 to be described below is installed in the groove 21a. The groove 21a is long enough to accommodate the vane 23 completely.

The roller 22 is a ring member that has an outer diameter less than the inner diameter of the cylinder 21. As shown in FIG. 2, the roller 22 is in contact with the inner circumference of the cylinder 21 and is rotatably coupled with the eccentric portion 13 a. Accordingly, the roller 22 performs rolling motion on the inner circumference of the cylinder 21 while spinning on the outer circumference of the eccentric portion 13a when the driving shaft 13 rotates. The roller 22 revolves spaced apart by a predetermined distance from the rotation center due to the eccentric portion 13a during performing the rolling motion. Since an outer circumference of the roller 22 always contacts the inner circumference of the cylinder due to the eccentric portion 13a, the outer circumference of the roller 22 and the inner circumference of the cylinder define a separate fluid chamber 29 in the inner volume of the cylinder. The fluid chamber 29 is used to suck and compress the fluid in the rotary compressor.

The vane 23 is installed in the groove 21a of the cylinder 21 as described above. An elastic member 23 a is also installed in the groove 21a to elastically support the vane 23, and thus causes the vane 23 to continuously contact the roller 22. In other words, the elastic member 23a has one end fixed to the cylinder 21 and the other end coupled with the vane 23, and pushes the vane 23 toward the roller 22. Accordingly, the vane 23 divides the fluid chamber 29 into two separate spaces 29a and 29b as shown in FIG. 2. While the driving shaft 13 rotate or the roller 22 revolves, the volumes of the spaces 29a and 29b change complementarily. In other words, if the roller 22 rotates counterclockwise, the space 29b gets smaller but the other space 29a gets larger. However, the total volume of the spaces 29a and 29b is constant and approximately the same as that of the predetermined fluid chamber 29. When the driving shaft 13 rotates counterclockwise as shown in FIG. 2, the space 29a works as a suction chamber for sucking the fluid and the space 29b works as a compression chamber for compressing the fluid relatively. Accordingly, as described above, the compression chamber of the spaces 29b gets smaller to compress the previously sucked fluid and the suction chamber of the space 29a expands to suck the new fluid relatively according to the rotation of the roller 22.

The upper bearing 24 and the lower bearing 25 are, as shown in FIG. 1, installed on the upper and lower portions of the cylinder 21 respectively, and rotatably support the driving shaft 12. The cylinder 21, the upper bearing 24 and the lower bearing 25 are coupled with one another to seal the cylinder inner volume, especially the fluid chamber

29 using coupling members such as bolts and nuts.

In addition, though not shown in the drawings, a suction port and a discharge port are provided to the compressing unit 20. As shown in FIG. 1 , the suction port is formed at any one of the cylinder 21 and the bearings 24, 25 with being connected to the suction pipe 7, and the working fluid is supplied to the fluid chamber 29 through the suction port. Further, the discharge port is formed at any one of the bearings 24, 25 and is opened by a valve to discharge the compressed working fluid. Therefore, once the working fluid is supplied into the cylinder through the suction port, the roller 22 compresses the working fluid, rolling on the inner circumferential surface of the cylinder from the suction port to the discharge port. Then, the compressed working fluid is discharged out of the cylinder by the operation of the valve. This series of processes are repeatedly performed during the rotation of the driving shaft 13 to continuously produce the compressed working fluid.

Meanwhile, during the operation the compressor, mechanical elements such as the motor 11, 12, the driving shaft 13, and the roller 22 are in a high-speed rotation, and are exposed to a severer operational condition. Accordingly, a proper lubrication and a lubricating mechanism for such lubrication are fairly important for a stable operation of the compressor. The present invention provides an oil path as the lubricating mechanism , which is configured to supply oil, i.e. lubricant "O" to driving elements in the compressor, and this oil path will be specifically described as follows, referring relevant drawings. FIG. 3 is a front view showing the oil path of the dual capacity compressor according to the present invention. FIGS. 4-5B are drawings each illustrating a second path included in the oil path, and FIG. 6 is a graph showing an optimal setting angle of the second path.

As shown, the lubricating mechanism, i.e. the oil path 100 is formed along the driving shaft 13 and the bearings 24, 25. Journals 13b, 13c of the driving shaft 13 are surrounded by the upper and lower bearings 24, 25 respectively, and substantially form radial bearings supporting load normal to a center axis of the driving shaft. Additionally, collars 13d, 13e form together with the bearings 24, 25 thrust bearings supporting load in axial direction. The oil path 100 mainly comprises a shaft path 110 (hereinafter, referred to as "a first path") formed within the driving shaft 13.

More specifically, the first path 110 extends from a lower end of the driving shaft 13 to an upper end, and thus substantially passes through the driving shaft in a length direction thereof. In addition, at a lower end of the first path 110, an oil pump 111 is mounted. This oil pump 111 is a sort of a centrifugal pump, and includes an oil pickup Ilia and a propeller 111b inserted into the oil pickup Ilia. The oil pump 111 is dipped in the lubricant, i.e. the oil "O" in a bottom portion of the compressor (see FIG. 1), and thus the oil can flows in the first path 110 through the oil pump 111. Then, the oil is pumped along the first path 110 and is dispersed at the upper end of the driving shaft 13 in order to be supplied to corresponding driving parts. Additionally, the first path 110 further includes holes 112a, 112b formed at an upper portion and a lower portion of the eccentric portion 13a respectively to communicate with the first path 110. The oil is first supplied into the cylinder 21 though the holes 112a, 112b so as to lubricate the roller 22 and the eccentric portion 13 a. The holes 112a, 112b also allows the oil to be supplied to the upper and lower bearings 24, 25 and the driving shaft 13, accurately the journals 13b, 13c.

However, as the journals 13b, 13c and the bearings 24, 25 form large frictional surfaces as illustrated, the oil could not reach ends of the frictional surfaces only with a small amount of supply through the holes 112a, 112b. That is, the oil could not be spread all over the frictional surfaces, and could not entirely form oil films thereon for a prevention of abrasion. To solve such a problem, the oil path 100 in the present invention has a bearing path 120 (hereinafter, referred to as "a second path") formed at any one of the bearings 24, 25 as shown in FIG. 3 and FIGS. 4-5B. The second path 120 is substantially formed as a groove formed on an inner circumferential surface in any one of the bearings. The second path 120 communicates with the driving shaft 13, more accurately any one of the holes 112a, 112b adjacent thereto in order to be provided with the oil by the first path 110. In addition, the second path 120 preferably extends continuously between an upper end and a lower end of the inner circumferential surface. Therefore, the oil is supplied to the second path 120 from any one of the holes 112a, 112b, and then flows between both ends of the inner circumferential surface along the second path 120. Namely, due to the second path 120, the oil path 100 is configured to allow the oil to uniformly flow between the bearings 24, 25 and the driving shaft 13. The oil then spreads equally on the frictional surfaces, and forms the oil films entirely in order to effectively prevent the abrasion. It is desirable that such second path 120 is formed at the upper bearing 24 at least. This is because in the lower bearing, the oil can flows downward to some extent by gravity from the holes 112b. However, it is more desirable for suitable lubrication that the second paths 120 are formed at both of the upper and lower bearings 24, 25 respectively.

As shown in FIG. 5B, the second path 120 could be formed as a helical groove. This helical groove expands a substantial flow passage and enables a sufficient oil supply. However, the helical groove can allow the oil to flow therein in any one direction of the rotations of the driving shaft 13 due to its geometric characteristic. More specifically, the helical groove can allow the oil to flow and ascend therein only when it extends in a direction opposite to the rotational direction of the driving shaft 13. For that reason, the second path 120 preferably comprises a single straight groove as shown in FIG. 5 A. The straight groove is not affected by the geometrical characteristic contrary to the helical groove, and can allow the oil to flow therein by centrifugal force generated by the driving shaft 13 regardless of the rotational direction of. the driving shaft. Meanwhile, referring to FIG. 4, clearances C with predetermined sizes are formed between the bearings 24, 25 and the driving shaft 13 (more accurately, the journals 13 b, 13 c), and the oil fills such clearances C using the second paths 120 to form the oil films therein. The driving shaft 13 is subject to pressure from the compressed working fluid during the operation of the compressor, and thus rotates eccentric from centers O of the bearings 24, 25. In addition, as the second paths 120 damage the inner circumferential surfaces of the bearings continuously along their length directions, the clearances C are increased around the second paths 120 and the sufficient oil films are not formed around the second paths 120 due to the increased clearances C. Accordingly, if the second paths 120 are positioned where an eccentricity of the driving shaft 13 is greatly generated , the driving shaft 13 may be in contact with the inner circumferential surfaces of the bearings

24, 25. In this case, the abrasion between the bearings 24, 25 and the driving shaft 13 may occur, and simultaneously, nose may be made during the operation of the compressor. Also, the power loss of the driving shat 13 may occur due to the excessive abrasion. Therefore, it is preferable for the second paths 120 to be positioned where the eccentricity of the driving shaft 13 is small. More specifically, the second paths 120 are formed at portions of the inner circumferential surfaces in the bearings 24, 25, which confront positions where the eccentricity of the driving shaft 13 is small.

In the present invention, optimal positions of the second paths 120 were determined by experiments, and FIG. 6 shows experimental result considered for the optimal positions of the second path 120.

As illustrated, FIG. 6 is graph showing change of an eccentricity ratio to an angle. First, the angle is set to be 0° at the vane 23 positioned beneath and above the bearings 24,

25, and is also set to increase in the rotation direction of the driving shaft 13. The compressor was set to compress the working fluid in the counterclockwise rotation in the experiment, and thus the angle was set to increase in the counterclockwise direction as shown in FIG. 4. The eccentricity ratio is defined as a ratio of an eccentric distance (i.e. a distance from the bearing center O to a center of the driving shaft) to the clearance C. This eccentricity ratio is a dimensionless index showing how much the driving shaft 13 is close to the inner circumferential surfaces of the bearings 24, 25. As the clearance C is constant, the great eccentricity ratio means that the driving shaft has a great amount of the eccentricity and is close to the inner circumferential surfaces of the bearings 24, 25. As a result of the experiment, such eccentricity ratios were not greatly changed and rather showed almost identical tendencies, with regard to various specifications of the compressors subject to the experiment.

First, as the working fluid is maximally compressed near the vane 23, the eccentricity ratio has relatively great values at 0° (360°), i.e. at the vane 23. In addition, if the second path 120 is positioned above or beneath the vane 23, the working fluid having the maximum pressure near the vane 23 may leak into such second path 120. In view of these conditions, it is preferable that the second path 120 is basically spaced apart from the vane 23 in the clock or counterclockwise direction with reference to the center O. More specifically, the eccentricity ratio has relatively small values in a range of

170° - 210°. Accordingly, the second path 120 is preferably spaced apart from the vane 23 by an angle A of 170° - 210° in the counterclockwise direction, hi addition, the compressor of the present invention could be designed to compress the working fluid in the clockwise rotation. Even in this case, it would be appreciated that the same result as FIG. 4 is obtained, when the angle is set to increase in the clockwise direction in which the compression is performed. Therefore,_, the second path 120 could be spaced apart from the vane 23 by the angle of 170° - 210° in the counterclockwise or clockwise direction. Additionally, the eccentric ratio has the smallest value at 240°. This means that chances to be contact with shaft are minimized in both of the clockwise and counterclockwise rotations. Accordingly, it is most preferable for the angle A to be 240°. Further, the second path 120 has appropriate width w and depth d in order to allow the sufficient amount of the oil to flow therein as well as to reduce the damage on the inner circumferential surfaces of the bearings interrupting a formation of the oil films. These width w and depth d are preferably 3.8mm and 1.67mm respectively, although they are slightly varied according to the specifications of the compressors. •

Further, to allow the oil to flow more sufficiently between the bearings 24, 25 and the driving shaft 13, the oil path 100 additionally includes an auxiliary path 130 as shown in FIG. 4 and FIGS. 7A-7B. This auxiliary path 130 comprises groove formed along the journals 13b, 13c, and preferably extends over entire lengths of the journals 13b, 13c.

Similar to the second path 120, the auxiliary path 130 comprises a single straight groove as shown in FIG. 7 A, or two helical grooves 130a, 130b as shown in FIG. 7B. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Industrial Applicability

In the present invention, uniform oil films are formed between a driving shaft and bearings by a lubricating mechanism as explained above. Accordingly, an abrasion of the driving shaft is effectively prevented under the severe operational environment. Further, such lubricating mechanism allows the oil to flow therein in all the rotational directions of the driving shaft and is positioned where an eccentricity of the driving shaft is small. Therefore, the lubrication for preventing the abrasion becomes more stable and effective.

Claims

Clairns

1. A rotary compressor comprising: a driving shaft and having an eccentric portion of a predetermined size; a cylinder defining a predetermined inner volume; a roller installed rotatably on an outer circumference of the eccentric portion so as to contact an inner circumference of the cylinder, and performing a rolling motion along the inner circumference; a vane installed elastically in the cylinder to contact the roller continuously; upper and lower bearings installed respectively in upper and lower portions of the cylinder, for supporting the driving shaft rotatably and sealing the inner volume hermetically; and an oil path including; a first path extending within the driving shaft and being configured to pump an oil, and a second path formed at any one of bearings and configured to allow the pumped oil to uniformly flow between the bearings and the driving shaft.

2. The rotary compressor of claim 1, wherein the second path comprises a single straight groove allowing the oil to flow therein regardless of rotational directions of the driving shaft.

3. The rotary compressor of claim I₅ wherein the second path comprises at least one groove each configured to allow the oil to flow therein in corresponding rotation of the driving shaft.

4. The rotary compressor of claim 3, wherein the second path extend in direction opposite to a rotation direction of the driving shaft.

5. The rotary compressor of claim 1, wherein the second path is positioned where an eccentricity of the driving shaft is small.

6. The rotary compressor of claim 1, wherein the second path is positioned where the driving shaft does not closely approach.

7. The rotary compressor of claim 1, wherein the second path is spaced apart from the vane in clockwise or counterclockwise direction.

8. The rotary compressor of claim 1, wherein the second path is spaced apart from the vane by a range of 170°-210° in clockwise or counterclockwise direction.

9. The rotary compressor of claim 1, wherein the second path is spaced apart from the vane by 190° in clockwise or counterclockwise direction.

10. The rotary compressor of claim I₅ wherein a width of the second path is 3.8mm.

11. The rotary compressor of claim I₅ wherein a depth of the second path is 1.67mm.

12. The rotary compressor of claim I₅ wherein the second path is formed at the upper bearing at least.

13. The rotary compressor of claim 1, wherein the second path is formed on an inner circumferential surface of the bearing:

14. The rotary compressor of claim 1, wherein the second path continuously extends from an upper end to a lower end of the bearing.

15. The rotary compressor of claim 1, wherein the second path is provided with the oil from the first path.

16. The rotary compressor of claim 1, wherein the second path communicates with the first path.

17. The rotary compressor of claim 1, wherein the first path includes at least one hole formed at the driving shaft and connecting the first path with the second path.

18. The rotary compressor of claim 1, wherein the first path is configured to disperse the oil toward driving parts of the compressor.

19. The rotary compressor of claim 1, wherein the first path continuously extends from a lower end to an upper end of the driving shaft.

20.. The rotary compressor of claim 1, wherein the first path passes through the driving shaft in an axial direction of the driving shaft.

21. The rotary compressor of claim 1, wherein the oil path further comprises an auxiliary path formed at any one of journals in the driving shaft.

22. The rotary compressor of claim 21, wherein the auxiliary path is formed on an outer circumferential surface of the journal.

23. The rotary compressor of claim 21, wherein the auxiliary path comprises at least one straight groove.

24. The rotary compressor of claim 24, wherein the auxiliary path comprises at least one helical groove.