Scroll compressor with centrifugal oil pump

Abstract

A scroll compressor (1) is provided with: a compression unit (6); a vertically oriented drive shaft (16); upper and lower bearing means (27, 28) configured to rotatably support the drive shaft (16); a centrifugal oil pump (29) comprising an extraction tube (32) attached to the lower end portion (23) of the drive shaft (16) and provided with an oil inlet submerged in the oil sump (31), the centrifugal oil pump (29) being configured to deliver oil to the compression unit (6) and to the upper and lower bearing means (27, 28); and a stationary cowl member (35) fixed to a non-rotating portion of the scroll compressor (1) and including a stationary tubular portion (36) immersed in the oil groove (31) and surrounding the extraction pipe (32) at a predetermined distance such that a gap is formed between an inner surface of the stationary tubular portion (36) and an outer surface of the extraction pipe (32).

Description

[0001] This application is a divisional application of a patent application (application date February 18, 2022, application number 202210154531.0, invention name “Scroll compressor with centrifugal oil pump”). Technical Field

[0002] The present invention relates to a scroll compressor, and in particular to a scroll refrigeration compressor. Background Art

[0003] As we all know, scroll compressors include:

[0004] - a closed casing provided with a suction inlet intended for receiving low-pressure refrigerant gas from a component of a refrigeration cycle and a discharge inlet intended for delivering compressed refrigerant gas at high pressure to another component of the refrigeration cycle;

[0005] - a compression unit comprising at least a first scroll element and a second scroll element, the second scroll element being configured to perform an orbital motion relative to the first scroll element during operation of the scroll compressor;

[0006] - a drive shaft, the drive shaft being vertically oriented and configured to cooperate with the second scroll element;

[0007] - an electric motor comprising a stator connected to a closed housing and a rotor fixed to a drive shaft, the electric motor being configured to drive the drive shaft in rotation about a rotation axis;

[0008] - upper and lower bearing means configured to rotatably support the drive shaft within a closed housing, the upper and lower bearing means being connected to the closed housing; and

[0009] a centrifugal oil pump comprising an extraction pipe attached to a lower end portion of the drive shaft and provided with an oil inlet arranged at the lower end of the extraction pipe, the oil inlet being immersed in an oil sump arranged in a bottom section of the closed casing, the oil pump being configured to deliver oil to the compression unit and the upper and lower bearing means during operation of the scroll compressor through an oil supply channel formed in the drive shaft and extending over at least a portion of the length of the drive shaft.

[0010] This simple centrifugal oil pump is widely used in fixed speed scroll compressors due to its low manufacturing cost. For variable speed scroll compressors, this centrifugal oil pump must be modified to ensure sufficient oil supply over the entire operating speed range (eg, at high operating speeds).

[0011] US 7,351,045 B2 discloses a scroll compressor including a pump device provided with a centrifugal extraction pump attached to the lower end of a drive shaft and an oil cup attached to the bottom of a compressor housing. The side wall of the oil cup surrounds the centrifugal extraction pump and is provided with a through hole that communicates the interior of the oil cup with an oil tank. In order to prevent excessive rotation of the oil in the oil cup, a blade element is attached to the inner wall surface of the oil cup, and the blade element extends radially toward the centrifugal extraction pump.

[0012] JP 2014-118932 A discloses a scroll compressor having another shield for a centrifugal oil pump. Here, a cylindrical skirt member is attached to a lower bearing seat and surrounds the centrifugal oil pump at a certain distance. The axial end of the cylindrical skirt member is arranged below the oil inlet of the centrifugal oil pump. A cup-shaped oil filter is attached to the cylindrical skirt member and surrounds the lower end and the oil inlet of the centrifugal oil pump.

[0013] Both solutions disclosed in US 7,351,045 B2 and JP 2014-118932 A are relatively expensive for some reason and cannot completely prevent eddy currents or rotations of the oil at the oil inlet of the extraction oil pump, so that a stable oil supply cannot be ensured at very high compressor speeds. Summary of the invention

[0014] An object of the present invention is to provide an improved scroll compressor which overcomes the disadvantages encountered in conventional scroll compressors.

[0015] In particular, an object of the present invention is to provide a scroll compressor having a low-cost, reliable oil pump that enables stable oil supply to upper and lower bearing devices and a compression unit.

[0016] Another object of the present invention is to provide a scroll compressor having improved efficiency and lifespan compared to conventional scroll compressors.

[0017] According to the present invention, the scroll compressor comprises:

[0018] - a closed casing, the closed casing being provided with a suction port and a discharge port, the suction port being configured to supply the scroll compressor with refrigerant gas to be compressed, and the discharge port being configured to discharge the compressed refrigerant gas;

[0019] - a compression unit comprising at least a first scroll element and a second scroll element, the second scroll element being configured to perform an orbital motion relative to the first scroll element during operation of the scroll compressor;

[0020] - a drive shaft, the drive shaft being vertically oriented and configured to cooperate with the second scroll element;

[0021] - an upper bearing arrangement and a lower bearing arrangement, the upper bearing arrangement and the lower bearing arrangement being configured to rotatably support the drive shaft within the closed housing;

[0022] a centrifugal oil pump comprising an extraction pipe attached to a lower end portion of the drive shaft and provided with an oil inlet arranged at the lower end of the extraction pipe, the oil inlet being immersed in an oil sump arranged in a bottom section of the closed casing, the centrifugal oil pump being configured to deliver oil to the compression unit and to the upper bearing arrangement and the lower bearing arrangement during operation of the scroll compressor;

[0023] Therein, the scroll compressor further comprises a stationary fairing member fixed to a non-rotating part of the scroll compressor, the stationary fairing member comprising a stationary tubular portion, the stationary tubular portion being at least partially immersed in the oil tank and surrounding the extraction pipe at a predetermined distance so that a gap is formed between an inner surface of the stationary tubular portion and an outer surface of the extraction pipe, the minimum radial distance between the inner surface of the stationary tubular portion and the outer surface of the extraction pipe being between 0.5 mm and 5 mm, and advantageously being about 2 mm.

[0024] The specific configuration of the stationary tubular portion, and in particular the fact that it is separated from the extraction tube by a small predetermined distance, avoids (or at least minimizes) rotation, eddy currents or turbulence in the oil at the oil inlet of the extraction tube, since the surface area of ​​the rotating extraction tube exposed to the oil sump volume is relatively small.

[0025] In particular, the specific configuration of the stationary tubular portion allows, especially at high compressor speeds, to minimize the agitation of the lubricating oil in the oil sump and thus substantially reduce the formation of bubbles or even foaming of the lubricating oil contained in the oil sump. Thus, the amount of oil entering the centrifugal oil pump is increased compared to conventional scroll compressors, and the amount of oil delivered to the various surfaces to be lubricated and / or to be sealed of the compressor is also increased. This results in reduced friction in the various surfaces to be lubricated of the compressor and thus improved efficiency and longer life of the compressor, while using a low-cost, reliable oil pump.

[0026] Furthermore, by minimizing oil agitation at the upper free surface of the oil sump in contact with the suction flow of the refrigerant gas, undesirable increases in oil circulation rates within the refrigeration system may be avoided.

[0027] The scroll compressor may also include one or more of the following features, alone or in combination.

[0028] According to an embodiment of the invention, the stationary tubular portion shields the submerged wall portion of the extraction pipe submerged in the oil sump from the oil contained in the sump, except for an area of ​​the submerged wall portion of the extraction pipe adjacent to the oil inlet.

[0029] According to an embodiment of the invention, the stationary tubular portion shields the immersed wall portion of the extraction pipe immersed in the oil sump from the oil contained in the oil sump.

[0030] According to an embodiment of the invention, the stationary tubular portion surrounds the lower end of the extraction duct and thus extends over the lower end of the extraction duct.

[0031] According to an embodiment of the invention, the stationary fairing component is arranged coaxially with the extraction duct.

[0032] According to an embodiment of the invention, the gap formed between the inner surface of the stationary tubular portion and the outer surface of the extraction tube is annular.

[0033] According to an embodiment of the invention, the width of the gap is selected such that negligible friction is generated between the inner surface of the stationary tubular portion and the outer surface of the extraction pipe and such that an oil-free area is avoided at the oil inlet of the extraction pipe.

[0034] According to an embodiment of the invention, the stationary tubular portion comprises a lower tubular part, which surrounds the lower tubular part of the extraction tube, for example with a constant gap.

[0035] According to an embodiment of the present invention, the inner surface of the stationary tubular portion and the outer surface of the extraction tube are configured such that the width of the gap formed between the outer surface of the extraction tube and the inner surface of the stationary tubular portion is substantially uniform along the longitudinal axis of the extraction tube and / or along the circumference of the extraction tube.

[0036] According to an embodiment of the invention, the inner surface of the stationary tubular portion and the outer surface of the extraction tube are substantially complementary.

[0037] According to an embodiment of the present invention, the stationary tubular portion extends axially from the lower end of the extraction pipe. In other words, the lower end of the stationary tubular portion is located below the lower end of the extraction pipe.

[0038] According to an embodiment of the invention, the axial distance between the lower end of the stationary tubular portion and the lower end of the extraction tube is between 1 mm and 3 mm, and is advantageously about 2 mm.

[0039] According to an embodiment of the invention, an axial distance between a lower end of the stationary tubular portion and a lower end of the extraction pipe is greater than a minimum radial distance between an inner surface of the stationary tubular portion and an outer surface of the extraction pipe.

[0040] According to an embodiment of the present invention, the inner surface of the stationary tubular portion directly faces the outer surface of the extraction pipe. In other words, no other structural part of the scroll compressor is located between the inner surface of the stationary tubular portion and the outer surface of the extraction pipe.

[0041] According to an embodiment of the invention, the stationary tubular portion comprises an inlet opening which is arranged at a lower end of the stationary tubular portion and faces the oil inlet port of the extraction pipe.

[0042] According to an embodiment of the present invention, the flow cross-sectional area of ​​the inlet opening of the stationary tubular portion substantially corresponds to or is larger than the flow cross-sectional area of ​​the oil inlet port of the extraction pipe.

[0043] According to an embodiment of the invention, the stationary fairing component comprises inlet guide vanes extending radially from an outer surface of the stationary tubular portion.

[0044] According to an embodiment of the invention, the stationary fairing component is arranged coaxially with the radial bearing seat.

[0045] According to an embodiment of the invention, the extraction tube is attached (eg by press-fitting) in an axial recess formed at the axial lower end of the drive shaft.

[0046] According to an embodiment of the invention, the stationary tubular portion is cylindrical or cannulated and has a substantially uniform inner diameter along a longitudinal axis of the stationary tubular portion.

[0047] According to an embodiment of the present invention, the stationary tubular portion comprises an upper tubular portion and a lower tubular portion, the upper tubular portion being cylindrical or canister-shaped and the lower tubular portion converging towards a lower end of the stationary tubular portion.

[0048] According to an embodiment of the invention, the centrifugal oil pump is configured to deliver oil to the compression unit and the upper bearing arrangement during operation of the scroll compressor through an oil supply passage formed in the drive shaft and extending over at least a portion of its length.

[0049] According to an embodiment of the present invention, the lower bearing device includes a radial bearing seat, which is configured to rotatably support the lower end portion of the drive shaft, and the radial bearing seat includes an inner radial bearing surface, which surrounds the outer surface of the lower end portion of the drive shaft.

[0050] According to an embodiment of the invention, the stationary fairing component is fixed to the radial bearing seat.

[0051] According to an embodiment of the present invention, the lower bearing device also includes an upper axial thrust bearing and a lower axial thrust bearing and a pressurized oil chamber, wherein the upper axial thrust bearing and the lower axial thrust bearing are configured to limit the axial movement of the drive shaft during operation, and the pressurized oil chamber is fluidly connected to the centrifugal oil pump, and the pressurized oil chamber is at least partially defined by the outer surface of the lower end portion of the drive shaft, the inner radial bearing surface, and the upper axial thrust bearing and the lower axial thrust bearing.

[0052] According to an embodiment of the present invention, the pressurized oil chamber is defined in the axial direction by the upper axial thrust bearing and the lower axial thrust bearing, respectively.

[0053] According to an embodiment of the invention, the lower end portion of the drive shaft comprises a radial opening, which is fluidly connected to an oil outlet of the centrifugal oil pump, which faces the radial bearing seat and emerges into the pressurized oil chamber.

[0054] According to an embodiment of the present invention, the scroll compressor is a variable speed scroll compressor or a fixed speed scroll compressor.

[0055] According to an embodiment of the present invention, the scroll compressor includes an electric motor including a stator connected to the hermetic housing and a rotor fixed to the drive shaft, the electric motor being configured to drive the drive shaft to rotate around a rotation axis.

[0056] According to an embodiment of the invention, the radial clearance ratio, which is the ratio between the minimum radial distance and the outer diameter of the extraction tube, is between 2% and 25%, preferably between 5% and 15%.

[0057] According to an embodiment of the present invention, the width of the gap is substantially uniform along the longitudinal axis of the upper tube portion of the extraction tube and along the outer circumference of the upper tube portion of the extraction tube, and the width of the gap increases along the longitudinal axis of the lower tube portion of the extraction tube and toward the lower end of the extraction tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The following detailed description of various embodiments of the present invention may be better understood when read in conjunction with the appended drawings; however, it should be understood that the invention is not limited to the particular embodiments disclosed.

[0059] Figure 1 is a partially cutaway perspective view of a scroll compressor according to a first embodiment of the present invention.

[0060] Figure 2 yes Figure 1A magnified view of the details.

[0061] Figure 3 yes Figure 1 A partial longitudinal cross-sectional view of a scroll compressor.

[0062] Figure 4 is a partial longitudinal sectional view of a scroll compressor according to a second embodiment of the present invention.

[0063] Figure 5 is a partial longitudinal sectional view of a scroll compressor according to a third embodiment of the present invention. DETAILED DESCRIPTION

[0064] Figure 1 A scroll compressor 1 according to a first embodiment of the present invention is described.

[0065] The scroll compressor 1 comprises a hermetic shell 2 provided with a suction port 3 configured to supply refrigerant gas to be compressed to the scroll compressor 1, and a discharge port 4 configured to discharge the compressed refrigerant gas. In particular, the suction port 3 is intended for receiving low-pressure refrigerant gas from one part of a refrigeration cycle, and the discharge port 4 is intended for delivering compressed refrigerant gas at high pressure to another part of the refrigeration cycle.

[0066] The scroll compressor 1 further includes a support device 5 fixed to the hermetic shell 2 and a compression unit 6 disposed inside the hermetic shell 2 and supported by the support device 5. The compression unit 6 is configured to compress the refrigerant gas supplied through the suction port 3.

[0067] According to the embodiment shown in the drawings, the compression unit 6 comprises a first scroll element 7, which is fixed relative to the closed housing 2, and a second scroll element 8, which is supported by and in sliding contact with an upper thrust bearing surface 9 provided on the support device 5. The second scroll element 8 is configured to perform an orbiting movement relative to the first scroll element 7 during operation of the scroll compressor 1.

[0068] The first vortex element 7 comprises a fixed base plate 11 having a lower surface and an upper surface, the lower surface being oriented toward the second vortex element 8 and the upper surface being opposite to the lower surface of the fixed base plate 11. The first vortex element 7 further comprises a fixed spiral wrap 12 extending from the lower surface of the fixed base plate 11 toward the second vortex element 8.

[0069] The second scroll element 8 includes an orbiting base plate 13, which has an upper surface and a lower surface, the upper surface is oriented toward the first scroll element 7, and the lower surface is opposite to the upper surface of the orbiting base plate 13 and is slidably mounted on the upper thrust bearing surface 9. The second scroll element 8 also includes an orbiting spiral scroll 14, which extends from the upper surface of the orbiting base plate 13 toward the first scroll element 7. The orbiting spiral scroll 14 of the second scroll element 8 is engaged with the fixed spiral scroll 12 of the first scroll element 7 to form a plurality of compression chambers 15 between the orbiting spiral scroll 14 and the fixed spiral scroll 12. Each of the compression chambers 15 has a variable volume, and when the second scroll element 8 is driven to orbit relative to the first scroll element 7, the variable volume of each of the compression chambers 15 decreases from the outside to the inside.

[0070] Furthermore, the scroll compressor 1 comprises a drive shaft 16 oriented vertically and configured to drive the second scroll element 8 in an orbital motion, and an electric motor 17 , which may be, for example, a variable speed electric motor, coupled to the drive shaft 16 and configured to drive the drive shaft 16 in rotation about the rotation axis A. The electric motor 17 comprises in particular a stator 18 connected to the hermetic housing 2 and a rotor 19 fixed to the drive shaft 16 .

[0071] The drive shaft 16 includes a longitudinal main body portion 21, which includes an upper end portion 22 and a lower end portion 23. The drive shaft 16 further includes a drive portion 24, which is arranged at the upper end of the longitudinal main body portion 21 and deviates from the longitudinal axis of the drive shaft 16. The drive portion 24 is partially mounted in a hub portion 25 provided on the second vortex element 8, and the drive portion 24 is configured to cooperate with the hub portion 25 to drive the second vortex element 8 to orbit relative to the first vortex element 7 when the electric motor 17 is operated.

[0072] The drive shaft 16 also includes an oil supply passage 26 formed in the drive shaft 16 and extending over at least a portion of the length of the drive shaft 16. According to the embodiment shown in the drawings, the oil supply passage 26 extends along the entire length of the drive shaft 16 and emerges in the axial upper end surface of the drive shaft 16.

[0073] The scroll compressor 1 further includes an upper bearing device 27 and a lower bearing device 28 connected to the closed casing 2 and configured to rotatably support the upper end portion 22 and the lower end portion 23 of the longitudinal body portion 21, respectively.

[0074] The scroll compressor 1 further comprises a centrifugal oil pump 29 which is arranged at the lower end of the drive shaft 16 and is partially immersed in an oil sump 31 arranged in the bottom section of the closed housing 2. The centrifugal oil pump 29 is configured to deliver oil from the oil sump 31 to the compression unit 6 and to the upper bearing device 27 and the lower bearing device 28 during operation of the scroll compressor 1. The centrifugal oil pump 29 is particularly configured to deliver oil to the compression unit 6 and to the upper bearing device 27 through the oil supply channel 26 formed in the drive shaft 16 during operation of the scroll compressor 1.

[0075] The centrifugal oil pump 29 includes an extraction pipe 32 which is attached (e.g., by press-fitting) in an axial recess 33 formed at the axial lower end of the drive shaft 16. The extraction pipe 32 includes an oil inlet 34 which is arranged at the lower end of the extraction pipe 32 and immersed in the oil sump 31. Figures 1 to 3 In the illustrated embodiment, the extraction pipe 32 comprises an upper pipe portion 32 . 1 which is cylindrical and a lower pipe portion 32 . 2 which extends coaxially with the upper pipe portion 32 . 1 and converges toward the lower end of the extraction pipe 32 .

[0076] The scroll compressor 1 further comprises a stationary cowling member 35 fixed to a non-rotating part of the scroll compressor 1 and arranged coaxially with the extraction pipe 32. The stationary cowling member 35 comprises a stationary tubular portion 36 which is partially immersed in the oil sump 31. Figures 1 to 3 In the illustrated embodiment, the stationary tubular portion 36 is cylindrical and has a substantially uniform inner diameter along the longitudinal axis of the stationary tubular portion 36 .

[0077] The stationary tubular portion 36 surrounds the extraction pipe 32 at a predetermined distance so that a gap 37 is formed between the inner surface of the stationary tubular portion 36 and the outer surface of the extraction pipe 32. The stationary tubular portion 36 particularly surrounds the lower end of the extraction pipe 32 and thus surrounds the oil inlet 34.

[0078] The width of the gap 37 is selected so that negligible friction is generated between the inner surface of the stationary tubular portion 36 and the outer surface of the extraction pipe 32 and so that the formation of an oil-free zone at the oil inlet 34 of the extraction pipe 32 is avoided. In particular, the minimum radial distance Dr between the inner surface of the stationary tubular portion 36 and the outer surface of the extraction pipe 32 is between 0.5 mm and 5 mm, and is advantageously about 2 mm.

[0079] According to an embodiment of the present invention, the radial void ratio, which is the ratio between the minimum radial distance Dr and the outer diameter of the extraction tube 32 , is between 2% and 25%, preferably between 5% and 15%.

[0080] according to Figures 1 to 3 In the illustrated embodiment, the width of the gap 37 is substantially uniform along the longitudinal axis of the upper tube portion 32 . 1 of the extraction tube 32 and along the outer circumference of the upper tube portion 32 . 1 of the extraction tube 32 , and the width of the gap 37 increases along the longitudinal axis of the lower tube portion 32 . 2 of the extraction tube 32 and toward the lower end of the extraction tube 32 .

[0081] The stationary tubular portion 36 comprises an inlet opening 38 which is arranged at the lower end of the stationary tubular portion 36 and faces the oil inlet 34 of the extraction pipe 32. Figures 1 to 3 In the illustrated embodiment, the inlet opening 38 and the oil inlet port 34 each have a circular shape, and the flow cross-sectional area of ​​the inlet opening 38 of the stationary tubular portion 36 is larger than the flow cross-sectional area of ​​the oil inlet port 34 of the extraction pipe 32 .

[0082] like Figure 3 As shown, the stationary tubular portion 36 axially extends from the lower end of the extraction tube 32. In other words, the lower end of the stationary tubular portion 36 is located below the lower end of the extraction tube 32. The axial distance Da between the lower end of the stationary tubular portion 36 and the lower end of the extraction tube 32 is between 1 mm and 3 mm, and is advantageously about 2 mm. In particular, the axial distance Da between the lower end of the stationary tubular portion 36 and the lower end of the extraction tube 32 is greater than the minimum radial distance Dr between the inner surface of the stationary tubular portion 36 and the outer surface of the extraction tube 32.

[0083] The provision of the stationary fairing member 35, and in particular the configuration of the stationary tubular portion 36, avoids (or at least minimizes) rotation, swirl or turbulence in the oil at the oil inlet 34 of the extraction tube 32, since the surface area or surface area of ​​the rotating extraction tube 12 that is exposed to the oil sump volume is relatively small.

[0084] Furthermore, the configuration of the stationary tubular portion 36 allows, in particular at high compressor speeds, to minimize the agitation of the lubricating oil in the sump and thus substantially reduce the formation of bubbles or even foaming of the lubricating oil contained in the sump 31. This results in reduced friction in the various thrust and radial bearing surfaces supplied with oil by the centrifugal oil pump 29, increasing the efficiency and life of the compressor.

[0085] Furthermore, by minimizing oil agitation at the upper free surface of the oil sump in contact with the suction flow of the refrigerant gas, undesirable increases in oil circulation rates within the refrigeration system may be avoided.

[0086] As in Figure 2As better shown, the lower bearing device 28 comprises a radial bearing seat 39 configured to rotatably support the lower end portion 23 of the drive shaft 16. The radial bearing seat 39 surrounds the lower end portion 23 of the drive shaft 16 and is arranged coaxially with the drive shaft 16. Advantageously, the radial bearing seat 39 has an overall tubular shape and is formed by a radial bearing sleeve.

[0087] According to the embodiment shown in the drawings, the radial bearing seat 39 comprises an inner radial bearing surface 40 which is cylindrical and surrounds the outer surface of the lower end portion 23 of the drive shaft 16. The inner radial bearing surface 40 has a first inner diameter. The radial bearing seat 39 also comprises an inner circumferential surface 41 which has a second inner diameter greater than the first inner diameter. Advantageously, the radial bearing seat 39 also comprises a frustoconical inner surface 42 which is located between the inner radial bearing surface 40 and the inner circumferential surface 41 and which gradually expands towards the inner circumferential surface 41.

[0088] The lower bearing device 28 further includes a bracket member 43 fixed to the inner surface of the closed housing 2, and the radial bearing seat 39 includes a mounting portion 44, which has an annular shape and is fixed to the bracket member 43, for example, by using screws or bolts. Advantageously, the stationary fairing member 35 is arranged coaxially with the radial bearing seat 39 and arranged below the radial bearing seat 39, and the stationary fairing member 35 is fixed to the mounting portion 44 of the radial bearing seat 39.

[0089] The stationary fairing component 35 may include a centering rib 45 that is annular and configured to cooperate with the radial bearing seat 39 to center or center the stationary fairing component 35 relative to the longitudinal axis of the radial bearing seat 39 .

[0090] Furthermore, the lower bearing arrangement 28 comprises an upper axial thrust bearing 46 and a lower axial thrust bearing 47, which are configured to limit the axial movement of the drive shaft 16 during operation. According to the embodiment shown in the drawings, the upper axial thrust bearing 46 is formed by an axial upper end surface 48 of the radial bearing seat 39 and a shoulder surface 49 fixed to the drive shaft 16. The shoulder surface 49 can be formed integrally with the drive shaft 16, or can be formed by a separate annular portion 50 fixed to the drive shaft 16. Advantageously, the axial upper end surface 48 and the shoulder surface 49 are each annular.

[0091] According to the embodiment shown in the drawings, the lower axial thrust bearing 47 is formed by the axial lower end surface 51 of the drive shaft 16 and the inner bottom surface 52 of the radial bearing seat 39. Advantageously, the axial lower end surface 51 and the inner bottom surface 52 are each annular, and the radial bearing seat 39 includes a radially inwardly protruding annular flange 53, which includes the inner bottom surface 52.

[0092] The lower bearing device 28 also includes a pressurized oil chamber 54, which is fluidly connected to the centrifugal oil pump 29. The pressurized oil chamber 54 is defined by the outer surface of the lower end portion 23 of the drive shaft 16, the inner radial bearing surface 40, the inner circumferential surface 41, and the upper axial thrust bearing 46 and the lower axial thrust bearing 47. Advantageously, the pressurized oil chamber 54 is defined in the axial direction by the upper axial thrust bearing 46 and the lower axial thrust bearing 47, respectively.

[0093] like Figure 2 As preferably shown, the pressurized oil chamber 54 comprises an annular pressurized oil volume 55 which surrounds the lower end portion 23 of the drive shaft 16 and is externally delimited by the radial bearing seat 39 and in particular by the inner circumferential surface 41 and the frustoconical inner surface 42. Advantageously, the annular pressurized oil volume 55 is located below the inner radial bearing surface 40 and adjacent to the inner bottom surface 52.

[0094] According to the embodiment shown in the figures, the lower end portion 23 of the drive shaft 16 comprises at least one radial opening 56 which is fluidically connected to the oil outlet of the centrifugal oil pump 29. Advantageously, the radial opening 56 faces the inner surface of the radial bearing seat 39 and emerges in the pressurized oil chamber 54 and in particular in the annular pressurized oil volume 55. Advantageously, the oil outlet of the centrifugal oil pump 29, which is fluidically connected to the radial opening 56, extends radially and is arranged on the side wall of the extraction pipe 32.

[0095] The pressurized oil chamber 54 further includes an oil passage 57 formed between the outer surface of the lower end portion 23 of the drive shaft 16 and the inner surface of the radial bearing seat 39. Advantageously, the oil passage 57 extends along an extension direction substantially parallel to the longitudinal axis of the drive shaft 16. The oil passage 57 is particularly configured to fluidly connect the upper axial thrust bearing 46 with the annular pressurized oil volume 55 of the pressurized oil chamber 54. The oil passage 57 may be formed as a flat surface portion provided on the outer periphery of the lower end portion 23 of the drive shaft 16.

[0096] At high rotational speeds of the rotor 19 and the drive shaft 16, the oil delivered by the oil outlet of the centrifugal oil pump 29 is high and therefore a high oil centrifugal velocity occurs at the radial opening 56 of the drive shaft 16, resulting in a significant hydrodynamic pressure in the pressurized oil chamber 54. When the pressurized oil chamber 54 is closed by the upper axial thrust bearing 46 and the lower axial thrust bearing 47, a hydrostatic force is formed, which can have the same magnitude as the gravity force originating from the mass of the drive shaft 16. Due to the reduced friction losses, this improves the lubrication of the upper axial thrust bearing 46 and the lower axial thrust bearing 47 and thus further improves the compressor efficiency. In addition, the wear on the thrust bearing surface of the upper axial thrust bearing 46 and the thrust bearing surface of the lower axial thrust bearing 47, and in particular the wear on the thrust bearing surface of the lower axial thrust bearing 47, is reduced, which further improves the life of the scroll compressor 1.

[0097] Figure 4 A scroll compressor 1 according to a second embodiment of the present invention is shown. Figures 1 to 3 The main difference of the first embodiment shown is that the inner surface of the stationary tubular portion 36 is substantially complementary to the outer surface of the extraction tube 32, so that the width of the gap 37 formed between the outer surface of the extraction tube 32 and the inner surface of the stationary tubular portion 36 is substantially uniform along the longitudinal axis of the extraction tube 32 and along the outer circumference of the extraction tube 32. In particular, the stationary tubular portion 36 comprises an upper tubular portion 36.1, which is cylindrical, and a lower tubular portion 36.2, which extends coaxially with the upper tubular portion 36.1 and converges towards the lower end of the stationary tubular portion 36. The upper tubular portion 36.1 surrounds the upper tubular portion 32.1, while the lower tubular portion 36.2 surrounds the lower tubular portion 32.2.

[0098] According to the second embodiment of the invention, the flow cross-sectional area of ​​the inlet opening 38 of the stationary tubular portion 36 substantially corresponds to the flow cross-sectional area of ​​the oil inlet opening 34 of the extraction pipe 32 .

[0099] Figure 5 A scroll compressor 1 according to a third embodiment of the present invention is shown. Figure 4 The main difference of the second embodiment shown is that the stationary fairing component 35 comprises inlet guide vanes 58 extending radially from the outer surface of the stationary tubular portion 36. Advantageously, the inlet guide vanes 58 are regularly distributed around the longitudinal axis of the stationary fairing component 35.

[0100] The inlet guide vanes 58 may, for example, include a first set of inlet guide vanes 58 having a first axial length and a second set of inlet guide vanes 58 having a second axial length, such that the lower ends of the second set of inlet guide vanes 58 extend below the lower ends of the first set of inlet guide vanes 58. However, the lower ends of all of the inlet guide vanes 58 may extend in the same plane.

[0101] Of course, the invention is not limited to the embodiments described above by way of non-limiting examples, but on the contrary, the invention encompasses all its embodiments.

Claims

1. A scroll compressor (1), include: - a closed casing (2), the closed casing (2) being provided with a suction port (3) and a discharge port (4), the suction port (3) being configured to supply the refrigerant gas to be compressed to the scroll compressor (1), and the discharge port (4) being configured to discharge the compressed refrigerant gas; - a compression unit (6), the compression unit (6) comprising at least a first scroll element (7) and a second scroll element (8), the second scroll element (8) being configured to perform an orbiting motion relative to the first scroll element (7) during operation of the scroll compressor (1); - a drive shaft (16) which is vertically oriented and configured to cooperate with the second scroll element (8); - an upper bearing device (27) and a lower bearing device (28), the upper bearing device (27) and the lower bearing device (28) being configured to rotatably support the drive shaft (16) within the closed housing (2); - a centrifugal oil pump (29), the centrifugal oil pump (29) comprising an extraction pipe (32) attached to the lower end portion (23) of the drive shaft (16) and provided with an oil inlet (34) arranged at the lower end of the extraction pipe (32), the oil inlet (34) being immersed in an oil sump (31) arranged in the bottom section of the closed casing (2), the centrifugal oil pump (29) being configured to deliver oil to the compression unit (6) and to the upper bearing arrangement (27) and the lower bearing arrangement (28) during operation of the scroll compressor (1); The scroll compressor (1) further comprises a stationary fairing member (35) fixed to a non-rotating portion of the scroll compressor (1), the stationary fairing member (35) comprising a stationary tubular portion (36), the stationary tubular portion (36) being at least partially immersed in the oil tank (31) and surrounding the extraction pipe (32) at a predetermined distance so that a gap (37) is formed between an inner surface of the stationary tubular portion (36) and an outer surface of the extraction pipe (32), and a minimum radial distance (Dr) between the inner surface of the stationary tubular portion (36) and the outer surface of the extraction pipe (32) is between 0.5 mm and 5 mm; wherein the lower bearing device (28) comprises a radial bearing seat (39), the radial bearing seat (39) being configured to rotatably support the lower end portion (23) of the drive shaft (16), the radial bearing seat (39) comprising an inner radial bearing surface (40), the inner radial bearing surface (40) surrounding an outer surface of the lower end portion (23) of the drive shaft (16); wherein the lower bearing arrangement (28) further comprises an upper axial thrust bearing (46) and a lower axial thrust bearing (47) and a pressurized oil chamber (54), wherein the upper axial thrust bearing (46) and the lower axial thrust bearing (47) are configured to limit axial movement of the drive shaft (16) during operation, and the pressurized oil chamber (54) is fluidly connected to the centrifugal oil pump (29) and is at least partially defined by an outer surface of the lower end portion (23) of the drive shaft (16), the inner radial bearing surface (40), and the upper axial thrust bearing (46) and the lower axial thrust bearing (47); The inner radial bearing surface (40) has a first inner diameter, and the radial bearing seat (39) further comprises an inner circumferential surface (41), the inner circumferential surface (41) having a second inner diameter greater than the first inner diameter, Wherein, the radial bearing seat (39) further comprises a truncated cone inner surface (42), the truncated cone inner surface (42) being located between the inner radial bearing surface (40) and the inner circumferential surface (41) and gradually expanding toward the inner circumferential surface (41); wherein the radial opening (56) of the drive shaft faces the inner surface (42) of the truncated cone; wherein the stationary tubular portion (36) extends axially from the lower end of the extraction tube (32); wherein an axial distance (Da) between the lower end of the stationary tubular portion (36) and the lower end of the extraction tube (32) is between 1 mm and 3 mm; and The stationary fairing component (35) includes inlet guide vanes (58), the inlet guide vanes (58) radially extending from the outer surface of the stationary tubular portion (36), the inlet guide vanes (58) including a first group of inlet guide vanes (58) having a first axial length and a second group of inlet guide vanes (58) having a second axial length, so that the lower ends of the second group of inlet guide vanes (58) extend below the lower ends of the first group of inlet guide vanes (58), or so that the lower ends of the second group of inlet guide vanes (58) extend in the same plane as the lower ends of the first group of inlet guide vanes (58).

2. The scroll compressor (1) according to claim 1, in, The gap (37) formed between the inner surface of the stationary tubular portion (36) and the outer surface of the extraction tube (32) is annular.

3. The scroll compressor (1) according to claim 1 or 2, in, The stationary tubular portion (36) comprises a lower tubular part (36.2), which surrounds the lower tubular part (32.2) of the extraction tube (32) with a constant gap.

4. The scroll compressor (1) according to claim 1 or 2, in, The inner surface of the stationary tubular portion (36) and the outer surface of the extraction tube (32) are configured such that the width of the gap (37) formed between the outer surface of the extraction tube (32) and the inner surface of the stationary tubular portion (36) is substantially uniform along the longitudinal axis of the extraction tube (32) and / or along the circumference of the extraction tube (32).

5. The scroll compressor (1) according to claim 1 or 2, in, The axial distance (Da) between the lower end of the stationary tubular portion (36) and the lower end of the extraction tube (32) is greater than the minimum radial distance (Dr) between the inner surface of the stationary tubular portion (36) and the outer surface of the extraction tube (32).

6. The scroll compressor (1) according to claim 1 or 2, in, A radial clearance ratio, which is a ratio between the minimum radial distance (Dr) and the outer diameter of the extraction tube (32), is between 2% and 25%.

7. The scroll compressor (1) according to claim 1 or 2, in, The inner surface of the stationary tubular portion (36) directly faces the outer surface of the extraction tube (32).

8. The scroll compressor (1) according to claim 1 or 2, in, The stationary tubular portion (36) comprises an inlet opening (38) which is arranged at a lower end of the stationary tubular portion (36) and faces the oil inlet port (34) of the extraction pipe (32).

9. The scroll compressor (1) according to claim 8, in, The flow cross-sectional area of ​​the inlet opening (38) of the stationary tubular portion (36) substantially corresponds to the flow cross-sectional area of ​​the oil inlet (34) of the extraction pipe (32), or is larger than the flow cross-sectional area of ​​the oil inlet (34) of the extraction pipe (32).

10. The scroll compressor (1) according to claim 1, in, The stationary fairing member (35) is fixed to the radial bearing seat (39).

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