Rolling bearing with optimized lubrication for screw compressors

Abstract

A track bearing arrangement (1) for an electrically operated screw compressor.

Description

Technical Field

[0001] This invention relates to a bearing device in a screw compressor. Background Technology

[0002] A screw compressor is used as a refrigeration compressor or heat pump. A screw compressor has a compressor wheel with a helical shape, typically arranged as a groove or channel at the end of the compressor wheel. The compressor wheel is driven by a motor shaft. Within the scope of this invention, the motor shaft is driven by an electric motor capable of autonomous operation relative to the powertrain. The rotation of the motor shaft causes the compressor wheel to move along a circular trajectory without rotating itself about the compressor wheel axis. A track bearing is used to support the compressor wheel on the motor shaft. Therefore, the term "track bearing" derives from the fact that a bearing rotates not only about its own axis but also about an axially offset axis. According to the invention, the axis of rotation of the track bearing coincides with the compressor wheel axis of the compressor wheel, and the axially offset axis is depicted by the axis of rotation of the motor shaft. Therefore, the track bearing, along with its inner ring, is also located on the axially offset journal of the motor shaft. The journal has an eccentricity relative to the motor shaft.

[0003] During operation, the refrigerant (when operating as a refrigeration compressor) is thermodynamically treated on the helical side of the compressor wheel to achieve the desired cooling effect (such as warm-up).

[0004] On the helical side facing away from the compressor wheel—the bearing side—the motor shaft is defined by a track bearing and the chamber is defined by a balance ring. A mixture of lubricant and refrigerant can accumulate in this chamber and form a lubricant mixture. The lubricant enters the chamber through a lubricant channel. Due to the structural design of the screw compressor and the kinematics of the aforementioned components, targeted lubrication of the track bearing, for example, via guide oil holes that carry oil to the rolling elements, is not feasible. Summary of the Invention

[0005] Therefore, the object of the present invention is to provide an improved lubricant supply and an improved lubricant distribution for lubricating rail bearings.

[0006] The present invention relates to the configuration of a cage for a track bearing. For this purpose, the cage has at least one guide structure configured as a void, which can significantly and better guide lubricant or a lubricant mixture axially from the chamber through the rolling bearing. The guide structure is positioned outside the areas required for cage strength and for cage guidance, so as not to impair cage function and avoid increasing the structural space and weight required for the track bearing assembly.

[0007] The guide structure, positioned outside the stated area, ensures that the stability and guiding quality of the cage—in the case of cage guidance—do not have to yield to material voids. This arrangement is also advantageous because it eliminates the need to widen, for example, the radial gap between the cage and the outer ring for guiding or directing the lubricant, in order to achieve a greater lubricant mixing flow. This would require more structural space and degrade the quality of kinematic conditions, as the screw compressor operates at high speeds. Simply widening the gap for lubricant supply is also considered particularly negative in terms of vibrations present in the automotive environment of the application in question. By abandoning this technique of scaling the gap, the objective is clearly better achieved by the solution according to the invention.

[0008] Placing the guide structure in areas where strength is not critical is advantageous because the cage material is not further weakened in such areas, and the additional guide structure can complement the conventional cage and be optimized in terms of lubricant mixture without changing the existing dimensions of the cage.

[0009] Discretely placing the guide structures will not impair cage guidance, as long as the surface not used for cage guidance—that is, the surface used to place the guide structures—is smaller than the remaining surface used for cage guidance. The sacrifice of the cage guidance surface is not a sacrifice of the guide surface in the sense that the guide structures are placed "outside" the area required for cage guidance, and that the guide structures are actually placed outside the area required for cage guidance. The emphasis of stating "outside" the area required for cage guidance can also be in the sense of being within the surface required for guidance, which can also be interrupted or divided by placing the guide structures, with one or more remaining surfaces continuing to fulfill the initial function of cage guidance.

[0010] In other words, cage guidance can be achieved as long as the opposing surfaces of the cage guide, located on the outer or inner ring, bridge the guide structure in its circumferential extension in the circumferential direction. For this purpose, arrangements outside the area required for cage guidance will be provided here.

[0011] The kinematics of the track bearing are essentially unaffected by this invention. The reduced cage mass allows for a smaller counterweight for the balance ring. This positively impacts the dynamics of the screw compressor's operation in terms of speed variations based on consumer load requirements. The smaller counterweight size further improves the dynamics.

[0012] The guiding structure improves the flow of the lubricant mixture used to lubricate the track bearing, passing through the track bearing not only through the gap lubrication but also in the axial direction, thus extending the service life of the track bearing. The aforementioned gaps are located between the rolling elements and the cage; between two adjacent rolling elements; and / or between the cage section limited by two adjacent rolling elements and the outer or inner ring. Insufficient lubrication through these gaps is only advantageous.

[0013] The guide structure here has a geometry optimized for the flow and targeted distribution of the lubricant mixture, particularly when exiting the track bearing. In this regard, optimized distribution of the lubricant mixture upon exiting the track bearing is crucial, ensuring that the lubricant reaches the bearing housing within the compressor impeller without generating back pressure that would otherwise impede flow. Otherwise, only the "front" side of the track bearing would be wetted, while the "rear" side (within the housing) would experience insufficient lubrication. The guide structure significantly improves both the inflow into and outflow from the bearing.

[0014] A track bearing is housed within a receiving portion of the compressor wheel. The outer ring of the track bearing is received by the compressor wheel via its outer side surface, such that the outer side surface of the outer ring abuts against the inner side surface of the receiving portion. In the axial direction, the receiving portion is at least within the upper limit of space by abutting against the end sides of the compressor wheel and the outer ring.

[0015] The inner ring of the track bearing rests on the journal of the balance ring, which in turn rests on an eccentric journal formed by the end side of the motor shaft. Therefore, the balance ring has a cantilever that compensates for imbalances determined by the eccentricity and the eccentrically positioned mass during operation. A chamber exists diametrically opposite the cantilever, bounded by a component housing, main bearing, motor shaft, balance ring, track bearing, and compressor wheel. Lubricant accumulates in the chamber, which is supplied via orifices. The lubricant mixture, consisting of coolant and lubricant, within the chamber is now rolled and distributed by the rotational movement of the balance ring during operation. The surface of the chamber, which distributes and atomizes the components surrounding the boundary chamber during operation, thus wets and atomizes the end side of the track bearing facing the chamber—or rather, the section of that end side. The resulting flow introduces the lubricant mixture into the track bearing. From this point onward, to create an improved flow through the track bearing, the guide structure according to the invention is positioned on the side of the cage facing the compressor wheel. The guiding structure facilitates the distribution of the lubricant mixture on the circumferential side of the track bearing, thereby also improving lubrication. Furthermore, the guiding structure allows for better lubricant circulation transverse to the direction of cage rotation, thus allowing flow around the cage, as the geometry of the guiding structure promotes and improves flow.

[0016] In an advantageous embodiment of the invention, the guide structure is asymmetrically configured between two cage pockets, which are designed to accommodate rolling elements. Therefore, the guide structure is positioned less from one cage pocket than from the adjacent cage pocket. This asymmetrical spacing improves the flow of lubricant mixture through the track bearing without increasing the clearance between the cage and the outer ring, thus avoiding any adverse effects on the guidance of the rolling elements.

[0017] The asymmetrical spacing can be advantageously configured in relation to the direction of rotation. Since the screw compressor rotates only in a predefined direction during operation, the track bearing can be strategically and directionally mounted using the asymmetrical arrangement of the guide structure. Preferably, the guide structure is positioned downstream of the rolling elements in the direction of rotation of the track bearing, and ideally on the side facing the compressor wheel.

[0018] In an advantageous alternative configuration, the guide structures are symmetrically arranged between the cage pockets, thus independent of the direction of rotation. This independence from the direction of rotation is advantageous only if the rotation direction of the screw compressor is reversed, or if an asymmetrical arrangement of the guide structures on the side facing the compressor wheel is ineffective in terms of the required volume of the lubricant mixture. The symmetrical configuration of the guide structures increases the volume available for the flow of the lubricant mixture.

[0019] In the cage of the track bearing according to the invention, not only can asymmetrical guide structures be configured, but also symmetrical guide structures can be configured. For example, the guide structures can be alternately arranged in the circumferential direction in order to combine the advantages of the more aligned distribution of the asymmetrical guide structures with the advantages of the increased volume of the symmetrical guide structures.

[0020] According to the invention, when the track bearing rotates rapidly, the advantageous configuration of the asymmetrical guide structure has less impact on cage guidance via the outer side of the cage to the inner side of the outer ring compared to a symmetrical configuration of the guide structure, because sufficient contact surface is maintained to reliably guide the cage at high speeds.

[0021] The lubricant mixture flows through the track bearing as follows without the guide structure according to the invention. The volume within the chamber moves and rolls in the circumferential direction at a motor speed via a balance ring. The cage and rolling elements rotate at half the shaft speed within the track bearing, thereby allowing the lubricant mixture to be discharged at a lower pressure than it enters. Back pressure is generated by the delay in discharge from the track bearing. This back pressure resists the entry of the lubricant mixture. The guide structure according to the invention reduces the back pressure because this not only increases the volumetric throughput of the lubricant but also facilitates its distribution.

[0022] Alternatively, the guide structure can be positioned on the chamber-facing side of the cage, which increases the pressure entering the raceway bearing, thereby counteracting back pressure and improving flow. The guide structure can be configured as blades in another embodiment of the invention. Preferably, the cage does not have a completely closed cage pocket on the chamber-facing side, but rather has an opening on that side. Therefore, the chamber pocket does not completely surround the rolling elements, but only to a degree that prevents axial displacement of the rolling elements relative to each other. A blade-shaped guide structure can be configured on the circumferential side between two such openings, which significantly improves the introduction of the lubricant mixture into the bearing, where the geometry of the blade adapts to the flow of the lubricant mixture during operation. Thus, the blade forces more volume into the bearing, thereby improving flow. The blade-shaped guide structure according to the invention is also positioned outside the areas required for cage strength and / or for cage guidance. Attached Figure Description

[0023] The following figures illustrate some embodiments of the present invention. The figures show:

[0024] Figure 1 A partial view of a screw compressor having a track bearing assembly according to the invention is shown.

[0025] Figure 2A The cage of the track bearing device according to the invention, with an asymmetrical guide structure, is shown from a first-person perspective.

[0026] Figure 2B Showing the basis from another perspective Figure 2A The cage,

[0027] Figure 2C Showing according to Figure 2B The cross-section of the cage,

[0028] Figure 2D Showing according to Figure 2C Detailed view,

[0029] Figure 3A This illustrates the lubricant flow through the track bearing device according to the invention.

[0030] Figure 3B Showing according to Figure 3A Detailed view,

[0031] Figure 4A The cage of the track bearing device according to the invention, with a symmetrically configured guide structure, is shown from a first-person perspective.

[0032] Figure 4B Showing the basis from another perspective Figure 4A The cage,

[0033] Figure 5A The cage of the track bearing device according to the invention, having a blade-shaped guide structure, is shown from a first-person perspective.

[0034] Figure 5B Shown in detail in cross-section according to Figure 5A The cage. Detailed Implementation

[0035] Figure 1 A partial view is shown of a screw compressor having a track bearing device 1 according to the invention. The screw compressor and the track bearing device 1 according to the invention are shown in order to illustrate... Figure 1 The device includes the following components: housing 20, main shaft bearing 19, motor shaft 4, compressor wheel 17 with compressor screw 2 (not shown in detail here), balance ring 12, track bearing 3 and sealing ring 21.

[0036] Reference numeral 2 indicates the compressor helix on the shown end face of the compressor wheel 17, which should only be located on said end face; however, the geometry is not fully shown here. The compressor wheel 17 has a sealing ring 21 on the end side opposite to the compressor helix 2, which seals the compressor chamber by abutting against the housing 20, in which the compressor helix 2 compresses the coolant.

[0037] The compressor wheel 17 also has a receiving portion for the rolling bearing 3 on the end side opposite to the compressor screw 2. The rolling bearing 3, also called a track bearing, consists of an outer ring 6, an inner ring 5 concentrically arranged with the outer ring, and rolling elements 7 configured as balls disposed between the two rings 5 ​​and 6. The rolling elements 7 are typically spaced apart in the circumferential direction by a cage 8. The outer ring 6 of the track bearing 3 is torsionally located within the receiving portion of the compressor wheel 17.

[0038] The motor shaft 4 has an eccentrically positioned journal on which the balance ring 12 is positioned anti-torsional relative to the motor shaft 4. The inner ring 5 of the track bearing 3 is positioned anti-torsional on the balance ring 9. If the motor shaft 4 rotates about its own axis of rotation 10, the eccentrically positioned journal causes the balance ring 9 and the track bearing 3, and thus also the compressor wheel 17, to “slip” about the axis of rotation 10.

[0039] The balance ring 9 has a cantilever 12, which is used to compensate for imbalances during operation of the eccentric device. Therefore, a chamber 13 is located on one diametrically opposed side of the cantilever 12. In this chamber 13, introduced coolant accumulates and mixes with the lubricant present therein to form a lubricant mixture.

[0040] The lubricant mixture is distributed circumferentially via the cantilever 12 during operation, reaching not only the main shaft bearing 19 but also the track bearing 3. Due to kinematic relationships, the track bearing 3 is subjected to a higher load than the main shaft bearing 19.

[0041] In order to meet the higher load under the condition of narrow structural space, the cage 8 has a guide structure 14 according to the invention for guiding the lubricant mixture from the side of the track bearing 3 facing the chamber 13 to the side of the track bearing 3 facing away from the chamber 13, the guide structure being illustrated in the figure below.

[0042] Figure 2A The cage 8 of the guide structure 14 with an asymmetrical configuration of the track bearing device 1 according to the present invention is shown from a first-person perspective. Figure 2B Showing the basis from another perspective Figure 2A 8. The retainer.

[0043] The guide structure 14 is asymmetrical, giving it a trapezoidal shape when viewed from the outer circumferential surface. Advantageously, the trapezoidal side edges, which do not have right angles relative to adjacent side edges, are oriented in a direction such that the lubricant mixture can be better discharged as the cage rotates from one end of the cage toward the other, or in other words, the lubricant mixture itself can be better distributed in the region between the track bearing 3 and the compressor wheel 17 under the vortex / rotational motion that introduces the lubricant mixture through the trapezoidal shape.

[0044] Furthermore, a guide structure 14 is positioned between two cage pockets 18, each accommodating a rolling element 7. While the area between the two cage pockets 18 is absolutely necessary for the strength of the cage 8, it is not the most critical point for strength. In this regard, placing the guide structure 14 in an area where strength is not essential is advantageous because the material of the cage 8 is not further weakened in this area, and the additional guide structure 14 can complement the conventional cage 8 and be optimized in terms of lubricant mixture without changing the existing dimensions of the cage.

[0045] Discretely placing the guide structure 14 will not impair cage guidance, as long as the surface not used for cage guidance—that is, the surface used for placing the guide structure 14—is smaller than the remaining surface used for cage guidance. The sacrifice of the cage guidance surface is not a sacrifice of the guidance surface in the sense that the guide structure 14 is placed "outside" the area required for guiding the cage 8, and that the guide structure 14 is actually placed outside the area required for guiding the cage 8—the cage guidance is not shown here. The emphasis of "outside" the area required for guiding the cage 8 is on the surface required for guidance, which can also be interrupted or divided by placing the guide structure 14, while still fulfilling the initial function of cage guidance.

[0046] In other words, in the described embodiment, cage guidance can be achieved simply by having, for example, opposing surfaces provided on the outer ring 6 for cage guidance bridging the guide structure 14 in its circumferential extension in the circumferential direction. In this regard, arrangements outside the area required for cage guidance will be provided here.

[0047] Figure 2C Showing according to Figure 2B The cross-section of the cage 8, and Figure 2D Showing according to Figure 2C Detailed view.

[0048] Especially in Figure 2D In the embodiment described, the guide structure 14 is clearly visible in the cross-sectional view of the spatial configuration. On the end side of the retainer 8, the guide structure 14 has a geometrically imprinted portion 22 in the axial direction, which initially stores the lubricant mixture. On the end side of the retainer, the retainer pocket 18 is closed by a region 15 requiring strength. A ramp 23, descending or ascending on the outer side in the axial direction, is used to selectively widen the gap for guiding the lubricant mixture through, thereby reducing the back pressure from the gap to the receiving area of ​​the imprinted portion 22, thus enabling a better throughput of the lubricant mixture through the gap. This gap is located here between the outer side of the retainer 8 and the outer ring 6. Therefore, the ramp 23 is part of the gap.

[0049] Figure 3A The flow of lubricant through the track bearing device 1 according to the invention is shown. Figure 3B Showing according to Figure 3A Detailed view.

[0050] The lubricant mixture accumulated in chamber 13 enters the track bearing 7 during operation via the open end side of the cage 8, which has a cage pocket 18. Figure 3BIt can be clearly seen that a gap is formed between the inner circumferential surface of the outer ring 6 and the cage 8. The lubricant mixture passes over the rolling surface of the rolling element 7 and enters the guide structure 14. The ramp 23 facilitates entry into the guide structure 14, thereby allowing the lubricant mixture to be collected and distributed in the geometric imprint 23 for lubrication of the area between the track bearing 3 and the compressor wheel 17. Furthermore, this also improves the flow around the cage 8—according to Figure 3B This can be seen along the counterclockwise arrow in the cross-section of cage 8.

[0051] Figure 4A The cage 8 of the track bearing device 1 according to the invention, having a symmetrically configured guide structure 14, is shown from a first-view perspective. Figure 4B Showing the basis from another perspective Figure 4A 8. The retainer.

[0052] According to Figure 2A In a different implementation, the guide structure 14 is symmetrically arranged between two adjacent retainer pockets 18. The geometric embossed portion of the guide structure 14 is also symmetrical about the dividing body edge of the guide structure 14 via an imaginary line of symmetry 24, which is centrally located between the two adjacent retainer pockets 18 and its position is precisely determined by the two adjacent retainer pockets. The dividing body edge of the guide structure 14 is mirrored via the line of symmetry 24; as in Figure 4A As can be seen from this, the distinctive symmetrical guide structure 14 is patterned on the circumference of the cage 8, so that the guide structure 14 is always present between two adjacent cage pockets 18.

[0053] according to Figure 2A , Figure 2B The view in the middle and the line of symmetry 24 there are obvious, according to Figure 2A and Figure 2B The guide structure 14 involves an asymmetrical configuration of the guide structure 14—not a mirror image—and an asymmetrical arrangement between the two cage pockets 18.

[0054] Figure 5A The cage 8 of the track bearing device 1 according to the invention, having a blade-shaped guide structure 14, is shown from a first-view perspective. Figure 5B Shown in detail in cross-section according to Figure 5A 8. The retainer.

[0055] Contrary to the preceding embodiments of the present invention, in accordance with Figure 5A , Figure 5BIn this embodiment, the guide structure 14 is disposed on the side of the cage 8 facing the chamber 13. The guide structure 14 has a blade shape and conveys the lubricant mixture from the chamber 13 to the track bearing 3. In the sense of the invention, the flow of the lubricant mixture should be improved—this is done here on the inlet side where the lubricant mixture enters the track bearing 3—to counteract back pressure with a significantly increased inlet volume, thereby conveying the lubricant mixture to the side of the track bearing 3 facing the compressor wheel 17 and increasing throughput. The blade-shaped guide structure 14 not only facilitates the collection of the lubricant mixture in the chamber 13 but also facilitates the introduction of the lubricant mixture into the track bearing 3 through its asymmetrical shape. In the rotational direction of the rolling bearing 3, the lubricant mixture is captured and guided to the outer surface of the cage 8 by the specific blade geometry. The blade geometry serves a guiding function to introduce the lubricant mixture into the track bearing 3.

[0056] To improve the discharge of the lubricant mixture from the rolling bearing 3, the guide structure 14 described in the foregoing embodiments can be provided. The guide structure 14 described in the foregoing embodiments effectively complements... Figure 5A , Figure 5B 14. Leaf-shaped guide structure.

[0057] List of reference numerals

[0058] 1. Rail bearing assembly

[0059] 2. Compressor spiral

[0060] 3 Rolling bearings / rail bearings

[0061] 4 motor shafts

[0062] 5 Inner Ring

[0063] 6 Outer Ring

[0064] 7. Rolling element

[0065] 8. Cage

[0066] 9. Balance ring

[0067] 10. Motor shaft rotation axis

[0068] 11. Eccentricity

[0069] 12 cantilever

[0070] 13 chambers

[0071] 14. Guiding Structure

[0072] 15. Area required for cage strength

[0073] 16. Area required for cage guidance

[0074] 17 Compressor wheel

[0075] 18 cage pockets

[0076] 19 Spindle bearings

[0077] 20. Housing

[0078] 21 Seals

[0079] 22 Geometric Imprint Section

[0080] 23 Slope

[0081] 24. Lines of Symmetry

Claims

1. A track bearing device (1) having a rolling bearing (3) for supporting a compressor wheel (17) having a compressor helix (2) relative to a motor shaft (4), wherein the rolling bearing (3) has an inner ring (5) and an outer ring (6), wherein a plurality of rolling elements (7) are disposed between the inner ring and the outer ring (5, 6), the rolling elements being spaced apart from each other in the circumferential direction or in the rotational direction of the outer ring (6) relative to the inner ring (5) by means of a cage (8), wherein - The outer ring (6) is torsionally and coaxially housed by the compressor wheel (17), and the inner ring (5) is torsionally housed by the balance ring (9), wherein - There is an eccentricity (11) between the rotation axis of the inner ring (5) and the rotation axis (11) of the motor shaft, wherein the balance ring (9) is eccentrically arranged relative to the rotation axis (11) of the motor shaft. - The balance ring (9) has a cantilever (12) extending radially from the balance ring as a counterweight for the rotatable mass of the compressor wheel (17), thereby - A chamber (13) is defined on one side opposite the cantilever (12) along the diameter, the chamber being capable of containing a lubricant mixture and supplying the lubricant mixture to the rolling bearing (3) adjacent to the chamber (13), in particular the rolling element (7). - The cage (8) has at least one guide structure (14) configured as a void, the guide structure being capable of axially guiding the lubricant mixture from the chamber (13) through the rolling bearing (3), wherein the guide structure (14) is disposed outside the area required for cage strength and / or the area (15, 16) required for cage guidance, and on the axial end side of the cage (8), the guide structure (14) has a geometric imprint (22) which is closed by the area (15) required for cage strength.

2. The track bearing device (1) according to claim 1, characterized in that, The cage (8) forms the guide structure (14) on the side of the rolling bearing (3) facing away from the chamber.

3. The track bearing device (1) according to claim 1, characterized in that, The cage (8) forms the guide structure (14) on the side of the rolling bearing (3) facing the chamber.

4. The track bearing device (1) according to any one of the preceding claims, characterized in that, The guide structure (14) is symmetrically positioned between the two cage pockets (18).

5. The track bearing device (1) according to any one of claims 1 to 3, characterized in that, The guide structure (14) is asymmetrically positioned between the two cage pockets (18).

6. The track bearing (1) according to claim 1, characterized in that, The cage (8) constitutes a plurality of guide structures (14), which are combinations of the arrangement and configuration according to claims 2 to 5.

7. A screw compressor having a track bearing (1) according to any one of the preceding claims.

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