Spring-loaded scroll compressor bearing

Abstract

Electromechanically operated spiral compressor (20) with an orbital bearing arrangement (1) comprising an orbital bearing (3) for supporting a compressor wheel (17) having a compressor spiral (2) relative to a motor shaft (4), wherein the orbital bearing (3) has an inner ring (5) and an outer ring (6), wherein a plurality of balls (7) are arranged between the inner and outer rings (5, 6), which are spaced apart from each other by means of a cage (8) in the circumferential direction, or in the direction of rotation of the outer ring (6) relative to the inner ring (5), wherein the outer ring (6) is rotationally fixed and coaxially supported by the compressor wheel (17) and the inner ring (5) is rotationally fixed by a balancing ring (9), wherein an eccentricity (22) exists between the axis of rotation (16) of the inner ring (5) and the axis of rotation (11) of the motor shaft, wherein the balancing ring (9) is eccentric to the motor shaft rotation axis (11) is arrangedwherein the balancing ring (9) has a radially projecting extension (12) as a counterweight to the rotatable mass of the compressor wheel (17), whereby a chamber (13) is defined on the side diametrically opposite the extension (12), which can receive a lubricant mixture and supply this lubricant mixture to the orbital bearing (3) adjacent to the chamber (13), in particular to the balls (7), characterized in that a spring element (8) is arranged axially between the orbital bearing (3) and the compressor wheel (17), the spring element (8) is supported on the compressor wheel (17), and the spring element (8) can axially preload the inner ring (5) to the outer ring (6) so that there is no longer any axial play in the orbital bearing (3).

Description

The invention relates to a spring-loaded ball bearing of a spiral compressor. DE 10 2021 100 612 B3 discloses a bearing arrangement in a spiral compressor. For this purpose, the cage has at least one guide structure designed as a recess, which can guide the lubricant or lubricant mixture axially from the chamber through the rolling bearing much more effectively. The guide structure is arranged outside the area necessary for cage strength and cage guidance in order not to impair the cage's function and to avoid increasing the required installation space and weight of the orbital bearing arrangement. JP 2011 094546 A and JP 2012 207547 A show spiral compressors with shaft bearings, with JP 2011 202671 A showing a ball bearing with a cage. A scroll compressor, as described in JP 2011-247209A, consists of an orbital scroll with spiral lobes on both sides of the end plate. Fixed scrolls are arranged on both sides of the orbital scroll, having spirals that interlock with the scroll. The fixed scroll on opposite sides supports each of the crankshafts of the rotary supports, which are mounted on the outer circumferential surface of the scroll for rotational movement. This rotational movement occurs on the crankshaft, which is supported by several bearings. At least one of these bearings, supporting the crankshaft, is a ball bearing. This ball bearing is mounted with clearance in the bearing sleeve of the fixed scroll and in the outer race of the ball bearing. A retaining element prevents the outer race of the ball bearing from rotating circumferentially and restricts its movement. A damping material is located between the bearing sleeve and the retaining element.The damping material, consisting of a resin material, reduces the wear of the retaining element caused by mechanical vibration and creep forces between the bearing sleeve and the retaining element. KR 10 2012 0 095 711 A refers to a preload spring for bearings with a viscoelastic coating. Specifically, it concerns a preload spring for bearings that is provided with a viscoelastic coating layer, which dampens vibrations even when acting upon them, thus preventing noise. Generally, a rotating shaft, such as in a motor or compressor, is supported by a bearing. High stiffness is required in a bearing to reduce vibrations and noise, as this affects the performance and lifespan of the machine. A preload spring is therefore interposed to apply a load to the bearing and prevent wear during machine operation. The preload spring is excited by an external or internal factor during machine operation, which can generate noise. WO 2023 / 121160A1 shows an electromechanically operated spiral compressor with an axially pre-tensioned motor shaft. In the course of the transformation towards electric passenger car drives, energy-efficient climate control of the passenger compartment, battery, and other drive components is of paramount importance for achieving further increases in driving range. To this end, the power density and service life of electric air conditioning compressors are to be further increased. The invention described below relates to the "scroll compressor" air conditioning compressor design and its performance enhancement through reduction of the loads on the cage in the scroll bearing. This allows the bearing performance to be improved, and the compressor can provide even greater cooling capacity through higher rotational speeds, higher operating pressures, or a larger eccentric. In the known state of the art, the motor shaft and the compressor wheel are usually supported by a total of three deep groove ball bearings. The task is to improve the electromechanically operated spiral compressor. Scroll compressors are used as refrigeration compressors or heat pumps. They have a compressor wheel with a spiral shape, usually arranged as a groove or channel on one end face of the wheel. This compressor wheel is driven by a motor shaft. The motor shaft is driven by an electric motor that operates independently of the drive train. The rotation of the motor shaft moves the compressor wheel in a circular path without it rotating around its own axis. An orbital bearing is used to support the compressor wheel on the motor shaft. The term "orbital bearing" derives from the fact that the bearing rotates both around its own axis and around an axis offset from it. The axis of rotation of the orbital bearing coincides with the axis of rotation of the compressor wheel, and the axis offset from it is defined by the axis of rotation of the motor shaft.Consequently, the orbital bearing, with its inner ring, also sits on this axially offset journal of the motor shaft. The journal has an eccentricity relative to the motor shaft. During operation, the refrigerant (operating as a refrigeration compressor) is thermodynamically processed on the spiral-shaped side of the compressor wheel to achieve the desired cooling (or heating) effect. Electromechanically operated spiral compressors exert different forces and loads on the cage than are known from conventional deep groove ball bearing applications. The stresses in ordinary deep groove ball bearings are typically due to two causes. Firstly, the cages are subjected to high centrifugal forces due to high rotational speeds (such as those occurring in rotor bearings in electric motors). The expansion in the cage diameter caused by this centrifugal force puts such a strain on the cages that they break within the rolling element pockets. Secondly, cages can be subjected to very high lead-in and lead-out of the rolling elements, which increases cage deformation due to the pulling and pushing of the rolling elements against the cage pockets, resulting in disproportionately high stress in the thinnest cross-section of the cage pocket. Electromechanically driven spiral compressors (e-scroll) have an eccentric design, resulting in significantly different forces acting on the orbital bearing cage than those described above. These significantly different forces and loads on the orbital bearing cages arise because conventional deep groove ball bearings are mounted concentrically to the shaft system, whereas the orbital bearing is mounted eccentrically. The eccentric design means that the rolling elements are subjected to highly variable acceleration and deceleration. These processes are strongly dependent on the position of the compressor and the eccentric design. This specific design results in a unique kinematic pattern in which the orbital bearing partially rotates around individual balls. This unique kinematic pattern, characterized by the strong acceleration and deceleration of the rolling elements and the orbital motion of the entire bearing, results in high ball forces acting on the cage pockets. The cage's function is to maintain the balls at their specified distance and absorb these high ball forces. Consequently, there are situations where the cage must continue to push the balls forward while other balls simultaneously attempt to slow the cage down. In typical deep groove ball bearing applications, the balls run concentrically around the bearing center, which is why the forces described have a minor influence on the cage load. Furthermore, due to their design and operation, e-scroll bearings are subject to insufficient lubrication. To ensure proper bearing function, the contact area between the rolling elements, outer ring, and inner ring must always be adequately lubricated. A lack of lubrication would lead to increased friction and ultimately to bearing failure. General lubrication of the bearing is not possible due to refrigerant contamination. This means the bearing has access only to a refrigerant-oil mixture located in the bearing environment (the so-called back-pressure chamber). The more oil from the environment reaches the bearing, the longer its service life. The orbital bearing must therefore be able to reliably withstand the rolling element forces resulting from the alternating acceleration and deceleration processes as well as from the orbital bearing rotation. The aim of the invention is to improve the orbital bearing in such a way that the rotational speed, force / working pressure, and eccentric length can be further improved in order to increase the power density of the scroll compressor. The most heavily loaded bearing point in the system is the single bearing point in the compressor wheel. Here, in addition to the usual rolling bearing stresses from shaft rotation and the working pressure present in the scroll compressor, further forces are added due to the orbiting movement of the eccentric crankshaft bearing journal. The ball bearing cage has emerged as a weak point within the deep groove ball bearing, as it can break at high speeds / loads. The eccentric motion of the orbital bearing results in alternating tensile and compressive forces acting on the cage in the circumferential direction. These forces in the cage's circumferential direction are caused by the inertia of the balls due to their changing velocity. This change in ball velocity occurs as the balls enter and exit the load zone, as well as due to the constraints imposed by the kinematics of the bearing. Unlike a conventional deep groove ball bearing, the balls do not run on a constant circular path. Due to the eccentric design, the balls run on alternating circular paths. At the point where the circular path changes, the ball is decelerated significantly and then accelerated again onto the new path. This leads to high contact forces between the ball and the cage, especially when the ball is not currently running in the load zone. The task is accomplished with an electromechanically operated spiral compressor with an orbital bearing arrangement, the orbital bearing being used to support a compressor wheel having a compressor spiral relative to a motor shaft. The orbital bearing has an inner ring and an outer ring, with a plurality of balls arranged between the inner and outer rings. These balls are spaced apart from each other by means of a cage in the circumferential direction, or in the direction of rotation of the outer ring relative to the inner ring. The outer ring is mounted non-rotatably and coaxially on the compressor wheel, and the inner ring is mounted non-rotatably by a balancing ring. There is an eccentricity between the axis of rotation of the inner ring and the axis of rotation of the motor shaft. The balancing ring is arranged eccentrically to the axis of rotation of the motor shaft and has a radially projecting extension as a counterweight to the rotatable mass of the compressor wheel.wherein a chamber is defined on the side diametrically opposite the boom, which can receive a lubricant mixture and supply this lubricant mixture to the orbital bearing adjacent to the chamber, in particular to the balls, is solved according to the invention in that a spring element is arranged axially between the orbital bearing and the compressor wheel, the spring element is supported on the compressor wheel, and the spring element can axially preload the inner ring to the outer ring so that there is no longer any axial play in the orbital bearing. Applying a preload between the outer and inner rings reduces the pre- and post-roll of the ball(s) and eliminates changes in ball speed when entering and exiting the load zone. The load zone ideally covers 360°, but at least 270°. When the spherical rolling element, during the eccentric rotation, changes its circular path within the load zone, most of the ball contact force, which would otherwise be applied to the cage, is absorbed by friction between the ball and the rings. The two bearing rings (outer and inner) guide the balls. The spring element can be a separate component. It can be functionally integrated into the bearing or designed as a (gas mixture) pressure generated by the back-pressure chamber. The inner ring of the orbital bearing is positioned on the balancing ring, with the inner ring being rotationally fixed to the balancing ring's journal by means of an interference fit. The outer ring of the orbital bearing, on the other hand, is axially movable within the compressor wheel's orbital bearing housing, but with minimal radial play. When the spring element is supported in the base of the orbital bearing housing, the outer ring is pushed away from the base, thus preloading the orbital bearing. This causes the orbital bearing balls to make firm contact in the raceways of the rolling bearing rings – the contact angle of the force between the balls and the rings is thus inclined by approximately 5° to 20° from the vertical. The axial preload also displaces the balancing ring axially along the motor's axis of rotation. Since the balancing ring is rigidly connected to the motor shaft and has an axial stop against the motor shaft, the motor shaft also tends to shift axially. This is countered by the main shaft bearing of the motor shaft, which supports the motor shaft on the compressor side of the unit relative to the housing. The main shaft bearing sits on the motor shaft and supports it relative to the housing. The preload also causes a displacement of the inner ring of the main shaft bearing, so that the main shaft bearing is also axially preloaded – since the outer ring of the main shaft bearing has its axial stop in the housing. Thus, the contact angle of the contact force between the balls and the rings of the main shaft bearing is also increased by approximately...inclined 5° to 20° to the vertical - however in the opposite or mirror-image direction to that of the orbital bearing. The orbital bearing arrangement, consisting of the orbital bearing and the main shaft bearing, exhibits an X-shaped contact angle pattern due to the preload of the spring element located on the orbital bearing. Such an X-shaped arrangement is particularly stable in operation. The end of the motor shaft facing away from the compressor side has a bearing opposite the housing, which is designed as a floating bearing and is neither preloaded nor has a press fit of one of its rolling bearing rings. The solution according to the invention is based on the aim of reducing the load in the rolling bearing (orbital bearing) in such a way as to prevent the destruction of a rolling bearing component. Furthermore, the performance of the electromechanically operated spiral compressor is improved and increased. This solution can also include a preload on the main shaft bearing analogous to the described preload on the orbital bearing, achieved by a spring element, resulting in an X-arrangement of the contact force angles to the orbital bearing. Alternatively, both bearings, the main shaft bearing and the orbital bearing, can each have a spring element for preloading the bearing arrangement, resulting in an X-arrangement of the contact force angles analogous to the embodiment described here. One embodiment of the invention is explained in more detail with reference to the figure. Figure 1 shows an orbital bearing arrangement in an electromechanically operated spiral compressor. Fig. 1 shows an orbital bearing arrangement 1 in an electromechanically operated spiral compressor 20. Fig. 1 shows an orbital bearing arrangement 1 in an electromechanically operated spiral compressor 20. The spiral compressor 20 and the orbital bearing arrangement 1 comprise the following components for the illustration in Fig. 1: a housing 28, a main shaft bearing 19, a motor shaft 4, a compressor wheel 17 with a compressor spiral 2 (not explicitly shown here), a balancing ring 9, an orbital bearing 3, and a sealing ring 27. Reference numeral 2 indicates a compressor spiral on the shown end face of the compressor wheel 17, which is located only on this end face but is not shown geometrically in its entirety here. The compressor wheel 17 has a sealing ring 27 on the end face opposite the compressor spiral 2, which seals the compressor chamber, in which the compressor spiral 2 compresses the coolant, by contacting the housing 28. The compressor wheel 17 also has a receptacle for the orbital bearing 3 on its end face opposite the compressor spiral 2. This orbital bearing 3 consists of an outer ring 6, an inner ring 5 arranged concentrically to it, and rolling elements arranged between these two rings 5, 6, which are designed as balls 7. The balls 7 are typically held spaced apart circumferentially by a cage. The outer ring 6 of the orbital bearing 3 is rotationally fixed in the receptacle of the compressor wheel 17. The motor shaft 4 has an eccentrically arranged journal on which the balancing ring 9 is fixedly mounted relative to the motor shaft 4. The inner ring 5 of the orbital bearing 3 is fixedly mounted on this balancing ring 9. When the motor shaft 4 is rotated about its own axis of rotation 11, the eccentrically arranged journal causes the balancing ring 9 and the orbital bearing 3, and thus also the compressor wheel 17, to spin around the axis of rotation 11. The balancing ring 9 has a cantilever 12, which serves to compensate for the imbalance during operation of the eccentric arrangement. Thus, a chamber 13 is located on the diametrically opposite side of the cantilever 12. The coolant collected in this chamber 13 mixes with the lubricant present there to form a lubricant mixture. This lubricant mixture is distributed circumferentially during operation by the boom 12 and reaches both the main shaft bearing 19 and the orbital bearing 3. Due to the kinematic conditions, the orbital bearing 3 is subject to higher stresses than the main shaft bearing 19. The spring element 8 is positioned within a blind-hole orbital bearing receptacle 10 of the compressor wheel 17 and is supported at the base of the receptacle 10. The inner ring 5 of the orbital bearing 3 sits on a journal of the balancing ring 9 and rests axially on one side against a step 14 formed by the balancing ring 9. The outer ring 6 of the orbital bearing 3 is received by its cylindrical outer surface by the inner surface of the blind-hole orbital bearing receptacle 10. In this embodiment, the outer ring 6 is axially displaceable within the orbital bearing receptacle 10. The inner ring 5 can be press-fitted onto the journal of the balancing ring 9 or it can also be axially displaceable if the balancing ring 9 has a step 14 for the one-sided axial stop of the inner ring 5.If the balancing ring 9 does not have a step 14, a press fit of the inner ring 5 is mandatory so that the force applied to the inner ring 5 by the spring element 8 can axially displace both the inner ring 5 and the balancing ring 9. This positive or force-fit coupling is important so that the spring element 8 also influences the preload of the main shaft bearing 19 and both bearings can form an X-arrangement of their rotated contact force vectors. The spring element 8 is supported at the base of the blind-hole orbital bearing receptacle 10 of the compressor wheel 17 and is simultaneously in contact with the outer ring 6 and the inner ring 5. This causes both rings 5 ​​and 6 to be axially displaced relative to each other in order to rotate the contact force vector 15 – specifically, viewed above the axis of rotation 16, into an angular range of 5° to 20° from the vertical in a clockwise direction, as shown. Due to the symmetry of the axis of rotation 16 with respect to the orbital bearing 3, the rotation of the contact force vector below the axis of rotation 16 is effected in the opposite direction. To prevent the spring element 8 from displacing both rings 5 ​​and 6 by the same axial distance, the inner ring 23 of the main shaft bearing 19 rests against an axial end face 18 on one side, so that the displacement of the balancing ring 9 can be transmitted to the inner ring 23. However, the outer ring 24 rests against an axial contact surface 26 of the housing 28 on one side. This causes the inner ring 23 and the outer ring 24 to be displaced axially relative to each other in such a way that the balls 25 of the main shaft bearing 19 also come into one-sided contact with the rings 23, 24, so that the contact force vector 29 of the main shaft bearing 19 is rotated – namely, viewed above the motor shaft axis of rotation 11, into an angular range of 5° to 20° counterclockwise from the vertical, as shown.Due to the symmetry of the motor shaft rotation axis 11 to the main shaft bearing 19, the rotation of the contact force vector 29 in the opposite direction is caused below the motor shaft rotation axis 11. Due to the load on the motor shaft 4 by the spring element 8, the countershaft bearing 21, which supports the motor shaft 4 at the other end (of the main shaft bearing 19), must be axially displaceable relative to the motor shaft 4 and the housing 28. One-sided contact of the countershaft bearing 21, or its rings, counteracts the intended purpose of the solution according to the invention, which is to stabilize the orbital bearing arrangement 1 – between the orbital bearing 3 and the main shaft bearing 19 – and to protect the cage of the orbital bearing 3 from damage. The rotated contact force vectors 29 and 15 intersect the respective axes of rotation 11 and 16 belonging to bearing 19 and 3, respectively. Even though the two axes of rotation 11 and 16 are not aligned with each other, but have an eccentricity 22, this results in an X-arrangement of the tensions of both bearings 19 and 3, stabilizing the bearing arrangement. The spring element 8 reduces the load on the cage of the kinematically active orbital bearing 3, particularly during the entry and exit of the balls 7 into and out of the load zone. This also affects the performance of the electromechanically operated spiral compressor 20 (e-Scroll). Reference symbol list 1 Orbital bearing assembly 2 Compressor spiral 3 Orbital bearing 4 Motor shaft 5 Inner ring (orbital bearing) 6 Outer ring (orbital bearing) 7 Ball (orbital bearing) 8 Spring element 9 Balancing ring 10 Orbital bearing housing 11 Motor shaft axis of rotation 12 Boom 13 Chamber 14 Stage 15 Contact force vector (orbital bearing) 16 Axis of rotation 17 Compressor wheel 18 End face 19 Main shaft bearing 20 Electromechanically driven spiral compressor 21 Subsidiary shaft bearing 22 Eccentricity 23 Inner ring (main shaft bearing) 24 Outer ring (main shaft bearing) 25 Balls (main shaft bearing) 26 Contact surface 27 Sealing ring 28 Housing 29 Contact force vector (main shaft bearing)

Claims

Electromechanically operated spiral compressor (20) with an orbital bearing arrangement (1) comprising an orbital bearing (3) for supporting a compressor wheel (17) having a compressor spiral (2) relative to a motor shaft (4), wherein the orbital bearing (3) has an inner ring (5) and an outer ring (6), wherein a plurality of balls (7) are arranged between the inner and outer rings (5, 6), which are spaced apart from each other by means of a cage (8) in the circumferential direction, or in the direction of rotation of the outer ring (6) relative to the inner ring (5), wherein the outer ring (6) is rotationally fixed and coaxially supported by the compressor wheel (17) and the inner ring (5) is rotationally fixed by a balancing ring (9), wherein an eccentricity (22) exists between the axis of rotation (16) of the inner ring (5) and the axis of rotation (11) of the motor shaft, wherein the balancing ring (9) is eccentric to the motor shaft rotation axis (11) is arrangedwherein the balancing ring (9) has a radially projecting extension (12) as a counterweight to the rotatable mass of the compressor wheel (17), whereby a chamber (13) is defined on the side diametrically opposite the extension (12), which can receive a lubricant mixture and supply this lubricant mixture to the orbital bearing (3) adjacent to the chamber (13), in particular to the balls (7), characterized in that a spring element (8) is arranged axially between the orbital bearing (3) and the compressor wheel (17), the spring element (8) is supported on the compressor wheel (17), and the spring element (8) can axially preload the inner ring (5) to the outer ring (6) so that there is no longer any axial play in the orbital bearing (3). Electromechanically operated spiral compressor (20) according to claim 1, characterized in that the spring element (8) is placed within the orbital bearing receptacle (10) of the compressor wheel (17) which is designed as a blind hole and is supported on the bottom of the orbital bearing receptacle (10). Electromechanically operated spiral compressor (20) according to claim 1, characterized in that the spring element (8) displaces the inner ring (5) to the outer ring (6) of the orbital bearing (3) in an axial direction and clamps them together, so that the contact force vector (15) between the balls (7) and the rings (5, 6) above the axis of rotation of the orbital bearing (3) rotates clockwise to a range between 5° and 20° from the vertical. Electromechanically operated spiral compressor (20) according to claim 1, characterized in that the inner ring (5) and the balancing ring (9) arranged thereon are displaced in the axial direction, so that the balancing ring (9) displaces the inner ring (23) of the main shaft bearing (19) in the axial direction relative to the outer ring (24) of the main shaft bearing (19). Electromechanically operated spiral compressor (20) according to claim 4, characterized in that the contact force vector between the balls (25) and the rings (23, 24) of the main shaft bearing (19) is rotated counterclockwise in a range between 5° and 20° from the vertical above the axis of rotation of the main shaft bearing (19). Electromechanically operated spiral compressor (20) according to one of the preceding claims, characterized in that the spring element (8) is designed as a spiral spring, wave spring or rubber ring. Electromechanically operated spiral compressor (20) according to one of claims 1 to 5, characterized in that the spring element (8) axially displaces the inner ring (5) as gas pressure, wherein the gas pressure originates from the chamber (13). Electromechanically operated spiral compressor (20) according to one of the preceding claims, characterized in that the motor shaft (4) is supported at the shaft end opposite the main shaft bearing (19) by a secondary shaft bearing (21), wherein the secondary shaft bearing (21) is axially movable relative to the motor shaft (4) and has neither a stop step nor a spring element. Electromechanically operated spiral compressor (20) according to claims 3 and 5, characterized in that the contact force vectors form an X-arrangement and thereby stabilize the main shaft bearing (19) and the orbital bearing (3) mutually during operation. Orbital bearing (3) of the electromechanically operated spiral compressor (20) according to one of the preceding claims.

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