Shaft bearing point and shaft bearing device

Abstract

The invention relates to a shaft bearing point with a radial bearing in which a drive shaft is supported, which is arranged in a machine housing wall, which separates a lubricant space from a space free of lubricant, the radial bearing has in each case one side in the axial direction which faces and which faces away from the lubricant space, a radial shaft seal is arranged which is axially spaced apart from the sealing side of the radial bearing, so that a lubricant chamber is produced therebetween, in which a chamber partition wall is arranged, characterized in that the chamber partition wall divides the lubricant chamber into a bearing chamber between the sealing side and the chamber partition wall and a sealing chamber between the chamber partition wall and the radial shaft seal ring, which are connected to one another by a partition wall throttle, which has an annular gap as a connection for the guided fluid between the two chambers, the annular gap is formed between the chamber partition wall and the drive shaft, and the annular gap has a height in the radial direction which can be flowed through, which is greater than 0.1 mm and less than 3 mm.

Description

Technical Field

[0001] The present invention relates to a shaft support portion having a sealing device and a shaft support device having such a shaft support portion. Background Technology

[0002] The invention is explained below with reference to an electric drive system in a motor vehicle, but this should not be construed as limiting the invention to this application. For electric drive systems in motor vehicles, particularly electric motors / generators, aluminum alloy is typically used as the housing material, and steel is used for one or more shafts; the same applies to transmission mechanisms and other drive components. Due to temperature variations—which are unavoidable in planned operation—and due to different coefficients of thermal expansion, different length variations occur in the components, which are addressed by appropriate support schemes. Furthermore, drive components in motor vehicles are periodically lubricated with oil, thus requiring the shaft support locations to be sealed with sealing rings. These temperature variations and temperature differences can affect the sealing performance of the sealing rings. Additionally, increased preload in the sealing rings improves the sealing performance and reduces its dependence on pressure conditions, but the increased preload relative to the shaft sealed by the sealing ring increases the frictional power at the sealing points.

[0003] DE19841099C1 proposes a radial shaft seal, in which, in order to provide a radial shaft seal ring capable of achieving pressure balance between the internal space and the external space of the housing, and to prevent fluid, such as oil, inside the housing from flowing out of the internal space of the housing, a splash protection device is proposed on the side facing the internal space of the housing. Summary of the Invention

[0004] The objective of this invention is to provide a shaft support portion with a sealing device that has improved efficiency. This objective is achieved by a shaft support portion with a radial bearing according to the invention, and by a shaft support device having such a shaft support portion.

[0005] In the context of this invention, the shaft support portion can be understood as a support portion for rotatably supporting a drive shaft relative to a housing member. The shaft support portion has a radial bearing in which the drive shaft is rotatably supported relative to the machine housing. Preferably, the machine housing is constructed as an electric motor / generator housing, and more preferably, the electric motor or electric motor / generator is housed within the machine housing. The radial bearing is particularly constructed as a rolling bearing, and preferably as a roller bearing or, more preferably, as a ball bearing, and particularly preferably as a grooved ball bearing. The radial bearing is indirectly or directly housed within the machine housing wall, i.e., within a housing section of the machine housing. Here, the machine housing wall can be constructed as a single piece with the machine housing, or the machine housing wall can preferably be constructed as a separate bearing housing.

[0006] The machine housing wall separates the wet space (which can be understood as the lubricant space) from the non-lubricant space (the so-called dry space). In other words, the drive shaft passes through the machine housing wall from the lubricant space into the non-lubricant space. In the sense of the invention, the lubricant space or wet space can be understood as a region of the machine housing in which at least one component—at least temporarily—is arranged to be supplied with fluid, preferably a liquid lubricant, wherein such a component can be particularly understood as a rolling bearing or gear or the like. Preferably, the fluid contained in the wet space is lubricating oil, preferably transmission oil. More preferably, in the most general case, the dry space can also be understood as the environment surrounding the machine housing. Preferably, this non-lubricant space is to be understood as a section of the machine housing in which the pilot voltage of an electromechanical energy converter, preferably a motor / generator, is contained. In particular, the dry space (non-lubricant space) must be protected to prevent fluid, especially liquid lubricant, from entering the dry space from the wet space (lubricant space), as contamination or functional interference may occur there.

[0007] Furthermore, to prevent fluid from overflowing from the lubricant space into the non-lubricant space, a radial shaft seal with at least one radial shaft sealing ring is provided. The radial bearing is inserted into the machine housing wall such that, with respect to the axial direction, i.e., the direction of the rotation axis of the drive shaft housed in the radial bearing, the radial bearing has a side facing the lubricant space (i.e., the so-called lubricant side) and a side away from the lubricant space. In particular, the side of the radial bearing away from the lubricant space faces the non-lubricant space and can be understood as the so-called sealing side of the radial bearing.

[0008] The radial shaft seal is arranged axially spaced from the sealing side of the radial bearing, creating a lubricant chamber between the sealing side and the radial shaft seal ring in the axial direction. Furthermore, a chamber partition wall is provided within the lubricant chamber, dividing the lubricant chamber at least partially into two sub-chambers.

[0009] One of these sub-chambers formed by the lubricant chambers through the chamber partition wall can be understood as a so-called support chamber because it is located between the sealing side of the radial bearing and the chamber partition wall. The second chamber of these two chambers formed by the lubricant chambers through the chamber partition wall can be understood as a sealing chamber because it is located between the chamber partition wall and the radial shaft seal, particularly the radial shaft sealing ring.

[0010] However, the two sub-chambers (support chamber and sealing chamber) formed by the lubricant chamber via a chamber partition wall are not sealed apart from each other, but rather, more precisely, the two sub-chambers are fluid-guidedly connected by a throttling section of the partition wall. Therefore, the present invention specifically proposes that the pressure appearing in the support chamber, particularly the pressure caused by the pumping action of the radial bearing, does not act indirectly and directly on the sealing chamber as would be the case without the chamber partition wall, but rather achieves pressure balance between the support chamber and the sealing chamber through the throttling section of the partition wall.

[0011] The partition wall throttling section (particularly composed of a chamber partition wall and a drive shaft) has an annular gap for fluid-guided connection between the support chamber and the sealed chamber, the annular gap being formed between the chamber partition wall and the drive shaft. Furthermore, the annular gap is configured such that it has a height in the radial direction, i.e., perpendicular to the axis of rotation of the drive shaft, that allows fluid to pass through, the height being greater than 0.1 mm and less than 3 mm.

[0012] Studies have shown that, in particular, the use of this partition wall throttling section can, on the one hand, ensure that a sufficient amount of lubricant can reach the radial shaft seal from the support chamber to lubricate the contact between the radial shaft seal, especially the radial shaft sealing ring, during the operation of the drive shaft; and on the other hand, the partition wall throttling section reduces pressure fluctuations on the radial shaft seal, thereby preventing unsealing in the direction of the unlubricated space.

[0013] As is known from existing technology, when a leak occurs in a radial shaft seal ring, a radial shaft seal ring with a higher preload is used, which increases the normal force from the radial shaft seal ring to the shaft to be sealed. This increased normal force, while improving the sealing effect, also leads to higher losses (frictional power). In contrast, compared to radial shaft seal rings with a higher preload but without a partition wall throttling section, the proposed solution achieves the same sealing effect under different operating conditions while maintaining a constant preload, by reducing the pressure effect acting on the radial shaft seal.

[0014] In a preferred embodiment of the invention, the radial bearing is indirectly housed within the machine housing wall because it is housed within a support canister that radially—at least substantially or preferably completely—encloses the radial bearing. Preferably, the machine housing and, more preferably, the machine housing wall are also made of or composed of an aluminum alloy. More preferably, the support canister is made of or composed of steel. Particularly in applications where the radial bearing is constructed as a so-called floating bearing and its outer support ring is movably housed relative to a support seat, the support canister made of steel has higher wear resistance than that of aluminum alloy. Here, the support canister enables static housing within the machine housing wall (steel / aluminum pair) and, furthermore, the movable outer support ring of the radial bearing within the support canister (steel / steel pair), thereby allowing relative movement, particularly in the axial direction, between the material pairs with higher wear resistance. More preferably, the chamber partition wall is constructed as a single piece with the support canister. In particular, the chamber partition wall forms a shoulder to receive forces in the axial direction, especially when the radial bearing on the outer support ring is loaded with axial force using a spring support device.

[0015] In a preferred embodiment of the invention, the chamber partition wall has a throttling baffle radially opposite the drive shaft. Figuratively, the chamber partition wall is positioned close to the drive shaft in the radial direction, i.e., perpendicular to the axis of rotation of the drive shaft, such that a throttling portion is formed between the chamber partition wall and the drive shaft. Therefore, the chamber partition wall, or the end of the chamber partition wall facing the drive shaft, can be understood as a throttling baffle. Furthermore, the throttling portion has a cross-section that is at least substantially annular and gap-shaped. Additionally, the chamber partition wall has an axial longitudinal extension dimension greater than 0.25 mm and less than 5 mm in the region directly opposite the drive shaft (this region of the chamber partition wall is referred to as the throttling baffle within the scope of this invention). In particular, the small longitudinal extension dimension causes minimal fluid friction between the chamber partition wall and the drive shaft during rotation of the drive shaft, and the large length of the throttling baffle improves the throttling effect.

[0016] Studies have shown that longitudinal extension dimensions within this range are compatible with the available structural space on the one hand, and reduce pressure pulsations in the sealed chamber relative to the support chamber on the other.

[0017] In a preferred embodiment of the invention, a spring support device is arranged in the axial direction on the sealing side of the radial bearing, preferably between the outer support ring of the radial bearing and the chamber partition wall. Furthermore, the spring support device is configured such that a support preload can be applied to the outer support ring of the radial bearing in the axial direction. In particular, the preferred "small" preload on the radial bearing can positively influence its load-bearing capacity. More preferably, despite the presence of the spring support device, the radial bearing can still move in the axial direction relative to the machine housing wall, at least within a defined area, and particularly until the spring support devices are completely pressed together (aufBlock). Therefore, the radial bearing can move at least temporarily in the axial direction relative to the housing wall. As long as the radial bearing is housed in a support can and therefore not directly but indirectly within the machine housing wall, the radial bearing is also movable relative to the support can fixed in the machine housing wall.

[0018] In a preferred embodiment of the invention, the drive shaft has a drive shaft support diameter to accommodate a radial bearing; this diameter or region of the drive shaft can also be understood as a so-called support seat. Furthermore, the drive shaft has a so-called drive shaft throttling diameter opposite the chamber partition wall, which can also be understood as a diameter orientation, i.e., a region, with an outer diameter that is variable in the axial direction (direction of the drive shaft's axis of rotation). Preferably, this drive shaft throttling diameter, together with a throttling baffle, forms an annular gap for the partition wall throttling portion. The drive shaft throttling diameter, or the outer diameter of the drive shaft within the range previously described as the drive shaft throttling diameter, is preferably smaller than the drive shaft support diameter. In particular, this design of the invention results in a very effective throttling effect, thereby reducing pressure pulsations in the sealed chamber.

[0019] In a preferred embodiment of the invention, the throttling baffle has an inner diameter through which the drive shaft is concentrically guided, thereby creating an annular gap between the throttling baffle and the drive shaft for separating the throttling portion of the baffle. Furthermore, the inner diameter of the throttling baffle is selected from a range such that, with respect to the drive shaft support diameter, the inner diameter of the throttling baffle is at most 1 mm smaller than and at most 1 mm larger than the drive shaft support diameter. In other words, the inner diameter of the throttling baffle is selected from a range of + / - 1 mm with respect to the drive shaft support diameter. Studies have shown that a particularly space-saving structure in the lubricant chamber region can be achieved by using a throttling baffle inner diameter that approximately corresponds to the drive shaft support diameter (drive shaft support diameter + / - 1 mm).

[0020] In another embodiment of the invention, a drive shaft support device, a so-called shaft support device, is proposed, wherein the drive shaft is supported at at least two locations spaced apart from each other in the axial direction, and wherein at least one of these radial support locations is configured as a shaft support location according to one of the previously described embodiments of the invention.

[0021] In a preferred embodiment of the shaft support device, one of the radial support portions is configured as a so-called fixed support portion. In the context of the invention, a fixed support portion is particularly understood to mean that the drive shaft is fixed in the axial direction, in addition to a rotatable support for the drive shaft at that location. Specifically, through this axial fixation, the drive shaft is fixed in the axial direction to the fixed support portion, and furthermore, the second radial support portion of the shaft support device is therefore implemented as a shaft support portion according to one of the previously described embodiments of the invention. This support arrangement is often also referred to as a so-called fixed-floating support device, wherein, in the present case, the floating support side can be preloaded in the axial direction by means of a spring support device.

[0022] Furthermore, it is proposed that the fixed support portion is arranged axially on one side of the lubricant space side of the radial bearing and spaced axially from that lubricant space side. This arrangement alters the throttling effect of the partition wall throttling section when the drive shaft thermally expands relative to the machine housing, particularly when the drive shaft throttling diameter changes axially, i.e., when the drive shaft throttling diameter decreases from its maximum diameter, particularly the drive shaft support diameter, to its minimum diameter, particularly the drive shaft seal diameter (where the radial shaft seal contacts the drive shaft), decreasing axially from the radial bearing towards the radial shaft seal ring. Specifically, this configuration results in a small annular gap at "high operating temperatures" because the drive shaft has its maximum longitudinal elongation in this state. In this state, the inner diameter of the throttling baffle is relative to the "large" drive shaft throttling diameter. If the operating temperature decreases, the longitudinal elongation of the drive shaft also decreases, and in this case, compared to the previously described higher operating temperature situation, the inner diameter of the throttling baffle is relative to a smaller drive shaft throttling diameter.

[0023] Here, this positively influences the operating behavior of the shaft support device through the variable size of the annular gap with respect to operating temperature, because the lubricant contained in the wet space is thinner at "high" operating temperatures than at "low" operating temperatures. Due to the effect of the aforementioned variation in the size of the annular gap of the partition wall throttling section, the flow-through annular gap is larger at "low" operating temperatures and smaller at "high" operating temperatures. This configuration of the invention has proven to be particularly reliable in operation because the viscosity of the fluid in the wet space and the size of the annular gap develop in opposite directions, thus providing sufficient lubrication to the radial shaft seal ring and generating small pressure pulsations in the sealing chamber over a wide operating temperature range. Attached Figure Description

[0024] The various features and embodiments of the present invention are described in more detail below with reference to the accompanying drawings. In principle, combinations of features other than those shown are also feasible. (See the drawings:)

[0025] Figure 1 A partial sectional view of the shaft support section (without the radial bearing) is shown.

[0026] Figure 2 The pressure change curves are shown for a sealed chamber with and without chamber partition walls.

[0027] Figure 3 A partial sectional view of the shaft support section is shown. Detailed Implementation

[0028] exist Figure 1The machine housing wall 2 is shown in cross-sectional view, within which a support can 16 for accommodating a radial bearing (not shown in this figure) is placed. The drive shaft 1 is rotatably supported about a rotation axis 8 and extends in the axial direction 6. The support can 16 has a chamber partition wall 12 that divides the lubricant chamber into a sealed chamber 14 and a support chamber 13, which are fluidly connected to each other via a partition wall throttling section 15. The partition wall throttling section 15 is formed by an annular gap that is created between the chamber partition wall 12 and the drive shaft 1, particularly the drive shaft throttling diameter 19. The drive shaft throttling diameter 19 extends in the axial direction 6 (in... Figure 1 (From left to right in the diagram) the diameter decreases, that is, drive shaft 1 has a tapered configuration here.

[0029] The annular gap 12 between the annular gap 12 and the drive shaft 1 has a flow-through height 21 in the radial direction 7, wherein the height varies in this region as the tapered drive shaft 1 extends longitudinally, provided that a fixed bearing for supporting the drive shaft 1 is provided and as long as the fixed bearing is in Figure 1 The lubricant chamber 4 is arranged to the left of the support tank 16 and spaced apart from it in the diagram. Furthermore, the lubricant chamber 4 is sealed relative to the unlubricated space 5 by means of a radial shaft sealing ring 11. The throttling baffle 16 has a longitudinal extension dimension 17, which can be understood as the wall thickness of the chamber partition wall 12 opposite to the drive shaft 1.

[0030] It should generally be noted that the small longitudinal extension dimension 17 of the throttling baffle 16 can further reduce friction, especially fluid friction, between the chamber partition wall 12 and the drive shaft 1.

[0031] The throttling baffle 16 has a throttling baffle inner diameter 20, and the drive shaft 1 has a drive shaft support diameter for accommodating a radial bearing, which is also accommodated in the support canister 16. Furthermore, the drive shaft 1 has a drive shaft sealing diameter 22, wherein the drive shaft sealing diameter is configured such that a radial shaft sealing ring 11 extends over the diameter 22 and thus seals the lubricant space 4 relative to the unlubricated space 5.

[0032] exist Figure 2The diagram shows two qualitative pressure variation curves for alternating operation with respect to the rotational speed of drive shaft 1. Curves 26a and 26b, respectively, relate to the pressure acting on the radial shaft seal. Overpressure 24 is plotted upwards from zero line 23 (atmospheric pressure), and correspondingly negative pressure 25 is plotted downwards. Pressure variation curve 26a is plotted with respect to time 27a, where it can be seen that the rotational speed change on drive shaft 1 causes pressure fluctuations in the space between radial bearing 3 and radial shaft seal 11.

[0033] Here, in Figure 2 a and Figure 2 b shows the same running state, however Figure 2 'a' represents the pressure variation curve 26a for the shaft support portion without the partition wall throttling section 15, or in other words, the pressure fluctuations—such as those that can be generated, particularly by the pumping action of the radial bearing 3—act directly on the radial shaft seal 11. Figure 2 b shows the connection with Figure 2 The same operating state applies, however, to the proposed shaft support portion with a partition wall throttling section. The support chamber is fluid-guided to the sealing chamber through this partition wall throttling section, but in a manner with the throttling effect of the partition wall throttling section. In other words, pressure changes in the support chamber here only indirectly affect the radial shaft seal 11, which can be seen in particular by means of the reduced negative pressure value of the pressure change curve 26b relative to FIG. 26a.

[0034] A critical negative pressure limit 28 exists in relation to the pre-tightening of the radial shaft seal 11. Here, the critical negative pressure limit represents a negative pressure that can cause the radial shaft seal 11 to lift off the drive shaft. If the radial shaft seal 11 lifts off the drive shaft 1, liquid may flow from the lubricant space 4 into the unlubricated space 5, even in the presence of negative pressure.

[0035] Depend on Figure 2 As can be seen from a and 2b, compared to an arrangement without a partition wall throttling section, the negative pressure acting on the radial shaft seal is reduced by the partition wall throttling section 15. This allows for the use of a radial shaft seal with a smaller preload compared to an arrangement without partition wall throttling section, without compromising operational safety. Therefore, the present invention significantly reduces the frictional power on the radial shaft seal, and thus improves the efficiency of the drive system with the proposed shaft support configuration compared to conventional shaft support devices without partition wall throttling sections.

[0036] exist Figure 3Another partial cross-sectional view of the proposed shaft support portion is shown. The drive shaft 1 is rotatably supported relative to the machine housing wall 2 about the axis of rotation 8 by a radial bearing 3. Here, the radial bearing 3 is indirectly housed in the machine housing wall 2 by a support can 16 and is constructed as a grooved ball bearing having an outer support ring 30 and an inner support ring 29. The radial bearing 3 is mounted on the drive shaft support diameter with the inner support ring 29 and is fixed to the drive shaft 1 in the axial direction 6. The outer support ring is movably housed in the support can 16 in the axial direction 6, wherein a preload is applied to the outer support ring by means of a spring support device 31, particularly to the end side facing the radial shaft seal 11, i.e., the so-called sealing side 32. The radial bearing 3 has a lubricant side 9 facing the lubricant space 4 on the end side opposite to the spring support device 31.

[0037] The chamber partition wall 12 of the support tank 16 divides the space between the sealing side 32 and the radial shaft seal 11, the so-called lubrication chamber, into a support chamber 13 and a sealing chamber 14, wherein these two chambers (13, 14) are fluid-guided but throttling connected to each other through a partition wall throttling section 15. The partition wall throttling section 15 has an annular gap formed between the drive shaft 1 and the chamber partition wall 12 through which flow can pass, the annular gap having a height extension dimension orthogonal to the axis of rotation 8, i.e., in the radial direction 7.

[0038] In particular, the proposed configuration of the partition wall throttling section 15 in terms of its height in the radial direction 7 and its longitudinal extension in the axial direction 6 allows for the avoidance of directly reflecting pressure changes in the sealing chamber 14 that may arise from the alternating operation of the drive shaft 1 and appear in the support chamber 13. Specifically, negative pressure fluctuations in the support chamber caused by the alternating operation of the drive shaft 1 are mitigated, and radial shaft seals 11, particularly radial shaft sealing rings, with a "small" preload can be used without affecting the sealing effect relative to the unlubricated space 5.

Claims

1. A shaft support portion having a radial bearing, wherein a drive shaft (1) is rotatably supported in the radial bearing relative to a machine housing, wherein, A radial bearing (3) is disposed indirectly or directly in a machine housing wall (2) that separates a lubricant space (4) from a non-lubricant space (5). The radial bearing (3) has a lubricant side (9) facing the lubricant space (4) and a sealing side (10) facing away from the lubricant space in the axial direction (6). A radial shaft seal (11) is provided, which is arranged axially spaced from the sealing side (10) of the radial bearing (3), such that a lubricant chamber is formed between the sealing side (10) and the radial shaft seal (11) in the axial direction, and a chamber partition wall (12) is arranged in the lubricant chamber. The feature is that the chamber partition wall (12) divides the lubricant chamber into a support chamber (13) and a sealing chamber (14), the support chamber being arranged between the sealing side (10) and the chamber partition wall (12), the sealing chamber being arranged between the chamber partition wall (12) and the radial shaft seal (11), and the support chamber (13) and the sealing chamber (14) being fluid-guidedly connected to each other through a partition wall throttling section (15), the partition wall throttling section (15) having an annular gap as a connecting part for guiding fluid between the support chamber (13) and the sealing chamber (14), the annular gap being formed between the chamber partition wall (12) and the drive shaft (1), and the annular gap having a height (21) in the radial direction (7) that can be flowed through, the height being greater than 0.1 mm and less than 3 mm.

2. The shaft support portion according to claim 1, characterized in that, The radial bearing (3) is housed in a support tank (16) that radially surrounds the radial bearing (3), and the chamber partition wall (12) is constructed as a single piece with the support tank (16).

3. The shaft support portion according to claim 1 or 2, characterized in that, The chamber partition wall (12) has a throttling baffle that is radially opposite to the drive shaft (1), the throttling baffle having an axial longitudinal extension dimension (17) in the region opposite to the drive shaft (1), the longitudinal extension dimension being greater than 0.25 mm and less than 5 mm.

4. The shaft support portion according to claim 1 or 2, characterized in that, A spring support device (31) is arranged in the axial direction (6) between the sealing side (10) and the chamber partition wall (12) so that the spring support device can apply a support preload to the outer support ring (30) of the radial bearing (3) in the axial direction, and the radial bearing (3) can move in the axial direction (6) at least temporarily relative to the machine housing wall (2).

5. The shaft support portion according to claim 1 or 2, characterized in that, The drive shaft (1) has a drive shaft support diameter (18) to accommodate the radial bearing (3), and the drive shaft (1) has a drive shaft throttling diameter (19) opposite to the chamber partition wall (12), and the drive shaft throttling diameter (19) is smaller than the drive shaft support diameter (18).

6. The shaft support portion according to claim 3, characterized in that, The drive shaft (1) has a drive shaft support diameter (18) to accommodate the radial bearing (3), and the drive shaft (1) has a drive shaft throttling diameter (19) opposite to the chamber partition wall (12), and the drive shaft throttling diameter (19) is smaller than the drive shaft support diameter (18).

7. The shaft support portion according to claim 6, characterized in that, The throttling baffle has an inner diameter (20), and the inner diameter (20) of the throttling baffle is selected from a diameter range with reference to the drive shaft support diameter (18), and the diameter range extends from 1 mm smaller than the drive shaft support diameter (18) to 1 mm larger than the drive shaft support diameter (18).

8. A shaft support device having at least two radial support portions, characterized in that, At least one of the radial support portions is constructed according to any one of claims 1 to 7.

9. The shaft support device according to claim 8, characterized in that, One of the radial support portions is configured as a so-called fixed support portion, such that the drive shaft is fixed in the fixed support portion in the axial direction (6), and the second radial support portion is configured as a shaft support portion according to any one of claims 1 to 7, and the fixed support portion is arranged in the axial direction (6) on one side of the lubricant space (4) of the radial bearing (3) and is arranged axially spaced apart from the side of the lubricant space.

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