Bearing unit for a coolant pump

Abstract

The invention relates to a bearing unit (1, 1') for a coolant pump, comprising an outer bearing part (3, 4) having a bore (5, 6) and an inner bearing part (7) accommodated therein, which inner bearing part is mounted so as to slide hydrodynamically against the outer bearing part. The inner bearing part and the outer bearing part are mounted with conical or parabolic bearing surfaces (8, 11; 9, 12) so as to slide both axially and radially hydrodynamically against one another.

Description

[0001] Bearing unit for a coolant pump

[0002] The invention relates to a bearing unit for a coolant pump, comprising an outer bearing part with a bore and an inner bearing part received therein, which is hydrodynamically slidably supported against the outer bearing part. The coolant pump is in particular an electric wet-rotor pump.

[0003] A storage unit is understood to be a pre-assembled and deterioration-protected assembly that can either not be disassembled into its components without damage or only with targeted disassembly steps.

[0004] DE 10 2022 116 192 A1 discloses a bearing unit with hydrodynamic sliding bearing of the type mentioned above.

[0005] The present invention is based on the objective of constructively improving a generic bearing unit.

[0006] The solution to this problem arises from the features of claim 1. Accordingly, the inner bearing part and the outer bearing part are to be supported by conical, i.e., frustoconical, or parabolic bearing surfaces, allowing for both axial and radial hydrodynamic sliding contact with each other. This geometric design of the bearing surfaces results in a particularly compact construction as well as self-centering of the inner bearing part within the outer bearing part.

[0007] Advantageous embodiments of the invention are the subject of the dependent claims.

[0008] Further features of the invention will become apparent from the following description and the figures, which illustrate exemplary embodiments of the bearing units according to the invention. Unless otherwise stated, identical or functionally equivalent components or features are designated with the same reference numerals. The figures show:

[0009] Figure 1a: a first storage unit in perspective assembly;

[0010] Figure 1b: the first storage unit in longitudinal section; Figure 1c: the first storage unit in perspective exploded view;

[0011] Figure 1d: a first outer storage part of the first storage unit in perspective view;

[0012] Figure 1e: a second outer storage section of the first storage unit in perspective view;

[0013] Figure 1f: an alternative outer storage part for the first storage unit in a first perspective view;

[0014] Figure 1g: the outer part of the storage unit according to Figure 1f in a second perspective view;

[0015] Figure 2a: a second storage unit in perspective assembly;

[0016] Figure 2b: the second storage unit in longitudinal section;

[0017] Figure 2c: the second storage unit in perspective explosion;

[0018] Figure 2d: the outer part of the storage unit of the second storage unit in perspective view.

[0019] Figures 1a to 1e together show the views essential for understanding the invention of a first embodiment of a bearing unit 1 according to the invention, which is intended for use as a plain bearing in an electric coolant pump of the wet rotor type. The bearing unit 1 comprises the following components: A bearing sleeve 2, which can be made of case-hardening steel 16MnCr5, two outer bearing parts 3 and 4 with bores 5 and 6, which are fixedly mounted therein, and an inner bearing part 7, which is mounted in the bores 5 and 6. The outer bearing parts 3 and 4, which can be made of the plain bearing materials carbon or sintered metal, have conical bearing surfaces 8 and 9 on their facing end faces that are mirror-symmetrical to each other with respect to a cross-sectional plane through the plain bearing, each with three circumferential segments 8a, 8b and 8c, respectively.9a, 9b and 9c, which rise in a wedge shape in the circumferential direction, similar to so-called wedge-shaped sectors according to Micheli. The circumferential wedge orientation of segments 8a to 8c and 9a to 9c corresponds – as is usual for hydrodynamic sliding bearings – to the relative direction of rotation of the inner bearing part 7 to the outer bearing parts 3, 4.

[0020] The inner bearing part 7 can also be made of 16MnCr5 and is essentially a cylindrical pin with a central shoulder 10. On this shoulder, axially conical bearing surfaces 11 and 12 are located on both sides. These bearing surfaces are complementary to the wedge-shaped bearing surfaces 8 and 9 with respect to their cone angle, but are perfectly rotationally symmetrical to them. The bearing surfaces 8 and 11, as well as 9 and 12, form two pairs of conical bearing surfaces. Due to their cone angles, these surfaces provide hydrodynamic sliding bearings for the inner bearing part 7 and the outer bearing parts 3 and 4, both radially and in both axial directions. The respective cone angle is optimized with respect to the bearing load-bearing capacity and the axial and radial forces acting on the bearing.The coolant supplied by the coolant pump serves as the sliding bearing medium. It enters the interior of the axially permeable bearing unit 1 and the wedge gap between the bearing surfaces 8 and 11 or 9 and 12 via three axial grooves 13 and 14 on the circumference of the outer bearing parts 3 and 4. The number, width, and depth of the grooves 13 and 14 are variable and adapted to the application-specific coolant flow rate required through the grooves 13 and 14. The shoulder 10 is either an integral part of the inner bearing part 7 or is joined to it, for example, by means of a press fit.

[0021] The outer bearing parts 3, 4 have diameter expansions at their axial end sections facing away from the hydrodynamic sliding bearing and are only locally pressed into the bearing sleeve 2 at the diameter expansions 15, 16. The bores 5, 6 of the outer bearing parts 3, 4 are each enlarged in diameter in the axial region of the diameter expansions 15, 16 by means of a chamfer 17 and 18 to prevent radial jamming of the inner bearing part 7 in the outer bearing parts 3, 4 as a result of their press fit with the bearing sleeve 2. For this purpose, the chamfers 17, 18 are dimensioned axially and radially larger than the diameter expansions 15, 16.

[0022] The outer bearing parts 3, 4 and the bearing sleeve 2 are also secured against relative rotation by a positive locking mechanism. For this purpose, the bearing sleeve 2 is provided with three circumferentially distributed tabs 19 and 20 at each of its axial end sections, and the outer bearing parts 3, 4 are provided with three circumferentially distributed recesses 21 and 22 at each of their axial end sections, the positive locking being formed by the engagement of the tabs 19, 20 in the recesses 21, 22. Before the bearing unit 1 is mounted, the tabs 19 are bent approximately 90° towards the outer surface of the bearing sleeve 2 and, after the bearing unit 1 is mounted, engage in the corresponding recesses 21 of the outer bearing part 3. After the mounting of the bearing unit 1, the tabs 20 are bent by significantly less than 90° and engage in the corresponding recesses 21 of the outer bearing part 4. Furthermore, the forming of the tabs 19, 20 establishes a predetermined bearing clearance within the sliding bearing.

[0023] Figures 1f and 1g show a constructive alternative to the bearing outer parts 3 and 4. In this alternative, the bearing unit 1 comprises two identical bearing outer parts 3. The axial end sections of the bearing sleeve 2 remain asymmetrical with respect to the bent tabs 19, 20, specifically with respect to their shapes and bending angles. This asymmetry is compensated for by the fact that the bearing outer parts 3 have circumferentially distributed recesses 21 for the tabs 19 and circumferentially distributed recesses 22 for the tabs 20. In the present embodiment, the bearing outer part 3 has three recesses 21 and three recesses 22, with only three tabs 19 engaging in one bearing outer part 3 and only three tabs 20 engaging in the other bearing outer part 3. Consequently, the number of tabs 19, 20 is six and is less than the twelve number of recesses 21, 22 of both outer bearing parts 3 together.

[0024] The outer bearing part 3 shown in Figure 1f is also provided with a bore 5 which has at least one continuous longitudinal groove 26. Like the axial grooves 13 and 14, the longitudinal groove 26 facilitates the flow of coolant through the bearing unit 1 and also promotes the lubrication of the inner bearing part 7 in the bore 5. In addition, the longitudinal groove 26 can collect dirt particles that could otherwise lead to increased bearing friction and even to the point of blockage of the bearing unit 1. The outer bearing parts 3 and 4 according to Figures 1a to 1e and 2a to 2d can each also be provided with one or more such longitudinal grooves 26.

[0025] In an alternative version not shown, the outer bearing part 3 can have three continuous longitudinal grooves 26, which are uniformly distributed around the circumference and merge in a straight line into three transverse grooves 27 in the bearing surface 8. The transverse grooves 27 promote the formation of the hydrodynamic sliding bearing film and separate the segments 8a, 8b, and 8c from one another. In the embodiment shown in Figure 1g, these are not formed as wedge-shaped gap sectors, but rather as (completely raised) surface sections of a truncated circular cone.

[0026] Figures 1f and 1g further illustrate that the outer bearing parts 3 do not have a circular cross-section, but rather a rounded polygonal cross-section. In this case, the polygon is a rounded triangle. The rounded polygonal cross-section facilitates, on the one hand, an optimal press fit between the outer bearing part 3 and the bearing sleeve 2, with minimal deformation relative to the bearing sleeve 2, and on the other hand, it creates a larger coolant flow cross-section between the outer circumference of the outer bearing part 3 and the inner circumference of the bearing sleeve 2. This press fit can extend over the entire axial length of the three highest circumferential elevations (vertices of the triangle).

[0027] The bearing unit 1 is configured operationally such that the bearing sleeve 2 with the outer bearing parts 3, 4 attached therein rotates with the impeller of the coolant pump, while the inner bearing part 7 is fixed in the (non-rotating) housing of the coolant pump.

[0028] A second embodiment of a bearing unit 1' according to the invention, which is explained below with reference to Figures 2a to 2d, is configured in reverse. In this embodiment, the inner bearing part 7 rotates with an impeller connected to it, while the single outer bearing part 3 is fixed in a plastic housing of the coolant pump. A bearing sleeve, as in the first embodiment, does not exist. Instead, the outer bearing part 3 is overmolded with the housing plastic and includes circumferentially distributed recesses 23, which provide a positive-locking anti-rotation device for the plastic housing relative to the outer bearing part 3.

[0029] The inner bearing part 7 and the outer bearing part 3 are radially and axially supported against each other hydrodynamically via only one pair of conical bearing surfaces 8 and 11. In this design, the bearing surface 8 has six segments 8a to 8f, and the shoulder 10 has only the single conical bearing surface 11. The impeller, which rotates with the inner bearing part 7, is configured such that the pressure differential at the impeller always presses the bearing surface 11 against the bearing surface 8.

[0030] The bore 5 in the outer bearing part 3 has a diameter expansion 24 at its axial end section, which faces away from the sliding bearing. A retaining ring 25, in the form of a pressed-on collar sleeve and attached to the inner bearing part 7, is received in this expansion. The retaining ring 25 prevents the unassembled bearing unit 1' from falling apart and, at the same time, allows the bearing clearance of the sliding bearing to be adjusted by its axial positioning on the inner bearing part 7.

[0031] The construction details explained above can also be combined in other ways as desired.

Claims

Patent claims 1. Bearing unit (1 , 1 ') for a coolant pump, comprising an outer bearing part (3, 4) with a bore (5, 6) and an inner bearing part (7) received therein, which is hydrodynamically slidably mounted against the outer bearing part (3, 4), characterized in that the inner bearing part (7) and the outer bearing part (3, 4) are hydrodynamically slidably mounted against each other both axially and radially with conical or parabolic bearing surfaces (8, 11 ; 9, 12).

2. Bearing unit (1 , 1 ') according to claim 1, characterized in that the bearing surface (8, 9) of the outer bearing part (3, 4) comprises circumferential segments (8a to 8f; 9a to 9c) which rise in a wedge shape in the circumferential direction.

3. Bearing unit (1) according to claim 1 or 2, characterized in that the bore (5) has one or more continuous longitudinal grooves (26) which transition into transverse grooves (27) in the bearing surface (8) of the outer bearing part (3, 4).

4. Bearing unit (1) according to one of the preceding claims, characterized by a bearing sleeve (2), two bearing outer parts (3, 4) received therein and two pairs of conical or parabolic bearing surfaces (8, 11; 9, 12) which hydrodynamically slide the bearing inner part (7) and the bearing outer parts (3, 4) against each other in both axial directions.

5. Bearing unit (1) according to claim 4, characterized in that the outer bearing parts (3) are rounded polygonal in cross-section.

6. Bearing unit (1) according to claim 4 or 5, characterized in that the outer bearing parts (3, 4) and the bearing sleeve (2) are positively secured against mutual rotation, wherein the bearing unit (1) has tabs (19, 20) on the axial end sections of the bearing sleeve (2) and circumferential recesses (21, 22) on the outer bearing parts (3, 4) and the positive locking is formed by the engagement of the tabs (19, 20) formed into the recesses (21, 22).

7. Bearing unit (1) according to claim 6, characterized in that the axial end sections of the bearing sleeve (2) are asymmetrically aligned with respect to the tabs (19, 20). the are, wherein the bearing outer parts (3) are identical parts and the number of tabs (19, 20) is less than the number of recesses (21, 22) of both bearing outer parts (3).

8. Bearing unit (1) according to one of claims 4 to 7, characterized in that the outer bearing parts (3, 4) are locally enlarged in diameter at their axial end sections, which are facing away from the hydrodynamic sliding bearing, and are pressed into the bearing sleeve (2) at the diameter expansions (15, 16), wherein the bores (5, 6) of the outer bearing parts (3, 4) are each enlarged in diameter in the axial region of the diameter expansions (15, 16).

9. Bearing unit (1 ') according to claim 1 or 2, characterized in that the inner bearing part (7) and the outer bearing part (3) are slidably mounted against each other in only one axial direction.

10. Bearing unit (1 ') according to claim 9, characterized by a retaining ring (25) attached to the inner bearing part (7), wherein the bore (5) of the outer bearing part (3) has a diameter extension (24) at its axial end section, which is away from the sliding bearing, in which the retaining ring (25) is received.

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