Double-acting hydrodynamic axial sliding bearing

Abstract

The invention relates to a double-acting hydrodynamic axial sliding bearing (1) comprising: a bearing housing (2) in which there is located a first bearing body (3) having a first axial bearing surface (4), and a second bearing body (5) having a second axial bearing surface (6); and a shaft (7) comprising at least one thrust collar (8), wherein the at least one thrust collar is located in the bearing housing between the first axial bearing surface and the second axial bearing surface and can be supported against the first or second axial bearing surface depending on the axial position of the shaft, and a first or second annular chamber (9, 12) is formed depending on whether the thrust collar is supported against the first or second axial bearing surface.

Description

Double-acting hydrodynamic axial sliding bearing The invention relates to a double-acting hydrodynamic axial sliding bearing according to the preamble of independent claim 1. Double-acting hydrodynamic axial sliding bearings are widespread and are used to support axially loaded shafts. A double-acting hydrodynamic axial sliding bearing of the type in question comprises a bearing housing and a shaft with a thrust collar. At the respective axial ends in the bearing housing, axial bearing surfaces are formed on which it is possible to support the thrust collar of the shaft that is to be supported. Even if reference is made below to contact of the thrust collar against the bearing surfaces, in the case of a hydrodynamic bearing there is never any direct contact between the thrust collar and the corresponding bearing surface; there is always a lubricating film between the thrust collar and the bearing housing. The lubricant used is usually a bearing oil. When the thrust collar bears against one of the bearing surfaces, an annular chamber is formed which is closed off from the rest of the bearing housing and is delimited in the radial direction by the outer diameter of the shaft and the inner diameter of the bearing body, and in the axial direction by an axial wall (for example, the wall of the bearing housing) and a side of the thrust collar facing the axial bearing surface. The bearing oil and / or air can collect in the annular chamber. In the case of multi-phase filling states (air and oil) in the "chamber", the compressibility of the air results in a delay between the force and the counterforce acting on the axial bearing. This delay may lead to instability of the shaft bearing system, the instability being characterized by pressure differences between the two chambers. The multi-phase state may arise during operation if the amount of oil provided is not sufficient to always completely fill the chamber with oil. Due to the pressure differences between the annular chambers and the remaining space, an axial force is exerted on the shaft, which moves the shaft axially to the shaft collar side which has not been in contact up to now. As a result, a gap is formed in the annular chamber which has been in contact up to now, said gap promoting the presence of an air component in this chamber during the next vibration period, because the amount of oil supplied to the bearing is generally not sufficient to completely fill the lubricating gap with oil on the side which is not in contact. When the shaft then moves again from the side which is initially not in contact to the side which is in contact, the air present there first of all has to be displaced. If this does not happen sufficiently quickly, the instability described above with the axial forces associated therewith may arise. By means of these alternately arising axial forces, an axial vibration is generated in the shafting, which may also be increased by an axial natural frequency possibly present in the shafting. The resulting axial vibration may lead to damage or to failure of the axial bearing. In addition to axial sliding bearings with one thrust collar, axial sliding bearings with two thrust collars are also known, in which the above-described instabilities also occur. It is therefore an object of the invention to provide a doubleacting hydrodynamic axial sliding bearing in which the axial vibration excitation is at least significantly reduced, if not avoided. This object is achieved by the features of independent claim 1. Further refinements of the invention, which can be used individually or in combination with one another, are the subject matter of the dependent claims. The double-acting hydrodynamic axial sliding bearing according to the invention, comprising a bearing housing having a first bearing body, which is arranged in the bearing housing and has a first axial bearing surface, and having a second bearing body, which is arranged in the bearing housing and has a second axial bearing surface, and a shaft, comprising at least one thrust collar, wherein the at least one thrust collar is arranged in the bearing housing between the first axial bearing surface and the second axial bearing surface and, depending on the axial position of the shaft, can be supported on the first or second axial bearing surface, and, depending on whether the thrust collar is supported on the first or second axial bearing surface, - a first annular chamber is formed which is closed off from the rest of the bearing housing and is delimited in the radial direction by the outer diameter of the shaft (7) and the inner diameter of the first bearing body, and in the axial direction by a first axial wall and that side of the thrust collar which faces the first axial bearing surface, or - a second annular chamber is formed which is closed off from the rest of the bearing housing and is delimited in the radial direction by the outer diameter of the shaft and the inner diameter of the second bearing body, and in the axial direction by a second axial wall and that side of the thrust collar which faces the second axial bearing surface, is characterized in that a pressure equalization device is provided via which a pressure difference between the first or the second annular chamber and the remaining space, which is separated from the first or second annular chamber, can be reduced or equalized. As a result of the pressure equalization, the axial vibration arising as a result of the alternating axial forces is at least effectively reduced, if not completely eliminated, and therefore no damage or even failure of the bearing occurs. A first refinement of the invention makes provision that the pressure equalization device comprises a first and a second pressure equalization line, which are arranged and designed in such a way that in each case one end of the respective pressure equalization line connects the first or second annular chamber, which is formed depending on the position of the thrust collar, to the surroundings, and the respective other pressure equalization line connects the remaining space, which is separated from the first or second annular chamber, to the surroundings. The pressure equalization is not produced directly between the two annular chambers, but in each case between the individual spaces (chambers) and the surroundings. This refinement can be produced particularly simply and without great structural outlay and may optionally even also be formed retrospectively. A further refinement of the invention makes provision that the pressure equalization device comprises a first and a second pressure equalization line, which are arranged and designed in such a way that in each case one end of the pressure equalization lines opens into the first or second annular chamber, which is formed depending on the position of the thrust collar, and the respective other ends of the pressure equalization lines are operatively connected to one another directly or via a pressure equalization chamber. By means of the lines communicating directly or internally directly with one another, pressure equalization between the respective annular chamber and the space separated from the annular chamber can in turn be produced in a simple manner. This solution may optionally also be formed retrospectively. A further alternative refinement of the invention is characterized in that the pressure equalization device comprises a first and a second pressure equalization line, which are arranged and designed in such a way that in each case the first end of the respective pressure equalization lines opens into the first or second annular chamber, which is formed depending on the position of the thrust collar, and the respective other end of the pressure equalization line opens into the space which is separated from the annular chamber. In contrast to the previous solution, such a solution has lower bearing losses. Further advantages of the invention will be explained below on the basis of exemplary embodiments. In the drawings: - Fig. 1 shows: A first exemplary embodiment of a doubleacting hydrodynamic axial sliding bearing according to the invention, with pressure equalization in relation to the surroundings. - Fig. 2 shows:  A second exemplary embodiment of one according to the invention, with pressure equalization by means of a pressure equalization chamber. - Fig. 3 shows: A third exemplary embodiment of a doubleacting hydrodynamic axial sliding bearing according to the invention, with internal pressure equalization by means of two separate pressure equalization lines. - Fig. 4 shows: A third exemplary embodiment of a doubleacting hydrodynamic axial sliding bearing according to the invention, with two thrust collars. The figures show illustrations of the double-acting hydrodynamic axial sliding bearing according to the invention that are in each case only schematic and not necessarily to scale. Essentially only the components necessary for the invention are illustrated. Identical or functionally identical components are provided with the same reference signs throughout the figures. In the case of the double-acting hydrodynamic axial sliding bearing illustrated, there are exemplary embodiments of such a bearing; there are further exemplary embodiments deviating therefrom on the market to which the invention can be applied and which are encompassed by the scope of protection of the invention. Fig. 1 shows a first exemplary embodiment of a double-acting hydrodynamic axial sliding bearing 1 according to the invention. The axial sliding bearing 1 comprises a bearing housing 2, which can also be formed in multiple parts for simpler assembly. On the axial walls 10, 13 of the bearing housing 2, bearing bodies 3, 5 are formed with an in each case axial contact surface 4, 7, on which it is possible to support a correspondingly formed shaft collar 8 of the shaft 7 that is to be supported. Depending on the axial (end) position of the shaft 7 or of the thrust collar 8: - a first annular chamber 9 is formed which is closed off from the rest of the bearing housing 2 and is delimited in the radial direction by the outer diameter DW of the shaft 7 and the inner diameter dK of the first bearing body 3, and in the axial direction by the first axial wall 10 and that side 11 of the thrust collar 2 which faces the first axial bearing surface 4, or - a second annular chamber 12 is formed which is closed off from the rest of the bearing housing 2 and is delimited in the radial direction by the outer diameter DW of the shaft 7 and the inner diameter dK of the second bearing body 5, and in the axial direction by the second axial wall 13 and that side 14 of the thrust collar 8 which faces the second axial bearing surface 6. Fig. 1 shows the position in which the thrust collar is in the first end position and the first annular chamber 9 is formed. In this position, bearing oil and air are located in the first annular chamber 9. Due to the multi-phase filling states (air and oil) in the annular chamber 9, the compressibility of the air results in a delay between the force and the counterforce acting on the axial bearing. This delay may lead to instability of the shaft bearing system, the instability being characterized by pressure differences between the annular chamber 9 and the remaining space 15, which is separated from the first annular chamber 9. In order to equalize the pressure differences, a pressure equalization device is provided. The pressure equalization device comprises a first and a second pressure equalization line 16, 17, which are arranged and designed in such a way that in each case one first end of the respective pressure equalization line 16, 17 connects the first or second annular chamber 9, 12, which is formed depending on the position of the thrust collar 8, to the surroundings, and the respective other pressure equalization line 9 connects the remaining space 15, which is separated from the first or second annular chamber 9, 12, to the surroundings. By this means, substantial pressure equalization between the spaces 9 and 12 and 15, which are (substantially) separated by the thrust collar, is made possible, as a result of which the instability of the shaft bearing system is at least significantly reduced, if not avoided. The pressure equalization line 16, 17 can be formed by simple bores in the bearing housing 2. Fig. 2 shows a second exemplary embodiment of a double-acting hydrodynamic axial sliding bearing 1 according to the invention. The basic construction corresponds to the axial sliding bearing described in fig. 1, to the more detailed description of which reference is therefore made here. The essential difference in relation to the first exemplary embodiment is that, in the exemplary embodiment according to fig. 2, the pressure equalization lines 16, 17 are connected directly to one another by one end of the pressure equalization lines 16, 17 opening into the first or second annular chamber 9, 12, which is formed depending on the position of the thrust collar 8, and the respective other ends of the pressure equalization lines 16, 17 are in operative connection with one another directly, or, as illustrated in the exemplary embodiment, via a pressure equalization chamber 18. Both embodiments, with or without an equalization chamber, permit effective pressure equalization between the first or second annular chamber 9 or 12 and the space 15, which is separated from the first or second annular chamber 9 or 12, and thereby in turn effectively prevent axial vibrations of the shaft 13. The pressure equalization chamber 18 is optional, the pressure equalization chamber being able to damp pressure surges of the multi-phase fluid in the pressure equalization lines 16, 17. Fig. 3 shows a third exemplary embodiment of a double-acting hydrodynamic axial sliding bearing 1 according to the invention. The exemplary embodiment substantially corresponds to the construction of the axial sliding bearing 1 from fig. 2, to the detailed description of which reference is made. In contrast to the exemplary embodiment according to figure 2, the pressure equalization lines 16, 17 are not connected to one another directly or via a pressure equalization chamber. Rather, the pressure equalization lines 16, 17 are arranged in such a way that in each case the first end of the respective pressure equalization lines 16, 17 opens into the first or second annular chamber 9, 12, which is formed depending on the position of the thrust collar 8, and the respective other end of the pressure equalization line 16, 17 opens independently of one another into the space 15, which is separated from the first or second annular chamber 9, 12. The embodiment according to fig. 3 thus also permits effective pressure equalization between the annular chambers 6, 8 and thereby in turn prevents axial vibrations of the shaft 13, which could otherwise lead to damage or even to destruction of the bearing. Fig. 4 shows a fourth exemplary embodiment of a double-acting hydrodynamic axial sliding bearing 1 according to the invention. This involves a bearing with two thrust collars 8 and 8a, the annular chambers 9 and 12 are formed by the outer diameter of the shaft dw, the inner diameter of the axial bearings dk, the inner surfaces of the thrust collars 11 and 14 and the outer surfaces 10 and 13 of a part located inbetween of the bearing housing 2. In the case of a combined axial-radial sliding bearing, this part located inbetween of the bearing housing 2 can comprise the radial sliding bearing and can be designed as a separate component. In this example, the pressure equalization can be formed by pressure equalization lines 16 and 17 in the bearing housing. The pressure equalization lines described in the context of this invention are not limited by definition to bores or closed channels of another design, but also comprise open channels, such as channels / grooves, which are introduced into the bearing housing by milling. In principle, all of the pressure equalization measures described may also be retrofitted to existing bearings. The outlay required for this purpose and the costs arising with such a conversion are manageable, and at the same time axial vibrations of the shaft are prevented and thus an essentially reliable operation of the bearing is ensured.

Claims

1. A double-acting hydrodynamic axial sliding bearing (1), comprising a bearing housing (2) having a first bearingbody (3), which is arranged in the bearing housing (2) andhas a first axial bearing surface (4), and having a secondbearing body (5), which is arranged in the bearing housing(2) and has a second axial bearing surface (6), and a shaft (7), comprising at least one thrust collar (8), wherein the at least one thrust collar (8) is arranged inthe bearing housing (2) between the first axial bearingsurface (4) and the second axial bearing surface (6) and, depending on the axial position of the shaft (7), can be supported on the first or second axial bearing surface (4,6), and, depending on whether the thrust collar (8) is supported on the first or second axial bearing surface (4,6), - a first annular chamber (9) is formed which is closed off from the rest of the bearing housing (2) and is delimited in the radial direction by the outer diameter (DW) of the shaft (7) and the inner diameter (dK) ofthe first bearing body (3), and in the axial direction by a first axial wall (10) and that side (11) of the thrust collar (2) which faces the first axial bearing surface (4), or- a second annular chamber (12) is formed which is closed off from the rest of the bearing housing (2) and is delimited in the radial direction by the outer diameter (DW) of the shaft (7) and the inner diameter (dK) ofthe second bearing body (5), and in the axial direction by a second axial wall (13) and that side (14) of the thrust collar (8) which faces the second axial bearing surface (6), characterized in thata pressure equalization device is provided via which a pressure difference between the first or the second annular chamber (9,  12) and the remaining space (15),which is separated from the first or second annular chamber (9, 12), can be reduced or equalized.

2. The double-acting hydrodynamic axial sliding bearing (1) as claimed in claim 1, characterized in thatthe pressure equalization device comprises a first and a second pressure equalization line (16,  17), which arearranged and designed in such a way that in each case oneend of the respective pressure equalization line (16, 17)connects the first or second annular chamber (9,  12),which is formed depending on the position of the thrust collar (8), to the surroundings, and the respective other pressure equalization line (9) connects the remaining space (15), which is separated from the first or second annular chamber (9, 12), to the surroundings.

3. The double-acting hydrodynamic axial sliding bearing (1) as claimed in claim 1, characterized in thatthe pressure equalization device comprises a first and a second pressure equalization line (16,  17), which arearranged and designed in such a way that in each case one end of the pressure equalization lines (16, 17) opens intothe first or second annular chamber (9,  12), which isformed depending on the position of the thrust collar (8),and the respective other ends of the pressure equalization lines (16, 17) are operatively connected to one anotherdirectly or via a pressure equalization chamber (18).

4. The double-acting hydrodynamic axial sliding bearing (1) as claimed in claim 1, characterized in thatthe pressure equalization device comprises a first and a second pressure equalization line (16, 17), which are arranged and designed in such a way that in each case the first end of the respective pressure equalization lines (16, 17) opens into the first or second annular chamber (9, 12), which is formed depending on the position of the thrust collar (8), and the respective other end of the pressure equalization line (16, 17) opens into the space (15), which is separated from the first or second annular chamber (9, 12).

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