LUBRICANT FLOW

Abstract

A lubricant feedthrough for transferring lubricant between a housing (4) and a shaft (1) rotatably mounted on the housing (4) comprises opposing recesses (5, 9), each with an outlet (6) or an inlet (11) for lubricant at the housing (4) and shaft (1), and a transfer sleeve (13) that engages in the recesses (5, 9) to define a lubricant channel (14) between the outlet (6) and the inlet (11). A first of the recesses (5) and the transfer sleeve (13) have opposing conical sealing surfaces (19, 22) oriented to be subjected to overpressure of the lubricant in the lubricant channel (14) and to clamp a sealing ring (15) between them.In a gap (23) between a second (9) of the recesses and the transition sleeve (13) a sealing structure is formed which counteracts a flow of lubricant from the lubricant channel (14) through the gap (23).

Description

[0001] The present invention relates to a lubricant feedthrough, in particular for the lubricant supply of a rotor of an electrical machine.

[0002] Lubrication feedthroughs for supplying a shaft rotating within a housing, in which a lubricant outlet on the housing and an inlet at one end of the shaft are located opposite each other, are known per se. An escape of lubricant between the housing and the shaft is generally desirable in this case to maintain a lubricant film between opposing surfaces of the housing and the shaft. As long as the proportion of lubricant reaching the inlet at the end of the shaft corresponds to approximately half the mass flow at the outlet, it can be assumed that this proportion will be sufficient to also lubricate a bearing at the opposite end of the shaft.

[0003] In electrical machines, another function is that the lubricant is required to dissipate waste heat from the machine's rotor. To achieve this, the proportion of lubricant passing through the inlet must be greater than that lost between the housing's outlet and the inlet.

[0004] The object of the present invention is to provide a lubricant feedthrough which makes it possible to reduce outflows of lubricant between an outlet of the housing and an inlet of the shaft.

[0005] The object is achieved according to one aspect of the invention in that, in a lubricant feedthrough for the transmission of lubricant between a housing and a shaft rotatably mounted on the housing, in which the housing and the shaft have mutually opposing recesses, each with an outlet or an inlet for lubricant, and a transfer sleeve engages in the recesses to define a lubricant channel between the outlet and inlet, a first of the recesses and the transfer sleeve have mutually opposing conical sealing surfaces which are oriented to be acted upon by an overpressure of the lubricant in the lubricant channel and to clamp a sealing ring between them.

[0006] To generate the high lubricant flow rate required for cooling a rotor, a lubricant pump can be provided on the housing side. The overpressure generated by this pump is also useful for pressurizing the sealing surfaces against each other.

[0007] In order to fix the sealing ring axially, at least one of the conical sealing surfaces can be a side flank of an annular groove.

[0008] An engagement of the transfer sleeve in the second recess with at least radial, preferably also axial play, helps to minimize the transmission of tilting or radial movements of the shaft to the transfer sleeve and the sealing ring.

[0009] Preferably, opposing surfaces of a second of the recesses and the transfer sleeve are separated by a gap. This allows both to rotate relative to each other with minimal friction.

[0010] To prevent lubricant from flowing through the gap, a sealing contour can be formed on at least one of the surfaces. The sealing contour can be a known, rotationally symmetrical labyrinth contour. According to a preferred embodiment, it is helical, particularly in the form of an external thread of the transfer sleeve, in order to exert a pumping effect that counteracts the lubricant's flow.

[0011] As the shaft and the transfer sleeve, which are located opposite each other on either side of the gap, rotate against each other, they also impart a circular motion to the lubricant in the gap, resulting in an axial force on the helical sealing contour. The handedness of the helix is ​​selected so that the resulting axial force directs the lubricant toward the lubricant channel.

[0012] The second recess may be provided with a friction-reducing lining.

[0013] The lining can in particular be realized as a sleeve inserted axially into the shaft.

[0014] The transfer sleeve is preferably a molded plastic part.

[0015] The invention further relates to an electrical machine with a lubricant feedthrough as described above, wherein the shaft carries a rotor of the electrical machine.

[0016] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying figures. Fig. 1 shows an axial section through a suspension of a shaft in an electrical machine, in particular a drive motor of an electrically driven motor vehicle; and Fig. 2 an enlarged detail from Fig. 1.

[0017] Fig. Figure 1 shows one end of a shaft 1 of an electrical machine, which is held by a rolling bearing 2 in a recess 3 in a wall of a housing 4 of the machine. The recess 3 comprises a large-diameter outer region, on whose walls 8 an outer ring of the rolling bearing 2 is held, and a smaller-diameter recess 5 at the bottom of this outer region. An outlet 6 for lubricant is connected to a lubricant pump 7 and opens at the bottom of the recess 5.

[0018] Opposite the recess 5, a recess 9 is formed on an end face 10 of the shaft 1 facing the receptacle 3. An inlet 11 of a lubricant passage 12 extending axially through the shaft 1 to a rotor (not shown) and a bearing at the opposite end of the shaft 1 is formed at the bottom of the recess 9.

[0019] A substantially tubular transfer sleeve 13 engages the recesses 5 and 8 of the housing 4 and the shaft 1. Its hollow interior defines a lubricant channel 14 from the outlet 6 to the inlet 11. The transfer sleeve 13 is an inexpensive molded plastic part.

[0020] A sealing ring 15 is held in a circumferential groove 16 of the part of the transfer sleeve 13 engaging in the recess 5. The groove 16 is formed on its side facing the shaft 1 by a steep flank 18, which in the simplest case is perpendicular to the rotational axis 17 of the shaft 1; a conical flank 19 is provided on the side facing the outlet 6.

[0021] The recess 5 has an inner surface 21 concentric with the bottom surface 20 and a conical flank 22 adjacent thereto. When the axis of rotation 17 of the shaft 1 and a longitudinal axis of the recess 5 coincide exactly, the sealing ring 16 contacts both the inner surface 21 and the bottom surface 20 over its entire circumference. An overpressure of the lubricant on the side facing the outlet 6 acts on the sealing ring 16 and the transfer sleeve 13 in the direction of the shaft 1, whereby the sealing ring 16 is clamped between the conical flanks 19, 22.

[0022] If the shaft 1 performs slight tilting movements around an axis perpendicular to the rotational axis 16 during operation, the transfer sleeve 13 can follow these tilting movements by moving the sealing ring 16 away from the flank 22 along part of its circumference and thereby tilting around an axis that runs through an opposite part of the circumference of the sealing ring. Due to this axial mobility, cross-sectional deformation of the sealing ring 16 remains minimal, thus ensuring a long service life for the sealing ring 16.

[0023] Due to friction of the sealing ring 16 on the surfaces of the recess 5 and the transfer sleeve 13, the latter is held substantially rotationally fixed to the housing 4, and the shaft 1 rotates around the part of the transfer sleeve 13 engaging in its recess 9.

[0024] When the axis of rotation 17 of the shaft 1 and a longitudinal axis of the transfer sleeve 13 coincide exactly, a circumferential gap 23 of constant width extends between the transfer sleeve 13 and the inside of the recess 9, which gap is constantly filled with lubricant escaping at the downstream end of the transfer sleeve 13 and through which the rolling bearing 2 is supplied with lubricant. The filling dampens radial movements of the shaft 1. Since the gap 23 should be as narrow as possible to prevent excessive lubricant from flowing out via it, radial movements of the shaft can nevertheless lead to contact between the transfer sleeve 13 and the inside of the recess 9. The inside is therefore formed by a friction-reducing lining, here in the form of a bushing 24 made of plastic, which is inserted into a front bore of the shaft 1.

[0025] As a further measure to reduce the outflow of lubricant via the gap 23, the part of the transfer sleeve 13 engaging in the recess 9 is provided on its outer side with a helical sealing contour 25, which exerts a pumping effect on the lubricant in the gap 23 upon rotation of the shaft 1 relative to the transfer sleeve 13. The direction of rotation of the shaft 1 is fixed; therefore, the handedness of the sealing contour 25 can be selected to match the direction of rotation of the shaft 1 such that the pumping effect of the sealing contour 25 is directed toward the inlet 11. The pumping effect is not strong enough to cause a flow of lubricating fluid in the gap 23 toward the inlet 11; it merely reduces the outflow of lubricant from the channel 14 through the gap 23 to the rolling bearing 2, driven by the overpressure of the pump 7.

[0026] A corresponding thread (not shown in the drawing) can be provided at an opposite end of the shaft 1 in order to reduce the outflow of the lubricant to a rolling bearing there and in this way to have a larger proportion of the lubricant flow available for cooling the rotor.

[0027] According to an alternative embodiment, the thread 25 could be replaced by an internal thread of the sleeve 24.

[0028] A design in which the transfer sleeve 13 is mirrored to the Fig. 1 is mounted. As the sealing ring frictionally fixes the transfer sleeve 13 in the shaft, the part thereof engaging in the recess 5 rotates relative to the housing, and the gap in which the thread counteracts the flow of lubricant extends between an inner side of the recess 5 and the part of the transfer sleeve 13 engaging therein.

[0029] The channel 14 may be tapered at its end facing the inlet 11 in order to accelerate the flow of lubricant towards the inlet and thus exert a suction effect on the lubricant in the gap 23 by means of a jet pump effect. Reference symbol 1 wave 2 rolling bearings 3 Recording 4 housings 5 Recess 6 Outlet 7 Lubricant pump 8 Wall 9 Recess 10 Frontal surface 11 Entrance 12 Lubricant passage 13 Transfer sleeve 14 Lubricant channel 15 Sealing ring 16 grooves 17 axis of rotation 18 flank 19 flank 20 floor space 21 inner surface 22 flank 23 gap 24 socket 25 threads

Claims

[1] Lubricant feedthrough for the transmission of lubricant between a housing (4) and a shaft (1) rotatably mounted on the housing (4), wherein the housing (4) and the shaft (1) have mutually opposite recesses (5, 9), each with an outlet (6) or an inlet (11) for lubricant, and a transfer sleeve (13) engages in the recesses (5, 9) in order to define a lubricant channel (14) between the outlet (6) and the inlet (11), wherein a first of the recesses (5) and the transfer sleeve (13) have mutually opposite conical sealing surfaces (19, 22) which are oriented in order to be acted upon by an excess pressure of the lubricant in the lubricant channel (14) and to clamp a sealing ring (15) between them. [2] Lubricant feedthrough according to claim 1, wherein at least one of the conical sealing surfaces (19) is a side flank of an annular groove (16). [3] Lubricant feedthrough according to one of the preceding claims, in which the transfer sleeve (13) engages with play in the second recess (9). [4] Lubricant feedthrough according to one of the preceding claims, in which a gap (23) is delimited by opposing surfaces of a second (9) of the recesses and the transfer sleeve (13) and a sealing contour (25) is formed on at least one of the surfaces. [5] Lubricant feedthrough according to claim 4, wherein the sealing contour (25) is helical. [6] Lubricant feedthrough according to claim 4 or 5, wherein the sealing contour (25) is an external thread of the transfer sleeve (13). [7] Lubricant feedthrough according to one of claims 3 to 6, wherein the second recess (9) is provided with a friction-reducing lining. [8] Lubricant feedthrough according to claim 7, wherein the lining is a sleeve (24) inserted axially into the shaft (1). [9] Lubricant feedthrough according to one of the preceding claims, in which the transfer sleeve (13) is a molded part made of plastic. [10] Electrical machine, in particular for a motor vehicle, with a lubricant feedthrough according to one of the preceding claims, wherein the shaft (1) carries a rotor of the electrical machine.

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