MOTOR UNIT HAVING A LUBRICANT CIRCUIT

Abstract

A motor unit is provided having an electric motor and a transmission, which are mechanically joined together and arranged in a housing, wherein the motor unit comprises a lubricant circuit, which lubricates the electric motor and the transmission, wherein a lubricant pump is provided, having an outlet and at least two inlets for lubricant. Furthermore, a lubricant sump is provided, which is arranged beneath the electric motor and/or the transmission in the housing during use, having at least two suction points. A method is also provided for the circulation of lubricant in a motor unit.

Claims

1. A motor unit, comprising: an electric motor and a transmission, which are mechanically joined together and arranged in a housing; a lubricant circuit, which lubricates the electric motor and the transmission; a lubricant pump having an outlet and at least two inlets for lubricant, wherein the outlet is connected by conduits to the electric motor and the transmission; and a lubricant sump arranged beneath the electric motor and/or the transmission in the housing during use, and having at least two suction points separated from each other in a horizontal direction, and wherein each of the suction points is connected by a conduit to an inlet of the lubricant pump.

2. The motor unit according to claim 1, wherein the lubricant sump is situated beneath the electric motor during use and a lubricant shell is arranged beneath the transmission during use, being provided to catch the lubricant from the transmission, and the transmission comprises at least one transmission gear, which dips partly into the lubricant caught in the lubricant shell, the transmission gear delivering lubricant from the lubricant shell to the lubricant sump during use.

3. The motor unit according to claim 2, wherein the lubricant sump is situated above the lubricant shell in the vertical direction during use and a protrusion is arranged between the lubricant sump and the lubricant shell, which extends beyond the lubricant level in the lubricant sump in the vertical direction during use.

4. The motor unit according to claim 2, wherein at least one lubricant guiding element is provided in the housing adjacent to the transmission gear, guiding the lubricant flow from the transmission gear to the lubricant sump.

5. The motor unit according to claim 1, wherein the lubricant pump comprises an electric drive and is situated inside or outside the housing.

6. The motor unit according to claim 5, wherein the lubricant pump is configured as an external gear pump, wherein two gears are provided, each of which suctions lubricant from one of the two inlets.

7. The motor unit according to claim 5, wherein the lubricant pump is configured as a vane pump, wherein the vane pump comprises two suction openings which are staggered by 180 with respect to each other in the circumferential direction, each of which forms one inlet of the lubricant pump.

8. The motor unit according to claim 1, wherein the lubricant sump has larger dimensions during use in the horizontal direction than in a vertical direction, wherein a length and a width of the lubricant sump in the horizontal direction is larger by at least a factor of 8 than a height in the vertical direction, and the suction points are situated respectively in the horizontal direction at a distance from an outer edge of the lubricant sump corresponding to as much as 20% of the distance between two opposite outer edges in the horizontal direction.

9. The motor unit according to claim 1, wherein a heat exchanger is arranged between the lubricant pump and the transmission and/or spray rings delivering lubricant to the electric motor are arranged next to the electric motor in the housing.

10. The motor unit according to claim 1, wherein at least the electric motor has a coolant circuit different from the lubricant circuit.

11. A method for the circulation of lubricant in a motor unit having: an electric motor and a transmission, which are mechanically joined together and arranged in a housing; a lubricant circuit, which lubricates the electric motor and the transmission; a lubricant pump having an outlet and at least two inlets for lubricant, wherein the outlet is connected by conduits to the electric motor and the transmission; and a lubricant sump arranged beneath the electric motor and/or the transmission in the housing during use, and having at least two suction points separated from each other in a horizontal direction, and wherein each of the suction points is connected by a conduit to an inlet of the lubricant pump, the method comprising: suctioning of lubricant from the lubricant sump, wherein the lubricant is suctioned from both suction points or from only one suction point by the lubricant pump, wherein the number of suction points used depends on the transverse acceleration acting on the lubricant during use; transporting of the lubricant by the lubricant pump to the transmission and to the electric motor through conduits; and conducting of the lubricant by gravity and/or centrifugal force through the transmission and the electric motor, the lubricant being caught in the lubricant sump after the lubricant passes through.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0027] Embodiments are represented schematically with the aid of the drawings and shall be further described with reference to the drawings.

[0028] FIG. 1 shows in a schematic view, an embodiment of a motor unit described herein.

[0029] FIG. 2 shows in a sectional view, an embodiment of the motor unit described herein installed in a motor vehicle.

DETAILED DESCRIPTION

[0030] FIG. 1 shows in a schematic view an embodiment of a motor unit 1. In FIG. 1, the functional principle of a motor unit 1 is represented. At the left side, in the housing 13, multiple gears can be seen, symbolizing the transmission 12. At the right side in the housing 13 there is shown, partly sectioned, the electric motor 11. The electric motor 11 and the transmission 12 are mechanically connected to each other, although this is not represented. The rotor shaft of the electric motor 11 transfers a rotary motion to the transmission 12, which in turn puts out a rotary motion through a power takeoff shaft, not shown. A lubricant pump 14 in the embodiment shown is arranged outside the housing 13. The outlet of the lubricant pump 14 supplies through conduits both the transmission 12 and the electric motor 11 with lubricant. In one of the conduits there is arranged a heat exchanger 17, which serves for cooling down the lubricant supplied for the lubrication. In this way, the lubricant circuit can also be used for the cooling of the transmission 12 and/or the electric motor 11.

[0031] Directly adjacent to the electric motor 11 inside the housing 13 are arranged multiple spray rings 18, which spray the lubricant finely divided onto the electric motor 11. In this way, a uniform supply of lubricant to the electric motor 11 is assured. The spray rings 18 are connected by conduits to the outlet of the lubricant pump 14. Inside the housing, the lubricant moves, driven by gravity or a centrifugal force, downward through the transmission 12 and the electric motor 11. The lubricant is represented symbolically by a collection of dots. The lubricant gathers in a lubricant sump 15, which in the embodiment shown is arranged beneath the electric motor 11. The lubricant sump 15 serves for gathering and storing the lubricant inside the housing 13. The lubricant sump 15 is flat in configuration. The length and the width of the lubricant sump 15 in the horizontal direction are distinctly larger than its height in the vertical direction. In this way, the lubricant sump 15 can be integrated in a compact housing 13. The design space required for the overall motor unit 1 is thus small. Because the lubricant sump 15 is low and flat in configuration, it may happen in certain operating states that the lubricant in the lubricant sump 15 will be forced to one edge by transverse accelerations, while in another place, such as at the opposite edge, no lubricant is present.

[0032] For this reason, the lubricant sump 15 has at least two suction points 151a, 151b, which are arranged in the lower bottom surface and spaced apart from each other in the horizontal direction. These suction points 151a, 151b serve for the removal of the lubricant from the lubricant sump 15 and are connected each by a conduit to an inlet of the lubricant pump 14. The two suction points 151a, 151b are situated in the vicinity of two mutually opposite outer edges of the lubricant sump 15. In the embodiment shown, the suction point 151b is situated at a distance from the right-hand outer edge corresponding to around 10% of the distance between the two mutually opposite right and left outer edges in the horizontal direction Likewise, the suction point 151a is situated at a distance from the left-hand outer edge likewise corresponding to around 10% of the distance between the two outer edges. Thanks to this arrangement of the suction points 151a, 151b in the vicinity of the outer edges of the lubricant sump 15, it is assured that lubricant will constantly be present at least at one of the two suction points 151a, 151b, even when transverse accelerations are acting on the motor unit 1. This ensures that the lubricant pump 14 at all times takes in lubricant and accordingly can deliver it through its outlet to the transmission 12 and to the electric motor 11.

[0033] Of course, it is possible to arrange more than two suction points 151a, 151b at different positions on or in the lubricant sump 15. Beneath the transmission 12 in the embodiment shown there is situated a lubricant shell 16, which catches and collects lubricant from the transmission 12. The lubricant sump 15 is arranged above the lubricant shell 16 in the vertical direction. For this reason, the lubricant does not flow by gravity from the lubricant shell 16 and back to the lubricant sump 15. In order to take the lubricant from the lubricant shell 16 back to the lubricant sump 15 and thus bring it back into the lubricant circuit, at least one transmission gear 121 is arranged such that it dips into the lubricant in the lubricant shell 16 and delivers the lubricant during use to the lubricant sump 15 by its rotary motion. The teeth of this transmission gear 121 act like scoops and lift the lubricant out from the lubricant shell 16 and into the lubricant sump 15. Thanks to this delivery of the lubricant by the transmission gear 121, it is not necessary to provide an additional suction point 151a, 151b on the transmission and the lubricant shell 16. In this way, the motor unit 1 takes on a compact design and has fewer components than the prior art.

[0034] FIG. 2 shows in a sectional view an embodiment of the motor unit 1 installed in a motor vehicle (not shown). In FIG. 2, one sees an embodiment of a motor unit 1 with a more detailed design than the embodiment in the schematic view of FIG. 1. For basic, functional relationships, also refer to the description for FIG. 1. The embodiment represented in FIG. 2 is designed as the rear axle of a motor vehicle with electric drive. The common housing 13 surrounds the electric motor 11, situated here on the left side, and the transmission 12, situated on the right side. On the left side beneath the electric motor 11 is arranged the lubricant sump 15. On the right side beneath the transmission 12 is arranged a lubricant shell 16. A protrusion 131 is located in the horizontal direction between the lubricant sump 15 and the Lubricant shell 16, which extends beyond the lubricant level in the lubricant sump 15 in the vertical direction. This protrusion 131 must be overcome when delivering lubricant from the lubricant shell 16 to the lubricant sump 15 by the transmission gear 121. The transport of the lubricant is symbolized by small arrows. The transmission gear 121 delivers the lubricant from the lubricant shell 16, which adheres temporarily to the teeth during the rotation of the transmission gear 121 and is thus transported in the direction of the lubricant sump 15. At least one lubricant guiding element can be provided for specific guidance of the lubricant. Such a lubricant guiding element can be formed, for example, by a specially shaped partial region of the housing 13 or by an inserted baffle plate. In the embodiment shown, the lubricant pump 14 is situated inside the housing 13. The lubricant pump 14 here is designed as an external gear pump with two gears. Such an external gear pump is simple to build and it has two inlets and one outlet. Each of the two gears takes in lubricant from one inlet of the lubricant pump 14. Alternatively, the lubricant pump 14 may also be arranged outside the housing 13 or be formed by another type of pump, such as a vane pump.

[0035] German patent application no. 10 2022 117957.5, filed Jul. 19, 2022, to which this application claims priority, is hereby incorporated herein by reference, in its entirety.

[0036] Aspects of the various embodiments described above can be combined to provide further embodiments. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled.