US-12618463-B2 - Motor unit having a lubricant circuit

US12618463B2US 12618463 B2US12618463 B2US 12618463B2US-12618463-B2

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.

Inventors

Ivo Greiter

Assignees

AUDI AG

Dates

Publication Date: 20260505
Application Date: 20230718
Priority Date: 20220719

Claims (8)

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; a lubricant sump, which stores gathered lubricant and is arranged beneath the electric motor and/or the transmission in the housing during use, wherein the lubricant sump has at least two suction points separated from each other in a horizontal direction, and wherein each of the suction points is connected by a respective conduit to a respective one of the at least two inlets of the lubricant pump; and a lubricant shell, which is arranged beneath the transmission during use and catches lubricant from the transmission, wherein the transmission comprises at least one transmission gear which dips partly into the lubricant caught in the lubricant shell, wherein teeth of the at least one transmission gear lift lubricant out from the lubricant shell and deliver lubricant directly to the lubricant sump during use, wherein the lubricant sump is situated above the lubricant shell in the vertical direction.
2 . The motor unit according to claim 1 , wherein 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.
3 . The motor unit according to claim 1 , 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.
4 . The motor unit according to claim 1 , wherein the lubricant pump is configured as an external gear pump, wherein two gears are provided, each of which suctions lubricant from a respective one of the at least two inlets of the lubricant pump.
5 . 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.
6 . 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.
7 . The motor unit according to claim 1 , wherein at least the electric motor has a coolant circuit different from the lubricant circuit.
8 . 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; a lubricant sump, which stores gathered lubricant and is arranged beneath the electric motor and/or the transmission in the housing during use, wherein the lubricant sump has at least two suction points separated from each other in a horizontal direction, and wherein each of the suction points is connected by a respective conduit to a respective one of the at least two inlets of the lubricant pump; and a lubricant shell, which is arranged beneath the transmission during use and catches lubricant from the transmission, wherein the transmission comprises at least one transmission gear which dips partly into the lubricant caught in the lubricant shell, wherein teeth of the transmission gear lift lubricant out from the lubricant shell and deliver lubricant directly to the lubricant sump during use, wherein the lubricant sump is situated above the lubricant shell in the vertical direction, 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 the conduits connected to the transmission and to the electric motor; 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

BACKGROUND Technical Field The present disclosure relates to a motor unit 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 or the transmission in the housing during use, having at least two suction points. The disclosure also relates to a method for the circulation of lubricant in a motor unit. Description of the Related Art Motor units, which comprise an electric motor and a transmission connected to it in a common housing, are used, for example, as axle drives for motor vehicles. For such motor units it is basically required that the electric motor and the transmission must be both lubricated and cooled, in order to assure long-term operating safety. In order to assure this operating safety in all load situations, a dry sump lubrication can be used, for example, in which lubricant is suctioned out from the transmission and the electric motor and stored in a lubricant tank. Then, from this lubricant tank, the lubricant is taken at different pressure levels on the one hand to the transmission and on the other hand to the electric motor. This concept achieves a reliable lubrication of all components in all load situations, but it is expensive and it requires a multitude of components. The document JP2014000848A describes a cooling system for the electric motor of a hybrid vehicle. This cooling system comprises two lubricant pumps, one of which is driven mechanically by an internal combustion engine and the other electrically. The lubricant is stored in a lubricant sump and can be suctioned out by both oil pumps and taken to the electric motor. In the document DE 10 2014 205 881 B3 there is described a transmission motor having an electric motor, where a transmission is arranged inside the rotor of the electric motor. The lubricant circuit for the transmission motor comprises two lubricant pumps, one of which pumps the lubricant to a lubricant tank situated outside the transmission motor and the other lubricant pump takes the lubricant stored there temporarily back to the transmission motor. The document DE 10 2010 062 952 A1 discloses a transmission for off-road vehicles. Inside the transmission housing there is arranged a lubricant tank. The lubricant circuit is configured such that lubricant from a dry sump is at first pumped to the lubricant tank and taken from this lubricant tank to the components being lubricated. The lubricant circuit comprises at least two lubricant pumps. BRIEF SUMMARY Embodiments of the disclosure propose solutions with which the lubricant supply of a motor unit having an electric motor and a transmission can be simplified and the number of components required for the lubricant supply can be reduced. Some embodiments include a motor unit 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, wherein the outlet is connected by conduits to the electric motor and the transmission, a lubricant sump is provided, which is arranged beneath the electric motor or the transmission in the housing during use, and having at least two suction points separated from each other in the horizontal direction, and each of the suction points is connected by a conduit to an inlet of the lubricant pump. The motor unit described herein comprises a housing, inside which are arranged an electric motor and a transmission. The housing may comprise multiple chambers, preferably having passages between each other, through which air and lubricant can get from one chamber to another chamber. The motor unit comprises a lubricant circuit, which supplies both the electric motor and the transmission with lubricant. In some embodiments, the lubricant is a lubricating oil. The lubricant serves here primarily for the lubrication of moving components, but it can also be used for cooling of the electric motor and/or the transmission. The motor unit comprises only a single lubricant pump, having an outlet from which lubricant is pumped through one or more conduits to the transmission and to the electric motor. The lubricant pump has at least two inlets, by which lubricant is sucked in from the lubricant sump. A lubricant sump is arranged during use beneath the electric motor and/or beneath the transmission within the housing. By the term “during use” is meant a situation in which the motor unit is in the normal operating state. By “normal operating state” is meant, in turn, a state in which the motor unit is being used