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DE-102024210835-A1 - Drive system for a motor vehicle

DE102024210835A1DE 102024210835 A1DE102024210835 A1DE 102024210835A1DE-102024210835-A1

Abstract

A drive unit (100) for a motor vehicle (105) comprises a machine housing section (300) with an electric machine (115) and a transmission housing section (305) with a transmission (130), as well as a hydraulic system (135) for cooling and/or lubricating thermal and/or mechanical consumers in the machine housing section (300) and in the transmission housing section (305). The hydraulic system (135) comprises a pump system (200, 600) with a first pump (601). The machine housing section (300) has a first suction point (310) which is hydraulically connected to the first pump (601) via a first suction line (225), and the transmission housing section (305) has a second suction point (400) which is hydraulically connected to the first pump (601) via a second suction line (230). Here, the first pump (601) is designed as a gear pump, which includes more than two externally toothed pump gears (611, 612, 613).

Inventors

  • Tobias Zürn
  • Marco Berner
  • Arthur Strehlau

Assignees

  • ZF FRIEDRICHSHAFEN AG

Dates

Publication Date
20260513
Application Date
20241112

Claims (17)

  1. Drive unit (100) for a motor vehicle (105), comprising a machine housing section (300) with an electric machine (115) and a transmission housing section (305) with a transmission (130), and a hydraulic system (135) for cooling and/or lubricating thermal and/or mechanical consumers in the machine housing section (300) and in the transmission housing section (305), wherein the hydraulic system (135) comprises a pump system (200, 600) with a first pump (201, 601), and wherein the machine housing section (300) has a first suction point (310) which is hydraulically connected to the first pump (201, 601) by a first suction line (225), wherein the transmission housing section (305) has a second suction point (400) which is connected to the first pump (201) or to a further pump of the hydraulic system by a second suction line (230) of the first pump (201). (135) is hydraulically connected, characterized in that the first pump (601) is designed as a gear pump which comprises more than two externally toothed gears (611, 612, 613).
  2. Drive system for a motor vehicle according to Claim 1 , characterized in that the first pump (601) is designed as an external gear pump, which has three externally toothed pump gears (611, 612, 613) and two suction ports (726, 731), wherein the first pump gear (611) is in engagement with both the second pump gear (612) and the third pump gear (613), and wherein the suction ports (726, 731) are each hydraulically connected to one of the two suction points (310, 400).
  3. Drive system for a motor vehicle according to Claim 2 , characterized in that of the three pump gears (611, 612, 613) only the first pump gear (611) can be driven by a pump shaft (610) by a drive unit (615).
  4. Drive system for a motor vehicle according to Claim 3 , characterized in that the three externally toothed pump wheels (611, 612, 613) have different or the same number of teeth.
  5. Drive system for a motor vehicle according to Claim 4 , characterized in that the first pump (601) has a pump housing (614) which is arranged concentrically to the drive unit (615) which drives the first pump (601), wherein the first pump gear (611) is rotationally fixed to a pump shaft (610) of the drive unit (615) and the second (612) and third pump gear (613) are spaced radially apart from the first pump gear (611) and offset from each other by 180°.
  6. Drive system for a motor vehicle according to Claim 5 , characterized in that the first pump gear (611) and the second pump gear (612) form a first pump unit with a first dry sump pump inlet (727), and the first pump gear (611) and the third pump gear (613) form a second pump unit with a second dry sump pump inlet (732), wherein the first and the second dry sump pump inlet (727, 732) are each hydraulically connected to the first (310) and second suction point (400) by a first suction port (726) and a second suction port (731).
  7. Drive system for a motor vehicle according to Claim 6 , characterized in that the first pump (201, 601) has a first pump outlet (247) and that the hydraulic system (135) comprises a reservoir (235), wherein both pump units of the first pump (201, 601) are hydraulically connected to the reservoir (235) via the first pump outlet (247) in such a way that the operating medium drawn in at the first and/or second suction point (310, 400) can be pumped into the reservoir (235) by means of the first pump (201, 601).
  8. Drive system for a motor vehicle according to Claim 7 , characterized in that the pump system (600) comprises, in addition to the first pump (201, 601), a second pump (205, 605) which is hydraulically connected to a suction point in the reservoir (235) via a third suction line (245) and is hydraulically connected to the gearbox housing section (305) and/or the machine housing section (300) via a second pump outlet (247) in such a way that the second pump (205, 605) acts as a pressure pump and can pump the operating medium from the reservoir (235) to the thermal and/or mechanical consumers in the gearbox housing section (305) and/or the machine housing section (300) for cooling and/or lubrication.
  9. Drive unit (100) for a motor vehicle according to Claim 8 , characterized in that the second pump (605) acting as a pressure pump is designed as an internal gear pump.
  10. Drive unit (100) for a motor vehicle according to Claim 9 , characterized in that the second pump (605) is designed as a gerotor pump and has an externally toothed inner pump rotor (621) and an internally toothed pump The pump outer rotor (622) comprises the pump inner rotor (621) being arranged non-rotatably on the pump shaft (620) and being driven by the drive unit (615).
  11. Drive unit (100) for a motor vehicle according to Claim 10 , characterized in that the second pump (605) comprises a second pump housing (624) within which the inner pump rotor (621) and the outer pump rotor (622) are rotatably arranged, and wherein within the pump system (600) the second pump housing (624) is arranged concentrically to the pump shaft (610) and to the first pump housing (614) and adjacent to the latter and the drive unit (615).
  12. Drive unit (100) for a motor vehicle according to one of the Claims 8 until 11 , characterized in that the volume flow rate of one of the two pump units of the first pump (201, 601) is greater than the delivered volume flow rate of the second pump (605).
  13. Drive unit (100) for a motor vehicle according to Claim 1 , characterized in that the first pump (201) is designed as a multi-wheeled external gear pump, which has four meshing pump gears and three suction ports and thus forms three pump units, each with a suction port, wherein the suction ports (226, 231) of the first and second pump unit are hydraulically connected to the first (310) and second suction point (400) and the third suction port of the third pump unit is connected to the reservoir (235), so that the third pump unit acts as a pressure oil pump like the second pump (205).
  14. Drive device (100) for a motor vehicle according to one of the preceding claims, characterized in that the drive unit (215, 615) comprises an electric motor with which the pump shaft (210, 610) can be driven.
  15. Drive device (100) for a motor vehicle according to one of the preceding claims, characterized in that a winding head cooling (320) of the electric machine (115) is hydraulically connected to a gearbox compartment (335) of the gearbox housing section (305), wherein a cooling and/or lubricating medium received in the gearbox compartment (335) can be drawn off at least indirectly to the first intake point (310) and to the second intake point (400) via at least one bypass (350) in the machine housing section (300).
  16. Electric drive axle comprising a drive unit (100) according to one of the preceding claims.
  17. Motor vehicle (105), comprising a drive unit (100) according to one of the Claims 1 until 15 or an electric drive axle Claim 16 .

Description

The present invention relates to a drive unit for a motor vehicle comprising a dry-sump hydraulic system for cooling and lubricating mechanical and/or electrical components, and an electric drive axle. The present invention also relates to a motor vehicle with such a drive unit. From the unpublished DE 10 2023 212 588.9 The applicant is aware of a drive device comprising an electric machine and a transmission unit, which are at least partially arranged in a common housing or interconnected sub-housings. A liquid operating medium is stored in the interconnected sub-housings or in a common housing for cooling and lubricating the mechanical and electrical components. The fact that the operating medium is stored in both sub-housings and can flow back and forth between them via the connection is hereinafter also referred to as a hydraulic connection between the sub-housings. In general, a hydraulic connection between several components is understood to mean that the operating medium can flow from one component to another through it. The liquid operating medium is usually a hydraulic fluid such as gear oil, hereinafter also referred to simply as oil. The operating fluid is transported to the points requiring cooling and lubrication by a lubricating/cooling oil pump, referred to below as a pressure pump. After dripping from the components requiring lubrication and cooling, which represent the consumers of the hydraulic system, the oil collects in a section of the housing. From this area, it is extracted by at least one pump and conveyed to a reservoir. This principle is also known as dry sump lubrication, and the extraction pump is referred to below as a dry sump or suction pump. The pressure pump then supplies the oil from the reservoir to the consumers. Such a hydraulic system with dry sump lubrication is used, for example, in... DE 10 2019 126 914 A1 known. Since the drive unit is used to propel a motor vehicle and is located within it, it, and consequently the operating fluid, is subject to vehicle dynamics, resulting in forces that occur during longitudinal and/or lateral acceleration. This is the case, for example, when braking, accelerating, or cornering. These inertial and centrifugal forces cause the operating fluid to shift within the housing, so that in certain situations the suction point of the dry sump pump becomes exposed, preventing the operating fluid from being drawn in and pumped into the reservoir. As an undesirable consequence, the reservoir is no longer filled, and the pressure pump can no longer deliver operating fluid to the consumers, potentially causing them to overheat, run dry, and wear out. For this reason, as in the example of the DE 10 2021 207 694 A1 The disclosed design provides two suction points, each connected to a dry sump pump designed as a gerotor pump. The suction points are positioned such that at least one is below the fluid level of the operating medium in every operating condition. This allows the operating medium to be drawn from the dry sump and the reservoir filled in any operating condition. The pressure pump is also designed as a gerotor pump, so the hydraulic system comprises a total of three gerotor pumps, driven by an electric motor. A disadvantage of this design is that the two dry sump pumps result in two sets of pump rotors, the torque losses of which due to viscous friction must be overcome by the electric motor, even when no oil is being pumped. This increases the energy consumption of the drive unit, negatively impacting its efficiency. Another specific embodiment of such a hydraulic system with a dry sump pump, which can pump oil from two different suction points, is described in the DE 10 2019 201 863 B3 The design reveals that the drive unit incorporates a double-stroke vane pump as a dry sump pump. By design, this pump has two independent delivery zones but only one rotor, which results in torque loss. The double-stroke vane pump thus acts like two dry sump pumps with a single rotor. Each of the two delivery zones of the double-stroke vane pump is connected to a suction point in the dry sump. A disadvantage of this design is the high cost of a double-stroke vane pump due to the high manufacturing precision required for this pump type. In addition to the double-stroke vane pump, this hydraulic system also requires a pressure pump to supply the consumers. The object of the present invention is to provide a drive device with an improved hydraulic system for reliable lubrication and/or cooling, independent of vehicle dynamics. to create influences on the operating medium. In particular, the hydraulic system should have low energy consumption and be cost-effective to manufacture. The invention solves this problem by means of the subject matter of the independent claim. The dependent claims describe a preferred embodiment. Accordingly, a drive system for a motor vehicle comprises a machine housing section with an electric motor and a transmission housing sect