LIQUID-COOLED ELECTRIC DRIVE SYSTEM

Abstract

A liquid-cooled electric drive system for a motor vehicle and a method of operating the drive system.

Claims

1. A liquid-cooled electric drive system for a motor vehicle, which has at least two drive units comprising: an electric machine and associated power electronics and which are connected to a coolant circuit of the motor vehicle, and a drive control unit which is set up to distribute the drive power produced by the drive system between the drive units as a function of the temperature of the components of the drive units.

2. The liquid-cooled electric drive system of claim 1, wherein the drive control unit is adapted to reduce the drive power provided by the drive unit, the components of which have the higher temperature and to increase the drive power provided by the drive unit, the components of which have the lower temperature.

3. The liquid-cooled electric drive system of claim 1, the coolant circuit of which comprises no coolant pump other than the electric machines.

4. The liquid-cooled electric drive system of claim 1, wherein the coolant is conveyed through the coolant circuit by centrifugal forces occurring in the electric machines.

5. The liquid-cooled electric drive system of claim 1, wherein each wheel is individually driven by an associated drive unit.

6. A method for operating a liquid-cooled electric drive system for a motor vehicle which has at least two drive units comprising: an electric machine and power electronics assigned to it, in which the drive power produced by the drive system is divided between the drive units as a function of the temperature of the components of the drive units.

7. The method of claim 6, in which the drive power provided by the drive unit, the components of which have the higher temperature, is reduced and the drive power provided by the drive unit, the components of which have the lower temperature, is increased.

8. The method of claim 6, in which the electric machines are operated at a speed at which the coolant is conveyed through the coolant circuit by centrifugal forces occurring in the electric machines.

9. The liquid-cooled electric drive system of claim 2, the coolant circuit of which comprises no coolant pump other than the electric machines.

10. The liquid-cooled electric drive system of claim 2, wherein the coolant is conveyed through the coolant circuit by centrifugal forces occurring in the electric machines.

11. The liquid-cooled electric drive system of claim 3, wherein the coolant is conveyed through the coolant circuit by centrifugal forces occurring in the electric machines.

12. The liquid-cooled electric drive system of claim 2, wherein each wheel is individually driven by an associated drive unit.

13. The liquid-cooled electric drive system of claim 3, wherein each wheel is individually driven by an associated drive unit.

14. The liquid-cooled electric drive system of claim 4, wherein each wheel is individually driven by an associated drive unit.

15. The method of claim 7, in which the electric machines are operated at a speed at which the coolant is conveyed through the coolant circuit by centrifugal forces occurring in the electric machines.

Description

BRIEF DESCRIPTION OF THE FIGURE

[0033] The invention is shown schematically in the drawing by means of an embodiment and is described schematically and in detail with reference to the drawing. In the drawings:

[0034] FIG. 1 is a schematic view of an embodiment of the drive system according to the invention.

DETAILED DESCRIPTION

[0035] FIG. 1 shows a schematic view of an embodiment of the drive system 10 according to the invention. The image shows a two-axle motor vehicle. A first axle 11 is assigned a first electric machine 12 (EM) and a first power electronics unit 13 (PE) controlling it. A second axle 21 is assigned a second electric machine 22 (EM) and a second power electronics unit 23 (PE) controlling it. A drive control unit 31 (DCU) communicates with the respective drive units 12/13 and 22/23, each comprising an electric machine 12, 22 and the associated power electronics unit 13, 23.

[0036] The DCU 31 reads the component temperatures of the installed e-machines 12, 22 and the power electronics 13, 23, and distributes the drive power between the axles 11 and 21 depending on the current actual temperature of the components. If the temperature of the components of EM 12 and PE 13 of axle 11 is higher than the temperature of the components of EM 22 and PE 23 of axle 21, the DCU 31 shifts drive power from axle 11 to axle 21. Conversely, the DCU 31 shifts drive power from axle 21 to axle 11 if the temperature of the components of EM 22 and PE 23 of axle 21 is higher than the temperature of the components of EM 12 and PE 13 of axle 11.

[0037] The DCU 31 automatically distributes the available drive power of the drive units 14 and 24 to reduce the power loss of the currently hotter drive unit, on the one hand, whileon the other handproviding the torque required to reach the speed threshold at which the speed of the electric machines 12 and 22 is sufficient to provide adequate coolant flow through the coolant circuit of the electric drive system 10.

[0038] Experience shows that from a speed of approx. 40 km/h, an adequate coolant volume flow is generated by the centrifugal forces acting in the electric machines 12 and 22. Test drives show that, in normal customer cycles, propulsion can be maintained for an unlimited period of time with slightly reduced drive power. Higher final speeds can therefore also be achieved without a separate coolant pump.