ELECTRICAL DRIVE SYSTEM

Abstract

An electric drive system comprising an electric machine, a transmission connected to the electric machine, and an inverter. The electric drive system further comprising an at least two-part housing. The electric drive system having two mutually separate cooling circuits for the inverter and the electric machine, wherein the two cooling circuits are thermally connected via a heat exchanger that is installed, between the inverter and the electric machine, in the housing.

Claims

1. An electric drive system comprising an electric machine, a transmission connected to the electric machine, and an inverter, the electric drive system comprising an at least two-part housing, and the electric drive system having two mutually separate cooling circuits for the inverter and the electric machine, wherein the two cooling circuits are thermally connected via a heat exchanger that is installed, between the inverter and the electric machine, in the housing, wherein the heat exchanger has a base and a cover, both of which serve as a heat-exchanger surface between the first and second cooling circuit, and wherein the heat exchanger has structures for deaerating the second fluid, which consist of fins and knobs, the fins extending in a flush manner between the base and the cover of the heat exchanger.

2. The electric drive system according to claim 1, wherein the knobs extend at a distance from the cover of the heat exchanger.

3. The electric drive system according to claim 1, wherein oil outlets are shielded by a wall.

4. The electric drive system according to claim 1, wherein oil outlets have a siphon that leads into a narrowed oil pipe.

Description

DRAWINGS

[0026] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. In this regard:

[0027] FIG. 1 shows a schematic representation of the electric drive unit;

[0028] FIG. 2 also shows a cooling jacket of the electric drive unit;

[0029] FIG. 3 shows a view of a heat exchanger;

[0030] FIG. 4 shows a cover of the heat exchanger;

[0031] FIG. 5 shows a top view of the inside of the heat exchanger;

[0032] FIG. 6 shows a detail of a drain of the heat exchanger; and

[0033] FIG. 7 shows a section through the drain.

DESCRIPTION OF THE INVENTION

[0034] Represented schematically in FIG. 1 is an electric drive system 1 that is arranged in a highly integrated manner in a housing 7. The housing 7 in this case is composed mainly of two housing parts 7a, 7b which are pre-assembled and connected to each other. The housing part 7a of the housing 7 comprises an electric machine 14 and a transmission 2, as well as an oil pump 17. The housing part 7b mainly comprises an inverter 3.

[0035] The electric drive system 1 is constructed with a first cooling circuit 4, which is designed for water or glycol/water cooling as a first fluid. The first cooling circuit 4 has an inlet 5 and an outlet 13, and runs in cooling channels in the inverter 3 close to the components of the power electronics of the inverter 3. The first fluid of the first cooling circuit 4 then flows into a cooling jacket 12 of the first cooling circuit, which surrounds a stator 23 of the electric machine 14. The cooling jacket 12 in this case comprises cooling channels 12a, which extend as a helix around the cylindrical jacket around the stator 23.

[0036] The electric drive system 1 also comprises a second cooling circuit 10 carrying a second fluid, namely oil. The second cooling circuit 10 comprises an oil sump 16, which is constructed as a common oil sump for the electric machine 14 and the transmission 2, with a split structure also being possible. The electric machine 14 advantageously has a dry sump, while the transmission 2 has a normal wet sump.

[0037] From the oil sump, the oil is pumped by an oil pump 18 through a filter 17 into the second cooling circuit 10. The oil serves in this case to cool a rotor 24 of the electric machine 14 by a concept for spraying the second fluid, as well as for lubricating the existing bearing structures in the electric drive system 1.

[0038] FIG. 2 again shows the cooling jacket 12 of the stator 23 with the cooling channel 12a. FIG. 2 also shows the housing part 7a, which contains the electric machine as the main component, and the housing part 7b with the inverter 3.

[0039] FIG. 3 shows a heat exchanger 19, which is installed in the housing part 7a of the housing 7 and in the housing part 7b. The housing part 7a has a base 9 of the heat exchanger 19 on its cylindrical outer skin. This base 9 of the heat exchanger 19 is attached to the structurally highest point of the housing part 7a. The base 9 covers the cooling structure of the cooling jacket 12, such that the temperature of the base 9 is influenced by the temperature in the cooling channels 12a of the first cooling circuit 4.

[0040] The base 9 is shaped like a trough, and has both knobs 27 and fins 26 distributed over its surface. The fins 26 in this case extend to such a height that they are closed off by a lid 25. The knobs, on the other hand, do not contact the lid 25. An oil-air mixture drawn in by the oil pump 18 is pumped into the heat exchanger 19 through an oil inlet 20. The inflowing fluid of the second cooling circuit 10 in this case impinges on the wall and a fin 26 and spreads out inside the bottom. The oil outlets 21, 22 are concealed behind fins 26, such that the foaming oil-air mixture already settles on its way to the oil outlets 21, 22 as a result of flowing against the fins 26. The knobs 27 enhance the effect and help with deaerating.

[0041] The base 9 of the heat exchanger 19 is closed by the cover 25.

[0042] The oil outlets 21, 22 of the heat exchanger 19 are specially designed.

[0043] As can be seen in FIGS. 6 and 7, the oil drains 21, 22 are designed with a siphon 33. The respective oil drain 21, 22 in this case is provided with a shielding wall 34, which extends approximately to the height of the knobs 27. The siphon 33 is located downstream of the wall 34 and leads into a cooling channel 35. The air in this case is sucked out of the heat exchanger 19 via the siphon 33. For this purpose, the outlet cross-section is reduced in the region of the two oil outlets 21, 22.

[0044] The upper side of the cover 25 is connected to the inverter 3, which is cooled by the first cooling circuit 4. Thus, both outer sides of the heat exchanger 19, the base 9 and the cover 25, are each in contact with cooling lines of the first cooling circuit 4, such that heat from the second cooling circuit 10, the oil circuit, in the heat exchanger 19 is transferred from the second cooling circuit 10 to the first cooling circuit 4 of the heat-exchanger surface.