Electric drive device for a motor vehicle with a cooling system

Abstract

The invention relates to an electric drive device for a motor vehicle comprising a machine housing (12) which has a housing section for enclosing an electric machine (10) and a housing section for enclosing a transmission arrangement (8) coupled to the electric machine (10), wherein the electric machine (10) comprises a stator (13) fixedly arranged in the housing and a rotor (15) rotatably mounted about an axis of rotation (14) with respect to the stator (13), wherein the electric machine (10), the transmission arrangement (8) and a coolant collection tank (40) provided in the machine housing (12) are or can be integrated into a coolant circuit, wherein the stator windings of the stator (13) can be supplied with phase currents by a power electronics (50) via phase connections (19a, 19b, 19c).To optimize the cooling of the phase terminals of the stator (13) and to achieve an improved efficiency of the electric machine (10), the phase terminals (19a, 19b, 19c) are positioned vertically below the rotor shaft 30 of the rotor in the coolant collection tank (40).

Description

Field of invention

[0001] The present invention relates to an electric drive device for a motor vehicle with cooling, wherein the electric drive device is an electric machine with a stator arranged in a machine housing and a rotor rotatably mounted about an axis of rotation with respect to the stator, wherein in the installed position of the electric drive device a coolant sump with coolant is provided in the machine housing below the rotor, and wherein the stator can be connected to an inverter via a phase connection. State of the art

[0002] Intelligent cooling and heating management increases the range of electric vehicles, thereby enhancing their appeal and everyday usability. Therefore, it is common practice to use cooling systems in electric vehicles with electric drive systems. Here, the components of the electric drive system are temperature-controlled by a cooling circuit. The components to be cooled include the rotor and stator of the electric motor, as well as the power electronics or the power system with phase connections (busbars).

[0003] High-performance electric drives with high energy density utilize partially or fully cooled electric machines. In these machines, the rotor shaft and / or stator are cooled with coolant. In fully cooled electric machines, the coolant requirement for the rotor shaft and stator varies depending on the operating point, primarily due to copper, iron, and electromagnetic losses within the machine. Therefore, to ensure maximum thermal availability and minimize power losses, a demand-based distribution of the partial flow rates to the rotor shaft and stator is required. Conventional electric traction drives equipped with an electrically driven coolant pump utilize the coolant supplied by the positive displacement pump – usually a toothed ring or rotary displacement pump.Gerotor pump – the provided flow rate is generally used exclusively for the on-demand cooling of temperature-critical active components such as the stator and / or rotor of the electric drive motor. The electrically driven coolant pump is switched on and off as needed and / or operated at a controlled speed.

[0004] Cooling and lubrication of the transmission components is generally passive, utilizing the pumping action of a differential spur gear or an intermediate shaft spur gear in combination with a suitable housing that acts as a coolant guide. This results in a limited pumping effect that depends on the vehicle speed or gear rotational speed, and consequently, hydrodynamic losses that are strongly dependent on the rotational speed and coolant temperature. With passive lubrication of transmission components such as gears, rolling bearings, and radial shaft seals, churning losses occur.

[0005] Active cooling of the phase connections is achieved, for example, by using pressure lines. This has the disadvantage of incurring additional costs due to the necessary lines. Furthermore, a longer coolant line, in combination with demand-based flow control via throttles, can lead to higher pressure losses.

[0006] Document US 8,040,001 B2 discloses an assembly for mounting on or as part of the stator assembly of an electric machine. A multitude of component modules are arranged at angularly spaced locations around the assembly and contain power electronic components. Electrically conductive annular inlet and outlet manifolds are provided to convey coolant to and from the component modules. The inlet and outlet manifolds have a dual function as a coolant circuit for conveying coolant and as busbars. Summary of the invention

[0007] It is an object of the invention to provide an electric drive device for a motor vehicle with an electric machine, which is characterized by optimized cooling of the phase terminals of the stator and an improved efficiency of the electric machine.

[0008] This need can be met by the subject matter of the present invention according to independent claim 1. Advantageous embodiments of the present invention are described in the dependent claims.

[0009] The electrical drive arrangement according to the invention for a motor vehicle comprises an electric machine with a stator arranged in a machine housing and a rotor rotatably mounted about an axis of rotation with respect to the stator.

[0010] Improved cooling of the stator phase terminals is achieved by positioning the phase terminals within the coolant collection chamber in a position vertically below the rotor shaft.

[0011] During the cooling and lubrication of the electric machine's components, the coolant flow is routed through the phase terminals and back into the coolant reservoir, thus contributing to heat dissipation from the phase terminals. This results in improved cooling of the phase terminals without the need for additional pressure lines. Furthermore, pressure losses are avoided.

[0012] Furthermore, the efficiency of the electric machine at low temperatures can be improved by the arrangement of the phase terminals in the coolant collection chamber according to the invention. This is achieved by energizing the phase terminals, so that the heat exchange between the phase terminals located in the coolant and the coolant results in faster heating of the coolant.

[0013] The design according to the invention allows for an increase in current density with improved cooling. Cost savings can be achieved by minimizing the copper cross-section.

[0014] The design of the electrical drive device according to the invention makes it possible to generate optimized cooling of the phase connections of the stator of the electric machine in a simple manner.

[0015] In an advantageous design, the coolant is an oil. Brief description of the drawings

[0016] The invention is described below by way of example with reference to the drawings. Fig. Figure 1 shows a longitudinal section through an electric drive device for a motor vehicle with an electric machine. Fig. Figure 2 shows a cross-section through the electric drive device along section AA in Fig. 1. Detailed description of the invention

[0017] In Fig. Figure 1 shows a longitudinal section through an electric drive device for a motor vehicle with an electric machine 10.

[0018] The electric machine 10 is arranged with a gear assembly 8 in a common machine housing 12. The machine housing 12 includes an enclosure 17 for the electric machine 10.

[0019] The electric machine 10 has a stationary stator 13 and a rotor 15 rotatably mounted about an axis of rotation 14 in the housing 17.

[0020] The stator 13 comprises a stator core, also called a stator lamination stack, at each of whose two axial ends 22, 23 a winding head made of stator windings is formed – at a first axial end 22 a first winding head 22a is formed and at a second axial end 23 a second winding head 22b is formed. The stator windings of the first winding head 22a are supplied with phase currents by the power electronics (inverter) via three phase connections 19a, 19b, 19c.

[0021] The phase connections 19a, 19b, 19c have connection terminals 20a, 20b, 20c on the side associated with the power electronics. These are electrically contacted by means of corresponding electrical lines to associated connection terminals of the power electronics 50.

[0022] As can be seen from the figures, the phase connections 19a, 19b, 19c are located vertically below the rotor shaft 3 of the rotor 15 and are electrically contacted accordingly. "Vertically below" preferably means in the region of the 6 o'clock position.

[0023] The direction specification “axial” essentially corresponds to a direction along or parallel to the axis of rotation 14 of the electric machine 10. The direction specification “radial” essentially corresponds to a direction normal to the axis of rotation 14 of the electric machine 10.

[0024] The rotor 15, for example, is designed as a rotor lamination stack and comprises a multitude of rotor laminations. Furthermore, the rotor 15 includes a rotor shaft 30 on which the rotor 15 is fixedly mounted. The rotor shaft 30 has a longitudinal axis with a first and a second end section 30a, 30b. The rotor shaft 30 forms the axis of rotation 14.

[0025] On both sides of the rotor shaft 30, cover-shaped bearing shields 49 are arranged. The bearing shields 49 are designed as housing sections 12a of the machine housing 12 and form the enclosure 17. The bearing shields 49 are arranged orthogonally to the motor shaft 30 and serve to receive the bearings for the rotatable mounting of the rotor 15 of the electric machine 10. The bearing shields 49 consist of a second bearing shield 49a, which closes off the machine housing 12 at its end face, and a first bearing shield 49b, which is arranged inside the machine housing 12 and separates the electric machine 10 from the gearbox assembly 8.

[0026] The second end section 30b of the rotor shaft 30 is equipped with a rotor shaft gear 32. As can be seen from the Fig. As can be seen in Figure 2, the rotor shaft gear 32 meshes with an intermediate shaft gear 33. The intermediate shaft gear 33 in turn meshes with a differential spur gear 34. The rotor shaft gear 32, intermediate shaft gear 33, and differential spur gear 34 rotate in a further housing 18. The two housings 17 and 18 form the machine housing 12 and are connected to each other directly via at least one opening or indirectly via several openings.

[0027] A coolant circuit, usually an oil circuit, is provided for cooling and lubricating the electric machine 10 and the gear assembly, into which a coolant collection chamber / coolant collection tank 40 is integrated.

[0028] The coolant (preferably an oil) circulates in the coolant circuit, for which it is conveyed or pumped by means of a conveying device (not shown).

[0029] The coolant collection chamber 40 is formed in the lower area of ​​the machine housing 12 and extends axially along the housing 17 of the electric machine 10 and the housing 18 of the gearbox assembly 8. The oil as coolant collects in the coolant collection chamber 40 due to gravity.

[0030] The coolant collection chamber 40 is bounded by a bottom area 12a of the machine housing 12 and by vertical ribs formed inside the machine housing.

[0031] Depending on the current operating state of the electric drive device, different fill levels result in the coolant collection tank 40. Fig. Figure 1 shows an example of a coolant level with a fill height H Kühlmittel .

[0032] The cooling and lubrication of the transmission components is generally passive, utilizing the pumping action of the differential spur gear 34 or the intermediate shaft spur gear 33 in combination with the suitable housing 18, which acts as a coolant guide. In this process, spray oil is generated by the immersion of the differential spur gear 34 in the coolant reservoir, the oil collected there, and the rotating gears of the transmission assembly.

[0033] Typically, the cooling of the engine and transmission components occurs through alternating operation between active operation with pressure lubrication and passive operation with spray lubrication.

[0034] This design of the cooling lubricant circuit is generally known and will not be described in more detail here.

[0035] As can be seen from the Fig. 1 and Fig. As can be seen in Figure 2, the phase connections 19a, 19b, 19c are arranged such that they are positioned in the coolant collection tank 40.

[0036] For this purpose, the phase connections 19a, 19b, 19c are held through a hole 42 in the first bearing shield 49a.

[0037] The coolant flow, not shown, which cools the rotor 15 and the winding heads 22a, 22b of the stator 13 in the coolant circuit, thus flows back into the coolant reservoir via the phase terminals 19a, 19b, 19c and thus causes heat dissipation from the phase terminals 19a, 19b, 19c.

[0038] As can be seen from the Fig. As can be seen in Figure 1, the phase connections are arranged in such a way that they are completely surrounded by coolant. The coolant level H Kühl-mittel It lies vertically above.

[0039] In a further development of the inventive concept, it can be provided that, at low temperatures, the coolant surrounding the phase terminals 19a, 19b, 19c is heated by energizing the phase terminals in the coolant collection tank 40. This results in an improved efficiency in the electric drive device. Reference symbol list 1 electric drive device 8 Gear arrangement 10 Electric Machine 12 machine housings 13 Stator 14 axis of rotation 15 Rotor 17 Enclosure 18 Enclosure 19a, 19b, 19c Phase connections 20a, 20b, 20c connection terminals 22 axial end stator 22a first winding head 22b second winding head 23 axial end stator 30 Motor shaft 30a first end area 30b second end area 32 Rotor shaft gear 33 Intermediate shaft spur gear 34 Differential spur gear 40 Coolant collection chamber 42 Breakthrough 49 Warehouse sign 50 Power Electronics QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 8,040,001 B2

[0006]

Images