Cooling and lubrication supply for an electric drive axle of a vehicle

Abstract

A cooling and lubrication supply for an electric machine (3) coupled to a gearbox (2) with a rotor (4) and a stator (5) is proposed, wherein at least one supply pump (11) is connected to a cooling and lubrication supply line (12) for cooling and lubricating the gearbox and to a coolant supply line (13) for cooling the stator (5) of the electric machine (3) as well as to a coolant supply line (14) for cooling the rotor (4) of the electric machine (3), wherein at least one flow-limiting element is arranged in the gearbox line, cooling and lubrication supply line (12) and in the coolant supply line (13), and wherein a pressure relief valve (17) is provided in the coolant supply line (14) for pressure-dependent control of the coolant quantity for the rotor (4).Furthermore, an electric drive axle and a vehicle (1) with the electric drive axle are proposed.

Description

[0001] The present invention relates to a cooling and lubricant supply system for an electric machine coupled to a transmission, having a rotor and a stator. Furthermore, the invention relates to an electric drive axle with the cooling and lubricant supply system, as well as to a vehicle with the electric drive axle.

[0002] For example, from the document DE 10 2019 215 048 A1, an electric drive device for a vehicle and a method for cooling the electric drive device are known. The drive device comprises an electric machine with a rotor shaft connected to a rotor, which is designed as a hollow shaft defining a rotor shaft interior. The rotor shaft is kinematically coupled to a transmission shaft of a transmission, wherein the transmission shaft is designed as a hollow shaft defining a transmission shaft interior. The rotor shaft interior and the transmission shaft interior are hydraulically connected to one another, such that a fluid can be pumped from the transmission shaft interior into the rotor shaft interior. A pump pumps the fluid from a fluid reservoir into a first fluid line, which is provided for supplying the transmission. A second fluid line connects the pump to the transmission shaft interior.A control valve for varying the flow is located in the second fluid line. The second fluid line directs the fluid through the gearbox shaft interior into the rotor shaft interior to cool the rotor.

[0003] The present invention is based on the object of proposing a coolant and lubricant supply and an electric drive axle with the coolant and lubricant supply as well as a vehicle with the electric drive axle, in which a supply of the gearbox and the stator as well as the rotor of the electric machine is ensured in a structurally simple and particularly cost-effective manner and efficiency is optimized.

[0004] This object is achieved according to the invention by the features of patent claims 1, 5, and 8, respectively. Advantageous and claimed developments emerge from the respective subclaims and the description as well as the drawings.

[0005] Thus, a coolant and lubricant supply is proposed for an electrical machine coupled to a transmission, having a rotor and a stator, wherein at least one supply pump is connected to a coolant and lubricant supply line for cooling and lubricating the transmission and to a coolant supply line for cooling the stator of the electrical machine, as well as to a coolant supply line for cooling the rotor of the electrical machine, wherein at least one flow-limiting element is arranged at least in the coolant and lubricant supply line and in the coolant supply line, and wherein a pressure relief valve is provided in the coolant supply line for pressure-dependent control of the coolant quantity for the rotor.

[0006] In this way, a coolant and lubricant supply to the gearbox, stator, and rotor of the electric machine is achieved without complex control systems, in a simple design and thus cost-effective, while optimizing efficiency. The rotor cooling is controlled by the pressure relief valve, at a predetermined pressure depending on the power of the supply pump and the provided flow-limiting elements, opening the coolant supply line to cool the rotor. Various fluids, preferably oil, can be used for the coolant and lubricant supply.

[0007] This control of the rotor cooling is implemented in a structurally simple and cost-effective manner without the need for complex control components. This is achieved by setting a predetermined pressure in the coolant supply line for pressure-dependent control of the pressure relief valve as a function of the speed of the supply pump in conjunction with the provided flow-limiting elements in the coolant and lubricant supply line and the coolant supply line. Thus, the coolant supply to the rotor is achieved via a speed control of the supply pump. The rotor or rotor shaft is supplied with coolant or oil in a targeted manner, and this supply can be switched on and off almost automatically. The rotor only throws off the coolant at the high-load operating point. At this operating point, good efficiency is secondary, whereas at low-load operation, no coolant is supplied to the rotor in order to optimize efficiency.

[0008] Preferably, a flow-limiting element can also be arranged in the coolant supply line downstream of the pressure relief valve in the flow direction. This makes it possible to use a standardized pressure relief valve cost-effectively, since the pressure in the coolant supply line can be easily adjusted using the flow-limiting elements.

[0009] For example, particularly cost-effective and structurally simple orifices or throttles can be used as flow-limiting elements.

[0010] The object underlying the invention is also achieved by an electric drive axle for a vehicle with a cooling and lubricant supply system as described above. This results in the advantages already described and further advantages.

[0011] Preferably, the electric drive axle can have at least one electric machine with a rotor and a stator in a housing, wherein a rotor shaft of the rotor can be coupled via at least one gear to at least one wheel output shaft as an output, wherein at least one supply pump is connected to a coolant and lubricant supply line for cooling and lubricating the gear and to a coolant supply line for cooling the stator of the electric machine as well as to a coolant supply line for cooling the rotor of the electric machine, wherein at least one flow-limiting element is arranged at least in the coolant and lubricant supply line for the gear and in the stator line for the stator, and wherein a pressure relief valve is provided in the coolant supply line for pressure-dependent control of the coolant quantity for the rotor.

[0012] A particularly advantageous feature of the electric drive axle is that the transmission driven by the electric motor consists of only one spur gear stage, which is coupled to the wheel output shafts via a differential gear. This creates a so-called single-stage gear set, which is particularly optimized in terms of efficiency and installation space.

[0013] The object underlying the invention is also achieved by a vehicle with at least one electric drive axle as described above. This results in the advantages already described and further advantages.

[0014] The present invention is further explained below with reference to the drawing.

[0015] The sole figure of the invention shows a schematic view of a possible embodiment of the invention of a coolant and lubricant supply according to the invention, for example in an electric drive axle of a vehicle 1.

[0016] In the vehicle 1, the electric drive axle is shown by way of example in a housing 2. The electric drive axle comprises an electric machine 3 with a rotor 4 and a stator 5 in the housing 2, wherein a rotor shaft 6 of the rotor 4 is coupled via at least one gear designed as a spur gear stage 7 via a differential gear 8 to wheel output shafts 9, 10 to be driven as output.

[0017] The proposed coolant and lubricant supply has a supply pump 11 which is connected to a coolant and lubricant supply line 12 for cooling and lubricating the transmission and to a coolant supply line 13 for cooling the stator 5 of the electric machine 3 as well as to a coolant supply line 14 for cooling the rotor 4 of the electric machine 3.

[0018] A first throttle 15 is provided in the coolant and lubricant supply line 12 as a flow-limiting element. Furthermore, a second throttle 16 is provided in the coolant supply line 13, with a pressure relief valve 17 provided in the coolant supply line 14 for pressure-dependent control of the coolant quantity for the rotor 4. A third throttle 18 is provided in the coolant supply line 14 downstream of the pressure relief valve 17 in the flow direction.

[0019] The supply pump 11 sucks the required coolant and lubricant from a coolant and lubricant sump or oil sump 19 in the gearbox 2 and thus supplies the connected gearbox line coolant and lubricant supply line 12 to the gearbox and the connected coolant supply line 13 to the stator 5 as well as the connected coolant supply line 14 to the rotor 4, which leads the coolant into the rotor shaft 6 designed as a hollow shaft.

[0020] The components to be lubricated include the spur gear stage 7 of the gearbox with its gearing and the corresponding bearings. The components to be cooled are the stator 5 and the rotor 4 of the electric motor 3.

[0021] The coolant and lubricant quantities are adjusted in the coolant and lubricant supply line 12, the coolant supply line 13, and the coolant supply line 14 using the provided throttles 15, 16, and 18. The pressure relief valve 17 integrated in the coolant supply line 14 only opens above a predetermined pressure. At low-load operating points, the supply pump 11 delivers sufficient coolant and lubricant to adequately cool and lubricate the transmission and stator 5. The pressure in the coolant and lubricant supply line 12 and the coolant supply line 13 can be adjusted using the throttles or orifices 15, 16 such that the pressure relief valve 17 is not yet opened. If the driver switches to a higher-load operating point, at which the rotor 4 is heated more significantly, the speed of the oil supply pump 11 is increased.The pressure thereby rises to a level at which the pressure relief valve 17 opens and the coolant supply line 14 is released, so that the rotor 4 is also supplied with coolant and is thus sufficiently cooled. Reference symbol 1 vehicle 2 housings 3 electric machine 4 Rotor 5 Stator 6 Rotor shaft 7 spur gear stage 8 differential gears 9 Wheel output shaft 10 Wheel output shaft 11 Supply pump 12 Coolant and lubricant supply line (gearbox) 13 Coolant supply line (stator) 14 Coolant supply line (rotor) 15 first throttle 16 second throttle 17 Pressure relief valve 18 third throttle 19 Coolant and lubricant sump or oil sump QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 10 2019 215 048 A1

[0002]

Claims

[1] Coolant and lubricant supply for an electrical machine (3) coupled to a transmission (2) having a rotor (4) and a stator (5), wherein at least one supply pump (11) is connected to a coolant and lubricant supply line (12) for cooling and lubricating the transmission and to a coolant supply line (13) for cooling the stator (5) of the electrical machine (3) and to a coolant supply line (14) for cooling the rotor (4) of the electrical machine (3), wherein at least one flow-limiting element is arranged at least in the coolant and lubricant supply line (12) and in the coolant supply line (13), and wherein a pressure relief valve (17) for pressure-dependent control of the coolant quantity for the rotor (4) is provided in the coolant supply line (14). [2] Cooling and lubricating agent supply according to claim 1, characterized bythat a predetermined pressure in the coolant supply line (14) for pressure-dependent control of the pressure relief valve (17) is adjustable as a function of a speed of the supply pump (11) in conjunction with the provided flow-limiting elements in the coolant and lubricant supply line (12) and the coolant supply line (13). [3] Cooling and lubricating agent supply according to one of the preceding claims, characterized by that in the coolant supply line (14) a flow-limiting element is arranged in the flow direction behind the pressure relief valve (17). [4] Cooling and lubricating agent supply according to one of the preceding claims, characterized by that an orifice or throttle (15, 16, 18) is provided as the flow-limiting element. [5] Electric drive axle with a cooling and lubricant supply according to one of the preceding claims. [6] Electric drive axle according to claim 5, characterized byin that at least one electrical machine (3) with a rotor (4) and a stator (5) is provided in a housing (2), wherein a rotor shaft (6) of the rotor (4) can be coupled via at least one gear to at least one wheel output shaft (9, 10) as an output, wherein at least one supply pump (11) is connected to a coolant and lubricant supply line (12) for cooling and lubricating the gear and to a coolant supply line (13) for cooling the stator (5) of the electrical machine (3) as well as to a coolant supply line (14) for cooling the rotor (4) of the electrical machine (3), wherein at least one flow-limiting element is arranged at least in the coolant and lubricant supply line (12) and in the coolant supply line (13), and wherein a pressure relief valve (70) for pressure-dependent control of the coolant quantity for the rotor (4) is provided in the coolant supply line (14). [7] Electric drive axle according to claim 6, characterized by that a spur gear stage (7) is provided as the transmission driven by the electric machine (3), which is coupled via a differential gear (8) to the wheel output shafts (9, 10) to be driven. [8] Vehicle with at least one electric drive axle according to claim 5 or 6.

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