Axle drive unit for a motor vehicle

Abstract

The invention relates to an axle drive unit for a motor vehicle, comprising at least the following components: - a traction machine for providing drive torque; - traction power electronics for the traction machine; - an electric differential actuator with actuator power electronics and an actuator electric motor; - a cooling circuit for cooling the traction power electronics and the electric differential actuator by means of a coolant; The axle drive unit is characterized in particular by the fact that a coolant interface is arranged between the electric differential actuator and the traction power electronics, wherein the coolant interface has an axial offset nozzle and a radial compensating seal, wherein the axial offset nozzle is received in the radial compensating seal and is sealed against the traction power electronics or the differential actuator by means of this seal.An axle drive unit with a coolant interface for compensating for radial misalignment is proposed.

Description

[0001] The invention relates to an axle drive unit for a motor vehicle, as well as a motor vehicle with such an axle drive unit.

[0002] In electrically powered motor vehicles, it is known from industrial practice to apply a differential torque between two wheels of an axle by means of an additional electric motor, thus forming a controllable differential.

[0003] Such a solution requires a considerable amount of installation space, is quite heavy, and involves significant assembly effort, particularly for the necessary additional components. These additional components include, for example, a control system for the additional electric motor (e.g., using separate power electronics), a gearbox, and / or cooling components.

[0004] Based on this, the present invention aims to overcome, at least partially, the disadvantages known from the prior art. The features of the invention are defined in the independent claims, for which advantageous embodiments are shown in the dependent claims. The features of the claims can be combined in any technically meaningful way, whereby the explanations in the following description and features from the figures, which comprise supplementary embodiments of the invention, can also be used.

[0005] The invention relates to an axle drive unit for a motor vehicle, comprising at least the following components: - a traction machine for providing a driving torque; - a traction power electronics unit for the traction motor; - an electric differential actuator with actuator power electronics and an actuator electric machine; - a cooling circuit for cooling the traction power electronics and the electric differential actuator using a coolant;

[0006] The axle drive unit is characterized primarily by the fact that a coolant interface is arranged between the electric differential actuator and the traction power electronics. wherein the coolant interface has an axial offset nozzle and a radial compensating seal, wherein the axial offset stub is received in the radial compensating seal and is sealed against the traction power electronics or the differential actuator by means of this.

[0007] In the following, reference is made to the aforementioned axis of the axial offset fitting whenever the axial direction, radial direction, or direction of rotation and corresponding terms are used without explicit indication otherwise. Ordinal numbers used in the preceding and subsequent descriptions serve solely for unambiguous identification and do not, unless explicitly stated otherwise, indicate any order or ranking of the components referred to. An ordinal number greater than one does not necessarily imply the presence of another such component.

[0008] Herein lies a proposed axle drive unit for a motor vehicle. The motor vehicle is preferably a purely battery-electric vehicle [BEV] or a hybrid vehicle, with an internal combustion engine and an electric traction motor.

[0009] Preferably, the axle drive unit is designed as a rear-wheel drive unit, i.e., to drive the rear wheels of the motor vehicle.

[0010] The axle drive unit includes a traction motor, traction power electronics, an electric differential actuator and a cooling circuit.

[0011] The traction motor is an electric drive motor that provides controlled drive torque to a motor vehicle. For example, the traction motor is a permanent magnet synchronous motor designed for direct transmission of the drive torque to the vehicle's wheels. In another embodiment, the traction motor is an asynchronous motor that allows the drive torque to be controlled by varying the frequency of the supplied electrical energy. Both variants are known to those skilled in the art and suitable for integration into an axle drive unit.

[0012] The traction power electronics are designed to regulate and control the power supply for the traction motor. Such traction power electronics include, for example, power semiconductors like IGBTs (Insulated Gate Bipolar Transistors) or MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) for adjusting the voltage and frequency of alternating current. Furthermore, the traction power electronics preferably include a microcontroller, which allows the power semiconductors to be controlled, thus enabling the desired rotation of the traction motor to be achieved with the drive torque. Microcontrollers and power semiconductors are components known to those skilled in the art and are used for controlling electric drive motors.

[0013] The electrical differential actuator features actuator power electronics and an actuator electric machine.

[0014] Preferably, the differential actuator has an actuator housing in which the actuator power electronics and the actuator electric motor are arranged.

[0015] The differential actuator is connected to transmit torque to at least one of the drive wheels of the corresponding axle, preferably the rear axle.

[0016] The differential actuator is designed to implement torque vectoring on the corresponding axle, preferably the rear axle. With this type of torque vectoring, the drive torque is distributed differently to the wheels, specifically the left and right drive wheels of the axle. This actively controls the yaw angle of the vehicle.

[0017] For this purpose, the actuator electric motor is connected to at least one of the drive wheels in a torque-transmitting manner. This allows a differential torque between the two drive wheels to be applied for torque distribution.

[0018] Preferably, the actuator electric machine is designed to operate in both motor and generator modes. Preferably, the actuator electric machine is designed to operate in all four quadrants of an electric machine's characteristic curve, i.e., at positive speed and positive torque, at negative speed and negative torque, at negative speed and positive torque, and at positive speed and negative torque.

[0019] For example, the actuator electric machine has a maximum power output between 5 kW [five kilowatts] and 20 kW [twenty kilowatts], preferably between 8 kW [eight kilowatts] and 15 kW [fifteen kilowatts].

[0020] The cooling circuit is designed to cool the traction power electronics and the differential actuator. For this purpose, a coolant is circulated through the traction power electronics and the differential actuator via the cooling circuit. Preferably, the coolant is also circulated through other components, such as the electric traction motor.

[0021] The coolant is, for example, a dielectric fluid or a water-glycol mixture.

[0022] The cooling circuit comprises a pump for circulating the coolant and a temperature control unit, which preferably includes a recooling unit. These components are not necessarily part of the axle drive unit. Preferably, the traction power electronics and the differential actuator are connected in series within the cooling circuit; more preferably, other components in the cooling circuit, such as the traction motor, are also connected in series with these components.

[0023] Preferably, the traction power electronics are arranged downstream of the differential actuator with respect to the cooling circuit. Preferably, the actuator electric motor is arranged downstream of the actuator power electronics within the differential actuator.

[0024] The coolant interface is located between the electrical differential actuator and the traction power electronics, connecting them via a coolant conductor. Preferably, the traction power electronics are located adjacent to the differential actuator. For example, there is a gap between the traction power electronics and the differential actuator, or rather their housings (i.e., the actuator housing and an electronics housing).

[0025] The traction power electronics and the differential actuator each have a coolant inlet, for example, in their respective housings. This coolant inlet is connected to the coolant interface and / or the coolant interface passes through the coolant inlet. Preferably, the two coolant inlets are arranged coaxially and / or aligned with each other in a predetermined position.

[0026] For example, the traction power electronics are located above the differential actuator with respect to the Earth's gravitational field and overlap with the differential actuator at least partially in the horizontal direction.

[0027] The coolant interface features an axial offset fitting and a radial compensating seal. The axial offset fitting is designed to bridge an axial offset, preferably the gap that separates the coolant openings from each other in the axial direction. Preferably, the axial offset fitting is substantially tubular. The axial offset fitting is, for example, formed integrally with a housing of the traction power electronics and / or the differential actuator, or it is designed as a separate component. Preferably, the axial offset fitting is made of metal or a hard plastic, particularly preferably of aluminum.

[0028] The radial compensating seal is designed to accommodate the axial offset fitting at one end. The radial compensating seal compensates for any radial offset between the two coolant openings and their intended position. Preferably, a sealing contact between the radial compensating seal and the axial offset fitting is formed by an outer wall of the axial offset fitting, which faces radially outwards, and an inner wall of the radial compensating seal. Preferably, the radial compensating seal is essentially ring-shaped. For example, the seal comprises an elastic sealing material, preferably a rubber, and most preferably an ethylene propylene diene monomer (EPDM).

[0029] Preferably, the axial offset nozzle has a length along the axial direction of at least 0.5 mm [zero point five millimeters], particularly preferably at least 0.8 mm [zero point eight millimeters] or 10 mm [ten millimeters].

[0030] The radial compensating seal is located between the axial offset fitting and the traction power electronics or the differential actuator. By means of such a compensating seal, the axial offset fitting is thus sealed against at least one of the two components that are connected via the coolant interface.

[0031] Preferably, the radial compensating seal is in contact with a housing section and / or a coolant connection of the traction machine of the axial offset nozzle, preferably by means of a radially outwardly directed sealing surface.

[0032] The proposed axle drive unit is particularly compact and allows for efficient cooling of the components. Furthermore, the axle drive unit is especially easy to install and robust.

[0033] In an advantageous embodiment of the axle drive unit, it is further proposed that the radial compensating seal is designed to compensate for a radial offset of the axial offset nozzle of at least half a millimeter, preferably at least one millimeter, and particularly preferably two millimeters.

[0034] By means of the radial compensating seal, a radial offset of the axial offset fitting of at least half a millimeter, preferably at least one millimeter, and particularly preferably at least two millimeters from a central target position of the axial offset fitting can be compensated. Preferably, the axial offset fitting is arranged centrally in the radial compensating seal in the central target position and more preferably coaxially with it.

[0035] Deviations from the central target position can occur, for example, due to assembly tolerances and / or manufacturing tolerances, such as when mounting the traction power electronics, the differential actuator and / or the axial offset nozzle.

[0036] In an advantageous embodiment of the axle drive unit, it is further proposed that the axial offset nozzle has a support shoulder on which the radial compensating seal can be supported along the axial direction.

[0037] In this embodiment, the axial offset fitting has a support shoulder on which the radial compensating seal is supported or can be supported. The support shoulder projects radially outwards from the axial offset fitting, preferably circumferentially, and preferably from an otherwise cylindrical outer surface of the axial offset fitting.

[0038] Preferably, the support shoulder tapers along the axial direction towards the radial compensating seal. Preferably, the support shoulder is located on a side facing away from the wet chamber of the traction power electronics or differential actuator, which is sealed by the radial compensating seal. Thus, for example, coolant pressure against the radial compensating seal allows the radial compensating seal to be pressed against the support shoulder, thereby preventing leakage, inversion, or slippage of the radial compensating seal.

[0039] In an advantageous embodiment of the axle drive unit, it is further proposed that the radial compensating seal comprises a spring for providing a contact force of a sealing surface of the radial compensating seal against a complementary sealing surface.

[0040] According to this embodiment, the radial compensating seal has a spring. Preferably, the spring is designed to press a radially inner sealing surface radially inwards against the axial offset stub by means of a restoring force, and / or a radially outer sealing surface radially outwards against the traction power electronics or the differential actuator.

[0041] Preferably, the spring is encased in a sealing material. Preferably, the sealing material is softer than the spring material. For example, the spring material is a metal, preferably steel.

[0042] In an advantageous embodiment of the axle drive unit, it is further proposed that the differential actuator has a sealing seat with a sealing surface.

[0043] According to this embodiment, the axial offset fitting is sealed in the differential actuator, for example in its actuator housing or a separate coolant connection, by means of the radial compensating seal. For this purpose, the differential actuator, or its actuator housing and / or coolant connection, has a sealing seat with a sealing surface. Preferably, the sealing surface is substantially cylindrical. Preferably, the sealing seat has a cross-section that is substantially U-shaped parallel to the axial direction.

[0044] The sealing surface of the differential actuator is in sealing contact with the complementary sealing surface of the radial compensating seal.

[0045] In an advantageous embodiment of the axle drive unit, it is further proposed that the sealing seat of the differential actuator has a diameter which is 1.5 to 2.5 times larger than the diameter of a sealing surface of the axial offset stub.

[0046] According to this embodiment, the sealing seat or the sealing surface of the sealing seat has a diameter 1.5 to 2.5 times larger than a sealing surface of the axial offset fitting, by means of which the axial offset fitting is sealed in the sealing seat by means of the radial compensating seal. Preferably, the diameters and the radial compensating seal are designed to allow a radial offset of two millimeters between the axial offset fitting and the differential actuator.

[0047] Preferably, the sealing surface of the axial offset nozzle is in sealing contact with the complementary, radially inward directed sealing surface of the radial compensating seal.

[0048] In an advantageous embodiment of the axle drive unit, it is further proposed that the axial offset nozzle is connected to an electronics housing of the traction power electronics in a fluid-tight manner.

[0049] According to this embodiment, the axial offset connector is permanently connected to the electronics housing of the traction power electronics, for example by soldering, gluing, or welding. Thus, the axial offset connector is sealed against the electronics housing and fixed axially and radially.

[0050] In an advantageous embodiment of the axle drive unit, it is further proposed that the differential actuator and the traction power electronics are attached to a drive housing of the traction machine.

[0051] According to this embodiment, the traction power electronics and the differential actuator are attached to a drive housing of the traction machine. For example, the differential actuator is preferably attached to the drive housing of the traction machine by means of an actuator housing of the differential actuator circumferentially around a shaft of the actuator electric motor, for example by flange mounting.

[0052] For example, the actuator power electronics are located between the actuator electric motor and the coolant interface. Thus, the coolant interface is separated from the mounting point between the differential actuator and the drive housing of the traction motor, at least by the actuator power electronics. The resulting lever arm between the coolant interface and the differential actuator mounting means that even small rotational tolerances in this mounting result in a large radial offset at the coolant interface.

[0053] The drive housing of the traction machine is preferably an integral housing that encloses both the traction machine and a gearbox.

[0054] In an advantageous embodiment of the axle drive unit, it is further proposed that the radial compensating seal has a sealing mantle with a differential actuator-side sealing surface and a sealing lip extending radially inwards from the sealing mantle with an axial offset nozzle-side sealing surface.

[0055] According to this embodiment, the radial compensating seal is thus arranged in the differential actuator. The compensating seal comprises a sealing mantle and a sealing lip. The sealing mantle is preferably cylindrical and forms a sealing surface on the differential actuator side, which is in contact with the differential actuator. The sealing lip extends radially inwards from the sealing mantle and is in contact with the axial offset fitting by means of a sealing surface on the axial offset fitting side.

[0056] The sealing lip and the sealing mantle are thus pressed radially towards each other by the differential actuator and the axial offset nozzle, generating a radially acting contact force, so that a sealing effect is ensured and a radial offset of the axial offset nozzle can be compensated for by means of a deformation of the sealing lip.

[0057] According to another aspect, a motor vehicle is proposed, whereby the motor vehicle has at least the following components: - an axle drive unit according to an embodiment as described above; and - two drive wheels in torque-transmitting connection with the axle drive unit.

[0058] According to one embodiment, the radial compensating seal also has an additional dust lip. This reduces the risk of contaminants entering the cooling circuit.

[0059] The invention described above is explained in detail below against the relevant technical background with reference to the accompanying drawings, which show preferred embodiments. The invention is in no way limited by the purely schematic drawings, although it should be noted that the drawings are not dimensionally accurate and are not suitable for defining size relationships. It is illustrated in Fig. 1: An axle drive unit in a perspective view; Fig. 2: a coolant interface of the axle drive unit according to Fig. 1 in a cross-sectional view; Fig. 3: a rear axle of a motor vehicle with an axle drive unit according to Fig. 1 in a perspective view; and Fig. 4: a motor vehicle with a rear axle to Fig. 3 in a schematic representation.

[0060] In Fig. Figure 1 shows an embodiment of an axle drive unit 1 in a perspective view. The axle drive unit 1 comprises a traction motor 3, traction power electronics 4, a differential actuator 5, and a cooling circuit 8.

[0061] For the sake of clarity, only the housings of the traction machine 3 and traction power electronics 4 are shown here, i.e. an integral housing or drive housing 20 of the traction machine 3 and an electronics housing 19 of the traction power electronics 4.

[0062] Here, an inlet 27 from the cooling circuit 8 to the differential actuator 5, or rather its actuator housing 25, is shown. A power connection 28 for the differential actuator 5 is shown on the left side.

[0063] The differential actuator 5 comprises an actuator electric motor 7 and actuator power electronics 6. The actuator electric motor 7 provides a controlled torque, which is used to distribute torque to the corresponding axle of the vehicle 2. This provided torque distributes the differential torque between the drive wheels 23, 24 of an axle (not shown here), preferably the rear axle 26, such that the yaw angle of the vehicle 2 can be actively controlled. Preferably, the actuator electric motor 7 is suitable for operation in both motor and generator modes, and particularly preferably in all four quadrants of an electric motor's operating range. In one embodiment, the actuator electric motor 7 has a maximum power output of between five kilowatts and twenty kilowatts, preferably between eight kilowatts and fifteen kilowatts.

[0064] As shown in the illustration, a section of the drive housing 20 is depicted at the rear. The actuator housing 25 and the electronics housing 19 are attached to the drive housing 20. The traction power electronics 4 are arranged above the drive housing 20. The differential actuator 5 is arranged laterally in front of the drive housing 20 and partially below the traction power electronics 4.

[0065] As shown, the actuator housing 25 of the differential actuator 5 is attached to the drive housing 20 by means of a gearbox housing 29. The gearbox housing 29 contains a transmission to transfer a torque from the actuator electric motor 7 to at least one drive wheel 23 (not shown here) and thus generate a differential torque between this drive wheel 23 and another drive wheel 24 of the same axle.

[0066] The actuator housing 25 is attached to the gearbox housing 29 around an axis of the actuator electric motor 7, flanged as shown. The gearbox housing 29 is in turn attached to the drive housing 20, flanged as shown. The electronics housing 19 is screwed onto the drive housing 20 from above.

[0067] A coolant interface 9 is arranged between the electronics housing 19 and the differential actuator 5, which connects the traction power electronics 4 and the differential actuator 5 via coolant flow. The coolant interface 9 is, for example, in Fig. 2 explained in detail.

[0068] A coolant circulated through the cooling circuit 8 flows, for example, through the inlet 27 into the differential actuator 5. Thus, the differential actuator 5, or its components, which include at least the actuator electric motor 7 and the actuator power electronics 6, can be cooled.

[0069] The coolant can be routed to the traction power electronics 4 via the coolant interface 9 in order to cool it.

[0070] Due to the arrangement and fastening of the electronics housing 19 and the actuator housing 25 to the drive housing 20, even small tolerances in the mounting position lead to a significant radial offset at the coolant interface 9. Such a radial offset can be compensated for by means of the coolant interface 9, as described in relation to Fig. 2 explained.

[0071] In Fig. 2 is a coolant interface 9 of the axle drive unit 1 according to Fig. 1 shown in a cross-sectional view.

[0072] The axial offset nozzle 10 is arranged coaxially to the axial direction 35, thus defining the axial direction 35. The radial direction 36 is arranged orthogonally to the axial direction 35.

[0073] The coolant interface 9 is located between the electric differential actuator 5 and the traction power electronics 4. The coolant interface 9 is designed to connect the traction power electronics 4 and the differential actuator 5 via coolant flow. It comprises an axial offset fitting 10 and a radial compensating seal 11, wherein the axial offset fitting 10 is received in the radial compensating seal 11 and sealed against the differential actuator 5 by means of it.

[0074] The radial compensating seal 11 is also designed to compensate for a radial offset of the axial offset fitting 10. Thus, an axial and / or radial offset between the traction power electronics 4 and the differential actuator 5 can be compensated for by means of the coolant interface 9.

[0075] The radial compensating seal 11 has a sealing mantle 21 and a sealing lip 22. A sealing contact exists between the radial compensating seal 11 and the axial offset fitting 10 by means of a sealing surface 17 formed by an outer wall of the axial offset fitting 10 and a sealing surface 15 formed by the sealing lip 22. A sealing surface 14 formed by the sealing mantle 21 is in contact with a sealing seat 18 of the differential actuator 5. Thus, the axial offset fitting 10 is sealed against the differential actuator 5 or its actuator housing 25.

[0076] The axial offset fitting 10 has a support shoulder 12. The radial compensating seal 11 is axially supported on the support shoulder 12. Thus, the sealing lip 22 is secured against slipping out when internal pressure is applied in the actuator housing 25. The radial compensating seal 11 has a spring 13, which here is designed in the form of two metal rings and presses the sealing lip 22 and the sealing mantle 21 apart, thereby ensuring a more reliable sealing contact between the sealing surfaces 14, 15, 16, 17.

[0077] At an upper end as shown, the axial offset nozzle 10 is welded to the electronic housing 19 of the traction power electronics 4 and is thus attached to it in a coolant-tight manner.

[0078] In Fig. 3 is a rear axle 26 of a motor vehicle 2 with an axle drive unit 1 according to Fig. 1 shown in a perspective view.

[0079] The traction machine 3 is connected to the two drive wheels 23 and 24 via a main gearbox 30, thus transmitting torque. The drive wheels 23 and 24 can therefore be driven by the traction machine 3 to propel the vehicle 2. The differential torque is applied to the right-hand drive wheel 23 (relative to the direction of travel 31) by means of a gearbox located in the gearbox housing 29, as shown in the illustration. The differential actuator 5 is designed to apply a torque that is either opposite to or in the same direction as the drive torque.

[0080] In Fig. 4 is a motor vehicle 2 with a rear axle 26 towards Fig. 3 shown in a schematic representation.

[0081] The motor vehicle 2 has a traction battery 34 which is connected to the traction motor 3 to provide electrical energy for driving the motor vehicle 2. Preferably, the traction battery 34 is connected to the differential actuator 5 to provide electrical energy for generating the torque or differential torque.

[0082] For example, the motor vehicle 2 has a central control unit 32 and / or a CAN bus 33, by means of which / by which the actuator power electronics 6 and traction power electronics 4 can be controlled to operate the differential actuator 5 and the traction machine 3.

[0083] An axle drive unit with a coolant interface for compensating for radial misalignment is proposed.

Claims

[1] Axle drive unit (1) for a motor vehicle (2), comprising at least the following components: - a traction machine (3) for providing a driving torque; - a traction power electronics (4) for the traction machine (3); - an electric differential actuator (5) with actuator power electronics (6) and an actuator electric motor (7); - a cooling circuit (8) for cooling the traction power electronics (4) and the electric differential actuator (5) by means of a cooling fluid; characterized by , that a coolant interface (9) is arranged between the electric differential actuator (5) and the traction power electronics (4), wherein the coolant interface (9) has an axial offset nozzle (10) and a radial compensating seal (11), wherein the axial offset nozzle (10) is received in the radial compensating seal (11) and is sealed against the traction power electronics (4) or the differential actuator (5) by means of this. [2] Axle drive unit (1) according to claim 1, wherein the radial compensating seal (11) is designed to compensate for a radial offset of the axial offset nozzle (10) of at least half a millimeter, preferably at least one millimeter, particularly preferably two millimeters. [3] Axle drive unit (1) according to claim 1 or claim 2, wherein the axial offset nozzle (10) has a support shoulder (12) on which the radial compensating seal (11) can be supported along the axial direction (35). [4] Axle drive unit (1) according to one of the preceding claims, wherein the radial compensating seal (11) comprises at least one, preferably two, springs (13) for providing a contact force of a sealing surface (14,15) of the radial compensating seal (11) against a complementary sealing surface (16,17). [5] Axle drive unit (1) according to one of the preceding claims, wherein the differential actuator (5) has a sealing seat (18) with a sealing surface (16). [6] Axle drive unit (1) according to one of the preceding claims, wherein the sealing seat (18) of the differential actuator (5) has a diameter which is 1.5 times to 2.5 times larger than the diameter of a sealing surface (17) of the axial offset nozzle (10). [7] Axle drive unit (1) according to one of the preceding claims, wherein the axial offset nozzle (10) is connected in a liquid-tight manner to an electronics housing (19) of the traction power electronics (4). [8] Axle drive unit (1) according to one of the preceding claims, wherein the differential actuator (5) and the traction power electronics (4) are attached to a drive housing (20) of the traction machine (3). [9] Axle drive unit (1) according to one of the preceding claims, wherein the radial compensating seal (11) has a sealing mantle (21) with a differential actuator-side sealing surface (14) and a sealing lip (22) extending radially inwards from the sealing mantle (21) with an axial offset nozzle-side sealing surface (15). [10] motor vehicle (2) wherein the motor vehicle (2) shall have at least the following components: - an axle drive unit (1) according to one of the preceding claims; and - two drive wheels (23,24) in torque-transmitting connection with the axle drive unit (1).

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