Drive system for an electrically powered vehicle

Abstract

The invention relates to a drive system for a vehicle with a primary electric drive axle and a secondary electric drive axle 1, comprising an electric drive 2, a transmission 3, a differential 4, two wheels 5, and two wet service brakes 6. The electric drive 2 is connected to an input of the differential 4 via the transmission 3. Each wheel 5 is connected to an output of the differential 4 via one of the two wet service brakes 6. Each of the two wet service brakes 6 is assigned an actuator 7 for controllable brake actuation, and a disconnect device 8 is provided between the electric drive 2 and at least one of the wet service brakes 6.The drive system according to the invention is characterized in that the separating devices 8 are each connected to one of the actuators 7 and can be actuated by it. The invention also relates to a vehicle with a primary electric drive axle and a secondary electric drive axle 1, which has a drive system according to the invention.

Description

[0001] The invention relates to a drive system for a vehicle with a primary electric drive axle and a secondary electric drive axle according to the preamble of claim 1, and to a vehicle therewith. The drive system is particularly suitable for motor vehicles such as passenger cars, vans, etc. The field of application of the invention lies particularly in the automotive industry in the field of electric or hybrid vehicles.

[0002] The performance of electric or hybrid vehicles can be increased by better linking synergy effects between the service braking system and the drive system by utilizing energy recovery (recuperation braking, or recuperation for short) in order to recharge the energy storage (accumulator, or battery for short) or to convert excess heat energy from the drive and braking system or to use it for heating purposes.

[0003] The state of the art in drive systems for passenger cars features either two primary electric drive axles or one primary and one secondary electric drive axle. In vehicles with one primary and one secondary electric drive axle, the primary electric drive axle is mainly used for propulsion, braking, and recuperation, while the secondary electric drive axle is only operated as a motor or generator under very high performance demands and / or when all-wheel drive is required.

[0004] The secondary electric drive axle experiences drag losses at the bearings and gears, as well as magnetic field losses from the electric motor. These losses, especially during towing operation when the car is rolling without accelerating, cause unwanted braking. This is particularly true when recuperation is not desired, for example, when the battery is already fully charged, resulting in unintended braking of the vehicle.

[0005] In normal driving conditions, where maximum power and all-wheel drive are not required, the secondary electric drive axle, also known as the all-wheel drive axle, is decoupled from the electric drive via a mechanically, electronically, or hydraulically actuated disconnect unit (DCU). This prevents drag losses at the secondary electric drive axle. Ideally, the disconnect unit is positioned very close to a wheel.

[0006] In practical applications, electrically powered vehicles also employ a service braking system with one service brake per wheel. These service brakes may include an actuator designed to operate the service brake. This actuator can simultaneously operate a parking brake and may have various positions in which the parking brake and / or the service brake are engaged, or in which the actuator is neither connected to the service brake nor the parking brake.

[0007] If a disconnecting device is also present on the secondary electric drive axle, the prior art always requires an additional actuator for operating the disconnecting device. This causes additional effort and costs in the manufacturing of the secondary electric drive axle and requires additional installation space. The additional actuator must also be integrated into and synchronized with the existing systems.

[0008] The object of the invention is to provide a drive system for a vehicle with a primary electric drive axle and a secondary electric drive axle, in which the secondary electric drive axle can be decoupled without requiring an additional actuator for actuating each disconnecting device.

[0009] The object of the invention is achieved by the features of the independent patent claims. Advantageous embodiments are specified in the dependent patent claims.According to the invention, a vehicle with a primary electric drive axle and a secondary electric drive axle, comprising an electric drive, a transmission, a differential, two wheels and two wet service brakes, wherein the electric drive is connected via the transmission to an input of the differential, the wheels are each connected via one of the two wet service brakes to an output of the differential, each of the two wet service brakes is assigned an actuator for controllable brake actuation and a disconnecting device is provided between the electric drive and at least one of the wet service brakes, in that the disconnecting devices are each connected to one of the actuators and can be actuated by it.

[0010] By connecting the separating device to an actuator that also operates one of the wet-running service brakes, no additional actuator is required for the separating device. This saves effort and costs in manufacturing, and the drive system requires less installation space.

[0011] The design of the primary electric drive shaft is immaterial to the invention. It can be implemented according to the prior art and can also be driven non-electrically. The design of the separating device is also immaterial to the invention. It can, for example, be implemented as a positive-locking claw or according to another prior art design.

[0012] The secondary electric drive axle can, in particular, be the rear drive axle or the rear axle of a vehicle with two drive axles.

[0013] Each disconnecting device is designed to disconnect and / or reconnect the connection between a wet service brake and a wheel to a differential output. This allows the wet service brake and the wheel connected to the differential output via the wet service brake to be disconnected from and subsequently reconnected to the electric drive.

[0014] Each actuator can be advantageously controlled hydraulically. A hydraulic brake system can be provided for the hydraulic control of each actuator. The hydraulic system can be designed to control several different actuators.

[0015] The wet service brakes can also be hydraulically actuated and / or designed as oil-bath-based multi-disc wet brakes. If at least one of the wet service brakes and at least one of the actuators is hydraulically actuated, at least one of the wet service brakes and at least one of the actuators can be advantageously arranged in a common housing so that they share a common oil supply.

[0016] The wet-running service brakes can also be designed as fluid-cooled lamellar wet brakes.

[0017] Each actuator can be adjusted between a service brake range, within which it is connected to one of the wet service brakes, a separation range, within which it is connected to one of the separation devices, and a neutral range, between the service brake range and the separation range, within which the respective actuator is not connected to either one of the wet service brakes or one of the separation devices.

[0018] The problem is solved for a vehicle with a primary electric drive axle and a secondary electric drive axle, wherein the secondary drive axle comprises an electric drive, a transmission, a differential, two wheels and two wet service brakes, wherein the electric drive is connected via the transmission to an input of the differential, the wheels are each connected via one of the two wet service brakes to an output of the differential, each of the two wet service brakes is assigned an actuator for controllable brake actuation and a disconnecting device is provided between the electric drive and at least one of the wet service brakes, by the fact that the disconnecting devices are each connected to one of the actuators and can be actuated by it.

[0019] The vehicle's drive system can be designed according to the described embodiments.

[0020] The invention is explained in more detail below using an exemplary embodiment. The drawings show: Fig. 1: a schematic representation of a secondary electric drive axle in a first embodiment, in which a separating device is arranged between each electric drive and the two wet-running service brakes, Fig. 2: a schematic representation of a secondary electric drive axle in a second embodiment, in which a separating device is arranged between the electric drive and one of the wet service brakes, and Fig. 3: Diagrams illustrating an exemplary sequence of states and state transitions of an actuator, the service brake and the disconnecting device.

[0021] All embodiments of the invention relate to an electric drive system for a vehicle with a primary electric drive axle (not shown in the drawings) and a secondary electric drive axle 1, which is located in Fig. Figure 1 is shown in a first embodiment. The secondary electric drive axle 1 has an electric drive 2 which is connected via a transmission 3 to an input of a differential 4. The transmission 3 is designed to convert a torque generated by the electric drive 2 into another torque and transmit it to the differential 4. Each wheel 5 is connected to an output of the differential 3 via one of the two wet service brakes 6. The differential 4 is separably connected to each of the service brakes 6, which is designed as a wet brake, and to each of the wheels 5 by means of a disconnecting device 8 (DCU). When the differential 4 is connected to both wheels 5, the wheels 5 can be driven by the electric drive 2.At the same time, the wheels 5 can transmit torque to the electric drive 2, enabling it to be operated as a generator and allowing recuperation to take place.

[0022] Each service brake 6 is connected to an actuator 7, which is advantageously hydraulically controllable. Each actuator 7 is designed to trigger a service brake 6. For this purpose, the actuator 7 can be moved into a service brake range B. Simultaneously, the actuator 7 fulfills another function: It is also designed to actuate the disconnect device 8 and thus bring it into a different state by moving it into a disconnect range C. The actuator 7 can also be moved into a neutral range N, in which it is neither connected to the service brake 6 nor to the disconnect device 8. The letters "L" and "R", which denote the actuator positions in Fig. The numbers assigned to position 1 indicate whether a position is assigned to actuator 7 of the left or right service brake 6. In the Fig. In the embodiment of the secondary electric drive axle 1 shown in Figure 1, a hydraulic brake system 9 is also provided, which is designed for (controlling) the two actuators 7.

[0023] The disconnecting devices 8 can be, for example, friction clutches or positive-locking clutches, such as jaw clutches, as are widely known in the prior art. Depending on the design of the secondary electric drive axle 1, it may be advantageous to install several disconnecting devices 8 at different positions. By installing the disconnecting devices 8 between each of the two outputs of the differential gear 4 and one of the two wet service brakes 6, the connection between the wheels 5 of the secondary electric drive axle 1 and the electric drive 2 can be disengaged. By disengaging this connection, drag losses, such as those caused by friction, can be avoided during towing operation.

[0024] A secondary electric drive axle 1 in a second version is in Fig. Figure 2 shows only a disconnecting device 8 for the right wheel 5 between the electric drive 1 and the right wet service brake 6. With a suitably designed differential 4, this configuration also allows the entire secondary electric drive axle 1 to be disconnected. The states of the actuator 7 are shown here only for the right side of the secondary electric drive axle 1.

[0025] At the in Fig. In the second version shown, the wet-running service brake 6 and the actuator 7 of the right and left sides are each located in a common housing (indicated by dashed lines) and share an oil chamber or an oil supply.

[0026] In Fig. Figure 3 shows the states and state transitions of the service brake 6, the actuator 7, and the disconnecting device 8. The actuator 7 is connected to both the service brake 6 and the disconnecting device 8. Only the states of the left actuator 7, the left service brake 6, and the left disconnecting device 8 are shown as examples. Fig. 3 shown.

[0027] At time t0, a vehicle with a drive system according to the invention requires deceleration, and the disconnect device 8 is open. The secondary electric drive axle 1 is therefore coupled to the electric drive 2. At time t0, the braking effect is minimal, and the actuator 7 is in the neutral range NL. The actuator 7 begins to move into the service brake range BL at or shortly thereafter. As the actuator 7 moves into the service brake range BL, the service brake 6 begins to transmit the braking effect to the wheel 5. At time t1, the actuator 7 has reached the service brake range BL, and the braking effect is at its maximum. The disconnect device 8 remains in the open state. At time t2, there is no longer a need for deceleration, the braking effect is still at its maximum, and the actuator 7 is in the service brake range BL.At time t2 or shortly thereafter, actuator 7 begins to move into the neutral position NL. At time t3, actuator 7 reaches the neutral position NL and the braking effect reaches its minimum. The disconnecting device 8 is still open. The state transitions of the service brake 6 are continuous.

[0028] The state transitions of the disconnecting device 8, however, are discrete. At time t4, the actuator 7 is in the neutral range, the braking effect is at its minimum, and the disconnecting device 8 is in an open state. Now, the secondary electric drive axle 1 is to be decoupled. The reasons for this can vary. For example, the drag torque generated by the secondary electric drive axle 1 may need to be decoupled because acceleration is required and / or because recuperation is not desired or possible. The actuator 7 begins to move into the disconnecting range CL. At time t5, the actuator 7 has reached the disconnecting range CL, and the disconnecting device 8 is moved from the open state to a closed state by the actuator 7. The braking effect remains minimal.After actuator 7 reaches the separation zone CL, it remains there for a predetermined time before returning to the neutral zone NL. The separation device 8 remains open even after actuator 7 has moved to the neutral zone NL. At time t6, actuator 7 is back in the neutral zone NL, the braking effect is minimal, and the separation device 8 is closed. Now, the secondary electric drive axle 1 is to be re-engaged, for example, because there is no longer a need for acceleration and / or because recuperation is to take place (again). Actuator 7 therefore moves once more to the separation zone CL. At time t7, when actuator 7 reaches the separation zone CL, actuator 7 moves the separation device 8 from the closed to the open state. The braking effect is still minimal.

[0029] The in Fig.The 3 states and state transitions shown are to be understood as one of many possible sequences of states and state transitions, all of which can be carried out with the drive system according to the invention. Reference sign 1 secondary electric drive axle 2 electric drive 3 transmission gears 4 differential gears 5 wheels 6 Service brake 7 Actuator 8 Separating device 9 Hydraulic brake system B Service brake area C separation area N Neutral zone t0-t7 Time

Claims

Drive system for a vehicle with a primary electric drive axle and a secondary electric drive axle (1), comprising an electric drive (2), a transmission (3), a differential (4), two wheels (5) and two wet service brakes (6), wherein: - the electric drive (2) is connected via the transmission (3) to an input of the differential (4), - the wheels (5) are each connected via one of the two wet service brakes (6) to an output of the differential (4), - each of the two wet service brakes (6) is assigned an actuator (7) for controllable brake actuation, and - a disconnecting device (8) is provided between the electric drive (2) and at least one of the wet service brakes (6), characterized in that the disconnecting devices (8) are each connected to and actuated by one of the actuators (7). Drive system according to claim 1, characterized in that each of the actuators (7) is hydraulically controllable. Drive system claim 2, characterized in that at least one hydraulic brake system (9) is provided which is designed to control at least one of the actuators (7). Drive system according to one of the preceding claims, characterized in that the wet-running service brakes (6) are designed as oil bath-based lamellar wet brakes. Drive system according to claim 4, characterized in that at least one of the wet-running service brakes (6) and at least one of the actuators (7) are arranged in a common housing, so that they share a common oil supply. Drive system according to one of claims 1 to 3, characterized in that the wet service brakes (6) are designed as fluid-cooled lamellar wet brakes. Drive system according to one of the preceding claims, characterized in that each of the actuators (7) is adjustable between a service brake range (B) within which it is in contact with one of the wet service brakes (6), a separation range (C) in which it is in contact with one of the separation devices (8), and a neutral range (N) between the service brake range (B) and the separation range (C) in which the respective actuator (7) is neither in contact with one of the wet service brakes (6) nor with one of the separation devices (8). Vehicle with a primary electric drive axle and a secondary electric drive axle (1), wherein the secondary electric drive axle (1) comprises a drive system according to one of the preceding claims.

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