Power assembly for electric vehicle and electric vehicle

Abstract

The invention relates to a drive train (1) for an electric vehicle, comprising a drive unit (2), a differential (3), a transmission stage (4), two drive wheels (5) which are each connected to the differential (3) by means of an axle, at least one first brake system (11), the first brake system is located on one of the axles and is composed of a wet-running service brake (8), a parking brake (9) and an actuator (10) for actuating the wet-running service brake (8) and the parking brake (9) in a controllable manner. In order to improve the driving and braking characteristics and to avoid shift effects and torsion play, the transmission stage (4) is arranged between the drive unit (2) and the differential (3), and the drive wheels (5) are operatively connected directly to the differential (3).

Description

Technical Field

[0001] The invention relates to a powertrain for an electric vehicle, comprising a drive unit, a differential, a gear stage, two drive wheels each connected to the differential via a wheel axle, and at least one first braking system, which is located at one of the wheel axles and consists of a wet-running service brake, a parking brake, and an actuator for actuating the wet-running service brake and the parking brake in a controllable manner. Background Art

[0002] During driving, electric vehicles are often decelerated by means of energy recuperation. In addition, drum brakes and disc brakes are mainly used as service brakes, which are usually installed on each drive wheel of the vehicle. Both variants use brake pads, which are pressed against a surface firmly connected to one of the drive wheels when activated and move with the drive wheel. A torque is generated by friction that acts in opposition to the movement of the drive wheel, thereby braking the electric vehicle.

[0003] A special form of disc brake is the oil sump brake, also called wet-running service brake or wet brake, in which one or more brake discs rotate in an oil sump. When the brake is activated, the brake discs are pressed against the intermediate discs located between the brake discs by means of pressure plates, so that the friction between the brake discs, intermediate discs and pressure plates generates the braking torque. In this case, in the most common embodiment, the pressure plates are rotated relative to each other from the outside by an actuator, wherein balls are mounted between the pressure plates in elongated, shallow recesses, which can move the pressure plates away from or closer to each other. Since the entire surface of the brake disc is involved in generating the braking torque, this type of brake is called a full-disc brake or laminated brake. The advantages of these brakes are integrated cooling and maintenance-free, since the closed design prevents contamination and the oil sump reduces wear on the brake disc and allows heat to be dissipated.

[0004] Electric vehicles have a handbrake or parking brake in addition to the service brake, with which the wheels can be locked. The handbrake or parking brake can be activated by a rope or electrically and works independently of the service brake.

[0005] Patent document DE 10 2006 012 065 A1 discloses a brake system with a laminated plate brake as a service brake and with a hand brake. The patent document discloses a modularly constructed brake module for a drive shaft, which is arranged in a brake housing between the axle bridge and the shaft center of the drive shaft. The laminated plate brake is hydraulically actuated as a service brake and a hand brake, but with a separate hydraulic circuit. To trigger the service brake, a piston is pressed directly onto the laminated plate brake, wherein the service brake is released, for example, by spring force. The hand brake is designed as a negative brake, so that when the pressure in its corresponding hydraulic circuit decreases, it is moved, for example by spring force, in the direction of the piston of the service brake, which then locks the laminated plate brake via the piston.

[0006] In the prior art, when wet brakes are used, a gear ratio changer is usually arranged between the laminated brake and the drive wheel assigned to the laminated brake. Such a gear ratio changer is absolutely necessary, especially for electric vehicles. However, if it is arranged between the brake system and the drive wheel assigned to it, the force acting on the corresponding drive wheel is transmitted to the brake system after the conversion. In addition, the braking torque caused by the wet-running brake must also be converted before it acts on the drive wheel. This may have a negative impact on the driving and braking characteristics of the vehicle. In addition, for this arrangement, the design-related rotational clearance between the differential and the gear ratio changer and the elasticity present in the powertrain are a major problem for the brake. Therefore, it is desirable to minimize or even completely eliminate these effects. Summary of the invention

[0007] The object of the present invention is to provide a drive train which minimizes the adverse effects of the gear stage and the differential on the braking system and thus on the braking and driving characteristics of the vehicle.

[0008] For the powertrain mentioned at the outset, this object is achieved by arranging the transmission stage between the drive unit and the differential and by operatively connecting the drive wheels directly to the differential. Since the transmission stage is no longer arranged between the drive wheels and the brake system and is no longer located on the axle, the transmission stage no longer has a direct influence on the brake system or the drive wheels. As a result, there is no longer any transmission influence and torsional play on the axle and the brake system. In this way, the driving and braking characteristics of the vehicle are improved.

[0009] In an advantageous design, the brake system is adapted in such a way that the actuator can be mechanically or hydraulically shifted between a service brake range, a parking range, and a neutral range, in which the actuator is connected to the service brake, in which the actuator is connected to the parking brake, and in which the actuator is connected neither to the service brake nor to the parking brake. By installing an additional parking brake, the problem of microslippage of wet-running brakes, which results in the inability to park the vehicle for a long time on a slope, is solved. By introducing a parking brake range and a service brake range, separate control of the service brake and the parking brake is achieved.

[0010] It is particularly advantageous here if the neutral range is arranged between the service brake range and the parking range, thereby preventing the wet-running brake and the parking brake from being actuated simultaneously.

[0011] In an alternative advantageous design, the powertrain includes a second brake system, wherein the first brake system and the second brake system are respectively arranged at one of the wheel axles and are effectively connected to the corresponding wheel axle. This improves the braking characteristics and the braking effect. This also enables additional functions, such as wheel-selective braking intervention for vehicle dynamics regulation (ESC / Electronic Stability Control: electronic stability control) or for traction control (ASR, Antriebsschlupfregelung: traction slip regulation). In addition, the corresponding brake system can be designed to be more compact in this way. In principle, the first brake system and the second brake system can be configured in different ways. However, it is particularly advantageous that the second brake system is configured identically to the first brake system, because this improves the weight distribution and the rigidity and friction coefficient values ​​of the vehicle and the braking characteristics. Costs can also be saved by using the same parts.

[0012] In another advantageous embodiment, the transmission stage is a spur gear stage or a gear set. This type of transmission is particularly suitable for use between a drive unit and a differential.

[0013] The object is also achieved by a vehicle having the drive train just described.

[0014] It goes without saying that the features mentioned above and the features still to be explained below can be used not only in the combination specified but also in other combinations or alone, without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention is explained in more detail below based on embodiments with reference to the accompanying drawings, which also disclose features essential to the present invention. These embodiments are for illustration only and should not be construed as restrictive. For example, the description of an embodiment with multiple elements or components should not be construed as all of these elements or components being necessary for implementation. More specifically, other embodiments may also include alternative elements and components, fewer elements or components, or additional elements or components. Unless otherwise specified, the elements or components of different embodiments may be combined with each other. The modifications and variations described for one of the embodiments may also be applicable to other embodiments. To avoid repetition, the same or mutually corresponding elements in different drawings are represented by the same reference numerals and are not explained again. Among them:

[0016] Figure 1 A powertrain having a first braking system and a second braking system is shown; and

[0017] Figure 2 An alternative embodiment of a drive train is shown. DETAILED DESCRIPTION

[0018] Figure 1 The schematic structure of a powertrain 1 of an electric vehicle (BEV, HEV or PHEV) is shown, which includes a drive unit 2 (hereinafter also referred to as motor 2), which generates torque, which is transmitted to two axles each having a drive wheel 5 via a transmission stage 4 and then via a differential 3. The differential 3, the axle and the drive wheel 5 are also collectively referred to as axles below. In particular, there is no speed ratio conversion device between the differential 3 and the drive wheel 5, so that the differential and the drive wheel are directly connected. The drive unit 2 may include one or more electric motors, which may be separate drives or work as part of a hybrid drive. The drive unit 2 includes all necessary electronic components for its control and operation as well as necessary or optional sensor components. The electric vehicle may also include multiple electrically driven axles with corresponding drive units 2.

[0019] The powertrain 1 has a braking system on each side of the differential 3, which is designed in different ways and is effectively connected to the corresponding wheel axle on which it is located. Depending on the type of electric vehicle, it is possible to provide a brake housing with a first braking system 11 consisting of a wet-running service brake 8, an actuator 10 and a parking brake 9 on one side of the powertrain 1. The parking brake 9 is preferably configured as a brake with a form-fitting connection here and in other embodiments. On the side opposite to the first braking system 11, there is a second braking system 12, which includes another service brake 8a. The second braking system 12 differs from the first braking system 11 in that there is no parking brake 9 and the associated actuator 10. In this embodiment, it is generally irrelevant on which side of the powertrain 1 the first braking system 11 and the second braking system 12 are located. Therefore, the first braking system 11 can also be arranged on Figure 1 , while the second brake system 12 is located on the left.

[0020] The first brake system 11 has a service brake range in which the actuator 10 is connected to the service brake 8. In this range, a change in the position of the actuator 10 causes a change in the braking effect, wherein the braking effect increases to its maximum value as the actuator 10 moves further away from the adjacent neutral range. In the neutral range, the actuator 10 is no longer connected to the service brake 8, so that the service brake does not produce any braking effect. If the position of the actuator 10 moves further away from the service brake range, it reaches the parking range, in which the actuator is connected to the parking brake 9. The braking effect is at one level here, because the wheel axle on which the first brake system 11 is located is locked or fixed by the form-fit connection.

[0021] The transmission stage 4 arranged between the drive unit 2 and the differential 3 is a spur gear stage or a gear set. The torque generated by the drive unit 2 is directly converted and transmitted to the differential 3. By arranging the transmission stage 4 between the drive unit 2 and the differential 3, the influence of the transmission on the brake system 11, 12 is reduced. If the deceleration torque is transmitted to the wheel axle by the wet-running service brake 8, 8a, then for the arrangement mode in which a ratio change device is arranged between the corresponding drive wheel 5 and the brake system 11, 12, the deceleration torque is transmitted to the corresponding drive wheel 5 after conversion. This has an adverse effect on the braking characteristics of the electric vehicle and thus has an adverse effect on the driving characteristics of the electric vehicle. In addition, braking will generate a large force, which will bring a large load to the ratio change device. In addition to these undesirable speed change effects, if one or both wheel axles have a ratio change device arranged between the corresponding drive wheel 5 and, for example, the corresponding brake system 11, 12 in addition to the differential 3, a torsional backlash will appear on the wheel axle between the differential 3 and the corresponding ratio change device. This can also be avoided by arranging the transmission stage 4 between the drive unit 2 and the differential 3 .

[0022] Depending on the vehicle, it may be sensible to provide a second brake system 12 on both sides of the drive train 1 which is configured identically to the first brake system 11, i.e., in addition to a further wet-running service brake 8a, also comprises a further parking brake 9a and a further actuator 10a associated with the brake system. Figure 2 As shown. This arrangement has the advantage that both wheel axles can be fixed, which improves the safety of the electric vehicle when it is parked. In addition, the identical structure of the brake systems 11 and 12 also ensures a more uniform weight distribution.

[0023] Both embodiments can integrate additional functions, which, for example, prevent the vehicle from unintentional wheel rolling. This will be explained below using the first brake system 11 as an example.

[0024] In order to start the electric vehicle, the actuator 10 is first disconnected from the parking brake 9 by moving the actuator 10 from the parking area into the neutral area while the actuator 10 is still in the parking area, so that the axle is released and no braking torque acts on the axle. The electric vehicle can now be accelerated by rolling the wheels of the electric vehicle on a slope or by causing the electric machine 2 to generate torque.

[0025] If braking is subsequently performed, for example when the electric vehicle is parked, the actuator 10 is moved from the neutral region to the service brake region, so that the actuator is connected to the service brake 8 and the service brake 8 generates a braking torque on the axle. If the electric vehicle is to be parked after use, the currently stationary electric vehicle is fixed in the following manner, that is, the actuator 10 is moved from the service brake region through the neutral region to the parking region, so that the actuator 10 is connected to the parking brake 9 and the axle is fixed by means of the positive connection of the parking brake 9.

[0026] When the neutral region is passed by the actuator 10, the axle is temporarily released from the brakes, so that the electric vehicle may undesirably roll its wheels. This can advantageously be prevented by means of a further service brake 8a of the second brake system 12, which also acts when the electric vehicle is stopped, by triggering the further service brake 8a, so that a braking effect is produced on the axle by the further service brake 8a. When the electric vehicle is immobilized, the actuator 10 of the first brake system 11 maintains the braking effect during the movement from the service brake region through the neutral region to the parking region, and the axle is not released until the actuator 10 is connected to the parking brake 9, so that the axle is immobilized by means of the parking brake 9.

[0027] If the second brake system 12 also includes a further parking brake 9a and a further actuator 10a, the further wet-running service brake 8a is preferably triggered by the further actuator 10a, which is then located in the further service brake area and triggers the further parking brake 9a after the axle is released by moving the further actuator toward the further parking area and connecting with the further parking brake 9a. This takes place after the axle has been secured by the first brake system 11 with the aid of the parking brake 9 and serves to additionally secure the axle. The actuators 10, 10a of the two brake systems 11, 12 are therefore not moved simultaneously, but rather one after the other into their respective parking areas, so that the electric vehicle is braked at all times.

[0028] After the electric vehicle has been completely immobilized by both brake systems 11, 12, the electric vehicle can be released again using exactly the same method in reverse, without having to briefly release the axle. Before releasing the connection of the actuator 10 to the parking brake 9, the other actuator 10a is moved to another service brake area and connected to another service brake 8a, so that the other service brake produces a braking effect on the axle and fixes the axle. The connection between the actuator 10 and the parking brake 9 is then released at the first brake system 11, and the actuator 10 is moved from the parking area to the neutral area. Once completed, the connection between the other actuator 10a and the other service brake 8a is released again by moving the other actuator from another service brake area to another neutral area, so that the axle is released and the electric vehicle can accelerate. Therefore, in this case, the electric vehicle is also braked at any time and prevented from undesired wheel rolling.

[0029] By providing two brake systems, redundancy is provided, so that even if one of the brake systems fails, the vehicle's operational safety is maintained. Optionally, a holding torque can also be provided by the drive unit, more precisely, the motor 2, when the actuator passes through the neutral position, so as to prevent the vehicle's undesired wheel rolling.

[0030] List of reference numerals:

[0031] 1 Powertrain

[0032] 2 Drivers

[0033] 3 Differential

[0034] 4 speed levels

[0035] 5 Drive wheels

[0036] 8 Service brakes

[0037] 9 Parking brake

[0038] 10 Actuator

[0039] 8a Other service brake

[0040] 9a Other parking brake

[0041] 10a Another actuator

[0042] 11. First brake system

[0043] 12 Secondary braking system.

Claims

1. A powertrain for an electric vehicle, comprising a drive unit (2), a differential (3), a gear stage (4), two drive wheels (5) each connected to the differential (3) via a wheel axle, at least one first braking system (11), the first braking system being located at one of the wheel axles and consisting of a wet-running service brake (8), a parking brake (9) and an actuator (10), the actuator being used to controllably actuate the wet-running service brake (8) and the parking brake (9), characterized in that: The gear stage (4) is arranged between the drive unit (2) and the differential (3), and the drive wheel (5) is directly and effectively connected to the differential (3).

2. The powertrain for an electric vehicle according to claim 1, characterized in that: The actuator (10) can be shifted between a service brake range, a parking range and a neutral range in a mechanical or hydraulic manner. In the service brake range, the actuator is connected to the service brake (8), in the parking range, the actuator is connected to the parking brake (9), and in the neutral range, the actuator (10) is neither connected to the service brake (8) nor to the parking brake (9).

3. The powertrain for an electric vehicle according to claim 2, characterized in that: The neutral area is arranged between the service brake area and the parking area.

4. The powertrain for an electric vehicle according to any one of claims 1 to 3, characterized in that: The power assembly (1) comprises a second brake system (12), wherein the first brake system (11) and the second brake system (12) are respectively arranged at one of the wheel axles and are operatively connected to the corresponding wheel axle.

5. The powertrain for an electric vehicle according to claim 4, characterized in that: The second brake system (12) is configured identically to the first brake system (11).

6. The powertrain for an electric vehicle according to any one of claims 1 to 5, characterized in that: The transmission stage (4) is a cylindrical gear stage or a gear set.

7. An electric vehicle comprising a drive train (1) according to any one of claims 1 to 6.

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