Vehicle axle for a two-track vehicle

Abstract

The invention relates to a vehicle axle for a two-track vehicle, having an axle differential (15) the input side of which is drivingly connected to a drive unit (EM) and the output sides of which output to drive shafts (17, 18) leading to the two vehicle wheels, wherein the vehicle axle has vehicle brakes (7) which can be controlled by a control unit for a uniform or non-uniform vehicle braking on the two sides of the vehicle. According to the invention, each of the vehicle brakes (7) is designed as a multi-disc brake arranged on each output side of the axle differential (15).

Description

[0001] Vehicle axle for a two-track vehicle

[0002] DESCRIPTION:

[0003] The invention relates to a vehicle axle, in particular a rear axle, for a two-track vehicle according to the preamble of claim 1.

[0004] A typical vehicle axle features an axle differential that allows for a 50 / 50 torque distribution. Its input side is connected to a drive unit, such as an electric motor, while its output side is connected to output shafts leading to the two vehicle wheels. Sports vehicles, in particular, usually feature a torque vectoring system on the rear axle. This system directs the drive torque generated by the drive unit past the axle differential directly to the vehicle wheels. This allows the drive torque to be freely distributed on each vehicle axle.

[0005] Such a torque vectoring system is designed in a complex manner with a superposition gear on each side of the vehicle, for example a planetary gear with a multi-plate clutch, which can be controlled by a control unit for torque redistribution between the vehicle wheels of the rear axle.

[0006] A conventional rear axle also features disc brakes on the rear wheels, which can be controlled by the control unit to apply even or uneven braking to both rear wheels. The disc brakes are controlled using hydraulic pressure, a complex signaling system. Furthermore, the vehicle's parking management system is equipped with parking brakes, which are integrated into the disc brakes on the rear axle, requiring considerable installation space. In addition to the two parking brakes installed on the rear axles, the parking management system also features a parking lock integrated into the drive module. The parking lock and the parking brakes operate independently of each other to provide sufficient redundancy. This means that if one system fails, the other system takes over the holding function.

[0007] DE 10 2010 020 535 A1 discloses a differential arrangement for a drive train of a motor vehicle, comprising a differential for transmitting and dividing an engine torque between two output shafts, and comprising a coupling device and an actuating device. The coupling device is designed to be openable and closable and is arranged in the torque flow between the differential and one of the output shafts such that the torque flow between the output shaft and the differential can be separated and connected using the coupling device, and the coupling device can be actuated using the actuating device. Complex coupling and uncoupling of at least the output shaft is avoided by the actuating device acting on the differential in such a way that the differential is at least partially locked when the coupling device is open.

[0008] A braking system for a vehicle is known from DE 10 2020 211 442 A1. This system comprises an electric machine with a stator, a rotor, and a rotor shaft connected to the rotor. The electric machine is designed to provide a torque to the rotor shaft. The braking system comprises a first drive shaft, which is kinematically coupled to the rotor shaft such that the torque can be transmitted from the rotor shaft to the first drive shaft. Furthermore, a first multi-disk brake arranged on the first drive shaft has a first multi-disk brake housing and multi-disk discs arranged in the first multi-disk brake housing. At least one multi-disk disc is fixedly connected to the first drive shaft, and at least two multi-disk discs are fixedly connected to the first multi-disk brake housing.The multi-plate discs can be pressed axially against each other in such a way that a braking force can be generated to decelerate the first drive shaft. Another differential arrangement for a drive train of a motor vehicle is known from DE 10 2011 103 249 A1.

[0009] The object of the invention is to provide a vehicle axle for a two-track vehicle which, compared to the prior art, can be implemented with reduced component expenditure and is structurally simple.

[0010] The object is solved by the features of claim 1. Preferred developments of the invention are disclosed in the subclaims.

[0011] The invention relates to a vehicle axle for a two-track vehicle, having an axle differential whose input side is drivingly connected to a drive unit. The two output sides of the axle differential drive on output shafts leading to the two vehicle wheels. The vehicle axle has vehicle brakes that can be controlled by a control unit for uniform or uneven vehicle braking on both vehicle sides. According to the characterizing part of claim 1, the vehicle wheel brakes are implemented as wet-running multi-disk brakes, one of which is arranged on each output side of the axle differential. The two multi-disk brakes can be controlled by an electronic control unit for uniform or uneven vehicle braking on both vehicle wheels.

[0012] By providing two wet-running multi-disk brakes, the use of conventional vehicle wheel disc brakes, which each consist of a brake disc positioned on the vehicle wheel output shaft and interacting with a brake caliper, can be eliminated. This prevents brake wear, which is otherwise emitted into the environment by conventional vehicle brakes.

[0013] In one technical implementation, each of the two multi-disk brakes consists of an inner disc carrier, an outer disc carrier, and an intermediate disc pack. Each of the two multi-disk brakes acts directly on the respective output shaft. For example, the inner disc carrier of the multi-disk brake can be connected to the respective output shaft in a rotationally fixed and power-transmitting manner, while the outer disc carrier of the multi-disk brake can be connected to a transmission housing wall in a rotationally fixed and power-transmitting manner.

[0014] The two multi-disk brakes can each be equipped with a hydraulic cylinder that can be controlled by the electronic control unit and that applies contact pressure to the disc pack of the multi-disk brake via an annular piston in order to carry out uniform or uneven vehicle braking between the vehicle wheels during ferry operation.

[0015] When braking is requested on only one side of the vehicle, the associated hydraulic cylinder is pressurized to move the annular piston through a closing stroke. During the closing stroke, the annular piston closes the disc pack of the multi-disk brake, consuming a clearance, while the hydraulic cylinder on the opposite side of the vehicle remains depressurized.

[0016] When braking is carried out evenly on both sides of the vehicle, the hydraulic cylinders on both sides of the vehicle are subjected to the same hydraulic pressure, whereby the respective annular pistons are adjusted via identical closing strokes, utilizing the brake clearance.

[0017] The hydraulically operated actuator of each multi-disk brake, i.e., the hydraulic cylinder, cannot guarantee a permanent vehicle hold or parking function due to the tendency of the hydraulic pressure acting on the hydraulic cylinder to dissipate. Against this background, the vehicle's parking management system includes an additional multi-disk brake parking actuator on each of the two multi-disk brakes, with which a vehicle hold function can be engaged or disengaged by actuating the multi-disk brake. The multi-disk brake parking actuators are controlled electrically, not hydraulically, by the control unit.

[0018] In a preferred embodiment, the hydraulic cylinder and the multi-disk brake parking actuator act on the disc pack of the respective multi-disk brake on axially opposite sides. For sufficient redundancy, it is advantageous if the vehicle's parking management system, in addition to the two multi-disk brake parking actuators, includes a parking lock that acts with a pawl on a parking lock gear installed in the vehicle axle. The parking lock can be integrated into the drive module of the vehicle axle. Furthermore, the parking lock and the two multi-disk brake actuators operate independently of each other, meaning that if one system fails, the other system takes over the holding function.

[0019] In a first embodiment, the multi-disk brake parking actuator can be implemented as follows: This actuator can have a pressure mechanism integrated into the multi-disk brake, comprising a ball-ramp unit and a preferably self-locking spindle drive. The spindle drive can drive the ball-ramp unit by building up / releasing a contact pressure acting on the multi-disk brake. Due to the self-locking nature of the electrically operated spindle drive, the set contact pressure can be maintained even without power. When the multi-disk brake parking actuator is activated, the hydraulic pressure in the hydraulic cylinder of the multi-disk brake can be depressurized at the same time. Furthermore, when the multi-disk brake parking actuator is activated, the vehicle can be secured on the front axle using the vehicle brakes.

[0020] Exemplary embodiments of the invention are described below with reference to the accompanying figures. They show:

[0021] Figures 1 to 4 each show different views illustrating the structure and operation of the vehicle axle according to the invention. Figure 1 shows an electrified vehicle rear axle with an electric motor EM and a transmission 3. The electric motor EM is connected to a high-voltage battery (not shown). Conventional vehicle wheel disc brakes are omitted from the vehicle rear axle. Instead of such vehicle wheel disc brakes, the rear axle has multi-disk brakes 7, by means of which vehicle braking can be carried out.

[0022] The electric motor EM is connected via its rotor shaft 9, with a countershaft stage 11 interposed, to the input side of an axle differential 15. Its output sides are connected to the vehicle's rear wheels via output shafts 17, 18. In Figure 1, the electric motor EM is installed transversely in the vehicle axle. Accordingly, the rotor shaft 9 and the output shafts 17, 18 are axially parallel to one another. Likewise, the multi-disk brakes 7 installed in the rear axle are axially parallel to one another in the vehicle's transverse direction y.

[0023] The vehicle axle has one of the multi-disk brakes 7 on each side of the vehicle, viewed in the vehicle's transverse direction y. These can be controlled by an electronic control unit for uniform or uneven vehicle braking on both vehicle wheels.

[0024] The intermediate gear stage 11 is connected to an input-side axle differential gear 21. The axle differential gear 21 is connected in a rotationally fixed manner to a rotating differential housing 25. According to Figure 1, when the multi-disk brakes 7 are open, the axle differential 15 drives the power in the vehicle's transverse direction y in a 50 / 50 distribution on both sides to the two output shafts 17, 18 leading to the vehicle wheels.

[0025] In Figure 1, the two multi-disk brakes 7 each act directly on the output shafts 17, 18. This means that the multi-disk brake 7 is connected with its inner disc carrier 31 to the respective output shaft 17, 18, while the outer disc carrier 39 is fixedly connected to a transmission housing wall 55. The disc pack located between the outer disc carrier 39 and the inner disc carrier 31 can be pressurized via an annular piston 63, indicated in Figure 2. This piston is adjustable by a horizontal stroke using a hydraulic cylinder 49 in order to actuate the multi-disk brake 7 to a predetermined braking level. The multi-disk brake 7 is power-shiftable and has slip control.

[0026] As can be seen from Figures 1 and 2, a parking management system PM of the vehicle consists of a multi-disk brake parking actuator 58 acting on the respective multi-disk brake 7, as well as a parking lock 60 installed on the rotor shaft 9 of the electric motor EM. The two multi-disk brake parking actuators 58 and the parking lock 60 provide independently operating parking systems that are controlled electrically rather than hydraulically by the control unit. As can be seen from Figure 2, the hydraulic cylinder 49 and the respective multi-disk brake actuator 58 are arranged on axially opposite sides of the disc pack of the respective multi-disk brake 7. When the vehicle hold function is engaged, the multi-disk brake parking actuator 50 acts on the multi-disk brake 7 to apply the required braking force.

[0027] In Figure 2, the multi-disk brake parking actuator 58 is designed with a pressure mechanism integrated into the multi-disk brake 5, including a ball-ramp unit 65. The disc pack located between the outer disc carrier 61 and the inner disc carrier 59 can be pressurized via the annular piston 63, which is adjustable by the horizontal stroke by means of the hydraulic cylinder 49. On the other hand, the ball-ramp unit 65 acts on the disc pack on the side axially opposite the annular piston 63. The ball-ramp unit 65 consists of a fixed disc 67 and a rotatable disc 69, between which balls 71 are arranged. The rotatable disc 69 is extended radially outward with a toothing 73, which interacts with a drive spindle (not shown) of the multi-disk brake parking actuator 57.

[0028] The following error scenarios are conceivable in the parking management system PM. In a first error scenario, one of the two multi-disk brake parking actuators 58 may fail. In this case, the parking lock 60 and the still functional multi-disk brake parking actuator 58 assume the minimum holding function. In a second error scenario, the parking lock 60 may fail, so that the two functional multi-disk brake parking actuators 58 assume the minimum holding function.

[0029] With regard to a self-locking mechanism that is easier to implement, reference is made to the exemplary embodiment in Figures 3 or 4. In Figure 3, the multi-disk brake parking actuator 57 is essentially structurally identical to that in Figure 2. Reference is therefore made to the description of Figure 2. In contrast to Figure 2, in Figures 3 and 4 the multi-disk brake parking actuator 58 is not implemented with a ball-ramp unit 65, but with a ramp unit 70. No balls 71 are installed in the ramp unit 70, whereby a much simpler self-locking mechanism can be achieved compared to Figure 2.

[0030] In Figure 3, the self-locking ramp unit 70 consists of a fixed disc 67 and a coaxial rotatable disc 69. Both the fixed disc 67 and the rotatable disc 69 have ramp-shaped inclined surfaces 72 (Figure 4) that are in sliding / frictional contact with each other. The rotatable disc 69 is formed with external teeth 73, which are drivingly connected to a drive spindle (not shown) of the multi-disk brake parking actuator 57. Depending on the direction of rotation of the rotatable disc 69, pressure builds up or decreases.

[0031] LIST OF REFERENCE SYMBOLS:

[0032] 3 gearboxes

[0033] 7 multi-disk brake

[0034] 9 Rotor shaft

[0035] 11 countershaft

[0036] 15 axle differential

[0037] 17, 18 Output shafts

[0038] 21 axle differential gear

[0039] 25 differential housing

[0040] 31 Inner disc carrier of the multi-disk brake

[0041] 39 Outer disc carrier of the multi-disk brake

[0042] 49 Hydraulic cylinder of the multi-disk brake

[0043] 55 Gearbox housing wall

[0044] 58 disc brake parking actuator

[0045] 60 parking lock

[0046] 63 ring pistons

[0047] 65 Ball Ramp Unit

[0048] 67 fixed disc

[0049] 69 rotating writing

[0050] 70 Ramp Unit

[0051] 71 ball

[0052] 72 inclined surfaces

[0053] EM electric machine

[0054] PM Park Management

Claims

PATENT CLAIMS:

1. Vehicle axle for a two-track vehicle, with an axle differential (15), the input side of which is drivingly connected to a drive unit (EM) and the output sides of which drive onto output shafts (17, 18) leading to the two vehicle wheels, the vehicle axle having vehicle brakes (7) which can be controlled by a control unit for uniform or uneven vehicle braking on both sides of the vehicle, characterized in that each of the vehicle brakes (7) is designed as a multi-disk brake arranged on each output side of the axle differential (15).

2. Vehicle axle according to claim 1, characterized in that each of the multi-disk brakes (7) is constructed from an inner disc carrier (31), an outer disc carrier (39) and an intermediate disc pack.

3. Vehicle axle according to claim 2, characterized in that the inner disk carrier (31) of the multi-disk brake (7) is connected in a rotationally fixed manner to one of the output shafts (17, 18), while the outer disk carrier (39) of the multi-disk brake (7) is connected in a rotationally fixed manner to a transmission housing wall (55).

4. Vehicle axle according to one of the preceding claims, characterized in that the multi-disk brake (7) has at least one hydraulic cylinder (49) which can be controlled by the control unit, in particular by means of the hydraulic cylinder (49) the multi-disk brake (7) can be subjected to a contact pressure, and in particular that the hydraulic cylinder (49) is, when the vehicle is parked, the hydraulic pressure acting on the hydraulic cylinder (49) does not guarantee a permanent vehicle holding function.

5. Vehicle axle according to one of the preceding claims, characterized in that the vehicle axle is assigned a parking management system (PM), in which each of the multi-disk brakes (7) is assigned a multi-disk brake parking actuator (58) for engaging or disengaging a vehicle holding function, with which the multi-disk brake (7) can be actuated, and in that in particular the multi-disk brake parking actuator (58) can be controlled by the control unit, in particular not hydraulically but electrically, and in that in particular the two multi-disk brake parking actuators (58) can be controlled independently of one another, and in that in particular the hydraulic cylinder (49) and the multi-disk brake parking actuator (58) act on the multi-disk brake (7) on axially opposite sides.

6. Vehicle axle according to claim 5, characterized in that the parking management (PM) of the vehicle has, in addition to the two multi-disk brake parking actuators (58), a parking lock (60) which acts with a pawl on a parking lock wheel installed in the vehicle axle.

7. Vehicle axle according to one of the preceding claims, characterized in that the multi-disk brake parking actuator (57) has a pressure mechanism integrated in the multi-disk brake (5) with a ball-ramp unit (65) and with a preferably self-locking spindle drive, that the ball-ramp unit (65) consists of a fixed disc (67) and a coaxial rotatable disc (69), between which at least one ball (71) rolls, that the spindle drive drives the rotatable disc (69) of the ball-ramp unit (65) by building up / reducing a contact pressure acting on the multi-disk brake (5), and that in particular the self-locking spindle drive keeps the set contact pressure de-energized.

8. Vehicle axle according to one of claims 5 or 6, characterized in that the multi-disk brake parking actuator (57) has a pressure mechanism integrated in the multi-disk brake (5) with a particularly self-locking ramp unit (70) and a spindle drive, that the ramp unit (70) consists of a fixed disc (67) and a rotatable disc (69) coaxial therewith, that inclined surfaces of the fixed disc (67) and the rotatable disc (69) are in sliding / frictional contact with one another, that the spindle drive drives the rotatable disc (69) of the ramp unit (65) while building up / reducing a contact pressure acting on the multi-disk brake (5), and that a pressure build-up or reduction takes place depending on the direction of rotation of the rotatable disc (69).

9. Vehicle axle according to one of claims 5 to 8, characterized in that when the multi-disk brake parking actuator (57) is activated, the hydraulic pressure in the hydraulic cylinder (51) of the multi-disk brake (5) is simultaneously depressurized, and / or that in particular when the multi-disk brake parking actuator (58) is activated, the vehicle can be secured by means of the vehicle brakes of the front axle.

10. Vehicle according to one of the preceding claims, characterized in that the multi-disk brakes (7) serve as a replacement for conventional vehicle disc brakes.

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