Vehicle axle for a two-track vehicle

Abstract

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

Description

The invention relates to a vehicle axle, in particular a rear axle, for a two-track vehicle according to the preamble of claim 1.A vehicle axle has an axle differential with which a 50 / 50 distribution can be carried out. Its input side is drivingly connected to a drive unit, for example an electric machine, while its output sides drive off on output shafts leading to the two vehicle wheels. Sports vehicles in particular usually have a torque vectoring system on the rear axle of the vehicle. This directs a drive torque generated by the drive unit past the axle differential directly to the vehicle wheels. As a result, the drive torques can be distributed freely on the respective vehicle axle.Such a torque vectoring system is designed with a superposition gearing on each side of the vehicle in a structurally complex manner, for example a planetary gearing with a multiplate clutch, which can be controlled by a control unit for torque redistribution between the vehicle wheels of the rear axle.In a conventional rear axle, disc brakes are also installed on the rear wheels, which brakes can be controlled by the control unit for uniform or non-uniform vehicle braking on both rear wheels. The disc brakes are actuated by means of hydraulic pressure in a signal-technical manner, which is complex. In addition, the parking management of the vehicle is equipped with parking brakes which are integrated on the disc brakes of the rear axle in a space-consuming manner. In addition to the two parking brakes installed on the rear axles, the parking management system additionally has a parking lock integrated in the drive module. The parking lock and the parking brakes operate independently of each other to provide sufficient redundancy. That is, if one system fails, the other system performs the hold function.A vehicle axle of the generic type is known from DE 10 2022 205 937 A1. A brake device is known from DE 10 2016 108 238 A1. DE 10 219 921 A1 discloses a drive axle for an electrically operated vehicle. DE 10 2010 020 535 A1 discloses a differential arrangement for a drive train of a motor vehicle, having a differential for forwarding and dividing a torque of an engine to two output shafts and having a coupling device and having an actuating device, wherein the coupling device is designed such that it can be opened and closed 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 to the coupling device, and wherein the coupling device can be actuated with the actuating device. A complicated coupling and decoupling of at least the output shaft is avoided in that the adjusting device acts on the differential in such a way that the differential is at least partially locked in the open state of the coupling device.From DE 10 2020 211 442 A1 a brake system for a vehicle is known. This has 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 on the rotor shaft. The brake system has a first drive shaft which is kinematically coupled to the rotor shaft in such a way 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 disks arranged in the first multi-disk brake housing. At least one disk is fixedly connected to the first drive shaft and at least two disk disks are fixedly connected to the first disk brake housing. The disk disks can be pressed axially against one another in such a way that a braking force for braking the first drive shaft can be generated. DE 10 2011 103 249 A1 discloses a further differential arrangement for a drive train of a motor vehicle.The object of the invention is to provide a vehicle axle for a two-lane vehicle which can be realized with reduced component outlay and in a simple manner of construction compared to the prior art.The object is achieved by the features of claim 1. Preferred developments of the invention are disclosed in the dependent claims.The invention relates to a vehicle axle for a two-track vehicle, which axle axle has an axle differential, the input side of which 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 which can be controlled by a control unit for uniform or non-uniform vehicle braking on both vehicle sides. According to the invention, the vehicle wheel brakes are implemented as wet-running multi-disk brakes, of which one multi-disk brake is arranged on each output side of the axle differential. The two disk brakes can be controlled by an electronic control unit for uniform or non-uniform vehicle braking at both vehicle wheels.By providing the two wet-running disk brakes, it is possible to dispense with the use of conventional vehicle wheel disk brakes which are each formed from a brake disk positioned on the vehicle wheel output shaft and having a brake caliper interacting therewith. This makes it possible to avoid brake abrasion which is otherwise emitted into the environment in conventional vehicle brakes.In a technical realization, each of the two disk brakes is made up of an inner disk carrier, an outer disk carrier and an intermediate disk pack. Each of the two disk brakes acts directly on the respectively associated output shaft. For example, the inner disk carrier of the disk brake can be connected to the respective output shaft in a rotationally fixed and force-transmitting manner, while the outer disk carrier of the disk brake can be connected to a transmission housing wall in a rotationally fixed and force-transmitting manner.The two disk brakes are each equipped with a hydraulic cylinder that can be controlled by the electronic control unit and that applies a contact pressure to the disk set of the disk brake via an annular piston in order to perform a uniform or non-uniform vehicle braking between the vehicle wheels during the driving operation.In the event of a braking request on only one vehicle side, the associated hydraulic cylinder is acted upon with hydraulic pressure in order to adjust the ring piston via a closing stroke. During the closing stroke, the annular piston closes the disk pack of the disk brake while utilizing an air clearance, while the hydraulic cylinder located on the opposite side of the vehicle remains pressureless.In the event of uniform braking on both vehicle sides, the hydraulic cylinders located on both vehicle sides are acted upon by the same hydraulic pressure, as a result of which the respectively associated ring pistons are adjusted over identical closing strokes while exploiting the brake air clearance.The hydraulically operating actuator of the respective multi-disk brake, i.e. the hydraulic cylinder, does not ensure a permanent vehicle holding function or parking function due to volatilization tendencies of the hydraulic pressure acting on the hydraulic cylinder. Against this background, the parking management of the vehicle has an additional multi-disk brake parking actuator on each of the two multi-disk brakes, with which an engine holding function can be engaged or disengaged, specifically by actuating the multi-disk brake. The multi-disk brake parking actuators are not hydraulically controllable, but rather electrically controllable by the control unit.In a preferred embodiment, the hydraulic cylinder and the multi-disk brake parking actuator act on axially opposite sides on the disk set of the respective multi-disk brake. For sufficient redundancy, it is advantageous if the parking management system of the vehicle has, in addition to the two multi-disk brake parking actuators, a parking lock which acts with a pawl on a parking lock wheel installed in the vehicle axle. The parking lock can be integrated in the drive module of the vehicle axle. In addition, the parking lock and the two disk brake actuators operate independently of one another, that is to say, if one system fails, the other system assumes the holding function.In a first embodiment variant, the multi-disk brake parking actuator can be realized as follows: This actuator can thus have a pressing mechanism integrated in the multi-disk brake, with a ball ramp unit and with a preferably self-locking spindle drive. The spindle drive can drive the ball-ramp unit with the build-up / dissipation of a contact pressure acting on the multi-disk brake. By self-locking the electrically operated spindle drive, the set contact pressure can also be maintained without current. When activating the multi-disk brake parking actuator, the hydraulic pressure in the hydraulic cylinder of the multi-disk brake can be switched to unpressurized at the same time. Additionally, upon activation of the multi-plate brake park actuator, the vehicle may be secured to the vehicle front axle using the vehicle brakes.Exemplary embodiments of the invention are described below with reference to the attached figures. The following are shown: FIGS. 1 to 4 each show different views, on the basis of which the structure and the mode of operation of the vehicle axle according to the invention are illustrated.In FIG. 1, an electrified vehicle rear axle is shown with an electric machine EM and a transmission 3. The electric machine EM is connected to a high-voltage battery, not shown. In the vehicle rear axle, conventional vehicle wheel disc brakes are omitted. Instead of such vehicle wheel disc brakes, the rear axle has multi-disc brakes 7, by means of which a vehicle braking can be carried out.The electric machine EM is connected via its rotor shaft 9 with the interposition of a countershaft stage 11 to the input side of an axle differential 15. Its output sides are in driving connection with the vehicle rear wheels via output shafts 17, 18. In FIG. 1, the electric machine EM is installed in the vehicle axle in transverse installation. 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 oriented axis-parallel to one another in the vehicle transverse direction y.The vehicle axle has one of the multi-disk brakes 7 on each vehicle side as viewed in the vehicle transverse direction y. These can be controlled by an electronic control unit for uniform or non-uniform vehicle braking at both vehicle wheels.The countershaft stage 11 is in driving connection with an input-side axle differential gearwheel 21, and the axle differential gearwheel 21 is connected to a rotating differential housing 25 in a rotationally fixed manner. According to FIG. 1, when the multi-disk brakes 7 are open, the axle differential 15 drives in the vehicle transverse direction y in a 50 / 50 distribution on both sides onto the two output shafts 17, 18 leading to the vehicle wheels.In FIG. 1, the two disk brakes 7 act directly on the output shafts 17, 18, respectively. This means that the disk brake 7 is connected with its inner disk carrier 31 to the respective output shaft 17, 18, while the outer disk carrier 39 is connected in a fixed manner to a transmission housing wall 55. The disk set located between the outer disk carrier 39 and the inner disk carrier 31 can be pressurized by means of an annular piston 63 indicated in FIG. 2. This can be adjusted by a horizontal stroke by means of a hydraulic cylinder 49 in order to actuate the multi-disk brake 7 up to a predetermined braking degree. The multi-disk brake 7 can be shifted under load and controlled with slip.As can be further seen from FIGS. 1 and 2, a parking management system PM of the vehicle comprises a multi-disk brake parking actuator 58 acting on the respective multi-disk brake 7 and a parking lock 60 installed on the rotor shaft 9 of the electric machine EM. The two multi-disk brake parking actuators 58 and the parking lock 60 are used to provide parking systems which operate independently of one another and which can be actuated not hydraulically but electrically by means of the control unit. As can be further seen from FIG. 2, the hydraulic cylinder 49 and the respective multi-disk brake parking actuator 58 are arranged on axially opposite sides of the multi-disk pack of the respective multi-disk brake 7. When the vehicle holding function is engaged, the multi-disk brake parking actuator 58 acts on the multi-disk brake 7 in order to apply the required braking force.In FIG. 2, the multi-disk brake parking actuator 58 is designed with a pressing mechanism with a ball-ramp unit 65 integrated in the multi-disk brake 5. The disk set located between the outer disk carrier 61 and the inner disk carrier 59 can be pressurized on the one hand via the annular piston 63 which can be adjusted by the horizontal stroke by means of the hydraulic cylinder 49. On the other hand, on the side axially opposite the annular piston 63, the ball-ramp unit 65 acts on the disk pack. 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 outwards with a toothing 73 which interacts with a drive spindle, not shown, of the multi-disc brake parking actuator 58.The following fault cases are conceivable in the parking management system PM. In a first fault case, 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 further fault case, the parking lock 60 can fail, so that the two functional multi-disk brake parking actuators 58 assume the minimum holding function.With regard to a self-locking that is simpler to realize, reference is made to the exemplary embodiment of FIG. 3 or 4. In FIG. 3, the multi-disk brake parking actuator 58 is substantially of identical construction as in FIG. 2. Reference is therefore made to the description of FIG. 2. In contrast to FIG. 2, in FIGS. 3 and 4 the multi-disk brake parking actuator 58 is not realized with a ball ramp unit 65, but with a ramp unit 70. no balls 71 are installed in the ramp unit 70, whereby a substantially simpler self-locking compared to FIG. 2 can be achieved.In FIG. 3, the self-locking ramp unit 70 consists of a fixed disk 67 and a rotatable disk 69 coaxial thereto. The rotatable disc 69 is formed with an external toothing 73 which is in driving connection with a drive spindle, not shown, of the multi-disc brake parking actuator 57. Depending on the direction of rotation of the rotatable disc 69, a pressure build-up or pressure reduction takes place.LIST OF REFERENCE CHARACTERS:3 Transmission 7 Disk brake 9 Rotor shaft 11 Countershaft 15 Axle differential 17, 18 Output shafts 21 Axle differential gear 25 Differential housing 31 Inner disk carrier of the disk brake 39 Outer disk carrier of the disk brake 49 Hydraulic cylinders of the disk brake 55 Transmission housing wall 58 Disk brake parking actuator 60 Parking lock 63 Ring piston 65 Ball ramp unit 67 Fixed disk 69 Rotatable disk 70 Ramp unit 71 Ball 72 Inclined surfaces EM Electric machine PM Parking management

Claims

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 are driven off onto output shafts (17, 18) leading to the two vehicle wheels, the vehicle axle having vehicle brakes (7) which can be actuated by a control unit for uniform or non-uniform vehicle braking on both vehicle sides, each of the vehicle brakes (7) being designed as a multi-disk brake arranged on each output side of the axle differential (15), characterized in that the multi-disk brake (7) has at least one hydraulic cylinder (49) which can be actuated by the control unit, in that a contact pressure can be applied to the multi-disk brake (7) by means of the hydraulic cylinder (49), the hydraulic cylinder (49), when the vehicle is shut off, does not ensure a permanent vehicle holding function due to volatilization tendencies of the hydraulic pressure acting on the hydraulic cylinder (49), that a parking management (PM) is assigned to the vehicle axle, in which a multi-disk brake parking actuator (58) is assigned to each of the multi-disk brakes (7) for engaging or disengaging a vehicle holding function, with which multi-disk brake parking actuator the multi-disk brake (7) can be actuated, that the multi-disk brake parking actuator (58) can be electrically actuated by the control unit, and that the hydraulic cylinder (49) and the multi-disk brake parking actuator (58) act on the multi-disk brake (7) on axially opposite sides.Vehicle axle according to Claim 1, characterized in that each of the disc brakes (7) is constructed from an inner disc carrier (31), an outer disc carrier (39) and an intermediate disc pack.Vehicle axle according to Claim 2, characterized in that the inner disc carrier (31) of the disc brake (7) is connected in a rotationally fixed manner to one of the output shafts (17, 18), while the outer disc carrier (39) of the disc brake (7) is connected in a rotationally fixed manner to a transmission housing wall (55).Vehicle axle according to Claim 1, 2 or 3, characterized in that the parking management system (PM) of the vehicle has, in addition to the two disc brake parking actuators (58), a parking lock (60) which acts with a pawl on a parking lock wheel installed in the vehicle axle.Vehicle axle according to one of the preceding claims, characterized in that the multi-disk brake parking actuator (57) has a pressing mechanism integrated in the multi-disk brake (5) and having a ball ramp unit (65) and having a spindle drive, in that the ball ramp unit (65) consists of a fixed disk (67) and a rotatable disk (69) coaxial thereto, between which at least one ball (71) rolls, in that the spindle drive drives the rotatable disk (69) of the ball ramp unit (65) with the build-up / reduction of a pressing pressure acting on the multi-disk brake (5).Vehicle axle according to one of Claims 1 to 4, characterized in that the multi-disc brake parking actuator (57) has a pressing mechanism integrated in the multi-disc brake (5) and having a ramp unit (70) and a spindle drive, in that the ramp unit (70) consists of a fixed disc (67) and a rotatable disc (69) coaxial thereto, in that inclined surfaces of the fixed disc (67) and of the rotatable disc (69) are in sliding / frictional contact with one another, in that the spindle drive drives the rotatable disc (69) of the ramp unit (65) with build-up / reduction of a contact pressure acting on the multi-disc brake (5), and in that a pressure build-up or reduction takes place depending on the direction of rotation of the rotatable disc (69).Vehicle axle according to one of the preceding claims, characterized in that, when the multi-disc brake parking actuator (57) is activated, the hydraulic pressure in the hydraulic cylinder (51) of the multi-disc brake (5) is switched to be unpressurized at the same time, and / or in that, when the multi-disc brake parking actuator (58) is activated, the vehicle can be secured by means of the vehicle brakes of the front axle.Vehicle according to one of the preceding claims, characterized in that the disc brakes (7) serve as a replacement for conventional vehicle disc brakes.

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