Axle with a braking system comprising a service brake, a parking brake and a common stator-rotor arrangement

Abstract

Axle, in particular drive axle, with a first axle shaft (3), a second axle shaft (4) coaxial thereto and a braking device comprising a hydraulically actuated service brake (7) and a parking brake (8), wherein a common stator-rotor arrangement (6) having at least two brake rotors (6a, 6b) is provided and at least one brake rotor (6a, 6b) is coupled to one of the axle shafts (3, 4), characterized in that the parking brake (8) is designed as an electromagnetically actuated spring-applied brake.

Description

[0001] The invention relates to an axle, in particular a drive axle, having a first axle shaft, a second axle shaft coaxial therewith and a braking device having a hydraulically actuated service brake and a parking brake, wherein a common stator-rotor arrangement having at least two brake rotors is provided and at least one brake rotor is coupled to one of the axle shafts.

[0002] A generic axle is the subject of DE 196 48 979 B4. In this axle, designed as a drive axle, the parking brake is actuated by a cable against the force of a spring.

[0003] DE 102 25 038 A1 discloses a drive axle with an integrated brake.

[0004] DE 198 22 767 A1 discloses a running axle for work machines.

[0005] DE 20 2011 106 849 U1 discloses a wheel axle.

[0006] DE 38 13 528 A1 discloses a braking system.

[0007] The object of the present invention is to provide an axle of the type mentioned at the outset in which the braking device is improved with regard to ease of use, low maintenance and safety while having a compact design.

[0008] This object is achieved according to the invention in that the parking brake is designed as an electromagnetically actuated spring-loaded brake.

[0009] The essential idea of ​​the invention is therefore not to design the parking brake in the axle's braking device as a brake that is applied mechanically against the force of a spring, but instead to use a brake that is initially closed by spring force and is opened by energizing an electromagnet. As a result, the parking brake of the axle according to the invention acts as a safety brake with what is known as a fail-safe behavior, i.e., a behavior in which, in the event of brake actuation failure, the safe state in which the brake is applied is automatically assumed. Furthermore, levers and cables – and the resulting complexity of the braking system outside the axle – are eliminated, as is the need to keep them functional through regular maintenance (particularly lubrication).By appropriately controlling the electromagnetically actuated spring-loaded brake, additional convenience functions can be achieved, such as the automatic engagement of the parking brake when stopping and / or leaving a vehicle equipped with the axle according to the invention. This also increases safety, as the activation of the parking brake cannot be forgotten.

[0010] The result is an axle, preferably a drive axle, with electro-hydraulic service and parking brakes, which is characterized by small dimensions, efficient and low-maintenance operation and a high degree of integration.

[0011] The braking device is advantageously arranged at the inner ends of the aligned axle shafts. The axle shafts can be driven axle shafts of a drive axle or non-driven axle shafts of a running axle.

[0012] According to an advantageous embodiment of the invention, it is proposed that a brake actuator for the service brake be provided in the inner end region of the first axle shaft, and a brake actuator for the parking brake be provided in the inner end region of the second axle shaft, with the stator-rotor assembly being located axially between the brake actuators. This design, in which the brake actuators for the parking brake and the service brake are arranged, so to speak, around the stator-rotor assembly, thus enclosing it, not only requires little installation space, but also makes it possible to generate axial braking forces from both the first axle shaft and the second axle shaft and to transmit them to the stator-rotor assembly.

[0013] The parking brake advantageously comprises a brake housing provided with a coil body and a spring device operatively connected to an axially movable armature disk designed to engage the stator-rotor assembly. When de-energized, the armature disk exerts an axial force due to the action of the spring force, which urges the stator-rotor assembly into the closed position. To release the parking brake, current flows through the coil body, generating a magnetic force acting in the opposite direction to the spring force, which switches the stator-rotor assembly into an open position in which the brake rotors can rotate freely.

[0014] It proves expedient for the service brake to have a hydraulically actuated brake piston, centrally penetrated by the first axle shaft, which is designed to engage with the stator-rotor assembly. As soon as the brake piston is subjected to hydraulic pressure, a closing force acting axially on the stator-rotor assembly is generated, with which a vehicle equipped with the axle according to the invention can be braked in a controlled manner when the parking brake is released.

[0015] With a view to the smallest possible number of components and a compact design, an embodiment of the invention is advantageous according to which the stator-rotor arrangement has a first brake stator on a side of the first brake rotor near the axle shaft, a second brake stator on a side of the second brake rotor near the axle shaft and a third brake stator axially between the brake rotors.

[0016] If the armature disc can be subjected to force and locked by a manual brake release device against the action of the spring device, the parking brake can be released in the event of a power failure and a vehicle equipped with the axle can be moved, for example to tow it away.

[0017] When the axle according to the invention is designed as a drive axle, the axle shafts can be designed as drive shafts of two traction motors.

[0018] According to a no less advantageous variant of a drive axle, in which it is designed as a so-called differential axle, i.e. has only one drive motor, it is proposed that the first axle shaft is designed as a hollow shaft of a drive motor and is operatively connected at one end to a differential gear and that the second axle shaft is connected to one of the outputs of the differential gear and is guided centrally through the first axle shaft, wherein the braking device is arranged at the end of the first axle shaft opposite the differential gear.

[0019] In this case, a brake actuator of the service brake is advantageously arranged in the end region of the first axle shaft opposite the differential gear, and axially adjoining it are the stator-rotor arrangement and a brake actuator of the parking brake.

[0020] If the parking brake has a brake housing equipped with a coil body and a spring device that are operatively connected to an axially movable armature disk designed to engage the stator-rotor assembly, the armature disk—similar to the axle designs already described—exerts an axial force, acting on the stator-rotor assembly in the closed position, when de-energized due to the action of the spring force. If the parking brake is to be released, current flows through the coil body, generating a magnetic force that counteracts the spring force and switches the stator-rotor assembly to an open position, allowing the brake rotors to rotate freely.

[0021] In this embodiment of the invention, it is also advantageous for the service brake to have a hydraulically actuated brake piston, centrally penetrated by the first axle shaft, which is designed to engage with the stator-rotor assembly. Applying hydraulic pressure to the brake piston creates a closing force acting axially on the stator-rotor assembly, which makes it possible to apply controlled braking to a vehicle equipped with the axle when the parking brake is released.

[0022] A particularly advantageous embodiment is one in which the at least one brake rotor coupled to the first axle shaft can be fixed relative to a component fixed to the axle, and the at least one brake rotor coupled to the second axle shaft can be fixed relative to a brake stator carrier coupled to the first axle shaft. Such a construction thus essentially consists of a brake and a differential lock. When engaged, the brake blocks the first axle shaft relative to an axle tube or a component fixed to the axle (and thus simultaneously blocks the input of the differential gear), while the differential lock fixes the second axle shaft relative to the first axle shaft (and thus simultaneously blocks the first output of the differential gear). Consequently, the second output of the differential gear is also necessarily blocked.

[0023] Further advantages and details of the invention are explained in more detail with reference to the exemplary embodiments shown in the schematic figures. Fig. 1 a partial longitudinal section through the central region of an axle designed as a two-motor drive axle according to the invention and Fig. 2 a partial longitudinal section through an axle center body of an axle designed as a differential axle according to the invention.

[0024] In the axis of the Fig. 1, two electric traction motors 1, 2 are integrated, in particular three-phase motors, whose drive shafts form a first axle shaft 3 and a second axle shaft 4. The two axle shafts 3, 4 are arranged axially one behind the other in alignment with each other and end on the inside of the axle in a housing area 5 arranged in the center of the axle or approximately in the center of the axle, in which a braking device with a stator-rotor arrangement 6 is located, which is assigned to both a hydraulic service brake 7 and a parking brake 8.

[0025] The common stator-rotor assembly 6 consists of a first brake rotor 6a that is torsionally rigid but axially movable with the first axle shaft 3, a second brake rotor 6b that is torsionally rigid but axially movable with the second axle shaft 4, a first brake stator 6c on a side of the first brake rotor 6a near the axle shaft, a second brake stator 6d on a side of the second brake rotor 6b near the axle shaft, and a third brake stator 6e located axially between the brake rotors 6a, 6b. The brake stators 6c, 6d, and 6e are mounted in the housing area 5 of the axle in a torsionally rigid but axially movable manner.

[0026] A brake actuator of the service brake 7, designed as a brake piston 7a, is arranged in the inner end region of the first axle shaft 3, and a brake actuator of the parking brake 8, designed as an armature disk 8a, is arranged in the inner end region of the second axle shaft 4. The stator-rotor assembly 6 is located axially between the two brake actuators.

[0027] In the present exemplary embodiment, a spring device 9 designed as a compression spring bears against the armature disk 8a, which acts as the brake actuator of the parking brake 8. The second axle shaft 4 extends through this spring device and is arranged within a brake housing 10 provided with a coil body 11. The armature disk 8a is guided relative to the brake housing 10 by means of a fitting screw 12, which also serves for the pre-assembly of the parking brake 8 (several fitting screws are provided distributed over the circumference of the brake housing). A shaft seal of the traction motor 2, which is on the right in the figure, can be supplied with lubricating oil through a channel 13 machined into the brake housing 10.

[0028] The parking brake 8, which is thus designed as an electromagnetically actuated spring-loaded brake, is in the closed position in the de-energized state, in which the armature disk 8a presses the brake rotors and brake stators of the stator-rotor arrangement 6 together under the action of the spring device 9.

[0029] To drive, a current pulse introduced into the coil body 11 generates a magnetic force, thereby applying force to the armature disk 8a against the action of the spring device 9. This releases the brake rotors 6a and 6b and allows them to rotate. After the armature disk 8a is lifted ("released"), a holding current lower than the current pulse is sufficient to keep the armature disk 8a in the engaged position. The power requirement of the coil body 11 is thus lower.

[0030] The hydraulically actuated brake piston 7a, through which the first axle shaft 3 passes, is sealed with O-rings 14. During operation, the service brake 7 is hydraulically moved into the closed position by pressure buildup in front of the brake piston 7a. Depending on the pressure acting on the brake piston 7a, a vehicle equipped with the axle can be controlled and thus braked in a controlled manner. If no pressure is applied, the brake piston 7a is reset by the force of a spring 15. The spring 15 is preloaded by a fitting screw 16, which also serves as an assembly aid (several springs and screws are provided distributed around the circumference of the brake piston). A brake pressure connection 17 is located in the housing area 9 to supply the brake piston 7a with brake pressure.

[0031] The brake pressure can be generated, for example, by foot force using a master cylinder. However, it is also possible to apply pressure to the brake piston 7a from a hydraulic system present in the vehicle, for example, from a forklift's lifting and steering hydraulic system. In this case, the operator controls a brake valve to meter the hydraulic brake pressure and thus the braking force generated by the stator-rotor assembly 6.

[0032] In the event of a power failure, the parking brake 8 acts as an emergency brake. In this case, the armature disk 8a is no longer released by a magnetic force and therefore, under the action of the spring device 9, applies an axial braking force to the stator-rotor assembly 6. The parking brake 8 is thus engaged.

[0033] In order to be able to release the parking brake 8 even in the event of a power failure, for example in order to tow a vehicle equipped with an axle, a clamping piece 18 which can be actuated from outside the axle is pressed against the armature disk 8a, for example by a screw not shown in the figure. For this purpose, bevels A are formed on the clamping piece 18 and the armature disk 8a. When a force directed radially towards the axle is applied by a screw to the clamping piece 18 serving as the brake release device, the armature disk 8a is moved to the right in the figure against the force of the spring device 9, thereby relieving the tension in the stator-rotor arrangement 6. For reliable operation, it is expedient to provide at least two such clamping pieces distributed around the circumference.

[0034] In the Fig. 2, the axle is designed as a differential axle, which has only a single drive motor 19. Components which functionally correspond to the already described embodiment according to Fig. 1 are provided with unchanged reference symbols.

[0035] The drive shaft of the traction motor 19, designed as a hollow shaft, thus corresponds to the first axle shaft 3. The first axle shaft 3 is connected to the input of a differential gear 20 arranged axially adjacent to the traction motor 19. The second axle shaft 4 is connected to one of the outputs of the differential gear 20 and passes centrally through the first axle shaft 3.

[0036] In the present embodiment, the braking device is located at the end of the first axle shaft 3 opposite the differential gear 20 and has - analogous to the embodiment according to Fig. 1 - via a brake actuator of the service brake 7, which is arranged in the end region of the first axle shaft 3 and is designed as a hydraulically actuated brake piston 7a, and axially adjoining thereto via a stator-rotor arrangement 6 and a brake actuator of the parking brake 8. The parking brake 8 has a brake housing 10 which is provided with a coil body 11 and a spring device 9, which are operatively connected to an axially movable armature disk 8a provided for engagement with the stator-rotor arrangement 6 and thus form the brake actuator of the parking brake 8.

[0037] The brake rotors and brake stators of the rotor-stator arrangement 6 can be designed as lamellae, as shown, or as relatively thick disc elements (as in Fig.1). Independently thereof, the brake rotor(s) 6a coupled to the first axle shaft 3 can be fixed relative to an axle-fixed component (here: an axle center body 21), and the brake rotor(s) 6b coupled to the second axle shaft 4 can be fixed relative to a brake stator carrier 22 coupled to the first axle shaft 3.

[0038] Thus, the braking system essentially consists of a brake, in which the first axle shaft 3 is braked against a torsionally rigid housing, and a simultaneously operating differential lock, which acts like a locking mechanism by blocking two of the three rotating components of the differential gear 20. By locking the first axle shaft 3 relative to the axle center body 21, the input of the differential gear 20 is blocked. At the same time, the second axle shaft 4 is locked relative to the first axle shaft 3, thus blocking the first output of the differential gear 20 relative to its input.

Claims

[1] Axle, in particular drive axle, with a first axle shaft (3), a second axle shaft (4) coaxial therewith and a braking device having a hydraulically actuated service brake (7) and a parking brake (8), wherein a common stator-rotor arrangement (6) having at least two brake rotors (6a, 6b) is provided and at least one brake rotor (6a, 6b) is coupled to one of the axle shafts (3, 4), characterized by that the parking brake (8) is designed as an electromagnetically actuated spring-loaded brake. [2] Axle according to claim 1, characterized by that the braking device is arranged at the inner ends of the axle shafts (3, 4) which are aligned with one another. [3] Axle according to claim 2, characterized bythat a brake actuator of the service brake (7) is provided in the axle-inside end region of the first axle shaft (3) and a brake actuator of the parking brake (8) is provided in the axle-inside end region of the second axle shaft (4), wherein the stator-rotor arrangement (6) is located axially between the brake actuators. [4] Axle according to one of claims 1 to 3, characterized by that the parking brake (8) has a brake housing (10) which is provided with a coil body (11) and a spring device (9) which is operatively connected to an axially movable armature disk (8a) provided for engagement with the stator-rotor arrangement (6). [5] Axle according to one of claims 1 to 4, characterized by that the service brake (7) has a hydraulically actuated brake piston (7a) through which the first axle shaft (3) passes centrally and which is intended to engage with the stator-rotor arrangement (6). [6] Axle according to one of claims 1 to 5, characterized by that the stator-rotor arrangement (6) has a first brake stator (6c) on a side of the first brake rotor (6a) near the axle shaft, a second brake stator (6d) on a side of the second brake rotor (6b) near the axle shaft, and a third brake stator (6e) axially between the brake rotors (6a, 6b). [7] Axle according to one of claims 1 to 6, characterized by that the armature disc (8a) can be subjected to force and locked by a manual brake release device against the action of the spring device (9). [8] Axle according to one of claims 1 to 7, characterized by that the axle shafts (3, 4) are designed as drive shafts of two traction motors (1, 2). [9] Axle according to claim 1, characterized bythat the first axle shaft (3) is designed as a hollow shaft of a traction motor (19) and is operatively connected at one end to a differential gear (20) and that the second axle shaft (4) is connected to one of the outputs of the differential gear (20) and is guided centrally through the first axle shaft (3), wherein the braking device is arranged at the end of the first axle shaft (3) opposite the differential gear (20). [10] Axle according to claim 9, characterized by that in the end region of the first axle shaft (3) opposite the differential gear (20) there is arranged a brake actuator of the service brake (7) and, axially adjoining thereto, the stator-rotor arrangement (6) and a brake actuator of the parking brake (8). [11] Axle according to claim 9 or 10, characterized bythat the parking brake has a brake housing (10) which is provided with a coil body (11) and a spring device (9) which is operatively connected to an axially movable armature disk (8a) provided for engagement with the stator-rotor arrangement (6). [12] Axle according to one of claims 9 to 11, characterized by that the service brake has a hydraulically actuated brake piston (7a) through which the first axle shaft (3) passes centrally and which is intended to engage with the stator-rotor arrangement (6). [13] Axle according to one of claims 9 to 12, characterized by that the at least one brake rotor (6a) coupled to the first axle shaft (3) can be fixed relative to a component fixed to the axle and the at least one brake rotor (6b) coupled to the second axle shaft (4) can be fixed relative to a brake stator carrier (22) coupled to the first axle shaft (3).

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