Differential having a brake device

Abstract

Differentials having plate packs for exerting a braking torque onto the output shafts of the gear unit are known. The brake device is intended to be designed such that effective braking can be achieved using it and that it is easy to service. To this end, the invention makes provision for the brake device to be a drum brake having a passive element, exhibiting a cylindrical frictional surface, and brake shoes, the frictional surfaces of which brake shoes can be placed against the cylindrical frictional surface of the passive element. The passive element can be a brake drum or a radial brake disk, the cylindrical edge of which serves as a frictional surface. The passive element is fastened to the differential cage and/or one of the shafts. The brake shoes are held in a pivotable manner on a carrier plate fastened to the outside of the differential housing.

Claims

1. A differential having a brake device, comprising: a drive shaft, two output shafts, a differential housing which has an inlet opening for the drive shaft and two opposite outlet openings for the output shafts, a differential cage and at least two brake devices, wherein each of the at least two brake devices is a drum brake which has a passive element, which exhibits a cylindrical frictional surface, and brake shoes, frictional surfaces of which brake shoes can be placed against the cylindrical frictional surface of the passive element, wherein in each case the passive element of a respective one of the at least two brake devices is fastened to the differential cage and/or a respective one of the two output shafts in such a way that the cylindrical frictional surface is installed coaxially in relation to the respective opening of the respective one of the two output shafts, and the brake shoes are held in a pivotable manner on a carrier plate which is flange-connected to an edge of the respective opening.

2. The differential as claimed in claim 1, wherein the passive element is formed by a pot comprising a base and an encircling wall, wherein an inner side of the wall forms the cylindrical frictional surface, the open side of the pot faces the differential housing of the differential, and the brake shoes are arranged within the pot.

3. The differential as claimed in claim 1, wherein the passive element is formed by a radial brake disk, the lateral surface of which radial brake disk forms the cylindrical frictional surface.

4. The differential as claimed in claim 3, wherein a cover is detachably fastened on the carrier plate, so that the carrier plate, the brake shoes and the radial brake disk are enclosed.

5. The differential as claimed in claim 1, wherein the passive element of one brake device of the at least two brake devices is coupled to the differential cage, and the passive element of another brake device of the at least two brake devices is coupled to one of the output shafts.

6. The differential as claimed in claim 5, wherein the differential cage, on a side which is coaxial in relation to the output shaft there, is extended by means of an extension sleeve in order to allow fastening of the passive element.

7. The differential as claimed in claim 1, wherein the carrier plate projects radially outward beyond the differential housing, and has, on the carrier plate's rear side, a hydraulic or electrical connection for an actuating device of the brake shoes.

8. The differential as claimed in claim 1, wherein the differential cage is coupled to an output shaft of an electric motor, wherein the output shaft of the electric motor is of hollow design and runs coaxially in relation to one of the output shafts of the differential.

9. The differential as claimed in claim 8, wherein a compensating gear in form of a spur gear is mounted deaxially in relation to the output shafts in the differential cage, and in that the output shafts, by way of in each case one output gear which is designed as a spur gear, engage into the toothing of the compensating gear.

10. The differential as claimed in claim 8, wherein the electric motor and the differential cage are accommodated in a common cylindrical housing, wherein the output shafts are passed through the end side of the housing, and in each case one brake device of the at least two brake devices is arranged on one or both end side/sides.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Aspects of the invention will be explained in more detail below on the basis of three exemplary embodiments. In the figures:

(2) FIG. 1: shows a first embodiment of the invention,

(3) FIG. 2: shows a second embodiment of the invention, and

(4) FIG. 3: shows a third embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) For the purpose of describing the differential, reference is first of all made to the first two figures. Said figures each show, in section, a differential 1 which is provided with a brake device 2.

(6) The differential 1 has a differential housing 3 comprising an inlet opening 4 and two outlet openings 5 and 6. A drive shaft 7 is rotatably mounted in the inlet opening 4. Said drive shaft drives, by means of a bevel gear 8, a differential cage 9 which is rotatably mounted in the differential housing 3 transversely in relation to the axis of the drive shaft 7.

(7) The differential cage 9 contains a bevel gear arrangement 10 with the aid of which a first output shaft 11 and a second output shaft 12, which project laterally out of the outlet openings 5 and 6, are driven. The output shafts are connected to the front and, respectively, rear wheels of a vehicle, while the drive shaft 7 is coupled to the motor of the vehicle.

(8) If the two output shafts 11, 12 are loaded in the same way, the bevel gear arrangement 10 is, in effect, blocked. The rotation speed of the output shafts 11, 12 corresponds to the rotation speed of the differential cage 9. If one drive shaft can rotate only more slowly than the other because, for example when traveling around a bend, the one drive shaft drives the inner wheel, rotation speed compensation is performed by means of the bevel gear arrangement 10.

(9) The brake device 2 acts on the differential cage 9 and therefore, when it is operated, brakes the two output shafts. To this end, the differential cage 9 exhibits an extension sleeve 20, which is passed out of one of the outlet openings 6, and is connected in a rotationally fixed manner to a passive element of the brake device 2.

(10) In accordance with the design according to FIG. 1, the brake device is realized by a drum brake, as is customary in vehicle engineering. Accordingly, the passive element is a pot-like brake drum 21 which consists of a disk-like base 22 and an encircling wall 23 on said base, the inner side of the encircling wall forming a cylindrical frictional surface which serves as a braking surface for two brake shoes 25. The extension sleeve 20 is connected in a rotationally fixed manner to the center of the base 22.

(11) The brake shoes 25 are arranged in a pivotable manner on a carrier plate 26 which is arranged around the opening 6 and coaxially in relation thereto and is fastened to the differential housing 3.

(12) Operating devices, for example hydraulic or electromotive operating devices for the brake shoes 25, are located on the carrier plate 26this not being illustrated in any detail here. Said operating devices are supplied with power by means of a connection 27 which is located on the rear side of the carrier plate 26, specifically in a region which protrudes radially beyond the differential housing 3. The brake drum 21 has approximately the same outside diameter as the carrier plate 26, so that said brake drum and carrier plate form a chamber in which the brake shoes 25 are located in a manner protected against external effects.

(13) An alternative form of the brake device 2 is illustrated in FIG. 2. Here, the brake drum is designed as a radial brake disk 30 which is connected to the differential cage 9 and the wide lateral surface of which serves as a cylindrical frictional surface. The brake shoes 25 are located on a pot-like carrier plate 31 and, for the purpose of operating the brake, are pressed inward against the frictional surface. A cover 32 closes the carrier plate 31 to the outside. It is possible to connect the radial brake disk 30 directly to the drive shaft 7 in the case of this arrangement too.

(14) In principle, it is true of both designs that the brake drum 21 or radial brake disk 30 is coupled not only to the differential cage 9 but, instead, directly to the respective output shaft 11, 12. In this case, the two output shafts 11, 12 should be provided with a brake device 2. However, it would also be conceivable for a brake device 2 which acts on the differential cage 9 to be provided, while a brake device 2 is provided on the other side of the differential housing, which brake device is connected to the output shaft there.

(15) Furthermore, only one brake device 2 which acts on the drive shaft 7 can be provided. According to the illustrations in FIGS. 1 and 2, the brake device is fastened to the inlet opening 4 instead of one of the outlet openings 5, 6.

(16) FIG. 3 describes a third embodiment of the invention, in which the brake devices 2 are arranged on a cylindrical housing 40 for an electric motor 41 and a differential cage 9.

(17) The rotor 42 and stator 43 are only symbolically indicated here in order to show that any form of electric motor is possible.

(18) The output shaft 44 of the electric motor 41 is of hollow design and widens to form a flat pot 45 in which the differential cage 9 is held, so that it establishes a rotationally fixed connection with the output shaft 44.

(19) The differential housing 3 consists of an annular carrier 46 which has an inwardly facing flange 47 to which two sheet-metal half-shells 48 are fastened, wherein output gears 49 which receive the output shafts 11, 12 in a rotationally fixed manner in their centers are mounted in the hollow space formed in this way.

(20) The two output gears 49 engage into a compensating gear 50 which is rotatably mounted deaxially in relation to the output shafts 11, 12 between the two half-shells 48.

(21) One of the output shafts 11 is passed through the hollow output shaft 44 of the electric motor 41 and rotatably mounted there. Further bearings are located in the end sides of the housing 40.

(22) As has already been described further above, brake drums 21 are fitted in a rotationally fixed manner to the output shafts 11, 12 outside the housing 40. Brake shoes 25 are mounted on the end sides of the housing 40, this not being explained in any detail here, which brake shoes can be pressed against an encircling wall 23 of the brake drum 21 by spreading means, not illustrated, in order to exert a braking moment onto the output shafts 11, 12. This corresponds to the design according to FIG. 1. However, a design of the brake device as is illustrated in FIG. 2 is also conceivable.

(23) TABLE-US-00001 List of reference symbols 1 Differential 2 Brake device 3 Differential housing 4 Inlet opening 5 Outlet opening 6 Outlet opening 7 Drive shaft 8 Bevel gear 9 Differential cage 10 Bevel gear arrangement 11 Output shaft 12 Output shaft 20 Extension sleeve 21 Brake drum 22 Base 23 Encircling wall 25 Brake shoe 26 Carrier plate 27 Connection 30 Radial brake disk 31 Carrier plate 32 Cover 40 Cylindrical housing 41 Electric motor 42 Rotor 43 Stator 44 Output shaft 45 Pot 46 Carrier 47 Flange 48 Half-shells 49 Output gears 50 Compensating gear