Locking differential

Abstract

In a locking differential (1), a locking torque is set by the rotation of ramp rings (11, 12) with respect to one another. An elastic element (15) couples the ramp rings (11, 12) to one another and exerts a restoring force on the ramp rings (11, 12), which restoring force supports passive self-opening of the locking differential (1).

Description

[0001] Limited-slip differential

[0002] The invention relates to a limited-slip differential, primarily for the automotive sector.

[0003] Limited-slip differentials have long been known in the automotive sector. It is also known that the locking torque of a limited-slip differential can be variably adjusted. This can be achieved in a conventional manner, for example, using ramp rings. By rotating the ramp rings relative to each other, the axial distance between the ramp rings is changed, which in turn changes the locking torque of the limited-slip differential.

[0004] One of the requirements for a modern limited-slip differential is, on the one hand, that a desired locking torque, in particular the maximum possible for the respective limited-slip differential, can be reliably set within a specified time period. An actuator, often an electric actuator, is used for this purpose. On the other hand, the limited-slip differential must be able to open passively, even without the action of the actuator, i.e., to reduce the locking torque to a value of zero or close to zero, or to a specified value that is lower than the maximum possible value. This is particularly important because an excessively high locking torque of the limited-slip differential can lead to systems such as ABS / ESP not functioning correctly in all situations, which in turn represents a safety risk.

[0005] The object of the invention is to provide a limited-slip differential in which a reliable reduction of the locking torque is possible.

[0006] This object is achieved by a limited-slip differential according to claim 1. Claim 7 relates to a drive train with such a limited-slip differential and claim 8 to a motor vehicle with a corresponding drive train.

[0007] The limited-slip differential according to the invention comprises a first ramp ring and a second ramp ring, which are arranged, ultimately in a known manner, such that a rotation of the first ramp ring relative to the second ramp ring causes a change in the locking torque of the limited-slip differential. According to the invention, an elastic element is provided that is connected to the first and second ramp rings. The connection is designed such that when the ramp rings rotate relative to one another in such a way that the locking torque is increased, the elastic element exerts a restoring force on the ramp rings.

[0008] This restoring force supports the opening, i.e., the reduction of the locking torque, of the limited-slip differential. This reduction is thus possible more reliably than with the current technology.

[0009] In one embodiment, an electric actuator is provided to cause the first ramp ring to rotate relative to the second ramp ring. If this actuator is used to increase the locking torque and then fails, or if the locking differential is intended to open passively, i.e., without actuator actuation, a reliable reduction of the locking torque is possible due to the restoring force exerted by the elastic element.

[0010] In one embodiment, the first and second ramp rings each have a projection. This projection can, for example, protrude radially outward on the respective ramp ring. The elastic element mechanically connects the two projections. A rotation of the ramp rings relative to each other in such a way that the locking torque is increased leads to a change in the distance between the projections and thus to an extension or compression of the elastic element, resulting in a restoring force that the elastic element exerts on the projections and thus on the ramp rings.

[0011] The elastic element may be a spring element, for example, but without limiting the invention thereto, a tension spring, a compression spring, a bow spring, a wrap spring, a torsion spring or a spiral spring.

[0012] In one embodiment, the elastic element is designed and attached to the ramp rings in such a way that the restoring force exerted by the elastic element only rotates the ramp rings to such an extent that a defined locking torque remains which is not equal to zero.

[0013] A drivetrain according to the invention for a motor vehicle comprises a limited-slip differential according to the invention as described above. The more reliable reduction of the locking torque improves the function of the drivetrain and further ensures that other functions implemented in the drivetrain, such as ABS or ESP, are not impaired by an excessively high remaining locking torque. A motor vehicle according to the invention has a drivetrain according to the invention specified above. The advantages of the drivetrain according to the invention enable safer operation of the motor vehicle.

[0014] The invention and its advantages are described in more detail below with reference to the accompanying drawings.

[0015] Figure 1 shows a limited-slip differential with ramp rings and actuator according to the state of the art.

[0016] Figure 2 shows a limited-slip differential according to the invention.

[0017] Figure 3 shows a motor vehicle according to the invention with a drive train according to the invention.

[0018] The drawings show only embodiments of the invention and are not to be construed as limiting the invention to the illustrated embodiments.

[0019] Fig. 1 shows a limited-slip differential 1 according to the prior art. Shown are the actual differential gear 2, the first ramp ring 11, the second ramp ring 12, and the actuator 3, with electric motor 31 and actuator gear 32. The actuator 3 is designed to rotate the first ramp ring 11 relative to the second ramp ring 12 about axis 100 by operating the electric motor 31 via actuator gear 32. This rotation causes a distance in the direction of axis 100 (axial distance) between the first ramp ring 11 and the second ramp ring 12 to change. This relative displacement in the axial direction influences elements of the limited-slip differential 1 in a manner that causes a change in the locking torque of the limited-slip differential 1.

[0020] Fig. 2 shows a sectional view of a limited-slip differential 1 according to the invention. Shown are the actual differential gear 2, the first ramp ring 11 and the second ramp ring 12, as well as an actuator 3, which is provided for rotating the first ramp ring 11 relative to the second ramp ring 12 about axis 100. As also explained in the prior art and with reference to Fig. 1, rotating the first ramp ring 11 relative to the second ramp ring 12 about axis 100 here causes a change in the distance in the direction of axis 100 between the first ramp ring 11 and the second ramp ring 12, and thus ultimately a change in the locking torque of the limited-slip differential 1.

[0021] A projection 13 is provided on the first ramp ring 11, and a projection 14 is provided on the second ramp ring 12. The projections 13 and 14 are connected to each other via an elastic element, more precisely a spring 15. The spring 15 is attached to each of the projections 13, 14 with a connecting element 16.

[0022] When the first ramp ring 11 rotates relative to the second ramp ring 12 in a direction that increases the locking torque of the limited-slip differential 1, the projections 13 and 14 move relative to each other in such a way that the spring 15 is stretched. The resulting spring force acts as a restoring force on the ramp rings 11 and 12. This restoring force is thus directed such that it can cause the ramp rings 11 and 12 to rotate in a direction that reduces the locking torque of the limited-slip differential 1. The restoring force supports the passive opening of the limited-slip differential 1.

[0023] If the effect of the restoring force is only to last until a defined locking torque other than zero is reached, one possibility for achieving this with the configuration shown would be to design one connecting element 16 or both connecting elements 16 with a suitable length so that when the ramp rings 11, 12 move to increase the locking torque, the connecting elements 16 (assumed without relevant elasticity) are initially tightened before further movement of the ramp rings 11, 12 leads to an extension of the spring 15. During a movement to reduce the locking torque, for example when the limited-slip differential 1 is passively opened, the restoring force of the spring 15 only acts on the projections 13 and 14, and thus on the ramp rings 11, 12, as long as the connecting elements 16 are taut. This is the case as long as the spring 15 is not relaxed.As soon as the spring 15 is relaxed, a further rotation of the ramp rings 11, 12 against each other in the direction of a reduction of the locking torque is no longer supported by a force from the spring 15.

[0024] Fig. 3 shows a motor vehicle 200 according to the invention with a drive train 201 according to the invention, which includes an electric motor 210 and a limited-slip differential 1 according to the invention. The electric motor 210 is supplied with energy from a battery 220. List of reference symbols

[0025] 1 limited-slip differential

[0026] 2 differential gears

[0027] 3 Actuator

[0028] 11 first ramp ring

[0029] 12 second ramp ring

[0030] 13 projection (at the first ramp ring)

[0031] 14 projection (on the second ramp ring)

[0032] 15 spring

[0033] 16 Connecting element

[0034] 31 electric motor

[0035] 32 actuator gears

[0036] 100 axle

[0037] 200 motor vehicles

[0038] 201 Powertrain

[0039] 210 electric motor

[0040] 220 battery

Claims

Patent claims 1 . Limited-slip differential (1 ) comprising: a first ramp ring (11 ) and a second ramp ring (12 ), which are arranged such that a rotation of the first ramp ring (11 ) against the second ramp ring (12) causes a change in a locking torque of the limited-slip differential (1 ); characterized by an elastic element (15 ) which is connected to the first (11 ) and second ramp ring (12) such that when the ramp rings (11 , 12 ) are rotated against one another such that the locking torque is increased, the elastic element (15 ) exerts a restoring force on the ramp rings (11 , 12 ).

2. Limited-slip differential (1) according to claim 1, wherein an electric actuator (3) is provided to cause a rotation of the first ramp ring (11) against the second ramp ring (12).

3. Limited-slip differential (1) according to one of the preceding claims, wherein the first (11) and the second ramp ring (12) each have a projection (13, 14) and the elastic element (15) mechanically connects the two projections (13, 14) to one another.

4. Limited-slip differential (1) according to one of the preceding claims, wherein the elastic element is a spring element (15).

5. Limited-slip differential according to claim 4, wherein the spring element (15) is a tension spring, compression spring, arc spring, wrap spring, torsion spring or spiral spring.

6. Limited-slip differential (1) according to one of the preceding claims, wherein after a reset of the ramp rings (11, 12) by the elastic element (15), a defined locking torque not equal to zero remains.

7. Drive train (201) for a motor vehicle (200) with a limited-slip differential (1) according to one of claims 1 to 6.

8. Motor vehicle (200) with a drive train (201) according to claim 7.

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