GB2385100A

GB2385100A - Differential with rheological fluid filled for inhibiting rotation

Info

Publication number: GB2385100A
Application number: GB0200884A
Authority: GB
Inventors: Steven John Collins
Original assignee: Dana Spicer Europe Ltd
Current assignee: Dana Spicer Europe Ltd
Priority date: 2002-01-16
Filing date: 2002-01-16
Publication date: 2003-08-13
Also published as: GB0200884D0

Abstract

A differential comprises an input member 10 and differential gearing having bevel gearing 16, 17 and 18. Flange part 27 forms with part 23 of the input member a chamber 24 and is rotationally fast with the bevel gear 17. In the chamber 23 are sets of annular plates 30, 31 which are attached via splines to the flange part 27 and part 23 respectively. The space in the chamber 24 between the sets of plates 30, 31 is filled with a rheological fluid, eg magneto-rheological or electro-rheological, that is electrically energised by a coil 35 disposed concentrically around the chamber 24 which, in the case of a magneto-rheological fluid, induces a magnetic field to increase the viscosity of the magneto-rheological fluid. This increase in viscosity prevents relative rotation between the plates 30, 31, locking the bevel gear 17 to input member 10 and thereby inhibiting the differential action from taking place.

Description

PATENTS ACT 1977 Title: Differential Gear Description of Invention This invention relates to a differential gear device for use in a motor vehicle.

Differential gear devices or mechanisms, commonly referred to as differentials, are well known devices used in motor vehicle drivelines. A differential is designed to distribute torque from an input element to two output elements, while permitting the two output elements to rotate at different speeds under certain conditions. The outputs may be connected to two wheels alongside one another at opposite either sides of a vehicle, in which case the wheels are required to rotate at different speeds when the vehicle is cornering, or the differential may be an inter-axle differential in a multiple-wheel-drive system, in which case the wheels on the two axles may be required to rotate at different speeds from one another, again for example when cornering.

It is known to provide differentials with means for inhibiting the differential action thereof, in order to cope with the situation where a wheel or wheels driven by one of the differential's outputs is on a slippery surface while the wheel or wheels driven by the other of the outputs is on a surface which is not slippery. Under these circumstances, a differential without any means for inhibiting or locking its differential action directs most or all of its torque to a slipping wheel or wheels and little or none to the gripping one (s) thus potentially immobilising the vehicle. Differentials are known incorporating friction clutch arrangements for controlling their differential action, as also are differentials incorporating viscous couplings for this purpose.

However some differential locking arrangements are not able satisfactorily to be brought into operation at high speeds, and there is a

requirement for this to be done under some circumstances. It is broadly an object of the present invention to address this requirement.

According to the invention, we provide a differential comprising: an input member; first and second rotatable output members ; differential gearing means operative between said input member and said first and second output members, for transmitting rotation from said input member to said first and second output members and providing for differential rotation of said first and second output members relative to one another; rotation-inhibiting means providing resistance to relative rotation between said first and second output members, said rotation-inhibiting means comprising at least one first coupling member and at least one second coupling member said first and second coupling members being connected to respective relatively rotatable parts of the differential ; said first and second coupling members being disposed within a chamber at least partially filled with a rheological fluid adapted to increase in viscosity when subject to an electric or magnetic field and thereby provide a resistance to rotation of said at least one first coupling member relative to said at least one second coupling member; and means for inducing said electric or magnetic field in said rheological fluid.

Preferably said rheological fluid is a magneto-rheological fluid, whose increase in viscosity occurs in response to the application of a magnetic field thereto. Said means for inducing a magnetic field may then comprise an electrically-energisable coil disposed about or adjacent said chamber.

Preferably said at least one first coupling member is non-rotatably coupled to said input member or one of said output members and said at least one second coupling member is non-rotatably coupled to one of said output members or to said input member.

Preferably there is a plurality of plates constituting said at least one further coupling member, and a plurality of plates constituting said at least one second coupling member, interleaved with the first plates.

Preferably said first and second output members are rotatable about an output drive axis, and said chamber and rotation-inhibiting means are disposed concentrically about said axis.

The invention will now be described by way of example with reference to the accompanying drawing, which is a diagrammatic cross-section through a differential in accordance with the invention.

Referring to the drawing, the differential comprises an input member in the form of a differential carrier 10 which includes a flange 11 for attachment of an input gear not shown by which input torque is transmitted to the carrier 10. At one end the carrier has a spigot 12 and at the other end a removable end cover 13 with a spigot 14: bearings on the spigots 12,14 provide for support of the differential in a casing (not shown) for rotation about an axis 15.

Two bevel side gears 16,17 are supported in the carrier 10 for relative rotation therewithin, and mesh with bevel differential gears 18,19 rotatably carried by a transverse pin or shaft 20 held in the carrier 10. The interior of the side gear 16 is splined at 21 for torque-transmitting connection with an output shaft (not shown) extending outwardly through the spigot 12, while the interior of the side gear 17 is splined at 22 to engage a further output shaft (not shown) extending outwardly through the interior of spigot 14.

- Within a portion 23 of the differential carrier adjacent the end cover 13 there is defined an annular chamber indicated generally at 24. The outwardly facing radially innermost circumferential wall of the chamber 24 is afforded by a sleeve 25 which is rotatably supported on an internal spigot 26 of end cover 13 and also on the side gear 17. A flange part 27 extending radially inwardly from the sleeve 25 is splined to engage the non-illustrated output shaft which is in engagement with the splined interior 22 of the side gear 17, so that the sleeve

25 is rotationally fast with the side gear 17 and associated output shaft. The external surface of sleeve 25 is provided with circumferentially spaced axially extending teeth or splines at 28, and the internal surface of the part 23 of the carrier 10 is likewise splined or toothed at 29.

In the chamber 24 between the sleeve 25 and part 23 of the carrier there are disposed first and second coupling members, there being a plurality of first coupling members in the form of annular plates 30 rotationally fast with the sleeve 25 by engaging the teeth 28, and a plurality of second coupling members in the form of annular plates 31 interposed between the plates 30 rotationally fast with the carrier part 23, engaging the teeth 29 thereon. The space in the chamber 24 between the sets of plates constituting the first and second coupling members is filled or substantially filled with a magneto-rheological fluid.

Magneto-rheological fluids are known, and in principle comprise a suspension in a liquid of small colloidal particles each of which contains many tiny randomly oriented magnetic grains. An externally applied magnetic field orients the magnetic grains and induces a large magnetic moment in each particle, which becomes a magnet whose strength is controlled by the applied magnetic field strength. When this happens, the particles coalesce within the fluid and greatly increase the fluid's viscosity, in effect rendering it solid. Thus while relative rotation between the plates constituting the coupling members ( respectively fast with the sleeve 25 and carrier part 23 is possible, when the magneto-rheological fluid is not subject to any magnetic field, when a field of sufficient strength is applied the fluid effectively prevents relative rotation between the plates, locking the side gear 17 to the carrier 10 of the differential and preventing the differential action from taking place.

To apply a magnetic field as above described to the magneto-rheological fluid in the chamber 24, a coil which is electrically energisable has to be disposed in a position in relation to the chamber suitable to establish the magnetic field, and the drawing shows a coil 35 disposed concentrically around

the chamber. A suitable electrical power supply for the coil 35 would be provided, and a control means operable to apply electrical power to the coil when the differential is required to be locked.

It will be appreciated that variations may be made in the construction described above while still remaining with the broadest scope of the present invention. For example, the invention is applicable to differentials in which the differential gearing is of a type other than the bevel gearing illustrated, for example planetary gearing. The coupling members such as plates rotatably fast with respective relative rotational parts of the differential, within the magnetorheological fluid for inhibiting or locking the differential action when required, may be disposed in any appropriate operative position.

As well as known magneto-rheological fluids as described above, there are also known electro-rheological fluids wherein the increase in viscosity takes place when subject to an electric field. It would be within the broadest aspect of the invention if such an electro-rheological fluid were to be used, the requirement then being for the provision of means for establishing a suitable electric field in such fluid when the differential is required to be locked.

In the present specification"comprises"means"includes or consists of and"comprising"means"including or consisting of.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS 1. A differential comprising: an input member; first and second rotatable output members ; differential gearing means operative between said input member and said first and second output members, for transmitting rotation from said input member to said first and second output members and providing for differential rotation of said first and second output members relative to one another ; rotation-inhibiting means providing resistance to relative rotation between said first and second output members, said rotation-inhibiting means comprising at least one first coupling member and at least one second coupling member said first and second coupling members being connected to respective relatively rotatable parts of the differential; said first and second coupling members being disposed within a chamber at least partially filled with a rheological fluid adapted to increase in viscosity when subject to an electric or magnetic field and thereby provide a resistance to rotation of said at least one first coupling member relative to said at least one second coupling member; and means for inducing said electric or magnetic field in said rheological fluid.
2. A differential according to Claim 1 wherein said rheological fluid is a magneto-rheological fluid, whose increase in viscosity occurs in response to the application of a magnetic field thereto.
3. A differential according to Claim 2 wherein said means for inducing a magnetic field comprises an electrically-energisable coil disposed about or adjacent said chamber.

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4. A differential according to any one of Claims 1 to 3 wherein said at least one first coupling member is non-rotatably connected to said input member or one of said output members and said at least one second coupling member is non-rotatably coupled to one of said output members or to said input member.
5. A differential according to any one of the preceding claims wherein said first and second output members are rotatable about an output drive axis, and said chamber and rotation-inhibiting means are disposed concentrically about said axis.
6. A differential according to any one of the preceding claims wherein said coupling members comprise a plurality of plate elements.
7. A differential substantially as hereinbefore described with reference to the accompanying drawing.
8. Any novel feature or novel combination of features described herein and/or in the accompanying drawings.