GB2182735A - Differential gear - Google Patents

Abstract

Two half shafts (8, 8a) leading to the wheels are driven via a fluid friction clutch (10, 10a). In order to increase the speed difference in the fluid friction clutch and hence achieve a reduction in the dimensions, two identical planetary gears (6, 6a) having the same axis are each provided with an associated fluid friction clutch (10, 10a). The two planetary gears (6, 6a) have a common carrier (5). The two sun wheels (7, 7a) of the planetary gears (6, 6a) are connected to the half shafts (8, 8a) and to one (9, 9a) of the two coupling parts (9, 9a), of the fluid friction clutches (10, 10a). The other coupling parts (12, 12a) are rigidly connected to the two ring gears (13, 13a) of the planetary gears (6, 6a). <IMAGE>

Description

SPECIFICATION Differential gear The present invention relates to a differential gear for a driven axle of a vehicle with two driven axles, in which the two half shafts leading to the wheels are driven via a fluid friction clutch.

In known differential gears of this kind (EP A-00,068,309, DE-A 3,145,279), the fluid friction clutch is provided in place of the usual differential bevel pinions. The housing, filled with viscous fluid of the fluid friction clutch designed as a multiple disk clutch is connected to a ring ger for driven and serves as a support for the outer disks, while the inner disks rest on each half of the two half shafts which form the drive. With this arrangement, speed differences occurring in the fluid friction clutch are only as great as the differential speeds of the wheels of the two driven axles.

Since this difference in speed between the wheels of the front and rear driven axles is relatively small, the fluid friction clutch must be correspondingly dimensioned in order to transfer a torque determined on the basis of different vehicle parameters. The transferable torque of a fluid friction clutch depends, in fact, mainly on the difference in speed between the two coupling parts, i.e. between the inner and outer disks. However, there is frequently insufficient room for a fluid friction clutch with large dimensions.

An object of the invention is to provide a differential gear having adequate performance and with relatively smaller overall dimensions.

The invention provides a differential gear as claimed in claim 1.

If, in this arrangement, differences in slippage occur at the wheels of the two driven axles, then these differences are increased by the two planetary gears which are connected upstream of the fluid friction clutches, in accordance with the transmission ratio of these gears. Furthermore when there is a predetermined torque to be transferred, the entire differential gear may have a smaller design owing to the reduction in the dimensions of the fluid friction clutches, made possible by the increase in the speed difference. Alternatively, when the fluid friction clutches have a given dimension, a greater moment may be produced.

An embodiment of a differential gear according to the invention is shown diagrammatically in the enclosed drawing.

A driven axle, for which the differential gear according to the invention is intended, is driven by the other driven axle via a cardan shaft 1. A ring gear 2 of a bevel drive 2, 3 is rigidly connected to a housing 4 which itself forms the common planet wheel carrier 5 of two identical planetary gears 6, 6a having the same axis. Sun wheels 7, 7a of the two planetary gears 6, 6a are connected to half shafts 8, 8a leading to wheels of the vehicle and carry inner disks 9, 9a of a fluid friction clutch 10, 10a associated with each of the planetary gears 6, 6a. Outer disks 12, 1 2a associated with the housing 11, 11 a filled with viscous fluid are rigidly connected to the ring gears 13, 13a of the planetary gears 6, 6a via the housing 11.

1. A differential gear for a driven axle of a vehicle with two driven axles, in which two half shafts leading to the wheels are driven via a fluid friction clutch, wherein two identical planetary gears are provided having a common planet wheel carrier drivably connected to the other axle of the vehicle and each having an associated fluid friction clutch, sun wheels of the two planetary gears being connected to the half shafts and to one of two coupling parts of the fluid friction clutches, the other coupling parts being rigidly connected to two ring gears.

2. A differential gear for a driving shaft of a vehicle with two driven axles substantially as herein described with reference to the accompanying drawing.

3. A vehicle having two driven axles and a differential gear as claimed in claim 1 or 2.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Differential gear The present invention relates to a differential gear for a driven axle of a vehicle with two driven axles, in which the two half shafts leading to the wheels are driven via a fluid friction clutch. In known differential gears of this kind (EP A-00,068,309, DE-A 3,145,279), the fluid friction clutch is provided in place of the usual differential bevel pinions. The housing, filled with viscous fluid of the fluid friction clutch designed as a multiple disk clutch is connected to a ring ger for driven and serves as a support for the outer disks, while the inner disks rest on each half of the two half shafts which form the drive. With this arrangement, speed differences occurring in the fluid friction clutch are only as great as the differential speeds of the wheels of the two driven axles. Since this difference in speed between the wheels of the front and rear driven axles is relatively small, the fluid friction clutch must be correspondingly dimensioned in order to transfer a torque determined on the basis of different vehicle parameters. The transferable torque of a fluid friction clutch depends, in fact, mainly on the difference in speed between the two coupling parts, i.e. between the inner and outer disks. However, there is frequently insufficient room for a fluid friction clutch with large dimensions. An object of the invention is to provide a differential gear having adequate performance and with relatively smaller overall dimensions. The invention provides a differential gear as claimed in claim 1. If, in this arrangement, differences in slippage occur at the wheels of the two driven axles, then these differences are increased by the two planetary gears which are connected upstream of the fluid friction clutches, in accordance with the transmission ratio of these gears. Furthermore when there is a predetermined torque to be transferred, the entire differential gear may have a smaller design owing to the reduction in the dimensions of the fluid friction clutches, made possible by the increase in the speed difference. Alternatively, when the fluid friction clutches have a given dimension, a greater moment may be produced. An embodiment of a differential gear according to the invention is shown diagrammatically in the enclosed drawing. A driven axle, for which the differential gear according to the invention is intended, is driven by the other driven axle via a cardan shaft 1. A ring gear 2 of a bevel drive 2, 3 is rigidly connected to a housing 4 which itself forms the common planet wheel carrier 5 of two identical planetary gears 6, 6a having the same axis. Sun wheels 7, 7a of the two planetary gears 6, 6a are connected to half shafts 8, 8a leading to wheels of the vehicle and carry inner disks 9, 9a of a fluid friction clutch 10, 10a associated with each of the planetary gears 6, 6a. Outer disks 12, 1 2a associated with the housing 11, 11 a filled with viscous fluid are rigidly connected to the ring gears 13, 13a of the planetary gears 6, 6a via the housing 11. CLAIMS

1. A differential gear for a driven axle of a vehicle with two driven axles, in which two half shafts leading to the wheels are driven via a fluid friction clutch, wherein two identical planetary gears are provided having a common planet wheel carrier drivably connected to the other axle of the vehicle and each having an associated fluid friction clutch, sun wheels of the two planetary gears being connected to the half shafts and to one of two coupling parts of the fluid friction clutches, the other coupling parts being rigidly connected to two ring gears.

2. A differential gear for a driving shaft of a vehicle with two driven axles substantially as herein described with reference to the accompanying drawing.

3. A vehicle having two driven axles and a differential gear as claimed in claim 1 or 2.