TORQUE VECTORING DEVICE

Abstract

A torque vectoring device (4-18) for two half-axles of a vehicle drive axle, provided with a conventional differential (20-27), through which drive torque is supplied from a propulsion motor, is connected on one hand to one of the half-axles (1), on the other hand to the cage (24) of the differential (20-27). An electric motor (15) of the torque vectoring device is connected via a differential transmission in the form of a planetary gearing (10) to said one of the half-axles (1) and the cage (24). The arrangement is such that the electric motor stands still, when the rotational speed of the half-axle (1) and the cage (24) is the same.

Description

TECHNICAL FIELD

The present invention relates to torque vectoring device for two half-axles of a vehicle drive axle, provided with a conventional differential, through which drive torque is supplied from a propulsion motor, for example a combustion engine.

BACKGROUND OF THE INVENTION

In a road vehicle, especially a car, it is advantageous to be able to freely distribute drive torque to different wheels in order to enhance the driving dynamics of the vehicle. Devices for accomplishing this desired result are in the art referred to as torque vectoring devices.

Generally speaking, torque vectoring devices may be used in either two-wheel drive vehicles or four-wheel drive vehicles.

A prior torque vectoring device is shown in WO 2010/101506, to which reference is made for a better general understanding of the field of torque vectoring devices and their use in road vehicles. The torque vectoring device of this publication is shown to be used together with an electric propulsion motor, but this is per se no limitation, and the used power source may equally well be a combustion engine.

The torque vectoring device of the publication is constructed to transfer torque between two half-axles of a vehicle drive axle via a differential mechanism and has a torque source in the form of an electric motor.

The main object of the present invention is to attain a torque vectoring device to be used as a unit together with a conventional differential of a vehicle. It is a further object to make this unit compact, light-weight, easier to integrate and cheaper than present torque vectoring devices.

THE INVENTION

This is according to the invention attained in that

the torque vectoring device is connected on one hand to one of the half-axles, on the other hand to the cage of the differential or to the other half-axle, and

a rotative torque source of the torque vectoring device is connected via a differential transmission in the form of a planetary gearing to said one of the half-axles and the cage or the other half-axle,

the arrangement being such that the rotative torque source stands still, when the rotational speed of said one of the half-axles and the cage or the other half-axle is the same.

It is an important aspect that no rotation is imparted to the rotative torque source, when the two driving half-axles of the vehicle rotate with the same speed, and thus that the torque vectoring device according to the invention operates on the rotational speed difference between the two half-axles.

A hollow shaft may in a practical case be connected to the cage of the differential, whereas a shaft connected to said one of the half-axles may extend through the hollow shaft.

A first gear train may be arranged between the shaft and a shaft arrangement connected to a planet carrier of the planetary gearing, the planet carrier carrying planet gears, whereas a second gear train may be arranged between the hollow shaft and a ring wheel of the planetary gearing, a last gear of the second gear train being rotatable on the shaft arrangement.

The rotative torque source may be connected to the sun gear of the planetary gearing.

The rotative torque source is preferably an electric motor. Due to the operating conditions of the torque vectoring device according to the invention, this electric motor may be operated by the ordinary electric system of the vehicle, and no increased voltage level is needed.

A reduction gearing may be arranged between the electric motor and the sun gear of the planetary gearing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in further detail under reference to the accompanying drawings, in which

FIG. 1 is an isometric view of a torque vectoring device according to the invention,

FIG. 2 is a section through the same device,

FIG. 3 is an isometric view of the same device from a slightly different angle compared to FIG. 1, and

FIG. 4 is a schematic illustration of a conventional differential with means for connecting a torque vectoring device according to the invention.

DESCRIPTION OF EMBODIMENTS

The torque vectoring device according to the invention is intended for a vehicle drive axle, comprising two half-axles connected to a conventional differential, to which drive torque is provided, for example via a cardan shaft in a rear wheel driven car. Each half-axle is provided with a wheel.

A shaft 1 is connected to one of the side gears of the differential (shown in FIG. 4). The shaft 1 is connected to a first driving half-axle (not shown) of the vehicle via for example a flange 2. A hollow shaft 3, through which the shaft 1 extends, is connected to the crown wheel or cage of the differential.

A first gear 4 is attached to the shaft 1 and is in engagement with a second gear 5. This in turn is in engagement with a third gear 6, connected via a shaft arrangement 7 to a planet carrier 8 for planet gears 9 in a planetary gearing 10. These gears 4-6 may together be called a first gear train.

As a modification, the first and third gears 4, 6 may be in direct engagement, omitting the second gear 5.

Correspondingly, a fourth gear 11 is attached to the hollow shaft 3 and is in engagement with a fifth gear 12. This in turn is in engagement with a sixth gear 13, rotatable on the shaft arrangement 7 and connected to a ring wheel 14 of the planetary gearing 10. These gears 11-13 may together be called a second gear train.

As a modification (in line with the modification mentioned above) the fourth and sixth gears 11, 13 may be in direct engagement, omitting the fifth gear 12.

A rotative torque source 15, preferably an electric motor, is connected to a sun gear 16 of the planetary gearing 10, for example via a reduction gearing, comprising a smaller seventh gear 17 on the shaft of the electric motor in engagement with a larger eight gear 18 on the shaft of the sun gear 16.

The different gear ratios of the planetary gearing 10 and the first-sixth gears 4-6, 11-13 are so calculated that when the shaft 1 and the hollow shaft 3 are rotating with the same speed, i.e. when the left and right wheels of the vehicle rotate with the same speed, the electric motor 15 does not operate or rotate. A rotational speed differential between the two wheels and thus between the shaft 1 and the hollow shaft 3 may then be counteracted by applying a torque by means of the electric motor 15. Alternatively, the electric motor 15 may be used for creating any desired rotational speed differential between the two wheels.

The arrangement and mounting of the torque vectoring device described under reference to FIGS. 1-3 is schematically illustrated in FIG. 4, depicting a conventional differential. Shown therein is the shaft 1, the flange 2 and the hollow shaft 3. The shaft 1 is connected to one side gear 20, whereas a second side gear 21 is connected to a second driving half-axle 22. The side gears 20, 22 are connected to planet gears 23 journalled in a cage 24 of the differential. Connected to the cage 25 is a crown wheel 26 in engagement with a pinion 27 on a cardan shaft 28.

An important advantage with the device according to the invention in comparison with other torque vectoring devices is that it can be built as a self-sustained unit, which can be installed in certain car models but not in others without any other modifications of the vehicle.

Modifications are possible within the scope of the appended claims.

Claims

1. A torque vectoring device for an existing arrangement of two half-axles of a vehicle drive axle, provided with a conventional differential, through which drive torque is supplied from a propulsion motor, comprisingthe torque vectoring device including a rotative torque source thereof is a self-sustained unit, connected to the existing arrangement only on one hand to one of the half-axles, on the other hand to the cage of the differential or to the other half-axle, andthe rotative torque source is connected via a differential transmission in the form of a planetary gearing to said one of the half-axles and the cage or the other half-axle,the arrangement being such that the rotative torque source stands still, when the rotational speed of said one of the half-axles and the cage or the other half-axle is the same.

2. A device according to claim 1, wherein a hollow shaft is connected to the cage of the differential and a shaft connected to said one of the half-axles extends through the hollow shaft.

3. A device according to claim 2, wherein a first gear train is arranged between the shaft and a shaft arrangement connected to a planet carrier of the planetary gearing, the planet carrier carrying planet gears, and a second gear train is arranged between the hollow shaft and a ring wheel of the planetary gearing, a last gear of the second gear train being rotatable on the shaft arrangement.

4. A device according to claim 3, wherein the rotative torque source is connected to the sun gear of the planetary gearing.

5. A device according to claim 4, wherein the rotative torque source is an electric motor.

6. A device according to claim 5, wherein a reduction gearing is arranged between the electric motor and the sun gear of the planetary gearing.