WO2017072329A1

WO2017072329A1 - Torque vectoring device

Info

Publication number: WO2017072329A1
Application number: PCT/EP2016/076144
Authority: WO
Inventors: Lars Severinsson; Gustaf LAGUNOFF; Kristoffer Nilsson
Original assignee: Borgwarner Sweden Ab
Priority date: 2015-10-30
Filing date: 2016-10-28
Publication date: 2017-05-04

Abstract

A torque vectoring device for a vehicle, comprising an electrical motor (110) being connected to a differential mechanism (20) via a transmission (120) comprising a first planetary gear set (140a) and a second planetary gear set (140b), wherein the electrical motor (110) is connected to the input shaft (100) and to an output shaft (130a) of the differential mechanism (20) for torque vectoring, wherein the input shaft (100) of the differential mechanism (20) is connected to a planet carrier of the first planetary gear set (140a) and an output shaft of the differential mechanism (20) is connected to a planet carrier of the second planetary gear set (140b), and wherein the planet gears of the first (140a) and second (140b) planetary gear sets are in engagement with a common gear (150).

Description

TORQUE VECTORING DEVICE

Technical Field

The present invention relates to a torque vectoring device for distributing torque to the wheels of a vehicle. More specifically, the invention relates to a torque vectoring device comprising an electrical motor for distributing torque between the wheels of a front and/or a rear axle of a vehicle.

Background

In modern four wheeled vehicles, such as cars, electrical motors may provide additional control of drive torque distribution by so called torque vectoring where the electrical motor controls a torque difference between output shafts from a differential. While the demands on safety systems in vehicles increase development of improved drive lines is necessary. As torque vectoring improves the driving characteristics of a vehicle, it is becoming increasingly more common that such a device is incorporated into the drive line of vehicle. To enable fitting of torque vectoring devices to more vehicles, the device needs to be improved by for instance reducing the required physical space of the device, by improving the durability and reducing the complexity of the device.

Summary

It is an object of the teaching herein to provide a torque vectoring device which can alleviate some of the problems with prior art. It is also an object of the invention to provide a vehicle axle comprising said torque vectoring device and a vehicle using said axle which is improved over prior art. This object is achieved by a concept having the features set forth in the appended independent claims; preferred embodiments thereof being defined in the related dependent claims.

In a first aspect of the teachings herein, a torque vectoring device for a vehicle is provided. The torque vectoring device comprises an electrical motor being connected to a differential mechanism via a transmission comprising a first planetary gear set and a second planetary gear set, wherein the electrical motor is connected to the input shaft and to an output shaft of the differential mechanism for torque vectoring. The input shaft of the differential mechanism is connected to a planet carrier of the first planetary gear set and an output shaft of the differential mechanism is connected to a planet carrier of the second planetary gear set, and the planet gears of the first and second planetary gear sets are in engagement with a common gear. The torque vectoring device presented is thus made particularly robust and the number of components in the device may be kept low while improving the functionality of the device. The device may be fitted to a front and/or a rear axle of a vehicle.

In one embodiment of the teachings herein, a torque vectoring device is provided wherein the electrical motor is driving the sun gear, directly or indirectly, of the first planetary gear set.

In one further embodiment, a torque vectoring device is provided further comprising a reduction gear arranged between the electrical motor and the first planetary gear set or a reduction gear arranged between the input shaft of the differential mechanism and the planet carrier of the first planetary gear set. The reduction gear allows the torque vectoring device to achieve beneficial gear ratios, which allows the electrical motor to operate at an effective RPM, providing higher efficiency and improved functionality of the torque vectoring device.

In one embodiment, the gear ratio of the reduction gear between the electrical motor and the first planetary gear set is in the range of about 3 : 1 to about 16: 1 , preferably about 5 : 1 to about 16: 1 and most preferred about 14: 1. The specified gear ratio of the reduction gear allows the electrical motor to operate at beneficial RPMs whilst providing torque variations between the output shafts of the differential mechanism. In one further embodiment, the gear ratio of the reduction gear between the input shaft of the differential mechanism and the planet carrier of the first planetary gear set is in the range of about 3 : 1 to 8: 1 and more preferably about 5 : 1. The specified reduction gear ratio of the reduction gear allows the electrical motor to operate at beneficial RPMs whilst providing torque variations between the output shafts of the differential mechanism.

According to one further embodiment, a torque vectoring device is provided wherein the planet gears of the first and second planetary gear sets each comprise a first and a second planet gear, the first and second planet gears of each planetary gear set being rotationally coupled and wherein the first planet gear of each planetary gear set is connected to a sun gear and the second planet gear is connected to a common gear. The first and second planet gears of each planetary gear set may also have differing diameters. As the first planet gear of each planetary gear set being in engagement with the sun gear is separate from the second planet gear of each planetary gear set being in engagement with the common gear, the number of engagements per planet gear is decreased. This may increase durability of the gears and thereby allow maintained functionality of the gears. In one embodiment, a torque vectoring device is provided wherein the sun gear of the second planetary gear set is fixed such that it does not rotate.

In one embodiment of the teachings herein, a torque vectoring device is provided wherein the rotational axes of the planet carriers of the first and the second planetary gear sets are essentially coaxial with the longitudinal axis of an output shaft of the differential mechanism connected to the planet carrier of the second planetary gear set. Thus is the torque vectoring device made compact, and occupies little space in the vehicle drive line.

In one further embodiment, a torque vectoring device is provided wherein the rotational axis of the electrical motor is essentially parallel and radially offset in relation to the longitudinal axis of an output shaft of the differential mechanism. The electrical motor may thus be a conventional electric motor arranged in the vicinity of the output shafts of the differential as long as the rotational axis of the electrical motor, or more specifically the axis of the output shaft of the electrical motor, is essentially parallel with an output shaft of the differential mechanism. The torque vectoring device may thereby be arranged in a flexible way thus fitting in more vehicles. For instance, the length of the electrical motor output axis and diameter of the thereto attached gearing may be adapted to allow the electrical motor to be placed at various positions in relation to the differential mechanism.

In one further embodiment of teachings herein, a torque vectoring device is provided wherein the rotational axis of the electrical motor is essentially coaxial with the longitudinal axis of an output shaft of the differential mechanism. By arranging the electrical motor around an output shaft of the differential, a compact and robust torque vectoring device is provided.

In one embodiment of the teachings herein, a torque vectoring device is provided wherein the rotational axis of the electrical motor is essentially coaxial with the longitudinal axis of an output shaft of the differential mechanism connected to the planet carrier of the second planetary gear set. The electrical motor may thus be arranged around the output shaft of the differential connected to the planet carrier of the second planetary gear set, thus providing an integrated and compact torque vectoring device.

In one embodiment of the teachings herein, a torque vectoring device is provided, wherein the rotational axis of the electrical motor is essentially coaxial with the longitudinal axis of an output shaft of the differential mechanism not connected to the planet carrier of the second planetary gear set. The electrical motor may thus be arranged around the output shaft of the differential not connected to the planet carrier of the second planetary gear set, thus providing an integrated and compact torque vectoring device.

According to a second aspect of the teachings herein, a vehicle axle is provided comprising a torque vectoring device according to the first aspect. The vehicle axle may be a front and/or a rear axle of a vehicle. A vehicle axle comprising a torque vectoring device according to the teachings herein is thus improved over prior art in that it provides improved durability, is more compact and is more robust.

In a third aspect of the teachings herein, a vehicle is provided comprising a vehicle axle according to the second aspect.

Brief Description of Drawings

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

Fig. 1 shows a schematic cross-sectional view of a torque vectoring device according to an embodiment,

Fig. 2 shows a schematic cross-sectional view of a torque vectoring device according to an embodiment,

Fig. 3 shows a schematic cross-sectional view of a torque vectoring device according to an embodiment,

Fig. 4 shows a schematic cross-sectional view of a torque vectoring device according to an embodiment,

Fig. 5 shows a schematic cross-sectional view of a torque vectoring device according to an embodiment,

Fig. 6 shows a schematic cross-sectional view of a torque vectoring device according to an embodiment, and

Fig. 7 shows a schematic cross-sectional view of a torque vectoring device according to an embodiment.

Detailed Description

In Fig. 1 , an embodiment of the torque vectoring device is shown. The torque vectoring device is adapted to be fitted to an axle, front and/or rear, in a vehicle. The device provides the possibility of vectoring torque between the wheels of the vehicle for improved driving characteristics and safety when operating the vehicle. For instance, the torque vectoring device may be arranged to intervene when it is detected that vehicle is in an over steer situation by altering the torque ratio between the wheels of the front and/or the wheels of the rear axle of the vehicle. A control unit (not shown) may be arranged to detect sensor signals from wheel sensors or turn angle sensors etc and determine that active torque vectoring is required to improve handling and thus controlling the torque vectoring device accordingly. The control unit may be arranged to control an electrical motor 1 10 of the torque vectoring device.

In an embodiment, the electrical motor 1 10 is a switched reluctance motor (SRM). Such a motor in principle can only supply a lower torque than asked for at a defect rotor position signal. At disruption of one or more phase conductors, total loss of the control electronics, or shortcut, an SRM motor will not supply any torque at all, which is of great advantage for the safety.

In an embodiment, the electrical motor 1 10 is an induction motor, e.g. such as a Squirrel-Cage Induction Motor (SCIM) or a Wound-Rotor Induction Motor (WRIM).

In an embodiment, the electrical motor 1 10 is a separately excited synchronous motor, also referred to as a wound rotor synchronous motor (WRSM).

In an embodiment, the electrical motor 1 10 is a variable reluctance motor or a synchronous reluctance motor.

In an embodiment, the electrical motor 1 10 is a permanent magnet motor.

In an embodiment, the electrical motor 1 10 is a brushless DC motor.

In an embodiment, the electrical motor 1 10 is a DC motor.

In an embodiment, the electrical motor 1 10 is arranged with or without rotor position sensor feedback.

The front axle may in some embodiments be connectable with the rear axle for allowing all wheel drive by means of the internal combustion engine (or any other propulsion unit normally driving the front axle). The connection may e.g. be implemented by means of a limited slip coupling and a cardan shaft and where the torque vectoring device provides a torque transfer between the rear wheels and/or the front wheels of the vehicle.

It should be understood that various driveline configurations are applicable for the torque vectoring device of the present application; e.g. the torque vectoring device could be used with an all-electric vehicle, it may be arranged on the front axle instead of the rear axle, etc. The presented embodiments have been developed and invented as solutions for predetermined conditions. For a typical passenger car, the maximum torque for torque vectoring is assumed to be 1200 Nm, and the desired gear reduction for torque vectoring is assumed to be approximately 20. Further assuming that the efficiency of the complete transmission (gears and differential) is 90%, while the efficiency of the gears only is 95%, the maximum torque of the electrical motor is calculated to be approximately 67 Nm. Below are a presented a number of embodiments all of which fall within the scope of the teachings herein. The device shown in Fig. 1 comprises an driving torque input shaft 100, which is connected to a primary engine. The primary engine may be an internal combustion engine or a hybrid engine or an electric motor which is the prime means for propulsion of the vehicle. The torque is transferred from the engine optionally via a transmission (not shown) to the input shaft 100 and onwards through the differential mechanism 20 to output shafts 130a, 130b of the differential mechanism 20. The output shafts 130a, 130b are connected to the front or rear wheels of the vehicle.

The electrical motor 1 10 is connected to the input shaft 100 and to an output shaft (i.e. one of the output shafts 130a, 130b of the differential 20) of the differential mechanism 20 via a transmission 120 comprising a first planetary gear set 140a and a second planetary gear set 140b. A torque difference (i.e. torque vectoring) between the output shafts 130a, 130b is thereby possible to be controlled to a certain extent by the electrical motor 1 10 by applying positive or negative torque in relation to the torque that it provided to the output shafts 130a, 130b through the differential 20. The input shaft 100 is connected to a planet carrier of the first planetary gear set 140a, via the gearing between the input shaft 100 and the ring gear of the differential 20. Hence, the planet carrier of the first planetary gear set 140a is directly connected with the differential cage. An output shaft 130a of the differential mechanism 20 is connected to a planet carrier of the second planetary gear set 140b thus rotating with the same rotational speed. It is to be understood that the transmission 120 may be arranged around either output shaft 130a, 130b and the planet carrier of the second planetary gear set 140b may thus be connected to either output shaft 130a, 130b.

The first 140a and second 140b planetary gear sets are further connected through their respective engagement (i.e. meshing) with a common gear 150. Said gear 150 may be a ring gear with internal teeth or another type of gear, the planetary gears of the first and the second planetary gear sets 140a, 140b are configured to mesh with teeth on axially opposing sides of the gear 150.

The transmission 120 is configured such that the above specified gear reduction is achieved. Generally, in all embodiments, the electrical motor 1 10 drives, directly or indirectly, the sun wheel of the first planetary gear set 140a. To achieve the above gear reduction in a beneficial manner, a reduction gear 140c may be arranged between the electrical motor 1 10 and the sun gear of the first planetary gear set 140a. In the specific embodiment in Fig. 1 , the reduction gear 140c comprises an intermediate gear between the electrical motor 1 10 and the sun gear of the first planetary gear set 140a. The intermediate gear comprises two rotationally coupled gears with different diameters, the gear with the larger diameter meshes with the gear on the output shaft of the electrical motor 1 10 and the gear with the smaller diameter meshes with the sun gear of the first planetary gear set 140a. The gear reduction ratio of the reduction gear 140c may be in the range of about 3 : 1 to about 16: 1 , preferably about 5 : 1 to about 16: 1 and most preferred about 14: 1. In the embodiment of Fig. 1 , a preferred gear reduction of the reduction gear 140c is approximately 14: 1 while the gear reduction of each of the first 140a and second 140b planetary gear sets is approximately 3 : 1. In the embodiment shown in Fig. 1 , the electrical motor 1 10 is arranged such that the rotational axis of the motor 1 10 is essentially parallel and radially offset in relation to an output shaft 130a, 130b of the differential 20. This may be beneficial e.g. since it allows large freedom of the positioning of the electrical motor 1 10, thus making it possible to fit the torque vectoring device to more vehicles without having to largely alter the design of the vehicle itself.

The sun gear of the second planetary gear set 140b is fixedly arranged such that it is not allowed to rotate, as illustrated in figs 1 to 7.

Turning to Fig. 2, an alternative embodiment of the torque vectoring device is shown. As large portions of the torque vectoring device are essentially the same for all embodiments, mainly the features which are specific for an embodiment will be described for each following embodiment. In the embodiment shown in Fig. 2, the electrical motor is arranged such that the rotational axis of the electrical motor 1 10 is essentially coaxial with the longitudinal axis of an output shaft 130b of the differential mechanism 20 not directly connected to the planet carrier of the second planetary gear set 140b. I.e., the stator and rotor of the electrical motor 1 10 are adapted to be arranged surrounding the output shaft 130b such that an integrated axle is formed. The electrical motor 1 10 is connected to the sun gear of the first planetary gear set 140a via a reduction gear 140c in a similar way as described in relation to the embodiment of Fig. 1. The reduction gear 140c has a reduction gear ratio in the range of approximately 6: 1 to 3 : 1 while the reduction ratio of each planetary gear set 140a, 140b is approximately 5 : 1.

In Fig. 3, a further embodiment is shown where the electrical motor 1 10 is positioned essentially parallel and radially offset in relation to an output shaft 130a, 130b of the differential 20. The electrical motor 1 10 is connected to the sun gear of the first planetary gear set 140a through a reduction gear 140c. In the specific embodiment in Fig. 3, the reduction gear 140c is constituted by a small diameter gear attached to the output shaft from the electrical motor 1 10 and a larger diameter gear rotationally coupled to the sun gear of the first planetary gear set 140a. The reduction gear 140c has a reduction gear ratio in the range of approximately 4: 1 to 3 : 1 while the reduction ratio of each planetary gear set 140a, 140b is approximately 5 : 1. Figs 4 to 7 show embodiments of the torque vectoring device in which the rotational axis of the electrical motor 1 10 is essentially coaxial with the longitudinal axis of an output shaft 130a of the differential mechanism 20 connected, directly or via a reduction gear 140c, to the planet carrier of the second planetary gear set 140b. The electrical motor 1 10 is arranged surrounding the output shaft 130a in a position between the differential 20 and the first 140a and second 140b planetary gear set. In the embodiment shown in Fig. 4, the electrical motor 1 10 is connected directly to the sun gear of the first planetary gear set 140a. In the embodiment of Fig. 4, the torque vectoring device further comprises a planetary (epicyclical) reduction gear 140d arranged between the input shaft of the differential mechanism 20 and the planet carrier of the first planetary gear set 140a. The planet carrier of the first planetary gear set 140a is rotationally coupled to the sun gear of the reduction gear 140d, a planet carrier of the reduction gear 140d is rotationally coupled to the input shaft 100 (via the gearing between the input shaft 100 and the ring gear of the differential 20) and the ring gear of the reduction gear 140d is rotationally fixed. The reduction gear ratio of the reduction gear 140d is approximately 5 : 1 and the reduction gear ratio of each planetary gear set 140a, 140d is approximately 5 : 1.

Fig. 5 shows an embodiment of the torque vectoring device wherein the planet gears of the first and second planetary gear sets 140a, 140b each comprise a first and a second planet gear, the first and second planet gears of each planetary gear set 140a,

140b being rotationally coupled and wherein the first planet gear of each planetary gear set 140a, 140b is connected to individual sun gears and the second planet gear of each planetary gear set 140a, 140b is connected to a common gear 150. The common gear 150 of the embodiment in Fig. 5 is a sun gear 150 with external teeth in two rows on axially opposite sides of the gear 150 for engagement with the second planet gear of each planetary gear set 140a, 140b. The first planet gear of each planetary gear set 140a, 140b may have a larger diameter than the second planet gear of each planetary gear set 140a, 140b. The gear ratio between the electrical motor and the input shaft 100 is approximately 20: 1.

Fig. 6 shows an embodiment comprising a planetary reduction gear 140c between the electrical motor 1 10 and the sun gear of the first planetary gear set 140a. The electrical motor 1 10 output shaft is rotationally coupled to the sun gear of reduction gear 140c, the planet carrier of the reduction gear 140c is rotationally coupled to the sun gear of the first planetary gear set 140a and the ring gear of the reduction gear 140c is rotationally fixed such that it does not rotate. The reduction gear ratio of the reduction gear 140c is approximately 5 : 1 and the reduction gear ratio of each planetary gear set 140a, 140d is approximately 5 : 1 such that the reduction gear ratio between the electrical motor and the input shaft 100 is approximately 25 : 1.

The embodiment of Fig. 7 is similar to that of Fig. 6; however no further reduction gear is presented except for the reduction of the first and second planetary gear sets 140a, 140b, and thus is the gear ratio of the first and second planetary gear sets 140a, 140b adapted accordingly. The gear ratio of the first and second planetary gear sets 140a, 140b are in the range of approximately 2,5 : 1 to approximately 9: 1 , preferably approximately 3 : 1.

It should be mentioned that the inventive concept is by no means limited to the embodiments described herein, and several modifications are feasible without departing from the scope of the invention as defined in the appended claims.

Claims

1. A torque vectoring device for a vehicle, comprising an electrical motor (1 10) being connected to a differential mechanism (20) via a transmission (120) comprising a first planetary gear set (140a) and a second planetary gear set (140b), wherein the electrical motor (1 10) is connected to the input shaft (100) and to an output shaft (130a) of the differential mechanism (20) for torque vectoring, wherein the input shaft (100) of the differential mechanism (20) is connected to a planet carrier of the first planetary gear set (140a) and an output shaft of the differential mechanism (20) is connected to a planet carrier of the second planetary gear set (140b), and wherein the planet gears of the first (140a) and second (140b) planetary gear sets are in engagement with a common gear (150).

2. The torque vectoring device according to claim 1 , wherein the electrical motor (1 10) is driving the sun gear of the first planetary gear set (140a).

3. The torque vectoring device according to any one of claims 1 to 2, further comprising a reduction gear (140c) arranged between the electrical motor (1 10) and the first planetary gear set (140a) or a reduction gear (140d) arranged between the input shaft of the differential mechanism (20) and the planet carrier of the first planetary gear set (140a).

4. The torque vectoring device according to claim 3, wherein the reduction gear ratio of the reduction gear (140c) between the electrical motor (1 10) and the first planetary gear set (140a) is in the range of about 3 : 1 to about 16: 1 , preferably about 5 : 1 to about 16: 1 and most preferred about 14: 1.

5. The torque vectoring device according to claim 4, wherein the reduction gear ratio of the reduction gear (140d) between the input shaft of the differential mechanism (20) and the planet carrier of the first planetary gear set (140a) is in the range of about 3 : 1 to 8: 1 and more preferably about 5 : 1.

6. The torque vectoring device according to any one of the preceding claims, wherein the planet gears of the first and second planetary gear sets (140a, 140b) each comprise a first and a second planet gear, the first and second planet gears of each planetary gear set (140a, 140b) being rotationally coupled and wherein the first planet gear of each planetary gear set (140a, 140b) is connected to a sun gear and the second planet gear is connected to a common gear (150).

7. The torque vectoring device according to any one of the preceding claims, wherein the sun gear of the second planetary gear set (140b) is fixed such that it does not rotate.

8. The torque vectoring device according to any one of the preceding claims, wherein the rotational axes of the planet carriers of the first (140a) and the second (140b) planetary gear sets are essentially coaxial with the longitudinal axis of an output shaft of the differential mechanism (20) connected to the planet carrier of the second planetary gear set (140b).

9. The torque vectoring device according to any one of the preceding claims, wherein the rotational axis of the electrical motor (1 10) is essentially parallel and radially offset in relation to the longitudinal axis of an output shaft of the differential mechanism (20).

10. The torque vectoring device according to any one of the preceding claims, wherein the rotational axis of the electrical motor (1 10) is essentially coaxial with the longitudinal axis of an output shaft (130a, 130b) of the differential mechanism (20).

1 1. The torque vectoring device according to any one of the preceding claims, wherein the rotational axis of the electrical motor (1 10) is essentially coaxial with the longitudinal axis of an output shaft (130a) of the differential mechanism (20) connected to the planet carrier of the second planetary gear set (140b).

12. The torque vectoring device according to any one of claims 1 to 10, wherein the rotational axis of the electrical motor (1 10) is essentially coaxial with the longitudinal axis of an output shaft (130b) of the differential mechanism (20) not connected to the planet carrier of the second planetary gear set (140b).

13. A vehicle axle, comprising a torque vectoring device (100) according to any one of the preceding claims.

14. A vehicle, comprising a vehicle axle according to claim 13.