Technical field

The present invention relates to a torque vectoring device for a road vehicle. It also relates to a method of regulating the driving dynamics of the road vehicle by controlling the torque vectoring device.

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.

Torque vectoring devices may be used in either two-wheel drive vehicles or four-wheel drive vehicles, although the latter case may be regarded as more common. It can also be used for either rear or front drive shafts or in the cardan shaft for distributing torque between the front and rear drive shafts.

In order to obtain the desired result with regard to the driving dynamics, it may in certain situations be advantageous to provide a drive wheel with a positive torque in relation to the other drive wheel on the drive shaft. Such a positive torque may be obtained in a way known per se by a mechanical gear device for gearing-up or increasing the rotational speed of the drive shaft for the wheel in question by for example 10%.

Many examples of such mechanical gear devices are known. In a typical arrangement torque vectoring devices are arranged at either side of the central differential for the two drive shafts. A typical example is shown in WO2007/079956. The arrangement is expensive, heavy and is locked at a certain torque distribution. It is therefore advantageous to find solutions to the problem of having one torque vectoring device which is more compact and allows for further controllability.

The main object of the invention is to provide such a torque vectoring device which is as cheap and light-weight as possible without in any way impairing its reliability or effectiveness.

Summary

Accordingly, the present invention preferably seeks to mitigate, alleviate or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination and solves at least the above-mentioned problems by providing a device according to the appended claims.

It is thus an object of the invention to provide a torque vectoring device which overcomes the above mentioned problems.

According to an aspect of the invention the torque vectoring device is meant for a road vehicle and is adapted to selectively distribute torque to a first wheel shaft and a second wheel shaft and comprises a torque transferring device. The torque transferring device is further adapted to distribute torque between said first wheel shaft and second wheel shaft. Preferably, the torque transferring device is arranged between the first and second wheel shaft so as to allow torque distribution between said wheel shafts. The torque vectoring device may further comprise a control unit connected to the torque transferring device. Advantageously, the torque transferring device is a variator which is adapted to variably adjust the transmission ratio between said first and second wheel shaft, whereby the control unit is configured to based on at least one input signal variably adjust the transmission ratio of the variator. Thus, the torque transferring device may depending on the transmission ratio provide a torque vectoring effect between said first and second wheel shaft.

Hence, a more compact and light-weight torque vectoring device can be achieved since it does not require complex gear trains in order to provide the desired torque vectoring effect. Also, the torque vectoring device can be fitted in a simpler manner to an existing driveline.

According to a second aspect of the invention the first and second wheel shafts are connected to a differential encased in a differential housing which is connected to a drive pinion. Said drive pinion may as is conventional be connected to a prime mover of the road vehicle. Advantageously, the variator may be connected to the first wheel shaft and the differential housing or the second wheel shaft so as to be able to variably adjust the transmission ratio between said wheel shafts.

According to a third aspect of the invention the variator may be arranged coaxially between the first and second wheel shaft. Accordingly the variator is connected to a drive shaft which is connected to the prime mover of the road vehicle. Preferably, the variator is adapted to receive torque from said drive shaft and distribute it between the first and the second wheel shaft. Hence, a torque vectoring device replacing a conventional differential can be achieved, which enables a lighter and less complex driveline with torque vectoring capabilities.

According to another aspect of the invention the variator may be a mechanical variator, such as for example a toroidal traction drive. The variator may also be hydraulic variator or an electrical variator. Brief Description of the Drawings

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

Fig 1 is a schematical top view of a rear differential with a torque vectoring device according to a first embodiment the invention,

Fig. 2 is a schematical layout of a road vehicle with a rear differential with the torque vectoring device according to the first embodiment of the invention,

Fig. 3 is a schematical top view of a rear differential with a torque vectoring device according to a second embodiment of the invention,

Fig. 4 is a schematical layout of a road vehicle with a rear differential with the torque vectoring device according to the second embodiment of the invention,

Fig. 5 is a schematical top view of a a torque vectoring device according to a third embodiment of the invention,

Fig. 6 is a schematical layout of a road vehicle with the torque vectoring device according to the third embodiment of the invention,

Fig. 7 is a block diagram illustrating the method of controlling a torque vectoring device according to an embodiment of the invention, and

Fig. 8 is a schematic view of driveline configurations for use with a torque vectoring device according to various embodiments.

Detailed Description

The present invention relates to a torque vectoring device which comprises a torque transferring device arranged between the first wheel shaft and the second wheel shaft. Hence, the torque transferring device can be adapted to distribute torque between the wheel shafts.

In order to control when the re-distribution of torque will take place, the torque transferring device is connected to a control unit, which is configured to adjust the torque distribution between the wheel shafts by controlling the torque transferring device.

By using a conventional variator as a torque transferring device a more compact, light-weight torque vectoring device with increased controllability can be achieved. Variators enables stepless transmission by mechanical, hydraulic or electrical means by variably adjusting the gear ratio between input and output by changing the transmission ratio of the comprised elements therein.

In the present invention a controller is connected to the variator and is configured to, based on at least one input signal, variably adjust the gear ratio of the variator, whereby the variator is arranged so as to variably adjust the gear ratio between said first and second wheel shaft. Depending on the provided gear ratio a torque vectoring effect can be provided between the wheel shafts. The arrangement of the variator in the torque vectoring device between the first and second wheel shaft allows the variator to alter and control the gear ratio between the first and second wheel shaft. This in turn means that the torque provided to each wheel shaft can be altered and controlled by controlling the variator.

Variators are sometimes used as a mean to control torque distribution between shafts in for example gear boxes. In some cases the variator is coupled to a torque input and a torque output whereby the variator is able to receive torque via the input and variably adjust the provided output torque by variably adjusting the gearratio between the transmission elements included therein.

For illustrating the function of the torque transferring device in below discussed figures 1-6 a mechanical variator i.e. a toroidal traction device has been shown. As is easily realized by a person skilled in the arts the mechanical variator can be replaced with a hydraulic variator controlled by a hydraulic control unit or an electrical variator controlled by an electrical control unit.

Fig. 1 very schematically illustrates a top view of a torque vectoring device 100 implemented in a vehicle with a differential 120. The differential 120 is a conventional differential which receives a drive shaft 192, i.e. a cardan shaft.

Fig. 2 depicts said torque vectoring device 100 implemented in a road vehicle which in this example has a rear differential 120. The drive shaft 192 is connected to the prime mover 191 of the road vehicle and is adapted to transfer torque from the prime mover 191 to the differential 120. As is conventional for a differential gearing, the differential 120 is arranged between a first wheel shaft 101 with a first wheel 103 and a second wheel shaft 102 with a second wheel 104. According to this example the first 101 and second 102 wheel shafts are driven rear wheel shafts.

Referring again to Fig. 1 and 2, the differential 120 is encased by a differential housing 123. The drive shaft 192 is provided with a pinion drive gear 121 in gear engagement with a crown wheel 122. The crown wheel 122 is attached to the differential housing 123. The rear drive shafts, i.e. the first wheel shaft 101 and the second wheel shaft 102 extend into the differential housing 123 and are there provided with conical drive gears in gear engagement with conical differential gears rotatably journal ed in the differential housing 123. This design is well known for any person skilled in the art of car design. The differential may alternatively have another design.

The torque vectoring device 100 comprises a torque transferring device in the form of a variator 110 which is connected to the first wheel shaft 101 and the differential housing 123. By being connected to the differential housing 123 and the first wheel shaft 101, the variator 1 10 can variably adjust the transmission ratio between the first wheel shaft 101 and the second wheel shaft 102 which receives drive torque from the differential housing 123. The torque vectoring device 100 comprises a controller 160 which is configured to control the variator 110 so as to control the variable adjustment of the gear rate therein. Hence, a torque vectoring effect between the first 101 and second 102 wheel shaft and thus torque vectoring between the first 103 and second 104 driven wheels can be achieved by controlling the variator 1 10 via the controller 160.

As seen in Fig.1 the variator 1 10 is connected to the first wheel shaft 101 via a first gear train 140 which in this example comprises at least a first gear 141 and a second gear 142. Advantageously, the first gear 141 is attached to the first wheel shaft 101 while the second gear 142 is connected to the variator 1 10. Accordingly, the variator 1 10 has a torque output which is connected to the first wheel shaft 101 via the first gear train 140 and a torque input which is connected to the differential housing 123.

The variator 140 may be connected to the differential housing 123 via a belt or a chain drive 195 and a variator shaft 106. The chain drive includes at least a first 196 and a second 197 transmission element joined by a belt or a chain adapted to transfer torque between said transmission elements. The first transmission element 196 is connected to the variator shaft 106 which in turn is connected to the torque input of the variator 1 10. Preferably, the transmission element 197 is connected to the differential housing 123. As a result, a torque vectoring effect between the first 101 and second 102 wheel shafts can be provided by means of the variator 1 10 by variably adjusting the gear ratio of the variator 110 and consequently between the first 101 and second 102 wheel shafts.

As seen in Fig. l the variator shaft 106 may be arranged substantially parallel to the first 101 and second 102 wheel shafts, thus a more compact torque vectoring device which takes up less space on the vehicle can be achieved.

The manner of which the variator 1 10 is connected to the differential housing

123 is not limited to a belt or a chain drive; a gear train could also be used.

The variator 110 may also be connected with the first wheel shaft 101 via a first clutch 131. Said clutch may be a disconnect clutch such as for example a dog clutch, which enables complete disconnection of the torque vectoring device when torque vectoring is not desired. Such configuration thus results in reduced losses due to the friction of the components of said torque vectoring device. Said clutch may also be a wet disc clutch, which gives further possibilities to control the torque distribution between the driven wheel shafts by controlling the torque provided by the torque output of the variator 1 10.

The variator 1 10 may also be connected to a ground 190 via a freewheeling clutch 133 adapted to prevent the variator 110 from rotating in one direction. Hence, no torque vectoring can be achieved when the road vehicle reverses.

Fig. 3 very schematically illustrates a top view of a torque vectoring device 200 implemented in a vehicle with a differential 220. The differential 220 is a conventional differential which receives a drive shaft 292, i.e. a cardan shaft.

Fig. 4 depicts said torque vectoring device 200 implemented in a road vehicle which in this example has a rear differential 220. The drive shaft 292 is connected to the prime mover 291 of the road vehicle and is adapted to transfer torque from the prime mover 291 to the differential 220. As is conventional for a differential gearing, the differential 220 is arranged between a first wheel shaft 201 with a first wheel 203 and a second wheel shaft 202 with a second wheel 204. According to this example the first 203 and second 204 wheel shafts are driven rear wheel shafts.

The torque vectoring device 200 is connected to a differential arrangement identical to the one described in Fig. 1 and Fig. 2.

The variator 210 is connected to the first wheel shaft 201 as well as the second wheel shaft 202. Hence, the variator 210 can variably adjust the transmission ratio between the first wheel shaft 201 and the second wheel shaft 202 directly. The torque vectoring device 200 comprises a controller 260 which is configured to control the variator 210 so as to control the variable adjustment of the transmission rate therein. Hence, a torque vectoring effect between the first 201 and second 202 wheel shafts can be achieved by controlling the variator 210 with the controller 260.

As seen in Fig.3 the variator 210 is connected to the first wheel shaft 201 in arrangement similar to the one disclosed in Fig. 1, i.e. via a first gear train 240 which in this example comprises at least of a first gear 241 and a second gear 242.

Advantageously, the first gear 241 is attached to the first wheel shaft 201 and the second gear 242 is connected to the variator 210. Accordingly, the variator 210 has an output which is connected to the first wheel shaft 201 via the first gear train 240 and a second output which is connected to the second wheel shaft 202.

The variator 240 may be connected to the second wheel shaft 202 via a belt or a chain drive 295 and a variator shaft 206. The chain drive 295 includes at least a first 296 and a second 297 transmission element joined by a belt or a chain adapted to transfer torque between said transmission elements. The first transmission element 296 is connected to the variator shaft 206 which in turn is connected to the one output of the variator 210. The transmission element 297 is connected to the second wheel shaft 202. In some cases the first transmission element 296 may be attached to the variator shaft 206 while the second transmission element 297 is attached to second wheel shaft 202. As a result, a torque vectoring effect between the first 201 and second 202 wheel shafts can be provided by means of the variator 210.

The manner of which the variator 210 is connected to the second wheel shaft

202 is not limited to a belt or a chain drive; a gear train could also be used.

The variator 210 may also be connected with the first wheel shaft 201 via a first clutch 231. Said clutch may be a disconnect clutch such as for example a dog clutch, which enables disconnection of the torque vectoring device when torque vectoring is not desired and thus results in lesser losses due to the friction of the components of said torque vectoring device. Said clutch may also be a wet disc clutch, which gives further means to control the variator 210.

The variator 210 may also be connected to a ground 290 via a freewheeling clutch 233 adapted to prevent the variator 210 from outputting torque in one rotary direction. Hence, no torque vectoring can be activated when the road vehicle reverses.

Fig. 5 very schematically illustrates a top view of a torque vectoring device 300 according to another embodiment being implemented in a road vehicle. In this example the differential gearings are replaced by the torque vectoring device 300 which is connected to a drive shaft 392, i.e. a cardan shaft.

Fig. 6 depicts said torque vectoring device 300 implemented in a road vehicle.

The drive shaft 392 is connected to the prime mover 391 of the road vehicle and is adapted to transfer torque from the prime mover 391 to the torque transferring device i.e. the variator 310. The variator 310 is arranged between a first wheel shaft 301 with a first wheel 303 and a second wheel shaft 302 with a second wheel 304. According to this example the first 303 and second 304 wheel shafts are driven rear wheel shafts.

Referring again to Fig. 5 and 6, the variator 310 is encased by a variator housing 367. The drive shaft 392 is provided with a pinion drive gear 321 in gear engagement with a crown wheel 322. The crown wheel 322 is attached to the variator housing 367. The rear drive shafts e.g the first wheel shaft 301 and the second wheel shaft 302 extend into the variator housing 367 and are there connected to the variator 310.

The variator 310 is according to this embodiment arranged so as to be connected to the drive shaft 392 which transfers torque from the prime mover 391. This can be achieved in several ways. For example, the variator 310 may be directly connected to the drive shaft 392 via torque input of the variator. Two separarate torque outputs of the variator 310 may be directly connected with respective wheel shaft 301 and 302. Thus, a compact torque vectoring device can be achieved. However it may also be advantageous to provide a solution which enables the torque vectoring device to be implemented in a conventional driven axle arrangement. Such a torque vectoring device is easier to assemble on an existing road vehicle. An example of a torque vectoring device according to that concept is shown in Figs. 5 and 6.

As seen in Fig. 5 the drive shaft 392 is connected to variator 310 which in turn is coaxially arranged between the first wheel shaft 301 and the second wheel shaft 302. The variator 310 replaces in this example a conventional differential of the road vehicle by receiving torque from the driven pinion 321 to a torque input of said variator 310 and by the first wheel shaft 301 being connected to a first torque output of the variator 310 and the second wheel shaft being connected to a second torque output of the variator 310. The variator 310 may thus work as a traditional differential by variable adjustment of the transmission ratio of the first and second wheel shaft by controlling of the variator 310.

Additionally the torque vectoring device including said variator 310 also provides additional means to variably adjust the transmission ratio between the first 301 and the second 302 wheel shafts and therefore the torque provided to said shafts.

As seen in Fig. 6 the variator 310 may be arranged coaxially between the first 301 and the second 302 wheel shaft via clutches 331 and 332, the first wheel shaft 301 being connected to the variator 310 via a first clutch 331 and/or the second wheel shaft 302 being connected to the variator via a second clutch 332. Advantageously, said clutches may be lamella cluthes, which provides additional means for the torque provided to each wheel shaft to be further controlled thus enhancing the achieved torque vectoring.

The variator 310 may also be connected to the drive shaft via a third clutch 333 which may be a wet disc clutch or a shut-off clutch which enables controllability of the torque provided to variator 310 depending on the desired driving characteristic. It may also be advantageous to, in a four wheel driven road vehicle, occasionally completely decouple the driven rear shaft to reduce losses due to the friction of the gearings.

A method of controlling the driving dynamics of a vehicle by controlling the torque vectoring device 100, 200, 300 is described in Fig. 7. The method comprises the controller 160, 260, 360 receiving 401 at least one input signal representing a respective current driving characteristic for the road vehicle. The at least one input signal could for example be indicative of the traction of the driven wheels of the road vehicle or direct instructions from the driver of the road vehicle. Said at least one input signal is then analyzed 402 so as to determine whether a change in the driving dynamics is required. Such an event could for example be if one of the driven wheels have lost traction and is spinning. If it is determined that a change in the driving dynamics is required, the torque vectoring device 100, 200, 300 and the variator 1 10, 220, 320 is controlled 403 so as to adjust the gear ratio between said first 101, 201, 301 and second 101, 201, 301 wheel shafts so as to provide a torque vectoring effect between the first 101, 201, 301 and second 101, 201, 301 wheel shafts.

Now turning to Fig. 8 various vehicle driveline configurations are shown, which drivelines are provided with a torque vectoring device 100, 200, 300. In these embodiments, the vehicle has a front axle being connected to a rear axle, and a torque vectoring device 100, 200, 300. Starting in the uppermost embodiment of Fig. 8, the front axle is driven by means of a transmission, and the rear axle is driven by means of an electrical motor. The torque vectoring device 100 ,200, 300 is arranged at the rear axle. In the next embodiment, a similar configuration is shown but here the rear axle is driven by means of a transmission, and the front axle is driven by means of an electrical motor. Consequently, the torque vectoring device 100, 200, 300 is arranged at the front axle. The next two embodiments show configurations where the front axle or the rear axle is driven by an electrical motor, wherein the torque vectoring device 100, 200, 300 is arranged at the driven axle. As a further example, the bottom illustration shows a configuration in which the front axle and the rear axle are driven by electrical motors. Hence, the torque vectoring device may be incorporated in electrical axles.

Although the present invention has been described above with reference to specific embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the invention is limited only by the accompanying claims.