Propulsion system for all-wheel drive motor vehicles

Abstract

The invention relates to a propulsion system for all-wheel drive motor vehicles, having a device for propulsion distribution to the front and the rear differential which transmit the drive output to the wheels assigned at the time, and with a device for coupled, variable distribution of the propulsion forces in the transverse and longitudinal directions of the vehicle depending on the operating situation of the vehicle for influencing the driving behavior, especially for improving the driving agility and driving stability. In the process the rear differential (18) is combined with an overriding drive (22), by means of which the drive torques can be shifted to the rear wheels (20) in alternation in the transverse direction of the vehicle, the rpm ratio or rpm error being dictated by means of the overriding drive (22) at the design point so that at a given curve radius which is assigned to the design point and which does not correspond to the narrowest curve, a reversal of the direction of the rotational speed difference takes place and thus the torque is not shifted to the wheel on the outside of the curve. By means of the propulsion distribution device (24, 26; 44, 46; 52) the drive torques can be shifted in alternation between the front differential (14) and rear differential (18) in the longitudinal direction of the vehicle.

Description

Several embodiments of the invention will be explained below with further details. The drawings are schematic.

FIG. 1 shows a first propulsion system for an all-wheel drive vehicle, with a drive engine, a speed change gearbox, a front differential, a rear differential combined with an overriding drive, and a propulsion distribution device with an interaxle differential and hydraulically actuated multiple disk clutch,

FIG. 2 shows a second propulsion system as shown in FIG. 1 with a propulsion distribution device with two hydraulically actuated clutches,

FIG. 3 shows a third drive system as shown in FIG. 1, but with a self-locking Torsen differential as the propulsion distribution device, and

FIG. 4 shows a fourth propulsion system as shown in FIG. 1, with an auxiliary gear for producing a defined rotational speed difference.

Claims

1. Propulsion system for all-wheel drive motor vehicles, comprising a device for propulsion distribution to the front and the rear differential which transmit drive output to wheels assigned at the time with a device for coupled, variable distribution of propulsion forces in transverse and longitudinal directions of the vehicle depending on an operating situation of the vehicle for influencing driving behavior, such that a rear differential is combined with an overriding drive, by means of which drive torques can be shifted to rear wheels in alternation in the transverse direction of the vehicle, an rpm ratio or rpm error being dictated by means of the overriding drive at a design point so that at a given curve radius which is assigned to the design point and which does not correspond to a narrowest curve, a reversal of a direction of rotational speed difference takes place and thus torque is not shifted to a wheel on the outside of the curve, andthat by means of a propulsion distribution device the drive torques can be shifted in alternation between a front differential and the rear differential in the longitudinal direction of the vehicle.

2. The propulsion system according to claim 1, wherein the curve radius at the design point has a value between 10 and 25 m to which an rpm error in the range from 15 to 28% is assigned.

3. The propulsion system according to claim 1, wherein the propulsion distribution device is an interaxle differential which can preferably be locked by way of a clutch, with an asymmetrical basic distribution.

4. The propulsion system according to claim 3, wherein the propulsion distribution device is a lockable interaxle differential which, for a rear-emphasized basic distribution with increasing locking, routes the drive torque to the front differential or, for a front-emphasized basic distribution with increasing locking, routes the drive torque to the rear differential.

5. The propulsion system according to claim 4, wherein the propulsion distribution device is an interaxle differential which can be locked via a clutch and wherein the front differential and the rear differential have slightly different transmission ratios such that with increasing locking of the interaxle differential the drive torque is increasingly routed to the front differential for a rear-emphasized basic distribution of the interaxle differential.

6. The propulsion system according to claim 4, wherein the propulsion distribution device is an interaxle differential which can be locked via a clutch and wherein the front differential and the rear differential have slightly different transmission ratios such that with increasing locking of the interaxle differential the drive torque is increasingly routed to the rear differential for a front-emphasized basic distribution of the interaxle differential.

7. The propulsion system according to claim 3, wherein for essentially the same transmission ratios between the rear and the front differential, between the mid-differential of the clutch there is furthermore an auxiliary gear for producing a defined rotational speed difference in the clutch.

8. The propulsion system according to claim 7, wherein the counterstage is a ring gear stage or planetary gear or as a spur gear stage.

9. The propulsion system according to claim 3, wherein the clutch is a slip-controlled, multiple disk clutch, andwherein the lockable interaxle differential is an open differential.

10. The propulsion system according to claim 1, wherein the propulsion distribution device is formed by two clutches which are located in the drive line to the front differential and to the rear differential and by means of which the drive output to be transmitted at the time can be applied.

11. The propulsion system according to claim 10, wherein the two clutches are hydraulically activated multiple disk clutches which are located in a drive casing which is connected downstream of the change speed gear box.

12. The propulsion system according to claim 10, wherein at least one of the clutches is simultaneously designed as the starting clutch of the vehicle.

13. The propulsion system according to claim 1, wherein when driving through curves, upon detection of a vehicle oversteering tendency exceeding a predetermined value, the clutches can be controlled such that the drive torque of the rear differential is reduced and the drive torque of the front differential is increased.

14. The propulsion system according to claim 1, wherein when driving through curves, upon detection of a vehicle oversteering tendency exceeding a predetermined value, the clutches can be controlled such that the drive torque of the front differential is reduced and the drive torque of the rear differential is increased.

15. The propulsion system according to claim 1, wherein the propulsion distribution device is connected using control engineering to an electronic driving stability program or electronic antislip control of the vehicle.

16. The propulsion system according to claim 1, wherein the propulsion distribution device is a torque-sensing, self-locking differential, especially a self-locking Torsen differential.

17. The propulsion system according to claim 1, wherein the propulsion system is used in conjunction with longitudinal motorization.

18. A method for propelling an all wheel-drive motor vehicle the vehicle comprising a device for propulsion distribution to the front and the rear differential which transmit the drive output to the wheels assigned at the time, the method comprising: distributing propulsion forces in transverse and longitudinal directions of the vehicle depending on the operating situation of the vehicle for influencing the driving behavior, especially for improving the driving agility and driving stability such thatshifting torques to rear wheels of the vehicle in alternation in the transverse direction of the vehicle through a rear differential which is combined with an overriding drive,calculating an rpm ratio or an rpm error being through an overriding drive at a design point so that at a given curve radius which is assigned to the design point and which does not correspond to a narrowest curve, comprising reversing direction of rotational speed difference, and thus not shifting the torque to the wheel on the outside of the curve, andalternatively shifting drive torques between a front differential and a rear differential in the longitudinal direction of the vehicle through a propulsion distribution device the drive torques can be shifted.

19. A propulsion system for an all-wheel drive motor vehicle comprising: a drive engine;a change speed gearbox;a front differential for driving front wheels of the vehicle;a rear differential for driving rear wheels of the vehicle; andan overriding drive combined with the rear differential, comprising: a countershaft parallel to driven shafts of the rear differential, and driven via a first gear set by a differential case of the differential with a higher rpm than the driven shafts, wherein the countershaft is propulsion-connected via a second gear sets to the driven shafts the gears of the second gear set are floating gears which can be alternately coupled to the countershaft via hydraulically slip-controlled multiple disk clutches; anda propulsion distribution device between the front differential and the rear differential with an interaxle differential and a hydraulically actuated multiple disk clutch.