FORM 2
THE PATENT ACT 1970 (39 of 1970)
&
The Patents Rules, 2 0 03 COMPLETE SPECIFICATION
(See Section 10, and rule 13)
1.TITLE OF INVENTION VEHICLE

2.APPLICANT(S)
a) Name
b) Nationality
c) Address

ZF FRIEDRICHSHAFEN AG GERMAN Company
88038 FRIEDRICHSHAFEN GERMANY

3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed : -

ENGLISH TRANSLATION VARIFICATION
CERTIFICATE u/r. 20(3)0?)
I, Mr. HIRAL CHANDRAKANT JOSHI, an authorized agent for the applicant, ZF FRIEDRICHSHAFEN AG do hereby verify that the content of English translated complete specification filed in pursuance of PCT International application No. PCT/DE2006/001650 thereof is correct and complete.

The invention relates to a vehicle with a vehicle structure, at least two wheels connected to the vehicle structure and displaceable with respect to it, a stabiliser comprising two legs mechanically connected to one another via a torsion spring, two actuators via which the legs are coupled with the wheels, and a control unit by means of which the coupling behaviour of the actuators can be varied.
Stabilisers are known from the prior art and a problem that is often associated with them is that they have fixedly predefined spring rates and can therefore not be adapted to different peripheral conditions, which has a detrimental effect on comfort. For this reason, stabilisers with controllable actuators have been developed, which are able to vary the behaviour of the stabiliser.
Patent specification DE 101 34 715 Al discloses a device for stabilising the rolling movement of vehicles, whereby a coupling bracket comprising a torsion-resistant support extending more or less transversely to the vehicle longitudinal direction with cantilever arms mounted on its ends connects two wheels to one another. Disposed respectively between the cantilever arms and the wheels is a spring and damper unit, which has a cylindrical housing in which a piston is guided in displacement. The piston divides the interior of the cylindrical housing into two chambers, in each of which a spring is disposed so that when the piston moves in the cylindrical housing, the piston has to work against the spring force of at least one of the two springs. Overflow valves which can be closed by valves are provided in the piston in order to provide a hydraulic connection between the two chambers in the cylindrical housing.
This subject matter is not comparable with a rotary stabiliser because the support disposed between the two cantilever arms is torsion-resistant. Furthermore, it is necessary to provide relatively large springs in order to guarantee roll stabilization, which means that the spring/damper unit overall is of a very large construction. In view of the problems of space intrinsic to smaller vehicles, for example passenger vehicles, such an arrangement is therefore somewhat unsuitable and is preferably used in the commercial vehicle sector, for example for trucks, where there is a relatively large


amount of space for the wheel suspension.
Patent specification EP 0 829 383 A2 discloses a stabiliser for a vehicle, which has a torsion spring disposed between two legs, and a first leg is connected to a first steering arm via a pendulum-type strut and the second leg is connected to a second steering arm via a hydraulic actuator. The hydraulic actuator has a cylinder connected to the second steering arm, in which a piston connected to the second leg can be guided in displacement. The piston divides the interior of the cylinder into two hydraulic chambers and a gas spring disposed in the cylinder adjoins the first of the hydraulic chambers. In order to compensate for the effect of the gas spring, an additional spring is provided in the second hydraulic chamber. A controllable valve is provided in the piston in order to hydraulically connect the two hydraulic chambers to one another or separate them from one another. When the valve is closed, the spring rate of the stabiliser is defined solely by the spring rate of the torsion spring, and when the valve is opened, the piston is able to move inside the cylinder so that the spring rate of the stabiliser is lower than the spring rate of the torsion spring.
Patent specification EP 0 270 327 Al discloses a stabiliser for a vehicle, which has two legs and a torsion spring disposed between them, and a first leg is connected to a first vehicle wheel by means of a pendulum-type strut and the second leg is connected to a second vehicle wheel via a controllable hydraulic damper and a bottom suspension arm. The hydraulic damper has a cylinder connected to the suspension arm and a piston guided in it in displacement, which is connected to the stabiliser via a piston rod. The piston therefore divides the interior of the cylinder into two hydraulic chambers, which are connected to a hydraulic control device. By means of the control device, a movement of the piston relative to the cylinder can be blocked or released and the piston is pushed in opposing directions by means of a pair of springs disposed in the hydraulic chambers. When the piston is in the blocked state, the spring rate of the stabiliser is defined by the spring rate of the torsion spring. When the piston is released on the other hand, it can be moved in the cylinder, which imparts a spring stiffness to the stabiliser that is lower than the spring stiffness of the torsion spring. It is also


possible to provide one of the control cylinders at each end of the stabiliser.
The two pre-tensioned springs are used to provide self-centring for the piston and when the control cylinder is in the expandable state, a torsional moment of the stabiliser does not act on the bottom arm. Accordingly, these springs are of a relatively small design and are not able afford any notable resistance to the rolling movements of the vehicle.
The objective of the invention is to improve a vehicle of the type outlined above, so that the stabiliser is able to assume at least two different spring rates and at the same time does not require a large amount of space.
This objective is achieved by the invention on the basis of a vehicle defined in claim 1. Preferred embodiments are defined in the dependent claims.
The vehicle proposed by the invention, in particular the automotive vehicle, has a vehicle structure, at least two wheels connected to the vehicle structure and displaceable with respect to it, a stabiliser comprising two legs mechanically connected to one another via a torsion spring, two actuators via which the legs are coupled with the wheels, and a control unit by means of which the coupling behaviour of the actuators can be varied, and an additional spring extends round the outside of each of the actuators respectively, and the legs are additionally connected to the wheels via the additional springs.
In the vehicle proposed by the invention, the additional springs may be of a sufficient size to assume the task of stabilising the rolling movements of the vehicle in conjunction with the torsion spring. Since the additional springs are also disposed around the outside of the actuators, the actuators may be of a relatively small design, thereby achieving an overall saving on space compared with systems in which the additional springs are integrated in the actuators, which therefore necessarily have to be of a larger construction than the additional springs. An actuator and a spring are also provided respectively on each leg, so that the system is able to centre itself without having to


provide two springs in each actuator for this purpose. However, particularly for compensating or centring purposes, it is possible to provide one or more springs in each actuator in addition, but, because of their small size, they contribute nothing or only slightly to the roll stabilising function. Since two actuators are provided, the maximum stroke per actuator can be reduced, preferably halved, resulting in a smaller height for the actuators than is the case with conventional systems in which only one actuator is provided for each stabiliser. The solution proposed by the invention therefore permits a space-saving design of a stabiliser, the spring rate of which can be varied by means of the control unit.
The actuators may be mechanically, electrically or pneumatically operated. However, the actuators are preferably hydraulically operated and are hydraulically connected to the control unit. This being the case, the control unit may have at least one or two valve blocks connected to the actuators, by means of which the actuators are hydraulically switched. In a first variant, a single valve block is hydraulically connected to the two actuators, whereas in a second variant, each actuator is hydraulically connected to a valve block respectively. The valve block or blocks can be electrically switched in particular, and are preferably connected to an electronic control system. To this end, each of the valve blocks may have an electrical interface, which permits an electrical connection to the electronic control system, for example by cable and/or plugs. The expression one valve block in this context should be understood as meaning in particular an arrangement of at least one or more hydraulic valves which are hydraulically connected to the respective actuator or to the actuators and are able to influence the damping and/or force-coupling behaviour of the actuator or actuators by hydraulic means. In this respect, the actuators are preferably provided in the form of hydraulic dampers, in particular as hydraulic linear dampers.
The actuators can preferably be switched to at least two states and when the respective actuator is in a first blocked state, a rigid connection is established between the respective leg and the respective wheel. In this situation, the additional springs can not be operated and the spring rate of the stabiliser is therefore determined solely by the


spring rate of the torsion spring. The first state is also referred to as the "hard" stage of the stabiliser. When the actuators are in a second, unblocked state, each actuator permits relative movement between the respective leg and the respective wheel with the additional spring interconnected so that the total spring stiffness of the stabiliser is reduced by the additional springs. In the unblocked state, the stabiliser therefore has a lower spring stiffness than in the blocked state due in particular to the serial connection of the two additional springs to the torsion spring. The second state is therefore also referred to as the "soft" stage of the stabiliser. In the unblocked state, the actuators preferably expend no or only a negligible force opposing a rolling movement of the vehicle. The additional springs may also each have a lower spring stiffness than the torsion spring, in which case the total spring rate of the stabiliser in the unblocked state is defined solely or essentially by the additional springs in a preferred embodiment of the invention. Alternatively or in addition, it may be that the actuators act as a damper in the unblocked state or in a third state and damp the rolling movements of the vehicle so that both or at least one of the legs is coupled with the respective wheel via a parallel connection of the damper and additional spring. Irrespective of this, each of the wheels is preferably also connected to the vehicle structure via a shock absorber and/or a vehicle spring or is spring-mounted on it in particular.
The blocked state can be switched on and off by means of the control unit or by means of the valve block or blocks in particular, and the switched-off, blocked state preferably corresponds to the unblocked state, fulfilling a failsafe function.
The stabiliser, in particular the torsion spring, is preferably mounted on the vehicle structure by means of at least one but preferably two stabiliser bearings so that it can rotate. A steering arm may also be connected between each of the wheels and the respective actuator as well as the respective additional spring by means of which the respective wheel is mounted on the vehicle structure so that it can pivot in particular. In this case, the legs are coupled with the wheels at least indirectly via the actuators and additional springs with the steering arms connected in between. Alternatively, however, the actuators and additional springs may also act directly on the wheel


support of the respective wheel.
In another embodiment of the invention, the vehicle proposed by the invention may have at least a third and a fourth wheel, which are connected to the vehicle structure and are able to move with respect to it. These wheels may also be connected to one another via a stabiliser, two actuators and two additional springs in the same manner as the two aforementioned wheels. This stabiliser, these actuators and these additional springs may also be configured in the same way as described above in connection with the other stabiliser, the other actuators and the other additional springs.
The stabiliser arrangement proposed by the invention with a comfortable "soft" stage and a switch able and/or automatically controllable additional stage, specifically has the following characterising features:
a) A stabiliser of a standard type, two actuators in a pendulum strut configuration and a hydraulic valve block.
b) The valve block contains a mechanical or electronic control system for either open/closed or an automatically controllable configuration.
c) The actuator components are identical components whether for the automatically controlled and non-automatically controlled configuration. A spring extending around the outside of the actuator corresponds to the soft stage of the stabiliser and is not pre-tensioned or is so only slightly.
d) The actuators are mounted on each side of the stabiliser (two per axle) in order to minimise the structural length. In addition, the spring extends around the outside of the actuator in order to minimise mounting space.
e) The actuator becomes shorter on actuation, which also has a positive effect on the mounting space needed.
In particular, the following advantages can be achieved as a result of the invention:
• uncoupling of rolling and spring travel,
• increased comfort when driving in a straight line and low transverse


accelerations by switching the stabiliser rate,
• increased comfort of the system in the "soft" position due to automatically controllable stabiliser damping rate,
• safety due to 50/50 stabiliser acting as a mechanical failsafe. The soft and/or hard stage is adjusted in connection with the front axle and the rear axle and permits the basic setting of the vehicle's intrinsic steering behaviour in the different system operating modes (including failsafe) based on a selection of the force elements-characteristics.
• higher system dynamics (adjustment dynamics) compared with electromechanical systems,
• consumes little or no additional energy.
The invention will be described below with reference to preferred embodiments illustrated in the appended drawings. Of the drawings:
Fig. 1: is a schematic diagram illustrating a first embodiment of the vehicle
proposed by the invention,
Fig. 2: is a schematic diagram illustrating a second embodiment of the vehicle
proposed by the invention,
Fig. 3: is a characteristic curve plotting the stabiliser moment as a function of the
stabiliser angle of twist, in the situation where the actuators are not under
automatic control,
Fig. 4: is a characteristic curve plotting the stabiliser moment as a function of the
stabiliser angle of twist in the situation where the actuators are under
automatic control,
Fig. 5: is a characteristic curve plotting the damping moment as a function of the
twisting speed of the stabiliser and
Fig. 6: is a schematic view in section showing one of the actuators illustrated in
Fig. 1.


Fig. 1 is a schematic view showing part of a vehicle 1, which has a front axle 2 with a left-hand wheel 3 and a right-hand wheel 4, and the two wheels 3, 4 are each displaceably and spring-mounted on a vehicle structure 7 via a wheel suspension 5 respectively 6. An additional spring 8 is connected to the left-hand wheel 3 respectively to the wheel suspension 5 and an additional spring 9 is connected to the right-hand wheel 4 respectively to the wheel suspension 6. The springs 8 and 9 are also connected to a stabiliser 10 comprising two legs 11 and 12 and a torsion spring 13 disposed between them. The two legs 11 and 12 extending at an angle with respect to the torsion spring 13 are non-rotatably connected to the ends of the torsion spring 13, which is mounted on the vehicle structure 7 by means of two stabiliser bearings 14 and 15 so that it can rotate about its longitudinal axis. Leg 11 is therefore connected to the left-hand wheel 3 with the additional spring 8 connected in between, whilst leg 12 is connected to the right-hand wheel 4 with the additional spring 9 connected in between. Leg 11 is also connected to the left hand wheel 3 respectively to the wheel suspension 5 via an actuator 16 and leg 12 is connected to the right-hand wheel 4 respectively to the wheel suspension 6 via an actuator 17. The hydraulic actuators 16 and 17 each have a cylinder 18 and a piston 41 mounted so as to be guided in it in displacement (see Fig. 6), which is connected to a piston rod 19 extending out from the respective cylinder 18. The piston rod 19 of actuator 16 is therefore connected to the leg 11, whereas the cylinder 18 of actuator 16 is connected to the left-hand wheel 3 respectively to the wheel suspension 5. The piston rod 19 of actuator 17 is also connected to the leg 12, whereas the cylinder 18 of actuator 17 is connected to the right-hand wheel 4 respectively to the wheel suspension 6.
The actuator 16 is connected via a hydraulic actuation line 20 to a control unit 21, which is also connected via a hydraulic actuation line 22 to the actuator 17. The control unit 21 has a centrally disposed hydraulic valve block 23.
When the actuators 16 and 17 are blocked, a relative movement of the piston rod 19 and cylinder 18 of the respective actuator is no longer possible, so that the additional springs 8 and 9 are bridged. In this situation, the spring rate of the stabiliser 10 is defined by


and corresponds to the spring rate of the torsion spring 13 and the stabiliser 10 therefore exhibits a "hard" behaviour.
When the actuators 16 and 17 are in an unblocked state, the piston rods 19 are displaceable relative to the respective cylinders 18 so that the additional springs 8 and 9 reduce the overall stiffness of the stabiliser 10. In this situation, the stabiliser 10 exhibits a "soft" behaviour. By means of the control system 21 respectively the valve block 23, it is possible to switch the actuators 16 and 17 from the blocked state to the unblocked state or vice versa.
Arrow 24 indicates the direction of travel or longitudinal axis of the vehicle 1. The torsion spring 13 extends perpendicular to the direction of travel, whereas the legs 11 and 12 extend substantially parallel with the direction of travel. Arrow 25 also indicates the inward and outward springing of the left-hand wheel 3, whilst arrow 26 indicates the inward and outward springing of the right-hand wheel 4. The stabiliser 10 does not come into play unless the inward springing movements 25 and 26 are different. In this situation, the torsion spring 13 and/or the additional springs 8 and 9 are actuated or tensed. However, if the inward and outward springing movements of the two wheels 3 and 4 are the same, the stabiliser 10 rotates in the stabiliser bearings 14 and 15 only, without one of the springs 8, 9,13 being tensed.
Fig. 2 is a schematic diagram illustrating a second embodiment of the vehicle 1 proposed by the invention, in which similar and identical features are denoted by the same reference numbers as those used to described the first embodiment. The mechanical structure of the second embodiment is essentially the same as the mechanical structure of the first embodiment, except that the hydraulic switching system of the actuators 16 and 17 is different. In the second embodiment, the control unit 21 has two valve blocks 27 and 28, valve block 27 being connected to the actuator 16 and valve block 28 being connected to the actuator 17. Accordingly, the valve blocks 27 and 28 are connected to the piston rods 19 of the respective actuators 16,17 and the piston rods 19 of the second embodiment may therefore be longer than the piston rods


of the first embodiment. The valve block 27 is also hydraulically connected to the actuator 16, whereas the valve block 28 is hydraulically connected to the actuator 17. This being the case, the actuator 16 can be controlled by the valve block 27, in particular can be switched to the blocked state and/or to the unblocked state, whilst the actuator 17 can be controlled in the same way by valve block 28. The valve blocks 27 and 28 are electrically switchable and each has an electrical interface 29 across which an electrical connection of the respective valve block 27, 28 to an electronic control system 30 is established via a cable 31.
Fig. 3 shows a characteristic curve of the stabiliser 10, plotting the stabiliser moment as a function of the stabiliser angle of twist. Curve 32 therefore represents the blocked state of the actuators 16, and 17, whilst curve 33 represents the unblocked state of the actuators 16 and 17. A maximum or minimum stroke of the actuators is reached at point 34, where the piston hits the cylinder (optionally with a buffer connected in between) in each actuator, for example, so that a further twisting of the stabiliser in the same direction corresponds to a rigid coupling in the blocked state. For this reason, curve 33 extends through a portion 35 at point 34 which extends parallel with curve 32. Point 34 can be adjusted by the configuration of the actuators 16 and 17. The behaviour illustrated in Fig. 3 corresponds to a system that is not under automatic control and it is only possible to switch backwards and forwards between the blocked and the unblocked state of the actuators 16,17. The region 39 between the two curves 32 and 33 is characterised by a gain in comfort.
Fig. 4 shows a characteristic curve of the stabiliser 10 plotting the stabiliser moment as a function of the stabiliser angle of twist. By contrast with Fig. 3, the actuators 16 and 17 shown in Fig. 4 are operated under the automatic control of the control unit 21 respectively the electric control system 30. Curve 32 in this instance is identical to curve 32 in Fig. 3 and corresponds to the blocked state of the actuators 16 and 17. Point 34, on the other hand, can now be automatically controlled and can be shifted along curve 33 and the distance 40 between the original point 36 and the value of the angle of twist at point 34 can be varied. Between the original point 36 and point 34, curve 33 initially


corresponds to curve 33 shown in Fig. 3. However, since the control range-switching point 34 can now be varied by the control unit 21, curve 33 may follow different courses in the direction of an increasing stabiliser angle of twist from point 34. This results in an automatically controllable roll damping for the vehicle axle 2 and a so-called "skyhook algorithm" may be used to control the degree of freedom of rolling. Range 39 in this case also represents the automatic control range.
Fig. 5 shows a characteristic curve of the stabiliser 10, plotting the damping moment of the stabiliser as a function of the twisting speed of the stabiliser. Curve 37 describes strong damping of the actuators, whilst curve 38 represents weak damping of the actuators. Damping in this case mans that the actuators are configured as hydraulic dampers, the damping behaviour of which can be controlled by means of the control unit 21. Curves 37 and 38 represent threshold lines of the damping and it is also possible to pre-set intermediate control positions.
Fig. 6 is a schematic view in section showing actuator 16 illustrated in Fig.l, in which the piston 41 divides the interior of the cylinder 18 into two hydraulic chambers 42 and 43, which are hydraulically connected to one another via a bypass 45 provided in the piston 41. The hydraulic chamber 42 is also hydraulically connected to the valve block 23 via the hydraulic line 20. The piston 41 is guided in the cylinder 18 in displacement and in the unblocked state is able to move in and opposite the direction of arrow 44, in which case hydraulic liquid (hydraulic fluid) is switched between the two chambers 42 and 43 via the bypass 45. Hydraulic fluid is also conveyed via line 20 to the valve block 23 or drawn from it due to the fact that a switch able valve 46 is provided and a hydraulic storage 47 which is able to take in and discharge the differential fluid (differential oil) when the valve 46 is in the opened state. This being the case, line 20 is connected to the storage 47 with valve 46 connected in between. In the blocked state, on the other hand, valve 46 is closed, which means that no differential fluid can be conveyed, as a result of which a movement of the piston 41 is blocked. Although not explicitly illustrated, actuator 17 is of the same construction as actuator 16.


List of reference numbers

1 Vehicle
2 Front axle
3 Left-hand wheel
4 Right-hand wheel
5 Wheel suspension
6 Wheel suspension
7 Vehicle structure
8 Additional spring
9 Additional spring
10 Stabiliser
11 Leg of the stabiliser
12 Leg of the stabiliser
13 Torsion spring of the stabiliser
14 Stabiliser bearing
15 Stabiliser bearing
16 Actuator
17 Actuator
18 Cylinder
19 Piston rod
20 Hydraulic actuation line
21 Control unit
22 Hydraulic actuation line
23 Valve block
24 Direction of travel
25 Inward and outward springing of the left-hand wheel
26 Inward and outward springing of the right-hand wheel
27 Valve block
28 Valve block
29 Electric interface


30 Electric control system
31 Cable
32 Curve
33 Curve
34 Point
35 Curve portion
36 Original point
37 Curve
38 Curve
39 Range
40 Distance
41 Piston
42 Hydraulic chamber
43 Hydraulic chamber
44 Arrow
45 Bypass
46 Switchable valve
47 Hydraulic storage

WE CLAIM:
1. Vehicle with a vehicle structure (7), at least two wheels (3, 4) connected to the vehicle structure (7) and displaceable with respect to it, a stabiliser (10) comprising two legs (11,12) mechanically connected to one another via a torsion spring (13), two actuators (16,17) via which the legs (11,12) are coupled with the wheels (3,4), and a control unit (21) by means of which the coupling behaviour of the actuators (16,17) can be varied, characterised in that an additional spring (8,9) respectively extends around the outside of each of the actuators (16,17) and the legs (11,12) are additionally connected to the wheels (3,4) via the additional springs (8, 9).
2. Vehicle as claimed in claim 1, characterised in that the actuators (16,17) can be hydraulically actuated and are hydraulically connected to the control unit (21).
3. Vehicle as claimed in claim 2, characterised in that the control unit (21) has a hydraulic valve block (23) which is hydraulically connected to both actuators (16, 17).
4. Vehicle as claimed in claim 2, characterised in that the control unit (21) has two valve blocks (27, 28), each of which is hydraulically connected to one of the actuators (16,17) respectively.
5. Vehicle as claimed in claim 3 or 4, characterised in that the valve block or blocks (23; 27,28) can be electrically controlled and are connected to an electric control system (30).
6. Vehicle as claimed in one of the preceding claims, characterised in that the actuators (16,17) are configured as hydraulic dampers.


7. Vehicle as claimed in claim 6, characterised in that each damper (16,17) has a cylinder (18) and a piston (41) which can be guided therein in displacement, which divides the interior of the cylinder (18) into two hydraulic chambers (42, 43) filled with hydraulic fluid, and the piston (41) is connected to a piston rod (19) extending out from the cylinder (18).
8. Vehicle as claimed in one of the preceding claims, characterised in that the wheels (3,4) are additionally spring-mounted on the vehicle structure (7).
Dated this 14th day of March, 2008


ABSTRACT
Vehicle with a vehicle structure (7), at least two wheels (3,4) connected to the vehicle structure (7) and displaceable with respect to it, a stabiliser (10) comprising two legs (11, 12) mechanically connected to one another via a torsion spring (13), two actuators (16, 17) via which the legs (11,12) are coupled with the wheels (3,4), and a control unit (21) by means of which the coupling behaviour of the actuators (16,17) can be varied, and an additional spring (8, 9) extends around the outside of each of the actuators (16,17) respectively, and the legs (11,12) are additionally connected to the wheels (3,4) via the additional springs (8, 9).
To,
The Controller of Patents,
The Patent Office,
Mumbai

7 I
14
(Fig. 1)