WO2008156386A1

WO2008156386A1 - Method and a system for stabilizing a vehicle

Info

Publication number: WO2008156386A1
Application number: PCT/SE2007/000608
Authority: WO
Inventors: Benny Liljeblad; Hayder Wokil; Ulf GRANÄNG
Original assignee: Volvo Lastvagnar Ab
Priority date: 2007-06-21
Filing date: 2007-06-21
Publication date: 2008-12-24

Abstract

The present invention relates to a method for stabilising a vehicle (1) comprising a driver's cab (2) and an equipment (7) which, in use, causes movement of the total centre of gravity of the vehicle (1), comprising - when using said equipment (7), causing a displacement the cab (2) so as to counteract the movement of the total centre of gravity of the vehicle (1) caused by the equipment. (7). The invention also relates to a system for performing such a method, and to a vehicle incorporating such a system.

Description

Method and a system for stabilizing a vehicle

TECHNICAL FIELD

The invention relates to the field of vehicles having equipment which, in use, causes movement of the total centre of gravity of the vehicle, such as e.g. trucks, refuse collection trucks, mixer trucks, or the like, which have load carriers which may be tipped in relation to the vehicle chassis so as to unload the content thereof, concrete pumps, sky lifts etc.

BACKGROUND OF THE INVENTION

Vehicles having tillable load carriers, such as trucks, refuse collection trucks, mixer trucks or the like, which have load carriers which may be tipped in relation to the vehicle chassis so as to unload the content thereof are widely spread. The load carrier of this type of vehicle may be tilted, usually backward in relation to the vehicle, so as to unload the content of the load carrier.

If the vehicle is heavily loaded, and the load carrier is tilted to a relatively acute angle in order to unload the contents thereof, there is an issue that the vehicle may, during certain circumstances become somewhat instable. This is particularly the case if the vehicle is placed on uneven or sloping ground.

The condition of the ground upon which the vehicle is placed is also of concern in this context. If the ground is relatively soft, and in particular if the softness of the ground is very varying, an unfavourable tilted position of the vehicle may result. This could add on to the instability caused by e.g. a tipping situation as mentioned above.

Similar problems may arise with other equipment than tippable load carriers, but which also may cause a movement of the centre of gravity of the vehicle when in use. Such equipment is for example concrete pumps or sky lifts.

The object of the invention is to improve the stability of a vehicle when an equipment causing movement of the centre of gravity of the vehicle is used, so as to enable safe use of the equipment in an increased number of situations, such as e.g. on sloping ground. It is an additional object of the invention to improve the stability of the vehicle in an efficient and cost-effective manner.

It is an additional object of the invention to improve the stability of the vehicle without adding substantial weight to the vehicle.

SUMMARY OF THE INVENTION

At least one of the above-mentioned objects is achieved by a method for stabilising a vehicle comprising a driver's cab and an equipment which, in use, causes movement of the total centre of gravity of the vehicle,, comprising when using said equipment, causing a displacement of the cab so as to counteract the movement of the total centre of gravity of the vehicle caused by the use of the equipment.

According to the method, the cab is used as a counter-acting element, so as to balance the movement of the total centre of gravity of the vehicle caused by the use of the equipment. Generally, the vehicle is optimised for the centre of gravity being as when in a neutral or normal position. Use of certain equipment may cause movement of the total centre of gravity of the vehicle, such as use of a sky lift, a concrete pump or tipping of a tippable load carrier.

The displacement of the cab functions so as to counter-act the movement of the centre of gravity of the vehicle. This increases the stability of the vehicle, as it brings the centre of gravity of the vehicle closer to the neutral or normal position. It is understood that it is not necessary to fully counteract the effect of the equipment. However, also a relatively small displacement of the cab will have the advantageous effect of diminishing the movement of the centre of gravity, which will enhance the stability of the vehicle during use of the equipment.

It is understood that it is not necessary to displace the cab as soon as the relevant equipment is used. Instead, it may be determined during which circumstances the use of the equipment results in a movement of the centre of gravity of the vehicle which is large enough to motivate a counter-acting displacement of the cab. Advantageously, the method may be used where the equipment causing movement of the centre of gravity of the vehicle is a tippable load carrier. The tipping of the load carrier, in particular during the first phase of the tipping, before the content of the load carrier has been unloaded, will dislocate the centre of gravity of the entire vehicle as the mass of the load carrier plus the load is moved from a normal position to a tipping position. This means that the centre of gravity of the vehicle is moved from the optimal position corresponding to a normal position to a less than optimal position.

As mentioned previously, it is not necessary to completely counteract the movement of the centre of gravity as caused by the tippable load carrier. In particular when the load carrier is heavily loaded, and before the load has become unloaded, the total mass of the load carrier and the load may be substantially larger than the mass of the cab. Hence, it is not realistic to displace the cab to such an extent that it would completely neutralise the effect of the movement of the load carrier plus the load on the centre of gravity of the vehicle.

Advantageously, the displacement of the cab includes lowering the cab. As the use of most types of equipment will generally imply that weight is transferred upwardly in relation to the chassis of the vehicle, lowering the cab towards the chassis of the vehicle will counteract the movement of the total centre of gravity of the vehicle caused by the use of said equipment.

In a preferred embodiment, the cab may be lowered so as to rest on lower support means, such as the lower bumper stoppers or the like. This position has the additional advantage that, as the dampening effect of any dampers provided between the cab and the frame is out of play when the cab rests solidly on the lower bumper stoppers, the driver will more easily sense if the vehicle is close to tipping over.

Another advantageous way of counteracting the movement of the total centre of gravity includes tilting the cab in a forward direction in relation to the vehicle. This would naturally counteract the backward tilt of the load carrier. Tilting of the cab in the forward direction may be used as a single measure or advantageously in combination with the above- mentioned lowering of the cab. Further, the displacement of the cab may advantageously include tilting the cab in a sideway direction. Sideway tilting may be particularly advantageous if the vehicle is positioned on sideway leaning ground when the content of the load carrier is to be emptied. Sideway tilting may optionally be combined with forward tilting and/or lowering of the cab.

Advantageously, the displacement of the cab may be created using the suspension means provided for suspending the cab to the chassis of the vehicle. This is advantageous since the suspension means already provided at the vehicle may be used, which is cost and weight efficient. Hence, no additional displacement means have to be arranged between the chassis and the vehicle, besides the necessary suspension.

Preferably, the method comprises controlling at least two suspension means being provided between the chassis of the vehicle and the cab. With two suspension means, forward and/or sideways tilt may be accomplished.

More preferably, the method comprises controlling at least four suspension means being provided between the chassis of the vehicle and the cab. With four suspension means, advantageously positioned in the vicinity of each comer of the cab, the displacement of the cab may virtually be controlled completely as desired in order to counteract the movement of the vehicle's centre of gravity.

Advantageously, the suspension means form part of the vibration damping system of the cab. The vibration damping system is generally suitable for control as there is a certain freedom of movement of the cab inherent in the system.

Preferably, the suspension means comprises air springs which may be controlled so as to displace the cab. In this case, the displacement may be controlled by controlling the pressure in said air springs.

Advantageously, the displacement of the cab may be automatically initiated upon use of the equipment. In a rather simple embodiment, the displacement of the cab may be readily activated upon use of the equipment. In this case, the displacement may even be a standard displacement, such as a forward tilt of the cab, which is or can be arranged to be synchronised with the use of the equipment, e.g. with backward tilting of the load carrier.

In more sophisticated embodiments, the displacement of the cab may be automatically controlled using the output from at least one inclination sensor. For example, an inclination sensor may be provided at the load carrier, and the output thereof may be used so as to synchronise the tilting of the cab in time and in direction with the tilting of the load carrier. Alternatively, or in combination with such a sensor, an inclination sensor may be provided at the vehicle chassis, so as to take other parameters such as whether the vehicle is parked on sloping ground into account.

In a second aspect the invention relates to a system for stabilising a vehicle in accordance with the method as described above. The invention also relates to a vehicle comprising such a system.

Other features and advantages of the present invention will appear fro the following description of preferred embodiments thereof which are to be understood as non-limitative examples only.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is made to the appended drawings wherein:

Fig. 1 is a schematic side view of a vehicle having a tiltable load carrier and in which a system for performing an embodiment of a method is installed. Fig. 2 is a schematic side view of the vehicle of Fig. 1 when the load carrier is tilted and the cab is displaced in accordance with a first embodiment of the method.

Fig. 3 is a schematic side view of the vehicle of Fig. 2 when the load carrier is tilted and the cab is displaced in accordance with a second embodiment of the invention.

Fig. 4 is a block diagram illustrating an embodiment of control of the suspension means of the vehicle of Fig. 1. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Fig. 1 is a schematic side view of a vehicle 1 having a tiltable load carrier 7, in a neutral or driving position where the load carrier 7 is resting in parallel with the vehicle frame 4. The vehicle cab 2 is also in an initial position, suspended to the frame 4.

As is conventional in the art, the vehicle cab 2 is suspended using suspension means. The suspension means are usually combined with some type of vibration damping system, so as to dampen vibrations from the frame 4 to the cab 2. Dampening means may include hydraulic, mechanic and pneumatic dampening.

For the method of the invention, it is generally advantageous if the dampening is accomplished by active control of the suspension means, which control may in this case be used also for the purpose of the method for stabilization of the vehicle.

Fig. 2 illustrates the vehicle 1 in a first tipping position, where the load carrier 7 is tilted backwards so as to allow tipping of the contents thereof. It is understood, that in this position, the total centre of gravity of the vehicle 1 is dislocated as compared to the initial position in Fig. 1. To counteract the movement of the total centre of gravity, in the illustrated embodiment the cab 2 is displaced in that it is lowered with respect to the initial position in Fig. Un a lowermost position, the cab 2 may advantageously rest on bumper stoppers provided as a part of the vibration dampening system of the suspension of the cab 2.

Fig. 3 illustrates the vehicle 1 in a tipping position, where again the load carrier 7 is tilted backwards so as to allow tipping of the contests thereof. In this embodiment, the cab 2 is tilted forwardly so as to counteract the movement of the total centre of gravity caused by the backward tilting of the load carrier 7.

It is understood that, although not illustrated herein, the cab may alternatively be tilted sideways. As previously mentioned, this is believed to be particularly advantageous if the vehicle is positioned on sloping ground. Sideways tilting may be performed as a single measure or in combination with lowering and/or forward tilting. Although not illustrated in Figs. 1 to 3, it is readily understood that the cab 2 is attached to the frame 4 via suspension means. Further, the displacement of the cab 2 in relation to the frame 4 is controlled using such suspension means.

There are several existing suspension and/or damping systems that may be used to perform the desired displacement of the cab is adequately controlled. See e.g. WO 2004/018243 describing a suspension system including a strut module having a strut, and air spring and a control module, US 2005/0274557 or EP 1 584 545. In particular, it is preferred to use an actively controlled air spring suspension system.

Systems for tilting a cab have previously been proposed, such as US 6 540 283. However, in prior systems, the tilting is generally performed to allow for inspection of the engine compartment 3. For certain types of vehicles, such as agricultural tractors, it has been proposed to tilt the cab when the vehicle is working e.g on sloping ground, so as to keep the cab more horizontal than what would otherwise be the case. See e.g. US 6 273 203 or US 6 029 764. The constructions used for tilting the cab in these prior systems may generally be adapted to the present invention. Nevertheless, none of the prior systems have proposed displacing the cab so as to stabilise the vehicle during tilting of a load carrier.

Fig. 4 is a block diagram illustrating the function of control of the suspension means. A sensor or indicator 10 provides an input signal to a control unit 20. For example, the sensor could be an inclination sensor provided at the load carrier 7, so as to indicate the inclination of the load carrier, in which case the control unit 20 may determine a displacement of the cab 2 to counteract the movement of the centre of gravity caused by the inclination of the load carrier 7. Alternatively, or in addition to an inclination sensor 10 provided at the load carrier 7, an inclination sensor could be provided on the frame 4 of the vehicle 1 , so as to indicate whether the vehicle is positioned or sloping ground. If so, the slope could be taken into account by the control unit 20 when determining a displacement of the cab 20 so as to stabilise the vehicle. The cab 2 may then advantageously be tilted towards the opposite side of the slope so as to stabilise the vehicle.

Naturally, the control unit 20 may take other information than that provided by sensors into account. For example, information regarding the inclination of the load carrier 7 may be provided via internal control signals used in a tipping control system effecting the tilting of the load carrier 7. In this case, no sensor 10 would be necessary. Clearly, a person skilled in the art may readily envisage suitable programming protocols in order to achieve a well- functioning control of the displacement, using appropriate input to the control unit 20.

The control unit 20 controls the activators 30, 32, 34, 36 which controls the suspension units 40, 42, 44, 6 which supports the cab 2, so as to elongate or shorten each suspension unit 40, 42, 44, 46 to achieve the desired displacement of the cab 2. In the illustrated embodiment, four suspension units 40, 42, 44, 46 are arranged, one in each corner of the cab 2. This configuration will provide a large degree of freedom when controlling the displacement of the cab, as the displacement of each corner thereof may be controlled independently.

However, it is understood that two or three suspension means with corresponding actuators may be sufficient to achieve adequate displacement of the cab. If two suspension means are used, they may advantageously be arranged at the front end of the cab 2. If three suspension means are used, two of them may advantageously be arranged at the front end of the cab 2, and the third in a central position at the back end of the cab.

Indeed, only one suspension means with corresponding actuator may be arranged. In this case however, the cab should be suspended at two additional locations, although these suspensions need no corresponding actuator. Furthermore, four or more suspension means with corresponding actuators may be used.

In the preferred air spring suspension system, the suspension means 40, 42, 44, 46 comprise air springs, the pressure of each air spring being individually controllable by means of a solenoid valve. The air spring suspension means simultaneous function as dampening means to dampen the vibrations of the cab during driving. Advantageously, an active control of the pressure of the air springs is used also to control the dampening characteristics of the springs.

Numerous alternative embodiments may be envisaged within the scope of the appended claims. For example, although air spring suspension systems are preferred, it is understood that the displacement may be effected using other suspension systems such as hydraulic suspension.

Claims

1. Method for stabilising a vehicle (1) comprising a driver's cab (2) and an equipment (7) which, in use, causes movement of the total centre of gravity of the vehicle (1), comprising when using said equipment (7), - causing a displacement the cab (2) so as to counteract the movement of the total centre of gravity of the vehicle (1) caused by the equipment. (7).

2. Method according to claim 1, wherein the equipment (7) is a tiltable load carrier, and the movement of the total centre of gravity of the vehicle (1 ) is caused by the tilting of the load carrier (7) from a normal position.

3. Method according to claim 1 or 2, wherein the displacement of the cab (2) includes lowering the cab (2).

4. Method according to any one of the previous claims, wherein the displacement of the cab (2) includes tilting the cab (2) in a forward direction

5. Method according to any one of the previous claims, wherein the displacement of the cab (2) includes tilting the cab (2) in a sideway direction.

6. Method according to any one of the previous claims, comprising creating the displacement of the cab (2) using suspension means (40, 42, 44, 46) provided between the chassis (4) of the vehicle and the cab (2).

7. Method according to claim 6, comprising controlling at least two suspension means (40, 42) being provided between the chassis (4) of the vehicle and the cab (2).

8. Method according to claim 6 or 7, comprising controlling at least four suspension means (40, 42, 44, 46) being provided between the chassis (4) of the vehicle and the cab (2).

9. Method according to any one of the claims 6 to 8, wherein the suspension means (40, 42, 44, 46) form part of the vibration damping system of the cab (2).

10. Method according to any one of the claims 6 to 9, wherein the suspension means (40, 42, 44, 46) comprises air springs.

11. Method according to claim 10, wherein the displacement is controlled by controlling 5 the pressure in said air springs.

12. Method according to any one of the previous claims, wherein the displacement of the cab (2) is automatically initiated upon use of the equipment (7).

10 13. Method according to any one of the previous claims, wherein the displacement of the cab (2) is automatically controlled using the output from at least one inclination sensor (10).

14. Method according to claim 13, wherein said inclination sensor (10) is provided at the 15 equipment (7).

15. Method according to claim 13 or 14, wherein said inclination sensor (10) is provided at the vehicle chassis (4).

20 16. System for stabilising a vehicle, said system being arranged to perform a method in accordance with any one of the preceding claims.

17. Vehicle comprising a driver's cab (2) and an equipment (7) which, in use, causes movement of the total centre of gravity of the vehicle (1 )„ the vehicle further comprising a 25 system for stabilising the vehicle being arranged to perform a method in accordance with any one of the claims 1 to 15.

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