WO2005084970A1

WO2005084970A1 - Torsion bar

Info

Publication number: WO2005084970A1
Application number: PCT/NO2005/000077
Authority: WO
Inventors: Sven BJØRKGÅRD
Original assignee: Kongsberg Automotive ASA
Current assignee: Kongsberg Automotive ASA
Priority date: 2004-03-05
Filing date: 2005-03-03
Publication date: 2005-09-15
Anticipated expiration: 2006-09-05
Also published as: SE0400549D0

Abstract

The invention relates to a roll stabiliser device system that is mounted for use in a vehicle. The roll stabiliser device comprises a torsion bar and two arms which at their first ends are each rigidly connected to the ends of the torsion bar. The arms are at their second ends subjected to a force which results in a bending moment in the torsion bar. The system is characterised in that the end portions of the torsion bar close to the attachment area of the arms have a certain size and an area inertia moment that is greater than the area inertia moment at the central portion of the torsion bar. In this way, the bending resistance of the torsion bar is increased.

Description

Torsion bar

The present invention relates to a roll stabiliser device system for use in a vehicle in accordance with the preamble of independent claim 1.

A roll stabiliser device for use in a vehicle is utilised for an element that is connected to the rest of the vehicle in such manner that it is subjected to a rolling motion relative to the rest of the vehicle. It is desirable to reduce this rolling motion. The roll stabiliser device may, for example, be located between a driver's cab and the vehicle chassis or between an axle and the vehicle.

In a lorry, the element whose rolling is to be reduced will preferably be the driver's cab. The roll stabiliser device is used to hold the driver's cab in place relative to the rest of the vehicle, and in particular in the lateral direction. The term "lateral direction" as used herein means the direction oriented perpendicular to the direction of the vehicle when the vehicle is seen in top plan view, i.e., the lateral direction coincides with the extent of the vehicle in its transverse direction.

A roll stabiliser device of the above-mentioned type comprises a torsion bar and two arms. Each one of the arms' first ends is rigidly connected to its respective end of the torsion bar. The roll stabiliser device is supported by suitable bearing devices. The roll stabiliser device can be connected to the element whose rolling is to be reduced and to the rest of the vehicle in different ways. One possibility is to arrange the bearing devices on the element, whilst the second ends of the arms are attached to a part of the vehicle by suitable means. Alternatively, the second ends of the arms may be attached to the element by suitable means, whilst the bearing devices are attached to the vehicle.

The forces from the driver's cab act, in three directions on the arms: laterally, longitudinally and vertically. The lateral direction has already been defined. By "longitudinal direction" is meant a direction that is coincident with the longitudinal direction of the vehicle. By "vertical direction" is meant a direction perpendicular to the longitudinal and transverse directions of the vehicle which constitute the horizontal plane of the vehicle, the vertical direction running essentially coincident with, or parallel to, the vertical direction of the driver's cab.

Vertical forces produce torsion in the torsion bar, longitudinal forces run essentially directly through the arm to the bearing device, whilst lateral forces produce a bending moment in the torsion bar. For the driver to feel he is in control of the vehicle, it is important that the lateral rigidity of the driver's cab is of a certain level, and this is obtained through the lateral rigidity of the amis. The rigidity of the roll stabiliser device is determined by the inherent rigidity of the arms, the rigidity of the bearing devices and the bending resistance of the torsion bar.

In vehicles where it is important to obtain lateral rigidity of the driver's cab, the bearing devices can be arranged so that a rigid support is obtained in the lateral direction. This rigid support may, for example, be provided by the torsion bar being supported by four bearings, two at each end of the torsion bar. The bearings in each of the two pairs of bearings are spaced apart from each other, and a rigid support is obtained which contributes to the lateral rigidity of the roll stabiliser device. An example of such an arrangement will be described below with reference to the figures.

The aforementioned arrangement of the bearings means that stringent requirements must be met as regards tolerances in the manufacture of the torsion bar and bearing parts, and also the bearing houses in hich the bearings rest and which are screwed onto the vehicle frame. This means that the solution is costly to produce.

In view of the drawbacks of this bearing arrangement, there is a desire to use a different bearing arrangement than the aforementioned. Therefore, one of the basic requirements of the present invention is that the bearings that are to be used should be capable of taking up tolerance variations in the parts of the rolling device. A type of bearing of this kind will preferably be a spherical bearing. For example, a spherical bearing can be provided at each end of the torsion bar.

When a type of bearing is used that is tolerant of variations in the parts of the roll stabiliser device, the lateral rigidity is reduced because the contribution to this rigidity from the support is lost. The lateral rigidity will then be determined by the bending resistance of the torsion bar and the rigidity of the arms, the bending resistance of the torsion bar making the least rigid contribution.

It is an object of the present invention to arrange the roll stabiliser device in such manner that the lateral rigidity is maintained, even though flexible bearings are used which do not necessarily make a significant contribution to the lateral rigidity.

Another object of the present invention is to improve the bending resistance of the torsion bar. However, it is necessary that the bending resistance of the torsion bar should be improved without this having a significant effect on the torsional rigidity of the torsion bar. This is because an increase in the torsional rigidity of the torsion bar impacts on the vertical rigidity of the driver's cab and results in poorer ride comfort. One way of solving this problem is to use a torsion bar of large cross-section. The disadvantage of this solution is that the torsional rigidity of the torsion bar is affected, resulting in poorer comfort in the driver's cab.

The objects of the invention are obtained according to the invention in that selected portions of the torsion bar, preferably the ends of the torsion bar, are given an increase in cross-section. This results in an increase in the bending resistance, whilst there is almost no increase in the torsional rigidity.

In accordance with the independent patent claim, the invention relates to a roll stabiliser device comprising a torsion bar and two arms which at their first ends are each are rigidly connected to the ends of the torsion bar. The arms are at their second ends subjected to a force, for example, from the driver's cab of the vehicle, which results in a bending moment in the torsion bar. Furthermore, the system is characterised in that the end portions of the torsion bar close to the attachment area of the arms have a certain size and an area inertia moment that is greater than the area inertia moment at the central portion of the torsion bar. In this way, the bending resistance of the torsion bar is increased

According to an advantageous embodiment of the invention, the bending resistance of the torsion bar is increased by the increase in cross-section of the torsion bar being made at the ends in a direction that is dependent upon the direction of the forces acting on the arms. These forces act preferably in a lateral direction on the arms and the increase in cross-section thus has an extent essentially in, or parallel to, the horizontal plane of the vehicle defined by the vehicle's-longitudinal and transverse directions.

Because this increase in. cross-section is made along the torsion bar solely in the plane where the increased rigidity is required, the solution is economical as regards space and the material necessary to produce the torsion bar. In addition, the actual production process, for example, upset forging, will be easier, as there is less material to be formed and it is therefore possible to manage with a shorter blank.

The invention will be explained in the following by means of an example of an embodiment of the invention that is illustrated in the attached figures, wherein:

Figure 1 is a schematic diagram of the side view of a vehicle, shown here with the roll stabiliser device._.

Figure 2 is a schematic diagram showing rigid support of the torsion bar.

Figure 3 is a schematic diagram showing flexible support of the roll stabiliser device.

Figure 4 is a top view of a part of the roll stabiliser device.

Figure 5 is a sectional view of a part of the roll stabiliser device. Figure 1 shows a vehicle 1 with a driver's cab 2. A roll stabiliser device 3 comprises a arm 4 which at the free end 4b thereof is shown attached to the driver's cab 2 of the vehicle by a rubber bushing 5. Spring devices 6 are attached to the vehicle chassis 11 and the driver's cab 2 at each of the corners of the driver's cab (only illustrated by one spring device in the figure). The mounting of the rolling device to the vehicle chassis 11 is shown at 7.

Figure 2 shows the roll stabiliser device 3 as it would be mounted on the vehicle, seen in top plan view. It can be seen here that two aπns 4 are rigidly connected to a torsion bar 8 at their first ends 4a. The torsion bar 8 is positioned on the vehicle 1 coincident with the transverse direction of the vehicle, and the arms are coincident with the longitudinal direction of the vehicle. Lateral forces from the driver's cab which act on the second,. free end 4b of the arm are shown illustrated by arrows 9. In the illustrated embodiment of the invention, the torsion bar 8 is shown supported by two bearings 10 at one end of the torsion bar 8 arid two more bearings 20 at the other end of the torsion bar 8. The two bearings in each pair are spaced apart, a rigid support of the torsion bar thereby being obtained. This arrangement provides a lateral rigidity of the driver's cab 2.

Figure 3 shows the roll stabiliser device 3 as shown in Figure 2, but in this case supported by two spherical bearings 12, 13 positioned close to their respective ends of the torsion bar. The other reference numerals refer to the same components as in Figure 2.

Figure 4 shows a part of the roll stabiliser device 3 with the spherical bearing 12. Upon the introduction of the spherical bearing 12 it is necessary, in accordance with the present invention, to increase the bending resistance of the torsion bar 8 in order to provide sufficient lateral rigidity which counteracts the lateral forces exerted on the second ends of the arms (see Figure 3). This is achieved in that the end portion 8b of the torsion bar is given an increase in cross-section compared with the central portion 8a of the torsion bar. The increase in cross-section has an extent essentially in, or parallel to, the horizontal plane of the vehicle. The area inertia moment of the end portions 8b of the torsion bar is thus greater than the area inertia moment of the central portion 8a of the torsion bar. The length of the end portion 8b constitutes about 1/5 of the total length of the torsion bar.

In Fig. 4 the end portion 8 a is shown divided into a first portion 8 c and a second portion 8d. The cross-section of the first portion 8c may, for example, be oval in shape, see the section A- A, but may of course also be of other shapes. Each of the end portions of the torsion bar comprises a first portion 8c which has a cross- section wherein a first distance from the midpoint of the cross-section (the area centre.) to the outer contour thereof is greater than a second distance from the midpoint to the outer contour of the cross-section. The first distance extends in the longitudinal direction of the vehicle, whilst the second distance extends perpendicular to the horizontal plane of the vehicle. The end portion of the torsion bar also comprises a second portion 8d that is positioned closer to the attachment area of the arms. In the second portion 8d, both the first and the second distance are increased so that the cross-section of the second portion 8d has a shape that is different from the shape of the cross-section of the first portion. The second distance preferably increases more than the first distance. The end portion is given an advantageous configuration in its portion 8e next to the attachment area of the arms which is favourable as regards distribution of force in the attachment area.

When the cross-section of the first portion 8c has an essentially oval shape, the second distance corresponds to the smallest distance from the midpoint 14 to the outer contour 15, and the first distance is the largest distance from the midpoint 14 to the outer contour 15. The end portion 8b of the torsion bar comprises a second portion 8d having a cross-section that is shown in this figure having an essentially circular shape.

Figure 5 shows the end portion 8b of the torsion bar by the bearing device 13. It can be seen in this figure that the torsion bar is attached to the first end 4a of the arm by welding, and that the bearing device is attached to the first end 4a of the arm. The width 16 of the first portion 8c corresponds to the distance between the points 15a and 15b on the outer contours 15; see Figure 4.

To obtain an optimal transition to the weld 17, where stress concentrations due to the ovality of the portion are avoided, the oval-shaped cross-section is altered by both the smallest and largest distance being increased in the second portion 8d. The increase is made by the smallest distance of the oval being increased first and most, whilst the increase of the largest distance is smaller and takes place in an area closer to the weld 17. This early and relatively large increase of the smallest distance results in load transfer from the largest distance of the oval. The cross- section of the portion 8d may, for example, be circular as shown in Figure 4, but the cross-section may of course also be of another shape, for example, super-oval. The second portion 8d passes into a third portion 8e which has a cylindrical shape, and thus the stresses are distributed evenly towards the weld.

Claims

PATENT CLAIMS

1. A roll stabiliser device system that is mounted for use in, a vehicle, the roll stabiliser device comprising a torsion bar and two arms which at their first ends are each rigidly connected to the ends of the torsion bar, and which arms are at their second ends subjected to a force which results in a bending moment in the torsion bar, characterised in that the end portions of the torsion bar close to the attachment area of the arms have a certain size and an area inertia moment that is greater than the area inertia moment at the central portion of the torsion bar, thereby increasing the bending resistance of the torsion bar.

2. A system according to claim 1, characteris ed in that the arms are at their second ends attached to an element whose rolling is to be reduced, and the bearing devices are arranged on the vehicle.

3. A system according to claim 1, characterised in that the arms are at their second ends attached to the vehicle, and the bearing devices are arranged on an element whose rolling is to be reduced.

4. A system according to one of claims 1-3, characterised in that the first ends of the arms are attached to the torsion bar by welding and/or that the second ends of the arms are attached to the driver's cab by a rubber bushing.

5. A system according to one of claims 1-4, characterised in that the element whose rolling is to be reduced is a driver's cab.

6. A system according to claims 1-5, characterised in that spring devices are attached to the vehicle chassis and the driver's cab and that a spring is attached to each of the corners of the driver's cab.

7. A system according to one of claims 1-6, characteris ed in that each of the end portions of the torsion bar comprise a first portion, wherein a first distance from the midpoint (the area centre) of the cross-section of the first portion to the outer contour of the cross- section is greater than a second distance from the midpoint to the outer contour of the cross-section.

8. A system according to claim 7, characterised in that the end portions of the torsion bar further comprise a second portion, which second portion is positioned closer to the attachment area of the arms, both the first and second distance increasing in the second portion so that the cross-section of the second portion changes shape, preferably that the second distance increases more than the first distance.

9. A system according one of claims 7 or 8, characterised in that the cross-section of the first portion has an essentially oval shape, the second distance corresponding to the smallest distance from the. midpoint to the outer contour, and the first distance being the largest distance from the midpoint to the outer contour.

10. A system according one of claims 1-9, characterised in that the bearing devices are tolerant of variations in the parts of the roll stabiliser device, the bearing devices preferably consisting of two spherical bearings.