EP2828105A1

EP2828105A1 - Asymmetrical axle installation

Info

Publication number: EP2828105A1
Application number: EP13764408.4A
Authority: EP
Inventors: Pär Friberg
Original assignee: Scania CV AB
Current assignee: Scania CV AB
Priority date: 2012-03-21
Filing date: 2013-03-11
Publication date: 2015-01-28
Also published as: EP2828105A4; CN104245370A; SE1250276A1; WO2013141778A1

Abstract

The invention relates to a method and an axle installation (1) for damping of oscillation movements in a vehicle, particularly in a heavy vehicle, e.g. a bus or truck, with the object of effecting a change in resonance frequencies which occur during operation, in order to achieve a more comfortable ride during movement of the vehicle, comprising components such as a wheel shaft (2) suspended in the vehicle's chassis (8) by means of springs (5a-d), spring beams (4a, b) and shock-absorbers (7a-d). The invention is achieved by altering the geometry of the axle installation so that the characteristic and/or distance (a) of a first spring (5a-d) from the wheel shaft (2) differs from the characteristic and/or distance from the wheel shaft (2) of a second spring (5a-d), so that an asymmetry is created in the axle installation (1), causing the natural symmetrical movements of the axle installation (1) to change to asymmetrical movements whose amplitudes/effects in the vehicle are quickly reduced or damped out.

Description

ASYMMETRICAL AXLE INSTALLATION

TECHNICAL FIELD

The present invention relates generally to an axle

installation and a method for damping/reduction of vibrations and resonance movements in a vehicle. The invention relates in particular to a rear axle installation for a heavy

commercial vehicle such as a bus. It relates also to a vehicle equipped with such an axle installation.

STATE OF THE ART

Rear axle installations in heavy commercial vehicles such as buses are usually constructed symmetrically as regards

components of the suspension. The springs are for example attached to a spring beam at the same distances from the wheel shaft, but one of them is situated in front, and the other to the rear, of the wheel shaft, as viewed in the vehicle's longitudinal direction.

The predominant movements of a vehicle' s rear axle are

generally so-called bounce and pitch movements which may in principle be characterised as symmetrical movements. Bounce movements are usually movements of the spring beam in vertical directions, i.e. the spring beam moves upwards and downwards. Pitch movements are usually rotational movements of the spring beam about the wheel shaft. Every possible endeavour is made, by means of said springs, to insulate road-induced movements and vibrations. How these springs are installed affects significantly the magnitude of vibrations which make their way into the vehicle' s chassis from the carriageway via wheels and axle suspensions.

Today' s rear axle installations are very heavy and have natural symmetrical resonance movements in the frequency range 5-20 Hz. This is also a frequency range to which human beings are very sensitive and may well experience discomfort. It is therefore desirable to reduce these resonances, to lower the response to or effects of them, potentially resulting in a significantly more comfortable ride for passengers and drivers on board the vehicle.

Known rear axle installations currently have important

components such as springs and the like arranged symmetrically in front, and to the rear, of the wheel shaft. This

unfortunately results in significant resonances because such an arrangement causes natural symmetrical

movements /oscillations in the axle installation which are not altogether easy to damp. If the symmetry of the structure can be altered, the effects of the resonances may be reduced. The basic idea of the invention is therefore to achieve in a simple and cost-saving way a change in the assumptions for the rear axle installation so that bounce and pitch movements become to a lesser extent natural movements of the structure, i.e. so that the natural freguency of the wheel suspension is altered so that resonance movements initiated are damped out more quickly.

Attempts have previously been made to solve this problem.

US4196786 refers for example to a device for damping

vibrations of a rear axle by associating annular weights with the vehicle's driveshaft. The annular weights are each placed symmetrically on their respective sides of the axle's centrally positioned differential gear to impart to the driveshaft a mass or weight which alters the resonance

frequency of the axle and hence of the whole structure. The disadvantages of this solution is that further components are added to the structure, rendering it heavier and more

expensive and adding a further assembly step during the vehicle's manufacture.

There is therefore a need for a novel and improved axle installation which solves said problem and is simple in construction and structure. Such an axle installation should preferably not add further components or weight to the vehicle and should help to make the vehicle inexpensive to manufacture while nevertheless eliminating the disadvantages of the state of the art and therefore solving the problem of vibrations and resonances in the structure.

This may be achieved by altering or disrupting the symmetry of the axle installation so that its resonance frequency is shifted to a more acceptable frequency range.

There is no reference in prior art to any axle installation which in a simple and cost-effective way reduces vibrations and resonance movements in an axle installation.

SUMMARY OF THE INVENTION

One object of the invention is therefore to solve the

abovementioned problem and propose an axle installation and a method which alter or disrupt the symmetry of the structure of the axle installation so that the resonance frequency of the structure is altered and the resonance movements are damped more effectively.

A further object of the invention is to make it possible for components available on the market to be used in the

structure, with a view to keeping the costs down.

A further object of the invention is that the structure should consist of as few components as possible and thereby help to minimise the component costs and achieve cost-effective manufacture .

A further object of the invention is that it be possible to implement it in an existing structure or installation without having to make extensive changes.

These and further objects and advantages are achieved

according to the invention by a device in accordance with the features indicated in the characterising part of claim 1. The invention thus relates generally to an axle installation in a vehicle which is so constructed that the symmetry of the axle installation and its components is altered or disrupted with the object of achieving a reduction in vibrations and resonance movements within a frequency range which a vehicle's driver and passengers find troublesome when the vehicle is in operation .

This is achieved according to the invention by at least one first spring' s characteristic and/or distance from the wheel shaft being different from a second spring' s characteristic and/or distance from the wheel shaft, so that an asymmetry is created in the axle installation, causing the natural

symmetrical movements of the axle installation to change to asymmetrical movements whose amplitudes/effects in the vehicle are quickly reduced or damped out. The movement-reducing effect according to the invention is not achieved, however, if the location or characteristic of the two springs is altered on one spring beam but not on the other. The asymmetrical positioning of the springs has to be relative to the location of the wheel shaft in the vehicle's longitudinal direction.

The springs may for example be air or steel springs, with different stiffnesses/characteristics and be situated on both sides of the axle, or alternatively the springs may be

fitted/fastened at different geometrical locations in the axle installation. Altering the symmetry and/or characteristic of the structure in this way also causes the axle installation's natural frequency to change and the vehicle's bounce and pitch movements to be no longer natural symmetrical movements in the vehicle axle, so that they quite simply do not allow the axle installation to oscillate/vibrate as powerfully. This means that when bounce and pitch frequencies are excited from the carriageway via the wheels, a natural damping effect on the movements in the axle installation occurs, since the structure begins to oscillate at a "forced" frequency instead of its normal natural resonance frequency. The damping of the movements in the rear axle installation therefore increases automatically within the frequency range which drivers and passengers find particularly troublesome.

Despite its simplicity, the invention eliminates the

disadvantages of the state of the art and achieves a reliable springing and damping function.

Moreover, the invention makes it possible for components available on the market to be used, rendering the structure cost-effective and easy to implement. Since the structure according to the invention consists of few components, at least no more than in known solutions, the cost of the

components involved will be low and the structure therefore inexpensive to make.

The invention is also implementable in an existing axle installation without having to make extensive structural changes, e.g. by replacing the springs by ones which are similar but have a different spring characteristic.

Further features and advantages of the invention are indicated by the more detailed description of the invention set out below and the attached drawings and other claims.

BRIEF LIST OF DRAWINGS

The invention is described in more detail below in the form of some preferred embodiment examples with reference to the attached drawings.

Figure 1 is a perspective view of an exposed rear axle

installation of a known kind intended for a heavy vehicle, e.g. a bus . Figure 2 depicts in more detail a section through the rear axle according to Figure 1, in the form of a side view of one side of the rear axle installation. Figure 3 is the same side view as in Figure 2 but showing the location and fastening in the spring beam of one of the springs (the left spring in the diagram) displaced somewhat rearwards towards the rear axle with the object of altering the symmetry of the structure.

Figure 4 is the same side view as in Figures 2 and 3 but in this case showing the location and fastening in the spring beam of the other spring (the right spring in the diagram) displaced somewhat forwards in the vehicle and nearer to the rear axle.

Figure 5 is the same side view as in Figures 2 to 4 but using springs which differ in size, stiffness and/or characteristic. Figure 6 shows how the location of the wheel shaft on the spring beam may be displaced to achieve a change in the structure's resonance frequency.

DESCRIPTION OF PREFERRED EMBODIMENTS

The invention thus relates to an axle installation for damping and reduction of the vibrations and resonance movements which occur in a vehicle during operation. It relates in particular to a rear axle installation for a heavy commercial vehicle, e.g. a bus.

Figure 1 is a perspective view of an exposed rear axle

installation 1 of a known kind, here intended for a bus and mainly comprising a wheel shaft 2 provided with a centrally positioned differential gear 3 via which the propulsion of the vehicle takes place, which wheel shaft is suspended in the vehicle's chassis (not depicted) by means of two spring beams 4a, b each provided with two springs 5a-d situated at or near to the end portions of the spring beams. The springs 5a-d, which may be of various types/structures, e.g. so-called air springs/air bellows, steel springs or the like, are situated on the spring beams 4a, b, at the same distances from the wheel shaft 2, one of them in front, and the other to the rear, of the wheel shaft as viewed in the vehicle's longitudinal direction. The rear axle installation 1 is further provided with two wheel pairs 6a, b and the vibrations and movements which occur during the vehicle' s operation are damped by means of four shock absorbers 7a-d preferably likewise situated at the end portions of the spring beams 6a, b, close to the springs 5a-d, in order to achieve maximum damping effect.

Figure 2 depicts in more detail a section through the rear axle 2 along the vehicle' s longitudinal direction as in Figure 1, showing a side view of one side of the rear axle

installation 1. The two springs 5a, b, here in the form of air bellows, are fitted at the end portions of the spring beam 4a and have their respective opposite upper sides fastened in the vehicle's chassis 8 (here represented by broken lines). At the middle of the spring beam, the wheel shaft 2 is situated in a spring seat 9. A wheel or wheel pair 6a is fitted at the outer end of the axle 2. Two arrowheads linked by a broken straight line represent the axle installation' s bounce

movements x, which are the spring beam's movements in vertical directions, and arrowheads linked by a curved line similarly represent the installation' s pitch movements y, which are the spring beam's rotational movements, turning movements, about the wheel shaft.

Figure 3 depicts substantially the same structure as in Figure 2 but here showing the location and fastening in the spring beam of one forward spring 5a (the left spring in this drawing) displaced somewhat towards the rear axle 2, i.e. somewhat rearwards in the vehicle, with the object of altering the symmetry of the structure and reducing the distance a between the forward spring 5a and the wheel shaft 2. The distance b from the rear spring 5b to the wheel shaft remains unchanged and is therefore now relatively greater.

Figure 4 depicts substantially the same structure as in

Figures 2 and 3 but showing in this case the location and fastening in the spring beam of the rear spring 5b displaced somewhat forwards in the vehicle towards the wheel shaft 2. The distance b from the rear spring 5b to the wheel shaft is therefore smaller and the distance from the forward spring 5a to the wheel shaft remains unchanged. It is of course

possible for the location of both of the air springs 5a, b to be shifted in the same structure but, if so, in such a way as to achieve an asymmetry of the wheel suspension.

Figure 5 shows how components with different characteristics, e.g. different sizes, stiffnesses or characteristics, may be used (here depicted as springs 5a, b of different sizes), but with the same fastening points in the spring beam 4a.

A combination of arrangements is of course also possible. It is for example possible for two components, e.g. springs 5a, b, which have different sizes and characteristics to be used, while at the same time their location in the structure, e.g. on the spring beam, forms an asymmetry in the structure.

Figure 6 shows how the location of the wheel shaft 2 on the spring beam 4a may be altered to achieve a change

in/ad ustment of the structure's resonance frequencies. In this case the fastening point of the wheel shaft has been moved rearwards (depicted in a slightly exaggerated way in the drawing) on the spring beam 4a so that the distance a to the forward spring 5a has increased and the distance b to the rear spring 5b has decreased. It is of course also conceivable that the spring beam might itself be longer and have a longer extent either forwards or rearwards in the vehicle so that the location of one spring 4a, b creates an asymmetry in the structure .

The above description is primarily intended to make the invention easier to understand. The invention is of course therefore not limited to the embodiments indicated above, as other variants of it are also possible and conceivable within the scope of the inventive concept and the protective scope of the claims set out below.

Claims

1. An axle installation (1) for damping of oscillation

movements in a vehicle, particularly in a heavy vehicle, e.g. a bus or truck, in order to achieve a more comfortable ride during movement of the vehicle, comprising components such as a wheel shaft (2) suspended in the vehicle's chassis (8) by means of springs (5a-d), spring beams (4a, b) and shock- absorbers (7a-d),

characterised

in that the characteristic and/or distance (a) of a first spring (5a-d) from the wheel shaft (2) differs from the characteristic and/or distance from the wheel shaft (2) of a second spring (5a-d) so that an asymmetry is created in the axle installation (1), causing the natural symmetrical

movements of the axle installation (1) to change to

asymmetrical movements whose amplitudes/effects in the vehicle are quickly reduced or damped out.

2. An axle installation (1) according to claim 1,

characterised

in that the springs (5a-d) are attached to the spring beams (4a, b) at different distances from the wheel shaft (2) so that than an asymmetry in the axle installation (1) is achieved.

3. An axle installation (1) according to claim 1 or 2,

characterised

in that the springs (5a-d) situated on one and the same spring beam (4a, b) differ in size/characteristic.

4. A method for achieving damping of oscillation movements in a vehicle, particularly in a heavy vehicle, e.g. a bus or truck, with the object of effecting a change in resonance frequencies which occur during operation, in order to achieve a more comfortable ride during movement of the vehicle, comprising components such as a wheel shaft (2) suspended in the vehicle's chassis (8) by means of springs (5a-d), spring beams (4a, b) and shock-absorbers (7a-d),

characterised

by altering the geometry of the axle installation so that the characteristic and/or distance (a) of a first spring (5a-d) from the wheel shaft (2) differs from the characteristic and/or distance from the wheel shaft (2) of a second spring (5a-d) , so that an asymmetry is created in the axle

installation (1) , causing the natural symmetrical movements of the axle installation (1) to change to asymmetrical movements whose amplitudes/effects in the vehicle are quickly reduced or damped out .

5. A method according to claim 4,

characterised

by the springs (5a-d) being located at different distances from the wheel shaft (2) on the spring beam (4a, b) so that than an asymmetry in the axle installation (1) is achieved.

6. A method according to claim 4 or 5,

character sed

by springs (5a-d) with different characteristics being located on one and the same spring beam (4a,b) .

7. A vehicle provided with an axle installation (1) according to any one of claims 1-3.