Patent Description:
A load-carrying vehicle part of wheeled, specifically off-road vehicles, such as a forwarder or a dumper, usually has no other springing that the springing capacity of the tyres themselves. The springing properties will thereby be adjusted to driving with full load, which implies a relatively hard springing, which is practically non-existent when driving without load. A goods vehicle that advances on an uneven foundation and can come across various types of obstacles in the terrain. In order to work efficiently, a vehicle with good driving comfort, both loaded and unloaded, must be able to move quickly in terrain where the characteristics and nature of the foundation can vary greatly.

It has turned out that even small obstacles can lead to significant vertical accelerations of the vehicle when driving an unloaded vehicle. Vertical acceleration is a measure of a vehicle's acceleration from an imaginary centre of curvature when driving in vertical curves, i.e. in practice when the vehicle passes obstacles or a rise in the terrain. Also in cases where the foundation's surface structure has relatively low obstacle height of the "washboard" type, such large accelerations of <NUM>-<NUM> can occur also at such relatively low vehicle speeds as <NUM>-<NUM>/h.

Vertical accelerations and driving of unloaded vehicles are thus very strenuous for both the driver and the vehicle whereby the driver can experience considerable discomfort and at the same time, the vehicle is exposed to unnecessary wear and large mechanical strains. Lateral accelerations also occur.

Known wheel suspensions for vehicles of the type described above moreover implies that the theoretical maximum speed and hence capacity of the vehicle cannot be fully utilised. Add to this that the surface structure and vegetation of the foundation will to a large extent be exposed to wear and damage due to the jumping movements of the vehicle. <CIT> discloses a tracked vehicle having a suspension, <CIT> also discloses a known tracked vehicle having a suspension.

An object of the present invention is to provide a wheel suspension for an off-road goods vehicle with which the disadvantages outlined above can be avoided. Another object is to provide a vehicle, which at a given obstacle height in the terrain can advance at a higher speed without increasing momentarily occurring vertical accelerations.

The first objective of the invention is obtained by means of a load-carrying vehicle part of the type stated in claim <NUM>. The second object of the invention is obtained, according to claim <NUM>, by equipping a load-carrying vehicle of the type that have bogie-mounted wheels, specifically an articulated vehicle with a load-carrying vehicle part according to the invention.

With the wheel suspension according to the invention, the vehicle's springing properties can be adjusted to the prevailing ground conditions and the load weight carried so that the vehicle can offer softer springing when the vehicle is unloaded, whereby unevenness in the foundation can be captured so that they give rise to smaller vertical accelerations in the body or chassis of the vehicle.

In the following, an exemplary embodiment of the invention is described in further detail with reference to the accompanying drawing, in which,.

<FIG> shows a wheeled vehicle <NUM>, which in the exemplary embodiment described in the following is constituted by an articulated forest machine in the form of a forwarder, but which could clearly comprise any wheeled goods vehicle, such as a dumper or the like.

The vehicle <NUM> comprises a combination, which substantially comprises a front 1A respectively rear 1B vehicle unit, which is articulately joined via a steering joint <NUM>. Said front vehicle unit 1A sustains a superstructure, comprising a propulsion engine <NUM> and a driving cab <NUM>, and the rear vehicle unit 1B a superstructure comprising a lifting crane <NUM> and a cargo compartment <NUM> for timber. The vehicle <NUM> can comprise eight in a hydrostatic manner individually drivable wheels, which are arranged in pairs <NUM>, <NUM>, in a line after each other on a respective bogie element, on said front respectively rear vehicle unit.

As shown in <FIG>, the wheels <NUM>, <NUM> are mounted in pairs on bogie elements <NUM>, which are individually pivotably suspended relative to the chassis in a manner that will appear in more detail from the following. Each wheel is rotatably lodged in a hub <NUM> in the bogie element and arranged at an outer side of the bogie element <NUM>.

It should be understood that the vehicle's <NUM> front 1A respectively rear vehicle part 1B substantially can be identical. For the sake of simplicity, only the rear substantially load-carrying vehicle part 1B is described below and is shown in more detail in <FIG>.

The read vehicle part 1B comprises a first wheel pair <NUM> and a second wheel pair <NUM>, wherein the wheels in each pair are located after each other (one after the other). Each wheel pair <NUM>, <NUM> is via said hub <NUM> suspended in a respective bogie element <NUM> so as to support a longitudinal frame member <NUM> between them, extending along a centre line (CL) between said first and second wheel pairs <NUM>, <NUM>.

Between each bogie element <NUM> and the central frame member <NUM>, a suspension, generally designated <NUM>, is arranged on each side of the vehicle, involving spring legs 25A, 25B, which hereby are constituted by hydraulically acting piston-cylinder means. This suspension <NUM> is intended to enable manipulation of the frame member <NUM>, via the hydraulic action, raising and lowering the frame member <NUM> relative to the respective wheel pairs <NUM>, <NUM>. The suspension <NUM> also makes it possible to position check the frame member <NUM> angle to the foundation.

Each suspension <NUM> comprises rocker arms 26A, 26B, configured as a first respectively a second double-arm lever, one lever arm <NUM>:<NUM> respectively second lever arm <NUM>:<NUM> of which are mutually joined via an intermediate web <NUM>:<NUM>. The intermediate web <NUM>:<NUM> of each lever is pivotably lodged in a hub sleeve <NUM> in a respective joint in the frame member <NUM>, so that said respective rocker arms 26A, 26B can swing in one plane A-A, which is parallel to a plane of rotation of the respective wheel pairs <NUM>, <NUM>. Each of said rocker arms 26A, 26B can suitably be made in shell formation or at least have an axially travelling duct through the entire rocker arm from end to end. Above said bogie element <NUM>, it can also suitably be made in shell formation or be configured as a hollow case structure.

As most clearly appears from <FIG>, the central frame member <NUM> forms part of a vehicle unit 1B constituent in the load-carrying body or chassis, which in the known manner can support a drive train, control arrangement etc. To be torsionally rigid, lightweight and accommodate components that form part of the present invention, the load-carrying body has been given a box-like shape with an internal space B, see also <FIG>.

The frame member <NUM> is made of two longitudinal beams, so-called longerons, travelling substantially parallel to the longitudinal direction of the vehicle unit, each of which beams has an upper flange, a lower flange and a connection web. By means of a selection of suitable hydraulic components, for example by the action of check valves and/or gas accumulators (gas hydraulics), each of the above-mentioned piston-cylinder means <NUM>, which form part of the suspension <NUM>, can be caused to have a springy action in the same manner as spring legs.

Each suspension <NUM> on each side of the frame member <NUM> comprises a combination of a first spring leg 25A and a first rocker arm 26A as well as a combination of a second spring leg 25B and a second rocker arm 26B, with which combinations the frame member <NUM> is spring-supported to a front respectively a rear end of the bogie element <NUM>. The first rocker arm 26A is located in front of the second rocker arm 26B viewed in the vehicle's normal forward direction of driving. Each rocker arm 26A, 26B is with its one end pivotably fastened to a joint via said hub sleeve <NUM>, <NUM> in the chassis frame member <NUM> and with its other end pivotably fastened to a joint via a hub sleeve <NUM>, <NUM> in the bogie beam <NUM>.

As most clearly appears from <FIG>, each spring leg 25A, 25B is with its one end <NUM>, <NUM> articulately fastened in the chassis frame member <NUM> and with its other end <NUM>, <NUM> articulately fastened in a rocker arm 26A, 26B. It should be understood that each of said first and second rocker arms 26A, 26B can swing in planes that are parallel to the plane of rotation A, A of the wheel pairs <NUM>, <NUM>.

As most clearly appears from <FIG> and <FIG>, each spring suspension <NUM>, on each side of the frame member <NUM>, comprises a swing arm device with said first and second rocker arms 26A, 26B each of which is pivotably connected between the chassis frame member <NUM> and the bogie element <NUM>. Said rocker arms 26A, 26B acting in pairs are articulately attached to a side of the bogie element <NUM> facing the frame member <NUM>, while the wheels <NUM>, <NUM> in each pairs, via a respective hub <NUM>, are rotatably lodged suspended in an opposite other side of the bogie element <NUM>. In an embodiment, each rocker arm's 26A, 26B respective joint <NUM>, <NUM> in the bogie element <NUM> and the wheels' <NUM>, <NUM> respective hub <NUM> are located substantially facing each other, but on opposite sides of the bogie beam <NUM>. Suitably, said joints <NUM>, <NUM> can at least for the front first rocker arm 26A and said hub <NUM> in the bogie beam <NUM> have coinciding or substantially concentric shafts as appears from <FIG>.

Of the both rocker arms 26A, 26B acting in pairs, one is located in front of the other one viewed in the vehicle's normal forward direction of driving and each of said rocker arms can be oriented inclined forward or rearward so that each of the rocker arms acting in pairs with portions coupled thereto forms a kind of geometric parallelogram.

As most clearly appears from <FIG> and <FIG>, each rocker arm 26A, 26B with its one end is pivotably fastened to a joint <NUM>, <NUM> in the chassis frame member <NUM> and with its other end in a joint <NUM>, <NUM> in the bogie element <NUM>. Furthermore, each spring leg 25A, 25B with its one end <NUM>, <NUM> is articulately fastened to the chassis frame member <NUM> and with its other end <NUM>, <NUM> articulately fastened in a rocker arm 26A, 26B. Furthermore, said rocker arms 26A, 26B are arranged to swing in planes that are parallel with the wheel pairs' <NUM>, <NUM> plane of rotation A-A, which is illustrated in <FIG>.

As shown in <FIG> and as mentioned above, in one embodiment of the invention, the first and second rocker arms 26A, 26B comprise double-arm levers with two substantially V-shaped angularly directed first and second lever arms <NUM>:<NUM>, <NUM>:<NUM>, which are interconnected in an intermediate web <NUM>:<NUM>. The first rocker arm's 26A intermediate web <NUM>:<NUM> is pivotably lodged in a first joint, which is defined by a hub sleeve <NUM> in a portion, indicated in <FIG>, of a frame beam of the chassis frame member <NUM>. Correspondingly, the second rocker arm's 26B intermediate carcass <NUM>:<NUM> is pivotably lodged in a second joint, which is defined by a hub sleeve <NUM> in a portion, indicated in <FIG>, of a frame beam that is comprised in the chassis frame member <NUM>.

With reference to <FIG>, it is schematically shown how the first and second rocker arms 26A, 26B longer one lever arm <NUM>:<NUM> respectively shorter second lever arm <NUM>:<NUM> are arranged to swing in one respective plane A-A, which is parallel to each other but located at a distance from each other.

As shown in <FIG>, the respective rocker arms' 26A, 26B longer one lever arm <NUM>:<NUM> in a side space, generally designated B1, which is delimited between the chassis frame member <NUM> and the bogie element <NUM>, while the shorter second lever arm <NUM>:<NUM> swings in one plane, which is located in the space B, which is delimited within the chassis' box-shaped frame member <NUM>.

Also referring to <FIG>, the first rocker arm's 26A substantially longer one lever arm <NUM>:<NUM> is thus at its free end equipped with a pivot pin by which it is pivotably lodged in a hub sleeve <NUM> in a first joint in the bogie element <NUM> and the substantially shorter second lever arm <NUM>:<NUM> is in force-transmitting connection with the chassis frame member <NUM> via said first spring leg 25A. Correspondingly, the second rocker arm's 26B substantially longer one lever arm <NUM>:<NUM> is at its free end equipped with a pivot pin by which it is pivotably lodged in a hub sleeve <NUM> in a second joint in the bogie element <NUM>, and the substantially shorter lever arm <NUM>:<NUM> is in force-transmitting connection with the chassis frame member <NUM> via said second spring leg 25B.

Said respective spring legs 25A, 25B are at their ends jointly connected partly with the rocker arm's 26A, 26B shorter second lever arm <NUM>:<NUM>, partly with the chassis frame member <NUM>.

It should be understood that due to each spring leg 25A, 25B comprising a hydraulic cylinder, via a valve function in a hydraulic circuit not shown in the figures, a pressure medium flow applies a moment force to said second lever arm <NUM>:<NUM>, whereby the frame member's <NUM> state relative to the wheel pair <NUM>, <NUM> and hence the foundation can be position- or level-checked independently of the ground conditions. In the embodiment according to the invention in which the spring legs 25A, 25B comprise hydraulic cylinders, it is possible to actively swing or raise/lower the chassis frame member <NUM> relative to the bogie element <NUM>. Alternatively, the hydraulic fluid can be throttled, blocked so that said respective hydraulic cylinder offers a limited resilience/alleviation adjusted to the load's relative weight, or the chassis frame member <NUM> can simply be locked in a specific position relative to the wheel pair <NUM>, <NUM> and thereby the foundation.

In the exemplary embodiment described here, the arrangement comprises an eccentrically operating alternating motion mechanism <NUM> in connection with the joints between the rocker arms 26B and the bogie element <NUM>. The alternating motion mechanism <NUM> comprises an eccentric clutch of the type schematically shown in the enlarged detail in <FIG> and is selected so that it can convert the rotary motion in the joints <NUM>, <NUM> to a forward and backward translation motion so in this manner to present a distance-adjusting means between said joints, which ensures that the centre-to-centre distance c/c in the joints <NUM>, <NUM> between the rocker arm 26A, 26B and the bogie element <NUM> can be varied depending on the prevailing relative swing movements between the frame member <NUM> and the bogie element <NUM>.

It should hereby be understood that in the embodiment described here, only the (rear) second rocker arm 26B is equipped with said motion conversion arrangement <NUM>. The first rocker arm 26A is thus devoid of said arrangement, but could in an alternative embodiment clearly easily be equipped with such arrangement instead of the said second rocker arm 26B. Alternatively, each rocker arm 26A, 26B could be equipped with a motion conversion arrangement <NUM> capable of converting a rotary motion in a joint for either lever arm to a forward and backward translation motion. The translation motion should suitably take place in a controlled manner within a limited angle area that is less than <NUM>°.

Claim 1:
A load-carrying vehicle part of a wheeled vehicle comprising,
- a first wheel pair (<NUM>) and a second wheel pair (<NUM>), wherein the wheels are tyred wheels and in each pair located in sequence and suspended in a respective bogie element (<NUM>) on each side of a longitudinal frame member (<NUM>), which extends along a centre line (CL) between said first and second wheel pairs,
- a suspension (<NUM>), which is arranged between each bogie element (<NUM>) and the frame member (<NUM>) on each side of the vehicle part to enable manipulation of the frame member state relative to the respective wheel pairs (<NUM>, <NUM>) or to carry the frame member between them in a springing manner,
characterized in that
each suspension (<NUM>) comprises
- a first rocker arm (26A) and a second rocker arm (26B), wherein the first rocker arm is located in front of the second rocker arm viewed in the vehicle part's normal forward direction of driving,
- each rocker arm (26A, 26B) with its one end is pivotably fastened to a joint (<NUM>, <NUM>) in the frame member (<NUM>) and with its other end pivotably fastened in a joint (<NUM>, <NUM>) in the bogie element (<NUM>).
- a first spring leg (25A) and a second spring leg (25B), wherein each spring leg with its one end (<NUM>) is articulately fastened to the frame member (<NUM>) and with its other end (<NUM>) is articulately fastened to a rocker arm (26A, 26B).
- a motion conversion arrangement (<NUM>) capable of converting a rotary motion in a joint (<NUM>, <NUM>) for one of the rocker arms (26A, 26B) to a forward and backward translation motion to accommodate changes in distance between the rocker arms' joints.