ADJUSTABLE SUSPENSION ARRANGEMENT. AND A HEAVY VEHICLE PROVIDED WITH SUCH AN ARRANGEMENT

Technical field

The present invention relates to a suspension arrangement for a heavy vehicle enabling adjustment of a clearance between a vehicle frame and the ground.

Technical background

A vehicle suspension system of the beam axle type typically comprises leaf springs to which the beam axle is bolted. Each leaf spring is mounted to the vehicle frame at one end by means of fixed bracket, and in the other end by means of a shackle. The fixed bracket provides an anchor point, and the shackle allows the spring to lengthen or shorten according to the loads applied.

In order to provide adjustability of the clearance between the vehicle frame and the ground, JP 07-251 622 teaches to arrange a pivotable cradle between the shackle and the frame. One end of the cradle is connected to the shackle, while the other end is connected to a piston rod of a hydraulic cylinder fixed in relation to the frame. By controlling the cylinder, the cradle can be pivoted, thereby controlling the vertical position of the shackle and thus the leaf spring. This allows adjusting the vertical position of the axle in relation to the frame, and thus the clearance of the vehicle, in response to driver demand or road surface conditions.

A drawback with prior art solutions is that the pivoting cradle is subject to two lever arms, one between the pivoting point and the shackle, and one between the pivoting point and the piston. This creates a double non-linearity, and a complex relationship between applied piston motion and clearance adjustment.

Summary of the invention

It is an object of the present invention to eliminate or mitigate this problem, and provide a suspension for a heavy vehicle enabling improved adjustment of vehicle clearance. This and other objects are achieved by a suspension arrangement comprising a first spring member intended to be arranged in a longitudinal direction of the vehicle for suspending a first wheel axle from a frame of the vehicle, a first link member arranged to be pivotable in dependence of a vertical position of the first spring member in relation to the vehicle frame, comprising a rod rotatable around its longitudinal axis, in engagement with the first link member, so that a pivoting motion of the first link member is converted to rotational motion of the rod, the rotatable rod being lockable in a at least two different positions, each position corresponding to a different vertical position of the spring member in relation to the frame. The invention is based on the realization that it is advantageous to adjust the pivoting link members by means of a rotatable rod. By rotatabel rod is intended any generally elongate member that is arranged to be rotatable around its longitudinal axis.

The rod is lockable in different positions, so that each position corresponds to a different adjustment of the clearance. The rod can be lockable in two or more predefined positions, or may be lockable at a selected position within a certain angular range.

The point of engagement of the rotatable rod and the link member does not need to be vertically displaced from a pivoting point of the link member, but the rod can engage the link member directly in its pivoting point. In this way, the force transfer can be effected in a more space economic fashion, without the need for any longitudinal movement and extra space above or under the link member. Thus, a greater degree of freedom regarding dimensioning and planning of the vehicle is accomplished. Further, each link member will only require one lever, acting between the link member and the spring member. This simplifies the relationship between desired clearance adjustment and required applied motion.

The rod is preferably arranged in a plane substantially normal to a pivoting axis of the link member. Thereby, the rod can have an extension

which allows for a space economic arrangement in relation to other components of the chassis. For example, the rod can be arranged in the longitudinal direction of the vehicle, parallel to the spring member.

The rotatable rod can be actuated by an actuator, which may be mechanically, electrically, pneumatically or hydraulically operated. This will enable clearance adjustment after mounting of the suspension, possibly even when the vehicle is moving. That will allow a driver to adjust the clearance in dependence of the road conditions, e.g. a lower "highway" clearance when travelling on even roads, and a larger "off-road" clearance when travelling on rough roads or terrain.

The rotatable rod can comprise a first portion in engagement with the first link member, and a second portion, wherein the first and second portions are independently rotatable and lockable in a plurality of different relative positions. If the second rod portion is fixed in relation to the frame, this provides a simple adjustability of the link member.

A suspension with a divided rod can advantageously be implemented in a system comprising a second spring member intended to be arranged in a longitudinal direction of the vehicle for suspending a second wheel axle from the frame, and a second link member pivotable in dependence of a vertical position of the second spring member, wherein the second rod portion is in engagement with the second link member, so that a pivoting motion of the second link member is converted to rotational motion of the second rod portion. Such a suspension provides relative adjustment between two spring members, and thus between two axles. Such an arrangement may be particularly useful for two wheel axles provided with a load share arrangement.

Brief description of the drawings

The present invention will now be described in more detail with reference to the accompanying schematic drawings which show preferred embodiments of the invention.

Figure 1 shows schematically a vehicle provided with a suspension system according to a first embodiment of the invention.

Figure 2 shows schematically a suspension system according to a second embodiment of the invention. Figure 3 shows schematically a suspension system according to a third embodiment of the invention.

Detailed description of preferred embodiments

Figure 1 illustrates a wheel axle 1 , here a beam type axle, suspended under a longitudinal beam 2 of a frame of a vehicle using a suspension system according to an embodiment of the invention. The suspension system is arranged to allow relative movement between the axle 1 and the frame 2, and comprises two or more spring members 3, typically leaf springs, to which the axle is bolted. As figure 1 is a side view, only one of the spring members 3 is shown. The leaf spring 3 is pivotally connected in one end; in the illustrated case a spring eye 4 in its front end is connected to a first spring hanger 5 which is mounted to the beam 2.

In the other end of the spring 3, here in its rear end, the spring is pivotally connected to one end of a link member 6, here comprising a shackle 7 and a lever 8.

The lever is in one end pivotally connected to a second spring hanger 9 mounted to the beam 2. The shackle 7 is pivotally connected in one end to the spring 3, and in the other end to the lever 8, thereby allowing the rear connection point of the spring to move in the longitudinal direction of the vehicle in dependence of the load applied to the wheel axle 1 and spring 3.

The suspension system further comprises a rod 10 that is arranged to be rotatable around its longitudinal axis. The rod is arranged in rotational engagement with the lever 8, here in one of the ends of the rod. A geometric pivot axis of the link member 6, such as the pivot axis A of the lever 8, and the geometric rotation axis of the rod 10 are preferably substantially perpendicular relative to each other. The geometric pivot axis of the link member 6 can preferably be arranged in parallel with the wheel axle direction. As indicated in the illustrated embodiment, the rod is rotatable around its

longitudinal axis and can be arranged essentially in the longitudinal direction of the vehicle, i.e. essentially perpendicular to the wheel axles.

In the illustrated example, the rod 10 and the lever 8 are both provided with meshing gears, such as meshing gear wheels 11, 12, to allow a rotational movement of the rod 10 to be transferred to a pivoting motion of the lever 8.

The rod 10 is preferably arranged essentially perpendicularly to the pivoting axis A of the lever, i.e. in a plane parallel to the longitudinal direction of the vehicle, and for this purpose, the gear wheels 11 , 12 are preferably beveled.

The second end of the rod 10 is fixed in relation to the beam 2, and lockable in a plurality of different positions, corresponding to different positions of the lever 3 and thus spring 3.

According to the embodiment in figure 1 , the rod 10 is simply releasably mounted, here by means of a spline and sleeve arrangement. The rod 10 is provided with splines 13 along a portion of its length, and this portion is engaged by a sleeve 14 of a holder 15 that is slidably in a guide 16 mounted to the beam 2. In order to adjust the position of the rod 10, the holder 15 is slid along the guide until the splines 13 no longer engage the sleeve 14. The rod 10 can then be rotated to a desired position, and the holder be brought back to its original position and locked. As an alternative, a short rod portion provided with splines is fixedly mounted to the frame 2, and the sleeve 14 is arranged to engage the splines of the rod 10 and the splines of the short rod portion. This alternative is similar to the fixation of two rod portions described below with reference to figure 3.

According to the embodiment in figure 2, the rod 10 is actuated by an actuating device 18, preferably comprising a power gear and a suitable actuator, such as an electrical motor, a pneumatic actuator or a hydraulic actuator. Such an arrangement allows for automatic control of the position, e.g. by a control unit accessible to the driver of the vehicle.

The rod 10 may be adapted to have a certain degree of flexibility between its two ends, so as to act as a torsion spring or damper. This will

provide an additional comfort when the vehicle is operated with small spring excitations.

A further embodiment is illustrated in figure 3, showing a suspension system with two axles 1a, 1b, and a load share arrangement between the two axles.

In the system in figure 3, each wheel axle is suspended by respective leaf springs 3a, 3b, of which only one is shown for each axle 1a, 1 b. Each leaf spring 3 is connected to the frame in a similar way as described above with reference to figure 1 , i.e. with to a hanger 5 in one end and with a link member 6 in the other. The load share arrangement comprises a rotatable rod 10 that is arranged to transfer vertical forces acting on one axle 1b to the other axle 1a via a rotational moment of the rod 10. The illustrated load share arrangement is described in more detail in a co-pending application with the title "Load share arrangement", herewith incorporated by reference. Here, the rod 10 is sectioned in two portions, 10a, 10b, arranged to allow adjustment of the relative position of the link members 6. The portions are lockable in different relative positions, here by means of a sliding sleeve 14 adapted to engage splines 13a, 13b on each rod portion 10a, 10b.

A torsion spring or damper (not shown) can be arranged between the rod portions, possibly integrated in the sleeve 14.

The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, the link members could be arranged on the front end of each spring member. Also, many alternatives may be considered for locking the rod in different positions.