WO2009072937A1

WO2009072937A1 - Load sharing arrangement

Info

Publication number: WO2009072937A1
Application number: PCT/SE2007/001087
Authority: WO
Inventors: John NORDSTRÖM
Original assignee: Volvo Lastvagnar AB
Current assignee: Volvo Truck Corp
Priority date: 2007-12-06
Filing date: 2007-12-06
Publication date: 2009-06-11
Anticipated expiration: 2010-06-06

Abstract

A load sharing arrangement for a vehicle having a frame, a first wheel axle and a second wheel axle, comprising a first link member pivotable in reponse to vertical forces acting on the first axle, a second link member pivotable in reponse to vertical forces acting on the second axle, and a force transmission element connected to transfer forces between the pivotable link members in order to balance vertical forces acting on the first and second wheel axles, wherein the force transmission element is a rotatably arranged rod. The present invention can advantageously provide load sharing between two steered axles of a vehicle, for example two steered front wheel axles, as it provides load sharing between corresponding ends (e.g. the rear ends) of the spring members.

Description

LOAD SHARING ARRANGEMENT

Technical field

The present invention relates to a load sharing arrangement for balancing vertical forces acting on a first wheel axle and a second wheel axle of a vehicle. The invention also relates to a vehicle provided with such a load sharing arrangement.

Technical background

Some heavy vehicles have two steered front wheel axles, where the wheels on each axle are coupled to the steering system of the vehicle. When a heavy vehicle is driven on an uneven road, e.g. over a bump or a hole, these front axles will experience different loads. Similarly, the cargo load of the vehicle may cause an inclination of the vehicle frame, again resulting in different load on each front wheel axle.

In both cases, there is a need to balance the load on each front axle. For non-steered rear axles, relatively simple load sharing mechanisms exist, that mechanically connect the adjacent ends of the springs of each axle around a pivoting point. However, due to the fact that the wheels of the front axles are coupled to the steering system of the vehicle, such a simple solution is not feasible for front axles. Instead, load sharing arrangements of the above-mentioned type are used for distribute the load on the front wheels axles with two steering front wheel axles.

As an example, JP08118930 discloses a front axle load sharing system in which a first laminated spring onto which a first front axle is mounted, is connected to a connection rod through a first lever member. The outer end of the connecting rod is coupled to a second laminated spring onto which a second front axle is mounted through a second lever member that supports. Up and down motion of the first front axle is converted by the first lever member into push and pull motion of the connecting rod. This push and pull motion is converted by the second lever member into an opposite motion of the second axle. In this way, a portion of the load from the first front axle is transferred to the second front axle.

However, such a load sharing arrangement is bulky and involves a large inertia due to the longitudinal movement of the connection rod. Also, the connecting rod needs to engage the lever member at a distance from their pivoting points, in order to create a lever. This in turn requires additional space for the connecting rod.

Further, as each lever member operates by means of two levers (one connected to the connection rod, and one connected to the spring), there is a complex non-linear relationship between the position of the spring and the transfer of force.

Hence, there is a need for an improved load sharing arrangement which eliminates or mitigates at least some of the above problems.

Summery of the invention

The present invention relates to load sharing between a first and a second wheel axles of a vehicle, each axle being supported by at least two spring members extending in a longitudinally direction of said vehicle, each spring member being pivotally mounted in a first end, and vertically movably suspended in a second end.

A first aspect of the invention relates to a load sharing arrangement comprising a first link member pivotable in reponse to vertical forces acting on said first axle, a second link member pivotable in reponse to vertical forces acting on said second axle, and a force transmission element connected to transfer forces between the pivotable link members in order to balance vertical forces acting on the first and second wheel axles, wherein the force transmission element is a rotatably arranged rod.

The invention is based on the realization that it is advantageous to transfer forces between the pivoting link memers by means of a rotatatable rod.

The present invention can advantageously provide load sharing between two steered axles of a vehicle, for example two steered front wheel axles, as it provides load sharing between corresponding ends (e.g. the rear ends) of the spring members. However, the invention may also be applied to non-steered axles, or between a steered axle and a non-steered axle.

The rotatable rod does not need to be vertically displaced from a pivoting point of the link member, but can engage the link member directly at 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 wheel axle (typically via a spring member, suspending the axle). This simplifies the relationship between force transfer and spring position and thus an improved axle load distribution is achieved. According to a preferred embodiment, the first link member pivotally connectable in a first end to the second end of a spring member of the first front axle and in a second end to the frame, and a second link member pivotally connectable in a first end to the second end of a spring member of the second front axel and in a second end to the frame, and a force transmission element adapted to balance vertical forces acting on each link member.

The link members are preferably adapted to engage said rotatable rod so as to transform a pivoting motion of each link member to a rotational movement of said rod, and vice versa, in order to balance forces acting on the spring members.

The expression "vice versa" is here intended to indicate that the engagement between the rotatable rod and the link members also is capable of transforming a rotating motion to a pivoting motion.

The arrangement is preferably designed so that a clock wise pivoting motion of said first link member is converted to a clock wise pivoting motion of the second link member. This allows for an asymmetrical arrangement of the link members, e.g. both extending away from the rotatable rod.

During rotation, an upwards directed movement on one side of the rod is accompanied by a downwards directed movement on the opposite side. The link members can therefore be adapted to engage the rotatable rod on opposite sides of a centreline of the rod in order to ensure the desired motion.

Each link member may be arranged to engage the rotatable rod at a horizontal distance from a point of connection between said link member and said spring member, along the axis of rotation of the link member. This allows mounting the rotatable rod at a distance from the spring members, which may be advantageous due to restricted space immediately above the spring members. Note that the use of rotational force avoids the creation of an additional lever when moving the point of engagement away from the connection between link member and spring member. According to one embodiment the rotatable rod is provided with meshing gears in each end of the rod, and each link member is provided with meshing gears formed to engage the meshing gears in one end of the rotatable rod.

Meshing gears are a simple and effective way to achieve the engagement between link member and rotatable axle, which is cost effective and requires little space. Various types of meshing gears may be used to provide the desired force transfer, and possible solutions include bevelled gear wheels. Bevelled gear wheels make it possible to transfer a movement from the rotatable axle directly to the horizontal axle positioned perpendicular to the rotatable axle. Hence, by this way a compact configuration of the load sharing arrangement is achieved.

According to a further embodiment, each link member comprises a link arm which is pivotable in a first end around a horizontal axis fixed in relation to the frame, and a suspension member, pivotally connected in a first end to a second end of the link arm, and pivotally connected in a second end to the second end of the spring member.

Such a link member provides the required freedom for the spring member, while allowing transfer of force from the rotatable rod.

In this case, the link member can further comprise meshing gears fixedly connected to said link arm and having an axis of rotation coinciding with the horizontal axis. The rotatable rod can then engage the meshing gears, in turn forcing the link arm to pivot, thereby transferring the force to the suspension member and further to the spring member.

In the case mentioned above, where the point of engagement between the rotatable rod and the link member is separated by a horizontal distance from the connection point between link member and spring member, the meshing gears can be connected to the link arm by an axle. This axle can then be received by a hole in the frame or other support structure, thus providing the pivoting arrangement of the link arm.

According to an embodiment of the invention, the rotatable rod comprises two separate portions, which are independently rotatable and lockable in a plurality of different relative positions.

By adjusting the relative position of the two axle portions, a relative adjustment of the vertical position of each respective wheel axle is effected, leading to a change of the clearance between the vehice frame and the ground. According to this embodiment of the invention, such clearance adjustment can thus be made during or after mounting the load share arrangement. One load sharing arrangement can thus be used to produce trucks with different set ups.

An actuator can be arranged to effect such adjustments, making it possible to automatically adjust the driving height. Further, a torsion spring or damper can be arranged between the two rod portions, to thereby give a better comfort at low road excitations, when the spring members themselves are more stiff.

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.

Fig. 1 shows schematically a portion of a vehicle having two steered front wheel axles. Fig. 2 shows a load sharing arrangement according to prior art.

Fig. 3 shows a load sharing arrangement according to an embodiment of the present invention.

Fig. 4 shows a perspective view of the arrangement in fig. 3.

Fig. 5 shows schematically a portion of a vehicle equipped with the load sharing arrangement of figure 3 and 4.

Fig. 6 shows a load sharing arrangement according to a further embodiment of the present invention. Fig. 7 shows a load sharing arrangement according to a further embodiment of the present invention.

Detailed description of preferred embodiments

The vehicle illustrated in figure 1 has two front beam axles 1a, 1 b, each supporting two front wheels 2. Each beam axle 1a, 1b is bolted to two spring members 3, here leaf springs, extending in the longitudinal direction of the vehicle. The springs are in turn mounted to the frame of the vehicle, here illustrated as two longitudinal frame members.

In order to allow a yielding suspension, each spring 3 is pivotally mounted in one end 3a, and suspended by a shackle 4 in the other end 3b. This allows the fixation point of the axle to move up and down, under springing action of the spring member. A damper 5 is arranged to each spring member, to reduce the spring movement. Typically, the shackle 4 is arranged in the rear end 3b of each spring member 3. However, this is not a limitation of the applicability of the present invention. Each wheel is arranged on a steering joint 23, which is operated by a steering arm 24 connected via a link arm 25 to a pitman arm 26a, 26b. The front pitman arm 26a is operated by a steering gear controlled by the steering wheel 27. The rear pitman arm 26b is connected to the front pitman arm 26a via a relay rod 28, so as to synchronize the steering of the front and rear wheels. The steering of the wheels on each axle is synchronized by a track rod 29.

In a vehicle of the kind illustrated in figure 1 , a load sharing arrangement may be arranged to balance an increased force on one front wheel axle to the other front wheel axle.

Figure 2 schematically shows such a load sharing arrangement according to prior art. Here, the shackles 4 of each leaf spring 3 is connected to a lever 6, pivotally arranged around a pivoting point 6c and connected in one end 6a to the shackle 4. The free ends 6b of corresponding levers 6 are connected by a force transmission element 7 in the form of a rod arranged to move back and forth in the longitudinal direction of the vehicle, which rod thereby can transfer forces between the levers.

Figures 3 and 4 show a load sharing arrangement according to an embodiment of the present invention. Here, again the front ends 31a, 32a of each spring member 31 , 32 is pivotally mounted to the frame 9 of the vehicle. The rear end 31b, 32b of each spring member 31 , 32 is further supported by a link member 10a, 10b which is pivotally arranged around an axis A that is fixed in relation to the frame. A force transmission element 11 is connected between the link members of two spring members. According to the present invention, the force transmission element is a rotatable rod, which is arranged to engage the link members to transmit a pivoting movement of one link member 10a to a pivoting movement of the other link member 10b via a rotational movement of the rod 11. A geometric pivot axis of the first link member 10a and the geometric rotation axis of the rod 11 are preferably substantially perpendicular relative to each other. In the same way a geometric pivot axis of the second link member 10b and the geometric rotation axis of the rod 11 are preferably substantially perpendicular relative to each other. The geometric pivot axes of the link members 10a, 10b are preferably substantially parallel to each other, and the geometric pivot axes of the link members 10, 10b can 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. The link members act as cradles that transfer a rotational moment to a vertical force acting on the spring member and further onto the wheel axle. As indicated in figures 3 and 4, a force B acting upwards on the front spring member 31 will create a rotational moment C on the rod 11 , and finally a force D acting downwards on the rear spring member 32.

The use of rotational motion to transfer force from one link member to another avoids the need of a lever between the pivoting axis A of the link member and the force transmission element, as required in the prior art system in figure 2. Instead, the rotatable rod can engage each link member directly in the pivoting axis A of the link member.

In the illustrated embodiment, each link member 10a, 10b comprises a pivoting link arm 12a, 12b. Here, the link arm is formed with a hole adapted to receive an axle or pin extending from the frame or a support mounted to the frame. The link member 10a, 10b further comprises a shackle 13 connected in one end to the spring member 31 , 32, and in the other end to the link arm 12a, 12b, at a distance from the axis A.

The engagement between the rod and the link members can be provided by suitable meshing gears. In the illustrated example, meshing gears 14 having an axis of rotation coinciding with the axis A are integrally formed with each link arm 12a, 12b. The link arm 12a, 12b and meshing gears 14 may be molded in one piece, or be attached to each other by means of suitable fasteners or welding. Corresponding meshing gears 15 are provided on each end of the rod 11 , so that rotation of the rod can be converted to pivoting of the link arms 12a, 12b.

Any meshing gears providing a sufficient change in axis of rotation may be used. In the example in figure 3, beveled gear wheels 14, 15 are used. Note that it may not be necessary to provide complete gear wheels, having gear teeth all around 360 degrees. In fact, the expected rotation of the rod is normally quite limited, and the gear wheels 14, as well as the gear wheels 15, may be formed as sectors of complete wheels. In the example illustrated in figure 3, the gear wheels 14 on the link members 10a, 10b are 180 degree sectors of complete gear wheels.

In order to balance forces, the load share arrangement must be arranged so that an upwards motion of one spring member is transferred to a downwards motion of the other spring member. In the illustrated example, the link arms of the first and second spring members are arranged symmetrically, i.e. they are connected to their respective spring member 3 on different sides of their respective pivoting axis A. In other words, in order to move the first spring member 31 in one direction (e.g. upwards, arrow B), and the second spring member 32 in a different direction (e.g. downwards, arrow D), the link arms 12a, 12b must be rotated in the same direction (e.g. clock wise) around the axis A.

Therefore, with the illustrated arrangement of the link members, the gear wheels 14 of each link member 12a, 12b are preferably arranged to engage the gear wheels 15 on opposite sides of the centre axis of the rod 11. Thereby, when one spring member 31 is moved up (arrow B), the rod will rotate (arrow C) and push the second spring member 32 down (arrow D).

Figure 5 shows a vehicle provided with the load sharing arrangement in figures 3 and 4. In a further embodiment, illustrated in figure 6, the point of engagement between the rod and the link members is moved sideways, here in a direction under the vehicle. The link member gear wheel 14 is here connected to the link arm 12a, 12b via an axle 16, which is pivotally arranged in a hole 17 in the frame or a support mounted to the frame. The rod 11 engages the gear wheels 14 in the same way as in figure 3, but at a position sideways separated from the link arms 12a, 12b. As a result, the entire rod 11 can be mounted at a horizontal distance from the spring member, where may be advantageous from a design perspective. Note that the gear wheels 14 also in this arrangement are arranged on different sides of the rod 11. Figure 7 illustrates a further embodiment of the invention, according to which the rotatable rod comprises two individually rotatable portions 11a, 11 b. The portions are lockable in different relative positions, here by means of a sliding sleeve 18 adapted to engage splines 19 on each rod portion 11a, 11b. According to this embodiment, the relative position of the link members can be adjusted by releasing the sleeve, rotating the rod portions in relation to each other, and then replacing the sleeve. Such adjustment can be performed manually, during production or service, or automatically, by arranging suitable actuating means 20 such as stepping motors or hydraulic actuators. Optionally, a torsion spring or damper 21 can be arranged between the rod portions. Such a spring or damper will increase comfort at low road excitations. 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.

Claims

1. A load sharing arrangement for a vehicle having a frame (9), a first wheel axle (1a) and a second wheel axle (1 b), comprising: a first link member (10a) pivotable in reponse to vertical forces acting on said first axle, a second link member (10b) pivotable in reponse to vertical forces acting on said second axle, and a force transmission element (11 ) connected to transfer forces between the pivotable link members in order to balance vertical forces acting on the first and second wheel axles, c h a r a c t e r i z e d in that said force transmission element is a rotatably arranged rod (11).

2. The load sharing arrangement according to claim 1 , wherein each axle is supported by at least two spring members (31 , 32) extending in a longitudinally direction of said vehicle, each spring member being pivotally mounted in a first end (31a, 32a), and vertically movably suspended (31b, 32b) in a second end, said first link member (10a) being pivotally connectable in a first end to the second end of a spring member (31 ) of the first axle (1a) and in a second end to said frame (9), and said second link member (10b) being pivotally connectable in a first end to the second end of a spring member (32) of the second axel (1 b) and in a second end to said frame (9), and said link members being adapted to engage said rotatable rod (11 ) so as to transform a pivoting motion of each link member to a rotational movement of said rod, and vice versa, in order to balance forces acting on said spring members.

3. The load sharing arrangement according to claim 1 or 2, wherein a clock wise pivoting motion of said first link member is converted to a clock wise pivoting motion of the second link member.

4. The load sharing arrangement according to claim 3, wherein the link members (10a, 10b) are adapted to engage the rotatable rod (11 ) on opposite sides of a centreline of said rod.

5. The load sharing arrangement according to one of claims 1-4, wherein each link member (10a, 10b) is arranged to engage the rotatable rod (11) along an axis of rotation (A) of the link member at a horizontal distance from a point of connection between said link member and said spring member.

6. The load sharing arrangement according to any one of the preceding claims, wherein said rotatable rod (11 ) is provided with meshing gears (15) in each end of the rod, and each link member (10a, 10b) is provided with meshing gears (14) formed to engage the meshing gears in one end of the rotatable rod.

7. The load sharing arrangement according to claim 5 or 6, wherein said meshing gears are sectors of a gear wheel

8. The load sharing arrangement according to claim 7, wherein said gear wheels are beveled gear wheels.

9. The load sharing arrangement according to any one of the preceding claims, wherein each link member (10a, 10b) comprises a link arm (12a, 12b) which is pivotable in a first end around a horizontal axis (A) fixed in relation to the frame, and a suspension member (13), pivotally connected in a first end to a second end of said link arm (12a, 12b), and pivotally connected in a second end to the second end of said spring member (31 , 32).

10. The load sharing arrangement according to claim 9, wherein said link member (10a, 10b) further comprises meshing gears (14) fixedly connected to said link arm (12a, 12b) and having an axis of rotation coinciding with said horizontal axis.

11. The load sharing arrangement according to claim 10, wherein said meshing gears are connected to said link arm by an axle (16).

12. The load sharing arrangement according to any of the preceding claims, wherein said rotatable rod (11 ) comprises two separate portions (11a, 11b), which are independently rotatable and lockable in a plurality of different relative positions.

13. The load sharing arrangement according to claim 12, further comprising an actuator (20) for adjusting a relative position of said rod portions.

14. The load sharing arrangement according to claim 12 or 13, further comprising a damping element (21 ) arranged between said rod portions (11a, 11 b).

15. A vehicle having a first and a second wheel axles (1a, 1b), each axle being supported by at least two spring members (31>, 32) extending in a longitudinally direction of said vehicle, each spring member being pivotally mounted in a first end (31a, 32a), and vertically movably suspended in a second end (31b, 32b), c h a r a c t e r i z e d by a load sharing arrangement according to any one of claims 1-11.