METHOD FOR CONTROLLING WHEEL AXLE SUSPENSION OF A VEHICLE

Abstract

The present invention relates to a method for controlling wheel axle suspension of a vehicle (100), said vehicle (100) comprising a vehicle chassis (116), a prime mover (122) for propulsion of said vehicle (100), said prime mover (122) being connected to the vehicle chassis (116); and a front wheel axle (132) comprising an individually adjustable wheel axle suspension arrangement (104, 106) on a respective left and right hand side of the front wheel axle (132) as seen in the longitudinal direction of the vehicle (100), said individually adjustable wheel axle suspension arrangement (104, 106) being connected between the front wheel axle (132) and the vehicle chassis (116); the method being comprising the steps of: determining (S1) an output torque from said prime mover (122); determining (S2) a rotation (302) of said vehicle chassis (116) caused by the determined output torque from the prime mover (122); comparing (S3) said rotation (302) with a predetermined threshold limit; and controlling (S4) the individually adjustable wheel axle suspension arrangement (104, 106) on at least one of the left and right hand sides of the front wheel axle (132) such that the rotation (302) of said vehicle chassis (116) is below said predetermined threshold limit.

Claims

1. A method for controlling wheel axle suspension of a vehicle, said vehicle comprising a vehicle chassis, a prime mover for propulsion of said vehicle, said prime mover being connected to the vehicle chassis; and a front wheel axle comprising an individually adjustable wheel axle suspension arrangement on a respective left and right hand side of the front wheel axle as seen in the longitudinal direction of the vehicle, said individually adjustable wheel axle suspension arrangement being connected between the front wheel axle and the vehicle chassis; the method being characterized by the steps of: determining an output torque from said prime mover; determining a rotation of said vehicle chassis caused by the determined output torque from the prime mover; comparing said rotation with a predetermined threshold limit; and controlling the individually adjustable wheel axle suspension arrangement on at least one of the left and right hand sides of the front wheel axle such that the rotation of said vehicle chassis is below said predetermined threshold limit.

2. The method according to claim 1, comprising the steps of: determining a moment of inertia of the vehicle chassis; and calculating a rotation of the vehicle chassis by means of the moment of inertia of the vehicle chassis and the determined output torque from the prime mover.

3. The method according to claim 1, wherein the vehicle comprises a propeller shaft arranged between the prime mover and a rear wheel axle of the vehicle, wherein the step of determining the output torque of the prime mover is executed by determining an output torque on said propeller shaft.

4. The method according to claim 3, wherein the output torque on the propeller shaft is determined by means of receiving a signal from a torque sensor connected to the propeller shaft.

5. The method according to claim 3, wherein said vehicle further comprises a gearbox arranged between the prime mover and the propeller shaft, wherein the output torque on the propeller shaft is determined by means of receiving a signal indicative of a rotational speed of the prime mover and a current gear ratio between an input shaft and an output shaft of the gearbox.

6. The method according to claim 1, wherein each of the individually adjustable wheel axle suspension arrangements of the front wheel axle is connected to a respective portion of the vehicle chassis, wherein the individually adjustable wheel axle suspension arrangement is controlled such that the portions of the vehicle chassis are positioned at a substantially same vertical level relative to the front wheel axle.

7. The method according to claim 1, wherein each of the individually adjustable wheel axle suspension arrangements comprises a pneumatically controlled air bellows, wherein the step of controlling the individually adjustable wheel axle suspension arrangement on at least one of the left and right hand sides of the front wheel axle is executed by increasing or decreasing an air pressure level of at least one of said pneumatically controlled air bellows.

8. The method according to claim 1, wherein the vehicle further comprises a first and a second rear wheel axle, said first rear wheel axle being position in front of said second rear wheel axle, said method further comprising the steps of: determining a wheel axle load on the front wheel axle; comparing said wheel axle load with a predetermined minimum threshold limit; and increasing the wheel axle load on the second rear wheel axle if the wheel axle load on the front wheel axle is below said predetermined threshold limit.

9. The method according to claim 8, wherein an individually adjustable wheel axle suspension arrangement is connected between the first rear wheel axle and the vehicle chassis, wherein the step of increasing the wheel axle load on the second rear wheel axle is executed by reducing a load pressure of the individually adjustable suspension arrangement of the first rear wheel axle.

10. The method according to claim 9, wherein the individually adjustable suspension arrangement connected to the first rear wheel axle comprises a pneumatically controlled air bellows, wherein the step of increasing the wheel axle load on the second wheel axle is executed by reducing an air pressure level of said pneumatically controlled air bellows.

11. The method according to claim 8, wherein the first rear wheel axle is a liftable wheel axle, wherein the step of increasing the wheel axle load on the second wheel axle is executed by lifting the first rear wheel axle.

12. A system for controlling wheel axle suspension of a vehicle, said vehicle comprising a vehicle chassis, a prime mover for propulsion of said vehicle, said prime mover being connected to the vehicle chassis; and a front wheel axle comprising an individually adjustable wheel axle suspension arrangement on a respective left and right hand side of the front wheel axle as seen in the longitudinal direction of the vehicle, said individually adjustable wheel axle suspension arrangement being connected between the front wheel axle and the vehicle chassis; wherein the system comprises a control unit configured to control the system to: determine an output torque from said prime mover; determine a rotation of said vehicle chassis caused by the determined output torque from the prime mover; compare said rotation with a predetermined threshold limit; and control the individually adjustable wheel axle suspension arrangement on at least one of the left and right hand sides of the front wheel axle such that the rotation of said vehicle chassis is below said predetermined threshold limit.

13. The system according to claim 12, wherein the vehicle further comprises the system.

14. The method of claim 1 wherein the steps are performed by a computer program contained on a computer readable medium and said program is run on a computer.

15. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of exemplary embodiments of the present invention, wherein:

[0038] FIG. 1 is a side view of a heavy duty vehicle, in the form of a truck according to an example embodiment of the present invention;

[0039] FIG. 2 is a perspective view illustrating in detail an example embodiment of portions of the vehicle chassis and suspension arrangements of the vehicle in FIG. 1;

[0040] FIGS. 3a-3b are front views of the vehicle in FIG. 1 during acceleration thereof; and

[0041] FIG. 4 is an example embodiment of a flow chart of a method for controlling wheel axle suspension of the vehicle in FIG. 1.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

[0042] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness. Like reference character refer to like elements throughout the description.

[0043] With particular reference to FIG. 1, there is provided a vehicle 100 arranged to be provided with a control unit 102 having computer program stored therein for controlling wheel axle suspension arrangement(s) of the vehicle 100. As depicted in FIG. 1, the vehicle 100 comprises a vehicle chassis 116 which in turn comprises a vehicle frame 118 and a vehicle cabin 120. Furthermore, the vehicle 100 comprises a prime mover 122, preferably in the form of an internal combustion engine. The prime mover 122 is connected to a gearbox 124 which in turn is connected to a first 126 and a second 128 rear wheel axle by means of a propeller shaft 130 and a rear propeller shaft 131. The propeller shaft 130 is connected to the first rear wheel axle 126 by means of a first joint coupling (see 202 in FIG. 2). The rear propeller shaft 131 is arranged between the first joint coupling 202 and a second joint coupling (204 in FIG. 2) for connection to the second 128 rear wheel axle. The first 126 and second 128 rear wheel axles are each provided with wheels 127, 129 on a respective left and right hand side of the vehicle 100 as seen in the longitudinal direction thereof. Although the gearbox 124 is depicted as positioned between the prime mover 122 and the propeller shaft 130, it may also be positioned further downstream the propeller shaft 130, such as between the first joint coupling (202 in FIG. 2) and the rear propeller shaft 131.

[0044] Moreover, the vehicle 100 comprises a front wheel axle 132, which front wheel axle 132 is a steerable wheel axle. Furthermore, the vehicle 100 comprises wheel axle suspension arrangements 104, 106, 108, 110, 112, 114 for connecting the respective front wheel axle 132, the first rear wheel axle 126 and the second rear wheel axle 128 to the vehicle chassis 116. In the following, the wheel axle suspension arrangements 104, 106 connected to the front wheel axle 132 will be referred to as the front wheel axle suspension arrangement 104, 106, the wheel axle suspension arrangements 108, 110 connected to the first rear wheel axle 126 will be referred to as the first rear wheel axle suspension arrangement 108, 110, and the wheel axle suspension arrangements 112, 114 connected to the second rear wheel axle 128 will be referred to as the second rear wheel axle suspension arrangement 112, 114. These wheel axle suspension arrangements and their connection to the chassis 116 and the respective wheel axles will be described in further detail below in relation to the description of FIG. 2.

[0045] Turning now to FIG. 2, which is a perspective view illustrating in detail an example embodiment of the vehicle chassis 118 and suspension arrangements 104, 106, 108, 110, 112, 114 of the vehicle in FIG. 1. For simplicity of illustration, the wheels and vehicle cabin have been omitted from FIG. 2.

[0046] As described above, the vehicle 100 comprises a front wheel axle suspension arrangement 104, 106 connected between the front wheel axle 132 and the vehicle chassis 116 on a respective left and right hand side of the front wheel axle 132. The front wheel axle suspension arrangement 104, 106 are each individually adjustable wheel axle suspension arrangements which mean that they can be controlled independently of the remaining wheel axle suspension arrangements of the vehicle 100. In detail, the front wheel axle suspension arrangement 104 on the left hand side of the front wheel axle 132 can be controlled individually in relation to the front wheel axle suspension arrangement 106 on the right hand side of the front wheel axle 132, and vice versa. The front wheel axle suspension arrangement 104 on the left hand side of the front wheel axle 132 can, for example, be raised while keeping the front wheel axle suspension arrangement 106 on the right hand side stationary.

[0047] Moreover, the front wheel axle suspension arrangement 104, 106 comprises a pneumatically controlled air bellows 206, 208 on the respective left and right hand sides of the front wheel axle 132. Hereby, compressed air or other pneumatic medium is provided into the respective air bellows 206, 208 when there is a desire to raise the vehicle chassis 116 relative to the front wheel axle 132, and air is provided out from the respective air bellows 206, 208 when there is a desire to lower the vehicle chassis 116 relative to the front wheel axle 132.

[0048] As further illustrated in FIG. 2, the front wheel axle suspension arrangements 104, 106 are connected to the vehicle chassis 216 at a respective portion 214, 216 thereof. In more detail, the front wheel axle suspension arrangement 104 on the left hand side of the front wheel axle 132 is connected to the vehicle frame 118 at a left frame portion 214, while the front wheel axle suspension arrangement 106 on the right hand side of the front wheel axle 132 is connected to the vehicle frame 118 at a right frame portion 216.

[0049] Furthermore, the vehicle 100 comprises first rear wheel axle suspension arrangements 108, 110 connected between the first rear wheel axle 126 and the vehicle chassis 116, and second rear wheel axle suspension arrangements 112, 114 connected between the second rear wheel axle 128 and the vehicle chassis 116. The first 108, 110 and second 112, 114 rear wheel axle suspension arrangements are each preferably individually adjustable wheel axle suspension arrangements.

[0050] It should thus be readily understood that each of the first 108, 110 and second 112, 114 rear wheel axle suspension arrangements are individually adjustable according to the same principle as described above in relation to the front wheel axle suspension arrangement 104, 106. The first rear wheel axle suspension arrangement 110 on the right hand side of the first rear wheel axle 126 can, for example, be controlled individually in relation to the remaining wheel axle suspension arrangements of the vehicle 100.

[0051] As is further depicted in FIG. 2, each of the first 108, 110 and second 112, 114 rear wheel axle suspension arrangements comprises a respective leaf spring arrangement 210 and a pneumatically controlled air bellows 212. It should however be readily understood that other suspension arrangements for the first 108, 110 and second 112, 114 rear wheel axle suspension arrangements are also conceivable and within the scope of the present invention. For example, the first 108, 110 and second 112, 114 rear wheel axle suspension arrangements may comprise only pneumatically controlled air bellows 212, i.e. the leaf springs are omitted. Also, the first 108, 110 and second 112, 114 rear wheel axle suspension arrangements may comprise a hydraulically controlled suspension arrangement, or a combination of hydraulically and pneumatically controlled suspension arrangements, or a hydraulically controlled suspension arrangement in combination with the leaf spring arrangement 210.

[0052] Furthermore, the first rear wheel axle 126 is arranged to be liftable. Hereby, during traveling, the first rear wheel axle 126 can be lifted such that no contact is present between the wheels 127 on the first rear wheel axle 126 and the ground surface. By lifting the first rear wheel axle 126, the wheel axle load on the front wheel axle 132 can be increased for improving the steerability of the vehicle 100, especially during acceleration thereof. The wheel axle load on the front wheel axle 132 can also be increased by reducing the wheel axle load on the first rear wheel axle 126 by controlling the first rear wheel axle suspension arrangements 108, 110. The second rear wheel axle 128 may also be liftable.

[0053] Still further, the prime mover 122 is also connected to the vehicle chassis 116. This is in FIG. 2 illustrated by means of a plurality of attachment portions 218. Also, although the vehicle cabin 120 is excluded from the illustration in FIG. 2, it should be readily understood that also the vehicle cabin 120 is connected to the vehicle chassis 116.

[0054] Reference is therefore made to FIGS. 3a and 3b in combination with the illustration in FIG. 2, in order to describe the method for controlling the wheel axle suspension of the vehicle 100 in further detail. FIGS. 3a-3b are illustrating the general principle of the present invention. In detail, the continuous lines in FIG. 3a illustrates the effects of the vehicle 100 without the use of the inventive method and system of the present description, while the dashed lines, and FIG. 3b, illustrate the vehicle 100 when accelerating with high output torque on the propeller shaft 130 with the use of the inventive method.

[0055] As described above, the prime mover 122 is connected to the vehicle chassis by means of the plurality of attachment portions 218, and the propeller shaft 130 is connected to the first wheel axle 126. Therefore, when driving at relatively slow speed and accelerating the vehicle 100 with a high output torque from the prime mover 122, the vehicle chassis 116 will be exposed to a torque which will create a rotation 302 of the vehicle chassis 116 around a geometric axis 304 extending in the longitudinal direction of the vehicle 100. This is thus caused by the rotation and torque on the propeller shaft 130 which provides a rotation on the prime mover 122 and also the vehicle chassis 116, to which the prime mover 122 is fixedly connected.

[0056] Accordingly, the rotation 302 of the vehicle chassis 116 may be proportional to the output torque from the prime mover 122 and in particular to the output torque on the propeller shaft 130. The specific amount of the rotation also depends on the specific vehicle 100 with regards to e.g. its weight, structural stiffness, moment of inertia, etc. The moment of inertia for the vehicle can preferably be set as an indicative parameter determining the rotation of the vehicle chassis 116 for a given output torque on the propeller shaft 130. As clearly depicted in FIG. 3a, at high output torques on the propeller shaft 130, the front wheel axle suspension arrangement 106 on the right hand side of the front wheel axle 132 is compressed while the front wheel axle suspension arrangement 104 on the left hand side of the front wheel axle 132 is expanded.

[0057] By means of the present invention, when determining the output torque from the prime mover 122 the rotation 302 of the vehicle chassis 116 can be determined. Thereafter the front wheel axle suspension arrangements 104, 106 on the left and right hand side of the front wheel axle 132 can be controlled such that the vehicle chassis 116 will be substantially parallel relative to the front wheel axle 132 as depicted in FIG. 3b. According to the example depicted in FIG. 3b, compressed air is provided to the air bellows 216 of the front wheel axle suspension arrangement 106 on the right hand side, while the air bellows 214 on the front wheel axle suspension arrangement 104 on the left hand side is relieved from air.

[0058] When adjusting for the rotation 302 caused by the output torque on the propeller shaft 130 also the first 108, 110 and second 112, 114 rear wheel axle suspension arrangements may be controlled and adjusted according to similar principles as the front wheel axle suspension arrangements 104, 106.

[0059] Finally, in order to sum up, reference is made to FIG. 4 which illustrates an example embodiment of a flow chart of a method for controlling wheel axle suspension of the vehicle 100 described above in relation to FIGS. 1-3b.

[0060] Firstly, during operation of the vehicle, the output torque from the prime mover 122 is determined S1. Preferably, the output torque on the propeller shaft 130 is determined. The output torque on the propeller shaft 130 may be determined by receiving a signal from a torque sensor 220 positioned on the propeller shaft 130. The output torque may also be determined by receiving a signal indicative of a present, or upcoming predicted rotational speed of the prime mover 122, which in combination with a gear ratio for a current gear stage of the gearbox 124 can be used for calculating the output torque. A rotation 302 of the vehicle chassis 116 is thereafter determined S2. The determined rotation 302 is compared S3 with a predetermined threshold limit. Hereby, it can be determined if the rotation 302 is too severe and adjustment is needed. If the rotation 302 is determined to be above the predetermined threshold limit, i.e. too severe, the individually adjustable wheel axle suspension arrangement 104, 106 on at least one of the left and right hand sides of the front wheel axle 132 is controlled S4 such that the rotation 302 of the vehicle chassis 116 will be below the predetermined threshold limit.

[0061] It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims. The invention should not be limited to vehicle comprising three wheel axles as depicted in the figures. The invention is equally applicable for vehicles comprising e.g. four or five wheel axles, etc.