METHOD FOR DETERMINING AGING OF A VEHICLE SUSPENSION ARRANGEMENT

Abstract

The present invention relates to a method for determining aging of a vehicle suspension arrangement (100) arranged between a frame and a wheel axle of a vehicle, said suspension arrangement (100) comprising a flexible bellows (102) for damping motions from said wheel axle, the method comprising the steps of determining a distance moved by a portion of the flexible bellows (102) when the suspension arrangement is exposed to an external load; determining a gas pressure level within said flexible bellows (102) when the portion of said flexible bellows (102) has moved said distance; determining a relationship between the determined gas pressure level within said flexible bellows and said distance moved by the portion of the flexible bellows; comparing the relationship with a predetermined threshold level; and determining that said flexible bellows is aged if a difference between the relationship and the predetermined threshold level is outside a predetermined threshold range.

Claims

1. A method for determining aging of a vehicle suspension arrangement arranged between a frame and a wheel axle of a vehicle, the suspension arrangement comprising a flexible bellows for damping motions from the wheel axle, the method comprising the steps of: determining a distance moved by a portion of the flexible bellows when the suspension arrangement is exposed to an external load; determining a gas pressure level within the flexible bellows when the portion of the flexible bellows has moved the distance; determining a relationship between the determined gas pressure level within the flexible bellows and the distance moved by the portion of the flexible bellows; comparing the relationship with a predetermined threshold level; and determining that the flexible bellows is aged if a difference between the relationship and the predetermined threshold level is outside a predetermined threshold range.

2. The method according to claim 1, wherein the predetermined threshold level corresponds to a relationship between a gas pressure level within a reference flexible bellows and a distance moved by a portion of the reference flexible bellows.

3. The method according to claim 1, wherein the suspension arrangement comprises a piston comprising a first, cylindrical portion and a second portion, the second portion has a geometric shape different in comparison to the geometric shape of the first portion, wherein the flexible bellows is at least partially connected to the first portion of the piston and arranged to move relative to the first portion when the suspension arrangement is exposed to the external load.

4. The method according to claim 3, wherein the flexible bellows is exposed to an external load moving the portion to reach the second portion of the piston, the method further comprising the steps of: determining the distance moved by the portion of the flexible bellows when the portion of the flexible bellows reaches the second portion of the piston; comparing the determined distance to the second portion with a predetermined reference distance to reach the second portion; and determining that the flexible bellows is aged if a difference between the determined distance and the predetermined reference distance is outside a predetermined distance range.

5. The method according to claim 3, wherein the second portion of the piston comprises a taper shaped surface.

6. The method according to claim 1, wherein the suspension arrangement comprises a level indicator for determining distance moved by the portion of the flexible bellows.

7. The method according to claim 6, wherein the external load is a compression force acting on the suspension arrangement, the compression force being determined based on the distance detected by the level indicator and a detected mass of the vehicle.

8. The method according to claim 1, wherein the suspension arrangement comprises a gas pressure sensor arranged inside the flexible bellows for measuring the gas pressure level.

9. A control unit arranged for determining aging of a vehicle suspension arrangement arranged between a frame and a wheel axle of a vehicle, the suspension arrangement comprising a flexible bellows for damping motions from the wheel axle, the control unit being configured to: receive a signal from a level indicator for determining a distance moved by a portion of the flexible bellows when the suspension arrangement is exposed to an external load; receive a signal from a gas pressure sensor for determining a gas pressure level within the flexible bellows when the portion of the flexible bellows has moved the distance; determine a relationship between the determined gas pressure level within the flexible bellows and the distance moved by the portion of the flexible bellows; compare the relationship between the determined gas pressure level within the flexible bellows and the distance moved by the portion of the flexible bellows with a predetermined threshold level; and determine that the flexible bellows is aged if a difference between the relationship between the determined gas pressure level within the flexible bellows and the distance moved by the portion of the flexible bellows and the predetermined threshold level is outside a predetermined threshold range.

10-12. (canceled)

13. A non-transitory computer-readable storage medium comprising a computer program product including instructions to cause at least one computer to: determine a distance moved by a portion of a flexible bellows when a suspension arrangement is exposed to an external load; determine a gas pressure level within the flexible bellows when the portion of the flexible bellows has moved the distance; determine a relationship between the determined gas pressure level within the flexible bellows and the distance moved by the portion of the flexible bellows; compare the relationship with a predetermined threshold level; and determine that the flexible bellows is aged if a difference between the relationship and the predetermined threshold level is outside a predetermined threshold range.

14. A non-transitory computer-readable storage medium comprising a computer program product including instructions to cause at least one computer to: receive a signal from a level indicator for determining a distance moved by a portion of a flexible bellows when a suspension arrangement is exposed to an external load; receive a signal from a gas pressure sensor for determining a gas pressure level within the flexible bellows when the portion of the flexible bellows has moved the distance; determine a relationship between the determined gas pressure level within the flexible bellows and the distance moved by the portion of the flexible bellows; compare the relationship between the determined gas pressure level within the flexible bellows and the distance moved by the portion of the flexible bellows with a predetermined threshold level; and determine that the flexible bellows is aged if a difference between the relationship between the determined gas pressure level within the flexible bellows and the distance moved by the portion of the flexible bellows and the predetermined threshold level is outside a predetermined threshold range.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] 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:

[0030] FIG. 1 is a lateral side view illustrating an example embodiment of a vehicle in the form of a truck;

[0031] FIG. 2 is cut-out view of a suspension arrangement and flexible bellows according to an example embodiment;

[0032] FIG. 3 is a graph illustrating the characteristics of the flexible bellows according to an example embodiment; and

[0033] FIG. 4 is a flow chart illustrating a method according to an example embodiment.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

[0034] 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.

[0035] With particular reference to FIG. 1, there is provided a vehicle 1 in the form of a truck for which the vehicle suspension arrangement 100 according to the invention is particularly suitable for. The vehicle 1 comprises a front vehicle suspension arrangement 100 connecting the frame 2 to the front wheel axle 3, and a rear vehicle suspension arrangement 100′ connecting the frame 2 to the rear wheel axle 4. Hence, each of the vehicle suspension arrangement 100, 100′ is arranged to damp/absorb loads from the respective wheel axles during motion of the vehicle 1. The vehicle 1 may of course comprise more than two wheel axles. As can be seen in FIG. 1, the vehicle suspension arrangement 100 comprises a flexible bellows 102 into which gas can be added or drained. Hereby, the air suspension arrangement 100 can be used for controlling the height of the frame relative the ground level.

[0036] The vehicle 1 further comprises a control unit 200 arranged to receive control signals and deliver control signals for determining aging of the flexible bellows as will be described below.

[0037] In order to describe the vehicle suspension arrangement 100, and in particular the flexible bellows 102 in further detail, reference is made to FIG. 2. As can be seen in FIG. 2, a flexible bellows 102′ is indicated with solid lines. This flexible bellows 102′ will in the following be referred to as a reference flexible bellows 102′. The reference flexible bellows 102′ corresponds to a new and unused flexible bellows. A flexible bellows that has been used for a certain period of time is indicated with reference numeral 102.

[0038] As can be seen in FIG. 2, the vehicle suspension arrangement 100 further comprises a piston 104 having a lower portion 105 which is connected to one of the wheel axles 3, 4. The lower portion 105 of the piston 104 may be either directly connected to the wheel axle 3, 4 by means of a suitable fixation arrangement, such as a bolt 101, or indirectly connected to the wheel axle 3, 4 via, for example, a bracket or the like (not shown). In the example embodiment depicted in FIG. 2, the piston has a first, cylindrical portion 106 and a second portion 108 arranged below the first portion 106. According to the embodiment depicted in FIG. 2, the second portion 108 may be arranged in a tapered shape configuration, whereby the diameter of the second portion 108 is continuously reduced as seen in a direction from the first portion 106 towards the lower portion 105 of the piston 104. The first 106 and second 108 portions are divided by means of a notch 110 separating the first 106 and second 108 portions from each other. The second portion 108 should however not be construed as limited to the depicted taper shaped surface. The second portion 108 may equally as well take other shapes, such as concave shape or an indentations, etc. However, the shape of the second portion should preferably differ from the cylindrical shape of the first portion a below the notch 110.

[0039] As further depicted in FIG. 2, the flexible bellows 102, 102′ comprises an upper portion 140 having an open structure 141. A plate structure 120, or the like, is connected to the upper portion 140 of the flexible bellows for providing an enclosed spaced within the flexible bellows 102, 102′. The plate structure 120 may either be directly connected to the frame 2 of the vehicle 1 via a suitable fixation arrangement (not shown), or indirectly connected to the frame 2 via, for example, a bracket or the like (not shown). The flexible bellows 102, 102′ is the movable portion of the vehicle suspension arrangement 100 and is thus preferably made of a rubber material to be able to move up/down on the first 106 and second 108 portions of the piston 104, i.e. the flexible bellows is “rolling” on the surface of the piston 104. Hence, when inflating gas, preferably in the form of air into the flexible bellows 102, 102′ via a gas inlet 130 the plate structure 120 is moved in a direction away from the piston 104 such that the frame 2 is raised in relation to the wheel axle 3, 4. Likewise, when air is deflated from the flexible bellows 102, 102′, the plate structure 120 is moved in a direction towards the piston 104 such that the frame 2 is lowered in relation to the wheel axle 3, 4.

[0040] Moreover, portions of the flexible bellows 102, 102′ are arranged in contact with the piston 104. In particular, a portion of the flexible bellows 102, 102′ is arranged in contact with the first, cylindrical portion 106 of the piston 104. A portion of the flexible bellows 102, 102′ is also arranged in contact with the second portion 108 of the piston if a sufficient amount of external load in the form of a compression force F is compressing the flexible bellows 102, 102′. Hereby, a rolling lobe 202, 202′ of the flexible bellows 102. 102′ is rolling up and down on the surface of the piston 104 when the flexible bellows is exposed to cyclic and dynamic loads during operation of the vehicle 1.

[0041] As is further depicted in FIG. 2, the vehicle suspension arrangement comprises a level indicator 160 for determining a distance moved by the flexible bellows 102, 102′ during operation thereof, and a gas pressure sensor 170 arranged inside said flexible bellows for measuring the gas pressure level within the flexible bellows 102, 102′. The level indicator 160 and the gas pressure sensor 170 are preferably connected to the control unit 200.

[0042] As described above, a reference bellows 102′ is indicated with solid lines while an aged flexible bellows 102 is indicated in dashed lines. As can be seen in FIG. 2, an aged flexible bellows 102 have an increase diameter 204 in comparison to the diameter 206 of the reference flexible bellows 102′. This is due to the effect that the rolling lobe 202 of the aged flexible bellows 102 will roll-up on the piston 104, and in particular on the first, cylindrical portion 106 of the piston 104. Hereby, an increase in effective area for the aged flexible bellows 102 can be observed. As the rolling lobe 202 of the aged flexible bellows 102 has rolled-up on the first, cylindrical portion 106 of the piston 104, a distance d2 to reach the second portion 108 of the piston 104 is larger than a distance d1 for the reference bellows to reach the second portion 108 of the piston 104. Accordingly, the distance d2 from the rolling lobe 202 of the aged flexible bellows to the notch 110 is larger than the distance d1 from the rolling lobe 202′ of the reference flexible bellows 102′. The comparison of distance d1 and distance d2 should of course be made when the two flexible bellows are exposed to similar external loading and at similar environments. Preferably, the comparison is made for unloaded flexible bellows.

[0043] Due to the difference is effective area and the difference in rolling lobe position for the reference flexible bellows 102′ and the aged flexible bellows 102, a relation between measured gas pressure and distance moved by the flexible bellows can be used for comparison. In detail, when the aged flexible bellows 102 and the reference flexible bellows 102′ are exposed to a compression force F resulting in a specific distance of compression of the respective flexible bellows 102, 102′, the gas pressure level within the flexible bellows 102, 102′ are measured. Hereby, a relationship between the distance moved by the respective flexible bellows and the measure gas pressure level can be determined. For an aged flexible bellow 102, the gas pressure will be lower when moved a certain distance in comparison to the gas pressure for the reference bellows when the reference bellows is moved the same distance. It is thus possible to compare the pressure response for the aged flexible bellows 102 with the corresponding pressure response for the reference flexible bellows 102′ to determine if the aged flexible bellows is in need of replacement or not. Preferably, when evaluating the pressure response, each of the flexible bellows 102, 102′ are moved the distance to reach the second portion 108 of the piston 104.

[0044] Reference is therefore made to FIG. 3 in order to describe the comparison between the aged flexible bellows 102 and the reference flexible bellows 102′. FIG. 3 is a graph illustrating the compression force needed for moving the respective rolling lobe 202, 202′ to reach the second portion 108 of the piston 104.

[0045] In FIG. 3, the horizontal axis represents the vertical distance moved by the portion, i.e. the rolling lobe when the flexible bellows 102, 102′ is exposed to an external compression force F. The vertical axis represents the external compression force F. The solid lines 302 represents the characteristics for the aged flexible bellows 102 while the dashed lines represents the characteristics for the reference flexible bellows 102′. Moreover, the distance d2, d1 corresponds to the distance from the rolling lobe 202, 202′ to the second portion 108 of the piston 106 for the aged flexible bellows 102 and the reference flexible bellows 102′, respectively. Hence, the distances d1, d2 corresponds to the distances d1, d2 depicted in FIG. 2. Accordingly, although d1 and d2 are depicted on the same horizontal position in FIG. 3, they correspond to the distance to the second portion 108 of the piston 106 as depicted in FIG. 2 unless specified otherwise.

[0046] As can be seen in FIG. 3, the force F1 required for the reference flexible bellows 102′ to reach the second portion 108 of the piston 104 is lower than the force F2 required for the aged flexible bellows 102 to reach the second portion 108 of the piston 104. This is, for one reason, due to the fact that the distance d1 between the rolling lobe of the reference flexible bellows 102′ and the second portion 108 of the piston 104, i.e. to the notch 110, is smaller than the distance d2 between the rolling lobe of the aged flexible bellows 102 and the second portion 108 of the piston 104, i.e. to the notch 110.

[0047] As is further depicted in FIG. 3, when the rolling lobe 202, 202′ reach the second portion 108 of the piston 104, i.e. when the rolling lobe 202, 202′ reach the notch 110, the flexible bellows 102, 102′ will lose some force due to that the effective area decreases. As there is a significant change in the force, a distinct change in pressure within the flexible bellows will be detected. Hereby, it may be relatively easy to determine the pressure and traveled distance of the flexible bellows.

[0048] Reference is finally made to FIG. 4 in order to summarize the method for determining aging of a vehicle suspension arrangement 100 comprising a flexible bellows 102. Firstly, a distance moved by a portion, e.g. the rolling lobe 202 of the flexible bellows 102 when the suspension arrangement is exposed to an external load is determined S1. At the same time, i.e. when the portion of the flexible bellows 102 has moved the distance, a gas pressure level within the flexible bellows 102 is determined S2. A relationship, i.e. what is the pressure within the flexible bellows 102 when the portion of the flexible bellows 102 has moved the determined distance, is determined S3. The relationship is thereafter compared S4 with a predetermined threshold level for determining S5 whether the flexible bellows 102 is aged or not. The relationship is thus preferably compared with the pressure level for a corresponding distance moved by the above described reference bellows 102′.

[0049] According to a further example for determining aging of a vehicle suspension arrangement, which is not depicted in the figures, the flexible bellows may be inflated with air for lifting the chassis relative to the wheel axles. Hereby, the distance, preferably the vertical distance, moved by the frame is detected and the amount of air inflated into the flexible bellows is also detected. The amount of inflated air for the determined distance moved by the frame, or the flexible bellows), is compared to a predetermined threshold level. For lifting the frame a specific distance, different amount of inflated air will be needed for a new flexible bellows in comparison to an aged flexible bellows. As an alternative to detect the amount of inflated air, the number of opened valves needed to reach the detected distance can be determined.

[0050] 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.