WO2000027688A1

WO2000027688A1 - Wheel suspension device for a heavy goods vehicle

Info

Publication number: WO2000027688A1
Application number: PCT/SE1999/001944
Authority: WO
Inventors: Peder Westerberg
Original assignee: Volvo Lastvagnar AB
Current assignee: Volvo Truck Corp
Priority date: 1998-11-05
Filing date: 1999-10-29
Publication date: 2000-05-18
Anticipated expiration: 2001-05-05
Also published as: SE9803782D0

Abstract

Wheel suspension arrangement for a heavy goods vehicle for distribution of the load between two adjacent wheel axles (3, 4). The wheel suspension is provided with two air bellows (8-11) which are adapted for each wheel axle and which are installed between the vehicle's frame (1) and the corresponding wheel axle in order to maintain, on the one hand, a selected relative level for the frame and, on the other hand, a selected load between the frame and the wheel axles. During certain operating conditions the load is distributed, so that one of the wheel axles absorbs a smaller part of the load. The arrangement is provided with a compressed air system for supply of compressed air to the air bellows and detects and controls the relative level and reduces the air pressure in the air bellows (10, 11) associated with one of the wheel axles. The arrangement comprises means (32, 35) for increasing the air pressure in those air bellows (8, 9) which are associated with the wheel axle (3, 4), that is driving axle.

Description

Wheel Suspension Device for a Heavy Goods Vehicle.

TECHNICAL FIELD: The present invention relates to a wheel suspension arrangement for a heavy goods vehicle, which arrangement is adapted for distributing the load between at least two adjacent wheel axles of which at least one wheel axle is driving axle. The wheel suspension comprises at least two air bellows which are adapted for each wheel axle and which are installed between the vehicle's frame and the corresponding wheel axle in order to maintain, on the one hand, a selected relative level for the frame and, on the other hand, a selected load between the frame and the wheel axles and to distribute the load during certain operating conditions, so that one of the wheel axles absorbs a smaller part of the load. The arrangement comprises a compressed air system for supply of compressed air to said air bellows, comprising means for detection and control of said relative level and reduction of the air pressure in the air bellows associated with one of the wheel axles.

BACKGROUND OF THE INVENTION:

In wheel suspensions for heavy goods vehicles, air bellows normally are included which convey the load from the vehicle frame to the vehicle's wheel axles by means of resilience properties. The air bellows form part of a compressed air system which enables a level regulation of the vehicle frame in relation to the wheel axles and thereby the ground according to the load conditions and other driving conditions. For heavy goods vehicles having several adjacent axles, i.e. of the boogie suspension type, the surface pressure becomes so low during certain conditions that the gripping power is reduced to a disadvantageuos level. From EP-B1-0 238 891, it is previously known for wheel suspensions for heavy goods vehicles having double axles to connect the air bellows of one of the wheel axles to the atmosphere when pressure sensors at the other wheel axle register a load which is below a predetermined value. The object of this is to increase the load on the other wheel axle and the corresponding wheel, which in this case is driving wheel, in order to improve the gripping power. From experience, however, it has shown that the desired redistribution of the load becomes comparatively limited due to several concurrent factors, namely the low resilient weight which prevails when the vehicle has a small load or no load at all, the remaining lifting force in the bellows and frictions in bearings for the various bars in the wheel suspension. SUMMARY OF THE INVENTION:

The object of the present invention is to provide an arrangement, which in a controlled manner enables the desired redistribution of the load between adjacent wheel axles, by means of which a satisfactory gripping power can be maintained during most driving conditions.

Said object is achieved by means of an arrangement by means of the present invention, which is characterized by means for increasing the air pressure in the air bellows which are associated with the other of said two adjacent wheel axles.

BRIEF DESCRIPTION OF THE DRAWINGS:

The invention will be further described in the following with reference to a preferred embodiment and to the appended drawings, in which

Fig. 1 shows an example of a wheel suspension for a heavy goods vehicle of such a type, to which the invention can be applied,

Fig. 2 shows schematically a first example of the arrangement according to the invention, and

Fig. 3 shows schematically a second example of the arrangement according to the invention.

PREFERRED EMBODIMENT:

By means of a partly broken simplified perspective view, Fig. 1 shows specifically the rear part of a vehicle frame 1, which in its rear end is supported by a wheel suspension 2 having two axles. For the understanding of the present invention, the main parts of the wheel suspension have been included. Thus, a front wheel axle 3 and a rear wheel axle 4 are included of which at least one, for example the front wheel axle, is driving. It is also possible that both wheel axles 3, 4 are driving, wherein it is implied that these, by means of a differential lock, should be mutually lockable as regarding the drive. Vehicle wheels 5, 5' are indicated by means of dotted lines and are arranged at each end of the wheel axles 3, 4 in the form of single or double wheels at each axle end. Furthermore, the wheel suspension 2 includes an axle beam 6, 6' which is arranged at each axle end and has corresponding axle attachment joints. Each axle beam 6, 6' supports one pair of air bellows 8, 9, 10, 11 each. More precisely, in order to convey the load from the vehicle's resilient parts to the wheel axles 3, 4, each air bellows is at its upper part anchored in a longitudinal frame side member 12, 13 which runs along the respective vehicle side. In order to absorb side thrusts, several various bars are conventionally included in the wheel suspension, which bars, on the one hand, connect the axle beams 6, 6' and the lower end of the air bellows 8-11 with the frame side members 12, 13 and, on the other hand, connect the bars on one side of the vehicle with the corresponding bars on the other side of the vehicle. For the sake of simplicity, only the bars on one side have been shown. The bars are constituted by reaction bar brackets 14, stabilizers 15, 16, stabilizer bars 17, 18, and reaction bars 19, 20, etc. In order to absorb resilience movements and level regulation movements, the bars are provided with several pivot means 21, 22, 23, 24, 25.

Thus, the air bellows 8-11 convey the vertical load between the resilient part of the vehicle, i.e. from the vehicle frame, and the wheel axles 3, 4 with a resilient load absorption, and form part of a level regulation system for regulation of the level of the load frame in relation to the wheel axles, i.e. the ground 26. In the shown example, the level regulation is an automatic level regulation, the purpose of which is to maintain a selected level for the vehicle frame or the driving height independently of the load.

For the arrangement according to the invention, the air bellows 8-11 have an additional purpose, namely to improve the gripping power during special conditions by redistributing, from the resilient parts of the vehicle, i.e. via the vehicle frame 1 to both the adjacent wheel axles 3, 4, the load that is comparatively even during normal driving conditions. This is provided by means of the fact that the air bellows 8-11 form part of a compressed air system, the principal construction of which first shall be described with reference to the first example according to Fig. 2. The compressed air system consists of a compressed air tank 27, which, by means of a not shown air compressor, is caused to maintain an air pressure within a selected interval. By means of compressed-air lines, the compressed air tank is connected to the air bellows 8, 9 and 10, 11 , respectively, via a level regulation valve 28, henceforth called level valve, which feeds in parallel compressed air to the air bellows corresponding with the respective wheel axles 3, 4 for level regulation of the load frame, normally so that a constant level or driving height for the load frame, e.g. in relation to at least one of the wheel axles 3, is maintained independently of the load of the vehicle. This is provided by means of the fact that the system supplies the desired amount of compressed air to the air bellows, the purpose of which is to thereby affecting the pressure and the volume, respectively, in the bellows, which thus are adapted for varying their volume, alternatively that the pressure varies during constant volume.

In the first example according to Fig. 2, the above-described level regulation is provided by means of the fact that the level valve 28 is installed on the load frame and is provided with a level detecting device in the form of a detector arm 29, which is connected to a fixed point 30 on one of the wheel axles 3. Furthermore, in order to block the air flow to one of the wheel axle's air bellows as well as to evacuate air from said wheel axle's air bellows, a member in the form of a valve 31, for example a magnetic valve, is included in the compressed air system and is installed in a compressed-air line between the level valve 28 and the air bellows 10, 11 to one of the wheel axles, for example the rear wheel axle 4. By means of this blocking and evacuation, the air pressure in these air bellows is reduced, by means of which the rear wheel axle 4 at least partly is relieved from the load from the vehicle frame 1. As initially mentioned, based on previous experience, the desired effect will not be sufficiently attained, which is due to several concurrent factors. The most important factors are the comparatively high unresilient weight for the relieved part of the wheel suspension, i.e. in the first place the corresponding wheels 5', the axle beams 6', the bars 16, 20, and, not least, the high friction in the bearings 21 , 22, 23, 24, 25 of the bars, by means of which the contact pressure of the wheels 5' against the ground 26 to a large extent remains.

Therefore, according to the invention, the wheel suspension arrangement is provided with means for increasing the air pressure in those air bellows 8, 9 which are associated with the other of said two adjacent wheel axles, for example the front wheel axle 3. In the first embodiment according to the invention, see Fig. 2, this is provided by means of the fact that the detector arm 29 of the level valve 28 is divided by means of an air controlled device 31 which is connected between the level valve and the point 30 on the wheel axle and which is adapted for varying the length of the detector arm 29. In the example in question, this device is constituted by an air cylinder, which for example is fixed at the wheel axle 3 with its cylinder part 33 and is connected to the detector arm 29 with its piston part 34 in order to be able to vary its length. Furthermore, the air cylinder 32 is connected to the compressed air tank 24 via a valve 35, for example a magnetic valve, by means of which the position of the piston part 34 in relation to the cylinder part can be controlled by control of the supply of the air content. The shown solution is entirely schematical, but detail solutions are evident to the skilled person. For example, it is in principal sufficient with a single-acting air cylinder 33, where the air pressure in the air cylinder is balanced by means of a not shown mechanical spring, alternatively that the air cylinder is double-acting and that the air content can be guided to both sides of the piston part 34 in the air cylinder.

In the second embodiment according to Fig. 3, the level valve is replaced by a level indicator 36, for example a potentiometer, which is adapted for controlling two valves 31 , 38 via a programmable, for example computerized control unit 37. The two valves are for example magnetic valves of which the valve 31 is adjustable between an open position for connection with the compressed air tank 27 and a closed position against this connection. In the closed position, however, a drainage port is open, which is adapted for emptying the second axle's air bellows towards the atmosphere. In the same manner, the valve 38 is adjustable between an open and a closed position for connection from the compressed air tank 27 to the air bellows 8, 9, 10, 11.

During so called air dump, i.e. in the event of a demand for an increased contact pressure against the ground, which is controlled by means of the level indicator 36 via the control unit 37, the valve 31 will be closed against the compressed air tank 37 and opened towards the atmosphere, wherein the valve 38 at the same time is opened in order to fill the first axle's bellows 8, 9 to an elevated driving height.

Thus, by means of the arrangement according to the invention, the air pressure in the air bellows 8, 9 corresponding with one of the wheel axles 3 can be increased in combination with reduction of the air pressure to the air bellows at the other wheel axle 4, by means of which a reinforced redistribution of the load is provided and the contact pressure at the corresponding wheel 5' against the surface 26 and therefore the gripping power clearly can be improved.

The invention is not limited to the embodiments which are described above and shown in the drawings, but may be varied within the scope of the appended claims.

Claims

CLAIMS:

1. Wheel suspension arrangement for a heavy goods vehicle, which arrangement is adapted for distributing the load between at least two adjacent wheel axles (3, 4) of which at least one wheel axle is driving axle, wherein the wheel suspension comprises at least two air bellows (8-11) which are adapted for each wheel axle and which are installed between the vehicle's frame (1) and the corresponding wheel axle in order to maintain, on the one hand, a selected relative level for the frame and, on the other hand, a selected load between the frame and the wheel axles and to distribute the load during certain operating conditions, so that one of the wheel axles absorbs a smaller part of the load, which arrangement comprises a compressed air system for supply of compressed air to said air bellows, comprising means (28, 29, 30, 31, 36, 37) for detection and control of said relative level and reduction of the air pressure in the air bellows (10, 11) associated with one of the wheel axles, characterized by means (32, 35, 37, 38) for increasing the air pressure in those air bellows (8, 9) which are associated with the one of said adjacent wheel axles (3, 4), that is driving axle.

2. Arrangement according to claim 1, characterized in that said means (32, 35, 37, 38) comprises means (31) for blocking the supply of compressed air as well as evacuating air from those air bellows (10, 11) which are associated with the one or those of said wheel axles (3, 4) which is/are not driving axle/axles.

3. Arrangement according to claim 1, characterized in that said means are constituted by a level detecting device (29, 32) which is adjustable by means of control of air supply.

4. Arrangement according to claim 3, characterized i n that said level detecting device (29, 32) is constituted by a detector arm (29) for control of a level regulation valve (28) which arm (29) comprises an air controlled device (32), which is adapted for varying the length of the detector arm.

5. Arrangement according to claim 4, ch a ra cte ri ze d i n that said air controlled device (32) is constituted by an air cylinder, which is connected to the detector arm (29) with its piston part (34), which detector arm is adapted to be adjusted by means of supply of compressed air from the compressed air system via an adjustable valve (35).

6. Arrangement according to claim 1, characterized in that said means (36, 37, 38) for increasing the air pressure comprise a level indicator (36) and a control unit (37) which is controlled by said level indicator and which is adapted for controlling a valve (38) for increasing the air pressure in those air bellows (8, 9) which are associated with the one of said adjacent wheel axles (3, 4), that is driving axle.