| WO/2000/027659 | ENHANCED COMPUTER OPTIMIZED ADAPTIVE AIR SPRING SUSPENSION |
| JP2007022287 | SUSPENSION DEVICE FOR VEHICLE |
| JP03109117 | SUSPENSION DEVICE FOR VEHICLE |
Kuiphuis, Tom (Värdsholmsgatan 1A/125, Södertälje, S-151 32, SE)
Sjögren Paulsson, Stina (Scania CV AB, Södertälje, S-151 87, SE)
| 1. | A method of distributing load between at least two axles of a vehicle, the axle loads normally being at their respective normal values, characterized by sensing vehicle speed and axle loads, at vehicle speeds <a first limit value, increasing the load on at least one first axle to a first predetermined value and decreasing the load on at least one second axle, if the load on said at least one second axle is ≥a, second predetermined value, maintaining the increased load on said at least one first axle and the decreased load on said at least one second axle, and if the load on said at least one second axle is < the second predetermined value at vehicle speeds >a second limit value, decreasing the load on said at least one first axle to its normal value and increasing the load on said at least one second axle to its normal value. |
| 2. | The method according to claim 1, characterized by increasing the load on said at least one first axle and decreasing the load on said at least one second axle after that the vehicle speed has been ≤said first limit value for a predetermined first time period. |
| 3. | The method according to claim 1, characterized by decreasing the load on said at least one first axle and increasing the load on said at least one second axle after that the vehicle speed has been ≥said second limit value for a predetermined second time period. |
| 4. | The method according to any of claims 1 3, characterized in that said second limit value is ≥said first limit value. |
| 5. | A computer program (21) for controlling distribute of load between at least two axles (1, 3) of a vehicle by controlling pressure of respective air bellows (5, 5', 6, 6', 9, 9') associated with the axles (1, 3), the axle loads normally being at their respective normal values, characterized by computer readable program code means which, when run on a computer (17) connected with one input terminal (25) to receive a vehicle speed signal (S), with other input terminals (23, 24) to output terminals of air bellow pressure sensors (28, 29, 31, 32) and with its output terminal (26) to a valve unit (12) for controlling flow of air to and from the air bellows (5, 5', 6, 6', 9, 9')5 causes the computer (17) to determine vehicle speed and axle loads, at vehicle speeds <a first limit value, increase the load on at least one first axle (1) to a first predetermined value and decrease the load on at least one second axle (3), if the load on said at least one second axle (3) is ≥a. second predetermined value, maintain the increased load on said at least one first axle (1) and the decreased load on said at least one second axle (3), and if the load on said at least one second axle is (3) < the second predetermined value at vehicle speeds >a second limit value, decrease the load on said at least one first axle (1) to its normal value and increase the load on said at least one second axle (3) to its normal value. |
| 6. | The computer program (21) according to claim 5, comprising computer readable program code means which, when run on a computer (17) causes the computer (17) to increase the load on said at least one first axle (1) and decrease the load on said at least one second axle (3) after that the vehicle speed has been ≤said first limit value for a predetermined first time period. |
| 7. | The computer program (21) according to claim 5, comprising computer readable program code means which, when run on a computer (17) causes the computer (17) to decrease the load on said at least one first axle (1) and increasing the load on said at least one second axle (3) after that the vehicle speed has been ≥said second limit value for a predetermined second time period. |
| 8. | A computer program product (20) comprising a computer program according to claim 5 and a computer usable medium on which the computer program is stored. |
| 9. | A computer (17) adapted to send control signals to a valve unit (12), comprising a storage unit and a computer program according to claim 5 stored in the storage unit. |
TECHNICAL FIELD The invention relates generally to vehicles and more specifically to a method and a computer program for distributing load between axles of a vehicle.
BACKGROUND OF THE INVENTION
In vehicles with a bogie, e.g. buses and trucks with or without trailers, there is significant wear of the tires particularly in city traffic during cornering at relatively low speed.
SUMMARY OF THE INVENTION
The object of the invention is to bring about a method and a computer program for reducing tire wear.
In the method according to the invention of distributing load between at least two axles of a vehicle, the axle loads normally being at their respective normal values, this is attained by sensing vehicle speed and axle loads, at vehicle speeds <a first limit value, increasing the load on at least one first axle to a first predetermined value and decreasing the load on at least one second axle, if the load on said at least one second axle is ≥a second predetermined value, maintaining the increased load on said at least one first axle and the decreased load on said at least one second axle, and if the load on said at least one second axle is < the second predetermined value at vehicle speeds ≥a second limit value, decreasing the load on said at least one first axle to its normal value and increasing the load on said at least one second axle to its normal value.
In one embodiment, the load on said at least one first axle is increased and the load on said at least one second axle is decreased after that the vehicle speed has been ≤said first limit value for a predetermined first time period.
In one embodiment, the load on said at least one first axle is decreased and the load on said at least one second axle is increased after that the vehicle speed has been ≥said second limit value for a predetermined second time period.
In one embodiment, said second limit value is ≥said first limit value.
The object of the invention is also attained by a computer program for controlling distribute of load between at least two axles of a vehicle by controlling pressure of respective air bellows associated with the axles, the axle loads normally being at their respective normal values, in that the computer program comprises computer readable program code means which, when run on a computer connected with one input terminal to receive a vehicle speed signal, with other input terminals to output terminals of air bellow pressure sensors and with its output terminal to a valve unit for controlling flow of air to and from the air bellows, causes the computer to sense vehicle speed and axle loads, at vehicle speeds ≤a first limit value, increase the load on at least one first axle to a first predetermined value and decrease the load on at least one second axle, if the load on said at least one second axle is >a second predetermined value, maintain the increased load on said at least one first axle and the decreased load on said at least one second axle, and if the load on said at least one second axle is < the second predetermined value at vehicle speeds >a second limit value, decrease the load on said at least one first axle to its normal value and increase the load on said at least one second axle to its normal value.
By means of the method and the computer program according to the invention, tire wear will be greatly reduced on vehicles.
BRIEF DESCRIPTION OF THE DRAWING
The invention will be described more in detail below with reference to the appended drawing on which Fig. 1 is a schematic top view of a vehicle with an embodiment of the invention, and Fig. 2 is a flow chart illustrating steps of one embodiment of the method according to the invention.
DESCRIPTION OF THE INVENTION
Fig. 1 is a schematic illustration of an embodiment according to the invention for distributing load between a drive axle 1 with double wheels 2 and a tag axle 3 with single wheels 4 of a vehicle (not shown in any detail).
The vehicle may be a bus with or without trailer, a truck with or without trailer or a truck with semitrailer or any similar vehicle.
In the embodiment in Fig. 1, in a manner known per se, for the drive axle 1, there are two air bellows 5, 5' on the left hand side of the vehicle and two air bellows 6, 6' on the right hand side of the vehicle between the vehicle frame 7 and suspension beams 8.
For the tag axle 3, also in a manner known per se, air bellows 9 and 9' are provided between the vehicle frame 7 and the tag axle 3 on the respective side of the vehicle.
The air bellows 5, 5' and 6, 6' for the drive axle 1 are connected by means of tubes 10 and 11, respectively, to electrically controlled valves (not shown) of a valve unit 12 that is supplied with compressed air from an air source 13, e.g. a compressor, and the air bellows 9 and 9' for the tag axle 3 are connected by means of tubes 15 and 16, respectively, to valves of the valve unit 12.
The electrically controlled valves of the valve unit 12 control the flow of compressed air to and from the air bellows 5, 5', 6, 6', 9, 9' in response to control signals from a computer 17 via a cable harness 18.
The computer 17 comprises a processor 19 that is connected to a computer program product 20 in the form of a storage unit that comprises a computer program 21 stored on a computer usable medium, and another storage unit that stores a memory 22 for limit values.
The storage units can be e.g. ROMs, PROMs, EPROMs, EEPROMs, and flash memories.
In the embodiment in Fig. 1, the processor 19 is connected to three input ports 23, 24, 25 and one output port 26 of the computer 17. It is to be understood that, the computer 17 can comprise additional input and output ports.
The input port 23 of the computer 17 is connected via a wire 27 to respective output terminal of two pressure sensors 28, 29 that are connected to the air bellows 5 and 6, respectively, for the drive axle 1 to sense the air pressure of the respective air bellow 5, 6 and supply data about the air pressure to the processor 19 via the input port 23.
From the air pressure data, the processor 19 calculates the load on the drive axle 1 under control of the computer program 21.
The input port 24 of the computer 17 is connected via a wire 30 to respective output terminal of two pressure sensors 31, 32 that are connected to the air bellows 9 and 9', respectively, for the tag axle 3 to sense the air pressure of the respective air bellow 9, 9' and supply data about the air pressure to the processor 19 via the input port 24.
From the air pressure data, the processor 19 calculates the load on the tag axle 3 under control of the computer program 21.
The input port 25 of the computer 17 is adapted to receive a vehicle speed signal S indicative of the speed of the vehicle.
In accordance with the invention, a first and a second predetermined vehicle speed limit value are set in the memory 22. The first vehicle speed limit value can be set to e.g. 30 km/h and the second vehicle speed limit value can be set to e.g. 60 km/h. However, it is to be understood that the second vehicle speed limit value can be the same as the first vehicle speed limit value.
Also in accordance with the invention, predetermined limit values for the drive axle load and the tag axle load are set in the memory 22.
Under normal conditions of the vehicle, the loads on the drive axle 1 and the tag axle 3 are kept at normal values as determined by the characteristics of the air bellows.
Normally, the air pressure is kept the same in all air bellows, 5, 5', 6, 6', 9, 9' by means of the valve unit 12.
With reference to the flow chart in Fig. 2, an embodiment of the method according to the invention will be described.
In Step Sl in Fig. 2, the processor 19 in Fig. 1 receives data about the air pressure in the drive axle air bellows 5, 6 via input port 23, data about the air pressure in the tag axle air bellows 9, 9' via input port 24, and data about vehicle speed via input port 25 of the computer 17.
It is supposed that the vehicle is standing still from the beginning in Step Sl .
In accordance with the invention, to reduce tire wear particularly of the wheels 4 of the tag axle 3 in the embodiment in Fig. 1, e.g. when cornering at low speed, the load on the tag axle 3 is decreased at the same time as the load on the drive axle 1 is increased to the predetermined value set in memory 22.
To accomplish this, it is queried in Step S2 whether or not the vehicle speed is ≤the first limit value, i.e. 30 km/h in this embodiment.
If the answer is NO to the query in Step S2, the axle loads remain unchanged at their normal values.
If the answer to the query in Step S2 is YES, in Step S3, the processor 19 under control of computer program 21 controls the valves of the valve unit 12 in such a manner that the
air bellows 9, 9' of the tag axle 3 are deflated via tubes 15, 16 to decrease the air pressure in tag axle air bellows 9, 9' to thereby decrease the tag axle load at the same time as the air bellows 5, 5', 6, 6' of the drive axle 1 are inflated via tubes 10, 11 to increase the air pressure in drive axle air bellows 5, 5', 6, 6' to thereby increase the drive axle load to the predetermined value set in memory 22. Deflation of the tag axle air bellows 9, 9' is stopped when the pressure in the air bellows 5, 5', 6, 6' reaches the predetermined pressure corresponding to a maximum allowable load set in memory 22.
Preferably, in order to minimize air consumption, the load on the drive axle 1 is not increased and the load on the tag axle 3 is not decreased until the vehicle speed has been at or below 30 km/h for a predetermined first time period, e.g. a few seconds.
In Step S4, it is queried whether or not the load on the tag axle 3 is >a predetermined value set in memory 22 in correspondence to a load at which the vehicle behaviour is satisfactory.
If the answer is YES to the query in Step S4, the increased drive axle load and the decreased tag axle load from Step S3 are maintained.
If the answer is NO to the query in Step S4, i.e. the tag axle load is < the predetermined value, it is queried in Step S5 whether or not the vehicle speed is ≥the second limit value set in memory 22, i.e. 60 km/h in this embodiment.
If the answer is NO to the query in Step S5, the axle loads from Step S3 are maintained.
If the answer is YES to the query in Step S5, i.e. the processor 19 has detected from the vehicle speed signal S via input port 25 that the vehicle speed is >60 km/h, in Step S6, the processor 19 under control of computer program 21 controls the valves of the valve unit 12 in such a manner that the air bellows 9, 9' of the tag axle 3 are inflated via tubes 15, 16 to increase the air pressure in tag axle air bellows 9, 9' to thereby increase the tag axle load to its normal value at the same time as the air bellows 5, 5', 6, 6' of the drive
axle 1 are deflated via tubes 10, 11 to decrease the air pressure in drive axle air bellows 5, 5', 6, 6' to thereby decrease the drive axle load to its normal value. Thus, the load distribution between the axles is back to the normal distribution.
Preferably, in order to minimize air consumption, the load on the tag axle 3 is not increased and the load on the drive axle 1 is not decreased until the vehicle speed has been at or above 60 km/h for a predetermined second time period that can equal the first time period, i.e. a few seconds.
The pressures of the air bellows 5, 5', 6, 6' and 9, 9' will then be maintained at their respective normal values until the next time the processor 19 in Step S2 detects that the vehicle speed again is at or below 30 km/h, i.e. the first speed limit value set in memory
22.
As mentioned above, the second speed limit value can be equal to or higher than the first speed limit value.
By means of the invention, in the described embodiment, tire wear will be reduced on particularly the tag axle.
The invention is equally applicable also to vehicles with a bogie that comprises more than two axles.
Example In e.g. a bus at curb weight, i.e. an empty bus with a driver, having a total mass of 14300 kg, the load is distributed as follows: front axle 4200 kg, drive axle 5800 kg and tag axle 4300 kg.
When the invention is applied, i.e. at low speed, e.g. at a vehicle speed <30 km/h, the load is distributed as follows: front axle 3400 kg, drive axle 9500 kg (predetermined value) and tag axle 1400 kg.
This means a reduction of nearly 70 % of the tag axle load which implies that wear of the tag axle tires will be reduced.
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