The present invention generally relates to articulated lorries or vehicles and more particularly to a method and a system for determining the load transferred from a semi-trailer to a first axle of a towing vehicle, which has at least one further, second axle, the semi-trailer being partly supported by the towing vehicle at a supporting site thereof.
U.S. Pat. No. 6,203,045 discloses an articulated lorry with a control system for redistributing the weight among wheel axles. A plurality of sensors is associated with the plurality of wheel axles on the vehicle, and an electronic controller gathers information from the sensors and determines the weight at each axle.
This known system comprising at least one weight sensor at each wheel axle is rather complicated. While the rear wheel axle(s) is/are usually suspended by fluid springs the front axle is usually suspended by mechanical springs. Because it is more complicated and expensive to install an efficient weight sensor when a wheel axle is suspended by mechanical springs than when it is suspended by fluid (hydraulic and/or gas) springs, it would be advantageous if installation of a load or weight sensor at a selected wheel axle could be avoided.
WO03/044471 discloses a load calculation system for a truck with a fixed fifth-wheel coupling.
This is obtained by the present invention, which provides a method of determining the load transferred from a semi-trailer to a first axle of a towing vehicle, which has at least one further, second axle, the semi-trailer being partly supported by the towing vehicle at a supporting site thereof, said method comprising determining a first value representing the load transferred from the semi-trailer to said at least one further, second axle and determining a second value representing the position of the supporting site in relation to said axles using a position detecting device, and the system according to the invention is characterised in calculating a value representing the load transferred from the semi-trailer to the first axle based on said first and second values. Such a towing vehicle is often referred to as a tractor.
By the method according to the invention it is possible to determine how an unknown load transferred from a semi-trailer to at vehicle towing the same is distributed to the axels of the towing vehicle, provided that the load supported by the said second axle and the position of the supporting site or the so-called “fifth wheel” are known. Since the supporting site or “fifth wheel” is moveable, the position of the supporting site or “fifth wheel” is determined using a position detecting device. The load transferred to the first axle or a value representing the same may, for example, be calculated by using static calculations. The net weight or unladen weight of the towing vehicle and also the fraction of such weight supported by the axels of the vehicle are usually known. Therefore, also the total load or weight supported by each of the first and second axle may be determined, if desired.
The position of the supporting site or “fifth wheel” in relation to the axles of the towing vehicle may be changed in order to obtain a desired weight or load distribution on the axles of the towing vehicle, for example to maintain desired braking and/or steering characteristics of the combined vehicle and semi-trailer. The movement of the “fifth wheel” may be manually operated or performed automatically by means of an electronic control device in accordance with predetermined programs.
The supporting site or “fifth wheel” is advantageously displaced between predetermined positions along a track extending longitudinally of the towing vehicle. The “fifth wheel” may, for example, be releasable locked in any of the predetermined positions. The actual position of the supporting site or “fifth wheel” may be determined by any conventional means. In the presently preferred embodiment the supporting site is defined by a displaceable supporting member, which is connected to a fixed part of the towing vehicle by means of an articulated rod member, and the position of the supporting member may then be determined based on the mutual angular position of the rod member parts.
The first axle is usually a front axle while the second axle is a rear axle, and the supporting site is positioned between the front and rear axles of the towing vehicle. However, the said first axle may also be a rear axle. The towing vehicle may have a rear axle in the form of a bogie, or a pair of closely adjacent rear axles. In the latter case the load transferred to such pair of second axles may be determined for each such axle or at a common point of load application.
The load L1 transferred from the semi-trailer to the first axle may be calculated based on the following equation:
L1*d1=L2*d2
or
L1=L2*d2/d1
where the load transferred from the semi-trailer to the second axle is L2 and the longitudinal distances between the supporting site and the first and second axles are d1 and d2, respectively.
If desired, the total load L3 transferred from the semi-trailer to the towing vehicle at said supporting site may be calculated from the equation
L3=L1+L2
The present invention also provides a system for determining the load transferred from a semi-trailer to a first axle of a towing vehicle, which has at least one further, second axle, the semi-trailer being partly supported by the towing vehicle at a supporting site thereof, said system comprising a load sensing device for determining a first value representing the load transferred from the semi-trailer to said at least one further, second axle and a position detecting device for determining a second value representing the position of the supporting site in relation to said axles, and the system according to the invention is characterised in an electronic calculator adapted to receive signals from the load sensing device and from the position detecting device representing said first and second values, respectively, and to calculate a value representing the load transferred from the semi-trailer to the first axle based on said first and second values. Such system may further comprise a display device communicating with the electronic calculator and adapted to display any of the values received and/or calculated by the calculator. The display device is preferably arranged within the driver's cab so that it can be surveyed by the driver.
The invention will now be further described with reference to the drawings, wherein
The tractor 10 is in this example equipped with a leaf sprig as the front axle suspension and an air spring as the rear axle suspension. The axle load for an axle suspended by a leaf spring is difficult to measure in a direct way. This is normally done with a displacement sensor that senses the displacement of the axle and this signal is then transferred to a load value using an equation that compensates for the spring characteristics. The axle load for an axle suspended by an air spring is on the other hand easy to determine, since the axle load can be derived from the air pressure in the air bellows. The air pressure in the air bellows is normally measured on vehicles with air springs. The axle load for that axle is therefore normally available from the electronic air suspension system.
The total load or weight supported by the rear axle 9 is determined by a weight sensor 17, which may be arranged in connection with a hydraulic and/or gas spring suspension system. A known contribution to this total load resulting from the net weight of the towing vehicle 10 should be deducted from the value determined by the sensor 17 in order to arrive at the load value L2. A position detector 18 described more in detail below determines the position of the coupling device or “fifth wheel” 15. In
When the values L2, d1 and d2 have been determined the value L1 can be calculated from the equation:
L1*d1=L2*d2
or
L1=L2*d2/d1
L1 is the load contribution from the load L3 supported by the front axle 8. If the total load or weight supported by the front axle 8 is to be determined a known contribution from the net weight of the vehicle 10 has to be added. It should be understood that in this way it is possible to determine the total loads supported by the front and rear axles 8 and 9, respectively, and/or the relative weight distribution on the front and rear axles when the load L2 and the spacing d1 and d2 are determined by means of the sensor 17 and the detector 18, respectively. As indicated in
It should be understood that various amendments of the embodiments described above could be made without departing from the scope of the present invention. As an example, any other conventional type of position detector than that described above could be used for determining the position of the coupling device or “fifth wheel” 15 in relation to the positions of the front and rear axles, respectively, of the towing vehicle 10.
Number | Date | Country | Kind |
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0402633-2 | Oct 2004 | SE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/SE05/01553 | 10/18/2005 | WO | 00 | 4/19/2007 |