GB2313203A

GB2313203A - Measurement of vehicle loading

Info

Publication number: GB2313203A
Application number: GB9609992A
Authority: GB
Inventors: Ronald Keith Brind
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-05-14
Filing date: 1996-05-14
Publication date: 1997-11-19
Anticipated expiration: 2016-05-14
Also published as: WO1997043605A1; GB2313203B; GB9609992D0; EP0898696A1; KR20000011058A; JP2000509482A

Abstract

A torsion rod 21 is connected by a block 22 to a vehicle body 11, and by a radial arm 19 to an upright am 18 coupled to the vehicle axle 15, so that the vertical deflection of the vehicle axle 15 relative to the vehicle body 11 as a result of the vehicle loading, produces in the torsion rod 21 a torque whose magnitude is sensed to indicate the vehicle loading. The sensor(s) 23 may be a strain gauge, or load cell, or linearly variable differential transformer. The static load may be displayed to the driver, or a warning signal given of excessive load. The system is calibrated by loading with a known load. A torsion rod 21 may be provided at each rear wheel.

Description

VEHICLE LOADING This invention relates to vehicle loading. In particular it is concerned with establishing whether a load carried by a vehicle exceeds a pre-determined load limit for the vehicle. For a vehicle to make use of public roads and other locations to which members of the public have access it has to meet a range of safety requirements. One of these is a loading requirement. This is particularly significant for heavy goods vehicles but is also applicable to passenger carrying cars and derivatives thereof. In considering a weight limit there is not only the question of static load transmitted to the ground through the wheels of the vehicle but also the dynamic effects the load has on the handling and behaviour of the loaded vehicle. An excessive and/or badly distributed load can result in a serious deterioration in the handling behaviour of the vehicle especially to an inexperienced driver. The handling situation can be further aggravated by adverse weather conditions such as arise from heavy rainfall or snow and ice.

In order to establish the size of the load carried by a vehicle it is known to weigh it on a weigh bridge when loaded and subtracting the unloaded vehicle weight to give the weight of the load. However it would be a matter of considerable benefit to have an accurate weighing system which did not require a weighing device external to the vehicle.

According to a first aspect of the present invention there is provide a weighing device in the form of a member for mounting between a vehicle body and a support adapted for movement with a ground engaging means such as a wheel or track for the vehicle characterised in that the member is subject to torsion when the support moves relative to the body the amplitude of the torsion relative to some datum value serving as a measure of the displacement of the support relative to vehicle body and so of the load generating the displacement.

According to a second aspect of the present invention there is provided a vehicle having a body supported by ground engaging means such as wheels or tracks; a support for the ground engaging means providing for the rotation of the ground engaging means to drive the vehicle; the support further serving to provide for vertical motion of the support relative to the vehicle body in response to vertical loading of the support; a longitudinal member located by one end on the body member and by the other end to the one end on the support such that motion of the support relative to the body results in the member being subject to torsion; and means for detecting the amplitude of the torsion or a function thereof and for relating the amplitude to the vehicle loading.

Typically the torsion can be measured by means of, amongst other possible transducers, a strain gauge or a load cell or a linearly variable differential transformer. Such devices provide for a friction free transducer with few or no moving parts which can be readily housed so as be shielded from dirt and impact damage.

An exemplary embodiment of the invention will now be described with reference to the accompanying drawing of which the sole figure is a diagrammatic view of a part of a vehicle suspension unit.

A vehicle body 11, shown only in part, is supported on a ground engaging wheel 12 by means of a suspension unit made up of a hub 13 mounted on end 14 of an axle 15 and attached to the body by way of a convention suspension unit made up of a spring 16 and a shock absorber 17. The axle 15 has an upwardly extending arm 18 which is coupled by radial arm 19 to end 20 of a torsion rod 21. End 22 of torsion rod 21 is anchored by block 22 to body 11.

As the arm 18 and block 22 are constrained so that the torsion rod 21 is only subject to torque arising from the vertical motion of axle 15 relative to the body 11.

The torsion rod 21 carries a compact network 23 of strain gauges and amplifiers enabling the amplitude of the torque to which the rod 21 to be sensed and fed as an output signal by way of lead 25 to a processor/display unit 26 in the vicinity of the driver of the vehicle. The output signal is processed by way of the unit 26 and displayed as at least a static vehicle load figure to the driver. This displayed figure can either be a direct reading of the adual load (at least with the vehicle still) or a warning signal indicating that the safe working load has been exceeded.

In this latter case the display could be maintained until the vehicle load has been reduced below the threshold of the safe working load.

For a quantitative read out the system is readily calibrated by establishing a datum reading with the vehicle in an unloaded condition and then applying known loading and establishing an operating curve from the indicated outputs.

The torsion rod arrangement described is applied to one wheel or axle of a vehicle which can be used to provide a reasonably accurate representation of the proportion of the load acting at the mounting point from which the overall load on the vehicle can be extrapolated. However it is also envisaged that separate torsion measuring units can be provided for each of two wheels (such as two rear wheels) on opposite sides of a vehicle to provide two outputs to enable the load to be determined and also to establish the existence of an out-of- balance loading needing correction before the on the public highway. Apart from use in a static condition the output of the transducer or transducers can be used to establish the occurrence of weight changes however generated such as when the vehicle is on the move. One example involves the use of transducers on two rear wheels of a vehicle towing a trailer such as a caravan. In the event that the trailer starts to yaw then the transducers will serve to indicate a periodic weight oscillation. Such information suitably displayed could be particularly significant in warning a vehicle driver when towing a trailer with little or no towing experience that control input is urgently required. In addition the nature of the required input could be generated.

The present invention provides for the ready display of an accurate indication of vehicle loading by means of a relatively cheap self contained measuring system.

various versions of the invention are applicable to a wide range of vehicles.

However it is particularly, though not exclusively, intended for use with a light goods vehicle where a wide range of loadings can be experienced in the course of a relatively short working period. It could also usefully be used in a passenger car subject to occasional load carrying so that even an inexperienced driver can readily and unequivocally establish whether the vehicle is approaching or exceeding a safe working load.

Claims

CLAIMS:

1 According to a first aspect of the present invention there is provided a weighing device in the form of a member for mounting between a vehicle body and a support adapted for movement with a ground engaging means such as a wheel or track for the vehicle characterised in that the member is subject to torsion when the support moves relative to the body the amplitude of the torsion relative to some datum value serving as a measure of the displacement of the support relative to vehicle body and so of the load generating the displacement.

2 According to a second aspect of the present invention there is provided a vehicle having a body supported by ground engaging means such as wheels or tracks; a support for the ground engaging means providing for the rotation of the ground engaging means to drive the vehicle; the support further serving to provide for vertical motion of the support relative to the vehicle body in response to vertical loading ofthe support; a longitudinal member located by one end on the body member and by the other end to the one end on the support such that motion of the support relative to the body results in the member being subject to torsion; and means for detecting the amplitude of the torsion or a function thereof and for relating the amplitude to the vehicle loading.