LOAD MEASURING DEVICE FOR A VEHICLE

Abstract: 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. The invention utilises a torsion bar (21) fitted between the vehicle suspension unit and the vehicle body (11) supported by the suspension unit. A torsion distension detection device (23) is fitted to the torsion bar which provides a signal whose amplitude is relative to the distortion of the torsion bar and, hence, the vehicle loading. This signal is passed to a display unit (26) which presents at least a static vehicle load figure to the driver. This displayed figure can either be a direct reading (250) of the actual 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.

Description: LOAD MEASURING DEVICE FOR A VEHICLE Field of the Invention 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 Background to the Invention 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 Summary of Invention 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 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 bodv supported by ground engaging means; 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. Preferred features of the invention are set out in the accompanying claims 2 to 5 and 7 to 10 Brief Description of the Drawing The sole figure is a diagrammatic view of a pan of a vehicle suspension unit Description of the Preferred Embodiment An exemplary embodiment of the invention will now be described with reference to the sole figure of the accompanying drawing 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 conventional 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 1 1. 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 actual 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 propoπion 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 vehicle is used 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 loads 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 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 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 A weighing device as claimed in claim 1, wherein the ground engaging means is a wheel or track 3. A weighing device as claimed in claim 1, wherein the member subject to torsion includes means for converting the torsion to an electrical signal 4 A weighing device as claimed in claim 1, wherein the member subject to torsion comprises at least one strain gauge 5 A weighing device as claimed in claim 1 , further comprising another member for mounting between a vehicle body and a support adapted for movement with a ground engaging means for the vehicle 6 A vehicle having a body supported by ground engaging means, the vehicle comprising 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 substantially 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. 7. A vehicle as claimed in claim 6, wherein the ground engaging means is a wheel or track 8 A vehicle as claimed in claim 6, wherein the means for detecting the amplitude of the torsion includes means for converting the torsion to an electrical signal. 9. A vehicle as claimed in claim 8, wherein the means for converting torsion to an electrical signal comprises at least one strain gauge 10. A vehicle as claimed in claim 6, further comprising another 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

Inventors: BRIND RONALD KEITH, BRIND, RONALD, KEITH
Applicants: BRIND RONALD KEITH, BRIND, RONALD, KEITH
Application year: 1997
Main classification: G01G19
IPC codes: G01G19