GB2546466A - Leaf spring load sensor - Google Patents

Abstract

A system for indicating the state of loading on a leaf or multi leaf spring of a vehicle suspension system, comprises at least one wireless or hard-wired load sensor attached to at least one leaf spring such that a signal relating to the stress force or strain field acting on the leaf spring can be generated; and a hand held wireless or hard-wired weight indicator configured to receive the signal and generate an output representative of the state of loading of the vehicle. The system may be employed on each of the leaf springs present in the suspension system of the vehicle. The hand held wireless or hard-wired weight indicator may include a means for providing an indication of the load or weight carried by the vehicle on each wheel, each axle, and the total load of the vehicle.

Description

Abstract Title: Leaf spring load sensor.

DESCRIPTION

This invention is directed to vehicle and machine suspension systems with load bearing leaf spring suspension assemblies, particularly to vehicle suspensions with at least but not limited to one mechanical single leaf spring or multi-leaf spring. This invention is a non-invasive attachable sensor or transducer for measuring the state of load of a vehicle having leafed springs comprising: at least one load sensor (figures 1, 2 and 3) mountable on at least one leaf of a leafed spring (fig 1, 2 and 3) such that a signal relating to the linear stress or bending force on the upper and/or lower surfaces of the leaf spring can be generated and a wireless or hardwired signal transmits measured data to a handheld device or wireless device/s or handheld weight indicator (controller) configured to receive the signal and generate an output representative of the measured load of the individual wheel, axles, load and/or total vehicle.

The present invention relates to a non-invasive attachable load sensor or transducer or plurality of load sensor transducers for measuring the state of loading of (for example) a commercial vehicle, it’s wheels, axles, payload, partial loads and gross load whilst the vehicle is in motion, static, being loaded or unloaded. The leaf spring load sensor is a device that can be fitted to new and existing vehicles and when connected to an output controller or weight indicator device alerts the driver and where wirelessly connected telematically to others to a potential hazardous and illegal overload or vehicle mass.

Vehicle weight measuring load sensor/s or transducer is provided. In the vehicle weight measuring apparatus, linear stress load sensor/s or bending stress sensor/s are installed to the leaf or leafed spring/s of a vehicle and a user receives measured values from the sensors through an electronic device in or out of the vehicle in a wireless or handheld manner, so that the weight of the vehicle, its axles and wheels can be measured in real-time and vehicle overload can be prevented.

Installation and maintenance can be easily performed in comparison with a conventional method where an invasive load cell is connected to the electronic device. In addition, replacement load sensors can be easily performed in comparison with the conventional method of load monitoring where the invasive load cell is installed to a vehicle. In addition, a degree of linear stress caused by the bending force on a leaf spring according to the weight exerted on the vehicle is detected by using the load passing through the leafed spring load sensor to measure the weight of each wheel, axle, payload and total vehicle weight.

DETAILED DESCRIPTION

[0001] The leaf spring measuring sensor works in real-time to provide accurate load data giving users information to overt axle and total vehicle overloads and to reposition loads to maintain gross limits whilst maintaining legal maximum axle and gross vehicle weights. There are many reasons for fitting to a commercial or passenger vehicle, sensors for indicating the state of payload or loading or individual axle or individual wheel loading; e.g. vehicle safety, remote monitoring, load optimisation, fuel efficiency, brake assist and to prevent an overload which is an prosecutable offence under the Road Traffic Act. Commercial motor vehicles are designed to move quantities of materials or goods on public and private roads. These vehicles are subject therefore to the interests of local, regional or national authorities who are particularly interested in vehicle overloads which may lead to dangerous driving conditions for the operator and other road users. Another interest arises from the perspective of road, bridge or underground services damaged by prolonged use by overloaded vehicles. The responsible vehicle operator also has a need to ensure that the payload per journey is maximised safely for commercial and duty-of-care reasons. Payload monitoring increases fuel efficiency as excessive loads result in increased fuel usage. Excessively loaded vehicles endure increased breaking distances in the event of an emergency stop. A heavily loaded vehicle will require additional braking pressure. Overloaded vehicles are unstable and therefore unsafe.

[0002] Weight regulations limiting the loaded weight of commercial vehicles are almost universally in effect. These regulations generally specify the maximum load of each vehicle axle as well as the maximum total or gross load or mass. Fines are usually levied against the driver and/or vehicle operator who are found violating these regulations. To maximize profits, vehicle operators normally load their vehicles as close as possible to the legal load limit. In order to do this, the vehicle operator must be able to accurately measure the vehicle’s weight while the vehicle is being loaded.

[0004] Other on-board load measuring systems utilize load cells placed on structural members between the axles and the load. However, these systems have shortcomings. While these systems can be highly accurate, they typically are more expensive. They are invasive and can change the handling ability of the vehicle. In addition, they are difficult to retrofit on existing vehicles and cannot sense the extra weight added to a vehicle by dirt and other debris collected on the surfaces of the vehicle suspension beneath the load cells.

[0005] Other on-board load measuring systems measure the relative displacement of the springs or the relative displacement between the vehicle frame and axle. However, the accuracy of these devices is adversely affected by wear, friction and debris and suffer from repeatability problems.

[0006] A commercial vehicle is typically made up of three major components for description purposes, namely multi-component suspension assemblies, a chassis and a load carrying body. Each suspension assembly itself is made-up of a number of components such as axle housings, spring suspension members, leafed springs, leaf springs, airbags, damping components and bearings. Under loading conditions, these leafed springs will flex in proportion to the mass acting upon it. Stresses projected through the leafed spring are measured using this leaf spring load sensor relative to each other and relative to the load acting on the chassis and/or load carrying body. These stresses result in bending stresses apparent on the lea or leafed springs producing a linear or unlinear stress-strain characteristic which can be measured using a secondary or primary strain gauge based load sensor/s installed to measure the bending tension or compression stresses apparent on the spring. The present invention measures changes in the leaf spring caused by an increase in mass exerted on the spring leaf due to additional loads added to the vehicle.

[0007] Early weighing systems to indicate axle or vehicle overloading rely on sensors which react to the movement of one of these components relative to another of these components within the suspension assembly or one of these components relative to the chassis or body. These early weighing systems therefore rely on a dynamic device, which is attached physically to a number of components that move relative to each other in order to indicate the relative position of one component to another. The dynamic device may be considered as a two or more part device and the extent to which parts move (or are affected by the movement of other parts) can be related to the payload weight. One such device is disclosed in US-A-6566864 and GB 2444277A, in addition inclinometer based weighing systems of this type are adversely affected by the very harsh environmental conditions in which it is installed and special measures are required to enable adequate sealing or shielding of the device in service. These weighing systems are inherently susceptible to damage from large resilient objects caught or thrown up from a road surface. A device can be damaged if the axle or wheel encounters an over-travel event not typically seen in service such as travelling on a particularly poor surface or because of a vehicle collision. These systems are also subject to inaccuracies due to road camber or incline and require addition error corrective devices to improve accuracy. The present invention is inherently accurate and therefore does not require additional sensing devices to improve accuracy.

[0008] The present invention relates to a system for measuring the state of loading of a vehicle’s wheels and/or axles that exploits a load sensor intimately attached (bolted or bonded) to a single leaf spring or multi-leaf leaf spring of a suspension assembly. It does not rely on a separate load cell or additional block of metal such as a load cell blank or related fixings.

[0009] Thus viewed from one aspect the present invention provides a system for indicating the state of weight of loading of a vehicle having leafed springs comprising: a load sensor attached directly to the spring leaf to measure the stress acting on the load bearing leafed spring can be generated; a wireless device or handheld weight indicator (controller) configured to receive the signal and generate an output representative of the state of loading of the vehicle.

[0010] Retrofitable: The vast majority of on-board load measuring systems are fitted to new vehicles. These systems are retrofitable at considerable time, cost and vehicle modification. The embodiment of this invention reduces the installation time of fitting an onboard weighing and/or overloads protection system to any road-going vehicle comprising at least on but not limited to single leaf spring or multi-leaf leaf suspension springs. The claim is the case of installation together with weighing accuracy and ease of installation, which are unique features of this invention. This strain gauge load sensor is specifically designed and manufactured for this invention.

[0011] The system of the invention has the advantage that the leaf spring load sensor measuring the linear force or compression or tensile force caused by a change in mass is mountable to transmit stress apparent on the leafed spring onto a strain amplifier load sensor on a leafed spring and does not suffer the disadvantages occasioned by debris and is resilient to over-travel events. There are also no disadvantages as are typically experienced with systems of the prior art whereby mechanical wear can be a significant drawback and the connecting portions of two or more pieces require sealing. The present sensor can be easily removed and refitted to another vehicle in a matter of minutes and function without adverse effects.

[0012] Wireless or handheld hardwired torque or linear load sensor. The present invention is a one-piece sensor comprising a full, half or quarter Wheatstone bridge electronic measuring circuit installed directly to the single leaf spring or multi-leaf leaf suspension springs. An output signal from the load sensor is connected to a strain analogue to digital converter and amplifier.

[0013] FIG. 1 is a plan (top) view and embodies the present invention it is directed to a vehicle having single leaf spring or multi-leaf leaf suspension systems having at least one equalizing leafed spring suspension member. One or more leaf spring load sensor measuring linear force or compression or tensile force on the spring leaf are attached to the leafed spring substantially along the upper, lower of neutral axis of the spring suspension member so the load sensor assemblies maintain accuracy but do not adversely affect the strength or fatigue life of the Leaf suspension spring.

[0014] FIG. 2 is a front view of a vehicle leaf spring unloaded with the sensor attached. FIG 3 is a front view of a leafed spring loaded showing the leafs bent horizontally with the sensor attached. The force on the leaf spring is greater under load resulting in a linear or compression or tensile force generating a stress through the spring. The sensor detects this stress force in a primary or secondary strain manner and produces an output relative to the change in mass exerted on the vehicle.

[0015] Typically, the leafed spring load sensor is a one-piece measuring device or an assembly of part. In a preferred embodiment, the system comprises a plurality of one-piece devices, each mountable to a stress carrying leafed spring. Preferably, each of the plurality of one-piece devices or assemblies is mountable on a leafed spring of a different suspension assembly, e.g. each of the offside and nearside, front and rear suspension assemblies.

[0016] The load sensor is a static device. The load sensor is a strain sensor, which does or does not detract from the strain field acting on the leafed spring.

[0017] The (or each) reference device (load sensor) is typically fixed directly to the leaf of the vehicle suspension leafed spring.

[0018] Preferably the method further comprises: measuring the tare stress or strain force of at least one leafed spring using a load sensor or strain multiplier or strain amplifier mounted on a leafed spring, storing said stress or strain condition in the handheld wireless or hardwired weight indicator (controller) and setting a lower threshold corresponding to said tare stress or strain force; measuring the load stress or strain force of at least one leafed spring using a strain sensor load sensor or strain multiplier or strain amplifier mounted on a leafed spring, storing said stress or strain in the handheld wireless or hardwired weight indicator (controller) and setting an upper threshold corresponding to said load stress or strain force; comparing the stress or strain force to the upper and lower threshold and using said comparison to determine the load condition; and generating an output signal from the handheld or wireless weight indicator (controller) when either of the upper or lower threshold is reached.

[0019] In a preferred embodiment, the vehicle has at least two front suspension assemblies, each suspension assembly having at least one leafed spring, the method further comprising: generating an output signal from the wireless or handheld weight indicator (controller), which is representative of the load condition with reference to the stress force or strain field acting on the leafed spring.

[0020] In a preferred embodiment, the vehicle has at least two rear suspension assemblies, each suspension assembly comprising at least one leafed spring, the method further comprising the steps of: generating an output signal from the wireless or handheld weight indicator (controller) which is representative of the load condition with reference to the rear suspension assemblies only.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example and illustrations, with reference to the accompanying drawings, wherein:

Figure 1 is a plan (from the top) view assembly diagram representing a typical vehicle suspension single leaf spring or multi-leaf leaf spring with sensor attached.

Figure 2 is an assembly side view of an unloaded vehicle leaf suspension spring showing an arrangement of the leaf spring load sensor for use in a first embodiment of a system and method for determining a mass or load or weight carried by the suspension system of the vehicle when static or in motion and unloaded.

Figure 3 is a schematic side view of a loaded vehicle leaf spring showing an arrangement or the leaf spring load sensor for use in a first embodiment of a system and method for determining a mass or load or weight carried by the suspension system of the vehicle when static or in motion, partly or fully loaded.

Documents cited:

US8230734 B2 US4037675A US4215754 A US 4022288 A US4072202 A

Claims (27)

1. A non-invasive attachable sensor or transducer which measures the stress on a vehicle single leaf suspension spring or multi-leaf suspension spring which is relative to the mass or weight or load exerted (Figs 1,2 & 3) wherein the sensor is a load sensor which communicates weight or mass or load data to a handheld or hardwired device configured to display the vehicle weight or axle or wheel weight.

2. A non-invasive attachable sensor or transducer which measures the stress on a vehicle single leaf suspension spring or multi-leaf suspension spring which is relative to the mass or weight or load exerted (Figs 1,2 & 3) wherein the sensor is a load sensor which communicates weight or mass or load data to a wireless device or wireless system configured to display or monitor in real time or to record the vehicle weight or axle or wheel weight.

3. A sensor or transducer as claimed in claim 1 or claim 2, a sensor that measures the linear stress values or any component of strain relative to the mass applied to the leaf spring or supporting leaf spring.

4. A sensor or transducer as claimed in claim 1 or claim 2, a sensor that measures the stress on any one or more points on a single leaf spring or multi-leaf suspension spring relative to the load applied to a vehicle or static machine or stationary machine or rail guided machine.

5. A sensor or transducer as claimed in claim 1,2, 3 or 4 wherein said load sensor comprises a strain gauged load sensor attached directly to one leaf of a suspension leaf spring.

6. A sensor or transducer as claimed in claim 1, 2, 3 or 4 wherein said load sensor comprises a strain gauged load sensor attached directly to each leaf spring responding to structural strains in said spring and a second load sensor mechanically fixed to leaf springs responding to linear strains in said spring.

7. A sensor or transducer as claimed in any preceding claim further comprising a display.

8. A sensor or transducer as claimed in claim 7 wherein the display is the sensory output device.

9. A sensor or transducer as claimed in claim 7 wherein the display, the handheld or wireless output device or weight indicator or controller are integrated to form a single unit.

10. A sensor or transducer as claimed any of claims 7, 8 and 9 wherein the display is used to program the handheld or wireless device or weight indicator and or controller.

11. A sensor or transducer as claimed in any preceding claim wherein the load sensor is a one-piece device.

12. A sensor or transducer as claimed in any preceding claim comprising a plurality of load sensors each bondable or mechanically attached on a single load carrying or nonload carrying vehicle suspension leaf spring.

13. A sensor or transducer as claimed in claim 12 wherein each of the plurality of load sensors is bolted or bonded on a different leaf spring.

14. A sensor or transducer as claimed in either of claims 12 and 13 wherein each of the plurality of load sensors is mountable on a leaf spring of a different suspension assembly.

15. A sensor or transducer as claimed in any of claims 12,13 and 14 wherein a load sensor is mountable on a leaf spring of each suspension assembly.

16. A wheeled vehicle having leaf springs comprising: a sensor as claimed in any preceding claim, wherein a load sensor is mechanically attached to one leaf of a leafed spring.

17. A sensor for monitoring the linear stress or strain field acting on or through the single leaf spring or multi-leaf spring and generating an output signal to and from a handheld wireless or hardwired weight indicator and or controller which is representative of the load condition.

18. A method further comprising: measuring the linear or bending force or strain field acting on the leaf or leafed spring of at least one fixing point using a wireless or hardwired load sensor or strain multiplier or strain amplifier mounted on a leaf spring, storing said strain data in the handheld wireless or hardwired weight indicator (controller) and setting a lower threshold corresponding to said tare stress; measuring the stress force or strain field acting on at least one leaf spring using said load sensor or strain multiplier or strain amplifier mounted on a leaf spring, storing said stress force or strain field in the handheld wireless or hardwired weight indicator (controller) and setting upper threshold values corresponding to said load stress force or strain field; comparing the stress force or strain field to the upper and lower threshold and using said comparison to determine the load condition and generating an output signal from the handheld or wireless weight indicator (controller) when either of the upper or lower threshold is reached.

19. A method wherein the vehicle has at least two front suspension assemblies, each suspension assembly having at least one leaf spring, the method further comprising: generating an output signal from the handheld or wireless weight indicator or controller or inbuilt vehicle information screen which is representative of the load condition with reference to the front suspension assemblies only.

20. A method wherein the vehicle has at least two rear suspension assemblies, each suspension assembly comprising at least one leaf spring, the method further comprising the steps of: generating an output signal from the handheld or wireless weight indicator or controller or inbuilt vehicle information screen which is representative of the load condition with reference to the rear suspension assemblies only.

21. A method further comprising: setting an intermediate threshold, the value of the intermediate threshold being between 1 % and 120% of the value of the upper threshold; and, the handheld or wireless weight indicator or controller or inbuilt vehicle information screen generating an output signal when the torsional stress or strain field reaches the intermediate threshold point.

22. A method for mechanically clamping or fixing said load sensor to a vehicle leaf spring to maintain a fixed position relative to the lower threshold value.

23. A sensor as claimed in any of claims 1 to 16 for maintaining load values relative to the upper threshold values.

24. A sensor as claimed in any of claims 1 to 16 where the load sensor in mounted to the outer, inner, upper or below one or more leafs of a vehicle leaf spring.

25. A sensor as claimed in any of claims 1 to 16 having as least one fixing point on the leaf spring.

26. A sensor as claimed in any of claims 1 to 16 having more than one fixing point on the lead spring.

27. A sensor as claimed in any of claims 1 to 16 that is mounted to a vehicle suspension leaf spring.