WO2003085355A1

WO2003085355A1 - Camber, caster and kpi measurement method and device therefore

Info

Publication number: WO2003085355A1
Application number: PCT/SE2003/000454
Authority: WO
Inventors: Torben Larsson
Original assignee: Josam Lastbilteknik Ab
Priority date: 2002-04-04
Filing date: 2003-03-18
Publication date: 2003-10-16
Also published as: AU2003210104A1; SE521797C2; SE0201021D0; SE0201021L

Abstract

The present invention relates to providing a device and a method, which measures the bending of an elongated staff due to the effect of earth gravity for performing wheel angle measurements. More specifically the present invention relates to securing an elongated staff in a fixed relationship to a wheel adaptor spindle having an axle in parallel relationship to a wheel axle. Depending on the angle of the wheel axle the elongated staff will bend with a different amount under the influence of gravity. A strain gauge measure the bending of the elongated staff and a calculating means computes the angle of the wheel axle.

Description

CAMBER, CASTER AND KPI MEASUREMENT METHOD AND DEVICE THEREFORE

TECHNICAL FIELD

The present invention relates to measurement of angles and particularly wheel angles, more specifically the present invention relates to measurement of camber, caster and KPI.

BACKGROUND OF THE INVENTION

In vehicles the alignment of wheels and axles are an important task to reduce tire wear and fuel consumption. Moreover, the behaviour of the vehicle on the road is also affected by the interface area of the wheels with the road. This is important regarding, for instance, road safety issues. Commercial trucks for transporting goods spend considerable time on the roads and in fact, the profitability of the truck is dependent on mileage covered. It is thus important for truck owners to minimize tire wear, which can be a considerable cost, and fuel consumption. For society road safety is an important issue.

One prior art angle measurement gauges, such as the AM301 angle gauge from the present applicant is attached to a wheel adaptor spindle, which has been compensated to be aligned with the wheel axle.

To measure Camber with the AM301 a first bubble level is adjusted, a lock is applied and a second bubble level is adjusted. The Camber can then be read from a dial on the AM301 angle gauge.

For measurement of caster an angle ruler is placed on the floor next to the wheel to be measured. A laser on the wheel adaptor axle is used to align to ruler correctly with the wheel. The AM301 angle gauge is fixed to the wheel adaptor axle and the wheel is turned 20 degrees outwards with aid of the angle ruler. A bubble level is adjusted on the AM301 angle gauge and a lock is applied. A second bubble level is adjusted and the dial on the AM301 angle gauge is zeroed. The wheel is now turned 20 degrees inwards using the angle ruler. The first bubble level is adjusted, a lock is applied, the second bubble level is adjusted and the caster can be read from the dial.

The process for measuring KPI (KingPin Inclination) is in principle the same with minor adjustments. For instance, the break has to be on in order to prevent the wheel to rotate during measurement and the AM301 angle gauge is not adjusted using the first bubble level after turning the wheel inwards.

Even though the above procedure gives excellent results and a skilled craftsman can indeed perform the measurements quite rapidly, the process comprises multiple manual steps which each stand a small risk of being performed wrongly resulting in faulty measurements or increased time for performing the measurements.

It therefore exists a need in the art to reduce the manual intervention, decrease the time for performing the measurements without being forced to use extensive, expensive equipment. It would also be beneficial to have a more exact measurement of the different wheel angles.

FR 2 326 679 "Dispotif pour mesure des angles de chasse et d'inclinaison du pivot d'une roue avant de vehicule" shows a vehicle castor and inclination angle measurement device which uses an electrical potentiometer with a pendulum.

US 4,157,618 "Method and apparatus for determining caster, camber, and toe-in" discloses a mechanical device for wheel angle measurements .

US 4,430,802 "Vehicle wheel alignment testing apparatus" shows a wheel alignment testing apparatus for reading the caster, camber, toe-in and turning radius angles. The apparatus is equipped with strain gauges.

SUMMARY OF THE INVENTION

It is a main object of the present invention to provide such apparatus and method that improves the reliability of measurements of angles, particularly wheel angles, reduces the possibility of human error and simplifies the measurement process while keeping the cost of equipment relatively low.

It is still a further object of the invention to provide such apparatus and method so that the instrument is automatically calibrated without involving any adjustment made by the operator.

These objects among others are, according to a first aspect of the present invention, attained by providing a device and a method, which measures the bending of an elongated staff due to the effect of earth gravity for performing the angle measurements .

More specifically, according to a preferred embodiment of the invention, these objects are attained by securing an elongated staff in a fixed relationship to a wheel adaptor spindle having an axle in parallel relationship to a wheel axle. Depending on the angle of the wheel adapter axle the elongated staff will bend with a different amount under the influence of gravity. A strain gauge measure the bending of the elongated staff and a calculating means computes the angle of the wheel axle .

According to another preferred embodiment two strain gauges are arranged on the elongated staff with a known angle, e.g. orthogonal, in relation to each other. Thus, two angles can be measured at the same time. One of the strain gauges can then be used for calibration and the other for actually performing the measurement.

It therefore exists a need in the art to reduce the manual intervention, decrease the time for performing the measurements without being forced to use extensive, expensive equipment. It would also be beneficial to have a more exact measurement of the different angles.

An advantage of the present invention is that the number of steps for performing a specific angle measurement is reduced, thereby reducing the risk for error.

Another advantage of the present invention is that the time for performing a measurement is decreased.

Another advantage of the present invention is that with two orthogonal related gauges, more than one angle can be measured at the same time.

Another advantage of the present invention is that the instrument does not have to be placed in right up position in order to take measurements .

Another advantage of the present invention is that very exact measurements of the angles can be performed.

Yet another advantage of the present invention is that the apparatus are relatively low cost and easy to handle.

Further characteristics of the invention and advantages thereof will be evident from the following detailed description of embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description of embodiments of the present invention given herein below and the accompanying Figs. 1 to 3, which are given by way of illustration only, and thus are not limitative of the present invention.

Figure la shows a schematic front view of an elongated staff according to a preferred embodiment of the invention having strain gauges for measuring bending of the staff.

Figure lb shows a schematic view from the side of the elongated staff in figure la having strain gauges for measuring bending of the staff.

Figure 2 shows a perspective view of a wheel adaptor spindle and a laser and a gauge device according to a preferred embodiment of the invention mounted thereon.

Figure 3 shows a blown perspective view of a gauge device according to a preferred embodiment of the invention.

PREFERRED EMBODIMENTS

In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular techniques and applications in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known methods and apparatuses are omitted so as not to obscure the description of the present invention with unnecessary details.

Figures la and lb shows, in a front and a side view, an elongated staff 101 having first strain gauge 102 and second strain gauge 103 for measuring the bending of the staff 101. The first and second strain gauges 102 and 103 are mounted in orthogonal relationship to each other. The staff 101 comprises a fastening means 104 for securing the staff 101 in a fixed relation with a wheel adapter spindle (described in greater detail below) arranged in a first top end of said staff 101. A weight 105 is arranged in a second bottom end of said staff

101. The weight is present to actuate the bending of the staff 101 due to the gravitational field.

As an alternative each strain gauge device may be positioned on individual elongated staffs. Thus with two strain gauge devices two individual staffs would be required. Each of the staffs may then comprise individual weights.

As yet an alternative the two strain gauges need not be positioned orthongonaly, indeed they may take any known angle with reference to each other. They may however not be parallell.

If, when the staff 101 is fixed to an axle by fastening means 104, the axle is not perfectly orthogonal to the gravitational field, the staff 101 will bend slightly. This bending will affect the strain gauges 102 and 103 respectively, which will affect an electrical property of said strain gauges 102 and 103, e.g. the resistance. The change of e.g. resistance is measured and a computing unit (not shown) can calculate the amount of bending of the staff 101 and thereby the amount the axle deviates from the orthogonal relationship with the gravitational field.

Figure 2 shows a perspective view of a wheel 201 with a per ce conventional wheel adaptor spindle 202 attached. The wheel adaptor spindle 202 comprises means for adjusting the spindle 202 so that an axle 203 is parallel to the axle of the wheel 201 in a conventional manner. A laser 204 is mountable on the wheel adaptor axle 203 and cooperates with grade rulers on the vehicle or on the floor (not shown) for use in controlling the positioning of the wheel.

Figure 2 also shows the gauge device 205 according to the invention mounted on the wheel adaptor axle 203.

Figure 3 shows a partly blown view of the gauge device 205 in figure 2 according to the invention. The elongated staff 101 is shown mounted in the gauge device 205. The gauge device 205 comprises a batter pack 301, a display arrangement 302 having buttons for making selections is arranged at the top for easy viewing. A one-hand grip 303 is used for securing the gauge device 205 onto the wheel adapter spindle axle 203.

To measure camber using the new inventive gauge device 205, the handle 303 is pressed and the wheel adapter axle 203 is introduced into an orifice, which exit end is denoted 304. A button is pressed on the top of the gauge device 205 indicating that a camber measurement should be performed. The gauge device 205 (or more specifically a computer device, not shown) reads the bending of the elongated staff 101 in two orthogonal directions and calculates and displays the camber on the display 302.

For caster and KPI measurements the gauge device is fixed to the axle 203 the same way as for the camber measurement. The wheel is turned outwards e.g. 20 degrees using the laser 204 and an angle ruler (not shown). A button is pressed on the top of the gauge device 205 indicating the selected measurement, e.g. caster, and that the wheel has been turned outwards. The gauge device 205 then records a reading of the bending of the elongated staff 101. The wheel is then turned inwards 20 degrees and another button on top of the gauge device 205 is pressed indicating the same measurement, i.e. caster and that the wheel has been turned inwards . The gauge device records a new reading of the bending of the elongated staff 101 and from these two recordings calculates the selected measurement or measurements .

The gauge device 205 may comprise means for updating the software of the device and may comprise additional software for performing calculations relating to measurements of wheel angles, which otherwise would be performed on a paper.

The calculations of the wheel angles are requiring that the outwards and inwards turns are made to the same angles . In that way the angles (turning and lye of the axle) are not depending on each other. Caster and KPI are then calculated with a factor dependent on the turned angle. If inwards and outwards angle differs an extra measurement in straightforward wheel position has to be done in order to calculate caster and KPI.

It will be obvious that the invention may be varied in a plurality of ways. For instance may the device be used for measuring other characteristics than wheel angles. The device could for instance be positioned on a beam in a vehicle to measure the angle of a side of said beam.

Such variations are not to be regarded as a departure from the scope of the invention. All such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the appended claims.

Claims

1. An apparatus for measuring at least a first angle of a part of a vehicle characterised in,

- an elongated staff connectable in a first end to said part,

- a gauging device arranged to measure the bending of said elongated staff under the influence of gravity,

- a calculating device arranged to calculate the angle of said part from the measured bending of said staff.

2. The apparatus according to claim 1, wherein said part is a wheel of a vehicle, said apparatus comprises an adaptor for mounting onto said wheel having an axially protruding member parallel to the axle of said wheel, and

- said elongated staff is connectable in a first end to said protruding member.

3. The apparatus according to claim 1 or 2 , wherein said gauge device is at least one strain gauge device.

4. The apparatus according to claims 1 or 2, wherein said gauge device comprises at least two strain gauge devices having a known relation to each other.

5. The apparatus according to claim 4, wherein said gauge device comprises at least two strain gauge devices having an orthogonal relation to each other.

6. The apparatus according to claim 4 or 5, wherein said two strain gauges is mounted on separate elongated staffs arranged substantially in parallell relation to each other.

7. The apparatus according to claim 4 or 5, wherein said two strain gauges is mounted on two sides on said elongated staff.

8. The apparatus according to any of the claims above, wherein said elongated staff is arranged in a mainly vertical plane when mounted on said axially protruding member .

9. The apparatus according to any of claims 1-5 or 7-8, wherein said elongated staff comprises a weight member mounted in a second distal end of said staff.

10. The apparatus according to any of claims 6-8, wherein each of said two elongated staffs comprises individual weight members mounted on respective second distal ends of each of said two elongated staffs.

11. A method of measuring an angle of part of a vehicle comprising the steps of:

- mounting an angle measurement device comprising an elongated staff on said part,

- measuring the bending of said elongated staff under the influence of gravity,

- calculating said angle from the measured bending of said elongated staff.

12. A method according to claim 11, wherein said part is a wheel of said vehicle and said angle measurment device is mounted on a protruding member extending axially in parallel relationship with the axis of said wheel.

13. The method according to claim 11 or 12, further comprising the step:

- presenting said calculated angle on said angle measurement device using an electronic display.

14. The method according to claim 11 or 12, further comprising the step: - transmitting said calculated angle to a remote location for presentation.

15. The method according to any of claims 11-14, wherein said measuring is performed using at least one strain gauge.

16. The method according to any of claims 11-14, wherein said measuring is performed using two strain gauges mounted with a known angle in relation to each other on said elongated staff.

17. The method according to claim 16, wherein said measuring is performed using two strain gauges mounted on two different elongated staffs and having a known angle in relation to each other.

18. The method according to any of claims 11-17, wherein said wheel angle is the camber angle.

19. The method according to any of claims 11-17, wherein said wheel angle is the caster angle or the KPI angle, further comprising the steps:

- turning said wheel to a first position in a first direction and recording a first reading of said bending of said elongated staff,

- turning said wheel to a second position in a second direction and recording a second reading of said bending of said elongated staff, - calculating caster and/or KPI from said first and second recordings.