GB2025064A - Wheel Alignment - Google Patents

Abstract

A system for generating a sequence of steps to instruct a mechanic in aligning the wheels of a vehicle has means 29 for sensing the camber of a wheel 27, means 26 for sensing its rotational position and computer means for calculation of a table of camber corrections at a series of rotational positions. The sensors which include a toe in sensor 44, are carried by a wheel clamp assembly 22. The rotational position of the steering wheel is also supplied so that it can be squared up with respect to the vehicle when the vehicle travels straight ahead. <IMAGE>

Description

SPECIFICATION Wheel Alignment System, Apparatus and Method This invention pertains to a system, apparatus and method for generating a sequence of wheel alignment instructions to a mechanic wherein the instructions are derived from inputs supplied by sensors which serve to measure various physical dispositions of the wheels being aligned.

Heretofore, alignment of the wheels of a vehicle has entailed the use of lights, mirrors, rotatable support plates for the front wheels, and various other types of devices whereby information can be obtained directly by inspection and adjustments made on the basis of one or two observations.

As disclosed herein, however, a wheel alignment system is provided employing computer means such as a micro-processor or other computer means coupled to a number of sensors for recording in the computer various physical dispositions of the wheels as described below. Primarily the system employs means for sensing the camber of a wheel at any given rotational position of the wheel and associating the camber with that rotational position so as to be able to record a camber correction table in the computer which can later be employed for reference. Thus, after establishing the table and recording it in the computer means, it is possible for the computer to know the amount of camber correction for any given rotational position of the wheel.

Further, toe readings are directly entered into the computer and corrected to compensate for runout by reference to the camber correction table. Having corrected the camber and toe readings it is possible for the computer to compute the appropriate caster change for each wheel in order to have the caster of the wheel correspond to its manufacturer's specifications.

Further, by employing the system herein it is possible for the mechanic to monitor his change in caster directly since it has been observed that adjustments to the caster angle serve to cause the wheel to roll whereby by entering the rotational position of the wheel caster correction changes are entered into the computer system to provide a continuous monitor of the alignment being conducted.

Finally, a simulated steering wheel disposed in conjunction with the console which contains the computer means is arranged to provide an additional input to the computer representative of the angle of the steering wheel when the vehicle is driven in a forwardly direction. This feature serves to automatically reference the rear wheels, the front wheels and the straight ahead axis of the vehicle, eliminating the costly and time consuming combined manual, mechanical and electrical procedures now in use. Thus, if the axis of the vehicle is not normal to the axis of the rear wheels, the front wheels will need to be turned in the same direction to compensate sufficiently to cause the vehicle to travel straight ahead.

Accordingly, when a vehicle is driven directly ahead if the steering wheel is not "square" with the vehicle, the computer means calculating the corrections to be made to camber, caster and toe is advised of this misdirected steering wheel and appropriate compensation is entered in the foregoing calculations for providing instructions for adjusting the tie rods in a manner straightening the steering wheel.

Further, an embodiment of the invention described herein pertains to a system and method not employing the simulated steering wheel for "squaring" the steering wheel with respect to the vehicle when the vehicle moves straight ahead.

In general, the system as herein described employs a microprocessor or other computer means and a display associated therewith. A plurality of sensors serve to detect physical positions of the wheels which are to be aligned and supply this information to the microprocessor for the various positions of the wheels. A simulated sterring wheel associated with the computer means supplies an input to the computer whereby the steering wheel input is initially set to a position corresponding to the vehicle, steering wheel when the vehicle moves straight ahead. The microprocessor then, acting in response to the data received and according to its program, displays a succession of instruction steps to a mechanic.The physical adjustments as presented on the display are then carried out by the mechanic for correcting alignment of the wheels of the vehicle according to a sequence of steps dictated by the computer program.

In general, the present invention provides a wheel alignment system in which the technician or mechanic is instructed in a step by step manner as to adjustments to be made to a vehicle.

The present invention further provides a computer controlled system in which camber correction for run-out is directly sensed and transmitted to a computer for construction of a table or graph associated camber correction for each of a number of rotational positions of the wheel.

The present invention also provides a system of the kind described in which toe angle is directly sensed and corrected in response to reference to the "camber correction for run-out" table.

Further, the present invention is arranged to easily enter into the computer system an indication as to the rotational position of a steering wheel of the vehicle, when the vehicle is travelling in a straight line so that this information can be incorporated into the computations noted above.

Finally, the invention includes a wheel clamp assembly which can support a sensor assembly containing the means for sensing the foregoing angles and corrections and which can be quickly and easily applied to the rim of a wheel.

Figure 1 shows a diagrammatic view of the system according to the invention with a portion shown in plan and other portions shown in perspective; Figure 2 shows a front elevation view of a tire and wheel assembly supported free of the ground during one phase of the alignment, according to the invention; Figure 3 shows an enlarged perspective view of a transducer support assembly mounted on a wheel to be aligned according to the invention; Figure 4 shows an enlarged diagrammatic view of a camber sensor assembly; Figure 5 shows a front elevation view of an illustrative diagram including a wheel and tire assembly having an exaggerated degree of camber for illustration purposes; Figure 6 shows a curve derived from sensing the state of the camber sensors in Figure 5 through 3600;; Figure 7 shows a front elevation view of an illustrative diagram including a wheel and tire assembly and also including the transducer support assembly for demonstrating the effect on toe readings derived from changes in camber at different rotational wheel positions; Figure 8 shows a curve derived from the camber correction readings corresponding to Figure 6 but including additional information relative to changes in the toe sensor corrections; Figure 9 shows a diagrammatic exploded perspective view of an end of one of the transducer support assemblies according to the invention; Figure 10 shows a view similar to Figure 9 in assembled relation; Figure 11 shows a plan view taken along the line 11-11 of Figure 10 and viewing the toe sensor assembly from beneath;; Figure 12 shows a diagrammatic plan view of a wheel and tire assembly with a transducer support assembly carried thereon mounted to move as a parallelogram; Figure 1 3 shows an exploded partially broken away perspective view of the interior of the housing of the transducer support assembly according to the invention; Figure 14 shows an elevation section view taken along the line 14-14 of Figure 13 showing a run-out sensor and its connection to the axis of a wheel being aligned; Figure 1 5 shows an elevation view partially broken away of the upper operating end of a wheel clamp assembly according to the invention; Figure 1 6 shows an enlarged detail elevation view of the lower clamping unit carried on the clamp assembly according to the invention;; Figure 1 7 shows an enlarged detail view partially in section of a rim engaging stud assembly carried by the clamp assembly according to the invention; Figure 18 shows an alternate positioning of the stud assembly shown in Figure 17; Figure 1 9 shows a diagram explaining derivation of data for truing the steering wheel with respect to front wheels, according to the invention; Figure 20 shows an explanatory diagram; and Figure 21 shows a perspective view of an enlarged detail of the invention.

Briefly, sensors for detecting pertinent physical positions of the wheels are contained in a transducer support assembly 21 as shown in Figure 3. Assembly 21 is slung pivotally from a wheel clamp assembly 22 carried by the vehicle wheel being aligned. The support assembly 21 is hung in a manner to pivot about the axis 23 of its associated wheel axle 24. Transducer support assemblies 21 on each side of the vehicle extend forwardly thereof whereby the leading end of each assembly can be coupled by a flexible cable 26 to the leading end of the other support assembly carried by a wheel on the other side of the vehicle.

Cable 26 preferably is very flexible and in the present instance can constitute a braided polyester cable characterized by being substantially inelastic.

Each support assembly 21 carries a run-out sensor 28 which generates information indicative of the rotational position of the wheel; a camber sensor 29 which generates information indicative of the camber of the wheel; and a toe sensor 44 which generates information indicative of the toe angle of its associated wheel.

As more fully described further below, by recording or storing a plot of camber readings against each of a number of detected rotational positions of a wheel in a microprocessor or other computer means represented by console 19, the actual camber of each wheel can be compared to the desired camber taken from pre-recorded or pre-stored specifications for the vehicle entered into the computer means 1 9. Thus, using this plot or table, a correction can be displaced by the computer means 19 to all camber readings for that wheel which may be measured later. As noted herein, the above entry of a table or plot of camber against rotational position of a given wheel is generated while the wheel is lifted clear of the ground whereas adjustments to the wheel are made while it is disposed in contact with the ground.Thus, with the wheel on the ground and the rotational position of the wheel detected by sensor 28, the computer will be able to find and employ the corresponding camber correction associated with that particular rotational position by reference to the above plot stored therein.

The transducer support assembly 21 shown in Figure 3 is diagrammatically represented in Figure 5 by showing only two of the sensor devices 28, 29 involved with assembly 21. Accordingly, a runout sensor 28 in the form of a potentiometer of a type which can operate continuously cyclically through 2600 with a corresponding varying voltage detects the position of axis 23. Data from potentiometer 28 is fed to computer means 1 9 in response to sampling requests from the computer at predetermined intervals.

As shown in Figure 4, a camber sensor 29 comprises a tubular element 31 of known construction containing a low conductive fluid 32 of suitable viscosity to inhibit the formation of waves within tube 31. A plurality of three conductive probes 33a, 33b, 33c extend into tube 31 via the sidewall thereof so as to protrude upwardly above the surface level of fluid 32. From the foregoing it will be readily evident that as tube 31 is tipped from one side to the other the degree to which the probes 33 are individually exposed above the level of the fluid will vary as presented, for example, by the two phantom lines 34a, 34b, representative of surface level of fluid 32.

The exterior ends of probes 33a, 33b, 33c are connected by leads 35a, 35b, 35c respectively.

Resistors 37 therebetween together with resistances 36 form a bridge circuit with output signals on leads 38, 39 indicative of the angle of tube 31.

From the foregoing it will be evident that as the wheel and tire assembly 27 rotates with axle 24, any camber present will tend to tip tube 31 to provide camber signals in a pattern characteristic of the particular wheel, as shown best in the diagram of Figure 5.

As shown in the latter figure a diagrammatic axle 41 carries a wheel and tire assembly 27 thereon for rotation. It has been observed that each wheel assembly has its own fixed camber characteristic. Therefore, by rotating assembly 27 and taking camber readings from camber sensor 29 in conjunction with indications of associated rotary positions derived from the run-out sensor 28 it is possible to record in computer means 1 9 a camber correction curve 42 which constitutes a sine wave about the axis 43. Accordingly, axis 43 corresponds to the mean plane of rotation 43t of wheel and tire assembly 27.

As noted above, as the wheel rotates and in response to requests from the microprocessor, run-out sensor 28 will send position signals to the microprocessor in computer unit 1 9. At such times camber sensor 29 is sampled to define the camber correction for run-out of the wheel and wheel clamp assembly at each of the rotary positions, i.e. the angular displacement of wheel and assembly from the mean plane of its rotation.

With this information microprocessor 1 9 will make an associated compensation corresponding to the previously determined angular displacement of the wheel from the mean plane thereof. It has been observed that the foregoing mean plane displacement readings will remain the same even though the wheel may sag at an angle when lifted free of the ground in an unsupported position. Curve 42 is plotted at intervals of 1 80 for purposes of illustration only inasmuch as far greater numbers of samplings are achievable in conjunction with the actual samplings by a computer.

In view of the fact that curve 42 represents the actual displacement of the wheel and tire assembly 27 from the mean plane of rotation 43, 43' of the tire and wheel assembly, and considering that it is desired to dispose the wheel and tire assembly 27 to rotate in its mean plane of rotation, then it is evident that by subtracting the camber corrections located above axis 43 and adding the camber corrections located below axis 43 at their associated rotational positions the wheel and tire assembly can be caused to rotate in its mean plane.

As shown in Figure 3, as well as in Figures 9 11, the toe sensor comprises a potentiometer 44 of a type adapted to have its wiper rotate to provide an output signal on leads 46. The wiper (not shown) is rotated by movements of the bifurcated guide arm 47 which is formed with a downwardly depending split end portion arranged to flank cable 26 for leading the cable onto a pulley 49. One end of arm 47 is coupled to the wiper mounting pin 48 so that as the angle of cable 26 changes with respect to the direction of the tubes 52, 53, of assembly 21 the wiper of potentiometer 44 will be adjusted accordingly thereby providing an output signal via leads 46 indicative of toe angle.

A constant force is applied to cable 26 by means of a spring loaded pulley 51 (Figure 13). A clock or constant tension spring (not shown) can be used for winding cable 26 around pulley 51 whenever diengaged from the cable from the opposite side.

It has been observed that as a wheel rotates, the run-out of the wheel introduces an error into the toe signals from leads 46 as now to be described with respect to Figure 7.

From inspection as shown in the diagram of Figure 5 it will be readily evident that the camber sensor 29 tips up and down in response to rotation of tire and wheel assembly 27. This rocking movement of assembly 21 serves to introduce an error in the angle of toe as detected by toe sensor 44. Note, for example, in Figure 7 where transducer support assembly 21 is first shown with wheel and tire assembly 27 having a negative camber whereby the housing 45 containing toe sensor 44 is disposed generally at line 54. On the other hand as wheel and tire assembly 27 are rotated about axis 23 the housing 45 and toe sensor 44 move leftwardly, as shown, to line 56. Thus, the camber correction for run-out, Figure 6 and 8, introduces a displacement 57 representing lateral movement of toe sensor 44 caused by rotational movement of the wheel and tire assembly 27.

A predetermined relationship has been observed between the corrections required for camber sensor 29 and for toe sensor 44. Thus, since, the camber and toe sensors act in planes disposed at 900 to each other in the plane of the wheel, the toe sensor correction for run-out is displaced 900 from the camber correction for runout as shown in Figure 8. Thus, having the camber sensor correction table or curve already in storage, microprocessor 1 9 can readily retrieve the required toe sensor correction for any given rotational position of the wheel.

Accordingly, the degree of toe correction to compensate for displacement 57 can be detected 900 ahead or behind the camber correction reading for run-out depending upon the direction of rotation of the wheel. In the present instance, and typically, the wheel when being aligned will be rotated forwardly from the top. As shown in Figure 8, the toe-pot correction is shown 900 ahead on curve 42 previously constructed for camber correction.

The angle defined between positive and negative camber positions in Figure 5 is greatly exaggerated for purposes of illustration only since this angle will normally run of the order of +30 Means for generating an angle of toe to be supplied electrically to the microprocessor in computer unit 19, includes cable 26. Each cable carries a coupling element 58 formed with a hook 58a (Figure 9). By interconnecting the hooks 58a of each cable 26 as shown in Figure 1 and entering a series of readings from each of the toe sensor elements 44 as the wheels are moved step-wise through the angle x (Figure 1) the toe angle for the wheels can be determined by detecting the difference between the left and the right hand readings. If this difference is divided by two the toe angle for each wheel is determined as distinguished from the toe angle for both wheels taken together.

As referred to above the angle of toe is measured generally by toe sensors 44. By applying the toe correction derived from the curve for camber correction for run-out, as previously stored in computer 19, it is possible to correct the toe sensor input and obtain accurate results as to toe angle.

Figure 14 shows the run-out sensor 28 in the form of a potentiometer whose wiper is coupled by means of shaft 59 to an axle extension portion 24' mounted on the axis 23 by wheel clamp assembly 22, described further below. The weight of assembly 21 together with the bearings 61 serve to maintain the bearing housing portion 62 of assembly 21 in a position generally parallel to the ground below while axle 24, extension portion 24', and wiper stem 59 of potentiometer 28 all rotate together on a common axis 23. As shown in Figure 13 bearing housing portion 62 forms an integral portion of the housing 25 of assembly 21.

The pair of elongate rigid tubes 52, 53 which support toe sensor 44 open into housing 25. Tube 53 passes cable 26 from pulley 49 to be wrapped about pulley 51 loaded by a suitable spring as noted above. Tube 52 passes three electrical leads 46 from sensor 44 to be coupled to a printed circuit chassis 63 where signals from potentiometer 44 are fed to a preamplifier and oscillator, for example, for conditioning the signals as is known, and then supplied to the microprocessor for correction as above.

Camber sensor 29, as described above, is carried within housing 25 and supported by a protruding ledge 64. A transversely extending mounting plate 66 is secured to ledge 64 by screws 67 which extend through oval shaped opening 68, 69 so as to permit sensor 29 to be adjusted to a level position. Mounting plate 66 serves to support a transversely extending, bifurcated cradle element 71 formed to hold and support camber sensing tube 31 in a nested manner therein.

Each wheel clamp assembly 22 comprises a spacer body 72 carrying a pair of guide rods 73.

Rods 73 support a pair of spaced mounting head assemblies 74, 76. Each of heads 74, 76 carries clamping stud means for engaging the rim 27a of wheel 27, either from the inside (Figure 3) or outside (Figure 18). Thus, heads 74, 76 carry rim connection assemblies 77 for engaging rim 27a and connecting clamp assembly 22 thereto.

Spacer body 72 is formed with a central opening 78 for receiving and by means of set screws (not shown) mounting, an axle extension portion 24' therein on axis 23.

Head assemblies 74, 76 are arranged to be cammed apart or drawn together after being disposed substantially in their lockup positions dependent upon clockwise or counterclockwise rotation of the locking lever 1 03 of assembly 76.

Head assembly 74 comprises a rigid spreader bar 79 formed with a pair of spaced openings 81, 82 formed with cylindrical wear bushings therein for receiving rods 73.

The confronting exterior surfaces of rods 73 are formed with a series of spaced detents 86 for engaging spring loaded steel balls 83, 84 therein carried by bar 79 and acting outwardly from each other. Bar 79 carries a pair of rim connector assemblies 77 disposed in a plane at an angle substantially normal to a plane including rods 73 and spaced from a plane parallel thereto taken through bar 79. This position of assemblies 77 and a limited clearance defined between rods 73 and the wear bushing in openings 81, 82 permits bar 79 to be tipped slightly clockwise as shown in Figure 1 6 so as to become locked onto rods 73 when force is applied downwardly on rods 73 as shown by arrow 87. In addition, force applied in an opposite direction also causes locking to occur.

This dual action becomes useful so as to permit assembly 22 to engage wheel 27 by drawing the heads 74, 76 together or by urging them apart.

Connector assemblies 77 comprises a hollow support housing 88 containing a generally cylindrical post 89 disposed therein to extend to a selected degree and secured by a set screw 91.

Post 89 includes a threaded extension element 92, and an enlarged tapered crown portion 93 for engaging rim 27a. It is to be noted that crown portion 93 engages rim 27a when assembly 76 is urged radially outwardly of the wheel 27, while element 92 is employed when the heads 74, 76 are drawn together to engage the outside of rim 27a.

Head assembly 76 is arranged to be "cammed" selectively between contracted and extended positions relative to head 74 as now to be described. Thus head assembly 76 comprises a hollow rigid body 94 containing radially outer and inner locking plates 96, 97 separated by springs 98 and maintained in spaced relation by the top and bottom of body 94. Bars 73 pass through the end of plates 96,97.

Plates 96, 97 each have a rigid U-shaped bail portion 96a, 97a extending radially inwardly of the wheel from the back edge of their respective plates 96, 97 so that plate 96 can be drawn downwardly from its rear edge by rotating a cam 99 against a portion of bail 96a.

Plate 97 can be urged upwardly from its rear edge by rotating cam 99 in an opposite direction so that cam 99 engages surface 101 along the back edge margin of plate 97. Cam 99 is mounted on shaft 102 for rotation by lever 103.

The position of lever 103 in Figure 3 constitutes an intermediate positioning of cam 99 between moving head 76 inwardly or outwardly.

In the position shown it can be assumed that both the plates are out of engagement with cam 99.

In operation, when rotating locking lever 103 counterclockwise cam 99 engages the depending bail portion 96a of locking plate 96 and draws it downwardly from the back edge thereby cocking locking plate 96 to cause plate 96 to engage bars 73. Further counterclockwise rotation of locking lever 103 serves to push the remaining portions of the head assembly radially outwardly of the wheel and away from the locked position of plate 96.

When lever 103 is released to a central position of cam 99 springs 98, interposed between locking plates 96, 97, serve to lift the top plate as the cam moves up and away from the depending loop portion of bail 96a.

Clockwise rotation of locking lever 103 causes cam 99 to act upwardly against the cam follower surface 101 of plate 97. Thus, the initial upward movement applied to the rear edge of plate 97 by the cam 99 causes plate 97 to grip guide rods 73 whereby further clockwise rotation of lever 103 urges the entire head assembly 76 radially inwardly toward the other head assembly 74.

This latter motion can then be used in locking onto the outer edge margin of rim 27a where it is not possible to engage rim 27a from inside.

It is to be observed that tubes 52, 53, as shown best in Figure 12, serve to support the toe angle sensor 44 in a parallelogram manner so as not to introduce error into the toe sensor in response to angular movement of tubes 52, 53 relative to wheel 27.

As shown in Figure 11, it is to be observed that the periphery of the sheave portion 49a of pulley 49 carries cable 26 directly through the center of wiper pin 48 of potentiometer 44. Thus, only the angular displacement of cable 26 from its point of departure 55 from sheave portion 49a is measured. Since sheave portion 49a passes directly through the center of pin 48 the angular movement of arm 47 is all that effects the angle of arm 47. Further, it is to be noted that pulley 49 and not wiper pin 48 takes the load tension of cable 26 as cable 26 passes through the center line of wiper pin 48 guided by the depending tabs 47a, 47b of arm 47. Arm 47, as noted is secured to pin 48 by the loop portion 50 formed on one end.

Thus, according to the system described above, a camber correction table is first prepared from camber readings taken with respect to a series of rotational positions of each wheel. Then toe readings are directly entered into a microprocessor or other computer means and corrected for run-out derived from using the table previously entered.

The microprocessor or computer means employed also stores technical data such as steering ratio information and other data pertinent to a number of different vehicles. Accordingly, using this pre-stored information together with the camber correction table and the corrected toe readings it is possible for computer means 1 9 to determine an appropriate caster correction for a given vehicle.

The foregoing system further includes means providing a correction for orienting the steering wheel of a vehicle to be "square" or "true" with regard to the vehicle when the vehicle is moving straight ahead.

In this aspect of the invention the vehicle is first driven straight into an alignment bay where a system of the type disclosed above is located.

After entering the bay, cables 26 are withdrawn from the ends of their related transducer arms to be coupled together by elements 58 carried on the ends of each of cables 26 as shown in Figure 1.

The foregoing functions serve to adjust the toe sensors to a position whereby values representing the angles "a" and "b" in Figure 19 can be entered directly into console 1 9 and stored in known computer means therein As shown in Figure 1 9 the transverse axis 106 represents a common axis from which the sensor arms pivot (thereby indicating no front wheel setback). Lines 107, 108 represent a direction normal to axis 106 at the pivot point for the left and right sensor arms respectively.

The angles a, b represent the toe angle of the left and right wheel respectively. Angles x, y ; represent the variation in the wheel direction caused by rotating the steering wheel to a "squared" position relative to the vehicle. Angles s, t represent the additional toe correction for left and right wheels to square up the steering wheel while creating proper toe to cause the vehicle to move straight ahead.

After the vehicle has been driven directly into the alignment bay wheel clamp assemblies are applied to each of the two front wheels and the ends of cables 26 are coupled together. In this manner, using the techniques described above, the toe angle for each of the two front wheels will be represented by the output from each of the two toe sensors. At this point the toe readings can be entered into the computer means by suitable controls such as represented by the data entry key 104 (Figure 1) on console 19.

As shown in the diagram of Figure 1 9 the angle of toe for the left and right hand wheel is represented by the characters "a" and "b". In order to effect an averaging of any error in the toe for the two wheels the sum of the toe for each of the two wheels is divided by 2 so that it can be assumed that "a" equals "b".

Next, the steering wheel is straightened to a "true" position with respect to the vehicle and locked in place by a steering wheel harness of known style so as to maintain the steering wheel in its "true" position while tie rods are adjusted.

Data entry key 104 is again activated to enter the new angular values x, y of the front wheels.

When the steering wheel is moved to its "straightened" position, in the present example as shown in Figure 19, it is assumed that the wheels are moved leftwardly through angles x, y.

As diagrammatically shown in Figure 19 a correction to the toe of the left hand wheel will need to be made in the amount of "s" and in the amount of "t" on the right hand wheel in order to cause the steering wheel to be "squared" with the vehicle while still permitting the vehicle to move straight ahead. Values of "s" and "t" are respectively solved by the computer means using the equations shown on Figure 1 9. Since the data for each of these values is already entered as noted above the solving of these equations can be readily accomplished using a suitable computer routine.

One such routine derives the correction to be made, i.e. "s" or "t", by vectorially adding the angles "a" and "x" for the left wheel while vectorially adding the angles "b" and "y" for the right wheel. In order to minimize error, averaging has been accomplished as noted above wherein the angles "a" and "b" are summed and divided by two.

According to another embodiment of the foregoing method for "truing" the steering wheel with respect to the toe of the wheels, the vehicle is again driven straight into an alignment bay containing the disclosed system. After entering the bay, cables 26 are withdrawn from the ends of their respective transducer arms and coupled together as noted in Figure 1.

The foregoing functions serve, as noted, to adjust the toe sensors to a position whereby values "a" and "b" can be entered directly into console 1 9 and stored in known computer means therein as noted above.

Console 1 9 carries a representational steering wheel 40 coupled to means for entering data into a computer system (represented by console 19) wherein the data represents the angular position of the steering wheel of the vehicle as it is driven straight into the bay. For example, the rotational axis of wheel 40 can carry a wiper coupled to a potentiometer 95 so as to provide a varying analog output from varying rotational positions.

Then, using known analog to digital conversion means, digital information as to the position of wheel 40 can be supplied to the computer means in console 19.

Console 1 9 can further store pertinent technical specifications for a number of vehicles such as steering ratio data.

Accordingly, given the information entered by means of steering wheel 40, and using the technique described above, a toe correction for each of the wheels can be readily generated which will serve to orient the steering wheel to a "true" position while at the same time aligning the wheels so that the vehicle will move straight ahead.

Accordingly, in one embodiment angles x and y are detected by movement of the simulated steering wheel 40 whereas in another embodiment angles x and y are determined by sens;ng actual movement of the front wheels.

The position of wheel 40 supplies an electrical indication of the tracking angle of the rear wheels with respect to the front wheels as explained with reference to the diagram in Figure 20. From inspection it is evident that the track of rear wheels 1 09 lies to the left of the track of front wheels 111. Under such circumstances if the front wheels were disposed in parallel with the axis 112 of the vehicle so as to "square up" the steering wheel, the vehicle would progress forwardly in a clockwise circle.

Thus, in order to drive the vehicle represented in Figure 20 in a straight ahead direction the steering wheel must be rotated counterclockwise from its straight ahead position through the angle 113 so that all four wheels move in parallel tracks.

Angle 113 will be the angle introduced into computer means 1 9 by disposing simulated steering wheel 40 in a position comparable to the vehicle's steering wheel as it is driven directly forwardly into the bay.

From the foregoing it will be readily evident that the above system can be employed to carry out the method of aligning front wheels of a vehicle of a type directionally controlled by a steering wheel following the steps of detecting substantially the toe angle of each of the front wheels. As noted above, the foregoing step can iiiclude averaging of the toe angles as directly measured. The next step is to detect the angular change in the direction of each of the front wheels required to orient the steering wheel to a true position with respect to the vehicle. Then, for each wheel, the angular change associated therewith is vectorially added to the toe angle thereof so as to define a correction for each of the wheels. Finally, while holding the steering wheel against movement, each wheel is adjusted to the extent of its associated correction.

Further, in the foregoing method the step of detecting the angular change noted can comprise the steps of observing the rotational position of the steering wheel with respect to the vehicle when the vehicle moves straight ahead and then providing an electrical signal representative of the angular displacement of the observed steering wheel position from a true position thereof relative to the vehicle.

Claims (18)

Claims

1. A wheel alignment system having computer means characterized by means for sensing the camber of a wheel at a series of rotational positions thereof, means for detecting rotational position of the wheel substantially simultaneously with sensing camber and for supplying information indicative of both to the computer means for calculation of a table of information providing a series of camber corrections in association with a series of rotational positions of the wheel to be applied by the computer to camber information detected at said series of positions.

2. A wheel alignment system having a transducer support assembly characterized by means carrying said assembly from a wheel to be aligned, the last named means serving to permit the wheel to rotate while said assembly remains substantially stationary, said assembly including means serving to provide an indication of the rotational position of the wheel and an electrical indication of the camber of the wheel.

3. A wheel alignment system according to Claim 2 further in which said assembly includes means for providing an electrical indication of the angle of toe of the wheel.

4. For a wheel alignment system a wheel clamp assembly having rigid guide means, first and second radially spaced mounting head assemblies carried by said guide means and having means for engaging the rim of a wheel to be'aligned for holding said assembly to the wheel during alignment, characterized by cam means carried by one of said head assemblies, operated by movement of said cam means in a first direction to lock said one of said head assemblies to said guide means and urge said one assembly radially outwardly to engage the rim of the wheel, and means operated by movement of said cam means in a second direction for lodking said one of said head assemblies to said guide means and drawing said one assembly radially inwardly to engage the rim of the wheel.

5. A wheel alignment system having computer means for storing a table of camber corrections derived from a wheel to be aligned and pertinent specifications for the vehicle whose wheel is to be aligned, characterized by a positionable device serving to provide an electrical input to the computer means serving to enter information indicative of the rotational position of the steering wheel when the vehicle wheels guide the vehicle straight ahead to supply information to the computer means representative of that degree of angular displacement of the front wheels required to orient the steering wheel to a true position with respect to the vehicle.

6. A wheel alignment system according to Claim 3 in which the last named means is characterized by an elongate arm assembly disposed to extend forwardly of a wheel being aligned, a potentiometer carried on the distal end of said arm assembly, and means serving to rotate the wiper of said potentiometer in response to steering movement of the wheels, the last named means including a pulley.

7. For a wheel alignment system a tranducer support assembly characterized by means for carrying said assembly from a wheel to be aligned, the last named means serving to permit the wheel to rotate while said assembly remains substantially stationary, said assembly including means serving to conjointly provide an indication of the rotational position of the wheel and an electrical indication of the toe angle of the wheel.

8. For a wheel alignment system a transducer support assembly characterized by means for carrying said assembly from a wheel to be aligned, the last named means serving to permit the wheel to rotate while said assembly remains substantially stationary, sensor means carried by said assembly for electrically indicating the angle of toe for the wheel carrying said assembly.

9. A wheel alignment system according to Claim 8 characterized by means for coupling said sensor to another of said sensors carried by another wheel to be aligned for electrically indicating the angular relationship between the wheels.

10. The method of aligning front wheels of a vehicle of a type directionally controlled by a steering wheel characterized by the steps of detecting substantially the toe angle for each of the front wheels, steering the wheels to a position orienting the steering wheel to a true position with respect to the vehicle, detecting the angular change in the direction of each of the front wheels caused by said steering change, and vectorially adding for each wheel said angular change associated therewith and substantially the toe angle associated with the same wheel to define the correction for each wheel, and while holding the steering wheel against movement adjusting each wheel to the extent of its associated said correction.

11. The method of aligning the front wheels of a vehicle of a type directionally controlled by a steering wheel characterized by the steps of detecting substantially the toe angle of each of the front wheels, detecting the angular change in the diraction of each of the front wheels required to orient the steering wheel to a true position with respect to the vehicle, and vectorially adding said angular change associated with each wheel to said toe angle thereof to define the correction for each wheel, and while holding the steering wheel against movement adjusting each wheel to the extent of its associated said correction.

12. The method of aligning the front wheels of a vehicle according to Claim 11 in which the step of detecting said angular change is characterized by the steps of observing the rotational position of the steering wheel with respect to the vehicle when the vehicle moves straight ahead, and providing an electrical signal representative of the angular displacement of said observed steering wheel position from a true position thereof relative to the vehicle.

13. A wheel alignment system characterized by means for sensing the angle of toe for each front wheel of a vehicle and providing electrical information substantially representative thereof when said wheels are disposed in a first position serving to cause the vehicle to move straight ahead and also when said wheels are disposed in a second position to provide electrical information representative of the required angular displacement of the front wheels to dispose the steering wheel in a true position with respect to the vehicle, computer means for storing said information substantially representative of the toe angle of each of said wheels in said first position, said computer means storing said inforniation representative of said second position to permit said computer means to vectorially add said information representative of said angular displacement of each wheel with its associated toe angle to provide a correction serving to cause said steering wheel to be disposed in a true position with respect to the vehicle when the wheels are aligned to cause the vehicle to proceed straight ahead.

14. A wheel alignment system having computer means, characterized by means for sensing the camber of a wheel at a series of rotational positions thereof, means for detecting rotational position of the wheel, means for sensing camber at said rotational position and for supplying information indicative of both to the computer, means for calculation of a table of information providing a series of camber corrections in association with a series of rotational positions of the wheel to be applied by said computer to camber information detected at said series of positions.

15. For a wheel alignment system a transducer support assembly, means for carrying said assembly from a wheel to be aligned in which the last named means serves to permit said assembly to pivot about the axis of the wheel, said assembly including means serving to provide an electrical indication of the camber of the wheel.

1 6. A transducer support assembly according to Claim 15 further in which said assembly includes means for providing an electrical indication of the angle of toe of the wheel.

1 7. A transducer support assembly according to Claim 1 6 in which the last named means is characterized by an elongate arm assembly disposed to be carried by and extend in a direction substantially normal to the axle of a wheel being aligned, a potentiometer carried by said arm assembly, and means serving to vary the output of said potentiometer in response to steering movements of the wheel.

18. A method of aligning the wheels of a vehicle substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

1 9. Apparatus for use in aligning the wheels of a vehicle substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.