U.S. patent number RE33,144 [Application Number 06/443,381] was granted by the patent office on 1990-01-09 for vehicle wheel alignment apparatus.
This patent grant is currently assigned to Hunter Engineering Company. Invention is credited to Lee Hunter, Daniel B. January.
United States Patent |
RE33,144 |
Hunter , et al. |
January 9, 1990 |
**Please see images for:
( Certificate of Correction ) ( Reexamination Certificate
) ** |
Vehicle wheel alignment apparatus
Abstract
Vehicle wheel alignment apparatus having active alignment
determining means operatively mounted on the steerable and
non-steerable wheels so as to be substantially insensitive to
mechanical distortion of the vehicle wheels and operable in
combination with wheel run out compensation means to produce wheel
alignment results of improved accuracy, and utilizing the improved
arrangement of alignment apparatus for supplying information which
can be used for computing the important angular relationship of the
wheels to a vehicle reference.
Inventors: |
Hunter; Lee (Creve Coeur,
MO), January; Daniel B. (Bel-Ridge, MO) |
Assignee: |
Hunter Engineering Company
(Bridgeton, MO)
|
Family
ID: |
26765197 |
Appl.
No.: |
06/443,381 |
Filed: |
November 22, 1982 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
81102 |
Oct 2, 1979 |
4302104 |
Nov 24, 1981 |
|
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Current U.S.
Class: |
356/139.09;
33/288; 33/203.18; 356/155 |
Current CPC
Class: |
G01B
11/2755 (20130101); G01B 2210/283 (20130101) |
Current International
Class: |
G01B
11/275 (20060101); G01B 011/26 (); G01B
005/24 () |
Field of
Search: |
;356/152,155
;33/288,203.18,336,337 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Buczinski; Stephen C.
Attorney, Agent or Firm: Gravely, Lieder & Woodruff
Claims
What is claimed is:
1. In apparatus for determining the alignment positions of vehicle
wheels in relation to a reference axis of the vehicle and to the
thrust line of the non-steerable wheels, the improvement which
comprises:
(a) first alignment determining instruments carried by each of a
set of steerable wheels so as to be in a substantially vertical
plane containing the axis of rotation of said steerable wheels;
(b) second alignment determining instruments carried by each of a
set of non-steerable wheels so as to be in a substantially vertical
plane containing the axis of rotation of said non-steerable
wheels;
(c) third alignment determining instruments supported from said
steerable wheels in position to be in line-of-sight with each other
transversely of the vehicle;
(d) radiant energy beam projectors and beam sensors in each of said
first, second and third alignment determining instruments in
positions such that the radiant energy beams from first instruments
are in the line-of-sight to be sensed by said beam sensors in
second instruments, radiant energy beams from second instruments
are in the line-of-sight to be sensed by said beam sensors in first
instruments, said first and second instruments are arranged in
cooperating pairs along opposite longitudinal sides of the vehicle
so as to be spaced in the longitudinal direction between said
steerable and non-steerable wheels; and
(e) radiant energy beam projectors and beam sensors in said third
alignment determining instruments in positions of cooperation
transversely of the vehicle adjacent the steerable wheels, whereby
said first and third instruments cooperate to generate signals
determinative of the alignment positions of the steerable wheels
relative to the vehicle reference axis and said second instruments
cooperate with said first instruments to generate signals
determinative of the thrust line effect of the non-steerable wheel
on said steerable wheels.
2. Apparatus for determining the angular relationship of the
steerable and non-steerable wheels of a vehicle relative to a
longitudinal reference axis of the vehicle and the thrust line of
the non-steerable wheels, the apparatus being associated with the
wheels in sets longitudinally spaced a distance representing the
vehicle wheel base and the wheel tread width, said apparatus
comprising:
(1) first and second wheel position determining instruments carried
by each wheel of the steerable wheel set;
(a) a first one of said instruments being in line-of-sight with
each other transversely of the vehicle;
(2) a single angle determining instrument carried by each
non-steerable wheel in position to be in line-of-sight with a
second instrument carried by a steerable wheel at the same
longitudinal side of the vehicle,
(a) said single instruments and said second instruments being
located in substantial alignment with the axis of rotation of the
vehicle wheels on which each is carried, such that each instrument
represents the plane of wheel rotation;
(3) and all of said instruments being cooperatively operable for
generating signals representative of the positions of the
individual wheels in said sets for determining the thrust line
positions of the non-steerable wheels relative to the longitudinal
reference axis of the vehicle, and for determining the effect on
the positions of the steerable wheels of the thrust line alignment
of the non-steerable wheels.
3. Apparatus for determining the angular alignment relationship of
the steerable and non-steerable wheels of a vehicle relative to a
longitudinal reference axis of the vehicle to the thrust line of
the non-steerable wheels, the apparatus being associated with the
arrangement of the longitudinally and transversely spaced wheels
representing the vehicle wheel base and tread width dimensions,
said apparatus comprising:
(1) a pair of alignment determining instruments mounted on each of
the steerable wheels,
(a) with a first one of said instruments on each steerable wheel
being positioned to align substantially with the axis of wheel
rotation so as to have a minimum of lateral displacement to the
vehicle longitudinal reference axis upon turning of the steerable
wheels,
(b) and a second one of said instruments on each steerable wheel
being positioned forwardly of the wheels so that said second
instruments are in position for obtaining cooperation therebetween
transversely of the vehicle wheels;
(2) a single measuring instrument on each of the non-steerable
wheels in position to align substantially with the axis of wheel
rotation, such that each instrument represents the plane of wheel
rotation,
(3) said first ones of said instruments being positioned to be in
alignment determining cooperative relationship with said single
instruments positioned at the same side of the vehicle wheel base,
and said second ones of the instruments being in alignment
determining cooperative relationship with each other across the
tread width of the vehicle,
(a) said instruments generating signals representive of the
position of the respective wheels relative to the vehicle reference
axis and the thrust line of the non-steerable wheels;
(4) and alignment computer means operatively connected with each of
said instruments and including means to display the values of the
computed angles from the signals generated by said instruments,
(a) such that the toe alignment determination of the steerable
wheels and the non-steerable wheels and the thrust line alignment
determination of the non-steerable wheels is displayed in relation
to the vehicle longitudinal reference axis.
4. Apparatus for determining the existing alignment of the
steerable and non-steerable vehicle wheels relative to a
longitudinal reference axis of the vehicle and to the thrust line
of the non-steerable wheels, in which the apparatus comprises:
(1) six alignment determing instruments, each embodying a radiant
energy projector and signal generating radiant energy sensor means
mounted such that
(a) each non-steerable vehicle wheel supports one instrument in
position to represent the plane of rotation of that wheel and in
alignment with its axis of rotation,
(b) each steerable vehicle wheel supports a first instrument in
position to represent the plane of rotation of that wheel and in
alignment with its axis of rotation, and
(c) each steerable vehicle wheel also supports a second instrument
in position to represent the angular position of the plane of
rotation of that wheel relative to the longitudinal reference axis
of the vehicle;
(2) said one instrument at each non-steerable wheel being in
line-of-sight with said first instrument at each steerable wheel at
the same longitudinal side of the vehicle for mutual cooperation
therewith, such that
(a) the radiant energy sensors in said one instrument and said
first instrument are energized by the radiant energy projected from
the projectors in said first instrument and said one instrument
respectively;
(3) said second instruments being in mutual cooperative
line-of-sight positions such that
(a) the radiant energy sensor in each instrument is energized by
the radiant energy projected from the projector in the cooperative
instrument;
(4) said signals generated by said sensors representing the
position of the respective vehicle wheels;
(5) and means operatively connected to each individual instrument
for processing the signals generated by each of said radiant energy
sensors such that
(a) the toe alignment of the steerable wheels and the toe alignment
and thrust line of the non-steerable wheels is determined in
relation to the longitudinal reference axis of the vehicle.
.Iadd.
5. A wheel alignment measuring apparatus designed for measuring
wheel alignment angles of the vehicle having front and rear wheels
and comprising:
six angle measuring units,
first and second said angle measuring units adapted for connection
respectively to the left and right front wheels of the vehicle and
including angle pickup means for measuring and producing signals
indicating the total tracking angles of both front wheels,
third and fifth said angle measuring units adapted for connection
respectively to the left front wheel and a left rear wheel and
including angle pickup means for measuring and producing signals
indicating the angles of these wheels,
and fourth and sixth said angle measuring units adapted for
connection respectively to the right front wheel and a right rear
wheel and including angle pickup means for measuring and producing
signals indicating the angles of these wheels,
means rigidly joining the first said angle measuring unit with said
third angle measuring unit,
means rigidly joining said second angle measuring unit with said
fourth angle measuring unit, and
an electrical circuit means for receiving signals from said angle
pickup means and for producing a reading for wheel alignment data
from the angles measured by said angle measuring units. .Iaddend.
.Iadd.
6. The structure as claimed in claim 5 wherein said angle measuring
units have relative placements and polarities arranged to cut out
effects produced by track differences and wheel base differences so
that output readings are produced free of such differences.
.Iaddend.
Description
BACKGROUND OF THE INVENTION
The ideal geometric configuration of a four wheel vehicle is a
rectangle in which: the steerable wheels will run parallel with
each other and are equidistant from the center of the connecting
axle or its equivalent; in which the non-steerable wheels will run
parallel with each other and are equidistant from the center of the
connecting axle or its equivalent; in which the non-steerable
wheels either track with the steerable wheels or are equally off
set from the steerable wheel tracks; and in which the vehicle body
has its longitudinal geometric center line coincident with the
longitudinal center line for the steerable and non-steerable
wheels.
The practical and economic considerations involved in the
production of wheeled vehicles taken into account the complications
in connection with manufacturing tolerances present in the various
parts and the possibility that tolerance mis-matching can build up
variations from the ideal geometric configuration. As a consequence
of the possible mis-matching of tolerances in the parts making up a
finished vehicle provision is made for mechanically adjusting wheel
positions relative to the chassis or body of a vehicle. In some
vehicles all adjustments are found in the steerable wheel
assemblies, while in others the adjustments are provided in both
the steerable and non-steerable wheel assemblies. Generally
vehicles are permitted to have some deviations from the ideal
conditions of wheel alignment and wheel to body alignment. As along
as the deviations are not regarded as serious the vehicle is put
into use.
Wheel alignment apparatus has been disclosed by Manlove U.S. Pat.
No. 3,181,284 of May 4, 1965 in relation to the steerable and
non-steerable wheels of a vehicle. The objective of this disclosure
is limited to mechanical apparatus in which mounting members are
connected to the rim of the vehicle wheels without being
compensated for run out or for mechanical variations in the shape
of the wheel rims, and in which wheel alignment measurements are
made from positions of the measuring apparatus which is displaced
from positions representing the true alignment measuring positions.
Vehicle wheel alignment apparatus of the electronic type is
disclosed by Florer in U.S. Pat. No. 4,095,902 of June 20, 1978, by
Lill in U.S. Pat. No. 4,097,157 of June 27, 1978, and by Senften in
U.S. Pat. No. 4,126,943 of Nov. 28, 1978.
In connection with the hereinafter to be described wheel
compensating means, advantage is taken of the run out compensator
method disclosed in Senften U.S. Pat. No. 3,892,042 of July 1,
1975.
BRIEF DESCRPTION OF THE INVENTION
This invention relates to improvements in vehicle wheel alignment
apparatus, and is particularly concerned with the application of
instrumentation mounted on the steerable and non-steerable wheel
sets so that greatly improved alignment data may be found.
It is a further object of the present invention to dispose the
active instruments on the various vehicle wheels by mounting means
located in the most advantageous position so as to substantially
nullify the physical inaccuracies in forming the wheel rims and the
components of the instruments to improve the accuracy of alignment
results.
It is an additional object of the present invention to provide, in
addition to compensating the instruments for normal wheel run out,
location of the instruments in positions so as to be substantially
independent of any deviation of the wheel from the true plane of
wheel rotation, whereby mechanical tolerances in wheel as well as
in instrumentation components can be accounted for without
substantial interference in the alignment measuring results.
A preferred embodiment comprises alignment instruments carried by
the vehicle wheels in position to be compensated for wheel run out,
and to be operative for measuring alignment angles of the steerable
wheels from the non-steerable wheel, for measuring the alignment
angles of the non-steerable wheels from the steerable wheels, and
for measuring the alignment angles of the steerable wheels from
each other in relation to a vehicle reference.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention is illustrated in a presently preferred form
in the accompanying drawings, wherein:
FIG. 1 is a side elevational view of steerable and non-steerable
wheels related to a typical vehicle shown in silhouette;
FIG. 2 is a diagrammatic plan view of a representative alignment
pattern for the wheels of the vehicle seen in FIG. 1;
FIG. 3A is a diagrammatic view of a vehicle wheel and cooperating
alignment instrumentation to illustrate the negligable effect of
mechanical variations in the structure;
FIG. 3B is a side elevation view taken along line 3B--3B in FIG.
3A;
FIG. 4 is a diagrammatic layout of the vehicle wheels for the
purpose of illustrating the measurement of the angles of the
respective wheels relative to a geometric center line;
FIG. 5 is a fragmentary front view on an enlarged scale of a
typical electro-optic transducer to illustrate the organization of
components without particular regard to the details of the
housing;
FIG. 6 is a further view of the transducer components as seen along
the line 6--6 in FIG. 5;
FIG. 7 is still another view of the transducer components as seen
along the line 7--7 in FIG. 5;
FIG. 8 is a block diagram of the electronic circuitry in which one
typical emitter-detector transducer combination has been shown in
association with signal computation means; and
FIGS. 9A and 9B are diagrams of the transducer components and their
effects on the optical path of the radiant energy beam projected
from an emitter.
DETAILED DESCRIPTION OF THE EMBODIMENT
Reference will now be directed to the drawings for a more complete
understanding of the intent and scope of the invention presented in
terms of an embodiment presently preferred. The view of FIG. 1 is
of a passenger vehicle 14 which will serve to illustrate the
utility of the presently preferred embodiment of the invention. As
seen from the left side, the left steerable wheel 15L is shown in
association with one form of an instrument support 16 adapted to
grip the flange of the wheel rim. The support 16 carries a pivotal
housing 17 the axis of which is substantially centerable to the
spindle axis (not shown) on which the wheel 15L rotates. A bracket
18 is hung from the housing 17 so it may assume a substantially
vertical position even though the wheel 15L is jacked up so it may
rotate. At times, with the wheel 15L resting on its support, it may
be desirable to secure the bracket 18 against pendulus movement by
tightening up on a knob 19 (FIG. 2). The bracket 18, in addition to
the housing 17, carries a support arm 20 which extends forwardly of
the housing 18 to clear the tread of wheel 15L and be in position
so that its end portion may be used for supporting an instrument
device 21L. The support arm 20, or some associated part of the
assembly, is usually provided with a spirit level (not shown) for
purposes of locating the arm in substantially horizontal position,
which positioned is retained by tightening up on the knob 19.
FIG. 1 shows the vehicle non-steerable wheel 22L to be provided
with an instrument support 16 which is identical to the support
attached to the steerable wheel 15L. The several parts are
designated by similar reference numerals and need not be described
again. It is particularly important to observe that the support 16
at the left steerable wheel 15L carries an instrument 23L and the
support 16 for the left non-steerable wheel 22L carries a companion
instrument 24L. These instruments 23L and 24L are made up of
cooperating components which are intended to function with each
other in a manner set forth in the contemporaneously filed
copending patent application of James M. Grossman et al, Ser. No.
080,274, filed Oct. 1, 1979, and entitled VEHICLE WHEEL ALIGNMENT
APPARATUS.
FIG. 2 shows a schematic plan view of all vehicle wheels, such as
those at the left side seen in FIG. 1, and companion right side
wheels 15R and 22R. The wheels at the left side are distinguished
by adding the suffix "L", and those at the right side are
distinguished by the suffix "R". However, each wheel 15R and 22R is
provided with an instrument support 16 having the construction
generally described above. Also, the support 16 on steerable wheel
15R has a support arm 20 which carries an instrument 21R to
cooperate with the left side instrument 21L. In addition, the
support 16 at the non-steerable wheel 22R carries an instrument 24R
to cooperate with an instrument 23R carried by the support 16 at
the steerable wheel 15R. These instruments 21L and 21R, as well as
instruments 23R and 24R, cooperate with each other and are made up
of components operating in a manner described in the said Grossman
et al patent application.
In view of FIG. 2, the instruments 21L and 23L are operatively
connected into a console assembly 25 by a lead 26L, and the
transducer instruments 21R and 23R are similarly connected by a
lead 26R to the console 25. In like manner the instruments 24L and
24R are connected respectively by leads 27L and 27R into console
25. Signal processing and alignment computation are performed in
the console 25 and the results can be displayed by means indicated
collectively at 28. More particularly in FIG. 2, the instruments
21L and 21R cooperate with each other in the process of measuring
the angles LWT (left wheel toe) and RWT (right wheel toe). For that
purpose instrument 21L has radiant energy detector means which is
responsive to a source of radiant energy from instrument 21R, and
instrument 21R has radiant energy detector means responsive to a
source of radiant energy from instrument 21L. The essence of this
cooperation is that projectors of radiant energy are disposed to
direct beams in criss-cross paths transversely of the vehicle, and
which paths have boundaries within the field of vision of the
detector means arranged to look at the position from which the beam
is projected.
In a like manner, it is indicated in FIG. 2 that instruments 23L
and 24L, each containing radiant energy beam projectors and radiant
energy detectors, cooperate with each other in the process of
measuring the respective angles relative to a vehicle reference
axis 30 which is established by a line joining the center points of
the axles 31 and 32, which center points are centered between the
spacing of the wheel sets 15L and 15R, and 22L and 22R. The angle
LFW is formed between the axle 31 and the longitudinal
line-of-sight L of the radiant energy beam from the instrument 24L
at wheel 22L. The angle LRW is formed between the axle 32 and the
longitudinal line-of-sight L of the radiant energy beam from the
instrument 23L at wheel 15L. Similarly, the instruments 23R and 24R
cooperate with each other for measuring the angles RFW and RRW by
the criss-crossing of the radiant energy beams depicted by the dash
line R representing the longitudinal line-of-sight between the
detector means in the instruments 23R and 24R. In the example seen
in FIG. 2, the wheels 15L and 15R have planes of rotation PR which
are substantially perpendicular to the axle 31, while the planes of
rotation PR of the wheels 22L and 22R are also substantially
perpendicular to axis 33. This arrangement shows that the angles
LWT and RWT are substantially ninety degrees (90.degree.) since it
is presumed that the instrument support arms 20 are substantially
parallel to the planes of rotation PR for wheels 15L and 15R.
However, it is shown in FIG. 2 that the tread spacing for wheels
22L and 22R is greater than for the tread spacing of the wheels 15L
and 15R. In addition, wheel 22L is toed out relative to the
reference axis 30 while wheel 22R is toed in relative to the same
axis 30. The angular positions for the respective wheels 15L, 15R,
22L and 22R are arbitrary for purposes of illustrating the unique
advantages of having active instruments at each wheel for measuring
wheel position angles from each other and relative to the reference
axis 30 for the vehicle.
The Transducers
Turning now to FIGS. 5, 6 and 7, there has been shown in some
diagrammatic detail a typical transducer instrument, such as the
one designated at 21R in FIG. 2. It is to be understood that all of
the transducer instruments 21L, 23L, 24L and 21R, 23R and 24R are
substantially the same. Thus, the instrument 21R has a panel 34
formed with an aperture 35 used to control the radiant energy beam.
The aperture 35 may be produced photographically as a transparent
area in an opaque material, or the aperture may be an opening in a
sheet of solid material. At a suitable distance behind the aperture
35 there are mounted a pair of photodiodes 36 and 37. The width of
the aperture 35 is substantially equal to the width of the face of
either one of these photodiodes, and it is centered so that, in a
null position with radiant energy impinging at 90.degree. to the
plane of panel 34, the exposure of each photodiode to the radiant
energy should be substantially equal. The photodiodes are carried
by a printed circuit board PC which also carries preamplifiers for
converting the photodiode output current into voltage, and the
operative electronic components associated with radiant energy
emitter means 38 which illuminate a cooperative transducer
instrument attached to an adjacent wheel. The photodiodes 36 and 37
are illuminated by the radiant energy emitter means of that
cooperative transducer instrument.
FIG. 8 is a schematic block diagram of a typical electronic
transducer instrument composed of signal conditioning means 39
connected to an emitter 38. The radiant energy beam generated by
the emitter 38 is directed at detector means in another instrument
spaced therefrom where such other instrument has a pair of
detectors 36 and 37 located behind a window 35 in an opaque mask
34. The detectors may be photodiodes having preamplifier means 41
and 42 for converting the current generated in the photodiodes into
voltage. These voltage signals are processed in conditioning means
43 to produce output signal A from detector means 41 and output
signal B from detector means 42, which serves the purpose of
electronically filtering the detector amplifier signals to isolate
the emitter signals and eliminate interference due to noise and
ambient light. The filters are matched to the characteristics of
the emitter signals, which may be square wave or sine wave at audio
frequency (10 KHz for example) so that the detector signals are
conditioned by bandpass filters whose center frequency matches the
emitter signal. In order to obtain angular information the detector
signals from the preamplifiers 41 and 42 and means 43 must be
processed in separate circuits (or in time shared circuit means) in
signal computer means 44 so as to be able to produce results which
can be displayed. When optical filter means 45 is employed it is
positioned over the aperture 35 and is selected to have
transmission characteristics which maximizes all other light.
Reference will now be directed to FIGS. 9A and 9B to present a full
description of the interaction of the component parts of the
tranducer. The boundary of the portion of the radiant energy beam
from emitter 38 falling through aperture 35 is shown by the dashed
lines 38A and 38B. The center of the beam is denoted the line of
sight LS. In FIG. 9A the line of sight LS is coincident with the
normal axis of the aperture 35. This is the null position in which
equal amounts of energy fall on detectors 36 and 37. In FIG. 9B the
detector and aperture assembly, and hence the normal axis NA, is
rotated from the line of sight LS. As seen in the drawing, the
effect of the aperture 35 is to bound the energy beam such that
more light now falls on detector 36 than on detector 37. The
electronic current flowing in each detector is proportional to the
amount of light incident upon it. The detector signal conditioning
means 43 of FIG. 8 must measure these currents and convert them to
a DC voltage suitable for signal computation.
A further unique feature of the present embodiment is the way the
measuring instruments are mounted on or supported by the vehicle
wheels. The views of FIGS. 3A and 3B will serve to show that
mechanical run out present in the wheel, as well as tolerances
present in the wheel and instrument, does not materially affect the
operation of the instruments 21R and 23R. It is assumed in this
case that the instrument 23R is provided with run out compensation
means of the type disclosed in Seften U.S. Pat. No. 3,892,042
(supra) so that the instrument has obtained for its electronic
memory the data developed by rotating the wheel 15R from a starting
position to a position at 180 degrees of rotation displaced from
the start, and computing the average of any run out disturbance
generated in that change of position. For example in FIG. 3A, the
instrument 23R has an ideal position on the axis X--X of wheel
rotation. However, the components may have mechanical deviations or
physical irregularities from a perfectly formed system, in which
case the instrument might be located off the axis X--X to the
extent of the angle D. Since the irregularities or deviations are
local to the wheel 15R, the path along which the instrument may be
positioned is the arc C. The chordal portion of the arc C joining
the possible extremes of the angle D is substantially a straight
line that essentially coincides with the compensated plane of
rotation of wheel 15R. The mechanical deviation or physical
irregularities which may be present in any vehicle wheel and also
present in an instrument attached thereto include production
tolerances in the components, misshaped wheels, and similar
departures from an ideal mechanical assembly. While each instrument
23L, 23R, 24L and 24R embodies the electronic means disclosed in
FIG. 5 of Senften U.S. Pat. No. 3,892,042 to compensate for wheel
wobble to find the plane of wheel rotation it also embodies the
means of FIG. 8 herein, or it may embody means of the character
seen in Senften U.S. Pat. No. 4,126,943.
In the views of FIGS. 3A and 3B it can be seen that the instrument
21R is carried on a support 20 which is directly related with the
instrument 23R. Assuming that the support 20 is related at ninety
degrees to the axis X--X for the wheel 15R, it must follow that the
angle D of deviation of the instrument 23R, as above outlined, will
also be the same angle D of deviation for instrument 21R. Both
instruments 21R and 23R are seen to assume positions along a
substantially straight line or chord of the arc C and C-1, which
positions are dictated by the presence of mechanical run out in the
system. Each instrument embodies radiant energy emitter means and
radiant energy detector means sensitive to received radiant energy,
but the possible amount of deviation of the line-of-sight is
insignificant and can be disregarded.
FIG. 4 is a diagrammatic view of the wheels 15L, 15R, 22L and 22R
of the vehicle 14 of FIGS. 1 and 2, but in this view the wheels
have been intentionally misaligned to illustrate the geometry of
wheel alignment investigation using the foregoing principle
instrumentation. The instruments are generally shown and designated
by the reference characters appearing in FIG. 2, and the alignment
is calculated with reference to a geometric center line 30 (FIGS. 2
and 9) of the vehicle. It is necessary to understand that there is
a line-of-sight T between the instruments 21L and 21R which
represents the radiant energy beam path from the respective
instruments 21L and 21R. The line-of-sight may not be the center of
the beam, but the beam has a sufficient spread or fan to be seen by
the opposing beam sensors. Normally the wheels will not be so far
out of alignment as is depicted in FIG. 4 that the beam will not be
seen. In like manner there is a line-of-sight L between the
instruments 23L and 24L representing the radiant energy beam path
from the respective instruments 23L and 24L. The line-of-sight R
between the instruments 23R and 24R depicts the path of the radiant
energy beams from those respective instruments. There are
construction lines on the drawing of FIG. 4 to assist in visualing
the angles to be investigated, such as the dash lines which are
parallel to the geometric center line 30, and act as a reference
for the angles. It is herein assumed that all measured angles have
been compensated electronically for wheel run out, as disclosed in
the Senften U.S. Pat. No. 3,892,042, to eliminate from the
following description need to complicate the calculations.
The angles indicated in FIG. 4 are shown in tabular form with
reference to the position of the beam projectors, and beam sensors
used to determine those angles.
______________________________________ Projector Location Sensor
Location Measured Angle ______________________________________
Right front toe arm Left front toe arm Left cross LC Left front toe
arm Right front toe arm Right cross RC Left rear wheel Left front
wheel Left front longitudinal LF Right rear wheel Right front wheel
Right front longitudinal RF Left front wheel Left rear wheel Left
rear longitudinal LR Right front wheel Right rear wheel Right rear
longitudinal RR ______________________________________
The signal information about the angles LC, RC, LF and RF is
produced in the respective instruments (see FIG. 8) and the results
are fed into the alignment computer 25 where the following
computations relative to the geometric reference line 30 are worked
out for the several angles pertinent to the alignment
determination, as follows:
__________________________________________________________________________
The angles computed The computation
__________________________________________________________________________
LFT (left front toe) 1/2(LC + RC + LF - RF) RFT (right front toe)
1/2(LC + RC - LF + RF) TFT (total front toe) LFT + RFT = LC + RC SB
(set back) 1/2(RC - LC + LF - RF) LRT (left rear toe) LFT - LF + LR
= (LC + RC - LF - RF) + LR RRT (right rear toe) RFT - RF + RR =
1/2(LC + RC - LF - RF) + RR TRT (total rear toe) LRT + RRT = LC +
RC - LF - RF + LR + RR TL (thrust line) 1/2(LRT - RRT) = 1/2(LR -
RR) LFTTH (left front toe LFT - TL relative to thrust line) RFTTH
(right front toe relative RFT + TL to thrust line)
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After the computation has been made it is in a form suitable for
driving the display 28. The display may be a group of meters (not
shown) for showing the values of the computed angles identified in
the left column above. It is usual in the make up of display 29 to
provide meters and circuit selectors for connecting the meters
selectively to display left, right and total toe for the steerable
wheels, or left, right and total toe for the non-steerable wheels,
or wheel set back, or the relationship of steerable wheel toe
relative to the thrust line for the non-steerable wheels.
In view of the foregoing disclosure it is apparent that the present
apparatus has certain unique characteristics which are adapted to
produce more accurate vehicle wheel alignment information by means
which enables an alignment service shop to determine quickly and
easily the respective angular relationships of the individual
wheels of a vehicle with respect to a vehicle reference line. A
unique feature resides in the way that the instruments are mounted
on the respective wheels so that signals representative of the
individual wheel positions are generated directly and can be fed
into a remote computer console for computation and display. In the
mounting of the instruments at each of the vehicle wheels a support
is selected for the instrument to place it in a position such that
the instrument will be substantially independent of any mechanical
irregularities of the character above defined. This latter feature
is disclosed in FIGS. 3A and 3B where it has been disclosed that
mechanical irregularities might result in positioning the
instrument 23R at any place along the path of arc C, and regardless
of the precise position along this arc, the emitter and detector
means will not be displaced to any significant degree since there
is extremely slight shifting of the poisition away from the arcuate
path C. In like manner, with respect to the instrument carried by
the front support arm, instrument 21R on the support 20 would be
insignificantly displaced since the emitter and sensor would be
moving in the arcuate path C-1 which has only slight lateral
displacement of an amount that can be ignored.
The present disclosure has set forth a unique arrangement for
vehicle wheel alignment apparatus which will produce greatly
improved accuracy in determining the position of the respective
vehicle wheels relative to a vehicle reference line, which in
connection with the view of FIG. 2 has been indicated to be the
geometric center line of the vehicle. While the foregoing
disclosure has set forth a preferred embodiment of the present
invention it should be understood that variations therefrom may
come to mind after the principals of the disclosure have been
understood, and it is desired to include all reasonable variations
within the scope of this disclosure.
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