Optics: measuring and testing – Angle measuring or angular axial alignment – Wheel alignment with photodetection
Reexamination Certificate
2000-02-10
2002-06-04
Buczinski, Stephen C. (Department: 3662)
Optics: measuring and testing
Angle measuring or angular axial alignment
Wheel alignment with photodetection
C033S203180, C033S203190, C033S288000, C356S004030
Reexamination Certificate
active
06400451
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to a wheel alignment measuring method and system, and, in particular, to a method and system for measuring wheel alignment characteristics of a wheel of a vehicle such as an automobile.
2. Description of the Prior Art
A wheel of a vehicle, such as an automobile, is set with various alignments, such as toe-in and camber angles, and it is important to measure such alignments with high accuracy. In measuring such alignment characteristics of a wheel of a vehicle, there are basically two categories of measuring technologies, i.e., the contact type measuring technology and the non-contact type measuring technology.
In the contact type measuring technology, a measuring apparatus is brought into direct contact with a wheel to be measured for measuring toe-in and camber angles. The contact type measuring apparatus tends to be inexpensive, but its measuring accuracy is limited and difficulty is often encountered in taking measurements for various reasons.
On the other hand, in the case of the non-contact type measuring technology, it is typically based on the triangulation and a rather complicated calculation is required in processing an image of a wheel obtained by a CCD imaging device. An example the non-contact type wheel alignment measuring technology was proposed by one of the present inventors and described in the Japanese Pat. Laid-open Pub. No. 9-280843, assigned to the assignee of this application. As a result, the structure of the non-contact type measuring apparatus tends to be complicated in structure and thus difficulty is encountered in manufacturing the apparatus. Thus, the non-contact type measuring apparatus tends to be expensive.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, there is provided a method for measuring an alignment characteristic of a vehicle, comprising:
(a) projecting a first pair of light beams, which are in parallel to each other and separated by a predetermined distance, to a first area of a side wall of a tire of said wheel or to a flat surface detachably attached to said wheel;
(b) receiving reflected light from said first projected pair of light beams incident on said side wall or said flat surface and forming images from said reflected light at an image-forming surface of a first photo-electric converting device at a first location, said first photo-electric converting device being at a fixed distance from said wheel in an approximately axial direction;
(c) measuring a length of a first space between said images formed on said first photo-electric converting device;
(d) calculating a first distance to a first point on said side wall or said flat surface between the points of incidence of said first pair of light beams on said side wall or to said flat detector plate from said first photo-electric converting device, using said length of said first space;
(a
2
) projecting a second pair of light beams, which are in parallel to each other and separated by a predetermined distance, to a second area of said side wall of a tire of said wheel or to said flat surface detachably attached to said wheel;
(b
2
) receiving reflected light from said second projected pair of light beams incident on said side wall or said flat surface and forming images from said reflected light at an image-forming surface of a second photo-electric converting device at a second location, said second imaging device being at a fixed distance from said wheel in an approximately axial direction;
(c
2
) measuring a length of a second space between said images formed on said second photo-electric converting device;
(d
2
) calculating a second distance to a second point on said side wall or said flat surface between the points of incidence of said second pair of light beams on said side wall or said flat surface from said second photo-electric converting device, using said length of said second space; and
(e) calculating an angle of said wheel from said first and said second distances and said first and second locations of said first and said second photo-electric converting devices.
Preferably, the alignment characteristic is selected from the group essentially consisting of a toe-in angle and a camber angle. When the toe-in angle is selected as an alignment characteristic to be measured, the at least two different measuring locations include at least two locations which are set substantially along a horizontal line on the outer side surface of the tire, which horizontal line is defined by a horizontal plane extending along the axis of rotation of the wheel. Alternatively, when the camber angle is to be measured, the at least two different measuring locations include at least two locations which are set substantially along a horizontal line on the outer side surface of the tire, which horizontal line is defined by a horizontal plane extending along the axis of rotation of the wheel, and also at least one location which is set substantially along a vertical line on the outer side surface of the tire, which vertical line is defined by a vertical plane extending along the axis of rotation of the wheel.
Preferably, the step (e) is carried out at the same time for each of the at least two different locations.
In accordance with another aspect of the present invention, there is provided an apparatus for measuring a distance to a surface, the apparatus comprising:
projecting means for projecting a pair of light beams in parallel to each other, while keeping a separation therebetween at a constant, toward said surface;
a photo-electric converting device having an image forming surface, said photo-electric converting device being capable of converting one or more images formed on said image forming surface into an electrical signal indicating the locations of said one or more images on said image-forming surface relative to a reference location on said image forming surface;
image forming means for receiving light from said projected pair of light beams reflected from said surface and forming a pair of images on said image forming surface; and
processing means for processing said electrical signal produced by said photo-electric converting device responsive to said pair of images formed by said image forming means, and capable of measuring an image separation between said images, and to calculate a distance to a portion of said surface between said pair of projected light beams from a predetermined reference point from said image separation.
Preferably, the image forming means includes an optical lens and the predetermined reference point for measurement is set at the center of the optical lens. The optical lens preferably has a fixed focal distance. The photo-electric converting device preferably includes a CCD image sensor having a predetermined number of pixels along a line defined on the image-forming surface having the predetermined reference location at its end.
Preferably, the processing means includes a central processing unit (CPU) for implementing a calculation according to the predetermined formula to determine a distance to a point of interest (measurement point) on the wheel. The processing means also includes means for determining a toe-in angle according to another formula based on at least two distance measurements obtained for at least two different locations of a wheel and also for determining a camber angle according to a further formula based on at least three distance measurements obtained for at least three different locations of a wheel.
In accordance with a further aspect of the invention, there is provided an apparatus for measuring alignment of a wheel of a vehicle, comprising:
a plurality of measurement apparatuses, each of said measuring apparatuses including:
projecting means for projecting a pair of light beams, in parallel to each other while keeping a separation therebetween at constant, toward a side wall of a tire of said wheel or a flat surface detachably attached to said wheel;
a photo-electric converting device having an image forming
Fukuda Yutaka
Funakoshi Kenji
Anzen Motor Car Co., Ltd.
Buczinski Stephen C.
Skjerven Morrill & MacPherson LLP
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