Geometrical instruments – Gauge – Wheel
Reexamination Certificate
1998-12-03
2002-07-02
Gutierrez, Diego (Department: 2859)
Geometrical instruments
Gauge
Wheel
C033S203180, C356S139090
Reexamination Certificate
active
06412183
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wheel alignment measuring device and wheel alignment measuring method for measuring wheel alignment to three-dimensionally detect displacement and inclination of a wheel of a driven vehicle with a vehicle basic characteristics detecting device.
2. Related Art
A vehicle basic characteristics detecting device is known as a test device for measuring the basic characteristics of a vehicle, such as suspension characteristics or steering characteristics, in a test chamber.
In such a vehicle basic characteristics detecting device, the vehicle to be measured is fixed in a predetermined position, and rotational force, horizontal force, and vertical force are applied to the wheels. By processing the measurement data obtained from the reaction force, the basic characteristics can be detected.
As a part of the vehicle basic characteristics detecting device, there is a wheel alignment measuring device for measuring wheel alignment, such as spin angle, camber angle, and toe angle, based on the distance from a reference position to the side surface of the wheel.
A conventional wheel alignment measuring device is fixed onto a platform which supports the wheel and is driven by an actuator. Being connected to the wheel, it generally detects movement of the wheel. The problem with this type of mechanical wheel alignment measuring device is that measurements cannot be made at high speed because of a decrease in measuring accuracy caused by friction of the moving parts and restrictions due to the inertial mass of the components or the like.
First Embodiment of the Prior Art
To solve the problem, a non-contact type wheel alignment measuring device provided with a non-contact type distance sensors such as laser beam sensors and ultrasonic sensors.
More specifically, a conventional optical wheel alignment measuring device comprises a measuring unit provided with a plurality of optical sensors (laser displacement gauges, for instance). This measuring unit is disposed on the platform on the side of a wheel. The distance from a predetermined reference position to the measuring plate attached to the side surface of the wheel is optically measured by moving the measuring unit in the longitudinal direction of the vehicle. Based on the obtained measurement data, the camber angle and toe angle are determined.
In the optical wheel alignment measuring device of the first example, the measuring plate is attached to the wheel with a jig which is provided to the wheel beforehand. An adjuster of the attachment jig adjusts the center of the attachment jig to the center of the wheel. A fitting provided to the measuring plate for restricting the attachment position is then connected to the attachment jig by a magnet provided to the attachment jig.
With the wheel alignment measuring device of the first example, the position of the measuring plate needs to be adjusted by the adjuster of the attachment jig, which is time-consuming.
Due to the attachment jig, the distance from the center of the width of the wheel to the measuring surface of the target plate becomes longer, i.e., the radius of the rotational axis of the measuring surface becomes larger. So, if the wheel inclines at a large angle, or if the camber angle greatly varies during the measurement, the amount of movement of the measuring surface becomes large. This results in a problem that the area of the limited measuring surface cannot be effectively utilized.
Also, the laser displacement gauges of the first example of the prior art are driven in a two-dimensional stage based on the origin of the measuring plate, so that the laser displacement gauges follow the movement of the measuring plate, and that the laser beam is always emitted onto the measuring plate.
As a result, the structure of the device becomes complicated, and the manufacturing cost becomes high.
Also, the two-dimensional driving control operation for driving the laser displacement gauges becomes complicated, so does the adjustment operation of the laser displacement gauges for improving the measuring accuracy.
Second Embodiment of the Prior Art
In an optical wheel alignment measuring device of the second example of the prior art, three laser displacement gauges are employed for measuring the camber angle and toe angle. Two of the laser displacement gauges are a first laser displacement gauge and a second laser displacement gauge. The first laser displacement gauge irradiates measuring light onto a position at a first predetermined distance from the rotational center of the wheel in a first horizontal direction on the measuring plate. The second laser displacement gauge irradiates the measuring light onto a position at a second predetermined distance in the vertical direction. The remaining third laser displacement gauge irradiates the measuring light onto a position at a third predetermined distance from the rotational center in a second horizontal direction opposite from the first horizontal direction. The position irradiated by the third laser displacement gauge is situated on a line perpendicular to the vertical line extending through the rotational center.
In such a case, the camber angle is calculated from the displacement difference between the distance from the measuring plate measured by the first laser displacement gauge and the distance from the measuring plate measured by the second laser displacement gauge, and the distance LZ′ between the laser beam irradiation point of the first laser displacement gauge and the laser beam irradiation point of the second laser displacement gauge.
More specifically, the camber angle &thgr;CAM can be calculated by the following formula:
&thgr;CAM=tan
−1
(|
L
1
−
L
2
|)/
LZ′
where the distance from the measuring plate measured by the first laser displacement gauge is L
1
, and the distance from the measuring plate measured by the second laser displacement gauge is L
2
.
The toe angle is calculated from the displacement difference between the distance from the measuring plate measured by the third laser displacement gauge and the distance from the measuring plate measured by the first (or second) laser displacement gauge, and the distance LX between the laser beam irradiation point of the third laser displacement gauge and a line in parallel with the Z-direction (vertical direction) including the laser beam irradiation point on a plane containing the laser beam irradiation point of the first (or second) laser displacement gauge.
More specifically, the camber angle &thgr;CAM can be calculated by the following formula:
&thgr;CAM=tan
−1
(|
L
3
−
L
1
|)/
LX
where the distance from the measuring plate measured by the third laser displacement gauge is L
3
, and the distance from the measuring plate measured by the first laser displacement gauge is L
1
.
In this case, even if the amount of movement in the Z direction is large, the distance LZ′ between the first laser displacement gauge and the second laser displacement gauge cannot be made long.
This is because the laser beam emitted from all the laser displacement gauges is required to irradiate the measuring plate in the camber angle and toe angle measurement, in both cases where the measuring plate is situated in the highest possible position in the Z direction and where the measuring plate is situated in the lowest possible position in the Z direction.
In other words, the laser beam irradiation points of all the laser displacement gauges should exist within an area surrounded by the highest possible position and the lowest possible position that the measuring light from the laser displacement gauges can be emitted onto the measuring plate.
As a result, the measuring accuracy of the camber angle &thgr;CAM cannot be ensured.
On the other hand, if the measuring accuracy of the camber angle &thgr;CAM is increased, the distance LZ′ between the laser beam irradiation point of the first laser displacement gauge and the laser beam irrad
Baker & Daniels
Gutierrez Diego
Kabushiki Kaisha Saginomiya Seisakusho
Smith R Alexander
LandOfFree
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