Optics: measuring and testing – Angle measuring or angular axial alignment – With screen
Reexamination Certificate
2000-06-26
2003-12-02
Adams, Russell (Department: 2851)
Optics: measuring and testing
Angle measuring or angular axial alignment
With screen
C356S004030, C356S139090, C356S141100, C356S152100, C033S203120, C033S203180, C033S203190, C033S288000, C358S003050, C700S279000, C702S113000, C280S086758
Reexamination Certificate
active
06657711
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an alignment measuring apparatus for an automotive vehicle wheel in which the inclination angles, including the toe-in angle and the camber, of a wheel mounted through the suspension of a vehicle are measured using a non-contact measuring technique by optical length measurement with the wheel rotating and stationary.
The inclination angles used for indicating the mounting position of the wheels of an automotive vehicle or the like include the inclination angle of the wheel or the tire surface with respect to the direction of progress of the vehicle (toe-in angle), the degree of inclination of the wheel or the tire surface with respect to the vertical plane (camber angle), and the caster. Accurate measurement and adjustment of the wheel alignment including all of these angles is an important factor for improving the driving characteristics.
In this specification, the “wheel” is defined to include the tire portion and the rim flange of the. wheel.
The toe-in angle is an angle indicating whether the tires are wider apart at the front or at the back as viewed from above the vehicle body and concerns both the front and rear wheels. If wheels are wider apart at the front, this is called toe-out, and if the wheels are wider apart at the rear, this is called toe-in.
The camber angle is an angle indicating whether the wheel is wider apart at the top or at the bottom as viewed from the direct front or rear of the vehicle, and represents the angle formed by the normal to the ground contact point of the tire and a straight line along the tire. When the tire is perpendicular to the ground, the camber is zero; when the tire is inclined inward, the camber is negative; and the tire inclined outward is positive in camber. The camber angle is measured for the purpose of facilitating the steering operation, reducing the vertical load and preventing the wheel from becoming wider apart at the bottom.
The caster, which is required for maintaining the straight-line stability, is defined as the angle between the vertical at the wheel center and the inclination of the king pin shaft as viewed directly sideways from the wheel. A positive caster is involved if the king pin shaft is inclined rearward, a negative caster is involved if the king pin shaft is inclined forward, and a zero caster is involved if the king pin shaft is in a vertical position.
2. Description of the Related Art
As a conventional alignment measuring apparatus, a direct contact measuring apparatus for measuring the angle by bringing the measuring unit into direct contact with the tire disclosed in Japanese Examined Patent Publication (KOKOKU) No. 62-121128 is known.
In recent years, as disclosed in Japanese Unexamined Patent Publication (KOKAI) No. 7-081853, a non-contact wheel alignment measuring apparatus, using optical length measurement, free of mechanical wear or degeneration which imposes no stress on the object of measurement has been realized in place of the wheel alignment measuring apparatus of contact type. The newly-developed apparatus uses a light beam based on trigonometry.
A method of measuring the wheel alignment statically by optical length measurement without using the light beam for trigonometry is the method disclosed in Japanese Examined Patent Publication (KOKOKU) No. 6-025661. In this method, a point corresponding to a reflected image of a slit light is determined by one camera, and the position of the corresponding point is calculated by another camera using the geometric restraints of the slit light. For this reason, a vast amount of calculations is required between the image data of the two cameras. Therefore, the application of this method to the dynamic in-line wheel alignment measurement requiring the high-speed determination of the inclination angle is very difficult, and practically limited to static wheel alignment measurement. In the measurement and adjustment of the wheel alignment of the vehicle with the wheels mounted, the wobbling of the wheel rim is a major cause of an error. Currently, therefore, the dynamic wheel alignment measurement is essential in which the wobbling of the wheels or the rim is corrected. With the method disclosed in Japanese Examined Patent Publication (KOKOKU) No. 6-025661, however, accurate dynamic wheel alignment measurement is difficult.
Among the apparatuses for non-contact measurement of the wheel alignment of a vehicle while rotating the wheels of the vehicle, the techniques disclosed in Japanese Examined Patent Publication (KOKOKU) No. 6-011420 and Japanese Unexamined Patent Publication (KOKAI) No. 9-329433 concern a method using a spot laser displacement meter based on triangulation. In the method disclosed in KOKOKU No. 6-011420, however, the distance measuring sensor is the spot laser displacement meter, and therefore, as the conditions. for accurate measurement, the tire side profile is required to be exactly symmetrically homogeneous diametrically about the wheel center around the whole wheel. Actually, however, the tire side section has a complicated shape, has an unevenness due to letters or the like and it is not symmetrically homogeneous. Further, unless a pair of distance measuring sensors and the swivel axes thereof are arranged equidistantly coaxially with the center of the wheel involved, the radiation point of the laser spot is deviated and constitutes a cause of a serious error. Taking into account the behavior of the vehicle while the wheels are rotating at the time of measuring the manufacturing variations of the wheel base of the vehicle, however, accurate positioning is very difficult and a high-accuracy wheel alignment measurement is impossible. In the method disclosed in KOKAI No. 9-329433, on the other hand, the distance measuring sensor is mechanically scanned, and therefore, the scanning mechanism is worn or unavoidably deteriorated on the one hand, and a considerable time is required for determining the number of measuring points required for correcting the wheel frame. The higher the measuring speed, the earlier the wear or deterioration occurs, leading to the disadvantages of a reduced accuracy and a higher maintenance cost.
Among the apparatuses for measuring the wheel alignment of the vehicle in non-contact fashion while rotating the wheels, the technique disclosed in KOKOKU No. 7-081853 is a method using a two-dimensional laser displacement meter based on triangulation. This method, in spite of its advantage of compensating for the disadvantage of the spot laser method described above, has the disadvantage that the laser projection width and pattern are fixed so that the portions requiring no measurement are also exposed to the light, and irregular reflection occurs for some objects of measurement due to the difference in the edge shape or the material. In these methods using the two-dimensional area photo detector, a screen (or field) is instantaneously exposed to light, and therefore, in the worst case, the irregular reflection may have an adverse effect even on the portions which would have otherwise been normally measured. Such adverse effect is very difficult to identify and remove, thus often resulting in a considerable measurement error or making the measurement impossible.
In the situation requiring a rotational angle of the wheel of at least 10° when measuring the steering angle or the caster by turning the steering wheel using the conventional method in which the angle detection mechanism is brought into contact with the tire side surface, it is difficult for the detection mechanism to track and detect the tire side uniformly following the wheel center. This causes a measurement error of the toe and the camber, thereby making it impossible to measure the steering angle and the caster with high accuracy. Even in the conventional non-contact measuring apparatus, the detection point defining the tire side is a specific spot on the tire side wall or a point nearest to the tire side wall from the detector, so that the steering angle cannot be mea
Kitagawa Hideo
Takagi Hiroshi
Adams Russell
Anzen Motor Car Co., Ltd.
Cruz Magda
Paul & Paul
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