JPH0141921B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring wheel alignment.

The front wheel H of the bicycle has a toe-in angle θ 1, which indicates how much the front wheel is inclined inward when viewed from above, as shown in Fig. 1, and a toe-in angle θ ₁ , which indicates how much the front wheel is inclined inward when viewed from above, as shown in Fig. The king pin K of this wheel H has a camber angle θ ₂ that indicates how far the upper side is inclined outward, and the king pin K of this wheel H has a king pin angle θ ₃ that indicates how much this king pin K is inclined inward. and, as shown in FIG. 3, there is a caster angle θ ₄ that indicates how far forward the kingpin K is inclined when viewed from the side.

Conventionally, the method of measuring wheel alignment specifications such as the above-mentioned toe-in angle θ ₁ , camber angle θ ₂ , kingpin angle θ ₃ and caster angle θ ₄ is to measure each angle by bringing a spirit level into contact with the wheel. However, this method was difficult as it required determining the center of the wheel prior to measurement. There are also measurement methods such as the roller method, but this is also a contact method, and the amount of wheel fluctuation is large for measurements such as kingpin angle θ ₃ and caster angle θ ₄ , which cannot be determined unless the steering wheel is turned. This makes it particularly unsuitable.

The present invention was made in view of these points,
Wheel alignment specifications using laser light,
In particular, the kingpin angle and caster angle, which have been difficult to measure in the past, can be easily measured.

An embodiment of the present invention will be described based on FIG. 4.

An X-direction guide 2 is fixed to the base 1, and an X-direction drive screw 3 is rotatably provided, and the
The X-direction movable base 4 is fitted into the direction guide 2 so as to be movable back and forth, and the X-direction movable base 4 is screwed onto the X-direction drive screw 3, and further fixed onto the base 1 by the X-direction drive screw 3. Connect the X-direction drive motor 5. In addition, along the moving direction of the X-direction moving base 4, an
A directional position detecting device 6 is provided, and a slider 7 of the X-direction position detecting device 6 is connected to the X-direction moving base 4.

Further, a Y-direction guide 8 is vertically fixed to the X-direction movable base 4, and this Y-direction guide 8 is
A Y-direction drive screw 11 is rotatably provided between the mounting plate 9 at the upper end and the X-direction movable base 4, and
The laser optical bench 12 is fitted into the direction guide 8 so as to move forward and backward, and the laser optical bench 12 is screwed onto the Y-direction drive screw 11, and further fixed onto the mounting plate 9 at the upper end of the Y-direction drive screw 11. Connect the Y-direction drive motor 13. Further, a Y-direction position detecting device 14 such as a direct-acting potentiometer is provided vertically along the moving direction of the laser optical bench 12, and a slider 15 of the Y-direction position detecting device 14 is attached to the laser optical bench 12. Connecting.

Further, the laser optical bench 12 is provided with a laser optical system consisting of a laser light projecting section 16 and a light receiving section 17. The light projecting section 16 generates laser light using helium neon gas or the like, and the light receiving section consists of a lens system 18 and a screen 10 made up of a large number of microscopic light receiving element groups such as photodiode arrays. be. Then, the laser beam is irradiated onto the object surface and reflected diffusely, and a part of the diffusely reflected light, that is, the scattered light that is emitted from one point in the shape of a solid angle to the lens aperture with the same density, is passed through the lens system 18, The light is focused on a screen 19, such as a photodiode array placed at the imaging position of the lens system 18, which can measure changes in the imaging position, and changes in the depth of the object plane are measured through fluctuations in the optical axis that constitutes the solid angle. The image is extracted as a change in the imaging position on the screen 19.

The measurement principle of the laser optical system will be explained in more detail with reference to FIGS. 5 and 6.

Diffusely reflected light can be thought of as light rays emitted from a point light source P ₀ on the object surface at the same density at all angles. First, if we take a solid angle up to the lens aperture consisting of a point light source P ₀ , the diffusely reflected light beam within that solid angle will not intersect and will form an image point on the rear screen 19 as shown in Figure 6a. Tie. Next, the object moves and becomes a point light source of diffusely reflected light.
Due to the movement of P ₀ (due to a change in depth), the above-mentioned solid angle changes somewhat, and the optical axis also changes somewhat.
Therefore, the imaging point moves as shown in Fig. 6b, and by performing differential processing on its output, the amount of movement l ₀ can be clearly detected as shown in Fig. 7, and the change in the depth of the object can be detected. Recognize. Note that the photodiode array forming the screen 19 is generally 15 μm thick.
There are some that have a resolution of about 25 mm and an imaging surface of about 25 mm. Therefore, it is necessary to set the reference position of the screen 19 before starting the work. In addition, since the image forming surface of the screen 19 is limited in this way, by replacing or shifting the lens system 18, changes in the depth of various object planes can be adjusted appropriately within the range of the screen 19. make it possible to capture

Next, a method of measuring wheel alignment using the above laser beam will be explained. Note that the wheel H, which is the object to be measured, is placed on the turntable 21 while being attached to the vehicle body.

First, based on FIG. 8, the toe-in angle θ ₁ of the wheel H
seek. The laser optical bench 12 is set toward the knuckle spindle S, fixed in the Y direction, and scanning with laser light is performed while moving the X direction movable base 4 back and forth by the X direction drive screw 3. That is, the X-direction position detection device 6 intermittently detects the moving positions of the light projecting section 16 and the light receiving section 17, and at each of the moving positions, a laser beam is emitted from the light projecting section 16 toward the side surface of the wheel H. A part of the diffusely reflected light from the wheel H is sent to the lens system 18 of the light receiving section 17.
The image is formed on the screen 19 made up of the large number of tiny light-receiving element groups through the screen 19, and the change in depth in the depth direction of the side surface of the wheel H when, for example, the Knuckle spindle S is used as a reference point is imaged on the screen 19. Detection is based on changes in position. By storing changes in depth at each moving position in the X direction in a computer, a locus _L1 of irregularities in the longitudinal direction at approximately the center height of the side surface of the wheel H can be obtained as shown in FIG. So, for example, this trajectory
It is possible to determine how much the straight line l ₁ connecting the vertices of the two bulges of L ₁ is inclined with respect to the base line l _x in the front-rear direction (X direction), and the toe-in angle θ ₁ can be determined.

Further, the laser optical bench 12 is set toward the nutacle spindle S, the X-direction movable base 4 is fixed, and the laser optical bench 12 is moved vertically by the Y-direction drive screw 11 to emit laser light. If scanning is performed, the locus of unevenness in the vertical direction at approximately the center position of the side surface of the wheel H can be obtained in the same manner as in determining the toe-in angle θ ₁ above.
L ₂ is obtained as shown in Figure 9. For example, how much does the straight line l ₂ connecting the vertices of the two bulges of this locus L ₂ incline with respect to the base line l _y in the vertical direction (Y direction)? camber angle θ ₂ can be found.

Note that in the above embodiment, the toe-in angle θ ₁ or the camber angle θ ₂ is determined after scanning in the X direction or the Y direction to obtain the locus L ₁ or the locus L ₂ . For example, if the wheels H are set at a constant location and direction relative to the base 1 of the laser optical bench 12, the laser optical bench 12 can be moved in the X and Y directions without performing countless irradiations. At least 3 points on the wheel H determined in advance for each diameter
Simply irradiate laser light to the positions P ₁ , P ₂ , and P ₃ and measure the change in depth at these three points P ₁ , P ₂ , and P ₃ .
The inclination state of the wheel H in the X direction and the Y direction is known, and the toe-in angle θ ₁ and the camber angle θ ₂ can be determined.

Next, the case where the caster angle θ ₄ and the kingpin angle θ ₃ of the kingpin K are determined are shown in FIGS. 10 and 11.
The diagram will be explained.

As shown in Fig. 10a, for example, tighten the steering wheel to the right and turn the wheel to the right by an angle θ ₅ , and then set the toe-in angle to the side of the wheel H as shown in Figs. 10b and c. In the same way as when determining θ ₁ and camber angle θ ₂ , laser scanning is performed in the X and Y directions to determine the trajectory L ₄ in the X direction and the trajectory L ₃ in the Y direction of the side surface of the wheel H ₁ . Coordinates of at least three points of the vertices of the bulges of the trajectories L ₃ and L ₄ P ₄ (X ₁ , Y ₁ , Z ₁ ), P ₅ (X ₁ , Y ₂ , Z ₂ ), P ₆
(X ₃ , Y ₃ , Z ₃ ) and the equation m of the plane F ₁ including these three points P ₄ , P ₅ , P ₆ seek. Next, as shown in Fig. 11a, tighten the handle to the left and rotate the wheel to the left by an angle -θ ₅ about the king pin K, and as shown in Fig. 11b and c, this wheel _H2 In the same way as when determining the toe-in angle θ ₁ and camber angle θ ₂ for the side surface again, laser scanning is performed in the X direction and Y direction, and the trajectory L ₆ of the side surface of the wheel H ₂ in the X direction after this rotation is calculated. and a trajectory L ₅ in the Y direction, and calculate the coordinates P _{4 ′} (X _{1 ′} , Y ₁ ′, Z ₁ ′), P ₅ ′ ( X ₁ ′, Y ₂ ′, Z ₂
′),
Find P ₆ ′ (X ₃ ′, Y ₃ ′, Z ₃ ′), and use these three points P ₄ ′, P ₅ ′
,
Equation n of plane F ₂ containing P ₆ ′ seek.

Then, from the planes F ₁ and F ₂ before and after the rotation about the king pin K, the inclination state of the king pin K can be determined conversely, so the equation m of the planes F ₁ and F ₂ ,
By calculating n, the caster angle θ ₄ of the kingpin K is obtained.
and find the kingpin angle θ ₃ .

Further, in the above embodiment, the base 1 of the laser optical bench 12 and the turntable 21 were provided independently, but the base and the turntable 21 are directly connected to rotate the wheel H and the laser optical system integrally. You may also do so. In this way, the laser optical system can be downsized in measuring the caster angle θ ₄ and the kingpin angle θ ₃ .

The reason for this will be explained with reference to FIG. 12. First, for ease of explanation, each of the toe-in angle θ ₁ , camber angle θ ₂ and caster angle θ ₄ is set to 0 as shown in FIG. Consider a model with Then, the wheel H shown in FIG. 12a has an inclination angle θ ₆ =
If the handle is rotated around the king pin K by an angle θ ₅ =180° based on the handlebar angle from its normal position of 90°, the inclination angle θ ₆ will be 90° + 2θ ₃ . The inclination angle θ ₆ of the wheel that changes with the above angle θ ₅ is θ ₆ ≒90° + (1-
cos θ ₅ ) increases inward at θ ₃ and reaches a maximum at θ ₅ =180° as described above. Note that from the above equation, the king pin θ ₃ is determined by the angle θ ₅ and the inclination angle θ ₆ . Furthermore, since the contact point P ₇ does not change within a small change in the angle θ ₅ due to its structure, as shown in FIG.
The variable detected by the laser optical system A, which rotates integrally with the turntable 21 rotated by the contact force at point _P7 , is mainly due to the change in the above-mentioned inclination angle _θ6 . In other words, the cause of the wheel H falling is a large factor. On the other hand, when the laser optical system A is installed at a fixed position, the above-mentioned inclination angle θ ₆
In addition to the variable due to the change in the rotation of the turntable 21, extra measurement capability (for example, increasing the size of the screen 19 as the change in depth becomes longer) is required for the variable ΔT = T ₁ - _T 2 due to the rotation of the turntable 21. .
Therefore, the turntable 21 that rotates the wheel H
It is advantageous for downsizing the laser optical system to directly connect the base 1 of the laser optical system to the wheel and rotate the wheel and the laser optical system integrally.

According to the present invention, a wheel is rotated around a kingpin, the inclination state of the wheel is determined using a laser beam before and after this rotation, and the caster angle and the kingpin angle are determined from the inclination state of the wheel before and after this rotation. Therefore, the caster angle and kingpin angle can be easily measured without contact.

[Brief explanation of drawings]

Fig. 1 is a plan view to explain the toe-in angle, Fig. 2 is a front view to explain the camber angle and kingpin angle, Fig. 3 is a side view to explain the caster angle, and Fig. 4 is a side view to explain the caster angle.
The figure is a perspective view showing an embodiment of the wheel alignment measuring method of the present invention, FIG. 5 is an explanatory diagram of the measurement principle of the laser optical system, FIG. 6 is an explanatory diagram of the light reception state on the screen, and FIG. 7 is an explanatory diagram of the measurement principle of the laser optical system. Figure 8 is an explanatory diagram for determining the toe-in angle, Figure 9 is an explanatory diagram for determining the camber angle, and Figures 10 and 11 are graphs for determining the camber angle and kingpin angle. The explanatory diagram, FIG. 12, is an explanatory diagram for explaining the advantage of integrally rotating the wheel and the laser optical system. H...Wheel, K...King pin, _θ3 ...Kingpin angle, _θ4 ...Cast angle, 16...Light emitting part of the laser optical system, 17...Light receiving part of the laser optical system.

Claims (1)

[Claims] 1. A wheel is rotated around a kingpin, and before and after this rotation, a laser beam is irradiated onto the side surface of the wheel, and changes in the depth of the side surface of the wheel are detected by the reflected light of this laser beam. The measuring laser optical system is moved relative to the side of the wheel, detects changes in the depth of the side of the wheel, determines the state of inclination of the wheel from this change in depth, and calculates the state of inclination of the wheel before and after this rotation. A wheel alignment measuring method characterized in that the caster angle and kingpin angle of the kingpin are determined. 2. The wheel according to claim 1, characterized in that the base of the laser optical system is directly connected to a turntable that rotates the wheel, so that the wheel and the laser optical system rotate integrally. Alignment measurement method.