JP2790752B2 - Inspection method of cam assembly - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cam assembly in which the actual assembling accuracy of a cam with respect to a cam shaft of the cam assembly can be accurately determined by numerically processing data obtained optically. The inspection method.

[0002]

2. Description of the Related Art A cam assembly such as an engine assembly camshaft used for a vehicle-mounted engine is assembled by inserting and fixing a separate cam to a camshaft. The assembly accuracy becomes a problem.
However, with such a cam assembly, it is necessary to inspect the actual cam assembly accuracy for each individual product, and to examine the shape of the cam peripheral surface, especially the shape of the cam surface of the cam lobe, which is the life of the cam assembly, the conventional cam shaft rotation The relationship between the angle and the distance from the shaft center to the cam surface was actually measured using a contact, and the camshaft rotation angle giving the maximum lift was determined based on the result of the measurement.

More specifically, as shown in FIG. 4, first, both ends of a cam shaft 2 of a cam assembly 1 are appropriately supported,
The camshaft 2 and the cam 3 can be integrally rotated only around the axis. Next, the roller 4a of the contact 4 with a roller is pressed against the cam surface 3a in a state where it can be displaced only in the vertical direction, and the cam shaft 2 is slowly rotated. Then, the relationship between the camshaft rotation angle θ and the displacement amount of the contact 4, that is, the lift amount L is sequentially measured using data, and the measured data is displayed as a list on a single item basis or as a graph on a two-dimensional coordinate plane. Finally, based on the list or the graph, the inspector himself determines whether or not the camshaft rotation angle θo giving the maximum lift is within a specified allowable error range. The three-dimensional object was determined to be defective.

[0004]

The above-described conventional method for inspecting a cam assembly requires a minimum necessary for data collection until the camshaft 2 is slowly rotated with the contact 4 pressed. It can be called work. However, the work of measuring the relationship between the camshaft rotation angle θ and the lift amount L one by one for each data, and displaying the measured data in a list for each item or displaying the graph on a two-dimensional coordinate plane is all performed by the inspector himself. Despite having to be done manually and the quality of the work being able to influence the pass / fail decision itself, only experience has relied on it. Normally, the camshaft 2 needs to be rotated with a smaller angle as it approaches the maximum point of the lift amount. Even if the displacement amount of the contact 4 can be read with the rotation angle fixed, the maximum displacement of the contact 4 is given. Stopping the camshaft 2 at the camshaft rotation angle θo is an extremely difficult technique, and in practice, usually only data of rotation angles before and after the desired camshaft rotation angle θo can be obtained. Therefore,
It is often not possible to accurately determine the camshaft rotation angle θo that gives the maximum value of the lift amount L just by looking at the measurement results in a list. The work of connecting the discrete plots with a curve must take the skill of the inspector. Therefore, there is a problem that individual differences cannot be avoided even in the pass / fail judgment based on the maximum point read from the graph. In addition, it is a fact that it takes a considerable amount of time to inspect the cam assembly 1 alone, whether using a list or a graph, and even if various measures are taken to improve the work efficiency, the judgment is made. In order to maintain the accuracy, the time taken for data processing cannot be reduced inevitably, and the conventional inspection method has a problem that the working efficiency is essentially low.

The present invention has been made in view of these points, and a cam assembly in which a separate cam is assembled to a cam shaft is mechanically inspected regardless of the experience of an inspector. The purpose is to automatically determine whether the cam assembly accuracy is acceptable or not.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to a cam assembly in which a separate cam is assembled to a camshaft to project parallel light that vertically traverses the cam surface of the cam. Then, the relationship between the projection length from the axis to the cam surface and the camshaft rotation angle is measured by rotating the camshaft around the axis, a curve approximating the relationship is obtained from the measurement result, and the obtained approximate curve is obtained. The camshaft rotation angle that gives the maximum projection length is calculated, and the accuracy of the cam assembly of the cam assembly is determined based on the calculation result.

[0007]

The above inspection method projects parallel light that traverses the cam surface onto the cam assembly, and measures the relationship between the projection length from the axis to the cam surface and the cam shaft rotation angle while rotating the cam shaft around the axis. Then, the cam shaft rotation angle that gives the maximum projection length is calculated from a curve approximating the relationship obtained from the measurement result, and the cam assembly accuracy of the cam assembly is determined based on the calculation result. Automatically determine cam assembly failure.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic perspective view showing an embodiment of a cam inspection apparatus to which the inspection method of a cam assembly according to the present invention is applied, and FIG. 2 is a flowchart for explaining the operation of the function processing determiner shown in FIG. FIG. 3 is a diagram showing an example of an approximate curve that approximates the relationship between the projection length from the axis to the cam surface and the camshaft rotation angle.

A cam inspection apparatus 11 shown in FIG. 1 comprises a rotation driver 12 for holding a cam assembly 1 to be inspected and rotating it around an axis, and a cam 3 of the cam assembly 1 using laser light.
And a function processing determiner 14 that determines the cam rotation angle θo that gives the maximum lift amount from the measurement result of the laser outer shape measuring device 13 and determines whether or not the cam rotation angle is acceptable according to the regulations. The rotation drive unit 12 supports the cam shaft 2 of the cam assembly 1 to be inspected in a cantilever manner or both ends, and functions to rotate the cam shaft 2 around the axis accurately without eccentricity. The camshaft rotation angle θ is externally output as an electric signal.

The laser contour measuring device 13 comprises a laser light generator 15 and a laser light receiver 16 which are opposed to each other with a space for measuring the contour being interposed therebetween.
Is equipped with a semiconductor laser, an octahedral polygon mirror, a reflecting mirror, a collimator laser, etc., and after reflecting the laser light emitted by the semiconductor laser with an octahedral polygon mirror and a reflecting mirror, the laser light is converted into a parallel laser beam through a collimator lens. A light-receiving lens (not shown) is provided in front of a laser light receiver 16 that emits light and is arranged to face the laser light generator 15, and a parallel laser beam is emitted by the light-receiving lens into the laser light receiver 16. The light-emitting elements 15a and the light-receiving elements 16a are arranged in a vertical line. At the time of inspection, the cam assembly 1 is connected to the laser light generator 15 so that a parallel laser beam that traverses the cam surface 3a of the cam 3 is projected.
The laser light receiver 16 and the laser light receiver 16 are arranged so as to be orthogonal to the optical path surface of the laser light.

The function processing determining unit 14 is a laser light receiving device 1
A buffer memory 17 for storing the lift amount L output by the motor 6 and the camshaft rotation angle θ output by the rotary driver 12 as a pair of measurement data; measurement data (θ ₁ , L ₁ ) stored in the buffer memory 17; (Θ ₂ , L ₂ ),. . . A curve approximating the relationship between the lift amount L and the camshaft rotation angle θ is obtained from
It has an arithmetic processing unit 18 that calculates the camshaft rotation angle θo that gives the maximum lift amount from the obtained approximate curve, and determines whether or not the cam assembly 1 is acceptable based on the calculation result. Here, a quadratic curve whose coefficient a and constants θo and Lo are unknown is used as the approximate curve. Measurement data is plotted on a two-dimensional coordinate plane with the rotation angle θ of the camshaft 2 as the horizontal axis and the projection length L as the vertical axis. In order to approximate the plotted point with a minimum error, the unknown coefficient a and the constants θo and Lo are determined using the least squares method.

At the time of measurement, first, the cam assembly 1 is connected to the laser light generator 15 and the laser light
Is attached to the rotary driver 12 so as to be orthogonal to the optical path surface of the laser light connecting the two. Next, the rotation driver 12 is operated in a state where the laser light is generated. As a result, the cam assembly 1 slowly rotates in the optical path plane of the laser light in accordance with the rotation of the cam shaft 2. When the cam assembly 1 rotates,
A signal indicating the rotation angle θ of the camshaft 2 is supplied from the rotation driver 12 to the function processing determination unit 14.

The function processing determiner 14 calculates the rotation angle θ sent from the rotary driver 12 and the lift amount L sent from the laser beam receiver 16 as shown in step (101) of FIG. (Θ ₁ , L ₁ ), (θ
₂ , L ₂ ),. . Is stored in the buffer memory 17 as shown in FIG. Then, when the camshaft 2 has completed one rotation, as shown in the following step (102), the buffer memory 17
N measurement data (θ ₁ , L ₁ ) to (θ _n ,
A function approximation by the least squares method is executed based on the range of Lo to Lo−ΔL in L _n ).

Here, as described above, the curve used for function approximation is a quadratic curve having three unknowns a, θo, and Lo.

[Number 1] are established the L = -a (θ-θo) 2 + Lo as empirical formula.

In the least square method, the unknowns a, θo, and Lo are determined as values that minimize the sum of the square errors.
8 is built in. However, in order to increase the approximation accuracy of the hyperbolic approximation near the local maximum point, the camshaft rotation angle θ used for the approximation may be limited to data within the fixed range θo ± Δθ shown in FIG. In this case, an empirical value is used for Δθ, but a design data value may be used for θo.

When the hyperbolic function waveform is determined by the least square method approximation, the maximum point that gives dL / dθ = 0 is obtained. However, here, since a quadratic curve is formulated as an empirical formula, θ = θo is simply the camshaft rotation angle to be obtained. Therefore, the camshaft rotation angle θo giving the maximum lift amount is calculated in the step (102). Then, in order to compare the specified camshaft rotation angle θs and the camshaft rotation angle θo specified in the design stage for the cam assembly 1, in step (103), the difference θo−θ
Calculate s. And further, the following step (104)
It is determined whether or not the absolute value of the difference θo−θs is equal to or smaller than a predetermined allowable tolerance ε.

If | θo−θs | <ε, a pass determination is made for the cam assembly 1 in step (105). However, if not, step (10)
In 6), rejection is determined as a defective product.

In general, the projection length of the cam 3 in which the cam surface 3a changes continuously changes smoothly before and after the maximum point, so that when determining the coefficient a of the approximate curve and the constants θo and Lo, the approximate curve It is not necessary to plot all points on the top, and the camshaft rotation angle θo giving the maximum lift can be calculated sufficiently accurately from the maximum point obtained from the approximate curve determined based on several discrete data. . Therefore, unlike the conventional method of finding the maximum point based on the experience of the inspector from the measurement data indicating the relationship between the camshaft rotation angle θ and the lift amount L, the inspection including the pass / fail judgment is consistently and reliably performed. Is possible.

Also, Since the cam inspection device 11 approximates the measurement data indicating the relationship between the lift amount L and the camshaft rotation angle θ with an unknown curve prepared in advance and determines an approximate curve by the least squares method, The coordinates themselves indicating the intersection of the asymptote are included in the function formula of the curve as the camshaft rotation angle θo that gives the maximum lift amount, and therefore, without having to take the procedure of finding the maximum value of the obtained approximate curve by differential operation or the like. , It is possible to immediately start the pass / fail judgment.

The approximate curve is not limited to a quadratic curve, and may be a part of an ellipse or a cubic or higher function curve as long as it is an upwardly convex curve having the maximum lift as a maximum value. It may be arbitrarily determined in consideration of projection data expected with reference to the design data of the cam 3.

[0021]

As described above, according to the present invention,
Projecting parallel light that traverses the cam surface to the cam assembly, measuring the relationship between the projection length from the axis center to the cam surface and the cam shaft rotation angle while rotating the cam shaft around the axis, and calculating the relationship from the measurement result. The cam shaft rotation angle that gives the maximum projection length is calculated from the curve approximating the relationship, and the cam assembly accuracy of the cam assembly is determined based on the calculation result. If attention is paid to the point where the projection length also changes smoothly before and after the maximum point, only a few points of discrete data are required to determine the coefficients and constants of the approximate curve, and the maximum calculated from the determined approximate curve is sufficient. From this point, it is possible to accurately determine the camshaft rotation angle that gives the maximum lift. Even if the actual maximum point is buried in the middle of the data of the two points, the maximum point can be calculated accurately within the range of the accuracy of the approximated curve, thereby making a decision based on the experience of the inspector. The present invention has excellent effects such as significantly shortening the inspection time of the cam assembly alone, which can improve the inspection efficiency.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing an embodiment of a cam inspection apparatus to which a cam assembly inspection method according to the present invention is applied.

FIG. 2 is a flowchart for explaining the operation of the function processing determiner shown in FIG. 1;

FIG. 3 is a diagram illustrating an example of an approximate curve that approximates a relationship between a projection length from a shaft center to a cam surface and a cam shaft rotation angle.

FIG. 4 is a view for explaining a conventional cam assembly inspection method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 cam assembly 2 cam shaft 3 cam 3 a cam surface 11 cam inspection device 12 rotation driver 14 function processing judgment unit

Continued on the front page (56) References JP-A-56-103304 (JP, A) JP-A-4-132906 (JP, A) JP-A-61-139409 (JP, U) (58) Fields investigated (Int) .Cl. ⁶ , DB name) G01B 11/00-11/30 F16H 51/00-55/30

Claims (2)

(57) [Claims] 1. A cam assembly in which a separate cam is assembled to a camshaft. A parallel light projecting parallel to a cam surface of the cam is projected, and the camshaft is rotated around the axis to move the camshaft from the shaft center. Measure the relationship between the projection length to the cam surface and the camshaft rotation angle, determine a curve that approximates the relationship from the measurement results, calculate the camshaft rotation angle that gives the maximum projection length from the obtained approximate curve, A method for inspecting a cam assembly, comprising determining whether or not the cam assembly accuracy of the cam assembly is acceptable based on the calculation result. 2. The approximate curve is obtained by approximating a measurement result indicating a relationship between a projection length from the axis center to a cam surface and a rotation angle of a cam shaft by an empirical formula whose coefficients and constants are determined in advance. 2. The method for inspecting a cam assembly according to claim 1, wherein the coefficient and the constant are determined by the least square method.