JPH0577243B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a tire sidewall unevenness inspection device, which detects excess or deficiency in the overlapping of the joints of tire cords constituting the carcass of a pneumatic automobile tire. It is used to detect minute irregularities that occur on the tire sidewall due to unevenness, and to determine pass/fail based on the degree of the irregularities.

(Prior art) As a device for detecting irregularities on tire sidewalls,
No. 122931 discloses that a capacitive sensor is provided close to the sidewall surface of a tire under internal pressure in a non-contact manner, and the tire is rotated around its axis of rotation to form a capacitive sensor. A detection signal corresponding to a change in the relative distance to the sidewall surface is transmitted, this detection signal is digitized by an A/D converter, and the detection signal is detected to have a rise change of more than a certain value or a constant value within a predetermined time. A device has been disclosed in which, when the above-mentioned falling change occurs, this is determined to be abnormal.

Furthermore, in Japanese Patent Application Laid-Open No. 58-200140, an optical non-contact displacement detector is provided in place of the capacitive sensor described above, and a voltage signal corresponding to the unevenness of the tire sidewall is transmitted, and this is digitized. By delaying the wavelength range corresponding to minute irregularities in the voltage signal by a preset short time and comparing the difference between the original signal and the delayed signal with a preset tolerance value, the tire A device has been disclosed in which the influence of long period irregularities on the side wall is eliminated and only short period irregularities are accurately detected.

(Problems to be solved by the invention) The device disclosed in Japanese Patent Application Laid-Open No. 122931/1983 is
Because it uses a capacitive sensor, if the concave component of a defect overlaps with the convex component of the letters placed on the tire sidewall, they are averaged out, and the problem is that the concave component is not detected as a defect. It was hot. Also, since the length of the time axis from the rise to the fall of a specific inclination angle is within a predetermined range, it is considered a defect, so for example, if the top of a convex part is flat and there is no need to make it a defect, However, there have been problems in that this may be determined as a defect, or a convex portion that is large enough to extend beyond the above-mentioned predetermined range or a simple step may not be considered a defect.

Furthermore, in the device disclosed in Japanese Patent Application Laid-open No. 58-200140, although the width (length of time axis) of the defective part is not necessarily constant, the delay time is always constant depending on the setting. There was a problem in that the difference between the defect and the noise became small, causing non-defects to be mistakenly determined to be defects. Additionally, when multiple protrusions or depressions exist, even if the individual protrusions or depressions are not very large, if they are concentrated to some extent, the appearance becomes poor, but conventionally, this is detected as a defect. I couldn't do it.

By using an optical displacement detector, this invention enables detection similar to human visual judgment, and even if the front and rear slopes are steep, it is possible to detect convex parts with flat tops and recesses with flat bottoms. In this method, this is not determined as a defect, but the height of the convex portion within a predetermined cut width, the depth of the interval, and the defect are used as elements for determining the defect.

(Means for solving the problem) In FIG. 1, 1 is a tire filled with air at a predetermined pressure. It is designed to rotate around. Above and below this tire 1, an optical displacement detector 2 is provided which projects a light beam onto the side wall of the tire 1, receives the reflected light, continuously detects the distance from the side wall, and converts it into a voltage strength. . An A/D converter 4 for digitizing the output signal of the optical displacement detector is connected to the output side of the optical displacement detectors 2, 2 via a switching means 3. A differential comparison circuit that differentiates the output signal on the output side of the circuit and divides the obtained differential coefficient into three parts: a part above the positive differential coefficient set value, a part below the negative differential coefficient set value, and a part in between. 5, and the time axis length of the intermediate portion sandwiched between the part above the positive differential coefficient setting value and the part below the negative differential coefficient setting value, that is, the turning width, is set to the preset turning width setting value. Convex portion identification circuit 6A for comparing and extracting convex portions and concave portions having the above-mentioned reversing widths equal to or less than the reversing width setting value.
and recess identification circuit 6B, calculates the time-axis coordinates of the respective peak portions of the convex portions and recesses whose turning width is less than the set value, and determines a predetermined judgment width set before and after the time-axis coordinates as the center. The gate setting circuit 7A for the convex portion has the width of the convex portion defined as the width of the convex portion from the start of the portion equal to or higher than the positive differential coefficient setting value to the end of the portion equal to or less than the negative differential coefficient set value within a range not exceeding , and the above judgment width a recess gate setting circuit 7B whose width is defined as the width of the recess from the start of the part below the negative differential coefficient setting value to the end of the part above the positive differential coefficient setting value within a range not exceeding , and the A/D conversion described above. The displacement signal within the above determination range is extracted from the output of the device 4, and the heights from both the front and rear ends of each of the convex portions and concave portions to the peak portion are averaged, and the heights of multiple convex portions or A convex part interval determination circuit 8A and a concave part interval determination circuit 8B, which determine a defective part when the interval in the time axis direction of the concave parts is within a limit value, are connected in this order.

(Function) Irregularities on the upper or lower surface of the tire 1 are detected as a difference in distance from the optical displacement detector 2, and this is sent to the A/D converter 4 as a voltage signal (see FIG. 3).
This digitized detection signal is input to the differential comparison path 5 and differentiated (see Figure 4), and its differential coefficient is a preset positive value. It is divided into three parts: a part above the differential coefficient set value, a part below the negative differential coefficient set value, and a part between these. for example,
Three values, +1, -1, and 0, are given to the negative part above the positive differential coefficient setting value, the part below the differential coefficient setting value, and the intermediate part, respectively, and the above differential output is ternarized. (See Figure 5).

The portion where the ternary signal outputted from the differential comparison circuit 5 changes from +1 to 0 to -1 indicates a convex portion, and the slopes on both sides of the convex portion have a predetermined inclination angle determined by the differential coefficient setting value. The part where the ternary signal changes from -1 to +1 through 0 indicates the opposite concave part. That is, among the many protrusions and recesses on the side wall of the tire 1, the protrusions and recesses whose slopes on both sides are particularly steep are extracted by the differential comparison path 5.

In the output signal of the differential comparison circuit 5, the intermediate portion where the portion changes from the portion above the positive differential coefficient setting value to the portion below the negative differential coefficient setting value is a 0-value portion of the ternary signal indicating a convex portion. The lengths of the time axis t ₁ and t ₂ of this 0-value portion are the width of the portion above the position where the inclination angle of the convex portion exceeds a predetermined limit (the length measured along the tire rotation direction). ), that is, it represents the turning width, and this turning portion is compared with the turning width setting value in the convex portion identification circuit 6A, and only those whose turning width is less than the setting value are taken out. In other words, in a convex part with steep slopes on both sides, the turning width is narrow, in other words, only the narrow and sharp convex part at the top is taken out, and even if the slopes on both sides are steep, the top is wide and flat. is excluded. Similarly, in the convex part identification circuit 6B, only the concave part with steep slopes on both sides of the concave part and a narrow turning width and a sharp bottom is extracted.

In the convex part gate setting circuit 7A, the time axis coordinate of the peak position of the convex part is determined from the convex part switching width of the output signal of the convex part identification circuit and the output signal of the A/D converter 4, and further A predetermined setting width (see M in Figure 6) is provided before and after the peak position, and the rising point from 0 to 1 and the rising point from -1 to 0 of the ternary signal is determined within a range that does not exceed this judgment width. Gate signals with an interval l on the time axis are output (see FIG. 7). In this case, in the output signal of the A/D converter 4,
Since the number of signals included within the above switching width setting value, that is, the number of samples, is extremely small,
Calculating the peak position by comparing the output signals (displacement signals) of the A/D converter 4 can be performed very easily and in a short time. Similarly, in the concave gate setting circuit 7B, the rising point of the ternary signal from 0 to -1 and the transition from 1 to 0 within a range that does not exceed the judgment width set before and after the time axis coordinate where the peak exists. A gate signal having an interval l on the time axis between the rising points of is output.

Next, the convex interval determination circuit 8A extracts the convex waveform within the determination width l (see FIG. 8), and calculates the height from the front end to the peak and the height from the rear end to the peak, respectively. The average value is determined, this average value is compared with a tolerance value, and furthermore, the distance between the convex portions exceeding the tolerance value is compared with a limit value to determine pass/fail. In the recess interval determination circuit 8B, the depth of the recess is similarly calculated by the average value before and after, this average value is compared with the tolerance value, and the interval between the recesses exceeding the tolerance value is compared with the limit value to determine pass/fail. It will be judged.

(Example) In FIG. 2, 2 is the above-mentioned optical displacement detector, 4 is an A/D converter, and the output of the optical displacement detector 2 for one rotation of the tire, that is, an example of the sensor output V is It is shown in FIG. In addition, in FIG. 3, the horizontal axis shows the sample number obtained by digitization, and "512" represents the first rotation of the tire.

The output of the A/D converter 4 is differentiated by a differentiation circuit 51 to output a differential coefficient shown in the graph of FIG. The image is ternarized as shown in the figure. For example, when there are convex portions and concave portions of 0.05 mm or more for a length of 3 mm in the rotational direction of the tire 1,
+1 and -1 respectively, 0.05mm (slope
0 is given to irregularities less than 0.05/3). The differential comparison circuit 5 of FIG. 1 is formed by the differential circuit 51 and the comparison circuit 52.

0 in the middle of changing from +1 to -1 in the above ternary signal
The signal is sent to the convex portion identification circuit 6A, and the length on the horizontal axis of the 0 signal, that is, the width of the turn t ₁ , t _{2 ,} etc., is compared with the width of the width set T 1 , t 2 , etc.
(10 mm in length, 3 samples) t ₂ is output. Similarly, the 0 signal in the middle of changing from -1 to +1 of the ternary signal is sent to the recess identification circuit 6B,
Those whose cutback width is less than the set value are output.

Both the output of the A/D converter 4 and the output of the protrusion identification circuit 6A are input to the convex portion peak detection circuit 71A, and the output of the A/D converter 4 included within the switching width _t1 is inputted to the convex portion peak detection circuit 71A. The maximum value, ie, the peak value, is calculated by comparison, and its abscissa (time axis coordinate), ie, the sample signal, is found. FIG. 6 is an enlarged view of a portion of FIG. 5, and the abscissa of the peak value is indicated by P. In addition, in FIG. 6, B indicates the width of the convex portion. Next, in the gate circuit 72A, equal widths (for example, 10
The gate signal 0 shown in FIG. 7 is created by setting a determination width M of 25 mm) and limiting the width exceeding the determination width M. Similarly, peak detection circuit 71A for convex portion
A gate signal is generated by the recess gate circuit 72B. Note that the peak detection circuit 71A and gate circuit 72A for convex portions constitute the gate setting circuit 7A in FIG. 1, and the peak detection circuit 71B and gate circuit 72B for concave portions constitute the gate setting circuit 7B in FIG. .

The convex part pickup circuit 81A synthesizes the displacement signal outputted by the A/D converter 4 (see FIG. 3) and the gate signal outputted by the convex part gate circuit 72A (see FIG. 7), for example, as shown in FIG. A convex waveform indicated by N is extracted. An enlarged view is shown in FIG.
Next, in the height calculation circuit 82A, the height a from the front end and the height b from the rear end of the convex waveform N are calculated.
The average value ((a+b))/2) is calculated. Then, in the first convex portion determination circuit 83A, it is compared with a first convex allowable value Ha (for example, 0.3 mm), and the interval in the time axis direction of two adjacent convex portions that exceed this first convex allowable value Ha is determined. In the interval determination circuit 84, the distance is sequentially compared with a distance limit value L (for example, 90 degrees), and if the distance is less than or equal to the distance limit value L, it is determined to be defective. Similarly, a recess that exceeds the first recess allowance Hb is extracted by the recess pickup circuit 81B, the recess height calculation circuit 82B, the first recess determination circuit 83B, and the first recess allowance Hb. The interval is compared with the limit value L in the interval determining circuit 84 described above.

On the other hand, the calculation of the average value by the height calculation circuit 82A is performed for one rotation of the tire 1, the average values of all the numbers are compared, and the maximum value is determined by the second convex portion determination circuit 85A. It is compared with a second convex allowable value Hc (for example, 0.5 mm) which is larger than the allowable value Ha, and if the maximum value exceeds the second convex allowable value Hc, it is determined to be a defect. Similarly, the maximum value of the recess is determined by the recess pickup circuit 81B, the recess height calculation circuit 82B, and the second recess determination circuit 85B, and is compared with the second recess allowable value Hd. In addition, the pick-up circuit 81 for the convex portion
A, the arithmetic circuit 82A, the first convex part determination circuit 83A, and the interval determination circuit 84 constitute the convex part interval determination circuit 8A in FIG. 1, and the concave part pickup circuit 81
B, the arithmetic circuit 82B, the first recess determination circuit 83B, and the interval determination circuit 84 constitute the recess interval determination circuit 8B in FIG.

In this embodiment, a step pickup circuit 91,
The comparison circuit 92, the height calculation circuit 93, and the level difference determination circuit 94 constitute the level difference identification circuit 9.
For example, the step signal shown in FIG. 9 is input from the A/D converter 4 to the step pickup circuit 91, while the differential signal shown in FIG. It is compared with the differential set value S (for example, the slope is 25/1000) and the first
As shown in FIG. 1, the differential coefficient part is binarized into a differential coefficient part greater than or equal to the step differential set value S and a part less than S, and this binarized signal is input to the above-mentioned pickup circuit 91.
The waveform is synthesized with the step signal shown in FIG. 9, and as shown in FIG. Calculated by the arithmetic circuit 93,
This height H is compared with a level difference allowable value H ₀ (for example, 0.8 mm) in a level difference determination circuit 94, and if it exceeds this, a level difference determination signal shown in FIG. 13 is output.

That is, in this embodiment, the second convex portion determination circuit 8
5A and a second recess determination circuit 85B, the presence of even one protrusion or recess with a height or depth exceeding the allowable value can be detected as a failure. Even if only one of the rising portion and the falling portion is present, if a portion with a gradient greater than or equal to the set value extends beyond the set height, this can be detected as a defective step.

(Effects of the Invention) Since the present invention uses an optical displacement detector, by narrowing the light beam and making the spot small, small-area irregularities can be individually captured and their sizes can be detected. In addition, if both a rising part and a falling part of a predetermined angle or more exist within a predetermined length of time axis (turning width), this is captured, so a convex part with a flat top and a concave part with a flat bottom It is possible to obtain a judgment similar to that obtained by visual inspection, without determining it as a defect.
In addition, since the peak is searched by comparing the magnitude of the A/D converter output signal (displacement signal) only for the portion where the differential coefficient is within the upper and lower limit values, the number of samples is small and the peak position can be easily searched. be able to.
Then, a determination width is set before and after this peak position as the center, and the height of the peak is calculated based on both the front and rear ends of the defect, which are determined within a range that does not exceed this determination width. This improves reproducibility and enables accurate determination.Moreover, it is determined as a defect when uneven parts of a predetermined size are closely spaced at a predetermined interval, so it is relatively easy to use. Even if there are slight irregularities, deterioration in appearance due to their concentration can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of this invention;
1 is a detailed block diagram of the main part of the apparatus shown in FIG. 1, and FIGS. 3 to 13 are graphs of output signals in the main part of the apparatus shown in FIG. 1: Tire, 2: Optical displacement detector, 4: A/
D converter, 5: differential comparison circuit, 6A: convex part identification circuit, 6B: concave part identification circuit, 7A: convex part gate setting circuit, 7B: concave part gate setting circuit, 8A: convex part interval determination circuit, 8B: Recess interval determination circuit.

Claims (1)

[Claims] 1. A tire rotation device that rotates a tire filled with air at a predetermined pressure at a constant speed around the center axis of the tire, and a device that projects a light beam onto the side wall of the tire and receives the reflected light to calculate the distance from the side wall. an optical displacement detector that continuously detects and converts the voltage into strength and weakness; an A/D converter that converts the output signal of the optical displacement detector into a digital signal at minute time intervals;
A differential comparison circuit that differentiates the output signal of the A/D converter and divides the differential coefficient into three parts: a part whose differential coefficient is greater than or equal to the positive differential coefficient setting value, a part which is less than the negative differential coefficient set value, and an intermediate part between these; The time axis length of the intermediate portion sandwiched between the part above the differential coefficient setting value and the part below the negative differential coefficient setting value, that is, the turning width, is compared with the turning width setting value set in advance to determine the turning width. The identification circuit extracts the convex portions and concave portions whose reversing width is less than the set value, and calculates the time axis coordinates of the peak portions of the convex portions and concave portions whose reversing width is less than the preset value, and calculates the time axis coordinates of the peak portions with this time axis coordinate as the center. A gate for a convex part whose width is from the start of the part above the positive differential coefficient set value to the end of the part below the negative differential coefficient set value within a range not exceeding the predetermined judgment width provided before and after the convex part. A setting circuit and a gate setting circuit for a concave portion whose width is defined as the width of the concave portion from the start of the portion below the negative differential coefficient setting value to the end of the portion above the positive differential coefficient setting value within a range not exceeding the above judgment width. , extract the displacement signal within the judgment range from the output of the A/D converter, average the heights from both front and rear ends of each of the convex portions and concave portions to the peak, and determine the number of cases where this average value exceeds the allowable value. An apparatus for inspecting irregularities on a tire sidewall, comprising a protrusion interval determination circuit and a recess interval determination circuit for determining a defect when the interval in the time axis direction of convexities or concave parts is within a limit value.