JPH06147835A - Tire tread length measuring method - Google Patents

Abstract

PURPOSE:To provide a method for measuring any tread length of tire accurately and automatically regardless of the profile of tread upper face. CONSTITUTION:The tire tread length measuring system comprises a plurality of light reflective sensors(hereinafter referred to edge sensor) 2 arranged at a constant interval at a lower part of a roller conveyor 1 between rollers 1a, an image sensor 3 and a phototube 4 arranged on the upstream side of the edge sensor 2. The edge sensors 2 are fixed to a conveyor frame 5 in the direction intersecting a tread W perpendicularly. In a preferred embodiment, a first edge sensor 2 is arranged at a position spaced apart by 1600mm from the center of view O and total ten edge sensors 2 are arranged at an interval of 100mm in the tread carrying direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire tread length measuring method, and more particularly to a measuring method capable of accurately measuring the tire tread length without being influenced by the upper surface profile of the tire tread. It is a thing.

[0002]

2. Description of the Related Art Conventionally, a method of measuring a tire tread length is, for example, by irradiating a laser beam at a right angle to the flow direction of the tread and counting the tread advance with a pulse while the laser beam is shielded. Measure the tire tread by detecting the front end of the tread by irradiating laser light diagonally above the front end of the tread, detecting the rear end of the tread with an image sensor, and converting the distance detected by both. It is known how to do it.

However, the tread extruded by the extruder has various profiles depending on the lot, and the lower surface has a flat shape. That is, the pushed tread W is cut at an inclination angle of a dozen degrees with respect to the lower surface of the tread W because the front and rear end surfaces W1 and W2 of the tread W are joined to each other later as shown in FIG. There is. When the tread W is viewed from above, the upper end of the tread W has a wavy shape due to the influence of the profile, and the lower end is flat.

[0004]

SUMMARY OF THE INVENTION Therefore, the tread W
When attempting to measure the total length L of the profile, if the measurement is performed at the projecting portion t of the profile, a measurement error occurs, and an accurate tread length cannot be measured. Therefore, in the latter case of the related art, there is a problem in that the flapping of the tip of the tread causes flapping in the front end detection, which affects the measured value.

Further, there is a problem in that the length conversion error per pulse accumulates and an accurate measured value cannot be obtained, and an image sensor with a wider field of view is required, and the reading speed is limited. It was In addition, in detecting the position of an object using an image sensor, it is known that the more the image is deviated from the center of the visual field, the more blurred the image on the image sensor is, and the lower the accuracy of detecting the position of the object becomes.

The present invention has been devised in view of such conventional problems, and tire tread length for accurately and automatically measuring the tread length without being affected by the profile of the tread upper surface. It is intended to provide a measuring method of. Another object of the present invention is to provide a tire tread length measuring method capable of accurately measuring tread lengths of any length.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention, when the tip of a tread cut into a certain length and conveyed by a conveyer shields the photocell,
When the signal input of the first light reflection type sensor is gated through the microcomputer and then the tread advances and the first light reflection type sensor detects the bottom surface of the tread, the signal is sent to the microcomputer. Enter, count the number of bits in the dark part of the image of the image sensor that detects the rear end of the tread at that time, and determine whether all bits are dark.If the tread shields the entire field of view of the image sensor, the microcomputer Thus, the gate is sequentially switched to the signal input of the second and subsequent light reflection type sensors, and after all the bits of the image sensor are not dark, a plurality of (n) tread rear end portions are made by the image sensor until the entire visual field becomes bright. ) Times, and of the detected values, the bit number of the image sensor of the light reflection type sensor closest to the center of the visual field of the image sensor is calculated. Selected, it is an tread length. That is,

Tread length (L _n ) = {(dark part bit number) _n
-(Total number of bits / 2)} x bit coefficient + (distance from the center of the visual field to the light reflective sensor) _no bit coefficient = length of visual field / total number of bits. From the formula, | (dark part bit number) _n − (total bit number /
2) The gist is to set the tread length where L _n that minimizes | is the tread length (L).

[0009]

The present invention is configured as described above, and after all the bits of the image sensor 3 are not dark, the rear end of the tread is detected by the image sensor 3 a plurality of times until the entire visual field becomes bright. Of the detected values, the bit number of the image sensor 3 of the light reflection type sensor 2 closest to the visual field center O of the image sensor 3 is selected by calculation, and the tread length is calculated by the above formula to obtain the tread length. Of. As a result, the error due to the lens aberration of the image sensor can be resolved, and highly accurate measurement can be performed.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an overall perspective view of an embodiment of the present invention. A measuring device according to the present invention comprises a plurality of light reflection type sensors 2 (hereinafter Called edge sensor 2)
And an image sensor 3 and a photoelectric tube 4 arranged upstream of the edge sensor 2. The edge sensor 2 is attached to the conveyor frame 5 (see FIG. 3) in a direction orthogonal to the tread W. In this embodiment, the first edge sensor 2 is located 1600 mm from the visual field center point O shown in FIG. , And a total of 10 edge sensors 2 are arranged at 100 mm intervals from the edge sensor 2 in the tread conveying direction.

Therefore, the measuring range is 1600 mm to 2600
Although it is mm, the measurement range can be freely selected by changing the geometrical dimensions of the arrangement of these edge sensors 2. These geometrical dimensions are stored in a microcomputer (not shown) and used in the measurement operation described later. Further, a fluorescent lamp 6 is arranged below the image sensor 3, and a reflecting plate 7 is also arranged below the photoelectric tube 4.

The image sensor 3 and the photoelectric tube 4 are
It is attached to a frame 8 installed on the roller conveyor 1. 2 shows the tread W used in this embodiment.
The front end face W1 is cut at an inclination angle of a dozen degrees with respect to the lower surface of the tread W, and the bottom face on the rear end face W2 side is flat.

This example is an embodiment, and the obtuse-angled end may be the tip or the rear end of the tread, or the obtuse-angled end may be the upper surface. At that time, the reflective sensor is mounted on the upper side. Next, the measuring method will be described with reference to FIGS. 3, 4A, 4B, and 5. FIG. 4A is a diagram when the edge sensor 2 has not yet detected the bottom surface of the tread W. The narrow beam Q emitted from the edge sensor 2 is OFF because the reflected light Q1 from the front end cut surface W1 of the tread W is not reflected by the edge sensor 2 itself. When the tread progresses a little more (FIG. 4 (b)), the reflected light Q1 is reflected by the edge sensor 2 itself at the cut line on the bottom surface and turned on. That is, the edge sensor 2 goes from OFF to O
When N, the bottom edge (obtuse angle end) of the tread W is directly above the edge sensor 2.

The photoelectric tube 4 in FIG. 3 is for detecting whether or not there is a tread W on the measuring device, and on the optical axis S thereof, a tread is provided between the tread W and a reflecting plate arranged below the roller conveyor 1. Turns on when W progresses. This photocell 4
Is the first edge sensor 2 and the image sensor 3
It can be anywhere between the cameras. The camera of the image sensor 3 is mounted in such a direction that the amount of light blocked by the fluorescent lamp 6 in the traveling direction of the tread W can be detected.

The camera of the image sensor 3 used in this embodiment was 512 bits, and the heights of the camera of the image sensor 3 and the surface of the roller conveyor 1 were selected so that the visual field on the surface of the roller conveyor 1 was 200 mm. Image sensor 3
The number of bits and the field of view are related to the measurement accuracy, and in the embodiment, 20
0 / 512≈0.39 mm. As shown in FIG. 1, the roller conveyor 1 in the visual field is divided so that the roll 1a of the roller conveyor 1 does not enter the visual field. Further, the center O of the visual field of the image sensor, that is, the point where the image sensor 3 is exactly half shadow is called the visual field center O, and the distance between the point and the first edge sensor is stored as a constant.

The tread W flowing from the left hand of FIG. 3
When the tip W1 of the light shields the photoelectric tube 4, the input signal to the microcomputer (not shown) is turned from OFF to ON, and the signal input of the first edge sensor 2 is gated. At this time, the field of view of the image sensor 3 is shielded by the tread W, so that the image on the image sensor 3 is all dark. When the tread W further advances and the first edge sensor 2 detects the bottom surface of the tread W, a signal is input to the microcomputer, and the bit number of the dark portion of the image of the image sensor 3 at that time is counted. If it's not all bit dark,

Tread length (L _n ) = {(dark part bit number) _n
-(Total number of bits / 2)} x bit coefficient + (distance from the center of the visual field to the light reflective sensor) _no bit coefficient = length of visual field / total number of bits. Here, the bit coefficient = the length of the field of view / the total number of bits is calculated, the measurement is completed, and the O of the photocell is adjusted for the next measurement.
Wait for ON change from FF. If all bits are dark, that is, when the entire field of view of the image sensor 3 is shielded by the tread W, the microcomputer switches the gate to the signal input of the second edge sensor 2. When the tread W further progresses and the second edge sensor 2 detects the bottom surface of the tread W, similarly, the number of bits of the dark portion of the image sensor 3 is counted to determine whether or not all the bits are dark. It is determined whether the length is calculated by the equation (1) or the gate is switched to the input of the next edge sensor 2.

When the longest tread W comes in, the above operation is gated to the edge sensor 2 farthest from the camera of the image sensor 3 until it detects the bottom surface.
Repeat the same operation. The flow of the program of the microcomputer is shown in FIG. Due to the aberration of the lens, the further the distance from the center O of the field of view, the more blurred the image becomes, and the linearity becomes worse. Therefore, in the embodiment, the image of the tread tail is imaged as follows: The measurement value close to the center of the sensor 3 was used as the measurement result for optimization. That is, after all the bits of the image sensor 3 are no longer dark, the rear end of the tread is detected a plurality of times by the image sensor 3 until the entire visual field becomes bright, and among the detected values, the visual field center O of the image sensor 3 is detected. The number of bits of the image sensor 3 of the nearest light reflection type sensor 2 is selected by calculation, and the tread length is calculated by the above formula to obtain the tread length. As a result, the error due to the lens aberration of the image sensor can be resolved, and highly accurate measurement can be performed.

[0019]

Since the present invention is constructed as described above, it has the following excellent effects. (A). It is not affected by the profile of the tread upper end, and there is no error movement, and the tread length is accurate,
And the tread length can be automatically measured. (B). In addition, regardless of the length of the tread, the measurement accuracy can always be kept below a certain value, and by further selecting the installation distance between the light reflection type sensor and the image sensor,
It can measure tread length of any length. (C). After all bits of the image sensor are no longer dark, the rear edge of the tread is detected multiple times by the image sensor until the entire field of view becomes bright. Since the tread length is calculated by calculating the tread length by selecting the bit number of the image sensor of the image sensor by calculation, it is possible to solve the error due to the lens aberration of the image sensor and perform an accurate measurement. is there.

[Brief description of drawings]

FIG. 1 is an overall perspective view of a measuring device for carrying out the present invention.

FIG. 2 is an overall perspective view of a tread.

FIG. 3 is an explanatory diagram showing a method for measuring a tread length.

FIG. 4A is an explanatory diagram showing a method for measuring a tread length. (B) is explanatory drawing which shows the measuring method of tread length.

FIG. 5 is a block diagram illustrating the flow of a program of a microcomputer.

[Explanation of symbols]

1 Conveyor (roller conveyor) 2 Light reflection type sensor (edge sensor) 3 Image sensor W tread

Claims (1)

[Claims] 1. When a tip of a tread cut into a certain length and conveyed by a conveyor cuts off a photocell,
When the signal input of the first light reflection type sensor is gated through the microcomputer and then the tread advances and the first light reflection type sensor detects the bottom surface of the tread, the signal is sent to the microcomputer. Enter, count the number of bits in the dark part of the image of the image sensor that detects the rear end of the tread at that time, and determine whether all bits are dark.If the tread shields the entire field of view of the image sensor, the microcomputer Thus, the gates are sequentially switched to the signal input of the second and subsequent light reflection type sensors, and after all the bits of the image sensor are not dark, a plurality of (n ) Times, and of the detected values, the bit number of the image sensor of the light reflection type sensor closest to the center of the visual field of the image sensor is calculated. Selected, | (number dark portion bits) _n -
When L _n that minimizes (total number of bits / 2) | is the tread length (L), the tread length is calculated by the following formula to obtain the tread length. Measuring method. Tread length (L _n ) = {(dark part bit number) _n− (total bit number / 2)} × bit coefficient + (distance from center of visual field to light reflection type sensor) _no bit coefficient = visual field length / total bit number.