JPH0562924B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) This invention is a tire tread residual groove measurement method that measures the tread residual groove of an automobile tire using ultrasonic waves and indicates whether the tread groove depth is appropriate or not. Regarding equipment.

(Prior Art) When the treads of automobile tires wear out over time, the number of braking systems decreases, increasing the risk of slip accidents. Therefore, in order to avoid this danger, conventionally the driver or vehicle maintenance personnel inspected the remaining groove of the tread and measured the groove depth visually.
Methods such as inserting a gauge into the remaining tread groove and numerically measuring the groove depth have been used. However, since the former method is based on visual measurement, there are individual differences and the judgment of suitability tends to be inaccurate, so there is a problem of overlooking dangerous situations, and the latter method also tends to vary in measurement values, making it difficult to make accurate measurements. In addition to being difficult, there was also the drawback that the operation of the measuring instrument was cumbersome.

Therefore, in view of the above problem, the groove depth of the tire tread is optically detected using a non-contact optical displacement meter installed below the light-transmitting cover plate on which the tire rides, and this detected value and reference value are We have previously filed an application for a tire tread groove measuring device that can immediately indicate the adequacy of the remaining tread groove by comparing the remaining tread grooves (Utility Application No. 127642/1983).

(Problem to be solved by the invention) However, since this type of measuring device uses laser light etc., it can measure the groove depth instantly, but an optical displacement meter uses a light emitting diode, a receiving/emitting lens, and a displacement detector. Since it consists of optical instruments such as, the mechanism is complicated and expensive, and each attached instrument requires fine adjustment and periodic maintenance, so maintenance remains a problem.

The present invention was made in order to solve the above-mentioned conventional problems, and is a tire that can instantaneously and extremely accurately measure the depth of a tire's remaining tread groove with a simple and inexpensive configuration, and also displays whether or not the tire is in compliance. The object of the present invention is to provide a tread residual groove measuring device.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a tire tread remaining groove measuring device configured as follows. That is, the tire is laid on the top surface, and a cover plate is provided with a slit that is longer than the width of the tire, and a node is formed along the slit at a position directly below the slit with a step smaller than the width of the remaining tread groove. a transducer that is installed to move and intermittently transmits ultrasonic waves and receives the reflected waves; a cylindrical cone portion with an inner wall surface perpendicular to the top surface of the transducer; a waveguide comprising a horn section connected to the cone section and having a funnel-shaped tapered toward a distal end facing the slit and having a sound absorbing section expanding outward at the distal end; and the wave transmitting/receiving wave. A signal processing section that measures the propagation time of the ultrasonic wave from the time of transmission to the time of reception and outputs distance information, and calculates the depth of the remaining tread groove by processing the output value of the signal processing section and a reference value. a calculation unit that calculates the maximum output value of the calculation unit, a determination unit that extracts the maximum output value from this calculation unit, a comparison unit that compares the output of the determination unit with a reference setting value, and a determination unit that determines whether the tread remaining groove is appropriate based on the output of the comparison unit. The present invention is characterized by comprising a display section that displays.

(Function) When a car tire is placed on the cover plate across the slit, the ultrasonic waves emitted from the transducer become beam-like due to the cylindrical cone part of the waveguide, and the ultrasonic wave is formed into a tapered shape. The horn unit converges the ultrasonic beam, changes it into a finer ultrasonic beam, and emits it from the slit in the cover plate. At the same time, the reflected wave from the tire tread or the bottom of the remaining groove is introduced from the sound absorbing part at the tip of the waveguide, and is transmitted and received. received by the radio transmitter. At this time, the diffusely reflected reflected waves are cut off by the sound absorption part, and only the reflected waves with good straightness are introduced into the transducer, improving the directivity and propagation characteristics in the air. In addition to being emitted as a sound wave beam, it becomes possible for the ultrasonic waves to enter the small diameter tread grooves of the tire.

When the reflected wave is received by the transducer, the signal processing unit counts the propagation time from the time the ultrasonic wave is transmitted to the time it is received by the transducer and obtains distance information from the transducer to the reflecting surface. Output to the calculation section. In the arithmetic section, a reference value preset to correspond to the distance between the transducer and the tread is subtracted from the information signal from the signal processing section to calculate the depth of the remaining groove of the tread.

The transducer transmits ultrasonic waves intermittently while moving in steps smaller than the width of the tread remaining groove along the slit, which is longer than the width of the tire.
No matter where the tire cover plate is placed on the measurement position, the ultrasonic waves will always hit the tread remaining groove. The maximum value of the output signals from the calculation section obtained for one tire to be measured in this manner is extracted by the determination section. Therefore, signals for the remaining tread grooves that are clogged with mud and stones are excluded, and only the signal for the depth of the deepest groove bottom is extracted, thereby preventing erroneous measurements. This extracted output indicating the depth of the remaining tread groove is compared with a reference setting value corresponding to a proper tread groove bottom in the comparing section, and based on this comparison output, the display section shows whether the amount of wear of the remaining tread groove is appropriate or not. Is displayed.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 1 is a schematic configuration diagram partially showing a measuring device according to the present invention in cross section.

The tire tread remaining groove measuring device includes an ultrasonic sensor main body 8, a temperature correction sensor 15, a photo sensor 16, etc. housed in a measurement box 2 in which a tire 1 is placed, and an external operation panel as shown in FIG. Pulse generation circuit 19 and signal processing section 20 provided
It is configured to include a calculation section 22, etc., and a measurement display 25, a display section 28, etc., which are arranged so as to be visible.

The measurement box 2 is formed by burying a cover plate 2a made of aluminum mat that covers the upper opening so as to be flush with the ground surface. The cover plate 2a is provided with a slit 2b having a width of several mm and a length direction larger than the width of the tire, and the circumferential surface of the tire 1, that is, the tread 1a, is positioned on the slit 2b. In addition, a guide rod 3 is mounted in the measurement box 2 at a position directly below the slit 2b and parallel to the slit 2b, and a screw rod 4 is freely rotatable parallel to the guide rod 3. It is mounted on a shaft. A boss portion 5 that holds an ultrasonic sensor main body 8, which will be described later, is screwed into the threaded rod 4. One end of the threaded rod 4 is connected to a stepping motor 7 via a speed reducer 6, and the threaded rod 4 rotated by the motor 7 causes the ultrasonic sensor main body 8 to move directly below the slit 2b. It is designed to move back and forth.

The stepping motor 7 moves in response to a drive signal from the motor controller 18, and the steps of the motor 7 are set to be sufficiently smaller than the width of the remaining tread groove 1b. Even if the tire 1 is placed on an arbitrary location at the measurement position 2a, the ultrasonic waves emitted from the ultrasonic sensor body 8 will always hit the tread residual groove 1b, and the reflected waves can be received. .

The ultrasonic sensor main body 8, as shown in FIG.
It consists of a wave transceiver 9, a waveguide 10, etc., and is fixed to the upper surface of the boss portion 5. The transducer 9 is a resonator such as a crystal oscillator, and the back side is fixed to a damper 8b buried in the base 8a.
Based on this signal, it is now possible to transmit ultrasonic pulses with good directionality. The transducer 9 is of a receiving and transmitting type, and is capable of receiving a reflected wave caused by reflection of an ultrasonic wave, converting it into an electric signal, and sending it to the signal processing 20 .
Note that a dust filter 1 is installed above the transducer 9.
4 is fitted to prevent dust from adhering to the transducer 9. The waveguide 10 includes a cone portion 11, a horn portion 12, an outer cylinder portion 13, etc.
It is erected on the base 8a. Cone part 11
are cylindrical and have the same inner diameter from the rear end side, which is the transducer 9 side, to the tip side, and the transducer 9
The diameter is approximately larger than the outer diameter of. The transducer 9 is disposed inside the outer cylindrical portion 13 so that the inner wall surface 11 a is perpendicular to the upper surface of the transducer 9 . Further, the open end 11b of the tip is provided with a roundness that expands outward, so that the ultrasonic waves emitted from the transducer 9 are changed into a beam shape on the inner wall surface 11a, and the reflected waves are expanded. The configuration is such that it can be easily guided from the open end 11b side to the transducer 9 side. Horn part 12
is funnel-shaped, and the inner diameter of the opening on the distal end side 12a is, for example, about 0.8 mm, and is tapered toward the distal end side 12a by curving at a predetermined curvature. Further, the rear end side 12b has a diameter substantially larger than the inner diameter of the cone portion 11. Then, the female threaded part carved on the rear end side 12b is screwed into the male threaded part provided on the outer periphery of the outer cylindrical part 13, so that it is held with a small gap from the tip of the cone part 11. ing. Note that the tip side 12a is provided with a sound absorbing portion 12c that expands outward, and converges the ultrasonic waves that have become beam-shaped at the cone portion 11 toward the tip side 12a, creating an ultrasonic beam with a smaller diameter. At the same time, the reflected waves that are diffusely reflected and impinge on the sound absorbing portion 12c are cut out, and only the reflected waves with good straightness are guided to the transducer 9 side. As a result, the directivity and propagation characteristics of ultrasonic waves in the air are improved, and the ultrasonic waves can easily enter a small diameter part, which has been difficult in the past, and distance measurement using ultrasonic waves becomes possible.

The temperature correction sensor 15 consists of a transducer, a horn section, etc., and is fixed to the side wall 2c of the measurement box 2 with its tip side facing the back surface of the cover plate 2a. Note that the distance between the transducer of the temperature correction sensor 15 and the back surface of the cover plate 2a is the distance between the tread 1a of the tire 1 to be measured and the ultrasonic sensor body 8.
The interval is set to be approximately equal to the distance from the transducer 9 to the transmitter/receiver 9. To explain in more detail, ultrasonic waves have a property of being extremely dependent on temperature in the air, and in order to measure the distance of an object with high precision, it is necessary to correct the sound speed depending on the temperature at the time of measurement. There is. Therefore, data on the speed of sound is important, but in this example, a sensor for temperature correction is provided in order to accurately and easily realize temperature correction. That is, the distance between the transducer of the temperature correction sensor 15 and the shielding surface 2a is set to approximate the distance between the toread 1a, which is the object to be measured, and the transducer 9 of the ultrasonic sensor body 8. , from this standard distance, the ultrasonic propagation time, the ultrasonic propagation time data during the actual measurement of the tread, etc., the ultrasonic sensor body 8 and the tread 1a are
The distance l ₁ from

l ₁ = T ₁ - τ / T ₂ - τ × l ₂ However, l ₁ = Distance between the ultrasonic sensor body and the tread l ₂ = Distance between the temperature compensation sensor and the cover plate T ₁ = Ultrasonic sensor body side Ultrasonic propagation time T ₂ = Ultrasonic propagation time τ on the temperature correction sensor side = Fixed delay time of each sensor The photo sensor 16 has a built-in photo diode, is attached to the side wall 2d of the measurement box 2, and is mounted on the cover plate 2a. The presence of the tire 1 at a predetermined measurement position is detected when the tire is mounted on the vehicle.

FIG. 3 is a block diagram of a tire tread groove measuring device.

The photo sensor 16 is connected to a control section 17, and a motor controller 18 for controlling the stepping motor 7 based on a signal from the photo sensor 16 is connected to the control section 17. Further, a pulse generation circuit 19 having a built-in changeover switch is connected to the control section 17, and can selectively send pulse signals to the temperature correction sensor 15 and the ultrasonic sensor main body 8. And the ultrasonic sensor body 8
and the temperature correction sensor 15 includes a clock counter,
It is connected to a signal processing section 20 equipped with a CRT or the like. This signal processing section 20 is connected to a calculation section 22 via an A/D converter 21, and is capable of digitally converting the distance signal and introducing it into the calculation section 22. This calculation section 22 is connected to the control section 17,
In response to the start-up of the measuring device, the trend 1 is set based on the outputs of the temperature correction sensor 15 and the ultrasonic sensor main body 8.
Calculate the groove depth of a. Further, a discriminating circuit 24 having a built-in limiter circuit is connected to the arithmetic unit 22 via a converter 23. Then, the discrimination circuit 2
A measurement display 25, a comparison circuit 26, etc. are connected to 4, and a reference value from a reference setting section 27 is introduced. Further, a display section 28 and a buzzer 29 are connected to the comparison circuit 26,
It is possible to display whether or not the groove depth is appropriate.

Next, the operation of this embodiment will be explained.

When the tire 1 of the automobile is placed on the cover plate 2a, the photo sensor 16 detects the tire 1. When an operation signal is sent from the control section 17 to the pulse generation circuit 19 based on the detection signal, the changeover switch is activated and a transmission pulse is output to the temperature correction sensor 15. When an ultrasonic wave is emitted from the temperature correction sensor 15 and its reflected wave is received, the received signal is input to the calculation unit 22 via the signal processing unit 20 and A/D converter 21, and the propagation time is It is stored as data.

Subsequently, the motor controller 1 is sent from the control unit 17.
When an operation signal is sent to 8 and the stepping motor 7 is driven, the ultrasonic sensor body 8 moves. At this time, the changeover switch is actuated by the operation signal of the control section 17, and the pulse generation circuit 19 outputs 5 to 50 pulses.
Transmission pulses are output to the ultrasonic sensor main body 8 in the range of (MHz). As a result, as shown in FIG. 4a, ultrasonic waves are intermittently transmitted from the transducer 9 every pulse, which is one measurement time _Wp . This ultrasonic wave is made into a beam by a waveguide 12 and is transmitted to the tread 1a and the groove bottom surface 1 of the tire 1 shown in FIG.
c, and its reflected wave is received. and,
When this received signal is input to the signal processing section 20,
A clock counter counts up and its propagation time is measured. On the other hand, the signal processing section 20
As shown in FIG. 4b, a distance measurement window _W2 having a dead time zone _W1 for cutting noise contained in the received signal is formed in synchronization with the rising edge of the transmission pulse. Then, as shown in FIG. 4c, the received signal S falls within the measurement window.
When caught within W ₂ , a received pulse P ₁ is formed corresponding to the time from the rising edge of the transmitted pulse to the input of S of the received signal (see FIG. 4d). Note that if the received signal S is not caught, P ₁
A received pulse with a width of +P ₂ is output to determine if measurement is impossible.

By the way, the received pulse _P1 indicates the ultrasonic propagation time until the ultrasonic wave is emitted from the transducer 9, hits the tread 1a or the groove bottom surface 1c, is reflected, and is received by the transducer 9 again. ing. Then, when the received pulse P ₁ is input as a digital value to the calculation unit 22 via the A/D converter 21, the distance from the tread 1a to the groove bottom 1c is calculated based on the data from the temperature correction sensor 15. be done. Further, the groove bottom surface 1c and the tread 1a are subtracted based on the distance information of the tread 1a surface,
The groove depth l ₀ of the tread remaining groove 1b shown in FIG. 1 is determined. These subtraction processes are performed at high speed as the ultrasonic sensor body 8 moves, and the propagation time information of the temperature correction sensor 15 is newly input every time the ultrasonic sensor body 8 scans, so it is not affected by changes in ambient temperature. Groove depth l ₀ can be measured without being affected.

When the output of the calculation unit 22 is input to the discrimination circuit 24, the built-in limiter circuit is set to exclude distances other than those corresponding to the deepest tread groove 1b of various tires.
For example, if the remaining groove 1b is clogged with mud or stones, measurement signals from both sides of the tire 1 other than the contact surface are excluded, and the groove depth l ₀ indicating the deepest groove bottom surface 1c is removed.
only is output. When this signal is input to the comparison circuit 26, it is compared with a reference value 27 corresponding to a preset proper tread groove bottom. When this comparison signal is input to the display unit 28, if it is appropriate,
The display is blue, red indicates inappropriateness, and yellow indicates caution is required, and the buzzer 29 sounds if it is inappropriate. Note that the measured value is digitally displayed on the measured value display 25 based on the measurement signal from the discrimination circuit 24, but this information processing is performed by the control section 17, and the remaining groove 1b of the tread 1a is measured and displayed. is done quickly.

(Effects of the Invention) As described above, according to the tire tread groove measuring device of the present invention, the ultrasonic waves transmitted from the transmitter and receiver are converted into a beam by the cylindrical cone portion of the waveguide, and the ultrasonic wave is converted into a beam by the cylindrical cone portion of the waveguide. After being converged by the horn and changed into a finer ultrasonic beam, it is emitted from the slit in the cover plate, and the reflected wave from the bottom of the tire's tread or remaining groove is introduced from the sound absorbing part at the tip of the waveguide. By receiving the waves into the transducer, the diffused reflected waves can be cut off by the sound absorbing part and only the reflected waves with good straightness can be introduced into the transducer, improving directivity and propagation characteristics in the air. By transmitting the ultrasonic wave as a fine ultrasonic beam using the waveguide described above, it has become possible for ultrasonic waves to enter the small diameter remaining groove of the tire, which was difficult in the past. Depth can be measured using ultrasonic waves using a simple, inexpensive, and easily maintainable configuration.

In addition, the transducer is configured to move in steps smaller than the width of the tread grooves along the slit, which is longer than the width of the tire, while transmitting ultrasonic waves intermittently. Even if the tire is placed on any part of the tire, the ultrasonic wave can always hit the remaining tread groove, and the determination unit extracts the maximum value of the output signal from the calculation unit obtained for the tire under test. With this configuration, it is possible to exclude signals from the tread grooves clogged with mud and stones, thereby reliably preventing erroneous measurements. Therefore, the automatic measurement of the remaining tread groove can be carried out extremely accurately and quickly, and the suitability of the measurement can be instantly displayed.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram partially showing a measuring device according to the present invention in cross section, FIG. 2 is a vertical cross-sectional view of a transducer and a waveguide, FIG. 3 is a block diagram of the measuring device, and FIG.
The figure is a timing chart of the circuit shown in FIG. DESCRIPTION OF SYMBOLS 1... Tire, 2a... Cover plate, 2b... Slit, 9... Transducer/receiver, 10... Waveguide, 11...
Cone section, 12... Horn section, 12c... Sound absorbing section, 20... Signal processing section, 22... Arithmetic section, 24
...Discrimination section, 28...Display section.

Claims (1)

[Claims] 1. A cover plate that is laid so that the tire rests on the top surface, and has a slit that is longer than the width of the tire.
a transducer and receiver installed at a position directly below the slit so as to move along the slit in steps smaller than the width of the tread remaining groove, and which transmits ultrasonic waves intermittently and receives the reflected waves; A cylindrical cone portion whose inner wall surface is perpendicular to the upper surface of the corrugator, and a funnel-shaped cone portion connected to the cone portion and tapered toward the tip portion facing the slit, and an outer portion at the tip portion. a waveguide consisting of a horn section having a sound absorbing section that expands into a waveguide; a signal processing section that measures the propagation time from the time of transmission of the ultrasonic wave to the time of reception of the ultrasonic wave of the transducer and outputs distance information; A calculation unit that calculates the depth of the remaining tread groove by processing the output value of the signal processing unit and a reference value, a determination unit that extracts the maximum output value of this calculation unit, and a reference setting for the output of the determination unit. A tire tread remaining groove measuring device comprising: a comparing section for comparing the remaining tread groove values; and a display section for displaying the suitability of the remaining tread groove based on the output of the comparing section.