JP2004150815A - Ultrasonic measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inclination angle measuring instrument highly precisely measuring an inclination without being affected by reverberation. <P>SOLUTION: This ultrasonic measuring instrument comprises a circuit having a little leakage inductance and not forming a resonance circuit with a capacitance of a transmission ultrasonic sensor 1 as much as possible and is provided with a transformer 2 raising a voltage fed from a primary side according to a turn ratio and impressing to the transmission ultrasonic sensor 1, and switching elements 3-5 comprising a push/pull system short-circuiting the primary side of the transformer 2 after the transmission ultrasonic sensor 1 transmits ultrasonic wave. After transmitting the ultrasonic wave, the primary side of the transformer 2 is short-circuited, so that an electrostatic energy stored in the capacitance of the transmission ultrasonic sensor 1 and an electric energy by the vibration of its periphery immediately return to the primary side of the transformer 2 and vanish to quickly mitigate excessive vibration of the transmission ultrasonic sensor 1 and its periphery. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ultrasonic measuring device used for an inclination angle measuring device or an obstacle detecting device using an ultrasonic sensor.
[0002]
[Prior art]
In a conventional transmission ultrasonic sensor, a resonance circuit is formed between an inductance adjusted by a gap in a transformer core and a capacitance of the ultrasonic sensor, and a resistance matched to the impedance of the resonance circuit is formed. Are connected to the primary side of the transformer, and one FET for driving the transformer is connected to the primary side of the transformer. At the time of transmission by the ultrasonic sensor, the FET is turned on, and a voltage boosted to a turn ratio of the transformer or more is applied to the ultrasonic sensor by utilizing the resonance effect of the resonance circuit. Also, after transmission by the ultrasonic sensor, the FET is turned off, and the electrostatic energy stored in the capacitance of the ultrasonic sensor and the vibration around the ultrasonic sensor are connected by the matched resistor connected to the primary side of the transformer. The electric energy generated by the ultrasonic sensor is returned to the primary side of the transformer and is extinguished, so as to suppress the extraneous vibration of the ultrasonic sensor and its surroundings (for example, see Patent Document 1).
[0003]
Further, in the conventional ultrasonic sensor for reception, two diodes connected in parallel with opposite polarities are incorporated on the output side of the electric signal converted by the ultrasonic sensor, so that an excessive electric signal can be prevented. It is to clamp.
[0004]
[Patent Document 1]
JP-A-10-268036
[Problems to be solved by the invention]
Since the conventional ultrasonic sensor is configured as described above, after the transmission of the transmitting ultrasonic sensor, the electrostatic energy accumulated in the capacitance of the ultrasonic sensor and the electric energy due to the vibration around the ultrasonic sensor are transmitted. In order to return to the primary side of the transformer, the inductance of the transformer is adjusted by the gap of the core, etc., and since the leakage inductance is large, electric energy is generated by the resonance action consisting of the inductance of the transformer and the capacitance of the ultrasonic sensor. Do not return to the primary side immediately. Further, the electric energy returned to the primary side of the transformer has a low voltage depending on the turns ratio of the transformer, but cannot be quickly eliminated because it is configured to be eliminated via a resistor.
[0006]
Further, after receiving the ultrasonic sensor for reception, a clamp effect can be expected for an excessive electric signal by two diodes connected in parallel with opposite polarities, but in these two diodes, the forward direction of the diode Unnecessary inputs smaller than the voltage cannot be limited.
[0007]
As described above, in the conventional ultrasonic sensor for transmission, even if reverberation occurs in the vicinity after transmission, it cannot be eliminated quickly, and in the conventional ultrasonic sensor for reception, the obstacle of the transmitted wave and the road surface cannot be eliminated. For example, there is a problem that reverberation due to direct reception which is not reflected due to reflection or the like cannot be performed, and it is not possible to detect an obstacle at a short distance or measure a tilt angle with high accuracy.
[0008]
The present invention has been made in order to solve the above-described problems, and is an ultrasonic measurement apparatus capable of detecting a short-range obstacle and measuring a highly accurate tilt angle without being affected by reverberation. The purpose is to obtain.
[0009]
[Means for Solving the Problems]
The ultrasonic measuring apparatus according to the present invention has a small leakage inductance and has a circuit configuration in which a resonance circuit is not formed as much as possible with the capacitance of the ultrasonic sensor, and boosts the voltage supplied from the primary side according to the turns ratio. A transformer that applies a voltage to the primary side of the transformer during transmission of ultrasonic waves by the ultrasonic sensor, and a switching element that short-circuits the winding of the transformer after transmission of the ultrasonic waves by the ultrasonic sensor. It is provided.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described.
Embodiment 1 FIG.
FIG. 1 is a circuit diagram showing a driving circuit of a transmission ultrasonic sensor used in an inclination angle measuring apparatus according to Embodiment 1 of the present invention. In the figure, a transmission ultrasonic sensor (ultrasonic sensor) 1 is made of ceramic. It is constituted by a vibrator or the like, and is capable of mutually converting an electric frequency pulse and an ultrasonic wave. Although the first embodiment will be described as an ultrasonic sensor dedicated to transmission, it may be applied to an ultrasonic sensor shared for transmission and reception.
[0011]
The transformer 2 has a circuit configuration that has no gap in the core and little leakage magnetic flux, that is, has a small leakage inductance, and has an inductance as small as possible so as not to form a resonance circuit with the capacitance of the transmitting ultrasonic sensor 1 as much as possible. It becomes. Therefore, a voltage obtained by boosting the voltage supplied from the primary side only by the turns ratio is applied to the transmitting ultrasonic sensor 1.
[0012]
A PchFET (switching element, field effect transistor) 3 is connected between the DC power supply and the central portion B of the primary winding of the transformer 2, and NchFETs (switching element, field effect transistor) 4, 5 Are connected between the ends A and C of the primary winding and the ground. The primary winding of the transformer 2 and the PchFET 3 and the NchFETs 4 and 5 supply a voltage from the central portion B of the primary winding and transmit both ends A and C of the primary winding alternately when transmitting ultrasonic waves. The push-pull system is configured to supply a voltage to the primary side of the transformer 2 by short-circuiting.
[0013]
The inverter 6 inverts the power control signal and supplies it to the gate of the PchFET 3, and the inverter 7 inverts the drive signal. The NAND gate 8 supplies the NAND of the power control signal and the inverted drive signal to the gate of the NchFET 4, and the NAND gate 9 supplies the NAND of the power control signal and the drive signal to the gate of the NchFET 5. It is.
[0014]
Next, the operation will be described.
The tilt angle measuring device according to the first embodiment is provided in a vehicle or the like, transmits ultrasonic waves toward a road surface by an ultrasonic sensor, receives ultrasonic waves reflected by the road surface by the ultrasonic sensor, and transmits and receives the ultrasonic waves. The inclination angle of the vehicle with respect to the road is measured based on the ultrasonic waves.
[0015]
FIG. 2 is a waveform diagram showing the drive signal and the voltage applied to the ultrasonic sensor, and FIG. 3 is a timing chart showing the operation of each FET.
In FIG. 1, during transmission of ultrasonic waves by the transmission ultrasonic sensor 1, the power supply control signal is set to the “H” level, and as shown in FIG. A pulse that repeats the L "level is supplied.
[0016]
As a result, as shown in FIG. 3, a power control signal of “L” level is supplied to the gate of the PchFET 3 through the inverter 6 and turned on, and a voltage is applied from the DC power supply to the central portion B of the primary winding of the transformer 2. Supply. A drive signal and an inverted drive signal are supplied to the gate of the NchFET 4 through the inverter 7 and the NAND gate 8, and to the gate of the NchFET 5 through the NAND gate 9, and the NchFET 4 and the NchFET 5 are turned on alternately. By alternately short-circuiting both ends A and C of the primary winding to the ground, the voltage supplied from the central portion B is alternately applied between both ends A and C, and the primary of the transformer 2 is so-called push-pull system. Supply voltage to the side.
[0017]
Thereby, the transformer 2 boosts the voltage supplied from the primary side and applies an electric frequency pulse as shown in FIG. 2 to the transmission ultrasonic sensor 1, and the transmission ultrasonic sensor 1 It is converted into an ultrasonic wave corresponding to the applied electric frequency pulse and transmitted toward the road surface. Here, between the inductance of the transformer 2 and the capacitance of the transmitting ultrasonic sensor 1, the inductance is set to be small so as not to form a resonance circuit as much as possible. Instead, the voltage boosted only by the turns ratio is applied to the transmitting ultrasonic sensor 1.
[0018]
When an ultrasonic wave is transmitted for a predetermined period by the transmission ultrasonic sensor 1, the transmission of the ultrasonic wave is stopped. To stop the ultrasonic wave, the power supply control signal is set to “L” level in FIG. Done by
[0019]
As a result, as shown in FIG. 3, a power control signal of “H” level is supplied to the gate of the PchFET 3 through the inverter 6 and turned off, and the gate of the PchFET 3 is supplied from the DC power supply to the central portion B of the primary winding of the transformer 2. Cut off the voltage supply. Further, the drive signals of “H” level are supplied to the gates of the NchFETs 4 and 5 through the NAND gates 8 and 9, respectively, and are turned off to short-circuit both ends A and C of the primary winding to the ground at the same time. .
[0020]
The voltage is not supplied to the transmitting ultrasonic sensor 1 from the transformer 2, and the electrostatic energy stored in the capacitance of the transmitting ultrasonic sensor 1 and the electric energy generated by the vibration around the transmitting ultrasonic sensor 1 are generated. Energy returns to the primary side of the transformer 2.
[0021]
At this time, since the leakage inductance of the transformer 2 was small, the resonance operation was not repeated by the resonance circuit composed of the capacitance of the transmission ultrasonic sensor 1 and the inductance of the transformer 2, but remained at the capacitance of the transmission ultrasonic sensor 1. The electrostatic energy and the electric energy due to the vibration around the transmission ultrasonic sensor 1 quickly return to the primary side of the transformer 2 and disappear, and the excessive vibration around the transmission ultrasonic sensor 1 and its surroundings can be quickly calmed down. .
[0022]
As a result, there is no extra reverberation around the transmission ultrasonic wave after transmission by the transmission ultrasonic sensor 1, and when the ultrasonic wave is received, the normal ultrasonic wave returning from the road surface and returning is superimposed. Thus, a highly accurate tilt angle can be measured without making it difficult to detect regular ultrasonic waves.
[0023]
As described above, according to the first embodiment, since the leakage inductance of the transformer 2 is small, after transmitting the ultrasonic wave by the transmission ultrasonic sensor 1, the capacitance is accumulated in the transmission ultrasonic sensor 1. The electrostatic energy and the electric energy due to the vibration around the transmission ultrasonic sensor 1 are quickly converted into the primary voltage of the transformer 2 without repeating the resonance operation by the resonance circuit including the capacitance of the transmission ultrasonic sensor 1 and the inductance of the transformer 2. As a result, the transmission ultrasonic sensor 1 and its surroundings can be quickly quenched. As a result, after transmission by the transmission ultrasonic sensor 1, there is no extra reverberation in the vicinity thereof, and only the ultrasonic wave returning from the road surface and returning can be accurately received, and the tilt angle with high accuracy can be measured. can do.
[0024]
Further, since the primary side of the transformer 2 is of the push-pull type, during transmission of an ultrasonic wave, an alternating voltage having a positive and negative uniform amplitude can be supplied to both ends of the transmission ultrasonic sensor 1. Thereafter, even when a positive or negative voltage is applied to both ends of the transmission ultrasonic sensor 1, the electrostatic energy can be quickly returned to the primary side of the transformer 2 and disappear.
[0025]
Further, since the switching elements are constituted by the PchFET 3 and the NchFETs 4 and 5, the electrostatic energy returned from the transmitting ultrasonic sensor 1 to the primary side of the transformer 2 becomes a low voltage depending on the turns ratio of the transformer 2, Since the ON resistances of the NchFETs 4 and 5 are small and there is no saturation voltage between the collector and the emitter of the bipolar transistor, short-circuiting can be performed even with a low potential difference.
[0026]
Embodiment 2 FIG.
FIG. 4 is a circuit diagram showing an output circuit of a receiving ultrasonic sensor used in a tilt angle measuring device according to a second embodiment of the present invention. In the drawing, a receiving ultrasonic sensor (ultrasonic sensor) 11 is a ceramic. It is constituted by a vibrator or the like, and is capable of mutually converting an electric frequency pulse and an ultrasonic wave. Although the second embodiment will be described as an ultrasonic sensor dedicated to reception, it may be applied to an ultrasonic sensor shared for transmission and reception.
[0027]
The current limiting resistor 12 limits the current of the output circuit of the ultrasonic sensor 11 for reception, and the diode 13 is connected between the ground and the ground in the forward direction to clamp an excessive electric signal. is there. As shown in Reference 1, two diodes of the conventional configuration are required in opposition and in parallel, but a parasitic diode can be used in the case of an FET, and in this circuit configuration, it is connected in parallel with the reverse polarity of Reference 1 One of the two diodes can be reduced.
[0028]
An NchFET (field effect transistor) 14 as a switching element is connected between the output circuit of the receiving ultrasonic sensor 11 and the ground, and the receiving ultrasonic sensor 11 transmits ultrasonic waves affected by reverberation. It turns on during a predetermined time and short-circuits the output circuit to ground.
[0029]
The DC blocking capacitor 15 blocks a DC component of the output circuit of the receiving ultrasonic sensor 11, and the amplifier 16 amplifies and outputs an electric signal.
[0030]
Next, the operation will be described.
In the first embodiment, the means for avoiding the influence of the reverberation of the transmitting ultrasonic sensor 1 has been described. In the second embodiment, the means for avoiding the effect of the reverberation of the receiving ultrasonic sensor 11 will be described. Things.
[0031]
FIG. 5 is a waveform diagram showing the voltage signal of each section.
As described in the first embodiment, in the inclination angle measuring apparatus, the ultrasonic wave is transmitted from the transmission ultrasonic sensor 1 toward the road surface, and the ultrasonic wave reflected by the road surface is received by the reception ultrasonic sensor 11. Then, the inclination angle of the vehicle with respect to the road is measured based on the transmitted and received ultrasonic waves, but the ultrasonic sensor for reception 11 directly transmits from the ultrasonic sensor for transmission 1 in addition to the ultrasonic wave reflected by the road surface. The ultrasonic wave that is traveling is received.
[0032]
The first input waveform of the input signal of the receiving ultrasonic sensor 11 shown in FIG. 5 is due to the reverberation of the ultrasonic wave which proceeds directly. The reception of an unnecessary signal such as reverberation may make it difficult to detect a signal corresponding to a normal ultrasonic wave that returns after reflecting off the road surface.
[0033]
Therefore, in the NchFET 14, the output circuit is short-circuited to the ground so that the receiving ultrasonic sensor 11 is turned on for a predetermined time during which the reverberation is affected. The predetermined time for short-circuiting is such that it does not hinder reception of regular ultrasonic waves reflected by the road surface, and is a period of time from transmission of ultrasonic waves until reception of ultrasonic waves reflected by the road surface, in other words. , May be set according to the detection distance between the ultrasonic sensor and the road surface.
[0034]
As shown in FIG. 5, by short-circuiting the output circuit to the ground by the NchFET 14, the on-resistance of the field-effect transistor is small and there is no saturation voltage between the collector and the emitter of the bipolar transistor. The vibration can be eliminated, and unnecessary vibration due to reverberation of the receiving ultrasonic sensor 11 can be quickly suppressed. Further, the effect of reverberation on the subsequent stage of the output circuit can be completely prevented.
[0035]
After the lapse of a predetermined time, if the NchFET 14 is turned off, then the ultrasonic wave reflected by the road surface is received by the receiving ultrasonic sensor 11, but the current of the output circuit is limited by the current limiting resistor 12, and the polarity is reversed. The voltage is clamped to ± 0.7 V by the diode 13 connected in parallel and the parasitic diode of the NchFET 14, the DC component is cut off by the DC cutoff capacitor 15, amplified by the amplifier 16, and output to the subsequent circuit.
[0036]
As described above, according to the second embodiment, the NchFET 14 causes the receiving ultrasonic sensor 11 to be short-circuited for a predetermined time after transmission of ultrasonic waves affected by reverberation, thereby reducing the on-resistance of the field-effect transistor. Is small, the electric signal due to reverberation can be reliably short-circuited, and only the normal ultrasonic wave that reflects off the road surface and returns can be accurately received, and the tilt angle with high accuracy can be measured.
[0037]
Although the above description has been given of the ultrasonic sensor in the system for measuring the tilt angle, a means for reducing the reverberation of the ultrasonic sensor is also effective for detecting an obstacle at a short distance. The above-mentioned inclination angle measurement uses the phase difference of the ultrasonic signal reflected and returned from the road surface, but the ultrasonic signal used for obstacle detection measures the time from transmission to reflection and back. Used to
[0038]
In addition, two ultrasonic signals are required for the tilt angle measurement, and two pairs of ultrasonic transmission and reception sensors are used. However, in order to measure the time until the reflected wave for obstacle detection returns, It can function with a pair of ultrasonic transmission and reception sensors.
[0039]
Also, in the obstacle detection, in order to make the detection distance of the obstacle extremely short, the transmission and reception sensors must be provided independently. Even with the ultrasonic sensor for detecting obstacles, the ultrasonic signal reflected from an obstacle at a short distance may be buried in the reverberation in a measurement system with long reverberation. The mechanism that cannot be detected as a reflected signal is the same as that of the tilt angle measuring system.
[0040]
Therefore, if the circuit described for the tilt angle measurement is used as the drive circuit or input circuit of the ultrasonic sensor used for obstacle detection, an obstacle at a short distance can be detected.
[0041]
【The invention's effect】
As described above, according to the present invention, since the leakage inductance is small, the winding of the transformer is short-circuited by the switching element after the transmission of the ultrasonic wave by the ultrasonic sensor, so that the capacitance is accumulated in the capacitance of the ultrasonic sensor. The electrostatic energy and the electric energy due to the vibration around the ultrasonic sensor return to the primary side of the transformer immediately without repeating the resonance operation by the resonance circuit composed of the capacitance of the ultrasonic sensor and the inductance of the transformer, and disappear. Excessive vibration around the sensor and its surroundings can be quenched quickly. As a result, after transmission by the ultrasonic sensor, there is no extra reverberation in the surroundings, and only the ultrasonic wave that reflects off the road surface and returns can be accurately received, and it is possible to detect short-range obstacles and improve accuracy. There is an effect that a high inclination angle can be measured.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a drive circuit of a transmitting ultrasonic sensor used in a tilt angle measuring device according to a first embodiment of the present invention.
FIG. 2 is a waveform diagram showing a drive signal and a voltage applied to an ultrasonic sensor.
FIG. 3 is a timing chart showing the operation of each FET.
FIG. 4 is a circuit diagram showing an output circuit of a receiving ultrasonic sensor used in a tilt angle measuring device according to a second embodiment of the present invention.
FIG. 5 is a waveform chart showing voltage signals of respective units.
[Explanation of symbols]
1 transmission ultrasonic sensor (ultrasonic sensor), 2 transformer, 3 PchFET (switching element, field effect transistor), 4,5 NchFET (switching element, field effect transistor), 6,7 inverter, 8,9 NAND gate, 11 ultrasonic sensor for reception (ultrasonic sensor), 12 current limiting resistor, 13 diode, 14 NchFET (field effect transistor), 15 DC cutoff capacitor, 16 amplifier.

Claims (4)

A transformer that has a small leakage inductance and does not form a resonance circuit with the capacitance of the ultrasonic sensor as much as possible, boosts the voltage supplied from the primary side according to the turns ratio, and applies the transformer to the ultrasonic sensor. ,
An ultrasonic measuring device having a switching element for supplying a voltage to the primary side of the transformer when transmitting the ultrasonic wave by the ultrasonic sensor and short-circuiting the winding of the transformer after transmitting the ultrasonic wave by the ultrasonic sensor; . In the transformer, switching elements are connected to the center and both ends of the primary winding.When transmitting ultrasonic waves, a voltage is supplied from the center of the primary winding and both ends of the primary winding are alternately short-circuited. This is a push-pull system that supplies voltage to the primary side.After transmission of ultrasonic waves, the supply of voltage from the center of the primary side winding is cut off, and both ends of the primary side winding are simultaneously short-circuited. 2. The ultrasonic measuring device according to claim 1, wherein the measuring device is short-circuited. The ultrasonic measurement device according to claim 1, wherein the switching element is a field-effect transistor. An ultrasonic sensor that converts an electric signal according to the received ultrasonic wave,
An ultrasonic measuring device comprising: a short-circuit element connected to an output side of an electric signal converted by the ultrasonic sensor, wherein the ultrasonic sensor short-circuits for a predetermined time after transmission of ultrasonic waves affected by reverberation. .

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