JP2686528B2 - Ultrasonic distance sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultrasonic distance sensor for detecting a proximity distance by transmitting and receiving ultrasonic waves by a single ultrasonic transmitter / receiver and measuring the arrival time of reflected waves. Regarding the improvement of. [Prior Art] Recently, various ultrasonic distance sensors have been developed which are mounted on a vehicle and measure the vehicle height distance and the distance between the vehicle and surrounding obstacles. The ultrasonic distance sensor for measuring the vehicle height distance (hereinafter, simply referred to as “road surface sensor”) is a sensor that is installed under the floor of the vehicle and is developed for measuring the distance between the vehicle floor and the road surface. It is a sensor that measures the distance between the road surface and the vehicle body while the vehicle is running in time series. The output signal of the road surface sensor is connected to a suspension control device that controls the hardness and the vehicle height of the suspension. It is used to control the suspension while controlling the suspension softly or lowering the vehicle height when the distance is relatively unchanged due to the flat road surface. Also, an ultrasonic distance sensor (hereinafter simply referred to as an "obstacle sensor") for measuring a distance from an object around the vehicle or a pedestrian or the like.
Is installed near the bumper of the vehicle or on the side of the vehicle to detect obstacles and pedestrians that are relatively close to the vehicle when the vehicle is put in the garage or when the vehicle is turned left or right. It is used as a so-called alarm sensor in a device for generating a warning sound or a voice warning sound for displaying a distance on a display unit or for preventing contact. These ultrasonic distance sensors generally include a pair of a transmitter (sender) and a receiver (receiver). For example, as disclosed in Japanese Patent Application Laid-Open No. 50-129252, a single unit is used. It can be said that the configuration using a single ultrasonic transmitter / receiver is advantageous in terms of cost, size and weight, and reduction in the number of parts. [Problems to be Solved by the Invention] However, when a single ultrasonic transmitter / receiver is mounted on a vehicle and is used as an ultrasonic distance sensor, it is necessary to solve the following problems. a) For example, the road surface sensor needs to measure a vehicle height distance of about 20 to 30 [cm]. When transmitting and receiving ultrasonic waves between the adjacent distances, the time required from the ultrasonic wave transmission / reception timing to the timing of receiving reflected waves on the road surface is approximately room temperature.
It is 1.2 to 1.8 [mSec]. However, the ultrasonic transmitter / receiver transmits the ultrasonic waves for a while, for example, the time shown in FIG.
At t7, for example, about 20 [mSec], a reverberant sound is emitted, and the received signal r is buried in the reverberant signal s, and it is difficult to detect the arrival time of the reflected wave. This problem also applies to the obstacle sensor. b) The ultrasonic transmitter / receiver is driven through the output transistor by the timing signal from the control circuit. The timing signal is, for example, a signal having a pulse width of a short time of about 0.3 [mSec], and is a signal transmitted in time series every predetermined time, for example, about every 20 [mSec]. Therefore, the power consumption of the output transistor is small,
Therefore, small output transistors can be used. However, for example, due to control circuit failure or incorrect wiring,
If the output transistor remains on as indicated by time t6 in FIG. 6, the power consumption of the output transistor increases at a stretch by several tens of times, and the output transistor burns out. c) Since the ultrasonic transmitter / receiver is installed in a place where a large amount of rain or car wash water is frequently splashed, water and moisture are introduced into the case from the case opening where the vibrating surface of the ultrasonic transmitter / receiver is located due to a capillary phenomenon or the like. There was a problem that the [Means for Solving Problems] The present invention has been made to address the above-mentioned problems, and is an ultrasonic distance sensor in which a single ultrasonic transmitter / receiver is press-fitted and fixed to a case via an elastic member. Where the elastic member is formed into a cylindrical shape and is attached to the outer circumference and side surfaces of the vibrating surface of the ultrasonic transceiver, and the elastic member is formed into a disc shape and is attached to the back surface of the ultrasonic transceiver. And a second bead provided at one end of the first elastic member, the first bead being provided at one end of the first elastic member is disposed in the opening of the case where the vibrating surface of the ultrasonic transmitter / receiver is located. There is provided an ultrasonic distance sensor characterized in that a second bead provided at an end is arranged between a side surface of the ultrasonic transmitter / receiver and an inner wall of a housing portion of a case. [Operation] The single ultrasonic transmitter / receiver emits ultrasonic waves in time series according to the timing signal from the control circuit and receives the reflected wave. The ultrasonic transmitter / receiver has a property of generating reverberant sound like a speaker or a musical instrument generating other audible sound. However, the ultrasonic transmitter / receiver is press-fitted and fixed to the case by the elastic member having the beads as described above, and since the ultrasonic transmitter / receiver is firmly fixed to the case by the beads, the reverberant sound is attenuated. Further, the ultrasonic transmitter / receiver is mounted toward the outside of the vehicle, and is installed in a place where a large amount of rain or water for car washing is frequently splashed, and the bead also serves as a waterproof packing. In particular, by disposing the first bead provided at one end of the first elastic member in the opening of the case where the vibrating surface of the ultrasonic transmitter / receiver is located, water from the case opening into the case due to a capillary phenomenon or the like Ingress of moisture is prevented. Also, since the case opening is closest to the vibration surface of the ultrasonic transceiver,
By providing a bead at this position, the reverberation sound attenuation effect is further improved. [Embodiment] FIGS. 1 to 5 are drawings showing a preferred embodiment of the present invention. FIG. 1 is a sectional view in which an ultrasonic transmitter / receiver is attached to a case, and FIG. 2 is FIG. 3 is an exploded perspective view of what is shown in FIG. 3, FIG. 3 is an exploded top view of what is shown in FIG. 1, and FIG.
FIG. 5 is an electric circuit diagram showing an example of a circuit including the ultrasonic transceiver shown in FIG. 1, and FIG. 5 is an electric characteristic diagram of each part in FIG. In the drawings, 1 is an ultrasonic transmitting / receiving body, 2 is a first elastic member, 3 is a second elastic member, 4 is a case, 5 is a cover, 6 is a tapping screw, and 7 is a lead wire. The ultrasonic transmitter / receiver 1 is a vibrating body in which a piezoelectric element (not shown) is installed, and has a vibrating surface 11, a side surface 12, and a back surface 13. Then, by the other excitation, for example, an ultrasonic wave of about 30 [KHz] is generated. The first elastic member 2 is formed by molding rubber or the like into a cylindrical shape, and has a first bead 21 at one end and a second bead 22 at the other end. The first bead 21 is arranged in the opening 41 of the case 4 where the vibrating surface 11 of the ultrasonic transceiver 1 is located, and the second bead 22 is a side surface of the ultrasonic transceiver 1.
It is arranged between 12 and the inner wall of the storage part 42 of the case 4. The second elastic member 3 is formed by molding the same material as the first elastic member 2 into a disk shape, and has a first bead 31 on the inner peripheral edge.
The ultrasonic transmitter / receiver 1 has a second bead 32 on the outer periphery thereof.
It is attached to the back surface 13 of the to form a watertight structure. The case 4 and the cover 5 are molded products such as plastic or die cast.
The storage section 42 with an inner diameter d2 slightly smaller than the outer diameter d1 of the
have. Here, the order of assembling the components will be described. First, the first elastic member 2 is attached to the ultrasonic transmitting / receiving body 1, and then the combined product is fitted into the case 4. At this time, the outer diameter dimension d1 of the first elastic member 2 is equal to the overhang dimension of the second bead 22 in the case 4.
Is formed to have an outer diameter larger than the inner diameter d2. Therefore, the combination product is press-fitted and mounted in the case. Next, the second elastic member 3 is placed on the ultrasonic transmitter / receiver 1, the cover 5 is further covered, and the cover 5 is fastened and fixed to the case 4 with tapping screws 6. By tightening the self-tapping screw 6, the first bead 21 of the first elastic member is
Is pressed against. As described above, since the ultrasonic transmitter / receiver 1 is press-fitted and fixed to the case 4 by the first elastic member 2 and the second elastic member 3, reverberation is attenuated as shown in a transmission waveform S shown in FIG. 5E. You. Next, the configuration and operation of the circuit diagram shown in FIG. 4 will be described. In FIG. 4, reference numeral 10 denotes a control circuit, 11 denotes a protection circuit, 12 denotes an oscillation circuit, 13 denotes an output circuit, 14 denotes a high-pass filter, 15 denotes an amplification circuit, 16 denotes a detection circuit, and 17 denotes a waveform shaping circuit. The control circuit 10 includes a transistor 101, resistors 102 and 103, and an inverter 104. The base of the transistor 101 is connected to a circuit such as a microcomputer (not shown). As shown in FIG. 5A, the control circuit 10 outputs a timing pulse signal having a time width t1 [mSec], for example, t1 = 0.3 [mSec], for every t2 [mSec], for example, t2 = 20 [mSec], according to a program of the microcomputer. It is a circuit for outputting to the protection circuit 11 in the subsequent stage. The protection circuit 11 is a gate circuit composed of a timer circuit 111 and an AND circuit 112.
2a is connected to the control circuit 10, and the other input section 112b is connected to the control circuit 10 via the timer circuit 111. The timer circuit 111 is, for example, a circuit composed of a one-shot multivibrator, and has a time width t3 [mSec], for example, every time a timing pulse signal is input from the control circuit 10 at the previous stage as shown in the characteristic of FIG. 5B. t3 = 1 [mSe
This circuit outputs the one-shot pulse signal [c] to the AND circuit 112 in the subsequent stage. The AND circuit 112 outputs a “1” level signal when both inputs are “1” level signals. That is, the AND circuit 112
When signals as shown in FIGS. 5A and 5B are input,
The signal having the shorter time width is selected and output as a signal as shown in FIG. 5C. Therefore, even if the signal shown in FIG. 5A is maintained at the “1” level state due to a failure of the internal wiring of the control circuit 10, the signal shown in FIG. 5C becomes a one-shot pulse signal output from the timer circuit 111. The pulse signal is regulated and has a time width t3 [mSec], the output circuit 13 is prevented from continuing to be in the on-operation state, and the output transistor 133 and the like are prevented from being burnt. The oscillation circuit 12 is a gate circuit composed of an oscillation unit 121 and an AND circuit 122. One input unit 122a of the AND circuit 122 is connected to the protection circuit 11, and the other input unit 122a is an oscillation unit.
It is connected to 121. And the AND circuit 122 is shown in FIG.
While the timing pulse signal is being input through the protection circuit 11 in the front stage as shown in FIG. The output circuit 13 is composed of resistors 131, 132, an output transistor 133 and an output transistor 134. Specifically, the output transistor 133 is composed of Darlington connected transistors, and the output transformer 134 is the primary side, that is, the side connected to the output transistor 133. The winding ratio of the primary side and the secondary side is set so as to boost the applied voltage of and output to the secondary side. Further, the high-pass filter 14, the amplification circuit 15, the detection circuit 16 and the waveform shaping circuit 17 are constituted by known circuits. Incidentally, as shown in FIG. 5E, a transmission waveform S and a reception waveform R of the ultrasonic wave output by the ultrasonic transmitting and receiving body 1 are output to the output section of the amplifier circuit 15. Then, by measuring the time t5 [mSec] until the reception waveform R shown in FIG. 5E is obtained, the distance from the ultrasonic transceiver 1 to the reflector can be known. Note that the present invention is a technology suitable for measuring a close distance such as a vehicle height distance or a distance between a vehicle and a surrounding obstacle mounted on a vehicle, but has a wide application range, for example, for an automatic door or a factory. It can also be used for automated lines and robots in the field. Also, it can be used for a liquid level gauge and the like. EFFECTS OF THE INVENTION The present invention relates to an ultrasonic distance sensor in which a single ultrasonic transmitter / receiver is press-fitted and fixed to a case via an elastic member. The elastic member is formed into a cylindrical shape, and the ultrasonic transmitter / receiver is used. The first elastic member is attached to the outer circumference and the side surface of the vibrating surface of the body, and the second elastic member is attached to the back surface of the ultrasonic transmitter / receiver and is formed into a disk shape. One end of the first elastic member is provided. The provided first bead is arranged in the opening of the case where the vibrating surface of the ultrasonic transmitter / receiver is located, and the second bead provided at the other end of the first elastic member is provided between the side surface of the ultrasonic transmitter / receiver and the case. It is characterized in that it is placed between the inner wall of the storage part and the reverberation sound in the ultrasonic distance sensor can be quickly attenuated, and the proximity distance like the vehicle height distance of the vehicle can be reduced. Not only can it be measured, It has a plurality of effects such that water and moisture are prevented from entering the inside of the case due to a capillary phenomenon or the like through the case opening.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 to FIG. 5 are drawings showing a preferred embodiment of the present invention, and FIG. 1 is a cross-sectional view in which an ultrasonic transmitting / receiving body is attached to a case. FIG. 2 is an exploded perspective view of the one shown in FIG. FIG. 3 is an exploded top view of the one shown in FIG. FIG. 4 is an electric circuit diagram including the ultrasonic transceiver shown in FIG. FIG. 5 is an electrical characteristic diagram of each part in FIG. FIG. 6 and FIG. 7 are electric characteristic diagrams in the prior art. DESCRIPTION OF SYMBOLS 1 ... Ultrasonic transmission / reception body, 2 ... 1st elastic member, 3 ... 2nd elastic member, 4 ... Case, 5 ... Cover, 21 ... 1st
First bead of elastic member, 22 ... second bead of first elastic member, 31 ... first bead of second elastic member, 32 ... second bead of second elastic member, 10 ... control circuit, 11 .... Protection circuit,
12: oscillation circuit, 13: output circuit, 111: timer circuit, 112: AND circuit.

Claims (1)

(57) [Claims] In an ultrasonic distance sensor in which a single ultrasonic transmitter / receiver (1) is press-fitted and fixed to a case (4) via elastic members (2, 3), the elastic member (2, 3) is formed into a cylindrical shape. A first elastic member (2) which is molded and mounted on the outer circumference and side surface (12) of the vibrating surface (11) of the ultrasonic transceiver (1), and the ultrasonic transceiver (1) which is molded into a disc shape. A second elastic member (3) mounted on the back surface (13) of the first bead (2) provided at one end of the first elastic member (2).
A second portion provided on the other end of the first elastic member (2), the first elastic member (2) being arranged in the opening (41) of the case (4) where the vibrating surface (11) of the ultrasonic transceiver (1) is located. An ultrasonic distance sensor characterized in that a bead (22) is arranged between a side surface (12) of the ultrasonic transmitter / receiver (1) and an inner wall of a housing section (42) of a case (4).