JP2007240261A - Ultrasonic sensor and obstacle sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive ultrasonic sensor that can detect an obstacle in an arbitrary direction regardless of an attachment site and has a simple structure.
A thin diaphragm 12 having an aspect ratio other than 1: 1 and emitting or receiving ultrasonic waves, and a plurality of linearly arranged on the diaphragm in the longitudinal direction of the diaphragm. The driving elements 13a and 13b and the plurality of driving elements are sequentially driven while shifting the phase to generate a traveling wave in the diaphragm, thereby controlling the radiation direction of the ultrasonic wave and received by the diaphragm. And a control circuit 2 that controls the detection direction of the ultrasonic wave by sequentially performing synchronous detection while shifting the phases of the multiple signals generated by the multiple drive elements based on the ultrasonic wave.
[Selection] Figure 2

Description

  The present invention relates to an ultrasonic sensor and an obstacle sensor that detect an object by transmitting / receiving ultrasonic waves, and more particularly to a technique for controlling the transmission / reception direction of ultrasonic waves.

  Conventionally, an ultrasonic transmitter / receiver installed at the rear bumper or four corners of a vehicle or an ultrasonic wave is transmitted, and an ultrasonic wave reflected by the obstacle is received and analyzed by a control circuit to detect the obstacle. Ultrasonic sensors that emit alarms and the like are known. In such an ultrasonic sensor, the ultrasonic transducer is usually attached to the outer surface of the vehicle such that the direction in which the obstacle is detected does not excessively face downward with respect to the horizontal direction. However, depending on the outer shape of the vehicle, the outer surface of the vehicle to which the ultrasonic transducer can be attached may overhang from a vertical surface with respect to the ground. In this case, an ultrasonic sensor that transmits and receives ultrasonic waves in a direction perpendicular to the mounting surface of the ultrasonic transducer has a problem that the ground is erroneously detected as an obstacle.

  In order to solve such a problem, an ultrasonic wave transmitter / receiver is installed by using an adapter for orienting a diaphragm for generating ultrasonic waves built in the ultrasonic wave transmitter / receiver in a direction substantially perpendicular to the ground. The device is attached to the outer surface of the vehicle. As another ultrasonic sensor for solving the above-described problem, as shown in Patent Document 1, a plurality of diaphragms are provided, and a plurality of ultrasonic waves having a phase difference are generated by sequentially driving each diaphragm. Therefore, a device that controls the transmission / reception direction of ultrasonic waves by using the principle of a phased array that changes the direction of the combined wavefront has been put into practical use.

  As a related technique, Patent Document 2 discloses an ultrasonic transducer that can generate ultrasonic vibration of a linear traveling wave with an energy efficient and compact configuration. This ultrasonic vibrator has a predetermined length and a membrane-plate-like diaphragm portion that is narrower than the length, and is integrally fixed and supported by an elongated frame-like portion. Resonantly supported by standing waves of different orders at the same frequency, and a vibration means comprising a piezoelectric element is fixed to the position of the antinode of standing waves of different orders of the diaphragm part. Different standing waves are formed with different phases at the same frequency, and apparently linear traveling waves are formed.

JP 2000-139926 A JP 2003-159666 A

  As described above, the ultrasonic sensor to which the ultrasonic transducer is attached using the conventional adapter has a problem that the vibration plate of the ultrasonic transducer has an inclination with respect to the outer plate of the vehicle, which is unpleasant. is there. Also, the conventional ultrasonic sensor using the phased array principle requires a large number of diaphragms, a large number of drive elements for driving them, and a large number of transmission circuits and reception circuits for driving the drive elements. Therefore, there is a problem that both the mechanism part and the circuit part are complicated and expensive.

  The present invention has been made to solve the above-described problems, and the problem is that an obstacle in an arbitrary direction can be detected regardless of the attachment site, and an inexpensive structure having a simple structure is provided. It is to provide an ultrasonic sensor and an obstacle sensor.

  In order to solve the above problems, an ultrasonic sensor according to the present invention has an aspect ratio other than 1: 1, a thin plate-like diaphragm that emits or receives ultrasonic waves, and the diaphragm on the diaphragm. A plurality of drive elements arranged in a straight line in the longitudinal direction of each and a plurality of drive elements are sequentially driven while shifting the phase to generate a traveling wave on the diaphragm to control the direction of ultrasonic radiation And a control circuit that controls the detection direction of the ultrasonic waves by sequentially performing synchronous detection while shifting the phases of the plurality of signals generated by the plurality of drive elements based on the ultrasonic waves received by the diaphragm. Yes.

  The obstacle sensor according to the present invention is used by being attached to a vehicle. The obstacle sensor has an aspect ratio other than 1: 1, a thin plate-like diaphragm that emits ultrasonic waves, and a plurality of linearly arranged on the diaphragm in the longitudinal direction of the diaphragm. A drive element and a control for causing each of the plurality of drive elements to sequentially drive while shifting the phase to generate a traveling wave in the diaphragm, so that the ultrasonic radiation direction is higher than the direction perpendicular to the side surface of the vehicle; and Alternatively, the detection direction of the ultrasonic wave can be changed from the direction perpendicular to the side surface of the vehicle by sequentially performing synchronous detection while shifting the phases of the multiple signals generated by the multiple drive elements based on the ultrasonic wave received by the diaphragm. And a control circuit that performs upward control.

  According to the ultrasonic sensor of the present invention, since the ultrasonic radiation direction and / or detection direction can be controlled, an obstacle in any direction can be detected regardless of the attachment site. In addition, since a large number of diaphragms are not required, the structure of ultrasonic control is simplified. As a result, an inexpensive ultrasonic sensor can be provided.

  Further, according to the obstacle sensor according to the present invention, the ultrasonic radiation direction is controlled to be higher than the direction perpendicular to the side surface of the vehicle, and / or the ultrasonic detection direction is from the direction perpendicular to the side surface of the vehicle. Since it can be controlled upward, even if the vehicle has an overhanged outer plate, the ground is not mistakenly detected as an obstacle, and a large number of diaphragms are not required. It becomes simple and can provide an inexpensive ultrasonic sensor.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1 FIG.
1 is a diagram showing a configuration of an ultrasonic sensor according to Embodiment 1 of the present invention. This ultrasonic sensor is composed of an ultrasonic transducer 1 and a control circuit 2, and these are connected by, for example, a cable 3.

  2A and 2B are diagrams showing the structure of the ultrasonic transducer 1, in which FIG. 2A is a front sectional view and FIG. 2B is a bottom view. The ultrasonic transducer 1 is fixed to a cylindrical frame portion 11 forming the side surface thereof, and a cut surface of the frame portion 11 (a cut surface in a direction perpendicular to the axis of the cylinder constituting the frame portion 11). The plate-shaped diaphragm 12 forming the upper surface, and the first drive element 13a and the second drive element 13b fixed to the back surface of the diaphragm 12 are configured.

  A nose portion 14 that protrudes to the inside of the cylinder is formed at the approximate center of the side surface in the longitudinal direction (X-axis direction) of the frame portion 11. The diaphragm 12 is molded such that a portion corresponding to the nose portion 14 has a constricted shape (the shape of a heel). The diaphragm 12 is made of a metal plate such as aluminum, a plastic plate, or the like. The first drive element 13a and the second drive element 13b are composed of, for example, piezoelectric elements.

  The operation of the ultrasonic transducer 1 having the above structure will be described. For example, as shown in Patent Document 2, when the aspect ratio of the diaphragm 12 is increased, the resonance frequency of the standing wave standing in the longitudinal direction (X-axis direction) is reduced in the short direction of the diaphragm 12 (Y-axis). The change in the resonance frequency due to the order of the standing wave is small, and the n (n = 0, 1,...) Standing wave standing in the longitudinal direction and the n + 1 order It is known that traveling waves can be generated in the diaphragm 12 by exciting the standing waves simultaneously. In the first embodiment, the simplest example of “n = 0” will be described. In this ultrasonic transducer 1, a zero-order standing wave standing in the longitudinal direction of the diaphragm 12 as shown in FIG. 3A and a primary standing wave as shown in FIG. A traveling wave propagating in the longitudinal direction of the diaphragm 12 is generated using the wave.

  In the first embodiment, the traveling wave propagating in the longitudinal direction of the diaphragm 12 is generated from the lowest order using the standing waves of the two modes (the zero-order mode and the first-order mode). The aspect ratio cannot be increased excessively. For this reason, if the nose portion 14 is not present, the resonance frequency of the first-order standing wave is significantly higher than the resonance frequency of the zero-order standing wave. In the container 1, the nose portion 14 is provided to increase the support rigidity of the central portion of the diaphragm 12, thereby increasing the resonance frequency of the zeroth-order standing wave and bringing it closer to the resonance frequency of the first-order standing wave. By driving the first driving element 13a and the second driving element 13b at a frequency near the middle between the resonance frequency of the zeroth-order standing wave and the resonance frequency of the first-order standing wave, the diaphragm 12 is low. A standing wave having a large amplitude can be obtained with the driving voltage.

  FIG. 4 is a block diagram showing the configuration of the control circuit 2. The control circuit 2 includes a transmission circuit 20, a reception circuit 30, and a distance calculation circuit 40.

  The transmission circuit 20 includes an oscillation circuit 21, a phase delay circuit 22, an amplification circuit 23, and an amplification circuit 24. The oscillation circuit 21 generates a signal alternating at a frequency intermediate between the zeroth-order resonance frequency and the first-order resonance frequency, and sends the signal to the phase delay circuit 22, the amplifier circuit 23, the reception circuit 30, and the distance calculation circuit 40. The amplification circuit 23 amplifies the signal sent from the oscillation circuit 21 and sends it to the first drive element 13 a of the ultrasonic transducer 1. The phase delay circuit 22 delays the phase of the signal sent from the oscillation circuit 21 by θd and sends it to the amplifier circuit 24 and the receiving circuit 30. The amplifier circuit 24 amplifies the signal sent from the phase delay circuit 22 and sends it to the second drive element 13 b of the ultrasonic transducer 1.

  The reception circuit 30 includes an amplification circuit 31, an amplification circuit 32, a phase delay circuit 33, and a synchronous detection circuit 34. The amplifier circuit 31 amplifies the signal sent from the first drive element 13 a and sends it to the synchronous detection circuit 34. The amplifier circuit 32 amplifies the signal sent from the second drive element 13 b and sends it to the phase delay circuit 33. The phase delay circuit 33 delays the phase of the signal sent from the amplifier circuit 32 by θd and sends it to the synchronous detection circuit 34. The synchronous detection circuit 34 sequentially receives the signal sent from the amplifier circuit 31 and the signal sent from the phase delay circuit 33 based on the phase information sent from the oscillation circuit 21 and the phase delay circuit 22 of the transmission circuit 20. Synchronous detection. A signal obtained by synchronous detection by the synchronous detection circuit 34 is sent to the distance calculation circuit 40.

  The distance calculation circuit 40 receives the time taken for the ultrasonic wave radiated from the diaphragm 12 to be received by the diaphragm 12 after being reflected by the obstacle and the signal sent from the oscillation circuit 21 of the transmission circuit 20. Calculation is performed based on the signal sent from the synchronous detection circuit 34 of the circuit 30 and the distance to the obstacle is calculated based on the time obtained by this calculation.

  Next, the operation of the ultrasonic sensor according to Embodiment 1 of the present invention configured as described above will be described. When the ultrasonic wave is emitted from the ultrasonic transducer 1 and the delay amount θd delayed by the phase delay circuit 22 of the transmission circuit 20 is “0”, the first drive element 13a and the second drive element 13b are Since it is driven in phase, only the 0th-order standing wave is excited in the diaphragm 12. Therefore, similarly to the conventional ultrasonic transducer, ultrasonic waves are radiated in a direction perpendicular to the diaphragm 12 (Z-axis direction).

On the other hand, when the delay amount θd is not “0”, the zero-order standing wave and the first-order standing wave are excited simultaneously on the diaphragm 12, so that the left end of the diaphragm 12 shown in FIG. Assuming 0, the right end is x = 1, the drive angular frequency is ω, and the time is t, the displacement Z in the vertical direction (Z-axis direction) at each point of the diaphragm 12 can be expressed by the following equation. Note that a, b, and α are constants.

  For example, by adjusting the drive amplitude and phase difference (delay amount) θd of the first drive element 13a and the second drive element 13b, a = b = 1, α = π / 2, and the displacement Z of the diaphragm 12 is FIG. 5 shows a plot for each time normalized by the time of one cycle. Moreover, when the same displacement is represented by a time change for each position, it is as shown in FIG.

  Referring to FIG. 6, the displacement at the position of x = 0.8 and x = 0.6 is ahead of the phase of the displacement at the position of x = 0.4 and x = 0.2. It can be seen that the diaphragm 12 travels from the right side to the left side. When the phase of vibration of the diaphragm 12 changes as shown in FIGS. 5 and 6, the main propagation direction of the ultrasonic waves is the direction in which the phases are aligned according to the principle of the phased array. As shown, the light is radiated with an inclination in a direction in which the phase is delayed from the direction perpendicular to the diaphragm 12.

  Therefore, by changing the frequency for driving the first drive element 13a and the second drive element 13b and the phase difference θd applied between the first drive element 13a and the second drive element 13b, the inclination of the ultrasonic radiation direction can be changed. Since it can be controlled, it becomes possible to electrically control the detection direction of the obstacle.

  When ultrasonic waves are received by the ultrasonic transducer 1, the operation is as follows. That is, the diaphragm 12 is oscillated by the ultrasonic wave radiated from the diaphragm 12, reflected by an obstacle or the like, and returned to the diaphragm 12 again. The first drive element 13a and the second drive element 13b are driven in phase with respect to the ultrasonic wave returned from the front surface of the diaphragm 12, but when driven by the ultrasonic wave returned from the tilted direction, As in the case of the transmission described above, a traveling wave is generated on the diaphragm 12, and a phase difference is generated between the signal obtained from the first drive element 13a and the signal obtained from the second drive element 13b. Therefore, similarly to the transmission circuit 20, the reception circuit 30 is also provided with a phase delay circuit 33. By controlling the amount of delay by the phase delay circuit 33, the detection direction of the ultrasonic waves can be controlled.

  As described above, according to the ultrasonic sensor according to the first embodiment of the present invention, since the ultrasonic radiation direction and the detection direction can be controlled, the ultrasonic transducer 1 is not dependent on the attachment site. Obstacles in any direction can be detected. In addition, since the traveling wave is generated on one diaphragm 12, the principle of the phased array can be realized with an extremely small number of driving elements as compared with the conventional case. As a result, the structure of the ultrasonic sensor is simplified, and an inexpensive ultrasonic sensor can be provided.

  The ultrasonic sensor according to Embodiment 1 described above can be attached to a vehicle and used as an obstacle sensor such as a corner sensor or a back sensor. In this case, in the transmission circuit 20 of the control circuit 2, the traveling wave is generated in the diaphragm 12 by sequentially driving the first driving element 13a and the second driving element 13b while shifting the phase, and the radiation direction of the ultrasonic waves Is controlled to be higher than the direction perpendicular to the side surface of the vehicle. In the receiving circuit 30, the ultrasonic wave is detected by sequentially performing synchronous detection while shifting the phases of a plurality of signals generated in the first driving element 13a and the second driving element 13b based on the ultrasonic wave received by the diaphragm 12. The detection direction is controlled to be higher than the direction perpendicular to the side surface of the vehicle.

  According to this obstacle sensor, the obstacle detection direction can be electrically controlled, so that, for example, the outer surface of the vehicle that can be mounted for convenience of the outer shape of the vehicle overhangs from the vertical surface with respect to the ground. Even in this case, it is possible to make the detection direction of the obstacle more than horizontal with respect to the ground while keeping the inclination of the diaphragm 12 parallel to the outer surface of the vehicle. .

  Further, the ultrasonic sensor according to Embodiment 1 described above can be attached to a vehicle and used as a vehicle height sensor. In this case, in the transmission circuit 20 of the control circuit 2, the traveling wave is generated in the diaphragm 12 by sequentially driving the first driving element 13a and the second driving element 13b while shifting the phase, and the radiation direction of the ultrasonic waves Is controlled to be downward from a direction perpendicular to the side surface of the vehicle. In the receiving circuit 30, the ultrasonic wave is detected by sequentially performing synchronous detection while shifting the phases of a plurality of signals generated in the first driving element 13a and the second driving element 13b based on the ultrasonic wave received by the diaphragm 12. The detection direction is controlled to be lower than the direction perpendicular to the side surface of the vehicle.

  In the ultrasonic sensor according to Embodiment 1 described above, two drive elements such as the first drive element 13a and the second drive element 13b are arranged on the vibration plate 12, but three or more drive elements are arranged. A drive element may be arranged. In this case, the diaphragm 12 is constricted between adjacent drive elements.

It is a figure which shows the structure of the ultrasonic sensor which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the ultrasonic transducer of the ultrasonic sensor which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the standing wave which stands in the longitudinal direction of the diaphragm of the ultrasonic sensor which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of the control circuit of the ultrasonic sensor which concerns on Embodiment 1 of this invention. It is the figure which plotted the displacement Z of the diaphragm of the ultrasonic sensor which concerns on Embodiment 1 of this invention for every position. It is the figure which plotted the displacement Z of the diaphragm of the ultrasonic sensor which concerns on Embodiment 1 of this invention for every time. It is a schematic diagram which shows the ultrasonic wave radiated | emitted from each position of the diaphragm of the ultrasonic sensor which concerns on Embodiment 1 of this invention with a phase difference.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ultrasonic transmitter / receiver, 2 Control circuit, 3 Cable, 11 Frame part, 12 Diaphragm, 13a 1st drive element, 13b 2nd drive element, 14 Nose part, 20 Transmission circuit, 21 Oscillation circuit, 22 Phase delay circuit , 23 amplifier circuit, 24 amplifier circuit, 30 receiver circuit, 31 amplifier circuit, 32 amplifier circuit, 33 phase delay circuit, 34 synchronous detection circuit, 40 distance calculation circuit.

Claims (8)

A thin diaphragm having an aspect ratio other than 1: 1 and emitting ultrasonic waves;
A plurality of drive elements arranged linearly in the longitudinal direction of the diaphragm on the diaphragm,
An ultrasonic sensor comprising: a transmission circuit that controls a radiation direction of ultrasonic waves by generating a traveling wave in the diaphragm by sequentially driving each of the plurality of drive elements while shifting a phase. The diaphragm has an aspect ratio such that the resonance frequency of the standing wave standing in the longitudinal direction (n = 0, 1,...) Is close to the resonance frequency of the n + 1 order.
The transmission circuit generates a traveling wave on the diaphragm by sequentially driving each of the plurality of driving elements at a frequency near the middle between the nth-order resonance frequency and the n + 1st-order resonance frequency while shifting the phase. The ultrasonic sensor according to claim 1, wherein the ultrasonic radiation direction is controlled. A thin diaphragm having an aspect ratio other than 1: 1 and receiving ultrasonic waves;
A plurality of drive elements arranged linearly in the longitudinal direction of the diaphragm on the diaphragm,
A receiving circuit that controls the detection direction of ultrasonic waves by sequentially performing synchronous detection while shifting the phases of the plurality of signals generated by the plurality of drive elements based on the ultrasonic waves received by the diaphragm; Sonic sensor. The diaphragm has an aspect ratio such that the n (n = 0, 1,...) Order resonance frequency of the standing wave standing in the longitudinal direction is close to the n + 1 order resonance frequency.
The receiving circuit is identified by sequentially detecting synchronously while shifting the phases of a plurality of signals generated in a plurality of drive elements using a frequency in the vicinity of the middle of the n-th order resonance frequency and the n + 1-order resonance frequency. 4. The ultrasonic sensor according to claim 3, wherein a traveling wave generated on the diaphragm is detected by ultrasonic waves incident from a direction to control a detection direction of the ultrasonic waves. A thin diaphragm having an aspect ratio other than 1: 1 and emitting or receiving ultrasonic waves;
A plurality of drive elements arranged linearly in the longitudinal direction of the diaphragm on the diaphragm,
Each of the plurality of driving elements is sequentially driven while shifting the phase to generate a traveling wave in the diaphragm to control the radiation direction of the ultrasonic wave, and based on the ultrasonic wave received by the diaphragm. An ultrasonic sensor comprising: a control circuit that controls a detection direction of ultrasonic waves by sequentially detecting a plurality of signals generated by the plurality of drive elements sequentially while shifting phases. The diaphragm has an aspect ratio such that the resonance frequency of the standing wave standing in the longitudinal direction (n = 0, 1,...) Is close to the resonance frequency of the n + 1 order.
The control circuit generates a traveling wave in the diaphragm by sequentially driving each of the plurality of driving elements at a frequency near the middle between the n-th resonance frequency and the n + 1-order resonance frequency while shifting the phase. The diaphragm is controlled by ultrasonic waves incident from a specific direction by controlling the radiation direction of ultrasonic waves and sequentially performing synchronous detection while shifting the phases of the plurality of signals generated in the plurality of drive elements using the frequency. The ultrasonic sensor according to claim 5, wherein a traveling wave generated in the step is detected to control a detection direction of the ultrasonic wave. 7. The diaphragm according to claim 2, wherein the diaphragm is fixed to the frame portion and has a constriction between adjacent drive elements among the plurality of drive elements arranged. 8. Ultrasonic sensor. An obstacle sensor attached to a vehicle,
A thin diaphragm having an aspect ratio other than 1: 1 and emitting ultrasonic waves;
A plurality of drive elements arranged linearly in the longitudinal direction of the diaphragm on the diaphragm,
Controlling each of the plurality of drive elements to generate a traveling wave in the diaphragm by sequentially driving each of the plurality of drive elements while shifting the phase, so that an ultrasonic radiation direction is higher than a direction perpendicular to a side surface of the vehicle; and / or Alternatively, the detection direction of the ultrasonic wave is perpendicular to the side surface of the vehicle by sequentially performing synchronous detection while shifting the phases of the multiple signals generated by the multiple drive elements based on the ultrasonic wave received by the diaphragm. An obstacle sensor comprising a control circuit that performs control upward from a direction.

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