JP2006003124A - Ultrasonic sensor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic sensor device having detection accuracy not deteriorating even if a reception level changes by a temperature change or the like. <P>SOLUTION: This ultrasonic sensor device has an ultrasonic sensor 90 usable for both transmission and reception having a structure wherein a piezoelectric oscillator 1 is stuck on one face of a casing 21, and has a frequency variable means changing a drive frequency of the piezoelectric oscillator 1 and a reception level decision means deciding the reception level of an ultrasonic wave. The drive frequencies F<SB>S</SB>, F<SB>L</SB>, F<SB>H</SB>of the piezoelectric oscillator are scanned in step 120 by the frequency variable means, and the drive frequency of the piezoelectric oscillator 1 is set as the drive frequency present within a range of a prescribed reception level or a maximum reception level obtained by the reception level decision means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultrasonic sensor device used for an obstacle detection device or the like in the automobile field.

  An ultrasonic sensor device that is mounted on a vehicle such as an automobile and detects the distance between the vehicle and an obstacle at the time of parking or turning is disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-16694 (Patent Document 1) and Japanese Patent Application Laid-Open No. Hei 03. No. 24490 (Patent Document 2) and JP-A 61-186880 (Patent Document 3).

  5A and 5B are schematic views showing the ultrasonic sensor and its mounting structure disclosed in Patent Document 1, FIG. 5A is a front view, and FIG. 5B is an ultrasonic wave. It is sectional drawing in the axial direction of a sensor.

  5 (a) and 5 (b), the ultrasonic sensor 90 covers the inner casing 21 having the piezoelectric vibrator 1 attached to the bottom surface portion 21a with a vibration absorber 3 such as rubber, and the flange portion 22a. It has a structure inserted into the provided outer casing 22. The inner housing 21 is a metal can made of bottomed cylindrical aluminum or the like. As shown in FIG. 5B, the ultrasonic sensor 90 is mounted by making a hole in the vehicle bumper 10 and fitting the bottom surface portion 21a toward the outside of the vehicle so as to fit into the hole. The ultrasonic sensor 90 attached to the bumper 10 transmits the ultrasonic wave by vibrating the bottom surface portion 21 a forming the diaphragm by the piezoelectric vibrator 1, and receives the ultrasonic wave reflected by the obstacle by the same piezoelectric vibrator 1. Then, the obstacle is detected.

In the ultrasonic sensor device disclosed in Patent Document 2, measurement is performed by changing the driving energy during transmission of ultrasonic waves in two ways in order to reduce the dead zone due to the reverberation of ultrasonic waves and enable detection of short distances. Then, the presence / absence of the object to be detected and its distance are determined from each measurement result. Further, in the ultrasonic sensor device disclosed in Patent Document 3, in order to stabilize the detection of the detected object in the vicinity of the boundary of the detection area, the gain in the receiving circuit is increased as the distance to the detected object is shorter. An amplification factor varying means for reducing the size is provided.
Japanese Patent Laid-Open No. 2001-16694 Japanese Patent Laid-Open No. 03-24490 JP 61-186880 A

  In an ultrasonic sensor device including an ultrasonic sensor having a structure in which a piezoelectric vibrator is attached to one surface of a housing (for example, the inner housing 21 shown in FIG. 5B), the elastic coefficient of the housing is changed due to a temperature change. Change. Accordingly, the resonance frequency of the housing also changes from a predetermined value as the temperature changes, and the reception level of the ultrasonic wave decreases even if the detection distance to the detected object is constant. In particular, when using resin instead of metal as the housing material for cost reduction and weight reduction, the elastic coefficient changes greatly with temperature, the reception level fluctuates greatly, and the presence or absence of the detected object and its distance Detection accuracy is reduced.

  Therefore, the present invention is an ultrasonic sensor device including an ultrasonic sensor having a structure in which a piezoelectric vibrator is attached to one surface of a housing, and the detection accuracy is reduced even if the reception level varies due to a temperature change or the like. It is an object of the present invention to provide an ultrasonic sensor device that does not.

  The invention according to claim 1 includes an ultrasonic sensor having a structure in which a piezoelectric vibrator is attached to one surface of a housing, transmits ultrasonic waves from the ultrasonic sensor having the structure, and is reflected by an object to be detected. An ultrasonic sensor device that receives an ultrasonic wave with an ultrasonic sensor having the above-described structure, wherein the ultrasonic sensor that transmits the ultrasonic wave and the ultrasonic sensor that receives the ultrasonic wave include the same ultrasonic sensor, and the piezoelectric sensor A frequency variable means for changing a drive frequency of the vibrator; and a reception level determination means for judging a reception level of the ultrasonic wave. The frequency variable means scans the drive frequency of the piezoelectric vibrator and receives the reception signal. The drive frequency of the piezoelectric vibrator is set to a drive frequency within a range of a maximum reception level or a predetermined reception level obtained by the level determination means.

  According to this, in the ultrasonic sensor device, even if the elastic coefficient of the casing changes due to temperature change, and the resonance frequency of the casing fluctuates from a predetermined value accordingly, the frequency variable means and the reception level determination Using the means, the drive frequency of the piezoelectric vibrator is set to a drive frequency within the range of the maximum reception level or a predetermined reception level. Therefore, it is possible to provide an ultrasonic sensor device in which the detection accuracy does not decrease even if the reception level varies due to temperature change or the like.

As described in claim 2, wherein the ultrasonic sensor device, as the driving frequency of the piezoelectric vibrator, are determined in one of the reference drive frequency F _S is, as the reception level, one of the reference reception level R ₀ has been decided, when the reception level is lower than the reference reception level R ₀ is the drive frequency is set to the reference drive frequency F _S, the reception level is above the reference reception level R ₀ when the scanning of the driving frequency can be made to be performed includes the reference drive frequency F _S.

For example, the reference drive frequency F _S to the resonant frequency of the casing at room temperature, and the reference reception level R ₀ and is reflected by the target object in the maximum detection distance ultrasonic reception level. Thus, the presence or absence of the detected object at the maximum detection distance proximity detected by the reference drive frequency F _S, when the target object is within the distance range scans the driving frequency of the piezoelectric vibrator as the The driving frequency within the range of the maximum reception level or a predetermined reception level can be set. Therefore, it is possible to accurately detect the detected object from a long distance to a short distance.

As described in claim 3, wherein the drive frequency is selected by the scan is made from the resonant frequency of the housing, including the reference drive frequency F _S, may be two or more.

  The housing can have a plurality of resonance frequencies depending on its shape. By using the plurality of resonance frequencies as drive frequencies selected by scanning as described above, high-sensitivity detection using the resonance of the housing is possible.

Resonance frequency said selecting, for example, as described in claim 4, three, said reference drive frequency F _S is, it may be an intermediate resonance frequency of the three resonance frequencies. As a result, even when the elastic coefficient of the casing at room temperature changes depending on the temperature change, the optimum drive frequency can be selected.

The invention described in claim 5 includes an ultrasonic sensor having a structure in which a piezoelectric vibrator is attached to one surface of a housing, transmits ultrasonic waves from the ultrasonic sensor having the structure, and is reflected by an object to be detected. An ultrasonic sensor device that receives an ultrasonic wave with the ultrasonic sensor having the structure, wherein the ultrasonic sensor that transmits the ultrasonic wave and the ultrasonic sensor that receives the ultrasonic wave are different ultrasonic sensors, Amplification factor variable means for changing the amplification factor of the received signal in the ultrasonic sensor for use, and the ultrasonic wave (hereinafter referred to as “direct wave”) that directly reaches the ultrasonic sensor for reception from the ultrasonic sensor for transmission And a direct wave reception level determination means for determining the reception level of the direct wave. One reference reception level Rt ₀ is determined as the reception level of the direct wave, and the reception level of the direct wave is the reference reception level R. When in less than t _0, as the reception level of the direct wave is the reference reception level Rt ₀ or more, by the amplification factor changing means, amplification factor of the received signal is characterized in that it is set.

According to this, in the ultrasonic sensor device, a direct wave that directly reaches the receiving ultrasonic sensor from the transmitting ultrasonic sensor is used as a reference. The reception level of the direct wave is determined by the amplification factor varying means and the direct wave reception level even if the elastic coefficient of the casing in the transmitting and receiving ultrasonic sensors changes due to temperature change and the resonance frequency fluctuates from a predetermined value. Using the determination means, the amplification factor of the received signal is set so that the reference reception level Rt ₀ or higher. In other words, the amplification factor of the received signal is calibrated with a temperature change using the direct wave reference reception level as a calibration reference. By setting the amplification magnification, the reception level of the ultrasonic wave reflected from the detection object at a predetermined distance is ensured to be a predetermined value regardless of the temperature change. Therefore, even if there is a change in the reception level due to a temperature change or the like, it is possible to provide an ultrasonic sensor device in which the reception sensitivity does not change and the detection accuracy does not deteriorate.

  Preferably, the directivity of the ultrasonic sensor for transmission is wider than the directivity of the ultrasonic sensor for reception. For this purpose, for example, as described in claim 7, the one surface of the housing to which the piezoelectric vibrator in the transmission ultrasonic sensor is attached is attached to the one surface of the casing in the reception ultrasonic sensor. What is necessary is just to be smaller than one surface of the provided housing.

The invention described in claim 8 includes an ultrasonic sensor having a structure in which a piezoelectric vibrator is attached to one surface of a housing, transmits ultrasonic waves from the ultrasonic sensor having the structure, and is reflected by an object to be detected. An ultrasonic sensor device that receives an ultrasonic wave with an ultrasonic sensor having the above-described structure, wherein the ultrasonic sensor that transmits the ultrasonic wave and the ultrasonic sensor that receives the ultrasonic wave include the same ultrasonic sensor, and Amplification factor variable means for changing the amplification factor of the received signal in the acoustic wave sensor, and direct wave reception level judgment means for judging the reception level of the ultrasonic wave (hereinafter referred to as “direct wave”) at the time of transmission of the ultrasonic sensor. One reference reception level Rt ₀ is determined as the direct wave reception level. When the direct wave reception level is less than the reference reception level Rt ₀ , the direct wave reception level is in front As a reference reception level Rt ₀ or more, by the amplification factor changing means, amplification factor of the received signal is characterized in that it is set.

  In the ultrasonic sensor for both transmission and reception, not only the ultrasonic wave reflected by the object to be detected but also the ultrasonic wave at the time of transmission of the ultrasonic sensor is monitored as a received signal. Therefore, by using this direct wave as a reference, the reception sensitivity does not change even if there is a change in the reception level due to a temperature change or the like, as in the ultrasonic sensor device according to claim 5, and the detection accuracy decreases. It can be set as the ultrasonic sensor apparatus which does not do.

  As described in claim 9, the ultrasonic sensor device is suitable when the casing is made of resin.

  A housing made of resin is lighter and easier to mold than a conventional housing made of metal such as aluminum. On the other hand, the temperature change of the elastic modulus of the case made of resin is larger than that of the case made of metal. When a resin having such a large elastic coefficient of temperature change is used as the housing material of the ultrasonic sensor, the reception level fluctuates due to the temperature change as described above. Therefore, the ultrasonic sensor device in which the detection accuracy does not decrease even if the reception level varies due to a temperature change or the like is suitable for an ultrasonic sensor device including an ultrasonic sensor using a housing made of resin, Thereby, the weight reduction and cost reduction of an ultrasonic sensor apparatus can be achieved.

  The resin is preferably a polyphenylene sulfide (PPS) resin having a relatively small coefficient of thermal expansion as described in claim 10, for example. Moreover, resin containing glass fiber as a filler as described in claim 11 may be used.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
The ultrasonic sensor device according to the present embodiment is an ultrasonic sensor having a structure in which a piezoelectric vibrator is attached to one surface of a housing, similarly to the ultrasonic sensor device shown in FIGS. The ultrasonic sensor device includes an ultrasonic sensor that transmits ultrasonic waves from an ultrasonic sensor and receives ultrasonic waves reflected by a detection object using the same ultrasonic sensor. In addition, the ultrasonic sensor device according to the present embodiment includes a frequency variable unit that changes the drive frequency of the piezoelectric vibrator and a reception level determination unit that determines the reception level of the ultrasonic wave.

  The operation of the ultrasonic sensor device of the present embodiment will be described with reference to FIGS. 1 and 2A to 2C. FIG. 1 is a flowchart showing a drive frequency setting process of the ultrasonic sensor device. FIGS. 2A to 2C are diagrams showing the detected object reception level when the drive frequency of the piezoelectric vibrator is scanned.

  In the ultrasonic sensor device of the present embodiment, for example, three resonance frequencies of the casing at room temperature are used as the driving frequency of the piezoelectric vibrator. The housing can have a plurality of different resonance frequencies in this way depending on its shape. By using the resonance frequency of the housing as the driving frequency, the vibration energy of the piezoelectric vibrator can be maximized by utilizing the resonance of the housing, and highly sensitive detection is possible.

Of the three resonant frequencies used to drive the piezoelectric vibrator, for example, it determines the intermediate resonance frequency and the reference drive frequency F _S. Further, the resonance frequency on the lower frequency side than the reference drive frequency F _S is F _L , and the resonance frequency on the higher frequency side than the reference drive frequency F _S is F _H. Also, one reference reception level _R0 is determined as the reception level of the ultrasonic wave reflected by the detected object. The reference reception level _R0 is the reception level of the ultrasonic wave reflected by the detected object at the maximum detection distance.

As shown in FIG. 1, first, at step 100, it sets the driving frequency of the piezoelectric vibrator to the reference drive frequency F _S.

Then, the determination in step 110, the reception level determining unit, whether the reception level R _S of the ultrasonic wave reflected by the object to be detected or in less than the reference reception level R _0, in the reference reception level R ₀ or more To do. Here, if it is determined that the reception level R _{S of the} ultrasonic wave reflected by the detection object is lower than the reference reception level R ₀ , the process returns to step 110, and the piezoelectric vibrator is driven as it is at the reference drive frequency F _S. Is done. In other words, when the detected object is far away, since the reception level R _S is small and less than the reference reception level R ₀ , the piezoelectric vibrator continues to transmit ultrasonic waves at the reference drive frequency F _S. When the object to be detected approaches, the time from transmission to reception is shortened, and the ultrasonic reception level R _S gradually increases. If the detected object falls within the maximum detection distance range and the reception level determination means determines that the ultrasonic reception level R _S is equal to or higher than the reference reception level R ₀ , the process proceeds to the next step 120.

FIG. 2A shows an example in which the drive frequency of the piezoelectric vibrator is set to the reference drive frequency F _S and the reception level R _{S of the} ultrasonic wave reflected by the detected object is equal to or higher than the reference reception level R _0. is there. The reception level _{RS of the} ultrasonic wave reflected by the detected object indicated by the dotted line in the figure is equal to or higher than the reference reception level _R0 indicated by the dotted line on the right side of the figure.

In step 120 of FIG. 1, the frequency variable means scans the driving frequency of the piezoelectric vibrator with respect to the three resonance frequencies F _S , F _L , and F _H described above.

Next, at step 130, the reception level determination means determines the reception levels R _S , R _L , and R _{H of the} ultrasonic waves reflected by the detected object, and selects the drive frequency at the maximum reception level.

FIGS. 2A to 2C show the reception levels of ultrasonic waves reflected by the detected object when the driving frequency of the piezoelectric vibrator is scanned with respect to the three resonance frequencies F _S , F _L , and F _H , respectively. This is an example of R _S , R _L , and R _H. In FIG. 2 (a) ~ (c) , when the driving frequency is the resonant frequency _{F H} of the piezoelectric vibrator, the largest receiving level _{R H} is obtained _{(R S <R L <R} H).

Finally, in step 140 of FIG. 1, the frequency variable means sets the driving frequency of the piezoelectric vibrator to the driving frequency at the maximum reception level, and the distance to the object to be detected is the driving frequency at which the maximum sensitivity is obtained. Detected. 2A to 2C, the driving frequency of the piezoelectric vibrator is set to the resonance frequency F _{H at} which the maximum reception level _RH is obtained.

In the ultrasonic sensor apparatus shown in above FIGS 2 (a) ~ (c) , the presence or absence of the detected object at the maximum detection distance proximity detected by the reference drive frequency F _S, the object to be detected within the distance range In this case, the driving frequency of the piezoelectric vibrator is scanned as described above, and the driving frequency at the maximum reception level is set. Therefore, it is possible to accurately detect the detected object from a long distance to a short distance.

In the ultrasonic sensor device of FIG. 1, the driving frequency has three stages of F _S , F _L , and F _H , but it may be two or more stages. Further, the drive frequency at the maximum reception level is selected at step 130, and the drive frequency is set to the value at step 140. However, the present invention is not limited to this, and the drive frequency within the range of the predetermined reception level is selected. You may make it set a drive frequency to a value. Further, when the detected object is separated from the maximum detection distance, the reference driving frequency F _S may be returned to stand by for the approach of the detected object.

In the ultrasonic sensor device driven by the setting process described above, the elastic coefficient of the casing (for example, the inner casing 21 shown in FIG. 5B) changes due to a temperature change, and accordingly, the resonance frequency of the casing is predetermined. Even if the value fluctuates from this value, the drive frequency of the piezoelectric vibrator is set to the drive frequency at the maximum reception level using the frequency variable means and the reception level determination means. Therefore, it is possible to provide an ultrasonic sensor device in which the detection accuracy does not decrease even if the reception level varies due to temperature change or the like. In the ultrasonic sensor device shown in FIG. 1 and FIGS. 2A to 2C, the reference drive frequency F _S is an intermediate resonance frequency among the three resonance frequencies F _S , F _L , and F _H. . As a result, even when the elastic coefficient of the casing at room temperature changes depending on the temperature change, the optimum drive frequency can be selected.

  The ultrasonic sensor device driven by the above setting process is suitable when the casing is made of resin.

  A housing made of resin is lighter and easier to mold than a conventional housing made of metal such as aluminum. On the other hand, the temperature change of the elastic modulus of the case made of resin is larger than that of the case made of metal. When such a resin having a large temperature change in elastic modulus is used as the casing material of the ultrasonic sensor, the reception level fluctuates due to the temperature change as described in the problem to be solved by the invention. growing. Therefore, the ultrasonic sensor device in which the detection accuracy does not decrease even if the reception level varies due to a temperature change or the like is suitable for an ultrasonic sensor device including an ultrasonic sensor using a housing made of resin, Thereby, the weight reduction and cost reduction of an ultrasonic sensor apparatus can be achieved. However, the resin used for the casing of the ultrasonic sensor is preferably a polyphenylene sulfide (PPS) resin having a relatively low coefficient of thermal expansion. Moreover, the resin which contains glass fiber as a filler may be sufficient.

(Second Embodiment)
Unlike the ultrasonic sensor device according to the first embodiment, the ultrasonic sensor device according to this embodiment is an ultrasonic sensor device including two ultrasonic sensors each having a structure in which a piezoelectric vibrator is attached to one surface of a housing. is there. In the ultrasonic sensor device according to the present embodiment, ultrasonic waves are transmitted from one ultrasonic sensor, and ultrasonic waves reflected by the object to be detected are received by the other ultrasonic sensor.

  FIG. 3A is a diagram showing the arrangement of two ultrasonic sensors and the state of transmission / reception of ultrasonic waves.

  In the ultrasonic sensor device using two ultrasonic sensors for transmission and reception, as shown in FIG. 3A, the ultrasonic wave reflected by the detected object indicated by the solid arrow (hereinafter referred to as “reflection”). In addition to the “wave”, an ultrasonic wave (hereinafter referred to as “direct wave”) that directly reaches from the transmitting ultrasonic sensor indicated by a one-dot chain line arrow enters the receiving ultrasonic sensor.

  The directivity of the transmitting ultrasonic sensor in FIG. 3A is preferably wider than the directivity of the receiving ultrasonic sensor. For this purpose, for example, if the one surface of the casing to which the piezoelectric vibrator of the transmitting ultrasonic sensor is attached is smaller than the one surface of the casing to which the piezoelectric vibrator of the receiving ultrasonic sensor is attached. Good.

  The ultrasonic wave incident on the ultrasonic sensor for reception is converted into an electric signal by a piezoelectric vibrator, and is then electrically amplified at a constant magnification to become a reception signal. On the other hand, the ultrasonic sensor device according to the present embodiment includes an amplification factor variable unit that changes the amplification factor of the reception signal in the reception ultrasonic sensor, and a direct wave reception level determination unit that determines the reception level of the direct wave. is doing.

  FIG. 3B is a flowchart showing the amplification factor setting process of the reception signal in the reception ultrasonic sensor.

In the ultrasonic sensor device of the present embodiment, one reference reception level Rt ₀ is determined as the direct wave reception level.

In Figure 3 step 200 (b), determines whether the direct wave reception level determining unit, whether the reception level Rt of the direct wave is below the reference reception level Rt _0, in the reference reception level Rt ₀ or more.

FIG. 4A shows an example of the case where the direct wave reception level Rt is less than the reference reception level Rt ₀ . In the reception ultrasonic sensor shown in FIG. 3A, the reception level Rt of the direct wave that reaches fast and the reception level R of the reflected wave that arrives late are detected. The direct wave reception level Rt indicated by the dotted line in the figure is less than the reference reception level Rt ₀ indicated by the dotted line on the right side of the figure.

If it is determined in step 200 of FIG. 3B that the reception level Rt of the direct wave is equal to or higher than the reference reception level Rt ₀ , the amplification factor of the reception signal is maintained as it is. On the other hand, as shown in FIG. 4A, when the direct wave reception level Rt is determined to be less than the reference reception level Rt ₀ by the direct wave reception level determination means, the process proceeds to the next step 210.

In step 210, as the reception level Rt of the direct wave becomes a reference reception level Rt ₀ or more, the amplification factor changing means, amplification factor of the received signal is set.

FIG. 4B shows an example in which the amplification factor of the received signal is changed by the amplification factor variable means so that the reception level Rt of the direct wave in FIG. 4A is equal to or higher than the reference reception level Rt _0. It is. As can be seen by comparing FIG. 4A and FIG. 4B, when the amplification factor of the received signal is changed by the amplification factor variable means, the reception level R of the reflected wave is also similar to the reception level Rt of the direct wave. It is changed to the same amplification factor. In step 210, as the reception level Rt of the direct wave becomes a reference reception level Rt ₀ or more, was set amplification factor of the received signal. However, the present invention is not limited to this, and the amplification factor of the reception signal may be set so that the reception level Rt of the direct wave always becomes the reference reception level Rt ₀ .

In the above-described ultrasonic sensor device, a direct wave transmitted between two ultrasonic sensors for transmission and reception at a certain distance is used as a reference for determining the amplification factor of the received signal. In the direct wave reception level Rt, the elastic coefficient of the casing in the ultrasonic sensors for transmission and reception changes as the temperature changes. However, even if the resonance frequency fluctuates from a predetermined value, the direct wave reception level Rt is equal to or higher than the reference reception level Rt ₀ as described above by using the amplification factor varying unit and the direct wave reception level determination unit. The amplification factor of the received signal is set. In other words, the amplification factor of the received signal is calibrated with a temperature change using the direct wave reference reception level Rt ₀ as a calibration reference. By setting the amplification factor, the reception level R of the reflected wave from the detected object at a predetermined distance is ensured to be a predetermined value regardless of the temperature change. Therefore, the ultrasonic sensor device of the present embodiment can also be an ultrasonic sensor device in which the reception sensitivity does not change and the detection accuracy does not deteriorate even if the reception level varies due to a temperature change or the like. .

(Third embodiment)
The ultrasonic sensor device according to the second embodiment is an ultrasonic sensor device that includes two ultrasonic sensors for transmission and reception, and an ultrasonic wave that directly reaches the ultrasonic sensor for reception from the ultrasonic sensor for transmission. The ultrasonic sensor device calibrates the amplification factor of the received signal with reference to the above. The ultrasonic sensor device according to the present embodiment achieves the same effect in an ultrasonic sensor device that includes one ultrasonic sensor for both transmission and reception.

  In the transmission / reception ultrasonic sensor, not only the ultrasonic wave reflected by the object to be detected but also the ultrasonic wave at the time of transmission of the ultrasonic sensor (hereinafter referred to as “direct wave”) is monitored as a reception signal. Therefore, by using this direct wave as a reference, the reception sensitivity does not change and the detection accuracy is improved even if there is a change in the reception level due to a temperature change or the like, as in the ultrasonic sensor device described in the second embodiment. It can be set as the ultrasonic sensor apparatus which does not fall. The received signal amplification factor setting process and the obtained effects are the same as those described in the second embodiment, and a detailed description thereof will be omitted.

It is a flowchart which shows the drive frequency setting process of the ultrasonic sensor apparatus of 1st Embodiment. (A)-(c) is a figure which shows the to-be-detected object reception level when the drive frequency of a piezoelectric vibrator is scanned in the ultrasonic sensor apparatus of 1st Embodiment. (A) is a figure which shows the mode of arrangement | positioning of two ultrasonic sensors, and the state of transmission / reception of an ultrasonic wave in the ultrasonic sensor apparatus of 2nd Embodiment. (B) is a flow chart showing amplification factor setting processing of a received signal in a receiving ultrasonic sensor. (A) is an example in the case where the direct wave reception level Rt is less than the reference reception level Rt ₀ in the ultrasonic sensor device of the second embodiment. (B) is an example when the amplification factor of the received signal is changed by the amplification factor varying means so that the reception level Rt of the direct wave in (a) is equal to or higher than the reference reception level Rt ₀ . (A), (b) is a schematic diagram which shows an ultrasonic sensor and its mounting structure, (a) is a front view, (b) is sectional drawing in the axial direction of an ultrasonic sensor.

Explanation of symbols

90 Ultrasonic sensor 1 Piezoelectric vibrator 21 Inner housing 21a Bottom surface part 10 Bumper

Claims (11)

An ultrasonic sensor with a structure in which a piezoelectric vibrator is attached to one surface of the housing,
An ultrasonic sensor device that transmits ultrasonic waves from the ultrasonic sensor having the structure and receives ultrasonic waves reflected by a detection object by the ultrasonic sensor having the structure,
The ultrasonic sensor that transmits the ultrasonic wave and the ultrasonic sensor that receives the ultrasonic wave are the same ultrasonic sensor,
Frequency variable means for changing the drive frequency of the piezoelectric vibrator;
Reception level determination means for determining the reception level of the ultrasonic wave,
The frequency variable means scans the driving frequency of the piezoelectric vibrator,
The ultrasonic sensor device, wherein the drive frequency of the piezoelectric vibrator is set to a drive frequency within a range of a maximum reception level or a predetermined reception level obtained by the reception level determination means. Wherein as the driving frequency of the piezoelectric vibrator, a reference drive frequency F _S has been determined,
As the reception level, one reference reception level R ₀ is determined,
When the reception level is less than the reference reception level R ₀ , the drive frequency is set to the reference drive frequency F _S ;
Wherein when the reception level is above the reference reception level R ₀ is the scan of the drive frequency, ultrasonic sensor device according to claim 1, characterized in that it is made comprising said reference drive frequency F _S. The drive frequency selected by the scanning is composed of the resonance frequency of the housing,
The selected the resonance frequency, including the reference drive frequency F _S, the ultrasonic sensor device according to claim 2, characterized in that two or more. The selected resonant frequencies are three;
The reference drive frequency F _S is, among the three resonance frequencies, the ultrasonic sensor device according to claim 3, characterized in that an intermediate resonance frequency. An ultrasonic sensor with a structure in which a piezoelectric vibrator is attached to one surface of the housing,
An ultrasonic sensor device that transmits ultrasonic waves from the ultrasonic sensor having the structure and receives ultrasonic waves reflected by a detection object by the ultrasonic sensor having the structure,
The ultrasonic sensor that transmits the ultrasonic wave and the ultrasonic sensor that receives the ultrasonic wave are composed of different ultrasonic sensors,
Amplification magnification variable means for changing the amplification magnification of the received signal in the reception ultrasonic sensor;
Direct wave reception level determination means for determining a reception level of an ultrasonic wave (hereinafter referred to as “direct wave”) that directly reaches the reception ultrasonic sensor from the transmission ultrasonic sensor;
A reference reception level Rt ₀ is determined as the reception level of the direct wave,
Wherein when the reception level of the direct wave is less than the reference reception level Rt _0, as the reception level of the direct wave is the reference reception level Rt ₀ or more, by the amplification factor changing means, amplification of the received signal An ultrasonic sensor device in which a magnification is set.   The ultrasonic sensor device according to claim 5, wherein the directivity of the ultrasonic sensor for transmission is wider than the directivity of the ultrasonic sensor for reception.   The one surface of the casing to which the piezoelectric vibrator of the ultrasonic sensor for transmission is attached is smaller than the one surface of the casing to which the piezoelectric vibrator of the ultrasonic sensor for reception is attached. Item 7. The ultrasonic sensor device according to Item 6. An ultrasonic sensor with a structure in which a piezoelectric vibrator is attached to one surface of the housing,
An ultrasonic sensor device that transmits ultrasonic waves from the ultrasonic sensor having the structure and receives ultrasonic waves reflected by a detection object by the ultrasonic sensor having the structure,
The ultrasonic sensor that transmits the ultrasonic wave and the ultrasonic sensor that receives the ultrasonic wave are the same ultrasonic sensor,
Amplification magnification variable means for changing the amplification magnification of the received signal in the ultrasonic sensor;
Direct wave reception level determination means for determining a reception level of ultrasonic waves (hereinafter referred to as “direct wave”) at the time of transmission of the ultrasonic sensor;
A reference reception level Rt ₀ is determined as the reception level of the direct wave,
Wherein when the reception level of the direct wave is less than the reference reception level Rt _0, as the reception level of the direct wave is the reference reception level Rt ₀ or more, by the amplification factor changing means, amplification of the received signal An ultrasonic sensor device in which a magnification is set.   The ultrasonic sensor device according to claim 1, wherein the housing is made of resin.   The ultrasonic sensor device according to claim 9, wherein the resin is polyphenylene sulfide (PPS) resin.   The ultrasonic sensor device according to claim 9 or 10, wherein the resin contains glass fiber as a filler.

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