JP5732616B2 - Intrusion sensor - Google Patents

Description

The present invention relates to intrusion sensor relates intrusion sensor using ultrasonic sensor for detecting an object in particular using ultrasound.

  Document 1 (Japanese Patent Laid-Open No. 2008-151506) discloses a moving body detection device (object detection device) using an ultrasonic sensor that detects an object (moving body) using ultrasonic waves. The ultrasonic sensor includes a transmitter that outputs an ultrasonic wave and a receiver that receives the ultrasonic wave. The transmitter is, for example, an ultrasonic speaker that converts an electrical signal into an ultrasonic wave. The receiver is an ultrasonic microphone that converts ultrasonic waves into electrical signals. The mobile body detection device is installed in the vehicle in order to prevent theft of the vehicle and theft on the vehicle, for example.

  When such a moving body detection apparatus is installed in a vehicle, a baffle is disposed in front of the electroacoustic transducer to hide the electroacoustic transducer. The baffle has an opening for passing ultrasonic waves. Therefore, there is a possibility that foreign matters such as dust enter the baffle through the opening and adhere to the electroacoustic transducer. If foreign matter adheres to the electroacoustic transducer, the ultrasonic characteristics may change.

  In addition, the dimension in the horizontal direction (the longitudinal direction and the lateral direction of the vehicle) is larger in the vehicle (the space in which the object detection device wants to detect an object) than in the height direction. However, conventionally proposed transmitters and receivers have uniform directivity. That is, the directivity is constant regardless of the angle in a plane parallel to the front direction (directivity 0 ° direction) of the transmitter or receiver. Therefore, if a transmitter or a receiver is selected according to the horizontal dimension in the vehicle, the directivity becomes too wide compared to the height dimension in the vehicle. Conversely, if a transmitter or receiver is selected according to the height dimension in the vehicle, the directivity becomes too narrow compared to the horizontal dimension in the vehicle.

The present invention has been made in view of the above circumstances. An object of the present invention is to provide an intrusion sensor that can suppress wasteful power consumption and can prevent foreign matter from adhering to an electroacoustic transducer of an ultrasonic sensor.

The intrusion sensor according to the present invention is an intrusion sensor that is attached to a structure in a vehicle such as an automobile and detects an intruder who has entered the inside of the vehicle. An intrusion sensor according to the present invention includes an electroacoustic transducer that converts an electrical signal into an ultrasonic wave or an ultrasonic wave into an electric signal, and detects the object using the ultrasonic wave, and the electric sensor. A baffle for protecting the acoustic transducer. The electroacoustic transducer has a circular sound hole through which the ultrasonic waves pass. The baffle includes a plate-like mask that covers the front surface of the electroacoustic transducer, an opening formed in the mask through which the ultrasonic waves pass, and a plurality of the openings arranged in the opening along a predetermined direction. And a bar that is divided into slits. The opening is formed in a quadrilateral shape having different vertical and horizontal lengths. The size of the opening is smaller than the size of the sound hole. The vertical length of the opening is less than 8 mm and less than 80% of the diameter of the sound hole. The horizontal length of the opening is 4 mm or less. The width of the bar is not more than about 1.5 times the width of the slit.

  In this case, the slits are preferably arranged along the lateral direction of the opening. Or it is preferable that the said slit is located in a line along the vertical direction of the said opening.

  In this case, it is preferable that a recess is formed on the front surface of the mask, and the opening is formed on the bottom surface of the recess.

Preferably, the angle between the normal direction of the inner surface of the opening and the thickness direction of the mask is an acute angle .

(A) is sectional drawing which shows the transmitter and baffle of the intrusion sensor of one Embodiment of this invention, (b) is a front view of an intrusion sensor . It is a block diagram of the ultrasonic sensor used for an intrusion sensor . It is a graph which shows the horizontal directivity of an ultrasonic wave. It is a graph which shows the vertical directivity of an ultrasonic wave. It is a graph which shows the vertical directivity of an ultrasonic wave. It is a graph which shows the frequency dependence of the sound pressure of the front of an ultrasonic wave. It is a graph which shows the relationship between the sound pressure of the front of an ultrasonic wave, and opening thickness. It is a graph which shows the directivity of an ultrasonic wave. It is a graph which shows the frequency dependence of the sound pressure of the front of an ultrasonic wave. It is a figure which shows the modification of a baffle. It is a figure which shows the modification of a baffle. (A), (b) is a figure which shows the modification of a baffle. (A), (b) is a figure which shows the modification of a baffle. (A), (b) is a figure which shows the modification of a baffle. (A), (b), (c) is a figure which shows the modification of a baffle. (A), (b) is sectional drawing which shows the modification of a baffle.

The intrusion sensor according to an embodiment of the present invention is used as an intrusion sensor that detects an intruder (suspicious person) who has entered a vehicle such as an automobile. In the present embodiment, the intrusion sensor is attached to a structure in the vehicle. The structure in the vehicle includes, for example, an overhead module (overhead console) installed on a ceiling of a car, a room lamp, a pillar (for example, an A pillar, a B pillar, a C pillar, a D pillar, etc.), a ceiling surface, Walls, dashboards and backdoors.

As shown in FIGS. 1 and 2, the intrusion sensor of the present embodiment includes an ultrasonic sensor 10 that detects an object (intruder) existing in a monitoring space (for example, in a vehicle) using ultrasonic waves.

  As shown in FIG. 2, the ultrasonic sensor 10 includes a transmitter 11, an oscillator 12, a drive circuit 13, a receiver 14, a receiver circuit 15, a phase detector circuit 16, and a calculator 17. .

  The transmitter 11 is configured to generate ultrasonic waves (transmitted waves). The transmitter 11 is, for example, an ultrasonic speaker, that is, an electroacoustic transducer that converts an electric signal into an ultrasonic wave. The transmitter 11 is configured to output an ultrasonic wave forward (upward in FIG. 1A). In the present embodiment, the transmitter 11 has a sound hole (opening) 111 through which an ultrasonic wave passes, as shown in FIG. The sound hole 111 of the transmitter 11 has a circular shape (circular shape). The diameter of the sound hole 111 (opening diameter of the transmitter 11) is, for example, 10 mm. However, the shape of the sound hole 111 is not limited to a perfect circle shape.

  The oscillator 12 is configured to output an oscillation signal (transmitted signal) having a predetermined oscillation frequency (for example, 40 kHz).

  The drive circuit 13 is configured to cause the transmitter 11 to generate an ultrasonic wave having a frequency equal to the oscillation frequency of the oscillation signal by driving the transmitter 11 using the oscillation signal output from the oscillator 12. .

  The receiver 14 receives ultrasonic waves (reflected waves, received waves) reflected by an object existing in the monitoring space after being output from the transmitter 11 to the monitoring space, and an electrical signal corresponding to the received ultrasonic waves. (Received signal) is output. The receiver 14 is, for example, an ultrasonic microphone, that is, an electroacoustic transducer that converts ultrasonic waves into electric signals. In the present embodiment, the receiver 14 has a sound hole (not shown) through which an ultrasonic wave passes on the front surface. The sound hole of the receiver 14 has a circular shape (a perfect circular shape). The diameter of the sound hole of the receiver 14 (opening diameter of the receiver 14) is, for example, 10 mm. However, the shape of the sound hole of the receiver 14 is not limited to a perfect circle shape.

  The transmitter 11 and the receiver 14 may be combined with an ultrasonic transducer that is an electroacoustic transducer that converts an electric signal into an ultrasonic wave and converts an ultrasonic wave into an electric signal.

  The receiving circuit 15 is configured to amplify the received signal received from the receiver 14, shape the waveform of the received signal, and output the waveform to the phase detection circuit 16.

  The phase detection circuit 16 mixes the reception signal received from the reception circuit 15 and the transmission signal received from the oscillator 12 to have a beat corresponding to the phase difference between the reception signal and the transmission signal. A phase detection signal (Doppler signal) is generated and output to the computing unit 17.

  The computing unit 17 is configured to obtain the amount of movement of the object based on the Doppler signal obtained from the phase detection circuit 16. When the value indicating the amount of movement of the object exceeds a predetermined value, the computing unit 17 is configured to determine that a moving body (intruder) exists in the monitoring space and output a detection signal. The computing unit 17 is configured using a microcomputer.

In addition, the intrusion sensor of this embodiment includes a baffle (acoustic mask) 20 that is a cover that protects the transmitter 11 of the ultrasonic sensor 10. The baffle 20 functions as a horn for adjusting the directivity of the electroacoustic transducer (transmitter 11 or receiver 14).

  The baffle 20 is arrange | positioned ahead of the transmitter 11 of the ultrasonic sensor 10, as shown to Fig.1 (a). In FIG. 1A, the baffle 20 and the transmitter 11 are in contact with each other, but the baffle 20 may be disposed away from the transmitter 11.

  The baffle 20 includes a mask 21, an opening 22, and a bar 23.

  The mask 21 is formed in a plate shape. The material of the mask 21 is, for example, metal or resin. For example, the mask 21 is formed in a square plate shape with a side of 25 mm. The P.4 thickness of the mask 21 is not less than 1.00 mm and not more than 1.50 mm. In the present embodiment, the thickness of the mask 21 is 1.25 mm. The mask 21 may be formed in a square plate shape having a side of 130 mm. In short, the mask 21 may be of a size that can cover the front surface of the transmitter 11 and hide the transmitter 11.

  The opening 22 is formed in the mask 21 for passing the ultrasonic wave generated by the transmitter 11 of the ultrasonic sensor 10. The size of the opening 22 is smaller than the size of the sound hole 111 of the transmitter 11. The opening 22 has a quadrilateral shape as shown in FIG.

  In the present embodiment, the opening 22 has a rectangular shape with different vertical and horizontal lengths. That is, the opening 22 is an elongated hole. Hereinafter, the vertical length (long axis direction) of the opening 22 is referred to as an opening length L, and the horizontal length (short axis direction) of the opening 22 is referred to as an opening width D. The thickness of the opening 22 is referred to as an opening thickness T.

  In this embodiment, the opening length L is 7 mm, the opening width D is 3 mm, and the opening thickness T is 1.25 mm. In the present embodiment, the thickness of the opening 22 is equal to the thickness of the mask 21, the bar 23, and the slit 24.

In this embodiment, since the intruder is detected using ultrasonic waves, it is preferable that the directivity of the ultrasonic waves is wide. For example, when the intrusion sensor is used in a vehicle, the half-value angle of directivity in the horizontal direction is preferably 140 ° or more, particularly 160 ° or more.

  FIG. 3 is a graph showing the directivity in the horizontal direction of the opening 22 (hereinafter abbreviated as “lateral directivity”). The horizontal axis is the angle [deg], and the vertical axis is the gain [dB] of the ultrasonic intensity (sound pressure). The reference for the gain is the sound pressure of the ultrasonic wave when there is no baffle 20.

  The graph D0 shows the horizontal directivity of the ultrasonic wave when the baffle 20 is not provided. The graph D1 shows the horizontal directivity of the ultrasonic wave when the opening width D is 7 mm. The graph D2 shows the horizontal directivity of the ultrasonic wave when the opening width D is 5 mm. A graph D3 shows the horizontal directivity of the ultrasonic wave when the opening width D is 3 mm.

  As is clear from the graph of FIG. 3, it can be seen that the lateral directivity of the ultrasonic wave becomes wider as the opening width D becomes smaller.

  Further, according to the result of the experiment, when the opening width D exceeds 4 mm, the half-value angle decreases rapidly. Therefore, in order to make the half-value angle 155 ° or more, the opening width D is preferably 4 mm or less. Note that the temperature characteristics (temperature characteristics in the range of −40 ° C. to + 85 ° C.) do not change greatly due to the change in the opening width D. If the opening width D is at least 3 mm to 5 mm, the temperature characteristics are ± 1 dB. Within the range of.

  FIG. 4 is a graph showing the directivity of ultrasonic waves in the vertical direction of the opening 22 (hereinafter abbreviated as “vertical directivity”). The horizontal axis is the angle [deg], and the vertical axis is the ultrasonic sound pressure gain [dB]. The reference for the gain is the sound pressure of the ultrasonic wave when there is no baffle 20.

  The graph F0 shows the vertical directivity of the ultrasonic wave when the baffle 20 is not present. Graph F1 shows the vertical directivity of the ultrasonic wave whose frequency is 38 kHz. Graph F2 shows the vertical directivity of the ultrasonic wave whose frequency is 40 kHz. Graph F3 shows the vertical directivity of the ultrasonic wave having a frequency of 42 kHz. Graph F4 shows the longitudinal directivity of the ultrasonic wave having a frequency of 44 kHz. Graph F5 shows the longitudinal directivity of the ultrasonic wave having a frequency of 46 kHz. In addition, in the graphs F1-F5 shown in FIG. 4, the opening length L of the opening 22 of the baffle 20 is 9 mm.

Normally, even if the frequency of the ultrasonic wave changes, the shape of the ultrasonic wave directivity does not change, only the size thereof changes. However, as is apparent from the graph of FIG. 4, depending on the aperture length L, a large frequency dependence occurs in the directivity of ultrasonic waves (mainly vertical directivity). In particular, in the graph F3, unlike the other graphs F1, F2, F4, and F5, a valley is generated in the vicinity of 0 °. As described above, when the vertical directivity greatly changes depending on the frequency of the ultrasonic wave, the detection range of the intrusion sensor changes greatly, and the performance becomes unstable.

  Here, there is a correlation between the frequency and the sound speed, and the sound speed depends on the temperature. Therefore, the frequency of the ultrasonic wave output from the transmitter 11 varies depending on the temperature. That is, frequency dependence (frequency characteristics) can be considered synonymous with temperature dependence (temperature characteristics).

Therefore, in order for the intrusion sensor to exhibit stable performance under various environments, it is necessary to stabilize the temperature characteristics.

  FIG. 5 is a graph showing the vertical directivity of ultrasonic waves. The horizontal axis is the angle [deg], and the vertical axis is the ultrasonic sound pressure gain [dB]. The reference for the gain is the sound pressure of the ultrasonic wave when there is no baffle 20.

  The graph L0 shows the vertical directivity of the ultrasonic waves when the baffle 20 is not present. The graph L11 shows the vertical directivity of the ultrasonic wave when the opening length L is 9 mm. The graph L12 shows the longitudinal directivity of the ultrasonic wave when the opening length L is 8 mm. Show directivity. The graph L13 shows the vertical directivity of the ultrasonic wave when the opening length L is 7 mm. Show directivity. The graph L14 shows the vertical directivity of the ultrasonic wave when the opening length L is 6 mm. In the graph shown in FIG. 5, the frequency of the ultrasonic wave is 42 kHz.

  As apparent from the graph of FIG. 5, when the opening length L is 8 mm or more, a valley is generated in the vicinity of the 0 ° direction.

  Next, FIG. 6 shows the frequency dependence of the sound pressure in front of the ultrasonic waves. The horizontal axis represents the ultrasonic frequency [kHz], and the vertical axis represents the sound pressure gain [dB] in front of the ultrasonic waves. In addition, the reference | standard of a gain is the sound pressure of the front surface of an ultrasonic wave when the baffle 20 is not provided.

  In FIG. 6, the graph L21 shows the frequency dependence of the sound pressure in front of the ultrasonic wave when the opening length L is 9 mm. The graph L22 shows the frequency dependence of the sound pressure in front of the ultrasonic wave when the opening length L is 8 mm. The graph L23 shows the frequency dependence of the sound pressure in front of the ultrasonic wave when the opening length L is 7 mm. The graph L24 shows the frequency dependence of the sound pressure in front of the ultrasonic wave when the opening length L is 6 mm.

  As apparent from the graph of FIG. 6, it was found that the frequency characteristics were stabilized when the opening length L was less than 8 mm. As described above, frequency characteristics and temperature characteristics are synonymous. Therefore, in order to obtain stable temperature characteristics, the opening length L is preferably less than 8 mm, and particularly preferably the opening length L is 7 mm or less. Here, the opening diameter of the transmitter 11 used in the experiment is 10 mm. Therefore, in other words, the opening length L is preferably less than 80% of the opening diameter of the transmitter 11, and more preferably 70% or less of the opening diameter of the transmitter 11. This also applies to the receiver 14. That is, the opening length L is preferably less than 80% of the opening diameter of the electroacoustic transducer, and particularly preferably 70% or less of the opening diameter of the electroacoustic transducer.

  FIG. 7 is a graph showing the relationship between the sound pressure in front of the ultrasonic wave and the opening thickness T. The horizontal axis is the opening thickness T [mm], and the vertical axis is the gain [dB] of the ultrasonic intensity (sound pressure). The reference for the gain is the sound pressure of the ultrasonic wave when there is no baffle 20.

  As is apparent from the graph of FIG. 7, the gain is maximized when the opening thickness T is 1.25 mm. Further, when the opening thickness T is in the range of 1.0 mm to 1.5, the gain change is small. Therefore, if the opening thickness T is set to 1.0 mm or more and 1.5 or less, a change in gain due to a molding error of the baffle 20 can be suppressed.

  The bar 23 is formed in a straight line shape. The bar 23 is formed integrally with the mask 21, for example. The bar 23 is disposed in the opening 22 so as to divide the opening 22 into a plurality of slits 24 arranged along a predetermined direction. The baffle 20 of this embodiment includes one bar 23 that crosses the opening 22 in the vertical direction (long axis direction). Therefore, the opening 22 is divided into two slits 24 arranged along the minor axis direction. The bar 23 is disposed so as to pass through the center of the opening 22. Therefore, the widths d2 of the two slits 24 are equal to each other.

  When the baffle 20 having the shape shown in FIG. 1B was examined for the influence of the width d1 of the bar 23 on the directivity (vertical directivity) of the ultrasonic wave, the results shown in FIGS.

  FIG. 8 shows the directivity (vertical directivity) of ultrasonic waves. The horizontal axis is the angle [deg], and the vertical axis is the sound pressure gain [dB] in front of the ultrasonic waves. The reference for the gain is the sound pressure of the ultrasonic wave when there is no baffle 20.

  Graph B11 shows the directivity of the ultrasonic wave when the width d1 of the bar 23 is 1.0 mm. Graph B12 shows the directivity of the ultrasonic wave when d1 is 1.2 mm. Graph B13 shows the directivity of the ultrasonic wave when d1 is 1.4 mm. Graph B14 shows the directivity of the ultrasonic wave when d1 is 1.6 mm. Graph B15 shows the directivity of the ultrasonic wave when d1 is 2.0 mm. Graph B16 shows the directivity of the ultrasonic wave when d1 is 2.5 mm. The opening width D is 4 mm, and the widths d2 of the two slits 24 are equal to each other. The frequency of the ultrasonic wave is 42 kHz.

  As is apparent from the graph of FIG. 8, if the width d1 of the bar 23 is 2.0 mm or less, the presence of the bar 23 hardly affects the gain. However, when the width d1 of the bar 23 is 2.5 mm, the gain is greatly reduced.

  Therefore, when the opening width D = 4.0 mm, the width d1 of the bar 23 is 2.0 mm or less, that is, D / 2 or less (the width d2 of the slit 24 is 1.0 mm or more). There is no adverse effect on directivity. That is, with respect to directivity, d1 ≦ 2 × d2 may be satisfied.

  FIG. 9 shows the frequency dependence of the sound pressure in front of the ultrasonic waves. The horizontal axis represents the ultrasonic frequency [kHz], and the vertical axis represents the sound pressure gain [dB] in front of the ultrasonic waves. In addition, the reference | standard of a gain is the sound pressure of the front surface of an ultrasonic wave when the baffle 20 is not provided.

  Graph B21 shows the frequency dependence of the sound pressure in front of the ultrasonic wave when the width d1 of the bar 23 is 1.0 mm. Graph B22 shows the frequency dependence of the sound pressure in front of the ultrasonic wave when d1 is 1.2 mm. Graph B23 shows the frequency dependence of the sound pressure in front of the ultrasonic wave when d1 is 1.4 mm. Graph B24 shows the frequency dependence of the sound pressure in front of the ultrasonic wave when d1 is 1.6 mm. Graph B25 shows the frequency dependence of the sound pressure in front of the ultrasonic wave when d1 is 2.0 mm. Graph B26 shows the frequency dependence of the sound pressure in front of the ultrasonic wave when d1 is 2.5 mm.

As is apparent from the graph of FIG. 9, if the width d1 of the bar 23 is 1.6 mm or less, the presence of the bar 23 hardly affects the frequency characteristics of the ultrasonic waves. While either the tooth, the width d1 of the bar 23 is equal to or greater than 2.0 mm, the gain is reduced as the frequency increases.

  Therefore, when the opening width D = 4.0 mm, if the width d1 of the bar 23 is 1.6 mm or less, that is, 2/5 × D or less (the width d2 of the slit 24 is 1.2 mm or more), There is no adverse effect on the temperature characteristics of the ultrasonic waves. That is, regarding temperature characteristics, d1 ≦ 4/3 × d2 may be satisfied.

  As a result of repeating the same experiment, if the width d1 of the bar 23 is about 1.5 times or less the width d1 of the slit 24, the temperature characteristics of the transmitter 11 of the ultrasonic sensor 10 due to the presence of the bar 23. And the result that directivity did not deteriorate was obtained. In particular, the width d1 of the bar 23 is preferably not more than 1.5 times the width d1 of the slit 24.

As described above, the intrusion sensor of the present embodiment includes the ultrasonic sensor 10 that includes the transmitter 11 that converts an electrical signal into an ultrasonic wave and detects an object using the ultrasonic wave, and the transmitter 11. Baffle 20 to protect. The transmitter 11 has a sound hole 111 through which an ultrasonic wave passes. The baffle 20 includes a plate-like mask 21 that covers the front surface of the transmitter 11, and an opening 22 that is formed in the mask 21 and allows the ultrasonic waves generated by the transmitter 11 to pass through. The opening 22 is formed in a quadrilateral shape with different vertical and horizontal lengths. The size of the opening 22 is smaller than the size of the sound hole 111.

According to the intrusion sensor of the present embodiment, the opening 22 is formed in a quadrilateral shape having different vertical and horizontal lengths. In this case, the directivity becomes narrow in the vertical direction of the opening 22 and the directivity becomes wide in the horizontal direction of the opening 22. In general, the height dimension (vertical dimension) is smaller than the width dimension (horizontal dimension) inside the vehicle. Therefore, the detection range of the intrusion sensor can be set to a range according to the shape of the interior of the automobile. Therefore, by installing the baffle 20 so that the vertical direction of the opening 22 coincides with the height direction in the vehicle, the directivity of the ultrasonic wave of the intrusion sensor is narrow in the vehicle height direction and in the vehicle width direction. Can be wide. In this way, ultrasonic waves can be output in a necessary and sufficient range within the vehicle. Therefore, ultrasonic energy can be used efficiently, and wasteful power consumption can be suppressed. Moreover, since the size of the opening 22 is smaller than the size of the sound hole 111, it is possible to prevent foreign matter from adhering to the electroacoustic transducer (transmitter 11) of the ultrasonic sensor 10. Further, the transmitter 11 can be made inconspicuous as compared with the case where the size of the opening 22 is larger than the size of the sound hole 111.

  Note that the baffle 20 may be disposed only in front of the receiver 14 that is an electroacoustic transducer that converts ultrasonic waves into an electrical signal. In this case, the mask 21 of the baffle 20 is formed in a size that can cover the front surface of the receiver 14 and hide the receiver 14. Further, the size of the opening 22 is smaller than the size of the sound hole of the receiver 14. A baffle 20 may be disposed in front of each of the transmitter 11 and the receiver 14. In short, the baffle 20 is used to protect an electroacoustic transducer that converts an electric signal into an ultrasonic wave or an ultrasonic wave into an electric signal.

  The opening length L is preferably less than 8 mm. In particular, the opening length L is preferably 7 mm or less. By making the opening length L 7 mm or less, it is possible to prevent the temperature characteristics from deteriorating. The lower limit value of the opening length L is the opening width D.

Further, in the intrusion sensor of the present embodiment, the baffle 20 has a linear bar 23 that is disposed in the opening 22 and divides the opening 22 into a plurality of slits 24 arranged along a predetermined direction. The width d1 of the bar 23 is about 1.5 times or less than the width d2 of the slit 24.

According to the intrusion sensor of the present embodiment, since the bar 23 is disposed in the opening 22, foreign substances such as dust can be prevented from adhering to the transmitter 11 of the ultrasonic sensor 10 through the opening 22. Therefore, it is possible to prevent the performance of the ultrasonic sensor 10 from being deteriorated due to adhesion of foreign matter. In addition, as described above, the temperature characteristics and directivity do not deteriorate due to the bar 23. Therefore, it is possible to prevent foreign matter from adhering to the transmitter 11 of the ultrasonic sensor 10 while maintaining temperature characteristics and directivity. By providing the bar 23 as described above, the transmitter 11 can be made inconspicuous, and the design can be improved.

  Note that the widths of the slits 24 are not necessarily equal to each other. Similarly, the widths of the bars 23 are not necessarily equal to each other. In short, the width of the widest bar 23 may be about 1.5 times or less the width of the narrowest slit 24.

  By the way, in the example shown in FIG.1 (b), the shape of the opening 22 is a rectangular shape. However, the shape of the opening 22 may be a quadrilateral shape as shown in FIG. 10, for example, or may be a circular shape as shown in FIG. Further, the shape of the opening 22 may be a square shape or an elliptical shape. Furthermore, the shape of the opening 22 may be a quadrilateral shape with a corner as shown in FIGS.

  In the example shown in FIG. 1B, the number of bars 23 is one. However, as shown in FIG. 12A, the number of bars 23 may be two. In short, a plurality of bars 23 may be provided. Therefore, the number of slits 24 may be three or more.

  In the example shown in FIG. 12A, the slits 24 (bars 23) are arranged along the lateral direction (short axis direction) of the opening 22. However, as shown in FIG. 12B, the slits 24 (bars 23) may be arranged along the longitudinal direction (major axis direction) of the opening 22.

  Further, as shown in FIG. 13A, a recess 25 may be formed on the front surface of the mask 21. In FIG. 13A, a slit 24 (opening 22) is formed on the bottom surface of the recess 25. The recess 25 is provided to adjust the thickness of the opening 22 (opening thickness T). In this way, the thickness of the mask 22 can be made larger than the thickness of the opening 22. Therefore, the thickness of the opening 22 can be set to a desired size, for example, 1.0 mm to 1.5 mm as described above, while increasing the mechanical strength of the mask 21.

  Further, as shown in FIG. 13B, a groove 26 may be formed on the front surface of the mask 21. However, the groove 26 is preferably arranged so as not to be aligned with the opening 22 in a direction in which the directivity of ultrasonic waves is to be expanded. For example, when it is desired to increase the lateral directivity, it is preferable that the groove 26 and the opening 22 are not aligned in the short axis direction of the opening 22.

  In addition, as shown to Fig.14 (a), (b), the baffle 20 does not necessarily need to be provided with the bar 23. FIG.

  Further, as shown in FIG. 15A, the slits 24 may be arranged in the vertical direction and the horizontal direction of the opening 22. In the example shown in FIG. 15A, the baffle 20 has a bar 23 (231) that divides the opening 22 into two slits 24 arranged in the horizontal direction and a bar that divides the opening 22 into two slits 24 arranged in the vertical direction. 23 (232).

  Further, as shown in FIG. 15B, the shape of the bar 23 is not necessarily a straight line. In the example shown in FIG. 15B, the opening 22 is formed in a quadrilateral shape with a corner, and the slit 24 is formed in an elliptical shape. In the example shown in FIG. 15B, the width d2 of the slit 24 is the length in the minor axis direction.

  Moreover, as shown in FIG.15 (c), the slit 24 may be formed in the perfect circle shape. In the example shown in FIG. 15C, the opening 22 is formed in a quadrilateral shape with a corner. The baffle 20 includes a bar 23 (231) that divides the opening 22 into two slits 24 arranged in the horizontal direction, three bars 23 (232) that divide the opening 22 into four slits 24 arranged in the vertical direction, It has.

  In the example shown in FIG. 1B, the angle between the normal direction of the inner surface of the opening 22 and the thickness direction of the mask 21 (vertical direction in FIG. 1B) is a right angle. In other words, the thickness direction of the opening 22 matches the thickness direction of the mask 21.

  However, as shown in FIG. 16A, the inner surface of the opening 22 may be inclined. That is, the angle between the normal direction of the inner surface of the opening 22 and the thickness direction of the mask 21 may be an acute angle. In other words, the thickness direction of the opening 22 and the thickness direction of the mask 21 may intersect. In this way, it is possible to prevent foreign matter from entering the baffle 20 through the opening 22.

  Further, the inner surface of the opening 22 may be formed stepwise along the thickness direction of the mask 22 as shown in FIG. If it does in this way, it can control that a foreign material penetrates into baffle 20 through opening 22 like the example shown in Drawing 16 (a).

Claims (5)

An intrusion sensor that is attached to a structure in a vehicle such as an automobile and detects an intruder that has entered the inside of the vehicle,
An ultrasonic sensor having an electroacoustic transducer for converting an electric signal into an ultrasonic wave or an ultrasonic wave into an electric signal, and detecting an object using the ultrasonic wave;
A baffle for protecting the electroacoustic transducer,
The electroacoustic transducer has a circular sound hole on the front surface through which the ultrasonic wave passes,
The baffle is
A plate-like mask covering the front surface of the electroacoustic transducer;
An opening formed in the mask and through which the ultrasonic waves pass;
A bar arranged in the opening and dividing the opening into a plurality of slits arranged in a predetermined direction,
The opening is formed in a quadrilateral shape with different vertical and horizontal lengths,
The size of the opening is smaller than the size of the sound hole,
The vertical length of the opening is less than 8 mm and less than 80% of the diameter of the sound hole;
The lateral length of the opening is 4 mm or less,
The intrusion sensor according to claim 1, wherein the width of the bar is not more than about 1.5 times the width of the slit. The intrusion sensor according to claim 1, wherein the slits are arranged along a lateral direction of the opening. The intrusion sensor according to claim 1, wherein the slits are arranged along a vertical direction of the opening. A recess is formed on the front surface of the mask,
The intrusion sensor according to claim 1, wherein the opening is formed in a bottom surface of the recess. The intrusion sensor according to claim 1, wherein an angle between a normal direction of an inner surface of the opening and a thickness direction of the mask is an acute angle.

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