JP7369455B2 - Living body occupancy detection device - Google Patents

Description

The present invention relates to a living body occupancy detection device that detects that an object on a seat installed in a vehicle such as a vehicle is a living body.

For example, unlocking the accelerator lever of a car so that it can only be operated when a living person is seated, or opening an air bag installed in a vehicle to a seat where a living person is sitting. There is a demand for a living body occupancy detection device that can detect whether an object on a seat is luggage or a living body.

For example, the living body occupancy detection device disclosed in Patent Document 1 is one such example. The living body occupancy detection device described in Patent Document 1 detects the occupant's presence by detecting the occupant's body movement on the seat based on a cable-shaped piezoelectric sensor arranged on a seat of a vehicle body and an output signal from the piezoelectric sensor. and presence determination means for determining the seat. After the output signal of the piezoelectric sensor is filtered by a filter section in the presence determination means, it is determined whether or not it exceeds a preset value range (voltage determination value range). Based on the presence of movement, it is determined that the occupant is seated.

Japanese Patent Application Publication No. 2005-204871

By the way, the conventional living body occupancy detection device described above passes the output signal from the piezoelectric sensor through a filter having a predetermined filtering characteristic that allows signals of 10 Hz or less to pass through and amplifies the signal, and then passes the output signal through a band pass filter of 4 Hz to 6 Hz. After that, it is compared with a preset value, and if the set value is exceeded, it is determined that the occupant's body movement is a minute body movement due to heartbeat activity, and the seating of the occupant is detected. In the conventional living body seating detection device described above, a frequency component corresponding to the body movement of the living body included in the output signal from the piezoelectric sensor is extracted using a filter, and the body movement of the living body is determined based on the magnitude of the extracted signal. are doing.

By the way, the piezoelectric sensor used in the living body occupancy detection device of Patent Document 1 includes a resin-based cylindrical polymer piezoelectric material such as polyvinylidene fluoride, and a piezoelectric sensor provided on the outer peripheral surface of the cylindrical polymer piezoelectric material. and a cylindrical outer electrode formed into a cable shape. Such piezoelectric sensors do not necessarily have frequency characteristics that sufficiently reflect the movement of a living body on the seat, and cannot obtain accurate seating determination accuracy with respect to individual differences between living bodies.

The present invention has been made against the background of the above-mentioned circumstances, and its purpose is to provide a living body occupancy detection device that can obtain accurate seating determination accuracy regardless of individual differences between living organisms. be.

As a result of various studies against the background of the above circumstances, the inventor of the present invention found that, for example, if a seating sensor that uses a single-crystal piezoelectric vibrator has an order of magnitude higher frequency characteristic, the output signal from the seating sensor found that there is a waveform derived from a living body that had not been noticed in the past, and that by determining whether a living creature is sitting on the basis of this waveform, accurate seating detection accuracy can be obtained for a large number of living creatures. The present invention has been made based on this knowledge.

That is, the gist of the first invention is (a) a living body occupancy detection device that determines that an object on a seat is a living body, and (b) a part of the load received by the seat is applied. a load detection unit including a load sensor having a single-crystal load detection element; seating determination means for determining that the object above is a living body; (d) the load sensor is configured to detect a load applied to the single crystal load detection element and an oscillation circuit including the single crystal load detection element; The load is determined based on the frequency of the oscillation circuit including the actual single-crystal load detection element from a predetermined relationship with the oscillation frequency, and has a measurement load range of 10 −3 N to ¹⁰ 3 ^N. There is a particular thing.

The gist of a second invention is that, in the first invention, a frequency analysis means performs frequency analysis to obtain a frequency spectrum by using Fourier transform on the load signal from the load sensor; frequency component determining means for determining that a frequency component of a waveform originating from the activity of the living body is present in the spectrum; The object of the present invention is to determine that the object on the seat is a living body when it is determined that the frequency component exists.

The gist of the third invention is that in the first or second invention, the frequency component of the waveform derived from the activity of the living body is a frequency component corresponding to the heartbeat of the living body.

The gist of the fourth invention is that in the first or second invention, the frequency component of the waveform derived from the activity of the living body is a frequency component corresponding to the breathing of the living body.

The gist of the fifth invention is that in the first or second invention, the frequency component of the waveform derived from the activity of the living body is a frequency component corresponding to the conversation of the living body.

The gist of the sixth invention is that in the first or second invention, the frequency component of the waveform derived from the activity of the living body is at least one frequency component of 0.2Hz to 10Hz included in the waveform showing the frequency spectrum. It is the spectral average value within the frequency band that includes the

The gist of the eighth invention is as follows: (a) A living body occupancy detection device that determines that an object on a seat is a living body, (b) a single crystal to which a part of the load applied to the seat is applied. a load detection unit including a load sensor having a load detection element; (c) a load detection unit that includes a load sensor having a load detection element; (d) the load sensor includes a thin plate-shaped quartz single crystal plate as the single crystal load detection element; a surface of the quartz single crystal plate; A pair of electrodes formed at the center of the back surface have the same length and width dimensions as the length and width dimensions of the single crystal quartz plate, but have a thickness dimension larger than the thickness dimension of the single crystal quartz plate. and a pair of holding plates which are made of a material having the same coefficient of thermal expansion as the single crystal quartz plate and which hold the peripheral edge of the single crystal quartz plate.

The gist of the seventh invention is to calculate a moving average value of a load signal representing the load detected by the load sensor, and to compare the moving average value of the load signal with a preset load judgment value. load determining means for determining whether the load applied to the seat is applied by a living adult or a living infant based on the load, the load determining means The object of the present invention is to detect whether the living body seated on the seat is an adult or an infant based on the above.

According to the living body occupancy detection device of the first invention, (a) the living body occupancy detection device determines that an object on the seat is a living body, and (b) a portion of the load received by the seat is applied. a load detection unit including a load sensor having a single-crystal load detection element; Since the seating determination means includes a seating determination means for determining that the object above is a living body, the seating determination means determines that a signal originating from the activity of the living body is present in the load signal from the load sensor having high frequency characteristics. Since it is determined that the object on the seat is a living body based on the above, accurate seating determination accuracy can be obtained regardless of individual differences among living bodies.
(d) The load sensor detects the actual single crystal load based on a predetermined relationship between the load applied to the single crystal load detection element and the oscillation frequency of an oscillation circuit including the single crystal load detection element. The load is determined based on the frequency of the oscillation circuit including the detection element, and since it has a measurement load range of 10 ^-3 N to 10 ³ N, a load signal that clearly includes signals derived from the living body can be obtained.

According to the living body occupancy detection device of the second aspect of the invention, the frequency analysis means performs frequency analysis to obtain a frequency spectrum by using Fourier transform on the load signal from the load sensor, and the frequency spectrum obtained by the frequency analysis means includes: and a frequency component determining means for determining the presence of a frequency component of a waveform originating from the activity of the living body, the seating determining means determining whether a frequency component of the waveform originating from the activity of the living body is present by the frequency component determining means. If it is determined that the object on the seat exists, it is determined that the object on the seat is a living body, so that accurate seating determination accuracy can be obtained regardless of individual differences among living bodies.

According to the living body seating detection device of the third invention, since the frequency component of the waveform derived from the living body's activity is a frequency component corresponding to the living body's heartbeat, it is possible to accurately determine the living body's seating.

According to the living body seating detection device of the fourth invention, since the frequency component of the waveform derived from the living body's activity is a frequency component corresponding to the living body's breathing, it is possible to accurately determine the living body's seating.

According to the living body seating detection device of the fifth aspect, since the frequency component of the waveform derived from the living body's activity is a frequency component corresponding to the living person's conversation, it is possible to accurately determine the living body's seating.

According to the living body seating detection device of the sixth aspect of the invention, the frequency component of the waveform derived from the living body's activity is within a frequency band including at least a part of 0.2 Hz to 10 Hz, which is included in the waveform showing the frequency spectrum. Since it is a spectral average value, it is possible to accurately determine whether the living body is sitting.

According to the living body occupancy detection device of the eighth invention, (a) the living body occupancy detection device determines that an object on the seat is a living body, and (b) part of the load received by the seat is applied. a load detection unit including a load sensor having a single-crystal load detection element; Since the seating determination means includes a seating determination means for determining that the object above is a living body, the seating determination means determines that a signal originating from the activity of the living body is present in the load signal from the load sensor having high frequency characteristics. Since it is determined that the object on the seat is a living body based on the above, accurate seating determination accuracy can be obtained regardless of individual differences among living bodies.
(d) The load sensor includes a thin-plate-shaped quartz single crystal plate as the single crystal load detection element, a pair of electrodes formed at the center portions of the front and back surfaces of the quartz single crystal plate, and A material having the same length and width dimensions as the length and width dimensions of the single crystal plate, but having a thickness dimension larger than the thickness dimension of the single crystal quartz plate, and having the same coefficient of thermal expansion as the single crystal quartz plate. and a pair of holding plates that sandwich the peripheral edge of the single crystal quartz plate, so that when a load is applied, elastic deformation of the pair of holding plates causes minute distortion of the single crystal quartz plate. is allowed, so there is no sliding friction when micro-distortions occur in response to changes in load. Therefore, the frequency response of the measurement is sufficient, the waveform of the measured biological information etc. is not distorted, and there is no hysteresis caused by sliding friction, so the measured load does not contain hysteresis. Since there is no influence from temperature, sufficient accuracy can be obtained for the load waveform and the absolute value of the load.

According to the living body seating detection device of the seventh invention, a moving average value of a load signal representing the load detected by the load sensor is calculated, and the moving average value of the load signal is compared with a preset load determination value. Based on this, the load determining means determines whether the load applied to the seat is applied by a living adult or a living infant, and the load determining means Based on the determination, the purpose is to detect whether the living organism sitting on the seat is an adult or an infant, so it is possible to detect not only whether the living organism is sitting but also whether the living organism is an adult or an infant. I can do it.

FIG. 1 is a perspective view illustrating a seat on which a living body occupancy detection device according to an embodiment of the present invention is installed. 2 is a plan view showing the seat of FIG. 1. FIG. FIG. 2 is a side view illustrating the configuration of a load detection unit attached to the seat of FIG. 1. FIG. FIG. 4 is a perspective view showing an enlarged main part of a load sensor used in the load detection unit of FIG. 3; FIG. 5 is an assembly diagram showing the component parts separated in order to explain the configuration of the main parts of the load sensor of FIG. 4. FIG. FIG. 5 is a vertical cross-sectional view taken along line VI-VI in FIG. 4 for explaining the configuration of essential parts of the load sensor in FIG. 4; FIG. 2 is a diagram illustrating the electrical configuration of the living body occupancy detection device of FIG. 1, and is a block diagram illustrating the configuration of a load measurement circuit and an electronic control device. 2 is a diagram showing a load signal obtained when an object is placed on the seat of FIG. 1. FIG. FIG. 2 is a diagram showing a load signal obtained when a living body passenger of a vehicle is placed on the seat of FIG. 1; 9 is a diagram showing a frequency spectrum obtained by frequency-analyzing the load signal of FIG. 8 by fast Fourier transform. FIG. 10 is a diagram showing a frequency spectrum obtained by frequency-analyzing the load signal of FIG. 9 by fast Fourier transform. FIG. 11 is a diagram showing an enlarged view of the frequency band from 0 Hz to 10 Hz in the frequency spectrum of FIG. 10. FIG. FIG. 12 is a diagram showing an enlarged view of the frequency band from 0 Hz to 10 Hz of the frequency spectrum of FIG. 11; FIG. 3 is a diagram showing the magnitude and dispersion of the signal strength in the frequency band of 0 Hz to 10 Hz of the frequency spectrum obtained by frequency analysis of the load signal by fast Fourier transform for three types of objects and four types of living organisms. 8 is a flowchart illustrating a main part of the control operation of the electronic control device of FIG. 7. FIG.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, the figures are simplified or modified as appropriate, and the dimensional ratios, shapes, etc. of each part are not necessarily drawn accurately.

FIG. 1 is a perspective view showing a vehicle seat 12 to which a biological occupancy detection device 10 according to an embodiment of the present invention is applied. 2 is a plan view of the seat 12 provided in the vehicle interior, and FIG. 3 is a side view illustrating the configuration of the load detection unit 20 attached to the seat 12. The seat 12 includes a seating section 14 on which a living person, for example, a passenger, sits, and a backrest section 16 rising from the rear end of the seating section 14. The seat portion 14 and the backrest portion 16 are each made of a cushioning material 18 such as urethane foam supported by a steel pipe frame (not shown).

A load detection unit 20 for detecting the load of the occupant is provided in the seating portion 14 that supports the weight of the occupant sitting on the seat. As shown in detail in FIG. 3, the load detection unit 20 includes a pair of load receiving plates 22 and a substrate 24 that are embedded in the cushion material 18 and face each other at a predetermined distance, and are fixed to the center of the substrate 24. , a load sensor 30 that detects the load received by the load receiving plate 22 and transmitted through the deflection of the load receiving plate 22.

FIG. 4 is an enlarged perspective view showing the main parts of the load sensor 30. As shown in FIG. FIG. 5 is an assembly diagram showing the component parts separated in order to explain the configuration of the main parts of the load sensor 30 of FIG. 4. As shown in FIG. FIG. 6 is a vertical cross-sectional view taken along the line VI-VI in FIG. 4, illustrating the configuration of main parts of the load sensor in FIG. In FIGS. 4 to 6, the load sensor 30 includes a single crystal load sensing element 32 that is made of a thin plate-shaped quartz single crystal plate and functions as a single crystal oscillator, and a single crystal load sensing element 32 that has the same length and width dimensions as the single crystal load sensing element 32. It is made of a material such as a single-crystal quartz plate, which has length and width dimensions, but has a thickness dimension larger than that of the single-crystal load detection element 32, and has the same coefficient of thermal expansion as the single-crystal load detection element 32, A pair of holding plates 34 and 36 that sandwich the peripheral edge of the single-crystal load detection element 32 are provided. Shallow rectangular recesses 34a and 36a are formed on the surfaces of the pair of holding plates 34 and 36 facing the single crystal load sensing element 32 so as to sandwich the single crystal load sensing element 32 only at their peripheral edges. has been done.

On the front and back surfaces of the single crystal load detection element 32, a pair of circular central electrodes 38 and 40 are formed at the center so as to face each other in the thickness direction, and a single crystal load detection element A pair of conductor patterns 38a and 40a are formed opposite to each other in the diagonal direction of the element 32, respectively. Concave grooves 34b and 36b are formed in a pair of side surfaces of the holding plates 34 and 36, respectively, and conductor patterns 38a and 36b formed on the front and back surfaces of the single crystal load sensing element 32 are inserted into the concave grooves 34b and 36b, respectively. The tip of 40a is exposed. Conductive wires (not shown) are electrically connected to the tips of the conductor patterns 38a and 40a, so that the single crystal load detection element 32 is connected to an oscillation circuit 56, which will be described later. Rectangular fixing surfaces 32a and 32b formed on the periphery of the front and back surfaces of the single crystal load sensing element 32, respectively, and rectangular fixing surfaces 34c and 34c formed on the periphery of the holding plate 34 to face the fixing surface 32a. A rectangular fixing surface 36c formed on the peripheral edge of the retaining plate 36 so as to face the fixing surface 32b is surface-bonded to each other with an adhesive or the like, so that the single-crystal load sensing element 32 and the pair of retaining plates 34 and 36 are bonded together. are fixed to each other. As a result, the single-crystal load detecting element 32 is held in a reinforced state in which the peripheral edge thereof is held between the pair of retaining plates 34 and 36 by the single-crystal load detecting element 32.

For the single crystal load detection element 32, for example, an AT cut crystal with excellent temperature stability is used. The AT-cut single-crystal load sensing element generates thickness shear vibration in the electrode portion due to an externally applied voltage, and can obtain an output as an electrical periodic signal at a resonant frequency that is accurately proportional to the external force. The single crystal load detection element 32 has a length in the longitudinal direction L, for example, in order to increase the stress applied to the crystal against the applied load and improve the sensitivity by reducing the cross section in the longitudinal direction L, that is, the load application direction. , is longer than the length in the width direction W perpendicular to the longitudinal direction L.

The single-crystal load sensing element 32 configured as described above is constructed by using a lift-off process to form a thin film conductor on both sides of a thin plate-shaped AT-cut crystal wafer by sputtering or vapor deposition, and attaching it to the central electrodes 38 and 40 and the conductor pattern. It is formed by forming a large number of 38a and 40a and dividing them into individual parts by dicing. Specifically, a sacrificial layer is first patterned on an AT-cut crystal wafer, then Cr and Au are sputtered to form electrodes, and then the sacrificial layer is removed. This series of processes is performed on both sides to pattern the electrodes, and after the electrodes are completed, they are cut with a dicing saw to form a plurality of single crystal load sensing elements 32.

In the load sensor 30 configured in this manner, the pair of holding plates 34 and 36 are elastically deformed when subjected to a load in the longitudinal direction, causing minute distortions in the single crystal plate. There is no sliding friction when there is minute strain in response to. Therefore, sufficient frequency response is obtained for measurement, and the waveform of the measured biological information is not distorted.Furthermore, there is no hysteresis caused by sliding friction, and hysteresis is not included in the measured load. Therefore, sufficient accuracy can be obtained for the load waveform and the absolute value of the load. In addition, the load sensor 30 can be started up easily. The load sensor 30 configured in this manner has a wide measurement load range, such as 10 ⁻³ N to 10 ³ N, for example.

FIG. 7 shows a load detection circuit 52 and an electronic control device 54 provided in the living body occupancy detection device 10. The load detection circuit 52 includes an oscillation circuit 56 for continuously oscillating the load sensor 30 and the single-crystal load detection element 32, which is a main part of the load sensor 30, and a frequency of a periodic signal output from the oscillation circuit 56. It includes a frequency counter 58 for reading, a power supply circuit 60 for supplying power to the oscillation circuit 56, etc. The frequency counter 58 sequentially outputs an oscillation frequency signal representing the oscillation frequency of the oscillation circuit 56 at every sampling period of, for example, about 1 to 10 ms.

The electronic control device 54 is a so-called microcomputer including, for example, a CPU (not shown), a RAM, a ROM, and an input/output interface. A seating signal ST indicating whether or not the driver is seated on the seat 14 is output to other control devices and the like. The electronic control device 54 includes a load calculation means 62, a frequency analysis means 64, a frequency component determination means 66, a load determination means 68, and a seating determination means 70 as main parts of the control function.

The load calculation means 62 calculates the oscillation frequency signal from the load detection circuit 52 based on a pre-stored relationship between the applied load applied to the single crystal load detection element 32 and the vibration frequency of the single crystal load detection element 32, for example. Based on the frequency, a load signal SW representing the load (N) received by the load sensor 30 is sequentially output. FIG. 8 shows the waveform of the load signal SW obtained by the load calculation means 62 when nine plastic bottles weighing a total of 18 kg as an example of objects are placed on the seating portion 14 of the seat 12 in FIG. 1 while the vehicle is idling. It shows. FIG. 9 shows a load signal obtained by the load calculation means 62 when a passenger with a weight of 57 kg and a height of 177 cm, as an example of a living body, is seated on the seating portion 14 of the seat 12 in FIG. 1 while the vehicle is idling. It shows SW.

The waveform of the load signal SW in FIG. 8 includes a fine pulsation waveform that is considered to be engine vibration, but shows a constant load without undulations. On the other hand, in FIG. 9, a large period pulsation waveform that continues with a large period T1 of about 3.5 to 4.2 seconds, a medium period pulsation waveform that continues with a medium period T2 of about 0.8 seconds, for example, Also shown is a waveform derived from a living body, including a continuous short period pulsation waveform with a short period T3 of, for example, about 0.27 seconds. The waveform of the large period T1 corresponds to, for example, the respiratory cycle of the living body, and the waveform of the medium period T2 corresponds to, for example, the heartbeat (pulse) cycle of the living body. Further, it is estimated that the waveform of the small period T3 corresponds to a harmonic of the waveform of the large period T1 or the waveform of the medium period T2.

The frequency analysis means 64 performs frequency analysis on the load signal SW output from the load calculation means 62 using fast Fourier analysis, and outputs a frequency spectrum. FIG. 10 shows the frequency analysis of the load signal SW obtained when nine 2L bottles, that is, objects weighing a total of 18 kg, are placed on the seating part 14 of the seat 12 shown in FIG. 8, using fast Fourier analysis. FIG. 11 shows the load signal SW obtained when a passenger with a weight of 57 kg and a height of 177 cm is seated on the seating portion 14 of the seat 12 shown in FIG. 9 using fast Fourier analysis. This shows the frequency spectrum obtained by frequency analysis.

In the frequency spectrum of Fig. 10 obtained by frequency analysis of the load signal SW obtained when a total of 18 kg of objects are placed, there is a slight amount of vehicle noise including engine vibration noise EN around 34 Hz, but a slight amount of vehicle noise above 10 Hz. However, as shown in FIG. 12, noise is not recognized in the wavelength band of 0 to 10 Hz. On the other hand, in the frequency spectrum of FIG. 11 obtained by frequency analysis of the load signal SW obtained when a passenger weighing 57 kg and height 177 cm is seated, the engine vibration noise EN around 34 Hz is Larger vehicle noise than in the case of FIG. 10 is generated in a band of 10 Hz or higher, and as shown in FIG. 13, a large signal originating from biological activity is recognized in the wavelength band of 0 to 10 Hz. Among the spectra within the wavelength band of 0 to 10 Hz, the spectrum in the wavelength band of 0 to 2 Hz is estimated to be a signal corresponding to the fundamental wave derived from the respiratory activity of the living body and the heartbeat activity, but at least 2 Large biological signals are also generated in the ~7Hz frequency band.

The frequency component determination means 66 determines whether the frequency spectrum obtained by the frequency analysis means 64 includes a frequency component derived from a living body. The frequency components of waveforms derived from living organisms include the basic frequency components of pulsations related to the breathing cycle of living organisms, the frequency of pulsations related to heartbeat cycles, and the frequency components of pulsations related to conversation (speech) and chewing movements of living organisms. frequency and harmonic frequencies. The frequency component determination means 66 corresponds to the frequency spectrum obtained by the frequency analysis means 64, for example, to the signal strength of the frequency component of a continuous large period pulsating waveform with a large period T1 of about 3.5 to 4.2 seconds. The average value of the signal strength of the frequency spectrum within the frequency band of 0.23 to 0.28 Hz exceeds a preset first threshold, for example, a medium-period pulsating waveform that continues with a medium-period T2 of about 0.8 seconds. that the average value of the signal strength of the frequency spectrum within the frequency band of 1.1 to 1.4 Hz corresponding to the frequency components of 2 to 7 Hz, which are estimated to be harmonics thereof, exceeds a preset second threshold; Based on the determination that at least one of the fact that the average value PWA of the signal strength of the frequency spectrum of the frequency band exceeds a preset third threshold value, biological origin is added to the frequency spectrum obtained by the frequency analysis means 64. Determine whether a frequency component is included. In the frequency band of 2 to 7 Hz in FIG. 13, an average signal strength PWA of the frequency spectrum is shown, and preferably the third threshold value is lower than the average signal strength PW of the frequency spectrum. Preset to the value.

FIG. 14 is a boxplot BP1 showing the distribution of signal intensity in the 2-7 Hz wavelength band of the frequency spectrum of the load signal SW obtained from three types of objects having a total load of 6 kg, 12 kg, and 18 kg, respectively; The distribution of signal intensity in the wavelength band of 2 to 7 Hz of the frequency spectrum of the load signal SW obtained from BP2, BP3, and four occupants (living bodies) with body weights of 55 kg, 57 kg, 62 kg, and 65 kg, respectively. Boxplots BP4, BP5, BP6, and BP7 are shown, respectively.

As shown in FIG. 14, the maximum values of boxplots BP1, BP2, and BP3 showing variations in the signal strength of the frequency spectrum of the load signal SW from the object and the signal strength of the frequency spectrum of the load signal SW from the passenger are shown. Using the fourth threshold value H4 set between the minimum values of box plots BP4, BP5, BP6, and BP7 showing the dispersion of By comparing the signal strength of the frequency spectrum within the frequency band that includes at least a portion of the signal, it can be determined whether or not a frequency component derived from a living body is included. The frequency component determination means 66 determines whether or not the frequency spectrum obtained by the frequency analysis means 64 includes a frequency component derived from a living body, based on the fact that the signal strength exceeds the fourth threshold H4. good.

The load determination means 68 calculates a moving average value of the load signal SW output from the load calculation means 62, and compares the moving average value of the load signal SW with a preset load determination value. It is determined whether the load applied to the seating portion 14 of is applied by a living adult or a living infant. For example, if the moving average value of the load signal SW exceeds a load judgment value preset for determining an adult, it is determined that an adult is seated, and if the moving average value of the load signal SW falls below the load judgment value. In this case, it is determined that the infant is seated.

The seating determination means 70 determines whether a frequency component of a waveform derived from a living body is included in the frequency spectrum obtained by the frequency analysis means 64 by the frequency component determination means 66 when a load of a predetermined value or more is applied to the seating portion 14 of the seat 12. If it is determined that the object has not been placed on the seating portion 14, it is determined that the object has been placed on the seating portion 14, but the frequency component determination means 66 determines that the frequency spectrum obtained by the frequency analysis means 64 contains a biologically derived frequency component of the waveform. If it is determined that the living body is seated, it is determined whether the living body is seated. In this case, based on the determination result of the load determining means 68, it is also determined whether an adult or a child is seated.

FIG. 15 is a flowchart illustrating the main part of the control operation of the electronic control device 54. In FIG. 13, in step S1 (hereinafter, step is omitted), it is determined whether a load of a predetermined value or more is detected on the seating portion 14 of the seat 12. As long as the judgment in S1 is negative, the system is kept on standby, but if the judgment in S1 is affirmative, in S2 corresponding to the load calculation means 62, from the pre-stored relationship shown in FIG. A load signal SW representing the load (N) received by the load sensor 30 is sequentially calculated based on the frequency represented by the oscillation frequency signal. Next, in S3 corresponding to the frequency analysis means 64, frequency analysis is performed on the load signal SW using fast Fourier analysis, and a frequency spectrum is output.

Next, in S4 corresponding to the frequency component determining means 66, a preset living body-derived frequency component is added to the frequency spectrum, for example, a frequency component of a large period pulsating waveform that continues with a large period T1 of about 4 seconds, for example 0. It is determined whether or not a frequency component of a continuous medium-period pulsating waveform is included at a medium-period T2 of about .8 seconds. If the determination in S4 is negative, it is determined in S8 that the object is placed on the seating portion 14 of the seat 12. However, if the determination in S4 is affirmative, it is determined in S5 corresponding to the load determination means 68 whether or not the load applied to the seating portion 14 of the seat 12 exceeds a preset adult determination value. Ru. If the determination in S5 is negative, it is determined in S7 that an infant or child is seated, but if the determination in S5 is affirmative, it is determined in S6 that an adult is seated. These S6, S7, and S8 correspond to the seating determination means 70.

As described above, the living body occupancy detection device 10 of the present embodiment includes a load detection unit 20 including a load sensor 30 having a single crystal vibrator to which a portion of the load received by the seating portion 14 of the seat 12 is applied. , seating determination means for determining that the object on the seating portion 14 of the seat 12 is a living body based on the presence of a waveform derived from the activity of the living body in the load signal SW representing the load detected by the load sensor 30; 70, the seating determining means 70 detects the presence of the waveform derived from the activity of the living body in the load signal SW from the load sensor 30 having high frequency characteristics. Since it is determined that the object is a living body, accurate seating determination accuracy can be obtained regardless of individual differences among living bodies.

According to the living body occupancy detection device 10 of this embodiment, the frequency analysis means 64 performs frequency analysis to obtain a frequency spectrum using fast Fourier transform on the load signal SW from the load sensor 30; The seating determination means 70 includes a frequency component determining means 66 that determines whether a frequency component of a waveform originating from the activity of the living body is present in the frequency spectrum, and the seating determination means 70 determines whether the frequency component of the waveform originating from the activity of the living body is present in the frequency spectrum. If it is determined that the frequency component exists, it is determined that the object on the seating portion 14 of the seat 12 is a living body, so that accurate seating determination accuracy can be obtained regardless of individual differences among living organisms.

According to the living body seating detection device 10 of this embodiment, since the frequency component corresponding to the heartbeat of the living body is used as the frequency component of the waveform derived from the living body's activity, it is possible to accurately determine whether the living body is sitting.

According to the living body seating detection device 10 of this embodiment, since the frequency component corresponding to the living body's breathing is used as the frequency component of the waveform derived from the living body's activity, it is possible to accurately determine the living body's seating.

According to the living body seating detection device 10 of the present embodiment, since the frequency component corresponding to the living body's conversation is used as the frequency component of the waveform derived from the living body's activity, it is possible to accurately determine the living body's seating.

According to the living body seating detection device 10 of this embodiment, the frequency component of the waveform derived from the living body's activity is at least one frequency component of 0.2 Hz to 10 Hz included in the waveform representing the frequency spectrum obtained by the frequency analysis means 64. Since this is the average value of the spectrum within the frequency band that includes the area, it is possible to accurately determine whether the living body is seated.

According to the living body occupancy detection device 10 of this embodiment, the load sensor 30 includes the load applied to the single crystal load detection element (single crystal vibrator) 32 and the single crystal load detection element (single crystal vibrator) 32. The load is determined based on the frequency of the oscillation circuit 56 including the actual single-crystal load detection element 32 from a predetermined relationship with the oscillation frequency of the oscillation circuit 56, and the load is calculated from 10 ⁻³ N to 10 ³ N. Since the measurement load range is provided, a load signal SW that clearly includes a signal derived from a living body can be obtained.

According to the living body occupancy detection device 10 of this embodiment, the load sensor 30 is formed in a thin plate-shaped quartz single crystal plate as the single crystal load detection element 32, and in the center portions of the front and back surfaces of the quartz single crystal plate. a pair of center electrodes 38, 40 having the same length and width as the length and width of the single crystal quartz plate, but having a thickness larger than the thickness of the single crystal quartz plate; A pair of holding plates 34 and 36 are made of a material having the same coefficient of thermal expansion as the single crystal quartz plate and sandwich the peripheral edge of the single crystal quartz plate. Since the elastic deformation of the quartz crystal plates 34 and 36 allows the generation of minute distortions in the single crystal plate, there is no sliding friction when the single crystal plates undergo minute distortions in response to changes in load. Therefore, sufficient frequency response is obtained for measurement, and the waveform of the measured biological information is not distorted.Furthermore, there is no hysteresis caused by sliding friction, and hysteresis is not included in the measured load. Since there is no influence from temperature, sufficient accuracy can be obtained for the load waveform and the absolute value of the load.

Although the embodiments of the present invention have been described above in detail based on the drawings, the present invention can also be applied to other aspects.

For example, in the living body occupancy detecting device 10 of the above-described embodiment, the occupancy determination means 70 detects the frequency component determined by the frequency component determination means 66 and the frequency analysis means 64 when a load of a predetermined value or more is applied to the seating portion 14 of the seat 12. If it is determined that a frequency component derived from a living body is not included in the frequency spectrum obtained, it is determined that an object is placed on the seating portion 14, but the frequency component determination means 66 determines that the frequency component derived from the frequency analysis means 64 is not included. If it was determined that the spectrum contained a frequency component derived from a living body, it was determined whether the living body was sitting. However, the seating determination means 70 stores, for example, a waveform derived from a living body in advance, and uses a pattern matching method to determine whether or not the stored waveform derived from a living body is included in the load signal SW output from the load detection circuit 52. By determining whether or not the load signal SW includes a waveform derived from a living body, if it is determined that the waveform is included, it may be determined whether the living body is seated.

Further, in the above embodiment, the load signal SW is based on the actual frequency based on the predetermined relationship between the frequency of the oscillation circuit 56 including the single crystal load detection element 32 of the load sensor 30 and the load applied to the load sensor 30. was calculated. However, due to the relationship between the output voltage corresponding to the charge generated by the single crystal crystal that constitutes the single crystal load detection element 32 of the load sensor 30 and the load applied to the load sensor 30, the load signal SW is determined based on the actual output voltage. It may be calculated.

Further, the load sensor 30 of the above-described embodiment is not equipped with a circuit device related to temperature compensation. However, since the temperature inside the vehicle may fluctuate greatly, in such a case, a circuit device that performs temperature compensation may be provided in order to maintain load detection accuracy. As a circuit device that performs such temperature compensation, a temperature reference load sensor configured similarly to the load sensor 30 is added in a state where no load is applied, and the load signal SW obtained from the load sensor 30 and the temperature The difference value from the load signal SWr obtained from the reference load sensor may be used as the load signal. In addition, as another circuit device that performs temperature compensation, a temperature sensor such as a thermistor or a thermocouple is installed in the load sensor 30 to detect the temperature of the load sensor 30, and the temperature correction value obtained experimentally in advance and the A temperature correction value may be determined based on the actual temperature of the load sensor 30 in relation to temperature, and the load signal SW may be corrected using the temperature correction value.

The above-mentioned embodiment is merely one embodiment, and the present invention can be implemented with various changes and improvements based on the knowledge of those skilled in the art.

10: Living body occupancy detection device 12: Seat 14: Seating section 16: Backrest section 18: Cushion material 20: Load detection unit 22: Load receiving plate 24: Substrate 30: Load sensor 32: Single crystal load detection element 32a, 32b: Rectangle Fixed surface 34, 36: Holding plate 34a, 36a: Recessed part 34b, 36b: Concave groove 34c, 36c: Rectangular fixed surface 38, 40: Center electrode (pair of electrodes) 38a, 40a: Conductor pattern 52: Load detection Circuit 54: Electronic control device 56: Oscillation circuit 58: Frequency counter 60: Power supply circuit 62: Load calculation means 64: Frequency analysis means 66: Frequency component determination means 68: Load determination means 70: Seating determination means ST: Seating signal SW: load signal

Claims (8)

A living body seating detection device that determines that an object on a seat is a living body,
a load detection unit comprising a load sensor having a single crystal load detection element to which a portion of the load received by the seat is applied;
seating determination means for determining that an object on the seat is a living body based on the presence of a waveform derived from the activity of the living body in a load signal representing the load detected by the load sensor; ,
The load sensor is configured to perform oscillation including the actual single crystal load sensing element based on a predetermined relationship between a load applied to the single crystal load sensing element and an oscillation frequency of an oscillation circuit including the single crystal load sensing element. It calculates the load based on the frequency of the circuit, and has a measurement load range of 10 ^-3 N to 10 ³ N.
A biological occupancy detection device characterized by the following. Frequency analysis means for performing frequency analysis to obtain a frequency spectrum using Fourier transform on the load signal from the load sensor;
comprising a frequency component determination means for determining that a frequency component of a waveform originating from the activity of the living body is present in the frequency spectrum obtained by the frequency analysis means;
The seating determining means determines that the object on the seat is a living body when the frequency component determining means determines that a frequency component of a waveform derived from the activity of the living body is present. The living body occupancy detection device according to claim 1. The living body seating detection device according to claim 1 or 2, wherein the frequency component of the waveform derived from the living body's activity is a frequency component corresponding to the heartbeat of the living body. The living body seating detection device according to claim 1 or 2, wherein the frequency component of the waveform derived from the living body's activity is a frequency component corresponding to the breathing of the living body. The living body seating detection device according to claim 1 or 2, wherein the frequency component of the waveform derived from the living body's activity is a frequency component corresponding to a conversation of the living body. A claim characterized in that the frequency component of the waveform derived from the activity of the living body is a spectral average value within a frequency band including at least a part of 0.2 Hz to 10 Hz, which is included in the waveform showing the frequency spectrum. 1 or 2 biological occupancy detection device. A moving average value of a load signal representing the load detected by the load sensor is calculated, and the load applied to the seat is determined based on comparing the moving average value of the load signal with a preset load judgment value. , comprising a load determining means for determining whether the load is applied by a living adult or a living child,
7. The living body seating detection device according to claim 1, wherein the living body sitting on the seat is detected as an adult or an infant based on a determination made by the load determining means. A living body seating detection device that determines that an object on a seat is a living body,
a load detection unit comprising a load sensor having a single crystal load detection element to which a portion of the load received by the seat is applied;
seating determination means for determining that an object on the seat is a living body based on the presence of a waveform derived from the activity of the living body in a load signal representing the load detected by the load sensor;
The load sensor is
a thin plate-shaped quartz single crystal plate as the single crystal load detection element;
a pair of electrodes formed at the center of the front and back surfaces of the single crystal quartz plate;
It has the same length and width dimensions as the length and width dimensions of the single crystal quartz plate, but has a thickness dimension larger than the thickness dimension of the single crystal quartz plate, and has the same coefficient of thermal expansion as the single crystal quartz plate. A living body occupancy detecting device comprising: a pair of holding plates that are made of a material that holds the peripheral edge of the single crystal quartz plate .

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