JP2018149278A - Biological information detection sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biological information detection sensor that can contrive simplification of a structure.SOLUTION: There are loaded on a common substrate 10, a first sensor part 20 which has a first piezoelectric element 23 for outputting a signal corresponding to a pressure and a second sensor part 30 which has a second piezoelectric element 31 for outputting a similar signal. In addition, on the substrate 10, there is arranged a protective member 40 that covers the first sensor part 20 and the second sensor part 30 and that is impressed by a pressure having origin in biological information. Then, the first sensor part 20 is so structured that a structure 21 and the first piezoelectric element 23 are successively laminated from the substrate 10 side and that outputs a signal containing biological information, when a biological body sits on a seat, by the biological information being propagated through the protective member 40. The structure 21 is so composed that the height is made higher than the height of the second sensor part 30 and that, even when the biological body sits on the seat 2, the height becomes higher than the height in the second sensor part 30.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a biological information detection sensor that is disposed on a seat on which a living body is seated and detects biological information of the living body.

  Conventionally, the following is proposed as this kind of living body information detection sensor (for example, refer to patent documents 1). That is, the biological information detection sensor includes a first substrate on which the first piezoelectric element is mounted and a second substrate on which the second piezoelectric element is mounted. The biological information is in contact with the living body on the first substrate. An applied rigid body is provided. In addition, between the first substrate and the second substrate, a buffer member made of a material having hardness that attenuates biological information is disposed.

  In such a biological information detection sensor, biological information such as a pulse or a heartbeat of the living body is applied to the first piezoelectric element via the rigid body and the first substrate, and accompanying the vibration of the living body via the first substrate. Noise is applied. Further, since the buffer member is disposed between the first substrate and the second substrate in the second piezoelectric element, the biological information applied to the rigid body is difficult to be applied to the second substrate, and noise is mainly applied. Is done. For this reason, the first piezoelectric element outputs a signal corresponding to biological information and noise, and the second piezoelectric element outputs a signal corresponding to noise. Therefore, by calculating the difference between the signal output from the first piezoelectric element and the signal output from the second piezoelectric element, the signal due to noise is canceled.

Japanese Patent Laid-Open No. 2006-129635

  However, in the biological information detection sensor as described above, for example, when applied to detect biological information of an occupant disposed on a vehicle seat, due to a large pressing force caused by the occupant sitting on the vehicle seat, The buffer member may be crushed. And if a buffer member is crushed, biological information will become easy to be propagated to the 2nd substrate via the buffer member concerned. For this reason, in the living body information detection sensor as described above, a signal corresponding to the living body information is also output from the second piezoelectric element, and the detection accuracy may be lowered. That is, the biological information detection sensor has a problem in that the detection accuracy may be lowered when used in a situation where a large pressing force can be applied.

  An object of this invention is to provide the biological information detection sensor which can suppress that a detection accuracy falls even in the condition where a big pressing force is applied in view of the said point.

  In order to achieve the above object, in claim 1, a biological information detection sensor that is disposed on a seat (2) on which a living body is seated and detects biological information of the living body, the substrate (10) having one surface (10a), The first sensor unit (20) having a first piezoelectric element (23) that outputs a signal according to pressure, and the second sensor unit (30) having a second piezoelectric element (31) that outputs a signal according to pressure ), A protective member (40) that is provided on the substrate in a state of covering the first sensor unit and the second sensor unit, to which pressure caused by biological information is applied, a signal output from the first piezoelectric element, and a second A signal processing circuit (60) that outputs a detection signal based on a difference from a signal output from the piezoelectric element, and the first sensor unit and the second sensor unit are mounted on a common substrate and are protected The member abuts when the living body is seated from the board. The first sensor unit is configured to laminate the structure (21) and the first piezoelectric element from the substrate side in order from the substrate side. When the living body is seated on the seat, the biological information is propagated through the protective member to output a signal including the biological information, and the height of the structure from the one surface of the substrate is the substrate in the second sensor unit. When the living body is seated on the seat, the height from the one surface of the substrate is higher than the height from the one surface of the substrate in the second sensor unit.

  According to this, even when the living body is seated on the seat, the structure is configured such that the height from one surface of the substrate is higher than the height from one surface of the substrate in the second sensor unit. For this reason, when the living body is seated on the seat, the structure prevents the portion of the protective member on the substrate side from being crushed. Therefore, it can suppress that the pressure resulting from biometric information is applied to the 2nd sensor part located in the board | substrate side from a structure, and can suppress that detection accuracy falls.

  The first sensor unit and the second sensor unit are mounted on a common substrate. That is, the first piezoelectric element and the second piezoelectric element are mounted on a common substrate. For this reason, simplification of the structure can be achieved.

  In addition, the code | symbol in the bracket | parenthesis in the said and the claim shows the correspondence of the term described in the claim, and the concrete thing etc. which illustrate the said term described in embodiment mentioned later. .

It is sectional drawing which shows the structure of the biometric information detection sensor in 1st Embodiment. It is a circuit diagram which shows the electrical structure of the 1st piezoelectric element and 2nd piezoelectric element which are shown in FIG. It is a perspective schematic diagram which shows the example of application which provided the biological information detection sensor shown in FIG. 1 in the vehicle seat. It is a cross-sectional schematic diagram which shows the example of application which provided the biological information detection sensor shown in FIG. 1 in the vehicle seat. It is a schematic diagram at the time of a biological pressure being applied to the 1st sensor part which has the lower elastic member comprised using the material different from the lower elastic member of FIG. It is a schematic diagram at the time of a biological pressure being applied to the 1st sensor part shown in FIG. It is sectional drawing which shows the structure of the biometric information detection sensor in 2nd Embodiment. The measurement result which shows the 1st sensor signal output from the 1st piezoelectric element in which the upper elastic member in Drawing 6 is arranged, and the 1st sensor signal outputted from the 1st piezoelectric element in which the upper elastic member is not arranged It is a measurement result when a high frequency component is applied. The measurement result which shows the 1st sensor signal output from the 1st piezoelectric element in which the upper elastic member in Drawing 6 is arranged, and the 1st sensor signal outputted from the 1st piezoelectric element in which the upper elastic member is not arranged It is a measurement result when a low frequency component is applied. It is sectional drawing which shows the structure of the biometric information detection sensor in 3rd Embodiment. FIG. 9 is a measurement result showing a first sensor signal output from the first piezoelectric element when vibration is randomly applied in the biological information detection sensor shown in FIG. 8. FIG. 9 is a measurement result showing a second sensor signal output from the second piezoelectric element when vibration is randomly applied in the biological information detection sensor shown in FIG. 8. It is the figure which accumulated the 1st sensor signal of Drawing 9A, and the 2nd sensor signal of Drawing 9B. It is the result of calculating the difference of the 1st sensor signal of Drawing 9A, and the 2nd sensor signal of Drawing 9B. It is the result of having frequency-converted the 1st sensor signal shown in Drawing 9A. It is the result of having frequency-converted the 2nd sensor signal shown in Drawing 9B. It is the result of having frequency-converted the 1st sensor signal shown in Drawing 9C, and the 2nd sensor signal. It is the result of having frequency-converted the calculation result shown in FIG. 9D. FIG. 9 is a measurement result showing a first sensor signal output from the first piezoelectric element when a vibration of 1.5 Hz is applied in the biological information detection sensor shown in FIG. 8. FIG. 9 is a measurement result showing a second sensor signal output from the second piezoelectric element when 1.5 Hz vibration is applied in the biological information detection sensor shown in FIG. 8. It is the figure which accumulated the 1st sensor signal of Drawing 11A, and the 2nd sensor signal of Drawing 11B. It is the result of having calculated the difference of the 1st sensor signal of Drawing 11A, and the 2nd sensor signal of Drawing 11B. It is the result of having frequency-converted the 1st sensor signal shown in Drawing 11A. It is the result of having frequency-converted the 2nd sensor signal shown in Drawing 11B. It is the result of having frequency-converted the 1st sensor signal shown in Drawing 11C, and the 2nd sensor signal. It is the result of having frequency-converted the calculation result shown in FIG. 11D. FIG. 9 is an experimental result showing a first sensor signal output from the first piezoelectric element when the vehicle is driven in the biological information detection sensor shown in FIG. 8. FIG. 9 is an experimental result showing a second sensor signal output from the second piezoelectric element when the vehicle is driven in the biological information detection sensor shown in FIG. 8. It is the figure which accumulated the 1st sensor signal of Drawing 13A, and the 2nd sensor signal of Drawing 13B. It is the result of having calculated the difference of the 1st sensor signal of Drawing 13A, and the 2nd sensor signal of Drawing 13B. It is sectional drawing which shows the structure of the biometric information detection sensor in the modification of 3rd Embodiment. It is sectional drawing which shows the structure of the biometric information detection sensor in 4th Embodiment. It is sectional drawing which shows the structure of the biometric information detection sensor in other embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
A first embodiment will be described with reference to the drawings. Note that the biological information detection sensor of this embodiment is preferably used for detecting biological information such as a heartbeat and a pulse of the living body.

  First, the configuration of the biological information detection sensor of this embodiment will be described with reference to FIGS. 1 and 2. As shown in FIG. 1, the biological information detection sensor 1 includes a substrate 10. In this embodiment, the board | substrate 10 is comprised with the polyurethane etc. whose Asuka-C hardness is about 5-29. In the present embodiment, the substrate 10 is provided with the signal processing circuit 60 shown in FIG. 2, and the signal processing circuit 60 is provided with the differential amplifier 61.

  On the one surface 10 a of the substrate 10, the first sensor unit 20 is disposed. In the present embodiment, the first sensor unit 20 is configured by sequentially laminating the structure 21, the lower elastic member 22, and the first piezoelectric element 23 from the substrate 10 side through an adhesive or the like (not shown) as appropriate.

  The structure 21 is made of foamed rubber such as NBR sponge or silicone sponge having Asuka-C hardness of 30 to 50. That is, the structure 21 is made of a material having a higher Asker-C hardness than the substrate 10 and hardly deformed. The structure 21 has a height from the one surface 10a of the substrate 10 higher than a height from the one surface 10a of the substrate 10 in the second sensor unit 30 described later. In other words, the structure 21 is thicker than the second piezoelectric element 31 described later.

  The lower elastic member 22 is made of a material having a lower Asker-C hardness than the structure 21. In this embodiment, the lower elastic member 22 is made of urethane foam or the like as a porous member having an Asuka-C hardness of 5 or less.

  As the first piezoelectric element 23, a general element is used in which a thin film piezoelectric film is sandwiched between a pair of electrodes and a signal corresponding to pressure is output. In this case, the piezoelectric film may be composed of an inorganic piezoelectric material such as lead zirconate titanate (that is, PZT), or may be composed of a polymer material such as polyvinylidene fluoride (that is, PVDF). . Furthermore, the piezoelectric film may be made of a polymer material such as a chiral polymer and may have a directivity.

  In the present embodiment, the configuration having directivity can also be referred to as a configuration having sensitivity in a direction in which biological information such as a pulse and a heartbeat is applied when arranged as shown in FIG. 4 described later. Further, the first piezoelectric element 23 is provided with wiring on the electrode in a cross section different from that of FIG. As shown in FIG. 2, the first piezoelectric element 23 is connected to one input terminal of the differential amplifier 61 provided on the substrate 10 via the wiring. That is, the first sensor signal output from the first piezoelectric element 23 is input to one input terminal of the differential amplifier 61.

  A second sensor unit 30 is disposed on the one surface 10 a of the substrate 10. That is, the first sensor unit 20 and the second sensor unit 30 are mounted on the common substrate 10. The second sensor unit 30 has a second piezoelectric element 31. In the present embodiment, the second piezoelectric element 31 is configured in the same manner as the first piezoelectric element 23. As shown in FIG. 2, the second piezoelectric element 31 is connected to the other input terminal of the differential amplifier 61 provided on the substrate 10 via a wiring. That is, the second sensor signal output from the second piezoelectric element 31 is input to the other input terminal of the differential amplifier 61. For this reason, the differential amplifier 61 outputs a difference between the first sensor signal output from the first piezoelectric element 23 and the second sensor signal output from the second piezoelectric element 31 as a detection signal.

  Furthermore, a protective member 40 is disposed on the one surface 10 a of the substrate 10 so as to cover the first sensor unit 20 and the second sensor unit 30. Specifically, the protective member 40 has a recess 40 a having a wall surface formed along the outer shape of the first sensor unit 20, and a recess 40 b larger than the outer shape of the second sensor unit 30. Is formed. In the present embodiment, the length of the recess 40b from the one surface 10a of the substrate 10 to the bottom surface of the recess 40b is higher than the height from the one surface 10a of the substrate 10 in the structure 21 of the first sensor unit 20. Have been long.

  The protective member 40 is disposed so that the first sensor unit 20 is accommodated in the recess 40 a and the wall surface of the recess 40 a contacts the first sensor unit 20. More specifically, the protection member 40 is disposed so as to contact the first piezoelectric element 23. The protection member 40 is disposed on the one surface 10a of the substrate 10 so that the second sensor unit 30 is accommodated in the recess 40b and does not contact the recess 40b. That is, the protection member 40 is disposed on the one surface 10 a of the substrate 10 so that the space 50 is formed between the protection member 40 and the second sensor unit 30.

  The protective member 40 is made of urethane foam or the like having an Asker C hardness lower than that of the structure 21 and an Asker C hardness of about 5. Further, when the protective member 40 is crushed, the hardness is increased and the pressure is easily transmitted. In other words, the portion of the protective member 40 that is not crushed exhibits a function as a buffer member that attenuates the pressure.

  The above is the configuration of the biological information detection sensor 1 in the present embodiment. Next, the operation of the biological information detection sensor 1 will be described. Hereinafter, as an example, an example will be described in which the biological information detection sensor 1 is arranged on a vehicle seat to configure a biological information detection device and is applied to detect occupant biological information.

  As shown in FIGS. 3 and 4, when the biological information detection sensor 1 is disposed on the vehicle seat 2 having the seat portion 2 a and the backrest portion 2 b, for example, the biological information detection sensor 1 is the It arrange | positions inside the seat part 2a. That is, the biological information detection sensor 1 is disposed so as to be positioned below the thigh of the occupant when the occupant is seated on the vehicle seat 2. More specifically, the biological information detection sensor 1 is arranged such that when the occupant sits on the vehicle seat 2, the substrate 10 is positioned on the opposite side of the occupant's thigh with the protective member 40 interposed therebetween. That is, the biological information detection sensor 1 is disposed on the side of the protective member 40 that comes into contact with the passenger when the occupant sits on the vehicle seat 2 from the substrate 10.

  For this reason, pressure (hereinafter referred to as biological pressure) resulting from biological information such as the occupant's pulse or heartbeat is applied from the protective member 40 side toward the substrate 10 side. In other words, the living body pressure is applied to the protection member 40 along the stacking direction of the structure 21, the lower elastic member 22, and the first piezoelectric element 23 in the first sensor unit 20 (hereinafter simply referred to as the stacking direction). Is done.

  When a passenger is seated on the vehicle seat 2 and a large pressing force is applied, a portion of the protective member 40 on the side opposite to the substrate 10 is crushed and the living body pressure is easily transmitted. It becomes a state. For this reason, when a biological pressure is applied to the protective member 40, the biological pressure is applied from the protective member 40 to the first piezoelectric element 23 located on the opposite side of the substrate 10 from the structure 21, and in accordance with biological information. A signal is output. That is, the first sensor signal output from the first piezoelectric element 23 includes a signal corresponding to biological information.

  Moreover, in this embodiment, the lower elastic member 22 is comprised with the porous member whose Asuka-C hardness is 5 or less. For this reason, the sensitivity can be improved. Here, with respect to the state of the lower elastic member 22 when the living body pressure is applied in the stacking direction of the first sensor unit 20, the lower elastic member 22 is composed of a porous member having the above hardness, A description will be given in comparison with the case of being composed of other members. In addition, since the structure 21 is comprised using the material whose Asker-C hardness is higher than the lower elastic member 22 as mentioned above, it is hard to deform | transform with living body pressure.

  First, with reference to FIG. 5A, the case where the lower elastic member J22 is made of a material different from the lower elastic member 22, for example, urethane rubber having an Asker-C hardness of about 50 will be described. When such a lower elastic member J22 is used, when a living body pressure is applied in the stacking direction of the first sensor unit 20, the Asker-C hardness of the structure 21 is high, and therefore, it is indicated by a dotted line in FIG. 5A. Thus, the lower elastic member J22 is deformed so that the surface on the first piezoelectric element 23 side is displaced downward as a whole and the side surface swells outward. At this time, the first piezoelectric element 23 is displaced downward along with the displacement of the lower elastic member J22 because the lower elastic member J22 is displaced downward as a whole, but due to the displacement of the lower elastic member J22. There is little deformation to do. For this reason, the first piezoelectric element 23 outputs a signal corresponding to the living body pressure applied to the first piezoelectric element 23 itself.

  On the other hand, as shown in FIG. 5B, when the lower elastic member 22 is composed of a porous member having an Asker C hardness of 5 or less, when biological pressure is applied in the stacking direction of the first sensor unit 20. As shown by the dotted line in FIG. 5B, the lower elastic member 22 is deformed so that the central portion of the surface on the first piezoelectric element 23 side contracts inside. Since the first piezoelectric element 23 is fixed to the lower elastic member 22, the first piezoelectric element 23 is deformed along with the deformation of the lower elastic member 22. That is, the first piezoelectric element 23 is deformed so that the central portion is displaced toward the structure 21 side. For this reason, the first piezoelectric element 23 outputs a signal corresponding to the living body pressure applied to the first piezoelectric element 23 itself and the deformation of the first piezoelectric element 23. That is, it can be said that the lower elastic member 22 also has a function as an amplifier that amplifies biological information. Therefore, the sensitivity can be improved by using such a lower elastic member 22.

  The lower elastic member 22 also has a function of attenuating the living body pressure by being deformed. For this reason, like this embodiment, by arrange | positioning under the 1st piezoelectric element 23, it can suppress that a biological pressure is propagated to the structure 21 side, improving the sensitivity of the 1st piezoelectric element 23. FIG. .

  On the other hand, the 2nd sensor part 30 is arrange | positioned so that the space 50 may be comprised between the protection members 40. FIG. In other words, it is difficult for the second sensor unit 30 to be directly applied with the living body pressure from the protection member 40.

  Further, the portion of the protective member 40 closer to the substrate 10 than the structure 21 is not easily crushed by the structure 21. For this reason, propagation of the living body pressure from the protective member 40 to the substrate 10 is also suppressed, and propagation of the living body pressure to the second sensor unit 30 via the substrate 10 is suppressed.

  In addition, as described above, the structure 21 is made of a material having a high Asuka-C hardness and hardly deformed, but more specifically, even if an assumed pressure is applied to the protective member 40. Consists of materials that are difficult to deform. In addition, the pressure assumed here means not only what originates in the biometric information of a detection target but the pressure assumed on the conditions applied. For example, when arranged on the vehicle seat 2, not only the occupant's biological information but also pressure generated when the occupant is seated or moved is included.

  Furthermore, in the present embodiment, the substrate 10 has a lower Asker-C hardness than the structure 21 in the first sensor unit 20. For this reason, compared with the case where the board | substrate 10 is made more than the Asker-C hardness of the structure 21, when a biological pressure is applied to the board | substrate 10, a biological pressure will become easy to be attenuate | damped by the said board | substrate 10. FIG. Therefore, the biological pressure applied to the substrate 10 from the protective member 40 via the first sensor unit 20 and the biological pressure directly applied to the substrate 10 from the protective member 40 are prevented from being propagated to the second sensor unit 30. Is done. That is, in the present embodiment, it is difficult for the second piezoelectric element 31 to output a signal associated with the living body pressure.

  The biological information detection sensor 1 also includes vibrations of the vehicle on which the vehicle seat 2 is mounted, fine movement of the body surface due to muscle contraction of the occupant, and when the occupant changes body posture or shakes the thigh. Vibration generated is also applied. In this case, the vibration accompanying these movements is extremely large compared to the biological information, and in the case of such a large vibration, the entire seat portion 2a vibrates. That is, the whole biological information detection sensor 1 vibrates, and the whole substrate 10 vibrates. Therefore, the first piezoelectric element 23 is applied with pressure (hereinafter referred to as noise pressure) due to vibration from the substrate 10 and outputs a signal corresponding to the noise pressure. That is, the first piezoelectric element 23 outputs a signal corresponding to the living body pressure and a signal corresponding to the noise pressure as the first sensor signal. The second piezoelectric element 31 receives a noise pressure from the substrate 10 and outputs a signal corresponding to the noise pressure. The differential amplifier 61 outputs the difference between the first sensor signal output from the first piezoelectric element 23 and the second sensor signal output from the second piezoelectric element 31 as a detection signal. At this time, since the noise signal included in the first sensor signal and the noise signal included in the second sensor signal are canceled, a signal in which the signal corresponding to the noise pressure is reduced is output as the detection signal.

  As described above, in the present embodiment, the structure 21 is made of a material having a hardness higher than that of the protective member 40, and the height from the substrate 10 is higher than the height from the substrate 10 in the second sensor unit 30. Yes. For this reason, when a large pressing force is applied when the occupant is seated on the vehicle seat 2, the portion of the protective member 40 closer to the substrate 10 than the structure 21 is suppressed. Therefore, it can suppress that biometric information is applied to the 2nd sensor part 30 via the part by the side of the board | substrate 10 from the structure 21 of the protection members 40. FIG. Therefore, it can suppress that detection accuracy falls.

  In addition, the protection member 40 is formed with a recess 40 b that forms a space 50 between the protection member 40 and the second sensor unit 30. For this reason, it can suppress that living body pressure is directly applied to the 2nd sensor part 30 from protection member 40, and can control that detection accuracy falls further.

  Furthermore, the first sensor unit 20 and the second sensor unit 30 are mounted on the common substrate 10. That is, the first piezoelectric element 23 and the second piezoelectric element 31 are mounted on the common substrate 10. For this reason, simplification of the structure can be achieved, and as a result, the manufacturing process can be simplified.

  The lower elastic member 22 is made of a porous member having an Asker C hardness of 5 or less, and the structure 21 is made of a material having an Asker C hardness higher than that of the lower elastic member 22. For this reason, when a living body pressure is applied from the first piezoelectric element 23 side, the lower elastic member 22 is deformed so that the central portion of the surface on the first piezoelectric element 23 side contracts inside. The first piezoelectric element 23 is also deformed as the lower elastic member 22 is deformed. Accordingly, the lower elastic member 22 can also function as an amplifier, and the sensitivity can be improved.

  Further, the substrate 10 is made of a material having a lower Asuka-C hardness than the structure 21. For this reason, compared with the case where the board | substrate 10 is comprised with the material more than the Asker-C hardness of the structure 21, when a biological pressure is applied to the board | substrate 10, it will be easy to attenuate a biological pressure in the said board | substrate 10. Become. Therefore, it is possible to suppress the biological pressure from being applied to the second sensor unit 30 via the substrate 10. That is, it can suppress that the signal according to a living body pressure is contained in the 2nd sensor signal.

  Further, when the first piezoelectric element 23 and the second piezoelectric element 31 are made of a directional material, the first piezoelectric element 23 and the second piezoelectric element 31 are sensitive in the direction in which the living body pressure is applied. Be placed. That is, it arrange | positions so that it may have a sensitivity in the up-down direction in FIG. For this reason, when the first piezoelectric element 23 and the second piezoelectric element 31 are made of a directional material, even if the substrate 10 vibrates in the longitudinal direction of the vehicle due to vibrations in the longitudinal direction of the vehicle, the vibrations Does not output the pressure caused by For this reason, it can suppress that detection accuracy falls further.

(Second Embodiment)
A second embodiment will be described. In the second embodiment, an upper elastic member is added above the first piezoelectric element 23 with respect to the first embodiment, and the other parts are the same as those in the first embodiment. Omitted.

  In the present embodiment, as shown in FIG. 6, the first sensor unit 20 includes an upper elastic member 24 disposed on the opposite side of the lower elastic member 22 with the first piezoelectric element 23 interposed therebetween. That is, the first sensor unit 20 includes the upper elastic member 24 disposed above the first piezoelectric element 23. In other words, the first sensor unit 20 is configured by sequentially laminating the structure 21, the lower elastic member 22, the first piezoelectric element 23, and the upper elastic member 24 from the substrate 10 side. The upper elastic member 24 is made of a material that is easier to attenuate the high frequency component than the lower elastic member 22 and is less likely to attenuate the lower frequency component than the lower elastic member 22. For example, the upper elastic member 24 is made of a urethane elastomer material or silicone gel having an Asuka-C hardness of about 30 and having viscoelasticity as a material having such characteristics.

  In addition, the pressure resulting from biological information, such as a heartbeat and a pulse of a biological body, is a low frequency component of about 1 to 1.2 Hz. In addition, the movement due to the vibration of the living body in the fine movement of the body surface due to the muscle contraction becomes a high frequency component of about 20 to 30 Hz, and the vibration generated when the occupant changes the posture or shakes the thigh. Further, the vibration of the vehicle and the like are higher frequency components than the pressure caused by the biological information. For this reason, it can be said that the upper elastic member 24 is made of a material that easily attenuates a high-frequency component caused by biological vibrations and the like and hardly attenuates a low-frequency component caused by biological information.

  Here, the present inventors examined the case where the upper elastic member 24 was made of a urethane elastomer material having an Asuka-C hardness of 30, and obtained measurement results shown in FIGS. 7A and 7B. FIG. 7A shows a measurement result when the biological information detection sensor 1 is arranged on the vehicle seat 2 of the driving simulator having a vibration excitation function, and vibration having a high frequency of 10 to 100 Hz is randomly applied. . FIG. 7B is a measurement result when the biological information detection sensor 1 is arranged on the vehicle seat 2 of the driving simulator having the vibration excitation function, and vibration having a low frequency of 1 to 1.5 Hz is applied at random. . 7A and 7B are diagrams in which measurement is performed separately when the upper elastic member 24 is arranged and measurement when the upper elastic member 24 is not arranged, and the obtained measurement results are overlapped. is there.

  As shown in FIG. 7A, it is confirmed that when the upper elastic member 24 is arranged, the signal related to the high frequency component is smaller than when the upper elastic member 24 is not arranged. Further, as shown in FIG. 7B, it is confirmed that even when the upper elastic member 24 is arranged, the signal has the same amplitude as when the upper elastic member 24 is not arranged. That is, in the present embodiment, it is confirmed that the upper elastic member 24 is made of a material that easily attenuates the high frequency component and hardly attenuates the low frequency component. In addition, although the measurement result at the time of comprising the upper elastic member 24 with a urethane elastomer material was shown here, even if it comprises the upper elastic member 24 with a silicone gel, the same result is obtained.

  In the present embodiment described above, the upper elastic member 24 is disposed above the first piezoelectric element 23. The upper elastic member 24 is made of a material that can attenuate the high frequency component more easily than the lower elastic member 22. For this reason, the first piezoelectric element 23 is restrained from applying noise pressure from the protective member 40 via the upper elastic member 24. That is, application of noise pressure from the upper side of the first piezoelectric element 23 is suppressed. For this reason, the difference between the noise pressure applied to the first piezoelectric element 23 and the noise pressure applied to the second piezoelectric element 31 can be reduced, and the detection accuracy can be improved.

  The upper elastic member 24 is made of a material that is less likely to attenuate low frequency components than the lower elastic member 22. For this reason, it is possible to suppress the biological pressure from being attenuated by the upper elastic member 24. That is, it can suppress that a sensitivity falls.

(Third embodiment)
A third embodiment will be described. In the third embodiment, an upper elastic member is added above the second piezoelectric element 31 with respect to the second embodiment, and the other parts are the same as those in the second embodiment, and therefore will be described here. Is omitted.

  In the present embodiment, as shown in FIG. 8, the second sensor unit 30 has an upper elastic member 32 disposed on the opposite side of the substrate 10 with the second piezoelectric element 31 interposed therebetween. That is, the second sensor unit 30 has an upper elastic member 32 that is disposed above the second piezoelectric element 31. In other words, the second sensor unit 30 is configured by laminating the second piezoelectric element 31 and the upper elastic member 32 in this order from the substrate 10 side. In the present embodiment, the upper elastic member 32 in the second sensor unit 30 is configured by the same as the upper elastic member 24 in the second sensor unit 30.

  Here, the present inventors examined the biological information detection sensor 1 of the present embodiment by disposing it on the vehicle seat 2 of a driving simulator having a vibration excitation function, and FIG. 9A to FIG. 9D and FIG. The measurement results shown in FIGS. 10D, 11A to 11D, and 12A to 12D were obtained. 9A and 9B show measurement results when vibration having a frequency of 0.1 to 10 Hz is randomly applied in a state where an occupant is seated on the vehicle seat 2. FIG. 11A and FIG. 11B are measurement results when vibration having a frequency of 1.5 Hz is applied in a state where an occupant is seated on the vehicle seat 2.

  As shown in FIGS. 9A, 9B, 10A, 10B, 11A, 11B, 12A, and 12B, a first sensor signal is output from the first piezoelectric element 23, and a second piezoelectric element 31 is output. It is confirmed that the second sensor signal is output. Then, as shown in FIGS. 9C, 10C, 11C, and 12C, when the first sensor signal and the second sensor signal are superimposed, the first sensor signal and the second sensor signal completely coincide with each other. It is confirmed that a shift occurs in each peak portion. This is because, as described above, the first sensor signal becomes a signal corresponding to the living body pressure and the noise pressure, and the second sensor signal becomes a signal corresponding to the noise pressure.

  For this reason, as shown in FIGS. 9D, 10D, 11D, and 12D, when the difference between the first sensor signal and the second sensor signal is calculated, the noise signal and the second sensor included in the first sensor signal are calculated. The noise signal included in the signal is a canceled detection signal. From the above, it is confirmed that the detection signal is a signal in which the signal corresponding to the noise pressure is reduced. That is, the present inventors have confirmed that the detection signal becomes a signal in which the signal corresponding to the noise pressure is reduced on the measurement result with the driving simulator having the vibration excitation function.

  For example, in FIG. 9D and the like, a small peak indicated by an arrow B is shown after a large peak indicated by an arrow A. This minute peak is not caused by noise pressure, but is a peak corresponding to a Q wave in the atrial systole and an S wave in the isovolumetric systole of the cardiac cycle. Further, as shown in FIGS. 10D and 12D, it is also confirmed that the pressure caused by the biological information is a low frequency component of about 1.2 Hz.

  Then, the present inventors arranged the biological information detection sensor 1 of the present embodiment on the vehicle seat 2 and actually traveled the vehicle, and obtained experimental results shown in FIGS. 13A to 13D. 13A to 13D show experimental results when the vehicle is driven at 80 km / h.

  As shown in FIGS. 13A and 13B, it is confirmed that the first sensor signal is output from the first piezoelectric element 23 and the second sensor signal is output from the second piezoelectric element 31. Then, as shown in FIG. 13C, when the first sensor signal and the second sensor signal are superposed, the first sensor signal and the second sensor signal are completely matched, as in FIGS. 9C and 11C. In other words, it is confirmed that a deviation occurs at each peak portion.

  For this reason, as shown in FIG. 13D, when the difference between the first sensor signal and the second sensor signal is calculated, the noise signal included in the first sensor signal and the noise signal included in the second sensor signal are canceled. Detection signal. That is, it is confirmed that the same result as the measurement result is obtained. Note that the signal processing circuit 60 may also output the result of frequency conversion based on the first sensor signal and the second sensor signal, as in the measurement result.

  In the present embodiment described above, the upper elastic member 32 is also disposed above the second piezoelectric element 31. The upper elastic member 24 disposed above the first piezoelectric element 23 and the upper elastic member 32 disposed above the second piezoelectric element 31 have the same configuration. For this reason, the difference between the influence of noise applied to the first piezoelectric element 23 from the substrate 10 side and the influence of noise applied to the second piezoelectric element 31 from the substrate 10 side can be reduced. Therefore, the detection accuracy can be further improved.

  Further, the second sensor unit 30 is arranged so that a space 50 is formed between the second sensor unit 30 and the protection member 40, and the substrate 10 vibrates in comparison with the first sensor unit 20 in contact with the protection member 40. When this occurs, it is likely to vibrate more greatly than the first sensor unit 20. However, in this embodiment, since the upper elastic member 32 is also disposed above the second piezoelectric element 31, a predetermined weight member is disposed on the second piezoelectric element 31. For this reason, when the board | substrate 10 vibrates, it can suppress that the 2nd sensor part 30 vibrates more largely than the 1st sensor part 20. FIG. That is, when the substrate 10 vibrates, the difference in the magnitude of vibration between the first sensor unit 20 and the second sensor unit 30 can be reduced. Therefore, the difference in the magnitude of the noise signal included in the first sensor signal and the second sensor signal can be reduced, and the detection signal can be prevented from including a signal corresponding to the noise pressure.

(Modification of the third embodiment)
A modification of the third embodiment will be described. In the said 3rd Embodiment, as FIG. 14 shows, the 1st sensor part 20 may be set as the structure by which the upper side elastic member 24 is not arrange | positioned. That is, the upper elastic member 32 as a weight member may be disposed only on the second sensor unit 30. Even in such a configuration, when the substrate 10 vibrates, the difference in the magnitude of vibration between the first sensor unit 20 and the second sensor unit 30 can be reduced. Therefore, the substrate 10 is included in the first sensor signal and the second sensor signal. The difference in the magnitude of the noise signal can be reduced. In the case of such a configuration, a member that functions as a weight member may be disposed on the second piezoelectric element 31 and may not be an elastic member.

(Fourth embodiment)
A fourth embodiment will be described. In the fourth embodiment, a stopper portion is arranged with respect to the third embodiment, and the other parts are the same as those in the third embodiment, and the description thereof is omitted here.

  In the present embodiment, as shown in FIG. 15, a stopper unit 70 is disposed on one surface 10 a of the substrate 10 in addition to the first sensor unit 20 and the second sensor unit 30. Specifically, the stopper unit 70 is disposed on the opposite side of the first sensor unit 20 with the second sensor unit 30 interposed therebetween. That is, the stopper part 70 is arranged so that the second sensor part 30 is arranged between the first sensor part 20 and the stopper part 70.

  The stopper portion 70 is configured by laminating a structure 71 and an elastic member 72. In the present embodiment, the structure 71 is made of the same material as the structure 21 in the first sensor unit 20, and the elastic member 72 is made of the same material as the lower elastic member 22 in the first sensor unit 20. . The length in the direction along the stacking direction of the structure 21 and the lower elastic member 22 in the first sensor unit 20 and the length in the direction along the stacking direction of the structure 71 and the elastic member 72 in the stopper unit 70 are as follows. Are equal. That is, the height of the structure 71 in the stopper portion 70 from the one surface 10 a of the substrate 10 is higher than the height from the one surface 10 a of the substrate 10 in the second sensor portion 30.

  According to the present embodiment described above, the stopper portion 70 is disposed on the opposite side of the first sensor portion 20 with the second sensor portion 30 interposed therebetween. For this reason, in the part between the structure 21 in the 1st sensor part 20 and the structure 71 in the stopper part 70 among the protection members 40, it is suppressed that it is further crushed. Therefore, it is further suppressed that the pressure resulting from biological information is applied to the second sensor unit.

(Other embodiments)
The present invention is not limited to the embodiment described above, and can be appropriately changed within the scope described in the claims.

  For example, in each of the above embodiments, the signal processing circuit 60 may not be provided on the substrate 10, and may be provided in an external circuit provided separately from the substrate 10.

  In each of the above embodiments, the signal processing circuit 60 may include an analog-digital conversion circuit (that is, an A / D conversion circuit) together with the differential amplifier 61. In this case, an analog-digital conversion circuit may be provided between the differential amplifier 61 and the first piezoelectric element 23 and the second piezoelectric element 31. That is, since the first sensor signal output from the first piezoelectric element 23 and the second sensor signal output from the second piezoelectric element 31 are analog signals, these sensor signals are converted into digital signals and a differential amplifier. 61 may be input. Further, the detection signal output from the differential amplifier 61 may be input to the analog-digital conversion circuit. That is, the analog signal output from the differential amplifier 61 may be converted into a digital signal and output to an external circuit.

  Furthermore, in each said embodiment, the 1st piezoelectric element 23 and the 2nd piezoelectric element 31 may be comprised with a different material. In this case, for example, the characteristic of each sensor signal may be corrected by providing a correction circuit or the like in the signal processing circuit 60, and then each sensor signal may be input to the differential amplifier 61.

  Moreover, in each said embodiment, the hollow part 40b is not formed in the protection member 40, but the 2nd sensor part 30 and the protection member 40 may contact | abut. Even with such a configuration, the portion of the protective member 40 closer to the substrate 10 than the structure 21 is suppressed from being crushed. That is, the protective member 40 in the vicinity of the second sensor unit 30 functions as a buffer member that attenuates the living body pressure by being not crushed. For this reason, it is suppressed that a living body pressure is applied to the 2nd sensor part 30, and a detection accuracy falls.

  Furthermore, in the said 1st Embodiment, as FIG. 16 shows, the lower side elastic member 22 does not need to be provided. That is, the first sensor unit 20 may be configured to include only the structure 21 and the first piezoelectric element 23. Although not particularly illustrated, the lower elastic member 22 may not be provided in the second to fourth embodiments.

  In each of the above embodiments, the structure 21 is maintained such that the height of the structure 21 is higher than the height of the second sensor unit 30 when the protective member 40 is crushed and the structure 21 is crushed. If it is, it may be comprised with the material which has the hardness below the hardness of the protection member 40. For example, the structure 21 may be made of urethane foam, chloroprene rubber, or the like having an Asuka-C hardness of 5 or less. In the case of such a configuration, for example, in a state before the structure 21 is crushed, the height of the structure 21 is set to be higher than the height of the second sensor unit 30 by a predetermined amount. That's fine.

  Moreover, in each said embodiment, the arrangement | positioning location of the biometric information detection sensor 1 can be changed suitably. For example, the biological information detection sensor 1 may be disposed under the buttocks in the vehicle seat 2. The biological information detection sensor 1 may be disposed inside the backrest 2b of the vehicle seat 2. When the biological information detection sensor 1 is disposed inside the backrest 2b, the substrate 10 is disposed on the opposite side of the back of the occupant with the protective member 40 interposed therebetween. And when the 1st piezoelectric element 23 and the 2nd piezoelectric element 31 are comprised with the material which has directivity, even if the board | substrate 10 vibrates in the vertical direction of a vehicle by the vibration in the vertical direction of a vehicle, etc. Output of the resulting pressure as a signal is suppressed. Moreover, when arrange | positioning the biological information detection sensor 1 in the backrest part 2b, the biological information detection sensor 1 can be arrange | positioned in the part which opposes a passenger | crew's waist | hip | lumbar part, or its vicinity, for example. In such a configuration, even when the occupant changes his / her posture, the waist is likely to remain in contact with the vehicle seat 2, so that the living body pressure can always be applied to the living body information detection sensor 1.

  Further, in each of the above embodiments, the biological information detection sensor 1 is not provided in the vehicle seat 2, but a seat of a health device that vibrates in a seated state, a seat in a play device such as a roller coaster, or a strategy It may be provided in a sheet or the like provided in Moreover, the biological information detection sensor 1 may be provided on a sheet that does not move, or may be provided on a sheet in a driving simulator. Furthermore, the biological information detection sensor 1 may be provided in a cushion or a cushion as a seat on which an occupant sits.

  Furthermore, in the said 4th Embodiment, the stopper part 70 may be comprised only with the structure 71. FIG. Moreover, the height of the structure 71 or the elastic member 72 may be adjusted so that the stopper part 70 may become equal to the height from the one surface 10a of the board | substrate 10 in the 1st sensor part 20, or on the elastic member 72 Different members may be laminated.

DESCRIPTION OF SYMBOLS 10 Board | substrate 10a One surface 20 1st sensor part 23 1st piezoelectric element 30 2nd sensor part 31 2nd piezoelectric element 40 Protection member 50 Space 60 Signal processing circuit

Claims (10)

A biological information detection sensor arranged on the seat (2) on which the living body is seated to detect biological information of the living body;
A substrate (10) having one surface (10a);
A first sensor unit (20) having a first piezoelectric element (23) that outputs a signal corresponding to pressure;
A second sensor unit (30) having a second piezoelectric element (31) for outputting a signal corresponding to the pressure;
A protective member (40) that is provided on the substrate in a state of covering the first sensor unit and the second sensor unit, and to which pressure caused by the biological information is applied;
A signal processing circuit (60) for outputting a detection signal based on a difference between a signal output from the first piezoelectric element and a signal output from the second piezoelectric element;
The first sensor unit and the second sensor unit are mounted on a common substrate,
The protective member is disposed on the side of the substrate that comes into contact when the living body is seated, and propagates the pressure by being crushed when the living body is seated on the seat,
In the first sensor unit, the structure (21) and the first piezoelectric element are sequentially stacked from the substrate side, and the biological information is propagated through the protective member when the living body is seated on the seat. To output a signal including the biological information,
In the structure, the height from one surface of the substrate is higher than the height from one surface of the substrate in the second sensor unit, and even when the living body is seated on the seat, the height from the one surface of the substrate is increased. A biological information detection sensor in which the height of the second sensor unit is higher than the height from one surface of the substrate.   The biological information detection sensor according to claim 1, wherein the structure is made of a material having a hardness higher than that of the protective member.   The biological information detection sensor according to claim 1, wherein the protective member is formed with a hollow portion (40 b) that forms a space (50) between the protective member and the second sensor portion. The first sensor unit includes a lower elastic member (22) disposed between the structure and the first piezoelectric element,
The biological information detection sensor according to any one of claims 1 to 3, wherein the lower elastic member is made of a material having lower hardness than the structure.   The biological information detection sensor according to claim 4, wherein the lower elastic member is formed of a porous member having an Asuka-C hardness of 5 or less.   The first sensor unit includes an upper elastic member (24) made of a material that is laminated on the first piezoelectric element and attenuates a high frequency component higher than a frequency component caused by the biological information. Item 6. The biological information detection sensor according to any one of Items 1 to 5.   The biological information detection sensor according to claim 6, wherein the second sensor unit includes an upper elastic member (32) stacked on the second piezoelectric element and made of the same material as the upper elastic member.   The living body information detection sensor according to claim 2 with which said 2nd sensor part has weight member (32) laminated on said 2nd piezoelectric element.   The one surface of the substrate is made of the same material as the structure in the first sensor portion on the opposite side of the first sensor portion across the second sensor portion, and the height from the one surface of the substrate is The biological information detection sensor according to any one of claims 1 to 8, wherein a stopper portion (70) including a structure (71) that is higher than a height from one surface of the substrate in the second sensor portion is disposed. .   The biological information detection sensor according to claim 1, wherein the substrate has a hardness lower than that of the structure.

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