Biological information detection device

Abstract

A biological information detection device (10) for detecting biological information comprises: a plurality of piezoelectric sensors (30) that measure a load from a living body and detect a plurality of pieces of vibration information generated by the living body; a seat cushion (20) that comes into contact with the living body and pressure receiving portions (30a) of the plurality of piezoelectric sensors (30); a seat frame (21) that slidably supports the seat cushion (20); and a signal processing unit (40) that separates a predetermined vibration signal from the plurality of pieces of vibration information. The plurality of pieces of vibration information include a biological signal and a body movement signal of the living body. The seat cushion (20) is elastic and / or viscous. The plurality of piezoelectric sensors (30) include: a direct measurement sensor (30A) that is installed directly below a load input region to which the load is inputted, and that has a main detection direction coinciding with the direction of the load; and an indirect measurement sensor (30B) that detects, among the body movement signals, a second body movement signal having a phase delayed relative to a first body movement signal detected by the direct measurement sensor (30A), by the load from the living body being transmitted via the seat cushion (20).

Description

Biological information detection device

[0001] The present invention relates to a biological information detection device.

[0002] In a running vehicle, a system is known in which sensors are arranged in a seat and the pulse wave of a driver on the seat is detected. In Citation Document 1, a plurality of piezoelectric sensors are arranged in the seat, and after removing the stationary noise detected by the sensors by an adaptive filter, blind source separation (BSS) is used to remove non-stationary noise such as body movement. As a result, even when strong noise is mixed in the observation signal, it is possible to detect the pulse wave of the driver of the automobile.

[0003] Japanese Patent Application Laid-Open No. 2019-084069

[0004] In BSS, each signal is estimated and separated based on the assumption that the vibration signal detected by the sensor includes a plurality of independent signals. Therefore, when separating the noise signal and the target signal, in the vibration signals detected by a plurality of sensors, for example, only the noise signals have a phase difference, and the target signals do not have a phase difference. It is easier to infer or separate the target signal when there is a difference in the phase shift between a plurality of independent signals.

[0005] However, since the driver's biological signal and the main noise signals during driving such as body movement are generated from the same human body, when each sensor is arranged at a close position in the seat, it is difficult for either the pulse wave or the noise signal to generate a phase difference. On the other hand, when the installation positions of each sensor are separated, there is a possibility that the body movements of other people in the vehicle are input to each sensor, and there is a problem that signal separation becomes more difficult.

[0006] The present invention has been made in view of such circumstances, and an object thereof is to easily detect a target signal in a noise environment.

[0007] A biological information detection device according to one aspect of the present invention is a biological information detection device for detecting biological information, comprising: a plurality of piezoelectric sensors that measure a load from a living body and detect a plurality of vibration information emitted by the living body; an intermediate body that comes into contact with the living body and the pressure-receiving parts of the plurality of piezoelectric sensors; a support that slidably supports the intermediate body; and a signal processing means for separating a predetermined vibration signal from the plurality of vibration information, wherein the plurality of vibration information includes a biological signal and a body motion signal of the living body, the intermediate body has at least one property of elasticity and viscosity, and the plurality of piezoelectric sensors include a direct measurement sensor installed directly below a load input area to which a load is input and whose main detection direction coincides with the direction of the load, and an indirect measurement sensor that detects a second body motion signal among the body motion signals that is in phase later than a first body motion signal detected by the direct measurement sensor, as the load from the living body is transmitted through the intermediate body.

[0008] According to the present invention, it becomes possible to easily detect a target signal in a noisy environment.

[0009] This figure shows an overview of the functional block diagram of the bio-information detection device according to the first embodiment. This figure shows an example of the signal processing result in the bio-information detection device according to the first embodiment. This figure shows an example of the signal processing result in the bio-information detection device according to the first embodiment. This figure shows an example of vibration information detected by the bio-information detection device according to the first embodiment. This figure shows an example of the configuration of the bio-information detection device according to the first embodiment. This figure shows another example of the configuration of the bio-information detection device according to the first embodiment. This figure shows an example of the configuration of the bio-information detection device according to the second embodiment. This is a graph showing the relationship between the sensor position and the phase difference of the pulse wave in the bio-information detection device according to the second embodiment. This figure shows an example of the configuration of the piezoelectric sensor 30 in the bio-information detection device according to the second embodiment. This figure shows a modified example of the configuration of the piezoelectric sensor 30 in the bio-information detection device according to the second embodiment. This figure shows another modified example of the configuration of the piezoelectric sensor 30 in the bio-information detection device according to the second embodiment. This figure shows a modified example of the piezoelectric sensor 30 in the bio-information detection device according to the second embodiment. This figure illustrates the arrangement of the piezoelectric sensor 30 according to the modified example. This figure shows another This diagram illustrates the arrangement of the piezoelectric sensor 30 in a modified example. This diagram shows another modified example of the biometric information detection device according to the second embodiment.

[0010] Embodiments of the present invention will be described below with reference to the drawings. The drawings of this embodiment are illustrative, and the dimensions and shapes of each part are schematic; the technical scope of the present invention should not be limited to this embodiment.

[0011] <First Embodiment> First, the configuration of the biological information detection device according to the first embodiment of the present invention will be described with reference to Figures 1 to 5. Figure 1 is a diagram showing an overview of the functional block diagram of the biological information detection device according to this embodiment. Figures 2A and 2B are diagrams showing an example of the signal processing result in the biological information detection device according to the first embodiment. Figure 3 is a diagram showing an example of vibration information detected by the biological information detection device according to this embodiment. Figure 4 is a diagram showing an example of the configuration of the biological information detection device according to the first embodiment. Figure 5 is a diagram showing another example of the configuration of the biological information detection device according to the first embodiment. Figures 2 to 5 show an embodiment in which the biological information detection device is used as a device to detect pulse wave information of a driver seated on a seat 11 in a moving object such as a vehicle.

[0012] As shown in Figures 1 and 4, the biological information detection device 10 in this embodiment may include a seat 11 on which a living person sits, a seat cushion 20, a seat frame 21 that slidably supports the seat cushion, a plurality of piezoelectric sensors 30, and a signal processing unit 40. The seat 11 includes a seat surface 11a and a back surface 11b. The seat cushion 20 is an example of an "intermediate body". The seat frame 21 is an example of a "support". In this embodiment, as shown in Figures 4 to 6, the seat cushion 20 and the seat frame 21 are provided on both the seat surface 11a and the back surface 11b of the seat 11, but they may be provided on either the seat surface 11a or the back surface 11b.

[0013] In this embodiment, the piezoelectric sensor 30 measures multiple vibration information emitted by, for example, the driver of a moving object (an example of a "living organism") as a load from the driver. Here, the multiple vibration information emitted by the driver includes biological signals and body movement signals. Biological signals include, for example, pulse waves, cardiac pulsations, and respiration. From these biological signals, pulse rate, respiratory rate, etc., can be estimated. In this embodiment, the configuration of a biological information detection device that detects pulse wave signals as biological signals is shown. Body movement signals refer to vibrations caused by body movements other than biological signals. For example, body movement signals may include vibrations of the driver's body while driving due to road noise, body movements due to driving actions, and unconscious body movements of the driver. The piezoelectric sensor 30 may be, for example, a quartz crystal load sensor or a pressure sensor, and the vibration information may be measured as pressure.

[0014] The piezoelectric sensor 30 includes a direct measurement sensor 30A and an indirect measurement sensor 30B. Here, indirect measurement refers to measuring vibration information emitted by a living organism, for example, through an intermediate body, as vibration information with a phase delay to the load input. Therefore, the vibration information measured by indirect measurement is vibration information with a phase delay to the vibration information measured by direct measurement, which will be described later. Measuring through an intermediate body means, for example, that vibration information from a living organism is transmitted to the sensor by the intermediate body and measured. For example, in this embodiment, the load and pressure are transmitted to the indirect measurement sensor 30B by utilizing the slippage that occurs in the seat cushion 20, which is an intermediate body, on the seat frame 21, and a body motion signal with a phase delay is measured. Alternatively, the intermediate body may be a viscous fluid, and the load and pressure may be transmitted to the sensor by the propagation of stress within the fluid. Direct measurement refers to measuring vibration information with respect to a load input without the phase delay that occurs in indirect measurement. Therefore, even in direct measurement, it is not necessarily required that the sensor measure the vibration information emitted by the living body by making contact with the living body; it may also include measurement via an intermediate.

[0015] The seat cushion 20 has at least one of the properties of elasticity and viscosity. Elasticity refers to the property of deforming when stress is applied and returning to its original state when the stress is removed, and is sometimes expressed as flexibility, which indicates the ease of elastic deformation. Viscosity refers to the property of generating stress that uniformizes the flow velocity of a fluid. The intermediate material may be, for example, polyurethane foam, gel, rubber, or a viscous fluid.

[0016] The seat cushion 20 is supported such that its first surface 20a contacts the driver seated in the seat, and its second surface 20b, which is the opposite side of the first surface 20a, contacts the seat frame 21.

[0017] In this embodiment, a direct measurement sensor 30A and an indirect measurement sensor 30B are installed between the seat frame 21 and the seat cushion 20, and the pressure-receiving parts 30a of the direct measurement sensor 30A and the indirect measurement sensor 30B are in contact with the second surface 20b of the seat cushion 20. Therefore, the load from the driver is first transmitted to the seat cushion 20, and then transmitted to the direct measurement sensor 30A and the indirect measurement sensor 30B via the seat cushion 20, thereby allowing the direct measurement sensor 30A and the indirect measurement sensor 30B to measure the vibration information of the body. The number and arrangement of the direct measurement sensors 30A and the indirect measurement sensors 30B are not limited to the example shown in Figure 4. For example, as shown in Figure 5, there may be multiple direct measurement sensors 30A and indirect measurement sensors 30B installed, and they may be installed on the back surface 11b of the seat.

[0018] In this embodiment, the mechanism by which the direct measurement sensor 30A and the indirect measurement sensor 30B detect body movement signals will be described. The direct measurement sensor 30A is a sensor that measures the driver's body movement signals as signals with almost no phase delay to the load input. Therefore, the direct measurement sensor 30A is installed, for example, directly below the load input area where the driver's load is input, and is configured so that the main detection direction coincides with the direction of the load. As a result, it is possible to detect body movement signals with almost no phase difference from the driver's load input compared to the body movement signals measured by the indirect measurement sensor 30B, which will be described later. Note that "directly below the load input area" refers to the area on the first surface 20a of the seat cushion 20 where the load input of the living body is concentrated. For example, it may be directly below bony prominences such as the ischial tuberosity or sacrum, or directly below the area where the back is in contact with the back surface 11b of the seat 11 in a driving posture. Furthermore, it is not necessarily limited to a single point, but may include the entire area where the input load is concentrated. Furthermore, "directly below" is not limited to an arrangement where the biological body and the measurement sensor 30A are in direct contact, but also includes being positioned in a direction directly below. Therefore, the direct measurement sensor 30A may be installed on the first surface 20a of the seat cushion 20 and in contact with the driver, or it may be placed on the contact surface between the seat frame 21 and the seat cushion 20.

[0019] On the other hand, the indirect measurement sensor 30B measures the body motion signal as a load transmitted through an intermediate body. As a result, the indirect measurement sensor 30B measures a body motion signal with a phase delay compared to the body motion signal measured by the direct measurement sensor 30A. It is desirable that the indirect measurement sensor 30B be installed in a position where, for example, no body motion signals from living organisms other than the driver are input, and away from the load input area, and where the load is transmitted through the seat cushion 20, and that the main detection direction is set to a direction other than the load direction. In the embodiment shown in Figure 4, the sensor is installed on the side of the seat frame 21 on the driver's leg side, with the main detection direction set to a direction approximately perpendicular to the load direction. By installing the indirect measurement sensor 30B away from the load input area and with the main detection direction set to a direction different from the load direction, the indirect measurement sensor 30B no longer directly measures the compressive load F1. Therefore, it becomes possible to measure the body motion signal of living organisms only by the load transmitted through the intermediate body, and it is possible to measure a body motion signal with a phase delay compared to the direct measurement sensor 30A.

[0020] Next, the mechanism by which a phase delay occurs in the body motion signal during indirect measurement in this embodiment will be explained. In this embodiment, a seat cushion 20 is used as an example of an intermediate body. When a compressive load F1 from a driver seated on the seat 11 is applied to the seat cushion 20, the seat cushion 20 sinks, and the load is transmitted to the seat frame 21 along the direction of F1. Here, the direction of the compressive load F1 from the driver is not strictly perpendicular to the stacking direction of the seat cushion 20 and the seat frame 21 due to the unevenness of the seat cushion and the driver's body, and because the body motion signal includes vibrations of the driver's body during driving due to road noise. Therefore, a frictional force f1 is generated between the seat cushion 20 and the seat frame 21 in a direction along the contact surface, depending on the direction in which the compressive load F1 is applied to the seat cushion 20. At this time, the seat frame 21 supports the seat cushion 20 so that it can slide. Therefore, the seat cushion 20 slides or shifts on the seat frame 21 in the direction of the frictional force f1. Consequently, the end of the seat cushion 20 that is in contact with the pressure-receiving part 30a of the indirect measurement sensor 30B is displaced, and a body motion signal due to the transmitted load is input to the indirect measurement sensor 30B. In this way, the indirect measurement sensor 30B measures the driver's load via the seat cushion 20 and detects a body motion signal with a phase delay. In this embodiment, as described above, the indirect measurement sensor 30B indirectly measures the driver's load and detects a body motion signal with a larger phase delay of several tens to several hundred ms compared to the body motion signal detected by the direct measurement sensor 30A.

[0021] Figure 3 shows only the motion signal measurement data from the vibration information measured by the direct measurement sensor 30A and the indirect measurement sensor 30B. It can be seen that there is a phase delay between the measurement value of the direct measurement sensor 30A and the measurement value of the indirect measurement sensor 30B.

[0022] The structure for the direct measurement sensor 30A and the indirect measurement sensor 30B to detect motion signals with a phase difference is not limited to the above. For example, even if the seat cushion 20 does not slip, the intermediate body may compress and deform, increasing the volume of the end of the seat cushion 20, and a load may be input to the pressure receiving part 30a of the indirect measurement sensor 30B.

[0023] Next, the mechanism by which the direct measurement sensor 30A and the indirect measurement sensor 30B measure pulse waves, which are biological signals, will be explained in this embodiment. A pulse wave is a wave of propagating pressure fluctuations within the arteries, caused by the pumping of blood by the heart's pulsations. The pulse wave propagates within the arteries along the direction of arterial flow from the heart to the toes. The direction of pressure fluctuations within the arteries is perpendicular to the blood vessels. The direct measurement sensor 30A and the indirect measurement sensor 30B measure these pressure fluctuations as load and pressure from the body and detect the pulse wave.

[0024] However, the load applied to the seat cushion 20 by pulsation is very small compared to the body motion signal, and no displacement of the edges of the seat cushion 20 occurs due to the seat cushion 20 sliding. Therefore, pulse waves with a phase delay are not detected by the indirect measurement sensor 30B in the same way as the body motion signal described above. On the other hand, the load due to pulsation does not concentrate in the load input area like the load due to body motion, but originates from the entire body of the living organism. As a result, the load due to pulsation is directly measured by the direct measurement sensor 30A and the indirect measurement sensor 30B from the arteries of the body that are in contact directly above or near each sensor. Consequently, although the pulse wave has a phase difference along the flow of pulsation from the heart to the feet, it is measured by both the direct measurement sensor 30A and the indirect measurement sensor 30B as a signal without the large phase difference that occurred with the body motion signal.

[0025] In this way, the vibration information measured by the direct measurement sensor 30A and the indirect measurement sensor 30B shows almost no phase difference between biological signals, while the body motion signals show a sufficiently large phase difference of about 10 ms or more compared to the phase difference between biological signals. Therefore, it is possible to create a phase difference in the body motion signals measured by each piezoelectric sensor 30 without having to install the piezoelectric sensors 30 so far apart that body motion signals other than those of the driver would be input.

[0026] Next, the signal processing method in the signal processing unit 40 will be described. The signal processing unit 40 separates the biological signal, which is the target signal in this invention, from the vibration information. For example, in this embodiment, the biological signal is separated by BSS.

[0027] As shown in Figure 1, the vibration information emitted by a living organism includes both biological signals and body motion signals. Therefore, as shown in Figure 2A, the direct measurement sensor 30A and the indirect measurement sensor 30B measure vibration information that is a mixture of biological signals and body motion signals. However, the signal-to-noise ratio (S / N ratio) of the biological signals and body motion signals in the measured vibration information is very small, for example, about 1 / 10 to 1 / 100. Therefore, while the pulse wave, which is a biological signal, can be recognized when the vehicle is stationary, the body motion signal is larger than the pulse wave when the vehicle is moving, and in this state, it is not possible to detect pulsation during movement from the vibration information. According to the present invention, even when the S / N ratio is very small, it is possible to remove the body motion signal, which is noise, and detect the biological signal, which is the target signal.

[0028] BSS is a signal processing method that separates and estimates the unknown original signals, i.e., source signals, from observed signals obtained by measuring signals output from n signal sources with m sensors. Let xi (i=1,...,m) be observed signals of length N measured at each of the m observation points, and let X := [xT1,...,xTm]T be the matrix of observed signals. On the other hand, let sj (j=1,...,n) be the n source signals, and let S := [sT1,...,sTn]T be the matrix of source signals. If A is the m x n mixture matrix, the relationship between the observed signal matrix X and the source signal matrix S is expressed as X = AS. The observed signal matrix X is vibration information in this embodiment and is known, but A and S are unknown and cannot be solved in general. Therefore, BSS performs signal source separation based on some assumption, such as that each signal source is statistically independent of the others.

[0029] Therefore, when estimating and separating each source signal using BSS, if it is possible to create almost no phase difference in either the biological signal or the body movement signal measured by each sensor, while creating a large phase difference in only one of them, this can be used as material for estimating that these two signals are independent and separate signals, making signal separation easier.

[0030] In this embodiment, the indirect measurement sensor 30B measures the load transmitted from the living body via the seat cushion 20. As described above, the vibration information measured by the multiple piezoelectric sensors 30 has a large phase difference between the body motion signals compared to the phase difference between the biological signals. Therefore, the BSS processing of the signal processing unit 40 can easily remove the body motion signals, which are noise information, and separate the biological signals, which are target information. As a result, as shown in Figure 2B, vibration information can be obtained with the body motion signals removed and the biological signals extracted.

[0031] Note that the processing performed in the signal processing unit 40 is not limited to BSS. For example, biological signals may be separated using other signal separation methods such as beamforming or independent component analysis.

[0032] As described above, the biological information detection device 10 according to one aspect of this embodiment detects biological information and includes a plurality of piezoelectric sensors 30 that measure the load from the living body and detect a plurality of vibration information emitted by the living body, a seat cushion 20 that contacts the living body and the pressure receiving portion 30a of the plurality of piezoelectric sensors 30, a seat frame 21 that slidably supports the seat cushion 20, and a signal processing means for separating a predetermined vibration signal from the plurality of vibration information, wherein the plurality of vibration information includes biological signals and body movement signals of the living body, the seat cushion 20 has at least one property of elasticity and viscosity, and the plurality of piezoelectric sensors 30 include a direct measurement sensor 30A installed directly below a load input area to which a load is input and whose main detection direction coincides with the direction of the load, and an indirect measurement sensor 30B that detects a second body movement signal among the body movement signals that is in phase later than the first body movement signal detected by the direct measurement sensor 30A, as the load from the living body is transmitted through the seat cushion 20.

[0033] As a result, in multiple piezoelectric sensors 30, vibration information can be measured as a signal with a large phase difference only for the body movement signal and other biological signals of the living organism. Therefore, the biological signal, which is the target signal, can be easily detected in a noisy environment.

[0034] In the above embodiment, the second motion signal detected by the indirect measurement sensor 30B may be a signal whose phase is delayed by 10 ms or more compared to the first motion signal detected by the direct measurement sensor 30A.

[0035] This allows for a large phase difference to be generated in the body movement signal compared to the biological signal (e.g., pulse wave signal), making it easy to separate the body movement signal from the biological signal.

[0036] In the above embodiment, the indirect measurement sensor 30B is installed on the seat frame 21 such that the pressure-receiving portion 30a of the piezoelectric sensor 30 is in contact with the seat cushion 20, the main detection direction of the pressure-receiving portion 30a is different from the direction of the load, and the vibration information detected by the indirect measurement sensor 30B may be the load transmitted through the seat cushion 20.

[0037] As a result, the indirect measurement sensor 30B can measure the load of the living body as a load transmitted through the seat cushion 20. Therefore, the indirect measurement sensor 30B can measure a body movement signal with a phase delay compared to the body movement signal measured by the direct measurement sensor 30A.

[0038] <Second Embodiment> Next, a second embodiment of the present invention will be described with reference to Figures 6 and 7. In the second embodiment and subsequent embodiments, descriptions of matters common to the first embodiment will be omitted, and only the differences will be described. In particular, similar effects and advantages due to similar configurations will not be mentioned sequentially for each embodiment.

[0039] Figure 6 shows an example of the configuration of the biological information detection device 10A according to the second embodiment. Figure 7 is a graph showing the relationship between the distance between the multiple piezoelectric sensors 30 and the phase difference of the pulse waves detected by each sensor. This embodiment is a biological information detection device that, among the biological vibration information measured by the multiple piezoelectric sensors 30, hardly generates any phase difference between the body motion signals, while generating a significant phase difference only between the biological signals.

[0040] In this embodiment, as shown in Figure 6, the multiple piezoelectric sensors 30 are installed together at a location where load input from the living body to the seat cushion 20 is concentrated, and are installed at a certain distance apart along the direction of arterial flow from the heart to the feet of the living body.

[0041] The positions where the load input from the living body to the seat cushion 20 is concentrated are, for example, the area around the pelvis when the living body is seated on the seat 11, or the area around bony prominences such as the ischial tuberosity and sacrum. These sensors may be installed on either the seat surface or the backrest, or on both. By arranging multiple piezoelectric sensors 30 together at the positions where the load input is concentrated, body motion signals can be measured almost simultaneously, preventing large phase differences from occurring between the measured body motion signals. Furthermore, body motion signals measured near the pelvis are less affected by the movement of the feet and lower body, allowing for stable measurement of body motion signals.

[0042] On the other hand, as described above, the pulse wave is a wave of the propagation of pressure fluctuations in the artery generated by the ejection of blood due to the pulsation of the heart. Since the pulse wave propagates through the artery along the direction of the blood flow in the artery from the heart to the toes, a phase difference occurs along the direction of the blood flow in the artery from the heart to the toes, such that the pulse wave measured at a position farther from the heart is detected with a delay compared to the pulse wave measured near the heart. Therefore, as shown in FIG. 6, by arranging a plurality of piezoelectric sensors 30 along the direction of the blood flow in the artery from the heart to the toes of the living body and at a certain distance apart, a phase difference can be generated between the measured pulse waves.

[0043] From the above, in the present embodiment, the body movement signals measured by each piezoelectric sensor 30 hardly generate a phase difference, and as shown in FIG. 7, a phase difference of up to about 10 ms can be generated only in the pulse wave, which is a biological signal. As a result, when performing BSS in the signal processing unit 40, it becomes easier to presume that the biological signal and the body movement signal are independent and separate signals, and it becomes easier to separate the biological signal, which is the target signal in the present invention.

[0044] Next, the configuration of the piezoelectric sensor 30 will be described while referring to FIG. 8. The piezoelectric sensor 30 includes a pressure receiving portion 30a, an upper base portion 30b, and a lower base portion 30c.

[0045] The upper base portion 30b and the lower base portion 30c are provided, for example, in a circular shape when viewed in plan in the Z-axis direction. Further, the lower base portion 30c is disposed on the outer peripheral side of the upper base portion 30b, and they form a laminated structure. Also, the pressure receiving portion 30a is provided, for example, at the center of the upper base portion 30b when viewed in plan in the Z-axis direction. The upper base portion 30b is provided in a frame shape around the pressure receiving portion 30a, and the lower base portion 30c is provided in a frame shape around the upper base portion 30b.

[0046] The pressure receiving portion 30a is a portion that receives the load acting on the piezoelectric sensor 30.

[0047] <Modification Example 1> A modification example of the piezoelectric sensor 30 used for the direct measurement sensor 30A will be described while referring to FIGS. 9 and 10.

[0048] Figures 9 and 10 are cross-sectional views showing modified examples of the piezoelectric sensor 30 shown in FIG. 8. An attachment 31 as shown in FIGS. 9 and 10 may be attached to the piezoelectric sensor 30. The piezoelectric sensor 30 is stored inside the attachment 31. At this time, the pressure receiving portion 30a receives force from the second surface 20b of the seat cushion 20 via the attachment 31. In the present disclosure, "contact" includes not only the case where the surface of the pressure receiving portion 30a directly contacts the seat cushion 20, but also the case where the seat cushion 20 contacts via an attachment 31, a coating material, or another member attached to the piezoelectric sensor 30.

[0049] The attachment 31 shown in FIG. 9 is formed such that the load measurement area 31A is accommodated in the central portion of the upper base 31B. For example, the upper surface of the load measurement area 31A is located on substantially the same plane as the upper surface of the upper base 31B, and the upper base 31B is provided so as to surround the periphery of the load measurement area 31A. Further, the lower base 31C supports the upper base 31B from below, and constitutes a laminated structure as a whole.

[0050] The attachment 31 shown in FIG. 10 is the same as the configuration of FIG. 9 in that it includes a load measurement area 31A, an upper base 31B, and a lower base 31C.

[0051] The attachment 31 shown in FIG. 10 is formed such that the load measurement area 31A is disposed in the central portion of the upper base 31B and protrudes in a hemispherical shape in the positive Z-axis direction from the upper surface of the upper base 31B. With such a shape, for example, since the load measurement area 31A can receive force evenly over the entire curved surface, even if there is variation in the load input direction between sensors, each sensor is less likely to be affected by the difference in the load direction. Therefore, even when a plurality of direct measurement sensors 30A are used, it becomes easier to suppress the phase variation between the sensors.

[0052] <Modification Example 2> Next, a modification example of the piezoelectric sensor 30 used for the indirect measurement sensor 30B will be described while referring to FIGS. 11 to 16. FIGS. 11, 13, and 15 are perspective views showing modification examples of the piezoelectric sensor 30 shown in FIG. 8. FIGS. 12, 14, and 16 are diagrams for explaining the arrangement of the piezoelectric sensor 30 according to the modification example.

[0053] An attachment 32, as shown in Figures 11, 13, and 15, may be attached to the piezoelectric sensor 30. The piezoelectric sensor 30 is housed inside the attachment 32. In this case, the pressure-receiving part 30a receives force from the second surface 20b of the seat cushion 20 via the attachment 32. In this disclosure, "contact" is not limited to cases where, for example, the surface of the pressure-receiving part 30a directly contacts the seat cushion 20, but may also include cases where it contacts the seat cushion 20 via the attachment 32 attached to the piezoelectric sensor 30, a covering material, or another component.

[0054] The attachment 32 shown in Figure 11 has a linear load measurement area 32A on a flat base 32B. By having a linear load measurement area 32A, the load measurement area can be extended linearly even if the pressure receiving portion 30a of the piezoelectric sensor 30 is point-shaped as shown in Figure 8. As shown in Figure 12, the piezoelectric sensor 30 with the attachment 32 attached is positioned so that the load measurement area 32A is in contact with the second surface 20b of the seat cushion 20. In this embodiment, the piezoelectric sensor 30 with the attachment 32 attached is positioned so that the linear load measurement area 32A crosses the direction of arterial flow from the heart to the toes. This makes it easier to capture the position of the arteries in the body and allows for better measurement of pulse waves.

[0055] Furthermore, an attachment 32, as shown in Figure 13, may be attached to the piezoelectric sensor 30. The attachment 32 shown in Figure 13 has a flat load measurement area 32A. As shown in Figure 14, the piezoelectric sensor 30 with the attachment 32 attached is positioned so that the load measurement area 32A is in contact with the second surface 20b of the seat cushion 20.

[0056] Furthermore, an attachment 32, as shown in Figure 15, may be attached to the piezoelectric sensor 30. The attachment 32 shown in Figure 15 has a notch 32C in a part of the flat load measurement area 32A. Note that the position and number of notches 32C are not limited to the example shown.

[0057] As shown in Figure 16, the notch 32C is formed to prevent the load measurement area 32A from directly contacting the second surface 20b of the seat cushion 20, which is located on the side in the direction of the compressive load F1 applied by the driver. Therefore, a predetermined gap G is formed between the load measurement area 32A and the second surface 20b of the seat cushion 20. As a result, the piezoelectric sensor 30 can primarily measure the load transmitted through the seat cushion 20. Therefore, the phase delay can be made more pronounced. This makes it possible to create a clearer time difference between the output signal of the direct measurement sensor 30A and the piezoelectric sensor 30.

[0058] In the above modified example, the piezoelectric sensor 30 may be sealed in a package having a similar shape instead of the attachments 31 and 32.

[0059] <Modification 3> Next, another modification of the second embodiment will be described with reference to Figure 17. Figure 17 is a diagram showing an overview of another modification of the biometric information detection device according to the second embodiment.

[0060] As shown in Figure 17, the seat cushion 20 may have a projection 20A on the second surface 20b in the portion that contacts the pressure-receiving portion 30a of the piezoelectric sensor 30. The projection 20A is provided in a linear shape, oriented to cross the direction of arterial flow from the heart to the toes.

[0061] In this embodiment, a recess is provided on the second surface 20b of the seat cushion 20 in the area corresponding to the portion where the piezoelectric sensor 30 is installed. Furthermore, since the projection 20A is provided in this recess, the pressure-receiving portion 30a of the piezoelectric sensor 30 is in contact with the seat cushion 20 only at the portion of the projection 20A. As a result, the piezoelectric sensor 30 can detect pulse waves using the linear load measurement area as described above, making it easier to capture the position of arteries in the body and enabling better measurement of pulse waves.

[0062] Although only one projection 20A and one piezoelectric sensor 30 are shown in Figure 17, multiple projections 20A may be provided to accommodate multiple piezoelectric sensors 30.

[0063] As described above, another embodiment of this biological information detection device 10A detects information of a living organism seated on the seat 11 and comprises a plurality of piezoelectric sensors 30 that measure the load from the living organism and detect a plurality of vibration information emitted by the living organism, and a signal processing means that separates a predetermined vibration signal from the plurality of vibration information, wherein the vibration signal includes a biological signal and the body movement signal of the living organism, and the plurality of piezoelectric sensors 30 are configured to be located near the pelvis when the living organism is seated on the seat 11 and to be located at a certain distance apart along the direction of arterial flow from the heart to the feet of the living organism.

[0064] As a result, in multiple piezoelectric sensors 30, vibration information can be measured as a signal with a large phase difference only for the biological signal (e.g., pulse wave signal) among the biological body movement signal and biological signal. Therefore, the target signal, the pulse wave signal, can be easily detected in a noisy environment.

[0065] In the above embodiment, the plurality of piezoelectric sensors 30 may have linear load measurement areas that cross the direction of arterial flow.

[0066] This makes it easier to pinpoint the location of arteries in the body compared to measuring pulse waves with a point-like pressure-receiving area, resulting in better measurement of pulse wave signals. Consequently, a significant phase difference can be generated only in the pulse wave signal compared to the body motion signal.

[0067] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. The present invention can be modified or improved without departing from its spirit, and equivalents thereof are also included. That is, any design modifications made to each embodiment by a person skilled in the art are also included within the scope of the present invention, as long as they retain the features of the present invention. For example, the elements and their arrangement, materials, conditions, shapes, sizes, etc., of each embodiment are not limited to those exemplified and can be modified as appropriate. Furthermore, each embodiment is illustrative, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible, and these are also included within the scope of the present invention as long as they retain the features of the present invention.

[0068] 10, 10A... Biometric information detection device 11... Seat 11a... Seat surface 11b... Backrest 20... Seat cushion 20a... First surface 20b... Second surface 20A... Protrusion 21... Seat frame 30... Piezoelectric sensor 30a... Pressure receiving part 30b... Upper base 30c... Lower base 31, 32... Attachment 30A... Direct measurement sensor 30B... Indirect measurement sensor 31A... Load measurement area 31B... Upper base 31C... Lower base 32A... Load measurement area 32B... Base 32C... Notch 40... Signal processing unit F1, F2... Compression load f1... Friction force G... Gap

Claims

1. A biological information detection device for detecting biological information, comprising: a plurality of piezoelectric sensors that measure a load from a living organism and detect a plurality of vibration information emitted by the living organism; an intermediate body that contacts the living organism and the pressure-receiving parts of the plurality of piezoelectric sensors; a support that slidably supports the intermediate body; and a signal processing means for separating a predetermined vibration signal from the plurality of vibration information, wherein the plurality of vibration information includes a biological signal and a body motion signal of the living organism; the intermediate body has at least one property of elasticity and viscosity; and the plurality of piezoelectric sensors include a direct measurement sensor installed directly below a load input area into which the load is input and whose main detection direction coincides with the direction of the load; and an indirect measurement sensor that detects a second body motion signal among the body motion signals that is in phase later than a first body motion signal detected by the direct measurement sensor, as the load from the living organism is transmitted through the intermediate body.

2. The biological information detection device according to claim 1, wherein the second body motion signal detected by the indirect measurement sensor is a signal whose phase is delayed by 10 ms or more compared to the first body motion signal detected by the direct measurement sensor.

3. The biological information detection device according to claim 1 or claim 2, wherein the intermediate is a sheet cushion and the support is a sheet frame.

4. The bio-information detection device according to claim 3, wherein the indirect measurement sensor is installed on the seat frame such that the pressure receiving portion is in contact with the seat cushion, the main detection direction of the pressure receiving portion is a direction different from the direction of the load, and the vibration information detected by the indirect measurement sensor is the load transmitted through the seat cushion.

5. A biological information detection device for detecting information of a living organism seated on a seat, comprising: a plurality of piezoelectric sensors that measure the load from the living organism and detect a plurality of vibration information emitted by the living organism; and a signal processing means for separating a predetermined vibration signal from the plurality of vibration information, wherein the vibration signal includes a biological signal and a body movement signal of the living organism, and the plurality of piezoelectric sensors are configured to be located near the pelvis when the living organism is seated on the seat, and to be located at a certain distance apart along the direction of arterial flow from the heart to the feet of the living organism.

6. The biological information detection device according to claim 5, wherein the biological signal is a pulse wave signal.

7. The biological information detection device according to claim 5 or 6, wherein the plurality of piezoelectric sensors have linear load measurement areas that cross the direction of arterial flow.

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