JP7831773B2 - Biological information detection device - Google Patents

Description

This disclosure relates to a biometric information detection device for detecting the biometric information of a seated person. Biometric information refers to information emitted by the body, such as respiratory rate and heart rate.

For example, the invention described in Patent Document 1 includes a bio-information sensor and an acceleration sensor for detecting external vibrations. In this invention, after estimating noise components using the values detected by the acceleration sensor, bio-information is detected by removing these noise components from the values detected by the bio-information sensor.

Japanese Patent Publication No. 2016-136989

In the invention described in Patent Document 1, a complex processing step is required to estimate the noise component from the detected value of the acceleration sensor, and therefore a computing device is necessary to perform this processing.
In view of the above, this disclosure discloses an example of a biological information detection device capable of detecting biological information without performing complex processing steps.

A biometric information detection device capable of acquiring biometric information of a person seated in seat (1) is preferably equipped with at least one of the following configuration requirements.
In other words, the configuration requirements include a first sensor (11) provided on the sheet, comprising: a first sensor (11) for detecting biological information; a second sensor (12) for detecting vibrations of the sheet (1); and a biological information calculation unit (13) that outputs biological information using the difference between the output value of the first sensor (11) and the output of the second sensor (12) multiplied by a real number, or the difference between the output value of the first sensor (11) divided by a real number and the output value of the second sensor (12), wherein the second sensor (12) is positioned in the opposite direction to the first sensor (11) and in the opposite direction to the cushioning material (32, 52) of the sheet.

Furthermore, "reverse direction" refers to the direction from the surface of the sheet toward the back of the sheet in the input direction. The input direction refers to the direction parallel to the imaginary line (Lo) that passes through the area where the first sensor (11) is located and is approximately perpendicular to the surface of the sheet.

Furthermore, since the second sensor (12) is positioned offset from the cushioning material (32, 52) of the seat, vibrations emitted by the body, such as respiratory rate and heart rate, are absorbed and blocked by the cushioning material (32, 52). Therefore, the second sensor (12) primarily detects external vibrations input to the seat and does not detect seat vibrations caused by biological information.

Therefore, the absolute value of the difference between the output value of the first sensor (11) and the output value of the second sensor (12) multiplied by a real number, or the difference between the output value of the first sensor (11) divided by a real number and the output value of the second sensor (12), generally represents vibrations emitted by the body, such as respiratory rate and heart rate, i.e., biological information.

Furthermore, external vibrations are generally transmitted from the back of the sheet towards the front of the sheet, along the direction of input. In this bio-information detection device, the second sensor (12) is offset relative to the first sensor (11) in the direction of input.

Therefore, the phase difference between the external vibration detected by the first sensor (11) and the external vibration detected by the second sensor (12) becomes smaller. Consequently, this biological information detection device can detect biological information without performing complex processing steps.

Incidentally, the symbols within the parentheses above are examples illustrating the correspondence with the specific configurations described in the embodiments below, and this disclosure is not limited to the specific configurations indicated by the symbols within the parentheses above.

This figure shows a vehicle seat according to the first embodiment. This diagram shows the arrangement of the first and second sensors. This is a block diagram of a biological information detection device according to the first embodiment. This is an exploded view of the second sensor according to the first embodiment. This is a graph showing the first detected value. This is a graph showing the second detection value. This is a graph that overlays the first and second detection values.

The following "Embodiments of the Invention" are examples of embodiments that fall within the technical scope of this disclosure. In other words, the features defining the invention as described in the claims are not limited to the specific configurations and structures shown in the embodiments below.

This embodiment is an example in which the biometric information detection device according to this disclosure is applied to a seat installed in a vehicle or other vehicle (hereinafter referred to as a "vehicle seat"). The directional arrows and diagonal lines in each figure are included to facilitate understanding of the relationships between the figures and the shapes of the components or parts.

Therefore, the biometric information detection device is not limited to the directions shown in each figure. The directions shown in each figure are those of the vehicle seat according to this embodiment when it is installed in a vehicle.

Unless otherwise specified, such as "one," at least one of the components or parts described with reference numerals is provided. The biometric information detection device shown in this disclosure comprises at least one of the components, such as those described with reference numerals, and at least one of the illustrated structural parts.

(First Embodiment)
<1. Overview of Vehicle Seats>
As shown in Figure 1, the vehicle seat 1 includes at least a seat cushion 3 and a seat back 5. The seat cushion 3 is the part that supports the seated person's buttocks. The seat back 5 is the part that supports the seated person's back.

Each of the seat cushion 3 and seat back 5 has at least frames 31 and 51 and cushioning materials 32 and 52, etc. The frames 31 and 51 are structural members that constitute the frame. In this embodiment, the frames 31 and 51 are made of steel plates such as SPCC or SPHC.

The cushioning materials 32 and 52 are elastically deformable components. Specifically, the cushioning materials 32 and 52 are made of foamed resin such as foamed urethane. The cushioning material 32 of the seat cushion 3 is supported, for example, by multiple S-springs 33 (see Figure 2).

Each S-spring 33 is a spring formed in a wave shape. Each S-spring 33 is held by the frame 31. Figure 2 shows a cross-section of the seat cushion 3 perpendicular to the seat's front-to-back direction.

<2. Biological Information Detection Device>
<2.1 Configuration of the Biological Information Detection Device>
As shown in Figure 3, the biological information detection device 10 includes at least a first sensor 11, a second sensor 12, and a biological information calculation unit 13.

<First Sensor>
The first sensor 11 is provided on the vehicle seat 1, that is, the seat cushion 3 or seat back 5 (in this embodiment, the seat cushion 3) (see Figure 2), and is a sensor for detecting biological information.

The first sensor 11 in this embodiment is a thin-film pressure sensor utilizing the piezoelectric effect. This first sensor 11 primarily detects pressure in the direction parallel to the virtual line Lo shown in Figure 2 (hereinafter referred to as the input direction).

In other words, the first sensor 11 is positioned on the seat cushion 3 such that its direction approximately perpendicular to the thin film surface (hereinafter referred to as the main detection direction) coincides with the input direction. The virtual line Lo is a virtual line that passes through the area where the first sensor 11 is positioned and is approximately perpendicular to the sheet surface.

The first sensor 11 is positioned in a location where the direction of pressure generated by the seated person's weight substantially coincides with the main detection direction. Therefore, as long as the direction of pressure substantially coincides with the main detection direction, the first sensor 11 may be located on the surface or back of the seat upholstery (not shown), or within the cushioning material 32.

When pressure fluctuations, such as those caused by respiratory rate or heart rate, are input to the first sensor 11—that is, biological information—the first sensor 11 outputs a value (voltage in this embodiment) corresponding to the pressure fluctuations. In other words, this change in output voltage is output from the first sensor 11 as biological information.

<Second Sensor>
The second sensor 12 is a sensor for detecting vibrations of the vehicle seat 1, that is, vibrations input from the vehicle body to the vehicle seat 1 (hereinafter referred to as input vibrations). In this embodiment, the second sensor 12 is composed of a thin-film pressure sensor, similar to the one used in the first sensor 11.

Specifically, as shown in Figure 4, the second sensor 12 comprises at least a thin-film pressure sensor 12A, a weight 12B, a slab 12C, and case members 12D, 12E, etc. The weight 12B has a mass that is sufficiently small compared to the mass of a seated person (for example, 20 g).

Then, when acceleration in the main detection direction acts on the weight 12B, the weight 12B exerts an inertial force proportional to that acceleration on the pressure sensor 12A. In other words, the second sensor 12 outputs a value (voltage in this embodiment) corresponding to the input vibration.

The pressure sensor 12A is positioned such that its primary detection direction is parallel to the primary detection direction of the first sensor 11. In other words, the pressure sensor 12A is positioned so that its primary detection direction and input direction coincide.

Therefore, the weight 12B is primarily displaced in the main detection direction, and its displacement in directions intersecting the main detection direction is restricted. Specifically, the case member 12D is provided with a guide portion (not shown) that guides the displacement direction of the weight 12B.

The slab 12C is an elastic member that supports the weight 12B in a displaceable manner. Specifically, the slab 12C is made of foamed resin. The case members 12D and 12E house the pressure sensor 12A, the weight 12B, and the slab 12C.

Furthermore, the slab 12C is held by the case member 12E, with its displacement restricted by the case member 12E. The case member 12D and the case member 12E are integrated by adhesive or screws.

<Biological Information Processing Unit>
The bio-information calculation unit 13 is a calculation unit that calculates bio-information by utilizing the difference between at least the output value of the first sensor 11 (hereinafter also referred to as the first output value) and the value obtained by multiplying the output of the second sensor 12 by a real number (hereinafter also referred to as the second output value).

Furthermore, the second output value is a value that correlates with "the value obtained by multiplying the output of the second sensor 12 by a real number." Specifically, this second output value is (1) the value obtained by directly multiplying the output value of the second sensor 12 by a real number, (2) the value obtained by applying bandpass processing to the value obtained by directly multiplying the output value of the second sensor 12 by a real number, or (3) the value obtained by applying bandpass processing to the output value of the second sensor 12 and then multiplying the processed value by a real number.

The biometric information processing unit 13 then outputs a value obtained by subtracting the second output value from the first output value as biometric information. In this embodiment, the output biometric information is used as a parameter for vehicle driving assistance.

In this embodiment, the "real number" is a value determined by testing, numerical simulations using a large computer, etc. Incidentally, the reason why the output value of the second sensor 12 is used as the second output value is that it is a real number multiplied by the output value of the second sensor 12 is as follows:

In other words, the force acting on the first sensor 11 due to input vibration is an inertial force with the seated person as its mass. In contrast, the force acting on the pressure sensor 12A due to input vibration is an inertial force with the weight 12B as its mass.

Furthermore, the mass of weight 12B is sufficiently small compared to the mass of the seated person. Therefore, the absolute value of the output of the second sensor 12 is smaller than the absolute value of the output of the first sensor 11, and thus cannot sufficiently cancel out the input vibration.

<2.2 Arrangement relationship between the first and second sensors (see Figure 2)>
The first sensor 11 is positioned in a location capable of detecting the pressure generated by the weight of the seated person. Specifically, in this embodiment, the first sensor 11 is positioned, for example, on the back surface of the seat surface of the seat cushion 3, that is, between the seat surface and the cushioning material 32.

The second sensor 12 is positioned in a direction opposite to that of the first sensor 11, and also in a direction opposite to that of the cushioning material 32. "Opposite direction" refers to the direction from the surface of the sheet toward the back of the sheet in the input direction.

Specifically, the second sensor 12 is positioned below the first sensor 11 and also below the cushioning material 32. In other words, in Figure 2, since the input direction coincides with the vertical direction, "reverse direction" corresponds to "downward direction."

In this embodiment, the second sensor 12 is mounted on a resin plate 34 fixed to the S-spring 33. Therefore, the second sensor 12, or pressure sensor 12A, is positioned at a distance from the cushioning material 32 and on the opposite side of the cushioning material 32 from the first sensor 11.

<3. Features of the biological information detection device according to this embodiment>
In the biological information detection device 10 according to this embodiment, the second sensor 12 is positioned offset from the cushioning material 32 in the opposite direction. As a result, vibrations emitted by the body, such as respiratory rate and heart rate, can be absorbed and blocked by the cushioning material 32, etc.

The cushioning material 32, etc., refers, for example, to the cushioning material 32, the S-spring 33, the resin plate 34, and the gap between the cushioning material 32 and the second sensor 12. Therefore, the second sensor 12 positioned in this location primarily detects input vibrations and does not detect vibrations caused by biological information.

Specifically, Figure 5 shows experimental values illustrating the change in the first output value when the input vibration is zero, i.e., when the vehicle is stationary. Therefore, the graph in Figure 5 represents biological information and electromagnetic noise. Figure 6 shows experimental values illustrating the change in the second output value when the input vibration is zero, i.e., when the vehicle is stationary. Therefore, the graph in Figure 6 represents electromagnetic noise.

Comparing Figure 5 and Figure 6 with the effects of electromagnetic noise removed, the second output value shows almost no influence from the first output value, i.e., biological information. Therefore, the second sensor 12 positioned as described above primarily detects input vibrations and does not detect vibrations caused by biological information.

Furthermore, the input vibration is generally transmitted from the back surface of the sheet towards the front surface of the sheet, along the direction of input. In this embodiment, the second sensor 12 is offset in the input direction relative to the first sensor 11.

Therefore, as shown in Figure 7, the phase difference between the input vibration detected by the first sensor 11 and the input vibration detected by the second sensor 12 becomes smaller. Note that the first and second output values shown in Figure 7 are the values after bandpass processing.

Therefore, the absolute value of the difference between the output value of the first sensor 11 and the output value of the second sensor 12 multiplied by a real number generally represents vibrations emitted by the body, such as respiratory rate and heart rate, i.e., biological information. Consequently, the biological information detection device 10 can detect biological information without performing complex processing steps.

(Other embodiments)
The bio-information calculation unit 13 according to the above embodiment calculated bio-information using the difference between the output value of the first sensor 11 and the value obtained by multiplying the output of the second sensor 12 by a real number. However, the disclosure is not limited thereto.

In other words, the disclosure may, for example, mean that the bio-information calculation unit 13 calculates bio-information using the difference between the output value of the first sensor 11 divided by a real number and the output value of the second sensor 12.

Furthermore, the first output value can be any value that correlates with the "value obtained by dividing the output of the first sensor 11 by a real number," such as the value obtained by dividing the output of the first sensor 11 by a real number, the value obtained by applying bandpass processing to the value obtained by dividing the output of the first sensor 11 by a real number, or the value obtained by applying bandpass processing to the output of the first sensor 11 and then dividing the processed value by a real number.

In the above-described embodiment, the first sensor 11 and the second sensor 12 were arranged to be approximately located on the virtual line Lo. However, this disclosure is not limited to this. That is, in this disclosure, for example, it is sufficient if the first sensor 11 and the second sensor 12 are offset in the input direction, while the main detection direction coincides with the input direction.

In other words, either (1) the first sensor 11 projected onto a virtual plane orthogonal to the input direction and the main detection direction overlaps with the second sensor 12 projected onto the said virtual plane, or (2) the projected first sensor 11 and the projected second sensor 12 do not overlap.

In the embodiment described above, one first sensor 11 and one second sensor 12 were provided. However, this disclosure is not limited thereto. That is, the disclosure may include, for example, multiple sensors, at least one of the first sensor 11 and the second sensor 12.

In the above-described embodiment, the first sensor 11 and the second sensor 12 were arranged on the seat cushion 3. However, this disclosure is not limited to this. That is, in this disclosure, for example, the first sensor 11 may be arranged on the surface of the seat back 5, and the second sensor 12 may be arranged on the back side of the seat back 5. In this configuration, the input direction is inclined with respect to the front-to-back direction of the seat.

The second sensor 12 in the above-described embodiment was mounted on a resin plate 34 fixed to an S-spring 33. However, this disclosure is not limited to this. That is, the disclosure may also be configured to be mounted on, for example, a frame 31 or a vehicle body.

The first sensor 11 and second sensor 12 in the above-described embodiment were constructed as pressure sensors utilizing the piezoelectric effect. However, this disclosure is not limited thereto. That is, the disclosure may also be constructed using other types of pressure sensors or acceleration sensors.

In the embodiments described above, the vehicle seat according to this disclosure was applied to a vehicle. However, the application of the invention disclosed herein is not limited to this. That is, the disclosure can also be applied, for example, to seats used in vehicles such as railway cars, ships, and aircraft, as well as to stationary seats used in theaters, homes, etc.

Furthermore, this disclosure is not limited to the embodiments described above, but is sufficient to be consistent with the intent of the disclosures described in the embodiments described above. Therefore, it may also include configurations combining at least two of the embodiments described above, or configurations in which any of the illustrated or reference-referenced components described in the embodiments described above are omitted.

1... Vehicle seat 3... Seat cushion 5... Seat back 10... Biometric information detection device 11... First sensor 12... Second sensor 13... Biometric information calculation unit 31... Frame 32... Cushioning material 33... S-spring 34... Resin plate

Claims (3)

A biometric information detection device applied to a seat having a frame and cushioning material, capable of acquiring biometric information of a person seated in the seat,
A first sensor provided on the sheet for detecting biological information , the first sensor being a thin-film pressure sensor utilizing the piezoelectric effect ,
A second sensor for detecting vibrations of the seat , comprising a weight with a mass sufficiently small compared to the mass of the person sitting, an elastic member that supports the weight so as to be displaceable, and a thin-film pressure sensor that utilizes the piezoelectric effect to detect the inertial force acting on the weight ,
The system includes a bio-information processing unit that outputs bio-information using the difference between the output value of the first sensor and the output value of the second sensor multiplied by a real number,
When the input direction is defined as the direction parallel to a virtual line passing through the area where the first sensor is located and substantially perpendicular to the surface of the sheet, and the direction from the surface of the sheet toward the back of the sheet in that input direction is defined as the "reverse direction",
The direction substantially perpendicular to the membrane surface of the first sensor and the direction substantially perpendicular to the membrane surface of the second sensor coincide with each other, and these directions coincide with the input direction .
Furthermore, the bio-information detection device is positioned such that the second sensor is offset in the opposite direction from the first sensor and is also offset in the opposite direction from the cushioning material in the input direction . The cushioning material is supported by an S-spring,
The biological information detection device according to claim 1, wherein the second sensor is mounted on a resin plate fixed to the S spring. The biological information detection device according to claim 1 or 2, wherein the second sensor is arranged on a virtual line substantially perpendicular to the membrane surface of the first sensor.