Seat

Abstract

To provide a seat which can increase strain amount of a piezoelectric sensor.SOLUTION: A seat comprises: a main pad (15) which receives weight of a seated person; a sub pad (16) which is fitted into a recess part (17) formed on a face opposite to a face of the main pad (15) receiving the weight; a piezoelectric sensor (21) which is arranged at the face of the sub pad (16) receiving the weight to perform sensing BCG (ballistocardiogram) of the seated person; and an inclusion member (23) which lies between the piezoelectric sensor (21) and a bottom face (17A) of the recess part (17) facing the piezoelectric sensor (21) to have a prescribed height from the piezoelectric sensor (21) a part of which can be pressed down.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a seat cushion provided on a moving body.

Background Art

[0002] Patent Document 1 describes a seat cushion for a vehicle in which a piezoelectric film sensor is disposed in a recess of a base cushion material, and a cover cushion material is disposed in the recess so as to cover the piezoelectric film sensor.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The seat cushion described in Patent Document 1 has a problem that the amount of strain of the piezoelectric film sensor decreases.

[0005] In view of the above problems, an object of the present disclosure is to provide a seat cushion capable of increasing the amount of strain of a piezoelectric sensor.

Means for Solving the Problems

[0006] In order to solve the above problems, a seat cushion according to Aspect 1 of the present disclosure includes a main pad that receives the load of a seated person, a sub-pad that is fitted into a recess formed on a surface opposite to the surface of the main pad that receives the load, a piezoelectric sensor that is disposed on the surface of the sub-pad that receives the load and senses the heartbeat of the seated person, and an intervening member having a predetermined height that is interposed between the piezoelectric sensor and the bottom surface of the recess facing the piezoelectric sensor and is disposed so as to press a part of the piezoelectric sensor.

[0007] According to the above configuration, the main pad applies the load of the seated person by pressing a portion of the piezoelectric sensor through an intervening member of a predetermined height. This makes it possible to increase the amount of strain on the piezoelectric sensor caused by the seated person's load compared to the amount of strain when the intervening member is not in place.

[0008] In the seat according to Embodiment 2 of the present disclosure, in Embodiment 1, the piezoelectric sensor is elongated, and the intervening member is positioned in the center of the piezoelectric sensor in the longitudinal direction.

[0009] According to the above configuration, since the intervening member is positioned in the center of the piezoelectric sensor in the longitudinal direction, the piezoelectric sensor can be partially pressed, and therefore the amount of strain on the piezoelectric sensor when subjected to the load of the seated person can be increased.

[0010] In the seat according to embodiment 3 of the present disclosure, in embodiment 2, the intervening member is formed such that the dimension of the piezoelectric sensor in the direction perpendicular to the longitudinal direction is greater than or equal to the width of the piezoelectric sensor in the short direction.

[0011] According to the above configuration, the intervening member presses the central part of the piezoelectric sensor in the longitudinal direction across its entire width in the short direction, thereby increasing the amount of strain on the piezoelectric sensor when subjected to the weight of the seated person.

[0012] Furthermore, in the seat according to embodiment 4 of the present disclosure, in embodiment 2 or 3 above, the main pad and the sub-pad are included in the seat cushion that constitutes the seat surface, the piezoelectric sensor is arranged along the front-rear direction of the seat cushion, and the central portion of the piezoelectric sensor in the longitudinal direction is positioned to face at least one of the left or right buttocks of the sitter seated on the seat cushion.

[0013] According to the above configuration, the elongated piezoelectric sensor is positioned along the front-to-back direction of the seat cushion, with its central portion facing at least one of the sitter's left or right buttocks. This suppresses variations in the piezoelectric sensor's sensitivity due to the sitter's posture and seating position. Furthermore, since the load applied to the piezoelectric sensor from the left or right buttock is greater than the load applied from the left or right thigh, the amount of strain on the piezoelectric sensor can be increased. As a result, the amplitude of the sitter's cardiac elasticity waveform output from the piezoelectric sensor can be increased.

[0014] Furthermore, in the seat according to embodiment 5 of this disclosure, in embodiment 4, the piezoelectric sensors are arranged in parallel in the left-right direction of the seat cushion.

[0015] With the above configuration, since multiple piezoelectric sensors are arranged in parallel in the left-right direction of the seat cushion, it becomes possible to select the cardiac resilience waveform with the largest amplitude among the cardiac resilience waveforms of the seated person output from each piezoelectric sensor.

[0016] Furthermore, in the seat according to embodiment 6 of this disclosure, the intervening member is fixed to the piezoelectric sensor in embodiment 1 or 2.

[0017] With the above configuration, since the intervening member is fixed to the piezoelectric sensor, it is possible to prevent the loss of the intervening member when assembling the seat.

[0018] Furthermore, in the seat according to embodiment 7 of the present disclosure, in embodiment 6, the intervening member is made of synthetic resin or metal, with a flat lower surface and a spherical upper surface.

[0019] According to the above configuration, the intervening member is made of synthetic resin or metal, and since the lower surface is formed in a planar shape, it can be easily fixed to the piezoelectric sensor by adhesion or the like. Further, since the upper surface of the intervening member is formed in a spherical shape, it can prevent wear of the main pad and achieve a longer life of the main pad.

[0020] Also, in the seat sheet according to Aspect 8 of the present disclosure, in the above Aspect 1 or 2, the intervening member is integrally provided on the bottom surface of the recess.

[0021] According to the above configuration, since the intervening member is integrally provided on the bottom surface of the recess of the main pad, it is possible to reduce the number of man-hours during the assembly of the seat sheet.

[0022] Also, in the seat sheet according to Aspect 9 of the present disclosure, in the above Aspect 2 or 3, the main pad and the sub-pad are included in a seat back that serves as a backrest, the piezoelectric sensor is arranged along the vertical direction of the seat back, and the central portion in the longitudinal direction of the piezoelectric sensor is arranged so as to face at least one of the left waist or the right waist of the seated person.

[0023] According to the above configuration, the long piezoelectric sensor is arranged along the vertical direction of the seat back, and the central portion in the longitudinal direction is arranged so as to face at least one of the left waist or the right waist of the seated person. Thereby, it is possible to suppress variations in the sensitivity of the piezoelectric sensor depending on the posture and seating position of the seated person. Further, the load applied to the piezoelectric sensor from the left waist or the right waist can increase the amount of strain of the piezoelectric sensor. As a result, it is possible to increase the amplitude of the cardiac pulsation waveform of the seated person output from the piezoelectric sensor.

[0024] Also, in the seat sheet according to Aspect 10 of the present disclosure, in the above Aspect 9, a plurality of the piezoelectric sensors are arranged in parallel in the left-right direction of the seat back.

[0025] According to the above configuration, since a plurality of piezoelectric sensors are arranged in parallel in the left-right direction of the seat back, it is possible to adopt the heartbeat waveform with the largest amplitude among the heartbeat waveforms of the seated person output from each piezoelectric sensor.

Advantages of the Invention

[0026] According to one aspect of the present disclosure, the amount of strain of the piezoelectric sensor can be increased.

Brief Description of the Drawings

[0027] [Figure 1] It is a perspective view showing an example of the appearance of the seat sheet. [Figure 2] It is a view showing an example of the seat surface of the seat sheet. [Figure 3] It is a view showing an example of a cross-sectional view taken along the arrow III-III of FIG. 2. [Figure 4] It is a perspective view showing an example of the intervening member. [Figure 5] It is a view showing an example of the deformed states of the piezoelectric sensor before and after the seated person sits down. [Figure 6] It is a view showing an example of the signal waveform of the heartbeat of the seated person sensed by the piezoelectric sensor of the seat sheet in each of the states with and without the intervening member under static conditions. [Figure 7] It is a view showing an example of the ratio of the RRI estimation accuracy obtained from the sensing results measured in each of the states without and with the intervening member under static conditions. [Figure 8] It is a view showing an example of the ratio of the RRI estimation accuracy obtained from the sensing results measured in each of the states without and with the intervening member under dynamic conditions. [Figure 9] It is a view showing an example of a distribution diagram for explaining the RRI correct answer rate. [Figure 10] It is a view showing an example of the seat surface of the seat sheet according to Modification 1. [Figure 11] It is a perspective view showing an example of the appearance of the seat sheet according to Modification 2. [Modes for carrying out the invention]

[0028] One embodiment of this disclosure will be described in detail below.

[0029] [1. Example of seat configuration] The seat 1 according to this embodiment will be described with reference to Figures 1 to 5. Figure 1 is a perspective view showing an example of the exterior of the seat 1. The front, back, left, right, up, and down directions shown appropriately in each figure in this embodiment correspond to the directions seen by an occupant (not shown) when seated on the seat 1, as shown in Figure 1.

[0030] As shown in Figure 1, the seat 1 has a seat cushion 11, a seat back 12, and a headrest 13. The seat cushion 11 constitutes the seat surface of the seat 1, and the seat back 12 and headrest 13 constitute the back of the seat 1. The seat 1 is covered with a surface material 14 made of fabric, leather, vinyl leather, etc., or a combination thereof.

[0031] Hereinafter, seat 1 will be described as being installed in a moving body, but is not limited to this, and may be installed in a stationary location such as a building. Also, the moving body will be described as a vehicle, but is not limited to this, and may be a ship or an aircraft, etc. Furthermore, seat 1 is not limited to being installed in the driver's seat of the moving body, but may be installed in the passenger seat of the moving body.

[0032] The seat cushion 11 is the seat on which the occupant sits, and the surface material 14 is attached so as to cover the upper surface. The seat cushion 11 will be described with reference to Figures 2 and 3. Figure 2 is a diagram showing an example of the seat surface of the seat 1. Figure 3 is a diagram showing an example of a cross-sectional view taken along the line III-III in Figure 2. As shown in Figures 2 and 3, the seat cushion 11 comprises a main pad 15 and a sub-pad 16.

[0033] The main pad 15 is made of foamed polyurethane foam, which is a type of soft polyurethane foam. Fitting grooves 15D are formed on the front edge and left and right side edges of the lower surface 15E of the main pad 15, into which a seat cushion frame (not shown) which is roughly U-shaped in plan view in Figure 2 is fitted. The main pad 15 is then supported on the seat cushion frame by the fitting grooves 15D formed on the front edge and left and right side edges of the lower surface 15E engaging with the seat cushion frame.

[0034] The main pad 15 bears the weight of the seated occupant. On the lower surface 15E of the main pad 15, opposite to the upper surface that bears the weight of the seated occupant, a recess 17 with a bottom and a roughly rectangular shape in plan view is formed, opening downwards. The sub-pad 16, which is also roughly rectangular in plan view, is fitted into the recess 17 from below.

[0035] The sub-pad 16 is made of foamed polyurethane foam, which is a soft polyurethane foam. The main pad 15 is supported by a plurality of springs 19 that are stretched between left and right seat cushion frames (not shown) that fit into fitting grooves 15D on the left and right side edges of the lower surface 15E, with the sub-pad 16 fitted into the recess 17.

[0036] As shown in Figures 2 and 3, the bottom surface 17A of the recess 17 is formed to include a first region 15A facing the left buttock area around the ischial tuberosities of a seated person, and a second region 15B facing the right buttock area around the ischial tuberosities of the seated person. Therefore, the upper surface 16A of the sub-pad 16 that receives the load of a seated person and abuts against the bottom surface 17A of the recess 17 is formed to face the first region 15A facing the left buttock area around the ischial tuberosities of the seated person, and the second region 15B facing the right buttock area around the ischial tuberosities of the seated person.

[0037] The piezoelectric sensor 21 is a long, rectangular piezoelectric film sensor located inside the seat cushion 11. The piezoelectric sensor 21 senses the ballistocardiography (BCG) of the seated person. The piezoelectric sensor 21 is a sensor that utilizes the piezoelectric effect of a piezoelectric element, which generates a voltage when pressure is applied. The signal indicating the ballistocardiography sensed by the piezoelectric sensor 21 is supplied to the controller 25.

[0038] Specifically, the piezoelectric sensor 21 is positioned along the front-to-back direction on the upper surface 16A of the sub-pad 16, which is fitted into the recess 17, so as to face the first region 15A that is opposite to the left buttock area around the seated person's ischial tuberosity. The piezoelectric sensor 21 is fixed to the upper surface 16A with adhesive or the like. The wiring of the piezoelectric sensor 21 is routed downward along the rear side of the sub-pad 16 and electrically connected to the controller 25.

[0039] Furthermore, the controller 25 associated with the seat 1 measures the seated person's heart rate by referring to the electrical signal, which is the sensing result supplied from the piezoelectric sensor 21. The controller 25 also determines whether the sensing result from the piezoelectric sensor 21 satisfies predetermined conditions regarding the seated person's heart rate, and if it determines that the predetermined conditions are met, it outputs a signal to notify the user of this fact.

[0040] As shown in Figures 2 and 3, an intervening member 23 is positioned between the piezoelectric sensor 21 and the bottom surface 17A of the recess 17 in the longitudinal direction of the piezoelectric sensor 21, so as to be able to press a portion of the piezoelectric sensor 21. For example, as shown in Figure 2, the intervening member 23 is positioned such that the position at a distance L1 from the front and rear ends of the piezoelectric sensor 21 in the longitudinal direction approximately coincides with the central position in the front-rear direction of the lower surface 23A of the intervening member 23 (see Figure 4). In other words, the central position in the longitudinal direction of the piezoelectric sensor 21 and the central position in the front-rear direction of the lower surface 23A of the intervening member 23 are positioned approximately to coincide.

[0041] Furthermore, the state in which the front edge or rear edge of the lower surface 23A of the intervening member 23 is positioned near the central position in the longitudinal direction of the piezoelectric sensor 21 is also included in the state in which the intervening member 23 is positioned in the central part in the longitudinal direction of the piezoelectric sensor 21.

[0042] The intervening member 23 will be explained with reference to Figure 4. Figure 4 is a perspective view showing an example of an intervening member 23 fixed to the upper surface of the piezoelectric sensor 21. As shown in Figure 4, the intervening member 23 is made of synthetic resin such as thermosetting elastomer or thermoplastic elastomer, or of metal such as aluminum or iron, with the lower surface 23A formed in a planar shape and the upper surface 23B formed in a substantially spherical shape.

[0043] The lower surface 23A of the intervening member 23 is formed in a substantially rectangular shape in plan view, having a length of at least the width L2 of the piezoelectric sensor 21, preferably a width L3 in the left-right direction that is the same length as the width L2 in the direction perpendicular to the longitudinal direction of the piezoelectric sensor 21, and a length L4 in the front-rear direction that is approximately the same as the width L2 in the direction perpendicular to the longitudinal direction of the piezoelectric sensor 21. Alternatively, the lower surface 23A of the intervening member 23 may be formed in a substantially circular shape or polygonal shape, having a length of at least the width L2 of the piezoelectric sensor 21, preferably a diameter approximately the same length as the width L2 of the piezoelectric sensor 21.

[0044] The lower surface 23A of the intervening member 23 is fixed by adhesive or the like to the surface facing the bottom surface 17A of the piezoelectric sensor 21, that is, to the center of the upper surface of the piezoelectric sensor 21 in the longitudinal direction. Furthermore, the height from the lower surface of the intervening member 23, that is, the height from the piezoelectric sensor 21 to the top of the upper surface 23B, is a predetermined height, for example, a height of approximately 3 mm to approximately 15 mm, and is formed to a height that does not cause a foreign body sensation to the person sitting on the seat cushion 11.

[0045] Next, an example of the deformation state of the piezoelectric sensor 21 when a person sits on the upper surface of the seat cushion 11 will be explained based on Figure 5. Figure 5 shows an example of the deformation state of the piezoelectric sensor 21 before and after a person sits down. As shown in Figure 5, before a person sits down, no upward pressing force acts on the intervening member 23 via the main pad 15. Therefore, the piezoelectric sensor 21 fixed to the upper surface 16A of the sub-pad 16 is in a nearly horizontal state and does not receive upward pressing force, so the amount of strain on the piezoelectric sensor 21 is almost zero.

[0046] As shown in Figure 5, after a person sits down, the first region 15A of the main pad 15 facing the left buttock of the person sitting down is elastically deformed to protrude in the direction of the load applied by the person sitting down, that is, downward. Therefore, the bottom surface 17A of the recess 17 formed on the lower surface 15E of the main pad 15 is also elastically deformed so that the portion facing the first region 15A protrudes downward.

[0047] Furthermore, the piezoelectric sensor 21, to which the intervening member 23 is fixed, is fixed to the upper surface 16A of the sub-pad 16 along the front-rear direction via the intervening member 23 so as to abut against the portion of the bottom surface 17A of the recess 17 that faces the first region 15A. As a result, the portion of the sub-pad 16 to which the piezoelectric sensor 21 is fixed is elastically deformed to protrude downward from the position indicated by the dashed line P1, depending on the height of the intervening member 23. Consequently, the piezoelectric sensor 21 is elastically deformed to extend further in the longitudinal direction, that is, in the direction of the bidirectional arrow 27 shown in Figure 5.

[0048] Therefore, by placing the intervening member 23 in the central part of the piezoelectric sensor 21 in the longitudinal direction, the amount of strain in the piezoelectric sensor 21 caused by the load of the seated person can be increased compared to the amount of strain when the intervening member 23 is not placed. As a result, the output voltage output from the piezoelectric sensor 21 can be made larger than when the intervening member 23 is not placed. Furthermore, since the intervening member 23 applies the load of the seated person to the central part of the piezoelectric sensor 21 in the longitudinal direction and across the entire width of the piezoelectric sensor 21, the amount of strain in the piezoelectric sensor 21 under the load of the seated person can be made even larger than when the intervening member 23 is not placed.

[0049] [2. Effects of Seat 1] [Example of measuring the signal waveform of cardiac ripple] Next, the effects of seat 1 will be explained based on Figures 6 to 9. First, an example of detecting the signal waveform of a seated person's heart rate in seat 1 under static conditions with the vehicle engine stopped will be explained based on Figure 6. Figure 6 shows an example of the signal waveform of a seated person's heart rate sensed by the piezoelectric sensor 21 of seat 1, under static conditions with the vehicle engine stopped, both with and without the intervening member 23. The signal waveform of heart rate sensed by the piezoelectric sensor 21 was detected through a 0.8Hz to 20Hz bandpass filter.

[0050] As shown in output waveform diagram 101 of Figure 6, when the intervening member 23 is located in the longitudinal center of the piezoelectric sensor 21, a signal waveform with a sufficient output voltage of the piezoelectric sensor 21 was measured, for example, as indicated by the vertically elongated circles 28 and 29. On the other hand, as shown in output waveform diagram 102 of Figure 6, when the intervening member 23 is not located in the longitudinal center of the piezoelectric sensor 21, the output voltage of the piezoelectric sensor 21 was low, and a signal waveform that was difficult to separate from noise was measured.

[0051] Therefore, by placing the intervening member 23 in the center of the piezoelectric sensor 21 in the longitudinal direction, the amount of strain in the piezoelectric sensor 21 caused by the load of the seated person can be increased compared to the amount of strain when the intervening member 23 is not placed. As a result, the output voltage output from the piezoelectric sensor 21 can be made larger than when the intervening member 23 is not present, making it possible to obtain a core elasticity signal waveform with a sufficient output voltage.

[0052] [Example of measuring RRI estimation accuracy] Next, an example of measuring RRI estimation accuracy under static conditions with the vehicle engine stopped will be explained based on Figure 7. Figure 7 shows an example of the percentage of RRI estimation accuracy obtained from sensing results measured by the piezoelectric sensor 21 of the seat 1, under static conditions with the vehicle engine stopped, both with and without the intervening member 23. In the graph of Figure 7, each rectangle represents the range of the top 75% to 25% of RRI estimation accuracy, and the horizontal line within the rectangle represents the median value of RRI estimation accuracy. The lines extending above and below each rectangle represent the range from the maximum to the minimum value of RRI estimation accuracy.

[0053] As shown in the estimation accuracy measurement diagram 103 of Figure 7, when there is no intervening member 23 in the longitudinal center of the piezoelectric sensor 21, the output voltage of the piezoelectric sensor 21 of the seat 1 is low, and the RRI estimation accuracy ratio is approximately 0.7 to approximately 0.8. On the other hand, as shown in the estimation accuracy measurement diagram 104 of Figure 7, when there is an intervening member 23 in the longitudinal center of the piezoelectric sensor 21, the output voltage of the piezoelectric sensor 21 of the seat 1 becomes higher, and the RRI estimation accuracy ratio is approximately 0.97 to approximately 1.0. Therefore, by placing the intervening member 23 in the longitudinal center of the piezoelectric sensor 21, the RRI estimation accuracy ratio under static conditions when the vehicle engine is stopped is increased by approximately 13%.

[0054] Next, an example of measuring RRI estimation accuracy under dynamic conditions where the vehicle was traveling at 80 km / h will be explained based on Figure 8. Figure 8 shows an example of the percentage of RRI estimation accuracy obtained from sensing results measured by the piezoelectric sensor 21 of the seat 1, under dynamic conditions where the vehicle was traveling at 80 km / h, both with and without the intervening member 23. In the graph of Figure 8, each rectangle represents the range of the top 75% to 25% of RRI estimation accuracy, and the horizontal line within the rectangle represents the median value of RRI estimation accuracy. The lines extending above and below each rectangle represent the range from the maximum to the minimum value of RRI estimation accuracy.

[0055] As shown in the estimation accuracy measurement diagram 105 of Figure 8, when there is no intervening member 23 in the longitudinal center of the piezoelectric sensor 21, the output voltage of the piezoelectric sensor 21 of the seat 1 is low, and the RRI estimation accuracy ratio is approximately 0.1 to approximately 0.3. On the other hand, as shown in the estimation accuracy measurement diagram 106 of Figure 8, when there is an intervening member 23 in the longitudinal center of the piezoelectric sensor 21, the output voltage of the piezoelectric sensor 21 of the seat 1 becomes higher, and the RRI estimation accuracy ratio is approximately 0.45 to approximately 0.7. Therefore, by placing the intervening member 23 in the longitudinal center of the piezoelectric sensor 21, the RRI estimation accuracy ratio under dynamic conditions when the vehicle is traveling at 80 km / h is increased by approximately 42%.

[0056] Therefore, as shown in Figures 7 and 8, the accuracy of RRI estimation can be improved by placing the intervening member 23 in the center of the piezoelectric sensor 21 in the longitudinal direction. Furthermore, the higher the RRI estimation accuracy, the higher the RRI correct answer rate. In other words, the RRI correct answer rate can be improved by placing the intervening member 23 in the center of the piezoelectric sensor 21 in the longitudinal direction.

[0057] [Explanation of RRI accuracy rate] The aforementioned "RRI accuracy rate" will now be explained based on Figure 9. Figure 9 is a diagram illustrating an example of a distribution chart used to explain the RRI accuracy rate. The horizontal axis of Figure 9 shows the ratio of each RRI to the average value of the RRI (RR Interval) of cardiac elasticity over a predetermined period (labeled "Average RRI" in Figure 9), and the vertical axis shows the number of times each ratio value was reached. In other words, Figure 9 shows the distribution of "RRI / mean(RRI)". Here, the denominator "mean(RRI)" means the average value of the RRI over the predetermined period, and the numerator "RRI" means the value of each RRI in question. Furthermore, the predetermined period mentioned above is not limited to a specific time; for example, it could be 5 minutes or 30 minutes.

[0058] When the ratio is close to 1, the RRI value in question is close to the average value and therefore highly reliable. When the ratio is significantly different from 1, the RRI value in question is unreliable. In heart rate measurement, it is possible to improve measurement accuracy by excluding or adjusting for RRI values ​​with low reliability.

[0059] The RRI accuracy rate refers to the percentage of RRIs measured over a predetermined period in which the ratio falls within a predetermined range. Typically, the predetermined range is defined as a fixed range centered around 1 for the ratio value. In Figure 9, frame 31 is an example of the predetermined range, showing the range where the ratio value is between 0.95 and 1.05.

[0060] For example, in Figure 9, an RRI accuracy rate of 50% means that the ratio corresponding to 50% of the RRI measured during a predetermined period falls within the range of frame 31.

[0061] Furthermore, when the controller 25 calculates the heart rate of a seated person, if the value of the target RRI is within the predetermined range, it may use the value of the RRI as is, or if the target RRI is outside the predetermined range, it may use the most recently measured RRI value.

[0062] Alternatively, the ratio used by the controller 25 to calculate the RRI accuracy rate may be the ratio of the currently measured RRI to the most recently measured RRI. In this configuration, the distribution diagram corresponding to Figure 9 shows the distribution of "RRI(k) / RRI(k-1)". Here, the denominator "RRI(k-1)" represents the RRI value measured in the k-1 time, which is the most recent k time, and the numerator "RRI(k)" represents the RRI value measured in the k time, which is the current k time.

[0063] Furthermore, the controller 25 uses the measured RRI value y(k) and the most recent estimated value x(k-1) to calculate a new estimated value x(k) using the following formula as the RRI value used to calculate heart rate. x(k) = w*y(k) + (1-w)*x(k-1) You may also use [this].

[0064] Here, w is a weighting coefficient corresponding to the variance value in the distribution diagram, and can take values ​​of 0 ≤ w ≤ 1. The initial value x(0) that forms the basis of the estimated value x may be calculated by the controller 25, for example, by cepstrum analysis. The controller 25 may also reset the initial value x(0) each time the main power supply of the vehicle (mobile body) is started up, or it may be reset at predetermined intervals.

[0065] Furthermore, if the controller 25 determines that the seated person's heart rate, calculated based on the sensing results from the piezoelectric sensor 21, indicates an abnormality in the seated person, it performs predetermined processing (hereinafter simply referred to as "predetermined processing"), such as notifying the seated person of this fact. In a broader sense, the controller 25 performs the predetermined processing when the sensing results from the piezoelectric sensor 21 satisfy predetermined conditions regarding the seated person's heart rate. Here, the condition that the sensing results from the piezoelectric sensor 21 satisfy the predetermined conditions may include, for example, when the number of heartbeats of the seated person in a predetermined time is below a lower limit or above an upper limit, or when it changes by more than a reference value.

[0066] Furthermore, the controller 25 may perform the following example of processing as a predetermined process, which involves outputting a signal to notify information regarding the seated person's status. • A process that outputs audio, video, light, or text to notify the seated person that they are experiencing drowsiness, excitement, fatigue, etc. • A process that outputs a control signal to operate the seat or other movable parts of a mobile body in order to notify the seated person that they are experiencing drowsiness, excitement, fatigue, etc. This process involves transmitting information indicating that an abnormality has occurred in the seated person to a designated contact person via radio communication or similar means.

[0067] Furthermore, the controller 25 may perform the following example processes related to the movement of the vehicle as the predetermined processing. • The process of stopping the vehicle on the shoulder of the road, etc. • Process to reduce the vehicle's speed This process involves moving the vehicle to a designated location such as a hospital or home.

[0068] Furthermore, if predetermined conditions regarding the occupant's heart rate are met, the controller 25 may perform both the above-described process of outputting a signal to notify information regarding the occupant's state and the above-described process regarding the movement of the vehicle (mobile body) as predetermined processing.

[0069] [3. Variant] Modified examples of the above embodiments will now be described. For the sake of convenience, in the following description, components having the same function as those described in the above embodiments will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0070] [Example 1] The seat cushion 11 of the seat 41 according to Modification 1 will be described with reference to Figure 10. Figure 10 is a diagram showing an example of the seat surface of the seat 41 according to Modification 1. The seat 41 has substantially the same configuration as the seat 1 according to the above embodiment. However, as shown in Figure 10, the seat cushion 11 may have a plurality of piezoelectric sensors 21, for example, two piezoelectric sensors 21 arranged in parallel in the left-right direction on the upper surface 16A of the sub-pad 16 which is fitted into a recess 17 formed on the lower surface 15E of the main pad 15.

[0071] Furthermore, each piezoelectric sensor 21 is positioned along the front-to-back direction of the seat cushion 11. Each piezoelectric sensor 21 is fixed to the upper surface 16A of the sub-pad 16 by adhesive or the like, so as to face the first region 15A that is opposite to the left buttock area around the ischial bones of the seated person.

[0072] Furthermore, the wiring for each piezoelectric sensor 21 is routed downward along the rear side of the sub-pad 16 and electrically connected to the controller 25. Note that each piezoelectric sensor 21 may be arranged in parallel in the left-right direction, facing not only the first region 15A opposite the left buttock around the seated person's ischial bones, but also the second region 15B opposite the right buttock around the seated person's ischial bones, and fixed to the upper surface 16A with adhesive or the like.

[0073] Furthermore, an intervening member 23 is positioned between each piezoelectric sensor 21 and the bottom surface 17A of the recess 17, in the longitudinal center of each piezoelectric sensor 21, so as to be able to press a portion of each piezoelectric sensor 21. The planar lower surface 23A of each intervening member 23 is fixed by adhesive or the like to the surface of each piezoelectric sensor 21 facing the bottom surface 17A of the recess 17, that is, to the longitudinal center of the upper surface of each piezoelectric sensor 21. In addition, the height of each intervening member 23 from the lower surface 23A, that is, the height from the piezoelectric sensor 21 to the top of the upper surface 23B of each intervening member 23, is formed to be approximately the same predetermined height. For example, the height from the lower surface 23A to the top of the upper surface 23B of each intervening member 23 is approximately 3 mm to 15 mm, and is formed to a height that does not cause a foreign body sensation to a person sitting on the seat cushion 11.

[0074] The seat 41 configured as described above can achieve substantially the same effects as the seat 1 according to the above embodiment. Furthermore, the controller 25 can adopt the heart rate waveform with the largest amplitude among the heart rate waveforms (BCG waveforms) of the seated person output from each piezoelectric sensor 21, thereby further improving the RRI accuracy rate.

[0075] [Differentiation 2] A modified example of the seat 51 according to the second modification will be described with reference to Figure 11. Figure 11 is a perspective view showing an example of the appearance of the seat 51 according to the second modification. The seat 51 has substantially the same configuration as the seat 1 according to the above embodiment. However, as shown in Figure 11, the seat back 12 may include a main pad 52, a sub-pad 16, a piezoelectric sensor 21, and an intervening member 23. The seat back 12 is mounted so as to be covered by the surface member 14.

[0076] The main pad 52, like the main pad 15, is made of foamed polyurethane, which is a soft polyurethane foam. On the back side of the main pad 52, opposite to the front side which receives the load from the sitter's waist, a recessed area 17 with a bottom, roughly rectangular in shape when viewed from the front, is formed and opens to the rear. The sub-pad 16, which is roughly rectangular in shape when viewed from the front, is fitted into the recess 17 from the rear. The bottom surface 17A of the recess 17 is formed to include a third area 53 facing the left waist area around the ischial tuberosities of the sitter when seated and leaning against the main pad 15, and a fourth area 54 facing the right waist area around the ischial tuberosities of the sitter.

[0077] Therefore, the upper surface 16A of the sub-pad 16, which receives the load of a seated person, is formed to face a third region 53 facing the left hip area around the seated person's ischial tuberosities and a fourth region 54 facing the right hip area around the seated person's ischial tuberosities.

[0078] The elongated piezoelectric sensor 21 is positioned vertically on the upper surface 16A of the sub-pad 16, which is fitted into the recess 17, so as to face the third region 53, which is opposite to the left hip area around the seated person's ischial bones, and is fixed to the upper surface 16A with adhesive or the like. The wiring of the piezoelectric sensor 21 is routed rearward along the lower side of the sub-pad 16 and electrically connected to the controller 25. Note that the piezoelectric sensor 21 is not limited to the third region 53, which is opposite to the left hip area around the seated person's ischial bones, but may also be positioned vertically so as to face the fourth region 54, which is opposite to the right hip area around the seated person's ischial bones, and fixed to the upper surface 16A with adhesive or the like.

[0079] Furthermore, an intervening member 23 is positioned between the piezoelectric sensor 21 and the bottom surface 17A of the recess 17 in the longitudinal direction of the piezoelectric sensor 21, so as to be able to press a portion of the piezoelectric sensor 21. The lower surface 23A of the intervening member 23 is fixed by adhesive or the like to the surface of the piezoelectric sensor 21 that faces the bottom surface 17A of the recess 17, that is, to the longitudinal direction of the piezoelectric sensor 21. In addition, the height of the intervening member 23 from the lower surface 23A, that is, the height from the piezoelectric sensor 21 to the top of the upper surface 23B of the intervening member 23 is formed to a predetermined height. For example, the height from the lower surface of each intervening member 23 to the top of the upper surface 23B of the intervening member 23 is, for example, about 3 mm to about 15 mm, and is formed to a height that does not cause a foreign body sensation to a seated person who is sitting and leaning against the seat back 12.

[0080] Therefore, by placing the intervening member 23 in the center of the piezoelectric sensor 21 in the longitudinal direction, the amount of strain in the piezoelectric sensor 21 generated by the pressing force of the left hip of a seated person leaning against the seat back 12 increases compared to the amount of strain when the intervening member 23 is not placed. As a result, the output voltage output from the piezoelectric sensor 21 can be made larger than when the intervening member 23 is not present, making it possible to obtain a pulsating signal waveform with a sufficient output voltage.

[0081] [Difference 3] Furthermore, for example, the seat back 12 of the seat 51 shown in Figure 11 may have multiple piezoelectric sensors 21, for example, two piezoelectric sensors 21 arranged in parallel in the left-right direction on the upper surface 16A of the sub-pad 16. Each piezoelectric sensor 21 is also arranged along the vertical direction of the seat back 12. Each piezoelectric sensor 21 is fixed to the upper surface 16A of the sub-pad 16 by adhesive or the like so as to face a third region 53 that is opposite to the left hip area around the ischial bones of the seated person.

[0082] Furthermore, the wiring for each piezoelectric sensor 21 is routed backward along the lower side of the sub-pad 16 and electrically connected to the controller 25. Note that each piezoelectric sensor 21 may be arranged in parallel in the left-right direction, facing not only the third region 53 opposite the left hip area around the seated person's ischial bones, but also the fourth region 54 opposite the right hip area around the seated person's ischial bones, and fixed to the upper surface 16A with adhesive or the like.

[0083] Furthermore, an intervening member 23 is positioned between each piezoelectric sensor 21 and the bottom surface 17A of the recess 17, in the longitudinal central portion of each piezoelectric sensor 21, so as to be able to press against a portion of each piezoelectric sensor 21. The planar lower surface 23A of each intervening member 23 is fixed by adhesive or the like to the surface of each piezoelectric sensor 21 facing the bottom surface 17A of the recess 17, that is, to the longitudinal central portion of each piezoelectric sensor 21. In addition, the height of each intervening member 23 from the lower surface 23A, that is, the height from the piezoelectric sensor 21 to the top of the upper surface 23B, is a predetermined height, for example, a height of approximately 3 mm to approximately 15 mm, and is formed to a height that does not cause a foreign body sensation to a seated person leaning against the seat back 12.

[0084] The seat according to Modification 3, configured as described above, can achieve almost the same effect as the seat 51 according to Modification 2. Furthermore, the controller 25 can adopt the heart rate waveform with the largest amplitude among the heart rate waveforms of the seated person output from each piezoelectric sensor 21, thereby further improving the RRI accuracy rate.

[0085] [Differentiation Example 4] For example, the upper surface 23B of the intervening member 23 may be fixed in advance by adhesive or the like to the bottom surface 17A of the recess 17 into which the sub-pad 16 is fitted, so that they are integrally provided. For example, a spherical recess may be formed in the bottom surface 17A of the recess 17, and the upper surface 23B of the intervening member 23 may be fitted into this recess and fixed by adhesive or the like. Alternatively, for example, a protrusion may be formed in the bottom surface 17A of the recess 17, and a recess may be formed in the upper surface 23B of the intervening member 23 into which this protrusion is fitted. Then, the protrusion formed in the bottom surface 17A may be fitted into the recess formed in the upper surface 23B of the intervening member 23 and fixed by adhesive or the like.

[0086] In this case, the upper surface 23B of the intervening member 23 is fixed to the bottom surface 17A of the recess 17, in a position opposite to the longitudinal center of the piezoelectric sensor 21 fixed to the upper surface 16A of the sub-pad 16 fitted into the recess 17. As a result, the intervening member 23 is integrally provided on the bottom surface 17A of the recess 17 of the main pad 15, thereby reducing the number of steps required when assembling the seat 1.

[0087] [Additional Notes] This disclosure is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of this disclosure. [Explanation of Symbols]

[0088] 1, 41, 51 Seat cushion, 11 Seat cushion, 12 Seat back, 15, 52 Main pad, 15A First area, 15B Second area, 16 Sub pad, 16A Top surface, 17 Recess, 17A Bottom surface, 21 Piezoelectric sensor, 23 Intervening member, 53 Third area, 54 Fourth area

Claims

1. The main pad that bears the weight of the seated person, A sub-pad fitted into a recess formed on the side of the main pad opposite to the load-receiving surface, A piezoelectric sensor is disposed on the load-receiving surface of the sub-pad to sense the pulsation of the seated person, An intervening member is provided between the piezoelectric sensor and the bottom surface of the recess facing the piezoelectric sensor, and is positioned so as to be able to press a portion of the piezoelectric sensor, and is at a predetermined height from the piezoelectric sensor. Equipped with, The piezoelectric sensor is elongated, The intervening member is, The piezoelectric sensor is positioned in the central part in the longitudinal direction, A seat in which the dimension of the piezoelectric sensor in the direction perpendicular to the longitudinal direction is greater than or equal to the width of the piezoelectric sensor in the short direction.

2. The main pad and the sub-pad are included in the seat cushion that constitutes the seat surface. The piezoelectric sensor is The aforementioned seat cushion is arranged along the front-to-back direction, The central portion of the piezoelectric sensor in the longitudinal direction is positioned to face at least a portion of the buttocks and thighs of the person seated on the seat cushion. The seat according to claim 1.

3. Multiple piezoelectric sensors are arranged in parallel in the left-right direction of the seat cushion. The seat according to claim 2.

4. The intervening member is fixed to the piezoelectric sensor. The seat according to claim 1.

5. The intervening member is, Made of synthetic resin or metal, with a flat bottom surface and a convex curved top surface. The seat according to claim 4.

6. The intervening member is integrally provided on the bottom surface of the recess. The seat according to claim 1.

7. The main pad and the sub-pad are included in the seatback that forms the backrest. The piezoelectric sensor is Arranged along the vertical direction of the aforementioned seat back, The central portion of the piezoelectric sensor in the longitudinal direction is positioned to face at least one of the left or right hip of the seated person. The seat according to claim 1.

8. Multiple piezoelectric sensors are arranged in parallel in the left-right direction of the seat back. The seat according to claim 7.

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