Piezoelectric sensor and seat
By using long strip piezoelectric elements and wide-form laminated films in piezoelectric sensors, the problem of increased cost in improving detection accuracy is solved, and high-precision core impact detection and improved sensor robustness are achieved.
Patent Information
- Application Number
- CN202410769387.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-06-21
- Filing Date
- 2024-06-14
- Publication Date
- 2024-12-24
AI Technical Summary
Existing sensors have increased costs when expanding electrode widths to improve detection accuracy.
The length of the short side direction of the piezoelectric element is adopted and the wide-format film covering the surrounding area is more than twice the short side direction of the piezoelectric element. The robustness of the sensor is improved by the design of the laminated film and Detection accuracy.
While suppressing costs, the detection accuracy of the sensor is improved, the RRI inference accuracy of the heart impact detection results is enhanced, the life of the sensor is extended and noise interference is reduced.
Smart Images
Figure CN119178455A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to a piezoelectric sensor and a seat. Background Art
[0002] Patent Document 1 discloses a strain sensor in which a sensor element having a piezoelectric film is stacked on one surface of a plate-like base plate. Electrodes are stacked on both surfaces of the piezoelectric film of the sensor element.
[0003] [Prior art literature]
[0004] [Patent Document]
[0005] [Patent Document 1] Japanese Patent Application Publication No. 2020-8397 Summary of the invention
[0006] [Problems to be Solved by the Invention]
[0007] In the sensor described in Patent Document 1, there is a problem that the cost increases when the width of the electrode of the sensor element is increased in order to improve the detection accuracy of the sensor.
[0008] The present disclosure has been made in view of the above-mentioned problems, and an object of the present disclosure is to provide a piezoelectric sensor capable of improving the detection accuracy of the sensor while suppressing the cost, and a seat including the piezoelectric sensor.
[0009] [Means for solving the problem]
[0010] In order to solve the above-mentioned problems, a piezoelectric sensor according to one embodiment of the present disclosure includes: a long strip-shaped piezoelectric element, in which a piezoelectric body is arranged between a first electrode and a second electrode; and a long strip-shaped film covering the periphery of the piezoelectric element. The film has a wide width portion, and the length of the short side direction of the film in the wide width portion is more than twice the length of the short side direction of the piezoelectric element.
[0011] [Effects of the invention]
[0012] According to one aspect of the present disclosure, it is possible to improve the detection accuracy of a sensor while suppressing costs. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Figure 1 This is a schematic side view showing the structure of a seat including a piezoelectric sensor according to an embodiment of the present disclosure.
[0014] Figure 2 Yes means Figure 1 A top view of the overall structure of the piezoelectric sensor.
[0015] Figure 3 It is along Figure 2 Cross-sectional view along line III-III.
[0016] Figure 4 Observed from above Figure 1 Schematic diagram of the structure of a seat.
[0017] Figure 5 Observed from the front Figure 1 A schematic cross-sectional view of a seat.
[0018] Figure 6 It means according to Figure 1 A box plot showing an example of the ratio of the estimated accuracy of the RRI obtained from the cardiac impact detection results of each occupant using the piezoelectric sensor.
[0019] Figure 7 It is a plan view showing the overall structure of a piezoelectric sensor as a comparative example.
[0020] Figure 8 It means according to Figure 7 A box plot showing an example of the ratio of the estimated accuracy of the RRI obtained from the cardiac impact detection results of each occupant using the piezoelectric sensor.
[0021] Fig. 9 It is a plan view showing the shape of the wide width portion of the film of the piezoelectric sensor according to Modification 1 of the embodiment.
[0022] Fig.10 It is a plan view showing the shape of the wide width portion of the film of the piezoelectric sensor according to Modification 2 of the embodiment.
[0023] Fig.11 It is a plan view showing the shape of the wide width portion of the film of the piezoelectric sensor according to Modification 3 of the embodiment.
[0024] [Explanation of Reference Numerals]
[0025] 10, 10A, 10B, 10C Piezoelectric Sensors
[0026] 11 Piezoelectric element
[0027] 12, 12A, 12B, 12C Laminated film
[0028] 16 Adhesive
[0029] 20 Controller
[0030] 100 seats
[0031] 110 Piezoelectric film
[0032] 111 First electrode
[0033] 112 second electrode
[0034] 121, 121A, 121B, 121C wide section
[0035] B Heart attack
[0036] M, M1, M2 Crew DETAILED DESCRIPTION
[0037] Below, refer to Figure 1 to Figure 8 A seat 100 including the piezoelectric sensor 10 according to an embodiment of the present disclosure will be described.
[0038] [Seat]
[0039] Figure 1 1 is a schematic side view showing the structure of a seat 100 equipped with a piezoelectric sensor 10. Figure 1 1 shows a state where the passenger M is seated on the seat 100. Figure 1 As shown, the seat 100 includes a seat cushion 101, a seat back 102, a headrest 103, a piezoelectric sensor 10, a controller 20, and a seat moving device 30. Figure 1 , the back of the occupant M in contact with the seat back 102 and the buttocks of the occupant M in contact with the seat cushion 101 are indicated by dotted lines.
[0040] The seat 100 is provided in a vehicle, for example. The vehicle is an example of a mobile body. The passenger M sits on the seat 100. The seat 100 is, for example, a driver's seat. In addition, the seat 100 may also be a passenger seat or a rear seat. Figure 1 As shown by the arrows, the up-down direction and the front-back direction of the seat 100 are defined.
[0041] The seat cushion 101 is a member for supporting the buttocks of the occupant M. The seat cushion 101 includes a seat cushion frame (not shown), a cushion pad covering the seat cushion frame, and a surface skin. The cushion pad is formed of a foamed resin such as polyurethane foam.
[0042] The seat back 102 is a component for supporting the back of the occupant M. The seat back 102 is provided at the upper rear portion of the seat cushion 101 and includes a back frame (not shown), a back cushion covering the back frame, and a surface. The back cushion is formed of a foamed resin such as polyurethane foam. The headrest 103 is a component for supporting the head of the occupant M and is mounted on the upper end portion of the seat back 102.
[0043] The piezoelectric sensor 10 is disposed inside the seat cushion 101 , and will be described in detail later. The piezoelectric sensor 10 detects ballistocardiology (BCG) B of the occupant M sitting on the seat 100 . Alternatively, the piezoelectric sensor 10 may be fixed to the upper surface of the surface of the seat cushion 101 .
[0044] The piezoelectric sensor 10 is electrically connected to the controller 20. A signal indicating the cardiac impulse B detected by the piezoelectric sensor 10 is sent to the controller 20. The controller 20 measures the heart rate of the occupant M sitting in the seat 100 based on the signal indicating the cardiac impulse B from the piezoelectric sensor 10.
[0045] The controller 20 measures the heart rate of the occupant M based on the cardiac impulse B of the occupant M detected by the piezoelectric sensor 10 . Then, the controller 20 analyzes the fluctuation of the measured heart rate to obtain the RRI (RR Interval) of the occupant M. RRI refers to the interval between adjacent R waves when the electrocardiogram of the occupant M is measured.
[0046] The seat moving device 30 is a device for supporting the seat cushion 101 and sliding the seat 100 in the front-rear direction. Although not shown, the seat moving device 30 includes a pair of left and right slide rails and a pair of left and right seat lifters for raising and lowering the seat 100. The seat moving device 30 is disposed on the floor surface F of the vehicle.
[0047] [Structure of piezoelectric sensor]
[0048] Figure 2 It is a plan view showing the overall structure of the piezoelectric sensor 10. Figure 3 It is along Figure 2 The cross-sectional view of line III-III. Figure 2 As shown in FIG. 1 , the piezoelectric sensor 10 includes a piezoelectric element 11, a laminate film 12, a flat cable 13, a shrink tube 14, and a shielded cable 15. Figure 2 and Figure 3 , the structure of the piezoelectric sensor 10 is described.
[0049] like Figure 2 As shown in FIG. 1 , the piezoelectric element 11 is a long strip-shaped component. Figure 3 As shown, the piezoelectric element 11 includes a piezoelectric film 110 , a first electrode 111 , and a second electrode 112 . The piezoelectric film 110 is an example of a piezoelectric body, and is disposed between the first electrode 111 and the second electrode 112 .
[0050] The piezoelectric film 110 is formed by forming a material having a piezoelectric effect, such as polyvinylidene fluoride (PVDF), into a film shape and cutting it into a long strip shape. The piezoelectric film 110 outputs a voltage according to minute compression and deformation.
[0051] In addition, as a material of the piezoelectric film 110 , trifluoroethylene (TrEF), polylactic acid, polyuric acid, polyamino acid, or the like may be used in addition to PVDF.
[0052] A first electrode 111 is bonded to one surface of the piezoelectric film 110. The first electrode 111 is, for example, a thin film component made of silver. The first electrode 111 is, for example, a positive electrode. A second electrode 112 is bonded to the other surface of the piezoelectric film 110. The second electrode 112 is, for example, a thin film component made of silver. The second electrode 112 is, for example, a negative electrode.
[0053] The first electrode 111 and the second electrode 112 are connected to the flat cable 13. The flat cable 13 is a cable formed by bundling a plurality of wirings made of copper wires covered with a resin insulator in parallel to form a thin plate. The flat cable 13 is thinner and more flexible than the first electrode 111 and the second electrode 112, and thus has excellent bending properties such as bending. The flat cable 13 is arranged inside the seat cushion 101 so as to be bent toward the controller 20 side.
[0054] The flat cable 13 is connected to the shielded cable 15 via the shrinkable tube 14. The shrinkable tube 14 fixes the flat cable 13 and the shielded cable 15 by covering the peripheries of the flat cable 13 and the shielded cable 15.
[0055] The shielded cable 15 is electrically connected to the controller 20. A shielding member for shielding noise from the outside is arranged on the outer periphery of the shielded cable 15. The shielding member is formed of a metal foil such as copper.
[0056] When force is applied to the piezoelectric sensor 10, the piezoelectric film 110 deforms and outputs voltage, and current is energized to the first electrode 111 and the second electrode 112. When the cardiac impulse B of the occupant M sitting in the seat 100 is transmitted to the piezoelectric sensor 10 via the seat cushion 101, the piezoelectric film 110 deforms and outputs voltage.
[0057] The voltage output from the piezoelectric film 110 is transmitted to the flat cable 13 and the shielded cable 15 via the first electrode 111 and the second electrode 112, and then input to the controller 20. The controller 20 measures the heart rate of the occupant M based on the detection result of the piezoelectric sensor 10.
[0058] The laminate film 12 is an example of a long film covering the periphery of the piezoelectric element 11, and protects the piezoelectric element 11. The laminate film 12 is made of, for example, polyester. The thickness of one laminate film 12 is preferably about 5 μm to 110 μm, for example.
[0059] In addition, the material of the laminate film 12 is not limited to polyester, and may be polyolefin, polymethyl methacrylate resin, polyvinylidene fluoride, etc. In addition, the material of the laminate film 12 may be a mixture of multiple materials. In addition, the laminate film 12 may be formed by overlapping multiple raw materials.
[0060] like Figure 2As shown, the laminate film 12 has a wide portion 121 and a connecting portion 122. The length L2 of the wide portion 121 in the short-side direction is greater than or equal to 2 times and less than or equal to 6 times the length L1 of the short-side direction of the piezoelectric element 11. More preferably, the length L2 of the wide portion 121 in the short-side direction is about 3 times the length L1 of the short-side direction of the piezoelectric element 11.
[0061] By providing the wide width portion 121 on the laminate film 12 , the robustness of the piezoelectric sensor 10 can be improved, and even if the occupant M has variations in physique, the output accuracy of the piezoelectric sensor 10 can be ensured.
[0062] The length L1 of the short-side direction of the piezoelectric element 11 may be, for example, approximately 11 mm to 15 mm. More preferably, the length L1 of the short-side direction of the piezoelectric element 11 may be, for example, 13 mm.
[0063] In addition, the length L2 of the short side direction of the wide width portion 121 is about 30 mm to 70 mm, and more preferably about 30 mm to 50 mm. More preferably, the length L2 of the short side direction of the wide width portion 121 is, for example, 40 mm. As described in detail later, when the length L2 of the short side direction of the wide width portion 121 is about 30 mm to 50 mm, the detection accuracy of the piezoelectric sensor 10 is higher than when the length L2 of the short side direction of the wide width portion 121 is about 50 mm to 70 mm.
[0064] The connection portion 122 is a portion other than the wide portion 121 and extends from one end of the wide portion 121 along the piezoelectric element 11. The length L3 of the short side of the connection portion 122 is several mm longer than the length of the short side of the piezoelectric element 11. A shrinkable tube 14 is attached to one end of the connection portion 122.
[0065] like Figure 3 As shown in FIG. 1 , the laminated film 12 is formed by bending and overlapping a laminated film in a manner of sandwiching the piezoelectric element 11, and is composed of a first film 12a, which is a portion disposed on the first electrode 111 side of the piezoelectric element 11, and a second film 12b, which is a portion disposed on the second electrode 112 side of the piezoelectric element 11. The first film 12a and the second film 12b are composed of a single laminated film, and therefore have the same thickness. However, even if it is a single laminated film, when the thickness of the portion that becomes the first film 12a and the portion that becomes the second film 12b are different from each other, the thickness of the first film 12a is naturally different from the thickness of the second film 12b.
[0066] The laminate film 12 may be formed by stacking two laminate films so as to sandwich the piezoelectric element 11. In this case, the thickness of the laminate film serving as the first film 12a and the thickness of the laminate film serving as the second film 12b may be the same or different.
[0067] The first film 12a and the second film 12b are fixed by the adhesive 16 in a state where the piezoelectric element 11 is sandwiched therebetween. Specifically, the surface of the first film 12a on the first electrode 111 side and the surface of the second film 12b on the second electrode 112 side are bonded by the adhesive 16 over the entire area where these surfaces face each other. The thickness of the adhesive 16 is preferably about 40 μm, for example. In addition, the thickness of the adhesive 16 is not limited to 40 μm and can be appropriately changed.
[0068] In addition, the laminated film 12 may not be bonded by the adhesive 16 over the entire relative area of the surface of the first film 12a on the first electrode 111 side and the surface of the second film 12b on the second electrode 112 side. For example, the laminated film 12 only needs to be bonded by the adhesive 16 over at least a few mm from the outer periphery of the piezoelectric element 11 in a plan view in a manner that can fix the piezoelectric element 11.
[0069] [Configuration of piezoelectric sensor]
[0070] Figure 4 1 is a schematic structural diagram of the seat 100 viewed from above. Figure 4 As shown, the piezoelectric sensor 10 is arranged at a position to the left of the center inside the seat cushion 101 in order to improve the detection accuracy of the sensor by being close to the heart of the occupant M. In addition, the piezoelectric sensor 10 is in an elongated shape and is arranged in a manner such that the length direction of the piezoelectric sensor 10 is along the front-rear direction of the seat cushion 101.
[0071] [Effect of piezoelectric sensor]
[0072] Figure 5 is a schematic cross-sectional view of the seat 100 as viewed from the front. Figure 5 The left thigh of the occupant M is shown in FIG. Figure 5 As shown, when the occupant M sits on the seat 100, the cardiac impact B of the occupant M is transmitted from the thigh of the occupant M to the piezoelectric sensor 10. In addition, vibration noise N is also transmitted to the piezoelectric sensor 10. The vibration noise N includes vibration transmitted from the road surface when the vehicle moves and vibration of the vehicle engine.
[0073] Figure 6 It is a box plot showing the ratio of the estimated accuracy of the RRI obtained from the detection result of the cardiac impulse B of the occupant by the piezoelectric sensor 10 of the seat 100 under the dynamic condition of the vehicle traveling at a speed of 80 km / h. Figure 6 2 shows the ratio of the estimated accuracy of the RRI of each of the two test subjects, ie, the passengers M1 and M2, who are the detection objects of the cardiac impulse B. The passengers M1 and M2 have different physiques.
[0074] exist Figure 6In the example shown, the ratio of the RRI estimation accuracy of the occupant M1 is about 0.875 to about 0.950, and the ratio of the RRI estimation accuracy of the occupant M2 is about 0.750 to about 0.825.
[0075] Here, Figure 7 1 is a plan view showing the overall structure of a piezoelectric sensor 10D as a comparative example. Figure 8 It means according to Figure 7 The box plot of the ratio of the estimated accuracy of the RRI obtained by the detection result of the cardiac impulse B of the occupant using the piezoelectric sensor 10D shown in FIG. Figure 7 The two subjects, namely, passengers M1 and M2, who are the objects of the detection of the cardiac impulse B by the piezoelectric sensor 10D are respectively Figure 2 The occupants M1 and M2 who are the detection targets of the cardiac impulse B of the piezoelectric sensor 10D are the same persons.
[0076] like Figure 7 As shown, the piezoelectric sensor 10D and Figure 1 Unlike the piezoelectric sensor 10, it does not have an equivalent Figure 1 The piezoelectric sensor 10 includes a wide portion 121. The length L2D of the laminate film 12D in the short-side direction is longer than the length L1 of the piezoelectric element 11 in the short-side direction by about several mm.
[0077] like Figure 8 As shown, the ratio of the RRI estimation accuracy of the occupant M1 is about 0.500 to about 0.800, and the ratio of the RRI estimation accuracy of the occupant M2 is about 0.575 to about 0.6125.
[0078] according to Figure 6 and Figure 8 It can be seen that the piezoelectric sensor 10 having the wide width portion 121 has a higher output voltage than the piezoelectric sensor 10D having no wide width portion, and the estimation accuracy of the RRI is improved.
[0079] Thus, according to the piezoelectric sensor 10 of this embodiment, the RRI estimation accuracy of both the occupant M1 and the occupant M2 can be improved. In addition, the higher the RRI estimation accuracy, the higher the RRI correct rate. That is, by configuring the piezoelectric sensor 10 of this embodiment in the seat 100, the RRI correct rate can be improved. The RRI correct rate here represents the difference between the RRI of the occupant M1 and the occupant M2 measured during a specified period and the RRI of the occupant M1 and the occupant M2 measured during a specified period. Figure 6 The probability that the difference in estimated RRI of the occupant M1 and the occupant M2 falls within 50 msec is shown. The predetermined period is not limited to a specific time.
[0080] [Effects of Embodiment]
[0081] According to the piezoelectric sensor 10 of the present embodiment described above, by setting the length L2 of the wide portion 121 of the laminate film 12 in the short side direction to be greater than twice and less than six times the length L1 of the piezoelectric element 11 in the short side direction, the pressure receiving area of the pressure applied to the piezoelectric sensor 10 by the occupant M sitting on the seat 100 can be enlarged, the output accuracy of the piezoelectric sensor 10 can be improved, and the robustness of the piezoelectric sensor 10 can be improved.
[0082] In particular, since the sizes of the first electrode 111 and the second electrode 112 of the piezoelectric element 11 do not need to be increased, the cost can also be suppressed. In addition, according to the piezoelectric sensor 10 of this embodiment, the RRI estimation accuracy can be improved.
[0083] In addition, if Figure 4 As shown, the piezoelectric sensor 10 is arranged on the left side of the center portion inside the seat cushion 101 , that is, at a position closer to the heart of the occupant M, and thus can detect the cardiac impulse B of the occupant M with high accuracy.
[0084] Moreover, if Figure 4 As shown, the piezoelectric sensor 10 is configured in a manner such that the length direction of the piezoelectric sensor 10 is along the front-to-back direction of the seat cushion 101. Therefore, the pulse of the femoral artery extending along the left thigh of the occupant M can be easily detected by the piezoelectric sensor 10, thereby improving the detection accuracy of the cardiac shock B of the occupant M.
[0085] In addition, if Figure 3 As shown, the surface of the first film 12a on the first electrode 111 side and the surface of the second film 12b on the second electrode 112 side of the laminate film 12 are fixed by the adhesive 16 over the entire area of these surfaces. Therefore, the distance until water vapor and corrosive gas penetrate from the outside of the piezoelectric sensor 10 to the piezoelectric element 11 side, that is, the penetration distance can be extended. As a result, the deterioration of the piezoelectric element 11 can be suppressed, and the life of the piezoelectric sensor 10 can be extended. In addition, the amount of noise N mixed from the vehicle into the piezoelectric sensor 10 can be reduced.
[0086] Furthermore, by using polyester as the material of the laminate film 12, the rigidity of the laminate film 12 can be ensured. In particular, in the wide portion 121 of the laminate film 12, the bonding area between the first film 12a and the second film 12b is increased, so that the bending resistance of the laminate film 12 can be improved.
[0087] Below, refer to Figure 9~Figure 11 Piezoelectric sensors 10A to 10C according to Modifications 1 to 3 of the above embodiment will be described. For convenience of description, components having the same functions as those described in the above embodiment are denoted by the same reference numerals, and description thereof will not be repeated.
[0088] [Variant 1]
[0089] First, refer to Fig. 9 A piezoelectric sensor 10A according to Modification 1 will be described. Fig. 9 FIG. 1 is a plan view showing the shape of a wide portion 121A of a laminate film 12A of a piezoelectric sensor 10A according to Modification 1. Fig. 9 In the figure, the flat cable 13, the shrink tube 14 and the shielded cable 15 are omitted.
[0090] like Fig. 9 As shown, the laminate film 12A has a wide portion 121A. A rectangular notch 122A is formed in the wide portion 121A. That is, the wide portion 121A is cut into a rectangular shape in the short side direction of the piezoelectric element 11 at the middle of one end of the wide portion 121A.
[0091] The length L2A of the wide portion 121A in the short direction is about 4 times the length L1 of the piezoelectric element 11. The length L2A of the wide portion 121A in the short direction only needs to be 2 times or more and 6 times or less.
[0092] The piezoelectric sensor 10A of Modification 1 can also achieve the same effects as the piezoelectric sensor 10 of the above-described embodiment. That is, the robustness of the piezoelectric sensor 10A can be improved, and the output accuracy of the piezoelectric sensor 10A can be improved while suppressing the cost.
[0093] [Variant 2]
[0094] Next, refer to Fig.10 A piezoelectric sensor 10B according to Modification 2 will be described. Fig.10 FIG. 1 is a plan view showing the shape of a wide portion 121B of a laminate film 12B of a piezoelectric sensor 10B according to Modification 2. Fig.10 In the figure, the flat cable 13, the shrink tube 14 and the shielded cable 15 are omitted.
[0095] like Fig.10 As shown, the laminate film 12B has a wide portion 121B. A triangular notch 122B is formed in the wide portion 121B. That is, the wide portion 121B is cut into a triangular shape in the short side direction of the piezoelectric element 11 at the middle of one end of the wide portion 121B.
[0096] The length L2B of the wide portion 121B in the short direction is about 4 times the length L1 of the piezoelectric element 11. The length L2B of the wide portion 121B in the short direction only needs to be 2 times or more and 6 times or less the length L1 of the piezoelectric element 11 in the short direction.
[0097] The piezoelectric sensor 10B of Modification 2 can also achieve the same effects as the piezoelectric sensor 10 of the above-described embodiment. That is, the robustness of the piezoelectric sensor 10B can be improved, and the output accuracy of the piezoelectric sensor 10B can be improved while suppressing the cost.
[0098] [Variant 3]
[0099] Next, refer to Fig.11 A piezoelectric sensor 10C according to Modification 3 will be described. Fig.11 FIG. 1 is a plan view showing the shape of a wide portion 121C of a laminate film 12C of a piezoelectric sensor 10C according to Modification 3. Fig.11 In the figure, the flat cable 13, the shrink tube 14 and the shielded cable 15 are omitted.
[0100] like Fig.11 As shown, the laminate film 12C has a wide portion 121C. A plurality of rectangular notches 122C are formed in the wide portion 121C. That is, the wide portion 121C is a corrugated shape in which the laminate film 12C in the short side direction of the piezoelectric element 11 is cut into a plurality of rectangular portions in the middle of one end of the wide portion 121C.
[0101] The length L2C of the wide portion 121C in the short direction is about 4 times the length L1 of the piezoelectric element 11. The length L2C of the wide portion 121C in the short direction only needs to be 2 times or more and 6 times or less.
[0102] The piezoelectric sensor 10C of Modification 3 can also achieve the same effects as the piezoelectric sensor 10 of the above-described embodiment. That is, the robustness of the piezoelectric sensor 10C can be improved, and the output accuracy of the piezoelectric sensor 10C can be improved while suppressing the cost.
[0103] [Other implementation methods]
[0104] In the above-mentioned embodiment, the seat 100 is provided in a vehicle as an example of a mobile body, but the present invention is not limited thereto. For example, the seat 100 may be provided in a train, an airplane, a ship, or the like.
[0105] In the piezoelectric sensor 10 of the above embodiment, the outer shape of the wide portion 121 of the laminate film 12 is as follows: Figure 2 The shape shown is rectangular, but it is not limited thereto, and may be, for example, an elliptical shape or a polygonal shape.
[0106] In the above-mentioned embodiment, the piezoelectric sensor 10 is arranged at a position on the left side of the center portion inside the seat cushion 101, but the present invention is not limited thereto. For example, the piezoelectric sensor 10 may be arranged at a position on the right side of the center portion inside the seat cushion 101, or may be arranged inside the seat back 102.
[0107] In the above embodiment, the controller 20 measures the heart rate of the occupant M based on the detection result of one piezoelectric sensor 10 , but the present invention is not limited thereto. The controller 20 may measure the heart rate of the occupant M based on the detection results of a plurality of piezoelectric sensors 10 provided in the vehicle.
[0108] In the above-mentioned embodiment, the seat 100 includes the seat cushion 101, the seat back 102, and the headrest 103, but the present invention is not limited thereto. The seat 100 may not include the seat back 102 and the headrest 103, or may include only the seat cushion 101. In addition, the seat 100 may also include a bed and a cushion.
[0109] The present disclosure is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the technical scope of the present disclosure.
Claims
1. A piezoelectric sensor, characterized in that: The piezoelectric sensor comprises: A long piezoelectric element is formed by disposing a piezoelectric body between a first electrode and a second electrode; and The long film covers the periphery of the piezoelectric element. The film has a wide portion, and the length of the film in the short-side direction in the wide portion is at least twice the length of the piezoelectric element in the short-side direction.
2. The piezoelectric sensor according to claim 1, characterized in that The length of the wide portion in the short-side direction is 6 times or less the length of the piezoelectric element in the short-side direction.
3. The piezoelectric sensor according to claim 1, characterized in that: A notch is formed in the wide portion.
4. The piezoelectric sensor according to claim 1, characterized in that: The film includes a first film disposed on the first electrode side of the piezoelectric element and a second film disposed on the second electrode side of the piezoelectric element. The surface of the first film on the first electrode side and the surface of the second film on the second electrode side are fixed by an adhesive over the entire areas of these surfaces.
5. A seat, characterized in that: The seat has: The piezoelectric sensor according to any one of claims 1 to 4; and A seat, provided on a moving body, The piezoelectric sensor is disposed on the seat and detects cardiac impact of an occupant sitting on the seat.
6. The seat according to claim 5, characterized in that: The seat has a seat cushion that supports the buttocks of the occupant. The piezoelectric sensor is disposed on the left side of the center portion inside the seat cushion.
7. The seat according to claim 6, characterized in that The piezoelectric sensor is in a long strip shape and is arranged such that a longitudinal direction of the piezoelectric sensor is along a front-rear direction of the seat cushion.