pressure sensor

Abstract

The pressure sensor of this disclosure can simultaneously detect pressure and extension or tensile force. [Solution] The pressure sensor comprises two pairs of stretchable nonconductive sheets, an electrode portion, and a dielectric. Each of the nonconductive sheets is provided with a conductive electrode portion that expands and contracts in any direction of stretchability, and the flexible dielectric is sandwiched between the two pairs of nonconductive sheets. The sensor detects pressure in the planar direction of the nonconductive sheets and elongation or tensile force perpendicular to the planar direction.

Description

[Technical Field]

[0001] This disclosure relates to a capacitive pressure sensor. [Background technology]

[0002] Conventional technologies exist for capacitive sensors.

[0003] For example, a technology relating to a capacitive, expandable touchpad has been disclosed (see Patent Document 1). Patent Document 1 relates to a capacitive touchpad composed of a resistance strain gauge and an insulating material. In this technology, changes in the strain gauge are used to correct changes in the capacitance of a capacitive touch sensor, and the stretching of the fabric and the direction of stretching are monitored. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-139108 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, regarding the technology described in Patent Document 1, there is a problem in that if one side of each electrode of the strain gauge is connected to GND or if the two strain gauges are connected to the same potential, capacitance cannot be generated between the two strain gauges, and it cannot function as a capacitive sensor (see FIG. 1b / FIG. 2 of Patent Document 1). Furthermore, although the capacitance (Cp) of a finger or similar object is described in the technology of Patent Document 1, the capacitance of the sensor itself is not mentioned. Therefore, while it is assumed that contact from a finger or stylus can be detected, a problem arises in that contact or stress from other objects that do not have capacitance cannot be detected (see FIG. 2 of Patent Document 1).

[0006] This disclosure is made in view of the above circumstances and aims to provide a pressure sensor capable of simultaneously detecting pressure and extension or tensile force. [Means for solving the problem]

[0007] To achieve the above objective, the pressure sensor of this disclosure comprises two pairs of stretchable nonconductive sheets, an electrode portion, and a dielectric, wherein each of the nonconductive sheets is provided with a conductive electrode portion that expands and contracts in any of the stretchable directions, and the flexible dielectric is sandwiched between the two pairs of nonconductive sheets, and the pressure in the planar direction of the nonconductive sheets and the extension or tensile force perpendicular to the planar direction are detected. [Effects of the Invention]

[0008] The pressure sensor of this disclosure can simultaneously detect pressure and extension or tensile force. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows the capacitive pressure sensor of this embodiment. [Figure 2] Figure 2 is an image showing a simulated configuration of the pressure sensor in this embodiment. [Figure 3] Figure 3 shows an example of the configuration of a conductive electrode section. [Figure 4] Figure 4 shows an example of the sensor characteristics of the electrode section. [Figure 5] Figure 5 shows a comparison of the relationship between the pitch and elongation rate of the electrode portion. [Figure 6] Figure 6 shows a comparison of the resistance change rate in relation to the pitch and elongation rate of the electrode section. [Figure 7] Figure 7 shows an example of a detection circuit configuration corresponding to a pressure sensor. [Figure 8] Figure 8 shows an example of detection when a load is applied to the pressure sensor. [Figure 9] Figure 9 is a schematic diagram showing the load on the pressure sensor. [Figure 10] Fig. 10 shows an example of a circuit configuration in which a pressure sensor includes a CV converter. [Figure 11] Fig. 11 shows an example of detection of pressure and tension in a sensor output. [Figure 12] Fig. 12 shows an example of use of the pressure sensor according to the present embodiment. MODE FOR CARRYING OUT THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0011] Fig. 1 is a diagram showing a capacitive pressure sensor according to the present embodiment. As shown in Fig. 1, the pressure sensor 10 includes two pairs of non-conductive sheets 100 (100A, 100B), electrode sections 102 (102A, 102B), and a dielectric 104. In the pressure sensor 10, the dielectric 104 is sandwiched between the non-conductive sheets 100 provided with the conductive electrode sections 102 to form a capacitor structure. Electrode wirings L (L-A1, L-A2, L-B1, L-B2) are provided at both ends of the electrode sections 102.

[0012] The non-conductive sheets 100 have stretchability and stretch in the up, down, left, and right directions (or any of the up, down, left, and right directions). As shown in Fig. 1, for each of the non-conductive sheets 100, each of the conductive electrode sections 102 that expands and contracts following any of the stretchable directions is provided. The electrode sections 102 have flexibility, and their electrical characteristics change due to elongation or tensile force. The flexible dielectric 104 is sandwiched between the two pairs of non-conductive sheets 100, and detects pressure in the plane direction of the non-conductive sheets 100 and elongation or tensile force perpendicular to the plane direction. In addition, since the electrode sections 102 output the generated elongation or tensile force as electrical resistance, the elongation or tensile force can be detected. Note that elongation and tensile force differ in terms of the force applied to the pressure sensor 10: elongation refers to the application of a force that stretches the non-conductive sheets 100 of the pressure sensor 10, and tensile force refers to the application of a pulling force that acts on the non-conductive sheets 100 at a plurality of force points.

[0013] Figure 2 is an image of a simulated configuration of the pressure sensor according to this embodiment. A flexible cloth or the like can be used as the non-conductive sheet.

[0014] Figure 3 shows an example of the configuration of a conductive electrode section. In Figure 3, the upper thread is a non-conductive thread and the lower thread is a conductive thread. In the example configuration of electrode section 102 in Figure 3, the electrode was formed by embroidery. Alternatively, this configuration may be reversed, with the upper thread being a conductive thread and the lower thread a non-conductive thread, or both the upper and lower threads being conductive threads. In this example, Fujix's Smart X was used as the conductive thread and nylon thread as the non-conductive thread. Note that configurations where both the upper and lower threads are non-conductive are not covered.

[0015] The principle of detecting elongation / tensile force using the expandable electrode portion 102 will be explained. Figure 4 shows an example of the sensor characteristics of the electrode portion. The electrode portion 102 can be manufactured by zigzag sewing conductive threads onto a stretchable fabric or the like. The sensor characteristics of the electrode portion 102 can be changed by adjusting the sensor length, sensor width, and sensor pitch.

[0016] Figure 5 compares the relationship between electrode pitch and elongation rate. The sensor pitches are pitch A, pitch B, and pitch C, and the figures compare elongation rates from 0% to 33%. Pitch A has the narrowest spacing, while pitches B and C have progressively wider spacing. As the elongation rate increases, the contact between adjacent threads decreases, increasing electrical resistance. Furthermore, by changing the pitch, sensing can be performed according to the magnitude of the strain.

[0017] Figure 6 compares the resistance change rate in relation to the pitch and elongation rate of the electrode section. It shows that as the elongation rate increases, the resistance change rate increases in the order of pitch A, pitch B, and pitch C. Conversely, the resistance change rate with increasing elongation rate tends to saturate in the order of pitch C, pitch B, and pitch A. By utilizing these sensor characteristics, the electrode section 102 can be configured with a sensor pitch corresponding to the target strain. For example, if you want a sensor that can detect large strains, you can improve the detection sensitivity by using a sensor characteristic like pitch A. Conversely, if you want to improve the detection sensitivity of small strains, you can use a sensor characteristic like pitch C.

[0018] Next, an example of the detection circuit configuration for the pressure sensor 10 will be shown. Figure 7 is a diagram showing an example of a detection circuit configuration corresponding to the pressure sensor. The detection circuit has a transmitting unit and a receiving unit on the non-conductive sheet 100A side, and the output V of the transmitting unit cs and the output V of the receiving unit cr The pressure sensor 10 takes the output V of the transmitting unit. cs This is the electrode wiring L-A1 (output destination of P1), and the output V of the receiving unit. cr This is compatible with electrode wiring L-A2. The output V of the receiver section of electrode wiring L-A2. cr The AC component is detected in the waveform, and the output V of electrode wiring L-B2 (output destination of P2) is detected. r The DC component is detected in the waveform. Output V on the non-conductive sheet 100B side. r This corresponds to tensile or shear force.

[0019] Figure 8 shows an example of detection when a load is applied to the pressure sensor. Figure 9 is a schematic diagram showing the load on the pressure sensor. (A1) is no load, (A2) is pressure load, (A3) is tension, and (A4) is tension + pressure load, and the voltage changes for each can be compared. Referring to (A2), when pressure is applied in the planar direction of the sheet, the distance between the electrodes with the dielectric 104 in between narrows and the capacitance increases. As the capacitance increases, the waveform (V) observed in the receiving unit changes. cr), the time constant increases and the voltage rise is delayed. Pressure can be detected by observing this. On the other hand, referring to (A3), when tension is applied in the left-right direction, the electrical resistance of the electrode portion 102 increases due to the change in electrical resistivity with respect to elongation described on the entire page. This resistance change causes output V r 's voltage decreases, and tensile force can be detected by observing this. However, as shown in (A4), although the electrical resistance of the electrode portion 102 also decreases when pressure is applied, the waveform of the receiving unit (V cr ), pressure and tension can be detected simultaneously by observing them at the same time as the change of ). As described above, the pressure sensor 10 can detect the pressure in the plane direction of the non-conductive sheet 100 and the shear force caused by elongation or tensile force perpendicular to the plane direction of the non-conductive sheet 100 individually or simultaneously.

[0020] Figure 10 is an example of a circuit configuration in which a pressure sensor is provided with a CV converter. The CV converter includes a transmitter-receiver circuit configuration. Capacitance can be detected as a direct current by the CV converter. As described above, in the pressure sensor 10, a capacitance detector (CV converter) that measures capacitance can be provided on one of the two electrode portions 102. Accordingly, the pressure sensor is provided with an electric circuit configuration that detects a capacitance change accompanying the displacement of the dielectric 104 sandwiched between the non-conductive sheets 100 in the plane direction or a capacitance change generated between a human body and the sheet. In this electric circuit configuration, a DC voltage is applied to the electrode portion 102 not provided with a capacitance detector (CV converter), whereby a DC component V r detects the voltage drop of . Tension can be detected from the detection of the voltage drop.

[0021] Figure 11 is an example of detection of pressure and tension in sensor output. Output V cv and output V rPressure and tension can be detected from these. Figure 12 shows an example of using the pressure sensor of this embodiment. By attaching the pressure sensor 10 of this embodiment to the surface of a complex-shaped object made of a soft material, such as a seat installed in an automobile (or by sewing it directly in the case of conductive thread), the pressure and shear force acting on it can be detected. This is also effective for soft objects such as people, and can be incorporated into clothing and used as a wearable sensor.

[0022] As described above, the pressure sensor 10 according to this embodiment can simultaneously detect pressure and extension or tensile force.

[0023] This disclosure is not limited to the embodiments described above, and various modifications and applications are possible without departing from the spirit of the invention.

[0024] The following is further disclosed regarding the embodiments described above.

[0025] (Note 1) A capacitive pressure sensor comprising two pairs of stretchable nonconductive sheets, an electrode portion, and a dielectric, Each of the non-conductive sheets is provided with a conductive electrode portion that expands and contracts in any of the expandable directions. A pressure sensor comprising a flexible dielectric material sandwiched between two pairs of nonconductive sheets, which detects pressure in the planar direction of the nonconductive sheets and elongation or tensile force perpendicular to the planar direction.

[0026] (Note 2) The pressure sensor as described in Appendix 1, wherein the electrode portion is flexible, and at least one of the electrode portions changes its electrical properties due to extension or tensile force, and outputs the generated extension or tensile force as electrical resistance.

[0027] (Note 3) The pressure sensor described in Appendix 2, which individually or simultaneously detects the pressure in the planar direction of the nonconductive sheet and the shear force due to the elongation or tensile force of the nonconductive sheet.

[0028] (Note 4) The pressure sensor according to Appendix 1 or Appendix 2, comprising an electrical circuit configuration that includes a capacitance detector for measuring capacitance on one of the two electrode portions, and detects capacitance changes due to planar displacement of the dielectric sandwiched between the nonconductive sheets or capacitance changes occurring between the human body and the nonconductive sheet.

[0029] (Note 5) The pressure sensor described in Appendix 4, wherein the electrical circuit configuration includes applying a DC voltage to the electrode portion where the capacitance detector is not provided, and detecting the voltage drop. [Explanation of Symbols]

[0030] 10 Pressure Sensor 100 Non-conductive sheets 102 Electrode section 104 Dielectrics

Claims

1. A capacitive pressure sensor comprising two pairs of stretchable nonconductive sheets, an electrode portion, and a dielectric, Each of the non-conductive sheets is provided with a conductive electrode portion that expands and contracts in any of the expandable directions. A pressure sensor comprising a flexible dielectric material sandwiched between two pairs of nonconductive sheets, which detects pressure in the planar direction of the nonconductive sheets and elongation or tensile force perpendicular to the planar direction.

2. The pressure sensor according to claim 1, wherein the electrode portion is flexible, and at least one of the electrode portions changes its electrical properties due to elongation or tensile force, and outputs the generated elongation or tensile force as electrical resistance.

3. The pressure sensor according to claim 2, which individually or simultaneously detects the pressure in the planar direction of the nonconductive sheet and the shear force due to the elongation or tensile force of the nonconductive sheet.

4. The pressure sensor according to claim 1, comprising an electrical circuit configuration that includes a capacitance detector for measuring capacitance on one of the two electrode portions, and for detecting capacitance changes due to planar displacement of the dielectric sandwiched between the nonconductive sheets or capacitance changes occurring between the human body and the nonconductive sheet.

5. The pressure sensor according to claim 4, wherein in the electrical circuit configuration, a DC voltage is applied to the electrode portion where the capacitance detector is not provided, and a voltage drop is detected.

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