Load sensor and load detection device

Abstract

A load sensor (1) is provided with: a first electrode (20) having elastic conductive first protrusions (21) and second protrusions (22) on the same surface; a second electrode (40) facing the first electrode (20) so as to sandwich the first protrusion (21) and the second protrusion (22); and a dielectric (30) disposed on the facing surface (41) of the second electrode (40). The number of protrusions in contact with the dielectric (30) increases in accordance with an increase in the load.

Description

Technical Field

[0001] This invention relates to a load sensor and a load detection device that detects externally applied loads based on changes in electrostatic capacitance. Background Technology

[0002] Previously, capacitive load sensors have been used as HMIs (Human Machine Interfaces) in various devices such as keyboards and game controllers. For example, a load sensor can be configured with: a first electrode having multiple protrusions that are elastic and conductive; a second electrode facing the first electrode, clamping the protrusions; and a dielectric disposed on the facing surface of the second electrode. When a load is applied to either the first or second electrode, the protrusions contract according to the load. This changes the contact area between the dielectric and the protrusions, and reduces the distance between the dielectric and the first electrode. Consequently, the electrostatic capacitance between the first and second electrodes changes. The load is detected based on this change in electrostatic capacitance.

[0003] Such a load sensor is described in the following patent document 1.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-118545 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] In load sensors with the aforementioned structure, the load detection range is typically set within a range that allows the protrusion to deform reversibly. However, in cases such as an object accidentally falling onto the load sensor, a high load exceeding the yield stress may be applied to the protrusion. If such a high load causes irreversible deformation, i.e., plastic deformation, in the protrusion, the load cannot be properly detected.

[0009] In view of such problems, the object of the present invention is to provide a load sensor and a load detection device that can suppress plastic deformation of the protrusion even when a large load is accidentally applied to the load sensor.

[0010] Solution for solving the problem

[0011] The load sensor according to a first aspect of the present invention comprises: a first electrode having a plurality of protrusions on the same surface, the protrusions being elastic and conductive; a second electrode facing the first electrode in a manner that clamps the plurality of protrusions; and a dielectric disposed on the facing surface of the second electrode. The number of protrusions in contact with the dielectric increases with increasing load.

[0012] According to the load sensor described in this method, since the number of protrusions in contact with the dielectric increases with the increase of the load, even if a large load is accidentally applied to the load sensor, the stress generated in each of the multiple protrusions is mitigated. Therefore, the stress generated in each protrusion is unlikely to exceed the yield stress, and plastic deformation of each protrusion can be suppressed.

[0013] The load sensor according to the second aspect of the present invention comprises: a first electrode having a plurality of first protrusions, the first protrusions being elastic and conductive; a second electrode facing the first electrode in a manner that clamps the plurality of first protrusions; a plurality of second protrusions, the second protrusions being elastic and insulating, the second protrusions being disposed on the facing surface of the second electrode in a manner that protrudes into a space where the first protrusions are not present; and a dielectric disposed on the facing surface of the second electrode. In a no-load state, the tips of the plurality of first protrusions are in contact with the dielectric, and the tips of the plurality of second protrusions are separated from the first electrode.

[0014] According to the load sensor described herein, since the second protrusion contacts the structure on the first electrode side as the load increases, even if a large load is accidentally applied to the load sensor, the stress generated on each of the multiple first protrusions is mitigated. Therefore, the stress generated on each first protrusion is unlikely to exceed the yield stress, and plastic deformation of each first protrusion can be suppressed. Furthermore, since the second protrusion is disposed on a second electrode different from the first electrode on which the first protrusion is disposed, it is easy to place the second protrusion in the gap between the first protrusions. Therefore, there is no need to reduce the number of first protrusions to accommodate the second protrusion, thus maintaining the detection sensitivity of the load sensor.

[0015] The load detection device according to the third aspect of the present invention includes: a load sensor according to the first or second aspect; and a control unit that detects the load based on the electrostatic capacitance between the first electrode and the second electrode.

[0016] According to the load detection device described in this method, plastic deformation of each protrusion in the load sensor is suppressed. Therefore, even after a large load is applied to the load sensor, the control unit can appropriately and continuously detect the load.

[0017] Invention Effects

[0018] As described above, according to the present invention, it is possible to provide a load sensor and a load detection device that can suppress plastic deformation of the protrusion even when a large load is accidentally applied to the load sensor.

[0019] The effects or significance of the present invention become clearer through the following description of the embodiments. However, the embodiments shown below are merely illustrative examples of carrying out the present invention, and the present invention is not limited in any way by the manner described in the following embodiments. Attached Figure Description

[0020] Figure 1 This is an exploded perspective view schematically showing the structure of the load sensor according to Embodiment 1.

[0021] Figure 2 (a) is a schematic cross-sectional view of the load sensor in the no-load state according to Embodiment 1. Figure 2 (b) is a schematic cross-sectional view of the load sensor under the load condition according to Embodiment 1.

[0022] Figure 3 (a) is a cross-sectional view schematically showing the deformation of the protrusion in the comparative example when it was subjected to a load beyond the detection range. Figure 3 (b) is a cross-sectional view schematically showing the deformation of the protrusion in the case of being subjected to a load beyond the detection range according to Embodiment 1.

[0023] Figure 4 (a) and Figure 4 (b) is a top view schematically showing the deformation of the first protrusion involved in the comparative example.

[0024] Figure 5 (a) and Figure 5 (b) is a top view schematically showing the deformation of the first protrusion and the second protrusion involved in Embodiment 1.

[0025] Figure 6 This is a diagram schematically illustrating the relationship between load and compressive stress in the comparative example and embodiment 1.

[0026] Figure 7 (a) is a graph schematically showing the relationship between load and electrostatic capacitance in the comparative example and in the case where the second protrusion is not conductive, according to Embodiment 1. Figure 7 (b) is a graph schematically showing the relationship between load and electrostatic capacitance in the comparative example and in the case where the second protrusion is conductive, according to Embodiment 1.

[0027] Figure 8This is a block diagram showing the structure of the load detection device according to Embodiment 1.

[0028] Figure 9 (a) is a perspective view schematically showing the structure of the first electrode involved in the comparative example. Figure 9 (b) is a perspective view schematically showing the structure of the first electrode involved in structure 1 of embodiment 1.

[0029] Figure 10 (a) is a perspective view schematically showing the structure of the first electrode involved in structure 2 of embodiment 1. Figure 10 (b) is a perspective view schematically showing the structure of the first electrode involved in structure 3 of embodiment 1.

[0030] Figure 11 (a) is a perspective view schematically showing the structure of the first electrode involved in structure 4 of embodiment 1. Figure 11 (b) is a perspective view schematically showing the structure of the first electrode involved in structure 5 of embodiment 1.

[0031] Figure 12 (a) and Figure 12 (b) is a graph showing the simulation results of structures 1 and 2 of the comparative example and embodiment 1.

[0032] Figure 13 (a) and Figure 13 (b) is a graph showing the simulation results of structures 2 and 3 of the comparative example and embodiment 1.

[0033] Figure 14 (a) and Figure 14 (b) is a graph showing the simulation results of structures 4 and 5 of the comparative example and embodiment 1.

[0034] Figure 15 (a) and Figure 15 (b) is a cross-sectional view schematically showing the structure of the first electrode involved in an example of a change in the shape of the protrusion.

[0035] Figure 16 (a) and Figure 16 (b) is a cross-sectional view schematically showing the structure of the first electrode involved in an example of a change in the shape of the protrusion.

[0036] Figure 17 (a) and Figure 17 (b) is a top view schematically showing the structure of the first electrode involved in a modified example of the configuration of the protrusions.

[0037] Figure 18 (a) and Figure 18(b) is a top view schematically showing the structure of the first electrode involved in a modified example of the configuration of the protrusions.

[0038] Figure 19 (a) and Figure 19 (b) is a schematic diagram illustrating an example of the formation process of the first electrode involved in Embodiment 1.

[0039] Figure 20 (a) and Figure 20 (b) is a schematic diagram illustrating an example of the formation process of the first electrode involved in Embodiment 1.

[0040] Figure 21 (a) and Figure 21 (b) is a schematic diagram illustrating the formation process of the first electrode involved in Embodiment 1.

[0041] Figure 22 (a) is a schematic cross-sectional view of the load sensor in the no-load state according to Embodiment 2. Figure 22 (b) is a cross-sectional view schematically showing the deformation of the protrusion when subjected to a load beyond the detection range according to Embodiment 2.

[0042] Figure 23 (a) is a perspective view schematically showing the structure of the first electrode involved in the comparative example. Figure 23 (b) is a perspective view schematically showing the structure of the first electrode involved in structure 6 of embodiment 2.

[0043] Figure 24 (a) and Figure 24 (b) is a graph showing the simulation results of the comparative example and structure 6 of embodiment 2.

[0044] Figure 25 (a) and Figure 25 (b) is a top view schematically showing the structure of the first electrode involved in a modified example of the configuration of the protrusions.

[0045] Figure 26 (a) and Figure 26 (b) is a schematic diagram illustrating an example of the formation process of the first electrode involved in Embodiment 2.

[0046] Figure 27 (a) and Figure 27 (b) is a schematic diagram illustrating an example of the formation process of the first electrode involved in Embodiment 2.

[0047] Figure 28 (a) and Figure 28(b) is a schematic diagram illustrating the formation process of the first electrode involved in Embodiment 2.

[0048] Figure 29 (a) is a schematic cross-sectional view of the load sensor in the no-load state according to Embodiment 3. Figure 29 (b) is a cross-sectional view schematically showing the deformation of the protrusion when subjected to a load beyond the detection range according to Embodiment 3.

[0049] Figure 30 (a) and Figure 30 (b) is a cross-sectional view schematically showing the structure of the first electrode involved in an example of a change in the shape of the protrusion.

[0050] However, the accompanying drawings are mainly for illustration and do not limit the scope of the invention. Detailed Implementation

[0051] This invention can be applied to input units for receiving inputs corresponding to a given load. Specifically, it can be applied to input units of electronic devices such as PC keyboards, input units of game controllers, surface units for robotic arms to detect objects, input units for inputting volume, airflow, light intensity, and temperature, input units of wearable devices such as smartwatches, input units of wearable devices such as wireless headphones, input units of touch panels, input units for adjusting ink levels in electronic pens, input units for adjusting light intensity and color in flashlights, input units for adjusting light intensity in luminous clothing, and input units for adjusting volume in musical instruments, etc.

[0052] The following embodiments are load sensors typically installed in devices as described above. Such load sensors are referred to as "electrostatic capacitive pressure-sensitive sensor elements," "capacitive pressure sensing sensor elements," "pressure-sensitive switching elements," etc. The following embodiments are one embodiment of the present invention, and the present invention is not limited to any of the following embodiments.

[0053] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. For convenience, the X, Y, and Z axes are labeled as mutually orthogonal in each figure. The Z-axis direction is the height direction of the load sensor 1.

[0054] <Implementation Method 1>

[0055] Figure 1 This is an exploded perspective view schematically showing the structure of load sensor 1.

[0056] The load sensor 1 includes a substrate 10, a first electrode 20, a dielectric 30, a second electrode 40, and a substrate 50. The substrate 10, the first electrode 20, the dielectric 30, the second electrode 40, and the substrate 50 have approximately the same square shape when viewed from above.

[0057] Substrates 10 and 50 are plate-shaped components with a specified thickness. The upper and lower surfaces of substrates 10 and 50 are parallel to the XY plane. Substrate 10 is a support member for mounting the first electrode 20, the dielectric 30, and the second electrode 40. Substrates 10 and 50 are made of, for example, at least one resin material selected from polyethylene terephthalate, polycarbonate, polyimide, etc.

[0058] The first electrode 20 has a base 20a, a plurality of first protrusions 21 and a plurality of second protrusions 22. The base 20a is a plate-shaped component, and the first protrusions 21 and second protrusions 22 are formed in such a way that they protrude upward from the upper surface (the surface on the negative side of the Z-axis) of the base 20a in the upward direction (negative direction of the Z-axis).

[0059] A plurality of first protrusions 21 and a plurality of second protrusions 22 are formed in a lattice-like arrangement on the upper surface of the base 20a. That is, the plurality of first protrusions 21 and the plurality of second protrusions 22 are arranged alternately on the upper surface of the base 20a in the Y-axis and X-axis directions. The distance between the first protrusions 21 and the second protrusions 22 in the Y-axis direction is fixed, and the distance between the first protrusions 21 and the second protrusions 22 in the X-axis direction is also fixed. Figure 1 In the example shown, a total of thirty-six first protrusions 21 and second protrusions 22, six in the X-axis direction and six in the Y-axis direction, are formed on the upper surface of the base 20a. In this embodiment, the first protrusions 21 and second protrusions 22 are arranged adjacent to each other in the X-axis and Y-axis directions.

[0060] In this embodiment, the cross-sectional areas of the first protrusion 21 and the second protrusion 22 decrease as they move towards the negative Z-axis direction. A surface 21a parallel to the XY plane is formed at the front end of the first protrusion 21, and a surface 22a parallel to the XY plane is formed at the front end of the second protrusion 22. The first protrusion 21 has a frustum shape obtained by cutting a predetermined conical shape at the position of surface 21a, and the second protrusion 22 has a frustum shape obtained by cutting a predetermined conical shape at the position of surface 22a. The conical shapes that form the basis of the first protrusion 21 and the second protrusion 22 are identical. Surface 21a is located closer to the negative Z-axis side than surface 22a; therefore, the first protrusion 21 is longer than the second protrusion 22 in the Z-axis direction.

[0061] The first protrusion 21 and the base 20a are made of the same first material and are integrally formed. The second protrusion 22 is made of a second material and is integrally formed with the base 20a. Figure 1 For clarity, the second protrusion 22 is shown using dots. The first material constituting the first protrusion 21 and the base 20a is composed of a non-conductive elastic material and a conductive filler mixed into the elastic material. In the first material, the conductive filler is dispersed within the elastic material. Thus, the first protrusion 21 and the base 20a possess both conductivity and elasticity. On the other hand, the second material constituting the second protrusion 22 is composed of a non-conductive elastic material.

[0062] The elastic materials used in the first and second materials are composed of resin and rubber materials. Examples of resin materials include styrene-based resins, silicone-based resins (such as polydimethylpolysiloxane (PDMS)), acrylic resins, rotaxane resins, and polyurethane resins. Examples of rubber materials include silicone rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, polyisobutylene, ethylene propylene rubber, chlorosulfonated polyethylene, acrylic rubber, fluororubber, epichlorohydrin rubber, polyurethane rubber, and natural rubber. In this embodiment, the elastic material is silicone rubber.

[0063] The conductive filler used in the first material is, for example, at least one material selected from Au (gold), Ag (silver), Cu (copper), C (carbon), ZnO (zinc oxide), In2O3 (indium oxide (III)) and SnO2 (tin oxide (IV)). In this embodiment, the conductive filler is C (carbon).

[0064] The base radius of the first protrusion 21 and the second protrusion 22 is, for example, 0.01 mm or more to 0.34 mm. The height of the first protrusion 21 and the second protrusion 22 is, for example, 0.05 mm or more and 0.15 mm or less. The distance between adjacent first protrusions 21 and second protrusions 22 in the X-axis direction and the Y-axis direction is, for example, 0.215 mm or more to 0.7 mm.

[0065] A detection circuit 2a (see reference) for the outside of the load sensor 1 is provided at the base 20a. Figure 8 The wire (not shown) is electrically connected to the base 20a.

[0066] The second electrode 40 is a plate-shaped component facing the first electrode 20, sandwiching the first protrusion 21 and the second protrusion 22. The second electrode 40 is made of a conductive metallic material. The material of the second electrode 40 is selected from, for example, In₂O₃, ZnO, and SnO₂. An external detection circuit 2a (see reference 1) is provided on the second electrode 40 for receiving the load sensor 1. Figure 8The wire (not shown) is electrically connected to the second electrode 40.

[0067] The dielectric 30 is disposed on the opposing surface 41 (the surface on the positive Z-axis side) of the second electrode 40. The opposing surface 41 is parallel to the XY plane, and the surface on the negative Z-axis side of the dielectric 30 is also parallel to the XY plane. The dielectric 30 is made of an electrically insulating material. The material of the dielectric 30 is selected, for example, from polypropylene resin, polyethylene terephthalate resin, polyimide resin, polyphenylene sulfide resin, Al2O3, and Ta2O5. The dielectric 30 is formed on the opposing surface 41 of the second electrode 40, for example, by insert molding.

[0068] During the assembly of the load sensor 1, the first electrode 20 is disposed on the upper surface of the substrate 10, and a structure consisting of a dielectric 30 and a second electrode 40 is superimposed on the upper surface of the first electrode 20 such that the dielectric 30 faces the first electrode 20. Then, the substrate 50 is covered on the second electrode 40, and the periphery of the substrate 50 is disposed on the substrate 10 by a mounting member. Thus, the load sensor 1 is completed.

[0069] Figure 2 (a) is a schematic cross-sectional view of load sensor 1 in an unloaded state (a state in which no load is applied). Figure 2 (b) is a schematic cross-sectional view of the load sensor 1 under load (the state in which a load has been applied). Figure 2 In (a) and (b), a cross-section of the load sensor 1 is shown when it is cut by a plane parallel to the YZ plane passing through the center of the first protrusion 21 and the second protrusion 22. Figure 2 In (a) and (b), for convenience, the number of the first protrusion 21 and the second protrusion 22 arranged in the Y-axis direction is five.

[0070] like Figure 2 As shown in (a), in the initial state without a load, only the front surface 21a of the first protrusion 21 is in contact with the dielectric 30. Subsequently, when a load is applied to the upper surface of the substrate 50, as... Figure 2 As shown in (b), the first protrusion 21 contracts as the load increases. As a result, the contact area between the first protrusion 21 and the dielectric 30 increases, and the distance between the dielectric 30 and the base 20a decreases.

[0071] When the contact area between the first protrusion 21 and the dielectric 30, and the distance between the dielectric 30 and the base 20a, change with the load, the electrostatic capacitance between the second electrode 40 and the first electrode 20 also changes with the load. This electrostatic capacitance is proportional to the total contact area between the first electrode 20 and the dielectric 30, and inversely proportional to the thickness of the dielectric 30 and the distance between the dielectric 30 and the base 20a. Furthermore, through the external control circuit 2b (refer to...) Figure 8 The load is detected by measuring the potential that reflects the change in the electrostatic capacitance.

[0072] Furthermore, in load sensors, the load detection range is typically set within a range that allows the protrusion to deform reversibly. However, in cases such as when an object accidentally falls onto the load sensor, a high load may be applied to the protrusion, such that the compressive stress generated on the protrusion exceeds the yield stress. If the protrusion undergoes irreversible deformation, i.e., plastic deformation, due to such a high load, the load cannot be properly detected.

[0073] For example, such as Figure 3 As shown in (a), in the comparative example consisting only of first protrusions 21 of equal height, when a load exceeding the detection range is applied, the compressive stress generated in the first protrusions 21 is prone to exceed the yield stress, and the first protrusions 21 may undergo irreversible deformation (plastic deformation). Thus, if the first protrusions 21 undergo irreversible deformation, subsequent load detection cannot be properly performed.

[0074] In contrast, in this embodiment, when the magnitude of the applied load is within the detection range, such as Figure 2 As shown in (b), the elastic modulus of the first protrusion 21, the height and shape of the first protrusion 21 and the second protrusion 22, and the arrangement of the first protrusion 21 and the second protrusion 22 are set in such a way that the front end surface 22a of the second protrusion 22 does not contact the dielectric 30.

[0075] Moreover, such as Figure 3 As shown in (b), when the applied load exceeds the detection range, the second protrusion 22 comes into contact with the dielectric 30, and the load applied to the load sensor 1 is also distributed to the second protrusion 22. Thus, if the number of protrusions in contact with the dielectric 30 increases with the increase of the load, the compressive stress generated by the first protrusion 21 is mitigated, and the compressive stress generated by the first protrusion 21 is unlikely to exceed the yield stress. Therefore, even when an applied load is applied to the dielectric 30, the compressive stress is mitigated. Figure 3 Under the same load (a), the deformation of the first protrusion 21 is also limited to the range of reversible deformation, so that subsequent load testing can be carried out appropriately.

[0076] Reference Figure 4(a)~ Figure 5 (b) will be used to further explain in detail the deformation of the protrusion of the first electrode 20 in the comparative example and embodiment 1.

[0077] Figure 4 (a) and (b) are schematic top views illustrating the deformation of the first protrusion 21 involved in the comparative example. Figure 4 In (a) and (b), for convenience, the structure other than the first electrode 20 is omitted, and the area shown by the diagonal line shows the part where the first protrusion 21 contacts the dielectric 30.

[0078] In the comparative example, compared with embodiment 1, the second protrusion 22 is omitted, and all protrusions are composed of the first protrusion 21.

[0079] like Figure 4 As shown in (a), in the unloaded state, only the front surface 21a of the first protrusion 21 contacts the dielectric 30. If a load within the detection range is applied to the load sensor of the comparative example from the unloaded state, the contact area between the first protrusion 21 and the dielectric 30 is larger than the contact area in the unloaded state, but the deformation of the first protrusion 21 is limited to reversible deformation. In this case, if no load is applied, the first protrusion 21 can appropriately return to its original shape.

[0080] On the other hand, such as Figure 4 As shown in (b), if a load exceeding the detection range is applied to the load sensor of the comparative example from an unloaded state, the first protrusion 21 undergoes irreversible deformation (plastic deformation). In this case, even if no load is applied, the first protrusion 21 cannot properly return to its original shape.

[0081] Figure 5 (a) and (b) are schematic top views illustrating variations of the first protrusion 21 and the second protrusion 22 according to Embodiment 1. Figure 5 In (a) and (b), for convenience, the structure other than the first electrode 20 is omitted. The area shown by the diagonal lines indicates the part of the first protrusion 21 and the second protrusion 22 that are in contact with the dielectric 30.

[0082] In implementation method 1, with Figure 1 Similarly, the first protrusion 21 and the second protrusion 22 are arranged in an alternating adjacent manner.

[0083] like Figure 5As shown in (a), in the unloaded state, only the front surface 21a of the first protrusion 21 contacts the dielectric 30. If a load within the detection range is applied to the load sensor 1 from the unloaded state, the contact area between the first protrusion 21 and the dielectric 30 is larger than the contact area in the unloaded state, but the deformation of the first protrusion 21 is limited to reversible deformation. At this time, the second protrusion 22 does not contact the dielectric 30. In this case, if no load is applied, the first protrusion 21 can appropriately return to its original shape.

[0084] On the other hand, such as Figure 5 As shown in (b), if a load exceeding the detection range is applied to the load sensor 1 from an unloaded state, the second protrusion 22 comes into contact with the dielectric 30. At this time, the load applied to the load sensor 1 is supported not only by the first protrusion 21 but also by the second protrusion 22. Therefore, the compressive stress generated in each of the first protrusions 21 is easily less than the yield stress of the first protrusion 21, and the deformation of each of the first protrusions 21 is easily limited to reversible deformation. In this case, if no further load is applied, the first protrusions 21 can appropriately return to their original shape.

[0085] Furthermore, in Embodiment 1, to prevent load from being applied only to the first protrusion 21 regardless of where the object falls onto the upper surface of the substrate 50, a plurality of first protrusions 21 and a plurality of second protrusions 22 are arranged such that at least one first protrusion 21 is sandwiched between two second protrusions 22. Specifically, as Figure 5 As shown in (a) and (b), the first protrusion 21 and the second protrusion 22 are arranged in an alternating adjacent manner. At this time, the spacing between adjacent first protrusions 21 and second protrusions 22 is determined so that both the first protrusion 21 and the second protrusion 22 are included within the range of the load imparted by the falling object.

[0086] Figure 6 This is a diagram schematically illustrating the relationship between load and compressive stress in the comparative example and embodiment 1.

[0087] In the comparative examples, such as Figure 4 As shown in (a) and (b), all the protrusions are composed of the first protrusion 21. In embodiment 1, as... Figure 5 The first protrusion 21 and the second protrusion 22 are distributed as shown in (a) and (b). The horizontal axis represents the load applied to the upper surface of the substrate 50 of the load sensor. The vertical axis represents the value obtained by dividing the load applied to the load sensor by the contact area of ​​all the protrusions abutting the dielectric 30. That is, the vertical axis represents the average compressive stress generated by each protrusion in contact with the dielectric 30. In either the comparative example or embodiment 1, the first range is set as the load detection range.

[0088] In the comparative example, as shown by the thick dashed line, when the load exceeds the maximum value R1 of the first range and reaches L1, the compressive stress generated in each of the first protrusions 21 reaches the yield stress of the first protrusion 21, and the first protrusion 21 undergoes irreversible deformation.

[0089] On the other hand, in Embodiment 1, as shown by the thick solid line, when the load exceeds the maximum value R1 of the first range and reaches L21, the second protrusion 22 comes into contact with the dielectric 30. Therefore, the load is distributed to the second protrusion 22, and within the subsequent load range, the increase in compressive stress generated in each of the first protrusions 21 becomes slow. Then, when the load reaches L22, the compressive stress generated in each of the first protrusions 21 reaches the yield stress of the first protrusion 21, and the first protrusion 21 undergoes irreversible deformation. At this time, L22 is larger than L1, and during the period before the load reaches L22, the compressive stress generated in the first protrusion 21 does not reach the yield stress of the first protrusion 21. Therefore, in Embodiment 1, compared to the comparative example, the load range within which the first protrusion 21 is limited to reversible deformation is wider.

[0090] Figure 7 (a) is a graph schematically showing the relationship between load and electrostatic capacitance in the comparative example and embodiment 1.

[0091] The horizontal axis represents the load applied to the upper surface of the substrate 50 of the load sensor. The vertical axis represents the electrostatic capacitance between the first electrode 20 and the second electrode 40. In both the comparative example and Embodiment 1, within the first range that serves as the detection range, the electrostatic capacitance increases with the increase of the load, and therefore can be controlled by the control circuit 2b (refer to...) connected to the subsequent stage of the load sensor. Figure 8 Load is detected based on electrostatic capacitance.

[0092] However, in the comparative example, if an irreversible deformation occurs due to an unexpectedly large load (e.g., loads of L1 to L22), the electrostatic capacitance will not change appropriately within the first range afterward, making it impossible to properly detect the load. On the other hand, in Embodiment 1, even if a load of the same magnitude is applied, irreversible deformation is unlikely to occur, and the electrostatic capacitance changes appropriately within the first range afterward, thus enabling proper load detection.

[0093] Furthermore, in Embodiment 1, the first protrusion 21 does not undergo irreversible deformation before the load reaches L22. Therefore, not only can the first range be set as the load detection range, but also a second range with a load value larger than the first range can be set as the load detection range. However, in Figure 1 In Embodiment 1 shown, the second material constituting the second protrusion 22 is made of a non-conductive resin material, therefore the change in electrostatic capacitance is as follows: Figure 7As shown in (a), the change slows down in the second range. In this case, it is difficult to obtain the change in electrostatic capacitance (resolution) corresponding to the load in the second range, thus making it difficult to detect the load with high precision. Therefore, when the detection range includes the second range, similar to the first material of the first protrusion 21, the second material is composed of a non-conductive resin material and a conductive filler mixed into the resin material. As a result, the second protrusion 22 is conductive, therefore, as shown in (a), the change in electrostatic capacitance (resolution) becomes slow in the second range. Figure 7 As shown in (b), the electrostatic capacitance also varies with the load in the second range.

[0094] Figure 7 (b) is a graph schematically showing the relationship between load and electrostatic capacitance in Embodiment 1 when the second protrusion 22 is conductive.

[0095] In this case, as shown by the thick solid line, when the load applied to the load sensor 1 reaches L21, the second protrusion 22 contacts the dielectric 30, thereby causing the electrostatic capacitance to temporarily increase, and then slowly increase thereafter. Thus, while the second protrusion 22 is conductive, although the electrostatic capacitance does not change linearly with respect to the load in the second range, it increases with the increase of the load. Therefore, the first and second ranges can be set as the detection range, which can be controlled by the control circuit 2b (refer to...). Figure 8 Load is detected based on electrostatic capacitance.

[0096] Figure 8 This is a block diagram showing the structure of the load detection device 2.

[0097] The load detection device 2 includes the load sensor 1, detection circuit 2a and control circuit 2b described above.

[0098] The detection circuit 2a detects the electrostatic capacitance between the first electrode 20 and the second electrode 40 based on the voltage change when a DC voltage is applied between them. The detection circuit 2a outputs a signal corresponding to the electrostatic capacitance between the first electrode 20 and the second electrode 40 to the control circuit 2b. The control circuit 2b includes a CPU and other arithmetic processing circuits and a memory, and controls each part according to a predetermined program. Furthermore, the control circuit 2b detects the load applied to the load sensor 1 based on the detection result of the detection circuit 2a, and sends the load detection result to an external device (e.g., a personal computer).

[0099] Control circuit 2b pre-stores the load detection range in its memory. When the detected load is within the detection range, control circuit 2b sends the detected load as a valid load to an external device. For example, in the case of an electrostatic capacitor... Figure 7When the load changes as shown in (a), the control circuit 2b stores the first range as a detection range in its memory, and when the detected load is within the first range, it sends the detected load to an external device. On the other hand, when the electrostatic capacitance is as shown in (a), the control circuit 2b stores the first range as a detection range in its memory, and when the detected load is within the first range, it sends the detected load to an external device. Figure 7 When the load changes as shown in (b), the control circuit 2b stores the first range and the second range as detection ranges in the memory, and sends the detected load to an external device when the detected load is within the first range and the second range.

[0100] Furthermore, even in electrostatic capacitors such as Figure 7 If the load changes as shown in (b), the control circuit 2b can also store the first range as the detection range in the memory, and send the detected load to an external device when the detected load is within the first range.

[0101] <Study on the height and hardness of the first and second protrusions>

[0102] The inventors verified through simulation that, in such cases... Figure 9 (a)~ Figure 11 As shown in (b), compressive stress and electrostatic capacitance change with load in various structures where the height and stiffness of the protrusion are altered.

[0103] Figure 9 (a) is a perspective view schematically showing the structure of the first electrode 20 involved in the comparative example.

[0104] Figure 9 The structure shown in (a) illustrates a portion of the first electrode 20, which is repeatedly formed in the X-axis and Y-axis directions. Figure 1 Similarly, a substrate 10, a dielectric 30, a second electrode 40, and a substrate 50 are disposed above and below the first electrode 20.

[0105] In the comparative example, with Figure 1 Compared to the structure shown, the second protrusion 22 is omitted. The radius R of the bottom surface of the first protrusion 21 is 0.34 mm. The distance P between two adjacent first protrusions 21 in the X-axis and Y-axis directions is 0.7 mm. The height H1 of the first protrusion 21 is 0.15 mm. The hardness of the first protrusion 21 is 40 degrees. The first protrusion 21 and the base 20a are conductive and elastic.

[0106] Figure 9 (b) is a perspective view schematically showing the structure of the first electrode 20 involved in the structure 1 of embodiment 1.

[0107] In structure 1, with Figure 1The structure shown also includes a second protrusion 22 that is lower than the first protrusion 21. The radius R of the bottom surface of both the first protrusion 21 and the second protrusion 22 is 0.34 mm. The distance P between adjacent first protrusions 21 and second protrusions 22 in both the X-axis and Y-axis directions is 0.7 mm. The height H of the first protrusion 21 is 0.15 mm, and the height H2 of the second protrusion 22 is 0.05 mm. The hardness of both the first protrusion 21 and the second protrusion 22 is 40 degrees. The first protrusion 21 and the base 20a are conductive and elastic, while the second protrusion 22 is non-conductive and elastic.

[0108] Figure 10 (a) is a perspective view schematically showing the structure of the first electrode 20 involved in the structure 2 of embodiment 1.

[0109] In structure 2, the height H2 of the second protrusion 22 is 0.1 mm compared to structure 1. The other structural features and dimensions of structure 2 are the same as those of structure 1.

[0110] Figure 10 (b) is a perspective view schematically showing the structure of the first electrode 20 involved in the structure 3 of embodiment 1.

[0111] In structure 3, compared to structure 2, one of the second protrusions 22 is replaced by a third protrusion 23 that is lower than the second protrusion 22. A surface 23a parallel to the XY plane is formed at the front end of the third protrusion 23. The height H2 of the second protrusion 22 is 0.12 mm. The height H3 of the third protrusion 23 is 0.1 mm, and the radius R of the bottom surface of the third protrusion 23 is 0.34 mm. The third protrusion 23, like the second protrusion 22, is made of a non-conductive elastic material and is integrally formed with the base 20a. The other structures and dimensions of structure 3 are the same as those of structure 2.

[0112] Figure 11 (a) is a perspective view schematically showing the structure of the first electrode 20 involved in the structure 4 of embodiment 1.

[0113] In structure 4, the second protrusion 22 has a hardness of 50 degrees compared to structure 2. The other structural features and dimensions of structure 4 are the same as those of structure 2.

[0114] Figure 11 (b) is a perspective view schematically showing the structure of the first electrode 20 involved in the structure 5 of embodiment 1.

[0115] In structure 5, the second protrusion 22 has a hardness of 30 degrees compared to structure 2. The other structural features and dimensions of structure 5 are the same as those of structure 2.

[0116] Figure 12(a) and (b) are graphs showing the simulation results of structures 1 and 2 of the comparative example and embodiment 1.

[0117] Figure 12 (a) shows the relationship between load and compressive stress before the first protrusion 21 undergoes plastic deformation. Figure 12 In (a), the horizontal axis represents the load (N) applied to the load sensor. (Compared to...) Figure 6 Similarly, the vertical axis represents the average compressive stress (MPa) generated by each protrusion.

[0118] In the comparative example, as shown by the dashed line, the first protrusion 21 undergoes plastic deformation when the load rises to approximately 20 N. In structure 1, as shown by the solid line, when the load rises to approximately L31 and the second protrusion 22 contacts the dielectric 30, the first protrusion 21 undergoes plastic deformation again when the load rises to approximately 20 N, similar to the comparative example. In structure 2, as shown by the thick solid line, when the load rises to approximately L32 and the second protrusion 22 contacts the dielectric 30, the compressive stress rises slowly compared to the comparative example and structure 1, and the first protrusion 21 undergoes plastic deformation when the load rises to approximately 32 N.

[0119] According to structure 2, the load is supported by the second protrusion 22 before the first protrusion 21 is significantly compressed. Therefore, in structure 2, compared with the comparative example, the increase in compressive stress at the first protrusion 21 is smoothly mitigated by the second protrusion 22, and the first protrusion 21 is less prone to plastic deformation. As a result, the load-bearing capacity of the load sensor 1 can be improved.

[0120] In contrast, in structure 1, the load causing plastic deformation of the first protrusion 21 is approximately the same as in the comparative example. This is believed to be because, due to the excessive height of the second protrusion 22, the load applied to the first protrusion 21 cannot be smoothly distributed within the load range after the second protrusion 22 comes into contact with the dielectric 30. Therefore, it is understood that to achieve sufficient load-bearing capacity, it is necessary to adjust the ratio of the height of the second protrusion 22 to the height of the first protrusion 21, etc.

[0121] Figure 12 (b) shows the relationship between load and electrostatic capacitance before the first protrusion 21 undergoes plastic deformation. Figure 12 In (b), the horizontal axis represents the load (N / cm) applied to the load sensor. 2 The vertical axis represents the electrostatic capacitance between the first electrode 20 and the second electrode 40.

[0122] like Figure 12As shown in (b), in structure 2, compared with the comparative example and structure 1, the rise of electrostatic capacitance is slow. Therefore, although the sensitivity of load sensor 1 is slightly reduced, the protrusion is difficult to undergo plastic deformation, thus enabling the detection of a wide range of loads.

[0123] Figure 13 (a) and (b) are graphs showing the simulation results of structures 2 and 3 of the comparative example and embodiment 1. Figure 13 (a) and (b) are respectively with Figure 12 The same charts as (a) and (b).

[0124] like Figure 13 As shown in (a), in structure 3, as indicated by the thick solid line, when the load rises to near L41 and the second protrusion 22 contacts the dielectric 30, the compressive stress changes slowly compared to structure 2. Furthermore, after the load rises to near L42 and the third protrusion 23 contacts the dielectric 30, the compressive stress also changes slowly compared to structure 2. When the load rises to near 36 N, the first protrusion 21 undergoes plastic deformation.

[0125] According to structure 3, the load is supported by the third protrusion 23 together with the second protrusion 22, thus the first protrusion 21 is less prone to plastic deformation compared to structure 2. Therefore, the load-bearing capacity of the load sensor 1 can be improved compared to structure 2. In structure 3, the height of the lower third protrusion 23 is 0.1 mm, therefore it is believed that the third protrusion 23, together with the second protrusion 22, can help alleviate the compressive stress at the first protrusion 21.

[0126] like Figure 13 As shown in (b), in structure 3, as indicated by the thick solid line, the rise of electrostatic capacitance is slower compared to structure 2. Therefore, although the sensitivity of load sensor 1 is slightly reduced, the protrusion is difficult to undergo plastic deformation, thus enabling the detection of a wide range of loads.

[0127] Figure 14 (a) and (b) are graphs showing the simulation results of structures 4 and 5 of the comparative example and embodiment 1. Figure 14 (a) and (b) are respectively with Figure 12 The same charts as (a) and (b).

[0128] like Figure 14As shown in (a), in structure 4, as indicated by the thick solid line, when the load rises to around L51 and the second protrusion 22 contacts the dielectric 30, the compressive stress increases slowly compared to the comparative example. When the load rises to around 34 N, the first protrusion 21 undergoes plastic deformation. According to structure 4, since the hardness of the second protrusion 22 is higher than that of the first protrusion 21, the load is supported more reliably by utilizing the second protrusion 22. Therefore, compared to structure 2 described above, where the hardness of the first protrusion 21 and the second protrusion 22 are equal, the load-bearing capacity of the load sensor 1 can be improved.

[0129] On the other hand, in structure 5, as shown by the dashed line, after the load rises to near L51 and the second protrusion 22 comes into contact with the dielectric 30, when the load rises to near 14N, the second protrusion 22 undergoes plastic deformation earlier than the first protrusion 21. Figure 14 In structure 5 of (a), a diagram is shown before the second protrusion 22 undergoes plastic deformation.

[0130] In this case, when the load is released after the second protrusion 22 has undergone plastic deformation, the second protrusion 22 is in a state of minimal plastic deformation. Therefore, when a load is subsequently applied, the compressive stress is similar to... Figure 12 The compressive stress of structure 1 in the case of the lower second protrusion 22 shown in (a) changes approximately the same. Therefore, in this case, the range of loads before the first protrusion 21 undergoes plastic deformation is considered to be the same as that in the comparative example, similar to structure 1.

[0131] Thus, according to structure 5, since the hardness of the second protrusion 22 is lower than that of the first protrusion 21, the second protrusion 22 undergoes plastic deformation earlier than the first protrusion 21, resulting in a lower load-bearing capacity, similar to structure 1. Therefore, it can be said that it is preferable for the hardness of the second protrusion 22 to be higher than that of the first protrusion 21.

[0132] like Figure 14 As shown in (b), in structure 4, as indicated by the thick solid line, the rise of electrostatic capacitance is slower compared to the comparative example and structure 5. Therefore, although the sensitivity of load sensor 1 is slightly reduced, the protrusion is difficult to undergo plastic deformation, thus enabling the detection of a wide range of loads.

[0133] Furthermore, according to structure 4, it can be seen that by increasing the hardness of the second protrusion 22, the load-bearing capacity of the load sensor 1 can be set to a higher level. Therefore, in Figure 12 In structure 1 shown in (a), by making the hardness of the second protrusion 22 higher than that of the first protrusion 21, high load-bearing capacity can be expected even when the height of the second protrusion 22 is low, as in structure 1.

[0134] <Effects of Implementation Method 1>

[0135] According to implementation method 1, the following effects are achieved.

[0136] like Figure 1 As shown, the first electrode 20 has a first protrusion 21 and a second protrusion 22 (multiple protrusions) on the same surface, wherein the first protrusion 21 and the second protrusion 22 are elastic and conductive protrusions. The second electrode 40 faces the first electrode 20 in a manner that sandwiches the first protrusion 21 and the second protrusion 22 (multiple protrusions). A dielectric 30 is disposed on the facing surface 41 of the second electrode 40. Figure 5 As shown in (a) and (b), the number of the first protrusion 21 and the second protrusion 22 (protrusions) in contact with the dielectric 30 increases with the increase of the load.

[0137] According to this structure, since the number of protrusions in contact with the dielectric 30 increases with the increase of the load, even if a large load is accidentally applied to the load sensor 1, the stress generated in each of the multiple protrusions is mitigated. Therefore, the stress generated in each protrusion is unlikely to exceed the yield stress, and plastic deformation of each protrusion can be suppressed.

[0138] like Figure 1 As shown, the first electrode 20 has multiple protrusions, including multiple first protrusions 21 and multiple second protrusions 22. Figure 2 As shown in (a), in the unloaded state, the surfaces 21a (front ends) of the plurality of first protrusions 21 are in contact with the dielectric 30, and the surfaces 22a (front ends) of the plurality of second protrusions 22 are separated from the dielectric 30.

[0139] According to this structure, such as Figure 5 As shown in (b), due to the increase of load, the state changes from a state in which multiple first protrusions 21 are in contact with the dielectric 30 to a state in which multiple second protrusions 22 are also in contact with the dielectric 30. Thus, the number of protrusions in contact with the dielectric 30 can be increased with the increase of load.

[0140] like Figure 2 As shown in (a), dielectric 30 is formed on the planar opposing surface 41 of the second electrode 40. A plurality of first protrusions 21 and a plurality of second protrusions 22 protrude from the upper surface (same reference plane) of the base 20a on the first electrode 20. The height of the plurality of second protrusions 22 is lower than the height of the plurality of first protrusions 21.

[0141] According to this structure, the number of protrusions in contact with the dielectric 30 can be increased with the increase of load using a simple structure.

[0142] like Figure 1As shown, a plurality of first protrusions 21 and a plurality of second protrusions 22 are arranged such that at least one first protrusion 21 is sandwiched between two second protrusions 22.

[0143] According to this structure, since there are second protrusions 22 on both sides of at least one first protrusion 21, the second electrode 40 and the dielectric 30 can be well supported in a balanced manner by the first protrusions 21 and the second protrusions 22 when the dielectric 30 is in contact with the second protrusions 22 due to increased load. Therefore, it is possible to suppress the generation of off-center loads and improve the load detection accuracy.

[0144] In addition, such as Figure 1 As shown, if the first protrusion 21 and the second protrusion 22 are alternately arranged on the first electrode 20, the load applied to the load sensor 1 can be further balanced and well supported by the first protrusion 21 and the second protrusion 22.

[0145] exist Figure 11 In structure 4 shown in (a), the hardness of the second protrusion 22 is higher than that of the first protrusion 21. In other words, the elastic modulus of the second protrusion 22 is higher than that of the first protrusion 21.

[0146] According to this structure, such as Figure 14 As shown in (a), the load-bearing capacity of the load sensor 1 can be improved by using the second protrusion 22 to further reliably support the load.

[0147] like Figure 2 As shown in (a), the cross-sectional areas of the plurality of first protrusions 21 and the plurality of second protrusions 22 decrease as they approach surfaces 21a and 22a (front ends). The contact area between the dielectric 30 and the first protrusion 21 under no-load conditions is smaller than the contact area between the dielectric 30 and the second protrusion 22 when they begin to contact each other.

[0148] According to this structure, the first protrusion 21, which initially contacts the dielectric 30, has a smaller contact area. Therefore, the change in contact area corresponding to the increase of load increases, and the rise in electrostatic capacitance becomes faster. This improves the sensitivity of the load sensor 1 when a load is initially applied. Furthermore, the second protrusion 22, which subsequently contacts the dielectric 30, has a larger contact area. Therefore, even when a large load is applied rapidly, the second protrusion 22 can absorb the applied load and suppress plastic deformation of the protrusion.

[0149] A surface 21a (first plane) is formed at the front end of a plurality of first protrusions 21, and a surface 22a (second plane) is formed at the front end of a plurality of second protrusions 22. The area of ​​surface 21a (first plane) is smaller than the area of ​​surface 22a (second plane).

[0150] According to this structure, when the initial load is applied, the contact area between the dielectric 30 and the first protrusion 21 increases slowly, thus further improving the linearity of the sensitivity characteristics.

[0151] like Figure 5 As shown in (b), by applying a load smaller than the range of the load that produces the yield stress in the first protrusion 21 ( Figure 6 The load L1), the second protrusion 22 is in contact with the dielectric 30.

[0152] According to this structure, it is difficult to generate yield stress in the first protrusion 21, and the plastic deformation of the first protrusion 21 can be appropriately suppressed.

[0153] exist Figure 10 In the structure 3 shown in (b), the first electrode 20 has a plurality of protrusions, which also include a plurality of third protrusions 23. In the unloaded state, the surfaces 23a (front ends) of the plurality of third protrusions 23 are further separated from the dielectric 30 compared to the surfaces 22a (front ends) of the plurality of second protrusions 22.

[0154] According to this structure, due to the increase in load, the state changes from a state in which multiple first protrusions 21 and second protrusions 22 are in contact with the dielectric 30 to a state in which multiple third protrusions 23 are also in contact with the dielectric 30. Thus, as... Figure 13 As shown in Figure (a), the number of protrusions in contact with dielectric 30 can be increased with the increase of load, thereby further suppressing plastic deformation of each protrusion.

[0155] like Figure 2 As shown in (a), the cross-sectional area of ​​the first protrusion 21 and the second protrusion 22 (multiple protrusions) decreases as they approach the surfaces 21a and 22a (front end).

[0156] According to this structure, the contact area between the first protrusion 21 and the dielectric 30 increases with the increase of load. This improves the linearity of the sensitivity characteristics.

[0157] like Figure 8 As shown, the load detection device 2 includes a control circuit 2b (control unit) that detects the load based on the electrostatic capacitance between the first electrode 20 and the second electrode 40.

[0158] According to this structure, plastic deformation of each protrusion is suppressed in the load sensor 1. Therefore, even after a large load is accidentally applied to the load sensor 1, the control circuit 2b can continue to detect the load appropriately.

[0159] like Figure 7As shown in (b), the control circuit 2b (control unit) detects a load based on electrostatic capacitance within a first range below a second range, which is the range that reduces the sensitivity characteristics of the load sensor 1.

[0160] According to this structure, since the load is detected within a range of high sensitivity characteristics (first range), the reliability of the load detected by the load detection device 2 can be improved.

[0161] <Examples of changes in the shape of the protrusion>

[0162] In a no-load state, the structure for contacting the tip of the first protrusion 21 with the dielectric 30 and separating the tip of the second protrusion 22 from the dielectric 30 is not limited to... Figure 2 The structure of embodiment 1 shown in (a) can also be, for example, Figure 15 (a)~ Figure 16 The structure shown in (b).

[0163] exist Figure 15 In the example shown in (a), compared to Embodiment 1, the height (length in the Z-axis direction) of the first protrusion 21 is equal to the height (length in the Z-axis direction) of the second protrusion 22. Furthermore, the placement position of the second protrusion 22 in the first electrode 20 (the placement position of the second protrusion 22 on the base 20a) is separated from the dielectric 30 compared to the placement position of the first protrusion 21 in the first electrode 20 (the placement position on the base 20a). That is, the distance d2 between the lower surface of the dielectric 30 and the placement position of the second protrusion 22 is longer than the distance d1 between the lower surface of the dielectric 30 and the placement position of the first protrusion 21. Therefore, similar to Embodiment 1, the number of protrusions in contact with the dielectric 30 can increase with increasing load.

[0164] exist Figure 15 In the example shown in (b), compared to Embodiment 1, the front ends of the first protrusion 21 and the second protrusion 22 are located at the same position in the height direction (Z-axis direction). Specifically, the height (length in the Z-axis direction) of the first protrusion 21 is equal to the height (length in the Z-axis direction) of the second protrusion 22. Furthermore, the portion of the dielectric 30 located above the second protrusion 22 is positioned above the portion of the dielectric 30 located above the first protrusion 21 (negative Z-axis direction). In this case, the distance d2 between the lower surface of the dielectric 30 and the placement position of the second protrusion 22 is also longer than the distance d1 between the lower surface of the dielectric 30 and the placement position of the first protrusion 21. Therefore, similar to Embodiment 1, the number of protrusions in contact with the dielectric 30 can increase with increasing load.

[0165] exist Figure 16In the example shown in (a), compared to Embodiment 1, the first protrusion 21 and the second protrusion 22 are similar in shape to each other, with the first protrusion 21 being larger than the second protrusion 22. In this case, the area of ​​the front end face 21a of the first protrusion 21 is larger than the area of ​​the front end face 22a of the second protrusion 22. Furthermore, when the load is initially applied, from the viewpoint of improving the linearity of the sensitivity characteristics by slowly increasing the contact area between the dielectric 30 and the first protrusion 21, it is preferable that the area of ​​face 21a is smaller than the area of ​​face 22a, as described in Embodiment 1 above.

[0166] exist Figure 16 In the example shown in (b), compared to embodiment 1, the shapes of the first protrusion 21 and the second protrusion 22 are obtained by cutting off the upper ends of hemispherical shapes of the same shape and size with a plane parallel to the XY plane. In this case, under no-load conditions, the front end face 21a of the first protrusion 21 is also in contact with the dielectric 30, and the front end face 22a of the second protrusion 22 is also separated from the dielectric 30. If the first protrusion 21 and the second protrusion 22 have hemispherical shapes, the contact area between the first protrusion 21 and the second protrusion 22 and the dielectric 30 increases smoothly with the increase of load. Therefore, the linearity of the sensitivity characteristics can be improved.

[0167] Furthermore, the first protrusion 21 and the second protrusion 22 can also be conical, pyramidal, or frustum-shaped. Additionally, if the second protrusion 22 is non-conductive, it can also be a columnar shape with a fixed cross-sectional area towards the top.

[0168] <Example of configuration change for protrusion>

[0169] The configuration of the first protrusion 21 and the second protrusion 22 in the first electrode 20 is not limited to... Figure 1 The configuration shown in Implementation 1 can also be, for example, as follows: Figure 17 (a)~ Figure 18 As shown in (b), the first protrusion 21 is sandwiched between two second protrusions 22. In the figures, the second protrusions 22 are shown in half dots for convenience.

[0170] exist Figure 17 In the example shown in (a), the columns of first protrusions 21 arranged in the X-axis direction and the columns of second protrusions 22 arranged in the X-axis direction are alternately arranged in the Y-axis direction. In this case, even if a large load is accidentally applied to the load sensor 1, plastic deformation of the individual protrusions can be suppressed. Furthermore, in cases such as Figure 17When the first protrusion 21 and the second protrusion 22 are arranged in a row as shown in (a), it is preferable to arrange the row of the second protrusion 22 on the outer edge of the first electrode 20. As a result, the load applied to the vicinity of the outer edge of the first electrode 20 is easily supported by the second protrusion 22.

[0171] exist Figure 17 In the example shown in (b), with Figure 17 Compared to the structure in (a), a plurality of columns of first protrusions 21 are arranged between the columns of second protrusions 22. In this case, compared with Figure 17 Compared to the structure in (a), more first protrusions 21 are configured, thus improving the sensitivity of the load sensor 1 even though the load is more difficult to support by the second protrusions 22. Alternatively, multiple rows of second protrusions 22 can be configured adjacent to each other, similar to the first protrusions 21.

[0172] exist Figure 18 In the example shown in (a), the first protrusion 21 and the second protrusion 22 are arranged concentrically with respect to the center of the first electrode 20. In this case, the large load applied to the center of the load sensor 1 is easily supported uniformly by the second protrusion 22, thus suppressing plastic deformation of each protrusion.

[0173] exist Figure 18 In the example shown in (b), the second protrusion 22 is arranged radially relative to the center of the first electrode 20. In this case, the large load applied to the center of the load sensor 1 is also easily supported uniformly by the second protrusion 22, thus suppressing plastic deformation of each protrusion.

[0174] <The formation process of the first electrode>

[0175] Figure 19 (a)~ Figure 21 (b) is a schematic diagram illustrating an example of the formation process of the first electrode 20. Figure 19 (a)~ Figure 21 (b) shows the cross-section when the parts are cut off by a plane perpendicular to the XY plane.

[0176] like Figure 19 As shown in (a), the formation of the first electrode 20 utilizes a material injection section 110, a material guiding section 120, a mask 130, and a protrusion forming section 140. In the protrusion forming section 140, multiple recesses 141 and 142 are formed corresponding to the positions of the first protrusion 21 and the second protrusion 22. In the mask 130, a through hole 131 is formed at a position corresponding to the position of the second protrusion 22.

[0177] like Figure 19As shown in (b), the mask template 130 is embedded in the protrusion forming portion 140, and the material injection portion 110 and the material guide portion 120 are provided on the upper surface of the mask template 130. In this state, the second material 152, which forms the basis of the second protrusion 22, is injected from the material injection portion 110. The second material 152 is filled into the recess 142 through the flow path 121 of the material guide portion 120 and the hole 131 of the mask template 130.

[0178] like Figure 20 As shown in (a), the material injection section 110, the material guide section 120, and the mask template 130 are separated from the protrusion forming section 140. As a result, the second protrusion 22 is formed.

[0179] like Figure 20 As shown in (b), a material guide section 160 is provided at the lower end of the material injection section 110 to replace the material guide section 120.

[0180] like Figure 21 As shown in (a), a material injection section 110 and a material guide section 160 are provided on the upper surface of the protrusion forming section 140. In this state, a first material 151, which serves as the base of the first protrusion 21 and the base 20a, is injected from the material injection section 110. The first material 151 is filled into the recess 141 via the flow path 161 of the material guide section 160, and is filled to the position corresponding to the base 20a.

[0181] like Figure 21 As shown in (b), the material injection section 110 and the material guiding section 160 separate from the protrusion forming section 140, and the first electrode 20 is taken out from the protrusion forming section 140. In this way, the first electrode 20 is completed.

[0182] Furthermore, the formation process of the first electrode 20 is not limited to... Figure 19 (a)~ Figure 21 The example shown in (b) could also be other formation processes.

[0183] in addition, Figure 19 (a)~ Figure 21 The formation process shown in (b) is the formation process when the first material 151 of the first protrusion 21 and the second material 152 of the second protrusion 22 are different materials. In contrast, when the first material 151 and the second material 152 are the same material, it is not necessary to form the first protrusion 21 and the second protrusion 22 separately. Therefore, the first protrusion 21 and the second protrusion 22 can also be formed simultaneously by filling all the recesses 141 and 142 with a single material.

[0184] <Implementation Method 2>

[0185] In Embodiment 1, the second protrusion 22 is formed on the upper surface (the negative Z-axis side) of the base 20a of the first electrode 20. In contrast, in Embodiment 2, the second protrusion 22 is formed on the base 20a such that it penetrates the base 20a along the Z-axis direction. In top view, the arrangement of the first protrusion 21 and the second protrusion 22 is the same as that in Embodiment 1.

[0186] Figure 22 (a) is a schematic cross-sectional view of the load sensor 1 in the unloaded state (the state in which no load is applied) according to Embodiment 2.

[0187] In implementation method 2, with Figure 2 Compared to Embodiment 1 shown in (a), the second protrusion 22 extends through the base 20a along the Z-axis direction and protrudes toward the second electrode 40 (towards the negative Z-axis direction). The lower surface of the second protrusion 22 (the surface on the positive Z-axis side) and the lower surface of the base 20a (the surface on the positive Z-axis side) are contained in the same plane.

[0188] In this case, in the initial state without a load, only the front surface 21a of the first protrusion 21 is in contact with the dielectric 30. Then, if the electrostatic capacitance between the second electrode 40 and the first electrode 20 changes with the load, the load is detected based on the potential reflecting the change in electrostatic capacitance.

[0189] Figure 22 (b) is a cross-sectional view schematically showing the deformation of the protrusion when subjected to a load beyond the detection range according to Embodiment 2.

[0190] In embodiment 2, even when the applied load exceeds the detection range, the second protrusion 22 also comes into contact with the dielectric 30, and the load applied to the load sensor 1 is distributed to the second protrusion 22. Therefore, even when a load exceeding the detection range is applied, the deformation of the first protrusion 21 is suppressed within the range of reversible deformation.

[0191] like Figure 22 As shown in (a) and (b), in Embodiment 2, since the second protrusion 22 penetrates the base 20a, the lower surface of the second protrusion 22 is supported by the upper surface of the substrate 10. Therefore, the indentation of the second protrusion 22 into the base 20a, as would occur if the second protrusion 22 were formed on the upper surface of the base 20a, is suppressed, and the load is easily supported by the second protrusion 22. Thus, plastic deformation of the first protrusion 21 can be further suppressed.

[0192] <Study on the height and hardness of the first and second protrusions>

[0193] The inventors also performed the same simulation as in Embodiment 1 in the structure of Embodiment 2.

[0194] The inventors set up two comparative examples in the simulation. One comparative example is compared with... Figure 9 The same structure as (a) has two first protrusions 21 formed on the first electrode 20 within a specified range. In another comparative example, such as Figure 23 As shown in (a), four first protrusions 21 are formed on the first electrode 20 within a specified range. Figure 23 The structure and dimensions of the comparative example (a) are the same as those of the first protrusion 21, except for the number of protrusions 21. Figure 9 The comparative example shown in (a) has the same structure and dimensions.

[0195] Figure 23 (b) is a perspective view schematically showing the structure of the first electrode 20 involved in the structure 6 of embodiment 2.

[0196] In structure 6, such as Figure 22 As shown in (a), the second protrusion 22 penetrates the base 20a and protrudes in the negative Z-axis direction. The lower surface of the second protrusion 22 and the lower surface of the base 20a are contained in the same plane. Furthermore, the hardness of the second protrusion 22 is 80 degrees. The structure and dimensions of structure 6, except for the position of the lower surface of the base 20a and the hardness of the second protrusion 22, are similar to those of structure 6. Figure 11 The structure and dimensions of structure 4 shown in (a) are the same.

[0197] 24(a) and (b) are shown Figure 9 The comparative example shown in (a) Figure 23 The comparative example shown in (a), and Figure 23 (b) is a graph showing the simulation results of structure 6 of embodiment 2.

[0198] like Figure 24 As shown in (a), in Figure 9 In the comparative example shown in (a) (two first protrusions 21), as indicated by the dashed lines, the first protrusions 21 undergo plastic deformation when the load increases to around 20 N. Figure 23 In the comparative example shown in (a) (four first protrusions 21), as indicated by the dashed line, the first protrusions 21 undergo plastic deformation when the load rises to around 39 N. In the comparative example with four first protrusions 21, compared to the comparative example with two first protrusions 21, the load applied to the load sensor 1 is distributed among each first protrusion 21, and is therefore considered to result in a larger load causing plastic deformation.

[0199] In contrast, in structure 6, as shown by the thick solid line, when the load rises to around L61 and the second protrusion 22 comes into contact with the dielectric 30, the compressive stress rises slowly compared to the comparative examples where there are two and four first protrusions 21. When the load rises to around 62N, the first protrusion 21 undergoes plastic deformation.

[0200] According to structure 6, the load is supported by the second protrusion 22 before the first protrusion 21 is significantly compressed. Therefore, in structure 6, compared to comparative examples where there are two or four first protrusions 21, the increase in compressive stress at the first protrusion 21 is considered to be smoothly mitigated by the second protrusion 22, making it difficult for the first protrusion 21 to undergo plastic deformation. Thus, even when the second protrusion 22 is formed in a manner that penetrates through the base 20a, the load-bearing capacity of the load sensor 1 can also be improved.

[0201] like Figure 24 As shown in (b), in structure 6, as indicated by the thick solid line, compared to the comparative examples where there are two and four first protrusions 21, the rise of electrostatic capacitance is slow. Therefore, although the sensitivity of load sensor 1 is slightly reduced, the protrusions are difficult to undergo plastic deformation, thus enabling the detection of a wide range of loads.

[0202] <Effects of Implementation Method 2>

[0203] According to implementation method 2, the following effects are achieved.

[0204] like Figure 22 As shown in (a) and (b), a first protrusion 21 protrudes from an elastic base 20a toward the second electrode 40, and a second protrusion 22 penetrates the base 20a and protrudes toward the second electrode 40. The lower surface of the second protrusion 22 and the lower surface of the base 20a are contained in the same plane.

[0205] According to this structure, since the second protrusion 22 is not supported by the elastic base 20a, the second protrusion 22 can efficiently bear the load when the dielectric 30 on the second electrode 40 side comes into contact with the second protrusion 22 due to the increase of load. As a result, plastic deformation of the first protrusion 21 caused by overload can be suppressed more reliably, and the load resistance of the load sensor 1 can be improved.

[0206] Furthermore, in the structure of Embodiment 1, the thickness of the region of the base 20a where the second protrusion 22 is disposed can be smaller than the thickness of other regions of the base 20a (regions where neither the first protrusion 21 nor the second protrusion 22 is disposed). That is, the second protrusion 22 can be formed in the recess formed on the upper surface of the base 20a, protruding toward the second electrode 40. As a result, when a load is applied to the second protrusion 22, the second protrusion 22 is less likely to sink into the base 20a, and the load can be easily supported by the second protrusion 22. Therefore, compared with the structure of Embodiment 1, plastic deformation of the first protrusion 21 caused by overload can be suppressed more reliably, and the load resistance of the load sensor 1 can be improved.

[0207] <Example of configuration change for protrusion>

[0208] In embodiments 1 and 2, the size and arrangement of the first protrusion 21 and the second protrusion 22 in the first electrode 20 are not limited to... Figure 1 The example shown can also be, for example, as Figure 25 As shown in (a) and (b).

[0209] exist Figure 25 In the examples shown in (a) and (b), when viewed from above, the second protrusion 22 is smaller than the first protrusion 21, and each of the second protrusions 22 is arranged in such a way that it is surrounded by a plurality of first protrusions 21.

[0210] More specifically, in the cross-sectional area of ​​the first protrusion 21 and the second protrusion 22 when cut by a plane including the upper surface of the base 20a, the second protrusion 22 is smaller than the first protrusion 21. Furthermore, each of the second protrusions 22 is surrounded by a plurality of first protrusions 21 in such a manner that these cut surfaces are brought close to each other.

[0211] exist Figure 25 In the examples shown in (a) and (b), multiple first protrusions 21 are respectively positioned at positions that are rotationally symmetric about a second protrusion 22. Figure 25 In the example shown in (a), the plurality of first protrusions 21 are arranged in a position that is rotationally symmetric three times. That is, three first protrusions 21 are arranged at 120° intervals along the circumference relative to a second protrusion 22. Figure 25 In the example shown in (b), the plurality of first protrusions 21 are arranged in a position that is rotationally symmetric four times. That is, four first protrusions 21 are arranged at 90° intervals along the circumference relative to a second protrusion 22. Figure 25 In (b), when the plurality of first protrusions 21 are arranged in a matrix with their proximity to each other, a second protrusion 22 is arranged such that it falls into the area surrounded by four adjacent first protrusions 21.

[0212] Thus, if, when viewed from above, the second protrusion 22 is smaller than the first protrusion 21 and each second protrusion 22 is surrounded by multiple first protrusions 21, then in a load sensor 1 with a fixed detection area, the second protrusions 22 can be efficiently arranged among multiple first protrusions 21 while suppressing the reduction in the number of first protrusions 21 caused by the arrangement of the second protrusions 22. Therefore, the detection sensitivity of the load sensor 1 based on multiple first protrusions 21 can be maintained, and the load applied to the load sensor 1 can be efficiently distributed to the first protrusions 21 and the second protrusions 22, suppressing plastic deformation of the first protrusions 21 due to overload.

[0213] Furthermore, when the second protrusion 22 is smaller than the first protrusion 21 when viewed from above, the load-bearing capacity of the second protrusion 22 also decreases; therefore, it is preferable to increase the hardness of the second protrusion 22. However, since the second protrusion 22 is conductive and included within the detection range... Figure 7 In the second range shown in (b), if the hardness of the second protrusion 22 is increased, the detection sensitivity in the second range decreases. Therefore, it is preferable to... Figure 7 The stiffness and top-view size of the second protrusion 22 are set in a manner that makes the support force and sensitivity of the second protrusion 22 exceed the desired values ​​within the second range shown in (b).

[0214] Furthermore, if the multiple first protrusions 21 are arranged in a position that is rotationally symmetrical about one of the second protrusions 22, the area of ​​the multiple first protrusions 21 and the multiple second protrusions 22 can be increased relative to the fixed detection surface of the load sensor 1. As a result, the multiple first protrusions 21 and the multiple second protrusions 22 can be arranged efficiently. In addition, since the multiple second protrusions 22 are regularly arranged around the first protrusions 21, the detection surface of the load sensor 1 can be uniformly supported by the multiple second protrusions 22.

[0215] Furthermore, from the viewpoint of increasing the number of first protrusions 21 relative to the fixed detection surface of load sensor 1 to improve detection sensitivity, it is preferable that the area of ​​the second protrusion 22 (the area of ​​the cut surface when the second protrusion 22 is cut by a plane including the upper surface of the base 20a) is smaller than the area of ​​the first protrusion 21 (the area of ​​the cut surface when the first protrusion 21 is cut by a plane including the upper surface of the base 20a). For example, the area of ​​the second protrusion 22 is set to be less than 1 / 2 of the area of ​​the first protrusion 21, more preferably less than 1 / 3 of the area of ​​the first protrusion 21.

[0216] Furthermore, if two adjacent first protrusions 21 are arranged close together to a degree that they will not hinder each other's deformation when subjected to load, and a second protrusion 22 with an area so small that it cannot hinder the deformation of the first protrusions 21 is arranged in a gap formed by a plurality of first protrusions 21, then the area of ​​the second protrusion 22 can be set to the minimum.

[0217] <The formation process of the first electrode>

[0218] Figure 26 (a)~ Figure 28 (b) is a schematic diagram illustrating an example of the formation process of the first electrode 20 involved in Embodiment 2. Figure 26 (a)~ Figure 28 (b) shows the cross-section when the parts are cut off by a plane perpendicular to the XY plane.

[0219] like Figure 26 As shown in (a), during the formation of the first electrode 20, with Figure 19 Compared to (a), a mask template 170 is also used. In the mask template 170, a through hole 171 is formed at a position corresponding to the configuration position of the second protrusion 22. The hole 171 is formed to match the shape of the end of the second protrusion 22 on the negative Z-axis side.

[0220] like Figure 26 As shown in (b), mask templates 130 and 170 are embedded in protrusion forming portion 140, and material injection portion 110 and material guide portion 120 are provided on the upper surface of mask template 130. In this state, second material 152, which forms the basis of second protrusion 22, is injected from material injection portion 110. Second material 152 is filled into recess 142 and hole 171.

[0221] like Figure 27 As shown in (a), the material injection section 110, the material guide section 120, and the mask 130 are separated from the mask 170 and the protrusion forming section 140. Then, the mask 170 is separated from the protrusion forming section 140, thereby... Figure 27 The second protrusion 22 is formed as shown in (b). Then, a material guide 160 is provided at the lower end of the material injection section 110 instead of the material guide 120.

[0222] like Figure 28 As shown in (a), a material injection section 110 and a material guide section 160 are provided on the upper surface of the protrusion forming section 140. In this state, a first material 151, which serves as the base of the first protrusion 21 and the base 20a, is injected from the material injection section 110. The first material 151 is filled into the recess 141 via the flow path 161 of the material guide section 160, and is filled to the position corresponding to the base 20a.

[0223] like Figure 28 As shown in (b), the material injection section 110 and the material guiding section 160 separate from the protrusion forming section 140, and the first electrode 20 is taken out from the protrusion forming section 140. In this way, the first electrode 20 is completed.

[0224] Furthermore, the formation process of the first electrode 20 in Embodiment 2 is not limited to... Figure 26 (a)~ Figure 28 The example shown in (b) could also be other formation processes.

[0225] <Implementation Method 3>

[0226] In Embodiment 2, the second protrusion 22 is formed on the first electrode 20. Conversely, in Embodiment 3, the second protrusion 61 is formed on the second electrode 40. In top view, the arrangement of the first protrusion 21 and the second protrusion 61 is the same as that in Embodiment 1.

[0227] Figure 29 (a) is a schematic cross-sectional view of the load sensor 1 in the unloaded state (the state in which no load is applied) according to Embodiment 3.

[0228] In implementation method 3, with Figure 2 Compared to Embodiment 1 shown in (a), only a first protrusion 21 is formed on the first electrode 20, while a plurality of second protrusions 61 are formed on the opposing surface (the surface on the positive side of the Z-axis) of the second electrode 40. A surface 61a parallel to the XY plane is formed at the front end of each second protrusion 61. The second protrusions 61 are made of a non-conductive elastic material. Furthermore, in Embodiment 3, a support portion 70 with a higher elastic modulus than the base 20a is provided in the region facing the front end of the second protrusions 61 at the base 20a. The support portion 70 is, for example, made of an insulating material.

[0229] In this case, in the initial state without a load, only the front surface 21a of the first protrusion 21 is in contact with the dielectric 30. Then, if the electrostatic capacitance between the second electrode 40 and the first electrode 20 changes with the load, the load is detected based on the potential reflecting the change in electrostatic capacitance.

[0230] Figure 29 (b) is a cross-sectional view schematically showing the deformation of the protrusion when subjected to a load beyond the detection range according to Embodiment 3.

[0231] In embodiment 3, when the applied load exceeds the detection range, the second protrusion 61 abuts against the support portion 70, and the load applied to the load sensor 1 is also distributed to the second protrusion 61. Therefore, even if a load exceeding the detection range is applied, the deformation of the first protrusion 21 is suppressed within the range of reversible deformation.

[0232] like Figure 29 As shown in (a) and (b), in Embodiment 3, depending on the applied load, the front end of the second protrusion 61 abuts against the support portion 70, whose elastic modulus is higher than that of the base 20a. When the second protrusion 61 abuts against the support portion 70 as the load increases, the front end of the second protrusion 61 is less likely to be excessively recessed relative to the base 20a, thus the load is stably supported by the second protrusion 61. Therefore, plastic deformation of the first protrusion 21 can be further suppressed.

[0233] <Effects of Implementation Method 3>

[0234] According to implementation method 3, the following effects are achieved.

[0235] like Figure 29 As shown in (a) and (b), the first electrode 20 has a plurality of first protrusions 21, which are elastic and conductive. The second electrode 40 faces the first electrode 20, sandwiching the plurality of first protrusions 21. A plurality of second protrusions 61 are disposed on the facing surface of the second electrode 40, protruding into the space where the first protrusions 21 are not present, and are elastic and insulating. A dielectric 30 is disposed on the facing surface 41 of the second electrode 40. In the unloaded state, the tips of the plurality of first protrusions 21 are in contact with the dielectric 30, and the tips of the plurality of second protrusions 61 are separated from the first electrode 20.

[0236] According to this structure, since the second protrusion 61 contacts the support portion 70 on the first electrode 20 side as the load increases, even if a large load is accidentally applied to the load sensor 1, the stress generated in each of the multiple first protrusions 21 is mitigated. Therefore, the stress generated in each first protrusion 21 is unlikely to exceed the yield stress, and plastic deformation of each first protrusion 21 can be suppressed. Furthermore, since the second protrusion 61 is disposed on a second electrode 40 different from the first electrode 20 on which the first protrusion 21 is disposed, it is easy to place the second protrusion 61 in the gaps between the first protrusions 21. Therefore, there is no need to reduce the number of first protrusions 21 to accommodate the second protrusion 61, thus maintaining the detection sensitivity of the load sensor 1.

[0237] The first protrusion 21 protrudes from the elastic base 20a, and a support portion 70 with a higher elastic modulus than the base 20a is disposed in the region facing the front end of the second protrusion 61.

[0238] Since the support portion 70 is harder than the base portion 20a, the second protrusion 61 can efficiently bear the load when it comes into contact with the support portion 70 as the load increases. This allows for more reliable suppression of plastic deformation of the first protrusion 21 caused by overload, thereby improving the load-bearing capacity of the load sensor 1.

[0239] In addition, Figure 29 In structures (a) and (b), the second protrusion 61 is formed on the lower surface (positive Z-axis side) of the second electrode 40. Alternatively, the second protrusion 61 may penetrate the second electrode 40, and the upper surface (negative Z-axis side) of the second protrusion 61 and the upper surface (negative Z-axis side) of the second electrode 40 may be contained in the same plane. Furthermore, the upper surface of the second protrusion 22 may be positioned between the upper and lower surfaces of the second electrode 40. That is, the second protrusion 61 protruding towards the first electrode 20 may also be formed in a recess formed on the lower surface of the second electrode 40.

[0240] In addition, the support portion 70 is not limited to being made of an insulating material, but may also be made of a conductive material.

[0241] <Examples of changes in the shape of the protrusion>

[0242] The structure of the protrusion provided on the side of the second electrode 40 is not limited to... Figure 29 The structure of embodiment 3 shown in (a) can also be, for example, Figure 30 The structures shown in (a) and (b) are as follows.

[0243] exist Figure 30 In the example shown in (a), compared to embodiment 3, a plurality of third protrusions 62 with a height lower than that of the second protrusion 61 are formed on the opposing surface (the surface on the positive side of the Z-axis) of the second electrode 40. A surface 62a parallel to the XY plane is formed at the front end of the third protrusion 62. The third protrusion 62, like the second protrusion 61, is made of a non-conductive elastic material. In top view, the second protrusion 61 and the third protrusion 62 are arranged, for example, alternately adjacent to each other on the opposing surface of the second electrode 40. A support portion 70 is also provided in the region of the base 20a facing the front end of the third protrusion 62.

[0244] In this case, in the initial state without any load, only the front surface 21a of the first protrusion 21 is in contact with the dielectric 30. Furthermore, as the load increases, the state changes from only the first protrusion 21 contacting the dielectric 30 to the second protrusion 61 also contacting the support portion 70, and then to the third protrusion 62 also contacting the support portion 70. Thus, with... Figure 10Similarly, the structure 3 shown in (b) can increase the number of protrusions that contact the first electrode 20 side and the second electrode 40 side as the load increases, and can further suppress plastic deformation of each protrusion.

[0245] exist Figure 30 In the example shown in (b), the support portion 70 is omitted compared to embodiment 3. In this case, the front end of the second protrusion 61 tends to recess towards the base 20a as the load increases, thus slightly reducing the supporting force of the second protrusion 61. Therefore, in order to more stably utilize the second protrusion 61 to support the load, it is preferable to arrange the support portion 70 at the abutment position of the second protrusion 61 as described in embodiment 3 above.

[0246] <Other Change Examples>

[0247] The structures of the load sensor 1 and the load detection device 2 can be modified in various ways, except for the structures shown in the above embodiments.

[0248] In embodiments 1 and 2 described above, surfaces 21a and 22a are formed at the front ends of the first protrusion 21 and the second protrusion 22, but the front ends of the first protrusion 21 and the second protrusion 22 may also be sharp. Similarly, in Figure 10 In structure 3 shown in (b), the front end of the third protrusion 23 can also be sharp. In embodiment 3 and Figure 30 In the modified examples shown in (a) and (b), the front end of the second protrusion 61 can also be sharp. Figure 30 In the modified example shown in (a), the front end of the third protrusion 62 can also be sharp.

[0249] In embodiments 1 and 2 described above, the first protrusion 21 may also be formed separately from the base 20a, similar to the second protrusion 22 in embodiments 1 and 2. In embodiment 1, the second protrusion 22 may also be integrally formed with the base 20a, similar to the first protrusion 21 in embodiment 1. Alternatively, in embodiment 1, the first electrode 20 may be formed by superimposing the first protrusion 21 and the second protrusion 22 onto a metal electrode and integrating them.

[0250] In embodiments 1 and 2 described above, the first electrode 20 has a plurality of first protrusions 21 and a plurality of second protrusions 22. However, the first protrusion 21 and the second protrusion 22 disposed on the first electrode 20 may also be a single protrusion. In embodiment 3 described above, the first electrode 20 has a plurality of first protrusions 21 and the second electrode 40 has a plurality of second protrusions 61. However, the first protrusion 21 and the second protrusion 61 disposed on the first electrode 20 may also be a single protrusion.

[0251] In embodiments 1 and 2 described above, the number of first protrusions 21 and the number of second protrusions 22 may also be different. To suppress plastic deformation of the first protrusions 21, it is more preferable that the number of second protrusions 22 is greater than the number of first protrusions 21. In embodiment 3 described above, the number of first protrusions 21 and the number of second protrusions 61 may also be different. To suppress plastic deformation of the first protrusions 21, it is more preferable that the number of second protrusions 61 is greater than the number of first protrusions 21.

[0252] In the above embodiments, the first protrusion 21 and the second protrusions 22 and 61 can also be elongated rib shapes in the X-axis or Y-axis directions. In this case, the rib shape can be either prism or semi-cylindrical.

[0253] In the above embodiment, the first protrusion 21 and the second protrusions 22 and 61 are arranged on the upper surface of the base 20a at a fixed spacing in the X-axis direction and the Y-axis direction, but the spacing between the first protrusion 21 and the second protrusions 22 and 61 may not be fixed.

[0254] In the above embodiments, the elastic material constituting the first protrusion 21 and the second protrusions 22 and 61 may also be a material other than silicone rubber. The elastic material constituting the first protrusion 21 and the elastic material constituting the second protrusions 22 and 61 may also be different materials.

[0255] In such Figure 10 Structure 3 shown in (b) and Figure 30 In the modified example shown in (a), where three protrusions are formed, the hardness of the three protrusions can also be different. For example, the hardness of the first protrusion 21 and the second protrusions 22 and 61 can be set to 40 degrees, and the hardness of the third protrusions 23 and 62 can be set to 50 degrees. In this way, if the hardness of the lower protrusions is set to be greater than that of the higher protrusions, it is expected that the effect of suppressing plastic deformation of the protrusions can be further improved.

[0256] and Figure 15 Similarly, in embodiment 2, the heights of the first protrusion 21 and the second protrusion 22 can be set to be equal by deforming the shape of the base 20a and the second electrode 40. In embodiment 3, the heights of the first protrusion 21 and the second protrusion 61 can also be set to be equal by deforming the shape of the base 20a and the second electrode 40.

[0257] and Figure 16Similarly, in embodiment 2, the first protrusion 21 and the second protrusion 22 may have similar shapes, with the first protrusion 21 being larger than the second protrusion 22. Similarly, in embodiment 3, the first protrusion 21 and the second protrusion 61 may have similar shapes, with the first protrusion 21 being larger than the second protrusion 61. Figure 16 (b) Similarly, in embodiment 2, the shapes of the first protrusion 21 and the second protrusion 22 can be set based on the hemispherical shape, and in embodiment 3, the shapes of the first protrusion 21 and the second protrusion 61 can also be set based on the hemispherical shape.

[0258] In addition, in embodiments 2 and 3, the first protrusion 21 and the second protrusions 22 and 61 can also be conical, pyramidal, or frustum-shaped. Furthermore, if the second protrusions 22 and 61 are non-conductive, they can also be cylindrical with a fixed cross-sectional area towards the top.

[0259] exist Figure 25 In the modified examples of the protrusion configuration shown in (a) and (b), the value of n, which represents the number of rotational symmetries, is not limited to 3 or 4 as mentioned above, but can also be 5 or more.

[0260] and Figure 17 (a)~ Figure 18 Similarly, in embodiment 2, the top view configuration of the first protrusion 21 and the second protrusion 22 can also be set, and in embodiment 3, the top view configuration of the first protrusion 21 and the second protrusion 61 can also be set.

[0261] A load sensor system can also be constructed by arranging multiple load sensors according to the above embodiments in a planar direction. In this case, when a load is applied across the upper surface of the substrate 50 of the multiple load sensors 1, the control circuit 2b (refer to...) Figure 8 The loads calculated by the multiple load sensors 1 are added together to detect the load applied to the upper surface of the multiple load sensors 1.

[0262] Furthermore, various modifications can be appropriately made to the embodiments of the present invention within the scope of the technical concept shown in the claims.

[0263] <Postscript>

[0264] Based on the description of the above embodiments, the following technology is disclosed.

[0265] (Technology 1)

[0266] A load sensor, characterized in that it comprises:

[0267] The first electrode has multiple protrusions on the same surface, the protrusions being elastic and conductive.

[0268] The second electrode faces the first electrode in a manner that clamps the plurality of protrusions; and

[0269] A dielectric material disposed on the opposing surface of the second electrode.

[0270] The number of protrusions in contact with the dielectric increases with the increase of load.

[0271] According to this technology, since the number of protrusions in contact with the dielectric increases with the increase of load, even if a large load is accidentally applied to the load sensor, the stress generated in each of the multiple protrusions is mitigated. Therefore, the stress generated in each protrusion is unlikely to exceed the yield stress, thus suppressing plastic deformation of each protrusion.

[0272] (Technology 2)

[0273] The load sensor according to technology 1 is characterized in that,

[0274] The plurality of protrusions includes a plurality of first protrusions and a plurality of second protrusions.

[0275] In a no-load state, the front ends of the plurality of first protrusions are in contact with the dielectric, and the front ends of the plurality of second protrusions are separated from the dielectric.

[0276] According to this technology, due to the increase of load, the state changes from multiple first protrusions in contact with the dielectric to multiple second protrusions also in contact with the dielectric. Therefore, the number of protrusions in contact with the dielectric can be increased with the increase of load.

[0277] (Technology 3)

[0278] The load sensor according to technology 2 is characterized in that,

[0279] The dielectric is formed on the planar opposing surface.

[0280] The plurality of first protrusions and the plurality of second protrusions protrude from the same reference surface on the first electrode.

[0281] The height of the plurality of second protrusions is lower than the height of the plurality of first protrusions.

[0282] According to this technology, the number of protrusions in contact with the dielectric can be increased with increasing load using a simple structure.

[0283] (Technology 4)

[0284] The load sensor according to technology 2 or 3 is characterized in that,

[0285] The plurality of first protrusions and the plurality of second protrusions are configured such that at least one first protrusion is sandwiched between two second protrusions.

[0286] According to this technology, since there are second protrusions on both sides of at least one first protrusion, the second electrode and the dielectric can be well supported in a balanced manner by the first and second protrusions even when the dielectric comes into contact with the second protrusion due to increased load. This suppresses the generation of off-center loads and improves the accuracy of load detection.

[0287] (Technology 5)

[0288] The load sensor according to any one of techniques 2 to 4 is characterized in that,

[0289] The elastic modulus of the second protrusion is higher than that of the first protrusion.

[0290] According to this technology, the load-bearing capacity of the load sensor can be improved by using the second protrusion to further and reliably support the load.

[0291] (Technology 6)

[0292] The load sensor according to any one of techniques 2 to 5 is characterized in that,

[0293] The cross-sectional area of ​​the plurality of first protrusions and the plurality of second protrusions decreases as they move toward the front end.

[0294] The contact area between the dielectric and the first protrusion when there is no load is smaller than the contact area between the dielectric and the second protrusion when the dielectric begins to contact the second protrusion.

[0295] According to this technology, the first protrusion, which initially contacts the dielectric, has a smaller contact area. Therefore, the change in contact area increases with increasing load, and the electrostatic capacitance rises more rapidly. This improves the sensitivity of the load sensor at the initial application of load. Furthermore, the second protrusion, which then contacts the dielectric, has a larger contact area. Therefore, even under rapidly applied large loads, the second protrusion can absorb the applied load and suppress plastic deformation of the protrusion.

[0296] (Technology 7)

[0297] The load sensor according to technology 6 is characterized in that,

[0298] A first plane is formed at the front end of the plurality of first protrusions.

[0299] A second plane is formed at the front end of the plurality of second protrusions.

[0300] The area of ​​the first plane is smaller than the area of ​​the second plane.

[0301] According to this technology, when the initial load is applied, the contact area between the dielectric and the first protrusion increases slowly, thus further improving the linearity of the sensitivity characteristics.

[0302] (Technology 8)

[0303] The load sensor according to any one of techniques 2 to 7 is characterized in that,

[0304] The second protrusion comes into contact with the dielectric by applying a load smaller than the range of the load that produces yield stress in the first protrusion.

[0305] According to this technology, it is difficult to generate yield stress in the first protrusion, and the plastic deformation of the first protrusion can be appropriately suppressed.

[0306] (Technology 9)

[0307] The load sensor according to any one of techniques 2 to 8 is characterized in that,

[0308] The plurality of protrusions also includes a plurality of third protrusions.

[0309] In the unloaded state, the front ends of the plurality of third protrusions are further away from the dielectric than the front ends of the plurality of second protrusions.

[0310] According to this technology, due to the increase of load, the state changes from multiple first and second protrusions in contact with the dielectric to multiple third protrusions also in contact with the dielectric. Therefore, the number of protrusions in contact with the dielectric can increase with the increase of load, thereby further suppressing plastic deformation of each protrusion.

[0311] (Technology 10)

[0312] The load sensor according to any one of techniques 1 to 9 is characterized in that,

[0313] The dielectric is formed on the planar opposing surface.

[0314] The plurality of protrusions extend from the same reference surface on the first electrode.

[0315] It is configured with multiple columns containing multiple of the aforementioned protrusions.

[0316] The height of the protrusions in each column is selectively set to any of a plurality of heights.

[0317] According to this technology, the first electrode can be easily formed even when the protrusion is small.

[0318] (Technology 11)

[0319] The load sensor according to any one of techniques 1 to 10 is characterized in that,

[0320] The cross-sectional area of ​​the plurality of protrusions decreases as they move toward the front end.

[0321] According to this technology, the contact area between the protrusion and the dielectric increases with increasing load. This improves the linearity of the sensitivity characteristics.

[0322] (Technology 12)

[0323] The load sensor according to technology 5 is characterized in that,

[0324] The first protrusion extends from the elastic base toward the second electrode.

[0325] The second protrusion penetrates the base and protrudes toward the second electrode.

[0326] The lower surface of the second protrusion and the lower surface of the base are contained in the same plane.

[0327] According to this technology, since the second protrusion is not supported by an elastic base, it can efficiently bear the load when the dielectric on the second electrode side comes into contact with the second protrusion as the load increases. This allows for more reliable suppression of plastic deformation of the first protrusion due to overload, thereby improving the load-bearing capacity of the load sensor.

[0328] (Technology 13)

[0329] The load sensor according to any one of techniques 2 to 9 and 12 is characterized in that,

[0330] When viewed from above, the second protrusion is smaller than the first protrusion, and each of the second protrusions is surrounded by a plurality of the first protrusions.

[0331] According to this technology, in a load sensor with a fixed detection area, a second protrusion can be efficiently configured among multiple first protrusions while suppressing the reduction in the number of first protrusions caused by the configuration of the second protrusion. Thus, while suppressing the decrease in load detection sensitivity, the load applied to the load sensor can be efficiently distributed to the first and second protrusions, thereby suppressing plastic deformation of the first protrusions.

[0332] (Technology 14)

[0333] The load sensor according to technology 13 is characterized in that,

[0334] The plurality of first protrusions arranged around a second protrusion are arranged in a rotationally symmetrical position centered on a second protrusion.

[0335] According to this technology, the area of ​​the plurality of first protrusions and the plurality of second protrusions can be increased relative to the fixed detection surface of the load sensor, resulting in the efficient configuration of the plurality of first protrusions and the plurality of second protrusions. Furthermore, since the plurality of second protrusions are regularly arranged around the first protrusions, the detection surface of the load sensor can be uniformly supported by the plurality of second protrusions.

[0336] (Technology 15)

[0337] A load sensor, characterized in that it comprises:

[0338] The first electrode has a plurality of first protrusions, the first protrusions being elastic and conductive protrusions;

[0339] The second electrode faces the first electrode in such a way that it clamps the plurality of first protrusions;

[0340] A plurality of second protrusions, the second protrusions being elastic and insulating, are disposed on the opposing surface of the second electrode in such a manner that they protrude into a space where the first protrusions are absent; and

[0341] A dielectric material disposed on the opposing surface of the second electrode.

[0342] In the unloaded state, the front ends of the plurality of first protrusions are in contact with the dielectric, and the front ends of the plurality of second protrusions are separated from the first electrode.

[0343] According to this technology, since the second protrusion contacts the first electrode side as the load increases, even if a large load is accidentally applied to the load sensor, the stress generated on each of the multiple first protrusions is mitigated. Therefore, the stress generated on each first protrusion is unlikely to exceed the yield stress, and plastic deformation of each first protrusion can be suppressed. Furthermore, since the second protrusion is disposed on a second electrode different from the first electrode on which the first protrusion is disposed, it is easy to place the second protrusion in the gap between the first protrusions. Therefore, there is no need to reduce the number of first protrusions to accommodate the second protrusion, thus maintaining the detection sensitivity of the load sensor.

[0344] (Technology 16)

[0345] The load sensor according to technology 15 is characterized in that,

[0346] The first protrusion protrudes from the elastic base.

[0347] A support portion with a higher elastic modulus than the base portion is disposed in the region facing the front end of the second protrusion.

[0348] According to this technology, since the support portion is harder than the base, the second protrusion can efficiently bear the load when the second electrode contacts the support portion as the load increases. This more reliably suppresses plastic deformation of the first protrusion caused by overload, thereby improving the load-bearing capacity of the load sensor.

[0349] (Technology 17)

[0350] A load detection device, characterized in that it comprises:

[0351] The load sensor according to any one of techniques 1 to 16; and

[0352] The control unit detects the load based on the electrostatic capacitance between the first electrode and the second electrode.

[0353] According to this technology, plastic deformation of each protrusion is suppressed in the load sensor. Therefore, even after a large load is accidentally applied to the load sensor, the control unit can continue to detect the load appropriately.

[0354] Explanation of reference numerals in the attached figures

[0355] 1: Load sensor

[0356] 2: Load detection device

[0357] 2b: Control circuit (control unit)

[0358] 20: First electrode

[0359] 20a: Base

[0360] 21: First protrusion (protrusion)

[0361] 21a: Face (front end, first plane)

[0362] 22: Second protrusion (protrusion)

[0363] 22a: Face (front end, second plane)

[0364] 23: Third protrusion (protrusion)

[0365] 23a: Front end

[0366] 30: Dielectric

[0367] 40: Second electrode

[0368] 41: Opposing planes

[0369] 61: Second protrusion

[0370] 62: Third protrusion (Second protrusion)

[0371] 70: Support section.

Claims

1. A load sensor, characterized in that, have: The first electrode has multiple protrusions on the same surface, the protrusions being elastic and conductive. The second electrode faces the first electrode in a manner that clamps the plurality of protrusions; as well as A dielectric material disposed on the opposing surface of the second electrode. The number of protrusions in contact with the dielectric increases with the increase of load.

2. The load sensor according to claim 1, characterized in that, The plurality of protrusions includes a plurality of first protrusions and a plurality of second protrusions. In a no-load state, the front ends of the plurality of first protrusions are in contact with the dielectric, and the front ends of the plurality of second protrusions are separated from the dielectric.

3. The load sensor according to claim 2, characterized in that, The dielectric is formed on the planar opposing surface. The plurality of first protrusions and the plurality of second protrusions protrude from the same reference surface on the first electrode. The height of the plurality of second protrusions is lower than the height of the plurality of first protrusions.

4. The load sensor according to claim 2, characterized in that, The plurality of first protrusions and the plurality of second protrusions are configured such that at least one first protrusion is sandwiched between two second protrusions.

5. The load sensor according to claim 2, characterized in that, The elastic modulus of the second protrusion is higher than that of the first protrusion.

6. The load sensor according to claim 2, characterized in that, The cross-sectional area of ​​the plurality of first protrusions and the plurality of second protrusions decreases as they move toward the front end. The contact area between the dielectric and the first protrusion when there is no load is smaller than the contact area between the dielectric and the second protrusion when the dielectric begins to contact the second protrusion.

7. The load sensor according to claim 6, characterized in that, A first plane is formed at the front end of the plurality of first protrusions. A second plane is formed at the front end of the plurality of second protrusions. The area of ​​the first plane is smaller than the area of ​​the second plane.

8. The load sensor according to claim 2, characterized in that, The second protrusion comes into contact with the dielectric by applying a load smaller than the range of the load that produces yield stress in the first protrusion.

9. The load sensor according to claim 2, characterized in that, The plurality of protrusions also includes a plurality of third protrusions. In the unloaded state, the front ends of the plurality of third protrusions are further away from the dielectric than the front ends of the plurality of second protrusions.

10. The load sensor according to claim 1, characterized in that, The dielectric is formed on the planar opposing surface. The plurality of protrusions extend from the same reference surface on the first electrode. It is configured with multiple columns containing multiple of the aforementioned protrusions. The height of the protrusions in each column is selectively set to any of a plurality of heights.

11. The load sensor according to claim 1, characterized in that, The cross-sectional area of ​​the plurality of protrusions decreases as they move toward the front end.

12. The load sensor according to claim 5, characterized in that, The first protrusion extends from the elastic base toward the second electrode. The second protrusion penetrates the base and protrudes toward the second electrode. The lower surface of the second protrusion and the lower surface of the base are contained in the same plane.

13. The load sensor according to claim 2, characterized in that, When viewed from above, the second protrusion is smaller than the first protrusion, and each of the second protrusions is surrounded by a plurality of the first protrusions.

14. The load sensor according to claim 13, characterized in that, The plurality of first protrusions arranged around a second protrusion are positioned in a rotationally symmetrical manner about a second protrusion.

15. A load sensor, characterized in that, have: The first electrode has a plurality of first protrusions, the first protrusions being elastic and conductive protrusions; The second electrode faces the first electrode in such a way that it clamps the plurality of first protrusions; Multiple second protrusions, the second protrusions being elastic and insulating protrusions, are disposed on the opposing surface of the second electrode in such a way that they protrude into a space where the first protrusions do not exist; as well as A dielectric material disposed on the opposing surface of the second electrode. In the unloaded state, the front ends of the plurality of first protrusions are in contact with the dielectric, and the front ends of the plurality of second protrusions are separated from the first electrode.

16. The load sensor according to claim 15, characterized in that, The first protrusion protrudes from the elastic base. A support portion with a higher elastic modulus than the base portion is disposed in the region facing the front end of the second protrusion.

17. A load detection device, characterized in that, have: The load sensor according to any one of claims 1 to 16; and The control unit detects the load based on the electrostatic capacitance between the first electrode and the second electrode.

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