JP7625969B2 - Electronics - Google Patents

Description

The present invention relates to an electronic device equipped with a piezoelectric sensor.

As an example of an invention related to conventional electronic devices, the distribution sensor described in Patent Document 1 is known. This distribution sensor includes a portion corresponding to a piezoelectric element, a base substrate, and a supporting spacer. The base substrate has, for example, a rectangular shape. The supporting spacers are disposed at the four corners of the base substrate. The portion corresponding to the piezoelectric element is disposed on the base substrate. The portion corresponding to the piezoelectric element is supported by the supporting spacers.

JP 2000-337979 A

In electronic devices equipped with piezoelectric sensors, there is a demand for improving the detection sensitivity of the piezoelectric sensors. However, in the distributed sensor described in Patent Document 1, the support spacer may inhibit the deformation of the piezoelectric element. For this reason, it may be difficult to improve the detection sensitivity of this distributed sensor.

Therefore, the object of the present invention is to provide an electronic device that can improve the detection sensitivity of a piezoelectric sensor.

An electronic device according to one embodiment of the present invention includes:
An operation plate having an upper main surface and a lower main surface, wherein a part of a user's body or an operation member comes into contact with the upper main surface of the operation plate;
a piezoelectric sensor provided on the lower main surface of the operation plate, the piezoelectric sensor detecting deformation of the operation plate and outputting a detection signal;
an opposing member having an opposing surface facing the lower main surface of the operation plate;
a support member in contact with the lower main surface of the operation plate and the opposing surface of the opposing member;
Equipped with
the support member is spaced from an outer edge of the piezoelectric sensor by 10 mm or more when viewed in a vertical direction,
The support member applies an upward force of 2N or less to the operation plate.

In this specification, an axis or member extending in the front-rear direction does not necessarily refer only to an axis or member that is parallel to the front-rear direction. An axis or member extending in the front-rear direction refers to an axis or member that is inclined within a range of ±45° with respect to the front-rear direction. Similarly, an axis or member extending in the up-down direction refers to an axis or member that is inclined within a range of ±45° with respect to the up-down direction. An axis or member extending in the left-right direction refers to an axis or member that is inclined within a range of ±45° with respect to the left-right direction.

In the following, the first member, second member, and third member are structures that an electronic device has. In this specification, "the first member is supported by the second member" includes cases where the first member is attached to the second member so as to be immovable relative to the second member (i.e., fixed or held), and cases where the first member is attached to the second member so as to be movable relative to the second member. In addition, "the first member is supported by the second member" includes both cases where the first member is directly attached to the second member, and cases where the first member is attached to the second member via the third member.

In this specification, the first and second members aligned in the front-rear direction refer to the following state. When the first and second members are viewed in a direction perpendicular to the front-rear direction, both the first and second members are arranged on an arbitrary straight line indicating the front-rear direction. In this specification, the first and second members aligned in the front-rear direction when viewed in the up-down direction refer to the following state. When the first and second members are viewed in the up-down direction, both the first and second members are arranged on an arbitrary straight line indicating the front-rear direction. In this case, when the first and second members are viewed from a left-right direction different from the up-down direction, either the first or second member does not have to be arranged on an arbitrary straight line indicating the front-rear direction. Note that the first and second members may be in contact with each other. The first and second members may be separated from each other. A third member may be present between the first and second members. This definition also applies to directions other than the front-rear direction.

In this specification, a first member being placed in front of a second member refers to the following state: A part of the first member is placed within the area through which the second member passes when it translates forward. Thus, the first member may be contained within the area through which the second member passes when it translates forward, or may protrude from the area through which the second member passes when it translates forward. In this case, the first member and the second member are lined up in the front-to-rear direction. This definition also applies to directions other than the front-to-rear direction.

In this specification, a first member being placed in front of a second member when viewed in the left-right direction refers to the following state: When viewed in the left-right direction, the first member and the second member are lined up in the front-to-back direction, and when viewed in the left-to-right direction, the part of the first member that faces the second member is placed in front of the second member. In this definition, the first member and the second member do not have to be lined up in the front-to-back direction in three dimensions. This definition also applies to directions other than the front-to-back direction.

In this specification, the term "the first member is placed in front of the second member" refers to the following state: The first member is placed in front of a plane that passes through the front end of the second member and is perpendicular to the front-to-rear direction. In this case, the first member and the second member may or may not be aligned in the front-to-rear direction. This definition also applies to directions other than the front-to-rear direction.

In this specification, unless otherwise specified, each part of the first member is defined as follows. The front part of the first member means the front half of the first member. The rear part of the first member means the rear half of the first member. The left part of the first member means the left half of the first member. The right part of the first member means the right half of the first member. The upper part of the first member means the upper half of the first member. The lower part of the first member means the lower half of the first member. The front end of the first member means the front end of the first member. The rear end of the first member means the rear end of the first member. The left end of the first member means the left end of the first member. The right end of the first member means the right end of the first member. The upper end of the first member means the upper end of the first member. The lower end of the first member means the lower end of the first member. The front end of the first member means the front end of the first member and its vicinity. The rear end of the first member means the rear end of the first member and its vicinity. The left end of the first member means the left end of the first member and its vicinity. The right end of the first member means the right end of the first member and its vicinity. The top end of the first member means the top end of the first member and its vicinity. The bottom end of the first member means the bottom end of the first member and its vicinity.

In this specification, the phrase "the first member and the second member are electrically connected" has the following two meanings. The first meaning is that the first member and the second member are in physical contact with each other, allowing a direct current to flow between the first member and the second member. The second meaning is that the first member and the third member are in physical contact with each other, and the third member and the second member are in physical contact with each other, allowing a direct current to flow between the first member and the second member. In the second meaning, the first member and the second member may or may not be in physical contact with each other. In the second meaning, the third member may be a single member, or may include multiple members.

The electronic device according to the present invention can improve the detection sensitivity of the piezoelectric sensor.

FIG. 1 is a top view of the electronic device 1. FIG. FIG. 2 is a cross-sectional view of the electronic device 1 taken along line AA. FIG. 3 is a cross-sectional view of the electronic device 1 taken along the line BB. FIG. 4 is a bottom view of the piezoelectric sensor 13 and a cross-sectional view taken along the line CC. FIG. 5 is a cross-sectional view of the experimental setup 100. FIG. 6 is a top view of the experimental device 100. FIG. 7 is a graph showing the results of Experiment 1. FIG. 8 is a top view of the experimental device 100. FIG. 9 is a graph showing the results of Experiment 2. FIG. 10 is a top view of the experimental device 100. FIG. 11 is a graph showing the results of Experiment 3. FIG. 12 is a top view of the experimental device 100. FIG. 13 is a graph showing the results of Experiment 3.

(Embodiment)
The configuration of an electronic device 1 according to an embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a top view of the electronic device 1. Fig. 2 is a cross-sectional view of the electronic device 1 taken along line A-A. Fig. 3 is a cross-sectional view of the electronic device 1 taken along line B-B. Fig. 4 is a bottom view of the piezoelectric sensor 13 and a cross-sectional view taken along line C-C.

In addition, in this specification, directions are defined as follows. In the electronic device 1, the direction in which the normal vector of the upper main surface S11 of the operation plate 2 extends is defined as the upward direction. The direction in which the normal vector of the lower main surface S12 of the operation plate 2 extends is defined as the downward direction. The direction in which the long side of the operation plate 2 extends is defined as the front-rear direction. The direction in which the short side of the operation plate 2 extends is defined as the left-right direction. The up-down direction, left-right direction, and front-rear direction are mutually perpendicular. Note that the definitions of directions in this specification are merely examples. Therefore, the directions in the actual use of the electronic device 1 do not need to match the directions in this specification. Also, the up-down direction may be reversed in FIG. 1. Similarly, the left-right direction may be reversed in FIG. 1. The front-rear direction may be reversed in FIG. 1.

The electronic device 1 is a portable electronic terminal such as a smartphone or a tablet computer. As shown in Figs. 1 to 3, the electronic device 1 includes an operation plate 2, a housing 3, an opposing member 4, a support member 5, and a piezoelectric sensor 13. The housing 3 is a box. The housing 3 has a rectangular shape when viewed in the vertical direction. However, the top surface of the housing 3 is open. The opening of the housing 3 has a rectangular shape when viewed in the vertical direction. The operation plate 2 has a plate shape. The operation plate 2 has an upper main surface S11 and a lower main surface S12. The operation plate 2 has a rectangular shape with long sides extending in the front-back direction and short sides extending in the left-right direction when viewed in the vertical direction. As a result, the operation plate 2 covers the opening of the housing 3. The operation plate 2 may include a touch panel, a fingerprint sensor, and a display. A part of the user's body or an operation member contacts the upper main surface S11 of the operation plate 2.

The operation plate 2 includes a first conductive part 21. As shown in FIG. 3, the first conductive part 21 is exposed on the lower main surface S12 of the operation plate 2. The first conductive part 21 is connected to ground. The first conductive part 21 is, for example, a wiring layer or a ground conductor layer provided on the operation plate 2. The first conductive part 21 may be a metal plate, a metal foil, an electrode provided on glass, an electrode provided on a film, or a conductive cushion. The operation plate 2 and the housing 3 form a space inside. A battery, a circuit board, a CPU (Central Processing Unit), a frame, and the like (not shown) are provided in this space.

The facing member 4 has a facing surface S21 facing the lower main surface S12 of the operation plate 2. More specifically, the facing member 4 is disposed in a space formed by the operation plate 2 and the housing 3. The facing member 4 has an upper main surface (facing surface S21) and a lower main surface S22. The facing member 4 also includes a second conductive part 41. As shown in FIG. 3, the second conductive part 41 is exposed on the facing surface S21 of the facing member 4. The second conductive part 41 is connected to the ground. In this embodiment, the facing member 4 is a frame. However, the facing member 4 may be a circuit board, a battery, or the like. When the facing member 4 is a frame, the second conductive part 41 is, for example, a metal frame formed of a conductive material such as metal. When the facing member 4 is a battery, the second conductive part 41 is a ground for grounding provided on the surface of the facing member 4. When the facing member 4 is a circuit board, the second conductive part 41 is a wiring layer, a ground conductor layer, or the like.

The piezoelectric sensor 13 outputs a detection signal that detects deformation of the operation plate 2. More specifically, the piezoelectric sensor 13 outputs a detection signal for detecting that the user has pressed the operation plate 2. That is, the piezoelectric sensor 13 outputs a detection signal corresponding to the deformation caused in the operation plate 2 by the user pressing the operation plate 2. As shown in FIG. 2, the piezoelectric sensor 13 is provided on the lower main surface S12 of the operation plate 2. More specifically, the piezoelectric sensor 13 has a rectangular shape with long sides extending in the left-right direction when viewed in the up-down direction. When viewed in the up-down direction, the piezoelectric sensor 13 extends in the left-right direction at the center of the front-rear direction of the operation plate 2. Below, the details of the piezoelectric sensor 13 are described with reference to FIG. 4.

The piezoelectric sensor 13 includes a piezoelectric film 14, an upper electrode 15a, a lower electrode 15b, a substrate 16, and adhesive layers 18 and 20. As shown in FIG. 4, the piezoelectric film 14 has a sheet shape. Therefore, the piezoelectric film 14 has an upper main surface S1 and a lower main surface S2. The length of the piezoelectric film 14 in the left-right direction is longer than the length of the piezoelectric film 14 in the front-rear direction. In this embodiment, the piezoelectric film 14 has a rectangular shape with long sides extending in the left-right direction when viewed in the up-down direction. The piezoelectric film 14 generates an electric charge according to the amount of deformation of the piezoelectric film 14. In this embodiment, the piezoelectric film 14 is a PLA film. The piezoelectric film 14 will be described in more detail below.

The piezoelectric film 14 has a characteristic that the polarity of the electric charge generated when the piezoelectric film 14 is stretched in the left-right direction is opposite to the polarity of the electric charge generated when the piezoelectric film 14 is stretched in the front-back direction. Specifically, the piezoelectric film 14 is a film formed from a chiral polymer. The chiral polymer is, for example, polylactic acid (PLA), particularly L-type polylactic acid (PLLA). PLLA, which is made of a chiral polymer, has a helical structure in the main chain. PLLA has a piezoelectricity in which the molecules are oriented by uniaxial stretching. The piezoelectric film 14 has a piezoelectric constant of d14. The uniaxial stretching direction (orientation direction) of the piezoelectric film 14 forms an angle of 45 degrees with respect to each of the front-back direction and the left-right direction. This 45 degrees includes, for example, an angle of about 45 degrees ± 10 degrees. As a result, the piezoelectric film 14 generates an electric charge when the piezoelectric film 14 is stretched in the left-right direction or compressed in the left-right direction. For example, when the piezoelectric film 14 is stretched in the left-right direction, it generates a positive charge. For example, when the piezoelectric film 14 is compressed in the left-right direction, it generates a negative charge. The magnitude of the charge depends on the amount of deformation of the piezoelectric film 14 due to the stretching or compression. More precisely, the magnitude of the charge depends on the differential value of the amount of deformation of the piezoelectric film 14 due to the stretching or compression.

The upper electrode 15a is a signal electrode. A detection signal is output from the upper electrode 15a. As shown in FIG. 1, the upper electrode 15a is provided on the upper main surface S1. The material of the upper electrode 15a is, for example, a conductive polymer such as PEDOT. The upper electrode 15a may be disposed on the substrate 16 so that the lower main surface of the upper electrode 15a faces the upper main surface S1, and the piezoelectric film 14 and the substrate 16 may be joined by an adhesive layer 18. In this case, the upper electrode 15a is formed on the substrate 16, for example.

The lower electrode 15b is a ground electrode. The lower electrode 15b is connected to ground. As shown in FIG. 1, the lower electrode 15b is provided on the lower main surface S2. The material of the lower electrode 15b is, for example, a conductive tape or a conductive polymer such as PEDOT. An adhesive, double-sided tape, etc. may be present between the piezoelectric film 14 and the upper electrode 15a.

The substrate 16 is provided on the upper electrode 15a, and by holding the piezoelectric film 14, the upper electrode 15a, and the lower electrode 15b, it deforms together with the piezoelectric film 14. The substrate 16 has a sheet shape. The substrate 16 has an upper main surface and a lower main surface. The length of the substrate 16 in the left-right direction is longer than the length of the substrate 16 in the front-rear direction. In this embodiment, the substrate 16 has a rectangular shape with long sides extending in the left-right direction when viewed in the up-down direction. The long sides of the substrate 16 are longer than the long sides of the piezoelectric film 14, the long sides of the upper electrode 15a, and the long sides of the lower electrode 15b. The short sides of the substrate 16 are longer than the short sides of the piezoelectric film 14, the short sides of the upper electrode 15a, and the short sides of the lower electrode 15b. The piezoelectric film 14, the upper electrode 15a, and the lower electrode 15b are arranged within an area surrounded by the outer edge of the substrate 16 when viewed in the up-down direction.

The material of the substrate 16 is, for example, polyurethane or PET. It may also be made of a flexible substrate or a printed wiring board.

As shown in FIG. 3, the adhesive layer 18 fixes the piezoelectric film 14, the upper electrode 15a, and the lower electrode 15b to the substrate 16. More specifically, the adhesive layer 18 is provided on the lower main surface of the substrate 16. The adhesive layer 18 covers a portion of the lower main surface of the substrate 16. The adhesive layer 18 also covers the entire upper main surface of the upper electrode 15a. The outer edge of the adhesive layer 18 is surrounded by the outer edge of the substrate 16 when viewed in the vertical direction. The adhesive layer 18 bonds the upper electrode 15a and the substrate 16. As a result, the deformation of the substrate 16 is transmitted to the piezoelectric film 14. The material of the adhesive layer 18 is, for example, a double-sided tape, a thermosetting adhesive, or a thermoplastic adhesive.

The adhesive layer 20 is provided on the upper main surface of the base material 16. The adhesive layer 20 fixes the base material 16 to the operation plate 2. In this embodiment, the adhesive layer 20 fixes the base material 16 to the lower main surface S12 of the operation plate 2. The material of the adhesive layer 20 is, for example, a double-sided tape, a thermosetting adhesive, or a thermoplastic adhesive.

As shown in FIG. 3, the support member 5 is in contact with the lower main surface S12 of the operation plate 2 and the opposing surface S21 of the opposing member 4. More specifically, the support member 5 has a columnar shape extending in the vertical direction. In this embodiment, the support member 5 has a cylindrical shape. The support member 5 is in contact with the first conductive portion 21 and the second conductive portion 41. The upper end of the support member 5 is in contact with the first conductive portion 21. The lower end of the support member 5 is in contact with the second conductive portion 41. The support member 5 is also conductive. As a result, the support member 5 electrically connects the first conductive portion 21, which is connected to ground, and the second conductive portion 41, which is connected to ground.

Furthermore, the support member 5 is an elastic body. Therefore, the support member 5 elastically deforms when subjected to an external force. Here, the natural length of the support member 5 is slightly longer than the distance in the vertical direction between the lower main surface S12 and the opposing surface S21. The natural length of the support member 5 is the length of the support member 5 when the support member 5 is not in contact with the lower main surface S12 and the opposing surface S21. Therefore, when the support member 5 is in contact with the lower main surface S12 and the opposing surface S21, the support member 5 is slightly compressed in the vertical direction. Therefore, the support member 5 applies an upward force of 2N or less to the operation plate 2. The material of such a support member 5 is, for example, metal, conductive resin, etc.

Next, the arrangement of the support member 5 will be described with reference to FIG. 1. The support member 5 is at least 10 mm away from the outer edge of the piezoelectric sensor 13 when viewed in the vertical direction. Furthermore, the support member 5 is at least 10 mm away from the outer edge of the operation plate 2 when viewed in the vertical direction. Therefore, the support member 5 is arranged in the arrangement areas A1 and A2 hatched in FIG. 1. The arrangement area A1 is located in front of the piezoelectric sensor 13. The arrangement area A2 is located behind the piezoelectric sensor 13. In this embodiment, the support member 5 is arranged behind the center in the left-right direction of the piezoelectric sensor 13. Therefore, the support member 5 is arranged in the arrangement area A2.

(experiment)
The inventors of the present application conducted the following experiment to clarify the effects of the electronic device 1. Fig. 5 is a cross-sectional view of an experimental device 100. First, the experimental device 100 will be described.

The experimental device 100 includes waterproof double-sided tape 201L, 201R and housings 202L, 202R. The left end of the operation plate 2 is fixed to the housing 202L with waterproof double-sided tape 201L. The right end of the operation plate 2 is fixed to the housing 202R with waterproof double-sided tape 201R. The material of the housings 202L, 202R is aluminum. The housings 202L, 202R correspond to the housing 3 of the electronic device 1.

The operation plate 2 includes a glass plate 101, an ultraviolet curing adhesive 102, a PET film 103, a glass plate 104, an adhesive 105, and a stainless steel plate 106. The glass plate 101, the ultraviolet curing adhesive 102, the PET film 103, the glass plate 104, the adhesive 105, and the stainless steel plate 106 are layered in this order from top to bottom. The operation plate 2 corresponds to a display and a cover glass. The operation plate 2 and the housings 202L and 202R form a rectangular parallelepiped box.

The entire surface of the piezoelectric sensor 13 is fixed to the lower main surface of the stainless steel plate 106 with an adhesive. The thickness of the adhesive is 75 μm. The elastic modulus of the adhesive is 2 MPa. The center of the piezoelectric sensor 13 in the left-right direction coincides with the center of the operation plate 2 in the left-right direction. The long side of the piezoelectric sensor 13 is parallel to the short side of the operation plate 2.

The conditions for the experimental device 100 are described below.

Dimensions of glass plate 101: 143.5 mm x 66.6 mm
Thickness of glass plate 101: 0.7 mm
Dimensions of UV-curable adhesive 102: 133.9 mm x 64.1 mm
Thickness of ultraviolet curing adhesive 102: 0.1 mm
Dimensions of PET film 103: 133.9 mm x 64.1 mm
Thickness of PET film 103: 0.15 mm
Dimensions of glass plate 104: 133.9 mm x 64.1 mm
Thickness of glass plate 104: 0.5 mm
Dimensions of adhesive 105: 133.9 mm x 64.1 mm
Thickness of adhesive 105: 0.2 mm
Dimensions of stainless steel plate 106: 133.9 mm x 64.1 mm
Thickness of stainless steel plate 106: 0.15 mm
Dimensions of the piezoelectric sensor 13: 48 mm x 10 mm
Thickness of waterproof double-sided tape 201L, 201R: 0.35 mm
Elastic modulus of waterproof double-sided tape 201L, 201R: 2 MPa
Dimensions of housings 202L and 202R: 145.5 mm x 68.6 mm x 10 mm
Thickness of the housings 202L and 202R: 2 mm
Shape of the housings 202L and 202R: hollow rectangular parallelepiped with an open top
Material of the support member 5: Silicone sponge
Product name of support member 5: ZSR2101
Manufacturer: Hakko Electric
Shape of the support member 5: Rectangular parallelepiped with each side having a length of 10 mm [Experiment 1]
The inventors of the present application conducted Experiment 1 to clarify that it is preferable that the support member 5 is spaced 10 mm or more from the outer edge of the piezoelectric sensor 13 when viewed in the vertical direction. FIG.

The inventor applied a downward force to the upper main surface S11 of the operation plate 2. Specifically, the inventor applied a downward force to the center (position P1) of the piezoelectric sensor 13 in the left-right direction. The inventor applied the force by lowering a 100 g weight at a speed of 2 mm/s from a position 0.3 mm above the upper main surface S11 of the operation plate 2. The inventor set the magnitude of the force applied by the support member 5 to the operation plate 2 to 2 N.

In addition, in experiment 1, the inventor placed the support member 5 behind position P1. The inventor changed the distance D1 between the support member 5 and the piezoelectric sensor 13 to three values: 10 mm, 20 mm, and 30 mm. The inventor then measured the strength of the detection signal from the piezoelectric sensor 13. Figure 7 is a graph showing the results of experiment 1. The horizontal axis represents the distance D1. The vertical axis represents the strength of the detection signal from the piezoelectric sensor 13.

As shown in FIG. 7, when the distance D1 is smaller than 10 mm, the strength of the detection signal decreases. This means that the support member 5 prevents the piezoelectric sensor 13 from deforming. Therefore, based on Experiment 1, it is preferable that the support member 5 is 10 mm or more away from the outer edge of the piezoelectric sensor 13 when viewed in the vertical direction. This allows the electronic device 1 to improve the detection sensitivity of the piezoelectric sensor 13.

[Experiment 2]
The inventors of the present application conducted Experiment 2 in order to clarify that it is preferable that the support member 5 is spaced 10 mm or more from the outer edge of the operation plate 2 when viewed in the up-down direction. FIG. 8 is a top view of the experimental device 100.

The inventor applied a downward force to the upper main surface S11 of the operation plate 2. Specifically, the inventor applied the downward force to position P2, which is 30 mm behind and 30 mm to the right of the center of the piezoelectric sensor 13 in the left-right direction. Position P2 is located near the right end (right long side) of the operation plate 2. The inventor applied the force by lowering a 100 g weight at a speed of 2 mm/s from a position 0.3 mm above the upper main surface S11 of the operation plate 2. The inventor set the magnitude of the force applied by the support member 5 to the operation plate 2 to 2 N.

In addition, in experiment 2, the inventor placed the support member 5 to the left of position P2. The inventor changed the distance D2 between the support member 5 and the right end (right long side) of the operation plate 2 to 10 mm, 20 mm, and 30 mm. The inventor then measured the strength of the detection signal of the piezoelectric sensor 13. Figure 9 is a graph showing the results of experiment 2. The horizontal axis represents the distance D2. The vertical axis represents the strength of the detection signal of the piezoelectric sensor 13.

As shown in FIG. 9, when the distance D2 becomes smaller than 10 mm, the strength of the detection signal decreases. This means that the support member 5 prevents the piezoelectric sensor 13 from deforming when the user presses the end of the operation plate 2. Therefore, based on experiment 2, it is preferable that the support member 5 is 10 mm or more away from the outer edge of the operation plate 2 when viewed in the vertical direction. This allows the electronic device 1 to improve the detection sensitivity of the piezoelectric sensor 13.

[Experiment 3]
The inventors of the present application conducted Experiment 3 to clarify that it is preferable for the support member 5 to apply an upward force of 2 N or less to the operation plate 2, and that it is preferable for the pressure applied by the support member 5 to the lower main surface S12 of the operation plate 2 to be 0.02 MPa or less. Fig. 10 is a top view of the experimental device 100. Fig. 11 is a graph showing the experimental results of Experiment 3.

The inventor applied a downward force to the upper main surface S11 of the operation plate 2. Specifically, the inventor applied a downward force to the center (position P1) of the piezoelectric sensor 13 in the left-right direction. The inventor applied the force by lowering a 100 g weight at a speed of 2 mm/s from a position 0.3 mm above the upper main surface S11 of the operation plate 2.

In addition, in Experiment 3, the inventor placed the support member 5 behind position P1. The inventor set the distance D1 between the support member 5 and the piezoelectric sensor 13 to 30 mm. At this time, the inventor changed the magnitude F of the force applied by the support member 5 to the operation plate 2 from 0.5 N to 2.5 N. The inventor then measured the strength of the detection signal from the piezoelectric sensor 13. Figure 11 is a graph showing the results of Experiment 3. The horizontal axis indicates the magnitude of the force F. The vertical axis indicates the strength of the detection signal from the piezoelectric sensor 13. The magnitude of the force F was measured using the following procedure. The inventor pressed the operation plate 2 downward against the housings 202L and 202R. The inventor then used a force gauge to measure the magnitude of the force F when the upper main surface S11 of the operation plate 2 and the upper ends of the housings 202L and 202R were positioned at the same height in the vertical direction.

As shown in FIG. 11, when the magnitude of the force F becomes greater than 2N, it can be seen that the strength of the detection signal decreases. This means that the support member 5 prevents the piezoelectric sensor 13 from deforming. Therefore, based on Experiment 3, it is preferable for the support member 5 to apply an upward force of 2N or less to the operation plate 2. This allows the electronic device 1 to improve the detection sensitivity of the piezoelectric sensor 13.

The shape of the support member 5 is a rectangular parallelepiped with each side having a length of 10 mm. Therefore, when the support member 5 applies a force of 2 N, the support member 5 applies a pressure of 0.02 MPa or less. Therefore, it is preferable that the pressure applied by the support member 5 to the lower main surface S12 of the operation plate 2 is 0.02 MPa or less.

[Experiment 4]
The inventors of the present application conducted Experiment 4 to clarify that the electronic device 1 including the support member 5 suppresses the variation in sensitivity of the piezoelectric sensor 13 depending on the position at which the operation plate 2 is pressed. Fig. 12 is a top view of the experimental device 100. Points 1 to 25 in Fig. 12 indicate the positions of the upper main surface S11 of the operation plate 2.

The inventor applied a downward force to the upper main surface S11 of the operation plate 2. Specifically, the inventor applied a downward force to each of points 1 to 25 in FIG. 12. The inventor applied the force by lowering a 100 g weight at a speed of 2 mm/s from a position 0.3 mm above the upper main surface S11 of the operation plate 2.

In Experiment 4, the inventors conducted an experiment using an experimental device 100 with a support member 5 and an experimental device 100 without a support member 5. In the experimental device 100 with the support member 5, the inventors placed the support member 5 behind position P1. The inventors set the distance D1 between the support member 5 and the piezoelectric sensor 13 to 30 mm. The inventors set the magnitude of the force that the support member 5 applies to the operation plate 2 to 2 N. The inventors then measured the strength of the detection signal of the piezoelectric sensor 13 of the experimental device 100 with the support member 5 and the experimental device 100 without the support member 5. Figure 13 is a graph showing the experimental results of Experiment 3. The horizontal axis indicates points 1 to 25. The vertical axis indicates the strength of the detection signal of the piezoelectric sensor 13.

As shown in FIG. 13, in the electronic device 1 that does not have the support member 5, it can be seen that there is a large difference in the intensity of the detection signal when the user presses the left-right center of the operation plate 2 (particularly points 8, 13, and 18) and when the user presses a part other than the left-right center of the operation plate 2. On the other hand, as shown in FIG. 13, in the electronic device 1 that has the support member 5, it can be seen that there is a small difference in the intensity of the detection signal when the user presses the left-right center of the operation plate 2 (particularly points 8, 13, and 18) and when the user presses a part other than the left-right center of the operation plate 2. In this way, by providing the support member 5 to the electronic device 1, the variation in sensitivity of the piezoelectric sensor 13 depending on the position at which the operation plate 2 is pressed is suppressed.

As can be seen from FIG. 13, the outputs of points 17, 18, and 19 behind the operation plate 2 are also reduced. This is because the support member 5 is placed behind the piezoelectric sensor 13. The experimental device 100 has a structure that is symmetrical from front to back. Therefore, if the support member 5 is placed in front of the piezoelectric sensor 13, it is clear that the outputs of points 7, 8, and 9 located in front of the operation plate 2 will decrease. Therefore, it is preferable that the support member 5 is placed in two locations, in front of and behind the piezoelectric sensor 13. This makes it possible to make the outputs of points 7, 8, and 9 located in front of the operation plate 2 and points 17, 18, and 19 located behind the operation plate 2 approximately the same.

Other Embodiments
The electronic device 1 according to the present invention is not limited to the electronic device 1, and can be modified within the scope of the gist thereof.

In addition, in the electronic device 1, the support member 5 does not have to be more than 10 mm away from the outer edge of the operation plate 2 when viewed in the vertical direction.

In addition, in the electronic device 1, the operation panel 2 does not have to have a rectangular shape when viewed in the vertical direction.

In addition, in the electronic device 1, the piezoelectric sensor 13 does not have to extend in the left-right direction at the center of the front-rear direction of the operation plate 2 when viewed in the up-down direction. The piezoelectric sensor 13 may be disposed in front of or behind the center of the front-rear direction of the operation plate 2. The piezoelectric sensor 13 may also extend in the front-rear direction.

In addition, in the electronic device 1, either or both of the first conductive part 21 and the second conductive part 41 may not be present.

In the experimental device 100, a spring may be used as the support member 5. The magnitude of the force F is adjusted by adjusting the spring constant. In this case, the spring constant is, for example, 0.4 or more and 1 or less.

In addition, in the electronic device 1, the piezoelectric film 14 may be a PVDF (polyvinylidene fluoride) film.

In the electronic device 1, it is sufficient that the first conductive part 21 and/or the second conductive part 41 are connected to ground. Therefore, the first conductive part 21 or the second conductive part 41 does not have to be connected to ground.

1: Electronic device 2: Operation plate 3: Housing 4: Opposing member 5: Support member 13: Piezoelectric sensor 14: Piezoelectric film 15a: Upper electrode 15b: Lower electrode 16: Base material 18, 20: Adhesive layer 21: First conductive portion 41: Second conductive portions A1, A2: Arrangement area

Claims (6)

An operation plate having an upper main surface and a lower main surface, wherein a part of a user's body or an operation member comes into contact with the upper main surface of the operation plate;
a piezoelectric sensor provided on the lower main surface of the operation plate, the piezoelectric sensor detecting deformation of the operation plate and outputting a detection signal;
an opposing member having an opposing surface facing the lower main surface of the operation plate;
a support member in contact with the lower main surface of the operation plate and the opposing surface of the opposing member;
Equipped with
the support member is spaced from an outer edge of the piezoelectric sensor by 10 mm or more when viewed in a vertical direction,
The support member applies an upward force of 2 N or less to the operation plate.
Electronic devices. The support member is spaced 10 mm or more from the outer edge of the operation plate when viewed in the vertical direction.
2. The electronic device according to claim 1. The operation plate has a rectangular shape having a long side extending in a front-rear direction and a short side extending in a left-right direction when viewed in a vertical direction,
The piezoelectric sensor extends in the left-right direction at the center of the front-rear direction of the operation plate when viewed in the up-down direction.
3. The electronic device according to claim 1 or 2. A first conductive portion is exposed on the lower main surface of the operation plate,
a second conductive portion is exposed on the opposing surface of the opposing member,
the first conductive portion and/or the second conductive portion are connected to ground,
The support member is in contact with the first conductive portion and the second conductive portion.
4. The electronic device according to claim 1. The support member is disposed in two locations, in front of and behind the piezoelectric sensor.
5. The electronic device according to claim 1. The pressure applied by the support member to the lower main surface of the operation plate is 0.02 MPa or less.
6. The electronic device according to claim 1.

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