Sensor module

Abstract

This sensor module comprises: an elastic member including a resin; a first sensor provided in contact with the elastic member and including an upper electrode, a piezoelectric film, and a lower electrode; and a switch. The first sensor outputs a first signal corresponding to deformation of the elastic member. The switch has a function of causing a short circuit between the upper electrode and the lower electrode. The lower electrode is a signal electrode.

Description

Sensor Module

[0001] The present invention relates to a sensor module including a sensor that detects deformation of a member.

[0002] Patent Document 1 describes a grip load detection device that detects a load applied by a user. The grip load detection device includes a housing and a sensor. The housing is gripped by a user. The sensor is attached to the housing. The sensor detects a load applied to the housing by the user's grip. Specifically, the sensor includes a piezoelectric film, a first electrode, and a second electrode. The sensor outputs a signal based on the potential difference between the first electrode and the second electrode.

[0003] International Publication No. 2020 / 153075

[0004] In the field of the grip load detection device described in Patent Document 1, there is a demand for a sensor module in which the sensor that detects deformation of a member is less likely to malfunction.

[0005] An object of the present invention is to provide a sensor module in which a sensor that detects deformation of a member is less likely to malfunction.

[0006] The inventors of the present application have considered the malfunction of a sensor that detects deformation of a component and that includes a piezoelectric film, a signal electrode, and a reference electrode. The sensor outputs a signal based on the potential difference between the signal electrode and the reference electrode.

[0007] After careful consideration, the inventors realized that if the member to which the sensor is attached contains a resin that easily becomes charged, the sensor may malfunction when the sensor is attached to the member so that the signal electrode is in close proximity to the member. For example, friction or the like occurs on the member, causing the member to become positively charged. The signal electrode may become negatively charged due to the influence of the charge on the member. In this case, the potential difference between the signal electrode and the reference electrode changes. As a result, the inventors realized that the sensor may output a signal indicating that the member is deformed even when the member is not deformed.

[0008] Based on the above considerations, the inventors of the present invention have studied a sensor module in which the sensor is less likely to malfunction, and as a result have come up with the following invention.

[0009] A sensor module according to one embodiment of the present invention comprises: an elastic member containing resin; a first sensor in contact with the elastic member and including an upper electrode, a piezoelectric film, and a lower electrode; and a switch, wherein the first sensor outputs a first signal corresponding to deformation of the elastic member, the switch has a function of short-circuiting the upper electrode and the lower electrode, and the lower electrode is a signal electrode.

[0010] In the following, X and Y are parts or members of the sensor module. In this specification, unless otherwise specified, each part of X is defined as follows: The front part of X means the front half of X. The rear part of X means the rear half of X. The left part of X means the left half of X. The right part of X means the right half of X. The upper part of X means the upper half of X. The lower part of X means the lower half of X. The front end of X means the front end of X. The rear end of X means the rear end of X. The left end of X means the left end of X. The right end of X means the right end of X. The upper end of X means the upper end of X. The lower end of X means the lower end of X. The front end of X means the front end of X and its vicinity. The rear end of X means the rear end of X and its vicinity. The left end of X means the left end of X and its vicinity. The right end of X means the right end of X and its vicinity. The upper end of X means the upper end of X and its vicinity. The lower end of X means the lower end of X and its vicinity.

[0011] Furthermore, "X is located above Y" means that X is located directly above Y. Therefore, when viewed in the vertical direction, X overlaps with Y. "X is located above Y" means that X is located directly above Y and that X is located diagonally above Y. Therefore, when viewed in the vertical direction, X may or may not overlap with Y. This definition also applies to directions other than the upward direction.

[0012] According to the sensor module according to one embodiment of the present invention, the sensor that detects deformation of a member is less likely to malfunction.

[0013] FIG. 1 is a perspective view showing the exterior of the sensor module 1. FIG. 2 is a diagram showing an example of connections between the first sensor 11, the switch 12, and the arithmetic circuit 13. FIG. 3 is a diagram showing the first sensor 11 viewed from below. FIG. 4 is a cross-sectional view taken along the line A-A in FIG. 3. FIG. 5 is a diagram showing an example of deformation of the piezoelectric film 111. FIG. 6 is a diagram showing an example of a first signal Sig1 generated when the elastic member 10 is charged. FIG. 7 is a diagram showing an example of a first signal Sig1 generated when the elastic member 10 is deformed so as to twist around the central axis CAX. FIG. 8 is a flowchart showing an example of processing P executed by the arithmetic circuit 13. FIG. 9 is a diagram showing the waveform of the first signal Sig1 when the arithmetic circuit 13 is executing processing P. FIG. 10 is a perspective view showing the exterior of a sensor module 1a according to Modification 1. FIG. 11 is a diagram showing an example of connections between the switch 12, the arithmetic circuit 13, and the second sensor 14a. FIG. 12 is a diagram showing the second sensor 14a. FIG. 13 is a diagram showing an example of processing executed by the arithmetic circuit 13b included in a sensor module 1b according to Modification 2. Fig. 14 is a block diagram showing an example of a sensor module 1c according to Modification 3. Fig. 15 is a block diagram showing an example of a sensor module 1d according to Modification 4.

[0014] First Embodiment A sensor module 1 according to a first embodiment of the present invention will now be described with reference to the drawings. FIG. 1 is a perspective view showing the appearance of the sensor module 1. FIG. 2 is a diagram showing an example of the connection between a first sensor 11, a switch 12, and an arithmetic circuit 13. FIG. 3 is a diagram showing the first sensor 11 viewed from below. FIG. 4 is a cross-sectional view taken along line A-A in FIG. 3. In FIG. 4, the bottom end, left end, and right end of the elastic member 10 are omitted. FIG. 5 is a diagram showing an example of deformation of a piezoelectric film 111.

[0015] In this embodiment, directions are defined as follows. As shown in FIG. 1 , the direction in which the sensor module 1 extends is defined as the left-right direction. The direction in which the elastic member 10 and the first sensor 11 are lined up is defined as the up-down direction. The direction in which the elastic member 10 and the first sensor 11 are lined up in this order is defined as the up direction. The direction in which the first sensor 11 and the elastic member 10 are lined up in this order is defined as the down direction. The direction perpendicular to the left-right direction and the up-down direction is defined as the front-rear direction. However, the left-right direction, the up-down direction, and the front-rear direction are directions defined for the purpose of explanation. Therefore, the left-right direction, the up-down direction, and the front-rear direction when the sensor module 1 is actually used do not necessarily match the front-rear direction, the up-down direction, and the left-right direction in this embodiment.

[0016] The sensor module 1 is used in, for example, a training device. As shown in Figures 1 and 2, the sensor module 1 includes an elastic member 10, a first sensor 11, a switch 12, and an arithmetic circuit 13.

[0017] The elastic member 10 includes a resin. The elastic member 10 includes, for example, an acrylic resin. As shown in FIG. 1 , the elastic member 10 is rod-shaped. Specifically, the elastic member 10 has a rod shape with a central axis CAX extending in the left-right direction. The elastic member 10 has elasticity. The elastic member 10 deforms around the central axis CAX. Specifically, a user grasps the left and right portions of the elastic member 10. For example, looking to the right, the user twists the left portion of the elastic member 10 clockwise around the central axis CAX. As a result, as shown in FIG. 1 , a circumferential force F1 is applied to the left portion of the elastic member 10. Also, looking to the right, the user twists the right portion of the elastic member 10 counterclockwise around the central axis CAX. As a result, as shown in FIG. 1 , a circumferential force F2 is applied to the right portion of the elastic member 10. As a result, the elastic member 10 deforms so as to twist around the central axis CAX.

[0018] The first sensor 11 has a rectangular shape with long sides extending in the left-right direction and short sides extending in the front-rear direction, as shown in Fig. 3. The first sensor 11 includes a piezoelectric film 111, an upper electrode 110, a lower electrode 112, and a detection circuit 113, as shown in Fig. 2.

[0019] 3 and 4, the piezoelectric film 111 has a sheet shape with long sides extending in the left-right direction and short sides extending in the front-rear direction. The piezoelectric film 111 has an upper main surface SF1 and a lower main surface SF2 aligned in the vertical direction. The upper main surface SF1 and the lower main surface SF2 are aligned in this order in the downward direction.

[0020] The piezoelectric film 111 generates electric charges according to the amount of deformation of the piezoelectric film 111. The piezoelectric film 111 has a characteristic that the polarity of the electric charges generated when the piezoelectric film 111 is stretched in a right-rear or left-front direction is opposite to the polarity of the electric charges generated when the piezoelectric film 111 is stretched in a right-front or left-rear direction. Specifically, the piezoelectric film 111 is a film formed from a chiral polymer. An example of a chiral polymer is polylactic acid (PLA), particularly poly-L-lactic acid (PLLA). PLLA has a helical main chain structure. PLLA has piezoelectric properties in which the molecules are oriented when uniaxially stretched. Therefore, the piezoelectric film 111 has piezoelectric properties. The piezoelectric film 111 has a piezoelectric constant of d14. As shown in FIGS. 3 and 5 , the uniaxial stretching direction OD of the piezoelectric film 111 forms an angle of 0 degrees or 180 degrees with respect to the left-right direction. This 0 degree angle includes, for example, an angle of approximately 0 degrees ±10 degrees. Similarly, this 180 degrees includes, for example, angles of approximately 180 degrees ±10 degrees. As a result, the piezoelectric film 111 generates an electric charge when the piezoelectric film 111 is stretched in the right-rear direction, the left-front direction, or the right-front or left-rear direction. For example, the piezoelectric film 111 generates a positive electric charge when stretched in the right-rear direction or the left-front direction. For example, the piezoelectric film 111 generates a negative electric charge when stretched in the right-front or left-rear direction. The magnitude of the electric charge depends on the amount of deformation of the piezoelectric film 111 due to the stretching or compression.

[0021] The upper electrode 110 is a reference electrode connected to a reference potential VE. For example, the upper electrode 110 is connected to a ground potential. The upper electrode 110 is fixed to the upper principal surface SF1 by an adhesive (not shown) such as OCA (Optical Clear Adhesive). Therefore, the upper electrode 110 is located on the piezoelectric film 111. The upper electrode 110 covers the upper principal surface SF1. The upper electrode 110 includes, for example, a PET film and an ITO layer. The ITO layer of the upper electrode 110 is in contact with the lower surface of the PET film of the upper electrode 110. The ITO layer of the upper electrode 110 covers the lower surface of the PET film of the upper electrode 110.

[0022] The lower electrode 112 is a signal electrode. The lower electrode 112 is fixed to the lower main surface SF2 by an adhesive (not shown) such as OCA. Therefore, the lower electrode 112 is located below the piezoelectric film 111. The lower electrode 112 covers the lower main surface SF2. The lower electrode 112 includes, for example, a PET film and an ITO layer. The ITO layer of the lower electrode 112 contacts the upper surface of the PET film of the lower electrode 112. The ITO layer of the upper electrode 110 covers the upper surface of the PET film of the upper electrode 110. The lower electrode 112 is in contact with the elastic member 10, as shown in FIGS. 1 and 4 . The elastic member 10 is located below the lower electrode 112.

[0023] 2, the detection circuit 113 is electrically connected to the upper electrode 110 and the lower electrode 112. The detection circuit 113 includes a voltage follower (not shown), an AD converter (not shown), etc. The voltage follower converts the charge generated by the piezoelectric film 111 into a voltage signal. The AD converter generates a digital signal by AD converting the voltage signal.

[0024] The first sensor 11 outputs a first signal Sig1 based on the potential difference between the upper electrode 110 and the lower electrode 112. The first sensor 11 outputs the first signal Sig1 in response to the deformation of the elastic member 10. As shown in FIG. 1 , the first sensor 11 is in contact with the elastic member 10. The first sensor 11 is in contact with the outer peripheral surface of the elastic member 10. The lower electrode 112 of the first sensor 11 is fixed to the outer peripheral surface of the elastic member 10 with an adhesive (not shown) such as OCA. This causes the first sensor 11 to deform in response to the deformation of the elastic member 10. The first sensor 11 outputs the first signal Sig1 in response to the deformation of the first sensor 11.

[0025] In this embodiment, the first sensor 11 detects deformation of the elastic member 10 around the central axis CAX. For example, when viewed to the right, a user twists the left portion of the elastic member 10 clockwise around the central axis CAX. At this time, the piezoelectric film 111 stretches in a left-front direction, as shown in FIG. 5 . Also, when viewed to the right, a user twists the right portion of the elastic member 10 counterclockwise around the central axis CAX. At this time, the piezoelectric film 111 stretches in a right-rear direction, as shown in FIG. 5 . Therefore, the piezoelectric film 111 generates a positive charge. As a result, the first sensor 11 outputs a first signal Sig1 having a positive polarity with respect to the reference potential VE.

[0026] The switch 12 has a function of short-circuiting the upper electrode 110 and the lower electrode 112. Specifically, the switch 12 is connected in parallel to the upper electrode 110 and the lower electrode 112. When the switch 12 is turned on, the upper electrode 110 is electrically connected to the lower electrode 112 via the switch 12. In other words, the switch 12 short-circuits the upper electrode 110 and the lower electrode 112. The switch 12 is, for example, a switching element such as a FET (Field Effect Transistor).

[0027] The arithmetic circuit 13 is, for example, a microcontroller including a CPU, ROM, and RAM. The arithmetic circuit 13 is electrically connected to the detection circuit 113 as shown in FIG. 2 . The arithmetic circuit 13 receives the first signal Sig1 from the detection circuit 113 at a predetermined sampling rate. For example, the arithmetic circuit 13 receives the first signal Sig1 from the detection circuit 113 at intervals of 50 msec. The arithmetic circuit 13 calculates the magnitude of the load applied to the elastic member 10 based on the first signal Sig1.

[0028] As shown in Fig. 2, the arithmetic circuit 13 is electrically connected to the switch 12. The arithmetic circuit 13 transmits to the switch 12 a signal related to an instruction to switch the switch 12 on / off. For example, if the switch 12 is an FET, the arithmetic circuit 13 transmits to the FET a signal related to an instruction to switch the gate of the FET on / off. The switch 12 switches the switch 12 on / off based on the signal received from the arithmetic circuit 13. The arithmetic circuit 13 transmits to the switch 12 a signal related to an instruction to turn on the switch 12, and then transmits to the switch 12 a signal related to an instruction to turn off the switch 12.

[0029] In this embodiment, when the arithmetic circuit 13 determines that the elastic member 10 is charged, it turns on the switch 12. The arithmetic circuit 13 determines whether or not the elastic member 10 is charged based on the first signal Sig1 received from the first sensor 11. Specifically, the arithmetic circuit 13 determines whether or not the elastic member 10 is charged by examining how the value of the first signal Sig1 attenuates.

[0030] The process of determining whether the elastic member 10 is charged (hereinafter referred to as process P) in the arithmetic circuit 13 will be described below with reference to the drawings. FIG. 6 is a diagram showing an example of the first signal Sig1 generated when the elastic member 10 is charged. FIG. 7 is a diagram showing an example of the first signal Sig1 generated when the elastic member 10 is deformed so as to twist around the central axis CAX. The horizontal axis in FIGS. 6 and 7 indicates time. The vertical axis in FIGS. 6 and 7 indicates the value of the first signal Sig1.

[0031] 6 and 7, the manner in which the value of the first signal Sig1 generated by deformation of the elastic member 10 attenuates differs from the manner in which the value of the first signal Sig1 generated by charging the elastic member 10. The value of the first signal Sig1 generated by charging the elastic member 10 attenuates based on the following Equation 1. On the other hand, the value of the first signal Sig1 generated by deformation of the elastic member 10 does not attenuate based on Equation 1.

[0032]

[0033] In Equation 1, Vt0 represents the value of the first signal Sig1 output from the first sensor 11 at a reference time. The reference time is the time when the arithmetic circuit 13 receives the first signal Sig1 from the first sensor 11. dt in Equation 1 represents a time before or after the reference time. a in Equation 1 represents the time constant in the sensor module 1 having an RC circuit. V(dt) in Equation 1 represents the value of the first signal Sig1 calculated based on Equation 1. For example, if Vt0 is 2.0 V, dt is 1 second later, and a is 3 seconds, V(dt) is approximately 1.4 V based on Equation 1.

[0034] The arithmetic circuit 13 determines whether the elastic member 10 is charged by comparing the calculation result obtained by Equation 1 with the value of the first signal Sig1. Specifically, as shown in Figures 6 and 7, the arithmetic circuit 13 calculates a calculated value MD indicating the manner of attenuation of the first signal Sig1 based on Equation 1. For example, as shown in Figure 6, the arithmetic circuit 13 obtains the calculated value MD by substituting the value of the first signal Sig1 at time p1 (reference time) into Equation 1.

[0035] The arithmetic circuit 13 determines whether the calculated value MD matches the value of the first signal Sig1. If the calculated value MD matches the value of the first signal Sig1, the arithmetic circuit 13 determines that the elastic member 10 is charged. In the example shown in FIG. 6, the calculated value MD matches the value of the first signal Sig1. Therefore, the arithmetic circuit 13 determines that the elastic member 10 is charged.

[0036] 7, the arithmetic circuit 13 obtains the calculated value MD by substituting the value of the first signal Sig1 at time q1 (reference time) into Equation 1. In the example shown in FIG. 7, the calculated value MD does not match the value of the first signal Sig1. Therefore, the arithmetic circuit 13 determines that the elastic member 10 is not charged.

[0037] The flow of the process P will be described below with reference to the drawings. Fig. 8 is a flowchart showing an example of the process P executed by the arithmetic circuit 13. Fig. 9 is a diagram showing the waveform of the first signal Sig1 when the arithmetic circuit 13 is executing the process P.

[0038] The arithmetic circuit 13 starts the process P when the power supply of the arithmetic circuit 13 is turned on (FIG. 8: START).

[0039] After the start, the calculation circuit 13 calculates the calculated value MD ( FIG. 8 : step S11). In this embodiment, as shown in FIG. 9 , the calculation circuit 13 calculates a calculated value MD1 indicating the value of the first signal Sig1 during a period PE1 after time u1 (reference time) based on the value of the first signal Sig1 at time u1. Specifically, the calculation circuit 13 calculates the calculated value MD1 during the period PE1 by substituting the value of the first signal Sig1 at time u1 into Equation 1. The period PE1 is the period between time u1 and time t1, which is after time u1. The length of the period PE1 is, for example, 2.5 seconds. In this case, the calculation circuit 13 calculates the calculated value MD1 indicating the value of the first signal Sig1 during the period from time u1 to time t1, which is 2.5 seconds later.

[0040] After step S11, the arithmetic circuit 13 compares the calculated value MD1 with the value of the first signal Sig1 that the arithmetic circuit 13 received from the first sensor 11 during the period PE1 ( FIG. 8 : step S12). Specifically, the arithmetic circuit 13 compares the calculated value MD1 with the value of the first signal Sig1 that the arithmetic circuit 13 received from the first sensor 11 during the period PE1 at a determination time that is later than the reference time. The determination time is the latest time during the period PE1. Therefore, the arithmetic circuit 13 executes the process of step S12 at time t1 (determination time).

[0041] In this embodiment, the arithmetic circuit 13 determines whether the value of the first signal Sig1 at each time point during the period PE1 is within a predetermined threshold value. The predetermined threshold value is, for example, within ±10% of the calculated value MD1. Therefore, the arithmetic circuit 13 determines whether the elastic member 10 is charged based on the calculated value MD1 and the value of the first signal Sig1 that the arithmetic circuit 13 receives from the first sensor 11 during the period PE1 (the period after the reference time).

[0042] The arithmetic circuit 13 continuously performs the processes of steps S11 and S12 a predetermined number of times (hereinafter referred to as the acquisition number) ( FIG. 8 : step S13). For example, the arithmetic circuit 13 continuously performs the processes of steps S11 and S12 10 times. For example, as shown in FIG. 9 , the arithmetic circuit 13 calculates the calculated value MD1, and then calculates the calculated value MD2 at time u2 (reference time) after time u1. As an example, if the sampling rate of the arithmetic circuit 13 is 50 msec, time u2 is 50 msec after time u1. The arithmetic circuit 13 calculates the calculated value MD2 based on the value of the first signal Sig1 at time u2. The calculated value MD2 indicates the value of the first signal Sig1 during a period PE2 between time u2 and time t2, which is after time u2. At time t2, the arithmetic circuit 13 compares the value of the first signal Sig1 received during period PE2 with the calculated value MD2. The arithmetic circuit 13 repeats the above process until the number of acquisitions reaches 10.

[0043] After step S13, the arithmetic circuit 13 detects the number of periods during which the value of the first signal Sig1 matches the calculated value MD (hereinafter referred to as the "count number") (FIG. 8: step S14). Specifically, the arithmetic circuit 13 detects the number of periods during which the value of the first signal Sig1 matches the calculated values ​​MD1 to MD10 in one cycle from period PE1 to period PE10. In the example shown in FIG. 9, the value of the first signal Sig1 does not match the calculated values ​​MD1 to MD10 in any of the periods from period PE1 to period PE10. In this case, the arithmetic circuit 13 calculates the "count number = 0."

[0044] If the count number is less than a predetermined number (hereinafter referred to as the determination number) (FIG. 8: step S15: No), the arithmetic circuit 13 determines that the elastic member 10 is not charged (FIG. 8: step S16). For example, if the count number is less than 7, the arithmetic circuit 13 determines that the elastic member 10 is not charged. In the example shown in FIG. 9, from period PE1 to period PE10, the arithmetic circuit 13 calculates "count number = 0". Therefore, the arithmetic circuit 13 determines that the elastic member 10 is not charged at time t10.

[0045] If the count is equal to or greater than a predetermined number (FIG. 8: step S15: Yes), the arithmetic circuit 13 determines that the elastic member 10 is charged (FIG. 8: step S17). For example, if the count is equal to or greater than 7, the arithmetic circuit 13 determines that the elastic member 10 is charged.

[0046] For example, as shown in FIG. 9 , the arithmetic circuit 13 determines whether the value of the first signal Sig1 matches the calculated values ​​MD15 to MD25 in one cycle from period PE15 to period PE25, similar to the one cycle from period PE1 to period PE10. Periods PE15 to PE25 are periods after period PE10. In the example shown in FIG. 9 , the value of the first signal Sig1 matches the calculated values ​​MD15 to MD25 in all periods from period PE15 to period PE25. Therefore, the arithmetic circuit 13 calculates the count as "10." In this case, the arithmetic circuit 13 determines that the elastic member 10 is charged at time t25 (determination time).

[0047] The arithmetic circuit 13 calculates the calculated value MD10 at a time that is the length of the period PE10 before the time t10. Similarly, the arithmetic circuit 13 calculates the calculated values ​​MD15 to MD25.

[0048] If the arithmetic circuit 13 determines that the elastic member 10 is charged, it turns on the switch 12 ( FIG. 8 : step S18). In the example shown in FIG. 9 , the arithmetic circuit 13 determines that the elastic member 10 is charged at time t25 (determination time). Therefore, the arithmetic circuit 13 turns on the switch 12 at time t25. In this case, the value of the first signal Sig1 at time t25 coincides with the reference potential VE.

[0049] The arithmetic circuit 13 repeats the processes of steps S11 to S18. For example, the arithmetic circuit 13 executes the processes of steps S11 to S18 every time the arithmetic circuit 13 receives the first signal Sig1 at a predetermined sampling interval from the first sensor 11. For example, the arithmetic circuit 13 executes process P, with one cycle consisting of periods PE1 to PE10, and then executes process P, with one cycle consisting of periods PE2 to PE11 (not shown).

[0050] The arithmetic circuit 13 ends the process P when, for example, the power supply to the arithmetic circuit 13 is turned off (FIG. 8: END).

[0051] (Effect) According to the sensor module 1, the first sensor 11 is less likely to malfunction. In this embodiment, the first sensor 11 is attached to the elastic member 10 so that the lower electrode 112, which is a signal electrode, is in close proximity to the elastic member 10. In this embodiment, the elastic member 10 is in contact with the lower electrode 112, which is a signal electrode, via an adhesive. The elastic member 10 contains a resin that is easily charged. The lower electrode 112 becomes charged, for example, due to the influence of the charge on the elastic member 10. In this case, the potential difference between the upper electrode 110 and the lower electrode 112 changes. As a result, the first sensor 11 may generate a first signal Sig1 having a negative or positive polarity with respect to the reference potential VE, even if the elastic member 10 is not deformed.

[0052] Therefore, the sensor module 1 according to this embodiment includes a switch 12 that has the function of short-circuiting the upper electrode 110 and the lower electrode 112. When the switch 12 is turned on, the potential difference between the upper electrode 110 and the lower electrode 112, which is generated by the charging of the elastic member 10, becomes zero. As a result, when the elastic member 10 is not deformed, the first sensor 11 does not output the first signal Sig1 having a positive or negative polarity with respect to the reference potential VE. In other words, the first sensor 11 is less likely to malfunction, outputting the first signal Sig1 indicating that the elastic member 10 is deformed, even though the elastic member 10 is not deformed.

[0053] In the sensor module 1, the arithmetic circuit 13 determines whether the elastic member 10 is charged based on the first signal Sig1. In this case, the arithmetic circuit 13 does not turn on the switch 12 when the elastic member 10 is not charged. Therefore, it is unlikely that the first sensor 11 will not detect deformation of the elastic member 10 due to the switch 12 being turned on unnecessarily.

[0054] The arithmetic circuit 13 determines whether the value of the first signal Sig1 matches the calculated value MD, for example, for one cycle from the period PE1 to the period PE10. Therefore, even if the first sensor 11 outputs an abnormal output value during one of the periods from the period PE1 to the period PE10, the arithmetic circuit 13 can accurately determine whether the elastic member 10 is charged.

[0055] For example, when the elastic member 10 is deformed, the first sensor 11 outputs a first signal Sig1. At this time, there is a possibility that the value of the first signal Sig1 output from the first sensor 11 matches the calculated value MD. In this embodiment, the arithmetic circuit 13 determines whether the value of the first signal Sig1 matches the calculated value MD, for example, with periods PE1 to PE10 being one cycle. This makes it less likely that the arithmetic circuit 13 will erroneously determine that the elastic member 10 is charged when the value of the first signal Sig1 output from the first sensor 11 momentarily matches the calculated value MD.

[0056] For example, the arithmetic circuit 13 determines whether or not the elastic member 10 is charged, with ten periods PE1 to PE10 constituting one cycle. In this case, the time required for the arithmetic circuit 13 to make this determination is, for example, 0.5 seconds (sampling rate (seconds) x 10 (times)). Therefore, the arithmetic circuit 13 can determine whether or not the elastic member 10 is charged in a short time.

[0057] [Modification 1] A sensor module 1a according to Modification 1 will now be described with reference to the drawings. Fig. 10 is a perspective view showing the appearance of the sensor module 1a according to Modification 1. Fig. 11 is a diagram showing an example of connections between the switch 12, the arithmetic circuit 13, and the second sensor 14a. Fig. 12 is a diagram showing the second sensor 14a.

[0058] The sensor module 1a differs from the sensor module 1 in that it further includes a second sensor 14a. As shown in Fig. 10, the second sensor 14a is in contact with the elastic member 10. The second sensor 14a is in contact with the outer circumferential surface of the elastic member 10. As shown in Fig. 11, the second sensor 14a includes a second sensor upper electrode 140, a film 141, a second sensor lower electrode 142, and a detection circuit 143.

[0059] In this modification, the second sensor 14a does not output a signal in response to deformation of the elastic member 10. As an example, the film 141 does not have piezoelectricity. The film 141 does not generate an electric charge in response to deformation of the elastic member 10. Such a film 141 is, for example, a PET film. As shown in FIG. 12 , the film 141 has an upper main surface SF1a and a lower main surface SF2a arranged in this order in the downward direction.

[0060] The second sensor upper electrode 140 is a reference electrode connected to a reference potential VE. The second sensor upper electrode 140 is fixed to the upper main surface SF1a with an adhesive (not shown) such as OCA. Therefore, the second sensor upper electrode 140 is located on the film 141.

[0061] The second sensor lower electrode 142 is a signal electrode. The second sensor lower electrode 142 is fixed to the lower main surface SF2a with an adhesive (not shown) such as OCA. The second sensor lower electrode 142 is located below the film 141.

[0062] 11, the detection circuit 143 is electrically connected to the second sensor upper electrode 140 and the second sensor lower electrode 142. The detection circuit 143 converts the charge generated by the film 141 into a voltage signal.

[0063] The second sensor 14a outputs a signal based on the potential difference between the second sensor upper electrode 140 and the second sensor lower electrode 142. The second sensor 14a outputs a signal (hereinafter referred to as the second signal) based on the charge of the elastic member 10. The second sensor lower electrode 142, which is a signal electrode, is in contact with the elastic member 10. The second sensor lower electrode 142 is charged by the influence of the charge of the elastic member 10. This changes the potential difference between the second sensor upper electrode 140 and the second sensor lower electrode 142.

[0064] In this modification, the arithmetic circuit 13 determines whether the elastic member 10 is charged based on the second signal. For example, the arithmetic circuit 13 compares the value of the second signal with a predetermined threshold. If the value of the second signal is equal to or greater than the predetermined threshold, the arithmetic circuit 13 determines that the elastic member 10 is charged. If the arithmetic circuit 13 determines that the elastic member 10 is charged, it turns on the switch 12.

[0065] (Effect) When the elastic member 10 is deformed, the second sensor 14a does not output the second signal. When the elastic member 10 is charged, the second sensor 14a outputs the second signal. The arithmetic circuit 13 determines whether the elastic member 10 is charged or not based on the second signal. This allows the arithmetic circuit 13 to reliably determine whether the signal is generated by the deformation of the elastic member 10 or the charge on the elastic member 10.

[0066] The program for the process of comparing the value of the second signal with the threshold value in this modification (hereinafter referred to as process Q) is simpler than the program for process P. Therefore, the load on the arithmetic circuit 13 when the arithmetic circuit 13 executes the program for process Q is smaller than the load on the arithmetic circuit 13 when the arithmetic circuit 13 executes the program for process P.

[0067] [Modification 2] A sensor module 1b (not shown) according to Modification 2 will now be described with reference to the drawings. FIG. 13 is a diagram showing an example of processing by the arithmetic circuit 13b provided in the sensor module 1b according to Modification 2. The horizontal axis in FIG. 13 represents time. The vertical axis in FIG. 13 represents the value of the first signal Sig1. In the example shown in FIG. 13, the arithmetic circuit 13b determines that the elastic member 10 is charged at time w1. In the example shown in FIG. 13, time w2 is a time after time w1.

[0068] The sensor module 1b differs from the sensor module 1 in that it includes an arithmetic circuit 13b that is different from the arithmetic circuit 13. When it is determined that the elastic member 10 is charged, the arithmetic circuit 13b further executes a process of offsetting the value of the first signal Sig1.

[0069] Specifically, the arithmetic circuit 13b determines whether the elastic member 10 is charged based on the first signal Sig1. In the example shown in FIG. 13 , the arithmetic circuit 13 determines that the elastic member 10 is charged at time w1. In this case, the arithmetic circuit 13b calculates a difference value DV between the reference potential VE and the value of the first signal Sig1 at time w1 (charging time) when it is determined that the elastic member 10 is charged. For example, if the value of the first signal Sig1 at time w1 is 2.0 V and the reference potential VE is 0 V, the difference value DV is 2.0 V.

[0070] The arithmetic circuit 13 calculates the value of the first signal Sig1 at a time after time w1 based on the difference value DV. Specifically, the arithmetic circuit 13 calculates the difference between the difference value DV and the value of the first signal Sig1 received from the detection circuit 113 at a time after time w1. The arithmetic circuit 13 estimates this difference as the value of the first signal Sig1. For example, at time w2, which is after time w1, the arithmetic circuit 13 receives the first signal Sig1 having a value of "2.0 V." In this case, the arithmetic circuit 13 estimates the value of the first signal Sig1 at time w2 to be "0 V" based on the "difference value: 2.0 V."

[0071] For example, when the arithmetic circuit 13b determines that the elastic member 10 has not been charged for a predetermined time, or when the sensor module 1b is restarted, the arithmetic circuit 13b turns on the switch 12. After turning on the switch 12, the arithmetic circuit 13b returns the reference to the value before the offset. In the example shown in FIG. 13 , the arithmetic circuit 13b returns the difference value DV from "2.0 V" to "0.0 V", for example. After returning the reference to the value before the offset, the arithmetic circuit 13b turns off the switch 12.

[0072] (Effect) If the elastic member 10 deforms while the switch 12 is on, the voltage generated in the first sensor 11 while the switch 12 is on is invalidated. Here, for example, when the elastic member 10 is deformed, the switch 12 is turned off. After the switch 12 is turned off, the value of the first signal Sig1 output from the first sensor 11 is offset by the invalid voltage. As a result, an error may occur in the value of the first signal Sig1 output from the first sensor 11 after the switch 12 is turned off. However, when the calculation circuit 13b determines that the elastic member 10 is charged, it calculates the value of the first signal Sig1 based on the difference value DV. In other words, the calculation circuit 13 calculates the value of the first signal Sig1 taking this error into account. As a result, the accuracy of detection of deformation of the elastic member 10 by the calculation circuit 13b is improved.

[0073] When the elastic member 10 is charged, the arithmetic circuit 13b does not turn on the switch 12. When the elastic member 10 is charged, the arithmetic circuit 13b calculates the first signal Sig1 based on the difference value DV. Therefore, the arithmetic circuit 13b can accurately detect the deformation of the elastic member 10 even when the elastic member 10 is charged.

[0074] [Modification 3] A sensor module 1c according to Modification 3 will now be described with reference to the drawings. Fig. 14 is a block diagram showing an example of a sensor module 1c according to Modification 3.

[0075] 14, the sensor module 1c differs from the sensor module 1 in that it further includes an LED 15 and a power button 16. The LED 15 and the power button 16 are electrically connected to the arithmetic circuit 13.

[0076] The LED 15 corresponds to the display device of the present invention that displays information according to the deformation of the elastic member 10. For example, the brightness of the LED 15 changes according to the deformation of the elastic member 10. For example, the arithmetic circuit 13 increases (brightens) the brightness of the LED 15 when the deformation of the elastic member 10 is large, and decreases (darkens) the brightness of the LED 15 when the deformation of the elastic member 10 is small.

[0077] The arithmetic circuit 13 may change the color of the LED 15 in addition to changing the brightness of the LED 15 in accordance with the deformation of the elastic member 10, or may change the number of lit LEDs if the LED 15 is configured with multiple LEDs. The arithmetic circuit 13 may also change the blinking speed of the LED in accordance with the deformation of the elastic member 10.

[0078] The sensor module 1c may include, for example, an organic EL display or a liquid crystal display instead of the LED 15. In this case, the organic EL display or the liquid crystal display displays, for example, the amount of deformation of the elastic member 10 as a numerical value as information corresponding to the deformation of the elastic member 10.

[0079] The power button 16 is an example of an interface in the present invention. The power button 16 receives an instruction from the user to turn on or off the power of the sensor module 1c. Pressing the power button 16 switches the power of the sensor module 1c on and off.

[0080] In this modification, when the arithmetic circuit 13 determines that the elastic member 10 is charged, it turns off the power to the sensor module 1c. When the power button 16 is pressed after the power to the sensor module 1c has been turned off, the power is turned on. When the power is turned on, the arithmetic circuit 13 turns on the switch 12.

[0081] If, for example, the elastic member 10 is charged while the user is twisting it and the switch 12 is turned on, the potential difference between the upper electrode 110 and the lower electrode 112 is reset to zero while the elastic member 10 is in a deformed state. Therefore, when the user releases the twisting operation and the elastic member 10 returns to its pre-deformation shape, the first sensor 11 may output a signal that detects the potential difference between the upper electrode 110 and the lower electrode 112 even though the elastic member 10 is not deformed.

[0082] When the power supply of the sensor module 1c is turned off, the LED 15 of the sensor module 1c goes out. This allows the user to recognize that the power supply of the sensor module 1c has been turned off. When the power supply is turned off, the user releases the twisting operation and presses the power button 16. When the power supply is turned on by the power button 16, the arithmetic circuit 13 turns on the switch 12 while the elastic member 10 is not deformed. When the elastic member 10 is not deformed, the potential difference between the upper electrode 110 and the lower electrode 112 is a potential difference due to charging, and turning on the switch 12 can reduce the potential difference to zero. Therefore, the first sensor 11 can more accurately detect the amount of deformation of the elastic member 10 even if charging occurs in the elastic member 10 when the user twists the elastic member 10.

[0083] [Modification 4] A sensor module 1d according to Modification 4 will now be described with reference to the drawings. Fig. 15 is a block diagram showing an example of a sensor module 1d according to Modification 4.

[0084] 15, the sensor module 1d differs from the sensor module 1c in that it further includes an alert LED 17. The alert LED 17 is electrically connected to the arithmetic circuit 13, as shown in FIG.

[0085] When the arithmetic circuit 13 determines that the elastic member 10 is charged, it turns on the alert LED 17 to notify the user that the elastic member 10 is charged. In other words, the alert LED 17 functions as an example of a notification means.

[0086] This allows the user to recognize that the elastic member 10 is charged. The user releases the twisting operation of the elastic member 10 and presses the power button 16. As a result, the power to the sensor module 1d is turned on while the elastic member 10 is not deformed. In addition, the arithmetic circuit 13 turns on the switch 12 when the power to the sensor module 1d is turned on. Therefore, similar to the sensor module 1c, when the elastic member 10 is not deformed, the potential difference between the upper electrode 110 and the lower electrode 112 is a potential difference due to charging, and turning on the switch 12 can make the potential difference zero. Therefore, the first sensor 11 can accurately detect the amount of deformation of the elastic member 10 even if charging occurs on the elastic member 10 while the user is twisting the elastic member 10.

[0087] The notification means in this application may be, for example, a speaker that has the function of emitting sound, or a vibrator that has the function of vibrating the sensor module.

[0088] Other Embodiments The sensor module according to the present invention is not limited to the sensor modules 1, 1a to 1d, and can be modified within the scope of the gist thereof. In addition, the configurations of the sensor modules 1, 1a to 1d may be combined in any manner.

[0089] The elastic member 10 does not necessarily have to be rod-shaped.

[0090] The elastic member 10 does not necessarily have to be cylindrical.

[0091] The switch 12 may include two FETs connected in series, which suppresses leakage current that occurs between the upper and lower electrodes of the sensor modules 1, 1a to 1d when the switch 12 is off, improving the accuracy with which the first sensor 11 detects deformation of the elastic member 10.

[0092] The sensor module 1 may be used in electronic devices such as smartphones.

[0093] The material of the elastic member 10 may be a resin other than acrylic resin.

[0094] The upper electrode 110 does not necessarily have to be connected to the ground potential.

[0095] The first sensor 11 does not necessarily have to be in contact with the outer peripheral surface of the elastic member 10. For example, the elastic member 10 has a cylindrical shape having an inner peripheral surface and an outer peripheral surface. In this case, the first sensor 11 may be in contact with the inner peripheral surface of the elastic member 10.

[0096] The process P for determining whether the elastic member 10 in the sensor module 1a is charged is an example. Therefore, the sensor module 1a does not necessarily need to determine whether the elastic member 10 is charged by the process P.

[0097] The arithmetic circuit 13 does not necessarily have to switch the switch 12 on / off based on the process P. For example, the arithmetic circuit 13 may transmit a signal to the switch 12 instructing it to turn on the switch 12 at predetermined intervals (e.g., once every 10 seconds).

[0098] If the second sensor 14a is configured not to output the second signal based on the torsional deformation of the elastic member 10, the film 141 may have piezoelectricity.

[0099] In the first embodiment, the conditions of the number of acquisitions, the number for judgment, and the count number can be adjusted. For example, in the first embodiment, the number of acquisitions does not necessarily have to be "10." For example, in the first embodiment, the number for judgment does not necessarily have to be "7."

[0100] In the first embodiment, the arithmetic circuit 13 may determine whether the elastic member 10 is charged based on the ratio (%) of the count number to the number of acquisitions. For example, the arithmetic circuit 13 may determine that the elastic member 10 is charged when the ratio of the count number to the number of acquisitions is 80% or more.

[0101] In the first embodiment, the arithmetic circuit 13 may determine that the elastic member 10 is not charged based on conditions other than the determination number and the count number.

[0102] The present invention has the following structure:

[0103] (1) A sensor module comprising: an elastic member containing resin; a first sensor in contact with the elastic member and including an upper electrode, a piezoelectric film, and a lower electrode; and a switch, wherein the first sensor outputs a first signal corresponding to deformation of the elastic member; the switch has a function of short-circuiting the upper electrode and the lower electrode; and the lower electrode is a signal electrode.

[0104] (2) The sensor module according to (1), wherein the upper electrode is a reference electrode connected to a reference potential.

[0105] (3) The sensor module according to (1) or (2), wherein the first sensor outputs the first signal based on a potential difference between the upper electrode and the lower electrode.

[0106] (4) The sensor module according to any one of (1) to (3), further comprising an arithmetic circuit, wherein the arithmetic circuit switches the switch on / off based on the first signal.

[0107] (5) The sensor module according to (4), wherein the arithmetic circuit determines whether the elastic member is charged based on the first signal received from the first sensor, and turns on the switch when it determines that the elastic member is charged.

[0108] (6) The sensor module according to (4), further comprising a power supply and an interface that receives an instruction to turn on the power supply, wherein the arithmetic circuit determines whether the elastic member is charged based on the first signal received from the first sensor, turns off the power supply if it determines that the elastic member is charged, and turns on the switch when the power supply is turned on via the interface after the power supply has been turned off.

[0109] (7) The sensor module according to (6), further comprising a display device that displays information according to the deformation of the elastic member, wherein the display on the display device is turned off when the power supply is turned off.

[0110] (8) The sensor module according to (4), further comprising a power source and a notification means for notifying that the elastic member is charged, wherein the arithmetic circuit determines whether the elastic member is charged based on the first signal received from the first sensor, notifies that the elastic member is charged via the notification means when it is determined that the elastic member is charged, and turns on the switch after the notification.

[0111] (9) A sensor module described in any of (5) to (8), wherein the arithmetic circuit calculates a calculated value indicating the value of the first signal in a period after the reference time based on the value of the first signal at a reference time when the arithmetic circuit receives the first signal from the first sensor, and determines whether the elastic member is charged or not based on the calculated value and the value of the first signal received by the arithmetic circuit from the first sensor in the period after the reference time.

[0112] (10) The sensor module according to any one of (1) to (3), further comprising an arithmetic circuit, which determines whether the elastic member is charged based on the first signal, and if it is determined that the elastic member is charged, calculates a difference value between a reference potential and the value of the first signal at the charging time when it is determined that the elastic member is charged, and calculates the value of the first signal at a time after the charging time based on the difference value.

[0113] (11) The sensor module according to any one of (1) to (3), further comprising a second sensor, the second sensor being in contact with the elastic member, the second sensor including a film, a second sensor upper electrode, and a second sensor lower electrode, and the second sensor outputs a second signal based on the charge of the elastic member.

[0114] (12) The sensor module according to (11), further comprising an arithmetic circuit, which determines whether the elastic member is charged based on the second signal, and turns on the switch when it determines that the elastic member is charged.

[0115] (13) The sensor module according to any one of (1) to (12), wherein the elastic member has a rod shape.

[0116] (14) The sensor module according to any one of (1) to (13), wherein the elastic member has a rod shape having a central axis extending in the left-right direction, the elastic member deforms around the central axis, and the first sensor detects the deformation of the elastic member around the central axis.

[0117] (15) The sensor module according to (14), wherein the elastic member deforms so as to twist around the central axis.

[0118] 1, 1a to 1d: Sensor module 10: Elastic member 11: First sensor 110: Upper electrode 111: Piezoelectric film 112: Lower electrode 12: Switch 13, 13b: Arithmetic circuit Sig1: First signal

Claims

1. An elastic member containing a resin; a first sensor in contact with the elastic member and including an upper electrode, a piezoelectric film, and a lower electrode; Switch, An arithmetic circuit; It is equipped with The first sensor outputs a first signal corresponding to the deformation of the elastic member, the switch has a function of short-circuiting the upper electrode and the lower electrode, the lower electrode is a signal electrode, The arithmetic circuit includes: switching the switch on / off based on the first signal; determining whether the elastic member is charged based on the first signal received from the first sensor; When it is determined that the elastic member is charged, the switch is turned on. Sensor module.

2. The upper electrode is a reference electrode connected to a reference potential. The sensor module according to claim 1 .

3. the first sensor outputs the first signal based on a potential difference between the upper electrode and the lower electrode. The sensor module according to claim 1 or 2.

4. the sensor module further includes a power supply and an interface that receives an instruction to turn on the power supply; The arithmetic circuit includes: When it is determined that the elastic member is charged, the power source is turned off; turning on the switch when the power supply is turned on via the interface after the power supply is turned off; The sensor module according to claim 1 or 2.

5. A display device that displays information according to the deformation of the elastic member is further provided. When the power supply is turned off, the display of the display device is turned off. The sensor module according to claim 4 .

6. The sensor module further includes a power source and a notification means for notifying that the elastic member is charged. The arithmetic circuit includes: When it is determined that the elastic member is charged, notifying the user through the notification means that the elastic member is charged; After the notification, the switch is turned on. The sensor module according to claim 1 or 2.

7. The arithmetic circuit includes: calculating a calculated value indicating a value of the first signal during a period after a reference time based on a value of the first signal at a reference time when the arithmetic circuit receives the first signal from the first sensor; determining whether or not the elastic member is charged based on the calculated value and a value of the first signal received by the arithmetic circuit from the first sensor during a period after the reference time; The sensor module according to claim 1 or 2.

8. The arithmetic circuit comprises: When it is determined that the elastic member is charged, a difference value between a reference potential and a value of the first signal at a charging time when it is determined that the elastic member is charged is calculated; calculating a value of the first signal at a time after the electrification time based on the difference value; The sensor module according to claim 1 or 2.

9. The sensor module further includes a second sensor, the second sensor is in contact with the elastic member, the second sensor includes a film, a second sensor upper electrode, and a second sensor lower electrode; The second sensor outputs a second signal based on the charge of the elastic member. The sensor module according to claim 1 or 2.

10. The arithmetic circuit comprises: determining whether the elastic member is charged based on the second signal; When it is determined that the elastic member is charged, the switch is turned on. The sensor module according to claim 9.

11. The elastic member is rod-shaped. The sensor module according to claim 1 or 2.

12. The elastic member has a rod shape having a central axis extending in the left-right direction, The elastic member deforms around the central axis, The first sensor detects deformation of the elastic member around the central axis. The sensor module according to claim 1 or 2.

13. The elastic member deforms so as to twist around the central axis. The sensor module according to claim 12.

14. An elastic member containing a resin; a first sensor in contact with the elastic member and including an upper electrode, a piezoelectric film, and a lower electrode; Switch, An arithmetic circuit; Power supply, an interface that receives an instruction to turn on the power; It is equipped with The first sensor outputs a first signal corresponding to the deformation of the elastic member, the switch has a function of short-circuiting the upper electrode and the lower electrode, the lower electrode is a signal electrode, The arithmetic circuit includes: switching the switch on / off based on the first signal; determining whether the elastic member is charged based on the first signal received from the first sensor; When it is determined that the elastic member is charged, the power source is turned off; turning on the switch when the power supply is turned on via the interface after the power supply is turned off; Sensor module.

15. An elastic member containing a resin; a first sensor in contact with the elastic member and including an upper electrode, a piezoelectric film, and a lower electrode; Switch, An arithmetic circuit; Power supply, a notification means for notifying the user that the elastic member is charged; It is equipped with The first sensor outputs a first signal corresponding to the deformation of the elastic member, the switch has a function of short-circuiting the upper electrode and the lower electrode, the lower electrode is a signal electrode, The arithmetic circuit includes: switching the switch on / off based on the first signal; determining whether the elastic member is charged based on the first signal received from the first sensor; When it is determined that the elastic member is charged, notifying the user through the notification means that the elastic member is charged; After the notification, the switch is turned on. Sensor module.

16. An elastic member containing a resin; a first sensor in contact with the elastic member and including an upper electrode, a piezoelectric film, and a lower electrode; Switch, An arithmetic circuit; It is equipped with The first sensor outputs a first signal corresponding to the deformation of the elastic member, the switch has a function of short-circuiting the upper electrode and the lower electrode, the lower electrode is a signal electrode, The arithmetic circuit includes: determining whether the elastic member is charged based on the first signal; When it is determined that the elastic member is charged, a difference value between a reference potential and a value of the first signal at a charging time when it is determined that the elastic member is charged is calculated; calculating a value of the first signal at a time after the electrification time based on the difference value; Sensor module.

17. An elastic member containing a resin; a first sensor in contact with the elastic member and including an upper electrode, a piezoelectric film, and a lower electrode; Switch, A second sensor in contact with the elastic member; It is equipped with The first sensor outputs a first signal corresponding to the deformation of the elastic member, the switch has a function of short-circuiting the upper electrode and the lower electrode, the lower electrode is a signal electrode, the second sensor includes a film, a second sensor upper electrode, and a second sensor lower electrode; The second sensor outputs a second signal based on the charge of the elastic member. Sensor module.