Sensor module

Abstract

This sensor module comprises a sensor that outputs a signal corresponding to deformation of an elastic member, and a computation circuit that receives the signal from the sensor. The computation circuit measures the length of time of a target period in which the signal strength is outside a range defined by threshold values, calculates a signal gradient on the basis of the length of at least one portion of the target period and the amount of variation in the signal in the at least one portion of the target period, and computes a stress value representing the stress applied to the elastic member on the basis of the gradient and the length of time of the target period.

Description

Technical Field

[0001] The present invention relates to an arithmetic circuit that calculates a stress value indicating the stress applied to a member, and a sensor module including the arithmetic circuit.

Background Art

[0002] Patent Document 1 describes a pressure distribution detection device that calculates the pressure applied to a member. The pressure distribution detection device includes a piezoelectric element and a data processing device. The data processing device calculates the pressure applied to the member based on the discharge time of the piezoelectric element.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the field of the pressure distribution detection device described in Patent Document 1, there is a desire to accurately identify the stress value indicating the stress applied to a member.

[0005] An object of the present invention is to provide a sensor module and an arithmetic circuit that can easily and accurately identify the stress value indicating the stress applied to a member.

Means for Solving the Problems

[0006] A sensor module according to an embodiment of the present invention includes a sensor that outputs a signal corresponding to the deformation of an elastic member, an arithmetic circuit that receives the signal from the sensor, and the arithmetic circuit measures the length of time of a target period in which the intensity of the signal exists outside a range defined by a threshold value, Calculate the slope of the signal based on the length of at least a part of the target period and the amount of change of the signal in at least a part of the target period. Calculate a stress value indicating the stress applied to the elastic member based on the length of the target period and the slope.

[0007] The arithmetic circuit according to an embodiment of the present invention Receives a signal having a value that increases and then decreases over time from a sensor that outputs a signal corresponding to the deformation of an elastic member. Calculate a stress value that changes when the slope of the signal changes in at least a part of the period during which the intensity of the signal is increasing, and that changes when the length of the period from when the intensity of the signal increases to when it decreases changes.

[0008] Hereinafter, X and Y are components or members of the sensor module. In this specification, "X is located above Y." means that X is located directly above Y. Therefore, when viewed in the vertical direction, X overlaps Y. "X is located above Y." means that X is located directly above Y and that X is located obliquely above Y. Therefore, when viewed in the vertical direction, X may or may not overlap Y. This definition also applies to directions other than the upward direction.

Advantages of the Invention

[0009] According to the sensor module or arithmetic circuit according to an embodiment of the present invention, it becomes easier to accurately specify the stress value indicating the stress applied to the member.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

[0011] [First Embodiment] Hereinafter, the sensor module 1 according to the first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a view of an electronic device EE provided with the sensor module 1 according to the first embodiment as seen in the right direction. FIG. 2 is a view of the elastic member 10 and the sensor 11 as seen in the upward direction. FIG. 3 is a cross-sectional view taken along line A-A in FIG. 2.

[0012] In this embodiment, the directions are defined as follows. As shown in FIG. 1, the direction in which the elastic member 10 and the sensor 11 are arranged side by side is defined as the vertical direction. The direction in which the elastic member 10 and the sensor 11 are arranged in this order is defined as the downward direction. The direction in which the sensor 11 and the elastic member 10 are arranged in this order is defined as the upward direction. As shown in FIG. 2, the direction parallel to the direction in which the long side of the elastic member 10 extends is defined as the front-rear direction. The direction orthogonal to the vertical direction and the front-rear direction is defined as the left-right direction. However, the vertical direction, the front-rear direction, and the left-right direction are directions defined for the purpose of explanation. Therefore, the vertical direction, the front-rear direction, and the left-right direction during actual use of the sensor module 1 do not necessarily have to coincide with the vertical direction, the front-rear direction, and the left-right direction in this embodiment. For example, the direction parallel to the direction in which the long side of the elastic member 10 extends may be defined as the left-right direction.

[0013] As shown in FIG. 1, the sensor module 1 is a module provided in an electronic device EE such as a smartphone. The sensor module 1 includes an elastic member 10, a sensor 11, and an arithmetic circuit 12.

[0014] As shown in FIGS. 1 and 2, the elastic member 10 has a plate shape having a long side extending in the front-rear direction and a short side extending in the left-right direction. The elastic member 10 has elasticity. The elastic member 10 deforms by the force applied to the elastic member 10. For example, as shown in FIG. 1, the user 200 pushes the elastic member 10 downward. The elastic member 10 deforms by the downward force applied to the elastic member 10. The elastic member 10 is a member having components such as a touch panel.

[0015] As shown in FIG. 2, the sensor 11 has a rectangular shape having a long side extending in the front-rear direction and a short side extending in the left-right direction. The length of the sensor 11 in the left-right direction is shorter than the length of the elastic member 10 in the left-right direction. The length of the sensor 11 in the front-rear direction is shorter than the length of the elastic member 10 in the front-rear direction. As shown in FIG. 3, the sensor 11 includes a piezoelectric film 111, an upper electrode 110, a lower electrode 112, and a detection circuit (not shown).

[0016] As shown in FIGS. 2 and 3, the piezoelectric film 111 has a sheet shape having a long side extending in the front-rear direction and a short side extending in the left-right direction. The piezoelectric film 111 has an upper main surface SF1 and a lower main surface SF2 arranged one above the other in the up-down direction. The upper main surface SF1 and the lower main surface SF2 are arranged in this order downward.

[0017] The piezoelectric film 111 generates charges according to the amount of deformation of the piezoelectric film 111. The polarity of the charges generated when the piezoelectric film 111 is stretched in the left-right direction is opposite to the polarity of the charges generated when the piezoelectric film 111 is stretched in the front-rear direction. Specifically, the piezoelectric film 111 is a film formed from a chiral polymer. The chiral polymer is, for example, polylactic acid (PLA), particularly L-type polylactic acid (PLLA). PLLA has a helical structure in the main chain. PLLA has piezoelectricity in which the molecules are oriented by uniaxial stretching. The piezoelectric film 111 has a piezoelectric constant of d14. As shown in FIG. 2, the uniaxial stretching direction OD of the piezoelectric film 111 forms an angle of 45 degrees with respect to the front-rear direction and the left-right direction. This 45 degrees includes an angle including, for example, about 45 degrees ± 10 degrees. Thereby, the piezoelectric film 111 generates charges when the piezoelectric film 111 is stretched in the front-rear direction or compressed in the left-right direction. The piezoelectric film 111 generates positive charges, for example, when stretched in the front-rear direction. The magnitude of the charges depends on the differential value of the amount of deformation of the piezoelectric film 111 due to stretching or compression.

[0018] The upper electrode 110 is a reference electrode connected to the reference potential. The upper electrode 110 is fixed to the upper main surface SF1 by an adhesive (not shown) such as OCA (Optically Clear Adhesive). The upper electrode 110 covers the upper main surface SF1.

[0019] 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. The lower electrode 112 covers the lower main surface SF2.

[0020] The detection circuit includes a charge amplifier (not shown), an AD converter (not shown), etc. The charge amplifier converts the charge generated by the piezoelectric film 111 into a voltage signal. The AD converter generates a digital signal by performing AD conversion on the voltage signal.

[0021] The sensor 11 outputs a signal Sig corresponding to the deformation of the elastic member 10. Specifically, the sensor 11 is provided near the center in the front-rear direction and the left-right direction of the elastic member 10. The sensor 11 is fixed to the lower main surface of the elastic member 10 by an adhesive (not shown). Thereby, the sensor 11 deforms as the elastic member 10 deforms. The sensor 11 outputs a signal Sig corresponding to the deformation of the sensor 11.

[0022] In the present embodiment, the value of the signal Sig depends on the differential value of the displacement amount of the sensor 11. Specifically, as the elastic member 10 deforms, the piezoelectric film 111 of the sensor 11 deforms. The magnitude of the charge generated by the piezoelectric film 111 depends on the differential value of the deformation amount of the piezoelectric film 111. The sensor 11 obtains the signal Sig by converting the charge generated by the piezoelectric film 111 into a digital signal. The signal Sig includes an electrical parameter that changes according to the deformation of the elastic member 10. In the present embodiment, the electrical parameter is a voltage value.

[0023] Next, an example of the signal Sig output from the sensor 11 in response to the deformation of the elastic member 10 will be described with reference to the drawings. FIG. 4 is a diagram showing an example of the signal Sig output from the sensor 11 when the elastic member 10 is deformed. The horizontal axis in FIG. 4 represents time. The vertical axis in FIG. 4 represents the value (intensity) of the signal Sig. In FIG. 4, the value of the signal Sig is a voltage value. In FIG. 4, the time t13 is a time after the time t10. The time s10 is a time after the time t13. The time s11 is a time after the time s10.

[0024] For example, in FIG. 4, the user 200 starts to push the front part of the elastic member 10 downward at time t10. At this time, the piezoelectric film 111 is stretched in the front-rear direction. In this case, the piezoelectric film 111 outputs a positive charge. Therefore, the sensor 11 outputs a signal Sig having a positive polarity with respect to the reference potential VE between time t10 and time t13 as shown in FIG. 4. In this case, the signal Sig has an intensity (value) that increases and then decreases with the passage of time. The user 200 stops pushing the elastic member 10 downward. At this time, the stretching of the piezoelectric film 111 stops. Therefore, as shown in FIG. 4, the intensity (value) of the signal Sig does not change between time t13 and time s10. Next, the user 200 releases the finger from the elastic member 10 at time s10. At this time, the sensor 11 tries to return to its shape before deformation due to the stress generated in the sensor 11. Due to this stress, the piezoelectric film 111 is compressed in the front-rear direction. In this case, the piezoelectric film 111 outputs a negative charge. Therefore, the sensor 11 outputs a signal Sig having a negative polarity with respect to the reference potential VE between time s10 and time s11 (period PEs) as shown in FIG. 4.

[0025] The arithmetic circuit 12 is, for example, a microcontroller including a CPU, a ROM, and a RAM. As shown in FIG. 1, the arithmetic circuit 12 is provided, for example, inside the electronic device EE. The arithmetic circuit 12 is electrically connected to the sensor 11 via, for example, a signal line (not shown). The arithmetic circuit 12 receives the signal Sig from the sensor 11. The arithmetic circuit 12 removes the noise included in the signal Sig. For example, the arithmetic circuit 12 includes a low-pass filter. The low-pass filter removes the noise included in the signal Sig. The low-pass filter is, for example, an RC circuit including a resistor and a capacitor.

[0026] The arithmetic circuit 12 calculates a stress value indicating the stress applied to the elastic member 10 based on the signal Sig. In the present embodiment, the arithmetic circuit 12 calculates the stress value based on the slope of the signal Sig and the length of the time period (hereinafter referred to as the target period) during which the intensity (value) of the signal Sig exists outside the range defined by the threshold value. Specifically, the arithmetic circuit 12 calculates the stress value based on the slope of the signal Sig and the length of the time period (hereinafter referred to as the increase / decrease period) from when the intensity (value) of the signal Sig increases until it decreases. For example, when the user 200 presses the elastic member 10, the intensity (value) of the signal Sig increases. In this case, the intensity (value) of the signal Sig exceeds an arbitrary threshold value and then falls below the threshold value. At this time, the increase / decrease period is the period from when the intensity (value) of the signal Sig exceeds the threshold value until it falls below the threshold value. In the present embodiment, the slope of the signal Sig is a value obtained by dividing the amount of change in the signal during at least a part (hereinafter referred to as the first period) of the period during which the intensity (value) of the signal Sig is increasing by the length of the first period. The increase / decrease period is, for example, between time t10 and time t13 as shown in FIG. 4.

[0027] Hereinafter, the process in which the arithmetic circuit 12 calculates the stress value (hereinafter referred to as process P) will be described with reference to the drawings. FIG. 5 is a graph showing the relationship between the stress value applied to the elastic member 10 and the slope of the signal Sig. FIG. 5 is a graph obtained by performing a plurality of experiments of pushing the elastic member 10 at a predetermined speed. The speed at which the elastic member 10 is pushed is different in each of the plurality of experiments. The horizontal axis in FIG. 5 indicates the slope of the signal Sig. The vertical axis in FIG. 5 indicates a value obtained by dividing the stress value by the length of the time period of increase and decrease (hereinafter referred to as the division value). The straight line ST1 in FIG. 5 is a regression line showing the relationship between the division value and the slope of the signal Sig.

[0028] As shown in FIG. 5, there is a correlation between the slope of the signal Sig and the division value. Specifically, as the slope of the signal Sig increases, the division value tends to increase. That is, the division value tends to be directly proportional to the slope of the signal Sig. Therefore, the following mathematical formula 1 holds. Also, from mathematical formula 1, mathematical formula 2 holds.

[0029]

Number

[0030]

Number

[0031] The coefficient is obtained by performing a plurality of experiments of pushing the elastic member 10 at a predetermined speed. The coefficient is the slope of the straight line ST1. The coefficient is, for example, about 4.7. For example, when the slope of the signal Sig is “0.002”, the length of the increase and decrease period is 200 msec, and the coefficient is 4.7, the stress value is “4.7 × 0.002 × 200 ≈ 1.88 (N)” based on mathematical formula 2.

[0032] From Equation 2, the stress value is directly proportional to the slope of the signal Sig. Therefore, the stress value changes when the slope of the signal Sig changes during the first period (at least a part of the period in which the intensity (value) of the signal Sig is increasing). Specifically, when the slope of the signal Sig increases, the stress value increases. When the slope of the signal Sig decreases, the stress value decreases.

[0033] From Equation 2, the stress value is directly proportional to the length of time of the increase / decrease period. Therefore, the stress value changes when the length of time of the increase / decrease period (the period from when the intensity (value) of the signal Sig increases to when it decreases) changes. Specifically, when the length of time of the increase / decrease period increases, the stress value increases. When the length of time of the increase / decrease period decreases, the stress value decreases.

[0034] From the above, the arithmetic circuit 12 can obtain the stress value by executing a process P that includes a process of calculating the slope of the signal Sig and a process of calculating the increase / decrease period. Hereinafter, a series of flows of the process P will be described with reference to the drawings. FIG. 6 is a flowchart showing an example of the process P executed by the arithmetic circuit 12. FIG. 7 is a diagram showing the value of the signal Sig in the vicinity of the time t10 shown in FIG. 4. Hereinafter, a case where the arithmetic circuit 12 executes the process P based on the voltage value will be described as an example.

[0035] The arithmetic circuit 12 starts the process P, for example, when the power supply of the arithmetic circuit 12 is turned on (FIG. 6: START).

[0036] After starting, the arithmetic circuit 12 calculates the reference potential VE (FIG. 6: step S10). Specifically, the arithmetic circuit 12 calculates the moving average of the voltage values. For example, the arithmetic circuit 12 calculates the moving average of the voltage values received in one second. In the examples shown in FIGS. 4 and 7, the arithmetic circuit 12 calculates a value of the reference potential VE = 1.6V.

[0037] Next, the arithmetic circuit 12 determines whether the intensity (value) of the signal Sig exists outside the range defined by the threshold Th1. In the present embodiment, the range defined by the threshold Th1 is between the reference potential VE and the threshold Th1 (see FIG. 4). The threshold Th1 is a value greater than the reference potential VE. The arithmetic circuit 12 determines whether the voltage value has exceeded the threshold Th1 (FIG. 6: step S11). In the example shown in FIG. 4, the threshold Th1 is 1.7V. In this case, the arithmetic circuit 12 determines whether the voltage value exceeds 1.7V. For example, the ROM of the arithmetic circuit 12 stores the threshold Th1.

[0038] When the arithmetic circuit 12 determines that the voltage value has exceeded the threshold Th1 (FIG. 6: step S11 Yes), it specifies the time when the voltage value exceeded the threshold Th1 (hereinafter referred to as the second time) (FIG. 6: step S12). The second time is a time after the time when the voltage value exceeded the reference potential VE (hereinafter referred to as the first time). In the examples shown in FIGS. 4 and 7, the voltage value exceeds the threshold Th1 at time t11. Therefore, the arithmetic circuit 12 specifies time t11 as the second time.

[0039] After step S12, the arithmetic circuit 12 calculates the slope of the signal Sig (FIG. 6: step S13). Specifically, the arithmetic circuit 12 calculates the slope of the signal Sig based on the length of at least a part of the target period and the amount of change in the signal Sig in at least a part of the target period. In the present embodiment, the arithmetic circuit 12 calculates the slope of the signal Sig based on the length of the first period (at least a part of the period in which the intensity (value) of the signal Sig is increasing) and the amount of change in the signal Sig in the first period. Specifically, the arithmetic circuit 12 calculates the slope by dividing the increase amount of the voltage value in the first period by the length of the first period.

[0040] For example, the arithmetic circuit 12 records the intensities (values) of the signal Sig at times t8, t9, and t10, which are times before time t11 (the second time). Time t9 is before time t10. Time t8 is before time t9. At this time, the arithmetic circuit 12 calculates the slope p8 of the signal Sig by dividing the increase amount of the signal Sig between time t8 and time t11 by the length of the time between time t8 and time t11. Similarly, the arithmetic circuit 12 calculates the slope p9 by dividing the increase amount of the signal Sig between time t9 and time t11 by the length of the time between time t9 and time t11. The arithmetic circuit 12 calculates the slope p10 by dividing the increase amount of the signal Sig between time t10 and time t11 by the length of the time between time t10 and time t11.

[0041] The arithmetic circuit 12 selects, as the slope of the signal Sig, the slope having the largest value among the slopes p8, p9, and p10. In the example shown in FIG. 7, among the slopes p8, p9, and p10, the slope p10 has the largest value. Therefore, the arithmetic circuit 12 selects the slope p10 as the slope of the signal Sig. In this case, as shown in FIG. 7, the first period is the period PE1 between time t10 (the first time) and time t11 (the second time). For example, in the example shown in FIG. 7, the increase amount of the voltage value in the period PE1 is 0.1V. For example, the length of the period PE1 is 100 msec. In this case, the arithmetic circuit 12 calculates the slope as "0.001".

[0042] After step S13, the arithmetic circuit 12 measures the length of the time of the target period. In the present embodiment, the arithmetic circuit 12 measures the length of the time of the increase / decrease period (the length of time from when the intensity (value) of the signal Sig increases until it decreases). In the present embodiment, the arithmetic circuit 12 measures the length of the time of the period (hereinafter referred to as the second period) from when the voltage value exceeds the threshold Th1 until it falls below the threshold Th1 (FIG. 6: step S14). In the example shown in FIG. 4, the voltage value is below the threshold Th1 at time t12 (the third time). Time t12 (the third time) is a time after time t11 (the second time). In this case, the second period is the period PEt between time t11 and time t12 (see FIG. 4). The arithmetic circuit 12 acquires the length of the time of the period PEt as the length of the time of the second period.

[0043] After step S14, the arithmetic circuit 12 calculates the stress value based on Equation 2 (FIG. 6: step S15). Specifically, the arithmetic circuit 12 calculates the stress value based on the length of the time of the target period and the slope of the signal Sig. In the present embodiment, the arithmetic circuit 12 calculates an integrated value by integrating the slope of the signal Sig with the length of the time of the period PEt (the length of the time of the second period). The arithmetic circuit 12 calculates the stress value based on the integrated value. More specifically, the arithmetic circuit 12 calculates the stress value by integrating a coefficient with the integrated value based on Equation 2. For example, when the slope is "0.001", the length of the time of the period PEt is "100 msec", and the coefficient is 4.7, the stress value is "0.001 × 100 × 4.7 ≈ 0.47 (N)" based on Equation 2.

[0044] In step S11, the arithmetic circuit 12 may determine that the voltage value does not exceed the threshold Th1 (Fig. 6: step S11 No). For example, when the voltage value has a negative polarity with respect to the reference potential VE, the voltage value does not exceed the threshold Th1. At this time, the arithmetic circuit 12 determines whether the voltage value is below the threshold Th2 (Fig. 6: step S16). The threshold Th2 is a value smaller than the reference potential VE. In the example shown in Fig. 4, the arithmetic circuit 12 calculates a value of the threshold Th2 = 1.5V. When the arithmetic circuit 12 determines that the voltage value is below the threshold Th2 (Fig. 6: step S16 Yes), it specifies the time when the voltage value drops below the threshold Th2 (Fig. 6: step S17).

[0045] After step S17, the arithmetic circuit 12 calculates the slope of the signal Sig in the same manner as the process of step S13 (Fig. 6: step S18). Specifically, the arithmetic circuit 12 calculates the slope of the signal Sig based on the length of at least a part of the period during which the intensity (value) of the signal Sig is decreasing and the amount of change in the signal Sig in at least a part of the period during which the intensity (value) of the signal Sig is decreasing. In this case, the slope of the signal Sig is negative.

[0046] After step S18, the arithmetic circuit 12 specifies the length of the period from when the voltage value drops below the threshold Th2 until it exceeds the threshold Th2 (Fig. 6: step S19). After step S19, the arithmetic circuit 12 calculates the stress value based on Equation 2. Specifically, the arithmetic circuit 12 calculates the stress value based on the length of the time from when the intensity (value) of the signal Sig decreases until it increases and the slope of the signal Sig.

[0047] In step S16, when the arithmetic circuit 12 determines that the voltage value is not below the threshold Th2 (Fig. 6: step S16 No), it does not execute the process of calculating the stress value.

[0048] The arithmetic circuit 12 repeats the processes from step S10 to step S19. For example, every time the arithmetic circuit 12 receives the signal Sig from the sensor 11 at a predetermined sampling interval, it executes the processes from step S10 to step S19 as one cycle.

[0049] The arithmetic circuit 12 ends the process P, for example, when the power supply of the arithmetic circuit 12 is turned off (Figure 6:END).

[0050] (Effect) According to the sensor module 1, it becomes easier to accurately identify the stress value applied to the elastic member 10. Hereinafter, the arithmetic circuit 12 and the arithmetic circuit according to Comparative Example 1 will be compared and described with reference to the drawings. Figure 8 is a diagram showing the relationship between the length of time in the second period and the stress value. Figure 8 is a graph obtained by conducting an experiment of pushing the elastic member 10 at a predetermined speed nine times. In Figure 8, the horizontal axis represents the length of time in the second period, and the vertical axis represents the stress value.

[0051] Figure 9 is a graph showing the relationship between the length of time in the second period and the stress value, and is a graph obtained by conducting an experiment of pushing the elastic member 10 at different speeds three times. In Figure 9, the horizontal axis represents the length of time in the second period, and the vertical axis represents the stress value. In Figure 9, the straight line L1 is a regression line showing the relationship between the length of time in the second period and the stress value when the elastic member 10 is pushed at a speed of 1 mm / sec. The straight line L2 is a regression line showing the relationship between the length of time in the second period and the stress value when the elastic member 10 is pushed at a speed of 3 mm / sec. The straight line L3 is a regression line showing the relationship between the length of time in the second period and the stress value when the elastic member 10 is pushed at a speed of 6 mm / sec.

[0052] The arithmetic circuit according to Comparative Example 1 differs only in the method of calculating the stress value as compared with the first embodiment. Specifically, the arithmetic circuit according to Comparative Example 1 calculates the stress value by integrating the first coefficient with the length of time in the second period. Specifically, as shown in FIG. 8, the stress value is directly proportional to the length of time in the second period. Therefore, the arithmetic circuit according to Comparative Example 1 calculates the stress value based on the mathematical formula "stress value ≈ first coefficient × length of time in the second period".

[0053] However, as shown in FIG. 9, the slopes of the straight lines L1, L2, and L3 are different. Therefore, the value of the first coefficient varies according to the speed at which the elastic member 10 is pushed. For this reason, the arithmetic circuit according to Comparative Example 1 needs to calculate the stress value based on the value of the first coefficient corresponding to the speed at which the elastic member 10 is pushed. When the arithmetic circuit according to Comparative Example 1 calculates the stress value based on a value (first coefficient) that does not correspond to the speed at which the elastic member 10 is pushed, the stress value calculated by the arithmetic circuit according to Comparative Example 1 becomes an incorrect value. Therefore, the sensor module including the arithmetic circuit according to Comparative Example 1 may not be able to accurately identify the stress value applied to the elastic member.

[0054] On the other hand, in the sensor module 1, the arithmetic circuit 12 calculates the stress value in consideration of the speed at which the elastic member 10 is pushed. Specifically, when the elastic member 10 is pushed by the user 200, the arithmetic circuit 12 calculates the slope of the signal Sig. The slope of the signal Sig changes based on the speed at which the elastic member 10 is pushed. For this reason, the arithmetic circuit 12 can calculate the stress value applied to the elastic member 10 based on the slope of the signal Sig corresponding to the speed at which the elastic member 10 is pushed. Therefore, in the sensor module 1, an event does not occur in which the arithmetic circuit 12 calculates an incorrect stress value by using a value (first coefficient) that does not correspond to the speed at which the elastic member 10 is pushed. As a result, the sensor module 1 can easily and accurately identify the stress value applied to the elastic member 10.

[0055] According to the sensor module 1, the arithmetic circuit 12 can easily and accurately identify the stress value applied to the elastic member 10. Hereinafter, the arithmetic circuit 12 and the arithmetic circuit according to Comparative Example 2 will be compared and described with reference to the drawings.

[0056] FIG. 10 is a diagram showing the case where the sensor 11 outputs a signal Sig having a value exceeding the measurement range of the sensor 11. In FIG. 10, the horizontal axis represents time, and the vertical axis represents the value of the signal Sig. The time u1 in FIG. 10 is the time when the value of the signal Sig exceeds the measurement range of the sensor 11. The time u2 is the time when the value of the signal Sig falls below the measurement range of the sensor 11. In the example shown in FIG. 10, the upper limit UL of the measurement range of the sensor 11 is 3.0V.

[0057] Similarly for Comparative Example 2, the arithmetic circuit according to Comparative Example 2 differs only in the method of calculating the stress value as compared with the first embodiment. Specifically, the arithmetic circuit according to Comparative Example 2 calculates the stress value by integrating the value of the signal Sig received from the sensor 11. Here, there may be a case where the elastic member 10 deforms beyond the deformation amount measurable by the sensor 11. In the example shown in FIG. 10, between the time u1 and the time u2, the elastic member 10 deforms beyond the deformation amount measurable by the sensor 11. In this case, the sensor 11 does not output a signal Sig having a value exceeding the upper limit UL between the time u1 and the time u2. For example, the sensor 11 outputs the value of the signal Sig between the time u1 and the time u2 as 3.0V, which is the upper limit UL. At this time, the arithmetic circuit according to Comparative Example 2 performs an integration process for calculating the stress value with the value of the signal Sig between the time u1 and the time u2 being 3.0V. In this case, the stress value obtained by the calculation of the arithmetic circuit according to Comparative Example 2 becomes lower than the stress value indicating the stress applied to the elastic member 10. Therefore, the arithmetic circuit according to Comparative Example 2 may not be able to accurately identify the stress value applied to the elastic member 10.

[0058] On the other hand, the arithmetic circuit 12 calculates a stress value based on the slope of the signal Sig and the length of the second period (the length of the period from when the voltage value exceeds the threshold Th1 until it falls below the threshold Th1). In this case, the arithmetic circuit 12 does not calculate the stress value based on the value of the signal Sig obtained between the time u1 and the time u2 shown in FIG. 10. Therefore, even when the sensor 11 outputs a signal Sig having a value exceeding the upper limit UL, the arithmetic circuit 12 can accurately identify the stress value. That is, the sensor module 1 including the arithmetic circuit 12 can easily and accurately identify the stress value indicating the stress applied to the elastic member 10.

[0059] [Modification Example 1] Hereinafter, the sensor module 1a according to Modification Example 1 will be described with reference to the drawings. FIG. 11 is a flowchart showing an example of the process Q executed by the arithmetic circuit 12a provided in the sensor module 1a according to Modification Example 1. FIG. 12 is a diagram showing a case where noise occurs in the signal Sig between the time t14 and the time t15. The time t15 is a time after the time t14.

[0060] The sensor module 1a is different from the sensor module 1 in that it includes an arithmetic circuit 12a instead of the arithmetic circuit 12. As shown in FIG. 11, the arithmetic circuit 12a executes a process Q different from the process P. Since the processes from step S10 to step S19 in the process Q are the same as the processes from step S10 to step S19 in the process P, the description thereof is omitted.

[0061] In the process Q, after the process of step S14, the arithmetic circuit 12a determines whether the length of the second period (the period from when the voltage value exceeds the threshold Th1 until it falls below the threshold Th1) is equal to or greater than the threshold Th3 (FIG. 11: step S20). The threshold Th3 is, for example, 30 msec. In the example shown in FIG. 12, the arithmetic circuit 12a determines whether the length of the period PEt (the second period) is equal to or greater than the threshold Th3.

[0062] When the arithmetic circuit 12a determines that the length of the second period is equal to or greater than the threshold value Th3 (Fig. 11: step S20 Yes), it executes step S15. In the example shown in Fig. 12, the length of the period PEt is equal to or greater than the threshold value Th3. In this case, the arithmetic circuit 12a calculates the stress value in the period PEt.

[0063] On the other hand, when the arithmetic circuit 12 determines that the length of the second period is less than the threshold value Th3 (Fig. 11: step S20 No), it does not execute step S15. In the example shown in Fig. 12, between time t14 and time t15, after the voltage value exceeds the threshold value Th1 and then falls below the threshold value Th1. Therefore, the arithmetic circuit 12a determines whether the length of the time between time t14 and time t15 is equal to or greater than the threshold value Th3. The length between time t14 and time t15 is less than the threshold value Th3. For this reason, the arithmetic circuit 12a does not calculate the stress value between time t14 and time t15.

[0064] Similarly, in process Q, after step S19, the arithmetic circuit 12a determines whether the length of the time from when the voltage value falls below the threshold value Th2 to when it exceeds the threshold value Th2 is equal to or greater than the threshold value Th3 (Fig. 11: step S20).

[0065] (Effect) According to the sensor module 1a, the possibility of misjudgment by the arithmetic circuit 12a can be reduced. For example, between time t14 and time t15, the user 200 misoperates the sensor module 1a. The misoperation is, for example, an operation such as the user 200 placing the user 200's hand on the elastic member 10. In this case, as shown in Fig. 12, between time t14 and time t15, the voltage value may exceed the threshold value Th1. For this reason, an arithmetic circuit that does not execute the process of step S20 (hereinafter referred to as the arithmetic circuit according to Comparative Example 2) may erroneously determine that a pressing operation has been performed by the user 200 between time t14 and time t15.

[0066] On the other hand, by executing step S20, the arithmetic circuit 12a determines whether or not a pressing operation has been performed by the user 200. The threshold Th3 is, for example, a time shorter than the time required for the user 200 to perform a pressing operation. Thereby, for example, when the length of the time in the second period is less than the threshold Th3, the arithmetic circuit 12a can determine that the signal Sig has been generated due to a misoperation by the user 200. As a result, it becomes difficult for the arithmetic circuit 12a to erroneously determine a misoperation by the user 200 as a pressing operation by the user 200.

[0067] According to the sensor module 1a, it becomes easier for the arithmetic circuit 12a to calculate the stress value. For example, when the difference between the threshold Th1 and the reference potential VE is small, the voltage value generated by noise is likely to exceed the threshold Th1. For this reason, the arithmetic circuit according to Comparative Example 2 may erroneously determine that a pressing operation has been performed by the user 200 when no pressing operation has been performed by the user 200.

[0068] On the other hand, even if the voltage value exceeds the threshold Th1, when the length of the time in the second period is less than the threshold Th3, the arithmetic circuit 12a determines that no pressing operation has been performed by the user 200. For this reason, even if the threshold Th1 is a small value, it becomes difficult for the arithmetic circuit 12a to make an erroneous determination. That is, the value of the threshold Th1 can be made small. For this reason, the arithmetic circuit 12a can calculate the stress value even when the force applied to the elastic member 10 by the user 200 is small.

[0069] [Modification Example 2] Hereinafter, the sensor module 1b according to Modification Example 2 will be described with reference to the drawings. FIG. 13 is a diagram showing the sensor module 1b according to Modification Example 2.

[0070] The sensor module 1b is different from the sensor module 1 in that it includes two or more sensors. In the example shown in FIG. 13, the sensor module 1b includes sensors 11a, 11b, and 11c in addition to the sensor 11.

[0071] In this modification example, the sensor 11 is provided, for example, at the right end portion of the elastic member 10 (see FIG. 13). The sensor 11a is provided at the left end portion of the elastic member 10. The sensor 11b is provided at the rear end portion of the elastic member 10. The sensor 11c is provided at the front end portion of the elastic member 10. Since the other configurations of the sensors 11a, 11b, and 11c are the same as the configuration of the sensor 11, the description thereof is omitted.

[0072] In this modification example, the arithmetic circuit 12 calculates the load applied to the elastic member 10 based on the signals Sig output from each of the sensors 11, 11a, 11b, and 11c. In this modification example, the arithmetic circuit 12 can calculate the load applied to the elastic member 10 with high precision. Hereinafter, description will be made with reference to the drawings. FIG. 14 is a table Tb showing an example of the load value calculated by the arithmetic circuit 12 in the sensor module 1b. For example, nine regions Ar1 to Sr9 are defined on the elastic member 10. The sizes of the regions Ar1 to Ar9 are the same. FIG. 14 is obtained by conducting an experiment (hereinafter referred to as experiment Z) in which each of the regions Ar1 to Ar9 in the elastic member 10 is pushed with a load of 150 g.

[0073] In the example shown in FIG. 14, when the region Ar2 is pushed with a load of 150 g, the arithmetic circuit 12 estimates the load applied to the elastic member 10 as 161 g. The load of 161 g is the largest estimated load (hereinafter referred to as the maximum estimated load) among the estimated loads obtained in the experiment Z. In the example shown in FIG. 14, when the region Ar6 is pushed, the arithmetic circuit 12 calculates the load applied to the elastic member 10 as 143 g. The load of 143 g is the smallest estimated load (hereinafter referred to as the minimum estimated load) among the estimated loads obtained in the experiment Z. Here, a value obtained by integrating 100 with the value obtained by dividing the minimum estimated load by the maximum estimated load is defined as the in-plane distribution. At this time, the in-plane distribution in the example shown in FIG. 14 is "143 / 161×100≈89%". The arithmetic circuit 12 can calculate the load applied to the elastic member 10 while maintaining a high accuracy of the in-plane distribution of 89%.

[0074] [Other Embodiments] The sensor module according to the present invention is not limited to sensor module 1 and can be modified within the scope of its gist.

[0075] Note that the elastic member 10 does not necessarily have to be plate-shaped. The elastic member 10 may be, for example, rod-shaped.

[0076] Note that the electronic device EE does not necessarily have to be a smartphone. The electronic device EE can be any device as long as it is a device on which a pressing operation is performed by the user 200. The electronic device EE may be a tablet, TWS (True Wireless Stereo), etc. That is, regardless of the housing structure of the electronic device EE, the sensor 11 can be attached to the elastic member 10. Thereby, the arithmetic circuits 12, 12a can calculate the stress value regardless of the housing structure of the electronic device EE.

[0077] Note that the sensor module 1 may include two or three sensors. Note that the sensor module 1 may include five or more sensors.

[0078] Note that the elastic member 10 may be square-shaped.

[0079] Note that the electrical parameter included in the signal Sig does not necessarily have to be a voltage value. For example, the electrical parameter included in the signal Sig may be a current value.

[0080] Note that the uniaxial stretching direction OD does not necessarily have to form an angle of 45 degrees with respect to the front-rear direction and the left-right direction. For example, the uniaxial stretching direction OD may form an angle of 0 degrees with respect to the front-rear direction.

[0081] Note that when the arithmetic circuit 12 acquires a signal Sig having a negative polarity with respect to the reference potential VE, the waveform of the signal Sig may be inverted with respect to the reference potential VE. In this case, the intensity (value) of the signal Sig has a positive polarity with respect to the reference potential VE. Therefore, the arithmetic circuit 12 can calculate the stress value by executing the processes from step S10 to step S15.

[0082] Note that the arithmetic circuit 12 repeatedly executes the processing of one cycle from step S10 to step S19. At this time, the arithmetic circuit 12 adds the stress values acquired in each cycle. Thereby, the arithmetic circuit 12 calculates the stress value at the time when the process P is executed. For example, as shown in FIG. 4, the arithmetic circuit 12 calculates a stress value of 1.4 N (hereinafter referred to as the first stress value) in one cycle from time t10 to time t12. Next, the arithmetic circuit 12 calculates, for example, a stress value of -1.4 N (hereinafter referred to as the second stress value) in one cycle from time s10 to time s11. In this case, the value obtained by adding the second stress value to the first stress value is 0. Therefore, the arithmetic circuit 12 can determine that no force is applied to the elastic member 10 at time s11.

[0083] Note that the arithmetic circuit 12 may transmit a signal (hereinafter referred to as the first signal) corresponding to the calculated stress value to a device other than the arithmetic circuit 12. In this case, the value of the first signal depends on the slope of the signal Sig or the length of the second period. Therefore, when the slope of the signal Sig changes, the intensity (value) of the first signal changes. When the length of the second period changes, the intensity (value) of the first signal changes. Therefore, it is considered that a processing device that outputs the first signal having an intensity (value) that changes with the change of the signal Sig and having an intensity (value) that changes with the change of the length of the second period is executing the processing related to the arithmetic circuit 12.

[0084] Incidentally, the sensor module 1 may include a display for displaying the stress value. The display is, for example, an organic EL display or the like. In this case, when the slope of the signal Sig or the length of the second period changes, the stress value displayed on the display changes. Therefore, it is considered that a processing device (such as a smartphone) including a display that displays a stress value that changes with a change in the slope of the signal Sig and also displays a stress value that changes with a change in the length of the second period is executing the processing related to the arithmetic circuit 12.

[0085] Incidentally, the value of the signal Sig does not necessarily depend on the differential value of the displacement amount of the sensor 11. For example, depending on the frequency of the input signal, there may be a component that does not depend on the differential value.

[0086] The present invention has the following structure.

[0087] (1) A sensor that outputs a signal corresponding to the deformation of an elastic member, An arithmetic circuit that receives the signal from the sensor, and is provided with The arithmetic circuit measures the length of a target period in which the intensity of the signal exists outside a range defined by a threshold value, calculates the slope of the signal based on the length of at least a part of the target period and the amount of variation of the signal in at least a part of the target period, calculates a stress value indicating the stress applied to the elastic member based on the length of the target period and the slope, Sensor module.

[0088] (2) The arithmetic circuit measures the length of a period from when the intensity of the signal increases to when it decreases, calculates the slope based on the length of at least a part of the period in which the intensity of the signal is increasing and the amount of variation of the signal in at least a part of the period in which the intensity of the signal is increasing, Calculate a stress value indicating the stress applied to the elastic member based on the length of the period from when the intensity of the signal increases until it decreases and the slope. The sensor module according to (1).

[0089] (3) The arithmetic circuit Measures the length of the period from when the intensity of the signal decreases until it increases, Calculates the slope based on the length of at least a part of the period during which the intensity of the signal is decreasing and the amount of change in the signal in at least a part of the period during which the intensity of the signal is decreasing, Calculates a stress value indicating the stress applied to the elastic member based on the length of the period from when the intensity of the signal decreases until it increases and the slope. The sensor module according to (1) or (2).

[0090] (4) When the slope increases, the stress value increases, When the slope decreases, the stress value decreases. The sensor module according to any one of (1) to (3).

[0091] (5) The signal includes an electrical parameter that changes in response to the deformation of the elastic member. The sensor module according to any one of (1) to (3).

[0092] (6) The electrical parameter is a voltage value. The sensor module according to (5).

[0093] (7) The first time is the time when the voltage value exceeds the reference potential, The threshold value is a value greater than the reference potential, The second time is a time after the first time and is the time when the voltage value exceeds the threshold value, The third time is a time after the second time and is a time when the voltage value falls below the threshold value. The first period is a period between the first time and the second time. The second period is a period between the second time and the third time. The arithmetic circuit calculates the slope by dividing an increase amount of the voltage value in the first period by a length of time of the first period, and calculates the stress value based on an integrated value obtained by integrating the length of time of the second period with the slope. The sensor module according to (6).

[0094] (8) The arithmetic circuit calculates the stress value by integrating a coefficient with the integrated value. The sensor module according to (7).

[0095] (9) Receives a signal having a value that increases and then decreases over time from a sensor that outputs a signal corresponding to deformation of an elastic member, and calculates a stress value that changes when a slope of the signal changes in at least a part of a period during which the intensity of the signal increases, and that changes when a length of time of a period from when the intensity of the signal increases to when it decreases changes. Arithmetic circuit.

Explanation of Signs

[0096] 1, 1a, 1b: Sensor module 10: Elastic member 11, 11a, 11b, 11c: Sensor 12, 12a: Arithmetic circuit PE1, PEs, PEt: Period Sig: Signal Th1, Th2, Th3: Threshold value VE: Reference potential

Claims

1. A sensor that outputs a signal corresponding to the deformation of an elastic member, An arithmetic circuit that receives the signal from the sensor, and is provided with, The arithmetic circuit, measures the length of time of a target period in which the intensity of the signal exists outside the range defined by a threshold value, calculates the slope of the signal based on the length of time of at least a part of the target period and the amount of variation of the signal in at least a part of the target period, calculates a stress value indicating the stress applied to the elastic member based on the length of time of the target period and the slope, A sensor module.

2. The arithmetic circuit, measures the length of time of a period from when the intensity of the signal increases until it decreases, calculates the slope based on the length of time of at least a part of the period in which the intensity of the signal is increasing and the amount of variation of the signal in at least a part of the period in which the intensity of the signal is increasing, calculates a stress value indicating the stress applied to the elastic member based on the length of time of the period from when the intensity of the signal increases until it decreases and the slope, The sensor module according to Claim 1.

3. The arithmetic circuit, measures the length of time of a period from when the intensity of the signal decreases until it increases, calculates the slope based on the length of time of at least a part of the period in which the intensity of the signal is decreasing and the amount of variation of the signal in at least a part of the period in which the intensity of the signal is decreasing, calculates a stress value indicating the stress applied to the elastic member based on the length of time of the period from when the intensity of the signal decreases until it increases and the slope, The sensor module according to Claim 1 or Claim 2.

4. When the inclination increases, the stress value increases, When the inclination decreases, the stress value decreases, The sensor module according to claim 1 or claim 2.

5. The signal includes an electrical parameter that changes in response to the deformation of the elastic member. The sensor module according to claim 1 or claim 2.

6. The electrical parameter is a voltage value. The sensor module according to claim 5.

7. The first time is the time when the voltage value exceeds the reference potential, The threshold value is a value greater than the reference potential, The second time is a time after the first time and is the time when the voltage value exceeds the threshold value, The third time is a time after the second time and is the time when the voltage value falls below the threshold value, The first period is the period between the first time and the second time, The second period is the period between the second time and the third time, The arithmetic circuit, calculates the inclination by dividing the increase amount of the voltage value in the first period by the length of time of the first period, calculates the stress value based on the integrated value obtained by integrating the inclination with the length of time of the second period. The sensor module according to claim 6.

8. The arithmetic circuit calculates the stress value by integrating a coefficient with the integrated value. The sensor module according to claim 7.

Images