JP6970328B2 - One-point contact hardness measuring device and method - Google Patents

Description

The present invention relates to a one-point contact hardness measuring device and method.

The present inventor has been conducting research and development on a technique for measuring various characteristics such as hardness and ripeness of a fruit based on its vibration, and has proposed many techniques (for example, Patent Documents 1 to 1). 5).

Patent Documents 1, 4 and 5 disclose a measuring device for measuring the characteristics of a fruit by using a laser Doppler method. In these devices, a vibration device is used to apply vibrations in the frequency range of 0 to 2 kHz to the lower side of the fruit, irradiate with laser light, and measure the vibration on the upper side of the fruit.

Patent Documents 2 and 3 disclose an apparatus for measuring the characteristics of a fruit by holding and vibrating the fruit at two points. In these devices, the measurement is performed with both the vibration source and the vibration sensor pressed against the fruit. The second resonance frequency f ₂ is obtained by calculation from the measurement result, and the hardness index of the fruit is calculated using the formula [m ^2/3 × f ₂ ^{2 (m: weight of fruit)].}

Japanese Patent No. 3062071 Japanese Patent No. 3927996 JP-A-2015-28445 Japanese Patent No. 4696218 Japanese Patent No. 4899049

In the apparatus disclosed in Patent Documents 2 and 3, when measuring the hardness and ripeness of a fruit, it is necessary to sandwich the fruit by two-point contact. This work was complicated and the work time was increased.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hardness measuring device and a method capable of easily measuring the hardness of a fruit.

In order to achieve the above object, the hardness measuring device according to the first aspect of the present invention is
A first that has a first piezoelectric element that is in contact with the lower part of the sample and can be deformed while supporting it, and outputs a first voltage signal that is a voltage signal corresponding to the deformation of the first piezoelectric element. Sensor part and
It has a second piezoelectric element that can be deformed independently of the first piezoelectric element, and outputs a second voltage signal that is a voltage signal corresponding to the deformation of the second piezoelectric element and also outputs the first. The second sensor part that supports the sensor part of
A vibration unit for vibrating supports the previous SL second sensor portion,
A hardness determination unit that determines the hardness of the sample based on the phase difference between the first voltage signal and the second voltage signal during vibration of the vibration unit.
To prepare for.

In this case, an elastic member that supports the vibration-exciting portion is provided.
It may be that.

Depending on the weight of the sample, the elastic member can be replaced with one having a different spring strength.
It may be that.

The first piezoelectric element abuts on the lower part of the sample at the center thereof.
The first sensor unit has a first support unit that oscillateably supports the outer edge of the first piezoelectric element.
The second sensor unit has a second support unit that oscillateably supports the outer edge of the second piezoelectric element.
The second support portion supports the first support portion.
It may be that.

Auxiliary support for supporting the sample.
It may be that.

The hardness measuring method according to the second aspect of the present invention is
A first sensor unit having a first piezoelectric element that is in contact with the lower part of the sample and can be deformed while supporting it , and a second piezoelectric element that can be deformed independently of the first piezoelectric element. A support process in which the second sensor portion is supported and the vibration portion supports the second sensor portion.
A first voltage signal corresponding to the deformation of the first piezoelectric element while vibrating the sample via the first sensor unit and the second sensor unit using the vibration unit. A measurement step for measuring a voltage signal and a second voltage signal which is a voltage signal corresponding to the deformation of the second piezoelectric element.
A hardness determination step of determining the hardness of the sample based on the phase difference between the first voltage signal and the second voltage signal during vibration of the vibration unit.
including.

According to the present invention, the hardness of the sample can be measured by one-point contact, so that it is not necessary to sandwich and hold the sample. As a result, the work of sandwiching the sample becomes unnecessary, and the hardness of the sample can be easily measured.

It is a schematic diagram which shows the structure of the hardness measuring apparatus which concerns on embodiment of this invention. FIG. 2A is a diagram showing an example of the structure of the first piezoelectric element. 2 (B) and 2 (C) are views showing how the first piezoelectric element vibrates. It is a block diagram which shows the hardware structure of the hardness determination part of FIG. It is a flowchart which shows the flow of the hardness measurement in the hardness measuring apparatus of FIG. It is a graph which shows an example of the change of the phase difference between the output signal of a 1st piezoelectric element and the output signal of a 2nd piezoelectric element with respect to the vibration frequency of a vibration part. It is a graph which shows an example of the relationship between the hardness index of a fruit and the number of days after harvesting. It is a graph which shows an example of the relationship between the ripeness of a fruit and a hardness index. It is a figure which shows the use example of the hardness measuring apparatus of FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, the hardness measuring device 1 according to the present embodiment is a device for measuring the hardness of the fruit S as a sample. The hardness measuring device 1 includes a first sensor unit 11, a second sensor unit 12, and a vibrating unit 13 as basic components. These three components are stacked in the order of the vibration excitation unit 13, the second sensor unit 12, and the first sensor unit 11 from the bottom. Note that FIG. 1 shows a cross section of the first sensor unit 11 and the second sensor unit 12 parallel to the paper surface.

The first sensor unit 11 includes a first piezoelectric element 11A, a first support unit 11B, and a fixing plate 11C. The fixing plate 11C is a highly rigid disk-shaped member provided in the lower part of the first sensor unit 11. The first support portion 11B is a cylindrical hollow member and is mounted on the fixing plate 11C. The first piezoelectric element 11A is a disk-shaped piezo element. The outer edge of the first piezoelectric element 11A is connected on the first support portion 11B, and the first piezoelectric element 11A is supported by the first support portion 11B. The first piezoelectric element 11A abuts on the lower part of the fruit S at the center thereof and supports the fruit S.

Since the first piezoelectric element 11A is supported by the cylindrical first support portion 11B, the first piezoelectric element 11A can be bent and deformed.

As shown in the cross-sectional view of FIG. 2A, in the first piezoelectric element 11A, the base material layer 11Aa, the lower electrode layer 11Ab, the piezoelectric material layer 11Ac, and the upper electrode layer 11Ad are laminated in this order. ing. The bottom substrate layer 11Aa is made of silicon. A piezoelectric layer is formed by the lower electrode layer 11Ab, the piezoelectric material layer 11Ac, and the upper electrode layer 11Ad.

The lower electrode layer 11Ab and the upper electrode layer 11Ad are made of a conductive material (for example, a metal such as aluminum or copper), and the piezoelectric material layer 11Ac is a material such as PZT (lead zirconate titanate) (which exhibits piezoelectric properties). Material). The piezoelectric material layer 11Ac has a property of expanding and contracting when a voltage having a predetermined polarity is applied in the thickness direction.

As shown in FIG. 2B, when the first piezoelectric element 11A receives a vibration force and warps so that the upper side becomes convex, the piezoelectric layer expands and extends toward the piezoelectric layer in the direction of the surface. Stress is applied. As a result, a voltage having a polarity (hereinafter referred to as positive electrode property) in which the upper electrode layer 11Ad is positive and the lower electrode layer 11Ab is negative is generated.

On the other hand, as shown in FIG. 2C, when the first piezoelectric element 11A receives a vibration force and warps so that the lower side becomes convex, the piezoelectric layer shrinks, and the piezoelectric layer shrinks toward the piezoelectric layer in the plane direction. Stress is applied in the direction of contraction. As a result, a voltage having a polarity (hereinafter referred to as negative electrode property) in which the upper electrode layer 11Ad is negative and the lower electrode layer 11Ab is positive is generated.

Of course, in the first piezoelectric element 11A, when the piezoelectric layer shrinks, a voltage is generated between the two electrode layers so that the upper electrode layer 11Ad side becomes positive and the lower electrode layer 11Ab side becomes negative, and when the piezoelectric layer extends, the upper portion A piezoelectric material layer 11Ac that generates a voltage between both electrode layers may be used so that the electrode layer 11Ad side is negative and the lower electrode layer 11Ab side is positive. The first piezoelectric element 11A may bend and vibrate, and may generate a voltage corresponding to the vibration at both poles of the piezoelectric layer.

The magnitude of the generated voltage signal is an amount according to the degree of deformation. Since the polarization action differs depending on the material constituting the piezoelectric element (for example, depending on the bulk or thin film), the relationship between the polarity of the voltage and the expansion / contraction may be opposite to the above.

As described above, the first piezoelectric element 11A generates a voltage generated between the lower electrode layer 11Ab and the upper electrode layer 11Ad according to its deformation. The first sensor unit 11 outputs a first voltage signal, which is a voltage signal corresponding to the deformation of the first piezoelectric element 11A.

Returning to FIG. 1, the second sensor unit 12 includes a second piezoelectric element 12A and a second support unit 12B. The second support portion 12B is a cylindrical hollow member that supports the fixing plate 11C of the first sensor portion 11 and supports the first support portion 11B via the fixing plate 11C. The second support portion 12B is supported by the vibration portion 13.

The second piezoelectric element 12A is a disk-shaped piezo element, and is provided in the internal space of the cylindrical second support portion 12B. The second piezoelectric element 12A is connected to the second support portion 12B at its outer edge and is supported by the second support portion 12B. The second piezoelectric element 12A can be flexed and vibrated by the vibration force applied from the second support portion 12B. The second piezoelectric element 12A is the same as the first piezoelectric element 11A in that a voltage corresponding to the deformation is generated between the electrodes, and the structure and operation thereof are the same as those in FIGS. 2 (A) to 2 (C). It is the same as the first piezoelectric element 11A shown in. The second sensor unit 12 outputs a second voltage signal, which is a voltage signal corresponding to the deformation of the second piezoelectric element 12A.

The vibration-exciting unit 13 includes a driven unit 13A and a driving unit 13B. The driven unit 13A is arranged on the driven unit 13B, and the driven unit 13A vibrates up and down with respect to the driving unit 13B. The driven unit 13A supports the second sensor unit 12, and the vibration of the driven unit 13A is transmitted to the second piezoelectric element 12A of the second sensor unit 12, whereby the second piezoelectric element is transmitted. 12A vibrates. Further, the vibration of the driven portion 13A is transmitted to the first support portion 11B of the first sensor portion 11 via the second sensor portion 12 (second support portion 12B), and is transmitted to the first support portion 11B, and the first piezoelectric element. 11A vibrates. When the first piezoelectric element 11A vibrates, the vibration is transmitted to the fruit S.

The hardness determination unit 20 is an information processing device (computer) that determines the hardness of the fruit S based on the phase difference between the first voltage signal and the second voltage signal during the vibration of the vibration unit 13.

As shown in FIG. 3, the hardness determination unit 20 includes an internal bus 30, a control unit 31, a main storage unit 32, an external storage unit 33, an operation unit 34, a display unit 35, and a communication unit 36 as hardware configurations. .. The main storage unit 32, the external storage unit 33, the operation unit 34, the display unit 35, and the communication unit 36 are all connected to the control unit 31 via the internal bus 30.

The control unit 31 is composed of a CPU (Central Processing Unit) and the like. Each component of the hardness determination unit 20 is realized by the CPU executing the program 39 stored in the external storage unit 33.

The main storage unit 32 is composed of a RAM (Random-Access Memory) or the like. The program 39 stored in the external storage unit 33 is loaded into the main storage unit 32. In addition, the main storage unit 32 is used as a work area (temporary data storage area) of the control unit 31.

The external storage unit 33 is composed of a flash memory, a hard disk, a non-volatile memory such as a DVD-RAM (Digital Versatile Disc Random-Access Memory) and a DVD-RW (Digital Versatile Disc ReWritable). The external storage unit 33 stores in advance a program 39 for being executed by the control unit 31. Further, the external storage unit 33 supplies the data used when executing the program 39 to the control unit 31 according to the instruction of the control unit 31, and stores the data supplied from the control unit 31.

The operation unit 34 is composed of a pointing device such as a keyboard and a mouse, and an interface device for connecting the keyboard, the pointing device, and the like to the internal bus 30. Information about the content operated by the operator is input to the control unit 31 via the operation unit 34.

The display unit 35 is composed of a CRT (Cathode Ray Tube), an LCD (Liquid Crystal Display), or the like, and when an operator inputs operation information, an operation screen is displayed.

The communication unit 36 is composed of a serial interface or a parallel interface. The communication unit 36 is connected to the first sensor unit 11 and the second sensor unit 12 via a communication network, and receives voltage signals from the first sensor unit 11 and the second sensor unit 12.

Returning to FIG. 1, the hardness measuring device 1 further includes an elastic portion 14 and an auxiliary support portion 15. In FIG. 1, the auxiliary support portion 15 has a cross section parallel to the paper surface.

The elastic portion 14 is a spring member. The elastic portion 14 is inserted between the vibrating portion 13 and the bottom surface of the auxiliary support portion 15 to support the vibrating portion 13. The elastic portion 14 can be replaced with one having a different elastic modulus according to the weight of the fruit S. For example, when measuring a heavy fruit S such as watermelon, a spring member having a strong spring strength is selected as the elastic portion 14. When measuring a lightweight fruit S such as petit tomato, a spring member having a small spring strength is selected as the elastic portion 14. When measuring a medium-weight fruit S such as an apple or a pear, a spring member having a medium spring strength is selected as the elastic portion 14.

A circular through hole is provided in the upper part of the auxiliary support portion 15. The auxiliary support portion 15 supplementarily supports the fruit S at the edge of the through hole. The auxiliary support portion 15 supports the fruit S so that the fruit S supported by the first sensor portion 11 does not fall from the first sensor portion 11.

Next, the operation of measuring the hardness of the fruit S using the hardness measuring device 1 according to the present embodiment will be described.

As shown in FIG. 4, first, a spring member corresponding to the fruit S to be measured is installed as the elastic portion 14 (step S1). Specifically, a spring member having a spring strength corresponding to the weight of the fruit S is selected and installed as the elastic portion 14.

Subsequently, the fruit S is placed on the first piezoelectric element 11A of the first sensor unit 11 (step S2; support step). As a result, the first sensor unit 11 having the first piezoelectric element 11A that is in contact with the lower part of the fruit S and can be deformed while supporting it, and the first piezoelectric element 11A can be deformed independently. The fruit S is supported by the vibrating unit 13 via the second sensor unit 12 having the second piezoelectric element 12A. In this case, if necessary, the fruit S is supplementarily supported by the auxiliary support portion 15.

Subsequently, the vibration unit 13 is used to vibrate the fruit S via the first sensor unit 11A and the second sensor unit 12A, and the voltage signal corresponds to the deformation of the first piezoelectric element 11A. The first voltage signal and the second voltage signal, which is a voltage signal corresponding to the deformation of the second piezoelectric element 12A, are measured (step S3; measurement step). Specifically, the vibrating unit 13 obtains the phase difference between the voltage signal of the first piezoelectric element 11A and the voltage vibration of the second piezoelectric element 12A at each frequency while gradually increasing the frequency. ..

Subsequently, the hardness determination unit 20 determines the hardness of the fruit S based on the phase difference between the first voltage signal and the second voltage signal during the vibration of the vibration unit 13 (step S4; hardness determination). Process). Specifically, the phase difference between the voltage signal of the first piezoelectric element 11A and the voltage signal of the second piezoelectric element 12A at each frequency of the frequency in the vibrating unit 13 acquired in step S3. Based on the relationship, the resonance frequency of the fruit S is obtained, and the hardness and maturity of the fruit S are determined based on the obtained resonance frequency. Here, the ripeness is a sensual index meaning the ripeness of the fruit S, and is mainly used to determine when the fruit is ready to eat.

FIG. 5 shows a change in the phase difference between the output signal of the first piezoelectric element 11A and the output signal of the second piezoelectric element 12A with respect to the frequency of the exciting portion 13. The upper graph of FIG. 5 shows the relationship between the phase difference between the voltage signal of the first piezoelectric element 11A and the voltage signal of the second piezoelectric element 12A at a frequency when a large ball (large ball) is regarded as the fruit S. Is shown. Further, the graph in the middle of FIG. 5 shows the voltage signal of the first piezoelectric element 11A and the voltage signal of the second piezoelectric element 12A having a frequency when the medium ball (middle ball) is regarded as the fruit S. The relationship with the phase difference is shown. Further, the graph at the bottom of FIG. 5 shows the phase difference between the voltage signal of the first piezoelectric element 11A and the voltage signal of the second piezoelectric element 12A having a frequency when a small ball (small ball) is regarded as the fruit S. Shows the relationship between.

As shown in FIG. 5, in all the balls having different sizes of the large ball, the medium ball, and the small ball, a peak appears in the phase difference between some output signals. The present inventor has found that the frequency corresponding to this peak corresponds to the resonance frequency of the fruit S. It was confirmed that the measured resonance frequency was almost the same as the resonance frequency measured by the laser Doppler method. Therefore, the frequency corresponding to the peak of the phase difference between the two output signals can be considered to be the resonance frequency of the fruit S. The hardness determination unit 20 detects a resonance point (resonance frequency) corresponding to this peak.

As a result of the measurement, large piece, Nakatama, frequency ratio of _f 2 ~f ₈ to the peak frequency _{f 1} of the Kodama became almost the same.

Of the peaks of the phase difference which appears in a plurality of different frequencies, the resonance frequency corresponding to the first peak from the low frequency side as the first resonant frequency f _1. By using this first resonance frequency f ₁ , the hardness of the fruit S can be measured.

The hardness index is calculated by the following formula (1).
Hardness of fruit S = m ^2/3 × f ₁ ² (m: weight of fruit S, f ₁ : first resonance frequency)

The weight m of the fruit S may be measured in advance and input by the measurer, or may be automatically measured by the hardness measuring device 1. For example, if a load cell is installed under the elastic portion 14, the weight m of the fruit S can be measured.

It is known that the hardness thus obtained has a strong correlation with maturity as long as there are no defects. In general, the immature fruit S is hard and the overripe fruit S is soft. In addition, the fruit S, which is properly ripe, that is, when it is ready to eat, has an appropriate hardness. The harvested fruit S ripens and becomes soft with the passage of time.

FIG. 6 shows an example of the change over time in the hardness index of the fruit S. The hardness index of the harvested fruit S has a primary correlation with the elapsed time and simply decreases. Therefore, if the change over time of the hardness index of the fruit S is investigated in advance and converted into data, the subsequent change in hardness can be predicted from the measured hardness index of the fruit S.

FIG. 7 shows an example of the relationship between the hardness index of fruit S and the ripeness. The horizontal axis represents maturity, and the oval-shaped portion in the figure is a simplified representation of the data distribution. The degree of maturity is a sensual evaluation of overripe (overripe), appropriate ripeness (when eaten), and immature (underripe) by actually eating fruits with various hardness indexes.

Thus, there is a primary correlation between the hardness index and maturity. Therefore, if the correlation between the hardness index of the fruit S and the ripeness is investigated and converted into data, the ripeness can be evaluated from the measured hardness index of the fruit S.

As described in detail above, since the hardness of the fruit S can be measured by one-point contact, it is not necessary to sandwich and hold the fruit S. As a result, the work of sandwiching the fruit S becomes unnecessary, so that the hardness of the fruit can be easily measured.

For example, when the fruit S is in a high position, as shown in FIG. 8, if the hardness measuring device 1 is attached to the tip of the rod 50 and the fruit S is placed on the hardness measuring device 1, the hardness can be easily measured. Can be measured.

Further, the hardness measuring device 1 according to the present embodiment is provided with an elastic portion 14 that supports the vibrating portion 13. By doing so, the peak of the phase difference between the two voltage signals is more likely to appear more prominently corresponding to the resonance frequency of the fruit S. However, the present invention is not limited to this. The elastic portion 14 may not be provided. Further, although the elastic portion 14 is used as a spring member, an elastic member such as rubber may be used.

Further, in the hardness measuring device 1 according to the present embodiment, the elastic member used as the elastic portion 14 can be replaced with one having a different spring strength according to the weight of the fruit S. By doing so, the hardness can be measured with high accuracy regardless of the weight of the fruit S.

Further, in the hardness measuring device 1 according to the present embodiment, the cylindrical second support portion 12B supports the cylindrical first support portion 11B. As a result, the fruit S can be stably supported, and a space can be provided inside, and the first piezoelectric element 11A and the second piezoelectric element 12A can be vibrated and deformed in the space.

Further, the hardness measuring device 1 according to the present embodiment includes an auxiliary support portion 15. This makes it possible to prevent the fruit S from falling from the first sensor unit 11. However, the auxiliary support 15 is not essential.

Further, in the above embodiment, the first piezoelectric element 11A is composed of the electrode layer and the piezoelectric layer laminated on the silicon substrate, but a piezoelectric element having another configuration may be used.

Further, in the above embodiment, the hardness of the fruit S is measured, but the present invention is not limited to this. It can also be applied to the measurement of hardness and the like of other agricultural products.

In addition, the hardware configuration and software configuration of the hardness determination unit 20 (computer) are examples, and can be arbitrarily changed and modified.

The central part of computer processing can be realized by using a normal computer system, not by a dedicated system. For example, a computer program for performing the above operation is stored and distributed in a computer-readable recording medium (flexible disk, CD-ROM, DVD-ROM, etc.), and the computer program is installed in the computer. May configure a computer to perform the above processing. Further, the computer program may be stored in a storage device of a server device on a communication network such as the Internet, and the computer may be configured by downloading or the like by a normal computer system.

When the function of the computer is realized by the division of the OS (operating system) and the application program or the cooperation between the OS and the application program, only the application program portion may be stored in the recording medium or the storage device.

It is also possible to superimpose a computer program on a carrier wave and distribute it via a communication network. For example, a computer program may be posted on a bulletin board system (BBS, Bulletin Board System) on a communication network, and the computer program may be distributed via the network. Then, the computer program may be started and executed in the same manner as other application programs under the control of the OS so that the above processing can be executed.

The present invention allows for various embodiments and variations without departing from the broad spirit and scope of the invention. Further, the above-described embodiments are for explaining the present invention, and do not limit the scope of the present invention. That is, the scope of the present invention is shown not by the embodiment but by the claims. Then, various modifications made within the scope of the claims and within the scope of the equivalent invention are considered to be within the scope of the present invention.

The present invention can be applied to the measurement of fruit hardness, ripeness and the like.

1 hardness measuring device, 11 first sensor part, 11A first piezoelectric element, 11Aa base material layer, 11Ab lower electrode layer, 11Ac piezoelectric material layer, 11Ad upper electrode layer, 11B first support part, 11C fixing plate, 12 2nd sensor part, 12A 2nd piezoelectric element, 12B 2nd support part, 13 vibration part, 13A driven part, 13B drive part, 14 elastic part, 15 auxiliary support part, 20 hardness judgment part, 30 Internal bus, 31 control unit, 32 main storage unit, 33 external storage unit, 34 operation unit, 35 display unit, 36 communication unit, 39 program, 50 rods, S fruit (sample)

Claims (6)

A first that has a first piezoelectric element that is in contact with the lower part of the sample and can be deformed while supporting it, and outputs a first voltage signal that is a voltage signal corresponding to the deformation of the first piezoelectric element. Sensor part and
It has a second piezoelectric element that can be deformed independently of the first piezoelectric element, and outputs a second voltage signal that is a voltage signal corresponding to the deformation of the second piezoelectric element and also outputs the first. The second sensor part that supports the sensor part of
A vibration unit for vibrating supports the previous SL second sensor portion,
A hardness determination unit that determines the hardness of the sample based on the phase difference between the first voltage signal and the second voltage signal during vibration of the vibration unit.
A hardness measuring device. An elastic member that supports the vibrating portion.
The hardness measuring device according to claim 1. Depending on the weight of the sample, the elastic member can be replaced with one having a different spring strength.
The hardness measuring device according to claim 2. The first piezoelectric element abuts on the lower part of the sample at the center thereof.
The first sensor unit has a first support unit that oscillateably supports the outer edge of the first piezoelectric element.
The second sensor unit has a second support unit that oscillateably supports the outer edge of the second piezoelectric element.
The second support portion supports the first support portion.
The hardness measuring device according to any one of claims 1 to 3. Auxiliary support for supporting the sample.
The hardness measuring device according to any one of claims 1 to 4. A first sensor unit having a first piezoelectric element that is in contact with the lower part of the sample and can be deformed while supporting it , and a second piezoelectric element that can be deformed independently of the first piezoelectric element. A support process in which the second sensor portion is supported and the vibration portion supports the second sensor portion.
A first voltage signal corresponding to the deformation of the first piezoelectric element while vibrating the sample via the first sensor unit and the second sensor unit using the vibration unit. A measurement step for measuring a voltage signal and a second voltage signal which is a voltage signal corresponding to the deformation of the second piezoelectric element.
A hardness determination step of determining the hardness of the sample based on the phase difference between the first voltage signal and the second voltage signal during vibration of the vibration unit.
Hardness measuring method including.

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