JP7019435B2 - Push-in test device and push-in test method - Google Patents

Description

The present invention relates to an indentation test device for injecting an indenter into a food such as kamaboko or ham or a flexible tissue of a human and measuring the softness of the indenter, and an indentation test method thereof.

The following Patent Document 1 discloses an indentation test device for measuring the softness of a flexible food, a human body tissue, or the like as a subject.
As shown in FIG. 11, this device includes an indenter 10 pushed into the subject, a force sensor 30 that detects the force acting on the indenter 10 when the indenter 10 is pushed into the subject, and the softness of the subject. It is provided with a calculation unit 40 that calculates Young's modulus for evaluating Young's modulus 10 based on the force acting on the indenter 10, and a housing 20 in which they are arranged.
The indenter 10 is arranged in the housing so that a certain amount of the hemispherical portion at the tip protrudes from the end 21 of the housing 20.

この(数１)を用いて、力センサ３０で検出された押込荷重Ｆから被検体のヤング率Ｅを求めることができる。 The operator who operates this device grips the housing 20 portion and pushes the indenter 10 into the subject until the end portion 21 of the housing 20 abuts on the subject.
At this time, the force (pushing load) detected by the force sensor 30 when the end 21 of the housing 20 comes into contact with the subject is F, and the amount of protrusion of the indenter 10 protruding from the end 21 of the housing 20 (the amount of protrusion of the indenter 10 (pushing load). That is, assuming that the amount of indenter 10 pushed into the subject) is δ, the diameter of the hemisphere of the indenter 10 is φ, the Young's modulus of the subject is E, and the Poisson's ratio peculiar to the subject is ν. Has a relationship represented by (Equation 1).

Using this (Equation 1), the Young's modulus E of the subject can be obtained from the indentation load F detected by the force sensor 30.

This indentation test device can measure the softness of a subject at the place where the subject should be (so-called “in-situ measurement”), and can be expected to be used in a wide range of fields.

WO2017 / 164426

However, in this indentation test apparatus, when the indenter 10 is pushed into the subject, in the initial stage, only the indenter 10 protruding from the housing 20 comes into contact with the subject, so that the housing 20 is the subject. It is difficult to push in the direction perpendicular to the surface of.
When the traveling direction of the housing 20 when the indenter 10 is pushed into the subject is tilted from the vertical direction of the subject surface, the following situation occurs.

FIG. 12 (a) shows a state in which the indenter 10 is not tilted with respect to the surface of the subject, and FIG. 12 (b) shows a state in which the indenter 10 is tilted by θ with respect to the surface of the subject. There is.
Assuming that the load detected by the force sensor 30 in the case of FIG. 12 (a) is F, the component force F'of F detected by the force sensor 30 in the case of FIG. 12 (b) is
(Equation 2) F'= Fcosθ
Will be. If the absolute value of θ is 5 ° or less, the error between F and F'is 0.4% or less, which is not a problem in practice.

However, in this indentation test device, when the indenter 10 is tilted with respect to the surface of the subject, not only the error between F and F'but also when the end 21 of the housing 20 comes into contact with the subject. The amount of indenter 10 pushed in is different.
As shown in FIG. 12 (c), when the indenter 10 is not tilted with respect to the surface of the subject, the amount of the indenter 10 pushed in until the end 21 of the housing 20 comes into contact with the subject is δ. And. In addition, r is a radius in the outer diameter of the end portion 21 of the annular shape.
When the indenter 10 is tilted by θ with respect to the surface of the subject, as shown in FIG. 12 (d), the pushing amount δ'of the indenter 10 when the end portion 21 of the housing 20 comes into contact with the subject is ,
(Equation 3) δ'= δ-rsinθ
Will be.
Therefore, in (Equation 1), F and δ are replaced with F'and δ', so that the error of Young's modulus E becomes large.
Note that y in FIG. 12D indicates the distance between the subject and the subject at the end position symmetrical to the contact position when a part of the end 21 of the housing 20 comes into contact with the subject.

FIG. 13 shows the relationship between the inclination of the indenter 10 and the error of Young's modulus E, with the angle corresponding to θ on the horizontal axis and the error of Young's modulus E on the vertical axis. It can be seen that the inclination of the indenter 10 must be maintained within 0.2 ° in order to make the error of Young's modulus E 1% or less.
Further, the graph of FIG. 14 shows the results of measuring the softness of the same subject by four persons A, B, C, and D using a conventional indentation test device. The horizontal axis shows the inclination of the housing (angle corresponding to θ) at the time of measurement, and the vertical axis shows the calculated Young's modulus. As is clear from FIG. 14, the measurement results vary depending on the operator who operates the indentation test device.

The present invention has been devised in consideration of such circumstances, and an object of the present invention is to provide an indentation test apparatus and an indentation test method in which anyone can accurately measure the softness of a subject.

In the present invention, the indenter pushed into the subject, the housing in which the indenter is arranged so that at least a part thereof protrudes from the end portion, and the housing are operated so as to push the indenter into the subject. At that time, the force sensor has an abutting portion that comes into contact with the subject after the indenter, and the force acting on the indenter at the time when the abutting portion abuts on the subject with the operation is performed by the force sensor. It is a push-in test device that is detected and the softness of the subject is calculated based on the detection result of the force sensor, and supports the pushing direction of the indenter into the subject to be perpendicular to the surface of the subject. It is equipped with a push-in support means.
Regardless of who operates this device, the pushing direction is perpendicular to the surface of the subject, so that the softness of the subject can be accurately measured.

Further, in the indentation test apparatus of the present invention, as the indentation support means, an outer cylinder portion having a guide hole for guiding the movement of the housing in a direction perpendicular to the surface of the subject and one end of the outer cylinder portion. The guide member is provided with a large diameter portion having an outer diameter larger than the outer diameter of the outer cylinder portion, and the large diameter portion at one end of the guide member is arranged on the measurement surface of the subject. Then, the housing with the indenter side facing the subject is inserted through the guide hole opened at the other end of the guide member.
In this device, a guide member having a large diameter portion is arranged perpendicular to the surface of the subject, and is guided by the guide member so that the housing advances perpendicularly to the surface of the subject.

Further, in the indentation test apparatus of the present invention, it is preferable that the guide member includes a slide bush that smoothes the movement of the housing.
The presence of the slide bush eliminates the rattling of the housing that moves linearly, enabling accurate measurement.

Further, the indentation test apparatus of the present invention has a plurality of contact detection sensors forming the contact portion as the indentation support means, and the plurality of contact detection sensors substantially decimate the circumference centered on the indenter. It is arranged at a position that divides by a distance, and the softness of the subject is not calculated unless all of the plurality of contact detection sensors detect contact with the subject.
If all of the plurality of contact detection sensors detect contact with the subject, the circumference of the indenter is evenly in contact with the subject.

Further, in the indentation test apparatus of the present invention, each time each of the plurality of contact detection sensors detects contact with the subject, the value of the softness of the subject is calculated using the detection value of the force sensor at the time of detection. Then, after all of the plurality of contact detection sensors detect contact with the subject, the obtained plurality of said values may be averaged.
Even if the pushing direction of the indenter deviates slightly from the vertical direction of the surface of the subject, the softness of the subject can be calculated with high accuracy by taking the average value.

Further, in the indentation test apparatus of the present invention, a plurality of contact detection sensors may be configured by a vibrating body whose vibration state changes when in contact with a subject.

Further, in the present invention, the indenter pushed into the subject, the housing in which the indenter is arranged so that at least a part thereof protrudes from the end portion, and the housing are operated so as to push the indenter into the subject. This is an indentation test method for measuring the softness of a subject by an indentation test device having a plurality of contact detection sensors that come into contact with the subject after the indenter, and each of the plurality of contact detection sensors. Each time it detects contact with a subject, it detects the indentation load acting on the indenter and uses the indentation load to calculate the Young's modulus of the subject. Individual Young's modulus calculation step and multiple contact detection sensors. It includes an averaging step for averaging a plurality of Young's modulus values obtained in the individual Young's modulus calculation step after all have detected contact with the subject.
By this method, the softness of the subject can be calculated with high accuracy even when the pushing direction of the indenter is slightly deviated from the vertical direction of the surface of the subject.

Further, in the indentation test method of the present invention, the indentation test apparatus for the subject is used by using the indentation speed of the indentation test apparatus into the subject and the time difference between the times when a plurality of contact detection sensors detect contact with the subject. A tilt calculation step for calculating the tilt in the push-in direction, a push-in amount calculation step for calculating the push-in amount of the indenter when the first contact detection sensor comes into contact with the subject, and a push-in amount calculation step, and the first contact detection sensor. It may be provided with a young rate calculation step of calculating the young rate of the subject using the pushing load acting on the indenter when the sensor comes into contact with the subject and the pushing amount calculated in the pushing amount calculation step. ..
By this method, it is possible to correct the Young's modulus calculation error when the pushing direction of the indenter is tilted from the vertical direction of the surface of the subject.

The softness of the subject can be obtained with high accuracy by the indentation test apparatus and the indentation test method of the present invention.

The figure which shows the indentation test apparatus which concerns on 1st Embodiment of this invention. An exploded perspective view of the guide member of FIG. Explanatory drawing of slide bush The figure which shows the measurement result when using the indentation test apparatus of FIG. The figure which shows the deformation example of a guide member An exploded perspective view of the guide member of FIG. The figure which shows the contact detection sensor of the indentation test apparatus which concerns on 2nd Embodiment of this invention. The figure which shows the pin type contact detection sensor (A) A diagram showing the change in Young's modulus when the indentation test device is pushed into the subject at a constant speed, and (b) showing the relationship between the inclination and the error when calculating the Young's modulus by the method of the second embodiment. figure A flow chart showing a procedure for calculating Young's modulus by the method of the second embodiment. The figure which shows the conventional indentation test apparatus Diagram explaining the effect of indenter slope on Young's modulus calculation The figure which shows the relationship between the inclination and the error when calculating Young's modulus using the conventional indentation test equipment. The figure which shows the measurement result when using the conventional indentation test equipment.

(First Embodiment)
The indentation test apparatus of the first embodiment is used together with a guide member that guides the moving direction of the housing portion of the indentation test apparatus.
FIG. 1 shows a guide member 60 and an indentation test device 50 that can be indented perpendicularly to the surface of a subject by using the guide member 60.
The indentation test device 50 has a housing 20 in which an indenter 10 protruding by a predetermined amount from an end portion 21 that also serves as a contact portion is arranged inside, and a grip portion 51 attached to a part of the housing 20. ing.
As shown in the exploded perspective view of FIG. 2, the guide member 60 has a base 61 arranged so as to be in contact with a subject, and a cylindrical case 62 having one end screwed into a screw hole of the base 61 and fixed to the base 61. A coil spring 64 sandwiched between a pair of washers 63 and 65 in the cylindrical case 62, a slide bush 66 whose lower end is positioned and arranged in the cylindrical case 62, and a housing 20 of the indentation test device 50. It is provided with a cylindrical slider 67 that is coupled with and moves within the slide bush 66.

The outer diameter of the base 61 is set to be larger than the outer diameter of the cylindrical case 62 so that it can be in stable contact with the subject. The base 61 constitutes a "large diameter portion" as defined in the claims.
As shown in FIG. 3, the slide bush 66 has a ball that circulates in the axial direction inside the through hole, and the rolling of the ball causes a highly accurate linear motion of the slider 67 inserted into the through hole. It will be possible.
The lower end of the slider 67, which moves linearly in the direction of the base 61, abuts on the washer 65 (FIG. 1) and compresses the coil spring 64.
The housing 20 of the indentation test apparatus 50 is inserted into the hole of the slider 67 and fixed to the slider 67 with the tip protruding from the hole of the slider 67 by a predetermined amount. The amount of protrusion of the housing 20 from the slider 67 is set so that the end portion 21 protrudes from the lower end of the opening of the base 61 when the indentation test device 50 is pushed toward the subject.
When the end portion 21 of the housing 20 approaches the subject, the coil spring 64 exerts a repulsive force on the housing 20 via the slider 67 to urge the operator to perform a careful operation.

The operator who operates the indentation test device 50 holds the guide member 60 so that the lower surface of the base 61 of the guide member 60 comes into contact with the surface of the subject. Then, the grip portion 51 is operated, and the slider 67 fixed to the housing 20 is linearly moved toward the subject via the slide bush 66 until the end portion 21 at the tip of the housing 20 abuts on the subject. ..
At this time, the guide member 60 having the base (large diameter portion) 61 can stand vertically with respect to the surface of the subject in a stable state. Then, the indentation test device 50 guided by the guide member 60 can inject the indenter 10 perpendicularly to the surface of the subject.

The graph of FIG. 4 shows the results when three people A, B, and D operate the indentation test device 50 using the guide member 60 and measure the softness of the same subject. The horizontal axis and the vertical axis are the same as those in FIG.
As is clear from the comparison of FIGS. 14 and 4, the presence of the guide member 60 enables highly accurate measurement of softness.

FIG. 5 shows a modified example of the guide member. As shown in the exploded perspective view of FIG. 6, the guide member 70 includes a holder 76 that is coupled to the housing 20 of the indentation test device 50, and a case 75 that is screwed into the lower end of the holder 76 and moves together with the holder 76. , The slider 73 that guides the movement of the case 75 in the axial direction, the drivesh 72 that is arranged in the gap between the slider 73 and the case 75 so as to buffer the space between the slider 73, the lower end of the holder 76, and the upper end of the slider 73. It includes a coil spring 74 arranged between the two, and a base 71 fixed to one end of the slider 73 to form a large diameter portion.
When the housing 20 of the push-in test device 50 is pushed in and the holder 76 and the case 75 are moved downward, the coil spring 74 is compressed. When the housing 20 is pushed against the repulsive force of the coil spring 74, the housing 20 is fixed to the holder 76 so that the tip of the housing 20 protrudes from the hole of the base 71.
In this guide member, the linear motion of the case 75 with respect to the slider 73 is smoothly performed by the presence of the drivesh 72.

(Second embodiment)
As shown in FIG. 7, the indentation test apparatus of the second embodiment includes a plurality of contact detection sensors 22 at the end portion 21 of the housing 20. In this device, a plurality of contact detection sensors 22 form a contact portion. The plurality of contact detection sensors 22 are arranged at positions that divide the circumference around the indenter at substantially equal distances.
The contact detection sensor 22 may be any as long as it can detect contact with the subject, and the pressure-sensitive rubber whose electric resistance value changes due to contact with the subject or the vibration state changes due to contact with the subject. Various things such as vibrating bodies can be used.

When the vibrating body is used as a contact detection sensor, a plurality of piezoelectric bodies are arranged at the positions of the contact detection sensor 22 in FIG. 7, an AC voltage having a resonance frequency is applied to each piezoelectric body, and resonance vibration is applied to each piezoelectric body. Let me do it. When the piezoelectric body comes into contact with the subject, the vibration of the piezoelectric body stops or the amplitude becomes small, so that contact with the subject can be detected.
Further, FIG. 8 shows a device in which a pin-type contact detection sensor 221 whose frequency characteristic of an applied electric signal changes due to contact with a subject is arranged around an indenter 10.

In the indentation test apparatus of the second embodiment, the softness of the subject is not detected unless it is detected that all of the plurality of contact detection sensors 22 are in contact with the subject. By doing so, it is possible to ensure the detection of softness in a state where the periphery of the indenter evenly contacts the subject and the pushing direction of the indenter is maintained in the vertical direction of the subject surface.

FIG. 9A shows the results of measuring the transition of the Young's modulus of the subject while pushing the tip of the apparatus into the subject at a constant speed using a push-in test device equipped with two pin-type contact detection sensors. There is. The horizontal axis of FIG. 9A is time, and the vertical axis is Young's modulus.
Point A in FIG. 9A shows the magnitude of Young's modulus when one of the contact detection sensors comes into contact with the subject, and point B in FIG. 9A shows the other of the contact detection sensors on the subject. It shows the magnitude of Young's modulus at the time of contact. Here, since the indentation test device is slightly tilted with respect to the surface of the subject, the time points when the two contact detection sensors come into contact with the subject do not match.
During the time period until the point A, none of the contact detection sensors were in contact with the subject, and only the indenter was pushed into the subject, so that the Young's modulus increased.
In the time zone between points A and B, Young's modulus increases because one of the contact detection sensors and the indenter are pushed into the subject. Further, in the time zone from the point B to the peak of Young's modulus, the Young's modulus is increased by pushing the two contact detection sensors and the indenter into the subject.
After the peak, the pushing force is released and Young's modulus decreases.

In this case, the Young's modulus when the indentation test device is not tilted with respect to the surface of the subject and the two contact detection sensors come into contact with the subject at the same time is the Young's modulus at point A and the Young's modulus at point B. It can be calculated as an average value.
In this way, the Young's modulus is calculated using the indentation load detected by the force sensor when each of the plurality of contact detection sensors comes into contact with the subject, and the Young's modulus is averaged to obtain the Young's modulus of the subject. As shown in FIG. 12 (d), it is possible to calculate the Young's modulus with high accuracy even if the pressing direction of the indenter is slightly tilted with respect to the surface of the subject.

FIG. 9B shows the relationship between the error (vertical axis) of Young's modulus of the subject obtained by this method and the slope (horizontal axis) corresponding to θ in FIG. When the magnitude of the inclination is within 2 °, the error of Young's modulus is 3% or less, and it can be seen that the measurement result with extremely high accuracy can be obtained as compared with the characteristics of FIG.

The flow chart of FIG. 10 shows a procedure for calculating Young's modulus of a subject by this method.
When there is a contact detection sensor that newly detects contact with the subject among multiple contact detection sensors (Yes in step 1), Young's modulus is calculated by (Equation 1) using the pushing load at the time of detection. And record in the recording unit (step 2). This procedure is repeated until all contact detection sensors detect contact with the subject, and when all contact detection sensors detect contact with the subject (Yes in step 3), multiple Young's modulus recorded in the recording unit. Is averaged (step 4).

Here, the average value of a plurality of Young's modulus is calculated, but each time there is a contact detection sensor that newly detects contact with a subject among a plurality of contact detection sensors, it is pushed in at the time of detection. The load is recorded in the recording unit, and after all the contact detection sensors detect contact with the subject, the average value of multiple indentation loads recorded in the recording unit is calculated, and the Young's modulus is calculated using the average value. You may do so.

In addition, when a push-in test device equipped with a plurality of contact detection sensors is pushed into a subject at a known push-in speed, the tilt of the push-in test device with respect to the surface of the subject is caused by the deviation of the contact detection points of the plurality of contact detection sensors (Fig.). The angle corresponding to θ of 12 (d)) can be calculated.
Now, as shown in FIG. 12 (d), a push-in test device in which two contact detection sensors are arranged at positions that divide the circumference of the housing end into two is pushed into the subject at a constant push-in speed V. It is assumed that the time difference between the times when the two contact detection sensors detect the contact with the subject is t.
At this time, the distance corresponding to y in FIG. 12 (d) is
(Number 4) y = Vt
And the slope θ is
(Equation 5) θ = sin ^-1 (y / 2r)
It is represented by.
Using this θ, it is possible to calculate δ'of (Equation 3).
Then, according to (Equation 1), if the Young's modulus E is calculated using the indentation load F detected by the force sensor when the contact detection sensor detects the contact with the subject for the first time and the indentation amount δ', the indentation is performed. Even if the pushing direction of the test device is slightly tilted with respect to the surface of the subject, the softness of the subject can be calculated with high accuracy.

The number of contact detection sensors constituting the contact portion may be 2 or more.
Further, although an indenter having a hemispherical surface is shown here, the shape of the indenter is not limited to this. It may be a cylinder, a cylinder, a cube, or the like.

The indentation test apparatus and indentation test method of the present invention can measure the softness of a subject with high accuracy, and can be used in a wide range of fields such as food fields, medical fields, and materials handling fields that require measurement of softness. It can be used in the field.

10 Indenter 20 Housing 21 End 22 Contact detection sensor 30 Force sensor 40 Calculation unit 50 Push-in test device 51 Grip part 60 Guide member 61 Base 62 Cylindrical case 63 Washer 64 Coil spring 65 Washer 66 Slide bush 67 Slider 71 Base 72 Drivesh 73 Slider 74 Coil spring 75 Case 76 Holder 221 Pin type contact detection sensor

Claims (3)

The indenter pushed into the subject, the housing in which the indenter is arranged so that at least a part thereof protrudes from the end, and when the housing is operated so as to push the indenter into the subject, the said. It has a plurality of contact detection sensors provided at the end thereof, which come into contact with the subject after the indenter, and when the plurality of contact detection sensors come into contact with the subject in accordance with the operation. A push-in test device in which the force acting on the indenter is detected by the force sensor, and the softness of the subject is calculated based on the detection result of the force sensor.
The plurality of contact detection sensors are arranged at positions that divide the circumference around the indenter by approximately equal distances.
Each time each of the plurality of contact detection sensors detects contact with the subject, the value of the softness of the subject is calculated using the detection value of the force sensor at the time of detection, and the plurality of contacts are contacted. An indentation test device in which a plurality of obtained values are averaged after all of the detection sensors detect contact with the subject . The indenter pushed into the subject, a housing in which the indenter is arranged so that at least a part thereof protrudes from the end, and when the housing is operated so as to push the indenter into the subject, the said. It is an indentation test method for measuring the softness of the subject by an indentation test apparatus having a plurality of contact detection sensors that come into contact with the subject after being indented.
Each time each of the plurality of contact detection sensors detects contact with the subject, the indentation load acting on the indenter is detected, and the indentation load is used to calculate the Young's modulus of the subject. Calculation steps and
After all of the plurality of contact detection sensors have detected contact with the subject, an averaging step of averaging the values of the plurality of Young's modulus obtained in the individual Young's modulus calculation step, and
Indentation test method. The indenter pushed into the subject, a housing in which the indenter is arranged so that at least a part thereof protrudes from the end, and when the housing is operated so as to push the indenter into the subject, the said. It is an indentation test method for measuring the softness of the subject by an indentation test apparatus having a plurality of contact detection sensors that come into contact with the subject after being indented.
Using the pushing speed of the indentation test device into the subject and the time difference between the times when the plurality of contact detection sensors detect contact with the subject, the indentation direction of the indentation test device with respect to the subject is determined. The slope calculation step to calculate the slope and the slope calculation step
A push-in amount calculation step for calculating the push-in amount of the indenter when the first contact detection sensor comes into contact with the subject using the tilt, and a push-in amount calculation step.
Young's modulus for calculating Young's modulus of the subject using the indentation load acting on the indenter when the first contact detection sensor comes into contact with the subject and the indentation amount calculated in the indentation amount calculation step. Calculation steps and
Indentation test method.

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