Hardness evaluation apparatus and hardness evaluation method using a piezoelectric element

Abstract

The degree of hardness of an object is made measurable from a piezoelectric element by converting it into a pressure change of a gas. 【Solution means】 It is composed of a flexible member 2 with gas enclosed inside. When the flexible member is pressed from the outside, the pressure of the gas inside changes, and a piezoelectric element 6 provided correspondingly deforms due to this pressure change to generate a voltage. It is provided with a contact 1 and a table in which the relationship between the degree of hardness of the object and the magnitude of the generated voltage is determined in advance. The flexible member is pressed against the object with a constant pressure for a predetermined time, and by configuring it to refer to the voltage from the contact generated thereby and the table, the hardness of the object is evaluated.

Description

Technical Field

[0001] The present invention relates to a hardness evaluation apparatus and a hardness evaluation method using a piezoelectric element, which apply a force to an object such as a fruit and evaluate the hardness of the object from the reaction force generated in the object at that time.

Background Art

[0002] In the case of products such as fruits that become soft over time, deteriorate in quality, and have a lower commercial value, or those that are originally damaged and soft, it is a general criterion to inspect the degree of hardness of the product before shipping. However, it is difficult to make a quantitative judgment because it is easy to be arbitrary when manually examining the hardness by hand. Therefore, as a method for inspecting the hardness of articles such as fruits, for example, there is a known method of lightly tapping (tapping) at least one place of the article, resonating at the natural frequency, detecting the vibration signal generated at that time, and measuring the degree of hardness (see, for example, Patent Document 1). In addition, there is a known method of measuring the hardness of an object by pressing a contactor against the object, measuring the reaction force, and measuring the reaction force per unit area from the measured value and the contact area of the contactor at the time of pressing (see, for example, Patent Document 2).

[0003] However, in the method of Patent Document 2, the structure and calculation are complicated, such as the need to arrange a large number of tactile sensors constituting the contactor to measure the reaction force, and it cannot be said to be a simple method because precise hardness measurement is not required for the object of the present invention. In addition, in the method of Patent Document 1, the relationship between the natural frequency of the object and the hardness of the object as a commercial value is not clear, and similarly, it cannot be said to be a simple method.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] The problem to be solved is that in order to extract a signal for measuring the hardness of an object, it is necessary to use special measurement means or calculation methods, which requires complex processing. [Means for Solving the Problems]

[0006] The main feature of the present invention is that in order to measure the hardness of an object as the magnitude of the reaction force against pressing, the magnitude of the reaction force due to pressing is taken as the pressure change of the enclosed gas, and the pressure change is detected by a piezoelectric element. [Advantages of the Invention]

[0007] The hardness evaluation apparatus and hardness evaluation method using the piezoelectric element of the present invention are configured such that the degree of hardness of an object can be determined by referring to the output voltage of the piezoelectric element and a table defining the relationship between the preset output voltage and hardness. Therefore, it can be realized with a simple configuration, and there is an advantage that the sorting process of the object can be easily performed. [Brief Description of the Drawings]

[0008]

Figure 1

Figure 2

Figure 3

[0009] The object such as fruit is evaluated for the purpose of sorting etc. by examining its hardness, and this is realized with a simple configuration by utilizing a piezoelectric element and the pressure change of gas. Hereinafter, embodiments according to the present invention will be described with reference to the drawings.

Example

[0010] FIG. 1 is a diagram for explaining the operating principle of a contactor according to the present invention. In the figure, 1 is a contactor, 2 is a flexible cylindrical tube filled with gas such as air, 3 is a detection unit for detecting the pressure of the gas in the tube 2, 4 is a connection unit connecting the tube 2 and the detection unit 3, 5 is a gas introduction unit provided inside the detection unit 3 for guiding the gas in the tube 2 to the piezoelectric element, 6 is a piezoelectric element, and 7 is a substrate integrally connected to the piezoelectric element 6.

[0011] The tube 2 is formed of a flexible and flexible material such as plastic resin, has a hollow inside and is filled with gas such as air at a predetermined pressure, and has a structure with one end closed. It is known that the higher the internal pressure, the higher the sensitivity of the force applied to the tube 2 from the outside, and the gas pressure is adjusted so as to achieve the required sensitivity. The length and diameter of the tube 2 can be changed and used according to the location to be measured etc. The gas in the tube 2 acts on the piezoelectric element 6 through the connection unit 4 connected to one end and the gas introduction unit 4 in the detection unit 3. The piezoelectric element 6, together with the integrated substrate 7, is pressed downward in the figure as the gas pressure increases, and a voltage is generated from the substrate 7 due to the piezoelectric effect accompanying the deformation and vibration of the piezoelectric element 6. In this way, the deformation amounts of the piezoelectric element 6 and the substrate 7 are in a proportional relationship with the magnitude of the gas pressure fluctuation, and since a voltage corresponding to the deformation amount is generated from the substrate 7, a voltage proportional to the magnitude of the pressing force applied to the tube 2 is generated.

[0012] FIG. 2 is a diagram for explaining the content of a table according to the present invention. In the figure, 8 shows the recording state of a specific table. For example, when evaluating the hardness of fruits such as apples as the object, it is necessary to create Table 8 for each fruit in advance. In Table 8, using the tube 2 actually used for evaluation, when a certain force applied during evaluation is applied to the entire tube 2, the output voltage from the piezoelectric element 6 with respect to the deformation amount of the tube 2 (change in gas pressure) is recorded, and this deformation amount corresponds to the degree of hardness. That is, when the reaction force from the object is small, the deformation amount is small and the output voltage is also small, the object is judged to be soft, and as the reaction force increases and the deformation amount also increases, the object is judged to be hard.

[0013] Therefore, for each fruit such as an apple which is the object in this case, set in advance the allowable degree of hardness, that is, the allowable range of the output voltage. Thereby, it becomes possible to select only fruits with a certain hardness, and the others can be configured to be removed as defective products. In addition, since it becomes difficult to evaluate when the deformation amount (change in gas pressure) of the tube 2 is small, in practical use, the shape of the tube 2 used and the certain force applied during evaluation need to be configured appropriately so that evaluation can be performed depending on the object. Also, the content recorded in Table 8 needs to be corrected as the length, shape, etc. of the tube 2 used are changed.

[0014] To specifically evaluate the object, first, bring the entire tube 2 of the contactor 1 into contact with the object, and then configure to apply a certain pressure to the entire tube 2 for a predetermined time, and measure the voltage output at that time. Then, compare (refer to) the output voltage value with the voltage value in Table 8 recorded in advance for the object. If the voltage value is within the set allowable range, the object is evaluated to have an appropriate hardness. That is, across the entire length of the tube 2 in contact with the object, a voltage corresponding to the total reaction force on the tube 2 is generated from the piezoelectric element, and the degree of hardness is evaluated. The allowable range can be determined according to the type of the object, etc. In the case of fruits, the degree of ripeness, the degree of hardness in case of damage, etc. are converted into voltage values to set the range of allowable voltage values. The conversion of the hardness into voltage values can be obtained by measuring in advance the voltage values output for fruits with acceptable hardness.

[0015] Here, the predetermined time is the time when the object does not break when a constant pressure is continuously applied to the object. However, for example, there may be a case where the surface is soft and the inside is hard. When it is desired to evaluate based on the surface state, it is necessary to shorten the time for applying pressure so that the contact 1 does not reach the inside of the object. Also, in the above embodiment, the entire tube 2 is described as being in contact with the object, but it is also possible to configure it such that only a part of the tube 2 is in contact to apply pressure, and the table 8 is also configured to record the contact of a part of the tube 2. Since the tube 2 is flexible, it has the advantage that it can be deformed into an arbitrary shape to evaluate the hardness.

[0016] FIG. 3 is a diagram for explaining another embodiment of the evaluation apparatus according to the present invention. In the figure, 9 and 10 are slide doors that open and close left and right when passengers get on and off a railway vehicle, 11 and 12 are rubber members attached to the opening and closing ends of the slide doors 9 and 10, and 13 and 14 are flexible members (cylindrical tubes) of the same length with gas sealed inside the contactors according to the present invention. 15 is a detection unit incorporating a piezoelectric element connected to the flexible members 13 and 14, respectively. The flexible members 13 and 14 extend from top to bottom along the edges of the slide doors 9 and 10 and are configured to be inserted inside the rubber members 11 and 12. They have the same length and are configured as cylindrical tubes of the same shape so that the sensitivities are the same. While the slide doors 9 and 10 are closed, the rubber members 11 and 12 are pressed against each other with a predetermined pressure.

[0017] Conventionally, a piezoelectric material was inserted inside rubber members 11 and 12. When a foreign object was pinched by a passenger's body or carry-on items as the slide doors 9 and 10 opened and closed, the piezoelectric material converted the deformation of the rubber members 11 and 12 into an electrical signal and output it as an alarm, either automatically or when the crew noticed the abnormality and performed an operation to open the slide doors 9 and 10. However, the rubber members 11 and 12 are easily damaged or worn by foreign objects, etc. For this reason, even when a foreign object is pinched, the recognition by the piezoelectric material may become impossible, or the replacement of the expensive piezoelectric material may be required, etc., and maintenance work has occurred frequently.

[0018] By adopting the evaluation device according to the present invention, the cylindrical tubes 13 and 14 inserted inside the rubber members 11 and 12 themselves are deformed at some locations by pressing together with the members 11 and 12, and the pinching of a foreign object can be detected, and it is less affected by damage or wear of the rubber members 11 and 12. In addition, not only the presence or absence of pinching can be detected, but also the hardness of the foreign object pinched can be detected corresponding to the magnitude of the output voltage. Thereby, for example, when a passenger's body is pinched in the slide doors 9 and 10, etc., the urgency can be notified. The detection unit 15 is connected to the tubes 13 and 14 respectively, obtains the average value of the voltage generated by a piezoelectric element (not shown) from the change in the gas pressure of each, and compares and refers to the voltage value in a previously prepared table to detect the hardness of the foreign object. It should be noted that the gas in the tubes 13 and 14 can also be made into one, and it can be configured to compare and refer to the output voltage from one piezoelectric element.

Industrial Applicability

[0019] The present invention is not limited to the above-described embodiments. It is also possible to make the contactor portable and sandwich the object to be measured, and evaluate the hardness. Further, instead of the tube, it can be configured with a material having other shapes with flexibility. In the field of medical care, for example, in order to examine the body movement of a patient lying in a bed, a tube can be arranged under a pillow or on the bed, and it can be applied to monitor abnormalities of the patient such as breathing and pulse from the magnitude and occurrence frequency of the output voltage.

Description of Reference Numerals

[0020] 1 Contact 2, 13, 14 Tube 3, 15 Detection Unit 4 Connection Part 5 Gas Introduction Part 6 Piezoelectric Element 7 Substrate 8 Table 9, 10 Slide Door 11, 12 Rubber Member

Claims

1. A hardness evaluation device using a piezoelectric element, comprising: a contactor partially composed of a flexible member containing a gas sealed inside; when the flexible member is pressed from the outside, the pressure of the internal gas changes, and this pressure change causes a piezoelectric element provided in contact with the internal gas to deform and generate a voltage; and a table that predetermines the relationship between the degree of hardness of an object and the magnitude of the generated voltage, wherein the flexible member constituting the contactor is pressed against the object with a constant pressure for a predetermined period of time, and the voltage generated from the contactor and the table are referenced to evaluate the hardness of the object.

2. The hardness evaluation device using a piezoelectric element as described in claim 1, characterized in that the contactor is composed of a plurality of contactors, each of which is made of a tubular flexible material of the same length and shape with gas sealed inside, and one end of which is provided with the piezoelectric element so as to be in contact with the internal gas.

3. 3. The hardness evaluation device using a piezoelectric element as described in claim 2, characterized in that the contactor made of the tubular flexible member is arranged at the opening and closing portion of a sliding boarding and alighting door of a railway vehicle.

4. 3. The hardness evaluation device using a piezoelectric element according to claim 2, wherein the voltages generated from the plurality of contacts are averaged and referenced to the table.

5. 2. The hardness evaluation device using a piezoelectric element as described in claim 1, characterized in that the table is created for each type of object, and an allowable range for evaluation according to the hardness of the voltage generated from the piezoelectric element depending on the applied pressure is set.

6. A method for evaluating hardness, comprising pressing a contactor, part of which is made of a flexible material containing gas sealed inside, against an object with a constant pressure for a predetermined period of time, causing a piezoelectric element provided in contact with the internal gas to deform due to changes in pressure of the internal gas, thereby generating a voltage, and evaluating the hardness of the object from the relationship between a predetermined degree of hardness of the object and the magnitude of the generated voltage.

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