Sensor case, embedded sensor using the same, method for measuring strain of measurement object, and method for attaching the same

Abstract

To provide a sensor case which can measure the strain of such a metal mold as a measurement object, with a simple structure, an embedded sensor using the sensor case, a method for measuring the strain of a measurement object, and a method for attaching the sensor case.SOLUTION: A sensor case 1 according to one aspect of the invention includes: a pair of fitting parts 11; and a narrowed part 12 arranged between the fitting parts, the narrowed part being shaped to have a constricted portion thinner than the fitting parts; and a through-hole 13 passing through the fitting parts and the narrowed part for inserting a sensor unit 2. The embedded sensor S according to another aspect of the invention includes the sensor case and a sensor unit inserted into the through-hole. The method for measuring a strain according to another aspect of the invention measures a strain by embedding the embedded sensor in a measurement object.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sensor case, an embedded sensor using the same, a method for measuring strain on a measurement object, and a method for attaching the sensor case. [Background technology]

[0002] In industrial products, molds are commonly used to transform materials into desired shapes. For example, everyday resin products are manufactured by injecting molten resin into a mold with a cavity of the desired shape, cooling it down to solidify, and then removing the resin. Metal products, such as window frames, are manufactured by placing a flat metal sheet between a pair of molds (a press mold and a die mold) and engaging these molds to transform the flat metal sheet into the desired shape. Furthermore, in the mobility field, typified by automobiles, molds are used to manufacture key components such as shafts and gears that form the core of the drivetrain. In recent years, with the advancement of IoT and DX initiatives, attention has been focused on monitoring and managing the condition of molds during the manufacturing process in order to stabilize and streamline industrial production activities and improve quality control.

[0003] Incidentally, the material of a mold must be a hard material such as metal, and generally is not easily deformed, but deformation (distortion) can occur due to heat, impact, etc. This distortion affects the shape of the manufactured product, so understanding the state of this distortion is important from the perspective of manufacturing products with higher precision.

[0004] As a technique related to the above, for example, Patent Document 1 below describes a technique for attaching a strain gauge inside an attachment hole. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Utility Model Application Publication No. 2-67207 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the above-mentioned technology has problems in that the strain gauge has a complicated structure and requires complicated specifications such as using hydraulic pressure to press the strain gauge.

[0007] In view of the above problems, the present invention aims to provide a sensor case that can perform strain measurements on a measurement object such as a mold with a simpler structure, an embedded sensor using the same, a method for measuring strain on a measurement object, and a method for attaching the sensor case. [Means for solving the problem]

[0008] In other words, a sensor case according to one aspect of the present invention comprises a pair of fitting portions and a constricted portion disposed between the pair of fitting portions and having a narrower constriction than the fitting portions, and has a through hole formed through the fitting portions and the constricted portion for incorporating a sensor unit.

[0009] In addition, in this respect, although not limited thereto, it is preferable that the outer periphery of the fitting portion has a recess formed along the insertion direction.

[0010] In addition, from this viewpoint, it is preferable that the combination of the maximum outer diameter OD and minimum outer diameter CD of the constricted portion and the hole diameter ID of the through hole is within a range that satisfies the formula 140≦43.5×OD−0.243×ID−45.7×CD+138.649≦1000.

[0011] In this respect, it is also preferable that the pair of mating portions have a cylindrical outer diameter that is 0.04% to 0.20% larger than the mounting hole dimensions and have a truncated conical shape at the end. If possible, it is preferable that the cylindrical outer diameter be 0.05% to 0.15% larger than the mounting hole dimensions.

[0012] Another aspect of the present invention provides an embedded sensor comprising a sensor case including a pair of fitting portions and a constricted portion disposed between the pair of fitting portions and narrower than the fitting portions, the sensor case having a through-hole that passes through the fitting portions and the constricted portion and through which the sensor unit is incorporated, and a sensor unit that is inserted into the through-hole of the sensor case. The sensor unit inserted into the sensor case is attached using a fixing jig 3 and a fixing method such as a setscrew, crimping, or welding. At this time, it is desirable that the fixed sensor unit be subjected to a strain equivalent to 140 μST or more and 1000 μST or less.

[0013] Another aspect of the present invention provides a method for measuring strain in a measurement object by embedding an embeddable sensor in the measurement object, the embeddable sensor comprising: a pair of fitting portions and a constricted portion disposed between the pair of fitting portions and narrower than the fitting portions; a sensor case having a through-hole that penetrates the fitting portions and the constricted portion and through which a sensor unit is incorporated; and a sensor unit inserted into the through-hole of the sensor case. The maximum press-fit load for embedding the embeddable sensor in the measurement object is preferably in the range of 0.04 kN to 30 kN. Preferably, the load is controlled to be in the range of 0.1 kN to 3 kN, if possible.

[0014] In addition, a sensor installation method according to another aspect of the present invention involves press-fitting and fixing a sensor case having an outer diameter that is 0.04% to 0.20% larger than the dimensions of the mounting hole and having a truncated cone shape at the end into a measurement object having a mounting hole formed therein. [Effects of the Invention]

[0015] As described above, the present invention can provide a sensor case that can measure strain on a measurement object such as a mold with a simpler structure, an embedded sensor using the same, and a method for measuring strain on a measurement object. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 2 is a diagram illustrating an outline of a sensor case according to an embodiment. [Figure 2] 1 is a diagram showing an outline of an implantable sensor into which a sensor unit according to an embodiment is inserted. [Figure 3] 1 is an image diagram of a cross section of an embedded sensor according to an embodiment embedded in a measurement object. [Figure 4] 10A and 10B are diagrams illustrating an example of an arrangement when minute concaves and convexes are provided on a sensor case according to an embodiment. [Figure 5] FIG. 10 is a diagram showing an analytical model of distortion caused by the difference between a necked shape and a cylindrical shape according to an embodiment. [Figure 6] FIG. 10 is a diagram showing a formula and a determination range for evaluating the conformity of the case shape according to the embodiment. [Figure 7] FIG. 1 is a diagram illustrating an outline of a sensor unit according to an embodiment. [Figure 8] FIG. 1 is a diagram showing an outline of a multiple series arrangement according to an embodiment. [Figure 9] FIG. 2 is a diagram showing an outline of a sensor case according to an embodiment. [Figure 10] 1 is a diagram showing an outline of the process involved in fabricating an implantable sensor according to an embodiment. [Figure 11] FIG. 1 shows a test system for an implantable sensor according to an embodiment, and a graph of indentation load versus indentation amount. [Figure 12] FIG. 1 shows a measurement object in which the sensor of the embodiment is embedded, the state in which the sensor is embedded in the measurement object, the data logger and amplifier used, and the resulting signal waveform. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention can be embodied in many different forms and is not limited to the specific examples described in the following embodiments and examples.

[0018] (Embedded sensor system) Fig. 1 is a schematic diagram of a sensor case (hereinafter referred to as "this case") 1 according to this embodiment, and Fig. 2 is a schematic diagram of an embedded sensor (hereinafter referred to as "this sensor") S in which a sensor unit (hereinafter referred to as "this sensor unit") 2 is inserted into this case 1. Fig. 3 shows an image diagram of a cross section of a tubular sensor in which this sensor S is embedded.

[0019] As shown in the above diagram, the present case 1 is integrally formed with a pair of fitting portions 11 and a constricted portion 12 disposed between the pair of fitting portions 11. The constricted portion 12 is narrower than the fitting portions 11, and has a through-hole 13 that passes through the fitting portions 11 and the constricted portion 12 and into which the present sensor unit 2 is to be installed. The present sensor S is formed by installing the present sensor unit 2 in the through-hole 13 of the present case 1.

[0020] To reiterate, as described above, the case 1 has a pair of fitting portions 11 and a constricted portion 12 disposed between the pair of fitting portions 11 formed integrally therewith.

[0021] The fitting portion 11 in this case 1 is the portion that comes into contact with and is fixed to the inner wall of the sensor embedding hole MH when the sensor S is inserted into the sensor embedding hole MH formed in the measurement object M. In this case 1, by providing a pair of these fitting portions 11, the case 1 is stably fixed in two places.

[0022] Furthermore, in this case 1, although not limited thereto, it is preferable that the outer periphery of the fitting portion 11 has a recess 111 formed along the insertion direction. The effect of this will become clear from the description below, but the sensor unit 2 is connected to a conductor 22 for transmitting an electrical signal generated by strain, and this conductor 22 can be passed through. Furthermore, by providing this recess 111, it is possible to adjust the clearance of the fitting portion 11. Specifically, if the actual dimension of the fitting portion 11 is larger than the inner diameter of the sensor embedding hole MH, this recess 111 has the advantage of being able to sufficiently eliminate that misalignment.

[0023] Furthermore, although not limited thereto, it is also preferable that a notch 112 is provided from the end along the longitudinal direction of the fitting portion 11 of the present case 1. Providing the notch 112 has the advantage that, similar to the recess 111 described above, it is possible to easily embed the present sensor S in the measurement object M.

[0024] Furthermore, it is desirable that the fitting portion 11 of the present case 1 has a truncated cone shape 113 formed at its end. Providing this truncated cone shape 113 stabilizes the press-fit load for embedding the present sensor S in the measurement object M, and also has the effect of eliminating or reducing mutual damage caused by friction between the fitting portion 11 of the present case 1 and the mounting hole of the measurement object M during the press-fitting process.

[0025] Furthermore, the outer surface of the fitting portion 11 of the present case 1 may be provided with periodically formed minute asperities 114. Providing these minute asperities 114 has the advantage of enabling reliable contact with the sensor embedding hole MH, thereby improving adhesion. An example of this case is shown in FIG. 4. In the figure, (A) shows an example in which vertically elongated minute asperities 114 are arranged along the periphery along the long axis direction of the fitting portion 11, (B) shows an example in which multiple minute asperities 114 are arranged along the periphery of the fitting portion 11 in the long axis direction, (C) shows an example in which the above (A) is inclined spirally toward the long axis direction, and (D) shows an example in which the vertically elongated minute asperities 114 of the above (A) are divided into island-like shapes.

[0026] The constricted portion 12 is a narrowed portion that is thinner than the fitting portions 11. The constricted portion 12 is connected to the pair of fitting portions 11 and is formed integrally with them. That is, the case 1 is fixed to the inner wall of the sensor embedding hole MH by the pair of fitting portions 11, while the constricted portion 12 is spaced apart from the inner wall of the sensor embedding hole MH. That is, if distortion occurs in the object to be measured, the distance and orientation of the constricted portion 12 will change, and the stress generated by this change will be concentrated in the constricted portion 12. Therefore, by inserting the sensor unit 2 into this portion and performing detection, it becomes possible to detect distortion of the object to be measured M.

[0027] Furthermore, in this case 1, although not limited thereto, it is preferable that the combination of the maximum outer diameter OD and minimum outer diameter CD of the constricted portion 12 and the hole diameter ID of the through hole 13 satisfy the formula: 140≦43.5×OD−0.243×ID−45.7×CD+138.649≦1000. FIG. 5 shows an analytical model for comparing the magnitude of distortion caused by differences between a constricted shape and a cylindrical shape. Furthermore, multiple regression analysis was performed based on the analysis results to derive a formula for evaluating whether the shape parameters are compatible with this case 1 and a numerical range for determining the compatibility. FIG. 6 shows the formula and judgment range for evaluating the compatibility of the shape of this case 1 according to the embodiment. By providing the constricted portion 12, distortion of the measurement object M is concentrated as strain at the constricted portion 12, allowing the signal to be measured and handled as a value that changes more significantly than the strain experienced by a simple shape, such as a cylindrical shape. That is, there are advantages such as improved sensitivity to the occurrence of small distortions and ensuring strength that is not easily drowned out by disturbances or noise.

[0028] Furthermore, in this case 1, although not limited thereto, it is preferable that the pair of mating portions 11 have a cylindrical outer diameter that is larger than the mounting hole dimension by 0.04% to 0.20% and that the terminal has a truncated conical outer shape 113. This has the advantage of stabilizing the press-fitting load for embedding this sensor S in the measurement object M and eliminating or reducing mutual damage caused by friction between the mating portions 11 of this case 1 and the mounting hole of the measurement object M during the press-fitting process.

[0029] Furthermore, in this case 1, as described above, a through-hole 13 is formed that penetrates the fitting portion 11 and the constricted portion 12 and allows the sensor unit 2 to be embedded. By forming the through-hole 13, it becomes possible to insert the sensor unit 2. In this case, although the through-hole is configured to penetrate through, it is preferable that a step of different diameter is formed near the boundary between one of the fitting portions 11 and the constricted portion 12 so that the sensor unit 2 remains in the constricted portion 12. The sensor unit 2 will be embedded up to this part.

[0030] In the sensor S, the sensor unit 2 is inserted into the case 1. Fig. 7 shows an outline of the sensor unit 2. As shown in this figure, the sensor unit 2 includes a main body 21 and a conductor 22 connected to the main body 21.

[0031] The main body 21 of the sensor unit 2 is capable of outputting, when strain is applied, fluctuations in electrical properties such as charge or voltage caused by the strain as a signal via a conductor 22, and is not limited to this configuration as long as it has such a configuration, and may be, for example, a piezoelectric element or a strain gauge, but is not limited to these.

[0032] Furthermore, the sensor unit 2 is equipped with a conductor 22. By connecting the conductor 22 to a measuring device or the like that is separately provided outside the object to be measured M, an electrical signal can be detected, and the strain occurring in the object to be measured M can be quantified based on this electrical signal.

[0033] As is clear from the above description, the sensor S is embedded in the measurement object M. If the press-fit load required to embed the sensor S in the measurement object M is too small, the sensor S will come out, and if it is too large, the sensor S will buckle, so it is desirable that the maximum press-fit load be within the range of 0.04 kN or more and 30 kN or less. The measurement object M is not limited as long as it is something for which strain needs to be detected, but can be various materials such as metal, resin, glass, etc. More specific examples of metal include molds, pressure-receiving shafts of moving objects, and support columns of structures.

[0034] Furthermore, although this sensor S is inserted into the sensor embedding hole MH, it is also useful to arrange multiple sensors in series in one sensor embedding hole MH. An image of such a case is shown in Figure 8. By doing so, it is possible to detect strain at each position in the entire arrangement direction, which has the advantage of enabling higher accuracy.

[0035] (Measurement method) In addition, a method for measuring strain on a measurement object according to another aspect of the present invention involves embedding an embedded sensor in the measurement object, the embedded sensor having a pair of fitting portions, a constricted portion disposed between the pair of fitting portions and having a narrower constriction than the fitting portions, a sensor case having a through hole that penetrates the fitting portions and the constricted portion and for embedding a sensor unit, and a sensor unit that is inserted into the through hole of the sensor case.

[0036] As described above, this embodiment can provide a sensor case that can measure strain on a measurement object such as a mold with a simpler structure, a sensor system using the same, and a method for measuring strain on the measurement object. [Example]

[0037] The above-mentioned case 1, the system using the case, and the strain measurement method using the case were actually manufactured and their effects were verified. A detailed description will be given below.

[0038] A sensor case was designed for a base plate (diameter φ176 × thickness t25) with a mounting hole φ9, which is the object to be measured. The design requirements were that the pair of mating parts have a cylindrical outer diameter that is 0.04% to 0.20% larger than the mounting hole dimensions, and that the terminal has a truncated conical outer shape, and that the combination of the maximum outer diameter OD and minimum outer diameter CD of the constricted part that makes up constricted part 12 and the hole diameter ID of the through hole must satisfy the shape definition: 140≦43.5×OD-0.243×ID-45.7×CD+138.649≦1000.

[0039] In this example, the mating sections are cylindrical with a diameter of 9.01 mm, with chamfered ends (C1). The maximum outer diameter (OD) of the constricted section is 9.01 mm, the minimum outer diameter (CD) is 5.5 mm, and the through-hole diameter (ID) is 3.5 mm. This combination of dimensions results in a cylindrical outer diameter and a truncated cone that are 0.04% to 0.20% larger than the mounting hole dimensions. Substituting this into the formula 43.5 × OD - 0.243 × ID - 45.7 × CD + 138.649 yields 278.3835, which satisfies the shape definition of the present invention. An outline of the case 1 manufactured in this example is shown in Figure 9.

[0040] The case 1 can be manufactured by machining, plastic processing, casting, injection molding, or other methods, but in this example, it was shaped and manufactured using a metal 3D printer.

[0041] The fabricated case 1 was threaded to fit the fixture 3. After that, the sensor unit 2 was inserted into the case 1, and the lead wire 22 was soldered. After that, the sensor unit 2 was attached with a set screw that serves as the fixture 3, applying a compressive strain of approximately 260 μST. This completes the sensor S. Figure 10 shows an outline of the process for fabricating the sensor S.

[0042] The sensor S is embedded in a φ9 mounting hole, which is the object M to be measured. The truncated cone portion formed at the end of the sensor S is inserted into the mounting hole of the object to be measured. The upper jig is pressed down using a press machine, and the press-fit load is measured. The maximum press-fit load was 105N, and it was confirmed that it was within the range of 0.04kN to 30kN. Figure 11 shows the test system for the sensor S, and a graph of the press-fit load against the amount of pressing.

[0043] The signal cable from this sensor S attached to the measurement object M is connected to a data logger via an amplifier. When a load simulating the impact that the measurement object M will receive is applied with a hammer, the strain on the measurement object M caused by the external force is converted into a voltage, and it was confirmed that the data logger received this signal. Figure 12 shows the measurement object M in which this sensor S is embedded, the state of this sensor S embedded in this measurement object M, the data logger and amplifier used, and the resulting signal waveform.

[0044] As described above, this embodiment allows confirmation of the effects of this case, this system, and this method. [Industrial Applicability]

[0045] INDUSTRIAL APPLICABILITY The present invention has industrial applicability as a sensor case, a sensor system using the same, a method for measuring strain on a measurement object, and a method for attaching a sensor case. [Explanation of symbols]

[0046] 1. Sensor case 11...Mating part 111...dent 112...Notch 113...Truncated cone shape 114…Minute irregularities 12...Constriction 13...Through hole 2...Sensor unit 21...Main body 22...Conductor 3...Fixing jig S...Built-in sensor M: Measurement object MH: Sensor embedding hole

Claims

1. A pair of fitting portions; a constricted portion disposed between the pair of fitting portions and having a constriction formed therein that is narrower than the fitting portions, a sensor case having a through hole formed therein that passes through the fitting portion and the constricted portion and into which a sensor unit is to be incorporated;

2. The sensor case of claim 1, wherein the combination of the maximum outer diameter OD and minimum outer diameter CD of the constricted portion and the hole diameter ID of the through hole satisfies the formula 140≦43.5×OD−0.243×ID−45.7×CD+138.649≦1000.

3. 3. The sensor case according to claim 1, wherein the pair of fitting portions have an outer diameter that is larger than the size of the mounting hole by 0.04% to 0.20% and the terminals have a truncated conical outer shape.

4. 3. The sensor case according to claim 1, wherein the fitting portion has an outer periphery having a recess formed along the insertion direction.

5. a sensor case including a pair of fitting portions and a constricted portion disposed between the pair of fitting portions and having a constriction formed therein that is narrower than the fitting portions, the sensor case having a through hole formed therein that penetrates the fitting portions and the constricted portion and into which a sensor unit is incorporated; and a sensor unit that is inserted into the through-hole of the sensor case.

6. A method for measuring strain in an object to be measured, comprising embedding an embedded sensor in the object to measure strain, the embedded sensor comprising: a pair of fitting portions; a constricted portion disposed between the pair of fitting portions and having a constriction that is narrower than the fitting portions; a sensor case having a through hole that passes through the fitting portions and the constricted portion and through which a sensor unit is incorporated; and a sensor unit that is inserted into the through hole of the sensor case.

7. A sensor case mounting method in which a sensor case having an outer diameter that is 0.04% to 0.20% larger than the dimensions of a mounting hole and having a truncated cone shape at the end is press-fitted into a measurement object having a mounting hole formed therein.

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