Measurement device and tool holder

Abstract

To enable accurate measurement of strain on an object under measurement.SOLUTION: A measurement device (1) provided herein comprises a strain gauge (2) and a main body (3) having the strain gauge (2) attached to a first side face (31) thereof. When accommodated in a hole (101) of a tool holder (100), a first side edge (34), second side edge (35), and third side edge (36) of the measurement device are in contact with an inner wall surface (102) of the tool holder.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a measuring device for measuring the distortion of a measurement object, and to a tool holder equipped with said measuring device. [Background technology]

[0002] Conventionally, technology for measuring the strain of a measurement target with high accuracy has been researched and developed. For example, Patent Document 1 discloses a cutting force detector that includes a screw-shaped main body, a rectangular column provided at one end of the main body, and a strain gauge attached to the side of the rectangular column. This cutting force detector is fixed to the blade mounting base by inserting the rectangular column into a screw hole formed in the blade mounting base of a cutting machine and then tightening the main body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Registered Utility Model No. 3039407 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the cutting force detector disclosed in Patent Document 1, the rectangular column is separated from the screw hole of the blade mounting base, and does not follow the deformation of the screw hole caused by the generation of cutting force. Therefore, the effect of the deformation of the screw hole is not transmitted to the strain gauge via the rectangular column, and as a result, it is difficult to obtain highly accurate measurement results from the strain gauge.

[0005] One aspect of the present invention has been made in consideration of the above-mentioned problems, and has an object to measure the strain of a measurement object with high accuracy. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, a measuring device according to one embodiment of the present invention comprises a strain gauge and a main body having one or more planar side surfaces with the strain gauge attached to at least one of the planar side surfaces, and when the main body is accommodated in a cylindrical hole formed in an object to be measured by the strain gauge, two or more side ends including the longer sides of the planar side surfaces come into contact with an inner wall surface of the object to be measured that forms the hole.

[0007] In order to solve the above-mentioned problems, a tool holder according to one embodiment of the present invention is a tool holder equipped with a measuring device for holding a tool, the measuring device comprising: a strain gauge for measuring strain of the tool holder; and a main body having one or more planar side surfaces with the strain gauge attached to at least one of the planar side surfaces, wherein when the main body is accommodated in a cylindrical hole formed in the tool holder, two or more side end portions including longer sides of the planar side surface come into contact with an inner wall surface of the tool holder that defines the hole. Effect of the Invention

[0008] According to one aspect of the present invention, not only can the strain gauge measure the strain of the measurement object with high accuracy via the main body, but the orientation of the strain gauge with respect to the measurement object can also be easily adjusted. [Brief description of the drawings]

[0009] [Figure 1] 1 is a block diagram showing a functional configuration of a measurement system according to an embodiment of the present invention. [Diagram 2] 1 is a diagram showing a main configuration of a measuring device according to an embodiment of the present invention; [Diagram 3] Reference numerals 301 and 302 show the state in which the measuring device shown in FIG. 2 is housed in a hole of a tool holder. [Figure 4] Reference numerals 401 to 404 are top views showing modified examples of the measuring device shown in FIG. [Diagram 5]Reference numeral 501 denotes a photograph substituting a drawing showing a test method according to one embodiment of the present invention. Reference numeral 502 denotes a cross-sectional view of the acrylic plate shown in reference numeral 501 taken along line VV. [Figure 6] Reference numerals 601 and 602 denote graphs showing the measurement results of the measuring device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [1. Measurement system configuration] The configuration of a measurement system ST according to an embodiment of the present invention will be described with reference to Fig. 1. The measurement system ST is a system for measuring the strain of a measurement target. As shown in Fig. 1, the measurement system ST includes a tool holder 100, a wireless communication unit 200, and an information processing device 300.

[0011] The tool holder 100 is a holder that holds a tool. Although a tip holder that holds a cutting tip is given as an example of the tool holder 100, the tool holder 100 may be any holder that holds some kind of tool. The tool holder 100 is equipped with a measuring device 1. The measuring device 1 is an instrument equipped with a strain gauge 2 that measures the strain of the tool holder 100. That is, in this embodiment, the tool holder 100 is the measurement target of the measurement system ST.

[0012] Note that the measurement target of the measurement system ST (specifically, the measurement target of the measuring device 1) is not limited to the tool holder 100. In other words, the measuring device 1 may be provided on a measurement target other than the tool holder 100. For example, the measurement target may be a mold used in plastic processing, casting, injection molding, carbon fiber plastic molding, etc. In addition, for example, the measurement target may be a mold part such as a pressure holding pin or a guide pin, or a tool such as a wrench, a torque wrench, or a nipper.

[0013] The wireless communication unit 200 is a module that incorporates a small board on which a wireless chip, an antenna, and peripheral circuits are mounted, and in which software for wireless communication is installed. An example of wireless communication is a wireless LAN (Local Area Network). The wireless communication unit 200 also incorporates a Wheatstone bridge circuit 201. The Wheatstone bridge circuit 201 is wired-connected to the strain gauge 2 via gauge leads 202, and converts a resistance change in the strain gauge 2 caused by the strain of the tool holder 100 into a voltage value. Note that the wireless communication unit 200 is not an essential component of the measurement system ST, and for example, the tool holder 100 and the information processing device 300 may be wired-connected.

[0014] The information processing device 300 is a device that processes various types of information, and is, for example, a desktop / notebook personal computer, a tablet terminal, or a smartphone. The information processing device 300 also performs wireless communication with the wireless communication unit 200, and receives a voltage value output from the Wheatstone bridge circuit 201 via the wireless communication unit 200. The information processing device 300 also calculates a strain of the tool holder 100 using the voltage value acquired from the Wheatstone bridge circuit 201, and outputs the calculation result to an output unit (display unit, printer, etc.) not shown.

[0015] [2. Configuration of measuring equipment] The configuration of a measuring device 1 according to an embodiment of the present invention will be described with reference to FIG. 2. As shown in FIG. 2, the measuring device 1 includes a strain gauge 2 and a main body 3. In this embodiment, the strain gauge 2 is a biaxial strain gauge composed of a first strain gauge 21 and a second strain gauge 22. Specifically, the strain gauge 2 is a two-gauge two-active method (orthogonal arrangement) strain gauge in which the first strain gauge 21 and the second strain gauge 22 have the same configuration and are orthogonal to each other. The first strain gauge 21 and the second strain gauge 22 are both known strain gauges and have a general strain gauge structure.

[0016] By configuring the strain gauge 2 as described above, it is possible to avoid a decrease in the measurement accuracy of the strain gauge 2 caused by thermal expansion / contraction of the strain gauge 2 and the tool holder 100. Here, the thermal expansion / contraction occurs due to a rise / fall in temperature of the strain gauge 2 and the tool holder 100 during a series of processes for machining using a tool held by the tool holder 100.

[0017] There is no particular limitation on the configuration of the strain gauge 2, and for example, the first strain gauge 21 and the second strain gauge 22 may be arranged in parallel. For example, the strain gauge 2 may be a uniaxial strain gauge composed of a single strain gauge. For example, the strain gauge 2 may be a four-axis strain gauge composed of four strain gauges. Alternatively, a plurality of strain gauges 2 may be attached to the first side surface 31, or a strain gauge 2 may be attached to at least one of the second side surface 32 and the third side surface 33.

[0018] The main body 3 has one or more planar side surfaces, and the strain gauge 2 is attached to one or more of the planar side surfaces. With this configuration, when the measuring device 1 is accommodated in the hole 101 and before the main body 3 is adhesively fixed to the inner wall surface 102 by the adhesive 5, the user can check the orientation of the strain gauge 2 relative to the tool holder 100 by looking at the hole 101 from above. This makes it easy to determine whether or not to adjust the orientation of the strain gauge 2 relative to the tool holder 100. The details of the adhesive 5, the hole 101, and the inner wall surface 102 will be described later. The main body 3 also has two or more side ends including the longer sides of the planar side surfaces.

[0019] In this embodiment, the main body 3 has a generally triangular prism-like outer shape, and has a first side surface 31, a second side surface 32, and a third side surface 33 as planar side surfaces. The main body 3 also has a first side surface 34, a second side surface 35, and a third side surface 36 as side end portions. Furthermore, the main body 3 has a strain gauge 2 attached to the first side surface 31.

[0020] Here, the "plane" in "planar shape" does not refer to a perfect plane. For example, even if a part of the plane includes fine irregularities or curved areas, it still falls within the concept of "plane." Furthermore, the main body 3 may be either solid or hollow, but in this embodiment, the main body 3 is solid. Furthermore, there is no particular limitation on the material from which the main body 3 is formed.

[0021] The "approximately triangular prism shape" of the outer shape of the main body 3 will be specifically described below. The first side 31, the second side 32, and the third side 33 are each rectangular. In addition, of these three sides, the side in the height direction of the main body 3 is the long side (longer side), and the side on the bottom side of the main body 3 is the short side (short side). Furthermore, the short side of the first side 31 is the longest, and the short side of the second side 32 is the same length as the short side of the third side 33. Here, "same" in this specification does not mean completely same. Even if there is a slight error, it still falls within the concept of "same".

[0022] The first side surface 31 and the second side surface 32 are connected via a first end portion 34. That is, the first end portion 34 includes the long side of the first side surface 31 and the long side of the second side surface 32. The second side surface 32 and the third side surface 33 are connected via a second end portion 35. That is, the second end portion 35 includes the long side of the second side surface 32 and the long side of the third side surface 33. Furthermore, the third side surface 33 and the first side surface 31 are connected via a third end portion 36. That is, the third end portion 36 includes the long side of the third side surface 33 and the long side of the first side surface 31.

[0023] The first side end 34, the second side end 35, and the third side end 36 each have a curved surface that is convex toward the outside of the main body 3 over the entire height of the main body 3. In addition, the curvature of the surface of all three side ends is the same over the entire height of the main body 3. That is, the surfaces of all three side ends are rounded. The curvatures of the rounded surfaces of the three side ends may all be the same or may be different from each other. In this embodiment, the curvatures of the rounded surfaces of the three side ends are all the same. In addition, it is not necessary that the curvature of the surface of each of the three side ends is the same over the entire height of the main body 3. For example, the curvature may change or the shape may change to a flat shape in the middle of the height of the side ends.

[0024] To express the above features in another way, the cross section (hereinafter, "reference cross section") of the main body 3 when the main body 3 is cut on a virtual plane perpendicular to the central axis CA has an outer shape of an approximately isosceles triangle. The central axis CA is an axis that passes through the center of gravity G of the reference cross section and extends along the height direction of the main body 3. Specifically, the "approximately isosceles triangle" means that the longest side of the three sides included in this figure is the short side of the first side 31, and the remaining two sides of the same length are the short sides of the second side 32 and the third side 33. In addition, the curve connecting the two sides is a curve that forms the outer shape of each of the first side end 34, the second side end 35, and the third side end 36 when viewed in plan. In this embodiment, regardless of the height at which the main body 3 is cut on a virtual plane perpendicular to the central axis CA, the reference cross section is uniformly an approximately isosceles triangle. However, the reference cross section does not need to be a uniformly approximately isosceles triangle, and for example, the shape of the reference cross section may differ depending on the cut position in the height direction of the main body portion 3.

[0025] Next, a specific description will be given of how the strain gauge 2 is attached to the first side surface 31. The strain gauge 2 is attached to an end region 311 on the short side of the first side surface 31. When the measuring device 1 is housed in a hole 101 described below, the end region 311 is disposed on the bottom side of the hole 101 (see reference numeral 301 in FIG. 3).

[0026] More specifically, the first strain gauge 21 is attached to the end region 311 so that the end on the short side of the gauge base is located on the bottom side of the main body 3. Strictly speaking, the "end on the short side of the gauge base" refers to the end on the short side of the gauge base where the gauge lead 202 is not present. The second strain gauge 22 is attached to the end region 311 so as to cover the first strain gauge 21 from the outside of the main body 3 and to be perpendicular to the first strain gauge 21 (not necessarily completely perpendicular). "Perpendicular to the first strain gauge 21" specifically means that the center line extending in the longitudinal direction of the gauge base of the second strain gauge 22 is perpendicular to the center line extending in the longitudinal direction of the gauge base of the first strain gauge 21.

[0027] For example, a dedicated adhesive is used to attach each of the first strain gauge 21 and the second strain gauge 22. Specifically, a dedicated adhesive is applied to the back surface of the gauge base of each strain gauge and adhered to the end region 311, thereby adhesively fixing each of the first strain gauge 21 and the second strain gauge 22 to the end region 311. The back surface of the gauge base is the surface opposite to the surface on which the grid portion (gauge pattern) of the gauge base is laminated.

[0028] The manner of mounting the strain gauge 2 to the first side surface 31 is not limited to the example of this embodiment. For example, the mounting position of the strain gauge 2 is not particularly limited, and the mounting position can be changed as appropriate depending on the types of the strain gauge 2 and the tool holder 100, the location where the hole 101 is formed, the processing method using the tool holder 100, etc. Also, as for the mounting method of the strain gauge 2, a method other than the method of adhesively fixing it with a dedicated adhesive can be adopted.

[0029] 3. How the measuring device is accommodated in the hole With reference to Fig. 3, the manner in which the measuring device 1 is accommodated in the hole 101 will be described. For the sake of simplicity, the outer shape of the tool holder 100 is illustrated as a rectangular prism shape at 301 in Fig. 3. Furthermore, the adhesive 5 described below is not illustrated at 301 in Fig. 3. Furthermore, the gauge lead 202 is not illustrated at 302 in Fig. 3.

[0030] As shown in Fig. 3, a cylindrical hole 101 is formed in the tool holder 100. The hole 101 is defined by an inner wall surface 102 of the tool holder 100. The measuring device 1 is accommodated in the hole 101, whereby the measuring device 1 is provided in the tool holder. Here, the "cylinder" in "cylindrical shape" does not refer to a perfect cylinder. For example, even if the inner wall surface 102 forming the outer shape of the side surface of the cylinder includes a part with minute concaves and convexes / flat areas, it still falls within the category of the concept of a "cylinder."

[0031] The hole 101 may be a through hole or may have a closed bottom. In this embodiment, the bottom of the hole 101 is closed. There is no particular limitation on the location where the hole 101 is formed, and the hole 101 may basically be formed in any location on the tool holder 100. However, it is preferable that the hole 101 is formed in a location where the measurement accuracy of the strain gauge 2 is improved depending on the types of the strain gauge 2 and the tool holder 100, the machining method using the tool holder 100, and the like.

[0032] When the measuring device 1 is accommodated in the hole 101, two or more side ends of the main body 3 contact the inner wall surface 102. In this embodiment, when the measuring device 1 is accommodated in the hole 101, all of the first side end 34, the second side end 35, and the third side end 36 contact the inner wall surface 102 over the entire height of the main body 3. Here, the curvature of each surface of these three side ends may be the same as or different from the curvature of the inner wall surface 102. In this embodiment, as shown by reference numeral 302 in FIG. 3, the curvature of each surface of these three side ends is larger than the curvature of the inner wall surface 102. It is not necessary for all of these three side ends to contact the inner wall surface 102 over the entire height of the main body 3, and it is sufficient that these three side ends contact the inner wall surface 102 to an extent that they follow the deformation of the inner wall surface 102 caused by strain.

[0033] Furthermore, before being bonded and fixed to the inner wall surface 102 by the adhesive 5 (details will be described later), the main body 3 is rotatable inside the hole 101 about the rotation axis AR. Specifically, when the main body 3, i.e., the measuring device 1, is rotated about the rotation axis AR, each of the first side end 34, the second side end 35, and the third side end 36 slides on the inner wall surface 102. Here, the rotation axis AR coincides with the central axis of the hole 101. The central axis of the hole 101 is an axis that extends in the depth direction of the hole 101.

[0034] In this embodiment, the rotation axis AR is located on the first side surface 31. In other words, in the approximately isosceles triangle that forms the outline of the reference cross section, the longest side (the short side of the first side surface 31) is located on an imaginary straight line that indicates the hole diameter of the hole 101. That is, in this embodiment, the outline of the reference cross section is an approximately right-angled isosceles triangle. However, the outline of the reference cross section does not have to be an approximately isosceles triangle, and may be, for example, an approximately equilateral triangle.

[0035] It is preferable that the main body 3 has an outer shape in which the rotation axis AR is sandwiched between two side surfaces of the main body 3. In this embodiment, the main body 3 has an outer shape in which the rotation axis AR is located on the first side surface 31, but is sandwiched between the second side surface 32 and the third side surface 33. By giving the main body 3 such an outer shape, the three side ends can reliably slide on the inner wall surface 102, and the main body 3 can stably rotate inside the hole 101.

[0036] In addition, in this embodiment, when the measuring device 1 is housed in the hole 101, the bottom surface of the main body 3 on the side of the end region 311 abuts on the bottom of the hole 101, and the other bottom surface of the main body 3 is substantially flush with the surface of the tool holder 100. In other words, the depth of the hole 101 and the height of the main body 3 are substantially the same.

[0037] In this embodiment, when the measuring device 1 is housed in the hole 101, the space 4 between the first side surface 31 and the inner wall surface 102 is filled with adhesive 5, and the strain gauge 2 is embedded in the adhesive 5. Specifically, the entire area of ​​the space 4 is filled with adhesive 5, and the entire strain gauge 2 is embedded in adhesive 5. In this way, the measuring device 1 is adhered and fixed to the inner wall surface 102.

[0038] Such filling of adhesive 5 is performed after the orientation of strain gauge 2 relative to tool holder 100 has been determined to be favorable in terms of measurement accuracy. The favorable orientation of strain gauge 2 in terms of measurement accuracy may be determined at the time when measuring device 1 is accommodated in hole 101, or may be determined by rotating measuring device 1 around rotation axis AR after measuring device 1 is accommodated in hole 101.

[0039] The manner in which the measuring device 1 is fixed to the inner wall surface 102 is not limited to the example of this embodiment. For example, the adhesive 5 may be filled only in a part of the space 4. In this example, depending on the mounting position of the strain gauge 2 on the first side surface 31, a part or all of the strain gauge 2 is exposed from the adhesive 5, but there is no problem even if it is exposed. For example, instead of filling the space 4 with the adhesive 5, the adhesive 5 may be applied to at least one surface of the first side end 34, the second side end 35, and the third side end 36, and the adhesive 5 may be adhered and fixed to the inner wall surface 102. Alternatively, a jig that can be placed in the space 4 and can fix the main body 3 to the inner wall surface 102 may be attached to the main body 3, and the measuring device 1 and the jig may be housed in the hole 101 to fix the measuring device 1 to the inner wall surface 102. In other words, the measuring device 1 may be fixed to the inner wall surface 102 in some way while being housed in the hole 101.

[0040] Furthermore, in this embodiment, when the measuring device 1 is housed in the hole 101, the strain gauge 2 is spaced apart from the inner wall surface 102. Although a part of the strain gauge 2 may be in contact with the inner wall surface 102, it is preferable that the entire strain gauge 2 is spaced apart from the inner wall surface 102 from the viewpoint of measurement accuracy.

[0041] 4. Modifications A modified example of the measuring device 1 according to an embodiment of the present invention will be described with reference to Fig. 4. In order to simplify the drawing, Fig. 4 illustrates the outer shape of the strain gauge 2 in a plan view as a rectangle.

[0042] First, a first modified example of the present invention is a measuring device 1-1 equipped with a main body 3-1 having an outer shape as shown by reference numeral 401 in Fig. 4. The outer shape of the main body 3-1 is a substantially rectangular prism, and the surfaces of all four side ends are rounded. The reference cross section of the main body 3-1 is substantially square, but it may be, for example, substantially rectangular or substantially trapezoidal.

[0043] Next, a second modified example of the present invention is a measuring device 1-2 having a main body 3-2 with an external shape as shown by reference numeral 402 in FIG. 4. The main body 3-2 has an external shape of a triangular prism, and all three side ends are side edges. Specifically, in the main body 3-2, a long side edge of a side surface of a planar shape overlaps with a long side edge of a side surface of another planar shape to form one side edge. Then, when the measuring device 1-2 is housed in the hole 101, these three side edges come into contact with the inner wall surface 102.

[0044] Here, the "side edge" in this specification does not mean a complete side edge. Even if the side edge of the main body 3-2 is actually a long and narrow rectangular plane with a very small width, if the side edge is long and narrow enough to look like a side edge when a person skilled in the art holds the main body 3-2 and visually checks it, it corresponds to the "side edge" in this specification.

[0045] Next, a third modified example of the present invention is a measuring device 1-3 having a main body 3-3 having an external shape as shown by reference numeral 403 in FIG. 4. The main body 3-3 has an external shape of a thin rectangular plate, and each end face of the two side ends is flat. In addition, the center line (not shown) of the main body 3 extending in the width direction of the main body 3-3 in the reference cross section is located on an imaginary straight line indicating the hole diameter of the hole 101. Then, when the measuring device 1-3 is accommodated in the hole 101, both sides on the long sides of the side surface of the planar shape and both sides on the long sides of the side surface of the other planar shape contact the inner wall surface 102. These two sides constitute the external shape of each end face of the two side ends.

[0046] Next, a fourth modified example of the present invention is a measuring device 1-4 having a main body 3-4 having an external shape as shown by reference numeral 404 in FIG. 4. The main body 3-4 is configured by connecting a first main body 3-4-1 having an external shape of a thin rectangular plate and a second main body 3-4-2 having an external shape of a thin rectangular plate so that these two main body parts are perpendicular to each other. The width of the first main body 3-4-1 is approximately half the diameter of the hole 101, and the width of the second main body 3-4-2 is approximately the same as the diameter of the hole 101. The height of the first main body 3-4-1 is the same as the height of the second main body 3-4-2.

[0047] The main body 3-4 has a T-shaped reference cross section, and each end face of the three side ends is flat. In addition, in the main body 3-4, in a cross-sectional area corresponding to the first main body portion 3-4-1 in the reference cross section, a center line (not shown) extending in the width direction of the first main body portion 3-4-1 is located on an imaginary straight line indicating the hole diameter of the hole 101. In addition, in the main body 3-4, in a cross-sectional area corresponding to the second main body portion 3-4-2 in the reference cross section, a center line (not shown) extending in the width direction of the second main body portion 3-4-2 is located on an imaginary straight line indicating the hole diameter of the hole 101. The contact manner of the three side ends with the inner wall surface 102 is the same as that of the measuring device 1-3.

[0048] [5. Summary] The measuring device of aspect 1 of the present invention comprises a strain gauge and a main body having one or more planar side surfaces with the strain gauge attached to at least one of the planar side surfaces, and when the main body is accommodated in a cylindrical hole formed in an object to be measured by the strain gauge, two or more side end portions including the longitudinal sides of the planar side surfaces are in contact with the inner wall surface of the object to be measured that forms the hole.

[0049] According to the above configuration, when the main body is housed in a cylindrical hole, the two or more side ends come into contact with the inner wall surface of the measurement object. As a result, when the main body is rotated around the central axis of the hole, the two or more side ends slide on the inner wall surface. Therefore, the orientation of the strain gauge with respect to the measurement object can be easily adjusted, or when the measurement direction is predetermined, the orientation of the strain gauge can be easily aligned with the measurement direction. Furthermore, when warping or the like occurs on the inner wall surface due to strain in the measurement object, the main body also deforms in accordance with this warping or the like. As a result, the strain gauge can measure the strain of the measurement object with high accuracy via the main body.

[0050] The measuring device according to aspect 2 of the present invention may be such that the main body has a substantially rectangular prism-like outer shape in the above-mentioned aspect 1. The main body may have a variety of outer shapes, but by adopting a substantially rectangular shape as in the above-mentioned configuration, a measuring device that has a good balance between ease of adjusting the orientation of the strain gauge and the measurement accuracy of the strain gauge can be realized.

[0051] The measuring device according to aspect 3 of the present invention may be such that the main body has an approximately triangular prism shape in accordance with aspect 1. The main body may have various external shapes, but by adopting an approximately triangular shape as in the above configuration, a measuring device in which the orientation of the strain gauge can be easily adjusted can be realized.

[0052] A measuring device according to a fourth aspect of the present invention is any one of the first to third aspects, in which the strain gauge may be spaced apart from the inner wall surface when the main body is housed in the hole. When the strain gauge comes into contact with the inner wall surface, pressure is applied to the strain gauge due to warping of the inner wall surface caused by the strain of the object to be measured, and this pressure load leads to measurement errors. In this regard, according to the above configuration, since the strain gauge is spaced apart from the inner wall surface, no measurement error due to the pressure load occurs. This improves the measurement accuracy of the strain gauge compared to when the strain gauge comes into contact with the inner wall surface.

[0053] A measuring device according to a fifth aspect of the present invention is any one of the first to fourth aspects, in which the main body is fixed to the inner wall surface while housed in the hole. With this configuration, the main body can more easily follow warping or the like that occurs on the inner wall surface compared to when the main body is not fixed to the inner wall surface. This improves the measurement accuracy of the strain gauge compared to when the main body is not fixed to the inner wall surface.

[0054] A measuring device according to aspect 6 of the present invention is any of aspects 1 to 4, wherein when the main body is housed in the hole, the space between the planar side surface to which the strain gauge is attached and the inner wall surface is filled with adhesive, and the strain gauge is embedded in the adhesive.

[0055] According to the above configuration, the measuring device is adhesively fixed to the measurement object while the main body is housed in the cylindrical hole. As a result, if warping or the like occurs on the inner wall surface due to strain on the measurement object, the main body and adhesive also deform to follow the warping or the like. This allows the strain gauge to measure the strain on the measurement object with high accuracy via the main body and adhesive.

[0056] A seventh aspect of the present invention provides a tool holder for holding a tool and including a measuring device, the measuring device including a strain gauge for measuring strain in the tool holder, and a main body having one or more planar side surfaces to which the strain gauge is attached, the main body having two or more side ends including a longitudinal side of the planar side surface contacting an inner wall surface of the tool holder that defines the hole when the main body is accommodated in a cylindrical hole formed in the tool holder. With this configuration, the orientation of the strain gauge relative to the tool holder can be easily adjusted, and the strain gauge can measure the strain in the tool holder with high accuracy via the main body.

[0057] A tool holder according to an eighth aspect of the present invention is the tool holder according to the seventh aspect, wherein, when the body is housed in the hole, an adhesive is filled in a space between the planar side surface to which the strain gauge is attached and the inner wall surface, and the strain gauge is embedded in the adhesive. With this configuration, the strain gauge of a measuring device provided in the tool holder can accurately measure the strain of the measurement target via the body and the adhesive.

[0058] [6. Additional Notes] The present invention is not limited to the above-described embodiment and modifications, and various modifications are possible within the scope of the claims. For example, embodiments obtained by appropriately combining the technical means disclosed in the above-described embodiment and modifications are also included in the technical scope of the present invention.

[0059] 7. Examples An embodiment of the present invention will be described with reference to Figures 5 and 6. The inventors performed the following tests using a measuring device 1-5 according to a first embodiment of the present invention, a measuring device 1-6 according to a second embodiment of the present invention, and a measuring device CE according to a comparative example of the present invention, as shown in Figure 5, as test subjects, and analyzed and evaluated the test results.

[0060] <Test target configuration> As a first embodiment, a measuring device 1-5 was used in which only one first strain gauge 21 was adhesively fixed to the main body. Specifically, a solid triangular prism made of acrylic was used as the main body of the measuring device 1-5. In addition, the position of the first strain gauge 21 relative to the main body of the measuring device 1-5 was the same as the position of the first strain gauge 21 relative to the main body 3. Next, as a second embodiment, a measuring device 1-6 was used in which only one strain gauge 2 was adhesively fixed to the main body. Specifically, a solid triangular prism made of acrylic was used as the main body of the measuring device 1-6, similar to the main body of the measuring device 1-5. In addition, the position of the strain gauge 2 relative to the main body of the measuring device 1-6 was the same as the position of the strain gauge 2 relative to the main body 3. Next, as a comparative example, a commercially available uniaxial strain gauge (general-purpose foil strain gauge manufactured by Kyowa Electric Industry Co., Ltd., model number: KFGS-1-120-C1-11 L15C3R) was used as the measuring device CE.

[0061] The above-mentioned commercially available uniaxial strain gauge was used as the first strain gauge 21 of the measuring device 1-5. Also, a general-purpose foil strain gauge (two-axis overlapping arrangement, model number: KFGS-1-120-D16-11 L30C3S) manufactured by Kyowa Electric Industry Co., Ltd. was used as the strain gauge 2 of the measuring device 1-6. Also, the main body of each of the measuring devices 1-5 and 1-6 had a height of 60 mm, and the external shape of the reference cross section was an isosceles triangle (base 4 mm, height 2 mm).

[0062] <Test Method> First, an acrylic plate material was processed to produce an acrylic plate 40 having a rectangular shape in plan view as shown in Fig. 5. When producing the acrylic plate 40, the length of the short side of the acrylic plate 40 was set to 100 mm.

[0063] Next, three holes 41 as shown by reference numeral 502 in FIG. 5 were formed in the acrylic plate 40 at approximately equal intervals in the longitudinal direction. Specifically, holes 41 with a depth of 50 mm were formed from the longitudinal side surface of the acrylic plate 40 toward the inside of the acrylic plate 40. In addition, the central axis of each of the three holes 41 was set to approximately coincide with the central axis extending in the lateral direction of the acrylic plate 40 when the acrylic plate 40 was viewed from the lateral side of the lateral side. Furthermore, a through hole 42 penetrating the acrylic plate 40 in the thickness direction was formed in the end portion on the side where the three holes 41 were not formed, among both ends of the longitudinal side of the acrylic plate 40. For convenience of explanation, the main bodies of the measuring instruments 1-5 and 1-6 are separated from the inner wall surface of the hole 41 in reference numeral 502 in FIG. 5, but in reality, they were in contact with the inner wall surface.

[0064] Next, the measuring instruments 1-5, 1-6 and CE (hereinafter referred to as "three types of measuring instruments") were accommodated in the three holes 41. Specifically, the three holes 41 were filled with adhesive 5, and the three types of measuring instruments were accommodated in the three holes 41 so that the first strain gauge 21 of the measuring instrument 1-5, the strain gauge 2 of the measuring instrument 1-6, and the strain gauge of the measuring instrument CE were each facing upward. Then, the side surface of the main body of the measuring instrument 1-5 to which the first strain gauge 21 was bonded and fixed, and the inner wall surface of the hole 41 were fixed with adhesive 5. Similarly, the side surface of the main body of the measuring instrument 1-6 to which the strain gauge 2 was bonded and fixed, and the inner wall surface of the hole 41 were fixed with adhesive 5. For the measuring instrument CE, the strain gauge and the inner wall surface of the hole 41 were fixed with adhesive 5.

[0065] When the three types of measuring instruments were adhesively fixed to the three holes 41 in this manner, the main bodies of the measuring instruments 1-5 and 1-6 and the measuring instrument CE protruded 10 mm from the longitudinal side surface of the acrylic plate 40. Here, the "longitudinal side surface of the acrylic plate 40" specifically refers to the side surface on which the openings of the three holes 41 are formed, out of both longitudinal side surfaces of the acrylic plate 40.

[0066] Next, various devices and tools were placed on the experimental stand 50 indicated by reference numeral 401 in FIG. 5. Specifically, the end of the acrylic plate 40 on the side where the three types of measuring instruments were housed was fixed to the experimental stand 50 with two clamps 60. In addition, the gauge leads of the three types of measuring instruments were connected to a bridge box 70, and the three bridge boxes 70 were placed on the experimental stand 50. In addition, each of the three bridge boxes 70 was connected to a dynamic strain amplifier 80, and the three dynamic strain amplifiers 80 were placed on the experimental stand 50. A commercially available product (model number: DBT-A-1) manufactured by Kyowa Electric Industry Co., Ltd. was used as the bridge box 70, and a commercially available product (model number: AS2403, DC bridge type wideband type) manufactured by A&D Co., Ltd. was used as the dynamic strain amplifier 80.

[0067] Next, the three dynamic strain amplifiers 80 were connected to an analog signal input terminal (manufactured by Contec, model number: AIO-160802GY-USB) (not shown), and then (i) a weight (about 49 N) (not shown) was hung from the through hole 42 of the acrylic plate 40 at room temperature for a predetermined period of time to generate strain in the acrylic plate 40. In addition, (ii) the acrylic plate 40 was cooled using a commercially available mold cleaning agent spray, and then left for a predetermined period of time. Then, in both cases (i) and (ii), the change in voltage value was measured, and in the case of (i), the measurement results of the three types of measuring devices were displayed on the display unit of the analog signal input terminal, and the test results of this embodiment were analyzed and evaluated. On the other hand, in the case of (ii), the measurement results of the measuring devices 1-6 and CE were displayed on the display unit described above, and the test results of this embodiment were analyzed and evaluated. As the software for the analog signal input terminal, data recording software (product name: X-VIEWER (DITECT)) manufactured by Yokogawa Measurement Corporation was used.

[0068] <Test Results> As shown by reference numeral 601 in Fig. 6, in the case of (i) in the period from 0 ms to about 3000 ms, the voltage value of all three types of measuring instruments was about 0 V. Similarly, in the period from about 13000 ms to about 18000 ms, the voltage value of all three types of measuring instruments was about 0 V. In other words, since no weight was suspended in these periods, none of the three types of measuring instruments could measure strain at all.

[0069] The weight was suspended during the time period from about 3000 ms to about 13000 ms. As a result, the voltage value of measuring device 1-5 was about 0.12 V on average, and the voltage value of measuring device 1-6 was about 0.175 V on average, and both of these measuring devices were able to measure strain with high accuracy. Among them, the measurement accuracy of measuring device 1-6 was good. For measuring device CE, the voltage value was about -0.01 V on average, and almost no improvement in measurement accuracy was observed compared to other periods.

[0070] As shown by reference numeral 602 in Fig. 6, in the case of (ii), the voltage values ​​of both measuring device 1-6 and CE were approximately 0V during the time period from 0 ms to approximately 4000 ms, and strain was hardly measurable. During the time period from approximately 4000 ms to approximately 5000 ms, the voltage value of measuring device 1-6 was approximately 0V, and was almost unchanged from the voltage value during the time period from 0 ms to approximately 4000 ms. Meanwhile, the voltage value of measuring device CE changed to approximately -0.03V.

[0071] In the period from approximately 5000 ms to approximately 18000 ms, the voltage value of measuring device 1-6 changed very slowly, and even at approximately 18000 ms, the voltage value remained at approximately -0.02 V. On the other hand, the voltage value of measuring device CE continued to change at a rate similar to that of measuring device 1-6 after approximately 5000 ms, and at approximately 18000 ms, the voltage value was approximately -0.05 V. From these measurement results, it was found that measuring device 1-6 is less susceptible to the effects of thermal contraction due to cooling than measuring device CE, and can maintain good measurement accuracy even at low temperatures. [Explanation of symbols]

[0072] 1, 1-1, 1-2, 1-3, 1-4, 1-5, 1-6 Measuring equipment 2. Strain gauge 3, 3-1, 3-3, 3-3, 3-4 Main body 4 Space 5. Glue 31 First Side (Side) 32 Second Side (Side) 33 The Third Side (Aspect) 34 First side end portion (side end portion) 35 Second side edge (side edge) 36 Third side edge (side edge) 100 Tool holder (measurement object) 101 holes 102 Inner wall surface

Claims

1. A strain gauge and a main body having one or more planar side surfaces, the strain gauge being attached to any one or more of the planar side surfaces; A measuring instrument in which, when the main body is accommodated in a cylindrical hole formed in the object to be measured by the strain gauge, two or more side ends including the longer sides of the planar side surface come into contact with the inner wall surface of the object to be measured that form the hole.

2. The measuring device according to claim 1 , wherein the outer shape of the main body is a substantially rectangular prism shape.

3. The measuring device according to claim 1 , wherein the outer shape of the main body is a substantially triangular prism shape.

4. The measuring device according to claim 1 , wherein the strain gauge is spaced apart from the inner wall surface when the main body is housed in the hole.

5. The measuring device according to claim 1 , wherein the main body portion is fixed to the inner wall surface while being housed in the hole.

6. When the main body is housed in the hole, an adhesive is filled in a space between the side surface of the planar shape to which the strain gauge is attached and the inner wall surface; 5. The measuring device of claim 1, wherein the strain gauge is embedded in the adhesive.

7. A tool holder for holding a tool, the tool holder including a measuring device, The measuring device is a strain gauge for measuring a strain of the tool holder; a main body having one or more planar side surfaces, the strain gauge being attached to any one or more of the planar side surfaces; when the main body is accommodated in a cylindrical hole formed in the tool holder, two or more side end portions including longer sides of the planar side surface contact an inner wall surface of the tool holder that defines the hole.

8. When the main body is housed in the hole, an adhesive is filled in a space between the side surface of the planar shape to which the strain gauge is attached and the inner wall surface; The tool holder of claim 7 , wherein the strain gauge is embedded in the adhesive.

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