JP2017166847A - Force sensor design method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for designing a force sensor.SOLUTION: A design method of a force sensor 1 pertaining to the present invention is for the force sensor 1 comprising a tabular body 2, a columnar part 3 projecting from one face 2a of the tabular body, a strain part 8 consisting of an annular groove 4 formed at a base end of the columnar part, and a plurality of strain gauges R arranged on the other face 2b side of the tabular body, the groove consisting of a first side wall extending along the base end, a bottom 6 continuous to the first side wall 5 by a first angle 6a having a first curvature Ra, and a second side wall continuous to the bottom by a second angle having a second curvature Rb and extending opposite to the first side wall, the method causing a computer to execute processing including a step of setting a shape parameter of each of the first curvature, the second curvature, the thickness from the bottom to other faces, and the width of the groove, and a step of determining a solution to each of the shape parameters by structural analysis so that a maximum stress occurring in the strain part in a state of the columnar part being subjected to a prescribed load becomes smaller than a prescribed permissible stress.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a force sensor design method for detecting a force applied to an object.

  A force sensor is used to detect the force applied to the object. In a force sensor and a force detection device that receive a load due to an applied force, a strain generating portion (a strain generating portion) that is distorted by receiving the force is important. The shape of the strain generating portion and the position where the strain sensor for detecting the strain is arranged influence the characteristics of the force sensor. As a force sensor for detecting force, there is one described in Patent Document 1. This force sensor includes a circular plate-like body, a column provided protruding from one surface of the plate-like body, an annular groove provided along the base end of the column, and the other surface side of the plate-like body. A plurality of strain sensors provided. The groove portion is formed to have a rectangular cross section that is open in the axial direction of the cylinder, and a strain generating portion (diaphragm) that is a portion that generates strain in the plate-like body is formed by the groove portion. The plurality of strain sensors are arranged at the strain-generating portion on the other surface side of the plate-like body.

JP 2005-106679 A

The force sensor described in Patent Document 1 has a rectangular cross section in which the groove is opened in the axial direction of the cylinder, and stress generated when force is applied to the cylinder is applied to the corner of the rectangular cross section of the groove. concentrate. For this reason, in this force sensor, when a large force is applied to the cylinder, the strain generating portion may be damaged.
An object of this invention is to provide the design method of the force sensor which can raise the rigidity of the strain generation part for detecting the distortion produced by the applied force.

The present invention is a method of designing a force sensor having a plurality of strain sensors for detecting strain,
The force sensor includes a plate-like body,
A cylindrical portion provided so as to protrude from one surface of the plate-like body;
A strain-generating portion comprising an annular groove formed on the one surface side of the plate-like body so as to surround the periphery of the base end of the cylindrical portion;
A plurality of strain gauges disposed at the position of the strain-generating portion on the other surface side of the plate-like body;
The groove includes a first side wall extending along the base end, a bottom continuous with the first side wall and a first corner having a first curvature, and a second corner having the bottom and a second curvature. And a second side wall extending continuously opposite to the first side wall,
Setting each shape parameter of the first curvature (Ra), the second curvature (Rb), the thickness (Ts) from the bottom to the other surface, and the width (Ls) of the groove. When,
Determining a solution of each of the shape parameters so that a maximum stress generated in the strain generating portion is smaller than a predetermined allowable stress in a state where a predetermined load is applied to the cylindrical portion by structural analysis;
A method for designing a force sensor that causes a computer to execute a process having

  According to the present invention, with such a configuration, in the force sensor, the shape parameter for the curve is set for the corner portion of the strain generating portion having the first curvature and the second curvature, and the solution of the shape parameter is determined. . Accordingly, the present invention can be designed in a shape in which the strain generating portion disperses the stress. That is, the present invention can be designed so that the strain-generating portion of the force sensor has high rigidity.

  According to the method for designing a force sensor according to the present invention, it is possible to increase the rigidity of the strain generating portion for detecting the strain caused by the applied force.

It is the figure which showed the structure of the force sensor which concerns on embodiment of this invention. It is the figure which showed the bridge circuit of the distortion sensor arrange | positioned at a force sensor. It is the figure which showed the positional relationship of the strain sensor arrange | positioned at a force sensor, and its electrode. It is the figure which showed the wiring pattern which connects a bridge | bridging and an electrode. It is the figure which showed the example of the wiring pattern actually formed in a force sensor. It is the flowchart which showed the design method of the force sensor. It is the figure which showed the modification 1 of the force sensor. It is the figure which showed the modification 2 of the force sensor. It is the figure which showed the modification 3 of the force sensor. It is the figure which showed the arrangement | positioning relationship of the strain sensor of the force sensor of the modification 3, and an electrode. It is the figure which showed the wiring pattern which connects a bridge | bridging and an electrode.

  Hereinafter, embodiments of a method for designing a force sensor according to the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the force sensor 1 includes a circular plate-like body 2 and a column 3 provided so as to protrude from the center on the one surface 2 a side of the plate-like body 2. The plate-like body 2 and the column 3 are integrally formed of resin or the like. The plate-like body 2 constitutes the main body of the force sensor 1 and is fixed at a specific position of the object for detecting the force. A column 3 is provided on the one surface 2 a side of the plate-like body 2. The cylinder 3 is a structure for receiving forces from different directions. An annular groove portion 4 is formed on the base surface 3a side of the plate-like body 2 at the base end 3a of the column 3 so as to surround the periphery of the base end 3a.

  The groove part 4 has a U-shaped cross section. The groove portion 4 includes a first side wall 5 extending along the base end 3a, a bottom portion 6 continuous by the first side wall 5 and a first corner portion 6a having a first curvature Ra, and a bottom portion 6 and a second curvature Rb. The second side wall 7 is continuous with the second corner portion 6b and extends opposite to the first side wall 5. By forming the groove 4, the thickness Ts from the bottom 6 to the other surface 2 b side of the plate-like body 2 is thinner than the thickness of the plate-like body 2. For this reason, when a force is applied to the column 3, distortion occurs in this portion. A portion where this distortion occurs is referred to as a strain generating portion 8.

  That is, the strain generating portion 8 is formed in an annular shape having a width Ls and a thickness Ts. The shape parameters Ls, Ts, Ra, and Rb of the strain generating portion 8 are determined by a design method described later. On the other surface 2 b side of the plate-like body 2, a plurality of strain sensors R for detecting strain are arranged in the strain generating portion 8. As the strain sensor R, for example, a Cr—N thin film strain sensor can be used. The gauge factor of the Cr—N thin film strain sensor is 8 to 16, which is larger than the gauge factor 2 of a general strain sensor. The plurality of strain sensors R are arranged in a cross shape on the other surface 2b side of the plate-like body 2, for example. In the first quadrant on the other surface 2b side of the plate-like body 2, two strain sensors R are disposed along the vicinity of the X axis at the positions of the first corner 6a and the second corner 6b.

  Further, in the first quadrant on the other surface 2b side of the plate-like body 2, two strain sensors R are disposed along the vicinity of the Y axis at positions corresponding to the first corner 6a and the second corner 6b. ing. Similarly, a plurality of strain sensors R are arranged in the second to fourth quadrants. Accordingly, a total of 16 strain sensors R are arranged in a cross shape on the other surface 2 b side of the plate-like body 2. That is, a total of 16 strain sensors R are arranged, four in the vicinity of positions corresponding to the first corner 6a and the second corner 6b where the strain is the largest. In addition, on the other surface 2b side of the plate-like body 2, 16 electrodes P are arranged in an 8 × 2 array near the center.

As shown in FIGS. 2 and 3, four strain sensors R <b> 1 to R <b> 4 adjacent along the X axis form a bridge Br- 2 by the 4-active method. Potential difference E, from e _0, can be obtained by calculating the respective resistance values of the four strain sensors R1 to R4. Four bridges Br-1 to Br-4 are formed by the 16 strain sensors R1 to R16. Sixteen electrodes P1 to P16 are provided for the sixteen strain sensors R1 to R16.

  As illustrated in FIG. 4, for example, the bridge Br-1 is configured by a wiring L. The bridge Br-1 is integrally formed on the other surface 2b side of the plate-like body 2 in the same plane. An actual wiring pattern formed in the bridge Br-1 is shown in FIG.

  The force sensor 1 can detect at least three axial forces (Fx or Mx, Fy or My, Fz) applied to the cylinder 3 in the X-axis, Y-axis, and Z-axis directions with the above-described configuration. The force sensor 1 can then be designed to control the applied stress. For example, the force sensor 1 applies a safety factor 4 to the rated load (the load to be measured) so that the maximum stress at the load (often generated in the corners 6a and 6b) is less than the yield stress of the material. Alternatively, it can be designed such that the rated load is multiplied by a safety factor of 5 times, and the maximum stress at that load is less than the yield strength of the material. The force sensor 1 can be configured to have sufficient strain sensitivity and high rigidity while suppressing stress by using a Cr—N thin film having higher sensitivity (gauge rate) than a general strain sensor. In order to use a highly rigid strain generating body, it is desirable to use a stable Cr—N thin film having a gauge factor (sensitivity) of 10 or more and a TCR (temperature resistance coefficient) of around 0.

  Next, a method for designing the force sensor 1 will be described.

  As shown in FIG. 6, the design method of the force sensor 1 sets the mechanical characteristics (conditions) of the strain-generating structure material constituting the force sensor 1 (S100). For example, when the material of the force sensor 1 is a stainless steel material, the proof stress value is set. Next, conditions for force and moment applied to the force sensor 1 are set (S101). Next, the three-dimensional shape of the strain generating portion 8 is set by applying the strain generating body shape parameter (S102). Here, the shape parameters Ls, Ts, Ra, and Rb are applied.

  That is, in this step, the shape parameters of the first curvature Ra, the second curvature Rb, the thickness Ts from the bottom 6 to the other surface 2b of the plate-like body 2, and the width Ls of the groove 4 are set. . Next, structural analysis of the force sensor 1 is performed based on the applied shape parameters Ls, Ts, Ra, and Rb (S103).

  Next, it is determined whether or not the necessary and sufficient strain amount at the measurement point with respect to the rated load is a predetermined value or less (S104). The predetermined value of the strain amount is, for example, 4/1000 or 1/1000. When the necessary and sufficient strain amount is equal to or less than the predetermined value (S104: Yes), it is determined whether the maximum stress generated in the force sensor 1 is smaller than the allowable stress (S105). When the maximum stress is smaller than the allowable stress (S105: Yes), a solution of the optimum shape of the strain generating portion 8 of the force sensor 1 is obtained (S106). When the conditions are not satisfied in Steps S104 and S105 (No), the process returns to Step S103 and the structural analysis is performed again. That is, in Steps 103 to 106, the solution of each shape parameter is determined by structural analysis so that the maximum stress generated in the strain generating portion 8 is smaller than the predetermined allowable stress when a predetermined load is applied to the cylindrical portion 3. decide.

  As described above, according to the design method of the force sensor 1, by setting the shape parameter and determining the solution thereof, the rigidity of the strain generating portion 8 where the maximum stress is generated can be increased. According to the design method of the force sensor 1, it can be formed in a shape in which the stress applied to the strain generating portion 8 is dispersed by solving the shape parameter.

Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention. For example, the following modifications can be applied. The design method described above can also be applied to the following modifications.
[Modification 1]
The force sensor 1 is formed so as to detect a triaxial force. The force sensor 1 can be modified so as to detect a moment load in addition to the axial force. In the following, the same name and reference numeral are used for the same configuration as above, and the description of the same configuration is appropriately omitted.

  As shown in FIG. 7, the force sensor 20 detects a moment load Mz around the axis (Z axis) of the cylinder 23. The side surface of the plate-like body 22 of the force sensor 20 is linearly cut in parallel along the X axis and the Y axis. Thereby, when the force sensor 20 is fixed by the fixing member D, rotation about the Z axis is prevented. Therefore, the force sensor 20 can stably detect the moment load Mz.

[Modification 2]
As shown in FIG. 8, the force sensor 30 may include a cylinder 23 </ b> A in which a through hole S is formed with respect to the cylinder 23. The basic function of the force sensor 30 is the same as that of the force sensors 1 and 20 described above. The wiring L of the strain sensor R can be passed through the through hole S by the hollow cylinder 23A. According to the force sensor 30, the degree of freedom of arrangement of the strain sensor R can be increased in the design of an embedded sensor.

[Modification 3]
As shown in FIGS. 9 and 10, in the force sensor 40, the strain sensor R may be disposed obliquely with respect to the X axis and the Y axis. The circuit of each bridge Br-1 to Br-4 is the same as that of FIG. For the connection between the bridges Br-1 and Br-4 and the electrode P, for example, a wiring pattern shown in FIG. 11 can be used. The basic wiring pattern of the force sensor 40 is the same as that of the force sensor 1. In the force sensor 40, the wiring pattern of each bridge Br-1 to Br-4 in the force sensor 1 is rotated by 45 degrees.

  According to the force sensor 40, distortion due to the moment load Mz around the Z axis can be efficiently detected. According to the force sensor 40, with the configuration described above, at least three axial forces (Fx or Mx, Fy or My, Fz) applied to the cylinder 23 in the X-axis, Y-axis, and Z-axis directions, and a moment load Mz around the Z-axis. The four-axis force can be detected.

  The design method of the force sensors 1, 20, 30, 40 described above may be realized using a semiconductor processing apparatus including an ASIC (Application Specific Integrated Circuit). Further, these processes may be realized by causing a computer system including at least one processor (for example, a microprocessor, an MPU, and a DSP (Digital Signal Processor)) to execute a program. Specifically, one or a plurality of programs including an instruction group for causing the computer system to perform an algorithm related to the transmission signal processing or the reception signal processing may be created, and the programs may be supplied to the computer.

  These programs can be stored and supplied to a computer using various types of non-transitory computer readable media. Non-transitory computer readable media include various types of tangible storage media.

  Examples of non-transitory computer-readable media include magnetic recording media (for example, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (for example, magneto-optical disks), CD (registered trademark) -ROM (Read Only Memory), CD-R, CD-R / W, and semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (random access memory)) are included.

  The program may also be supplied to the computer by various types of transitory computer readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

DESCRIPTION OF SYMBOLS 1 ... Force sensor 2 ... Plate-shaped body 2a ... One side 2b ... Other side Br-1-Br-4 ... Bridge 3 ... Column 3a ... Base end 4 ... Groove 5 ... Side wall 6 ... Bottom 6a ... Corner 6b ... Corner 7 ... Side wall 8 ... Straining part 20 ... Force sensor 22 ... Plate-like body 23 ... Cylinder 23A ... Cylinder 30 ... Force sensor 40 ... Force sensor D ... Fixing member L ... Wiring P ... Electrode P1-P16 ... Electrode R ... Strain sensor R1 -R16 ... Strain sensor S ... Through hole

Claims (1)

A method for designing a force sensor having a plurality of strain sensors for detecting strain,
The force sensor includes a plate-like body,
A cylindrical portion provided so as to protrude from one surface of the plate-like body;
A strain-generating portion comprising an annular groove formed on the one surface side of the plate-like body so as to surround the periphery of the base end of the cylindrical portion;
A plurality of strain gauges disposed at the position of the strain-generating portion on the other surface side of the plate-like body;
The groove includes a first side wall extending along the base end, a bottom continuous with the first side wall and a first corner having a first curvature, and a second corner having the bottom and a second curvature. And a second side wall extending continuously opposite to the first side wall,
Setting each shape parameter of the first curvature (Ra), the second curvature (Rb), the thickness (Ts) from the bottom to the other surface, and the width (Ls) of the groove. When,
Determining a solution of each of the shape parameters so that a maximum stress generated in the strain generating portion is smaller than a predetermined allowable stress in a state where a predetermined load is applied to the cylindrical portion by structural analysis;
A method for designing a force sensor that causes a computer to execute a process including:

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