JP2017053727A - Load transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly-reliable and highly-accurate load converter, which is a strain body having a size appropriate to a load.SOLUTION: A sensing part 10 of a strain body 20 has a columnar shape along a measuring load axis Z. High rigidity is given to a sensing axis part 103 of a center part and a pair of thick wall parts 104, 105 of an outer edge part. A pair of thin planar strain parts 101, 102 are provided between right and left ends of the sensing axis part 103 and the pair of thick wall parts 104, 105. A cross-sectional shape including the strain parts 101, 102 and orthogonal to the measuring load axis has a shape obtained by combining the same two H shapes arranged side by side.SELECTED DRAWING: Figure 5

Description

  In the present invention, a shear type strain gauge is attached to a strain generating portion that generates shear strain when a tensile or compressive load is applied, and the electric resistance value of the shear type strain gauge that changes according to the magnitude of the load is expressed as a voltage. The present invention relates to a load transducer that performs measurement by detecting the signal or the like.

  Various shapes of the strain generating part of the load transducer have been proposed and put into practical use depending on the size of the measurement load, the usage environment required for the load transducer, such as small or thin, and accuracy. Yes.

  For measuring the tensile or compressive load, a load converter having an S-shaped rover valving body shown in FIG. 1 is widely used. The strain body 1 having this shape is made of a material rich in elasticity, for example, an aluminum alloy, and has a substantially S-shape. Therefore, for example, an aluminum extruded material having an S-shaped cross section is obtained, and this is cut into a desired length to obtain the S-shaped strain body 1 shown in FIG.

  The upper and lower sides 6 and 7 of the S-shaped strain generating body 1 are fixing portions for fixing the strain generating body 1 to other members such as a measuring instrument main body and a load receiving member.

  The strain body 1 has a substantially rectangular through-hole 2 at the center thereof to form two beam portions 3 and 4. The four corners of the through-hole 2 are composed of curved surfaces to avoid stress concentration, and strain gauges R1 to R4 are attached to the inner peripheral wall surface.

  The upper side 6 and the lower side 7 are formed by strain gauges R1 to R4 as shown in FIG. The amount of change in the electric resistance value is taken out as an electric quantity (voltage signal) from the Wheatstone bridge circuit, and the magnitude of the load is measured.

Utility Model Registration No. 2515754

  In the configuration shown in FIG. 1, the strain gauge to which the strain generated in the beam portions 3 and 4 is attached is distorted. In addition, since the amount of change in the electrical resistance value of the strain gauge is caused by the gauge factor, it is approximately 2 in a gauge using a general conductive foil. Here, when the section modulus is unchanged, in order to increase the amount of distortion, it is necessary to greatly deflect the beam portions 3 and 4 and increase the displacement of the portion receiving the force, which causes a problem in terms of rigidity.

  As a countermeasure, a method using a strain generator of a shear strain measurement method in which the displacement is suppressed to be small and the rigidity can be increased as shown in FIG. 9 has been adopted. However, in the method of measuring the shear strain, it is necessary to set the sensitivity direction of the strain gauge to 45 degrees with respect to the load measurement direction. If an angle error occurs here, it is likely to be affected by a load related to a direction other than the measurement direction, particularly a load related to the direction orthogonal to the measurement direction, and the corresponding error causes an error in measurement accuracy. .

In addition, in order to avoid a decrease in measurement accuracy, a technique has been adopted to increase the rigidity of the strain-generating body so as to suppress the generation of strain due to a load from a direction different from the measurement direction, and to remove the influence of the load related to other than the measurement direction. It was. However, increasing the rigidity has a problem that the strain generating body itself increases in size with respect to the magnitude of the load to be measured.

  An object of the present invention is to provide a highly accurate load transducer that avoids an increase in the size of the strain-generating body by a method of measuring shear strain.

In order to solve the above-mentioned problems, the following technical means have been taken in the present invention.
The load converter according to the present invention is a load converter that detects and converts a measured load into an electrical quantity,
A load introduction part, a first transmission part, a sensing part, a second transmission part and a load support part are arranged in parallel along the measurement load axis,
The sensitive part has a columnar shape along the measurement load axis, and toward the pair of opposing surfaces on the outer peripheral surface of the sensitive part, along the direction perpendicular to the measurement load axis, By forming a hole with a bottom surface of the same shape that reaches the same depth symmetrically across the measurement load axis, the sensor shaft part at the center and a planar shape at the left and right ends of the sensor shaft part A cross-sectional shape including the strain-generating portion with respect to the measurement load axis is perpendicular to the measurement load axis. On the other hand, it has a shape where two identical H-shapes are combined side by side,
The first transmission part and the second transmission part have a central axis on the measurement load axis, and the cross-sectional area with respect to a plane orthogonal to the measurement load axis is smaller than the cross-sectional area of the sensing part. One is connected to the sensitive shaft (103), the other is connected to the pair of thick parts,
A strain gauge is affixed to the bottom surface of the hole, which is the surface of the strain generating portion (101, 102).

  According to this means, since the strain generating portion can be formed into a shape that generates shear strain while maintaining the size of the strain generating body appropriately with respect to the load, the entire strain forming portion is configured with high rigidity. can do. Furthermore, with regard to the decrease in measurement accuracy caused by the force other than the measurement load axis direction, which is a problem in measurement with a shear type strain gauge, the shape of the cross section with respect to the measurement load axis direction is an H-shaped shape with a large section modulus for bending. By forming a shape in which two cross-sections are arranged side by side, the influence of the force can be made difficult. In addition, the strained portion to which the strain gauge is attached is a hole provided in the same shape at a symmetrical position with respect to the measurement load axis with respect to a pair of opposing surfaces on the outer peripheral side surface of the sensing portion. Since it is a bottom surface, the shear strain generated by the load is symmetrical on the left and right, and compensation by the Wheatstone bridge circuit can be greatly taken. Moreover, since each strain gauge is affixed to an independent surface, it can be affixed to a location where shear strain is generated most, and it also works favorably in sensitivity characteristics.

  In the load transducer according to the present invention, it is possible to increase the rigidity of the strain generating body within a range of an appropriate size with respect to the load, and the displacement due to the load is suppressed to be small, thereby improving the reliability and measuring error. A highly accurate load converter can be provided by avoiding as much as possible the influence of forces related to directions other than the measurement load direction.

External view of S-shaped Roverval type strain body used in conventional tension or compression load transducers Wheatstone bridge circuit diagram with strain gauges R1 to R4 affixed to S-shaped Roverval type strain body External view and partial cross-sectional view of a load transducer according to an embodiment of the present invention The strain body perspective view of the load converter which is embodiment of this invention Sectional view of strain body of load transducer according to embodiment of the present invention The figure showing the state to which the compressive force was related to the strain body of the load converter which is embodiment of this invention. The figure showing the state in which the tensile force was related to the strain body of the load converter which is embodiment of this invention. Wheatstone bridge circuit diagram using strain gauges G1 to G4 attached to the strain-generating portion of the load transducer according to the embodiment of the present invention. External view of strain generating body using shear strain measurement method used in conventional tension or compression load transducers Biaxial strain gauge appearance

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 3 shows a load transducer 8 for tensile or compressive load, which is an embodiment of the present invention. FIG. 3A is a diagram showing an appearance of the load converter 8, and the load load portion 21 is a portion to which a direct tensile or compressive load is applied. Casing 22 shows the housing which covers the whole strain generating body 20 mentioned below. FIG. 3B is a view showing the inside (cross section) of the casing 22 in the load converter 8.

In FIG. 3 (b), the strain body 20 is a portion where strain is generated in the load transducer 8 in accordance with the magnitude of the load, and the material is made of a material excellent in elasticity, for example, an aluminum alloy. Further, the shape is integrally formed by cutting out from a bar, for example, because it is necessary to achieve high accuracy.

As shown in FIG. 4, the strain body 20 mainly includes a load introduction part 9, a sensing part 10, a load support part 11, a first transmission part 12, and a second transmission part 13. The sensitive part 10 includes holes 14 to 17, strain-generating parts 101 and 102, a sensitive shaft part 103, and thick parts 104 and 105. In the present embodiment, the maximum load is about 500 N, and the outer diameter dimensions (maximum dimensions) of the load introduction part 9, the sensing part 10, and the load support part are generally within 10 mm to 20 mm.

The load introducing portion 9 is a portion for receiving a tensile or compressive load applied to the load loading portion 21 and transmitting the tensile or compressive load to a portion located behind the first transmission portion 12. 21 and the same axis. Moreover, the attachment part of the load load part 21 is provided in the edge part.

The first transmission unit 12 is a part that transmits the load received by the load introduction unit 9 to the sensing unit 10, and includes a central axis on the measurement load axis Z as shown in FIGS. 5, the cross-sectional area on the plane orthogonal to the measurement load axis Z is smaller than that of the load introducing portion 9 and is located at the center of the sensing portion 10. The slitting process is applied so as to be confined by a predetermined thickness from the outer peripheral surfaces positioned opposite to each other by 180 degrees so as to be connected to the sensitive part 103. The load thus transmitted can be concentrated around the measurement load axis Z of the sensing part 10, that is, on the sensing axis part 103. However, the first transmission portion 12 has a minimum necessary cross-sectional area that can sufficiently withstand even when a maximum load is applied.

The sensor unit 10 has a column shape in which the measurement load axis Z passes through the center thereof, and the sensor unit 103 having a high rigidity with respect to the load centered on the measurement load axis Z at the center thereof, A pair of strain-generating portions 101 and 102 that are positioned at the left and right ends of the shaft portion 103 and have a planar shape, and a pair of thick-walled portions 104 and 105 that are at the outer edge and enclose the strain-generating portion and have high rigidity. It has. The pair of strain generating portions 101 and 102 is a pair of surfaces (S1 surface and the S1 surface) that are in a positional relationship facing each other in the direction (Y direction) orthogonal to the measurement load axis Z on the outer peripheral surface of the columnar sensing unit 10. S2 surface) is formed by providing a total of four hole portions 14 to 17 each two. Therefore, the cross-sectional shape of the sensing part 10 with respect to the plane including the strain-generating parts 101 and 102 and orthogonal to the measurement load axis Z is 2 horizontally as shown by the cross-section BB in FIG. One side of the plate girder of the H-shaped steel arranged side by side is joined, and the strain generating portions 101 and 102 correspond to the two web plate portions of the joined H-shaped steel.

Moreover, since the holes 14-17 are formed in the bottom face of the same depth and the same shape, the sensitive part 10 includes two planes including the measurement load axis Z and orthogonal to each other, that is, FIGS. It has a line-symmetric shape that is bilaterally symmetric with respect to both the XZ plane and the YZ plane.

The second transmission unit 13 is a portion provided between the sensing unit 10 and the load support unit 11 and has a central axis on the measurement load axis Z, and further transmits the load transmitted to the sensing unit 10. 11 is transmitted. As for the shape, as shown by a cross-section CC in FIG. 5, the cross-sectional area on the surface orthogonal to the measurement load axis Z is smaller than the load support portion 11 and is located at the upper side of FIG. 5. An elliptical through-hole 18 is machined in the central portion so as to be connected to the pair of thick portions 104 and 105 provided on the outer edge portion of the ten. However, like the first transmission portion 12, the second transmission portion 13 has a minimum necessary cross-sectional area that can sufficiently withstand even when a maximum load is applied.

Strain gauges G1 to G4 are respectively attached to the front and back surfaces of the pair of strain generating portions 101 and 102, that is, the bottom surfaces of the holes 14 to 17 by adhesion, vapor deposition, sputtering, and other means. The strain gauges G1 to G4 form a Wheatstone bridge circuit shown in FIG. Here, the strain gauges G1 to G4 are all uniaxial strain gauges of the same type, and the sensitivity direction is attached at an angle of 45 degrees counterclockwise with respect to the measurement load axis Z direction. However, the sensitivity direction may be pasted at an angle of 45 degrees clockwise with respect to the measurement load axis Z direction.

Next, an explanation will be given based on FIGS. 6 and 7 regarding the operation in the above-described configuration. The load F applied to the load load portion 21 is transmitted to the load introduction portion 9 of the strain body 20 and is transmitted to the sensitive shaft portion 103 of the sensitive portion 10 through the first transmission portion 12. Further, since the thick portions 104 and 105 of the load support portion 11, the second transmission portion 13, and the sensing portion 10 have high rigidity in the direction to which the load F is applied, the reaction force causes the strain portions 101 and 102. Causes shear strain as shown in the figure.

Here, when the load applied to the load load portion 21 is a force having an arbitrary angle with respect to the measurement load axis Z, that is, an uneven load or a lateral load, the load introduction portion 9 includes the measurement load axis Z and A component force FS is generated in an orthogonal direction (an arbitrary direction on the XY plane in FIGS. 4 and 5).

However, the sensitive shaft portion 103 and the thick portions 104 and 105 in the sensitive portion 10 have sufficiently large rigidity with respect to the component force FS, and the cross section of the strain generating body 20 including the strain generating portions 101 and 102 is shown in FIG. As shown by the section B-B in FIG. 5, it is a shape in which two H-shaped shapes are arranged side by side, and has a high section modulus. Therefore, it is possible to prevent the occurrence of shear strain at the strain generating portions 101 and 102 due to the component force FS.

In addition, even if the influence of the uneven load and the lateral load is slightly generated in the strain generating portions 101 and 102, the pair of strain generating portions 101 and 102 are in a line-symmetrical positional relationship around the measurement load axis Z. Therefore, the generated shear strain is similarly line-symmetrical shear strain. As a result, compensation by the Wheatstone bridge circuit (FIG. 8) by the strain gauges G1 to G4 can be made large and can be sufficiently canceled, and an electric quantity (voltage signal) corresponding to only the load component in the measurement load axis Z direction can be obtained. Can do.

In addition, the strain gauges G1 to G4 are attached to four independent front and back surfaces of the strain generating portions 101 and 102, respectively, so that the center of sensitivity can be matched with the location where the shear strain is the largest. Therefore, excellent sensitivity characteristics are exhibited.

As mentioned above, although the detail of embodiment was demonstrated about the load converter 8 which is embodiment of this invention, this invention is not limited to said embodiment, A various deformation | transformation is possible. For example, in the strain body 20, even when the load introduction part 9 and the load support part 11, and the first transmission part 12 and the second transmission part 13 are interchanged, similar actions and effects are produced. Further, instead of the uniaxial strain gauge, a biaxial strain gauge as shown in FIG. 10 can be applied.

The load converter according to the present invention can be used for all weighing devices related to measurement of tensile or compressive load, and includes, for example, a large-area high-rigidity low floor balance, a long-time measurement dynamometer, and the like.

DESCRIPTION OF SYMBOLS 8 ... Load converter 9 ... Load introduction part 10 ... Sensitive part 11 ... Load support part 12 ... 1st transmission part 13 ... 2nd transmission part 14, 15, 16, 17 ... Hole 18 ... Through-hole 20 ... Strain Body 101, 102 ... Straining part 103 ... Sensitive shaft part 104, 105 ... Thick part G1, G2, G3, G4 ... Strain gauge 21 ... Load loading part 22 ... Casing 23 ... O-ring

Claims (4)

In the load transducer that detects the measurement load by converting it into an electrical quantity,
A load introduction part, a first transmission part, a sensing part, a second transmission part and a load support part are arranged in parallel along the measurement load axis,
The sensing part is formed in a column shape along the measurement load axis, and along a direction perpendicular to the measurement load axis, toward a pair of opposed surfaces on the outer peripheral surface of the sensing part, By forming a hole having a bottom surface of the same shape reaching the same depth symmetrically across the measurement load axis, a surface is provided at the center of the sensitive shaft and the left and right ends of the sensitive shaft. A cross-sectional shape including the strain-generating portion with respect to the measurement load axis is perpendicular to the measurement load axis. The shape is a combination of two H-shapes that are the same shape.
The first transmission part and the second transmission part have a central axis on the measurement load axis, and the cross-sectional area with respect to a plane orthogonal to the measurement load axis is smaller than the cross-sectional area of the sensing part. One is connected to the sensitive shaft part, the other is connected to the pair of thick parts,
A load transducer, wherein a strain gauge is attached to the bottom surface of the hole, which is the surface of the strain generating portion.   2. The load transducer according to claim 1, wherein all of the strain gauges are uniaxial strain gauges of the same type, and are attached so that sensitivity directions are at the same angle with respect to the measurement load axis. .   The load introduction part, the first transmission part, the sensing part, the second transmission part, and the load support part form a strain body processed from an integral material. 2. The load converter according to 2. The load transducer according to claim 3, wherein the strain body according to claim 3 has a maximum dimension of 10 mm to 20 mm in a direction orthogonal to the measurement load axis.