JP4605525B2 - Force transducer - Google Patents

Description

    The present invention relates to a force transducer for electrical detection, and relates to a small and highly accurate force transducer.

    Japanese Patent Publication No. 5-79930

(Conventional technology)
Peripheral part and central part are connected by a radial beam, holes are drilled from the side of the radially arranged beam to form a strain-generating part, the peripheral part is fixed, a force is applied to the central part, and electrical resistance detection means strain Force transducers using gauges are known.

  In FIG. 3, a load applying unit 13 that receives a load is provided at the center 12 of the force converter main body 11, and three beams 21 to 23 are provided between the load applying unit 13 and the peripheral portion 14. Connected through. Each beam 21-23 has a circular hole drilled in the transverse direction in each beam, there is a beam in a deep position through the through holes 24-26, a circular hole is drilled in the beam 21 through the 24 holes, Similarly, circular holes are formed in each of the beams, and electrical resistance detecting means strain gauges are provided by bonding or the like on the upper and lower surfaces of the strain-generating portion whose thickness in the vertical direction is reduced.

  In such a configuration, when a force (F) is applied to the load application unit, a strain is generated around the circular hole formed in each beam with a stress proportional to the force (F), and this strain is detected by electric resistance. By measuring with a means strain gauge, the magnitude of force (F) can be measured.

  However, especially in a small force transducer, the strain around the hole is limited by the deformation caused by the magnitude of the force and the maximum stress point moves or the required position interval is too small. There was a problem that the gauge could not be provided.

  Furthermore, since the maximum shear stress works at the position of the weakest part where the strain gauge is not provided above and below the hole, the force (F) to be applied is limited because it deviates from the elastic region other than the strain detection part. However, since the force (F) smaller than the elastic limit at the strain generating portion is set as the upper limit and the value from the strain gauge is also limited, there is a problem that high accuracy cannot be maintained by limiting the dynamic range to be small. It was. The weakest part is deformed by force (F), and the maximum stress point is moved, which causes a linearity error.

  With regard to the processing of the strained portion of the beam, the processing of the shape required as the strained portion and the dimensional accuracy can be maintained because the strained portion is processed into the beam in the deep position inside through the hole at the periphery. There is a problem that it is difficult and cannot sufficiently function as a strain generating portion.

  In addition, since the maximum shear stress is generated at the weakest position where the thickness of the top and bottom is thin due to a circular horizontal hole that can be barely machined in a deep beam, the dynamic range is limited and the strain gauge required position interval is small. Therefore, the linear stress error, the steric error, the reproducibility error, etc. are caused by the restriction that the strain gauge cannot be provided at the maximum stress point and the movement of the maximum response point due to the displacement generated in the shape of the round hole. There were problems such as having to keep it small.

In order to solve the above-mentioned problem, there are a plurality of beams that are connected by a plurality of beams that are substantially equally spaced from the center to the periphery, and are separated from each other in the axial direction. By making the phases different, the opening that can be machined for the formation of the roval is in the vertical load direction, so that the degree of freedom of the shape of the strain-generating portion in each beam can be greatly increased. .

  A plurality of strain generating portions in each beam are shaped so as to generate the maximum strain in each beam in force (F), and a dynamic range is provided by arranging an electric resistance strain detecting means strain gauge on the generating portion. The maximum is to avoid the movement of the maximum stress point.

Hereinafter, this embodiment will be described with reference to FIG. 1 of 1 is a top view of the present embodiment, and two cross-sectional views of the 1 are shown below. There is a group of beams 34 to 36 at an appropriate distance in the axial direction from the group of beams 31 to 33 from the central portion 12 to the peripheral portion 14, and the phase of each group of beams is shifted by 60 degrees. Has been placed.

  For this reason, the processing of the strained portions 31a and 31b of the beam 31 can be end milled from below in the figure, and the beam 34 can be end milled from above in the figure. There is no processing of the part, and the shape of the ideal strain generating part can be processed from a wide opening with a rigid tool. By providing two semicircular strain generating parts such as 31a and 31b, the movement of the maximum stress point can be prevented by the deflection.

One of the beams will be described. Strain gauges G1 and G2 are provided on the beam 31 by bonding, with the weakest portions of the beam as strain-generating portions 31a and 31b. When a force (F) is applied to the central portion 12 from above in the cross-sectional view of FIG. 1, the G1 strain gauge expands and the G4 strain gauge contracts.
That is, since the weakest part does not exist other than the strain generating part provided with the strain gauge, the strain generating part can be distorted to the elastic proportional limit, and a large signal can be obtained.

  Each beam works similarly, and in FIG. 2 is a Wheatstone bridge made of these strain gauges. In FIG. 2, the temperature compensation resistor, the sensitivity adjustment resistor, the input resistance adjustment resistor, and the zero point adjustment resistor are not shown.

The invention's effect

  As described above, according to the first or second aspect of the present invention, the shape of the strained portion of each beam can be made an optimal shape without being constrained from the machining surface, and a necessary number is provided at a necessary position. Strain gauges that are each strain detection means can be installed at the maximum stress point where the maximum stress point does not move, and high accuracy with a large measurement range in terms of linearity error, hysteresis error, repeatability error, and creep characteristics. A small force transducer can be obtained.

It is the upper side figure of the Example of this invention, and its sectional drawing. It is detection circuit explanatory drawing of the Example of this invention. FIG. 5 is a perspective view of an example of a conventional force transducer device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Force converter 12 Center part 13 Weight application part 14 Peripheral part 15 Detection base member 21,22,23 Beam 24,25, 26 Through-hole 31 Beam 31a, 31b Strain generation part G1-G12 Electrical resistance detection means Strain gauge

Claims (2)

In a single-axis force transducer manufactured by machining from a single unitary material, three or more beams are connected to the peripheral edge of the horizontal axis from the vicinity of the central axis subject to vertical load in an approximately even radial pattern. There is a group of beams that are equivalent to each other, and a group of beams equivalent to this is separated from each other in the vertical direction as appropriate, and at least two places are provided above and below. Alternatively, a force transducer characterized by a structure having a phase angle of approximately 30 to 60 degrees by shifting it counterclockwise. The force transducer according to claim 1, wherein the strained portion of the beam can be machine-cut only from the upper and lower openings in the vertical direction.