JPH0862061A - Detecting device for strain - Google Patents

Abstract

PURPOSE: To obtain a detecting device for strain capable of increasing the precision in detection without being affected by a distance of a point of action of a force acting on a strain generating tube. CONSTITUTION: A strain generating tube 10 is provided with an open window part 11 in the direction intersecting perpendicularly the direction of action of a force acting on the free end of the tube, while a beam 12 to be the elongation side in respect to the acting force and a beam 13 to be the contraction side in respect to the force are formed and strain gages 201 , 202 , 203 and 204 are stuck in the vicinity of the respective root parts on the opposite sides of these beams 12 and 13. By constructing a bridge circuit of these strain gages, a bending strain due to a bending moment is canceled and the bending strain due to a shear force is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strain detecting device for measuring a force acting on various structural members by attaching a strain-generating cylinder to the structural member and detecting a strain generated in the strain-generating cylinder.

[0002]

2. Description of the Related Art When measuring the force acting on various structural members,
As shown in FIG. 7, a force F acting on the structural member is applied to the free end portion of the strain-flexing cylinder 1 in the vertical direction, and the shear strain generated in the strain-flexing cylinder 1 at this time is detected by the strain gauge 20, and The acting force F is measured with the amount of strain.

Since the shear strain generated in the strain-generating cylinder 1 is smaller than the bending strain due to the bending moment M (M = F · x),
In order to accurately measure the acting force F even if the acting point distance x of the force F changes, the strain gauge 20 should originally be arranged on the neutral axis 1 _p of the strain-flexing cylinder 1 where the bending strain is 0. There is.

However, in reality, it is impossible to dispose the strain gauge 20 on the neutral axis 1 _p of the strain-flexing cylinder 1 without being displaced. Therefore, as shown in FIGS. The concave portion 2 is formed from both side surfaces to reduce the cross-sectional area near the neutral axis 1 _p to facilitate shear strain, and the strain gauge 20 detects the shear strain generated in the thin wall 3 having the small cross-sectional area. ing.

If a plurality of strain gauges 20 are used, the detection sensitivity can be increased and more accurate strain detection can be performed. Therefore, as shown in the figure, two strain gauges 20 ₁ , 20 ₁ are provided at the center positions on both side surfaces of the thin wall 3, respectively. 20 ₂ and 20 ₃ and 20 ₄ are attached in an intersecting state, and as shown in FIG. 9, strain gauges 20 ₁ and 2
Gauge resistances of 0 ₂ , 20 ₃ , 20 ₄ 20 _1R , 20 _2R , 2
A bridge circuit is formed of 0 _3R and 20 _4R , and shear strain is electrically detected by the output ε ₀ of the bridge circuit to measure the acting force F.

In FIG. 9, 30 is an input terminal of the bridge circuit, 3
Reference numeral 1 is a ground terminal, and 32 and 33 are output terminals.

This similar structure is obtained, for example, by the Kyowa Electronic Measuring Instruments '94 General Catalog No. 48 issued by Kyowa Denki Co., Ltd.
Shown on the page.

[0008]

As described above, in order to make shear strain easily occur in the strain-flexing cylinder 1, the recesses 2 are formed on both side surfaces of the strain-flexing cylinder 1 so as to break the strain in the vicinity of the neutral axis 1 _p. Although the thin wall 3 is formed by reducing the area, there is naturally a limit to reducing the cross-sectional area of the thin wall 3, and the longer the action point distance x of the force, the greater the influence. It is impossible to obtain sufficient shear strain with respect to the bending strain that increases.

In addition to this, the strain gauges 20 ₁ ,
20 ₂ , 20 ₃ , 20 ₄ have a certain length, and these strain gauges 20 ₁ , 20 ₂ , 20 ₃ , 20
It is difficult to attach ₄ so that the center position of its length is exactly the center position of the side surface of the thin wall 3 orthogonal to the neutral axis 1 _p. The strain gauges 20 ₁ , 20 ₂ ,
Since the sticking positions of 0 ₃ and 20 ₄ are likely to be displaced, it becomes very difficult to perform highly accurate strain detection which is hardly influenced by the action point distance x of the force.

Therefore, according to the present invention, the shear strain can be accurately detected by a simple structure without being affected by the distance of the point of action of the force acting on the strain-generating cylinder, and the strain capable of exhibiting a highly accurate detection function can be exerted. A detection device is provided.

[0011]

According to a first aspect of the present invention, a strain-flexing cylinder attached to an object to be measured is provided with a fenestration portion in a direction orthogonal to an acting direction of a force acting on its free end. A beam on the extension side and a beam on the contraction side with respect to this acting force are formed, and a strain gauge is attached to the beam surface near the roots on both sides of the extension side beam and the contraction side beam. While sticking symmetrically around the neutral axis, in the bridge circuit formed by the input terminal, the ground terminal and the pair of output terminals, the extension side beam and the contraction side beam are arranged on a diagonal line. Gauge resistances of the pair of strain gauges are arranged on opposite sides of the bridge circuit so as to cancel the bending strain generated by the bending moment.

In the second aspect, the strain gauges are attached to the central positions of the beam surfaces of the extension side beam and the contraction side beam.

According to the third aspect of the present invention, strain gauges are attached to the beam surfaces on the front sides of the extension side beam and the contraction side beam.

[0014]

According to the first aspect of the present invention, by the force acting in the vertical direction on the free end of the strain-flexing cylinder, the root portions on both sides of the beam on the extension side and the both sides of the beam on the contraction side with respect to this acting force are exerted. Bending strain due to a bending moment that is affected by the distance of the point of action of force and bending strain due to a shearing force that is not affected by the distance of the point of action of force occur at the root portion of the.

Accordingly, although the sum of the bending strain generated by the bending moment and the bending strain generated by the shearing force is generated at each of the root portions, in the bridge circuit, the bending moment is generated by the arrangement of the gauge resistance of the strain gauge. The bending strain due to is canceled and output, and in the end, the shearing force generated in the strain generating cylinder can be detected as the bending strain that is not affected by the distance of the force acting point, and highly accurate force measurement can be performed.

According to the second aspect, since the strain gauge is attached to the central position of the beam surface of each beam, the strain can be detected further without being influenced by the distance of the point of action of force, and the detection accuracy can be improved. Can be increased.

According to the third aspect, since the strain gauge is attached to the front beam surface of each beam, it is easy to attach the strain gauge to an appropriate position, and highly accurate strain detection can be performed. it can.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings.

In FIGS. 1 and 2, reference numeral 10 denotes a strain-generating cylinder having a rectangular cross section and made of a light metal material such as an aluminum alloy, which is attached to a measuring object 40, which will be described later, and has a force F acting on its free end at its central portion. The window opening 11 is formed in the direction orthogonal to the acting direction.
The beam 12 that forms the extension side with respect to this acting force F.
And a beam 13 on the contraction side are formed.

Strain gauges 20 ₁ , 20 ₂ , 20 ₃ , 20 ₄ are provided in the strain tube 10 on the beam surfaces near the roots on both sides of the beam 12 on the extension side and the beam 13 on the contraction side. They are adhered symmetrically around the vertical axis 10 _p .

On the other hand, as shown in FIG. 4, in the bridge circuit formed by the input terminal 30, the ground terminal 31, and the pair of output terminals 32 and 33, on the diagonal line of the beam 12 on the extension side and the beam 13 on the contraction side. Each pair of strain gauges 2 arranged
Gauge resistances 20 _1R , 2 of 0 ₁ , 20 ₃ and 20 ₂ , 20 ₄
0 _3R , 20 _2R , 20 _4R , bending moment M (M = F ·
It is arranged on the opposite side of the bridge circuit in order to cancel the bending strain generated by x).

Specifically, the gauge resistance 20 _1R of the strain gauge 20 ₁ is connected between the input terminal 30 and one output terminal 32,
And the gauge resistor 20 _3R of the strain gauge 20 ₃ is connected and arranged between the other output terminal 33 and the ground terminal 31, and the gauge resistor 20 _2R of the strain gauge 20 ₂ is connected between the input terminal 30 and the other output terminal 33. In addition, the gauge resistance 20 _4R of the strain gauge 20 ₄ is connected and arranged between the one output terminal 32 and the ground terminal 31, and is provided on the opposite side of the bridge circuit.

According to the above-described structure of the embodiment, when the force F acts on the free end of the strain-flexing cylinder 10 in the vertical direction, the strain gauges 20 ₃ , 20 _{4 of the} beam 12 on the extension side with respect to the acting force F. The bending strains σ _m generated by the bending moment and the shearing force are generated in the root portions on both sides where the affixing is applied and on the base portions on both sides where the strain gauges 20 ₁ and 20 ₂ of the beam 13 on the contraction side are affixed. Bending strain σ _τ is generated, and the strain σ of each root is detected as the sum of these bending strains σ _m and strain σ _τ (σ = σ _τ + σ _m ).

On the other hand, the output ε _{0 of the} bridge circuit is detected by the strain gauges 20 ₁ and 20 ₂ (electric quantity) of the beam 13 on the contraction side by the arrangement of the gauge resistors 20 _1R , 20 _2R , 20 _3R and 20 _4R. ) Ε ₁ and ε ₂ and the strain gauge 2 of the beam 12 on the extension side
The total amount of the detected amounts (electrical amounts) ε ₃ and ε ₄ of 0 ₃ , 20 ₄ (ε ₀ = ε ₁ −ε ₂ + ε ₃ −ε ₄ ) is obtained.

Further, the beam 13 on the contraction side has the acting force F.
Therefore, the bending strain σ _m generated by the bending moments detected by the strain gauges 20 ₁ and 20 _{2 in the} vicinity of the root portions on both sides of the bending strain σ _m is as a whole as shown by the chain line in FIG. Both are negative values (-σ
_m ) and the beam 12 on the extension side as a whole tends to bend and deform in the stretching direction as a whole. Therefore, bending strains generated by the bending moments detected by the strain gauges 20 ₃ and 20 _{4 in the} vicinity of the root portions on both sides thereof are caused. σ _m is a positive value (+
σ _m ).

On the other hand, both the contraction-side beam 13 and the extension-side beam 12 are fixed at both ends, and the acting force F causes both sides of each of the beams 12 and 13 as shown by the solid line in FIG. Since a shearing force acts by bending and deforming downward near the base while maintaining a substantially horizontal state, the shearing force detected by the strain gauge 20 ₁ at the base end of the front end of the beam 13 on the contraction side depends on the shearing force. The bending strain σ _τ has a positive value (+ σ _τ ) because the root of the front end is sheared in the stretching direction, and the bending strain σ _τ due to the shearing force detected by the strain gauge 20 ₂ at the root of the rear end is , The root of the rear end is sheared in the compression direction, and thus has a negative value (−σ _τ ).

Further, in the beam 12 on the extension side, the bending strain σ _τ due to the shearing force detected by the strain gauge 20 ₄ at the root portion of the front end of the beam 12 is that the root portion of the front end is shear in the compression direction. It becomes a negative value (-στ), and the bending strain σ due to the shearing force detected by the strain gauge 20 ₃ at the root of the rear end.
_τ is a positive value (+ σ _τ ) because the root of the rear end is sheared in the stretching direction.

Therefore, as described above, each strain gauge 20 ₁ ,
Distortion detection outputs ε ₁ , ε ₂ , 20 ₂ , 20 ₃ , 20 ₄ ,
Since ε ₃ and ε ₄ are obtained as the sum of the bending strain σ _m generated by these bending moments and the bending strain σ _τ generated by the shearing force, these bending strains σ _m and σ _τ are expressed by the above equation ε.
Substituting for ₀ = ε ₁ −ε ₂ + ε ₃ −ε ₄ ,

[Number 1] _{ε 0 = (σ τ -σ m} ) - (- σ τ -σ m) + (σ τ + σ m) - (- σ τ + σ m) = σ τ + σ τ + σ τ + σ τ -σ m + Σ _m + σ _m −σ _m = 4σ _τ , the bending strain σ _m generated by the bending moment is canceled, and the bending strain σ _τ generated by the shearing force is four times as sensitive as the single strain gauge 20. Is detected as the output ε ₀ .

Therefore, the shearing force generated in the strain tube 10 can be detected as the bending strain σ _τ without being affected by the distance x of the action point of the force, and the accurate action force F can be measured.

Here, as in the present embodiment, the strain gauge 20 is aligned with the neutral axis 10 _p line of the strain-flexing cylinder 10 and the beams 12, 13 are arranged.
If it is attached to the central position of the beam surface, the strain can be accurately detected without being affected by the distance x of the action point of the force.

Further, even if the strain gauge 20 is attached to either the front side or the back side of the beam surfaces of the beams 12 and 13, there is no difference in detection sensitivity. When the strain gauge 20 is attached to the front beam surface, the strain gauge 20 can be easily attached to an appropriate position and highly accurate strain detection can be performed.

Further, the beams 12 and 13 are both increased in bending rigidity of the strain-defining cylinder 10 which is obtained by the height h from the neutral axis 10 _p of the strain-defining cylinder 10 and the beam thickness t to reduce the shear rigidity. Bending strain σ _τ due to shearing force is likely to occur, but the thickness dimension t of these beams 12 and 13 is 1 of the thickness T of the strain generating tube 10.
If set to about / 10, bending strain due to bending moment σ _m
And the bending strain σ _τ due to the shearing force is σ _τ > σ _m, and the bending strain σ _{τ that} is not affected by the force action point distance x is
It becomes more dominant than the bending strain σ _m affected by the action point distance x, and a highly accurate detection result can be obtained.

If the thickness t of the beams 12 and 13 is made smaller than the above, the flexural rigidity of the strain-flexing cylinder 10 is lowered and the bending strain σ _τ is less likely to occur, which is not preferable.

The strain detecting device having such a structure is attached to the measuring object 40 as shown in FIGS. 5 and 6, and is used for detecting the strain of the measuring object 40.

In this example, a shift lever of an automobile is shown as the measurement object 40. A base bracket 14 is integrally extended to one side of one end of the strain-flexing cylinder 10 and the base bracket 14 is attached to the shift lever 40. It is fixed with a screw 17 so that the one end becomes the fixed end of the strain-flexing cylinder 10.

At the other end of the strain-flexing cylinder 10, an arm 15 is integrally extended in one direction, and a handle 16 is attached to the arm 15 with a screw 18.
The grip 16 is fixed to the end portion of the shift lever 40 and is positioned and fixed by a screw 19, and the other end is a free end for receiving the acting force F through the grip 16. Reference numeral 21 denotes a harness of the strain gauge 20.

Therefore, when the shift lever 40 is operated in the direction of the arrow in FIG. 5, the operating force acts in the direction perpendicular to the free end of the strain-flexing cylinder 10, that is, in the direction in which the beams 12 and 13 are bent, and the strain gauge 20 As described above, the bending strain σ _τ due to the shearing force is accurately detected by ₁ , 20 ₂ , 20 ₃ , and 20 ₄ , and the operating force F and the strength and rigidity of the shift lever 40 are measured with high accuracy. You can

[0038]

As described above, according to the present invention, the following effects can be obtained.

(1) Bending strains due to bending moments and bending strains due to shearing force at the joints on both sides of the beam on the extension side and the joints on both sides of the beam on the contraction side with respect to the acting force of the strain-flexing cylinder. Is generated, and this strain is detected by the strain gauges attached to each root, and the bending strain due to the bending moment is canceled by the bridge circuit and output, so the shear force generated in the strain tube is generated. Can be detected as a bending strain that is not affected by the distance of the point of application of force, and highly accurate force measurement can be performed.

(2) By attaching the strain gauges to the center position of the beam surface of each beam, the strain gauges are aligned on the neutral axis of the strain-flexing cylinder, and are further unaffected by the distance of the point of action of force. It is possible to accurately detect distortion.

(3) If the strain gauges are attached to the beam surface on the front side of each beam, the strain gauges can be easily attached to appropriate positions and highly accurate strain detection can be performed.

[Brief description of drawings]

FIG. 1 is a schematic side view of an embodiment of the present invention.

FIG. 2 is a schematic plan view of the same embodiment.

FIG. 3 is a schematic side view at the time of flexural deformation of the embodiment.

FIG. 4 is a bridge circuit diagram of the device of the embodiment.

FIG. 5 is a side view showing a usage example of the apparatus of the embodiment.

FIG. 6 is a view on arrow A in FIG.

FIG. 7 is a schematic side view of a conventional device.

8 is a sectional view taken along the line BB of FIG.

FIG. 9 is a bridge circuit diagram of a conventional device.

[Explanation of symbols]

 10 Strain tube 11 Window opening 12, 13 Beam 20 Strain gauge

Claims (3)

[Claims] 1. A beam having a fenestration portion provided on a strain-flexing cylinder attached to an object to be measured in a direction orthogonal to an acting direction of a force acting on a free end thereof, and a beam on an extension side with respect to the acting force. A beam to be the contraction side is formed, and a strain gauge is symmetrically attached to the beam surface near both the roots of the extension side beam and the contraction side beam around the neutral axis of the strain generating cylinder. , A bridge circuit formed of an input terminal, a ground terminal, and a pair of output terminals, a gauge resistance of each pair of strain gauges arranged diagonally on the extension side beam and the contraction side beam, by a bending moment. A strain detecting device, which is arranged on the opposite side of the bridge circuit so as to cancel the bending strain generated. 2. The strain detecting device according to claim 1, wherein a strain gauge is attached to a central position of each beam surface of the extension side beam and the contraction side beam. 3. A strain detecting device, wherein a strain gauge is attached to each front side beam surface of the extension side beam and the contraction side beam.