JPS5988632A - Strain gauge type load converter - Google Patents

Abstract

PURPOSE:To obtain the titled converter capable of lowering the height of a strain generating body, free from a buckling possibility light in wt. and high in capacity, by obtaining the electric signal corresponding to load to be applied from a wheatstone bridge circuit. CONSTITUTION:The strain generating part 8 by a columnar strain generating body is provided with a plurality of holes C1-C8 different in the depths thereof toward the center shaft 9 vertical to the load applying surface (not shown by the drawing) of the columnar strain generating body by drilling and strain gauges A1-A8 for detecting compression strain are provided to the bottom wall surface 10 along the center shafts 9 of the holes C1-C8 while strain gauges D1-D8 for detecting tensile strain are provided toward the direction along the center shafts 9 and the direction crossing the same at right angles. A double wheatstone bridge is constituted as a whole around the center shaft 9. When compression load is applied to the columnar strain generating body along the center shaft 9, eight strains at the center part and the peripheral edge part in the strain generating body 8 are detected meanly because of the constitution of the double wheatstone bridge circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a strain gauge type load transducer in which a strain gauge is attached to a strain-generating body, and the strain gauge obtains an electric signal corresponding to an applied load.

A conventional strain gauge type transducer of this type is shown in Fig. 1 (A).
A strain gauge is attached to the side circumferential surface of a columnar flexural body such as a prism or cylinder as shown in Figure 2 (Shu) in the direction along the load application direction and in the direction perpendicular to this. A Wheatstone bridge circuit was constructed using the Wheatstone bridge circuit, and an electric signal (output) corresponding to the applied load was obtained from this Wheatstone bridge circuit.This conventional load converter is shown in Fig. 1 (A). , (I
3) and FIGS. 2(A) and 2(B). FIG. 1(A) is a front view of the cylindrical strain body.

In the same figure (A), the load W (total load W per unit area) applied to the upper surface 2 of the cylindrical flexure element 1 is parallel to the central axis 4 on the side peripheral surface 3 of the cylindrical flexure element 1. The load is detected as an electrical signal proportional to the load by a strain gauge (for compressive strain detection) 5 and a strain gauge (for tensile strain detection) 6 orthogonal thereto.

In addition, the strain gauges 5 and 6 are attached to the front side and the back side in FIG.
A link bridge is configured. Here, ■4 indicates the height of the strain-generating portion 7 of the cylindrical strain-generating body 1, and D represents its diameter.

Figure 1 (B) shows the cross section a-a and b-a of Figure 1 (N).
The stress distribution diagram in the cross section is shown. FIG. 2(A) is a front view of a cylindrical flexural body 1' whose height H' is very low compared to the height H of the cylindrical flexural body shown in FIG. 1(A),
The figure FB) shows the middle part C- of the cylindrical strain body 1' of the figure FA).
The stress distribution diagram in the C section is shown.

In FIG. 1(S), a near the end of the cylindrical strain body 1
-' The stress distribution in cross-section a is largely different between the center and the periphery of the cylindrical flexure body 1, but the stress distribution in the bb section near the middle part away from the end of the cylindrical flexure body 1 is It can be seen that the stress distribution at is almost uniform.

If the height H' of the cylindrical flexural body 1' is made shorter than that shown in Figure 1 (A) as shown in Figure 2), the stress distribution diagram at the C-c cross section in Figure 3 (■3) shows that As can be seen, the stress distribution in the middle part of the cylindrical flexural body 1'd is not uniform;
It exhibits a complex distribution state. In this way, even if the cylindrical flexure element is short to some extent, or even if the cylindrical flexure element is long, if the strain gauge is attached not far from the end face of the cylindrical flexure element, the strain gauge In some cases, it is not possible to obtain an electrical signal that accurately corresponds to the applied load W. For this reason, in a conventional load converter in which a strain gauge is attached to the side circumferential surface of the cylindrical flexure element, it is necessary to increase the height of the cylindrical flexure element to some extent.

However, if the cylindrical flexure element is made too long, the applied load will cause the flexure element to buckle, making it more susceptible to tilted loads and reducing load detection accuracy. there were. Additionally, when a load transducer is inserted into a force transmission system, it is not possible to increase the length of the cylindrical flexure element, and if it were made thicker, the object to be measured would become larger. was there. Therefore, the height ri and the diameter of the cylindrical flexure element vary depending on the material, heat treatment method, shape, etc. of the flexure element, but are determined by a predetermined ratio (x4/I
)-i,,s~25).

In this way, in the conventional load converter described above, in order to improve the load detection accuracy, the height of the columnar strain body must be increased to a certain level without causing buckling. Not only will the transducer itself become larger and heavier, but the range of applicability to the objects to be measured (for example, forging machines, press machines, etc.) that need to be used for load measurement will be limited. The problem was that it was restricted.

The present invention was made in order to eliminate the drawbacks of the conventional strain gauge type load transducer described above, and its objectives are to be small, lightweight, free from buckling, and compatible with high capacity. It is an object of the present invention to provide a strain gauge type load transducer that can perform high measurement accuracy and has extremely high measurement accuracy.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 (Shu is a perspective view of the strain-generating part of the cylindrical strain-generating body according to the present invention, and FIG. 3 (■3) is a direction taken along line dd in FIG. 3A.

FIG. In the same figure, the strain-generating portion 8 of the cylindrical flexure body is arranged so that the load application surface of the cylindrical flexure body (
A plurality of holes 01 to C8 having different depths are bored toward the central axis 9 perpendicular to The strain gauges A1 to A8 for detection and the strain gauges DI to D8 for tensile strain detection are attached in the direction along the central axis 9 and the direction perpendicular thereto, for example, by means of adhesive or the like. In this example, the deep hole C1,,0
3, 05, 07 and shallow holes 02, 04.

06.08 are drilled alternately.

FIG. 4 (Δ) is a circuit diagram in which a lipoey 1-stone bridge is constructed using the strain gauge shown in FIG. In the figure, compressive strain detection strain gauges A1 and A5, A2 and A6 attached at symmetrical positions with respect to the central axis 9 are connected in series, respectively, and these series circuits are connected in parallel to form one side of the bridge. Similarly, strain gauges A3 and A7 for detecting compressive strain are attached at symmetrical positions with respect to the central axis 9. A, 4. A8 are connected in series, and these series circuits are connected in parallel to form the - side (A
I, A5. One side of the bridge corresponds to the opposite side of A-2, A6), and strain gauges for detecting tensile strain DI, D2. D5. Group D6 and D3. D
4. D7, 1) Group of 8 is similarly connected to the remaining 2 of the bridge.
Each side (opposite side) is connected to the circuit, and the whole constitutes a double hobby 1-1-1 bridge.

Here, ei represents the bridge power supply voltage, and eo represents the output voltage.

In the above embodiment configured in this way, when a compressive load is applied to the cylindrical flexure body along the direction of the central axis 9, the flexure element 8 produces compressive strain in the direction along the central axis 9. ,
The resistance value of strain gauges A1-88 for compressive strain detection decreases, and tensile strain is generated in the direction perpendicular to the central axis 9 of strain-generating portion 8, and the resistance of strain gauges D1-D8 for tensile strain detection decreases. The value increases. Therefore, these strain gauges are
As shown in FIG. 4 (N), since it is configured as a double Wheatstone bridge circuit, even if the strain at eight locations in the center and the periphery of the strain body 8 is averaged and detected, the overall , it is possible to detect the strain output proportional to the applied load.In other words, even if the strain differs depending on the distance from the central axis, as shown in Figure 2 ([)), the strain output in Figure 1 can be detected. It is possible to obtain substantially the same result as detecting the applied load at a location where the stress distribution is equal, such as the bb section of FA). This means that by configuring as in this embodiment, the height of the strain-generating portion 8 of the cylindrical strain-generating body can be reduced, and therefore, the load converter itself can be made smaller and lighter. In addition, when a load converter is installed in a forging machine, press machine, etc. to measure the load applied to a mold, the operating stroke is limited, so there is not much space for installing the load converter. However, according to the present invention, the load transducer can be made thin, and the range of application can be greatly expanded. Furthermore, since the height of the strain-generating portion 8 of the columnar strain-generating body can be reduced, there is no possibility of buckling occurring.

FIG. 4(B) is a circuit diagram showing another example of strain gauge connections. In this example, the 8
4 Otsumi gauges (
For compressive strain detection: 2 sheets, for tensile strain detection: 2 sheets) are attached to each hole, respectively.Eadstone Bridge B1
By configuring B1 to B8 and connecting these eight Points 1 to B1 to B8 in a row, the detection accuracy is improved compared to the case of configuring one Wheats L-) bridge. It is. In other words, it is theoretically possible to take into account the squared error and improve the double precision when using 8 wheel bridges than when using 1 point bridge. However, the present invention is not limited to the two embodiments shown in Example C, and various modifications can be made without departing from the gist of the present invention.

For example, in the above embodiment, the center axis 9 is attached to the strain generating portion 8.
Hole 01 for attaching the strain gauge so that it is symmetrical to
Although an example in which holes .about.08 are drilled is shown, the holes do not necessarily have to be symmetrical, and the depths of several holes may be the same.

Further, the shape of the strain body 8 is not limited to a cylinder, but may be a cylinder or a cylinder.
The shape may be a prism, a rectangular tube, or the like.

As detailed above, according to the present invention, it is possible to reduce the height of the strain-generating body while maintaining high load detection accuracy, so there is no risk of buckling. 1; a high capacity can be obtained, and a strain gauge type load transducer with an extremely wide range of application can be provided.

[Brief explanation of drawings]

Figures 1 (A) and (I3) are a front view of a cylindrical strain body of a conventional strain gauge type load transducer and a of Figure 1 (A).
- Stress distribution diagram in the a cross section and the b-b VfT plane, 2nd,
Figure (A) is a front view of a cylindrical flexure element with a lower height than that shown in Figure 1, and Figure 2 (B) is a cross section cc of the middle part of the cylindrical flexure element in Figure 1 (A). 3(A) and (Bl) are a perspective view of a strain-generating part showing the structure of an embodiment of the present invention, and a sectional view taken along line dd in FIG. 3(A), 4 (A) and (r+l) are respective circuit diagrams showing two connection examples of the strain gauge according to the present invention. 8... Strain-generating portion, 9... Central axis of cylindrical strain-generating body ,】0・・Bottom of hole, 01~C8・・hole, Δ”
~8 ・Strain gauge for compressive strain detection, D1~D
8...O strain gauge for tensile strain detection, 81~
B8: Bridge circuit, el: Bridge power supply voltage, eo: Bridge output voltage. Figure 1 (A) \4 Figure 2 Figure 3 (A) 4 (A)

Claims (1)

[Claims] Fil In a strain gauge type load transducer in which a strain gauge is attached to a columnar flexure element that elastically deforms when a load is applied, and the strain gauge obtains an electric signal according to the applied load, the side periphery of the columnar flexure element is A plurality of holes with different depths are bored from the surface toward the central axis perpendicular to the load application surface of the columnar strain body, and a strain gauge is installed on the bottom wall surface of each hole along the central axis. The strain gauge is attached in a direction along the central axis and in a direction perpendicular to the central axis, and the strain gauge constitutes a Wheatstone bridge, and the Wheatstone bridge circuit obtains an electric signal according to the applied load. Strain gauge type load transducer.