JPS5912326A - Load converter - Google Patents

Abstract

PURPOSE:To prevent the occurrence of lateral movement at a loading point, by connecting both ends of beams, which are laminated in two layers by connecting parts, making the central parts of the respective beams a load introducing part and a fixed supporting part, and attaching strain gages to the beams. CONSTITUTION:Two beams 7 and 8, which are thin in the direction of a load, are laminated in two stages. Both ends of said two beams 7 and 8 are connected so as to form a unitaly body by connecting parts 10 and 11. The center of one beam 7 is made to be a load introducing part and the center of the other beam 8 is made to be a fixed supporting part. Thus a sensing part is formed. Then, strain gages S1-S8 are attached to bending moment generating parts of the two beams 7 and 8.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a load transducer that electrically measures the magnitude of a load applied to a sensing section using a strain gauge.

There are various shapes of sensing parts of this type of conventional load transducer, which differ depending on the size of the load to be measured, the shape of the load transducer (for example, small size, thin profile, etc.), accuracy, etc.

Load transducers that measure relatively small loads generally use strain gauges to detect bending strain in beams. Beam systems include the cantilever type, where one end is fixed and the load is applied to the other end, the double-end fixed beam type, where both ends are fixed and the load is applied to the center of the beam, and the parallel beam type, which receives multiple beams. There are various methods such as the shaped beam method.

However, methods such as the above-mentioned cantilever type and parallelogram beam type 2, in which one end is fixed and a load is applied to the other end, have the disadvantage that when the beam is deflected by the load, the distance between the fixed end and the loaded end changes. Yes, a typical load transducer uses a diaphragm to prevent lateral loads and to prevent moisture absorption (sealing) of strain gauges, so it receives a reaction force in the axial direction of the beam.

On the other hand, in the case of a beam fixed at both ends, the load point does not move due to deflection of the beam (due to load), and the load point is located at the center of the sensing part. It is suitable as a sensing part of a load transducer that measures a relatively small load, and is very widely used as a sensing part of a load transducer that measures relatively small loads. Fig. 1 is a front view showing an example of a sensing section made of a beam that uses the conventional beam method fixed at both ends and is made thinner in the direction of the load. , both sides of which are connected to fixing parts 4 and 5 by thin strain-generating parts 2 and 3 in the load direction, respectively. Each of the fixing parts 4 and 5 is fixed to a case 6 of the load converter, and strain gauges 81 to S8 are bonded to the strain generating parts 2 and 3.

However, in this conventional method, both ends of the beam are fixed, so when the beam is deflected by a load, tension is generated in the beam in addition to the bending moment, which affects the deflection characteristics of the beam and reduces the load-output characteristics. It becomes non-linear. In particular, if the thickness of the beam in the load direction is reduced in order to measure small loads, the deflection will increase, so the influence of the tension on the beam will be large, and therefore,
It was not possible to achieve high precision.

In addition, when measuring a relatively large charge, the beam becomes thick and the deflection is small, but the generated tension increases and the problem arises with the method of fixing the fixed end, and hysteresis occurs due to slipping of the fixed end, resulting in accuracy. It had the disadvantage of impairing the

The present invention has been made in consideration of the shortcomings of the load transducers of the Upper Continuing Song Dynasty, and its purpose is to prevent lateral movement of the load point and to prevent tension from occurring in the beam. - Our objective is to provide a load transducer that maintains linearity in its output characteristics, does not generate hysteresis, and can achieve high accuracy.

That is, in order to achieve the above object, the present invention provides a load transducer that electrically measures the magnitude of the load applied to the sensing part using a strain gauge. These two beams are stacked in two stages at intervals, and both ends of these two beams are integrated with each other via a connecting part.
The center of one beam serves as a load introduction part and the center of the other beam serves as a fixed support part to form a sensing part, and a bending moment is generated in one or both of the two beams. It is characterized by having strain gauges attached to the parts.

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

FIG. 2 is a plan view showing the configuration of an embodiment of the sensing section of the load converter according to the present invention. In the figure, two beams 7 and 8
One of the beams 7 has a load introduction part 7a in the center that receives the measurement load F, and thin plate-shaped strain-generating parts 7b and 7c extend in the load direction on both sides of this load introduction part 7a. . The other beam 8 has a fixed support part 8a fixed to the load converter case 9 or the like in the center, and on both sides of this fixed support part 8a there are thin plate-like plates in the direction of the load. Strain-generating portions 8b and 8c corresponding to portions 7b and 7C are extended.

The strain-generating portions 7b and 7c, 8b and 80 are symmetrical with respect to the dashed-dot line in FIG. 2(b). Both ends of the beams 7 and 8 are integrally molded via highly rigid connecting portions 10 and 11, or connected by well-known fixing means such as welding or poles. Each strain-generating portion 7b is a plane that intersects with the load direction of each strain-generating portion.

Strain gauges 5l-88 are attached to each of the upper surface of 7C, the lower surface of 8b, and 8c in parallel to the longitudinal direction of the beams by adhesive, fusion, vapor deposition, or the like.

Strain gauges S], , S4 are installed in the parts of the strain-generating parts 7b, 7c and 8b, 8c away from the center of the beams 7, 8.
, S5, and SR are attached with strain gauges S2, S3, S6, and S7 near the center.

That is, when the load F is applied to the load introduction part 7a,
Strain gauge si, 84.85. Tensile strain occurs in the part of the beam to which S8 is attached, and strain gauges S2,
Compressive strain occurs at the positions where S 3 , S (+ , and S 7 are attached. As shown in Figure 4, the strain gauges are arranged so that a strain gauge that generates tensile strain due to load F and a strain gauge that generates compressive strain are adjacent to each other. A double point bridge circuit is formed and connected.The input e1 is supplied between the opposing connection parts a and b of the strain gauge that constitutes this wheel stone bridge, and the input e1 is connected to the other connection part C.
The output eo is taken out from between 3 and 1. Note that even if the circuit using strain gauges is a single small Ethos bridge circuit using four strain gauges, it can be used for measurement.

Next, the operation of the sensing section shown in FIG. 2 will be explained. When the measurement load F is applied to the load introduction part 7a, the load introduction part 7a moves in the direction of the fixed support part 8a, and a bending moment 1~ is generated in both the beams 7 and 8. As a result, the upper beam 7 is approximately U-shaped,
The lower beam 8 is bent in an approximately inverted 11 shape, and the strain gauge Sl
, S4, S5. The tensile U strain is measured in S8, and the strain gauge S2. S3. Compressive strain occurs in S6 and S7. Since the connecting parts 10 and 11 of the beam move freely in the longitudinal direction of the beam, unlike conventional beams fixed at both ends, no tension is generated, and good load-output characteristics can be obtained, resulting in an output proportional to the load. The output eO can be taken out between the connection parts c and d shown in FIG. Moreover, since no unreasonable force is applied to the fixed support portion 8a and hysteresis due to slippage between the fixed support portion 8a and the case 9 does not occur, highly accurate holding is possible.

FIG. 3 is a front cross-sectional view showing an embodiment in which a sensor similar to the sensing section shown in FIG. Lid 12a
and a stand 12c having a hole 12d for fixing the fixed support part 8a.
A large-diameter depression 12e is provided under the stand 12C. The lid 12a and the stand 12C together form a storage chamber 12'' for storing the sensing section.A through hole 8d is bored in the center of the fixed support section 8a fixed to the case 12, and a hole 8d is inserted into the through hole 8d. I-shaped connecting rod 13 (here, Pol 1
- shape, but it may be columnar), and its head 13a
The screw provided on the tail portion 13b on the opposite side is the load introducing portion 7a.
It is screwed and fixed into the slotted hole 7d. Load introduction part 7
a and the large diameter hole 12b of the case lid 12a, and between the connecting rod head 13a and the recess 12e of the case base 12C, there are metal diaphragms 14 of the same area and the same rigidity, which are brazed or welded to each other. It is sealed at 15.

The capacity of the storage chamber 12'' sealed by this metal diaphragm J4゜15 is such that even when the measurement load F is applied, the load introduction part 7a and the connecting rod 13 are fixed to each other and move, so the internal pressure of the storage chamber 12f is Changes in the load F do not apply a reaction force.Furthermore, changes in the external pressure oppose the load F, and the external pressure does not affect the sensing portion.

As described in detail above, according to the present invention, the thin 2
Two beams are stacked in two stages at a constant interval in the load direction, and both ends of these two beams are integrally formed or firmly connected to each other via a connecting part, and a load introducing part is placed in the center of one of the beams. The sensing part is configured so that the reaction force is received by the fixed support part provided in the center of the other beam, so that when the beam deforms due to the load, there is no lateral movement of the load point, and , since both ends of the beam connected by the connecting part can move freely almost symmetrically with respect to the axis connecting the fixed point and the load point, no tension is generated in the beam, and the load-output characteristic maintains linearity. In addition, it is possible to provide a highly accurate load converter in which no excessive force is applied to the portion fixed to the case, and there is no influence of hysteresis due to slipping or the like.

[Brief explanation of the drawing]

Fig. 1 is a front view of the sensing part of a conventional load transducer consisting of a beam fixed at both ends, Fig. 2 (a) is a plan view of the sensing part of the load transducer according to the present invention, and (b) is a plan view of the sensing part of the load transducer according to the present invention. 3 is a front sectional view showing the configuration of an example of the load converter according to the present invention, and FIG.
This figure is a connection circuit diagram of the strain gauge of the embodiment shown in FIG. 2. 81-S8...Strain gauge, F...Measurement load. 7, 8--beam, 7a--load introduction part J 7b
, 7c. 8b, 8C... strain generating part, 3a... fixed support part,
9゜12...Case, 10.11...Connection part,
13...1 package of four connected 14,15°゛°diaphragm, ei...input, eo...output. Patent applicant: Kyowa Dengyo Co., Ltd. Figure 1 Figure 3 Figure 4

Claims (2)

[Claims] (1) In a load transducer that electrically measures the magnitude of the load applied to a sensing part using a strain gauge, two thin beams are stacked in two stages at a constant interval in the load direction, and these two Both ends of two beams are integrally formed or firmly connected to each other via a connecting part, the center of one beam is used as a load introduction part, and the center of the other beam is used as a fixed support part to constitute a sensing part, A load transducer characterized in that a strain gauge is attached to a location where a bending moment occurs in one or both of two beams. (2) A through hole is provided in the center of the fixed support part, and one end of the connecting rod fitted into this through hole is fixed to the load introducing part, and the connection between the load introducing part and the case and the other end of the connecting rod and the case is The load transducer according to claim i1, wherein the space between the sensing portions is sealed with a metal diaphragm to eliminate the influence of external pressure on the sensing portion.