JPH0141208B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a load transducer for electrically measuring the magnitude of a load applied to a sensing section by a strain gauge.

There are various shapes of sensing parts of this type of conventional load transducers, 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 methods include the cantilever method, in which one end is fixed and the load is applied to the other end, the double-end fixed beam method, in which both ends are fixed and the load is applied to the center of the beam, and the double-bending method. There are various methods such as the parallelogram beam method.

However, methods such as the above-mentioned cantilever method and parallelogram beam method, in which one end is fixed and a load is applied to the other end, have the disadvantage that the load point moves outward when the beam is deflected by the load. In particular, when a diaphragm is attached to a beam to prevent lateral loads and strain gauges from absorbing moisture, tensile force acts on the diaphragm due to the movement of the load point, which affects the deflection characteristics of the beam and This was a factor that inhibited the linearity of the load-output characteristics.

Furthermore, when the above-mentioned beam with both ends fixed is bent by a load, tension is generated in the beam, which affects the deflection characteristics of the beam, and the load-output characteristic by the strain gauge becomes non-linear. In particular, a sensing section that measures a particularly small load is susceptible to the effects of this tension because the thickness of the beam becomes thinner and the deflection increases, making it difficult to realize a sensing section with high precision. In addition, when measuring a relatively large load, although the beam is thick and the deflection is small, the generated tension is quite large, causing problems with the method of fixing the fixed end, and hysteresis due to slipping of the fixed end. There are defects that impair accuracy.

The present invention has been made to eliminate the above-mentioned deficiencies of conventional load transducers.The purpose of the present invention is to have a simple structure, no movement of the load point, and no influence by a diaphragm for preventing lateral loads. The first object is to provide a load converter with good linearity of load-output characteristics.

That is, a feature of the present invention is that in a load transducer that electrically measures the magnitude of the load applied to a sensing part using a strain gauge, the inner part of the main body is The sensor body has a cantilever-like strain-generating part that protrudes toward the side and has a spherical or spherical protrusion at its tip, and the periphery is fixed to the main body part and a load is applied to the center part. A diaphragm having a load seat that receives the load and transmits the load to the protruding portion of the strain-generating portion located inwardly, and a strain gauge that is attached to the strain-generating portion and outputs an electric signal according to the load. That's true.

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

FIG. 1 is a front center cross-sectional view showing the configuration of an embodiment of the present invention, and FIG. 2 is a plan view of the main body of the sensing section in the embodiment.

In the figure, reference numeral 1 denotes a main body of the sensing section, which has a thick disk shape with a void inside, and has a large rigid main body section 1a, which has four mounting bolt insertion holes 1b. A cable pull-out hole 1c is drilled from the right side circumferential surface toward the center, and a piece that extends inward from the inner peripheral wall of the main body 1a (near the center position of the main body 1a) and is thinner than the main body 1a. It has a beam-shaped strain-generating portion 1d. This strain-generating portion 1d
A protruding portion 2 having a spherical shape is provided at the tip of the strain generating portion 1d.
A strain gauge SG for detecting the bending strain of is attached by adhesive or other means, and the output of this strain gauge SG is led out to the outside by a cable (not shown) inserted through the cable extraction hole 1c. . 3 is lateral load prevention and strain gauge SG
This is a thin disk-shaped diaphragm provided to have the function of preventing moisture absorption, and its peripheral portion is fixed to the upper end of the main body portion 1a, and its center portion has a
A load seat 4 receives a load W from the outside (from above in FIG. 1) and transmits the load W to the protrusion 2 of the strain-generating portion 1d located inside (from below in FIG. 1). It is fixed. A blind lid 5 in the shape of a thin disc is fixed to the lower end of the main body portion 1a by welding or the like at its peripheral edge. The blind cover 5 and the diaphragm 3 are attached to the main body part 1a by welding, for example, after finishing work such as processing the strain-generating part 1d, attaching the strain gauge SG, and connecting the strain gauge SG to the cable.
Attach to the top and bottom edges of.

The load converter configured in this way applies a load W to the load seat 4 of the diaphragm 3 from the direction of the arrow in FIG.
When is applied, the diaphragm 3 bends downward,
The spherical protrusion 2 of the strain-generating portion 1d is pressed down on the bottom surface of the load seat 4, and the strain-generating portion 1d is bent clockwise. When this strain-generating portion 1d bends and the protruding portion 2 slightly rotates clockwise in the figure, the contact position with respect to the load seat 4 shifts slightly, but the contact position on the load seat 4 is always the bottom surface of the load seat 4. Centrally located
It hardly moves. In other words, as the strain-generating portion 1d bends downward, the contact point of the spherical protrusion 2 with the load seat 4 gradually moves toward the fixed end side of the strain-generating portion 1d. The contact position with respect to the protrusion 2 does not change and always contacts at the center position of the bottom surface. Therefore, this load converter has a load W
Even if the strain generating part 1d bends in response to the bending, the distance between the fixed end (base end) and the load end (contact point with respect to the load seat 4) does not substantially change. By forming a Wheatstone bridge with the strain gauge SG, an electric signal corresponding to the load W can be obtained from the Wheatstone bridge. In this case, as before,
The diaphragm and the strain-generating portion are not connected, and the bottom surface (plane) of the load seat 4 provided on the diaphragm 3 is in contact with the top surface (spherical surface) of the protrusion 2 provided on the strain-generating portion 1d. Therefore, when a load is applied, no tensile force is applied to the diaphragm 3 due to the deflection of the strain-generating portion 1d, and the linearity of the load-output characteristic can also be improved in this respect compared to the conventional one.

Further, in the case of the above embodiment, machining of the sensing section main body 1, particularly the strain generating section 1d, can be easily performed. That is, the thick disk-shaped main body part 1 is turned, the portions corresponding to the upper gap 6 and the lower gap 7 are counter-turned, and the communicating hole 8 is formed which communicates the upper and lower gaps 6 and 7. Since it can be easily manufactured by drilling a hole in a U-shape (see Fig. 2) when viewed from above, inexpensive load converters can be supplied in large quantities.

Furthermore, a strain-generating portion 1d is formed so as to protrude inward from the peripheral wall of the main body portion 1a having high rigidity, and a mounting bolt insertion hole 1b is bored in a flange-shaped portion of the main body portion 1a. Due to the fact that
When this load transducer is attached to an object to be measured, the main body portion 1a is not easily deformed, and even if it is slightly deformed, the deformation hardly affects the strain generating portion 1d. The change in the initial unbalance value can be suppressed to an extremely small value.

It should be noted that the present invention is not limited to the embodiments described and illustrated above, and various modifications can be made without departing from the spirit thereof.

For example, the protrusion 2 provided at the tip of the strain-generating portion 1d
uses a screw whose tip is machined into a spherical shape, but instead of this, a hard ball may be embedded in the upper tip of the strain-generating portion 1d.

Further, although the sensing portion main body 1 shown in the drawing has a circular shape when viewed from the top, it may have a square shape or other shapes.

In addition, as shown in the figure, the sensing part main body 1 seals the strain generating part 1d with a diaphragm 3 and a blind lid 5, and also includes a cable, a cord gland fitting, and a cord fixing device, which are inserted through the cable pull-out hole 1c (not shown). From the viewpoint of moisture proofing the strain gauge SG, it is preferable to seal the inside using tubes, airtight terminals, etc. Further, the inside may be filled with an inert gas.

As described in detail above, according to the present invention, the configuration is simple, it is easy to attach to the object to be measured, etc., and there is little change in the initial unbalance value, and the strain-generating part is deflected under load. This is a load converter with good linearity of load-output characteristics, with no lateral movement of the load point, and despite the use of a diaphragm to prevent lateral loads, the diaphragm does not affect the strain-generating part. can be provided.

[Brief explanation of drawings]

FIG. 1 is a front center cross-sectional view showing the configuration of an embodiment of the present invention, and FIG. 2 is a plan view of the main body of the sensing section in the same embodiment. 1... Sensing section main body, 1a... Main body part, 1d...
Strain part, 2...Protrusion part, 3...Diaphragm, 4
...Load seat, 5...Blind lid.

Claims (1)

[Claims] 1 In a load transducer that electrically measures the magnitude of the load applied to the sensing part by a strain gauge,
A sensing part main body having a cantilever-like strain-generating part that protrudes inward from the main body part peripheral wall having high rigidity and has a spherical or spherical protrusion at the tip thereof, and a peripheral edge thereof. a diaphragm fixed to the main body portion and having a load seat in the center that receives a load and transmits the load to the protrusion of the strain-generating portion located inward;
A load transducer comprising: a strain gauge attached to the strain generating section and outputting an electric signal according to the load.