JP3268128B2 - Load sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load sensor and, more particularly, to a load sensor for detecting the magnitude of a load based on a change in resistance of a sensing element such as a strain gauge due to distortion of the element. The present invention relates to a load sensor provided with a protection means for a load equal to or more than a withstand load of a load detection unit provided with the sensor.

[0002]

2. Description of the Related Art A load sensor is known in which a sensing element is attached to a flexure element, that is, a sensing portion, and the applied load is measured by a change in resistance of the sensing element due to distortion of the sensing element when a load is applied. I have. In a load sensor of this type, when a load equal to or higher than the yield point of the detection unit, that is, a load equal to or more than the withstand load is applied, the detection unit plastically deforms, not only cannot accurately measure the load, but also damage to the detection element, etc. It also leads to sensor failure.

However, although the actual detected load is small or the measuring range is narrow, an unexpectedly large load may be applied, so that the above problem may occur. Therefore, in order to avoid the above problems,
In consideration of the unexpectedly large load, it was necessary to increase the load resistance of the detection unit more than necessary.

In general, the larger the withstand load, the larger the dimensions of the sensor. However, it is not advisable to increase the size of the sensor in consideration of a load larger than the withstand load, which is not a steady load that is repeatedly measured, because it increases the size and cost of a device incorporating the sensor.

Therefore, as a device for solving such a problem, the following sensor has been proposed (Japanese Patent Application Laid-Open No. 64-35331). In this sensor, when a load exceeding the withstand load is applied and the detection unit is greatly distorted, the stopper pin attached to one of the fixed side and the displacement side comes into contact with the other, and a larger load is applied to the detection unit. It was not added.

[0006]

The above-mentioned conventional sensor has the following problems. In this sensor, the detecting portion is formed of only one plate-like strain body, and when an unbalanced load is applied to the detecting portion, the strain body is twisted. For this reason, the stopper pin supported by the strain body is displaced in an inclined state, and the stopper pin does not abut on a mating side on a predetermined surface but abuts on a corner. When the stopper pin is tilted, the predetermined gap becomes substantially smaller, and the stopper pin operates with a measured load smaller than the predetermined load. As a result, it may happen that the load cannot be measured in spite of the measured load range of the detection unit.

Further, when the corner portion abuts on the other side while the stopper pin is inclined, the contact surface is close to a point or a line, stress is concentrated there, and the sensor is damaged by repetition. Is also possible. As described above, the conventional sensor has a problem that the detection unit does not correctly displace in the direction in which the load is applied, and in particular, the load cannot be accurately measured near the upper limit of the measured range.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to displace the detection unit in a predetermined direction and to reduce the load to be measured in a wide range even when an eccentric load is applied. An object of the present invention is to provide a load sensor that can measure accurately.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and to achieve the object, the present invention provides a housing in which a load detecting portion provided with a strain gauge for measuring a load to be measured is provided at the center. And a plurality of elastic plates comprising an inner peripheral portion fixed to the load detecting portion and an outer peripheral portion fixed to the housing, the first elastic plate being disposed at a right angle to the direction in which the load to be measured is applied. There are features.

Further, the present invention is characterized in further comprising a connecting portion joined to the load detecting portion, and a load applying portion having a stopper surface facing the peripheral end surface of the housing at a predetermined interval. There is a second feature.

[0011]

When a load to be measured is applied, distortion occurs in the elastic plate and the load detecting portion (hereinafter, simply referred to as a "detecting portion"), and the load is applied in a state where the load and the stress of the elastic plate are balanced. The size is measured. That is, distortion of the detection unit due to the load is transmitted to the detection element provided in the detection unit. Then, the magnitude of the distortion of the sensing element is measured as a resistance value by a sensing circuit which is not a main part of the present invention. In the present invention,
Since the detection unit is supported by multiple elastic plates,
The inclination due to the unbalanced load is small, and a highly accurate measurement result is obtained.

Further, according to the second feature, a load is transmitted to the detecting portion by the connecting portion. When the deformation of the elastic plate due to the applied load reaches the predetermined interval, the stopper surface comes into contact with the peripheral end surface of the housing. That is, when the applied load exceeds the measured range set in the gap, the load applied to the detection unit and the elastic plate is limited.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of a load sensor according to one embodiment of the present invention. In the figure, a bottomed cylindrical inner housing 1 has a threaded rod 2 at the bottom thereof for connecting a load to be measured. At the position concentric with the rod 2 in the inner housing 1, a detection diaphragm 3 provided with a strain gauge for load detection is arranged. A flange 4 as a load applying unit is connected to the center axis of the detection diaphragm 3 by appropriate means such as welding. The following configuration is employed to fix the detection diaphragm 3 at a predetermined position.

First, the detection diaphragm 3 is fitted on the inner periphery of an annular holder 5. The inner periphery of the annular support plates 6 and 7 is fitted to the outer periphery of the holder 5, and the support plates 6, 7
Is fixed between the inner bushes 8, 9 and the holder 5 by inner bushes 8, 9 joined to the outer periphery of the holder 5. On the other hand, a cylindrical main housing 10 is press-fitted into the outer periphery of the inner housing 1, and a claw 11 at an end thereof is bent inward to be connected to the inner housing 1. Between the end of the inner housing 1 and the main housing 10, the outer peripheral portions of the support plates 6 and 7 and the outer bush 12 are arranged, and these are connected to the inner housing 1 by the coupling of the claws 11. It is sandwiched and fixed.

A circuit board 13 for extracting a change in resistance of a strain gauge on the detection diaphragm 3 to the outside is fixed to one end of the holder 5 by an appropriate means such as adhesion. The substrate 13 and a strain gauge (both not shown) are connected by, for example, an Au wire 14.

The flange 4 is located at the center of the detection diaphragm 3, that is, the rod 2 of the inner housing 1.
Has a threaded rod 15 arranged concentrically with the center. An end face 16 on the outer periphery of the flange 4 serves as a stopper face, and faces the end face of the main housing 10 with a predetermined gap g. The gap g is set to be equal to or less than the withstand load of the detection diaphragm 3, that is, the maximum displacement amount of the support plates 6, 7 due to the measured load, that is, the displacement amount of the detection diaphragm 3. The closer to the maximum displacement, the larger the measurable range. By setting the gap g in this way and arranging the stopper surface 16 and the main housing 10 to face each other, when the load to be measured is arbitrarily set within the elastic limit of the detection diaphragm 3, The stopper surface 16 and the end surface of the main housing 10 are in contact with each other, so that it is possible to prevent a further load from being applied.

If the elasticity of the support plates 6 and 7 is within the elastic range, the strain of the detection diaphragm 3 is measured in a state where the load and the strain are balanced. Does not affect load measurement accuracy.

In this embodiment, the detection diaphragm 3
Although the example in which the and the flange 4 are joined is shown, they may be integrally manufactured in advance.

[0019]

As is apparent from the above description, according to the present invention, even if the load resistance is increased, the size of the detecting portion may be adjusted to the measured load, and the size may not be unnecessarily increased. Therefore, an increase in cost can be avoided, and the degree of freedom in layout due to miniaturization increases.
In addition, since the detection unit can be downsized, it becomes easy to form a strain gauge on the detection unit by sputtering or CVD.

Further, since the detection section is supported by a plurality of support plates, unlike the case where the detection section is supported by a single support plate, the support plate and the detection section are not twisted. Therefore, the load is correctly applied in the predetermined direction of the detection unit, and an accurate measurement result is obtained. Further, when the withstand load is exceeded, the stopper can function accurately with a predetermined load to limit the load.

[Brief description of the drawings]

FIG. 1 is a sectional view of a load sensor showing one embodiment of the present invention.

[Explanation of symbols]

1 ... inner housing 3 ... detection diaphragm 4
... Flange, 5 ... Holder, 6,7 ... Support plate, 8,
9 ... Inner bush, 10 ... Main housing, 1
2 ... Outabush, 13: Circuit board, 14: Wire, 16: Stopper surface

Continuation of front page (56) References JP-A-62-291530 (JP, A) JP-A-2-21231 (JP, A) JP-A-64-35331 (JP, A) , U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01L 1/22 G01L 1/26

Claims (3)

(57) [Claims] And 1. A load detection unit which strain gauges for measuring the load is from the holder to fix the load sensing element and the sensing element is provided, a load application part which is coupled to the load sensing portion, the load A plurality of elastic plates each including a housing in which a detection unit is provided at the center, and an inner peripheral portion fixed to the load detection unit and an outer peripheral portion fixed to the housing and arranged at right angles to a direction in which a load to be measured is applied. A load sensor comprising: 2. The method according to claim 1, wherein the load application unit is provided with a load detection unit.
Connections and predetermined spacing from the peripheral edge of the housing
The load sensor according to claim 1 , further comprising a stopper surface having an opposite surface . 3. The load sensor according to claim 2, wherein the interval is set to an amount corresponding to a displacement amount of the load detecting unit within a load range to be measured.