JP3234417B2 - 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 strain sensing element such as a strain gauge when the element is subjected to strain. The present invention relates to a load sensor that prevents an abnormal or erroneous output due to a mechanical load, disturbance vibration, or the like, and prevents disconnection of a wiring.

[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 caused by distortion of the sensing element when a load is applied. In a load sensor of this type, if a load exceeding the yield point or the withstand load of the detection part is applied, the detection part will be plastically deformed, not only will it be impossible to accurately measure the load, but will also be a failure of the sensor such as breakage of the detection element. Also leads to.

However, in actual load detection, it is inevitable that an unexpected excess load exceeding a specified measurement range is applied. As a countermeasure, it is conceivable to make the withstand load of the detection unit sufficiently larger than the rated value, but this would increase the dimensions of the sensor, which would lead to an increase in the size of the device incorporating the sensor and an increase in cost. it is obvious. Therefore, the present applicant has previously proposed a load sensor as shown in FIG. 2 (Japanese Patent Application No. 6-160768).

In FIG. 2, a housing 10 comprises a bottomed cylindrical under-housing 10A and a main housing 10B fitted thereto. A threaded rod for connecting a load to be measured is provided at the bottom of the under-housing 10A. 2 are provided. The under housing 10A
A detection diaphragm 3 provided with a strain gauge for load detection is disposed at a position concentric with the rod 2 in the inside. 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. In order to hold the detection diaphragm 3 at a predetermined position, the following configuration is adopted.

First, the detection diaphragm 3 is fitted on the inner periphery of an annular holder 5. The inner circumferences of annular elastic support plates 6 and 7 are fitted to the outer circumference of the holder 5, and the inner circumferences of the support plates 6 and 7 are formed by inner bushes 8 and 9 joined to the outer circumference of the holder 5. The inner bushes 8, 9 and the holder 5 are sandwiched and fixed. On the other hand, a cylindrical main housing 1 is provided around the outer housing 10A.
0B is press-fitted, and is connected to the under housing 10A by the claw 11 at the end. The outer peripheral portions of the support plates 6 and 7 and the outer bush 12 are arranged between the end of the under housing 10A and the main housing 10B. It is sandwiched and fixed.

A circuit board 13 for taking out 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, Au bonding wires 14.

The flange 4 has a threaded rod 15 that is arranged concentrically with the center axis of the detection diaphragm 3 and the rod 2. End face 16 of the outer periphery of the flange 4
Is a stopper surface, which faces the end surface of the main housing 10B with a predetermined gap g. The gap g is set to be equal to or less than a value corresponding to the withstand load of the detection diaphragm 3, that is, the maximum displacement of the elastic support plates 6, 7 due to the measured load. By arranging the stopper surface 16 and the main housing 10B to face each other with the gap g interposed therebetween, when an arbitrarily set allowable maximum load within the elastic limit of the detection diaphragm 3 is applied, Since the stopper surface 16 and the end surface of the main housing 10B are in contact with each other, it is possible to prevent the detection diaphragm 3 and the support plates 6 and 7 from being plastically deformed or damaged due to the application of a greater load. If the elasticity of the support plates 6 and 7 is within the elastic range, the distortion of the detection diaphragm 3 is measured in a state where the load and the strain are balanced. Does not affect the measurement accuracy of the load.

[0008]

It has been found that the above-described sensor has the following problems depending on environmental conditions. When a disturbance vibration is applied to the load sensor or an impact load is applied, the elastic support plates 7 and 8 vibrate, causing an abnormal output or an erroneous signal, a decrease in measurement accuracy, and a bonding. There is a problem that the wire 14 vibrates and causes disconnection. Further, depending on environmental conditions, there is also a problem that dew may be formed inside the housing to corrode internal components and wiring, or a measurement output signal may leak.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and has as its object the object of the present invention to provide an elastic support plate and a load control device that can be used even when disturbance vibration is applied to a load sensor or an impact load is applied. An object of the present invention is to provide a load sensor that suppresses vibration of a bonding wire and prevents dew condensation inside a housing regardless of environmental conditions.

[0010]

A load sensor according to the present invention comprises:
A load detecting element including a load detecting element provided with a strain gauge for measuring a load to be measured and a holder holding the detecting element; and a housing for accommodating the load detecting section in the center thereof. A plurality of sheets are disposed in a plane substantially perpendicular to the direction of application of the measurement load, and the inner peripheral portion thereof is fixed to the load detecting portion to hold the same, and the outer peripheral portion thereof is fixed to the inner peripheral surface of the housing. An elastic plate, a seal diaphragm that hermetically seals a gap between an inner peripheral surface end of the housing and an outer peripheral surface end of the holder of the load detection unit,
An insulating buffer fluid (for example, silicone oil or the like) filled in a sealed space surrounded by the housing, a load detection unit, and a seal diaphragm; An opening for distribution is formed to enable distribution.

[0011]

[Function] For example, an insulating buffer fluid such as silicone oil is filled in the housing, the holder of the load detecting section, and the sealed space surrounded by the seal diaphragm. Even if it is added, the vibration and displacement of the elastic support plate are suppressed by the action of the insulating buffer fluid, and the occurrence of abnormal output and erroneous signals and the decrease in measurement accuracy are prevented, and the vibration of the bonding wire is also suppressed. Also, the occurrence of disconnection is virtually completely prevented. Furthermore, dew condensation does not occur inside the housing, corrosion of internal components and wiring of the housing, leakage of measurement output signals and short circuit are prevented, and measurement accuracy can be maintained and a long life can be realized.

[0012]

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. 2, the same reference numerals as those in FIG. 2 indicate the same or equivalent parts. The gap between the inner periphery of the end of the main housing 10B and the outer periphery of the end of the holder 5 is sealed by a seal diaphragm 18 to form a sealed space therein, and an electric space is formed in the sealed space. An insulating buffer fluid 19 such as silicone oil oil, which is electrically insulating and chemically inert and exhibits a mechanical buffering action, is filled. The elastic support plates 6 and 7 are appropriately provided with a flow opening 20 through which the insulating buffer fluid 19 freely flows.

In operation, even if a disturbance vibration or an impulsive load is applied to the load sensor, the vibration of the elastic support plates 6 and 7 is suppressed by the action of the insulating buffer fluid 19, so that an abnormal output or an erroneous signal is generated. And the measurement accuracy does not decrease. Further, since the vibration of the bonding wire 14 is also suppressed, the occurrence of disconnection is substantially completely prevented. Further, the inside of the housing 10 is provided with an insulating buffer fluid 19.
, The dew condensation does not occur inside the housing, so that the components and wiring inside the housing do not corrode, and the measurement output signal does not leak. If the internal pressure changes due to expansion and contraction of the filling fluid due to a change in environmental temperature, the seal diaphragm 18 is deformed to maintain the internal pressure substantially constant, so that the basic output characteristics of the load sensor are maintained substantially constant. Dripping.

[0014]

According to the present invention, the seal diaphragm 1 is provided.
The insulating buffer fluid 19 is provided in the space inside the housing sealed with 8.
, The vibration of the elastic support plates 6 and 7 is suppressed by the action of the insulating buffer fluid 19 even when a disturbance vibration or a shocking load is applied to the load sensor, and an abnormal output or an erroneous signal is generated, and A decrease in measurement accuracy is prevented. Also, since the vibration of the bonding wire 14 is suppressed,
The occurrence of disconnection is virtually completely prevented. Further, since the inside of the housing 10 is filled with the insulating buffer fluid 19,
Condensation does not occur inside the housing, corrosion of components inside the housing and wiring, leakage of measurement output signals,
The short circuit can be prevented to maintain the measurement accuracy and extend the life. If the internal pressure changes due to expansion and contraction of the filling fluid due to a change in the environmental temperature, the seal diaphragm 18 is deformed and the internal pressure is kept substantially constant, so that the basic output characteristics of the load sensor are kept substantially constant. Can be.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view of the load sensor presented earlier by the present applicant.

[Explanation of symbols]

3 ... Detection diaphragm, 4 ... Flange, 5 ... Holder, 6,7 ... Support plate, 8,9 ... Inner bush, 1
0: Housing 10A: Under housing 10B: Main housing 12: Outer bush
DESCRIPTION OF SYMBOLS 13 ... Circuit board, 14 ... Wire, 16 ... Stopper surface 18 ... Seal diaphragm 19 ... Silicone oil (insulating buffer fluid) 20 ... Flow opening

────────────────────────────────────────────────── (5) References JP-A-50-104974 (JP, A) JP-A-6-2168 (JP, U) JP-A-4-38528 (JP, U) JP-A 52-104 110870 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01L 1/22

Claims (3)

(57) [Claims] 1. A load detecting unit comprising a load detecting element provided with a strain gauge for measuring a load to be measured, a holder for fixing and holding the detecting element, and the load detecting unit is housed in the center thereof. And a housing, each of which is arranged in a plane substantially perpendicular to the direction of application of the load to be measured, and whose inner peripheral portion is fixed to and holds the load detecting portion, and whose outer peripheral portion is formed on the inner peripheral surface of the housing. A plurality of fixed elastic support plates, a seal diaphragm that hermetically seals between an inner peripheral surface end of the housing and an outer peripheral surface end of a holder of the load detection unit, and the housing, a holder of the load detection unit, And an insulating buffer fluid filled in a sealed space surrounded by the sealing diaphragm, wherein the elastic support plate is provided with a flow opening for allowing the insulating buffer fluid to flow. Load sensor, characterized in that. 2. The load sensor according to claim 1, wherein said insulating buffer fluid is silicone oil. 3. The sealing diaphragm according to claim 1, wherein the sealing diaphragm deforms in response to expansion and contraction of the insulating buffer fluid, and maintains the pressure of the insulating buffer fluid substantially constant. The load sensor as described.