JPH0740185Y2 - Moisture-proof structure of strain gauge type transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a moisture-proof structure for a strain gauge type transducer, and more specifically, to the magnitude of the load applied to the load introducing portion of the strain-generating element. The present invention relates to a moisture-proof structure that shuts off the above strain gauge in a strain gauge type converter that converts the amount of electricity into electric quantity by a strain gauge attached to a sensitive portion of a strain generating body.

[Conventional technology]

Conventionally, as a moisture-proof structure (hereinafter referred to as "moisture-proof structure") of this type of strain gauge type transducer, there has been one as shown in Figs. 4 and 5.

In FIGS. 4 and 5, reference numeral 51 denotes a flexure element forming the main body of the load converter, which has a rectangular plate-like overall shape and two circular through-holes in the center of a square plate having an appropriate thickness. Has a spectacle-shaped through hole 52 for penetrating from one side to the other surface side and the two through-holes communicating with each other.
A pair of slits 53, 54 extending in the horizontal direction (direction orthogonal to the load axis direction) from the side end faces on the opposite sides of the upper and lower sides of the eyeglass-shaped through hole 52 to the intermediate portion passing above and below the eyeglass-shaped through hole 52. And female screw holes 55 reaching a predetermined depth from the upper end surface and the lower end surface, respectively.

In the flexure element 51 formed in this way, the beam at the central portion has a spectacle-shaped through hole 52 formed at the center thereof, and other portions (a load introducing beam, a load supporting beam, a connecting rigid body portion described later) are formed. The sensing beam 56 has a thin sensing portion that is thin and deforms by a load to function as a strain generating portion. A load introducing beam 58 is provided above the sensing beam 56 in parallel and one end thereof is integrally connected to one end of the sensing beam 56 via a rigid connecting portion 57 having a large rigidity. On the other hand, there is provided a load supporting beam 60 which is arranged in parallel below the sensing beam 56 and whose one end is integrally coupled to the other end of the sensing beam 56 via a rigid coupling portion 59 having a large rigidity. Four strain gauges SG1 to SG4 are bonded to the inner wall surface of the spectacle-shaped through hole 52 of the sensing beam 56 as shown in FIGS. 4 and 5.

Then, on the one end surface side and the other end surface side of the eyeglass-shaped through hole 52, a neck portion 61a is fitted in the eyeglass-shaped through hole 52, and a flange portion 61b abuts on one end surface and the other end surface of the sensing beam 56, respectively. In this state, the blocking plug 61 is attached, and the inside of the eyeglass-shaped through hole 52 is substantially shielded from the outside air.

Further, in the conventional example shown in FIG. 6, two reinforcing rods 63 connecting the upper and lower obstruction plugs 62, 62 are integrally provided.

The load converter configured as described above is provided with a load introducing beam 58.
When, for example, a tensile load is applied along the longitudinal direction of the strain generating body 51, the load is transmitted to one end of the sensing beam 56 via the rigid connecting portion 57 having high rigidity. On the other hand, the reaction force of this load is transmitted from the load supporting beam 60 to the other end of the sensing beam 56 via the rigid connecting portion 59 having high rigidity.
One end side (the left end side in the figure) of 56 is moved and displaced upward while maintaining a substantially parallel state to the load introducing beam 58 and the load supporting beam 60 by the principle of a parallelogram beam. The inner wall of the spectacle-shaped through hole 52 is deformed due to the displacement of the sensing beam 56, and this deformation is electrically detected by the strain gauges SG1 to SG4.

Since the inside of the through hole 52 is blocked from the outside air by the blocking plug 61 or 62, the outside air does not enter for a certain period,
Therefore, the strain gauges SG1 to SG4 are prevented from deterioration due to moisture absorption.

[Problems to be solved by the device]

By the way, among the matters described in the section of the related art, apart from the problems of the load converter itself, the moisture-proof structure of the strain gauge has the following problems.

First, in the conventional example shown in FIG.
Since both ends of 52 are closed by the closing plugs 61, 61, respectively, when the temperature inside the spectacle-shaped through hole 52 changes, for example, when the temperature rises, the internal pressure rises and the closing plugs 61, 61 move outward. There was a case where it bulged out greatly, and eventually a gap was created or dropped out.

In order to avoid such a situation, conventionally, an adhesive was applied to the outer periphery of the obstruction plug 61 to fix the space between the surfaces of the sensing beam 56, but the obstruction plug 61 itself is flexible. Therefore, there is a risk of bulging outward, peeling, and bursting with a rise in temperature, and it cannot be said that the reliability is sufficient.

Then, what was considered in order to cope with such a problem is, as illustrated in FIG. 6, a pair of obstruction plugs facing each other.
A reinforcing rod 63 having rigidity is connected between 62 and 62 to give strength. With such a configuration, although the large deformation, rupture, and drop of the obstruction plugs 62, 62 can be prevented to some extent, the adhesive strength of the adhesive portion 64 that adheres the periphery of the obstruction plug 62 with an adhesive is insufficient, or Due to deterioration due to long-term use, the airtightness of the outer peripheral part of the obstruction plug 62 can no longer be maintained, and finally the outside air enters and the strain gauges SG1 to SG4
In addition, there is a risk of deterioration due to oxidation and deterioration of insulation due to moisture absorption. In addition, in the structure shown in FIG. 6, the reinforcing rod 63 must be manufactured separately from the obstruction plug 62, and it is troublesome to assemble the both and the mounting to the sensing beam 56. In addition to the difficulty of high costs,
When it is used in a place subject to vibration, there is a problem in that the weight of the rod imposes a load on the adhesive portion and deteriorates it.

The present invention has been made in view of the above problems of the prior art, and its purpose is to provide a simple structure, inexpensive processing and assembly, and peeling due to temperature change. Another object of the present invention is to provide a moisture-proof structure of a strain gauge type transducer, which is capable of stably shutting off the strain gauge from the outside air for a long period of time without the risk of dropping and leakage, and reliably preventing deterioration due to moisture absorption.

[Means for Solving the Problems]

In order to achieve the above object, the present invention provides a strain for converting the magnitude of the load applied to the load introducing portion of the strain generating body into an electric quantity by a strain gauge attached to the sensitive portion of the strain generating body. In the gauge type transducer, a strain body having a spectacle-shaped through hole and two spectacle-shaped through-holes penetrating from the one surface side to the other surface side of the sensitizing portion so as to communicate with each other; The strain gauge attached to the inner wall of the through hole and at least a part of the two substantially cylindrical bodies are connected in parallel to each other so that the cross-sectional shape is substantially spectacle-shaped, and the outer diameters of the two cylindrical portions are the two penetrations described above. The spectacle-shaped flange portions, which are formed to have a diameter slightly smaller than the inner diameter of the hole, have a diameter larger than the inner diameter of the through hole and are spaced slightly smaller than the axial length of the through hole at both ends of the cylindrical portion. Sealing made of formed flexible elastic body And two cylindrical portions of the sealing member are fitted into the eyeglass-shaped through holes, and the eyeglass-shaped flange portions formed at both ends are engaged with one surface side and the other surface side of the sensing section, respectively. It is characterized in that the strain gauge is configured to be shielded from the outside air by being fixed together with an adhesive or the like.

[Action]

The sealing member of the moisture-proof structure of the strain gauge type transducer configured as described above has two cylindrical outer diameters slightly smaller than the inner diameters of the two circular through holes of the spectacle-shaped through hole and has a cross-sectional shape. It has the shape of a spectacle and has flanges with a diameter larger than the inner diameter of the through hole at both ends of the cylinder so as to straddle the two cylindrical parts. Will be closed by a slight sealed space surrounded by the outer periphery of the cylindrical portion of the sealing member, the spectacle-shaped flange portion, and the inner wall of the spectacle-shaped through hole. Therefore, even if the temperature in this slight space rises, the amount of expansion in the space is extremely small, the cylindrical portion of the sealing member only slightly expands inward, and the sealing member is damaged or wears glasses. There is no risk that the flange portion will float from the sensing portion. That is, most of the inside of the spectacle-shaped through-hole has a shape in which the sealing member is formed by connecting two hollow cylindrical portions in parallel with each other, and at least a part of the hollow cylindrical portions is connected to each other. Since it is in communication with, it is hardly affected by the expansion and contraction of the volume due to the temperature change.

Moreover, since the facing distance between the pair of eyeglass-shaped flange portions of the sealing member is set to a dimension slightly shorter than the axial length of the through hole, both eyeglass-shaped flanges are always provided on one side of the sensing portion and other portions. It fulfills the function of crimping to the surface side, and temporarily
Even if the adhesive force applied to the outer circumference of the spectacle-shaped flange portion is deteriorated, it works so as to sufficiently maintain the hermeticity, and no problem occurs even when it is used in a vibrating place.

〔Example〕

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

1 and 2 both show a moisture-proof structure of a load transducer which is an example of a strain gauge type transducer according to the present invention, in which FIG. 2 is a front view and FIG. It is a longitudinal cross-sectional view of FIG. FIG. 3 is a perspective view showing an embodiment of the sealing member used in the same embodiment.

In FIG. 1 and FIG. 2, reference numeral 1 denotes a strain-generating body that constitutes the load converter main body, and the strain-generating body 1 has a generally short columnar shape or a substantially disk-like outer appearance. Two circular through holes 2a, 2b reaching from the one end surface to the other end surface (front to back in the figure) are formed in the central portion so that some of them overlap each other, and as a result, the eyeglass-like through hole 2 is formed. Formed,
Horizontally (in a direction orthogonal to the load axis direction) extending upward and downward with the spectacle-shaped through hole 2 in parallel with each other and from an opposite side peripheral surface to an intermediate position passing above and below the through hole 2. A pair of slits 3 and 4
And further form the upper end and the lower end along the central axis of the spectacle-shaped through hole 2 to form a flat surface, and form female screw holes 5 reaching a predetermined depth from the upper end surface and the lower end surface, respectively. I am doing it.

Before forming the slits 3 and 4, for example, a drill (and a reamer) is used in the innermost portions 3a and 4a of the slits 3 and 4 to disperse the stress having a diameter larger than the slit width of the slits 3 and 4. A hole is formed.

In the flexure element 1 formed in this manner, the beam at the central portion has the above-mentioned eyeglass-shaped through hole 2 formed at the center thereof, and the other portions (the load introducing beam, the load supporting beam described below,
The receiving beam 6 is thinner than the connecting rigid body portion) and has a receiving portion that is deformed by the application of a load and functions as a strain generating portion.

A load introduction portion as a load introduction portion which is arranged above the sensing beam 6 in parallel at a predetermined interval and has one end integrally connected to one end of the sensing beam 6 via a rigid connecting portion 7 having high rigidity. A beam 8 is provided.

On the other hand, a load serving as a load support portion, which is arranged below the sensing beam 6 in parallel at a predetermined interval and is integrally connected to the other end of the sensing beam 6 via a rigid connecting portion 9 having a large rigidity. A support beam 10 is provided.

Further, of the two through holes 2a and 2b of the spectacle-shaped through hole 2 of the sensing beam 6, the inner wall surface of one of the through holes 2a is displaced by approximately + 30 ° and + 150 ° with respect to the load axis direction. Strain gauges SG1 and SG4, and on the inner wall surface of the other through hole 2b, strain gauges SG2 and SG2 at positions shifted by approximately −30 ° and −150 ° with respect to the load axis direction, respectively.
SG3 is attached by adhesion, vapor deposition, sputtering, welding, or other means. The strain gauges SG1 to SG4 thus attached are bridge-connected.

Reference numeral 11 denotes a terminal chamber composed of a circular through hole formed at a position between the slit 3 of the flexure element 1 and the connecting rigid body portion 9 so as to penetrate from one end surface to the other end surface of the flexure element 1. , 12 are communication holes as first communication holes formed so as to communicate with the spectacle-shaped through hole 2 from the terminal chamber 11, and 13 is communicated with the terminal chamber 11 from the outer circumference of the flexure element 1. A cable lead-out hole as a second communication hole that has been bored, 14 is a connection cable inserted into the cable lead-out hole 13, 14a is a sleeve that is a protective member for the connection cable 14, and 15 is the inner diameter of the terminal chamber 11. A printed circuit board having substantially the same height and having a width slightly smaller than the thickness of the strain-generating body 1, 16 is a connecting wire constituting the connecting cable 14, 17 is a connecting wire on each side of the strain gauges SG1 to SG4, 18 Is a lid member, 19 is a resistance as an electric element, and 20 is filled and solidified in the terminal chamber 11 to prevent moisture. It is a mold material.

The cable lead-out hole 13 and the communication hole 12 are arranged in the respective holes 12, 1 from the outer circumference on the right side of the strain element 1 toward the spectacle-shaped through hole 2.
It is drilled so that the axis of 3 is almost straight.

Further, the printed circuit board 15 is formed with a terminal portion on the front and back of one end thereof, and a mounting portion adapted to mount a resistor 19 and the like by a printed pattern on the end side opposite to the terminal portion. Further, a printed pattern, a through hole and the like are formed in the mounting portion, and the resistor 19 and the like are attached to the through hole. The printed pattern and through holes are not formed in the vicinity of the side portion of the printed circuit board 15 that contacts the inner circumference of the terminal chamber 11, and even if this side portion contacts the inner circumference of the terminal chamber 11, insulation is provided. Are configured to be retained.

Next, the moisture-proof structure which is the main part of the present invention will be described.

Reference numeral 21 denotes a sealing member made of a flexible elastic material such as silicon rubber. Particularly, as shown in FIG. 3, two substantially cylindrical bodies are arranged in parallel, and the upper end and the lower end thereof are integrally connected. It is provided, and as a result, its cross-sectional shape is substantially spectacles.

And, as the shape condition of this sealing member 21,
The outer diameters of the two cylindrical portions 22a and 22b are set so that the outer diameters of the two cylindrical portions 22a and 22b are not in contact with the strain gauges SG1 to SG4 attached to the inner walls of the two through holes 2a and 2b. The diameter is slightly smaller than the inner diameter. At both ends (upper end and lower end in FIG. 1) of the two cylindrical portions 22a and 22b, the diameters (upper and lower distances) of the through holes 2a and 2b are larger than the inner diameters of the two through holes 2a and 2b. Eyeglass-shaped (two continuous) flange portions 23, 2 at intervals slightly shorter than the axial length (that is, the thickness of the sensing beam 6 of the flexure element 1).
3 are integrally formed. Between the pair of spectacle-shaped flange portions 23 and the cylindrical portions 22a and 22b, there are two through holes which are concentric with the two cylindrical portions 22a and 22b and which have two outer diameters.
An eyeglass-shaped fitting portion 24 having substantially the same inner diameter as that of 2a and 2b is integrally formed. The inner wall of the sealing member 21 has an inner diameter that leaves a thickness such that the two cylindrical portions 22a and 22b have appropriate elasticity, and both ends thereof are open.

Prior to mounting the sealing member 21 in the spectacle-shaped through hole 2, the surface of the strain gauges SG1 to SG4 attached to the inner wall of the spectacle-shaped through hole 2 is thinly coated with a silicone resin having elasticity. Cover and apply moisture-proof treatment. Thereafter, one end of the sealing member 21 is crushed and fitted into the spectacle-shaped through hole 2, and as shown in FIG. 1, the upper and lower spectacle-shaped flange portions 23, 23 are fitted into the spectacle-shaped through hole. By engaging one end and the other end of 2 and fitting the eyeglass-shaped fitting portions 24, 24, which are connected to the upper and lower ends of the two cylindrical portions 22a and 22b, to the eyeglass-shaped through hole 2, Sealing material
21 is attached to the eyeglass-shaped through hole 2. After that, the adhesive 25 is applied to the outer peripheral portion of the spectacle-shaped flange portion 23 and solidified, whereby the spectacle-shaped flange portion 23 and the sensing beam 6 are adhered to each other, and airtightness is secured.

Next, the operation of the load converter thus configured will be described.

First, the object to be measured (not shown) and the flexure element 1 will be described below as being firmly connected by screwing mounting bolts (not shown) into the female screw holes 5, 5.

When a load along the direction (vertical direction in FIG. 2) orthogonal to the longitudinal direction of the sensitive beam 6 is applied to the load introducing beam 8 of the strain-flexing body 1, for example, a tensile load, the load has a large rigidity. It is transmitted to one end (the left end in the figure) of the sensitive beam 6 via the connecting rigid body portion 7.

On the other hand, since the reaction force of this load is transmitted from the load supporting beam 10 to the other end (right end in the figure) of the sensing beam 6 via the rigid connecting portion 9 having high rigidity, one end side of the sensing beam 6 ( The left end side in the figure) moves and displaces upward while maintaining a substantially parallel state with respect to the load introducing beam 8 and the load supporting beam 10 by the principle of a parallelogram beam. With the displacement (deflection) of the sensing beam 6, the eyeglass-shaped through hole 2
The inner wall of is deformed, and this deformation is electrically detected by strain gauges SG1 to SG4.

This detecting action will be described in more detail. When the sensing beam 6 is displaced upward, for example, as described above, the strain gauges SG1 and SG3 are compressed and their resistance values are reduced, and the strain gauges SG2 and SG4 are expanded. As a result, its resistance value increases.
Since the bridge is formed with the strain gauges SG1 to SG4 that show such changes in resistance, supplying the bridge voltage from the input end of the bridge changes the applied load (measured load) from the output end of the bridge. A corresponding output voltage can be obtained.

By the way, in the sensitive beam 6, the sealing member 21 is attached to the spectacle-shaped through hole 2, but since it is made of a flexible elastic body, there is no deformation (deflection) due to the applied load of the sensitive beam 6. Has no effect.

The sealing member 21 is fitted such that the spectacle-shaped fitting portion 24 is in close contact with the inner wall of the spectacle-shaped through hole 2, and the respective spectacle-shaped flange portions 23 are spaced apart by the thickness of the sensing beam 6. Since it is formed shorter, one side and the other side of the sensing beam 6 at the peripheral edge of the eyeglass-shaped through hole 2 are pressed against each other due to its compression habit, and further, the outer peripheral portion of the eyeglass-shaped flange portion 23. Since it is sealed with the adhesive 25, the minute space 26 surrounded by the sealing member 21 and the inner wall of the spectacle-shaped through hole 2 is substantially completely shielded from the outside air.
Therefore, the strain gauges SG1 to SG4 enclosed in the minute space 26 while being attached to the inner wall of the spectacle-shaped through hole 2 are provided.
Is completely shielded from the outside air, and there is no risk of absorbing moisture contained in the outside air to cause insulation deterioration or oxidation to cause deterioration.

Further, since the minute space 26 surrounded by the sealing member 21 and the inner wall of the spectacle-shaped through hole 2 has a small volume, even if the internal temperature rises, the expansion amount of the volume due to the increase of the internal pressure is extremely small. Therefore, the two cylindrical portions 22a and 22b are only slightly bulged inward, the force for pushing up the flange portion 23 is hardly applied, and there is no room for peeling, separation, or damage of the sealing member 21. Therefore, the airtightness of the minute space 26 formed by the sealing member 21 is ensured for many years.

Furthermore, since the distance between the pair of eyeglass-shaped flange portions 23 of the sealing member 21 is set to be shorter than the thickness of the sensing beam 6 as described above, the adhesiveness is high due to its own compression elastic force. Even if the adhesive 25 deteriorates due to aging, the airtightness between the adhesive beam 6 and the sensing beam 6 can be maintained, and a highly reliable moisture-proof structure can be obtained.

In addition, the sealing member 21 in the above embodiment
As described above, since the structure is simple, the manufacturing is easy, and the cost is extremely low because it is a single part, it is easy to assemble to the load converter, and the work man-hours are small. is there.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

For example, the moisture-proof structure according to the present invention can be applied not only to the so-called S-shaped load converter described above, but also to various load converters such as cantilever type, columnar type and washer type. Further, it is also applicable to various strain gauge type converters such as an acceleration converter, a displacement converter, a pressure converter, etc., in which a through hole is formed in the sensitive portion of the strain generating body.

In the above-described embodiment, the sealing member is shown as a spectacle by combining two substantially cylindrical bodies in parallel. However, the sealing member has a cross-sectional shape of a spectacle-shaped through hole which is formed in the sensing section. Depending on the design, it is up to the designer to set the shape appropriately.

Further, the shape of the spectacles is not limited to the one in which the outer diameters of the two circular shapes abut or overlap each other as in the above-described embodiment, and the outer diameters of the two circular shapes are arranged side by side. Is naturally included.

[Effect of device]

As described above in detail, according to the present invention, since the sealing member itself is a single member and the configuration thereof is simple, the sealing member is airtight even though the manufacturing cost and the assembly cost are low. The micro space that is held and contains the strain gauges only undergoes a slight volume change even if the temperature changes drastically, and the deformation of the sealing member is extremely small. Therefore, even if it is used for many years, the sealing member peels off, falls off, or bursts. It is possible to provide a moisture-proof structure of a strain gauge type transducer that can protect the strain gauge from the outside air stably for a long period of time without causing such problems, and can reliably prevent deterioration due to moisture absorption.

[Brief description of drawings]

1 and 2 both show a moisture proof structure of a load transducer which is an embodiment of the moisture proof structure of the strain gauge type transducer according to the present invention. Of these, FIG. 1 is a vertical plan view. ,
FIG. 2 is a front view, FIG. 3 is a perspective view showing an example of the sealing member in the same embodiment, and FIGS. 4 and 5 are first views.
FIG. 4 is a front view showing a moisture-proof structure of a conventional load converter, and FIG. 5 is a front view of FIG. 4A.
FIG. 6 is a cross-sectional view partially showing a cross section taken along line A-A in FIG.
The cross section of the moisture-proof structure of the load converter according to the second conventional example is shown in FIG.
It is sectional drawing shown similarly to a figure. 1 ... Strain element, 2 ... Glass-like through hole, 3,4 ... Slit, 6 ... Sensitive beam, 7,9 ... Connection rigid body part, 8 ... Load introduction beam, 10 ... Load support Beam, 11 …… Terminal room,
13 …… Cable outlet, 14 …… Connecting cable, 15 …… Printed circuit board, 16 …… Connecting wire, 17 …… Gauge side connecting wire, 18
...... Lid member, 20 ...... Mold member, 21 ...... Sealing member, 22a, 22b ...... Cylindrical part, 23 ...... Glasses-like flange part, 2
4 …… Mating part, 25 …… Adhesive, 26 …… Small space.

Claims (1)

[Scope of utility model registration request] 1. A strain gauge type converter for converting a magnitude of a load applied to a load introducing portion of a strain generating body into an electric quantity by a strain gauge attached to a sensitive portion of the strain generating body, Two circular through holes penetrating from the one surface side to the other surface side are formed in the sensing unit so as to communicate with each other, and the strain generating body having a spectacle-shaped through hole is attached to the inner wall of the spectacle-shaped through hole. The strain gauge and the two substantially cylindrical bodies are arranged in parallel at least in part so that the cross-sectional shape is substantially spectacles, and the outer diameters of the two cylindrical portions are slightly smaller than the inner diameters of the two through holes. A flexible elastic body integrally formed with spectacle-shaped flange portions on both ends of the cylindrical portion with a diameter larger than the inner diameter of the through hole and a distance therebetween is slightly shorter than the axial length of the through hole. And a sealing member made of The two cylindrical portions of the sealing member are fitted into the eyeglass-shaped through holes, and the eyeglass-shaped flange portions formed at both ends are engaged with one surface side and the other surface side of the sensing section, respectively, and fixed by an adhesive or the like. A moisture proof structure for a strain gauge type transducer, characterized in that the strain gauge is configured to be shut off from the outside air by being pressed.