JPH0413940A - Micro capacity type power-electricity quantity converter - Google Patents

Abstract

PURPOSE:To realize small scale and high accuracy by forming No. 1 to No. 4 slits and forming a wide power introducing beam having large rigidity between No.1 slit and No.2 slit, and narrow strain inducing beams between No.1 and No.3 and between No.2 and No.4 slits. CONSTITUTION:At the symmetrical positions to an imaginary line passing on a power introduction part 20 of a plate strain inducing body 14, No.1 slit 15 and No.2 slit 16 are formed, and at the outer symmetrical positions to these slits 15 and 16, No.3 and No.4 slits are formed. A wide power introducing beam having large rigidity is formed between No.1 and No.2 slits 15, 16, narrow strain introducing beams 21 and 22 are formed between No.1 and No.3 slits 15, 17 and No.2 and No.4 slits 16, 18. In this, the width and thickness of the strain inducing beams 21, 22 are set at the minimum limit and hence, a small scale and high accuracy converter can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a microcapacitance type force-to-electrical quantity converter, and more particularly, to a strain-generating beam that generates a [1+11b stress] when a force is applied. The present invention relates to a Kerr electrical quantity converter that has a strain gauge attached thereto and obtains an electrical signal corresponding to the force applied by the strain gauge.

[Conventional technology]

Among these types of converters, various types of load converters have been proposed and are in practical use.

Currently, resistance wire type load converters are most commonly used as load converters for detecting minute loads.

Figures 5 (A), (B), and (C) show the main part configuration of a conventional resistance wire type load converter, of which Figure 5 (
A) is a plan view, FIG. 5(B) is the X in FIG. 5(A),
- A sectional view in the direction of the X-ray arrow, and FIG. 5(C) is a rear view.

In the figure, reference numeral 1 denotes a frame having an inverted T-shape when viewed from the front (as viewed from the right side in FIG. 1B) and an L-shape when viewed from the side. A leaf spring 2 is fixed to the central upper end of the frame 1 by a backing plate 3 and screws 4, and the leaf spring 2 extends vertically downward.

A bent piece 5a of the movable plate 5 is attached to a screw 6 at the lower end of the leaf spring 2.
The movable plate 5 is fixed by the frame 1.
It is arranged parallel to the bottom plate 1a of the.

A shoulder portion 1b formed in the middle of the frame 1.

Two fixing plates 7 and 8 are horizontally fixed on the lc with screws 9. That is, the fixed plate 7.8 and the movable plate 5 are arranged on the same plane parallel to the bottom plate 1a of the frame 1. A total of eight insulating pins 10 are installed perpendicularly to each plate surface on the upper and lower surfaces of the fixed plates 7, 8 and the movable plate 5. Between each of the implanted insulating pins 10 and 10,
The resistance wire 11 is wound multiple times.

The operation of the resistance wire type load converter having such a configuration will be explained.

First, for example, the load introducing portion 5b at the tip of the movable plate 5 is
When a load (or force) is applied downward in FIG. 11 shrinks to reduce resistance. By applying a bridge voltage to the input terminal of a Wheatstone bridge (hereinafter referred to as "bridge"), each of these resistance wires 11 can detect voltage changes caused by bridge unbalance caused by increases and decreases in the electrical resistance of the resistance winding due to load. , that is, a voltage corresponding to the load is obtained from the output end of the bridge.

[Problem to be solved by the invention]

However, the conventional resistance wire type load transducer described above has the following drawbacks.

(1) Since the movable plate 5 is supported by the thin resistance wire 11, it is susceptible to vibration, and there is a risk that the resistance wire 11 may break.

(2) Due to its structure, it is impossible to avoid the negative effects of loads in directions other than the measurement direction, such as torsion and forces applied from the horizontal direction.

(3) Connect the resistance wire 1 between the fixed plates 7 and 8 side and the movable plate 5 side.
1, the difference in the coefficient of linear expansion of the supporting member consisting of the fixed plates 7, 8 and the movable plate 5 and the coefficient of linear expansion of the resistance wire 11 causes an adverse effect due to temperature changes.

(4) In order to form a resistance winding by winding the resistance wire 11 between the insulated pins 10.10, when the tension of the resistance wire 11 changes due to the load, the resistance wire 11 and the insulated pins 10.1
The contact position with zero changes, causing deterioration of non-linearity and generation of hysteresis, resulting in low measurement accuracy and poor repeatability (reproducibility) and stability.

(5) For the reasons stated in items (1) and (2) above, handling is extremely difficult, and damage accidents are likely to occur during installation and transportation.

Therefore, is it possible to overcome the drawbacks of the resistance wire type load transducer by using a strain gauge type load transducer?
Based on this idea, the present inventor attempted to realize it.

First, those shown in FIGS. 3 and 4 are the examples.

In the load converter shown in FIG. 3, 12 is a strain plate that elastically deforms when subjected to a load (force), and this strain plate 12 has a concave cut symmetrically with respect to an imaginary line N passing through its center. By drilling the notches 12a and 12b, a wide load introduction part 12c is formed in the center, and narrow strain-induced beams 12d and 12e are formed from both sides of this load introduction part 12c near the peripheral edge. It is. This load transducer is
As is clear from the figure, the structure is a double-end support beam with both ends fixed.

In addition, in the load converter shown in Fig. 4, 13 is the load (
It is a strain plate that elastically deforms when subjected to an imaginary line N passing through its center, and it is parallel to the imaginary line N from the vicinity of the periphery at a symmetrical position that is a certain distance away from the center by a predetermined amount. Two notches 13a and 13b are bored, and the notch 1 is connected so as to connect the inner ends of the notches 13a and 13b.
3C is drilled, and the whole is cut out in a mouth shape, and further, a cutout 13a is formed between the mouth shape notches 13d.

By making a small cutout 13e that is shorter and narrower than the cutout 13b, a load introduction part 13f is formed in the center, and a strain beam 13g is formed in a portion extending from the load introduction part 13f to near one peripheral edge. It is formed into a cantilevered beam structure.

A strain gauge (not shown) is attached to a portion of each strain beam near the fixed end.

According to such a strain gauge type load transducer, since no resistance wire is used, there is no risk of the resistance wire breaking, there is little adverse effect due to temperature, hysteresis and linearity are improved,
It is thought that it is possible to miniaturize the device and almost eliminate damage during handling and transportation.

However, when detecting minute capacitance force, load, etc. using such a strain gauge type load transducer, the following considerations are required.

In other words, in order to detect a minute capacity load, the bending moment of the strain beams 12d, 12e, and 13g is increased, and in order to obtain the bending strain, the length Q of the strain beams shown in FIGS. 3 and 4 is It is necessary to increase the width of the strain beam, or to reduce the width and thickness of the strain beam. However, even if the width of the strain beam is made smaller, there is a limit to its width because strain gauges are attached.

Furthermore, even when the thickness of the strain-generating beam is made thinner, the presence of the adhesive of the attached strain gauge reduces the accuracy of converting strain into an electrical signal, making it impossible to detect it accurately.

Therefore, in this respect as well, there is a limit to reducing the width and thickness of the strain beam.

By the way, the bending strain εb of the load transducer with fixed support at both ends shown in FIG. 3 is as follows, where b is the width of the strain beam, t is the thickness, and Ω is the length. 8b −t2・E).

Note that here, W is the load and E is the longitudinal elastic modulus.

As shown in the above equation, since there is a limit to reducing the width b and thickness t of the strain beam as described above, the length Q must be increased after all.

Therefore, if the load transducer shown in FIG. 3 is made to have a minute capacity, there is a problem that the length Q of the strain beam becomes very large. A similar problem exists with the load converter shown in FIG.

The present invention was made in view of the above circumstances, and its purpose is to simultaneously realize miniaturization, high precision, and microcapacity, which were previously considered impossible, and to improve vibration resistance and durability. Another object of the present invention is to provide a microcapacitance type force-to-electrical quantity converter that can also improve stability.

[Means to solve the problem]

In order to achieve the above object, the invention according to claim 1 attaches a strain gauge to a strain beam that generates bending stress when a force is applied, and bends the beam in response to the force applied by the strain gauge. In a Kerr electrical quantity converter that obtains an electric signal, a first line extending parallel to the opposite outer edge to the vicinity of the other end is placed symmetrically with respect to an imaginary line passing through the force-transmitting part of the elastic plate-shaped flexure body. 1 and a second sulin 1~,
Further, third and fourth slits extending parallel to the outer edges on the opposite side from the first and second slits to the vicinity of the other end are located at symmetrical positions on the outside of the first and second slits with respect to the virtual line. slit, and the distance between the first slit and the second slit is the same as the distance between the second slit and the third slit, and the distance between the second slit and the fourth slit. The width is sufficiently wider than the distance between the first slit and the third slit to increase the rigidity, and the distance between the first slit and the third slit and between the second slit and the third slit is increased. The spaces between the slits 4 and 4 are narrowly formed to form first and second strain-generating beams, respectively, and the outer portions of the third and fourth slits are formed as fixed support portions, and the first and second strain-generating beams are formed narrowly. The strain gauge is constructed by attaching strain gauges to each front surface and each back surface of the portion near the fixed end of the strain beam. In a Kerr electrical quantity converter in which a strain gauge is attached to the sensitive part and an electrical signal is obtained in accordance with the force applied by the strain gauge, the curve is applied to an imaginary line passing through the force introduction part of the elastic plate-shaped strain body. fifth and sixth slits are formed at symmetrical positions extending parallel to the outer edges of the same side to the vicinity of the other end, and further symmetrical positions on the outside of the fifth and sixth slits with respect to the virtual line; 5 above
and forming seventh and eighth slits extending in parallel from the outer edge on the opposite side of the sixth slit to the vicinity of the other end, and forming an interval between the fifth slit 1- and the sixth slit. The rigidity can be improved by forming the space to be sufficiently wider than the distance between the fifth slit and the seventh slit and the distance between the sixth slit and the eighth slit. is enlarged to form a force introduction beam, and the fifth slit and the seventh
A narrow width is formed between the slits and between the sixth slit and the eighth slit to form third and fourth strain beams, respectively, and outer portions of the seventh and eighth slits are formed. is used as a fixed support part, and strain gauges are attached to each surface and each back surface of the portions near the fixed ends of the third and fourth strain-generating beams.

[For production]

The microcapacitance type force-to-electrical quantity converter according to claim 2, configured as in item 2]--, by forming the first to fourth slits. A wide and rigid dog force introduction beam is formed between the second slit and the first slit. between the third slit and the second slit. By forming a narrow strain-induced beam between the fourth slits, the two strain-induced beams are arranged side by side and form a double-end fixed support beam that can be folded back. A similar strain beam length can be obtained, and the sensitivity can be doubled and the capacitance can be reduced to about 1/2.

Therefore, by setting the width and thickness of the strain beam to the very limits, it is possible to obtain a compact, highly accurate, microcapacitance power-to-electricity converter.

Further, in the microcapacitance type force-to-electrical quantity converter according to claim 2, the fifth to eighth slits are formed.
．． A wide and rigid dog force introduction beam is formed between the sixth sulin 1 and the fifth sulin 1. 7th Surin i・Ma and 6th. By forming narrow third and fourth strain-generating beams between the eighth span 1, the two strain-generating beams narrow the force introduction beam and are symmetrically arranged side by side with one end fixed. If the transducer is of the same size and the transducer is of the same size, the length of the strain-induced beam is nearly twice as long, which doubles the sensitivity and reduces the capacity to about 1/2.

Therefore, by setting the width and thickness of the strain beam to the very limits, it is possible to obtain a compact, highly accurate, microcapacitance power-to-electricity converter.

〔Example〕

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

FIGS. 1A and 1B are a plan view and a right side view showing the configuration of a Kerr electrical quantity converter according to a first embodiment of the present invention.

In the figure, reference numeral 14 denotes a plate-shaped strain-generating body made of an elastic material and having a disk-like overall shape.

This plate-shaped flexure element 14 has first and second plates arranged at symmetrical positions with an interval W1 at symmetrical positions with respect to an imaginary line N passing through the center thereof, and extending parallel to the outer edges on opposite sides to the vicinity of the other end side. Slits 15 and 16 are bored. Furthermore, this first
and symmetrical positions on the outside (with respect to the imaginary line N) apart from the second slits 15 and 16 by a distance W2, parallel to the outer edges on the opposite side to the first and second slits 15 and 16. Third and fourth slits 17 and 18 are provided near the other end.

The distance W1 between the first slit 15 and the second slit 16 is the same as the distance W2 between the first slit 15 and the third slit 17 and the distance between the second slit 16 and the fourth slit 16. The force introduction beam 1 is formed sufficiently wider than the distance W2 between the force introduction beam 1
9, and in the center there is a cylindrical force sensing part 20.
are provided integrally or integrally.

Further, a narrow interval W2 is formed between the first slit 15 and the third slit 17 and between the second slit 16 and the fourth slit 18, and the first strain beam 21 and a second strain-generating beam 22.

Portions of the plate-shaped strain body 14 outside the first and second strain beams 21 and 22 are substantially wide and rigid fixed support portions 23 and 24, respectively.

Strain gauges SG are attached to each front surface and each back surface of the first and second strain-generating beams 21 and 22 near the fixed support portions 23 and 24, respectively.

Next, the operation of the above embodiment having such a configuration will be explained.

It is assumed that a force or load is applied to the center of the force introduction beam 19 of the plate-shaped strain body 14 constituting the Kerr electric quantity converter, that is, the force sensing input part 2o, in the direction from the top surface to the bottom surface in FIG. 1(A). Then, the force introduction beam 19 is displaced downward while remaining substantially horizontal. Then, the movable ends of the first strain beam 21 and the second strain beam 22, which are connected to both ends of the force introduction beam 19, are similarly displaced downward, so that the first strain beam of length α The strain-generating beam 21 and the second strain-generating beam 22 bend in response to force (load).

Due to this deflection, the strain gauges SG attached to the upper surfaces of the first and second strain beams 21 and 22 are expanded to increase their resistance value, and the strain gauges SG attached to the lower surfaces are compressed and resist. Decrease value. Of these four strain gauges SG, the strain gauge SG attached to the upper surface is connected to the opposite side of the Wheatstone bridge, although not shown, and the strain gauge SG attached to the lower surface is connected to the adjacent side of the bridge. A circuit is connected to each side (opposite side).

Therefore, by supplying a bridge power source to the input end of the bridge, an electric signal corresponding to the force applied to the force sensing input section 20, that is, a detection voltage can be extracted from the output end.

At this time, the length of both strain beams 21 and 22 is the strain beam 12d of the load converter shown in FIG.

Assuming that Q is the same as the length of 12e, the above example is smaller in size and shape by about half that of the one shown in Fig. 3, although both have the same capacity. can be converted into In other words, when constructed with the same size, the sensitivity of the above embodiment is approximately twice that of the one shown in FIG. 3, and a corresponding reduction in capacity can be achieved. can.

Furthermore, by reducing the capacity and size, raw materials can be saved, and the processing method is not punching as shown in Figure 3, but simply forming slits. is the capacity, and the added cost can be reduced accordingly.

In addition, unlike the resistance wire type load transducer described above, the above example is strong against vibration, there is no risk of resistance wire breaking and breaking, and it also resists force (load) in directions other than the measurement direction, that is, torsion. Even if a force such as in a horizontal direction is applied, it has a large resistance to torsional force and horizontal force, and strain gauges SG are attached to the upper and lower surfaces of the strain beam 21 and 22 at equivalent positions, respectively, and the above-mentioned Since the bridge is constructed as shown in the figure, it has the advantage that it is electrically canceled out and is less susceptible to the effects of twisting, etc.

In addition, by using materials for the strain gauge and the strain beams 21 and 22 whose coefficients of linear expansion are similar, they can be constructed so as not to be adversely affected by temperature.

In addition, the strain gauge used as a strain detection element as in this example has good linearity and extremely small hysteresis, and furthermore, has high measurement accuracy and repeatability.
Stability is also good.

Furthermore, compared to resistance wire type load transducers, it is less likely to be damaged during installation or transportation.

FIGS. 2(A) and 2(B) are a plan view and a right side view showing the configuration of a Kerr electrical quantity converter according to a second embodiment of the present invention.

In the figure, reference numeral 25 denotes a plate-shaped strain-generating body made of an elastic material and having a disk-like overall shape.

This plate-shaped flexure element 25 has fifth and sixth slits extending parallel to the outer edge on the same side and extending to the vicinity of the other end side, at symmetrical positions with an interval W3 with respect to an imaginary line N passing through the center thereof. 26
and 27 are drilled.

Furthermore, the fifth and sixth slits 26 and 27
Seventh and eighth slits 28 and 29 are arranged at symmetrical positions on the outside and spaced apart by a distance W3 from the outer edge of the fifth and sixth slits 26 and 27, extending parallel to the outer edge on the opposite side to the other end side. is drilled.

The distance W3 between the fifth slit 26 and the sixth slit 27 is the same as the distance W4 between the fifth slit 26 and the seventh slit 28 and the distance W3 between the fifth slit 26 and the sixth slit 27.
and the eighth slit 29. Therefore, the force sensing beam 3o has a large rigidity, and a short cylindrical force sensing section is provided in the center of the beam 3o. 31 are provided.

Further, a narrow interval W4 is formed between the fifth slit 26 and the seventh slit 28 and between the sixth slit 27 and the eighth slit 29, and the third strain beam 32 and a fourth strain-generating beam 33.

Portions of the plate-shaped strain body 25 outside the third and fourth strain beams 32 and 33 are substantially wide and rigid fixed support portions 34 and 35.

Strain gauges SG are attached to the front and back surfaces of the third and fourth strain beams 32 and 33 near the fixed support portions 34 and 35, respectively.

Note that the second embodiment shown in FIGS. 2(A) and (B),
The basic difference from the embodiments shown in FIGS. 1(A) and 1(B) is that the slits are formed differently;
The latter is a cantilevered support beam, whereas the latter is a fixed support beam at both ends.

Therefore, since there is no need to explain its operation, I will omit it here. In terms of its effectiveness, the first
This provides the same effects as the embodiment.

Note that the present invention is not limited to the first and second embodiments described above, and can be implemented with various modifications.

For example, the present invention is very suitable as a load transducer, but if it is configured to transmit the displacement of the diaphragm and bellows to the force sensing input section 20.31 via the force transmission shaft, it is possible to detect minute pressure. It can also be applied to pressure transducers. In addition, strain detectors, displacement transducers, and acceleration transducers can be easily manufactured using the Kerr electrical quantity converter according to the present invention as a conversion element.

Furthermore, the number of slits formed in the plate-shaped flexure body may be increased. By doing so, a lower capacitance converter can be obtained. Whether the support beam is fixed at both ends or the cantilever beam can be determined depending on whether the directions of the slits in each pair are different or in the same direction.

〔Effect of the invention〕

As is clear from the detailed description above, the present invention achieves miniaturization, high precision, and microcapacity at the same time as compared to conventional products, and also has excellent vibration resistance and durability. , it is possible to provide a microcapacitance type force-to-electrical quantity converter that can also improve stability.

[Brief Description of the Drawings] Figures 1 (A) and (B) are a plan view and a right side view showing the configuration of the first embodiment of the present invention, and Figures 2 (A) and CB) are the main views of the present invention. A plan view and a right side view showing the configuration of the second embodiment of the invention, as well as FIGS. Plan views showing examples of plates, FIG. 5 (A
), (B) and (C) respectively show the configuration of a conventional resistance wire type load converter.
) is a plan view, FIG. 5(B) is a sectional view taken along the line X--X of FIG. 5(A), and FIG. 5(C) is a rear view. 14... Plate-shaped strain plate, 15.16, 17, 18... First, second, third
, fourth slit, 19... force sensing input beam, 20... force sensing input section, 21.22... first and second strain beams, 23
．． 24...Fixed support part. 25...Plate-shaped strain plate, 26.27, 28.29...5th, 6th, 7th
, eighth slit, 30... force sensing input beam, 31... force sensing input section, 32.33... third and fourth strain beams, 34
．． 35... Fixed support part, SG... Strain gauge.

Claims (2)

[Claims] (1) In a Kerr electrical quantity converter in which a strain gauge is attached to a strain beam that generates bending stress when a force is applied, and an electrical signal corresponding to the force applied by the strain gauge is obtained, an elastic plate is used. First and second slits are formed at symmetrical positions with respect to an imaginary line passing through the force introducing portion of the strain body, extending parallel to the outer edges on opposite sides to the vicinity of the other end, and further extending along the imaginary line. On the other hand, third and fourth slits are formed at symmetrical positions on the outside of the first and second slits, extending parallel to the outer edges on the opposite side to the first and second slits and reaching near the other end side. , the distance between the first slit and the second slit, the distance between the first slit and the third slit, and the distance between the second slit and the fourth slit. The rigidity is increased by forming the beam to be sufficiently wider than each interval between the first slit and the third slit, and between the second slit and the fourth slit. are formed narrowly to form first and second strain beams, respectively, outer portions of the third and fourth slits are fixed supports, and fixed ends of the first and second strain beams are formed to have a narrow width. A microcapacitance type force-to-electrical quantity converter characterized in that strain gauges are attached to each front surface and each back surface of the close portion. (2) A force-to-electrical quantity converter that has elasticity in which a strain gauge is attached to a strain beam that generates bending stress when a force is applied, and an electric signal corresponding to the force applied by the strain gauge is obtained. A fifth and a sixth slit are formed parallel to the outer edge on the same side to the vicinity of the other end side at symmetrical positions with respect to an imaginary line passing through the force introduction part of the plate-shaped flexure body, and On the other hand, seventh and eighth slits are formed at symmetrical positions on the outside of the fifth and sixth slits, extending parallel to the outer edges on the opposite side to the fifth and sixth slits and reaching near the other end side. The distance between the fifth slit and the sixth slit is the distance between the fifth slit and the seventh slit, and the distance between the sixth slit and the eighth slit. The rigidity is increased by forming the beam to be sufficiently wider than each interval between them to form a force introduction beam, and between the fifth slit and the seventh slit and between the sixth slit and the eighth slit. are formed into narrow widths to form third and fourth strain-generating beams, respectively, outer portions of the seventh and eighth slits are used as fixed support portions, and the third and fourth strain-generating beams are A microcapacitance type force-to-electricity converter characterized in that strain gauges are attached to each front surface and each back surface of a portion near a fixed end.