JPH01219645A - Weight detector - Google Patents

Abstract

PURPOSE:To reduce the dimension of a wt. detector in the width direction thereof, by providing a load transmission mechanism for transmitting load to a load sensor, wherein electrostatic capacity is formed by a fixed substrate and a movable substrate, to the upper surface of the load sensor through an elastomer and providing the stopper part, which is closely brought into contact with the outer periphery of the movable substrate with respect to the load limit of the elastomer, to the outer peripheral part of said transmission mechanism. CONSTITUTION:A load sensor 11 is formed between the fixed substrate 2 of a wt. detector and the movable substrate composed of an insulating substrate deformed by a wt. of said detector through a seal member 3 holding a desired gap. This sensor 11 is mounted and fixed to a sensor support plate 9 through a sensor support member 8 provided to the under surface thereof and a shaft 7 is vertically provided to the center upper surface thereof through a spherical point 6 and a leaf spring 4 and a load transmission mechanism 10 composed of a block 5 provided with a recessed part 52 in which the spring 4 is inserted is arranged to the center of the lower part. A plurality of stop parts 51 are provided to the block 5 in a protruding state along the under surface outer edge thereof at the position corresponding to the member 3 and a positioning metal fitting 53 for holding the position of the pointer 6 is provided to the inner periphery of the recessed part 52.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a weight detection device that detects the displacement of an elastic body in response to a load using an electric output using capacitance.

[Conventional technology]

Generally, a weight detection device is used in which the electrical output is a change in capacitance due to the spacing between two diaslums that deform due to a load. Conventionally, this type of weight detection device has a sealing member 3 that maintains a desired gap between a fixed substrate 2 and a diaphragm movable substrate 1 made of an insulating substrate such as an alumina plate that deforms under load, as shown in FIG. The setting is fixed board 2
A load sensor 11 serving as an air capacitor is used between the movable substrate 1 and the movable substrate 1. The lower surface of this load sensor 11 is placed on the sensor support plate 9 via the sensor support member 8, and the load transmission mechanism 10 is placed on the fulcrum part at the center of the upper surface of the movable substrate 1 via the cylindrical load point 6. has been done. The load transmission mechanism 1o is formed by a shaft 7 to which a load is applied at the center fixed vertically, a mouth-shaped block 5 with both sides straddling the load sensor 11, and a plate spring 4 installed across both sides. The load transmission mechanism 10 has the lower surface of the leaf spring 4 in contact with the upper surface of the load point 6, and the lower ends of both sides are in contact with the upper surface of the load point 6.
The 4' portion 51 is balanced with the sensor support plate 9 by maintaining a spacing to. Therefore, when a load is applied to the shaft 7 of the load transmission mechanism 10, the load transmission mechanism 10 descends as shown in FIG. increases, and the plate spring 4 also deforms. At this time, the stocking portions 51 at both ends of the block 5 contact the sensor support plate 9, and no further load is applied to the leaf spring 4 and the movable substrate 1.

The amount of displacement when a load is applied to the movable board 1 is usually 1 to 9.
The thickness of the sealing member 3 is about 50 microns, while the Young's modulus of the leaf spring 4 is sufficiently lower than that of the movable substrate 1. Therefore, the amount of displacement increases by one to two orders of magnitude, resulting in a displacement of several hundred microns per 1 kg. That is, since the amount of displacement of both side portions of the stopper portion 51 with respect to the load is smaller than the amount of displacement of the movable substrate 1, the load of the stopper portion 51 is set within a mechanical assembly precision that is feasible.

[The problem that the idea aims to solve]

However, in the conventional weight detection device, when there is no load at all, both side end surfaces of the stocking portion 51 and the sensor support plate 9
The interval dimension t. 4. The height of both sides of the storage part 51. The distance h1 between the tips of both side walls of the storage portion 51 and the leaf spring 4 holding portion is subtracted from the sum h1+h2+h3 of the initial height h2 of the load sensor 11 and the height h3 of the sensor support member 8. Therefore the dimension t. 9 includes dimensional errors of each part, resulting in non-uniformity of normally ±0.1 or more, making it difficult to set an accurate load to stop the stopper part 51 relative to the load. In addition, since the sensor support plate 9 is generally made by sheet metal processing, its flatness is poor and there is a warp of 0.1 to 0.2 m, so that even if the shaft 7 is vertically displaced, both sides of the stop/base portion 51 are It is also difficult to set a load that will come into contact with the sensor support plate 9 and stop the stop portion 51 accurately. Furthermore, since the distance between both sides of the stopper 9 portion 51 is required to be equal to or larger than the width of the load sensor 11, there is a drawback that the overall width of the weight detection device tends to be large.

[Means to solve the problem]

The present invention eliminates such drawbacks of the conventional method and provides a load transmission mechanism 11 that transmits a load from the upper surface of a load sensor 11, which forms a capacitance with a fixed substrate 2 and a diaphragm-like movable substrate 1, via a leaf spring 4 or a helical spring. A stopper portion 51 is provided on the outer side of the elastic body to stop the load transmission mechanism 11 by bringing it into close contact with the fulcrum portion on the outer periphery of the movable portion when the load limit of the elastic body is exceeded.
This is a weight detection device equipped with a

[Effect]

When the load causes a larger deformation than the displacement of the movable substrate 1, the stopper portion 51 prevents the load transmission mechanism 11 from further lowering, and the leaf spring and helical spring absorb the stress of the load.

〔Example〕

An embodiment of the heavy liability detection device of the present invention is shown in longitudinal cross-sectional side views in FIGS. 1 and 2.

As shown in the drawings, a load sensor 11 is formed by a sealing member 3 that maintains a desired gap between a fixed substrate 2 and a movable substrate 1 made of an insulating substrate that deforms under load. This load sensor 11 is mounted and fixed on a sensor support plate 9 via a sensor support member 8 on the lower surface, and a shaft 7 is erected on the center upper surface via a spherical load point 6 and a leaf spring 4 at the center of the upper surface. A load transmission mechanism 10 is provided, which is a block 5 having a recess 52 in the center of its lower surface into which the leaf spring 4 is fitted. Along the outer edge of the lower surface of the block 5 and at positions corresponding to the sealing member 3, a plurality of struts or portions 51 are provided protrudingly, and a positioning fitting 53 is provided around the inside of the recess 52 to maintain the position of the load point 6. . These load sensors 11 and blocks 5 form a weight detection device.

When the load to be measured F is now applied, this force is applied to block 5. Leaf spring 4. The displacement of the ζ leaf spring 4 transmitted to the movable substrate 1 of the load sensor 11 via the load point 6 is set to be about one order of magnitude larger than the displacement of the movable substrate 1.

In addition, the displacement of the leaf spring 4 remains the same as that of the block 5.
displacement amount δ of the part 51. This is the distance between the movable substrate l and the storage fitting 51 when there is no load. As shown in FIG. 2, when the load F=Fs, the strut horn and part 51 come into close contact with the fulcrum part of the movable board 1, and when the load becomes larger than F8, all the load of ΔF = F - Fs is applied to the fulcrum part of the load sensor 11. In addition, damage to the movable substrate 1 is prevented without applying any force to the central portion of the movable substrate 1.

3 and 4 show other embodiments of the present invention, in which the load sensor 11 is formed in the same manner as in FIG. A load point 6 provided with a spring 4a is fixed upright, and the helical spring 4a is balanced with the weight of the block 5.
is strongly supported. Hollow hole 5 in the center of block 5
4 is opened and a part of the load point 6 is inserted, and a stopper portion 51 is located along the outer edge of the lower surface of the load sensor 11 facing the seal portion 3 of the load sensor 11, that is, the fulcrum portion of the movable substrate 1.
is provided.

When a load F8 is applied to the block 5, the movable substrate 1 is deformed as shown in FIG. 4, and the stop/base portion 51 comes into contact with the movable substrate 1, thereby limiting further load and preventing damage. Hence the dimension δ. accuracy and stability during stock loading,
Excellent in reducing the overall external size.

In this type of load sensor 1, the capacitance C between the movable substrate 1 and the fixed substrate 2 is the dielectric constant ε of air, and the movable substrate 1
and the electrode area S formed on the fixed substrate 2, and the initial gap length d. , load F, and proportionality constant can be expressed as follows. Therefore, when the load F increases, the capacitance C
increases, the increase ΔC is detected by an electronic circuit, and the load F is measured.

〔Effect of the invention〕

As described above, according to the present invention, the initial interval δ0 between the stopper portion 51 and the load sensor 1 is different from the dimensional non-uniformity of the height h2 of the load sensor 11 and the sensor support member 8, as in the conventional example. Block 5. has nothing to do with the unevenness of height h3. Leaf spring 4. There is only the dimensional non-uniformity of the load point 6, and the number of dimensional non-uniformities of related parts is reduced, resulting in high precision δ. settings can be made.

Still, the flatness of the movable substrate 1 of the load sensor 11 is normally not good, but the surface waviness is less than 10 microns due to pin polishing, etc., and the stopper portion 51 has good reproducibility.
Closely attached to the fulcrum part of.

Furthermore, the external dimensions of the load transmission mechanism 10 can be easily limited to the external dimensions of the load sensor 11 due to its structure, and the external dimensions can be made smaller.

[Brief Description of the Drawings] Fig. 1 is a longitudinal sectional front view of an embodiment of the weight detection device of the present invention when no load is applied, and Fig. 2 is a longitudinal sectional front view when the load shown in Fig. 1 is applied. 3 is a longitudinal sectional front view of another embodiment of the present invention when no load is applied, and FIG.
Figure 5 is a vertical front view of an example of a conventional weight detection device when no load is applied, and Figure 6 is a front view of a vertical cross-section when the load shown in Figure 5 is applied. It is a diagram. Note that 1: movable substrate, 2: fixed substrate, 3: seal member. 4: Leaf spring, 41: Helical spring, 5 Niblock. 6: load point, 7: shaft, 8: sensor support member, 9: sensor support plate, 10: load transmission mechanism. 11: Load sensor, 51: Stopper part, 52: Recessed part,
53 Positioning metal fittings, 54: Hollow hole - N dimension C rear chart 9
=5 Noriaki Figure 4 Figure 5 M! F=0 Figure 6

Claims (1)

[Scope of Claims] 1. An outer peripheral portion of the load transmission mechanism 10 that transmits a load to the load sensor 11 via an elastic body on the upper surface of the load sensor 11 where the fixed substrate 2 and the movable substrate 1 form a capacitance. A weight detection device characterized in that a stopper portion 51 is provided in close contact with the outer periphery of the movable substrate 1 to meet the load limit of the elastic body. 2. The weight detection device according to claim 1, wherein the outer periphery of the load transmission mechanism 10 includes a load fulcrum portion of the movable substrate 1. 3. The weight detection device according to claim 1, wherein the elastic body is a leaf spring 4 or a helical spring 4a.