JPH0217067B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrode plate of a sensor in a capacitive electronic balance.

The weight is detected by a slender block-shaped flexure element (a plate spring may also be used), and the strain of the flexure element relative to this weight is converted into the gap between the sensor's two parallel flat electrode plates. In so-called capacitive electronic scales that convert the amount of change in capacitance that occurs in this gap into a weight value and display the weight, conventionally, the parallel plate electrode plates that are the sensors were mutually flat. . For this reason, if the load is biased towards the strain-generating body,
Along with the twisting direction of the flexure element, one of the parallel plates (the movable electrode plate) tilts, resulting in a large eccentricity error, which makes accurate weighing impossible. This was complicated, time-consuming, and difficult to adjust.

In order to solve the above-mentioned drawbacks, the present invention uses an electrode plate that is curved around the center axis due to the twisting of the flexure element, so that the gaps between the electrode plates are almost uniform against eccentric loads. It is an object of the present invention to provide a capacitance type electronic balance which is constructed so as to be maintained at 200 degrees Celsius, and which has as little influence as possible even if the strain body is twisted by the eccentric load.

Describing an embodiment of the present invention, reference numeral 1 is a strain-generating body that is an elongated block made of a predetermined material. This strain-generating body 1 has a strained portion 1 hollowed out in the middle portion.
a, and at both ends thereof, a fixed part 1b and a movable part 1c.
The fixed part 1b is fixed to the base 2, and the movable part 1c is fixed to the receiving tray 3 on which the weight W to be weighed is placed. Note that this strain body 1 is the seventh
As shown in the figure, it may be a strain body 1' formed of plate springs S1 and S2.

4 is a fixed electrode plate, and 5 is a movable electrode plate. Both electrode plates have a radius r around the torsion center O in the axial direction Q in the width direction of the strain-generating body 1 (see FIG. 3).
The movable electrode plate 5 is a conductive plate material having a curved surface formed into an arc shape or a spherical shape (not shown) with an angle of 1, r2, and has a wider area than the fixed electrode plate 4.

One end 4a of the fixed electrode plate 4 is held by an angle member 6 so as to be located directly below the flexure element 1 in the axial direction Q. It is fixed to the fixed part 1b or the base 2.

On the other hand, one end 5a of the movable electrode plate 5 is held by an angle member 8 so as to face the fixed electrode plate 4 (either the upper or lower side of the fixed electrode plate 4 is fine), and the other end of this angle member 8 is It is fixed to the movable portion 1c of the strain body 1 via an insulating material 9.

In another embodiment, the fixed electrode plate 4 and the movable electrode plate 5 are provided with flat portions 4b, 5b on part of their curved surfaces, as shown in FIGS. 5 and 6, in order to facilitate attachment of the angle members 6, 8. It may also have a different shape.

With the above configuration, for example, when the heavy object W to be weighed is placed biased at point D or point E of the receiving tray 3, the strain-generating body 1
The movable part 1c is slightly twisted around the axial direction Q and is distorted as it descends, and the movable electrode plate 5 is distorted by the fixed electrode plate 4.
The gap G increases in a substantially concentric state.

However, even if the strain-generating body 1 is twisted and deformed around the axial direction Q due to the eccentric load, the gap G' between the fixed electrode plate 4 and the movable electrode plate 5' is not fixed at any point on the curved surface. is almost constant (r2′−r1≒constant),
The gap G' between the electrode plates is maintained almost uniformly, and the error in the eccentric position of the receiving plate 3 with respect to points D and E is much smaller than that of the conventional flat electrode plate.
In addition, when the electrode plate is spherical, it has the same effect as described above against eccentricity not only at points B and C of the receiving tray 3 but also in all directions, and the capacitance type electronic balance has as little influence on eccentric loads as possible. Can be provided. Furthermore, even for the electrode plate in which some flat parts 4b and 5b are provided in other embodiments, since the area ratio of the flat parts 4b and 5b to the curved surface is small, the influence is as small as possible, and the flat part 4
By providing the angle members 6 and 5b, it is easy to attach the angle members 6 and 8, and a more accurate scale with a simple structure and less eccentricity error can be provided, which is highly effective.

[Brief explanation of drawings]

Figure 1 is an overall plan view of the present invention;
The figure is a side view. FIG. 3 is a cross-sectional view taken along line A-A' in a normal state and an eccentric load state (double-dashed line). FIG. 4 is a partial perspective view of the fixed electrode plate 4 and the movable electrode plate 5 to which angle members 6 and 8 are attached. FIG. 5 is a sectional view taken along line A-A' in another embodiment, and FIG. 6 is a partial perspective view of the fixed electrode plate 4 and the movable electrode plate 5 in FIG. FIG. 7 is a side view of a scale using a strain body 1' formed of leaf springs S1 and S2. 1, 1'...Strain element, 4...Fixed electrode plate, 5...
...Movable electrode plate.

Claims (1)

[Claims] 1. A fixed electrode plate is provided on the fixed part 1b of the Roberval type strain body, and a movable electrode plate is provided on the movable part 1c so as to face each other, and the amount of change in the distance between the electrode plates is detected and the weight is measured. 1. A capacitive electronic scale, characterized in that the fixed electrode plate and the movable electrode plate have curved surfaces curved in a direction surrounding a central axis of Roberval twist. 2. The capacitance type weigher according to claim 1, characterized in that each of the radii of the curved surfaces of the fixed electrode plate and the movable electrode plate is a distance from the central axis of approximately Roberval twist. Capacitive scale. 3. The capacitive scale according to claim 1, characterized in that one electrode plate is wider than the other electrode plate.