JPS62179614A - Weight detector - Google Patents

Abstract

PURPOSE:To enable accurate detection of weight, by reducing the size of a load detector section while it is made up of a pressure-sensitive sensor free from effect of external humidity or the like with limited displacement due to a load. CONSTITUTION:A pressure-sensitive sensor 1 has upper and lower flat plates 2-a and 2-b of insulator being elastic each with a printed electrode; the flat plates 2-a and 2-b are stuck together through a spacer 4 and they 2-a and 2-b employ ceramics or the like. This pressure-sensitive sensor 1 is so small in the size and limited in the displacement that an electrode gap can be intercepted easily from outside, hence free from moisture and dust. Then, a load of an object to be measured is applied to the upper flat plate 2-a through a hemi-spherical pressure point 6 and the lower flat plate 2-b is received on a sensor base 5, which is given a hole 5-a to be supported with the undersurface of a part in contact with the spacer 4 of the lower flat plate 2-b. So to speak, the load working on a shaft 9 acts on the upper flat plate 2-a of the sensor 1 through a stopper metal 8 and an elastic body 7 via the pressure point 6 to deform a pressure-sensitive part of the spacer 4.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a scale for measuring the weight of objects.

In addition, the present invention relates to a weight detection device as a means for detecting the weight of an object, effectively utilizing the weight information, and improving functions and performance. For example, there is a heating cooker that effectively utilizes weight information, and cooking performance can be improved by detecting the weight of food in a heating chamber and heating the food at the optimal output. The present invention relates to such a weight detection device.

2. Description of the Related Art In the conventional scale shown in FIG. 6, for example, an object to be measured is placed on a plate 18, and the load is connected to a parallel holding spacer 25 on the horizontal movement side by a load support fitting 26.

Further, the parallel movement side parallel holding spacer 25 is connected to the stationary side parallel holding spacer 24 via a temporary spring 23 which is fixed vertically in a parallel state. The fixed side parallel holding spacer 24 is fixed to a base 29 via a support fitting 27. The two sheet metal electrodes 28 are attached to the parallel movement side parallel holding spacer 25 and the stationary side parallel holding spacer 24, respectively.

When the object to be measured is placed on the plate 18, the load causes the leaf spring 2 to
3 is deformed, and the portion attached to the parallel movement side parallel holding spacer 25 is displaced downward. As a result, the distance between the two sheet metal electrodes 28 changes, and the capacitance between the sheet metal electrodes changes. The weight is measured by detecting this change in capacitance.

Problems to be Solved by the Invention However, such a weight detection device that detects changes in capacitance between sheet metal electrodes has the following problems.

First, there is air between the sheet metal electrodes, and the dielectric constant of the air changes depending on the humidity. As a result, the capacitance between the sheet metal electrodes changes, making accurate weight detection impossible. Furthermore, if the device is installed in a heating cooker or the like, it will be installed in the kitchen, or because water vapor will be generated from food, etc., the humidity will change sharply, making accurate weight detection even more difficult.

The second problem is that the capacitance between the sheet metal electrodes changes due to dust etc. adhering to the sheet metal electrodes and becoming moist.
Accurate measurement becomes impossible.

The other is the sheet metal electrode, which has an area of approximately 50JllX 501
It is large, with a size of 1 IM to 1010011 x 100, and an electrode spacing of 5 to 10 MM. This is because the change in electrode spacing due to load is about 2 to 3 ff, and in order to detect this as a change in capacitance, it is necessary to increase the electrode area. Since the area is large and the amount of displacement between the electrodes is large, it is difficult to isolate the space between the electrodes from the outside and eliminate the influence of humidity. As described above, the conventional method has a problem in that accurate weight detection is extremely difficult because it is difficult to deal with humidity, dust, and the like.

The present invention solves these conventional problems, and aims to eliminate the influence of humidity and dust on measurement accuracy and realize accurate weight measurement.

Means for Solving the Problems In order to achieve the above object, the weight detecting device of the present invention has a small load detecting section and is constructed with a pressure-sensitive sensor that has small displacement due to the load and is not affected by external humidity, etc. The purpose is to accurately detect weight. The structure of the pressure-sensitive sensor includes two flat plates made of elastic insulators, which are bonded parallel to each other with a constant gap between them using spacers, and electrodes are provided on each opposing surface of the flat plates. Then, the load of the object to be measured is applied to one flat plate, and the other flat plate supports this pressure sensor in a state where no force is applied. A flat plate subjected to a load undergoes flexural deformation due to the load, and a change in capacitance occurs due to a change in the distance between the two electrodes. The structure is such that the weight is detected by detecting this change in capacitance.

The elastic constants of the two flat plates constituting the working pressure sensor are generally not the same. Therefore, when force is applied to both sides, a combined deformation of the two sheets occurs, and the change in capacitance becomes unstable, making accurate weight detection difficult. Therefore, by applying a load to only one flat plate and supporting the other flat plate so that no force is applied, stable deformation occurs and accurate weight detection becomes possible. Furthermore, the upper and lower plates can be made of the same plate, which has the effect of reducing costs.

EXAMPLE Hereinafter, an example of the present invention will be described based on the drawings.

As shown in FIG. 2, the structure of the pressure-sensitive sensor 1 is that electrodes 3 are printed on two upper and lower insulating and elastic flat plates 2a and 2b, and these flat plates 2a and 2b are bonded together via a spacer 4. It is something that The flat plates 2a and 2b may be made of ceramic or the like as an elastic insulator.

Also, the size of the conventional sheet metal electrode is 50 MM x 50
jll~100mm x 100M11, electrode spacing is 5~1O
It was as large as NM. However, in the case of the present invention, the electrode spacing is 50 to 60/1 m with 2 flat plates 30 II x 30 gtx, and the thickness of the flat plates 2a and 2b is Q,
When configured with 5MM, the thickness of the pressure sensitive sensor 1 is 1.05~
It can be made as small as 1.1H. Furthermore, the capacitance as an electrical characteristic and its rate of change with respect to load can be obtained as in the conventional case.

The reason is that the electrode spacing between the two flat plates 2a and 2b is set at 50~
This is because they are bonded at a narrow interval of 60 μm, and can be easily realized on a par with the technology for bonding glasses such as liquid crystals used as display elements at present. Therefore, since the electrode spacing is small, the electrode area can be reduced in order to obtain the same capacitance as in the conventional case.

In addition, when the plate is made of alumina ceramic with a flat plate of 211゜2 b fil thickness t O,5, the displacement is 1 kg.
The load per unit is 10) Lm, which is very small. However, even if the displacement due to the load is small, the electrode spacing is small, so the rate of change in capacitance is large and is equal to or higher than that of the conventional method.

As described above, the pressure-sensitive sensor 1 replaces a function comparable to that of the conventional leaf spring 23 and sheet metal electrode 28, and is furthermore compact and has a small displacement, so the electrode gap can be easily isolated from the outside. Not affected by humidity changes or dust.

Then, the load of the object to be measured is applied to the upper flat plate 2a via the hemispherical pressure point 6. Further, the lower flat plate 2b is received and supported by the sensor stand 5.

A hole 5a is made in this sensor stand 5, and a hole 5a is made in the lower flat plate 2.
It is supported by the lower side of the part in contact with the spacer 4 of b. By extending the inner side of the spacer 4 through the hole 5a, no force is applied to the deformed portion of the lower flat plate 2b, that is, the pressure-sensitive portion.

That is, the load applied to the shaft 9 is transmitted to the pressurizing point 6 via the stopper fitting 8 and the elastic body 7. The force of the pressure point 6 is applied to the upper flat plate 2a of the pressure sensor 1. Since the upper flat plate 2a is supported by the spacer 4, when force is applied to the inner part of the spacer 4, that is, the pressure sensitive part, the flat plate 2& is elastic and deforms. However, even if a force is applied to a part other than the part supported by the spacer 4, that is, the part that can be pressure sensitive, the spacer 4
There is no deformation because it is supported by This load is supported by the sensor stand 5 via the portion of the lower flat plate 2b that is bonded to the spacer 4. This sensor stand 5 is provided with a hole 5a, and the hole 5a is for supporting the spacer 4 under the spacer 4, which is not supported by a portion inside the spacer 4, that is, a pressure-sensitive portion. By doing this, only the upper flat plate 2a deforms under the load, and the lower flat plate 2a
There is no deformation of b, and therefore a stable capacitance change can be obtained. If the sensor stand 5 does not have a hole 5a, that is, if it has a mere planar shape, the sensor stand 5 and the lower flat plate 2b will rarely have completely the same flatness. If the sensor stand 5 is even upwardly warped, the lower flat plate 2b may be pushed up and the lower flat plate 2b may be deformed. Furthermore, if there is a foreign object on the sensor stand 5 or there is a protrusion due to a scratch or the like on the surface of the sensor stand 5, the lower flat plate 2 will be deformed in the same way. And flat plates 2a+2b on both sides
When the flat plate 2b is deformed, the elastic constants of the upper and lower parts will be different, and the positions where the lower flat plate 2b is pressed by foreign objects or warping will vary. Therefore, the flat plates 2 a on both the upper and lower sides
+ 2 b complex capacitance changes or unstable changes occur.

In this case, accurate weight detection becomes difficult. As described above, in order to accurately detect weight, it is important to press only one side of the flat plate. In addition, the upper and lower flat plates can be constructed with the same thickness, so they can be assembled without the need to distinguish between the upper and lower plates, and the cost can be reduced.

FIG. 1 shows an embodiment of a load transmission mechanism to a pressure-sensitive sensor 1 and a support portion that receives the pressure-sensitive sensor 1. As shown in FIG. The load of the object to be measured is transmitted from the shaft 9 to the stopper fitting 8, and is applied to the pressurizing point 6 via the elastic body 7 composed of a leaf spring. The pressure point 6 is applied to the upper flat plate 2a of the pressure sensor 1,
Only the upper flat plate 2a is deformed, and the interval between the upper and lower electrodes 3 changes.

At this time, the lower flat plate 2b is supported by the sensor stand 5 not on the pressure-sensitive surface but at the lower part of the surrounding spacer 4, and there is no deformation of the lower flat plate 2b. In this way, stable and accurate deformation of only the upper flat plate 2a occurs in response to the load, and can be detected as a corresponding change in capacitance (i).

For protection against heavy loads, when a predetermined load is applied, the elastic body 7 deforms and the entire stopper fitting 8 is displaced downward. Then, the flanges on both sides of the stopper metal fitting 8 hit the sensor support metal A109, and the load exceeding the predetermined load is applied to the flanges on both sides of the stopper metal fitting 8, and up to the predetermined load, the pressure sensitive sensor 1 is applied. Protect.

FIG. 3 is a partially sectional perspective view showing the support machine 114 that supports the load of the object to be measured and transmits the load to the pressure sensor 1 as shown in FIG.

In actual weight measurement, the weight placed on the plate 18 is not limited to the center. Therefore, it is necessary to accurately concentrate and transmit the load to the pressure sensor 1 regardless of the mounting position. This includes a donkey pal mechanism commonly used in scales and the like.

The advantages of this are that accurate weight detection is possible regardless of the mounting position, and that the mounting table can be displaced while maintaining a parallel state.

The structure of the donkey pal mechanism is such that the four corners of a parallelogram are movably connected, the - side is fixed, and the opposite side is movable in parallel. The parallel movement metal fitting 11 is a side that can move in parallel,
The fixed support fitting 12 on the opposite side is defined as a fixed side. Then, the two parallel holding metal fittings 13 are fastened together with pins 14 at their four corners to form a parallelogram. And parallel movement fitting 11
The shaft 9 is attached to the 1777 structure in which the load is transmitted to the pressure sensor 1. By using the donkey-pal mechanism in this way, a small pressure-sensitive sensor 1 can be installed regardless of the mounting position.
This allows you to concentrate on your weight and make accurate weight measurements possible.

FIG. 4 is a side sectional view showing a case where the weight detection device of the present invention is mounted on a cooking appliance. By attaching it to the bottom of the heating chamber 20 in this way, the weight of the food 19 can be detected and the output of the magnetron 22 can be controlled accordingly, making it possible to accurately measure the weight without being affected by humidity or dust. Performance also improves.

FIG. 5 shows an oscillation circuit that converts a change in capacitance of the pressure-sensitive sensor 1 into an oscillation frequency, and is a circuit that converts a change in weight into a change in frequency. This circuit is the same as the conventional one for detecting a change in capacitance of the sheet metal electrode 28.

As described above, according to this embodiment, accurate weight detection is possible.

Effects of the Invention As described above, the weight detection device of the present invention provides the following effects.

(1) Pressure-sensitive sensors can be used with stable characteristics,
Accurate weight measurement is possible.

(2) The upper and lower two flat plates of the pressure sensor can be made of the same material, resulting in low cost.

(3) The upper and lower two flat plates of the pressure-sensitive sensor can be made of the same material, and there is no restriction on the pressure-sensitive surface of the pressure-sensitive sensor.

[Brief explanation of drawings]

Fig. 1 is a partial cross-sectional perspective view of a weight detecting device, which is an embodiment of the present invention, showing a pressure sensor and a load supporting device (°1η), and Fig. 4 is a side cross-sectional view showing the state in which the same is mounted on a heating cooker. Figure 5 is a circuit diagram showing the oscillation circuit, and Figure 6 is a side view showing the structure of a conventional scale. Flat plate, 2b...lower flat plate, 3...electrode, 4...spacer, 5...sensor stand,
5a... Hole, 6... Pressure point, 7
...Elastic body, 8...Stopper fitting, 9
...Shaft, 10...Sensor support fitting, 11...Parallel movement fitting, 12...
Fixed support metal fittings, 13... Parallel holding metal fittings, 14.
...Pin, 15...Motor, 16...
...Gear, 17...Turntable, 1st...
...Plate, 19...Food, 20...
・Heating chamber, 21... Door, 22... Magnetron, 23... Leaf spring, 24...
・Fixed side parallel holding spacer, 25...Parallel movement side parallel holding spacer, 26...Load supporting metal fittings,
27... Support metal fittings, 28... Sheet metal electrodes, 29... Base. Name of agent: Patent attorney Toshio Nakao and 1 other person/-
--Pressure sensor 5-1-palm 1 unit 6-11 Karos E point L Fig. 1 1O5-yu/--Ichikushitama Yanbu Fig. 2, 5-Yanbutai Otsu-hit,
Tamahonn F 5-a, --Ichianaku N Fig. 4

Claims (4)

[Claims] (1) A pressure-sensitive sensor that converts applied force into an electrical signal, a weight detection circuit that detects the weight from the electrical signal from the pressure-sensitive sensor, and a weight detection circuit that supports the load of the object to be measured and transfers the load to the pressure-sensitive sensor. and a sensor support means for supporting the pressure sensor, the sensor support means being supported by a portion of the pressure sensor other than a portion capable of sensing pressure. (2) The pressure-sensitive sensor is composed of two flat plates made of elastic insulators, a spacer for bonding the flat plates together in parallel with a constant gap, and electrodes provided on each opposing surface of the two flat plates. 2. The weight detection device according to claim 1, wherein the force at the time of pressurization is converted into an electrical signal as a change in capacitance due to a change in the distance between the electrodes due to the bending deformation of the flat plate. (3) The weight detection device according to claim 2, wherein a load is applied to one flat plate of the pressure sensor, and the sensor supporting means supports a portion of the other flat plate that does not undergo deformation. (4) The weight detection device according to claim 2, wherein the two flat plates of the pressure-sensitive sensor have the same thickness.