JPH0663875B2 - Weight detector - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The field of use of the weight detector of the present invention is in the field of a scale for measuring the weight of an object, or detects the weight of an object and uses the weight information to improve the function and performance. The present invention relates to a target weight detection function application device. For example, there is a microwave oven that effectively uses the weight information. In a microwave oven, the weight of food is measured and the optimum heating time, heating output, heating pattern, etc. are automatically determined according to the weight, and the cooking performance is improved.

2. Description of the Related Art Microwave ovens having a weight detection function of detecting weight and controlling heating are already known. In the case of a microwave oven, it cannot be expected to be treated as a measuring instrument like a general scale. Therefore, it becomes a very severe condition for an excessive load, an impact load, etc., and it is necessary to secure the mechanical strength for it in design. FIG. 5 shows a conventional weight detection device devised as an example of mounting on a microwave oven. (Japanese Patent Publication Sho 62
No. 59382) 1 is a support rotary shaft that supports food and its mounting tray and is driven to rotate by a motor 4.
It is supported by a bearing 18 and a bearing 18 so as to be movable in the vertical direction with an appropriate clearance. The load of the object to be measured transmitted in the thrust direction of the supporting rotary shaft 1 is the load transmitting means 2
Is transmitted to the diaphragm 7 with a constant pressure area.
Reference numeral 3 is a leaf spring for preventing the load transmitting means 2 from directly contacting the supporting rotary shaft 1 and being worn, and has a weak elasticity so as not to attenuate the transmission amount. Fig. 3 shows load detection means
16 is a sectional view, and FIG. 4 is a configuration diagram thereof. Reference numeral 7 is a diaphragm made of an alumina sintered body, and 6 is a substrate made of an alumina sintered body, which are joined by a glass seal 9 and face each other with a minute gap of several tens of microns.
Electrodes 5 made of a noble metal such as gold or platinum are printed and fired on the opposite surfaces of the respective alumina plates to form capacitors. The principle of weight detection is that the diaphragm 7 is deflected by the load transmitted by the load transmitting means 2 and the electrostatic capacitance changes depending on the gap. The capacitance is taken out to an external circuit by the lead wire 11, and signal processing and calculation are performed to calculate the weight. Further, in the structure of the sensor bed 6 for mounting the load detecting means 16, the pressure sensitive portion inside is hollowed out from the glass seal 9 in order to prevent the load from being applied to the substrate 8 from the mounting table side and changing the characteristics. Thereby, only the load from the diaphragm 7 side can be accurately detected. Returning to FIG. 5, the sensor bed 6 is placed on the sensor mounting bracket 10 and is covered with a sensor cover 19 to electrically shield the entire sensor.

The problem to be solved by the invention is that, in such a weight detecting device, when an excessive load or impact load is applied to the load detecting means 16, the diaphragm 7 bends and hits the substrate 8. But substrate 8
However, there is a problem in that the sensor bed 6 has no structure due to its structure and is flexibly destroyed. The breaking deflection of the alumina diaphragm was at most several tens of microns, and it was extremely difficult to process the depth of the hollow portion of the sensor bed to several tens of microns in order to limit this. For example, when the sensor bed 6 is made of sheet metal, the precision of step pressing is at most on the order of 100 microns, and tens of microns cannot be achieved at all.

The present invention solves such conventional problems,
The present invention provides an excellent weight detection device that limits displacement of a diaphragm and a substrate with a simple structure and does not break even under an excessive load or an impact load.

Means for Solving the Problems A weight detection device of the present invention includes a substrate made of a sintered body of alumina facing each other at a predetermined interval, a diaphragm, a capacitive electrode formed on the facing surface, and a substrate and a diaphragm. An electrostatic capacitance type pressure sensor consisting of a glass seal that is connected to the outer peripheral portion of the electrode, a load transmission means for transmitting a point load to the electrostatic capacitance type pressure sensor, and a sensor for mounting the electrostatic capacitance type pressure sensor. In a weight detection device consisting of a mounting part, the surface of this sensor mounting part is etched, and within the weighing range, there is no contact with the pressure sensitive part of this pressure sensor with a minute gap, and the gap is filled. It is configured to be sealed with an agent.

Action After the surface of the sensor mounting portion is masked leaving a portion right below the pressure sensitive portion of the substrate, the sensor mounting portion is subjected to etching treatment, so that a minute void is formed under the pressure sensitive portion. Therefore, the load is not applied to the sensor from the substrate side, the load of the object to be measured is accurately applied only from the diaphragm side through the load transmitting means, and there is no variation in characteristics, and reproducibility is very excellent. Moreover, when an excessive load or impact is applied, the voids under the pressure sensitive portion are so small that even if the substrate abnormally bends, only the distance of the voids bends and the substrate is less likely to be destroyed.

Moreover, abnormal deflection of the substrate is further regulated by a simple method of sealing this void with a filler, and the destruction of the substrate is drastically reduced.
Impact resistance is significantly improved.

Embodiment Hereinafter, a weight detection device of the present invention will be described with reference to the drawings. In FIG. 2, reference numeral 1 is a supporting rotary shaft that supports the object to be measured and its mounting table, and 4 is a motor that rotationally drives the supporting rotary shaft and is a synchronous motor that synchronizes with the power supply cycle.
We are aiming at low speed and high torque by using multiple gears such as 12, gear 13. Supporting rotary shaft 1 is bearing 17, bearing 18
It is held movably in the vertical direction by a proper clearance. Reference numeral 15 is a shaft stop pin to prevent the supporting rotary shaft 1 from falling off. Reference numeral 3 is a leaf spring which receives the supporting rotary shaft, which prevents the load transmitting means 2 from directly contacting and abrading the supporting rotary shaft 1 which is rotationally driven, and has elasticity sufficiently smaller than that of the diaphragm 7, and is ignored for weighing characteristics. It should be possible. Reference numeral 2 is a load transmitting means for transmitting a load from the support rotary shaft 1 to the load detecting means 16, and has a function of transmitting a point load defined by a contact area with the diaphragm 7. Reference numeral 20 denotes a sensor mounting portion 20 on which the load detecting means 16 is mounted, and a region located at the pressure sensitive portion at the bottom of the load detecting means 16 is corroded by about 10 μm by the etching process.
Reference numeral 21 denotes a filler sealing portion that fills and seals a gap between the pressure sensing portion of the load detecting means 16 and the sensor mounting portion 20. Reference numeral 10 is a sensor mounting bracket 10 for mounting the sensor mounting portion 20. Reference numeral 19 is a sensor cover for electrically shielding the load detecting means, and the capacitance of the load detecting means 16 is taken out to the external circuit by the lead wire 11. Support rotating shaft 1
Is held in the vertical direction by bearings 17 and 18, and the load is transmitted in the vertical direction. However, due to the clearance between the shaft and the bearing, the supporting rotary shaft 1 is actually tilted and an error occurs depending on the mounting position of the measured object. To do. In addition, other bearings 17,
Since there is a load transmission loss such as friction between the bearing 18 and the supporting rotary shaft 1, the output from the load detecting means 16 is integrated and averaged for a certain period while the supporting rotary shaft 1 is rotationally driven by the motor 4 to detect a more accurate weight. To do. Ideally, just support rotary shaft 1
It is desirable to perform integral averaging over a period of one rotation.

FIG. 1 shows that the load via the load transmitting means 2 is applied to the diaphragm 7.
And the substrate 8 is bent. Only the diaphragm 7 bends until the upper and lower two electrodes 5 come into contact with each other, but after the contact, the substrate 8 also keeps bending until it comes into contact with the sensor mounting portion 20. After this, the sensor mounting portion 20 which is a rigid body supports the load no matter how much the load is applied.
Also, the substrate 8 will not be abnormally bent and destroyed.
However, it is a necessary condition that the stress due to the bending so far does not exceed the elastic limit of the diaphragm 7 and the substrate 8,
It is the corrosion depth of the sensor mounting portion 20 due to etching that determines the amount of deflection. The adjustment of the corrosion depth by etching can be controlled in units of 1 μm depending on the time for which the object to be corroded is left in the etching solution.

However, in the case of this embodiment, the flatness of the bottom pressure-sensitive portion of the diaphragm 7 is also limited, and it is 5 μm by the dial gauge method.
Deflection of about m was always present. Therefore, it is necessary to set the corrosion depth due to etching to 5 μm or more, and depending on the elastic limit value of the substrate 8 and the diaphragm 7, it was confirmed that the substrate 8 and the diaphragm 7 are easily broken by bending of 5 μm. However, this problem has been solved by injecting the silicone rubber filler 21, which is a kind of adhesive, into the gap between the pressure-sensitive portion on the bottom of the diaphragm 7 and the sensor mounting portion 20.

Liquid silicone rubber expands into voids without creating unnecessary stress on the pressure-sensitive part to create a sealed state, and the cured silicone rubber remains stable as a rubber elastic body from a high temperature of 200 ° C to a low temperature of -50 ° C. While controlling the abnormal deflection of the diaphragm 7, it also exhibited shock absorption as an elastic body. By doing so, as shown in FIG. 2, when the load detecting means 16 is mounted on the sensor mounting portion 20, the minute gap due to the corrosion of etching is sealed with the silicone rubber filler 21 to measure the weight. Sometimes, no pressure is applied from the substrate 8 side, and only the load from the object to be measured can be measured extremely accurately. Further, even if an excessive load or a whale load is applied, the amount of bending of the substrate 8 and the diaphragm 7 is restricted by the etching depth of the sensor mounting portion 20 and the silicon rubber filler 21, and thus the conventional problem of breaking is caused. Is not generated at all, and the mechanical strength is remarkably improved.

EFFECTS OF THE INVENTION As described above, the weight detecting device of the present invention uses the electrostatic capacitance type pressure sensor in which the diaphragms made of two alumina sintered bodies having the capacitive electrodes on the surface are opposed to each other with a minute gap. .

In addition, the sensor mounting part is etched so that it does not come into contact with the sensor pressure sensitive part, and the etching depth is also controlled.There is no sensor mounting between the sensor mounting part and the substrate on the sensor mounting part side. There are extremely minute voids corresponding to the corrosion depth of the etching corrosion area of the rest portion. This void is sealed with a filler so that unnecessary stress is not applied to the sensor substrate, so that the pressure from the sensor substrate mounting part side during weighing is completely eliminated and the weight of the measured object is accurately measured on the upper sensor substrate. Can be applied to improve accuracy, variation in characteristics, and reproducibility.

Particularly, the present invention can withstand severe mechanical use conditions typified by applications to microwave ovens, can have excellent weighing characteristics, and has a simple structure and excellent impact resistance. An extremely advantageous weight detecting device is provided.

[Brief description of drawings]

FIG. 1 is a sectional view of a capacitance type pressure sensor used in a weight detecting device according to an embodiment of the present invention, FIG. 2 is a sectional view of a main part thereof, and FIG. 3 is a static pressure sensor used in a conventional weight detecting device. FIG. 4 is a sectional view of the capacitance type pressure sensor, FIG. 4 is an exploded perspective view of a conventional load detecting means, and FIG. 5 is a sectional view of essential parts of a conventional weight detecting device. 2 ... Load transmitting means, 5 ... Electrode, 7 ... Diaphragm, 8 ... Board, 9 ... Glass seal, 10 ... Sensor mounting metal fitting, 14 ... Surface coat, 16 ... Load detecting means,
20 …… Sensor mount, 21 …… Silicon rubber filler.

Claims (1)

[Claims] 1. A substrate made of a sintered body of alumina, a diaphragm made of a thin plate of an alumina sintered body and facing the substrate at a predetermined interval, and a capacitor electrode formed on the surfaces of the substrate and the diaphragm facing each other. A pressure sensor of a capacitance detection type, which comprises a glass spacer connecting the diaphragm and the substrate at an outer peripheral portion of the capacitance electrode, and a capacitance of which changes according to a pressure on the surface of the diaphragm.
The sensor mounting portion for mounting the pressure sensor, and a load transmitting means mounted near the electrode center of the diaphragm for transmitting a load from the outside to the pressure sensor, the surface of the sensor mounting portion being etched. A weight detecting device which is configured to seal the gap with a filler when a weight is processed and the weight is detected within a weighing range without contacting the pressure sensitive portion of the pressure sensor with a minute gap.