JP2723005B2 - Weight detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a weight detecting device used for a cooking device such as a microwave oven.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 7, a weight detection device of this type includes a cooking weighing dish 3 installed in a cooking chamber 2 and
The configuration was such that the entire weight of the food 5 and the weighing dish 3 was supported by the weight sensor 1 via the weight transmission unit 4. In such a configuration, the control unit 6 operates the magnetron 7 according to the weight of the food 5 detected by the weight detection unit 1. The radio wave radiated from the magnetron 7 was introduced into the cooking chamber 2 through the waveguide 8 to cook the food 5. The conventional weight transmitting unit and the conventional weight sensor are configured as shown in FIG. 8, and the weight of the food is installed under the weight transmitting unit 4 through a load point 9 in which the cross-sectional area of the weight transmitting unit 4 is constant. Was transmitted to the alumina diaphragm type weight sensor 1.

[0003]

However, in the above configuration, when measuring the weight of the object on the weighing dish, the contact area between the weight transmitting unit and the weight detecting unit is constant, so that the home is often used. There is a problem that the sensitivity is low in a small load region such as warming used rice, and the sensitivity is increased in a large load region such as pressure cooking.

The present invention solves the above-mentioned conventional problems. By providing a weight transmitting portion whose contact area with a weight sensor increases or decreases according to the weight of an object, the weight detecting device has high sensitivity in all load regions. It is another object of the present invention to provide a weight detection device that can prevent damage to a weight sensor by dispersing stress.

In order to solve the above-mentioned problems, a weight detecting device of the present invention detects a weighing dish on which an object is placed and a weight of the object.
Diaphragm type weight sensor and an object on the weighing pan.
Takenoko transmitting weight to the diaphragm type weight sensor
And a weight transmitting portion made of a spring. Also,
The bamboo shoot spring has a configuration in which the spring constant gradually decreases from the outside toward the inside .

[0006]

According to the weight detecting device of the present invention, since the weight transmitting section whose contact area with the weight detecting section increases or decreases according to the weight of the object, the contact area for pressing the weight detecting section is determined according to the weight of the object. Can be increased or decreased. For this reason, in the large load region, the contact diameter becomes large, and the amount of distortion of the alumina of the air capacitor used as the weight detecting unit becomes small. Further, in the small load area, the contact area is small, so that the strain amount can be very large as compared with the case where the diameter is constant. As a result, a very high sensitivity can be obtained even if the maximum strain amount at the time of applying the maximum load is the same as the conventional one.

[0007]

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

(Embodiment 1) FIG. 1 is a sectional view of a weight detecting device according to the present invention, and the same components as those in the conventional example are denoted by the same reference numerals. FIG. 2 shows a weight transmission unit 4 whose diameter increases and decreases in accordance with the weight of the object 5 and a diaphragm-type weight sensor 1 installed below the weight transmission unit 4 pressed by the increasing and decreasing diameter. The weight sensor 1 has a diameter of about 30 m.
m alumina substrates 11 and 12 (sheet thickness of about 0.5 mm
０．７0.7 mm), the periphery of which is fixed with an adhesive layer 13, and circular electrodes (about 11 mm in diameter) 14, 1
5 was used. At this time, the distance between both circular electrodes was about 45 μm. The weight of the object 5 placed on the round dish as the weighing dish 3 is transmitted to the lower alumina substrate 11 via the weight transmitting unit 4. The alumina substrate is deformed by this force. Due to this deformation, the circular electrodes 14 and 15
Then, the capacitance formed by the above changes, and the weight of the object 5 is detected as a change in the capacitance.

FIG. 3 shows a partial cross-sectional detail of a bamboo shoot spring 10 used as a weight transmitting portion of the weight detecting portion of the present invention shown in FIG. This bamboo shoot spring has a triangular cross section with a conical shape,
By making the width of the spring smaller toward the inner circumference, the spring constant is gradually reduced from the outer circumference to the inner circumference. As a result, the state shown in the upper diagram of FIG. 3 under no load is softer as the inner circumference of the spring. It comes into contact sequentially from the periphery to the outer periphery. For this reason, the contact diameter increases with the load.

FIG. 4 shows the amount of distortion of the alumina substrate 11 in the weight sensor 1 when pressed by the weight transmitting portion whose diameter increases or decreases according to the weight of the object of the present invention shown in FIGS.
2 shows a result of a distortion amount when the weight sensor 1 is pressed by a weight transmitting portion having a contact diameter of 4 mm using the conventional weight detecting device shown in FIG.

The thickness of the alumina substrate of the weight sensor 1 greatly affects the sensitivity of the weight detection device. In other words, the thinner the substrate, the greater the amount of strain of alumina and the better the sensitivity. However, if the thickness of the substrate is reduced, there is a risk of breakage. In this case, the amount of strain was set to about 33 μm with a maximum load of 9 kg conventionally used. Is 570
μm, and the thickness of the substrate of the conventional weight detection device is 635.
μm. In the figure, the horizontal axis indicates the applied load, and the vertical axis indicates the amount of strain of the alumina substrate 11. Symbol ● is contact diameter φ
The relation between [mm] and load W [kg] is φ = 2 + 0.7 × W
mm shows the results of the present invention.
The result of the conventional technique of 4 mm constant is shown. For example, load 2kg
When added, the amount of distortion in the present invention is about 11 μm,
When the load was 5 kg, it was about 24 μm. In the conventional case, the amount of strain when a load of 2 kg is applied is about 7.
5 μm, and about 18 μm when the load was 5 kg.

From these results, the weight detecting device of the present invention has a small contact diameter in a small load region and a small contact diameter in a large load region even if the maximum strain at the maximum load is the same as that of the conventional weight detector. Since the diameter can be increased, the thickness of the substrate can be reduced, and as a result, the strain amount can be increased not only in the small load region but also in the large load region.

Further, the thickness of the substrate is the same as that of the prior art (635 μm).
Then, a load of 10 kg is placed on a weighing dish from a height of 5 cm for 10
Dropping was repeated several times, and an impact load test was performed. When such an impact load test is performed using the ten weight detection units, in the case of the conventional weight detection device, cracks occur starting from the point of contact with the weight transmission unit, and about 4 to 5 weights are detected. The sensor has broken. However, when the weight detection device of the present invention is used, the contact area between the weight transmission unit and the weight sensor is
Since the stress increased and decreased according to the weight of the object on the weighing dish, the stress was dispersed, and no damage was found in the above impact test. From this, it can be said that the weight detection device of the present invention can also prevent the weight sensor from being damaged.

FIG. 5 shows a measurement result of the capacitance detected by the weight sensor 1 in FIG. In the figure, the horizontal axis indicates the applied load, and the vertical axis indicates the capacitance (Cw). The symbol ● indicates that the relationship between the contact diameter φ [mm] and the load W [kg] is φ = 2 +
The result of the present invention is 0.7 × Wmm, and the symbol ○ indicates a conventional result in which the contact diameter φ is constant at 4 mm. For example, when the load is 2 kg, the capacitance according to the present invention is about 22 pF, and when the load is 5 kg, the capacitance is about 31 pF.
pF. Further, in the conventional case, the capacitance when a load of 2 kg was applied was about 21 pF, and when the load was 5 kg, the capacitance was about 26 pF. From these results, the capacitance of the weight detection device of the present invention was about 18 pF at the time of no load, which was the same as that of the conventional weight detection device. Also,
With a conventional weight detection device, the capacitance is about 1 when no load is applied.
Although it was 8 pF, it became about 40 pF when the maximum load was applied, and changed only about 22 pF. As described above, the sensitivity (change in capacitance per load) of the weight detection device of the present invention can be increased by about 36% as compared with the conventional weight detection device.

FIG. 6 shows the load dependency of the sensitivity (change in capacitance per unit load) of the result obtained in FIG. As a result, the sensitivity of the weight detection device of the present invention could be improved over the entire load range as compared with the conventional weight detection device. The tendency was particularly strong in a small load area often used in homes.

Further, in the weight detecting device of the present invention, since the cylindrical bamboo spring is used for the weight transmitting portion, the minute movement of the alumina diaphragm of the weight sensor (maximum distortion amount is about 3).
5 μm) can be enlarged (about 2 mm) by moving the dish up and down. For this reason, it is easy to provide a stopper at the lower end 16 of the weighing pan 3 when the maximum load is applied, and to easily make contact with the upper support portion 17. May not be transmitted. As a result, the alumina substrate of the weight sensor 1 is not broken.

The weight detection device of the present invention can be applied not only to a cooking device such as a microwave oven but also to other devices for detecting the weight.

[0018]

As described above, according to the weight detecting device of the present invention, the following effects can be obtained.

(1) Even if the maximum strain amount when the maximum load is applied is the same as that of the conventional weight detecting device, the contact diameter can be reduced in the small load region and the contact diameter can be increased in the large load region. Sensitivity can be increased over the entire load range.

(2) Even if an overload equal to or greater than the maximum load is applied, the stopper can be provided at the lower end of the weighing pan so that the weight is not transmitted to the weight detector. Can be prevented from being damaged.

(3) The load dependency of the sensitivity can be set to some extent freely by appropriately selecting the load dependency of the contact diameter.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a weight detection device according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of the weight detection device.

FIG. 3 is a partial cross-sectional external view of a bamboo shoot spring used for a weight transmission unit.

FIG. 4 is a characteristic diagram of load and strain of the present invention and a conventional example.

FIG. 5 is a characteristic diagram of load and capacitance according to an embodiment of the present invention and a conventional example.

FIG. 6 is a characteristic diagram of load and sensitivity according to an embodiment of the present invention and a conventional example.

FIG. 7 is a configuration diagram of a conventional weight detection device.

FIG. 8 is an enlarged view of a main part of a conventional weight detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Weight sensor 3 Weighing pan 4 Weight transmission part 5 Object

Claims (2)

(57) [Claims] 1. A weighing dish on which an object is placed, a diaphragm-type weight sensor for detecting the weight of the object, and an object on the weighing dish
Of bamboo that transmits the weight of
A weight detecting device comprising: a weight transmitting unit including a child spring . 2. The weight detecting device according to claim 1, wherein the spring constant of the bamboo shoot spring is gradually reduced from the outside toward the inside .