JPH0132897B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating cooking device having a so-called weighing function, which is equipped with a function of measuring the weight of an object to be heated.

When heating food, which is an object to be heated, in a conventional microwave oven, for example, most of the high frequency energy is absorbed by the food, unlike when using a conventional heat source. Therefore, the time required for heating increases significantly as the weight of the food increases.
It is very difficult to set the optimal cooking time, especially when defrosting and heating, because if you heat for longer than the optimal time, for example, raw fish that is to be made into sashimi will end up being overcooked. However, setting the heating time was even more difficult.

From the above point of view, many microwave ovens have been proposed in which the microwave oven is equipped with a scale function and a microwave output control device that operates in conjunction with the scale function.

However, in reality, this type of microwave oven with a weighing function has not been put to practical use at all.

The first reason for this is the problem of the location of the receiving tray on which the food is placed. In other words, in order to measure the weight of food, there must be enough space around the receiving tray to place the food.

From this point of view, the simplest structure may be one in which a load receiving tray is installed on the top surface of the microwave oven main body, and a weighing device is provided in a part of the main body to detect the weight in conjunction with the movement of the load receiving tray. However, when considering the general usage conditions of cooking devices such as microwave ovens, the top surface of the main unit is often used for placing other items, is close to the ceiling, hanging shelves, etc., or is installed at a high location that is difficult to reach. It is stiff and sluggish and is very inconvenient to use.

Another idea is to use the turntable in the heating chamber of the microwave oven in conjunction with the load tray, and install a weighing device that works with the turntable, but in addition to being technically difficult and expensive, Even if this structure is created, when actually trying to measure the weight of food, it is necessary to subtract the weight of the food container (packaging, outer wrapper, bowl, etc.), so only the container must be weighed first. Next, it becomes necessary to perform operations such as adding food and weighing it again, and carrying out these operations in a narrow heating chamber is not a good structure if it is not very convenient to use.

The present invention aims to solve the above-mentioned conventional problems.

The present invention has a structure in which the function of a receiving tray for placing food is provided on a door that is attached to the front opening of the heating chamber so that it can be opened and closed, and is easy to use, has an excellent appearance, and is also technically and economically efficient. To provide a realistically superior heating cooking device.

An embodiment of the present invention will be described below based on the drawings.

In FIG. 1, a door 3 is freely openable and closable in a front opening 2 of a heating chamber 1 of a microwave oven, and is rotatable about a fulcrum 5 of a hinge 4 located at the lower part of the front surface. Furthermore, the door arm 6 of the door 3 is guided by a guide roller 7 rotatably provided on the hinge 4, and is always urged in the closing direction of the door 3 by a door spring 8.

When the door 3 is opened and is in a substantially horizontal position, the stopper part 9 of the door arm 6 comes into contact with the guide roller 7 to prevent the door 3 from being opened further. One end 10 of the hinge 4 is connected to a weight detecting section 11 having a weight detecting element, and this weight detecting section 11 is further provided on a fixture 12 . Fixture 1
2 is bolted to the bottom plate 13 of the main body. It should be noted that the above-mentioned configuration is exactly the same for the hinge portion on the other side, which is not visible in the figure.

Next, the main parts of the configuration will be explained with reference to FIG.

In FIG. 2, parts such as the hinge 4 and the door arm 6 are omitted to make the explanation easier to understand.

The weight detection section 11 is composed of one strain rod 14 and strain gauges 16A, 17A, 16B, and 17B that detect the strain of the strain rod 14 that changes depending on the weight.

The strain rod 14 has one end fixed to a part of the main body as a fixed end, and the other end as a load end connected to the door 3 via a hinge 4 as shown in FIG. (omitted).

FIG. 3 is a principle diagram for explaining the principle of weight detection operation in the present invention including the weight detection section 11, and a and b indicate its structure, and c indicates its electric circuit. FIG. 3c shows a so-called bridge circuit, and the output voltage Vo of the bridge 21 can be expressed by the following equation.

Vo=(△R ₁ −△R ₂ )×Vi/(2R) ………(1) However, △R ₁ , △R ₂ ≪R, and △R ₁ and △R ₂ are strain gauges 16A, 16B, and 17A , 17B, R represents the specific resistance of the strain gauges 16A to 17B, and Vi represents the voltage applied to the bridge 21. Here, if the gauge factor of the strain gauge is F ₁ and the amount of strain is ε, then from the commonly used formula for strain gauges, △R=ε・F・R ......(2), and the strain gauge's 2 Let the amount of strain at the two attachment points be ε ₁ and ε ₂ , let the amount of change in resistance of strain gauges 16A and 16B be △R ₁ , and let the amount of change in resistance of strain gauges 17A and 17B be △R ₂ and apply it to the above formula (2). Then, △R ₁ = ε ₁・F・R ………(3) △R ₂ = ε ₂・F・R ………(4), and converting equations (3) and (4) into equation (1) By substituting, we can derive the following equation.

Vo=F(ε ₁ −ε ₂ )×Vi/2 (5) Here, the strain amount ε ₁ of the strain gauges 16A to 16B
and the amount of strain ε ₂ in portions 17A and 17B. Setting the shape of the strain rod 14 as shown in Fig. 3a, and finding the amount of strain ε ₁ and ε ₂ at each gauge part, ε ₁ = 6Wl ₁ / (E・b・h ² ) ......(6) ε ₂ = 6Wl ₂ /(E・b・h ² ) (7) (where E is the Young's modulus of the strained rod 14).

By substituting these equations (6) and (7) into the above equation (5), the following equation (8) is obtained.

Vo=(3FW/Ebh ² )lo・Vi……(8) In formula (8), lo indicates the interval between the two attachment points of the strain gauge, and the distance between the load point and the strain gauge attachment point is the distance of the bridge 21. This indicates that it is not involved in the output voltage.

Based on the explanation of the operating principle of the weight detection section based on FIG. 3, the functions and effects of the configurations shown in FIGS. 1 and 2 will be explained.

Door 3 is opened almost horizontally. At this time, the strain rod of the weight detection unit 11 supports the entire weight of the door 3, the door arm 6, etc., as well as the load of the hinge 4, etc., and also supports the tensile force of the door spring 8 determined by the opening/closing position of the door 3. I am receiving a load. In this state, when the food 20 to be heated and cooked is placed on the back surface of the door 3, the strain rod is deflected by the load, and the resulting strain change is measured by the strain gauge 16A,
This is detected as the amount of change in the electrical resistance values of 16B, 17A, and 17B. What is important in this case is that, as can be seen from the explanation of the operating principle of the weight detection section based on _FIG .
Furthermore, even at the W ₂ position near the hinge 4, the output voltage of the bridge formed by the strain gauge is the same, and therefore the detected weight of the food 20 varies depending on the position before and after the food 20 is placed. There is no such thing.

Furthermore, in order to prevent the detected amount from changing depending on the left and right positions on which the food 20 is placed, in this embodiment, the two left and right hinges 4 are provided with weight detecting sections having exactly the same configuration, so that the two weight detecting sections 11 The sum of the outputs is the detection output. That is, in this embodiment, the weight of the food 20 can be accurately detected no matter where on the door 3 the food is placed.

Next, an outline of the electric circuit for detection and control will be explained based on the block diagram of FIG. However, for convenience of explanation, regarding the pair of left and right weight detection sections, each part number on the side not shown in Fig.
are attached to the weight detection part 11' and the strain rod 1, respectively.
4', strain gauges 16A', 16B', 17A', 17
Distinguish between the two as B′.

In FIG. 4, the strain gauges 16A, 16B, 17A, 1 of the pair of weight detection units 11 and 11' are measured based on the weight of the food 20 placed on the opened door 3.
Bridge 21 and strain gauge 1 composed of 7B
The output voltage of the bridge 21 composed of 6A', 16B', 17A', and 17B' changes and is amplified by differential amplifiers 22a and 22b, respectively, and then added by an adder 22c. The output voltage of the adder 22c is further converted into a digital quantity by an A/D converter, and is input to a CPU 24 consisting of a microcomputer.

The CPU 24 converts the weight into weight, sets the cooking sequence and cooking time corresponding to the weight, controls the start/stop operation of the magnetron 25, and displays the weight, cooking time, or operating status on the display tube 26. . This series of operations is executed by operating the operation keys 27.

According to the embodiment described above, a pair of weight detecting sections 11 and 11' whose detection output is constant in the front and rear positions are provided on the left and right hinges 4 of the door 3, and the pair of weight detecting sections 1
Since the weight of the food 20 is measured by detecting the sum of the outputs of 1, the weight error caused by the position of the food 20 can be minimized no matter where it is placed on the door 3, and accurate weighing can be achieved. Since a more accurate cooking time is displayed and cooking is performed according to that time, there are fewer cooking failures. Also door 3
Since it is used as a load receiving tray for the scale, it has a large mounting area and has a suitable height, making it very easy to use.

In the above embodiment, one weight detection section 11 is connected to two pairs (four pieces) of strain gauges 16A, 17A, 16.
B, 17B, but even if it is configured with a pair (two pieces) of strain gauges 16A, 17A or 16B, 17B, exactly the same characteristics can be obtained with only half the output voltage, and there are two weight detection sections on the left and right. 11,
11' Each pair of four strain gauges constitutes one bridge, and two weight detection parts 11, 11'
It is also possible to adopt a configuration in which a detection output of the sum of

Conversely, it is also possible to increase the sensitivity by attaching a plurality of strain gauges to the same strain point in order to increase the detected output voltage.

As described above, the present invention has a structure in which a weight detecting section that supports the weight of the door is provided at each of the left and right hinge sections, and the weight detecting section is provided with strain gauges at two locations spaced apart from each other in the longitudinal direction. By doing this, the weight of the food can be detected no matter where the food is placed on the door. By being able to accurately detect the weight of food regardless of the user's food placement position, it becomes possible to automate heating cooking (cooking patterns (output, time) are determined depending on the importance). In addition, since the food can be placed on a sufficiently large surface area, and it is located on the surface of the door through which food is taken in and out, for example, in the case of so-called tare measurement, in which the weight of the container is subtracted, the food can be placed on the surface of the door. It is possible to provide a heating cooking device that is extremely easy to use, such as being able to be placed on the device and put into the heating chamber as it is.

[Brief explanation of drawings]

Fig. 1 is an external perspective view of the main parts of a microwave oven which is an embodiment of the present invention, Fig. 2 is an explanatory diagram of the operation of the door section, and Figs. A principle explanatory diagram for explaining the principle of heavy cropping,
FIG. 4 is a block diagram of the detection control circuit. DESCRIPTION OF SYMBOLS 1... Heating chamber, 2... Front opening, 3... Door, 4... Hinge, 11... Weight detection part, 14...
...Strain rod, 16, 17...Strain gauge, 20...
...Food (object to be heated), 25...Magnetron (heating source).

Claims (1)

[Claims] 1. A heating chamber that accommodates an object to be heated, a heating source that heats the inside of the heating chamber, and a door that can be opened and closed freely and rotates around two left and right hinges located at the lower front of the front opening of the heating chamber. A weight detecting section that supports the weight of the door is provided on each of the left and right hinge sections, and the weight detecting section is fixed to a part of the main body using one end of the integrated strain rod as a fixed end, and the other end is used as a load end to support the door. The door load including the hinge part is supported by a strain rod, and the same number of strain gauges are arranged at two places on the strain rod at a constant interval in the longitudinal direction. A heating cooking device configured to measure the weight of an object to be heated by detecting a difference in strain amount by a change in electrical resistance of the strain gauge.