JPH0789077B2 - Weight detector - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a weight detection device application device for detecting the weight of an object and applying the weight information to improve the function and performance. For example, there is a heating / cooking device that effectively uses the weight information, and it is applied to detect the weight of food in the heating chamber and automate the optimum heating time, heating output, etc., and improve cooking performance. There is.

2. Description of the Related Art Heating cookers equipped with a weight detection device that controls the heating by measuring the weight of food to be heated are already known, and in the microwave oven, in the field of automation of cooking such as automatic thawing. Widely applied.

FIG. 4 is an explanatory view of the principle of a conventional weight detecting device having a Roberval mechanism. 1 is a placing table on which food is placed, but when the user actually places the food on the placing table,
It is not always placed in the center. Therefore, a mechanism for accurately transmitting the load of food to the weight detection element 6 regardless of the placement position is required. As a load transmission mechanism for achieving this, it is general to use a Roberval mechanism that is already known in the field of scales. The two parallel motion fittings 2 are connected to the fixed fitting 4 and the movable fitting 5 by four connecting pins 3 so as to be parallel to each other. The connecting pin 3 and each component are connected with a proper clearance and are slidable. This is the so-called Roberval mechanism. As for the operation, the mounting table 1 fixedly attached to the movable metal fitting 5 has a stroke only in the vertical direction, and the load is accurately transmitted to the weight detecting element 6 regardless of the mounting position of the food, and the mounting position is different. The error (hereinafter, position error) is significantly reduced. In this example, the load transmitted by the Roberval mechanism is
It is applied to the weight detecting element 6 via the impact absorbing leaf spring 8 and the load transmitting means 7. However, since it has become necessary to study the miniaturization of parts in order to meet the recent demand for small and lightweight orientation in the market, the Roberval mechanism is omitted, and the position error caused by that is eliminated by rotating the mounting table once. Techniques such as averaging and reducing have been devised. Fortunately, many microwave ovens are equipped with a motor for rotating the mounting table for the purpose of reducing uneven heating of food, which can be realized by utilizing it. FIG. 5 shows an example of a conventional weight detecting device in which the Roberval mechanism is omitted. The load W placed on the table is the rotating shaft 10 that can be smoothly displaced in the thrust direction of the motor 9.
Through the weight detecting element 6 and the weight transmitting member 7. The weight detecting element 6 is mounted and fixed on the mounting member 16. Now, the structure and principle of the weight detecting means will be described with reference to FIG. First of all, the weight detection element 6 has two diaphragms 11 made of ceramics such as alumina, which are upper and lower, made chemically by glass or the like.
A capacitor 13 is electrically constituted by a structure in which a spacer 13 made of an insulating material having physically stable characteristics is inserted and bonded with a minute gap, and an electrode 11 is bonded to the surface of each opposing diaphragm. Further, a weight transmission member 7 is placed on the weight detection element 6 to form weight detection means. Next, in principle, the load transmitted to the weight transmission means 7 presses the weight detection element 6 with a constant pressure area defined by the contact area between the upper side of the diaphragm 11 and the load transmission member 7, and the diaphragm 11 thereby. The deflection is detected as a change in the gap between the electrodes 12, that is, a change in capacitance, and the weight is obtained.

However, in such a weight detecting device, since the weight transmission member 7 and the rotating shaft 10 are in contact with each other, a large frictional force is always applied to the weight transmission member 7 while the motor is rotating. In the case of a microwave oven, a heavy load such as a casserole container for boiling is often placed over 4 kg, so it is predicted that the weight transmission member 7 will be significantly worn and the characteristics will be deteriorated or destroyed. To be done. If the wear further progresses, it is expected that the weight transmission member 7 will be completely consumed and the weight detection element 6 will be worn and eventually will be destroyed.

Not only the examples of sensors shown here, but also those generally called sensors are structurally robust, and in order to realize a configuration in which the Roberval mechanism is omitted and the motor shaft is directly received by the sensor The problem of abrasion due to the sliding of the above has been a major obstacle.

The present invention solves such a conventional problem, and the displacement in the thrust direction of the rotating shaft of the motor due to the load of food can be transmitted to the weight detecting means without contacting the rotating shaft, and the durability is improved. , Which provides a highly reliable and compact weight detection device.

Means for Solving Problems A weight detection device of the present invention includes a mounting table on which an object to be measured is mounted, a rotatable support rotating shaft that supports the mounting table and has a predetermined amount of displacement in a supporting direction, Rotation driving means for driving the support rotary shaft to rotate; and an elastic body composed of a leaf spring that directly receives the lower end of the support rotary shaft and is displaced in the supporting direction thereof.
The fixing fitting for supporting the elastic body and the fixing fitting for receiving a load transmitted in the supporting direction of the supporting rotary shaft in contact with the elastic body and converting the load into an electrical physical quantity corresponding to the load are integrally provided. The load detection means and a weight detection circuit for detecting the weight from the electrical physical quantity from the load detection means are provided, and both ends of the elastic body are supported by the fixing metal fittings.

Action In the weight detection device of the present invention, the displacement of the support rotation shaft in the support direction is transmitted to the load detection means via the elastic body made of a leaf spring. Note that this leaf spring has a structure in which both ends are supported by fixing metal fittings structurally integrated with the load detecting means,
Although the displacement of the supporting rotary shaft in the supporting direction is slightly hindered by the stress due to the leaf spring, the supporting rotary shaft that is rotationally driven transmits the load without directly contacting the load transmitting means and the load detecting means. The load transmitting means or the load detecting means is not worn or destroyed by mechanical wear due to sliding of the rotary shaft, and a thin structure can be easily realized.

Embodiment Hereinafter, a weight detection device of the present invention will be described with reference to the drawings. FIG. 2 is an external perspective view of a microwave oven with a weight detecting function equipped with the weight detecting device of the present invention. A door body 23 is pivotally supported on the front surface of the main body 22 so as to be openable and closable, and a key input section for selecting a cooking type and setting a cooking time is provided on an operation panel.
24 and a display tube 29 for the user to monitor the operating state or to have a dialogue. FIG. 3 is a block diagram showing a system of a microwave oven with a weight detection function. Reference numeral 25 is a heating chamber, 26 is food, and 1 is a mounting table on which the food 26 is mounted, which is rotationally driven by a motor to improve heating and cooking unevenness due to radio wave distribution. 27 is a weight detecting means, which receives the load of the food 26 and converts it into an electric signal. An interface circuit 30 with the microcomputer 28 converts the signal into an electric signal that can be detected by the microcomputer and transmits the electric signal. The microcomputer 28 performs a predetermined calculation from the signal to obtain the weight. 31 is a heating room for high frequency power
Magnetron to output in 25, 32 is that magnetron 31
Magnetron drive circuit for driving, 33 is commercial power supply,
Reference numeral 34 is a relay for controlling the power supply to the magnetron 31.

Therefore, the user selects cooking from the key input unit 24, the microcomputer 28 detects the weight of the food 26, and further performs a predetermined calculation from the weight information, such as cooking time, cooking process, and heating pattern. Is automatically determined. The weight detection device has such an application in a microwave oven.

FIG. 1 shows a partial cross-sectional view of a main part of a mechanical portion of a weight detecting device according to an embodiment of the present invention. Reference numeral 9 is a motor for rotating the mounting table 1, and 10 is a rotation shaft that supports the mounting table 1, and is supported in the vertical direction by shaft supporting portions 35 and 36. In addition, each contact part should have an appropriate clearance,
In some cases, lubricating oil or the like is applied to improve wear and slidability. The drive source of the motor 9 is a synchronous motor composed of a permanent magnet and a plurality of coils, which rotates in synchronism with the cycle of the power source. Further, a plurality of gears such as gears 20 and 21 are used to achieve low speed and high torque. In addition, the rotating shaft 10 has a through hole and the shaft stopper pin 19 is inserted.
Prevents 10 from falling off. Now, the load of the food 26 placed on the placing table 1 is transmitted in the thrust direction through the rotating shaft 10 and placed on the weight detecting element 6 via the leaf spring 17 supported by the fixing metal fitting 18. Push the weight transmission member 7. As described above, the principle is that the capacitance changes in proportion to the applied load, and the details are omitted. This capacitance is taken out to the external interface circuit 30 by the lead wire 37 and converted into frequency information that can be detected by the microcomputer 28. Microcomputer 28
Detects the frequency while rotating the motor 9 and detects the average data of one rotation to remove the position error or the mechanical hysteresis of the rotating shaft 10 to obtain the accurate weight. The weight detection element 6 is mounted on a ring-shaped element mount 19. This element mount 19 is provided with a space at the bottom so as to prevent a load from being applied from below the diaphragm, and avoids direct reception. Reference numeral 14 is an element cover that electrically shields the weight detection element 6. Components such as the element cover 14, the weight transmission member 7, the weight detection element 6, and the element mount 19 are mounted and fixed on the fixing metal fitting 18. In this configuration, the leaf spring 17 directly receives the lower end of the rotating shaft 10 supporting the mounting table 1 and is displaced in the supporting direction. When the leaf spring 17 and the weight transmission member 7 are in contact with each other,
The load transmitted in the support direction of the support rotary shaft 10 is transmitted to the load detection element 6. Therefore, in this configuration, the rotating shaft 10 and the weight transmitting member 7 can transmit the load to the weight transmitting member 7 without being in contact with each other, and the weight transmitting member 7 and the weight detecting element 6 are slid and worn or broken. The problem of doing is completely gone.

Since the leaf spring 17 is an elastic body, it exerts stress on the rotating shaft 10 and results in desensitizing the sensitivity of the weight detection element 6. Therefore, the influence can be neglected by making it sufficiently smaller than the elastic constant of the diaphragm 11. It is desirable to select a leaf spring with a different elastic constant.

EFFECTS OF THE INVENTION As described above, the weight detection device of the present invention detects the load transmitted in the thrust direction of the rotary shaft of the motor and rotates the motor to remove the error due to mechanical hysteresis. The position error is averaged to obtain an accurate weight, and an elastic body is interposed between the rotating shaft and the weight detecting means. Therefore, the vertical load transmitted through the rotary shaft is directly
Since the rotating shaft and the weight detecting means are transmitted to the weight detecting means without making contact with each other, the problem that the weight detecting means is worn or broken due to friction or vibration due to the rotating shaft does not occur at all. As a result, it is possible to realize a compact weight detection device having a Roberval mechanism omitted and having excellent durability and reliability, which is extremely practical.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a main part of a weight detection device according to an embodiment of the present invention, FIG. 2 is an external perspective view of a microwave oven with a weight detection function equipped with the device, and FIG. 3 is a system block diagram thereof. FIG. 4 is a structural diagram of a conventional weight detecting device equipped with a Roberval mechanism, FIG. 5 is a partial sectional view of a main part of a weight detecting device in which the conventional Roberval mechanism is omitted, and FIG. 6 is a weight detecting device used in the same. It is an exploded perspective view of a means. 1 ... Mounting table, 6 ... Weight detection element, 7 ... Weight transmission member, 9 ... Motor, 10 ... Rotating shaft, 17 ... Leaf spring, 26
…… Food, 27 …… Weight detection means, 28 …… Microcomputer, 30 …… Interface circuit.

Claims (1)

[Claims] 1. A mounting table for mounting an object to be measured, a rotatable support rotating shaft which supports the mounting table and has a predetermined displacement in a supporting direction, and for rotationally driving the supporting rotating shaft. Rotation driving means, an elastic body composed of a leaf spring that directly receives the lower end of the supporting rotary shaft and is displaced in the supporting direction thereof, a fixing metal fitting that supports the elastic body, and is transmitted in the supporting direction of the supporting rotary shaft. Load detection means integrally provided with the fixing fitting for receiving a load in contact with the elastic body and converting it into an electrical physical quantity corresponding to the load, and weight detection for detecting weight from the electrical physical quantity from the load detection means And a circuit, wherein the elastic body has both ends supported by the fixing metal fittings.