JPH0440085Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a weight detection device for a microwave oven.More specifically, the present invention relates to a weight detection device for a microwave oven. This invention relates to a device that detects the weight of heated objects.

<Prior art> Fig. 4 is a side sectional view of the main parts of a microwave oven, Fig. 5 is a top view of the bottom of the heating chamber with the turntable shown in Fig. 4 removed, and Fig. 6 is an enlarged detail of the turntable part. FIG.

In the figure, 1 is a heating chamber, 2 is a turntable on which the object to be heated is placed, and 3 is a support roller that supports the turntable 2 and rotates on the bottom of the heating chamber 1.
As shown in the figure, a Y-shaped arm 3a and the arm 3
The roller 3b is rotatably mounted on the tip of the heating chamber 1, and is rotated by the rotation of a turntable motor 5 attached to the lower surface of the bottom wall 1a of the heating chamber 1 with a motor mounting angle 4.

That is, the coupling 6 which is pivotally attached to the rotating shaft of the turntable motor 5 and the coupling part 3c of the arm 3a which is detachably fitted to the coupling 6 are fitted, and the rotational force of the motor 5 is transmitted to the support roller 3. The roller 3b traces a locus 7 on the bottom surface of the heating chamber 1 as shown by a dashed line in FIG.

Reference numeral 8 denotes a weight detection mechanism disposed on the back side of the rotation locus 7 of the bottom wall 1a of the heating chamber 1, the details of which will be described later with reference to FIG. 9 is a magnetron that generates high frequency radio waves, 10 is a waveguide that guides the high frequency radio waves into the heating chamber 1, 11 is a cabinet forming the outer shell of the microwave oven, and 12 is a door. FIG. 7 is a detailed cross-sectional view of the weight detection mechanism 8 , in which a piezoelectric element 18 as a weight detection element is placed in the recess of the holder 14, and output lead wires 16 and 17 are connected to holes 14a and 14b made in the holder 14. It passes through and goes outside. The holder 14 is screwed into the case 13 and integrated with the case. In case 13, the eighth
As shown in the figure, concentric semicircular slits 13a, 13
A knob 13b is integrally molded so as to be movable up and down by a..., and the tip of the knob 13b is inserted into the center hole 15 of a metal cover 15 screwed to the case 13.
It protrudes slightly from b. The case 13, holder 14, cover 15, and piezoelectric element 18 are integrally assembled to constitute the weight detection mechanism 8 . A fixture 12 is fixed to the bottom wall 1a of the heating chamber 1 by spot welding, and the weight detection mechanism 8 is attached to the fixture 12 with screws 19, 19. A hole 1b that is sufficiently larger than the tip of the knob 13b is bored in the bottom wall 1a of the heating chamber, and a protrusion 15a is provided on the upper surface of the cover 15 by, for example, half punching in press working to fit into the hole 1b. ing. The protrusion height of the protrusion 15a is the heating chamber bottom wall 1a.
The thickness of the protrusion 15a is approximately equal to the thickness of the protrusion 15a, and the bottom wall 1a is substantially flush with the upper surface of the protrusion 15a.

Reference numeral 20 denotes a flexible film affixed to the bottom wall 1a of the heating chamber so as to cover all the holes 1b, protrusions 15a, and knobs 13b. When the roller 3b rolls on the bottom wall 1a in the direction of arrow A, rides on the protrusion 15a of the cover 15, and passes over the knob 13b, it outputs a voltage. The peak value of this output voltage is detected an appropriate number of times by the control circuit 21 consisting of a microcomputer etc. through a filter circuit formed by a resistor R and a capacitor C shown in FIG. 9, and the average value is taken. 1
It is proportional to the weight applied to 3b, and the weight can be calculated from the average value.

<Problems to be solved by the invention> By the way, the impact pressure when the roller 3b rides on the knob 13b varies considerably depending on the rotational speed of the roller 3b, the protruding height of the knob 13b, etc. The method of calculating the weight by detecting the peak value described above has a problem in that the weight detection error is large.

<Means for solving the problem> Voltage conversion means applies the output voltage of the piezoelectric conversion element to the gate of the FET, converts the drain current of the FET into voltage, and calculates the weight based on the stable value of the voltage converted value. A weight detection means is provided.

<Function> The value obtained by converting the drain current of the FET into a voltage is proportional to the output voltage of the piezoelectric transducer, and
When the piezoelectric transducer outputs a stable voltage corresponding to the static load of the roller 3b when the roller 3b is completely mounted on the upper surface of the roller 3b, the value obtained by converting the drain current of the FET into a voltage is The weight is proportional to the static load, and accurate weight can be detected by detecting the stable voltage conversion value.

<Example> Hereinafter, an example of the present invention will be described based on the drawings.

Fig. 1 is a basic electrical circuit diagram of the weight detection device of the present invention, in which 18 is a piezoelectric element, 22 is a high impedance FET connected in series with a resistor R to a DC constant voltage power supply, and the piezoelectric element 18 is connected to the gate. Output voltage is being applied. 23 inputs the value Iv obtained by converting the drain current of the FET 22 into a voltage by the voltage drop of the resistor R, and detects the peak value when the output voltage of the piezoelectric element 18 becomes stable based on the flowchart of FIG. This is a control circuit that converts the value into weight.

20 mSec in the flowchart of Fig. 2 is as shown in the time chart of "value Iv obtained by converting the drain current of FET 22 into voltage" in Fig. 3, and the output voltage of the piezoelectric element 18 becomes stable from the time when pressure is applied to the piezoelectric element 18. sufficient time to
This is determined through experiments. Also, 80mSec is knob 13
This is determined based on the time during which the roller 3b passes over the point b in a stable state, and is also determined through experiments.

In addition to the time control described in the above embodiment, the control for detecting that the voltage-converted value of the drain current of the FET 22 has stabilized includes determining whether the rate of change of the voltage-converted value has become below a predetermined value. Control is possible.

<Effects> According to the present invention, it is possible to detect an accurate weight corresponding to the static load of the roller that is not affected by the impact pressure when the roller rides on the knob.

[Brief explanation of drawings]

Figure 1 is a basic electrical circuit diagram of the weight detection device of the present invention, Figure 2 is a flowchart of weight detection control according to the present invention, Figure 3 is a time chart of the detection voltage Iv, and Figure 4 is the essentials of a microwave oven. 5 is a top view of the bottom of the heating chamber with the turntable removed, FIG. 6 is an enlarged detailed sectional view of the turntable, and FIG. 7 is a conventional weight detection device. Figure 8 is a detailed sectional view of the main parts of the case. Figure 9 is a perspective view of the case.
The figure is a basic electrical circuit diagram of a conventional weight detection device. Code, 1a...Heating chamber bottom wall, 3b...Roller, 13b...Knob, 18...Piezoelectric element, 22...
...FET, 23...control circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] A support roller that supports the turntable and rotates on the bottom wall of the heating chamber is disposed inside the heating chamber, and is arranged so as to face a hole provided on the roller rotation locus on the bottom wall of the heating chamber. A force transmission body is provided, and when the roller rotates, the force of the roller is transmitted to the piezoelectric conversion element through the force transmission body, and the voltage generated in the piezoelectric conversion element is detected to calculate the weight of the object to be heated on the turntable. In the weight detection device configured to detect the voltage, the output voltage of the piezoelectric conversion element is applied to the gate of the FET, and a voltage conversion means converts the drain current of the FET into a voltage, and a stable value of the voltage converted value is detected. 1. A weight detection device for a microwave oven, comprising a weight detection means for calculating a weight by using a weight detection means.