JPH0315924Y2 - - Google Patents

Description

[Detailed description of the invention] <Technical 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. Regarding something that detects weight.

<Prior Art> Microwave ovens equipped with weight sensors that measure the weight of an object to be heated and control heating based on the measured weight have been rapidly becoming popular in recent years, and are expected to become even more popular in the future. However, the conventional microwave oven with a weight sensor has a disadvantage that the manufacturing cost is high because there are many parts that make up the weight sensor and precision in assembling the parts is required.

Therefore, in view of the above-mentioned drawbacks, a support roller that supports the turntable and rotates on the bottom of the heating chamber is disposed inside the heating chamber, and a piezoelectric transducer is applied to the roller rotation locus on the bottom of the heating chamber that generates stress due to the rotation of the support roller. By arranging an element to detect the voltage generated in the piezoelectric transducer when the support roller rotates, and detect the weight of the object to be heated placed on the turntable, A weight detection device for a microwave oven that has fewer components and is inexpensive has been proposed.

Hereinafter, the weight detection device for the microwave oven will be explained based on the drawings.

Figure 2 is a side sectional view of the main parts of the microwave oven, Figure 3 is a top view of the bottom of the heating chamber with the turntable shown in Figure 2 removed, and Figure 4 is an enlarged detailed sectional view of the turntable. .

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 FIG. an arm 3a, a roller 3b rotatably pivoted to the tip of the arm 3a,
3b, 3b, 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 attachment angle 4.

That is, a coupling 6 attached to the rotating shaft of the turntable motor 5 and a coupling portion 3c of the arm 3a that is removably fitted to the coupling 6.
The rotational force of the motor 5 is transmitted to the support roller 3, and the bottom surface of the heating chamber 1 and the rollers 3b, 3b,
3b draws a rotation locus 7 as indicated by a chain line in FIG.

8 is a Unimolk type piezoelectric element disposed on the back side of the rotation locus 7 of the bottom wall 1a of the heating chamber 1, the details of which are shown in Section 5.
This will be described later based on the figures.

Reference numeral 18 denotes a resin attachment member for attaching the disk-shaped piezoelectric element 8, and a round hole 18a, which is a recess for releasing stress strain of the piezoelectric element 8, is provided in the center. Reference numeral 19 denotes a mounting bracket for mounting the annular mounting member 18, and a hole having an inner diameter slightly larger than the outer diameter of the piezoelectric element 8 is provided in the center of the shallow dish-shaped downward bulge. A pilot hole for a screw is provided at the periphery of the protrusion, and is spot welded to the back surface of the bottom wall 1a. and 20 is the heating chamber bottom wall 1a
The upper end of the upper protrusion faces the hole 21 drilled on the roller rotation locus, and the end surface of the lower protrusion is brought into contact with the upper surface of the piezoelectric element 8. The height of the knob 20 is such that the upper end of the upper protrusion protrudes approximately 0.2 to 0.3 mm from the upper surface of the heating chamber bottom wall 1a when the knob 20 is installed.
The outer diameter of the lower protrusion is set smaller than the size of the round hole 18a of the mounting member 18. This is to apply a force to the center of the piezoelectric element 8 in a spot to obtain a large output with high precision.

The piezoelectric element 8 is mounted through the round hole 18 of the mounting member 18.
a and the piezoelectric element 8 are placed concentrically, the peripheral edge of the piezoelectric element 8 is placed on the mounting member 18 in a free state, and the knob 20 is placed concentrically on the piezoelectric element 8, and then the upper protrusion of the knob 20 is placed. The upper end of the heating chamber is inserted into the hole 2 in the bottom wall 1a of the heating chamber.
This is done by fixing the mounting member 18 to the mounting fitting 19 with screws 22, 22 so that the mounting member 18 faces the mounting member 1. A film sheet 23 is attached to the bottom wall 1a of the heating chamber so as to cover the upper end of the protrusion of the knob 20 in order to prevent foreign matter from entering through the hole 21.

Reference numeral 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.

The piezoelectric element 8 is constructed by laminating a base electrode plate 8a, a piezoelectric ceramic 8b, and a vapor deposited electrode 8c as shown in FIG. 5, and when the roller 3b passes the upper end of the knob 20, a voltage as shown in FIG. 6 is generated. is induced and output. The peak value V ₁ of this output voltage is the seventh
A detection circuit (not shown) detects the object a suitable number of times through a filter circuit formed by a resistor R and a capacitor C as shown in the figure, and the average value is calculated as shown in Figure 8. proportional to weight.

FIG. 9 is a circuit diagram for controlling the magnetron 9 according to the detected weight of the object to be heated.The microcomputer 13 detects the output voltage peak value of the piezoelectric element 8 that has passed through the filter circuit a predetermined number of times, and This circuit calculates the weight based on the value, controls the relay 14, controls the magnetron 9, and controls the heating of the object to be heated. In addition, 15 is a heating start switch, 16 is a fuse, and 17 is a high voltage transformer.

The above-described weight detection device for a microwave oven has a simple structure of the detection section, has a small number of component parts, and is easy to assemble. Furthermore, even though the table on which the object to be heated is placed is a turntable, the output voltage peak value of the piezoelectric element 8 is detected an appropriate number of times and the weight is detected based on the average value, so that uneven loads and center loads can be detected. The difference is small and the weight detection accuracy is high.

However, since the base electrode plate 8a of the piezoelectric element 8 is manufactured by press working, a press edge is generated at the circumferential edge, and when the circumferential edge of the piezoelectric element 8 is placed on the mounting member 18, the piezoelectric element 8 will not move as shown in FIG. If the piezoelectric element 8 is tilted, the mounting condition will not be stable, and the press edge will deform when a load is applied to the piezoelectric element 8 from above.
There is a drawback that a stable output of the piezoelectric element 8 cannot be obtained in proportion to the load.

It is possible to remove the press edge by machining, but this increases the cost.Also, the side without the press edge can be used as the mounting surface, but
Since the manufacturing process of the piezoelectric element 8 is automatic, it is necessary to assemble the piezoelectric element 8 by distinguishing between the side with the press edge and the side without the press edge, which also increases the cost.

<Purpose> The present invention was made in view of the above, and by providing a press edge groove in the press edge abutting part of the mounting member to which the piezoelectric element is attached, distortion variation in the piezoelectric element is reduced and highly accurate weight detection is achieved. The aim is to achieve stable results.

<Example> Hereinafter, one example of the weight detection device of the present invention will be described based on the drawings.

FIG. 1 is an enlarged sectional view of the main parts of the present invention, and the same or equivalent parts as in the conventional example are given the same reference numerals, and the explanation thereof will be omitted.

By integrally molding the press edge grooves 18b, 18b on the press edge abutting portion of the mounting member 18, the present invention stabilizes the mounting state, eliminates distortion variations in the piezoelectric element, and stably achieves highly accurate weight detection. It was designed so that

<Effects> In the present invention, a support roller that supports the turntable and rotates on the bottom wall of the heating chamber is disposed in the heating chamber, and when the support roller rotates, the voltage generated in the piezoelectric transducer is detected, and the voltage generated in the piezoelectric transducer is detected. In a weight detection device for a microwave oven configured to detect the weight of an object to be heated placed on a turntable, a hole is bored on the roller rotation locus of a support roller on the bottom wall of the heating chamber, and the heating chamber is A mounting member for mounting the piezoelectric transducer located below the hole on the outside of the bottom wall is provided with a recessed portion in the center to release the stress strain of the piezoelectric transducer, and a base electrode plate constituting the piezoelectric transducer is provided. A groove for a press edge is provided in a portion where the end portion is located, and the concave portion of the mounting member and the piezoelectric transducer are made concentric, and the end portion of the piezoelectric transducer is positioned in the groove for the press edge, so that the piezoelectric transducer A piezoelectric transducer is placed on a mounting member, a force transmitting body is placed on the piezoelectric transducer that transmits the force of the support roller to the piezoelectric transducer, and the mounting member is attached to the bottom wall of the heating chamber. The press edge formed on the base electrode plate during conversion element molding is released by the press edge groove, making it possible to stabilize the mounting condition of the piezoelectric conversion element, reducing strain variations in the piezoelectric conversion element, and ensuring highly accurate weight detection. This is something of high practical value.

[Brief explanation of the drawing]

Figure 1 is an enlarged sectional view of the main parts of the weight detection device of the present invention, Figure 2 is a side sectional view of the main parts of the microwave oven, and Figure 3 is the top view of the bottom of the heating chamber with the turntable in Figure 2 removed. 4 is an enlarged detailed sectional view of a conventional turntable section, FIG. 5 is a sectional view of a main part of a piezoelectric element section, and FIG. 6 is an output voltage waveform diagram of the piezoelectric element shown in FIG. Figure 7 shows the piezoelectric element output voltage R-
A C filter circuit diagram, FIG. 8 is a diagram of the relationship between the output peak voltage average value and weight, FIG. 9 is a magnetron control circuit diagram, and FIG. 10 is an enlarged sectional view of a conventional main part. Code, 1: heating chamber, 2: turntable, 3:
Support roller, 3b: Roller, 7: Roller rotation locus, 8: Piezoelectric element, 8a: Base electrode plate, 18:
Mounting member, 18b: groove for press edge.

Claims (1)

[Claims for Utility Model Registration] A support roller that supports a turntable and rotates on the bottom wall of the heating chamber is disposed in the heating chamber, and a voltage generated in a piezoelectric transducer when the support roller rotates is detected. , in a weight detection device for a microwave oven configured to detect the weight of an object to be heated placed on the turntable, a hole is formed on the roller rotation locus of the support roller on the bottom wall of the heating chamber; A mounting member for mounting the piezoelectric transducer located below the hole on the outside of the bottom wall of the heating chamber is provided with a recessed portion in the center to release the stress strain of the piezoelectric transducer, and a base electrode constituting the piezoelectric transducer. A groove for a press edge is provided in a portion where the end of the plate is located, the concave portion of the mounting member and the piezoelectric conversion element are made concentric, and the end of the piezoelectric conversion element is positioned in the groove for the press edge to perform piezoelectric conversion. The element is placed on a mounting member, a force transmission body that transmits the force of the support roller to the piezoelectric conversion element is placed on the piezoelectric conversion element, and the mounting member is attached to the bottom wall of the heating chamber. A weight detection device for microwave ovens.