JPH0618249Y2 - microwave - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to a microwave oven equipped with a weight detection device that utilizes a change in capacitance.

<Prior Art> FIG. 1 is a front sectional view of a conventional microwave oven weight detection device, and FIG. 2 is a schematic side view of the same.

In the figure, a turntable shaft 2 projects substantially in the center of a heating chamber 1, and a turntable plate 3 is placed on the upper end of the turntable shaft 2.
The boss portion 3-1 of the turntable plate is fitted to the turntable shaft 2 in an appropriate size to prevent vertical rattling of the flange portion 3-2 of the turntable plate 3 and to remove the turntable plate 3. Is smoothed. A turntable 4 on which food (not shown) is placed is placed on the turntable plate 3, and a protrusion 4-1 is provided below the turntable 4 with respect to the outer circumference of the turntable plate flange 3-2. Is formed to position the turntable 4. A choke eater 5 is attached to the lower side of the heating chamber 1 by a screw 6 to prevent microwave leakage, and a first bearing angle 7 for holding a bearing with respect to the choke eater 5 and forming a choke structure. Second
The bearing angle 8 of is fixed by screws 9. A bearing 10 is attached to each of the bearing angles 7 and 8 with a screw 11, and the turntable shaft 2
Has a turntable gear 12 penetrating through the two bearings 10 and in a space formed by the bearing angles 7 and 8, and the turntable gear 12 is provided with a pin 13 to the turntable shaft 2. It is fixed so as not to slip. Reference numeral 14 denotes a chassis fixed below the second bearing angle 8 with a screw 15, and an electrode case 16 made of an insulating material is fixed with a screw 17. A fixed electrode plate 18 is fixed in the electrode case 16 by screws 19, and a movable electrode plate 20 is provided above the fixed electrode plate 18 with a gap of, for example, about 1 mm, and is in close proximity to the movable electrode plate 20 at a pin 21. The spring is rotatably supported in the direction of the reference numeral A, and is a spring hooked in a hole 24 formed in the tip portion 20-1 of the spring. And one end is fixed by a nut 28 via an adjusting screw 27. The adjusting plate 26 and the adjusting screw 27 adjust the spring constant of the spring 23 and the initial setting of the gap between the fixed electrode plate 18 and the movable electrode 20 facing each other.

In addition, a ball receiver 30 made of an insulating material for receiving a steel ball 29 housed in a conical recess 2'formed at the lower end of the turntable shaft 2 is provided at the center of the movable electrode plate 20. The upper surface of the ball receiver 30, which is attached and is in pressure contact with the steel ball 29, is in a horizontal state.

Therefore, the turntable shaft 2 has a conical recess 2'formed by the bearing 10 in the radial direction and the lower end of the turntable shaft 2 in the thrust direction with respect to the load applied to the turntable 4. It is rotatably supported by a steel ball 29 housed in. On the other hand, a motor 31 is attached to the chassis 14, and a motor gear 32 attached to the motor 31 engages with the turntable gear 12 on a turntable shaft through a hole 33 provided in the second bearing angle 8. The rotation of the coupling motor 31 is transmitted to the turntable shaft 2, and the turntable 4 rotates.

The fixed electrode plate 18 and the movable electrode plate 20 are metal electrodes arranged so as to be insulated from each other and form a kind of air condenser. A frequency corresponding to the weight of the food placed on the turntable 4 can be obtained by measuring the oscillation frequency of this oscillator by combining the capacitance generated between them with an externally connected resistor and measuring the oscillation frequency of this oscillator. The heating time and the like can be automatically set based on the output signal.

Here, a state in which an object to be cooked is actually placed on a turntable will be described with reference to a measurement principle explanatory view shown in FIG. In addition, a and b are the diameter and radius of the movable electrode plate 20, d is the gap between the fixed electrode plate 18 and the movable electrode plate 20, and k is the spring 2.
The elastic modulus is 3.

First, when a load of weight Wg is applied to the turntable 4 at the substantially central portion, the turntable shaft 2 slides downward with the bearing 10 as a guide, and the movable electrode plate 2 through the steel ball 29.
The ball receiving portion 30 of 0 is pressed by the force of Wg weight. Then, the movable electrode plate 20 has the rotation spring 23 in the downward direction shown by the arrow A around the pin 21. Pull with the force of. By this power The weight of the food placed on the turntable 4 is balanced and balanced. At this time, the turntable shaft 2 Sliding, and the gap d between the two electrodes due to the rotation of the movable electrode plate 20 is closer to the spring 23 than the initial value (for example, the gap when food is not placed on the turntable 4 is about 1 mm). so However, the pin 21 side does not change as a matter of course. Due to the capacitance C of the capacitor formed by the two electrodes due to the displacement between the electrodes, The oscillation frequency represented by is output.

Therefore, the change amount of the capacitance C can be read as the change amount of the oscillation frequency, and an output signal substantially proportional to the weight W can be obtained. In this way, the weight of the food can be measured while it is placed on the turntable 4, so that the heating time and the like can be automatically measured according to the weight of the food. This is very convenient because it eliminates the need for the user to separately measure and input with the operation keys.

By the way, in the above-mentioned conventional example, as shown in FIGS. 4 (A) and 4 (B) showing the main part of FIG. 1, the turntable 4 is located at a substantially central portion of the bottom surface of the turntable shaft 2. Steel ball 2 fitted in a conical recess 2'formed
It is movably supported by coming into contact with a flat upper surface 30 ′ of a ball receiver 30 fixed to a substantially central portion of the upper surface of the movable electrode plate 20 via 9.

Next, the operation will be described with reference to FIG.
(A) shows the case where food is not placed on the turntable 4, the movable electrode plate 20 is in a horizontal state, and the steel ball 2 is placed at the substantially central portion 34 of the flat upper surface 30 ′ of the ball receiver 30.
9 is supported. Here, when food is placed on the turntable 4 and the turntable shaft 2 is pressed downward by a force of Wg, the movable electrode plate 20 is fitted into the recess 2'of the turntable shaft 2. 4 (B) because it is pressed downward through the steel balls 29 that are
At the same time, as shown in,
The steel ball 29 has a flat upper surface 30 ′ of the ball receiver 30 which is α
Will only move. At this time, the force that the steel ball receives from the electrode is the force W in the vertical direction, the force T _{1 in the} tangential direction that attempts to slide down on the electrode, and the force R in the normal direction of the electrode due to the combination of both. Now, assuming that the friction coefficient between the steel ball and the electrode is μ, when the food is placed on the turntable 4 and the steel ball 29 slides down the upper surface 30 ′ of the ball receiver 30, and when the food is removed and the upper surface 30 ′ is lifted. In contrast, the tangential force that the steel ball receives from the electrode was different from T-μR and T + μR, and there was a drawback in that the friction angle due to the inclination was added.

<Purpose> The present invention has been made in view of the above points, and an object of the present invention is to achieve a stable operation of a microwave oven having a weight detection device utilizing a change in electrostatic capacitance.

<Structure> The present invention has been made to achieve the above object, and is rotatably supported via a steel ball on the lower end of a turntable shaft of a turntable rotatably arranged in a heating chamber. A movable electrode plate and a fixed electrode plate disposed in proximity to and above the movable electrode plate, wherein the movable electrode plate and the fixed electrode plate change according to the weight of food placed on the turntable. In a microwave oven having a weight detection device for detecting the weight of food by detecting the capacity of the capacitor due to the gap of the gap, a substantially conical shape is formed on the upper surface of the ball receiver of the steel ball fixed to the substantially central portion of the movable electrode plate. It is characterized in that a recess is formed and the lower end surface of the rotary shaft of the turntable is in a flat state.

<Embodiment> An embodiment of the present invention will be described below with reference to the drawings.

In the figure, a schematic structure of a microwave oven having a weight detection device utilizing a change in capacitance is similar to the cross-sectional view of the main part shown in FIG. It will be omitted.

FIG. 5 is an enlarged view of a main part showing an embodiment of the present invention.
(A) shows the case where the food is not placed on the turntable 4, and (B) shows the case where the food is placed. For example, the turntable shaft 35 is pressed by the force of Wg weight. In this case, the steel ball 29 is the turntable shaft 35.
Of the movable electrode plate 20 while contacting the horizontal lower surface 36 of the
It is engaged with a substantially conical recess 38 formed on the upper surface 37 ′ of the ball receiver 37 mounted on. Therefore, the steel ball 2
9 is held in the recess 38, and the force point of the steel ball 29 moves on the upper surface 37 'of the ball receiver 37 of the movable electrode plate 20, but only the reaction force W acts on the contact point between the shaft and the steel ball. Without this, the frictional force acting during movement is only μW. Therefore, the stable capacitance of the capacitor is detected from the gap between the movable electrode plate 20 and the fixed electrode plate 18, converted into a frequency corresponding to the weight of the food, and heating is controlled.

<Effect> As described above, according to the present invention, the lower end of the turntable shaft of the turntable rotatably arranged in the heating chamber has one end rotatably supported through the steel ball and the other end elastic body. A movable electrode plate movably supported by
A fixed electrode plate disposed close to and above the movable electrode plate is provided, and the capacitance of the capacitor due to the gap between the movable electrode plate and the fixed electrode plate that changes according to the weight of the food placed on the turntable. In a microwave oven having a weight detecting device for detecting the weight of food by detecting a weight, a substantially conical concave portion is formed on the upper surface of the ball receiver of the steel ball fixed to the substantially central portion of the movable electrode plate. Since the steel balls are engaged and the lower end surface of the turntable shaft is made horizontal, when food is placed on the turntable and the turntable shaft moves downward, the movable electrode plate rotates with this movement. Even if the steel ball is pivoted obliquely downward around one end that is freely supported, the steel ball only moves to the right on the lower end surface of the turntable shaft. The force exerted is only the reaction force W in the vertical direction.

Therefore, when the food is placed on the turntable and weight is applied, the friction coefficient on the ball receiving surface of the steel ball generated when the food is removed is substantially equal, and a highly reliable weight detection device can be obtained. Therefore, it is possible to provide a microwave oven which is highly practical especially in thawing and cooking.

[Brief description of drawings]

FIG. 1 is a front sectional view of a conventional microwave oven weight detection device, FIG. 2 is a schematic side view of the same as above, FIG. 3, an explanatory view showing the measurement principle of the weight detection device, and FIG. (A), (B)
FIG. 5 is an enlarged view of a main part showing a use state in FIG. 1, and FIGS. 5A and 5B are enlarged views of a main part showing an embodiment of the present invention. 1 ... Heating chamber, 4 ... Turntable, 18 ... Fixed electrode plate, 20 ... Movable electrode plate, 29 ... Steel ball, 35 ... Turntable shaft, 37 ... Ball receiver, 38 ... Recessed portion.

Claims (1)

[Scope of utility model registration request] 1. A lower end of a turntable shaft of a turntable rotatably arranged in a heating chamber, one end of which is rotatably supported through a steel ball and the other end of which is movably supported by an elastic body. A movable electrode plate and a fixed electrode plate disposed in proximity to and above the movable electrode plate are provided, and the movable electrode plate and the fixed electrode plate change according to the weight of food placed on the turntable. In a microwave oven having a weight detection device for detecting the weight of food by detecting the capacity of a condenser due to a gap, a concave portion having a substantially conical shape on the upper surface of the ball receiver of the steel ball fixed to the substantially central portion of the movable electrode plate. And a lower end surface of the turntable shaft is formed into a horizontal shape while the steel ball is engaged with the steel ball.