JPH08320123A - Weight detection device for heating cooking utensil - Google Patents

Abstract

PURPOSE: To make compact the size of a weight detection device for heating cooking service at a low cost by converting the weight of an article to be measured into capacitance change produced by dimensional changes of a clearance between a movable electrode board and a fixed electrode board, which are formed in gimbal spring shape and whose peripheral areas are fixed with a main body and whose central part is laid out so as to receive the load of a support shaft. CONSTITUTION: A weight detection device 40 for heating cooking service comprises a fixed electrode board 42 and a movable electrode board 43 and is installed inside a main body 41. The fixed electrode board 42 is fixed by means of an insulating board 44 installed to the bottom of the main body 41. The movable electrode board 43 comprises a rectangular plate spring and supported on a knife edge 44A formed projectingly to both sides of the insulating board 44 and is opposed with the fixed electrode board 42 with a slight clearance, thereby forming an air condenser with both electrode boards 42 and 43. A projecting part 12A is supported substantially at the central part of the movable electrode board 43, and designed to reduce a rotary torque loss of a support shaft 12 and transmit accurately the weight of a turntable 11 and an article to be measured to the movable electrode board 43.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a weight detecting device for a heating cooker having a turntable such as a microwave oven, and more particularly to a weight for a heating cooker for measuring the weight of an object placed on the turntable by converting it into an electrostatic capacitance. Regarding a detection device.

[0002]

2. Description of the Related Art In recent microwave ovens, when an object is placed on a turntable during cooking, the weight is automatically measured and the food is cooked by heating according to the measured weight. A weight detection device (referred to as a conventional device) used in such a microwave oven will be described with reference to the drawings.

FIG. 5 is a vertical sectional front view showing an example of a conventional device. In the figure, 10 is a heating chamber and 11 is a heating chamber 10.
A turntable that is rotatably arranged in the inside, 12 is a support shaft of the turntable, 20 is a drive unit, which is provided below the heating chamber 10 and bearings 2 and 2 (not shown) that pivotally support the support shaft 12.
2, a driven gear 23, a drive gear, a motor, etc. are included.

The weight detection device 30 is provided on the lower side of the drive unit 20, and has a fixed electrode plate 31, a movable electrode plate 32, and both electrode plates 3.
It includes adjustment mechanisms 33 of 1 and 32. Fixed electrode plate 31
Are fixed to the weight detection device main body 34 via an insulating plate. The movable electrode plate 32 is arranged with a slight gap from the fixed electrode plate 31.

One end 35 of the movable electrode plate 32 is rotatably supported by a main body 34, and an intermediate portion receives a load of the support shaft 12 via a ball 36 provided at a lower end of the support shaft 12. . Further, the other end is formed in an L-shape, and the tip of the other end projects outside the main body 34 and includes the spring 37.
3 and is always elastically supported by the spring 37.

Both of the electrode plates 31 and 32 are made of metal and insulated from each other to form a kind of air condenser. The adjusting mechanism 33 adjusts the spring constant of the spring and the gap between the electrode plates 31 and 32. It is supposed to adjust the default settings of.

When an object is placed on the turntable 11, the support shaft 12 slides downward and presses the movable electrode plate 32.
The movable electrode plate 32 rotates about the end 35 in the direction indicated by the arrow A, pulls the spring 37 of the adjusting mechanism 33, and balances with the weight of the object. At this time, the size of the gap between the two electrode plates 31 and 32 changes more than when the object is not placed on the turntable 11 and the capacitance changes accordingly. The change in capacitance is measured by the oscillator (not shown) as the change in the oscillation frequency to measure the weight of the object.

In addition to the above-mentioned mechanism for changing the distance between the fixed electrode plate and the movable electrode plate, there is a mechanism for detecting a slight change in the gap between the fixed electrodes fixed to the outside of the platform mechanism or the Roverval mechanism as a change in capacitance. It is used.

[0009]

However, in the former case, it is very difficult to adjust the spring constant and the initial setting of the gap between the two electrodes by using the adjusting mechanism, which requires a lot of time for assembly and adjustment. Was. Also, in the latter case where the platform mechanism or the Roverval mechanism is used, the measurement accuracy is greatly improved, but the number of parts is larger than in the former case, it is disadvantageous in terms of cost, and it is difficult to structurally downsize. It was

The present invention was devised in view of the above circumstances, and an object thereof is to provide a weight detecting device for a heating cooker, which is low in cost and small in size.

[0011]

A weight detecting device for a heating cooker according to the present invention detects the weight of an object placed on a turntable in a heating chamber as a displacement amount in a thrust direction of a supporting shaft of the turntable, and detects the thrust direction. A weight detection device for a heating cooker that converts the amount of displacement into a capacitance change by changing the size of the gap between the fixed electrode plate and the movable electrode plate arranged below the support shaft, and detects the capacitance change to detect the weight. There
The movable electrode plate is formed in a gimbal spring shape, the periphery of the movable electrode plate is fixed to the main body, and the center portion is arranged to receive the load of the support shaft. The gimbal spring-shaped movable electrode plate is composed of a central plane portion, an outer peripheral portion, and a plurality of arm portions. The arm portion integrally connects the central flat portion and the outer peripheral portion so that they can be easily deformed under load. The second moment of area is sufficiently smaller than that of the central plane portion.

The gimbal spring-shaped movable electrode plate, which receives a load via the support shaft of the turntable, moves in parallel with the load at the outer peripheral portion and the central plane portion, so that the electrostatic capacitance is substantially equal to the load. It changes linearly.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Before describing an embodiment of the weight detecting device for a heating cooker according to the present invention with reference to the drawings, the weight detecting device for a heating cooker according to the present invention is used as a premise. The weight detection device will be described.

FIG. 1 is a front sectional view of a weight detecting device for a heating cooker, which is a premise of the weight detecting device for a heating cooker according to the present invention.
FIG. 2 is a side view illustrating a deformed state of the leaf spring under the load of FIG. The same parts as those in the prior art are designated by the same reference numerals.

In FIG. 1, the heating chamber 10 has a support shaft 12 protruding substantially in the center thereof, and a turntable plate 13 is provided at the upper end of the support shaft 12. The boss portion 13A of the turntable plate 13 is fitted to the support shaft 12 of the turntable with a predetermined size, and the flange portion 13
B is configured to mount the turntable 11.

On the lower side of the heating chamber 10, a motor mounting member 24, which is spot-welded to the heating chamber 10, is fixed. The turntable motor 25 for rotating the turntable 11 and the main body of the weight detecting device 40 are fixed to the motor mounting member 24. 41 is attached. The turntable motor 25 includes a motor (not shown) that rotates in synchronization with the power supply frequency, a speed reduction mechanism, and a support shaft 12 that outputs rotation reduced by the speed reduction mechanism and is slidable in the thrust direction. A conical or spherical projection 12A is formed at the lower end of the support shaft 12. The weight detection device 40 includes a fixed electrode plate 42 and a movable electrode plate 4.
3 and is provided in the main body 41.

The fixed electrode plate 42 is fixed to an insulating plate 44 provided on the bottom of the main body 41. The movable electrode plate 43 is composed of a rectangular leaf spring, and is supported by knife edges 44A formed on both sides of the insulating plate 44 so as to project therefrom, and faces the fixed electrode plate 42 with a slight gap. Four
An air condenser is formed by 3. The protrusion 12A is supported on the substantially central portion of the movable electrode plate 43,
The rotating torque of the support shaft 12 is reduced and the weight of the turntable 11 and the object is accurately adjusted.
Can be said. The insulating plate 44 and the support shaft 12 are preferably made of, for example, ceramic. A lead wire 45 is electrically connected to both electrode plates 42 and 43, and is connected to an external weight detecting device (not shown). Next, the operation of the weight detecting device for the heating cooker will be described.

When an object is placed on the turntable 11, the weight of the object and the turntable 11 is received by the central portion of the movable electrode plate 43 via the support shaft 12. Assuming that the weight of the turntable 11 is W1, the weight of the object is W2, and the distance between the left and right knife edges 44A is l, the deflection δ of the movable electrode plate 43 at a position separated by X distance from one of the knife edges 44A is given by the following equation. To be done.

[0019]

[Equation 1]

(Where E is the elastic modulus, I is the second moment of area, and the weight of the support shaft 12 is ignored), and its center is

[0021]

[Equation 2]

It is displaced by an amount represented by (see FIG. 2).

Due to the displacement, the electrostatic capacitance between the electrode plates 42 and 43 changes by a value corresponding to the displacement, is converted into weight by an external weight detection circuit, and is used for heating control.

According to the embodiment of the weight detecting device for the heating cooker, which is the premise of the weight detecting device for the heating cooker of the present invention, the structure is simple and the number of parts is small as compared with the conventional device.
Miniaturization and cost reduction can be realized. In this embodiment, the rectangular plate spring forming the movable electrode plate 43 is supported at both ends when a load is applied, and thus deforms with a curve having the central portion as the apex, as described above. Therefore, the relationship between load and capacitance change is non-linear,
It is necessary to prepare an arithmetic circuit having a non-linear characteristic corresponding to this.

Next, an embodiment of the weight detecting device for a heating cooker according to the present invention will be described. 3 is a plan view of a movable electrode plate used in the weight detecting device for a heating cooker according to the present invention, and FIG. 4 is a side sectional view for explaining a deformed state of the movable electrode plate under the load of FIG.

In the embodiment of the weight detecting device for a heating cooker according to the present invention, the movable electrode plate 50 is formed in a gimbal spring shape (for example, gimbal spring) instead of the rectangular plate spring, and has a central plane portion 51 and an outer periphery. It comprises a part 52 and a plurality of arm parts 53. The central plane portion 51 has an area that acts as a movable electrode, and the outer peripheral portion 52 is fixed to the main body 41 via an insulating plate 54.

The arm portion 53 includes a central plane portion 51 and an outer peripheral portion 5.
There are a plurality of two that are integrally connected, and the second moment of area is formed sufficiently smaller than that of the central plane portion 51 so that it can be easily deformed under load. The arm 53
Usually, 4 to 8 are preferable. When a load is applied to the central portion of the movable electrode plate 50, the central plane portion 51 is closer to a rigid body than the arm portion 53, and therefore, the central plane portion 51 moves in parallel while maintaining a substantially flat surface, and the gap with the fixed electrode plate 42 changes. To do. According to this embodiment, measurement accuracy comparable to that of the weight detection device using the Roberval mechanism can be obtained.

[0028]

As described above, in the device of the present invention, the movable electrode plate is formed in the shape of a gimbal spring, so that the structure is simplified and can be made compact, and the weight detecting device utilizing the Roberval mechanism is used. Measurement accuracy comparable to

[Brief description of drawings]

FIG. 1 is a front sectional view of a weight detection device for a heating cooker, which is a premise of the weight detection device for a heating cooker according to the present invention.

FIG. 2 is a side view for explaining a deformed state of the leaf spring under the load of FIG.

FIG. 3 is a plan view of a movable electrode plate of the weight detecting device for a heating cooker according to the present invention.

FIG. 4 is a side sectional view for explaining a deformed state of the movable electrode plate under the load of FIG.

FIG. 5 is a vertical sectional front view of a conventional weight detecting device for a microwave oven.

[Explanation of symbols]

 10 Heating Chamber 11 Turntable 12 Support Shaft 40 Weight Detector 42 Fixed Electrode Plate 43 Movable Electrode Plate 50 Movable Electrode Plate 51 Center Plane 52 Outer Perimeter 53 Arm

Claims (2)

[Claims] 1. A fixed electrode plate and a movable electrode in which a weight of an object placed on a turntable in a heating chamber is detected as a displacement amount of a support shaft of the turntable in a thrust direction, and the displacement amount in the thrust direction is disposed below the support shaft. A weight detecting device for a heating cooker that converts into a capacitance change by a gap size change with a plate and detects a capacitance change to detect a weight, wherein the movable electrode plate is formed in a gimbal spring shape, A weight detecting device for a heating cooker, the periphery of which is fixed to the main body, and the center of which is arranged to receive the load of the support shaft. 2. The gimbal spring-shaped movable electrode plate is composed of a central plane portion, an outer peripheral portion, and a plurality of arm portions, and the arm portion integrally connects the central flat portion and the outer peripheral portion, so that the arm portion can be easily loaded. 2. The weight detecting device for a heating cooker according to claim 1, wherein the second moment of area is formed sufficiently smaller than that of the central plane portion so as to be deformable.