JP2727643B2 - High frequency heating equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency heating device such as a microwave oven and a microwave oven, which includes a weight sensor and is configured to automatically control the end of heating.

2. Description of the Related Art Conventionally, a high-frequency heating device provided with a weight sensor generally measures a food weight at the start of cooking to determine a cooking time. However, in recent years, attention has been paid to the fact that the weight of the object to be heated is reduced with the progress of cooking, and a technique of detecting the weight by reducing the finished weight of food has attracted attention.

FIG. 4 shows a conventional weight detecting device invented as an example of mounting on a microwave oven. (Japanese Patent Application No. 62-59382).
In FIG. 1, reference numeral 1 denotes a supporting rotary shaft which supports the food A, its mounting tray B and the rotary mounting table C and is driven to rotate by a motor 2 and is supported by bearings 22 and 23 so as to be movable in a vertical direction with excessive clearance. The load of the object to be measured transmitted in the thrust direction of the support rotary shaft 1 is transmitted to the diaphragm 8 by the load transmitting means 7 with a constant pressing area. Reference numeral 6 denotes a leaf spring for preventing the load transmitting means 7 from directly contacting the support rotary shaft 1 and being worn, and has a weak elasticity so as not to attenuate the transmission amount.

FIG. 5 is a cross-sectional view of the capacitance type pressure sensor, and FIG. 6 is a configuration diagram thereof. Reference numeral 8 denotes a diaphragm made of an alumina sintered body, 9 denotes a substrate made of an alumina sintered body, which are joined by a glass seal 10 and face each other with a small gap of several tens of microns. Electrodes 10 made of a noble metal such as gold or platinum are provided on the opposite surfaces of each alumina plate.
Are printed and fired to form a capacitor. The principle of detecting the weight is that the capacitance changes depending on the deflection gap of the diaphragm 8 due to the load transmitted by the load transmitting means 7. The capacitance is taken out to an external circuit through the lead wire 13 and subjected to signal processing and calculation to calculate the weight. Further, the structure of the sensor mounting table 14 for mounting the capacitance type pressure sensor 19 has a structure in which a pressure-sensitive portion inside the glass seal 11 is cut out from the glass seal 11 in order to prevent a load from being applied to the substrate 9 from the mounting table side and changing characteristics. ing. Thereby, only the load from the diaphragm 8 side can be accurately detected. Returning to FIG. 6, the sensor mounting table 14 is mounted on a sensor fixing bracket 16 for mounting to the main body 15, and furthermore, a sensor cover for electrically shielding the entire sensor.
Covers the surface with 12. Referring to FIG.
Since the supporting rotary shaft 1 penetrates substantially the center of the groove, a high-frequency attenuation groove 25 for reducing leakage of high-frequency energy radiated from the firing tube (not shown) into the heating chamber outside the heating chamber.
Is constituted by an attenuation metal fitting 26 provided on the outer wall of the heating chamber. The leaked high frequency becomes noise with respect to a minute weight detection signal and hinders obtaining accurate weight information. For the same purpose, in order to reduce radio wave leakage to the outside of the heating chamber, a material made of a ceramic material is generally used instead of the metal supporting rotary shaft. Needless to say, ceramic is
Excellent in heat resistance, heat conduction, strength, chemical resistance, etc.

Problems to be Solved by the Invention However, this ceramic support rotating shaft has the drawbacks that it has extremely high hardness, shrinkage / warpage is easy to occur in the firing step, and it is difficult to obtain a desired shape, and a minute change in gravity is detected. This is extremely inconvenient as a pressure transmitting device to the gravity sensor. Taking alumina porcelain commonly used as a ceramic shaft as an example, Vickers hardness Hv is
It is 1300 kg / mm ² or more, and has several times the hardness of stainless steel. As shown in FIG. 4, when the supporting rotary shaft 1 rotates on the surface of the plate spring 6 made of stainless steel spring material under the weight of the object to be heated A or the rotary table C, the surface of the plate spring 6 is worn. It turned out to start. In the case of stewed dishes, the use of casserole can add up to 5 kg or more of food and casserole, in which case this tendency is further accelerated. Here, the outline of the manufacturing process of a ceramic shaft generally used in a microwave oven is shown in FIG.
The first step is molding, in which the temperature of the granular ceramic is increased under pressure and pressed into a desired shape (a). In the second step, this is baked to give a ceramic characteristic. What is important at this time is shrinkage, heat distribution of the kiln,
FIG. 4B shows that warpage occurs due to variations in the internal stress of the ceramic shaft and the density of the ceramic shaft. Since the support rotary shaft which has obtained the original characteristics of the ceramic through the second step is warped as shown in FIG. 2B, the outer diameter is polished by the x dimension to finish it to the desired dimension y. Since the hardness of the ceramic is extremely high in the polishing step, it is desirable to minimize the polishing step in terms of cost and quality. The shape after polishing is shown in FIG. Although the protrusion at the left end does not deviate from the center in the rotation shown in FIG. 3A, it is eccentric by the dimension z after firing and polishing. Further, the total length b is also b ', and its size changes depending on the variation of the firing step. y = φ8m
Experience has shown that the Z dimension can be up to about 0.4 mm for an alumina shaft having a size of m, b '= about 60 mm.

If the center of the supporting rotary shaft, which is a contact portion to the weight sensor, is displaced from the center, the trajectory of the leaf spring changes greatly as described above, so that the weight characteristics cannot be obtained correctly. FIG. 9 shows a change in weight detected by the weight sensor. The horizontal axis represents time, and the vertical axis represents weight. As shown in FIG. 6, the load transmitting means 7 to the weight sensor and the tip of the support rotary shaft 1 are eccentric by the dimension z. That is, the support rotation shaft 1 draws a circle having a radius z on the leaf spring 6. In the case of FIG. 9 (a), it can be seen that the weight value sharply decreased about 10 g on the way. This occurs when the tip of the support rotary shaft moves up and down along the unevenness of the surface of the leaf spring caused by the wear of the leaf spring described above. This occurs. In order to detect the finish of the food, it is necessary to recognize a change in weight of several grams since the start of heating,
Such a sudden change will cause premature disconnection due to incorrect information. FIG. 9 (b) shows the movement of the weight value (the weight has not changed by heating) when the surface of the leaf spring is smooth and not eccentric. Although the data fluctuates up and down, this is the weight movement due to rotation ±
It moves stably within a small range of 3g. In FIG. 10, the hole 28 at the end of the shaft on the side of the load transmitting means 7 to the weight sensor of the support rotary shaft 1 is provided before the firing step of the ceramic support rotary shaft 1, so that it is eccentric by the dimension z. doing.
When a pressing member 29 made of resin for preventing the abrasion of the leaf spring 6 is press-fitted thereto, the pressing portion of the temporary spring 6 is eccentric by the dimension z as before, as shown in the figure. In this case, the abrasion of the leaf spring 6 can be prevented, but only the change in weight as shown in FIG. Here, it is extremely difficult to drill the tip of the ceramic support rotary shaft after firing the ceramic, which greatly exceeds the price of a single component shaft of household electric appliances, and is not suitable for mass production. But it's a bug. Therefore, as shown in FIG. 11, a method of press-fitting the resin cap-shaped pressing member 30 with reference to the outer periphery having high dimensional accuracy is considered. The reason for press-fitting is to minimize the eccentricity between the support rotating shaft 1 and the pressing member 30;
This is because both are rotated in synchronization when driven to rotate, and the phenomenon described above with reference to FIG. 9 occurs in either case.

In this case, the eccentricity between the pressing member 30 and the load transmitting means 7 is remarkably improved.
Of but wear also possible to prevent, for providing the outside of the outer diameter d ₀ of the supporting rotary shaft 1, the outer diameter D of the pressing member 30 is larger than the inner diameter d ₁ of the bearing 23, the thrust movement of支接rotary shaft It is necessary to provide the above interval S. As a result, more space for accommodating these functional components is required by the S dimension than before, and the L dimension in FIG. 10 is enlarged to the L ′ dimension in FIG. In the case of microwave ovens and oven microwave ovens, the so-called horizontal type, which has an operation section on the right side of the heating chamber, is the main type of product. In the case of a horizontal type, it is desirable to set the overall height of the product to the height of the heating chamber just from the narrow kitchen situation. For this reason, it is better that the overall height is as small as 1 mm. From this, the plan of Fig. 11 is not satisfactory.

Therefore, an object of the present invention is to provide a high-frequency heating device that can obtain a delicate weight characteristic and realizes a space saving that is not different from the conventional one in terms of space.

Means for Solving the Problems In order to achieve the above object, the ceramic support rotary shaft according to the present invention is integrally formed of a resin material at a contact portion with the weight detecting means and transmits the point load to the weight detecting means as a point load. A pressure member is provided.

The high-frequency heating device according to the present invention integrally forms a resin sliding member having good slidability on a rotating contact portion between a ceramic supporting rotating shaft and a leaf spring interposed between a load transmitting means to a weight sensor. In this configuration, a stable operation is obtained because there is no wear of the leaf spring, and the center of the rotation center and the center of the load transmitting means to the weight sensor can be matched with high accuracy. Reading a subtle change in weight of the food during cooking can be realized without increasing the entire space because it can be configured with a dimension equal to or smaller than the diameter of the support rotation shaft.

Embodiment Hereinafter, a high-frequency heating apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3.

FIG. 2 shows a case where a supporting spring 1 made of ceramic of the present invention and a resin such as polyacetal which can be injection-molded and have good slidability are molded with a plate spring and a pressing member 29 for forming a sliding portion.
FIG. 3 is a conceptual diagram illustrating that the molding is performed integrally with a mold 31 on a side where resin 31 is injected and a resin. 33 is a mold dividing surface,
The resin raw material stored in 34 is heated by a heater 35 of an injection molding machine to be in a liquid state and pressurized, and is injected from a cylinder 36 through a gate 37 into a space 29 formed by a mold 32 and a ceramic support rotary shaft 1. Is done. When cooled, the resin material becomes a pressing member 29 integrally formed with the ceramic support rotating shaft 1. At this time, the total length l ₀ of the ceramic support rotary shaft 1
It has been found that when the shaft has a diameter of about 70 mm, it varies after firing about ± 0.6 mm. However, since the dimension l ₁ of the mold has extremely high dimensional accuracy, it is easy to keep it within ± 0.2 or less.

FIG. 3 shows a ceramic support rotary shaft according to the present invention.
The center of the hole 28 at the tip of the ceramic support rotating shaft 1 and the center of the shaft are eccentric by the dimension z. Experience has shown that the diameter of an alumina shaft having an outer diameter of φ8 varies by firing and polishing by about 0.4 mm. Outer diameter d ₂ of the pressure member 29 is dimensioned to be determined by the mold dimensions d ₀ of FIG. 10 (outer diameter of the ≒ ceramic shaft). This is the total length l ₀ of the ceramic support rotary shaft 1.
However, it is necessary to adjust the outer diameter to d ₀ , but d ₂ <
relationship d ₁ is established. As a result, even if the ceramic supporting rotary shaft 1 moves in the thrust direction and the pressing member 29 enters the bearing 23, it does not come into contact with the inner surface of the bearing 23. Since no force is applied, the life and reliability are stabilized. Numeral 38 denotes a rotating contact portion of the pressing member 29, the center of which coincides with the center line of the outer periphery of the shaft, so that the center can coincide with the center line of the load transmitting means 7. It goes without saying that the shape of the rotating contact portion 38 can be arbitrarily formed into the most suitable shape such as a spherical shape or a conical shape. 39
Is a lateral hole that functions to prevent the pressure member 29 from coming off the support rotary shaft 1 and to prevent rotation, and is also used as a hole for venting gas generated from the resin during resin molding.

FIG. 1 shows a weight detection device of the present invention mounted on an oven microwave oven. In the figure, a supporting rotary shaft 1 which supports a food A, its mounting tray B and a rotary mounting table C and is driven to rotate by a motor 2 is made of alumina, and the weight transmission to a weight sensor is integrally formed at a lower end. This is carried out via polyacetal, which is a material having good slidability. Since the weight sensor is composed of the alumina sintered bodies 8 and 9, there is a drawback that the weight sensor is easily broken when an impact load is applied thereto. However, according to the present invention, the load transmission made of the hard support rotary shaft 1 and metal is performed. Since the pressure member 29 made of a soft resin is interposed between the pressure sensor 29 and the means 7, even if the user drops the food A or the placing tray B in the heating chamber, the shock is absorbed and the weight sensor is absorbed. Works to protect

In addition, the dimensions of the supporting rotating shaft are often slightly different for each product of oven microwave oven and microwave oven,
In order to prevent erroneous use due to mixing, conventionally, marking was performed with a marker such as magic ink, and sorting was performed. However, according to the present invention, sorting is performed by coloring or changing the shape of the resin pressing portion. This makes it easy to prevent misuse.

Effects of the Invention As described above, according to the high-frequency heating device of the present invention, the following effects can be obtained.

(1) The support shaft made of ceramic such as alumina magnet is made of resin material with good slidability, and the pressurizing part for the weight sensor is integrally formed. Even so, stable weight maintenance can be obtained. By filling the resin material with components that improve lubricity and wear resistance,
There is no need to apply grease or the like to the contact portion.

(2) Even if the hole at the tip of the ceramic supporting rotary shaft is eccentric, the center deviation from the pressure transmitting means to the weight sensor can be configured with a mold that is based on the outer periphery with high accuracy to form a contact portion with the leaf spring. So it does not happen. Therefore, the resin contact portion, which is a pressurizing portion, and the pressure transmitting means of the weight sensor do not deviate from each other at the center.

(3) Since the pressurizing member is not mounted on the shaft by press-fitting, twisting, bonding or the like, it does not fall or come off, and it is not necessary to handle small parts with care. Since the anti-rotation function also has a slip-out prevention function, stable weight characteristics can be obtained without rotating asynchronously with the shaft.

(4) Since the pressure member is made of resin, even if it is molded with the same outer diameter as the ceramic shaft, the outer diameter is reduced by the larger shrinkage ratio, so that even if it enters the inside of the bearing, it will not be caught. Can rotate. Therefore, it does not come off,
There is no adverse effect such as damage to the bearing. As a result, the ceramic shaft moves in the thrust direction when detecting the weight, but does not require extra space, so it is not necessary to increase the height of the bottom of the heating chamber and the height of the entire product. And a compact design can be realized.

(5) Since the pressure member is formed by injection molding, the shape can be freely selected. In general, ceramics have very high compressive strength, but are extremely weak to the force in the peeling direction.In the experiment, polyacetal was pressed with a 0.4 mm press-in allowance and the outer diameter was 8 mm and the inner diameter was 3 m.
When inserted into a hole with a depth of 4 mm and a depth of 4 m, cracks may easily occur. This is a dimensional relationship that is sufficiently considered in consideration of the variation in the hole size of the alumina magnet and the size of the polyacetal molded product or cut product. However, since the pressing member of the present invention is formed by injection molding, quality can be ensured by controlling the injection pressure. It is possible to set molding conditions with a margin for the pressure up to breaking.

(6) Since the resin pressure member is interposed between the ceramic shaft and the gravity sensor, there is an effect of absorbing a shock when the food / food placing tray is dropped. In addition, since the weight sensor has high temperature dependency, it is necessary to secure accuracy by suppressing heat conduction. However, the pressing member of the present invention also serves as a heat insulating member.

(7) Although the length of the ceramic shaft varies greatly, the overall length after being integrally molded with the pressing member is stable because it is determined by the dimensions of the mold. Therefore, the position of the gear interposed in the middle and the position of the shaft tip on the heating chamber side are also stabilized, so that the quality such as cooking performance is stabilized.

(8) By changing the shape or the color of the pressing member, mixing of shafts having slightly different lengths, which has conventionally been distinguished by marking it indistinguishably, is prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a high-frequency heating apparatus according to one embodiment of the present invention, FIG. 2 is a view showing a resin injection molding process of a ceramic shaft in one embodiment of the present invention, and FIG. FIG. 4 is a partial cross-sectional view of a conventional high-frequency heating apparatus, FIG. 5 is a cross-sectional view showing a state where a weight sensor is pressed, and FIG. 6 is a weight sensor. FIG. 7 is a processing step diagram of an alumina shaft, FIG. 8 is a partial cross-sectional view of a conventional high-frequency heating device, FIG.
Figure (a) shows the change in weight of the conventional high-frequency heating device,
(B) is a diagram showing a change in weight of the high-frequency heating device of the present invention, and FIGS. 10 and 11 are partial cross-sectional views of a conventional high-frequency heating device. 1 ... rotating support shaft, 24 ... heating chamber, 27 ... heating means, 29
... Pressing member, A: Heated object, C: Rotary mounting table.

Continuation of the front page (56) References JP-A-60-82819 (JP, A) JP-A-1-174825 (JP, A) JP-A-60-232433 (JP, A) JP-A-2-29510 (JP) , A) Japanese Utility Model Showa 60-165711 (JP, U) Japanese Utility Model Showa 61-44106 (JP, U)

Claims (2)

(57) [Claims] 1. A heating chamber for heating an object to be heated, a heating means coupled to the heating chamber, a control unit for controlling power supply to the heating means, and a rotary mounting table for mounting the object to be heated. And a weight detecting means for detecting the weight of the object to be heated on the rotary mounting table, and a supporting rotary shaft for transmitting the weight of the material to be heated to the weight detecting means and for driving the rotary mounting table to rotate. The shaft is formed of ceramic, and a pressing member for transmitting the weight of the object to be heated to the weight detecting means as a point load is integrally formed of a resin material at a contact portion with the weight detecting means. apparatus. 2. The pressure member integrally formed on the supporting rotary shaft,
The high-frequency heating device according to claim 1, wherein the color is changed according to the type.