JPH0387522A - Microwave oven - Google Patents

Abstract

PURPOSE:To ensure efficient transfer of heat to a pyroelectric sensor and enhance detection performance, by a construction wherein a guide passage having a flow passage area smaller than the area of a heat-receiving surface of the pyroelectric sensor is provided in a duct above the sensor, facing the same, and the spacing between the guide passage and the sensor is set in a specified relationship with the inside size of the guide passage. CONSTITUTION:A material to be heated 6 placed in a heating chamber 7 is dielectrically heated with the result of a temperature rise, and a vapor generated by the heating passes through a vent hole 3 in the ceiling of the chamber 7, a first duct 9, a duct 2 and a guide passage 5 to make contact with a pyroelectric sensor 1. The spacing (d) between the sensor 1 and the lower end guide passages 5 disposed above the sensor 1 and facing the of the same is made to be about 1/10 of the inside diameter gamma of the flow passage of the duct 2. Even when the vapor guided through the duct 2 has a low flow pressure, the sensitivity of detection is prevented from being lowered, because the vapor is caused to flow through the restricted space. The flow passage area of the guide passage 5 is set smaller than the area of a heat- receiving surface of the sensor so that the vapor flows between the passage 5 and the sensor 1 without fail.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention detects hot air contained in steam and gas that come out depending on the heating state of the object to be heated, and determines the end time of heating the object as appropriate. This invention relates to automatic cooking using a high-frequency heating device that determines and achieves a good heating state.

Conventional technology Conventionally, automatic cooking using high-frequency heating equipment requires a detection means to detect the heating state of the food to be heated. A sensor is placed as a detection means in the middle of the exhaust gas passage, and by detecting the generation and concentration changes of water vapor gas etc. generated when food is heated, it is possible to indirectly determine the heating condition or doneness of food. This means that automatic heating cooking will be performed, such as switching the heating means or stopping heating based on the information provided.

A detection system using a pyroelectric element is being considered as a detection system for this method, but although this system uses a pyroelectric element, it does not require a complicated configuration such as a chopper, and it does not require an optical system. It has many advantages, such as being resistant to dirt because it does not utilize tX, and being very easy to use, such as having no problems with viewing angles, and being able to use tX at a low cost.

As shown in FIG. 0, which will explain a conventional example together with FIG. 4, an object to be heated 6 placed in a heating chamber 7 is dielectrically heated by 2450 MHz microwaves generated by a magnetron 1O. When the temperature of the heated object 6 rises and reaches near the boiling point of water contained in a large amount in the object 6, a large amount of high-temperature steam is generated and this steam rises toward the ceiling of the heating chamber 7. . This steam passes through the vent 3 provided on the ceiling of the heating chamber 7, is guided to the gas passage 2, and is directed to the pyroelectric sensor 1.
At this time, dew condenses on the surface of the pyroelectric sensor 1, giving the pyroelectric sensor 1 a large amount of energy mainly consisting of latent heat. As a result, the temperature of the pyroelectric sensor 1 rises and a voltage is generated due to the pyroelectric effect, so that the finished state of the heated object 6 can be determined by detecting this.

Invention tries to solve! ! l! However, in the above configuration, the water vapor from the object to be heated 6 generated in the heating chamber 7 is delivered to the pyroelectric sensor l, but the air sent into the heating chamber 7 is passed through the exhaust hole 3 and the exhaust hole 11. Heating chamber 7 as exhaust is exhausted from two places.
Only a portion of the water vapor gas generated in
In many cases, it takes a long time for the gas to reach the heat-receiving surface of the pyroelectric sensor 1 through the long path of the gas passage 2 depending only on the wind pressure of 18, so it is difficult to quickly detect the heating state of the heated object 6. As a result, the object to be heated 6 becomes overheated, and heating should be stopped at the optimum heating state of the object to be heated 6 as an automatic heating device, but heating cannot be stopped in the optimum state. However, there was a problem that the automatic heating device could not perform its original function.

Furthermore, when the heated object 6 is repeatedly heated, water vapor drops adhere to the heat receiving surface of the pyroelectric sensor. If the pyroelectric sensor is covered with the heat-receiving surface in this way, it will become less able to detect changes in the state of the hot air contained in the exhaust air from the heating chamber 1, and will no longer be able to perform its original function! There was also IHI.

Therefore, in order to solve these problems, the present invention arranges a guiding path and a pyroelectric sensor facing each other below the ventilation path for guiding steam from the heating chamber, and improves the positional relationship between the pyroelectric sensor and the guiding path. By devising the following, we provide a configuration that efficiently transfers heat to the pyroelectric sensor, and even when wind pressure is weak, steam is applied directly and efficiently to the heat receiving surface of the pyroelectric sensor, allowing automatic detection with high detection performance. An object of the present invention is to provide a high-frequency heating device having a cooking function.

In order to achieve the above-mentioned object, the present invention provides a guiding path having an area smaller than the heat-receiving surface of the pyroelectric sensor in the gas passage and facing above the pyroelectric sensor, so that the guiding path and the pyroelectric sensor The interrelationship between the gap between the heat receiving surfaces and the inner diameter of the heat receiving surface of the pyroelectric sensor and the flow path of the guide path is set so that heat is efficiently transferred to the pyroelectric sensor.

Function The high-frequency heating device of the present invention has a pyroelectric sensor that detects water vapor and gas from an object to be heated generated in a heating chamber, arranged opposite to a guide path that guides water vapor and gas to the pyroelectric sensor. By making the area of the wave path smaller than the area of the pyroelectric sensor heat receiving surface, the steam ejected from the guideway flows along the pyroelectric sensor heat receiving surface, making it possible to efficiently apply steam to the pyroelectric sensor. can. Furthermore, by setting the distance between the opposing pyroelectric sensor and the taxiway to approximately 1/10 of the flow path of the taxiway, even when the wind pressure of the steam guided from the taxiway is weak, the pyroelectric sensor and the taxiway can be easily Since the steam flows through a narrow space, the steam flows closer to the sensor's heat-receiving surface and the detection sensitivity does not decrease. In addition, the distance between the pyroelectric sensor and the guideway is extremely small compared to the inner diameter of the guideway, which increases the wind speed and stabilizes the transfer of thermal energy to the pyroelectric sensor. Since the wind speed on the heat-receiving surface of the pyroelectric sensor becomes faster, droplets of steam are less likely to adhere to the pyroelectric sensor, and detection of changes in the state of hot air can be prevented from being slowed down by drops.

EXAMPLE Hereinafter, a high-frequency heating device according to an example of the present invention will be explained with reference to the drawings.

Before entering into an explanation of the entire high-frequency heating device, first, the configuration and operation of the pyroelectric sensor 1, which is a detection element of the high-frequency heating device, will be explained. FIG. 3(a) is a detailed explanatory diagram of the pyroelectric sensor 1, showing a flat ceramic plate 14 having a pyroelectric effect, electrodes 15 and 16 formed on both sides of the plate, and a stainless steel plate bonded to one side of the plate. It consists of a metal plate 17 made of steel or the like. When high-temperature gas such as steam hits this metal plate 17 side, heat is transferred to the ceramic plate 14 via this metal plate 17, and the ceramic plate 14 generates a voltage due to the pyroelectric effect. Therefore, in the configuration shown in this figure, the surface of the metal plate 17 becomes the heat receiving surface. In the case of the cross-sectional view of the pyroelectric sensor 1 shown in Fig. 3), the electrode 16 on the side to be bonded to the metal plate 17 passes through a part of the circumferential edge of the ceramic plate 14 to the opposite surface. The lead from electrode 15.16 is extended! 111
8 can be drawn out only on the surface that is not bonded to the metal plate 17.

For example, the ceramic plate 14 may be made of PZT (lead zirconate titanate) or the like.

FIG. 1 is a schematic cross-sectional view of a high-frequency heating device according to the present invention. As shown in FIG. 1, the object to be heated 6 (food) placed in the heating chamber 7 is
Dielectric heating is performed by the microwave (high frequency) of M 1 (z. The temperature of the object to be heated 6 rises with the heating, and when the water contained in the object to be heated 6 reaches a temperature close to the boiling point, a large amount of steam is generated. , this steam passes through the vent 3 provided in the ceiling of the heating chamber 7, is led to the first ventilation passage 9, and is led to the gas passage 2,
The steam that hits the pyroelectric sensor 1 through the five guiding paths condenses on the surface of the pyroelectric sensor 1 and gives the pyroelectric sensor 1 a large amount of thermal energy mainly consisting of latent heat. 1, the temperature rises and a pyroelectric voltage is generated.

A guiding path 5 is connected to the gas passage 2 and is placed above and facing the pyroelectric sensor I, with the distance between the lower end of the guiding path 5 and the pyroelectric sensor 1 being set to be more extreme than the inner diameter of the flow path of the ventilation path 2. By making the size small, the steam guided by the ventilation B2 will flow through the narrow space between the guide path 5 and the pyroelectric sensor 1 even when the wind pressure is weak, and the detection sensitivity will not decrease. In addition, taxiway 5
Since the area of the flow path is smaller than the area of the heat-receiving surface of the pyroelectric sensor 1, steam attempting to flow from the inside of the guide path 5 to the outside always flows between the guide path 5 and the pyroelectric sensor 1. It turns out. FIG. 2(a) shows a detailed diagram showing the positional relationship between the guideway 5 and the pyroelectric sensor 1.

Here, assuming that the amount of steam passing through the guideway 5 is constant, by making the gap d between the guideway 5 and the pyroelectric sensor l smaller than the inner diameter dimension r of the flow path of the guideway 5, The wind speed of the steam flowing through the gap d increases, and heat transfer to the pyroelectric sensor l improves. (in Fig. 2) shows the change in the voltage level of the pyroelectric sensor depending on the ratio of the gap d to the inner diameter dimension r of the flow path of the guiding path 5. As d/r becomes smaller, the voltage level suddenly changes from a certain ratio. In other words, heat is efficiently transmitted to the pyroelectric sensor.

The detection level of the sensor can be set arbitrarily, but
The ratio of the gap d to the inner diameter dimension r of the guide path 5 is approximately 1.
An effective voltage level can be obtained by setting it to about 71O. In addition, when the gap d and voltage level change due to the ratio of the inner diameter r of the guide path 5 to the diameter 1 of the heat receiving surface of the pyroelectric sensor l, the inner diameter r of the guide path 5 and the pyroelectric sensor If the ratio 1/r of the diameter dimension 1 of the heat-receiving surface of l is 1, that is, if the dimensions are the same, even if the gap d is made small, no sudden change in voltage level will be obtained, but if 1/r is 0.
By setting the value to about 6, the heat of the steam is efficiently propagated to the pyroelectric sensor, and a predetermined level can be obtained.

In addition, the sensor holding case 4 is provided with a cold air mixing exhaust passage 12 for mixing and discharging cold air blown by the blower 8, and a mixing section 13 for mixing the cold air with steam narrows the passage and increases the wind speed of the cold air. By lowering the atmospheric pressure and widening the passage after mixing the cold air and steam, the steam is sucked in and the flow of steam to the pyroelectric sensor 1 is made smooth.

Effects of the Invention As described above, the high frequency heating device of the present invention provides the following effects.

A waveguide with an area smaller than the area of the heat-receiving surface of the pyroelectric sensor is connected to the gas passage, and the waveguide is placed facing above the pyroelectric sensor. By setting the inner diameter to approximately 1710, the steam led from the ventilation path will flow through the narrow space between the guideway and the pyroelectric sensor, and even if the wind pressure of the gas containing steam is weak, The wind speed in the space between the electric sensor and the pyroelectric sensor becomes faster and the transfer of thermal energy to the pyroelectric sensor becomes more stable, and the heating state of the heated object is detected without delay, making it possible to prevent the heated object from being overheated. It has the effect of preventing

In addition, since the wind speed on the heat receiving surface of the pyroelectric sensor becomes faster, it becomes difficult for vapor drops to adhere to the sensor, and it is possible to prevent the detection of changes in the state of hot air from becoming slow due to drops.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a high-frequency heating device according to an embodiment of the present invention, FIG. FIG. 3(a) is a diagram showing changes in voltage level depending on the ratio of the gap d between the pyroelectric sensor and the guide path dimension r. (b) is a top view and a cross-sectional view of a pyroelectric sensor, and FIG. 4 is a schematic cross-sectional view of a conventional high-frequency heating device.
...Pyroelectric sensor, 2... Gas passage, 5...
...Guidance path, 6...Heated object.

Claims (1)

[Claims] A heating chamber in which an object to be heated is placed, a gas passage for exhausting water vapor and gas from the object to be heated generated in the heating chamber, and a pyroelectric sensor that detects hot air of the water vapor and gas;
a guide path that guides water vapor or gas in the gas passage to the pyroelectric sensor, the area of the guide path flow path is smaller than the area of the heat receiving surface of the pyroelectric sensor, and the pyroelectric sensor is connected to the guide path. A high-frequency heating device having an automatic cooking function, in which the pyroelectric sensor and the guide path are arranged facing each other, and the distance between the pyroelectric sensor and the guide path is set to about 1/10 of the inner diameter dimension of the flow path of the guide path.