JPS6358024A - Electronic oven - Google Patents

Abstract

PURPOSE:To improve the reliability of an user on the electronic oven and to prevent the lowering of an output of an infrared ray detector by providing an infrared ray detector for detecting infrared rays passing through an infrared ray passing hole, radiated from a material to be heated, and a control circuit for controlling a high-frequency oscillator by an output from the infrared ray detector. CONSTITUTION:An infrared ray passing hole 5 is provided on the upper wall surface of a heating chamber 1, and a visional field limiting horn 7 is provided in the infrared ray passing hole 5. One end of an optical fiber 8 for infrared rays is connected to the visional field limiting horn 7. An infrared ray detector 10 is installed at the lower part outward of the heating chamber 1, and another end of the optical fiber 8 for infrared rays is coupled to the light receiving surface of the infrared ray detector 10. A control circuit for controlling a high frequency wave oscillator is constituted such that when the output of the infrared ray detector 10 is amplified by a pre-amplifier 20 and is compared with a preset temperature of a material to be heated by means of a comparator 21 and reaches the preset temperature, them a final stage amplifier 23 for imparting a stop signal to a high-tension lead switch 22 operates. Since the infrared ray detector 10 is provided at the lower part outside the heating chamber 1, the temperature rise is greatly lowered and a temperature difference between the material to be heated and the infrared detector increases. Therefore, the output of the detector is improved.

Description

[Detailed description of the invention] [Object of the invention] (Industrial application field) The present invention detects infrared rays emitted from a heated object,
This invention relates to a microwave oven that controls high frequency oscillation.

(Prior Art) In recent years, the amount of infrared rays emitted from a heated object 1, such as food, placed in a heating chamber is detected by an infrared detector, and a high-frequency oscillator is controlled from this output. Microwave ovens that provide good heating conditions have been put into practical use.

This type of microwave oven is known as
As shown in the publication, since it is necessary to detect infrared rays emitted from the surface of the heated object, an infrared passing hole is provided at the top of the heating chamber, and an infrared detector is placed directly above this passing hole. It is provided.

However, when the infrared detector is placed directly above the infrared passing hole, the temperature of the infrared detector itself increases due to heat convection from the heated object. To explain more specifically, the ambient temperature of an infrared detector normally rises to about 80°C. Therefore, the temperature difference between the heated body and the infrared detector is reduced. Here, the output of the infrared detector has a characteristic that it increases in proportion to the temperature difference between the heated object and the infrared detector, so when the above temperature difference is reduced, the output increases as shown in Figure 6. Output is significantly reduced. therefore.

Since the signal-to-noise ratio of temperature detection is significantly lowered, the problem that accurate temperature of the heated object cannot be detected tends to occur.

On the other hand, as shown in Figure 7, for example,
As disclosed in the above publication, a device has been developed that uses a mirror to reflect infrared rays that have passed through an infrared passing hole, thereby changing the installation location of an infrared detector.

This prevents the infrared detector from being installed directly above the infrared passing hole, so it is expected that the above-mentioned problem will be alleviated to some extent.

However, this type requires initial adjustment of the reflection angle of the 9-reflection inkstone, and the transport characteristics are -degrees.

If deviations from this initial adjustment occur, there is a reliability problem in that the output of the infrared detector is significantly reduced.

(Problems to be Solved by the Invention) As described above, in the conventional microwave oven, it is not possible to eliminate the decrease in the output of the infrared detector while maintaining reliability.

Therefore, the present invention is intended to solve the above problems.

It is an object of the present invention to provide a microwave oven that can solve the problem of low reliability and a decrease in the output of an infrared detector.

[Structure of the invention]

(Means for Solving the Problems) The microwave oven of the present invention includes a heating chamber in which an object to be heated is placed;
A high frequency oscillator that supplies microwave energy into the heating chamber, an infrared passing hole provided on the wall of the heating chamber, an optical fiber whose one end is placed in the infrared passing hole, and an optical fiber that is connected to the other end of the optical fiber and is It is constructed by comprising an infrared detector that detects infrared rays emitted from a heating body and passed through an infrared passing hole, and a control circuit that controls a high-frequency oscillator using the output of this infrared detector.

(Function) In the microwave oven of the present invention, an infrared passing hole is provided in the wall surface of the heating chamber by an optical fiber.

Since an optical path through which infrared rays are guided is formed between the infrared detector and the infrared detector, the installation location of the infrared detector can be changed from directly above the infrared passing hole without using a single reflecting mirror.

Therefore, reliability is improved and the problem of a decrease in the output of the infrared detector can be solved.

(Example) Examples of the microwave oven of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram of a microwave oven according to an embodiment of the present invention. That is, as shown in the figure, an opening 2 is provided in the wall surface of a heating chamber 1 in which an object to be heated A1 such as food is placed, and a waveguide 4 excited by a magnetron 3, which is a high frequency oscillator, is provided in the wall surface of the heating chamber 1. The conducted microwaves are supplied to the heating chamber 1.

Further, an infrared ray passage hole 5 is provided in the upper wall surface of the heating chamber 1. This infrared passing hole 5 is provided with a field-limiting horn 7 made of metal such as aluminum and held by a holder 6 as shown in an enlarged view in FIG. One end of an infrared optical fiber 8 is connected. What is the viewing angle of this viewing-limiting water tube 7?

When the heated object A is placed in the heating chamber 1, the heated object A
must be set so that it satisfies this viewing angle. Here, the infrared optical fiber 8 is supported by supporting members 9 spaced apart at a predetermined interval so as not to contact the wall surface of the heating chamber 1.
It is maintained by

On the other hand, an infrared detector 10 made of, for example, a thermistor is installed in the lower part outside the heating chamber 1, and its light-receiving surface is connected to the other end of the aforementioned infrared optical fiber 8.

Further, a control circuit (not shown) for controlling the high frequency oscillator has a configuration as shown in the block diagram of FIG. 3, for example.

In other words, the output of the infrared detector 10 driven by, for example, a DC constant power source (not shown) is amplified by the pre-amplifier 20 having a high input impedance. moreover.

This output is compared with a preset temperature of the object to be heated by a comparator 21, and when the set temperature is reached, the final stage amplifier sends a stop signal to, for example, a high voltage reed switch 22 that stops the operation of the high frequency oscillator. 23 is configured to operate.

The operation of the microwave oven according to this embodiment configured as above will be explained below.

The microwave excited by the magnetron 3 is absorbed by the heated object A placed in the heating chamber 1.

The temperature of this heated object A rises and emits infrared rays. The infrared rays that have passed through the infrared passing hole 5 provided on the wall of the heating chamber 1 are guided by an infrared optical fiber 8 and are incident on an infrared detector 10 provided at the bottom.

Here, considering the temperature rise of the infrared detector 10 caused by the convection of heat from the heated object A, in the non-embodiment, since the infrared detector 10 is provided at the bottom outside the heating chamber 1, Compared to the vicinity of the infrared passage hole, where the temperature rises to about 80°C, the temperature rise is significantly reduced. Incidentally, 1. According to the inventors' confirmation, when the temperature directly above the infrared passing hole 5 is approximately 80° C., the ambient temperature at the location where the infrared detector 10 in this embodiment is installed is The temperature was approximately 35°C.

Output voltage of the infrared detector when using a thermistor bolometer as an infrared detector and changing the ambient temperature from 30°C to 80°C and further changing the temperature of the heated object from 30°C to 100°C. Figure 4 shows the change in characteristics. Here, the figure shows 10 when the ambient temperature is 30'C.
It is a relative diagram based on the output voltage when a heated object heated to 0° C. is detected.

As can be understood from the figure, the above output can be obtained when the ambient temperature is 80°C.

The output of the infrared detector 10 whose output has been increased in this manner is input to the control circuit to control the operation of the high frequency oscillator, as described above.

As described above, according to this embodiment, the infrared detector can be disposed in a place where the ambient temperature is relatively low, so that the temperature rise of the detector itself is reduced. Therefore.

Since the temperature difference between the heated body and the infrared detector increases, the output of the detector can be improved.

Furthermore, since the location of the infrared detector can be changed without using a nine-reflector or the like, initial adjustment and the like are not required, and reliability is improved.

Next, another embodiment of the microwave oven according to the present invention will be described. FIG. 5 shows a partially cutaway schematic diagram showing the main parts of this embodiment, and the same parts as in the above embodiment are given the same reference numerals.

As shown in the figure, infrared passing holes 5 in the upper wall of the heating chamber 1
It may be the horn 7 for limiting the field of view installed in the.

The structure is such that an air flow can be formed inside the heating chamber. In other words, at the end of the field-limiting horn 7 facing the heating chamber 1, an infrared optical fiber 8 is placed at its center.
An insertion hole 7a is provided to which one end is connected, and a ventilation hole 7b is provided on the outside of each insertion hole 7a.

As described above, one end of the infrared optical fiber 8 is connected to the insertion hole 7a in order to guide light to the infrared detector 10. Further, one end of a blower tube 11 is connected to the blower hole 7b, that is, a blower path is formed around the infrared optical fiber 8.

Further, at the other end of the air pipe 11, a blower such as a rotary blade 12 is provided.

According to the configuration of the present embodiment described above, the airflow blown by the blower passes through the blower pipe 11 and is ejected from the air hole 7b of the field-of-view limiting horn 7, and from the infrared passing hole 5. An air flow into the heating chamber 1 is created.

Therefore, in this embodiment, water vapor generated by the heated object,
This example also has the advantageous effect of reducing the adhesion of the heated object to the end of the ultraviolet optical fiber 8 and the field-of-view limiting horn 7 due to scattering of the heated object.

In the above embodiments, the structure of a microwave oven according to the present invention has been explained in detail, but it can be used for various purposes.

Design changes may be made according to specifications, etc.

For example, in the embodiment, an infrared detector using a thermistor type sensor is used, but other detectors using a pyroelectric type sensor, for example, can also be used.

Further, in the embodiment, the viewing angle is set using a viewing field limiting horn, but the present invention need not be limited to this.

Furthermore, in order to form an air flow from the infrared passing hole to the inside of the heating chamber, a blowing hole is provided in the field-limiting horn, and a blowing path is further formed around the infrared optical fiber. A similar effect can be obtained by providing a rotating blade near the.

〔Effect of the invention〕

According to the present invention, it is possible to provide a microwave oven that can solve the problem of low reliability and a decrease in the output of an infrared detector.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a microwave oven according to the present invention. FIG. 2 is a partially cutaway enlarged view of the microwave oven shown in FIG. FIG. 3 is a block diagram showing an example of a control circuit. FIG. 4 is a characteristic diagram showing the dependence of the infrared detector output on the ambient temperature. FIG. 5 is a partially cutaway enlarged view of another embodiment of the microwave oven according to the present invention. Figure 6 shows the infrared detector output, the heated object and 1...
... Heating chamber, 3... Magnetron. 5...Infrared passing hole. 8...Infrared optical fiber. 10...Infrared detector, A...Between heated objects Yukio Yuyama Figure 1 Figure 2 Figure 3 Temperature of heated body (0C) Figure 4

Claims (2)

[Claims] (1) a heating chamber in which an object to be heated is placed; a high-frequency oscillator that supplies microwave energy into the heating chamber; an infrared passing hole provided in the wall surface of the heating chamber; an infrared detector connected to the other end of the optical fiber and detecting infrared rays emitted from the object to be heated and passed through the infrared passing hole; and an output of the infrared detector to activate the high frequency oscillator. A microwave oven characterized by comprising a control circuit for controlling the microwave oven. (2) The microwave oven according to claim 1, further comprising a blowing means for forming an air flow from the infrared passing hole to the inside of the heating chamber.