JPS599891A - High frequency heater with wireless probe - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-frequency heating device that wirelessly transmits and receives temperature data of a heated object and automatically performs heating control.

Conventionally, in high-frequency heating devices, the temperature of an object to be heated is detected by an exhaust temperature sensor, a humidity sensor, a gas sensor, or the like, and heating control is automatically performed. Since these methods indirectly detect the temperature of the object to be heated, it is difficult to accurately detect momentary temperature changes. As a method to eliminate these drawbacks, as shown in Fig. 1, a probe 6 equipped with a heat-sensitive element, such as a thermistor, is inserted into the heated object 2, and the temperature data is sent to the control system by wire 9, so that the temperature is automatically There are some that perform heating control.

Since this method can accurately detect the temperature of the heated object 2,
The temperature can be controlled to the user's preference.

However, this method cannot employ the turntable mechanism that is most effective for uniformly heating the object 2 to be heated.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a high-frequency heating device that accurately transmits and receives temperature data of a heated object wirelessly using ultrasonic waves as a medium, and automatically performs heating control. be.

The present invention is a wireless probe system that detects the temperature of a heated object with a probe equipped with a thermistor and transmits and receives the temperature data using ultrasonic waves. does not pass,
The ultrasonic wave is installed and fixed so that it can be received through a passing mechanism such as a punch hole or a mesh, thereby eliminating the effects of high frequency leakage.

Two embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is an overall perspective view of a high frequency heating device using a wireless probe. 1 is the high frequency heating device main body,
2 is an object to be heated, 3 is a heating chamber, 4 is a door for taking in and out the object 2 to be heated, and 5 is a turntable effective for uniformly heating the object 2 to be heated.

7 is a wireless probe that transmits the temperature of the object 2 to be heated. FIG. 3 shows an external view of the wireless probe, and FIG. 4 shows its configuration block diagram.

Reference numeral 9 denotes a part containing a power supply unit and an oscillation circuit, and 10 a protruding part that encloses a ped type SF mister and is inserted into the object to be heated 2. Moreover, 11 is a part provided with an ultrasonic transmitting element. The power supply section 12 can be implemented using a battery or by receiving microwaves in the heating chamber with an antenna and rectifying the waves with a diode to use as a power source. The entire wireless probe 7 is coated with metal, so there is no malfunction due to high frequency leakage. The oscillation section 13 is covered with a mesh or the like.

Eliminate the effects of high frequency, or remove the cover such as a mesh, and read the temperature data of the heated object when the high frequency power supply, which is repeatedly turned on and off, is turned off.

Implement a method to eliminate the effects of high frequencies. The wireless probe 7 is used by inserting the protrusion 10 in the case of meat, etc., and in the case of boiled soup, placing it inside the container and detecting the temperature. 15 is an amplifier, and 16 is a transmitting element section. Describe a system that detects temperature changes and transmits that data. A change in temperature of the object to be heated 2 is converted into a change in the resistance value of the thermistor 14, and the change in resistance value is replaced by a change in the oscillation cycle of the oscillation section 13, which is sent out from the transmitting element section 16.

Generally, as the temperature rises, the resistance value of the thermistor 14 tends to decrease (negative resistance); therefore, when used in an oscillation circuit such as an astable multivibrator, the oscillation period becomes shorter.

Next, the receiving system will be explained using FIG.

FIG. 5 is a schematic cross-sectional view of the heating chamber of FIG. 2. 17 is an ultrasonic receiving element, 1B is an amplifier circuit, 19 is a waveform shaping circuit,
20 is an I10 interface circuit, 21 is a microcomputer, and 22 is a high frequency heating drive power source.

23 is a magnetron that oscillates high frequency (for example, microwave). A signal transmitted from the wireless probe 7 inside the heating chamber 3 is received by an ultrasonic receiving element 17 provided outside the heating chamber 3. Since the received signal is a small signal, it is amplified by the amplifier circuit 18, rectified, and a pulse waveform is created by voltage comparison. Process this Norms waveform 10 Interface circuit 2
Connect to the microcomputer 21 through 0. Engineering 1
In the 0 interface circuit 20, for example, one period of transmission is counted at a constant frequency considerably higher than the transmission frequency of the probe 7, and the counted number is read by the microcomputer 21, and the relationship between the transmission period and the counted number is stored in the microcomputer 21 in advance. This is something you have to memorize so that you know the transmission cycle.

In the above method, when the set temperature is reached, that is, the transmission cycle for that temperature is reached, a signal is sent from the microcomputer 21 to the drive power supply 22, and the magnetron 23 is controlled.

In the transmission/reception system using ultrasonic waves as a medium described above, the means for installing the receiving element 17 will be described.

Figure 6 shows punch holes and mesh 25 in the open ceiling 24.
FIG. 7 is a schematic cross-sectional view of FIG. 6. The punch holes and the mesh 25 are mechanisms that have one function of not allowing the high frequency waves in the heating chamber 1 to pass through, but allowing the ultrasonic waves to pass therethrough. In an experiment, it was found that the higher the aperture ratio of the punched holes or mesh 25, the higher the received level of ultrasonic waves.

However, meshes with a large aperture ratio have the disadvantage that water droplets tend to adhere to them, causing clogging and reflecting ultrasonic waves. As a structure to overcome these drawbacks, the punch holes and the mesh 250 may be coated with a chemical substance that repels water, or air may be further blown to prevent clogging.

FIG. 8 shows an ultrasonic receiving element 17 mounted above the open ceiling 24.
The structure is such that the supporting base 27 is used as a guide to send cooling air from, for example, the magnetron 23 to prevent the punch holes and the mesh 25 from clogging.

FIG. 9 is a schematic cross-sectional view of FIG.
feed into the guide 27 in the direction of the punch hole or mesh 2
5 into the heating chamber.

A problem with such a structure is the effect of wind on the ultrasonic signal, but we have confirmed through experiments that although the wind slightly disturbs the waveform of the ultrasonic signal, it does not interfere with understanding it as a signal. There isn't. Therefore, it can be assumed that there is no influence from the wind.

Although the structure using the punched holes and the mesh 25 has been described above, a structure in which the ultrasonic element 17 is installed without using the punched holes or the mesh 25 will be described next. A structure without punch holes or mesh 25 has the advantage that there is no need to take measures against clogging such as water droplets, but the problem of radio wave leakage occurs.

FIG. 10 shows the same receiving element 1 placed above the cut-off waveguide 29.
7 is installed. As shown in the figure, the same waveguide 29
The opening size is a31. b32 and the length is 036. Generally, in a waveguide, let the free space wavelength of the microwave be λ, the guide wavelength be λg, and the cutoff wavelength be λC, and let us consider the forward wave exp' (=4βg) of the radio wave. here,
βg is a phase constant expressed as βg−2rrλg, and t represents the distance in the direction in which the radio wave travels within the waveguide. The relationship between the wavelengths of radio waves in the waveguide is expressed by the following equation.

λg −2a ・・・・・・・・・・・・(2
From equation 1 (1), if λC x λ, then βg becomes a positive real number, and the radio wave decays exponentially in the positive direction of t.

It will no longer propagate. Specifically a-b-10mm, c-
! Let's take a look at the Omm waveguide. The radio frequency used in domestic high-frequency heating equipment is 2450MH2, and λ is 122.4.
It will be 5mm. From formula (2), at λc-20mm, (1)
Calculate λg from the formula and find βg, βg −0
, 31. Therefore, the forward wave is eXp(-0,31t)
Then, when 1-30mm is substituted, the attenuation rate becomes 40 (iB) in terms of power, and the microwave leakage becomes significantly smaller and has no effect.

The following is a case where a nomend rejection filter is used. FIG. 12 shows a partially cutaway perspective view of the structure. A hole of about 30 mm square is made in the open ceiling wall 24, and a metal cylinder 35 of the same but slightly larger size is installed above the hole to determine its height.

30 mm (approx. 30 mm is approximately 1/4 wavelength of the radio waves (high frequency) used. A conductor plate 36 having a slit 37 is installed and fixed approximately vertically in the center of the metal cylinder 35, and the band Configure the rejection filter,
The ultrasonic receiving element 17 is fixed to a support base 38 on top of the ultrasonic receiving element 17 . FIG. 13 is a cross-sectional view of the conductor plate 360 having the slits shown in FIG. 12 in the plane direction. The width W40 of the slit 370 of the conductor plate 36 is set at a distance of 5 m to prevent discharge due to the strong electric field of high frequency.
m (Gap G-4 between square tube 35 and conductor plate 36
The length of the slit L39 is set to 5 mm to prevent any discharge from occurring, and if the length of the slit L39 is set to a little less than 1/4 of the free space wavelength of the radio waves (high frequency) used, the radio waves (high frequency) used can be reduced. 70-80d [Can be attenuated and satisfies legal regulations.

As described above, according to the present invention, it is possible to accurately detect the temperature of the object to be heated and automatically control the heating, and since the receiving element is easy to install, it can be done at low cost, and it also malfunctions due to the influence of high frequency. Therefore, it is possible to obtain a high-frequency heating device with excellent safety.

Note that the present invention can be implemented using transmission media other than ultrasonic waves, such as sound waves. ″

[Brief explanation of drawings]

FIG. 1 is an external view of a conventional high-frequency heating device using a wired probe, and FIG. 2 is an external view of a high-frequency heating device using a wireless probe according to an embodiment of the present invention. Third
The figure is an external view of the main body of the wireless probe, FIG. 4 is a block diagram of the configuration of the probe, and FIG. 5 is a plot diagram of the receiving system. FIG. 6 is a perspective view of a portion in which a receiving element is provided above the punched hole, and FIG. 7 is a sectional view of FIG. 6. FIG. 8 is a partial perspective view of the ventilation guide provided with a receiving element, and FIG. 9 is a sectional view of FIG. 8. 10th
The figure is a partial perspective view of a receiving element provided on the same cut-off waveguide, and FIG. 11 is a sectional view of FIG. 10. FIG. 12 is a partial perspective view of a receiving element provided on a band rejection filter of a conductor plate having the same slits, and FIG. 13 is a sectional view of FIG. 12. Explanation of symbols 1...High frequency heating device. 2...Object to be heated. 3... Heating chamber. 7...Wireless probe. 8... Turntable 17... Ultrasonic receiving element. 25... Punch hole or mesh. 27...Ventilation guide. 29...Cutoff waveguide. 35...Metal cylinder. 36...Band rejection filter. Applicant: Hitachi Thermal Equipment Co., Ltd. Figure 1 Figure 2 Figure 4 Figure 6 Figure 17 Figure 7 Figure 8 Figure 7 Figure 9 Figure 10 n Figure 11

Claims (1)

[Claims] A wireless probe has a heat-sensitive element that detects the temperature of the object to be heated in the heating chamber, an oscillation mechanism that changes the oscillation period or pulse period of the ultrasonic wave according to the detected signal, and a wireless probe that receives the signal from the glove. , an ultrasonic receiving element (17 ) is provided in a part of the wall of the heating chamber (5), which is a mechanism that does not allow high-frequency waves to pass through, but allows ultrasonic waves to pass through, such as a punched hole or a mesh (25). Or cut-off waveguide (29)
A high-frequency heating device equipped with a wireless glove, which is installed opposite to a metal cylinder (65) having a band rejection filter (36).