JPS599892A - 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 automates cooking control.

In conventional high-frequency heating equipment, as a method of automating heating sterilization, the temperature, humidity, or gas generated from the heated object is detected using a thermistor, humidity sensor, and gas sensor, respectively, and the finish of the heated object is detected. There is something. In addition, the surface temperature of the heated object is measured using an infrared sensor.
Some devices detect the finish of the heated object and perform automatic control.

These methods are installed outside the heating chamber, away from the objects to be heated, so that the detection sensor is not affected by high frequencies, etc., so the cooking operation is good, but the temperature, humidity, and Since gas is detected, it is difficult to control the heating at an intermediate temperature of the object to be heated, which results in slight variations in the finish. The method using infrared sensors has a narrow detection area and cannot be detected outside of that area, and has problems with the installation position of the object to be heated, the shape of the container, etc. To solve these problems, a probe equipped with a thermistor is inserted into the heated object.

There is a method that extracts the temperature data via wire and performs heating control. This method can accurately measure the temperature of the object to be heated, and also allows heating to be controlled at a temperature desired by the user. However, because the probe is connected by wire to a control circuit outside the heating chamber, the turntable method, which is effective in preventing uneven heating of the heated object, cannot be used.

A wireless probe can be considered as a method to eliminate the above-mentioned drawbacks. This transmits temperature data of the heated object from the globe using radio waves, ultrasonic waves, or light as a medium.
The signal is received outside the heating chamber and heating control is performed, and this method also allows the use of a turntable. In addition, this probe uses a bead-type thermistor as a temperature detection element sealed at the tip of the probe, detects changes in the temperature of the object to be heated as changes in resistance value, and sends signals as changes in resistance value as changes in voltage or changes in oscillation frequency. A battery can be considered as a power source for the electronic circuit for this transmission, but batteries have a limited lifespan and must be replaced. The antenna receives the high frequency waves inside the heating chamber without using batteries.

It is conceivable to rectify this with a diode and use it as a power source.

The present invention has been made to realize the above-mentioned wireless probe, and it is an object of the present invention to provide a high-frequency heating device equipped with a wireless probe that is stable against changes in ambient temperature and power supply voltage and is easy to use. purpose.

In order to achieve this goal, two oscillation circuits consisting of astable vibrators were provided, and the first oscillation circuit converted the resistance change of the heat-sensitive element into an oscillation frequency.

The second circuit oscillates a fixed frequency that resonates with the ultrasonic transmitting element, connects the output signals of both circuits to the ultrasonic transmitting element via an AND circuit, and transmits using ultrasonic waves as a medium.
Furthermore, the power source for the electronic circuit of the transmitting section is obtained by receiving high frequency waves with an antenna and rectifying them with a diode.

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

FIG. 1 is an overall perspective view of a high-frequency heating device using a wireless probe, in which 1 is the main body of the high-frequency heating device, 2 is a control panel, 3 is a heating chamber, and 4 is a door. 5 is a turntable.

6 is an object to be heated, and 7 is a wireless probe.

As shown in this figure, the wireless probe 7 is inserted into the object to be heated and transmits temperature data of the object. A receiving element is provided outside the heating chamber and connected to a control circuit. The medium for transmitting the signal is ultrasound. How to use this device and the order of operation.

(1) Place the object to be heated 6 on the turntable 5, insert the wireless probe 7, and close the door 4.

C) Set the desired temperature on control panel 2.

Press the start button.

6) When high frequency waves enter the heating chamber, the object to be heated 6 is heated and temperature data is transmitted from the probe 7.

(4) When the set temperature matches the value of the transmitted temperature data, the control circuit operates, the magnetron power supply circuit is turned off, and cooking is completed.

Next, the main body of the wireless probe 7 is shown in FIG. Reference numeral 8 denotes a protrusion in which a beat-shaped thermistor is enclosed, which is inserted into the heated portion 6 . 9 is a part containing a transmitting element. Further, the transmitting circuit section is housed in the main body 7.

A power source for the transmitting circuit is provided with a receptacle in a part of the probe 7, which receives high frequency waves within the heating chamber 3, and rectifies the waves with a diode.

In the Wireless Probe 7 system, the thermistor interprets temperature changes as changes in resistance.

The change in resistance value is converted into a change in oscillation frequency, and a temperature data signal is transmitted from the ultrasonic transmitting element. The transmitted signal is received by a receiving element installed outside the heating chamber 3, amplified and waveform-shaped, and a microcomputer reads the pulse period of this pulsed temperature data signal, performs arithmetic processing, and transmits the signal to the heated object. Understand the temperature of things.

FIG. 5 shows a block diagram of the transmitting circuit of the probe. 1
2 is a power supply section, 13 is a first oscillation circuit whose frequency changes according to changes in the heat sensitive element (thermistor) 14, and 15 is a second oscillation circuit that oscillates at a fixed frequency that resonates with the ultrasonic transmitting element 17.
16 is an AND circuit that ANDs the outputs of the two oscillation circuits, and 17 is an ultrasonic transmitting element.

In the block diagram of FIG. 3, the heat-sensitive element 14 and the first
A specific circuit of the oscillation circuit 16 is shown in FIG. The first oscillation circuit 13 is an innocent transistor (CM with low power consumption).
(using an OS inverter).

This is an astable multi-noise ibrator circuit that uses CR charging and discharging. The oscillation period T28 (shown in FIG. 5) of this circuit 13 is generally expressed as T-2,2RTCT. Therefore, if RT14 is a thermistor, the oscillation period T
2B changes depending on the temperature change, and as the thermistor has a tendency for the resistance value to decrease (negative resistance) as the temperature rises, the period becomes shorter. In the same circuit 13, the resistor R521 is a protective resistor for reducing the current flowing through the input protection diode of the input terminal A18. FIG. 5 shows voltage waveforms at the input and output of the inverter of the first oscillation circuit 13'. In this diagram.

For the power supply voltage, let the low level (ground) be VS[l.

When the high level is set to DD, the threshold voltage of the inverter is set to VTIli. The voltage waveform of fa125 is as follows.

The waveform of input voltage VI22 of inverter A18 is RT1
4 and C! Such a waveform is obtained due to repeated charging and discharging of T20. Also, the voltage waveform of (2) 26 shows the voltage waveform of T223, but since the inverter A18 operates (inverts) at the threshold voltage VTR, it becomes a rectangular wave with slow rises and falls. Furthermore, the output voltage ■.

Since the inverter B19 operates (inverts) at the threshold voltage of the voltage waveform 26 (indicated by c127), the voltage waveform 24 becomes a shaped rectangular wave.

Next, FIG. 6 shows a concrete circuit of the entire block diagram of FIG. 5. In FIG. 6, the first oscillation circuit 13 includes a differential circuit 30 composed of a capacitor C229 and a resistor R330.
A, inverter E32 and inverter P3302
The buffer 33A is connected to the buffer 33A.

Further, a second oscillation circuit 15 which is the same multivibrator circuit as the first oscillation circuit 13 is provided. The oscillation period T of this circuit 15 is expressed as T -2,2R201.

The frequency f becomes f-1. This oscillation frequency f.

The values of resistor R238 and capacitor +j (3t39) are determined to match the natural frequency of the ultrasonic transmitting element 17.

Fix it.

The output of the buffer 33A and the output of the second oscillation circuit 15 are
The signal is input to the ND circuit 16, and the ultrasonic transmitting element 17 is connected to the output of the AND circuit 16.

FIG. 7 shows voltage waveforms at each point in FIG. 6. Figure 7 Te (2
)44 is the voltage waveform of V24, CB45 is T331 +
7) Voltage waveform, IC546 is T434 voltage waveform, ■
)47 is the voltage waveform of T540, and O]4B is the voltage waveform of T643. Here, the power supply voltage assumes the low level to be 0,
...The level is set to VDD. (2) 44 is the fifth
It is the same as (C!127) in the figure.

A waveform of 03145 is obtained by differentiating this rectangular wave. The time constant τ of the differentiating circuit 30A is expressed as τ-C2·R3·, and determines the pulse width Tl49 of the output waveform of the buffer 33A at +0146. +D147 is a shaped rectangular wave (C!146 output waveform and 047 output waveform are A
When ND is taken, the output waveform of ■48 is obtained. When this output is applied to the ultrasonic transmitting element 17, when the pulse rises ('
T149'), ultrasonic waves are transmitted very efficiently and the period is T28.

FIG. 8 shows a block diagram of the receiving system. Ultrasonic waves transmitted from the wireless probe 7 at a period T28 are received by an ultrasonic receiving element 49 provided outside the heating chamber through a punch hole or a mesh. The received signal is amplified by an amplifier circuit 50 and rectified to create a rectangular wave using a comparator or the like, and waveform shaping 51 is performed. Furthermore, this waveform with period T28 is input to the interface circuit 52, and the microcomputer 53 reads the period T, that is, detects the temperature of the object to be heated 6, and the microcomputer 53 controls the power source 54 of the magnetron 55.

Therefore, according to the present invention, the temperature of the object to be heated can be grasped with high precision, cooking 9 can be automated, and a turntable, which is most effective in reducing heating unevenness in microwave heating, can also be used.

The external view of the thermal device, Figure 2 is from book #l! - An external perspective view of a wireless probe according to an embodiment of the present invention, and FIG. 3 is a block diagram of the configuration of the same probe. Figure 4 shows an astable multivibrator circuit using the same thermistor, and Figure 5 shows the astable multivibrator circuit using the same thermistor.
These are voltage waveforms at various parts in the figure.

Figure 6 shows the specific electrical circuit of the entire probe.

FIG. 7 shows voltage waveforms at various parts in FIG. 6.

FIG. 8 is a block diagram of the receiving system.

13.15...1st. Second oscillation circuit.

16...AND circuit.

17...Ultrasonic transmitting element.

30A... Differential circuit.

33A...Buffer.

Applicant: Hitachi Thermal Appliances Co., Ltd. Figure 4 Figure 5 Figure 7 Figure 8

Claims (1)

[Claims] A wireless probe that 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 frequency according to the detected signal, and a transmission mechanism that transmits ultrasonic waves, and receives signals from it. In a high-frequency heating device equipped with a wireless probe, which has a mechanism that reads the oscillation frequency with a microcomputer, captures the temperature of the heated object, and automatically controls cooking, two oscillation circuits (13 ) (1s), the first oscillation circuit (13) uses a heat-sensitive element such as a thermistor to convert the change in resistance value into a change in the oscillation frequency, and the second oscillation circuit (15) uses an ultrasonic transmitting element (17 )-, and the first oscillation circuit (13), the differentiating circuit (30A), and the buffer (33A) are connected in series, and the output signal of the buffer (33A) and the second oscillation circuit ( 15)
The output signal is connected to the ultrasonic transmitting element (17) via an AND circuit (16), and the power source is configured with a rectified high-frequency wave, thereby obtaining a stable oscillation frequency over a wide temperature range. A high-frequency heating device equipped with a wireless probe.