JPS5944790A - High frequency heater with wireless temperature 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 equipped with a wireless temperature glove that wirelessly transmits and receives temperature data of a heated object and automates heating control for cooking.

In conventional high-frequency heating equipment, the temperature, humidity, or gas generated from the heated object is detected using a thermistor, humidity separator, and gas sensor, respectively, as a method for automating heating control, and the complete finish of the heated object can be detected. There is something to do. There are also devices that measure the surface temperature of the heated object with an infrared sensor, detect the complete finish of the heated object, and perform automatic control.

In these methods, the detection sensor is installed outside the heating chamber away from the object to be heated so that it is not affected by high frequencies, etc., so although cooking operation 1 <] is good, the temperature of the atmosphere inside the heating chamber is , humidity and gas, there was some variation in finish, and it was difficult to detect the entire finish inside the heated object. Ushida infrared sensor'V
The area to be detected in the raw heating chamber is narrow, and it is impossible to detect if the area is too far away, and there are problems with the placement of the object to be heated and the shape of the stagnation. It was difficult to detect the internal finish of the heated object.

One way to solve these problems is to insert a glove equipped with a thermistor into the object to be heated, retrieve the temperature data via wire, and control the heating. : Since it is connected, there is a drawback that it cannot be used as a turntable, which is the most effective VC for preventing uneven heating of heated objects.

Therefore, they considered creating a wireless probe by incorporating a transmitting circuit into the probe, but because it uses a thermistor, it is difficult to make the relationship between temperature and oscillation frequency a completely linear characteristic, making it impossible to accurately capture it. The purpose of the present invention was to eliminate the above-mentioned drawbacks, and it is a wireless temperature sensor that uses a thermistor to make the relationship between temperature and frequency completely linear, and that can capture the temperature with high accuracy. To obtain a high frequency heating device equipped with a globe.

That is, in the above-mentioned wireless temperature glove, the temperature sensor is adjusted and the temperature is adjusted using the temperature control. The temperature change of the Jl-object is taken as a resistance value change, the resistance value change is converted into a voltage change, the linear voltage change is made through a logarithmic conversion circuit, and the above voltage is applied to a voltage controlled oscillator to change the 1 oscillation frequency. , it is transmitted via ultrasonic waves of 8 medium.

An embodiment of the present invention will be described below with reference to the drawings.

Figure 1 is a diagram of the entire microwave oven when using a wireless temperature globe. 11-. 1 is a main body of an electric oven, 2 is an object to be heated, 6 is a heating chamber, and 4 is a door. 5 is a turntable on which the object to be heated is placed, and has a rotating mechanism to prevent uneven heating during microwave heating. 6 is a wireless temperature glove of the present invention. In FIG. 1, a temperature probe 6 is inserted into the object 2 to be heated and transmits the temperature data of the object 2 to be heated. A receiving element is provided outside the heating chamber 6 and connected to a control circuit. The method of using this device and the operating order are as follows: 1) Place the object 2 to be heated on the tar table 5, fully insert the temperature globe 6, and close the door 4. 2
) The user sets the mold temperature on the control panel,
Press the start button/. 6) When microwaves enter the heating house, the object to be heated 2 is heated.

Temperature data is sent from the temperature glove 04) Reception 1
The temperature data on the cooking side is read in by a microcomputer, and when the temperature matches the set temperature, the control circuit 7i'l11 operates, and the red sea bream tron's power supply circuit becomes (,1P +-, indicating that cooking is complete).

Next, the main body of the wireless probe is shown in FIG.

7 is the 1-globe main body, and the internal IC has circuit parts and the like installed therein. 8 uses a thermistor as a temperature sensor,
1. Reference numeral 09, which is a part of the protrusion in which the thermistor is enclosed and is inserted into the object to be heated 2, is a part where the transmitting element f: is provided. The exterior of the glove is made of metal.

The inside of the glove should be sealed to prevent microwaves and moisture from leaking.

Figure 3 shows a diagram of the glove system.

FIG. 4 shows a specific circuit, and FIGS. 5 and 6 show the characteristics. In Fig. 6, 10 is a power supply section.

Reference numeral 11 denotes a part that converts a change in resistance value, which corresponds to the temperature of the thermistor, into a change in voltage. 12 is the logarithmic conversion circuit section 15
is a voltage controlled oscillator. 14 is a transmitting circuit section, and 15 is a transmitting element section. To explain this/stem, power supply 10
can be obtained by fully rectifying microwaves or using batteries. The resistance value of Zalmister used as a temperature sensor is generally expressed by a linear equation with negative resistance characteristics.

R" R25exp 11' (-!-yu) ・
・-・(1) 1' T2゜Here, "2s ViThe resistance value 13 of the thermistor at 25℃ is a positive constant, and +i'26 is the absolute temperature at 25℃.From equation (1), the resistance value 1 (, decreases exponentially with increasing temperature T (absolute temperature).

For example, in an oscillation circuit using an astable Margoux-by-break circuit, the relationship between temperature and oscillation frequency when a thermistor is installed in the gold resistance section is an exponential characteristic.

It is not possible to obtain linear characteristics. In order to make the above characteristics linear, even if a fixed resistance of 4=1 is added in parallel to the thermistor, it is not possible to obtain a completely linear characteristic 1r:σ. Therefore, with such characteristics, there is a drawback that it is impossible to improve the temperature accuracy.

A circuit configuration for solving these drawbacks will be explained below along with its operation. When a high resistor and a thermistor are connected in series, a multiple voltage is applied, and an electric current is output at the midpoint between the high resistor and the thermistor, the output type 1 is as follows: Decrease exponentially. Furthermore, when the above output voltage characteristic is manually inputted to the logarithmic conversion circuit section 12, the output voltage d changes linearly as the temperature rises. A voltage characteristic that changes linearly with respect to temperature is manually applied to a voltage controlled oscillator (hereinafter referred to as VCO) 13 to change the oscillation frequency. The VOO 13 generally has a linear voltage-frequency (vr) conversion, a large vr conversion gain, and good stability of the oscillation frequency even during thermal or long-time oscillation operations. Therefore, the system described above can convert temperature changes into linear changes in oscillation frequency.

FIG. 4 specifically shows the portion 11 that converts the temperature-induced resistance value change of the thermistor into a voltage change, and the logarithmic conversion circuit portion 12. As mentioned above, the thermistor RTH17 is connected in series with the high resistance 11.16, and the power supply voltage vcc18
is applied, and the voltage at the midpoint V, 19f: is output. This output voltage V119 corresponds to an increase in temperature.

As shown in FIG. 5, it decreases exponentially.

This characteristic is manually applied to a logarithmic conversion circuit composed of 20 operational amplifiers.
It uses the current-voltage characteristics of 1, and may also use the current-voltage characteristics of a diode.
), 22 is the output V of the 0 logarithmic conversion circuit for protection.
FIG. 6 shows the relationship between 223 and temperature. Looking at this characteristic, the output voltage v1 changes linearly with temperature. This characteristic VO(l) is manually applied to change the oscillation frequency linearly with respect to temperature, and the oscillation frequency output of VOO is transmitted from the transmitting element by manually applying the oscillation frequency to a transmitting circuit such as a series resonant circuit. The figure shows a block diagram of the receiver/stem.

24 is a receiving element r-, 25 is an amplifier circuit section, and 26 is a waveform shaping section. 27 is the I10 interface circuit section 2
8 is a microcomputer (hereinafter referred to as microcomputer). This is a power supply control circuit for Magnetro/60 that emits 29I'i microwaves.

This receiving system 'f: will be explained. A frequency corresponding to the internal temperature of the heated object 2 is transmitted from the wireless temperature globe 6 (
Ultrasonic waves with a period of '1') are transmitted. The receiving element 24 is installed through a hole 7 or a punched hole provided in the wall of the maven. The signal received by the receiving element 24 is amplified by an amplifier circuit 25, and the waveform shaping section 2 is composed of a parallel/parallel circuit, one/yoto multi-pipe circuit, etc.
At 6, the transmission signal (period 'r) of globe O is captured.

This signal (period 'I') is sent to I10 interface circuit 2.
Enter 7. 1.10 In the interface circuit 27,
An oscillation circuit for counting is provided, and one oscillation frequency (referred to as period To) is fixed.

The frequency should be greater than the transmitting frequency of the probe. Then, a counter is provided, the period T of the transmission signal is counted by the oscillation frequency for counting 1]'i''o, the counter is connected to the microcomputer 28, and the output of the counter is read by the microcomputer 28.The data read by the microcomputer 28 is processed. and detect the temperature of the glove.

Although not shown in the block diagram, it is also possible for the O5 to send signals from the Mico/28 and display the temperature. Once the temperature set by the user is reached.

Magnetron 60 power control circuit 29 VC microcomputer 2
A signal is sent from 8 and controlled.

As described above, according to the present invention, the temperature f of the heated object can be detected with high precision using a thermistor, and cooking can be automated. It has the effect of being able to be used for one person.

[Brief explanation of drawings]

FIG. 1 shows a wireless network according to an embodiment of the present invention. Overall vertical view of high-frequency heating device equipped with lobes, 2nd
Figure 1d is an external view of the same wireless probe, Figure 6 is a system block diagram of the wireless probe, Figure 4 is an explanatory diagram of the configuration of the logarithmic conversion circuit, Figure 5 is a voltage-temperature characteristic diagram of the thermistor, FIG. 6 is a temperature characteristic diagram of the output voltage of the homologarithmic conversion circuit, and FIG. 7 is a block diagram of the receiving nostem. 1...Microwave oven body. 2...Object to be heated. 5. Turntable. 6. Wireless temperature probe. 12... Logarithmic conversion circuit section. 16...Voltage controlled oscillator. Applicant: Hitachi Thermal Equipment Co., Ltd. Figure 1 Figure 2 Figure 5 Figure 6 Humidity t

Claims (1)

[Claims] A heat-sensitive element that detects the temperature of the object to be heated in the heating chamber, such as a thermistor, converts a change in resistance value of the heat-sensitive element due to a temperature change into a voltage, and converts it into a voltage through a logarithmic conversion circuit section 02 to convert the voltage into a linear voltage. Then, it is applied to the total voltage control oscillator θ3 to completely change the oscillation frequency. The transmission medium is characterized by transmitting through ultrasonic waves.
High frequency heating device with wireless temperature probe.