JPS60232690A - High frequency heating device - 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 Field of Industrial Application The present invention relates to a food temperature detection circuit using a temperature sensor, so-called meat probe, as a means for directly detecting food heating temperature in a high frequency heater. The present invention relates to a configuration for reducing a detected temperature error caused by an increase in contact resistance at the meat probe glue receptacle portion due to the formation of an insulating film.

Configuration of conventional example and its problems Conventionally, as shown in FIG. 1, in a high-frequency cooking device using the above-mentioned meat probe, an object to be heated such as beef 9 is placed on a food rotating table 3. A meat probe 7 serving as a temperature sensor for detecting the temperature of the object to be heated 9 is inserted into the food 9 for cooking. One end of this meat probe is attached to a rotating receptacle 8 provided on the ceiling of the heating chamber 2, and the receptacle
Temperature information from the food is transmitted to the control unit via the electrode (contact piece) in 8.

By the way, the food being cooked is heated evenly from the periphery of the food while being rotated by the rotary mounting table-3. Meat probe inserted into food as food rotates.
Of course, rotational force is also applied to 7. In order to prevent the meat probe from twisting or even falling off due to this rotational force, in the receptacle 8, both terminals of the meat probe 7 are connected to the electrode pieces (contactors) of the septa crew 8.
It has a structure that allows it to slide. FIG. 2 shows a sectional view of the meat probe 7 inserted into the receptacle 8, and its structure will be described. The tip of the meat probe 7 has electrode parts 10 and 11 connected to both ends of the temperature sensor, respectively, and maintains electrical contact with contacts 12 and 13 provided on the corresponding septa crew 8 side, respectively. That's why. And contactor 12.
The temperature sensor is connected from 13 to the control circuit via a lead wire 14. At this time, it is better to set the contact pressure between the contactor 12.degree. 13 and the electrode portion 10.11 of the meat probe 7 as small as possible so that the meat probe 7 can rotate smoothly.

Next, FIG. 3 shows a conventional example of a control circuit. IC1-15
is a one-chip microcombi unit (hereinafter abbreviated as microcomputer) that has an A/Di conversion function inside. Temperature sensor 1 installed at the tip of meat probe-7
6 and the voltage dividing resistor -17 constitute a voltage dividing circuit, and the divided voltage is inputted as analog data to the Φ port of the IC1-15.

Next, problems in the conventional example as described above will be described. As already mentioned, in order to prevent the meat probe from twisting due to rotation of the food product, the contact pressure between the meat probe 11 and the contacts 12 and 13 of the receptacle must be reduced. However, if the contact pressure is reduced, an insulating film is likely to form between the contacts, which not only makes it impossible to correctly detect the information from the temperature sensor, but also causes the contact resistance to increase even though the meat probe is inserted correctly. This may lead to a problem where it is mistakenly determined that the meat probe has been pulled out, and cooking is interrupted at that point.

OBJECT OF THE INVENTION Therefore, the present invention solves the above-mentioned conventional drawbacks.
Even if the contact pressure between the receptacle and the meat probe is small,
An object of the present invention is to provide a high frequency cooking device that can accurately detect information from a temperature sensor.

Structure of the Invention In order to achieve the above object, the temperature sensor circuit of the present invention has a switch means for periodically applying a high voltage to the temperature sensor, and by applying the high voltage,
It breaks the insulating film that forms on the contact area and inputs the correct information from the temperature sensor.

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

In Figure 4, the microcontroller's nonΦ port that inputs the signal from the temperature sensor has a voltage dividing resistor R1 connected to the temperature sensor resistor Rth and a reference voltage (Vve f, ) forming a voltage dividing circuit. , the collectors of transistor Q1 are connected. The emitter of this transistor Q1 is connected to the -18V power supply, and when the signal from the output port R8 of the microcontroller becomes high level (+9.V), this transistor Q1 becomes conductive, so that the A/I) port The voltage will be forced down to -18v.

As a result, although it is not shown on the drawing and at both ends of the temperature sensor Rth, the contact resistance existing between the contact of the receptacle and the meat probe has a voltage of 9V+18V.
A high voltage of 27 V is applied, which makes it possible to break through the insulating film, which is the cause of the increase in contact resistance. By the way, when the transistor Q1 is in a non-conducting state, the A/I) port of the microcomputer is separated from the -18V line, and the resistance Rth of the temperature sensor and the voltage dividing resistor R1
The voltage level is determined as temperature information from +9v to +4v.

Therefore, the timing at which the microcomputer takes in this temperature information must be at least when the transistor Q1 is in a non-conducting state.

FIG. 5 shows an example of these timings. First, Fig. 5 f and l are the output signals of the R8 port of the microcomputer, and when the voltage is +9V, the transistor Q1 is conductive.

Next, FIG. 5 (bl) shows the timing at which the microcomputer takes in the value of the A/I port and performs the Le Φ conversion process internally.
The process was performed more than m5ec ago. Next, the fifth
Figure (c) shows the voltage level of the Φ port of the microcontroller, in other words, the potential applied to the insulating film between the mead roller and the contact of the receptacle. Then, a high voltage is applied. FIG. 4(d) shows the current flowing through the temperature sensor when the temperature sensor resistance is 30Kf. From Figure 6, a graph of sensor resistance vs. temperature characteristics, when the sensor resistance is 30 Kr, the temperature is approximately 40°C.
It is. As the temperature rises and the resistance value reaches the order of IKr, the degree of adverse effects caused by the insulating film will still decrease. ), it becomes difficult to break through the insulation film. Therefore, regularly
It is necessary to apply a high voltage to the insulating film at a timing when the Φ conversion process is not performed to break the voltage.

On the other hand, if this high voltage is applied for a long time, the effect of self-heating of the temperature sensor element cannot be ignored.
The high level time of the R8 port is set so that the average self-heating of the temperature sensor itself is 10 mW or less. Further, the A/I) read timing is also set after the R8 port becomes low level (-1aV) and after waiting for the voltage level of the R8 port to stabilize after a sufficient period of time.

Furthermore, a system configuration in which the R8 port is also used for other key scan signals, etc. is also conceivable.

Effects of the invention The effects of the invention will be described below. First, even if the contact pressure between the meat probe and the contact of the receptacle is small, by applying a high potential, the insulating film formed between them can be broken and electrical continuity can be restored. The probe can rotate and slide smoothly within the receptacle, eliminating the possibility of the meat probe twisting or falling off, which was common in the past with rotary mounting type high-frequency heating devices. At the same time, since the contact pressure can be small, the contactor itself can be made smaller, and the cost of the receptacle can be reduced.

Second, if a high electric field is constantly applied to break the insulating film, accurate temperature information cannot be obtained due to self-heating of the temperature sensor.

Therefore, by periodically applying a pulsed high electric field as in the present application, the influence of self-heating of the temperature sensor can be minimized.

Finally, by applying the high electric field in a pulsed manner, the power consumed by the circuit system can be saved, and the cost of the power supply circuit can also be reduced.

[Brief explanation of the drawing]

Figure 1 is an external view of a high-frequency heating device with a rotary meat probe, Figure 2 is an explanatory diagram of the rotary meat probe with a glue receptacle installed, Figure 3 is an explanatory diagram of the control circuit of a conventional high-frequency heating device, and Figure 4 5 is a circuit diagram of a temperature sensor circuit section which is an embodiment of the present invention, FIG. 5 is an explanatory diagram of the operation of each part and function of the temperature sensor circuit of FIG. 4, and FIG. 6 is a resistance-temperature characteristic diagram of the temperature sensor. be. 3... Rotating mounting table, 7... Meat probe, 8... Receptacle, 10.11...
...Meat probe terminal section, 12.13...
Receptacle contact, 16...Temperature sensor,
17...Voltage dividing resistor, 19...Transistor. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 4 Figure 5 tL+-V”1 ↑ ↑

Claims (1)

[Claims] A heating chamber for storing food, a high-frequency oscillator for supplying high-frequency power to the heating chamber, a meat probe for detecting the internal temperature of the food, a circuit for converting information from the meat probe, and a circuit for controlling cooking. a control unit, a second voltage source different from the voltage applied to the meat probe during conversion, a switch means for applying the voltage of the second voltage source to the meat probe, and a control means thereof; A high-frequency heating device comprising: a high-frequency heating device configured to periodically apply a voltage from the second voltage source to the meat probe for a short period of time.