JPH03145083A - Temperature controller of heat cooking appliance - Google Patents

Abstract

PURPOSE:To prevent abnormal temperature increase in a heat cooking chamber by setting a second analog voltage input terminal to be at least or at most a prescribed voltage at the time of treatment of a first analog voltage input terminal and stopping a heating means when the first analog voltage input terminal is more than or equal to or less than or equal to a prescribed voltage. CONSTITUTION:Conversion means 4, 5 convert temperature of a heating chamber 12 or an object 13 to be heated into analog voltage and a microcomputer 3 has a first analog voltage input terminal 1 to control a heating means 11 by sending analog voltage and a second analog voltage input terminal 2 to send and process the other analog voltage. At the time of processing an input of the first analog voltage input terminal 1, the voltage of the second voltage input terminal 2 is set to be at least or at most a prescribed voltage and at the time that the first analog voltage is more than or equal to or less than or equal to a prescribed value, the heating means 11 is shut. In this way, abnormal temperature increase in the heating chamber is prevented beforehand.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a temperature controller in a heating cooker.

Conventional technology Traditionally, the temperature controller of a heating cooker uses an analog voltage input terminal (hereinafter referred to as A/D input) of a microcomputer (hereinafter referred to as "microcomputer") to capture changes in the resistance value of a thermistor due to temperature. Heaters and other heating means have been controlled by converting them into digital values inside a microcomputer and processing programs, but as microcomputers have become smaller, the distance between terminals has become smaller, resulting in problems with reliability, such as problems caused by short circuits between terminals. The number of issues has increased.

A conventional example will be described below with reference to the drawings.

As shown in Figure 5, A for detecting the heating chamber temperature of the microcomputer 3.
/D The voltage obtained by dividing the reference voltage 8 by the dividing resistor 6 and the heating chamber thermistor 4 is input to the human power 1. Further, a voltage obtained by dividing the reference voltage 8 by the dividing resistor 7 and the food temperature thermistor 5 is input to the A/D input 2 for food temperature detection. FIG. 6 is a flowchart showing the operation of this microcomputer 3. As shown in this figure, the microcomputer 3 turns off the heater output terminal 9 when the A/D human power 1 for heating chamber temperature detection is 5V or Ov. Turn off heater relay IO to cut off power to the heater. This is to detect a failure by determining that the heating chamber thermistor is disconnected when the A/D input 1 is 5V, and is short-circuited when it is 0.

If the above failure is not the case, compare the A/D manual input voltage with the voltage set as the voltage when the temperature inside the heating chamber is abnormal, and if the input voltage is low, it is determined that the temperature inside the heating chamber has risen abnormally. Turn off the heater 11. If the input voltage is higher than the set voltage, compare the voltage of A/D manual 2 with the voltage set as the temperature inside the food at the end of cooking, and if the input voltage is lower, the temperature inside the food will rise and the food will start cooking. It is determined that the process is finished and the heater is turned off.

Problems to be Solved by the Invention However, in this configuration, if there is a short circuit between the A/D input terminal 1 and other terminals of the microcomputer, the voltage at which that terminal is determined to be a failure in the A/D input processing, that is, Ov or 5V, is short-circuited. If it is, it can be determined that there is a failure, but if the voltage is between Ov and 5■, that is, analog voltage, the microcontroller cannot determine that it is a failure.
For example, if a short circuit failure occurs between A/D input 1 and A/D input 2 during heating operation, A/D input 1 will have parallel resistance values of dividing resistor 6 and dividing resistor 7, heating chamber thermistor 4, and food. A divided voltage of the parallel resistance value of the temperature thermistor 5 is input.

In other words, even though the thermistor is at high temperature, the microcontroller's A
A voltage at a low temperature is input to the /D input 1, and the temperature is controlled. Especially during self-cleaning, which requires high-temperature control, the limiting temperature will be higher than normal, which could lead to a fire! There was la.

Therefore, the present invention detects a short-circuit failure between terminals of a microcomputer before it reaches a dangerous condition, and stops the operation.
The purpose is to take appropriate measures.

Means for Solving the Problems In order to solve the above problems, the present invention provides a converting means for converting the temperature of a heating chamber or an object to be heated into an analog voltage, and a first converting means for controlling the heating means by inputting the analog voltage. A micro combinator has an analog voltage input terminal and a second analog voltage input terminal for inputting and processing another analog voltage, and when processing the input of the first analog voltage input terminal, the second analog voltage input terminal is used. Connect the terminals to the specified voltage or lower.
or more, and if the first analog voltage is below or above a predetermined voltage, the heating means is cut off.

Operation Due to the above tl, when the temperature is detected by the first A/D input and the heating means is controlled, the first A/D input and the second A/D input are
When the /D input is short-circuited, since the second A/D input is set at a predetermined voltage or higher or lower, the first A/D input also becomes the same voltage. Here, as a temperature detection process in the microcomputer program, if the first A/D input is above or below a predetermined voltage, it is determined to be an abnormal state and the heating means is turned off to prevent erroneous temperature detection. be able to.

EXAMPLE Hereinafter, a temperature controller for a heating cooker according to an example of the present invention will be explained with reference to the drawings.

As shown in FIG. 2, the heating chamber thermistor 4
A zero food temperature thermistor 5 is inserted into the food to detect the temperature inside the food and converts each temperature into a resistance value together with the heating chamber thermistor 4 described above. It is something. FIG. 3 shows the change in resistance value of each thermistor with respect to temperature. The heating chamber thermistor 4 divides the dividing resistor 6 and the reference voltage 8 and outputs A/
Apply to D input 1. This voltage is the reference voltage 8 VREF
.

The dividing resistor 6 is RD, the heating chamber thermistor 4 is RTtl,
If the voltage of A/D human power 1 is VTR, then VTH-VRE
FXRTH/RTR+RD.

The food temperature thermistor 5 divides the dividing resistor 7 and the reference voltage 8 and applies the divided voltage to the A/D input 2. This voltage is the reference voltage 8
[1EtF, divider resistor 7 RD, food temperature sensor 9
5 is RTH, A/D human power 2 voltage is VT)R: Then,
vTH-VREF XRTH/RT)I+RD.

The microcomputer during heating outputs the heater output terminal 9 according to the program.
is set high, heater relay IO is turned on, and heater 11 is energized, and A/D input 1 and A/D input 2 are processed in a time-sharing manner to control heater 11.

Figure 4 is a flowchart of temperature detection by the heating chamber thermistor and food temperature thermistor. The chamber thermistor 4 determines that the wire is disconnected and turns off the heater.

Otherwise, check if the voltage of A/D input 1 is OV.
If v, the heating chamber thermistor is shorted or A
/D It is determined that there is a short circuit between the power source 2 and the heater, and the heater is turned off.

If it is not Ov, compare the A/D input input hole voltage with the voltage set as the voltage when the heating chamber temperature is abnormal, and if the input voltage is low, it is determined that the temperature inside the heating chamber has risen abnormally, and the heater is turned off. Turn off. If the input voltage is higher than the set voltage, switch A/D input 2 to input, and
The input voltage of the D input 2 is compared with the voltage set as the temperature inside the food at the end of cooking, and if the input terminal is low, the temperature inside the food rises, and it is determined that cooking is completed, and the heater 11 is turned off.

Effects of the Invention As described above, the following effects can be obtained in the temperature controller of the heating cooker of the present invention.

By setting the voltage that is judged to be abnormal on the program and applying that voltage to other terminals, it is possible to detect short-circuit failures between other terminals without installing a special circuit. It is possible to prevent an abnormal temperature rise in the heating chamber at the time of the above short circuit.

Furthermore, since no voltage is applied to the thermostat except when the microcomputer processes the input voltage, electrolytic corrosion can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a temperature controller of a heating cooker according to an embodiment of the present invention, Fig. 2 is a configuration diagram of the heating cooker, and Fig. 3 is a temperature vs. resistance of a heating chamber thermistor and food temperature +1 star. FIG. 4 is a flowchart showing the processing of the microcomputer in an embodiment of the present invention, FIG. 5 is a circuit diagram of a temperature controller of a heating cooker in a conventional example, and FIG. 6 is a microcomputer in a conventional example. 3 is a flowchart showing the processing of FIG. 12...A/D input terminal, 3...Microcomputer, 4...Heating chamber thermistor, 5...
・Food temperature thermistor, 6.7... Division resistor,
8...Reference voltage, 9...Heater output terminal, lO...Heater relay, 11...
Heater, 12... Heating chamber, 13... Food.

Claims (1)

[Claims] a heating chamber, a heating means for heating the heating chamber or the object to be heated, a converting means for converting the temperature of the heating chamber or the object to be heated into an analog voltage, and heating by inputting the analog voltage obtained by the converting means. A first analog voltage input terminal for controlling the means and a second analog voltage input terminal for inputting and processing other analog voltages.
The microcomputer is equipped with a microcomputer having analog voltage input terminals, and when processing the first analog voltage input terminal, the second analog voltage input terminal is
A temperature controller for a heating cooker, characterized in that the first analog voltage input terminal is set to a predetermined voltage or below or above a predetermined voltage, and the heating means is cut off if the first analog voltage input terminal is below or above a predetermined voltage.