JPS621488B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electronically controlled cooking device that automatically cooks food by detecting the state, for example, the temperature, of food placed in a heating chamber. This type of cooker is usually equipped with a microcomputer (hereinafter referred to as μCOM) that controls electronic control, and in addition to μCOM, it basically has a temperature detection device that outputs a voltage value depending on the food temperature. , digital-to-analog conversion means, and comparison means. That is, when a temperature-corresponding digital signal is output from μCOM, this output is passed through a digital-to-analog conversion means to become a temperature-corresponding voltage value, and this voltage and the voltage value output from the temperature detection means are compared by a comparison means. , μCOM recognizes that the food temperature has reached the temperature corresponding to the digital signal when the comparison means outputs a matching signal. However, if the temperature detection means is of a non-contact type, such as one that measures the food temperature by detecting infrared rays emitted from the food, the temperature versus output voltage characteristics of the detection means have a non-linear relationship. . On the other hand, the input/output characteristics of the digital/analog conversion means are in a linear relationship, and therefore, before comparing with the comparison means, one of the output of the temperature detection means or the output of the digital/analog conversion means must be adjusted to the output characteristics of the other. Approximate correction is required. However, this type of correction circuit is complicated and its adjustment is also complicated. An object of the present invention is to make use of the characteristics of electronic control to eliminate the need for the above-mentioned correction circuit. FIG. 1 shows a microwave oven as an embodiment of the present invention. This microwave oven is equipped with μCOM1 as an electronic control means.
The cooking conditions corresponding to multiple menus, specifically each finishing temperature, are stored in the memory, and when you specify the desired menu using the keyboard 2, the μCOM1
controls the heating energy generating means 4 based on the comparison result between the finished temperature of the menu and the output of the non-contact temperature detecting means 3 that detects the food temperature. The heating energy generating means 4 includes a magnetron 5 for supplying microwaves to the heating chamber, a high voltage rectifier circuit 6 for applying a DC high voltage to the magnetron,
It consists of a switching circuit 8 that transmits power from a commercial power source 7 to a high voltage rectifier circuit 6. The switching circuit 8 includes a bidirectional thyristor and has a μCOM
When a heating instruction signal is given from 1, the thyristor becomes conductive due to the signal, and commercial power is transmitted to the high voltage rectifier circuit 6 through the thyristor in the conductive state. The keyboard 2 is provided with 20 menu designation keys A to T and a start key, assuming that cooking conditions corresponding to 20 types of menus are currently stored in the μCOM 1. The μCOM 1 includes an input register 9 that stores the type of menu input from the keyboard 2 as a 5-bit binary code, a fixed storage section 10 that stores in advance the cooking conditions (finishing temperature) for various menus, and I ₁ ~
It includes an 8-bit output register 11 that outputs to the output terminal of _I8 . As shown in the table below, the finishing temperature corresponding to each menu is stored in the fixed storage unit 10 as an 8-bit logic code at the address corresponding to each of the above menu codes, and a predetermined logic code is output when temperature is measured. Set in register 11.

[Table] The digital-to-analog conversion means 12 is constituted by a well-known resistance ladder circuit, and inputs an 8-bit logic code and outputs a voltage corresponding to each logic code. At this time, it should be noted that the input logic code is from [00……………0] to [11……………
1], the input signal versus output voltage characteristic is linear when changing in a binary manner. Straight line A in FIG. 2 shows this situation, in which the upper horizontal axis represents the 8-bit logic code in decimal notation, and the vertical axis represents the output voltage. The non-contact temperature detection means 3 includes a pyroelectric infrared sensor 13 made of lithium tantalate or the like, a semiconductor diode 14 for reference temperature measurement, and a perforated circular plate for intermittent infrared rays 15 entering the infrared sensor 13 at regular intervals. 16 and a motor 1 for rotating the disc.
7, a photointerrupter 18 for detecting the period of the perforated disk, and a processing circuit 19. The motor 17 receives power from the commercial power source 7 via a motor switching circuit 20 which is turned on in response to a motor instruction signal from μCOM1. The processing circuit 19 includes a photointerrupter 18
The output of the sensor 13 is synchronously rectified and amplified based on the output of the diode 14, and then the reference temperature is corrected based on the output of the diode 14. The temperature detecting means 3 itself is well known as seen in Japanese Patent Publication No. 10468/1983. The sensor 13 is attached near the upper wall of the heating chamber and detects infrared rays emitted from food placed in the heating chamber. Therefore, the temperature detection means 3 generates a voltage according to the temperature of the food, but it should be noted that the temperature vs. output voltage characteristic is non-linear. Curve B in FIG. 2 shows this situation, in which the lower horizontal axis represents the food temperature and the vertical axis represents the output voltage. Comparison means 21 is digital-to-analog conversion means 1
2 and the voltage value of the temperature detection means 3, and when the latter becomes larger than the former, a signal is output. The μCOM 1 receives this signal at a predetermined timing and controls the heating energy generating means 4. The operation of the above microwave oven is as follows. First, when a desired menu key is operated on the keyboard 2, a 5-bit menu code corresponding to the key is stored in the input register 9 of the μCOM 1. Next, when the start key is operated on the keyboard 2, the μCOM 1 uses the menu code stored in the input register 9 as an address, reads out the 8-bit logic code in the fixed storage unit 10 corresponding to the address, and sends this to the output register 11. Set to . It goes without saying that the logic code set in the output register 11 at this time represents the finishing temperature corresponding to the designated menu. A voltage corresponding to the temperature is generated from the digital-to-analog conversion means 12. The μCOM 1 then drives the heating energy generating means 4 and the motor 17, respectively, whereby the food is microwave heated and its temperature begins to rise, and the temperature detecting means 3 generates a voltage corresponding to the temperature. μ
COM1 then compares the comparison means 21 with a period of 1 second, for example.
When a matching output is generated, it is assumed that the food temperature has reached the expected finishing temperature, and the heating energy generating means 4 and the motor 17 are stopped, and the input register 9 and the output register 11 are checked. After clearing the contents, cooking is complete. Now, the embodiment of the present invention is characterized by the setting rules for the logic codes stored in the fixed storage unit 10. That is, referring to FIG. 2, if the planned finishing temperature is 80°C, for example, as shown by the dotted line in the figure, the output voltage value of the temperature detection means 3 when the food temperature is 80°C is determined from curve B. Then, from the straight line A, 139 (decimal representation), and therefore [10001011] (binary representation), is determined as the logic code corresponding to the output voltage of the temperature detection means. Therefore, there are non-linear and linear differences between the output characteristics of the temperature detection means 3 and the digital-to-analog conversion means 12, but as described above, the fixed storage section 10 has data that corrects the differences. Since the temperature-equivalent logic code is stored in the form, no comparison errors occur. Note that the heating energy generating means may also be constituted by an electric heater, and the sensor 13 may be one that detects humidity. As is clear from the above description, according to the present invention, the non-contact state detection means outputs a voltage according to the state of the food, for example, the temperature, and the state corresponding logic code output from the electronic control means is converted into a state corresponding voltage. In the electronically controlled cooking device, the heating energy generating means is controlled based on the comparison result of the output voltage of both the means, and the heating energy generating means is controlled based on the comparison result of the output voltage of both the means. Since the necessary correction based on the difference in output characteristics is completed within the electronic control means, highly accurate food condition detection can be performed without providing a correction circuit that is complicated and requires complicated adjustment as in the past.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is an output characteristic diagram. 1...Microcomputer, 3...Temperature detection means, 4...Heating energy generation means, 12...Digital-to-analog conversion means.

Claims (1)

[Claims] 1. A heating chamber, heating energy generation means for supplying heating energy to the heating chamber, non-contact state detection means that outputs a voltage according to the state of the food in the heating chamber and whose state-to-output voltage characteristic is non-linear, and logic. A digital-to-analog conversion means that inputs a code signal and outputs a voltage according to the signal, and has a linear input signal-to-output voltage characteristic, and each output voltage of the non-contact state detection means and the digital-to-analog conversion means. and an electronic control means for controlling the heating energy generation means based on the output of the comparison means, the control means checking the non-linear characteristics for each menu. It has a storage unit that stores in advance a logic code that is checked based on the desired voltage at the desired cooking finish state and with reference to the characteristics of the above-mentioned straight line, and when a predetermined menu is executed, the logic code corresponding to the menu is stored as above. An electronically controlled cooking appliance characterized in that the read data is read from a storage section and inputted to the digital/analog conversion means.