JPS6366037B2 - - Google Patents

Description

[Detailed description of the invention] The present invention detects infrared rays emitted from cooking food,
In a microwave oven that detects the surface temperature and cooks, the high-voltage relay that determines the output of the microwave oven is used.
The purpose is to avoid noise caused by ON/OFF.

Duty control is usually used to determine the output of a microwave oven. In other words, if the opening and closing cycle of the high voltage relay is 22 seconds, if it is High power, it will be closed for 22 seconds (ON), if it is Mediam, it will be closed for 11 seconds (ON) and open for 11 seconds (OFF), and if it is Low power, it will be 5 seconds. It closes for 1 second (ON) and opens for 17 seconds (OFF). There are various types of sensors that detect infrared rays, but the pyroelectric type has a sensitivity of only a few microvolts per degree Celsius, and requires an amplifier of about 60 dB to obtain the temperature signal. . Therefore, when turning on and off the high voltage relay, impulse noise is often superimposed on this temperature signal, causing malfunction.

FIG. 1 shows a block diagram of the microwave oven used in the present invention. 1 is an oven, 2 is a food to be cooked, 3 is a turntable, and 4 is an arrow indicating infrared rays. Further, 5 is a chopper that intermittents infrared rays, 6 is a temperature detection section (here, a pyroelectric PVF2 sensor), and 7 is a control section that recognizes the temperature. Also 8
is a window in the oven that allows infrared light to pass through. 9 is an interrupter that knows the opening and closing of the chopper.

FIG. 2 shows a circuit configuration diagram used in the present invention.

10 is an amplifier that amplifies the minute voltage of the temperature signal 6' from the temperature detection section 6 by about 60 dB. Generally, the temperature signal 6' from the temperature detection section has an AC waveform (several Hz) because it is chopping infrared rays. Figure 3 a). Also, since the signal when the chopper 5 is opened (that is, when the infrared light from the food is guided to the temperature detection section 6) detects the surface temperature of the food, the It is necessary to perform synchronous rectification. This operation is performed by the interrupter 9, and 11 is its synchronous rectifier circuit (waveforms are shown in FIG. 3b). 12 is a smoothing circuit for smoothing the signal from the synchronous rectifier circuit (the waveform is shown in FIG. 3c). 13
detects the chopper temperature and outputs a signal (voltage) according to the chopper temperature (waveform is shown in Figure 3 d).
14 is an adder that adds the signal from the smoothing circuit 12 and the signal from the chopper temperature detection circuit 13, and its output becomes a true temperature signal 14' that is output only in accordance with the amount of infrared rays emitted from the food. The waveform is shown in Figure 3e). 15 is a D-A converter, and 16 is a control unit (here, a microphone computer) that recognizes the surface temperature and controls the switch 17 that determines the decoy of the high-frequency output. In other words, a digital amount is output from the control section 16 to the A-D converter 15,
It is converted into an analog quantity using 15 AD converters. 18 is the summer temperature signal 14' and A-D
This is a comparator for comparing the output of the converter, and its output is also input to the control section 16. Since the control unit 16 can recognize the temperature using a digital quantity, the control unit 16 can recognize the temperature by inputting the signal from the comparator 18.
can recognize the surface temperature of the food by using the temperature signal. Reference numeral 19 denotes a drive section that drives the switch (high voltage relay in this case) 17, which is also controlled by the control section 16. 20 is a control signal for controlling the switch drive section 19, and 22 is a delay start signal sent to the delay circuit section 21. The delay circuit 21 is composed of a general timer (in this case, a 1-sec timer), and a delay end signal 23 is outputted and inputted to the control section 16. 24 is a reset signal for the delay circuit section 21. high voltage relay
The waveform of the control signal to the switch drive section 19 when turned on and off is shown in FIG. 4a. Further, the waveform of the true temperature signal 14' at that time is shown in FIG. 4b.

In other words, when the switch (high-pressure relay) is closed (ON), noise will be added to the true temperature signal 14', causing a malfunction when controlling the temperature of the food being cooked. Therefore, the control signal 20 of the switch drive section
The delay circuit 21 is driven by the delay start signal 22 in synchronization with the rise of
Until the delay end signal 23 is output, the control unit 16 cannot recognize the temperature by cutting off the signal from the comparator 18, but by retaining the previous temperature information in the memory, the control unit 16 can not recognize the previous temperature. can be maintained. When the delay end signal 23 is output, the control section 16 becomes capable of recognizing the temperature, and inputs the signal from the comparator 18 to recognize the temperature. Also, at this time, the delay circuit section 21 is reset by the reset signal 24 of the delay circuit section 21. In this way, malfunction due to noise caused by the switch 17 (high voltage relay) can be prevented. Figure 5 is a diagram showing this timing,
a is the waveform of the drive control signal 20 that drives the switch 17, b is the waveform of the delay start signal 22, c is the waveform of the delay end signal 23, d is the waveform of the reset signal 24,
That is, in synchronization with the rise of the drive control signal 20, the delay start signal 22 is output, and after a certain period of time T, the delay end signal 23 is output. The control section 16 detects this signal and outputs a reset signal 24' to reset the delay end signal. In the present invention, the delay circuit is driven only when the high voltage relay is closed (on), but it is also possible to easily drive the delay circuit when the high voltage relay is open (off).

If a configuration is adopted in which temperature is not detected for a certain period of time in synchronization with the closing (on) of the switch (high-voltage relay) of the present invention, malfunctions due to noise from the switch (high-voltage relay) will not occur, and Since the delay time T is on the order of several seconds, it does not pose a problem for cooking control, and a microwave oven can be configured with almost accurate surface temperature detection.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of the microwave oven used in the present invention.
Figure 2 is a block diagram of the control device used in the present invention.
Figure 3 is a signal waveform diagram of each part of the control device, Figure 4 is a diagram showing how noise is superimposed on the temperature signal when a switch (high voltage relay) is closed (on), and Figure 5 is a delay circuit. FIG. 3 is a diagram showing a timing chart of the control section and the control section. 2...Cooked food, 6...Temperature detection unit, 6'...Temperature signal, 16...Control unit, 17...Switch (high pressure relay), 21...Delay circuit, 22...Delay start signal, 23 ...Delayed end signal.

Claims (1)

[Claims] 1. Recognize the temperature using a temperature detection unit that detects the surface temperature of the food by detecting infrared rays emitted from the food, a switch for duty-controlling high frequency output, and a temperature signal from the temperature detection unit, It has a control unit that determines the duty of the switch, and outputs a delay start signal that starts a delay circuit in synchronization with opening and closing of the switch, until a delay end signal is output from the delay circuit, A control device for a microwave oven, characterized in that temperature recognition of the temperature signal is disabled.