JP2012013270A - Heating cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating cooker, in which no load operation can be detected early and can be eliminated, and the cost required for the detection and elimination can be inexpensive, in a heating cooker performing food heating by a microwave.SOLUTION: A heating cooker 1 includes a heating chamber 10, a magnetron 25 generating a microwave heating foods in the chamber 10, and a steam sensor 28 discriminating the existence or nonexistence of steam in the heating chamber 20, and a control part 30 performing whole control. After starting the heat by a microwave, the control part 30 monitors whether a detected peak value of the steam sensor 28 exceeds the designated lower limit, and when the detected peak value exceeds the designated lower limit, the time T1 when exceeding the designated lower limit is recorded. Next, the control part 30 checks whether the elapsed time from the T1 exceeds the designated time, and if the elapsed time does not exceed the designated time, the control part 30 monitors whether the detected peak value of the steam sensor 28 exceeds the designated upper limit, and when the detected peak value of the steam sensor 28 exceeds the designated upper limit before the elapsed time from the T1 exceeds the designated time, it is determined that a load exists in the heating chamber 20, then, operation is shifted to normal operation.

Description

  The present invention relates to a cooking device that heats food with microwaves.

  A cooking device that heats food with microwaves is generally called a “microwave oven” and is a household necessity. In this type of heating cooker, heating in a state where there is no object to be heated (load) such as food or beverage in the heating chamber, that is, in an unloaded state should be avoided. This is because if microwave heating is performed in a no-load state, a large amount of unconsumed microwaves returns to the magnetron and the temperature of the magnetron rises, leading to deterioration and breakage of the magnetron. In addition, microwaves are concentrated on a part of an article placed in the heating chamber, for example, a tray for placing food, the portion is damaged due to a temperature rise, or a synthetic resin part in the heating chamber is melted. The situation also occurs.

  In order to prevent the above-described no-load operation, various measures have been taken so far. For example, the temperature change in the heating chamber is monitored with an infrared sensor, and if there is an abnormal temperature rise, the magnetron is stopped. In the heating cooker described in Patent Document 1, the presence or absence of an object to be heated is determined based on the temperature detected by the thermistor and the humidity detected by the humidity sensor. When it is determined that there is no object to be heated in the heating chamber, microwave heating is performed. Has stopped.

JP-A-2005-241128

  In the method of monitoring the temperature change in the heating chamber with the infrared sensor, there is a time lag until the infrared sensor detects the temperature rise, so the articles in the warehouse may become hot until the magnetron stops . For example, if the ceramic glass that constitutes the bottom surface of the heating chamber is at a high temperature, there is a risk of burns if it is accidentally touched.

  In order to determine the presence or absence of an object to be heated based on the temperature detected by the thermistor and the humidity detected by the humidity sensor as in the heating cooker described in Patent Document 1, two types of detection parts, the thermistor and the humidity sensor, are required. There is a problem of high costs.

  The present invention has been made in view of the above points, and in a heating cooker that heats food with microwaves, it is possible to detect and eliminate no-load operation at an early stage, and the cost for that can be reduced. The purpose is to provide.

According to a preferred embodiment of the present invention, the heating cooker includes a heating chamber, a magnetron that generates microwaves for heating food in the heating chamber, and steam that determines the presence or absence of steam in the heating chamber from temperature fluctuations. The steam sensor includes a sensor and a control unit that performs overall control.The steam sensor detects a fluctuation in temperature around the steam sensor and outputs a detection peak value corresponding to the magnitude of the temperature fluctuation. After starting the heating by the wave, the next control step is performed.
(A) monitoring whether the detection peak value of the steam sensor exceeds a specified lower limit value (b) recording time T1 when the detection peak value of the steam sensor exceeds a specified lower limit value (c) from T1 Step (d) of monitoring whether or not the detection peak value of the steam sensor has exceeded a specified upper limit value, if not, the elapsed time from T1 exceeds the specified time Before the detection peak value of the steam sensor exceeds the specified upper limit value, it is determined that there is a load in the heating chamber, and the process proceeds to normal operation. (E) The detection peak value of the steam sensor exceeds the specified upper limit value Before, when the elapsed time from T1 exceeds the specified time, it is determined that there is no load in the heating chamber, and the output of the magnetron is reduced or stopped.

  According to a preferred embodiment of the present invention, in the cooking device configured as described above, the steam sensor is disposed outside the heating chamber and exposed to exhaust from the heating chamber.

The detection level of the steam sensor rises in a short time when steam is detected. For this reason,
Presence or absence of load in the heating chamber can be determined at an early stage. Moreover, since the steam sensor is a relatively inexpensive part, it does not cause a significant cost increase.

It is a front view of a heating cooker. It is sectional drawing which shows schematic structure of a heating cooker. It is a block block diagram of a heating cooker. It is a flowchart of the presence or absence of load. It is a graph which shows the example of a detection by a steam sensor.

  Hereinafter, the structure of the heating cooker 1 which is embodiment of this invention is demonstrated based on figures. In FIG. 1, the top and bottom of the paper coincide with the top and bottom of the heating cooker 1. Further, the left side of the paper surface is the left side of the heating cooker 1, and the right side of the paper surface is the right side of the heating cooker 1.

  The heating cooker 1 includes a cabinet 10 made of a sheet metal structure having a rectangular parallelepiped shape. Inside the cabinet 10, a heating chamber 20 made of a sheet metal structure having a rectangular parallelepiped shape is provided. The heating chamber 20 has an opening on the front side of the cabinet 10. A sheet metal door 11 that opens and closes the opening of the heating chamber 20 is provided in front of the cabinet 10. The door 11 opens and closes with the left end as a fulcrum.

  An operation unit 12 is formed in the cabinet 10 on the right side of the door 11. A display unit 13 composed of a liquid crystal panel is disposed above the operation unit 12, and a key input unit 14 having a plurality of operation keys is disposed below the display unit 13.

  A radio wave stirring chamber 21 is formed under the bottom of the heating chamber 20, and a radio wave stirring blade 23 that is rotated by a motor 22 is disposed therein. A ceramic glass 24 is fitted into an opening that forms a boundary between the heating chamber 20 and the radio wave stirring chamber 21. The microwave generated by the magnetron 25 is supplied to the radio wave stirring chamber 21 through the waveguide 26.

  An exhaust port 27 composed of a large number of small holes is formed above the side wall of the heating chamber 20. A steam sensor 28 is disposed outside the heating chamber 20 at a position exposed to the exhaust discharged from the exhaust port 27. By disposing the steam sensor 28 at this position, the steam sensor 28 can be protected from oil splashing from the food, or even if the food ruptures and the food fragments scatter.

  The control system of the heating cooker 1 has a configuration shown in FIG. The control unit 30 that controls the entire cooking device 1 is configured with a microcomputer as a core, receives output signals from various components, and outputs control signals to the various components.

  The components that output signals to the control unit 30 include an infrared sensor 31 that monitors the temperature of the food in the heating chamber 20 in addition to the key input unit 14 and the steam sensor 28.

  In addition to the motor 22, the components that operate by receiving a control signal from the control unit 30 include an inverter board 32 that oscillates the magnetron 25.

  Next, the operation of the heating cooker 1 will be described. First, the door 11 is opened, and the food that is to be heated is placed in the heating chamber 20. And the door 11 is closed, heating conditions are input through the key input part 14, and a heating is started. From here, the flow of FIG. 4 starts.

  In step # 101, the control unit 30 issues a command to the inverter board 32 to cause the magnetron 25 to oscillate. The magnetron 25 generates a microwave, and the microwave enters the radio wave stirring chamber 21 through the waveguide 26. The microwave that has entered the radio wave stirring chamber 21 is stirred by the radio wave stirring blade 23, passes through the ceramic glass 24, and enters the heating chamber 20. And the molecule | numerator of the foodstuff put into the heating chamber 20 is vibrated, and foodstuff is heated from the inside.

  In step # 102, detection of steam by the steam sensor 28 is started. The vapor sensor 28 includes a thermistor and an operational amplifier. Normally, the thermistor is used as a temperature sensor that measures the temperature by utilizing the change in the electrical resistance value depending on the temperature, and outputs a voltage corresponding to the temperature around the thermistor. At this time, if steam is generated in the vicinity of the thermistor, vapor is condensed on the surface of the thermistor and vaporizes repeatedly, so the temperature of the thermistor changes in small increments. A sensor for determining the presence or absence of steam using the fluctuation of the output due to the temperature change of the thermistor is the steam sensor 28, and the fluctuation component is extracted and amplified from the output of the thermistor via an operational amplifier and output. ing.

With this configuration, the steam sensor 28 detects a fluctuation in the output of the thermistor and outputs a voltage corresponding to the magnitude of the fluctuation to the control unit 30 when the exhaust gas discharged from the exhaust port 27 contains steam. To do.

  The steam sensor 28 may be of a type that determines the presence or absence of steam from fluctuations in the output of the thermistor, and may not be configured as described above.

  Here, the determination of the presence or absence of steam by the steam sensor 28 will be described with reference to FIG. The vertical axis in FIG. 5 is the voltage output from the vapor sensor 28 to the control unit 30. The control unit 30 reads the voltage output from the vapor sensor 28 at a predetermined sampling rate, smoothes it, and processes it as a stepped peak value shown in FIG.

  FIG. 5 is a graph of the experimental results, showing the transition of the detection peak value of the vapor sensor 28 when the heating chamber 20 is heated in the following four patterns. The four patterns are a case where 100 ml of water is put as a load, a case where 300 ml of water is also put as a load, a case where 500 ml of water is also put as a load, and a case where there is no load.

When 100 ml of water is added as a load, it has passed 60 seconds after the start of heating. When 300 ml of water is added as a load, the heating starts 120 seconds after the start of heating. When 500 ml of water is added as a load, heating starts. After 180 seconds, the peak value jumps up at once.
As described above, the steam sensor 28 has a characteristic that when the steam is detected, the detection level rises within a short time. Since the object to be heated such as food contains moisture, even when the object to be heated is started to start heating, the same characteristics as those of the experimental example of FIG.

  As described above, the steam sensor 28 is originally a sensor for determining the presence or absence of steam, and is expected to generate a specific pattern output when steam is present. As a result, the steam sensor 28 showed an output even when heating was started with no load, and it was found that the output was completely different from that when the load was present. That is, as shown in FIG. 5, when heating is started with no load, the steam sensor 28 shows a detection peak value lower than the detection level when detecting steam, and the detection peak value gradually increases with time. It shows the characteristic of going up. The flow of FIG. 4 is assembled using this characteristic.

  In step # 103, it is checked whether or not the detection peak value of the vapor sensor 28 has exceeded the specified lower limit value. The designated lower limit value can be set to 0.6 V, for example, in FIG. If the specified lower limit is exceeded, the process proceeds to step # 104, and the time (elapsed time from the start of heating) T1 when the value is exceeded is recorded. Then, the process proceeds to step # 105.

  In step # 105, it is checked whether the elapsed time from T1 has exceeded the specified time. If not, the process proceeds to step # 106.

  In step # 106, it is checked whether or not the detection peak value of the vapor sensor 28 exceeds a specified upper limit value. The designated upper limit value can be set to 1.5 V, for example, in FIG. If the specified upper limit is exceeded, the process proceeds to step # 107, and if not, the process returns to step # 105.

  Proceeding to step # 107 means that the detection peak value of the vapor sensor 28 has exceeded the specified upper limit value before the elapsed time from T1 reaches the specified time. 20, it is determined that a load exists. In FIG. 5, the load exceeds the specified upper limit value of 1.5 V within a short time after the specified lower limit value of 0.6 V is exceeded in any of the cases of 100 ml, 300 ml, and 500 ml. Accordingly, a relatively short time such as “10 seconds” can be set as the “specified time” in step # 105.

  The process proceeds from step # 107 to step # 108. In step # 108, since there is no concern about no-load operation, the control unit 30 operates the cooking device 1 in the normal mode. The heating cooker 1 performs normal heating until cooking is completed.

If the elapsed time from T1 exceeds the specified time in step # 105, the process proceeds to step # 109. In step # 109, the control unit 30 determines that there is no load in the heating chamber 20.

  The process proceeds from step # 109 to step # 110. In step # 110, since there is no load, the control unit 30 reduces the output of the magnetron 25. Alternatively, the oscillation of the magnetron 25 is stopped. This eliminates the negative effects of no-load operation.

  Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention.

  The present invention can be widely used in a cooking device.

DESCRIPTION OF SYMBOLS 1 Heating cooker 10 Cabinet 11 Door 20 Heating chamber 25 Magnetron 27 Exhaust port 28 Steam sensor 30 Control part

Claims (2)

A heating chamber, a magnetron that generates microwaves for heating the food in the heating chamber, a steam sensor that determines the presence or absence of steam in the heating chamber from temperature fluctuations, and a controller that performs overall control,
The steam sensor detects a fluctuation in temperature around the vapor sensor and outputs a detection peak value corresponding to the magnitude of the temperature fluctuation.
The control unit performs the following control step after the start of heating by microwaves:
(A) monitoring whether the detection peak value of the steam sensor exceeds a specified lower limit value (b) recording time T1 when the detection peak value of the steam sensor exceeds a specified lower limit value (c) from T1 Step (d) of monitoring whether or not the detection peak value of the steam sensor has exceeded a specified upper limit value, if not, the elapsed time from T1 exceeds the specified time Before the detection peak value of the steam sensor exceeds the specified upper limit value, it is determined that there is a load in the heating chamber, and the process proceeds to normal operation. (E) The detection peak value of the steam sensor exceeds the specified upper limit value Before, when the elapsed time from T1 exceeds the specified time, it is determined that there is no load in the heating chamber, and the output of the magnetron is reduced or stopped.   The cooking device according to claim 1, wherein the steam sensor is disposed outside the heating chamber and exposed to exhaust from the heating chamber.

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