JPH05108171A - Heater - Google Patents

Abstract

PURPOSE:To improve the reliability of a switching means turning on/off the supply of electricity to a heating body and to enable equal temperature heating under various temperature conditions by means of the stable operation of the disconnection means. CONSTITUTION:A synchronization circuit 6b generating a signal synchronized with the power source frequency of a commercial power source 5 is mounted to a control part 6 controlling on/off of a relay 4 switching the supply of electricity to the heating body, and the on-control of the relay 4 at the time of starting heating or at the time of normal operation is started at timing when the level of a interrupt port 6c of a microprocessor 6a is changed with a signal generated by the synchronization circuit 6b. The timing of generating an on- command to be given to the relay 4 each time is changed by the amount of prescribed time associated with the power source frequency with respect to the previous on-command generation timing and thus, the actual on-operation of the relay 4 can be prevented from concentrating on the same phase of the commercial power source 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided with a heating element such as a halogen heater which generates heat when supplied with power from a commercial power source, inside a heating chamber so as to perform isothermal heating near a preset target temperature. Regarding the device.

[0002]

2. Description of the Related Art Electric ovens that are widely used for heating and cooking foods generate heat from a heating element (halogen heater) arranged inside the heating chamber by supplying power from a commercial power source to the inside of the heating chamber. It is configured to heat the loaded object (food) to be heated.

In this electric oven, it is necessary to perform isothermal heating at a target temperature preset according to conditions such as the type of food to be heated and the contents of cooking.
Conventionally, a relay is arranged in the middle of the power supply circuit to the halogen heater, the internal temperature of the heating chamber is detected, and the relay is turned on / off based on the comparison result of the detected temperature and the target temperature. Temperature control is performed to maintain the internal temperature of the heating chamber in the vicinity of the target temperature by performing control so that the halogen heater is de-energized.

[0004]

In carrying out the temperature control as described above, when the voltage phase of the commercial power source is concentrated in the same phase when the relay is turned on a large number of times, the relay is damaged by the energization of an excessive current. However, there is a problem that the reliability is lowered, and a countermeasure against this is required.

Such a countermeasure is intended for the case where energization control to the motor is performed by turning on / off a relay.
It is disclosed in Japanese Patent Publication No. 2-132723. However, the impedance of the halogen heater depends on its own temperature. For example, the impedance at room temperature is only about 1/10 of that at steady heat generation, and the rush current at the start of heating becomes extremely large. In addition, the heating device as a cooker requires on / off control at various different temperatures, and duty operation is performed for output control. I don't get it.

The present invention has been made in view of such circumstances, and realizes interruption of energization of a heating element without lowering the reliability of a relay as an interruption means, and under various temperature conditions. It is an object of the present invention to provide a heating device capable of isothermal heating.

[0007]

A heating device according to the present invention comprises a heating element which is arranged in a heating chamber and should be connected to a commercial power source, and an engaging and disconnecting means for disconnecting and energizing the heating element. In the heating device, the controller controls ON / OFF of the engagement unit based on the detection result of the internal temperature of the heating chamber, and the controller operates to maintain the internal temperature at a predetermined target temperature. , A synchronizing circuit that generates a signal synchronized with the power frequency of the commercial power source, a history of heating start or the ON. First and second storage means for respectively storing the history of the off control,
Means for starting the heating start operation and the ON-side control operation in the ON / OFF control in synchronization with the signal generated by the synchronizing circuit, and the generation timing of the ON command to the interrupting means in each of the first or the first 2 means for changing only the predetermined time associated with the power supply frequency according to the stored value of the storage means.

In addition, a timer for counting the elapsed time after the end of heating is provided, and when the time measured by the timer is within a predetermined time, the timing is changed according to the stored value of the first storage means. If the temperature measurement result of the temperature measurement means is equal to or more than a predetermined value, the stored value of the first storage means is set to the stored value. Each is characterized in that the corresponding timing is not changed.

[0009]

In the present invention, the heating start operation and the on / off control on-side control operation are started with the commercial power supply having the same voltage phase, and the first storage means or the second storage means stores the data. By referring to the history of the heating start or ON / OFF control being performed, the ON command to the disconnecting means during the heating start operation and the ON-side control operation of the ON / OFF control is specified with respect to the previous generation timing. It is issued at a timing shifted by a half cycle of the power frequency of the commercial power supply, specifically, the actual ON operation of the disconnecting means at each time is performed in the opposite phase to the last time, and the disconnecting means By improving reliability, it is possible to achieve the target temperature reliably.

Further, when the heating start operation is carried out when the elapsed time from the end of the previous heating is short or when the temperature of the heating element is not sufficiently lowered, the previous heating step is continued. Assuming that the ON operation timing of the engaging / disengaging means is changed not to the previous heating start time but to the final ON control time in the previous heating process, and the ON operation of the engaging / disengaging means is not concentrated in the same phase. ..

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 1 is a schematic front sectional view of an electric oven which is a heating device according to the present invention. 1 in the figure is an outer box 10
It is a heating chamber configured inside, and a halogen heater 2 as a heating element is provided above the inside of the heating chamber, and a placing table 3 for placing food A to be cooked is provided on the bottom surface. The halogen heater 2 is connected to a commercial power supply 5 via a relay 4 serving as an engaging / disconnecting means, and heat is generated by energization from the commercial power supply 5 only when the relay 4 is on, and the food A stored in the heating chamber 1 It is designed to be heated and cooked.

The on / off operation of the relay 4 is performed in response to an on / off command from a control unit 6 arranged in an outer box 10 which covers the outside of the heating chamber 1. To the input side of the control unit 6, a temperature detector 7 fixed to face the inside of the heating chamber 1 and a key operation unit 8 installed on the front surface of the outer box 10 are connected. 6 to heating chamber 1 from the former
The detection result of the internal temperature of the above is given, and the latter gives the heating conditions such as the heating time and the heating temperature set by the operation thereof. On the other hand, the output of the control unit 6 is, as described above,
It is applied to the relay 4 for disconnecting the power supply to the halogen heater 2 and also applied to the display unit 9. The display unit 9 displays the heating conditions set in the key operation unit 8 and the heating progress state. For example, various information that needs to be notified to the user is displayed.

In the heating and cooking by the electric oven having the above-mentioned structure, the food A charged in the heating chamber 1 is placed on the placing table 3, and the key operating portion 8 is operated to set the heating condition. Then, it is started by turning on a start switch (not shown). The control unit 6 issues an ON command to the relay 4 in response to the heating start operation, the energization of the halogen heater 2 is performed by the ON operation of the relay 4 according to this operation, and the food A in the heating chamber 1 becomes the halogen heater 2 It is heated by the heat generation of.

ON state of the relay 4 according to the ON command,
That is, the energization state of the halogen heater 2 is continued until the internal temperature of the heating chamber 1 input from the temperature detector 7 to the control unit 6 reaches the heating temperature (target temperature) set in the key operation unit 8. After that, the control unit 6 issues an on command when the detection result of the temperature detector 7 exceeds the target temperature and outputs an on command when the detection result falls below the target temperature. Repeat until time passes.

FIG. 2 is a time chart showing the operating state of the relay 4 and the changing state of the internal temperature of the heating chamber 1 from the start to the end of heating. In this figure, the target temperature is set to 160 ° C. and the heating time is set to 20 minutes.

By the control operation of the control section 6 described above, the relay 4 is turned on at the same time as the heating is started, and the internal temperature of the heating chamber 1 rises as shown due to the heat generation of the halogen heater 2 accompanying the energization from the commercial power source 5. , This is the target temperature 1
After reaching 60 ° C., the process in which the relay 4 is in the off state in the period above the target temperature and the relay 4 is in the on state in the period below the target temperature is repeated. As a result, the internal temperature of the heating chamber 1 is within a predetermined temperature range across the target temperature of 160 ° C. until the elapsed time from the start of heating reaches the heating time (20 minutes) as shown in the figure. As a result of going up and down,
The food A in the heating chamber 1 is heated under a substantially isothermal temperature of around 160 ° C.

FIG. 3 is a block diagram showing the internal structure of the control unit 6. The control unit 6 uses the internal temperature of the heating chamber 1 input from the temperature detector 7, and controls the microprocessor 6a that actually performs the above-described control operation according to the heating conditions set in the key operation unit 8 and the commercial power supply 5. And a synchronizing circuit 6b which is connected and generates a signal synchronized with the frequency of the power supply 5.

FIG. 4 is a graph showing an example of the synchronizing signal generated by the synchronizing circuit 6b. As shown in this figure, the synchronization circuit 6b
Is configured to generate a high level signal having a width corresponding to a half cycle for each cycle of the power supply voltage. For example, when the power frequency of the commercial power source 5 is 50 Hz, the synchronization circuit 6b is
It emits a high level signal with a width of 10 msec every msec. The signal generated by the synchronizing circuit 6b is supplied to the interrupt port 6c which is a specific input port provided in the microprocessor 6a.
Each time the input to the high level changes to the low level,
The configuration is such that an external interrupt process described later is automatically executed.

5 to 7 are flowcharts showing the operation contents of the control unit 6. First, the operation contents of the main routine shown in FIG. 5 will be described. As described above, the control unit 6 sets the heating condition in the key operation unit 8, starts the operation when the start switch is operated, and first, the stored value of the internal register MEM1 which stores the history of the heating start in the past. Is stored in the internal register CNT1 that stores the history of ON / OFF control, specifically, the history of ON-side control operation (step 1), and after incrementing the stored value of the register MEM1 (step 2) , An ON flag for instructing turn-on of the relay 4 is set (step 3).

After that, the control unit 6 takes in the detection result of the internal temperature of the heating chamber 1 inputted from the temperature detector 7, and judges whether or not this is above the target temperature (step 4),
When the temperature is equal to or higher than the target temperature, the ON flag is reset and an OFF command is issued to the relay 4 (step 5).

If the result of determination in step 4 is that the detected temperature is below the target temperature, it is checked whether or not the relay 4 is in the ON state (step 6). If it is in the off state, the on flag is set, the stored value of the register CNT1 is incremented (step 7), and the process proceeds to step 8.

In step 8, the timed content of the built-in timer for measuring the elapsed time from the start of heating is checked, and if there is a remaining time, the process returns to step 4 to repeat the above operation, and if there is no remaining time, Resets the on-flag and issues an off command to the relay 4 (step 9) to stop the energization of the halogen heater 2 to end the operation and enter a standby state in preparation for the next heating start.

During the operation of the main routine as described above, when the internal temperature of the heating chamber 1 is equal to or higher than the target temperature, the relay 4
However, if the internal temperature of the heating chamber 1 is lower than the target temperature, or if the internal temperature of the heating chamber 1 is below the target temperature, the ON command for performing the ON operation of the relay 4 is not issued, Only the ON flag which instructs the turn-on of the relay 4 is set. Then, the actual ON command is issued in the timer interrupt process executed in response to the timed end of the timer set in the external interrupt process described above.

FIGS. 6 and 7 show the operation contents in the external interrupt processing and the timer interrupt processing, respectively. As described above, the external interrupt process is a process executed every time the input to the interrupt port 6c to which the signal generated by the synchronous circuit 6b is applied is changed from the high level to the low level.
As shown in, the start of the power supply voltage of the commercial power supply 5 is started at the same phase. First, the set state of the ON flag for instructing the turn-on of the relay 4 is checked (step 10). If so, return to the main routine.

On the other hand, if the ON flag is in the set state, then the stored value of the internal register CNT1 is checked (step 11), and N1 or N2 is set in the built-in interrupt timer register TMR2 according to the stored value. Then (steps 12 and 13), the clocking of the interrupt timer is started (step 14), and the process returns to the main routine.

Register CNT1 in the main routine
Is a register M that is incremented each time heating starts
The stored value of EM1 is stored and the subsequent register CNT
The stored value of 1 is incremented each time the ON control of the relay 4 is required. Therefore, the stored value of the register CNT1 at the time of executing the external interrupt process is the number indicating the number of times of heating in the past at the start of heating, and thereafter the number indicating the number of times of execution of ON control after the start of heating.

In step 11, the register CN
Only whether bit0 of T1 is "1" or "0" is checked, and if it is "1", N1 is set in step 12, and if it is "0", it is set in step 13. N2 is different from the time related to the frequency of the commercial power supply 5 by a half cycle of the power supply voltage. For example, when the commercial power source 5 has a power source frequency of 50 Hz and N1 is 2 msec, N2 is 12 (= N1 + 1
It should be 0) msec.

On the other hand, the timer interrupt process shown in FIG. 7 is a process which is automatically executed at the time when the interrupt timer finishes measuring the time set in the register TMR2. As the microprocessor 6a, for example, Sanyo. It can be realized by using "2C6514B" manufactured by Denki.

In the timer interrupt processing, first, the set state of the ON flag for instructing the turn-on of the relay 4 is checked (step 20). If it is in the reset state, the main routine is directly returned to, and if it is in the set state. First, an ON command is issued to the relay 4 and the ON flag is reset (step 21), after which the process returns to the main routine.

By the external interrupt processing and the timer interrupt processing as described above, the ON operation of the relay 4 at the start of heating is always based on the timing when the power supply voltage of the commercial power supply 5 is in phase, after the time N1 or N2 elapses. Since the selection of N1 or N2 is determined by whether the bit 0 of the register MEM1 that stores the past heating start history is "1" or "0", the previous heating start is started. When the ON operation of the relay 4 at the time point is performed in the positive side phase of the power supply voltage, this time is surely performed in the negative side phase.

Also, in the ON / OFF control of the relay 4 performed to maintain the target temperature after the start of heating, the ON control of the relay 4 at each time is performed by the register CNT1 which stores the history of the ON / OFF control. The relay 4 for each ON-side control operation is performed in exactly the same manner according to the stored value.
The actual ON operation of is always in the opposite phase to that in the previous ON control. That is, as a result, the risk of energizing an excessive current due to the ON operations of the relay 4 being concentrated in the same phase is avoided, the reliability of the relay 4 is improved, and the isothermal heating under various temperature conditions can be stably performed.

In the above configuration, even when the next heating is started without waiting time after the end of one heating,
The ON operation of the relay 4 occurs in a phase opposite to that at the time of starting the previous heating, but in this case, since the halogen heater 2 is in a high temperature state, it is considered that the previous heating process is continued, and It is preferable that the ON operation of the relay 4 at the start is performed at a phase opposite to the timing of the final ON control before the end of the previous heating.

The timing of such an ON operation is shown in FIG.
Before step 1 of the main routine shown in FIG.
Alternatively, it can be easily realized by adding the step shown in (b).

In FIG. 8A, the halogen heater 2
A temperature detector that detects the ambient temperature is provided, and if the detected temperature T is equal to or higher than a predetermined reference temperature, it is considered that the previous heating process is continued, and the stored value of the register MEM1 is stored in the register CNT1. , And register MEM
The step 2 of incrementing the stored value of 1 is skipped, and the processing from step 3 is executed.
Further, in FIG. 8 (b), a timer is provided for measuring the elapsed time after the heating is completed and the operation is shifted to the standby state. When the time t of the timer is within a predetermined reference time, the previous heating is performed. It is considered that the process is continued, and steps 1 and 2 are skipped in the same manner, and the processes from step 3 are executed.

That is, when the current heating start is regarded as the continuation of the previous heating process, the history of the previous ON / OFF control is stored in the register CNT1 as it is, and in this state, the above-mentioned main routine, external interrupt processing and Since the timer interrupt process is executed, the ON operation of the relay 4 accompanying the heating start is not the ON operation at the time of the previous heating start,
This is performed in the opposite phase to the timing of the ON operation for the final ON control before the end of the previous heating.

The reference temperature and the reference time are values set in consideration of various conditions such as the specifications of the halogen heater 2, the characteristics of the relay 4 and the surrounding environmental conditions. For example, the reference temperature is The temperature may be set at around 100 ° C and the reference time at around 2 minutes.

[0037]

As described above in detail, in the heating apparatus according to the present invention, the heating start operation and the ON control operation are performed in the state where the commercial power supplies are in the same phase, and further the actual operation of the disconnecting means at each of these operations. The ON operation of is performed at a timing shifted by a predetermined time, specifically, by a half cycle of the power supply frequency of the commercial power supply from the timing of the same kind of operation last time. The present invention has excellent effects such that the ON operation is always performed in the opposite phase to that of the previous time, the reliability of the disconnecting means is improved, and the isothermal heating is stably realized under various temperature conditions.

[Brief description of drawings]

FIG. 1 is a schematic front cross-sectional view of a heating device according to the present invention.

FIG. 2 is a time chart showing an operating state of the disconnecting means and a change state of the internal temperature of the heating chamber from the start to the end of heating.

FIG. 3 is a block diagram showing an internal configuration of a control unit of the heating device according to the present invention.

FIG. 4 is a graph showing an example of a synchronization signal generated by a synchronization circuit.

FIG. 5 is a flowchart showing the operation contents of the control unit of the heating device according to the present invention.

FIG. 6 is a flowchart showing the processing contents of an external interrupt processing carried out by the control unit of the heating device according to the present invention.

FIG. 7 is a flow chart showing the processing contents of timer interrupt processing executed in the control unit of the heating device according to the present invention.

FIG. 8 is a diagram showing additional steps to the flowchart shown in FIG.

[Explanation of symbols]

 1 heating chamber 2 halogen heater 4 relay 5 commercial power supply 6 control unit 6a microprocessor 6b synchronization circuit 7 temperature detector

Claims (3)

[Claims] 1. A heating element arranged in the heating chamber to be connected to a commercial power source, an engaging / disengaging means for interrupting energization of the heating element, and the detection result of an internal temperature of the heating chamber based on the detection result. In a heating device including a control unit that controls on / off of the disconnecting means and operates to maintain the internal temperature at a predetermined target temperature, the control unit outputs a signal synchronized with a power supply frequency of the commercial power supply. Generated synchronous circuit and heating start history or the ON. First and second storage means for respectively storing the history of the off control, means for starting the heating start operation and the on-side control operation of the on / off control in synchronization with the signal generated by the synchronous circuit, And a means for changing the generation timing of the ON command to the disconnecting means according to the stored value of the first or second storing means for a predetermined time related to the power supply frequency. apparatus. 2. A timer is provided for measuring the elapsed time after the end of heating, and when the time measured by the timer is within a predetermined time,
The heating device according to claim 1, wherein the timing is not changed in accordance with the stored value of the first storage means. 3. A temperature measuring means for detecting the temperature around the heating element is provided, and when the temperature measuring result of the temperature measuring means is a predetermined value or more, a timing corresponding to the stored value of the first storage means. The heating device according to claim 1, wherein the change is not made.