JPS643315B2 - - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a heater and a heater for both output terminals of a power supply.
A main switch, a control switch that is normally turned on later than the main switch, and a normally closed temperature switch that is turned off when the heated object heated by the heater reaches a predetermined temperature are connected in series. The present invention relates to a heater circuit state determination device.

(Prior art) For example, in the case of a coffee maker with a mill mechanism and a hot water supply (drip) mechanism, the
A lid switch, which is the main switch that responds to the opening and closing of the lid provided in the mill mechanism, a series circuit of the mill motor and a mill operation switch are connected, and a series circuit of the mill motor and mill operation switch is connected in parallel to the series circuit of the hot water supply mechanism. A series circuit of a heater, a drip operation switch, and a normally closed temperature switch that is turned off in response to a rise in temperature of the hot water supply mechanism upon completion of the drip operation is used. Therefore, when the lid is opened and the lid switch is turned off, the mill motor and heater are prevented from being energized, and when the dripping operation is completed, the heater is turned off when the temperature switch is turned off. is cut off. However, in recent years, such coffee makers have been required to have a function to display or notify when the lid has been forgotten to close, as well as a function to notify the end of the drip operation. lid switch,
There is a need for a device for determining the state of a heater circuit consisting of a series circuit of a heater, a drip operation switch, and a temperature switch, specifically, the on/off state of the lid switch and the on/off state of the temperature switch. For this reason, it has conventionally been considered to provide a detection circuit corresponding to each of the lid switch and the drip operation switch, and to determine the state of each switch based on the outputs of these detection circuits.

(Problems to be Solved by the Invention) However, in the above-mentioned conventional configuration, since detection circuits corresponding to each of the lid switch and the temperature switch are required, the overall circuit configuration inevitably becomes complicated. In addition, two input terminals are required for the control circuit that receives the output from each of the detection circuits and determines the status of each switch and controls the load. In this case, two input ports are used to receive the output from each detection circuit, resulting in a problem that the functions of the microcomputer are restricted.

The present invention has been made in view of the above circumstances, and its object is to be able to determine the on/off state of the main switch of the heater circuit and the temperature switch using one detection circuit, thereby simplifying the circuit configuration. It is an object of the present invention to provide a heater circuit state determination device that can be manufactured at low cost.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a heater for both output terminals of a power supply, a main switch, and a control that is normally turned on later than the main switch. The object of the present invention is a state determination device for a heater circuit in which a normally open type temperature switch that is turned off when a heated object heated by the heater reaches a predetermined temperature is connected in series. The heater and main switch are connected between a signal output point in the circuit and one output terminal of the power source, and the control switch and temperature switch are connected between the signal output point and the other output terminal of the power source. and a detection circuit that receives a detection current from the signal extraction point and outputs a detection signal only when the main switch is on and at least one of the control switch and the temperature switch is off; If the detection signal is output at the timing when the operation start command for turning on the switch is output, it is determined that the main switch is turned on, and the control switch is turned on by the operation start command. The configuration includes a determination circuit that determines that the temperature switch is turned off when the detection signal is output in a state where the temperature switch is turned off.

(Function) The detection circuit outputs a current detection signal only when the main switch is on and at least one of the control switch and the temperature switch is off. Therefore, at least the control switch is turned off at the timing when the operation start command for turning on the control switch is output, so if the output switch is in the on state, the detection signal is not output from the detection circuit. However, when the output switch is in the OFF state, no detection signal is output from the detection circuit. Therefore, when the detection signal is output at the timing when the operation start command is output, the determination result of the determination circuit that determines that the main switch is turned on will be correct. Furthermore, when the main switch and temperature switch are turned on, and the control switch is turned on by the above-mentioned operation start command, no detection signal is output from the detection circuit, but the temperature switch is turned off from this state. When this happens, the detection circuit will output a detection signal. Therefore, if a detection signal is output while the control switch is turned on by the operation start command, this and the judgment result of the judgment circuit that judges that the temperature switch is turned off are also correct. becomes.

(Embodiment) Hereinafter, an embodiment in which the present invention is applied to a coffee maker having both a hot water supply (drip) mechanism and a mill mechanism will be described with reference to the drawings.

Reference numeral 1 is a lid switch which is the main switch, and is turned on only when the lid of the case (none of which is shown), which is used for both grinding coffee beans and extracting coffee liquid, is properly set in a predetermined position. It consists of a lid switch 1, a heater 2, a bimetal switch 3 which is a temperature switch, and an output switch 4a of a heater drive circuit 4 which is a control switch (described later).
are connected in series in this order between both output terminals 5a and 5b of the AC power source 5, and these series circuits constitute the heater circuit A in the present invention.
Then, a series circuit of a mill motor 6 and an output switch 7a of a motor drive circuit 7 to be described later is connected in parallel with the series circuit of the heater 2, bimetal switch 3, and output switch 4a. In this case, motor 6
is attached to a mill mechanism (not shown), and the mill mechanism has a cutter rotated by a motor 6 in the case, and grinds coffee beans stored in the case by rotation of the cutter to produce coffee. Produces powder. The heater 2 is attached to a hot water supply mechanism (not shown), and the hot water supply mechanism converts water supplied from a water storage tank to a heater, which is an object to be heated, into boiling water using the heater 2, and heats the hot water thus generated. The boiling pressure is used to supply coffee powder into the case containing coffee powder to extract coffee liquid. Furthermore, the bimetallic switch 3 is of a normally closed type that is turned off when the heater reaches a predetermined temperature. On the other hand, 8
is a DC power supply circuit for rectifying the output of the AC power supply 5 and providing it as a power source for a control circuit 9, which will be described later. In the figure, only the low potential side (zero potential side) output line 8a is shown among the output lines. It shows.

Reference numeral 10 denotes a detection circuit which is a component of the state determination device for the heater circuit A, and will be described below. That is, the common connection point between the heater 2 and the bimetal switch 3 in the heater circuit A constitutes the signal extraction point 11 in the present invention, and this signal extraction point 11 is connected to the PNP in the detection circuit 10 via the resistor 12.
It is connected to the base of the type transistor 13. The emitter of the transistor 13 is connected to the output terminal 5b of the AC power supply 5, the collector of the transistor 13 is connected to the low potential side output line 8a of the DC power supply circuit 8 via the resistor 14, and the base of the transistor 13 is connected to the output terminal 5b of the AC power supply 5. - Connect a parallel circuit of a resistor 15 and a diode 16 between the emitters. and,
The collector of the transistor 13 forming the output end of the detection circuit 10 is connected to the line _L1 . Therefore,
In the detection circuit 10, when a detection current is applied from the signal extraction point 11, the transistor 13 which receives this current at its base is turned on, and the line _L1 is at a high level corresponding to the detection signal in the present invention. When a detection current is not applied from the signal extraction point 11, the transistor 13 remains turned off and outputs a low level signal, which is a non-detection signal, to the line _L1 .

Now, the configuration of the control circuit 9 will be described below. In this case, the control circuit 9 has the function of the determination means in the present invention, and
Most of its functions can be obtained by microcomputer programs, but for convenience of explanation, a combination of block circuits will be shown here.
That is, 17 is a frequency divider that divides the output of the AC power supply 5, and this outputs a counting pulse Pc at a period of, for example, 1 Hz. 18 is a set switch that is turned on only in manual operation mode, and only when this is turned on.
A Louis level signal is applied to one input terminal of the AND circuit 19. The other input terminal of the AND circuit 19 is connected to receive the counting pulse Pc, and therefore, the AND circuit 19 passes the counting pulse Pc only during the ON period of the set switch 18. 20 is a hexadecimal up counter, for example, which adds and counts the pulses input from the AND circuit 19 to the clock input terminal CK, and outputs the counted contents as a digital signal Sn.
21 is a 3-digit digital display made of a 7-segment light emitting diode, etc., which, when receiving the digital signal Sn via the transfer gate 22, displays a numerical value (maximum 2 digits) corresponding to the digital signal Sn. indicate. The transfer gate 22 has a configuration that exhibits low impedance and allows the signal to pass only when a high level signal is input to its control terminal 22a, and the other transfer gates described below have the same configuration. be. 23 is a display information signal Sd in a predetermined mode.
The information signal Sd is input to the digital display 21 when the transfer gate 24 becomes conductive. When the information signal Sd is input to the digital display 21, the digital display 21 displays, for example, "LId" as shown in FIG. On the other hand, 25 is a start switch that is turned on only in the manual operation state, and when this is turned on, the 3-input type AND circuit 26
A high level signal is given to one of the input terminals of the . Reference numeral 27 designates a stop switch that is also turned on only in the manual operation state, and when it is turned on, a high level signal is output to line _L2 . 28
is an R-S flip-flop whose set input terminal S is connected to the output terminal of the AND circuit 26 and whose reset input terminal R is connected to line _L2 ;
The output from the set output terminal Q is the delay circuit 2.
9 to one input terminal of the AND circuit 30, and also directly to one input terminal of another AND circuit 31, and the other input terminal of the AND circuit 31 is connected to the line
Connected to _L1 . At this time, the delay circuit 29
The delay time is set to about 20 ms, for example. The delay circuit 29 is located downstream of the delay circuit 29.
The output terminal of the AND circuit 30 is connected to the control terminal 22a of the transfer gate 22 via an inverter 32, and is also directly connected to the control terminal 24a of the transfer gate 24. is AND
The transfer gate 24 is conductive when the circuit 30 outputs a low level signal, and the transfer gate 24 is conductive when the AND circuit 30 outputs a high level signal. 33 is an R-S flip-flop whose set input terminal S is connected to the output terminal of the AND circuit 31 and whose reset input terminal R is connected to the line _L2 . is applied directly to the other input terminal of the AND circuit 30 and is applied directly to the monostable multivibrator 35 which outputs a high level signal for a short time when receiving a rising signal, and is also applied to the AND circuit 37 via a delay circuit 36. It is designed so that it can also be applied to one input terminal of the . 38 is a down counter having a preset function and a clear function;
This presets the numerical value corresponding to the input digital signal when a digital signal is input to the data input terminal D, and also presets the value corresponding to the input digital signal.
Each time a pulse is input to CK, the count is subtracted from the preset value, and when a high level signal is input to clear terminal CL, the count value is cleared to "0". Furthermore, this down counter 38 is configured to output a high level signal only during a period when its count value is other than "0", and operate the motor drive circuit 7 with this high level signal, so that the motor drive circuit 7 is operated. When the circuit 7 is operated in this manner, it turns on its output switch 7a. Further, the data input terminal D of the down counter 38 is connected to the output terminal D of the up counter 20 via the transfer gate 39, the clock input terminal CK is connected to the output terminal of the AND circuit 40, and the clear input terminal CL is connected to the output terminal D of the up counter 20. Connected to the line _L2 . One input terminal of the AND circuit 40 is connected to receive the counting pulse Pc, and the other input terminal is connected to the output terminal P of the down counter 38. still,
A control terminal 39a of the transfer gate 39 is connected to receive the output from the monostable multivibrator 35. Further down counter 3
The output terminal P of 8 is connected to 2 after passing through the inverter 41.
It is branched and connected to each input terminal of the AND circuits 26 and 37, and the remaining input terminals of the AND circuit 26 are connected to the AND circuit 3 via an inverter 42.
It is connected to the output terminal of 7. Also, above
The output terminal of the AND circuit 37 has a delay time of, for example, 10
AND circuit 44 via a delay circuit 43 of about ms
is connected to one input terminal of the AND
The other input terminal of circuit 44 is connected to line _L1 . 45 is a D flip-flop whose data input terminal D is connected to a high level signal source 46, whose clear input terminal CL is connected to line _L2 , and whose clock input terminal CK is connected to an AND circuit 44.
is connected to the output terminal of the 47 is a monostable multivibrator that outputs a high level signal for a predetermined time in response to the rise of the output of the D flip-flop 45 to a high level signal, and its output is sent to an AND circuit 49 via an inverter 48.
The signal is applied to one input terminal of the buzzer drive circuit 50 as well as directly to the buzzer drive circuit 50. This buzzer drive circuit 50 causes the buzzer 51 for notifying completion of extraction of coffee liquid to sound only during a period when a high level signal is input. On the other hand, said
The AND circuit 49 is connected to give its output to the heater drive circuit 4, and the heater drive circuit 4 is configured to operate while a high level signal is input to turn on the output switch 4a. be. Note that the other input terminal of the AND circuit 49 is connected to the output terminal of the AND circuit 37.

Next, the operation of this embodiment having the above configuration will be explained. When producing coffee liquid, an amount of water corresponding to the desired number of people is supplied into the water storage tank of the hot water supply mechanism, and with the corresponding amount of coffee beans stored in the case, the lid is placed on the case. A bottle for storing coffee liquid is placed on the heater of the hot water supply mechanism. Then, in this state, coffee beans are first milled. In this case, when the set switch 18 is turned on and kept in the on state, the count pulse Pc from the frequency divider 17 is given to the up counter 20 via the AND circuit 19, which adds and counts the count pulse Pc. The content of the count is then output as a digital signal Sn. At this time,
As will be clear from the description below, since the AND circuit 30 outputs a low level signal and the transfer gate 22 is conductive, the digital display 2
1 will now receive the digital signal Sn,
Therefore, on the digital display 21, the numerical values corresponding to the digital signal Sn are "0" → "1" → "2".
→ "3"... will be displayed in increasing numbers, so
The operator can display any number such as "12".
When this happens, the on operation of the set switch 18 is released. When the ON operation of the set switch 18 is released in this way, the high level signal is no longer input to the AND circuit 19, and the AND circuit 19 blocks the passage of the counting pulse Pc.
The up counter 20 stops the counting operation, stores the count value "12" as the count result, and outputs a digital signal Sn corresponding to the count value "12". Therefore, at this time, the digital display 21 continues to display "12".

After this, when the start switch 25 is turned on, in this case, as will be understood from the description below, a high level signal is output from the inverters 41 and 42, so a high level signal is output from the AND circuit 26, and this high level signal is output from the AND circuit 26. The R-S flip-flop 28 receives this at its set input terminal S, and is set, and a high level signal corresponding to the operation start command in the present invention is outputted from its set output terminal Q. However, in such a state, if the lid of the case is not properly set at the predetermined position, the lid switch 1 is off, and the output switch 4a is also off, so the signal extraction point 1
1 to the base of the transistor 13, which is a detection current, is not applied to the base of the transistor 13, and the transistor 13 is in an off state. Therefore, a low level signal (non-detection signal) corresponding to the potential of the low potential side output line 8a of the DC power supply circuit 8 is output to the line _L1 , and the AND circuit 31 continues outputting the low level signal. Therefore, the R-S flip-flop 33 also maintains the reset state and outputs a low level signal from its set output terminal Q. In other words, the state in which the low level signal is output in this way corresponds to the determination result that the lid switch 1 is turned off. As described above, when a high level signal is output from the R-S flip-flop 28, the high level signal is applied to one input terminal of the AND circuit 30 via the delay circuit 29, and An R-S flip-flop 33 is connected to the input terminal of
Since the low level signal from the AND circuit 30 is applied via the inverter 34, a high level signal is output from the AND circuit 30 and the transfer gate 24 becomes conductive. Then, the information signal Sd from the memory circuit 23 is input to the digital display 21, which starts to display "LId" (see Figure 2), thereby notifying the user that the lid is not properly set. It will be done. In addition, if the lid is not set properly, the start switch 2
When 5 is turned on, R-S is turned on as described above.
Since the flip-flop 33 does not output a high level signal, the monostable multivibrator 35 is not driven, and the transfer gate 39 remains non-conductive. Therefore, the digital signal Sn is not input to the data input terminal D of the down counter 38, and the down counter 38 continues in its initial state, that is, the state in which its count value is "0" and it outputs a low level signal. Therefore, the output switch 7a is not turned on by the motor drive circuit 7, and
Thus, the non-conducting state of the motor 6 is maintained. That is,
The mill operation will not start if the lid is not properly set. On the other hand, when the case lid is properly set in the predetermined position, the lid switch 1 is on and the output switch 4a is off, so that every half wave period when the output terminal 5b side of the AC power source 5 is at a high level. transistor 1 to
A base current, which is a detection current, is supplied from the signal extraction point 11 to the transistor 3, and the transistor 13 is turned on periodically according to the frequency of the AC power supply 5. Therefore, line L ₁ has transistor 1
3 is turned on, a high level signal (corresponding to the detection signal in the present invention) is intermittently output. Therefore, if the lid is not properly set and the start switch 25 is turned on, and then the lid is reset normally based on the display "LId" on the digital display 21 as described above, and the lid is When the start switch 25 is turned on in a state where it is set normally, a high level signal is input to both input terminals of the AND circuit 31 and this signal is turned on.
Since the AND circuit 31 outputs a high level signal,
The R-S flip-flop 33 is set and a high level signal is output from its set input terminal Q. In other words, the state in which the high level signal is output in this manner corresponds to the determination result that the lid switch 1 is turned on. As a result, the monostable multivibrator 3 driven by the above high level signal
5 outputs a high level signal for a short period of time to make the transfer gate 39 conductive, the digital signal Sn stored in the up counter 20 is applied to the data input terminal D of the down counter 38.
The down counter 38 presets the numerical value "12" corresponding to the input digital signal Sn, and outputs a high level signal from the output terminal P to operate the motor drive circuit 7. This turns on the output switch 7a and energizes the motor 6, which rotates the cutter and starts grinding the coffee beans in the case. Also, at the same time, a high level signal is applied to one input terminal of the AND circuit 40, and the counting pulse Pc applied to the other input terminal of the AND circuit 40 passes through this. The down counter 38, which receives the counting pulse Pc at its clock input terminal CK, starts a subtractive counting operation. Such a subtraction counting operation is started based on the preset value "12", and the counted value is "12" → "11" →
It will gradually decrease to "10"... When the count value of the down counter 38 reaches "0", a low level signal is output from the output terminal P instead of a high level signal, so the motor drive circuit 7 is stopped and its output is At the same time that the switch 7a is turned off, the motor 6 is cut off, and the grinding of coffee beans is completed, the AND circuit 40 is turned off.
The input of the counting pulse Pc to the down counter 38 is stopped. However,
The count value of the down counter 38 changes from "12" to "0"
Since the output period of the counting pulse Pc is 1 Hz, the time it takes to reach 1 is 12 seconds, and therefore, the coffee bean grinding time (mill time) as described above is controlled to 12 seconds. As mentioned above, when a high level signal is output from the set output terminal Q of the R-S flip-flop 33, the high level signal is inverted by the inverter 34 and inputted to the AND circuit 30, so the AND circuit 30 becomes low. A level signal is output, and therefore the transfer gate 22 is rendered conductive, and the digital display 21 begins to display the numerical value "12" corresponding to the digital signal Sn from the up counter 20. Furthermore, before the start switch 25 is turned on, the R-S flip-flop 28 in the reset state is outputting a low level signal, so the AND circuit 30 which receives this low level signal via the delay circuit 29 is operated as described above. A low level signal is being output. Further, the delay circuit 29 is provided to compensate for the intermittent nature of the high level signal (detection signal) output to the line _L1 .

Now, as mentioned above, R-S flip-flop 2
When the mill operation is completed by the operation start command (high level signal) from 8, the operation is automatically shifted to the drip operation. That is, when the down counter 38 outputs a low level signal and the mill operation is completed, the inverter 41 that received the low level signal
starts outputting a high level signal, and this high level signal is applied to one input terminal of the AND circuit 37. At this time, the high level signal is input to the other input terminal of the AND circuit 37 via the delay circuit 36 at the time when the high level signal is output from the flip-flop 33 (in other words, at the time when the mill operation is started). Therefore, as a result, the AND circuit 37 outputs a high level signal in place of the previous low level signal at the same time as the milling operation ends, and this high level signal is sent through the delay circuit 43. is applied to one input terminal of the AND circuit 44 and also directly applied to the other input terminal of the AND circuit 49. In this case, at the moment when the high level signal is output from the AND circuit 37, a low level signal is applied to one input terminal of the AND circuit 44 (the input terminal connected to the delay circuit 43), and the AND circuit 44 Since D flip-flop 45 is outputting a low level signal,
exhibits an initial state (clear state) and outputs a low level signal from its output terminal Q, and the monostable multivibrator 47 is also in a non-driven state and outputs a low level signal, which is received by the inverter 4.
8 outputs a high level signal. accordingly
At the moment when the high level signal is output from the AND circuit 37, the AND circuit 49 that receives this outputs a high level signal, so the heater drive circuit 4 is activated and turns on the output switch 4a, which turns on the heater 2. It starts to generate fever. Then, when the output switch 4a is turned on in this way,
Signal extraction point 1 with respect to the base of transistor 13
1, the base current serving as the detection current is no longer supplied and the transistor 13 is turned off, so a low level signal (non-detection signal) is sent to line _L1.
is now output, and therefore a low level signal is given to the input terminal of the AND circuit 44 connected to line _L1 . Here, the delay time of the delay circuit 43 is determined from the time when the high level signal is output from the AND circuit 37 to the time when the output switch 4
For example, 10 m longer than the delay time from when a is turned on and a low level signal is output to line _L1 .
Therefore, when a high level signal is output from the AND circuit 37, the delay effect of the delay circuit 43 prevents the high level signal from being input to both input terminals of the AND circuit 44 at the same time. be prevented. Due to this action, the D flip-flop 45 is maintained in its initial state. Now, as mentioned above, when the heater 2 is energized and generates heat, the water in the heater supplied from the water storage tank is heated by the heater 2 and becomes boiling water, and the hot water thus generated is heated by its boiling pressure. The coffee liquid is extracted by being supplied into the case, and the extracted coffee liquid flows down and is stored in a bottle placed on a heater. When all the water in the water storage tank is consumed by such coffee liquid extraction or dripping operation, the temperature of the heater will rise rapidly due to no heat exchange between the heater and the water. The high metal switch 3 detects this and turns off the heater 2, thereby completing the dripping operation. When the drip operation is completed as described above, that is, when the bimetal switch 3 is turned off, the base signal serving as the detection current is again applied to the base of the transistor 13 from the signal extraction point 11, and the transistor 13 is turned on. As a result, a high level signal (detection signal) is intermittently output to line _L1 . Then, a high level signal is input to both input terminals of the AND circuit 44, and the AND circuit 44 outputs a high level signal, so that the D flip-flop 45 is triggered and outputs a high level signal. In other words, like this, the D flip-flop 45
The state in which the switch outputs a high level signal corresponds to the determination result that the bimetal switch 3 is turned off.
In this case, the monostable multivibrator 47 outputs a high level signal for a predetermined period of time, so the buzzer drive circuit 50 is turned on for a predetermined period of time, and the buzzer 51 sounds during this period, thereby causing the drip operation. A notification will be sent to the effect that the process has been completed. Note that during the period when the buzzer 51 is ringing, that is, during the period when the monostable multivibrator 47 is outputting a high level signal, the high level signal is inverted to a low level signal by the inverter 48.
Since it is input to the AND circuit 49, the AND circuit 4
9 starts outputting a low level signal, and the operation of the heater drive circuit 4 is temporarily stopped.
After the above-described dripping operation is completed, the bimetal switch 3 is intermittently turned on and off to control the heater 2 to be turned on and off, and the coffee liquid in the bottle is kept warm by the heater.
To stop such heat retention, the stop switch 27 is turned on. Then, due to the high level signal output to line _L2 due to the on operation, the R-S flip-flops 28, 3
3. Down counter 38 and D flip-flop 45 are all reset or cleared, especially R-S
By resetting the flip-flop 33, a low level signal is input to the AND circuit 37, and a low level signal is output from the AND circuit 49 at the subsequent stage, thereby stopping the operation of the heater drive circuit 4 and turning off the heater 2. Electricity, that is, heat retention is stopped. Furthermore, if the stop switch 27 is turned on during the above-described dripping operation, the heater 2 is similarly cut off and the dripping operation is stopped midway. Furthermore, when the stop switch 27 is turned on during mill operation, the count value of the down counter 38 is cleared to "0" and a low level signal is output from now on, so the motor drive circuit 7 is stopped. The motor 6 is cut off, and the mill operation is stopped midway. Note that the delay circuit 36 is activated at the start of the mill operation, that is, when the R-S flip-flop 33
At the moment when a high level signal is output from
This is provided to prevent a situation in which high level signals are input to both input terminals of the AND circuit 37 at the same time.

In summary, according to the present embodiment described above, the ON state of the lid switch 1 and the OFF operation timing of the bimetal switch 3 in the heater circuit A can be determined based on the output from the only one detection circuit 10, so the circuit configuration can be changed. It can be done easily. Furthermore, if the input section of the control circuit 9 that receives the output of the detection circuit 10 is configured with a microcomputer, one input port can receive two types of input signals, so the remaining input port can be used for other functions. The functions of the control circuit 9 can be further diversified.

Note that the present invention is not limited to the above-mentioned embodiments, but can be applied to, for example, an electric rice cooker having a timer switch that is turned on after a desired time as a control switch and a lid switch as a main switch. The present invention may be modified and implemented as appropriate without departing from the gist thereof.

[Effects of the Invention] According to the present invention, as described above, a heater, a main switch, a control switch that is normally turned on later than the main switch, and an object to be heated by the heater are connected to both output terminals of a power source. In a heater circuit in which normally closed temperature switches are connected in series, which are turned off when the temperature reaches a predetermined temperature, the on/off state of the main switch and temperature switch of the heater circuit can be determined by one detection circuit. Accordingly, it is possible to provide a heater circuit state determination device that has effects such as a simple circuit configuration and low cost manufacturing.

[Brief explanation of drawings]

FIG. 1 is an electrical configuration diagram showing an embodiment of the present invention, and FIG. 2 is a front view showing an example of one state of a digital display in the embodiment. In the figure, 1 is the lid switch (main switch), 2 is the heater, 3 is the bimetal switch (temperature switch),
4a is an output switch (control switch), 5 is an AC power supply, A is a heater circuit, 9 is a control circuit (judgment means), 10 is a detection circuit, 11 is a signal extraction point, 21
is a digital display.

Claims (1)

[Claims] 1 For both output terminals of the power supply, there is a heater, a main switch, a control switch that is normally turned on later than the main switch, and a control switch that is normally turned off when the heated object heated by the heater reaches a predetermined temperature. In a heater circuit in which open temperature switches are connected in series, the heater and the main switch are connected between a signal output point in the heater circuit and one output terminal of the power source, and the signal output point and The control switch and temperature switch are connected between the other output terminal of the power source, and the detected current is output from the signal extraction point only when the main switch is on and at least one of the control switch and temperature switch is off. a detection circuit that outputs a detection signal while receiving the detection current, and the detection signal is output at the timing when an operation start command for turning on the control switch is output. determination means for determining that the main switch is turned on and determining that the temperature switch is turned off when the detection signal is output with the control switch turned on by the operation start command; What is claimed is: 1. A heater circuit state determination device comprising: