JPH10160167A - Cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an overcurrent from flowing when a safety switch fails, and judge that any one of two safety switches fails, and further simplify the construction and reduce the manufacturing cost. SOLUTION: The present heating cooker is adapted such that it includes a door for opening/closing an opening part of a heating chamber, two safety switches 24, 25 provided to be capable of interrupting both electrodes of power supply lines 31, 32 and acting as switches in response to opening and closing of the door, a control circuit 35 connected with a door opening side contact b connected with each common contact c of the two safety switches 24, 25 when the door is opened for detecting a conduction state between these door opening side contacts b, a door switch 29 for detecting the open/close state of the door, and a control circuit 35 for executing detection operation of detecting a trouble of the safety switches 24, 25 when the door is opened. At least any one of the safety switches 24, 25 is judged whether or not it is troubled on the basis of the combustion state between the door opening side contacts b of the safety switches 24, 25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooking device in which a safety switch that operates in response to opening and closing of a door is provided on a power supply line.

[0002]

2. Description of the Related Art FIG. 8 shows an example of a partial electric circuit configuration in which a safety switch is provided in a microwave oven which is a heating cooker of this kind. As shown in FIG. 8, power supply lines 2 and 3 are led out of a power supply plug 1 connected to a commercial AC power supply, and safety switches 4 and 5 are provided on these power supply lines 2 and 3, respectively. A fuse 6 is provided between the safety switch 4 and the power plug 1 on one power line 2.

A portion between the power supply lines 2 and 3 on the side opposite to the power supply with respect to the safety switches 4 and 5 is connected to a monitor switch 7 and a primary winding 8a of a transformer 8. The safety switches 4 and 5 are switches that turn off when the door is opened and turn on when the door is closed. The monitor switch 7 is a so-called short switch, which is turned on when the door is opened and turned off when the door is closed. The transformer 8 is
This is a transformer that constitutes a power supply circuit that supplies power to the magnetron.

In the above configuration, when the safety switches 4 and 5 fail and continue to be turned on, when the door is opened, the monitor switch 7 is turned on, so that a short circuit is formed and an overcurrent is generated. Then, the fuse 4 is blown. With this configuration, it is possible to prevent the use of the microwave oven in a state where the safety switches 4 and 5 have failed.

[0005]

However, in the above-described conventional configuration, when the fuse 4 is blown, an overcurrent flows although the time is short, so that it is not very safe. In addition, when the overcurrent flows, the breaker of the switchboard may perform a breaking operation. Furthermore, if any one of the two safety switches 4 and 5 fails, a short circuit is not formed, so that the microwave oven is used while one of the safety switches has failed. There was a defect.

Further, it is necessary to provide a time difference between the switch operation of the two safety switches 4 and 5 and the switch operation of the monitor switch 7. Specifically, when the door is opened, the monitor switch 7 is turned on after the safety switches 4 and 5 are turned off, and when the door is closed, the safety switch 4 is turned off after the monitor switch 7 is turned off. 5 had to be turned on. For this reason, a dedicated lever member for providing the time difference is required,
There are drawbacks in that the configuration becomes more complicated and the product cost increases.

FIG. 9 shows an example of a configuration in which the switches 4, 5, and 7 are provided in the main body of a microwave oven. As shown in FIG. 9, one safety switch 4 is operated by an operation unit 10 provided on the door 9, and the other safety switch 5 is operated by an operation unit 11 and an interlock lever 12 provided on the door 9. The switch is configured to be operated. The monitor switch 7 is operated by the operation unit 11 of the door 9.
The switch is operated by a dedicated lever 13 for providing a time difference.

Therefore, an object of the present invention is to prevent an overcurrent from flowing when a safety switch fails, and to judge that one of the two safety switches has failed. An object of the present invention is to provide a cooking device capable of simplifying the configuration and reducing the product cost.

[0009]

Means for Solving the Problems A cooking device according to the present invention comprises:
A door that opens and closes an opening of the heating chamber, at least two safety switches that are provided so as to be able to shut off both poles of a power supply line and that switch according to the opening and closing of the door, and that the door is opened when the door is opened. A switch detection unit connected to a door open-side contact connected to a common contact of each safety switch and configured to detect a conductive state between the door open-side contacts, a door detection unit configured to detect an open / closed state of the door, and the door And control means for causing the switch detection means to perform a detection operation when is opened.

According to the above configuration, the switch detecting means is operated when the door is open. Therefore, when one of the two safety switches fails, the conduction state between the door open side contacts is detected. The failure of the one safety switch can be determined based on the determination. In this configuration, even if the safety switch fails, no overcurrent flows. In addition, since the monitor switch can be dispensed with and the lever dedicated to the monitor switch can be dispensed with, the configuration is simplified and the product cost is reduced. Note that a door switch, for example, is separately required as a door detection unit for detecting the open / closed state of the door. However, the door switch may be operated in synchronization with the safety switch, so that a dedicated lever for the monitor switch is not required. .

Further, in the case of the above configuration, it is preferable that the switch detection means perform a detection operation for a predetermined time when the door is opened. Further, when it is determined by the switch detecting means that the abnormality is present, the abnormality may be notified and the heating operation may be prohibited.

Further, the switch detecting means is configured to detect the resistance between the contact points on the door open side of the two safety switches, and to switch the safety switch when the detected resistance value is infinite. It is preferable to determine that the failure has occurred. In this case, it is preferable that the switch detecting means determines that the second abnormal state is established when the detected resistance value is larger than the set value. Further, when the detected resistance value is smaller than the set value, it is good to determine that the state is the third abnormal state.

On the other hand, a plurality of loads and a plurality of relays for turning on and off each load are provided between the power supply lines, and the switch detecting means sequentially turns on the plurality of relays, so that each load has a fault. Is preferably determined. With this configuration, when a special operation is performed on a key on the operation panel with the door open,
It is an even more preferable configuration to make the switch detecting means perform a detecting operation.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment in which the present invention is applied to a microwave oven will be described below with reference to FIGS. First, the principle of detecting a failure of the safety switch according to the present embodiment will be described with reference to FIGS. FIG. 2 is a diagram showing a schematic structure around a safety switch in a machine room of a microwave oven. In FIG. 2, a front opening of a heating chamber (not shown) provided in a main body 21 of the microwave oven is configured to be opened and closed by a door 22.
In the main body 21, a machine room 23 is provided adjacent to the heating room, and two safety switches 24 and 25 are provided in the machine room 23.

The safety switches 24 and 25 are composed of, for example, micro switches. One (upper) of the safety switches 24 is configured to be switched by an operation unit 26 provided at the upper end of the door 22. The other (lower) safety switch 25
Is configured to be switched by an operation unit 27 provided at a lower portion of the end of the door 22 via an interlocking lever 28.

The safety switches 24, 25 are
As shown in the electric circuit diagram of FIG.
When the door 22 is closed, the contact (c-a) turns on, and when the door 22 is opened, the contact (c
-B) is configured to be turned on. in this case,
Each contact b of the safety switches 24 and 25 constitutes a door open side contact.

A door switch 29 (not shown in FIG. 2, but shown in FIG. 1) is arranged near the lower safety switch 25 so as to be arranged side by side with the safety switch 25. The door switch 29 is composed of, for example, a micro switch, and is operated by the operation lever 27 of the door 22.
, That is, the switch operation is performed in synchronization with the safety switch 25. The door switch 29 is configured to be turned on when, for example, the door 22 is closed, and to be turned off when the door 22 is opened. Thus, the open / close state of the door 22 can be detected by turning on / off the door switch 29. In this case, the door switch 29 constitutes a door detecting unit. Note that the door switch 29 may be configured so that the on / off operation for opening and closing the door 22 is opposite to the on / off operation described above.

In FIG. 1 showing the electrical configuration, power supply lines 31 and 32 are led out of a power supply plug 30 connected to a commercial AC power supply.
A fuse 33 and a safety switch 24 are provided on one of the power supply lines 31, and a safety switch 25 is provided on the other power supply line 32. The primary winding 34a of the transformer 34 is connected between the power supply lines 31 and 32.

Specifically, the contact a of the safety switch 24 is connected to one end of the fuse 33, and the common contact c is connected to one end of the primary winding 34a. Then, the contact a of the safety switch 25 is connected to the power plug 30, and the common contact c
Is connected to the other end of the primary winding 34a. Thereby, the safety switches 24 and 25 are connected to the power supply lines 31 and 32.
Are configured to be able to cut off both poles. Furthermore,
The contact b of the safety switch 24 is connected to a first terminal 36 of the control circuit 35, and the contact b of the safety switch 25 is connected to a second terminal 37 of the control circuit 35. The two contacts c and a of the door switch 29 are connected to the third
Terminal 38 and the fourth terminal 39.

On the other hand, the transformer 34 is a transformer constituting a power supply circuit for supplying a driving power supply to a magnetron (not shown), and its secondary winding 34b is provided with a main relay and a magnetron driving power supply circuit. The various electric components (and magnetrons) that make up are connected.

The control circuit 35 has various functions as a switch detecting means and a control means of the present invention. As shown in FIG. 3, the control circuit 35 includes a microcomputer (hereinafter, referred to as a microcomputer) 41 mounted on a printed wiring board 40 and various electric components. The microcomputer 41 has a function of controlling the overall operation of the microwave oven, and stores a control program therefor. Further, as shown in FIG. 1, the control circuit 35 is configured to be supplied with a constant voltage (for example, a DC voltage of 5 V) output from the DC power supply circuit 42. The DC power supply circuit 42 includes a portion of the power supply line 31 between the fuse 33 and the contact a of the safety switch 24 and a portion of the power supply line 32 between the power supply plug 30 and the contact a of the safety switch 25. And connected to.

Next, the safety switch 2 is controlled by the microcomputer 41.
The configuration for detecting the abnormalities (faults) 4 and 25 will be described with reference to FIG. As shown in FIG.
The contact b of the safety switch 24 is connected to the input terminal 41a of the microcomputer 41 via the resistor 43, is connected to the output terminal 41b of the microcomputer 41 via the resistor 44, and further includes a capacitor 45 for noise suppression. It is connected to a grounding conductor provided on the printed wiring board 40 via a ground and is grounded. The contact b of the safety switch 25 is connected to a grounding conductor provided on the printed wiring board 40 and grounded.

In this configuration, the microcomputer 41 outputs (applies) a DC constant voltage (for example, a DC voltage of 5 V) from the output terminal 41b, and A / D converts an analog voltage signal input to the input terminal 41a. The A / D-converted digital voltage signal is input to perform signal processing (for example, processing for determining a voltage value).

In the above configuration, when the door 22 of the microwave oven is opened, the safety switches 24 and 2
5 is turned on, the output terminal 41b of the microcomputer 41 to the resistor 44, between the contact (c-b) of the safety switch 24, and the transformer, as shown in FIGS. 34, the primary winding 34a and the contact (c-
b) A configuration is formed in which an energizing path that flows to the ground through the gap is formed.

In a state where the current path is formed, the DC voltage supplied from the output terminal 41b of the microcomputer 41 is applied between the resistor 44, the contact (c-b) of the safety switch 24, and the primary winding 34a of the transformer 34. And the contact (c) of the safety switch 25
-B) so that the voltage is divided by the current-carrying resistance of the current-carrying path A that passes between the two. The divided voltage signal is applied to an input terminal 41a of the microcomputer 41. Therefore, the microcomputer 41 has the input terminal 41a
It is possible to detect the magnitude of the current-carrying resistance of the current-carrying path A by the voltage signal given to the current path A.

Here, a case where one of the safety switches 24 and 25 has failed (contact point has been fused) will be described.
As shown in FIG. 4, for example, when the safety switch 24 breaks down, when the door 22 of the microwave oven is opened, the contact (c-b) of the safety switch 24 remains off. Resistance 4 connected to terminal 41b
4 and the ground are cut off. In this circuit state, the DC voltage supplied from the output terminal 41b of the microcomputer 41 is divided by the resistor 44 and the infinite resistor, so that the microcomputer 41 receives the divided voltage signal and It is determined that the energization resistance of the energization path A is infinite, that is, that at least one of the safety switches 24 and 25 is out of order (or that the wiring configuring the energization path A is broken). It has a configuration that can be used.

The microcomputer 41 is configured to detect the on / off state of the door switch 29. For example, one end of the door switch 29 is grounded and a constant DC voltage is applied to the other end via a resistor, and a connection point between the other end of the door switch 29 and the resistor is connected to an input terminal of the microcomputer 41. It is configured to be. Thus, the microcomputer 41 can detect whether the door switch 29 is on or off based on the level of the voltage signal applied to the input terminal. And the microcomputer 41
Is configured to determine that the door 22 of the microwave oven is closed when the door switch 29 is on, and to determine that the door 22 is open when the door switch 29 is off.

Next, the operation of the above configuration, in particular, the control for judging a failure of the safety switches 24, 25, etc., will be described with reference to FIG.
This will be described with reference to the flowchart shown in FIG. The flow chart of FIG. 5 shows the contents of the control portion for judging the failure of the safety switches 24, 25 and the like in the control program stored in the microcomputer 41.

First, in step S1 of FIG. 5, the microcomputer 41 determines whether or not the door 22 has been opened based on detecting the on / off state of the door switch 29. Here, if the door 22 is opened, the process proceeds to “YES” in step S1, and the microcomputer 41
It is configured to execute a detection operation for detecting a failure such as 4, 25 or the like for a predetermined period of time (for example, several seconds).

More specifically, the process proceeds to step S2, where the microcomputer 41 outputs a constant DC voltage from the output terminal 41b, and based on the voltage signal received at the input terminal 41a, the current path A (contact point (c -B) between and transformer 3
4 contact between the primary winding 34a and the safety switch 25 (c-
b) The resistance of the energized path passing between them is detected. Subsequently, the microcomputer 41 determines whether or not the detected resistance value R is infinite (step S3).

Here, if the detected resistance value R is infinite, it is determined that at least one of the safety switches 24 and 25 is out of order (or that the wiring constituting the current path A is broken). Then, the process proceeds to “YES” in step S3, and a first abnormality notification is performed (step S4). In this case, as the first abnormality notification, for example, "EEEE" is displayed on a display of the operation panel (specifically, a seven-segment display for displaying time), and a buzzer is sounded. I have. This first abnormality notification indicates that at least one of the safety switches 24 and 25 has failed. Subsequently, the process proceeds to step S5, and all the subsequent operation operations are stopped, that is, the heating operation operation is prohibited.

If it is determined in step S3 that the detected resistance value R is not infinite, the process proceeds to "NO" to determine whether or not the resistance value R is greater than a predetermined upper limit resistance value Rmax (step S3). Step S6). Here, when the two safety switches 24 and 25 are normal, the resistance value of the current path A is substantially determined by the resistance value of the primary winding 34a of the transformer 34, and varies depending on the product, but is set in advance. Value within a certain range. On the other hand, when the wear of the electric components progresses and, for example, the primary winding 34a of the transformer 34 wears, the resistance value R of the current path A becomes the above-mentioned constant range, that is, the predetermined upper limit resistance value Rmax. It becomes a value larger than. In addition, if the insulation deterioration of the electric components progresses, for example, the insulation deterioration of the primary winding 34a of the transformer 34 progresses, the current path A
Is a value within the above-mentioned fixed range, that is, a value smaller than the predetermined lower limit resistance Rmin.

Therefore, when the primary winding 34a of the transformer 34 is worn, the process proceeds to "YES" in the judgment in the step S6, and the second abnormality is notified (step S6).
7). In this case, as the second abnormality notification, for example, “E01” is displayed on the display of the operation panel, and the buzzer is sounded. This second abnormality notification indicates that the primary winding 34a of the transformer 34 has been consumed. In the case of the second abnormality, the execution of the heating operation as it is does not cause much trouble. Therefore, the execution (inspection operation) of the control routine for determining the failure of the safety switches 24 and 25 is completed, and the main routine is executed. The operation is returned to a standby state (a state of waiting for various operation keys on the operation panel to be operated).

On the other hand, if the resistance value R is not larger than the upper limit resistance value Rmax in the step S6, "N
The process proceeds to "O", and it is determined whether or not the resistance value R is smaller than the lower limit resistance value Rmin (step S8). Here, if the insulation deterioration of the primary winding 34a of the transformer 34 is advanced, the resistance value R becomes smaller than the lower limit resistance value Rmin.
Proceeding to "YES" in step S8, a third abnormality notification is performed (step S9). In this case, as the third abnormality notification, for example, “E02” is displayed on the display of the operation panel, and the buzzer is sounded. This third abnormality notification indicates that the insulation of the primary winding 34a of the transformer 34 has deteriorated.

Subsequently, in the case of the third abnormality, similarly to the case of the second abnormality, even if the heating operation is performed as it is, there is not much trouble. Therefore, the failure of the safety switches 24 and 25 is determined. After the execution of the control routine (inspection operation) to be performed is completed, the process returns to the main routine to be in an operation standby state.

It should be noted that the heating operation can be performed when it is determined that the above is the second abnormality or the third abnormality. Instead, all the subsequent operation operations are prohibited. May be configured.

According to the above configuration, when one of the two safety switches 24 and 25 fails, the detection operation is performed when the door 22 is opened, and each of the safety switches 24 and 25 is detected. Based on the detection of the conduction state between the contacts b, specifically, the resistance value of the current path A, when the detected resistance value is infinite, for example, when one of the safety switches 24, 25 fails, It can be determined that there is (that is, the first abnormal state). In the case of this configuration, even if the safety switches 24 and 25 fail, an overcurrent does not flow, so that the safety is further improved. Further, the monitor switch 7 of the conventional configuration (see FIGS. 8 and 9) can be eliminated and the lever 13 dedicated to the monitor switch can be eliminated, so that the configuration can be simplified and the product cost can be reduced.

In the above configuration, for example, a door switch 29 is provided as a door detecting means for detecting the open / closed state of the door 22, but this door switch 29 is a safety switch 2
Since the switch operation may be performed in synchronization with 5, the dedicated lever 13 for the monitor switch can be reliably eliminated. In addition, since the door switch 29 is usually provided separately from the monitor switch in the microwave oven of the conventional configuration,
The installation of the door switch 29 does not increase the manufacturing cost. Here, in the conventional configuration, the reason why the door switch 29 is provided is that the microcomputer recognizes the opening and closing of the door.

In the above configuration, the safety switch 24,
Since it is configured to prohibit all subsequent driving operations when it is determined that the failure is 25, it is possible to prevent the heating operation from being performed while one of the safety switches remains broken. . In this case, since the user cannot operate the microwave oven, the user has to send the microwave oven for repair, and the safety is improved accordingly.

Further, in the above configuration, when the detected resistance value R is larger than the set upper limit resistance value Rmax, a second abnormal state (for example, a state in which the primary winding 34a of the transformer 34 has been consumed). Thus, the second abnormal state can be notified, and the user can reliably recognize that the microwave oven has entered the second abnormal state. Furthermore, when the detected resistance value R is smaller than a lower limit resistance value Rmin which is a set value, it is determined that a third abnormal state (for example, a state where insulation of the primary winding 34a of the transformer 34 is deteriorated) is determined. This third
Can be notified, and the user can surely recognize that the microwave oven has entered the third abnormal state.

The configuration of the microwave oven described above is a configuration for explaining the principle of detecting an abnormality of a safety switch.
The actual configuration of the microwave oven is configured by adding various loads and a relay that cuts off the loads to the above-described configuration. Therefore, a specific configuration of, for example, a microwave oven with a heater as an actual microwave oven will be described with reference to FIGS. In the electric circuit diagram shown in FIG.
The same components as those in the electric circuit diagram of FIG.

In FIG. 6, a main relay 46 is provided at a portion of the power supply line 32 closer to the transformer 34 than the safety switch 25 is. The interior lamp 47 and the turntable are rotationally driven between a portion of the power supply line 31 closer to the transformer 34 than the safety switch 24 and a portion of the power supply line 32 closer to the transformer 34 than the main relay 46. RT motor 48 is connected in parallel.

The power supply lines 31 and 3
2 and in parallel with the interior light 47 and the motor 48,
A series circuit formed by serially connecting a grill cooking heater 49 and a grill relay 50 that cuts off the heater 49 is connected, and an oven cooking heater 51 and a hot air fan motor 52 are connected in parallel. A series circuit formed by connecting a parallel circuit and an oven relay 53 that cuts off electricity through the heater 51 and the motor 52 is connected in series.
A series circuit formed by connecting in series a motor 54 of a blower fan that blows air into the heating chamber and a fan motor relay 55 that cuts off the power of the motor 54 is connected.

The transformer 3 in the power supply line 31
A range relay 56 that cuts off electricity through the magnetron is provided at a portion connected to one end of the primary winding 34a. Also, the main relay 46, the grill relay 50,
The oven relay 53, the fan motor relay 55, and the range relay 56 are configured to be individually turned on and off by (the microcomputer 41 of) the control circuit 35.
An RT motor relay that cuts off the power of the RT motor 48 is configured to be connected in series to the RT motor 48, and the RT motor relay is turned on and off by the control circuit 35 (the microcomputer 41). 48 may be configured to independently control energization.

The control circuit 35 controls the display 57 provided on the operation panel and inputs switch signals from various operation keys 58 provided on the operation panel. ing. The display 57 includes a display for displaying a current time and a cooking time, a display for displaying a cooking menu, and the like. The various operation keys 58 include a cooking menu selection key, a time setting key, a start key, a cancel key, and the like.

Next, the operation of the above configuration, in particular, the control for judging the failure of the safety switches 24 and 25 (detection operation when the door is opened) will be described with reference to the flowchart shown in FIG. The flowchart of FIG.
3 shows the contents of a control portion for judging a failure of the safety switches 24, 25 and the like in the control program stored in the microcomputer 41 of FIG.

First, in step S101 of FIG.
The microcomputer 41 determines whether or not the door 22 has been opened based on detecting the on / off state of the door switch 29. Here, when the door 22 is opened, step S1
Then, the process proceeds to “YES” at 01, and the microcomputer 41 performs a detection operation (steps S102 to S113) for detecting a failure of the safety switches 24 and 25 described below in a predetermined time (for example, 1 to 2 seconds). Configured to run.

Specifically, the process proceeds to step S102, where the microcomputer 41 turns on the main relay 46, and then proceeds to step S103, where the microcomputer 41 first performs a process of detecting a failure of the safety switches 24 and 25. This detection processing is performed in the same manner as the processing in steps S2 and S3 described above. More specifically, the energization resistance between the contacts b of the safety switches 24 and 25 is detected, and when the detected resistance value is infinite, it is determined that at least one of the safety switches 24 and 25 has failed. . And the microcomputer 41
Stores the above determination result.

Then, the process proceeds to a step S104, wherein the interior lamp (lamp) 47 and the RT are determined based on the detected resistance value.
A check (detection) is performed to determine whether the motor 48 is worn out or the insulation is deteriorated. This detection processing is performed in the same manner as the processing in steps S6 and S8 described above. That is, the microcomputer 41 determines that the detected resistance value R is equal to the upper limit set value R.
If the resistance value R is smaller than the lower limit set value Rmin1, it is determined that a second abnormality has occurred (the interior lamp 47 and the RT motor 48 have been consumed). (Insulation deterioration of parts), and the result of the determination is stored.

Thereafter, after the main relay 46 is turned off, the process proceeds to step S105, in which the microcomputer 41 turns on the main relay 46 and the grill relay 50, and then proceeds to step S106, in which the microcomputer 41 sets the heater for grill cooking. A process for checking (detecting) whether or not the power supply 49 is depleted or the insulation is deteriorated is executed. This detection processing is performed in the same manner as the processing in steps S6 and S8 described above. That is, the microcomputer 41 detects the energization resistance between the contacts b of the safety switches 24 and 25, and if the detected resistance value R is larger than the upper limit set value Rmax2, the second abnormality (the heater 49 as an electric component) is detected. If the resistance value R is smaller than the lower limit set value Rmin2, it is determined that the abnormality is the third abnormality (insulation deterioration of the heater 49), and the result of the determination is stored.

Subsequently, after the main relay 46 and the grille relay 50 are turned off, the process proceeds to step S107, where the microcomputer 41 turns on the main relay 46 and the oven relay 53, and then proceeds to step S108, where the microcomputer 4
1 executes processing for checking (detecting) whether or not the heater 51 and the motor 52 for oven cooking have been consumed or insulation has deteriorated. This detection processing is performed in steps S6 and S
8 is performed in the same manner. That is, the microcomputer 41
Detects the energization resistance between the respective contacts b of the safety switches 24 and 25, and the detected resistance value R is equal to the upper limit set value Rmax3.
If it is larger than the second abnormality (heater 5 which is an electric component)
1 and the motor 52 are consumed), and if the resistance value R is smaller than the lower limit set value Rmin3, it is determined that the abnormality is the third abnormality (insulation deterioration of the electric component), and the result of the determination is stored.

Then, after the main relay 46 and the oven relay 53 are turned off, the process proceeds to step S109, and the microcomputer 41 turns on the main relay 46 and the range relay 56. Then, the process proceeds to step S110.
1 executes processing for checking (detecting) whether the primary winding 34a of the transformer 34 for range cooking has been worn out or has insulation deterioration. This detection processing is performed in steps S6 and S
8 is performed in the same manner. That is, the microcomputer 41
Detects the current-carrying resistance between the contacts b of the safety switches 24 and 25, and if the detected resistance value R is larger than the upper limit set value Rmax, the second abnormality (the transformer 34 which is an electric component) is detected.
Is consumed), and the resistance value R is set to the lower limit set value Rmi.
If it is smaller than n, it is determined to be the third abnormality (insulation deterioration of the electric component), and the result of the determination is stored.

Thereafter, after the main relay 46 and the range relay 56 are turned off, the process proceeds to step S111, where the microcomputer 41 sets the main relay 46 and the fan motor relay 5
Then, the microcomputer 41 executes (step S112) a process of checking (detecting) whether the fan motor 54 has worn out or has insulation deterioration. This detection processing is performed in the same manner as the processing in steps S6 and S8 described above. That is, the microcomputer 41 includes the safety switch 24,
25, the detected resistance value R is larger than an upper limit set value Rmax4, and it is determined that the second abnormality (wear of the fan motor 54 as an electric component) is present, and the resistance is determined. If the value R is smaller than the lower limit set value Rmin4, it is determined that there is a third abnormality (insulation deterioration of the electric component), and the result of the determination is stored.

Subsequently, after the main relay 46 and the fan motor relay 55 are turned off, the process proceeds to step S113. If the microcomputer 41 stores one or more types of abnormalities as the stored judgment result, The above abnormality is displayed on the display 57. If the safety switches 24 and 25 are out of order,
It is configured to stop all subsequent operation operations, that is, to prohibit the heating operation operation. here,
When an abnormality other than the failure of the safety switches 24 and 25 is detected, there is no problem even if the heating operation is performed as it is, so that the control routine for determining the failure of the safety switches 24 and 25 (inspection operation) is performed. Upon completion, the flow returns to the main routine, and the operation is in a standby state.
It should be noted that even when an abnormality other than the failure of the safety switches 24 and 25 is detected, all the subsequent driving operations may be stopped.

According to the present embodiment having such a configuration, the same operation and effect as those obtained by the configuration for explaining the principle of the detection operation can be obtained. In particular, in the above embodiment, by sequentially turning on a plurality of relays, it is possible to easily determine an abnormality or a failure of a plurality of electric components as a plurality of loads. Further, in the above embodiment, the safety switches 24 and 25 and the failure checking operation of the plurality of electric parts are configured to be executed in about 1 to 2 seconds. Even if there is a failure and the contacts (ca) are on, it takes about 3 seconds for the magnetron to oscillate,
The check operation can be completed before the magnetron is driven to oscillate, and safety can be sufficiently ensured.

In the above embodiment, when the door 22 is opened, the detection of the failure of the safety switches 24 and 25 and the detection of the failure of a plurality of electric components are executed. When the door 22 is opened, only the failure of the safety switches 24 and 25 is detected, and the failure of a plurality of electric components is detected by operating the operation key of the operation panel while the door 22 is open. It may be configured to execute when a predetermined special operation is performed. With such a configuration, when the door 22 is opened, almost no driving sound of the relay is generated, so that it is not annoying. Further, the detection method for starting the detection operation of the failure of the plurality of electric components by the special operation of the operation key can be used as one of the diagnosis methods when the service person repairs the microwave oven.

Further, in the above embodiment, the safety switch 2
After detecting the failure of the safety switches 4 and 25, the detection of the failure of the plurality of electrical components is performed. However, the invention is not limited thereto. May be stopped so that detection of a failure of a plurality of electric components is not executed. Further, in the above-described embodiment, when the door 22 is opened, the failure of the safety switches 24, 25 and the like is detected. However, the present invention is not limited to this. For example, when the door 22 is opened, , On the condition that a predetermined operation key among the operation keys of the operation panel is operated,
It may be configured to execute a failure detection operation such as 4, 25, etc. Further, in the above embodiment, the power supply lines 31, 32
Are provided with two safety switches 24 and 25, but instead of this, three or more safety switches may be provided. In this case, specifically, it is preferable that two or more safety switches are provided in one power supply line.

[0058]

As is apparent from the above description, the present invention is connected to a door open side contact which is connected to a common contact of at least two safety switches when the door is opened, and is connected between the door open side contacts. It has a switch detection means for detecting the conduction state of the switch and a control means for detecting the switch detection means when the door is open, thereby preventing an overcurrent from flowing when the safety switch fails. In addition, it is possible to determine that one of the two safety switches has failed, and it is possible to simplify the configuration and reduce the product cost.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram for explaining the principle of a detection operation showing one embodiment of the present invention.

FIG. 2 is a schematic vertical side view of a microwave oven.

FIG. 3 is an electric circuit diagram showing a main part of a control circuit and a safety switch.

FIG. 4 is a diagram corresponding to FIG. 1 when one of the safety switches has failed.

FIG. 5 is a flowchart.

FIG. 6 is an electric circuit diagram of a microwave oven with a heater.

FIG. 7 is a flowchart.

FIG. 8 is a diagram corresponding to FIG. 1 showing a conventional configuration.

FIG. 9 is a diagram corresponding to FIG. 2;

[Explanation of symbols]

21 is a main body, 22 is a door, 24 and 25 are safety switches, 2
9 is a door switch (door detection means), 31 and 32 are power supply lines, 34 is a transformer, 34a is a primary winding, 35 is a control circuit (switch detection means, control means), 40 is a printed circuit board, and 41 is a micro circuit board. Computer, 46 is a main relay, 50 is a grill relay, 53 is an oven relay, 55
Denotes a fan motor relay, and 56 denotes a range relay.

Claims (8)

[Claims] 1. A door for opening and closing an opening of a heating chamber, at least two safety switches provided so as to be capable of shutting off both poles of a power supply line, and performing a switching operation in accordance with opening and closing of the door; A switch detecting means connected to a door open-side contact connected to a common contact of each of the safety switches when the safety switch is opened, and detecting a conduction state between these door open-side contacts; and a door detecting an open / closed state of the door. A heating cooker comprising: a detection unit; and a control unit that performs a detection operation of the switch detection unit when the door is open. 2. The cooking device according to claim 1, wherein the control means causes the switch detection means to perform a detection operation for a predetermined time when the door is opened. 3. The heating cooking according to claim 1, wherein the control means notifies the abnormality when the switch detection means determines that the abnormality is present, and prohibits the heating operation. vessel. 4. The switch detecting means is configured to detect a resistance between two door open contacts of the safety switch, and when the detected resistance value is infinite, the safety switch of the safety switch is detected. The cooking device according to any one of claims 1 to 3, wherein the cooking device is determined to be malfunctioning. 5. The cooking device according to claim 4, wherein the switch detection means determines that the second abnormal state is established when the detected resistance value is larger than the set value. 6. The cooking device according to claim 4, wherein the switch detecting means determines that the third abnormal state is established when the detected resistance value is smaller than the set value. 7. A configuration in which a plurality of loads and a plurality of relays for turning on and off each load are provided between the power supply lines, and the switch detection means turns on the plurality of relays sequentially to detect a failure of each load. The heating cooker according to any one of claims 1 to 6, wherein the determination is made. 8. The cooking device according to claim 7, wherein the control means detects the operation of the switch detection means when the operation key of the operation panel is specially operated while the door is open.