JPH10125459A - Microwave oven - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such a microwave oven capable of detecting not only any trouble on high voltage parts, electronic parts and poor connection of wiring, but also any welding of a relay contact. SOLUTION: In a microwave over provided with a magnetron 2, a convection heater 7, a lower heater 5, and upper heater 6 and a current transformer 3 for detecting the value of a current flowing in a circuit to which the respective heating means are connected, and an operation panel 11 and a micro-computer 1 for controlling current flow to the respective heating means on the basis of input signals from the operation panel 11, the micro-computer 1 is transferred to an inspection mode by means of a prescribed input operation from the operation panel 11, and in this inspection mode, electrification is applied to the respective heating means in a sequence of a large electric flow consumption first, and by comparing the current value detected by the current transformer 3 of the precedingly electrified heating means with a current value detected by the current transformer 3 of the subsequently electrified heating means, the connection state of respective heating means is judged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the detection of erroneous wiring in the manufacture of a microwave oven and the abnormality of a circuit caused by welding of a relay contact.

[0002]

2. Description of the Related Art Recent microwave ovens are equipped with heater heating means using a heater in addition to microwave heating means using microwaves, and multi-functionalization is progressing. As the functions have increased, the circuits have become more complicated, and as a result, the wiring inside the set of the microwave oven has become complicatedly intertwined.

[0003] Further, when manufacturing a set of microwave ovens, wiring work has not yet been automated, and there are many places where the operator must rely on manual work. here,
The complexity of the above-mentioned internal wiring has been a factor of increasing erroneous wiring and erroneous insertion by an operator.

Conventionally, the inspection of the internal wiring of a microwave oven involves visually inspecting the wiring itself to make sure that the wiring is correct, actually operating the microwave oven, and checking whether the heater glows red and the fan to rotate. The worker visually inspected whether or not. Alternatively, by connecting a measuring instrument such as an ammeter to a microwave oven and checking the current value, power value, etc. of the measuring instrument,
Inspection was performed to check that the wiring was normal.

Various methods have been proposed as means for detecting an abnormal state of a microwave oven. When a magnetron or rectifier is damaged and a short-circuit current flows to the secondary side of a high-voltage transformer, a fuse cuts off the secondary circuit to prevent burning of the high-voltage transformer. It has been used in gazettes for a long time.

However, with the development of microcomputers, computerization has progressed, and a method of controlling energization by a current transformer has been proposed.
It is disclosed in JP-A-6-188072, JP-B-7-1712, JP-A-1-276590 and the like, and is widely used.

FIG. 6 shows a circuit of a microwave oven having a current transformer. In FIG. 6, the current transformer 103 is connected to a primary circuit of a power supply. The signal level detected by the current transformer 103 is compared with a reference level stored in advance, and the microcomputer 101 controls the magnetron 102 to stop.

In the above-mentioned conventional method, the failure is detected in the high voltage capacitor, the diode, the magnetron 102 and the like, and the energization is controlled. The failure detection by the current transformer 103 was easy because the current value flowing through the current transformer 103 greatly changed at the time of failure.

[0009]

As described above, the visual inspection or the inspection method using a measuring instrument for determining the quality of the wiring work depends on the eyes of the operator and lacks reliability. Then, a worker is required at the time of the inspection, and automation of the inspection does not proceed, which is a problem.

[0010] On the other hand, in the inspection method using the current transformer, control is performed such as capturing a place where a current value changes due to a failure or failure of a high-voltage component or an electronic component and stopping heating. However, the failure detection has been completed up to that point, and no failure such as contact welding of the relay has been detected. In addition, the failure detection of the relay detects the voltage of the coil terminal (low voltage side) of the relay by the microcomputer, and detects the failure that the relay contact does not turn on and cannot be heated regardless of the voltage being applied. Until and had been implemented. However, even if the relay is welded, it is irrelevant to the coil terminal voltage. Therefore, the welding of the relay contact cannot be detected only by inspecting the voltage of the coil terminal of the relay.

An object of the present invention is to provide a microwave oven capable of detecting not only failure of high-voltage components and electronic components, poor connection of wiring, but also welding of relay contacts.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and the invention according to claim 1 is applied to a plurality of heating means and a circuit connected to the plurality of heating means. Current detecting means for detecting a current value; input means for inputting an operation of the plurality of heating means; and control means for controlling energization to the plurality of heating means based on an input signal from the input means. In the microwave oven, the control unit shifts to an inspection mode by a predetermined operation from the input unit. In the inspection mode, the plurality of heating units are energized in order of increasing or decreasing current consumption, and are first energized. A current value detected by the current detection means of the heating means,
The connection state of the plurality of heating means is determined by comparing a current value detected by the current detection means of the heating means which is energized later.

According to a second aspect of the present invention, the control means detects the current value detected by the current detection means of the heating means which has been energized first, and detects the current value by the current detection means of the heating means which has been energized later. When the current value is small, it is determined that the heating means is erroneously connected.

According to a third aspect of the present invention, there are provided a plurality of connecting means for respectively connecting the plurality of heating means and the circuit, wherein the plurality of connecting means are arranged in order of increasing or decreasing current consumption of the heating means. They are arranged side by side.

According to a fourth aspect of the present invention, there is provided a heating means, a current detecting means for detecting a current value flowing to a circuit to which the heating means is connected, an input means for inputting an operation of the heating means, A microwave oven comprising: a plurality of relays for turning on / off energization of the means; and control means for controlling energization of the heating means based on an input signal from the input means.
The control means detects the welding of the relay contacts by comparing a current value detected by the current detection means when the heating means is not energized with a predetermined reference value.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a microwave oven according to the present invention will be described below with reference to FIGS. FIG. 1 is a circuit diagram according to an embodiment of a microwave oven of the present invention. In FIG. 1, reference numeral 1 denotes a control microcomputer, 2 denotes a magnetron for generating a high frequency, 3 denotes a current transformer, and 4 denotes a high-voltage transformer for generating a high voltage to be supplied to the magnetron 2. 5 is a lower heater disposed below the cooking chamber (not shown); 6 is an upper heater disposed near the ceiling in the cooking chamber;
7 is a convection heater for heating with hot air, 8 is a rectifying circuit for rectifying an AC power supply, 9 is a fan motor, 11 is an operation panel, 13 is an input key provided on the operation panel 11, and 17 is a fan motor 9 An oven lamp is connected in parallel to the oven and illuminates the cooking room.

A relay L1 is connected in series to the magnetron 2, a relay L2 is connected in series to the lower heater 5, a relay L3 is connected to the upper heater 6, and a relay L4 is connected to the convection heater 7. Are connected in series, a relay L4 is connected in series to the fan motor 9 and the oven lamp 17, and the relays L1 to L5 control the energization of the connected devices by a signal from the microcomputer 1.

At the time of microwave heating, the microcomputer 1 turns on the relay L1, energizes the high-voltage transformer 4, oscillates the magnetron 2, generates microwaves, and heats the food in the cooking chamber. After pressing various input keys 13 provided on the operation panel 11 to set cooking conditions, pressing a start key starts a cooking operation. The microcomputer 1 reads a signal from the input key 13 and responds to the input signal from the relay L.
1 to L5 are operated. The operation of the relays L1 to L5 is enabled by sending a signal from the microcomputer 1 to a base of a transistor connected to each of the relays L1 to L5 according to an instruction of the microcomputer 1. The operation and timing of each relay are commanded according to a predetermined program. If it is a range heating, the relay L1 is turned on as described above.

Further, with the multifunctionalization of microwave ovens, the number of microwave ovens to which heater heating is added in addition to microwave heating has recently increased. The heater is heated by the lower heater 5,
This is performed by the upper heater 6. In addition, these lower heaters 5,
The upper heater 6 can be disposed inside the oven or outside the wall. The heater heating is used for menus such as burning and baking food.

In convection heating, hot air is circulated in a cooking chamber in order to make cakes and sweets such as cookies. This means that the relay L4 is turned on to energize the convection heater 7, and the fan motor 9 is rotated to circulate hot air into the cooking chamber.

When the heating means operates, a current flows from the power supply. This current is taken out by the current transformer 3. In the current transformer 3, an induced voltage corresponding to the current flowing from the power supply to the heating means is generated. This induced voltage is converted into a direct current by the rectifier circuit 8 and read by the microcomputer 1 as a signal voltage.

The printed circuit board 12 of the relays L1 to L6
FIG. In FIG. 2, reference numeral 10 denotes a relay, which is fixed on the printed circuit board 12 by soldering. The coil portion of the relay 10 has a low voltage and is controlled by the microcomputer 1 as shown in FIG. But,
The contact side of the relay 10 is connected to the relay 10 as shown in FIG.
The case is disposed separately from the low-pressure side. The relay contact 10a is formed by a tab terminal. The connector 15 is inserted into the tab terminal. Faston terminals (not shown) are mounted inside the connector 15.
An electric wire 16 is fixed to the Faston terminal by caulking. The number of electric wires 16 to which the Faston terminal is crimped may be two.

Then, the connectors 15 are prepared according to the number of relays, and the operator looks at the instruction book to connect the connectors 1.
5 is connected to the corresponding tab terminal. If the connector 15 is correctly inserted, the microwave oven operates normally. Further, in the production line, the microcomputer 1 is programmed to shift to the wiring inspection mode when a predetermined special operation is performed on the input key 13 provided on the operation panel 11. In addition, the above-mentioned special operation means that a predetermined input key is continuously pressed, a predetermined input key is pressed in a predetermined order,
This is executed by keeping a predetermined input key pressed for a certain period of time.

The wiring inspection mode in the microwave oven according to the present embodiment will be described. The determination is made by comparing the numerical values of the signals V1 to V5 read from the current transformer 3 in the state in which the inspection mode has been entered by the special operation.

When the wiring is normal, a current consumption as shown in FIG. 3 flows to the heating means. This current consumption value has little variation. If the current consumption is large, the voltage of the current transformer also increases. Table 1 shows the relationship between the current consumption of each heating means and the voltage generated in the current transformer when each heating means is energized.

[0026]

[Table 1]

FIG. 3 shows a flowchart of the wiring inspection mode. In FIG. 3, in step S1, the inspection is performed by first turning on the relay L5,
The current consumed flows. This current consumption is about 1 A, and the voltage at this time is stored as V5 in step S1. Next, in step S3, when the relay L5 is turned off and the relay L1 is turned on, the range heating is performed and the current consumption is reduced to one.
1A flows. In step S4, the induced voltage generated in the current transformer is stored as V1. Step S5
Then, V5 and V1 are compared.

Here, if V1> V5, it is determined that the wiring is performed normally, and the process proceeds to step S6. However, V1 <
If it is V5, it is determined that the wiring is incorrect, and the process proceeds to step S16. In step S16, after the microcomputer 1 generates an error signal, a warning display and notification are performed. Since there are various warning and notification methods, if the error that has passed through this routine (the error that has shifted from step S6) is error number 1, it is immediately possible to know which wiring is wrong by just looking at the error number. .

In step S6, the relay L1 is turned off.
F, the relay L2 is turned on, and the voltage V2 of the current transformer 3 is stored in step S7. Next, step S8
Then, V2 and V1 are compared. If V2> V1, it is determined that the wiring is performed normally, and the process proceeds to step S9. But,
If V2 <V1, the wiring is determined to be incorrect and the process proceeds to step S16.

Further, at step S9, the relay L2 is
The FF and the relay L1 are turned on, and in step S10, the voltage V3 of the current transformer is stored. Next, step S1
At step 1, V3 and V2 are compared. If V3> V2, it is determined that the wiring is performed normally, and the process proceeds to step S12. However, if V3 <V2, it is determined that the wiring is wrong, and step S16
Move to

Then, in step S12, the relay L3 is turned off and the relay L4 is turned on. In step S13, the voltage V4 of the current transformer is stored. Next, step S
At 14, V4 and V3 are compared. If V4> V3, it is determined that the wiring is performed normally, and the process proceeds to step S15. However, if V4 <V3, it is determined that the wiring is wrong, and step S1
Move to 6. In step S15, it is determined that the normal wiring is OK, and the inspection mode ends. In the flowchart shown in FIG. 3, the voltages are compared in descending order of the detected voltage, but may be compared in descending order.

The actual relays are arranged side by side on a printed circuit board as shown in FIG. If the inspection is performed so that the relays are turned ON and OFF in the arranged order, the inspection accuracy can be further improved. First, the leftmost relay is turned on. Next, the relay is turned off, and the relay located next to the leftmost relay is turned on. Then, the voltage of the relay is compared with the voltage of an adjacent relay.

In this way, the comparison between the neighbors becomes easy, and the erroneous wiring with the neighbor having many mistakes can be immediately identified. With this configuration, the position in the actual wiring can be known, so that repair can be easily performed. This operation is performed only during production. The sold customer is not informed of how to press a specific key and cannot perform this operation. Conventional relays are appropriately combined and controlled in accordance with each heating condition.

Further, the plastic case of the connector 15 is colored so as not to make a mistake in wiring. As shown in FIG. 2, the colors are colored such that the first color is brown, the second color is red, and the like according to the color code in the order in which the relays 10 are arranged. By doing so, serviceability and workability are improved, and the reliability of erroneous wiring can be reduced.

A method for detecting the welding of the contact of the relay 10 by detecting the current value during the cooking operation will be described. As shown in FIG. 3, when the cooking start key is pressed, first, the relay L5 is turned on.
Then, the fan 9 and the oven lamp 17 are turned on. The current value at this time is small. After a few seconds, the heating means (magnetron 2, lower heater 5, upper heater 6, convection heater 7)
Is turned on). The current value at this time is large.

When the relay L5 is turned on, the other relay L1
When the current value in the OFF state is larger than a predetermined current value, the microcomputer 1 determines that the relay contact is welded, generates an error signal, and notifies the user with a buzzer or the like. I do. The detection of contact welding by the current transformer 3 is performed at a timing when the cooking operation is being performed but the heating means is not operating. For example, in order to defrost food, when cooking with microwave oven ON / OFF,
Current transformer 3 when microwave heating is OFF
Is checked, and if the current value when the signal voltage is OFF is larger than a predetermined current value, it is determined that relay welding has occurred.

That is, when a large voltage is generated in the current transformer while the relays L1 to L4 are not turned on, it is determined that the relays are welded. As a result, it is possible to detect the welding of the relay which could not be detected in the past, detect the defect at an early stage, and prevent an accident. Accordingly, the relay is welded during cooking, and the heating means is turned on even when the heating means should be turned off, so that it is possible to prevent the food from being overheated and the temperature rise of the parts from increasing.

[0038]

According to the first and second aspects of the present invention, erroneous wiring can be easily detected and a reliable inspection can be performed.

According to the third aspect, by comparing and judging adjacent connection means having the highest probability of erroneous wiring, it is possible to easily determine which connection is wrong and the position of erroneous wiring. Good inspection becomes possible.

According to the fourth aspect, the welding of the relay can be detected, and when the heating means is not operating, there is no overheating, so that an accident can be prevented beforehand.

[Brief description of the drawings]

FIG. 1 is a wiring diagram showing an embodiment of a microwave oven according to the present invention.

FIG. 2 is an enlarged view of a main part showing a substrate of the embodiment of the microwave oven of the present invention.

FIG. 3 is an explanatory diagram showing operation timings of a fan and a heating means of the present invention.

FIG. 4 is a flowchart illustrating an abnormality detection operation according to the present invention.

FIG. 5 is a circuit diagram of a microwave oven provided with a conventional current transformer.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 microcomputer 2 magnetron 3 current transformer 4 transformer 5 lower heater 6 upper heater 7 convection heater 8 rectifier circuit 9 fan motor 11 operation panel 12 printed circuit board 15 connector 16 electric wire

Claims (4)

[Claims] 1. A plurality of heating means, a current detection means for detecting a value of a current flowing in a circuit to which the plurality of heating means are connected, an input means for inputting an operation of the plurality of heating means, and the input means And a control means for controlling energization to the plurality of heating means based on an input signal from the control means, wherein the control means shifts to an inspection mode by a predetermined operation from the input means. The plurality of heating means are energized in order of increasing or decreasing current consumption, and the current value detected by the current detection means of the heating means which has been energized first and the current value detected by the current detection means of the heating means which has been energized later A connection state of the plurality of heating means is determined by comparing the current value with the measured current value. 2. The heating device according to claim 1, wherein the control unit is configured to perform heating when a current value detected by the current detection unit of the heating unit that is energized later is smaller than a current value detected by the current detection unit of the heating unit that is energized first. The microwave oven according to claim 1, wherein it is determined that the means is incorrectly connected. 3. A plurality of connecting means for connecting the plurality of heating means and the circuit, respectively, wherein the plurality of connecting means are arranged side by side in order of increasing or decreasing current consumption of the heating means. The microwave oven according to claim 1, wherein 4. A heating means, a current detecting means for detecting a current value flowing to a circuit to which the heating means is connected, an input means for inputting an operation of the heating means,
A microwave oven comprising a plurality of N / OFF relays; and a control means for controlling energization of the heating means based on an input signal from the input means, wherein the control means detects each of the currents detected by the current detection means. A microwave oven characterized in that a current value when the heating means is not energized is compared with a predetermined reference value to detect contact welding of the relay.