JPH0339392B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heating device having an electronic control circuit configured without a power transformer and a variable resistor for setting a heating method and the like.

Configuration of the conventional example and its problems Figure 1 is a circuit diagram of the configuration of the conventional example, in which the 100V AC supplied from the power outlet 1 is
When the door 17 of the heating device 16 shown in the figure is closed, the door switch 2 and the timer 6 are turned on.
The heater heating means 5 is applied only when the relay 8 is turned on via the timer switch 3, which is turned on by setting , and the latch switch 4, which is turned on by pressing the start button 7.

On the other hand, a low voltage power source is applied via a power transformer 9 to an electronic control circuit 10 that controls the heating device 16 . The applied low voltage is constant voltage section 1
1 supplies power to the relay 8 and the control unit 12. In the control unit 12, the temperature thermistor 1
Control is performed by comparing the temperature information in the heating chamber obtained in step 3 with the temperature information set by the variable resistor 14. When the temperature in the heating chamber is lower than the temperature information set by the variable resistor A14, the relay driving transistor 15 is turned on and the relay 8 is turned on.

With the above configuration, when power is supplied to the electronic control circuit 10 via the power transformer 9, the power transformer is a safety component that separates the AC 100V line from the electronic control side, and the heating device metal The distance between the chassis part and the temperature thermistor live part, and the distance between the variable resistor live part and the metal part of the heating device is 1.
There was no problem if the insulation distance was about mm.

In addition, to deal with power supply noise and static electricity noise, a certain potential of the electronic control circuit 10 may be grounded to the chassis of the heating device 16, or the metal case or metal operating shaft of the variable resistor A14 may be grounded to the chassis of the heating device 16. Countermeasures were easily taken by doing the following.

However, an electronic control circuit that does not use a power transformer is directly connected to the AC primary side, so it is difficult to ensure safety by connecting the electronic control circuit components and the heating device 16.
This was extremely difficult in terms of construction, as it was necessary to maintain a sufficient distance from the metal chassis. Furthermore, it is impossible to ground the electric potential of the electronic control circuit to the chassis of the heating device, and it is extremely difficult to take countermeasures against power supply noise and static electricity noise, which is a major factor in increasing costs.

Purpose of the Invention The present invention was devised in view of the above-mentioned problems, and aims to improve the safety of a heating device and improve its performance against noise and static electricity.

Structure of the Invention In order to achieve the above object, the heating device of the present invention has an electronic control circuit configured without a power transformer and a variable resistor for setting the heating method attached to a resin operation panel. The operating shaft of the type resistor is made of resin, and the sliding part of the operating shaft is made of an insulator on the variable resistor side, and the side operated by the user is made of metal such as aluminum metal foil. By arranging a metal sheet and grounding the metal sheet to the chassis of the heating device, the metal body absorbs static electricity and eliminates the effect on other electronic control circuits. Even if you touch the variable resistor, you will first touch the sheared metal body, so there will be no problem of electric shock, etc., and safety can be ensured sufficiently.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a perspective view of a heating device showing an embodiment of the present invention. A door 17 that can be opened and closed is pivotally supported on the front side of the main body of the heating device 16. A start button 7, a timer 6 for setting cooking time, and an operation knob 19 of a variable resistor B20 having a resin operation shaft 19a for setting cooking temperature are provided on the resin operation panel 18. .

Inside the heating chamber, a heater heating means 5 and a temperature thermistor 13 for obtaining temperature information inside the heating chamber are installed. Furthermore, on the back side of the operation panel, an electronic control circuit unit 21 is installed, which performs control by comparing the temperature information obtained by the temperature thermistor 13 and the set temperature set by the variable resistor B20, and has a configuration that does not involve a power transformer. ing.

FIG. 3 shows an electrical circuit diagram of the invention.

100V AC supplied from power outlet 1
By closing the door 17 of the heating device 16
The voltage is applied to the heater heating means 5 for the first time when the relay 28 is turned on through the door switch 2 which is turned on, the timer switch 3 which is turned on by setting the timer 6, and the latch switch 4 which is turned on by pressing the start button 7. .

Further, the electronic control circuit unit 21 is configured such that AC 100V power is supplied only when the door switch 2, timer switch 6, and latch switch 4 are all in the ON state. When AC 100V is supplied to electronic control circuit unit 21, DC 10V is generated by rectifier diode 22, limiting resistor 23, constant voltage diode 24 and smoothing capacitor 25, and is supplied to control section 12. The control unit performs control by comparing the temperature information inside the heating chamber obtained by the temperature thermistor 13 and the set temperature set by the variable resistor B20. The relay 8 transmits the high signal output from the control unit 12 to the high voltage transistor 2.
7 base and turn on relay 28.
The relay 28 is an AC relay, and the diode 26 absorbs the back electromotive force generated from the coil of the relay 28, and uses the magnetomotive force generated by flowing the back electromotive force to suppress the beat of the relay 28 even in the case of an AC half wave. This eliminates the worries of

FIG. 4 is a detailed view of the vicinity of the variable resistor B20 for setting the cooking temperature of this heating device. On the electronic control circuit unit 21 attached to the back side of the operation panel 18, there is a variable resistor with a resin operation shaft 19a. B20 is soldered, and the operation knob 19 of the operation shaft 19a is exposed on the front side of the operation panel 18.
A metal sheet 31 that is sufficiently larger than the outer diameter of the variable resistor B20 is attached to the back side of the resin operation panel 18 around the sliding part of the operating shaft 19a of the variable resistor B20. The metal sheet 31 is the operation panel 1
The 8 side is made of double-sided adhesive tape 33, the center is made of aluminum metal foil 29, and the variable resistor B20 side is made of an insulator 30 such as polyester or vinyl chloride. The tip end 32 of the metal sheet 31 is connected to the heating device 1
6 is in contact with a metal chassis (not shown) of the main body.

With the above configuration, if 100V AC were to get onto the metal body of the variable resistor B20 operated by the user for some reason, it would be an extremely dangerous situation. If 19a is made of resin, there is no need to worry about this at all. Also, static electricity is generated during winter, and the voltage can reach 10 to 20KV. For example, 20KV static electricity travels tens of millimeters through the space and along the creeping surface, so you can easily use the variable resistor B20.
reach the metal body. Static electricity that reaches the metal body destroys parts of the electronic control circuit and falls from the lowest voltage-resistant part, such as the lead wire, into the metal chassis of the main body. However, the static electricity flies to the aluminum metal foil 29 of the metal sheet 31 provided around the sliding part of the operating shaft 19a of the variable resistor B20 of this embodiment, and falls first to the one closest to it.
Furthermore, since the end face of the metal sheet 31 is an edge when viewed from static electricity, it is easy to fly off. ) The static electricity falls onto the metal chassis of the main body through the tip 32, so
Variable resistor B20 and electronic control circuit unit 21
has no effect at all.

In addition, lightning strikes often cause induced lightning in power supplies, and the voltage ranges from a few KV to
It will be close to 10KV. When such a high voltage is applied to the power supply line, it passes through the electronic control circuit without using a power transformer and immediately reaches the metal body of the variable resistor B20. At this time, the insulation distance between the resistance pattern of the variable resistor B20 and the metal body can only be about 2 to 3 mm at most, so if the induced lightning is about 10 KV, insulation breakdown will occur.

Induced lightning that reaches the metal body of the variable resistor B20 tends to strike a nearby metal part, but since the variable resistor B20 side of the metal sheet 31 is covered with the insulator 30, the aluminum metal of the metal sheet 31 It does not fall through the foil 29 onto the metal chassis of the main body, which means that there is no damage to the electronic control circuit components. In addition, there is sufficient insulation distance and insulation material between the AC 100V circuit and the metal chassis, so it is extremely safe not only during normal use, but also in the unlikely event that induced lightning strikes the power supply.

Furthermore, the opening 34 of the sliding part of the variable resistor B20
Even if a child or other child inserts a metal rod, it will first contact the aluminum metal foil that is grounded to the metal chassis of the main unit, so the internal AC 100V
It does not touch the line and is extremely safe.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

(1) Since the operating shaft of the variable resistor is made of resin, there is no risk of electric shock and it is safe even with an electronic control circuit that does not involve a power transformer.

(2) Even if static electricity enters the variable resistor through its sliding parts, it will fall on the aluminum metal foil first, so it will not destroy any electronic circuit components and is extremely reliable.

(3) Even if induced lightning enters from the power line and hits the metal body of the variable resistor, it is insulated by the insulator covered with the shear-grounded aluminum metal foil, so the induced lightning can be detected through the electronic control circuit. There is no ground fault, making it extremely safe.

(4) Even if a metal rod, etc. is inserted through the opening of the sliding part of the variable resistor, it will hit the sheared aluminum metal foil, so it will not touch the internal AC line and is extremely safe. Highly sexual.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional heating device, FIG. 2 is an external perspective view of a heating device according to an embodiment of the present invention, FIG. FIG. 5 is an external perspective view of the metal sheet. 5... Heater heating means, 16... Heating device, 1
9... Operating knob, 19a... Operating axis, 20...
Variable resistor, 21...Electronic control circuit unit, 2
9... Aluminum metal foil, 30... Insulator, 31...
Metal sheet, 32...Tip, 33...Double-sided adhesive tape.

Claims (1)

[Claims] 1. A heating chamber, a heating means such as a high-frequency oscillator and a heater supplied into the heating chamber, a variable resistor for setting heating conditions, and controlling the heating means, etc. based on the conditions set by the variable resistor. and an electronic control circuit configured without a power transformer, the electronic control circuit and the variable resistor are attached to a resin operation panel, and the operation shaft of the variable resistor is made of resin, A metal sheet that is sufficiently larger than the external shape of the variable resistor and covered with an insulator on the variable resistor side is arranged around the sliding part of the operating shaft, and one end of the metal sheet is connected to the metal of the main body. A heating device configured to be grounded to the chassis.