JPH0412631Y2 - - Google Patents

Description

[Detailed explanation of the invention] (a) Industrial application field This invention relates to a toaster oven equipped with an electronic timer circuit, and is particularly designed to prevent the heater from being continuously energized when the switch for starting roasting malfunctions. The present invention relates to a toaster oven equipped with a circuit.

(b) Prior art In a toaster oven that controls the energization time of the heater using an electronic timer circuit and can toast bread to the desired state, for example, a PNP transistor and an NPN transistor are combined to form a circuit equivalent to a thyristor. However, it is well known to turn on the transmission circuit using a switch such as a push button switch to start an electronic timer circuit. And its equivalent circuit is PNP
When the transistor opens the switch
When the switch is turned on, the NPN transistor is also turned on, and the PNP transistor is connected to the NPN transistor so that the PNP transistor continues to be turned on even after the switch is opened.

(c) Problems to be solved by the invention However, in the above configuration, if the switch is pressed and remains on, or if it continues to be on for some reason, the electronic timer circuit times up (stops operating). However, the heater would automatically restart and keep the heater continuously energized. This caused the heater to overheat, putting the toaster oven in a dangerous state where it could cause burns if touched or a fire if left unattended.

This idea was made in consideration of the above circumstances, and even if the switch continues to be in the ON state, electricity to the heater will be stopped after the set roasting time has elapsed, making it possible to improve the safety of the oven. It is intended to provide toasters.

(d) Means for Solving Problems The structure of this invention includes an energization control means for controlling energization to the heater, a control means for controlling the operation of the energization control means, and a setting for the operation of the control means. In the toaster oven, the control means is connected in series with a switch for activating the control means and a timer means for stopping the oven after the lapse of a predetermined period of time. This toaster oven is characterized by comprising a capacitor that outputs a signal, and a self-holding circuit that is activated by the signal output from the capacitor and continues to operate the control means even after the switch is opened.

(e) Operation Even if the switch is closed for a certain period of time or more, the capacitor outputs a signal of a predetermined length of time shorter than the time set by the timer means, and the self-holding circuit is activated. The self-holding circuit is then deactivated by the timer means after the time set by the timer means has elapsed.

(F) Example The example of this invention will be described below in detail with drawings.
This invention is not limited to the following examples.

In FIG. 1, reference numeral 1 denotes an exterior body, which has an oven door 2 on its front surface, and an operation panel 3 provided below the door 2. The operation panel 3 is provided with a timer knob 4 for setting the roasting time, an operation body 5a for a switch 5 for starting roasting (hereinafter referred to as a start switch), and an operation body 6a for a stop switch 6 for ending roasting. will be provided. Each of the operating bodies 5a and 6a protrudes slightly from the surface of the operating panel 3.

Next, in FIG. 2, 7 is a constant voltage power supply circuit, which is connected to a transformer 9 into which 100V AC is input from a power plug 8, a rectifier diode 10 connected to the secondary side of the transformer 9, and a rectifier diode 10. A transistor 11 for voltage stabilization, a Zener diode 12 connected to the base of the transistor 11, a resistor 13 connected between the base and collector of the transistor 11, and a smoothing capacitor 14
It consists of Reference numeral 15 denotes a control means, for example, a start switch 5 which is a mechanical push button switch having contacts, a capacitor 16 connected in series to the start switch 5, a resistor 17 directly connected to the capacitor 16, and a resistor 17 connected to the start switch 5 in series. A stop switch 6 which is a push button switch similar to the start switch 5 is connected in series, a first transistor 19 whose base is connected to a connection point 18 between a resistor 17 and the stop switch 6, and a ground GND and the base of the first transistor 19. a second transistor 21 whose emitter is connected to the power supply line Vcc; a resistor 22 connected between the collector of the second transistor 21 and the base of the first transistor 19; Power line Vcc
and the base of the second transistor 21 , the resistor 24 connected between the base of the second transistor 21 and the collector of the first transistor 19 , the start switch 5 and the capacitor 16 It is composed of a resistor 26 connected between the connection point 25 and the ground GND. Then, the first transistor 19 and the second transistor 2
1 and resistors 20, 22, 23, and 24 constitute a self-holding circuit 27, which is a circuit equivalent to a cycler. A timer means 28 and an energization control means 29 are connected to the collector of the second transistor 21 . The timer means 28 can set a time using a time constant circuit of a capacitor and a resistor, and may be constructed of a conventionally known so-called electronic timer circuit. Further, the energization control means 29 is, for example, a relay, and in this embodiment, a relay coil is connected to the collector of the second transistor 21, and a relay contact 30 is connected in series with a heater 31, and the relay contact 30 is closed. The heater 31 is connected to the power plug 8 so that the heater 31 starts to be energized when the heater 31 is activated. A third transistor 30 stops the control means 15 in response to a signal from the timer means 28, and has a collector connected to the connection point 19 and a base connected to the timer means 28 via a resistor 31. 32 is a resistor connected between the base of the third transistor 30 and the ground GND.

Next, the operation of this embodiment will be explained.

First, when the operating body 5a of the start switch 5 is pressed, the start switch 5 is closed and the DC voltage from the constant voltage power supply circuit 7 is applied to the capacitor 16. Then, a pulse signal of a predetermined time length generated by the capacitor 16 is input to the base of the first transistor 19, and the first transistor 19 is turned on (collector-emitter short circuit).
do. As a result, the base of the second transistor 21 becomes the ground GND level via the resistor 24, and therefore the second transistor 21 is turned on.
However, current flows to the base of the first transistor 19 via the resistor 22, and the first transistor 19 continues to be in the ON state even after the current from the resistor 17 is cut off.

As described above, the start switch 5 is closed and the control means 15 starts operating, and even after the start switch 5 is opened, the operation of the control means 15 is continued by the self-holding circuit 27. and,
Due to the operation of the control means 15, the timer means 28 and the energization control means 29 are also operated simultaneously, and the relay contact 3
0 is closed and energization of the heater 31 is started.

Even if for some reason, for example, the operating body 5a is pushed in by dirt in the gap between it and the operating panel 3, and the start switch 5 continues to be closed, the capacitor 16 does not allow the start switch 5 to close. Since no current flows after a transient current flows immediately after the start switch 5, the current does not flow into the base of the first transistor 19 via the start switch 5, the capacitor 16, and the resistor 17. Note that while the start switch 5 is open, the charge charged in the capacitor 16 is
It is discharged by the resistor 26.

Thereafter, when the roasting time set in the timer means 28 has elapsed, an OFF signal of the control means 15 is applied to the third transistor 30 via the resistor 31.
The third transistor 30 is turned ON, and no current flows to the base of the first transistor 19, and the first transistor 19 is turned OFF (collector-emitter open). As a result, the second transistor 2
Current flows into the base of the first transistor 1 through the resistor 23, and the second transistor 21 also flows into the base of the first transistor 1.
Same as 9, it will be OFF. Therefore, timer means 2
8 and the switch means 29 are stopped, the relay contact 30 is opened, and the power supply to the heater 31 is also stopped.

Separately from the above, when stopping the power supply to the heater 31 during the roasting time, the stop switch 6 is closed by pressing the operating body 6a of the stop switch 6. In other words, when the stop switch 6 is closed, it is the same as turning on the third transistor 30, and the current is no longer supplied to the base of the first transistor 19.
9 and the second transistor 21 are each OFF.
As a result, the operation of the control means 15 is stopped, and the operation of the timer means 28 and the energization control means 29 are also stopped.
Power supply to the heater 31 is stopped.

(g) Effects of the invention According to this invention, even if the start switch is kept pressed or its contact is closed due to a malfunction, the heater will not be energized once the roasting time has elapsed. A toaster oven is obtained in which the heater is stopped and the heating of the heater can be prevented. In other words, in the toaster oven of this invention, if the start switch is pressed continuously, the heater cannot be energized continuously unless the start switch is released once, making the switch operation reliable and safe. This improves performance and reliability.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of this invention, and FIG. 2 is an electrical circuit diagram of an embodiment of this invention. 5...Switch, 15...Control means, 27...
Self-holding circuit, 28... timer means, 29... energization control means, 31... heater.

Claims (1)

[Scope of utility model registration request] An oven toaster comprising: an energization control means for controlling the energization of the heater; a control means for controlling the operation of the energization control means; and a timer means for stopping the operation of the control means after a set time has elapsed. The control means includes a switch that operates the control means, a capacitor that is connected in series with the switch and outputs a signal of a predetermined length of time when the switch is closed, and a capacitor that is operated by the signal output from the capacitor and that is operated by the signal output from the capacitor. A toaster oven characterized by comprising a self-holding circuit that allows the control means to continue operating even after the switch is opened.