JPH0128355B2 - - Google Patents

Description

[Detailed description of the invention] In a conventional toaster oven, a relay is operated by the output of a mechanical timer device (for ovens) and a CR timer circuit whose time limit changes depending on the internal temperature.
A device equipped with an electronic timer device (for a toaster) that controls the time during which electricity is applied to the heater has been proposed. However, since it has two independent timer devices, it has the drawbacks of high cost and poor operability. Furthermore, if the load contact to the heater is closed using a mechanical timer device, there is a drawback that even if the electronic timer device operates, the power supply to the heater cannot be cut off.

The present invention solves the above-mentioned drawbacks, and by docking a mechanical timer device and an electronic timer circuit, the load contact for the heater is unified and shared, and an inexpensive and highly reliable timer for an oven toaster can be realized. It provides equipment.

Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

FIG. 1 shows the knob part of the timer device of the toaster oven of the present invention. When knob 1 is rotated to the right, it functions as a normal timer and can be used as a time limit for oven cooking. Rotate further to the left and
When knob 1 is set to the toast position, the built-in electronic timer circuit activates, and after a certain period of time has elapsed, the step motor is driven at a faster pulse cycle than when using a normal timer, and the heater is energized. are interrupted at the same load contact.

FIG. 2 is a block diagram showing the timer device of the present invention, and based on this diagram, the functions of the above-mentioned timer device will be explained in more detail. In the figure,
When the knob 1 is turned, the switching contact cam 2 and the load switching contact cam 3 are provided on the same axis, so they rotate in the same direction as the knob 1. Here, when the knob 1 is turned to the right, the switching contact 4 remains open and the load contact 5 closes. Then, at the same time as the heater 6 is energized,
Power is jointly supplied to the drive circuit 8 of the pulse motor 7,
The output has a waveform as shown in FIG. 3, and a pulse is generated once every 4 seconds. Therefore, the pulse motor 7 rotates in synchronization with this pulse. This rotation is decelerated by pinion 9 and gear 10,
The signal is transmitted to the cams 2 and 3. And knob 1
After a certain period of time proportional to the amount of angular displacement has elapsed, the cams 2 and 3 return to their initial positions, the load contact 5 opens, and the power to the heater 6 is cut off. The above is the operation of a timer device for normal oven cooking.

Next, the operation as a timer device for automatically roasting bread will be explained. When knob 1 is turned to the left, load contact 5 and switching contact 4 are closed. Therefore, the heater 6 is energized and power is supplied to the drive circuit 8 in the same way as the timer device for normal oven cooking. In this case, since the switching contact 4 is closed, power is also supplied to the electronic timer circuit 11, and its output stops the oscillation of the drive circuit 8. Therefore motor 7
does not rotate.

The timer circuit 11 includes a capacitor 12, a Zener diode 13, resistors 14 and 15, and a comparator circuit 16. When power is supplied to the timer circuit 11, charging of the capacitor 12 is started and the voltage between the resistor 15 and the capacitor 12 is increased. Charged with a time constant. The charging voltage waveform of this capacitor 12 is shown in FIG. The charging voltage is the reference voltage of the comparator circuit 16.
When V _S is reached (after _t1 ), a signal is transmitted from the comparison circuit 16 to the drive circuit 8, and the drive circuit 8 starts oscillating and generates a pulse output. At this time, since the switching contact 4 is closed, the oscillation period of the drive circuit 8 is
It is set shorter than when operating as the normal oven cooking timer device mentioned above, and a pulse output is output once per second. Therefore, the pulse motor 7 rotates quickly, opens the load contact 5, and cuts off the power to the heater 6. That is, the portion composed of mechanical parts such as the load contact 5, the cam 3, and the pulse motor 7 operates as a type of relay. Incidentally, the state of the output of such a drive circuit 8 is shown in FIG.

When load contact 5 opens, power to all circuits is cut off, circuit operation stops, and capacitor 1
The charge stored in 2 is first rapidly discharged through the Zener diode 13 and the comparator circuit 16, and
Thereafter, it is gradually discharged through the resistor 14. That is, as shown in FIG. 4, when the load contact 5 opens (after t ₂ ), the charging voltage of the capacitor 12 rapidly drops to the Zener voltage V _Z , and after that, the voltage of the capacitor 12 drops to the Zener voltage V Z.
It gradually discharges with a time constant determined by 4. Here, the time constant of this discharge will be described later, but it is set so as to have a correlation with the drop curve of the internal temperature of the toaster oven.

Next, after t ₃ , turn knob 1 and switch contact 4 again.
When the load contact 5 is closed, the operation is the same as in the case described above, but since the capacitor 12 is charged again from the point where it is not fully discharged,
Time until pulse motor 7 starts rotating (t ₄ −
t ₃ ) is shorter than the initial time t ₁ .

To explain the above operation as a function of the toaster oven, when knob 1 is turned to the left, it works as a timer device for automatically roasting bread. In other words, when baking bread for the first time, the internal temperature of the toaster oven is low, so a certain heating time t ₂ (3′40″ in the example) is required. However, once the heater 6 is energized, the temperature inside the toaster oven is low. As the internal temperature rises,
When baking bread consecutively, the baking time must be shorter than the first time to achieve the same brown color. That is, although it is necessary to change the time limit depending on the temperature inside the refrigerator, this is possible with the above-described configuration. In this embodiment, even if bread is baked continuously, the baked color hardly changes.

As is clear from the description of the above embodiments, the toaster oven timer device of the present invention has the following excellent effects.

(1) When operating as a timer device for automatically roasting bread, the load contacts of the timer device for normal oven cooking are shared, so there is no need to provide a separate relay, etc., and it can be manufactured at low cost.

(2) The timer function for normal oven cooking and the timer function for automatically roasting bread can be selected on the same operation axis, making it easy to operate.

(3) Since only one function can be selected,
This eliminates the drawback of providing independent timer devices as in the past (if both timer devices are operated at the same time, the power to the heater cannot be cut off until both load contacts open).

(4) Since a pulse motor is used as the drive source of the timer device, this pulse motor rotates in synchronization with the pulse output of the drive circuit, and as a result, there is no need to switch between 50 and 60 Hz.

(5) When used as a timer device for automatic bread roasting, the electronic timer circuit works and eventually rotates the pulse motor and opens the load contact, so the knob may move before roasting is complete. This makes it possible to give notice of termination.

[Brief explanation of drawings]

Fig. 1 is a front view of a knob showing an embodiment of the present invention, Fig. 2 is a circuit configuration diagram of a timer device, and Figs. 3 to 5 are drive circuit output waveforms for explaining the operation of each circuit. and a capacitor charging voltage waveform diagram. 1...Knob, 4...Switching contact, 5...Load contact, 6...Heater, 7...Pulse motor, 8...
Drive circuit, 11... electronic timer circuit.

Claims (1)

[Claims] 1. A switching contact cam and a load switching contact cam that are rotated by left and right rotation of a knob to control opening and closing of the switching contact and the load contact, a heater connected to the load contact, and the switching contact cam and the load switching contact cam. A pulse motor is used to rotate the contact cam, and this pulse motor is operated at two different pulse periods, and one of the pulse periods is selected by the switching contact, and the rotation operation direction of the knob is reversed. A pulse motor drive circuit that rotates the pulse motor, and an electronic timer circuit that is connected to the pulse motor drive circuit, starts with a signal from the switching contact, and controls the pulse motor drive circuit. A timer device for a toaster oven.