JPH0526448A - Oven toaster controller - Google Patents

Abstract

(57) [Abstract] [Purpose] The control device for setting the roasting time of the oven / toaster is a self-holding circuit that uses a relay so that a large current is cut off. To do. Also, the charging / discharging time constant of the CR timer can be set independently. [Structure] Two relays, one for self-holding and one for heater, are provided, and a resistor and a capacitor are connected to the output of the full-wave rectifier circuit to form a power source for driving the relay. When it exceeds, the transistor is turned on and the other transistor feeds back to keep the transistor on. The timer is turned off by the self-holding relay, and the heater relay is turned off when the capacitor discharges below the holding voltage. A diode and a resistor are connected in inverse parallel to the charging resistor of the CR timer for discharging so that they can be set independently.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time control device for use in an oven toaster used in general households to control the roasting time of toast or the like.

[0002]

2. Description of the Related Art Conventionally, a CR timer has been used as a control device for setting a roasting time in an oven toaster. An example of such a CR timer is shown in FIG.

In FIG. 3, reference numeral 1 is a resistor for determining a time constant, 2 is a variable resistor for changing the time constant provided for changing the time, and 3 is a resistor for determining the time constant. The capacitor charges through the resistor 1 and the variable resistor 2. The terminal voltage of the capacitor 3 is connected to the input of the voltage comparator 4, and compared with the reference voltage defined by the resistors 5 and 6, and when the terminal voltage of the capacitor 3 exceeds the reference voltage after a certain period of time, the relay 7 is driven, The contact 8 was opened to determine a short roasting time such as toast.

FIG. 4 shows a conventional example of such a CR timer, in which the capacitor 10 is charged through the resistor 9 and the terminal voltage of the capacitor 10 is detected by the N-gate thyristor 11 to stop the driving of the relay or the like. Further, here, these CR timers operate so that the first and second timer times are shorter in order to correct the temperature difference in the refrigerator between the first and second use. Figure 6 shows the status of this operation.
Shown in.

In FIG. 5, t1 indicates the first operation time, and the second time, the initial voltage V2 remaining in the capacitor.
The operating time t3 is shortened by the amount. here,
V2 is determined by the Zener diode 12 provided in the discharge path when the N gate thyristor is turned on. The resistor 13 connected to the capacitor is connected so that the V2 remaining in the capacitor decreases in accordance with the temperature decrease. If the time between the first time and the second time is t2, the voltage of V2 is decreased and t3 is It was configured to be that much longer.

[0006]

However, in the above configuration, there is a problem in that when the CR timer setting time elapses and the relay is turned off, it is always synchronized with the phase of the power supply. In addition, the phase is also synchronized with either positive or negative. For this reason, the timing at which the contacts of the relay are separated is synchronized with the peak voltage, and in this case, the contacts are transferred to cause welding. The same was true when the relay was turned on, which promoted the above tendency.

Further, since the voltage to be charged is converted into the DC voltage, it becomes impossible to charge when the leak current of the capacitor 3 or 10 increases. When the reference voltage was set high to take a long time, the difference between the capacitor terminal voltage and the charging voltage became small, and the leak current could not be ignored, resulting in a large time error. Further, if the discharge resistance 13 of the capacitor is set to a fixed value or less, the discharge current becomes larger than the charging current, so that there is a drawback that an arbitrary discharge time constant cannot be set in accordance with the temperature decrease of the oven toaster.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems and to provide a relay driving means which is not synchronized with the phase of the power source and a CR timer which can easily set the time.

[0009]

In order to achieve the above object, a control device for an oven / toaster according to the present invention operates a heater, a contact of a first relay for turning on / off the heater, and the first relay. An electronic timer, the electronic timer is connected to a switch connected in parallel with a power source via a second relay contact, and the drive power sources for the two relays are an AC power source and a DC resistance and a capacitor connected via a rectifier. The relay drive circuit consists of NPN transistor and PNP.
The capacitor and the base of the transistor are connected via the voltage detecting means and are configured to hold the conductive state by a combination with another transistor, and the electronic timer is configured to hold the conductive state when a predetermined time is reached. The roasting time is set so that the transistor for driving the second relay is turned off.

Further, it has a heater, a contact of a first relay for turning on and off the heater, and an electronic timer for operating the first relay, and the electronic timer has a switch and a second relay contact connected in parallel. Connected to an AC power supply via the AC power supply, and the power supplies of the two relays are composed of an AC power supply and a DC resistance and a capacitor connected via the first rectifier. A transistor that drives the second relay when an electronic timer reaches a predetermined time by connecting a variable capacitor and a base of the transistor through voltage detection means and holding the conductive state in combination with another transistor. Is turned off, and the electronic timer is a timer coil connected to a charging path composed of a second rectifier connected to an AC power source and a resistor. Wherein a series circuit of capacitor and resistor connected in parallel with the resistor of the charging passage and a third rectifier second
The electric discharge path connecting the cathode of the rectifier and the ground terminal of the timer capacitor, and the voltage detection means for detecting the terminal voltage of the timer capacitor constitute a control device for the toaster oven.

[0011]

With this configuration, when the relay is on, the drive power for the relay is obtained by full-wave rectification, so it turns on in either the positive or negative phase, and when it is off, the relay holding the power is first shut off. As a result, the relay that cuts off the large current is turned off because the voltage of the driving power supply drops to the holding voltage, so that the large current can be cut off asynchronously with the power supply.

By connecting a diode and a resistor in parallel with the charging resistor, the charging time constant can be set independently, so that the time setting of the CR timer can be easily performed.

[0013]

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

FIG. 1 is a circuit diagram of an oven / toaster showing an embodiment of the present invention, in which 14 is a heater, 15 is a contact of a first relay for turning the heater on and off, and 16 is a relay of the younger brother. It is an electronic timer that operates. The electronic timer and the power source are connected via a switch 17 and a second relay contact 18 which are connected in parallel.

The driving power source for the first and second relays comprises a full-wave rectifier 19, resistors 20, 21 and capacitors 22, 23, and the driving circuit for the relay is an NPN transistor 2
4 and a PNP transistor 25, and a voltage detecting means 26 composed of a Zener diode. Reference numeral 27 is a winding of the second relay, and 28 is a diode for preventing reverse voltage. Similarly, the drive circuit of the first relay is composed of the NPN transistor 29 and the PNP transistor 30, and the voltage detection means is also the one of the second relay.

Reference numeral 31 is a winding of the second relay, and 32 is a diode for preventing reverse voltage. The operation will be described with this configuration. When the switch 17 is operated to connect the power source, the capacitors 22 and 23 are charged through the full-wave rectifier 19, the resistor 20, and the resistor 21. When the terminal voltage of the capacitor rises and exceeds the set voltage of the voltage detecting means 26 set higher than the touching voltage of the relay, the NPN transistor 24 is turned on. As a result, the second relay contact 18 is closed and the power source is self-maintained.

On the other hand, transistor 24 also drives transistor 25, which results in transistors 29, 30.
Turns on and the first relay also operates. As a result, the heater is energized by the first relay contact 15 and cooking is performed. The timing of turning on this relay is either positive or negative due to full-wave rectification of the power supply.

Next, when the CR timer 16 has passed a certain time, the transistor 32 is turned on and the transistor 24 is turned off. For this reason, the second relay contact 18 opens and the power supply disappears. When the terminal voltage of the capacitor 23 becomes equal to or lower than the holding voltage of the first relay 31, the first relay contact 15 opens. Since this timing depends only on the discharge of the capacitor 23, it is not synchronized with the phase of the power supply.

FIG. 2 is a circuit diagram of a CR timer showing an embodiment of the present invention, in which 33 is a second rectifier connected to a power source, and 34 is a second rectifier.
Is a charging resistor, 35 and 36 are discharging resistors, 37
Is a third rectifier for preventing the discharging resistor from affecting charging, and 38 is a timer capacitor. Three
The resistors of 9, 40 and the variable resistor of 41 set a reference voltage and make the voltage variable. A voltage comparator 42 compares the terminal voltage of the capacitor 38 with the reference voltage. The timer operating time is set by the time until the capacitor 38 is charged through the resistor 34 and the terminal voltage reaches the reference voltage. When the timer time is reached, the transistor 44,
45 is conducted and the capacitor 38 is connected to the Zener diode 4
Discharge through 3. Further, the transistor 32 turns off the second relay.

Here, the capacitor 38 after the timer is operated
The discharge path is defined by the resistors 36, 34 and 35, and can be set independently of the charge path.

[0021]

As described above, the control device for an oven / toaster according to the present invention can turn on / off a large current relay without synchronizing with a power source, and the reliability of the relay contact is improved. In addition, the time constant of the CR timer can be set independently for charging and discharging, and the charging / discharging time corresponding to the shape of the main body can be set freely, which has great practical value.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an oven toaster according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a CR timer according to an embodiment of the present invention.

FIG. 3 is a circuit diagram of an oven toaster according to a conventional example.

FIG. 4 is a circuit diagram of an oven toaster according to a conventional example.

FIG. 5 is an operation characteristic diagram in a conventional example.

[Explanation of symbols]

14 heater 15 First relay contact 16 electronic timer 17 switch 18 Second relay contact 19 full-wave rectifier 20 and 21 resistors 22, 23 capacitors 24, 29 NPN transistor 25 30 PNP transistor 26 voltage detection means 33 Second rectifier 34 Charging path resistance 35, 36 Discharge path resistance 37 Third Rectifier 38 Timer Capacitor 42 voltage detection means

Claims (2)

[Claims] 1. A heater, a contact of a first relay for turning on and off the heater, and an electronic timer for operating the first relay, the electronic timer comprising a switch connected in parallel with an AC power source and a second relay. The drive power source for the two relays is composed of an AC power source and a DC resistance and a capacitor connected via a full-wave rectifier, and the drive circuit for the relay includes an NPN transistor, a PNP transistor, and a voltage detecting means. A transistor for driving the second relay when the electronic timer reaches a predetermined time by connecting the capacitor and the base of the transistor through a voltage detecting means so as to maintain a conductive state in combination with another transistor. A control device for the oven toaster that sets the roasting time so that the power is turned off. 2. A heater, a contact of a first relay for turning the heater on and off, and an electronic timer for operating the first relay, the electronic timer comprising a switch connected in parallel with a power source and a second relay. The drive power supply for the two relays is composed of an AC power supply and a DC resistance and a capacitor connected via the first rectifier.
It is composed of a PN transistor, a PNP transistor, and a voltage detecting means. The capacitor and the base of the transistor are connected through the voltage detecting means so that the conductive state is maintained by the combination with other transistors, and the electronic timer reaches a predetermined time. Then, the transistor for driving the second relay is turned off, and the electronic timer is connected in parallel with the timer capacitor connected to the charging path including the second rectifier connected to the AC power source and the resistor and the resistance of the charging path. A series circuit of a resistor connected to the third rectifier, a discharge path connecting the cathode of the second rectifier and the ground terminal of the timer capacitor, and voltage detection means for detecting the terminal voltage of the timer capacitor. A toaster oven control device that sets the roasting time.