JPH0128578B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an automatic roasting device for an oven or a toaster, and in particular, a time constant circuit determined by a capacitor and a resistor is used to control the current supply time to a roasting heater. Regarding the configuration for controlling.

[Technical background of the invention and its problems]

In conventional automatic roasting equipment, the roasting time is set and controlled using a mechanical timer using a spring or the like, or an electronic timer using a CR time constant circuit.

However, in this type of automatic roasting equipment, once the roasting time is set, the heating time remains the same no matter how many times it is roasted, so the disadvantage is that when continuously roasting, the degree of roasting differs between the first time and the second time onwards. It was hot. This is because the temperature of the roasting chamber has increased from the second time onwards, so the roasting is overbaked by the time required for the temperature of the roasting chamber to rise compared to the first time.

Therefore, in most cases, instruction manuals display the times for the first and second and subsequent firings in the case of continuous firing, and the operation is performed accordingly. There is also a method of preheating only the first time.
In any case, the drawback was that the timer operation was troublesome and extremely difficult to use.

In order to overcome this drawback, an automatic roasting device that automatically adjusts the time for the first and second roasting is known as described in Japanese Utility Model Publication No. 14057/1983.

This has the circuit structure shown in Figure 1,
When a bread platform (not shown) is operated, power switch 1 is closed by mechanical engagement, and discharge switch 2 is closed.
will be released. Therefore, the diode 4 and the resistors 5 and 6 are turned off at the same time that the heater 3 starts being energized.
Charging of the capacitor 7 is also started via the capacitor 7.

When this charging voltage reaches the primary breakdown voltage V of the transistor 8, the transistor 8 becomes conductive, and a gate current flows through the thyristor 9, which also becomes a conductive state.

Then, the electromagnetic coil 10 is energized and excited, thereby releasing the mechanical engagement and turning on the power switch 1.
is opened and the discharge switch 2 is closed. Therefore, the power supply to the heater 3 is stopped, and at the same time, the charge in the capacitor 7 starts discharging via the resistor 11.

Here, if the discharge curve of capacitor 7 is made proportional to the temperature drop time curve of the roasting chamber, in the case of continuous roasting, capacitor 7 will not complete discharging and will start charging again while the terminal voltage is V ₁ . As a result,
As shown in FIG _. 2, the second and subsequent roasting times _t2 are shorter than the first roasting time t1.

However, this configuration has a drawback that if the second roasting is started immediately after the first roasting is completed, the second roasting will be insufficiently finished.
In other words, in the case of continuous roasting, the temperature of the roasting chamber increases from the second time onwards, so the time required to heat the roasting chamber is not necessary, but no matter how high the temperature of the roasting chamber is, the temperature of the roasting chamber will increase. It takes a certain amount of time to roast objects such as bread. On the other hand, in the configuration described in the above-mentioned Utility Model Publication No. 45-14057, 1
If the interval between the first and second times is short, capacitor 7
This is because the electric discharge is not carried out sufficiently and the roasting time becomes extremely short, making it impossible to secure the above-mentioned fixed time necessary for roasting the object to be roasted.

[Object of the Invention] The present invention was made in view of the above-mentioned drawbacks, and it takes into consideration the temperature inside the roasting chamber during the second and subsequent roasting, and also maintains the constant temperature necessary for roasting the roasted material. To provide an automatic roasting device that secures time and achieves the same degree of roasting for the first and second and subsequent times.

[Summary of the invention]

The automatic roasting device of the present invention is equipped with a time constant circuit determined by a capacitor and a resistor, and when the terminal voltage of the capacitor reaches a set voltage, a switching circuit operates to cut off the current to the roasting heater and at the same time An automatic roasting device for discharging the charge of a capacitor, characterized by comprising a constant voltage circuit connected in series with the capacitor and increasing the charging start voltage of the capacitor to a predetermined value after the switching circuit operates. It is.

[Embodiments of the invention]

Next, one embodiment of the present invention will be described based on FIG.

Reference numeral 21 denotes this AC power supply that outputs AC100V, and a series circuit of a power switch 22 and a heater 23 is connected between both terminals. This power switch 22
constitutes a self-holding relay with a relay coil 24, which will be described later.

A diode 25 and a resistor 2 are connected in parallel to the heater 23.
6. Capacitor 27 and Zener diode 2
A DC constant voltage power supply consisting of 8 is connected.

Between the (+) end and (-) end of this constant voltage power supply, a series circuit consisting of a time constant circuit consisting of a resistor 29, a variable resistor 30, and a capacitor 31, and a Zener diode 32 is connected. 33,
34 series circuits are connected. A resistor 35 and a thyristor 36 are connected in parallel to the capacitor 31 and Zener diode 32, and the gate of the thyristor 36 is connected to a ground terminal via a resistor 37.

38 is a comparator, one input end of which is connected to the connection point between the variable resistor 30 and the capacitor 31, and the other input end connected to the connection point of the resistors 33 and 34. The output terminal of this comparator 38 is connected via a resistor 39 to the base of an NPN type transistor 40 serving as a switching circuit. The collector of this transistor 40 is connected to the (+) terminal via a parallel circuit of a relay coil 24 and a diode 41, to the gate of a thyristor 36 via a resistor 42, and further to a constant voltage circuit 43 including a Zener diode 32. has been done.

This constant voltage circuit 43 is configured as follows. A capacitor 46 is connected between the collector of the transistor 40 and the ground terminal via a diode 44 and a resistor 45, and a Zener diode 47 for keeping the charging voltage constant is connected in parallel to the capacitor 46. The connection point between the capacitor 46 and the resistor 45 is connected to the base of an NPN transistor 49 via a resistor 48. The collector of this transistor 49 is connected to the base of an NPN transistor 50 and a resistor 51
The emitter is connected to the (+) end through the terminal, and the emitter is connected to the ground end. Further, the collector of the transistor 50 is connected to the (+) terminal via the resistor 52 and also to the cathode of the Zener diode 32, and the emitter is connected to the ground terminal.

Next, the operation of this embodiment will be explained.

First, when you close the power switch 22 for the first time,
Power supply to the heater 23 is started. Further, one input terminal of the comparator 38 is at approximately 0V since the capacitor 31 is not charged, and the other input terminal is at a set voltage due to the voltage division between the resistors 33 and 34. Therefore, the output of the comparator 38 becomes "H" level, and the transistor 40 is turned on. Then, the relay coil 24 is energized and self-maintains the power switch 22 in the closed state. Furthermore, since the collector voltage of the transistor 40 is at the "L" level, the transistor 49 is turned off and the transistor 5
0 is in the on state, the Zener diode 32 is in the short-circuited state by the transistor 50, and the thyristor 36 is also in the off state. Therefore, the capacitor 31 is connected to the resistor 29 and the variable resistor 3.
Charging starts from 0V via 0.

When a predetermined time t ₁ elapses in this state, the capacitor 31 is charged to the set voltage V ₁ . Then,
The output of the comparator 38 is inverted and becomes the "L" level, turning off the transistor 40. Therefore, the relay coil 24 is no longer energized and the power switch 22 is opened.

Further, when the transistor 40 is turned off, the collector becomes "H" level for a moment. Then, the thyristor 36 is turned on and the charge in the capacitor 31 is completely discharged through the resistor 35, the thyristor 36, and the Zener diode 32. In addition, a capacitor 46 is connected via a diode 44 and a resistor 45.
is instantly charged to a voltage specified by the Zener diode 47. Note that the value of the resistor 48 is extremely large.

Next, when the power switch 22 is closed again after a short time _t0 , that is, before the roasting chamber and the heater 23 are cooled down, the transistor 40 is turned on in the same manner as described above, and the power switch 22 is connected to the relay coil 24. Self-maintained.

However, since the capacitor 46 is charged this time, the base voltage is applied to the transistor 49 and the transistor 49 is turned on. Then, the transistor 50
is turned off, and a Zener diode 32 is connected in series to the capacitor 31. When the power switch 22 is closed, this capacitor ₃₁ receives the Zener voltage V 2 of the Zener diode 32 via the resistor 29 and the variable resistor 30. Charging will begin soon.

In this way, in the case of continuous firing, the time constant is the same from the second time onwards compared to the first time, and the charging start voltage is higher by the Zener voltage, so the time t ₂ until the terminal voltage of the capacitor 31 reaches the set voltage V ₁ is becomes t ₂ < t ₁ . This is shown in FIG.

Then, the time of t ₁ - _{t 2} is changed between the roasting chamber and the heater 2.
If the setting is made so that 3 is the time required for heating, the degree of roasting of the object to be roasted in the first and second and subsequent times will be the same.

Furthermore, since the charge in the capacitor 46 is gradually discharged through the resistor 48 and between the base and emitter of the transistor 49, it is necessary to match the discharge time constant with the cooling time of the roasting chamber and the equipment such as the heater 23. Therefore, if the interval time is long and the device has cooled down, it will start from the same state as the first time.

Next, another embodiment will be described based on FIG. 4.
Note that the same parts as those in the circuit shown in FIG. 3 are designated by the same reference numerals, and a description thereof will be omitted.

A series circuit of a thyristor 36 and a resistor 35 is connected in parallel to a capacitor 31. A PNP transistor 61 is connected between the capacitor 31 and the ground terminal. The emitter of this transistor 61 is connected to the capacitor 31, the collector is connected to the ground terminal, and the base is connected to the capacitor 46 and the resistor 45.
connected to the connection point. Note that 62 is a resistor for discharging and has a large value.

Next, the operation of this embodiment will be explained.

First, the first time, as in the circuit shown in FIG. 3, the capacitor 46 is not charged, so the transistor 61 is turned on, and one end of the capacitor 31 is in the same state as if it were connected to the ground terminal. Therefore, charging starts from approximately 0V. Then, when the set time _t1 has elapsed, the terminal voltage of the capacitor 31 becomes the set voltage _V1 , and the transistor 4
0 is turned off, the power switch 22 is opened, and the charge in the capacitor 31 is transferred to the resistor 35 and the thyristor 3.
fully discharged through 6. Further, the capacitor 46 is instantly charged to a voltage V _c defined by a Zener diode 47 .

Then, after a short period of time, turn on the power switch 2 again.
2 is closed, the transistor 40 is turned on in the same manner as the first time, and the power switch 22 is self-held by the relay coil 24.

However, this time, since the capacitor 46 is charged with a voltage of V _c , the emitter of the transistor 61 becomes a voltage V _c +Vbe, which is the sum of V _c and the emitter-base voltage Vbe.

Therefore, the capacitor 31 is connected to the power switch 22.
Transistor 61, which is the reference voltage at the same time as the closing of
Charging will start from the emitter voltage V _c +Vbe, and this capacitor 31 will be charged at the set voltage V ₁
The time t ₂ until this happens is t ₂ <t ₁ .

Moreover, the charge in the capacitor 46 is gradually discharged through the resistor 62 during the interval time, and the terminal voltage V _c gradually decreases. Therefore, the emitter voltage V _c +Vbe of the transistor 61 also decreases as the interval time becomes longer. Here, by correlating the discharge characteristic curve of the capacitor 46 with the cooling of the device, as the interval time becomes longer and the temperature of the roasting chamber and heater decreases, the next energization time also becomes longer.

This is shown in FIG. Note that V ₂ is the terminal voltage immediately after the power switch 22 is opened, and V ₃ is the terminal voltage after the interval time t ₀ has elapsed.

In this way, in the case of continuous baking in this example, 2
After the first heating time, the heating time is controlled according to the temperature of the roasting chamber and the heater 23 even if the set time is the same.

Note that when the interval time becomes longer enough to completely cool down the roasting chamber and the heater 23, the charge in the capacitor 46 is also completely discharged via the resistor 62, so that the process starts from the same state as the first time.

Next, still another embodiment will be described based on FIG. 5. Note that the same parts as those in the circuit shown in FIG. 3 are designated by the same reference numerals, and the explanation thereof will be omitted.

A resistor 63 is connected between the capacitor 31 and the ground terminal.
is connected. This capacitor 31 and resistor 6
The connection point 3 is connected to the source of an N-channel junction FET 64. The gate of this FET 64 is connected to the connection point between the capacitor 46 and the resistor 45 via a resistor 65, and the drain is connected to the (+) end.

This embodiment also shows the same effect as the circuit shown in FIG. 4. First, the FET 64 is off because the capacitor 46 is not charged at the first time, and the resistance of the resistor 63 is low. Charging of the capacitor 31 is started from approximately 0V.

Next, from the second time onward, the capacitor 46 is charged and the terminal voltage becomes V _c , so the FET 64 is turned on and the source potential rises to V _c +V _GS . Note that V _GS is the gate-source voltage of the FET 64.

Here, the electric charge of the capacitor 46 increases as the interval time increases.
It is gradually discharged between the gate and source of the circuit and through the resistor 63, and the terminal voltage V _c decreases in correlation with the cooling of the device.

Note that, unlike the transistor 61, the FET 64 is a voltage control element, so it has the advantage that it does not adversely affect the charging and discharging characteristics of the capacitor 46.

Next, still another embodiment will be described based on FIG. 6. Note that the same parts as those in the circuit shown in FIG. 3 are given the same reference numerals, and the description thereof will be omitted.

A capacitor 66 forming a constant voltage circuit 43 is connected between the capacitor 31 and the ground terminal. This capacitor 66 also forms part of the time constant circuit. A resistor 67 is connected in parallel to this capacitor 66.

In this circuit, both capacitors 31 and 36 are charged from 0V during the first energization. When the set voltage is reached, the thyristor 36 is turned on and only the capacitor 31 is completely discharged. However, capacitor 66 is not discharged and resistor 67
Since the capacitor 66 is gradually discharged through the capacitor 66, when the second energization starts, charging starts from the terminal voltage _Vc of the capacitor 66. Therefore, the roasting time t ₂ for the second and subsequent roasting times is shorter than the roasting time t ₁ for the first roasting time.

Moreover, if the discharge characteristic curves of the capacitor 66 and the resistor 67 are correlated with the cooling of the roasting chamber and the heater 23, the same effect as that of the circuit shown in FIG. 4 can be obtained.

〔Effect of the invention〕

According to the present invention, in the case of continuous baking, from the second time onwards, the charging start voltage of the capacitor in the time constant circuit is increased to a predetermined value using the constant voltage circuit. It is possible to shorten the time required for roasting, and prevent over-baking of the items to be roasted from the second time onwards.Also, even if the interval between successive roasts becomes very short, a certain amount of time required for roasting the items to be roasted can be secured, and the You can make the doneness the same from the second time onwards.

In addition, as the interval time increases and the temperature of the roasting chamber decreases, the charging start voltage is gradually lowered in correlation with this, so that the degree of roasting for the first time and the second time onwards can be more similar.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional automatic roasting device, FIG. 2 is an explanatory diagram of the same operation as above, FIG. 3 is a circuit diagram showing an embodiment of the automatic roasting device of the present invention, and FIGS. 4 to 6 7 is a circuit diagram showing another embodiment of the present invention, FIG. 7 is an explanatory diagram of the operation of the circuit shown in FIG. 3, and FIG. 8 is an explanatory diagram of the operation of the circuit shown in FIG. 4. 23...Roasting heater, 29...Resistor, 30...
... Variable resistor, 31 ... Capacitor, 32 ... Zener diode, 40 ... Transistor as a switching circuit, 43 ... Constant voltage circuit, 61 ...
...PNP transistor, 64...N-channel junction FET, 66...capacitor.

Claims (1)

[Claims] 1. A time constant circuit determined by a capacitor and a resistor is provided, and when the terminal voltage of the capacitor reaches a set voltage, a switching circuit operates to cut off the current to the roasting heater, and at the same time, the capacitor is turned off. An automatic roasting device for discharging charged charges, comprising a constant voltage circuit connected in series to the capacitor and increasing the charging start voltage of the capacitor to a predetermined value after operation of the switching circuit. Device. 2 The constant voltage circuit uses a Zener diode,
2. The automatic roasting apparatus according to claim 1, wherein the Zener diode is connected in series to a capacitor after the switching circuit is activated. 3. The automatic control system according to claim 1, characterized in that the constant voltage circuit uses a PNP type transistor with an emitter connected to the capacitor side, and a reference voltage is applied to the base of this transistor after the switching circuit is operated. Roasting equipment. 4. The constant voltage circuit uses an N-channel junction type FET whose source is connected to the capacitor side, and a reference voltage is applied to the gate of this FET after the switching circuit is operated. automatic roasting equipment. 5. The automatic roasting apparatus according to claim 1, characterized in that two capacitors connected in series are used as the capacitors of the time constant circuit, and only one capacitor is completely discharged during operation of the switching circuit.