JPS6047605B2 - Heater control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a heater control circuit that can stably turn on and off a fixing heater lamp of, for example, a copying machine with less influence on other circuits. .

The present invention will be described below with reference to drawings of embodiments.
FIG. 1 shows an electrical wiring diagram of an embodiment of the present invention. In the figure, AC power supply ACIOOV supplied to input terminals 46 and 47
is added to the primary winding of transformer 1, and diodes 2, 3, 4, and 5 are connected to the secondary winding to perform double-wave rectification, and a double-wave rectified signal as shown in Figure 2 a is placed at point a in Figure 1. get. When this double-wave rectified signal is applied to transistor 8 via a resistor, transistor 8 turns on at a voltage higher than the voltage indicated by the dotted line in Figure 2a, so the collector of transistor 8 receives a pulse signal as shown in Figure 2. obtain. This pulse signal has a frequency twice as high as the AC power signal frequency. When this pulse signal is applied to the transistor 1.2 via the resistor 10, the collector of the transistor 12 is connected via the resistor 13 to the +B DC voltage input terminal 48, and the resistor 14 and capacitor 15
Since the series connection body of is connected between the ground and the ground, it is possible to obtain a rectangular wave signal as shown in Fig. 2 C at point c in Fig. 1 using this capacitor 15 and resistors 14 and 13. can.
This rectangular wave signal is sent to voltage comparator 2
It is added to the e terminal of 3. On the other hand, a constant voltage (for example, 7■) is applied to the e terminal of the voltage comparator 20 through resistors 51, 52, and 19, a +B power supply voltage (for example, 15■) is applied to the 4th terminal through the resistor 17, and the 4th terminal is grounded. A thermistor 16 for temperature detection is connected between them. The resistance value of this thermistor 16 changes with changes in the temperature of the fixing heater lamp (hereinafter referred to as lamp) 35, and the resistance value is large (approximately 200 to 400 KΩ) at a temperature of 20'C;
At a high temperature of about C, the resistance value becomes small (approximately 3 to 10 KΩ). As shown in FIG. 3, this thermistor 16 is provided with a rotating roller 60 outside the lamp 35 in a fixing device 59 of a copying machine, etc.
6 is provided and used to control the temperature of the roller 60. Therefore, since the thermistor 16 has a high resistance at room temperature, one terminal of the voltage comparator 20 is biased to a positive voltage, and the output of the voltage comparator 20 becomes a positive voltage. Therefore, the base of the transistor 42 is positively biased through the resistors 39 and 41, so that the transistor 42 becomes conductive, and one terminal of the voltage comparator 23 is negatively biased, as shown in FIG. 2c. If two levels of voltage are applied, the voltage comparator 23 outputs the signal shown in FIG. 2d. This signal is differentiated on the output side of the capacitor 25 to become the signal shown in FIG.
6 and 27 to form a total of transistors 28. added to the source. Then, below the dotted line in Figure 2e, transistor 2
Since transistors 8 and 29 are conductive, the signal f in FIG. 2 is output to the collectors of transistors 28 and 29, and pulse transformer 31
In addition to the primary winding, the secondary winding is connected via the diode 32! Join Gate 34. This triax 34 is connected in series with the lamp 35, and both ends are connected to the AC power supply A.
Since it is connected to the input terminals 49 and 50 of the CLOOV and AC power is applied, the triax 34 becomes conductive from the moment a pulse signal is applied to the gate of the triax 34, and continues to conduct until the AC signal becomes zero. Therefore, Figure 2g
Since an AC voltage such as is applied to the lamp 35, almost the AC power supply voltage is applied, resulting in a voltage of about 98V. The above explanation is about when the transistor 42 is 0N, but in reality, since the capacitor 40 is present, when the power supply voltage +B is applied and the equipment (such as a copying machine) starts operating, the capacitor 42 is
is in a discharged state, the transistor 42 is in a cut-off state, and the four terminals of the voltage comparator 23 are positively biased, and a voltage at level 1 in FIG. 2c is applied to the output of the voltage comparator 23. No signal is output,
Since the pulse signal j is not applied to the gate of the triax 34, the lamp 35 does not light up.

Then, as time passes, the charging voltage of the capacitor 40 rises and the transistor 42 gradually becomes conductive, so that the voltage at the four terminals of the voltage comparator 23 becomes the voltage at the first level, the second level voltage, and the first level voltage as shown in Figure 2c. and move.
Therefore, the voltages applied to the lamp 35 are those shown in diagrams o, h, and g in FIG. 2. That is, lamp 3
When the device starts operating in step 5, the voltage is gradually increased and applied. The lamp 35 is 1~ like a halogen lamp.
It is a large 2KW lamp, and when the lamp 35 is 0FF and the temperature is low, the resistance value is about 1/1 compared to when it is lit.
It has become as small as 0, and when a voltage of 100V is suddenly applied, a very large current flows. Then, if the power cord of AClOOV is long or the AC power supply has a small capacity, the voltage of AClOO■ will drop to about 90V, which may cause other lamps to suddenly dim or other circuits to malfunction. . For this purpose, the voltage is gradually increased and lamp 3
I am trying to add it to 5. That is, the phase of the AC power source is controlled to change gradually. Then, when the temperature during fixing rises to, for example, 200°C, the thermistor 16 is activated.
Ω, and the 4 terminals of the voltage comparator 20 are connected to the e terminal (7
V), the output of the voltage comparator 20 approaches the ground potential, and the midpoint between the resistors 38 and 39 becomes the ground potential.

At this time, the resistor 38 has a high resistance (approximately 330KΩ), and the resistor 39
has a low resistance (approximately 1KΩ), the voltage charged in the capacitor 40 is discharged through the resistor 39, and the base of the transistor 42 is biased through the resistor 41, so the transistor 42 is cut off, and the voltage One terminal of the comparator 23 becomes the level voltage shown in FIG. 2c, and the lamp 35 becomes 0FF. Then, the lamp 35 is gradually cooled down, and the resistance value of the thermistor 16 increases, and the lamp is turned on again, then turned off, and so on, and so on, so that the temperature can be kept around a certain constant level. At this time, the resistor 38 has a high resistance, so when the capacitor 40 is charged, the lamp 35 gradually becomes 0N, but the resistor 38 is charged gradually.
Since 9 has a low resistance, the capacitor 40 discharges relatively quickly.
The lamp 35 also operates to quickly turn off. The temperature characteristics at this time are shown in FIG. The above is an explanation of how to reduce the current flowing through the lamp 35, but when the temperature is 2000
Even when the C position becomes almost constant, the lamp 35 is set to 0N-O.
When the FF changes from 0FF to 0N, a current larger than the rated current flows.

Therefore, when the temperature is close to 200°C, for example 1000C or higher, instead of applying a voltage close to 100V when the lamp is OFF, apply a voltage of around 80V, so that even when the temperature rises and the lamp 35 is turned off, a small voltage will be applied to the lamp 35. Approximately 10 to 20 V is applied to the lamp 35 so that a current flows through the lamp 35. Then, since the internal resistance of the lamp 35 does not become very small, the rush current when the lamp 35 enters the ON state does not become very large. For this purpose, an additional circuit as shown in FIG. 1 is provided. e of voltage comparator 20
The terminals are biased by the resistor 19 and resistors 51 and 52, and the connection point between the resistors 51 and 52 is connected to the 4 terminals of the voltage comparator 53, and the θ terminal is connected to the voltage comparator 20.
As with the 4 terminals, the voltage change of the thermistor 16 is applied. The voltage of the resistors 51 and 52 is higher than the voltage at the connection point of the resistors 19 and 52 of the e terminal of the voltage comparator 20.
appears at the connection point [one terminal of voltage comparator 53]. Since the resistance of the thermistor 16 is higher when the temperature is lower, when the temperature rises to, for example, 180'C, the output of the voltage comparator 53 changes from the ground potential to the positive potential. Then, the transistor 56 becomes conductive, the collector of the transistor 56 becomes a low voltage, and the transistor 64 changes from the conductive state to the cutoff state. Therefore, the transistor 42 turns ON and the lamp 35 turns ON.
Since a resistor 63 is inserted in series with the terminal resistor 22, the voltage at the level H shown in FIG. Then, when the temperature of the thermistor 16 of the fixing device rises to 200 degrees Celsius, the output of the voltage comparator 20 turns off the transistor 42 so that the lamp 35 turns off.
shall be. However, the output of the voltage comparator 53 is 180
Since the voltage is positive above ℃, the base of the transistor 61 is positively biased through the resistor 60, so the transistor 61 becomes 0N, and the four terminals of the voltage comparator 23 are biased to the ground side through the resistors 62 and 22. The voltage at the voltage level shown in FIG. 2c biases one terminal of the voltage comparator 23. Therefore, the lamp 35 has a second
A voltage of about 10 to 20 V in FIG. 0 is applied. That is, when the power is turned ON when the fuser is cold, the lamp 35 gradually changes (approximately 0.5 to 1
seconds) is turned on, a voltage close to 100V (approximately 95 to 98V) is applied to the lamp 35, and the temperature of the fixing device is quickly raised.
When the temperature of the fixing device rises to about 180°C, a voltage of about 80V is applied to the lamp 35, and when it reaches about 200°C, the lamp 35 is not turned off completely, but a voltage of about 10 to 20V is applied to stop the temperature rise. When it cools down a little, a voltage of about 80V is applied repeatedly to keep it at about 200°C. This state is shown in FIG. That is, at temperatures above 180'C, temperature changes can be made gradual. And the temperature of the fuser is set to 1
Assuming that the temperature is about 80° C., it is necessary to operate the circuit of the copying machine so that copying is possible only when the temperature is above this temperature. For this purpose, a signal from the collector of the transistor 56 is applied to a control circuit 58 of the device. This control circuit 58 is a CP that instructs to rotate the motor for feeding copy paper and to turn on the light source lamp.
This is a circuit that uses a microcomputer, etc. that includes U. Below 180° C., the collector of transistor 56 is at a high potential, instructing control circuit 58 not to operate in the copy state.

This is used to prevent the colors from coming off if you touch the copied paper by hand, since the fixing unit will not fix the copy if it is cold. Next, when the temperature exceeds 180° C., the collector of the transistor 56 becomes a low voltage, instructing the control circuit 58 to operate in the copy state. Also, when you want to forcefully turn off the lamp 35) switch S1
is set to ON, the base of the transistor 44 is positively biased as described above, the transistor 44 becomes conductive, and the transistor 42 is cut off, so that the lamp 35 can be turned OFF in the same manner as described above.

Also, the diode 37 and resistor 36 switch the power supply of this circuit to 0F.
F and is used to discharge the voltage charged in the capacitor 40 through the diode 37 and the resistor 36 when the +B voltage becomes zero. During normal operation, the diode 37 is reverse biased, so no current flows through the diode 37. As described above, according to the present invention, it is possible to provide a heater control circuit that can stably operate the temperature control of a fixing heater of a copying machine or the like.

[Brief explanation of the drawing]

Fig. 1 is an electrical wiring diagram showing an example of the heater control circuit of the present invention, Fig. 2 is an explanatory diagram of its operation, Fig. 3 is a structural diagram showing an example of the heater, Figs. The figure is a temperature characteristic diagram of the same heater. 1...Trans, 2~5,32,37...
...Diode, 8, 12, 18, 29, 42, 44,
56, 61, 64...transistor, 13, 14...
...Resistor for first charging/discharging circuit, 15... Capacitor for second charging/discharging circuit, 16... Thermistor, 20, 23, 53... Voltage comparator, 3
1...Pulse transformer, 34...Triack, 35...Fixing heater lamp, 38,
39, 41... Resistor for second charge/discharge circuit, 40...
...Capacitor for the second charging/discharging circuit.

Claims (1)

[Claims] 1 Rectangular wave generation in which a pulse signal with a period twice the frequency of the AC power source is generated from an AC power signal, and a rectangular tooth wave signal is generated using this pulse signal using the first charge/discharge circuit of the capacitor. A circuit, a temperature detector whose resistance value changes depending on the temperature of the fixing heater lamp, and a voltage which changes in accordance with the change in the resistance value of this temperature sensor are input as one input, and the first set voltage is set as the first set voltage. The other input is a first voltage comparator, one input is a voltage that changes in response to changes in the resistance value of the temperature detector, and the other input is a second set voltage higher than the first set voltage. and a second voltage comparator which receives the rectangular wave signal from the rectangular wave generating circuit as input, and the other input voltage is controlled to be supplied to the fixing heater lamp. A third voltage comparator for controlling the voltage is provided, and the charging/discharging voltage of the capacitor of the second charging/discharging circuit controlled by the output of the first voltage comparator and the output of the second voltage comparator control the charging/discharging voltage of the capacitor of the second charging/discharging circuit. By changing the input voltage of the other voltage comparator No. 3, the fixing heater lamp is gradually turned on when the power is turned on, and then a large first voltage is applied to bring the fixing heater lamp to a predetermined set temperature. Start control is performed to quickly raise the temperature and slowly raise the temperature of the fixing heater lamp to the set temperature by applying a second voltage from the first voltage near the temperature lower than the predetermined set temperature, and When the fixing heater lamp reaches a steady state, a voltage considerably lower than the rated AC voltage is applied when the fixing heater lamp is turned on, and on/off control is performed to supply a slight voltage to the fixing heater lamp even when it is turned off. A heater control circuit featuring: