JPH06282199A - Heater lamp control method for electrophotographic printing device - Google Patents

Abstract

PURPOSE:To prevent the flowing of a high rush current, the reduction of the service lifes of a heater lamp, a connector, etc., and the increase of noise by always limiting a feed current lower for the first specified time in power feeding to the heater lamp. CONSTITUTION:A time from the tuning on of a photo-TRIAC 23 to that of a photo-TRIAC 25 is a period that the phase of a TRIAC 27 is controlled. Then, the temperature of the heater lamp 2 is raised in the period to increase the resistance value of the heater lamp 2, the photo-TRIAC 25 is turned on by the increase of the resistance value of the heater lamp 2 and even if the TRIAC 27 is turned on, the flowing of the high rush current is prevented. Moreover, in this case, the time from the turning on of the TRIAC 23 to that of the photo-TRIAC 25 is one that the rush current 10 times that of a constant current flows in a heater lamp control method by the conventional technique.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heater lamp control method in an electrophotographic printing apparatus such as a printer or a copying machine provided with a heat roll for fixing toner on a sheet by heat.

[0002]

2. Description of the Related Art FIGS. 3 and 4 show a conventional heater lamp drive circuit and an operation time chart of the heater lamp drive circuit in an electrophotographic printing apparatus such as a laser beam printer, and current waveforms flowing in the heater lamp. A control method from immediately after turning on the power of the printing apparatus to the operation of keeping the heat roll constant at the temperature to be controlled will be described.

In FIG. 3, the heater DRV-P signal is valid for the logic signal "1", and the soft start-N signal is valid for the logic signal "0".

First, immediately after the electrophotographic printer is powered on, the heater DRV-P signal input to one input of the NAND gate 12 is set to "1".

At this time, the resistance value of the thermistor (positive characteristic) 3 which is in contact with or close to the heat roll 1 is still low because the temperature of the heat roll 1 is low. Therefore, the relationship between the resistance value Rt of the thermistor 3 and the voltage Vt obtained by dividing the voltage Vcc2 by the resistor 8 and the voltage Vr obtained by dividing the voltage Vcc2 by the resistors 9 and 11 is Vt> Vr, and the comparator 10 The output from is 1 and is input to the other input of the NAND gate 12.

As a result, the two inputs of the NAND gate 12 both become "1", the output of the NAND gate 12 becomes "0", the SSR (solid state relay) 7 operates, and the heater lamp 2 receives the resistance 5. Therefore, the power supply current from the power supply 4 which is restricted to a low level flows.

The current limited to a low value by the resistor 5 raises the temperature of the heater lamp 2, and the heater lamp 2 is heated.
Is a current that is flown for the purpose of increasing the resistance value of and preventing a large inrush current from flowing through the heater lamp 2.

Next, as shown in the timing chart of FIG. 4, time t1 has passed since the heater DRV-P signal was set to "1".
Later, soft start input to AND gate 13
The N signal is set to "0".

When the soft start-N signal is set to "0", the output of the AND gate 13 becomes "0", and the relay 6
Is driven. Since the resistor 5 is short-circuited by the operation of the relay 6, the limitation of the current flowing through the heater lamp 2 is released, and the power supply current that does not pass through the resistor 5 flows through the heater lamp 2. At this time, since the temperature of the heater lamp 2 is also rising and the resistance value is also high, a current flows through the heater lamp 2 without a large rush current, and the heat roll 1 is heated. (By looking at the current waveform, as shown in FIG. 4, it is t1 until the soft start-N signal becomes “0”.
It is understood that the period is a limited low power supply current, and after the t1 period when the soft start-N signal becomes "0", a small inrush current flows, and then the power supply current with the limit released is flowing. it can. ) When the heating current is applied to the heater lamp 2 by releasing the restriction and the heat roll 1 is heated, the resistance value of the thermistor 3 rises as the temperature of the heat roll 1 rises. When the temperature of the heat roll 1 reaches the temperature to be controlled, the relationship between the voltage Vt and the voltage Vr is reversed and Vt <Vr is established.

When the voltage Vr becomes larger than the voltage Vt, the output of the comparator 10 is inverted and becomes "0". as a result,
Since one of the two inputs of the NAND gate 12 is "1" and the other input is "0", the output of the NAND gate 12 is "1" and the operation of the SSR 7 is stopped. When the operation of the SSR 7 is stopped, the power supply to the heater lamp 2 is stopped.

When the power supply to the heater lamp 2 is stopped, the temperature of the heat roll 1 will eventually drop, so the thermistor 3
Of the voltage Vt rises again, the relationship between the voltage Vt and the voltage Vr is inverted again, and the comparator 10
Is again "1" and is output to the NAND gate 12.

Since the two inputs of the NAND gate 12 also become "1", the output of the NAND gate 12 becomes "0", the SSR 7 operates again, and the power supply to the heater lamp 2 is restarted.

As described above, the relationship between the voltage Vt and the reference voltage Vr, which change according to the change in the resistance value of the thermistor 3, is repeatedly inverted, and the power supply current flowing through the heater lamp 2 is controlled by the SSR 7 operating according to this relationship. The temperature of 1 is controlled to be almost constant.

However, the power supply current from the power source 4 is limited by the resistor 5 and flows to the heater lamp 2 only the first time.

[0015]

In the conventional heater lamp control method, the power supply current flowing to the heater lamp is limited only the first time power is supplied to the heater lamp after the power supply of the electrophotographic printing apparatus is turned on. Therefore, if the temperature of the heat roll reaches a temperature that should be controlled to a certain level, power supply to the heater lamp is temporarily stopped, and then power supply to the heater lamp is restarted, the heater lamp cools while power supply to the heater lamp is stopped. As a result, the resistance value of the heater lamp becomes small, and a large inrush current flows. (When looking at the current waveform, as shown in FIG. 4, after the first power supply stop,
It can be understood that a large inrush current is flowing at the start of the next power feeding. Therefore, in the conventional heater lamp control method, there is a problem in that the inrush current causes the life of the heater lamp, the connector, the relay, etc. to be shortened and the noise to be increased.

Further, when a low-limited current is made to flow through the resistance for a fixed time each time the heater lamp is supplied with electricity, the amount of heat generated by the resistance is large and the winding of the resistance is deteriorated, resulting in disconnection.

The present invention has been made in order to solve the above-mentioned conventional problems. Every time the power is supplied to the heater lamp, the supply current, which is limited to a low level, is always supplied to the heater lamp for a certain period of time. It is an object of the present invention to prevent a large inrush current from flowing, to prevent the life of heater lamps, connectors, etc. from being shortened and to prevent noise from increasing.

[0018]

In order to achieve the above object, the heater lamp drive circuit is a circuit using semiconductor parts such as a triac to eliminate the use of parts having movable parts and to supply power to the heater lamp. This is a heater lamp control method in which a feed current that is limited to a low level for a certain period of time is supplied every time the temperature is raised to raise the temperature of the heater lamp, and then the limitation of the feed current is released.

Further, the above heater lamp control method should not affect the time until the temperature of the heat roll reaches a constant controlled temperature. Therefore, since the rush current when the heater lamp is cooled and the resistance value is reduced is small as the amount of heat for heating the heat roll,
Paying attention to the time of the inrush current flowing through the heater lamp, the power supply current is limited to a low level for a time substantially equal to the time during which the inrush current is about 10 times the steady current or more.

This achieves the object of not affecting the time taken for the heater lamp to reach a constant limited temperature.

[0021]

As a result, every time the heater lamp of the electrophotographic printing apparatus is supplied with power, the supply current which is controlled to be low is supplied for a certain period of time, and the inrush current to the heater lamp is surely prevented from flowing. it can.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1, 2 and 5. FIG. 1 shows the overall configuration of a heater lamp control method according to an embodiment of the present invention, and FIG.
FIG. 1 shows a detailed configuration of a portion which is a phase control circuit. FIG. 5 is a timing chart of the circuit operation of FIG. 1 and a current waveform.

In FIG. 1, the heater DRV-P signal, C
The LOCK-P signal, the heater READY-P signal, and the heater NOT READY-P signal are valid as the logic signal "1".

First, the process from immediately after the power supply of the electrophotographic printing apparatus is turned on to the operation for keeping the heat roll at a constant temperature to be controlled will be described with reference to FIGS. 1 and 5, and then the phase control circuit will be described with reference to FIGS. 2 and 5. And the method of limiting the power supply current flowing through the heater lamp will be described.

In FIG. 1, the heater DRV-P signal input to one input of the AND gate 15 is set to "1" immediately after the electrophotographic printer is powered on.

At this time, the resistance of the thermistor (positive characteristic) 3 which is in contact with or close to the heat roll 1 is still low and has not risen because the temperature of the heat roll 1 is low. Therefore, the relationship between the resistance value Rt of the thermistor 3 and the voltage Vt obtained by dividing the voltage Vcc2 by the resistor 8 and the voltage Vr obtained by dividing the voltage Vcc2 by the resistors 9 and 11 is Vt> Vr, and the comparator 10 The output from is 1 and is input to the other input of the AND gate 15.

As a result, since the two inputs of the AND gate 15 both become "1", the output of the AND gate 15 becomes "1" and the output of the inverter 16 to which the output is inputted becomes "0". A current flows through the resistor 24, and the phototriac 23 becomes conductive.

When the photo triac 23 becomes conductive, the triac 27 becomes conductive via the phase control circuit 14, and the power supply current flows through the heater lamp 2 for only a short period of the half cycle of the frequency of the power supply 4.

The feed current, which is limited to a low value by the triac 27, raises the temperature of the heater lamp 2, raises the resistance value of the heater lamp 2, and limits the inrush current.

The output of the AND gate 15 is also input to the reset inputs R of the counter 18 and the flip-flop 22, respectively. When the output of the AND gate 15 changes from "0" to "1", the counter 18 and The reset of the flip-flop 22 is released.

The counter 18 has a count input T
CLOCK- generated by an oscillator (not shown)
It is counted up by inputting the P signal via the AND gate 17, but at this time the heater NOT
Since the READY-P signal is set to be "1", the output from the output 8 of the counter 18 in the AND gate 19 becomes valid, and after waiting for a certain time T1 by counting up, the AND gate 19 It is output from 19, and the flip-flop 22 is set by the output via the OR gate 21.

By inputting the set signal, the output from the output Q of the flip-flop 22 becomes "0",
A current flows through the resistor 26 and the phototriac 25 becomes conductive.

When the photo triac 25 is turned on, the photo triac 23 is already turned on. Therefore, the triac 27 is almost always turned on, and the heater lamp 2 is constantly supplied with a current from the power source 4 to heat the heat roll 1. To do. (By looking at the current waveform, as shown in FIG. 5, during the T1 period until the output of the flip-flop 22 becomes “0”, the triac 27 is supplying the feeding current for a short time, and the output of the flip-flop 22 is It can be understood that a small inrush current flows after the T1 period when it becomes "0", and then the feed current with the restriction released is flowing.) When the heat roll 1 is heated, the temperature of the heat roll 1 rises and the thermistor increases. Since the resistance value of No. 3 also rises, the resistance value Rt of the thermistor 3 and the resistance 8 cause the voltage Vc to rise.
The voltage Vt obtained by dividing the voltage c2 decreases, and when the temperature of the heat roll 1 reaches the temperature to be controlled, the voltage Vt and the voltage Vt
The relationship of r is inverted and Vt <Vr.

When the voltage Vr becomes higher than the voltage Vt, the output of the comparator 10 is inverted and becomes "0". as a result,
One of the two inputs of the AND gate 15 is “1”,
Since the other input becomes "0", the output of the AND gate 15 becomes "0", and the output of the inverter 1 is input.
Since the output of 6 is "1", the phototriac 23
Becomes non-conductive, and the triac 27 becomes non-conductive.

If the triac 27 is not turned on, the heater lamp 2 is not supplied with power, so that the temperature of the heat roll 1 is lowered, and the resistance value of the thermistor 3 is lowered as the temperature of the heat roll 1 is lowered. The relationship of Vt> Vr is inverted again. Then, the conduction of the phototriac 23 is controlled.

Here, when the temperature of the heat roll 1 reaches the temperature to be controlled, the heater READY-P signal is "1".
Therefore, the heater NOT READY-P signal is set to "0". Therefore, the output from the output 2 of the counter 18 becomes valid, and the phototriac 23
The phototriac 25 becomes conductive after waiting for a certain period of time T2. The fixed time T2 is shorter than the fixed time T1.

When the photo triac 25 becomes conductive, the triac 27 then becomes conductive, and power supply to the heater lamp 2 is restarted. (When the current waveform is viewed, as shown in FIG. 5, after the output of the comparator 10 is inverted and the output becomes “1”, the triac 27 is provided during the T2 period until the output of the flip-flop 22 becomes “0”. Is flowing a small amount of power supply current, and it can be understood that after T2 period when the flip-flop 22 becomes "0", there is no rush current and a steady current is flowing.) After that, the resistance value of the thermistor 3 changes The relationship between the voltage Vt that changes with the reference voltage Vr is repeatedly inverted, and the power supply current flowing to the heater lamp 2 is controlled by the triac 27 that operates according to this relationship, and the temperature of the heat roll 1 is controlled to be substantially constant.

Now, referring to FIG. 2, the phase control circuit 14
A detailed explanation of the part will be given. When the photo triac 23 becomes conductive, the current from the photo triac 23 is rectified by the diodes 31 to 34, and the capacitor 37 is charged through the Zener diode 35.

As the capacitor 37 is charged, the resistor 3
The capacitor 30 is charged through 6 and the Zener diode 38. When the voltage across the capacitor 30 exceeds the sum of the breakover voltage of the switching diode 29 and the gate voltage of the triac 27, the switching diode 29 becomes conductive and the charge accumulated in the capacitor 30 is discharged as the gate trigger current of the triac 27. Then
The triac 27 is operated.

When the triac 27 operates and becomes conductive, a power supply current flows to the heater lamp 2 through the noise filter portion of the capacitor 44 and the choke coil 45.

Once the triac 27 is turned on, the above operation is performed every half cycle of the power supply frequency, the firing angle of the triac 27 becomes faster as the capacitor 37 is charged, and the power supply current flowing to the heater lamp 2 becomes smaller. Increase.

The function of each element of the phase control circuit other than those described above in FIG. 2 will now be described. Zener diode 38
Is a protection for preventing both ends of the capacitor 37 from exceeding a certain voltage, a resistor 36 is for discharging the capacitor 37, and a fuse resistor 43 and a fuse resistor 47 are for limiting a current flowing through the phototriac 23 and the phototriac 25 and for abnormal conditions. For protection, the resistor 48 is for limiting the current, the resistor 28 is for adjusting the charging time constant of the capacitor 30, the diodes 41 and 42 are for discharging unnecessary charges and protection in case of an abnormality, and the fuse resistor 39 and the resistor 40 are for limiting current. The arc suppressor 46 is for protection in case of abnormal condition, and is for surge absorption of the triac 27.

Explaining further, the photo triac 23
Is a period from when the photo triac 25 is conducted to when the photo triac 25 is conducted, and T1 and T2 are periods during which the phase control of the triac 27 is performed. By raising the temperature of the heater lamp 2 and raising the resistance value of the heater lamp 2 during this period, the phototriac 25 becomes conductive, and a large inrush current is prevented from flowing even if the triac 27 becomes conductive.

The times T1 and T2 from the conduction of the phototriac 23 to the conduction of the phototriac 25 are the times during which a rush current of 10 times or more the steady current was flowing in the heater lamp control method according to the prior art. .

Since the rush current did not contribute to the heating of the heater lamp 2 and became noise, even if the current is limited for a certain time each time the power is supplied to the heater lamp 2, it has almost no effect on the temperature control of the heat roll 1. .

[0046]

As described above, according to the present invention,
When the restriction of the power supply current flowing through the heater lamp is released, the temperature of the heater lamp is constantly rising and the resistance value of the heater lamp is sufficiently higher than that when it is cold. It is possible to prevent a large inrush current from flowing as described above.

As a result, the noise emitted from the path through which the rush current was flowing can be reduced, and the deterioration of the connector, pin header, heater lamp, etc. used around the heater lamp due to the rush current can be prevented and the life can be extended. .
In addition, since the capacity of the connector, pin header, cable, noise filter, and other components that have been conventionally selected according to the magnitude of the inrush current can be reduced, the components can be downsized and the price can be reduced. Also has.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is a partial detailed configuration diagram of an embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing a conventional example.

FIG. 4 is an operation timing chart and a current waveform chart of the conventional example shown in FIG.

FIG. 5 is an operation timing chart and a current waveform according to the embodiment of the present invention.

[Explanation of symbols]

 1 Heat Roll 2 Heater Lamp 3 Thermistor 8, 9, 11 Resistor 10 Comparator 14 Phase Control Circuit 15, 17, 19, 20 AND Gate 16 Inverter 18 Counter 21 OR Gate 22 Flip Flop 23, 25 Phototriac 27 Triac

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Sakaki 1060 Takeda, Katsuta City, Ibaraki Prefecture Hitachi Koki Co., Ltd.

Claims (4)

[Claims] 1. An electrophotographic printing apparatus in which a heat roll, a heater lamp for heating the heat roll, and a power supply current to the heater lamp are controlled according to the temperature of the heat roll, the power supply to the heater lamp is always performed. A heater lamp control method for an electrophotographic printing apparatus, characterized in that the power supply current is limited to a low value for the first fixed time. 2. The device according to claim 1, wherein the first constant time during which power is supplied to the heater lamp is approximately 10 times the steady current.
A heater lamp control method for an electrophotographic printing apparatus, wherein the time is set to be approximately equal to the time when a rush current more than twice as long as the current flows. 3. The electrophotographic printing according to claim 1, wherein a first fixed time for supplying power to the heater lamp is set by controlling a counter circuit by a signal according to the temperature of the heat roll. Heater lamp control method for device. 4. The electrophotographic printing apparatus according to claim 1, wherein a triac and a phase control circuit for controlling the triac and a phototriac are used to limit a current supplied to the heater lamp to a low level. Heater lamp control method.