JPH0420188B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heater drive device for a fuser for a copying machine that suppresses rush current without generating noise.

As a heater drive device for a fuser for a copying machine, for example, one that controls the heater power amount by controlling the phase so that the heater is turned on only when the instantaneous value of the sine wave power supply voltage falls below a predetermined level is available. be.

According to this heater drive device for a fuser for a copying machine, when the capacity of the heater becomes large, a zero-cross drive circuit that turns on the heater at the zero-cross point where the sine wave power supply voltage becomes zero generates noise that cannot be suppressed. Since the current can be suppressed to a certain extent, it is possible to prevent indoor lighting equipment such as fluorescent lights from flickering.

However, in the case of the heater drive device of the fuser for copying machines, the heater is turned on and off according to the phase angle of the sine wave power supply voltage, which may generate noise that may cause radio wave interference or malfunction of the equipment. There is.

The present invention has been made in view of the above,
In order to prevent the generation of noise and suppress the rush current, multiple heaters with different power consumption are provided, and the heater resistance is increased by pre-driving at a voltage lower than the predetermined voltage in order of decreasing power consumption, and then the heater resistance is increased before the predetermined voltage is applied. The present invention provides a heater drive device for a fixing device for a copying machine, which is driven by a heater drive device for a copying machine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A heater driving device for a fuser for a copying machine according to the present invention will be described in detail below.

FIG. 1 shows an embodiment of the present invention, in which a console 1 having various operation buttons, a display section, etc., and a platen 3 on which a document 2 is placed are provided at the top of the copying machine. Inside the copying machine, there is an optical system 4 that scans the original 2.
, a photosensitive drum 5 that is exposed to light based on the exposure of the optical system 4, a charging section 6, a developing section 7, a transfer section 8, and a cleaner section 9 arranged around the photosensitive drum 5.
and a paper feed tray 10a, 1 containing copy paper.
0b, a fixing section 11 that fixes the transferred copy paper, and a control section 12 that controls the operation of the copying machine.
(microcomputer) is installed. At the output end of the control unit 12, there is a first timer (for example, a mono multivibrator) 13 that is turned on for a predetermined time _T1 when the heater drive signal is output, and a first timer (for example, a mono multivibrator) 13 that is turned on for a predetermined time T1 after the heater drive signal is output. The first delay circuit 14 is delayed by time T ₂ and turns on until the output of the heater drive signal disappears (time T ₁ is set to the time required for the heater resistance to increase to a resistance value that prevents rush current; T ₂ is set to T ₁ T ₂ ), and a second timer 15 (for example, composed of a mono-multivibrator, which is turned on for a predetermined time T ₃ when the first delay circuit 14 is turned on, T ₃ is set to the time at which the heater resistance increases to a value that prevents rush current), the time (T ₂ + T ₃ ), and the time (T ₂ + T ₃ + T ₄ ) after the drive signal is output, respectively. Turns on late,
The second switch turns off when the drive signal output disappears.
and a third delay circuit 16, 17, and a third timer that detects the zero cross point of the power supply voltage when the first and second timers 13, 15 are on, turns on, and outputs the first and second heater activation signals. When the first and second drive circuits 18 and 19 and the second and third delay circuits 16 and 17 are on, they detect the zero cross point of the power supply voltage and turn on, and the third and fourth
Third and fourth drive circuits 20 and 21 are provided that output heater activation signals. In addition to this configuration, the first to fourth triaxes 22, which are turned on based on the first to fourth heater activation signals,
It has 23, 24, and 25. The power supply unit includes an AC 100 volt power supply 28 and a turn-on switch 27 that supplies power to the transformer 26, and the first triax 2
2 applies a voltage of 24 volts to a first heater 11a (for example, 450 watts), which will be described later, and a second triax 23 applies a voltage of 24 volts to a first heater 11a (for example, 450 watts), which will be described later.
700 watts), and the third and fourth triaxes 24, 25 apply a voltage of 100 volts to the first and second heaters 11a, 11b.

The fixing unit 11 also includes the heaters 11a and 1 described above.
1b, and a pressure roll 11d that presses the copy paper against the heating roll 11c.
The control unit 12 also includes a heater 11.
an input interface 12a for inputting operation signals from the console 1 and sensor signals from various sensors in the copying machine in addition to the temperature signals from the sensors a and 11b and the ON signal from the switch 27; and a ROM 12b for storing a program for processing the input signals. and a CPU that processes the input signals based on the program.
12d, a RAM 12c that temporarily stores input data, calculation results, etc., and a RAM 12c that outputs control signals (including the aforementioned driving signals) based on the calculations of the CPU 12d to control the display of the console 1, and performs various functions such as It has an output interface 12e that controls a controlled object (for example, a drive motor, etc.).

In the above configuration, the operation will be explained based on the time chart in _FIG . (setting operations etc. are omitted), the timer 13 is turned on for a time period _T1 . When the first drive circuit 18 detects the zero cross of the power supply voltage 28 while the timer 13 is on, it turns on (outputs the first heater activation signal) and turns on the first triac 22 (time t ₂ ). . As a result of this turning on, a voltage of 24b volts is applied to the first heating roll heater 11a until time _t3 to generate heat (the resistance increases to a predetermined resistance value as the temperature rises). At the same time, the delay circuit 14 is turned on when the delay time T ₂ has been counted from the output of the drive signal (time t ₄ ), and the second timer 15 is turned on.
Turn on only _T3 . During this time, the second drive circuit 19
detects the zero cross of the power supply voltage 28 (time
_t5 ), outputs the second heater activation signal to turn on the second triax 23, and turns on the first heater 11a.
The second heater 11b is already heated by
Apply 24 volts to. The second delay circuit 16 is turned on at the same time as the second triax 23 is turned off due to the timeout of time _T3 .
t ₆ ), and when time T ₄ has passed since then, the third delay circuit 17 is turned on (time t ₇ ). Since times t ₆ and t ₇ coincide with the zero crossing point, the third
The fourth drive circuit 20, 21, based on the third drive circuit 20, 21,
The fourth triaxes 24 and 25 are turned on, and the respective heater resistances have already increased.
1a, then a voltage of 100 volts is applied to the second heater 11b. When the temperature of the heating roll 11c reaches a predetermined value, the output of the drive signal is interrupted, and at time _t8 , the power supply to the first and second heaters 11a and 11b is cut off.

In the above description, explanations of obvious parts of the configuration and operation of the copying machine have been omitted. Further, the operations of the drive circuits 18, 19, 20, 21, timers 13, 15, delay circuits 14, 16, 17, etc. can also be replaced by microcomputer processing of the control section 12.

As explained above, according to the heater drive device for a fuser for a copying machine according to the present invention, a plurality of heaters having different power consumption are provided, and the heater resistance is pre-driven at a voltage lower than a predetermined voltage in order of decreasing power consumption. Since the device is driven at a predetermined voltage after increasing the voltage, the rush current can be suppressed without generating noise.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention. Second
The figure is the time chart shown in Figure 1. Explanation of symbols, 1...Console, 2...Manuscript,
3...Platen, 4...Optical system, 5...Photosensitive drum, 6...Charging section, 7...Developing section, 8...Transfer section, 9...Cleaner section, 10a, 10b... Paper feed tray, 11... Fixing section, 11a, 11b... Heater for heating roll, 12... Control section, 13, 15
...Timer, 14, 16, 17...Delay circuit, 1
8, 19, 20, 21...drive circuit, 22, 2
3, 24, 25...triack, 26...transformer, 27...switch.

Claims (1)

[Scope of Claims] 1. A copying machine equipped with a drive circuit that detects a zero cross of an alternating power supply voltage and applies the alternating power supply voltage to a heating roll heater of a fixing device, wherein the heating roll heater has a difference in power consumption. The drive circuit is characterized in that the drive circuit pre-drives the heaters at a voltage smaller than a predetermined voltage in order of decreasing power consumption of the heaters, and then drives the heaters at the predetermined voltage. Heater drive device for fuser for copying machines.