JPS58134666A - Controlling device of light quantity for image forming device - Google Patents

Abstract

PURPOSE:To prevent an element for lighting control from being damaged by preventing rush current at the initial time of lighting of a light source. CONSTITUTION:When a zero crossing signal is inputted to an interruption terminal and the interruption is permitted, a main routine is returned and a soft timer value T' is increased one by one in every input of the succeeding zero crossing signal until the soft timer value T' is made to coincide with a value T set up by a timer setting routine under control by a microcomputer. Therefore lighting of a halogen lamp is gradually increased. If the power conduct time to the halogen lamp is increased in every prescribed time alphamus from zero up to alphaTmus at the initial lighting of the lamp as shown in the figure, voltage values to be applied to the lamp are gradually increased, preventing the element for lighting control from being damaged.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an i amount control device for an image forming apparatus such as a copying machine.

2. Description of the Related Art Conventionally, as a device for controlling the amount of light in a copying machine or the like, there is a device that feeds back the voltage applied to the light source and compares it with a reference voltage to control the power supplied to the light source using the output obtained.

In such a control system, the light source generally starts to be energized when the device power is turned on or when a copy start command is input. In this case, the amount of current supplied to the light source -\ is often the same as that during normal copying operation.

However, if the same current is applied during the normal copying operation at the initial stage of lighting, there is a risk that the inrush current will damage elements such as transistors and triacs for lighting control.

The present invention has been made in view of the above points, and is intended to prevent inrush current at the initial stage of lighting of a light source and to prevent damage to elements for lighting control.

Hereinafter, the present invention will be further explained based on the drawings.

In this embodiment, an example will be explained in which the amount of light is controlled by detecting the power supply voltage of the device, but the present invention is also applicable to devices that are provided with means for detecting the amount of light emitted from a light source and perform control operations based on the detected value. Applicable.

FIG. 1 shows a sectional view of a copying apparatus to which the present invention is applied.

The surface of the photosensitive drum 1 is made of a photoconductor using a photoconductor, is rotatably supported on a shaft, and starts rotating in the direction of the arrow in response to a copy command.

The original placed on the original platen glass 2 and fixed with the original platen cover 3 is irradiated with light reflected by the halogen lamp 5 and the main reflector plate 6, which are integrated with the mirror 4, and the reflected light is , the first mirror 4 and the second mirror 7. By moving the first mirror 1-4 and the second mirror 7 at a speed ratio of 1.2, the original is scanned while the optical path length in front of the lens 8 is always kept constant.

The reflected light image passes through the lens 8, the third mirror 9, the fourth mirror 10, and is formed on the photosensitive drum 1 at the exposure section 11.

The photosensitive drum 1 is charged (for example, +
), the image irradiated by the halogen lamp 5 is subjected to slit exposure in the exposure section 11.

At the same time, electricity of opposite polarity (for example -) to the AC or - is removed using the remover 13, and then the entire surface exposure lamp 1
4, a high-contrast electrostatic latent image is formed on the photosensitive drum 1. The electrostatic latent image on the photosensitive drum 1 is then visualized as a toner image by the developing device 15. The transfer material P in the cassette 16 is fed into the machine by the paper feed roller 7, and further by the conveyance roller 8.19. It is sent to registration rollers 20 and 21.

Then, the registration rollers 20 and 21 take accurate timing and send the recording material toward the photosensitive drum 1.

Next, the transfer paper P is passed between the transfer charger 22 and the photosensitive drum 1.
The toner image on the photosensitive drum 1 is transferred onto the transfer paper while the toner image passes through the transfer paper.

・': After the transfer is completed, the transfer paper is separated by the separation roller 23 in a 1:1 ratio.
A paper holding roller 25 is provided on the conveyor belt 24, which is separated from the photosensitive drum 1 and further guided to the conveyor belt 24. Further, the paper is guided to a pair of fixing rollers 26 and 27, where it is fixed by pressure and heat, and then discharged to a tray 28 by paper discharge rollers 29 and 30.

After the transfer, the surface of the photosensitive drum 1 is cleaned by a cleaning device comprising an elastic blade 31, and the process proceeds to the next cycle. Further, 32 is a blank shutter for switching between image exposure and blank exposure to the photosensitive drum 1.

Psi, PS2. PS3 is a switch operated by an optical system consisting of a first mirror 4, a halogen lamp 5, and a second mirror 7, and PSl is a switch operated by an optical system that is operated by an optical system consisting of a first mirror 4, a halogen lamp 5, and a second mirror 7. Position sensor PS2 is a registration sensor that outputs a drive signal to drive the register rollers 20 and 21 at a predetermined timing, and P83 is a back position sensor that detects whether the optical system is at the exposure end position, that is, the reverse position. .

204 is a discharge port sensor, 205 is a paper discharge sensor, and 206 is a paper feed sensor.

FIG. 2 is a control circuit block diagram of the copying apparatus shown in FIG. 1. 200 is a control unit, which is a microcomputer with a built-in converter (Al1), and has the following inputs. 20
1 is the home position sensor PS1.2 shown in FIG.
02 is the registration sensor P82 shown in Fig. 1.203 is the back position sensor P83.204 shown in Fig. 1.
A discharge port sensor 205 detects whether the transfer paper is discharged onto the tray 28, and a paper feed sensor 205 detects whether the transfer paper is normally supplied to the paper feed roller 17.

Reference numeral 206 denotes a copy start/stop signal input from a key provided on an operation unit (not shown).

Further, 01 to 010 of the control unit 200 are output ports, and the following books are controlled by this output. 208 is photosensitive drum 1
, a main motor that drives the paper feed roller 17, registration rollers 20, 21, etc.; 209 is a halogen lamp lighting circuit;
210 is a paper feed clutch for transmitting the drive of the main motor to the paper feed roller 17; 211 is a registration clutch for transmitting the drive of the main motor to the registration rollers 20 and 21; 212 is a primary charger 12 and a transfer charger 22, etc., a high pressure source for supplying high pressure, 213 is a forward clutch that controls the forward movement of the optical system, 214 is a paper fish lamp that lights up when the cassette 16 is not installed in the device, and 215 is a paper fish lamp that lights up when the cassette 16 is not installed in the device. 216 is a 7-segment numerical display that displays the desired number of copies input from an operation unit (not shown); 221 is a power lamp provided on the operation unit that indicates that the power has been turned on; It is.

217 is a full-wave rectifier to which the AC power input to the copying machine is applied. 218 is input with an AC power source that has been subjected to full-wave rectification with an inverter at a predetermined threshold level. The output of the inverter 218 is input to the interrupt terminal INT of the control section 200.

FIG. 3 shows the voltage waveforms of the output voltage (a) of the full-wave rectifier 217 and the output voltage (b) of the inverter 218, respectively. As is clear from the figure, the output voltage (b) of the inverter 218 is output at the zero cross point of the output voltage (a). Hereinafter, the output voltage (b) will be referred to as a zero-cross signal.

220 is a peak value detection circuit to which the output voltage (a) of the full-wave rectifier 217 is input. The peak value detection circuit 220 detects the peak value of the power supply voltage. Incidentally, assuming that the power source voltage is a sine wave without distortion, this peak value can also be regarded as the average value or effective value of the power source voltage. The detected voltage value is input to the analog-to-digital conversion terminal A/D of the control section 200, and the control section 200 receives this input at a predetermined timing and converts it into an 8-bit digital value as shown in Table 1. ipa.

The port control unit 200 is connected to the input ports 11 to I6 and the interrupt terminal IN.
Sequence control of each part of the copying apparatus is performed according to a control program stored in advance in an internal read-only memory (ROM) based on inputs to T and analogue digital terminals A/D.

Table 1 Figure 4 shows the herogen lamp lighting circuit 209 shown in Figure 2.
FIG. 301 is a photocoupler, 302
is a rectifier that full-wave rectifies the input AC power, 5#ll
;l: halogen lamp; Tri and Tr2 are transistors;

The output of the output port 02 of the control unit 200 is applied to the base electrode of the transistor Tri, and the transistor Tri is turned on and off depending on the output level of the output port 02.

In this circuit, when transistor Tri is off,
The light emitting element of the photocoupler 301 is not energized and does not emit light. Therefore, the light receiving element of photocoupler 301 is off. As a result, the transistor Tr2 is also turned off, and no current is passed from the rectifier 302 to the halogen lamp 5.

On the other hand, when the transistor Tri is on, the light emitting element of the photocass 23010 emits light, thereby turning on the light receiving element. ,? As a result, the transistor Tr2 is also turned on, and the dihalogen lamp 5 is energized.

That is, the energization of the halogen lamp 5 can be controlled according to the output level of the output boat 02 of the control section 200.

In this embodiment, the amount of light emitted is maintained at a predetermined value by controlling the energization time to the halogen lamp 5 using an internal timer according to fluctuations in the power supply voltage. Note that the same effect can be obtained even if an external timer is newly provided in place of the internal timer. Hereinafter, light source stabilization according to the present invention will be explained in detail.

As mentioned above, in the present invention, the light source is stabilized by digital control. The control circuit shown in Figure 2 is 50H
Phase control of the power supplied to the halogen lamp 5 is performed using a 100V AC power supply of 100V or 60Hz so that the output effective voltage of the halogen lamp 5 becomes 75V.

5-1 to 5-4 are main routine control flowcharts of the control section 200 of the copying apparatus shown in FIGS.

When the copying apparatus is powered on, the control section 200 starts operating and performs initial control such as clearing the internal register W of the control section 200 (step 501). After enabling the interrupt, the ZEG 502) is input to the interrupt terminal ■. Thereafter, in step 503, a frequency detection timer (10
0msec). While this timer is counting time, external interrupts are prohibited.

In step 504, a flag X F indicating the end of frequency detection is set.
/Determine whether or not the frequency has been set, and if not set, proceed to step 505. Furthermore, in step 506, the 7-lag F/zero detection is reset, and in step 5
04, 505, and 506, it waits for the next zero-cross signal to be input to the interrupt terminal INT.

If there is a zero cross signal input, step 50 starts from the loop.
7, it is determined whether the flag F/zero detection is set, and if it is not set, the RAM is stored in step 508.
1 is added to the frequency memory of , furthermore, 7 lag F/zero detection is set, and the loop of steps 504, 505 and 506 is repeated to wait for the input of the next zero cross signal.

Through this loop, the number of times the zero cross signal is input during 100m5ec is stored in the frequency memory.

The timer started in step 503 is 100m11e
When the time e is completed, the frequency of the power supply voltage is detected by an interrupt program to be described later, and the flag 27 frequency is set. Therefore, step 504 of the aforementioned loop
2>-, the extraction is performed in step 509, the power rung 221 of the operation unit is turned on, and the range is set in advance in the predetermined area (X register, storage area of 0.1.2) of the key according to the detected frequency. (Table 2 shows the RAM map of the cicada stored in the case of 50 Hz). Enable Xerox interrupts. In addition, in Table 2,
The timer value is stored in areas 0 and 1 of the register, and the correction coefficient is stored in area 2.

Thereafter, the process waits until the flag F/copy, which is reset by a copy start command from the operation unit 206, is set (step 510). After determining the set, the main motor 208, paper feed clutch 210, high pressure source 212
The flag F/AUTO, which is set when the timer times up, is set in advance (step 51).
1).

In step 512, it is checked whether the flag F150Hz, which is set when the frequency of the power supply voltage is increased to 507 by the frequency detection of the interrupt program, is set. Then, if it is set, a 50-output pre-rotation timer is set, and if it is not set, a 60-Hz pre-rotation timer is set.

In step 513, the 2% flag F/AUTO is reset. As a result, a pre-rotation timer set according to the frequency is started in step 512, and step 51
Proceed to step 4.

In step 514 of Table 2, a timer setting routine OVR for determining the lighting time of the norogen lamp, which will be described later, is called, and the 7 lag F/
Repeat the routine until AUTO is set.

If the previous rotation timer times up, step 515
◇If the optical system is in the home position, the paper feed clutch 21 is activated in step 516.
0, the transfer paper is normally fed into the cassette 16 by the operation of the paper feed clutch 210, and the paper feed sensor 205
is operating, the process advances to step 517.O In step 517, the numerical display memory for displaying the desired number of copies is subtracted by 1, and if the subtraction result is "0", the flag F/stop is set; 0'', the process directly advances to step 518.

However, if the transfer paper is not being conveyed normally from the cassette 16, it is determined that there is no paper in the cassette, and in step 551, the paper fish flag 214 (f) lights up and the flag F/paper fish is set.
Proceed to step 38.

In step 518, the optical system forward clutch 213 is turned on to start exposure scanning of the document.Then, in step 519, a timer setting routine OVR is called. Then, the registration sensor P82 is operated by the optical system, thereby turning on the registration clutch 211 for conveying the transfer paper to the transfer area, and furthermore, the flag F/211 indicating the on state is turned on.
Registration ON is set (Stella 7'521)
is detected in step 520 and the routine is repeated until the optical system stops operating the registration sensor PS2 or the flag F/registration OFF indicating the end of operation is set (steps 522 and 523).

In step 524, the registration clutch 211 is turned off and a flag F/registration OFF indicating this is set, and in addition, the paper feed clutch 210 is turned off to proceed to the next step.In step 525, the transfer paper that has completed the previous transfer is normal. The discharge port sensor 204 detects whether or not the liquid is discharged to the tray 28. If the paper has been discharged, a flag F/discharge indicating a jam at the discharge port is reset, and if the paper has not been discharged normally, the process directly advances to step 526.

In step 526, the optical system reaches the forward end point and detects whether the back position sensor PS3 is being operated. If it has not been detected yet, proceed to step 519A and return to the timer setting routine 0.
Repeat until the VRt bar, controller, and sensor PS3 is turned on.In addition, in this case, the flag F/registration OF has already been set.
Since F@j is set, the process jumps from step 522 to step 525.

If the back position sensor PS3 is operated too much by the optical system, the optical system forward clutch 213'e will be turned off.
Okay, the optical system stops moving forward and starts backward movement.Also, when the optical system reaches the back position, check whether the flag F/ejection indicating a jam near the ejection port sensor 204 has already been set (step 528), or if the transfer paper is not detected by the discharge port sensor 204 at that point (step 530), it is determined that there is a jam, and the process jumps to step 549.

On the other hand, if flag F/discharge is not set, the aforementioned flag F/regist ON and 7 lag F/regist)
If the paper discharge sensor 205 is not on, wait until the back position sensor PS3 is turned off as the optical system moves backward in step 531, and then proceed to step 532. Check whether the flag F/stop, which is set when the operator presses the stop key or when the set number of copies is completed, is set.If it is not set, the flag F/stop is set to feed the transfer paper for the next copy from the cassette. The paper feed clutch 210 is turned on (step 533).
), if it is not set, the process proceeds to step 534 without performing the next paper feeding operation'=1 (7) At 34', the optical system moves back and forth.

The timer setting routine Cv is called repeatedly until the registration sensor PS2 is turned on, and when it is turned on, the process proceeds to step 535 and the developing bias is turned off. In step 536, the timer setting routine is repeated again until the operation of the registration sensor PS2 by the optical system is completed.

In step 537, it is determined whether the flag F/stop is set. If it has not been set, F/ejection is set and the process jumps to step 511 to perform the next copying operation.

If flag and F/stop are set, step 5
At step 38, the optical system is stopped at the home position, a retention jam timer is set, and the flag FZAUTO is reset to start this timer. and,
In step 539, the timer setting routine is repeated until the transfer paper is detected by the ejection port sensor 204, and depending on whether the transfer paper passes the ejection port sensor 204 by the time-up of the accumulated jam timer started in step 538. Detects occurrence of accumulated jam. That is, if the retention jam timer times up and the flag F/AUTO is set before the discharge port sensor 204 is turned off, it is determined that a jam has occurred, and the process jumps to step 5494C.

On the other hand, if the accumulated jam does not occur and the discharge port sensor 204 turns off before the accumulated jam timer times up, the 7 lag F'/AUTO is set in step 540 and the process proceeds to the next step. Detects the set state of flag F/paper fish and flag F/stop. If both 0 flag F/no paper and 7 lag F/stop are not set, step 5.
At step 42, the stop of the optical system is released and the state is set to a new forward CIJ' enable state, and the process returns to step 511 at step 9 to perform the next copying operation.On the other hand, if at least one flag is set, step 543 Step 2, turn off the high pressure source 212 to stop the copying operation of the apparatus, and set the post-rotation timer.
Flag F/AUT is set to start this timer.
Reset O. Then, the after-rotation operation of the device is controlled, and at step 544, the timer setting routine OVR'i is repeatedly performed until the time-up of the after-rotation timer.

In the next step 545, the stoppage of the optical system is completely released. Then, in step 546, the flag F/paper fish and the flag F are set again.
/Stop is detected, and if neither flag is set, the process returns to step 511 and the next copying operation is performed.On the other hand, if at least one flag is set, flag F is set in step 547. /Copy and flag F/stop are reset and the main motor 208 is turned off. Then, it is detected again whether the flag F/paper fish is set, and if it is set, this flag is reset, and if it is not set, the display is returned to the initial state and the process returns to step 510, and the next copy is made. Waits for flag F/copy to be set by command input.

Steps 549 and 550 are for jamming, and are the jump destinations when a jam is determined in any of steps 528, I'$30, and 539. In step 549, the main motor 208 is turned off, a flag F/JAMi indicating that a jam has been detected is set, the high pressure source 212 is turned off, and the optical system is driven.
"? Stops. Then, in step 550, the jam indicator 215 provided on the operating section is made to blink at 0.5 second intervals.

FIG. 6 is a flowchart showing the timer setting routine 0VRi in the flowcharts of FIG. 6rt and FIGS. 5-1 to 5-4. By this timer setting routine, 1/2 of the human power is generated.
The energization time to the halogen lamp 5 during the cycle is determined. That is, the length of time to energize the halogen lamp 5 from the zero-crossing point of the input power source is determined. Period α, μ formula (
For example, the first timer of 50 μvc) and the short cycle of the first timer:
The first timer measures the approximate time, and the second timer makes detailed time corrections. Figure 8 shows this situation. The flowchart shown in FIG. 6 will be explained. In step 601, when the timer setting routine is called in the main routine, the set state of the flag F/exposure calculation indicating whether or not to permit the timer setting operation by the timer setting routine is checked. If it is set, exposure calculation is performed, but if it is not set, the process returns to the main routine without performing exposure calculation.

If it is set, first in step 602 7 lag F
/Reset the exposure calculation. This reset operation causes
The timer setting routine does not operate unless the flag indicating the end of energization to the halogen lamp is set.

In step 603, the X register is set with the upper 4 bits □ of the voltage value converted into an 8-bit digital value by the N0 converter.For example, if the power supply voltage is 97.5V, the control unit 200 sets the The value is energized in the conversion table in Table 1, (56) 1@ in hexadecimal, (01010 in binary)
110) Convert to a digital value expressed as z. Therefore,
The upper 4 bits, ie (5)n, are set as the X register.

In step 604, the timer value T stored in the area where the X register is 0 or 1 is determined by the X register set in step 603 according to the RAM map in Table 2. For example, if the X register is (5\,...

As is clear from Table 2, the timer value T
is determined as (a'a)ts.

In step 605, the upper half of the voltage value is converted into an 8-bit digital value by the A/I converter. Set the X register again with the bit.

In step 606, the correction coefficient stored in the area where the X register is 2 is determined according to the RAM map in Table 2 using the X register set in step 605. For example, when the X register is set to (5)111, the correction coefficient is determined to be (3)u, as is clear from Table 2.

In step 607, a correction timer value t is determined from the lower 4 bits of the voltage value converted into an 8-bit digital value by the N0 converter and the correction coefficient determined in step 606 according to the correction timer table in Table 3. . For example, if the power supply voltage is 97.5V, the correction coefficient is (3)ts,
Furthermore, since the lower four bits of the voltage value of the input power supply are (6)1@, the correction timer value t is determined to be 6, as is clear from Table 3.

In step 608, step 604 and step 607
Based on the timer value T and the corrected timer value t determined in step 1, the halogen lighting time HT is determined based on equation (1).

HT=αT+β1 −...(1) (In the formula, α and β are the lengths of one cycle of the first timer and second timer, respectively.) As shown in Table 3 above, the power supply voltage is detected and the value is digitalized. The halogen lighting time HT is determined based on the digital value. Then return to the main routine.

Note that αT in the first term on the right side of equation (1) is the first timer with the above-mentioned period αμBee in the microcomputer, and the second
The term βt is measured by a second timer with a period βμ8ee in the microcomputer.If the power supply voltage is 97.5V, the timer value T is (34) 1 corrected timer value t as described above. is 6. Therefore, the halogen lighting time H
T is determined as follows from the following formula (1) O HT = a x (a4) ts + β × 6 [μSeC]
FIG. 88 shows the energization state of the halogen lamp 5 according to the halogen lighting time determined as above. FIG. 8a shows the full-wave rectified input AC power, the eighth figure shows the zero-cross signal input to the interrupt terminal INT, and FIG. 8C shows the energization time HT of the halogen lamp 50.

As is clear from the figure, the energization time is controlled from the input of a zero-cross signal to the input of the next zero-cross signal, and the first timer operates for a predetermined time from the input of the zero-cross signal; When the timer ends, the second timer starts counting, and when the second timer finishes counting, the energization to the halogen lamp 5 is stopped. The first timer determines the approximate energization time, and the second timer makes detailed corrections. As a result, the quantization error in control using digital values can be reduced and accurate light amount control can be performed.

FIG. 7 shows an interrupt program of the control section 200. Control unit 200 Interrupts are generated by a zero-cross signal input to the U interrupt terminal INT and by the time-up of a built-in timer.

The interrupt program shown in FIG. 7 has three functions as follows. The first step is to detect the frequency of the input power supply voltage, the second step is to perform a soft start at the initial stage of lighting of the 20% logen lamp 5, and the third step is to control the phase during normal lighting of the 100% logen lamp 5.

First, the first frequency detection function will be explained. As explained in the main routine, when the power is turned on, the frequency detection timer (10
0m5ec) starts timing (Figure 5-1).

While this timer is counting time, external interrupts due to zero-cross signals input to the interrupt terminal INT are prohibited. The timer is IQ□+msI! When the time measurement of e is completed, an internal interrupt is generated, the interrupt program shown in FIG. 7 is called, and 11J is executed in parallel with the main routine. In step 701, all internal and external interrupts are prohibited, and the process proceeds to step 702. In step 702, the set state of the flag 27 frequency indicating whether or not frequency detection has been completed is detected.

When the power is turned on, the RAM is cleared and all flags are reset, so the process advances to step 703.

In step 703, the aforementioned flag 27 frequency is set and further internal interrupts are prohibited. In step 704, the value of the frequency memory described in the main routine is checked.

That is, if the zero-crossing signal input while the timer is counting 100m5ec is 9 times or less, the input power source is determined to be 5oHz, a flag F/50Hz indicating this is set, and the process returns to the main routine. However, the value of frequency memory is 1
If it is 0 or more, it is determined that the input power is 60Hz, and flag F is set.
150) Return to main route □・t without setting h.

In this way, the frequency structure of the input power supply voltage is determined.

Next, the soft start function at the initial stage of lighting of the second halogen lamp 5 will be explained. Transistors, trybooks, and the like of lighting circuits for light sources such as halogen lamps may be damaged by inrush current that occurs during the initial lighting of the light source. In order to prevent this, the voltage value applied to the light source is gradually increased from O■ at the initial stage of lighting the light source, which is called a soft start.

FIG. 9 shows the soft start at the initial stage of lighting.

Frequency detection is completed, flag 27 frequency is set,
Further, after the zero-crossing interrupt is enabled in step 509 of the main routine, when a zero-crossing signal is input to the interrupt terminal INT, the interrupt program shown in FIG. 7 is called. In this case, the process proceeds from step 702 to step 705, and a flag F/copy indicating that the copy key has been operated is detected.If "i" is not set, step 7
At step 06, operation of the coffee key is detected. If the operation is performed, the flag F/copy is set, and if the operation is not performed, the interrupt by the zero-crossing signal is permitted and the process returns to the main routine.From then on, each time a zero-crossing signal is input, the flag F/copy is set. step 7 by inputting the zero cross signal when the flag F/copy is set.
Proceed to 07.

In step 707, it is checked whether the flag F/interrupt is set, which indicates that an interrupt process is in progress due to an interrupt input. If it is not set, the flag F is set in step 708.
/ Set an interrupt and proceed to step 709. Step 7
At 09, the state of the flag F/s OF T indicating that lighting of the halogen lamp 5 due to soft start has ended is detected.

Since this flag F/80FT is not yet set at the initial stage of lighting, the halogen lamp 5 is turned on in step 710, and 1 is added to the soft timer value T'. This soft timer value T' is the count value of a timer with a period of 50μ, like the first timer.

In step 711, the soft timer i T/ incremented by 1 in step 710 is compared with the timer value T of the first timer determined in the timer setting routine of FIG.

If they do not match, wait for the soft timer value T' to finish counting, and then proceed to step 716, turn off the halogen lamp,
The flag V interrupt is reset, internal interrupts are prohibited, and the flag F/exposure calculation indicating permission of the timer setting operation by the timer setting routine is set. Also, the interrupt by the zero cross signal is enabled, and the process returns to the main routine. After this, every time a zero-crossing signal is input, in step 711, the soft timer value T' and the timer value T set in the timer setting routine are set.
The soft timer value T' is increased by 1 at step 710 until the values match.

As a result, the lighting of the halogen lamp that starts lighting upon input of the zero-cross signal is gradually increased (by one count of the first timer, that is, αμ). Figure 9 shows the situation.

Then, when the soft timer value T' and the first timer value T match, the flag p/5opT is set and the process proceeds to step 716, and then the process returns to the main routine.

As described above, in the initial stage of lighting of the halogen lamp 5, by increasing the energization time to the halogen lamp 5 from O by a predetermined time (αμvc) by αT (μm=)t, as shown in FIG. The voltage value supplied to is gradually increased.

Next, the phase control function during the third normal lighting will be explained. When a zero-crossing signal is input to the interrupt terminal INT after the above-mentioned soft start in the early stage of lighting the halogen lamp, a 7-lag F/interrupt is set in step 708, and the process proceeds from step 709 to step 712, disabling external interrupts. At the same time, the first timer value determined by the timer setting routine of FIG. 6 starts counting. and step 7
If the flag F/stop is not set in step 13, the process proceeds to step 714, where the halogen lamp 5 is turned on. Then, the analog digital input terminal A of the control section 200
Take the input power supply voltage from /D, convert it to an 8-pit digital value according to the conversion table in Table 1 as described above,
The timer value is determined in the sixth timer setting routine based on the value stored in a predetermined area of RAM 0 and stored in the 6-th timer setting routine. Thereafter, in step 714, internal interrupts are enabled, further interrupts are enabled, and the process returns to the main routine.

When the first timer starts counting in step 712, an internal interrupt is generated in the control section 200, and the interrupt program shown in FIG. 7 is called. In this case, since flag F/interrupt is set, steps 707 to 71
Proceed to step 5. In step 715, the second timer determined in the timer setting routine of FIG. Return to

In this way, the control section 2 that performs sequence control of the copying operation
00 also controls the lighting of the halogen lamp 5, which simplifies the circuit configuration.

Although the present embodiment is an example of controlling the amount of light in an image forming apparatus, the present invention is also applicable to controlling the heater of a fixing device and controlling the operation of other members that operate by being energized.

You can also do that. ′□

[Brief explanation of drawings]

FIG. 1 is a sectional view of a copying apparatus to which the present invention is applied, FIG. 2 is a control circuit block diagram of the copying apparatus of FIG. 1, FIG. 3 is a diagram showing output voltage waveforms of each part, and FIG. 5-1 to 5-4 are control flowcharts of the copying machine shown in FIG. 1, FIG. 6 is a flowchart showing the timer setting routine, and FIG. 8 is a diagram showing the energization state of the halogen lamp, and FIG. 9 is a diagram showing the soft start at the initial stage of lighting. 1 is a photosensitive drum, 5 is a halogen lamp, 200 is a control unit, 209 is a halogen lamp lighting circuit, and 220 is a peak value detection circuit. Applicant Canon Co., Ltd. 485-6M

Claims (1)

[Claims] It has a light source for exposing the document, and a control means for maintaining the light emission of the light source at a predetermined amount of light according to the state of the light source or the power supply voltage, and the control means controls the light source to the light source in the initial stage of lighting of the light source. A light amount control device for an image forming apparatus, characterized in that the amount of energization is gradually increased until it reaches the above-mentioned redundant light amount.