JPH0555874B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a copying apparatus in which the lighting voltage of an exposure lamp is controlled by a microcomputer.

Conventionally, the power of a halogen lamp used in a document exposure lamp of a copying machine has been controlled by phase control using a lamp regulator (CVR). CVR
has a complicated circuit configuration and is large in size. As a result, the lighting voltage of the halogen lamp varies as shown in FIG. 1 in response to variations in the power supply voltage. That is, in FIG. 1, the curve shows the power supply voltage, and the curve shows the lighting voltage of the halogen lamp.
As you can see from this figure, the lighting voltage of the halogen lamp changes in response to large fluctuations in the power supply voltage, so when copying halftone originals, etc., there is a drawback that uneven shading appears in the finished product. .

Therefore, if the ON/OFF state of the fixing heater changes while a light source such as a halogen lamp is turned on, the power supply voltage fluctuates due to this change, resulting in a problem that an appropriate amount of light cannot be obtained. Even if the amount of current applied to the light source is controlled by detecting the voltage applied to the light source, there is a time lag between detecting the voltage fluctuation and controlling the appropriate amount of light accordingly, resulting in uneven shading as described above. You can't solve the problem.

This invention was made to eliminate the above-mentioned drawbacks, and the fixing heater is turned on/off while the light source is on.
It is an object of the present invention to provide a copying apparatus that can prevent variations in the amount of light of a light source caused by switching off and reduce unevenness in shading in copies.

FIG. 2 is a lamp control circuit diagram of a copying machine showing one embodiment of the present invention.

In FIG. 2, 1 is a power source, 2 is a halogen lamp, 3 is a triac, and 4 is a choke coil. A rectifier circuit 5 and a trigger element 6 are provided to control the phase of the gate of the triac 3. The trigger element 6 includes a light emitting diode 6a and a photothyristor 6b. 7 is a monitor transformer for power supply voltage, and a rectifier circuit 8 is connected to its secondary side.
Further, its output is applied to a Zener diode 9, a comparator 10, and a transistor 11. A zero-crossing circuit A is constituted by each of the above-mentioned parts 9 to 11, and a zero-crossing pulse signal 12 is generated at a zero-crossing point of each cycle of the AC voltage of the power supply 1.

13 is a thyristor, 14 and 15 are diodes,
16 and 17 are resistors, 18 is a capacitor,
Further, 19 is a resistor, 20 is a capacitor, and both constitute a low-pass filter 21. 22
is an operational amplifier, 23 is a transistor, and the above 13 to 23 constitute an effective value detection circuit B,
A lighting voltage monitor signal 24 is output. 25 is a switching transistor, and 26 is an OR circuit.

Reference numeral 27 denotes a microcomputer (hereinafter referred to as microcomputer), which is, for example, an 8-bit one-chip type, and is equipped with an internal timer 28, an AD converter 29, and the like. 30 is a fixing heater, and 31 is a magnification setting device. The fixing heater 30 starts with an on signal 32 issued from the microcomputer 27, and the heater temperature is determined by a temperature detection signal 3 from a temperature sensor (not shown).
3 is input to the microcomputer 27. Additionally, an exposure signal 34 and a trigger signal 35 are sent from the microcomputer 27.
is emitted. In addition, the microcomputer 27 controls whether the fixing heater 30 is turned on or off when it is turned on or off.
In order to offset fluctuations in the power supply voltage due to switching, the set energization period of the halogen lamp 2 is increased or decreased by a predetermined amount according to a flowchart described later. Note that symbols are omitted for those not particularly necessary for the explanation.

Next, regarding the outline of the operation, zero cross circuit A,
The lighting operation of the halogen lamp 2 and the effective value detection circuit B will be explained in this order, and the control by the microcomputer 27 will be explained using a flowchart.

First, the operation of zero cross circuit A will be described. The output of the rectifier circuit 8 connected to the secondary side of the monitor transformer 7 is applied to the inverting input terminal of the comparator 10. A constant resistance-divided voltage is applied to the non-inverting input terminal of the comparator 10, and therefore, the zero-cross point is output when the input voltage of the inverting input terminal becomes the same as that of the non-inverting input terminal. This is amplified by the transistor 11, becomes a zero-cross pulse signal 12, and is applied to the microcomputer 27, and the microcomputer 27 issues an interrupt every time this zero-cross pulse signal 12 is input.

Waveform b shown in Figure 3 is the zero-cross pulse signal 1.
2, which corresponds to the zero-cross point of the waveform of power supply 1 shown by the dotted line of waveform c.

Next, the lighting operation of the halogen lamp 2 shown in FIG. 2 will be explained. When the microcomputer 27 issues an exposure signal 34 and a trigger signal 35 shown in waveforms a and d in FIG. 3, these are applied to the base of the transistor 25 through the OR circuit 26, turning on the transistor 25. Therefore, the light emitting diode 6a in the trigger element 6 emits light, and the light enters the photothyristor 6b, thereby making the photothyristor 6b conductive. Therefore,
The output of the rectifier circuit 5 is applied to the gate of the triac 3, which turns on, and the voltage of the power source 1 is applied to the halogen lamp 2 via the choke coil 4, causing it to emit light. The shaded portion of the waveform c in FIG. 3 is the voltage waveform applied to the halogen lamp 2, and its rise coincides with the application point of the trigger signal 35 shown in the waveform d in FIG. Therefore, by changing the timing of application of the trigger signal 35, the lighting voltage of the halogen lamp 2 can be changed.

Next, the effective value detection circuit B will be explained. At the same time that the transistor 25 turns on and the light emitting diode 6a emits light, the transistor 23 becomes conductive and applies a voltage to the gate of the thyristor 13, making it conductive. Therefore, the output of the rectifier circuit 8 passes through the diodes 14 and 15 to the capacitor 18.
to charge. However, since the potential on the diode 15 side is lower than that on the diode 14 side, charging ends first, and thereafter charging is performed only from the diode 14 side. The terminal voltage of the capacitor 18 is then passed through the low-pass filter 21 to the operational amplifier 22.
The voltage follower inputs the lighting voltage monitor signal 24 to the microcomputer 27 as a lighting voltage monitor signal 24. Here, the reason why the capacitor 18 is charged in parallel through the resistors 16 and 17 is because the lighting voltage waveform of the halogen lamp 2 on the secondary side of the monitor transformer 7 is integrated by one CR circuit. The average value is detected,
If this is used as effective value detection, a non-negligible error will occur in the phase angle of the lighting voltage of the halogen lamp 2, and it cannot be used as the lighting voltage of the halogen lamp 2. For that purpose, resistor 1
By selecting appropriate values for 6 and 17 and charging the capacitor 18, the effective value of the lighting voltage of the halogen lamp 2 is approximately detected.

In this way, an interrupt is performed every time the zero-cross pulse signal 12 is input to the microcomputer 27, and the effective value of the voltage at the sampling point S as shown in the waveform e in FIG. It is input to the microcomputer 27 as . The timing of application of the trigger signal 35 is controlled by the microcomputer 27 so that the voltage monitored by the lighting voltage monitor signal 24 matches the target value.

The light source of this invention corresponds to the halogen lamp 2 (FIG. 2) of this embodiment, and the light amount control means and fixing control means correspond to the microcomputer 27 of this embodiment. Further, the detection means includes effective value detection means B and
Corresponding to the AD converter 29, the effective value of the lighting voltage of the light source is detected as a voltage value corresponding to the light amount of the light source.

The microcomputer 27, which is the light amount control means, receives the output ADn from the AD converter 29, which is the output of the detection means.
A first light amount control means (step C (59) in FIG. 5 to
Corresponding to (76), it should be noted that during such a step, N
is a subtraction value representing the difference between the AD conversion value and the target value Hn of the lighting voltage) and when the fixing heater is switched from the ON state to the OFF state while the light source is turned on (FIG. 5 C step (52 ) When the heater off switch F is set), in order to offset the change in light amount due to the increase in power supply voltage due to the switch, the energization period in the phase control is reduced (step (54)), and the fixing heater is turned off while the light source is on. When the heater is switched from the OFF state to the ON state (when heater on switch F is set in Step C (51) in Figure 5), the energizing period in the phase control is (same step (53))
and a second light amount control means.

Next, phase control by the microcomputer 27 will be explained using flowcharts shown in FIGS. 4 and 5 a to 5 c. Note that (1), (2), . . . represent each step, and F represents a flag.

FIG. 4 is a flowchart of an external interrupt using the zero-crossing pulse signal 12.

First, the internal timer 28 for phase control reference.
(1), then the lighting voltage monitor signal 2
4 is A/D converted by the AD converter 29 (2), stored in the memory (3), and checked whether the fixing heater 30 is ON or OFF (4). If the ON flag is set, turn on the fixing heater 30. Turn on (5).

5a to 5c show an internal timer interrupt routine by the internal timer 28. FIG. The explanation will be given below in order starting from FIG. 5a.

First, stop the internal timer 28 (11),
It is determined whether the halogen lamp 2 is ON (12), and if YES, the trigger signal 35 is made to fall (13), and when 200 μs has elapsed by the microcomputer 27 (14), it is made to rise (15) and a trigger pulse with a width of 200 μs is output. At this time, if the trigger signal 35 and the exposure signal 34 are input at the same time, the halogen lamp 2 is lit as already explained.

In the next step, check restart F (16). This restart F is a flag that is set when the halogen lamp 2 is turned off during each exposure scan of multi-copy (step (27) described later), and is set when starting the exposure scan for the second and subsequent copies. and if it has been set, proceed to step (17) and be reset.

Next, if the soft start F is not set (18), the ON/OFF state of the fixing heater at the end of the previous exposure scan is determined by referring to the heater memory F (19). This heater memory F is set or reset based on the heater ON F indicating the current ON/OFF of the fixing heater in the internal timer interrupt routine (steps (37) to (39) to be described later). However, since it is not updated while the halogen lamp 2 is off, the ON/OFF state of the fixing heater at the end of the previous exposure scan is stored at the start of the exposure scan for the second sheet.

Next, determine the current ON/OFF state of the fuser heater by referring to Heater ON F (20), (23), and if there is no change from the ON/OFF state of the fuser heater at the end of the previous exposure scan, A trigger signal 35 is generated (21) to start lighting the halogen lamp 2 at the final phase angle of original exposure. If it is currently in the OFF state, the phase angle is controlled by the internal timer 28.
Increase the temperature by 100 μs (22), check the status of the fixing heater 30 (23), and turn it on from the OFF state in the same way.
When the phase angle is in the state, the internal timer 28 reduces the phase angle by 200 μs (24). By steps (19) to (24), the fixing heater 30 is
The phase angle is corrected in advance based on the ON/OFF state of the fixing heater 30 to compensate for the voltage drop in the power supply 1 due to the ON/OFF state transition.

However, during the soft start in step (18), the control shifts to the control shown in FIG. 5b. Also, if the ON command F for the halogen lamp 2 is not set at the beginning of the internal interrupt routine, it is determined whether or not copying is currently in progress (25), and if copying is in progress,
Reset the phase angle calculation F (26) and restart F
(27), and turn off the exposure signal 34 (29). On the other hand, if it is not copying, restart F
, prepare for the next copy, set soft start F, set internal timer 28 to 4 ms (28), and turn off exposure signal 34 (29). Note that the internal timer 28 is set in step (28).
The reason for setting it to 4ms is that it is a necessary setting value to interrupt the internal interrupt routine.

Next, the routine to which step (18) is entered will be explained with reference to FIG. 5b.

First, the setting level Hn (8 bits), which is the target value of the lighting voltage of the halogen lamp 2, and the lighting voltage monitor signal are converted into AD by the AD converter 29.
A subtracted value N from the converted value ADn (8 bits) is determined (31), and whether the subtracted value N is positive or negative is determined (32). When the subtracted value N is negative, the lamp voltage match F and lamp voltage over F are reset and set, respectively, and the subtracted value N is replaced with its complement to obtain the absolute value (33).

Next, check the soft start F (34), and when the soft start F is set, set the internal timer 28 to 7ms (35), and reset the heater off switch F, heater on switch F, and phase angle calculation F, respectively. (36), turn on the fixing heater 30,
The OFF state is checked (37), and if it is ON, the heater memory F is set (39), and if it is OFF, the heater memory F is reset (38).

Heater off switch F shown in step (36),
Heater on switch F is a flag that is set by switching the fixing heater 30 on and off while the halogen lamp 2 is on.

Also, if soft start F is not set at step (34), check F during soft start (40), and if F is set during soft start, check lamp voltage over F (41). ,
During soft start, reset F (42) and end soft start. In this embodiment, since the microcomputer 27 is 8 bits, 2 ⁸ =256 bits can be used for the setting level Hn, so the setting value will be expressed in LSB. For example, 40LSB indicates a 40/256 division point. On the other hand, if the lamp voltage over F is not set (41), and if the value of the subtraction value N is 40LSB or less (43), the internal timer 28 is set to a smaller value in 5μs increments (45), and the subtraction value N≧
When it is 40LSB, the internal timer 28 is set in 40μs increments (44). That is, the speed of the soft start F is switched when the subtraction value N, which is the difference between the AD conversion value ADn and the set level Hn for the halogen lamp 2, reaches 40LSB. Here, in this invention, the input setting level Hn is 200LSB at the dividing point from the lower level, so (200-40)/200(LSB) That is, the setting voltage level of halogen lamp 2 is 80LSB.
The soft start is switched based on %.

Also, set levels Hn and AD in step (32).
When the two match when compared with the converted value ADn,
Set lamp voltage match F, reset lamp voltage over F, and proceed to step (34). on the other hand,
If the set level Hn is positive in the comparison in step (32), the lamp voltage match F and lamp voltage over F are reset (48), and the process goes to step (34).

Next, the routine to which step (40) is entered will be explained with reference to FIG. 5c.

First, the heater on switch F and heater off switch F are checked (51), (52). When the heater-on switch F is on, the internal timer 28 is subtracted by 200 μs (53), and when the heater-off switch F is on, the internal timer 28 is added 100 μs (54). These steps (53) and (54) turn the fixing heater 30 on and off.
Consider the voltage drop depending on the state. On the other hand, if both the heater-off switching F and heater-on switching flags are not set, check the phase angle calculation flag (55), and if this flag is not set,
Set the phase angle calculation flag (56) to control the next half wave with the same phase as the previous half wave, and when the phase angle calculation flag is set, step the phase angle of the next half wave. Calculated using the subtraction value N obtained in (31), the phase angle is changed once per cycle of the power supply frequency so that the lighting voltage of the halogen lamp matches the input setting voltage.

First, check the lamp voltage match F (57),
When this flag is set, the phase angle is not changed and the next cycle is controlled using the same phase angle as the previous cycle, and when lamp voltage match F is not set, lamp voltage over F is checked ( 58) When this flag is set, the lamp voltage is higher than the set level Hn, so the value of the subtraction value N is used to set the internal timer 28 to the previous 1.
The values are set larger than the values controlled between cycles (59) to (67). On the other hand, when the voltage over F is not set, the lamp voltage is smaller than the set level Hn, so the set value of the internal timer 28 is set to the previous level.
Set smaller than the value controlled between cycles (68) to (76). These steps (59) to (67),
By (68) to (76), the correction constant is changed according to the value of the subtraction value N, and the lighting voltage of the halogen lamp can be quickly converged to the set level Hn.

Next, temperature control of the fixing heater 30 related to phase control of the halogen lamp 2 will be explained with reference to the drawings.

FIG. 6 is a flow chart of temperature control of the fixing heater 30. Note that (81), (82), . . . represent each step, and F represents a flag.

A to D in FIG. 7 represent the halogen lamp 2, lighting voltage monitor signal 24, phase angle calculation F, and fixing heater 3.
0 is each control waveform diagram. The flowchart shown in FIG. 6 will be explained below with reference to FIG.

After turning on the power, when the roller surface temperature Lt reaches 180 (℃), it will WAIT・UP (81), and after WAIT・UP, the roller surface temperature Lt will be kept at 180 (℃) except when the halogen lamp 2 is turned on. For, Lt＜180(℃)
When the fixing heater 30 is turned on (92), (95),
(82), roller surface temperature Lt 1 second after heater is turned on
If the temperature has reached 180 (°C), the fixing heater 30 is turned off (87), (88), (89), (90). On the other hand, after 1 second, the roller surface temperature Lt reaches 180 (℃) WAIT・UP
If not, the fixing heater 30 is kept on for 1 second until Lt=180 (° C.) (91).

Also, after one second while the fixing heater 30 is off, the roller surface temperature Lt is detected again using the temperature detection signal 33 of the fixing heater 30, and if Lt<180 (°C), the fixing heater 30 is turned on again (83). , (84), (85),
(86). On the other hand, when Lt＞180(℃), Lt＜180(℃)
The fixing heater 30 is kept in the off state until . These steps (82) to (91) and (83) to
By step (86), the fixing heater 30 is turned on and
Depending on the temperature condition, the OFF control continues in either state for at least 1 second.

When the halogen lamp 2 is on, the fixing heater 30 is turned on.
During soft start (96) because switching between ON and OFF greatly affects the lighting voltage of the halogen lamp.
Switching of the fixing heater 30 is prohibited, and switching of the fixing heater 30 is permitted as necessary only when the phase angle calculation F is set (97). The reason why switching of the fixing heater 30 is permitted only when the phase angle calculation F is set in step (97) is that, as shown in FIG. 7, the sampling point S of the lighting voltage monitor signal 24 is Therefore, if the fixing heater 30 is turned on at the timing shown in FIG. 8, the next sampling point S(X
If the lighting voltage monitor signal 24 is sampled at the point ), the lighting voltage monitor signal 24 including the effect of turning on the fixing heater 30 can be monitored, and the phase angle α ₃ of the next cycle can be determined. For example, when the fixing heater 30 is turned on at _point
The convergence of the lighting voltage is delayed by one cycle.
Here, the lighting voltage monitor signal 24 is output every cycle.
was sampled because if there is a difference in the distortion between the upper half-wave and the lower half-wave of the commercial power supply, it is better to detect the lighting voltage monitor signal 24 in either half-wave for more accurate control. It is from.

Fig. 8 is a waveform diagram of the main part to explain the sequence in case of two copying, a is F during copying, b
is the exposure signal 34, c is the trigger signal 35, and d is the lighting waveform of the halogen lamp 2, indicating that the soft start lighting ST is performed only at the beginning of the first copy.

Next, a measurement example in which phase control is performed based on the present invention will be described with reference to FIGS. 9 and 10.

Figure 9 is a diagram showing the variation in power supply voltage vs. change in light intensity of a halogen lamp, where the curve shows the power supply voltage;
The curve represents the change in light amount.

FIG. 10 is a response characteristic diagram of the power supply voltage versus the lighting voltage of the halogen lamp, where a indicates the lighting voltage of the halogen lamp 2, and b indicates the voltage of the power supply 1.

As can be seen from Figure 9, the voltage of power supply 1
For voltage fluctuations of ±10% with respect to AC100V, fluctuations in the light intensity of the halogen lamp 2 could be suppressed to 4%.

Also, as can be seen from Figure 10, the voltage of power supply 1
The response time of the voltage of the halogen lamp 2 to a voltage fluctuation of ±10% with respect to AC100V quickly converged in 700ms.

As described above, according to the present invention, it is possible to prevent variations in the light amount of the light source due to ON/OFF switching of the fixing heater while the light source is turned on, and to reduce uneven shading in copying.

[Brief explanation of the drawing]

FIG. 1 is a variation characteristic diagram of input voltage versus lighting voltage of a halogen lamp, FIG. 2 is a lamp control circuit diagram of a copying machine showing an embodiment of the present invention, and FIG. 3 is an explanation of the operation of the embodiment of FIG. 2. Waveform diagram of main parts for 4th
Figure 5 is an external interrupt flowchart, Figures 5a to 5c are diagrams showing the internal timer interrupt routine, Figure 6 is a temperature control flowchart, Figure 7 is a control waveform diagram,
Figure 8 is a waveform diagram of the main part in the case of two-sheet copying, Figure 9
The figure is a correspondence diagram of fluctuations in the input voltage versus the lighting voltage of the halogen lamp, and FIG. 10 is a response characteristic diagram of the input voltage versus the lighting voltage of the halogen lamp. In the figure, 1 is a power supply, 2 is a halogen lamp, 3 is a triax, 4 is a choke coil, 5 and 8 are rectifier circuits, 6 is a trigger element, 7 is a monitor transformer, 9
is a Zener diode, 10 is a comparator, 11,2
3 and 25 are transistors, 12 is a zero-cross pulse signal, 13 is a thyristor, 14 and 15 are diodes, 16, 17, and 19 are resistors, 18 and 20 are capacitors, 21 is a low-pass filter, 22 is an operational amplifier, and 24 is a lighting voltage Monitor signal, 26 is an OR circuit, 27 is a microcomputer, 28 is an internal timer, 2
9 is an AD converter, 30 is a fixing heater, 31 is a magnification setting device, 32 is an on signal, 33 is a temperature detection signal, 34 is an exposure signal, 35 is a trigger signal, A is a zero cross circuit, and B is an effective value detection circuit. .

Claims (1)

[Scope of Claims] 1. A light source for exposing an original, a detection means for detecting a voltage value corresponding to the light amount of the light source, and controlling the light amount of the light source by controlling the phase of the amount of current supplied to the light source. It has a light amount control means and a fixing control means for controlling ON/OFF of a fixing heater, and the light amount limiting means has a first light amount control means for controlling the phase of the amount of electricity applied to the light source based on the output from the detection means. and a fixing heater is turned on from the ON state while the light source is turned on.
When the light source is switched to the OFF state, the energization period in the phase control is reduced in order to offset the change in light intensity due to the increase in power supply voltage due to the switching, and the fixing heater is switched from the OFF state to the ON state while the light source is turned on. a second light amount control means for increasing the energization period in the phase control when the switching occurs, in order to offset a change in light amount due to a decrease in power supply voltage due to the switching.