JPS62153948A - Dimmer for exposing lamp - Google Patents

Abstract

PURPOSE:To obtain a dimmer that changes amount of exposure responding to operation of an exposure setting key and lights up an exposing lamp efficiently by providing limitation to the reference value corresponding to an exposure setting key basing on reference voltage set to a differential amplifier. CONSTITUTION:In the case where voltage EC at the junction of a resistor 64 and the emitter of a transistor 65 is lower than voltage EL determined by resistors 62, 63, output voltage of a differential amplifier 66 is low level, and thereby, the transistor 65 is made on. Consequently, voltages ER, EM, ED are moved up and down by a resistor 67 for fine adjustment and a resistor 68 or 70 for coarse adjustment. However, when the voltage EC is higher than voltage EL, output voltage of the differential amplifier 66 becomes high level, and the transistor 65 becomes constant current control. Accordingly, voltages ER, EM, ED do not change above the voltage E even when the variable resistor 67 for fine adjustment and the variable resistor for coarse adjustment 68 or 70 are changed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an exposure lamp light control device that controls the amount of exposure of an exposure lamp applied to, for example, a copying machine.

[Technical Background of the Invention and Problems Therewith] Generally, a voltage feedback type light control device is used in an exposure lamp in a copying machine, for example.

This voltage feedback type light control device is provided with a limiter circuit that limits the exposure voltage near the rated value so that the exposure voltage of the exposure lamp does not exceed the rated value of the lamp. In other words, this limiter circuit allows the exposure lamp to expose at a voltage close to the rated value if the exposure voltage of the exposure lamp corresponding to the setting of the exposure amount setting key exceeds the rated value of the exposure lamp. ing. Therefore, even if the user changes the exposure amount setting key to change the copy density, if the exposure voltage corresponding to that setting exceeds the rated value of the exposure lamp, the exposure amount of the exposure lamp will remain constant. There was a problem in that the difference in copy density did not appear because of the difference in copy density.

[Object of the Invention] This invention was made in view of the above points, and its purpose is to change the exposure amount according to the operation of the exposure setting key and to efficiently light the exposure lamp. An object of the present invention is to provide a light control device for an exposure lamp that can control the exposure lamp.

[Summary of the Invention] In order to achieve the above object, the present invention limits the reference value corresponding to the exposure amount setting key based on the reference voltage set in the differential amplifier, thereby controlling the exposure of the exposure lamp. A limiter is formed on the voltage.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 3 shows a two-color copying machine as an example of an image forming apparatus to which the present invention is applied.

That is, 1 is a main body of a copying machine, and on the top surface of this main body 1 is a document table 2 that can freely move back and forth in the left-right direction (in the direction of arrow a in the figure).
is provided. Further, a paper feed cassette 3 is attached to the right side of the main body 1, and a paper discharge tray 4 is attached to the left side. The cassette cover 5 of the paper feed cassette 3 serves as a manual feeding table 6 for manually feeding paper P2 as appropriate.

Further, a photosensitive drum 7 is disposed approximately in the center of the main body 1. The photosensitive drum 7 is surrounded by a charging device 8, an optical system 9, developing devices 101, 102, and so on. A transfer charger 11, a peeling charger 12, a cleaning device 13, a static elimination lamp 14, and the like are arranged in this order. Also,
At the bottom of the main body 1, there are paper feed rollers 1 from the paper feed cassette 3.
5, or the paper P2 manually fed from the manual feeding table 6 is guided to the paper output tray 4 through the image forming section 16 between the photosensitive drum 7 and the transfer charger 11. A paper conveyance path 17 is formed. A registration roller 18 is disposed on the upstream side of the image transfer section 16 of the paper conveyance path 17, and a heat roller 19 and a paper discharge roller 20 as a fixing device are disposed on the downstream side.

Here, the optical system 9 has an exposure lamp 22 whose back portion is surrounded by a reflector 21, mirrors 23 to 26, and a lens 27.

The photosensitive drum 7 is driven by a drive mechanism (not shown) in the direction indicated by the arrow in the drawing in synchronization with the document table 2. First, an image of a document that is uniformly charged by the charging device 8 and uniformly irradiated with light by the exposure lamp 22 is formed on the photoreceptor drum 7 by the optical system 9, forming an electrostatic latent image. be done. This formed electrostatic latent image is transferred to the developing device 101.10.
The developer rollers 311 and 312 of No. 2 are selectively driven to develop with a developer of black or one other color, such as red, to form a developer image, and the developer is sent to the transfer charger 11 side. In addition, 401 and 402 are respectively developer stirring bodies, 421 and 422 are respectively developer concentration detectors, and 5
21.522 are developer supply rollers, 531.5 are respectively
32 are a pair of stirring rollers.

On the other hand, paper P1 or P fed automatically or manually
2 is supplied by a resist row 518, and a developer image previously formed on the photoreceptor drum 7 is transferred by the transfer charger 11. The paper PI (P2) to which this developer image has been transferred is peeled off from the photoreceptor drum 7 by a peeling charger 12, passes through a paper conveyance path 17, and is guided to a heat roller 19, where the transferred image is melted. After being fixed, the paper is discharged to the paper discharge tray 4 by the paper discharge roller 20.

Further, after the developer image is transferred onto the paper Pi (P2), the residual toner remaining on the photoreceptor drum 7 is cleaned by the cleaning device 13, and the residual image on the photoreceptor drum 7 is further erased by the static elimination lamp 14. , to prepare for the next copying operation.

-〇- In the main body 1, an upper frame and a lower frame (not shown) are pivotally supported at one end via a support shaft (not shown), and the other ends of both frames are rotated at a desired angle, e.g. It is configured so that it can be opened to approximately 30 degrees. The upper frame includes, around the photoreceptor drum 7, a charging device 8, an optical system 9, an exposure lamp 22, a developing device 101.
102, a cleaning device 13, a static elimination lamp 14, and other devices are attached by appropriate means, and a document table 2,
The paper feed roller 15 is also attached to the upper frame and constitutes the upper unit 1A. In addition, the lower frame has
Paper feed cassette 3, transfer charger 11, peeling charger 12
, heat roller 19, paper ejection roller 20. Each mechanism such as the paper ejection tray 4 and the main motor 28 are attached by appropriate means to constitute the lower unit 1B.

After rotating and removing the front cover of the main body 1, almost all of the paper Pi (R
2) is configured to be able to be opened and closed along the paper conveyance path 17.

Further, 29 is a cleaning blade 30 of the cleaning device 13.
This is a blade solenoid for bringing the photoconductor drum 7 into contact with and separating it from the photoreceptor drum 7.

FIG. 4 shows an operation panel 56 provided on the main body 1, in which a copy key 151 for executing a copy operation,
An interrupt key 152 for specifying an interrupt mode for interrupt copying, and an interrupt indicator 1 for indicating the interrupt mode.
53, a numeric keypad 154 for setting the number of copies, etc., a number display section 155 for displaying the number of copies, a color selection key 156 for selecting a copy color (for example, black, red), a color display 157 for displaying the selected color. .158, liquid crystal display section 161 that displays operating status, etc., exposure amount setting keys 328 to 32
A density setting section 162 for varying the copy density in nine steps according to the setting of c is provided. In the liquid crystal display section 161, 163 is a symbol for indicating that copying is possible, indicating that copying is possible; 164 is a symbol for indicating that copying is not possible, indicating that copying is not possible;
Reference numeral 65 is a symbol for indicating that there is no developer left in the hopper of the developing device 1o1 or 102.

FIG. 5 shows a control circuit of a light control device for an exposure lamp according to the present invention. In other words, 33 is an AC power supply,
The exposure lamp 22 is connected to this power source 33 via a bidirectional thyristor 34, which will be described later.

39 is a waveform shaping circuit, and this waveform shaping circuit 39 converts the voltage generated across the exposure lamp 22 into the primary coil 41.
A transformer 41 that generates the same voltage in the secondary coil 41B by being supplied to A, a full-wave rectifier 43 that full-wave rectifies the voltage generated by the transformer 41, and a full-wave rectifier 43 that performs full-wave rectification of the voltage generated by the transformer 41. Resistors R1, R2, which divide the voltage
Resistors R3 and R for integrating the voltage across the resistor R2 and obtaining a DC voltage proportional to the effective value of the voltage across the lamp.
4. Diodes D1, D2, and capacitor C1, and an amplifier 44 that shifts the obtained DC voltage to a predetermined level and outputs an appropriate voltage.The output from this amplifier 44 is integrated, and the voltage is used as an analog signal for exposure. lamp 2
The second trire is the resistor R supplied to the timing generation circuit 55.
7 and a capacitor 03. Note that the resistor R6 is for protecting the amplifier 44.

The timing generation circuit 55 includes an A/D converter 45 that converts an analog signal from the waveform shaping circuit 39 and a reference voltage from a reference voltage setting circuit 6o (described later) into digital data; A microcomputer (hereinafter abbreviated as microcomputer) 46 determines the trigger generation timing according to digital data from 45 and the settings of exposure layer setting keys 32a to 32c provided on the operation panel 56. The driving element 36 drives the lamp lighting circuit 37 in accordance with the generated trigger pulse.

The lamp lighting circuit 37 controls the lighting of the exposure lamp 22 by a photocoupler 38 that operates on and off in response to a trigger pulse supplied from the microcomputer 46, and a conduction angle corresponding to the on and off of this photocoupler 38. It is composed of the bidirectional thyristor 34 and the like.

Further, an interrupt cycle generation circuit 47 is connected to the power supply 33 . This interrupt period generation circuit 47 outputs a timing pulse synchronized with the power supply frequency, and includes a full-wave rectifier 48 that rectifies the power supply voltage, a photocoupler 49 that operates on and off with the output of this full-wave rectifier 48, and a photocoupler 49 that operates on and off with the output of this full-wave rectifier 48. a transistor 35 that operates on and off with the output of 49;
and resistors R9 to R11, capacitor C5, and diode D3 that invert and output the output of this transistor 35.
, D4, etc. The timing pulse output from this interrupt cycle generation circuit 47 is supplied to the interrupt terminal of the microcomputer 46 as an interrupt signal. Thereby, the microcomputer 46 executes interrupt processing and performs dimming control every time the interrupt signal is input.

FIG. 1 shows a reference voltage setting circuit 60 according to the present invention. This reference voltage setting circuit 60 is a circuit that sets a reference voltage for determining the timing of occurrence of a bird by the microcomputer 46. That is, resistors 62 and 63 are connected in series between the power supply terminal 61 and the ground, and the connection point of these resistors 62 and 63 is connected to the non-inverting input terminal of the differential amplifier 66. On the other hand, one end of a resistor 64 is connected to the power supply terminal 61, and the other end of this resistor 64 is a PN
It is connected to the emitter of the P-type transistor 65 and to the inverting input terminal of the differential amplifier 66. Further, power for the differential amplifier 66 is supplied from between the power supply terminal 61 and the ground.

On the other hand, the output terminal of this differential amplifier 66 is connected to the transistor 6
The collector of this transistor 65 is connected to one end of a variable resistor 67. The other end of this variable resistor 67 is connected to one end of variable resistor 68, 70, and the other end of these variable resistors 68, 70 is connected to each resistor 6.
Fixed contact 72 of analog switch 72 via 9.71
a172b, respectively. This analog switch 72 is provided with movable contact pieces 72c and 72d, and a resistor 73.
74 and 75 are connected in series.

The movable contact piece 72C1 of the analog switch 72
The connection point between 72d and resistor 73, the connection point with resistor 73.74, and the connection point with resistor 74.75 are A/
It is connected to the input terminal of the D converter 45.

The variable resistor 68.70 is connected to the developing device 101.10.
This is to roughly adjust variations in the exposure lamp 22 or the photosensitive drum 7 to correspond to the developer characteristics in the color selection key 156, and is selectively switched by the analog switch 72 in accordance with the setting of the color selection key 156. Further, the variable resistor 67 is used to finely adjust variations in the exposure lamp 22 or the photosensitive drum 7, which are coarsely adjusted by the variable resistors 68 and 70. Further, the A/D converter 45 includes the variable resistors 67, 68 or 70, and the resistors 64, 69, .
71. Voltage ER, EM determined by 73-75,
ED is supplied as a reference voltage corresponding to the brightest light, intermediate light, and darkest light of the exposure lamp 22, respectively.

For example, when the copying machine is powered on, the microcomputer 46 operates the A/D converter 45 and outputs brightest light, intermediate light,
Each reference voltage corresponding to the darkest light is converted into digital data and read.

Next, the microcomputer 46 sets the data corresponding to the brightest light, intermediate light, and darkest light to RA as fixed data.
M (random access memory) 46b,
Further, from these data, nine step data (reference values) corresponding to the exposure amount setting keys 328 to 32G shown in FIG. 2 are calculated and stored. In other words, the 9th row is E
D (corresponds to the setting of the exposure amount setting key 32G), 8th row is (EM+3ED)/4.7th row is (EM+ED)
/2.6th row is (3EM+ED)/4.5th row is EM(
corresponding to the setting of the exposure amount setting key 32b), and the fourth row is (corresponding to the setting of the exposure amount setting key 32b).
ER+3EM)/4.3rd row is (ER+3EM)/2.2
The first row stores (3ER+EM)/4. The first row stores ER (corresponding to the setting of the exposure amount setting key 32a).

On the other hand, the resistors 62 and 63 are resistors that create the reference voltage EL of the differential amplifier 66. That is, when the voltage Ec at the connection point between the resistor 64 and the emitter of the transistor 65 is lower than the voltage EL determined by the resistor 62.63,
The output voltage of the differential amplifier 66 is at a low level, which turns on the transistor 65. Therefore, the voltages E RzEM and ED are moved up and down by the resistor 67 for fine adjustment and the resistor 68 or 70 for coarse adjustment.

However, when the voltage Ec is higher than the voltage EL, the output voltage of the differential amplifier 66 becomes a high level, which causes the transistor 65 to perform constant current control, so that the voltage ER
, EM, and Eo, even if the variable resistor 67 for fine adjustment and the variable resistor 68 or 70 for coarse adjustment are changed, the voltage EL
Do not move further. Therefore, said resistance 62.63
The reference voltage E1- of the differential amplifier 66 determined by is the limit value EL that limits the upper limit of the step data.
It becomes. For example, as shown in FIG. 2, if the voltage EL is set so that the exposure voltage (voltage between terminals) of the exposure lamp 22 is 102V, each variable resistor 67.
Even if you change 68 or 7o, the voltages ER, EM, E
D is configured to move in the vertical direction within a range that does not exceed 102V, as shown by the arrow in the figure.

Next, the operation will be explained.

First, the CPU (central processing unit) 46a of the microcomputer 46 has variable resistors 67.68 or 70. and resistance 64.69.71
．． Voltages ER, EM, ED determined by 73-75
is read through the A/D converter 45, and the step data of the nine stages is stored as a reference value.

At this time, for example, the voltage EL of the differential amplifier 66 is
．． 63, the exposure voltage corresponding to the step data is 102V even at maximum exposure.
A limiter is formed to prevent this from occurring.

When the copying operation is executed in the above state, for example, if the frequency of the power supply 33 is 50Hz, the interrupt cycle generation circuit 47 outputs an interrupt signal once every 10 m5ec, and each time the interrupt signal is outputted in the microcomputer 46. CPU46a
executes the interrupt handling routine. In this interrupt processing routine, the CPU 46a first stores voltage (digital) data corresponding to the voltage across the exposure lamp 22 (exposure voltage) output from the A/D converter 45 in the RAM 46b.

Next, the CPU 46a selects the RAM 46b in response to signals from the exposure amount setting keys 32a to 32c as exposure amount selection means.
Determine the trigger pulse time corresponding to the level of the step data stored in . Next, the CPU 46a sets the trigger pulse time corresponding to the step data to an internal timer (counter), which is a timer function within the microcomputer 46, and starts the internal timer (counts every 250 μS, for example). At this time, the internal timer starts pulse 1.
Since there is a variation of a predetermined time (for example, 250J1s at maximum in this embodiment) before starting counting of the shots, a correction -17=time is determined to correct this. Note that even while this internal timer is operating, the microcomputer 46 is executing main program processing in parallel.

When the internal timer finishes counting, C
The PU 46a interrupts the main program routine and executes timer interrupt routine processing.

In this timer interrupt routine, first, the determined correction time is counted, and when the counting is completed, the determined trigger pulse time is counted, and when the counting is completed, the trigger pulse ( 50-100/l/S). In this lamp lighting circuit 37, when a trigger pulse is sent from the microcomputer 46, the photocoupler 38 operates to turn on the thyristor 34, and the power from this point to the next zero cross point of the AC voltage is supplied to the exposure lamp 22. Supplied. By repeating the above process every time an interrupt signal is input, the exposure lamp 22 is continuously lit by phase angle control. As a result, the exposure amount setting keys 32a~
Light control is performed according to the exposure setting corresponding to 32C.

According to the above embodiment, the step data as a reference value that is moved by the variable resistor 67, 68 or 70 is limited based on the reference voltage set in the differential amplifier.

Therefore, since the exposure amount changes in response to the operation of the exposure amount setting key, there is no unnaturalness, and moreover, the exposure lamp 22
can be efficiently controlled over a wide range near the rated value.

In the above embodiment, a case has been described in which the invention is applied to a light control device for an exposure lamp in a copying machine, but the present invention is not limited to this, and can be applied to a light control device for an exposure lamp in a laser printer or a facsimile machine, for example. It can also be applied to

[Effects of the Invention] As detailed above, according to the present invention, there is provided an exposure lamp dimming device that changes the exposure amount in accordance with the operation of the exposure setting key and is capable of efficiently lighting the exposure lamp. can be provided.

[Brief explanation of drawings]

Figure 3 is a side view schematically showing the configuration of the copying machine; Figure 4 is a plan view showing the configuration of the operation panel; Figure 5 is the configuration of the entire control circuit. FIG. 22... Exposure lamp, 32a-32c... Exposure amount setting key, 33... AC power supply, 34 River bidirectional thyristor, 37... Lamp lighting circuit, 39... Waveform shaping circuit, 41... ...Transformer, 45...A/D converter, 4
6... Mer 1': ] 7.46 a-CPU, 4
6 b-RAM, 47... interrupt cycle generation circuit, 5
5... Trigger timing generation circuit, 60... Reference voltage setting circuit, 66... Differential amplifier, 67.68.7
o...variable resistance.

Claims (4)

[Claims] (1) In a light control device that controls the exposure amount of an exposure lamp based on a set reference value, a selection means for arbitrarily selecting a reference value corresponding to the exposure amount, and a reference value selected by the selection means. a first setting means for setting the exposure voltage of the exposure lamp corresponding to the exposure lamp, a second setting means for setting the limit value of the exposure lamp, and a current supplied to the first setting means that sets the limit value. An exposure lamp characterized by comprising: a limiting means for not changing the first setting means when the amount exceeds the limit; and a control means for controlling the exposure amount of the exposure lamp according to the first setting means. Dimmer device. (2) The exposure lamp light control device according to claim 1, wherein the first and second setting means are comprised of resistors. (3) The exposure lamp dimming device according to claim 1, wherein the limiting means comprises a differential amplifier and a transistor controlled by the output signal of the differential amplifier. (4) The exposure lamp light control device according to claim 1, wherein the control means comprises a microcomputer.