JPH08110598A - Image forming device - Google Patents

Abstract

PURPOSE: To always attain excellent image formation by performing shifting to a normal lighting state in a specified period, even if the startability of a fluorescent lamp is reduced some degree in an electrophotographic system image forming device using the fluorescent lamp as a light source for exposing. CONSTITUTION: The first order side of an inverter transformer 3 is switched/ driven by a transistor 4, to light the fluorescent lamp 1 with a voltage generated on the second order side. Then, the light quantity of the fluorescent, lamp 1 is detected by a light quantity sensor 14 and the lighting and turning off of the fluorescent lamp 1 are switched with a frequency not affecting an image by a system controller 24, in accordance with the detection signal of the sensor 14, to control light. Moreover, when the fluorescent lamp 1 is lighted from a completely turned off state, the lighting and turning off are repeated at a specific ratio regardless of the signal from the sensor 14 for the prescribed period and then, the light quantity is controlled according to the signal from the sensor 14, from a prescribed ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus using a fluorescent lamp as a light source for exposure.

[0002]

2. Description of the Related Art Conventionally, a halogen lamp has been mainly used as a light source for exposure of a copying machine or the like. In addition, fluorescent lamps are often used in low-speed machines that do not require a large amount of light, but due to their low power consumption, there is a demand for switching to fluorescent lamp light sources even in higher-speed models.

FIG. 9 is a diagram showing a drive and control circuit for a fluorescent lamp mounted on a conventional copying machine. In the figure, 1 is a fluorescent lamp, 2 is an inductor for limiting the lighting current of the fluorescent lamp 1,
3 is an inverter transformer for lighting the fluorescent lamp 1,
A switching transistor 4 for driving the inverter transformer 3 is driven by an oscillation circuit (OSC) 5. 6 is a snubber capacitor, 7 is a diode bridge,
8 is a control transistor for turning on and off the fluorescent lamp 1,
9 and 10 are bypass capacitors, 11 and 12 are fluorescent lamps 1.
In the filament, 13 is a rectifying diode, 14 is a light amount sensor for detecting the light amount of the fluorescent lamp 1, 20 is a commercial AC power source, 21 is a commercial AC power source 20 to be used in the apparatus main body.
AC-DC converter for generating C low voltage Vdd, 22
Is a smoothing capacitor, and 23 is a system controller that controls the system of the apparatus.
CM that is a mode signal that outputs a signal (Light On Signal) and commands the output control of the AC-DC converter 21.
S signal (COPY Mode Signal) and SMS signal (STBY Mode S
ignal) is output.

Next, the operation of the above conventional example will be described with reference to the timing chart shown in FIG. First, when the power is turned on, the device enters a standby state. At this time, the controller 23 sends a standby mode signal (SMS signal) to the AC-DC converter 21.
As a result, the AC-DC converter 21 is controlled to a voltage output that is lower than the voltage during the copy operation, and here the voltage output is 12V.
It becomes an output.

On the other hand, although the fluorescent lamp 1 is naturally in the off state during standby, when starting the copying operation, a slight preheating current is applied to the filaments 11 and 12 in order to start lighting more smoothly. I need to put it. In the circuit of FIG. 9, AC- is connected to one end of the input winding of the inverter transformer 3.
The output voltage of the DC converter 21 is applied, and the other end is switched on and off at a frequency of 30 kHz. As a result, a high voltage Vh according to the winding ratio is generated at the output of the inverter transformer 3. This time,
Since the diode bridge 7 is short-circuited by the control transistor 8, the output side of the inverter transformer 3 is in a state in which a series circuit including the inductor 2, the filament 11, the bypass capacitor 9, the filament 12 and the bypass capacitor 10 is connected.

Therefore, the output winding I of the inverter transformer 3 is I = Vh / jωL. The value obtained by subtracting the current shunted by the bypass capacitors 9 and 10 from this is the filament 1 of the fluorescent lamp 1.
It becomes the preheating current that flows through 1 and 12. Here, it is assumed that a filament current of 350 mA flows as this preheating current, and this state is referred to as a half preheating state. Next, when the copy start key is pressed, the controller 23
A copy mode signal (CMS signal) is sent to the DC converter 21, and the AC-DC converter 21 raises its output to a voltage at which each unit of the apparatus can operate. Here, it is set to 24V. As a result, the voltage of the output winding of the inverter transformer 3 almost doubles, and the preheating current also doubles. At this time, in the present embodiment, it is assumed that a filament current of 700 mA flows and this is in a full preheated state. This full preheating immediately before the start of lighting is effective for promptly starting the lighting of the fluorescent lamp 1, and is generally an essential sequence.

Next, at the timing of exposure of the document, the short circuit of the diode bridge 7 due to the control transistor 8 is stopped, and the output voltage of the inverter transformer 3 is changed to the fluorescent lamp 1.
Is applied to both ends of the fluorescent lamp 1 and the fluorescent lamp 1 starts lighting. When the exposure is completed, the diode bridge 7 is short-circuited again and the fluorescent lamp 1 is turned off. Then, the preheating continues in the full preheating mode state until the apparatus finishes the post-processing of the copying operation and shifts to the standby mode again. Further, the case of having a dimming function is as follows.

That is, the output from the light amount sensor 14 which is the light amount detecting means of the fluorescent lamp 1 is input to the controller 23, and conversely, the controller 23 outputs a lighting signal when the target light amount is dark and when the light signal is bright. A turn-off signal is output. This switching between lighting and extinguishing is performed at a somewhat high frequency because it is necessary for the exposure light source of the electrophotographic apparatus to suppress the amount of light to a flicker level that does not cause a problem. For example, a system in which one cycle of lighting and extinguishing is switched at a cycle of about 1 ms can be considered.

[0009]

The image forming apparatus having the conventional fluorescent lamp lighting device as described above has the following problems.

For example, in a high-speed machine, in order to use a fluorescent lamp as a light source for exposure, a high light amount and a long life thereof are indispensable conditions, but in order to extend the life of the fluorescent lamp,
Smooth lighting start is one of the most important requirements.

However, in the conventional lighting system, since the light quantity control loop by the light quantity detecting means is always constructed by the software or the complete hardware of the microcomputer immediately after the filament full preheating immediately before the lighting signal, If the lighting does not shift immediately after the lighting signal is input due to the progress of life of the lamp or external environment such as low temperature, the lighting and extinguishing ratios for dimming move in the direction that the lighting ratio increases rapidly, and the filament preheating current changes with time. It decreases with the result and the filament temperature decreases rapidly with time. Therefore, a vicious cycle in which it becomes more and more difficult to shift to lighting is produced, and as a result, the life of the fluorescent lamp is effectively shortened.

The present invention has been made in view of the above-mentioned problems. Even when the startability of the fluorescent lamp is deteriorated to some extent due to a change with time or an external environment, the fluorescent lamp is normally turned on within a predetermined period. An object of the present invention is to obtain an image forming apparatus capable of shifting to a state, always performing good image formation, and substantially extending the life of a fluorescent lamp.

[0013]

The image forming apparatus according to the present invention is configured as follows.

(1) In an electrophotographic image forming apparatus using a fluorescent lamp as a light source for exposure, a light amount detecting means for detecting the light amount of the fluorescent lamp, and a fluorescent lamp according to a detection signal from the light amount detecting means. And a dimming means for dimming by switching on and off of the light at a frequency that does not affect the image,
The dimming means, when starting the lighting of the fluorescent lamp from a state of being turned off for a predetermined time, repeats lighting and extinguishing at a specific ratio for a predetermined period regardless of a signal from the light amount detection means, and then from a predetermined ratio. The light quantity control is performed according to the signal from the light quantity detecting means.

(2) In an electrophotographic image forming apparatus using a fluorescent lamp as a light source for exposure, a light quantity detecting means for detecting the light quantity of the fluorescent lamp, and a fluorescent lamp according to a detection signal from the light quantity detecting means. And a dimming means for dimming by switching on and off of the light at a frequency that does not affect the image,
The dimming means, when starting the lighting of the fluorescent lamp from a state of being turned off for a predetermined time, repeats lighting and extinguishing at a specific ratio for a predetermined period regardless of the signal from the light amount detection means, and then at a predetermined ratio. Only when it is confirmed that the predetermined light amount is obtained, the light amount control is performed according to the signal from the light amount detecting means.

(3) In the image forming apparatus of the above (2), when the dimming means starts the lighting of the fluorescent lamp from a state where the light is turned off for a predetermined time, the light control means does not depend on the signal from the light amount detecting means for a predetermined period. It is configured to repeat lighting and extinguishing at a specific ratio, and then when a predetermined light amount cannot be obtained at a predetermined ratio, an abnormality of the fluorescent lamp is displayed and the image forming operation is stopped.

[0017]

According to the present invention, when the lighting of the fluorescent lamp is started from the completely extinguished state, the lighting and extinguishing are repeated at a specific ratio for a predetermined period regardless of the signal from the light amount detecting means, and then a predetermined ratio. To the light amount control state according to the signal from the light amount detecting means, it is possible to shift to the normal lighting state within a predetermined period, and it is possible to always perform good image formation.

[0018]

1 is a block diagram showing a circuit configuration of a first embodiment of the present invention. In the figure, 1 to 14 and 20 to 22 are the same as those of the conventional example shown in FIG. 9, and thus the duplicate description is omitted, but the system controller 2 of FIG.
The system controller 24 corresponding to No. 3 switches lighting and extinguishing of the fluorescent lamp 1 at a frequency (duty) that does not affect the image according to the detection signal from the light amount sensor 14 that is the light amount detecting means, and changes the light amount at that ratio. A dimming unit that performs dimming by adjusting is configured.

Further, when the above-mentioned light control means starts the lighting of the fluorescent lamp 1 from a state where the light is continuously turned off for a predetermined time, that is, a completely turned-off state, a predetermined period is specified regardless of a signal from the light quantity sensor 14. The lighting and extinguishing are repeated at a ratio, and then the light amount control state according to the signal from the light amount sensor 14 is shifted from a predetermined ratio.

FIG. 2 is a diagram showing the timing of main signals during lighting in this embodiment. In the figure, T1 is a fully preheated state immediately before the start of lighting, T2 is a state in which a lighting signal and a turn-off signal are repeated at a fixed duty of 50%, and T3 is lighting so that a desired light quantity is obtained based on a signal from the light quantity sensor 14. , Shows the state of controlling the turn-off ratio. FIG. 3 is a diagram showing detailed timings of main signals having a smaller time scale during lighting. 3A is a base signal of the transistor 4, FIG. 3B is a collector current of the transistor 4, and FIG. 3C is a collector voltage of the transistor 4.
(D) shows the tube current when the fluorescent lamp is turned on.

First, the turn-on / turn-off signal of the fluorescent lamp 1 shown in FIG. 2A is naturally H (high level) during the period T1, and both ends of the fluorescent lamp 1 are connected by the diode bridge 7 and the transistor 8. I am shorted. Also, that T
During the period of 1, the filament current shown in FIG. 2 (e) continuously flows, heating the filaments 11 and 12 to a sufficient temperature.

Next, the turn-on / turn-off signal of the fluorescent lamp 1 is 5
A fixed duty of 0% is held for a predetermined time. This time,
Before the fluorescent lamp 1 is relatively new and has a clear change over time, as shown in (c) of FIG. 2, the fluorescent lamp tube current immediately flows in this lighting period immediately after the period of T2, and the lamp is lit. , Shows faithful follow-up to the turn-off signal. A more detailed internal waveform during the period when the fluorescent lamp current is flowing is as shown in FIG. 3A shows an output signal of the oscillation circuit 5, which is a signal to the drive transistor 4 of the inverter transformer 3. The fluorescent lamp current has a waveform as shown in FIG. 3D due to the current limiting inductor 2.

Here, as the aging of the fluorescent lamp 1 progresses, the above-mentioned fluorescent lamp tube current finally flows out while the lighting and extinguishing signals are repeatedly input as shown in FIGS. 2 (b) and 2 (d). Like At this time, if the dimming by the light quantity sensor 14 is started immediately after full preheating without repeating the lighting and extinguishing signals at a fixed duty for a predetermined period as in the present embodiment, for example, dimming is started from 100% lighting. Then, if it does not illuminate immediately after the lighting signal is input, the filament temperature will drop rapidly, and it will become even more difficult to illuminate, and eventually it will not illuminate at all, or will suddenly transition to lighting when the filament temperature falls significantly. Will result. Especially in the latter case, the influence on the life of the filaments 11 and 12 such as abnormal discharge in the vicinity of the filament and depletion of the lighting promoting substance is large, which causes rapid deterioration of the life of the fluorescent lamp 1. Also, in the former case, the function of the fluorescent lamp 1 is lost. Even if the dimming is started from about 50%, if the lighting does not shift immediately, the light amount control eventually leads to 100%.
Since it is controlled in the direction of lighting, it is essentially the same as above.

However, as in the present embodiment, the lighting and extinguishing signals are fixed at 50% for a predetermined period after the lighting is started, so that the lighting of T2 in FIG. During the period, half the electric power of full preheating is applied to the filaments 11 and 12 on average, so if the tube current starts to flow with several lighting signals, then the inside of the fluorescent lamp is activated, and as shown in FIG. As shown in (d), the normal lighting and extinguishing operations are followed.

In this embodiment, the repetition cycle of the lighting and extinguishing signals is set to 50% of 1 KHz. However, depending on the characteristics of the fluorescent lamp 1, about 40% is preferable, about 60% is preferable, and so on. Just set the ratio. Further, the fixed duty period is 50 in this embodiment.
Although it is set to ms, according to the required time until the dimming of the fluorescent lamp 1 is stabilized as the system configuration,
You can make a proper decision.

FIG. 4 shows the operation flow of this embodiment. As described above, for example, lighting is performed with a fixed duty of 50% (step S1), and dimming is started from 50% (step S2).

As described above, the fluorescent lamp 1 is completely turned off.
When starting the lighting, the lighting and extinguishing are repeated at a specific ratio for a predetermined period regardless of the signal from the light amount sensor 14, and then the light amount control state corresponding to the signal from the light amount sensor 14 is shifted from the predetermined ratio. Therefore, even when the startability of the fluorescent lamp 1 is deteriorated to some extent due to changes over time or the external environment, it is possible to shift to a normal lighting state within a predetermined period, and always good image formation can be performed. In addition, the life of the fluorescent lamp can be substantially extended.

Next, a second embodiment of the present invention will be described with reference to the flowchart of FIG. 5 and the timing chart of FIG. The configuration of this embodiment is the same as that of FIG. 1, but the controller 24 determines whether or not a predetermined light amount is obtained at a predetermined ratio after a predetermined period of a fixed duty at the start of lighting in the above-described first embodiment. Only when it is confirmed that a predetermined amount of light is obtained, the state is changed to the light amount control state according to the signal from the light amount sensor 14, and when the predetermined amount of light is not obtained, error processing ( Lighting failure processing)
And display the abnormality of the fluorescent lamp 1 to the outside,
Stop the image forming operation.

After the full preheating, the place to start with the lighting and extinguishing signal of 50% fixed duty (step S
11), which is the same as the first embodiment described above. Next, in the present embodiment, the fixed duty is switched to 100% (step S12). Therefore, it is determined whether the output from the light amount sensor 14 has reached a predetermined value (step S13). This is to confirm whether or not the fluorescent lamp 1 has shifted to stable lighting during the period of the 50% fixed drive. If the predetermined light amount has not been reached, the life of the fluorescent lamp 1 is deteriorated, and This indicates that it was not possible to shift to lighting due to a factor, and a predetermined error processing procedure is to be taken (step S15).

However, if the predetermined amount of light is reached in step S13, it is determined that the fluorescent lamp 1 has been turned on,
Enter light control (step S14). At this time, in this embodiment, dimming is started with 50% as the initial value. FIG. 6 shows these states, (a) shows the lighting and extinguishing signals of the fluorescent lamp 1, (b) shows the output of the light amount sensor 14, and the period T4 is particularly characteristic of this example. This is the period for determining the amount of light.

FIG. 7 is a flow chart showing the operation of the third embodiment of the present invention. The feature of this embodiment is that the light amount is determined during the period when a fixed-duty lighting and extinguishing signal is input, and if a predetermined light amount is obtained, then the target light amount detection means output corresponding to the target light amount is output. This is to calculate the ratio of the lighting and extinguishing signals of the obtained fluorescent lamp 1 and start the light control by using the result as an initial value.

That is, first, the fluorescent lamp 1 is lit at a fixed duty of 50% (step S21), and then lit at a duty of 100% (step S22). Then, during this period, it is determined whether or not the light amount has reached a predetermined value (step S23), and if not, the above-mentioned error processing is performed (step S25). If the predetermined light amount is reached at 100% driving, the dimming start value is calculated (step S
24), start dimming at that ratio (step S
26).

Here, the amount of light when the fluorescent lamp 1 is turned on at a rate of 100% is affected by the deterioration of the fluorescent lamp 1, the tube surface temperature, the continuous use time, etc.
From the difference between the amount of light at the time of lighting and the final target amount of light,
It can be estimated by various methods how much the target light quantity can be obtained. For example, as shown in FIG. 8, the target light amount is divided into 256 steps, and the optimal lighting / extinguishing signal duty at the start of dimming is set to 100.
It is conceivable to have a required number (here, four types) in memory as a table for each amount of light at the time of lighting.

According to the present embodiment, the period until the final target light quantity is obtained is the environmental temperature,
Since the value is a constant short value regardless of the variation of the target light amount setting value obtained from the image control conditions, it becomes possible to carry out the lighting and extinguishing sequence with a fixed duty at the start of lighting over a longer period, The probability of transition to lighting of the fluorescent lamp 1 becomes higher. Therefore, the effective life of the fluorescent lamp 1 can be greatly extended.

[0035]

As described above, according to the present invention,
When the lighting of the fluorescent lamp is started from the completely extinguished state, the fluorescent lamp is repeatedly turned on and off at a specific ratio for a predetermined period regardless of the signal from the light amount detecting means, and then the signal from the light amount detecting means is changed from the predetermined ratio. The light quantity control state is changed to a normal light state within a predetermined period even when the lighting startability is deteriorated to some extent due to factors such as a temporal change of the fluorescent lamp and a low environmental temperature. It is possible,
There is an effect that good image formation can always be performed, and the life of the fluorescent lamp can be effectively extended.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a first embodiment of the present invention.

FIG. 2 is a timing chart at the time of lighting in the first embodiment.

FIG. 3 is a detailed timing chart at the time of lighting in the first embodiment.

FIG. 4 is a flowchart showing the operation of the first embodiment.

FIG. 5 is a flowchart showing the operation of the second embodiment.

FIG. 6 is a timing chart of the second embodiment during lighting.

FIG. 7 is a flowchart showing the operation of the third embodiment.

FIG. 8 is an explanatory diagram showing a signal duty at the start of dimming in the third embodiment.

FIG. 9 is a circuit configuration diagram of a conventional example.

FIG. 10 is a conventional timing chart at the time of lighting.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fluorescent lamp 8 Control transistor 14 Light quantity sensor (light quantity detection means) 24 System controller (light control means)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location // H05B 41/16 310 B 41/392 F 6908-3K

Claims (3)

[Claims] 1. In an electrophotographic image forming apparatus using a fluorescent lamp as a light source for exposure, a light amount detecting means for detecting the light amount of the fluorescent lamp, and a fluorescent lamp according to a detection signal from the light amount detecting means. A dimming means for dimming by switching between turning on and off at a frequency that does not affect the image, the dimming means, when starting the lighting of the fluorescent lamp from a state where the lights are off for a predetermined time, a predetermined period Is an image forming apparatus characterized by repeating lighting and extinguishing at a specific ratio regardless of the signal from the light amount detecting means, and then performing light amount control according to the signal from the light amount detecting means from a predetermined ratio. 2. An electrophotographic image forming apparatus using a fluorescent lamp as a light source for exposure, wherein a light amount detecting means for detecting the light amount of the fluorescent lamp and a fluorescent lamp according to a detection signal from the light amount detecting means. A dimming means for dimming by switching between turning on and off at a frequency that does not affect the image, the dimming means, when starting the lighting of the fluorescent lamp from a state where the lights are off for a predetermined time, a predetermined period Is repeatedly turned on and off at a specific ratio regardless of the signal from the light amount detecting means, and then only when it is confirmed that a predetermined light amount is obtained at a predetermined ratio, the light amount control according to the signal from the light amount detecting means. An image forming apparatus characterized by performing. 3. The dimming means repeats lighting and extinguishing at a specific ratio for a predetermined period, regardless of a signal from the light quantity detecting means, when starting the lighting of the fluorescent lamp from a state in which the light is off for a predetermined time. 3. The image forming apparatus according to claim 2, wherein when a predetermined amount of light cannot be obtained at a predetermined ratio, an abnormality of the fluorescent lamp is displayed and the image forming operation is stopped.