JP4890392B2 - Laser tube life judgment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to predict the end of lifetime of a laser tube in advance and prevent the operation of an apparatus from stopping. <P>SOLUTION: Whether the lifetime of a laser tube has reached its end is determined based on the result of detection in which a time from when a laser power is driven in a low power state to when the state is switched to a high power state is made shorter than the time under the condition of normal use of the laser tube, and then the state is switched to the high power state and the power of laser light emitted from the laser tube is detected by a detection means. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a method for determining the life of a laser tube used, for example, as a light source for forming an electrostatic latent image in an electrophotographic apparatus.

  First, laser tube control of the electrophotographic apparatus will be described with reference to FIG. The gas-filled laser tube 5 has a total reflection mirror 6 and an output mirror 7 that transmits a part of the laser light at both ends thereof, and outputs a part of the laser light obtained by the oscillation phenomenon due to discharge. 7 is emitted.

  Part of the emitted laser light is split using the beam splitter 8, and the solar panel 14 is irradiated with the laser light. Since the transmittance and reflectance of the beam splitter 8 are specified values, the laser power emitted from the laser tube 5 can be known by measuring the laser power applied to the solar panel 14.

  When the solar panel 14 is irradiated with laser light by the above method, a voltage corresponding to the irradiated laser power is output. This signal is captured by the laser control unit 13 and the laser current is adjusted so as to obtain a desired voltage. Control and keep laser power constant.

  Most of the laser beam having a constant output obtained by the control is transmitted through the beam splitter 8 to turn on / off the laser beam, the polygon mirror 10 for scanning the laser beam, and F-θ. It passes through the lens 11 and is irradiated onto the photosensitive layer surface of the photosensitive drum 12 to form an electrostatic latent image.

  Here, a conventional method for determining the lifetime of a laser tube will be described with reference to FIGS. The laser startup sequence and the transition of the laser current under normal use conditions are shown on the left side of the drawing of FIG.

  When the laser power supply is turned on by the laser power supply device, the laser power shifts to the low output state P1 at time T1 to preheat the laser tube. The laser current at this time is I1. Next, the state shifts to a high output state P2 where printing is possible at time T2. If the laser current after shifting to the steady state in the high output state is I3, the relationship is I1 <I3. Here, the laser current I1 is a laser current in a standby state, and the laser current I3 is a laser current in a printable state.

  FIG. 2 is a characteristic diagram showing the relationship between the laser current required to keep the laser power at P2 and the lighting time. When the laser tube is new (that is, when the lighting time is 0), the laser current is I3 ′, but as the lighting time increases, the laser current necessary for maintaining the laser power at the high output state P2 increases. .

  As shown in the curve 3 of FIG. 2, as the lighting time becomes longer, the maximum laser current that can be discharged decreases due to the deterioration of the laser tube 5 represented by the deterioration of the electrode inside the laser tube 5 and the decrease of the gas pressure. Come on. As a result, when the lighting time that is the intersection of the curve 3 and the curve 4 in FIG. 2 exceeds T6, it becomes impossible to obtain a laser power higher than a specified value, and the laser tube 5 reaches the end of its life.

Therefore, a control method for taking an increase in the discharge current at the steady state as a sign of the end of life and issuing an alarm that the laser tube 5 is in the replacement period when the discharge current at the steady state exceeds a preset allowable value. Has been proposed.
JP-A-6-114579

  There are two causes for the end of the life of the laser tube: the above-mentioned decrease in laser power and the deterioration of laser lighting characteristics. Hereinafter, the end of the life of the laser tube due to the deterioration of the lighting characteristics will be described.

  In general, the laser tube 5 requires the most current at the start of discharge. For example, at the normal time shown in FIG. 1, the laser power is preheated for T2-T1 in the low output state P1, and then the peak current I2 higher than the current I3 flows when shifting to the high output state P2. The relationship between the laser current I2 and the lighting time is as shown by the curve 2 in FIG. 2. The laser current I2 ′ when the lighting time is 0 increases with the lighting time, and the laser power is maintained in the high output state P2. Therefore, it is located above the curve 4 of the laser current necessary for this.

  On the other hand, since the dischargeable peak current value of the laser tube 5 at the end of the life is reduced, the current at the start of discharge exceeds the dischargeable peak current and may not be lit. This phenomenon is due to the deterioration of the lighting characteristics, which corresponds to the lighting time T5 in FIG. 2 and appears earlier than T6.

  By the way, in the vicinity of T5, which is the end of life due to deterioration of the lighting characteristics of the laser tube 5, the current necessary for maintaining the laser power in the high output state P2 as shown by the curve 4 in FIG. In some cases, the life cannot be determined due to a constant increase in discharge current, that is, due to a decrease in laser power. In this case, there is a problem that the laser tube 5 reaches the end of life before replacing the laser tube 5 at the end of its life, and this causes an operation stop of an apparatus using the laser tube 5 such as an electrophotographic apparatus. .

  SUMMARY OF THE INVENTION An object of the present invention is to provide a laser tube lifetime determination method capable of eliminating the disadvantages of the prior art and predicting in advance the lifetime of a laser tube due to deterioration of lighting characteristics.

In order to achieve the above object, the first means of the present invention comprises a laser tube for emitting laser light,
Laser output switching means that is driven in a low output state in advance when the laser tube is turned on, and switches from the low output state to a high output state after a lapse of a predetermined time;
Detecting means for detecting the power of the laser light emitted from the laser tube;
Determination means for determining that the laser tube is at the end of its life when the detection result of the detection means falls below a specified value;
The time from driving the laser power in the low output state to switching to the high output state is shortened from the time under normal conditions for using the laser tube to switch to the high output state and emitted from the laser tube. The power of the laser beam is detected by the detecting means, and it is determined whether the laser tube has reached the end of its life based on the detection result.

  According to a second means of the present invention, in the first means, whether the laser tube has reached the end of its life based on a result of laser power detection when the laser life determination is performed a plurality of times for one laser tube. It is characterized by determining.

  According to a third means of the present invention, in the first or second means, the laser tube is a light source for forming an electrostatic latent image of an electrophotographic apparatus.

  According to the present invention, it is possible to quickly and easily detect the deterioration of the lighting characteristics that are the cause of the end of the life of the laser tube, and if the laser tube is replaced before the end of the life, the operation of the apparatus using the laser tube Stopping can be prevented.

  Further, by performing the determination a plurality of times, grasping the degree of deterioration of the lighting characteristics, and making the replacement time of the laser tube near the end of life, it is possible to maximize the replacement period.

A method for determining the lifetime of a laser tube having deteriorated lighting characteristics will be described with reference to FIGS.
When determining the deterioration of the lighting characteristics, the printer control unit 15 issues a command to start up the laser control unit 13 in a sequence in which the preheating time is shortened as shown in the life determination of FIG.

  When starting up to the low output state P1 at time T1 shown in FIG. 1, preheating is normally performed until time T2, but at the time T3 (T3 <T2) shorter than time T2 when determining the life. Start up to the high output state P2. That is, the preheating time is shortened by the period between the times T2 and T3.

  When the above-described method is implemented, for example, at the time of the life determination in FIG. 1, a peak current I4 higher than I3 is required when shifting to the high output state P2 at time T3. This is a value higher than the peak current I2 at the normal time.

  The relationship between the peak current I4 and the lighting time at the time of the life determination is as shown by a curve 1 in FIG. 2, and increases from I4 'when the lighting time is 0 as the lighting time increases. Since the curve 1 described above is located above the curve 2 of FIG. 2 showing the peak value of the laser current at the normal time, the intersection with the curve 3, that is, the time when the laser tube 5 cannot be lit in the high output state P2 is as follows. Compared with T5 at the normal time, the lifetime is determined to be T4 earlier than T5.

  Therefore, as a result of performing the lifetime determination for shortening the preheating time described above, it is determined that the laser tube 5 with the lighting time after T4 is not turned on, the laser power is less than the specified value, and the laser lighting characteristics are deteriorated. It becomes possible. If the laser power is less than the specified value, the voltage converted from the solar panel 14 becomes the reference voltage 19 (see FIG. 3) or less, and the laser power LOW signal 17 becomes the LOW level in the printer control unit 15. Can be detected.

  As shown in FIG. 3, the output of the solar panel 14 is taken into the printer control unit 15, and the reference voltage 19 corresponding to the lower limit value of the allowable laser power (for example, 90% of the high output state) is set to the − terminal of the comparator 18. The output voltage 16 corresponding to the laser power of the solar panel 14 is input to the + terminal of the comparator 18, and the laser power LOW signal 17, which is the output of the comparator 18, becomes LOW level. A decrease is detected and it is determined that the laser lighting characteristics have deteriorated.

  The life determination of the present invention will be described below with specific numerical values. For example, assuming that the life T6 of the laser tube 5 to be judged in FIG. 2 is 10,000 hours, the life end time due to the deterioration of the lighting characteristics is before T6, for example, between 9000 and 10,000 hours, and the replacement time at the time of life judgment. Is before T5, for example, between 8000 and 9000 hours. In FIG. 1, it is assumed that T2-T1 = 3 minutes and T3-T1 = 10 seconds.

  First, when the lifetime determination is performed when the lighting time of the laser tube 5 having the lifetime described above is 7500 hours, the preheating time at the lifetime determination is shorter than that at the normal time, so that I4> I2 at time T3. A laser current I4 flows. At that time, the peak current I4 on the curve 1 in FIG.

  Next, when the lifetime is determined when the laser tube is turned on for 8500 hours, the peak current I4 on the curve 1 in FIG. Further, when the lighting time of the laser tube 5 exceeds 9000 hours, the peak current I2 in the normal state in FIG. 1 located on the curve 2 in FIG. For this reason, there is a possibility that it will not light even during normal times.

  In this specific example, it is necessary to replace the laser tube 5 before 9000 hours, which may cause an error in normal times. However, by implementing the present invention, the laser tube 5 having a lighting time of 8000 to 9000 hours is determined. Thus, the replacement time of the laser tube 5 can be set near the end of life.

  In addition, due to variations in the peak value of the laser current at the time of lifetime determination, the laser may not be lit at a stage before the lighting time T4. Therefore, when the laser is not turned on at the time of the life determination, the same determination is performed a plurality of times. When the laser is not turned on at all, it is determined that the life of the laser tube 5 has ended due to deterioration of the lighting characteristics. 5 can be used until just before the end of its life.

  Since this method is less effective when the laser tube 5 is warm, it is desirable that the method be performed in a state where the laser tube 5 is cold, such as when starting in the morning.

  In the above embodiment, the laser tube used in the electrophotographic apparatus has been described. However, the present invention is not limited to this and can be applied to laser tubes used in other technical fields.

It is a figure which shows transition of the laser starting sequence in normal use conditions, the laser starting sequence at the time of lifetime determination, and a laser current. It is the figure which showed typically the replacement time at the time of implementing lifetime determination in this invention. It is a figure which shows one Example of the electrophotographic apparatus to which this invention is applied.

Explanation of symbols

  1: Maximum startup laser current at the time of life judgment, 2: Maximum startup laser current value during normal use, 3: Maximum laser current that can be discharged to the laser tube, 4: Steady laser current after the laser tube has sufficiently warmed 5: Laser tube, 6: Total reflection mirror, 7: Output mirror, 8: Beam splitter, 9: AO modulator, 10: Polygon mirror, 11: F-θ lens, 12: Photosensitive drum, 13: Laser controller 14: Solar panel, 15: Printer control unit, 16: Output voltage according to laser power, 17: Laser power LOW signal, 18: Comparator, 19: Reference voltage.

Claims (3)

A laser tube for emitting laser light;
Laser output switching means that is driven in a low output state in advance when the laser tube is turned on, and switches from the low output state to a high output state after a lapse of a predetermined time;
Detecting means for detecting the power of the laser light emitted from the laser tube;
Determination means for determining that the laser tube is at the end of its life when the detection result of the detection means falls below a specified value;
The time from driving the laser power in the low output state to switching to the high output state is shortened from the time under normal conditions for using the laser tube to switch to the high output state and emitted from the laser tube. A method for determining the life of a laser tube, comprising: detecting the power of laser light by the detecting means; and determining whether the laser tube has reached the end of its life based on the detection result.   2. The method of determining a life of a laser tube according to claim 1, wherein whether the laser tube has reached the end of its life based on a laser power detection result when performing the laser life determination for a single laser tube a plurality of times. A method for determining the life of a laser tube, characterized in that it is determined.   3. The method of determining a lifetime of a laser tube according to claim 1, wherein the laser tube is a light source for forming an electrostatic latent image of an electrophotographic apparatus.

Images