JPH0193766A - Ready-state detector for scanner motor - Google Patents

Abstract

PURPOSE:To prevent the reduction of the life of a laser oscillator and a photosensitive body by providing a timer means which detects the time, when a scanner motor reaches a velocity close to a rated velocity to permit the output of a laser. CONSTITUTION:The time when a scanner motor 5 reaches a velocity close to the rated rotative velocity is detected by a software timer which is provided in a printer control part 3 and monitor the time required for a rotative velocity slightly lower than the rated rotative velocity of the scanner motor 5, and turning-on/off of the laser light is started. When it is started, the printer control part 3 starts measurement of the period of detection pulses of a laser light detector; and when the measured period is equivalent to the rated rotative velocity of the scanner motor 5, it is judged that the scanner motor 5 enters the ready state to have the rated rotative velocity, and modulation of the laser light by an image signal is started.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ready state detection device for a scanner motor in an image forming apparatus such as a laser printer.

[Conventional technology]

As is well known, for example, in a laser printer, a laser beam generated from a laser light source is modulated with a signal to be recorded, and then deflected by a scanner such as a rotating polygon mirror to scan a latent image forming area on a photoreceptor. By doing this, a latent image is formed on the photoreceptor, and the latent image is made visible! The image is developed and transferred onto recording paper.

In such a laser printer, the scanner is rotationally driven by a scanner motor, but since the rotation speed of this scanner motor does not reach the rated rotation speed immediately after the rotation starts, the laser beam is turned off after reaching the rated rotation speed. It is necessary to start deflecting.

There is a point. If the deflection of the laser beam is started at a speed lower than the rated rotational speed, the scanning time of the photoreceptor in the direction of the main device becomes longer, making it impossible to record the intended image.

Therefore, as a detection device that detects when the scanner motor has reached the ready state of the rated rotational speed, there is a device that determines whether the output voltage of the tachogenerator connected to the rotating shaft of the scanner motor exceeds a predetermined voltage. Are known.

However, this detection device using a tachogenerator has a complicated mechanism, and there is a problem in that noise and the like are likely to be mixed into the tachogenerator output voltage signal, leading to many malfunctions.

Therefore, a laser beam detector is placed at the scan start position or scan end position of the laser beam scanning range, and the rotation command of the scanner motor (FIG. 7(a)) is sent as shown in the timing chart of FIG. At the same time, the laser beam LZ is turned on as shown in FIG. , is turned on again, and as a result of repeating this process, the period of the detection pulse 5osp of the detector as shown in FIG. A detection device that detects this is being considered.

[Problem that the invention seeks to solve]

However, in the detection device explained in FIG. 7, since the laser beam LZ is turned on and off from the low speed rotation state when the scanner motor starts rotating, the detection pulse 5O8P of the detector is turned on after the laser beam LZ is turned on. There is a problem in that it takes a long time to turn off the laser beam LZ, which shortens the life of the laser oscillator and the photoreceptor.

SUMMARY OF THE INVENTION An object of the present invention is to provide a scanner motor ready state detection device that detects when the scanner motor is ready at a rated rotation speed without adversely affecting a laser oscillator or a photoreceptor.

[Means for solving problems]

The present invention detects by means of a timer means that the time elapsed after the start of rotation of the scanner motor has exceeded a certain time,
After the detection output is generated, the output of the laser light from the laser light source is permitted, and after the output of the laser light is permitted, the period of the detection output signal of the laser photodetector is measured, and whether the period is within a predetermined range or not. The scanner motor is configured to detect whether the scanner motor has reached the ready state of the rated rotational speed.

[Effect]

It takes a certain amount of time for a scanner motor to reach its rated rotational speed after inputting a rotation start command.

Therefore, a timer is set for the time required to reach a rotational speed slightly lower than the rated rotational speed, and after the start of rotation, output of the laser beam is not permitted until the time set in the timer has elapsed. Then, after a set time has elapsed, output of the laser light is permitted, and - it is detected whether the ready state has been reached based on the period of the detection pulse of the laser light detector.

Therefore, since no laser light is output in the low-speed rotation state immediately after the start of rotation, it is possible to suppress a decrease in the lifespan of the laser oscillator and the photoreceptor.

〔Example〕

FIG. 1 is a block configuration diagram of a laser printer to which the present invention is applied. A laser oscillator 2 is provided inside a printer main body 1, and a laser beam output from this laser oscillator 2 is transmitted to a printer controller 3. The image signal is modulated by an image signal input from the host computer 4 via the host computer 4. This modulated laser light is deflected by a scanner 6 that is rotationally driven by a scanner motor 5, and is incident on a photosensitive drum 9 via a lens 7 and a mirror 8.

The photosensitive drum 9 is rotationally driven in the direction of the arrow in the figure to enable scanning in the sub-scanning direction with laser light, and in combination with scanning in the main scanning direction by the scanner 6, the image to be recorded is formed as an electrostatic latent image. Ru. The electrostatic latent image formed on the photosensitive drum 9 is developed by a developing device 10 and then transferred by a transfer corotron 13 onto a recording sheet sent out from a paper feed tray 11 or a manual feed tray 12. After the image has been transferred, the image is fixed on the recording paper by the fixing device 14, and then the recording paper is discharged to the paper discharge tray 15. Note that 16 and 17 are paper feed rolls.

The printer control unit 3 controls the entire image forming operation as described above, but in a standby state where it is waiting for input of an image signal from the host computer 4, it stops the scanner motor 5 and allows the scanner motor 5 to rotate at high speed. The aim is to reduce the accompanying noise. However, when an image signal to be recorded is input from the host computer 4, the scanner motor 5 starts rotating after storing this image signal in an internal buffer memory. When the scanner motor 5 reaches its rated rotation speed, an image signal is input to the laser oscillator 2 to start modulating the laser light, and the photosensitive drum 9 is exposed to the laser light, followed by development.

Image forming operations such as transfer are started.

At this time, the printer control unit 3 detects that the scanner motor 5 has reached the rated rotational speed using a timer configured by software and the output of a laser light detector provided near the laser light scanning start position.

That is, near the scanning start position of the laser beam in the main scanning direction of the photosensitive drum 9, there is a mirror 8 as shown in FIG.
A detector 18 that detects the laser beam LZ input through the
(hereinafter referred to as an SOS sensor for detecting the scan start position) is provided. Furthermore, as shown in FIG. 3, inside the printer control unit 3, there is a timer (see FIG. (not shown) is provided.

Therefore, the printer control section 3 detects that the scanner motor 5 has reached the ready state of the rated rotational speed SP1 in the following manner using the detection pulse 5osp of the SOS sensor 18 and the output of the timer.

FIG. 4 is a flowchart of ready state detection processing,
When the printer control unit 3 receives an image signal from the host computer 4, it first starts rotating the scanner motor 5 (Sl). Next, a timer for monitoring the time t2 is started, and the measured time value is updated at a predetermined period until it reaches a value corresponding to the time t2 (82 to 84).
. As a result, when the measured time value of the timer reaches a value corresponding to time t2, the laser oscillator 2 is turned on and output of the laser beam LZ is started (S5). At this time, as shown in the timing chart of FIG. 5, the time ta from when the SOS sensor 18 detects the laser beam LZ and the detection pulse 5osp is output until the output of the laser beam LZ is stopped.
Then, the time tb until the laser beam LZ is turned on for generation of the detection pulse 5osp in the next scanning period is set.

After that, when the detection pulse 5osp is output, the laser beam LZ is turned off after a time ta as shown in FIG.
86-88). When time tb has elapsed, the laser beam L is used to obtain the detection pulse 5O8P in the next scanning period.
Turn on Z.

The printer control unit 3 repeats such control and outputs the detection pulse 5 at a timing corresponding to the scanning start position in the main scanning direction.
Take out the osp. Therefore, from the point of time when the image signal is input, the laser beam LZ is controlled on/off after time t2, as shown in the timing chart of FIG. 6, and the detection pulse 5osp is detected at the scanning start position. .

Once the printer control unit 3 starts on/off control of the laser beam, it starts measuring the cycle of the detection pulse 5 osp, and if the measurement cycle is equivalent to the rated rotational speed of the scanner motor 5, the scanner Assuming that the motor 5 has reached the ready state of the rated rotational speed SP1, modulation of the laser beam LZ by the image signal is started.

As described above, in this embodiment, the laser beam is turned on/off only when the scanner motor 5 reaches a speed close to the rated rotation speed, and the rated rotation speed is controlled by the period of the detection pulse 5 osp obtained from the SOS sensor 18. Since it is detected whether or not the ready state has been reached, the ON time of the laser beam until the rated rotation speed SP1 is reached is shortened.
Adverse effects on the laser oscillator and photoreceptor can be prevented.

Note that the time t2 until the speed SP2 near the rated rotational speed is reached is not limited to the software timer, but may be configured by a hardware timer.

〔Effect of the invention〕

As explained above, in the present invention, the laser beam is turned on/off after a certain period of time has passed after the scanner motor starts rotating.
Since the off control is performed and the detection pulse obtained by the laser light detector is used to detect whether or not the ready state of the rated rotation speed has been reached, it is possible to prevent the laser light from being turned on for a long time while the scanner motor is rotating at low speed. It is possible to detect that the laser oscillator has reached a ready state without reducing the life of the laser oscillator or the photoreceptor.

[Brief explanation of the drawing]

Figure 1 is a block configuration diagram showing an embodiment of a laser printer to which the present invention is applied, Figure 2 is a layout diagram of a laser photodetector viewed from a plane parallel to the laser beam scanning plane, and Figure 3 is a diagram showing a scanner motor. A characteristic diagram showing the time required to reach near the rated rotational speed. Figure 4 is a flowchart of the ready state detection process executed by the printer control unit. Figure 5 is the detection pulse of the laser photodetector and the on/off of the laser beam. FIG. 6 is a timing chart showing the control timing; FIG. 6 is a timing chart showing the on/off state of the laser light until the rated rotational speed is reached; FIG. 7 is a timing chart showing the on/off state of the laser light in the prior art. 1...Printer main body, 2...Laser oscillator, 3...
・Printer control unit, 4... host computer, 5.
...Scanner motor, 6...Scanner, 9...Photosensitive drum, 1o...Developer, 18...Detector. Figure 1 Figure 3 Figure 5 Figure 6

Claims (1)

[Claims] A laser light source, a scanner that deflects and scans the laser light output from the laser light source, a scanner motor that rotationally drives the scanner, and detects the laser light at the start position or end position of the deflection scan. In an image forming apparatus equipped with a laser light detector, detecting that a time elapsed after the start of rotation of the scanner motor exceeds a certain time, and after generation of the detection output, outputting the laser light from the laser light source. a timer means for permitting the output of the laser beam; after the output of the laser beam is permitted, the period of the detection output signal of the laser light detector is measured, and depending on whether the period is within a predetermined range, the scanner motor reaches a predetermined rated rotational speed; A ready state detection device for a scanner motor, comprising means for detecting whether or not the scanner motor is ready.