JPH08276616A - Image forming apparatus - Google Patents

Abstract

PURPOSE: To suppress the abrasion such as wear of a photosensitive drum without delaying printing start timing by starting forward rotary processing by a control means after it is detected that a rotary polygon mirror rotates a predetermined number of times by a number-of-rotation detection means. CONSTITUTION: When it is judged that the interior of an engine is in a ready state, an engine control part 10 comes a state that it waits for a printing signal from a controller. When the engine control part 109 receives the printing signal, it starts the rising of a scanner motor 121 at first and periodically reads the position signal of the scanner motor 121 to start the scanner motor check task of estimating the time before the number of rotations of the scanner motor 121 reaches the steady number of rotations from the rising curve of the scanner motor 121. This task performs inverse operation from the time reaching a steady time to perform the permission of forward rotation or the start of paper feed before a time necessary for forward rotation being rising control and paper feed timing. When the scanner motor 121 reaches the number of rotations before reaches steady rotation, forward rotation and paper feed processing area started.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic printer.

[0002]

2. Description of the Related Art Conventionally, this type of electrophotographic printer has a structure as shown in FIG.

Here, 1 is a photosensitive drum for forming an electrostatic latent image, 2 is a charging roller for uniformly charging the photosensitive drum 1, and 3 is a laser beam scanning the photosensitive drum 1 on the photosensitive drum 1. Optical unit 4, a laser beam emitted from the optical unit 3, 5 a developing device for developing the electrostatic latent image formed on the photosensitive drum 1 by the laser beam with toner, and 6 a photosensitive unit. A transfer roller charger that transfers the toner image on the body drum 1 to a predetermined paper sheet, a fixing device 7 that melts the toner on the paper sheet and fixes it on the paper sheet, and 8 discharges the fixed paper sheet to the outside of the machine. A roller, 9 is a paper feed roller of an MP tray capable of printing a paper of indeterminate paper size, 11 is a size sensor for detecting the paper size,
12 is a registration sensor for detecting the leading edge of the paper, 13
Is an ejection sensor that detects that the paper has passed through the fixing device, 1
Reference numeral 4 is a paper feed roller of a cassette whose paper size is known in advance, and 15 is a paper cassette on which papers are stacked.

Further, the control unit of the printer having such a mechanism unit develops the image code data received from the host computer or the like into bitmap data to obtain printable information, and communicates with the printer controller. And a printer controller for recognizing printer information and sending a command for switching various printer modes, and an engine control unit for controlling each functional unit inside the printer based on the command of the printer controller and the like. .

Next, such a printer (engine control unit)
The printing sequence in the above will be described based on the flowchart of FIG.

First, the printer (engine control unit) checks whether or not it is ready to print. If it is ready, it waits for a print signal from the controller. When the print signal is received, the photosensitive drum and the main motor for conveying the sheet are started to be driven and the sheet is started to be fed. In addition, various high pressure (charging, developing,
(Transfer) is started, and the scanner motor that drives the rotary polygon mirror to transfer is started.

When the sheet reaches a predetermined position (registration position), the sheet feeding is stopped, and the scanner polygonal ready signal indicating that the rotary polygon mirror has reached the number of rotations required for printing is set. When the scanner motor ready signal is output, the printing is started, and after the printing is finished, the high-voltage fall processing is performed, and the driving of the main motor and the scanner motor is stopped after the paper discharge is completed.

[0008]

However, in the above-mentioned conventional example, the start-up of the scanner motor and the start-up of the high voltage are started at the same time at the start of printing.

Since the primary AC bias at a high voltage causes abrasion of the photoconductor drum, it is disadvantageous from the viewpoint of the life of the photoconductor to keep applying it to the photoconductor drum for a long time.

Although a method of starting the pre-rotation processing after the scanner ready signal is output is also conceivable, such a method causes a problem that it takes a long time to start printing.

An object of the present invention is to solve the above technical problems and to delay the print start timing without any delay.
An object of the present invention is to provide an image forming apparatus that suppresses abrasion such as abrasion of the photosensitive drum and is advantageous in extending the life of the photosensitive drum.

Another object of the present invention is to prevent the stain on the back side of the paper without causing insufficient cleaning of the photosensitive drum even when the stain on the photosensitive drum is large after jamming, etc., while achieving a long life of the photosensitive drum. It is to provide an image forming apparatus capable of performing the same.

[0013]

In order to achieve the above object, an image forming apparatus according to the present invention comprises an image forming means for forming an image by an electrophotographic process using a laser beam, and a laser beam scanning means. A signal output means for outputting a signal in accordance with the rotation of the rotary polygon mirror, a rotation speed detection means for detecting whether or not the rotary polygon mirror has reached a predetermined rotation speed based on a signal from the signal output means, and the electronic device. And a control means for controlling the pre-rotation processing for activating the photographic process, wherein the control means activates the pre-rotation processing based on the output from the rotation speed detection means.

[0014]

According to the present invention, the pre-rotation process is activated by the control means after the rotational polygon has reached a predetermined rotational speed by the rotational speed detection means, without delaying the print start timing. This is to prevent unnecessary application of high voltage during the period for starting up the scanner.

[0015]

【Example】

(Embodiment 1) The first embodiment of the present invention is applied to the laser beam printer shown in FIG.
The description of FIG. 1 is omitted.

FIG. 2 shows a control unit of the printer according to the present embodiment having the mechanism shown in FIG. Reference numeral 101 expands image code data received from a host computer or the like into bitmap data to make printable information, communicates with a printer controller to recognize printer information, and sets the printer mode. A printer controller for sending commands that can be switched,
Reference numeral 109 is an engine control unit that controls each functional unit inside the printer based on commands from the printer controller, and 103 is an automatic paper discharge control unit that discharges accumulated paper inside the printer body based on instructions from the engine control unit 109. Reference numeral 104 denotes a paper conveyance control unit that drives a paper conveyance system inside the printer body based on an instruction from the engine control unit 109.
Reference numeral 105 denotes a high-voltage control unit that controls output of high voltages for charging, development, and transfer based on an instruction from the engine control unit 109, and 110.
Is a laser emission based on an instruction from the engine control unit 109,
The optical system control unit 107 controls the optical system such as driving the scanner motor and transmits the FG signal which is the position signal of the scanner motor to the engine control unit 109. Reference numeral 107 denotes a paper inside the printer such as a registration sensor and a paper discharge sensor A sensor input unit that transmits sensor information to the engine control unit 109, 10
A fixing device temperature control unit 8 controls the temperature of the fixing device based on an instruction from the engine control unit 109. Engine control unit 1
Reference numeral 09 designates rotation speed information obtained from the optical system control unit 110 and controls the start-up timing to the high voltage control unit based on the information.

The optical system controller 110 and the engine controller 10
FIG. 3 shows in detail the interface portion with the interface 9. The optical system controller 110 includes a laser drive system (laser driver (110a)), a scanner motor drive system (scanner motor driver 110b), and a BD signal detector 110C.
It is composed of three functions.

Laser drive system (laser driver 110
The interface with a) consists of an analog signal for determining the laser light quantity, a monitor signal of the emitted light quantity, and a laser lighting signal. The interface with the scanner motor drive system (scanner motor driver 110b) includes a scanner motor drive permission signal and a scanner motor position detection signal.

The scanner motor driver 110b has an interface for turning on / off the scanner motor.
And an FG signal indicating the rotor position of the scanner motor 121. This FG signal is obtained by waveform-shaping the result of detecting the magnetic field lines of the rotor magnet in the motor with a magnetoelectric conversion element (for example, a Hall element).

Further, the BD signal detector 110C outputs a signal obtained by waveform-shaping the detection result obtained by detecting the scanned laser beam by the beam detector (BD) 120 as a BD signal. The engine control unit 109 monitors the FG signal, which is the position signal of the scanner motor 121 from the optical system control unit 110, and calculates the scanner motor rotation speed from the frequency. Then, by detecting the detection at a predetermined sampling cycle (the sampling cycle may change depending on the situation), the rising situation of the rotation speed of the scanner motor 121 can be recognized.

By using this rotation speed monitor function, the time from the start of driving the scanner motor to the high-voltage start timing is determined when the start-up process of the electrophotography at the time of actual printing is performed.

FIG. 4 is a flowchart showing the startup processing sequence in the engine control unit 109.

First, the engine control unit 109 determines whether or not the inside of the printer is in the ready state, and if it is in the ready state, it waits for a print signal from the controller 101. When receiving the print signal, first the scanner motor 12
Start up 1. When the driving of the scanner motor 121 is started, a scanner motor check task which is a sub task is started. In this scanner motor check task, the position signal of the scanner motor 121 is periodically read, and the scanner motor 1 is read from its rising curve.
The time required for the rotation speed of 21 to reach steady rotation is predicted. Then, the backward rotation is calculated from the time until the steady rotation is reached, and the pre-rotation, which is the startup control of the electrophotographic process,
It is a task of turning on a permission flag for processing such as start of pre-rotation and start of paper feeding before a time required for paper feeding timing. With respect to the number of rotations of the scanner motor 121, the pre-rotation process may be started at a predetermined number of times depending on the characteristics of the scanner motor 121 or the like. It is also possible to store the time required to reach steady rotation from the rotation speed, and set the rotation speed corresponding to the time during which the time for the pre-rotation processing or the like can be secured as the predetermined rotation speed. That is, in this embodiment,
The pre-rotation process is started when the scanner motor 121 reaches a predetermined number of rotations before reaching steady rotation. In the main task, after the scanner motor is started, the high voltage and paper feeding operations are performed after the permission flag becomes true. To detect the number of rotations in the scanner motor check task, the number of pulses of the position signal output per unit time may be counted, or the time when the position signal of a constant number of pulses is output may be measured. After that, when the scanner motor check task notifies that the number of rotations of the scanner motor has reached the steady rotation by the ready flag, the laser light amount is turned on, vertical synchronization processing is performed with the controller, and image printing is started. Hereinafter, the printing operation is performed in the same manner as described in the related art.

(Embodiment 2) In a second embodiment of the present invention, the case where the scanner motor rotational position detecting method is different will be described. In the first embodiment, the FG signal is used as the position signal. In the second embodiment, a case where a BD signal is used as the position signal will be described.

As a rotation detection method based on the BD signal, B
The D signal is input to the interrupt terminal of the CPU in the engine control unit 109, and the BD signal interval is detected by the software installed in the CPU internal ROM with time as a parameter.

The detection method is not limited to software, but it is also possible to detect the BD signal interval by hardware using a counter and a clock and read the result by software.

FIG. 5 shows a part of the reading process of the BD signal cycle by the above software. CPU
Reads the timer value set by the previous BD interrupt in the interrupt processing by the BD signal. The result is RAM
After storing in a certain area (Tmem), the timer is set again for the next measurement. Then, it is determined whether or not the stored timer value is within a predetermined range, that is, whether or not the scanner motor 121 has reached a predetermined rotation speed, and in accordance therewith, a paper feed permission flag or
A pre-rotation permission flag or the like is set, and finally, when the scanner motor reaches a steady rotation speed, that is, when the BD signal cycle enters a predetermined interval, it is determined to be ready.

In the present embodiment, only the cycle of the BD signal is judged, but the same processing can be performed by using the change amount (differential value) of the cycle and the absolute value of the cycle together.

FIG. 6 is a timing chart showing the processing in the above pre-rotation.

As shown in the figure, by performing processing such as paper feed start-up and high-voltage start-up according to the time interval of the BD signal, all of the printing for printing is finally performed when the scanner motor 121 reaches the steady rotation. After the processing is completed, the high-voltage application time to the photosensitive drum can be minimized without loss of the first print time.

(Embodiment 3) In the third embodiment of the present invention, the time for determining the start timing of paper feed or pre-rotation is traced back to the scanner motor ready timing when the scanner motor starts up. Switch according to the situation.

The pre-rotation processing of the printer has the meaning of the cleaning processing of the transfer roller in addition to the various high-voltage start-up processing. Therefore, for example, when the image has overflowed after being jammed and jammed last time or when a size smaller than a predetermined paper size has been fed, the transfer roller cleaning process is performed more than usual. It will be necessary to do it for a long time.

In this embodiment, a processing method for solving the above problem will be described.

Further, it goes without saying that the scanner motor rotation speed detecting means in this embodiment can be implemented by using the method of the above-mentioned first or second embodiment.

FIG. 7 shows a part of the processing of the scanner motor check task when deciding the timing when the high voltage starts.

In the case of printing for the first time after the occurrence of a jam, the pre-rotation is started from a time point when the number of revolutions is lower than usual in order to make the pre-rotation time longer than usual. Regarding the paper feed start timing, when the paper feed time is long, the paper feed is permitted from the time when the rotation speed of the scanner motor is low, and when the paper feed time is short, the rotation speed is relatively high. Optimal control becomes possible by starting feeding.

As described above, by providing the function of deciding the start timing of the high-voltage start-up process before printing based on the scanner motor rotation speed detection result in the present invention, the photosensitive drum is activated during the start-up period of the scanner motor. It is possible to prevent an excessive high voltage from being applied to the photosensitive drum, it is possible to prevent the photoconductor drum from being scraped to a minimum, and the photoconductor drum can be kept in high quality for a long period of time.

[0038]

As described above, according to the present invention, abrasion such as abrasion of the photosensitive drum can be suppressed and the life of the photosensitive drum can be extended without delaying the print start timing.

While extending the life of the photosensitive drum,
Even if the photoconductor drum is heavily soiled after a jam or the like, it is possible to prevent the backside stain of the paper without causing insufficient cleaning of the photoconductor drum.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a general electrophotographic printer.

FIG. 2 is a block diagram illustrating a configuration of a control unit of the printer according to the exemplary embodiment of the present invention.

FIG. 3 is a block diagram showing an optical system controller 110, an engine controller 109, and their interface parts.

FIG. 4 is an operation flowchart of the first embodiment.

FIG. 5 is a flowchart showing a part of a BD signal cycle reading process in the second embodiment.

FIG. 6 is a timing chart in an operation example of the second embodiment.

FIG. 7 is an operation flowchart of the third embodiment.

FIG. 8 is an operation flowchart of a conventional technique.

[Explanation of symbols]

 1 Photosensitive Drum 3 Optical Unit 5 Developing Device 101 Printer Controller 104 Paper Conveyance Control Unit 105 High Voltage Control Unit 109 Engine Control Unit 110 Optical System Control Unit 121 Scanner Motor

Claims (4)

[Claims] 1. An image forming means for forming an image by an electrophotographic process using a laser beam, a signal output means for outputting a signal according to rotation of a rotary polygon mirror for scanning the laser beam, and the signal. Based on a signal from the output means, a rotation speed detection means for detecting whether or not the rotary polygon mirror has reached a predetermined rotation speed lower than the rotation speed required for image formation, and a pre-rotation for starting the electrophotographic process. An image forming apparatus comprising: a control unit that controls a process, wherein the control unit starts the pre-rotation process based on an output from the rotation number detection unit. 2. The start of the pre-rotation process is performed by at least one of high voltage of charging, development and transfer in an electrophotographic process.
The image forming apparatus according to claim 1, further comprising one start-up. 3. The image forming apparatus according to claim 1, wherein the signal output unit has a unit for detecting a laser beam to be scanned at a predetermined position. 4. The control unit detects that the rotating polygon mirror has reached a first predetermined rotating speed by the rotating speed detecting unit for the first image forming operation after the jam. The pre-rotation process is started based on the detection result, and for other image forming operations, it is detected that the rotation speed polygon mirror has reached a second predetermined rotation speed different from the first predetermined rotation speed. The image forming apparatus according to claim 1, wherein the pre-rotation process is started based on the above.