JPH0553419A - Image forming device - Google Patents

Abstract

PURPOSE:To expedite a first copying time in starting image forming operation by conducting paper feed operation according to timing wherein a polygon motor reaches a lock state within a time from feeding start of a paper sheet to arrival thereof at a register roller. CONSTITUTION:An image forming device is provided with synchronism detector; a main scanning direction counter 31; a capture register 32; a detecting device; and a storage means for storing, with a certain period, record contents of the capture register 32 from rotation start of a polygon motor to arrival thereof at a lock state. This device is also provided with a control means for starting rotation of the polygon motor being in a stopped state at the time of starting image forming operation, inspecting a counter value of the capture register 32, and controlling to start feeding of transfer paper when a counter value stored in the storage means becomes less than the counter value of the capture register 32 which arrives at the lock state in a time from paper feed start to writing start. With such a constitution, a first copying time can be shortened without influence of fluctuation and aged deterioration of the polygon motor.

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 which uses a polygon scanner to write an electrostatic latent image on a photosensitive member with a laser beam.

[0002]

2. Description of the Related Art FIG. 6 shows a control block diagram of a polygon motor according to a conventional example. The conventional polygon motor control circuit obtains a phase difference from the output (FG) of the encoder directly connected to the polygon motor 50 with respect to the clock serving as the reference of the rotation speed of the polygon motor 50 by the phase comparator 51, and outputs this signal. Is obtained as a DC component through an LPF (low-pass filter) 52, and a pulse is generated from a VCO (voltage-controlled oscillator) 53 corresponding to the level to perform PWM (pulse width modulation) of the current to rotate the polygon motor 50. A PLL system (phase locked loop system) for controlling the signal is used. Then, it is judged from the output of the LPF 52 whether the rotation speed of the polygon motor 50 has reached the target rotation speed.

That is, the output of the LPF 52 is the comparator 5
If it is determined by 4, 55 that the polygon motor 50 is in a constant rotation range, the AND circuit 56 outputs the polygon motor lock signal indicating that the polygon motor 50 is rotating normally.
It is output to the CPU controlling the printer via. Then, the reference clock and the start signal are inputted from the CPU to the polygon motor control circuit. However, since the position of the polygon motor control circuit section is distant from the main control section, these signals are transmitted through the wire harness. It is being sent and received.

By the way, conventionally, the polygon motor 50 is stopped during standby, starts rotating at the start of the printing operation, and then starts feeding after detecting the polygon motor lock signal. I used the time to lock as the fast copy time. That is, the time until the polygon motor 50 is locked is predicted in advance, and the paper feed time and the time until the polygon motor 50 is locked are overlapped with each other to reduce the fast copy time. However, in reality, the polygon motor
Since the time until it locks varies from device to device and changes with time, the paper feeding should be started with some timing so that the paper feeding does not start before the polygon motor 50 locks. Was there.

Further, there has been proposed a method of rotating the polygon motor 50 at a rotational speed lower than the target rotational speed while the apparatus is on standby to shorten the time until the polygon motor 50 is locked in the first copy. Also in this case, the rotation speed of the polygon motor 50 is set higher than the optimum standby rotation speed (the rotation speed at which the polygon motor 50 locks in the time closest to the sheet feeding time) in consideration of the variation of the apparatus.

[0006]

As described above, in the conventional apparatus, the sheet feeding is started at a uniform timing with a margin in order to cope with the variation and the aging change of the polygon motor for each apparatus. As a result, there was a problem that the fast copy time was not shortened so much.

Further, when the polygon motor is rotated during the standby, the polygon motor is rotated at a higher speed than in the normal standby rotation in order to shorten the first copy time. There was a problem of shortening.

The present invention has been made on the basis of such a background, and the first copy time can be shortened as much as possible without being affected by the variation and deterioration with time of the polygon motor. An object of the present invention is to provide an image forming apparatus that can extend its life.

[0009]

In the image forming apparatus for writing an electrostatic latent image on a photosensitive member by a laser beam using a polygon scanner, an image forming area is set in order to keep a writing start position constant. A synchronization detector that detects a laser beam outside, a main scanning direction counter that starts and clears counting by a synchronization detection signal output from the synchronization detector, and a counter when the main scanning direction counter is cleared A capture register for temporarily recording the value, a detecting means for detecting that the polygon motor is in a lock state in which the polygon motor rotates at a rotation speed within a set range, and until the lock state is reached after the polygon motor is started to rotate. Storage means for storing the recorded contents of the capture register in a certain cycle, and the poly-state in the stopped state at the start of the image forming operation. The rotation of the drive motor is started, the counter value of the capture register is checked, and stored in the storage means rather than the counter value of the capture register that reaches the lock state in the time from the start of feeding to the start of writing. This is achieved by the first means provided with a control means for controlling the start of feeding the transfer paper when the counted counter value becomes small.

Further, in the image forming apparatus for writing the electrostatic latent image on the photosensitive member by the laser beam using the polygon scanner, the laser beam is emitted outside the image forming area in order to keep the writing start position constant. A synchronous detector for detection, a main scanning direction counter that starts and clears a count by a synchronization detection signal output from the synchronous detector, and a counter value when the main scanning direction counter is cleared are temporarily recorded. A capture register, a detection unit that detects that the polygon motor is in a lock state in which the polygon motor rotates at a rotation speed within a set range, and the capture unit that reaches the lock state in the time from the start of paper feeding to the start of writing. Do not perform the image forming operation by predicting the reference clock that defines the rotation speed of the polygon motor so that it becomes the counter value of the register. When, it is achieved by the second means and control means for controlling to rotate the polygon motor in 従Tsuta rotational speed to the reference clock.

[0011]

In the first means, when the polygon motor is stopped and the image forming operation of the image forming apparatus on standby is started, the control means reaches the locked state in the time from the start of feeding the paper to the start of writing. When the counter value stored in the storage means becomes smaller than the counter value of the capture register, the paper feeding is controlled so that the polygon motor can be locked even if the time elapses. , Paper feeding is always started at the optimum timing.

That is, the polygon motor is set to the locked state by the time when the sheet reaches the registration roller from the sheet feeding section and the writing of the electrostatic latent image on the photosensitive member is started. Since the time taken for the paper to reach the registration rollers from the paper feed unit is constant, by absorbing the rising time of the polygon motor to the locked state within this time, an extra fast copy time is not required as a result.

In the second means, when the polygon motor is rotated and the image forming operation of the image forming apparatus on standby is not performed, the control means reaches the lock state in the time from the start of paper feeding to the start of writing. A reference clock that defines the number of revolutions of the polygon motor that becomes the counter value of the capture register is predicted, and the polygon motor is controlled to rotate at the number of revolutions according to the reference clock.

Therefore, the polygon motor is set in the locked state until the paper reaches the registration rollers from the paper feeding section.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view schematically showing a writing optical system using a semiconductor laser according to an example. 1 is a semiconductor laser (LD), 2 is a polygon mirror, 3 is a photosensitive drum, 4
Is an fθ lens, 5 is a condenser lens, 6 is a cylindrical lens, 7 is a mirror, and 8 is a synchronous detector for keeping the writing start position constant.

In such a structure, the semiconductor laser 1
The laser light beam emitted from is converted into a parallel beam by the condenser lens 5, and the parallel beam is linearly condensed on the polygon mirror 2 by the cylindrical lens 6. The beam reflected by the polygon mirror 2 is imaged on the photoconductor drum 3 by the fθ lens 4, so that the laser light beam scans the photoconductor drum 3 by the rotation of the polygon mirror 2.

FIG. 2 shows a schematic construction of the printer apparatus of the present embodiment provided with the above-mentioned writing optical system, in which a dust-proof glass 12 is provided at the beam emitting portion of the writing optical system 11. The writing optical system 11 has a closed structure. Three
Is a photoconductor drum, 13 is a charger, 14 is a developing device, 15 is transfer paper, 16 is a cleaning device, 17 is a paper feed roller, 1
Reference numeral 8 is a registration roller. The photosensitive drum 3 is rotated in the arrow direction by a driving unit (not shown) and charged by the charger 13. After that, the writing optical system 1
Scanning exposure is performed by the laser beam from No. 1 to form a latent image. Then, it is visualized by the developing device 14, and the image is transferred onto the transfer paper 15 at the transfer point. The toner left on the photoconductor drum 3 is cleaned by the cleaning device 16
Are removed by.

FIG. 3 shows an overall control block diagram of the printer. This control circuit shows the main controller, the polygon motor controller, the LD (laser diode) driver, and the synchronization detector by paying attention to the mutual relationship between them.
U) 21 transmits to the polygon motor control unit (PMC) 22 a reference clock which is generated by the rectangular wave rate generator mode of the 16-bit timer 23 and serves as a reference of the motor rotation speed. When this reference clock is changed, the rotation speed of a polygon motor (not shown) that rotationally drives the polygon mirror 2 is changed by the control of the PMC 22. This is effective in changing the writing density of the printer device. For example, when the write density is 400 dpi, the frequency of the reference clock is 4.6 KHz and 300 d.
The rotation speed of the polygon motor can be changed according to the density of the image information source by changing the frequency in the order of pi, 240 dpi, and so on. It is possible to perform image formation without causing distortion.

On the other hand, the CPU 21 sends a start / stop signal for the polygon motor to instruct the rotation start and stop of the polygon motor. The image information is image data such as digital scanner data, host computer data, facsimile reception data, or the like, and these are composed of 4-bit (16 gradations) digital data, for example. The transfer clock for controlling the transfer speed of the image data is input to the video control gate array 24 together with the image information.

Transfer speed of image information and LD drive unit 25
Since the writing speed for writing on the photosensitive drum 3 is not the same due to the on / off state of, the writing clock is separately generated and input to the video control gate array 24. Further, for each line to be written on the photosensitive drum 3, one RA of image data for each line can be stored.
It has two RAMs (random access memories), M (1) 26 and RAM (2) 27, to perform toggle buffering. This is because the first one line sent is written to the RAM (1) 26 according to the transfer clock, and the next line is written to the RAM (2) 27.
The speed difference between the transfer clock and the write clock is adjusted by repeating the operation of reading the contents of M (1) 26 in accordance with the speed of the writing clock and then reading the contents of RAM (2) 27.

The image data read out according to the writing clock is converted into an LD lighting signal which is pulse width modulated in 15 steps within one dot time. As a result, one dot of light and shade can be expressed for each image data (light and shade information).
Next, the function of the sync detection signal output from the sync detector 8 placed in the vicinity of the photosensitive drum 3 in order to keep the write start position constant will be described. The video control gate array 24 is internally provided with a main scanning counter for counting write clocks, and when the counter value for causing the synchronization detector 8 to perform the synchronization detection, the LD 1 is forcibly turned on and the synchronization detector 8 receives the laser light. Allow light to pass through. At this time, a synchronization detection signal converted from an optical signal into an electric signal by receiving the laser light is input to the video control gate array 24.
The gate array 24 records the counter value of the main scanning counter at the time when this synchronization detection signal is input in a capture register described later, clears the main scanning counter, and repeats the operation of starting the counting of the write clock again.

FIG. 4 shows the circuit configuration of the peripheral portion of the main scanning counter in the video control gate array 24. The main scanning counter 31 is cleared by the synchronization detection signal, and the counter value at that time is output to and recorded in the capture register 32. Register 33 set by CPU 21 [forced lighting (address) 33a, writing start (address)
33b, synchronization detection (maximum address) 33c, synchronization detection (minimum address) 33d] are registered with preset values.

First, when the polygon motor is rotating normally, if the counter value exceeds the set value of the forced lighting (address) 33a, which is considered to pass the laser light beam through the synchronous detector 8, (A≤B by the comparator 34). LD1 is forcibly turned on, which causes the sync detector 8 to generate a sync detection signal. At the time when the polygon motor has just started to rotate, the time until the synchronization detection signal is detected is longer than that during steady rotation, and a counter value larger than the setting value of the synchronization detection (maximum address) 33c is stored in the capture register 32. Comparator 3 because it is recorded
The output of 6 goes low and the polygon lock signal does not go high. When the polygon motor is in steady rotation, the captured counter value is included in the counter values registered in the synchronous detection (maximum address) 33c and the synchronous detection (minimum address) 33d. Therefore, the polygon lock indicating the polygon motor lock state is displayed. A signal is issued to the CPU 21 (A ≧ B of the comparator 36, A of the comparator 37).
≤B, judgment by AND circuit 38).

When changing the write density, first change the write clock (switch the connection to a plurality of oscillators), change the reference clock of the polygon motor, and forcibly turn on (address) 33a and start writing (address) 33.
b, synchronization detection (maximum address) 33c, and synchronization detection (minimum address) 33d are rewritten to start rotation of the polygon motor. When the writing density changes, the synchronization detection cycle must be changed. Therefore, it is effective that the CPU 21 can set the range of the synchronization detection cycle as in the present embodiment, and the maximum and minimum of the synchronization detection cycle can be set. By making the synchronization detection range variable by means of this, it is possible to perform the synchronization detection control which absorbs the fluctuation of the rotation of the polygon motor within the allowable range.

Further, when the polygon motor is used for a long time and the end of its durable life is reached, the rotation becomes unstable, and sometimes the lock is lost. The polygon motor lock signal input to the CPU 21 can be inspected by the CPU 21 at regular time intervals (about 10 msec) to detect whether or not the lock has shifted, but miss the lock that has occurred at this inspection interval. Sometimes. Therefore, it is possible to use the CPU 21 as an interrupt process as a measure against lock-off, but the number of interrupt factors (to the CPU) for that is increased, and hardware for capturing it is required.
Interrupt processing also becomes complicated. Accordingly, the lock deviation can be detected based on the signal for inspecting the polygon motor lock signal, and if the lock deviation occurs for a certain number of times, the lock deviation state is latched, and the lock deviation signal is issued to the CPU 21. ..

FIG. 5 shows a lock deviation inspection circuit having such a structure. After starting the rotation of the polygon motor, the CPU 21 occasionally inspects and monitors the polygon motor lock signal. When the polygon motor lock signal goes into the lock state, a signal for loading the preset count of the lock deviation count to the down counter 41 is issued. The down counter 41 counts the clock generated when the polygon motor lock signal goes out of lock, and counts down. Even when the lock has come off,
Since the synchronization detection signal is added as the clock signal of the down counter 41 via the OR circuit 42, it is also counted down. A pulse signal is generated when the number of clocks at the time of lock deviation is counted for a predetermined number of lock deviations or more, and a pulse signal is output to the CPU 21 as a lock deviation signal. Since the lock-off signal is inverted and fed back through the AND circuit together with the clock, the lock-out state is latched because the clock is not input to the down counter 41 after the lock-off signal is output. It can always be recognized by examining the lock-off signal.

Further, it is confirmed that the lock signal is not in the lock-off state at regular intervals, and the load terminal is reloaded so that the lock-off count does not accumulate, so that the polygon motor is completely deteriorated. It is possible to detect the lock-off state only in the state. In other words, the life of the polygon motor can be detected only when a certain number of times of lock deviation occurs during a certain period of time.

Next, the startup control of the polygon motor of the present invention will be described. In this embodiment, the CPU 21 can read the recorded contents of the capture register 32 in FIG. CPU21 is PMC22 when power is turned on.
Then, a reference clock corresponding to the target rotation speed is given to and the rotation of the polygon motor is started. After that, an internal timer (interval timer) of the CPU 21 causes an interrupt process to occur at regular intervals (for example, 100 milliseconds), and the recorded contents of the capture register 32 are read each time.

This operation may be performed immediately after the rotation of the polygon motor is started, or if it takes about 6 seconds before the polygon motor is locked, it may be performed after about 3 seconds have elapsed after the rotation is started. The CPU 21 records all the recorded contents of the read capture register 32 on the work RAM until the polygon motor is locked.

In the following description, it is assumed that it takes 2.5 seconds from the start of paper feeding until the transfer paper reaches the registration roller 18. The writing operation by the LD 1 is started after the transfer paper reaches the registration roller 18, and the rotation of the registration roller 18 is started so that the writing position on the photoconductor 12 is aligned with the leading end of the transfer paper to transfer the visible image to the transfer paper. Transfer to.

First, the startup control when the polygon motor is stopped during standby will be described. The CPU 21 retrieves the recorded contents of the capture register 32 and checks the contents of the capture register 32 2.5 seconds before the lock state. When the CPU 21 receives a trigger to start the printing operation (for example, in the case of a digital copying machine, a command by pressing the copy start button of the operation unit), the polygon motor is started to rotate for a certain period (100 milliseconds).
An interval timer interrupt process is generated for each time, and each time the check register 32 is checked, the recorded contents are recorded in the work RAM.

When this value becomes smaller than the recording data checked 2.5 seconds before the lock, the paper feeding is started. From this time, writing by the LD 1 is started, that is, it takes 2.5 seconds until the transfer paper reaches the registration roller 18, so that the polygon motor is already locked when the transfer paper reaches the registration roller 18. CPU21
Similarly, when the power is turned on, the contents recorded in the capture register 32 are stored in the work RAM until the polygon motor is locked.
Record above.

That is, each time the printing operation is started from the standby state, the contents of the work RAM for recording the contents of the capture register 32 until the polygon motor is locked are updated. Therefore, even if the time until the polygon motor locks changes with time, a normal printing operation is guaranteed.

Next, the startup control for rotating the polygon motor during standby will be described. In order to shorten the fast copy time, it will be locked during standby 2.5
A target for printing at the same time as paper feeding at the start of the printing operation by rotating the polygon motor at a rotation speed corresponding to the recorded contents of the capture register 32 seconds before (that is, giving a reference clock corresponding to the rotation speed). A reference clock corresponding to the number of rotations is given to rotate the polygon motor.
As a result, the time required for the polygon motor to lock can be absorbed in the time required for the polygon motor to reach the registration roller 18 after being fed.

In the above description of the embodiment, whether the polygon motor is stopped during standby or when it is reduced to the number of rotations that locks after 2.5 seconds, the paper feeding from the first paper feeding stage is performed. Although it has been described on the assumption that the operation is performed, the number of paper feed stages is 2 to 4.
If there are multiple trays, the time from the start of sheet feeding to the start of resist feeding from each sheet feeding tray is different, so it was selected (selected by the host computer for a printer or the operation unit for a digital copying machine). The startup processing may be performed at a time corresponding to.

In the present embodiment, the time until the polygon motor locks is explained as 6 seconds, but this is the case where the reference clock corresponding to the target rotation speed is given to the polygon motor control unit 22, and other times. Depending on the control method, the time to lock can be shortened. That is, the reference clock is set to a rotation speed higher than the target rotation speed, and the polygon motor is started to rotate.

After that, the cap register 3 is set at a constant cycle.
The recorded value of 2 is monitored, and when it reaches a certain ratio (for example, 80%) of the synchronous detection cycle corresponding to the target rotation speed, the reference clock corresponding to the actual target rotation speed is switched. As a result, the time until the lock of the polygon motor can be shortened, and the method of absorbing the time between the start of sheet feeding and the start of resist feeding can be similarly applied.

[0038]

According to the first aspect of the present invention, when the image forming operation is started, the sheet feeding operation is performed at the timing when the polygon motor reaches the lock state within the arrival time of the sheet from the sheet feeding start to the registration roller. As a result, the first copy time can be accurately advanced even with respect to variations in the polygon motor device and deterioration over time.

According to the second aspect of the present invention, when the image forming operation is not performed, the polygon motor is driven by the reference clock corresponding to the period of the synchronization detection signal which reaches the lock state in the time from the start of sheet feeding to the start of resist feeding. Since the rotation is performed, the time until the polygon motor reaches the locked state at the start of the image forming operation is not included in the fast copy time, and as a result, the fast copy time can be shortened and the polygon motor can be prevented from premature deterioration. ..

According to the third aspect of the present invention, since the timing of starting sheet feeding is changed depending on the selected sheet storage unit, the time until the polygon motor reaches the locked state is absorbed in the sheet feeding time without waste. be able to.

According to the fourth aspect of the present invention, the number of revolutions of the polygon motor in the image forming standby state is changed depending on the selected paper storage unit, so that the time until the polygon motor reaches the locked state is supplied without waste. Can be absorbed in paper time.

According to the fifth aspect of the invention, a reference clock corresponding to a rotation speed higher than the target rotation speed is applied to the polygon motor to start rotation, and the value of the cap register corresponds to the cycle corresponding to the target rotation speed. When a certain ratio is reached, the reference clock corresponding to the target number of revolutions is switched to. Therefore, the time required to reach the lock state can be shortened and the fast copy time can be shortened.

[Brief description of drawings]

FIG. 1 is a perspective view showing a writing optical system using a semiconductor laser according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a printer device according to an embodiment of the present invention including a writing optical system using a semiconductor laser.

FIG. 3 is an overall control block diagram of the printer device.

FIG. 4 is a detailed circuit block diagram of a peripheral portion of a main scanning counter.

FIG. 5 is a block diagram showing a lock deviation inspection circuit.

FIG. 6 is a block diagram of a polygon motor control according to a conventional example.

[Explanation of symbols]

 2 polygon mirror 3 photoconductor drum 8 synchronization detector 17 paper feed roller 18 registration roller 21 CPU 22 polygon motor control unit 31 main scanning counter 32 capture register 33 register 34, 35, 36, 37 comparator 50 polygon motor

Claims (5)

[Claims] 1. An image forming apparatus for writing an electrostatic latent image on a photosensitive member by a laser beam using a polygon scanner, in which a laser beam is detected outside an image forming area in order to keep a writing start position constant. A detector, a main scanning direction counter that starts and clears counting by a synchronization detection signal output from the synchronization detector, and a cap that temporarily records the counter value when the main scanning direction counter is cleared. A register, a detection means for detecting that the polygon motor is in a lock state in which the polygon motor rotates at a rotation speed within a set range, and a record of the capture register from the start of rotation of the polygon motor until the lock state is reached. Storage means for storing the contents in a certain cycle, and at the start of the image forming operation, start rotation of the polygon motor in a stopped state, By checking the counter value of the capture register, if the counter value stored in the storage means becomes smaller than the counter value of the capture register that reaches the lock state in the time from the start of feeding to the start of writing. An image forming apparatus comprising: a control unit that controls the start of feeding the transfer paper when 2. In an image forming apparatus for writing an electrostatic latent image on a photosensitive member by a laser beam using a polygon scanner, synchronization for detecting a laser beam outside an image forming area in order to keep a writing start position constant. A detector, a main scanning direction counter that starts and clears counting by a synchronization detection signal output from the synchronization detector, and a cap that temporarily records the counter value when the main scanning direction counter is cleared. A register, a detection unit that detects that the polygon motor is in a lock state in which the polygon motor rotates at a rotation speed within a set range, and a counter of the capture register that reaches the lock state in the time from the start of sheet feeding to the start of writing. A reference clock that regulates the number of revolutions of the polygon motor is predicted, and when the image forming operation is not performed, the reference clock is determined. An image forming apparatus comprising: a control unit that controls to rotate the polygon motor at a rotation speed according to a lock. 3. The image forming apparatus according to claim 1, wherein the control means performs control to change a paper feed start timing in accordance with a paper storage unit having a different paper feed distance selected. 4. The control means according to claim 2, wherein when a paper storage section having a different paper feed distance is selected, the control means changes the reference clock that defines the rotation speed of the polygon motor according to the selected paper storage section. A characteristic image forming apparatus. 5. The control means according to claim 1 or 2, wherein the control means sets a reference clock, which defines the rotational speed of the polygon motor, at a frequency at which the rotational speed is initially higher than the target rotational speed at the start of the image forming operation. After the setting and rotation start, when the counter value of the cap register reaches a predetermined ratio of the counter value of the cap register corresponding to the target rotation speed, the control is switched to the reference clock corresponding to the target rotation speed. An image forming apparatus characterized by performing.