JPH0429585A - Polygon motor rotation speed control device - Google Patents

Abstract

PURPOSE:To shorten pixel density switching means by providing decelerating means for attenuating a rotational speed, and deceleration control means for operating the decelerating means when a high rotational speed is switched to a low rotational speed by rotational speed switching means. CONSTITUTION:When a code or data for designating a pixel density DPI is input from a host machine 58 through a controller 50, an engine driver 60 immediately sends a signal PMDI to a PM driver 70 to designate a rotational speed corresponding to the density. The driver 70 starts a PM 34 when a signal PMST is turned ON, outputs a signal PMLK when it reaches the designated speed in a synchronous state. The driver 60 detects the presence or absence of the signal PMLK to start printing. A signal PMBR is output when the signal PMDI is switched from a high speed to a low speed, the driver 70 brakes the PM 34 while the signal PMBR is ON, i.e., a braking period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polygon motor rotation speed control device for a laser scanning image forming apparatus capable of switching pixel density.

[Conventional technology]

Personal computer, EWS (Engineering Workstation)9 document creation device.

2. Description of the Related Art Image forming apparatuses are used as external or built-in output devices for office automation equipment such as digital copying machines and high-speed facsimile machines.

As image forming apparatuses that meet the demands for improved processing speed of OA equipment, i.e., host machines, and for high-quality images, laser scanning image forming apparatuses with excellent printing speed and resolution (pixel density), such as laser printers ( The use of laser beam printers (also called laser beam printers) is increasing.

Compared to other dot printers such as wire dot printers, LED (light emitting diode) printers, and LCA (liquid crystal array) printers, this laser printer not only has a higher maximum resolution but also has the ability to change the resolution. Because of these advantages, there are various models on the market that have different resolutions depending on the purpose and cost, and models that allow users to switch resolutions.

As a technique for changing the resolution, that is, the pixel density, for example, as shown in Japanese Patent Application Laid-Open No. 162547/1982, the reference clock is divided by a division ratio according to the pixel density, and the divided clock is used. There have been proposals to control the scanning speed (in the main scanning direction) of the relay spot, that is, the rotational speed of the polygon motor.

In laser printers that can switch pixel density in this way, the rotational speed of the polygon motor (also called a scanner monitor) is controlled to be high when the pixel density is high, and to maintain a low rotational speed when the pixel density is low. ing.

Therefore, when the pixel density is switched, the rotational speed switching means is operated to switch the rotational speed of the polygon motor, and after confirming that the rotational speed is stabilized at a predetermined rotational speed, the printing operation is started.

[Problem to be solved by the invention]

However, since the polygon mirror is integrally connected to the rotor of the polygon motor, each of them has been made as small and lightweight as possible to reduce its moment of inertia.
It takes time to stabilize at the changed rotational speed.

Even so, when switching the rotation speed from low speed to high speed, it stabilizes at the specified speed relatively quickly, but when switching the rotation speed from high speed to low speed, it takes much longer to reach the specified rotation speed and stabilize. It took a long time.

Therefore, even though other routines required for pixel density switching are completed instantaneously, the total switching time becomes longer.Even though the laser printer is capable of high-speed printing, if the work requires frequent pixel density switching. The problem was that the efficiency decreased.

In addition, pixel density switching is only done on a page-by-page basis;
There was no laser printer that could change the pixel density in the middle of printing one page.

This invention has been made in view of the above points, and an object thereof is to shorten the time for switching one pixel density and improve work efficiency.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a polygon motor rotation control device for a laser scanning image forming apparatus capable of switching pixel density, which is provided with a rotation speed switching means for switching the rotation speed of the polygon motor according to the pixel density.

The polygon motor is provided with a deceleration means for attenuating the rotational speed of the polygon motor, and a deceleration control means for operating the deceleration means when the rotational speed switching means switches from a high rotational speed to a low rotational speed.

[For production]

In the polygon motor rotational speed control device configured in this way, when the rotational speed switching means switches from a high rotational speed to a low rotational speed, the deceleration control means activates the deceleration means, so that the rotational speed of the polygon motor does not suddenly increase. Attenuates,
The time it takes to stabilize at a low rotational speed is shortened.

〔Example〕

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings.

FIG. 2 is a schematic diagram showing the internal mechanism of a laser printer according to an embodiment of the present invention.

Around the photosensitive drum 10 rotating clockwise as shown by the arrow, chargers 11 . Optical writing unit 12. Phenomenon unit 13, transfer charger 1
4. Cleaning units 15 are arranged respectively.

The surface of the photosensitive drum 10 is first uniformly charged by a charging charger 11, and then the photosensitive drum 10 is scanned in the main scanning direction by a spot on which a beam modulated by image data from the optical writing unit 12 and deflected in the main scanning direction forms an image. to form an electrostatic latent image.

The electrostatic latent image is developed by the developing unit 13 and converted into a visualized toner image, and then the toner image is transferred by the transfer charger 14 onto a sheet of paper conveyed along the route shown by the dashed line. be done.

The toner and charge remaining on the photosensitive drum 10 are removed by the cleaning unit 15, and the removed toner is collected by the cleaning unit 15.

The paper is fed by a paper feed roller 19 from a paper stack 18 on a paper feed cassette 17, and is fed by a pair of registration rollers 2.
o, the toner image is conveyed to the position of the transfer charger 14 by the registration roller pair 2o at a timing that matches the image written on the photoreceptor drum 10 by the optical writing unit 12. is transcribed.

The paper onto which the toner image has been transferred is conveyed to the fixing unit 21, pressed against the fixing roller 21b heated by the pressure roller 21a, and fixed by the heat and pressure, and then conveyed to the paper ejection roller 22. The paper is discharged from the paper discharge port 23 onto the paper discharge tray 24 .

FIG. 3 is a perspective view of essential parts showing an example of the optical writing unit 12. FIG.

The optical writing unit 12 includes an LD (laser diode) unit 30, which is a modulated light source, and a first cylinder lens 31. First mirror 32. A pre-object type imaging lens 33, a rotary deflector 36 consisting of a polygon motor 34 and a polygon mirror 35 rotationally driven in the direction of arrow A, and a second mirror 37. 2nd cylinder lens 3
8, and a third mirror 40.
゜Light receiving lens 41. It is constituted by a synchronous optical system consisting of a synchronous sensor 42.

The LD unit 30 has an LD, a collimator lens that converts a diverging beam emitted from the LD into a parallel light beam, and an aperture that regulates the thickness of the beam.

The parallel light beam emitted from the LD unit 30 passes through the first cylinder lens 31 and is reflected by the first mirror 32, and then passes through the imaging lens 33 and enters the reflective surface 35a of the polygon mirror 35.

The imaging lens 33 acts to form an image of the parallel main scanning direction component of the incident beam on the photoreceptor drum 10 (described later), and the first cylinder lens 31 uses the combined power of the imaging lens 33 to It acts to form an image of the sub-scanning direction component of the parallel beam once on the reflective surface 35a of the polygon mirror 35.

The beam reflected by the polygon mirror 35 and repeatedly deflected in the main scanning direction is reflected by the second mirror 37, passes through the second cylinder lens 38, and reaches the photosensitive drum 10 rotating in the direction of arrow B.

The second cylinder lens 38 re-images the sub-scanning direction component of the beam once imaged on the reflecting surface 35a onto the photoreceptor drum 10, so that the beam is focused in the main scanning direction where it is imaged by the imaging lens 33. The image is formed into a spot along with the components, and main scanning is performed on the main scanning line 10a of the photosensitive drum 10 in the direction of arrow C.

Further, just before the beam deflected by the rotary deflector 36 enters the effective image area on the main scanning line 10a, the beam is reflected by the third mirror 40 and focused on the light receiving surface by the light receiving lens 41. A synchronization sensor 42 that outputs a main scanning synchronization signal is also provided.

FIG. 4 is a block diagram showing an example of a control section of this laser printer.

The controller 50 is a main microcomputer (
rMPUJ) 51, programs and constant data required by the MPU 51.

A ROM 52 that stores character fonts, etc., a RAM 53 that stores temporal data, dot patterns, etc., and an l1054 that controls input and output of commands and data;
Operation panel 55 connected to MPU 51 via 1054
and an internal interface (I/F) 56, which are connected to each other via a data bus, an address bus, etc.

In addition, the host machine 58 that outputs print commands, character data, and image data is also connected to the MPU 51 via the l1054.
connected to.

The engine driver 60 includes a sub microcomputer (hereinafter referred to as rCPUJ) 61 and a ROM 62 that stores programs and constant data required by the CPU 61.
, a RAM 63 for storing temporal data, and an I 1064 for controlling data input/output, and are connected to each other by a data bus, an address bus, etc.

The l1064 is connected to the internal ink face 56 of the controller 50, and inputs video signals from the controller 50 and the states of various switches on the operation panel 55, and outputs status signals such as image clock and paper end to the controller 50.

The I 1064 is also connected to the optical writing unit 12 and other sequence equipment groups 66 constituting the printer engine 65, which are printing means, and to various sensors 67 including the synchronization sensor 42.

The controller 5o receives print commands, character codes, and image data from the host machine 58, edits these codes, and data, and if it is a character code, creates a dot pattern necessary for image writing using the character font stored in the ROM 52. After converting the dot patterns of those characters and images (hereinafter collectively referred to as "images") to
It is stored in memory in the VRAM (video RAM) area in the AM53.

When the image clock is input together with the ready signal from the engine driver 60, the controller 50 outputs the dot pattern stored in the VRAM area to the engine driver 60 serially or in parallel as a video signal synchronized with the image clock.

The engine driver 60 controls the optical writing unit 12 of the printer engine 65 based on data from the controller 50.
A video signal necessary for controlling the sequence equipment group 66 and image writing is input from the controller 50 and output to the optical writing unit 12, and signals indicating the status of each part of the engine are sent from the synchronization sensor 43 and other sensors 67. It inputs and processes it, and outputs necessary information and error signals to the controller 50.

FIG. 1 shows a polygon motor (hereinafter also referred to as rPMJ) 3 according to the pixel density among the control units shown in FIG. 4.
4 is a circuit diagram showing an example of a control system of a printer engine 65 and an engine driver 60, mainly including a PM (polygon motor) driver, which constitutes a polygon motor rotation speed control device that controls the rotation speed of a polygon motor 4, and is the same as FIG. 4. The same reference numerals are given to the parts and the explanation thereof will be omitted.

The printer engine 65 includes a PM (polygon motor) 34
and a PM driver 70 and MM (main motor) 71 that control it, an MM driver 72 that controls it, and a paper feed clutch (CL) 73° Registration clutch (CL)
Sequence equipment group 66 consisting of 75 and CL (clutch) drivers 74, 76 and others that operate them respectively.
and the LD (laser diode) 7 of the optical writing unit 12
7, an LD driver 78 that activates it, and a synchronization sensor 42. It is composed of a registration sensor 79 and other sensors 67.

Each part constituting the printer engine 65 is connected to the engine driver 60 either directly or via a driver.

The MM driver 72 inputs the on/off signal MMC,
Controls the constant speed rotation of MM71, which is a common power source for each part of the printer.

When the paper feed command signal FC is turned on, the CL driver 74 turns on the paper feed clutch 73, which is a one-way clutch that connects the paper feed roller 19 and MM71, and the paper is fed from the paper feed cassette 17 by the paper feed roller 19. When the paper sheet contacts the pair of registration rollers 20 and the registration sensor 79 detects this, the engine driver 60 turns off the signal FC.

The CL driver 74 turns off the paper feed clutch 73 and stops the paper feed roller 19.

The engine driver 6 is activated by the signal from the registration sensor 79.
0 starts printing, the signal VIDEO, which is an image signal sent from the control 50, is sent to the LD driver 78.
The LD driver 78 turns on and off the LD 77 while monitoring the light amount output according to the signal VIDEO to output a modulated laser beam.

The synchronization sensor 42 receives laser light for each scanning line and outputs a synchronization signal, and the engine driver 60 detects the synchronization signal and uses it as a reference timing for starting writing of the scan line.

Further, the engine driver 60 turns on the transport command signal RC at a timing from the start of writing to the photoreceptor drum 10.

The CL driver 76 operates a resist clutch 75 that connects the resist roller pair 20 and the MM 71 in response to a signal RC.
is turned on, and the registration roller pair 20 is rotated to convey the paper until the signal RC is turned off according to the length of the paper.

The engine driver 60 and the PM driver 70 are connected by four lines, and the engine driver 60 sends four signals: a signal PMST that instructs to start/stop the PM 34, and a signal that instructs the rotation speed by code or pulse. PMDI, a signal PMBR instructing braking (deceleration) is output, and the PM driver 7o outputs the PM
A signal PMLK is output which indicates whether the rotational speed of No. 34 is stable, that is, whether it is synchronized with the pulse signal of the reference frequency.

When a code or data indicating the pixel density DPI is input from the host machine 58 via the controller 50,
The engine driver 60 immediately sends a signal PMDI to the PM driver 70 to instruct the rotation speed corresponding to the pixel density.

The PM driver 70 outputs PM3 when the signal PMST is turned on.
4, and when the designated rotation speed is reached and a synchronized state is achieved (locked), a signal PMLK is output, and the engine driver 60 detects the presence or absence of the signal PMLK and starts printing.

The signal PMBR is output when the signal PMDI is switched from high speed to low speed, and the PM driver 70 outputs the signal PM
While the BR is on, that is, during the braking period, the PM 34 is braked.

Further, when the signal PMST is turned off and the PM driver 70 stops the PM 34, the signal PMBR may be outputted to apply the brake, but this is not necessary except for the purpose of stopping the PM 34 rapidly.

The signal PMDI that instructs the rotational speed includes, for example, a code system that instructs the rotation speed using a code, and a frequency system that instructs the rotation speed using the frequency of a pulse signal.

FIG. 5 is a circuit diagram showing an example of a code type PM driver 70a according to the first embodiment.

This code system PM driver 70a has a selector 80
and three oscillators 81, 82, 83 and a PLL (phase locked loop) circuit 84. Amplifier 85. It is composed of an MD (motor drive) circuit 86.

The selector 80 and the oscillators 81 to 83 constitute a reference pulse signal generation section, and the oscillators 81, 82, and 83 have pixel densities of, for example, dpi (dots per inch) of 300 and 4, respectively.
A pulse signal with a frequency corresponding to 00,480 is output to the selector 80.

The selector 80 selects, from among these pulse signals, a pulse signal corresponding to a coded signal PMDIa as shown in the table, which indicates the pixel density inputted from the engine driver 60, and sends it to the PLL circuit 84 as a reference pulse signal fo. Output to.

The front PLL circuit 84, amplifier 85, and MD circuit 86 are PM
34 and an FG (function generator) 87 that is coaxially coupled with it and outputs a pulse signal fc proportional to the rotation speed to form a phase-locked loop, and the reference pulse that PM 34 inputs from the selector 80 to the PLL circuit 84. Foot bank control is performed to rotate in synchronization with the signal fO.

Since the phase-locked loop is well known, a detailed explanation will be omitted, but the PLL circuit 84 compares the pulse signal fc input from the FG 87 with the reference pulse signal fO, and sends the difference signal to the MD circuit via the amplifier 85. 86.

Further, the PLL circuit 84 receives two pulse signals fo.

A signal PMLK is output to the engine driver 60, which is off while the fc is not synchronized and turned on when synchronized.

The MD circuit 86 is connected to the PM 34 through four lines,
Signal PMS input from each engine trailer 60
When the signal PMST is off, there is no output, and when it is on, pulse power signals Di and D2 are sent out of phase to four output lines according to the difference signal input from the amplifier 85. , D3. Outputs D4 and drives 2M34.

Since FG87 coaxially coupled with 2M34 generates N pulses (for example, N=6) per revolution of the shaft, 2
A pulse signal fc proportional to the rotation speed of M34 is output to the PLL circuit 84.

The phase-locked loop is stabilized (locked) when the frequency of the pulse signal fc and the frequency of the reference pulse signal fO match, so if the rotation speed of the 2M34 corresponding to the pixel density is R (r p m), then For example, the frequency of the reference pulse signal fo is set to (RX N /60) Hz.

FIG. 7 is a waveform diagram showing an example of a pulse power signal when the signal PMBR instructing braking is turned on and off, and the signal PMBR is shown in order from the top.

PMLK and pulsed power signals Di, D2. D3゜D4
It shows.

During normal operation with signal PMBR off, signals Di, D2 . The phases of D3 and D4 are sequentially delayed by 1/4 period, and the signal PMLK indicating synchronization
is on.

When the rotational speed of 2M34 is switched from high speed to low speed in response to switching from high pixel density to low pixel density, the signal PMBR output from the engine driver 60, which is a deceleration control means, is turned on, and at the rising edge of the signal PMBR, signals D1 to D4 is latched and remains there during the braking period (Tbr) until signal PMBR is turned off.

At the same time, the reference pulse signal fo is also switched to a lower frequency, so the synchronization with the signal fc from FG87 is lost and the signal P
MLK is turned off.

When the pulse power signals D1 to D4 are latched, a strong braking force acts on the PM (polygon motor) 34, and its rotational speed is rapidly reduced.

When 2M34 is decelerated and the frequency of the signal fc from FG87 matches the frequency of the new reference pulse signal fo, P
Since the signal PMLK output from the LL circuit 84 is turned on, the engine driver 60 detects its rising edge and outputs the signal P.
Turn off MBR, 2M34 receives new reference pulse signal f
Stabilizes in synchronization with O.

Since the braking period is a practically constant time depending on the combination of old and new rotational speeds, the signal PML
Instead of detecting the rising edge of K and turning off the signal PMBR,
The signal PMBR may be turned on and off by setting a braking period according to the combination of rotational speeds in advance.

In addition, although an example of an electrical deceleration means has been described above, a mechanical deceleration means, for example, a brake device is provided on the shaft of the polygon motor 34, and the brake device is controlled by a signal PM.
It may be controlled by BR.

FIG. 6 is a circuit diagram showing an example of a frequency type PM driver 70b according to the second embodiment,
The same parts as in the embodiment are given the same reference numerals.

The frequency type PM driver 70b shown in FIG. 6 uses the engine driver 6 as a signal PMDIb indicating pixel density.
Since the reference pulse signal fo corresponding to the pixel density is directly inputted from 0, the reference pulse signal generator in the first embodiment (FIG. 5) is not required.

The other parts have the same structure and function, so the explanation will be omitted.

FIG. 8 is a flow diagram showing an example of a subroutine DPI for switching the pixel density of the engine driver 60 (the CPU 61 thereof).

When the controller 50 issues a pixel density switching interrupt to the engine driver 6o, the engine driver 60 stores new pixel density data in the memory and sets a single pixel density switching flag FDPI.

From the main routine to the subroutine DPI shown in Figure 8
Step 1: Determine whether the flag FDP I is set or not, and if not, return directly.

If it is standing, Step 2: Determine whether or not image writing is in progress. If writing is in progress, return. If not, step 3: Switch the reference pulse signal fO according to the new pixel density, etc. (
Step 4: Determine whether the new rotation speed is slower than the old rotation speed, and if so, step 6.
Jump to. If not, step 5: Signal PMLK
It is determined whether or not it has risen, and if not, step 5 is repeated to wait for it to rise. If it starts up (synchronization is achieved), jump to step 9.

Step 6: Turn on signal PMBR (decelerate PM34), Step 7: Wait for signal PMLK to rise, and when it rises, Step 8: Turn off signal PMBR (cancel deceleration), Step 9: Reset flag FDP I and return.

As explained above, when changing the rotation speed of the polygon motor used for pixel density switching, especially when changing from high speed rotation to low speed rotation, which takes a long time, it is possible to simply switch the reference pulse signal as in the past. In addition, the time required for switching was significantly reduced by applying an electrical or mechanical brake.

Although an example in which the present invention is applied to a laser printer has been described above, the present invention is not limited to laser printers, and is applicable to OA devices such as digital copying machines and high-speed facsimile machines.
Needless to say, the present invention can be applied to a laser scanning image forming apparatus built into a device or a laser scanning image forming apparatus using photographic film, photosensitive resin, etc. as a photoreceptor.

〔Effect of the invention〕

As described above, the polygon motor rotation speed control device according to the present invention can significantly shorten the pixel density switching time and improve work efficiency.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a control system for controlling the rotational speed of a polygon motor according to the present invention, FIG. Similarly, FIG. 4 is a block diagram showing an example of the control section of the laser printer, and FIGS. 5 and 6 show the first implementation of the polygon motor driver. FIG. 7 is a waveform diagram showing an example of each signal, and FIG. 8 is a flow diagram showing an example of a subroutine for signal processing. 34... Polygon motor (PM) 35... Polygon mirror 50... Controller 58... Host machine 60... Engine driver (rotational speed switching means, deceleration control means) 61... CPU (microcomputer) 65...
・Printer engine 70.70a, 70b-PM (polygon motor) driver (rotation speed switching means) 80...Selector 81.82.83...Oscillator

Claims (1)

[Scope of Claims] 1. A polygon motor rotation speed control device for a laser scanning image forming apparatus capable of switching pixel density, which includes a rotation speed switching means for switching the rotation speed of the polygon motor according to the pixel density, comprising: A polygon motor rotational speed control comprising: a deceleration means for attenuating the rotational speed; and a deceleration control means for operating the deceleration means when the rotational speed switching means switches from a high rotational speed to a low rotational speed. Device.