JPS62251714A - Laser beam printer - Google Patents

Abstract

PURPOSE:To form high-quality colored pictures which are free from color mismatching, by making the facial phase of each polygon mirror coincident with each other and, at the same time, the sending-out timing of each beam detect signal coincident with each other. CONSTITUTION:Comparators COM1-COM4 compare light quantity levels of laser beams made incident on BD signal generating units 54C, 54M, 54Y, and 54BK with analog values obtained by converting reference levels outputted from the output port OUT of a control section COT by DA converters D/A1-D/A4 and, when the light quantity levels exceed the reference levels, comparator outputs CC1-CC4 are supplied to the input port IN of the control section COT. A counter CNT counts reference clocks CL1 oscillated from an oscillator X and outputted from the clock-out CLOUT of the control section COT from the first one of the comparator outputs CC1-CC4 outputted from the comparators COM1-COM4 and outputs count signals to the control section COT synchronously to the successively inputted comparator outputs.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laser beam printer that uses a recording medium such as a photoreceptor and a plurality of laser units.

[Conventional technology]

FIG. 7 is a sectional view illustrating the configuration of a conventional one-drum laser beam printer, in which reference numeral 21 is the main body of the apparatus, 22 is a paper feed cassette, and a paper feed roller 23 drives a recording paper cassette.
is fed. 25 is a transfer drum, and the recording paper 24 is wound around the transfer drum 25 by a gripper (not shown). A photosensitive drum 26 is irradiated with a laser beam emitted from a laser unit 27 via a scanning mirror 28 . A pre-transfer charger 29 charges the photosensitive drum 26 uniformly.
Make it electric. 30y, 30m, 30c are developing devices,
The latent image formed on the photosensitive drum 26 is developed with each developer and visualized. A transfer charger 31 transfers a developed image onto the recording paper 24 wound around the transfer drum 25. 3
A peeling claw 2 peels off the recording paper 24 on which the image forming process has been completed from the transfer drum 25. A conveyor belt 33 conveys the recording paper 24 to a fixing device 34 . 35 is a paper discharge tray. A potential sensor 36 detects the surface potential of the photosensitive drum 26. The developing device 30y develops the latent image formed on the photosensitive drum 26 with yellow toner, the developing device 30m develops the latent image formed on the photosensitive drum 26 with magenta toner, and the developing device 30c develops the latent image formed on the photosensitive drum 26 with magenta toner. The formed latent image is developed with cyan toner. In addition, the laser unit 27
is composed of a laser, a polygon mirror, an imaging lens, etc.

In preparation for the image forming process, the photosensitive drum 26 is uniformly charged by the pre-transfer charger 29, and a laser beam emitted from the laser unit 27 is irradiated onto the photosensitive drum 26 in the main scanning direction via the scanning mirror 28. A latent image is formed according to the image signal, and the latent image is visualized with yellow toner by the developing device 30y.Next, the paper is fed from the paper feed cassette 22 by the corona discharge of the transfer charger 31, and transferred to the transfer drum 2.
The yellow toner image formed on the photosensitive drum 26 is transferred onto the recording paper 24 wound around the photosensitive drum 26.

Next, magenta toner and cyan toner are transferred in the same manner. After the transfer process has been completed, the recording paper 24 is separated from the transfer drum 25 by the peeling claw 32 and conveyed to the fixing machine 34 by the conveyor belt 33, where it is fixed on the recording paper 24 by heat and pressure, and then discharged onto the paper discharge tray 35. Note that the photosensitive drum 26 and the transfer drum 25 are rotating at the same circumferential speed in the direction of the arrow.At this time, the potential sensor 36 detects the amount of charge on the photosensitive drum 26, and also controls the setting of the developing bias, etc. A control signal is sent to a control section (not shown),
The potential of the photosensitive drum 26 is controlled.

FIG. 8 is a sectional view illustrating an example of a conventional four-drum type laser beam printer, and parts having the same functions as those in FIG. 7 are given the same reference numerals.

In this figure, 41c is a laser unit that forms a latent image on a cyan photosensitive drum 45c according to color image data. 41M is a laser unit that produces color images.
- A latent image is formed on the magenta photosensitive drum 45m depending on the evening. 41Y is a laser unit that forms a latent image on a yellow photosensitive drum 45y according to color image data. At 418, a laser unit forms a latent image on the black photosensitive drum 45a according to the color image data. Toner hoppers 42c, 42M, 42y, and 428 are filled with cyan, magenta, yellow, and black toners. 43 is a conveyor belt,
The recording paper 24 is conveyed. 44c, 44M.

Transfer chargers 44Y and 448 transfer the toner image onto the recording paper 24 being conveyed. In addition, each laser unit 41
c, 41M, 41Y, and 418 have polygon mirrors (polygon mirrors) to be described later, which scan the laser light in the main scanning direction.

Uniformly charged photosensitive drums 45c and 45H.

45Y, 45a and laser unit 41c, 4
1M, 41Y, 418 irradiate laser light that turns on and off according to the color image signal, latent images are formed on the photosensitive drums 45c, 45s, 45Y, 458K, and the toner holes, bars 42c, 42T1.
42Y.

It is developed and visualized using 428K cyan, magenta, yellow, and black toners. Then, a transfer charger 44 is placed on the recording paper 24 on which the toner image is conveyed.
c, 44H, 44y, 448K transfer 0
Next, the recording paper 24 on which the toner image is fixed by the fixing device 34 and the color image is formed is discharged onto the paper discharge tray 34 .

9(a) and 9(b) are perspective views and image forming timing charts of the laser beam printer shown in FIG. 8, and the same parts as in FIG. 8 are given the same reference numerals.

In FIG. 9(a), 51c, 51M, 51
y, 51a is a polygon mirror, and each laser unit 4
The laser beams emitted from 1c, 41M, 41Y, 418K are passed through f10 lenses 52c, 52M.
.

Photosensitive drums 45c and 45 via 52Y and 528K
s, 45Y, and 458K. 53
c.

53M, 53Y, 538 are mirrors, and each laser unit 41c, 41M, 41Y, 41
The beam detect signal generation unit (
BD signal generation unit) 54c, 54s, 54
Scan to Y, 548K. In addition, each photosensitive drum 45C,
45M, 45Y, and 458 are arranged at regular intervals. Reference numeral 55 denotes a recording medium, which is sequentially conveyed in the direction of the arrow to form a color image.

In FIG. 9(b), T1 to T4 are each photosensitive drum 45.
A timer that measures the image formation timing at 45M, 45Y, and 458, each with a count value N.
Count from 1 to N4.

FIG. 10 shows the BD signal generation units 54c, 548 . . . shown in FIG. 9(a). 9 is a timing chart of beam detect signals BD to BD4 sent out from 54Y and 548K, and the same components as in FIG. 9(a) are given the same reference numerals.

In this figure, VENI indicates the image forming section of the cyan image, and the left margin LEFTI (the section until reaching the effective image area of the recording medium 55) is from the beam detect signal BDI to the image forming section VENI, which is not shown. A counter circuit counts. VEN2 indicates the image forming period of the magenta image, which is counted by a counter circuit (not shown).

As shown in FIG. 10, each photosensitive drum 45c.

There is a distance difference between 45M, 45Y, and 45t+K, which causes a time delay due to the counting operation of timers T1 to T4, and after the counter circuit provided for each forming color counts up to the left margin, the image is It is forming.

[Problem that the invention seeks to solve]

However, as shown in FIG. 10, since the polygon mirrors 51c, 51q, 51Y, and 518 have different surface phases, the BD signal generation unit 54c
, 54M, 54Y, and 548K are generated at random. Therefore, after the timer T1 finishes counting the count value N1, it is synchronized with the nearest beam detect signal BD+, and the cyan left margin LE FT 1 t teno count ends from the rising edge of the beam detect signal BDI. After that,
An image is formed on the photosensitive drum 45c. At this time, a time delay of time t1 inevitably occurs, and after timer T2 has finished counting the count value N2,
Image formation is performed on the photosensitive drum 45M in synchronization with the nearest beam detection signal Bl)2, but since the surface phases of the polygon mirror 51c and the polygon mirror 51M are different, an additional time delay of time t2 occurs, resulting in a total time delay of A time delay of t, +t2 occurs, and since the image is formed for the first time after the count from the rise of the beam detect signal BD2 to the magenta left margin LEFT2 is completed, the color registers do not match and the hue is distorted. This method has problems such as not only being unable to form a color image but also complicating the circuit configuration.

This invention was made to solve the above-mentioned problems, and by matching the plane phases of each polygon mirror and matching the sending timing of the beam detection signal, high quality without color shift can be achieved. An object of the present invention is to provide a laser beam printer that can form color images.

[Failure to solve the problem]

In the laser beam printer according to the present invention, the rotating surface of the single-rotation polyhedron is provided at a position perpendicular to the magnetic pole direction of the old and young motors, and a plurality of rotating polyhedrons are set at positions perpendicular to the direction of the magnetic poles of the old and young motors. Reference value level adjusting means for individually adjusting reference value levels set in the beam detecting means of the beam detecting means is provided.

[Effect]

In this invention, the rotating surface of the rotating polyhedron is provided at a position perpendicular to the magnetic pole direction of the drive motor, and in this state, the reference value level adjusting means is operated based on the sending timing of beam detect signals output from the plurality of beam detecting means. The reference value levels set for the plurality of beam detection means are individually adjusted using the method.

〔Example〕

FIGS. 1(a) and 1(b) are diagrams for explaining a scanning drive system of a laser beam printer showing an embodiment of the present invention. In FIG. It has a rotor 1a made of, for example, a permanent magnet.

The rotor 1d has Hall elements (rotational position detection means) 2a and 2b arranged at a fixed angle, for example, 135°, with respect to the rotational angular position of the rotor 1a. 3a-3d
is a stator, and when a current is applied to the stators 3a and 3d, the stators 3a and 3d facing the rotor 1a become S poles, and when the current is applied to the stators 3b and 3c, the stators facing the rotor 1a become the S poles. 3b and 3c are each thumb-turned so that they become north poles. 4 is Hall IC
It is arranged near the rotor 1a and feeds the detected frequency signal FG to the control section 5. The control section 5 includes a PLL control section 5a, a current amplifier 5b, and a current limiter circuit 5c, which control the current supplied to the stators 3a to 3d according to the frequency signal FG. Note that the Hall element 2
a, 2b, when the N pole of rotor 1a approaches, one side becomes "
The + side outputs an electromotive force of rlJ. Further, when the S pole of the rotor 1a approaches the Hall elements 2a and 2b, one side outputs an electromotive force of "1", and the + side outputs an electromotive force of "0".

In the figure (b), 6 is a polygon mirror composed of, for example, an octahedron, and has reflective surfaces 6a to 6h. The polygon mirror 6 is fixed to a D-shaped shaft 7 in the vertical direction.
is fitted into the D-shaped groove of the rotor 1a. Note that the D surface of the D-shaped shaft 7 is molded so that it coincides with the S magnetic pole line of the rotor 1a, with the center O of the D-shaped shaft 7 as a reference, and also coincides with a straight line connecting the centers of the reflective surfaces 6c and 8g, for example. That is, with the center 0 of the D-shaped shaft 7 as a reference, a line segment L1 passing through the center of the reflective surface 6a and a line segment connecting the right end of the reflective surface 6a (a line segment connecting the left end of the reflective surface 6b) L2 The D-shaped shaft 7 is formed so that the relationship between the angle θ2 between the angle 01 formed by the reflecting surface 6a and the line segment L2 connecting the right end of the reflecting surface 6a and the line segment L3 connecting the right end of the reflecting surface 6b is constant. There is.

At the position shown in FIG. 1(a), the Hall element 2a
Since the rotor 1a is N pole, the output Ha is "0",
As a current flows through the stator 3a and the stator 3a is magnetized to the south pole, the south pole of the rotor 1a is repelled and the north pole is attracted, generating rotational force and rotating in the direction of the arrow. Rotor 1
As a rotates and the N pole on the Hall element 2a moves away, the Hall element 2a loses its electromotive force, and the stator 3a
is in a cut-off state. On the other hand, since the S pole of the rotor 1a approaches the Hall element 2b, the output Hb becomes "O", and a current flows to the stator 3b, which is magnetized to the N pole. Therefore, the south pole is attracted. In this way, output Ha→output Hb→output Hc
→The output Hd becomes "0" in order, and in response, the stators 3a to 3d are sequentially magnetized, and the rotor 1a continues to rotate.

On the other hand, the rotation speed is determined by a frequency signal FG detected by a Hall IC 4 installed near the rotor 1a, which is sent to the rotation control unit 5 and applied to the stators 3a to 3d to maintain the rotation of the rotor 1a at a constant speed. The current that flows is controlled. Note that the rotor 1a is connected to each polygon mirror 51c.
, 51M, 51y, and 51e.

FIG. 2 is a rotation drive control block diagram of a laser beam printer showing an embodiment of the present invention, and the same components as in FIG. 1(a) are given the same reference numerals.

In this figure, 11c, 11M, 11Y.

118 is a driver circuit, and only the driver circuit 11a is provided with Hall elements 2a and 2b, and the remaining driver circuits I IN , llv and IIs have a configuration in which the rotor 1a is driven by switching the Hall elements 2a and 2b. It has become. 12c, 12n + 12Y
* 12e is the rotation drive circuit section, and each Hall IC 13
In response to the frequency signals FGc, FGM, FGy, and FCBK from the stators 3a to 3d, the rotation of the rotor 1a is maintained constant. In addition, each rotational drive circuit section 12c, 12M, 12y, 128K has the following.

The drive signal M and each frequency signal FGC, FCl2, FGy, FG input from the CPU (not shown)
Current control units 14c, 14M, 14Y control the current applied to the stators 3a to 3d.

148 and limiter circuits 15c, 15M, 15
y.

15 [1K.

Next, the rotational operation of the rotor 1a shown in FIG. 2 will be explained with reference to FIG.

FIG. 3 is a timing chart illustrating the BD signal generation operation by the rotor 1a shown in FIG. 2, and the same parts as in FIG. 7 are given the same reference numerals.

As can be seen from this figure, the beam detect signal BDI
~BD4 are generated completely synchronously on the same time axis, so after the timer T1 finishes counting the count value N1,
In synchronization with the nearest beam detect signal BDI, that is, after one time delay has elapsed, the cyan image is formed after counting from the rising edge of the beam detect signal BDI to the cyan left margin LEFT1. and the count value N2 by timer t2
After the count ends, in synchronization with the nearest beam detect signal BD2 that is synchronized with the beam detect signal BDI, that is, after one time delay has elapsed, the left margin LEFT1, which is the same as the count up to the left margin LEFT1 during cyan image formation, is added. After counting, a magenta image is formed, so the photosensitive drum 45
An image is written on the photosensitive drum 45- at the timing when the start position of image writing c and the left margin coincide,
Images with matching color registers are sequentially formed.

In this way, polygon mirrors 51c and 51M.

After matching the plane phases of 51y and 51s, the BD signal generation units 54c, 54s, 54Y, 54
Beam detect signal BD+ ~B sent from 8K
The timing of D4 is controlled as follows.

FIG. 4 is a beam detect signal detection timing control circuit diagram in a laser beam printer showing an embodiment of the present invention, and the same components as in FIG. 9(a) are given the same reference numerals.

In this figure, COMI to C0M4 are comparators, and BD signal generation units) 54c, 54M, 54
The light intensity level of the laser beam incident on Y, 54o and the reference level output from the output port OUT of the control unit COT are converted to the digital-to-analog converter D/A1-D/
Compare the analog values D/A-converted in A4, and if each light intensity level exceeds the reference level, transmit the beam detection signals BD+ to BD4 (comparate outputs CC1 to CC4) to the input capacitor of the control unit COT. ) IN. X is an oscillator, and the control unit COT receives a basic clock C.
Entering LI. CNT is a counter and the control unit CO
Oscillator X output from T's clock out CLOUT
The reference clock CL1 oscillated from the comparator C0
Comparator output CCI~CC4 output from M1~4
Counting is started from the first comparator output, and a count signal is output to the control unit COT in synchronization with the sequentially input comparator outputs. In addition, the control unit COT is
For example, it is composed of a general-purpose microcomputer,
Correction data do-d2 for correcting the set data D based on the set data D commonly output to the comparators C0M1-4 and the count data mO-m2 (details will be described later) output from the counter CNT is stored in the internal memory in advance. remembered. The correction data dO to d2 are data tables obtained in advance through experiments.

FIG. 5 is a diagram for explaining the operation of the beam detect signal detection timing control circuit shown in FIG. 54M, 54v, 54a
D is set data, which is initialized to the comparators C0M1 to C0M4 and becomes a reference level.

In this figure, LBPI to LBP4 are BD signal generation units 54c, 54M, 54y, 540.
In this figure, the amount of laser beam input to K is the BD signal generation unit 54c, 54M, 54Y.

54[1], the set data D is exceeded in this order.

At the initial setup stage, the digital-to-analog converter D/A
Set data D is set for ID/A 4 from the control unit COT. BD signal generation 22) When the laser beam lI and BPI incident on 54c exceed the level of set data D for the first time, the beam detect signal BD is generated.
+ is input to the input port N of the control unit COT. As a result, the control unit COT outputs a count start signal 5TART to the counter CNT, starts counting the reference clock CLI supplied from the first oscillator 4 exceeds the set data D, and the beam detect signal BD2 is detected.
~BD4 is detected, the count data mo'''zm2 counted up to that point is output to the control unit COT, and when the beam detect signal BD4 is detected and the count data m2 is output, the count end signal 5TOP is output to the control unit. It is output to COT and the counting operation of the counter CNT ends Y.Based on these count data mQ-m', the correction table registered in the internal memory of the control unit COT is accessed to correspond to the count data me-m2. The correction data do''d2 is read out, and the correction set data D-dθ, D-dX, D-d2 are calculated and reset to the digital-to-analog converter D/A ID/A4. As a result, beam detect signals BD2 to BD4
The output timings of the photosensitive drums 45c, 45 can all be matched with the beam detect signal BDI.
It becomes possible to match the color resists of s, 45y, and 458 with high accuracy.

FIG. 6 is a flowchart illustrating the beam detect signal output timing adjustment operation according to the present invention. Note that (1) to (25) indicate each step.

First, the control unit COT converts the digital-to-analog converter D/
Set data D to Al~D/A4) L(1), determine whether the first beam detect signal, for example beam detect signal BD+, is sent out 2), N
If o, clear the counter CNT.3), step (
Return to 1), if YES, count start signal 5TA
RT is output to the counter CNT (4), and the counting operation is started (5) 0. Next, it is determined whether the second beam detect signal, for example, the beam detect signal BD2 is sent out (8), and if NO, step ( 5)
If the answer is YES, the count data mQ counted so far is transferred to the control unit COT (7). Then,
Based on the transferred count data l110, access the correction table registered in the internal memory of the control unit COT8), read out the correction data do9), and send the correction set data D-do to the beam detect signal BD.
2 is transferred to the digital-to-analog converter D/A2 that sent it (10). Next, the correction set data D-do is applied to the inverting terminal of the comparator C0M2 (11).

Next, it waits for the third beam detect signal 1, for example, beam detect signal BD3, to be sent to the control unit COT (12), and when it is sent, the count data m1 counted so far is transferred to the control unit COT (12). 1
3) Next, based on the transferred count data m1, access the correction table registered in the internal memory of the control unit COT 14) and read out the correction data dl 15) Correction set data D - d 1 is transferred to the digital-to-analog converter D/A 3 that sent out the beam detect signal BD3 (1B), then the correction set data D-d1 is applied to the inverting terminal of the comparator C0M3 (17), and then the third The beam detect signal 1, for example, the beam detect signal BD4, is waited for to be sent to the control unit COT (18), and when it is sent, the count data m2 counted so far is transferred to the control unit COT (19), and then , access the correction table registered in the internal memory of the control unit COT based on the transferred count data m2.
0), reads the correction data d2 21), and transfers the correction set data D-d2 to the digital-to-analog converter D/A4 that sent the beam detect signal BD4 (22).
). Next, the correction set data D-d2 is applied to the inverting terminal of the comparator C0M4 (23). Next, the count is stopped (rM number 5 TOP is output from the control unit COT to the counter CNT (24)), and the counting operation of the counter CNT is stopped (25).

In the above embodiment, a case has been described in which the beam detect signal BD+''BO2 is counted by the counter CNT, but this may be omitted if the control unit CNT is a microcomputer with an internal counter.

〔Effect of the invention〕

As explained above, the present invention provides the rotating surfaces of each rotating polyhedron at different positions perpendicular to the direction of the magnetic poles of the drive motor, and further detects multiple beam detect signals based on the timing of transmitting beam detect signals output from multiple beam detectors. Since a reference value level adjustment means is provided to individually adjust the reference value level set in the beam detection means, it is possible to match the surface phase of each rotating polyhedron with the same one, and also to adjust the sending timing of each beam detection signal. Since it is possible to always match the values even when the values are changed due to external conditions such as the environment, it has an excellent advantage of being able to always form high-quality color images without color shift.

[Brief explanation of drawings]

FIGS. 1(a) and (b) are diagrams for explaining the scanning drive system of a laser beam printer showing an embodiment of the present invention, and FIG. 2 is a rotation drive system of a laser beam printer showing an embodiment of the present invention. A control block diagram, FIG. 3 is a timing chart explaining the BD signal generation operation by the roller shown in FIG. 2,
4 is a beam detect signal detection timing control circuit in a laser beam printer showing an embodiment of the present invention. FIG. 5 is a diagram explaining the operation of the beam detect signal detection timing control circuit shown in FIG. 4. The figure is a flowchart explaining the beam detect signal output timing adjustment operation according to the present invention, FIG. 7 is a sectional view explaining the configuration of a conventional one-drum laser beam printer, and FIG. 8 is a conventional four-drum laser beam printer. 9(a) and 9(b) are perspective views of the laser beam printer shown in FIG. 8 and its image forming timing chart, and FIG. 10 is shown in FIG. 9(a). B
This is a timing chart of the beam detect signal sent from the D signal generation unit. In the figure, 1. llc, IIM, llv, 11
8 is a driver circuit, 1a is a rotor, 2a and 2b are Hall elements f, 3a to 3d are stators, and 4 and 13C. 13M, 13y, 138, Hall ICl3 is a rotation control unit, 6 is a polygon mirror, 41c, 41M
. 41Y, 418 are laser units, 45c, 45
M, 45v, 458 has a photosensitive drum, 54c,
54N, 54Y, 54BK are BD signal generation units, CoT is a control unit, CNT is a counter, 00M1~
C0M4 is a comparator, and D/Al to D/A4 are digital-to-analog converters. Figure 1 (a) 5: Rotation control section Figure 1 (b) White 100Ω Cloudy -'' 5 Figure 6 Figure 7

Claims (1)

[Claims] Each laser beam emitted from multiple laser units is irradiated onto each recording medium by a rotating polyhedron driven by each drive motor, and when each laser beam is detected and exceeds a reference value level, the beam is In a laser beam printer having a plurality of beam detection means for outputting detection signals, the rotating surface of each of the rotating polyhedrons is provided at a position orthogonal to the magnetic pole direction of the drive motor, and the beams output from the plurality of beam detectors are further provided. A laser beam printer comprising reference value level adjusting means for individually adjusting reference value levels set in the plurality of beam detecting means based on the sending timing of a detect signal.