JPS62161177A - Laser beam printer - Google Patents

Abstract

PURPOSE:To greatly suppress current capacity and to shorten the startup by plural scanning systems by providing a startup control means which starts up the plural scanning systems in order at specific intervals of time and a potential measurement control means which measures the surface potential of a photosensitive body successively at specific intervals of time simultaneously with said startup. CONSTITUTION:The photosensitive drum 11 is charged electrostatically by a before- transfer charger 12 to a surface potential VD2 and an APC 14 sends out reference driving current data to the D/A converter 15b of a laser driver circuit 15a at an exposure point A. Then, a reference driving current I0 is applied to a semiconductor laser 15c to irradiate the photosensitive drum 11 with laser light 17. Then, it is decided whether or not an adjusting circuit N reaches the specific number (a) of times and when not, it is decided whether or not the photosensitive drum 11 reaches a potential measurement point B, namely, the printer is held in a stand-by state until surface potential measurement timing is reaches. The surface potential of a potential sensor 18 is detected at the timing and the output of the potential sensor 18 is converted by the A/D converter 19a of a potential measuring instrument 19 into a digital value, which is further converted by a microcomputer 19b into table data.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a laser beam printer each having a scanning system for scanning a plurality of photoreceptors with laser light emitted from a laser unit.

[Conventional technology]

FIG. 8 is a sectional view illustrating an example of a four-drum type laser beam printer.

In this figure, 31C is a laser unit that forms a latent image on the cyan photosensitive drum 35c according to color image data. A laser unit 31s forms a latent image on a magenta photosensitive drum 35 according to color image data. 31y is a laser unit that forms a latent image on the yellow photosensitive drum 35Y according to the color image data.

A laser unit 3111 forms a latent image on a black photosensitive drum 358K in accordance with the color image data. Toner hoppers 32c, 32M, 32Y, and 320 are filled with cyan, magenta, yellow, and blank toners. A conveyor belt 33 conveys the recording paper 38. 34c, 34M.

Transfer chargers 34Y and 341 transfer the toner image onto the recording paper 38 being conveyed. In addition, each laser unit 31
c, 31s, 31Y, and 318 have polygon mirrors (not shown), which scan the laser light in the main scanning direction.

Uniformly charged photosensitive drums 35c and 35M.

35y, 3511K and laser units 31c, 31+.

31v and 31oK are irradiated with laser light that turns on and off according to the color image signal, and the photosensitive drums 35c and 3
5s, 35v, 35[A latent image is formed on IK,
Each toner pump 32c, 32M, 32Y.

It is developed and visualized using cyan, magenta, yellow, and blank toners packed at 32nK. Then, the toner image is transferred to the recording paper 38] and transferred to the recording paper 17.
．． 1'e vessels 34c, 34M, 34Y.

3411K transfers. Next, the toner image is fixed by a fixing device 36 and the recording paper 38 on which a color image is formed is discharged onto a paper discharge tray 37 .

FIG. 9 is a schematic diagram illustrating the scanning operation of laser light,
4] is a scanner motor that rotates the rotating polygon mirror 42 at a constant speed. 43 is a laser oscillator that emits laser light according to image data. An imaging lens 44 scans the laser beam reflected by the rotating polygon mirror 42 onto the photosensitive drum 46 via a scanning mirror 45.

Fig. 10 is a diagram showing the )7 increase characteristics of the scanner motor 41 shown in Fig. 9, where the vertical axis shows current, the horizontal axis shows time, IA is the rush current value, and the current value during steady rotation. IS
This is a very large value compared to .

As can be seen from this figure, when the inertia of the scanner motor 41 is large, it takes tS time after the inrush current value IA is applied until the current value reaches Is. Therefore, even if the inrush current value IA reaches IA/3 (time td), it takes a considerable amount of time for the current value to reach Is,
First copy output is significantly delayed. Therefore, in a laser beam printer having a plurality of photoreceptors, the startup sequence of each scanner motor becomes complicated.

FIGS. 11(a) and 11(b) are diagrams for explaining the offset characteristics of a plurality of scanner motors, in which the vertical axis represents current and the horizontal axis represents time.

FIG. 5A shows a case where, for example, yellow, magenta, cyan, and blank scanner motors (not shown) are started at the same time.

FIG. 5B shows the case where yellow, magenta, cyan, blur, and yellow scanner motors (not shown) are activated in sequence.

As shown in Figure 10(a), when the yellow, magenta, cyan, and black scanner motors (not shown) are turned on at the same time, the inrush current is 4IA, which is four times the inrush current IA shown in Figure 10. After reaching steady rotation (time ts) l, we started measuring the surface potential of the photoreceptor (not shown) for 1 hour tp (tB+ty +tM+tc
) Thereafter, it will become the First Copy Permit F″; However,
tBK, tY.

ts and tt: represent the surface potential measurement times of the photosensitive drums for black, yellow, magenta, and cyan, respectively.

When a plurality of scanner motors are turned on and off at the same time in this way, the time required to reach the first copy enabled state can be shortened, but the current capacity becomes multiple times the inrush current of one scanner motor.

Also, as shown in the same figure (b), black.

If the yellow, magenta, and cyan scanner motors (not shown) are started up in sequence, the capacity of the inrush current IA can be suppressed, but the time ts required to reach steady rotation will be longer than in the figure (a). The time tp at the end of the surface potential measurement after that is also 4 times as long as in the same figure (a
) is significantly delayed compared to

[Problems to be Solved by the Invention] As described above, in a laser beam printer having multiple scanner motors, if an attempt is made to start up multiple scanner motors at the same time to shorten the start-up time, the current capacity will increase. If one were to become greedy and try to suppress the current capacity J1 by starting up multiple scanner motors one after another, there was a problem in that the start-up time would take a considerable amount of time. Furthermore, considering the time required to measure the surface potential of the photoreceptor, there is a problem in that it takes a considerable amount of time to output the first copy.

This invention was made in order to solve the problem described in L, and aims to provide a laser beam printer that can suppress the current capacity and shorten the start-up time of the scanner motor that drives the scanning system. .

[Means for solving problems]

The laser beam printer according to the present invention includes a start-up control means that sequentially starts up a plurality of scanning systems with a predetermined time difference, and a surface potential Δ111 of the photoreceptor that is set at a predetermined time difference in parallel with the start-up of the start-up control means. The device is equipped with potential measurement control means that sequentially performs the following steps.

[Effect]

In this invention, when the start-up control means starts up the plurality of scanning systems with a predetermined time difference, the potential measurement control means measures the surface of the photoreceptor with a predetermined time difference in parallel with the start-up of the rise control stage. Perform potential measurements sequentially.

〔Example〕

FIG. 1 is a driving circuit diagram of a scanning system of a laser beam printer showing an embodiment of the present invention. Reference numerals 1a to 1d designate stators, which rotate a rotor 2 in the direction of the arrow by applied current. 3a is a Hall element, and when the N pole of rotor 2 approaches (
An electromotive force is generated so that the -) side is "0" and the (+) side is "1".

3b is a Hall element, and when the S pole of rotor 2 approaches (-)
An electromotive force is generated so that the side becomes "0" and the (+) side becomes "1". 4 is a Hall IC that detects the rotational speed of the rotor 2 and sends the generated pulses to the scanner driver 5 (startup control 01).
If stage) is sent to the rotational speed control circuit 5a. 5b is a current amplifier that applies a drive current to each driver DI-04. Note that when current flows through the stators 1a and lb depending on the current direction and the winding direction of the coils of the stators 1a to 1d, the magnetic field facing the rotor 2 becomes an S pole, and the stator lc
, 1d, it is assumed to be a N pole. Although there are as many scanner drivers 5 as there are colors to be developed, for convenience of explanation, only one is shown.

FIG. 2 is a characteristic diagram illustrating the operation of the scanner driver 5 shown in FIG. 1, in which the vertical axis represents applied current and the horizontal axis represents time.

First, an inrush current of current value Ia is applied to the scanner driver 5 for black to start it up, and a predetermined time difference t
d, a rush current of current value Ia + ΔIa is applied to the scanner driver 5 for yellow to start it up, and at the same time, with a predetermined time difference td, a current value Ia + 2Δ1 . Start by applying an inrush current of . At this time, since the current value applied to the black scanner driver 5 converges to the current value at a predetermined rotation at time jS, at this time, the black scanner driver 5, which will be described later,
Measurement of the surface potential of the photosensitive drum 11 is started. Next, after a predetermined time tOK has elapsed, a rush current of current value I, +3Δ■ is applied to the cyan scanner driver 5 to start it up. At this time, since the current value applied to the yellow scanner driver 5 converges to the current value at the predetermined rotation after a predetermined time tBK has elapsed from time 11 t s, at this time, the yellow photosensitive drum [1] which will be described later surface potential of?
! Start I11 setting. Execute this operation one after another, 3t
Scanner driver 5 for each color is activated before S time elapses.
The measurement of the surface potential of the second photosensitive drum 1 for each color is completed. The current value applied to each scanner driver 5 (four pieces) at this point can be suppressed to a level slightly lower than twice (2Ia) the current value applied to one scanner driver 5.

FIGS. 3(a) and 3(b) are a block diagram and detailed circuit diagram illustrating the configuration of a laser beam printer showing an embodiment of the present invention.

In these figures, 11 is a photosensitive drum that rotates in the direction of the arrow. 12 is 1 before transcription? Electrically, photosensitive drum 11
1) Electrify, for example, by corona discharge. 1
A high voltage transformer 3 supplies power to the pre-transfer charger 12. Reference numeral 14 denotes an auto power controller (Arc), which sends drive current data for supplying a base drive current to a laser unit 15 having a laser driver circuit 15a and a D/A converter 15b, for example, at 8 pins. 16
is a power detector serving as a monitoring means of the present invention, which detects the emission power of the semiconductor laser 15c of the laser unit 15, and amplifies its output with an amplifier 16b.
Emission power data is converted to APC via the A/D converter 16a.
The data is sent to the 14 CPUs 14a. ] 7 is a laser beam, and the exposure point of the photosensitive drum 11 from the laser unit 15) A
is irradiated. ] 8 is a potential sensor, which is used to set the surface potential of the photosensitive drum 11 by 41 (1) due to the laser beam 17 irradiated at the exposure point A, and the surface potential is fixed at the potential 4111 and 411 at the point B. 19 is the potential With a measuring device,
The output of the potential sensor 18 is converted into a digital value by the A/D converter 19a, and the A
C14 (7) Feed back surface potential data to the CPU 14a. 20a is a developing sleeve, and a supply roller R
1 and R2, the developer is replenished. 20b is a transfer charger that charges the photosensitive drum 11 onto the recording paper 20c being conveyed.
Transfer the developed image to the

Next, the surface potential all constant operation according to the present invention will be explained with reference to FIGS. 4 and 5.

FIG. 4 is a diagram for explaining the surface potential characteristics of the photosensitive drum 11 shown in FIGS. 3(a) and 3(b), in which the vertical axis represents the surface potential, and the horizontal axis Iib represents time.

In this figure, VDI indicates the saturation potential;
The surface potential of the photosensitive drum 11 is charged to VD2 by the electric device 12. Vt is a predetermined potential, and the laser unit)・]5
This is the surface potential when the photosensitive drum 11 is irradiated with the reference drive current applied to the photosensitive drum 11.

FIG. 5 is a flowchart illustrating an example of surface potential measurement operation showing an embodiment of the present invention.

Note that (1) to (11) indicate each step.

First, the photosensitive drum 11 is charged to the 4th U by the pre-transfer charger 12.
91) is charged to the surface potential VD2 shown in A, and the exposed point)
When reaching A, the Arc 14 sends the reference drive current data to the D/A converter 15b of the laser driver circuit 15a, applies the reference drive current IO to the semiconductor laser 15c, and directs the laser beam 17 to the photosensitive drum 11. (1)
. Next, it is determined whether the number of adjustments N has reached the predetermined number a (2), and if YES, an error flag is set and the control is terminated (3), and if No, the photosensitive drum 11 has reached the potential measurement point B. In other words, wait for the surface potential measurement timing to arrive (4), and then detect the surface potential of the potential sensor 18 (5).
9a converts it into a digital value, and the microcomputer 19c further converts it into table data. Then 71
111 Determine whether the fixed potential has reached the desired potential Vl. e) If YES, store the applied laser drive current (base 1. drive current IQ + Δα) in a memory (not shown) and end the control. Do (7).

On the other hand, if the judgment in step (6) is NO, 411
1 constant number of times N@ [l'lj ink 1) me7t L, (8
), '/nii, al11 constant potential is predetermined potential V1
9), and if YES, apply a laser drive current (based on U drive current o + ΔIo) to increase the amount of laser light (10), and step (2)
), and if No, apply the laser drive current (reference drive current IO - ΔIO) to increase the laser light intensity (
11), return to step (2). Note that ΔIO is the minimum unit of the It current that can be increased or decreased by one control, and is the 11th current corresponding to a change in the LSB (least bit) of the D/A converter 15b. Also, Δα is N (number of adjustments) times ΔIo
becomes.

In this way, the amount of laser light PG with respect to the surface potential of the photosensitive drum 11 being V[ can be generated by the laser drive current (reference drive current 0-Δα).

Therefore, in order to keep the surface potential of the photosensitive drum 11 constant, it is equivalent to keeping the laser light amount Po constant, but the semiconductor laser 15c of the laser unit 15 is easily affected by environmental changes such as the surrounding temperature. , the relationship between the laser light intensity PO and the laser drive current (reference drive current IO - Δα) is
Because it is affected by this environmental change, the laser light m P o
In order to keep constant, environmental variation correction is performed on the laser drive current (reference drive current ro - Δα), and environmental variation correction value Δβ is taken into account in the laser drive current (reference drive current I (1 - Δα)). Therefore, the light intensity of the semiconductor laser 15c must be constantly controlled by the power detector 1.
The CPU 14a of the Arc14 monitors the light intensity fluctuations via the A/D converter 16a, and sends the light emission power data to the CPU 14a of the Arc14.
It is being sent to

Next, the monitoring control of the laser emission power according to the present invention will be explained with reference to FIG.

FIG. 6 is a flowchart illustrating an example of monitor control of laser emission power according to an embodiment of the present invention. Note that (1) to (8) indicate each step.

First, an image forming operation is performed while outputting laser light m P o with a laser drive current such that the surface potential of the photosensitive drum 1 becomes V[1). For example, between the recording paper being fed and the recording paper The semiconductor laser f of the laser unit 15 waits until the non-image area of
The power detector 16 measures the emission power of 15 c (
monitor), amplify its output with amplifier 16b, and
The light emission power data FD is converted to Arc via the D converter 16a.
14 CPU 14a (3). Next, it is determined whether the emission power data FD matches the initial laser light amount PO (4), and if YES, the laser drive current (reference drive current Io +Δα+Δβ) is applied to the laser driver circuit 15a and the control is ended (5) ).

On the other hand, if the determination in step (4) is NO, it is determined whether the emission power data PD is larger than the initial laser beam fl PO (8), and if YES, the laser driver circuit 15a is activated to reduce the amount of laser light. By applying a laser drive current (reference drive current 1.+Δα−ΔIo) to (
7), return to step (2), and if No, apply a laser drive current (reference drive current Io + Δα + ΔIQ) to the laser driver circuit 15a in order to increase the amount of laser light (8
), return to step (2). Note that ΔIO is the minimum unit of current that can be increased or decreased in one control, and
This is the unit of current corresponding to the change in the LSB (least bit) of b. Further, Δβ becomes ΔIo times N (the number of adjustments).

FIG. 7 is a schematic diagram of a laser beam printer explaining another embodiment of the present invention, in which 21 is an auto power controller (Arc), and a plurality of photosensitive drums 22Y
, 22M , 2'2c , 228 $ 23y , 23M , 23c .

23 [1K] is a potential sensor and photosensitive drum 22Y.

Measure the surface potentials of 22M, 22C, and 22U3.

Each surface potential measuring device 24y, 24sai, 24c.

Sends the surface potential value to 248K. In addition, each surface potential measuring device 24v, 24M, 24C, 24o converts the sent surface potential voltage into a digital signal and receives Ar
Microcomputer 25Y, 2 sending to c21
5s , 25c , 25[(has K.

26 is a monitor signal, and the amount of each laser beam irradiated from each laser unit (not shown) is sent to the Arc 21 from a power detector (not shown). 27 is a laser drive signal, which is sent to each laser unit.

Note that the constant operation of the surface potential 4111 and the monitoring control of the laser emission power are the same as those described above, so a description thereof will be omitted.

As a result, in a laser beam printer that forms color images using a plurality of photosensitive drums, a color image with an optimal hue can always be output.

〔Effect of the invention〕

As explained above, the present invention includes startup control means for sequentially starting up a plurality of scanning systems with a predetermined time difference, and measurement of the surface potential of a photoreceptor at a predetermined time difference in parallel with the start-up of the startup control means. Since the sequential potential measurement control means is provided, it is possible to suppress the current capacity applied to start-up of the plurality of scanning systems, and has the excellent advantage that the start-up time of the plurality of scanning systems can be significantly shortened.

[Brief explanation of drawings]

FIG. 1 is a drive circuit diagram of a scanning system of a laser beam printer showing an embodiment of the present invention, FIG. 2 is a characteristic diagram explaining the operation of the scanner driver shown in FIG. 1, and FIGS.
b) is a block diagram illustrating the configuration of a laser beam printer showing an embodiment of the present invention, FIG.
Figure 5 explaining the surface potential of the photosensitive drum shown in (b).
FIG. 6 is a flowchart illustrating an example of a surface potential measurement operation according to an embodiment of the present invention. FIG. 6 is a flowchart illustrating an example of laser emission power monitor control according to an embodiment of the present invention. A block diagram of a laser beam printer explaining another embodiment of the present invention, FIG. 8 is a sectional view explaining an example of a four-drum type laser beam printer, and FIG. 9 is a schematic diagram explaining the scanning operation of laser light. , FIG. 10 is a diagram showing the startup characteristics of the scanner motor shown in FIG. 9, and FIGS. 11(a) and (b) are diagrams explaining the startup characteristics of a plurality of scanner motors. In the figure, 1a to 1d are stators, 2 is a rotor, 3a, 3b
is a Hall element, 4 is a Hall IC, 5 is a scanner driver, 5a is a rotation speed control circuit, 11 is a photosensitive drum, 12
is a pre-transfer charger, 13 is a high voltage transformer, 14 is Arc,
15 is a laser unit, 15a is a laser driver circuit,
15b is a D/A converter, 15c is a semiconductor laser, 16 is a power detector, 17 is a laser beam, 18 is a potential sensor, 19 is a potential measuring device:! It is i. Fig. 1 5 Sukiyado Drino Fig. 2 1iii ■7”J>)-”T Fig. 3(a) Shi-21-)-20b-
Figure 4 Temporary Fs"f t" Figure 5 Figure 6 Figure 7 Figure 9 Figure Otsu 2 Figure 10-81 while

Claims (2)

[Claims] (1) In a laser beam printer having a scanning system that horizontally scans each of a plurality of photoreceptors with laser light emitted from a plurality of laser units, a startup control means for sequentially starting up the plurality of scanning systems with a predetermined time difference; A laser beam printer characterized by comprising potential measurement control means for sequentially measuring the surface potential of the photoreceptor at a predetermined time difference in parallel with the start-up of the start-up control means. (2) The laser beam printer according to claim (1), wherein the predetermined time difference of the surface potential measuring means is made to match the time difference of the start-up control means.