JPS6197670A - Electrophotographic printing device - Google Patents

Abstract

PURPOSE:To obtain a uniform picture quality, by controlling the light emitting quantity of a light emitting source in such a way that the quantity is successively changed in the axial direction of a photosensitive body so that the deviation of the photosensitive characteristics of the photosensitive body can be compensated. CONSTITUTION:When a difference in sensitivity exists between the right and left ends in the axial direction of a photosensitive body, the deviation is corrected by adjusting laser power. The output of a circuit 53 which generates a correcting waveform corresponding to the photosensitivity ratio between the right and left ends and a reference voltage are multiplied by each other by a multiplier circuit 52 and the multiplied result is inputted to a comparator circuit 51. The multiplied result is compared with the output of a laser power monitor at the circuit 51 and a signal proportional to the correcting waveform is supplied to a driving circuit 50, and then, a corresponding electric current is supplied to a laser 12. Therefore, even if the deviation of the photosensitivity characteristics is large in the axial direction of the photosensitive body, the deviation is corrected and a uniform picture quality is obtained. Moreover, the necessity of the adjustment of the exposing quantity is reduced and the manufacturing yield of the photosensitive body can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a printing device that performs printing operations using an electrophotographic method.

2. Description of the Related Art Electrophotographic printing devices are widely used because they can print on plain paper and can print various patterns. Such an electrophotographic printing apparatus uses a laser light source as an exposure source, and is constructed as shown in the overall configuration diagram of FIG. 5 and the optical system configuration diagram of FIG. 6.

That is, a photosensitive drum 4 having a photoconductor (photoreceptor) on its surface.
A charger 5, a developer 6 that performs development using -component magnetic toner, a transfer device 7, a static elimination unit 8, and a cleaner 9 are arranged around the electrophotographic unit, and a laser diode 12, a collimating lens 13, Polygon mirror 14, F-θ (imaging) 1/lens 16, mirror 1
7 constitutes an optical unit for exposure, and further includes a paper hopper 1, a feeding roller 2, a conveying roller 3, a fixing roller 10,
The stacker 11 constitutes a paper handling unit. In such an electrophotographic printer, a laser beam modulated according to a written image from a laser diode 12 as a laser source is transmitted through a collimating lens 13 to a polygon mirror 14 rotated by a spindle motor (servo motor) 15. The light is scanned and the F-θ lens 16
, the photosensitive drum 4 charged by the charger 5 is exposed through the mirror 17. As a result, a latent image is formed on the photosensitive drum 4, which is developed by the developing device 6. The sheet CP is fed out from the paper hopper 1 by the feeding roller 2, and transferred to the transfer unit by the conveyance port and roller 3. The developed image is transferred. Thereafter, the paper CP is fixed by the fixing device 10,
The photosensitive drum 4 is housed in a stacker 11, and is neutralized by a static eliminating unit 8, cleaned by a cleaner 9, and used for forming the next latent image.

In such a laser printer, as shown in FIG. 6, the optical system includes a laser source 12 and a polygon mirror (scanning mirror).
14 and a spindle motor 15 are provided, and the laser source 1
The spindle motor 15 rotates the polygon mirror 14 with the second spot light, thereby forming an image each time the photosensitive drum 4, which is rotated by the motor 4a, is scanned in the X direction in FIG. 6, that is, in the scanning direction. This laser source 12 is driven by a modulation signal LEDS according to the written image,
A written image is formed on the photosensitive drum 4 since the laser source 12 generates a dot train of light corresponding to the modulation signal LEDS.

Here, a control circuit for driving and controlling the laser source 12 will be explained using FIG. 7.

In the figure, 12 is a laser source, in this case a semiconductor laser.

This semiconductor laser 12 can obtain laser output light by being supplied with current in accordance with the modulation signal LEDS input to the drive circuit 50.

In order to keep the power of this laser output light constant, the laser power monitor output signal of the semiconductor laser 12 is used to constantly compare the reference voltage corresponding to the set laser power to the comparison circuit 51.
The drive circuit 50 controls the current supplied to the semiconductor laser 12 using the output signal from the comparison circuit 51.

In the laser printer described above, the photoconductor on which the electrostatic latent image is formed is a rotating drum with an aluminum substrate on which a photoconductor such as 5eTe (selenium-tellurium) is deposited. ing.

However, photoconductors such as 5eTe can be
Due to subtle changes in the deposition conditions such as the deposition direction, the film thickness and material composition change in the axial direction. The photoconductor layers are usually 2N, one is a 5eTe layer with a Te content of 15 to 25%, and the other is a 5eTe layer with a Te content of 1 to 25%.
It is composed of a 5% -3eTe layer, and is characterized in that the higher the Te content, the better the photosensitivity.

Therefore, as is well known in the art, there are manufacturing problems in that charging characteristics change in the axial direction due to changes in film thickness, and photosensitivity changes due to changes in material composition. For this reason, this type of printing apparatus has problems such as uneven density or changes in line width in the axial direction.

This change in line width will be explained below.

FIG. 8 is a diagram for explaining changes in line width.

In the figure, the horizontal axis shows the position on the surface of the photoreceptor, and the vertical axis shows the potential level on the surface of the photoreceptor. In addition, the development start voltage (140
V) is a voltage determined by the relationship between the electrostatic force of the toner and the magnetic force of the mag roll (not shown) in the developing device, and is a voltage that is determined by the relationship between the electrostatic force of the toner and the magnetic force of the mag roll (not shown) in the developing device. This is the minimum voltage required.

Furthermore, 5oov is the charging voltage on the photoreceptor when initial charging is performed by the charger 5.

Curves a and 2a show potential level distributions when laser light is irradiated on a modern photoreceptor whose photosensitivity is as specified.

Curves 2b and 3b show the potential level distribution when the charged potential of the photoreceptor is 850 V (however, the intensity of the laser beam is constant) or when the photosensitivity is low.

Curves c and 2c have an inverse relationship to the curves, and show the potential level distribution when the photoreceptor has a charging potential of 750 V or when the photosensitivity is high.

Note that h, hl, and h3 are character line widths (in the case of normal development), and dl is the scanning pitch of the laser beam.

As is clear from FIG. 8, the potential level of the portion irradiated with the laser beam varies significantly depending on the relationship between the charged potential of the photoreceptor surface and the photosensitivity.

Therefore, for example, when the photosensitivity or charging characteristics of the photoreceptor change, the apparent spot diameter of the laser beam on the photoreceptor changes. Therefore, in a printing device that performs normal development, if the photosensitivity is low or the charging characteristics are good, there will be a portion left unswept (as shown by h4 in Figure 8), and horizontal lines will appear on the image. The character line width becomes thicker (
hl-hy).

In addition, if the light sensitivity is high or the charging characteristics are poor, the line width of the characters (white, black, black part in the case of white) may be supplemented or disappear. There was a problem.

[Prior art]

Conventionally, in order to maintain uniformity in the image performance of print output, photoconductors with small charging deviations and sensitivity deviations were used, and in order to further correct deviations, charging strength was adjusted, and exposure amount was adjusted. Adjustments were being made.

FIG. 9 is a diagram showing a schematic configuration of a charger used for adjusting the charging strength, with FIG. 9(a) being a front view and FIG. 9(b) being a plan view.

In the figure, reference numeral 18 denotes a shield case made of an insulating material, to which a corona wire 19 is fixed by screws 20 and 21.

Reference numeral 22 denotes a height adjusting screw for adjusting the height of the corona wire 19, and the tip 22a of the screw adjusts the height of the corona wire 19.
Adjust the height by pushing up 9.

23 and 24 are edges for regulating the lateral position of the corona wire 9. .

FIG. 10 is a diagram showing the relationship between the height of the corona wire 19 from the photoconductor and the surface potential, where the horizontal axis represents the height of the corona wire from a position 10111 points away from the photoconductor. There is.

As shown in the figure, the surface potential changes linearly as the height changes. Although not shown, 10m
If the distance is less than m, the surface potential will be high with a similar pattern.

In the above-mentioned configuration, a maintenance person or a tester at the time of device shipment checks the print results and detects uneven density or
The height of the corona wire was adjusted to eliminate variations in line width.

Further, when adjusting the exposure amount, etc., operations such as adjusting the applied voltage (reference voltage in FIG. 8) using a voltage adjusting volume applied to the light source were performed while checking the printing results.

[Problem that the invention seeks to solve]

However, if only photoconductors with a small deviation in performance are used, the production yield of photoconductors decreases, the price of photoconductors increases, and it is difficult to provide inexpensive printing devices. Ta.

Further, there is a problem that adjustment of the charging strength and exposure amount usually requires a specialist and is extremely troublesome.

[Means for solving problems]

In view of the above-mentioned conventional problems, the present invention provides an electrophotographic printing apparatus that can improve the production yield of photoreceptors and minimize adjustments of charging strength, etc. The means includes a photoreceptor, a charger for charging the photoreceptor, a means for irradiating light from a light emitting source onto the charged photoreceptor to form a latent image, and a charger for charging the photoreceptor. The latent image forming means includes a developing device that develops an image, and a transfer device that transfers the visible image developed by the developing device onto a medium, and the latent image forming device affects the image in a direction perpendicular to the direction in which the photoreceptor is transported. An electronic printing device comprising means for creating a deviation in the amount of light irradiated onto the photoreceptor so as to correct the deviation that gives the light emitting source, the means for creating the deviation The electrophotographic printing apparatus is characterized in that the electrophotographic printing apparatus includes a light amount control means that sequentially controls the amount of light to be different in a direction perpendicular to the direction in which the photoreceptor is transported.

[For production]

That is, the present invention allows the light quantity characteristics of the light image irradiated onto the photoreceptor to have a deviation in a direction that cancels the characteristic deviation of the photoreceptor,
This is to obtain printing results with uniform image quality.

In other words, as explained using FIG. 8, when the charging characteristics are good (charging type 4M is high) or when the photosensitivity is poor, the potential level distribution on the photoreceptor is as shown by the curve already.
Since it is biased toward the higher side, the potential level distribution shown by curve a can be obtained by increasing the amount of light irradiated to the photoreceptor, or vice versa, by decreasing the amount of light.

That is, when the photosensitive drum 4 is irradiated with a light image to obtain an electrostatic latent image, in order to obtain good image quality, it is necessary to suppress variations in the photosensitivity characteristics of the photosensitive drum 4 to a certain value ΔE or less. .

Therefore, as shown in FIG.
Those with a variation of photosensitivity characteristics (vertical axis in FIG. 11) of ΔE or less (indicated by curve A in FIG. 11) can be used; however, those with a variation of 68 or more (the vertical axis in FIG. Curve B in the figure.

(indicated by symbol C) cannot be used (here, the range surrounded by diagonal lines (indicated by symbol G) is the range in which good image quality can be obtained). For this reason, in the past, photosensitive drums were sorted and photosensitive drums (B, C) with large variations in photosensitivity characteristics were not used, or charging characteristics and exposure characteristics were adjusted for each photosensitive drum, as shown in Figure 12. As shown, the range in which good printing can be obtained (with respect to curve B, the range is in the region marked with the mark, and with respect to the curve C, the range with the mark E) must be tilted.

Here, the amount of light irradiated to the photosensitive drum is adjusted in advance so that the deviation in the characteristics of the photosensitive drum is aligned in one direction (by reversing the photosensitive drum, the direction of the deviation is reversed), and the deviation in the characteristics of the photosensitive drum is canceled out. If there is a deviation, the 13th
As shown in the figure, photosensitive drums (B, C) with large variations in photosensitivity characteristics can also be used without adjustment.

In the case of Fig. 13, since the photosensitivity of the photoreceptor is upward to the left, the potential level distribution on the left side is the case of curve C in Fig. 8, so the good range of the image is defined as the area of symbol F. To achieve this, the amount of light on the left side should be reduced.

〔Example〕

FIG. 1 is a diagram for explaining the present invention in detail, and is a diagram for explaining a light amount control means for sequentially controlling the light amount of a light emitting source.

This light amount control means is obtained by adding a multiplication circuit 52 and a correction waveform generation circuit 53 to the control circuit for driving and controlling the laser source 12 shown in FIG. are given the same number.

The operation of the configuration shown in FIG. 1 will be explained.

If the optical sensitivity deviation in the axial direction of the photosensitive drum 4 is lower at the right end than at the left end as shown in FIG. This makes it possible to correct photosensitivity deviations. In this embodiment, the output of a correction waveform generation circuit 53 that generates a correction waveform (shown in FIG. 3(b)) corresponding to the photosensitivity ratio of the left end and right end is multiplied by a reference voltage by a multiplier circuit 52 and compared. input to circuit 51; The reference voltage used to correct the photosensitivity and the output of the laser power monitor are compared in the comparator circuit 51, and a signal proportional to the correction waveform is supplied to the drive circuit 50. A current corresponding to the waveform is supplied to the semiconductor laser 12.

Therefore, laser output light corresponding to the corrected waveform can be obtained.

Note that the correction waveform shown in FIG. 3(b) is obtained by the circuit shown in FIG.

In the figure, the correction waveform rises by supplying a constant current from the constant current circuit 55 to the capacitor 54, and is reset by supplying the laser scanning signal (the signal shown in FIG. 3(a)) to the transistor. Ru. Thereafter, by repeating this process, corrected waveforms are sequentially output.

Further, 58 is an amplifier.

Furthermore, this laser scanning position signal corresponded to the left end position of the drum, as shown in FIG.

This is the output of the photodiode 56 that receives the reflected light from the mirror 57 provided at the position.

The correction ratio of the correction waveform is set using the constant current circuit 5 in Fig. 2.
This is done by varying the current 1c in step 5 using a volume or the like.

As explained above, by using the circuit configuration shown in FIG. 1, it is possible to change the light intensity at the axial position of the photosensitive drum. C can also be used without adjustment.

Furthermore, even if the photosensitive drum B has large variations, the first
By inverting the photosensitive drum as shown in FIG. 3, it can be used without any adjustment.

Here, a configuration for reversing the photosensitive drum will be explained.

FIG. 4 is an explanatory diagram of a photosensitive drum used in an electrophotographic printing apparatus.

In the figure, 30 is a photosensitive drum made of an aluminum substrate with a 5e-Te layer formed on its surface, 31 is a left flange fitted to the left side of the photosensitive drum 30, 32 is a right flange fitted to the right side, and 33 and 34 are left and right flange. Flange 3
Bolts and nuts (three sets are used) for fixing 1.32 and 35.36 are bearings, respectively.

The photosensitive drum having the configuration shown in the figure is set by inserting it into the shaft fixed to the device, and its rotation is controlled by the left flange 31.
This is done by inserting a claw member (not shown) connected to the motor 4a into the cavity E (inserted from the photosensitive drum set).

Then, by performing a printing operation using an electrophotographic printing device in which the laser power of the laser source 12 is stronger on the right side in the direction of the drum axis, it is confirmed whether there is a difference in shading between the left and right sides of the image. .

If there is a difference in density, the apparatus is stopped, the photosensitive drum is removed, and the left and right flanges 31 and 32 are installed in reverse.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to improve the manufacturing yield of photoreceptors and to reduce the amount of exposure and other adjustments.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an embodiment of the light amount control means in the electrophotographic printing apparatus according to the present invention, FIG. 2 is an explanatory diagram of the correction waveform generation circuit, FIG. 3 is an explanatory diagram of the correction waveform, and FIG. 4 is an explanatory diagram of the correction waveform generation circuit. An explanatory diagram of a photosensitive drum, FIG. 5 is an overall configuration diagram of an electrophotographic printing device, FIG. 6 is a diagram of an optical system configuration, FIG. 7 is an explanatory diagram of a control circuit that drives and controls a laser source, and FIG. A diagram for explaining the change in line width, Figure 9 is a schematic configuration diagram of the charger, Figure 10 is a diagram for explaining the change in line width.
Figure 1 shows the relationship between corona wire and charging potential.
1 to 13 are explanatory diagrams of the relationship between the axial position of the photosensitive drum and the light sensitivity, and the good image area a. - In the figure, 12 is a laser source (semiconductor laser) 50 is a drive circuit;
1 is a comparison circuit, 52 is a multiplication circuit, and 53 is a correction waveform generation circuit. Figure 1 V Figure 2 Figure 3 (a,) (b) Figure 91!1 Figure 1θ corona wire &

Claims (1)

[Claims] (1) A photoconductor, a charger for charging the photoconductor, a means for irradiating light from a light emitting source onto the charged photoconductor to form a latent image, and developing the latent image on the photoconductor. and a transfer means for transferring the visible image developed by the developer onto a medium, and the latent image forming means is configured to prevent deviations that affect the image in a direction perpendicular to the direction in which the photoreceptor is transported. An electrophotographic printing apparatus comprising: means for varying the amount of light irradiated onto the photoreceptor so as to correct the amount of light emitted from the light emitting source; An electrophotographic printing apparatus characterized by comprising a light amount control means that controls the amount of light sequentially in a direction perpendicular to the direction in which the body is transported.