JP2002347274A - Electrophotographic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need of precise adjustment of a light quantity of an LD for writing an image which has been necessary heretofore, and to eliminate roughness of an image due to variation in the light quantities of the individual LDs generated in variation with time in an electrophotographic apparatus having the plurality of LDs for writing an image. SOLUTION: An exposing device in the electrophotographic apparatus comprises the plurality of LDs for writing an image, and forms a reference pattern by activating each of LDs with predetermined time intervals. The reflection density of the reference pattern is detected by a reflection density detecting sensor 11 and the exposing device respectively controls the light quantities of the LDs such that the detected output difference is in a predetermined range. In the detection of the reflection density, a plurality of data samples are used. When the amount of fluctuation exceeds a predetermined value, the detecting operation is retried redetermined times and the judging is executed based on the averaged value. As a result, it is possible to eliminate the influence by noise such as jitter and to adjust the light quantity of each of the LDs with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic apparatus, and more particularly, to a process control of a digital electrophotographic apparatus such as a digital copying machine.

[0002]

2. Description of the Related Art In recent years, digital electrophotographic apparatuses equipped with a plurality of writing LDs (Laser Diodes) have been put to practical use with the speeding-up of digital electrophotographic apparatuses. This is because, as in the prior art, a single writing LD requires high-speed image writing scanning on the photoreceptor at the time of image writing, and there is a limit to the performance of the scanning polygon motor. It is. If a plurality of LDs are used for writing, a plurality of lines can be written in one scan, so that the rotation speed of the polygon motor can be significantly reduced. However, the plurality of writing LDs must be set to the same light amount as a matter of course. Heretofore, when manufacturing the electrophotographic apparatus, the quantity of light was adjusted for individual writing LDs, and then shipped.

However, with the increase in sensitivity of photoreceptors, LD
The set value of the light amount is getting smaller. As such, L
D leads to a longer life and, although desirable,
On the other hand, when adjusting the light quantity, higher-precision adjustment is required. Further, when the LD is deteriorated due to aging, the decrease in the amount of light is not always uniform, so that a problem such as a halftone having a rough feeling may occur.

According to the present invention, a plurality of writing LDs are individually turned on to form a reference latent image pattern corresponding to each LD light amount on a photosensitive member, and the reference latent image pattern is developed.
The reflection density of the developed toner image is detected by a sensor,
The electrophotographic apparatus automatically adjusts the light intensity of each LD so that the reflection density difference falls within a certain range, thereby eliminating the light intensity adjustment conventionally performed in the factory, and causing the above-mentioned problem due to the decrease in light intensity with time. It is not so.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a plurality of image writing Ls.
An object of the present invention is to eliminate the fine adjustment of the light amount of the image writing LD, which has been conventionally performed, in the electrophotographic apparatus having D, and reduce the image roughness due to the light amount difference between the LDs caused by the aging. Therefore, in an electrophotographic apparatus having a plurality of image writing LDs, at predetermined intervals, the writing LDs are individually turned on to form a reference pattern, and the reflection density of the reference pattern is detected by a sensor. The writing LD light amount is individually controlled so that the detection output difference falls within a predetermined range.

Further, in the present invention, in order to achieve the above object, a plurality of data samples are taken when detecting the reference pattern reflection density, and when the fluctuation amount of the obtained data exceeds a predetermined value, The detection operation is repeated up to a predetermined number of times. By doing so, the influence of noise such as jitter can be eliminated and the LD light quantity can be adjusted with high accuracy.

[0007]

Means for Solving the Problems The present invention has been made to solve the above problems, and the invention of claim 1 has a plurality of image writing light sources, and the light sources for writing images are provided at predetermined intervals. The writing light sources are individually turned on to create a reference toner pattern, the reflection density of the reference toner pattern is detected, and if the detected output value deviates from a predetermined range, the writing light amount of the image writing light source is changed to In an electrophotographic apparatus in which a predetermined amount is changed for each image writing light source, when detecting the reflection density of the reference toner pattern, a plurality of data samples are performed, and when the variation amount of the data exceeds a predetermined value, the reflection density is calculated. The detection is repeated a predetermined number of times, and the predetermined amount is determined based on an average value of the obtained data.

[0008]

1 to 3 show an embodiment of the present invention.
A description will be given based on the embodiment shown in FIG. FIG. 1 is a side sectional view showing a main part of an electrophotographic apparatus embodying the present invention. Hereinafter, the configuration and operation of the electrophotographic apparatus will be described, and then the configuration and operation of the characteristic portion of the present invention will be described.
The main part of the electrophotographic apparatus includes a photosensitive member 1, a charging device 2, an exposure device (not shown), a developing device 3, a transfer belt 6, a cleaning device 7, a reflection density detection sensor 11, and the like. The reflection density detection sensor 11 detects the density of the toner image formed on the photoconductor 1 and the background density of the photoconductor 1. The exposure apparatus has a plurality of writing LDs as in the conventional electrophotographic apparatus, and individually turns on the writing LDs at predetermined time intervals, and uses the laser beam B emitted from the writing LDs as a reference. Create a pattern. The reflection density detection sensor 11 detects the reflection density of the reference pattern, and based on the obtained data, the control device of the electrophotographic apparatus writes data so that the detection output difference of the reflection density detection sensor falls within a predetermined range. The LD light quantity for each is individually controlled.

The image forming process of the electrophotographic apparatus will be described. First, the photosensitive member 1 is uniformly charged by the charging roller 2. Thereafter, the photoreceptor 1 is image-exposed by a laser beam emitted from an LD in an exposure device (not shown),
An electrostatic latent image is formed on the photoconductor 1. At the time of image exposure, a plurality of writing LDs emit light in accordance with an image signal. The developing device 3 contains a developer 4 which is a mixture of magnetic powder and non-magnetic toner called a carrier. When the developer is stirred, the toner is charged by frictional charging. The developer is conveyed onto the photoconductor by the developing sleeve 5, and develops the electrostatic latent image on the photoconductor 1 with toner. The amount of toner to be developed is determined by the difference between the image potential on the photoreceptor and the developing bias voltage applied to the developing roller.

A voltage having a polarity opposite to that of the toner is applied to the transfer belt 6 by a power supply (not shown). The toner image developed on the photoconductor 1 by the electric field between the transfer belt 6 and the photoconductor 1 is transferred onto a transfer paper sandwiched between the photoconductor 1 and the transfer belt 6. Thereafter, the transfer paper is conveyed by the transfer belt 6 and passes through a fixing device (not shown). On this occasion,
The toner image is thermally fused on the transfer paper. The toner that has not been transferred remains on the photoreceptor 1, is blocked by the cleaning blade 8 of the cleaning device 7, and is put on the collection coil 10 by the collection blade 9. The collection coil 10 returns the toner to the developing device 3 as recycled toner.

Next, the configuration and operation of the present invention will be described. When adjusting the light amount of a plurality of writing LDs,
The writing LD is individually turned on to create a reference pattern based on the electrostatic latent image by the laser beam B, and the toner 4 is adhered and developed in the developing device 3, and the reflection density of the formed toner image is measured by a reflection density detection sensor. The detection is performed at 11, and the light amount setting of the writing LD is changed so that the detection output value falls within a predetermined range. Here, in the present invention, when detecting the reflection density of the toner image of the reference pattern, a plurality of data samples are performed, and when the variation amount exceeds a predetermined range, the detection operation is repeated a predetermined number of times, and the data obtained as a result is obtained. The determination of changing the light amount setting of the writing LD is performed by taking the average value of.

FIG. 2 is a flowchart showing the processing of the electrophotographic apparatus of the present invention, and FIG. 3 is a flowchart continued from FIG. Hereinafter, description will be made with reference to the flowcharts of FIGS. Note that the case where the number of write LDs is two is described as an example. First, the control means (CPU) of the electrophotographic apparatus determines whether it is time to adjust the individual LD light amount. Whether or not the adjustment time has come is determined based on whether or not the number of output sheets of the electrophotographic apparatus has exceeded a predetermined number n (step 1). The number n is experimentally determined based on assumed use conditions of the electrophotographic apparatus. The adjustment interval may be freely changed by a service person. For adjustments before shipment from the factory,
The adjustment operation may be performed every time the electrophotographic apparatus operates, with n = 1.

When it is determined in step 1 that the adjustment time has come, a reference pattern image is formed. The developing bias and the charging output are output at experimentally determined values so that the pattern can be easily detected, and the reflection density detecting sensor is turned on and started (step 2). Next, a plurality of write LDs
Of only one of the write LD1s with a predetermined PWM
(Power Wide Modulation), and the reference pattern is written (step 3). Also for this PWM, a value that is easily detected by the reflection density detection sensor is experimentally obtained and determined. The reference pattern written by the writing LD 1 is developed and passes in front of the reflection density detection sensor 11. At this time, the output Vs corresponding to the reference pattern density
p1 is obtained from the reflection density detection sensor (step 4). Here, data sampling is performed a plurality of times, and the average value and the maximum / minimum difference Vsp1d of the obtained data are obtained. At the same time that the output Vsp1 corresponding to the reference pattern density is detected, the output V of the photoconductor background portion is detected by the reflection density detection sensor.
sg1 is obtained (step 5).

Similarly, another writing LD2 different from the writing LD1 is turned on at a predetermined PWM to write a reference pattern (step 6). L for writing
The reference pattern written by D2 is developed and passes in front of the reflection density sensor. At this time, an output Vsp2 corresponding to the reference pattern density is obtained from the P sensor (Step 7). Here, data sampling is performed a plurality of times to determine the average value of the data and the maximum / minimum difference Vsp2d. At the same time as detecting the output Vsp2 corresponding to the pattern density, the output Vsg2 of the background portion of the photoreceptor is obtained (step 8). It is determined whether or not the maximum and minimum differences Vsp1d and Vsp2d between Vsp1 and Vsp2 obtained in steps 4 and 7 are equal to or smaller than a predetermined value A (step 9).

If there is drive jitter or the like, these outputs may fluctuate, causing erroneous detection. In the electrophotographic apparatus of the present invention, when the difference between the maximum and the minimum is large in the sampled data, it is considered that the influence of the jitter is present, and it is determined whether or not the detection is performed by the number J of the values experimentally obtained (step 10). If the detection has not been performed J times, the number of detections is set to J times (step 11), and the process returns to step 3 to repeat the reflection density detection based on the reference pattern and correct the light amount of the writing LD based on the average value. Do (Step 1
1, Step 12).

The determination of the light quantity correction is made at the same time as Vsp1 and Vsp2, using the ratio of the reflection outputs Vsg1 and Vsg2 of the background portion of the photoreceptor detected in steps 5 and 8 (steps 13 and 15). This is to eliminate the influence of dirt on the P sensor element and dirt on the background of the photoconductor. It is determined whether or not the difference between Vsp1 / Vsg1 and Vsp2 / Vsg2 is within a predetermined range (step 13,
Step 15) If it is not within the predetermined range, the light amount setting of the writing LD 2 is increased or decreased by a predetermined amount to make the light amount equal to that of the writing LD 1 (steps 14 and 16). When the above flow is completed, the light amount difference adjustment is completed.

[0017]

As is apparent from the above description, the present invention relates to an electrophotographic apparatus having a plurality of image writing LDs, wherein the writing LDs are individually turned on at predetermined intervals to set the reference pattern. Since the reflection density of the reference pattern is detected by a sensor and the LD light quantity for writing is individually controlled so that the detection output difference falls within a predetermined range, the conventional method for writing an image is performed. The fine adjustment of the light amount of the LD is abolished, and it is possible to realize the reduction of the image roughness due to the light amount difference of each of the writing LDs generated when the time elapses. In addition, when detecting the reference pattern reflection density, a plurality of data samples are performed, and when the variation exceeds a predetermined value, the detection operation is repeated up to a predetermined number of times, and the average value of the data is used. In this way, it is possible to adjust the light amount of the individual LD for writing with high accuracy while eliminating the influence of the noise.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a configuration of a main part of an electrophotographic apparatus.

FIG. 2 is a flowchart illustrating processing of the electrophotographic apparatus.

FIG. 3 is a flowchart showing the processing of the electrophotographic apparatus, which is continued from FIG. 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photoreceptor, 2 ... Charging device, 3 ... Developing device, 4 ... Developer, 5 ... Developing sleeve, 6 ... Transfer belt, 7 ... Cleaning device, 8 ... Cleaning blade, 9 ... Recovery blade,
10: recovery coil, 11: reflection density detection sensor.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C362 AA53 AA54 AA56 AA66 CB73 2H027 DA10 DA32 DA44 DE02 DE07 DE09 EA02 EB01 EC06 EC07 EC10 EC18 EC20 ED06 EE01 EE07 HA02 HA03 HA12 HB05 HB16 ZA07 2H076 AB05 AB06 AB22 AB

Claims (1)

[Claims] 1. A light source for writing a plurality of images, a light source for writing is individually turned on at a predetermined interval, a reference toner pattern is created, and a reflection density of the reference toner pattern is detected. When the output value deviates from a predetermined range, in an electrophotographic apparatus that changes a writing light amount of the image writing light source by a predetermined amount for each of the image writing light sources, when detecting the reflection density of the reference toner pattern, a plurality of data An electrophotograph, wherein a sample is performed, and when the variation amount of data exceeds a predetermined value, the reflection density detection is repeated a predetermined number of times, and the predetermined amount is determined based on an average value of the obtained data. apparatus.