JP4078101B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic image forming apparatus applied to a copying machine, a printer, a facsimile machine, and the like.
[0002]
[Prior art]
Conventional techniques of this type include, for example, techniques described in JP-A-9-197776 and JP-A-10-181091.
[0003]
In an image forming apparatus described in Japanese Patent Laid-Open No. 9-197776, in an image forming apparatus that employs an overscan exposure method, a plurality of patterns are formed in advance, and an average toner density for each pattern measured by an average density measuring unit is used. The relationship between the beam light quantity and the image edge position is obtained and stored in the adjusting means. When an image is actually formed, the image forming process is performed regardless of the machine difference or environment by controlling the light amount of the beam based on this relationship.
[0004]
An image forming apparatus described in Japanese Patent Laid-Open No. 10-181091 discloses an image information source that supplies image data having a resolution twice that of an optical scanning apparatus, and a pattern in the sub-scanning direction of image data input from the image information source. Image pattern determining means for determining; exposure control means for outputting a light beam lighting signal and a light beam intensity signal for reproducing the image information by an optical scanning device having a resolution of 1/2 of the image data according to the image pattern; By providing a modulation exposure means for modulating the light beam based on the light beam lighting signal and the light beam intensity signal from the exposure control means, an image is formed with a resolution twice that of a writing apparatus having an optical scanning system. Is.
[0005]
[Problems to be solved by the invention]
An optical scanning system has a plurality of light beams (a single scanning system may have a plurality of beams, or a single beam may have a plurality of scanning systems), and light having the optical scanning system When forming an image with a resolution twice that of the writing device, in order to form a toner image with high accuracy,
The toner images formed by each light beam alone must be equal. The toner image formed by superimposing a plurality of light beams must be the same as the toner image formed by each light beam alone.
[0006]
However, the balance of the plurality of light beams changes due to machine differences, time-dependent environments, and the like.
[0007]
The present invention solves such problems, and by appropriately adjusting the balance of a plurality of light beams, it is possible to reproduce an output image that is more faithful to input image data. An object is to provide an apparatus.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention performs image exposure on an image carrier by light beam scanning according to image data, and exposes two light beams so as to have a resolution of 2 which the optical scanning system has. to reproduce the times of resolution, an image forming apparatus having a plurality of light beams, an optical detection means for detecting a density of the toner image on the image carrier, the two light beams for each operation interval set in advance , Only one of the first light beams, only the other second light beam , or the superposition of the first and second light beams, or the light beams emitted by superimposing the second and first light beams, respectively. A toner is attached to the electrostatic latent image formed on the image bearing member by a developing means to form a reference toner image, and each image formation image is formed so as to have an appropriate density according to the density of the reference toner image. Light bee Characterized in that an adjusting means for adjusting the amount of light beam when allowed amount of light or superimposed. Further, the present invention is characterized in that the preset operation interval is a predetermined number of printed sheets or an integrated operation time, and is a temperature, humidity or a change in temperature / humidity from the previous adjustment detected by the detection means. And With this configuration, a reference toner image is formed on the image carrier at each preset operation interval (number of sheets, time, detected temperature, humidity or change in temperature and humidity), and the density of the reference toner image Accordingly, the amount of light beam of each light beam is adjusted at the time of image formation, so that changes that affect the formed image due to changes over time of toner, image carrier, laser diode (hereinafter referred to as LD), etc. Can be corrected, and an output image that is more faithful to the input image data can be reproduced.
[0010]
The present invention also performs image exposure on the image carrier by light beam scanning according to image data, and reproduces a resolution twice as high as that of the optical scanning system by overlapping and exposing the two light beams. An image forming apparatus having a plurality of light beams, an optical detection means for detecting the density of the toner image on the image carrier, and two light beams as part of the condition setting operation of the image forming apparatus , only one of the first light beam, or only the other of the second light beam or first, superposition of the second light beam, or the second, the image in each of the light beams is emitted by the first light beam superposition A toner is attached to the electrostatic latent image formed on the carrier by a developing means to form a reference toner image, and each light beam at the time of image formation is adjusted to an appropriate density according to the density of the reference toner image. the amount of light of Others characterized by comprising adjusting means for adjusting the amount of light beam when superimposed. In addition, the present invention is characterized in that a part of the condition setting operation is an initial setting operation when the power is turned on. With this configuration, a reference toner image is formed on the image carrier as part of the condition setting operation of the image forming apparatus, and each light beam at the time of image formation is formed according to the density of the reference toner image. As the amount of light is adjusted, changes in toner, image carrier, LD, etc. that affect the formed image over time and environmental changes can be corrected, and more faithful to the input image data. Can reproduce the output image. In addition, since adjustment is performed as a series of operations together with other operations when the power is turned on or every 24 hours, etc., the adjustment operation does not interrupt during the frequent printing time period, or it is used after adjusting every day. Can be obtained.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0012]
FIG. 1 is a side view showing an internal configuration of an electrophotographic image forming apparatus according to an embodiment of the present invention. Reference numeral 1 denotes a photosensitive drum as an image carrier, and 2 denotes a uniform charging of the photosensitive drum 1. A charging unit 3 irradiates the photosensitive drum 1 with a light beam to form an electrostatic latent image on the photosensitive drum 1, and 4 develops a toner image by attaching toner to the electrostatic latent image. And 5, a transfer unit for transferring the toner image onto the transfer paper, 6 a fixing unit for fixing the toner image on the transfer paper by pressurizing and heating the transfer paper carrying the toner image, and 7 passing through the fixing unit 6. A reversal / discharge unit for switching the transfer path of the transfer paper to the outside or a double-sided printing unit 8 for duplex printing, 9 is a tandem LCT for storing transfer paper, and 10 is disposed below the tandem LCT 9. Universal tray for storing transfer paper, 11 is toner Bank, 12 is a waste toner bottle, 13 is a scanner unit that optically reads an image of a document, 14 is an ADF that automatically conveys the document to the scanner unit 13, 15 is a display unit that displays various information, and an input for inputting various commands. An operation panel having keys is shown.
[0013]
The photosensitive drum 1, the charging unit 2, the developing unit 4, the transfer unit 5, and the toner collecting unit and the photosensitive drum 1 for collecting toner remaining on the photosensitive drum 1 without being transferred to the transfer paper in the transfer unit 5. A neutralizing unit that removes residual charges is integrated into a drum unit that is detachable from the main body of the image forming apparatus.
[0014]
The photosensitive drum 1 is uniformly charged by the charging unit 2, and a light beam modulated based on image data of a document read by the scanner unit 13 or image data input from the outside is read from the optical writing unit 3. By irradiating the drum 1, an electrostatic latent image is formed on the photosensitive drum 1. Next, the electrostatic latent image is converted into a toner image by the developing unit 4, and the toner image is transferred from the photosensitive drum 1 to the transfer paper by the transfer unit 5. Thereafter, the image is fixed on the transfer paper in the fixing unit 6.
[0015]
Further, a photosensor (described later) is provided in the drum unit, and the optical reflection density of the toner image on the photosensitive drum 1 can be measured.
[0016]
FIG. 2 is a perspective view showing the main configuration of the optical writing unit. 20 is an LD unit, 21 is a polygon motor, 22 is a polygon motor driver for controlling the polygon motor 21, 23 is a cylinder lens, 24 is a first mirror, Reference numeral 25 denotes a first fθ lens, 26 denotes a second fθ lens, 27 denotes a BTL lens, 28 denotes a second mirror, 29 denotes dustproof glass, 30 denotes a third mirror, 31 denotes a synchronization detection sensor, 32 denotes an intake fan, 33 denotes a dustproof filter, Reference numeral 34 denotes an exhaust fan.
[0017]
The light beam generated from the LD unit 20 is applied to the polygon mirror provided in the polygon motor 21 via the cylinder lens 23 and the first mirror 24. Thus, the reflected light beam passes through the first fθ lens 25, the second fθ lens 26, and the BTL lens 27, is deflected to the photosensitive drum 1 by the second mirror 28, passes through the dust-proof glass 29, and enters the photosensitive drum 1. The surface of the photosensitive drum 1 is scanned with the light beam by the rotation of the polygon mirror. A part of the light beam outside the scanning range of the photosensitive drum 1 is deflected toward the synchronization detection sensor 31 by the third mirror 30. An intake fan 32 and an exhaust fan 34 are provided on both sides of the LD unit 20, and a dustproof filter 33 is provided in the vicinity of the intake fan 32.
[0018]
FIG. 3 is a perspective view showing the main configuration of the LD unit. The LD unit 20 includes a laser light source 35, a collimating lens 36, and a casing having an aperture 37. A photodiode 35a and an LD array 35b in which a plurality of LDs are arranged in a line are provided. In the present embodiment, an LD array 35 b having two LDs is provided, and these two light beams are emitted through the aperture 37.
[0019]
FIG. 4 is a block diagram showing an LD unit and its surrounding control system. 40 is a CCD (Cherge Coupled Device) which is a light receiving element of the scanner unit 13, 41 is a CCD 40, an amplifier circuit, an A / D converter circuit, etc. The SBU (Sensor Board Unit) 42 includes an SICU (Scanner & Image Processing Control Unit) which is an image system main board. The SICU 42 includes an IPU (Image Processing Unit) that performs image processing on image data from the SBU 41. ) 43, an MSU (Memory Supercharger Unit) 44 having an image compression / decompression, memory / HDD controller, and the like. Reference numeral 45 denotes an LDB (Laser Diode Drive Board). The LDB 45 includes an LD control circuit 46, a modulation circuit 47 having a pulse width modulation (PWM) circuit and a power modulation (PM) circuit, a laser. An LDD (Laser Diode Drive) circuit 48 that controls lighting of the light source 35 and a two-channel LD array 35b (LDA: Laser Diode Alley) are provided.
[0020]
In FIG. 4, two light beams LD1 and LD2 in the two-channel LD array 35b shown in FIG. 3 are emitted. The LD1 and LD2 are adjacent to each other. By irradiating the photosensitive drum 1 with the LD1 and LD2 superimposed, an image is formed with a resolution twice that of the input image data.
[0021]
FIG. 5 is a model diagram showing an exposure pattern when forming a reference toner image to be used for adjusting the beam light amount. Before performing image formation, what kind of profile is applied to input image data? It is determined whether an electrostatic latent image should be formed with a light beam, and an electrostatic latent image is formed based on the information (tuning data) at the time of actual image formation.
[0022]
More specifically, first, the LD 1 is caused to emit light at the position and size readable by the photo sensor in the drum unit at the timing shown in FIG. 5A to form a reference toner image. Here, as shown in FIG. 5B, it is assumed that the halftone image is formed by arranging the scanning lines of LD1 at a predetermined interval. Next, the optical density is measured by a photosensor, and feedback is performed so that the toner image has an appropriate density, and the PM circuit of the modulation circuit 47 is controlled to adjust the light amount of the light beam (if necessary, a plurality are formed. Adjust). Next, the LD 2 is caused to emit light at the timing shown in FIG. 5C, a reference toner image of only the LD 2 is formed, and the amount of light beam is similarly adjusted. This balances the light beams of LD1 and LD2. Finally, light is emitted in the timing shown in FIG. 5D, that is, in the order of LD1 and LD2, and a reference toner image is formed by superimposing LD1 and LD2, and similarly a light beam at the time of superimposition so as to obtain an appropriate density. Adjust the amount of light.
[0023]
FIG. 6 is a block diagram showing a control system for adjusting the light amount of the light beam, 50 is a CPU, 51 is a photosensor provided in the drum unit for detecting the optical reflection density of the toner image, and 52 is for counting the number of prints. Counter 53, a measuring instrument 53 for measuring the accumulated operation time, 54 a temperature sensor, and 55 a humidity sensor.
[0024]
The light amount adjustment of the light beam is performed by detecting the number of sheets and time using the counter 52 and the measuring device 53. For example, the number of prints set in advance such as “every 1000 prints”, “every hour of integration operation”, etc. A reference toner image is formed on the photosensitive drum 1 and adjusted every operation time.
[0025]
As a result, it becomes possible to balance the three patterns of LD1 and LD2 and to optimize the light quantity, and input corresponding to changes in sensitivity of photosensitive drum 1 and development characteristics due to aging and environment. It is possible to reproduce a more faithful output image with respect to the image data. Note that the overlapping pattern may be a pattern formed by LD2, 1 instead of LD1, 2 or both.
[0026]
In the embodiment described above, the light amount adjustment of the light beam is performed for each preset number of prints and operation time. However, the present invention is not limited to this, and the temperature sensor 54 and the humidity sensor 55 shown in FIG. 6 are used. Detects temperature and humidity, and adjusts the amount of light beam by forming a reference toner image on the photosensitive drum 1 when the amount of change in temperature, humidity, or temperature / humidity since the previous adjustment exceeds the threshold. May be.
[0027]
Further, as a part of the condition setting operation of the image forming apparatus, a reference toner image may be formed on the photosensitive drum 1 for adjustment. For example, when the power supply device 56 shown in FIG. 6 is turned on, an operation for adjusting the image forming conditions and an operation for stabilizing the charge amount of the developer may be performed. .
[0028]
As a result, three balances of LD1 and LD2 and superimposition of light amount are performed on the image data, and input corresponding to changes in sensitivity of the photosensitive drum 1 and development characteristics due to aging and environment, etc. A more faithful output image is reproduced for the image data. The overlapping pattern may be a pattern formed by LD2, 1 instead of LD1, 2, or both. If only LD1, only LD2, and one of the two overlapping patterns match, the four writing patterns should match, but the four patterns are adjusted to increase accuracy. Also good.
[0029]
Similarly, by adjusting a plurality of image data (for example, line width) and forming an image based on the data (adjustment value), the image can be reproduced more faithfully.
[0030]
In the above-described embodiment, the image forming apparatus having two light beams has been described. However, the number of light beams is not limited to two and may be more.
[0031]
7 is a perspective view showing the main configuration of the 4-beam LD unit, FIG. 8 is a block diagram showing the LD unit of FIG. 7 and its surrounding control system, and FIG. 9 is a reference toner image used when adjusting the light quantity of the light beam. It is a model figure which shows an exposure pattern at the time of forming. The same members as those shown in FIGS. 3 and 4 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0032]
4 beams LD unit, which has provided the LD array 35c of 4 tea down channel as shown in FIG. 7 in place of the LD array 35b of 2 tea down channel shown in FIG. 3, four LD of the LD array 35c On the other hand, as shown in FIG. 8, four modulation circuits 47 and LDD circuits 48 are made to correspond.
[0033]
Then, on the photosensitive drum 1, a pattern of only LD1 (see FIG. 9A), a pattern of only LD2 (see FIG. 9B), a pattern of only LD3 (see FIG. 9C), and only LD4. Pattern (see FIG. 8D), LD1 and LD3 overlay pattern (see FIG. 9E), LD2 and LD3 overlay pattern, LD3 and 4 overlay pattern, and LD4 and 1 overlay pattern , And the optical density is measured by the photosensor 51, and feedback is performed so as to obtain an appropriate density, and the PM circuit of the modulation circuit 47 is controlled to adjust the light quantity of the light beam. As a result, a more faithful output image can be reproduced with respect to the input image data.
[0034]
【The invention's effect】
As described above, according to the present invention constructed as described, for each operation interval set in advance, Oh Rui as part of the condition setting operation of the image forming apparatus, forming a reference toner image on the image bearing member, By adjusting the amount of each light beam at the time of image formation according to the density of this reference toner image, it becomes possible to correct changes that affect the formed image. A more faithful output image can be reproduced with respect to the processed image data.
[Brief description of the drawings]
FIG. 1 is a side view showing an internal configuration of an electrophotographic image forming apparatus according to an embodiment of the present invention. FIG. 2 is a perspective view showing a main configuration of an optical writing unit. FIG. 4 is a block diagram showing an LD unit and its surrounding control system. FIG. 5 is a model diagram showing an exposure pattern when forming a reference toner image used when adjusting the light amount of a light beam. FIG. 7 is a perspective view showing a main configuration of a 4-beam LD unit;
FIG. 8 is a block diagram showing the LD unit of FIG. 7 and its surrounding control system. FIG. 9 is a model diagram showing an exposure pattern when forming a reference toner image used for adjusting the beam light amount.
DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging part 3 Optical writing part 4 Developing part 5 Transfer part 6 Fixing part 7 Reverse / paper discharge part 8 Both sides part 9 Tandem LCT
10 Universal tray 11 Toner bank 12 Waste toner bottle 13 Scanner unit 14 ADF
15 Operation panel 20 LD unit 21 Polygon motor 22 Polygon motor driver 23 Cylinder lens 24 First mirror 25 First fθ lens 26 Second fθ lens 27 BTL lens 28 Second mirror 29 Dustproof glass 30 Third mirror 31 Synchronization detection sensor 32 Intake fan 33 Dustproof filter 34 Exhaust fan 35 Laser light source 35a Photo diode 35b, 35c LD array 36 Collimator lens 37 Aperture 40 CCD (cherge coupled device)
41 SBU (Sensor Board Unit)
42 SICU (Scanner & Image Processing Control Unit)
43 IPU (Image Processing Unit)
44 MSU (Memory Supercharger Unit)
45 LDB (Laser diode Drive Board)
46 LD control circuit 47 Modulation circuit 48 LDD (Laser diode Drive) circuit 48

Claims (5)

A plurality of light beams that perform image exposure on the image carrier by light beam scanning according to image data, and reproduce two times the resolution of the optical scanning system by overlapping and exposing the two light beams. An image forming apparatus having
Optical detection means for detecting the density of the toner image on the image carrier , and only one first light beam or only the other second light beam in the two light beams at a preset operation interval, or The electrostatic latent image formed on the image carrier with each of the light beams emitted by superimposing the first and second light beams or the second and first light beams is developed by a developing unit. A reference toner image is formed by attaching toner, and the light amount of each light beam at the time of image formation or the light beam amount at the time of superposition is adjusted so as to obtain an appropriate density according to the density of the reference toner image. An image forming apparatus comprising: an adjusting unit.   2. The image forming apparatus according to claim 1, wherein the preset operation interval is a predetermined number of printed sheets or an accumulated operation time.   2. The image forming apparatus according to claim 1, wherein the preset operation interval is defined as a temperature, humidity, or change in temperature and humidity from the previous adjustment detected by the detecting means. A plurality of light beams that perform image exposure on the image carrier by light beam scanning according to image data, and reproduce two times the resolution of the optical scanning system by overlapping and exposing the two light beams. An image forming apparatus having
And optical detection means for detecting a density of the toner image on the image bearing member, as a part of the condition setting operation of the image forming apparatus, wherein the two light beams, only one of the first light beam or the second other, The electrostatic latent image formed on the image carrier with only the light beam , or the light beam emitted by superimposing the first and second light beams or the superposition of the second and first light beams. The toner is attached by the developing means to form a reference toner image, and the light amount of each light beam at the time of image formation or the light beam at the time of superposition is set so as to have an appropriate density according to the density of the reference toner image . An image forming apparatus comprising an adjusting means for adjusting the amount of light .   5. The image forming apparatus according to claim 4, wherein a part of the condition setting operation is an initial setting operation when the power is turned on.

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