JP4287585B2 - Image forming method and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming method in an image forming apparatus such as a digital copying machine, a printer, and a facsimile machine that forms an image by irradiating a photoconductor with a light laser beam, and more specifically, reproducibility of an image having a halftone density. It relates to process control to ensure.
[0002]
[Prior art]
Conventionally, keeping the halftone density of an electrophotographic apparatus constant has been an important technical problem in keeping image quality stable. In the image forming apparatus, the following techniques are known as techniques for adjusting the halftone density.
[0003]
(1) Image forming apparatus disclosed in JP-A-6-208715
(2) Image forming apparatus disclosed in JP-A-8-265570
(3) Image forming apparatus disclosed in JP-A-8-297834
The technology disclosed in the above publication (1) stabilizes the density reproducibility of the intermediate density portion, which is particularly important in a multi-tone digital image forming apparatus among the image density fluctuations based on the sensitivity fluctuations of the photoconductor. The configuration of the image forming apparatus is to calculate the control potential VGS of the charging means 402 for charging the photosensitive member 401 with the target dark potential VHS, and the photosensitive member charged with the control potential VGS is used. Based on the detection potential of the latent image patch 401 and the exposure light amount of the latent image patch, the light laser beam light amount VLS for obtaining the target halftone potential VMS is calculated, and the development is performed by subtracting the fog prevention potential VC from the target dark potential VHS. Control means for calculating the bias potential VB and setting the charging control potential VGS, the light laser beam light quantity LDS, and the developing bias potential VB is provided.
However, the technique disclosed in the publication (1) is premised on potential detection, and requires an expensive electrometer.
[0004]
The technique disclosed in the above-mentioned publication (2) is related to an image forming apparatus, and an object thereof is to provide an image forming apparatus capable of accurately controlling the density of a halftone image. In an image forming apparatus for forming an image by attaching toner to an image, pattern forming means for forming an image density detection pattern on the image carrier and an image for detecting an image density due to the toner attached on the image carrier A density detection unit; a control unit that performs image density control according to the density detected by the image density detection unit; and a multi-stage gradation pattern that is provided in the control unit and created by the pattern formation unit And a gradation table for storing the relationship between the output of the image density detecting means and the image density.
[0005]
However, in the technique disclosed in the publication (2), when a halftone density is detected, a plurality of halftone patterns are created, so that detection control takes time. Further, since adjustment of the halftone density is performed by PWM (power wide modulation) (light emission time) of an LD (laser diode), the adjustment range is rough.
[0006]
The technique disclosed in the above-mentioned publication (3) is related to an image forming apparatus, and an object thereof is to provide an image forming apparatus capable of accurately performing toner adhesion amount control from halftone to solid. Is formed by a patch forming unit that forms a test solid patch and a test halftone patch on the image carrier, and the patch forming unit. The solid density control is performed by controlling the peripheral speed ratio of the developer carrying member by detecting the image density using the test solid patch, and detecting the image density of the test solid patch and the test halftone patch. Next, the halftone density is controlled by controlling the laser power by detecting the image density using the test halftone patch.
[0007]
However, in the technique disclosed in the publication (3), the peripheral speed ratio of the developing carrier is controlled in order to stabilize the solid density. However, the control of the peripheral speed ratio must make the drive system expensive. I must. In particular, in the case of two-component magnetic brush development, the change in the peripheral speed ratio may cause problems such as the background fogging being changed or the trailing edge of the halftone image being white out even if the density is the same. There are practically difficult points to implement.
[0008]
In addition, what is common to the techniques disclosed in the three known documents (1), (2), and (3) above may be based on scorotron charging as the charging means. While scorotron charging is excellent in charging stability, ozone is generated.
[0009]
As charging means with very little ozone generation, contact charging means can be mentioned. However, contact charging using a charging roller or the like has a problem in that fluctuation of charging potential is large while ozone generation is very small.
[0010]
In order to suppress the fluctuation of the charging potential, there is a technique for correcting the charging output by using a reflection density detection sensor. However, it was found that the change in the charging potential before and after the correction affects the halftone potential and the halftone density changes.
[0011]
[Problems to be solved by the invention]
One of the means to ensure halftone image reproducibility is to create a test pattern of halftone density on the photoconductor, detect its reflection density with a sensor, and create the test pattern according to the detection result It is conceivable to control the light emission amount of the light source used in the above. In other words, when the reflection density is low and high, the intensity of light emitted from the light source is controlled according to the change in the reflection density.
However, when forming a test pattern with a certain halftone density by controlling the amount of light emitted from the light source, if the amount of light emitted from the light source is excessively increased, the life of the light source is adversely affected. If the number is too small, reading by the detection sensor used for determining the writing start timing cannot be performed, so that the setting of the writing start time by the light source becomes inaccurate.
[0012]
In view of the problem in the conventional image forming method and apparatus, particularly the problem in generating a test pattern when ensuring the image reproducibility of halftone density, the present invention reduces the life of the light source used for test pattern generation. The first object is to satisfactorily perform synchronous detection at the time of writing by a light source, and to favorably form an image having a halftone density, and further, an adjustment to increase the light emission amount in the light source. The second object is to prevent the light source from being directly affected by a decrease in life even when the upper limit of the light emission amount is reached, and the light emission amount from the light source is set contrary to the second purpose. The third object is to prevent the detection timing of the reflection density from being detected accurately even when the light emission amount is below the lower limit when performing the adjustment to decrease.
[0013]
[Means for Solving the Problems]
  The invention described in claim 1An image in which a photosensitive member is charged by a contact charging unit, exposed to a laser beam to form an electrostatic latent image, and the electrostatic latent image is developed by a developing device containing a developer composed of a non-magnetic toner and a magnetic carrier. In the forming method, a charging potential adjustment for adjusting the charging potential by switching a voltage applied to the contact charging unit for a predetermined time at the end of a predetermined amount N of the job or immediately after the main switch of the image forming apparatus is turned on. A pattern is formed on the photosensitive member, the reflection density of the charging potential adjustment pattern is detected by a reflection density detection sensor, and when the detection output is outside a predetermined range, the charging output is changed to a predetermined value, and the development is performed. A toner density sensor for detecting the toner density of the developer is provided inside the apparatus, and the output of the toner density sensor is compared with a predetermined toner density reference value, to the developer. A control means for controlling toner supply is provided, and at the end of the predetermined amount N of jobs, a toner density adjustment pattern is exposed and developed on the photoconductor together with the creation of the charging potential adjustment pattern, When the reflection density is detected by the reflection density detection sensor and the detection output is outside a predetermined range, the toner density reference value is changed by a predetermined value, and when a job of a predetermined amount N ′ different from the predetermined amount N is completed. Or, at the time of charging output change by the control, after creating the charging potential adjustment pattern, write a halftone density adjustment reference pattern on the photoreceptor, develop it, detect the reflection density with the reflection density detection sensor, When the detected output is outside the predetermined range, the laser beam output should be changed to a predetermined value within the predetermined upper and lower limits.It is a characteristic feature.
[0014]
  The invention according to claim 2 is the aboveLaser beamA semiconductor laser is used as a light source, and the output of the semiconductor laser is controlled according to the reflection density of the reference pattern for halftone density adjustment.Settingupper limitvalueIs set to a limit value that affects the lifetime of the semiconductor laser.
[0015]
  The invention according to claim 3 is the aboveLaser beamThe output of the semiconductor laser used as the light source isSettingupper limitvalueWhen the above is required, the output of the semiconductor laserSettingupper limitvalueOn the other hand, it is judged that the semiconductor laser or the photoreceptor is deteriorated, and this state is alerted to the outside.
[0016]
  The invention according to claim 4 is the aboveLaser beamA semiconductor laser is used as the light source, and when the output of the semiconductor laser is set by the reflection density of the reference pattern for halftone density, the aboveSettinglower limitvalueIs set to a limit value at which reading by the synchronous sensor for determining the writing time by light emission from the light source is not disabled.
[0017]
  The invention according to claim 5 is the aboveLaser beamOutput from the semiconductor laser that forms the light sourceSettinglower limitvalueIn the case where the following is required, it is characterized in that the image forming conditions other than the writing light amount are adjusted.
[0018]
According to a sixth aspect of the present invention, the charging output to the photosensitive member is targeted as an image forming condition other than the amount of writing light.
[0019]
A seventh aspect of the invention is characterized in that a developing bias is used as an image forming condition other than the writing light amount.
[0021]
  Claim8The invention described in claims 1 to7The image forming method described in one of the above is used for an image forming apparatus.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0023]
The configuration and operation of an image forming apparatus to which an image forming method according to an embodiment of the present invention is applied will be described with reference to FIG.
FIG. 1 shows a configuration around a photosensitive member common to a digital copying machine, a printer, a facsimile, or the like that forms an image by irradiating the photosensitive member with light.
[0024]
In FIG. 1, a charging roller 2 as a contact charging means is in contact with a drum-shaped photosensitive member 1, and the charging roller 2 rotates with the photosensitive member 1 rotating in the direction of the arrow. ing. At the time of image formation, the photosensitive member 1 rotates in the direction of the arrow, and the photosensitive member 1 that has been previously discharged by the light from the discharging unit 25 during this rotation is then uniformly charged by the charging roller 2.
[0025]
Instead of the charging roller 2, a charging brush may be used as a contact charging unit. The charged photosensitive member 1 is then exposed to a laser beam 20 modulated with an image signal including image information, and an electrostatic latent image is formed on the photosensitive member 1.
[0026]
In the so-called reversal development method, the electrostatic latent image formed on the photoreceptor 1 is visualized by the toner adhering to the exposed portion while passing through the developing device 3. In the developing device 3, a developer 4 made up of a carrier made of nonmagnetic toner and magnetic powder is accommodated in a case, and in the case, a developing sleeve 5 that rotates in the vicinity of the photosensitive member 1, and the developing sleeve 5 includes a paddle roller 21 for supplying the developer 4.
[0027]
The developer 4 is agitated by the rotation of the paddle roller 21 and the toner is charged by frictional charging accompanying the agitation. The outer peripheral portion of the developing sleeve 5 is made of a nonmagnetic material that rotates outside the fixed magnet. The developer 4 containing the charged toner adheres in a brush shape around the developing sleeve 5 from the paddle roller 21, and the toner constituting a part of the brush-shaped ear comes into contact with the photosensitive member 1, and the electrostatic charge on the photosensitive member. The latent image adheres to the latent image and is developed to form a so-called toner image.
[0028]
The amount of toner adhering to the electrostatic latent image is determined by the difference between the image potential on the photoreceptor 1 and the developing bias voltage applied to the developing roller 2. The image potential is determined by the initial charging potential applied by the charging roller 2 and the light intensity of the laser beam 20.
[0029]
The toner image formed on the photoconductor 1 rotates with the photoconductor 1 and reaches the transfer portion where the transfer belt 6 is in contact with the photoconductor 1. The transfer belt 6 is in contact with the photosensitive member 1 and rotates at the same linear velocity in the same direction as the photosensitive member. A transfer bias voltage having a polarity opposite to that of toner is applied to the transfer belt 6 from a power source (not shown). .
[0030]
The transfer belt 6 is controlled to be separated from the photoconductor 1 every time one job corresponding to the image forming process for one transfer paper from the charging of the photoconductor 1 to the exposure and transfer processes by the charging roller 2 is completed. Is done. For example, immediately after the main switch is turned on, preparations for adjusting the image forming conditions are made, and each apparatus is operated for smoothing, and the charging roller 2, the laser beam 20, the developing device 3 and the like are in a functional state, which will be described later. Thus, a predetermined test image pattern, for example, a toner density adjustment pattern, a charging potential adjustment pattern, or the like is formed.
[0031]
  If the transfer belt 6 is always in contact with the photosensitive member 1, it is transferred to the transfer belt 6 and erased from the photosensitive member 1 before the above test pattern is detected. The transfer belt 6 is separated from the photosensitive member 1 during the running-in operation or at the end of the job, that is, between jobs, and the jobstartIt is configured so as to be brought into contact with the photoreceptor 1 in accordance with the above. In addition to the example shown in FIG. 4, for example, there is an image forming apparatus of a type that uses a transfer charger that is arranged apart from the photoreceptor 1 instead of the transfer belt 6.
[0032]
In FIG. 1, the transfer sheet S is sent out from the registration roller 24 at such a timing that the toner image is transferred to an appropriate transfer position when it reaches the transfer portion. The toner image on the photoconductor 1 is transferred between the photoconductor 1 and the transfer belt 6 by the transfer electric field between the transfer belt 6 and the photoconductor 1 and is conveyed on the transfer paper S conveyed at the same linear velocity as the photoconductor 1. Transcribed.
[0033]
The transfer sheet S is conveyed by the transfer belt 6 even after the toner image is transferred, and reaches a fixing device (not shown) located on the downstream side of the transfer belt 6 in the conveyance direction. The toner image transferred onto the transfer paper S is unfixed, and the unfixed toner image is fixed onto the transfer paper S by thermal welding when passing through the fixing device.
[0034]
On the other hand, the toner that cannot be transferred and remains on the photosensitive member 1 further moves in the rotational direction together with the photosensitive member 1, and is dammed up and collected by the cleaning blade 7 disposed in the cleaning device 10. Residual toner collected at the site of the cleaning blade 7 is fed onto the collection coil 9 by the cooperative action of the collection blade 8 and the mylar 22 that rotate counterclockwise. The collection coil 9 is a kind of screw conveyor formed by winding a wire in a spiral shape, and can convey the developer by rotation.
[0035]
  The recovery coil 9 is partially covered with a case in such a manner that toner can be taken in the cleaning device 10, and is stored in the recovery tube from the cleaning device 10.IsAre driven to rotate. The collection pipe constitutes a path from the cleaning device 10 to the developing device 3 and opens above the paddle roller 21 of the developing device 3. Residual toner from the photosensitive member 1 collected by the cleaning device 10 is collected by the developing device 4 through the collection tube by the rotation of the collection coil 9 and circulated for use.
[0036]
The image density adjustment in the image forming apparatus having the above configuration is performed according to the following procedure.
If the light intensity of the laser beam 20 is constant, the image density of the image formed on the photosensitive member 1 is always constant, and the developer concentration charged by the charging roller 2 is constant. As long as is constant, it should be constant. Actually, however, the photosensitive member 1 varies due to factors such as deterioration over time or a large variation in charging potential as a characteristic of the charging roller 2. .
[0037]
  In order to eliminate the fluctuation of the image density due to the above cause and maintain the image density at a predetermined constant level, the image density is adjusted. In order to adjust the image density, (a) on the photoreceptor 1For charging potential adjustmentThis forms a toner patternFor charging potential adjustmentAdjusting the charging voltage by the charging roller 2 so that the density of the toner pattern becomes a predetermined reference level, (b)A solid image toner pattern for adjusting toner density is formed on the photoreceptor 1 separately from the charging potential adjusting pattern, and the density of the toner density adjusting pattern is set to a predetermined reference level.Developer 4 carrier to toner ratioAdjustControl relating to the two adjustments is performed.
[0038]
A test image pattern is created on the photosensitive member 1 for the adjustment of the above (a) and (b), and a detecting means for detecting this image pattern is provided. This detection means is a reflection density detection sensor 16 (hereinafter referred to as a P sensor) provided around the photosensitive member 1 shown in FIG. 1 and between the transfer belt 6 and the cleaning blade 7. Detection information from the P sensor 16 is output to the control means 23 described later.
[0039]
In FIG. 2, the control means 23 has a function of controlling the entire image forming process in the image forming apparatus, and a P sensor 16 is connected to the input side via an I / O interface (not shown). On the output side of the control means 23, a drive control unit for the LD, a drive unit for adjusting the charging potential in the charging device (for the sake of convenience, reference numeral 2 shown in FIG. 1), and the developer concentration in the developing device are corrected. A drive unit (for convenience, reference numeral 3 shown in FIG. 1), a drive unit for changing the amount of writing light (for convenience, reference numeral 20 shown in FIG. 1), a drive part for forming various toner patterns, A drive unit for executing other image forming processes such as paper feeding, and a display unit AL and a transmission unit TM of an operation panel used for alarming are connected to each other, which will be described later.
[0040]
For the toner density adjustment (b), a toner density sensor (hereinafter referred to as a T sensor) 17 for detecting the toner density is provided in the developing device 3 shown in FIG. Detection information from the T sensor 17 is output to the control means 23. For this reason, the T sensor 17 is connected to the input side of the control means 23.
[0041]
  The output of the T sensor 17 is compared with a predetermined toner density control reference value in the control means 23. If it is determined that the toner density is low, toner supply from a toner bottle (not shown) is promoted in the developing device 3 so that the output of the T sensor 17 becomes a predetermined toner density control reference value. If it is determined that the toner concentration is higher than a predetermined toner concentration control reference value, the toner supply amount per time is adjusted so that the toner supply is suppressed to a predetermined toner concentration control reference value.
[0042]
The P sensor 16 is not operated immediately after the main switch is turned on for detection of the toner density adjustment pattern, but every time a fixed amount of jobs, that is, every time a fixed amount of image formation is performed, for example, every time a predetermined number of recording sheets S are output. To be operated. Since the control means 23 shown in FIG. 2 controls the entire image forming process, it grasps the progress of the image forming process and the job amount at that time.
[0043]
  When it is determined by the control means 23 that the P sensor 16 is operating, the control means2According to the program 3, the optical writing means is operated, and a black solid toner density adjustment pattern is written on the photosensitive member 1 with a predetermined size by the laser beam 20 emitted from the LD.
[0044]
The toner density adjustment pattern is developed by the developing device 3. In this process, the transfer belt 6 is separated from the photoreceptor 1 in advance so as not to erase the toner density adjustment pattern. Therefore, the toner density adjustment pattern passes through the transfer portion and passes in front of the P sensor 16 without any damage.
[0045]
  The P sensor 16 detects the reflection density of the toner density adjustment pattern and outputs the output to the control means 23. The control means 23 sets the output value from the P sensor 16 to a preset target.ReflectionCompared with standard concentrationDo. The toner density adjustment pattern is the targetReflectionJudged to be thinner than the standard concentrationWhenT sensor 17Toner densityControl reference valueThe toner supply is promoted and the shift is made so that the toner density is increased.
[0046]
  The toner density adjustment pattern is the targetReflectionJudged to be darker than the density reference valueWhenT sensor 17Toner densityControl reference valueThe shift is made so that the toner supply is suppressed and the toner density is lowered.In this way, the solid density of the black solid toner density adjustment pattern can be adjusted to a predetermined reference level, so that the solid density of the output image can be kept constant.
[0047]
  Output of P sensor 16Based onT sensorToner densityFor how much the control reference value is shifted,Determined experimentally.
[0048]
The above is the control for stabilizing the solid density by the toner density control.
Next, a procedure for correcting the charging output of the charging roller 2 using the P sensor 16 will be described. In accordance with the formation of the toner density adjustment pattern, a charging potential adjustment pattern is formed on the photosensitive member 1 with a shift from the formation position of the toner density adjustment pattern.
[0049]
This charge potential adjustment pattern is created only when a predetermined amount of job is completed, whereas the above-mentioned toner density adjustment pattern is formed at the end of a predetermined amount of job (when a fixed number of sheets are output), It is also created during idle running when the main switch of the device is on. As described above, the charging potential adjustment pattern is formed and the P sensor 16 is operated in both of the two cases immediately after the main switch is turned on and after the predetermined output. This is because, after the job is completed, after the image forming apparatus has been stopped for a long period of time, the charged potential fluctuations due to environmental changes may be large, so that it is necessary to correct the charge output even immediately after the main switch is turned on.
[0050]
  In the operation of the P sensor 16 for adjusting the charging output, the voltage applied to the charging roller 2 is switched to a predetermined charging output set in advance.To create a charging potential adjustment pattern.It is done.
[0051]
  Charge potential adjustmentforThe pattern isToner densityAs in the case of the adjustment pattern, it passes under the P sensor 16 without being disturbed by the transfer belt 6 being separated from the photoreceptor 1 in advance. The detection output of the charging potential adjustment pattern detected by the P sensor 16 during this passage is input to the control means 23 and compared with a preset reference value.
[0052]
In the comparison between the detection output of the charging potential adjustment pattern by the P sensor 16 and the reference value, when the density of the charging potential adjustment pattern is high, it is determined that the voltage value applied to the charging roller 2, that is, the charging output is low, When the density of the charge potential adjustment pattern is low so as to increase the charge output, it is determined that the charge output is high, and the control means 23 corrects the charge output so as to decrease the charge output.
[0053]
In this way, immediately after the main switch is turned on, the charging potential adjustment pattern is formed during idle running, which is the preparatory operation of the image forming apparatus, and the charging output is corrected if necessary. A charging potential adjustment pattern is formed on the toner, and if necessary, charging output is corrected, and a toner density adjustment pattern is formed to adjust toner density.
[0054]
  Next, the control of the halftone density will be described as follows. When adjusting the charging potentialBandIf the charge output is corrected based on the electric potential adjustment pattern, the charge output before the charge potential changeover is not used for the charge output changeover.PowerAs a result of the change in the halftone charging potential determined as a reference, it has been found that the halftone latent image potential also changes, and the halftone density may deviate from the target density. Therefore, in the control described above, when the voltage applied to the charging roller 2 is changed, the density is adjusted independently for the halftone. Therefore, a halftone density adjustment pattern is created and this halftone is adjusted. Based on the density adjustment pattern, when the reflection density is detected using the P sensor 16 as in the case of the charge potential adjustment pattern, and the detected output deviates from a predetermined output range for halftones, The halftone density was adjusted by changing the amount of image writing light. Since the LD (laser diode) is used as the image writing means in this example, the image writing light amount is a predetermined value (experimentally) determined by the amount of light emitted from the LD deviating from the predetermined output range. So that the halftone density is kept constant. Further, since the halftone latent image potential also changes due to the deterioration of the photoconductor over time, the halftone density is maintained even at a predetermined interval corresponding to a certain number of outputs of the transfer sheet S determined experimentally, for example. A reference pattern for adjustment was created.
[0055]
  On the other hand, when adjusting the halftone density by creating a reference pattern for adjusting the halftone density, if the output of the LD is increased in order to change the amount of light in the LD, the high output may adversely affect the life of the LD. Effect. On the other hand, when the output of the LD is lowered, the reference pattern by the synchronization sensor that detects the synchronization for starting the LD writing cannot be read depending on the reduction width, and the writing scanning timing by the LD becomes inaccurate. Also turned out. In the present invention, in view of such a problem that occurs when changing the amount of light in the LD, the change in the LD output is kept within a predetermined range. Especially in the predetermined rangeSettingThe upper limit is set to a limit value that does not adversely affect the life of the LD,SettingThe lower limit is set as a limit value at which unreadable reading does not occur in the synchronous sensor for setting the writing scanning timing.
[0056]
  In the present invention, the control means 23 sets the LD output within the predetermined range described above.SettingUpper limitValue (Setting upper limit value)If you need a higher output thanSettingWhile stopping at the upper limit, this state is warned to the outside that the light emission performance has been degraded including the life of the LD or that the photoreceptor has deteriorated. As the alarm means to the outside, as shown in FIG. 2, display on the operation panel in the image forming apparatus (for convenience, a display unit indicated by symbol AL in FIG. 2) or the like is possible. The alarm by is used. The alarm by communication means that a transmission means (a member indicated by symbol TM in FIG. 2 for convenience) is connected to the control means 23 in the image forming apparatus, and the aboveSettingupper limitvalueWhen the above output request occurs, the transmission means is operated. The transmission destination corresponds to a service center. For this reason, since a service man call can be automatically performed together with an alarm to the operator, there is no trouble that the operator cannot grasp the cause of the failure.
[0057]
  In the LD output setting, a predetermined range ofSettinglower limitValue (setting lower limit value)When a lower output is required, the LD output is not changed, and the charging output or development bias corresponding to the image forming conditions other than the writing conditions is changed. . In this case, the change amount under the image forming conditions is set to a change amount that can obtain the same state as the density of the intermediate density adjustment reference pattern due to the LD output change.
[0058]
  In the present embodiment, halftone density control is executed by the following procedure using the above configuration. 3 and 4 are flow charts for explaining the operation of the control means 23. In FIG.ofMain switch on is turned on or more than a predetermined amount of jobsofIt is determined whether it is an end time. It is determined whether the image forming apparatus is in any of these states and is in an idle state that is a preparation state for the image forming process (step P1).
[0059]
The condition that the job is completed in step P1 is that the image forming apparatus of the type in which the transfer belt 6 is in contact with the photosensitive member 1 as shown in FIG. Since it is configured to be automatically separated from the photosensitive member 1 and to be in contact with the photosensitive member 1 during a job, even if a charging potential adjustment pattern, a toner density adjustment pattern, or the like is formed on the photosensitive member 1, transfer is performed. This is because these patterns are transferred to the belt 6 and cannot be detected by the P sensor 16.
[0060]
On the other hand, since the transfer belt 6 is automatically separated from the photosensitive member 1 at the end of the job, even if a charging potential adjustment pattern, a toner density adjustment pattern, or the like is formed on the photosensitive member 1, these patterns are used. Can be detected by the P sensor 16. However, when a transfer charger is used instead of the transfer belt 6, the transfer charger is disposed apart from the photosensitive member 1, and even if these patterns are formed, the pattern is not disturbed. The time condition is no longer necessary.
[0061]
The reason why the job is a predetermined amount (predetermined number of times) is that it is preferable to correct the charging potential and the toner density at every interval where the toner density and the charging potential change with time. For example, assume that a predetermined amount of jobs is N = 10 output sheets of transfer paper. Whether or not these conditions are satisfied is determined by the control means 23.
[0062]
In the following process, the detection of the toner density adjustment pattern is performed every time the job by the image forming apparatus, that is, the image recording is the output of the transfer paper and the predetermined number N = 10 or more, and immediately after the main switch is turned on. Don't do it. If it is performed immediately after the main switch is turned on, only the control reference value of the toner density may be greatly shifted even though only the main switch is frequently turned on and off, even though the actual toner density does not change. It is.
[0063]
On the other hand, the output control of the applied voltage to the charging roller 2 is desirably performed immediately after the main switch is turned on. Immediately after the main switch is turned on, it is usually immediately after the image forming apparatus has not been operated for a while, such as 1 day, 2 days, etc., and the machine part remains stopped before the main switch is turned on. It means that I was doing. During this stop, the surrounding environment of the image forming apparatus often changes, and the charging performance by the charging roller 2 also often changes. Therefore, charging output correction and halftone potential correction are necessary. When these conditions are satisfied, the process proceeds to Step P2.
[0064]
In step P2, the charging output V, which is the voltage applied to the charging roller 2, is set to v-v1 obtained by dropping a predetermined value v1 from the existing value v for a predetermined time. 1 is charged, and a charging potential adjustment pattern in an area corresponding to the predetermined time is created. Further, the image forming apparatus is set to a mode in which data sampling can be performed by turning on the P sensor 16 so that it can be detected.
[0065]
Note that if the image forming apparatus is at the end of a predetermined amount of job, toner density adjustment is performed, and the charging output is charged with the existing value v by the laser beam 20 with the LD as the light source at full power in step P3. A predetermined area in the formed area is exposed with a toner density adjustment pattern and developed by the developing device 3 to create a toner density adjustment pattern.
[0066]
On the photoreceptor 1, a ground region with a charging potential of an existing value v, a charging potential adjustment pattern with a charging potential of v−v 1, and a predetermined LD close to full power on the background region with a charging potential of an existing value v. Three regions of the toner density adjustment pattern formed by the laser beam 20 by the output are formed. The background area is white with no toner on it, the charging potential adjustment pattern is slightly covered with toner, and the toner density adjustment pattern is solid black.
[0067]
In step P4, the P sensor 16 detects the density of these three regions. The P sensor 16 includes a pair of a light emitting element and a light receiving element, and the reflected light of the light emitted from the light emitting element is received by the light receiving element and input to the control means 23 as an electrical output obtained by photoelectric conversion.
[0068]
In step P4, the detection output Vsg of the P sensor 16 for the background area based on the charging potential of the existing value v from the detection data of the P sensor 16 collected at experimentally determined intervals on the surface of the photoreceptor 1, and v The detection output Vsdp of the P sensor 16 for the charging potential adjustment pattern based on the charging potential of −v1 and the detection output Vsp of the P sensor 16 of the toner density adjustment pattern are obtained. Furthermore, the ratio of these detection outputs, Vsdp / Vsg, Vsp / Vsg is calculated by the control means 23.
[0069]
Next, in a flow after Step P5, it is determined whether Vsdp / Vsg is within a predetermined range, and predetermined charging output correction is performed.
[0070]
In step P5, a predetermined lower limit value of Vsdp / Vsg is set to a, and an upper limit value is set to b. If it is determined in step P5 that a <Vsdp / Vsg is not satisfied, the charging potential adjustment pattern charging potential is lower than a predetermined lower limit value a. Therefore, in step P8, the charging output is a <Vsdp. The value is increased by a value that can satisfy the condition of / Vsg, and after that, the charging output is set so as to proceed to Step P9.
If it is determined in step P5 that a <Vsdp / Vsg, the relationship with the lower limit value a satisfies the condition, and the process proceeds to step P6. In step P6, Vsdp / Vsg is compared with the upper limit value b. If b> Vsdp / Vsg, the condition is also satisfied in relation to the upper limit value b, and the process proceeds to step P9.
[0071]
If b> Vsdp / Vsg is not satisfied in step P6, the charging potential adjustment pattern charging potential is higher than the reference upper limit value b, so that the charging output satisfies the condition of b> Vsdp / Vsg in step P7. Then, the value is lowered by a predetermined value, and after that, the charging output is set so as to proceed to Step P9.
[0072]
In Step P9, it is determined whether or not the toner density adjustment pattern has been written in the upstream flow.
[0073]
  As already mentioned,When the main switch is ON, not when the job endsNo toner density adjustment. Therefore,The toner density adjustment pattern is not written, and the process proceeds directly from step P9 to step P13 and the subsequent steps, and the process proceeds to a halftone density adjustment flow. If the current state is the end of the job, since the toner density adjustment pattern is written in step P3, the process proceeds from step P9 to step P10. In steps P10 and P11, Vsp / Vsg is within a predetermined range. Whether the toner density is adjusted or not is determined.
[0074]
In step P10, the predetermined upper limit value of Vsp / Vsg is set to c, and in step P11, the predetermined lower limit value is set to d. If it is determined in step P10 that c> Vsdp / Vsg is not satisfied, it means that Vsp / Vsg is larger than the predetermined upper limit value c, so that the density of the toner density adjustment pattern is lighter than the reference. In step P13, the toner density control reference value is increased by a predetermined amount to promote toner replenishment, and the process proceeds to step P14.
[0075]
If it is determined in step P10 that c> Vsp / Vsg, Vsp / Vsg is smaller than the predetermined upper limit value c, so that the density of the toner density adjustment pattern is at least in a range less than the upper limit value. Means. In this case, since it is necessary to check whether or not it is in the range exceeding the lower limit, the process proceeds to Step P11.
[0076]
  In step P11, Vsp / Vsg is compared with the lower limit value d, and if d <Vsp / Vsg, the condition is also satisfied in relation to the lower limit value d, so the process proceeds to step P14. D in step P11<If it is not Vsp / Vsg, it means that the density of the toner density adjustment pattern is higher than the reference. Therefore, the toner density control reference value is lowered by a predetermined amount in step P12 so that toner supply is suppressed, and the process proceeds to step P14.
[0077]
In the flow after Step P14, the halftone density is adjusted. First, in step P14, the reference of the halftone density has changed when the charge output has already been switched in step P7, step P8, etc. in the upstream flow, or a predetermined amount from the previous adjustment. When the number of output sheets of the transfer sheet is N ′ = 1000, and a job of a predetermined amount N ′ or more is being performed in step P14, the halftone density has changed due to deterioration of the photoreceptor over time or the like. When any of these conditions is met, the process proceeds to the next step P15. When charging output switching has already been performed in step P7, step P8, etc., the process proceeds to step P15 regardless of whether or not the job has ended.
[0078]
  In step P15, the LD is output under the charge output after being corrected by the charging roller 2 in step P7, step P8, or the like.ByA halftone density adjustment reference pattern is written.. During ~The dots constituting the halftone density adjustment reference pattern form a halftone density adjustment reference pattern with the laser beam 20 having a light amount (light emission time) that is halftone.
[0079]
  In step P16,Halftone densityAssuming that the detection output of the P sensor 16 for the adjustment pattern is Vsm, the control means 23 calculates a ratio with the detection output Vsg that has already been detected.
[0080]
  Vsm / Vsg in the flow after step P17Based onCorrection to make the halftone density constant is performed. In step P17, Vsm / VsgTo make halftone density constantLet e be the upper limit and f be the lower limit.. TheIn step P17, e> VsmIf it is determined that it is not / Vsg, the detected output of the reference pattern for halftone density adjustment is larger than the reference, which means that the density of the reference pattern for halftone density adjustment is lighter than the reference. Therefore, in step P20, the LD light amount is increased by a predetermined amount so that the halftone density falls between the lower limit value e and the upper limit value f. On the other hand, if it is determined in step P17 that e> Vsm / Vsg, the condition is satisfied in relation to the upper limit value e, and the process proceeds to step P18.
[0081]
In step P18, Vsm / Vsg is compared with the lower limit value f. If f <Vsdp / Vsg, the condition is satisfied even in relation to the lower limit f, and the LD light quantity condition is not changed.
If f <Vsm / Vsg is not satisfied in step P18, the detection output of the halftone density adjustment reference pattern is lower than the lower limit reference, and therefore the density of the halftone density adjustment reference pattern is darker than the reference. Means that. Therefore, in step P19, the LD light amount is lowered by a predetermined amount so that the halftone density falls between the upper limit value e and the upper limit value f.
When halftone density adjustment is completed in this way, multi-level halftone processing is performed by adjusting the conditions for the other halftone halftones based on the adjusted halftone writing conditions. The tone can be obtained stably.
[0082]
  If it is determined in step P17 that e> Vsdp / Vsg, the LD output is increased, but the output value to be increased in step P21 isSettingIt is determined whether or not the upper limit value is exceeded.This set upper limit value is a limit value that does not adversely affect the above-described LD life.
[0083]
  LD output is set in step P21upper limitIf this is the case, turn the LD outputSettingThe operation to the operation panel AL or transmission means of the image forming apparatus is performed in order to warn that the machine is in an abnormal state including stopping the upper limit value and indicating that the LD has reached the end of its life or that the photoreceptor has deteriorated. A signal is output from the control means 23 (step P22).
[0084]
  In Step P18, the result of comparing Vsm / Vsg with the lower limit f is not f <Vsdp / VsgIn addition,LD outputSettingMust be below the lower limitTheThe determination is made at step P23.The This setting lower limit value is a limit value at which reading by the synchronous sensor is not disabled. From the setting lower limitIf you need to lower it,SettingThe charging output or developing bias that changes the image forming condition other than the writing condition while changing to the lower limit value is changed. In this case, a method of increasing the charging potential of the photosensitive member during pattern formation or a method of decreasing the developing bias is employed.
[0085]
【The invention's effect】
  According to the first and second aspects of the present invention, when the amount of image writing light is changed by the control means, the amount of change is within a predetermined range.SettingSince the upper limit is set to a limit value that affects the life of the semiconductor laser used as the light source, it is possible to prevent a decrease in the life of the semiconductor laser caused by inadvertently increasing the light emission amount.
[0086]
  According to the invention of claim 3, the output of the light emission amount of the semiconductor laser used as the light source is within a predetermined range.SettingIf more than the upper limit is required, reduce the output of the semiconductor laser.SettingWhile stopping at the upper limit, it is possible to warn that the semiconductor laser or the photoreceptor is deteriorated. Accordingly, it is possible to shorten the image formation interruption period by promptly performing a service man call or the like.
[0087]
  According to invention of Claim 4, when setting the output of the semiconductor laser used as a light source in a predetermined range,SettingSince the lower limit is set to a limit value at which reading by the synchronous sensor for determining the writing time does not occur, it is possible to prevent the writing start time using the semiconductor laser from becoming inappropriate and to prevent writing failure. It becomes possible.
[0088]
  Claims 5 to7According to the described invention, the output of the semiconductor laser used as the light source is within a predetermined range.SettingIf requested below the lower limit, writeIncludedThe halftone density image reproducibility is reduced by changing the charging output or development bias, which is an image forming condition other than the amount of light, to obtain an image with a halftone density equivalent to that when changing the output of the semiconductor laser. It is possible not to let it.
[0089]
  Claim8According to the described invention, it is possible to reproduce halftone density images without reducing the life of the light source or causing an erroneous operation in the writing operation.Image forming apparatus can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a main configuration of an image forming apparatus to which an image forming method according to an embodiment of the present invention is applied.
FIG. 2 illustrates a configuration of a control unit used in the image forming apparatus illustrated in FIG.YouIt is a block diagram for
FIG. 3 is a flowchart for explaining the operation of the control means shown in FIG. 2;
4 is a flowchart showing an operation executed continuously from the flowchart shown in FIG. 3;
[Explanation of symbols]
2 Charging roller
16 Reflection density detection sensor
23 Control means
AL Operation panel display
TM transmission means

Claims (8)

After charging the photoreceptor by contact charging means,
An electrostatic latent image is formed by exposure with a laser beam ,
In the image forming method of developing the electrostatic latent image by a developing device containing a developer composed of a non-magnetic toner and a magnetic carrier ,
When the predetermined amount N of the job is completed or immediately after the main switch of the image forming apparatus is turned on, the charging potential adjustment pattern for adjusting the charging potential is exposed by switching the voltage applied to the contact charging unit for a predetermined time. Create on the body, detect the reflection density of the charge potential adjustment pattern with the reflection density detection sensor, change the charge output to a predetermined value when the detection output is outside the predetermined range,
A toner density sensor for detecting the toner density of the developer is provided in the developing device, and a control means for controlling the toner supply to the developer by comparing the output of the toner density sensor with a predetermined toner density reference value is provided. ,
At the end of the predetermined amount N of jobs, along with the creation of the charging potential adjustment pattern, the toner density adjustment pattern is exposed and developed on the photosensitive member, and the reflection density detection sensor detects the reflection density. When the detected output is outside the predetermined range, the toner density reference value is changed to a predetermined value,
At the end of a job of a predetermined amount N ′ different from the predetermined amount N, or when changing the charging output by the control, a halftone density adjustment reference pattern is written on the photosensitive member after development of the charged potential adjustment pattern and developed. The reflection density detection sensor detects the reflection density, and when the detection output is outside the predetermined range, the laser beam output is changed to a predetermined value within a predetermined range between the set upper limit value and the set lower limit value. image forming method, characterized in that. The image forming method according to claim 1.
A semiconductor laser is used as the laser beam light source, and the output of the semiconductor laser is controlled in accordance with the reflection density of the reference pattern for halftone density adjustment, and the set upper limit value affects the life of the semiconductor laser in the control. An image forming method, characterized in that a limit value is set. The image forming method according to claim 1 or 2,
While stopping the output of the semiconductor laser to set the upper limit value when the output of the semiconductor laser used as the laser beam source is requested or the set upper limit value, the deterioration determination and to this state of the semiconductor laser or the photoreceptor An image forming method characterized by alarming outside. The image forming method according to claim 1.
A semiconductor laser is used as the laser beam light source, and when the output of the semiconductor laser is set by the reflection density of the reference pattern for halftone density, the setting lower limit value is used to determine the writing timing by light emission from the light source. An image forming method, characterized in that the threshold value is set such that reading by a synchronous sensor is not disabled. The image forming method according to claim 1 or 2,
An image forming method comprising adjusting an image forming condition other than a write light amount when an output from a semiconductor laser constituting the laser beam light source is required to be equal to or lower than the set lower limit value . The image forming method according to claim 5.
An image forming method characterized in that a charging output to the photosensitive member is targeted as an image forming condition other than a write light amount. The image forming method according to claim 5.
A developing bias is used as an image forming condition other than the write light amount.   An image forming apparatus using the image forming method according to claim 1.

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