JP2002174930A - Method and device for forming image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming method for stabilizing halftone density by preventing the life of a light source used at the time of stabilizing the halftone density from being deteriorated and also preventing a writing operation using the light source from becoming instable. SOLUTION: The device is provided with a control means for adjusting an electrified potential by switching a voltage applied on a contact electrification means at prescribed intervals, also, forming a halftone density adjusting reference toner pattern in addition to the aforesaid toner pattern, then, adjusting the reflection density of the halftone density adjusting reference toner pattern by varying an image writing light quantity based on the detection output of the aforesaid sensor, and then, adjusting a halftone writing condition, and as for the control means, the variation of the image writing light quantity is set within a prescribed extent in the case of varying the image writing light quantity in accordance with the reflection density of the halftone density adjusting reference pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method for an image forming apparatus such as a digital copying machine, a printer, a facsimile, etc., which forms an image by irradiating a photoreceptor with a light laser beam. The present invention relates to a process control for ensuring reproducibility of an image having the following.

[0002]

2. Description of the Related Art Conventionally, maintaining a constant halftone density in an electrophotographic apparatus has been an important technical problem in maintaining stable image quality. The following is known as a technique for adjusting the halftone density in an image forming apparatus.

An image forming apparatus disclosed in JP-A-6-208715 An image forming apparatus disclosed in JP-A-8-265570 An image forming apparatus disclosed in JP-A-8-297834 The disclosed technology provides an image forming apparatus capable of stably performing density reproducibility of an intermediate density portion, which is important in a multi-gradation digital image forming apparatus, among image density fluctuations based on sensitivity fluctuations of a photoconductor. For the purpose of
The configuration is such that a control potential VGS of a charging unit 402 for charging the photosensitive member 401 at a target dark potential VHS is calculated, and a detection potential of a latent image patch on the photosensitive member 401 charged with the control potential VGS, and a latent image The amount of light laser beam VLS for obtaining the target halftone potential VMS is calculated based on the amount of exposure of the patch, and the fog prevention potential VC is subtracted from the target dark potential VHS to calculate the developing bias potential VB.
GS, the amount of light laser beam LDS, and the control means for setting the developing bias potential VB are provided. However, the technique disclosed in this publication presupposes the potential detection and requires an expensive electrometer.

[0004] The technique disclosed in the above publication relates to an image forming apparatus, which aims to provide an image forming apparatus capable of accurately controlling the density of a halftone image. An image forming apparatus for forming an image by adhering toner onto the image carrier, a pattern forming means for forming an image density detection pattern on the image carrier, and an image for detecting an image density by the toner adhered 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-step gradation pattern provided in the control unit and generated by the pattern formation unit. Output of the image density detecting means of
That is, a gradation table for storing a relationship with the image density is provided.

However, in the technique disclosed in this publication, a plurality of halftone patterns are generated when the halftone density is detected, so that detection control takes time. Also,
Adjusting the halftone density is done by PWM (pow) of LD (laser diode).
er wide modulation) (emission time)
The adjustment range is coarse.

The technique disclosed in the above-mentioned publication relates to an image forming apparatus, and an object thereof is to provide an image forming apparatus capable of accurately controlling a toner adhesion amount from a halftone to a solid image. An image forming apparatus for forming an image by adhering toner on an image carrier, comprising: a patch forming unit for forming a test solid patch and a test halftone patch on the image carrier; Image density detecting means for detecting the image density of the test solid patch and the test halftone patch,
The solid density is controlled by controlling the peripheral speed ratio of the developer carrier by detecting the image density using the test solid patch, and then controlling the laser power by controlling the image density using the test halftone patch to control the halftone density. I do.

However, in the technique disclosed in the above publication, 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 requires an expensive drive system. Must. In particular, in the case of two-component magnetic brush development, changing the peripheral speed ratio may cause problems such as fogging of the background and the trailing edge of a halftone image being whitened even if the density is the same. There are practical difficulties.

What is common to the techniques disclosed in the above three known documents is that scorotron charging is premised on the charging means in some cases.
Scorotron charging has excellent charging stability,
Ozone is generated.

Contact charging means can be cited as an example of a charging means that generates very little ozone. Contact charging using a charging roller or the like, however, has a problem in that although the generation of ozone is very small, the fluctuation of the charging potential is large. .

In order to suppress the fluctuation of the charging potential, there is a technique for correcting the charging output using a reflection density detecting sensor. However, it has been found that the change in the charging potential before and after the correction affects the halftone potential and changes the halftone density.

[0011]

As one of means for ensuring image reproducibility of halftone density, a test pattern of halftone density is formed on a photoreceptor, and the reflection density is detected by a sensor. It is conceivable to control the light emission amount of the light source used for creating the test pattern according to the result. That is, when the reflection density is low and high, the intensity of the light emission amount of the light source is controlled according to the change in the reflection density. However, when forming a test pattern having a constant halftone density by controlling the light emission amount of the light source, if the light emission amount of the light source is excessively increased, the life of the light source is adversely affected. If the number is too small, reading by a detection sensor used to determine the writing start timing cannot be performed, and the setting of the writing start timing by the light source becomes inaccurate.

The present invention has been made in view of the above-described problems in the conventional image forming method and apparatus, particularly, in generating a test pattern when ensuring image reproducibility of a halftone density, and thus a light source used for generating a test pattern. The first object of the present invention is to prevent a decrease in the life of the light source and to surely perform synchronization detection at the time of writing by a light source so that an image with a halftone density can be favorably formed. The second object is to prevent the life of the light source from being directly affected even when the light emission amount reaches the upper limit when performing the adjustment for the light source, and conversely to the second object, A third object of the present invention is to prevent the detection timing of the reflection density from being unable to be accurately detected even when the light emission amount has reached a lower limit or less when performing the adjustment for reducing the light emission amount. It is.

[0013]

According to the first aspect of the present invention,
In an image forming method in which a toner pattern is formed on a photoreceptor by a contact charging unit, a reflection density of the toner pattern is detected by a sensor, and a toner density and a charging potential by the contact charging unit are adjusted, the toner pattern is formed at predetermined intervals. The charging potential is adjusted by switching the voltage applied to the contact charging unit, and a halftone density adjusting reference toner pattern is created separately from the toner pattern, and the reflection density of the halftone density adjusting reference toner pattern is adjusted. Control means for adjusting the image writing light amount based on the detection output of the sensor to prepare a halftone writing condition, wherein the control means adjusts the image in accordance with the reflection density of the halftone density adjustment reference pattern. When the write light amount is changed, the change amount is set within a predetermined range.

According to a second aspect of the present invention, a semiconductor laser is used as the light source, and the output of the semiconductor laser is controlled in accordance with the reflection density of the halftone density adjustment reference toner pattern. Is set to a limit value that affects the life of the semiconductor laser.

According to a third aspect of the present invention, when the output of the semiconductor laser used as the light source is required to be higher than the upper limit of the predetermined range, the output of the semiconductor laser is stopped at the upper limit, while the output of the semiconductor laser or the photosensitive member is stopped. It is characterized in that it is determined that the battery has deteriorated and an alarm is issued to the outside of this condition.

According to a fourth aspect of the present invention, a semiconductor laser is used as the light source, and when the output of the semiconductor laser is set by the reflection density of the halftone density reference toner pattern, the lower limit of the predetermined range is set to the light source. It is characterized in that it is set to a limit value at which reading by a synchronous sensor for determining a writing time by light emission at the time is not disabled.

According to a fifth aspect of the present invention, when the output of the semiconductor laser as the light source is required to be lower than the lower limit of the predetermined range, image forming conditions other than the writing light amount are characterized.

According to a sixth aspect of the present invention, as the image forming condition other than the writing light amount, the charge output to the photosensitive member is targeted.

The invention according to claim 7 is characterized in that a developing bias is used as an image forming condition other than the writing light amount.

According to an eighth aspect of the present invention, the image forming conditions other than the writing light amount are such that the image density in the halftone density adjustment reference toner pattern corresponds to the halftone image density. I have.

According to a ninth aspect of the present invention, an image forming method according to one of the first to eighth aspects is used.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

The configuration and operation of the image forming apparatus to which the image forming method according to the embodiment of the present invention is applied will be described with reference to FIG. FIG. 1 shows a configuration around a photoreceptor common to a digital copying machine, a printer, a facsimile, etc., which irradiates a photoreceptor with light to form an image.

In FIG. 1, a charging roller 2 serving as a contact charging means is in contact with a photosensitive member 1 in a drum shape, and the charging roller 2 rotates along with the photosensitive member 1 rotating in the direction of an arrow. It has become. When forming an image,
The photoreceptor 1 rotates in the direction of the arrow, and during this rotation, the photoreceptor 1 that has been previously neutralized by light from the neutralization unit 25 is uniformly charged by the charging roller 2.

It should be noted that a configuration may be adopted in which a charging brush is brought into contact as contact charging means instead of the charging roller 2. The photoreceptor 1 charged in this way is thereafter exposed by receiving a laser beam 20 modulated with an image signal containing image information, and is exposed, so that an electrostatic latent image is formed on the photoreceptor 1.

In the so-called reversal development system, 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 case 4 contains a developer 4 composed of a carrier made of non-magnetic toner and magnetic powder. The case includes a developing sleeve 5 rotating close to the photoreceptor 1 and a developing sleeve 5. 5 is provided with a paddle roller 21 for supplying the developer 4 and the like.

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 non-magnetic material rotating outside the fixed magnet. The developer 4 containing the charged toner adheres from the paddle roller 21 to the periphery of the developing sleeve 5 in a brush-like manner, and the toner constituting a part of the brush-like spike comes into contact with the photoreceptor 1 and the electrostatic on the photoreceptor The latent image is adhered to the latent image by electrostatic action and developed to form a so-called toner image.

The amount of toner adhering to the electrostatic latent image is determined by
It is determined by the difference between the upper image potential and the developing bias voltage applied to the developing roller 2. Further, the image potential is set at the charging roller 2.
Of the initial charge given by the laser beam 2
It is determined by the light intensity of 0.

The toner image formed on the photoreceptor 1 rotates together with the photoreceptor 1 and reaches a transfer portion where the transfer belt 6 is in contact with the photoreceptor 1. The transfer belt 6 is in contact with the photoconductor 1 and rotates at the same linear velocity in the same direction as the photoconductor, and a transfer bias voltage having a polarity opposite to that of the toner is applied to the transfer belt 6 from a power supply (not shown). .

The transfer belt 6 is separated from the photoreceptor 1 each time one job corresponding to an image forming process for one transfer sheet from charging of the photoreceptor 1 by the charging roller 2 to exposure and transfer is completed. Is controlled as follows. For example,
Immediately after the main switch is turned on, preparations for adjusting image forming conditions are made, each device is operated in a smoothing mode, and the charging roller 2, the laser beam 20, the developing device 3 and the like are in a functional state. Then, a predetermined test image pattern, for example, a toner density adjustment pattern, a charging potential adjustment pattern, and the like are formed.

If the transfer belt 6 is always kept in contact with the photosensitive member 1, the test pattern is transferred to the transfer belt 6 and erased from the photosensitive member 1 before the test pattern is detected. The transfer belt 6 is separated from the photoconductor 1 during the running-in operation immediately after the power is turned on or at the end of the job, that is, between jobs, and is brought into contact with the photoconductor 1 according to the job. I have. FIG.
In addition to the example shown in FIG. 1, there is an image forming apparatus of a type that uses a transfer charger that is arranged separately from the photoconductor 1 instead of the transfer belt 6.

In FIG. 1, the transfer paper S is fed from the registration roller 24 at such a timing that the toner image is transferred to an appropriate transfer position when reaching the transfer portion. Due to the transfer electric field between the transfer belt 6 and the photoreceptor 1, the toner image on the photoreceptor 1 is transferred onto the transfer paper S sandwiched between the photoreceptor 1 and the transfer belt 6 and conveyed at the same linear speed as the photoreceptor 1. Transcribed.

The transfer paper S is conveyed by the transfer belt 6 even after the transfer of the toner image, and reaches a fixing device (not shown) located downstream of the transfer belt 6 in the conveyance direction. The toner image transferred onto the transfer sheet S is unfixed, and when passing through the fixing device, the unfixed toner image is fixed on the transfer sheet S by heat welding.

On the other hand, the toner remaining on the photoreceptor 1 that has not been completely transferred moves in the rotation direction together with the photoreceptor 1 and is stopped and accumulated by a cleaning blade 7 disposed in a cleaning device 10. The residual toner accumulated at the cleaning blade 7 is sent onto the collecting coil 9 by the cooperative action of the collecting blade 8 and the mylar 22 rotating counterclockwise. The collection coil 9 is a kind of screw conveyor formed by spirally winding a wire, and can transport the developer by rotation.

The collection coil 9 is partially covered with a case in a manner capable of taking in toner in the cleaning device 10, and is housed in a collection tube from the cleaning device 10 and is driven to rotate. It has become. The collection tube forms 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 photoconductor 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 is circulated and used.

The adjustment of the image density in the image forming apparatus having the above configuration is performed in the following procedure. The image density of the image formed on the photoconductor 1 is such that if the light intensity of the laser beam 20 is constant, the charging potential of the photoconductor 1 charged by the charging roller 2 is always constant and the density of the developer Should always be constant as long as is constant, but in practice, it varies due to reasons such as deterioration of the photoconductor 1 with time and large fluctuations in the charging potential as characteristics of the charging roller 2. .

Eliminating the fluctuation of the image density due to the above-mentioned causes,
In order to maintain the image density at a predetermined constant level, the image density is adjusted. To adjust the image density, (a) a solid image toner pattern is formed on the photoreceptor 1 and the charging voltage by the charging roller 2 is adjusted so that the density of the solid image toner pattern becomes a predetermined reference level. (B) adjusting the ratio of the carrier and the toner of the developer 4 to a predetermined reference level;
The control relating to the two adjustments is performed.

Photoconductor 1 for adjustment of (a) and (b) above
A test image pattern is formed thereon, and a detecting means for detecting the image pattern is provided. This detection means is a reflection density detection sensor 16 (hereinafter, referred to as a P sensor) provided around the photoreceptor 1 shown in FIG. 1 and between the transfer belt 6 and the cleaning blade 7. The detection information from the P sensor 16 is output to the control unit 23 described later.

In FIG. 2, the control means 23 has a function of controlling the entire image forming process in the image forming apparatus, and the P sensor 16 is connected to the input side via an I / O interface (not shown). Control means 23
On the output side, a drive control unit for the LD, a drive unit for adjusting the charging potential of the charging device (for convenience, reference numeral 2 shown in FIG. 1 is used), and a drive unit for correcting the developer concentration in the developing device ( For convenience, reference numeral 3 shown in FIG. 1 is used), and a drive unit for changing the writing light amount (reference numeral 20 shown in FIG. 1 for convenience)
), A drive unit for forming various toner patterns, a drive unit for executing other image forming processes such as paper feeding, and a display unit AL of an operation panel used for alarm, which will be described later, The means TM are respectively connected.

In order to adjust the toner density in (b), FIG.
Is provided with a toner density sensor (hereinafter, referred to as a T sensor) 17 for detecting the toner density. The detection information from the T sensor 17 is output to the control means 23. For this reason, the control means 23
The T sensor 17 is connected to the input side.

The output of the T sensor 17 is compared with a predetermined density reference value in the control means 23. If it is determined that the density is low, the supply of toner from a toner bottle (not shown) in the developing device 3 is promoted and And if it is determined that the density is higher than the predetermined density reference value, the toner supply is suppressed and the toner supply amount per time is adjusted so as to reach the predetermined density reference value. Is done.

The P sensor 16 is not operated immediately after the main switch is turned on to detect the toner density adjustment pattern, but is used for every fixed amount of jobs, that is, every time a certain amount of image formation is performed, It is operated every time the number of sheets is output. Since the control means 23 shown in FIG. 2 controls the entire image forming process, it knows the progress of the image forming process and the job amount at each time.

When it is determined by the control means 23 that the P sensor 16 is operating, the optical writing means is operated by the program of the control means 13 and the LD
A black solid toner density adjustment pattern of a predetermined size is written on the photoreceptor 1 by the laser beam 20 emitted from the photoreceptor 1.

The pattern for adjusting the toner density is developed by the developing device 3. In this process, in order to prevent the toner density adjustment pattern from being erased,
Is separated from the photoconductor 1. Therefore, the toner density adjustment pattern passes through the transfer portion without any damage and passes in front of the P sensor 16.

The P sensor 16 detects the reflection density of the toner density adjustment pattern and outputs its output to the control means 23. The control means 23 outputs the output value from the P sensor 16
Compare with the preset target toner density reference value,
If it is determined that the toner density adjustment pattern is thinner than the target toner density reference value, the control reference value of the T sensor 17 tends to be increased to increase the toner density. Shift to

If it is determined that the toner density adjusting pattern is darker than the target toner density reference value, the control reference value of the T sensor 17 is suppressed so that the toner supply is reduced so that the toner density is reduced. Shift to the tendency to be. With this configuration, the solid density of the black solid toner density adjustment pattern can be adjusted to the predetermined reference level, so that the solid density of the output image can be kept constant.

Conventionally, how much the control reference value of the T sensor, which is compared with the output of the T sensor 17 with respect to the output of the P sensor 16, is shifted,
Is determined from a fixed value experimentally obtained by a look-up table from the output value of.

The above is the control for stabilizing the solid density by controlling the toner density. Next, a procedure for correcting the charging output of the charging roller 2 using the P sensor 16 will be described. According to the formation of the toner density adjustment pattern, it is shifted from the formation position of the toner density adjustment pattern,
A charge potential adjusting pattern is formed on the photoreceptor 1.

The charge potential adjusting pattern is created only when the fixed amount of the job is completed, whereas the toner density adjusting pattern is formed only when the fixed amount of the job is completed (when the fixed number of sheets are output). It is also created during idle running when the main switch of the image forming apparatus is turned on. In this way, the charging potential adjusting pattern is formed and the P sensor 16 is operated in both the case immediately after the main switch is turned on and the case after the predetermined output. This is because charging potential fluctuations due to environmental changes may be large after the image forming apparatus has been stopped for a long period of time, other than after the end of the job, and thus, it is necessary to correct the charging output immediately after the main switch is turned on.

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. The area charged by the switched charging output is the laser beam 2
The pattern is partially exposed at 0, and by developing the pattern of the latent image formed by this exposure, a charge potential adjustment pattern for solid black is created.

The charging potential adjusting pattern passes under the P sensor 16 without being disturbed by the transfer belt 6 being separated from the photosensitive member 1 in advance, similarly to the charging potential adjusting pattern. At the time of this passage, the P sensor 16
The detection output of the charge potential adjusting pattern detected by the above is input to the control means 23 and compared with a preset reference value.

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, the voltage value applied to the charging roller 2, that is, when the charging output is low. When the determination is made, the charge output is increased, and when the density of the charge potential adjustment pattern is low, the charge output is determined to be high, and the charge output is corrected by the control means 23 so as to reduce the charge output.

As described above, immediately after the main switch is turned on, the charge potential adjusting pattern is formed during idling, which is the preparatory operation of the image forming apparatus, and the charge output is corrected if necessary. Each time a job is completed, a charge potential adjustment pattern is formed, and if necessary, the charge output is corrected. In addition, a toner density adjustment pattern is formed to adjust the toner density.

Next, the control of the halftone density will be described as follows. When the charge output is corrected based on the charge potential adjustment pattern of the solid black image at the time of charge potential adjustment, the charge output (solid black image) before the change of the charge potential is not used for switching the charge output for the correction. As a result, the halftone charging potential determined as a reference also changed, and as a result, it was found that the halftone latent image potential also changed, and the halftone density sometimes deviated from the target density. Therefore, in the above-described control, when the voltage applied to the charging roller 2 is changed, the density of the halftone is also adjusted independently. For this reason, a halftone density adjustment pattern is created and this halftone is adjusted. Based on the density adjustment pattern, the reflection density is detected using the P sensor 16 in the same manner as in the case of the charge potential adjustment pattern, and when this detection output deviates from a predetermined output range for halftone,
The image writing light amount was changed to adjust the halftone density. In this example, since the LD (laser diode) is used as the image writing means,
The amount of light emitted from D was changed by a predetermined value (determined experimentally) determined according to the amount deviated from the predetermined output range, so that the halftone density was kept constant. Further, since the halftone latent image potential also changes due to the deterioration of the photoconductor over time, for example, even at a predetermined interval corresponding to a constant number of outputs of the transfer paper S determined experimentally, the halftone latent image potential is changed. An adjustment reference pattern is created.

On the other hand, when adjusting the halftone density by creating a reference pattern for halftone density adjustment, if the output of the LD is increased in order to change the amount of light in the LD, the life of the LD depends on the high output. Adversely affect Conversely, when the output of the LD is lowered, the reference pattern cannot be read by the synchronous sensor that performs the synchronous detection for starting the writing of the LD depending on the decrease width, and the writing scan timing by the LD becomes inaccurate. Also turned out. In the present invention, in consideration of such a problem that occurs when the light amount is changed in the LD, the change in the LD output is kept within a predetermined range. In particular, the upper limit of the predetermined range is L
The limit value is set so as not to adversely affect the life of D, and the lower limit is set as a limit value at which no reading becomes impossible in the synchronous sensor for setting the write scan timing.

In the present invention, the control means 23 sets the LD output within the above-mentioned predetermined range. However, if the output needs to be higher than the upper limit of the predetermined range, the upper limit is set. On the other hand, a warning is issued to the outside on the assumption that the light emission performance is reduced including the life of the LD or that the photoconductor has deteriorated. As a warning means to the outside, as shown in FIG. 2, a display on an operation panel of the image forming apparatus (for convenience, a display unit indicated by a symbol AL in FIG. 2) can be used. Is used. The communication alarm means that a transmission unit (for convenience, a member indicated by a symbol TM in FIG. 2) is connected to the control unit 23 of the image forming apparatus, and the transmission unit is activated when an output request exceeding the upper limit occurs. . As the destination,
Service person center etc. correspond. For this reason, the serviceman call can be automatically performed together with the alarm to the operator, so that the operator does not have to worry about grasping the cause of the failure.

In the above LD output setting, when an output lower than the lower limit of the predetermined range is required,
Without changing the LD output, the charging output or the developing bias corresponding to the image forming conditions other than the writing condition is changed. In this case, the change amount under the image forming conditions is a change amount that can obtain the same state as the density of the intermediate density adjustment reference pattern by changing the output of the LD.

In the present embodiment, the control of the halftone density is executed by the following procedure using the above configuration. FIGS. 3 and 4 are flowcharts for explaining the operation of the control unit 23. In FIG. 3, the image forming apparatus is turned on when the main switch is turned on or when the job of a predetermined amount or more is completed. It is determined whether there is. It is determined whether the image forming apparatus is in one of these states and is in idle running, which is a preparation state for the image forming process (step P1).

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.
When the job is completed, the transfer belt 6 is automatically separated from the photoreceptor 1 and is kept in contact with the photoreceptor 1 during the job. Even if patterns are formed,
These patterns are transferred to the transfer belt 6,
This is because these patterns cannot be detected by the P sensor 16.

On the other hand, at the end of the job, the transfer belt 6 is automatically separated from the photoreceptor 1, so that a charge potential adjusting pattern, a toner density adjusting pattern, and the like can be formed on the photoreceptor 1. These patterns are used as P sensor 1
6 can be detected. However, when a transfer charger is used instead of the transfer belt 6, the transfer charger is disposed at a distance from the photoconductor 1, and even if these patterns are formed, the patterns are not disturbed. The condition of time becomes unnecessary.

The job of a predetermined amount (predetermined number of times) is as follows.
This is because it is preferable to perform correction of the charging potential and the toner density at intervals where the toner density and the charging potential change with time. For example, when a predetermined amount of jobs is output as the number of output sheets of transfer paper N =
There are 10 sheets. Whether these conditions are satisfied is determined by the control unit 23.

In the following process, the toner density adjustment pattern is detected by a job of the image forming apparatus, that is, the image recording is performed by outputting the transfer paper and the predetermined number N =
This is performed every time the number of sheets reaches 10 or more, and is not performed immediately after the main switch is turned on. If it is assumed that the operation is performed immediately after the main switch is turned on, there is a possibility that only the control reference value of the toner concentration is largely shifted even when the actual toner concentration does not change, for example, when only the main switch is frequently turned on and off. It is.

On the other hand, it is desirable to control the output of the voltage applied to the charging roller 2 immediately after the main switch is turned on. Immediately after the main switch is turned on is usually immediately after the image forming apparatus has not been operated for a while, such as one day or two days, and before the main switch is turned on, the stopped state of the mechanical part continues. Means that you were. During this stop, the surrounding environment of the image forming apparatus often changes, and the charging performance of the charging roller 2 often changes. Therefore, it is necessary to correct the charging output and the halftone potential. When these conditions are satisfied, the process proceeds to Step P2.

In step P2, the charging output V, which is the voltage applied to the charging roller 2, is set to v-v1 for a predetermined time, which is lower than the existing value v by a predetermined value v1, and this voltage is used to set the charging roller 2 Charge the photoreceptor 1 by
A charge potential adjusting pattern in an area corresponding to the predetermined time is created. Further, the P sensor 16 is set to the ON state in which detection is possible, and the image forming apparatus is set to a mode in which data sampling can be performed.

When the image forming apparatus has completed the job of a predetermined amount, the density of the toner is adjusted. In step P3, the LD as the light source is set to the full power, and the charged output is set to the existing value by the laser beam 20. A predetermined area in the area charged by v is exposed with a toner density adjustment pattern and developed by the developing device 3 to create a toner density adjustment pattern.

On the photoreceptor 1, a background area based on the charging potential of the existing value v, a pattern for adjusting the charging potential based on the charging potential of v-v1, and a background area based on the charging potential of the existing value v are close to full power. This means that three regions of the toner density adjustment pattern formed by the laser beam 20 with a predetermined LD output have been formed. The background area is a white background without toner, the charge potential adjustment pattern is in a state where toner is slightly applied, and the toner density adjustment pattern is in a solid black state.

In step P4, the P sensor 16 detects the density of these three areas. P sensor 1
Reference numeral 6 denotes a pair of a light emitting element and a light receiving element. The reflected light of the light emitted from the light emitting element is received by the light receiving element and is input to the control means 23 as an electrical output obtained by photoelectric conversion.

In step P4, the detection output Vsg of the P sensor 16 for the background area based on the charged potential of the existing value v is obtained from the detection data of the P sensor 16 collected on the surface of the photoreceptor 1 at experimentally determined intervals. And a detection output Vsdp of the P sensor 16 for the charge potential adjustment pattern based on the charge potential of v-v1, and a detection output Vsp of the P sensor 16 for the toner density adjustment pattern. Further, the ratio of these detection outputs, Vsdp / Vsg, V
The control means 23 calculates sp / Vsg.

Next, in the flow after step P5, V
It is determined whether or not sdp / Vsg is within a predetermined range, and predetermined charging output correction is performed.

In step P5, Vsdp / Vsg
Is a predetermined lower limit and b is an upper limit. Step P5
When it is determined that a <Vsdp / Vsg is not satisfied, the pattern charging potential for adjusting the charging potential is lower than the predetermined lower limit a which is a reference, and the charging output is set to a <Vsdp / Vsg in Step P8. The value is increased by such a value as to satisfy the condition (1), and thereafter, the charging output is set so that the charging output is obtained. In step P5,
If it is determined that a <Vsdp / Vsg, the condition is satisfied in relation to the lower limit value a, so that step P
Proceed to 6. In step P6, Vsdp / Vsg is compared with the upper limit b, and if b> Vsdp / Vsg, the upper limit b
Since the condition was satisfied also in relation to the above, the process proceeds to Step P9.

If it is not determined in step P6 that b> Vsdp / Vsg, the pattern charging potential for adjusting the charging potential is higher than the reference upper limit value b. Therefore, in step P7, the charging output is changed to b> Vsdp / Vsg. After decreasing by a predetermined value that satisfies the condition, and then setting the charging output to be the same, the process proceeds to step P9.

In step P9, it is determined whether or not the toner density adjustment pattern has been written in the upstream flow.

As described above, if the current state is in the middle of a job, the toner density adjustment is not performed, so that the toner density adjustment pattern has not been written, and step P9
Then, the process directly proceeds to step P13 and thereafter, and shifts to a halftone density adjustment flow. If the current state is the end of the job, since the toner density adjustment pattern has been written in Step P3, Steps P9 to P10
Then, in Steps P10 and P11, Vsp /
It is determined whether Vsg is within a predetermined range, and the flow of toner density adjustment is executed.

In step P10, Vsp / Vsg
Is a predetermined upper limit value, and a predetermined lower limit value is d in Step P11. In step P10, c> Vsdp / V
If it is not sg, 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 lower than the reference. Therefore, after the toner density control reference value is increased by a predetermined amount in step P13 so that toner supply is promoted, the process proceeds to step P14.

If it is determined in step P10 that c> Vsp / Vsg, Vsp / Vsg is smaller than the predetermined upper limit c, and the density of the toner density adjustment pattern is at least less than the upper limit. Means that In this case, it is necessary to check whether the value is in a range exceeding the lower limit value, and the process proceeds to Step P11.

In step P11, Vsp / Vsg is compared with the lower limit d. If d <Vsp / Vsg, the condition is satisfied in relation to the lower limit d, so that the routine proceeds to step P14. If d> Vsp / Vsg is not satisfied in Step P11,
This means that the density of the toner density adjustment pattern is higher than the reference. Then, after the toner density control reference value is lowered by a predetermined amount in step P12 so that toner supply is suppressed, the process proceeds to step P14.

In the flow from step P14, the adjustment of the halftone density is performed. First, in Step P14, when the charging output has already been switched in Steps P7, P8, etc. in the upstream flow, the reference of the halftone density has changed, or a predetermined amount from the previous adjustment. When the number of output sheets of transfer paper is N '= 1000 and the job of the predetermined amount N' or more is performed in step P14, the halftone density is changed due to the deterioration of the photoconductor over time. If any of these conditions is met, the routine proceeds to the next Step P15. In addition,
If the charging output switching has already been performed in steps P7, P8, etc., the process proceeds to step P15 regardless of whether the job has ended.

In step P15, based on the charging output corrected by the charging roller 2 in steps P7 and P8, the LD is set to a predetermined output close to full power, and the output is changed to PWM (power wide modulation). The halftone density adjustment reference pattern is written such that the (emission time) becomes a predetermined halftone time. Then, in the same manner as in the case of the charge potential adjustment pattern or the toner density adjustment pattern, in step P16, a laser beam having a light quantity (emission time) such that the dots constituting the halftone density adjustment reference pattern become halftone. At 20, a halftone density adjustment reference pattern is formed.

In step P16, the detection output of the P sensor 16 for the charge potential adjusting pattern is set to Vs
Assuming m, the control means 23 calculates the ratio with the detected output Vsg that has already been detected.

In the flow after step P17, Vsm /
It is determined whether or not Vsg is within a predetermined range, and correction is performed to set the halftone density to a constant level. Step P1
At 7, the predetermined upper limit value of Vsm / Vsg is e and the lower limit value is f. In this case, the upper limit value e is a limit value that does not adversely affect the life of the LD as described above, and the lower limit value f is a limit value at which a pattern can be formed to the extent that reading by the synchronous sensor is not disabled. Step P17
In the case where it is determined that e> Vsdp / Vsg is not satisfied, the detection output of the halftone density adjustment reference pattern is higher than the reference, and it is determined that the density of the halftone density adjustment reference pattern is lower than the reference. means. 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. If it is determined in step P17 that e> Vsm / Vsg, the condition satisfies the relationship with the upper limit value e, and the process proceeds to step P18.

At step P18, Vsm / Vsg is compared with lower limit value f. If f <Vsdp / Vsg, the condition is satisfied even in the relationship with the lower limit value f, and the condition of the LD light amount 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, so that the density of the halftone density adjustment reference pattern is higher than the reference. Means that. Therefore, in step P19, the LD light amount is reduced by a predetermined amount such that the halftone density falls between the upper limit value e and the upper limit value f. After the halftone density adjustment is completed in this way, another 2-3 is set based on the adjusted halftone writing conditions.
By adjusting the conditions for the halftone of the value and performing gradation processing, a multistage halftone can be stably obtained.

In step P17, e> Vsdp /
If it is determined that the output voltage is Vsg, the LD output is increased. In step P21, it is determined whether the output value to increase is equal to or higher than the upper limit value.

If the LD output is equal to or higher than the set value in step P21, the LD output is stopped at the upper limit value, and the machine is in an abnormal state including the life of the LD or deterioration of the photosensitive member. An operation signal to the operation panel AL or the transmission unit of the image forming apparatus is output from the control unit 23 in order to warn that there is (Step P2)
2).

In step P18, Vsm / Vsg
If the result of the comparison with the lower limit f is not f <Vsdp / Vsg, in other words, if the LD output must be lower than or equal to the lower limit, the determination is made in step P2.
This is performed in step 3, and if it is necessary to lower the value, the charging output or the developing bias, which is an image forming condition other than the writing condition, is changed to the lower limit value. In this case, a method of increasing the charging potential of the photoconductor at the time of pattern formation or a method of lowering the developing bias is adopted.

[0085]

According to the first and second aspects of the present invention,
When changing the image writing light amount by the control means, the change amount is set within a predetermined range, and in particular, the upper limit of the predetermined range is set to a limit value which affects the life of the semiconductor laser used as a light source, so carelessness is required. As a result, it is possible to prevent a decrease in the life of the semiconductor laser caused by increasing the light emission amount.

According to the third aspect of the present invention, when the output of the light emission amount of the semiconductor laser used as the light source is required to be higher than the upper limit of the predetermined range, the output of the semiconductor laser is stopped at the upper limit while the semiconductor laser or the laser is stopped. It is possible to warn that the photoconductor has deteriorated. This makes it possible to quickly perform a serviceman call or the like, thereby shortening the interruption period of image formation.

According to the fourth aspect of the present invention, when the output of the semiconductor laser used as the light source is set in a predetermined range, the lower limit of the range is set to the limit value at which the reading by the synchronous sensor for determining the writing timing does not occur. Therefore, it is possible to prevent the writing start timing using the semiconductor laser from becoming inappropriate, and to prevent the writing failure.

According to the present invention, when the output of the semiconductor laser used as the light source is required to be equal to or lower than the lower limit of the predetermined range, the charge output or the image forming condition other than the writing light amount is required. Since an image having a halftone density equivalent to that at the time of changing the output of the semiconductor laser is obtained by changing the developing bias, it is possible to prevent the image reproducibility of the halftone density from being reduced.

According to the ninth aspect of the present invention, it is possible to reproduce an image having a halftone density without reducing the life of the light source or causing an erroneous operation in the writing operation.

[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 is a block diagram for explaining a configuration of a control unit used in the image forming apparatus shown in FIG. 1;

FIG. 3 is a flowchart for explaining the operation of the control means shown in FIG. 2;

FIG. 4 is a flowchart showing an operation performed continuously from the flowchart shown in FIG. 3;

[Explanation of symbols]

 2 Charging roller 16 Reflection density detection sensor 23 Control means AL Display section of operation panel TM Transmission means

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G03G 15/08 115 G03G 21/00 386 2H077 21/00 386 H04N 1/29 H 5C074 H04N 1/29 B41J 3/00 D F-term (reference) 2C362 AA03 AA53 AA54 AA64 AA66 AA72 AA74 BB33 CB73 CB80 2H003 AA02 BB11 CC05 DD03 DD14 2H027 DA10 DD07 DE02 DE07 DE09 EA01 EA02 EA05 EA06 EA20 EB01 EC03 EC07 EC07 A072 EC07 AB05 AB75 AB85 DA07 DA22 EA21 2H077 AB03 AC03 AD06 AD35 AE06 DA03 DA10 DA42 DA47 DA63 DB02 DB08 EA03 GA17 5C074 AA02 AA09 AA12 AA15 BB03 BB26 CC26 DD08 EE11 FF05 GG12 GG16 GG19 HH02

Claims (9)

[Claims] An image forming method in which a toner pattern is formed on a photoreceptor by a contact charging means, a reflection density of the toner pattern is detected by a sensor, and a toner density and a charging potential by the contact charging means are adjusted. The charging potential is adjusted by switching the voltage applied to the contact charging means at predetermined intervals, and a halftone density adjusting reference toner pattern is created separately from the toner pattern. Control means for adjusting the reflection density of the pattern by changing the amount of image writing light based on the detection output of the sensor to adjust the halftone writing conditions; and the control means controls the reflection of the halftone density adjustment reference pattern. An image characterized in that when changing the image writing light amount according to the density, the change amount is set within a predetermined range. Forming method. 2. The image forming method according to claim 1, wherein a semiconductor laser is used as the light source, and the output of the semiconductor laser is controlled in accordance with the reflection density of the halftone density adjustment reference toner pattern. In this case, an upper limit of the predetermined range is set to a limit value affecting a life of the semiconductor laser. 3. The image forming method according to claim 1, wherein when the output of the semiconductor laser used as the light source is required to be higher than the upper limit of the predetermined range, the output of the semiconductor laser is stopped at the upper limit. An image forming method, comprising determining that a semiconductor laser or a photoconductor has deteriorated and alarming this condition to the outside. 4. The image forming method according to claim 1, wherein a semiconductor laser is used as the light source, and when the output of the semiconductor laser is set by the reflection density of the halftone density reference toner pattern, the predetermined range is set. An image forming method, wherein the lower limit is set to a limit value at which reading by a synchronous sensor for determining writing time by light emission from the light source is not disabled. 5. An image forming method according to claim 1, wherein when an output from said semiconductor laser as said light source is required to be lower than a lower limit of said predetermined range, image forming conditions other than a writing light amount are changed. Characteristic image forming method. 6. The image forming method according to claim 5, wherein the image forming condition other than the writing light amount is a charge output to the photosensitive member. 7. The image forming method according to claim 5, wherein a developing bias is used as an image forming condition other than the writing light amount. 8. The image forming method according to claim 5, wherein the image forming condition other than the writing light amount is such that the image density in the halftone density adjusting reference toner pattern is halftone image density. An image forming method, characterized in that the conditions correspond to the following. 9. An image forming apparatus using the image forming method according to claim 1. Description: