JP2000075575A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device where image forming with excessive density and surface staining are surely reduced. SOLUTION: A CPU firstly executes developer stirring processing for 30 seconds (substep sb1-2) after starting the rotation of a photoreceptive drum (substep sb1-1). The triboelecltricfication of two-component developer is accelerated by the developer stirring processing, so that the surface staining at the non- image part of the photoreceptive drum is reduced. Next, after a P-pattern is formed at a specified position on the photoreceptive drum by the CPU (substep sb1-3), the toner stuck amount measured value (hereinafter referred to as Vsp) of the P-pattern is referred to (substep sb1-4). Then, in the case of judging as Vsp<0.39 (yes at substep sb1-4), it is judged that the surface staining of a quantity exceeding a tolerance is caused on the photoreceptive drum, so that the sequence of control is looped with the substep sb1-2 so as to stir the two-component developer at the inside of a developing device more. Looping is executed until the CPU judges as Vsp>=0.39 at the substep sb1-4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, etc., and more particularly to a background dirt reducing means for reducing a background dirt on a non-image portion of a latent image carrier or a transfer body. It is related to the improvement of.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, an image having an excessively high density is formed by changing a charge amount of toner as image forming particles, or a photosensitive drum as a latent image carrier is used. In some cases, the non-image portion may have background stains, or the image density may be insufficient. For example, immediately after a new toner is set in an image forming apparatus, an insufficiently charged toner becomes excessive, and an image having an excessively high density may be formed or a background smear may occur (hereinafter, referred to as image formation). Immediately after new toner is set in the apparatus is referred to as “after toner setting”.

Accordingly, the present applicant has disclosed in Japanese Patent Application Laid-Open No. 8-26286.
In No. 5, an optical density reference value (Vsg) and an optical density detection value (Vsp) are detected by an optical sensor (hereinafter, referred to as a P sensor) as particle adhesion amount detection means, and based on the detection result, An image forming apparatus for determining a toner stirring time after toner setting has been proposed. Where Vsg
Is a reflected light amount detection value of the non-image portion on the latent image carrier when the toner in the developing device is sufficiently charged, and Vsp is a reflected light amount detected value of the non-image portion after the toner is set. is there. According to this image forming apparatus, the toner in the developing device after the toner setting can be stirred until sufficiently charged based on Vsg and Vsp. And the above-mentioned background contamination can be avoided.

The applicant of the present invention has disclosed Japanese Patent Application Laid-Open No. 4-158382.
In the item, prior to the first image formation after the toner setting, the toner of the two-component developer inside the two-component developing device is forcibly consumed or the toner is replenished.
An image forming apparatus that executes toner balance control for adjusting toner density has been proposed.

[0005]

By the way, the present inventor has made intensive studies and found that, other than after toner setting, image formation with excessive density and background fouling may occur.

For example, if the image forming apparatus is left for a long time in a state where the main power supply is turned off, that is, when the image forming apparatus is not used, the toner in the developing apparatus is left for a long time without stirring, and the main power supply is left. It was found that the background contamination and the like due to insufficient charging of the toner were caused after re-feeding. For this reason, even in the image forming apparatus described in Japanese Patent Application Laid-Open No. 8-262865, after the main power is turned on again after being left for a long period of time, there is a possibility that the background of the transfer paper or the like becomes stained.

In the case of an image forming apparatus using a two-component developing device, even if the toner density in the two-component developing device is kept constant, the image density changes due to changes in the environment such as humidity and temperature. . Therefore, conventionally, the toner density is adjusted by increasing or decreasing the toner supply amount to the two-component developing device according to the toner adhesion amount of the reference image formed on the photosensitive drum, thereby stabilizing the image density. Was. However, when the toner concentration is adjusted by increasing or decreasing the toner supply amount in this manner, even if the toner supply is stopped, the toner concentration cannot be reduced unless an image is formed. For this reason, it has been found that, when the environment changes significantly, an image with a background stain or an image with an excessive density is formed until the toner density decreases to an appropriate density. In particular, after the image forming operation has been on standby for a long time while the main power is on, it is highly likely that the environment has changed significantly compared to when the image forming operation was last performed. JP-A-4-158
The image forming apparatus of No. 382 forcibly consumes the toner after the toner is set, and does not forcibly consume the toner when the toner is not set. Therefore, when the environment is largely changed, the background is not transferred to the transfer paper or the like. There is a risk of causing stains and the like.

The present invention has been made in view of the above background, and an object of the present invention is to provide an image forming apparatus capable of forming an image having an excessively high density and more reliably reducing the background stain. is there.

[0009]

Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 provides a latent image carrier for forming a latent image on the surface, and charging the image forming particles by a particle charging means,
A developing device for developing the latent image with charged image forming particles,
An image forming apparatus comprising: a control unit configured to control these components; and a particle adhesion amount detection unit configured to detect an adhesion amount of image forming particles at a predetermined position on the surface. If the power is on and the time during which no image formation is performed exceeds a predetermined time, according to the amount of image forming particles attached to the reference image formed at the predetermined position,
It is characterized in that charge amount adjustment control for adjusting the charge amount of the image forming particles is executed to reduce the amount of the image forming particles attached to the latent image carrier.

In this image forming apparatus, the main power supply is O
N, or when the main power is turned on and the time during which no image formation is performed exceeds a predetermined time, the amount of adhered image forming particles of the reference image formed at a predetermined position on the latent image carrier , The charge amount adjustment control for adjusting the friction charge amount of the image forming particles is executed. That is, when there is a high possibility that the charge amount of the image forming particles is insufficient, the amount of the image forming particles attached to the non-image portion on the latent image carrier is detected.
In this charge amount adjustment control, if it is determined that the amount of the image forming particles adhered to the reference image exceeds the allowable range, for example, the charging of the image forming particles is promoted by the particle charging means, and thereby the latent image carrier is charged. Of the image forming particles is reduced.

According to a second aspect of the present invention, there is provided a latent image carrier for forming a latent image on a surface thereof, a two-component developing device for developing the latent image using a two-component developer containing image forming particles and a carrier, What is claimed is: 1. An image forming apparatus comprising: a particle supply unit configured to supply image forming particles to a two-component developer; and a control unit configured to control the particles. When the main power is turned on, or when the main power is turned on and the time during which no image formation is performed exceeds a predetermined time,
And when the attached amount of the image forming particles of the reference image exceeds a predetermined amount, a forced consumption control for forcibly consuming the image forming particles in the two-component developing device is executed. is there.

In this image forming apparatus, the main power supply is O
If N, or if the main power is on and the time during which no image formation is performed exceeds a predetermined time, the amount of image forming particles of the reference image is detected by the particle amount detecting means. I do. That is, when it is highly possible that the environment has greatly changed compared to when the image forming operation was performed last, the amount of the image forming particles attached to the reference image is detected. When the amount of the image forming particles exceeds a predetermined amount, the image forming particles in the two-component developing device are forcibly consumed. Thereby, before forming a desired image on the latent image carrier, the density of image forming particles in the two-component developing device can be reduced.

According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the image forming apparatus further comprises a particle concentration detecting means for detecting the concentration of image forming particles in the two-component developing device. Used to calibrate the particle concentration detecting means.

In this image forming apparatus, it is possible to avoid an increase in the detection error of the particle concentration detecting means after the above-mentioned forced consumption control. For example, if the concentration of image forming particles in the two-component developing device is out of the proper detection range of the particle concentration detecting means due to the forced consumption control, the detection error of the particle concentration detecting means increases. Then, due to this increase, the ability to adjust the concentration of image forming particles with respect to the two-component developer after the above-described forced consumption control is reduced. Therefore, in this image forming apparatus, by adjusting the appropriate detection area to the image forming particle density in the two-component developing device after the forcible consumption control by the calibration, the particle density detecting means generated after the forcible consumption control is adjusted. Avoid increase in detection error.

According to a fourth aspect of the present invention, in the image forming apparatus of the second or third aspect, the image forming particles in the two-component developing device are formed by forming a pattern image of a predetermined shape on the surface of the latent image carrier. Is forcibly consumed.

In this image forming apparatus, by forming a pattern image of a predetermined shape on the surface of the latent image carrier, the amount of reduction in the concentration of image forming particles per unit time is made uniform.

According to a fifth aspect of the present invention, in the image forming apparatus of the first, second, third or fourth aspect, at least the first charge amount adjustment control or the first forced consumption adjustment control is performed after the main power supply is turned on. In the meantime, the predetermined position where there is no background contamination is detected by the particle adhesion amount detecting means, and the particle adhesion amount detecting means is calibrated.

In this image forming apparatus, it is possible to avoid erroneous recognition of a background defect state from the first charge amount adjustment control or the forced consumption adjustment control after the main power supply is turned on. For example, when the particle adhesion amount detecting means is calibrated while detecting the predetermined position of the background contamination state by the particle adhesion amount detecting means, in the subsequent control, the predetermined position of the background contamination state is determined. They mistakenly think that they are not soiled. Therefore, in this image forming apparatus, prior to the first charge amount adjustment control or the forced consumption adjustment control, the particle adhesion amount detection unit detects the predetermined position in a state where there is no background stain, and Calibrate the detection means.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter, referred to as a copying machine) as an image forming apparatus will be described.

First, the basic configuration of the copying machine will be described. FIG. 1 is a sectional view showing a schematic configuration of an image forming portion of the copying machine according to the present embodiment. A photoconductor drum 1 as a latent image carrier on which an electrostatic latent image is formed is rotatably attached to the copying machine, and is driven clockwise by a drive system (not shown). Around the photosensitive drum 1, a charging device 2, a developing device 3, a transfer device 4 (not shown), a cleaning device 5 also having a function as a cleaning device, a discharging lamp 6 as a discharging device, a particle adhesion detecting device And the like, a P sensor 8, and the like. The developing device 3 is provided with a toner replenishing device 7 as a particle replenishing device for replenishing the developing device 3 with toner. The operation of the copying machine as a whole is a well-known electrophotographic process and will not be described.

The developing device 3 is a two-component developing device using a so-called two-component developer composed of a toner and a magnetic carrier. Inside the developing device 3, a developing roller pair 3a, a stirring paddle 3b, an agitator 3c, a particle density A T sensor 3d and the like are provided as detection means. Developing roller pair 3
a is provided such that the peripheral surface thereof is opposed to the peripheral surface of the photosensitive drum 1 at the opening of the developing device 3, and a magnet is provided inside to carry a magnetic carrier to which toner is attached. . The agitator 3c conveys the toner replenished from the toner replenishing device 7 to the stirring paddle 3b side while mixing and stirring with the two-component developer in the developing device 3. The stirring paddle 3b agitates the two-component developer conveyed from the agitator 3c and the two-component developer already existing around the paddle by a plurality of paddle-shaped members provided on the peripheral surface of the roller portion. Is supplied to the developing roller pair 3a. During this stirring, the toner in the two-component developer is promoted to be charged by friction with a magnetic carrier or the like. That is, the stirring paddle 3b has a function as particle charging means. The agitator 3c also has a function as a particle charging means because it promotes frictional charging of the toner during the mixing and stirring. The T sensor 3d is provided on the bottom wall of the developing casing below the agitator 3c.
The magnetic permeability of the two-component developer is detected in order to detect the toner concentration of the two-component developer near the agitator 3c (hereinafter, simply referred to as toner concentration).

In the developing device 3, the developing roller pair 3
a, the stirring paddle 3b, the agitator 3c, and the like are driven by a drive device (not shown), and the developing roller pair 3a and the stirring paddle 3b rotate counterclockwise, and the agitator 3c rotates clockwise. Due to these rotations, the two-component developer in the vicinity of the agitator 3c is sent to the stirring paddle 3b while being stirred, and the developing roller pair 3 is moved from the stirring paddle 3b.
a. Then, the electrostatic latent image formed on the peripheral surface of the photosensitive drum 1 is developed by being carried on the peripheral surface of the developing roller 3a and conveyed to a portion facing the peripheral surface of the photosensitive drum 1.

The toner replenishing device 7 contains therein toner for replenishing the developing device 3. A stirring member 7a is provided for sending the toner to the communication port side with the inside of the developing device 3 while stirring. Further, a toner replenishing roller 7b for replenishing the toner sent from the stirring member to the developing device 3 is provided in the communication port.

Next, control means of the copying machine will be described. FIG. 2 is a block diagram showing a part of the circuit configuration of the control unit 10 as control means of the copying machine. Control unit 1
Reference numeral 0 denotes an MPU 10a having an arithmetic function, a ROM 10b for storing a sequence program, a RAM 10c for temporarily storing arithmetic data, and the like. MPU
10a, the ROM 10b and the RAM 10c are connected by wire, and data exchange is performed between them. Further, the operation display unit 1 is provided on the MPU 10a.
1, T sensor 3d, P sensor 8, etc. are also connected.
The operation display unit 11 is configured by, for example, a touch panel display, and is for displaying predetermined information to an operator and receiving a key input from the operator. Further, the detection signals of the T sensor 3d and the P sensor 8 are appropriately read into the MPU 10a.

The MPU 10a includes a CPU, a PWM controller, and the like. A DC voltage is output from the PWM controller and applied to the T sensor 3d and the P sensor 8, respectively. The CPU changes the value of the control signal to the PWM controller (hereinafter, referred to as a PWM value) to change the value of the DC voltage (hereinafter, referred to as a control voltage) to be supplied to the T sensor 3d or the P sensor 8. Can be changed. Thereby, the output levels of the P sensor 8 and the T sensor 3d are adjusted. In the copying machine of the present embodiment, when a non-image portion on the photosensitive drum 1 is detected, the output voltage from the P sensor 8 is 4.0 ± 0.1.
The PWM value from the CPU is adjusted to adjust the value of the control voltage to the P sensor 8 so as to be [V].

Next, the toner supply control of the copying machine will be described. The P sensor 8 includes a light emitting unit including a light emitting diode and a light receiving unit including a photo sensor such as a phototransistor. The irradiation light from the light emitting unit is irradiated onto a predetermined position on the photosensitive drum 1, and the amount of reflected light is detected by the light receiving unit. The result of this detection is
It is output as a DC voltage from the P sensor 8 and the MPU 10a
Is input to Here, the amount of reflected light is
It changes depending on the toner adhesion amount at the upper predetermined position.
That is, the output voltage value from the P sensor 8 is
It changes depending on the toner adhesion amount at the upper predetermined position.
Thereby, the MPU 10a obtains the toner adhesion amount at the predetermined position. In the copying machine of the present embodiment, the output voltage value from the P sensor 8 decreases as the amount of adhered toner increases.

The T sensor 3d detects the toner density, and is composed of, for example, a magnetic permeability sensor that detects a magnetic permeability that changes with an increase or decrease in the toner amount. And
A DC voltage having a value corresponding to the toner density is output to the MPU 10a.

The RAM 10 stores a target value for the output voltage of the T sensor (hereinafter, referred to as a T target value). The MPU 10a calculates the T target value and the T sensor 3d
Of the toner replenishing device 7 based on the actual output voltage value from the printer, and turns on the toner replenishment to the developing device 3
/ OFF. Thereby, the toner density can be kept constant. However, the image density is affected not only by the toner density but also by the toner charge amount, the environment such as temperature and humidity, and the like. For this reason, in the copying machine of the present embodiment, an output target value (hereinafter, referred to as a P target value) from the P sensor 8 for detecting a reference image having a predetermined shape (hereinafter, referred to as a P pattern) is stored in the RAM 10c. ing. Then, the P sensor output value for the P pattern on the photosensitive drum 1 and P
Based on the comparison with the target value, the density of the image density is determined, and the T target value is appropriately corrected. As a result, the toner replenishment amount in the developing device 3 is increased or decreased to adjust the toner density, so that an image having a stable density is formed.

Next, the characteristic structure of the copying machine will be described. FIG. 3 is a flowchart showing a part of the control in the CPU. The CPU of the control unit 10 of the copier immediately after the main power of the copier is turned on and when the main power is turned on.
Immediately after the time during which the image forming operation is not performed (hereinafter, referred to as standby time) exceeds 1440 minutes as a predetermined time, a subroutine sb1 as charge amount adjustment control is performed.
Execute the processing of That is, when there is a high possibility that the toner charge amount is insufficient, the processing of the subroutine sb1 is executed. Specifically, when detecting that the main power supply is turned on (step S1), the CPU first resets the value of the standby time t to zero (step S2). This standby time t indicates the standby time of the copying machine in minutes. The processing of the subroutine sb1 will be described later in detail.

After the CPU starts the pre-rotation of the photosensitive drum 1 (step S2), the CPU outputs an output from the P sensor 8 for detecting a background portion of the photosensitive drum 1 where no toner adheres. An adjustment process of the PWM value to the PWM controller is executed so that the voltage becomes 4.0 ± 0.1 [V] (Step S3).

Here, when the PWM value of the P sensor 8 is adjusted while the P sensor 8 detects the background stain portion, in the subsequent control, the background stain portion on the photosensitive drum 1 also adheres toner to the CPU in the subsequent control. It will be mistaken as a background part without any. Therefore, in the copying machine of the first embodiment, in order to adjust the PWM value of the P sensor 8 while causing the P sensor 8 to detect a non-image portion having no background stain, the pre-rotation of the photosensitive drum 1 is started. The adjustment of the PWM value of the P sensor 8 is completed within a predetermined time. This predetermined time is set after the start of the pre-rotation.
Is set to be shorter than the time required for the background sensor to detect the background contamination by the P sensor, and this time is obtained by a preliminary test. .

As described above, immediately after the start of the pre-rotation of the photosensitive drum 1, the above-mentioned predetermined position free from the background contamination is detected by the P sensor 8.
By performing the PWM value adjustment process for the P sensor 8 while detecting the above, the above erroneous recognition can be avoided immediately after the main power is turned on.

Note that, depending on the configuration of the image forming apparatus, background contamination may occur on the photosensitive drum 1 immediately after the start of pre-rotation. In such a case, for example, the peripheral surface area (points P to Q in FIG. 1) of the photosensitive drum 1 which was at a position facing the developing device 3 before the start of the pre-rotation is changed to
The adjustment process of the PWM value for the P sensor 8 may be terminated before the photosensitive drum 1 is moved to the detectable area of the P sensor 8 by the rotation. In addition, a so-called scissoring operation is performed to remove toner carried by the developing roller 3a in the developing device 3 by abutment of a blade or reverse rotation of the developing roller 3, so that the toner is exposed from the casing of the developing roller pair 3a. The state may be such that the developer does not exist on the area where the developer exists.

After executing the process of adjusting the PWM value in step S3, the CPU outputs an output voltage value (hereinafter, referred to as Vsg) from the P sensor 8 which detects the toner adhesion amount at the predetermined position to be a non-image portion. ) (Step S)
4). If it is determined that Vsg> 4.1 (Y in step S4), a PWM value adjustment error error process for the P sensor 8 is executed (step S5).

In this adjustment error processing, for example, after cleaning the photosensitive drum 1 and the P sensor 8, a display urging an operation to reset the main power is displayed on the operation display unit. When the function of removing the toner on the developing roller 3a is provided, the PWM value of the P sensor 8 is adjusted again while the toner on the developing roller 3a is removed, and then the control sequence is performed. In step S5 in the figure.
It may be configured to make a loop.

The CPU determines in step S4 that Vsg ≦
If it is determined to be 4.1, the process of the subroutine sb1 is executed (step S6), and then the counting of the waiting time t is started (step S7). Then, it is determined whether or not there is an image forming command from the operator (step S8),
If it is determined that "there is an image forming instruction" (Y in step S8), a predetermined image forming process is executed (step S9). Further, after resetting the value of the standby time t to zero (step S10), the control sequence is looped to step S7. If it is determined that "there is no image forming command" (N in step S8), then the standby time t>
It is determined whether it is 1440 [minutes] (step S1).
1) If the standby time t> 1440 [minutes] (Y in step S11), the processing of the subroutine sb1 is executed (step S12). Then, after resetting the value of the standby time t to zero (step S13), the control sequence proceeds to step S14.

In this step S14, the CPU determines whether or not the main power supply has been turned off.
If it is determined that the sequence is ended,
If not, the sequence is looped to step S8.

Next, the processing of the subroutine sb1 will be described in detail. FIG. 4 is a flowchart showing the processing of the subroutine sb1 of the CPU. In the subroutine sb1, the CPU first starts the rotation of the photosensitive drum 1 (substep sb1-1), and then executes the agent stirring process for 30 seconds (substep sb1-2). In this agent stirring process, the stirring paddle 3b and the agitator 3c
Rotates for 30 seconds to stir the two-component developer in the developing device 3. This stirring promotes the triboelectric charging of the toner of the two-component developer in the developing device 3, and reduces the background stain on the non-image portion of the photosensitive drum 1.

Next, the CPU forms a P pattern at the predetermined position on the photosensitive drum 1 (substep sb).
1-3), the measured value of the amount of toner attached to the P pattern (hereinafter, V
sp (refer to sub-step sb1-4).
If it is determined that Vsp <0.39 (Y in sub-step sb1-4), it is assumed that the background dirt on the photosensitive drum 1 exceeds an allowable range, and In order to further stir the two-component developer, the control sequence is looped to the sub-step sb1-2. This loop is performed by the CPU in sub-step sb1-4.
The processing is executed until it is determined that sp ≧ 0.39. That is,
Until the degree of background contamination in the non-image portion of the photosensitive drum 1 falls within the allowable range, toner charging is promoted. In addition, the CPU determines that Vsp ≧ in sub-step sb1-4.
If it is determined to be 0.39 (substep sb
After the rotation of the photosensitive drum 1 is terminated (substep Sb1-5), the processing of the subroutine sb1 is terminated.

As described above, according to the copying machine of the first embodiment,
If there is a high possibility that the toner charge is insufficient,
Since the process of the subroutine sb1 is executed to promote the charging of the toner until the degree of the background stain in the non-image portion of the photosensitive drum 1 is suppressed to within an allowable range, the image formation with the background stain and excessive density is more reliably reduced. can do.

In the first embodiment, the configuration in which background contamination is reduced by promoting toner charging has been described. However, the "charge amount adjustment control" according to the present invention promotes charging of image forming particles. It is not limited to control. For example, in the case where background contamination is caused by an increase in the oppositely charged toner, the background contamination may be reduced by not promoting the charging of the toner. Such cases are also included.

Next, a second embodiment in which another characteristic configuration of the present invention is applied to a copying machine will be described. The basic configuration of the copying machine according to the second embodiment is described in the first embodiment.
The description is omitted because it is the same as that of the embodiment.

The CPU of the copying machine according to the second embodiment operates immediately after the main power of the copying machine is turned on, and during the time when the main power is turned on and the image forming operation is not performed (hereinafter referred to as standby time). Immediately after 1440 minutes as the predetermined time, the subroutine sb2 as the density adjustment control is executed. That is, when there is a high possibility that the environment has greatly changed compared to when the last image forming operation is performed, the processing of the subroutine sb2 is executed. Note that the flow of the sequence before the execution of the subroutine sb2 is omitted because the process of “subroutine sb1” in FIG. 3 is simply replaced with “subroutine sb2”.

FIG. 5 is a flowchart showing the processing of the subroutine sb2 of the CPU in the copying machine. In the subroutine sb2, the CPU first starts rotation of the photosensitive drum 1 (substep sb2-
1) A P pattern is formed at the predetermined position on the photosensitive drum 1 (substep sb2-2), and Vsp is referred to (substep sb2-3). And Vsp <0.3
9 (substep sb2-3
Y), it is considered that background contamination exceeding the allowable range has occurred on the photosensitive drum 1, and a toner consumption process is executed to reduce the toner concentration in the developing device 3 (substep sb2-4).

In this toner consumption process, 330
A linear toner consumption image pattern having a thickness of 3.3 [mm] (hereinafter, referred to as a consumption pattern) with respect to the entire width direction on the photosensitive drum 1 rotated at the surface linear velocity of [mm / sec]. Are formed at intervals of 6.6 [mm]. Since the formation time of this consumption pattern is 6 seconds, 200 consumption patterns are formed. Note that it is desirable to appropriately set the size of the consumption pattern in accordance with the storage amount of the two-component developer in the developing device 3 so as not to lower the toner concentration too much. The storage amount of the two-component developer in the developing device 3 of the first embodiment is about 1 [kg], and the toner concentration is adjusted to approximately 2.5 [wt%]. Also,
The toner of the consumption pattern formed on the photosensitive drum 1 is collected in the cleaning device 5 by cleaning, so that it is not wasted.

Here, in the copying machine of the second embodiment, when the toner charge amount is insufficient or when the environment is largely changed, the image density is reduced by such toner consumption processing. There are many. That is, when the charge amount is insufficient or when the environment is largely changed,
Since the toner density is reduced more than usual, the density of the formed image is reduced.

On the other hand, as described above, the CPU normally executes toner density control (hereinafter, simply referred to as toner density control) such that the output value from the P sensor for detecting the P pattern approaches the P target value. For this reason, even if the toner density is appropriately reduced in the toner consumption process, the toner density may be increased again by the subsequent toner density control, and the above-mentioned background stain may be re-occurred.
As a method of avoiding such a recurrence, the output value from the T sensor 3d immediately after the toner consumption processing is set to the T target within a predetermined time after the toner consumption processing, for example, a time until the toner is sufficiently charged. There is a method in which the toner density control is started after the predetermined time elapses. However, after the toner consumption processing, the toner density may be out of the proper detection range of the T sensor, and in such a case, the detection error of the toner density increases, and the accurate adjustment of the toner density becomes difficult. It becomes difficult.

Therefore, the CPU proceeds to the sub-step sb
3, it is determined that Vsg ≧ 3.9, that is, after it is determined that the degree of background contamination of the photosensitive drum 1 is within an allowable range, T is determined using the two-component developer in the developing device 3.
The sensor 3d is calibrated (substep sb2-
5).

In this calibration process, the CPU sets the center of the proper detection area of the toner concentration of the T sensor 3d to the toner concentration of the two-component developer immediately after the control in step S13. 3d
The PWM value of the T sensor is adjusted so that the output value of the T sensor becomes, for example, 2.5 [V] at the center. By such calibration of the T sensor 3d, the appropriate detection range of the toner density of the T sensor 3d is adjusted to the toner density after the toner consumption processing, so that an increase in the detection error of the toner density that occurs after the toner consumption processing is avoided.

After the calibration process of the T sensor 3d is executed, the rotation of the photosensitive drum 1 is terminated and the process of the subroutine sb2 is terminated (substep sb2-6).

If the toner density after the start of the toner density control becomes higher than the toner density immediately after the toner consumption processing, the T sensor 3d is calibrated again using the toner in the developing device 3. It is effective. More specifically, the CPU causes the CPU to compare the T target value after the start of the toner density control with the T target value immediately after the toner consumption process, and when the former value is smaller than the latter value, the T sensor It is configured to execute 3d calibration processing.

In the processing of the above subroutine sb2, when Vsp exceeds 0.39, which is a specific amount of the attached amount of the image forming particles, the toner in the developing device 3 is forcibly consumed. Thus, the toner density in the developing device 3 can be reduced before a desired image is formed on the photosensitive drum 1.

As described above, according to the copying machine of the second embodiment,
Before the desired image is formed on the photosensitive drum 1 by the processing of the subroutine sb2, the toner density in the developing device 3 can be reduced, so that the background stain on the transfer paper and the image formation with excessive density can be more reliably performed. Can be reduced.

In the second embodiment, the configuration in which the background density is reduced by reducing the toner density has been described. However, the "density adjustment control" according to the present invention is limited to the control for reducing the density of image forming particles. It is not something to be done.
For example, in the case where background contamination is caused by an increase in the oppositely charged toner, the background contamination may be reduced by replenishing a new toner to lower the relative concentration of the oppositely charged toner in the two-component developer. In some cases, that is, background contamination may be reduced by increasing the toner density, and the “density adjustment control” according to the present invention includes such an aspect.

[0055]

According to the first aspect of the present invention, when there is a high possibility that the charge amount of the image forming particles is insufficient, the image forming particles of the reference image formed at a predetermined position on the latent image carrier are provided. Since the amount of the image forming particles adhered to the latent image carrier is reduced according to the amount of adherence, the excellent effect that the background stain on the latent image carrier and the image formation with excessive density can be more reliably reduced. is there.

According to the second aspect of the present invention, if the amount of image forming particles adhered to the reference image exceeds a predetermined amount, the image in the two-component developing device is formed before a desired image is formed on the latent image carrier. Since the density of formed particles can be reduced, there is an excellent effect that background contamination of the latent image carrier and the transfer body and image formation with excessive density can be more reliably reduced.

According to the third aspect of the present invention, it is possible to avoid an increase in the detection error of the particle density detecting means which occurs after the above-mentioned forced consumption control. There is an excellent effect that it is possible to avoid a decrease in

According to the fourth aspect of the present invention, the amount of reduction in the concentration of image forming particles per unit time is made uniform, so that
There is an excellent effect that the concentration of the image forming particles can be adjusted accurately.

According to the fifth aspect of the invention, since the first image formation after the main power supply of the image forming apparatus is turned on, it is possible to reduce problems such as image formation with excessive density and the above-described background stain. There is an excellent effect that the inconvenience can be more reliably reduced.

According to the sixth aspect of the present invention, the main power supply is
Since it is possible to avoid erroneous recognition of the background defect state from the first charge amount adjustment control or the forced consumption control after N, the image formation with excessive density and the background contamination of the latent image carrier are more reliably reduced. There is an excellent effect that you can.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming portion of a copying machine according to an embodiment.

FIG. 2 is a block diagram showing a part of a circuit configuration in a control unit 10 of the copying machine.

FIG. 3 is a flowchart showing a part of control by a CPU of the control unit 10;

FIG. 4 is a flowchart showing processing of a subroutine sb1 in the CPU.

FIG. 5 is a flowchart showing the processing of a subroutine sb2 in the CPU of the copying machine according to the second embodiment.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 2 charging device 3 developing device 3a developing roller pair 3b stirring paddle 3c agitator 3d T sensor 4 transfer device 5 cleaning device 6 static elimination lamp 7 toner replenishing device 7a stirring member 7b toner replenishing roller 8 P sensor 10 control unit 10a MPU 10b ROM 10c RAM 11 Operation display unit

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[Procedure amendment]

[Submission date] November 9, 1998 (1998.11.
9)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 4

[Correction method] Change

[Correction contents]

FIG. 4

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Fig. 5

[Correction method] Change

[Correction contents]

FIG. 5

Continued on the front page (72) Inventor Ichiro Komuro Ricoh, 1-3-6 Nakamagome, Ota-ku, Tokyo (72) Inventor Toshihiro Sugiyama 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh, Inc. F term (reference) 2H027 DA10 DA40 DD07 DE02 DE04 EA01 EA06 EC03 EC06 EC10 EC12 ED03 ED08 ED10 EE02 EF01 EF15 2H077 DA04 DA10 DA24 DA43 DA47 DA54 DA63 DA81 DB02 DB14 DB22 EA01

Claims (5)

[Claims] 1. A latent image carrier for forming a latent image on a surface, a developing device for charging image forming particles by a particle charging means and developing the latent image with the charged image forming particles, and a control for controlling these devices Means for detecting the amount of attached image forming particles at a predetermined position on the surface, wherein the main power is turned on, or the main power is turned on. If the time during which the image formation is not performed exceeds a predetermined time, a charge amount adjustment control for adjusting the charge amount of the image forming particles according to the amount of the image forming particles attached to the reference image formed at the predetermined position is performed. An image forming apparatus configured to reduce the amount of image forming particles attached to the latent image carrier. 2. A two-component developing device for developing a latent image using a two-component developer containing image forming particles and a carrier, a latent image carrier for forming a latent image on the surface, and a two-component developer. What is claimed is: 1. An image forming apparatus comprising: a particle supply unit for supplying image forming particles; and a control unit for controlling the particles. , When the main power is turned on,
Alternatively, if the time during which the main power is on and no image formation is performed exceeds a predetermined time, and the amount of image forming particles adhered to the reference image exceeds a predetermined amount, the two-component development is performed. An image forming apparatus for performing a forced consumption control for forcibly consuming image forming particles in the apparatus. 3. An image forming apparatus according to claim 2, further comprising a particle concentration detecting means for detecting the concentration of the image forming particles in said two-component developing device, using said two-component developer after said forcible consumption control. An image forming apparatus, wherein a detecting unit is calibrated. 4. The image forming apparatus according to claim 2, wherein
An image forming apparatus, wherein a pattern image having a predetermined shape is formed on the surface of the latent image carrier, thereby forcibly consuming the image forming particles in the two-component developing device. 5. The image forming apparatus according to claim 1, wherein at least from when the main power is turned on to when the first charge amount adjustment control or the forced consumption adjustment control is executed. An image forming apparatus, wherein the predetermined position in which there is no background stain is detected by the particle adhesion amount detecting means, and the particle adhesion amount detecting means is calibrated.