JPH05134548A - Image forming device - Google Patents

Abstract

PURPOSE:To have the effect of density adjustment for a target image appear swiftly in a picture by changing over quantity of electrification at the time of reference image formation by a servicing person, etc. CONSTITUTION:In the device where the toner density is maintained at the specified density by controlling the driving time of a replenishing roll 14a by comparing a detected value T of a toner density detection sensor 18a with a control reference value T0 and carrying out the formation of a reference image and detection of the image density by an optical sensor 32 for every 500 copies, when density setting of the target image is adjusted during maintenance and inspection by the servicing person, change over of grid voltage of a uniform electrifying device 13, which is a condition of image formation, is carried out followed by compensation of the control reference value T0 according to the changeover and toner replenishing control is carried out utilizing the control reference value T0 after compensation, in copying until the compensation control is carried out of the control reference value T0 according to the formation of the reference image and its detection at the specified timing.

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 facsimile and a printer, and more particularly to controlling image density in the image forming apparatus.

[0002]

2. Description of the Related Art In this type of image forming apparatus, a developing device attaches toner to a latent image formed on an image carrier such as a photoconductor to visualize the latent image, and the visualized image is transferred onto a transfer paper as required. To form a final image. Since the toner in the developing device provided with a developer carrying member such as the developing roller in this developing device is consumed in accordance with image formation, toner is appropriately replenished from the replenishment toner container provided in this developing device. is doing.

As a method of supplying toner to the developing device,
As a first method, the toner concentration value detected by the toner concentration sensor provided in the developing device is compared with the target toner concentration value, and toner is added as necessary so that the toner concentration in the developing device becomes the target toner concentration. As a second method to replenish,
A predetermined reference latent image is formed on the image carrier, and the image density of the reference toner image obtained by developing the reference latent image with a developing device is detected by an optical sensor or the like, and the detected image density value and the target image density are detected. There is known a method in which the toner is replenished as necessary so that the image density of the reference toner image becomes a target image density corresponding to the target image density value by comparing the value with the value.

According to the first method, the toner concentration in the developing device can be maintained constant, and the toner scattering due to the excessive toner concentration in the developing device can be effectively prevented. However, when the developing characteristics of the developer change due to the fatigue of the developer over time and environmental changes such as temperature and humidity, the image density also changes. For example, if the charge amount (Q / M) of toner decreases at high humidity, the image density (ID) increases,
Characters are thickened or crushed, and toner is also scattered. On the contrary, when the toner charge amount becomes high, the image density decreases. According to the second method, the toner replenishment is controlled so that the image density value of the reference toner image becomes the target image density. Therefore, even if the developing characteristic of the developer changes, the developing device can be changed accordingly. The target image density can be obtained by correcting the target toner density value of. However, when the change in the developing characteristics of the developer is too large, the toner density of the developing device becomes abnormal and various problems occur. For example, when the charge amount of toner is excessively reduced at high humidity, the toner density in the developing device is controlled to be extremely low in order to maintain the image density at the target image density. The developer is agitated excessively, the life of the developer is shortened, and uneven development is likely to occur.
On the contrary, when the toner charge amount excessively increases at low humidity, the toner density in the developing device is controlled to be extremely high in order to maintain the image density at the target image density. In addition, there is a problem that the image quality becomes severe and the image quality is easily deteriorated with time, and maintenance in a short period is required.

As a third method for solving the problems in the first and second methods as described above, the toner replenishment using the toner density value detected by the toner density sensor is performed while the reference toner image is formed. It is also known that the image density is detected appropriately and the target toner density value is corrected as necessary so that the target image density value is reached according to the detected image density value (for example, JP-A-57). -1
See Japanese Patent No. 36667). According to the third method, similar to the first method, the detected toner density value from the toner density sensor is compared with the target toner density value and toner is replenished if necessary, whereby the developing device The inner toner concentration is maintained at the target toner concentration. Then, a predetermined reference latent image is formed on the image carrier at a predetermined timing, and the image density of the reference toner image obtained by developing the reference latent image with a developing device is detected by an optical sensor or the like. The target toner density value is corrected as necessary by comparing the density value with the target image density value, so that the image density becomes the target image density even if the developing characteristic of the developer changes. Therefore, the first
Unlike the above method, the image density does not change even if the developing characteristics of the developer change. Furthermore, since the upper and lower limits of normal control are set for this target toner density value, the detected image density value and the target image density value are compared as described above, and the target toner density value is set as necessary. Even when correcting, the correction is performed so that the upper and lower limits are not exceeded. Therefore, unlike the second method, even if the change in the developing characteristics of the developer is too large, the toner density of the developing device does not become abnormal, and the above-mentioned problems do not occur.

[0006]

However, in the image forming apparatus adopting the third method, when the setting of the target image density is adjusted at the time of maintenance and inspection by a service person or the like, the effect of the adjustment is obtained. There remains a problem that it takes a long time to appear on an actual image (it is necessary to repeat image formation many times).

Hereinafter, this problem will be described in detail in comparison with the image forming apparatus adopting the first method or the second method. Since the setting of the target image density in the image forming apparatus adopting the first method depends on the setting of the target toner density value, the setting of the target image density is adjusted by the service person or the like adjusting the target toner density value. ing.
Further, since the toner density detection by the toner density sensor and the toner replenishment based on the detected toner density value are executed every time the normal image forming operation is performed, the image forming operation after the adjustment of the target toner density value causes the rapid development. The toner density in the container is made to converge to the adjusted target toner density, whereby the image density can be brought close to the target image density quickly.

The adjustment of the target image density in the image forming apparatus adopting the second method is performed by developing the charge amount or the exposure amount or the reference latent image with respect to the image carrier in forming the reference latent image. This is performed by a service person or the like adjusting image forming conditions such as the developing bias at the time of forming the reference toner image.

The target image density can be adjusted by adjusting the image forming conditions when forming the reference toner image for the following reason.
That is, the reference toner image is formed on the image carrier so as not to overlap with the toner image of the formed image (for example, a toner image corresponding to a document in a copying machine; hereinafter referred to as a document toner image). The image forming conditions (charge amount, exposure amount or developing bias for the image carrier) at the time of forming the original toner image and the image forming condition at the time of forming the reference toner image can be adjusted independently. This is because the operator can adjust the image density when the original toner image is formed by appropriately adjusting the image density when the image is formed, and the image forming condition when the original toner image is formed by the operator is temporarily assumed. If the image forming conditions at the time of forming the reference toner image are also adjusted by the adjustment, the toner replenishment control based on the comparison between the detected image density value of the reference toner image and the target image density value causes the original toner image by the operator This is because the toner density in the developing device is controlled so as to achieve the target image density corresponding to the target image density value, regardless of the adjustment of the image forming conditions during image formation. Of the image forming conditions for forming the original toner image and the image forming conditions for forming the reference toner image that can be adjusted independently, the image forming condition for forming the reference toner image is maintained by a service person or the like. Adjust during inspection. Specifically, when it is desired to adjust the image density (the density of the image corresponding to the original document) to a higher level, the image forming conditions for forming the reference toner image are adjusted so that the reference toner image has a relatively low image density. (For example, reduce the amount of charge on the image carrier). As a result, the detected image density of the reference toner image becomes low, so that the detected image density value of the reference toner image is compared with the target image density value to obtain the image density corresponding to the target image density value. Replenishment is performed to control the toner density of the developing device to be relatively high. Therefore, in such a developing device in which the toner density is controlled to be relatively high,
When the original toner image is formed, the image density of the original toner image can be made relatively high. Conversely, if you want to adjust the image density (the density of the image corresponding to the original document) to a lower level,
The image forming conditions at the time of forming the reference toner image are adjusted so that the reference toner image has a relatively high image density (for example, the amount of charge on the image carrier is increased). As a result, the detected image density of the reference toner image becomes high, so that the detected image density value of the reference toner image and the target image density value are compared to obtain the image density corresponding to the target image density value. Replenishment is suppressed and the toner concentration in the developing device is controlled to be relatively low. Therefore, if the original toner image is formed by the developing device in which the toner density is controlled to be relatively low, the image density of the original toner image can be lowered.

As described above, in the image forming operation after the service person or the like has adjusted the image forming conditions at the time of forming the reference toner image,
The toner density in the developing unit is promptly converged to the adjusted target toner density, whereby the image density can be brought close to the target image density quickly.

On the other hand, in order to adjust the target image density in the image forming apparatus adopting the third method, a serviceman or the like adjusts the image forming condition at the time of forming the reference toner image, as in the second method. It is done by. That is,
If you want to adjust the image density (the density of the image corresponding to the original document) to a higher level, adjust the image forming conditions when forming the reference toner image so that the reference toner image has a relatively low image density, and vice versa. When it is desired to adjust the image density (the density of the image corresponding to the original document) to a lower level, the image forming conditions at the time of forming the reference toner image are adjusted so that the reference toner image has a relatively high image density (for example, image bearing). Increase the amount of charge on the body).

By this adjustment, the target image density value of the reference toner image formed under the adjusted image forming conditions is compared with the target image density value at the time of the target toner density value correction control by the subsequent formation and detection of the reference toner image. Then, the target toner density value is corrected so that the image density corresponding to the target image density value is obtained. Specifically, when the image density (the density of the image corresponding to the document) is adjusted to be higher by the adjustment by the service person, the image forming condition at the time of forming the reference toner image is set so that the reference toner image is relatively low. Adjust to obtain the image density. As a result, the image density of the reference toner image formed at a predetermined timing after this adjustment becomes low, and the detected image density value of this reference toner image and the target image density value are compared to correspond to the target image density value. The target toner density value is corrected to a value corresponding to a relatively high toner density so as to obtain the image density. Then, the toner concentration is detected by the toner concentration sensor and the toner is replenished based on the detected toner concentration value, which is executed every time the normal image forming operation is performed.
The toner density in the developing device is controlled to be high so that the toner density corresponds to the corrected target toner density value. Therefore, the image density of the original toner image is relatively high. On the contrary, when the image density (the density of the image corresponding to the original) is adjusted to a lower level by the adjustment by the service person or the like, the image forming condition at the time of forming the reference toner image is set so that the reference toner image has a relatively high image density. Adjust so that As a result, the image density of the reference toner image formed at a predetermined timing after this adjustment becomes high, so the detected image density value of this reference toner image and the target image density value are compared to correspond to the target image density value. The target toner density value is corrected to a value corresponding to a relatively low toner density so as to obtain the image density. Then, the toner density is detected by the toner density sensor and the toner is replenished based on the detected toner density value, which is executed every time the normal image forming operation is performed, so that the toner density corresponding to the corrected target toner density value is obtained. The toner concentration in the container is controlled to be low. Therefore, the image density of the original toner image is made relatively low.

However, the target toner density value correction control based on the reference toner image formation / detection is usually executed once every tens to hundreds of times of image formation. Therefore, even if a serviceman or the like adjusts the image forming conditions at the time of forming the reference toner image, the image forming is performed until the timing when the target toner density value correction control by the reference toner image formation / detection is executed thereafter. The effect of adjusting the image forming conditions at the time of forming the reference toner image by the service person or the like is not reflected on the actual image at all. That is, when the setting of the target image density is adjusted at the time of maintenance and inspection by a service person or the like, it takes a long time until the effect of the adjustment appears on the actual image (it is necessary to repeat the image formation many times. ).

The present invention has been made in view of the above problems, and an object of the present invention is to have a serviceman or the like in an image forming apparatus adopting the third method as a method of supplying toner to a developing device. It is an object of the present invention to provide an image forming apparatus capable of causing the adjustment effect of the target image density setting at the time of maintenance and inspection to appear on an actual image relatively quickly.

[0015]

In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention includes a developing device that supplies toner to a latent image formed on an image carrier, and a developing device that visualizes the latent image. Based on the result of comparing the output value of the toner replenishing means for replenishing toner to the developing device, the toner concentration detecting means for detecting the toner concentration in the developing device, and the target toner concentration set value. And a toner replenishment control means for controlling the toner replenishment means, and a reference image forming means for forming a reference latent image for detection on the image carrier and visualizing the reference latent image by the developing device to form a reference image. An image density detecting means for detecting the image density of the reference image, a first setting value correcting means for correcting the target toner density setting value based on the output of the image density detecting means, and a reference image forming means for forming the reference image. Switching image forming conditions Switching image forming conditions And the step, at the time of switching by the acting image condition switching means and is characterized in that a second setting value correcting means for correcting the target toner concentration setpoint in response to the switching. Here, the upper and lower limits of the target toner density set value may be set in the first set value correction means to prevent the toner density from being excessive or excessive. Furthermore,
When the corrected target toner density set value corresponds to the upper limit or the lower limit, the display means for notifying the fact is driven so that a service person or the like can appropriately judge the state of the image forming apparatus. Is also good.

An image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect, wherein the second setting value correcting means and the image forming condition switching means relatively set the image forming conditions for forming the reference image. When the target toner density setting value is switched to obtain a low image density, the target toner density setting value is set to a value corresponding to the relatively high toner density, and when the switching is performed to obtain a relatively high image density, the target toner density setting value is set to the target toner density setting value. The reference image formed by the image density detecting means is corrected to a value corresponding to a comparatively low toner density, and the corrected value is temporarily detected by the image forming condition switching means, and the reference image formed under the image forming condition is detected by the image density detecting means. In such a case, the correction amount is smaller than the target toner density setting value after being corrected by the first setting value correcting means based on the output of the image density detecting means. It is an butterfly.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the toner in the developing device is forcibly supplied onto the image carrier to consume the toner in the developing device. Toner consumption operation control means for executing a consumption operation, and driving of the toner replenishing means in accordance with the corrected target toner density set value when correcting the target toner density set value by the second set value correction means. The present invention is characterized in that a toner density stabilization control means for performing any one of the toner consumption operations by the toner consumption operation control means is provided.

An image forming apparatus according to a fourth aspect of the present invention is the image forming apparatus according to the third aspect, wherein the toner replenishment stabilization control means replenishes the toner when the target toner concentration set value is corrected by the second set value correction means. The driving of the means and the toner consumption operation by the toner consumption operation control means, the formation of the reference image by the reference image forming means,
The detection of the image density of the reference image by the image density detection means and the correction of the target toner density setting value by the first setting value correction means are performed by the detection image density value of the reference image by the image density detection means. It is characterized in that a repetitive control means for repetitively executing the process until it is within a range near the target image density value is provided. Here, by setting an upper limit on the number of repetitions by this repetition control means,
The execution time of this repetitive control may not be too long.

According to a fifth aspect of the present invention, the toner replenishment control means is configured to compare the output value of the toner density detection means with the target toner density set value by the toner replenishment control means. 2. The image forming apparatus according to claim 1, wherein the toner replenishing amount by the replenishing means is changed within a predetermined toner replenishing rate range by forcibly supplying the toner in the developing device onto the image carrier. At the time of correcting the target toner density set value by the toner consumption operation control means for executing the toner consumption operation for consuming the toner in the developing device and the second set value correction means, the target toner density set value after the correction Accordingly, the toner replenishment control means is driven and the toner consumption operation control means is driven at a replenishment rate smaller than the maximum toner replenishment rate during the image forming operation by the toner replenishment control means. In which it characterized in that a toner density stabilization control means for executing one of the toner consumption operation.

An image forming apparatus according to a sixth aspect of the present invention is a transfer device for transferring a toner image formed on an image carrier to a transfer material, and an image carrier after the toner image is transferred onto the transfer material by the transfer device. 4. The image forming apparatus according to claim 3, further comprising a cleaning device for removing residual toner from the surface of the body, wherein the toner consumption operation control means forms a latent image for adhering toner on the image carrier and develops the latent image. And a toner consumption amount on the image carrier is compared with the image forming condition at the time of forming the consumed toner image compared to the image forming condition at the time of image forming. The feature is that it is set to be relatively small.

An image forming apparatus according to a seventh aspect is the image forming apparatus according to the third aspect, wherein the transfer device transfers the toner image formed on the image carrier to a transfer material, and the transfer device causes the toner to be transferred onto the transfer material. 4. A cleaning device for removing residual toner from the surface of the image carrier after the image has been transferred.
In the above image forming apparatus, the toner consumption operation control means is configured such that the toner consumption image forming region on the surface of the image carrier passes the cleaning device facing portion twice or more. .

According to the image forming apparatus of claim 8, the toner image formed on the image carrier is transferred onto the intermediate transfer member to which the transfer electric field forming means can transfer the toner image, and the toner image on the intermediate transfer member. 4. The image forming apparatus according to claim 3, further comprising a cleaning device that removes residual toner from the surface of the image carrier after the transfer of the toner, and an intermediate transfer member cleaning device that removes the toner from the surface of the intermediate transfer member. The operation control means forms a latent image for toner adhesion on the image carrier, visualizes the latent image by the developing device to form a consumed toner image, and the consumed toner image is transferred to the intermediate transfer body. When facing each other, the transfer electric field forming means forms a transfer electric field smaller than that at the time of image formation. Here, as the intermediate transfer member,
A transfer material is held and the held transfer material is made to face the image carrier on which the toner image is formed, or the surface is directly made to face the image carrier on which the toner image is formed, and this toner image is transferred to the surface. After the transfer, the transfer toner image can be used. In the former case, the transfer material is not held when the consumed toner image faces the intermediate transfer member.

An image forming apparatus according to a ninth aspect is the image forming apparatus according to the eighth aspect, wherein the toner consumption operation control means is
The consumed toner image forming area on the surface of the image carrier is more than once,
The toner image transfer area on the intermediate transfer member passes through the cleaning device facing portion and passes through the intermediate transfer member cleaning device facing portion twice or more. is there.

[0024]

According to the image forming apparatus of the present invention, the toner replenishment control means controls the toner replenishment means based on the output of the toner concentration detection means to replenish the toner to the developing device, thereby the toner concentration in the developing device is increased. Is maintained at the target toner density value corresponding to the target toner density value. On the other hand, the reference image forming means forms a reference image on the image carrier at a predetermined timing, and the image density detecting means detects the reference image. When it is detected that the detected image density is higher than the desired density, the first set value correcting means corrects the target toner density value by an amount by which the image density of the reference image becomes the target image density, and the toner after that is corrected. The toner replenishment control by the replenishment control means is performed based on the corrected target toner density value, whereby the toner density is lowered and the image density becomes a desired density. Conversely, the detected image density is
When it is detected that the density is lower than the desired density, the first set value correction means corrects the target toner density value by an amount by which the image density of the reference image becomes the target image density, and the toner replenishment control thereafter is corrected by this correction. After the target toner density value,
As a result, the toner density is increased and the density of the image becomes a desired density.

When the target image density setting is adjusted by a service person or the like during maintenance and inspection, when it is desired to adjust the image density corresponding to the original document to a higher density by the image forming condition switching means, when the reference toner image is formed. Adjust the image forming conditions of so that the reference toner image has a relatively low image density, and conversely,
When it is desired to adjust the density of the image corresponding to the original document to a lower level, the image forming conditions for forming the reference toner image are adjusted so that the reference toner image has a relatively high image density (for example, the amount of charge on the image carrier). To increase). Subsequent to this switching, the second setting value correction means corrects the target toner density setting value in accordance with this switching. The correction of the target toner density set value is performed by adjusting the image forming condition at the time of forming the reference toner image by the image forming condition switching means in the adjustment of the target image density setting of the image corresponding to the document, which is obtained by an experiment in advance. This is performed based on the relationship with the toner density in the developing device for obtaining the predetermined image density to be obtained by the adjustment.

Toner replenishment control using the target toner density set value corrected by the second set value correction means at the time of image formation after adjustment of the target image density setting at the time of maintenance and inspection by a service person or the like. The toner replenishing means is controlled by the means to adjust the toner density in the developing device to obtain a predetermined image density to be obtained by this adjustment.

According to another aspect of the image forming apparatus of the present invention, the second setting value correcting means switches the image forming conditions when the reference image is formed by the image forming condition switching means so that a relatively low image density can be obtained. When the target toner density setting value is changed to a value corresponding to a relatively high toner density, and when the target toner density setting value is switched to obtain a relatively high image density, the target toner density setting value is changed to a value corresponding to a relatively low toner density. Correct to. The corrected value is output to the image density detecting means when the image density detecting means detects the reference image formed under the image forming condition after being switched by the image forming condition switching means. Based on the above, the correction amount is set to be smaller than the target toner density setting value after being corrected by the first setting value correcting means, whereby the second setting value correcting means excessively corrects the target toner density setting value. Prevent.

In the image forming apparatus according to the third aspect of the present invention, subsequent to the correction of the target toner density set value by the second set value correction means, the toner density stabilization control means sets the corrected target toner density set value to the target toner density set value. Accordingly, either the drive of the toner replenishing means or the toner consuming operation by the toner consuming operation control means is executed, so that the toner replenishing control by the toner replenishing control means during the image forming operation is immediately performed by this adjustment. The toner density in the developing device is set to obtain the desired image density.

In the image forming apparatus according to a fourth aspect of the present invention, following the correction of the target toner density set value by the second set value correction means, the toner replenishment means is driven and the toner consumption operation is controlled by the toner density stabilization control means. Means for performing any one of the toner consumption operations, the reference image forming means for forming the reference image, the image density detecting means for detecting the image density of the reference image, and the first set value correcting means for the target toner density. The correction of the set value is repeated until the detected image density value of the reference image by the image density detecting means falls within the range in the vicinity of the predetermined target image density value by the repetitive control means. The predetermined image density to be obtained by this adjustment is obtained immediately and accurately without depending on the toner replenishment control by the toner replenishment control means. To the toner density in the developing device of the fit.

According to a fifth aspect of the present invention, in the toner replenishment control means, the toner during the image forming operation is performed according to the result of comparison between the output value of the toner density detection means and the target toner density set value. The amount of toner replenished by the replenishing means is changed within the range of a predetermined toner replenishment rate.
The toner density in the developing device is promptly set to the toner density corresponding to the target toner density setting value. Then, following the correction of the target toner density set value by the second set value correction means, the toner density stabilization control means drives the toner replenishing means and toner in accordance with the corrected target toner density set value. Any one of the toner consuming operations by the consuming operation control means is executed, whereby the toner replenishing control means does not depend on the toner replenishing control during the image forming operation.
Immediately, the toner density in the developing device for obtaining the predetermined image density to be obtained by this adjustment is set. At this time, the toner replenishment means is driven by the toner density stabilization control means at a replenishment rate smaller than the maximum toner replenishment rate during the image forming operation by the toner replenishment control means.
This prevents the developer in the developing device from being insufficiently stirred when the toner is replenished at an excessively high toner replenishment rate.

According to a sixth aspect of the present invention, in the toner consumption operation control means, a latent image for toner adhesion is formed on the image carrier, and the latent image is visualized by the developing device to form a consumed toner image. By forming the toner, the toner density in the developing device is forcibly reduced. Then, the image forming condition at the time of forming the consumed toner image is set such that the toner adhesion amount on the image carrier is relatively smaller than the image forming condition at the time of forming the image. To prevent too much load on the cleaning device.

According to a seventh aspect of the present invention, in the toner consumption operation control means, the consumed toner image forming area on the surface of the image carrier passes the cleaning device facing portion twice or more. The toner in the consumed toner image forming area is sufficiently removed.

In the image forming apparatus according to the present invention, the toner consumption operation control means forms a latent image for adhering toner on the image carrier, and the latent image is visualized by the developing device to form a consumed toner image. When the toner image is formed and the consumed toner image faces the intermediate transfer body, the transfer electric field is formed by the transfer electric field forming means, whereby the toner constituting the consumed toner image on the image carrier is formed. After a part of the toner is transferred onto the intermediate transfer body, it is removed by the intermediate transfer body cleaning device, while the toner remaining on the image carrier after the transfer to the intermediate transfer body is removed by the cleaning device. Then, by making the transfer electric field by the transfer electric field forming means when the consumed toner image is opposed to the intermediate transfer member smaller than that at the time of image formation, the toner transferred onto the intermediate transfer member. It is prevented that the amount is too large and the intermediate transfer member cleaning device is overloaded.

According to a ninth aspect of the present invention, in the toner consumption operation control means, the consumed toner image forming area on the surface of the image carrier passes the cleaning device facing portion twice or more, and the intermediate transfer is performed. The consumed toner image transfer area on the body passes through the intermediate transfer body cleaning device facing portion twice or more, whereby the consumed toner image forming area on the surface of the image carrier and the above-mentioned intermediate transfer body. The toner in the consumed toner image transfer area is sufficiently removed.

[0035]

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) which is an image forming apparatus will be described below. First, the outline of the mechanism and operation of the copying machine will be described with reference to FIG. 1 showing the schematic configuration of the copying machine according to the present embodiment. In FIG. 1, a document table 2 on which a document is placed is attached to the upper surface of a case 1, and an optical system 3 is provided in the case 1 at a position facing the document table 2.
A reference density plate 42 for forming a reference latent image is provided at an end of one side edge of the document table 2. Light is radiated from the illumination lamp 4 onto the document on the document table 2, and reflected light from the document is reflected by the optical system 3
After being reflected by the mirrors 5 and 6 inside the case, reflected by the mirror 7 through the lens 8 and color-separated by the color separation filter 9, the image forming unit 10 provided below the optical system 3 in the case 1. Entered in.

A photoconductor 11 is provided in the image forming section 10, and a cleaning device 12 and a uniform charger 13 are provided so as to face the peripheral surface of the photoconductor 11. The incident light color-separated by the color separation filter 9 is guided to the image forming unit,
The peripheral surface of the photoconductor 11 that has been cleaned by the cleaning device 12 and uniformly charged by the uniform charger 13 is irradiated, and a latent image of the color is formed on the peripheral surface of the photoconductor 11.

The black developing device 1 is opposed to the peripheral surface of the photoreceptor 11.
4, a cyan developing device 15, a magenta developing device 16, and a yellow developing device 17 are provided, and each developing device has a toner density detecting sensor 18a, 18b, 1 which is a toner density detecting means.
8c and 18d are provided respectively. As the toner concentration detection sensor in this example, a magnetic permeability sensor whose output decreases as the toner concentration increases is used. Each of the developing units 14, 15, 16 and 17 described above has a toner cartridge 14b containing replenishment toner (toner cartridges of the yellow developing unit 17, the magenta developing unit 16 and the cyan developing unit 15 are shown in FIG. 2). Are arranged on the inner side of the container and not shown). Each developing device has a developing roller rotatably driven in the direction of the arrow at the opening facing the photoconductor 11 and a paddle as a developer stirring means at the bottom, and the paddle serves as a developer consisting of toner and carrier. Is mixed and stirred to be replenished on the developing roller. The toner cartridge 14b of the black developing device 14 has a replenishing roller 14c which is rotationally driven by a replenishing clutch 14a to which a drive from a motor (not shown) is transmitted in a toner discharging portion to the lower developing device 14a. The replenishing roller 14c and the replenishing clutch 14a constitute toner replenishing means for the black developing device 14.
Further, the toner cartridges (not shown) of the yellow developing device 17, the magenta developing device 16, and the cyan developing device 15 are communicated with each other by toner conveying means (not shown) for supplying toner into the corresponding developing devices. Each of these transporting means is configured to be driven by a motor and a motor drive circuit (both not shown), and constitutes toner replenishing means for each developing device. Photoconductor 1
The development of the toner image of the complementary color of the latent image formed on No. 1 is performed by the cyan developing device 15, the magenta developing device 16, and the yellow developing device 17.
One of them is selected and performed. If the light that has passed through the color separation filter 9 is blue, a complementary yellow toner image is formed. If the light is green, a complementary magenta toner image is formed. If the light is red, a complementary cyan toner image is formed. It is formed.

The image forming section 10 is provided with a transfer drum device 19 which is in contact with the photoconductor 11 and includes an intermediate transfer drum 19b which is an intermediate transfer member.
A registration roller 21 is provided in the vicinity of the registration roller 21, and a cleaning device 20, which is an intermediate transfer member cleaning device, is opposed to the transfer drum device 19 adjacent to the registration roller 21. A paper feeding device 23 is provided on one end side of the case 1, and a transfer paper transport path 24 is formed between the paper feeding device 23 and the registration roller 21. Further, in the case 1, a fixing device 25 is provided above the paper feeding device 23, a transfer paper delivery path 26 is formed between the fixing device 25 and the transfer drum device 19, and the transfer drum device 19 of the delivery path 26 is formed. A separation claw 27 is provided at the end portion on the side. The transfer paper sent from the paper supply device 23 is sent by the registration roller 21 at a timing with the transfer drum device 19, clamped by the clamper, and conveyed to the transfer position. A transfer device 28 is provided at the transfer position.
The toner image on the photoconductor 11 is transferred onto the transfer paper by 8. In the case of a color image, this transfer is performed the required number of times (third floor or fourth floor), and a color image by multiple transfer is formed on the transfer paper. The transfer paper on which the necessary number of times of multiple transfer has been performed is guided to the delivery path 26 by the separating claw 27 and fixed by the fixing device 25 to form a final color image on the transfer paper. An optical sensor 42 as an image density detecting means is also arranged so as to face the surface of the photoconductor 11.
The optical sensor 42 has a light emitting element that emits light toward the surface of the photoconductor 11 and a photoelectric conversion element that receives the reflected light from the surface of the photoconductor 11.

Next, with reference to FIG. 1 which shows the mechanism relating to the image density control and the schematic configuration of the electric component section, the outline of the electric component section relating to the image density control will be described. Note that FIG. 1 shows only the black developing device 14 among the plurality of developing devices. In FIG. 1, a power supply unit 30 and a control unit 31 are provided on the other end side of the case 1 (see FIG. 2), power is supplied from the power supply unit 30 to each unit, and the control unit 31 has an interface (I
/ O) 31a, CPU 31b, read-only memory (RO
M) 31c and read / write memory (RAM) 31d. The CPU 31b controls a series of copying operations. The interface 31a includes the toner concentration detection sensors 18a, 18b, 18c, 18
d, the optical sensor 42, the grid voltage circuit 13a for controlling the charge amount of the uniform charger 13, the replenishment clutch 14a (specifically, the solenoid drive circuit for the clutch), and the photoconductor 11
Drive motor 11a (specifically, a motor drive circuit),
A drive motor 19a (specifically, a motor drive circuit) for the transfer drum 19a and a drive circuit 28a for the transfer unit 28 are connected. Further, the interface 31a is also connected to an input means 40 for setting and adjusting a target image density at the time of maintenance and inspection by a service person or the like, and a display 41 for displaying a control value limit in the control value correction of toner density control described later. Has been done.

Next, the toner density control in this copying machine will be described. Toner concentration control in this copying machine is performed by each toner concentration detection sensor 18a, 18b, 18
The detection signal input to the interface from c and 18d is read into the CPU 31b for each copying operation using each developing device, and the detection value T is compared with the control reference value T ₀ which is the target toner density setting value. According to the result, a control signal is output to the replenishment clutch 14a via the interface 31a to rotate the replenishment roller 14c.
Replenish the toner in the toner cartridge to the developing device.
In this example, when the detected value T is equal to the control reference value T ₀ , the replenishment clutch 14a is turned on for a predetermined time that can replenish the toner amount consumed in an average copy of the original document, and the detected value T is the control reference value. When the value is larger than the value T _{0, the} supply clutch 14a is turned on for a time obtained by adding the time proportional to the difference (T-T ₀ ) between the respective values to the predetermined time, and the detected value T
Is smaller than the control reference value T ₀ , the replenishment clutch 1
Control so that 4a is not turned on. A toner replenishment control means is realized by the above toner replenishment control.

Next, correction control of the control reference value T ₀ in this copying machine will be described with reference to FIG. The correction control of the control reference value T ₀ is performed for every 500 copies, for example. First, the cumulative copy number stored in the number register is read, and it is determined whether or not it is time to perform the correction control of the control reference value T ₀ depending on whether or not it is a multiple of 500 (step 1). When it is determined that it is time to perform the correction control of the control reference value T ₀ , the uniformly charged area (the area uniformly charged by the uniform charger 13 and not irradiated with light) that is the reference latent image is determined by a predetermined developing device. To develop a reference image. The reference image forming means is realized by the drive control of the uniform charging device 13 and the developing device. When this reference image passes through the portion facing the transfer drum device 19 in which the transfer device 28 is in the inoperative state and faces the optical sensor 32,
The amount of toner attached is detected by the optical sensor 32, and the detected value P is read through the interface 31a (step 2). It is determined whether the detected value P is within a predetermined range, for example, 10 or more and 14 or less (step 3). This range is centered around a value corresponding to the target image density, for example, 12.5, and is set in advance in consideration of variations in control. When it is determined that the value is within this range (Y in step 3), the control reference value T ₀ is not corrected and the normal control is directly returned.
On the contrary, if it is determined that the value is not within this range, the detected value P
Is determined to be greater than 14 (step 4).
If it is determined that the value is greater than 14 (Y in step 4), it is determined that the toner adhesion amount is too small.
The control reference value T ₀ of the toner is corrected to a value smaller by, for example, 5 so that the toner density becomes higher (step 5), and the normal control is returned. Conversely, the detected value P is not greater than 14,
That is, if it is determined that the detected value is smaller than 10 (in step 4), it is determined that the toner adhesion amount is too large, and the toner control reference value T ₀ is corrected to be a large value, for example, by 5 so that the toner density becomes thin. Then (step 6), the control returns to the normal control. The first set value correction means is realized by the above steps 2 to 6.

Although not shown in the figure, the upper limit 150 and the lower limit 70 are set in the setting range of the control reference value T ₀ so that the correction cannot exceed the upper and lower limits.

Next, the adjustment of the target image density setting at the time of maintenance and inspection by a service person will be described. Before explaining this adjustment in the present embodiment, FIGS.
A conventional adjustment method will be described with reference to (a) and (b). 7 and 8A and 8B are flowcharts showing the procedure of image density setting value adjustment performed by a conventional service person. In FIG. 7, first, the toner concentration in the developing device is set to the current control reference value T _0.
To adjust the concentration to correspond to (T sensor stabilization)
Is performed (step SB1). This T-sensor stabilization operation is performed according to the procedure shown in the flowchart of FIG.

That is, in FIG. 8A, first, for example, by inputting a predetermined special coat from the ten keys on the operation unit, the toner density for a predetermined developing device (black developing device 14 in this example) For example, the detection value T of the detection sensor and the control reference value T ₀ at that time are set in the T sensor output display mode for displaying on a sheet counter or the like. The serviceman looks at this display and compares the detected value T with the control reference value T ₀ . Here, the detected value T is smaller, that is, the toner density at that time is the control reference value T.
If it is higher than the toner density corresponding to ₀ , the copy mode is selected by the copy mode selection key or the like to the black mode (BK mode) in which copying is performed using the black developing device 14, and the original pressing plate is opened. In this state, the copy start button is pressed to create a black solid copy, thereby consuming the toner in the developing device. On the contrary, the detected value T is larger, that is, the toner density at that time is the control reference value T _0.
When the toner density is lower than the toner density corresponding to, the copy mode is selected with the copy mode selection key or the like to the black mode (BK mode) in which copying is performed using the black developing device 14,
With the blank document set on the document table 2 and the document pressing plate closed, the copy start button is pressed to create a blank copy, whereby toner replenishment is performed by the above toner replenishment control. After such a black solid copy or a blank copy, the detected value T of the sheet counter (the detected value is also changing due to toner consumption) and the control reference value T are again provided.
₀ is compared (step 3), and thereafter, black solid copy or blank copy is repeated until the detected value T falls within ± 3 with respect to the control reference value T ₀ .

Returning to FIG. 7, when the above T-sensor stabilization operation is completed, the toner concentration in the developing device is next adjusted so that the toner adhesion amount of the reference image detected by the optical sensor 32 is near the target image concentration. An operation (stabilization of the P sensor) is performed to obtain an image density of a toner density (step S).
B2). The operation of stabilizing the P sensor is performed by the procedure shown in the flowchart of FIG.

That is, in FIG. 8B, first, for example, by inputting a predetermined special code from the ten keys on the operation unit, the predetermined developing device (black developing device 14 in this example) is forcibly forced. Specifically, a mode is set in which the reference image is formed and the image density is detected by the optical sensor 32, and the detection value T by the optical sensor 32 is displayed on, for example, a copy counter, and the copy button is pressed in that state. This allows the formation of the reference image,
The detection and the detection value P are displayed, and the serviceman looks at the display and determines whether or not the detection value P is within a predetermined range. Here, when the detected value P is within the predetermined range (N in step 2), the P sensor stabilization ends as it is. If the detected value P is not within the predetermined range, the control reference value T ₀ is changed, for example, by inputting a special code from the ten keys (step 3). Specifically, the detection value P is 10 or less, which is the lower limit value of the predetermined range, that is,
When the image density is too high, the control reference value T ₀ is corrected to a large value in order to reduce the toner density in the developing device. On the contrary, when the detected value P is 14 or more which is the upper limit value of the predetermined range, that is, when the image density is too low, the control reference value T ₀ is corrected to a small value in order to increase the toner density in the developing device.
After that, the T sensor is stabilized according to the above procedure (step 4), and thereafter, the P sensor check is executed in the same manner as in step 1 to display the detected value P. Or later,
While the serviceman is watching this display, the T sensor control is changed (step 3) until the detected value P falls within the predetermined range,
Repeat T sensor stabilization (step 4) and P sensor check (step 5).

Returning to FIG. 7, when the operation for stabilizing the P sensor is completed, next, for example, a reference document is placed on the document table 2 and the copy pressing button is pressed with the document pressing plate closed. A copy of this reference document is created (copy sample creation) (step 1). A serviceman evaluates this copy and determines whether the image density should be darkened, lightened, or left as it is (steps 2 and 3).
Here, when it is desired to increase the image density, for example, by inputting a predetermined special code from the ten-key pad on the operation unit, the exposure by the uniform charger 13 which is the image forming condition at the time of forming the reference latent image is performed. The charging potential of the body 11 is adjusted so that the image density of the reference image becomes relatively light. In particular,
The absolute value of the grid voltage of the uniform charger 13 is adjusted to be relatively small (step 4), and the image density setting adjustment is completed. On the contrary, when the image density is reduced, the absolute value of the grid voltage of the uniform charger 13 is adjusted to be relatively high so that the image density of the reference image is relatively high (step 5). Finish the adjustment. If it is not necessary to change the image density setting, the image density setting adjustment is ended as it is. In this copying machine, the grid voltage can be adjusted in steps of 20V.

According to the above-mentioned conventional image density setting adjustment, the grid voltage, which is an image forming condition at the time of forming the reference image, is adjusted to finish the image density adjustment. No adjustment effect appears until the reference value T ₀ is corrected and controlled.

Next, the image density setting adjustment in this embodiment will be described. 6 (a), (b), (c),
(D) and (e) show a flowchart of a density change mode which is control of image density setting adjustment of the present embodiment. The density changing mode of the present embodiment is selected, for example, by inputting a predetermined special code from the ten keys on the operation unit. At the time of this selection, the image density setting data at that time is checked. Here, in this example, it is possible to set the density in three steps, and as the image density setting data for grasping the image density setting step, the standard density data is "1", and the density data darker than the standard is used. The data is set to "0" and data "2" having a density lower than the standard density, but the number of steps is not limited to this. First, when the service person inputs image density switching data from the ten-key pad, this data is read and checked (step 1). Then, the image density setting data before switching (when this mode is selected) is compared with the image density setting data after switching, and the number of change steps is ± 0, +1, +2, -1, or -2. Is determined (steps 2 to 5). If the number of change steps is ± 0, the image density setting data is repeatedly checked until the mode is changed.

When the number of changing steps is +1, that is, when the image density is adjusted to be one step lighter (step 3
Y), the grid voltage of the uniform charger 13 which is the condition for forming the reference image is corrected by -20 V so that the image density of the reference image becomes relatively high (step 6).
The absolute value of the charging potential is increased by 20 V (in this example, OPC is used as the photoconductor 11 and the uniform charging polarity is set to be negative). Then, it is determined whether or not a value obtained by adding 10 which is a predetermined value to the control reference value T ₀ of the toner density is less than or equal to the upper limit value 150 of the setting range of the control reference value T ₀ (step 61). If the upper limit is 150 or less, the control reference value T ₀ is corrected to 10 (step 6).
2) As a result, the toner concentration in the developing device is controlled to be low. Here, the predetermined value 10 is obtained by correcting the grid voltage of the uniform charger 13 which is the formation condition of the reference image by -20 V, and then temporarily forming the reference image and correcting the control reference value T ₀ by the detection. correction amount of the control reference value T ₀ in the case of that, that is, is less than the correction amount of the control reference value T ₀ for the image density aimed by the minus 20V correct grid voltage. Specifically, the correction amount of the control reference value T ₀ for achieving the target image density by correcting the grid voltage by -20 V in this example is 15, and the predetermined value 10 is smaller than this. . Conversely, step 6
The value obtained by adding 10 which is a predetermined value to the control reference value T ₀ in 1 is
If the control reference value T ₀ exceeds the upper limit value 150 of the setting range, the control reference value T ₀ is corrected to the upper limit value 150 (step 63), and the fact is notified by flashing the display 41. (Step 64).

When the number of changing steps is +2, that is, when the image density is adjusted to be lighter by 2 steps (step 4
Y), the grid voltage of the uniform charger 13 which is the formation condition of the reference image is corrected to minus 40V which is twice the above minus 20V so that the image density of the reference image becomes relatively high (step 7). The absolute value of the charging potential to 4
Increase by 0V. After that, as in the case where the number of change steps is +1, is the value obtained by adding 20 which is the predetermined value to the control reference value T ₀ of the toner concentration is the upper limit value 150 or less of the setting range of the control reference value T ₀ ? Judge whether or not (step 7)
1). If the upper limit value is 150 or less, the control reference value T ₀ is corrected to a value obtained by adding 20 (step 72), whereby the toner density in the developing device is controlled to be low. Here, this predetermined value 20 is the grid voltage of the uniform charger 13 which is the formation condition of the reference image minus 40.
After V corrected, if the formation of the reference image, and the correction amount of the control reference value T ₀ in the case of a conducted correction control of the control reference value T ₀ by detecting, i.e., aim due to negative 40V correct grid voltage It is smaller than the correction amount of the control reference value T ₀ for achieving the image density. Specifically, the grid voltage in this example is minus 20
The correction amount of the control reference value T ₀ for achieving the target image density by V correction is 30, and the predetermined value 20 is smaller than this. A value obtained by adding a 20 is a predetermined value to control the reference value T ₀ in step 71 on the contrary, if it exceeds the upper limit value 150 of the setting range of the control reference value T ₀ is a control reference value T ₀ in the upper limit value Correct to 150 (Step 7
3) Then, the display 41 is informed by flashing the display 41 (step 74).

When the number of changing steps is -1, that is, when the image density is adjusted to be darker by one step (Y in step 5), the reference image forming condition is such that the image density of the reference image becomes relatively dark. The grid voltage of the uniform charger 13 is corrected by +20 V (step 8), and
The absolute value of the charging potential is reduced by 20V. Then, it is determined whether or not the value obtained by subtracting 10 which is the predetermined value from the control reference value T ₀ of the toner density is not less than the lower limit value 70 of the setting range of the control reference value T ₀ (step 81). Here, the lower limit value 70
If it is above, the value is corrected to a value obtained by subtracting 10 from the control reference value T ₀ (step 82), so that the toner density in the developing device is controlled to be higher. Here, the predetermined value 10 is the uniform charger 13 which is the condition for forming the reference image.
Correction of the control reference value T ₀ by the formation and detection of the reference image after correcting the grid voltage of +20 V, that is, the correction amount of the control reference value T ₀ , that is, the grid voltage is corrected by -20 V It is smaller than the correction amount of the control reference value T ₀ for achieving the target image density. Specifically, the correction amount of the control reference value T ₀ for achieving the target image density by correcting the grid voltage by +20 V in this example is 15, and the predetermined value 10 is smaller than this. ..
Conversely, at step 81, the control reference value T ₀ is a predetermined value 1
The value obtained by subtracting 0 is the lower limit value 7 of the setting range of the control reference value T _0.
If it is smaller than 0, the control reference value T ₀ is corrected to the lower limit value of 70 (step 83), and the display 41 indicates that effect.
Is flashed and notified (step 84).

When the number of change steps is -2, that is, when the image density is adjusted by 2 steps, the adjustment is performed (step 5
N), the grid voltage of the uniform charger 13 which is the formation condition of the reference image is corrected by plus 40V which is twice the plus 20V so that the image density of the reference image becomes relatively light (step 9). The absolute value of the charging potential to 40
Make V smaller. Thereafter, as in the case where the number of changing steps is -1, the value obtained by subtracting 20 which is the predetermined value from the control reference value T ₀ of the toner density is not less than the lower limit value 70 of the setting range of the control reference value T _0. It is determined whether or not (step 91).
If the lower limit value is 70 or more, the control reference value T ₀ is corrected to a value obtained by subtracting 20 from the control reference value T ₀ (step 92), whereby the toner concentration in the developing device is controlled to be higher. Here, the predetermined value 20 is obtained by temporarily correcting the grid voltage of the uniform charger 13 which is the formation condition of the reference image by plus 40 V, and then temporarily forming the reference image and correcting the control reference value T ₀ by the detection. If the control reference value T ₀ is corrected, that is, the grid voltage is increased by 40V.
The amount is smaller than the correction amount of the control reference value T ₀ for achieving the target image density by the correction. Specifically, the control reference value T for making the target image density by correcting the grid voltage by +40 V in this example.
The correction amount of ₀ is 30, and the predetermined value 20 is smaller than this. Conversely, in step 91, the control reference value T ₀
The value obtained by subtracting the 20 is a predetermined value from is less than the lower limit 70 of the setting range of the control reference value T ₀ is a control reference value T ₀ is corrected to 70 which is the lower limit (step 93),
This is notified by flashing the display 41 to light (step 94).

As described above, according to this embodiment, when the target image density setting is adjusted by the service engineer during maintenance and inspection,
Following the switching of the grid voltage of the uniform charger 13 which is an image forming condition, the control reference value T ₀ is changed according to this switching.
Is corrected, the output of the toner concentration detection sensor is corrected by using the corrected control reference value T ₀ even in copying until the control reference value T ₀ based on the formation and detection of the reference image is corrected and controlled. Since the toner replenishment control using the value T is performed, the effect of adjusting the target image density setting can be displayed on the image more quickly than in the conventional case.

Although the control reference value T ₀ is corrected by executing the density changing mode, the toner density in the developing device becomes the toner density corresponding to the corrected control reference value T _0. In the copying up to, it is not possible to obtain the image density targeted for adjustment. Therefore, in order to make it possible to obtain the image density targeted for adjustment from the copy by the operator immediately after that, by adjusting the target image density setting at the time of maintenance and inspection by a service person, the density stabilization described below. It is desirable to have a mode.

5 and 6 are flowcharts of the density stabilization mode. This concentration stabilization mode
For example, it is selected by entering a predetermined special code from the ten keys on the operation unit. When this mode is selected, first, the counter n is set to 1 (step 1). Here, when the copy start button is pressed (step 2), the detection value T of the toner density detection sensor of the predetermined developing device selected by the special code is read, and this detection value T becomes the control reference value T ₀ . It is determined whether it is larger than T ₀ +3 which is the upper limit value of the predetermined center range, that is, whether the toner density is too low (steps 3 and 4).

Here, when the detected value T is larger than T ₀ +3 which is the upper limit value of the predetermined range centered on the control reference value T ₀ (Y in step 4), the steps 2 to 5 are repeated thereafter. The replenishment clutch 14a is forcibly turned on for a second to replenish the developing device with toner, and after 0.5 seconds has elapsed (Y in step 8), the detection value T of the toner concentration detection sensor is read again and checked. Further, when 2.5 seconds have elapsed, it is determined whether or not the detected value T has become the upper limit value T ₀ +3 or less (steps 9, 10, 11). Here, when the detected value T is equal to or less than the upper limit value T ₀ +3, the process proceeds to step 12, and conversely, when the detected value T is not equal to or less than the upper limit value T ₀ +3, the following steps 5 to step are performed. 1
1 is repeated until it is determined in step 11 that the detected value T has become the upper limit value T ₀ +3 or less. In Steps 5 to 7, the forced toner replenishment time is set to 2 seconds in order to prevent toner scattering due to insufficient developer agitation in the developing device. is there. That is, it is smaller than the maximum replenishment time of 4 seconds in the toner replenishment control using the detection value T of the toner concentration detection sensor during normal copying, and the developer is hardly agitated in the normal toner concentration low state. The supply time does not occur.

On the contrary, when it is judged in step 4 that the detected value T is not larger than T ₀ +3 which is the upper limit value of the predetermined range centered on the control reference value T ₀ (N in step 4). Then, it is determined whether or not the detected value T is smaller than T ₀ -3 which is the lower limit value of a predetermined range centered on the control reference value T ₀ , that is, whether the toner density is too high (step 21). ). If the detected value T is smaller than the upper limit value T ₀ -3 (Y in step 21), the timer t is reset in step 22 and the toner in the developing unit is forcibly forced in step 23. A toner consumption pattern for consumption is formed. This toner consumption pattern can be formed by charging the surface of the photoconductor 11 with the uniform charging device 13 and developing the area not irradiated with any light with a predetermined developing device in an operating state to attach the toner. .

The image forming condition for forming the toner consumption pattern is set to be smaller than the maximum value of the toner adhesion amount during normal copying (toner adhesion amount at the latent image portion corresponding to the black portion of the document). It is preferable to set the above to reduce the load on the cleaning device 12 and the cleaning device 20. For example, the grid voltage of the uniform charger 13 is switched from the grid voltage during copying to obtain the charging potential of the photoconductor 11 of, for example, −800 V during normal copying, and the charging potential of the photoconductor 11 at around −550 V is set to To get it.

Further, in this example, while the toner consumption pattern passes through the transfer position, the transfer device 28 is operated to form the toner consumption pattern on the surface of the transfer drum 19b which does not hold the transfer paper. Part of the toner is transferred. The toner attached to the surface of the transfer drum 19b is removed by the cleaning device 20. In order to reduce the cleaning load of the cleaning device 20,
It is desirable to control the drive circuit 28a so that the transfer electric field by the transfer device 28 during the toner consumption pattern transfer is weaker than that during normal copying. For example, a voltage of −5.2 KV is applied during normal copying, whereas a voltage of −4.2 KV is applied during transfer of the toner consumption pattern.
The application is switched to about 3 KV.

After the toner consumption pattern is formed as described above, the detection value T of the toner density detection sensor is read and checked, and it is determined whether or not the detection value T is within a predetermined range around the control reference value T _0. (Step 25). here,
If the detected value T is within this range (Y in step 25), the process proceeds to step 12, and if it is not within this range (N in step 25), the content of the timer t is 5 in step 26. After (second), steps 22 to 26 are repeated until it is determined in step 25 that the detected value T falls within this range.

In step 26, the content of the timer t reset immediately before the toner consumption pattern is created is 5
After (seconds), the next toner consumption pattern is formed by cleaning the surface of the photoconductor 11 or the transfer drum 19b at least twice by the cleaning device 12 or the cleaning device 20 to remove the toner. This is to ensure sufficient removal. That is, in this example, the diameter of the photoconductor 11 is 120 mm and the transfer drum 19 has a diameter of 120 mm.
The diameter of b is 180 mm, and the surface linear velocity of both is 226 mm / sec.
Therefore, the toner consumption pattern forming interval is set to 5 seconds so that the transfer drum 19b having a relatively large diameter (one rotation in 2.5 seconds) can rotate twice.

On the contrary, when it is determined in step 21 that the detected value T is equal to or more than the lower limit value T ₀ -3 (N in step 21), the process directly proceeds to step 12.

As described above, the toner concentration or the toner consumption is forcibly supplied, or the detection value T of the toner density detection sensor is within a predetermined range around the control reference value T ₀ without performing such an operation. (Y in step 11,
Y in step 25, N in step 21), step 12
Then, the reference toner image is formed and detected (P sensor check). Then, it is determined whether the detected value P exceeds 14 which is the upper limit value of the predetermined range, that is, whether the image density is too low (step 13).

If it is determined that the detected value P is 14 or more, which is the upper limit value of the predetermined range (Y in step 13), the control reference value T ₀ is corrected by 10 (step 14). ), The toner density of the developing device is increased, and then it is determined whether the counter n is smaller than 3 (step 15). If it is smaller than 3, the counter n is incremented by 1 and step 5 Return to (step 16). After that, at steps 5 to 11, when the toner is forcibly replenished and the detection value T of the toner concentration detection sensor falls within a predetermined range centered on the control reference value T ₀ , the process proceeds to step 12 again. After that, until the detected value P becomes equal to or less than the upper limit value 14 of the predetermined range in step 13, or the content of the counter n becomes 3 in step 15, forced toner supply in steps 5 to 11 and steps 12 to 16 The correction of the control reference value T ₀ based on the P sensor check result in step ₁ is repeated. The reason why the normal control is returned when the content of the counter n becomes 3 in step 15 is to prevent the execution time of the concentration stabilization mode from becoming long.

On the contrary, when it is determined in step 13 that the detected value P is not more than 14 which is the upper limit value of the predetermined range (N in step 13), the detected value P is the lower limit value of the predetermined range in step 17. It is determined whether it is smaller than 10. Here, the detection value P is not less than the lower limit value 10, that is,
When it is determined that the detection value P is within the predetermined range (N in step 17), the normal control is returned to. Conversely, when it is determined that the detection value P is smaller than the lower limit value 10, that is, the image density is too high (Y in step 17),
The control reference value T ₀ is corrected to a value obtained by adding 10 (step 1
8) Then, after the toner density of the developing device is lowered, it is judged whether the counter n is smaller than 3 (step 19). If it is smaller than 3, the counter n is incremented by 1 and Return to step 5 (step 20). After that, at steps 22 to 26, when the toner is forcibly consumed and the detection value T of the toner density detection sensor falls within a predetermined range around the control reference value T ₀ , the process proceeds to step 12 again. Thereafter, until the detected value P is determined to be within the predetermined range in steps 13 and 17, or the content of the counter n becomes 3 in step 19, forced toner consumption and steps in steps 22 to 26 are performed. The correction of the control reference value T ₀ based on the P sensor check result in steps 12, 13, 17 to 20 is repeated. Note that step 19
At the time when the content of the counter n becomes 3, the normal control is resumed in order to prevent the concentration stabilization mode from being executed for a long time as in the case where N is determined in step 15. Is.

As described above, according to the density stabilization mode, the toner density in the developing device can be immediately set to the toner density corresponding to the control reference value T ₀ , and the control reference value T
_In order to obtain the target image density for adjusting the setting value of the grid voltage of the uniform charger 13 which is the image forming condition at the time of forming the reference image, ₀ itself may include some error. The control reference value T _{0 is} set so that the target image density can be obtained.
Can be corrected.

The density stabilization mode is not selected by inputting a predetermined special code from the ten keys on the operation section as described above, but instead of the toner density changing mode described above. Thus, when the correction of the control reference value T ₀ is completed (step 62 in FIG. 4,
72, 82, 92) may be automatically selected. In this case, step 2 of the density stabilization mode may be omitted.

[0069]

According to the image forming apparatus of the present invention, the image forming conditions can be switched by the image forming condition switching means at the time of adjusting the target image density setting at the time of maintenance and inspection by a service person or the like. Subsequently, the target toner density set value is corrected by the second set value correction means in accordance with this switching, so that the target toner density value correction control by the reference toner image formation / detection can be performed several tens to several hundreds of times. Even if it is set to execute at the timing of once,
At the time of image formation after the adjustment of the target image density setting such as at the time of maintenance and inspection by the service person or the like, the toner replenishment control means uses the target toner density set value corrected by the second set value correction means It is possible to adjust the toner density in the developing device to obtain a predetermined image density to be obtained by this adjustment by controlling the above. Therefore, until the target toner density value correction control by the reference toner image formation / detection is performed at a predetermined timing after the adjustment of the target image density setting by the service person or the like as in the conventional art, this target image density setting adjustment is not performed. The effect of this adjustment can be made to appear on the actual image more quickly than that which cannot be reflected in the density setting value.

In the image forming apparatus according to the second aspect of the present invention, the reference formed by the second set value correction means under the image forming condition after the corrected value is temporarily switched by the image forming condition switching means. When the image is detected by the image density detecting means, the correction amount is smaller than the target toner density setting value after being corrected by the first setting value correcting means based on the output of the image density detecting means. Therefore, it is possible to prevent the target toner density set value from being excessively corrected by the second set value correction means.

In the image forming apparatus according to the third aspect of the present invention, subsequent to the correction of the target toner density set value by the second set value correction means, the target toner density set value after the correction is made by the toner density stabilization control means. In accordance with the above, either the drive of the toner replenishing means or the toner consuming operation by the toner consuming operation control means is executed, so that the toner replenishing control by the toner replenishing control means during the image forming operation is immediately performed by this adjustment. Since the toner density in the developing device is set to obtain the desired image density to be obtained, the effect of the adjustment of the target image density setting by a service person or the like can be immediately displayed on the actual image.

In the image forming apparatus according to a fourth aspect of the present invention, following the correction of the target toner density set value by the second set value correction means, the toner replenishment means is driven and the toner consumption operation is performed by the toner density stabilization control means. Any one of the toner consumption operations by the control means, the formation of the reference image by the reference image forming means, the detection of the image density of the reference image by the image density detection means, and the target toner by the first set value correction means Correct the density setting value,
The repetition control unit repeats the process until the detected image density value of the reference image by the image density detection unit falls within a range in the vicinity of a predetermined target image density value. The toner density in the developing device is immediately set to obtain the predetermined image density to be obtained by this adjustment without depending on the replenishment control, so that the effect of the adjustment of the target image density setting by the service person or the like is immediately obtained on the actual image. Can appear in. Further, the repetitive control means detects the reference image actually formed under the image forming conditions at the time of forming the reference toner image after switching by the service person or the like by the image density detecting means, and the detected image density value is the predetermined target image. Depending on whether or not it falls within the range near the density value, the driving of the toner replenishing means by the toner density stabilizing control means and the toner consuming operation by the toner consuming operation control means are repeatedly executed. The toner density in the developing device can be accurately set to obtain the predetermined image density to be obtained by this adjustment.

In the image forming apparatus according to the fifth aspect of the present invention, the correction of the target toner density set value by the second set value correction means is followed by the toner density stabilization control means by the corrected target toner density set value. In accordance with the above, either the drive of the toner replenishing means or the toner consuming operation by the toner consuming operation control means is executed. Since the toner density in the developing device is set to obtain the desired image density to be obtained, the effect of the adjustment of the target image density setting by a service person or the like can be immediately displayed on the actual image. Further, at this time, the toner replenishing means is driven by the toner concentration stabilizing control means at a replenishment rate smaller than the maximum toner replenishment rate during the image forming operation by the toner replenishment control means. It is possible to prevent insufficient agitation of the developer in the developing device by replenishing the toner at a high toner replenishment rate, and thus it is possible to prevent toner scattering and image background stain.

According to another aspect of the image forming apparatus of the present invention, the toner consumption operation control means forms a latent image for adhering toner on the image bearing member, and the latent image is visualized by the developing device to consume the consumed toner image. When the toner density in the developing unit is forcibly reduced by forming a toner image, the toner deposition amount on the image carrier is compared with the image forming condition when forming the consumed toner image rather than the image forming condition when forming the image. To be smaller,
Since the toner amount of the toner consumption toner image is not too large and an excessive load is applied to the cleaning device, it is possible to prevent the image from being smeared due to poor cleaning.

In the image forming apparatus according to the seventh aspect, the toner consumption operation control means causes the consumed toner image forming area on the surface of the image carrier to pass the cleaning device facing portion twice or more. Since the toner in the consumed toner image forming area is sufficiently removed, it is possible to prevent the background stain of the image due to poor cleaning.

According to another aspect of the image forming apparatus of the present invention, when the consumed toner image formed on the image carrier is opposed to the intermediate transfer body by the toner consumption operation control means, the transfer electric field formation means is used. After the transfer electric field is formed to transfer a part of the toner constituting the consumed toner image on the image carrier onto the intermediate transfer member, the intermediate transfer member cleaning device removes the toner.
Since the toner remaining on the image carrier after the transfer to the intermediate transfer body is removed by the cleaning device, the cleaning device and the intermediate transfer body cleaning device can share the toner constituting the toner consumption toner. .. Further, the transfer electric field by the transfer electric field forming means when the consumed toner image faces the intermediate transfer body is set to a transfer electric field smaller than that at the time of image formation, so that the toner transferred onto the intermediate transfer body. To prevent the intermediate transfer member cleaning device from being overloaded with too much amount,
Normally, an intermediate transfer member cleaning device having a relatively small cleaning capacity and a small size can be used without increasing the size to a large extent in comparison with the conventional one in order to increase the cleaning capacity.

According to another aspect of the image forming apparatus of the present invention, in the toner consumption operation control means, the consumed toner image forming area on the surface of the image carrier passes the cleaning device facing portion twice or more, and the intermediate portion. The consumed toner image transfer area on the transfer body is made to pass through the intermediate transfer body cleaning device facing portion twice or more, whereby the consumed toner image forming area on the surface of the image carrier and the intermediate transfer body are transferred. Since the toner in the consumed toner image transfer area is sufficiently removed, it is possible to prevent background stains on the image and back stains on the transfer material due to poor cleaning.

[Brief description of drawings]

FIG. 1 is a front view showing a schematic configuration of a main part of an electrophotographic copying machine according to an embodiment.

FIG. 2 is a front view showing the overall configuration of the copying machine.

FIG. 3 is a flowchart of control reference value correction control based on the output of an optical sensor.

4A to 4E are flowcharts of a density changing mode in the copying machine.

FIG. 5 is a part of a flowchart of a density stabilization mode in the copying machine.

FIG. 6 is the rest of the flowchart of the same concentration stabilization mode.

FIG. 7 is a flowchart showing an image density setting adjustment procedure according to a conventional technique.

FIGS. 8A and 8B are flowcharts showing in detail some operations of the image density setting adjustment procedure.

[Explanation of symbols]

11 Photoreceptor, 12 Cleaning Device 13 Uniform Charging Device, 14 Black Developing Device 14a Replenishing Clutch, 14b Toner Cartridge 14c Replenishing Roller, 18a Toner Density Detection Sensor 19b Transfer Drum, 20 Cleaning Device 28 Transfer Device, 31 Control Unit 32 Optical Sensor Difference, 40 Adjusting means 41 Displaying means

Claims (9)

[Claims] 1. A developing device for developing a toner to supply toner to a latent image formed on an image bearing member, a toner replenishing means for replenishing the developing device with toner, and a toner concentration in the developing device. And a toner replenishment control means for controlling the toner replenishment means based on the result of comparison between the output value of the toner concentration detection means and the target toner concentration set value, and a toner replenishment control means for detection on the image carrier. Reference image forming means for forming a reference latent image and visualizing the reference latent image with the developing device to form a reference image; image density detecting means for detecting image density of the reference image; and image density detecting means. A first set value correction unit that corrects the target toner concentration set value based on the output of the image forming condition, an image forming condition switching unit that switches the image forming condition at the time of forming the reference image, and an image forming condition switching unit that switches the image forming condition. According to this switch An image forming apparatus characterized in that a second setting value correcting means for correcting the target toner concentration setpoint. 2. The target toner density setting when the second setting value correcting means is switched by the image forming condition switching means so as to obtain a relatively low image density by the image forming condition at the time of forming the reference image. When the value is switched to a value corresponding to a relatively high toner density, and when the image density is switched to obtain a relatively high image density, the target toner density setting value is corrected to a value corresponding to a relatively low toner density, and Based on the output of the image density detecting means when the reference image formed under the image forming condition after the corrected value is switched by the image forming condition switching means is detected by the image density detecting means. The image forming apparatus according to claim 1, wherein the correction amount is smaller than the target toner density setting value after being corrected by the first setting value correcting means. 3. Toner consumption operation control means for executing a toner consumption operation for forcibly supplying the toner in the developing device onto the image carrier to consume the toner in the developing device,
At the time of correcting the target toner density set value by the second set value correction means, either the driving of the toner replenishing means or the toner consumption operation by the toner consumption operation control means is performed according to the corrected target toner density set value. The image forming apparatus according to claim 1, further comprising: a toner density stabilization control unit that executes the process. 4. When the target toner density set value is corrected by the second set value correction means, either the toner replenishing means is driven by the toner density stabilization control means or the toner consumption operation is performed by the toner consumption operation control means. Image forming, the reference image forming means forms the reference image, the image density detecting means detects the image density of the reference image, and the first setting value correcting means corrects the target toner density set value. 4. The image forming apparatus according to claim 3, further comprising: a repetitive control unit that repetitively executes the detected image density value of the reference image by the density detection unit until it falls within a range near a predetermined target image density value. 5. A toner replenishing amount by the toner replenishing means during an image forming operation according to a result obtained by comparing the output value of the toner concentration detecting means with the target toner concentration set value by the toner replenishing control means. The image forming apparatus according to claim 1, wherein the toner in the developing unit is forcibly supplied onto the image carrier to change the toner in the developing unit. At the time of correcting the target toner concentration set value by the toner consumption operation control means for executing the toner consumption operation for consumption and the second set value correction means, according to the corrected target toner concentration set value,
Toner density stabilization control means for executing either driving of the toner replenishment means or toner consumption operation by the toner consumption operation control means at a replenishment rate smaller than the maximum toner replenishment rate during the image forming operation by the toner replenishment control means The image forming apparatus according to claim 1, further comprising: 6. A transfer device for transferring a toner image formed on an image carrier to a transfer material, and removing residual toner from the surface of the image carrier after the toner image is transferred onto the transfer material by the transfer device. The image forming apparatus according to claim 3, further comprising: a cleaning device that controls the toner consumption operation control means to form a latent image for adhering toner on the image bearing member, visualize the latent image by the developing device, and consume the latent image. A toner image is formed, and the image forming condition at the time of forming the consumed toner image is set so that the toner adhesion amount on the image carrier is relatively smaller than the image forming condition at the time of image forming. The image forming apparatus according to claim 3, wherein 7. A transfer device for transferring a toner image formed on an image carrier onto a transfer material, and removing residual toner from the surface of the image carrier after the toner image is transferred onto the transfer material by the transfer device. 4. The image forming apparatus according to claim 3, further comprising: a cleaning device for controlling the toner consumption operation control means so that the toner consumption image forming area on the surface of the image carrier passes the cleaning device facing portion twice or more. The image forming apparatus according to claim 3, wherein the image forming apparatus comprises: 8. An intermediate transfer body on which a toner image formed on the image carrier can be transferred under transfer electric field formation by a transfer electric field forming means, and an image carrier after the toner image is transferred to the intermediate transfer body side. 4. The image forming apparatus according to claim 3, further comprising: a cleaning device that removes residual toner from the surface of the body, and an intermediate transfer body cleaning device that removes the toner from the surface of the intermediate transfer body. A latent image for toner adhesion is formed on the latent image, the latent image is visualized by the developing device to form a consumed toner image, and when the consumed toner image faces the intermediate transfer member, 4. The image forming apparatus according to claim 3, wherein the transfer electric field forming unit is configured to form a transfer electric field smaller than that during image formation. 9. The toner consumption operation control means is configured such that the consumption toner image forming area on the surface of the image carrier passes the cleaning device facing portion two or more times, and the consumption toner image on the intermediate transfer body. 9. The image forming apparatus according to claim 8, wherein the transfer area is configured to pass through the intermediate transfer member cleaning device facing portion twice or more.