JPH06149057A - Image forming device - Google Patents

Abstract

PURPOSE:To grasp developer concentration in a developing means so that proper amount of developer can be supplied even though consecutive copying is performed by instructing the starting of concentration control on every switching timing of an original image. CONSTITUTION:A controller part 51 controls image forming process and patch detection ATR execution on each image forming station Pm, Pc, Py, or Pk. A toner concentration detecting means controls the turning-on timing of an LED 11M radiating near infrared light on each photosensitive drum, etc., processes concentration data from a photodiode 12M, etc., and controls the driving of the toner carrying screw of a toner hopper. The controller part 51 detects the switching timing of the original image carried by an RDF 13, and instructs to start the concentration control by every switching timing as scheduled so that the developer concentration in the developing devices 4M, 4C, 4Y, and 4K can be grasped; therefore, proper amount of the developer can be supplied even when the consecutive copying is performed.

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 for transferring a developed image onto a recording medium conveyed on a transfer belt,
The present invention relates to an image forming apparatus that supplies a developer while detecting the development density of a patch image on which a predetermined pattern has been developed.

[0002]

2. Description of the Related Art Conventionally, in this type of image forming apparatus,
As a recording method for forming a full-color image, an electrophotographic method, an inkjet recording method, a thermal transfer recording method, etc. are known. Among them, the electrophotographic method has been increasingly in demand in recent years because of its characteristics such as high throughput and use of plain paper as a developing and fixing medium.

In forming a full-color image of the electrophotographic system, many developing devices use a two-component developer having a toner and a carrier from the viewpoint of the tint of the image. In this case, the developing device is used for image formation. When the toner inside is consumed, it is necessary to replenish the developing device with toner corresponding to the consumption, so the toner concentration is detected and toner concentration control is performed, that is, by the developer concentration detecting device and the control device, Control (so-called patch detection ATR) is performed to keep the toner density constant.

FIG. 4 is a cross-sectional view of a main part for explaining a developer replenishing operation of a conventional image forming apparatus, which corresponds to, for example, a magenta station of a 4-drum type image forming apparatus.

In the figure, 11M is a bidirectional light emitting type LE.
D, an image of the reference density pattern 22 is formed on the photoconductor 1M, developed under a certain condition, and reflected light from this toner image is detected by the photodiode 12M. Then, toner corresponding to the difference between the detection signal and the reference value signal is supplied to the toner replenishing tank 3
It is configured to supply from 0 to the developing device 4M.
A transfer belt 6a is conveyed at a constant speed in the direction of the arrow in the figure. The transfer belt 6a transfers a toner image developed by the transfer charger 6M when a recording medium (recording sheet) electrostatically attracted by a charger (not shown) is passed directly below the photosensitive drum 1M. Reference numeral 31 indicates a toner conveying screw.

[0006]

However, in the above-mentioned conventional example, the transfer belt 6a is used as the endless movable means as the means for adsorbing and conveying the recording medium on which the toner image on the photosensitive drum 1M is transferred. There was such a problem.

First, after the toner image of the reference density pattern for performing the patch detection ATR is detected by the patch detection sensor including the LED 11M, the photodiode 12M, etc., the transfer belt 6a is contacted and transferred, and the transfer belt 6a is soiled. Therefore, the patch detection ATR is controlled not to be executed during continuous copying. Therefore, if the maximum number of continuous copies that can be set in a normal image forming apparatus is 99, 99
The toner replenishment control is not performed until the continuous copying of the sheets is completed, and the image density becomes unstable.

Further, in an image forming apparatus to which a sheet post-processing apparatus (sorter) can be connected, if the maximum number of sheets is set and the maximum set number of sheets (depending on the number of paper discharge bins) is set at the same time, the Since the patch detection ATR cannot be performed until the copying of 100 to several thousand sheets is completed, there is a problem that the image density becomes unstable due to the non-supply of the developer.

The present invention has been made to solve the above problems, and detects the document switching timing or the paper interval timing and executes the developer replenishment control during the continuous copy mode setting. An object of the present invention is to provide an image forming apparatus capable of constantly forming an image having a stable density by replenishing an appropriate amount of developer in an appropriate standby state while setting the continuous copy mode.

[0010]

SUMMARY OF THE INVENTION An image forming apparatus according to the present invention feeds a document to a predetermined position, and after the image reading of the document is completed, a document feeding unit capable of discharging the document to a predetermined position, and an image carrier. Developing means for developing the patch electrostatic latent image formed on the body, patch detecting means for detecting the density of the patch image developed by the developing means, and a developer replenishing section based on the detection result of the patch detecting means. First density control means for replenishing the developing device with developer to control the density level, and first detection means for detecting the switching timing of the document image fed by the document feeding means during the continuous copy mode setting. And a first instruction means for instructing the start of the density control by the first density control means at each switching timing of the document image detected by the first detection means.

Image reading means for reading an original image, image writing means for forming an electrostatic latent image on an image carrier based on an image signal output from the image reading means, and the image reading means for reading. A document is fed to a predetermined position, and after the image reading of the document is completed, a document feeding unit that can discharge the document to a predetermined position, a developing unit that develops the patch electrostatic latent image formed on the image carrier, Patch detecting means for detecting the density of the patch image developed by the developing means,
First density control means for controlling the density level by replenishing the developing device with the developer based on the detection result of the patch detecting means, and the document feeding means during the continuous copy mode setting. And a first detecting means for detecting the switching timing of the document image fed by
The first instruction means for instructing the start of the density control by the first density control means and the density level of the image signal output from the image reading means are integrated at each switching timing of the document image detected by the detection means. And a second concentration for controlling the concentration level by replenishing the developing device with developer from the developer replenishing unit according to the developer consumption converted by the converting means. A control means and a second means for detecting a timing between sheets of recording media sequentially fed;
And the second instructing means for instructing the start of the density control by the second density controlling means at the paper interval timing detected by the second detecting means.

[0012]

In the present invention, while the continuous copy mode is set, the first detecting means detects the switching timing of the document image fed by the document feeding means, and the first instructing means switches the document image. Since the start of the density control by the first density control means is instructed at each timing, it is possible to grasp the developer density in the developing means and replenish a proper amount of developer even during continuous copying.

Further, during the setting of the continuous copy mode, the first detecting means detects the switching timing of the document image fed by the document feeding means, and the first instructing means detects the switching timing of the document image at each timing. Since the start of the density control by the first density control means is instructed, the developer density in the developing means can be grasped and a proper amount of the developer can be replenished even during continuous copying. The density level of the image signal output from the reading means is integrated to convert the developer consumption amount, and the second amount is converted according to the conversion amount.
The density control means replenishes the developer from the developer replenishing section with the developer according to the density control start instruction from the second instructing means to control the density level, so that continuous copying can be performed without interruption. It is possible to replenish the appropriate amount of developer by grasping the amount of developer consumed, and to grasp the amount of developer consumed corresponding to the read image without interrupting continuous copying and replenishing an appropriate amount of developer. Is possible.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a cross-sectional structural view for explaining the structure of an image forming apparatus showing one embodiment of the present invention. The same parts as those in FIG. In the laser beam printer having the optical scanning means used, in particular,
It corresponds to a 4-drum type laser beam printer. The configuration and the image forming operation will be described below.

In the printer of this embodiment, the image forming stations Pm, Pc, Py and Pk each having an image forming means around the electrophotographic photosensitive member correspond to each color (yellow, magenta, cyan and black). 4 are provided, and the toner images of the respective colors formed on the respective photosensitive drums 1M, 1C, 1Y, 1K at the respective image forming stations face the respective photosensitive drums 1M, 1C, 1Y, 1K and are endless. The image is transferred onto a recording medium conveyed by a moving belt-shaped moving body (transfer belt 6a).

Further, yellow, magenta, cyan and black image forming stations Pm, Pc, Py and Pk are formed.
To the corresponding photosensitive drums 1M, 1C, 1Y, 1
K is arranged and rotated in the arrow direction (clockwise direction). In addition, around each photosensitive drum 1M, 1C, 1Y, 1K,
Corona chargers 2M, 2C, 2 forming image forming means
Y, 2K, scanning optical devices 3M, 3C, 3Y, 3K, developing devices 4M, 4C, 4Y, 4K, cleaning device 5M,
5C, 5Y, 5K and a transfer unit 6 (transfer belt 6a and transfer chargers 6M, 6C, 6Y, 6K for each drum) are arranged. The transfer belt 6 is used to form a full-color image.
This is achieved by sequentially transferring the toner images of the respective colors formed on the photosensitive drums 1M, 1C, 1Y, and 1K onto the transfer material P serving as a recording medium supported on a. The transfer material P is supplied from the paper feed cassette 7, and the transfer material P that has completed the transfer process is separated and discharged via a fixing device 8 to a vertically movable sorter bin 9 that can accommodate a plurality of copies.

Reference numeral 51 denotes a controller unit, which is a CPU 51a,
The image forming process is controlled by the ROM 51b and the RAM 51c, and the image forming stations Pm and P are provided.
The execution of the patch detection ATR on c, Py, and Pk is controlled according to the flowchart shown in FIG.

The toner concentration detecting means in this embodiment is the LED 11 for irradiating each photosensitive drum with near infrared light.
It is composed of M, 11C, 11Y, 11K and photodiodes 12M, 12C, 12Y, 12K for detecting each reflected light, and controls the lighting timing of the LEDs 11M, 11C, 11Y, 11K and the photodiode 12M,
Processing the density data from 12C, 12Y, 12K,
The drive of the toner conveying screw of the toner hopper (not shown) is controlled.

Further, the scanning optical devices 3M, 3C, 3Y, 3
K is a laser light source that is a light source (not shown), a rotating polygon mirror that scans the laser light from this laser light source,
An fθ lens for condensing the scanning beam on the generatrix of the surface of the photosensitive drum, a reflecting mirror for deflecting the light beam, and a beam detector for detecting a specific position of the scanning beam are provided.

An automatic document feeder (RDF) 13 sets a plurality of documents and then automatically feeds them to a document reading means (not shown). After scanning the document reading, the document is returned to the original place where it was set.

In the image forming apparatus thus configured, the controller unit 51 detects the switching timing of the original image fed by the RDF 13 during the continuous copy mode setting, and the density control is performed at each original image switching timing. Since the start of the process is instructed according to the flowchart shown in FIG. 2 described later, it is possible to grasp the developer concentration in the developing devices 4M, 4C, 4Y, and 4K and supply a proper amount of developer even during continuous copying. .

FIG. 2 is a flow chart showing an example of the control procedure of the patch detection ATR execution timing in the image forming apparatus according to the present invention, and the controller section 5 shown in FIG.
The steps processed by one CPU are indicated by (1) to (16).

First, it is judged whether the document to be copied is plural or singular (1), and if the first of the plural documents is supplied to the document reading means (not shown) by the RDF 13 (2). . Next, the document is read by a document reading means (not shown) (3). Next, each image forming station P
The image forming operation at m, Pc, Py, Pk is started.
(Four) . In this case, taking the first image forming station, that is, the station in which the developer color is magenta, as an example, the high voltage controller (not shown) in the corona charger 2M supplies a voltage from −4 to −.
A voltage of 9 KV is applied, and the charging current is -300 to -900.
The photosensitive drum 1M is uniformly charged with μA. After that, the scanning optical device 3M forms an electrostatic latent image on the photosensitive drum 1M based on an image signal from an image input system (not shown). It is developed by the developing device 4M for visualizing the electrostatic latent image with a predetermined bias. The developing method in this embodiment uses reversal development and uses toner of negative polarity. Hereinafter, similar image forming operations are performed in each of the yellow, magenta, cyan, and black stations. Then, it is transferred onto the transfer material P that has been adsorbed and conveyed to the transfer belt 6a, is fixed, and is ejected.

Next, the sorter bins 9 are moved up and down by the number of copies, and for example, one is put in each bin (5).
Next, after finishing the paper distribution process (paper discharge process) of the transfer material P to the designated bin, the copied document is returned to the original place and the next document is automatically sent (6 ). Then
In parallel with the replacement of originals, the patch inspection ATR is started (7).

In the patch detection ATR of this embodiment, a reference density patch is imaged on the photosensitive drum 1M and developed under a certain condition, and the reflected light from this toner image is reflected by the photodiode 1.
Detect at 2M. Then, the toner corresponding to the difference between the detection signal and the reference value signal is supplied from the toner hopper to the developing device 4M. At this time, the reference density patch is transferred to the transfer belt 6a, but is cleaned by the belt cleaner. However, the cleaner cannot be completely cleaned with one cleaning. Therefore, the cleaning process is executed once more, that is, twice, so that the transfer belt 6a
It is configured to prevent the contamination of.

Then, the same processes as in steps (3) to (7) are executed (8) to (12). Then, it is determined whether copying of all the originals set in the RDF 13 is completed (1
3), if YES, end the process, if NO, step
Return to (8) and repeat the same process.

On the other hand, when it is determined in step (1) that the original is one sheet, the same image forming operation as in steps (4) and (9) is executed (14), and then one sheet is printed. It is judged whether the image formation of the original is completed (15), and if NO, step
Returning to (14), if YES, the patch detection ATR similar to step (7) is started (16).

In the above embodiment, the case where the patch detection ATR is repeatedly executed at the original replacement timing has been described. However, in a sheet interval where the patch detection ATR cannot be executed during continuous copying, the second method according to another method is used. ATR
It may be controlled to be executed by the processing mechanism.

FIG. 3 is a view for explaining the developer concentration control mechanism in the image forming apparatus according to the present invention, and the same parts as those in FIG. 4 are designated by the same reference numerals. The developer concentration control of this embodiment corresponds to a video counter type developer concentration control method, that is, a control method of integrating the output levels of digital signals for each pixel and predictively supplying toner.

As shown in this figure, the image of the document 21 is read by an image reading sensor (image sensor) 23 composed of a CCD or the like, and the obtained analog image signal is amplified by an amplifier 24 to a predetermined level. An analog-digital converter (A / D converter) 25 converts the digital image signal into 8-bit (0 to 255 gradations) digital image signal. The output level of the image signal converted into a digital signal is integrated for each pixel, and the output level is converted into a video count number by the video counter 26 and sent to the CPU 27.
The CPU 27 converts the video count number into a replenishment amount and sends it as a toner replenishment signal to the motor drive circuit 28. The motor drive circuit 28 drives the motor 29 only for the time corresponding to the toner replenishment signal, and rotationally drives the toner conveying screw 31 in the toner replenishment tank 30 containing the toner for the above-mentioned predetermined time. An appropriate amount of toner is replenished therein to keep the toner concentration in the developing device 4M constant.

In the image forming apparatus constructed as described above, the controller unit 51 detects the switching timing of the original image fed by the RDF 13 during the continuous copy mode setting, and the density control is performed at each original image switching timing. 2 is instructed according to the flow chart shown in FIG. 2, so that the developing devices 4M and 4M
The developer concentration in C, 4Y, and 4K can be grasped so that an appropriate amount of developer can be replenished, and during the continuous copy mode setting, the CPU 27 integrates the concentration level of the image signal output from the image sensor 23. Convert the developer consumption,
The CPU 27 replenishes the developer from the toner replenishing tank 30 to the developing device 4M to control the density level according to the converted developer consumption amount. Therefore, even during continuous copying, the developer density in the developing means can be controlled. The developer can be replenished in an appropriate amount by grasping it, and the developer consumed corresponding to the read image can be grasped and an appropriate amount of developer can be replenished without interrupting continuous copying.

That is, the patch detection ATR is performed at the turn of the document.
Then, the toner is replenished by the video count ATR between other sheets, and the toner replenishment process is continued during continuous copying, so that the fluctuation of the image density due to the consumption of the developer can be suppressed.

In the above embodiment, the video count A
Although the case has been described in which the toner replenishment by TR is executed every time the image formation of one sheet is completed, in order to reduce the error at the time of toner replenishment as much as possible, the toner is replenished for every predetermined number of sheets or predetermined number of video counts, and the toner replenishment is collectively performed. May be configured to perform.

In the above embodiment, the case where the reflected light of the patch image on the photosensitive drum is read by a photodiode or the like to control the toner density is explained. However, the density reading sensor is provided at a predetermined position on the conveyance path of the transfer belt 6a. (If the sensor for registration correction image detection is provided, the sensor for registration correction image detection may be configured to read), and the reference density patch is directly transferred onto the transfer belt 6a, and the transfer is performed. A configuration may be used in which the toner density control is performed by reading the generated reference density patch. However, if the transfer belt 6a is made of a material having a color having a high light absorption property, the patch image with respect to the black toner may not be read, and in that case, the base area is formed with the yellow toner and the patch is formed on the base area. Needless to say, if the black toner is transferred, the patch image of the black toner on the transfer belt 6a can be read.

[0035]

As described above, according to the present invention, the first detection means detects the switching timing of the document image fed by the document feeding means during the continuous copy mode setting to give the first instruction. Since the means instructs the start of the density control by the first density control means every time the original image is switched, the developer density in the developing means is grasped and a proper amount of developer is replenished even during continuous copying. It can be carried out.

Further, during the continuous copy mode setting, the first detecting means detects the switching timing of the original image fed by the original feeding means, and the first instructing means detects the switching timing of the original image. Since the start of the density control by the first density control means is instructed, the developer density in the developing means can be grasped and a proper amount of the developer can be replenished even during continuous copying. The density level of the image signal output from the reading means is integrated to convert the developer consumption amount, and the second amount is converted according to the conversion amount.
The density control means replenishes the developer from the developer replenishing section to the developing device in accordance with the density control start instruction from the second instruction means to control the density level. An appropriate amount of developer can be replenished by grasping the developer concentration, and an appropriate amount of developer can be replenished by grasping the developer consumed corresponding to the read image without interrupting continuous copying. .

Therefore, even during continuous copying, it is possible to replenish an appropriate amount of developer at an appropriate timing, and it is possible to form an image having a stable density.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram illustrating a configuration of an image forming apparatus according to an exemplary embodiment of the present invention.

FIG. 2 is a diagram illustrating a patch inspection A in the image forming apparatus according to the present invention.
It is a flow chart which shows an example of a control procedure of TR execution timing.

FIG. 3 is a diagram illustrating a developer concentration control mechanism in the image forming apparatus according to the present invention.

FIG. 4 is a cross-sectional configuration diagram of main parts for explaining a developer replenishing operation of a conventional image forming apparatus.

[Explanation of symbols]

 4M developing device 4C developing device 4Y developing device 4K developing device 11M LED 11C LED 11Y LED 11K LED 12M photo diode 12C photo diode 12Y photo diode 12K photo diode 13 RDF 51 controller section

Claims (2)

[Claims] 1. A document is fed to a predetermined position, and after the image reading of the document is completed, a document feeding unit capable of discharging the document to the predetermined position and a patch electrostatic latent image formed on an image carrier are developed. A developing unit, a patch detecting unit for detecting the density of the patch image developed by the developing unit, and a developer replenishing unit to replenish the developing device with the developer based on the detection result of the patch detecting unit to adjust the density level. First density control means for controlling, first detection means for detecting switching timing of the document image fed by the document feeding means during the continuous copy mode setting, and the first detection means An image forming apparatus comprising: a first instruction unit for instructing the start of the density control by the first density control unit for each switching timing of the original image to be processed. 2. An image reading means for reading an original image,
An image writing unit that forms an electrostatic latent image on an image carrier based on an image signal output from the image reading unit and a document read by the image reading unit are fed to a predetermined position,
After the image reading of the document is completed, a document feeding unit that can discharge the document at a predetermined position, a developing unit that develops the patch electrostatic latent image formed on the image carrier, and a patch image developed by the developing unit. Patch detecting means for detecting the density, first density controlling means for controlling the density level by replenishing the developer from the developer replenishing portion to the developing device based on the detection result of the patch detecting means, and continuous copy mode setting First detecting means for detecting the switching timing of the document image fed by the document feeding means, and the first density control for each switching timing of the document image detected by the first detecting means. First instructing means for instructing the start of density control by means, converting means for integrating the density levels of the image signals output from the image reading means, and converting to developer consumption, and this converting means The second density control means for controlling the density level by supplying the developer from the developer replenishing section to the developing device according to the developer consumption amount converted by It is characterized by having a second detecting means for detecting and a second instructing means for instructing the start of the density control by the second density control means at the paper interval timing detected by the second detection means. Image forming apparatus.