JPH07234582A - Image forming device - Google Patents

Abstract

PURPOSE:To correctly detect the toner concn. of developing units without gener ating drifts between the detected toner concn. and the actual toner concn. CONSTITUTION:This image forming device is provided with toner concn. sensors 114c, 115c, 116c, 117c detecting the toner concn. in developing units 114-117, an output fluctuation calculation section 10 obtaining the output fluctuations of the toner concn. sensors for the elapsed periods with the elapsed periods after the drive of the developing units 114-117 is started and the toner concn. detected by the corresponding toner concn. sensors 114c-117c, and the first correction section 20 correcting the toner concn. detected by the toner concn. sensors or the toner concn. control reference value used in a controller 50 with the output fluctuations of the toner concn. sensors for the elapsed periods at the time of the normal image forming operation.

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 or a printer, and more particularly to an image forming apparatus which detects a toner concentration of a developer in a developing device to control a process.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, an image forming apparatus for detecting toner concentration of a developer in a developing device and performing process control such as toner replenishment based on the detection result. Is well known.

For example, in a conventional developing device using a two-component developer consisting of toner and carrier, in order to maintain the developing ability, the toner replenishment amount is appropriately controlled so that the toner concentration becomes a predetermined concentration. There is a need.

In general, the toner density of a two-component developing device is detected by utilizing the fact that the magnetic permeability of the developer varies depending on the toner concentration, or the optical reflection density for the developer varies depending on the toner concentration. Is being detected. That is, in the conventional image forming apparatus, the toner density is directly determined from the detection result of the magnetic permeability or the optical reflection density, and the process control such as toner replenishment is performed.

Here, the toner density sensor utilizing the change in magnetic permeability of the developer will be specifically described with reference to FIG. As shown in the figure, the output characteristic of the toner concentration sensor utilizing the change in magnetic permeability of the developer is that if the toner concentration is low, the amount of carriers near the sensor increases and the magnetic permeability increases,
The sensor output rises. On the contrary, if the toner concentration is high, the amount of carriers near the sensor decreases and the magnetic permeability decreases.
The sensor output drops.

However, since the toner concentration sensor as described above basically detects the toner concentration by the dynamic output obtained while the developer is moving, the detection output depends on the flow state of the developer. May fluctuate significantly.
In other words, the sensor output is determined by the dynamic carrier amount (permeability) in the vicinity of the sensor, so that the developer does not flow stably, the carrier fluidity changes due to carrier deterioration, Due to a change in the bulk density of the developer due to the charge amount of the toner, the output characteristics as shown in FIG. 15 may be destroyed, and the sensor output value may differ even with the same toner concentration.

Further, even in the toner concentration sensor utilizing the change in the optical reflection density of the developer, since it depends on the dynamic optical reflection density of the developer, the flow change of the developer near the sensor and the charging of the toner are caused. Depending on the amount of floating toner due to the amount of charge, the sensor output value may differ even for the same toner concentration.

[0008]

However, according to the conventional image forming apparatus described above, the output value of the toner concentration sensor may differ depending on the flow state of the developer, as described above, even if the toner concentration is the same. Since the toner concentration is directly determined from the output value of the toner concentration sensor without taking this point into consideration when determining the toner concentration, there may be a difference between the detected toner concentration and the actual toner concentration. However, there is a problem that the control accuracy of the process control is deteriorated.

For example, when the detected toner density deviates from the actual toner density and the toner density becomes higher than a predetermined density, the image density rises, the toner scatters, or the carrier moves outside the developing unit. Problems such as spillage and stains on the recording paper occur. On the contrary, when the toner density becomes low, the image density is lowered and the carrier adheres to the photoconductor.

The present invention has been made in view of the above, and an object of the present invention is to accurately detect the toner density of a developing device without causing a difference between the detected toner density and the actual toner density. And

[0011]

In order to achieve the above object, the present invention is directed to an image forming apparatus according to a first aspect of the invention, in which a toner concentration detecting means for detecting the toner concentration in a developing device and a developing device of the developing device are provided. In an image forming apparatus provided with a control unit for performing process control such as toner replenishment control based on the toner concentration detected by the toner concentration detecting unit during operation, the elapsed time from the start of driving the developing unit and the Using the toner density detected by the toner density detecting means, the output fluctuation amount calculating means for calculating the output fluctuation amount of the toner density sensor with respect to the elapsed time, and the output fluctuation amount calculating means during the normal image forming operation Using the output fluctuation amount of the toner concentration sensor with respect to the elapsed time, the toner concentration detected by the toner concentration detection means or the toner concentration used by the control means is detected. It is obtained by a correction means for correcting the over density control standard value.

An image forming apparatus according to a second aspect of the invention includes a toner concentration detecting means for detecting the toner concentration in the developing device,
In an image forming apparatus provided with a control unit that performs process control such as toner replenishment control based on the toner concentration detected by the toner concentration detection unit during the operation of the developing unit, after the driving of the developing unit is started, An output variation amount calculating unit for obtaining an output variation amount of the toner concentration sensor with respect to the elapsed time by using the elapsed time and the toner concentration detected by the toner concentration detecting unit, and the output variation amount calculation during a normal image forming operation. A first correction unit that corrects the toner concentration detected by the toner concentration detection unit or the toner concentration control reference value used by the control unit by using the output variation amount of the toner concentration sensor with respect to the elapsed time obtained by the unit. Measuring means for measuring the total developing drive time of the developing device, and based on the total developing drive time of the developing device measured by the measuring means. Te, in which a second correction means for correcting the correction result of the first correction means.

Further, in the image forming apparatus according to a third aspect of the present invention, the elapsed time from the start of driving the developing device is the elapsed time from the start of the stirring operation of the developer in the developing device. Is.

Further, in the image forming apparatus according to a fourth aspect of the present invention, the elapsed time from the start of driving the developing device is the elapsed time from the start of the spike-up operation of the developer in the developing device. It is a thing.

Further, in the image forming apparatus according to the fifth aspect, when a plurality of developing units are installed in the image forming apparatus, the respective units execute respective operations for each developing unit. .

[0016]

The image forming apparatus according to the first aspect of the present invention uses the elapsed time since the start of driving the developing device and the toner concentration detected by the toner concentration detecting means at a predetermined timing in advance. The output variation amount of the toner concentration sensor with respect to is calculated. After that, during normal image forming operation,
The correction unit corrects the toner concentration detected by the toner concentration detection unit or the toner concentration control reference value used by the control unit by using the output variation amount of the toner concentration sensor with respect to the elapsed time, thereby developing in the developing unit. Eliminates the deviation between the detected toner concentration and the actual toner concentration, which is caused by the unstable flow of the agent.

The image forming apparatus according to a second aspect of the present invention uses the elapsed time since the start of driving the developing device and the toner density detected by the toner density detecting means at a predetermined timing in advance with respect to the elapsed time. The output fluctuation amount of the toner concentration sensor is calculated. After that, at the time of normal image forming operation, in the first correction unit, the toner concentration detected by the toner concentration detection unit or the toner concentration control reference used by the control unit is used by using the output fluctuation amount of the toner concentration sensor with respect to the elapsed time. By correcting the value, and then correcting the correction result of the first correcting means based on the total developing drive time of the developing device in the second correcting means, the flow of the developer in the developing device becomes inaccurate. The deviation between the detected toner concentration and the actual toner concentration caused by the stability is eliminated, and the detected toner concentration and the actual toner concentration caused by the change of the bulk density or the fluidity of the developer due to the deterioration of the developer over time Eliminate the deviation of the toner density of.

Further, in the image forming apparatus according to the third aspect of the invention, the developer is corrected by correcting the output fluctuation amount of the toner concentration sensor with respect to the elapsed time after the stirring operation of the developer in the developing device is started. The deviation between the detected toner concentration and the actual toner concentration caused by the unstable flow of the toner is appropriately eliminated.

Further, in the image forming apparatus according to the fourth aspect, the development is performed by correcting the output fluctuation amount of the toner concentration sensor with respect to the elapsed time from the start of the spike-up operation of the developer in the developing device. Even if there is a time difference between the start of the stirring operation of the agent and the start of the spike, the deviation between the detected toner concentration and the actual toner concentration caused by the unstable flow of the developer is appropriately eliminated.

Further, in the image forming apparatus according to the fifth aspect, when a plurality of developing units are installed in the image forming apparatus, the respective units execute respective operations for the respective developing units, Even if the output fluctuation amount of the toner concentration sensor differs for each developing device, the toner concentration is properly corrected.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the case where the image forming apparatus of the present invention is applied to a color copying machine will be described in detail in the order of [First Embodiment] and [Second Embodiment] with reference to the drawings.

[Embodiment 1] FIG. 1 is a block diagram of a color copying machine according to Embodiment 1, showing a toner concentration sensor 114c for detecting the toner concentration in a Bk developing device 114 and a toner in a C developing device 115. A toner concentration sensor 115c for detecting the concentration, a toner concentration sensor 116c for detecting the toner concentration in the M developing device 116, a toner concentration sensor 117c for detecting the toner concentration in the Y developing device 117, and each of the developing devices (114 To 117), the toner concentration sensor (114c, 115) corresponding to the elapsed time from the start of driving
c, 116c, 117c) and the toner density detected in c), 116c, 117c), and an output fluctuation amount calculation section 10 for calculating an output fluctuation amount of the toner density sensor with respect to the elapsed time, and an output fluctuation amount calculation section 10 during a normal image forming operation The toner concentration detected by each toner concentration sensor or the control unit 5 using the output fluctuation amount of the toner concentration sensor with respect to the elapsed time obtained in
The first correction unit 20 that corrects the toner density control reference value used at 0, the measurement timers 31 to 34 that measure the total developing drive time of each developing device, and the respective development devices measured by the measurement timers 31 to 34 Based on the total developing drive time, the first correction unit 20
And a control unit 50 that performs process control such as toner replenishment control based on the toner concentration detected by each toner concentration sensor during the operation of each developing device. .

In the following, for the color copying machine of the first embodiment, the schematic structure and operation of the color copying machine are made. Synchronous timing of each developing device (developing slave and developing paddle) Creation of toner concentration sensor correction table in output fluctuation amount calculation part 2 The developer aging correction table used in the correction unit will be described in detail in the order of specific correction operations by the first correction unit and the second correction unit.

Schematic Structure and Operation of Color Copier FIG. 2 is a schematic structure of the color copier according to the first embodiment, and FIG. 3 is an explanatory diagram showing the arrangement of each color developing device and toner density sensor. The color copying machine of the first embodiment is roughly divided into a color scanner 101 for reading a color image and a color printer 102 for outputting the color image information read by the color scanner 101 to a recording sheet.

The color scanner 101 irradiates the original 103 placed on the contact glass with light from the illumination lamp 104, and forms an image of the reflected light on the color sensor 107 via the mirrors 105a to 105c and the lens 106, The color image information of the original 103 is, for example, blue,
Each green and red (hereinafter, referred to as B, G, R) separated light is read and converted into an electric image signal. The color sensor 107 is composed of, for example, B, G, and R color separation means and a photoelectric conversion element such as a CCD, and can read three colors simultaneously.

Based on the intensity levels of the color separated image signals (three colors B, G and R described above) read by the color scanner 101, color conversion processing is performed by an image processing unit (not shown), and black, cyan and magenta. , Yellow (hereinafter referred to as Bk, C, M, Y) color image data is generated. The color image data processed by the image processing unit is sent to the color printer 102, and Bk, C,
The image is visualized for each color of M and Y and output on the recording paper.

The operation method of the color scanner 101 for obtaining the Bk, C, M, and Y color image data is such that the illumination lamp 104 and the mirror are received in response to the scanner start signal in timing with the operation of the color printer 102. Documents 105a to 105c are shown in FIG.
Image data of one color is read by scanning once, and this operation is repeated four times in total to read image data of four colors sequentially. Further, the read image data is visualized by the color printer 102 each time, and the full-color image of four colors is formed by sequentially superposing them.

The color printer 102 converts the color image data input from the color scanner 101 into an optical signal, performs optical writing corresponding to the color image of the original 103, and forms an electrostatic latent image on the photosensitive drum 109. The writing optical unit 108 of FIG. The writing optical unit 108 includes a laser light source 108a, a light emission drive control unit (not shown) for the laser light source 108a, a polygon mirror 108b, a rotation motor 108c for the polygon mirror 108b, an f / θ lens 108d, and a reflection mirror 108.
e and the like.

Around the photosensitive drum 109, a cleaning unit 110 including a pre-cleaning static eliminator, a static erasing lamp 111, a charger 112, and a potential sensor 113.
A Bk developing device 114, a C developing device 115, an M developing device 116, a Y developing device 117, a development density pattern detector 118, an intermediate transfer belt 119 and the like are arranged.

Since the structures and operations of the developing devices 114 to 117 are basically the same, here, the Bk developing device 1 is used.
14 will be described as a typical example. The Bk developing device 114 includes a developing slave 114a, a developing paddle 114b, and a toner concentration sensor 114c. Development paddle 1
14b pumps up and agitates the developer. The developing sleeve 114a is rotated in a predetermined direction to bring the ears of the developer scooped up by the developing paddle 114b into contact with the outer peripheral surface of the photosensitive drum 109 to develop the electrostatic latent image formed on the photosensitive drum 109 ( To visualize). However, in the state where the developing operation is not performed (standby state), the developing sleeve 114a does not rotate, and the developer is in a spike-off state (development inoperative state) separated from the surface of the photosensitive drum 109.

In the figure, 115a, 116a,
Reference numeral 117a denotes a developing slave, and 115b and 1 respectively.
Denoted at 16b and 117b are developing paddles 115 and 115, respectively.
Reference numerals c, 116c and 117c respectively denote toner density sensors.

Next, the developing operation by each of the developing devices 114 to 117 will be described by taking the case where the developing order (that is, the color image forming order) is Bk, C, M, and Y as an example. However, the developing order is not particularly limited to that in the first embodiment.

First, when the copying operation by the color copying machine is started, the original 103 is read by the color scanner 101.
The Bk image information is read, and the Bk image data is generated by the image processing unit (not shown). The writing optical unit 108 uses the generated Bk image data to rotate the photosensitive drum 10 in the direction of arrow L in FIG.
9 shows an electrostatic latent image of Bk (hereinafter, the electrostatic latent image of Bk is referred to as a Bk latent image, and electrostatic latent images of C, M, and Y are similarly described as C latent image, M
Latent image, described as Y latent image).

In order to develop the Bk latent image formed on the photosensitive drum 109 from its tip, the Bk developing device 11
Before the leading edge of the latent image reaches the developing position of No. 4, the developing sleeve 114a is started to rotate, and the developer is spiked to develop the Bk latent image with Bk toner. Then, the developing operation of the Bk latent image area is continued, but the rear end of the latent image is the Bk developing device 1.
When the developer passes through the developing position 14, the developer on the developing sleeve 114a is quickly cut off to make the developing inoperative. This cutting is completed at least before the leading edge of the C latent image by the next C image data reaches the Bk developing device 114. The developer is cut off from the developing sleeve 114.
This is performed by switching the rotation direction of a to the direction opposite to that during the developing operation, and thereafter, the rotation of the developing sleeve 114a is stopped.

Now, the Bk formed by developing the Bk latent image
The toner image is transferred onto the intermediate transfer belt 119 which is in contact with the surface of the photoconductor drum 109 and is moving at a uniform speed (hereinafter, the transfer of the toner image from the photoconductor drum 109 to the intermediate transfer belt 119 will be referred to as belt transfer). Enter)). The belt transfer is performed by applying a predetermined bias voltage to the belt transfer bias roller 120 while the photosensitive drum 109 and the intermediate transfer belt 119 are in contact with each other.

Then, reading of C image information of the original 103 by the color scanner 101 is started at a predetermined timing, C image data is generated in the same manner as in the case of Bk image information, and C image data is generated on the photosensitive drum 109. Form a latent image.

The C developing device 115 starts the rotation of the developing sleeve 115a to lift the developer after the trailing edge of the Bk latent image has passed and before the leading edge of the C latent image reaches its developing position. Then, the C latent image is developed with C color toner.

In the following, for M color and Y color as well, each image information is similarly read, a latent image is formed, and development is performed with toner of the corresponding color. The operation is the above-mentioned Bk
Since the operation is the same for the colors and C, the description thereof is omitted.

On the other hand, on the intermediate transfer belt 119 to which the Bk toner image has been transferred, the C, M, and Y color toner images sequentially formed on the photosensitive drum 109 are sequentially transferred and combined to form a four-color superposition. A belt transfer image is formed. afterwards,
The four-color belt-transferred images are collectively transferred onto the recording paper.

Here, the unit including the intermediate transfer belt 119 will be described in more detail. The intermediate transfer belt 119 includes the above-mentioned belt transfer bias roller 120,
Drive roller 121 and driven rollers 125a and 125b
It is stretched around and is driven by a drive motor (not shown).

Further, as shown in the figure, the intermediate transfer belt 119 has a belt cleaning unit 122 for removing the residual toner remaining after the transfer of the belt transfer image onto the recording paper.
Are abutted and arranged. The belt cleaning unit 122 includes a brush roller 122a, a rubber blade 122b, and a contact / separation mechanism 1 for the intermediate transfer belt 119.
22c and the like. The belt cleaning unit 122 transfers the toner image of the second color from the toner transfer surface of the intermediate transfer belt 119 by the contact / separation mechanism 122c during the belt transfer of the toner images of the second to fourth colors after the first color Bk toner image is transferred onto the belt. It is separated.

The paper transfer unit 123 for transferring the four-color belt transfer image formed on the intermediate transfer belt 119 onto the recording paper includes a transfer bias roller 123a, a roller cleaning blade 123b, and the intermediate transfer belt 11.
The contact / separation mechanism 123c from 9 is configured. The transfer bias roller 123a is normally separated from the belt surface of the intermediate transfer belt 119. However, when the belt transfer images on the intermediate transfer belt 119 are collectively transferred onto the recording paper, the contact / separation mechanism 123c is set at a timing. And is pressed against the intermediate transfer belt 119. Subsequently, a predetermined bias voltage is applied, and the belt transfer image is collectively transferred onto the recording paper 124 guided between the transfer bias roller 123a and the intermediate transfer belt 119. The recording paper 124 is
The registration roller pair 126 (see FIG. 2) feeds the belt transfer image on the intermediate transfer belt 119 at the timing when the front end of the belt transfer image reaches the paper transfer position.

The intermediate transfer belt 119 can be moved by the following operation methods after the belt transfer of the Bk toner image of the first color is completed up to the rear end.
However, one of these methods or an efficient method according to the copy size is used in combination.

(A) Constant-speed constant-direction rotation system Even after the Bk toner image is transferred onto the belt, the rotation continues in the same direction at a constant speed. On the other hand, on the photosensitive drum 109, the front end position of the Bk toner image is again detected on the photosensitive drum 109.
When it reaches the contact portion (that is, the belt transfer position) with, the image formation is performed with timing so that the front end portion of the next C toner image is exactly at that position (the front end position of the Bk toner image). As a result, the C toner image is accurately aligned with the Bk toner image and is transferred onto the intermediate transfer belt 119 in a superposed manner.

After that, the same operation is performed to proceed to the M and Y image process, and a belt transfer image of four colors is obtained. Subsequent to the belt transfer process of the Y toner image of the fourth color, the belt transfer images of the four colors superimposed on the intermediate transfer belt 119 are collectively transferred onto the recording paper 124 while rotating as they are.

(B) Skip fixed direction rotation method After the belt transfer of the Bk toner image is completed, the intermediate transfer belt 119 is separated from the photosensitive drum 109, and the intermediate transfer belt 119 is skipped in the same direction at a high speed to move a predetermined amount. rear,
The initial rotation speed is restored, and the intermediate transfer belt 119 is brought into contact with the photosensitive drum 109 again. On the other hand, when the leading end position of the Bk toner image reaches the contact portion (that is, the belt transfer position) with the photosensitive drum 109 again on the photosensitive drum 109, the leading end portion of the next C toner image is just at that position. An image is formed at a timing so that it comes to (the front end position of the Bk toner image). As a result, the C toner image is Bk
The intermediate transfer belt 11 is accurately aligned with the toner image.
9 is transferred onto the belt.

After that, the same operation is performed to proceed to the M, Y image process, and a belt transfer image of four colors is obtained. Subsequent to the belt transfer process of the Y toner image of the fourth color, the belt transfer images of the four colors superimposed on the intermediate transfer belt 119 are collectively transferred onto the recording paper 124 while rotating as they are.

(C) Reciprocating rotation method After the belt transfer of the Bk toner image is completed, the intermediate transfer belt 119 is separated from the photosensitive drum 109 to stop the rotation, and at the same time, it is returned at a high speed in the opposite direction. The returned intermediate transfer belt 119 is Bk on the belt surface.
The leading edge position of the toner image passes through the belt transfer position in the opposite direction, and after moving by a preset distance, the toner image stops and stands by.

Next, when the front end position of the C toner image on the photosensitive drum 109 reaches a predetermined position before the belt transfer position, the intermediate transfer belt 119 is rotated in the initial direction again, and the intermediate transfer belt 119 is rotated. 119 to the photosensitive drum 109
Contact again. At this time, the C toner image is controlled and transferred on the intermediate transfer belt 119 under such a condition that it accurately overlaps the Bk toner image.

After that, the same operation is performed to proceed to the M and Y image process, and a belt transfer image of four colors is obtained. Subsequent to the belt transfer process of the Y toner image of the fourth color, the belt transfer images of the four colors superimposed on the intermediate transfer belt 119 are collectively transferred onto the recording paper 124 while rotating as they are.

The recording paper 124 to which the toner images of four colors are collectively transferred from the intermediate transfer belt 119 is sent to the fixing device 128 by the recording paper conveying belt 127, and the fixing roller 128a controlled to a predetermined temperature. The unfixed toner image on the recording paper 124 is fused and fixed by being nipped and conveyed by the pressure roller 128b. As a result, the full-color copy is completed, and then the recording paper 124 is ejected to the paper ejection tray 129.

The photosensitive drum 109 after the belt transfer
The surface is cleaned by the cleaning unit 110, and the charge is uniformly discharged by the discharge lamp 111. On the other hand, the intermediate transfer belt 119 after the toner image is transferred onto the recording paper 124 is pressed by the contact / separation mechanism 122c and pressed against the intermediate transfer belt 119.
The surface is cleaned by 22.

In the case of repeat copy, the first Y
Subsequent to the (fourth color) image process, the original image is read and the latent image is formed on the photosensitive drum 109 at a predetermined timing, and the second Bk (first color) image process is executed. In the intermediate transfer belt 119, the second Bk toner image is transferred onto the area of the belt surface cleaned by the belt cleaning unit 122, following the batch transfer process of the first four-color superimposed image. The subsequent color image process is the same as that for the first sheet.

In FIG. 2, 130, 131, 1
Reference numerals 32 and 133 denote paper feed cassettes, in which recording sheets of various sizes are stored. Further, the recording paper is fed toward the registration roller pair 126 from a paper feed cassette of a size designated by an operation panel (not shown) at a timing. Paper such as OHP paper or thick paper is fed from the manual feed tray 134.

The above description shows the case of the copy mode in which four full colors are obtained, but in the case of the three-color copy mode and the two-color copy mode, the same operation as described above is performed for the designated number of colors and the number of times. Will be done. Also, in the single-color copy mode, only the developing device of that color operates to develop until the specified number of sheets is completed (development of developer).
State, the intermediate transfer belt 119 is set to the photosensitive drum 109.
Is rotated at a constant speed while being in contact with the intermediate transfer belt 119, and the copying operation is performed while the belt cleaning unit 122 is still in contact with the intermediate transfer belt 119.

Synchronizing Timing of Each Developing Device (Developing Slave and Developing Paddle) Next, referring to FIGS. 4 and 5, the control unit 5 of the first embodiment will be described.
0-based development slaves (114a, 115a, 116
a, 117a) and developing paddles (114b, 115b, 1)
16b, 117b) will be described. Here, FIG. 4 shows the timing at the time of full-color copying, and FIG. 5 shows the timing at the time of mono-color copying.

In these figures, the high level indicates the on state of the development paddle, the development slave, and the toner density sensor (114c, 115c, 116c, 117c) of each color developing device, and the low level indicates the off state thereof. ing. That is, the rotation start and rotation end timings of the development paddle, the rotation start (brushing) of the development slave and the brush cutting end timing in the reverse operation, and the data acquisition start timing and the acquisition end timing by the A / D conversion of the toner concentration sensor are set. (However, the toner concentration sensor itself is always operating when the power of the copying machine main body is turned on). Also, Bk, C, and
M and Y represent developing devices of corresponding colors.

As shown in FIG. 4, the development paddles and the development slaves of the respective color developing devices are driven (turned on) after the development paddles and the development slaves of the previous color developing devices are turned off. Also, the toner concentration sensor of each color developing device is
If the sizes are the same, they are turned on after a predetermined time (A _{1 to} A ₄ in the figure) has passed since the development paddles and the development slaves of the color developing devices were started (turned on).

Further, in FIG. 5, the toner concentration sensor of the Bk developing device is driven at the timing of A ₁ , B ₁ , C _1, ... It is shown that the switch is turned on for the second time and the third time.

Creation of Toner Density Sensor Correction Table in Output Variation Amount Calculation Unit Next, creation of the toner density sensor correction table in the output variation amount calculation unit 10 will be described. The toner concentration sensor correction table (that is, the output variation amount table of the toner concentration sensor with respect to the elapsed time from the start of driving of the developing device) is used by the first correction unit 20 described later.

FIG. 6 shows the analog output of the toner density sensor 114c when the Bk developing device 114 is in mono color repeat. Output of toner concentration sensor (VT)
Varies depending on the flow state of the developer. As is clear from the figure, after the copy start, the sensor output is high at the beginning, but it becomes a stable level (the level shown by the dotted line in the figure) after the third A4 paper (A4Y) sideways. . This is because in the initial stage of driving, the developer does not move sufficiently and the carrier is clogged in the vicinity of the sensor due to gravity, and the output becomes high, but the developer gradually flows out and the developer is sewn by the spike operation. It is considered that the output gradually decreases and becomes stable because the volume decreases. In addition,
Needless to say, the relationship between the sensor output and time differs depending on the configuration of the developing device.

FIG. 7 shows the analog output of the toner density sensor for different toner densities. It can be seen that the output fluctuation amount is different compared to the standard toner density. This is probably because the fluidity of the developer changes depending on the toner concentration.

Therefore, in the first embodiment, a timer (not shown) is prepared for each developing device, and the output fluctuation amount calculating unit is provided when the power of the copying machine main body is turned on or after a series of copying operations are performed for every 100th sheet. A toner density sensor correction table (hereinafter referred to as a correction table) is created in 10, and during normal image formation (that is, during normal copying operation), the output detection of the toner density sensor is started from the start of driving the developing device. The first correction unit 20 obtains the correction amount (hereinafter, referred to as correction amount 1) of the toner concentration sensor corresponding to the time from the correction table by measuring the time until the time. By correcting the detection output of the toner concentration sensor with this correction amount 1,
Accurate correction can be performed by absorbing machine differences of copiers and developer differences.

Next, the first correction unit 20 determines the difference between the toner density when the correction table is created and the toner density when the normal toner density is detected by a predetermined T.S.T. A correction amount (hereinafter, referred to as correction amount 2) is calculated by multiplying the C difference correction coefficient, and the detection output of the toner concentration sensor is corrected by the calculated correction amount 2.

FIG. 8 shows an example of creating a correction table for each developing device by the output fluctuation amount calculating section 10, and FIGS.
(D) is a correction table for the Bk developing device, a correction table for the C developing device, a correction table for the M developing device, and Y.
It is a correction table for a developing device.

In the correction table of the same figure, VT detection start T is the time from the drive start for each developing device to the output detection start of the toner density sensor. Further, the correction amount 1 and the correction amount 2 are the output fluctuation amounts calculated by the output fluctuation amount calculation unit 10. Furthermore, the calculation formula is correction amount 1 and correction amount 2
From the calculation to the corrected toner density sensor output (corrected toner density) is expressed by one equation, and corresponds to the correction processing by the first correction unit 20. In the equation, VT1 to VT4 represent the corrected VT, and A to D represent the T.V. for adding the correction in consideration of the difference in toner density between when the correction table is created and when the normal toner density is detected. This is a C difference correction coefficient, and an appropriate value has been previously obtained and set by experiments. For example, in the Bk developing device in Example 1, A = 0.5, B = 0.3, C = 0.
The value 2, D = 0.1 is obtained and set.
If the effect of the difference in toner density can be ignored,
Each value of A to D may be set to 0.

Further, VT is a normal toner density sensor detection value, VTCAL1 to VTCAL4 are VT detection values of the developing devices when the correction table is created, and VTSTD is a VT detection value corresponding to two copies of A3 paper as a reference VT. Is what you use.

The corresponding paper size indicates the paper size corresponding to the time indicated by each run of VT detection start T. In other words, when a sheet of that size is used, the corresponding VT detection start T in the left column is used. It should be noted that Y and T after A4, B5, etc. indicating the paper size are symbols indicating the horizontal and vertical directions of the paper, respectively.

The correction table shown in FIG. 8 is created as a five-stage table for each developing device, but the method of dividing the correction time / number of times is not particularly limited to this. For example, if the relationship between the VT detection start time and the correction amount is held as a function, the correction can be performed steplessly.

Further, in the first embodiment, when selecting the correction table, a timer is prepared for each developing device, and the time from the start of driving to the start of output detection of the toner density sensor (Bk shown in FIG. 5). In the case of a developing device, it is A ₁ , B ₁ , C _1, etc. If this is a C developing device, it becomes like A ₂ , B ₂ , C _2, etc. The same applies to M developing device and Y developing device. However, if the time can be represented by the paper size, the number of repeat copies, and the copy mode (mono color, full color, special mode, etc.), the correction table can be selected so that the correction amount based on these data can be selected. It is also possible to make a setting and use the correction table to perform the correction.

In this case, in the mono-color mode, the correction amount is determined from the paper size using the correction table, and in the full-color mode, the correction table is used to determine the correction amount regardless of the number of copies. Make a correction.

Here, the procedure for creating the toner concentration sensor correction table by the output fluctuation amount calculation unit 10 will be specifically described with reference to the flowchart in FIG. In the first embodiment, as described above, the correction table is created when the power of the copying machine main body is turned on or after the series of copying operations are performed every 100th sheet. First, all color developing paddles (114b, 115b, 116b, 117b) without toner replenishment
Is rotated for 30 seconds (S901). This 30 sec
The time of 1 corresponds to one round of circulation of the developer in the developing device.

Next, the development paddles for all colors are stopped, and 5 sec
After c has elapsed, the Bk developing paddle of the Bk developing device and the developing slave are started to rotate (S902). The reason for waiting for 5 seconds to elapse is to allow the developer to stand still.

After rotating the Bk developing paddle and the Bk developing slave of the Bk developing device, at a plurality of detection points,
Vk of Bk developing device using moving average up to 7.700 sec
TCAL (VTCAL1 to 4, VTST in FIG. 8A)
D) is calculated (S903). In the first embodiment, the VT detection start T of the five stages shown in FIG. 8 as a plurality of detection points.
Time is used.

Subsequently, the VTs at the respective detection points are set as VTCAL1 to 4 and VTSTD, as shown in FIG.
The correction amount 1 and the correction amount 2 are obtained by importing into the correction table of (a), and the correction table of Bk is created (S90).
4). However, as the limit value, | VTCAL-VT
STD | ≦ 0.5.

Next, the Bk development paddle and the Bk development slave are stopped, the C development paddle and the C development slave of the C developing device are started to rotate (S905), and the moving average is calculated up to 7.900 seconds at a plurality of detection points. Using the VTCAL of the C developing device (VTCAL1 to 4, VT of FIG. 8B)
STD) is calculated (S906), and the VT at each detection point is taken as VTCAL1 to 4 and VTSTD into the correction table of FIG.
Then, the correction amount 2 is obtained and a correction table for C is created (S907).

Hereinafter, similarly, steps S908 to S910
VTCAL of the M developing device is calculated with VTCAL1 to 4 and VTSTD at each detection point.
As a result, the correction amount 1 and the correction amount 2 are obtained by taking in the correction table of FIG. 8C, and the correction table of M is created. In addition, VTCAL in steps S911 to S913
To calculate the VT at each detection point
As CAL1 to 4 and VTSTD, the correction amount 1 and the correction amount 2 are obtained by incorporating them into the correction table of FIG. 8D, and the Y correction table is created.

Regarding the correction table for the change with time of the developer used in the second correction section, FIG.
The analog output of the A4Y5th toner concentration sensor at the time of repeat copying is the same toner concentration over time (use time)
It is compared by. As shown in the figure, the output of the toner density sensor increases as the usage time (total driving time) increases. This is because the carrier of the developer deteriorates and the charging ability decreases, and the coating agent peels off from the carrier to increase the bulk density of the developer and increase the amount of carrier near the toner concentration sensor.

Therefore, in the first embodiment, the measurement timer 31
~ 34 to measure the developing device rotation time from the time the developer is charged for each developing device, and the second correction unit 40 obtains a developer temporal change correction table (hereinafter referred to as a temporal correction table). Correction amount (hereinafter referred to as correction amount 3) corresponding to the time, and the detection output of the toner concentration sensor (correction result of the first correction unit 20 in this case) is calculated based on the calculated correction amount 3. Make a correction and determine the toner density. FIG. 11 shows an example of the time-dependent correction table of the Bk developing device. The aging correction tables of the C, M, and Y developing devices are created in the same format.

Specific Correcting Operation by First Correcting Section and Second Correcting Section In the above configuration, referring to the flowchart of FIG. 12, the toner concentration sensor detection values by the first correcting section 20 and the second correcting section 40 A specific correction operation will be described. First, after the start of copying, the count of the corresponding timer is started by starting the driving of each developing device (S120).
1). Next, the toner density sensor of each developing device is used to start detection of the toner density, and the toner density sensor detection value VT and the timer count value at the time of toner density detection are stored, and the timer is 6 seconds (6000 sec). The counting is continued until (S1202). If the timer count value is 6 seconds or more, it is fixed at 6 seconds.

Next, the first correction unit 20 uses the toner density sensor detection value to be corrected and the timer count value,
By calculating the sum of the correction amount 1 and the correction amount 2 as shown by the arithmetic expression of the correction table of the corresponding developing device (see FIGS. 8A to 8D), and subtracting the sum from the toner concentration sensor detection value VT. , Toner concentration sensor output correction result 1 is obtained (S1
203).

Next, the second correction section 40 causes the measurement timer 31
To 34, the total drive time of the corresponding developing device is obtained, and the correction amount 3 is obtained from the total drive time and the corresponding correction table for aging (S1204). Subsequently, the correction amount 3 is subtracted from the toner concentration sensor output correction result 1 to obtain the toner concentration sensor output result 2 (S1205).

The control unit 50 finally determines the toner density based on the toner density sensor output result 2 (S
1206).

Although the toner concentration sensor detection value is corrected in the first embodiment, when the difference between the toner concentration control reference value and the toner concentration sensor detection value is used in the toner concentration control in the control unit 50, the toner concentration sensor detection value is corrected. The density control reference value may be corrected.

[Embodiment 2] Embodiment 2 shows an example in which the developing paddle in the developing unit and the driving timing of the developing slave are different from each other in the same configuration as in Embodiment 1. Since the other configurations and operations are common to those of the first embodiment, illustration and description thereof will be omitted.

With reference to FIGS. 13 and 14, the developing slaves (114a, 115a, 116a,
117a) and developing paddles (114b, 115b, 116)
b, 117b) will be described. Here, FIG. 13 shows the timing at the time of full-color copying, and FIG. 14 shows the timing at the time of mono-color copying.

As shown in FIG. 13, at the time of full-color copying, in each color developing device, after the driving of the developing paddle is started,
The drive of the developing sleeve is started after a predetermined time A (A _{1 to} A ₄ ) has elapsed. Also, after starting the development sleeve drive,
The output detection of the toner density sensor is started after a predetermined time E (E _{1 to} E ₄ ) has elapsed.

Further, as shown in FIG. 14, at the time of mono-color copying, E ₁ , F ₁ ,
The toner concentration sensor is turned on at the timing of G ₁ to.

In the second embodiment, the times A ₁ , A ₂ , A ₃ , and A ₄ shown in FIGS. 13 and 14 differ depending on the copy mode and the like and are not constant. There is no point in measuring the time until the start of detection. On the other hand, according to the experiment by the present inventor, in the copying machine of the second embodiment, the variation of the toner concentration sensor output at the initial stage of the repeat copying is almost constant from the start of driving the developing sleeve to the detection start of the toner concentration sensor output. Turned out to be dependent.

Therefore, in the second embodiment, the time from the driving start of the developing sleeve to the detection start of the toner density sensor output (E _{1 to} E ₄ , F ₁ ,
It is possible to correct the toner density by detecting G ₁ ) and performing the same correction as in the first embodiment based on this.

In the second embodiment, the time from the driving start of the developing sleeve to the detection start of the toner density sensor output is detected. However, as in the first embodiment, the paper size, the number of repeat copies, the copy mode (monocolor, When it can be represented by full color, special mode, etc.), a correction table may be set so that the correction amount can be selected by these data, and the correction table may be used to perform the correction.

Further, similarly to the first embodiment, the correction based on the toner density and the total driving time of the developing device can be added.
The correction method is the same as that in the first embodiment, and thus the description thereof is omitted.

[0093]

As described above, the image forming apparatus (Claim 1) of the present invention can be set in advance at a predetermined timing.
The amount of fluctuation in the output of the toner concentration sensor with respect to the elapsed time is obtained using the elapsed time since the start of driving of the developing device and the toner concentration detected by the toner concentration detecting means. afterwards,
During the normal image forming operation, the correction unit uses the output fluctuation amount of the toner concentration sensor with respect to the above elapsed time,
To correct the toner density detected by the toner density detecting means or the toner density control reference value used by the controlling means,
The toner density of the developing device can be accurately detected without causing a difference between the detected toner density and the actual toner density.

An image forming apparatus of the present invention (claim 2)
At a predetermined timing, the output variation amount of the toner concentration sensor with respect to the elapsed time is obtained by using the elapsed time since the driving of the developing device is started and the toner concentration detected by the toner concentration detecting means. After that, at the time of normal image forming operation, in the first correction unit, the toner concentration detected by the toner concentration detection unit or the toner concentration control reference used by the control unit is used by using the output fluctuation amount of the toner concentration sensor with respect to the elapsed time. The second correction means corrects the correction result of the first correction means on the basis of the total developing drive time of the development device, so that the flow of the developer in the development device is unstable. The difference between the detected toner concentration and the actual toner concentration caused by the above is eliminated, and further, the detected toner concentration and the actual toner concentration caused by the change of the bulk density or the fluidity of the developer due to the deterioration of the developer over time The toner density deviation can be eliminated, and the toner density of the developing device can be accurately detected.

The image forming apparatus of the present invention (claim 3).
Was detected because the flow of the developer was unstable by correcting the output fluctuation of the toner concentration sensor with respect to the elapsed time from the start of the stirring operation of the developer in the developing device. The difference between the toner concentration and the actual toner concentration can be eliminated, and the toner concentration in the developing device can be accurately detected.

Further, the image forming apparatus of the present invention (claim 4).
Is corrected by using the output fluctuation amount of the toner concentration sensor with respect to the elapsed time after the start of the spike operation of the developer in the developing device, so that the time difference between the start of the stirring operation of the developer and the start of the spike operation is Even in some cases, the deviation between the detected toner concentration and the actual toner concentration caused by the unstable flow of the developer can be eliminated, and the toner concentration of the developing device can be accurately detected.

Further, the image forming apparatus of the present invention (claim 5).
When a plurality of developing devices are installed in the image forming apparatus, each of the above-mentioned means executes respective operations for each developing device, so that the output fluctuation amount of the toner density sensor differs for each developing device. However, the toner density can be properly corrected.

[Brief description of drawings]

FIG. 1 is a block diagram of a color copying machine according to a first embodiment.

FIG. 2 is an explanatory diagram showing a schematic configuration of a color copying machine according to a first embodiment.

FIG. 3 is an explanatory diagram showing an arrangement of each color developing device and a toner density sensor.

FIG. 4 is an explanatory diagram showing a synchronization timing of the development slave and the development paddle in the first embodiment.

FIG. 5 is an explanatory diagram showing a synchronization timing of the development slave and the development paddle in the first embodiment.

FIG. 6 is an explanatory diagram showing an analog output of a toner density sensor during monocolor repeat of a Bk developing device.

FIG. 7 is an explanatory diagram showing the analog output of the toner concentration sensor with different toner concentrations.

FIGS. 8A to 8D are examples of creating a correction table for a Bk developing device, a correction table for a C developing device, a correction table for an M developing device, and a correction table for a Y developing device.

FIG. 9 is a flowchart showing a procedure for creating a toner density sensor correction table.

FIG. 10 is an explanatory diagram showing changes in the analog output of the toner concentration sensor depending on the total driving time (elapsed time) of the developing device.

FIG. 11 is an explanatory diagram showing an example of a time-dependent correction table.

FIG. 12 is a flowchart showing a specific correction operation of a toner density sensor detection value.

FIG. 13 is an explanatory diagram showing a synchronization timing of the development slave and the development paddle in the second embodiment.

FIG. 14 is an explanatory diagram showing a synchronization timing of a development slave and a development paddle in the second embodiment.

FIG. 15 is a graph showing an example of output characteristics of a toner concentration sensor using a change in magnetic permeability in a conventional image forming apparatus.

[Explanation of symbols]

 10 Output Fluctuation Calculator 20 First Corrector 31-34 Measurement Timer 40 Second Corrector 50 Controller 114 Bk Developer 114c Toner Density Sensor 115 C Developer 115c Toner Density Sensor 116 M Developer 116c Toner Density Sensor 117 Y Developer 117c Toner concentration sensor

Claims (5)

[Claims] 1. A toner density detecting means for detecting a toner density in a developing device, and a control for performing a process control such as a toner replenishing control based on the toner density detected by the toner density detecting means during the operation of the developing device. And a toner concentration detected by the toner concentration detecting unit, the amount of output fluctuation of the toner concentration sensor with respect to the elapsed time is calculated by using the toner concentration detected by the toner concentration detecting unit. Output fluctuation amount calculating means to be obtained,
During a normal image forming operation, the output fluctuation amount of the toner density sensor with respect to the elapsed time obtained by the output fluctuation amount calculating means is used to detect the toner density detected by the toner density detecting means or the toner density used by the control means. An image forming apparatus comprising: a correction unit that corrects a control reference value. 2. A toner density detecting means for detecting a toner density in a developing device, and a control for performing a process control such as a toner replenishing control based on the toner density detected by the toner density detecting means during the operation of the developing device. And a toner concentration detected by the toner concentration detecting unit, the amount of output fluctuation of the toner concentration sensor with respect to the elapsed time is calculated by using the toner concentration detected by the toner concentration detecting unit. Output fluctuation amount calculating means to be obtained,
During a normal image forming operation, the output fluctuation amount of the toner density sensor with respect to the elapsed time obtained by the output fluctuation amount calculating means is used to detect the toner density detected by the toner density detecting means or the toner density used by the control means. Based on the first correction means for correcting the control reference value, the measuring means for measuring the total developing drive time of the developing device, and the total developing drive time of the developing device measured by the measuring means, An image forming apparatus comprising: a second correction unit that corrects a correction result of the correction unit. 3. The elapsed time from the start of driving of the developing device is the elapsed time from the start of the stirring operation of the developer in the developing device. The image forming apparatus described. 4. The elapsed time from the start of driving of the developing device is the elapsed time from the start of the spike-up operation of the developer in the developing device. 2. The image forming apparatus according to 2. 5. The image according to claim 1, wherein when a plurality of developing devices are installed in the image forming apparatus, the respective means execute respective operations for each developing device. Forming equipment.