JPH10307434A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device where the fatigue of a developer is prevented by shortening the stirring time of the developer, the accurate toner concentration of the fluidized developer is obtained and a replenishment control value is decided based on the accurate toner concentration. SOLUTION: This image forming device is provided with a developer fluidizing mechanism fluidizing the developer, one main driving motor M4 and a developing driving mechanism M3 supplying the developer fluidizing mechanism with motive power followed after the main driving motor M4 and executes electrophotographic processing. The device is provided with a history data outputting means outputting history data in accordance with the history of the operation of the electrophotographic processing, a timing storing means respectively storing timing data indicating a time interval from the operation start of the developing driving mechanism to the read-in of a toner concentration signal in accordance with the history data and a controlling means 310 fetching the history data and reading in the toner concentration signal in the timing indicated by the timing data corresponding to the fetched history data.

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 forming an image by an electrophotographic process, and more particularly to an image forming apparatus capable of accurately controlling a toner concentration in a two-component developer.

[0002]

2. Description of the Related Art In an image forming apparatus for forming an image by an electrophotographic process using a two-component developer, it is necessary to keep the density of toner contained in the two-component developer constant so as to obtain an accurate image according to the original. It is known that a toner image cannot be formed. Therefore, various techniques have been proposed for newly replenishing toner in proportion to the amount of toner consumed in development. As an example of these, focusing on the fact that the magnetic permeability changes according to the toner concentration in the two-component developer, a coil is used as the detection unit of the toner concentration detection circuit to detect the change in inductance, and the toner is detected. Techniques for measuring the concentration are known. Japanese Unexamined Patent Publication No. 62-24286 discloses a technique relating to an image density control method of detecting an actual image time rate of a developing unit and controlling an image density adjusting means based on the actual image time rate.

In Japanese Patent Laid-Open No. 62-28780, a developer whose toner concentration has been detected is detected by delaying the time from the position where the toner concentration detecting means is arranged to the time when it is conveyed to the toner replenishing section. There is described a technique relating to an electrostatic latent image developing device that replenishes toner in an amount corresponding to the insufficient toner density.

However, if the toner concentration of the two-component developer is detected based on a change in the magnetic permeability corresponding to the toner concentration, the time required for the sensor output to stabilize changes due to the fatigue of the developer and the use environment. . Fatigue of the developer progresses according to the history of copy numbers and the driving time of the drum cartridge.

After the toner is newly replenished, stirring is performed to make the toner concentration uniform and charge the toner. It is also well known that even with a developer whose concentration has been made uniform by stirring, once the developing process is executed, the toner in the developer is unevenly distributed and the toner concentration becomes non-uniform. Therefore, every time the developing process is executed, the toner replenishment amount is obtained by the toner concentration detection circuit, and an appropriate amount of toner is replenished and sufficiently stirred.

Conventionally, the developer is agitated by driving the main drive motor. The main drive motor simultaneously supplied a driving force to a sheet feeding / conveying mechanism, a photosensitive drum, and the like in addition to the developer flowing mechanism. In a conventional copying machine or the like, the agitating of the developer is started at the time when the copy start switch is operated to start feeding and carrying. Therefore, the developer could be sufficiently stirred before the development was started. With sufficient agitation, the toner concentration becomes uniform and the toner flows at a stable flow rate, so the toner concentration detection circuit reliably detects the correct toner concentration when a predetermined time has elapsed since the start of driving the main drive motor. did it. For this reason, the amount of toner that needs to be replenished can be accurately determined.

However, it is well known that the more the developer is agitated, the more the fatigue proceeds. That is, if stirring is performed sufficiently to make the toner concentration uniform, the fatigue of the developer progresses, and the developability deteriorates.

[0008]

SUMMARY OF THE INVENTION The inventors of the present invention have an image forming apparatus provided with a developing drive mechanism for starting the drive of a developer flow mechanism after the start of drive of a main drive motor in order to prevent deterioration of the developer. Tried. In this image forming apparatus, the progress of the fatigue of the developer could be prevented, but on the other hand, a new problem that the toner density could not be read accurately occurred.

The toner concentration sensor is adapted to accurately detect the toner concentration of a flowing developer, and more specifically, it detects a change in magnetic permeability of the developer which is agitated by a developer flow mechanism. However, since the start of the stirring of the developer was delayed, the stirring time of the developer became insufficient. As a result, at the time when a predetermined period of time has passed from the start of driving of the main drive motor, the flow state of the developer is not stable, the detection signal of the toner detection sensor becomes unstable, and accurate toner concentration control cannot be performed. It was

Accordingly, the present invention is an image forming apparatus for preventing the fatigue of a developer by shortening the stirring time of the developer. It is an object of the present invention to supply an image forming apparatus capable of determining a replenishment control value.

[0011]

The object of the present invention can be solved by the image forming apparatus according to the first aspect.

In this image forming apparatus, since the developer flow mechanism starts to be driven later than the drive of the main drive motor, the progress of the fatigue of the developer can be delayed. The timing of reading the toner density signal is set as a time interval from the start of driving of the developing drive mechanism, that is, the timing of starting stirring. Moreover, the read timing is changed according to the history data corresponding to the fatigue level of the developer. Since the toner concentration signal of the toner concentration detecting means is read after setting the reading timing in this way, the development flow is started even if the drive start of the developer flow mechanism is delayed from the drive start of the main drive motor. The toner concentration signal can be read after the flow of the agent has stabilized. Therefore, an accurate toner density can be obtained.

In this image forming apparatus, the history data may be a total of the number of copies or a total of the driving time of the developer flowing mechanism.

The object of the present invention can also be solved by the image forming apparatus according to the third aspect.

In this image forming apparatus, since the developing drive mechanism starts driving the developer flowing mechanism with a delay from the start of driving of the main driving motor, the progress of the fatigue of the developer can be delayed. Further, the timing of reading the toner concentration signal is set as a time interval from the driving start of the developing drive mechanism, that is, the timing of starting the stirring of the developer. In addition, the first toner density signal and the second toner density signal are read with a time lag between each other to determine the reliability of the first and second toner density signals. If the result of the determination is that the first and second toner density signals are reliable, a replenishment control value corresponding to the toner replenishment amount is set by the average value of the first and second toner density signals. . Because it follows the reliable toner density signal,
The replenishment control value is determined based on the toner density signal when the flow state of the developer is unstable even though the drive start of the developer flow mechanism is later than the drive start of the main drive motor. No accurate toner density was obtained.

The object of the present invention can also be solved by the image forming apparatus according to the fourth aspect.

In this image forming apparatus, if it is determined that the first toner density signal is unreliable, the third reading is further executed after the second reading, and the third toner density signal is executed. To determine the reliability of the second and third toner density signals. For example, if it is determined from the second and third read signals that the second toner concentration signal is unreliable, the fourth read is executed and the third and fourth toner concentrations are If it is determined to be reliable, an average value of the third and fourth toner density signals is obtained. The fourth toner density signal in this example is an example of the third toner density signal of the present invention. In this manner, the reading of the toner density signal is repeated until a reliable toner density signal is obtained. Therefore, even though the driving of the developer flowing mechanism is started later than the driving of the main driving motor, reliable reading is possible. The replenishment control value was determined based on the toner density signal, and the toner density could be controlled based on the accurate toner density.

This image forming apparatus further delays the output of the stop instruction signal until the end of reading the third toner density signal and the stop instruction signal output means for outputting the stop instruction signal of the developing drive means. Control means may be provided.

The object of the present invention can also be solved by the image forming apparatus according to the sixth aspect.

In this image forming apparatus, the first reading of the toner density signal is started at a predetermined timing from the start of driving of the developing drive mechanism. Subsequently, the second and subsequent readings of the toner density signal are executed at time intervals. Since the replenishment control value is set based on the plurality of toner concentration signals thus obtained, the influence of each toner concentration signal obtained by each reading can be reduced. Even if the read toner density signal includes a signal having low reliability, the influence can be reduced. Further, the plurality of toner density signals are read at time intervals. For this reason, the reliability increases as the toner density signal is newly read, and there is less concern that many unreliable toner density signals will be read. Therefore, it is possible to accurately control the toner density after reducing the influence of the unreliable toner density signal.

Each of the image forming apparatuses may include a drum cartridge in which the photosensitive member and the developing device are mounted on the same casing, and the developing drive mechanism may also supply a driving force to the photosensitive member.

Each of the image forming apparatuses includes a paper feed transport mechanism that feeds and transports transfer paper for transferring the toner image,
The main drive motor is provided with a fixing device for fixing the toner image on the transfer paper, and a paper discharge mechanism for discharging the recording paper on which the toner image is fixed by the fixing device to the outside of the image forming apparatus. Driving force may be supplied to at least one of the sheet feeding / conveying mechanism, the fixing device, and the sheet discharging mechanism.

Further, the image forming apparatus includes a charger for charging the photoconductor, a pre-development exposure mechanism for removing a charge in a region on the surface of the photoconductor where the toner image is not developed, and the photoconductor. The drum cartridge includes a cleaning mechanism for wiping off the toner remaining on the surface of the photoconductor without being transferred from the body to the transfer paper, and a pre-charging exposure mechanism for uniformly removing charges on the cleaned surface of the photoconductor. May include at least one of the charger, the pre-development exposure mechanism, the cleaning mechanism, and the pre-charge exposure mechanism.

Further, each of the image forming apparatuses may include a toner replenishing means for replenishing the developing device with toner according to the control value.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a front view showing the overall configuration of an image forming apparatus according to this embodiment.

The copying machine 100 of this embodiment is an example of the image forming apparatus of the present invention, and forms an image corresponding to a document on a recording sheet by executing an electrophotographic process. Copier 100
Includes an automatic document feeder (hereinafter, abbreviated as RADF), a reading / scanning unit 120, an image forming unit 130, a paper feeding mechanism 140, and the like.

In the RADF, a plurality of read originals are set on the original setting table 111, and when the copy start button is pressed, each page of the original is sequentially fed by the original feeding roller 117 and predetermined on the platen glass 121. Automatically transport to position. In addition, the original having been read is removed from the platen glass 121 and discharged onto the original discharge tray 116, or a single-sided original is taken out and sent onto the platen glass 121 to complete the image reading on one side. In the reverse direction, the original is passed through the reverse path by the drive roller 115, turned over, and turned over to platen glass 121.
Is sent to a predetermined position. Thus, RADF
Is capable of handling double-sided originals and single-sided originals. The drive roller 112 and the driven roller 113, and the conveyor belt 114 and the like wound around the drive roller 112 and the driven roller 113 are properly rotated by a motor (not shown). Operate.

The reading / scanning section 120 includes a platen glass 121 on which an original is placed, and below the platen glass 121, an exposure lamp 122 and a first mirror 12 inside the apparatus main body.
3, a second mirror 124, a third mirror 125, a reflection mirror 127, and an imaging lens 126. Exposure lamp 1
Reference numeral 22 denotes a halogen lamp.

The exposure lamp 122 emits light and irradiates the original placed on the platen glass 121. The light reflected on the document surface becomes exposure light, and irradiates the photosensitive drum 131 via an optical path indicated by a two-dot chain line in FIG. In addition, the irradiation light was indicated by a two-dot chain line together with the optical path. Exposure lamp 122
And the first mirror 123 move in parallel in the direction indicated by arrow A. Further, the second mirror 124 and the third mirror 125 facing the exposure lamp 122 and the first mirror 123 integrally move in the same direction at a speed of 1/2 with respect to the first mirror 123. The image of the document placed on the platen glass 121 is displayed by the exposure lamp 122, the first mirror 123,
The second mirror 124 and the third mirror 125 are operated to scan from the tip to the tail, and the first mirror 123 and the second mirror 125 are scanned.
Mirror 124, third mirror 125 and imaging lens 126
Is reflected by the reflection mirror 127 through the
It is imaged up. A latent image is formed by the formed image of the exposure light. When scanning is completed, the first mirror 123, the second mirror 124, and the third mirror 125 return to their original positions, and stand by until the next image formation.

The copying machine 100 is capable of variable magnification copying. Magnification copying refers to changing the size of a recorded image with respect to the image size of a document. Imaging lens 12 in the optical path
When the position of 6 or the optical path length is changed, the image formed on the surface of the photosensitive drum 131 is enlarged or reduced. Therefore, when executing variable magnification copying, the position of the imaging lens 126 is set to a predetermined position according to the variable magnification. And the moving speed of each member of the reading and scanning unit 120 is changed.

The image forming section 130 includes a photosensitive drum 131
And pre-charging exposure device PCL, charging device 132, and pre-developing exposure device C
It includes an EL, a developing device 200, a transfer device 134, a separator 135, a cleaning device 136, and a fixing device 137, and executes each process after the exposure process of the electrophotographic process. Photoreceptor drum 131, pre-charge exposure PC
L, pre-development exposure device CEL, charger 132, developing device 20
The cleaning device 136 and the cleaning device 136 are housed in a cartridge so that they can be integrally removed from the main body when performing a jam processing or maintenance of each process member.

The photosensitive drum 131 is negatively charged O
PC (Organic PhotoConducto)
r) A drum coated with a photoconductor. Photoconductor drum 13
1 rotates at a linear velocity of 145.5 mm / sec. The linear velocity is
The image forming speed of the entire copying machine 100 is the same as the peripheral speed of the photosensitive drum 131, and the conveying speed of the recording paper is also the same as the linear speed.

As the charger 132, a scorotron charger was used. The charger 132 takes charge of a charging process for uniformly charging the photosensitive drum 131 to a predetermined voltage prior to the latent image forming process.

The pre-development exposure unit CEL is an LED array for exposing an area where a latent image is not formed on the surface of the photosensitive drum 131 uniformly charged. The pre-development exposure unit CEL changes the irradiation area in accordance with the size of the recording paper, and sets the charging potential of the area where no latent image is formed to approximately 0 V, thereby preventing unnecessary development.

In the developing device 200, the two-component developer in which the toner and the carrier are controlled to have a predetermined concentration (weight%) is stirred by a stirring screw to charge the toner to a predetermined charge, and the developing sleeve is rotated outside the magnet roller. A magnetic brush is formed on the outer circumference of the developing roller, and a predetermined bias voltage is applied to the developing sleeve to visualize the latent image in the developing area facing the photoconductor drum 131 as a toner image.

The transfer unit 134 superimposes the recording paper on the toner image electrostatically supported on the photosensitive drum 131 and discharges electric charges from the back side of the recording paper, as is well known. As a result, the toner is transferred onto the recording paper. The transfer device 134 shares the transfer process of the electrophotographic process. Although a scorotron discharger is used in the present embodiment, the present invention is not limited to this, and a corotron discharger or a device that electrostatically transfers a toner image onto recording paper by a charging roller can be used.

As is well known, the separator 135 separates the recording paper by removing static electricity from the recording paper electrostatically attracted to the photosensitive drum 131. The separator 135 shares the separation process of the electrophotographic process. Although the scorotron discharger is used in the present embodiment, it is also possible to use a corotron discharger, a charging roller, or the like.

The pre-charge exposure unit PCL is a photosensitive drum 131.
The remaining charge is removed.

As shown in FIG. 1, the cleaning device 136 presses a cleaning blade against the surface of the photosensitive drum 131 which further rotates after the transfer process, and removes and cleans the toner remaining on the surface of the photosensitive drum 131. The cleaning device 136 shares the cleaning process of the electrophotographic process.

As is well known, the fixing device 137 is a device for fixing the toner image on the recording paper by applying heat or heat and pressure to the recording paper carrying the toner image. The fixing device 137 is in charge of the fixing process of the electrophotographic process as one of the members constituting the image forming unit 130 and is also a part of the sheet feeding mechanism 140.

The exhaust device 138 is a device for exhausting air staying inside the copying machine 100. The exhaust device 138 includes a drive motor and a fan, and generates airflow by rotation of the fan. The exhaust device 138 is provided inside the image forming unit 130 and near the fixing device 137. Copier 10
The air staying inside 0 is heated to a high temperature by the heat generated by the exposure lamp 122 of the reading / scanning unit and the heat generated by the fixing device 137 provided in the copying machine 100.

The exhaust passage 138b is a passage for airflow from the reading scanning unit 120 to the image forming unit 130. Scanning unit 1
Since both 20 and the image forming unit 130 need to be shielded from light, they have a highly hermetic structure, so that air does not easily flow out.
Therefore, an exhaust passage 138b is provided to provide an air flow passage,
Air was made to flow through the reading scanning unit 120 and the image forming unit 130. An exhaust passage 138b is provided, and the reading and scanning unit 120 and the image forming unit 130 are exhausted by one fan.

The exhaust duct 138a is a duct for discharging air inside the copying machine 100 to the outside of the copying machine. Exhaust device 138
The ozone generated by the charging operation of the charger 132 is also exhausted by the exhausting operation of the photoconductor 132 to protect the photosensitive drum 131.

The paper feed mechanism 140 is for feeding the recording paper to the transfer portion and ejecting it from the fixing device 137 in synchronism with the toner image carried on the photosensitive drum 131. First paper feed rollers 141a, 142a, 143 for taking out and transporting the recording paper from 143
a, a guide member 141b, 142b, 143b, carry-out rollers 141c, 142c, 143c, a shutter front sensor 250, a resist shutter 145, a stack reversing unit 149, and a paper discharge sensor for jam detection arranged in front of the discharge roller of the fixing device 137. 260 and the like.

The registration shutter 145 is projected by the exciting operation of the solenoid S1 (not shown) to stop the feeding of the recording paper. As a result, the skew of the recording paper is corrected to ensure the synchronization with the toner image carried on the photosensitive drum 131.

The pre-shutter sensor 250 comprises, for example, an actuator and a photocoupler. The actuator is supported by a shaft, and rotates when the recording paper passes. As a result, the optical path of the photo coupler is blocked. Therefore, the photo coupler turns on / off the output depending on whether or not the recording paper has passed.

The paper feed cassettes 141, 142 and 143 are universal cassettes capable of storing recording paper of various sizes.

The main motor M4 (see FIG. 5) is the paper feed mechanism 14.
0, a motor for driving the fixing device 137;

By having the above-described structure, the paper feeding mechanism 140 has the first paper feeding roller 141, one by one, from the paper feeding cassettes 141, 142, 143, recording paper of a specified size.
a, 142a, 143a, and unloading roller 1
41c, 142c, 143c and the guide member 141b,
The sheet is fed toward the image transfer section via 142b and 143b. The recording paper is sent onto the photosensitive drum 131 by the registration shutter 145 which operates in synchronization with the toner image on the photosensitive drum 131. The toner image on the photoconductor drum 131 is transferred to the recording paper by the action of the transfer device 134, separated from the photoconductor drum 131 by the charge removal action of the separator 135, and then sent to the fixing device 137. After being fused and fixed by a heating roller and a pressure roller, the sheet is discharged to a discharge tray 139 outside the apparatus by a discharge roller in the case of one-sided copying.

On the other hand, when performing double-sided copying on recording paper,
The recording paper is conveyed to the circulation conveying unit 148 and the stacking reversing unit 149.
Is stored in. When a predetermined number of recording papers are stored in the stacking and reversing unit 149, they are carried out by the reversing paper feed roller 149a. The discharged recording paper is conveyed again to the position of the registration shutter 145, and is fed so as to match the toner image formed on the photosensitive drum 131, and recording is performed.

The copy condition input panel 150 is provided with an input unit for the operator to select a copy condition and a display unit for displaying the currently selected copy condition. Copier 10
The copying conditions included in 0 include image quality switching selection, variable magnification copying magnification selection, and copy number selection, and other copying conditions are also provided.

Subsequently, the developing device 2 according to the present embodiment.
00 will be described with reference to FIGS. 2 to 4.

2 is a vertical sectional view showing the structure of the developing device 200, FIG. 3 is a sectional view taken along the line AA of the developing device 200, and FIG. 4 is a perspective view of the developing device 200.

In FIG. 2, a developing device housing 221 is a housing for containing a two-component developer composed of a toner and a carrier. The lid 222 is a lid that closes the upper opening of the developing device housing 221. The magnet roll 224 has a magnet body in which magnetic poles are alternately fixed. The developing sleeve 223 has a magnet roll 224 inside and rotates along the outer circumference of the magnet roll 224. Supply roller 22
Reference numeral 5 is a member for supplying the developer in the developing device 200 to the developing sleeve 223. The developer layer thickness regulating member 226 is a member that regulates the developer layer thickness on the developing sleeve 223 to a predetermined amount. The developer stirring screws 227 and 228 are an example of the developer flowing mechanism of the present invention, and stir and flow the developer.

The stirring screw 227 and the stirring screw 2
Reference numeral 28 denotes a first stirring chamber 221B and a second stirring chamber 221C which are formed on both sides of a partition wall 221A standing upright from the bottom of the developing device housing 221.

The developing area E is a longitudinal space in which the photosensitive drum 131 and the developing sleeve 223 are close to and opposed to each other.
This is a region where the electrostatic latent image formed on the photoconductor drum 131 is developed by the developer carried by the developing sleeve 223.

The toner replenishing port 229 (see FIGS. 3 and 4) is opened in the upper part of the developing device housing 221, and receives the toner replenished from the toner cartridge (not shown) via the toner storing means and the toner conveying means. 1 into the stirring chamber 221B.

In FIG. 3, the developing sleeve 223 is rotatably supported by bearings 230A and 230B near both shaft ends. Also, in the vicinity of both shaft ends of the developing sleeve 223,
The butting rollers 231A and 231B are rotatably supported. The outer peripheral surfaces of the butting rollers 231A and 231B
Abut against the drum cartridge abutting surface (not shown),
The gap between the photosensitive drum 131 and the developing sleeve 223 is kept constant. Magnet roll 224 having a plurality of magnetic poles
Both shaft ends are fixedly supported. A driving gear G0 connected to a motor M3 (see FIG. 5) which is an example of a developing drive mechanism,
The gear G1, which is fixed to one shaft end of the supply roller 225,
G2 is driven and rotated. The gear G1 is the developing sleeve 223.
The drive is transmitted to a gear G3 fixed to the shaft end of. Gear G
2 is a gear G fixed to the rotating shaft of the stirring screw 228.
Drive to 4. Gear G5 fixed coaxially with G4
Is a gear G6 fixed to the rotating shaft of the stirring screw 227.
Drive is transmitted to. Thus, the driving rotation of the driving gear G0 causes the developing sleeve 223 and the supply roller 22 to rotate.
5. The stirring screws 227 and 228 are simultaneously rotated in the directions of the arrows shown in FIG. The surface of the developing sleeve 223 is rotated in the same direction as the photosensitive drum 131 at a position facing the photosensitive drum 131.

From the toner cartridge to the toner storage means,
Since the toner charged into the toner replenishing port 229 of the developing device 200 via the toner conveying means is powder, the toner is flown by the stirring screw 227 that is driven to rotate and flows in the arrow in the second stirring chamber 221C shown in FIG. X, first stirring chamber 22
In 1B, it is conveyed in the Y direction, and is sent into the second stirring chamber 221C through the opening 221D at the end of the partition wall 221A. The toner sent into the second agitating chamber 221C flows by the agitating screws 227 and 228 and is conveyed in the direction of the arrow in the figure, and is agitated and mixed with the developer accommodated in the second agitating chamber 221C and supplied. It is supplied to the roller 225.

A toner concentration sensor 40 is fixed to the bottom of the developing device housing 221. The toner concentration sensor 40 is provided in the second stirring chamber 221 of the developing device housing 221.
The toner is replenished into the developing device 200 from the toner replenishing port 229 based on the detection result of the toner concentration sensor 40 attached to C or the first stirring chamber 221B.

FIG. 5 is a block diagram showing a control circuit according to the present embodiment.

The control circuit according to the present embodiment controls the driving state of each process member in order to record a copy image by executing an electrophotographic process.

The CPU 310 is an example of the control unit of the present invention, and executes the overall control relating to the electrophotographic process. The CPU 310 has a ROM 311 and a non-volatile R
The AM 312, the A / D converter 50, the copy condition input panel 150, the main power supply 330, the high voltage power supply 340, the pre-shutter sensor 250, the paper discharge sensor 260, the shutter solenoid SD5, and the motors M1 to M4 are connected.

The motor M1 comprises an exposure lamp 122, a first mirror 123, and a second
4, a driving source for each member such as the third mirror 125; When variable-magnification copying is selected, the scanning speed of the reading scanning unit 120 is changed according to the magnification.

When the variable magnification copy is selected, the motor M2 moves the image forming lens 126 according to the magnification. Reflection mirror 1
Reference numeral 27 moves to an appropriate position in accordance with the movement of the imaging lens 126 via a cam mechanism.

The process drive motor M3 is an example of the developing drive mechanism of the present invention, and includes the photoconductor drum 131, the developing sleeve 223, the supply roller 225, the stirring screw 227, and the like.
It is a drive source of the stirring screw 228. The photosensitive drum 131, the developing sleeve 223, the supply roller 225,
Motor M which is a driving source of stirring screws 227 and 228
3 may be shared by a plurality of motors. Further, the process drive motor M3 may be eliminated, a clutch mechanism may be provided between the main motor M4 and the developing device 200, and the drive start timing of the developing device 200 may be determined by the on / off of the clutch. In this example, the clutch corresponds to the developing drive mechanism of the present invention.

The main motor M4 is an example of the main drive motor of the present invention, and the first paper feed roller 1
41a, 142a, 143a, reversing feed roller 149a
And carry-out rollers 141c, 142c, 143c, 149c
And a driving source such as a conveyance roller 144 and a fixing roller of the fixing device 137.

The high-voltage power supply 340 supplies power to the charger 132, the developing sleeve 223, the transfer unit 134, and the separator 135. The main power source 330 is a high voltage power source 340 and a CP.
Power is supplied to U310 and motors M1 to M4. The main power supply 330 starts or stops the supply of power by turning on / off the main switch ms.

The CPU 310 controls the copy condition input panel 15
In response to a copy start signal from 0, execution of the copying operation is started. When the copying operation is started, the motors M1 and M2 are started.
Starts driving, each unit of the reading and scanning unit 120 performs scanning of an original, while the main motor M4 starts driving, and the paper feeding mechanism 140 executes feeding and conveyance of recording paper. Main motor M
4, the process drive motor M3 starts to drive, and the photosensitive drum 131, the developing sleeve 223, the supply roller 225, the stirring screw 227, and the stirring screw 2 are started.
28 and the like also start rotating.

The toner density sensor 40 is a unit-shaped unit in which an air-core coil that directly detects a change in the inductance of the developer and a circuit that outputs the change in the inductance of the air-core coil as a change in voltage value are stored in a resin package. Sensor. The toner density sensor 40 is arranged so that the position of the air-core coil is located in the flow path of the developer in order to reliably detect a change in the magnetic permeability of the flowing developer. The output signal of the toner concentration sensor 40 has a low voltage value when the toner concentration is high, and a high voltage value of the output signal when the toner concentration is low. The toner concentration sensor 40 continuously outputs an analog output signal. The toner density sensor 40 is set to change by 0.6 v / wt% near the standard toner density of the copying machine 100.

When the A / D converter 50 receives the read command signal Re from the CPU 310, the toner density sensor 40
Is sampled and converted into digital data, and digital toner density data is output to the CPU 310.

The CPU 310 reads a predetermined timing data table from the ROM 311. In this timing data table, data on the timing at which the toner density detection signal is read into the CPU, that is, data on the output timing of the read command signal Re, is tabulated. As the output timing of the read command signal Re, each example shown in FIG.

In the copying machine 100 of this embodiment, the stirring screws 227 and 228 are set to have an outer diameter of 16 mm, a screw pitch of 16 mm, and a rotation speed of 216 rpm.
The developer has a carrier particle size of 80 μm and a toner particle size of 9.8 μm.
Then, the bulk density was set to 1.92 g / cm 2. The target toner concentration is 5 wt% with respect to the developer. With this setting, the time required for the output of the toner density detection circuit to stabilize was measured, and was 1.6 seconds. Therefore, the timing data table of the ROM 311 is created such that the output timing T4 of the read command signal Re is 1.6 seconds after the start of driving the process drive motor M3. Further, the toner concentration sensor 40 is
It is arranged in the vicinity of 8.

In this example, the time taken for the stirring screw 228 to make one rotation is about 0.28 seconds. This 0.28 second can be calculated from the set values of the stirring screws 227 and 228, and is the reciprocal of the rotation speed of the stirring screw per second. CPU
Reference numeral 310 denotes an output signal of the toner concentration sensor 40 which is intermittently sampled for 0.28 seconds from the output of the read command signal Re, converted into digital data by the A / D converter 50, and the average of the taken digital data is toner. Use the density value. The digital data output from the A / D converter 50 is an example of the toner density signal of the present invention,
The toner density value is obtained based on the toner density signal.

Needless to say, the shorter the interval, the better the intermittent sampling by the CPU 310.
Further, the output of the toner concentration detection circuit fluctuates in synchronization with the pitch of the rotating stirring screw. For this reason, the sampling period is preferably set to an integral multiple of the reciprocal of the rotation speed of the stirring screw. In the above example, the number is set to one time the reciprocal of the rotation speed.

Instead of the timing data table, a configuration may be employed in which conditional expressions are held, timing data is calculated each time according to various conditions, and a power supply start command signal is output. In any case, the timing data is temporarily stored in the register section of the CPU 310. The register section of the CPU 310 is an example of the timing storage means of the present invention.

The toner concentration sensor 40 and the A / D converter 50 constitute a toner concentration detecting circuit which is an example of the toner concentration detecting means of the present invention.

The entire circuit of the toner density detecting circuit does not need to be fixed to the developing device housing 221. It is sufficient that at least the air-core coil is attached along the toner flow path. Further, in the toner concentration detecting circuit, the air-core coil is attached along the toner flow path, and the inductance change detected by the air-core coil can be C
If it can be taken into the PU, it can be said that the toner concentration detection circuit is attached to the developing device housing 221.

The shutter solenoid SD5 drives the registration shutter 145 as described above. The paper discharge sensor 260 detects the passage of the recording paper by a photo coupler. The paper discharge sensor 260 switches the logic level and outputs it depending on whether the recording paper is passing or not.

The RAM 312 is an example of history data output means of the present invention, and is a non-volatile RAM. RAM312
Accumulates a cumulative value obtained by counting the number of times that one of the logic levels of the discharge sensor 260 appears. That is, RAM
Reference numeral 312 stores the number of recording sheets that have passed the sheet ejection sensor 260. The RAM 312 outputs copy number data, which is an example of the history data of the present invention, to the CPU 310.

In this embodiment, the copy number data is shown as an example of the history data. However, the history data may be data indicating the cumulative driving time of the developing device 200. In this case, the driving time of the developing device 200 is measured by a timer, and R
The AM 312 stores the measured value of the timer.

Next, the operation timing of the copying machine 100 according to the present embodiment will be described with reference to FIGS. 6 to 12.

FIG. 6 is a graph illustrating the relationship between the degree of fatigue of the developer and the time required for the output of the toner concentration detection circuit to stabilize.

In FIG. 6, the horizontal axis represents time and the vertical axis represents the output voltage VL of the toner concentration sensor 40. The output voltage VL on the vertical axis is closer to 0 V as the toner concentration is higher, and is higher as the toner concentration is lower, due to the circuit configuration of the toner concentration sensor 40. The timing T0 on the horizontal axis is the timing at which the process drive motor M3 starts driving, that is, the timing at which the stirring screw 227 and the stirring screw 228 start stirring and flowing the developer. Timing T1 to T
Reference numeral 3 indicates the timing at which the output of the toner density detection circuit enters the stable range.

Here, the stable range will be described. When the stirring screws 227 and 228 are stopped, the developer does not flow and stands still. When the stirring screws 227 and 228 start to rotate, the developer starts flowing along the rotating shafts of the stirring screws 227 and 228. The flow of the developer is powder and the developer is a stirring screw 227, 2.
It is in a state of being pushed out by 28 and continuously moving.
When the developer is not flowing, the developer may be accumulated in a sparse state or may be accumulated in a dense state. The output of the toner density sensor 40 corresponds to a low toner density state when the developer is dense, and corresponds to a high toner density state when the developer is sparse. That is, even if the toner concentration for all the developers in the developing device 200 is the same, the output voltage becomes low if the developer happens to be densely deposited near the toner concentration sensor 40. Conversely, if the developer happens to be loosely deposited near the toner concentration sensor 40, the output voltage will be high. When the flow starts, the density is gradually reduced, and when the flow becomes stable, the output of the toner concentration sensor 40 accurately reflects the toner concentration with respect to all the developers in the developing device 200. In the copying machine 100 of the present embodiment, the toner density is ± 0.1 watts.
When controlled within the range of t%, an output image with stable image quality can be obtained. The output of the toner concentration sensor 40 is 0.6 v / wt
%, The fluctuation range of the output signal of the toner concentration sensor 40 converges to ± 0.06 v, which is the stable range in the present embodiment.

The timing at which the output of the toner concentration detecting circuit enters the stable range varies depending on the degree of fatigue of the developer, and therefore, it is represented by three points T1 to T3. VLa and VLb
Is the output of the toner concentration sensor 40 before the timing T0, that is, before the stirring and the flow of the developer are started, and V
La indicates a relative output level when the toner density is low, and VLb indicates a relative output level when the toner density is high.

The curves VL1 to VL6 show how the output of the toner concentration sensor 40 converges in the stable region with the passage of time. VL1 and VL represented by the two-dot chain line
No. 2 shows the relationship when a developer which is hardly fatigued (hereinafter, also referred to as fatigue degree 1) is used.
VL3 and VL4 represented by the one-dot chain line show the relationship when a developer in a somewhat fatigued state (hereinafter, also referred to as fatigue degree 2) is used. VL5 and VL6 represented by broken lines
Indicates the relationship in a state where the fatigue of the developer is considerably advanced (hereinafter, also referred to as fatigue degree 3). Also, VL1,
Nos. 3 and 5 show changes from a state in which the developer is sparse before the toner starts to flow, and VLs 2, 4, and 6 show changes from a state in which the developer is dense. FIG. 6 shows the output of the toner density detection circuit by a simple curve, but the output actually undulates with a small amplitude.

FIG. 7 is a time chart showing the output timing of the read command signal Re executed according to the timing data table of the ROM 311. In FIG. 7, when a predetermined time elapses after the main body driving is started by the driving start of the main motor M4 at timing Ta, timing T
At 0, the process drive motor M3 starts driving. The drive of the process drive motor M3 starts driving the drum cartridge. When the fatigue level of the developer is 1, the read command signal Re is output at timing T1. When the fatigue level is 2, the read command signal Re is output at the timing T2. When the fatigue level is 3, the read command signal Re is output at timing T3.

In the timing data table of the ROM 311, data on the time from the drive start timing of the process drive motor M3 to the output timing of the read command signal Re is stored in association with the history of the electrophotographic process. The CPU 310 refers to the timing table of the ROM 311, and sets the read command signal Re corresponding to the history data stored in the RAM 312. Then, after starting the driving of the process drive motor M3, a read command signal Re is output at a set timing. If the output of the A / D converter 50 obtained in response to the read command signal Re is read, the read timing of the toner concentration is set according to the degree of fatigue of the developer.

Next, second, third, fourth and fifth embodiments of the image forming apparatus of the present invention will be described. The image forming apparatus of the second to fifth embodiments is different from the first embodiment in the timing data table held in the ROM 311.

FIG. 8 is a graph showing a change in the output of the toner concentration detection circuit when the developer deposition at the position of the toner concentration sensor 40 is sparse at the start of stirring the developer. The horizontal axis represents time, and the vertical axis represents the output voltage VL of the toner concentration sensor 40 as in FIG. The vertical axis represents the output voltage VL obtained when the read command signal Re is swung from T4 to T7. The developer whose fatigue has not progressed is indicated by the one-dot chain line New, and the output voltage VL obtained at the timing of T4 and T5.
Are shown as Snew1 and Snew2. The developer in which fatigue has progressed is indicated by a solid line Old, and the output voltage VL obtained at the timing of T4 to T7 is changed to Sold1, Sol.
d2, Sold3, and Sold4. Timing T0 is a timing when driving of the process drive motor M3 is started.

FIG. 9 is a time chart for explaining the output timing of the read command signal Re executed in accordance with the timing data table of the ROM 311 in the image forming apparatus of the second embodiment. In the example of FIG. 9, the process drive motor M3 starts driving a predetermined time after the drive start timing Ta of the main motor M4, and the stirring and flow of the developer start. After a predetermined time has passed since the process drive motor M3 was started, the read command signal Re is sent twice T4 and T5.
(See FIG. 8). CPU31
0 takes the difference between Snew1 and Snew2 of the output voltage VL obtained in response to the two read command signals Re, and when the difference between the toner concentration values corresponding to the difference is 0.2 wt%, the toner concentration is Judge that the reliability of the value is high. Here, the CPU 310 is an example of the determining means of the present invention. When it is determined that the reliability is high, the average value of the two toner density values is adopted as the toner density, and the toner replenishment is executed. The difference in toner concentration is not limited to the range of 0.2 wt%, but if the toner replenishment is performed while trusting the data having a difference of 0.2 wt% or more, the error with respect to the target concentration may not increase. I can't say that.

In the second embodiment shown in FIG. 9, as the fatigue of the developer progresses, the difference in toner concentration comes out of the range of 0.2 wt%. In the example of FIG. 8, Sold1 and S
The difference in toner density corresponding to old2 is 0.2 wt% or more.

FIG. 10 is a time chart showing the output timing of the read command signal Re executed according to the timing data table of the ROM 311 in the image forming apparatus of the third embodiment. In the example of FIG. 10, the process drive motor M
3 starts to drive, the stirring and flow of the developer start, the process drive motor M3 starts to drive, and outputs two read command signals Re at timings T4 and T5 (see FIG. 8). Subsequently, the read command signal Re is output at the timing of T6.

The difference between the toner density values obtained at T4 and T5 is 0.
When it exceeds 2 wt%, the CPU 310 determines that the reliability of the toner concentration value is low. Then, the CPU 310 newly outputs the read command signal Re at the timing of T6. The CPU 310 takes the difference between Solid2 and Solid3 corresponding to the output voltage VL obtained at the timings T6 and T5, and when the toner concentration corresponding to the difference between Solid2 and Solid3 falls within the range of 0.2 wt%, the toner concentration value It is determined that the reliability of the data is high. When it is determined that the reliability is high, the average value of the two toner density values of Sold2 and Sold3 is adopted as the toner density, and toner replenishment is executed.

On the other hand, toner density values Sold2 and Sold
3 difference, the difference between Sold2 and Sold3 is 0.2wt
If it is out of the range of%, it is determined that the reliability as data of the toner density value is low. If it is determined that the reliability is low, the read command signal Re is output at the timing of T7. In this way, when the reliability of the obtained toner density value is low, the toner density value is continuously read, and for example, when N times of reading is executed, the Nth and N-1th toner density values are read. , The reliability of the data is determined, and the average value of the two latest reliable sample data is adopted as the toner density value to execute the toner supply.

Further, the determination of the reliability of the toner density is not limited to the method of taking the difference of the toner density values.

FIG. 11 is a time chart showing the output timing of the read command signal Re in the image forming apparatus according to the fourth embodiment. In the image forming apparatus of the fourth embodiment, the same timing table as that of the third embodiment is recorded in the timing data table of the ROM 311. Further, the drum cartridge is used until the reliable reading of the toner density value is completed. Is not stopped. The timing T8 and the timing T9 indicate the timing at which the process drive motor M3 stops.

In the fourth embodiment shown in FIG.
After completion of the reading operation of the toner density according to the reading command signal Re in Step 5, the drive of the process drive motor M3 may be terminated before the output of the reading command signal Re in T6 or during the reading operation of the toner density. is there. For example, A
The time required to execute one copy on four sizes of recording paper is about six seconds. Further, in order to delay the progress of the fatigue of the developer, the process driving motor M3 is temporarily stopped about 2.9 seconds after the driving is started. A read command signal Re is output at a timing of T4 1.6 seconds after the start of driving of the process drive motor M3, and the read command signal Re is output every 0.7 seconds.
Is output, T6 is 3.0 seconds after the output of the process drive motor M3, and the process drive motor M3 is stopped at the timing T8 during the third toner density reading. When the process drive motor M3 stops, the developer does not flow, and the output signal of the toner density sensor 40 becomes inaccurate.

Therefore, in the fourth embodiment shown in FIG. 11, when the reliability of the toner density values obtained at T4 and T5 is low, the CPU 310 extends the drive time of the process drive motor M3. The extension time is set so that the intermittent sampling executed according to the read command signal Re output at the timing of T6 is sufficiently completed.
The timing T9 indicates the timing of stopping the drive of the process drive motor M3 after the extension. Therefore, the reading of the toner density, which is executed according to the reading command signal Re output at the timing of T6, is executed in the state where the developer is flowing.

FIG. 12 is a time chart showing the output timing of the read command signal Re in the image forming apparatus of the fifth embodiment. 16 is a time chart showing the output timing of the read command signal Re executed according to the timing data table of the ROM 311 in the image forming apparatus of the fifth embodiment. In the example of FIG. 12, the process drive motor M
3 starts to drive, the developer starts stirring and flowing, the process drive motor M3 starts to drive, and outputs three read command signals Re at timings T4, T5, and T6.

The CPU 310 uses the toner density data Sold1 and Sol obtained at the timings T4, T5, and T6.
The average value of d2 and Sold3 (see FIG. 8) is adopted as the toner density, and toner replenishment is executed. As described above, the number of reading times may be increased to reduce the influence of an error in read data per reading.

FIG. 13 is a sectional view of the drum cartridge 400 of the copying machine 100. Drum cartridge 400
In the drum cartridge casing 401.
1 is rotatably held, and around the photosensitive drum 131, a pre-charging exposure device PCL, a charging device 132, a pre-development exposure device CEL, a developing device 200, a separating claw 17B, and a cleaning device 136 are arranged. The drum cartridge housing 401 is made of resin and can be pulled out from the main body of the copying machine 100. Further, the drum cartridge housing 401 in the taken out state can be mounted on the copying machine 100. The drum cartridge 400 is provided with a power transmission mechanism for the process drive motor M3 and the main motor M4.

[0104]

According to the image forming apparatus of the present invention, it is possible to obtain an accurate toner concentration of a flowing developer by reducing the stirring time of the developer and preventing the fatigue of the developer. It has become possible to determine the replenishment control value based on the accurate toner density.

[Brief description of the drawings]

FIG. 1 is a front view showing the overall configuration of an image forming apparatus according to the present embodiment.

FIG. 2 is a vertical cross-sectional view showing the configuration of a developing device.

FIG. 3 is a sectional view taken along the line AA of the developing device.

FIG. 4 is a perspective view of a developing device.

FIG. 5 is a block diagram showing a control circuit.

FIG. 6 is a graph illustrating the relationship between the degree of fatigue of the developer and the time required until the output of the toner concentration detection circuit is stabilized.

FIG. 7 is a time chart showing an output timing of a read command signal Re executed according to a timing data table.

FIG. 8 is a graph showing a change in the output of the toner concentration detection circuit when the toner concentration is lower than a target value at the start of the stirring of the developer.

FIG. 9 is a time chart illustrating output timing of a read command signal Re in the image forming apparatus according to the second embodiment.

FIG. 10 is a time chart illustrating an output timing of a read command signal Re in the image forming apparatus according to the third embodiment.

FIG. 11 is a time chart showing the output timing of a read command signal Re in the image forming apparatus of the fourth embodiment.

FIG. 12 is a time chart showing the output timing of a read command signal Re in the image forming apparatus of the fifth embodiment.

FIG. 13 is a sectional view of a drum cartridge.

[Explanation of symbols]

 40 toner concentration sensor 50 A / D converter 100 copier 131 photoconductor drum 140 paper feed mechanism 200 developing device 227,228 stirring screw 310 CPU 400 drum cartridge M3 process drive motor M4 main motor

Claims (10)

[Claims] 1. A developer flow mechanism for flowing a developer,
A developing device, which is arranged along the path of flow of the developer and has a toner concentration detecting means for detecting the magnetic permeability of the developer and outputting a toner concentration signal, and a toner from the developing device during rotation. A photoreceptor that receives a supply of toner image and carries a toner image; at least one main drive motor that supplies a driving force for executing an electrophotographic process using the developing device and the photoreceptor; An image forming apparatus that is provided with a developing drive mechanism that supplies power to the developer flow mechanism with a delay and executes an electrophotographic process, wherein history data output that outputs history data according to a history of operations of the electrophotographic process. Means, and timing data indicating a time interval from the start of the operation of the developing drive mechanism to the reading of the toner density signal are stored according to the history data. A timing storage means, the historical data capture, image forming apparatus, characterized in that it comprises a control means for reading the toner concentration signal at the timing indicated by the timing data corresponding to the history data captured. 2. The image forming apparatus according to claim 1, wherein the history data is a cumulative number of copies or a cumulative driving time of the developer flow mechanism. 3. A developer flowing mechanism for flowing the developer,
A developing device provided along a path along which the developer flows and having a toner density detecting means for detecting the magnetic permeability of the developer and outputting a toner density signal; and Of the developing device and the developing device and at least one main driving motor that supplies a driving force for executing an electrophotographic process using the photosensitive member, and The first reading of the toner concentration signal is performed at a predetermined timing with respect to the start of driving to obtain a first toner concentration signal, and after the first reading is performed, the first reading of the toner concentration signal is performed at a predetermined timing. Reading control means for executing the second reading to obtain the second toner concentration signal; determining means for determining the reliability of the first and second toner concentration signals; and the determining means for the first and second When it is determined that the toner concentration signal of is reliable, a control value setting means for setting a replenishment control value corresponding to the toner replenishment amount based on the first and second toner concentration signals is provided. Image forming apparatus. 4. When it is determined that the first and second toner concentration signals are unreliable, the reading control means executes the third reading after the second reading and executes the third reading. Obtaining a toner density signal; the determining means determining reliability of the third and second toner density signals; and the control value setting means determining whether the third and second toner density signals are reliable. The image forming apparatus according to claim 3, wherein the replenishment control value is set based on the third and second toner concentration signals when it is determined that the replenishment control value is set. 5. A stop command signal output unit for outputting a stop command signal for the developing drive mechanism, and a control unit for delaying the output of the stop command signal until the reading of the third toner density signal is completed. The image forming apparatus according to claim 4, further comprising: 6. A developer flowing mechanism for flowing the developer,
A developing device provided along a path along which the developer flows and having a toner density detecting means for detecting the magnetic permeability of the developer and outputting a toner density signal; and A photosensitive member that carries a toner image in response to the supply of the developing device, at least one main drive motor that supplies a driving force for executing the electrophotographic process using the developing device and the photosensitive member, and Reading control means for executing reading of the plurality of toner density signals at predetermined intervals with respect to driving start at a time interval to obtain a plurality of toner density signals; and controlling the toner based on the plurality of toner density signals. An image forming apparatus comprising: a control value setting unit that sets a supply control value corresponding to a supply amount. 7. A drum cartridge in which the photoconductor and the developing device are mounted in the same casing, and the developing drive mechanism also supplies a driving force to the photoconductor. The image forming apparatus described in 4, 5, or 6. 8. A paper feeding and conveying mechanism for feeding and conveying transfer paper for transferring the toner image, a fixing device for fixing the toner image on the transfer paper, and a recording paper on which the toner image is fixed by the fixing device. And a paper discharging mechanism for discharging the paper to the outside of the image forming apparatus, wherein the main drive motor includes the paper feeding and conveying mechanism, the fixing device,
The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, or 7, wherein a driving force is supplied to at least one of the sheet discharging mechanisms. 9. The image forming apparatus includes a charger for charging the photoconductor, a pre-development exposure mechanism for removing charges in a region of the photoconductor surface where a toner image is not developed, and the photoconductor. A cleaning mechanism for wiping off the toner remaining on the surface of the photoconductor without being transferred from the transfer paper to the transfer paper, and a pre-charging exposure mechanism for uniformly removing charges on the surface of the cleaned photoconductor. 2. At least one of the charger, the pre-development exposure mechanism, the cleaning mechanism, and the pre-charge exposure mechanism is provided.
The image forming apparatus according to 2, 3, 4, 5, 6, 7, or 8. 10. The image forming apparatus according to claim 1, further comprising a toner replenishing unit for replenishing the developing unit with toner in accordance with the control value. Image forming apparatus.