JP2957376B2 - Developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device in an electrophotographic apparatus such as an optical printer or a copying machine utilizing an electrophotographic technique, and more particularly to a toner for detecting a toner concentration of a developer used in the developing device. The present invention relates to an improvement of the developer circulation system in a density detecting unit.

[0002]

2. Description of the Related Art In a color printer utilizing electrophotographic technology, a photosensitive member such as a photoconductive photosensitive drum or a photosensitive belt is rotated at a predetermined speed, and the surface of the photosensitive member is uniformly charged. Exposure control for forming an electrostatic latent image on the surface of the photoreceptor is performed by controlling blinking of a laser beam deflected and scanned in a direction perpendicular to the rotation direction of the photoreceptor according to video data corresponding to an image to be printed. The electrostatic latent image formed on the surface is developed to form a toner image, and the toner image is temporarily overlaid and transferred to an intermediate transfer drum arranged so as to partially contact the photoconductor. Each electrostatic latent image formed on the photoreceptor is formed by exposing with a laser beam that blinks according to video data corresponding to yellow, magenta, cyan, and black that constitute a color image. , To form a color toner image on the intermediate transfer drum surface by executing the transfer is developed with toner of the corresponding color.

In such a color printer, in order to obtain a high-quality color image, it is necessary to control the toner amount of each color toner image to be superimposed on the intermediate transfer drum with high accuracy, and this is realized. For this purpose, the toner concentration of a developer used in a developing device for each color is controlled.

A developer used in a developing device of this type of electrophotographic apparatus is a mixture of a magnetic carrier and a non-magnetic toner, and an inductance method is often used to detect a toner concentration, which is a mixing ratio between the two. . In this method, the toner concentration of the developer is measured by the amount occupied by the magnetic carrier, and the magnitude of the inductance of the sensing coil, which is affected by the magnetic permeability that changes according to the mixture ratio, is converted into an electric signal. When the concentration decreases, the amount of magnetic carrier per unit amount increases and the magnetic permeability of the developer increases,
The fact that the value of the inductance of the sensing coil increases is used.

In this inductance method, it is necessary that the developer acting on the sensing coil of the toner concentration detecting means moves while its density is stable. Even when a developer having a predetermined toner concentration acts on the sensing coil in a state of being compressed at a high density, the sensing coil reacts with a large amount of magnetic carriers. Has a value of inductance similar to that in which the action is performed, which causes a detection error.

In order to stably move the developer acting on the sensing coil and realize highly accurate toner concentration detection, a general toner concentration detecting means removes a part of the developer circulating in the developing container. A detection container to be passed is provided, and the sensing coil is installed facing the side wall of the detection container, and the sensing coil is configured to be sensitive to the developer moving in the detection container. The detection container has a lower opening for discharging the developer introduced with respect to an upper opening for introducing the developer, and a side wall therebetween is gradually narrowed, so that the detection container naturally flows down in the detection container. It is configured to suppress the flow of the developing agent and to realize the stable movement of the developer into the detection container.

However, in such a developer circulating system in the toner concentration detecting means, when the developing device is stopped, the flow of the developer is also stopped. Therefore, when the vibration or the like acts, the developer in the detecting container is compressed and detected. A clogging phenomenon occurs in the container. In order to prevent this clogging phenomenon, Japanese Patent Application Laid-Open No. 2-158
The developing device described in Japanese Patent No. 773 proposes to provide a bypass passage in a side wall of the detection container and discharge the developer in the detection container through the bypass passage when the developing device is stopped.

[0008]

In a color electrophotographic apparatus using a plurality of developing devices, each developing device is miniaturized in order to avoid an increase in the size of the device. Therefore, the lower opening of the detection container and the bottom surface of the developing container are required. The distance to is decreasing. For this reason, even if the developer in the detection container is to be discharged from the bypass passage when the developing device is stopped, the discharge of the developer stops because the surface level of the developer in the developer container rises and the bypass passage is blocked. As a result, the clogging phenomenon cannot be completely prevented because the developer remains in the detection container.

It is also conceivable to provide a discharge means for forcibly discharging the developer in the detection container after the developing device is stopped. However, when the developing device is restarted, the developer is stably stored in the detection container. The delay time until the formation of the circulation flow is long, and during this time, the toner concentration cannot be detected and the toner concentration of the developer cannot be controlled. In a color electrophotographic apparatus in which the operation is alternately started and stopped, it is difficult to perform accurate toner density control.

SUMMARY OF THE INVENTION It is an object of the present invention to stably operate a toner concentration detecting means even in a developing apparatus in which the operation and the stop are frequently repeated, and to reliably prevent a developer clogging phenomenon occurring in a detecting container. can be prevented in,
Accordingly, it is an object of the present invention to provide a developing device capable of accurately detecting and controlling the toner density.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a developing container for storing a developer, a developing roll for holding the developer in the developing container on its surface and acting on an electrostatic latent image holding surface, and a developing roll. A developer collecting means for separating the developer held in the developing roll from the developing roll and collecting the developer into the developing container, and introducing a part of the developer from the upper opening thereof, and a developing container from a lower opening smaller than the upper opening. a detection container to flow down within, the developing device and a sensing means in response to the developer passing through the detection cell for sensing the toner concentration in the developer, the developer along the inner side of the side wall of the said detection container And a swing member that directly vibrates the developer in the vicinity of the lower opening in the detection container outside the sensitive region of the sensing means.

[0012]

The swinging member directly vibrates the developer in the detection container so as not to affect the sensitivity of the toner concentration sensing means.
The developer clogging phenomenon that occurs near the lower opening of the detection container during stoppage can be reliably released, and a stable circulating flow can be formed in a short time.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 is a longitudinal sectional side view of the color laser printer.
Are stretched around rotating rolls 3, 4, and 5 and held rotatably. The rotating roller 3 for driving the belt rotates so as to convey the photosensitive belt 2 at a rotation speed of about 70 mm / s.
The rotating rolls 3 and 4 are arranged so as to form a flat developing area on the photosensitive belt 2, and the rotating rolls 4 and 5 are arranged so as to form a toner image transfer area described later. Further, the rotating roll 3 guides the photosensitive belt 2 so as to form a stable exposure surface for scanning exposure to be described later on the photosensitive belt 2.

A corona discharge type charger 6 and a laser beam scanning exposure unit 7 are arranged below the photosensitive belt 2. The laser beam 7a generated from the scanning exposure unit 7 under the control of the video signal supplied from the higher-level image signal generator is 1.225 ms in a direction crossing the surface of the photosensitive belt 2 rotating along the surface of the rotating roll 3. And the surface of the photosensitive belt 2 is scanned and exposed, and an electrostatic latent image having a pixel density of about 300 dpi is formed in the rotating direction of the photosensitive belt 2.

On the upper side of the photosensitive belt 2, developing devices 8 to 11 are detachably arranged so as to face the developing region where the photosensitive belt 2 rotates flat.
The electrostatic latent image is developed by rubbing the surface of the photosensitive belt 2 with a developer magnetic brush formed on the surfaces of a, 10a and 11a. The developing device 8 uses a developer containing yellow (Y) toner, the developing device 9 uses a developer containing magenta (M) toner, and the developing device 10 uses cyan (C). ) A developing device 1 using a developer containing a color toner
For 1, a developer containing a black (K) color toner is used. Then, the developing devices 8 to 11 are selectively applied to the photosensitive belt 2 in accordance with the corresponding color of the electrostatic latent image to develop each electrostatic latent image into a toner image of a corresponding color. In order to develop each electrostatic latent image, one developing device 8 (9 to 11) is selected to act on the photosensitive belt 2 for about 5 seconds.

The intermediate transfer drum 12 is arranged so as to rotate while being in contact with the photosensitive belt 2 positioned in the printer main body 1 at the toner image transfer area, and the toner image formed on the surface of the photosensitive belt 2 is The toner image is transferred in the toner image transfer area. Intermediate transfer drum 12 is also about 70mm
Rotate at a speed of / s. This speed is equal to the rotation speed of the photosensitive belt 2. Around the intermediate transfer drum 12, a pre-charger 13, a transfer roll 14, and a drum cleaner 15 are disposed so as to face the outer peripheral surface of the intermediate transfer drum 12. The toner image of each color is superimposed on the outer peripheral surface from the photosensitive belt 2. Are sequentially transferred to a color toner image.

The preliminary charger 13 is a corona discharger,
Corona discharge is generated by urging the surface of the intermediate transfer drum 12 to provide a charge that assists the transfer of the completed color toner image onto the recording paper 16. Drum cleaner 15
Is movable relative to the surface of the intermediate transfer drum 12, and is formed on the outer peripheral surface in the process of forming a color toner image by superimposing and transferring a plurality of single-color toner images from the photosensitive belt 2 to the intermediate transfer drum 12. From the recording paper 16
After the transfer to the surface of the intermediate transfer drum 12, an operation is performed to remove the toner remaining on the surface of the intermediate transfer drum 12 so as to contact the surface.

The paper feed mechanism is installed in the space below the scanning exposure unit 7, and is configured to extract and send out the recording paper 16 stored in the paper feed cassette 17 by the paper feed roll 18.

A registration roll 19 for adjusting the transfer timing of the color toner image formed on the surface of the intermediate transfer drum 12 and the recording paper 16 for transferring the toner image is provided between the paper supply roll 18 and the transfer roll 14. Paper feed roll 1
The recording paper 16 fed from 8 is fed to the transfer roll 14 with the transport timing adjusted. The registration roll 19 rotates so as to convey the recording paper 16 at about 70 mm / s (the same speed as the photosensitive belt 2).

A transfer guide 20 is provided downstream of the transfer roll 14.
And a fixing unit 21 and a paper discharge roll 22, and a paper discharge tray 23 on which the printed material (the recording paper 16 on which the toner image is fixed) sent out from the paper discharge roll 22 is formed on the upper surface of the printer main body 1. Is done.

The printer body 1 incorporates a control circuit device for controlling the operation of the color laser printer, but its illustration is omitted.

FIG. 3 is a vertical sectional side view of the developing device. The developing devices 8 to 11 have basically the same configuration and will be described with reference to the developing device 8 as an example. Developing container 8 of developing device 8
The developer 8c in b is a mixture of a magnetic carrier and an insulating toner, and is supplied to the developing roll 8a by a stirring and supplying device 8d. The developing roll 8a is driven after the stirring and supplying device 8d is rotated.
The developer 8c held on the surface by the magnetic force a is conveyed in the direction of arrow A while being cut to a predetermined thickness by a spike blade 8e made of a non-magnetic material, and is conveyed to the photosensitive belt 2
To develop the electrostatic latent image formed on the surface of the photosensitive bell 2.

The developer 8c that has passed through the developing area is transferred from the developing roll 8a to a transport roll 8f and transported to the upper portion of the developing container 8b, where the peeling blade 8 formed of a non-magnetic material is used.
g, the developer 8c is peeled off and falls down, and a part of the developer 8c is introduced into the detection container 8j.

Approximately 1 mg / cm
^Since the toner No. ² adheres, the toner of the developer 8c is consumed during the repetition of the development, and the toner density decreases. The inductance value of the toner concentration sensing coil 8k installed in the detection container 8j changes in response to the toner concentration (magnetic permeability) of the developer 8c moving in the detection container 8j. When a control circuit (not shown) for detecting the toner concentration of the developer 8c based on the magnitude of the inductance of the sensing coil 8k detects that the toner concentration is lower than a predetermined concentration, the toner supply roll 8 in the toner hopper 8m is detected.
By rotating n, new toner 8p is supplied into the developing container 8b. The discharge / stirring screw 8q and the stirring / supplying device 8d located below the detection container 8j move and stir the developer 8c accumulated at the bottom of the developing container 8b.

At the end of the developing process by the developing device 8, the rotation of the agitating and supplying device 8d is stopped and the developing roll 8a is stopped.
After the supply of the developer to the developing roll 8a is stopped, the rotation of the developing roll 8a and the transport roll 8f is continued for 1 to 2 seconds. As a result, the developer 8c held on the surface of the developing roll 8a moves to the transporting roll 8f and retreats from the developing area, and is peeled off from the transporting roll 8f by the peeling blade 8g to form the developing container 8b.
Collected inside. From the surface of the developing roll 8a to the developer 8c
The operation of retracting the toner images is necessary to prevent the toner images from being disturbed or mixed when the developing devices 9 to 11 of other colors are forming toner images on the photosensitive belt 2.

Next, the developer circulation system for the detection container will be described. FIG. 1 is a perspective view of a detection container, and FIG. 2 is an explanatory diagram of an operation of applying vibration to a developer in the detection container.

The developer 8c introduced from the upper opening 8r of the detection container 8j naturally flows down the internal space, and the lower opening 8s
Is discharged from The detection container 8j has an opening area of the lower opening 8s smaller than an opening area of the upper opening 8r in order to suppress the flow of the developer 8c that naturally flows down the internal space and stabilize the movement thereof. The side wall is formed so that the space gradually narrows. The sensing coil 8k is attached to the side wall so as to be sensitive to the developer 8c exposed in the detection container 8j and flowing down.

The developer 8 that has flowed down from the lower opening 8s of the detection container 8j is moved in the direction of arrow B by the discharge stirring screw 8q so as not to stagnate and accumulate.

The oscillating member 8t for preventing the developer 8c from clogging the detection container 8j and obstructing the circulation is made of a non-magnetic elastic thin plate, and sandwiches the upper edge of the side wall of the detection container 8j. It is fixed, its middle part hangs down along the inside of the side wall of the detection container 8j, and its lower end part passes through the lower opening 8s of the detection container 8j and contacts the spiral fin of the discharge stirring screw 8q located thereunder. It is installed so as to be in contact with it. When the discharge stirring screw 8q rotates, the lower opening 8s is pushed by the spiral fin and elastically deformed, and returns to the original position by elasticity when it comes off the spiral fin.
Rocks along one side of. The swing period of the swing member 8t is about 2 to 8 Hz, and the swing range is designed so that the vibration of the developer 8c stimulated by the swing does not reach the sensitive region of the sensing coil 8k.

In the developing device 8 configured as described above, the oscillating member 8t oscillates in the detection container 8j during its operation to directly vibrate the developer 8c in the detection container 8j. Even if a clogging phenomenon occurs in the vicinity of the lower opening, the clogging phenomenon is immediately released, and a stable circulating flow (downflow) can be formed in a short time. Therefore, the detection container 8j when stopped
It is no longer necessary to forcibly discharge the developer 8c inside.

Further, since the developer 8c in the area where the vibration is stimulated by the swing of the swing member 8t is outside the sensitive area of the sensing coil 8k, the vibration of the developer 8c adversely affects the toner density detection by the sensing coil 8k. Therefore, it is possible to accurately detect and control the toner concentration, prevent problems such as carrier pulling and image contamination, and obtain a high-quality color image.

This embodiment has the advantage that the oscillating power of the oscillating member 8t is obtained from the rotation of the discharge and stirring screw 8q, so that it can be realized with a simple structure, but it can also be provided by an electromagnetic device or the like. it can.

The same operation and effect can be obtained even if the sensing coil 8k for detecting the toner density in response to the developer 8c is replaced with another sensing means.

If this developing apparatus is applied to a monochromatic electrophotographic apparatus, a high quality monochromatic image can be obtained.

[0036]

According to the present invention, the inside of the side wall of the detection container is provided.
Along with the oscillating member arranged to come into contact with the developer .
As a result , the developer in the detection container is directly vibrated so as not to affect the sensitivity of the toner concentration sensing means, so that the developer clogging phenomenon occurring near the lower opening of the detection container during stoppage is surely achieved. After the release, a stable circulating flow can be formed in a short time, and therefore, the toner concentration can be detected and controlled with high accuracy, so that a high-quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of a detection container according to the present invention.

FIG. 2 is an explanatory diagram of an operation of applying vibration to a developer in a detection container.

FIG. 3 is a vertical sectional side view of the developing device according to the present invention.

FIG. 4 is a vertical sectional side view of a color laser printer to which the developing device according to the present invention is applied.

[Explanation of symbols]

 2 Photosensitive belt 8-11 Developing device 8a Developing roll 8b Developing container 8c Developing agent 8d Stirring supply unit 8j Detecting container 8k Sensing coil 8q Discharge stirring screw 8r Upper opening 8s Lower opening 8t Swing member

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tetsuro Akasaki 1-1-1, Higashitaga-cho, Hitachi City, Ibaraki Prefecture Inside the Information & Video Media Division, Hitachi, Ltd. (72) Inventor Susumu Akimaru Omikamachi, Hitachi City, Ibaraki Prefecture Hitachi 1-1, Hitachi, Ltd. Hitachi Research Laboratory (72) Inventor Yoshinori Aono 7-1-1, Omika-cho, Hitachi City, Ibaraki Pref. Hitachi Research Laboratory, Hitachi Research Laboratory (56) References JP-A 55-11253 ( JP, A) JP-A-59-136764 (JP, A) JP-A-60-39672 (JP, A) JP-A-2-158773 (JP, A) JP-A-1-67662 (JP, U) (58) ) Surveyed field (Int.Cl. ⁶ , DB name) G03G 15/08-15/095

Claims (4)

(57) [Claims] 1. A developing container for storing a developer, a developing roll for holding the developer in the developing container on its surface and acting on an electrostatic latent image holding surface, and developing the developer held on the developing roll. A developer collecting means for separating the developer from the roll and collecting the developer in the developing container, a detection container for introducing a part of the developer from the upper opening thereof and flowing down into the developing container from a lower opening smaller than the upper opening; A detecting means for sensing the toner concentration in the developer in response to the developer passing through the detection container, wherein the developer contacts the developer along an inner side wall of the detection container.
And a oscillating member for directly oscillating the developer in the vicinity of the lower opening in the detection container outside the sensitive region of the sensing means by the oscillating movement. 2. The device according to claim 1, wherein the swing member provided in the detection container is a non-magnetic material, and swings in conjunction with the movement of a developer moving means provided below the detection container. A developing device. 3. A developing container for storing a developer, a developing roll for holding the developer on its surface and acting on an electrostatic latent image holding surface, and a developer for supplying the developer in the developing container to the developing roll. A supply unit, a developer collecting unit that separates the developer held on the developing roll from the developing roll and collects the developer in the developing container, and a part of the developer is introduced from an upper opening thereof; A detection container that flows down from the side opening into the developing container, and a sensing unit that detects a toner concentration in the developer in response to the developer passing through the detection container,
In the developing apparatus designed to collect the developer of the developing roller surface in the developer container by rotating the developing roller in a state of rest of the developer supply means to pause the developing action, along the inner side of the side wall of the said detection container Contact with the developer
And a oscillating member for directly oscillating the developer in the vicinity of the lower opening in the detection container outside the sensitive region of the sensing means by the oscillating movement. 4. The device according to claim 3, wherein the swing member provided in the detection container is a non-magnetic material, and swings in conjunction with the movement of a developer moving means provided below the detection container. A developing device.