JPH05346735A - Developing device - Google Patents

Abstract

PURPOSE:To improve the circulation efficiency of developer, newly supplied toner and recycled toner in a developing device, to rapidly uniformize the distribution of toner concentration in the developer, and to improve a toner concentration detecting level so as to improve responsiveness in the control of the toner concentration. CONSTITUTION:This developing device consists of a main stirring member 103 stirring and supplying the developer to a developer carrier arranged in a developing device housing, and an auxiliary stirring member 104 mixing, stirring and supplying the developer refluxed from the member 103 and the supplied toner to the member 103; and the member 104 consists of spiral screw parts 104B and 104C carrying the developer in an axial direction and a fin part 104A connected to one-side ends of the screw parts 104B and 104C and discharging the developer in the normal direction of a rotary shaft. Then, a toner concentration sensor 106 is provided on the bottom of the developing device housing below the fin part 104A of the 2nd stirring member 104, and both ends of a blade forming the fin part 104A are chamfered or formed in a rounded shape in the developing device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for visualizing an electrostatic latent image formed on an image bearing member by a developer by an electrophotographic recording system or an electrostatic recording system, and more particularly to a developing device. It relates to developer circulation and toner replenishment.

[0002]

2. Description of the Related Art Generally, in an electrostatic image forming apparatus such as an electrophotographic copying machine, an electrostatic latent image on a charge carrier (photoreceptor drum, etc.) is converted into a visible toner image in a developing device, which is then converted into a visible toner image. A copy image is formed by transferring and fixing on a recording paper.

Conventionally, as a method for developing an electrostatic latent image formed on a photosensitive drum, a two-component developer containing a mixture of toner and a magnetic carrier or a one-component developer consisting of a magnetic toner is used, and a magnetic brush is used. A lot of development is performed by the developing device. In a magnetic brush developing device, a developing roller composed of a non-magnetic cylindrical developing sleeve and a magnetic roll composed of a plurality of permanent magnets inside the developing sleeve is arranged at a fixed position with respect to an image carrier. The developer magnetically attracted to the peripheral surface of the developing sleeve is conveyed to the developing area facing the image bearing member by the rotation of the developing sleeve to develop the electrostatic latent image. ..

That is, the developer, which is formed as a brush of the magnetic brush on the magnetic pole on the outer peripheral surface of the developing sleeve and is used for the development, is carried on the developing sleeve as the developing sleeve rotates, and the developer scraping plate. Alternatively, the toner is separated from the surface of the developing sleeve by the repulsive magnetic field, and is mixed and stirred by a stirring impeller with new toner supplied in a fixed amount from the toner container to prepare for new development. As a conventional technology related to the impeller for stirring,
-5102 is disclosed.

In the developing device using the above-mentioned two-component developer, when copying is repeated, the toner in the developing device is consumed. Therefore, the toner is replenished in an amount corresponding to the consumed amount, and the toner carrier is always used. If the mixing ratio (toner density) is not kept constant, copying with an appropriate density will not be performed. Therefore, the mixing ratio (toner density) of toner and carrier in the developing device can be detected with a density sensor, etc. The toner replenishing device automatically drops and replenishes toner.

As a toner density detecting device in a conventional developing device, Japanese Utility Model Laid-Open No. 63-96567 and Japanese Patent Laid-Open No. 53-77637 are disclosed.

[0007]

The toner concentration in the developer is extremely important for obtaining a good quality image, and in order to obtain a stable image, it is necessary to keep the toner concentration constant all the time. .. Further, when the density sensor detects a change in toner density, it is necessary to immediately replenish an appropriate amount of new toner to efficiently and promptly make the toner density in the developer uniform and constant.

An object of the present invention is to provide a developing device that can meet this demand.

[0009]

The developing device of the present invention which achieves the above object comprises a first stirring member which stirs and supplies the developer to a developer carrying member disposed in a housing of the developing device.
A developing device comprising: a second stirring member that mixes and stirs the developer recirculated from the first stirring member and the replenishment toner, and supplies the mixed toner to the first stirring member. A fin portion of the second stirring member, the spiral screw portion conveying the developer in the axial direction, and the fin portion connected to one end of the spiral screw portion to discharge the developer in the normal direction of the rotation axis. The toner density sensor is provided on the bottom of the developing device casing below the blade, and both ends of the blade forming the fin portion are chamfered or rounded.

[0010]

The present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an overall configuration diagram of an electrophotographic copying machine equipped with a developing device according to the present invention. The schematic structure and function of the copying machine will be described with reference to FIG.

A document table glass 1 is provided on the upper surface of the main body of the copying machine. The original D is set on the surface of the original platen glass 1 and is pressed and covered by the original pressing plate (platen cover) 2. Then, the copy start switch is operated.
Performs relative exposure scanning of the document D, and the slit light flux L of the optical image of the document D is moved by the moving mirror M1 which is integrated with the light source 3.
Through the moving mirrors M2 and M3 mounted on the carriage 4 that moves relative to each other at the same time. To be done.

The photosensitive drum 6 is formed by forming a photoconductive layer such as selenium or OPC on the outer peripheral surface of a grounded metal cylinder.
It rotates in the arrow (clockwise) direction in conjunction with the above exposure scanning.

Around the photosensitive drum 6, a strip electrode 7, a charge erasing LED 8, an exposure image forming section 9, a developing device 10, a transfer electrode 1
1, a separation electrode 12, a separation claw 13, a cleaning device 14, and an afterimage erasing (pre-charging exposure) device 15 are sequentially arranged.

In the photoconductor drum 6, the photoconductive layer is, for example, positively and uniformly charged by the band electrode 7 to which a high DC voltage is applied before an optical image is formed. When the photoconductive layer in this state receives the light image of the document D, the conductivity of the portion receiving the light becomes high, the charged electric charge of the portion escapes to the metal cylinder, and the dark portion depends on the degree of lightness and darkness. Positive charges are left to form an electrostatic latent image corresponding to the image of the original on the surface of the photoconductive layer. Next, the electrostatic latent image on the photosensitive drum 6 is subjected to the developing action of the developing device 10 to be visualized as a toner image. The photoconductor drum 6 carrying the visible toner image reaches the transfer portion.

On the other hand, the transfer paper P stored in the paper feed cassette 20 is conveyed through the first paper feed roller 21, the second paper feed roller 22 and the guide plate, and is temporarily moved by the third paper feed roller 23 and the stopper 24. After being stopped, the toner image is further fed in synchronization with the rotation of the photosensitive drum 6 and reaches the peripheral surface of the photosensitive drum 6, and the toner image is transferred at the transfer portion. That is, the transfer paper P supplied to the transfer portion is brought into close contact with the surface of the photosensitive drum 6, and the transfer electrode 11 receives a discharge having a polarity opposite to that of the toner, and the toner image is transferred onto the transfer paper P.

The transfer paper P on which the toner image has been transferred is then peeled off from the surface of the photosensitive drum 6 by the separation electrode 12 and the separation claw 13 and is further conveyed to the fixing device 25 where it is heated by the heating roller. It is heated and fixed, discharged by the paper discharge roller 26, and placed on the paper discharge tray 27.

On the other hand, the photosensitive drum 6 from which the transfer paper P is separated
Cleans the toner remaining on the surface with the cleaning device 14, removes the residual charge with the pre-charge exposure device 15, and returns to the original state. After that, the next image formation is repeated by the same operation as the above process.

FIG. 2 is a sectional view of the image forming process unit of the copying machine.

The developing device 10 is roughly classified into a developing section 100.
And a toner supply unit 110.

Inside the casing 101 of the developing section 100, a developing roller 102 composed of a developing sleeve and a magnet, a main stirring member (first stirring member) 103 having a plurality of stirring blades,
A spiral screw-shaped auxiliary stirring member (second stirring member) 104 is rotatably supported. Further, a bristling regulating plate 105 is provided above the developing roller 102, and a toner concentration detection sensor 106 is provided below the auxiliary stirring member 104.

Inside the casing 111 of the toner replenishing section 110, a cartridge accommodating chamber 112 in which a toner cartridge 120 accommodating replenishment toner is detachably attached and detached, and a ladder for carrying out the toner accumulated at the bottom of the casing 111 upwards. Wheel 113, ladder chain 114, toner scraping member 11
5 toner discharge means and toner supply screw 116
Further, a toner remaining amount detection sensor 117 is provided.

A high-voltage bias current applied to the developing roller 102 for development and a toner concentration detection sensor 10
6, developing device, such as each detection current of the toner residual detection sensor 117
Electric power transmitted and received to and from the main body of the copying machine is supplied from a power supply unit and a control unit.

When the portion of the photosensitive drum 6 on which the electrostatic latent image is formed reaches the proximity position (developing region) of the developing roller 102 of the developing portion 100, toner is stored in the charge holding portion on the photosensitive drum 6. It is attracted by electrostatic force to form a toner image.

When the amount of toner in the developing unit 100 decreases and the toner concentration decreases due to repeated copying, the toner concentration detecting sensor 106 detects this, and the toner unloading means in the toner replenishing unit 110 raises the replenishment toner upward. The toner is replenished by the toner replenishing screw 116 and is dropped from the opening of the casing 111 by the rotation of the auxiliary stirring member 104 of the developing unit 100 located below to be stirred / conveyed with the developer and further stirred by the main stirring member 103. Mixed, part of the development roller 102
Then, the other part is replenished on the auxiliary stirring member 104.

3 is a sectional view of the developing section 100 according to the present invention taken along the line AA in FIG. 2, FIG. 4A is a side view of the partition plate 107, and FIG. 4B is a side view of the auxiliary stirring member 104. , Fig. 4
FIG. 6C is a side view of the toner concentration detection sensor 106.

The main stirring member 103 comprises a plurality of elliptical plate-shaped stirring blades 103A fixed to a rotary shaft 103B, and a gear G1 fixed to the shaft end portion is developed by a gear G0 by a driving force from a developing roller 102. It is rotated in the opposite direction to the roller 102, and the developer in the developing unit 100 is mixed and stirred to supply the developer onto the developing roller 102.

The auxiliary stirring member 104 has a fin portion 104A having a plurality of blades formed substantially in the center of the shaft, and a right spiral screw portion 104B and a left spiral screw portion 104C are formed on both sides of the shaft. There is. A fin portion 104A composed of a plurality of blades (paddles) is formed between the left and right spiral screw portions 104B and 104C. The developer conveyed to the fin portion 104A near the center by the left and right spiral screw portions 104B and 104C of the auxiliary stirring member 104 that is driven to rotate is the fin portion 104A.
By the rotation of A, it is radiated in the direction normal to the rotation axis and is supplied to the main stirring member 103.

The auxiliary stirring member 104 is the main stirring member 103.
And the main stirring member 103 by the gear G3 via the intermediate gear G2.
Is rotated in the same direction as. Further, the right spiral screw portion 104B of the auxiliary stirring member 104 is further extended to the left, and the toner collected by the cleaning device 14 is carried into the screw end portion 104D through the recycling tube 16.

A toner concentration detection sensor 106 is installed directly below the fin portion 104A at the substantially central portion of the auxiliary stirring member 104, that is, at the bottom portion at the substantially central portion of the casing (housing) 101.

Above the auxiliary stirring member 104, the toner replenishing screw 116 is driven and rotated at appropriate times to drop an appropriate amount of new toner in the toner cartridge 120, and the auxiliary stirring member 1
Supply on 04.

A partition plate 107 is fixed to the casing 101 between the main stirring member 103 and the auxiliary stirring member 104, and the developing plate 100 is divided into left and right chambers shown in FIG. 2 by the partition plate 107. Has been converted.

As shown in FIG. 4 (A), the partition plate 107 has a gate-shaped developer outlet opening 107A at the lower center thereof.
However, a plurality of rectangular penetrating developer inflow openings 107B and 107C are formed above the opening.

FIG. 5B is a partial side view showing a state where the developer is discharged by the fin portion 104A of the conventional auxiliary stirring member 104,
FIG. 5A is a characteristic diagram of the developer ejection force by the fin portion 104A.

The fin portion 104A is composed of a plurality of rectangular blades (paddles), and by rotating integrally with the left and right spiral screw portions 104B and 104C, the arrow a,
b The developer conveyed from both directions is discharged in the direction of the normal line to the rotation axis (direction of double arrow C). As shown in the characteristic diagram of FIG. 5 (A), this developer ejection force is a curve having two maximum pressure portions near both ends of the fin portion 104A, and the center of the fin portion 104A at the center of the toner concentration detection sensor 106. The pressure will drop in the vicinity. Therefore, the toner concentration detection sensor
There is a drawback that the release rate of the developer passing through the detection surface of 106 is reduced and the toner concentration detection level is reduced.

FIG. 6B shows an auxiliary stirring member 10 according to the present invention.
6 is a partial side view showing an improved shape of the fin portion 104A of FIG.
FIG. 6A is a characteristic diagram of the developer ejection force by the fin portion 104A.

Each of the plurality of blades (paddles) of the fin portion 104A according to the present invention has a trapezoidal shape with both end surfaces chamfered. When the auxiliary stirring member 104 is rotated, the developer ejection force by the fin portion 104A having the above-described shape generates a maximum pressure portion in the central portion of the fin portion 104A,
The characteristic curve shown in FIG. 6A is formed. Therefore, the release rate of the developer passing through the detection surface of the toner concentration detection sensor 106 is maximized, the toner concentration detection level is improved, and quick toner concentration detection responsiveness becomes possible.

FIG. 7A shows an auxiliary stirring member 10 according to the present invention.
FIG. 9 is a partial side view showing another embodiment of the fourth fin portion 104A. Each blade shape of the fin portion 104A is such that both end portions of the blade are formed into an arcuate or curved chamfered portion R. With such both end shapes, the developer ejection force can be maximized in the vicinity of the center where the toner concentration detection sensor 106 is arranged.

FIG. 7B shows the fin portion 104A according to the present invention.
It is a partial side view showing another example of. Each blade of the fin portion 104A has a substantially trapezoidal shape with gentle slopes S formed at both ends of the blade. Even with such a blade shape, the developer can have a maximum ejection force near the center.

Next, the operation of the developing device of the present invention will be described with reference to FIGS. 2, 3 and 8. FIG. 8 is a perspective view of a main part of the developing device for explaining the developer circulating state.

In these figures, the arrow indicates the moving direction of the developer.

In the developing device having the above structure,
By the driving force from the driving source, the developing roller 102, the main stirring member 103 via the gears G0 and G1, and the auxiliary stirring member 104 via the gears G2 and G3 simultaneously rotate.

Toner replenishing screw 1 of the toner replenishing section 110
The new toner supplied from 16 to the right chamber of the developing unit 100 is propelled by the screws 104B and 104C of the auxiliary stirring member 104 having mutually opposite propulsion forces from both ends thereof in the directions a and b as shown by the arrows. , And the reflux developer containing the toner transported to the center is mixed with the reflux developer, which will be described later.
The toner is scattered radially by 4A and is fed into the chamber on the left side of the developing section 100 from the developer outflow opening 107A below the central portion of the partition plate 107.

When the developer passes from the fin portion 104A near the center of the auxiliary stirring member 104 to the developer outflow opening 107A of the partition plate 107, the toner concentration detecting sensor 106 disposed below the fin portion 104A develops. The toner concentration of the agent is detected.

The developer having passed through the opening 107A is mixed with the developer refluxed from the developing area by the stirring blade 103A of the rotating main stirring member 103, stirred and homogenized and supplied to the developing roller 102. The developer layer thickness is regulated by the upright regulation plate 105, and the developer layer is conveyed to the development area.

On the other hand, during the stirring by the main stirring member 103, the developer sent in the d direction shown in FIG. 3 is stirred by the main stirring member 103, and then a plurality of developer inflow openings of the partition plate 107. A circulation path is formed which passes through 107B and is returned to the auxiliary stirring member 104 again to proceed in the direction of arrow a.

Further, the developer sent in the direction e of the main stirring member 103 is agitated, and after the stirring, the other plurality of developer inflow openings 10 are introduced.
A circulation path is formed which passes through 7C and is returned to the auxiliary stirring member 104 again to proceed in the direction of arrow b.

By these two developer circulation paths, the new toner and the developer stored in the developing section 100 are uniformly mixed. Further, even if the toner concentration distribution in the developer in the developing unit 100 becomes non-uniform during the repeated copying process, it can be moved and stirred in the rotation axis direction by the circulation path to uniformly mix the toner. It is possible to solve the problem that the image becomes uneven.

Further, the toner collected from the cleaning device 14 is introduced through the recycle tube 16 into the screw end portion 104D of the rotating auxiliary stirring member 104, is conveyed in the direction of arrow f, and is conveyed in the direction of arrow a. It merges with the developer and passes through the fin 104A and opening 107A near the center,
The two loops of the left circulation path of d → a and the right circulation path of e → b are formed and uniformly stirred and supplied to the developing roller.

The fin portion 104 of the auxiliary stirring member 104
A blade and spiral screw 104B, 104C
However, the number of arrangement, the shape, the size, the position, etc. of these elements can be appropriately selected.

[0051]

In the developing device of the present invention, a plurality of spiral screw parts wound in opposite directions and a developer gathering at a position where the developer gathers in the middle of each spiral screw part are arranged in the normal direction of the rotating shaft. And a toner concentration detecting sensor disposed at the bottom of the developing device casing below the fin portion, and by making both ends of the fin portion blade chamfered or rounded. The ejection force of the developer passing through the central portion of the toner concentration detecting sensor in the vicinity of the center of the blade is maximized, and the toner concentration can be detected quickly and accurately when the developer circulation main path is passed. Therefore, due to the improvement of the toner concentration detection level, the toner concentration change of the developer stirred and circulated in the developing device is promptly detected and the toner replenishment control is performed, so that the constant toner concentration is always maintained.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a copying machine including a developing device according to the present invention.

FIG. 2 is a sectional view of an image forming process unit of the copying machine.

FIG. 3 is a cross-sectional view taken along the line AA in FIG. 2 of the developing unit according to the present invention.

FIG. 4 is a side view of each of an auxiliary stirring member, a partition plate, and a toner concentration detection sensor of the developing device.

FIG. 5 is a partial side view and a characteristic view of a conventional auxiliary stirring member.

FIG. 6 is a partial side view and a characteristic view of the auxiliary stirring member according to the present invention.

FIG. 7 is a partial side view showing another embodiment of the auxiliary stirring member according to the present invention.

FIG. 8 is a perspective view illustrating a developer circulating state of the developing device according to the present invention.

[Explanation of symbols]

 6 Photosensitive Drum 10 Developing Device 100 Developing Unit 101 Casing (Case) 102 Developing Roller 103 Main Stirring Member (First Stirring Member) 104 Auxiliary Stirring Member (Second Stirring Member) 104A Fin Part (Paddle) 104B Right Spiral Screw part 104C Left spiral screw part 104D Screw end part 106 Toner concentration detection sensor 107 Partition plate 107A Developer outflow opening 107B, 107C Developer inflow opening 110 Toner supply section 116 Toner supply screw 120 Toner cartridge a, b, c, d, e, f Developer transport direction

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display area G03G 15/09 Z

Claims (1)

[Claims] 1. A first agitating member for agitating and supplying the developer to a developer carrier disposed in a housing of the developing device, and a developer and a replenishment toner recirculated from the first agitating member. A developing device comprising a second stirring member for mixing and stirring and supplying the first stirring member to the first stirring member, wherein the second stirring member is a spiral screw portion for conveying a developer in an axial direction, and the spiral screw. A fin portion that is connected to one end of the developing portion and discharges the developer in the normal direction of the rotation axis, and a toner concentration sensor is provided on the bottom portion of the developing device housing below the fin portion of the second stirring member. A developing device, wherein both ends of a blade forming the fin portion are chamfered or rounded.