JPH063961A - Developing device - Google Patents

Abstract

PURPOSE:To improve the stirring efficiency of developer, newly supplied toner and recycled toner in a developing device, to rapidly uniformize the toner concentration distribution in the developer and to improve the responsiveness of toner concentration control. CONSTITUTION:This developing device is constituted of a main stirring member 103 stirring the developer and supplying it to a developer carrier, an auxiliary stirring member 104 mixing and stirring the developer refluxed from the main stirring member 103 and supply toner and resupplying it to the main stirring member 103 and a toner concentration detecting sensor 106 arranged on a developing device housing 101 bottom part under the fin part of the auxiliary stirring member 104 and detecting the toner concentration in the developer; and developer circulation in the direction of a rotary shaft normal line by the means of the auxiliary stirring member 104 is restricted by providing a projecting rib at the boundary part of the developing device housing 101 bottom part under the middle of the main stirring member 103 and the auxiliary stirring member 104, and also circulation performance of the developer is made excellent by making the boundary part of the developing device housing 101 bottom part near the detecting surface of the toner concentration detecting sensor 106 in a flat shape where the projecting rib is removed.

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. The present invention relates to stirring and conveying of developer 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 of 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 thereof 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 carrier by the rotation of the developing sleeve to develop the electrostatic latent image. .

That is, the developer, which is formed as a brush of a 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 according to the rotation of the developing sleeve, and the developer scraping plate. Alternatively, the magnetic field is separated from the surface of the developing sleeve by the repulsive magnetic field, and is mixed and stirred by the stirring blade with new toner supplied in a fixed amount from the toner container to prepare for new development.

In a 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 of toner and carrier in the developing device is detected, and the toner replenishing device automatically uses the toner supply device. Is designed to fall and be replenished.

As a developer stirring means in a conventional developing device, there are JP-A-58-194068, JP-A-50-155235, and JP-A-52-13033.
No. 5 publications are disclosed.

[0007]

The toner concentration in the developer supplied to the developer carrying member is extremely important for obtaining a good quality image, and in order to obtain a stable image, it is necessary to keep the inside of the developing device. It is necessary that the toner concentration of the developer is constantly made uniform and kept constant. Further, it is necessary to replenish new toner immediately after the density sensor detects a change in toner density to make the toner density in the developer uniform and constant.

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

[0009]

SUMMARY OF THE INVENTION A developing device of the present invention which achieves the above, is to stir a developer and a developer carrier which is arranged so as to face an image carrier that forms an electrostatic latent image and forms a developer layer. A second stirring member that mixes and stirs the first stirring member that is then supplied to the developer carrying member, the developer that has flowed back from the first stirring member, and the replenishment toner, and then circulates again to the first stirring member. A member, a developing device housing that supports the developer carrying member, the first stirring member, and the second stirring member by arranging the respective rotation axes in parallel, and below the fin portion of the second stirring member. A developing device casing, which is installed at the bottom of the developing device casing and comprises a toner concentration detection sensor for detecting the toner concentration in the developer, wherein the developing device casing is located intermediately below the first stirring member and the second stirring member. A rotating shaft provided by a second stirring member provided with a protruding rib at the boundary of the bottom of the body In addition to limiting the developer circulation in the line direction, the developer concentration is made flat by removing the protruding ribs near the detection surface of the toner concentration detection sensor at the boundary of the bottom of the developing device housing to improve developer circulation. It is characterized by the fact that

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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. An original D is set on the surface of the original platen glass 1 and is pressed and covered with an original pressing plate (platen cover) 2. After that, a 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 integrated with the light source 3.
Through the moving mirrors M2 and M3 mounted on the carriage 4 which moves at the same time, and is converged by the imaging lens 5 and further through the fixed mirror M4 to form an image on the surface of the photosensitive drum 6 which is an image carrier. 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 direction of the arrow (clockwise) 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.

The photoconductive layer of the photoconductor drum 6 is positively and uniformly charged, for example, by the band electrode 7 to which a high DC voltage is applied before the light 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. A positive charge is left, and an electrostatic latent image corresponding to the image of the original is formed 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 photosensitive drum 6 carrying a visible toner image reaches the transfer portion.

On the other hand, the transfer paper P accommodated 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 photoconductor drum 6, reaches the peripheral surface of the photoconductor 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 to transfer the toner image onto the transfer paper P.

The transfer paper P on which the toner image has been transferred is then separated 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 a heating roller. After being heated and fixed, the sheet is discharged by the sheet discharge roller 26 and placed on the sheet 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 spike control 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, there is 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 upward. Wheel 113, ladder chain 114, toner scraping member 11
5 toner discharge means and toner supply screw 116
Also, a toner remaining amount detection sensor 117 is provided.

A high-voltage bias current applied to the developing roller 102 during 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 the toner is dropped from the opening of the casing 111 by the rotation of the toner replenishing screw 116. Mixed, part of the development roller 102
Then, the other part is replenished on the auxiliary stirring member 104, respectively.

FIG. 3 is a sectional view of the developing unit 100 according to the present invention taken along the line AA in FIG. 2, FIG. 4A is a side view of the partition plate, and FIG. 4B is a projection of the developing device casing bottom. 4B is a plan view of the rib, FIG. 4C is a plan view of the auxiliary stirring member, and FIG. 4D is a plan view of the toner concentration detection sensor.

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

The auxiliary stirring member 104 is provided on the rotating shaft 104A connected to the drive source, the spiral screw portion integrated with the outer periphery of the rotating shaft 104A for conveying the developer, and provided on the spiral screw portion. Paddles 104PA, 104P for discharging the developer in the rotation direction when the roller rotates.
B, 104 PC. Further, the spiral screw portion is composed of a right spiral screw portion 104B in the forward direction and a left spiral screw portion 104C in the reverse direction in which the developer conveying direction is different. The developer is transported and concentrated near the center, which is the boundary between the spiral screws, by driving and rotating the spiral screws 104B and 104C in the forward and reverse directions.

The forward spiral screw portion 104B
A main paddle part 104PA of four blades arranged in the direction orthogonal to the axis of rotation 104A is integrally formed near the center of the boundary between the spiral screw part 104C and the reverse spiral screw part 104C. Further, a plurality of two blade-shaped auxiliary paddle portions 104PB forming an axis right angle to the rotating shaft 104A are provided at a plurality of locations (four locations shown in the drawing) of the one spiral screw portion 104B, and a plurality of locations of the other spiral screw portion 104C ( (4 locations in the figure)
Similarly, a plurality of sub paddle units 104PC are integrated respectively. The main paddle part 104PA and the sub paddle part 104P
B and 104PC respectively discharge the conveyed developer in the direction orthogonal to the rotation axis (normal direction) when the rotation shaft 104A is driven and rotated.

The rotating shaft 104A of the auxiliary stirring member 104 is rotated in the same direction as the main stirring member 103 by the gear G3 via the main stirring member 103 and the intermediate gear G2. In addition, the auxiliary stirring member 1
The right spiral screw 104B of 04 is further extended to the left, and the toner collected by the cleaning device 14 passes through the recycling tube 16 and the screw end 104B.
Carried to D.

Immediately below the main paddle portion 104PA in the substantially central portion of the auxiliary stirring member 104, that is, the casing (housing) 101.
A toner concentration detection sensor 106 is installed on the bottom of the substantially central portion.

Above the auxiliary agitating member 104, the toner replenishing screw 116 is driven and rotated at a proper time to drop an appropriate amount of new toner in the toner cartridge 120, and the auxiliary agitating 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 unit 100 is divided into the left and right chambers shown in FIG. 2 by the partition plate 107. Has been converted. That is, the left developing chamber 100A including the main stirring member 103 and the right toner replenishing chamber 100B including the auxiliary stirring member 104 are divided.

As shown in FIG. 4 (A), the partition plate 107 has a large gate-shaped developer outlet opening 10 at the lower center thereof.
7A is formed. The developer discharged from the main paddle portion 104PA and the plurality of sub paddle portions 104PB of the auxiliary stirring member 104 passes through the opening 107A of the partition plate 107 and is conveyed to the main stirring member 103 and stirred.

Above the opening 107A of the partition plate 107,
A plurality of rectangular penetrating developer inflow openings 107B, 107C
Has been drilled. All of the plurality of openings 107B are the right spiral screw portion 1 of the auxiliary stirring member 104.
It is provided on the upstream side of each of the plurality of sub paddle portions 104PB provided in 04B in the developer transport direction a. Similarly, the plurality of openings 107C of the partition plate 107 are respectively provided on the upstream side in the developer conveying direction b of the plurality of sub paddle portions 104PC provided on the left spiral screw portion 104C. Therefore, the developer refluxed from the main stirring member 103 passes through the plurality of openings 107B and 107C of the partition plate 107 and the auxiliary stirring member 104.
Of the left and right spiral screw portions 104B and 104C into the sub paddle portions 107PB and 107PC downstream of the openings.

FIG. 5 is a main part perspective view showing a part of the auxiliary stirring member 104 and the bottom of the developing device casing 101 of the developing device according to the present invention. FIG. 6 is an enlarged cross-sectional view of the developing device taken along the line B-B including the arrangement position of the toner concentration detection sensor 106, and FIG.
It is a C-enlarged sectional view.

In these figures, the inner wall of the boundary between the main agitating member 103 and the auxiliary agitating member 104, which is located below the middle of the developing device casing, has a long straight line parallel to the rotation axes of the agitating members 103 and 104. The protruding rib 101A that forms The length of the protruding rib 101A in the longitudinal direction is substantially equal to the developer outflow opening 107A of the partition plate 107, and near the center thereof, near the detection surface of the toner concentration detection sensor 106,
The protruding rib 101A is divided and removed, and a flat surface having a height substantially equal to the detection surface of the toner concentration detection sensor 106 in a range slightly longer than the length of the main paddle portion 104PA of the auxiliary stirring member 104 in the rotation axis direction. The surface 101B is formed.

The projecting rib 101A has an auxiliary stirring member 104.
This has the effect of limiting the circulation of the developer in the direction of the normal line of the rotation axis due to the drive rotation of. Further, the flat portion 101B has the effect of smoothing the developer circulating property in the vicinity of the detection surface of the toner concentration detection sensor 106 and facilitating the ejection, thereby improving the response of the toner concentration detection.

The amount of developer in the toner replenishing chamber 100B is the same as the protruding rib 101A provided at the boundary between the two chambers 100A and 100B.
By this, the developer circulation is regulated, and the height is kept constant by keeping it constant. Further, the toner concentration detection sensor 106 provided on the flat portion 101B having no protruding rib 101A detects the toner concentration quickly and accurately by the smooth ejection of the developer, and the toner in the developer is replenished by supplying an appropriate amount of toner. It is possible to stably control the density within a predetermined range, and it is possible to obtain stable image quality with almost no difference in image quality between the initial copy and the final copy during continuous multiple copy.

Next, the operation of the developing device of the present invention will be described with reference to FIGS.

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

In the developing device having the above structure,
Due to 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 supply screw 1 of the toner supply unit 110
The new toner supplied from 16 to the right chamber of the developing unit 100 drops from both ends thereof in the directions a and b as indicated by the left and right screw portions 104B and 104C of the auxiliary stirring member 104 having mutually opposite propulsive forces. The recirculating developer containing toner that has been conveyed to the central portion is radially scattered by the main paddle portion 104PA, and is then collected in the central portion. The developing chamber 100A on the left side of the developing unit 100 passes through the flattened portion 101B at the bottom of the body and the developer outlet opening 107A below the central portion of the partition plate 107.
Is sent to (direction a).

From the main paddle portion 104PA near the center of the auxiliary agitating member 104 to the developer outflow opening 107A of the partition plate 107.
The toner concentration detection sensor 106 disposed below the main paddle portion 104PA detects the toner concentration of the developer when the developer passes through the.

The developer which has passed through the opening 107A is mixed and stirred with the developer refluxed from the developing area by the stirring blade 103A of the rotating main stirring member 103 to be uniformized 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 developing area.

During the stirring by the main stirring member 103, the developer sent in the direction d shown in the drawing passes through the plurality of developer inflow openings 107B, 107C of the partition plate 107 and again the auxiliary stirring member 10
Reflux to 4.

The reflux developer and the replenishment toner that have passed through the openings 107B and 107C of the upstream partition plate 107 are stored in the auxiliary stirring member.
The left and right spiral screw portions 104B and 104C of 104 convey the toner from the directions indicated by the arrows b and c toward the central portion, while a part of the developer is partially rotated by the auxiliary paddle portions 104PB and 104PC on the downstream side. Is emitted to the main stirring member 103 through the opening 107A of the partition plate 107, and the remaining developer and replenishment toner are discharged to both spiral screw portions 104.
The developer is conveyed to the central portion by B and 104C, where it is emitted by the main paddle portion 104PA and the developer circulation is repeated toward the arrow a.

By these 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 agitated 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 into the screw end portion 104D of the rotating auxiliary stirring member 104 via the recycle tube 16, is conveyed in the direction of arrow b, and is conveyed in the direction of arrow c. It merges with the developer, and the main paddle part 104PA and the sub paddle part 104P are provided between them.
B, 104PC is discharged, passes through the opening 107A, forms the circulation path described above, is uniformly stirred, and is supplied to the developing roller 107.

The spiral screw portions 104B and 104C of the auxiliary stirring member 104 and the opening 107 of the partition plate 107
The A, 107B, and 107C are not limited to those in the above embodiment, and the number of arrangements, shapes, dimensions, positions, etc. of these can be appropriately selected.

[0052]

In the developing device of the present invention, the developing chamber and the toner replenishing chamber in the housing of the developing device are partitioned by the partition plate, and the projecting rib is provided on the bottom of the housing.
By regulating the reflux discharge amount of the developer, sufficient mixing, stirring, and carrying can be performed, and the uniformization of the developer can be stably obtained. In addition, by removing the protruding ribs in the vicinity of the position where the toner concentration detection sensor is arranged to make them flat, the circulation efficiency of the developer on the sensor surface is improved and the accuracy and responsiveness of the toner concentration accuracy are improved. Is significantly improved.

[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 sectional view taken along the line AA of the developing device according to the present invention.

FIG. 4 is a side view of a partition plate of the developing device and a protruding rib,
3A and 3B are plan views of an auxiliary stirring member and a toner concentration detection sensor.

FIG. 5 is a perspective view of a main part of the developing device according to the present invention.

FIG. 6 is an enlarged BB sectional view of the developing device.

FIG. 7 is an enlarged sectional view taken along line CC of the developing device.

[Explanation of symbols]

 6 Photoconductor drum 10 Developing device 100 Developing part 100A Developing chamber 100B Toner replenishing chamber 101 Casing (developing device housing) 101A Projecting rib 101B Flat surface 102 Developing roller 103 Main stirring member (first stirring member) 104 Auxiliary stirring member (Second stirring member) 104B Right spiral screw part 104C Left spiral screw part 104D Screw end part 104PA Main paddle part (fin part) 104PB, 104PC Sub paddle 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 a, b, c, d Developer conveying direction

Claims (1)

[Claims] 1. A developer carrying member which is arranged to face an image carrying member which forms an electrostatic latent image and forms a developer layer, and a first stirring member which stirs the developer and supplies the developer to the developer carrying member. A second stirring member that mixes and stirs the developer and replenishment toner that have flowed back from the first stirring member, and circulates again to the first stirring member; the developer carrying member and the first stirring member. A developing device housing for supporting the rotating shafts of the second stirring member in parallel with each other, and a toner concentration in the developer installed at the bottom of the developing device housing below the fin portion of the second stirring member. A developing device including a toner concentration detecting sensor for detecting, wherein a projecting rib is provided at a boundary portion of a developing device housing bottom portion below an intermediate portion between the first stirring member and the second stirring member. The developer circulation in the direction normal to the rotation axis by the stirring member is restricted, and A developing device, characterized in that the vicinity of the detection surface of the toner concentration detection sensor is made flat by removing the protruding ribs at the boundary of the bottom of the mounting case to improve the circulation of the developer.