JPH11184225A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the developing device which efficiently electrifies added toner and prevents toner from being scattered and leaked form the developing device. SOLUTION: In order to prevent the occurrence of stagnation in the upper surface of a flow of two-component developer which moves in a circle in developer storage part by the action of developer stir means, the internal face of the developer storage part has a filling member 183 which is situated higher than the rotating centers of the developer stir means and extends downstream in the directions of the rotations lions of the developer stir means, and has a shape following the rotating peripheral faces of the developer stir means near and opposite them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device provided in an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile.

[0002]

2. Description of the Related Art As a developing method of an electrophotographic apparatus, there are known a normal developing method used for a normal electrophotographic copying machine and the like, and a reversal developing method used for a digital printer and a digital electrophotographic copying machine. The reversal development method generally uses a laser, LED, or the like as a light source, and charges a latent image formed on an image carrier (photoconductor drum) by charging and exposure with toner charged to the same polarity as the charging polarity of the photoconductor drum. This is a method of developing a toner image. For example, when the charge polarity of the photoconductor drum is negative, the polarity of the toner is also negative, and development is performed using a potential difference generated by exposure to form a toner image on the photoconductor drum. After the development processing, the transfer material is charged to a polarity opposite to that of the toner by a transfer device using corona discharge or the like, and the toner image on the photosensitive drum is transferred by the transfer material. Then, AC corona discharge or DC
After the potential of the transfer material is lowered by corona discharge to reduce the adhesive force between the transfer material and the photosensitive drum, the transfer material is separated from the surface of the photosensitive drum, and the process proceeds to the next process.

In a conventional developing device, a rotating developer carrier (developing sleeve) is arranged near a rotating photosensitive drum. The developing sleeve is formed in a hollow cylindrical shape, and is housed in a housing having an opening on a side facing the photosensitive drum. For example, a DC voltage of -650 V, 2700 V,
A developing bias voltage on which an AC voltage of 8000 Hz is superimposed is applied. The developing sleeve has a fixed magnet inside, and carries a two-component developer in which toner particles and magnetic particles (magnetic carrier) are mixed on the outer peripheral surface of the developing sleeve.

FIG. 6 shows a conventional developing device. A developing device (developing device) 914 includes a developer accommodating portion 940 for accommodating a two-component developer composed of the toner and a magnetic carrier, and a fixed magnetic pole therein. Developer conveying body (developing sleeve) 94 having magnetic field generating means (magnet roll) 942 provided
1, the conveyance supply roller 945, the magnet roll 94
It comprises a layer thickness regulating means (layer thickness regulating member) 943 having magnetism for regulating the thickness of the developer layer on the developing sleeve 941 to a predetermined amount, facing the second magnetic pole, and a pair of stirring screws 946 and 947.

[0005] The toner supplied into the developer accommodating section 940 from a toner supply port (not shown) opened on the top plate 940A above the developer accommodating section 940 above the stirring screw 947 is rotated by a rotating stirring screw 946,947. The developer is stirred and mixed with the developer stored in the developer storage unit 940 to become a developer having a uniform toner concentration. The developer is conveyed to the layer thickness regulating member 943 by the rotating conveyance supply roller 945, and the layer thickness is adjusted. The toner is supplied to the outer peripheral surface of the developing sleeve 941 with a predetermined layer thickness by the regulating member 943. The developer that has developed the latent image on the photosensitive drum is scraped off by a scraping plate 948, stirred again by a feeding roller 945, and then transferred to the developing sleeve 941 again.

[0006] In the developer container 940, the stirring screw 9
The developer is accommodated to the extent that it sinks, and between the rotating agitating screw 946 and the developer accommodating portion 940, the inner wall of the accommodating portion is configured to face the agitating screw 946 with an appropriate gap on the bottom side. It had been. On the other hand, the space above the stirring screw 946 is not particularly limited, and a free space is provided above the top plate 940A having a flat shape. The gap between the casing and the stirring screw 946 is appropriately determined in consideration of only the circulation efficiency of the developer. Above the developer to be stirred and mixed, a space capable of absorbing fluctuations in the developer volume due to consumption and replenishment of the toner. Only the degree of consideration was given.

[0007]

There is also a great demand for downsizing of a developing device using a two-component developer, and the amount of developer contained is quantified so that newly supplied toner can be sufficiently stirred within a short time. To be charged and supplied to the developing sleeve. However, in reality, the replenishment toner is not sufficiently mixed and agitated and mixed into the well-mixed and agitated developer and supplied to the developing sleeve, which causes image problems such as fogging and color mixing, or problems of in-machine contamination such as toner scattering and toner spilling. It was a big challenge.

An object of the present invention is to provide a compact toner in which all of the supplied toner is efficiently charged and supplied to the developing sleeve, without toner scattering and toner spillage, and the image characteristics are constantly stably developed. An object of the present invention is to provide a developing device.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a developer accommodating section for accommodating a two-component developer containing a toner and a magnetic carrier; A developer stirring unit that rotates and mixes and stirs the two-component developer in the developer accommodating section; a developer carrier that carries the two-component developer supplied from the developer accommodating section and transports the developer to a development area; And a layer thickness regulating unit disposed on the surface of the developer carrier and regulating the layer thickness of the developer carried on the developer carrier. The inside of the developer accommodating portion has a protruding shape in which the inside of the developer accommodating portion partially approaches from above the developer stirring means to prevent stagnation on the upper surface of the flow of the two-component developer circulating in the portion. Developing device (claim 1) And a developer accommodating section for accommodating a two-component developer containing a toner and a magnetic carrier; and a two-component developer arranged in the developer accommodating section and having a stirring blade and rotating about a predetermined axis. A developer agitating means for mixing and agitating the developer, a developer carrier for carrying the two-component developer supplied from the developer accommodating portion and transporting the developer to a development area; and a developer provided on the surface of the developer carrier for development. A layer thickness regulating means for regulating the layer thickness of the developer carried on the developer carrier, wherein the two-component developer circulates and moves in the developer accommodating section by the action of the developer stirring means. In order to prevent stagnation from occurring on the upper surface of the flow of the developer, the inner surface of the developer accommodating portion is located above the rotation center of the developer agitating means and downstream of the developer agitating means in the rotational direction. It has a shape facing and close to the rotating outer peripheral surface of the means And a developer accommodating section for accommodating a two-component developer containing a toner and a magnetic carrier, and a spiral stirring blade disposed in the developer accommodating section. A plurality of spiral stirring means rotating about a predetermined axis to mix and stir the two-component developer in the developer accommodating portion, and a developer carrying the two-component developer supplied from the developer accommodating portion and transporting the developer to a developing area A developing device, comprising: a carrier; and a layer thickness regulating unit disposed on the developer carrier and regulating a layer thickness of the developer carried on the developer carrier. 2 circulates and moves in the developer storage section
The development wherein the pitch of the spiral stirring blade on the upstream side of the movement of the developer in the longitudinal direction of the spiral stirring means is relatively increased to prevent stagnation on the upper surface of the flow of the component developer. Apparatus (Claim 4)
A developer accommodating section for accommodating a two-component developer containing a toner and a magnetic carrier; and a spiral stirring blade disposed in the developer accommodating section. A plurality of spiral stirring means for mixing and stirring the developer, a developer carrying member for carrying a two-component developer supplied from the developer accommodating portion and transporting the developer to a developing area; A layer thickness regulating means for regulating a layer thickness of the developer carried on the developer carrying member, wherein the two-component developer circulates and moves in the developer accommodating section by the action of the spiral stirring means. The inside of the developer accommodating section is provided at a longitudinal end side of the plurality of spiral stirring means and at a downstream side of the flow of the two-component developer, to prevent stagnation on the upper surface of the flow of the developer. Near from above Is achieved by the developing device (the invention of claim 5), characterized in that it comprises protruding and the shape.

[0010]

Embodiments of the present invention will be described below. The description of the present application does not limit the technical scope of the claims and the meaning of terms. Also, the following assertive description in the embodiment of the present invention indicates the best mode, and does not limit the meaning of the terms of the present invention or the technical scope.

Prior to the description of an embodiment of the developing device of the present invention, an image forming process and each mechanism of a color printer which is an example of an image forming device equipped with a plurality of developing devices of the present invention will be described with reference to FIG. explain. FIG. 1 is a cross-sectional configuration diagram of a color printer as an example of an image forming apparatus equipped with a plurality of sets of the developing device of the present invention.

In this color printer, after superposing the color toner images sequentially formed on the image carrier, the superimposed color toner image formed on the image carrier is once transferred onto a transfer material by a transfer unit. Transfer to form a color image, and then
This is a color image forming apparatus of a type in which a recording sheet is separated from a surface of an image carrier by a separation unit and fixed by a fixing unit.

According to FIG. 1, reference numeral 10 denotes a photosensitive drum serving as an image carrier, which is formed by applying an OPC photosensitive member (organic photosensitive member) on a drum substrate, and is grounded and driven to rotate clockwise in the drawing. Is done. 11 is a scorotron charger is a charging means, provided by a corona discharge by a grid and the corona discharge wire which is the potential held at grid potential V _G uniform charging of the high voltage V _H to the photosensitive drum 10 peripheral surface. Prior to charging by the scorotron charger 11, a pre-charging static eliminator (PC) using a light emitting diode or the like to eliminate the history of the photosensitive drum 10 up to the previous print.
L) Exposure by 12 is performed to eliminate static electricity on the peripheral surface of the photosensitive drum 10. The history of the photoconductor drum 10 refers to an image pattern remaining on the photoconductor formed by charging and image exposure at the time of preceding image formation, and is also referred to as a photoconductor memory.

After the photosensitive drum 10 is uniformly charged, image exposure based on an image signal is performed by an exposure optical system 13 as image exposure means. The exposure optical system 13 uses a laser diode (not shown) as a light emitting light source, rotates a polygon mirror, an fθ lens, and a cylindrical lens to bend an optical path by a reflection mirror to perform main scanning. Rotation (sub-scanning) of the photosensitive drum 10 Forms a latent image. In the present embodiment performs exposure on a character portion, towards the exposed portion potential V _L to form an inverted latent image as a lower potential than the charge potential V _H.

Around the periphery of the photosensitive drum 10, Y, Y, M2, M, C, and C toners, each containing a two-component developer composed of a toner and a magnetic carrier, are incorporated. A developing device 14, which is an M, C, and K developing device, is provided. The developing device 14 for each color has a built-in magnet roll 142 serving as a magnetic field generating means, and a developing sleeve 14 serving as a developer transport body that holds and rotates the developer.
1 is provided.

First, yellow development by the Y developing device 14 for the first color is performed by the developing sleeve 141 which rotates while holding the Y developer. The developer is a magnetic carrier having an average particle diameter of 20 to 50 μm around which magnetite is coated with an insulating resin around a core, and a pigment and a charge control agent according to the color with a polyester as a main material, silica,
The toner is made up of a toner having an average particle diameter of 4 to 10 μm to which titanium oxide or the like is added. The developer is placed on the developing sleeve 141 by a layer thickness regulating member 143 which is a layer thickness regulating means described later and a developer receiving member 144. The developer is conveyed to the development area while being regulated to a developer layer thickness of 100 to 400 μm.

The gap between the developing sleeve 141 and the photosensitive drum 10 in the developing area is larger than the developer layer thickness.
5 to 1.0 mm, during which the AC bias V _AC and D
C bias _VDC is applied in a superimposed manner. DC bias V
_DC and the photosensitive member charge potential V _H, for charging the toner are the same polarity, AC bias toner given the opportunity to leave from the magnetic carrier by V _AC, during positive charging DC
Not adhere to a portion of the bias V _DC from a high potential photoconductor charge potential V _H, attached to a lower exposed portion potential V _L portion of potential than the DC bias V _DC, the photosensitive drum 10 above by non-contact reversal development Is developed (developed), and a Y toner image is formed on the photosensitive drum 10.

After the visualization of the first color is completed, the magenta image forming process of the second color is started, and the scorotron charger 1 is again turned on.
1 is performed, and a latent image based on image data of the second color is formed by the exposure optical system 13. At this time 1
The charge elimination by the PCL 12 performed in the color image forming process is not performed because the Y toner image attached to the image portion of the first color scatters due to a sharp drop in the surrounding potential.

[0019] Again among the photoreceptor drum 10 peripheral surface of the entire surface is charged to the photosensitive drum charge potential V _H across the photosensitive member, get the same latent image and a color for the portion having no first color image Then, an M toner image is formed by development in the M developing unit 14, but in a portion where the first color image is developed again, the light shielding by the toner attached to the first color and the toner itself are performed. the influence of the charge with a latent image of a slightly higher potential V _M than the first color of the exposed portion potential V _L is formed, D
Development according to the potential difference between C bias V _DC and the potential V _M is performed.

For the third color cyan and the fourth color black, the same image forming process as that for the second color magenta is performed, and the Y, M, C and K toner images are formed on the peripheral surface of the photosensitive drum 10. A color superimposed color toner image is formed.

A toner supply device for controlling and replenishing each of the Y, M, C, and K developing units 14 with a new color toner includes a detachable Y, M, C, and K toner cartridge 15,
A toner storage unit 16 for Y, M, C, and K, and a toner conveying unit 161 for Y, M, C, and K. When a decrease in toner density is detected for each color, toner storage from the toner cartridge 15 is performed. Means 16, toner conveying means 16
After 1, unused toner is supplied and supplied into the developing device 14 for each color from a toner supply port (not shown) formed in the top plate 140 </ b> A.

On the other hand, the half-moon roller 2
One transfer material (transfer paper or the like) P carried out through 1 is
The sheet is temporarily stopped near the registration sensor position via the intermediate sheet feeding roller pairs 22A and 22B, and is fed to the transfer area by the rotation operation of the registration roller pair 23 of the sheet feeding unit when the transfer timing is adjusted.

In the transfer area, a transfer roller 17 as transfer means for applying a voltage for transferring a color toner image on the peripheral surface of the photosensitive drum 10 to the transfer material P in synchronization with the transfer timing is pressed against the transfer area. The color toner image on the peripheral surface of the photosensitive drum 10 is collectively transferred onto the transfer material P while sandwiching the fed transfer material P.

Next, the transfer material P is neutralized by the sawtooth electrode 18 serving as a separating means, separated from the peripheral surface of the photosensitive drum 10 and conveyed to a fixing device 24 serving as a fixing means. Crimping roller (lower roller) 24
After the toner is welded by heating and pressurizing of 2, the toner is discharged onto a discharge tray 26 outside the apparatus via discharge rollers 25A, 25B, and 25C. After the transfer material P has passed through the transfer material P, the transfer roller 17 is retracted and separated from the peripheral surface of the photosensitive drum 10 to prepare for the formation of the next toner image.

On the other hand, the photosensitive drum 1 from which the transfer material P has been separated
In the case of No. 0, the residual toner is removed and cleaned by the pressure contact of the blade 191 of the cleaning device 19, and the charge is removed by the PCL 12 and charged by the scorotron charger 11 again to start the next image forming process. The blade 191
Moves immediately after the cleaning of the surface of the photosensitive drum, and retracts from the peripheral surface of the photosensitive drum 10. The waste toner scraped into the cleaning device 19 by the blade 191 is discharged by a screw 192 and then stored in a waste toner collecting container (not shown).

Regarding one embodiment of the developing device of the present invention,
This will be described with reference to FIGS. FIG. 2 is an enlarged sectional view of a plurality of sets of the developing device of FIG. 1, and FIG. 3 is an enlarged sectional view of the developing device of the present invention. The arrows in FIG. 3 indicate the rotation direction of each roller, and the double arrows indicate the direction in which the developer is conveyed.

Referring to FIG. 2 or FIG. 3, the developing devices 14 for each of the colors Y, M, C, and K are arranged such that the developing sleeve 141 of each of the developing sleeves 141 has a photosensitive drum 1 having an outer diameter of 100 mm, for example.
Opposite to the 0 photosensitive surface, they are arranged in the vertical direction in the order of Y, M, C and K.

The developing device 14, which is a developing device for each color, contains the above-described two-component developers of yellow (Y), magenta (M), cyan (C) and black (K), respectively.
The developing sleeve 141 rotates in the opposite direction (clockwise direction in FIG. 3) to the rotational direction (clockwise direction in FIG. 3) of the photosensitive drum 10 at the developing position while maintaining a predetermined gap with respect to the peripheral surface of the photosensitive drum 10. It has.

The developing device 14, which is a developing device for each color, is configured as follows.

In the developing device 14, reference numeral 140 denotes a developing device housing which is a developer accommodating portion for accommodating a two-component developer composed of toner and carrier; 142, a magnet roll as magnetic field generating means having fixed magnetic poles; Reference numeral 143 denotes a layer thickness regulating member which is a layer thickness regulating means made of a magnetic material for regulating the thickness of the developer layer on the developing sleeve 141 to a predetermined amount. A developer receiving member made of a non-magnetic material, 148 is a developer removing plate having a magnet plate 148a on the back surface, 145 is a feeding roller, and 146 and 147 are a pair of stirring screws.

A developing sleeve 141 as a developer conveying member
Is, for example, an outer shape of 8 mm to 60 mm using a stainless steel material.
The rotation of the photosensitive drum 10 with a predetermined gap kept between the peripheral surface of the photosensitive drum 10 and the abutting rollers (not shown) provided at both ends of the developing sleeve 141. It is rotated in the opposite direction (clockwise rotation in FIG. 3) (clockwise rotation in FIG. 3). When the outer diameter is 8 mm or less, the magnetic poles N1, S1, N2, S2 required for image formation.
If the magnet roll 142 having at least five magnetic poles made of N3 cannot be formed, and the outer diameter of the developing sleeve 141 exceeds 60 mm, the developing device 1
4 increases in size. In particular, in a color printer having a plurality of sets of developing units 14 (see FIG. 1), the volume occupied by the developing device is increased, and the outer diameter of the photosensitive drum 10 is increased, or the size of the photosensitive drum 10 is increased. The forming apparatus becomes large.

The magnet roll 142 is included in the developing sleeve 141 and includes a plurality of magnetic poles N1, N2, N3, S
1, S2 are alternately arranged, and are fixed concentrically with the developing sleeve 141, and apply a magnetic force to the peripheral surface of the non-magnetic sleeve.

A layer thickness regulating member 143 serving as a layer thickness regulating means.
Is made of, for example, a rod-shaped or plate-shaped magnetic stainless steel material which faces the magnetic pole N3 of the magnet roll 142 and is disposed at a predetermined gap from the developing sleeve 141.
The layer thickness of the two-component developer on the peripheral surface of 41 is regulated.

The receiving member 144 is made of a non-magnetic member using a resin member such as an ABS resin.
41 is disposed at a predetermined gap from the developing sleeve 141 on the downstream side in the rotation direction of the roller 41 and is adjacent to the end surface of the layer thickness regulating member 143, and is integrally formed by being fixed to the layer thickness regulating member 143 with an adhesive, for example. Further, the toner is prevented from spilling from the developer layer regulated by the layer thickness regulating member 143, and the developer layer of the two-component developer is stably kept on the peripheral surface of the developing sleeve 141. The receiving member 144 is the developing device housing 14.
0 and may be provided adjacent to the end face of the layer thickness regulating member 143.

The developer removing plate 148 is provided so as to face the magnetic pole N2 of the magnet roll 142.
The developer on the developing sleeve 141 is peeled off by the action of the repulsive magnetic field 3 and the magnet plate 148a provided on the back surface of the removing plate 148.

The transport supply roller 145 transports the developer peeled off by the removing plate 148 to the stirring screw 146 and supplies the developer stirred by the stirring screw 146 to the layer thickness regulating member 143. Reference numeral 145A is a blade provided on the transport / supply roller 145 for transporting the developer.

The agitating screws 146 and 147 rotate at a constant speed in directions opposite to each other, agitate and mix the toner and the magnetic carrier in the developing device 14, and form a two-component developer containing a predetermined toner component uniformly. And

The toner supplied into the developing device housing 140 from a toner supply port (not shown) opened on the top plate 140A above the developing device housing 140 above the stirring screw 147 rotates at a constant speed in directions opposite to each other. Developing device housing 14 by stirring screws 146 and 147
The developer is stirred and mixed with the developer contained in the toner container 0 to form a developer having a uniform toner concentration. The developer is conveyed to the layer thickness regulating member 143 by the rotating conveying / supplying roller 145, and is fixed by the layer thickness regulating member 143. Of the receiving member 14
4, the developer layer of the two-component developer is stably supplied onto the outer peripheral surface of the developing sleeve 141. The developer that has developed the latent image on the photoreceptor drum 10 is stripped off by the action of the repelling magnetic fields of the magnetic poles N2 and N3 and the magnet plate 148a provided on the back of the removing plate 148, and the stirring screw 146 is again fed by the feed roller 145. Transported to Photoconductor drum 1
The electrostatic latent image on 0 is reversely developed in a non-contact state by a non-contact development method by applying a developing bias voltage in which an alternating current (AC) bias AC1 is superimposed on a direct current (DC) bias E1 as necessary.

The developing device of the present invention comprises a stirring screw 146, 147 and a stirring screw 1
Since the top plate 140A above the portions 46 and 147 has the feature, such portions will be described in detail.

The present inventors have conducted various studies on the cause of a part of the replenishment toner being sufficiently stirred and mixed with the developer and supplied to the developing sleeve in a non-charged state. As a result, it has been found that the developer stagnation generated on the upper surface of the developer flow moving while being stirred by the stirring screw is significantly related. While the general developer moves at an appropriate speed while being stirred by the stirring screw, the developer stagnant portion refers to a portion where the developer stays as it is left out of the flow.

According to the observations made by the present inventors, the developer stagnation has a tendency that the toner having a low specific gravity floats and gradually grows. On the upper surface of the developer stagnation, the toner grows in a layered or lump shape. The developer stagnation sometimes collapses due to vibration or the like, and at this time, the toner that has grown in a lump enters the developer flow. Lumped toner mixed into the developer flow is supplied to the developing sleeve before the primary particles are evenly mixed, or even if mixed, is not sufficiently subjected to frictional charging by the carrier, causing toner scattering, toner spillage, and image contamination. Causes image fogging and the like.

The present inventors have investigated the cause of the developer stagnation from such a place and obtained the following conclusions.

The developer stagnation occurs on the surface of the developer flow where the stirring and transporting action of the stirring means is weakened.

If the developer in the developer accommodating portion is crawled so that the stirring means is buried, developer stagnation tends to occur.

The developer flow that is moved by the stirring screw swells on the downstream side of the casing of the developer accommodating portion, and the developer tends to stagnate on its surface.

In a stirring unit in which two stirring screws are horizontally arranged, developer stagnation is likely to occur on the upstream side of the portion where the developer flow makes a U-turn.

The present inventors provide a wall member to fill the space above or above the portion where the developer stagnation is likely to occur, and take measures to prevent the space where the developer stagnation occurs. Alternatively, it is possible to prevent developer stagnation from occurring by taking measures such as changing the pitch between the upstream side and the downstream side of the stirring screw, and succeeded in preventing image stains and image fogging. Hereinafter, the developing device of the present invention centering on the stirring screw will be described according to (Embodiment 1).

(Embodiment 1) FIG. 4 is a plan view showing a state in which a top plate 140A of the developing device of the present invention is removed. In the stirring screws 146 and 147, the gears G146 and G147 provided at the respective shaft ends are engaged with each other, and rotate in opposite directions at a constant speed. The toner dropped from the upper toner supply port 181 shown by the two-dot chain line is
The developer is mixed with the developer and transported in the direction indicated by the arrow (rightward in the figure) by the rotation of the roller, and makes a U-turn at the time of hitting the wall surface of the developing device housing 140. (Left direction), and some of the developer leaves the circuit path and goes into the housing. The other developer makes a U-turn when it hits the opposite wall surface of the developing device housing 140, and the developer circulates.

The stirring screw 146 and the stirring screw 1
A partition plate 182 is provided between the partition 47 and the partition 47 to prevent the circulation of the developer from being disturbed. Developer stagnation is likely to occur in the portion just above the partition plate 182 (the range of Y1 indicated by oblique lines) and the upper corner where the developer makes a U-turn (the range of Y2 indicated by oblique lines).

In the developing device of the present invention, a filling portion 183 is provided at a portion corresponding to the range of Y1 and Y2 above the partition plate 182, and a filling member 184 is provided at an upper corner where the developer makes a U-turn. ing. FIG. 5A shows a cross-sectional shape in the XX cross section near the center in FIG. Both stirring screws 146 and 147 have outer diameter φ
A 14.6 mm spiral screw member,
The space between the lower developing device housing 140 and the inner wall of the lower developing device housing 140 is 0.
A gap of 7 mm is provided. The filling member 183 has a protruding cross-sectional shape close to the screw from above, and is inserted into the partition plate 182 so as to be inserted into the partition plate 182.
And is attached to the top plate 140A. Filling member 1
If 83 is set at such a position, the top plate 140A
And it can be free. The filling member 183 has a gap of 1 mm between the stirring screws 146 and 147, and has an angle range of about 60 ° from the horizontal plane (θ in FIG. 5A).
(Indicated by) are formed along the stirring screws 146 and 147. is desirably set between 40 and 80 degrees. When θ is smaller than 40 °, developer stagnation occurs at a position along the filling member 184. When θ is larger than 80 °, a sufficient free space above the stirring screw is not secured. By securing a free space, fluctuations in toner concentration and fluctuations in developer volume due to changes in developer fluidity are absorbed while preventing generation of developer stagnation. Without this space, the density of the developer in the developing device housing 140 increases, causing a problem that the life of the developer decreases or the rotational load on the stirring screw increases. .

FIG. 5B shows a cross-sectional shape of the U-turn portion in FIG. A filling member 184 having a protruding shape is provided on the top plate 140A so that the upstream housing of the developer circulation channel approaches the screw stirring rotation surface from above. The filling member 184 has a triangular planar shape and an inclined end surface, and guides the developer moved in the axial direction by the upstream stirring screw 147 to the downstream stirring screw 146. It has a shape. Upstream stirring screw 147
Is covered by a filling member 184. The distance between the inner surface of the filling member 184 and the outer periphery of the stirring screw 147 is maintained between 0.7 mm and 3 mm. With this configuration, the developer conveyed in the axial direction on the stirring screw 147 is forcibly semi-forced and guided by the filling member 184 to make a U-turn, and is pushed out to the upstream portion of the downstream stirring screw 146. State. A sufficient space is provided on the upper surface on the upstream side of the stirring screw 146,
The U-turned developer is deposited without being restricted by the flow of the developer (claims 3 and 5).

The developer deposited on the upper surface of the upstream side of the stirring screw 146 is conveyed in the axial direction by the rotation of the stirring screw 146. The developer is pushed into the downstream agitating screw, and in the case of the same pitch, the transport speed of the developer is slowed down, and the accumulated developer stays and exhibits a state of developer stagnation. Even when a large amount of developer is contained in the circulation path of the developer, U
The pitch of the spiral stirring blade of the stirring screw 146 is higher on the upstream side than on the downstream side so as to prevent the accumulation of the stagnation developer which is not affected by the stirring screw from occurring on the upper side of the upstream stirring screw in the turn section. And rough.

In FIG. 4, the pitch P _N on the downstream side is 11 mm in the present embodiment, while the pitch P _L on the upstream side is
= 14 mm. By setting between P _N / P _L = 1.1~1.6 According to the experiments of the present inventors, it is possible to eliminate developer stagnation in the U-turn portion. It is desirable to gradually change the pitch of the stirring blades of the stirring screw, but a configuration in which the stirring blades are switched stepwise may be used (the invention of claim 4).

[0054]

According to the present invention, the replenished toner is charged efficiently, and toner scattering and toner spilling from the developing device are prevented. Therefore, when the developing device of the present invention is applied to an image forming apparatus, the occurrence of image stains due to fouling inside the image forming apparatus or fog is prevented. In particular, when the present invention is applied to an image forming apparatus, it is possible to prevent the occurrence of image contamination or the like due to toner color mixing between developing devices for each color and toner color mixing on an image.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a color printer as an example of an image forming apparatus equipped with a plurality of sets of developing devices of the present invention.

FIG. 2 is an enlarged sectional view of a plurality of sets of the developing device of FIG.

FIG. 3 is an enlarged sectional view of the developing device of the present invention.

FIG. 4 is a plan view of a stirring screw part.

FIG. 5 is a sectional view of a stirring screw part.

FIG. 6 is a view showing a conventional developing device.

[Explanation of symbols]

 Reference Signs List 10 photoreceptor drum 14 developing device 140 developing housing, developer container 140A top plate 141 developing sleeve 143 layer thickness regulating member 145 transport / supply roller 146,147 stirring screw 182 partition plate 183,184 filling member

Claims (5)

[Claims] 1. A developer accommodating portion for accommodating a two-component developer containing a toner and a magnetic carrier, and a stirring blade disposed in the developer accommodating portion and rotating around a predetermined axis to rotate the two components in the developer accommodating portion. A developer agitating means for mixing and agitating the component developer, a developer carrier for carrying the two-component developer supplied from the developer accommodating portion and transporting the developer to a development area; and a developer agitator provided on the surface of the developer carrier. A layer thickness regulating means for regulating a layer thickness of the developer carried on the developer carrying member, wherein the two-component developing device circulates and moves in the developer accommodating section by the action of the developer stirring means. A developing device for preventing stagnation on an upper surface of a flow of the developer, wherein the developer accommodating portion has a protruding shape in which the inside of the developer accommodating portion partially approaches from above the developer stirring means. . 2. A developer accommodating portion for accommodating a two-component developer containing a toner and a magnetic carrier, and a stirring blade disposed in the developer accommodating portion and rotating around a predetermined axis to rotate the developer container inside the developer accommodating portion. A developer agitating means for mixing and agitating the component developer, a developer carrier for carrying the two-component developer supplied from the developer accommodating portion and transporting the developer to a development area; and a developer agitator provided on the surface of the developer carrier. A layer thickness regulating means for regulating a layer thickness of the developer carried on the developer carrying member, wherein the two-component developing device circulates and moves in the developer accommodating section by the action of the developer stirring means. To prevent stagnation on the upper surface of the flow of the developer, the inner surface of the developer accommodating portion is located above the rotation center of the developer agitating means and extends downstream in the rotational direction of the developer agitating means. It has a shape that closely opposes the rotating outer peripheral surface of the stirring means A developing device, characterized in that: 3. An inner surface of the developer accommodating portion has a concave shape capable of securing a sufficient space between an upstream side of the circulating two-component developer and an upper surface of a flow of the two-component developer. The developing device according to claim 1, wherein: 4. A developer accommodating section for accommodating a two-component developer containing a toner and a magnetic carrier, and a spiral agitating blade disposed in the developer accommodating section and rotating around a predetermined axis to rotate inside the developer accommodating section. A plurality of spiral stirring means for mixing and stirring the two-component developer;
A developer carrying member that carries the component developer and transports it to the developing area; and a layer thickness regulating unit that is disposed on the surface of the developer carrying member and regulates a layer thickness of the developer carried on the developer carrying member. A developer in the longitudinal direction of the spiral stirring means, which prevents stagnation from occurring on the upper surface of the flow of the two-component developer circulating in the developer accommodating section due to the action of the spiral stirring means. A developing device characterized in that the pitch of the spiral stirring blade on the upstream side of the movement is relatively large. 5. A developer accommodating section for accommodating a two-component developer containing a toner and a magnetic carrier, and a spiral agitating blade disposed in the developer accommodating section. A plurality of spiral stirring means for mixing and stirring the two-component developer, a developer carrier for carrying the two-component developer supplied from the developer accommodating portion and transporting the developer to a development area, And a layer thickness regulating means for regulating the layer thickness of the developer carried on the developer carrying member, wherein the layer is circulated and moved in the developer accommodating section by the action of the spiral stirring means. To prevent stagnation from occurring on the upper surface of the flow of the component developer, the inside of the developer accommodating portion on the longitudinal end side of the plurality of spiral stirring means and on the downstream side of the flow of the two-component developer, Spiral stirring means upward A developing device having a protruding shape approaching from the front.