JP3522661B2 - Developing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for supplying a developer to a photosensitive drum and developing it in an image forming apparatus such as a copying machine or a printer. More specifically, a two-component developer comprising a toner and a carrier is used. The present invention relates to a developing device of the form.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus typified by a copying machine or a laser printer, a two-component developer composed of toner and carrier is used to develop an electrostatic latent image formed on a photosensitive drum. The developing device of the form is applied. This electrostatic latent image developing device is represented by a developing housing containing a developer, a developing sleeve forming a magnetic brush for supplying the developer in the developing housing to the electrostatic latent image on the photosensitive drum, and the like. From a developer supplying means, a developer stirring and conveying means typified by a spiral or a screw member that stirs the developer in the developing housing and conveys it in a predetermined direction, and a toner storage tank typified by a toner hopper in the developing housing. And a toner supply unit that supplies toner. The developer supplying means supplies toner to the electrostatic latent image in the developing area of the photosensitive drum,
The photosensitive drum is developed into a toner image. When the toner in the developing housing is consumed in accordance with the supply of the toner to the electrostatic latent image, the toner is supplied by the toner supply unit. The developer agitating / conveying means agitates the developer in the developing housing to agitate the toner and the carrier, mixes and triboelectrically charges the toner and the carrier, and conveys the toner and the carrier in a predetermined direction. As the prior art disclosing the above-mentioned requirements regarding the stirring and conveying of the two-component developer, Japanese Patent Application Laid-Open No. 10-142942 discloses a developer supply means for supplying a developer to a photosensitive drum and a developer supply means for this developer supply means. A first agitating / conveying means provided in the vicinity for agitating and conveying the developer in a first direction, and a developer provided below the first agitating / conveying means in the second direction opposite to the first direction. A second stirring / conveying unit that stirs the developer and a developer that is provided coaxially with the developer supplying unit, is driven by the driving of the developer supplying unit, and is conveyed by the second stirring and conveying unit. Is provided to the first agitating and conveying means. Further, this developing device can have a very compact structure by adopting a so-called "longitudinal circulation system" in which agitating and conveying means are vertically arranged separately as a method of agitating the two-component developer. Therefore, it is disclosed that it is particularly effective in a color copier of a four-tandem tandem development system.

Generally, in the developing device adopting the "longitudinal circulation system" represented by the above publication, the developer existing in the vertically stirring and agitating / conveying path is dropped from the top to the bottom in the gravity direction, and it is necessary to provide a feeding means (pumping unit) against gravity onto bring seen汲the developer from. For this reason, the developer has a region that horizontally moves in the divided stirring and conveying path, a region that moves while falling in the direction of gravity, and a region that moves against gravity, resulting in uneven developer. It is extremely difficult to smoothly carry and stir without stirring.

In order to solve such a technical problem, in the above publication, attention is paid to the feed means to pump the developer, by adopting a specific feeding means, puddle developer in the汲viewed raised region (developer conveying It is prevented that the part which is not stagnate) is generated. Specifically, the agitating and conveying path divided into upper and lower parts is formed sufficiently longer than the developing sleeve having a built-in magnet roller for developing the electrostatic latent image formed on the surface of the photoconductor, and is coaxial with the developing roll. It employs a structure in which a sleeve rotating shaft incorporating a magnet roller as a "feeding means" is provided.

[0005]

In the above publication, by adopting a specific "feeding means", smooth circulation can be ensured without applying stress to the developer. However, the length 3 is adopted here.
Since the "feeding means" containing the 70 mm magnet roll is coaxially arranged with respect to the developing sleeve containing the 08 mm magnet roller, the amount of protrusion in the longitudinal direction is extremely large with respect to the developing area. . Although there have been sufficient consideration to汲look up the developer from the bottom to the top, no consideration to the developer falling from the top to bottom. Therefore, there is still room for improvement in securing a smoother developer circulation and designing the developing device compactly. In particular, in color image formation, even if a slight toner density unevenness occurs in the developing area, the image is affected, and there is a problem that a desired color tone cannot be obtained.
Further improvement is desired.

According to the present invention, in a vertical stirring type developing device having a first stirring / transporting means and a second stirring / transporting means on the upper and lower sides, the developer is sufficiently stirred and the toner concentration of the developer in the developing area is increased. It is an object of the present invention to effectively prevent unevenness and reduce the size of the entire apparatus, particularly to shorten the length in the axial direction.

[0007]

In order to solve the above-mentioned problems, the invention of claim 1 provides a developer supplying means for supplying a developer to a latent image carrier in a developing region to visualize the latent image carrier. First agitating and conveying means provided near the developer supplying means for agitating and conveying the developer in a predetermined direction, and developing provided below the first agitating and conveying means and adjacent to the developer supplying means. Second agitating and conveying means for agitating the agent and conveying it in a direction opposite to the first agitating and conveying means; and developer scooping means for supplying the developer in the second agitating and conveying means to the first agitating and conveying means. , Developer dropping means for supplying the developer in the first stirring and conveying means to the second stirring and conveying means, and the developer scooping means and the developer dropping means are effective developing means of the developer supplying means. in the developing device provided respectively outside the region, the The new toner in 1 agitating transporting mechanism
Is replenished and the amount of conveyance of the first and second developers is kept constant , adjacent to the developer supply means.
Scraped toner is consumed in the above-mentioned developing area.
Scraping A new tray supplied from the first agitating and conveying device described above.
Replenished developer with appropriate toner density
For quick replacement, the developer transport speed by the second stirring and transporting means is made higher than the developer transporting speed by the first stirring and transporting means, and the developer dropping means and the first stirring and transporting means are provided between the developer dropping means and the first stirring and transporting means. Is characterized by having a blocking means for blocking the developer.

In the vertical circulation developing system as in the present invention, unless the amount of developer conveyed by the vertically divided agitating and conveying mechanism is made substantially constant, the developer is accumulated somewhere and is conveyed. So-called pulsation will occur. Therefore, the carry amounts of the first and second agitating and carrying mechanisms are controlled to be substantially constant within a range in which excessive bias does not occur. By the way, the first agitating / conveying mechanism replenishes the developer whose toner concentration is insufficient due to the development drawn up by the scooping means with new toner, and then mixes the toner so as to obtain a uniform toner concentration, It is desirable to sufficiently mix and stir with the carrier in order to impart sufficient charge.

On the other hand, the second agitating / conveying mechanism provided adjacent to the developer supplying mechanism is a developer whose toner is consumed in the developing area (a developer whose toner concentration is lower than the reference concentration). It is necessary to scrape off the toner, mix it with the surrounding developer, and stir to prevent an extreme lack of toner density. That is, needless to say, the second agitating / conveying device is not only mixed and agitated with the developer, but also promptly replaced with the developer having an appropriate toner concentration supplied from the first agitating / conveying device through the dropping means. Is desired. In this case, it is desirable that the first agitating / conveying means slowly moves the developer over time, and conversely, the second agitating / conveying means quickly moves within a range that does not apply excessive stress to the developer.

Therefore, according to the above-mentioned constitution of claim 1, in the so-called vertical circulation type developing device, both the developer scooping means and the dropping means are provided outside the effective developing area of the developer supplying means and the developer is provided. Since the blocking means for blocking the developer is provided between the dropping means and the first stirring and conveying means, the second stirring and conveying means is provided over the entire effective developing area of the developer supplying means. It is possible to secure the stirring and transporting only in the horizontal direction by means of the above. Further, since the blocking means is provided between the dropping means and the first stirring and transporting means, the developer is sufficiently secured in this portion. It becomes possible to stably supply the developer from the agitating and conveying means to the second agitating and conveying means, and further, the developer conveying speed (moving speed) of the second agitating and conveying means is set to the developer of the first agitating and conveying means. Set it higher than the transport speed (moving speed) and The mixing speed with more advancing, it is possible to perform quickly the exchange of the developer having a developer and the reference toner concentration which is the toner consumed.

Further, as the developer scooping means, a rotating body having a plurality of magnetic poles in the circumferential direction is used which is provided at approximately the center in the height direction between the first stirring and conveying means and the second stirring and conveying means. It is a developing device (claim 2). According to this structure, it can be pumped up by the second stirring and conveying means and supplied to the upper first stirring and conveying means with a compact structure.

Further, the developer dropping means is provided on a partition wall which divides an upper chamber in which the first agitating and conveying means is housed and a lower chamber in which the second agitating and conveying means is housed. The opening is provided (claim 3). According to this configuration, the developer is supplied from the first stirring / transporting means to the second stirring / transporting means by its own weight. As a result, the developing device itself can be designed compact.

Further, the first stirring and conveying means and the second stirring and conveying means.
The agitating and conveying means of the first agitating and conveying means is provided with a blade member formed in a spiral shape with the same pitch, and the blade member of the first agitating and conveying means is formed to have an outer diameter larger than that of the blade member of the second agitating and conveying means. The transport speed of the second stirring transport means is 1.1 to 1.5 with respect to the transport speed of the first stirring transport means.
It is set high in the double speed range (claim 4). According to this configuration, it is possible to stir and carry the developer without applying excessive stress to the developer.

Furthermore, the blocking means is provided with a cutout portion in the rotary shaft portion of the first stirring and conveying means (claim 5). By providing such a notch portion, the notch portion as a center can enter the developer dropping means so as to get over the blocking means, and as a result, the developer can be efficiently supplied to the second stirring and conveying means. .

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The developing device of the present invention will be described in detail below with reference to the drawings. [Outline of Image Forming Apparatus] FIG. 1 is a schematic configuration diagram of a color printer as an image forming apparatus according to an embodiment of the present invention.

A schematic structure of a color printer to which the present invention is applied will be described with reference to FIG. The color printer 2 includes a sheet feeding unit 4 that feeds sheet members 3 as transfer bodies one by one.
A conveying unit 6 that conveys the sheet member 3 sent out from the sheet feeding unit 4, an image forming unit 5 that forms a toner image to be transferred to the sheet member 3, and a toner image formed by the image forming unit 5. A transfer unit 7 for transferring to the sheet member 3, a fixing unit 8 for fixing the toner image of the sheet member 3 transferred by the transfer unit 7, and a paper discharge unit 10 for receiving the sheet member 3 discharged from the fixing unit 8. , And an image forming unit 11.

The paper feeding unit 4 includes a first paper feeding unit 15 that feeds the sheet members 3 stacked on the first paper feeding tray 12 one by one to a downstream side by a paper feeding roller 13 and a retard roller 14,
The manual feed tray 16 includes a second paper feed unit 18 that feeds the sheet members 3 one by one to the downstream side by a paper feed roller 17.

The carrying section 6 is a carrying path 20 for guiding the carrying of the sheet member 3 sent from the first paper feeding section 15 or the second paper feeding section 18, and a carrying roller arranged in the middle of the carrying path 20. 21, a pair of registration rollers 22 that receives the sheet member 3 from the conveyance roller 21, stops the leading end of the sheet member 3 once, regulates (corrects) oblique feeding, and sends the sheet to the image forming unit 5 on the downstream side. It is composed of a manual feed passage 23 connected to the feed passage 20 on the upstream side of the roller pair 22.

The image forming section 5 includes a first image forming section 24 having black toner, a second image forming section 25 having cyan toner, a third image forming section 26 having magenta toner, and a fourth image forming section having yellow toner. And part 27. The first to fourth image forming units 24, 25, 26, 27 include a cylindrical photosensitive drum 28, a developing device 30 for forming a toner image on the photosensitive drum 28, and a residual toner on the photosensitive drum 28. Fur brush 31 and cleaning blade 32 for removing toner
A cleaning device 33 including a photoconductor drum 28
The charging device 34 is configured to apply an electric charge to the surface of the photoconductor drum 28 to uniformly charge the surface of the photoconductor drum 28.

The transfer section 7 is arranged at a position opposed to the endless transfer belt 37 made of a fluorocarbon resin material, the driving roller 38 and the tension roller 40 for driving the transfer belt 37, and the respective photosensitive drums 28. Transfer roller 4
1a, 41b, 41c, 41d, and further has a function of carrying to the downstream side. The transfer rollers 41a, 41b, 41c, 41d and the photosensitive drums 28
It is configured to sandwich. In addition, the transfer belt 37
Guide rollers 42 and 43 are provided at appropriate positions on the inner peripheral side. Further, when forming only a black-and-white image, the transfer unit 7 uses only the black transfer roller 41a, and the other magenta, cyan, and yellow transfer rollers 41b, 41c,
41d is separated from the photosensitive drum 28. The fixing unit 8 includes a heating roller 44 having a built-in heater, a fixing roller 45, a metal endless belt 46 wound around the heating roller 44 and the fixing roller 45, and pressure applied to the fixing roller 45. And a roller 47.
The oil applying roller 48 for applying silicone oil to the outer surface of the endless belt 46 and the oil applying roller 4
An oil supply roller 50 for supplying oil to the printer 8 and a cleaning roller 51 for cleaning the surface of the oil supply roller 50 are arranged.

The paper discharge unit 10 receives the sheet member 3 discharged from the fixing unit 8 and stacks the first paper discharge unit 52 on which the image forming surface faces up and the sheet member 3 discharged from the fixing unit 8. The image forming apparatus main body 36 is guided to the upper part of the image forming apparatus main body 36 via the discharge path 53, and has a second sheet discharge section 54 for stacking with the image forming surface facing downward. It should be noted that when the first paper discharge section 52 is not used, it is housed in the image forming apparatus main body 36.

The optical unit 11 includes a polygon mirror 55.
The lenses 56 and 57 and the mirror 58 are arranged corresponding to each photoconductor drum 28, and the laser light is emitted toward each photoconductor drum 28 from the slit 61 formed in the optical unit support plate 60. It is like this.

In the color printer 2 thus constructed, the sheet member 3 is fed from the first paper feeding section 15 or the second paper feeding section 18.
When the sheet is sent out, the sheet member 3 is sent between the photosensitive drum 28 of the first image forming section 24 and the transfer belt 37 of the transfer section 7 by the conveying section 6. The sheet member 3 includes the photosensitive drum 28 and the transfer rollers 41a, 41b, 4
While being conveyed by the transfer belt 37 between 1c and 41d, the toner images formed on the black, magenta, cyan, and yellow photoconductor drums 28 are sequentially transferred to the sheet member 3. Then, the sheet member 3 on which the transfer of the color image is completed is further conveyed by the transfer belt 37 and is fed between the fixing roller 45 and the pressure roller 47 of the fixing unit 8, where the color image is fixed. After fixing, the sheet member 3
Is discharged to the first paper discharge unit 52 or the second paper discharge unit 54.

Next, the developing device according to this embodiment will be described in detail. [Overview of Developing Device] FIG. 2 is a perspective view showing a developing device constructed according to the present invention. FIG. 2A is a perspective view seen from the developing roller side, and FIG. 2B is a direction opposite to that of FIG. The partially cut-away perspective view seen is shown. Further, FIG. 3 is shown in FIG.
4 is a sectional view taken along line AA in FIG. 4, and FIG. 4 is a sectional view taken along line BB in FIG. FIG. 5 is a schematic diagram for explaining the arrangement and driving of the stirring and conveying device. A description will be given based on these FIG. 2 to FIG.

The developing device 30 has a developing housing 144 molded from a synthetic resin material. As shown in FIGS. 2 and 3, the developing housing 144 is adjacent to the first side wall 134 that extends substantially vertically upward from the bottom wall 132 in substantially the entire area, and is adjacent to the first side wall 134, and is located in a scooping region described later. The second side wall 136 forming a part and the front wall 13
8 (FIG. 2 (a)), a rear wall 140 (FIG. 2 (b)), and an upper wall 142 existing on the uppermost part of the developing housing 144,
It is mainly composed of.

The developing housing 144 is provided with a developer supplying means 146, a part of which is exposed on the side of the photosensitive drum for forming a latent image. The developer supplying means 146 is provided inside the developing sleeve 148, which is a cylindrical developing sleeve 148 made of a non-magnetic material such as aluminum extending over substantially the entire developing area in the axial direction (left and right direction in FIG. 2). It is composed of the magnetic material 150 disposed. The sleeve 148 is rotatably connected to a drive system described later. The magnetic material 150 is fixed at a predetermined position in the developing sleeve 148. As shown in FIG. 5, the rotary shaft 151 to which the developing sleeve 148 is fixed protrudes through the rear wall 140, and the input gear 152 is fixed to the protruding end portion. The driving force transmitted from a drive source (not shown) described later is transmitted to the input gear 152 through the output gear 154 and the idle gear 156. Then, it rotates in the direction indicated by arrow 158 in FIG.

Above the developer supplying means 146, a developer layer regulating means 160 is arranged. Developer layer regulating means 1
Reference numeral 60 is an ear cutting blade 62 and this ear cutting blade 62.
The holding unit 64 holds the The holding portion 64 is fixedly supported on the upper front surface of a partition wall 66 that accommodates a first stirring / transporting means 68 described later. The lower end edge of the bristle cutting blade 62 of the developer layer regulating means 160 is arranged so as to extend over substantially the entire axial direction in a region slightly downstream of the developing sleeve 148 in the rotational direction of the developing sleeve 148. The lower end edge of the blade 62 is located approximately at the center of the N and S poles above the magnet material 150. Developer 1 separated by the blade 62 and separated from the peripheral surface of the developing sleeve 148.
00 is agitated and mixed by the second agitating and conveying means 70 described later, and again attracted to the surface of the developing sleeve 148 by a magnetic force to be applied to the next development.

On the back surface of the developer supplying means 146 in the developing housing 144, two developer stirring and conveying means arranged in parallel in the vertical direction are provided. Specifically, the first agitating / conveying means 68 is provided on the upper side in the developing housing 144, and the second agitating / conveying means 70 is provided on the lower side in parallel with the developing sleeve 148. The two developer agitating and conveying means are separated by a partition wall integrally formed with the developing housing 144. On the front wall 138 side of the developing device, the developer pumping means 86 is located at an intermediate position in the height direction of the first and second agitating and conveying means 68, 70, and on the rear wall side of the developing device. Therefore, the toner concentration detecting means is provided on the back side of the first stirring and conveying means 68 (the side opposite to the developing sleeve 148).

[Developer Stirring / Conveying Means] Next, the developer stirring / conveying means will be described in detail with reference to FIG. This FIG. 5 is a schematic diagram for explaining the positional relationship in the longitudinal direction of the first and second stirring and conveying means, and is not a cross-sectional view of the developing device perspective view shown in FIG.
The developer stirring / conveying means is the first stirring / conveying means 68 and the second stirring / conveying means 7 provided immediately below the first stirring / conveying means 68.
It consists of 0 and.

The first agitating and conveying means 68 includes a front wall 138 of the developing housing 144 and a rotary shaft 72 rotatably mounted between an inner wall 141 provided on the inner side (left side) of the rear wall 140, The spiral blade 7 formed in substantially the entire axial direction of the rotary shaft 72, except for the region A1 at the downstream end of the developer 100 in the transport direction indicated by the arrow 108.
4 and. The rotary shaft 72 is attached to the front wall 138.
A gear 80 is provided at the left end of the gear 80 so as to project further outward. Further, a gear 75 is provided on the rotary shaft 72 also on the left side of the rear wall 140 and between the inner walls 141.

On the other hand, the second agitating / conveying means 70 includes a rotary shaft 76 rotatably mounted between the front wall 138 and the rear wall 140 of the developing housing 144, and a developing shaft 110 of the rotary shaft 76. The spiral blade 78 is formed in substantially the entire axial direction except the region A2 at the downstream end of the agent 100 in the transport direction. An output gear 154 is fixed to the right end of the rotary shaft 76, and the rotary shaft 76 is provided on the inner wall 141 between the front wall 138 and the rear wall 140.
A gear 81 is attached to the gear and is drivingly connected to the gear 75. Then, the first and second stirring and conveying means 68,
The rotation speed of the gear 70 is controlled by the gear ratio of the gears 75 and 81, and it can rotate so as to convey the developer in the opposite direction by the driving force from the same driving source (not shown).

The first and second agitating / conveying means constructed as described above basically achieve the smooth agitating / conveying circulation of the developer.
Are set so that the developer transporting force is substantially equal to each other, and the size, shape (twisting direction) of the spiral blades 74, 78, the pitch of the spiral, the turning direction (right-handed or left-handed), and the rotation speed of the spiral are set. Exactly the same,
Only the rotating directions of the spiral blades 74 and 78 may be different so that the conveying directions are opposite to each other.

However, in this embodiment, the developer carrying amounts of the first agitating / conveying means 68 and the second agitating / conveying means 70 are made substantially equal to each other, while the size of the spiral blades 74, 78 (in this embodiment, Diameter) and these blades 74, 7
The number of rotations of 8 is different, and the developer transport speed (V2) by the second stirring and transporting means 78 is set to be faster than the developer transporting speed (V1) by the first stirring and transporting means 68. Specifically, the outer diameter of the spiral blade 74 of the first stirring / conveying means 68 is φ20 mm, and the rotation speed is 161 rp.
m, the outer diameter of the spiral blade 78 of the second stirring and conveying means 70 is 16 mm, the number of rotations is 225 rpm, and the spiral pitch is 15 mm.

As a result, the first toner is newly supplied.
While slowly stirring the agitating and conveying means, the toner is conveyed from the left to the right in the figure, and the toner and the carrier are mixed and stirred for a sufficient time to ensure an appropriate and uniform toner concentration.
As a developer in which the toner is sufficiently charged, the second
It can be supplied to the stirring and conveying means. On the other hand, in the second agitating / conveying means, the developer conveying speed is increased so that the developer on the surface of the sleeve 148 whose toner concentration has decreased due to the development is replaced with another developer existing in the second agitating / conveying means. While being rapidly mixed and stirred, the mixture is moved at a higher speed to the pumping area provided in the short portion of the second stirring and conveying means. As a result, the first
The developer having the proper toner concentration supplied from the agitating / conveying means can be quickly replaced.

Specifically, the size of the spiral blade formed in the second stirring and conveying means is made smaller than that of the first stirring and conveying means, and conversely, the size of the spiral blade is set to be smaller than that of the first stirring and conveying means 68.
By setting the rotation speed of the stirring and conveying means 70 to be high (setting the gear ratio of the gears 75 and 81 described above), the conveying speed can be changed without changing the conveying amount of the developer. At this time, the size of the spiral blades and the number of rotations of the stirring and conveying means are as long as the above-described functions are achieved.
It can be set arbitrarily. However, if the number of rotations of the second stirring and conveying means is set to be excessively high, the developer is stressed. Therefore, the developing amount is 1.1 to 2 times that of the first stirring and conveying means, preferably 1.1 to 1. It is desirable to set it high in a speed range of about 5 times.

[Developer Scooping Means, Dropping Means, and Their Arrangement] Next, the developer scooping means, the dropping means, and their arrangement will be described. First, the developer scooping means 82 will be described in detail. As described above, the developer scooping means 82 is substantially at the central portion in the vertical direction of the first stirring / transporting means 68 and the second stirring / transporting means 70, and the developing housing front wall 138 of the first stirring / transporting means 68 and the second stirring / transporting means 70. It is arranged on the side.

More specifically with reference to FIG. 5, the pumping means 8
As shown in FIG. 5, reference numeral 2 denotes a magnetic roller (pumping roller 86) disposed on the front side (left side in FIG. 5) of the developing housing 144, outside the area of the developing sleeve 148, that is, in the axial direction. It is arranged outside the development area that effectively contributes to development. The scooping means 82 is rotatably mounted on the front wall 138 and the second rear wall 83 of the developing housing 144 by a rotary shaft 84. The rotating shaft 84 projects to the left of the front wall 138, and the gear 88 is fixed to this projecting portion. The gear 88 is screwed with a gear 80 attached to the rotary shaft of the first stirring and conveying means. A scooping roller 86 composed of the rotary shaft 84 is fixed to the rotary shaft 84. The pumping roller 86 is made of iron as a magnetic material in a substantially cylindrical shape over substantially the entire area in the axial direction, and has N poles and S poles having a magnetic force of, for example, 800 G gauss alternately arranged in the circumferential direction, and each has a total of 4 poles. Eight poles are magnetized over the entire axial direction.

On the other hand, the developer dropping means is located at the right end portion of the first stirring / transporting means 68 and the second stirring / transporting means 70 in the figure, and the first and second stirring / transporting means are integrally molded with the developing housing. Rear wall 14 of partition wall 66 for isolating the means
It is an opening provided on the 0 side, specifically, on the partition wall 66 located immediately above the end portion on the rear side wall 140 side of the first stirring and conveying means 70. The opening position is located on the right side (outside the effective development area) of the developer supply unit 146 (developing sleeve 148) in the drawing with respect to the effective development area D described above.

On the left side of the opening 200 in the drawing, that is, on the side where the developer is carried by the first agitating and conveying means 68, a rib as a closing means for blocking the developer 100 from the partition wall 66. 210 is provided. As shown in FIG. 2 (b), the rib 210 is formed above the rotary shaft 72 of the first stirring and conveying means 68. In this embodiment, the spiral of the first stirring and conveying means 68 is provided. The height is about 80% of the outer diameter of the blade 74. Due to the presence of the ribs 210, the developer 100 conveyed by the first stirring and conveying means 68 is temporarily blocked, and the notch portion 205 formed in the rotating shaft portion of the first stirring and conveying means 68 (see FIG. 3). Centering on the rib 210 so as to get over the rib 210,
As a result, the developer 100 is efficiently dropped onto the spiral blade 78 around the rotation shaft 76 of the second stirring and conveying means 70.

In this way, both the developer scooping means 82 and the developer dropping means 200 are arranged outside the effective developing area D.
As a result , the retention of the developer 100 at both ends of the effective developing area D of the developer supply unit 146 can be reliably prevented. That is, the rib 21 is provided at the downstream end of the first stirring and conveying means 68.
The developer 100 is partially blocked by 0, and the overflowed developer 100 is supplied to the dropping means 200. Therefore, the developer 100 is conveyed to the second stirring and conveying means 70 in the first stirring and conveying means 68. The developer 100 is supplied with the pulsation eliminated. As a result, in the second agitating / conveying means 70 immediately below the dropping means 200, the developer 100 can be conveyed in the leftward direction in the figure without remaining. As a result, at the right end portion of the effective developing area D in FIG. 5 in the second agitating / conveying means 70, the developer 100 in a state where the agitating / conveying is progressing smoothly is positioned, so that the development in this portion is performed. It is possible to effectively prevent the developer from blowing out and the toner from scattering due to excessive supply of the agent.

[Developer Circulation Path by Drive Connection Mechanism and Vertical Circulation] FIG. 6 shows the drive connection of the gears on the rear surface of the developing device, and FIG. 7 shows the drive connection of the gears on the front surface of the developing device. The description will be continued with reference to FIGS. 6 and 7. When the drive from a drive source (not shown) is transmitted to the output gear 154, it is transmitted to the gears 81 and 75 through the rotating shaft 72. The driving force transmitted to the gear 75 is transmitted to the gears 80 and 88 through the rotating shaft 72. On the other hand, when the drive from the drive source is transmitted to the output gear 154, the idle gear 15
6, also transmitted to the input gear 152. When the drive is transmitted as described above, the first agitating and conveying means 68 is moved to the position shown in FIGS.
Is rotated in the direction indicated by arrow 90, and the second stirring and conveying means 7 is rotated.
0 is rotated in the direction indicated by arrow 92, and the pumping means 82 is further rotated in the direction indicated by arrow 94.

As shown in FIG. 3, the developing housing 14
A developer 100 composed of a toner and a carrier is stored in the container 4. More specifically, the developer 100 is regulated by the partition wall 66 and is provided with the first stirring / conveying means 68.
Of the stirring area 102 and the partition wall 66, and
The developing unit 146 and the second developing unit 146, which are regulated by the first side wall 134,
The second stirring area 10 in which the stirring and conveying means 70 is arranged
4 and a third stirring and conveying means 68, a second stirring and conveying means 70 and a pumping means 82 as shown in FIG.
It is dispersed and accommodated in the stirring area (pumping area) 106.

The rotating shaft 72 of the first agitating and conveying means 68 is rotated in the direction indicated by the arrow 90, and the developer 100 is agitated and mixed in the first agitating area 102 in FIG. It is conveyed in the direction indicated by 108.

The rotating shaft 76 of the second agitating / conveying means 70 is rotated in the direction indicated by an arrow 92, and the developer 100 is agitated and mixed in the second agitating region 104 while being indicated by an arrow 110 in FIG. In the direction from the upstream side to the downstream side. At this time, a part of the developer 100 is supplied from the second agitating / conveying means 70 to the developer supplying means 146, and further from the developer supplying means 146 to the developing area of the photosensitive drum 28 rotating in the direction indicated by arrow 147. It is supplied and a toner image is formed.

Next, the route in which the developer 100 is stirred, mixed, conveyed, and circulated will be described in detail. First, by the action of the first stirring / transporting means 68, the developer 100 is transported in the first stirring region 102 while being stirred and mixed in the direction indicated by the arrow 108 in FIG. 5, that is, in the direction from the front side to the back side of the apparatus main body. It At this time, the first stirring area 102
Ribs 210 are provided at the downstream end of the developer, and the developer is partially blocked there. As a result, sufficient developer is always secured at this end, and the toner concentration of the developer 100 is monitored by the toner concentration detection means provided at this position. The area A1 formed on the downstream side of the rib 210 is provided with the opening 200 in the partition wall 66, and constitutes the dropping means 200. Therefore, the developer 100 that has been agitated and conveyed by the spiral blades 74 of the first agitating and conveying means 68 goes over the gap (about 1 mm in this embodiment) between the rib 210 and the rotating shaft 72 and the rib 210, and is lowered by its own weight. To fall. Developer 100 dropped
Is agitated and mixed in the second agitating region 104 by the action of the second agitating and conveying means 70, and arrow 1 in FIG.
It is conveyed in the direction indicated by 10, and is conveyed to the downstream end portion, that is, the area A2 at the left end portion in FIG. Left edge (area A2)
In the above, since the spiral blade 78 of the second stirring and conveying means 70 is not provided, the second stirring and conveying means 70 is not further conveyed to the downstream side. The roller 86 attracts the developer 100 to its peripheral surface by magnetic force and pumps it up.

On the other hand, in the pumping area 106, the partition wall 6 is provided at the central portion in the vertical direction of the first stirring / transporting means 68 and the second stirring / transporting means 70 over the entire width of the pumping roller 86 in the width direction.
6 is provided with an opening, and the developer 100 from the second agitating / conveying means 70 to the scooping roller 86 and the first agitating / conveying means 68.
To allow the flow of. The partition wall 66 between the first stirring / transporting means 68 and the second stirring / transporting means 70 is an isolation wall 112 that blocks the flow of the developer in the vertical direction of both the stirring / transporting means. The tip 113 of the isolation wall 112 is formed in an acute angle shape,
The clearance between the surface of the drawing roller 86 is 1.0 mm. Further, the developer 1 attached to the surface of the scooping roller 86
At 00, a magnetic brush is formed as shown in FIG. More specifically, the developer 1 is attached to the magnetized regions of the N pole and the S pole.
The ears formed by 00 are long, and the ears are low in the central region of the N pole and the S pole. In this embodiment, N
Since four poles and S poles are arranged alternately, four poles each are provided,
There is no zero gauss area, and therefore the developer pumping means 82
It is possible to increase the pumping force (conveyance force) of the developer 100 due to.

When the scooping roller 86 rotates in the direction indicated by the arrow 94, the magnetic brush also rotates in the same direction, and the developer 100
Is separated from the surface of the pumping roller 86 at the tip of the isolation wall 112. The peeled developer 100 is moved onto the isolation wall 112, and is stirred and conveyed in the direction indicated by the arrow 108 in FIG. 5 by the rotating action of the spiral blade 74 of the first stirring and conveying means 68. After that, the developer 100 is agitated, mixed and conveyed as described above, and circulated repeatedly.

In this example, a resin-coated ferrite carrier having a central particle size of 60 μm and a central particle size of 8.
A two-component developer is prepared from a toner containing a color pigment and various additives in a polyester resin of 5 μm and a toner concentration of 4 to 5
1% of the developer conveying force of the first stirring / conveying means 68 and the second stirring / conveying means 70 by controlling the rotation speed of the spirals having the different diameters as described above.
The developer conveying force of the scooping means 82 (length: 27 mm) is 1350 g / min with respect to g / min. That is, the developer conveying force of the developer pumping means 82 is set to be larger than the conveying force of the first and second agitating and conveying means. In this way, it is possible to bring seen汲to the first stirring carrying unit 70 without staying the developer carried in the region pumped by the second stirring and conveying means 68. The conveying force of the scooping means 82 is the same as that of the first and second stirring and conveying means 6.
It suffices if it is large with respect to the conveying force of 8, 70, and 150% with respect to the conveying force of the first and second stirring and conveying means 68,
It can be used in a range up to a degree.

In this way, by the action of the second agitating and conveying means 70, while being agitated and mixed in the second agitating region 104, it is conveyed in the direction indicated by the arrow 110 in FIG.
The developer 100 conveyed to the downstream end portion, that is, the area A2 at the left end portion in FIG. 5 is moved by the developer scooping means 82 in the third stirring area 106 by the scooping roller 86 which sucks the developer 100 on its peripheral surface. It is possible to suck up the liquid to the left end portion of the first agitating and conveying means 68 located above and draw it up reliably and quickly. Therefore, the stagnation and solidification of the developer 100 are prevented, and reliable and excellent stirring and feeding are repeated.

On the other hand, as described above, the toner concentration detector 230 for detecting the toner concentration in the developer 100 is disposed at the downstream end of the first stirring and conveying means 68. The toner concentration detector detects the toner concentration by detecting the magnetic permeability in the developer 100, for example. Then, the toner concentration detector 230 detects that the developer 10 has reached a predetermined toner concentration.
When it is determined that the toner density of 0 is low, the toner supply unit (not shown) automatically supplies the toner on the upstream side of the first stirring / conveying unit, in the shaded area C in FIG. When the predetermined value is reached, the toner supply is stopped. This makes it possible to keep the toner concentration in the developing housing 30 within a required range, and it is possible to perform development with a predetermined concentration.

The toner supply is replenished in the area C by effectively utilizing the length of the first agitating / conveying means 68 and giving a sufficient mixing and agitating time to the replenished toner so that the triboelectric charge is generated. This is because it is given sufficiently. In addition, by providing the region C at the right end portion of the scooping means 82 in FIG. 5 (downstream of the scooping means 82 when viewed as the transport direction of the developer 100), the first agitating and transporting means 68 causes the rightward direction in FIG. The new toner can be replenished to the developer 100 that has started to move to, so that the mixing with the developer is extremely smooth. The spiral blade 74 of the first agitating / conveying unit located in the toner replenishing area C is provided with the rib 220 over one pitch so as to accelerate the mixing and stirring of the replenished toner and the developer. ing.

In the above embodiment, the developer scooping means 82 is the first stirring / transporting means 68 and the second stirring / transporting means 70.
However, it is also possible to arrange it on the left side in the front view, and in this way, the area where the developing sleeve does not exist in the axial direction area is effective. It can be used, and the length in the width direction (left and right direction in FIG. 4) can be further shortened. By doing so, when the developing device of the present invention is applied to a color printer having a 4-tandem developing device as an image forming device, the width of the color printer main body as the image forming device can be narrowed. Become.

In the above embodiment, the developer scooping means 82 does not have a sleeve around the scooping roller 84, and the width direction length of the developer scooping means 82 in the front view is shortened as much as possible. Although the width is slightly wide, a configuration in which a sleeve is provided is also possible.

[0054]

As described above, according to the present invention, the developer scooping means and the dropping means are both arranged outside the effective developing area of the developer supplying means, so that the first and second stirring and conveying means are effective. It can be used for stirring and carrying over the entire developing area. Moreover, a rib as a blocking means is provided at the downstream end of the first agitating / conveying means and a boundary portion with the dropping means to block a part of the developer, thereby making it possible to prevent the developing device from increasing in size. Can be located outside the effective development area. Further, the developer transport speed of the second agitating and transporting means is made higher than the developer transporting speed of the first agitating and transporting means in a state where the transporting amounts of the upper first and second developers are constant. As a result, it is possible to effectively prevent the developer from being blown out and the toner from scattering due to the excessive amount of the developer supplied to the second agitating and conveying means.

[0055]

[Brief description of drawings]

FIG. 1 is a schematic diagram of an image forming apparatus according to the present invention.

2A and 2B are diagrams showing an internal mechanism of a developing device, FIG. 2A is a perspective view seen from a developer supply device side, and FIG.
It is the perspective view which notched one part seen from the back side of the figure.

FIG. 3 is a sectional view taken along the line AA in FIG.

FIG. 4 is a sectional view taken along line BB in FIG.

FIG. 5 is a schematic diagram showing a positional relationship of constituent elements.

FIG. 6 is a diagram showing a drive connection of gears on the rear surface of the developing device.

FIG. 7 is a diagram showing a drive connection of gears on the front surface of the developing device.

[Explanation of symbols]

28 ... Photosensitive drum 30 ... Developing device 68 ... First stirring and conveying means 70 ... Second stirring and conveying means 74, 78 ... Spiral blade 82 ... Means for drawing up developer 86 ... Pumping roller (rotating body) 100 ... Developer 146 ... Developer supplying means 200: developer dropping means 210 ... Blocking means

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-10-142942 (JP, A) JP-A-11-212345 (JP, A) JP-A-10-260580 (JP, A) JP-A-63- 193165 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/08

Claims (5)

(57) [Claims] 1. A developer supplying means for supplying a developer to a latent image bearing member in a developing area to develop the developer, and a developer provided in the vicinity of the developer supplying means and agitating the developer to convey the developer in a predetermined direction. First stirring / transporting means and below the first stirring / transporting means
In and a second for transporting in the opposite direction to the stirred first agitating transporting means developer provided adjacent to the developing agent supply means
Agitating / conveying means, and a developer pumping means for supplying the developer in the second agitating / conveying means to the first agitating / conveying means,
A developer dropping means for supplying the developer in the first stirring and conveying means to the second stirring and conveying means, and the developer scooping means and the developer dropping means are an effective developing area of the developer supplying means. In each of the developing devices provided outside, fresh toner is replenished to the first stirring / conveying mechanism, and the developer supply amount is kept constant while the conveying amounts of the first and second developers are constant. A developer which is provided adjacent to the means and whose toner has been consumed in the developing area is scraped off, and a new toner supplied from the first agitating / conveying device is quickly replaced with a replenished developer having an appropriate toner concentration. Therefore, the developer conveying speed by the second stirring and conveying means is set to be higher than the developer conveying speed by the first stirring and conveying means, and there is a current between the developer dropping means and the first stirring and conveying means. A developing device having a blocking means for blocking an image agent. 2. The developer scooping means is a rotating body having a plurality of magnetic poles in the circumferential direction, which are provided at substantially central portions in the height direction of the first stirring and conveying means and the second stirring and conveying means. The developing device according to claim 1. 3. The developer dropping means is provided on a partition wall which separates an upper chamber in which the first stirring and conveying means is stored and a lower chamber in which the second stirring and conveying means is stored. The developing device according to claim 1, which is an opening provided. 4. The first stirring and conveying means and the second stirring and conveying means are provided with blade members formed in a spiral shape having the same pitch, and the blade member of the first stirring and conveying means has an outer diameter. It is formed larger than the blade member of the second stirring and conveying means, and the conveying speed of the second stirring and conveying means is 1.1 to 1.5 times the conveying speed of the first stirring and conveying means. The developing device according to claim 1, which is set high. 5. The developing device according to claim 1, wherein the blocking means is provided with a cutout portion in a rotary shaft portion of the first stirring and conveying means.