JP3406961B2 - 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 developing and visualizing a latent image formed on an image carrier.

[0002]

2. Description of the Related Art A color copying machine shown in FIG. 1 will be described as a typical example of a conventional image forming apparatus.

As shown in FIG. 1, the color copying machine comprises a reader section R and a printer section Q. In the reader unit R, the original set on the platen 57 is first
The lamp 51a and the first mirror 51 that constitute the mirror base 51
It is read by scanning in the arrow direction at the same speed as the process speed Vp by b. The reflected light obtained by scanning the original document passes from the first mirror 51b to the second mirror 52a and the third mirror 52b forming the second mirror base 52, and then to the lens 5
3 forms an image on the CCD 54. Second mirror stand 52
Moves in the direction of the arrow at a speed of 1/2 Vp.

In the printer section Q, the image information of the original image formed on the CCD 54 is converted into an electric signal through the image processing section, and further converted into an optical signal by the laser scanner 55 and output. The light of the optical signal output from the laser scanner 55 is applied to the photosensitive drum 100 via the mirrors 56a and 56b.

Around the photosensitive drum 100, a device constituting a process unit, such as a primary charger 60, a pre-exposure lamp 61, a cleaner 62, a pre-cleaning charger 63, and a plurality of developing devices 20, is installed and further transferred. A transfer drum 70 that constitutes the apparatus is provided.

As the developing device 20, four types of developing devices 20M, 20C, 20Y, and 20 having magenta (M), cyan (C), yellow (Y), and black (K) toners are used.
Equipped with K. These four types of developing devices 20M-20K
Is integrally movable with respect to the photosensitive drum 100 in a direction indicated by an outline arrow, and the developing devices 20M to 20K are relatively moved one by one to a developing position facing the photosensitive drum 100 to expose the photosensitive drum 100. The latent images sequentially formed on the drum 100 are sequentially developed by the corresponding color developing devices to sequentially form toner images of the respective colors. First, for example, a magenta image is formed as the first color, and the photosensitive drum 1
The latent image formed on No. 00 is developed by the corresponding magenta developing device 20M to obtain a magenta toner image on the photosensitive drum 100.

On the other hand, as a transfer material, in the cassette 80a, 8
One of the sheet materials 81a and 81b accommodated in the sheet 0b is fed out by the sheet feeding / separating means 82a or 82b, and the fed sheet material is transferred by a registration roller 83 at a timing. It is conveyed to 70 and is adsorbed and carried on the transfer drum 70 by the action of the adsorption roller 71 and the adsorption charger 72 provided at the adsorption position. The sheet material carried on the transfer drum 70 is conveyed to the image transfer position facing the photosensitive drum 100 by the rotation of the transfer drum 70, and the transfer drum 7 is transferred there.
The magenta toner image on the photosensitive drum 70 is transferred onto the sheet material by the transfer charger 73 provided inside 0.
The sheet material on which the magenta toner image is transferred is conveyed again to the image transfer position by the rotation of the transfer drum 70.

Similarly, a cyan latent image as a second color is formed on the photosensitive drum 100 and developed by the cyan developing device 20C which has moved to the developing position to obtain a cyan toner image. Transfer from the top of the magenta toner image. This is also performed for yellow and black, and thus, a color image is obtained in which four color toner images of magenta, cyan, yellow, and black are superposed and transferred onto the sheet material. The peripheral speeds of the photosensitive drum 100, the transfer drum 70, and the suction roller 71 and the registration roller 83 are the same as the process speed Vp.

After the transfer of the four color toner images is completed, the sheet material is provided with charge-eliminating chargers 84a and 84b, a separation charger 84c and a separation claw 85 provided inside or outside the transfer drum 70.
Is separated from the transfer drum 70 by the action of
Is conveyed to a fixing unit 87, where the upper and lower fixing rollers 87a and 87b perform thermocompression bonding to mix the toner images of four colors and fix the toner images on the sheet material to form a full-color permanent image, and then the sheet discharge tray 88. Discharged on top.

The developing unit 20 will be further described. As shown in FIG.
a and a stirring chamber 4b, the developing container 4 is partitioned, and the developing roller 1 is rotatably supported by the developing container 4 in an opening 4c above the developing chamber 4a. Are arranged so as to face each other. The developing roller 1 is rotated in the direction of the arrow shown by a drive system (not shown) with respect to the rotating photosensitive drum 100, and is used for development.

Further, in the developing chamber 4a and the agitating chamber 4b, a first carrying screw 2 and a second carrying screw 3 are rotatably provided as developer carrying means, respectively. At both ends of the developing roller 1, a seal member 7 such as felt that prevents the developer from leaking is supported by the container 4 and pressed against it. The second screw 3 in the stirring chamber 4b is rotated by the drive of a drive system (not shown), and as shown in FIG. 8 or 9 showing a cross section taken along the line BB of FIG. 4 is conveyed in the arrow U direction while stirring the toner replenished from the toner replenishing port 4d on the front side opening of the developing chamber 4, and the developer is passed through the opening 6a at the tip end position of the partition plate 6 in the arrow U direction to the developing chamber 4a.
Hand it over. Similarly, the first screw 2 in the developing chamber 4a is rotated by the drive of a drive system (not shown), and the stirring chamber 4
b, the developer transferred to the inside of the developing chamber 4a is conveyed in the W direction opposite to the arrow U, and the developer is conveyed by the arrow W on the partition plate 6.
It returns to the inside of the stirring chamber 4b through the opening 6b at the front end position in the direction.

To position the developing device 20 with respect to the photosensitive drum 100, the abutting roller 8 on the shaft of the developing roller 1 is brought into contact with the tops 9 fixed to the side plates 10 and 11 on the front and rear of the main body of the image forming apparatus. Performed by.

The developer in the developing chamber 4a is drawn up by the rotating developing roller 1 while being conveyed by the screw 2 in the direction of the arrow W, and is regulated by the blade 5 placed close to the developing roller 1 in a predetermined manner. A developer layer having a predetermined layer thickness is formed on the developing roller 1 by being applied in a layer thickness. Then, as the developing roller 1 rotates, the opening 4c of the developing chamber 4a
Then, the developer is supplied to the electrostatic latent image formed on the surface of the photosensitive drum 100 to attach toner, and the electrostatic latent image is developed and visualized as a toner image.

Conventionally, as shown in FIG. 8, a length f _M of a developing roller 1 which is a magnet roller, a length f _S1 of a screw 2 which is a first conveying means, and a screw which is a second conveying means. The relationship with the length f _{S2 of} 3 is as follows: f _S1 ≈ f _S2 <f _M , or as shown in FIG. 9, f _S1 <f _M <f _S2. was there.

That is, in FIG. 8, the toner replenished from the toner replenishing port 4d is supplied with an arrow U by the second screw 3.
Is stirred and conveyed in the stirring chamber 4b in the direction to reach the inside of the developing chamber 4a, but since the path from the replenishing port 4d to the developing chamber 4a is short, the carrier of the developer and the replenished toner are sufficiently stirred. If this is not done, the toner density of the developer becomes non-uniform, causing a problem of unstable density in the image obtained by development. In order to prevent this, in order to perform sufficient agitation, the rotation speed of the screw 3 must be increased, the sliding end with the developer becomes large at the shaft end portion 3a of the screw 3, and the friction heat As a result, the toner is solidified to form a delicate solidified body, which causes an adverse effect such as white spots on the image.

Since the replenishment port 4d is located between the front and rear side plates 10 and 11 of the image forming apparatus main body, a hopper for replenishing toner must be arranged between the front and rear side plates 10 and 11 of the main body. There are drawbacks such as a problem that the forming device becomes large and complicated, the operability of setting the toner bottle in the hopper is deteriorated, and it becomes difficult to operate the toner bottle from the front surface of the main body. Further developing container 4
Since the volume cannot be large and the amount of developer accommodated is not sufficient, the image density becomes unstable in a short use time.

In the case of FIG. 9, since the replenishment port 4d extends forward from the side plate 10, the arrangement of the hopper is on the front side, and it is possible to avoid an increase in size and complexity, but as in the case of FIG. Cannot be sufficiently stirred. That is, in the case of FIG. 9, at first glance, the second screw 3 becomes longer,
Although the agitation seems to be better, the region where the carrier circulates is the part of Hb in the figure, and the subsequent H on the front side
In the portion a (the portion near the replenishing port 4d), only the toner is conveyed, so that the stirring cannot be sufficiently performed. If the toner is not sufficiently stirred, the image density becomes unstable as described above.

Further, when only the toner is conveyed in the Ha portion, the toner is directly rubbed against the screw 3 and the inner wall of the container 4, so that the toner is solidified and a defect such as a white spot easily occurs. Furthermore, the side plate 1 on the front side of the main body is also subjected to regular maintenance.
When the developer is collected from the developing device 20 before 0, the driving sources of the screws 2 and 3 are rotated in the reverse direction to convey the developer in the direction of the arrow W ′ → U ′ and face the replenishing port 4d. Since it is dropped from the recovery port 4e and recovered, a mechanism for switching the rotation of the drive source between the normal and reverse directions is required, which is complicated and costly.

The object of the present invention is to improve the developer without increasing the rotation speed of the first and second conveying means for stirring and conveying the developer installed in the developing container containing the developer. A good image with stable image density and no white spots can be obtained by stirring, and the degree of freedom in arranging the replenishing device that replenishes the developer in the developer container and the operability during setting, etc. To provide a developing device capable of improving

Another object of the present invention is to provide a developing device capable of simplifying the mechanism, which does not require a mechanism for switching the rotation of the drive source at the time of collecting the developer to the normal or reverse direction.

[0021]

The above object of the present invention relates to the present invention.
It is achieved by the developing device . In summary the present invention include magnetic
Developing roller with built-in roller, toner and carrier
A first screw for stirring and conveying the developer containing
A seal that prevents the developer from leaking at the end of the developing roller.
A developing chamber including a member and a developer between the developing chamber and the developing chamber.
Is a stirring chamber that constitutes a circulation path of
It is equipped with a second screw for transporting and is located upstream of the developer transport direction.
A stirring chamber that receives toner from the toner supply port provided
In a developing device having a developing container partitioned into
Length f _M of the developing roller, between the first screw length f _S1, the second screw length f _S2, holds the relationship of _{f M <f S1 ≒ f S2} , of the first screw The seal part
The diameter of the area facing the material is made smaller than the main part, and this diameter is made smaller.
The screw pitch of the
The developing device is characterized in that

According to another aspect of the present invention, a magnetro
Roller between the developing roller and the spiral blade for agitation
A fin is provided to stir the developer including toner and carrier.
A first screw for stirring and conveying, and an end portion of the developing roller
And a seal member that prevents the developer from leaking.
A developer circulation path is formed between the image chamber and the developing chamber.
The second screen that stirs and conveys the developer
And a toner supplement provided on the upstream side in the developer transport direction.
The current is divided into a stirring chamber that receives toner from the inlet.
In a developing device having an image container, the length of the developing roller is
F _M , the length f _S1 of the first screw , the second screw
The relationship of f _M <f _S1 ≈f _S2 is established between the length f _S2 of the Liu, and the seal portion of the first screw is formed.
The diameter of the area facing the material is made smaller than the main part, and this diameter is made smaller.
The pitch of the fins in
Or the size of the fiber in the reduced diameter section.
One of the width, thickness, or height of the
Make it smaller, or use the fins only on the main part
There is provided a developing device characterized by being provided.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the developing device of the present invention will be described below.

Embodiment 1 In this embodiment, the developing device of the present invention is used in the color copying machine shown in FIG . Therefore, detailed explanation of the image forming apparatus is omitted, the current is a feature of the present invention
The image device will be described in detail.

The developing device constructed in accordance with the present invention has the same sectional structure as the developing device described with reference to FIG. 2, but FIG. 3 shows the present embodiment as shown by the arrow BB in FIG. FIG. 3 is a diagram of a developing device according to an example.

In the present embodiment, as shown in FIG. 2, the developing device 20 has a developing container 4 whose interior is partitioned by a partition wall 6 into a developing chamber 4a and a stirring chamber 4b, and an upper portion of the developing chamber 4a. The developing roller 1 is rotatably supported by the developing container 4 in the opening 4c, and is disposed so as to face the photosensitive drum 100 of the image forming apparatus. The developing roller 1 is a photosensitive drum 10 that rotates.
0 is rotated by a drive system (not shown) in the direction of the arrow shown and used for development.

Further, in the developing chamber 4a and the stirring chamber 4b, a first conveying screw 2 and a second conveying screw 3 are rotatably provided as developer conveying means, respectively. At both ends of the developing roller 1, a seal member 7 such as felt that prevents the developer from leaking is supported by the container 4 and pressed against it. The second screw 3 in the stirring chamber 4b is rotated by the drive of a drive system (not shown), and as shown in FIG. 3 which is a sectional view taken along the line BB of FIG. While being agitated with the toner replenished from the toner replenishing port 4d of the side opening, the developer is conveyed in the direction of arrow U, and the developer is transferred into the developing chamber 4a through the opening 6a of the partition plate 6 at the tip position in the direction of arrow U. Similarly, the first screw 2 in the developing chamber 4a is rotated by driving by a drive system (not shown), and the developer transferred from the stirring chamber 4b into the developing chamber 4a is conveyed in the W direction opposite to the arrow U. Then, the developer is returned into the stirring chamber 4b through the opening 6b at the tip end position of the partition plate 6 in the arrow W direction.

To position the developing device 20 with respect to the photosensitive drum 100, the abutting roller 8 on the shaft of the developing roller 1 is brought into contact with the tops 9 fixed to the side plates 10 and 11 on the front and rear of the main body of the image forming apparatus. Performed by.

The developer in the developing chamber 4a is drawn up by the rotating developing roller 1 while being conveyed by the screw 2 in the direction of the arrow W, and is regulated by the blade 5 placed close to the developing roller 1 to a predetermined level. A developer layer having a predetermined layer thickness is formed on the developing roller 1 by being applied in a layer thickness. Then, as the developing roller 1 rotates, the opening 4c of the developing chamber 4a
Then, the developer is supplied to the electrostatic latent image formed on the surface of the photosensitive drum 100 to attach toner, and the electrostatic latent image is developed and visualized as a toner image.

According to the present invention, as shown in FIG. 3, the length f _M of the developing roller 1, which is a magnet roller, and the first roller
The relationship between the length f _S1 of the screw 2 as the conveying means and the length f _S2 of the screw 3 as the second conveying means is f _M <f _S1 ≈f _S2 .

According to the configuration of the present invention, the toner supply port 4
The toner stirring path of the stirring chamber 4b is sufficiently long when it is replenished into the stirring chamber 4b from d and is stirred in the stirring chamber 4b by the screw 3 in the direction of the arrow U with the developer carrier. Therefore, the toner can be sufficiently stirred with the carrier. Further, since the circulation path of the developer becomes long and the toner and the carrier circulate even immediately below the replenishment port 4d, it is possible to prevent only the toner from being conveyed and rubbed near the replenishment port 4d.

The volume of the developing container 4 is also increased by the amount that the agitating chamber 4b and the developing chamber 4a extend toward the front, and accordingly, the amount of developer accommodated can be increased.

In order to collect the developer, if the cap of the recovery port 4e is removed and the developer is driven in the forward direction,
The developer advances in the direction of arrow U → W and drops from the recovery port 4e,
It can be recovered, and there is no need to provide a mechanism for switching the rotations of the driving sources of the screws 2 and 3 between forward and reverse.

Embodiment 2 FIG. 4 is a sectional view showing a developing device according to Embodiment 2 of the present invention, and shows a section similar to that of FIG.

In the first embodiment, as shown in FIG.
The first conveying screw 2 in 4a is located at the end of the developing roller 1.
Go through the support part 4f of the seal member 7 and project to the front side
However, the screw 2 of this seal member supporting portion 4f
Side surface and the outer peripheral surface of the screw 2 do not interfere with each other.
The distance L between the centers of the image roller 1 and the screw 2 has been set to
Also the outer circumference of the developing roller 1 and the outer circumference of the screw 2
Gap between faces ₁Is slightly wider than before.
It

This wide gap G ₁ does not cause a problem when the magnetic pole for drawing up the developer of the magnet (not shown) in the developing roller 1 has a sufficiently large magnetic force, but since the developing roller 1 has a small diameter, it does not cause the problem. If the magnetic force cannot be increased sufficiently, the developer cannot be pumped well,
This may cause image defects.

Therefore, in this embodiment, as shown in FIG. 4, between the developing roller 1 and the screw 2 so as to cope with the case where the magnetic force of the developer scooping pole of the magnet in the developing roller 1 is insufficient. The gap is set to G ₂ which is smaller than the gap G _{1 in} Example 1, and the developing roller 1 and the screw 2 are brought close to each other. Therefore, in order to prevent the outer peripheral surface of the screw 2 from interfering with the support portion 4f of the seal member 7, as shown in FIG.
The outer diameter d ₂ of the portion F is smaller than the outer diameter d ₁ of the main portion E of the other portions (both the outer diameters d ₁ and d ₂ are to the outer end in the radial direction of the spiral blade of the screw 2). Is the distance).

In this embodiment, since the developing roller 1 and the first screw 2 are brought close to each other as described above, even when the magnetic force of the developer pumping pole of the magnet in the developing roller 1 is insufficient, the developing roller 1 The developer can be satisfactorily pumped up, and the instability of the image due to poor pumping of the developer can be eliminated and the stability can be improved.

Third Embodiment FIG. 6 shows a first embodiment of the developing device according to the third embodiment of the present invention.
It is sectional drawing which shows a screw.

In the second embodiment, the first screw 2 shown in FIG. 5 has a main portion E and a small diameter portion if the outer diameter difference between the main portion (outer diameter d ₁ ) and the small diameter portion F (outer diameter d ₂ ) is small. Since the difference in the developer conveying force of F is small, the developer can be conveyed without any problem.

However, when the difference in outer diameter becomes large (d
₂ / d ₁ ≈ 0.8 or less), the carrying force of the small diameter part F is E
As a result, the developer is pushed from the main portion E on the upstream side of the small diameter portion F into the small diameter portion F. Therefore, the developer is accumulated in the portion Ea immediately before entering the small diameter portion F and circulates. May not be performed well, and the developer may be accumulated on the immediately preceding portion Ea, so that there is a possibility that an image obtained by development may have a high density only at a portion corresponding to the immediately preceding portion Ea.

Therefore, in the present embodiment, as shown in FIG. 6, the pitch of the spiral blades in the small diameter portion F of the first screw 2, that is, the screw axial lead (advance amount) h ₂ per rotation of the spiral blades is set. H rather than lead h ₁ in main part E
₂ > h ₁ is set to a large value to compensate for the decrease in the developer conveying force of the small diameter portion F due to the decrease in the outer diameter, and the conveying force of the small diameter portion F and the main portion E are made substantially equal.

Therefore, according to the present embodiment, the developer is pushed from the main portion E on the upstream side of the screw 2 to the small diameter portion F, and the developer is retained in the portion Ea immediately before the main portion E. It is possible to surely prevent the image density of a portion corresponding to the immediately preceding portion Ea from increasing and to obtain an image with uniform density.

Fourth Embodiment FIG. 7 shows the first embodiment of the developing device according to the fourth embodiment of the present invention.
It is sectional drawing which shows a screw.

In the third embodiment, the imbalance of the developer conveying force of the small diameter portion F with respect to the main portion E of the first screw 2 is changed by changing the lead (pitch) per rotation of the spiral blade of the small diameter portion F. However, as shown in FIG. 7, the main portion E and the small diameter portion F of the screw 2 may be provided with fins 2a and 2b for agitating the developer, which project between the spiral blades.

The fin 2a of the main portion E is a rectangular plate having a width b ₁ , a thickness t ₁ and a height g ₁ , and projects outward from the shaft portion of the screw 2 at a pitch interval P ₁ . Width b ₂ at the fin 2b likewise rectangular cross section of the plate of the small diameter portion F, the thickness t _2, the height g _2, and protrudes outward from the shaft portion of the screw 2 in the pitch P _2.

In the above, when the number of fins 2a, 2b is increased, the stirring ability of the developer is improved, but the conveying ability of the developer is lowered. Therefore, by changing the size and the arrangement pitch of the fins 2a and 2b, the imbalance of the conveying force in the main part E and the small diameter part F of the screw 2 is eliminated. In the present embodiment, the fin 2a of the main part E of the screw 2 and the fin 2b of the small diameter part F have a pitch P ₁
<P ₂ , width b ₁ > b ₂ , thickness t ₁ > t ₂ , height g ₁ > g
_In the main part E, thick fins are arranged at a fine pitch, and in the small diameter part F, thin small fins are arranged at a coarse pitch.

According to this, in terms of the size of the fins and the pitch thereof, the developer conveying force of the small diameter portion F becomes high, but the screw outer diameter d ₁ of the small diameter portion F is the screw outer diameter of the main portion E. Since it is smaller than d _2, the conveying force of the small diameter portion F and the main portion E are substantially equal. Therefore, there is no possibility that the developer is pushed from the main portion E on the upstream side of the screw 2 to the small diameter portion F and the developer is retained in the immediately preceding portion Ea of the main portion E, and the portion corresponding to the immediately preceding portion Ea is eliminated. It is possible to surely prevent the image density from becoming high and obtain an image with uniform density.

In the above, the fins 2a of the main portion E and the fins 2b of the small diameter portion F have their pitches, widths, thicknesses, and heights changed from each other. However, one of the conditions, for example, the pitch is changed. The developer transporting forces of the portion E and the small diameter portion F may be balanced, or may be balanced by changing two conditions or three conditions. Further, the fin 2 of the small diameter portion F of the screw 2
b may be omitted. It is also possible to combine the above-described installation of the fins 2a, or the installation of the fins 2b with the modification of the lead of the spiral blade in the small diameter portion F of the screw 2 of the third embodiment.

As described above, according to the first to fourth embodiments,
The length h of the developing roller of the imager 20_MAnd the first screw 2
Length f_S1And the length f of the second screw 3_S2The relationship of f_M
<F_{S 1}≒ f_S2Therefore, the toner of the toner replenished to the developer is
The mixing path with the carrier
-Good stirring can be performed without increasing the rotation speed of 2 and 3.
The density of the image obtained by development is stable, and white spots etc.
The image defect of is also eliminated. In addition, the toner replenishing port d is connected to the image forming device.
Since it is provided outside the side plates 10 and 11 on the front and rear of the mounting body,
The degree of freedom in the placement of the hoppers for
The toner bottle's operability is improved, and the device is smaller and easier.
Simplification is possible. Furthermore, the capacity of the developing device 4 is increased.
Therefore, the amount of developer accommodated increases and the image stability increases.
There is also a fruit. Furthermore, the developer recovery is in the same direction as the transport during development.
Because it can be done by one-way conveyance,
No reverse rotation mechanism is required, which simplifies the developer drive system and reduces costs.
It is possible to downgrade.

[0051]

As described above, according to the present invention, (A) a developing roller having a built-in magnet roller and a toner
The first scoop that stirs and conveys the developer including the carrier
Liu and the end of the developing roller prevent the developer from leaking.
Between the developing chamber equipped with a seal member for
It is a stirring chamber that forms a circulation path for the image developer and stirs the developer.
It is equipped with a second screw for stirring and conveying, and is upstream in the developer conveying direction.
The toner supply port provided on the side
A developing device having a developing container partitioned into a stirring chamber and
Te, the length f _M of the developing roller, the first screw length f _S1, between the second screw length f _S2, holds the relationship of _{f M <f S1 ≒ f S2} , the sealing member of the first screw Opposite
The diameter of the area to be cut is smaller than that of the main part.
The screw pitch is larger than that of the main part.
Or (B) a developing roller with a built-in magnet roller
A fin for stirring is installed between the blades of the toner and carrier.
The first screw that stirs and conveys the developer containing
A seal member that prevents the developer from leaking at the end of the image roller
And a developer chamber between the developer chamber and the developer chamber.
It is a stirring chamber that forms a path, and stirs and conveys the developer.
It is equipped with a second screw and is provided on the upstream side in the developer transport direction.
And a stirring chamber that receives toner from the toner supply port.
In a developing device with a developing container cut off,
La length f _M , 1st screw length f _S1 , 2nd screw
The relationship of f _M <f _S1 ≈ f _S2 is established between the lengths of the fuses f _S2 , and the seal member of the first screw is
The diameter of the facing area is smaller than that of the main part.
The fin pitch in the
The width or thickness of the fin in the part that is made thinner or has a reduced diameter
Or one of the heights is made smaller than the main part
Or, the fins may be provided only on the main part.
Therefore, even if the rotation speed of the first and second screws that stir and convey the developer installed in the developer container containing the developer is not increased, the developer is well stirred and the image density is stable. It is possible to obtain a good image without white spots, and it is possible to improve the degree of freedom of arrangement of a replenishing device for replenishing the toner in the developer in the developing container and the operability at the time of setting. . Furthermore, a mechanism for switching the rotation of the drive source at the time of collecting the developer to the forward or reverse direction is not required, and the mechanism can be simplified.

[Brief description of drawings]

FIG. 1 is a sectional view showing the overall configuration of an embodiment of an image forming apparatus to which the present invention can be applied.

FIG. 2 is a cross-sectional view showing the developing device according to the first embodiment of the present invention.

FIG. 3 is a sectional view taken along line BB of FIG.

FIG. 4 is a sectional view similar to FIG. 3, showing a developing device according to Embodiment 2 of the present invention.

5 is a plan view showing a first screw of the developing device of FIG. 4. FIG.

FIG. 6 is a plan view illustrating a first screw of a developing device according to a third exemplary embodiment of the present invention.

FIG. 7 is a plan view illustrating a first screw of a developing device according to a fourth exemplary embodiment of the present invention.

FIG. 8 is a sectional view similar to FIG. 3, showing a conventional developing device .

FIG. 9 is a sectional view similar to FIG. 3, showing a developing device in another example of the conventional developing device .

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Development roller 2 1st conveyance screw 3 2nd conveyance screw 4 Development container 4a, 34a Development chamber 4b, 34b Agitation chamber 7 Seal member 20, 20C-20Y Developing device (developing device) 70 Transfer drum 100 Photosensitive drum

Claims (2)

(57) [Claims] 1. A developing roller having a built-in magnet roller.
And stir and convey the developer including toner and carrier
At the end of the first roller and the developing roller, the developer is
A developing chamber having a seal member for preventing leakage, and a stirring chamber forming a developer circulation path between the developing chamber and the developing chamber.
Is equipped with a second screw that stirs and conveys the developer.
E From the toner replenishing port provided on the upstream side in the developer conveying direction
A developer container that is partitioned into a stirring chamber that receives toner supply
In the developing device having the length f _M of the developing roller, between the first screw length f _S1, the second screw length f _S2, holds the relationship of _{f M <f S1 ≒ f S2} , The region of the first screw facing the seal member
The diameter is made smaller than that of the main part, and the
It is characterized in that the fuse pitch is made larger than that of the main portion.
Developing device . 2. A developing roller having a built-in magnet roller.
And a fin for stirring is installed between the spiral blades
And a first screw that stirs and conveys the developer including carrier
And prevent the developer from leaking at the end of the developing roller.
A developing chamber having a seal member for forming a developer circulation path between the developing chamber and the developing chamber.
Is equipped with a second screw that stirs and conveys the developer.
E From the toner replenishing port provided on the upstream side in the developer conveying direction
A developer container that is partitioned into a stirring chamber that receives toner supply
In the developing device, the length f _{M of} the developing roller and the length of the first screw
Between f _S1 and the length f _S2 of the second screw, a relationship of f _M <f _S1 ≈f _S2 is established, and a region of the first screw facing the sealing member is defined as follows.
The diameter is smaller than the main part,
Whether the pitch of the fins is larger than that of the main part ,
Width, thickness, and height of the fin in the reduced diameter portion
Either one of them is smaller than the main part, or if
Or, the fins are provided only on the main part,
Developing device.