JPH1124382A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device where the driving torque of a screw and the stress of developer are restrained by smoothly drawing up the developer from a lower part to an upper part. SOLUTION: In this vertical type developing device; the developer is supplied to/recovered from a developing roll 18 while the developer is made to circulate by a supply screw 14 and a recovery screw 16 which are arranged up and down. In the draw-up part 9 of the developing device, where the developer is drawn up from a lower stage (recovery screws 16) to an upper stage (supply screws 14); the supply screw 14 at the upper stage achieves stronger carrying force than the recovery screw 16 at the lower stage. Thus, the developer is sucked up to the upper stage side at the draw-up part 9, and the developer is smoothly drawn up against the hindrance of gravity. Therefore, the retention of the developer at the draw-up part 9 is prevented and the deterioration (flocculation, etc.), caused by the necessary rise of the driving torque of the recovery screw 16 caused by the increase of rotational resistance and the stress of the developer is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a developing device used in an electrophotographic image forming apparatus such as a copying machine or a printer. More specifically, the developer is smoothly pumped from the vertical recovery screw to the upper supply screw so that the drive torque of the screw and the stress applied to the developer are increased. The present invention relates to a development device in which the development is prevented.

[0002]

2. Description of the Related Art An example of a conventional developing device is disclosed in
No. 3,336,91. As shown in FIG. 14, this developing device has two upper and lower augers (screws) 82 and 85 arranged in parallel so that their transport directions are opposite to each other. And this gives
While circulating the developer as indicated by arrows c and d,
Developer carrier (developing roll) 8 provided adjacent to 2
7, and develops the electrostatic latent image on the photoconductor through this. In this developing device, the upper auger 82
Is responsible for supplying the developer to the developer carrier 87, and the lower auger 85 is responsible for collecting the developer from the developer carrier 87. The developer carrying capacity of the augers 82 and 85 is higher than the developer carrying capacity of the developer carrier 87.

[0003]

However, in the conventional developing device described above, the developer is pumped from the lower auger 85 to the upper auger 82 (arrow d in FIG. 14).
Was not necessarily smooth because the direction was against gravity. Therefore, the developer easily stayed in the pumping portion. And by this, auger 82,
In some cases, the necessary driving torque increases due to an increase in the rotational resistance of the 85, or the developer may be stressed to cause deterioration such as adhesion.

[0004] The present invention has been made to solve the above-mentioned problems of the conventional developing device. That is, the problem is to provide a developing device in which the developer is smoothly pumped from the lower screw to the upper screw, and the necessary driving torque of the screw and the stress applied to the developer are reduced. Is to do.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a developing device according to the present invention comprises a lower screw for transporting a developer in an axial direction, and a developer arranged above the lower screw and dispensing the developer. An upper screw that conveys the developer in the axial direction, wherein a conveying capacity of the upper screw in a pumping portion where the developer is pumped from the lower screw to the upper screw is larger than a conveying capability of the lower screw in the portion. Specified as

In this developing apparatus, generally, an upper screw is a supply screw which supplies the developer to the developing roll while transporting the developer, and a lower screw recovers the developer from the developing roll and transports the developer. It is a screw. In such a developing device, the developer is supplied upward (supply).
While being conveyed in the axial direction by the screw, it is supplied to the developing roll. Then, the developer remaining on the developing roll after the development is recovered by a lower (recovery) screw and transported in the axial direction. The developer that has reached the downstream end in the transport direction of the lower screw is pumped up by the upper screw. Here, in the pumping portion, since the upper screw has a larger transfer capacity (the maximum amount of developer that can be transferred per unit time) as compared with the lower screw, the upper screw side has a substantially negative pressure. In state. Therefore, the developer that has been conveyed to the lower screw and reached the pumping portion is sucked up by the upper screw, so that the developer is smoothly pumped against gravity. Therefore, the developer does not stay in the pumping portion, so that the rotation resistance of the screw does not increase and the developer does not receive excessive stress. As a result, the required driving torque of the screw and the deterioration (adhesion and the like) of the developer are suppressed.

[0007] Alternatively, the upper screw is a stirring screw for stirring the developer while transporting the developer, and the lower screw is a supply screw for supplying the developer to the developing roll while transporting the developer. The developer may be provided with a collecting screw for collecting the developer from the developing roll and conveying the developer.

In the present invention, as means for increasing the conveying capacity of the upper screw in the pumping portion to be larger than the conveying capacity of the lower screw, for example, the following means can be mentioned. That is, the rotation speed of the upper screw is higher than that of the lower screw,
In this part, the pitch of the upper screw should be larger than the pitch of the lower screw. In this part, the number of the upper screw should be larger than that of the lower screw. In this part, the effective area of the screw blade of the upper screw should be reduced by the lower screw. Larger than the effective area of the screw blade. The present invention also includes a case where the lower screw has no conveying force of the developer in the pumping portion and only the upper screw has the conveying force.

According to another aspect of the present invention, there is provided a developing device comprising: a developing roll; a supply screw for supplying a developer to the developing roll while conveying the developer in an axial direction; A collection screw that collects the developer from the developing roll and transports the developer in the axial direction; and a stirring screw that is disposed above the supply screw and agitates while transporting the developer in the axial direction. In at least one of a first pumping portion where the developer is pumped to the supply screw and a second pumping portion where the developer is pumped from the supply screw to the stirring screw, the transport capability of the upper screw is lower than the transport capability of the lower screw. The first pumping portion is larger than the second pumping portion and the recovery screw is larger. It is identified as being provided on the downstream side in the conveying direction of.

In this developing device, the three functions of stirring the developer, supplying the developer to the developing roller, and collecting the developer from the developing roller are shared by three screws: a stirring screw, a supply screw, and a collecting screw. . Then, the developer is pumped from below to above in the first pumping portion from the collecting screw to the supply screw, and also in the second pumping portion from the supply screw to the stirring screw. Here, since the first pumping portion is provided downstream of the second pumping portion in the transport direction of the recovery screw, the developer may be concentrated on the first pumping portion of the supply screw and hinder the pumping. Absent. Therefore, the developer does not stay in the first pumping portion, the rotational resistance of the screw does not increase, and the developer is not subjected to excessive stress. Therefore, the driving torque required for the screw and the deterioration of the developer ( Adhesion, etc.) are suppressed.

The upper screw is a supply screw in the first pumping section and a stirring screw in the second pumping section. The lower screw is a recovery screw in the first pumping part, and
It is a supply screw in the pumping part. Means for increasing the transport capacity of the upper screw in the first pumping portion or the second pumping portion to be greater than the transport capability of the lower screw include the above-mentioned and the like.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments embodying the present invention will be described below in detail with reference to the drawings. Each embodiment described below is a developing device used for developing an electrostatic latent image formed on a photosensitive drum in an electrophotographic image forming apparatus.

[First Embodiment] As shown in FIG. 1, a developing device 1 according to the present embodiment includes a supply screw 14 and a recovery screw 16 in a developer storage tank 10 for storing a developer. The books are provided in parallel with each other. In each of these, a large number of screw blades are obliquely provided on a rotatable shaft. However, the inclination directions of the respective screw blades are opposite to each other. The shafts of the supply screw 14 and the collection screw 16 are connected by a gear train 28 outside the developer storage tank 10. Further, the shaft of the collection screw 16 is provided with a motor 30 controlled from the main body side of the image forming apparatus. In the gear train 28, the gear 26 of the recovery screw 16 has more teeth than the gear 24 of the supply screw 14. An intermediate gear 25 is provided between the gear 26 and the gear 24. Thus, when the motor 30 is rotated, the supply screw 1
4 and the collection screw 16 are oriented in the same direction, and the supply screw 14 is rotated faster than the collection screw 16.

These two screws are arranged in the vertical direction as shown in the side sectional view of FIG. 2, and the supply screw 14 is located at the upper stage and the recovery screw 16 is located at the lower stage. In addition, the supply screw 14
A developing roll 18 is provided at a height position between the developing screw 18 and the collecting screw 16 with a part thereof protruding from the developer accommodating tank 10. The developing roll 18 is located close to the photosensitive drum 90 of the image forming apparatus, and
The toner is applied to the 0 electrostatic latent image and developed.

A partition 20 is provided between the supply screw 14 and the recovery screw 16. However, the partition wall 20 does not extend over the entire area of the developing device 1 in the width direction (horizontal direction in FIG. 1), and the upper and lower sides communicate with each other on both sides. The upper and lower portions of the partition wall 20 in FIG. 1 communicate with each other at a lower collecting screw 16 as described later.
This is a pumping section 9 where the developer is pumped from the upper side to the supply screw 14.

The operation of the developing device 1 will be described. When the motor 30 is rotated by control from the image forming apparatus main body, the collection screw 16 coaxial with the motor 30 is rotated. The rotation is also transmitted to the supply screw 14 via the gear train 28, and the supply screw 14 rotates in the same direction as the recovery screw 16 at a higher speed. By the rotation of the supply screw 14 and the recovery screw 16,
A conveyance force for the developer in the developer storage tank 10 is generated. However, as described above, the supply screw 14 and the recovery screw 16 have the screw blades whose inclination directions are opposite to each other, so that the developer is also conveyed vertically. In FIG. 1, it is conveyed leftward by the upper supply screw 14 and conveyed rightward by the lower recovery screw 16. The developer transported by the supply screw 14 and reaching the left end portion falls and moves to the lower recovery screw 16. The developer conveyed by the recovery screw 16 and reaching the right end, that is, the pumping portion 9 spills upward and moves to the supply screw 14. Thus, the developer circulates clockwise around the partition 20 in the developer storage tank 10.

Then, with the circulation of the developer, a part of the developer of the upper supply screw 14 is supplied to the developing roll 18. As a result, the developing roll 18 is moved to the photosensitive drum 9.
Thus, development for applying toner to the 0 electrostatic latent image becomes possible. Excess developer on the developing roller 18 is collected by the lower collecting screw 16.

In the circulation of the developer, since the upper supply screw 14 rotates at a higher speed than the lower recovery screw 16, the developer supply capacity of the upper supply screw 14 is stronger. Therefore, in the pumping section 9, the supply screw 14 side is in a slightly negative pressure state. Therefore, the developer conveyed by the collecting screw 16 and having reached the pumping portion 9 is sucked up from above, so that the developer is smoothly pumped from the lower stage to the upper stage against the hindrance of gravity, and the developing is performed. The circulation of the agent is not interrupted. For this reason, the developer does not stay on the lower side of the pumping portion 9 to increase the rotational resistance of the collection screw 16 or apply excessive stress to the developer.

As described in detail above, in the present embodiment, the developing device which supplies and collects the developer to and from the developing roll 18 while circulating the developer by the supply screw 14 and the collection screw 16 arranged vertically. In the above, the upper supply screw 14 is rotated at a higher speed than the lower recovery screw 16 so as to exert a stronger conveying force, so that the developer is pumped from the lower stage to the upper stage. The developer is sucked up, and the pumping of the developer is smoothly performed against the hindrance of gravity. As a result, the developer is prevented from staying in the pumping portion 9, and the required driving torque is not increased due to an increase in the rotational resistance of the collecting screw 16 and the deterioration (adhesion or the like) due to the stress of the developer is not caused. Has been realized.

The present embodiment is merely an example, and does not limit the present invention. Therefore, naturally, the present invention can be variously modified and modified without departing from the gist thereof. For example, the supply screw 14 and the recovery screw 16 may have the same direction of inclination of the screw blades, and the rotation direction may be reversed by changing the gear train 28 instead.

[Second Embodiment] In this embodiment, instead of providing a difference in the rotation speed between the supply screw 14 and the recovery screw 16, a difference is provided between the screw pitches in the pumping section 9 in the vertical direction. In the pumping section 9, the conveying capacity of the upper supply screw 14 is further enhanced.

That is, the developing device 2 according to the present embodiment
3, in the pumping section 9, the pitch a of the upper supply screw 14 is made larger than the pitch b of the lower recovery screw 16 in the pumping portion 9. In addition,
"The pitch of the screw is large" means that the interval between adjacent screw blades is increased by increasing the inclination of the screw blades with respect to the axis (the screw blades and the axis become closer to parallel). Conversely, “small screw pitch” means that the spacing between adjacent screw blades is reduced by weakening the inclination of the screw blades with respect to the axis (the screw blades and the shaft become more vertical). Say. If the pitch of the screw is large, the distance in which the developer is conveyed in the axial direction during one rotation of the screw is long, so that the conveying ability is correspondingly strong.

On the other hand, in the gear train 29 of the developing device 2, the supply screw 14 and the recovery screw 16 have the same rotation speed. Other parts are the first
There is no particular difference from the embodiment.

In the developing device 2, when the motor 30 is rotated under the control of the image forming apparatus main body, the collection screw 16 and the supply screw 14 rotate. As in the case of the first embodiment, the developer in the developer storage tank 10 is circulated, whereby the supply and recovery of the developer to and from the developing roller 18 are performed.

In the circulation of the developer, since the pitch of the upper supply screw 14 is larger than that of the lower recovery screw 16 in the pumping portion 9, the developer supply capacity of the upper supply screw 14 is stronger. Therefore, in the pumping section 9, the supply screw 14 side is in a slightly negative pressure state, and the developer transported by the collecting screw 16 and reaching the pumping section 9 is sucked up from above. Therefore, the pumping of the developer from the lower stage to the upper stage is smoothly performed against the hindrance of gravity,
There is no delay in the circulation of the developer. For this reason, the developer does not stay on the lower side of the pumping portion 9 to increase the rotational resistance of the collection screw 16 or apply excessive stress to the developer.

As described above, in the present embodiment, the pitch of the upper and lower screws is made different in the pumping portion 9 so that the upper supply screw 14 exerts a stronger conveying force than the lower recovery screw 16. The developer is sucked up to the upper side at the pumping section 9 where the developer is pumped from the upper part to the upper part, and the developer is smoothly drawn up against the hindrance of gravity. This prevents the developer from staying in the pumping section 9 and increases the necessary driving torque due to an increase in the rotational resistance of the collecting screw 16 and prevents the deterioration (adhesion, etc.) of the developing device 2 caused by the developer stress. Has been realized. Note that the present embodiment is merely an example and does not limit the present invention in any way. Therefore, naturally, the present invention can be variously modified and modified without departing from the gist thereof.

[Third Embodiment] In this embodiment, instead of providing a difference in the rotational speed between the supply screw 14 and the recovery screw 16, a difference is provided between the number of screws in the pumping portion 9 in the vertical direction. As a result, the conveying capacity of the upper supply screw 14 in the pumping portion 9 is further enhanced. That is, in the developing device 3 according to the present embodiment, as shown in FIG. 4, in the pumping portion 9, two screw blades are provided in the upper supply screw 14. On the other hand, the lower recovery screw 16 has only one screw blade. If the number of screws is large, the developer is conveyed by the screw blades in many places, so that the conveying ability is correspondingly strong. On the other hand, the gear train 29 of the developing device 3 has the same rotation speed for the supply screw 14 and the recovery screw 16 as in the case of the above-described second embodiment. Other parts are not particularly different from those of the above-described embodiments.

In the developing device 3 as well, when the motor 30 is rotated under the control of the image forming apparatus main body, the collecting screw 16 and the supplying screw 14 rotate. As in the first and second embodiments, the developer in the developer storage tank 10 is circulated, whereby the supply and recovery of the developer to and from the developing roller 18 are performed.

In the circulation of the developer, since the number of the upper supply screw 14 in the pumping section 9 is larger than that of the lower recovery screw 16, the developer supply capacity of the upper supply screw 14 is stronger. For this reason, in the pumping section 9, the supply screw 14 side is in a slightly negative pressure state as in the above-described embodiments, and is conveyed by the recovery screw 16 to be pumped.
Is reached from above. Therefore, the pumping of the developer from the lower stage to the upper stage is smoothly performed against the hindrance of gravity, and the circulation of the developer is not interrupted. For this reason, the developer does not stay on the lower side of the pumping portion 9 to increase the rotational resistance of the collection screw 16 or apply excessive stress to the developer.

As described above, in the present embodiment, the number of the upper and lower screws is different in the pumping portion 9 so that the upper supply screw 14 exerts a stronger conveying force than the lower recovery screw 16. The developer is sucked up to the upper stage at the pumping section 9 where the developer is pumped from the lower stage to the upper stage, and the developer is smoothly pumped up against the hindrance of gravity. As a result, the developer is prevented from staying in the pumping portion 9, and the required driving torque is not increased due to an increase in the rotational resistance of the collecting screw 16 and the deterioration (adhesion or the like) due to the stress of the developer is not caused. Has been realized. Note that the present embodiment is merely an example and does not limit the present invention in any way. Therefore, naturally, the present invention can be variously modified and modified without departing from the gist thereof.

[Fourth Embodiment] In this embodiment, by providing a vertical difference in the effective area of the screw blades in the pumping section 9, the conveying capacity of the upper supply screw 14 in the pumping section 9 is increased. It is to become. That is, in the developing device according to the present embodiment, a screw blade having a small effective area as shown in any of FIGS. FIG. 6 shows the effective area reduced by reducing the central angle of the screw blade. FIG. 7 shows a screw blade in which a notch is provided to reduce the effective area. FIG. 8 shows an example in which the effective area is reduced by reducing the outer diameter of the screw blade. FIG. 9 shows that
The effective area is reduced by increasing the shaft diameter of the screw. On the other hand, a screw blade having a large effective area as shown in FIG. 5 is used for the upper supply screw 14.

On the other hand, as for the gear train 29, the rotation speeds of the supply screw 14 and the recovery screw 16 are the same as in the second and third embodiments described above. Other parts are not particularly different from those of the above-described embodiments.

Also in this developing device, when the motor 30 is rotated under the control of the image forming apparatus main body, the collecting screw 16 and the supplying screw 14 rotate. As in the case of the embodiment, the developer in the developer storage tank 10 is circulated so that the developing roller 1
The supply and recovery of the developer to and from the developer 8 are performed.

In this circulation of the developer, the upper supply screw 14 has a larger effective area of the screw blades in the pumping section 9 than the lower recovery screw 16. Stronger. For this reason, in the pumping section 9, as in the above-described embodiments, the supply screw 14 side is in a slightly negative pressure state, and the developer conveyed by the recovery screw 16 and reaching the pumping section 9 is sucked up from above. Will be. Therefore, the pumping of the developer from the lower stage to the upper stage is smoothly performed against the hindrance of gravity, and the circulation of the developer is not interrupted. For this reason, the developer stays on the lower side of the pumping portion 9 and the collecting screw 1
No increase in rotational resistance and no excessive stress on the developer.

As described above, in the present embodiment, the effective area of the upper and lower screw blades is made different in the pumping portion 9 so that the upper supply screw 14 exerts a stronger conveying force than the lower recovery screw 16. , A pumping portion 9 where the developer is pumped from the lower stage to the upper stage
The developer is sucked up to the upper side, and the pumping of the developer is smoothly performed against the hindrance of gravity. Thereby, the stagnation of the developer in the pumping portion 9 is prevented,
The required driving torque increases due to an increase in the rotational resistance of the recovery screw 16 and the deterioration due to the stress of the developer (adhesion etc.)
An excellent developing device 3 that does not cause the problem is realized.

The present embodiment is merely an example, and does not limit the present invention. Therefore, naturally, the present invention can be variously modified and modified without departing from the gist thereof. For example, in the description of FIGS. 5 to 9, the center angle, outer diameter, shaft diameter, and the like of the screw blade are set as a means for making the effective area of the lower screw blade smaller than the effective area of the upper screw blade. Although it is used, conversely, it may be used as a means for increasing the effective area of the upper screw blade based on the effective area of the lower screw blade.

[Fifth Embodiment] In the present embodiment, the lower collecting screw 16 in the pumping section 9 has no transfer capability. That is, in the developing device 5 according to the present embodiment, as shown in FIG.
In the pumping section 9, the lower recovery screw 16 is provided with blades 17 parallel to the axis instead of the screw blades. Alternatively, as shown in FIG. 11, no blade may be provided at the lower recovery screw 16 in the pumping section 9. On the other hand, the upper supply screw 14 is provided with a screw blade. Therefore, in the pumping section 9, only the upper supply screw 14 has a transfer capability, and the lower recovery screw 16 has no transfer capability.

In the gear train 29, the supply screw 14 and the recovery screw 16 have the same rotational speed as in the second to fourth embodiments. Other parts are not particularly different from those of the above-described embodiments.

In the developing device 5, when the motor 30 is rotated under the control of the image forming apparatus main body, the collection screw 16 and the supply screw 14 are rotated, and the supply screw 14 and the collection screw 16 are rotated. As in the case of each embodiment, the developer in the developer storage tank 10 is circulated, whereby the developing roller 1
The supply and recovery of the developer to and from the developer 8 are performed.

In the circulation of the developer, only the upper supply screw 14 has the ability to transport the developer in the pumping section 9 and has no transport ability in the lower recovery screw 16. As in the above-described embodiments, the supply screw 14 has a slightly negative pressure, and the developer that has been conveyed by the recovery screw 16 and has reached the pumping portion 9 is sucked up from above. Therefore, the pumping of the developer from the lower stage to the upper stage is smoothly performed against the hindrance of gravity, and the circulation of the developer is not interrupted. For this reason, the developer stays on the lower side of the pumping portion 9 and the collecting screw 1
No increase in rotational resistance and no excessive stress on the developer.

As described above, in the present embodiment, only the upper supply screw 14 exerts the developer conveying force in the pumping section 9, so that the pumping section in which the developer is pumped from the lower stage to the upper stage is performed. At 9, the developer is sucked up to the upper side, and the pumping of the developer is performed smoothly against the hindrance of gravity. As a result, the developer is prevented from staying in the pumping portion 9, and the required driving torque is not increased due to an increase in the rotational resistance of the collecting screw 16 and the deterioration (adhesion or the like) due to the stress of the developer is not caused. Has been realized. Note that the present embodiment is merely an example and does not limit the present invention in any way. Therefore, naturally, the present invention can be variously modified and modified without departing from the gist thereof.

[Sixth Embodiment] As shown in FIG. 12, a developing device 6 according to the present embodiment
4, a collection screw 16 and a stirring screw 12 are provided in parallel with each other. These three are arranged in the vertical direction. That is, the stirring screw 12 is located at the top, the recovery screw 16 is located at the bottom, and the supply screw 14 is located at the middle. Each screw receives rotational drive from a motor outside the tank and is controlled from the main body side of the image forming apparatus, as in the above-described embodiments.
In addition, the feeding direction of the developer by each screw is such that the supply screw 14 and the recovery screw 16 are rightward in the drawing, and the stirring screw 12 is leftward in the drawing.

In the first pumping portion 9A where the developer is pumped from the recovery screw 16 to the supply screw 14, the lower recovery screw 16 is provided with a small-diameter screw blade as shown in FIG. I have. Thus, in this portion, the upper supply screw 14 exerts a greater conveying force than the lower recovery screw 16. In addition, the supply screw 14
In the second pumping section 9B where the developer is pumped from the hopper to the stirring screw 12, a small diameter screw blade is provided in the lower supply screw. As a result, the upper stirring screw 12
Exerts a greater conveying force than the lower supply screw 14.

In the developing device 6, in the first pumping section 9A and the second pumping section 9B where the developer is pumped, the conveying force of the upper screw is stronger than the conveying force of the lower screw. As in the case of (1), the upper screw side is in a slightly negative pressure state, and is conveyed by the lower screw to each of the pumping portions 9.
The developer that has reached A and 9B is sucked up from above. Therefore, the pumping of the developer from the lower stage to the upper stage is smoothly performed against the hindrance of gravity, and the circulation of the developer is not interrupted. Therefore, each pumping part 9
The developer does not stay on the lower side of A and 9B, so that the rotational resistance of the screw does not increase, and no excessive stress is applied to the developer.

As described above, according to the present embodiment, the upper screw exerts a stronger conveying force than the lower screw in each of the pumping portions 9A and 9B.
At each of the pumping portions 9A and 9B where the developer is pumped from the lower stage to the upper stage, the developer is sucked to the upper stage side,
The developer is smoothly pumped up against the hindrance of gravity. This prevents the developer from staying in each of the pumping portions 9A and 9B, and increases the necessary driving torque due to an increase in the rotational resistance of the screw and prevents deterioration (adhesion, etc.) due to the stress of the developer. Of the developing device 6 is realized.

The present embodiment is merely an example, and does not limit the present invention. Therefore, naturally, the present invention can be variously modified and modified without departing from the gist thereof. For example, each pumping part 9A,
In 9B, the means for providing a difference in the conveying force between the upper and lower screws is not limited to the diameter of the screw, but may be any of those described in the first to fifth embodiments. Further, of these, different means may be employed for the first pumping portion 9A and the second pumping portion 9B.

[Seventh Embodiment] As shown in FIG. 13, a developing device 7 according to the present embodiment
The sixth embodiment is common to the sixth embodiment in that it has a three-axis configuration in which three screws 4, a collection screw 16 and a stirring screw 12 are arranged in the vertical direction. However, in the developing device 7, the supply screw 1
First pumping portion 9 where developer is pumped to 4
A is the transport direction of the collection screw 16 (rightward in FIG. 13) from the second pumping portion 9B where the developer is pumped from the supply screw 14 to the stirring screw 12.
And located downstream. Therefore, the screw blade of the supply screw 14 in the first pumping portion 9A is turned in the opposite direction.

In the first pumping portion 9A where the developer is pumped from the recovery screw 16 to the supply screw 14, the number of the lower recovery screw 16 is reduced. Thus, in this portion, the upper supply screw 14 exerts a greater conveying force than the lower recovery screw 16. In the second pumping portion 9B where the developer is pumped from the supply screw 14 to the stirring screw 12,
The number of the lower supply screw 14 is reduced. As a result, the upper stirring screw 12
Exerts a greater conveying force than the lower supply screw 14.

In the developing device 7, in the first pumping section 9A and the second pumping section 9B where the developer is pumped, the conveying force of the upper screw is stronger than the conveying force of the lower screw. As in the case of (1), the upper screw side is in a slightly negative pressure state, and is conveyed by the lower screw to each of the pumping portions 9.
The developer that has reached A and 9B is sucked up from above. In particular, the developer conveyed rightward in FIG. 13 by the supply screw 14 is the second pumping portion 9B
Is pumped up by the stirring screw 12 above,
It does not reach the first pumping portion 9A. Therefore, the first
The developer is not concentrated on the upper supply screw 14 in the pumping portion 9A, and the pumping of the developer is further smoothed. Therefore, the pumping of the developer from the lower stage to the upper stage is smoothly performed against the hindrance of gravity, and the circulation of the developer is not interrupted. Therefore, the developer does not stay on the lower side of each of the pumping portions 9A and 9B, so that the rotational resistance of the screw does not increase and the developer does not receive excessive stress.

As described above, according to the present embodiment, in each pumping portion 9A, 9B, the upper screw exerts a stronger conveying force than the lower screw.
At each of the pumping portions 9A and 9B where the developer is pumped from the lower stage to the upper stage, the developer is sucked toward the upper stage. Further, the first pumping portion 9A is replaced with the second pumping portion 9A.
Since it is arranged downstream of B in the transport direction of the collection screw 16, the concentration of the developer on the upper side of the first pumping portion 9A is eliminated. For this reason, the developer is smoothly pumped up against the hindrance of gravity. This gives
An excellent three-axis developing device that prevents the developer from staying in each of the pumping portions 9A and 9B and prevents the required driving torque from increasing due to an increase in the rotational resistance of the screw and deterioration (adhesion, etc.) due to the stress of the developer. 7 is realized.

The present embodiment is merely an example, and does not limit the present invention. Therefore, naturally, the present invention can be variously modified and modified without departing from the gist thereof. For example, each pumping part 9A,
In 9B, the means for providing a difference in the conveying force between the upper and lower screws is not limited to the number of screws, but may be any of the above-described first to fifth screws.
May be described in any of the embodiments. Also,
Of these, different means may be employed for the first pumping portion 9A and the second pumping portion 9B.

[0052]

As is apparent from the above description, according to the present invention, the conveying capacity of the upper screw is made larger than the conveying capacity of the lower screw in the developer pumping portion. There has been proposed a developing device in which the developer is smoothly pumped to the developer and the driving torque required for the screw and the stress applied to the developer are reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a developing device according to a first embodiment.

FIG. 2 is a side sectional view of the developing device in FIG. 1;

FIG. 3 is a diagram illustrating a configuration of a developing device according to a second embodiment.

FIG. 4 is a diagram illustrating a configuration of a developing device according to a third embodiment.

FIG. 5 is a diagram showing an example of the shape of a screw blade.

FIG. 6 is a diagram illustrating an example of a shape of a screw blade.

FIG. 7 is a diagram illustrating an example of a shape of a screw blade.

FIG. 8 is a diagram showing an example of the shape of a screw blade.

FIG. 9 is a diagram showing an example of the shape of a screw blade.

FIG. 10 is a diagram illustrating a configuration of a developing device according to a fifth embodiment.

FIG. 11 is a diagram illustrating a configuration of a modification of the developing device according to the fifth embodiment.

FIG. 12 is a diagram illustrating a configuration of a developing device according to a sixth embodiment.

FIG. 13 is a diagram illustrating a configuration of a developing device according to a seventh embodiment.

FIG. 14 is a diagram illustrating a configuration of a conventional developing device.

[Explanation of symbols]

 9 Pumping Part 9A First Pumping Part 9B Second Pumping Part 12 Stirring Screw 14 Supply Screw 16 Recovery Screw 18 Developing Roll

Claims (6)

[Claims] A lower screw for transporting the developer in the axial direction; and an upper screw disposed above the lower screw and for transporting the developer in the axial direction. A developing device, wherein a conveying capacity of the upper screw at a pumping portion where the developer is pumped is larger than a conveying capability of the lower screw at the pumping portion. 2. The developing device according to claim 1, wherein
The rotation speed of the upper screw is higher than the rotation speed of the lower screw. 3. The developing device according to claim 1, wherein
A pitch of the upper screw in the pumping portion is larger than a pitch of the lower screw in the portion. 4. The developing device according to claim 1, wherein
2. The developing device according to claim 1, wherein the number of the upper screws in the pumping portion is larger than the number of the lower screws in the portion. 5. The developing device according to claim 1, wherein
The effective area of the screw blade of the upper screw in the pumping portion is larger than the effective area of the screw blade of the lower screw in the portion. 6. A developing roll, a supply screw that supplies the developer to the developing roll while transporting the developer in the axial direction, and is disposed below the supply screw and collects the developer from the developing roll to move in the axial direction. And a stirring screw disposed above the supply screw and agitating the developer while transporting the developer in the axial direction. The first screw from which the developer is pumped from the recovery screw to the supply screw is provided. In at least one of a pumping section and a second pumping section in which the developer is pumped from the supply screw to the stirring screw, the conveying capacity of the upper screw is larger than the conveying capacity of the lower screw, and the first pumping section is the first pumping section. 2
A developing device is provided downstream of a pumping portion in a conveying direction of the collecting screw.