JPH11119549A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device by which the occurrence of fogging on an image and toner smoke are prevented by suppressing the occurrence of blowing-up and blowing-down of the developer. SOLUTION: As for the developing device making the developer circulate by a supply screw 14 and a recovering screw 16 arranged up and down; the recovering screw 16 generates larger pressure in a normal direction than the supply screw 14. Thus, the blowing-down of the developer by which the developer fed by the supply screw 14 is moved to the recovering screw 16 while being fed is prevented. Thus, since the developer is sufficiently stirred during toner is replenished at a toner replenishing port 40 and is supplied to a developing roller 18, the developer which is sufficiently stirred and where the toner is uniformly dispersed is supplied to the developing roller 18, so that the occurrences of the fogging on the image and the toner smoke are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an electrophotographic image forming apparatus such as a copying machine or a printer. In more detail, the developer being conveyed by each screw arranged vertically is suppressed from moving to another screw during the conveyance, so that the developer can be sufficiently stirred, so that the fog on the image The present invention relates to a developing device that prevents generation of toner smoke.

[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. 10, the 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 in the direction of the arrow, the developer is supplied to a developer carrier (developing roller) 87 provided adjacent to the auger 82, and the electrostatic latent image on the photoconductor is developed through the developer. . 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.

[0003]

However, in the above-mentioned conventional developing device, the upper auger 82 and the lower auger 85 rotate in the same shape and at the same rotational speed, so that the upper auger 82 is rotated. Gives the lower auger 85 the same pressure as the lower auger 85 applies to the upper auger 82. For this reason, the developer moves to the lower auger 85 while being conveyed by the upper auger 82 due to gravity. When the developer rolls down, the newly supplied toner is supplied to the developer carrier (developing roller) 87 in an insufficiently charged state without being sufficiently stirred by the upper auger 82. In some cases, fogging and toner fumes occurred on the image.

Accordingly, the present invention has been made to solve the above-mentioned problems, and it is possible to prevent the developer from rolling down and prevent fogging and toner fumes on an image. It is an object to provide a developing device.

[0005]

According to the present invention, there is provided a developing device comprising: a first screw for conveying a developer in an axial direction; a first screw disposed above the first screw; A second screw that conveys the developer in the axial direction, wherein a normal component of pressure generated by rotation of the first screw is larger than a normal component of pressure generated by rotation of the second screw. It is characterized by the following.

In this developing device, the developer is transported by the first and second screws. Thus, the developer is stirred while being circulated. In the circulation of the developer,
Supply and recovery of the developer to the developing roller are performed. Here, since the first screw generates a greater pressure in the normal direction than the second screw, the developer being conveyed to the second screw does not move to the first screw during the conveyance. Therefore, the developer does not roll down. Therefore, when the toner is newly supplied, the newly supplied toner is sufficiently stirred, and then the developer is supplied to the developing roller. As a result, the occurrence of fogging and toner fumes on the image is suppressed.

In the present invention, means for making the normal component of the pressure generated by the rotation of the first screw larger than the normal component of the pressure generated by the rotation of the other screw include, for example, the following: Things. That is, the rotation speed of the first screw is higher than the rotation speed of the other screws, the pitch of the first screw is smaller than the pitch of the other screws, and the number of the first screws is greater than the number of the other screws. More, providing paddles on the first screw, and so on. Here, the paddle of the screw refers to a paddle without applying a conveying force (axial pressure) to the developer.
This member applies pressure only in a direction (normal direction) perpendicular to the transport direction.

According to another aspect of the present invention, there is provided a developing device including a developing roller, a first screw that supplies the developer to the developing roller while conveying the developer in the axial direction, and is disposed below the first screw. A second screw that collects developer from the developing roller and transports the developer in the axial direction; and a third screw that is disposed above the first screw and transports the developer in the axial direction. A normal component of pressure generated by rotation of one screw is larger than a normal component of pressure generated by rotation of the second and third screws.

In this developing device, three functions of stirring the developer, supplying the developer to the developing roller, and recovering the developer from the developing roller are shared by three screws of a third screw, a first screw, and a second screw. Have been. The third screw generated during the conveyance of the developer by each screw is used.
It is necessary to prevent movement of the developer from the screw to the first screw (winding) and movement from the second screw to the first screw (winding). When the curling occurs, the developer is supplied to the developing roller in a state where the toner is not sufficiently stirred, and when the curling occurs, the collected developer is directly supplied to the developing roller. This is because it causes fogging on the image and toner fumes. Thus, the first screw generates a greater normal pressure as compared to the second and third screws, so that the developer drops from the third screw to the first screw, and
The developer is prevented from winding up from the screw to the first screw. Therefore, when the toner is newly supplied, the newly supplied toner is sufficiently stirred by the third screw, and then the developer is supplied to the developing roller. Further, the collected developer is not supplied to the developing roller as it is. As a result, the occurrence of fogging and toner fumes on the image is suppressed.

Means for making the normal component of the pressure generated by the rotation of the first screw larger than the normal component of the pressure generated by the rotation of the other screw include the above-mentioned methods.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a developing device according to an embodiment of the present invention. The present embodiment is a developing device used for developing an electrostatic latent image formed on a photosensitive drum in an electrophotographic image forming apparatus.

First, a first embodiment will be described. As shown in FIG. 1, a developing device 1 according to the present embodiment has a supply container 14 for storing a developer and a supply screw 14 and a collection screw 16 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 directions of inclination of the respective screw blades are opposite to each other. The shafts of the supply screw 14 and the recovery screw 16 are connected by a gear train 28 outside the developer container 10. Further, a motor 30 controlled from the main body side of the image forming apparatus is provided on the shaft of the collection screw 16. Gear train 2
At 8, the gear 26 of the collection 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 14 and the collection screw 16 are oriented in the same direction, and the supply screw 14 is rotated faster than the collection screw 16. Further, the toner supply port 4 is located upstream of the supply screw 14 (right side in FIG. 1).
0 is provided, from which toner is supplied into the developer storage tank 10.

The two screws are arranged in a vertical direction as shown in a side sectional view of FIG. 2, and a supply screw 14 is located at an upper stage and a recovery screw 16 is located at a lower stage. In addition, the supply screw 14
A developing roller 18 is provided at a height position between the developing roller 18 and the collecting screw 16 with a part thereof protruding from the developer storage tank 10. The developing roller 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.

The operation of the developing device 1 will be described. When the motor 30 is rotated under the control of 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 also rotates in the same direction as the recovery screw 16 at a lower speed than the recovery screw 16. By the rotation of the supply screw 14 and the recovery screw 16, a conveying force for the developer in the developer storage tank 10 is generated. However, as described above, supply screw 1
Since the inclination of the screw blades is opposite between 4 and the recovery screw 16, the direction of transport of the developer is also upside down. In FIG. 1, the paper is conveyed leftward by the supply screw 14 in the upper stage, and conveyed rightward by the recovery screw 16 in the lower stage. 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 collection screw 16 and reaching the right end portion overflows upward and moves to the supply screw 14. Thus, the developer circulates counterclockwise 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 roller 18. As a result, the developing roller 18 moves 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 recovery screw 16 is rotating at a higher speed than the supply screw 14, the recovery screw 16 also has a larger normal component of the pressure generated by the rotation of the screw. Therefore, the developer that is being agitated while being conveyed by the supply screw 14 does not move to the collection screw 16 during the conveyance, so that the developer does not fall down. For this reason, the developer is sufficiently stirred between the time when the toner is supplied at the toner supply port 40 and the time when the toner is supplied to the developing roller 18. Therefore, the developer in which the toner is sufficiently stirred and the toner is uniformly dispersed is supplied to the developing roller 18.

As described above in detail, in the present embodiment, the developing device which supplies and collects the developer to and from the developing roller 18 while circulating the developer by the supply screw 14 and the collection screw 16 disposed vertically. In the above, the recovery screw 16 is rotated at a higher speed than the supply screw 14 to generate a larger pressure in the normal direction, so that the developer transported by the supply screw 14 moves to the recovery screw 16 during the transportation. The developer can be prevented from rolling down. As a result, the toner supplied from the toner supply port 40 is sufficiently stirred, and then the developer is supplied to the developing roller 18, so that fogging on the image and toner fumes can be suppressed.

The present embodiment is merely an example, and does not limit the present invention. Therefore, of course, the present invention provides various improvements without departing from the gist thereof.
Deformation is possible. For example, the supply screw 14 and the recovery screw 16 may have the same direction of inclination of the screw blades, and instead, the gear train 28 may be changed so that the rotation direction is reversed.

Next, a second embodiment will be described. The developing device according to the present embodiment includes a supply screw 1
Instead of making a difference between the rotation speed of the recovery screw 4 and the rotation speed of the recovery screw 16, a vertical component is provided in the pitch of the screw so that the component of the pressure generated by the recovery screw 16 in the normal direction becomes larger. .

That is, in the developing device according to the present embodiment, the pitch b of the collecting screw 16 shown in FIG.
The pitch a of the supply screw 14 shown in FIG. In addition, "the pitch of the screw is small" means that the interval between the adjacent screw blades is reduced by weakening the inclination of the screw blades with respect to the axis (the screw blades and the axis approach more perpendicularly). Say. Conversely, “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). Say. If the pitch of the screw is small, the distance that the developer is conveyed in the axial direction during one rotation of the screw becomes shorter,
The pressure component generated by the rotation of the screw has a small axial component and a large normal component.

On the other hand, in the gear train 29 of the developing device, the rotation speeds of the supply screw 14 and the recovery screw 16 are the same. The other parts are not particularly different from those of the first embodiment.

In such a developing device, 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, the pitch of the collection screw 16 is smaller than that of the supply screw 14.
The normal component of the pressure generated by the rotation of the screw is larger in the recovery screw 16. Therefore, the developer being transported and agitated while being transported by the supply screw does not move to the recovery screw 16 during the transport, so that the developer does not fall down. Therefore, after the toner is supplied at the toner supply port 40, the developing roller 1
In the meantime, the developer is sufficiently stirred. Therefore, the developer in which the toner is sufficiently stirred and the toner is uniformly dispersed is supplied to the developing roller 18.

As described above, in the present embodiment, the pitch of the upper and lower screws is differentiated so that the recovery screw 16 generates a pressure in the normal direction larger than the supply screw 14. It is possible to prevent the developer that has been transported to the collection screw 16 during transportation from falling down. As a result, the toner supplied from the toner supply port 40 is sufficiently stirred, and then the developer is supplied to the developing roller 18, so that fogging on the image and toner fumes can be suppressed. 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.

Next, a third embodiment will be described. The developing device according to the present embodiment includes a supply screw 1
Instead of making a difference between the rotation speeds of the screw 4 and the collecting screw 16, a vertical difference is provided in the number of threads of the screw, so that the normal component of the pressure generated by the collecting screw 16 becomes larger. is there. That is, in the developing device according to the present embodiment, as shown in FIG. 6, the collection screw 16 is provided with two screw blades. On the other hand, the supply screw 14 is provided with only one screw blade as shown in FIG. When the number of screw threads is large, the developer receives a force from more screw blades, and therefore, the pressure, which is a force acting per unit area, also increases. On the other hand, the gear train 29 of the developing device
As in the second embodiment, the supply screw 14 and the recovery screw 16 have the same rotation speed as in the second embodiment. Other parts are not particularly different from those of the above-described embodiments.

In this developing device, when the motor 30 is rotated under the control of the main body of the image forming apparatus, the collecting screw 16 and the supplying screw 14 are rotated. 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 recovery screw 16 is larger than that of the supply screw 14, the normal component of the pressure generated by the rotation of the screw is larger in the recovery screw 16. Therefore, the developer that is being agitated while being conveyed by the supply screw 14 does not move to the collection screw 16 during the conveyance, so that the developer does not fall down. Therefore, after the toner is supplied at the toner supply port 40, the developing roller 18
The developer is sufficiently agitated until the developer is supplied.
Therefore, the developer in which the toner is sufficiently stirred and the toner is uniformly dispersed is supplied to the developing roller 18.

As described above, in this embodiment, the number of the upper and lower screws is different so that the recovery screw 16 generates a pressure in the normal direction larger than the supply screw 14. It is possible to prevent the developer that has been transported to the collection screw 16 during transportation from falling down. This allows
After the toner supplied from the toner supply port 40 is sufficiently stirred, the developer is supplied to the developing roller 18.
It is possible to suppress the occurrence of fog and toner fumes on the image. Note that the present embodiment is merely an example and does not limit the present invention in any way. Therefore, the present invention is, of course,
Various improvements and modifications can be made without departing from the spirit of the invention.

Next, a fourth embodiment will be described. The developing device according to the present embodiment includes a supply screw 1
Instead of providing a difference between the rotation speeds of the recovery screw 4 and the recovery screw 16, a paddle is provided on the recovery screw 16 so that the component of the pressure generated by the recovery screw 16 in the normal direction becomes larger. That is, in the developing device according to the present embodiment, a screw blade having a paddle as shown in FIG. On the other hand, as shown in FIG. 7, a screw blade without a paddle is used for the supply screw 14. In the present embodiment, the supply screw 1
4 has no paddle, but if it is smaller than the paddle area of the recovery screw 16, the supply screw 1
4 may be provided with paddles.

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. Other parts are not particularly different from those of the above-described embodiments.

In this developing device 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 are rotated. 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 the circulation of the developer, since the collecting screw 16 has a paddle, the component of the pressure generated by the rotation of the screw in the normal direction is the collecting screw 16.
Is larger. Therefore, the developer that is being agitated while being conveyed by the supply screw 14 does not move to the collection screw 16 during the conveyance, so that the developer does not fall down. For this reason, the developer is sufficiently stirred between the time when the toner is supplied at the toner supply port 40 and the time when the toner is supplied to the developing roller 18. Therefore, the developer in which the toner is sufficiently stirred and the toner is uniformly dispersed is transferred to the developing roller 18.
Supplied to

As described above, in the present embodiment, the recovery screw 16 is padded, and the recovery screw 16 generates a pressure in the normal direction larger than the supply screw 14. It is possible to prevent the developer that moves to the collection screw 16 during transportation from falling down. As a result, the toner supplied from the toner supply port 40 is sufficiently stirred, and then the developer is supplied to the developing roller 18, so that fogging on the image and toner fumes can be suppressed. 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.

Next, a fifth embodiment will be described. As shown in FIG. 9, the developing device 2 according to the present embodiment is provided with three supply screws 26, a collection screw 22, and a stirring screw 24 in parallel with each other. The supply screw 26 is the same as the recovery screw 16 in the second embodiment shown in FIG. Further, the stirring screw 24 is the same as the supply screw 14 in the second embodiment shown in FIG. Further, the recovery screw 22 is obtained by reversing the inclination of the screw blades of the supply screw 14 in the second embodiment shown in FIG. These three are arranged in the vertical direction. That is, the stirring screw 24 is located at the top, the recovery screw 22 is located at the bottom, and the supply screw 26 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. As for the direction of transport of the developer by each screw, the supply screw 26 and the recovery screw 22 are directed rightward in the drawing, and the stirring screw 24 is directed leftward in the drawing.

The pitch b of the supply screw 26 is smaller than the pitch a of the stirring screw 24 and the recovery screw 22. As a result, the component in the normal direction of the pressure generated by the supply screw 26 is maximized. In the present embodiment, the pitches of the stirring screw 24 and the collecting screw 22 are equal, but these pitches may be different as long as the pitch is larger than the pitch b of the supply screw 26.

In the developing device 2, the supply screw 26
Is greater than the normal component of the pressure generated by the stirring screw 24 and the recovery screw 22. Therefore, as in the above-described embodiments, the developer is transferred between the screws during conveyance. Will not move. Therefore, the developer agitated by the stirring screw 24 does not move to the supply screw 26 during the conveyance, so that the developer does not roll down. To
The developer does not move to the supply screw 26 and the developer does not roll up. Therefore, the toner supply port 40
The developer is sufficiently agitated between the time when the toner is supplied and the time when the toner is supplied to the developing roller 18. The developer recovered by the recovery screw 22 is supplied to the supply screw 2.
6 is not supplied to the developing roller 18 as it is.

As described above, according to the present embodiment, the supply screw 26 generates a pressure in the normal direction larger than the stirring screw 24 and the recovery screw 22. Of the developer moving to the supply screw 26 during the conveyance, and curling of the developer moving to the supply screw 26 during the conveyance of the developer being conveyed by the collection screw 22 can be prevented. As a result, the toner supplied from the toner supply port 40 is sufficiently stirred, and then the developer is supplied to the developing roller 18, while the developer recovered by the recovery screw 22 is directly supplied to the developing roller 18. Therefore, the occurrence of fogging and toner fumes on the image can be suppressed.

The present embodiment is merely an example, and does not limit the present invention. Therefore, of course, the present invention provides various improvements without departing from the gist thereof.
Deformation is possible. For example, the means for giving a pressure difference in the normal direction between the supply screw 26, the stirring screw 24, and the recovery screw 22 is not limited to the pitch of the screws, but may be any of the first to fourth embodiments. May be done. Among these, different means may be employed between the supply screw 26 and the stirring screw 24 and between the supply screw 26 and the recovery screw 22.

[0039]

As described above, according to the developing device of the present invention, the normal component of the pressure generated by the first screw is made larger than the normal component of the pressure generated by the other screws. The developer conveyed by one screw moves to another screw during conveyance, and the developer does not roll down (and curl up). As a result, the developer is supplied to the developing roller after the supplied toner is sufficiently stirred by the first screw, so that it is possible to suppress the occurrence of fogging and toner fumes on the image.

[Brief description of the drawings]

FIG. 1 is a plan cross-sectional view 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 shape of a screw blade of a supply screw in a developing device according to a second embodiment and a shape of a screw blade of a stirring screw in a developing device according to a fifth embodiment.

FIG. 4 is a diagram illustrating a shape of a screw blade of a recovery screw in a developing device according to a second embodiment and a shape of a screw blade of a supply screw in the developing device according to a fifth embodiment;

FIG. 5 is a diagram illustrating a shape of a screw blade of a supply screw in a developing device according to a third embodiment.

FIG. 6 is a diagram illustrating a shape of a screw blade of a recovery screw in a developing device according to a third embodiment.

FIG. 7 is a diagram illustrating a shape of a screw blade of a supply screw in a developing device according to a fourth embodiment.

FIG. 8 is a diagram illustrating a shape of a screw blade of a recovery screw in a developing device according to a fourth embodiment.

FIG. 9 is a plan cross-sectional view illustrating a configuration of a developing device according to a fifth embodiment.

FIG. 10 is a diagram illustrating a configuration of a conventional developing device.

[Explanation of symbols]

 14, 26 Supply screw 16, 22 Recovery screw 18 Developing roller 24 Stirring screw 40 Toner supply unit 90 Photoconductor drum

Claims (6)

[Claims] A first screw that conveys the developer in the axial direction; and a second screw that is disposed above the first screw and conveys the developer in the axial direction. A developing device, wherein a normal component of pressure generated by rotation is larger than a normal component of pressure generated by rotation of the second screw. 2. A developing roller, a first screw that supplies the developer to the developing roller while conveying the developer in the axial direction, and is disposed below the first screw and collects the developer from the developing roller. Second transporting in the axial direction
A third screw that is disposed above the first screw and that conveys the developer in the axial direction, wherein a normal component of pressure generated by rotation of the first screw is the second component. And a pressure component generated by rotation of the third screw is larger than a normal component. 3. The developing device according to claim 1, wherein a rotation speed of the first screw is higher than a rotation speed of another screw. 4. The developing device according to claim 1, wherein a pitch of the first screw is smaller than a pitch of another screw. 5. The developing device according to claim 1, wherein the number of the first screw is greater than the number of the other screws. 6. The developing device according to claim 1, wherein at least the first screw is provided with a paddle, and even if another screw is provided with a paddle, the area of the first screw is smaller than that of the first screw. A developing device characterized in that the area is smaller than a paddle area of the screw.