JP2972598B2 - 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,
In particular, the present invention relates to a developing device that develops using an electrophotographic process.

[0002]

2. Description of the Related Art A conventional image forming apparatus using an electrophotographic process such as a copying machine, a facsimile, an electrophotographic apparatus, or an electrostatic printer is known. As shown in FIG. 3, the image forming apparatus includes a photosensitive drum 11 and a developing device 12 for attaching toner to an electrostatic latent image formed on the surface of the photosensitive drum 11 and developing the electrostatic latent image.

[0005] The developing device 12 includes a toner storage chamber 16 and a developing chamber 18 which are adjacent to each other. Toner storage room 1
The partition plate between the developing chamber 6 and the developing chamber 18 is formed with a communication port 14 for communicating the two. Inside the toner storage chamber 16, there is provided a toner mixer 20 which rotates in the clockwise direction in the figure and sends out the toner 13 from the communication port 14 to the developing chamber 18 side.

A developing chamber 18 includes a developing roller 15 for supplying the toner 13 to the photosensitive drum 11 and a toner storage chamber 16.
A supply roller 17 that supplies the toner 13 sent from the developing roller 15 to the developing roller 15, and regulates a height of the toner layer attached to the surface of the developing roller 15 from the surface of the roller 15, and removes the toner 13 on the surface of the roller 15. A toner blade (toner layer regulating member) 19 for frictionally charging is provided. The toner blade 19 is made of a flexible member protruding from the upper wall portion of the developing chamber 18 toward the developing roller 15,
The leading end thereof is in contact with the surface of the developing roller 15 at a predetermined pressure. A seal blade 21 for preventing the toner 13 from leaking to the outside of the developing chamber 18 is provided below the developing roller 15 in the developing chamber 18.

In the image forming apparatus having the above structure, the photosensitive drum 11 is charged by a charging member (not shown), and then an electrostatic latent image is formed on the drum surface by laser light or the like.
At this time, the height of the toner layer attached to the surface of the developing roller 15 from the surface is regulated by the toner blade 19,
The toner is triboelectrically charged while being thinned to an appropriate thickness. Next, the charged toner 13 is supplied to the surface of the developing roller 15 and attached to the electrostatic latent image to form (develop) a toner image. Thereafter, while feeding the recording paper in synchronization with the rotation of the photosensitive drum 11, a bias voltage having a polarity opposite to that of the toner layer is applied from the back side of the recording paper to remove the unfixed toner image on the photosensitive drum. Transfer to recording paper. Furthermore,
The unfixed toner image is fixed on recording paper by a fixing mechanism.

[0006]

The above-mentioned conventional developing device 1
In the case of No. 2, the amount of the toner 13 sent from the communication port 14 to the developing chamber 18 side when the developing is performed immediately after the toner 13 is replenished or the like and the unused toner 13 is filled in the toner accommodating chamber 16. Is excessive, and the toner blade 19
The toner 13 may overflow to the back surface of the developing roller 15 and press the blade 19 toward the developing roller 15. In this case, the toner blade 19 comes into contact with the developing roller 15 with a force of a predetermined pressure or more, so that the height of the toner layer on the developing roller 15 from the roller surface becomes difficult to be regulated to a predetermined dimension.
There is a problem that a stable image density cannot be obtained.

[0007] In view of the above, the present invention can be applied to a case where the toner accommodating chamber is filled with toner, such as immediately after toner replenishment.
It is an object of the present invention to provide a developing device capable of accurately regulating the height of a toner layer on a developing roller from the roller surface, stabilizing image density and improving image quality.

[0008]

In order to achieve the above object, a developing device according to the present invention comprises a developing roller for supplying toner to a photosensitive drum having an electrostatic latent image formed on a surface thereof; A toner supply unit that supplies toner, a toner layer regulating member that regulates a height of the toner layer attached to the surface of the rotating developing roller from the surface by elastically contacting a front end portion with the surface of the developing roller. In the developing device, a protective wall portion is provided on the toner supply side of the toner layer regulating member to protect the toner layer regulating member from toner pressure.

According to the developing device of the present invention, the protective wall portion is
Since the toner pressure is prevented from being applied to the toner layer regulating member, it is possible to stably secure the contact pressure of the toner layer regulating member with respect to the developing roller even when the toner is fully filled in the toner storage chamber immediately after toner replenishment. Thus, the height of the toner layer on the developing roller can always be regulated to a predetermined size, and the image density can be stabilized and the image quality can be improved.

[0010] Preferably, a sheet-shaped sealing member arranged in a bridge shape is provided between the respective tip portions of the toner layer regulating member and the protective wall portion. Preferably, the tip of the toner layer regulating member is formed as a bent portion toward the protection wall, and one edge of the sheet-shaped sealing member is fixed to the tip of the protection wall, and the other edge is formed. Is in contact with the bent portion at the tip of the toner layer regulating member. According to this configuration, the sheet-shaped sealing member can be more reliably brought into contact with the leading end of the toner layer regulating member, and the movement of the toner layer regulating member with respect to the developing roller is substantially prevented by the sheet-shaped sealing member. Elastic contact can be made smoothly.

[0011]

The present invention will be described in more detail with reference to the drawings. FIG. 1 is a cross-sectional view of a developing device according to an embodiment of the present invention together with a photosensitive drum in a direction perpendicular to the rotation axis of the photosensitive drum. FIG. 2 is an enlarged view of a main part of the developing device of FIG. FIG. 1 and 2, the same reference numerals are given to the same parts and elements as those in the apparatus in FIG. 3, and the description thereof will be omitted.

As shown in FIG. 1, a developing device 12 has a developing roller 15 having a rotating shaft 15a opposed to the photosensitive drum 11 rotating counterclockwise and parallel to the rotating shaft 11a.
And a toner blade (toner layer regulating member) 22 adjacent to the developing roller 15.

The toner blade 22 is provided on the photosensitive drum 11.
2 is made of an elastic member extending in the rotation axis direction of FIG.
As shown in FIG. 3, the base end is fixed to the upper wall of the developing device 12 and the front end is bent toward the developing chamber 18 to form the bent portion 2.
2a is formed. A protection wall 23 is provided on the toner storage chamber side (toner supply side) of the toner blade 22 so as to protect the toner blade 22 from the pressure of the toner 13, corresponding to the toner blade 22. Protective wall 23
Is made of a relatively hard member, and protrudes downward from the upper wall portion of the developing chamber 18 as much as the toner blade 22. The protection wall 23 extends in the rotation axis direction of the photoconductor drum 11 at a predetermined distance from the toner blade 22 on the toner storage chamber side.

One edge of the upper surface of a sheet-like sealing member 25 made of a polyester film such as Mylar (trade name) is attached to the lower end of the protective wall 23 at the tip of the protective wall 23. . The other edge of the upper surface of the sheet-shaped sealing member 23 is, due to its elasticity, the toner blade 22.
Is in contact with the bent portion 22a of As a result, the toner 13 is placed behind the toner blade 22.
A space 26 is formed so as not to come into contact with. Note that the supply roller 17 and the toner mixer 20 constitute a toner supply unit.

In the developing device 12 configured as described above, when the image forming operation is started, the toner 13 in the toner containing chamber 16 is
Is sent from the communication port 14 to the developing chamber 18 while being stirred by the toner mixer 20 rotating in the clockwise direction (the direction of the arrow 24). Toner 1 sent into developing chamber 18
3 is supplied to a supply roller 17 rotating counterclockwise. Toner 13 scraped up by supply roller 17
Adheres to the surface of the developing roller 15 rotating in the counterclockwise direction, reaches the contact portion between the tip of the toner blade 22 and the surface of the developing roller 15, and passes through the contact portion. The tip is appropriately scraped off, regulated to a predetermined thickness, and triboelectrically charged. As a result, a charged toner layer having a substantially uniform height from the surface in the rotation axis direction is formed on the surface of the developing roller 15.

Thereafter, the charged toner layer is placed on the photosensitive drum 1
The toner is attached to the electrostatic latent image formed in advance on the surface of the drum and developed while moving to the closest part to the surface of the drum 1 and in contact with the surface of the drum. The toner image resulting from the development is transferred to a supplied recording paper (not shown) in a subsequent transfer step, and is then fixed on the recording paper by a fixing unit (not shown). In addition, the charged toner layer remaining on the surface of the developing roller 15 after the development passes between the roller 15 and the seal blade 21 and is transported to a contact portion with the supply roller 17 as the developing roller 15 rotates, and is counterclockwise. Supply roller 1 that rotates in the direction
7, the toner is scraped off from the developing roller 15 and mixed with other toner 13 in the developing chamber 18. Thus, a series of development steps is completed.

In general, when the development is performed immediately after the toner 13 is replenished or the like and the unused toner 13 is filled in the toner storage chamber 16, the amount of the toner 13 sent to the development chamber 18 is reduced. Too much toner blade 19
Toner 13 overflows to the back surface of the toner. However, in the present developing device, the hard protective wall 23 is located on the back surface of the toner blade 22, and the sheet-like sealing member 2 is located between the respective tips of the toner blade 22 and the protective wall 23.
5 is closed to close the gap therebetween, the protective wall portion 23 pressed in the direction of arrow 28 in FIG. 2 and the sheet-like sealing member 2 pressed in the direction of arrow 27 by the toner 13.
3 cooperates to prevent the toner 13 from entering the space 26. As a result, the toner 13 does not come into contact with the back surface of the toner blade 22, so that the leading end of the toner blade 22 can always contact the charged toner layer on the developing roller 15 with a stable pressure. Therefore,
The charged toner layer can always be formed at a constant height on the surface of the developing roller 15, so that the image density can be stabilized and the image quality can be improved.

The edge of the sheet-like sealing member 25 on the side of the protective wall 23 is fixed, and the edge of the toner blade 22 on the side of the toner blade 22 is simply in contact with the bent portion 22a of the blade 22. The movement of the developing roller 15 is hardly restricted by the sheet-shaped sealing member 25.
Can always be smoothly and elastically contacted.

As described above, the present invention has been described based on the preferred embodiment. However, the developing device of the present invention is not limited only to the configuration of the above-described embodiment, and is not limited to the configuration of the above-described embodiment. Developing devices with various modifications and changes,
It is included in the scope of the present invention.

[0020]

As described above, according to the developing device of the present invention, even when the toner is fully filled in the toner storage chamber, for example, immediately after the toner is replenished, the toner layer regulating member is used by the toner layer regulating member. Since no pressure is applied, the contact pressure of the toner layer regulating member with respect to the developing roller can be stably maintained, and the height of the toner layer from the roller surface can always be regulated to a predetermined dimension. Therefore, it is possible to stabilize the image density and improve the image quality.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a developing device according to an embodiment of the present invention, along with a photosensitive drum, in a direction perpendicular to a rotation axis of the photosensitive drum.

FIG. 2 is an enlarged cross-sectional view illustrating a main part of the developing device of FIG. 1;

FIG. 3 is a cross-sectional view of a conventional developing device together with a photosensitive drum, taken along a direction perpendicular to a rotation axis of the photosensitive drum.

[Explanation of symbols]

 Reference Signs List 11 photoconductor drum 12 developing device 13 toner 15 developing roller 17 supply roller 20 toner mixer 22 toner blade (toner layer regulating member) 22a bent portion 23 protective wall portion 25 sheet-shaped seal member

Claims (2)

(57) [Claims] A developing roller configured to supply toner to a photosensitive drum having an electrostatic latent image formed on a surface thereof; a toner supplying unit configured to supply toner to the developing roller; And a toner layer regulating member that regulates the height of the toner layer adhering to the surface of the rotating developing roller from the surface, and a toner layer regulating member disposed on the toner supply side of the toner layer regulating member. A developing device having a protective wall portion for protecting a member from toner pressure, comprising a sheet-shaped seal member between both ends of the toner layer regulating member and the protective wall portion. . 2. A tip portion of the toner layer regulating member is formed as a bent portion toward the protection wall portion, and one edge of the sheet-shaped sealing member is fixed to a tip portion of the protection wall portion, The developing device according to claim 1, wherein the other edge portion is in contact with a bent portion at a tip portion of the toner layer regulating member.