JPH11161023A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image of high quality with magnetic one-component toner, in particular. SOLUTION: The image forming device is provided with a developing housing 40, a developing sleeve 50, a magnet roller 51, a regulating member, a developer moving means and a recovery voltage applying means. As the developer moving means, the magnet roller 51 is freely rotatably provided and a magnetic pole is fixed in a photoreceptor drum 6 and in the vicinity of the upstream side of a developing region. Each magnetic pole of the magnet roller 51 is provided to be stronger than that in the drum 6. Further, the following method can be adopted as well; the magnet roller 51 is fixed, the magnetic pole is fixed in the drum 6 and in the vicinity of the developing region and the magnetic pole of the magnet roller 51 can be arranged in a part nearer to the downstream side than the magnetic pole in the drum 6 across the developing region. The magnetic pole of the magnet roller 51 has a polarity reverse to or the same as that of the magnetic pole in the drum 6 and is set to be stronger than that in the drum 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a developing device for an image forming apparatus, and more particularly to a developing device for an image forming apparatus using a developer containing a magnetic toner. In the present invention, the developing area refers to an area where the developer layer on the developing sleeve and the photosensitive drum are close to each other. Fogging refers to a phenomenon in which toner adheres to an area where no image is formed.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine,
For example, an electrostatic latent image based on image data is formed on the photosensitive drum by a laser scan unit. A developing device is provided adjacent to the photosensitive drum, and the developing device causes toner to adhere to the electrostatic latent image on the surface of the photosensitive drum to form a visible image. A developing device using a magnetic toner as a toner includes a developing housing for storing a developer containing the magnetic toner, a developing sleeve disposed close to the photosensitive drum, and a magnet for transporting the developer while rotating on the developing sleeve. And a roller.

In such a developing device, various devices have been devised in order to obtain a high-quality image, especially when a magnetic one-component toner is used. For example, in a device in which a photosensitive drum is arranged above a developing device, and a collecting roller to which an AC voltage is applied is provided close to a lower side of the photosensitive drum, and the toner is sent upward, the inside of the photosensitive drum and the collecting roller , A configuration in which magnets substantially facing each other are provided.

[0004]

According to the above-mentioned structure, the photosensitive drum is brought into contact with a pool of magnetic toner formed on the upstream side of a portion where the photosensitive drum and the collecting roller are opposed to each other, and the toner is transferred to the electrostatic latent image. Attach to the area. The toner adhering to an area where the electrostatic latent image is not formed on the photosensitive drum (hereinafter referred to as a non-image area) is collected by a magnetic force acting between the photosensitive drum and the collecting roller and a voltage applied to the collecting roller. I do.

However, in the above-described configuration, a large amount of uncharged toner is present in the magnetic one-component toner having no carrier, and in fact, considerable fogging occurs. Also,
In order to prevent toner from leaking from the developing device to the outside, the developing position is limited to the lower side of the photosensitive drum, and it is difficult for the toner to accumulate under the developing device and use up the toner to the end. It is easy to waste.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a developing device for an image forming apparatus, which can form a high-quality image using a one-component toner.

[0007]

According to the present invention, there is provided a developing device for an image forming apparatus for developing an electrostatic latent image formed on a photosensitive drum, comprising: a developing housing; Provided is a developing device of an image forming apparatus including a developing sleeve, a magnet roller, a regulating member, a developer moving unit, and a recovery voltage applying unit.

The developing housing contains therein a developer containing a magnetic toner. The developing sleeve has a cylindrical shape, is adjacent to the photosensitive drum, and is rotatably provided in the developing housing, and forms a toner image on the electrostatic latent image on the photosensitive drum. The magnet roller is provided coaxially with the developing sleeve and in the developing sleeve. The regulating member is provided near the developing sleeve, and regulates the height of the developer on the developing sleeve. The developer moving unit is configured to move the magnetic toner from the developing sleeve to the electrostatic latent image formed on the photoconductor drum, and to move the developer layer on the developing sleeve and the photoconductor drum upstream of the developing area where the photoconductor drum is close to the developing layer. To form a magnetic field. The collecting voltage applying means applies a DC voltage and / or an AC voltage between the photosensitive drum and the developing sleeve in order to collect the magnetic toner from the area of the photosensitive drum where the electrostatic latent image is not formed to the developing sleeve. Apply.

The magnetic toner alternately receives magnetic forces of opposite polarity by a magnet roller, is conveyed while rotating on a rotating developing sleeve, and is charged by repeating contact with the developing sleeve and contact between the developers. The regulating member regulates the height of the developer at a constant level and further frictionally charges the toner. The developer conveyed to the upstream of the developing area moves on the electrostatic latent image by receiving an electrostatic force acting between the toner and the photosensitive drum and an appropriate magnetic force formed by the developer moving means. Due to this magnetic force, the toner temporarily moves to the photosensitive drum side, and at the upper part of the developing area, the surface of the photosensitive drum rotates and moves along with the rotation of the developing sleeve and the photosensitive drum by the force mainly composed of the magnetic attraction, and the toner is statically moved. Development is performed so that the edge effect acts on the latent image. Next, when the developer moves to the developing area, the developing sleeve and the photosensitive drum come close to each other,
The photosensitive drum acts as a counter electrode to the developing sleeve, and positive development of the solid image portion is promoted. At the same time, since a bias voltage is applied between the developing sleeve and the photosensitive drum, toner causing fogging is removed. As a result, excellent reproducibility can be achieved for both fine line reproducibility of a character portion and the like by development with the edge effect and solid image portion by the counter electrode effect.

It is preferable to provide a rotatable stirring paddle in front of the developing sleeve because the toner can be more frictionally charged. According to a second aspect of the present invention, in the developing device of the image forming apparatus, the image forming apparatus further includes a magnet roller rotatably provided, and a magnetic pole fixed inside the photosensitive drum and near an upstream side of the developing area. I have. Each magnetic pole of the magnet roller is provided stronger than the magnetic pole inside the photosensitive drum.

For example, when the magnetic pole of the magnet roller of the opposite polarity is located opposite to the magnetic pole inside the photosensitive drum with the developing area interposed therebetween and slightly downstream of the magnetic pole, the developer spikes and the developing sleeve. The opposite end receives an attractive force from a magnetic pole inside the photosensitive drum. According to the aspect of the present invention, by using a rotatable magnet roller,
As a result of the fact that the magnetic field in the developing area can be changed, a force for swinging the magnetic toner acts, and the magnetic toner can be attached to and detached from the electrostatic latent image. Therefore, it is possible to positively vibrate the magnetic toner for developing the electrostatic latent image and improve the gradation in the development characteristics.

According to a third aspect of the present invention, in the developing device of the image forming apparatus, the fixed magnet roller, the magnetic pole fixed inside the photosensitive drum and in the vicinity of the developing area, and the developing area are sandwiched. And a magnetic pole of a magnet roller located downstream of a magnetic pole inside the photosensitive drum. The magnetic pole of the magnet roller has a polarity opposite to that of the magnetic pole inside the photoconductor drum, and is provided stronger than the magnetic pole inside the photoconductor drum.

The operation of the toner in this case is the same as that in the case of the second invention in which the magnetic poles of the opposite polarity are located across the development area. According to a fourth aspect of the present invention, there is provided the developing device of the image forming apparatus, wherein the fixed magnetic roller, a magnetic pole fixed inside the photosensitive drum and near the developing region, and the photosensitive member sandwiching the developing region. And a magnetic pole of a magnet roller located downstream of the magnetic pole inside the drum. The magnetic pole of the magnet roller has the same polarity as the magnetic pole inside the photoconductor drum, and is provided stronger than the magnetic pole inside the photoconductor drum.

The operation of the toner in this case is the same as that of the second invention in the case where magnetic poles of the same polarity are located across the development area. The fifth invention of the present application uses a magnetic one-component toner as a developer. Since the transfer of the toner from the developing sleeve to the photosensitive drum is promoted by magnetic force, a high-quality image can be obtained even if a one-component toner that is less easily charged than a two-component developer is used.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <Overall Configuration> An image forming apparatus to which an embodiment of the present invention is applied will be described with reference to FIG.
In FIG. 1, a document table 2 is provided on an upper surface of an image forming apparatus main body 1.
Are fixed, and a document holder 3 is provided on the document table 2 so as to be openable and closable. Paper feed cassettes 13, 14, 15 and a paper feed deck 16 are provided below the image forming apparatus main body 1.

Inside the main body 1 of the image forming apparatus, an exposure section 4 for reading a document is provided at an upper portion thereof. The exposure unit 4 includes a light source, a mirror, a lens unit, and the like. Further, an image forming section 5 for forming a toner image of a read document is provided at a central portion of the image forming apparatus main body 1. The image forming section 5 has a photosensitive drum 6 on the surface of which an electrostatic latent image is formed. Around the photosensitive drum 6, a charging device 7, a developing device 8, a transfer device 9, and a cleaning device 10 are arranged.

A vertical transport path 26 for guiding paper upward is provided between the paper feed cassettes 13, 14, 15 and the paper feed deck 16 and the image forming section 5 constituted by the photosensitive drum 6 and the like. Have been. Further, on the downstream side of the image forming unit 5, there are disposed a sheet discharge conveyance path 30, a fixing unit 31 for fusing and fixing the toner image on the sheet, and discharge rollers 32 and 33 for discharging the sheet passing through the fixing unit 31. ing. <Developing Apparatus> FIG. 2 is a view showing an embodiment of the developing apparatus 8 in which a magnetic pole is mounted inside a photosensitive drum, and FIG. 3 is a view specifically showing a configuration of a developer moving means provided in the developing apparatus. FIG. 3 is a diagram illustrating a case where different poles form a magnetic field across the development region, and FIG. 4 is a diagram illustrating a case where the same pole forms a magnetic field across the development region.

As shown in FIG. 2, the developing device 8 has a developing housing 40, in which a developing sleeve 50, a magnet roller 51, a blade 60, and a stirring paddle 70 are provided. A toner cartridge 80 containing magnetic toner as a one-component developer is mounted on the upper part of the developing housing 40, and supplies the magnetic toner into the developing housing 40.

The developing sleeve 50 has a cylindrical shape and is disposed in the developing housing 40 adjacent to the photosensitive drum 6.
The developing housing 40 is rotatably provided between both side walls (not shown) and rotates in the same direction as the magnetic toner conveying direction.
A power supply 54 including an AC component and a DC component is connected to the developing sleeve 50 in series. Inside the cylindrical developing sleeve 50, a built-in magnet roller 51 is provided rotatably coaxially with the developing sleeve 50, and rotates in the direction opposite to the magnetic toner conveying direction. The magnet roller alternately shows the magnetic poles of the opposite polarity in the circumferential direction, and carries the toner while rotating.

Outside the developing sleeve 50, a blade 6
0 is provided close to the surface of the developing sleeve 50 and at least over the width of the developing sleeve 50, and regulates the height of the toner on the developing sleeve 50 to a certain range. The stirring paddle 70 is provided in the developing housing 40 in parallel with the developing sleeve 50 and close to the developing sleeve 50, and is rotatably mounted between both side walls (not shown) of the developing housing 40.

A magnet 52 is disposed inside the photosensitive drum 6 near the developing sleeve 50. Magnet 52
Is located near the upstream side of the developing region 53, and is fixed with the N pole approaching the inner surface of the photosensitive drum. Magnet 5
The N pole of No. 2 is set to be weaker than each magnetic pole of the magnet roller. <Operation of Magnetic Toner> The operation of the magnetic toner in the developing device will be described.

The magnetic toner is supplied from the stirring paddle 70 to the developing sleeve 50. The magnetic toner supplied to the developing sleeve 50 is conveyed on the rotating developing sleeve 50 while receiving the magnetic force of the magnet roller 51 and rotating in the direction opposite to the rotation direction of the magnet roller 51, and is brought into contact with the developing sleeve 50. The contact between the magnetic toners is repeated to cause frictional charging. Furthermore, the magnetic toner is
As a result, friction occurs between the blade 60 and the magnetic toner, and frictional charging is further promoted.

As shown in FIG. 3, when the S pole 55 of the magnet roller is positioned slightly downstream of the N pole 52a of the magnet 52 inside the photosensitive drum with the developing region 53 interposed therebetween, the magnetic poles 52a attract each other. A magnetic field due to 55 is formed in the development area 53. Conversely, as shown in FIG. 4, the N pole 56 of the magnet roller 51 is located slightly downstream of the N pole 52a of the magnet 52 provided inside the photosensitive drum 6 with the upstream side of the developing region 53 interposed therebetween. When positioned, a magnetic field is created in the development region 53 by the repelling magnetic poles 52a, 56.

The toner temporarily moves to the photosensitive drum 6 side by the magnetic force of the magnetic field formed in the developing area 53. Then, in the upper part of the developing area 53, the surface of the photosensitive drum 6 is rotated with the rotation of the developing sleeve 50 and the photosensitive drum 6 by the force mainly including the magnetic attraction,
Development is performed so that an edge effect acts on the electrostatic latent image. Next, when the toner moves to the developing area 53, the developing sleeve 50 and the photosensitive drum 6 come close to each other, so that the photosensitive drum 6 acts as a counter electrode with respect to the developing sleeve 50, and a solid image is formed. Aggressive development of the part is promoted. At the same time, since a bias voltage is applied between the developing sleeve 50 and the photosensitive drum 6, toner causing fogging is removed. As a result, the reproducibility of fine lines such as character parts by development with edge effect,
Both solid image portions can perform excellent development by the counter electrode effect.

By using a rotatable magnet roller, a magnetic field generated by the attracting magnetic poles 52a and 55 and a magnetic field generated by the repelling magnetic poles 52a and 56 are alternately formed in the developing area 53. The magnetic field can be varied. As a result, a force for rocking the magnetic toner acts, and the magnetic toner sticks to or peels off from the electrostatic latent image. Therefore, it is possible to positively vibrate the magnetic toner for developing the electrostatic latent image, and to enhance the gradation in the developing characteristics.

Uncharged toner or non-satisfactorily charged toner attached to the non-image area receives a voltage difference between the non-image area and the developing sleeve. Is also strongly collected by the S pole 55 of the magnet roller and collected by the developing sleeve. <Other Embodiments> (a) In the above-described embodiment, a one-component magnetic toner is used as a developer.
Component developers can also be used. (B) Although the magnet roller 51 is rotatably provided in FIGS. 3 and 4, the magnet roller 51 may be fixed and only the developing sleeve 50 may be rotatably attached. In this case, similarly to the case shown in FIG. 3, the magnetic pole 55 of a different polarity is positioned slightly downstream of the magnetic pole 52a in the photosensitive drum 6 with the developing region 53 interposed therebetween, or as shown in FIG. The magnetic poles 5 in the photosensitive drum 6
The magnet roller is adjusted so that the magnetic pole 56 of the same polarity is located slightly downstream of 2a. When the former different magnetic poles 52a and 55 are provided, the magnetic poles 52a and 55 have the same action as the magnetic field generated by the mutually attracted magnetic poles in the developing region 53 in the above-described embodiment. The same magnetic pole 5 of the latter
In the case where 2a and 56 are arranged, the same effect as in the case where the repelling magnetic field is formed in the development region 53 in the above embodiment. (C) In the above embodiment, the AC voltage and the DC voltage for collecting the toner in the non-image area are applied to the developing sleeve 50, but the method of applying the voltage is not particularly limited. It is only required that a voltage difference between the photosensitive drum 6 and the developing sleeve 50 can be provided so that the toner in the non-image area can be collected without collecting the toner in the latent image area. For example, an AC voltage or a DC voltage may be applied to the photosensitive drum 6, or may be applied to both the photosensitive drum 6 and the developing sleeve 50. An AC voltage may be separately applied to the developing sleeve 50 and a DC voltage may be separately applied to the photosensitive drum 6, or vice versa.

[0027]

According to the developing device of the present invention, a sufficient amount of toner is supplied to the developing sleeve by forming a magnetic field for positively moving the toner in the developing area where the photosensitive drum and the developing sleeve are close to each other. In addition, unnecessary toner can be collected, and a high-quality image can be provided.

[Brief description of the drawings]

FIG. 1 is an image forming apparatus to which an embodiment of the present invention is applied.

FIG. 2 shows a developing device 8 having a magnetic pole mounted in a photosensitive drum.
The figure which shows one Embodiment example.

FIG. 3 is a diagram illustrating a case where a different magnetic field forms a magnetic field across a development region.

FIG. 4 is a view for explaining a case where the same pole forms a magnetic field across a developing region.

[Explanation of symbols]

 6; photoreceptor drum 40; developing housing 50; developing sleeve 51; magnet roller 52; magnet 53 in the photoreceptor drum; developing area 54; power supply 55, 56;

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Seiichi Yamashita 1-2-28 Tamazo, Chuo-ku, Osaka-shi Inside Mita Industries Co., Ltd. (72) Inventor Yuichiro Hisagawa 1-2-28 Tamazo, Chuo-ku, Osaka Mita (72) Inventor Masahiro Tsutsumi 1-2-28 Tamazo, Chuo-ku, Osaka-shi Inside Mita Kogyo Co., Ltd.

Claims (5)

[Claims] 1. A developing device for an image forming apparatus for developing an electrostatic latent image formed on a photosensitive drum, comprising: a developing housing in which a developer containing a magnetic toner is housed; A cylindrical developing sleeve which is provided adjacently and rotatably in the developing housing and forms a toner image on an electrostatic latent image on the photosensitive drum; and A magnet roller provided in the sleeve; a regulating member provided in close proximity to the developing sleeve, for regulating a height of a developer layer on the developing sleeve; and a regulating member formed on the photosensitive drum from the developing sleeve. A developer moving means for forming a magnetic field on an upstream side of a developing area where the developing sleeve and the photosensitive drum are close to each other to move the magnetic toner onto the electrostatic latent image; A recovery voltage application for applying a DC voltage and / or an AC voltage between the photosensitive drum and the developing sleeve in order to recover the magnetic toner from the area of the drum where the electrostatic latent image is not formed to the developing sleeve. And a developing device of the image forming apparatus. 2. A developing device for the image forming apparatus, comprising: a magnet roller rotatably provided having a plurality of magnetic poles; and a magnetic pole fixed inside the photosensitive drum and near an upstream side of a developing area. The developing device of the image forming apparatus according to claim 1, wherein each magnetic pole of the magnet roller is provided stronger than a magnetic pole inside the photosensitive drum. 3. A developing device of the image forming apparatus, comprising: a fixed magnet roller; a magnetic pole fixed inside the photosensitive drum and in the vicinity of a developing area; 2. The magnetic roller according to claim 1, further comprising: a magnetic pole located on the downstream side, having a polarity opposite to a magnetic pole inside the photoconductor drum, and having a stronger polarity than a magnetic pole inside the photoconductor drum. 3. A developing device of the image forming apparatus. 4. A developing device of the image forming apparatus, comprising: a fixed magnet roller; a magnetic pole fixed inside the photosensitive drum and in the vicinity of a developing area; 2. The image according to claim 1, further comprising: a magnetic pole of the magnet roller that is located downstream and has the same polarity as a magnetic pole inside the photoconductor drum and is stronger than a magnetic pole inside the photoconductor drum. 3. The developing device of the forming device. 5. The developing device for an image forming apparatus according to claim 1, wherein the developer is a magnetic one-component toner.