JPS63231470A - Developing device - Google Patents

Abstract

PURPOSE:To obtain a good visible image by consisting a developer carrier of a roller consisting of a central shaft which is made of a rigid body having electrical conductivity, an intermediate layer which is formed on the outer circumference of the central shaft and has elasticity and a surface layer which is formed on the outer circumference of the intermediate layer and has elasticity. CONSTITUTION:The developing roller 4 which is the developer carrier is made into the 3-layered structure consisting of the central shaft 5 which is made of the rigid body having the electrical conductivity, the intermediate layer 6 which is formed on the outer circumference of the shaft 5 and has the elasticity, and the surface layer 7 which is formed on the outer circumference of the layer 6 and has the elasticity. The hardness of the carrier 4 can, therefore, be lowered and the fluctuation in the friction load against an electrostatic latent image carrier can be suppressed. The pressing force in the axial direction is uniformized and the projection from a nip width is obviated. The good visible image having no uneven densities is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device used in electrophotographic recording devices, electrostatic recording devices, etc., and particularly relates to a developing device that uses a one-component non-magnetic insulating developer to a developing roller. The present invention relates to a developing device that is transported to a developing area and performs development.

[Conventional technology]

Two-component developer used as a developing device in electrophotographic recording devices, etc.? It is well known that there are two types: one that uses a developer to develop the electrostatic latent image on an electrostatic latent image carrier into a visible image, and the other that uses a -component developer to develop the electrostatic latent image. Among these, developing devices that use two-component developers mix and stir the two components of toner and carrier as a developer, and the resulting friction charges the toner and supplies it to the electrostatic latent image, producing a good image. However, since the mixing ratio of toner and carrier must be kept constant, the structure is complicated, and maintenance must be performed periodically to prevent deterioration of print quality due to carrier deterioration. There is an inconvenience that it must be done.

On the other hand, some developing devices using -component developers use magnetic toner and non-magnetic insulating toner as the -component developer, and although both do not have the above-mentioned disadvantages,
The former type of developing device using magnetic toner has the disadvantage that clear colors cannot be obtained when performing color development because the toner contains a magnetic substance.

Therefore, the latter type of developing device using a non-magnetic insulating toner and a non-magnetic insulating developer is attracting attention.

A developing device using this -component non-magnetic insulating toner includes:
A non-contact type in which the developer carrier faces the electrostatic latent image carrier with a certain gap in the development area, and a contact type in which the entire developer carrier is brought into pressure contact with the electrostatic latent image carrier. However, in recent years, both of these methods have been published, for example, in JP-A-60-230673, or JP-A-60-
As shown in Japanese Patent No. 238876, a developer carrier is formed into a roller or a belt, and a frictional charging member is placed on the outer periphery of the roller or belt, and a frictional charging member is brought into contact with or closely opposed to the roller, and one-component non-magnetic insulating toner is passed between them. Many structures have been proposed in which the toner is charged and developed using the friction caused by soil removal.

Therefore, among the developing devices that charge the -component non-magnetic insulating toner in this way, in the above-mentioned contact type developing device, the electrostatic latent image carrier is a conductive rigid pipe,
For example, when the developer carrier is formed of a pipe and a base material such as aluminum, the developer carrier is formed of an elastic material,
By coming into pressure contact with the electrostatic latent image carrier, it is possible to obtain uniform contact in the entire axial direction, and also to obtain a predetermined nip width (contact length) that becomes the development area.

FIG. 2 is a partial sectional view showing a conventional developing device of this type.
In the figure, 1 is an electrostatic latent image carrier (hereinafter referred to as a photosensitive drum) having a photoconductive layer formed using a conductive rigid pipe as a base material.
It rotates at a constant speed in the direction of arrow a.

2 is a device housing (hereinafter referred to as a toner tank); 3 is a one-component non-magnetic insulating developer (hereinafter referred to as a toner) stored in the toner tank 2; 8
9 is a flexible member such as a leaf spring fixed to the bottom of the toner tank 2, and 9 is a frictional charging member (hereinafter referred to as a blade) fixedly held at the free end of the flexible member 8.

Reference numeral 12 denotes a developer carrier (hereinafter referred to as a developing roller) made of an elastic material such as rubber.
The toner is held in the toner tank 2 so as to press against the surface of the photosensitive drum 1 with a predetermined pressure to obtain a predetermined nip width, and rotates in the direction of the arrow mark, so that the toner has a predetermined circumference. The blade 9 comes into contact with the spot.

In this configuration, the toner 3 in the toner tank 2 is stirred by an agitation member (not shown) and is sent to the contact area between the developing roller 12 and the blade 9, where pressure is applied between the surfaces of the two to create friction. It is electrically charged.

Then, this frictionally charged toner 3 is transferred to the developing roller 12.
The layer of toner 3 attached to the developing roller 212 is regulated into a uniform thin layer by the blade 9, and then transported to the developing area as the developing roller 12 rotates. Toner 3 is supplied from the developing roller 12 to the electrostatic latent image carried and conveyed by the photosensitive drum 1 in the development area and adheres to the electrostatic latent image, so that the electrostatic latent image becomes a toner image or a visible image. becomes.

Note that the circumferential speed of the developing row 212 is generally set to be faster than the circumferential speed of the photosensitive drum 1 in order to increase the toner supply capacity.

[Problem that the invention seeks to solve]

However, the conventional developing device described above has the following problems.

That is, FIG. 3 is an enlarged view of the main part of FIG. 2, and as seen in this figure, the developing roller 12 is in pressure contact with the photosensitive drum 1, so the photosensitive drum 1 is moved from the free state shown by the two-dot chain line. It is recessed along the circumferential surface and rotates in this state, but since the developing roller 12 is made of a relatively hard elastic material such as rubber, the rotation direction is affected by friction with the photosensitive drum 1 during rotation. 12a' protruding from the nip width on the rear side
occurs.

This protrusion 12a is restored when the elasticity of the developing roller 12 overcomes the frictional force, but the occurrence and recovery of the protrusion 12a are repeated during the rotation of the developing roller 12, and this phenomenon causes density unevenness in the toner image. However, since load fluctuations are caused not only to the engine but also to the power system, there is a problem in that it becomes difficult to obtain a good visible image.

Further, since the rotational load on the photosensitive drum 1 and the developing roller 13 is large due to the above-described frictional load fluctuation, a power system having a large driving force is required to rotate them, which leads to an increase in cost.

The present invention was made to solve these problems, and aims to provide excellent visible images without uneven density. It is an object of the present invention to realize a developing device that can obtain the above-mentioned results and reduce costs.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention brings a developer carrier (developing roller) into pressure contact with an electrostatic latent image carrier (photosensitive drum), and also provides a triboelectric charging member (
A developing device having a configuration in which the blades (blade) are in contact with each other or facing each other with a predetermined gap therebetween, and uses a one-component non-magnetic insulating developer as a developer, and the developer carrier is electrically conductive. a central shaft made of a rigid body; an intermediate layer formed of an elastic porous foam formed around the central shaft;
It has a three-layer structure with an elastic surface layer formed around the outer periphery of the intermediate layer.

[Effect]

In the present invention having the above-described structure, the developer carrier has a structure having an intermediate layer made of porous foam and an elastic surface layer, so that the hardness of the developer carrier is lower than that of the conventional hardness. This can suppress frictional load fluctuations with the electrostatic latent image carrier, and also equalizes the pressing pressure in the axial direction. Since the protrusion from the surface can be eliminated, a good visible image without density unevenness can be obtained.

In addition, since frictional load fluctuations can be suppressed, rotational loads on the electrostatic latent image carrier and developer carrier can be reduced.
This makes it possible to use a power system with a smaller driving force than in the past, thereby reducing costs.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view showing one embodiment of the developing device according to the present invention. In the figure, 1 is the same photosensitive drum as in FIGS. It rotates at high speed.

2 is a toner tank, 3 is toner, 4 is a developing roller consisting of a central shaft 5, an intermediate layer 6 and a surface layer T, 8 is a flexible member such as a leaf spring, 9 is a blade, 10 is a stirring member, 11 1 is a toner blocking member, and these members 2 to 11 constitute the developing device of this embodiment, the details of which will be described below.

First, a predetermined amount of toner 3 is stored in a toner tank 2, an opening is provided on the side of the toner tank 2 facing the photosensitive drum 1, and the developing roller 4 is placed in an intermediate layer. The photosensitive drum 1 is elastically deformed until the surface layer 7 reaches a predetermined nip width.
The driving force is transmitted to the central shaft 5 from a drive source (not shown) in the clockwise direction indicated by the arrow as the photosensitive drum 1 rotates. It is designed to rotate.

The center shaft 5 of the developing roller 4 is made of a conductive rigid body such as stainless steel, and the intermediate layer 6 formed around the outer periphery of the center shaft 5 is made of elastic porous foam such as polyurethane foam. is not used.

The surface layer formed around the outer periphery of this intermediate layer 6 has fine irregularities with a roughness of 3 to 30 ttm over the entire surface in order to obtain toner conveyance force, and has a surface layer that is separated from the toner 3. It is made of an elastic material with good moldability, but its thickness is preferably 150 μm or less in order to maintain the clarity of the image, and the material has a frictional electrification series that is far away from the toner 3. Preferably. -Z'' Note that, for example, when the photosensitive drum 1 has a negative charging polarity, the charging polarity of the toner 3 due to frictional charging is positive for normal development and negative for reverse development.

On the other hand, the blade 9 is for frictionally charging the toner 3 to form a uniform thin layer of the toner 3 on the surface layer 7 of the developing roller 4. The flexible member 8 is brought into contact with the pressure of
The material is the surface layer 7.
Similarly, it is desirable that the triboelectrification series be separated from the toner 3.

The flexible member 8 is fixed to the bottom of the toner tank 2 by suitable fixing means.

The stirring member 10 is rotatably disposed within the toner tank 2 so as to be located behind the pressure contact portion between the developing roller 4 and the blade 9, and the stirring member 10 has a rotating shaft that is rotated by a drive source (not shown). It is composed of a plurality of agitating blades and the like provided around the agitating blade, and functions to agitate the toner 3 in the toner tank 2 and supply the toner 3 to the pressure contact portion.

Further, the toner blocking member 11 is for preventing leakage of toner 3 from inside the toner tank 2.
The upper end is fixed to the ceiling of the toner tank 2, and the lower end lightly contacts the surface layer T of the developing roller 4 due to its flexibility.

In addition to the developing device configured as described above, a charger and an exposure device (not shown) are provided around the photosensitive drum 1.

A transfer device, a static eliminator, a cleaning device, a fixing device, and the like are arranged according to the recording process.

Next, to explain the operation, first, while the photosensitive drum 1 is rotating in the direction of arrow a, the surface of the photosensitive drum 1 is uniformly charged by a charger (not shown).
Subsequently, exposure is performed using an exposure device (not shown).
As a result, an electrostatic latent image is formed on the photosensitive drum 1, and this electrostatic latent image is conveyed by rotation of the photosensitive drum 10 to a position where it contacts the developing roller 4, that is, a developing area.

On the other hand, in the developing device, simultaneously with the rotation of the photosensitive drum 1, the developing roller 24 is rotated in the direction of the arrow by a drive source (not shown).
Further, the stirring member 1o is also rotated in a predetermined direction by a drive source (not shown).

As the agitating member 10 rotates, the toner 3 in the toner tank 2 is agitated and is pushed and supplied to the pressure contact portion between the developing roller 4, the surface layer 1, and the blade 9. The toner 3 is charged by friction between the surface layer 1 and the hybrid 9.

Here, the charged toner 3 adheres to the surface layer T,
The toner 3 is conveyed to the developing area by the rotation of the developing roller 4, and at this time, the layer of toner 3 adhering to the surface layer γ is uniformly thinned by the blade 9.

This thin layer of toner 3 is supplied to the electrostatic latent image on the photosensitive drum 1 in the development area, and development is performed by attracting and adhering to the electrostatic latent image. be converted into

This toner image is conveyed to the next transfer area by the rotation of the photosensitive drum 1, where it is transferred to the paper by a transfer device (not shown), and then fixed to the paper by a fixing device, and the toner image remains on the photosensitive drum 1. After the toner 3 undergoes a static eliminating process using a static eliminating device, it is removed by a cleaning device.

On the other hand, after the development, the toner 3 remaining on the surface of the developing roller 4, that is, the surface layer 7, passes through the position of the toner blocking member 11 during the rotation of the developing roller 4, is collected in the toner tank 2, and is recycled. used.

Although one embodiment of the present invention has been described above, the present invention is not limited to this. For example, in the above-mentioned embodiment, the blade 9 is entirely in contact with the developing roller 4, but there is a predetermined gap. It is also possible to have a configuration in which they face each other via a.

〔Effect of the invention〕

As explained above, the present invention provides an electrostatic latent image carrier having a central axis made of a rigid body having conductivity, an intermediate layer made of an elastic porous foam formed around the central axis, and this intermediate layer. Because the structure consists of an elastic surface layer formed on the outer periphery of the material, the hardness can be lowered compared to conventional products.
This makes it possible to suppress fluctuations in frictional load when the electrostatic latent image bearing member is rotated in pressure contact with the electrostatic latent image bearing member, and the pressing pressure in the axial direction is also uniform, making it possible to avoid the nip to the developer bearing member as in the conventional case. Since no protrusion from the width occurs, there is an effect that a good visible image without density unevenness can be obtained.

Furthermore, since frictional load fluctuations can be suppressed as described above, the rotational load on the electrostatic latent image carrier and developer carrier is also reduced.
As a result, the driving force of both power systems can be small, so that it is possible to reduce costs.

[Brief explanation of drawings]

FIG. 1 shows a cross section (
Unfortunately, Figure 2 is a partial sectional view showing the conventional example, and Figure 3 is an enlarged view of the main parts of Figure 2. 1: Photosensitive drum 2: Toner tank 3: Toner 4: Developing roller 5: Center Shaft 6: Intermediate layer 7: Surface layer 8: Flexible member 9 Blade 10: Stirring member 11: Toner blocking member Patent applicant: Oki Electric Industry Co., Ltd. Representative Patent attorney Takashi Kanakura 2 An embodiment of the present invention is shown. Cross-sectional view axis 1-

Claims (1)

[Scope of Claims] 1. A developer carrier that rotates in pressure contact with an electrostatic latent image carrier that rotates at a constant speed; the one-component non-magnetic insulating developer supplied between the tribo-charging member and the developer carrier; In a developing device that develops an electrostatic latent image on an electrostatic latent image carrier by conveying a developer to a pressure contact portion with the electrostatic latent image carrier by a developer carrier, the developer carrier is made of a conductive material. The roller is made up of a central shaft made of a rigid body having a central axis, an intermediate layer made of a porous foam having elasticity formed around the outer periphery of the central axis, and a surface layer having elasticity formed around the outer periphery of the intermediate layer. Characteristic developing device.