JP3184625B2 - 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 apparatus used for an image forming apparatus such as an electrophotographic apparatus, and more particularly to a developing apparatus for developing an electrostatic latent image with a dry type one-component developer.

[0002]

2. Description of the Related Art In a dry type one-component developing apparatus, a developing member is provided at a position upstream of a rotation direction of a developer carrying member with respect to a regulating member for regulating the thickness of a developer layer carried and conveyed to a developing section. A developer removing / supplying member that removes the developer from the surface of the developer carrying member after passing through the portion and supplies the developer to the surface of the developer carrying member that advances toward the regulating member. preferable.

As the developer removing / supplying member, an open-cell foamed rubber roller in contact with a developer carrying member in a container is known.

When the elastic roller is made of an open-cell foam such as a polyurethane foam having relatively low hardness (a foam in which each cell communicates with each other), the elastic roller is brought into contact with the developer-carrying member with a light pressure. It is possible to supply the developer onto the developer carrying member and remove the remaining developer that is not consumed by the development with appropriate unevenness on the foam surface without applying excessive pressure to the developer. It became.

[0005]

However, in such a developing apparatus, since the elastic roller is formed of a relatively low-density open-cell foam, the developer having a small particle diameter is particularly subjected to a high-humidity environment. In the case of using the developer, the developer gradually enters the deep portion of the elastic roller as the developing operation is repeated many times. When such intrusion of the developer reaches the entire foam of the elastic roller, the elastic roller is hardened, and the contact pressure of the elastic roller against the developer carrying member becomes excessive, thereby increasing the driving torque of the developer carrying member and the elastic roller. The application and peeling of the developer of the elastic roller to and from the developer carrying member became uneven, and the thickness of the developer layer on the developer carrying member became uneven, which was not preferable.

[0006]

According to the present invention, a single-cell foamed elastic body (one in which individual cells are not communicated with each other) is used as the above elastic roller. A single-cell foamed elastic roller having a C hardness of 8 to 15 degrees is supported by a shaft, and the amount of radial deformation at a contact portion with a developer carrying member is 0.5 to
It is 1.5 mm.

[0007]

FIG. 1 shows a developing container 2 containing a non-magnetic toner 6 as a one-component developer.
Has a developing sleeve (developing roller) 3 installed in the developing container 2 so as to face the electrophotographic photosensitive drum 1 rotating in the direction of arrow a in the drawing.

The elastic blade 4 for regulating the thickness of the toner layer conveyed to the developing section is provided so as to be inclined downward toward the upstream side in the rotational direction (arrow b) of the developing sleeve 3. The surface is in contact with the sleeve in the counter direction with respect to the rotation direction.

The elastic roller 5 is in contact with the sleeve 3 in the container 2 and is rotatably supported in the container 2 on the upstream side of the blade 4 in the rotation direction of the developing sleeve 3.

The elastic roller 5 rotates in the direction of arrow C to carry the toner 6 in the container 2 and supplies the toner 6 to the vicinity of the developing sleeve 3, so that the developing sleeve 3 and the elastic roller 5 come into contact with each other. In the contact portion (nip portion), the toner 6 on the elastic roller 5 is rubbed against the developing sleeve 3 so that
The toner 6 adheres to the developing sleeve 3.

Thereafter, as the developing sleeve 3 rotates, the toner 6 adhered on the developing sleeve 3
At the abutting portion of the developing sleeve 3 and between them, when passing therethrough, they are rubbed by both the surface of the developing sleeve 3 and the elastic blade 4 and are sufficiently triboelectrically charged.

The toner 6 charged as described above is
A thin layer is formed on the developing sleeve 3 and transported to the developing section. Then, by applying an oscillating voltage obtained by superimposing an alternating current to a direct current as a developing bias voltage from a power source 8 to the developing sleeve 3, the toner 6 on the developing sleeve 3 is developed in the developing section.
Moves in accordance with the electrostatic latent image on the photosensitive drum 1, and the electrostatic latent image is developed and visualized as a toner image.

By the way, the toner 6 remaining on the developing sleeve 3 without being consumed for development in the developing section is collected in the developing container 2 with the rotation of the developing sleeve 3. A seal member 7 is provided at a toner collecting portion of the developing container 2. The seal member 7 allows the toner 6 remaining on the developing sleeve 3 to pass into the developing container 2 and prevents the toner 6 in the developing container 2 from leaking from a lower portion of the container 2.

The toner 6 collected in the developing container 2 is peeled off from the developing sleeve 3 by the elastic roller 5 at a portion where the toner 6 comes into contact with the developing sleeve 3. At the same time, new toner 6 is supplied onto the developing sleeve 3 by the rotation of the elastic roller 5, and the new toner 6 is again supplied to the developing sleeve 3.
Is transported to the contact portion between the developing sleeve 3 and the elastic blade 4 with the rotation of.

On the other hand, most of the peeled toner 6 is
As the elastic roller 5 rotates, the toner 6 is conveyed into and mixed with the toner 6 in the developing container 2, and the charged charge of the peeled-off toner 6 is dispersed.

By the way, the surface of the developing sleeve 3 is formed with an appropriate roughened surface, so that the probability of friction between the surface of the developing sleeve 3 and the toner 6 is increased, and the transportability of the toner 6 is improved. Has been enhanced.

The uneven surface of the developing sleeve 3 has a surface roughness Rz of 1 μm to 10 μm.
Is formed by subjecting the surface to sandblasting with irregular alundum abrasive grains or sandblasting with regular (spherical) glass beads. Or,
For example, conductive particles such as metal oxide particles, graphite, and carbon are bound with a binder resin such as a phenol resin or a fluororesin to coat the surface of the sleeve base, thereby forming a rough surface on the surface of the developing sleeve 3. It may be formed.

In this embodiment, as the developing sleeve 3,
For example, it is possible to use an aluminum sleeve having a diameter of 16 mm and blasting the surface of the aluminum sleeve with regular glass beads (# 600) to a surface roughness Rz of about 3 μm.

The elastic blade 4 is pressed against the developing sleeve 3, and the toner 6 having entered between them is applied on the developing sleeve 3 to form a thin layer.

The elastic blade 4 is formed of a rubber member such as silicon rubber or urethane rubber (having a hardness of 40 ° to 90 ° specified by JIS). A part of the opposing surface contacts the surface of the developing sleeve 3 by surface contact.

In the present invention, the contact pressure of the elastic blade 4 against the developing sleeve 3 is preferably 5 g / cm to 200 g / cm as a linear pressure in the generatrix direction of the developing sleeve 3.
In the present embodiment, a blade made of urethane rubber having a hardness of 65 ° and a thickness of 1.2 mm was used as the elastic blade 4 and was brought into contact with the developing sleeve 3 at a linear pressure of 50 g / cm.

The linear pressure is measured by stacking three thin plates having a known coefficient of friction, inserting the thin plate into the contact portion between the elastic blade 4 and the sleeve 3, pulling out the central thin plate with a spring balance, and pulling out at that time. The linear pressure is converted from the force and the coefficient of friction.

The non-magnetic toner 6 is used as a non-magnetic one-component developer, and includes a styrene resin, an acrylic resin,
A pigment such as carbon is dispersed in various thermoplastic resins such as polyethylene resin. In the present embodiment, as the toner 6, a toner powder having an average particle diameter of 8 μm, which is composed of a copolymer of styrene / acrylic resin and styrene-butadiene resin and a pigment, and 1.0% of colloidal silica is externally added was used.

Next, the elastic roller 5 in this embodiment will be described in detail.

The elastic roller 5 removes the toner 6 remaining on the developing sleeve 3 and supplies new toner 6 as described above.

As shown in FIG. 1, as the elastic roller 5, a metal core 51 is used as a support shaft, and the outer wall of the bubble communicates with an adjacent bubble, such as silicon rubber, EPDM rubber, or CR rubber. A roller-shaped single-cell foam 52 that is not bonded may be used.

In this embodiment, as the elastic roller 5, a metal core metal 51 having an outer diameter of 5 mm and a silicon rubber foam 52 coated in a roller shape with a thickness of 5 mm and an outer diameter of 15 mm is used. Then, the center of rotation A of the elastic roller 5 can be moved on a straight line connecting the center of rotation and the center of rotation B of the developing sleeve 3 with respect to the outer diameter developing sleeve 3, and the distance x between the axes of the developing sleeve 3 and the elastic roller 5 is reduced. It has a configuration that can be changed.

By forming the roller 5 using a single-cell foam, the toner is appropriately applied to and stripped from the developing sleeve by appropriate irregularities on the roller surface, and the toner is clogged in the roller. Hardening can be prevented.

However, if the elastic roller is formed of a single-cell foam having a rubber hardness that is too high, if the elastic roller is arranged so as to securely contact the developing sleeve 3, the developing roller and the toner may not be contacted. When the contact pressure becomes excessive and the roller using the conventional open-cell foam is hardened, the torque increases, and the toner fusing to the developing sleeve and the fog increase accompanying the toner deterioration are caused.

On the other hand, if the elastic roller is made of a single-cell foam having a rubber hardness that is too low, the foam contains a large amount of low-molecular-weight components of rubber, and the low-molecular-weight rubber becomes less repetitive as the developing operation and toner replenishment are repeated. The components ooze out and adhere to the developing sleeve, and the elasticity is significantly reduced. Adhesion (contamination) of low-molecular-weight components of rubber to the developing sleeve causes the toner newly supplied on the developing sleeve to generate fog or reduce elasticity without being given proper and sufficient triboelectric charging. As a result, poor contact of the elastic roller with the developing sleeve occurs, which causes poor solid black image reproducibility due to insufficient toner supply and stripping.

Further, together with the hardness of the elastic roller, the amount of deformation δ in the radial direction due to pressure contact with the elastic roller developing sleeve is also
It was found that the quality of the developed image was affected.

That is, when the amount of deformation δ in the radial direction of the elastic roller is too large, even if the amount of deformation δ is within the appropriate range when the elastic roller made of open-cell foam is used, Since the foam has a higher hardness than the open-cell foam, the contact pressure of the elastic roller with the developing sleeve and the toner is excessive, and the action of rubbing the toner on the developing sleeve is too strong. The fog increases due to the fusion of the toner and the change (deterioration) of the physical properties of the toner, and the driving torque of the developing sleeve and the elastic roller is significantly increased.

If the amount of deformation δ is too small, the contact of the elastic roller with the developing sleeve in the longitudinal direction is likely to be uneven, causing unevenness in applying and peeling the toner to the developing sleeve of the elastic roller, This was not preferable because density unevenness in the longitudinal direction was caused on the image.

In the present specification, the radial deformation amount δ (mm) of the elastic roller is defined by the following equation. Δ = (1/2) × (δ + β) -x where δ (mm) is the diameter of the developing sleeve, β (mm) is the diameter of the elastic roller, and x (mm) is the developing sleeve and the elastic roller. Is the distance between the axes.

The rubber hardness of the single-cell foamed roller is preferably 8 ° to 15 ° in Asker C hardness, and the radial deformation δ is preferably 0.5 mm to 1.5 mm. found. This will be described below.

Rubber hardness (Asker C) is 5 °, 6 °, 8
Using a silicone rubber foam of °, 15 °, 17 °, and 20 °, an elastic roller 5 having an outer diameter of 15 mm was formed by coating a metal core 61 having an outer diameter of 5 mm with a thickness of 5 mm in the form of a roller. It is incorporated in a developing device having an aluminum sleeve, and this developing device is a copier FC- manufactured by Canon Inc.
2 was installed. The other conditions are that the surface potential of the electrostatic latent image on the photoconductor 1 is set to -600 V in the dark area and -150 V in the light area,
The developing bias applied between the developing sleeve 3 and the developing sleeve 3 is obtained by superimposing a DC voltage of -250 V on an AC voltage having a frequency of 1800 Hz and a peak-to-peak voltage of 1200 V. The peripheral speed of the developing sleeve 3 was set to 70 mm / s, and the gap between the sleeve 3 and the photoconductor 1 was set to about 250 μm. The peripheral speed of the elastic roller 5 was set to 50 mm / s.

Further, by changing the distance x between the shafts, the deformation amount δ (mm) is set to 0.2,
0.3, 0.5, 1.0, 1.5, 2.0, 2.5.

At the time when 2,000 sheets of A4 paper were copied, the results shown in Tables 1 and 2 were obtained.

Table 1 is a table in which rubber hardness is used as a parameter, and Table 2 is a table in which radial deformation δ is used as a parameter.

In Tables 1 and 2, .largecircle. Means good, .DELTA. Means good, and x means bad.

[0041]

[Table 1]

[0042]

[Table 2]

As is apparent from Table 1, the rubber hardness is 5
When a foam having a rubber degree of 20 ° (Asker C) is used, a low molecular weight component of rubber adheres to the developing sleeve 2 to cause fogging. The contact pressure was excessive, and the durability of the toner was deteriorated, and fogging occurred, which was not preferable.

Accordingly, the usable range of the rubber hardness of the single-cell foam rubber forming the supply roller 6 is 6 ° to 17 °.
(ASKER C), and the optimum range is 8 ° to 15 ° (ASKER C). Within this range, no fogging occurs due to adhesion of low molecular weight components of rubber and deterioration of toner, and the developing sleeve 2 and the undeveloped toner 6 can be stably and favorably supplied, and an image faithful to the electrostatic latent image on the photoconductor 1 can be obtained.

In Table 1, whether the fog at the time of 2,000 sheets is due to the deterioration of the toner 6 or the adhesion of the low molecular weight component to the developing sleeve 3 is determined after the developing sleeve 3 is cleaned with MEK after 2,000 sheets. When the image was formed and the fogging still occurred, it was judged that the toner 6 was deteriorated, and when the fog had disappeared, it was judged that the foam rubber low molecular weight component adhered (contaminated) to the developing sleeve 3. .

On the other hand, as is apparent from Table 2, when the amount of deformation δ of the elastic roller 5 in the radial direction is set to 0.2 mm, the application and peeling of the toner 6 onto the developing sleeve 3 by the elastic roller 5 cause unevenness in the longitudinal direction. And uneven density was caused on the image, which was not preferable.

On the other hand, if the deformation amount δ is set to 2.5 mm, the toner 6 is deteriorated and the toner 6 is fused to the developing sleeve 3, resulting in fogging.

Therefore, the appropriate range of the radial deformation δ of the elastic roller 5 made of a single-cell foam is 0.3 mm to
2.0 mm, more preferably 0.5 mm to 1.
5 mm.

In the above range, the density unevenness due to uneven contact of the elastic roller 5 with the developing sleeve 3 and the fog due to the deterioration of the toner 6 due to the excessive contact pressure with the developing sleeve 3 do not occur. Can stably supply the toner 6 to the developing sleeve 3 and strip off the undeveloped toner 6 satisfactorily, and an image faithful to the electrostatic latent image on the photosensitive drum 1 can be obtained. .

FIG. 3 shows a developing device according to another embodiment of the present invention. In this embodiment, a flexible belt photoconductor is used as the photoconductor 1, and the developing sleeve 3 is brought into contact with the belt photoconductor 1 unlike FIG.
The belt photoreceptor 1 is formed by forming, for example, an OPC photosensitive layer on the surface of a belt base layer such as polyethylene terephthalate (trade name Mylar) having aluminum evaporated on the surface layer, and is driven to move in the direction of arrow a. In this embodiment, the peripheral speed of the belt photoreceptor 1 is about 50 mm / s, and the peripheral speed of the developing sleeve 3 is higher than this, and the peripheral speed is about 100 mm / s.
The thin toner layer on the developing sleeve 3 is rubbed with the relative speed with respect to the belt photoreceptor 1, and the contact portions on both sides are also rubbed.
The tribo imparting to the toner 6 is actively performed.

In this embodiment, the bias voltage applied to the developing sleeve 3 is only a DC (direct current) component, and development is performed by a potential difference from the belt photosensitive member 1.

In this embodiment, when a foamed rubber roller having a low hardness is used, a low molecular weight component of rubber adheres to the developing sleeve 3 and further moves onto the photosensitive member 1 so that the latent image on the photosensitive member 1 is disturbed, New adverse effects other than fog such as contamination of the photosensitive layer on the body 1 and generation of cracks occurred.

In this embodiment, since the toner is also subjected to pressure at the nip between the photosensitive member 1 and the sleeve 3, the rubber hardness of the elastic roller 5 is high. It was found that fusion was easily promoted.

However, the rubber hardness of Asker C is 8 ° to 1 °.
When the angle was 5 ° and the amount of deformation in the radial direction was 0.5 mm to 1.5 mm, the above-mentioned inconvenience was not observed, and a good developed image was obtained.

Although the developing device using a one-component non-magnetic developer has been described above, the present invention can also be applied to a developing device using a one-component magnetic developer. In that case, a magnet is provided in the developing sleeve.

[0056]

According to the present invention, the low molecular weight component of the elastic body does not bleed into the developer carrying member, and the developer carrying member and the developer on the developer carrying member can be used for a long period of time. Provided is a developing device having an elastic roller capable of satisfactorily supplying and removing a developer onto a developer carrying member without applying excessive pressure.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of one embodiment of the present invention.

FIG. 2 is an explanatory diagram of a radial deformation amount of an elastic roller.

FIG. 3 is an explanatory view of another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 3 developing sleeve 5 elastic roller 51 cored bar 52 single-cell foam rubber roller

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 15/08

Claims (3)

(57) [Claims] A container accommodating a one-component developer; a rotatable developer carrying member for carrying out the one-component developer from the container and transporting the developer to a developing unit for applying the developer to the electrostatic latent image carrier; A regulating member that regulates a layer thickness of the one-component developer that the developer carrying member conveys to the developing section; and a regulating member that is disposed in the container at a position upstream of the regulating member with respect to a rotation direction of the developer carrying member. Removing the developer from the surface of the developer carrying member that has come into contact with the developer carrying member and has passed through the developing unit and returned to the container, and proceeds toward the regulating member. A rotatable elastic roller for applying a developer to the surface of the member, wherein the elastic roller has an Asker C hardness of 8 to
A 15-degree single-cell foamed elastic roller is supported by a shaft, and the amount of radial deformation at a contact portion with a developer carrying member is 0.5 to 1.5 mm. Developing device. 2. The developing device according to claim 1, wherein the one-component developer is a non-magnetic one-component developer. 3. The developing device according to claim 1, wherein an oscillating bias voltage is applied to the developer carrying member.