JP2995819B2 - Developing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used for a copying machine, a printer, and the like by an electrophotographic method.

[Conventional technology]

Conventionally, as a developing device of this type, as shown in FIG. 6, one end of a developer carrying rotary member S which holds and transports a developer on an outer peripheral surface is provided at a downstream side in a developer transport direction by the rotary member. The cantilevered regulating plate B is pressed into contact, the regulating plate frictionally charges the developer supplied to the rotating body, and regulates the amount of the developer attached to the rotating body. There is known a developing device which supplies an electrostatic latent image on an electrostatic latent image carrier and develops the electrostatic latent image.

In the developing device of this type, the free end of the regulating plate is pressed against the developer-carrying rotating body in surface contact, and is taken in between the rotating body and the free end of the regulating plate as the rotating body rotates. The developer thus deposited adheres to the rotating body with a constant layer thickness while being frictionally charged between the regulating plate and the rotating body.

[Problems to be solved by the invention]

However, since the regulating plate is in surface contact with the rotating body, there is a sufficient contact width between the developer and the regulating plate, so that the developer chargeability is high, and because of the surface contact, the contact pressure per unit area is low. Although it has the advantage that it is small and that the developer hardly adheres to the regulating plate, it has a problem that the chargeability is rather high.

In other words, when the developing device is started to be used, particularly when the device is used in a low-humidity environment, the charge amount of the developer that is frictionally charged between the regulating plate and the developer-carrying rotating body is increased. Is generally high, and the amount of developer adhered to the rotating body is increased.

Therefore, even when the developer comes into surface contact with the rotating body as in the case of the regulating plate and the developer is initially used in a low humidity environment, the charged amount of the developer becomes extremely high, and The amount of the developer attached to the body becomes abnormally large.

When an image is formed by supplying the developer from the rotating body to the electrostatic latent image carrier in this state, the background fogging that the toner adheres to the white background portion of the image-formed paper and becomes dirty, In the worst case, self-bias development occurs with the toner, and the entire image is stained black. As a result, not only is the quality of the image deteriorated, but also the image cannot be formed.

Therefore, the present invention does not cause background fog or toner scattering around the image even when the developing device of the above type is started to be used in a low humidity environment. It is an object of the present invention to obtain a high-quality image and obtain a high-quality image stably even during long-term use.

[Means for solving the problem]

In order to solve the above-described problems, the present invention includes a developer carrying rotary member that holds and transports a developer on an outer peripheral surface, and a regulating plate having one end supported at one end on the downstream side in the developer transport direction by the rotary body. By pressing, the regulating plate frictionally charges the developer supplied to the rotating body, regulates the amount of the developer attached to the rotating body, and transfers the developer on the rotating body to the electrostatic latent image carrier. In the supply developing device, the free end of the regulating plate is bent in a direction opposite to the rotating body so that a bending angle is in a range of 90 ° ± 10 ° so as to obtain an arc outer surface, and the bent arc outer surface is formed. The angle θ formed between the contact surface F of the rotating body at the pressure contact position P between the arc outer surface and the rotating body and the portion of the regulating plate on the regulating plate supporting side adjacent to the arc outer surface is 1 ° ≦ θ ≦ 8 °. And the pressure contact position P Is arranged on the upstream side in the developer conveying direction by the rotating body with respect to the cantilever support portion, and the angle θ is such that the rotation of the rotation at the outer surface of the circular arc is performed without bending the regulating plate from the pressing position P. When a portion where a line perpendicular to the 10 μm movement line intersects with the regulation plate passing through a point that has moved linearly by 10 μm toward the cantilever support side of the regulation plate in parallel with the regulation plate when in contact with the body is A. Angle of ∠
An object of the present invention is to provide a developing device characterized by FPA.

The angle θ will be described later in more detail in the embodiments.

The bending angle of the regulating plate for obtaining the outer surface of the arc is 90 degrees.
゜ or about 90 ゜ (90 ゜ ± 10 ゜).

The arc outer surface actually comes into contact with the rotating body in a line contact (edge contact) state with a small nip width. In this case, as shown in FIG.
If the angle is smaller than ゜, the nip width becomes large (surface contact occurs when θ = 0), and the chargeability of the developer becomes too high. If the angle θ is larger than 8 °, the nip width becomes small and the chargeability becomes small. Is too low.

(Operation)

According to the developing device of the present invention, the regulating plate has a bent arc outer surface at a free end thereof in linear contact with the developer-carrying rotating body, thereby appropriately charging the developer passing through the contacting portion and rotating. Apply a moderate amount on the body. Also,
Since the bent portion of the regulating plate comes into contact with the developer-carrying rotating body and exerts an edge effect, when the fixing or filming of the developer on the rotating body occurs, it is scraped off.

〔Example〕

 Hereinafter, embodiments of the present invention will be described.

FIG. 1 is a sectional view showing a mechanism common to the embodiments described below, FIG. 2 is a perspective view of a regulating plate, and FIG. 3 is a diagram showing contact between the regulating plate and a developing sleeve which is a developer carrying rotary member. It is an explanatory view of a state.

The developing device 10 shown in FIG. 1 is mounted on an electrophotographic printer, and has a toner storage tank 11 for storing a toner 1 which is a one-component developer. It has a first stirring member 12 that is driven to rotate clockwise and a second stirring member 14 that is driven counterclockwise.

A developing sleeve 13 is disposed in the opening of the toner storage tank 11, and a driving roller 15 is disposed in the sleeve.

The developing sleeve 13 has an inner diameter of 25m formed by electroforming.
m, a thickness of 35 μm, and a surface roughness Rz of the outer peripheral surface of about 2 μm made of nickel. The outer diameter of the drive roller 15 is slightly smaller than the inner diameter of the sleeve, and is 24 mm.

Both ends of the sleeve 13 are pressed against the drive roller 15 by a pressing guide member (not shown), thereby forming a slack portion 130 facing outward, and the slack portion is formed on the photosensitive drum PC which is an electrostatic latent image carrier. Contact.

A regulating plate 16 is disposed in the toner storage tank 11, and the regulating plate is pressed against the developing sleeve 13. The driving roller 15 is driven to rotate in a counterclockwise direction in the figure by driving means (not shown), and accordingly, the developing sleeve 13 also rotates in the same direction.

The regulating plate 16 has an end at the downstream side in the toner conveying direction by the developing sleeve 13, in other words, an upper end thereof is cantilevered by the toner storage tank 11 as shown in the drawing, and a lower end thereof is the sleeve 13.
The bent outer surface is an arcuate outer surface R, and this surface R is in linear contact with the developing sleeve 13.

As shown in FIG. 3, the center position (line) P of the portion where the surface R contacts the developing sleeve 13, in other words, the contact surface F of the developing sleeve 13 at the pressure contact position P of the surface R, and the regulating plate 16 The angle formed by the upper portion 16a adjacent to the R surface is set to θ.

The details of the method for determining the angle θ in the present embodiment are as follows.

Assuming that the outer surface bending of the free end of the blade 16 is a right angle, it was obtained from the equation of blade deflection.

For example, as shown in FIG. 5, the bent outer surface of the free end of the blade 16 is pressed against the sleeve 13 at the position Q, and a predetermined pressing force is considered (in this embodiment, 3.5 / mm) from a state where the blade 16 is horizontally arranged. When the cantilevered support position is moved to the actual set position and bent (however, the initial horizontal arrangement is limited to the position where the edge is maintained after bending), the bent blade A position P where the free end contacts the sleeve 13;
A straight line connecting a point A where a perpendicular drawn from a point moved in the direction of the supporting point in parallel with the blade before bending in 10 μm horizontally from the position, in other words, intersects with the blade after bending, and a blade free end contact point P The angle ∠FPA formed by the sleeve contact surface F is defined as θ. Applying this to FIG. 3, the angle θ is determined by developing the outer surface R without bending the regulating plate 16 from the pressure contact position P between the bent outer surface R of the free end of the regulating plate 16 and the developing sleeve 13. When in contact with the sleeve 13, 10 μm parallel to the regulating plate 16 toward the cantilever support side of the regulating plate.
The angle ΔFPA is defined as A, where a line passing through the point moved m linearly and perpendicular to the 10 μm movement line β intersects the regulating plate 16 is A. In FIG. 3, the length of the 10 μm movement line β is exaggerated.

According to this developing device, the toner 1 stored in the toner storage tank 11 is stirred by the first stirring member 12 and is supplied onto the developing sleeve 13 by the second stirring member 14, where the toner 1 is frictionally charged by the regulating member 16. A predetermined amount is attached on the sleeve.

The amount of toner adhering to the developing sleeve 13 is conveyed to the developing area by the rotation of the developing sleeve 13 along with the rotation of the driving roller 15, where the toner is applied to the electrostatic latent image on the photosensitive drum PC under the application of a developing bias voltage. Attach and develop the latent image.

The toner image on the photosensitive drum PC thus obtained is transferred onto a transfer sheet conveyed from transfer sheet supply means (not shown), fixed by a fixing device (not shown), and discharged.

Next, specific examples and comparative examples in which the angle θ is changed in the developing device 10 will be described.

In Examples and Comparative Examples described below,
The restricting plate 16 was formed using a SUS301 steel plate having a thickness of t = 0.1 mm, the bending angle α at the lower end was 90 °, and the curvature of the arc outer surface R obtained by the bending was 0.2 mm. The free length L of the regulating plate and the length l of the bent portion (see FIG. 3) were all the same (L = 17.5 mm).

The used toner is a negatively charged toner, and is a bisphenol A type polyester resin (AV: 19, OHV: 23, softening point 123 ° C.,
Tg: 65 ° C.), 100 parts by weight of carbon black MA # 8 (manufactured by Mitsubishi Kasei Kogyo Co., Ltd.), 3 parts by weight of Bontron S-34 (manufactured by Orient Chemical Industry Co., Ltd.), and Viscol TS
-200 (manufactured by Sanyo Chemical Industry Co., Ltd.) 2.5 parts by weight is kneaded, crushed and classified by a known method, and has an average particle size of 10 μm and is distributed in an amount of 80% by weight in a range of 7 to 13 μm. Toner particles were prepared, and hydrophobic silica (Taranox 500, manufactured by Talco) was added to the toner particles as a fluidizing agent.
5% by weight was added and mixed and stirred for 1 minute at a rotation speed of 2000 rpm by a homogenizer.

The system speed of the printer was 35 mm / sec, the pressing force of the regulating plate 16 was about 3 g / mm, and the peripheral speed of the developing sleeve 13 was 105 mm / sec.

As the print mode, two modes are adopted: a blank paper print and a B / W ratio (black / white ratio) 5% chart print under the L / L environment (10 ° C, 15% RH). N environment (23
(° C., 45% RH), a mode for printing a 5% B / W ratio chart was adopted.

Example 1 Printing was performed with the angle θ set to 5 °.

As a result, during the blank printing (5 sheets) in the L / L environment and in the early stage of the use of the developing device, the phenomenon that the toner 1 excessively adheres to the developing sleeve 13 does not occur, and the B / W ratio 5% chart printing mode is used. , A good image was obtained even when 200 sheets were printed, and the toner regulation amount on the developing sleeve 13 during that time was stable, and no significant change was observed.

Furthermore, in the printing mode of the B / W ratio 5% chart under the N / N environment (hereinafter referred to as “N / N running”),
Even after printing 000 sheets, no toner sticking or filming occurred on the developing sleeve 13, and no background fogging or scattering due to a decrease in charge due to toner deterioration was observed.

Example 2 When printing was performed in the same mode as in Example 1 with the angle θ set to 1 °, the developing sleeve was slightly improved when five blank sheets were printed in the initial stage of use of the developing device in an L / L environment.
Although the amount of toner on 13 increased, image fouling such as background fogging and abnormal fogging did not occur, and even when printing 200 sheets in the B / W ratio 5% chart print mode under L / L environment, A high-quality image was obtained with the toner regulation amount on 13 kept stable.

Further, even after 1000 sheets of N / N running, toner adhesion and filming on the sleeve 13 were slight, and background fogging and toner scattering due to a decrease in charge due to toner deterioration were not observed.

Example 3 When the angle θ was set to 8 ° and printing was performed in the same mode as in Example 1, the initial blank paper print 5 was obtained under the L / L environment.
The phenomenon that the toner excessively adheres to the developing sleeve 13 does not occur even at the time of printing, and the sleeve 1 is printed even when printing 200 sheets of the B / W ratio 5% chart under the L / L environment.
No significant change was seen in the toner regulation amount above.

After 1000 sheets of N / N running were completed, no toner adhesion and filming occurred on the sleeve 13. However, scattering around the characters, which is considered to be caused by a decrease in charge due to toner deterioration, occurred within an allowable range but slightly.

Comparative Example 1 When the angle θ was set to 0.5 ° and printing was performed in the same manner as in Example 1, the toner 1 excessively adhered to the sleeve 13 in an L / L environment, at the initial stage of use of the developing device, and during blank paper printing. In addition, an abnormal fogging phenomenon, such as the background of the image (white paper) being stained with black, occurred, and this phenomenon
Lasted up to ~ 100 sheets.

Comparative Example 2 When the angle θ was set to 10 ° and printing was performed in the same manner and mode as in Example 1 below, the image was printed on the sleeve 13 in the L / L environment, at the initial stage of use of the developing device, and when printing a blank sheet. Although the phenomenon of excessive adhesion of toner to the toner was not observed, background fogging and scattering around the characters, which are thought to be caused by the decrease in charge due to toner deterioration, were observed at a considerable frequency after 1000 sheets of N / N running, good Image was not obtained.

 The following table summarizes the above results.

In the above table, the symbol ○ indicates that there is no abnormality, the symbol 異常 indicates a state in which there is some abnormality but is allowable, and the mark x indicates a state in which an abnormality has occurred and cannot be permitted. In the evaluation of the background fog and scattering, a limit sample specified by the present applicant was used as a sample, and a rank of 3 or higher was judged as acceptable.

〔The invention's effect〕

According to the present invention, a regulating plate whose one end is supported by a cantilever at a downstream side of the developer carrying direction by the rotating body is pressed against the developer-carrying rotating body that holds and transports the developer on the outer peripheral surface, and the regulation is performed. A developing device that frictionally charges the developer supplied to the rotating body with the plate and regulates the amount of the developer attached to the rotating body, and supplies the developer on the rotating body to the electrostatic latent image carrier. Even when this is started in a low-humidity environment, there is no occurrence of background fogging or toner scattering around the image, and a high-quality image is obtained from the beginning of use of the developing device. High quality images can be stably obtained even in long-term use.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of the structure of a developing device common to the embodiments of the present invention, FIG. 2 is a perspective view of a regulating plate, FIG. 3 is an explanatory view of a contact state between the regulating plate and a developing sleeve, and FIG. FIG. 5 is an explanatory diagram showing the relationship between the nip width and the contact angle between the plate bending portion and the developer carrier, FIG. 5 is a diagram illustrating a method for determining the angle θ, and FIG. 6 is a diagram illustrating a conventional example. DESCRIPTION OF SYMBOLS 1 ... Toner 10 ... Developing device 11 ... Toner accommodating layer 12, 14 ... Mixing stirring member 13 ... Developing sleeve 15 ... Driving roller 16 ... Regulatory plate 16a ... Part of regulatory plate R ... Arc Outer surface L: Blade length P: Regulator contact position F: Contact surface PC: Photoconductor drum

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-75563 (JP, A) JP-A-61-221769 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/08

Claims (1)

(57) [Claims] A regulating plate having one end pressed against a developer carrying rotary member for holding and transporting the developer on the outer peripheral surface, the regulating plate having one end supported at a downstream side in a developer transport direction by the rotary body; A developing device that frictionally charges the developer supplied to the rotating body with the plate and regulates the amount of the developer attached to the rotating body, and supplies the developer on the rotating body to the electrostatic latent image carrier. The bending angle of the free end of the regulating plate in the direction opposite to the rotating body is 90 ° ± 10 so as to obtain an arcuate outer surface.
規 制, and the bent circular arc outer surface is provided on the regulating plate supporting side adjacent to the contact surface F of the rotating body at the pressure contact position P between the circular arc outer surface and the rotating body and the arc outer surface of the regulating plate. Is pressed against the rotating body so that the angle θ formed by the portion becomes 1 ° ≦ θ ≦ 8 °, and the pressed position P is upstream of the cantilever support portion in the developer conveying direction by the rotating body. And the angle θ is
From the press-contact position P, the restricting plate passes through a point that has moved linearly by 10 μm toward the cantilever support side of the restricting plate in parallel with the restricting plate when the restricting plate is in contact with the rotating body on the outer surface of the arc without bending. An angle こ と FPA when a portion where a line perpendicular to the 10 μm movement line intersects with the regulation plate is defined as A, wherein the angle ∠FPA.