JPS6167065A - Developing device - Google Patents

Abstract

PURPOSE:To perform density detection with high reliability by covering the detection surface of a toner density detecting member with an antistatic agent. CONSTITUTION:A developer 2 after being recovered is agitated and mixed on screws 9 and 9' together with toner 2a discharged from a toner tank 10 through the rotation of a toner supplementing roll 13, and the mixture is attracted onto a nonmagnetic sleeve 4 and used for development. When the developer 2 passes over a scraper member 15 after passing through a development gap D, a toner density detecting member 8 which contacts a developer layer detects the toner density in the developer and sends out an external signal corresponding to the detected toner density and a driving means controls the rotation of the toner supplementing roller 13. The toner density detecting member 8 is used as a known member. Then, the toner density detecting member 8 detects detects variation in toner density as variation in the magnetic permeability of the developer to detect variation in the inductance of a detection coil.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a developing device for visualizing an electrostatic charge image formed on the surface of an image carrier by a magnetic brush method.

Conventional technology In image forming devices such as electrophotographic devices and electrostatic recording devices, an electrostatic latent image is formed on the surface of an image carrier (selenium photoreceptor, zinc oxide photoreceptor, organic photoconductor, dielectric material, etc.). , developing the electrostatic latent image by a magnetic brush method using a magnetic developer,
The image is then fixed, or the developed image is transferred onto a transfer sheet such as plain paper and then fixed to obtain the final image.

As the magnetic developer used in the magnetic brush method, a two-component developer which is a mixture of a ferromagnetic carrier and toner particles is often used. This magnetic carrier is made of iron powder, ferrite powder, nickel powder, etc., or its surface is coated with a specific polymer, and the toner particles are made of resin containing additives such as coloring pigments and dyes. The materials are selected so that the carrier particles and toner particles are triboelectrically charged to opposite polarities when mixed.

When an electrostatic latent image is developed using the above-mentioned two-component developer, toner particles are consumed during development, so that when development is repeated, the toner concentration in the developer decreases. If development is performed while the toner density remains low, the image density will decrease.

Therefore, when using a two-component developer, in order to maintain the toner concentration in the developer at a predetermined level (approximately 3 to 10%), a means for detecting the toner concentration is installed, and a means for detecting the toner concentration is installed. Generally, a developing device is configured to replenish toner in response to a signal.

Toner concentration detection methods often utilize the fact that the toner concentration in the developer changes and the apparent magnetic permeability of the developer changes. For example, a Hall element is installed in the magnetic field of a permanent magnet member. , it has been proposed to detect the leakage magnetic flux from the developer (see Japanese Patent Laid-Open No. 117047/1983), but Hall elements have high detection accuracy, but are susceptible to temperature changes and have poor reliability. There's a problem. Therefore, normally, a part of the magnetic circuit of the detection coil is made up of the developer, and the toner concentration is often detected as a change in the inductance of the detection coil.
No. 7 and No. 54-159233).

Problems to be Solved by the Invention In addition, in a developing device using a two-component developer, it is necessary to mix the developer after development with newly replenished toner. In order to scrape off the magnetic sleeve, a scraper member is often provided close to the non-magnetic sleeve (for example, Japanese Utility Model Publication No. 55-50685,
(Refer to each publication of No. 53-34921).

By the way, when detecting toner concentration by detecting changes in the inductance of the detection coil, the detection coil is brought into contact with the developer, but it is best to install the detection coil in a place where the developer is flowing stably. Such a setting is difficult. That is, a change in the flow state of the developer near the detection coil portion causes a change in the apparent magnetic permeability of the developer, which changes the inductance of the detection coil and appears as a detection error.

Therefore, toner concentration has conventionally been detected by taking out a portion of the developer as a sample and performing it at a position that is not exposed to the magnetic field of a permanent magnet (for example, in Japanese Patent Laid-Open No. 53-1269
44 and No. 54-76165). However, in this case, there is a problem that the toner concentration detection member becomes larger and more complicated.

Therefore, in order to dispose the detection coil along the developer flow without providing a sampling mechanism, the detection surface of the toner concentration detection member should face the above-mentioned upper surface of the scraper member, or The top surface is matched. However, in this case, a problem arises in that the developer adheres to the detection surface and a detection error occurs. Therefore, for example, Utility Model Application No. 58-121056.

Although it has been proposed to cover the detection surface with a thin film of synthetic resin, as described in Japanese Patent Application Laid-Open No. 58-140764, the effect is still not sufficient.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art described above and to provide a current (!Jl) device capable of detecting toner concentration with high reliability.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a non-magnetic sleeve that holds a developer containing a magnetic carrier and toner particles, and a plurality of non-magnetic sleeves provided on the surface of the non-magnetic sleeve. a permanent magnet member having magnetic poles, a developer tank that absorbs the developer, a scraper member provided close to the non-magnetic sleeve, and a detection surface in contact with the developer layer flowing along the scraper member. The developing device includes a toner concentration detecting member, in which a detection surface of the toner concentration detecting member is coated with an antistatic agent.

Example Embodiments of the present invention will be described below based on the drawings.

The figure is a sectional view of a developing device showing an embodiment of the present invention.

In the figure, a developer 2 consisting of a magnetic carrier and toner is housed in a developer tank 3, and inside the developer tank 3 there is a cylindrical developer facing the photosensitive drum 1 rotating in the direction of arrow Z in the figure. A non-magnetic sleeve 4 is rotatably arranged. A permanent magnet member 7 having a plurality of magnetic poles (four in the figure) fixed to a shaft 6 is fixedly arranged in the non-magnetic sleeve 4 on its surface. Among the magnetic poles, the N1 pole is a developing magnetic pole located opposite the developing gap D, and the S1 pole is a developing magnetic pole located opposite to the developing gap D.
The poles indicate scraped magnetic poles, and the N2 and S2 poles indicate transport magnetic poles, respectively.

A scraper member 15 is installed horizontally above the S1 pole, and its tip substantially coincides with the vertical line i1 passing through the central axis O of the sleeve 4. It is bent downward in the middle to make it easier.

A pair of screws 9 and 9' are rotatably installed on the opposite side of the non-magnetic sleeve 4 from the photosensitive drum 1, and above the screws 9 and 9' is a toner tank 10 containing toner 2a. is formed. A toner supply roll 13 having a porous elastic layer 12 fixed around a shaft 11 is rotatably provided at the lower opening of the toner tank 10 . Further, a doctor member 14 for regulating the thickness of the developer on the non-magnetic sleeve 4 is installed in the developer tank 3 .

Then, the toner concentration detection member 8 is connected to the scraper member 15.
The detection surface is provided on the back side of the scraper member 15.
It is located almost in line with the top surface of. Furthermore, the detection surface is coated with an antistatic agent 16.

In this toner concentration detection operation, the detection surface comes into contact with the developing layer flowing along the scraper member 15, but since the detection surface is covered with an antistatic agent as described above, the contact between the developer and the detection surface is This prevents the developer from electrostatically adhering to the detection surface. In addition, the detection surface and the developing layer can come into smooth contact. Therefore, malfunctions due to developer adhesion to the detection surface do not occur, and it is possible to detect toner concentration with high reliability.

Known antistatic agents can be used to coat the detection surface, such as inorganic salts such as sodium chloride, anion activators such as fatty acid salts and higher alcohol sulfate salts, quaternary ammonium salts, and fats. Examples include cationic activators such as group amino salts, nonionic activators such as polyhydric alcohols, and the like. The coating may be formed by, for example, dissolving the antistatic agent in water, thoroughly mixing and stirring the solution, spraying or applying the solution onto the detection surface, and then drying the solution. The coating thickness of the antistatic agent should be 10 to 200 t1m, because if it is too thin, it will easily peel off, and if it is too thick, it will reduce the detection sensitivity.
More preferably, the range is 30 to 90 μm.

In addition, according to the above embodiment, the detection surface contacts the lower surface of the phenomenon agent layer on the scraper member 15 in a substantially constant state.

In other words, since the toner concentration is detected while the developer density is approximately constant, the fluctuation width of the output signal can be narrowed (approximately 1 V or more).
This enables highly accurate detection. However, it goes without saying that the positions of the scraper member 15 and the detection surface are not limited to this, and may be other positions that do not reduce the detection accuracy.

The operation of the above-mentioned developing device will be explained as follows.

First, when the non-magnetic sleeve 4 is rotated in the direction of arrow X in the figure, the developer 2 adsorbed onto the sleeve is conveyed from the doctor gap d toward the development gap D. Near the developing gear D, a magnetic brush formed by the developer 2 rubs the surface of the photosensitive drum 1, and an electrostatic latent image (not shown) formed on the drum is developed. The developer 2 after passing through the phenomenon gap D is transferred to the scraper member 1
5 and is scraped off from the non-magnetic sleeve 4 and collected into the developer tank 3.

Next, the collected developer 2 is stirred and mixed with the toner 2a discharged from the toner tank 10 by the rotation of the toner supply roll 13 on the screw 9.9', and then absorbed onto the non-magnetic sleeve 4 again. and then subjected to development.

Further, when the developer 2 passes over the scraper member 15 after passing through the development gap D, the toner concentration in the developer is detected by the toner concentration detection member 8 that comes into contact with the developer layer there, and the toner concentration in the developer is detected according to the detected toner mi. toner supply roll 1 by a driving means (not shown).
Controls the rotation of 3.

The toner concentration detection member 8 is disclosed in Japanese Patent Application Laid-Open No. 54-1592.
No. 33 or JP-A No. 59-99462, No. 59-9
Known materials described in Japanese Patent No. 9463 and the like can be used. These toner concentration detection members detect changes in toner concentration as changes in magnetic permeability of the developer and changes in inductance of a detection coil.

In the figure, the photoreceptor drum 1 is an Se drum (outer diameter 1
20IllIIlφ1 circumferential speed 150n+m/sea), and the non-magnetic sleeve 4 has an outer diameter of 3211+1Rφ.
-Used a ferrite magnet. Also, in the permanent magnet 5,
The N1 pole is 800G, N2, S+, and 82 poles are all 650G (all values on the sleeve).
Angle between θ2. θ3 and θ4 were 90'', 120° and 60'', respectively. However, the angle θ1 formed by the line connecting the N1 pole and the center O of the permanent magnet member 7 and the horizontal line 1 was set to 10''. Toner particles with a diameter of 5 to 20 μm were used.

Then, the doctor gap d and the developing gear D are both set to 4 mm, and the non-magnetic sleeve 4 is set to 20 Or,
I), +1. The reference value of the toner concentration in the developer was set to 5%, and the temperature was set at 25°C, 50% R9H and 35°C.
A copy test was conducted on 2000 sheets each with 80% R and 80% H.

Here, the detection member (according to JP-A No. 59-99462)
Two types were used: one coated with an antistatic agent (Band-29A, manufactured by ThreeBond Co., Ltd.) to a thickness of 50 μm on the detection surface, and one without.

The toner density after the copy test was 4.9% at 25°C and 50% R and H at 35°C.

Even at 80% R and H, the toner density after the copy test was 5.
It became 2%, and detection with accuracy was possible.

For those without coating, the toner concentration is 4.6% at 25°C, 50% R2H, and 6% at 35°C, 80% R2H.
As a result, detection accuracy decreased, and toner adhesion to the detection surface was observed.

Effects of the Invention As described above, the present invention can be said to be an invention with excellent practical effects, since it is possible to expect a developing device capable of detecting toner concentration with high reliability.

[Brief explanation of the drawing]

The figure is a sectional view of a developing device according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 2... Developer, 3... Developer tank, 4... Non-magnetic sleeve, 7... Permanent magnet member,
8... Toner concentration detection member, 15... Scraper member, 16... Antistatic agent.

Claims (1)

[Claims] a non-magnetic sleeve that holds a developer containing a magnetic carrier and toner particles; a permanent magnet member provided within the non-magnetic sleeve and having a plurality of magnetic poles on its surface; a developer tank that absorbs the developer; A developing device including a scraper member provided close to a magnetic sleeve, and a toner concentration detection member having a detection surface in contact with a developer layer flowing along the scraper member, wherein the detection surface of the toner concentration detection member is A developing device characterized by being coated with an antistatic agent.