JP2877163B2 - Electrophotographic developing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic developing apparatus such as a copying machine, a printer or a facsimile, and more particularly, to a developing apparatus using a developer comprising a carrier and a toner. It concerns improvement.

[Conventional technology and problems]

With respect to electrophotography, as a method of forming and developing a magnetic brush, a carrier such as iron powder and a non-magnetic toner are used, and a DC voltage is applied between a photoconductor and a non-magnetic sleeve as a developer carrier. 2. Description of the Related Art A two-component developing method for performing development has conventionally been employed. This method is the earliest established method, in which a carrier and a toner are mixed at a predetermined ratio, the toner is charged to a predetermined polarity by frictional charging, and adheres to an electrostatic latent image portion on a photoconductor, In addition to facilitating transfer, a method for colorization, which has become popular in recent years, is a preferable method because a toner containing no magnetic component is used. However, in order to charge the toner and the carrier satisfactorily and keep the toner concentration in the consumed developer uniform, a means for stirring the developer and a toner concentration monitoring device are required. However, it has the disadvantages of increased complexity and complexity, and increased cost. Such a problem is a common name using a resin carrier, which has been put into practical use as a method for solving the problem of carrier adhesion in the two-component developing method.
It is also built in the 1.5-component system, and in the 1-component development system using magnetic toner, which is proposed as an alternative to the 2-component development system, the toner aggregation caused by the use of the insulating toner is also caused. A carrier is used in combination to solve the white spots on the image, and it is necessary to keep the toner concentration in the developer constant in order to stabilize the image quality, causing the same problem.

[Means for solving the problem]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a developing device using a developer comprising a carrier and a toner, wherein a device for monitoring the toner concentration in the developer and a stirring device for keeping the toner concentration constant. The purpose of the present invention is to eliminate the need for a device and to reduce the size and cost of the device.

The present invention relates to a magnetism generating device having a movable portion for forming a magnetic brush by attaching and transporting a developer in a developing container arranged in close proximity to a photoconductor for forming a latent image and a visible image, A developing device provided with a developer regulating plate that regulates an amount of developer conveyed in front of a brush forming region, wherein the developer includes a carrier and a toner, and the developer regulating plate is sandwiched between the developer regulating plate to generate magnetism. The apparatus forms two magnetic poles of the same polarity, has a magnetic force of at least 50 gauss or more in the valley of the magnetic distribution between the magnetic poles, and has an angle between the upstream magnetic pole and the developer regulating plate of 25 to 80.
傾 き, the inclination of the magnetic field distribution at the position of the developer regulating plate is 4 Gauss / 1 ゜ or more, and the carrier is screwed by the magnetic force of the magnetic generator before the developer regulating plate. And an electrophotographic developing apparatus characterized in that the image forming apparatus is formed.

According to another aspect of the present invention, there is provided a magnetic generator having a movable part for forming a magnetic brush by attaching and transporting a developer in a developing container disposed in proximity to a photoreceptor for forming a latent image and a visible image. And a developing device provided with a developer regulating plate for regulating the amount of developer conveyed before the magnetic brush forming region, wherein the developer comprises a carrier and a toner, and an upstream side of the developer regulating plate. A developer regulating auxiliary plate is provided, two magnetic poles having the same polarity are formed by a magnetic generator with the developer regulating auxiliary plate interposed therebetween, and a magnetic force of at least 50 gauss or more is formed in a valley of a magnetic distribution between the magnetic poles. And the angle between the upstream magnetic pole and the developer regulating auxiliary plate is 25 to 80 °, and the inclination of the magnetic field distribution at the position of the developer regulating auxiliary plate is 4 Gauss / 1 ° or more, In front of the developer regulating auxiliary plate, Carrier is one which the contents of the electrophotographic developing apparatus is characterized by being configured so as to form a screw of the carrier by the magnetic force of the magnetic generator.

Further, the present invention provides a magnetic generator having a movable portion for forming a magnetic brush by attaching and transporting a developer in a developing container disposed in proximity to a photoreceptor for forming a latent image and a visible image. And a developing device provided with a developer regulating plate for regulating the amount of developer conveyed before the magnetic brush forming region, wherein the developer comprises a carrier and a toner, and an upstream side of the developer regulating plate. A developer regulating auxiliary plate is provided, two magnetic poles having the same polarity are formed by a magnetic generator with each of the developer regulating plate and the developer regulating auxiliary plate interposed therebetween, and a valley of magnetic distribution between the magnetic poles is formed. The part has a magnetic force of at least 50 Gauss or more, the angle between the upstream magnetic pole and the developer regulating plate and the angle between the upstream magnetic pole and the developer regulating auxiliary plate are 25 to 80 °, respectively, The developer regulating plate and the developer regulating The inclination of the magnetic field distribution at each position of the auxiliary plate is 4 gauss / 1 ゜ or more, and the carrier is caused by the magnetic force of the magnetic generator before the developer regulating plate and the developer regulating auxiliary plate. And an electrophotographic developing apparatus characterized in that the screw is formed.

In the present invention, the magnetic brush forming region refers to a magnetic brush forming region formed by a developing pole in a magnetic generator.

That is, the present invention provides an apparatus which solves the problem of using a carrier and a toner as a developer in an electrophotographic development system, and which can be effectively applied regardless of whether the toner used is non-magnetic or magnetic. It is.

Carriers usable in the present invention are ferrite,
Iron, fine grains of steel, or fine grains obtained by treating them with a resin coating or an oxide film, and the average grain size is appropriately selected from those having a particle size of 30 to 150 μm. Is important, and the saturation magnetization is desirably 20 to 200 emu / g, depending on the usage.
Desirably, it is 50 to 200 emu / g. When the toner to be used is a magnetic toner, it is preferable that the saturation magnetization of the magnetic toner be at least about 10 emu / g or more as a preferable condition at the time of development.

The toner that can be used in the present invention contains a styrene / acrylic copolymer resin or a polyester resin as a main component,
The toner may be a non-magnetic toner containing necessary pigments and others, or may contain a styrene / acrylic copolymer resin or a polyester resin as a main component, and may contain magnetic fine powders such as magnetite and ferrite, and may contain a pigment and a charge controlling agent. , Etc., in which case the content of the magnetic fine powder is desirably 15 wt% or more. In any case, the toner is not the main element of the present invention, but it is preferable that the insulation resistance is high in view of the conditions during development.

The gist of the present invention is that, by the magnetic force of the magnetic generator, before the developer regulating plate, or when the developer regulating plate and a developer regulating auxiliary plate provided upstream thereof, the developer regulating auxiliary plate,
Or, a carrier forms a screw in front of each of the developer regulating plate and the developer regulating auxiliary plate, and a non-magnetic sleeve or a belt which is a movable portion for transporting a developer provided outside the magnetic generator. The object is to cause the screw to rotate with the rotation and movement, and to function to take in the toner near the screw into the carrier.

As the magnetic field distribution created by the magnetic generator to form the screw of the carrier, the developer regulating plate is sandwiched, or, when the developer regulating plate and the developer regulating auxiliary plate are provided, the developer It is preferable that two magnetic poles of the same polarity are formed with the regulating auxiliary plate or the developer regulating plate and the developer regulating auxiliary plate interposed therebetween. The magnetic field distribution and device as shown in the figure are not suitable for the present invention.

That is, the type of the two-peak magnetic pole shown in FIG. 1 is used for regulating the portion of the developer ear formed by the magnetic pole (the portion where the amount of the developer becomes the coarsest), where θ
{20-32} and θ ₄ (θ ₃ ) {10-16}.
FIG. 2 is disclosed in JP-A-59-231566, and as described in the publication, a magnetic particle restraining member (magnetic blade) (1)
By providing a magnet (18) downstream of 5), the magnet (1
The magnetic flux density of the magnetic field formed by 4) is rapidly weakened, and a thin layer of developer (non-magnetic) (17) is formed without the magnetic particles (16) leaking before the magnetic blade (15). Things. In the figure, (1) is a photoreceptor, (12) is a sleeve, (13) is a developing container, (19) is a bias power supply, (20)
Is a seal member.

As the magnetic field distribution according to the present invention, for example, in the developing device having the configuration shown in FIG. 3, the one shown by a broken line in FIG. 4 is preferable. That is, the magnetic poles (85), (82) having the same polarity across a developer regulating plate (hereinafter referred to as a doctor blade) (4) by a magnetic field distribution (8) created by a magnetic roll (3) as a magnetic generator. Are formed.

Non-magnetic sleeve (2) which is a movable part for transporting the developer
Is rotated in the direction of the arrow, the magnetic force of the magnetic roll (3) moves the carrier (7) held on the sleeve (2) in the direction of the broken line in FIG. At this time, a part of the carrier is conveyed to the developing zone through a gap between the doctor blade (4) and the sleeve (2), and the remaining part forms a stagnant portion (41) just before the doctor blade (4). Ears are formed by the magnetic pole (82) in front of the stagnation portion (41), but when the carrier is continuously fed into the stagnation portion (41) by the rotation of the sleeve (2), some of the carriers become carriers. It becomes a chain (42) and separates from the staying part (41), and forms a part of the ear in front of the staying part. When this is repeated, the spikes formed by the magnetic poles (82) are pushed toward the upstream by the carrier chains (42) supplied from the stagnation section (41), and the uppermost stream is taken into the carrier layer (44). I will be. Here, the spikes formed by the magnetic poles (82) become the screws (43) of the carrier and rotate in the opposite direction (arrow) to the rotation direction (arrow) of the sleeve (2). Here, as shown in FIG. 3, when the toner (6) is present on the upper portion, the toner (6) is taken into the carrier as the carrier moves, and the developer (carrier) (7) and the toner (6) are mixed. Stirring will take place continuously and without the need for special stirrers.

The magnetic field distribution of the present invention is described in more detail below.

Angle theta ₁ of the magnetic pole (doctor pole) (85) and the doctor blade (4) downstream side across the doctor blade (4) is appropriately set between 5 and 35 ° following the transfer force by the doctor pole. The angle θ ₂ formed between the magnetic pole (hereinafter referred to as a stirring pole) (82) and the doctor blade (4) on the upstream side is the space required for forming the carrier retaining portion (41) and the carrier screw (43). It must be secured, and it must be 25-80 ° because the upstream carrier must be sufficiently conveyed.
゜ is preferred. The magnetic force of the valley (84) between the two magnetic poles (85) and (82) must be such that the carrier is held on the sleeve (2) and depends on the saturation magnetization of the carrier. Must be greater than or equal to 50 Gauss. Furthermore, the magnetic field distribution (8) at the position of the doctor blade (4)
Is represented by an amount of change in magnetic force as shown in FIGS. 6 and 7 as an index for giving an appropriate conveying force to the developer.
ΔG / Δθ ゜ must be at least 4 Gauss / 1 ゜, and 4
At less than Gauss / 1 ゜, the shortage of the transport amount is noticeable.

 To describe the magnetic field distribution in more detail,
In relation to (5), the opening of the developing tank (9) as shown in FIG.
Degree α₀If there is a distribution of magnetic poles (82) over the entire area of
Both non-magnetic toner and magnetic toner are transported without any problem.
However, as shown by a broken line in FIG.
(9) opening angle α₀′, The magnetic toner becomes
Conveyed by magnetic force, but in the case of non-magnetic toner
Dead space is created, and used toner is used.
Wasteful. Therefore, when using non-magnetic toner,
The magnetic field distribution (8) changes the polarity of the magnetic pole (82) (ie,
Power The point (83) is outside the developing container (5)
It is necessary to take such a distribution.

In the above description, the screw of the carrier is formed before the doctor blade (4), and the carrier and the toner are agitated. As shown in FIG. 8, the developer is regulated before the doctor blade (4). It goes without saying that the same effect can be obtained by providing the auxiliary plate (11) and forming the screw of the carrier in front of the auxiliary plate (11). In this case, the gap between the auxiliary plate (11) and the sleeve (2) needs to be larger than the gap between the doctor blade (4) and the sleeve (2). Also, the case where the movable portion for transporting the developer is a non-magnetic sleeve has been described above,
The part to be conveyed may be a belt.

Now, regarding the amount of the carrier used in the present invention,
With the configuration shown in the figure, the diameter of the non-magnetic sleeve is 20 mm and the length in the axial direction is
230mm, opening angle is about 80 °, gap between doctor blade (4) and sleeve (2) is about 0.3mm. When ferrite carrier is used, it depends on the position of stirring pole (82). It is preferable in forming a screw, and the upper limit is until the screw of the carrier is buried in the carrier. When the amount of the carrier is small, the developer becomes toner rich, and when the amount of the carrier is large, the toner concentration of the developer naturally becomes low. In the case of a magnetic toner, since the toner itself is controlled by the magnetic roll (3), good image quality can be obtained even when the toner is relatively rich. However, in the case of a non-magnetic toner, if the toner becomes too rich, ground fog undesirably occurs. In this sense, it can be said that a better result can be obtained when the developer concentration is lower than that in the case of the magnetic toner, and there is no problem if the developer concentration is 10% or less as is usually performed.

〔Example〕

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the examples.

Example 1 In a developing device having the structure shown in FIG.
The photosensitive member 1 is rotated in the direction of the arrow at a peripheral speed of about 47 mm / sec,
A non-magnetic sleeve (2) made of S316 having a diameter of about 20 mm and an axial length of about 230 mm is rotated at a peripheral speed of about 320 mm / sec in the direction of the arrow, and a bias voltage of -550 V is applied to an image potential of about -620 V on the drum. After applying reversal development by rubbing with the developer spikes, transferring to paper and heat fixing, the resolution was about
A good printed matter having an image density of 300 to 400 dpI and an image density of about 1.38 was obtained. The carrier used was a ferrite mainly composed of nickel-zinc, having an average particle size of about 104 μm and an electric resistance of about 2 μm.
It has various characteristics of × 10 ⁹ Ω-cm and saturation magnetization of about 60 emu / g, and uses about 70 g. The used toner has an average particle size of about 12 μm, an electric resistance of about 4 × 10 ¹⁶ Ω-cm, and a saturation magnetization of about
Negative charge (approximately -25%) composed mainly of 30emu / g styrene / acrylic resin, containing about 30wt% of magnetite fine powder, and also containing carbon black, charged material, silica gel, etc.
μq / g) Magnetic toner.

In this embodiment, the carrier forms a screw of a carrier having a diameter of about 15 to 20 mm by the mechanism already described in detail,
With the rotation of the sleeve, the sleeve was rotated in the opposite direction to produce a toner stirring action. Incidentally, unlike the case of the carrier alone, the screw of the carrier is reduced to a diameter of about 10 to 15 mm when the toner is charged, but this is because the toner is charged,
This is probably because the average saturation magnetization of the developer was reduced, or the frictional resistance was reduced by the toner.

If the magnetic field distribution (8) by the magnetic roll (3) is described according to the symbols in FIG. 4, the doctor pole (85) is 660 gauss, the stirring pole (82) is 615 gauss, and the valley (84) between both poles is Three
The change ΔG / θ ゜ of the magnetic force at the position of 90 gauss and the doctor blade (4) is about 6 gauss / 1 ゜, and the magnetic poles (85) and (82) have θ ₁ = 16 ° and θ ₂ = 34, respectively.゜ was formed with the doctor blade in between. The gap between the doctor blade (4) and the sleeve (2) was about 0.4 mm.

Example 2 The carrier had substantially the same structure as that of Example 1 except that the carrier was made of magnetite and the surface was treated with a violet treatment.
μm, electric resistance about 1 × 10 ⁶ Ω-cm, saturation magnetization about 180 emu /
g, use amount to about 150g, and toner with an average particle size of about 12
μm, electrical resistance of about 1 × 10 ¹⁵ Ω-cm. Changed to a negatively charged non-magnetic toner containing styrene / acrylic resin as the main component.
I, a good printed matter with an image density of about 1.3 was obtained.

〔The invention's effect〕

As described above, according to the present invention, the screw of the carrier is formed, which eliminates the necessity of the agitating device and other auxiliary members conventionally required when using the carrier and the toner. The present invention is extremely useful.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a conventional developing device and its magnetic field distribution, FIG. 2 is a schematic diagram of a developing device described in JP-A-59-231566, and FIG. 3 is a schematic diagram showing an example of a developing device of the present invention. FIG. 4 is a schematic diagram showing the magnetic field distribution of the apparatus shown in FIG. 3, FIG. 5 is a conceptual diagram of the main part of FIG. 3, and FIGS. 6 and 7 are magnetic field distributions near the doctor blade, respectively. FIG. 8 is a schematic diagram showing another example of the developing device of the present invention. DESCRIPTION OF SYMBOLS 1 ... Photoreceptor, 2 ... Sleeve 3 ... Magnetic roll 4, ... Doctor blade 5 ... Developing container, 6 ... Toner 7 ... Carrier, 8 ... Magnetic field distribution 9 ... Developing tank

Claims (6)

(57) [Claims] A magnetic generating device having a movable portion for attaching and transporting a developer into a developing container disposed in proximity to a photoreceptor for forming a latent image and a visible image to form a magnetic brush; A developing device provided with a developer regulating plate for regulating the amount of developer conveyed in front of the magnetic brush forming region, wherein the developer comprises a carrier and a toner; Two magnetic poles having the same polarity are formed by the magnetic generator, and have a magnetic force of at least 50 gauss or more in the valley of the magnetic distribution between the magnetic poles, and the angle between the upstream magnetic pole and the developer regulating plate is 25 to 25. 80 °, the gradient of the magnetic field distribution at the position of the developer regulating plate is 4 gauss / 1 ° or more, and the carrier is moved by the magnetic force of the magnetic generator before the developer regulating plate. Forming screw Electrophotographic developing apparatus is characterized in that the sea urchin configuration. 2. A magnetic generator having a movable portion for attaching and transporting a developer into a developing container disposed in close proximity to a photoreceptor for forming a latent image and a visible image to form a magnetic brush. A developing device provided with a developer regulating plate for regulating an amount of developer conveyed in front of a magnetic brush forming region, wherein the developer comprises a carrier and a toner, and an upstream side of the developer regulating plate. A developer regulating auxiliary plate is provided, and two magnetic poles of the same polarity are formed by a magnetic generator with the developer regulating auxiliary plate interposed therebetween, and a magnetic force of at least 50 gauss or more is formed in a valley of a magnetic distribution between the magnetic poles. And the angle between the upstream magnetic pole and the developer regulating auxiliary plate is
25 to 80 °, the gradient of the magnetic field distribution at the position of the developer regulating auxiliary plate is 4 gauss / 1 ° or more, and the carrier is located at a position before the developer regulating auxiliary plate, An electrophotographic developing apparatus, wherein a screw of a carrier is formed by force. 3. A magnetic generating device having a movable portion for attaching and transporting a developer into a developing container disposed in close proximity to a photoreceptor for forming a latent image and a visible image to form a magnetic brush. A developing device provided with a developer regulating plate for regulating an amount of developer conveyed in front of a magnetic brush forming region, wherein the developer comprises a carrier and a toner, and an upstream side of the developer regulating plate. A developer regulating auxiliary plate is provided, two magnetic poles having the same polarity are formed by a magnetic generator with each of the developer regulating plate and the developer regulating auxiliary plate interposed therebetween, and a valley of a magnetic distribution between the magnetic poles is formed. At least
Having a magnetic force of 50 gauss or more, the angle between the upstream magnetic pole and the developer regulating plate and the angle between the upstream magnetic pole and the developer regulating auxiliary plate are each 25 to 80 °, and the developer The inclination of the magnetic field distribution at each position of the regulating plate and the developer regulating auxiliary plate is 4 gauss / 1 ゜ or more, and the carrier is disposed in front of each of the developer regulating plate and the developer regulating auxiliary plate. An electrophotographic developing device, wherein a screw of a carrier is formed by a magnetic force of a generator. 4. The carrier is selected from ferrite, iron, and steel fine grains having a saturation magnetization of 20 to 200 emu / g, and fine grains obtained by treating them with a resin coating or an oxide film.
4. The developing device according to any one of items 3 to 3. 5. The developing device according to claim 1, wherein the toner is a non-magnetic toner containing a styrene / acrylic copolymer resin or a polyester resin as a main component. 6. The magnetic toner according to claim 1, wherein the toner is a magnetic toner containing a styrene / acrylic copolymer resin or a polyester resin and a magnetic fine powder as main components, and having a content of the magnetic fine powder of 15% by weight or more. The developing device described in each item.