JPH09311551A - Developing device and color electrophotographic device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably execute development with high image quality at a high speed and to prevent filming onto a developing roll at the time of printing at a high speed ant at the time of using a low-temperature-fixed toner in the case where development is executed by bringing the developing roll having a surface where a toner layer is formed into contact with a photoreceptor. SOLUTION: In this developing device, the toner layer is formed on the developing roll 2 and a latent image formed on the photoreceptor 1 is developed by bringing the roll 2 into contact with the photoreceptor 1. In such a case, the roll 2 is constituted by fitting a rubber roll to a sleeve 2 whose surface is formed of non-magnetic substance or weak magnetic substance. A carrying roll 3 equipped with a magnet body magnetized to be multipolar at equal intervlas is rotatably arranged proximately to the roll 2, and a regulating plate 4 regulating the layer thickness of developer 11 including carrier and toner is provided on the outer periphery of the roll 3. The developer layer 11 regulated by the regulating plate 4 is brought into contact with the roll 2 while rotating, and electric field is allowed to act on a gap between the rolls 3 and 2, whereby the toner layer is formed on the roll 2 and development is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an electrophotographic apparatus such as a copying machine, a printer, a facsimile, and a color electrophotographic apparatus using the developing apparatus.

[0002]

2. Description of the Related Art Conventional developing devices include a two-component developing device using a two-component developer containing a carrier and a toner and a one-component developing device using a one-component developer containing only toner.
The one-component developing device is advantageous in downsizing and cost reduction because it does not need to use a carrier and does not require a developer mixing ratio control mechanism, and also has an advantage that no carrier is attached to the photoconductor. , Is used in a color electrophotographic apparatus in which a plurality of developing devices are arranged. As shown in FIG. 2, a conventional one-component developing device 21 using a non-magnetic color toner used in a color electrophotographic apparatus includes a developing roll 2, a blade 18, a conveying roll 20, and a toner hopper 6 facing a photoconductor 1. The stirring blade 7 and the toner leakage prevention member 19 are provided, and the toner in the toner hopper 6 is supplied from the opening 13 to the vicinity of the conveying roll 20 by the stirring blade 7 and further conveyed to the vicinity of the developing roll 2 by the conveying roll 20. Then, the toner layer 1 is formed on the developing roll 2 by the blade 18.
2 is formed and is conveyed to a portion facing the photoconductor 1 by the rotation of the developing roll 2, and the toner layer 12 is brought into contact with the electrostatic latent image on the photoconductor 1 and a developing electric field is applied to the developing portion to form the toner. The image was formed.

Regarding such a non-magnetic one-component developing device, Japanese Patent Publication No. 7-43546 and Japanese Utility Model Publication No. 7-2068.
Those described in Japanese Laid-Open Patent Publication No. 3-9 are known. Regarding the magnetic one-component developing device, the one described in Japanese Patent Publication No. 2-48901 is known.

Further, as an example of using a magnet roll as a conveying roll in a non-magnetic one-component developing device that does not use magnetic toner, a sponge roll is used as a developing roll as described in JP-A-55-77764. Contact-developing, and as described in JP-A-3-59576 and JP-A-61-239266, non-contact development is performed by providing a space between the toner layer on the developing roll and the photoconductor. A method of performing the same is known.

[0005]

However, if a conventional non-magnetic one-component developing device is used to obtain a high-speed and high-definition color image or to apply low-temperature fixing required for power saving, There is a tendency that toner filming occurs on the developing roll, image quality is deteriorated, and the replacement life of the developing device is shortened.

Further, in a developing device that applies only non-magnetic toner to a developing roll, in order to perform high-definition, high-definition, high-quality image development at high speed, there are the following problems for each element of the developing machine. It was The challenge is to improve the durability of the developing roll.

A sufficient toner adhesion amount is secured in order to form a uniform toner layer on the developing roll and obtain a high image density.

The carrier is prevented from adhering to the developing roll.

To maintain the toner concentration of the developer held on the conveyance roll having a magnet body.

To improve the reproducibility of fine halftone dot images and gradations.

It is something like that.

That is, for example, in the method of performing contact development using a sponge roll as the developing roll, when used at a high speed, the shape of the developing sponge roll is apt to be deformed and the replacement cycle tends to be shortened. There was a problem in terms of roll durability. Further, in the method of performing non-contact development by providing a space between the toner layer on the developing roll and the photoconductor, the reproducibility of fine halftone dot images and gradation tends to be insufficient, and the above-mentioned fine There was a problem in reproducibility of various halftone images and gradations.

The present invention has been made in view of the above-mentioned circumstances of the prior art. A first object of the present invention is to provide a toner filming on a developing roll in a developing device for applying only toner to the developing roll to perform development. An object of the present invention is to provide a developing device capable of preventing the occurrence of

A second object of the present invention is to provide a developing device capable of stably maintaining high-speed and high-quality development over a long period of time.

Further, a third object is to provide a color electrophotographic apparatus equipped with these developing devices.

[0016]

In order to achieve the above object, the present invention is configured as follows.

That is, the first means is a surface of a developing device for forming a toner layer on a developing roll and bringing the developing roll into contact with a photoconductor to visualize the latent image formed on the photoconductor. A developing roller is formed by fitting an elastic roll to a sleeve formed of a non-magnetic material or a weak magnetic material, and is provided with magnet bodies magnetized in multiple poles at equal intervals in proximity to the developing roller. A transport roll is rotatably disposed, a regulation plate for regulating the layer thickness of the developer containing the carrier and toner is provided on the outer periphery of the transport roll, and the developer layer regulated by the regulation plate is provided on the development roll. It is characterized in that the toner layer is formed on the developing roll by contacting while rotating and applying an electric field to the gap between the transport roll and the developing roll.

In this case, the toner reservoir for temporarily storing the toner supplied from the toner hopper is provided at a position on the opposite side of the transport roll from the developing roll,
A developer chamber in which the developer circulates and a guide plate for guiding the toner from the lower part of the toner reservoir to the developer chamber are further provided, and the toner is removed from the toner reservoir according to the volume change of the developer in the developer chamber. It may be configured to be supplied.

The magnet body may be constructed by disposing a plurality of pairs of magnetic pole portions having the same polarity. The magnet body has 8 to 64 magnetic poles, and the ratio of the peripheral speed of the magnet body to the peripheral speed of the developing roll is 1.5 to 5.0.
Should be set in the range.

The absolute value of the difference between the first gap formed by the developing roll and the conveying roll and the second gap formed by the regulating plate and the conveying roll is 0 to 0.4 mm. The bias voltage applied to the developing roll is preferably a combination of a DC voltage and an AC voltage.

The developing device described above.

A second means is to arrange a plurality of developing devices respectively accommodating a developer corresponding to each color around a plurality of photoconductors, and the photoconductors rotate one or more times to form a plurality of latent images corresponding to each color. And a latent image is developed by a plurality of developing devices to form toner images of a plurality of colors on a photoconductor in the color electrophotographic apparatus. Is used to control at least one of the electric field or the peripheral speed ratio of the gap between the developing roll and the conveying roll based on the toner image of each color.

A third means is to provide a regulation plate for regulating the layer thickness of the developer containing the carrier and toner on the outer periphery of the carrying roll having a magnet body, and to form a magnetic brush on the carrying roll to form the magnetic layer. In a developing device for developing by bringing a brush into contact with a photoconductor, a multi-pole magnetized magnet body is rotatably arranged, in which the conveying rolls are provided with a plurality of pairs of magnetic pole portions having the same polarity at equal intervals. And is developed by applying an electric field to the gap between the transport roll and the photoconductor.

According to a fourth means, a regulation plate for regulating the layer thickness of the developer containing the carrier and toner is provided on the outer periphery of the carrying roll having a magnet body, and a magnetic brush is formed on the carrying roll, and In a developing device that transfers toner from a brush to a photosensitive member to perform development, the developing device is provided at a position on the opposite side of the transfer roller from the photosensitive member and a toner reservoir for temporarily storing toner supplied from a toner hopper. A developer chamber in which the agent circulates and a guide plate for guiding the toner from the lower part of the toner reservoir to the developer chamber are provided, and the toner is supplied from the toner reservoir according to the volume change of the developer in the developer chamber. It is characterized by being configured as follows.

In the first means or the fourth means, the guide plate is provided on the upper part of the transport roll.

Further, in the first to fourth means,
The developer is composed of a conductive resin coated carrier having a particle diameter of 30 to 80 μm and a toner to which a conductive additive having a particle diameter of 5 to 8 μm is added.

According to this structure, a blade for contacting the developing roll is not provided, but a carrying roll having a magnet body is provided with a gap between the developing roll and the developer (carrier and toner held on the outer periphery of the carrying roll. ) Is contacted with the developing roll to form a toner layer on the developing roll, and the developer layer is rotationally contacted with the developing roll in the counter direction to develop the electrostatic latent image on the photoconductor 1. Since the toner remaining on the developing roll can be scraped off later, toner filming does not occur on the developing roll.

Since the surface of the metal sleeve is made of a non-magnetic material or a weak magnetic material, the surface of the metal sleeve can be prevented or suppressed from being magnetized by the magnet body of the transport roll.
This can prevent the carrier from adhering to the developing roll.

By covering the elastic roll with the metal sleeve, the durability of the developing roll can be improved while maintaining elasticity.

Further, the volume of the developer in the developer chamber is reduced as the toner is consumed, and in response thereto, the toner from the toner reservoir is supplied to the developer chamber and mixed with the developer. The toner concentration can be maintained substantially constant only by the mechanical structure.

[0031]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a schematic configuration diagram of the developing device according to the exemplary embodiment. In FIG. 1, the developing device 8 includes a developing roller 2 facing the photoconductor 1, a conveying roller 3, a regulating plate 4, a stirring blade 7 provided in the toner hopper 6, a developing roller 2 and a conveying roller 3.
Bias power supplies 14 and 15 applied to the developer guide plate 5, and the like.

In the developing device 8 having the above general structure, the toner in the toner hopper 6 is supplied from the opening 13 to the vicinity of the upper portion of the transport roll 3 by the stirring blade 7. A developer guide plate 5 is provided on the upper portion of the transport roll 3 and regulates the movement of the toner dropped from the opening 13 to the transport roll 3 side so as to extend downward from a portion along the developer guide plate 5. While forming the toner reservoir 9,
The direction of toner movement is regulated. The toner moves below the toner pool 9, in other words, from the opening 9a on the lower end side of the developer guide plate 5 to the transport roll 3 side. In addition, the regulation plate 4 is provided in a portion that is continuous with the developer guide plate 5 on the downstream side in the rotation direction of the transport roll 3 and that is in contact with the upper portion of the transport roll 3, and is held by the transport roll 3. The layer thickness of the layer 10 is regulated. As a result, the toner scraped into the toner reservoir 9 by the stirring blade 7 is regulated by the regulation plate 4 and is accompanied by the circulation of the developer 11 which is recirculated (U-turn).
The developer 11 containing the magnetic substance carrier and the non-magnetic toner mixed with 1 and held by the transport roll 3 is held by the transport roll 3 and moves in the direction of the regulation plate 4 and is not regulated by the regulation plate 4. Moves to the developing roll 2 side, and the regulated developer 11 returns to the lower side of the toner reservoir 9 along the developer guide plate 5 to repeat the process.

The developer 11 regulated by the regulation plate 4 and having a predetermined layer thickness and moved to the developing roll 2 side rotates the conveying roll 3 in the counter direction with respect to the developing roll 2 to bring it into contact with the developing roll 2. An electric field is applied between the transport roll 3 and the developing roll 2 to transfer the toner onto the developing roll 2 to form the toner layer 12. The toner layer 12 has a toner charge amount of 5 to 30 μC / g (preferably 7 to 20 μC / g).
g), the toner adhesion amount is 0.4 to 1.5 mg / cm ² (preferably 0.6 to 1.2 mg / cm ² ). After that, the toner layer 12 is conveyed to a portion facing the photoconductor 1 by the rotation of the developing roll 2, and is brought into contact with the electrostatic latent image on the photoconductor 1, and a developing electric field is applied to the developing portion to cause the electrostatic charge. Toner is attached to the latent image to form a visible image, and a toner image is formed on the photoconductor 1.

The carrier roll 3 having the magnet body as described above.
The developer (magnetic brush) 11 adsorbed on and conveyed by
It contacts the developing roll 2. As described above, the developer 11 is composed of the toner and the carrier, and is charged in the opposite directions by frictional charging associated with agitation and conveyance, so that an electric field (forward electric field) is applied between the conveyance roll 3 and the developing roll 2. When,
Only the toner is separated from the developer 11 held by the magnet body and moved onto the developing roll 2 to form a substantially uniform toner layer 12. Thereafter, the toner layer 12 on the developing roll 2 contacts the electrostatic latent image portion on the photoconductor 1 to transfer the toner, and development is performed.

As described above, in the present embodiment, unlike the conventional example shown in FIG. 2, the blade 18 that contacts the developing roller 2 is not provided, and the toner is charged and the developing roller 2 has a substantially uniform layer thickness. Since the toner layer 12 can be formed and development is performed using the substantially uniform toner layer 12, filming due to the toner does not occur on the developing roll 2.

Further, as shown in FIG. 12, which will be described later, a control unit for controlling the rotation speed and bias voltage of the transport roll 3 is provided, and the rotation speed of the transport roll 3 can be changed by this control unit.
The bias voltage of the transport roll 3 can be adjusted, the electric field strength applied between the transport roll 3 and the developing roll 2 can be adjusted, and the layer thickness of the toner layer 12 adhered onto the developing roll 2 can be adjusted. With this configuration, the stability of the image density can be improved, and the image quality of the color image can be kept constant for a long period of time.

[0038] The rotation direction of the developing roller 2 and the photosensitive member 1 may be either the same direction or counter direction, the peripheral speed ratio k (≡U _s / U _P) is 2 or less. More preferably, a peripheral speed ratio k is 1 ≦ k ≦ 1.5 in the same direction, the speed difference ΔV (≡U _S -U _P) is 0 ≦ ΔV ≦ 5
What is necessary is just 0 mm. In particular, by superimposing a bias voltage of 1 to 10 KHz and an AC voltage of 100 to 1000 V in such a configuration, it is possible to achieve both image uniformity and photoconductor abrasion prevention.

The developing roll 2 has a metal sleeve of about 20 to 60 μm whose surface is made of a non-magnetic material or a weak magnetic material and has a low hardness (for example, a rubber hardness of about 15 to 35 degrees (J).
The IS-A)) rubber roller 60 is fitted into the developing roller 2 having elasticity. This metal sleeve will be described in detail below.

Both non-magnetic and magnetic materials can be used for the metal sleeve material. However, non-magnetic SUS, copper alloy,
When using Al, Ni, etc., a single-layer metal sleeve 40 is used as shown in FIG.
When US or the like is used, as shown in FIG.
It is desirable that the metal sleeve 40 has two layers of the surface layer 36 made of a non-magnetic material or a weak magnetic material. The surface layer 3
6 includes, for example, rubber, resin coat, resin tube,
Either a non-magnetic or weak magnetic metal coating (metal powder is coated with resin as a binder), or a non-magnetic or weak magnetic metal plating is used.

Here, for comparison, a developing roll 2 having a magnetic Ni (single layer) electroformed sleeve, and 8 to 3 were used.
Peak magnetic force of 400 to 800 G (Gauss) with 2 magnetic poles
Of the ferrite carrier having a saturation magnetization of 50 to 100 emu / g and a particle size of 30 to 100 μm as a magnetic carrier. Alternatively, when a developer prepared by using a magnetite carrier and having a toner concentration of 5 to 20% was used, it was found that the Ni electroformed sleeve of the developing roll 2 was magnetized and the carrier was attached.

On the other hand, as a specific example of the two-layer metal sleeve 41 in FIG. 4, a two-layer type in which the surface layer 36 of the magnetic Ni electroformed sleeve 37 is coated with 5 to 20 μm of a fluorine resin, magnetic Ni electroformed When a two-layer type in which an Al layer of 10 to 30 μm is arranged on the surface layer 36 of the sleeve 37 was used, it was possible to prevent the carrier from adhering to the developing roll 2. In this case, the developing roll used had a diameter of 15 to 40 mm.

This is achieved by covering the surface of the magnetic Ni electroformed sleeve with a non-magnetic material or a weak magnetic material, and
Magnetization of the surface of the metal magnetic sleeve 41 can be prevented or reduced by the magnetic field of the magnet body of the transport roll 3 via the magnetic carrier adsorbed on the carrier, and as a result, the surface of the metal magnetic sleeve 41 of the carrier, that is, the developing roll 2 It is considered that the adhesion to

Examples of the coatable rubber or resin include fluororesin, silicon resin, fluororubber, and those obtained by adding a conductive agent to them.
As the tube type, there are silicone rubber, PFA tube, nylon tube, or those in which a conductive agent is added. As the metal coating agent, non-magnetic SUS304, 305, 316 powder or thin film powder and polyurethane, epoxy, vinyl chloride, silicone,
It is desirable to use acrylic resin as a binder. As the metal plating, in addition to a non-magnetic metal such as Cr, a weak magnetic material such as Ni can be used.

Further, by covering with a thin metal sleeve capable of retaining the elasticity of the rubber roll, it is possible to prevent the developing roll 2 from being scratched or worn, and to obtain a soft contact with the photoconductor 1 even if it is brought into contact with the photoconductor 1. There are advantages. This allows
Even when the printing speed is fast or the peripheral speed ratio k between the developing roll 2 and the photoconductor 1 is slightly high (k = 1.5 to 2.0), the replacement cycle of the developing roll 2 and the photoconductor 1 Can be long. .

The rubber roll may be either insulating or conductive, but in the case of an insulating roll (for example, a resistance value of about 10 ¹³ to 10 ¹⁶ Ωcm), the power supply for applying the developing bias is the developing. The conductive roll (for example, the resistance value is about 10 ⁷ to 10 ⁸⁾ is performed from the surface of the roll.
Ωcm) has an advantage that power can be supplied by using the shaft of the developing roll.

When the printing speed is relatively slow, or when the peripheral speeds of the developing roll 2 and the photoconductor 1 are substantially equal to each other, a metal sleeve is not used for the developing roll 2 and low hardness (for example,
A rubber roll having a rubber hardness of about 15 to 55 degrees (JIS-A) may be formed alone (or surface-coated).

The transport roll 3 is rotatably arranged with a gap (first gap G1) from the developing roll 2, and is provided with magnet bodies of evenly spaced multipole magnetization. A regulation plate 4 for setting the second gap G2 is provided on the outer periphery of the transport roll 3 so as to regulate the amount (layer thickness) of the developer held on the transport roll 3 on the developing roll 2 side. The developer layer 10 is rotated in the counter direction with respect to the developing roll 2 to be in contact therewith, and an electric field is applied to the gap between the transport roll 3 and the developing roll 2 to form a toner layer on the developing roll 2. There is. It is more preferable that the electric field is formed between the transport roll 3 and the developing roll 2 by superimposing a direct current and an alternating current of 1 to 10 KHz.

As shown in FIGS. 5 and 6, the magnet body constituting the transport roll 3 has magnet rolls (42-1, 42-).
2) A single so-called sleeveless mag roll 38 is used, or as shown in FIG. 7, a mag roll 43 in which a rotatable sleeve 44 is arranged concentrically with the magnet roll 42-3.
Can also be configured.

First, the case where the sleeveless mag roll 38 is used will be described.

In this case, the first gap G1 formed by the developing roll 2 and the transport roll 3 is set to 0.5 to 1.2.
The second gap G2 formed by the regulation plate 4 and the transport roll 3 is set to be equal to or wider than the first gap G1 (the difference between the two is in the range of 0 to 0.4 mm).

FIG. 5 shows a first example using a magnet body 42-1 in which N and S poles are alternately magnetized at equal intervals as the sleeveless magnet roll 38.

In this example, the number of magnetic poles is 10 to 64,
The magnetic force of the magnetic pole portion is 250 to 1000 gausses, preferably 16 to 32 magnetic poles, and 350 to 800 gausses. This is because when the number of magnetic poles is less than 10 poles, striped unevenness occurs on the developing roll 2 and the toner layer becomes non-uniform, and when the number of magnetic poles is more than 40 poles, the magnetic force of the magnetic pole portion tends to decrease. Because it will be.

The developer 11 attracted by the magnetic force of the magnet body 42-1 in the transport roll 3 forms a magnetic brush (developer layer) 10 and makes a rotary contact with the developing roll 2 to apply toner to the developing roll 2. , The peaks and troughs of the magnetic brush move periodically with the rotational movement of the magnetic poles, so that the number of magnetic poles is small and the peripheral speed ratio K2 (≡Ut / U) of the magnet body 42-1 is small.
When s) is small, striped unevenness occurs on the developing roll 2 and the toner layer tends to be uneven. Therefore,
The peripheral speed Ut of the magnet body 42-1 is equal to the peripheral speed U of the developing roll 2.
s is preferably 1.3 to 5.0 times, more preferably 2.0 to 4.0 times, so that stripe unevenness on the developing roll 2 can be prevented and the image density can be improved. It was possible to make it almost uniform.

A second example using a magnet body 42-2 magnetized as N, N, S, S ... by arranging a plurality of pairs of the same polarity as the sleeveless magnet roll 38 in FIG. Show.

In this example, the number of magnetic poles is 16 to 32,
The magnetic force of the magnetic pole portion is 350 to 800 gauss, and the difference between the magnetic force of the magnetic pole portion and the magnetic force between the poles of the same magnetic pole is 50 to 200
Gauss range. In the case of this example, the first with the same number of magnetic poles
In comparison with the above example, the toner adhesion amount on the developing roll 2 was increased and the striped unevenness on the developing roll 2 was reduced. A possible reason for this is the difference in the magnetic force distribution on the surface of the magnet body. That is, as shown in FIG. 8 (first example) and FIG. 9 (second example), the magnetic force distributions on the surfaces of the magnet bodies in the first and second examples are different from each other, and the second example (FIG. In 9), as compared with the first example (FIG. 8), the high magnetic force portion corresponding to the crest of the magnetic brush is widened. That is, in the second example, the ratio of the peaks of the magnetic brush having good toner adhesion is larger. In other words,
It is thought that this is because the width of the mountain has expanded and the number of valleys has decreased.

Further, the magnet body is usually made of a ferrite material, and the resistance value tends to be high. in this case,
In order to improve the conduction between the roll shaft and the magnet body and reduce the resistance value between the roll shaft and the magnet body surface, a conductive adhesive is used or conductive members are arranged at both ends of the magnet body,
The bias voltage is applied from the roll shaft, the resistance value of the developer is lowered, and the bias voltage is also applied to the regulation plate 4 as shown in FIG.
As a result, the first gap G between the developing roll 2 and the magnet body 3
It is possible to prevent a decrease in the electric field strength at 1.

Further, the surface of the magnet body is a conductive non-magnetic member,
For example, the metal sleeve may be covered with the material used for the surface layer so that the roll shaft and the conductive non-magnetic member are electrically connected. In this example, the mag roll becomes a little expensive, but the bias voltage need only be applied from the roll shaft, and there is an advantage that it is not necessary to apply the bias voltage to the regulation plate.

Next, as shown in FIG.
A case will be described in which the sleeve 44 that is rotatable concentrically with the magnet body 42-3 is arranged and configured. In this case, the first gap G1 formed by the developing roll 2 and the transport roll 3 is set in the range of 0.5 to 1.2 mm, and the second gap G2 is equal to or narrower than the first gap G1 ( The difference between the two is set to 0 to 0.4 mm). Further, the magnet layer 42-3 has 8 to 24 magnetic poles, and the developer layer 10 is rotated in the counter direction with the developing roller 2 by using a carrier roll magnetized in a magnetic pole portion having a magnetic force of 400 to 1000 gauss. The magnetic body 42-
3 is rotated clockwise, the sleeve 44 is rotated counterclockwise, and the peripheral speed of the sleeve 44 and the peripheral speed U of the developing roll 2 are increased.
The ratio to s is set in the range of 1.0 to 3.0, preferably 1.2 to 2.0, and the rotational speed of the magnet body 42-3 is 1.5 to 4 of the rotational speed of the sleeve 44. The range was set to 0.0. With such a configuration, it is possible to secure a toner adhesion amount on the developing roll 2 and prevent stripe unevenness, and obtain a substantially uniform and high-density image.

Bias power sources 14 and 15 are connected to the developing roll 2 and the transport roll 3, respectively.
Alternatively, a voltage in which a DC voltage and an AC voltage are superimposed is applied. Also, a sleeveless mag roll 38 is provided on the transport roll 3.
When using, the magnet body 42-
Bias voltage is applied to 1, 42-2 and regulation plate 4
A bias power supply 15 is also connected to apply a bias voltage. Thereby, when the resistance values of the magnet bodies 42-1 and 42-2 are high, the decrease of the electric field strength in the first gap G1 is prevented, and the resistance values of the magnet bodies 42-1 and 42-2 are low. In this case, it is possible to prevent electric discharge through the second gap G2.

Next, the toner replenishing system in this embodiment will be described.

As shown in FIGS. 10 and 11, the toner replenishing system is provided with the developer guide plate 5 on the upper portion of the conveying roll 3 having the magnet body, and is on the opposite side of the conveying roll 3 from the developing roll. A developer chamber 45 in which the developer 11 circulates and a toner reservoir 9 are formed in a portion of the developer chamber 4.
In accordance with the volume change of the developer 11 of No. 5, the toner enters the developing chamber 45 from the toner reservoir 9 and mixes with the developer 11 of the developer chamber 45. The developer chamber 45 has a space defined by the part opposite to the developing roll 2 with the transport roll 3 in between, the regulating plate 4, the developer guide plate 5, the partition plate 47, and the developing device bottom plate 46. In other words, the toner reservoir 9 is formed in a part of the developer chamber 45 located below the portion along the developer guide plate 5. The toner in the toner reservoir 9 is supplied from the toner hopper 6 by the stirring blade 7, but when the toner in the toner reservoir 9 becomes excessive, the toner automatically overflows and returns to the toner hopper 6. In such a toner supply system, when toner is consumed, the
0, the developer 11 in the developer chamber 45
Since the volume of the toner is small, the toner drops from the toner reservoir 9 by its own weight and is supplied to the developer chamber 45, and the regulating plate 4
Developer 1 which is regulated by U-turn and goes downward
Mix with 1. In this case, a replenishment member 48 may be arranged as shown in the figure, and the replenishment member 48 may accelerate the supply of the toner by dropping and the mixing of the developer 11.

When the toner is not consumed, the volume of the developer 11 in the developer chamber 45 increases and the toner pool 9 formed in the developer chamber 45 shrinks, as shown in FIG. And
The developer is regulated by the regulation plate 4 and makes a U-turn, and is located outside the circulation path of the developer 11 directed downward. As a result, the toner in the toner reservoir 9 is not taken in by the circulating developer 11. Therefore, the toner can be supplied to the developer 11 according to the consumption of the toner, so that the toner concentration of the developer 11 can be maintained substantially constant, and the image quality such as image density and fog can be improved with time. . This allows mechanical control of toner concentration.

In addition, in FIG. 12, a current detection section 49, a toner replenishment control section 50, and a drive transmission mechanism 51 such as a clutch are added to the example of FIG. This is an example in which the determination is made by measuring the secondary side current value, and the stirring blade 7 is actuated in accordance with the determination, and the toner is intermittently supplied to the toner reservoir 9.

The current detector 49 measures the secondary side current I of the bias power supply 15 and generates an output signal corresponding to the current I. On the other hand, the toner concentration of the developer 11, the bias potential difference between the developing roll 2 and the transport roll 3, and the current I
13 has a relationship as shown in FIG. 13, and the current value data I ^* corresponding to the lower limit value Tc ^* of the toner concentration can be obtained in advance and stored in the toner replenishment controller 50. it can. Further, in the toner replenishment controller 50, by inputting the current I and the bias potential difference, it is determined whether or not the lower limit of the toner concentration is reached based on the above-mentioned stored data, and when the lower limit of the toner concentration is reached, It is configured to generate a stirring blade / operation signal. In the drive transmission mechanism 51, the electromagnetic clutch is turned on based on the stirring blade / operation signal to operate the stirring blade 7. In this example, since the stirring blade 7 can be operated intermittently, it is not necessary to constantly operate the stirring blade 7, reducing the stress of the toner in the toner hopper 6 and reducing the power consumption of the entire developing device. There is an advantage that it can be reduced. When the method of detecting the toner concentration of the developer 11 based on the measurement of the development current is used, it is necessary that the difference between the resistance values of the carrier and the toner is large and the resistance of the carrier is stable. Value is 1/100 to 1/1 of toner resistance
It is preferable to use a range of 10,000 and a toner resistance value of 10 ¹⁰ to 10 ¹³ Ωcm.

As a method of obtaining the lower limit value of the toner density, a method of detecting the magnetic permeability of the developer 11 may be used. Alternatively, the accumulation state of toner in the toner reservoir 9 may be measured by an optical sensor, and the operation signal of the stirring blade 7 may be generated based on the measurement.

Next, the developer 11 held on the magnet body 3
Will be described.

To obtain a high-definition image (800 to 2000 DPI), a toner having a particle size of 5 to 8 μm is used, and the carrier has a particle size in view of fluidity of the developer 11 and toner chargeability. Those having a thickness of 20 to 100 μm, preferably 30 to 80 μm were used. Then, the toner was compounded so as to be 5 to 50% by weight (ratio to the total weight of the toner and the carrier), and both were mixed to obtain a developer 11.

As a material for the carrier, an iron powder carrier having a particle size of 30 to 80 μm is most desirable from the viewpoint of the ability to scrape off the toner remaining on the developing roll 2 after developing the electrostatic latent image on the photoreceptor 1. understood. However, the magnet body 3
It is also possible to use a resin carrier and a ferrite carrier by increasing the magnetic force and the peripheral speed of the resin carrier. The resin carrier has a bulk specific gravity of 1.0 to 1.6 g / cm ³ and a saturation magnetization of 60 to 80 emu / g. thing,
The ferrite carrier has a bulk specific gravity of 2.2 to 2.7 g /
It was found that a substantially spherical one having a cm ³ and a saturation magnetization of 20 to 70 emu / g can also be used.

As the toner, a binder resin having a glass transition point Tg of 55 to 65 ° C. is used for low-temperature fixing, and further 10 to 100 nm for improving fluidity.
1 to 2 types of crude water-treated silica having different particle sizes, or
The crude water-treated silica and an additive other than silica (for example, an inorganic oxide such as titanium oxide or aluminum oxide or a conductive agent) were used together as an external additive to form a toner.

The binder resin of the toner is preferably a styrene-acrylic resin or a polyester resin having a small oxidation value because it has a small moisture absorption amount and good environmental resistance, and it is possible to reduce fusion (spent) of the toner to the carrier. It has been found that a combination with a toner obtained by adding a conductive additive to a conductive resin-coated carrier is desirable. This is because first, the resin can be applied to the carrier to reduce the stress on the toner, and secondly, by making the coating agent conductive, electrostatic charge-up can be suppressed. It is considered that by using the toner to which the developer is applied, even if the toner is fused to the carrier (spent), the fluctuation of the resistance value of the developer can be suppressed.

An organic photoconductor (OPC) is used as the photoconductor 1 by applying such a developing device to an electrophotographic printer device.
Is used to form an electrostatic latent image with a contrast potential of about 450 V on the photoconductor 1 having a peripheral speed of 100 to 400 mm / sec, and the peripheral speed Us of the developing roller (sleeve) 2 is set to about 1 to the peripheral speed Up of the photosensitive member. The image density was 1.3 to 1.4 (OD) when the reversal development was carried out by applying a developing bias of 250 to 350 V to the developing roll (sleeve) 2 to approximately double.

Even when long-term printing is performed,
Toner filming on the developing roll 2 did not occur.

[Second Embodiment] This embodiment is an example in which the developing device of the present invention is applied to a color electrophotographic apparatus in which four image forming units corresponding to respective colors are arranged.

FIG. 14 is a schematic block diagram of a color electrophotographic apparatus according to this embodiment. In the figure, the color electrophotographic apparatus includes four developing devices 8-1, 8-2, 8-- which store developers corresponding to respective colors of Y, M, C and K.
3, 8-4 are four photoconductors 1-1, 1-corresponding to each color.
It is arranged around 2, 1-3, 1-4 and is exposed 24-1, 24-2, 24-- in consideration of the transfer timing to the paper 22.
3, 24-4 sets the latent image writing timing, forms latent images corresponding to the respective colors on the photoconductors 1-1, 1-2, 1-3, 1-4, and develops the respective colors. 8-
1, 8-2, 8-3, 8-4 to develop toner images of respective colors, and transfer devices 25-1, 25-2, 2
5-3 and 25-4 are sequentially transferred to the sheet 22 to superimpose the toner images of the respective colors to obtain a full-color image. In this embodiment, the developing devices 8-1, 8-2, 8-3, 8-of this color electrophotographic apparatus are used.
Of the four, only the developing device 8-1 in the first stage will be described as an example. In this case, since it is full color, the other three developing 8-
Although omitted in Nos. 2, 8-3, and 8-4, each unit described below is provided.

An example in which the developing device 8 of the first embodiment is applied to the developing device 8-1 will be described in detail below.

As can be seen from FIG. 14, the bias power sources 14-1 and 15-1 are connected to the developing roll 2-1 and the transport roll 3-1 of the developing unit 8-1, and the rolls 2-1 and 2-1 are connected. 3-1 designates rotary drive units 16-1 and 17 respectively.
It is driven to rotate by -1. On the other hand, the color image sensor 27-1 that detects the toner image of the developed color is
The output of the color image sensor 27-1 is input to the image controller 28-1. The bias power sources 14-1 and 15-1 are controlled by a bias control unit 30-, and the bias control unit 30-
-1 sets the aforementioned bias voltage and bias frequency according to the control output from the image control unit 28-1.
The rotation drive units 16-1 and 17-1 are rotation control units 29-
The rotation speed is controlled by 1, and the rotation control unit 29-1 similarly sets the speed according to the control output from the image control unit 28-1.

A transfer device 25-is provided around the photosensitive member 1.
Cleaners 26-1, 26-2 for cleaning the toner remaining on the photoconductors 1-1, 1-2, 1-3, 1-4 after the transfer by 1, 25-2, 25-3, 25-4. 26-3, 26
-4 is arranged, and further, the fixing device 31 for melting and fixing the unfixed image on the paper 22 is arranged behind the transfer device 25-4 at the final stage.

In such a structure, when a color toner image is formed on the photosensitive member 1 and color printing is performed, at least the electric field between the developing roll 2 and the transporting roll 3 or the circumference is determined based on the toner image after development. Since at least one of the speed ratios can be controlled, a desired amount of toner development on the photoconductor 1 can be secured, and even in long-term printing, the image density does not drop or fluctuate and the color image does not deteriorate.

In this embodiment, fan hold paper is used to continuously form a color image, but the same applies to cut paper, and
For example, even when a color image of two colors is formed, the same configuration and the same operation are performed only by providing a device such as a photoconductor and a developing device for two colors.

[Third Embodiment] FIG. 15 is a schematic block diagram of a developing device according to the third embodiment. The same reference numerals are given to the same parts as those in the first embodiment. The description will be omitted and only different components will be described.

In this embodiment, as can be seen from FIG. 15, in the first embodiment, the conveying roller 3 and the toner reservoir 9 are provided.
The second transport roll 32 is provided in the opening 9a between the two, and all other parts are configured in the same manner as in the first embodiment.

In this embodiment, the second transfer roll 32 is composed of a sponge roll or a rotating brush, and is brought into contact with or close to the developer guide plate 5. As a result, the toner pool 9 is collected on the second transport roll 32.
15 which forms a toner layer 12 containing new toner from the above, and which is regulated by the regulation plate 4 and flows back in the direction of the arrow in FIG.
It comes into contact with the developer 11 that is adsorbed on and moves.

With the above-mentioned structure, the effect of reducing the fog was observed as compared with the first embodiment.

[Fourth Embodiment] FIG. 16 is a schematic structural view of a developing device according to a fourth embodiment. The same reference numerals are attached to the same parts as those in the first and third embodiments. The description will be omitted, and only different components will be described.

In this embodiment, a second stirring member 33 is provided in place of the second carrying roll 32 in the third embodiment, and the toner in the toner reservoir 9 and the developer 11 are mixed. The other parts are configured in the same manner as in the first and third embodiments described above.
As the stirring member, for example, a stirring blade or a screw auger is used.

With the above-mentioned structure, the effect that the image density unevenness does not occur even in the long-term printing and the fog is reduced can be seen.

[Fifth Embodiment] In the fifth embodiment,
In the fourth embodiment, as shown in FIG.
In addition to the stirring member 33, the two stirring members 34 and 35 are provided below the stirring member 33. Stirring member 3
In this case, two screw augers 4 and 35 different in the transport direction (in the axial direction) are arranged. It is preferable that these stirring members 34 and 35 have not only the mixing and stirring ability in the rotating direction but also the ability to move the developer in the direction parallel to the transport roll 3. Specifically, it is preferable to use a screw-shaped member or an inclined fin member which can change the moving direction of the developer 11 by switching the rotating directions of the stirring members 34 and 35.

In the fifth embodiment, in long-term printing, the image density unevenness in the axial direction did not occur, and the effect of further reducing the fog was observed.

[Sixth Embodiment] In the first to fifth embodiments, the carrier roll 3 holds the developer 10 composed of toner and carrier, and an electric field is applied to the developing roll 2 to apply only the toner. Development is carried out by transferring the toner to the developing roll 2 and contacting the photoconductor 1 with the toner to adhere the toner to the latent image. However, the developing roll 2 is omitted and the toner is directly transferred from the transport roll 3 to the photoconductor 1. It is also possible to develop it. In this case, the developing roller 2 and the transport roller 4 are arranged such that the surface of the developing roller 2 is separated from the surface of the transport roller 4 by the first gap G1. It is sufficient to dispose only G1 away from the surface of the transport roll 3. In addition, the particle diameters of the toner and the carrier, the mixing ratio of the two, the state of the electric field, the toner replenishing structure, and the like are all the same as those of the first to fifth embodiments.

[0091]

As apparent from the above description, the present invention has the following effects.

That is, according to the invention of claim 1,
In a developing device that applies only non-magnetic toner to a developing roll, it is possible to prevent carrier adhesion to the developing roll, uniformly form a toner layer on the developing roll, and maintain the toner concentration of the developer held on the magnet body. Therefore, stable high-quality development can be performed at high speed.

When high speed printing or low temperature fixing toner is used, toner filming does not occur on the developing roll for a long period of time.

According to the second aspect of the invention, the toner replenishment control can be executed only by the mechanical structure.
Reliable toner supply and toner concentration control can be performed at low cost.

According to the third aspect of the invention, since the high magnetic force portion corresponding to the mountain of the magnetic brush is widened, the toner adhesion amount on the developing rule is increased, and the striped unevenness on the developing roll is suppressed. be able to.

According to the invention described in claim 4, since the movement of the peaks and valleys of the magnetic brush is finely set, it is possible to prevent unevenness on the stripes on the developing roll and to make the image density uniform. The same effect as the item 3 is obtained.

According to the fifth aspect of the present invention, it is possible to charge the toner and form a toner layer having a substantially uniform layer thickness on the developing roll without providing a blade that contacts the developing roll. It is possible to prevent the occurrence of filming due to.

According to the sixth aspect of the invention, since the bias voltage in which the DC voltage and the AC voltage are superimposed is applied to the developing roll, it is possible to achieve both the uniformity of the image and the prevention of the abrasion of the photoconductor.

According to a seventh aspect of the present invention, the developing device according to any one of the first to sixth aspects is used as a plurality of developing devices, and the developing roll and the transport roll are based on the toner image of each color. Since at least one of the electric field and the peripheral speed ratio of the gap between and is controlled, it is possible to prevent the image density variation, and thereby a clear color image can be stably obtained.

According to the invention described in claim 8, the two-component type developing device for forming and developing the developer layer containing the carrier and the toner on the outer periphery of the transport roll is also the invention described in any one of claims 1 to 6. Has the same effect.

According to the ninth and tenth aspects of the present invention, the toner replenishment control can be executed only by the mechanical structure, and the toner replenishment and the toner density control can be reliably performed at low cost. .

According to the eleventh aspect of the present invention, since the carrier can secure the fluidity of the developer and the chargeability of the toner, the toner having the particle size of 5 to 8 μm and the conductive additive imparts a high definition. An image can be formed.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of a developing device according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a schematic configuration of a conventional developing device.

FIG. 3 is a cross-sectional view showing an example of a metal sleeve that constitutes a developing roll in the first embodiment.

FIG. 4 is a cross-sectional view showing another example of the metal sleeve that constitutes the developing roll in the first embodiment.

FIG. 5 is a cross-sectional view showing an example of a sleeveless mag roll used as a transport roll in the first embodiment.

FIG. 6 is a cross-sectional view showing another example of the sleeveless mag roll used for the carrying roll in the first embodiment.

FIG. 7 is a cross-sectional view showing an example of a mag roll with a rotary sleeve used as a transport roll in the first embodiment.

8 is a diagram showing a surface magnetic force distribution of the sleeveless mag roll of the single pole alternating magnetization shown in FIG.

9 is a diagram showing a surface magnetic force distribution diagram of the sleeveless mag roll of the same polarity alternating magnetization shown in FIG.

FIG. 10 is a partial cross-sectional view of the developing device showing the toner replenishing section in the first embodiment.

FIG. 11 is a partial cross-sectional view of the developing device showing a state of toner supply in FIG.

FIG. 12 is an explanatory diagram showing a toner replenishment control system according to the first embodiment.

13 is a diagram showing the relationship between the current of the transport roll bias power supply and the toner concentration in FIG.

FIG. 14 is a diagram showing a schematic configuration diagram of a color electrophotographic apparatus according to a second embodiment of the present invention.

FIG. 15 is a sectional view showing a schematic configuration of a developing device according to a third embodiment of the present invention.

FIG. 16 is a sectional view showing a schematic configuration of a developing device according to fourth and fifth embodiments of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Developing roll 3 Conveying roll 4 Regulation plate 5 Developer guide plate 6 Toner hopper 7 Stirring blade 8 Developing device 9 Toner reservoir 10 Developer layer 11 Developer 12 Toner 32 Second conveying roll 33 Second stirring member 34 , 35 screw auger 36 non-magnetic material 37 magnetic material 38 sleeveless mag roll 40 single layer type sleeve 41 two layer type sleeve 42-1, 42-2, 42-3 magnetic material 43 sleeved mag roll 44 sleeve 45 developer chamber 48 Replenishment member 49 Current detector 60 Rubber roll

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kunio Fukuchi, Inventor 7-1, 1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd., Hitachi Research Laboratory (72) Masaho Anzai 1060 Takeda, Hitachinaka-shi, Ibaraki Hitachi, Ltd. Machine Co., Ltd.

Claims (11)

[Claims] 1. A developing device in which a toner layer is formed on a developing roll, and the developing roll is brought into contact with a photoconductor to visualize the latent image formed on the photoconductor. An elastic roll is fitted to a sleeve made of a magnetic material to form the developing roll, and the conveying roll provided with a magnet body magnetized with multiple poles at equal intervals can be rotated near the developing roll. A regulating plate for regulating the layer thickness of the developer containing the carrier and toner is provided on the outer periphery of the conveying roll, and the developer layer regulated by the regulating plate is brought into contact with the developing roll while rotating. A developing device, wherein an electric field is applied to a gap between the transport roll and the developing roll to form a toner layer on the developing roll. 2. A toner reservoir for temporarily accumulating toner supplied from a toner hopper, a developer chamber provided at a position on the opposite side of the carrying roll from the developing roll, in which a developer circulates, and the toner reservoir. A guide plate for guiding the toner from the lower part of the developer chamber to the developer chamber, and the toner is supplied from the toner reservoir according to the volume change of the developer in the developer chamber. The developing device according to claim 1. 3. The magnet body is configured by arranging a plurality of pairs of magnetic pole portions having the same polarity.
The developing device described. 4. The magnet body has 8 to 64 magnetic poles, and the ratio of the peripheral speed of the magnet body to the peripheral speed of the developing roll is set in the range of 1.5 to 5.0. The developing device according to claim 1, wherein the developing device is a developing device. 5. An absolute value of a difference between a first gap formed by the developing roll and the transport roll and a second gap formed by the regulation plate and the transport roll is 0 to 0.4 mm. The developing device according to claim 1, wherein the developing device is set in a range. 6. The developing device according to claim 1, wherein the bias voltage applied to the developing roll is a superposition of a DC voltage and an AC voltage. 7. A plurality of developing devices, each accommodating a developer corresponding to each color, are arranged around a plurality of photoconductors, and the photoconductors form one or more rotations to form a plurality of latent images corresponding to each color. Developing the latent image with a plurality of developing devices,
A color electrophotographic apparatus having a step of forming toner images of a plurality of colors on a photoconductor, wherein the plurality of developing devices are the developing devices according to any one of claims 1 to 6, and toner images of each color are formed. At least one of the electric field and the peripheral speed ratio of the gap between the developing roll and the conveying roll is controlled based on the above. 8. A regulation plate for regulating the layer thickness of a developer containing a carrier and toner is provided on the outer periphery of a conveyance roll having a magnet body, a magnetic brush is formed on the conveyance roll, and the magnetic brush is used as a photoconductor. In a developing device for developing by bringing it into contact with a roller, a multi-pole magnetized magnet body constituted by a plurality of pairs of magnetic poles of the same polarity arranged at equal intervals is rotatably arranged. A developing device which develops by applying an electric field to a gap between the transport roll and the photoconductor. 9. A regulation plate for regulating the layer thickness of a developer containing a carrier and toner is provided on the outer periphery of a conveyance roll having a magnet body, a magnetic brush is formed on the conveyance roll, and the magnetic brush is used to form a photoconductor. In a developing device that transfers toner to a developing device, the toner is temporarily supplied from a toner hopper, and the developer is circulated at a position on the opposite side of the conveying roll from the photoconductor. A developer chamber and a guide plate for guiding the toner from the lower part of the toner reservoir to the developer chamber are provided, and the toner is supplied from the toner reservoir according to the volume change of the developer in the developer chamber. The developing device is characterized by being provided. 10. The guide plate is provided on an upper portion of the transport roll, according to claim 2 or 9.
The developing device described. 11. The developer has a particle size of 30 to 80.
Conductive resin coated carrier with μm and particle size of 5 to 8
The developing device according to any one of claims 1, 2, 7, 8 and 9, further comprising a toner to which a conductive additive having a thickness of μm is applied.