JPH09288418A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent developer from being deteriorated by efficiently executing the recovery of the developer and the supply of the new developer without mechanically peeling the developer on a developing roll as to a developing device visualizing a latent image on an image carrier by using the two- component developer including toner and carrier. SOLUTION: A belt-like member 15 having plural projection parts 18 on the circumferential surface thereof is arranged at a position faced to the developing roller 12. The belt-like member 15 is circulated so as to carry the developer. Then, the developer is dropped down from the upper part of the roller 12 along the circumferential surface. On the other hand, the roller 12 is constituted so that S poles and N poles are alternately placed by magnetization at short intervals along the circumferential surface and a small quantity of developer can be attracted. The developer on the roller 12 is peeled by the collision of the flowing-down developer and the flowing-down developer is replaced with it. Besides, it is good that the developer is recovered and supplied by bringing a magnetic brush stirred and carried by varied magnetic field into contact with the developer on the roller 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device which is used in an electrophotographic recording device or an electrostatic recording device, and selectively transfers toner to a latent image due to a difference in electrostatic potential to visualize the toner. The present invention relates to a developing device using a two-component developer in which a carrier and a toner are mixed.

[0002]

2. Description of the Related Art Electrophotographic or electrostatic recording devices are widely used as image forming devices such as copying machines and printers. Such an apparatus is configured to form an electrostatic latent image on an image carrier, transfer toner to the latent image to form a visible image, and then transfer the toner image to recording paper or the like. In the developing device for developing the electrostatic latent image on the image carrier, a so-called contact type two-component developing system in which a two-component developer composed of a toner and a magnetic carrier is brought into contact with the surface of the image carrier to develop the toner by transferring the toner. There is a device. Although this developing device has a problem that it is necessary to control the toner concentration in the developer, a mechanism for stirring the developer is required, and the device becomes large, however, in terms of image quality characteristics and transportability of the developer, etc. It has excellent characteristics and is the mainstream of developing devices.

Such a developing device has a developing roll having a magnet roll and a sleeve which is rotationally driven around the magnet roll, and a developer layer having an appropriate thickness is formed on the sleeve by a layer thickness regulating member. Form. This developer layer forms a magnetic brush in which magnetic carriers are connected in a spike shape according to the magnetic field of the magnet roll, and contacts the image carrier in the developing area to transfer only the toner in the two-component developer. There is.

On the other hand, in the above-mentioned contact type two-component developing device, since the magnetic brush of the developer mechanically rubs the surface of the image bearing member, image defects such as so-called brush marks and sweeping due to the magnetic brush are likely to occur. In order to avoid this drawback, there have been proposed many non-contact type two-component developing devices for developing without bringing the developer into contact with the surface of the image carrier.

In the contact type or non-contact type two-component developing device as described above, the developer which has passed through the developing area and has been once developed is separated from the surface of the developing roll and a new developer is supplied. It is necessary to form a layer. Examples of means for peeling off the developer include, for example, a technique in which adjacent magnetic poles of the same polarity are provided at a portion facing the developer peeling portion of a magnet roll, and the developer is peeled off by a repulsive magnetic pole, or a thin plate called a scraper. A technique of bringing the strip-shaped member into contact with a developing roll to peel off the developer is used. Further, as a means for supplying a new developer to form a layer,
For example, a technique has been adopted in which the developer is conveyed to the vicinity of the developing member by a paddle or an auger and supplied, and the developer adhering on the developing member is regulated to a desired layer thickness by a layer regulating member and made uniform.

[0006]

However, the developing device as described above has the following problems. With respect to the means for peeling off the developer, the method of magnetizing the magnet roll adjacent to the magnet roll limits the arrangement of the magnetic poles and the magnetic pole spacing. Therefore, when it is desired to make the magnetic pole spacing as small as possible, or when the magnet rolls are integrally rotated, it is extremely difficult to apply the peeling method using the repulsive magnetic poles.

Further, in the method using a scraper, abrasion with time occurs because the scraper and the developing roll are rubbed against each other. When the surface of the developing roll wears, there is a problem in that the amount of developer conveyed changes due to changes in surface roughness, magnetic flux density, and the like, and image quality changes. Further, when the scraper is worn, a peeling failure of the developer occurs. In this case, the efficiency of exchange between the developing roll and the developer in the developer accommodating portion is lowered, and the developer whose toner has been consumed by the development is hardly separated from the developing roll. Therefore, when images having a high image area ratio are continuously formed, there is a problem that the image density decreases. Further, there is a problem that foreign matter is clogged in the contact portion between the scraper and the developing roll, and uneven contact of the scraper causes uneven image density.

Regarding the means for supplying or forming a layer of the developer, when the above-mentioned layer thickness regulating member is used, the developer is provided on the back surface of the layer thickness regulating member, that is, on the upstream side in the developer conveying direction. Is overfilled,
A strong compressive force acts on the developer, and a strong frictional force acts on the developer when the developer passes through the gap between the layer thickness regulating member and the developing member. There is a problem that the developer is deteriorated.

The present invention has been made in view of the above circumstances, and an object of the present invention is to collect the developer on the developing roll after passing through the developing area and to newly install the developer on the developing roll. It is an object of the present invention to provide a developing device that efficiently supplies a stable developer without causing deterioration of the developer, and thereby has excellent image quality stability and maintainability.

[0010]

In order to solve the above problems, the invention according to the present application is provided in close proximity to or in contact with an image bearing member on the surface of which an electrostatic latent image is formed. A developing member rotatably supported and a developing bias power source for applying a developing bias voltage between the developing member and the carrier are provided, and a toner and a carrier are mixed on the peripheral surface of the developing member. An apparatus for carrying and carrying a component developer, and transferring toner to the image carrier in an electric field formed at a position where the image carrier and the developing member face each other to form a toner image, A developer recovery unit for recovering the upper developer and a developer supply unit for supplying the developer onto the developing member to form a layer are provided (Claim 1).

As the developer collecting means and the developer supplying means, for example, a developer flow-down means for flowing down the developer from above the developing member along the peripheral surface of the developing member (claim 2), An alternating magnetic field generating means (claim 3) is used, which closely opposes the developing member and generates an alternating magnetic field to convey the developer carried on the surface. With such a configuration, the developer on the developing member can be peeled off and a new developer can be supplied to form a layer.

Further, as the developer flow-down means, for example, one having a belt-like member which has a width substantially the same as the developable width of the developing member and which is stretched so as to be rotatable (claim 7),
What has an impeller which picks up a developer and conveys it above the above-mentioned development member (claim 8) is used. With such a configuration, the developer in the developer accommodating portion can be conveyed above the developing member and flow down along the peripheral surface thereof. Further, a partition member is provided above the developing member to form a developer accommodating portion, and the partition member has openings for discharging the developer substantially evenly in the width direction of the developing member (claim 9). It can also be adopted, and similarly, the developer in the developer accommodating portion can be made to flow down along the peripheral surface of the developing member.

In such a developing device, when the developer is caused to flow down from above the developing member along the peripheral surface by the developer flowing means, a part of the developer is developed on the developing member having passed through the developing area. Collide with the agent. On the downstream side in the developer flow-down direction, since the developer flow-down speed is high, the flow-down developer peels off the developer on the developing member due to this collision,
It falls with this peeling developer and is collected in the developer accommodating portion. On the upstream side in the developer flow-down direction, a part of the developer that has flowed down is magnetically restrained on the developing member after the developer is peeled off, and a predetermined amount of developer layer is formed on the surface. . Therefore, in the developing device, the developer that has passed through the developing area can be separated from the developing member without using a mechanical means such as a scraper, and then a new developer can be supplied to form a layer. Therefore, it is possible to prevent deterioration when the developer is peeled off.

Further, it is desirable that the developer flow-down means causes the developer to flow down from the downstream side to the upstream side in the circumferential direction of the developing member (claim 6). As a result, the developer is peeled off on the downstream side in the developer flow-down direction, that is, on the upstream side in the circulating direction of the developing member, and then by the circulating movement of the developing member,
New developer can be supplied on the downstream side in the circulating direction of the developing member, that is, on the upstream side in the developer flowing direction, and the peeling and supply of the developer and the layer formation can be performed efficiently.

As the alternating magnetic field generating means, for example,
A magnetic field generating means having a plurality of magnetic poles on the circumferential surface, which is capable of orbiting;
A sleeve having a sleeve supported outside the peripheral surface of the magnetic field generating means, and the developer carried on the sleeve surface is conveyed on the outer peripheral surface of the sleeve by relative movement of the magnetic field generating means and the sleeve (claim 10). ) Is used. With such a configuration, the developer carried on the sleeve is carried along the circumferential surface of the sleeve to the vicinity of the position close to and facing the developing member, and forms the developer layer on the developing member. In order to form a stable and uniform developer layer by supplying the developer onto the developing member, it is desirable to supply the developer onto the developing member which has passed through the closest position between the developing member and the sleeve ( Claim 1
1).

In the developing device having the above structure, the developer adsorbed on the sleeve is conveyed, and the developer is supplied from above the sleeve to the surface of the developing member which has passed through the position where the sleeve and the developing member are closest to each other to form the developer layer. Therefore, the developer can be supplied to the developing member without being mechanically scraped by the magnetic brush when passing through the closest position, scraped by the magnetic force on the sleeve side, or affected by the layer regulation. Therefore, in the developer supply area, a sufficient amount of developer is always supplied to the developing member, and excessive developer that cannot approach the surface of the developing member has a small magnetic conveying force and is not conveyed. Can be formed to visualize the latent image with stable image quality.

In the developing device having the above-described structure, for example, the developer carried on the sleeve surface comes into contact with the surface of the developing member and is conveyed in a direction different from the conveying direction of the developing member in the area facing the developing member. Achieved (claim 12). The developer carried on the surface of the sleeve is brought into contact with the surface of the developing member and is conveyed in a direction different from the conveying direction of the developing member in a region facing the developing member, so that the developing member is passed over the closest position between the developing member and the sleeve. Supplying developer. As a result, since a sufficient amount of the developer member surface is constantly and softly contacted with the developer member surface, it is possible to reliably cover the developer member surface with carrier particles, and only the magnetically adsorbed developer is conveyed. A uniform thin developer layer is formed, and the latent image can be visualized with stable image quality.

More preferably, the area where the developer is provided on the developing member is provided at a position where gravity acting on the developer acts in a direction away from the developing member (claim 13). In this developing device, the developer is supplied onto the developing member that has passed the position where the sleeve and the developing member are closest to each other to form a developer layer. Since the developer in the developer supply region always has a gravity acting in the direction of peeling it from the developing member, a sufficient amount of the developer is in contact with or very close to the surface of the developing member, and strong development Only the developer attracted to the developing member side by the magnetic field of the member adheres to the surface of the developing member and is carried to the developing area. In such a developing device, the developer layer is always stably and uniformly formed on the surface of the developing member, and high-quality images can be printed without density unevenness.

In order to more reliably remove the developer, supply the new developer, and form a layer as described above, magnetic poles of different polarities are alternately provided along the peripheral surface as the developing member, and adjacent magnetic poles are provided. It is desirable to use those magnetized so that the distance between them is 25 μm or more and 250 μm or less (claim 4). When the magnetic poles are arranged at such narrow intervals, as shown in FIG. 18, the lines of magnetic force are directed to the adjacent magnetic poles having different polarities, so that the magnetic field component in the direction perpendicular to the surface of the developing member 100 is on the surface of the developing member. Attenuates rapidly in the vicinity. Further, when the layer of the magnetic carrier 102 is formed on the peripheral surface, the magnetic force lines pass through the layer of the magnetic carrier that is in contact with the peripheral surface of the developing member 100 and are hardly distributed outside thereof. Therefore, the carriers are not concentrated and adhered to the portion on the magnetic pole, but are adsorbed in a state in which only one layer is lined up orderly along the magnetic field.

Therefore, in the developing device having the developing member having the above-mentioned structure, for example, when the developing device has a flow-down means, when the developer is flowed down along the peripheral surface of the developing member 100, the flowed-down magnetic carrier 101 is developed on the developing member. The magnetic carrier 102 that collides with the developer and is adsorbed on the developing member is repelled. In this way, the magnetic carrier 102 away from the surface of the developing member is not constrained by the magnetic force,
Re-adhesion to the surface of the developing member does not occur, and the magnetic carrier 102 drops downward together with the developer flowing down with the toner attached.

On the other hand, on the upstream side in the developer flow-down direction, the developer flow-down speed is small, so that the magnetic carrier 101 flowed down.
Is attracted by the magnetic pole of the developing member and forms a thin layer of developer on the developing member together with the toner adhering to the magnetic carrier. As described above, the magnetic field component in the direction perpendicular to the surface of the developing member is rapidly attenuated near the surface of the developing member, so that the developer is arranged in an orderly manner along the magnetic field. A developer layer having an approximately constant layer thickness, which does not have an adhesion portion and does not have a peak-valley structure, is formed, and is held and conveyed by magnetic force.

In such a developing device, due to the action of the magnetic pole of the developing member, the developer can be peeled off and a new developer can be supplied and a layer can be formed without using mechanical means such as a scraper. It is possible to prevent deterioration of the developer without imposing a heavy load on the developer. Further, since the developer on the developing member during the peeling and supplying is efficiently exchanged, that is, the developer is efficiently replaced, there is no difference in toner concentration between the developer on the developing member and the developer accommodating portion, so that the image density is reduced. No decrease occurs. Also,
Since the developer layer is formed only by the magnetic force of the developing member at the same time as the supply without using the layer thickness regulating member or the like, a great burden is not applied to the developer here either.

Further, in the case where the developing member having a small magnetic pole gap is provided with the alternating magnetic field generating means, similarly, the developer on the developing member is peeled off, a new developer is supplied,
Layer formation can be performed more reliably. For example, when the magnetic field generating means having a plurality of magnetic poles on its peripheral surface and capable of orbiting, and the alternating magnetic field generating means including a sleeve supported outside the peripheral surface of the magnetic field generating means are provided, the sleeve and the developing member are The developer on the developing member comes into contact with the magnetic brush and is ejected in the vicinity of the position where the developer is close to the magnetic brush. When separated from the surface of the developing member, the binding force due to the magnetic force sharply decreases, and before the opportunity of re-adhesion is given, it is taken into the inside of the magnetic brush by the action of the alternating magnetic field, and new developer appears on the tip of the magnetic brush instead. To contact the surface of the developing member to form a developer layer on the developing member.

Particularly, when the developer is supplied onto the developing member which has passed through the closest position between the developing member and the sleeve, a sufficient amount of the developer is constantly and softly contacted with the surface of the developing member. The surface can be reliably covered with carrier particles. Excessive developer that does not come close to the surface of the developing member has a small magnetic carrying force and is not carried, so only the magnetically adsorbed developer is carried, and almost one layer of carrier is almost uniformly arranged on the developing member surface. Layers can be formed.

In the state of the developer as described above, for example, the developer carried on the surface of the sleeve comes into contact with the surface of the developing member, and in a region facing the developing member, a direction different from the conveying direction of the developing member. It is achieved by being transported. Furthermore, by providing the developer supply region at a position where gravity acting on the developer acts in a direction away from the developing member,
Since the gravity of the developer in the developer supply area always acts in the direction of peeling it from the developing member, a sufficient amount of the developer is in contact with or very close to the surface of the developing member, and strong Only the developer attracted to the developing member side by the magnetic field of the member adheres to the surface of the developing member and is carried to the developing area.

In such a developing device, the developer can be peeled off, the new developer can be supplied, and the layer can be formed without using the layer regulating member. The deterioration of the developer can be prevented. Further, on the surface of the developing member, a developer layer in which almost one layer of carrier is closely adhered is formed uniformly,
It is possible to print a high quality image without density unevenness.

On the other hand, the carrier is made of a high resistance material, and instead of the magnetic pole, a plurality of linear or strip electrodes are provided on the peripheral surface of the developing member.
It may be arranged to have a thickness of less than or equal to μm, and a voltage may be applied between adjacent electrodes from a power supply device (claim 5).
At this time, it is desirable to apply a voltage so that a potential difference of about 0.8 V / μm or more is generated between the adjacent electrodes.
When an electric field is formed along the peripheral surface of the developing member in this way,
Carriers in the periphery are polarized by inducing + and-poles. The carrier is attracted to the peripheral surface of the developing member by an electric force and forms a thin layer of the developer together with the toner attached to the carrier. At this time, most of the lines of electric force between the adjacent electrodes pass through the carrier made of a high-resistance material, and almost no lines of electric force appear outside the carrier layer that contacts the developing member. Therefore, almost one carrier layer is formed substantially evenly on the peripheral surface of the developing member.

Therefore, in the developing device having the developing member having the above-described structure, for example, when the developing device has a flow-down means, when the developer is flowed down along the peripheral surface of the developing member 100, the flowed-down developer is the developer on the developing member. And the magnetic carrier adsorbed on the developing member is ejected. In this way, the magnetic carrier separated from the surface of the developing member is not electrically restrained by the electrode, and therefore the magnetic carrier does not re-adhere to the surface of the developing member, and the separated magnetic carrier adheres the toner. It falls down as it is.

On the other hand, on the upstream side in the developer flow-down direction, since the developer flow-down speed is small, the magnetic carrier that has flowed down is adsorbed to the peripheral surface of the developing member by an electric force, and together with the toner adhering to the carrier. Form a thin layer of developer. At this time, since almost no lines of electric force appear outside the carrier layer in contact with the developing member, there is no developer non-adhered portion on the developing member, and the developer has a substantially constant layer thickness and does not have a ridge-valley structure. A layer is formed.

In the developing device as described above, it is possible to recover the developer from the developing member, supply the developer to the developing member and form a layer without applying an excessive force to the developer,
It is possible to prevent the deterioration of the developer. Further, since the developer on the developing member is exchanged, that is, replaced at the time of collecting and supplying the toner efficiently, there is no difference in toner concentration between the developer on the developing member and the developer accommodating portion, and therefore, the image density is reduced. No decrease occurs. Further, when the developer layer is formed, the developer layer is formed by bringing the developer into soft contact with the developing member without using a layer forming member and adsorbing it only by an electric force. There is no need to pay.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. [Image Forming Apparatus Using Invention of Present Application] FIG.
1 is a schematic configuration diagram showing an example of an image forming apparatus in which a developing device according to the present application is used. This image forming apparatus includes a photosensitive drum 1 in which a photosensitive layer is provided on a peripheral surface of a substantially cylindrical conductive substrate, and the photosensitive drum 1 rotates in the direction of arrow A shown in the figure. It is designed to be driven. Further, around the photosensitive drum 1, along the rotation direction thereof, a charger 2, an exposure device 3, and a developing device 4 in which a developing member 12 made of a cylindrical member is opposed to the photosensitive drum 1,
It has a pre-transfer corotron 5, a transfer corotron 6, a peeling corotron 7, a cleaner 8, and an optical static eliminator 9.

The conductive substrate of the photosensitive drum 1 is electrically grounded. In addition, a negatively charged organic photoreceptor (OPC) is used for the photoreceptor layer. When the photoreceptor layer is almost uniformly charged and then irradiated with image light, the charge in the exposed portion flows to the conductive substrate, and the potential is reduced. It is designed to attenuate. The photosensitive drum 1 can be set, for example, to have an outer diameter of 100 mm and a peripheral surface moving speed, that is, a process speed of about 160 mm / s.

The exposure device 3 has a laser generator which blinks based on an image signal, and a polygon mirror which reflects the laser beam emitted from the laser generator while rotating, and the circumference of the photosensitive drum 1 is improved. The surface is exposed and scanned to form an electrostatic latent image. This exposure scan is
The image area may be exposed or the non-image area may be exposed, and the toner is transferred to the image area by appropriately selecting the charging polarity of the photoconductor and the charging polarity of the toner. Can be visualized. In this image forming apparatus, the photosensitive member and the toner are negatively charged, and are set so as to expose the image portion.

Next, the operation of the image forming apparatus will be described. First, the surface of the photosensitive drum 1 is uniformly charged to -450 V by the charger 2 (FIG. 2A). Subsequently, the image portion is exposed by a laser beam to form a negative latent image having an exposed portion potential of approximately -200 V [FIG.
(B)]. Then, the toner is transferred to the exposed portion of the negative latent image by the developing device 4 to be visualized [FIG.
(C)].

The toner image formed on the photosensitive drum 1 as described above is transferred onto the recording paper by the charging of the transfer corotron 6. Thereafter, the recording paper is peeled off from the surface of the photosensitive drum 1 by the charging of the peeling corotron 7, and is conveyed to a fixing device (not shown). In the fixing device, the toner image is fixed on the recording paper by heating and pressing. On the other hand, the surface of the photosensitive drum 1 on which the steps of transferring the toner image and peeling off the recording paper have been completed is cleaned of residual toner by the cleaner 8, and the residual charge is removed by the exposure by the optical neutralizer 9 to record the next image. Prepared for the process.

Incidentally, the pre-transfer corotron 5 provided on the downstream side of the developing device 4 in the rotation direction of the photosensitive drum 1.
Is used when investigating the amount of carrier transferred to the photoconductor drum during development, and uniformly negatively charges the toner image formed on the photoconductor drum 1. As a result, the carrier transferred onto the photosensitive drum 1 unintentionally during the development is negatively charged and is transferred together with the toner onto the recording paper. An assessment can be made.

[First Embodiment] Next, a developing device according to an embodiment of the present invention will be described. FIG.
Is a developing device that can be used in the image forming apparatus, and is a schematic view showing one form of the developing device according to the invention of claim 1, claim 2, claim 4, claim 6, or claim 7. It is a block diagram. In this developing device 4, an opening for development is provided in a portion of the developing housing 11 in which the developer is contained, which is opposed to the photosensitive drum 1, and the developing roll 12 is provided in this opening, and the rear lower portion thereof. It is equipped with two screw augers 13 and 14. Further, a belt-like member 15 is provided above the screw auger and at a position facing the developing roll 12 so as to flow down the developer from above the developing roll 12 along the peripheral surface.

The screw augers 13 and 14 are provided in two developer agitating / conveying chambers partitioned by a partition wall 19 in the developing housing, and are rotationally driven so as to convey the developer in opposite directions. is there. The two developer stirring / transfer chambers communicate with each other at both ends, and the developer conveyed by the screw augers 13 and 14 circulates and moves in the two developer stirring / transfer chambers while being stirred.

As shown in FIG. 4, the developing roll 12 comprises a cylindrical conductive substrate 12a supported so as to be rotatable about its axis and a magnetic recording layer 12b formed on the peripheral surface thereof. The main part is composed. This developing roll 1
2 has an outer diameter of 18 mm and a peripheral speed of 320 mm /
s, the gap between the photosensitive drum 1 and the developing member 12 is 300 μ
m, respectively, and the developer layer is held in a non-contact state with the photosensitive drum 1.

A developing bias voltage is applied to the conductive substrate 12a by a developing bias power source (not shown). An AC voltage obtained by superimposing a DC voltage is employed as the developing bias voltage, and the DC component is set to -400 V in order to prevent occurrence of background fog. The AC component of the developing bias voltage is a rectangular wave having a frequency of 6 kHz, and the peak-to-peak voltage is set to 1.5 kV.

On the other hand, in the magnetic recording layer 12b, S poles and N poles are alternately arranged at equal intervals (25 to 200 μm) over the entire circumference.
It is magnetized so as to be parallel to each other. This magnetization will be described later. The magnetic recording layer 12b is formed by coating a conductive resin 12a in which a powdery material of a ferromagnetic material is dispersed in a binder resin with a layer thickness of 50 μm. -Fe ₂ O
_3. Polyurethane is used as the binder resin. As this magnetic material, any known material such as a magnet material or a magnetic recording material can be used.
_In addition to ₂ O ₃ , CrO ₂ or the like can be used. As the binder resin, any known resin for forming magnetic recording layers such as tapes, disks and cards can be used. For example, polycarbonate, polyester, polyurethane, etc. can be used. Further, conductive fine particles and the like can be added to the magnetic recording layer 12b as needed.

The belt-shaped member 15 is an endless belt stretched by a supporting roll 16 arranged to face the screw auger 14 and a supporting roll 17 arranged to face the developing roll 15, and is shown in the figure. It is orbitally driven in the direction of the arrow. The belt-shaped member 15 has a width substantially the same as the developable width of the developing roll 12, and a plurality of protrusions 18 are provided on the peripheral surface at substantially equal intervals. By the circular movement of the protrusion 18, the screw auger 14
The developer in the vicinity can be picked up and conveyed to above the developing roll. On the other hand, the developing roller 12 is rotationally driven at a position facing the belt-shaped member 15 so that they both move in opposite directions, and the developer conveyed above the developing roller 12 by the belt-shaped member 15 causes the developing roller 12 to move. It is designed to flow from the downstream side to the upstream side in the orbiting direction. The belt-shaped member 15 is formed by integrally molding the protrusion 18 and the belt using a rubber material, and the height of the protrusion is set to 3 mm and the interval is set to 3 mm. As the belt-shaped member 15, in addition to the above rubber material, any material such as a flexible metal or resin can be used.

The developer used in the above-mentioned developing device is a two-component developer in which a non-magnetic toner and a magnetic carrier are mixed. As the toner, a polyester toner having a weight average particle diameter of 7 μm and a negative charge property is used. Has been done. As the carrier, a so-called magnetic powder-dispersed resin carrier in which magnetic powder is dispersed in a binder resin, or a so-called ferrite carrier in which spherical ferrite particles are coated with a resin are used.

Next, a method of magnetizing the magnetic recording layer 12b will be described. The magnetization of the magnetic recording layer is performed by a magnetic recording head 200 arranged close to the peripheral surface of the developing roll 12 as shown in FIG. The magnetic recording head 200 has a core 201 made of a soft magnetic material and having both ends arranged side by side at intervals and a coil 202 wound around the core 201. It is arranged so as to be close to the peripheral surface of the developing roll. A magnetizing current is supplied from a power supply to the coil 202 via a magnetizing signal generator. When a current flows through the coil 202, a magnetic flux is generated in the core 201, and the magnetic flux is generated from the tip of the core 201. It passes through the magnetic recording layer 12b. Thereby, the magnetic recording layer 12b is magnetized. Coil 202
The magnetizing current supplied to the developing roller 12 is supplied intermittently or by changing the direction of the current intermittently through a magnetizing signal generator, and as shown in FIG. Magnetized. In this embodiment, the N poles and the S poles are alternately magnetized in the circumferential direction of the developing roll 12 in a sine wave pattern, and the peak value of the magnetic flux density in the radial direction on the surface of the developing roll is set to 50 mT.

In the developing device 4 as described above, the developer in the developer agitating / conveying chamber is pumped up by the protruding portion 18 of the belt-shaped member 15 and is conveyed above the developing roll 12 as the belt-shaped member 15 moves around. It Then, as shown in FIG. 6, the developer 20 is transferred from the belt-shaped member 15 to the developing roll 1.
It falls along the peripheral surface of No. 2 and collides with the developer 21 after passing through the developing area on the developing roll 12. At this time, since the developer flowing speed is high on the downstream side in the developer flowing direction, this collision causes the magnetic carrier adsorbed on the developing roll to be repelled. Since the magnetic flux generated by the magnetic pole of the developing roll 12 is directed to the adjacent magnetic pole of opposite polarity, the magnetic field component in the direction perpendicular to the developing roll surface is rapidly attenuated near the developing roll surface. Therefore, the magnetic carrier repelled from the surface of the developing roll is dropped at a large speed and is hardly reattached to the surface of the developing roll due to the restraining force of the magnetic pole. To fall.

On the other hand, on the upstream side in the developer flow-down direction, since the developer flow-down speed is small, the magnetic carrier that has flowed down is adsorbed by the magnetic poles on the surface of the developing roll 12 after the developer is peeled off and adheres to the magnetic carrier. A thin layer of developer is formed on the developer roll along with the toner that is being formed. At this time, since the magnetic field component in the direction perpendicular to the surface of the developing roll is rapidly attenuated, the developer is not concentrated and attached to the uppermost portion, and is arranged in an orderly manner along the magnetic field. Therefore, there is no developer non-adhered portion on the developing roll, and a developer layer having a substantially constant layer thickness having no peak-valley structure is formed. This developer layer is held by the magnetic force of the developing roll 12, and is conveyed to the developing area facing the photosensitive drum 1 as the developing roll 12 rotates. Then, it is used for developing the electrostatic latent image on the photosensitive drum 1.

Next, in the developing device shown in FIG. 3, a development test of an electrostatic latent image is conducted, and the type and particle size of the carrier and
The results of investigating the image density, carrier adhesion, and image uniformity by changing the magnetic pole spacing of the magnetic recording layer 12b will be described. Generally, in a developing method using a thin layer of a two-component developer, it is preferable to use a carrier having a small average particle diameter in order to obtain a fine-grained image. When a carrier with a large average particle size is used, the spacing between the chains of carriers arranged along the magnetic field is wide and coarse, so that it is difficult to obtain a thin layer with high uniformity. Therefore, poor image uniformity and poor edge reproduction of the line image occur. Therefore, the average particle size of the carrier is preferably 100 μm or less, and in this test, carriers having an average particle size of 50 μm and 100 μm are used. The four types of carriers used are shown in Table 1.

[0048]

[Table 1]

Carriers in Table 1 are magnetic powder-dispersed resin carriers, and are ferrite carriers. The average particle diameter is a weight average particle diameter. The magnetization is the magnetization per unit weight in a magnetic field of 10 ⁶ / (4π) A / m. The mixing ratio of the toner in the developer to the carrier is 15% by weight of the toner in the developer, and 15% by weight in the carrier of 7.9% by weight of the carrier, and the toner amount per unit volume is almost equal. It is set to be. Also, the toner charge amount is -15
It is adjusted in the range of -20 mC / kg. The developing roller 12 has a magnetic pole spacing of 13 μm on its surface.
m, 25 μm, 50 μm, 100 μm, 250 μm, 5
Six kinds of 00 μm were used.

The image density is evaluated by developing a solid image and measuring the density by a reflection densitometer (trade name: X-RITE31).
The measurement is performed in step 0). If the measured value is 1.8 or more, both the solid image and the line image have a sufficient density.
8 or more is evaluated as ○, and less than 1.8 is evaluated as ×.

Further, the carrier is adhered by developing a so-called alternating line in which an image portion and a background portion are arranged in parallel at a constant cycle in a direction perpendicular to the process proceeding direction as shown in FIG. The amount was measured and evaluated. The cycle of the alternating lines is 2 cycles / mm, and the ratio of the image portion to the background portion is 1: 1. In the development of such an alternating line, an electrostatic latent image in which the image portion and the background portion are adjacent to each other at a very small interval exists on the surface of the photoreceptor, so that a so-called fringe electric field exists near the surface of the photoreceptor layer. Is generated, and in the peripheral portion of the image, electrostatic attraction acts on the carrier charged to the opposite polarity to the toner. Therefore, the alternating line is an image in which the carrier is likely to adhere, and is suitable for evaluating the carrier adhesion. The evaluation index of the carrier adhesion amount was the area ratio of carrier particles on the background portion of the alternating line. An image analysis device (trade name: LUZ
EX-5000) was used. If the area ratio of the carrier particles is 1.0% or less, there is no problem in practical use. Therefore, 1.0% or less is ◯, and 1.0% or more is ×.
And

Further, the image uniformity was evaluated by visually observing a solid image. When the density unevenness was not visually confirmed, it was ○, when there was a small amount of density unevenness, there was no problem in practical use, and it was unusable. The level was set as x.

Table 2 shows the results of the evaluation performed by the above method. In this table, in the comprehensive evaluation, those with no x in all the above three items were marked with o, and those with at least one were marked with x. (Below margin)

[Table 2]

From Table 2, the magnetic pole spacing is 25 μm or more and 250
It can be seen that in the range of μm or less, sufficient image density can be obtained without causing carrier adhesion or poor uniformity. When the magnetic pole spacing is narrower than 25 μm, it becomes difficult to arrange the magnetic carriers along the magnetic field, and the developer layer becomes sparse as a whole. Therefore, a sufficient concentration cannot be obtained,
Image uniformity is also compromised. Further, the magnetic field in the portion far from the surface of the developing roll 12 is rapidly attenuated and weakened as the magnetic pole spacing is narrower. Therefore, when the magnetic pole spacing is narrower than 25 μm, the magnetic restraint acting on the magnetic carrier on the developing roll is obtained. The force becomes weak, and carrier adhesion occurs due to the action of the fringe electric field described above. Further, a phenomenon was observed in which the developer was scattered due to the centrifugal force acting when the developing roll was rotated.

On the other hand, when the magnetic pole spacing is wider than 250 μm, the magnetic restraining force acting on the magnetic carrier in the magnetic pole space becomes extremely weak. For this reason, the developer adheres intensively near the magnetic pole. Therefore, the state of the developer layer forms peaks and troughs according to the magnetization pattern, and unevenness in the magnetization pattern occurs in the developed image.
Further, as described above, since the magnetic restraining force acting on the magnetic carrier attached between the magnetic poles is weak, carrier attachment and developer scattering occur.

In contrast to these, the magnetic pole spacing is 25 μm or more 2
When the thickness is 50 μm or less, the magnetic carriers are regularly arranged on the developing roll along the magnetic field. For this reason, there is no developer-deposited portion on the developing roll, and a developer layer having a substantially constant layer thickness that does not have a ridge-valley structure is formed.

Therefore, it is possible to obtain a highly uniform image without using a layer thickness regulating member. Further, since the developer conveyance amount does not depend on the component accuracy, high-precision assembly accuracy is not required. Furthermore, since a strong magnetic binding force acts on the developer layer on the developing member, the carrier does not adhere to the photoreceptor and the developer does not scatter. Also, FIG.
In the developing device shown in FIG. 3, the belt-shaped member 15 causes the developer to flow down along the peripheral surface of the developing roll 12. Therefore, as described above, the developer is collected and collected from the developing roll having the magnetic pole interval of 25 μm or more and 250 μm or less. It is possible to uniformly supply a new developer and form a layer. Therefore, it is possible to form a uniform developer layer in the longitudinal direction and the circumferential direction of the developing roll 12, and it is possible to obtain a highly uniform image.

Next, the result of an image forming test conducted by using the developing device shown in FIG. 3 to investigate the stability of the image density will be described. In this test, the carriers in Table 1 were used, and the toner used was the same as the above test. The mixing ratio of the toner in the developer and the carrier is 7.9% by weight based on the weight of the toner in the developer. The charge amount of the toner at this time is adjusted to about -15 mC / kg.
Further, the magnetic pole interval of the developing roll 12 is set to 100 μm.

In this experiment, the image area is divided into two parts in the longitudinal direction of the photosensitive drum 1, and the half area is divided into the area ratio 10
Using a solid image of 0% and the remaining half area as a white background area having an area ratio of 0%, continuous development on A4 paper is performed using the image forming apparatus shown in FIG. Then, after a predetermined number of sheets, a predetermined uniform image is developed, and the difference in image density in both areas is investigated to evaluate the stability of the image density. The evaluation item is density unevenness in the longitudinal direction, and at the time of evaluation, a solid image having an area ratio of 100% is formed in a solid development area and a white background area, and the image density of these is measured by a reflection densitometer. Further, during the experiment, the toner is replenished so that the toner amount in the developer becomes constant.

Table 3 shows the results of evaluation by the above method. (Below margin)

[Table 3] From Table 3, the difference in image density between the solid development area and the white background area after the continuous development of 50, 75, and 100 sheets is as follows:
Both are within the range of variation before continuous development (initial in Table 3), and it can be seen that there is no density reduction in the 100% solid development area.

Like the main developing device, the belt-shaped member 15 causes the developer to flow down along the peripheral surface of the developing roll 12 to collect the developer on the developing roll and supply a new developer. To replace the developer during collection and supply,
That is, the replacement occurs with high efficiency. For this reason, as in the present experiment, even when the development in which the image area ratio is biased in the longitudinal direction of the photosensitive drum 1 is continuously performed and the toner consumption amount on the development roll is biased, There is no difference in toner density due to this in the developer layer. Therefore, the image density does not decrease even in the region where the toner consumption is large. In this test, the magnetic pole spacing on the surface of the developing roll was set to 100 μm, but the same effect can be obtained when the magnetic pole spacing is set to 25 μm or more and 250 μm or less.

Next, an experiment conducted on the maintainability of the developing device shown in FIG. 3 will be described. In this experiment, the image forming apparatus shown in FIG. 1 is used to continuously develop 100,000 sheets of solid images with the developing apparatus shown in FIG. Then, after developing a predetermined number of sheets, the development density of the solid image and the charge amount of the toner are measured,
Investigate the transition when the number of developed sheets is piled up.

In this experiment, the following developers are used. ◎ Carrier: Ferrite carrier Average particle size 50 μm True density 4.5 g / cm ³ Magnetization 50 A · m ² / kg ◎ Toner: Negatively chargeable polyester toner Weight average particle size 7 μm Electric charge −15 mC / kg Contains 400 g of the developer, and the toner weight ratio in the developer is 7.5 to
The toner is appropriately supplied so as to be 8.5% by weight. The magnetic pole spacing on the surface of the developing roll is 100.
μm.

FIGS. 8 and 9 show changes in the solid image density and the toner charge amount when developing 100,000 sheets using the developing apparatus shown in FIG. From these figures, it is understood that in the developing device 4 according to the present invention, the image density and the toner charge amount are maintained well through the development of 100,000 sheets. In the developing device 4, the belt-shaped member 1
5, the developing roll 1 without exerting an excessive force on the developer
Since the developer is collected from above and the new developer is supplied, the developer peeling member, the layer thickness regulating member, etc. are not required, and the deterioration of the developer can be prevented. In the above experiment, the toner and carrier after the long-term development experiment were in the same state as in the initial stage, and no deterioration state was observed. Further, there is almost no fluctuation in the developer transport amount through 100,000 sheets.

As described above, in the developing device of the present invention,
It can be seen that good image quality can be stably maintained for a long period of time. In this experiment, the magnetic pole spacing on the surface of the developing roll was set to 1
It was set to 00 μm, but the magnetic pole spacing is 25 μm or more and 250
Similar effects can be obtained even when the thickness is set to less than or equal to μm.

In the developing device shown in FIG. 3, the developer layer on the developing roller 12 is not in contact with the photosensitive drum 1, but the developer layer is in contact with the photosensitive drum 1. Similar results are obtained even when set to. Although the magnetic recording layer 12b has the magnetic material dispersed in the binder resin in the developing device, the same result can be obtained when the magnetic metal material is used. In this case, as the magnetic metal material, any known material such as a magnet material or a magnetic recording material can be used, and for example, Co—Ni—P, Co—Ni, or Co—Cr can be used.

Further, similar results can be obtained when the magnetic recording layer 12b has a structure in which a magnetic material is dispersed in a flexible material. In this case, as the material having flexibility, any material capable of mixing a large amount of magnetic material and capable of maintaining flexibility can be used, for example, Hypalon, polyisobutylene, neoprene rubber,
Nitrile rubber, chlorinated polyethylene, etc. can be used. Further, in this developing device, N poles and S poles are alternately magnetized in the circumferential direction of the developing roll 12, but even when N poles and S poles are alternately magnetized in the longitudinal direction of the developing roll 12. Similar results are obtained.

In the developing device, the magnetic recording layer 12b of the developing roll 12 is magnetized by using the magnetic recording head 210 shown in FIG. 10 instead of the magnetic recording head 200 shown in FIG. You can also do it. When such a magnetic recording head 210 is used, the developing roll is assumed to have the magnetic recording layer 122b provided on the soft magnetic layer 122a. Any known material can be used as the soft magnetic material 122a, and examples thereof include iron, iron-silicon alloy, and iron-nickel alloy.

The magnetic recording head 210 has a shape in which the cross section is reduced so that one end 211a of the core has a small end face, while the other end 211b has a large end face facing the peripheral surface of the developing roll. Has become. When an electric current is supplied to the coil 212 wound around the core 211, the magnetic flux generated in the core 211 passes through the magnetic recording layer 122b from a small end surface and further passes through the soft magnetic layer 122a below the magnetic recording layer 122b. The other end 2 of the core whose end face is large
Continue to 11b. Therefore, the small end face 2 of the magnetic recording layer
At the position facing 11a, the N pole and the S pole are formed in the thickness direction of the magnetic recording layer 122b, while the portion facing the large end face is hardly magnetized. By performing such magnetization over substantially the entire peripheral surface of the developing roll, magnetic poles arranged in the thickness direction of the magnetic recording layer 122b can be formed over substantially the entire peripheral surface. By thus magnetizing in the thickness direction of the magnetic recording layer, a magnetic field having a large magnetic flux density can be formed, and the magnetic pole spacing,
Such a magnetization pattern can be adopted depending on the carrier used.

[Second Embodiment] FIG. 11 shows a developing roll used in a developing device which is an embodiment of the invention described in claim 1, claim 2, claim 5, claim 6 or claim 7. It is a partial expanded sectional view shown. The developing roll 22 is formed by providing an insulating layer 22b on a conductive substrate 22a, and further laminating a strip-shaped electrode 22c extending over substantially the entire length of the developing roll in the axial direction. The electrodes 22c are connected to each other at both ends of the developing roll, and have a shape protruding from both sides in a comb shape. An insulating material layer 22d is formed between these electrodes, and the surface of the developing roll is finished to be smooth.

A developing bias voltage is applied to the conductive substrate 22b of the developing roll 22 from a developing bias power source (not shown). This developing bias voltage is a DC voltage superimposed on an AC voltage, and the DC component is -400.
The V and AC components have a frequency of 6 KHz and a peak-to-peak voltage of 1.
It has a rectangular wave of 5 KV. Further, a DC component of the developing bias voltage is applied to every other electrode 22c from the end of the developing roll, and a voltage obtained by superimposing a DC voltage of 100V on the DC component of the developing bias voltage is applied to the other electrodes. It As a result, an electric field is generated between the adjacent electrodes on the developing roll 22. This DC voltage is set so that a potential difference of 1 V per 1 μm is generated as an electric field generated between the adjacent electrodes. The developing roll 22
The other configuration of the developing device using is the same as that of the developing device shown in FIG.

When the developer is supplied near the peripheral surface of the developing roll 22 as described above, an induced electric charge is generated in the carrier and polarized by the electric field between the electrodes 22c. Then, it is adsorbed on the peripheral surface of the developing roll 22 by the action of the electric field to form a developer layer. At this time, the electrode interval is 25
Since it is set to ˜200 μm and is not so large as compared with the particle size of the carrier, the lines of electric force pass through the inside of the carrier adsorbed on the peripheral surface of the developing roll and hardly advance to the outside thereof. Therefore, the carrier cannot adhere in multiple layers on the peripheral surface of the developing roll, and a thin developer layer is formed almost uniformly.

In such a developing device, when the developer flows down along the peripheral surface of the developing roll 22 by the belt-shaped member, a part of the developer passes through the developing area on the downstream side in the developer flowing direction. The developer collides with the developing agent on the developing roll 22. Then, the developer on the developing roll is peeled off, and is dropped together with the peeled developer to be collected in the developer stirring and conveying chamber. On the upstream side in the developer flow-down direction, the magnetic carrier in the developer that has flowed down is the developing roll 22.
And the toner adhering to the magnetic carrier to form a thin layer of developer as described above.

Therefore, similarly to the developing device shown in FIG. 3, the recovery of the developer from the developing roll and the supply of the developer to the developing roll can be uniformly performed, and the deterioration of the developer can be prevented. it can. Further, since the developer is replaced or replaced at the time of the collection and supply efficiently, the toner density of the developer layer on the developing roll does not become non-uniform, and the image density does not decrease. Further, since a member such as a layer thickness regulating member that rubs the developing roll is not used, the developer transport amount does not change with time. Therefore, it is possible to perform high-quality development for a long period of time.

[Third Embodiment] FIG. 12 is a schematic block diagram showing a developing device which is an embodiment of the invention described in claim 1, claim 2, claim 4, claim 6 or claim 8. is there.
The developing device is provided with a rotatable impeller 35 in which a screw auger 34 on the back side of the housing 31 is arranged above the other screw augers 33, and the screw auger 34 is rotatable in a position close to the screw auger 34.

The impeller 35 has a width substantially the same as the developable width of the developing roll 32 and is arranged so as to face the developing roll 32 closely. The impeller 35 is formed by integrally molding the shaft center and the blade member using aluminum. Further, the shaft diameter is set to 6 mm, and the outer shape of the impeller is set to 16 mm. The impeller can be formed using any other material such as metal or resin. Further, the developing roll 32 has magnetic poles with different polarities on the peripheral surface of 100 μm like the developing roll 12 shown in FIG.
It is formed alternately at intervals of m. The other structure of this developing device is the same as that of the developing device shown in FIG.

In such a developing device, the impeller 35 pumps up the developer in the developer agitating / conveying chamber, and the developer is conveyed above the developing roll 32 by rotating in the direction of the arrow shown in the drawing. After that, the developer falls along the peripheral surface of the developing roll 32, and a part of the developer collides with the developer on the developing roll that has passed through the developing area on the downstream side in the developer flow-down direction and is separated from the developing roll 32. To do. Then, together with the peeled developer, the developer falls into the developer stirring and conveying chamber. on the other hand,
On the upstream side in the developer flow-down direction, the developer that has flowed down is restrained by the magnetic force of the surface of the developing roll, and a thin layer of the developer is formed on the developing roll 32. After that, the thin layer of the developer formed on the developing roller 32 is conveyed to the developing area as it is rotated, and is provided for developing the electrostatic latent image on the photosensitive drum 1. After the development, the developer on the developing roll 32 is conveyed to a position facing the impeller 35, and similarly, the developer is collected and a new developer is supplied.

When an image is formed using such a developing device, a uniform developer layer is formed on the developing roll 32, and carrier adhesion and developer scattering do not occur.
A high quality image with high uniformity was obtained. In addition, FIG.
When a confirmation test of image density stability was performed in the same manner as in the developing device shown in (1), uneven toner density on the developing roll due to uneven toner consumption did not occur, and in a region where toner consumption is high, No decrease in image density occurred. Further, when a long-term development test was conducted on 100,000 sheets using this developing device, the image density and the toner charge amount were maintained good over 100,000 sheets, and no deterioration state was found in the developer after the experiment. As described above, it is understood that the developing device of the invention according to the present application can stably maintain good image quality for a long period of time. Further, in the developing device used in this embodiment, the interval between the adjacent magnetic poles on the developing roll is set to 100 μm, but the same result can be obtained when the magnetic pole interval is set to 25 μm or more and 250 μm or less.

[Fourth Embodiment] FIG. 13 is a schematic structural view showing a developing device which is an embodiment of the invention described in claim 1, claim 2, claim 4, claim 6 or claim 9. is there.
In this developing device, the screw auger 44 on the back side of the housing 41 is arranged above the other screw augers 43, and a partition plate 45 is provided between the developing roll 42 and the screw auger 44. A developer accommodating portion 46 having 44 inside is formed. A developer discharge port 47 is provided above the partition plate 45 at a position facing the developing roll 42. The discharge port 47 discharges the developer in the developer container 46 almost uniformly to a position facing the developing roll 42, and the vertical width of the discharge port 47 is set to about 8 mm. Although the partition plate 45 is formed integrally with the housing 41 in this example, it goes without saying that both may be separated. The other structure of this developing device is the same as that of the developing device shown in FIG.

In such a developing device, the developer is agitated by the screw augers 43 and 44, and the developer in the developer accommodating portion 46 is discharged from the discharge port 47 of the partition plate 45.
Is discharged above the developing roll 42. The developer falls along the peripheral surface of the developing roll 42, and a part of the developer collides with the developer on the developing roll 42 that has passed through the developing area, and separates it from the developing roll 42. Then, the peeled developer falls into the developer agitating / conveying chamber as the developer flows down. On the upstream side in the developer flow-down direction, a part of the developer that has flowed down is restrained by the magnetic force of the surface of the developing roll after the developer is peeled off, and a thin layer of the developer is formed on the surface.

When an image forming test was conducted using the developing device of this example, it was confirmed that good image quality could be stably maintained for a long period of time as in the developing device shown in FIG. Further, in the above developing device, the interval between the adjacent magnetic poles on the developing roll is set to 100 μm, but the magnetic pole interval is 25 μm.
Similar results are obtained even when the thickness is set to be not less than μm and not more than 250 μm.

In this example, the vertical width of the discharge port 47 is the same over the entire length of the opening. May be set as follows. As a result, the amount of the developer, which decreases as it goes downstream in the developer transport direction, is less likely to be affected, and the developer can be discharged almost uniformly over the entire length of the opening. Therefore, it is possible to generate a substantially uniform flow of the developer along the peripheral surface of the developing roll 42, and it is possible to further reduce the occurrence of density unevenness in the width direction.

[Fifth Embodiment] FIG. 14 is a schematic structural view showing a developing device according to an embodiment of the present invention described in claims 1, 3, and 10. In this developing device 54, a developing opening 53 is provided in a portion of the housing 61, in which the developer is contained, which faces the photosensitive drum 50. The developing roller 52 is disposed at the position where the developing opening 53 is provided, and closely faces the photoconductor drum 50. A plurality of magnetic poles are magnetized at a small pitch on the peripheral surface of the developing roll 52, which adsorbs the developer 51 to form a thin developer layer and conveys it to a developing area facing the photoconductor drum 50. Is. Further, on a side different from the position facing the photosensitive drum 50, an agitating roll 55 faces the developing roll 52 with a predetermined gap as an alternating magnetic field generating means for generating an alternating magnetic field, and develops via the roll end. It is applied so as to have the same potential as the roll 52. The stirring roll 55 is composed of a rotatable hollow cylindrical non-magnetic sleeve 55a and a magnet roll 55b located inside thereof. The developer is magnetically adsorbed on the sleeve 55a, and the carriers are connected in a spike shape. It is designed to form a magnetic brush.

A toner hopper 56 and a toner supply roller 58 for supplying a required amount of toner 57 from the toner hopper 56 to the developer on the stirring roll 55 are provided above the stirring roll 55. The inner surface of the housing 61 faces the peripheral surfaces of the developing roll 52 and the agitating roll 55 with a substantially constant gap therebetween, and accommodates a large amount of developer or agitates the developer. Is not provided.

The magnet roll 55b included in the stirring roll 55 has magnetic poles of different polarities alternately arranged over the entire circumference, and is rotatably supported independently of the outer sleeve 55a. This magnet roll 55
The magnetic brush b forms a magnetic brush on the surface of the sleeve 55a in which the developer is in the shape of an ear due to the magnetic field formed between the adjacent magnetic poles. Then, only the magnet roll 55b or both the magnet roll 55b and the sleeve 55a rotate in different directions or at different rotation speeds, so that the magnetic brush is conveyed while being stirred. In this embodiment, the outer diameter of the sleeve 55a is 18 mm, the number of magnetic poles is 12, the magnetic pole gap is about 5 mm, and the peak value of the magnetic flux density in the radial direction on the surface of each magnetic pole is 50 mT.
Is set to On the other hand, the developing roll 52 used was the same as the developing roll 12 shown in FIG.

Next, the operation of this developing device will be described. A predetermined amount of the developer is pre-supplied around the stirring roll 55, and is adsorbed substantially uniformly over the entire length of the stirring roll 55, and both the magnet roll 55b and the sleeve 55a are shown in the figure. By rotationally driving in the directions indicated by the arrows, the spike-shaped developer on the sleeve 55a is agitated and conveyed as the magnetic field fluctuates, and the toner is triboelectrically charged. Further, due to the rotation of the magnet roll 55b, the magnet roll 55b is conveyed in a direction opposite to this rotation direction, and is conveyed in the same direction as the conveyance direction of the developing roll 52 in a region facing the developing roll 52, so that the stirring roll 55 and the developing roll 52 come close to each other. Reach the vicinity of the facing position.

Further, in the present embodiment, the developer layer thickness on the stirring roll 55 is about 600 μm on the magnetic pole, the gap between the stirring roll 55 and the developing roll 52 is 400 μm, the sleeve 55a has a peripheral speed of 30 mm / sec, and a magnet. Roll 5
5b was rotated at a peripheral speed of 800 mm / sec.

The developing roll 52 and the stirring roll 55 are opposed to each other with a gap slightly narrower than the rising of the developer on the stirring roll 55 (height above the magnetic pole). When passing through the closest contact point with the developing roll 52, the tip of the magnetic brush comes into contact with the developer layer that has passed through the developing area on the developing roll 52 and scrapes it. When the developer is separated from the surface of the developing roller 52 even a little, the restraining force due to the magnetic force is rapidly reduced, and the developer is taken into the inside of the magnetic brush by the action of the alternating magnetic field before the opportunity of re-adhesion is given, and a new developer is replaced. It appears at the tip of the magnetic brush and contacts the surface of the developing roll 52 to form a developer layer on the developing roll 52.

The developer supplied to the developing roll 52 is adsorbed on the surface of the developing roll 52 by the magnetic field of the magnetic recording layer, and the magnetic recording layer has a small magnetizing interval of 100 μm, so the developer is thin. A uniform developer layer is formed on the developing roll 52. Further, since the developing roll 52 and the sleeve 55a have the same potential, the developing roll 5
2. When the developer is supplied on the second layer to form a layer, the toner is not peeled off from the carrier due to the influence of the development bias, and the developer in the state where the toner is sufficiently adhered to the carrier surface at the stirring portion is almost one layer A uniform developer layer is formed.

The developer on the developing roll 52 is the developing roll 5.
With the rotation of 2, the toner is conveyed to the developing area facing the photoconductor drum 50, and only the toner attached to the carrier is transferred to the electrostatic latent image on the photoconductor drum 50 and developed. At this time, the developer layer is held in a non-contact state with the photosensitive drum 50. The developer carried on the developing roll 52 and passed through the developing area is again conveyed to a position facing the stirring roll 55, and is collected by contact with the magnetic brush on the stirring roll 55.

The developer collected on the agitating roll 55 is conveyed in the form of ears on the sleeve 55a, and the toner 57 corresponding to the amount of consumed toner is turned on the agitating roller 55 by the rotation of the toner supply roller 58. It will be supplied directly. Then, the toner concentration is made uniform by the stirring movement of the developer layer on the sleeve 55a, and the toner is charged and the process proceeds to the next step.

In this embodiment, the stirring roll 55 not only supplies and collects the developer to the developing roll 52, but also stirs the toner.
Although charging was also performed, a stirring member may be separately provided to perform stirring charging. Further, it is preferable that the sleeves of the developing roll and the stirring roll have the same potential, but a potential difference may be provided if necessary. Further, the method of supplying the toner to the collected developer after passing through the developing area is the method of supplying the toner corresponding to the toner amount according to the consumption amount in the present embodiment, but it is not limited to this. .

Next, in the developing device shown in FIG. 14, a test similar to the electrostatic latent image developing test carried out by the developing device shown in FIG. The evaluation items and evaluation criteria were the same as in the first embodiment. Table 4 shows the evaluation results. (Below margin)

[Table 4]

From Table 4, the magnetic pole spacing is 25 μm or more and 250 μm.
It can be seen that in the range of m or less, sufficient image density can be obtained without causing carrier adhesion or poor uniformity.
Similar to the evaluation result in the first embodiment, the magnetic pole spacing is 25
When it is narrower than μm, the developer layer becomes sparse as a whole, carrier adhesion and developer scattering are observed, and when the magnetic pole interval is wider than 250 μm, developer scattering and magnetic pattern unevenness occur. Occurred. Therefore, the developing roller having a magnetic pole interval of 25 μm or more and 250 μm or less as described above is provided by causing the alternating magnetic field generating means for carrying and carrying the developer on the surface to closely face the developing member as in the present embodiment. On the other hand, it is possible to uniformly collect and supply the developer and form the layer. Therefore, a uniform developer layer can be formed on the developing roll, and an image with high uniformity can be obtained.

Next, the result of investigation of image density stability similar to that carried out by the developing device shown in FIG. 3 will be described using the developing device shown in FIG. The evaluation items and evaluation criteria were the same as in the first embodiment. Table 5 shows the evaluation results.

[0096]

[Table 5] From Table 5, the difference in image density between the solid print area and the white background area after continuous printing is within the range of variation before continuous printing (initial in Table 5), and the density is 100% in the solid print area. It can be seen that the decrease has not occurred.

Next, with respect to the maintainability of the developing device shown in FIG. 14, a continuous 100,000-sheet printing test was conducted as in the first embodiment. The amount of charge was maintained well. In the developing device 54, the developer is removed from the developing roll, the new developer is supplied, and the layer is formed without applying an excessive force to the developer by the magnetic brushes close to each other. A forming member or the like is unnecessary, and deterioration of the developer can be prevented. In the above experiment,
The toner and carrier after the long-term development experiment were in the same state as in the initial stage, and no deterioration was observed. Further, there is almost no fluctuation in the developer transport amount through 100,000 sheets. As described above, in the developing device of the present invention, good image quality
It can be seen that it can be maintained stably over a long period of time.

In this experiment, the magnetic pole spacing on the surface of the developing roll 52 was set to 100 μm.
Similar results are obtained. It is also possible to separately provide the collecting means before the stirring roll is close to the developing roll.

[Sixth Embodiment] FIG.
It is a schematic block diagram which shows the developing device which is one Embodiment of invention of Claim 12. In the developing device 74, a developing opening 73 is provided in a portion of the housing 68, in which the developer is contained, which faces the photosensitive drum 70. And
The developing roll 62 is provided at the position where the developing opening 73 is provided.
Is disposed and closely faces the photoconductor drum 70. A plurality of magnetic poles are magnetized at a small pitch on the peripheral surface of the developing roll 62, which adsorbs the developer 71 to form a thin developer layer and conveys it to a developing area facing the photoconductor drum 70. Is. Further, on the side opposite to the position facing the photoconductor drum 70, a stirring roll 75 carrying a developer 71 on the surface is faced with a predetermined gap so that the developer can contact the surface of the developing roll 62, and the roll end They are provided so as to have the same potential through the parts. The stirring roll 75 is a rotatable hollow cylindrical non-magnetic sleeve 75a.
And a magnet roll 75b located inside thereof, magnetically adsorbs the developer on the sleeve 75a to form a magnetic brush in which the carriers are connected in a spike shape.

Further, a toner hopper 76 and a toner supply roller 78 for supplying a required amount of toner 77 from the toner hopper 76 to the developer on the stirring roll 75 are provided above the stirring roll 75. The inner surface of the housing 68 opposes the peripheral surfaces of the developing roll 62 and the stirring roll 75 with a substantially constant gap, and accommodates a large amount of developer and augers for stirring the developer. Is not provided.

Further, in this embodiment, the developer layer thickness on the stirring roll 75 is about 600 μm on the magnetic pole, the gap between the stirring roll 75 and the developing roll 62 is 400 μm, the sleeve 75a has a peripheral speed of 30 mm / sec, and the magnet. Roll 7
5b was rotated at a peripheral speed of 800 mm / sec. The stirring roll 75 and the developing roll 62 are the same as those used in the fifth embodiment.

The developing roll 62 is rotationally driven in the direction shown by the arrow in FIG. 15, and the developer adsorbed on the surface moves as the developing roll 62 rotates. On the other hand, the stirring roll 7
5, the sleeve 75a and the built-in magnet roll 75b are rotationally driven in the directions indicated by the arrows in FIG. 15, and the developer carried on the surface of the sleeve 75a is the developing roll 62.
In the area which is in contact with the surface of the developing roll 62 and faces the developing roll 62, the developing roll 62 is conveyed in a direction different from the conveying direction.

Next, the operation of this developing device will be described. A predetermined amount of developer is previously supplied around the stirring roll 75, and is adsorbed substantially uniformly over the entire circumference of the stirring roll 75. And sleeve 7
5a and the magnet roll 75b are respectively driven to rotate in the directions of the arrows shown in the drawing, whereby the sleeve 7
The spike-shaped developer on 5a is agitated as the magnetic field fluctuates, and is conveyed while the toner is frictionally charged, and reaches the vicinity of the position facing the developing roller 62. The developing roll 62 and the stirring roll 75 are opposed to each other with a gap slightly narrower than the height of the developer spikes (height above the magnetic pole) on the stirring roll 75, and are conveyed to the vicinity of the position facing the developing roll 62. The tip of the developer layer contacts the surface of the developing roll 62. In the area facing the developing roll 62, the developer is conveyed in a direction different from the moving direction of the peripheral surface of the developing roll 62,
Since the surface of the developing roll 62 is moving away from the position closest to the stirring roll 75, only the developer near the surface of the developing roll 62 is adsorbed and conveyed along with the movement of the surface of the developing roll 62. In addition, the developer which is blocked by the other developer and cannot reach the vicinity of the surface of the developing roll 62 is left behind and stays in the front area where the stirring roll 75 and the developing roll 62 closely face each other, and the developing roll 62 surface Be prepared for the opportunity to contact. Here, since the developer that contacts the surface of the developing roll 62 forms a pool and constantly covers the surface of the developing roll 62, the developer layer formed on the surface of the developing roll 62 will not run short. Further, the developing roll 6
Since the magnetic recording layer on the second surface has a small magnetizing interval of 100 μm, a strong magnetic binding force acts only on the developer in the vicinity of the surface of the developing roll 62 out of the excessively supplied developer, and the upper layer thereof. Since the magnetic restraining force hardly acts on the developer of the part, the developer layer conveyed with the movement of the developing roll 62 is a uniform layer in which almost one carrier is closely arranged.

The uniform thin developer layer formed on the developing roll 62 is conveyed to the developing area facing the photoconductor drum 70 as the developing roll 62 rotates, and only the toner adhering to the carrier is exposed. The electrostatic latent image on the body drum 70 is transferred and developed. At this time, the developer layer is held in a non-contact state with the photosensitive drum 70. The developer carried on the developing roll 62 and passed through the developing area is conveyed to a position facing the stirring roll 75.

On the other hand, among the developers not supplied to the developing roll 62 in the region where the developing roll 62 and the stirring roll 75 face each other closely, the developer near the surface of the stirring roll 75 is a strong magnetic binding force of the built-in magnet roll 75b. Upon receipt, it passes the position closest to the developing roll 62. At the position where the developing roll 62 and the stirring roll 75 are closest to each other,
The magnetic brush rubs the surface of the developing roll 62 by the alternating magnetic field acting on the surface of the stirring roll 75. Since the developer that has passed through the developing area on the developing roll 62 is moving in a direction against the sliding friction of the magnetic brush, most of the developer is peeled off from the surface of the developing roll 62. When the surface of the developing roller 62 is separated from the surface of the developing roller 62, the magnetic force on the surface of the developing roller 62 is drastically reduced and the magnetic force is collected by the magnetic brush on the stirring roller 75. The collected developer is the sleeve 75a.
The toner 77 corresponding to the amount of the toner that has been conveyed in the form of ears and is consumed is replenished directly to the developer on the stirring roller 75 by the rotation of the toner supply roller 78. Then, the toner density is made uniform by stirring and moving the developer layer on the sleeve 75a, and the toner is charged, and the process proceeds to the next step.

In this embodiment, the stirring roll 55 not only supplies and collects the developer to the developing roll 52, but also stirs the toner.
Although charging was also performed, a stirring member may be separately provided to perform stirring charging. Further, it is preferable that the sleeves of the developing roll and the stirring roll have the same potential, but a potential difference may be provided if necessary. Further, the method of supplying the toner to the collected developer after passing through the developing area is the method of supplying the toner corresponding to the toner amount according to the consumption amount in the present embodiment, but it is not limited to this. .

In such a developing device, the stirring roll 75
Since the developer conveyed from is supplied to the surface of the developing roll 62 that has passed through the closest position before the closest position, the area where the developer is supplied from the stirring roll 75 to the developing roll 62 becomes the developer. It is possible to supply the developer and form a layer by bringing the developer into soft contact with the developing roll 62 without applying too much pressure. In the developing device, the developing roll 62 and the sleeve 7 of the stirring roll 75 are used.
5a and the magnet roll 75b rotate in the region where the developing roll 62 and the stirring roll 75 face each other.
The present invention is not limited to the illustrated one as long as it is conveyed in a direction different from the second conveying direction.

An image forming test was conducted using the developing device 74 of this example, and it was confirmed that a good image could be stably maintained for a long period of time like the developing device 54 shown in FIG. Further, in the developing device 74, the interval between the adjacent magnetic poles on the developing roll is set to 100 μm, but similar results can be obtained when the magnetic pole interval is set to 25 μm or more and 250 μm or less.

[Seventh Embodiment] FIG.
1 is a schematic configuration diagram illustrating a developing device that is an embodiment of the invention described in FIG. In the developing device 84, a developing opening 83 is provided in a portion of the housing 91 facing the photosensitive drum 80, and a developing roll 72 is disposed in the opening 83, and a position facing the photosensitive drum 80. On the opposite side, a stirring roll 85 carrying the developer 81 on the surface is opposed to the surface of the developing roll 72 with a predetermined gap so that the developer comes into contact with the surface. The potential of this stirring roll is set so as to have the same potential as that of the developing roll through the end portion thereof. Further, a developer recovery roll 95 for temporarily recovering the developer having passed through the development area on the development roll 72 before the position closest to the stirring roll 85 is provided on the development roll 72. It is provided above the stirring roll 85 so as to face each other. Sleeve 8 of developing roll 72 and stirring roll 85
5a and the magnet roll 85b are rotationally driven in the direction of the arrow shown in FIG. 16, whereby the developer on the sleeve 85a is conveyed in the area facing the developing roll 72 in the conveying direction of the developing roll 72. And transported in a different direction. The developer on the agitating roll 85 is supplied to the developing roll 72 in a region where gravity acts in a direction away from the developing roll 72. Further, above the stirring roll 85, a toner hopper 86 and a toner supply roller 88 for supplying a required amount of toner 87 from the toner hopper 86 to the developer on the stirring roll 85 are provided. .

The developer recovery roll 95 is a cylindrical non-magnetic conductive sleeve 95a having a hollow portion with a distorted shape.
And a magnetic field generating member 95b located inside thereof. The magnetic field generating member 95b has magnetic poles of different polarities alternately magnetized over the entire circumference, and the outer sleeve 95a is formed.
It is provided so that it can rotate independently of. In this embodiment, the outer diameter of the sleeve is 10 m.
In S, 4 poles of S poles and N poles are alternately arranged at equal intervals, and the magnetic flux density in the radial direction on the surface of each magnetic pole is set to 80 mT.

The other construction of the developing device 84 is the same as that shown in FIG.
5 is the same as the developing device 74 shown in FIG. Further, in this embodiment, the developer layer thickness on the stirring roll 85 is about 600 on the magnetic pole.
μm, the gap between the stirring roll 85 and the developing roll 72 is 40
0 μm, the gap between the developer collecting roll 95 and the developing roll 72 is 400 μm, and the sleeve 85a has a peripheral speed of 30 m.
m / sec, magnet roll 85b, peripheral speed 600m
m / sec, the peripheral speed of the magnetic field generating member 95b is 800 mm
Each was rotated at / sec.

Next, the operation of the developing device 84 will be described. A predetermined amount of the developer 81 is provided around the stirring roll 85.
Is previously supplied and is adsorbed almost uniformly over the entire circumference of the stirring roll 85. Then, both the sleeve 85a and the magnet roll 85b are rotationally driven in the directions of the arrows shown in the figure, so that the developer that has become spike-like on the sleeve 85a is agitated as the magnetic field fluctuates, and the toner In a region facing the developing roll 72 while being triboelectrically charged, it is conveyed in a direction different from the conveying direction of the developing roll 72, and the gravity acting on the developer acts in a direction away from the developing roll 72. It reaches near the portion facing the developing roller 72. The developing roll 72 and the stirring roll 85 are opposed to each other with a gap slightly narrower than the rising of the developer on the stirring roll 85 (height above the magnetic pole).
The tip of the developer layer conveyed near the position facing the developing roll contacts the surface of the developing roll 72. In the area facing the developing roll 72, the developer on the stirring roll is conveyed in a direction different from the conveying direction of the developing roll 72, and the surface of the developing roll 72 is located at the closest position to the stirring roll 85. Since it is moving in the direction away from, only the developer near the surface of the developing roll 72 is adsorbed and conveyed along with the movement of the surface of the developing roll 72.

In addition, the developing roll 7 is blocked by another developer.
(2) The developer that cannot reach the vicinity of the surface is left behind, part of the developer is conveyed along the sleeve 85a, and the other part of the developer stays in the front area where the stirring roll 85 and the developing roll 72 face each other. In preparation for an opportunity to contact the surface of the developing roll 72. Here, the developer contacting the surface of the developing roll 72 is
Since the surface of the developing roll 72 is always covered by forming the pool, the developer layer formed on the surface of the developing roll 72 will not run short. Further, since the magnetic recording layer on the surface of the developing roll 72 has a small magnetizing interval of 100 μm, it is strong against only the developer near the surface of the developing roll 72 among the excessively supplied developers. The magnetic binding force works, and almost no magnetic binding force works on the developer on the upper layer. Further, in the area where the developer conveyed from the stirring roll 85 is supplied / layer-formed on the developing roll 72, gravity acts in the direction in which the developer separates from the developing roll 72. Only the carrier whose magnetic restraining force acting from overcomes gravity is transported. Therefore, for example, the surface of the developing roll 72 is firmly fixed.
The carrier in contact with the surface is conveyed without separating from the developing roll 72, but the carrier on the carrier cannot come into direct contact with the surface of the developing roll 72 and falls off and stays in the developer pool. Or fall and develop roll 85
Since it is returned to the upper position, the developer layer conveyed along with the movement of the developing roll 72 is stably a uniform layer in which the carriers are lined up more closely.

The uniform thin developer layer formed on the developing roll 72 is conveyed to the developing area facing the photosensitive drum 80 as the developing roll 72 rotates, and adheres to the carrier. Only the toner is transferred to the electrostatic latent image on the photosensitive drum 80 to develop it. At this time, the developer layer is held in a non-contact state with the photosensitive drum 80.

The developing roll 72 carrying the developer layer that has passed through the developing area reaches a position facing the developer collecting roller 95. The developer collecting roll 95 is closely opposed to the developing roll 72, and most of the development on the developing roll 72 is performed by the strong magnetic force of the magnetic field generating member 95b inside the developer collecting roll 95. The agent is recovered and moved onto the developer recovery roll 95. The developer that has moved onto the developer collecting roll 95 is rotated by the magnetic field generating member 95b, and the sleeve 9 is rotated.
5a in the direction shown in the drawing, and a developer recovery roll 95
When the magnetic field generating member 95b built in the head reaches a portion farther away, the magnetic restraining force weakens and the sleeve 95a
From the developer collecting roll 95, and adheres to and is conveyed on the stirring roll 85 located below the developer collecting roll 95. The developer on the stirring roll 85 is stored in the magnet 85b and the sleeve 8
By the rotation of 5a, the toner is conveyed in the rotation direction shown by the arrow in FIG. 16, a predetermined amount of toner is replenished, agitated, and the toner is triboelectrically charged, so that the gravity acting on the developer moves away from the developing roll. The developing roll is opposed to the developing roll in the area to be processed, and the process proceeds to the next step.

In such a developing device, the developer conveyed from the stirring roll is supplied to the surface of the developing roll passing through the closest position before the closest position, so that the developer is stirred. In the area supplied from the roll to the developing roll, too much pressure is not applied to the developer and the developer can be brought into soft contact with the developing roll, and only the developer that overcomes gravity is conveyed. And a uniform developer layer is stably formed.

An image forming test was conducted using the developing device 84 of this example, and it was confirmed that a good image could be stably maintained for a long period of time as in the developing device 54 shown in FIG. In the developing device 84, the developing roll 7
The gap between the adjacent magnetic poles on 2 was set to 100 μm,
Similar results are obtained when the magnetic pole spacing is set to 25 μm or more and 250 μm or less.

[Eighth Embodiment] FIG. 17 is a schematic structural view showing a developing device according to another embodiment of the present invention. In the developing device 94, a developing opening 93 is provided in a portion of the housing 101 facing the photosensitive drum 90, the developing roll 102 is disposed in the opening 93, and the developing device 94 faces the photosensitive drum 90. On the opposite side of the developing roller 102, the developer carried on the surface of the developing roller 102 is kept in contact with the developing roller 102. A guide member 99 that guides the replenishment toner 97 so as to come into contact with it, and a guide member 9 that guides the toner 97 while loosening the stored toner 97.
9, a toner conveying member 98 that conveys the toner to the upper surface 9 and a guide member 99.
Replenishment toner amount regulation member 10 for regulating the amount of toner carried upward
0. Further, although not shown, a toner box for replenishing the toner 97 is connected to an end portion of the toner containing portion 96 in the axial direction.

The developing roll 102 and the stirring roll 105 are provided so as to have the same potential through the end of the roll. The sleeve 105a of the developing roll 102 and the stirring roll 105 and the magnet roll 105b rotate in the direction of the arrow shown in FIG. 17, so that the developer on the sleeve 105a faces the developing roll 102. The developing roll 1 is conveyed in a region different from the conveying direction of the developing roll 102, and in the region where gravity acts in a direction away from the developing roll 102.
02, the developer 111 can be supplied. The developing roll 102 and the stirring roll 105 of the developing device 94 are the same as those of the developing device 74 shown in FIG.

Next, the operation of the developing device 94 will be described. The operations up to the supply of the developer 111 from the stirring roll 105 to the developing roll 102 and the development are the same as in the seventh embodiment, and the stirring roll 10 after the development is finished.
The operation of collecting toner in No. 5 is the same as that of the sixth embodiment, and since it has been described in detail in each of the embodiments, it is omitted here, and toner is replenished to the developer collected on the stirring roll 105. Will be explained.

The stored toner 97 accommodated in the toner accommodating portion 96 is conveyed while being unraveled by the toner conveying member 98,
The toner amount regulating member 100 and the guide member 99 are conveyed along the guide member 99 through the supply ports facing each other, and are conveyed to a position close to the stirring roll 105. The tip of the guide member 99 slightly contacts the developer layer on the stirring roller 105, and the replenishment toner 97 conveyed along the guide member 99 contacts the developer on the stirring roller 105. The toner that has come into contact with the surface of the carrier is electrostatically attached and taken in, and the excessive toner remains without being taken in until the next carrier. The developer in contact with the replenishment toner is replenished with toner to such an extent that the surface of the carrier is covered with the toner, and is returned to a constant toner concentration.
While being conveyed to the vicinity of the position opposite to 02, stirring and charging are performed, and the process proceeds to the next step.

In such a developing device 94, the developer 111 conveyed from the stirring roll 105 is supplied to the surface of the developing roll 102 which has passed the closest position before the closest position. In a region where the developer is supplied from the stirring roll 105 to the developing roll 102, the developer is not contacted with the developing roll 102 softly without a large pressure applied to the developing roll 102. It is possible to stably form a uniform developer layer in which only the carriers are transported and the carriers are more closely arranged.

An image forming test was conducted using the developing device 94 of this example, and it was confirmed that a good image could be stably maintained for a long period of time as in the developing device 54 shown in FIG. Further, in the developing device 94, the interval between the adjacent magnetic poles on the developing roll 102 is set to 100 μm, but the same result can be obtained when the magnetic pole interval is set to 25 μm or more and 250 μm or less.

[Modifiable Configurations of the Above Embodiments] The embodiments of the invention according to the present application are not limited to those described above. For example, the following items may be changed by changing the settings or conditions. can do. In the above embodiment, the moving speed of the peripheral surface of the developing roll is 3
Although it is set to 20 mm / s, the state of formation of the developer layer does not depend on the moving speed of the peripheral surface, but is 10 mm / s.
It is possible to form a uniform developer layer in a region of about 900 mm / s to 900 mm / s, and the developer does not scatter when the developing roll rotates. The direction of movement of the peripheral surface of the developing roll may be the same as or different from the direction of movement of the peripheral surface of the photosensitive drum. Although the developing bias voltage is an alternating voltage superposed with a direct current voltage and the waveform of the alternating voltage is a rectangular wave, the present invention is not limited to this, and any developing bias voltage according to the purpose or application can be used. It is possible. Although the above-described embodiment is a monochromatic image recording apparatus, a color image recording apparatus that forms a color image with a plurality of color toners on the electrostatic latent image carrier and collectively transfers the toner images onto recording paper is also applicable. It is applicable as well. In the above-described embodiment, the photoconductor drum is used. However, a dielectric is used, and for example, an electric discharge recording head used in an electrostatic printer or an ion flow control disclosed in JP-A-59-190854. The electrostatic latent image may be formed by a head or the like.

[0125]

As described above, in the developing device of the invention according to the present application, the developer flow-down means for causing the developer to flow down along the peripheral surface of the developing member, or the alternate means provided in close proximity to the developing member. It has a developer collecting means such as an alternating magnetic field generating means for generating a magnetic field and carrying the developer carried on the surface, and a developer supplying means, so that the developer from the developing member can be operated without applying an excessive force to the developer. The developer can be collected and a new developer can be supplied onto the developing member. For this reason,
It is possible to prevent the deterioration of the developer at the time of collecting and supplying the developer. Further, since the developer on the developing member is replaced or replaced at the time of collecting and supplying the developer efficiently, there is no difference in toner concentration between the developer on the developing member and the developer in the developer accommodating portion. Therefore, the image density does not decrease.

By forming magnetic poles or electrodes on the peripheral surface of the developing member with a small pitch, the carrier of the two-component developer can be adsorbed on the peripheral surface of the developing member in a thin layer. For this reason, it is possible to efficiently collect the developer, supply the new developer, and form a layer when the developer is caused to flow down or the alternating magnetic field is closely opposed to each other, and it is possible to more reliably prevent uneven image density. can do. Further, it is possible to form a thin layer of the developer on the peripheral surface of the developing member for use in development without using a layer thickness regulating member or the like, and it is possible to further reduce the deterioration of the developer. Therefore, a high-quality image having excellent image quality stability and maintainability can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus using a developing device according to the present invention.

FIG. 2 is a diagram showing a change in potential on the surface of an image carrier when forming a toner image in the image forming apparatus shown in FIG. 1;

FIG. 3 Claim 1, Claim 2, Claim 4, and Claim 6
FIG. 8 is a schematic configuration diagram showing a developing device that is an embodiment of the invention described in claim 7.

4 is a partially enlarged cross-sectional view of a developing roll used in the developing device shown in FIG.

5 is a diagram showing a method of magnetizing the developing roll shown in FIG.

FIG. 6 is a diagram showing an operation of supplying a developer to a developing roll in the developing device shown in FIG.

7 is a diagram showing an image pattern used for investigating the amount of carrier of the developing device transferred to the photosensitive drum in the image forming apparatus shown in FIG.

8 is a diagram illustrating a relationship between the number of prints and the solid image density in the developing device illustrated in FIG. 3;

9 is a diagram showing the relationship between the number of prints and the amount of toner charge in the developing device shown in FIG.

10 is a diagram showing another method of magnetizing the developing roll that can be used in the developing device shown in FIG.

FIG. 11 is a partially enlarged view of a developing roll used in the developing device which is an embodiment of the invention described in claim 1, claim 2, claim 5, claim 6, or claim 7.

FIG. 12 is a schematic configuration diagram showing a developing device which is an embodiment of the invention described in claim 1, claim 2, claim 4, claim 6, or claim 8.

FIG. 13 is a schematic configuration diagram showing a developing device which is an embodiment of the invention described in claim 1, claim 2, claim 4, claim 6, or claim 9.

FIG. 14 is a schematic configuration diagram showing a developing device according to an embodiment of the invention described in claim 1, claim 3, or claim 10.

FIG. 15 is a schematic configuration diagram showing a developing device according to an embodiment of the invention described in claim 11 or claim 12.

FIG. 16 is a schematic configuration diagram showing a developing device according to an embodiment of the present invention.

FIG. 17 is a schematic configuration diagram showing a developing device according to another embodiment of the invention as set forth in claim 13.

FIG. 18 is a diagram illustrating the operation of the developing device according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photoconductor drum 2 Charging device 3 Exposure device 4 Developing device 5 Corotron before transfer 6 Transfer corotron 7 Peeling corotron 8 Cleaner 9 Optical static eliminator 11, 31, 41 Housing 12, 32, 42 Developing roll 12a Conductive substrate 12b Magnetic recording layer 13, 33, 43 Screw auger 14, 34, 44 Screw auger 15 Belt-shaped member 16, 17 Support roll 18 Projection portion 19, 39 Partition wall 22 Developing roll 22a Conductive substrate 22b Insulating layer 22c Electrode 22d Insulating material layer 35 Impeller 45 Partition plate 46 Developer container 47 Discharge port 50, 70, 80, 90 Photoreceptor drum 51, 71, 81, 111 Developer 52, 62, 72, 102 Development roll 53, 73, 83, 93 For development Opening 54,74,84,94 Developing device 55,75, 5,105 Agitation roll 55a, 75a, 85a, 105a Sleeve 55b, 75b, 85b, 105b Magnet roller 56, 76, 86 Toner hopper 57, 77, 87, 97 Toner 58, 78, 88 Toner supply roller 95 Developer recovery roll 95a Sleeve 95b Magnetic field generating member 61, 68, 91, 101 Housing 96 Toner accommodating portion 98 Toner conveying member 99 Guide member 100 Toner amount regulating member

Continued Front Page (72) Inventor Isao Ito 430 Nakai-cho, Ashigagami-gun, Kanagawa Prefecture Green Tech Nakai Fuji Xerox Co., Ltd.

Claims (13)

[Claims] 1. A developing member, which is provided in close proximity to or in contact with an image carrier on which an electrostatic latent image is formed, and whose peripheral surface is rotatably supported, and the developing member and the image carrier. And a developer bias power source for applying a development bias voltage between the two, and a two-component developer in which toner and carrier are mixed is carried on the peripheral surface of the developing member and conveyed, and the image carrier and the developing In a developing device for transferring toner to the image carrier to form a toner image in an electric field formed at a position facing a member, a developer collecting unit for collecting the developer on the developing member; A developing device having a developer supplying unit for supplying a developer to form a layer thereon. 2. The developing device according to claim 1, wherein the developer collecting unit and the developer supplying unit flow down the developer from above the developing member along a peripheral surface of the developing member. And a developing device. 3. The developing device according to claim 1, wherein the developer collecting unit and the developer supplying unit are provided close to and facing the developing member, and generate an alternating magnetic field to carry the developer on the surface. A developing device, characterized in that the developing device is an alternating magnetic field generating means for transporting. 4. The developing device according to claim 1, wherein magnetic poles of different polarities are alternately provided along a peripheral surface of the developing member, and a distance between adjacent magnetic poles is 25 μm or more. , 25
A developing device, which is magnetized so as to have a thickness of 0 μm or less. 5. The developing device according to claim 1, wherein the carrier is made of a high resistance material, and a plurality of linear or strip electrodes are adjacent to the peripheral surface of the developing member. 200μm when the distance between the centers is 25μm or more
A developing device comprising: a power supply device that is provided as follows and applies a voltage between adjacent electrodes. 6. The developing device according to claim 2, wherein the developer flow-down means causes the developer to flow down from a downstream side to an upstream side in a circulating direction of the developing member. 7. The developing device according to claim 2 or 6, wherein the developer flow-down means has a width substantially the same as the developable width of the developing member, and is a belt shape stretched around the circumference. A developing device comprising a member. 8. The developing device according to claim 2 or 6, wherein the developer flow-down means has a width substantially the same as the developable width of the developing member, and scoops up the developer to remove the developer. A developing device having an impeller that conveys upward. 9. The developing device according to claim 2, wherein the developer flow-down means has a partition member that forms a developer accommodating portion above the developing member, and the partition member has a partition member. The developing device is provided with openings for discharging the developer substantially evenly in the width direction of the developing member. 10. The developing device according to claim 3, wherein the alternating magnetic field generating means is supported by an orbiting magnetic field generating means having a plurality of magnetic poles on a peripheral surface and an outer peripheral surface of the magnetic field generating means. A developing device having a sleeve, and the developer carried on the surface of the sleeve is conveyed on the outer peripheral surface of the sleeve by the relative movement of the magnetic field generating means and the sleeve. 11. The developing device according to claim 10, wherein the developer is supplied onto the developing member that has passed the closest position between the developing member and the sleeve. 12. The developing device according to claim 11, wherein the developer carried on the surface of the sleeve is in contact with the surface of the developing member, and in a region opposite to the developing member, a direction different from a conveying direction of the developing member. A developing device that is conveyed. 13. The developing device according to claim 12, wherein a region for supplying the developer onto the developing member is provided at a position where gravity acting on the developer acts in a direction away from the developing member. apparatus.