JP2000147902A - Developing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent black spots from being put on an output image due to developing flocculated toner and to prevent an abnormal image from being formed due to irregularities in the case of forming a magnetic brush caused by clogging with the flocculated toner between a layer thickness regulating member and a developer carrier. SOLUTION: This developing device 30 forms a magnetic brush on a developer carrier 31 by a magnetic carrier and toner, and development bias is applied to the developer carrier 31 so as to develop the toner on a latent image carrier. In this case, a rotatable roller type developer leveling member 36 is installed on the upstream side from a layer thickness regulating member 35 which regulates the developer layer thickness on the developer carrier 31. The developing device 30 such as this is installed in the image forming device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for developing a toner on an electrostatic latent image on a latent image carrier and visualizing the electrostatic latent image in an image forming apparatus such as a copying machine or a printer, and the developing device. The present invention relates to an image forming apparatus having a toner recycling mechanism for installing the apparatus.

[0002]

2. Description of the Related Art In the developing process of an electrophotographic image forming apparatus, it is essential to properly charge toner in order to obtain a uniform image free from background stains and density unevenness. The conditions for properly charging the toner are to provide a developing unit with a stirring mechanism that can sufficiently mix the carrier and the toner with the two-component developer, and to develop a stable charging characteristic against aging and environmental changes. It is desirable to develop agents. Due to technological advances, the charging ability of the toner has been improved, and the charge amount distribution has been optimized. The developing unit also has a sufficient stirring ability, which contributes to providing an image with a high uniformity. However, the problem of abnormal image generation due to the generation of dirt or black spots on the background and the disturbance due to the formation of the magnetic brush has not been completely solved. A typical abnormal image due to the disturbance of the magnetic brush formation is a white stripe on the output image. Further, with the recent improvement in image quality of output images, an AC bias is often used as a developing bias. At this time, white discharge marks (hereinafter, referred to as white spots) are generated on a solid image. May be. This white spot is also a cause of disturbance in the formation of the magnetic brush.

On the other hand, the toner developed on the latent image carrier from the developing step and remaining on the photoreceptor after the transferring step is collected by a cleaning means such as a cleaning blade, and the collected toner is sent to the developing step again for use. An image forming apparatus having a toner recycling mechanism is used. This image forming apparatus is frequently used for the purpose of environmental consideration or efficient supply of toner. Recycled toner tends to exhibit different properties from unused toner (new toner) normally included in the developer. The reasons include deformation and crushing of the toner due to friction with the cleaning blade, and detachment of various additives adhering to the toner surface. As a result, the fluidity is reduced, and the toner is more likely to be agglomerated as compared with a standard newly supplied toner. Because the agglomerated toner has a low diffusion rate in the developing device, it takes a certain amount of time for the agglomerated toner to be uniformly dispersed on the carrier surface and agglomerated to be appropriately charged, or the agglomerated state remains. It may be involved in development in the development area. In this case, the aggregated toner causes black spots on the image.

Furthermore, clogging occurs between the developer carrier and the layer thickness regulating member, preventing the formation of a normal magnetic brush.
In particular, when an alternating electric field is applied as a developing electric field, this may cause white spots in an output image. JP-A-7-20719 can be cited as an example in which the layer thickness regulating member has a mechanism for alleviating toner aggregation. In this method, an elastic plate formed into a semi-cylindrical shape is brought into contact with a developer carrying member by a pressing member so as to reduce aggregation of the developer. Japanese Patent Application Laid-Open No. 5-12 / 1993 discloses an example in which a mechanism for alleviating toner aggregation is provided in a developer carrying member.
No. 7511, and the like. This is intended to provide a stable developer layer by subjecting the surface of the developer carrier to irregularities so that clogging due to foreign matter is less likely to occur, and the aggregated toner and the developer mass are excellent in pulverizability.

[0005]

However, the above-described developing device and image forming apparatus have the following problems. In the developing device proposed in Japanese Patent Application Laid-Open No. 7-20719, the semicylindrical plate is always in contact with the developer carrying member at a constant pressure. At the start of rotation, there is a concern that the developer may stagnate on the contact surface and cause clogging of the developer. Also, at the stage where the developer is stagnated on the contact surface, the amount of the developer in the developing area is reduced, and there is a possibility that the formation of the magnetic brush is hindered. Furthermore, as described above, the toner is fixed to the developer roll and the semi-cylindrical elastic plate when it is used for a long period of time because it is in constant contact, causing scratches on the surface of the developer carrier or generating heat due to friction. This makes it difficult to provide a normal image. In addition, shavings of the developer carrier and the semi-cylindrical elastic plate are mixed into the developer, and when an AC bias or the like is applied, an abnormal image such as a white spot occurs in the output image. There is. Further, in the developing device proposed in JP-A-5-127511, a change with time due to abrasion of the surface of the developer carrier is large,
When used for a long period of time, the transport amount of the developer changes, and the image density may gradually decrease. Furthermore, since the friction with the developer is large in the early stage of use, the impact on the layer thickness regulating member is large, and the toner sticks and the gap with the developing roll is reduced to reduce the amount of the developer on the developing roll. Occurs.

In view of the above problems, it is an object of the present invention to provide a developing apparatus and an image forming apparatus for preventing the occurrence of black spots on an output image due to the development of aggregated toner. It is. Another object of the present invention is to provide a developing device and an image forming apparatus that prevent an abnormal image from being generated due to disturbance of magnetic brush formation due to clogging of aggregated toner between a layer thickness regulating member and a developer carrying member.

[0007]

According to a first aspect of the present invention, a magnetic brush is formed by a magnetic carrier and a toner on a developer carrier, and a developing bias is applied to the developer carrier. A developing device for developing toner on the latent image carrier by applying a developing roller, a roller-shaped developer leveling member rotatable upstream of a layer thickness regulating member for regulating a developer layer thickness on the developer carrier. Is a developing device. According to a second aspect of the present invention, there is provided the developing device according to the first aspect, further comprising a mechanism capable of driving the developer leveling member by itself. The invention according to claim 3 is the developing device according to claim 1 or 2, wherein an alternating electric field is applied to the developer leveling member.

Further, according to the present invention, a magnetic brush is formed by a magnetic carrier and a toner on a developer carrier, and a developing bias is applied to the developer carrier to apply a toner to the latent image carrier. An image forming apparatus having a toner recycling mechanism for developing and recovering the toner remaining on the latent image carrier after the transfer step and returning the collected toner to the developing step; The image forming apparatus is provided with a roller-like developer leveling member rotatable upstream of a layer thickness regulating member for regulating the thickness. Claim 5
The present invention provides an image forming apparatus having a mechanism capable of driving the developer leveling member alone. The invention according to claim 6 is the image forming apparatus according to claim 4 or 5, wherein an alternating electric field is applied to the developer leveling member.

Here, the image forming apparatus may be a so-called digital type or an analog type latent image forming means as long as it is an electrophotographic type. Further, the image forming apparatus includes devices such as a copying machine that creates a copy of a document, a printer that creates an image in which a record in an information recording medium is visualized, and a facsimile that creates an image in which transmitted information is visualized. .

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic sectional view of a developing device showing an embodiment of the developing device according to the present invention.
As shown in FIG. 1, the first rotary stirring screw 32,
The second rotation stirring screw 33, the developer carrier 31, and the photosensitive drum 14 are arranged in parallel to the developing device 30, and have a mechanism that can rotate independently. The rotation direction is the direction of the arrow shown in the figure.
Further, a developer leveling member 36 is provided upstream of the layer thickness regulating member 35. The developer carrier 31 has a magnetic pole fixed inside and a cylindrical non-magnetic developer carrier 31 around the magnetic pole.
Is configured to rotate. As shown in FIG. 3, the developer leveling member 36 may be supported by an elastic member such as a spring, and may be set so that the distance from the developer carrier 31 changes according to the stress applied to the member. Further, even if the developer carrier 31 and the developer leveling member 36 are in contact with each other,
There may be a minute space (5 mm or less). These settings are based on the angle and strength of the pumped magnetic pole of the developer carrier 31.
An appropriate value is set according to the linear speed of rotation, the gap between the developer carrier 31 and the layer thickness regulating member 35, the flow rate of the developer A, and the like.

Here, as the developer leveling member 36,
A rotatable roller is used, and the material of this roller may be a resin material or a metal material. Specifically, as the resin material, ethylene-based resin, vinyl-based resin, ethylene-based resin,
A resin such as a rosin-modified resin, an acrylic resin, a polyamide resin, an epoxy resin, or a polyester resin, or a copolymer resin or a mixed resin thereof such as a styrene-acrylic resin or an acrylic-epoxy resin is preferable. ABS resin, modified PPE resin, PC resin, PETP
Resin, PF resin, POM resin, PBT resin, PA resin,
A resin material such as a PAI resin may be used. As a metal material,
A non-magnetic metal which is easy to form with high linearity and flatness is preferable, and copper, copper-zinc, copper-cadmium, phosphor bronze, copper-
Metals and alloys such as beryllium, aluminum, aluminum alloys, magnesium alloys, titanium alloys, stainless steel alloys, and mixtures thereof can be used. Particularly, among these, it is preferable to use a stainless alloy from the viewpoint of cost, flexibility and the like. Further, ceramics may be used. This is because it has high strength and is lighter than metal. When a metal material is used, the developer carrier 31 due to friction is used.
It is desirable to set the contact pressure weakly or to install it with a small gap in order to prevent the temperature rise and the generation of metal powder due to the friction with the metal. The surface state may be processed so as to have a plurality of grooves or the like in the axial direction, or may be smooth.

Next, the situation of the developer A in the developing device 30 will be described below. The two-component developer A stored in the developing device 30 is transported while being stirred by the rotary stirring screws 32 and 33. At this time, the two-component developer A
The toner particles in the inside are charged to a predetermined charge amount by friction with the carrier, and electrostatically adhere to the surface of the carrier particles. Both the sufficiently charged toner particles and carrier particles move to the developer carrier 31 side and adhere to the surface of the non-magnetic developer carrier 31 by the magnetic force in the developer carrier 31. The two-component developer A conveyed to the developer carrier 31 is attracted to the surface of the non-magnetic developer carrier 31 by the magnetic poles provided therein, and the layer thickness is controlled to be constant by the layer thickness regulating member 35. A brush-shaped developer layer (hereinafter, referred to as a magnetic brush) is formed. Thereafter, the magnetic brush formed on the developer carrier 31 is conveyed while rotating to a position facing the photosensitive drum 14 by the rotation of the carrier 31. At this time, an electric field is formed between the photoconductor drum 14 and the developer carrier 31 by the developing bias voltage applied to the developer carrier 31, whereby toner particles are separated from the carrier particle surface, and 14 is attracted to the electrostatic latent image recorded on it and used in the developing process. In particular, the developing device 30 is a two-component developing system,
Before the upper developer A is controlled to a predetermined layer thickness by the layer thickness regulating member 35, the developer A is rotated by using the rotatable leveling member 36.
By applying a fray stress (shear force), the developer A
It is possible to prevent the toner from aggregating therein, and to relax the already agglomerated toner and return the toner to the original state again. Aggregation often occurs because the resin forming the toner has a lower molecular weight and a lower melting point than the resin forming the carrier. In addition, since the surface of the carrier particles is also coated with the resin, agglomeration may occur between the toner and the carrier or between the carriers, and the developer leveling member 36 acts on any of them to reduce or prevent the aggregation.

Since the developer leveling member 36 is rotatable, aggregation of the developer A on the developer carrier 31 can be prevented, and the aggregated toner and the like can be reduced. Further, since the stress applied to the developer A by the layer thickness regulating member 35 can be reduced, it is possible to reduce adverse effects such as crushing of the carrier and the toner and dropping of the additive attached to the toner surface. Further, since the developer leveling member 36 is rotating, it is possible to prevent a temperature rise due to friction with the developer carrying member 31 and a displacement of the surface of the developer leveling member 36. Further, since an unnecessary stress is not applied to the developer A, there is no abnormal increase in the toner charge amount.

FIG. 2 shows a multiple transfer type full-color image forming apparatus incorporating the developing device according to the first aspect of the present invention. It is to be noted that components having the same function are denoted by the same reference numerals. Image input unit 2 that reads an image and converts it into a signal
And an image processing unit 3 that corrects the read image, performs processing such as conversion and editing, and converts an electric signal into a light signal, forms an electrostatic latent image, and forms an image using an electrophotographic method. And a printer unit 1 that performs Here, the image input unit 2
Can read a color image by an optical system using a halogen lamp, a mirror, and a lens and a CCD color sensor. In the image processing unit 3, C (cyan) M (magenta) Y (yellow) Bk
After generating a (black) signal and performing image processing, a control signal is sent to the printer unit 1. Printer unit 1
Is represented by B based on the color image data from the image processing unit 3.
k, C, M, and Y toners are sequentially used to form a toner image based on the image data, and these are superimposed to form a final toner image.
Create a full color image of the color. Here, the printer unit 1
The laser output device 11 converts the color image data from the image processing unit 3 into an optical signal and performs optical writing corresponding to the original image on the photosensitive drum 14 to form an electrostatic latent image. The laser output device 11 includes a laser light emitting element, a light emission drive control unit for controlling the light emission drive thereof, a polygon mirror, a motor for rotating the polygon mirror, an f / θ lens 12,
It is composed of a reflection mirror 13 and the like.

The photoreceptor drum 14 rotates as indicated by an arrow, around which a static eliminator 22, a cleaning device 40,
Charger 23, yellow developing device 30Y, magenta developing device 30M, cyan developing device 30C, black developing device 3
0Bk, an intermediate transfer belt 15, and the like. As shown in FIGS. 1 and 2, each of the developing devices 30Y, 30C, 30M, and 30Bk attaches the ears of the developer A to the surface of the photosensitive drum 14 to develop the electrostatic latent image on the photosensitive drum 14. It comprises a developer carrier 31 that rotates in contact with the developer, and first and second stirring rotation screws 32 and 33 that rotate to pump up and agitate the developer A. In the standby state, all of the four developing devices 30 are in a non-contact state with the photosensitive drum 14 and the developer A
Is in a cutting edge state, but the order of each developing operation of the developing device 30 (the order of each image formation of Bk, C, M, and Y) is B
The electrostatic latent images are developed in the order of k, C, M, and Y. However, the order of image formation for each color is not limited to this, and may be any order.

At the start of the copying operation, the photosensitive drum 14
Rotates and is uniformly charged by the charger 23. Then, the image input unit 2 starts reading for obtaining Bk image data at a predetermined timing, the image processing unit 3 obtains Bk image data from the image data from the image input unit 2, and based on the Bk image data. Laser output device 1 for writing
1 performs optical writing on the photosensitive drum 14 with laser light to form a latent image. Hereinafter, the electrostatic latent image based on the Bk image data is referred to as a Bk latent image. Similarly, the electrostatic latent images based on the C, M, and Y image data are also referred to as C latent images, M latent images, and Y latent images. In order to make this Bk latent image developable from its tip,
Before the leading end of the latent image reaches the developing position of the Bk developing device 30Bk, the developer carrier 31 starts rotating before the leading end of the Bk latent image reaches the developing position of the Bk developing device 30Bk, and the developer A And develop the Bk latent image with Bk toner. Thereafter, the developing operation of the Bk latent image area on the photosensitive drum 14 is continued. When the rear end of the Bk latent image has passed the Bk development position, the developer A on the developer carrier 31 of the Bk developing device 30Bk is immediately cut off to bring the development inoperative state. This is completed at least before the leading end of the C latent image based on the next C image data arrives. The cutting of the developer A is performed by switching the rotation direction of the developer carrier 31 to a direction opposite to that during the developing operation. At this time, the other developing devices 30Y, 30M, and 30C remain in the development inoperative state. The Bk toner image on the photoconductor drum 14 is transferred to an intermediate transfer belt 15 that is driven at the same speed as the photoconductor drum 14.
Is transferred to the surface of The transfer is performed by applying a predetermined bias voltage to the paper transfer roller 18 which is in contact with the intermediate transfer belt 15 constituting an electrode in a state where the photosensitive drum 12 and the intermediate transfer belt 15 are in contact with each other. After the transfer of the Bk toner image, the photoconductor drum 14 is subjected to static elimination and cleaning by the photoconductor cleaning device 40 including the static eliminator 22, and is uniformly charged again by the charger 23.
The intermediate transfer belt 15 transfers the toner images of Bk, C, M, and Y sequentially formed on the photosensitive drum 14 to the same surface in order, and transfers the toner images. An image is formed, and then the drum transfer image is transferred onto a transfer paper.

On the photosensitive drum 14 side, the process proceeds to the C image forming process after the Bk image forming process. In the C image forming process, the image input unit 2 reads at predetermined timing to obtain C image data. First, the image processing unit 3 obtains C image data based on the image data from the image input unit 2, and the laser output device 11 transmits the photosensitive drum 14 based on the C image data.
Is written with a laser beam L to form a C latent image. The C developing device 30C starts rotating after the rear end of the Bk latent image has passed and before the leading end of the C latent image has reached the developing position, so that the C developer carrier 31C starts rotating. The agent A is raised and the C latent image is developed with the C toner. Thereafter, the C developing device 30C continues to develop the C latent image area on the photosensitive drum 14, but when the rear end of the C latent image has passed, the C developing device is similar to the case of the Bk developing device 30Bk. The ears of the developer A on the support 31C are cut off. This is also completed before the leading end of the next M latent image arrives. The C toner image on the photosensitive drum 14 is transferred onto the surface of the intermediate transfer belt 15 driven at a constant speed with the photosensitive drum 14. After the transfer of the C toner image, the photosensitive drum 14
Then, the photosensitive member is subjected to static elimination and cleaning by the photoreceptor cleaning device 40, and is uniformly charged again by the charger 23.

On the photosensitive drum 14 side, the process proceeds to the M image forming process after the C image forming process. In the M image forming process, the image input section 2 starts reading for obtaining M image data at a predetermined timing. The image processing unit 2 obtains M image data based on the image data from the image input unit 2, and based on the M image data, the laser output device 11 for writing performs optical writing on the photosensitive drum 14 with laser light to generate an M latent image. To form The M developing device 30M moves the C
After the rear end of the latent image has passed and before the leading end of the M latent image has arrived, the M developer carrier 31M starts rotating and the developer A
And develop the M latent image with M toner. Since then
The M developing device 30M continues the development of the M latent image area on the photosensitive drum 14, but when the rear end of the M latent image passes, the M developer carrier as in the case of the C developing device 30C described above. 31
The developer A on M is cut off. This is also completed before the leading end of the next Y latent image arrives. The M toner image on the photoconductor drum 14 is transferred onto the surface of the intermediate transfer belt 15 that is driven at the same speed as the photoconductor drum 14. After the transfer of the M toner image, the photosensitive drum 14 is subjected to static elimination and cleaning by the cleaning device 40 including the static eliminator 22, and
Again, it is uniformly charged by the charger 23.

On the photosensitive drum 14 side, the M image forming step is followed by the Y image forming step. In the Y image forming step, the image input unit 2 starts reading for obtaining Y image data at a predetermined timing. The image processing unit 3 obtains Y image data from the image data from the image input unit 2, and based on the Y image data, the laser output device 11 for writing performs optical writing on the photosensitive drum 14 by laser light to form a Y latent image. To form The Y developing device 30Y moves the M
After the trailing end of the latent image has passed and before the leading end of the Y latent image has arrived, the Y developer carrier 31Y starts rotating and the developer A
And the Y latent image is developed with the Y toner. Since then
The Y developing device 30Y continues the development of the Y latent image area on the photosensitive drum 14, but when the rear end of the Y latent image passes, the Y developer carrier is similar to the case of the preceding M developing device 30M. 31
The developer A on Y is cut off. This is also completed after the rear end of the Y latent image has arrived. The Y toner image on the photosensitive drum 14 is transferred to the surface of the intermediate transfer belt 15 driven at a constant speed with the photosensitive drum 14. Paper transfer roller 18
Is normally separated from the intermediate transfer belt 15, but is transferred to the intermediate transfer belt 15 at a timing when the four-color superimposed image formed on the intermediate transfer belt 15 is collectively transferred onto the transfer paper. A predetermined bias voltage is applied to the paper transfer roller 18 from a bias power supply, and a four-color superimposed image on the intermediate transfer belt 15 is transferred to transfer paper passing between the paper and the intermediate transfer belt 15. In the paper feeding device 16, the transfer paper is fed from the transfer paper cassette to the paper feed roller 17, and the paper feed roller 45 transfers the transfer paper to the intermediate transfer belt 1.
The paper is fed in accordance with the timing when the leading end of the four-color superimposed image 5 reaches the paper transfer position.

The transfer paper onto which the four-color superimposed toner image has been transferred from the intermediate transfer belt 15 is conveyed to a fixing device 20 by a paper conveying unit, and is fixed to a fixing roller controlled at a predetermined temperature of the fixing device 20. The toner image is fused and fixed by the pressure roller and is carried out as a full-color copy. In addition, the photosensitive drum 14 after the transfer is uniformly discharged by the discharging device 22 by the cleaning device 40, and the surface is cleaned by the rubber blade 41. The surface of the intermediate transfer belt 15 after the transfer of the toner image to the transfer paper is cleaned by a cleaning device (not shown). When the developing device 30 without the developer leveling member 36 is used, an aggregate of the toner of each color is formed from the beginning of the development, and the image is developed as spots on the image. Further, the aggregated toner or the like causes toner clogging between the layer thickness regulating member 35, the developer carrier 31 and the photosensitive drum 14, and white stripes or white spots are generated on an output image. Further, the toner aggregates due to long-term use, environmental fluctuation, and the like, which adversely affects an output image. On the other hand, the developing device 31 having the developer leveling member 36 has an adverse effect on the output image by providing the developing device 31 upstream of the developing nip region and before the developer layer thickness regulating member 35 regulates the developer layer thickness. The influence of the aggregated toner on the developing process can be reduced, and a good image free from speckles, white stripes, etc. can be obtained.

(Embodiment 2) FIG. 4 is a schematic structural view showing one embodiment of the developing device according to the first aspect of the present invention.
FIG. 5 is a schematic configuration diagram showing a single-color image forming apparatus using the developing device. As shown in FIGS. 4 and 5, the first recycling auger 42 that conveys the collected recycling toner (hereinafter referred to as “recycled toner C”) in the cleaning device 40 to the recycled toner discharge section 44 and the cleaning unit Second recycling auger 4 for transporting recycled toner from device 40 to developing device 30
3 is provided. The recycling mechanism transfers the developed toner as described above and discharges the toner together with the transfer paper, but collects the untransferred toner in the cleaning device 40. Cleaning device 4
The untransferred toner, that is, the collected toner scraped off from the surface of the photoconductor via the cleaning blade 41
Cleaning device 4 by rotation of first recycling auger
It is moved to the side to be aggregated at one end of 0. The recycled toner C is transported into the developing device 30 by the second recycling auger 43 of the toner recycling mechanism. The second recycling auger 43 is connected to the photosensitive member 1 via the main motor.
The rotation of the second recycling auger 43 causes the amount of recycled toner returned from the cleaning device 40 into the developing device 30 to increase in proportion to the number of copies because the second recycling auger 43 rotates continuously. . The recycled toner C may be returned to the inside of the developing device 30 or may be returned to the toner storage device 37 for supplying the toner. It may be returned inside.

FIG. 6 shows a situation where the recycled toner is being conveyed in the developing device. Toner storage device 37
The toner supplied into the developing device 30 from the inside is stirred and mixed with the carrier by the first stirring screw 32 rotating in the direction of the arrow and the second stirring screw 33 rotating so as to overlap with each other in the opposite direction. And the developer A is sent to the developer carrier 31 as a developer A by toner. Similarly, the recycled toner C is also conveyed to the front side of the second stirring screw 33 machine. Here, it is mixed with the replenished unused new toner. The first stirring screw 31 and the second stirring screw 32 are screw-shaped members that rotate in opposite directions to each other.
The carrier and the toner conveyed to the back side of the machine by the thrust of 2 sequentially move over the partition plate 34 arranged in the developing device 30 and move to the first stirring screw 32 side, and are conveyed to the inside of the machine by the thrust. In the meantime, the carrier and the toner are mixed, and as a result, the toner is frictionally charged to a predetermined charge amount, the toner is uniformly adsorbed on the carrier, and then the magnetic force of the magnetic pole in the developer carrier 31 and the magnetic force of the carrier are changed. Thereby, the developer A adheres to the surface of the developer carrier 31 in a layered manner.

Here, by the developer leveling member 36,
It is possible to prevent and reduce the aggregation of the toner whose fluidity is reduced and which is easily aggregated. This prevents the agglomerated toner from lowering in mixing speed with the carrier in the developing device 30 and uniformly disperses it on the carrier surface, so that the developer A having an appropriate charge amount and charge amount distribution can be used.
Can be formed. Thereby, fogging of a white background can be prevented. Further, by preventing agglomeration of toner and the like, clogging is prevented between the developer carrier 31 and the layer thickness regulating member 35 and the like, and a normal magnetic brush is formed. In particular, an alternating electric field is applied as a developing electric field. In this case, it is possible to prevent white spots in the output image.

(Embodiment 3) The developing device described in Embodiment 3 is basically the same as Embodiments 1 and 2. It is characterized in that the developer leveling member 36 has a mechanism that can be driven alone. The developer leveling member 36 is composed of a rotating shaft portion rotatably supported by bearing members provided on both side walls of the developing device 30, and is further connected to a gear on a rotating shaft portion protruding outside the developing device 30. Driven by a rotating motor. The direction of rotation, the number of rotations and the timing of rotation can be adjusted by controlling the motor. The developer leveling member 36 has a linear speed ratio of 0.9 to 1.5 with respect to the developer carrier 31 in the developer A feed direction and a linear speed of the developer carrier 31, more preferably, 1.0-1.
When the rotation is performed at 2, the stress applied to the developer A at the leveled portion is greatly reduced. In addition, since the rotation can reduce the aggregation of the toner and the like, the magnetic brush formation in the developing region does not disturb. By providing the function as in the present embodiment, even when the fluidity of the developer A, the linear velocity of the developer carrier 31, or the distance between the photosensitive drum 14 and the developer carrier 31 is changed. , The rotation speed of the leveling member 36 can be set. Thereby, aggregation of the developer A can be prevented and reduced, and the output image can be optimized.

(Embodiment 4) The developing device described in Embodiment 4 is basically the same as that described in Embodiments 1, 2, and 3. As shown in FIG. 7, an alternating electric field is applied to the developer leveling member 36. In order to apply an alternating electric field, it is constituted by an AC power supply 24, a DC power supply 25, a resistor for controlling current, a reed switch, and a circuit for controlling these. By providing such a power supply, in addition to shear stress of the developer leveling member 36, it is possible to apply vibration to the passing developer A and the aggregated toner contained therein, and to prevent aggregation. Can be. The DC power supply 25 generates a high-voltage AC voltage from a power supply in the control unit by a DC / DC converter, converts the DC voltage to DC by a rectifier, generates a DC voltage, and connects the DC voltage to the AC power supply 24. The AC power supply 25 is a DC / A
A high AC voltage is generated by a C converter. This makes it possible to generate a voltage in which an AC voltage and / or a DC voltage are superimposed. The alternating electric field has a DC voltage of -400 to
In the range of +400 V, the polarity is preferably opposite to that of the toner. For a negatively charged toner, a positive polarity direct current is preferable. This is to increase the vibration of the toner. AC voltage-
The voltage is preferably 1000 to +1000 V, and the frequency is preferably 1 to 20 KHz. The AC component has a symmetrical waveform, an asymmetrical waveform,
An intermittent waveform may be used. The voltage preferably vibrates only the toner and suppresses the vibration of the carrier, and the frequency is preferably such that the toner can sufficiently follow the vibration of the electric field. These can be appropriately set according to the characteristics of the developer A.

By vibrating the developer A in this manner, the efficiency of the developer leveling member 36 in relaxing the aggregated toner is improved. Further, since the developer A is activated by the alternating electric field when passing through the developer leveling member 36, the toner easily flies when moving to the development area, and a clear image with high uniformity can be obtained.

[0027]

As described above, in the developing device according to the first aspect, the shearing force (shearing force) is applied to the developer to prevent the toner from aggregating in the developer and to prevent the toner from being agglomerated. And the toner can be returned to the original state again. Further, since the stress exerted on the developer itself by the layer thickness regulating member can also be reduced, it is possible to reduce adverse effects such as crushing of the carrier and the toner and dropping of the additive attached to the toner surface. Further, a developer having an appropriate charge amount distribution without abnormality of the toner charge amount can be obtained because no unnecessary stress is applied to the developer. As a result, it is possible to obtain an appropriate image without fogging on a white background and without white stripes or black spots. In the developing device according to the second aspect, by having a mechanism that can be driven alone,
It is possible to greatly reduce the stress of the developer,
Further, an appropriate output image can be obtained. Claim 3
In the developing device described in (1), it is possible to vibrate between the developer leveling member and the developer carrying member, to prevent and ease the aggregation of the toner, and to facilitate the flying in the developing area. And a clear image can be obtained.

Further, the image forming apparatus according to the fourth aspect is an image forming apparatus having a recycling mechanism in which toner aggregation and the like are particularly likely to occur, wherein the speed of mixing the recycled toner with the carrier in the developing device is set. And a developer having an appropriate charge amount and charge amount distribution can be formed by uniformly dispersing the developer on the carrier surface. Thereby, fogging of a white background can be prevented, and generation of white spots and white stripes can be prevented. According to the image forming apparatus of the fifth aspect, it is possible to reduce the stress of the layer thickness regulating member of the recycled toner and the like, and obtain an appropriate image. In the image forming apparatus according to claim 6, prevention of toner aggregation,
Relaxation can be promoted, and flying in the developing region can be facilitated, so that a clear image can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of a developing device of the present invention.

FIG. 2 is a schematic sectional view showing a multi-transfer type full-color image forming apparatus incorporating the developing device of the present invention.

FIG. 3 is a schematic sectional view showing a structure of a developer leveling member in the developing device of the present invention.

FIG. 4 is a schematic sectional view showing an embodiment of the developing device of the present invention.

FIG. 5 is a schematic configuration diagram illustrating an image forming apparatus having a recycling mechanism of the present invention.

FIG. 6 is a schematic plan view showing the structure of the developing device of the present invention.

FIG. 7 shows a developing device in which a power source is provided to a developer leveling member in the developing device of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Printer part 2 Image input part (scanner part) 3 Image processing part 11 Laser output device 12 Lens 13 Mirror 14 Photoconductor drum 15 Intermediate transfer belt 16 Paper feeder 17 Paper feed roller 18 Paper transfer roller 18'Transfer device 19 Belt transfer Roller 20 Fixing device 21 Discharge unit 22 Charge remover 23 Charger 24 AC power supply 25 DC power supply 30 Developing device 30Y Yellow developing device 30M Magenta developing device 30C Cyan developing device 31 Developer carrier 31Y Yellow developer carrier 31M Magenta developer Carrier 31C Cyan developer carrier 32 First stirring rotation screw 33 Second stirring rotation screw 34 Partition plate 35 Layer thickness regulating member 36 Developer leveling member 36a Developer leveling member support 36b Spring member 37 Toner storage device 38 Toner supply roller 40 clear Cleaning device 41 Cleaning blade 42 First recycled auger 43 Second recycled auger 44 Recycled toner discharge section A Developer B Collected toner C Recycled toner L Laser beam

Claims (6)

[Claims] 1. A developing device for forming a magnetic brush on a developer carrier with a magnetic carrier and toner and applying a developing bias to the developer carrier to develop the toner on the latent image carrier. A developing device comprising a roller-shaped developer leveling member rotatable upstream of a layer thickness regulating member that regulates a developer layer thickness on a carrier. 2. The developing device according to claim 1, further comprising a mechanism capable of driving the developer leveling member by itself. 3. The developing device according to claim 1, wherein an alternating electric field is applied to the developer leveling member. 4. A method of forming a magnetic brush on a developer carrier by using a magnetic carrier and toner, applying a developing bias to the developer carrier to develop the toner on the latent image carrier, and, after the transfer process, completing the latent image forming process. In an image forming apparatus having a toner recycling mechanism for collecting toner remaining on an image carrier and returning the collected toner to a developing step, a layer thickness regulating member for regulating a developer layer thickness on the developer carrier is provided. An image forming apparatus comprising: a rotatable roller-like developer leveling member installed on an upstream side. 5. The image forming apparatus according to claim 4, further comprising a mechanism capable of driving the developer leveling member by itself. 6. An image forming apparatus according to claim 4, wherein an alternating electric field is applied to said developer leveling member.