JPH0713435A - Developing device - Google Patents

Abstract

PURPOSE:To eliminate the unevenness of an image by forcibly peeling and stirring residual developer on a developing sleeve and forcedly mixing it with the developer in a developer container. CONSTITUTION:A magnet 55 is arranged inside the rotatable developing sleeve 52. Carrying magnetic poles N2 and N3 having the same polarity, among the magnetic poles of the magnet 55, are adjacently arranged on the developer container 51 side. Since repulsive magnetic field is formed between the magnetic poles N2 and N3, the developer D consisting of hard ferromagnetic particles and toner is apt to retain near the magnetic pole N2 on an upstream side. A developer peeling means 57 is arranged to be opposed to the magnetic pole N2. The peeling means 57 is provided with a rotary shaft 57a and a blade member 57b and rotated in the direction shown by an arrow so as to peel and stir the developer D.

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 by attaching toner to an electrostatic latent image formed on an image bearing member by an electrophotographic method, an electrostatic recording method or the like with a magnetic brush.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying apparatus, an electrostatic recording apparatus and a magnetic recording apparatus, a developing apparatus for developing an electrostatic latent image formed on an image carrier such as a photosensitive drum. As one of them, a magnetic brush type developing device is widely used.

This developing device has, for example, a non-magnetic cylinder (hereinafter referred to as "developing sleeve") as a developer carrier rotatably attached to a developing container, and a magnet fixed in the developing sleeve. Then, the developer is conveyed by the rotation of the developing sleeve. This magnet has a plurality of magnetic poles along the rotation direction of the developing sleeve. One is a developing magnetic pole arranged at a developing position facing the surface of the image carrier on which the electrostatic latent image is formed, and the other is a plurality of carrier magnetic fields for carrying the developer through the developing sleeve. Is. A magnetic brush (brush) is formed on the surface of the developing sleeve with a magnet, and the surface of the image bearing member is rubbed with this magnetic brush to adhere toner to the electrostatic latent image on the surface of the image bearing member for development. . In this type of developing method, a developer that contributes to the development can be sufficiently supplied to the developing area, so that a high image density can be obtained, but at the developing position, the ears of the magnetic brush are sparse. In particular, there was a case where a halftone image was rough and poor.

In recent years, digitalization of copying machines and printers has been progressing along with full colorization and systemization.

Further, there is an increasing demand for high quality images, especially for full color images. 2. Description of the Related Art Recently, a copying machine and a printer that have achieved high definition and high gradation by digitizing using a laser beam have been provided. In this method, halftone formation is performed by pulse width modulation (PWM) of a laser beam with an image signal. According to this method, an image with high resolution and high gradation can be formed.

The above-mentioned digitization has become indispensable for improving the image quality of a full-color image, but the minute latent image formed on the image carrier is not sufficiently reproduced at the time of development, and is particularly high. There were many times when the light part got rusty.

As a countermeasure against this, for example, by using a hard and strong carrier as a magnetic carrier of the two-component developer, the ears of the developer are made dense to improve the reproducibility of minute dots, and a smooth highlight portion free of rattling is formed. Obtainable.

Among them, as described above, the developing device for fixing the magnet for forming the magnetic brush and rotating the developing sleeve, that is, the so-called magnet fixing / sleeve rotating type developing device has a simple device configuration. Although it has the advantage of being able to do so, in order to use a hard ferromagnetic material as the developer, it is necessary to devise a means for sufficiently replacing the developer on the developing sleeve.

[0009]

However, the above-mentioned magnet fixing / sleeve rotating type developing device has the following problems in practical use.

That is, the difference in image history causes a difference in image density. In particular, density unevenness is likely to occur in the halftone portion, and in extreme cases, characters are thickened or thinned. Here, the image history means a process of forming an image and a non-image on the electrostatic latent image bearing surface of the image bearing member, and in the image portion, the toner on the developing sleeve is consumed at the developing position. In the image area, the toner is not consumed and remains on the developing sleeve as it is.

Therefore, the residual developer on the developing sleeve after development causes unevenness in toner density due to the difference in image history. When the stirring and replacement of the remaining developer on the developing sleeve is insufficient, the image density becomes uneven according to the toner density unevenness during the next development.

The above-mentioned phenomenon is a problem commonly occurring not only when a hard ferromagnetic material is used as a developer but also when a soft magnetic material is used.

However, when a soft magnetic material is used, as shown in FIG.
As shown in the first developing device (developing device) 50M, conventionally, in the developing sleeve 52, the adjacent carrier magnetic poles N ₂ and N of the same polarity are provided.
It has already been done to peel off the developer D by disposing ₃ and the repulsive magnetic field, but when applied to the hard ferromagnetic material,
Due to the strong cohesive force between the developers, the residual developer D on the developing sleeve 52 may be insufficiently stripped, replaced, or agitated, and the final image may be uneven due to the difference in image history. It was

Therefore, in the present invention, the developer stripping means forcibly removes and agitates the residual developer remaining on the developer carrying member (developing sleeve) to eliminate the unevenness of the image based on the image history. It is an object of the present invention to provide a developing device having the above structure.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and accommodates a two-component developer containing a mixture of a hard ferromagnetic material and a toner and has an opening facing the image carrier. A developing container having a portion, a cylindrical developer carrier rotatably disposed in the opening, a plurality of developer carriers disposed inside the developer carrier along the rotation direction of the developer carrier. A magnetic field generating means having a magnetic pole, the developer in the developing container is carried on the surface of the developer carrier as a magnetic brush, and is conveyed to a developing position facing the image carrier, and at the developing position. In a developing device in which toner is attached to an electrostatic latent image on the image carrier, magnetic poles of the same polarity are arranged adjacent to each other on the developing container side among a plurality of magnetic poles of the magnetic field generating means, The developer carrier in the vicinity of these adjacent magnetic poles And a developer peeling means for removing the residual developer carried on the surface of the developer carrier and collected in the developing container via the developing position, at a position facing the surface. To do.

In this case, the developer removing means can be formed of a magnetic member or a non-magnetic member having a magnetic field generating means of at least one pole inside.

Further, it is preferable that the developer peeling means moves in a forward direction or a counter direction with respect to the moving direction of the surface of the developer carrying member.

Further, the developer stripping means is disposed at a position facing the surface of the developer carrier in the vicinity of the upstream magnetic pole of the adjacent magnetic poles of the same polarity on the developing container side. Good.

In addition, it is preferable that the developer removing means has a cleaning means or has an opening communicating with the rotation direction.

The developer removing means may also serve as a developer stirring means or a developer supplying means.

Further, the length of the developer removing means in the longitudinal direction is the same as the length of the developer carrying member in the longitudinal direction, or
Alternatively, it is preferable to set it longer than that.

[0022]

Based on the above construction, the magnetic field generating means has adjacent magnetic poles of the same polarity on the side of the developing container, and a repulsive magnetic field is formed between them, so that they are carried on the surface of the developer carrier. The residual developer, which is about to move from the upstream magnetic pole to the downstream magnetic pole, is blocked by the repulsive magnetic field and stays near these magnetic poles. The staying developer is forcibly removed by the developer removing means and stirred. This allows the residual developer to be mixed well with the new developer.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> FIG. 1 schematically shows a typical electrophotographic color printer. This printer is an electrophotographic photosensitive drum (hereinafter simply referred to as "photosensitive drum") as an image carrier that rotates in the direction of the arrow (counterclockwise in the figure).
1 around the photosensitive drum 1, a rotary developing device 3 including a charging device 2, developing devices 3M, 3C, 3Y, 3BK, a transfer charging device 5, a cleaning device 6, and a photosensitive drum 1 above the photosensitive drum 1. An exposure unit 7 including a laser beam scanner and the like is provided.

The sequence of the entire color printer will be briefly described by taking the case of the full color mode as an example. First, the photosensitive drum 1 is uniformly charged by the charger 2. Next, an image of a document (not shown) is exposed with a laser beam E modulated by a magenta image signal, an electrostatic latent image is formed on the photosensitive drum 1, and then, a magenta image previously fixed at the developing position. Development is performed by the developing device 3M.

On the other hand, the transfer material P contained in the paper feed cassette 9 is fed by the paper feed roller 10, is conveyed through the paper feed guide 11, the paper feed roller 12, and the paper feed guide 13 and is predetermined. It is held by the gripper 15 in synchronism with the timing, and electrostatically wound around the transfer drum 17 by the contact roller 16 and its opposite pole. Transfer drum 17
Is rotated in the direction of the arrow (clockwise in the figure) in synchronization with the photosensitive drum 1, and the visible image (toner image) developed by the magenta developing device 3M is transferred by the transfer charger 5 at the transfer portion. It is transferred to the material P. The transfer drum 17 continues to rotate and prepares for the transfer of the next color (cyan in the figure).

On the other hand, the photosensitive drum 1 is decharged by the charging device 19, cleaned by the cleaning device 6, charged again by the charging device 2, and exposed as described above by the next cyan image signal. During this time, the developing device 3 rotates to set the cyan developing device 3C at a predetermined developing position and perform predetermined cyan development.

Subsequently, the series of image forming processes as described above are performed for yellow and black, respectively, and when the transfer of the four color toner images onto the transfer material P on the transfer drum 17 is completed, the transfer material P becomes Separating charger 20,
The charge is removed by 21 and the gripper 15 is released and separated from the transfer drum 17 by the separation claw 22. The transfer material P is further sent to a fixing device (heat pressure roller fixing device) 25 by a conveyor belt 23, and after the toner image is melted and fixed there, a discharge roller 26 discharges a sheet of paper 27.
Discharged on top. As a result, a series of full-color print sequences is completed, and a desired full-color print image is formed.

The above-mentioned laser beam scanner constituting the exposure means 7 has a semiconductor laser portion 7a, a collimator lens system 7b, a focus adjusting means 7c, a polygon mirror 7d and an f-θ lens group 7e as shown in FIG. , Reflector 7f,
The semiconductor laser unit 7a has a CCD 7g and the like, and the semiconductor laser unit 7a receives a time-series digital pixel signal that is arithmetically output by an electronic calculator or the like of the image reading apparatus, and outputs a laser beam PWM-modulated in accordance with the signal. It oscillates and exposes the surface of the photosensitive drum 1.

More specifically, the semiconductor laser section (solid-state laser element) 7a which is a light source section is connected to a laser driver 7h which is a light emission signal generator for sending a light emission signal for generating a laser beam, and the laser driver It blinks in response to the light emission signal of 7h. The laser light flux emitted from the fixed laser element 7a is made into substantially parallel light by the collimator lens system 7b. The collimator lens system 7b can be moved by a predetermined amount in the arrow A direction which is the optical axis direction of the laser light by the focus adjusting means 7c.

Polygon mirror, that is, rotating polygon mirror 7d
By rotating at a constant speed in the direction of arrow B,
The parallel light emitted from the collimator lens system 7b is reflected and scanned in a predetermined direction indicated by an arrow C. An f-θ lens group 7e (7e ₁ , 7e ₂ , 7) provided in front of the rotating polygon mirror 7d
e ₃ ) forms an image of the laser light flux L deflected by the rotary polygon mirror 7d on a surface to be scanned, that is, a predetermined position on the photosensitive drum 1, and makes the scanning speed constant on the surface to be scanned.

The laser light flux L is guided through a reflecting mirror 7f onto a CCD (solid-state image pickup device) 7g as a detecting means and scanned on the photosensitive drum 1 as a surface to be scanned. CC
D7g is a photosensitive drum 1 with a plurality of photodetectors in the direction of arrow C.
The surface and the light source unit are arranged in positions that are substantially optically equivalent.

The CCD 7g is connected to a control unit 7i which controls the laser driver 7h and the focus adjusting means 7c. Further, the image processing unit 7j causes the laser driver 7h
And the controller 7i.

In the above structure, when a desired image is formed, first, the image processing unit 7j inputs the image output signal p ₁ to the control unit 7i and the image signal p ₂ to the laser driver 7h to set a predetermined image. The solid-state laser element 7a is blinked at the timing.

The laser light emitted from the solid-state laser element 7a is converted into almost parallel light by the collimator lens system 7b, further scanned by the rotary polygon mirror 7d rotating in the direction of arrow B in the direction of arrow C, and f-.theta. Lens group 7e
As a result, an image is formed in a spot shape on the photosensitive drum 1. The photosensitive drum 1 is scanned by the laser beam L thus scanned.
An exposure distribution for one scan of the image is formed on the surface, and the photosensitive drum 1 is rotated by a predetermined amount for each scan, and an electrostatic latent image having an exposure distribution according to the image signal p ₂ is formed on the photosensitive drum 1. It is formed. The electrostatic latent image is then transferred to the transfer material P by a well-known electrophotographic process to which toner is attached to form a visible image (toner image).

[0035] The image output signal p ₁ is output from the image processing unit 7j prior to the image signal p _2, the output of the image signal p ₂ is completed after completion. The control unit 7i stops operating while the image output signal p ₁ is input from the image processing unit 7j. Therefore, the pixel size and the contrast can be kept constant during the image forming operation.

Next, the operation of the focus adjusting means 7c for the laser beam L will be described.

First, the operation signal p ₃ is inputted from the control section 7i to the laser driver 7h, and the laser driver 7h
Square wave that turns on and off at regular intervals (see Figure 3 (a))
For a predetermined period, the solid-state laser element 7a blinks in response to this signal. The laser light from the solid-state laser element 7a is scanned as described above, reflected by the reflection mirror 7f, and projected and scanned on the CCD 7g arranged at a position optically equivalent to the photosensitive drum 1.

The control section 7i resets the accumulated charge of each pixel of the CCD 7g before the laser beam L scans the CCD 7g, and after the charge is accumulated in each pixel of the CCD 7g by the spot scanning of one line, this charge is stored. Read as an electric signal.

When the solid-state laser element 7a blinks the laser light and scans it once, the CCD 7g is in a position optically equivalent to the photosensitive drum 1. Therefore, the exposure distribution on the surface of the CCD 7g is
As shown in FIG. 4, the distribution shape of the intensity according to the spot diameter of the laser light flux L is shown. Therefore, the output of each pixel of the CCD 7g has a distribution as shown in FIG. 3B, and the signal is sent to the control unit 7i. In the control unit 7i, C
The maximum value of the output of CD7g is θmax, and the minimum value is θmin.
Then, the contrast V is calculated and measured by the formula of V = (θmax−θmin) / (θmax + θmin) (1).

In this case, since the contrast V increases as the spot diameter in the scanning direction decreases, the preset value V ₀ is compared with V calculated by the equation (1), and V is the predetermined value V ₀ . If they are not equal, a drive signal is sent from the controller 7i to the focus adjusting means 7c to move the collimator lens system 7b in the direction of arrow A by a predetermined amount. Then, the above-mentioned contrast V is measured at the position where the collimator lens system 7b is moved, and if the collimator lens system 7b is fixed at a position where this value is equal to V ₀ , the defocus of the optical system is corrected. The scanning spot diameter of the laser light flux L can be minimized.

FIG. 5 is a circuit diagram of the PWM circuit, and FIG. 6 is a PWM circuit.
6 is a timing chart showing the operation of the circuit.

In FIG. 5, the PWM circuit generates a TTL latch circuit 31 for latching an 8-bit image signal, a level converter 32 for converting a TTL logic level into a high-speed ECL logic level, an ECLD / A converter 33, and a PWM signal. ECL comparator 34, which sets the ECL logic level to T
A level converter 35 for converting to a TL logic level, a clock oscillator 36 for generating a clock signal 2f having a double frequency of the pixel clock signal f, and a triangular wave generator 37 for generating a substantially ideal triangular wave signal in synchronization with the clock signal 2f. , And a 1/2 divider 38 for dividing the clock signal 2f by 1/2. In addition, in order to operate the circuit at high speed, E
CL logic circuit is arranged.

The operation of this configuration will be described with reference to FIGS.

The signal S1 shows the clock signal 2f, and the signal S2 shows the pixel clock signal f having a double period thereof, which is associated with the pixel number as shown in the figure. Triangular wave generator 37
Even internally, in order to keep the duty ratio of the triangular wave signal at 50%, the triangular wave signal S3 is generated after the clock signal 2f is once divided by 1/2. Further, the triangular wave signal S3 is converted to the ECL level (0 to -1V) and becomes the triangular wave signal S4.

On the other hand, the pixel signal is 00H (white) to FFH.
It changes in 256 gradation levels up to (black). The symbol H is hexadecimal. The image signal S5 indicates an ECL voltage level obtained by D / A converting some image signal values. For example, the first pixel is a black pixel level FF
H, the second pixel shows a voltage of a halftone level of 80H, the third pixel shows a voltage of a halftone level of 40H, and the fourth pixel shows a voltage of a halftone level of 20H. The comparator 34 outputs the triangular wave signal S4
And by comparing the image signal S5, the pulse width T according to the pixel density to be formed, to generate a PWM signal as _{t 2, t 3, t 4} . Then, this PWM signal is converted to a TTL level of 0V or 5V, and the PWM signal S6
And is input to the circuit of the laser drive 7h.

In the circuit of FIG. 5, the latch circuit 31
A lookup table (not shown) is provided in the front stage of the. This look-up table is for performing γ correction of image data, and is a memory in which the data of the γ correction result is stored, and the memory is accessed by using an image signal of 1 pixel 8 bits as address data, and a desired γ correction is performed. The image signal of the corrected data is output. Normally, one specific γ correction table is used in one screen, but a plurality of types of γ correction tables can be switched and used in one screen as needed. That is, for example, three types of tables are sequentially and repeatedly used for each line scanning by the laser beam,
The configuration is such that the γ correction in the sub-scanning direction can be changed for each line to perform gradation correction.

The look-up table is a so-called "standing γ table" when the toner density is low so that it is not affected by the density unique to each color, for example, four colors of yellow, magenta, cyan, and black. Is set, and when the density is high, a γ table having the opposite characteristic is set and provided for each forming color. A non-linear color masking circuit, for example, in order to correct the turbidity of the color of each color toner is provided in the preceding stage of the lookup table.
A secondary color masking circuit can be provided.

The above-mentioned PWM method is characterized in that dot area gradation is performed for each pixel and halftone can be expressed at the same time without lowering the pixel density to be recorded.

In this embodiment, the spot diameter of the laser beam on the surface of the photosensitive drum 1 (Gaussian distribution spot 1 / e
² ) main scanning direction 1 / e ² is 42 μm, sub-scanning direction 1 / e ²
and the e ² to 70μm, to the text document and a photograph document,
Recording density 400 lines / inch (pixel size 63.5μ
m) and 200 lines / inch (pixel size 127 μm), and the light emission time is controlled by the above-mentioned PWM control.

The results obtained by simulating the latent image width in the main scanning direction when the pixel signal is changed from 10H to FFH (black) when the recording density is 200 lines / inch are shown above. , FIG. The latent image width is slightly deviated from the straight line with respect to the pixel signal in the portion where the latent image width is about 42 μm or less of the spot diameter of the laser beam, but linearly changes in the portion where the spot diameter is about 42 μm or more.

The evaluations of "halftone image roughness" and "highlight portion reproducibility" in this example were carried out under the condition that the latent image width by the simulation shown in FIG. 7 was about 30 μm.

The present invention will be further described below with reference to examples. In addition, the developing device (developing device) shown in the following drawings
Is the developing device shown in FIG. 1 (for example, magenta developing device 3M).
FIG. 2 is an enlarged view of FIG. 1 viewed from the back side.

FIG. 8 is an enlarged cross-sectional view of the vicinity of one developing device (for example, magenta developing device 3M) of the rotary developing device 3 used in the laser beam printer shown in FIG.
The developing device 3M is arranged at a developing position facing the photosensitive drum 1. Hereinafter, the developing devices 3M, 3C, 3Y and 3BK will be collectively referred to as the developing device 50.

The developing device 50 develops a latent image formed on the image carrier (photosensitive drum) 1 such as a photoconductor or a dielectric by electrophotography, electrostatic recording or the like. Includes a developing container 51, a developing sleeve (developer carrying body) 52 as a developer carrying body, a blade 53 as a developer layer regulating member, and the like. That is, the developing container 5
An opening 51A is formed at a position close to the photosensitive drum 1 of No. 1, and the developing sleeve 52 is rotatably disposed in the opening 51A.
The above-mentioned blade 53 is attached above the above with a predetermined gap.

The developing sleeve 52 is formed of a non-magnetic material into a cylindrical shape and rotates in the direction of the arrow (counterclockwise) in the drawing during the developing operation.
The surface of the developing sleeve 52 rotates in the forward direction. Inside the developing sleeve 52, a magnet (magnetic field generating means) 55 as a magnetic field generating means is fixed. The magnet 55 has a large number of magnetic poles along the circumferential direction, and these magnetic poles are the developing magnetic pole N ₁
And carrier magnetic poles N ₂ , N ₃ , S ₁ and S ₂ .
The former developing magnetic pole N ₁ includes the photosensitive drum 1 and the developing sleeve 5.
A magnetic field is generated in the vicinity of the developing position where 2 is opposed to the magnetic field, and the magnetic brush MB of the developer D on the surface of the developing sleeve 52.
To form the developer D on the developing sleeve 52.
Is attached to the electrostatic latent image on the photosensitive drum 1 and developed. On the other hand, the latter carrier magnetic poles N ₂ , N ₃ , S ₁ , S ₂
Is to convey the developer D as the developing sleeve 52 rotates. The above-described developing sleeve 52 and magnet 55 constitute a developing roller 56.

The blade 53 is made of a non-magnetic material such as aluminum (Al) or SUS316,
As described above, this is attached with a predetermined gap provided between it and the surface of the developing sleeve 52. The gap regulates the amount of the developer D conveyed on the developing sleeve 52 to the developing portion (developing position), specifically, the layer thickness of the developer D on the developing sleeve 52. Therefore, in this embodiment, the non-magnetic toner and the hard ferromagnetic particles (carriers) are provided between the tip of the blade 53 and the surface of the developing sleeve 52.
The developer D having both of the above is passed and sent to the developing section.
The developer D regulated by the blade 53 has a thickness such that it contacts the surface of the photosensitive drum 1 at the developing position.
The developer D is a two-component developer D composed of a non-magnetic toner and hard ferromagnetic particles (carrier), which will be described later. The developer D is transported to the developing section to develop the electrostatic latent image on the photosensitive drum 1, and the developer D is not held for development but is held by the developing sleeve 52 as it is and is transported to the transport magnetic pole N ₂ ( Residual developer).

Of the plurality of carrier magnetic poles N ₂ , N ₃ , S ₁ and S ₂ , the carrier magnetic poles N ₂ and N ₃ are adjacent to each other and arranged on the side of the developing container 51. These carrier magnetic poles N ₂ , N ₃
Have the same polarity, and a repulsive magnetic field is formed between them. Therefore, the residual developer D carried to the carrying magnetic pole N ₂ while being held by the developing sleeve 52 is prevented from being carried in the carrying magnetic pole N ₃ direction by the action of this repulsive magnetic field, and is near the carrying magnetic pole N ₂ . Accumulated.

A developer peeling means 57, which will be described later, is rotatably disposed near the carrying magnetic pole N _2, and is arranged in the direction of the arrow (counterclockwise) in the drawing, and thus in the counter direction with respect to the developing sleeve 52. Is rotating.

The residual developer D accumulated in the vicinity of the above-mentioned transport magnetic pole N ₂ and having undergone the development history is peeled and removed by the developer peeling means 57, drops to the stirring member 59, and is sufficiently stirred and mixed. , New developer D is the developer supply means 6
0, it is supplied to the vicinity of the carrier magnetic pole N ₃ on the developing sleeve 52. The developer supply unit 60 includes two rollers 60a that rotate in the direction of the arrow and a conveyor belt 60b that is stretched around the rollers, and a large number of protrusions 60c on the conveyor belt 60b cause the vicinity of the stirring member 59. The developer D is scratched and transported to the vicinity of the transport magnetic pole N ₃ . As a result, since the developer D having a uniform toner concentration and having no difference in image history is stably supplied, a stable and good image can be obtained.

As shown in the cross section of FIG. 8, the developer stripping means 57 is radially fixed so as to divide the outer periphery of the rotary shaft 57a into four parts and extends in the longitudinal direction.
It is composed of a single plate-shaped blade member 57b,
The material is a non-magnetic material such as aluminum (Al) or SUS316. When the leading edge of the blade member 57b comes closest to the surface of the developing sleeve 52, the developer peeling means 57 has a gap of approximately 1 m between the leading edge and the developing sleeve 52.
The blade member 57b is rotated in the counter direction with the rotation of the developing sleeve 52, so that the residual developer D staying in the vicinity of the transport electrode N ₂ is stripped off.

Further, in the vicinity of the transport magnetic pole N ₂ , the developer D peeled off by the rotation of the developer peeling means 57 is prevented from adhering to the transport magnetic pole N ₃ , so that the developer scatters of a non-magnetic material. A prevention plate 61 is provided.

If the length of the developer stripping means 57 in the longitudinal direction is shorter than the length of the developer carrying area on the developing sleeve 52 in the longitudinal direction, the residual developer D staying on the conveying magnetic pole N ₂ is retained. Among them, the afterimage developer D in the area not contacted by the developer peeling means 57 cannot be peeled off, and the developer D sticks out to the front surface of the developing sleeve 52, that is, the developing magnetic pole N ₁ side, so that an appropriate amount is obtained. It becomes impossible to develop.

Therefore, the length of the developer stripping means 57 in the longitudinal direction is set equal to or longer than the length of the developer carrying area on the developing sleeve 52 in the longitudinal direction. There is a need.

Next, the developer D in the present invention will be described in detail. The developer D suitably used in the present invention is a two-component developer D composed of a non-magnetic toner T and hard ferromagnetic particles (carrier) C.

In the present invention, the toner is externally added with colored resin particles (containing a binder resin, a colorant and, if necessary, other additives) and an external additive such as hydrophobic colloidal silica fine powder. The colored resin particles are included. In this embodiment, a toner T having a negatively chargeable polyester resin and a volume average particle diameter of 8 μm is used. The volume average particle diameter was measured using a Coulter Counter TA-II with an aperture of 100 μm.

That is, a Call Counter TA-II type (manufactured by Coulter) is used as a measuring device, and an interface (manufactured by Nikkaki) and a CX-i personal computer (manufactured by Canon) for outputting number average distribution and volume average distribution are used. Connected electrolyte is 1% using first grade sodium chloride
Adjust the aqueous NaCl solution.

As a measuring method, the electrolytic aqueous solution 100 to 1 is used.
To 50 ml, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant, and 0.5 to 50 mg of a measurement sample is further added.

The electrolytic solution in which the sample is suspended is dispersed by an ultrasonic disperser for about 1 to 3 minutes, and the Coulter counter T is used.
According to the A-II type, a particle size distribution of particles of 2 to 40 μm is measured using a 100 μm aperture as an aperture, and a volume average distribution is obtained.

The volume average particle diameter is obtained from the obtained volume average distribution.

The hard ferromagnetic particles C applied to the present invention include, for example, surface-oxidized or unoxidized metals such as iron, nickel, cobalt, manganese, chromium and rare earths, and alloys or oxides or ferrites thereof. Is used, and the method for producing these magnetic particles is not particularly limited.

The above-mentioned hard ferromagnetic particles C may be used as a core material coated with a resin by a known method.

In this embodiment, the hard ferromagnetic particles C have a weight average particle size of 20 to 100 μm, preferably 30 to 100 μm.
Neodymium, samarium, having a coercive force of 70 Om and a coercive force of 100 Oersteds or more, preferably 200 Oersteds or more,
A ferrite particle containing barium or the like was coated with a resin and had a resistance value of 10 ⁷ Ω · cm or more, preferably 10 ⁸ Ω · cm or more.

The resistance value of the hard ferromagnetic particles C is measured by
Using a sandwich type cell with a measuring electrode area of 4 cm ² and a gap between the electrodes of 0.4 cm, an applied voltage E (V / cm) between the two electrodes was applied to one of the electrodes under a pressure of 1 kg, and the circuit was applied. The method is to obtain the resistance value of the magnetic particles from the flowing current.

The coercive force was measured by a vibrating sample magnetometer (trade name: VSM-P-1 type manufactured by Toei Industry Co., Ltd.) at a maximum of 10
Hard ferromagnetic particles C placed in a magnetic field of 000 oersteds
Was measured and determined based on the hysteresis curve drawn on the recording paper.

In this embodiment, negatively charged toner is used, the dark potential is -700V, and the light potential is -200V.
And the alternating voltage (frequency 2000H
z, a DC voltage of −550V was superimposed on an AC voltage of 2000V of peak-to-peak voltage, and reverse development was performed.

The outer diameter of the photosensitive drum 1 as an image carrier is φ
80 mm, the outer diameter of the developing sleeve 52 is 32 mm, and the distance between the developing sleeve 52 and the regulating blade 53 is 500 μ.
m, the distance between the developing sleeve 52 and the photosensitive drum 1 is 500
.mu.m, the peripheral speed of the photosensitive drum 1 was 160 mm / s, the peripheral speed of the developing sleeve 52 was 280 mm / s, and an image was formed using the developing device 3 described above. A smooth, high-quality image could be stably obtained.

Further, there was no occurrence of image density unevenness due to the difference in image history. <Comparative Example 1> Next, a comparison between this embodiment and a conventional apparatus will be described.

As shown in FIG. 31, this comparative example is an example of a two-component magnetic brush developing device using a soft magnetic material which has been widely used in the past, and the developer D on the developing sleeve is acted by the action of a repulsive magnetic field. Is to be stripped and replaced.

The peeling / conveying means for the developer D is different from that of the first embodiment. Instead of the developer peeling means 57, a non-magnetic screw is used as the first conveying means 62, and the second conveying means is used. The difference is that a screw is used as the means 63.

In this comparative example, since the soft magnetic material is used, the repulsive magnetic field of the carrier magnetic poles N ₂ and N ₃ causes the developer D constrained by the carrier magnetic pole N ₂ to have a certain amount. In the above case, the carrier magnetic pole N ₂ cannot be held and falls, so that the developer D can be sufficiently peeled off. Since the screw which is the first conveying means 62 is arranged in this falling portion, the developer D which has undergone the development history is conveyed while being agitated and mixed, and is supplied again onto the developing sleeve 52. No unevenness in image density due to the difference in development history occurred.

However, as compared with Example 1, the reproduction of the highlight portion was slightly inferior, and the image was slightly rough.

This is because the soft magnetic material is used as the developer D, so that the magnetic brush (ears) of the developer D is slightly sparse as compared with the case where the hard ferromagnetic material is used. Seem. Comparative Example 2 This comparative example uses the developing device shown in FIG. 31, and is different from Comparative example 1 only in the developer D.

That is, this comparative example uses the two-component developer D composed of the hard ferromagnetic particles C and the non-magnetic toner T, and is the same developer D as in the first embodiment.

When an image was formed using the above-mentioned developing device, the reproduction of the highlight part was good in the initial stage,
I got a smooth, high-quality image with no rustling,
Subsequently, as the image was formed, the developer D stayed on the conveying magnetic pole N ₂ and on the upstream side of the conveying magnetic pole N ₂ , causing image unevenness. <Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

The developing device 50A of this embodiment differs from the developing device 50 of the first embodiment in the direction of rotation of the developer peeling means 57. In the second embodiment, the rotation direction of the developer removing unit 57, which is counterclockwise in the first embodiment, is clockwise as shown in FIG.

With such a structure, the developer D staying on the conveying magnetic pole N ₂ is stripped by the developer stripping means 57 in the rotational direction of the developing sleeve 52, and the stripped developer D is removed. -Smooth stripping is possible without being pushed out to the front surface of the developing sleeve 52.

Using the developing device 50A of this embodiment, the first embodiment is used.
When an image was formed in the same manner as in Example 1, the same effect as in Example 1 was obtained. <Third Embodiment> FIG. 10 shows a third embodiment.

The third embodiment shows a structure in which the structure of the developing device can be simplified as compared with the above-described first and second embodiments.

The developer D is agitated by the agitating member 59 which also agitates and supplies, is magnetically attracted to the carrier magnetic pole N ₂ of the magnet 55, and is in the arrow direction (clockwise direction) of the developing sleeve 52.
It rotated by a magnetic brush (ear standing) MB in conveying pole S ₂ of
Is uniformly formed by the blade 53, and then is conveyed to the developing magnetic pole N ₁ . And the developer D at this position
The magnetic brush MB comes into contact with the photosensitive drum 1, and the toner T develops the electrostatic latent image on the photosensitive drum 1 by a bias electric field (not shown) between the two. The developer D after development tends to stay at the position of the transport magnetic pole N ₂ , but the developer peeling means 57 rotates in the arrow direction (clockwise; therefore, in the counter direction with respect to the rotation direction of the developing sleeve 52). It is stripped off by and carried to the stirring member 59.

With such a structure, the developer supplying means 60 in Embodiments 1 and 2 (see FIGS. 8 and 9).
A mechanism for pumping up and supplying the developer D as described above is unnecessary, and the configuration of the developing device 50B can be greatly simplified. <Fourth Embodiment> FIG. 11 shows a fourth embodiment.

In the vicinity of the carrier magnetic pole N _{2 of the} magnet 55, a developer separating means 65 (hereinafter, appropriately referred to as “magnetic member 65”) made of a magnetic member, which will be described later, is rotatably arranged, and is shown in the direction of the arrow in the figure. (Counterclockwise), and therefore, the developing sleeve 52 is rotating in the counter direction.

The developer D accumulated near the carrying magnetic pole N _2.
After being peeled off by the magnetic member 65, the magnetic pole 65 is agitated and mixed by the oblique ribs 65d made of a non-magnetic member projecting on the outer periphery of the rotation shaft 65a (see FIG. 14) of the magnetic member 65, and the carrier magnetic pole N ₃ Developer D is newly supplied in the vicinity.

That is, the developer D that has undergone the development history on the developing sleeve 52 is peeled and removed, and a sufficiently mixed new developer D is constantly supplied to the developing sleeve 52, so that a stable and good image is obtained. can get.

Next, consideration will be given to how the developer peeling means using the magnetic member 65 peels and removes the hard ferromagnetic developer D from the developing sleeve 52 (FIGS. 12A to 12C and FIG. 13). A description will be given with reference to schematic diagrams of a) to (c). In addition,
Hereinafter, the whole is referred to as a developer D, and each of the particles is referred to as a hard strength magnetic particle.

12A to 12C are schematic diagrams showing the behavior of the hard ferromagnetic developer D in the example using the magnetic member 65, and FIG. 12A is a state diagram when the magnetic member 65 is not present. Therefore, the hard ferromagnetic developer D is connected in a chain shape almost along the lines of magnetic force of the repulsive magnetic fields of the carrier magnetic poles N ₂ and N ₃ . (B) is a state diagram of the developer D when the magnetic member 65 has come to a position substantially opposite to the transport magnetic pole N _2, and the S pole is induced at the tip of the magnetic member 65. The N-pole side of the hard ferromagnetic particles is attracted to the induced S-pole.

When the magnetic member 65 is separated from the carrier magnetic pole N _2, a part of the hard ferromagnetic particles of the developer D is peeled off and removed from the developing sleeve 52 to the magnetic member 65 as shown in (c). It moves together with the magnetic member 65 while being held.

On the other hand, FIGS. 13 (a) to 13 (c) are schematic views showing the behavior of the hard ferromagnetic developer D in the example using the nonmagnetic member. As shown in FIG. 12A, even when the non-magnetic member 65A comes to a position almost opposite to the carrier magnetic pole N ₂ , as shown in FIG. The ferromagnetic particles are not attracted to the nonmagnetic member 65A. Hard ferromagnetic particles also nonmagnetic member 65A is separated from the transport pole N ₂ is (c), the developing sleeve 52
It remains chained above.

By using the magnetic member 65 as the developer removing means as described above, the hard ferromagnetic developer D held on the developing sleeve 52 can be removed.

FIG. 14 is a partially enlarged perspective view of a cross section of the developer removing means 65 at a substantially central position in the longitudinal direction.
A plate-shaped blade member 65b having an opening 65c is fixed to the rotary shaft 65a, and a non-magnetic rib 65d is fixed obliquely to the rotation direction of the rotary shaft 65a.

Therefore, when the developer peeling means 65 is rotationally driven, as described above, when the developer peeling means 65 comes to a position substantially opposite to the transport magnetic pole N ₂ , the magnetic force induced in the magnetic member 65 causes the hard magnetic force on the developing sleeve 52. The hard magnetic developer D held by the magnetic member 65 after the ferromagnetic developer D is peeled off and removed.
Is the magnetic member 65 as it moves away from the carrier magnetic pole N _2.
The magnetic pole induced at the tip of the magnetic material disappears, and the hard ferromagnetic developer D is detached from the magnetic member 65.

The detached developer D is the non-magnetic rib 6
While being stirred and mixed by 5d, it is conveyed from the back side to the front side in the figure. As described above, the above-mentioned developer removing means 65 can also serve as a stirring / mixing and conveying means for the developer D.

By the way, the inside of the developing container 51 is
As shown in FIG. 11, the partition wall 66 extending in the direction perpendicular to the paper surface.
By the developing chamber (first chamber) 51a and the stirring chamber (second chamber) 5
1b and a partition wall 51d above the stirring chamber 51b.
A toner accommodating chamber 51c is formed with a space therebetween, and replenishment toner (non-magnetic toner) T is accommodated in the toner accommodating chamber 51c. A replenishment port 51e is opened in the partition wall 51d, and the replenishment toner T in an amount commensurate with the amount of toner consumed is dropped and replenished into the stirring chamber 51b through the replenishment port 51e. In addition, the developing chamber 51a and the stirring chamber 5 described above
The developer D is contained in 1b. Note that the partition wall 66 is not formed at the front and rear ends of the developing container 51 in FIG. 11, and at both ends of the developing container 51, an opening (not shown) for communicating the developing chamber 51a with the stirring chamber 51b is formed. (Shown) is formed.

In the developing chamber 51a, however, the developer D is located in the inner bottom of the developing container 51 near the developing sleeve 52 and rotates in the direction of the arrow (counterclockwise) to move the developer D from the back side to the front side in FIG. A developer peeling means 65 which also serves as a first carrying means for carrying is provided, and is located in the stirring chamber 51b at substantially the same horizontal position as the first carrying means 65 and rotates in the direction of the arrow (counterclockwise) shown in the drawing. A second carrying unit 63 is provided for carrying the developer D from the front side to the back side in FIG.

The second carrying means 63 is, specifically,
It is configured by fixing ribs that are oblique to the rotation axis.

When images were formed using the developing device shown in FIG. 11, as shown in Table 1, the reproduction of the highlight portion was good, there was no shading, and smooth and high-quality images were stable. I was able to get it. Further, there was no unevenness in image density due to the difference in image history. In addition,
In the same table, Example 4 is the above-mentioned Example and Examples 5 to 5.
Example 8 is an example described below. Further, Comparative Examples 1 and 2 are the same as those described in Example 1.

[0106]

[Table 1] <Fifth Embodiment> Next, a fifth embodiment of the present invention will be described with reference to FIG.

In the developing device 50D of the fifth embodiment, the same parts as those in the fourth embodiment are designated by the same reference numerals and the description thereof will be omitted.

This embodiment is different from the fourth embodiment in that the second conveying means 6
3, the absence of the partition wall 66, the provision of the stirring means 69, and the configuration of the developer removing means 67 (developer removing means 65 in the fourth embodiment) are different.

As the stirring means 69, a known means such as a non-magnetic bucket roller can be applied.

FIG. 16 shows the developer removing means 67 of this embodiment.
FIG. 7 is a partially enlarged view of the rotating shaft 67a, showing an opening 67c.
A plate-shaped blade member 67b made of a magnetic member having is fixed.

This opening 67c has the effects of preventing packing of the developer D and reducing the load on the developer peeling means 67.

When an image was formed in the same manner as in Example 4 using the developing device 50D described above, the same effects as in Example 4 were obtained as shown in Table 1. <Sixth Embodiment> Next, a developing device 50E according to a sixth embodiment of the present invention will be described with reference to FIG.

The same parts as those of the fourth embodiment are designated by the same reference numerals and the description thereof will be omitted.

This embodiment is different from Embodiment 4 in that the developing sleeve 5
The difference is that the rotation direction of 2 is opposite, the first transporting means 71 is provided separately from the developer removing means 70, and the shape of the developing container 51 is changed by these.

FIG. 18 shows the developer removing means 70 of this embodiment.
FIG. 4 is a partially enlarged view of FIG. 4, in which a plate-shaped blade member 70b made of a magnetic member is fixedly mounted on the rotating shaft 70a. With this configuration, the developer D can be more effectively peeled and removed.

Image formation was carried out using the main developing unit 50E in the same manner as in Example 4, and as shown in Table 1, the same effects as in Example 4 were obtained. <Seventh Embodiment> Next, a developing device 50F according to a seventh embodiment of the present invention will be described with reference to FIG.

The same parts as those in the fourth embodiment are designated by the same reference numerals and the description thereof will be omitted.

This embodiment differs from the fourth embodiment (shown in FIG. 11) in that a cleaning member 73 for cleaning the tip of the blade member 65b of the developer removing means 65 is provided. According to this configuration, the developer removing means 65 can be always cleaned,
The developer D can be peeled and removed more reliably.

When image formation was carried out using the main developing device 50F in the same manner as in Example 4, the same effects as in Example 4 were obtained as shown in Table 1. <Embodiment 8> Next, a developing device 50G according to Embodiment 8 of the present invention will be described with reference to FIG.

The same parts as those of the sixth embodiment are designated by the same reference numerals and the description thereof will be omitted.

This embodiment is different from the sixth embodiment in that the first and second conveying means 71, 72 and the partition wall 66 are not provided, and the construction of the developer peeling means 75 is different.

The developer removing means 75 of this embodiment has the same structure as that of the fifth embodiment shown in FIG.

The developer removing means 75 described above is arranged at the bottom of the developing container 51 and also serves as a means for supplying the developer D.

Image formation was carried out in the same manner as in Example 4 using the main developing device 50G, and as shown in Table 1, the same effects as in Example 4 were obtained. <Ninth Embodiment> FIG. 21 shows a ninth embodiment.

In the vicinity of the carrier magnetic pole N _{2 of the} magnet 55, a developer peeling means 76 made of a non-magnetic member (to be referred to as “non-magnetic member 76” hereinafter) and a fixed magnetic roller (magnetic field generating means) 77, which will be described later, are provided. The developing sleeve 52 is rotatably arranged, and therefore in the direction of the arrow (counterclockwise) in the drawing, and accordingly
And is rotating in the counter direction.

The developer D accumulated near the carrying magnetic pole N _2.
Are separated and removed by the non-magnetic member 76, and then agitated and mixed by the skewed ribs 76d made of a non-magnetic member protruding from the outer periphery of the rotating shaft 76a (see FIG. 24) of the non-magnetic member 76, and the carrier magnetic poles are agitated. The developer D is newly supplied in the vicinity of N ₃ .

That is, the developer D that has undergone the development history on the developing sleeve 52 is peeled off and removed, and the sufficiently mixed new developer D is constantly supplied to the developing sleeve 52, so that a stable and good image is obtained. can get.

Next, the developer removing means 7 using a non-magnetic member
A consideration of peeling and removing the hard ferromagnetic developer from the developing sleeve 52 and stirring the peeled developer and the fresh developer will be described with reference to the schematic diagrams of FIGS. 22 and 23.

FIG. 22 is a schematic diagram showing the behavior of the developer D when the hard ferromagnetic developer D is forcibly peeled off by the non-magnetic member 76. FIG. FIG. 4 is a state diagram in which the hard ferromagnetic particles are connected in a chain shape almost along the lines of magnetic force of the repulsive magnetic field of the carrier magnetic poles N ₂ and N ₃ .
FIG. 6B is a state diagram of the developer D when the non-magnetic member 76 has come to a position substantially opposite to the carrier magnetic pole N ₂ , and at this time, the non-magnetic member 76 from the upper part of the figure causes the hard ferromagnetic particles to move. Is applied with an external force in the direction of the arrow in the figure, and the hard ferromagnetic particles connected in a chain are sheared from the portion A (shown by the dotted line in the figure).

When the non-magnetic member 76 is separated from the carrier magnetic pole N ₂ , a part of the hard magnetic particles of the developer D is peeled off / removed from the developing sleeve 52, and the developer D is peeled off. Due to the strong cohesive force between the particles arranged side by side, the hard ferromagnetic particles thus formed become a lump as it is and move together with the non-magnetic member 76.

Further, when the hard ferromagnetic particles moved by the non-magnetic member 76 escape from the influence range of the repulsive magnetic field, they are aggregated in a more stable state, for example, as shown in (d).

On the other hand, FIG. 23 is a schematic diagram when the developer Da and the fresh developer Db that have become a lump and are peeled off are stirred.

(A) is a diagram showing a state where the separated developer Da and the fresh developer Db are in the form of clusters, respectively.

When a magnetic field from the fixed magnetic roller 77 inside the developer removing means 76 is applied thereto, as shown in (b), ears are formed between the particles located at close positions. That is, the peeled developer Da and the fresh stain Db are mixed with each other.

Further, when the developer D moves to the range where the magnetic field does not reach by stirring, a lump is formed in a state where the peeled developer Da and the fresh developer Db are mixed.

FIG. 24 is a partially enlarged perspective view of a cross section of the developer removing means 76 at a substantially central position in the longitudinal direction.
A plate-shaped blade member 76b having an opening 76c is fixed to the rotating shaft 76a, and a non-magnetic rib 76d is fixed to the rotating shaft 76a in a direction oblique to the rotation direction of the rotating shaft 76a.

Therefore, when the developer peeling means 76 is rotationally driven, as described above, when the developer peeling means 76 comes to a position substantially opposite to the transport magnetic pole N ₂ , the magnetic force induced on the fixed magnetic roller 77 causes the magnetic force on the developing sleeve 52. After the hard ferromagnetic developer D has been peeled off and removed, the hard magnetic developer D held by the non-magnetic member 76 disappears as the magnetic pole is induced at the tip of the non-magnetic member 76 as it moves away from the transport magnetic pole N _2. , The hard ferromagnetic developer D is detached from the non-magnetic member 76.

The detached developer D is the non-magnetic rib 7
While being stirred and mixed by 6d, they are conveyed from the back side to the front side in the figure. As described above, the developer removing means 76 can also serve as a stirring / mixing and conveying means for the developer D.

Further, the developer removing means 76 in FIG.
Of the inside of the fixed magnetic roller 77 as shown in FIG. 21 (b), in addition to the magnetic pole 77a for stirring promotion, poles of opposite polarity at a position substantially opposite to the conveying poles N ₂ in the developing sleeve 52 (S ) By providing 77b, the developing sleeve 5
The peeling of the developer D from 2 can be further promoted. At this time, the magnetic pole 77a is preferably the same as the magnetic pole 77b.

When an image was formed using the developing device shown in FIG. 21, as shown in Table 2, the reproduction of the highlight portion was good, there was no shading, and a smooth and high-quality image was stabilized. I was able to get it. Further, there was no unevenness in image density due to the difference in image history. In addition,
In the table, Example 9 is the above-mentioned Example and Example 10.
-Example 13 is an example described below. Further, Comparative Examples 1 and 2 are the same as those described in Example 1.

[0141]

[Table 2] <Embodiment 10> Next, Embodiment 10 of the present invention will be described with reference to FIG.

In the developing device 50I of the tenth embodiment, the same parts as those in the ninth embodiment are designated by the same reference numerals and the description thereof will be omitted.

This embodiment is different from the ninth embodiment in that the second conveying means 6
3, the absence of the partition wall 66, the provision of the stirring means 69, and the configuration of the developer removing means 90 (the developer removing means 76 in the ninth embodiment) are different.

As the stirring means 69, a known means such as a non-magnetic bucket roller can be applied.

FIG. 26 is a developer stripping means 90 of this embodiment.
FIG. 3 is a partially enlarged view of FIG.
A plate-shaped blade member 90b made of a non-magnetic member having is fixed. A fixed magnetic roller 91 is provided inside the rotating shaft 90a.

The opening 90c has the effects of preventing packing of the developer D and reducing the load on the developer peeling means 90.

When an image was formed in the same manner as in Example 9 using the above-mentioned developing device 50I, the same effects as in Example 9 were obtained as shown in Table 2. <Embodiment 11> Next, a developing device 50J according to an embodiment 11 of the present invention.
Will be described with reference to FIG.

The same parts as those of the ninth embodiment are designated by the same reference numerals and the description thereof will be omitted.

This embodiment is different from Embodiment 9 in that the developing sleeve 5
The difference is that the rotation direction of 2 is opposite, the first transporting means 71 is provided separately from the developer removing means 92, and the shape of the developing container 51 is changed by these.

FIG. 28 shows the developer removing means 92 of this embodiment.
FIG. 9 is a partially enlarged view of a plate-shaped blade member 92b made of a non-magnetic member is fixed to the rotating shaft 92a. With this configuration, the developer D can be more effectively peeled and removed.

Image formation was carried out using the main developing unit 50J in the same manner as in Example 9, and as shown in Table 2, the same effects as in Example 9 were obtained. <Embodiment 12> Next, a developing device 50K according to Embodiment 12 of the present invention.
Will be described with reference to FIG.

The same parts as those of the ninth embodiment are designated by the same reference numerals and the description thereof will be omitted.

This embodiment differs from the ninth embodiment (shown in FIG. 21) in that a cleaning member 95 for cleaning the tip of the blade member 76b of the developer removing means 76 is provided. According to this configuration, the developer removing means 76 can be always cleaned,
The developer D can be peeled and removed more reliably.

Image formation was carried out in the same manner as in Example 9 using the main developing device 50K, and as shown in Table 2, the same effects as in Example 9 were obtained. <Embodiment 13> Next, a developing unit 50L according to Embodiment 13 of the present invention.
Will be described with reference to FIG.

The same parts as those of the eleventh embodiment are designated by the same reference numerals and the description thereof will be omitted.

This embodiment is different from the eleventh embodiment in that the first and second conveying means 71, 72 and the partition 66 are not provided and the construction of the developer peeling means 97 is different.

The developer removing means 97 of this embodiment has the same structure as that of the tenth embodiment shown in FIG.

The developer peeling means 97 described above is arranged at the bottom of the developing container 51 and also serves as a means for supplying the developer D.

Image formation was carried out in the same manner as in Example 9 using the main developing device 50L, and as shown in Table 2, the same effects as in Example 9 were obtained.

In all of the above-mentioned embodiments, the laser beam is used as the image exposure to form the minute latent image on the highlight portion by the PWM method. The invention has a particularly great effect.

An example of a digital latent image by the PWM method using a laser beam has been shown above, but an LED may be used as an image exposure source, and a dither method or a density pattern method may be used as a digital latent image forming method. Etc. may be used.

Needless to say, the same effect can be obtained for an analog latent image. Although the example in which the two-component developer D is used as the developer DD has been shown, the present invention can be applied to a one-component developing method using a magnetic toner having hard ferromagnetism.

[0163]

As described above, according to the present invention,
Adjacent magnetic poles of the same polarity are provided by providing developer peeling means for removing the residual toner at a position facing the surface of the developer bearing member in the vicinity of the magnetic poles of the same polarity arranged adjacent to each other on the developing container side. The residual developer having an image history, which tends to stay due to the repulsive electric field, can be peeled and removed and mixed well with the new developer D, so that the difference in the image history of the developer can be eliminated and The reproduction of the light portion is good, there is no shakiness, and a smooth and high-quality image can be stably formed. Further, the structure can be simplified, and a compact and low-priced developing device can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing an image forming apparatus equipped with a developing device according to the present invention.

FIG. 2 is a schematic diagram showing the configuration of an exposure apparatus.

FIG. 3A is a diagram showing ON / OFF of a laser light source.
(B) is an output distribution chart of each pixel of the CCD.

FIG. 4 is a diagram showing a distribution state of laser spot diameters.

FIG. 5 is a PWM circuit diagram.

FIG. 6 is a timing chart showing the operation of the PWM circuit.

FIG. 7: Latent image width 1 / e by pixel signal and simulation
^The figure which shows the relationship with ² .

FIG. 8 is a vertical cross-sectional view of the developing device according to the first embodiment.

FIG. 9 is a vertical sectional view of the developing device according to the second embodiment.

FIG. 10 is a vertical cross-sectional view of the developing device according to the third embodiment.

FIG. 11 is a vertical cross-sectional view of the developing device according to the fourth embodiment.

FIGS. 12A, 12B, and 12C are operation explanatory views showing the peeling of the developer from the developing sleeve by the magnetic member.

FIGS. 13A, 13B, and 13C are operation explanatory views showing the separation of the developer from the developing sleeve by the non-magnetic member.

FIG. 14 is a perspective view illustrating a configuration of a developer removing unit according to a fourth exemplary embodiment.

FIG. 15 is a vertical cross-sectional view of a developing device according to a fifth embodiment.

FIG. 16 is a perspective view showing the configuration of a developer removing unit according to the fifth embodiment.

FIG. 17 is a vertical sectional view of the developing device according to the sixth embodiment.

FIG. 18 is a perspective view showing the structure of a developer removing unit according to the sixth embodiment.

FIG. 19 is a vertical cross-sectional view of the developing device according to the seventh embodiment.

FIG. 20 is a vertical sectional view of the developing device according to the eighth embodiment.

FIG. 21A is a vertical cross-sectional view of a developing device according to a ninth embodiment.
FIG. 6B is a vertical cross-sectional view showing the configuration of the developer removing unit.

22 (a), (b), (c) and (d) are operation explanatory views showing the peeling of the developer from the developing sleeve by the developer peeling means.

FIG. 23A, FIG. 23B, and FIG. 23C are operation explanatory views showing stirring of the developer.

FIG. 24 is a perspective view showing the structure of a developer removing unit according to a ninth embodiment.

FIG. 25 is a vertical sectional view of the developing device according to the tenth embodiment.

FIG. 26 is a perspective view showing the structure of a developer removing unit according to the tenth embodiment.

FIG. 27 is a vertical cross-sectional view showing the structure of the developing device of Example 11.

FIG. 28 is a perspective view showing the structure of a developer removing unit according to an eleventh embodiment.

FIG. 29 is a vertical cross-sectional view of the developing device according to the twelfth embodiment.

FIG. 30 is a vertical sectional view of the developing device according to the thirteenth embodiment.

FIG. 31 is a vertical cross-sectional view of a conventional developing device.

[Explanation of symbols]

1 image carrier (photosensitive drum) 50, 50A to 50M developing device (developing device) 51 developing container 51A opening 52 developer carrier (developing sleeve) 55 magnetic field generating means (magnet) 57, 65, 67, 70, 75 , 76, 90, 92, 9
7 developer stripping means 65c, 67c, 76c, 90c openings 73, 95 cleaning means 77, 91, 93, 99 magnetic field generating means C hard ferromagnetic material (hard ferromagnetic particles, carrier) D developer T toner MB magnetic brush ( Hot stand) N ₁ magnetic pole (developing magnetic pole) N ₂ upstream magnetic pole (conveying magnetic pole) of adjacent magnetic poles of the same pole N ₂ downstream magnetic pole (conveying magnetic pole) of adjacent magnetic poles of the same polarity S ₁ , S ₂ magnetic pole (transport magnetic pole)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenichiro Waki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (11)

[Claims] 1. A developing container containing a two-component developer containing a mixture of a hard ferromagnetic material and a toner and having an opening facing the image carrier, and a cylindrical container rotatably arranged in the opening. A developing agent carrier, and a magnetic field generating means disposed inside the developing agent carrier and having a plurality of magnetic poles along the rotation direction of the developing agent carrier, and developing the developer in the developing container. In a developing device, which is carried as a magnetic brush on the surface of an agent carrier, is conveyed to a developing position facing the image carrier, and toner is attached to the electrostatic latent image on the image carrier at the developing position. Among the plurality of magnetic poles of the magnetic field generating means, magnetic poles of the same polarity are arranged adjacent to each other on the developing container side, and at positions facing the surface of the developer carrier in the vicinity of the adjacent magnetic poles, The developing position is carried on the surface of the developer carrier. Disposing the developer peeling means for removing the residual developer collected into the developer container via the developing device, characterized in that. 2. The developing device according to claim 1, wherein the developer removing unit is made of a magnetic member. 3. The developing device according to claim 1, wherein the developer removing unit is made of a non-magnetic member having a magnetic field generating unit having at least one pole inside. 4. The developing device according to claim 1, wherein the developer peeling unit moves in a forward direction with respect to a moving direction of the surface of the developer carrying member. 5. The developing device according to claim 1, wherein the developer removing unit moves in a counter direction with respect to a moving direction of the surface of the developer carrier. 6. The developer stripping means is disposed at a position facing the surface of the developer carrying member in the vicinity of an upstream magnetic pole of adjacent magnetic poles of the same polarity on the developing container side. The developing device according to claim 1, wherein the developing device is a developing device. 7. The developing device according to claim 1, wherein the developer removing unit has a cleaning unit. 8. The developing device according to claim 1, wherein the developer removing unit has an opening communicating with the rotation direction. 9. The developing device according to claim 1, wherein the developer removing unit also serves as a developer stirring unit. 10. The developing device according to claim 1, wherein the developer removing unit also serves as a developer supplying unit. 11. The length in the longitudinal direction of the developer peeling means is set to be equal to or longer than the length in the longitudinal direction of the developer carrier. Item 11. The developing device according to item 10.