JP2001166575A - Developing device, processing cartridge and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device, a process cartridge and an image forming device capable of sufficiently agitating a developer in a short time, supplying the developer with uniform toner concentration to a developer carrier and always stably forming an image of high quality without any image failure. SOLUTION: In the device, magnet 17 (forming means for exposed part) by which an area of agitating and carrying members (developer agitating and carrying members) 11 and 12 is exposed from the contained toner (developer) is included.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image on a recording material such as a copier, a printer (for example, an LED printer, a laser beam printer, etc.), a facsimile machine, and a word processor. The present invention relates to a developing device and a process cartridge for visualizing an electrostatic latent image formed on an image carrier.

[0002]

2. Description of the Related Art Conventionally, a two-component developer composed of a non-magnetic toner (toner) and a magnetic carrier (carrier) has been used as a developer in order to make an electrostatic latent image formed on an image carrier visible. That is, a so-called two-component developing method is employed.

[0003] In the two-component developing method, a developer stirring / conveying member (hereinafter, referred to as a "container") provided in a developer container for accommodating a developer.
This will be referred to as a "stirring and conveying member". ) To stir the two-component developer and frictionally charge the toner, and then convey the toner toward a developing sleeve as a developer carrier having a fixed magnet roller inside. Further, the developer is carried by being carried on the surface of the developing sleeve, and supplied to an electrostatic latent image on the image carrier to develop the electrostatic latent image.

In recent years, in order to increase needs for color images (for example, color documents) or to save space,
Inexpensive and small developing devices are increasing. Further, a process cartridge system in which a process unit acting on an electrophotographic photosensitive member is integrally formed into a cartridge and is detachably mountable to an image forming apparatus main body has been widely used. According to this process cartridge system, the maintenance of the apparatus can be performed by the user himself without relying on a serviceman.
Operability can be remarkably improved. Therefore, this process cartridge system is widely used in electrophotographic image forming apparatuses.

In such a developing device and the process cartridge, since the developing device is provided in a limited space around the electrostatic latent image carrier, the capacity of storing the developer is small. Therefore, a toner supply device (hereinafter, referred to as a toner supply device)
Call it a hopper. ) Is provided separately to reduce the running cost in many cases by providing a configuration in which only the toner can be supplied when the toner is consumed.

FIG. 11 is a schematic sectional view of an example of a conventional developing device. Reference numeral 101 denotes a photosensitive drum which is an electrophotographic photosensitive member; 103, a developing device for developing a latent image on the photosensitive drum 101; 107, a developer container provided in the developing device 103 for containing a two-component developer; .

[0007] Inside the developer container 107, stirring and conveying members 111 and 112 are provided. Developer container 107
A hopper 114 for storing toner to be replenished is provided above one end in the longitudinal direction. Hopper 114
Has an opening 115 on a stirring and conveying member 112 provided in the developer container 107.
In the vicinity, a toner supply member 116 is rotatably provided.

[0008] The toner supply member 116 rotates in response to a signal from a toner sensor 113 that is a means for detecting the amount of toner in the developer, and supplies toner from the hopper 114 to the developer container 107. I do.

The toner is supplied from the hopper 114 by rotating a toner supply member 116 in the hopper 114 in response to a toner concentration detection signal from a toner sensor 113 disposed in the developer container 107. When the toner sensor 113 indicates “no toner (developer container 107
Is smaller than a predetermined value level), the toner supply member 116 in the hopper 114 is driven to supply toner. The toner supply amount is given from a function determined in advance based on a value when the toner sensor 113 detects “no toner”.

The toner supplied from the hopper 114 onto the stirring / conveying member 112 provided in the developer container 107 is rotated by the rotation of the stirring / conveying member 112 and the stirring / conveying member 111 to cover the entire area of the developer container 107 in the longitudinal direction. Will be replenished. The stirring and conveying members 111 and 112 have a screw shape, and are each rotatable in the direction of the arrow in the figure.

The stirring and conveying members 111 and 112 rotate in synchronization with the rotation of the developing sleeve 104 or rotate only when toner is supplied.

Here, in order to form an image having a uniform density, it is essential to stably supply a developer having a uniform toner density to the developing sleeve 104. For this purpose, it is desired that the supplied toner is immediately stirred.

The shape of the stirring and conveying member for improving the stirring force is such that a spiral blade is formed on the outer periphery of the rotary shaft, and the developer is conveyed in the axial direction of the developing sleeve 104 and stirred. Furthermore, in order to further improve the stirring ability, a method of providing a plate-like rib extending radially from a rotation axis to perform stirring and transport is known.

[0014]

However, in the above-mentioned conventional developing device and process cartridge, the stirring and conveyance of the developer, particularly the two-component developer having the toner and the carrier, can be always performed satisfactorily through the durable operation against the environmental fluctuation. It is difficult to perform this operation, and there is a problem that image defects such as uneven density occur in the final image.

As a cause of the image density unevenness, there is a cause due to insufficient stirring power of the stirring member. That is, it takes time until the toner replenished from the hopper 114 is evenly loosened in the carrier, and if the developer is supplied to the developing sleeve 104 before reaching a uniform toner concentration, image density unevenness occurs. I do.

Further, the insufficient stirring has caused a malfunction of the toner sensor 113 as the developer amount detecting means. In other words, the lack of stirring of the developer creates a state in which the carrier and the toner remain separated, so that the toner sensor 113 detects the toner concentration in the developer as “no toner” even though the toner is supplied. In such a case, further toner replenishment is required, which may lead to density unevenness due to excessive toner supply.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. It is an object of the present invention to provide a developer having a uniform toner concentration that can sufficiently stir the developer in a short time. To provide a developing device, a process cartridge, and an image forming apparatus that can supply a developer carrier to a developer carrier, and can always stably form a high-quality image without image defects.

[0018]

In order to achieve the above object, according to the present invention, a developer accommodating container accommodating a developer, and a developer agitated in the developer accommodating container are agitated. A developer stirring / conveying unit that stirs and conveys the developer with a conveying member; and a developing device that visualizes an electrostatic latent image formed on an image carrier with the developer. And an exposing portion forming means for exposing the developer from the stored developer.

It is preferable that the developer container has an opening for supplying toner substantially above the partial area.

The developer comprises magnetic particles and toner,
It is also preferable that the exposed portion forming means includes a magnetic field generating means for generating a magnetic field so as to restrain the developer by a magnetic force.

The magnetic field generating means preferably includes an electromagnet as a magnetic field generating source.

It is also preferable that the magnetic field generating means can arbitrarily control generation of a magnetic field.

It is also preferable that the magnetic field generating means controls to generate a magnetic field at least at the time of toner supply operation by the toner supply means.

[0024] It is also preferable that the exposed portion forming means includes movable support means for movably supporting the magnetic field generating means.

It is also preferable that the movable support means fixes the magnetic field generating means at at least two fixed positions.

It is also preferable that the movable support unit takes a first position among the at least two fixed positions during a toner supply operation by the toner supply unit.

It is also preferable that the movable support unit takes a second position among the at least two fixed positions when the toner supply is not performed.

It is also preferable that the movable supporting means changes the position of the magnetic field generating means continuously or intermittently at least during a toner replenishing operation by the toner replenishing means.

A process cartridge is characterized by including at least the image carrier and the developing means described above.

The image forming apparatus is provided with an image forming means having the above-described developing device or process cartridge, and forms an image on a conveyed recording material.

It is also preferable that the developing device is of a cartridge type detachable from the main assembly of the device.

[0032]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The material, the shape, and the relative arrangement thereof should be appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions, and are not intended to limit the scope of the invention to the following embodiments.

(Embodiment 1) FIG. 1 is a schematic structural view of an embodiment of an image forming apparatus using a developing device according to the present invention. The image forming apparatus according to the present embodiment is an electrophotographic image forming apparatus that forms an image on a recording material using an electrophotographic image forming process.

The image forming apparatus shown in FIG. 1 has a cylindrical electrophotographic photosensitive member as an image carrier, that is, a photosensitive drum 1, a charging device for charging the photosensitive drum 1, and an electrostatic latent image formed on the photosensitive drum 1. Exposure device 18 to be formed, developing device 3 for visualizing the electrostatic latent image on photosensitive drum 1 using a developer, hopper 14 as toner replenishing means for replenishing toner to developing device 3, photosensitive drum 1 A transfer device 19 for transferring the toner image formed on the recording material P, a fixing device 20 for fixing the toner image transferred to the recording material P, and a transfer residual toner remaining on the photosensitive drum 1 are removed. Cleaning device 21 for cleaning.

The electrophotographic image forming process will be described.
First, an electrostatic latent image is formed on the surface of the photosensitive drum 1 by an electrostatic latent image forming unit. That is, after the charging device 2 uniformly charges the surface of the photosensitive drum 1, the exposure device 1
8 forms an electrostatic latent image on the photosensitive drum 1 by exposing.

Thereafter, the electrostatic latent image is developed by the developing device 3 with magnetic particles (carrier) and non-magnetic toner (toner).
The non-magnetic toner in the two-component developer containing the toner is adhered and is visualized as a so-called toner image.

The toner image on the photosensitive drum 1 is supplied to the photosensitive drum 1 by a sheet feeding means (recording material conveying means) such as a sheet feeding cassette 27, a sheet feeding roller 22, and a pair of registration rollers 23.
The image is transferred onto a recording material P fed at a predetermined timing to a transfer unit where the transfer device 19 and the transfer device 19 are opposed to each other by the operation of the transfer device 19. Next, the recording material P is transferred to the fixing device 20.
, And the unfixed toner image is fixed on the recording material P by heat and pressure to form a permanent fixed image.

Thereafter, the recording material P is discharged out of the image forming apparatus. The transfer residual toner remaining on the photosensitive drum 1 is transferred to the cleaning blade 21a and the waste toner container 21.
The cleaning is performed by the cleaning device 21 provided with b. Image formation is repeated by repeating the above process.

In this embodiment, the photosensitive drum 1
And a charging device 2, a developing device 3 and a cleaning device 21 as process means acting on the photosensitive drum 1 are integrally formed by a frame 25, and are mounted via a mounting means 24 provided in the main body of the image forming apparatus. The process cartridge C is detachable from the main body of the image forming apparatus.

Next, the developing device 3 of the present embodiment will be described in more detail with reference to FIG. FIG. 2 is a schematic sectional view of the developing device 3 of the present embodiment as viewed from above.

The developing device 3 stores a two-component developer having a toner and a carrier as a developer in a developer container 7 serving as a developer storage container. A developing sleeve 4 is provided in an opening area of the developer container 7 on the side of the photosensitive drum 1 so as to face the photosensitive drum 1. The developing sleeve 4 is
A fixed magnet roller 5 is provided inside.

By the rotation of the developing sleeve 4 indicated by the arrow in FIG. 1, the developer is attracted around the developing sleeve 4 to form a magnetic brush. In the vicinity of the developing sleeve 4, there is provided a regulating blade 6 for regulating the height of the ears of the magnetic brush to be constant and for attaching an appropriate amount of toner to the electrostatic latent image on the photosensitive drum 1.

In this embodiment, a negatively charged toner having an average particle diameter (weight average particle diameter) of 6 μm is used as the toner.
The carrier has an average particle size (weight average particle size) of 35 μm,
A magnetic carrier having a saturation magnetization of 2050 C / cm ³ (205 emu / cm ³ ) was used. A mixture of toner and carrier at a weight ratio of 8:92 was used as a two-component developer.

The developer container 7 is provided with a developer agitating / conveying means, and its configuration will be described. The developer container 7 has two developer conveying paths (hereinafter, simply referred to as “conveying paths”) 8 and 9 parallel to the developing sleeve 4, and the developing sleeve 4 is provided between the conveying paths 8 and 9. A partition wall 10 substantially parallel to the longitudinal direction is provided. Opening regions 10a and 10b are provided at both ends in the longitudinal direction of the partition wall 10.
In addition, the conveying paths 8 and 9 are provided with stirring and conveying members 11 and 12 as developer stirring and conveying members, respectively. The stirring and conveying members 11 and 12 are arranged substantially parallel to the developing sleeve 4.

In this embodiment, the stirring and conveying members 11, 1
Numeral 2 is a screw-shaped transport screw provided with spiral blades 11a and 12a in a spiral shape on the outer periphery of the rotating shaft. Further, in the present embodiment, the stirring and conveying member 1
1 stirs counterclockwise in FIG. 1 and the stirring and conveying member 12 stirs while conveying the developer in the axial direction by rotating clockwise in FIG. That is, as shown in FIG. 2, the stirring and conveying members 11 and 12 respectively convey and stir the developer in the directions of the arrows X and Y.

More specifically, the developer agitated and conveyed in the conveying path 9 and frictionally charged with the toner is sent to the conveying path 8 through an opening area 10 a provided at one longitudinal end of the partition wall 10. Is supplied to the developing sleeve 4 in the transport path 8.

At the same time, the developer whose toner concentration has been reduced by developing the electrostatic latent image formed on the photosensitive drum 1 is transported through the transport path 8 and provided at the other longitudinal end of the partition wall 10. Again through the opened area 10b.
Return to Thus, the developer circulates inside the developer container 7.

A toner density sensor (toner sensor) 13 which is a means for detecting the amount of toner in the developer as a means for detecting the remaining amount of developer is disposed near the uppermost stream portion of the transport path 9.
In other words, as described later, the toner supply port 15 is disposed upstream of the toner supply port 15 serving as a toner supply opening for supplying toner. Accordingly, the toner sensor 13 can detect the toner concentration of the developer immediately after participating in the development of the electrostatic latent image on the photosensitive drum 1.

In this embodiment, the toner sensor 13
Detects the toner concentration (mixing ratio between carrier and toner) by comparing the magnetic permeability of a magnetic carrier with the magnetic permeability of a developer comprising a non-magnetic toner and a magnetic carrier. In addition,
The present invention does not limit the developer amount detecting means to the toner sensor 13 of the present embodiment.
Any developer remaining amount detecting means using another detection method such as a light transmission type can be used.

A toner supply port 15 which is an opening for toner supply is provided above the transport path 9. As a toner supply means provided adjacent to the developing device 3 through the toner supply port 15. Hopper 14 supplies toner. As shown in FIG. 1, a rotary blade 16 as a toner supply member is provided below the hopper 14.

The rotating blades 16 rotate so as to replenish the toner amount detected by the toner sensor 13 with a toner amount determined from a function given in advance, and pass through the toner replenishing port 15 to the conveying path. 9 is supplied with toner.

As described above, the developer in the developer container 7 circulates and the toner is replenished, so that the developer having a predetermined toner concentration is always supplied to the developing sleeve 4.

Here, as described above, in order to form an image having a uniform density, it is essential to stably supply the developing sleeve 4 with a developer having a uniform toner density. For that purpose, the supplied toner must be stirred in a short time.

The present inventors have studied conditions for the toner immediately after replenishment to be sufficiently stirred in a short time and to have a uniform toner concentration. As a result, it has been concluded that the amount of exposure of the stirring member from the upper surface of the developer in the developer container 7 (hereinafter, referred to as the developer surface) is important. In the case of the developing device of the present embodiment, it is important that the stirring and conveying member 12 in the conveying path 9 in which the toner supply port 15 is provided at the top is exposed from the developer surface.

More specifically, the carrier and the toner constituting the developer have a large difference in specific gravity and do not mix as they are. Therefore, the shape of the stirring and conveying member with increased stirring power as described above, that is, a shape in which spiral blades are formed on the outer periphery of the rotating shaft, or a shape in which plate-shaped ribs extending radially from the rotating shaft are provided is required. It is.

However, even if the stirring and conveying member having such a shape is used, if the developer covers the stirring and conveying member and new toner is replenished thereon, the newly replenished toner is Since the agitating / conveying member is not exposed from the developer surface of the developer, a sufficient agitation force cannot be exerted because the agitating / conveying member is floating above. Thus, in order to sufficiently stir the toner and achieve a uniform toner concentration in a short time, the stirring and conveying member must be sufficiently exposed from the developer surface.

Here, as a method for changing the amount of exposure of the stirring member from the developer surface,
As shown in FIG. 3, the diameter of the stirring member is increased (D →
Two methods are conceivable: D ') method (A) and method (B) for reducing the amount of developer (H → H').

However, in the method (A), it is necessary to increase the diameters of the stirring and conveying members 11 and 12 and at the same time, increase the conveying paths 8 and 9 and the developer container 7 (W
→ W '). For this reason, there are restrictions on downsizing the developing device and the image forming device, or realizing the form of the process cartridge.

When the amount of the developer is reduced as in the method (B), it is difficult to achieve a satisfactory image density. Further, unduly reducing the amount of the developer is disadvantageous for the deterioration of the developer, and hinders an attempt to extend the life of the developer to reduce the running cost.

Accordingly, the present invention is configured so that the agitating and conveying member can partially form a region where the stirring and conveying member is exposed from the upper surface of the developer in the developer conveying direction by the exposed portion forming means. By supplying the toner to the area, the toner and the carrier can be quickly mixed.

In this embodiment, as shown in FIG. 2, a magnet 17 as a magnetic field generating means is disposed on the outer wall surface 7a of the developer container 7 adjacent to the transport path 9.

The magnet 17 restrains a part of the developer containing the magnetic carrier and the non-magnetic toner by its magnetic force. By doing so, a region where the developer surface of the developer partially changed from the steady state in the transport path 9 is generated, and the stirring and transporting unit 12 can form a portion sufficiently exposed from the developer surface. Become. In this state, the stirring and conveying of the developer by the stirring and conveying member 12 is performed.

More specifically, in this embodiment, FIG.
As shown in FIG. 4A and FIG. First, as shown in FIG. 4A, the magnet 17a is provided on the outer wall surface 7a of the developer container 7 corresponding to the upstream side of the toner supply port 15 in the developer transport direction.

In the region affected by the magnetic field from the magnet 17a, the developer is restricted and the amount of the developer becomes excessive. Then, on the downstream side in the developer transport direction of the region where the developer is constrained, the developer amount becomes too small. Therefore, in the developer insufficient region, the stirring and conveying member 12 is sufficiently exposed on the developer surface, and a sufficient stirring force can be obtained.

In the arrangement example shown in FIG. 4A, the toner supply port 15 is provided at a position where the amount of developer is too small by the action of the magnet 17a, so that the toner immediately after supply is sufficiently stirred. It is possible to obtain a developer having a uniform toner concentration in a shorter time.

In the arrangement example shown in FIG.
A configuration is adopted in which a magnet 17b longer in the developer transport direction than that used in the configuration of (a) is used, and the magnetic field of the magnet 17b reaches a wide area sandwiching the toner supply port 15 in the developer transport direction. In this case, by optimally selecting the magnetic force and the arrangement position of the magnet 17b, it is possible to form an angle on the developer surface of the developer as shown in FIG.

By forming an appropriate angle on the developer surface in the transport path 9 in this way, the developer is constrained and the area of the magnet 17b on which the developer amount becomes excessive, and the developing area away from the magnet 17b A region where the amount of the developer is too small can be formed, and the portion where the stirring and conveying member 12 is sufficiently exposed from the surface of the developer can be formed. Then, by supplying toner to this area, a developer having a uniform toner concentration can be obtained in a short time.

As described above, by appropriately selecting the magnet 17 which generates an appropriate magnetic field capable of restraining the developer, and by appropriately selecting its shape and arrangement position, the stirring and conveying member is sufficiently exposed from the developer surface. It is possible to form an area of any length. For example, the portion where the stirring and conveying member 12 is exposed from the developer surface is formed longer in the developer conveying direction as shown in FIG. Even when the amount of toner to be removed is large, a sufficient stirring force can be obtained.

In this embodiment, the magnet 17
A rectangular parallelepiped electromagnet was used. The strength of the magnetic field generated by supplying power to the electromagnet is about 0.09 Wb / m ² (900 G) on the surface of the magnet, but is not limited to this and can be appropriately selected. Further, it is also possible to change the shape of the magnet 17 and the shape of the region that the magnetic field can reach, if necessary.

In the present embodiment, the following comparative experiments were performed to confirm the effects of the present invention.

Using the developing device of the present embodiment shown in FIGS. 4A and 4B and a developing device having no magnet 17 as a comparative example, toner is supplied while the stirring and conveying means 12 is driven. The toner was supplied through the opening 15 and the toner concentration was measured at various points in the longitudinal direction of the transport path 9 accompanying the stirring and transport of the developer.

The toner concentration was measured by the magnetic permeability of the developer using the toner sensor 13 and a similar toner sensor as described above.

Further, in the developing devices of the present embodiment and the comparative example, the agitating / conveying means is accommodated in the conveying path without using the magnet 17 such that the respective stirring / conveying means are almost covered with the developer. The toner concentration in the developer to be supplied to the developing sleeve 4 is 8% (carrier:
(Toner = 8: 92), stirring, conveyance, and toner replenishment were performed in a state where the toner concentration was reduced to about 6% in the vicinity of the most upstream part of the conveyance path 9 in the developer conveyance direction. FIG. 6 shows the results.

From the results shown in FIG. 6, FIG. 4 (a) and FIG.
It will be understood that the developing device 3 of this embodiment shown in FIG. 3B sufficiently agitates the toner immediately after replenishment in a short time. As a result, the replenished toner is mixed with the developer in a very short time, and becomes a developer having a uniform toner concentration. Therefore, the developer having a uniform toner concentration can be stably supplied to the developing sleeve 4. FIG. 4 (a)
An image was formed using the image forming apparatus equipped with the developing device 3 of the present embodiment shown in FIG. 4B, and the effect of the present invention was further confirmed.

As described above, when the toner contained in the developer is consumed by image formation, the toner sensor 13 detects "no toner". The rotating blade 16 serving as a toner supply member provided below the hopper 14 rotates so as to replenish the toner amount detected in advance with respect to the detected toner concentration.
The toner is supplied to the transport path 9.

In the present embodiment, the magnetic field generating means is capable of arbitrarily controlling the generation of the magnetic field, and supplies power to the electromagnet as the magnet 17 during the toner supply operation.

By supplying power to the electromagnet at least during the toner replenishing operation, the effect of sufficiently stirring the toner immediately after replenishment in a short time can be obtained. In addition, wasteful power consumption other than during toner replenishment is achieved. Can be eliminated.

With the above arrangement, a good final image without image density unevenness could be obtained.

Further, since the insufficient stirring of the developer has been improved, the malfunction of the toner sensor 13 caused by detecting the toner concentration in a state where the toner and the carrier are separated from each other does not occur.

As described above, according to the present invention, the two-component developer can be sufficiently stirred in a short time, and the developer having a uniform toner concentration can be supplied to the developing sleeve 4. Further, by swiftly stirring and mixing the two-component developer, erroneous detection of the toner concentration by the toner sensor 13 can be prevented.

In the image forming apparatus according to the present embodiment, an electrophotographic image forming apparatus of a process cartridge type has been described. However, the present invention is not limited to this. For example, as shown in FIG. The present invention is also applicable to an image forming apparatus in which a developing device is fixed to an image forming apparatus main body and toner can be supplied from a toner replenishing device.

The present invention is also applicable to an image forming apparatus in which the developing device is a cartridge detachably mountable on the image forming apparatus main body.

In this case, in FIG. 1, the photosensitive drum 1, the charging device 2, the developing device 3 and the cleaning device 21 are integrally formed as a process cartridge C by the frame 25, and can be attached to and detached from the image forming apparatus main body via the mounting means 24. However, only the developing device 3 can be attached to and detached from the image forming apparatus main body via the same mounting means.

(Embodiment 2) In Embodiment 2, when performing image formation using an image forming apparatus equipped with the developing device 3 described in Embodiment 1, the magnetic field generating means
At least during the toner replenishment operation, control is performed such that power is intermittently supplied to the electromagnet serving as the magnet 17. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

As described in the first embodiment, when the toner contained in the developer is consumed by the image formation, the toner sensor 13 detects "no toner". The rotating blade 16 serving as a toner supply member provided below the hopper 14 rotates so as to replenish the toner amount detected in advance with respect to the detected toner concentration. The toner is supplied to the conveyance path 9.

During the toner supply operation, the magnetic field generating means
In synchronization with the rotation of the rotary blade 16 as a toner supply member,
Electric power is intermittently supplied to the electromagnet as the magnet 17. In the present embodiment, power supply is repeated at intervals of 0.2 seconds, but the present invention is not limited to this.

While power is being supplied, the magnet 17
Due to the magnetic force, a part of the developer including the magnetic carrier and the non-magnetic toner is restrained, so that the toner immediately after replenishment can be sufficiently stirred in a short time. Conversely, while power is not supplied, the restraint is released with the disappearance of the magnetic force, and the restrained developer is transported downstream of the transport path 9 by the agitating transport means 12.

Therefore, the developer in the area affected by the magnetic field of the electromagnet 17 can be replaced before the power is supplied again, and while a part of the developer performs the toner supply operation, As a result, the developer can be stably stirred and transported.

In the above configuration, the replenished toner is mixed with the developer in a very short time, and becomes a developer having a uniform toner concentration. Therefore, the developer having a uniform toner concentration can be stably supplied to the developing sleeve 4, and a good final image without image density unevenness can be obtained.

Further, since the insufficient stirring of the developer has been improved, the malfunction of the toner sensor 13 caused by detecting the toner concentration in a state where the toner and the carrier are separated from each other does not occur.

As described above, according to the present invention, the two-component developer can be sufficiently stirred in a short time, and the developer having a uniform toner concentration can be supplied to the developing sleeve 4. Further, by swiftly stirring and mixing the two-component developer, erroneous detection of the toner concentration by the toner sensor 13 can be prevented.

The image forming apparatus according to the present embodiment
Although an electrophotographic image forming apparatus of a process cartridge type has been described, the present invention is not limited to this.

The present invention is also applicable to an image forming apparatus in which the developing device is a cartridge detachably mountable on the image forming apparatus main body.

(Embodiment 3) In Embodiment 3, as shown in FIG. 8, a magnet is provided outside the developing device 3 and adjacent to the conveyance path 9 by a movable supporting means. 17c is rotatably arranged. Note that the same components as those in the above embodiment are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIGS. 9A and 9B, the magnet 17c can be fixed at two fixed positions (first and second positions) by rotation. At the position shown in FIG. 9A, since the binding force of the developer by the magnetic force of the magnet 17c is weak, the developer surface is not actively changed.

In the position shown in FIG. 9B, a part of the developer is restrained by the magnetic force of the magnet 17c, and the area of the transport path 9 where the developer surface changes from the steady state (the restrained area and the excessively small area). Area).

As a result, as shown in FIG. 9 (c), it becomes possible to sufficiently expose the stirring and conveying member 12 from the developer surface in an insufficient area, and the toner supply port 15 from the hopper 14 is disposed in this portion. By replenishing toner
By sufficiently stirring the toner and the carrier, it becomes possible to convey a developer having a uniform toner concentration in a shorter time than before.

9 (b) and 9 (c), the effect can be obtained if it is created only at the time of toner replenishment. Therefore, during a normal operation, the steady state of FIG. To release.

According to the present embodiment, the conventional example causes the toner and the carrier to flow into the conveyance path 8 without being sufficiently mixed, and causes image density unevenness, due to the durable operation and environmental fluctuations. Even in a similar situation, the replenished toner is mixed with the developer in a very short time, and becomes a developer having a uniform toner concentration.
, The image density unevenness does not occur.
Further, the toner and the carrier are not separated through the durability, the malfunction of the toner sensor can be prevented, and a good image can be maintained.

As described above, the developing device, the process cartridge, and the developing device or the process cartridge capable of sufficiently stirring the two-component developer in a short time and supplying the developing agent having a uniform toner concentration to the developing sleeve. An image forming apparatus having a process cartridge can be provided.

In the present embodiment, the magnet 17 as the magnetic field generating means is rotatably provided so as to have two fixed positions, but is not limited to this.

That is, as shown in FIG. 10A, a magnetic circuit is formed around the magnet 30 by the member 31 having a high magnetic permeability, and the toner is not replenished. It is also possible to minimize the amount of the agent, which is effective in an image forming apparatus in which miniaturization is particularly required.

Further, as shown in FIG. 10B, the magnet 32 can be disposed so as to be movable in the distance direction.
By bringing the magnet 32 close to the developing device at least during toner replenishment, the same effect as in the first embodiment can be obtained.

As shown in FIGS. 10C and 10D, at least at the time of toner supply, the magnets 33 and 34 can be rotated or rocked continuously or intermittently. At this time, the developer surface can be changed to add the stirring effect at the supply port. Further, in the example in which the developer is rotated, the developer that is constrained may be constantly replaced by the rotation of the magnet 33.

In the embodiment described above, the rotation direction is on the horizontal plane. However, if the magnetic force acting on the developer is changed by the rotation, the rotation direction may be on a vertical plane, on a plane having an angle with the horizontal plane, or the like. There is no particular limitation. As for the position for fixing the magnet, in addition to the two positions of the working position and the non-working position as in Embodiment 1, in addition to the non-working position as in the example of the swinging operation in FIG. A plurality of fixing positions may be provided to cope with differences in the purpose of stirring the developer and the amount of toner replenishment.

[0106]

As described above, according to the present invention,
Since the exposure section forming means for exposing a part of the developer stirring and conveying member from the stored developer is provided, the developer stored in the developer storage container can be sufficiently stirred and transported in a short time. In addition, it is possible to supply a developer having a uniform toner concentration to a developer carrying member, and it is possible to provide an apparatus that constantly and stably forms a high-quality image without image defects.

Further, the exposed portion forming means ensures that a part of the developer stirring and conveying member is exposed from the contained developer by restraining the developer having the magnetic particles by the magnetic field generating means, and the exposed portion is formed in a short time. Can sufficiently agitate the developer, so that the malfunction of the developer remaining amount detecting means can be prevented, and a highly reliable apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a main part of an image forming apparatus according to Embodiment 1 of the present invention;

FIG. 2 is a schematic top view of the developing device according to the first embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of a developing device for explaining a possible method for exposing a developer stirring and conveying member from a developer.

FIG. 4 is a schematic diagram illustrating an example of an arrangement of magnets of the developing device according to the first embodiment of the present invention and an operation thereof.

FIG. 5 is a schematic cross-sectional view of the developing device showing a state where an angle is provided to a developer surface of the developer.

FIG. 6 is a diagram illustrating a result of measuring a toner concentration at various points in a developer conveying direction in a developing container in a developing device to which the present invention is applied and a comparative example.

FIG. 7 is a schematic configuration diagram illustrating another image forming apparatus including a developing device to which the present invention is applied.

FIG. 8 is a schematic top view showing a main part of a developing device according to a third embodiment of the present invention.

FIG. 9 is a schematic diagram illustrating an example of an arrangement of magnets of a developing device according to a third embodiment and an operation thereof.

FIG. 10 is a schematic diagram illustrating another example of the arrangement of the magnets of the developing device according to the third embodiment and the operation thereof.

FIG. 11 is a schematic sectional view showing a conventional developing device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photosensitive drum (image carrier) 2 Charging device 3 Developing device 4 Developing sleeve 5 Magnet roller 6 Regulator blade 7 Developer container (developer accommodating container) 8, 9 Transport path (developer transport path) 10 Partition wall 10a, 10b Opening areas 11, 12 Stirring / conveying member (developer stirring / conveying means) 11a, 12a Spiral blade 13 Toner sensor 14 Hopper (toner replenishing means) 15 Toner replenishing port (opening) 16 Rotating blade 17, 17a, 17b, 17c, 30 , 32,33,3
4 Magnet (magnetic field generating means) 18 Exposure device 19 Transfer device 20 Fixing device 21 Cleaning device 22 Paper feed roller 23 Paper feed means 27 Paper feed cassette C Process cartridge P Recording material

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H031 AA16 AB02 AC08 AC17 AC29 BA04 BC03 DA01 2H071 BA13 DA08 2H077 AA05 AB02 AC02 AD06 AD13 AD18 DA03 DA10 DA16 DA47 DA52 DA59 DB03 EA03 FA19

Claims (14)

[Claims] 1. A developer accommodating container for accommodating a developer, and a developer agitating / conveying means for agitating and conveying the developer accommodated in the developer accommodating container with a developer agitating / conveying member, A developing device for visualizing an electrostatic latent image formed on an image carrier by a developer, comprising: an exposed portion forming unit configured to expose a partial area of the developer stirring and conveying member from the stored developer. Developing device. 2. The developing device according to claim 1, wherein the developer container has an opening for supplying toner substantially above the partial area. 3. The developer according to claim 1, wherein the developer includes magnetic particles and a toner, and the exposed portion forming unit includes a magnetic field generating unit that generates a magnetic field so as to restrain the developer by a magnetic force. 3. The developing device according to 2. 4. The developing device according to claim 3, wherein said magnetic field generating means includes an electromagnet as a magnetic field generating source. 5. The developing device according to claim 3, wherein said magnetic field generating means can arbitrarily control generation of a magnetic field. 6. The developing device according to claim 5, wherein the magnetic field generation unit controls so as to generate a magnetic field at least at the time of toner supply operation by the toner supply unit. 7. The developing device according to claim 3, wherein said exposed portion forming means includes movable supporting means for movably supporting said magnetic field generating means. 8. The developing device according to claim 7, wherein said movable support means fixes said magnetic field generating means at at least two fixed positions. 9. The developing device according to claim 8, wherein the movable support unit takes a first position among the at least two fixed positions during a toner supply operation by the toner supply unit. 10. The developing device according to claim 8, wherein the movable support unit takes a second position among the at least two fixed positions when the toner supply operation is not performed. 11. The apparatus according to claim 7, wherein the movable supporting means changes the position of the magnetic field generating means continuously or intermittently at least during a toner replenishing operation by the toner replenishing means. The developing device as described in the above. 12. A process cartridge comprising at least the image carrier and the developing unit according to claim 1. Description: 13. An image forming means comprising the developing device according to claim 1 or the process cartridge according to claim 12, wherein an image is formed on a recording material to be conveyed. Image forming apparatus. 14. The developing device according to claim 13, wherein the developing device is of a cartridge type which can be attached to and detached from an apparatus main body.
An image forming apparatus according to claim 1.