JPH0934255A - Developing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device for preventing developer from being scattered even in the case of increasing the number of rotations of a developing sleeve and a magnetic roller. SOLUTION: When a belt photoreceptor 1 starts to be driven at the start of copying, an image is read and two-color conversion processing is performed, and a 1st color developing device and a 2nd color developing device start to be driven, and first of all, the 1st color image is developed. Then, the 1st color developing device starts to be driven, simultaneously, a magnet roller 9-2 and a developing sleeve 9-1 for the 2nd color developing device are rotated at a prescribed rotating speed. Besides, after a prescribed time passes, the magnet roller 9-2 is elevated up to a prescribed position shown in a figure (b) by mechanisms for vertically driving the magnet roller 20-1 to 20-7, then, the 2nd color image is developed. Thereafter, when the final image area passes through the developing area of the 2nd color developing device, the magnet roller 9-2 is turned back to a position shown in a figure (a), each developing device operation is stopped.

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 an electrostatic latent image formed on an image bearing member having a photosensitive layer by an electrophotographic method, and a plurality of developing devices for multiplexing a plurality of color images. The present invention relates to an image forming apparatus that develops and collectively transfers it onto a recording material.

[0002]

2. Description of the Related Art Conventionally, such an image forming apparatus is shown in FIG.
The configuration is as shown in FIG. In the figure, reference numeral 100 denotes a photoconductor serving as an image carrier. The surface of the photoconductor 100 is uniformly charged by a primary charger 101, and a first color image (for example, black) is first formed by a first exposure 102. , The first developing device 103, which is one of the developing devices, visualizes the image.
Next, the photoconductor 100 is recharged by the recharger 104, and the second color image (for example, red) is similarly exposed to the second exposure 10
5. Then, the second developing device 106, which is the other developing device, visualizes the image of the second color. The visualized two-color toner image is transferred to a transfer charger 1
The recording sheet 108 is transferred to a recording sheet 108 as a recording material by 07, and the recording sheet 108 is separated from the photoconductor 100 by a separation charging device 109 and is conveyed to a fixing device (not shown).

On the other hand, the residual toner on the photoconductor 100 is removed by the cleaner 110, and the residual charge on the photoconductor 100 is removed by the pre-exposure unit 111.

By the way, in such one-pass two-color development, the second color developer is held in a non-contact state with the photoconductor 100 in order not to disturb the toner image of the first color. For this reason, the spike of the developer in the second developing device 106 is shortened, and the distance between the developing sleeve 201 of the second developing device 106 and the photoconductor 100 is usually set to several 100 μm to 1 mm. In order to perform good development with such a wide gap, when the second developer is composed of two components, that is, toner and carrier, the movement of the developer is activated,
In order to sufficiently replenish the toner, a method of providing a magnet roller 202 in the developing sleeve 201 as shown in FIG. 8 and rotating the magnet roller 202 at a high speed in the direction of the arrow is adopted.

Further, as shown in FIG. 8, the rotation center axis of the developing sleeve 201 and the rotation center axis of the magnet roller 202 are eccentric in order to efficiently supply the toner to the developing section. That is, in the developing section, the restraint of the carrier is strengthened by the magnetic force to increase the density of the developer, and in the lower portion of the surface of the developing sleeve 202 where the magnetic force is weak, the magnetic carrier is dropped downward by its own weight to efficiently replace the developer. . The magnetic carrier dropped down is uniformly mixed with the toner by the stirring roller 203, and is supplied to the surface of the developing sleeve 201 by the scooping roller 204. At this time, the amount of developer coating on the surface of the developing sleeve 202 is regulated to a predetermined amount by the blade 205.

By configuring the developing device for the second color in this way, the image for the second color can be of high quality as well as the first color.

[0007]

However, in order to increase the copy speed without degrading the image quality of the second color in such a one-pass two-color (multicolor) image forming apparatus,
It is necessary to increase the amount of developer supplied to the image area by an amount corresponding to the speedup. for that reason,

The rotation speed of the developing sleeve is increased, and the developer is sufficiently supplied to the developing area. The number of magnetic poles of the magnet roller is increased to increase the change of the magnetic poles and activate the movement of the developer to facilitate the toner flying. Increase the number of rotations of the magnet roller and obtain the same effect as.

Etc. are considered. Here, there is a difficulty in the manufacturing method of the magnet roller, and when the number of poles exceeds a certain level, the gap between the poles may be narrowed and the magnetic field may be weakened. Therefore, the following measures are mainly taken.

By the way, when the rotational speed of the developing sleeve and the rotational speed of the magnet roller are increased in order to increase the copy speed and obtain a high quality image, the following phenomenon occurs.

That is, when the number of rotations of the developing sleeve and the magnet roller increases, the supply of the developer onto the developing sleeve increases and the movement of the carrier also becomes active, so that the toner scattering amount increases.

In particular, when the developing sleeve or the magnet roller starts to rotate, the carrier and the toner are easily separated from the developing sleeve due to the inertial force, and the scattering amount may increase as the rotation ON / OFF increases. Further, if the developing sleeve and the magnet roller are rotated in the same direction in order to correct the sagging of the edge portion of the image, the collision of the developer at the start of rotation becomes severe, and the amount of scattering may increase.

An object of the present invention is to provide a developing device and an image forming apparatus which do not scatter the developer even when the number of rotations of the developing sleeve and the magnet roller is increased.

[0014]

According to the first invention of the present application, the object is to provide a developer container containing a developer composed of magnetic carrier particles and toner particles, and rotatably arranged. In a developing device comprising a developing sleeve made of a non-magnetic metal and a magnet roller rotatably arranged therein and having alternating magnetic poles, a center axis of rotation of the magnet roller is the rotation axis of the developing sleeve. Coaxial position of
Also, the magnet roller is movably arranged at a position close to the developing area side, and the magnet roller is moved to the close position after the developing sleeve or the magnet roller reaches a predetermined rotation speed at the time of development, and at the end of the development sleeve. Alternatively, it is achieved by providing a driving means for moving the magnet roller to the coaxial position before the rotation of the magnet roller is stopped.

According to the second invention of the present application,
The object is an image carrier having a photosensitive layer and arranged to be movable endlessly, and a plurality of developing devices arranged to face the image carrier along the moving direction of the image carrier. And a transfer device for collectively transferring a multi-color developed image formed on the image carrier by the plurality of developing devices onto a recording material, wherein the developing device for developing at least a second color or more is a magnetic carrier particle. And a developer container containing a developer consisting of toner particles, a developing sleeve made of non-magnetic metal rotatably arranged, and a magnet roller rotatably arranged with alternating magnetic poles inside. In the image forming apparatus, which is a developing device including a developing roller, the magnet roller of the developing device that develops the second color and subsequent colors has a central axis of rotation coaxial with the rotational axis of the developing sleeve and a position close to the developing area side. Movably arranged When the developing sleeve or magnet roller reaches a predetermined rotation speed during development, the magnet roller is moved to the proximity position, and at the end of development, the developing roller or magnet roller is rotated before the rotation is stopped. This is achieved by providing driving means for moving to the position.

[0016]

According to the first aspect of the present invention, the magnet roller can be freely contacted with and separated from the developing sleeve in the developing area where the image carrier and the developing sleeve face each other, and the magnet roller is moved when the developing sleeve and the magnet roller start to rotate. Separated from the developing sleeve, rotationally driven in a state where the developer is not restrained as much as possible on the developing sleeve surface, and when the rotation speed of the developing sleeve and the magnet roller becomes constant, the magnet roller is brought close to the developing sleeve in the developing area, Minimize the scattering of the developer.

According to the second aspect of the present invention,
A multi-color developed image is formed on the image bearing member by a plurality of developing devices and is collectively transferred onto the recording material by the transfer device. However, the developing device for developing at least the second and subsequent colors is the image bearing member. When the developing sleeve is in the opposite developing area,
The magnet roller can be contacted and separated from the developing sleeve.When the developing sleeve and the magnet roller start rotating, the magnet roller is separated from the developing sleeve, and the developing roller and the magnet roller are driven to rotate without restraining the developer on the developing sleeve surface as much as possible. Since the magnet roller is made to approach the developing sleeve in the developing area when the rotation speed becomes constant, a predetermined gap is provided between the developing sleeve and the image carrier so as not to disturb the developed image of the first color. Even when the above condition is maintained, the scattering of the developer is suppressed as much as possible, and an excellent image is formed.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) FIG. 1 shows a process speed 1 using a belt photosensitive member according to an embodiment of the present invention.
FIG. 6 is a block diagram illustrating a configuration of an image forming process of a high-speed copying machine with two-pass colors.

In FIG. 1, 1 is a belt photosensitive member which is an image carrier composed of a transparent substrate and an organic semiconductor photosensitive layer, 2 is a driving roller for driving the belt photosensitive member 1 in the direction of the arrow, 3
Is a tension roller, 4 is a primary charger, and 5 is 600 dp.
A first exposing device for forming a first latent image having a resolution of i, 6 is a first developing device which is a developing device for developing the first latent image with a black two-component developer, and 7 is a first developing device. 1 Recharger for recharging belt photoreceptor 1 after development, 8 is 60
A second exposure device for forming a second latent image of 0 dpi, a second developing device 9 which contains a magnetic carrier and non-magnetic red toner, and is a developing device for developing the second latent image, 9-
1 is a developing sleeve made of non-magnetic metal with an outer diameter of 20 inches, 9
-2 is a 14-pole magnet roller having an outer diameter of 17 inches. Reference numeral 10 is a static eliminator, 11 is a transfer charger, 12 is a separation charger, 13 is a paper conveyance belt, 14 is a fixing device, 15 is a pre-cleaner static eliminator, 16 is a cleaner device, 17 is a paper supply guide, and 18 is a developing device. Sleeve rotation drive mechanism, 19
Is a magnet roller rotation drive mechanism, 20 is a magnet roller up-and-down drive mechanism which will be described in detail later, 21 is a control circuit for controlling each mechanism of the developing sleeve rotation drive mechanism 18 and the magnet roller rotation drive mechanism 19 and other overall system, Reference numeral 22 is an operation input panel.

The two-color printing operation in the apparatus of this embodiment will be described below. First, when a color document is placed on a scanner device (not shown) and the start button of the operation panel 22 is pressed, the scanner device reads image data, and a black image which is a first image is read by an image processing circuit (not shown). And a second image, which is a red image, is separated into two-color images. When the start button is pressed, the belt photosensitive member 1 starts to move in the direction shown in the figure by the driving roller 2. Next, a predetermined voltage is applied to the primary charger 5 from a high voltage power source (not shown), and the belt photosensitive member 1 is charged to a uniform negative potential. Then, light modulated according to the first image information is emitted from the first exposure device 5, and an electrostatic latent image of the first image is formed on the belt photosensitive member 1.

The first electrostatic latent image is reversely developed by the first developing device 6 with negative toner having a particle size of 9.5 μm.

Next, the visualized developing area is uniformly charged again to a negative potential by the recharging device 7, and the light modulated according to the second image information is irradiated from the second exposing device 8 to expose the belt. An electrostatic latent image of the second image is formed on the surface of the body 1.

By arranging the second exposure device 8 on the back surface of the belt photosensitive member 1 and using a transparent substrate for the belt photosensitive member 1, a latent image is also formed on the photosensitive layer portion overlapping with the first image information. Can be formed.

Next, the operation of the second developing device 9 in the apparatus of this embodiment will be described with reference to FIGS.

When the copy start button is pressed as shown in the time chart (1) of FIG. 2, the belt photosensitive member 1 starts to be driven by the driving roller 2 as described above. Then, when the image reading and the two-color conversion process are completed, or at a stage in the middle of the process, the second developing device 9 starts driving, and the first exposing device 5 starts the latent image formation of the first image. On the other hand, at the same time when the driving of the first developing device 6 is started, the magnet roller rotation driving mechanism 19 and the developing sleeve rotation mechanism 1 of the second developing device 9 are
8 starts driving, and as shown in time charts (3) and (4), the magnet roller 9-2 and the developing sleeve 9
-1 is rotationally driven at a predetermined rotation speed in the direction shown in the figure (the same direction as the developing sleeve). For example, the developing sleeve 9
The rotation speed of -1 is about 535 rpm, and the rotation speed of the magnet roller is about 3000 rpm.

Then, as shown in the time chart (5), the magnet roller up-and-down drive mechanism 2 after a predetermined time T1.
By 0, the magnet roller 9-2 is lifted to a predetermined position. It should be noted that T1 is set to be longer than the time required for the developing sleeve 9-1 and the magnet roller 9-2 to rotate in a regular shape.

This magnet roller vertical drive mechanism 20
Has the configuration shown in FIG. In FIG.
-1 is an operation positioning member that regulates the upper portion of the magnet roller rotation shaft, and is set so that the distance between the surface of the magnet roller 9-2 and the surface of the developing sleeve 9-1 during operation is s2 as shown in FIG. Has been done. Here, the value of s2 is set to a distance at which a magnetic flux density (for example, 900 gauss or more) sufficient to capture the developer on the surface of the developing sleeve 9-1 is obtained. Reference numeral 20-2 denotes a positioning member at the time of stop for restricting the lower part of the magnet roller rotation shaft, as shown in FIG.
It is a support member for supporting the magnet roller 9-2 at the time of non-operation as shown in FIG. Reference numeral 20-3 is a left and right fixing member for fixing the left and right positions. In addition, at rest,
Center of rotation of developing sleeve 9-1 and magnet roller 9-
The center of rotation of 2 is adjusted to be coaxial. 20
-4 is a drive transmission member that moves up and down in conjunction with the operation of the plunger 20-5. Where the plunger 20-5
When a signal is input to the control circuit 21 in FIG.
As shown in (b), the rotating member 20-6 has a rotating shaft 20-7.
Is pulled toward the plunger side, and the opposite end pushes up the drive transmission member.

In this state, the second developing device 9 is ready for development, and at least the period during which the image area on the belt photosensitive member 1 passes through the developing area (the period indicated by D in FIG. 2), (b) in FIG. ) Is maintained. 2 time chart (5)
In the period D in which the plunger 20-5 is ON, the magnet roller 9-2 is in the time when the image area passes through the developing area.
It is sufficient if the time is more than the time taken to consider the vertical movement time of the magnetic roller 9-.
2 holds the state shown in FIG.

When the last image area passes through the second developing area, the plunger 20-5 is turned off, and the magnet roller 9-2 and the developing sleeve 9-1 are turned on as shown in FIG. 3 (a). The distance from the surface is s1. Then, after a predetermined time T2, the rotation driving of the developing sleeve of the first developing device 6 and the rotation driving of the developing sleeve 9-1 and the magnet roller 9-2 of the second developing device 9 are stopped. It should be noted that T2 is set to be equal to or longer than the moving time from the state shown in FIG. 3B to the magnet roller 9-2 resting at the position shown in FIG.

By controlling the drive of the second developing device 9 in this way, the following effects are obtained. That is, when the developing sleeve 9-1 and the magnet roller 9-2 are rotationally driven in the state shown in FIG. 3C, since the magnetic flux density on the surface of the developing sleeve 9-1 is low, the developing sleeve 9-1 The upper developer coat amount is small, and the developing sleeve 9-
It is possible to reduce the amount of the developer that receives the inertial force when rotating 1 and the amount of the toner scattered from the developing sleeve 9-1. Further, before the rotation of the developing sleeve 9-1 is stopped, the rotating shaft of the magnet roller 9-2 is moved to a position coaxial with the rotating shaft of the developing sleeve 9-1 to reduce the magnetic flux density on the surface of the developing sleeve 9-1. Since the developer coating amount is reduced, it is possible to reduce the amount of toner scattered by the inertial force received when the rotation of the developing sleeve 9-1 is stopped.

The two-color toner image formed on the belt photoconductor 1 as described above is supplied from the paper supply guide 17 by the transfer charger 11 after the charge of the belt photoconductor 1 is removed by the charge remover 10. Is transferred to recording paper.
The recording paper is separated from the belt photosensitive member 1 by the separation charging device 12 and conveyed to the fixing device 14 by the paper conveying belt 13 to fix the toner image.

(Second Embodiment) Next, a second embodiment of the present invention will be described. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the first embodiment, the second developing device 9
The rotation start and stop times of the developing sleeve 9-1 and the magnet roller 9-2 are the same.
For the purpose of gradually changing the movement of the developer on -1, as shown in FIG. 4, when the drive is started, the developing sleeve is rotated, the magnet roller is started, and the plunger is turned on in this order. When the drive is stopped, the plunger is rotated. The drive may be controlled in the order of OFF → rotation of magnet roller → stop rotation of developing sleeve.

Further, the start and stop of the rotational driving of the developing sleeve and the magnet roller may be gradually performed as shown in FIG.

Further, in the present embodiment, the magnet roller is driven up and down by the second developing device which is composed of the developing sleeve and the magnet roller which rotate at a high speed in order to compensate the development deterioration caused by the non-contact development. It is possible to reduce toner scattering by performing the same control in the first developing device that performs the above. The timing chart at this time is shown in FIG. That is, the developing sleeves and the magnet rollers of the first and second developing devices start to rotate (a), and after the rotation speed is stabilized, the magnet rollers in the first and second developing devices are moved upward to move the second roller. After finishing the development of, return the magnet roller to the rest position,
Then, the rotation of the sleeves and the magnet rollers of the first and second developing devices is stopped.

In the above embodiment, the image forming apparatus for performing two-color development has been described, but the present invention is not limited to this and can be applied to a multi-color image forming apparatus of two or more colors.

[0038]

As described above, the first embodiment according to the present application is described.
According to the invention, the magnet roller can be freely contacted with and separated from the developing sleeve in the developing area where the image carrier and the developing sleeve face each other, and the developing roller and the magnet roller are separated from the developing sleeve at the start of rotation so that the developer is developed as much as possible. Rotational drive is performed without being restrained by the sleeve surface, and the magnet roller is made to approach the developing sleeve in the developing area when the developing sleeve and magnet roller rotation speed becomes constant. It is possible to reduce the amount of the developer bound to the sleeve surface, particularly to the developing area exposed to the outside, and it is possible to reduce toner scattering that occurs when the developing sleeve starts and stops rotating,
It has become possible to reduce contamination inside the machine and toner consumption.

According to the second invention of the present application,
A multi-color developed image is formed on the image bearing member by a plurality of developing devices, and is collectively transferred onto a recording material by a transfer device. A developing device that develops at least a second color or later is
In a developing area where the image carrier and the developing sleeve face each other, the magnet roller can be brought into and out of contact with the developing sleeve, and when the developing sleeve and the magnet roller start rotating, the magnet roller is separated from the developing sleeve so that the developer is not restrained on the developing sleeve surface as much as possible. Rotation drive with
Since the magnet roller is made to approach the developing sleeve in the developing area when the rotational speeds of the developing sleeve and the magnet roller become constant, the developing sleeve and the image bearing member are arranged so as not to disturb the developed image of the first color. Even when a predetermined gap is maintained between the two, it is possible to suppress the scattering of the developer as much as possible, and it is possible to form a multicolor image satisfactorily.

[Brief description of drawings]

FIG. 1 is a process configuration block diagram of a 1-pass 2-color copying machine that is a first embodiment of the present invention.

FIG. 2 is a time chart for explaining the operation of the developing device according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram of a developing device that is the first embodiment of the present invention.

FIG. 4 is a time chart for explaining the second embodiment of the present invention.

FIG. 5 is a time chart for explaining the second embodiment of the present invention.

FIG. 6 is a time chart for explaining the second embodiment of the present invention.

FIG. 7 is a diagram for explaining a conventional 1-pass 2-color copying process.

FIG. 8 is a diagram for explaining a conventional 1-pass 2-color copying process.

[Explanation of reference numerals] 1 belt photoreceptor (image carrier) 6 first developing device (developing device) 9 second developing device (developing device) 9-1 developing sleeve 9-2 magnet roller 20 magnet roller vertical drive mechanism (driving) 21) Control circuit (driving means)

Claims (2)

[Claims] 1. A developer container containing a developer composed of magnetic carrier particles and toner particles, a developing sleeve made of a non-magnetic metal rotatably arranged, and having an alternating magnetic pole inside thereof and being rotatable. And a magnet roller disposed on the developing roller, the magnet roller is movably disposed at a position where a center axis of rotation of the magnet roller is coaxial with a rotation axis of the developing sleeve and a position close to the developing area side. When the developing sleeve or magnet roller reaches a predetermined rotation speed during development, the magnet roller is moved to the proximity position, and at the end of development, the magnet roller is moved to the coaxial position before the developing sleeve or magnet roller stops rotating. A developing device comprising a driving means for moving the developing device. 2. An image carrier having a photosensitive layer and movably arranged endlessly, and a plurality of developing devices arranged so as to face the image carrier along a moving direction of the image carrier. And a transfer device for collectively transferring the multi-color developed image formed on the image carrier by the plurality of developing devices onto a recording material, and the developing device for developing at least the second and subsequent colors is a magnetic carrier. A developer container containing a developer composed of particles and toner particles, a developing sleeve made of non-magnetic metal rotatably arranged, and a magnet roller rotatably having alternating magnetic poles inside thereof. In the image forming apparatus, which is a developing apparatus including: a magnet roller of the developing device that develops the second and subsequent colors, the central axis of rotation is coaxial with the rotational axis of the developing sleeve, and is close to the developing area side. It is arranged so that it can be moved to any position. When the developing sleeve or magnet roller reaches a predetermined rotation speed during development, the magnet roller is moved to the proximity position, and at the end of development, the magnet roller is moved before the rotation of the developing sleeve or magnet roller is stopped. An image forming apparatus comprising: a driving unit that moves the coaxial position.