JPH10307461A - Image forming device - Google Patents

Abstract

[PROBLEMS] To provide a developing device capable of effectively preventing scattering of a developer that passes through a developing area and is taken into a developing container. A magnet 10 in the developing sleeve 3 has a capture pole S ₃ of the toner on the downstream side of the developing region, the length of the developing sleeve 3 facing the developing sleeve 3 between the developing region and the capture electrode S ₃ A conductive member 16 of equal or greater size is provided.
A DC voltage is applied to the conductive member 16 from the power supply 17 until 500 ms before the rotation of the developing sleeve 3 and 500 ms after the rotation of the developing sleeve 3 stops. Since the voltage is always applied to the conductive member 16 while the developing sleeve 3 is rotating, it is possible to prevent the toner from scattering outside the developing device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic or electrostatic recording type image forming apparatus such as a copying machine or a printer, and has a developing device.

[0002]

2. Description of the Related Art An example of a conventional developing device will be described. A developing device disposed opposite a photosensitive drum as an image carrier includes a developing container, a developing sleeve as a developer conveying means, and a developer reservoir. And a blade as a developer height control member. The inside of the developing device is divided into a developing chamber (first chamber) and a stirring chamber (second chamber) by a partition extending in the vertical direction, and the upper part of the partition is open. A two-component developer containing a non-magnetic toner and a magnetic carrier is contained in the developing chamber and the stirring chamber. First and second stirring screws are disposed in the developing chamber and the stirring chamber, respectively.

The developing chamber has an opening at a position corresponding to a developing area facing the photosensitive drum, and a developing sleeve is rotatably arranged so as to partially expose the opening. The developing sleeve is made of a non-magnetic material, rotates during the developing operation in the direction of the arrow in the figure, and has a magnet (magnet roller) serving as a magnetic field generating means fixed inside. The thickness of the developing sleeve is regulated by a blade.
The layer of the component developer is carried and conveyed, and the developer is supplied to the photosensitive drum in a development area facing the photosensitive drum to develop the latent image. In order to improve the developing efficiency, a developing bias voltage in which, for example, a DC voltage is superimposed on an AC voltage is applied to the developing sleeve from a power supply.

[0004] With the above-described configuration, the developing device holds the developer supplied to the surface of the developing sleeve by the first and second stirring screws in a state of a magnetic brush by the magnetic force of a magnet roller, and holds the developer by the developing sleeve. The developer is conveyed to a portion (developing area) facing the photosensitive drum based on the rotation of the photosensitive drum, and the developer returning member and the blade cut off the magnetic brush to maintain an appropriate amount of developer conveyed to the developing area.

More specifically, the magnet roller of such a conventional developing device has a five-pole structure, and the developer stirred by the stirring screw in the developing chamber is used as a magnetic pole for conveyance (pumping pole) for pumping. It is constrained by the magnetic force and is conveyed to the developer reservoir by the rotation of the developing sleeve. The amount of the developer is regulated by the developer return member, and in order to restrain the stable developer, the developer is sufficiently constrained by a transport magnetic pole (cut pole) having a certain or more magnetic flux density, and while forming a magnetic brush. Conveyed.

Next, the magnetic brush is cut off by a blade, that is, a spike height regulating member, so that the amount of the developer is made appropriate, and the developer is conveyed by the conveying magnetic pole. Further, a DC and / or DC voltage is applied to the developing sleeve via a bias power supply provided on the image forming apparatus body side at the developing pole.
Alternatively, a bias voltage on which an alternating electric field is superimposed is applied, the toner on the developing sleeve is moved to the electrostatic latent image side of the photosensitive drum, and the electrostatic latent image is visualized as a toner image.

In such a developing device, a part of the toner or the developer is scattered with the rotation of the developing sleeve or the like, and contaminates the image or adheres to other devices existing in the vicinity. It may cause adverse effects. In order to prevent such a scattering phenomenon, various measures have conventionally been taken.

For example, a conductive member is provided between the developing electrode and the take-in electrode so as to face the developing sleeve, and a voltage having the same polarity as that of the toner in the developer is applied, so that the unidirectional direction from the conductive member to the developing sleeve is applied. Is a typical example.

[0009]

However, in the above-mentioned prior art, since the timing of applying the voltage to the conductive member is not optimized, the voltage is applied, for example, while the developing sleeve is rotating. It is not possible to obtain a sufficient effect on scattering, or when a voltage is applied for a long time while the rotation of the developing sleeve is stopped,
There is a drawback in that so-called toner, which causes toner to adhere to the surface of the developing sleeve, causes contamination of the developing sleeve.

Accordingly, an object of the present invention is to provide an image forming apparatus provided with a developing device capable of effectively preventing a developer from passing through a developing area and being taken into the inside of a developing container without causing the above-mentioned adverse effects. It is to be.

[0011]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
A developer conveying device incorporating a magnetic field generating means for carrying a developer contained in a developing container and transporting the developer to a developing area facing the image carrier, and applying a voltage obtained by superimposing an alternating voltage on a DC voltage. The means having a developing device rotatably mounted on the developing container, the magnetic field generating means having one or more magnetic poles on the downstream side of the developing area with respect to the rotation direction of the developer conveying means, Within the range from the development region to the magnetic field formed by the one or more magnetic poles, and in the longitudinal direction, a single or a single surface facing the developer conveyance unit in a range equal to or more than the range of the developer conveyance unit. In an image forming apparatus in which a plurality of conductive members are provided and a voltage having the same polarity as the triboelectric charging polarity of the toner in the developer is applied to the conductive members, the voltage applied to the conductive members is the Rotation of agent transfer means It is applied to the predetermined time before the start simultaneously with or rotation start a and image forming apparatus, characterized by terminating the predetermined time after the application of the rotation stopping simultaneously or stop of the rotation of said developer carrying means.

It is preferable that the voltage applied to the conductive member be applied 1000 ms before or after the rotation of the developer conveying means starts. Further, it is preferable that the application of the voltage applied to the conductive member is terminated before 1000 ms after the rotation of the developer conveying unit is stopped. It is preferable that the AC voltage applied to the developer conveying means is applied only while the latent image passes through the developing area of the developer conveying means.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings. In the embodiments described below, the present invention will be described as being embodied in, for example, an electrophotographic image forming apparatus as shown in FIG. 3, but the present invention is not limited to this. Referring to FIG. 3, the electrophotographic image forming apparatus includes a rotatable photosensitive drum 4 serving as an image carrier, and uniformly charges the photosensitive drum 4 with a primary charger 21 and then emits light such as a laser. The information signal is exposed by the element 22 to form an electrostatic latent image, and is visualized by the developing device 9. Next, the visible image is transferred to a transfer paper 24 by a transfer charger 23 and further fixed by a fixing device 25 to obtain a permanent image. The transfer residual toner on the photosensitive drum 4 is removed by the cleaning device 26.

First Embodiment First, a first embodiment of a developing device according to the present invention will be described with reference to FIG. The developing device 9 includes a developing container 8, a developing sleeve 3 as a developer conveying unit, a developer return member 1 for regulating a developer pool 5, and a blade 2 as a developer spike height regulating member. The inside of the developing device 9 is provided with a developing chamber 13 by a partition 6 extending vertically.
In this embodiment, the developing chamber 13 and the stirring chamber 14 each include a non-magnetic toner and a magnetic carrier.
A component developer is contained.

First and second stirring screws 11 and 12 are disposed in the developing chamber 13 and the stirring chamber 14, respectively. The first stirring screw 11 stirs and conveys the developer in the developing chamber 13, and the second stirring screw 12 moves from the toner replenishing tank (not shown) under the control of the developer concentration controller. The toner supplied to the upstream side of the toner supply unit 12 and the developer already in the stirring chamber 14 are stirred and conveyed to uniform the toner concentration.

The partition wall 6 has a developer passage (not shown) for communicating the developing chamber 13 and the stirring chamber 14 with each other at the front and rear ends in FIG.
The developing chamber 1 in which the toner is consumed by the development due to the conveying force of the second stirring screws 11 and 12 and the toner concentration is reduced.
3 is configured to move into the stirring chamber 14 from the other passage.

The developing chamber 13 of the developing device 9 includes the photosensitive drum 4
The developing sleeve 3 is rotatably arranged so as to be partially exposed in the opening. The developing sleeve 3 is made of a non-magnetic material, rotates during the developing operation in the direction of the arrow in the figure, and has a magnet (magnet roller) 10 as a magnetic field generating means fixed inside. The developing sleeve 3 carries and conveys a layer of a two-component developer whose thickness is regulated by the blade 2, and supplies the developer to the photosensitive drum 4 in a developing area facing the photosensitive drum 4 to develop a latent image.

In order to improve the development efficiency, that is, the toner application rate to the latent image, a development bias voltage in which, for example, a DC voltage is superimposed on an AC voltage is applied to the development sleeve 3 from a power supply 15.

The developing device 9 holds the developer supplied to the surface of the developing sleeve 3 by the first and second stirring screws 11 and 12 in the state of a magnetic brush by the magnetic force of the magnet roller 10 with the above configuration. The toner is conveyed to a portion (developing area) facing the photosensitive drum 4 based on the rotation of the developing sleeve 3, and the magnetic brush is cut off by the developer return member 1 and the blade 2 to be conveyed to the developing area. Maintain the developer amount properly.

More specifically, the magnet roller 10 of the developing device has a five-pole configuration, and the developer stirred by the stirring screw 11 of the developing chamber 13 is supplied with a magnetic force of a transport magnetic pole (pumping pole) S ₂ for pumping. And is conveyed to the developer reservoir 5 by the rotation of the developing sleeve 3. The developer amount is regulated by the developer flashing member 1, in order to restrain a stable developer, sufficiently restrained by carrying pole (cutting pole) N ₂ with a certain level of magnetic flux density in, and a magnetic brush Conveyed while forming.

Next, the magnetic brush is cut off by the blade, that is, the spike height restricting member 2, so that the amount of the developer is adjusted properly.
Conveyed by ₁ . Furthermore, superimposed bias voltage of a DC and / or alternating electric field is applied through a bias power source 15 provided in the image forming apparatus main body by a developing pole N ₁ to the developing sleeve 3, the toner on the developing sleeve 3 is photosensitive The drum is moved to the electrostatic latent image side of the drum 4, and the electrostatic latent image is visualized as a toner image.

In the developing device 9, a conductive member 16 is provided on the opposite side of the blade 2 with respect to the developing sleeve 3 and in parallel with the developing sleeve 3. The length of the conductive member 16 is set to be equal to the length of the developing sleeve 3. A power supply device 17 is connected to the conductive member 16. In this embodiment, the toner has a negative charge as the triboelectric charge polarity. A DC voltage of -300 V and an alternating voltage having an amplitude of 1000 V are applied to the developing sleeve 3 by the power supply device 15 as a developing bias.

The developer transported from the transport magnetic pole S1 to the developing magnetic pole N1 with the rotation of the developing sleeve 3 is used for development while passing through a portion facing the photosensitive drum 4.

The developer whose toner has been consumed in this way is taken into the developing chamber 13 by the transfer magnetic pole (take-in pole) S _3. At this time, the transfer magnetic pole N _{1 is} transferred from the development magnetic pole N _1.
When the developer is taken into ₃ , toner mainly having a low charge amount scatters. However, here, the conductive member 16 is supplied from the power supply device 17 with the same polarity of −8 as the triboelectric charging polarity of toner.
When a voltage of 00V is applied, an electric field is generated between the conductive member 16 and the developing sleeve 3 facing each other and in the vicinity thereof. This electric field changes its direction according to the alternating voltage of the power supply device 15, but as a whole, it is generated in a direction that directs the scattered toner toward the developing sleeve 3. The scattered toner is pushed back onto the developing sleeve 3 by the force received from this electric field, and the scatter is controlled.

Next, the timing of voltage application between the developing sleeve 3 and the conductive member 16 will be described. FIG. 2 is a sequence diagram showing the timing of the rotation of the developing sleeve 3, the application of the voltage, and the application of the voltage to the conductive member 16 in this embodiment.

First, a DC voltage of -800 V is applied to the conductive member 16, a DC voltage of -300 V and an amplitude of 10 are applied to the developing sleeve 3.
An AC voltage of 00 V is applied at the same time, the developing sleeve 3 rotates after 500 ms, and the tip of the latent image passes through the developing area of the developing sleeve 3 after 300 ms.

Next, 300 ms after the rear end of the latent image has passed the developing area of the developing sleeve 3, the rotation of the developing sleeve 3 is stopped, and after 500 ms, the voltage application to the conductive member 16 and the developing sleeve 3 is terminated. .

From when the present inventors apply a voltage to the conductive member 16 until the developing sleeve 3 rotates (or until the application of the voltage to the conductive member 16 ends after the rotation of the developing sleeve 3 is stopped). The relationship between the time (T) and the scattering and contamination of the developing sleeve was examined, and the results shown in Table 1 below were obtained.

[0029]

[Table 1]

As can be seen from this result, in this embodiment, while the developing sleeve 3 is rotating, the voltage is always applied to the conductive member 16, so that the toner does not scatter outside the developing device. . Since the time during which the developing sleeve 3 is not rotating is less than 1000 ms, the toner is pressed against the same portion of the surface of the developing sleeve 3 for a long time by the force received from the electric field by the voltage applied to the conductive member 16. No development sleeve contamination by toner occurs.

Second Embodiment Next, a second embodiment of the developing device according to the present invention will be described with reference to FIG. In the first embodiment, since the AC voltage is applied to the developing sleeve 3 even during the time when the latent image passes through the developing area of the developing sleeve 3, the direction of the electric field between the developing sleeve 3 and the conductive member 16 changes during that time. Thus, a force is applied to push the scattered toner back in the opposite direction to the developing sleeve 3, that is, toward the conductive member 16 side. As a result, there is a problem that the toner adheres to the conductive member 16 and the effect of controlling the scattering becomes weak after long-term use.

Therefore, in this embodiment, the AC voltage applied to the developing sleeve 3 is applied only while the latent image passes through the developing area of the developing sleeve 3. As a result, only when the latent image passes through the developing region of the developing sleeve 3, only a DC voltage is applied to the developing sleeve 3, and the electric field between the developing sleeve 3 and the conductive member 16 does not change its direction. The toner is constantly pushed back onto the developing sleeve 3, and the scattering is effectively suppressed over a long period of time. Of course, an alternating voltage is applied while the latent image passes through the developing region of the developing sleeve 3, but this alone does not cause a problem that the effect of controlling the scattering is weakened especially after long-term use.

[0033]

As is apparent from the above description, according to the present invention, the voltage applied to the conductive member and having the same polarity as the triboelectric charging polarity of the toner in the developer is applied simultaneously with the start of rotation of the developer conveying means. Alternatively, the developer is applied a predetermined time before the start of rotation, and the application is stopped at the same time as the stop of the rotation of the developer transporting unit or after a certain time after the stop of the rotation. The scatter generated in the developer present area on the developer conveying means before being taken in,
It can be suppressed effectively near the developer intake port. Therefore, even if the development is performed for a long period of time, the resulting image is not stained by the scattering of the developer, a good image can be stably obtained, and the durability of the apparatus main body can be further improved. it can.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating developing devices according to first and second embodiments of the present invention.

FIG. 2 is a sequence diagram for explaining the first embodiment of the present invention.

FIG. 3 is a sequence diagram for explaining a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of an electrophotographic image forming apparatus that can be embodied by the present invention.

[Explanation of symbols]

 3 Developing Sleeve (Developer Conveying Means) 4 Photosensitive Drum (Image Carrier) 8 Developing Container 9 Developing Device 10 Magnet (Magnetic Field Generating Means) 16 Conductive Member 17 Power Supply Device

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takao Ogata 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Takahiro Kubo 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (4)

[Claims] 1. A magnetic field generating means for carrying a developer contained in a developing container and transporting the developer to a developing area opposed to an image carrier, wherein a voltage obtained by superimposing an alternating voltage on a DC voltage is provided. The applied developer conveying means has a developing device rotatably installed in the developing container, and the magnetic field generating means has one or more magnetic poles on the downstream side of the developing area with respect to the rotation direction of the developer conveying means. Having a range from the development region to the magnetic field formed by the one or more magnetic poles,
And, in the longitudinal direction, a single or a plurality of conductive members facing the developer conveying means is disposed in a range equal to or more than the range of the developer conveying means, and the conductive member is In the image forming apparatus that applies a voltage having the same polarity as the triboelectric charging polarity of the toner, the voltage applied to the conductive member is applied simultaneously with the start of rotation of the developer transporting unit or a predetermined time before the start of rotation, The image forming apparatus is characterized in that the application is terminated simultaneously with the stop of the rotation of the developer conveying means or after a certain period of time after the stop of the rotation. 2. The image forming apparatus according to claim 1, wherein the voltage applied to the conductive member is applied 1000 ms before and after the developer transport unit starts rotating. 3. The image forming apparatus according to claim 1, wherein the application of the voltage applied to the conductive member is terminated 1000 ms after the rotation of the developer conveying unit is stopped. 4. The image according to claim 1, wherein an AC voltage applied to the developer transporting means is applied only while the latent image passes through a developing area of the developer transporting means. Forming equipment.