JPH0631480Y2 - Development device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a developing device in an image forming apparatus, and more particularly to a developing device having an improved structure of bias voltage applying means of a developing sleeve.

[Prior art]

Conventionally, a belt or a developing sleeve has been used as a developer bearing member made of a non-magnetic hollow cylinder, and a magnet roller provided therein is used to convey the developer to the developing position due to the relative speed difference between the two. The device is known. A bias voltage is generally applied to the developing sleeve, and the polarity and magnitude of the bias voltage are appropriately selected to obtain various results including suppression and enhancement of developing characteristics and complete reversal of the developing electric field. ing.

In the developing device in which the magnet roller is fixed (or rotated) and the developing sleeve is rotated, the conductive brush is conventionally urged into contact with the non-image forming portion on the outer surface of the developing sleeve, and the conductive brush is used. Bias voltage is applied to the developing sleeve.

However, in such a conventional method, scattered toner or dust may adhere to the contact portion of the conductive brush and the developing sleeve to cause defective conduction, and an appropriate image may not be obtained.

In addition, for example, the jumping development method described in Japanese Patent Publication No. 41-9475 and the AC jumping development in which an alternating bias voltage is applied between the developing sleeve and the photosensitive drum as described in JP-A-55-18656-9. In the method, in order to cause the space transfer of the toner from the developing sleeve to the photosensitive drum by the electric force, and in order to perform the space transfer of the toner from the developing sleeve to the photosensitive drum, the developing sleeve is placed on the surface of the photosensitive drum. It is necessary to make it extremely close to (for example, about 100 μ to 500 μ) and to keep the excitement constant. However, when the method of bringing the conductive brush into contact with the outer surface of the developing sleeve to bring the developing sleeve into conduction as described above, conductive chips are generated due to the rubbing of the developing sleeve and the conductive brush, and the chips are extremely narrow. Since it enters the gap, a leak may occur at this portion, which causes a so-called bias drop phenomenon in which the bias voltage is not applied, and an appropriate image may not be obtained.

In order to improve such a phenomenon, JP-A-59-34562
Japanese Patent Laid-Open Publication No. 2005-242242 discloses a developing device in which a conductive brush for applying a bias voltage is rubbed against the inner surface of the developing sleeve (FIG. 5).

However, as the size and weight of the image forming apparatus have been reduced and the cost has been reduced in recent years, the development sleeve has been required to be lightweight and low in cost, and an aluminum material has been used in many cases.

In such a case, in the bias voltage applying method using the conductive brush, as the use progresses, the inner peripheral surface of the sleeve is abraded, chips are generated and grooves grow, and leakage of the bias voltage due to leakage of chips and the like. There has been a drawback in that a proper image cannot be obtained due to defective conduction due to the groove.

On the other hand, if the sleeve is made of a high-grade material, the sleeve may be in an unstable rotating state due to the load when moving in the developer pool when the developer is transported. , The developed image is disturbed.

[Purpose of device]

The object of the present invention is to eliminate the above-mentioned conventional drawbacks, reduce the driving load of the developer carrier, obtain stable rotation, expand the selection range of the material of the developer carrier, and develop reliable power. To provide a developing device that can be surely applied to the agent carrier.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, an electrophotographic copying machine using the jumping developing method will be described, but the developing method is not limited to this.

FIG. 3 is a schematic sectional view of an electrophotographic copying machine body embodying the present invention. Reference numeral 1 denotes a document placing table made of a transparent member, which reciprocates in the horizontal direction (left and right directions in the drawing). Reference numeral 2 denotes a short-focus small-diameter image-forming element array, and an original image placed on the original table 1 is slit-exposed on the photosensitive drum 3 via this element array. A charger 4 uniformly charges the photosensitive drum 3. An image of the uniformly charged drum 3 is exposed by the element array 2 to form an electrostatic image. Then, it is visualized by the developing device 5 according to the present invention.

On the other hand, the transfer paper P is fed onto the drum 3 by the paper feed roller 6 and the registration roller 7 which rotates at a timing so as to register with the image on the photosensitive drum 3, and then on the photosensitive drum 3 by the transfer charger 8. Toner image is transferred onto the transfer paper. After that, the transfer paper P is separated from the drum 3, guided by the guide 9 to the fixing device 10 to fix the toner image on the transfer paper, and then discharged onto the tray 12 by the paper discharge roller 11.

FIG. 4 is a sectional view showing details of the developing device. In this embodiment, development is performed by a jumping development method using a component developer. In the figure, 13 is a cylindrical developing sleeve made of a non-magnetic material such as stainless steel or aluminum, which is driven to rotate counterclockwise as indicated by an arrow in the figure. A magnet roller 14 is inserted in the hollow. In this embodiment, the magnet roller does not rotate. The magnetic toner 15 is attracted onto the developing sleeve 13 by the magnetic force of the magnet roller 14. The toner on the developing sleeve 13 is applied and adjusted to a thickness smaller than the gap between the magnetic blade 16 as a thickness regulating member and the opposing magnetic pole N ₁ provided on the magnet roller 14 in cooperation with each other. Next, the toner applied to the surface of the developing sleeve 13 adheres to the electrostatic latent image on the photosensitive drum 3 at a position facing the photosensitive drum 3 to be developed. Reference numeral 17 in the drawing denotes a housing which also serves as a hopper portion of the developing device.

By the way, the content of the magnetic powder in the developer to be used is because the toner image on the transfer paper is fixed to the transfer paper, so that the toner is bound to the transfer paper by means of heat or pressure. , I am naturally limited. In practice, the magnetic powder occupies 10 to 60% by weight of the toner particles, but the volume content of the magnetic powder in the toner particles is about 20% or less due to the difference in specific gravity between the resin and the magnetic powder. Since the volume ratio of the magnetic powder in the toner is very small, the toner behavior in the magnetic field is different from that of the magnetic powder alone.
It becomes difficult to form a long brush having a low density at the magnetic pole position.
Therefore, when the thickness of the toner layer on the sleeve 13 is regulated to several mm or less, the toner layer on the sleeve 13 is likely to be uneven and become uneven.

The non-uniformity of the toner layer on the support member is easily reproduced directly on the developed image. Further, since it is a dense toner layer, if the layer thickness varies, there is a risk that the toner is pressed against the surface of the photoconductor, which is an electrostatic layer holding member, and the toner agglomerates or damages the photoconductor. Therefore, in this sense, as a developing method using the one-component magnetic toner, it is necessary to form a uniform thin layer of toner on the sleeve 13.

Under such circumstances, in order to regulate the layer thickness of the toner on the surface of the sleeve 13, the magnetic blade 16, which is a thickness regulating member, must be brought very close to the surface of the sleeve. Incidentally, in this embodiment, the gap between the two is 250 μ, and the toner layer thickness is about 80 to 100 μ. Further, the toner coated on the surface of the sleeve 13 adheres to the latent image on the photosensitive drum 3 and is used for development, but the coating on the sleeve is a thin layer and the space of the toner from the sleeve to the drum by the electric force. In order to cause the transfer, the developing sleeve 13 is brought close to the surface of the photosensitive drum 3 (300 in this embodiment).
.mu.), and it must be held constant. In order to ensure such accuracy, the outer dimensions of the sleeve 13 are required to have mechanical accuracy in units of several tens of μ. Although not shown, an alternating bias voltage is applied between the sleeve and the drum in order to improve the image quality, as described in JP-A-55-18656-9.

FIG. 1 is a sectional view of a developing sleeve of the present invention, and FIG. 2 is an assembled exploded view of a conductive brush as a transmission member.

The magnet roller 14 of FIG. 1 has its shaft ends 18a and 18b directly supported and fixed to the housing 17 of the developing device. The sleeve 13 is rotatably supported by the developing device housing 17 via bearings 19 and 20 separately from the magnet roller 14. 21 and 22 are spacer rollers for forming a gap with the photosensitive drum, 23 is a flange,
Reference numeral 24 is a drive gear. Reference numeral 25 is a conductive brush and is made of a material having a spring property, for example, a phosphor bronze plate, and is provided with several claws such as 25a shown in FIG. 2 (3 or more are preferable for fixed installation. (4 pieces) are fixed to the inner peripheral surface of the sleeve. The leading end portion 25b of the conductive brush 25 comes into contact with the surface 26a of the conductive plate 26 as a power feeding portion for transmitting an alternating bias power source (not shown).

The contact portion between the leading end 25b of the conductive brush 25 and the conductive plate 26 is constantly urged by the spring property of the conductive brush 25 and abutted on the contact surface 26a with a constant pressure, and stable conduction can be obtained. Further, by selecting a material that is resistant to abrasion such as stainless steel or phosphor bronze plate as the material of the conductive plate 26, it becomes possible to prevent abrasion due to sliding.

FIG. 5 shows an explanatory view showing the position of a conventional conductive brush as a comparative example. The conductive brush 27 is in contact with the outer surface of the non-image forming portion of the developing sleeve 13. An alternating bias voltage is applied between the developing sleeve 13 and the photosensitive drum 3. In this case, the cutting dust generated by the rubbing between the conductive brush 27 and the developing sleeve 13 is sent to the developing unit along the rotation direction of the developing sleeve 13, and the photosensitive drum 3 and the developing sleeve 13 are separated from each other.
When the minute gap is reached, a leak occurs between the photosensitive drum 3 and the developing sleeve 13, and a phenomenon (bias drop) in which the alternating bias voltage is not applied occurs. Further, although it is a non-image forming portion, the contact portion between the conductive brush 27 and the developing sleeve 13 may be contaminated due to toner scattering.

On the other hand, in the present embodiment shown in FIGS. 1 and 2, since the contact portion between the conductive brush 25 and the conductive plate 26 is inside the sleeve, the risk of contamination of the contact portion by toner or dust is small. Further, since the material is strong against abrasion, the contact pressure can be increased, and more reliable conduction can be ensured.

In this embodiment, the jumping development using a one-component developer has been described, but it is naturally applicable to a developing device using a two-component developer. Further, as a matter of course, the present invention can be applied to a developing device using another developing method, for example, a magnetic brush developing method.

As described above, the simple structure of fixing the conductive brush to the developing sleeve and providing the conductive contact portion with the conductive plate, which is resistant to abrasion, inside the developing sleeve allows the conductive brush to be removed without being contaminated with toner, dust, etc. It is possible to suppress the chips caused by the movement as much as possible, which is effective in ensuring reliable conduction.

[Effect of device]

According to the present invention, the driving load on the developer carrier is reduced,
A sufficient and stable and reliable developing bias can be applied to the developer carrying member.

[Brief description of drawings]

1 is a sectional view of a developing sleeve of the present invention, FIG. 2 is an assembly diagram of a conducting portion of the present invention, FIG. 3 is a schematic sectional view of an electrophotographic apparatus, FIG. 4 is a sectional view of a developing apparatus, and FIG. FIG. 6 is a sectional view of a conventional inner peripheral contact type conductive brush, and FIG. 6 is a sectional view of a conventional outer peripheral contact type conductive brush. 13: development sleeve, 25: conduction brush, 26: conduction plate

Claims (1)

[Scope of utility model registration request] 1. A developing member having a power feeding portion for transmitting power from a developing bias source and a transmitting member for feeding power from a power feeding portion to a rotating developer carrier. In a developing device that applies a bias to develop an electrostatic image,
The developer carrying member is a cylindrical sleeve, the transmitting member is fixed to the cylindrical sleeve by contacting at least three points inside the cylindrical sleeve, and the power feeding portion is arranged inside the cylindrical sleeve and apart from the cylindrical sleeve. The developing device, wherein the contact point between the transmission member and the power feeding portion is inside the cylindrical sleeve.