JP2986511B2 - Developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to supplying a toner to a rotatable toner carrier, carrying the toner on the surface of the carrier and carrying the toner, and The present invention relates to a developing device for visualizing an electrostatic latent image formed on a latent image carrier by a toner carried on the toner carrier in a development area where the toner carriers are opposed to each other.

[Conventional technology]

In an image forming apparatus such as an electronic copying machine, a laser printer, or a facsimile that obtains a recorded image by visualizing an electrostatic latent image formed on a latent image carrier, a toner externally added with an auxiliary agent as necessary, It has been well known to employ a developing device of the above-mentioned type using a one-component developer.

This type of developing device has the advantage that the maintenance of the device can be simplified and the structure of the device can be reduced, as compared with a developing device using a two-component developer containing a carrier.

However, in a conventional developing device using a one-component developer, it was difficult to transport a sufficient amount of toner required to form a high-quality visible image of a predetermined density to a developing area. .

Therefore, there has been proposed a developing device in which irregularities are formed on the surface of a toner carrier, and the irregularities are filled with and carried by toner to increase the amount of toner conveyed to a developing area. However, according to this configuration, although the amount of toner that can be conveyed increases, a large amount of insufficiently charged toner is contained in the conveyed toner, so that the image quality of the visible image formed by this may be reduced. There is.

[Problems to be solved by the invention]

An object of the present invention is to provide a developing device which eliminates the above-mentioned conventional disadvantages.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a developing device of the type described at the outset, wherein the entire surface of the toner-carrying surface carrying the toner used for visualizing the electrostatic latent image has a charge holding property. And a charge applying means for selectively applying an electric charge to the surface of the toner carrier and forming a minute closed electric field in the vicinity of the surface. I do.

At this time, the charge applying means is constituted by a plurality of electrodes which are arranged close to the surface of the toner carrier and spaced apart from each other by a minute distance, and which generate a discharge to the toner carrier by applying a predetermined voltage. It is advantageous.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic view showing an example of a developing device according to the present invention, and first, its overall configuration and operation will be clarified.

In FIG. 1, a drum-shaped photoconductor 1, which is an example of a latent image carrier, is driven in the direction of arrow A, and a developing device 2 is provided to face the photoconductor. In the toner container 3 of the developing device 2, a powdery non-magnetic toner 4, to which an auxiliary agent is added as necessary, that is, a non-magnetic one-component developer is stored. The specific volume resistivity of the toner is, for example, 10 ⁷ to 10 ¹² Ω.
・ It is about cm. On the front and rear side plates of the toner container 3, a developing roller 5 is supported in a state where a part thereof is exposed from the opening of the container. The developing roller 5 is rotated clockwise in FIG. You. The developing roller 5 is an example of a toner carrier, but a belt-shaped toner carrier may be used instead of the roller 5. Further, a toner supply roller 6 as an example of a toner supply member is supported on the front and rear side plates of the toner container 3, and the roller 6 is driven to rotate counterclockwise, for example, while being in contact with the developing roller 5.

The toner 4 in the toner container 3 is conveyed to the toner supply roller 6 while being stirred by the agitator 7 rotating clockwise, and then supplied to the developing roller 5 by the roller 6. At the time of this supply, the toner is frictionally charged to a predetermined polarity, in this example, a positive polarity opposite to the electrostatic latent image of the photoconductor 1,
It is electrostatically attached to the peripheral surface of the developing roller 5 and is carried on the developing roller 5 (see FIG. 2). The configuration and operation related to this will be described later in detail.

As described above, the toner supplied and carried on the peripheral surface of the developing roller 5 is conveyed by the rotation of the roller 5, and is leveled by the doctor blade 8, which is an example of a layer thickness regulating member, and its thickness is regulated. Next, the toner is conveyed to a developing area 9 where the photoconductor 1 and the developing roller 5 are opposed to each other, where the toner is electrostatically transferred to an electrostatic latent image formed on the photoconductor 1,
The latent image is visualized. The visible image formed on the photoreceptor 1 is transferred to a transfer paper (not shown) and fixed on the transfer paper by a fixing device. In FIG. 1, reference numeral 70 denotes a charger for charging the photoreceptor 1, reference numeral 71 denotes a light image exposing the photoreceptor surface after charging, and reference numeral 72 denotes a visible image formed on the photoreceptor surface. This is a transfer charger for transferring the image to the printer.

A bias voltage is applied to the developing roller 5 and the toner supply roller 6 by a power supply 50, and the conductive support that supports the photosensitive layer of the photosensitive member 1 is grounded.

As described above, the illustrated developing device 2 supplies the toner to the toner carrier configured as the developing roller 5 that is driven to rotate, carries the toner on the surface of the toner carrier, and conveys the toner. The electrostatic latent image formed on the latent image carrier is visualized by the toner carried on the toner carrier in the developing region 9 where the latent image carrier and the toner carrier are opposed to each other.

The above-described configuration itself is no different from a conventional developing device. In such a conventional developing device, a predetermined amount of charged toner sufficient to form a high-quality visible image is transported to a developing area. Was difficult. In order to eliminate such disadvantages, the illustrated developing device is configured as follows.

First, as shown in an enlarged manner in FIG.
It has a conductive base made of a conductive roller 10 of a metal such as aluminum, for example, and a dielectric 32 laminated on the entire surface thereof. On the other hand, on the upstream side of the toner supply roller 6 in the rotation direction of the developing roller 5 and on the downstream side of the developing area 9, a conductive discharging roller 33 which is an example of a discharging unit is provided.
Charge applying means 34 are sequentially arranged in the rotation direction of the developing roller 5.

The charge removing roller 33 rotates while contacting the developing roller 5,
An AC voltage is applied by an AC power supply 35 to remove the charge on the surface of the developing roller 5 passing through the developing area 9 and to scrape off the residual toner. The charge removing roller 33 is made of, for example, a conductive foam, conductive rubber, or metal. Instead of the charge removing roller 33, a charge removing means such as a blade may be used, and an AC voltage may be applied to the charge removing means so that the blade is brought into contact with the surface of the developing roller 5.

On the other hand, as shown in FIG. 1 and FIG. 3, the charge applying means 34 is arranged at a predetermined interval in the axial direction of the developing roller 5, and the tip thereof is on the surface of the developing roller 5, for example, about 200 μm. Numerous needle-shaped electrodes 5 that are close to each other with an interval d1
The base ends of these electrodes 51 are fixed in a comb shape while being embedded in the support member 52. The support member 52 is fixed to the toner container 3 via a bracket. electrode
Numeral 51 is made of, for example, a conductive material such as stellenless or other metal, and the diameter d2 of the tip and the distance d3 between the electrodes are set to, for example, about 200 μm. The base end of each electrode 51
The power supply 50 described above is electrically connected to each other through a conductor 53.
Is configured to be applied with a voltage by another power supply 37 connected thereto. The power supply 37 is an example of a voltage applying means for applying a predetermined voltage to the electrode 51. In this case, in this example, a pulse-like alternating voltage as shown in FIG. Is applied to each electrode 51, and the polarity thereof is negative, which is opposite to the charging polarity of the toner. With such a configuration, the developing roller portion which has been subjected to the charge removing operation by the charge removing roller 33 and from which the residual toner has been removed is used as an electrode.
When facing the electrode 51, a corona discharge is generated by the above-mentioned high voltage applied to the electrodes 51, and a corona ion flow is directed to the developing roller 5, and the dielectric 32 on the surface thereof has a predetermined polarity, in this example, a negative polarity. Charge. At this time, the developing roller 51 is rotating, and the respective electrodes 51 are shown in FIG.
And the electrodes 51 are separated by d3 from each other, so that the surface of the developing roller 5 passing through the electrodes 51 has an infinite number of dots as shown by broken lines in FIG. A large number of charges are applied so as to be said. As described above, the electrode 51 selectively applies a charge to a portion of the surface of the developing roller 5 where a discharge is generated. Here, assuming that a surface portion of the developing roller 5 to which electric charge is applied is represented by X1, and a portion to which substantially no electric charge is applied is represented by X2, the surface potentials of both portions are greatly different from each other, for example, there is a potential difference of about 250V. Innumerable minute charge patterns X1 are formed. For this reason, in the vicinity of the developing roller surface, adjacent portions having different charging potentials
A small closed electric field (microfield) is generated between X1 and X2. That is, as schematically shown in FIG. 6, in the space near the surface of the developing roller 5, between the developing roller portion X1 that has given an electric charge and the portion X2 where no electric charge is given substantially, An electric force line E represented by a large number of arc-shaped lines is formed. At this time, the charged portion X1 and the non-charged portion X2 are adjacent to each other with a very small area, so that the intensity of each minute closed electric field is greatly increased by the edge effect or the peripheral electric field effect. Thus, an electric field having a large electric field gradient is formed near the surface of the developing roller 5.

On the other hand, as described above, the toner 4 supplied to the developing roller 5 by the toner supply roller 6 has a predetermined polarity due to friction with both rollers 5, 6 as shown in FIG. Strongly triboelectrically charged. The illustrated toner supply roller 6 includes the core member 14 to which the voltage is applied by the power supply 50 and the foamed body 15 of, for example, urethane resin laminated around the cored body 15 as described above. A brush or the like can also be used. As described above, the toner 4 charged to the positive polarity is supplied to the developing roller 5. At this time, a large number of minute charge patterns are formed on the surface of the developing roller 5 as described above, thereby forming a minute closed electric field. Therefore, the toner is attracted and carried on the developing roller 5 by the electric field. As described above, since the intensity of the electric field is strong and the toner is strongly charged, a large amount of toner having a high charge is carried on the developing roller 5.

The toner thus carried passes through a doctor blade 8 made of, for example, urethane resin, and its layer thickness is regulated. In this step, even if the toner having a small charge amount is mixed in the carried toner. Such toner is removed by the contact pressure with the doctor blade 8, so that only the toner having a large charge amount is conveyed to the developing area 9 in a large amount while being strongly held by the minute closed electric field. Visualize the image. For example, in order to prevent background contamination of the visible image and increase its sharpness, 8 to 15 μc /
g as charged 0.6 to 2.0 mg / cm ^2, preferably 0.8 to 1.
A large amount of toner of ^{2 to} 1.2 mg / cm ² can be conveyed to the development area 9. Therefore, even if the toner is black or other chromatic colors, the quality of the visible image can be improved. In the developing area 9, the lines of electric force from the developing roller 5 move toward the electrostatic latent image on the photoconductor 1,
The holding power of the toner on the developing roller is weakened, and the latent image can be effectively visualized.

The surface of the developing roller 5 that has passed the developing area 9 is discharged again by the discharging roller 33, and then the charge applying means is again provided.
As described above, the electric charge is applied by the transfer roller 34, and the toner is carried to the developing area 9 while carrying the toner.

If charge is always applied to the same portion of the developing roller by each electrode 51, the charge removing means such as the charge removing roller 33 can be omitted. The portion X1 where the charge is applied to the developing roller 5, that is, the size, shape and pitch of the charge pattern can be appropriately set in consideration of the amount of toner to be conveyed to the developing region and other conditions, and are shown in FIG. As described above, the diameter D and the pitches P and P1 are, for example, 100 μm to 5 μm.
It is about 00 μm. Such values include the diameter d2 of each electrode 51, the interval d3, the interval d1 between the electrode tip and the developing roller 5, the
, The voltage application time T (the fourth
(A), the surface linear velocity (peripheral velocity) of the developing roller 5 and the like can be determined as appropriate. For example, if the frequency of the alternating electric field applied to the electrode 51 is f (Hz), its cycle is T (sec), and the peripheral speed of the developing roller 5 is V (mm / sec), these are The relationship between the pattern X1 and the pitch P (mm) is represented by T (sec) = P (mm) / V (mm / sec) or P (mm) = V (mm / sec) / f (l / sec). For example, when V = 100 (mm / sec), if it is desired to obtain a charge pattern X1 having a density of P = 400 (μm), f = 100 / (400 × 10 ⁻³ ) = 250 (Hz ) May be applied to the electrode 51. Further, in order to set P in the range of 0.1 mm to 0.5 mm, it is sufficient to set 2 (mm) × V ≦ f ≦ 100 (mm) × V.

In this manner, the shape, pitch, and size of the charge pattern X1 can be set to desired values that meet the requirements of each developing device.

The voltage applied to the electrode 51 may be, in addition to the voltage shown in FIG. 4 (a), a voltage obtained by superimposing a direct current on an alternating voltage as shown in FIG. 4 (b). On the surface of the roller 5, a charge pattern having a difference in surface potential corresponding to the high potential portion (T _H ) and the low potential portion (T _L ) is formed, so that a large number of minute closed electric fields can be generated.

Further, instead of the alternating voltage as shown in FIGS. 4A and 4B, a DC, AC, or DC superimposed voltage may be constantly applied to the electrode 51. A charge pattern X1 extending in the circumferential direction of the developing roller 5 is formed on the dielectric 32 as shown by a broken line in FIG.

In each of the above-described embodiments, if the resistance value of the surface of the developing roller is low, the charge is likely to leak, the charge cannot be held, the electric field strength of the minute closed electric field is weakened, and the toner holding force is reduced. , The dielectric 32 on the developing roller surface
Volume resistivity of 10 ⁹ Ω
・ It is desirable to set it to cm or more.

Instead of the dielectric 32, a photosensitive layer (photoconductive layer) that is insulative in the dark and that is conductive when exposed to light may be laminated on the surface of the conductive roller 10. Even if such a developing roller is used, the charge can be selectively applied by the charge applying means 34. Further, as the charge removing means for the developing roller, a lamp for irradiating the photosensitive layer with light, a corona discharger, or the like can be used.

In short, as the toner carrier, a carrier that has a charge holding property on the entire surface carrying the toner to be used for visualizing the electrostatic line image is used, and selectively with respect to the surface of the toner carrier. What is necessary is just to provide the charge provision means which supplies a charge and forms a minute closed electric field near the said surface. Further, in this example, the charge applying means is provided with a plurality of electrodes which are arranged close to the surface of the toner carrier and spaced apart from each other by a minute distance, and which generate a discharge to the toner carrier by applying a desired voltage. Since it is configured, there is no danger of damaging the electrode or the toner carrier. The same configuration can be applied when the toner carrier is formed of a belt.

Further, in each of the above-described embodiments, the developing device using a one-component developer of a non-magnetic toner particularly suitable for color development is exemplified. However, the present invention comprises a magnetic toner to which an auxiliary agent is externally added as necessary. The present invention can be applied to a developing device using a one-component developer.

Further, it is also possible to adopt a structure in which charge having the same polarity as that of the toner is selectively applied to the surface of the toner carrying member by the charge applying means, and the toner is carried by a minute closed electric field formed by this.

〔The invention's effect〕

According to the configuration of the first aspect, a toner having a high charge amount is transported to a required amount of the developing area, and a visible image having a desired density can be formed.

According to the second aspect of the present invention, the charge applying means can form a desired charge pattern on the toner carrier, and its electrodes are not in contact with the toner carrier. There is no danger of damaging the electrodes or the electrodes.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a developing device, FIG. 2 is an explanatory view schematically showing toner particles in an enlarged manner, and FIG. 3 is an enlarged view of a charge applying means viewed from the left side of FIG. FIGS. 4 (a) and 4 (b) are diagrams illustrating modes of voltages applied to the electrodes, FIG. 5 is an explanatory diagram showing a charge pattern formed on the developing roller, and FIG. FIG. 7 is an explanatory diagram showing electric lines of force of a minute closed electric field formed near the surface, and FIG. 7 is an explanatory diagram similar to FIG. 5, showing another embodiment of the charge pattern. 2 ... developing device, 4 ... toner, 9 ... developing area 34 ... charge applying means, 51 ... electrodes

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Naoki Iwata 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (72) Inventor Yuichi Ueno 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Noriyuki Kimura 1-3-6 Nakamagome, Ota-ku, Tokyo, Japan Ricoh Co., Ltd. (56) References JP-A-4-27984 (JP, A) Patent 2911996 (JP, B2) (58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 15/08

Claims (2)

(57) [Claims] 1. A method according to claim 1, further comprising the step of supplying toner to a rotatable toner carrier, carrying the toner on the surface of the carrier, and transporting the toner. In a developing area where the latent image carrier and the toner carrier are opposed to each other, In a developing device for visualizing an electrostatic latent image formed on a latent image carrier by toner carried on a toner carrier, the developing device is used for visualizing the electrostatic latent image as the toner carrier. Applying means for using a carrier having a charge retaining property on the entire surface carrying the toner, selectively applying a charge to the surface of the toner carrier, and forming a minute closed electric field near the surface. A developing device comprising: 2. The method according to claim 1, wherein the charge applying means is arranged in close proximity to the surface of the toner carrier and arranged at a small interval from each other, and a predetermined voltage is applied thereto to generate a discharge to the toner carrier. The developing device according to claim 1, wherein: