JP2001027848A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a good image with satisfactory image density, and also, to suppress toner from scattering outside, in the case of carrying developer including the toner and carrier by a developer carrier into a developing area facing an image carrier and developing. SOLUTION: As for the developing device, a magnet member 11a with plural magnetic poles is fixed inside the developer carrier for carrying the developer 2 including the toner and the carrier into the developing area facing the image carrier 1. In this case, the volumetric packing ratio of the developer is controlled to be 5 to 40% in the developing area, and the magnetic poles N1 and N2 having the same polarity are adjacently arranged on the magnetic member 11a so as to be positioned facing the image carrier 1, and as for the magnetic poles, the peak of the vertical magnetic force lies in the developing area, and also, a difference between the mean value of the vertical magnetic force at the peak and the smallest vertical magnetic force between the magnetic poles is controlled to be within the extent of 1/ 10 to 1/3 of the mean value of the vertical magnetic force at the peak.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used for an image forming apparatus such as a copying machine or a printer, and more particularly, to a developer containing a toner and a carrier to a developing area facing an image carrier. In a developing device in which a magnet member having a plurality of magnetic poles is fixedly provided inside a developer carrier to be developed, and the toner in the developer is supplied to the image carrier in the above-described development area to perform development, the image carrier is provided. In addition to supplying a sufficient amount of toner to obtain an image having a sufficient image density, preventing the carrier from adhering to the image carrier, and preventing the toner image formed on the image carrier from It is characterized in that it is prevented from being scraped off by the developer and from scattering the toner to the outside.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, various developing devices have been used to develop an electrostatic latent image formed on an image carrier. As a device, a two-component developing system using a developer containing a toner and a carrier has been known in addition to a one-component developing system using only toner as a developer.

As a developing device using a developer containing a toner and a carrier as described above, a developing device as shown in FIG. 1 is generally used.

In this developing device, as shown in FIG. 1, a cylindrical developer carrier 11 is provided so as to be opposed to the image carrier 1 with a predetermined distance Ds therebetween. A plurality of magnetic poles N,
A magnet member 11a having S, N,... Is provided, and the developer 2 contained in the apparatus main body 10 is supplied to the surface of the developer carrier 11 by a developer supply member 12 such as a bucket roller. Was.

Further, the developer 2 supplied to the surface of the developer carrier 11 is held on the surface of the developer carrier 11 by the magnetic force of the magnet member 11a, and the developer carrier 11 is Rotate the developer carrier 1
1, the developer 2 is conveyed in a state of a magnetic brush,
After regulating the amount of the developer 2 conveyed by the regulating member 13, the developer 2 is guided to the developing area, and the toner in the developer 2 is transferred to the electrostatic latent formed on the image carrier 1. The electrostatic latent image was developed by supplying the electrostatic latent image to the image.

Here, in such a developing device, when the development is performed as described above, the carrier in the developer 2 adheres to the image carrier 1 and carrier fog occurs in the formed image. Conventionally, the magnetic force of the magnetic pole N in the portion of the magnet member 11a opposed to the image carrier 1 is increased so that the developer 2 is strongly attracted to the developer carrier 11.

However, when the magnetic force of the magnetic pole N in the portion facing the image carrier 1 is increased to strongly attract the developer 2 to the developer carrier 11, the magnetic brush of the developer 2 in the developing area is Becomes harder, so that toner existing inside the magnetic brush is hardly supplied to the electrostatic latent image formed on the image carrier 1, so that an image having a sufficient image density cannot be obtained, and the hard developer The toner supplied to the image carrier 1 is scraped off by the magnetic brush 2 to cause a problem that the formed image is blurred.

[0008]

SUMMARY OF THE INVENTION The present invention relates to the above-described problems in a developing device used for developing an electrostatic latent image formed on an image carrier in an image forming apparatus such as a copying machine or a printer. It is an object to solve the above.

That is, according to the present invention, a developer containing a toner and a carrier is supplied to a developing region opposed to an image carrier by a developer carrier provided with a magnet member having a plurality of magnetic poles fixed therein. In the developing area, a sufficient amount of toner is supplied to the image carrier when the toner in the developer is supplied from the developer carrier to the electrostatic latent image formed on the image carrier and development is performed. As well as
A good image having a sufficient image density can be obtained by preventing the carrier from adhering to the image carrier and suppressing the toner image formed on the image carrier from being scraped off by the magnetic brush of the developer. It is another object of the present invention to prevent toner from scattering outside.

[0010]

In order to solve the above-mentioned problems, the developing device according to the present invention carries a developer containing toner and a carrier to a developing area opposed to an image carrier. In a developing device in which a magnet member having a plurality of magnetic poles is fixedly provided inside the body, and the toner in the developer is supplied to the image carrier in the development area to perform development, the developer carrier The amount of the developer conveyed to the developing area is w (g / cm ² ), the bulk specific gravity of the developer is ρ (g / cm ³ ), and the distance between the opposed image carrier and the developer carrier in the developing area is When Ds (cm) is used, the bulk filling ratio (%) of the developer in the developing region determined by the following equation (1) is set to 5 to 40%, and the portion facing the image carrier is adjusted. Above magnet part The magnetic poles of the same polarity are provided adjacent to each other, and the peak of the perpendicular magnetic force at each of the same magnetic poles is present in the above-described developing region, and the average value of the perpendicular magnetic force of the peaks at the respective magnetic poles of the same polarity is the same as that of the magnetic pole. The difference ΔG from the minimum perpendicular magnetic force between the magnetic poles is set in a range of 1/10 to 1/3 of the average value of the peak perpendicular magnetic force.

Bulk filling rate (%) = [w / (ρ · Ds)] × 100 (1)

When the bulk filling rate of the developer in the developing region is set to 5 to 40% as in the developing device of the present invention, the amount of the developer guided to the developing region is generally guided to the developing region. The amount of the developer is smaller than the amount of the developer, so that the carrier is prevented from adhering to the image carrier, and the toner supplied to the image carrier is scraped off by the magnetic brush of the developer, so that the formed image is blurred. The occurrence is also suppressed. When the bulk filling rate is less than 5%,
The amount of the developer guided to the developing area becomes too small, so that an image having a sufficient image density cannot be obtained.

Further, when the same magnetic pole is provided adjacent to the magnet member at the portion facing the image carrier as described above, the vertical magnetic field between the same magnetic poles is generated by the repulsive magnetic force between the same magnetic poles. The magnetic force is reduced, the magnetic brush of the developer in the developing area becomes soft, and the toner in the developer is sufficiently supplied to the image carrier, so that an image having a sufficient image density can be obtained.

When the peaks of the perpendicular magnetic force due to the magnetic poles of the same polarity are respectively present in the developing area, the magnetic brushes softened between the magnetic poles of the same polarity on both sides of the magnetic poles as described above. The developer is strongly attracted to the developer carrier by the peak perpendicular magnetic force at the magnetic pole, and the toner is prevented from scattering outside, and the carrier adheres to the image carrier from the softened magnetic brush as described above. Even so, the carrier is strongly attracted to the magnetic pole on the downstream side in the transport direction of the developer and is collected, so that the carrier is prevented from adhering to the image carrier.

Further, the difference ΔG between the average value of the perpendicular magnetic force of the peak at each magnetic pole of the same polarity and the minimum perpendicular magnetic force between the magnetic poles of the same polarity is 1/10 to 1/10 of the average value of the perpendicular magnetic force of the peak. When the range is 1/3, the toner is sufficiently supplied from the magnetic brush of the developer between the magnetic poles of the same polarity to the image carrier, and the carrier is prevented from adhering to the image carrier. Will be done. That is,
When ΔG decreases and becomes smaller than 1/10 of the average value of the perpendicular magnetic force at the peak, the magnetic brush of the developer is strongly attracted to the developer carrier even between the magnetic poles of the same polarity, and the toner is transferred to the image carrier. , While ΔG
Becomes larger, and 1 / of the average value of the perpendicular magnetic force of the above peaks
If it is larger than 3, the binding force of the developer between the magnetic poles of the same polarity becomes very weak, and a large amount of carrier adheres to the image carrier. Will not be collected.

When development is performed by the developing device of the present invention, a sufficient amount of toner is supplied to the image carrier as described above, and the carrier is prevented from adhering to the image carrier, and The toner image formed on the carrier is prevented from being scraped off by the magnetic brush of the developer, so that a good image having a sufficient image density can be obtained, and the toner is prevented from scattering to the outside. You.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a developing device according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings.

In the developing device of this embodiment, FIG.
As shown in FIG. 1, a developer 2 containing a non-magnetic toner and a magnetic carrier is accommodated in a main body 10 of the apparatus, and is formed in a cylindrical shape so as to face the image carrier 1 with a required distance Ds. , And a magnet member 11a having a plurality of magnetic poles N, S,... Provided on the inner peripheral side of the developer carrier 11 is provided.
The developer 2 is held on the surface of the developer carrying member 11 by the magnetic force of.

Here, in the developing device of this embodiment, two magnetic poles N ₁ and N ₂ having the same polarity are provided adjacent to the magnet member 11a at a portion facing the image carrier 1, and the magnet member 11a is provided adjacent to the magnet member 11a. The peak of the perpendicular magnetic force at each of the magnetic poles N ₁ and N ₂ of the poles is made to be present in a developing region for supplying the toner in the developer 2 from the developer carrier 11 to the image carrier 1. The difference ΔG (= G _H −G) between the average value _GH of the peak of the vertical magnetic force at each of the magnetic poles N ₁ and N ₂ and the minimum vertical magnetic force _GL between the magnetic poles N ₁ and N _{2 of the} same polarity.
_L ) is 1/10 to 1 of the average value _GH of the peak perpendicular magnetic force.
/ 3 range.

The developer 2 is supplied to the developer carrier 11 by the developer supply member 12 provided in the apparatus main body 10, and the developer 2 is supplied by the magnetic force of the magnet member 11a. 11 on the surface,
The developer carrier 11 is rotated in a direction opposite to that of the image carrier 1, and the developer 2 is conveyed in a state of a magnetic brush by the developer carrier 11.

After the amount of the developer 2 conveyed by the developer carrier 11 is regulated by the regulating member 13, the developer 2 is transferred to the image carrier in the state of a magnetic brush by the developer carrier 11. 1 is directed to a development area opposite to the development area 1. Here, in the developing device of this embodiment, when the developer 2 is guided to the developing area by the developer carrier 11, the bulk filling rate of the developer 2 in the developing area is 5%.
４０40%.

Then, a developing bias voltage in which an AC voltage is superimposed on a DC voltage is applied from the developing bias power source 14 to the developer carrier 11 so that the developer carrier 11 and the image carrier 1 face each other. An oscillating electric field is applied to the area, and in this development area, the toner in the developer 2 is supplied from the developer carrier 11 to the electrostatic latent image formed on the image carrier 1 to perform development.

Here, when the development is performed as described above,
The toner in the developer 2 is easily separated from the carrier, so that the toner is sufficiently supplied to the portion of the electrostatic latent image formed on the image carrier 1 and that the carrier adheres to the image carrier 1. In addition, the toner image formed on the image carrier 1 is prevented from being scraped off by the magnetic brush of the developer 2, and a good image having a sufficient image density can be obtained. Spattering is also prevented.

[0024]

Next, a developing device according to an embodiment satisfying the conditions of the present invention will be described. The following experiments show that the developing device of this embodiment is superior to a developing device not satisfying the conditions of the present invention. Reveal by

(Experimental Example 1) In Experimental Example 1, a commercial copying machine (CF900 manufactured by Minolta Co.) was modified, and in the developing device, as shown in FIG. , The magnet member 11a has
Two magnetic poles N ₁ and N ₂ are provided adjacent to each other with an interval of 5.2 mm, and the magnetic poles N ₁ and N ₂ are provided in a developing area for supplying the toner in the developer 2 from the developer carrier 11 to the image carrier 1. The peaks of the perpendicular magnetic force due to the magnetic poles N ₁ and N ₂ were respectively present.

Here, with respect to the developing area, a developing bias voltage is applied to the developer carrier 11 from the developing bias power supply 14 while the image carrier 1 and the developer carrier 11 are stopped. The width of the portion where the toner adhered was measured. In the first experimental example, the width of the developing region was 6.5 mm.

In Experimental Example 1, the average value G _H of the peak of the perpendicular magnetic force by the magnetic poles N ₁ and N ₂ of the same polarity is set to 1000 Gauss (G). poles N _1, N of the average value G _H the same polarity peak
Difference is minimum vertical force G _L in between _{2 ΔG} (= G
_H - _GL ) is 50G, 100G, 200G, 300
G, 350G, and the value of ΔG / _GH is
As shown in Table 1 below, 1/20, 1/10, 1/5,
3/10 and 7/20.

As the developer 2, a resin-coated carrier obtained by coating ferrite with a resin and having an average particle diameter of 35 μm is used, and a negatively chargeable toner for CF900 having a weight average particle diameter of 8 μm is used. In this case, the carrier 2 and the toner were mixed, and the developer 2 having a toner concentration of 10% by weight was used. Incidentally, the bulk specific gravity ρ of this developer 2 was 2.01 g / cm ³ .

In this experimental example 1, while the image carrier 1 having a diameter of 100 mm is used, the developer carrier 11 having a diameter of 20 mm is used, and the image carrier 1 and the developer carrier are used. The distance Ds facing the body 11 is changed in the range of 0.20 to 0.50 mm, and the peripheral speed v1 of the developer carrier 11 and the peripheral speed v2 of the image carrier 1 are changed.
So that the ratio θ (= v1 / v2) becomes 1.8,
The image carrier 1 and the developer carrier 11 are rotated in opposite directions, and the amount of the developer 2 transported by the developer carrier 11 to the development area per unit area is 3 to 20 mg / c.
m ² , and the bulk filling rate of the developer 2 in the developing area was 3%, 5%, 10% as shown in Table 1 below.
%, 25%, 40%, and 45%.

Then, the initial surface potential Vo of the image carrier 1 is set to −550 V, and the surface potential Vir in the exposed portion of the electrostatic latent image is set to −50 V. −450 with respect to carrier 11
V DC voltage Vb and the frequency f is 3k
When applying an AC voltage composed of a rectangular wave having a frequency of 1: 1 and a duty ratio of 1: 1, the peak-to-peak value of the AC voltage corresponds to the interval Ds at which the image carrier 1 and the developer carrier 11 face each other. The value Vpp is changed in the range of 1000 to 2250 V so that an alternating electric field acting between the image carrier 1 and the developer carrier 11 becomes 5000 Vpp / mm to perform reversal development to form an image. did.

The image formed under each of the above conditions was evaluated for image density, carrier adhesion and blurring, and toner scattering was evaluated. The results are shown in Table 1 below.

Here, regarding the image density, the amount of toner adhered to the formed image portion is measured, and when the amount of toner is less than 0.5 mg / cm ² , ×, 0.5 mg / c
The case of m ² or more was indicated by ○.

Regarding the adhesion of the carrier, the formed image was visually evaluated, and the case where the carrier was attached was indicated by x, and the case where the carrier was not attached was indicated by ○.

Regarding blurring, the formed image is visually evaluated, and if a blurring has occurred, x is indicated.
The case where no fray occurred was indicated by ○.

Regarding toner scattering, the amount of toner scattering per 1000 sheets was determined, and the amount of toner scattering was 50 mg.
X when the number is more than / 1000 sheets, ○ when less than 50 mg / 1000 pieces
Indicated by

[0036]

[Table 1]

As a result, in the portion facing the image carrier ₁ , the peak of the perpendicular magnetic force at each of the magnetic poles N ₁ and N ₂ of the same polarity provided on the magnet member 11a exists in the developing area, and , The bulk filling rate of the developer 2 is in the range of 5 to 40%, and the average value _GH of the peaks of the perpendicular magnetic force in the magnetic poles N ₁ and N ₂ of the same polarity and the minimum between the magnetic poles of the same polarity are small. Difference Δ from the perpendicular magnetic force _GL
G is 1/10 to 1/1 / the average value _GH of the peak perpendicular magnetic force.
In the developing device of the embodiment satisfying the condition of the present invention, which falls within the range of 3, the toner having a sufficient image density is supplied by sufficiently supplying the toner to the portion of the electrostatic latent image formed on the image carrier 1. And the carrier is prevented from adhering to the image carrier 1 and the toner image formed on the image carrier 1 is prevented from being scraped off by the developer 2, and the toner is also prevented from scattering outside. It became so.

(Experimental Example 2) In Experimental Example 2, two magnetic poles N ₁ and N of the same polarity as the magnet member 11a in the portion facing the image carrier 1 in Experimental Example 1 described above.
_{In the case where 2} are provided adjacent to each other with an interval of 5.2 mm, as shown in FIG. 4, the position of the peak of the perpendicular magnetic force at the magnetic pole N ₁ located on the upstream side in the transport direction of the developer 2 is larger than the developing area. The distance from the developer 2 to the upstream side in the transport direction was 1 mm.

Other than that, in the same manner as in the above-mentioned Experimental Example 1, an image was formed by performing reversal development under each condition.
Evaluation of image density, carrier adhesion and blurring was performed, and toner scattering was evaluated. The results are shown in Table 2 below.

[0040]

[Table 2]

As a result, the bulk filling rate of the developer 2 in the developing region is within the range of 5 to 40%, and the average value G _H of the peak of the perpendicular magnetic force in each of the magnetic poles N ₁ and N ₂ of the same polarity. Difference Δ from perpendicular magnetic force _GL, which is minimum between the magnetic poles
G is 1/10 to 1/1 / the average value _GH of the peak perpendicular magnetic force.
Even within 3 range, the position of the peak of the vertical force in the magnetic pole N ₁ located on the upstream side in the transport direction of the developer 2 as described above, 1 mm in the conveying direction upstream side of the developer 2 the developing region When it came off, toner scattering occurred.

(Experimental Example 3) In Experimental Example 3, two magnetic poles N ₁ , N 2 having the same polarity as the magnet member 11 a in the portion facing the image carrier 1 in Experimental Example 1 described above.
_{In the} case where the magnetic poles ₂ are provided adjacent to each other with an interval of 5.2 mm, as shown in FIG. 5, the position of the peak of the perpendicular magnetic force at the magnetic pole N2 located on the downstream side in the transport direction of the developer 2, The distance from the developer 2 to the downstream side in the transport direction was 1 mm.

Other than the above, in the same manner as in the above-described Experimental Example 1, an image was formed by performing reversal development under each condition.
Evaluation of image density, carrier adhesion and blurring was performed, and toner scattering was evaluated. The results are shown in Table 3 below.

[0044]

[Table 3]

As a result, the bulk filling ratio of the developer 2 in the image area is in the range of 5 to 40%, and the average value _GH of the peak of the perpendicular magnetic force in the magnetic poles N ₁ and N ₂ of the same polarity is the same. Difference ΔG between the perpendicular magnetic force G _L and the minimum between the magnetic poles
Is 1/10 to 1/3 of the average value _GH of the peak perpendicular magnetic force.
Even within the range of the position of the peak of the vertical force in the magnetic pole N ₂ located downstream in the transport direction of the developer 2 as described above, the developing region in the transport direction downstream side of the developer 2 1
mm, carrier adhesion and toner scattering occurred.

Therefore, in order to suppress carrier adhesion and toner scattering, when two magnetic poles N ₁ and N ₂ having the same polarity are provided adjacent to the magnet member 11 a in a portion facing the image carrier ₁ , It was necessary that the position of the peak of the perpendicular magnetic force at each of the magnetic poles N ₁ and N ₂ of the same polarity exist in the developing region.

[0047]

As described in detail above, in the developing device according to the present invention, a magnet member having a plurality of magnetic poles is fixedly provided inside a developer carrying member for carrying a developer containing a toner and a carrier. In supplying the toner in the developer to the image carrier in the development area to perform development,
The bulk filling ratio of the developer in the developing region determined by the above formula (1) is set to 5 to 40%, and the same magnetic pole is provided adjacent to the magnet member at a portion facing the image carrier. The peak of the perpendicular magnetic force at each magnetic pole of the pole exists in the developing region, and the difference ΔG between the average value of the perpendicular magnetic force of the peak at each magnetic pole of the same pole and the perpendicular magnetic force that is minimized between the magnetic poles of the same polarity is Since the average value of the peak perpendicular magnetic force is in the range of 1/10 to 1/3, a sufficient amount of toner is supplied to the image carrier, and
The carrier is prevented from adhering to the image carrier, and the toner image formed on the image carrier is prevented from being scraped off by the magnetic brush of the developer, and the toner is prevented from scattering outside. .

As a result, in the developing device according to the present invention, a satisfactory image having a sufficient image density and no carrier fogging or blurring can be obtained, and the toner is scattered from the developing device to the outside. The inside of the forming apparatus is also prevented from becoming dirty.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a conventional developing device.

FIG. 2 is a schematic explanatory diagram of a developing device according to an embodiment of the present invention.

FIG. 3 shows a state in which the peaks of the perpendicular magnetic force at two adjacent magnetic poles N ₁ and N ₂ of the same polarity provided on the magnet member at the portion facing the image carrier in the experimental example 1, respectively, in the developing region. FIG.

FIG. 4 shows a magnetic pole located on the upstream side in the developer transport direction among two adjacent magnetic poles N ₁ and N ₂ provided on the magnet member at a portion facing the image carrier in Experimental Example 2. FIG. 7 is a schematic diagram showing a state in which the position of the peak of the perpendicular magnetic force due to N ₁ is located on the upstream side in the developer conveyance direction from the development region.

FIG. 5 shows a magnetic pole located on the downstream side in the developer conveyance direction among two adjacent magnetic poles N ₁ and N ₂ of the same polarity provided on the magnet member at a portion facing the image carrier in Experimental Example 3. FIG. 9 is a schematic diagram showing a state in which the position of the peak of the perpendicular magnetic force due to N ₂ is located on the downstream side in the developer conveyance direction from the development area.

[Explanation of symbols]

Pole adjacent the poles provided on the magnet member in one image carrier 2 developer 11 developer carrying member 11a magnet member N _1, N ₂ image carrier portion facing the

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Yoshiyuki Iguchi 2-3-13 Azuchicho, Chuo-ku, Osaka-shi Osaka International Building Minolta Co., Ltd. (72) Yoshiyoshi Shimizu 2--3, Azuchicho, Chuo-ku, Osaka-shi No. 13 Osaka International Building Minolta Co., Ltd. (72) Inventor Yoshio Sakakawa 2-3-13 Azuchicho, Chuo-ku, Osaka City Osaka International Building Minolta Co., Ltd. F-term (reference) 2H031 AC19 AC20 AC30 AD09 BA04 BA09 CA11

Claims (1)

[Claims] And a magnet member having a plurality of magnetic poles fixedly provided inside a developer carrier for transporting a developer containing a toner and a carrier to a development region facing the image carrier. In the developing device for performing the development by supplying the toner in the developer to the image carrier, the amount of the developer conveyed to the development area by the developer carrier is set to w.
(G / cm ² ), the bulk specific gravity of the developer is ρ (g / cm ³ ),
When the distance between the image carrier and the developer carrier facing each other in the development area is Ds (cm), the bulk filling rate (%) of the developer in the development area obtained by the following equation (1) is 5 to 5. At the same time, a magnetic pole of the same polarity is provided adjacent to the magnet member at a portion facing the image carrier, and the peak of the perpendicular magnetic force at each magnetic pole of the same polarity is within the developing area. And the difference ΔG between the average value of the peak perpendicular magnetic force of each magnetic pole of the same polarity and the minimum perpendicular magnetic force between the magnetic poles of the same polarity is 1/10 to 1/1/1 of the average value of the peak perpendicular magnetic force. 3. The developing device according to claim 1, wherein Bulk filling rate (%) = [w / (ρ · Ds)] × 100 (1)