JPH0815989A - Developing roller in image forming device - Google Patents

Abstract

PURPOSE:To surely peel developer and to prevent the developer from deteriorating and scattering by making a magnetic flux density becomes zero in the area on the magnet roller corresponding to the peeling area of the developer. CONSTITUTION:The developing roller 4 is constituted so that different plural magnetic poles S1, N1, S2, S3 and N2 are arranged in this order in the peripheral direction inside the magnet roller 3 disposed in still state at the inside of the rotating sleeve roller 2. The peeling area B of the carrier is formed between the two magnetic poles S2 and S3 among the poles. The device is composed that the magnetic flux density of the peeling area B substantially becomes 0 Gs. Thus, the adverse phenomenon that the carrier after passing the peeling area B continues stuck on the developing roller is eliminated. The magnetic flux density is adjusted to 0 Gs, by setting the height of the soft iron electromagnetic yoke and the electromagnetic coil, the space between the poles S2 and S3 for magnetizing, the current largeness and the shapes after various considerations in taking the above into account.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing roller for use in an image forming apparatus such as an electrostatic photocopier, which has a magnet roller inside a sleeve roller and supplies a developer to a photosensitive member. .

[0002]

2. Description of the Related Art Conventionally, a developing device used in this type of image forming apparatus is a one-component type developer consisting only of a magnetic toner as a developer, and a two-component type mixture of a non-magnetic toner and a magnetic carrier. The developing roller that supplies the developer to the photoconductor, the stirring roller that stirs the developer, the supply roller that supplies the developer to the developing roller, and the cutting edge that regulates the developer adsorbed on the developing roller It has a plate and a sensor for detecting the toner concentration.

By the way, in the developing device used in the image forming apparatus as described above, the developing roller is conventionally rotated by the magnet roller 01 and the magnet roller 01 in the counterclockwise direction as shown in FIG. It is composed of a non-magnetic sleeve 02 that is externally fitted in this way. The magnet roller 01 has a plurality of magnetic poles N1, N2, S1, S2, S3 for supplying the developer to the photoconductor 03. Each of the plurality of magnetic poles has a function of adsorbing and transporting the developer, and forming a magnetic brush in a state where the developer stands in a portion near the photoconductor 03. The magnetic flux density distribution is as shown in FIG. 6, and the developer is peeled off at the lower right portion of the developing roller in the figure, that is, the portion 04 corresponding to the opposite side of the S1 magnetic pole. It is composed. Specifically, by arranging the same magnetic poles S2 and S3 next to each other, a configuration is adopted in which the magnetic flux distribution is zero between both S magnetic poles.

[0004]

However, as described above,
Even if the magnetic flux distribution in the developer peeling area 04 is set to 0, the S1 magnetic pole exists on the opposite side of this area.
Due to the influence of the magnetic poles, a magnetic field 05 (N-pole or S-pole) always tends to be always formed in the developer peeling area, as shown in FIG. The developer cannot be peeled off satisfactorily, and as a result, the developing roller continues to operate with the developer attached forever. Therefore, for example, in the case of a two-component type developer, the charge amount decreases as the carrier deteriorates, and desirable toner adhesion cannot be expected. In any case, there is a drawback that the developer scatters or an image defect occurs. It was

Therefore, the present invention was developed in view of the above-mentioned drawbacks of the conventional structure. By eliminating the magnetic field generated in the peeling area of the developing roller, the magnetic attraction force to the developer in this peeling area is substantially increased. It is an object of the present invention to provide a developing roller in an image forming apparatus that can completely remove the toner by setting it to 0, thereby effectively preventing the scattering of the developer and the image defect.

[0006]

In order to achieve the above object, the developing roller in the image forming apparatus of the present invention has a magnet roller inside the sleeve roller, and supplies the developer to the photoconductor. In the developing roller of
An area of the magnet roller corresponding to a portion where the developer is peeled off after being supplied to the photoconductor is substantially 0 gauss.

[0007]

In the developing roller in the image forming apparatus of the present invention configured as described above, since the developer peeling area of the magnet roller is substantially 0 gauss, the developer is reliably peeled. As in the conventional case, the phenomenon that the developer continues to adhere to the developing roller forever is eliminated. Specifically, with a two-component developer, there is no deterioration of the carrier,
It maintains a preferable amount of charge and enables good toner adhesion.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 is a schematic cross-sectional view showing a structure in the vicinity of a developing portion in an image forming apparatus such as an electrostatic photocopier having a developing device using a developing roller according to the present invention. ing.

In the electrostatographic copying machine of this embodiment, as shown in FIG.
As shown in FIG. 5, the photoconductor 1 is horizontally installed inside the main body of the copying machine, and the developing roller 4 in which the magnet roller 3 is statically provided inside the rotating sleeve roller 2, the toner and the carrier. A stirring rotor 5 for mixing the above into a developer and a supply roller 6 for supplying the developer stirred by the stirring rotor 5 to the developing roller 4 are built in the developer accommodating case 7. A spike-cutting member (spike plate) 8 that regulates the height of the spikes of the developer on the developing roller 4, and the excess developer after the spike-cutting is diverted above the supply roller 6 to provide a toner replenishing device. A partition plate 10 for returning the toner to the toner replenishment section from 9 is provided, and a rectifying plate 11 is provided on the partition plate 10 at a predetermined interval in the rotation axis direction of the supply roller 6, and Plate 11 is toner More flow-down direction downstream side deviate to one side of the rotational axis direction is provided.

A toner concentration sensor S for driving the toner replenishing device 9 based on the detection of the concentration of the excessive developer is provided in the vicinity of the ear cutting member 8 and agitates the developer dropped from the partition plate 10. In addition, the developer is formed so as to be supplied to the stirring rotor 5 side while being transported toward the other end side in the rotation axis direction.

The partition plate 10 has a chevron shape when viewed from the direction of the rotation axis of the supply roller 6, and the surplus developer cut off by the ear cutting member 8 while being pushed up by the supply roller 6 is moved upward or rearward. Upstream swash plate part 10 to be refluxed
a and a swash plate portion on the downstream side that recirculates the developer that has passed over the swash plate portion 10a toward the stirring rotor 5 obliquely rearward and downward.
Equipped with 10b.

In FIG. 5, reference numeral 12 denotes a toner replenishing roller arranged at the lower end of the toner replenishing device 9, and supplies the toner in the toner replenishing device 9 to the stirring rotor 5.

As shown in FIG. 5, the developing roller 4 has a plurality of different magnet rollers 3 (five in the example shown in the drawing, but not shown) disposed inside the rotating sleeve roller 2 in a stationary state. There are various numbers of magnetic poles S1, N
1, S2, N2, S3 are arranged in this order in the circumferential direction, and two magnetic poles S2 and S3 among these magnetic poles are arranged.
Is formed in the peeled region B of the carrier.

The separation area B is formed to have substantially zero gauss as shown in the explanatory view showing the distribution of the magnetic flux density in FIG. As a result, the bad phenomenon that the carrier continues to adhere to the developing roller 4 even after passing through the peeling area B is improved, and the carrier is not subjected to magnetic attraction at all in the peeling area B.
It is reliably separated from the developing roller 4. Therefore, carrier deterioration and toner scattering are eliminated, and a clear image can be obtained.

Next, a method of manufacturing the magnet roller 3 will be described. The magnet roller 3 is integrally formed using a known material, for example, a mixture of magnetic powder and synthetic resin powder.

FIG. 2 is an enlarged cross-sectional view of a magnetizing device for the magnet roller 3 formed as described above. The magnetizing device 13 causes the magnet roller 3 to move as shown in FIG.
A magnetic field is magnetized at five points at the same time, and a region B of substantially 0 gauss is formed between S2 and S3. Specifically, the same number of soft iron electromagnetic yokes and electromagnetic coils are provided corresponding to the positions and the numbers of the plurality of magnetic poles. As shown in this figure, the soft iron electromagnetic yokes 14a and the electromagnetic coils 14b are A portion for magnetizing the N1 pole on the magnet roller 3, an electromagnetic yoke 15a made of soft iron
The electromagnetic coil 15b is a portion for magnetizing the S1 pole on the magnet roller 3, the soft iron electromagnetic yoke 16a and the electromagnetic coil 16b are portions for magnetizing the N2 pole on the magnet roller 3, and the soft iron electromagnetic yoke 17a and the electromagnetic coil 17b are magnets. Laura 3
The S3 pole is magnetized, and the soft iron electromagnetic yoke 18a and the electromagnetic coil 18b are the magnetized roller 3 magnetized with the S2 pole.

The soft iron electromagnetic yoke 19a and the electromagnetic coil
Reference numeral 19b is an N pole or an S pole, which is provided to make the space between the S2 pole and the S3 pole, which is the separation area B of the magnet roller 3, substantially 0 gauss, and magnetizes the S1 pole. At this time, the magnetic field lines of the N pole generated in the peeled region B under the influence of the S1 pole are regulated. As shown in FIG. 3, the magnetic field lines are regulated by changing the magnetic field lines of the N pole generated in the separation area B to the electromagnetic yoke 19a made of soft iron and the electromagnetic coil.
It is done by repulsing at 19b.

This soft iron electromagnetic yoke 19a and electromagnetic coil 19
By taking into consideration various factors such as the height of b, the distance between the magnetized poles S2 and S3, the magnitude and shape of the current, it is possible to optimally set the region of substantially 0 gauss.

In FIG. 2, 20 is a magnetic path yoke for connecting the magnetic paths of the respective electromagnetic yokes, and 21 is a resin spacer for supporting the magnet roller 3.

In this way, the magnet roller 3 after formation is formed.
Are housed in a magnetizing device 13, and magnetic poles N1, N2, S1, S2, S3 corresponding to respective positions on the outer periphery thereof are magnetized, and in addition, the substantially 0 gauss region is also formed. As shown in FIG. 5, the magnetized magnet roller 3 is housed and fixed in the sleeve roller 2 after a shaft 22 made of stainless steel, for example, is press-fitted.

The magnet roller 3 is of a fixed type in the illustrated example, but is not necessarily limited to this structure, and a rotary type can also be used.

Further, although the magnetic poles are provided at five places and the arrangements thereof are also arranged in the order of S1, N1, S2, S3 and N2, various different forms are adopted also in this point. Needless to say.

[0023]

As described above, according to the present invention, the area of the magnet roller corresponding to the developer peeling area is substantially zero.
Since it is Gaussian, unlike the conventional structure, in the developer peeling area of the developing roller, reliable and good peeling of the developer can be performed, and as a result, undesired phenomena such as deterioration of the developer and reduction of the charge amount. Can be prevented well, there is no scattering of the developer,
It also enables the formation of clearer images.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a magnetic flux density distribution of a developing roller according to an embodiment of a developing roller and its manufacturing method in an image forming apparatus of the present invention.

FIG. 2 is a sectional view of a magnetizing device for manufacturing the developing roller, showing an embodiment of the developing roller and the manufacturing method thereof in the image forming apparatus of the present invention.

FIG. 3 is a conceptual diagram of a magnetizing device for manufacturing the developing roller, showing an embodiment of the developing roller and its manufacturing method in the image forming apparatus of the present invention.

FIG. 4 is a schematic cross-sectional view of a developing device using the developing roller, showing an embodiment of the developing roller and the manufacturing method thereof in the image forming apparatus of the present invention.

FIG. 5 is a partially enlarged cross-sectional view of the vicinity of the developing roller, showing an embodiment of the developing roller and the manufacturing method thereof in the image forming apparatus of the present invention.

FIG. 6 is an explanatory diagram showing a magnetic flux density distribution of a conventional developing roller.

[Explanation of symbols]

1-photoreceptor, 2-sleeve roller, 3 ... magnet roller, 4-developing roller, B-peeling area.

Claims (1)

[Claims] 1. A developing roller of an image forming apparatus that has a magnet roller inside a sleeve roller and supplies a developer to a photoconductor, and corresponds to a portion where the developer is peeled off after being supplied to the photoconductor. The developing roller in the image forming apparatus, wherein the area of the magnet roller is substantially 0 gauss.