JPH04355478A - Permanent magnet roller - Google Patents

Abstract

PURPOSE:To provide a permanent magnet roller capable of regulating the magnetic force of a sleeve surface with a simple structure. CONSTITUTION:A magnet structure 7 within a developing sleeve 6 is formed of a plurality of permanent magnets 8 and a support member 9 on which each permanent magnet 8 is provided. The support member 9 has a guide groove formed thereon, and a sawtooth part 16 having an inclined surface 16A extending in the direction of the developing sleeve 6 is formed on the guide groove bottom part. On the permanent magnet 8 bottom part received in the guide groove, also, a reversed sawtooth part 17 having an inclined surface 17A is formed in the sliding direction with the inclined surface 16A of the sawtooth part 16. A tension spring 18 is laid between the permanent magnet 8 and the guide groove bottom part to regularly energize the permanent magnet 8 on a magnet roller shaft 10 side, and at least one permanent magnet 8 is disposed in such a manner as to be displaceable in the direction approaching to and separating from the developing sleeve 6. This permanent magnet 8 is displaced by a regulating screw 20 making contact with one end side of the permanent magnet 8.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet roller used as a developer conveying roller or a developing roller in a developing section of an image forming apparatus such as an electronic copying machine.

0002

[Prior Art] Conventionally, for example, the developing section of an electronic copying machine is shown in FIG.
The developer housing 1 is configured as shown in FIG. The frictionally charged developer is conveyed to roller 3.
The developer is conveyed to the side of a developing roller 5 disposed opposite to the photoreceptor drum 4, and the conveyed developer is rubbed against the photoreceptor drum 4 by the developing roller 5, whereby the developer is formed on the photoreceptor drum 4. The latent image is developed by attaching toner to it. Here, as will be described later, the developing roller 5 has a structure in which a developing sleeve is rotatably provided on the outside of a fixed magnet structure to which a plurality of permanent magnets are fixed (the conveyance roller 3 also has an internal magnet structure). The magnetic brush of the developer formed on the surface of the developing sleeve by the magnetic force from the internally fixed magnet structure is transferred to the photoreceptor drum 4 by the rotation of the developing sleeve. It is designed to be rubbed.

FIG. 6 shows a specific example of the structure of the developing roller 5, in which 6 is a cylindrical developing sleeve made of a non-magnetic material such as aluminum, and 7 is inside the developing sleeve 6 and is attached to the surface of the developing sleeve 6. This is a magnet structure for forming a magnetic brush, and the magnet structure 7 is made up of a plurality of permanent magnets 8 and a support member 9 to which each of the permanent magnets 8 is fixed with an adhesive or the like. It is press-fitted or adhesively fixed to the magnet roller shaft 10. Reference numerals 11 and 12 denote flanges that are press-fitted into both open end surfaces of the developing sleeve 6, and one flange 11 has a driving shaft portion 11A formed therein.
The other flange 12 is formed with an insertion hole 12A that allows one end 10A of the magnet roller shaft 10 to protrude to the outside, and the protruding one end 10A of the magnet roller shaft 10
is fixed to the developing housing 1. Reference numerals 13 and 14 denote bearings (in this case, ball bearings) that support the magnet roller shaft 10 and the developing sleeve 6. Each of the bearings 13 and 14 has a steel ball as a rolling element and an outer ring (outer ring) and an inner ring (inner ring). The magnet roller shaft 10 is press-fitted into the inner ring of each of the inner rings.
Flanges 11 and 12 are press-fitted into the outer ring.

[0004] Therefore, the developing sleeve 6 has a flange 11,
The magnet roller shaft 10 is rotatably supported by bearings 13 and 14 via the magnet roller shaft 12. For example, when the copy button on the main body of the copying machine is pressed, the rotational driving force from the drive source is applied to the belt (or pulley). , gears, etc.), and rotates so as to rub the magnetic brush of the developer against the photoreceptor drum 4.

[0005]

[Problems to be Solved by the Invention] However, since the developing roller of this conventional configuration uses a permanent magnet with a constant magnetic force, the magnetic force on the surface of the developing sleeve may vary due to manufacturing errors or assembly errors of the permanent magnet, for example. If the magnetic force differs from the standard value, the magnetic force cannot be adjusted, and if it is a permanent magnet part (for example, the main pole part) that has a large effect on development performance, it may cause poor image quality during development. It had become. Therefore, it has been proposed to configure one or more of the permanent magnets of the magnet structure with an electromagnet whose magnetic force can be adjusted, but since the electromagnet consists of a coil and a magnetic core, the developing roller is compact. In addition, there was a risk that the heat generated by the electromagnet when energized would have an adverse effect on other permanent magnets (decreased magnetic force due to heat). Furthermore,
A separate power supply device is required to supply drive current to the electromagnet, which complicates the overall configuration and increases costs. The present invention has been made in view of these points, and an object of the present invention is to provide a permanent magnet roller that can adjust the magnetic force on the sleeve surface with a simple configuration.

[0006]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a permanent magnet roller in which a magnet structure in which permanent magnets are arranged is fixed to a magnet roller shaft, and a sleeve is rotatably provided on the outside of the magnet structure. , a permanent magnet of the magnet structure is provided with means for adjusting magnetic force,
Specifically, the means includes support means for disposing the permanent magnet of the magnet structure so as to be movable in a direction toward and away from the sleeve;
and a displacing means for displacing a permanent magnet which is displaceably disposed by the supporting means.

[0007]

[Function] According to this configuration, when the permanent magnet, which is freely displaceable in the direction of approaching and separating from the sleeve, is displaced in the direction of approaching the sleeve, the magnetic force on the surface of the sleeve becomes stronger, and conversely, the permanent magnet is displaced in the direction of moving away from the sleeve. This will weaken the magnetic force on the sleeve surface.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The use of the permanent magnet roller of the present invention as a developing roller will be described below with reference to the drawings. It should be noted that the same parts as those in the prior art will be given the same reference numerals and the explanation thereof will be omitted. In this embodiment, at least one of the plurality of permanent magnets 8 of the magnet structure 7 (in this case, the permanent magnet serving as the main pole closest to the photoreceptor drum) is displaced in a direction toward and away from the developing sleeve 6. The permanent magnet 8 is freely disposed on a support member 9 and can be manually displaced from the outside. Specifically, as shown in FIGS. 1 and 2, a guide groove 15 is formed in the support member 9, and a sawtooth portion 16 having an inclined surface 16A extending in the direction of the developing sleeve 6 is formed at the bottom of the guide groove 15. Also formed on the bottom of the permanent magnet 8 housed in the groove 15 is a reverse sawtooth section 17 having an inclined surface 17A in the direction of sliding contact with the inclined surface 16A of the sawtooth section 16.
By tensioning a tension spring 18 as shown in the figure between the permanent magnet 8 and the bottom of the guide groove 15, the permanent magnet 8 is always urged toward the magnet roller shaft 10 side. Then, the tip of the adjustment screw 20 screwed into the support rib 19 of the support member 9 is brought into contact with one end side of the permanent magnet 8, and by screwing in and loosening this adjustment screw 20, the permanent magnet 8 is moved into the developing sleeve 6. It is designed to be displaced in the direction of approaching and separating from. The adjustment of the adjustment screw 20 can be carried out using a screwdriver inserted from the outside through the adjustment hole 21 formed in the flange 12. After the adjustment, the adjustment hole 21 is closed with the cap 22 and the developer, etc. is kept inside. It is designed to prevent foreign objects from entering.

Therefore, for example, when the adjustment screw 20 is screwed in and its tip presses the permanent magnet 8 in the thrust direction,
The permanent magnet 8 is slid obliquely upward (in the direction of arrow Y) along the inclined surface 16A while resisting the biasing force of the tension spring 18, that is, is displaced in a direction approaching the developing sleeve 6, and the magnetic force on the surface of the developing sleeve 6 is It will be strengthened. Conversely, when the adjusting screw 20 is loosened, the permanent magnet 8 is moved from the tension spring 18.
Due to the applied force, the developing sleeve 6 is slid diagonally downward (in the opposite direction of arrow Y) along the inclined surface 16A, that is, displaced in a direction away from the developing sleeve 6, and the magnetic force on the surface of the developing sleeve 6 is weakened. Therefore, in the developing roller having such a configuration, if the magnetic force on the surface of the developing sleeve 6 differs from the standard value due to manufacturing errors or assembly errors of the permanent magnet 8, the magnetic force can be adjusted using the adjusting screw 20. I can do it,
Further, even if the magnetic force of the permanent magnet 8 itself decreases due to aging or the like, the adjustment can be made in the same way.

Furthermore, in FIG. 1, one permanent magnet 8 is displaceably disposed on the support member 9, but as shown in FIG. 3, a plurality of permanent magnets 8 are disposed displaceably. Alternatively, instead of the tension spring 18, a stretchable annular elastic film 23 may be partially or entirely covered to bias it toward the magnet roller shaft 10. still,
In this embodiment, a type has been described in which development is performed by rotating the developing sleeve and fixing the internal magnet structure, but a type in which both the developing sleeve and the internal magnet structure are rotated may be used. Further, in this embodiment, a case has been described in which a plurality of permanent magnets are arranged in a magnet structure fixed to a magnet roller shaft located at the center of the roller, but the present invention is not limited to this. A configuration may also be used in which a plurality of magnet structures each having magnets arranged thereon are respectively fixed to a plurality of magnet roller shafts located off the center of the roller. Further, in this embodiment, the case where it is used as a developing roller has been described, but it may also be used as a conveying roller, and in that case, the magnetic force on the surface of the conveying sleeve can be adjusted.

[0011]

As described above, according to the permanent magnet roller of the present invention, since the magnetic force is adjusted by displacing the permanent magnet of the magnet component in the direction toward and away from the sleeve, the sleeve surface The magnetic force of the magnetic field can always be maintained at the standard value, and the overall configuration can be made simpler and more compact than the conventional system that uses electromagnets to adjust the magnetic force.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional side view of a developing roller of the present invention.

[Fig. 2] A cross-sectional view of its main parts.

FIG. 3 is a sectional view of a main part showing another embodiment.

FIG. 4 is a cross-sectional view of main parts showing another embodiment.

FIG. 5 is a schematic cross-sectional view showing the configuration of a conventional developing section.

FIG. 6 is a longitudinal side view of the developing roller.

[Explanation of symbols]

6 Developing sleeve 7 Magnet structure 8 Permanent magnet 9 Support member 15 Guide groove 16, 17 Serrated part 18 Tension spring 20 Adjustment screw

Claims (2)

[Claims] 1. A permanent magnet roller in which a magnet assembly having permanent magnets arranged thereon is fixed to a magnet roller shaft, and a sleeve is rotatably provided on the outside of the magnet assembly, in which the magnetic force of the permanent magnet of the magnet assembly is adjustable. A permanent magnet roller characterized by being provided with means. 2. The means includes support means for displacing the permanent magnets of the magnet structure so as to be freely displaceable in a direction toward and away from the sleeve, and a displacement member for displacing the displaceably disposed permanent magnets by the support means. A permanent magnet roller according to claim 1, further comprising means.