JPH04355480A - Developing device - Google Patents

Abstract

PURPOSE:To provide a developing device capable of regulating the magnetic force on the developing sleeve surface of a developing roller with a simple structure and providing an optional image quality by this magnetic force regulation. 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 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 in the sliding direction with the inclined surface 16A of the sawtooth part 16 is formed. 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 provided in such a manner as to be displaceable in the direction approaching to and separating from the developing sleeve 6. The permanent magnet 8 is displaced by a rack plate 20 geared with a pinion gear 19 rotated and driven according to the operation of an operation button for image quality regulation.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device equipped with a developer conveying roller, a developing roller, etc. in an image forming apparatus such as an electronic copying machine.

0002

2. Description of the Related Art Conventionally, for example, a developing device of an electronic copying machine is constructed as shown in FIG. A two-component developer) is stirred by a paddle roller 2, and the developer frictionally charged by this stirring is transported by a transport roller 3 to the side of a developing roller 5 disposed facing the photoreceptor drum 4, and the transported developer is By rubbing the toner on the photoreceptor drum 4 with the developing roller 5, the toner is attached to the latent image formed on the photoreceptor drum 4 and developed. 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. 9 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 has a structure on 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. Flanges 11 and 12 are press-fitted into both open ends of the developing sleeve 6, and one flange 11 has a driving shaft 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, in a developing device with such a conventional configuration, since a permanent magnet with a constant magnetic force is used for the developing roller, the surface of the developing sleeve may be damaged due to, for example, manufacturing errors or assembly errors of the permanent magnet. If the above magnetic force differs from the standard value, the magnetic force cannot be adjusted, and the image quality during development may be affected, especially if it is a permanent magnet part (for example, the main pole part) that has a large effect on development performance. It was a factor that made things worse. 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 can be made more compact. In addition, the heat generated by the electromagnet when energized may have an adverse effect on other permanent magnets (decreased magnetic force due to heat). Furthermore, a separate power source is required to supply drive current to the electromagnet, which increases the complexity and cost of the entire device. The present invention has been made in view of these points, and provides a developing device that can adjust the magnetic force on the surface of the developing sleeve of the developing roller with a simple configuration, and can obtain any desired image quality by adjusting the magnetic force. The purpose is to provide.

[0006]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a developing roller in which a magnet structure in which a permanent magnet is arranged is fixed to a magnet roller shaft, and a developing sleeve is rotatably provided on the outside of the magnet structure. In the developing device equipped with
a support means disposed on the magnet structure so that the permanent magnet of the developing roller can be freely displaced in a direction toward and away from the developing sleeve; and a drive means for driving the permanent magnet displaceably disposed by the support means. , and a control means for driving and controlling the driving means in accordance with an image quality adjustment operation on the operation panel section.

[0007]

[Operation] According to such a configuration, the permanent magnet of the developing roller, which can be freely displaced in the direction of coming into contact with and separating from the developing sleeve,
When the image quality adjustment operation is performed on the operation panel, moving the sleeve closer to the sleeve will strengthen the magnetic force on the sleeve surface, and conversely, moving it away from the sleeve will weaken the magnetic force on the sleeve surface, changing the developed image quality. become.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The developing device of the present invention will be explained 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 developing roller (in this case, the permanent magnet serving as the main pole closest to the photoreceptor drum)
is arranged on the support member 9 of the magnet structure 7 so as to be freely displaceable in the direction toward and away from the developing sleeve 6, and the permanent magnet 8 is driven to be displaced from the outside of the developing housing 1. Specifically, as shown in FIGS. 1 and 2, the support member 9
A guide groove 15 is formed in the guide groove 15, and a sawtooth part 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, and the sawtooth part 16 is also formed at the bottom of the permanent magnet 8 housed in the guide groove 15. By forming an inverted sawtooth section 17 having an inclined surface 17A in the direction of sliding contact with the surface 16A, and by tensioning a tension spring 18 as shown in the figure between this permanent magnet 8 and the bottom of the guide groove 15, a permanent The magnet 8 is always energized toward the magnet roller shaft 10 side. Then, a rack plate 20 that is moved in the direction of arrow X by meshing with a pinion gear 19 outside the developer housing 1 is brought into contact with one end of the permanent magnet 8, and the pinion gear 19 is driven by a stepping motor 21 that can freely rotate in forward and reverse directions. By rotating,
The permanent magnet 8 is displaced and driven by a rack plate 20 in a direction toward and away from the developing sleeve 6. Here, the stepping motor 21 is connected to, for example, operation buttons 23 and 2 for adjusting image quality arranged on an operation panel section 22 on the side of the main body of the electronic copying machine.
4, the control section 25 (
For example, a microcomputer) controls the rotational drive according to the operation (see FIG. 3).

Therefore, for example, when one operation button 23 of the operation panel section 22 is pressed, the stepping motor 21
is driven in the forward direction by the control unit 25 to rotate the pinion gear 19 clockwise, and the rack plate 20 moves in the X direction and presses the permanent magnet 8 to the left, so the permanent magnet 8 tilts. The developing sleeve 6 is slid obliquely upward (in the direction of arrow Y) along the surface 16A while resisting the biasing force of the tension spring 18, that is, displaced in the direction approaching the developing sleeve 6.
The magnetic force on the surface will be strengthened. Conversely, when the other operation button 24 of the operation panel section 22 is pressed, the stepping motor 21 is driven to rotate in the opposite direction by the control section 25, and the pinion gear 19 is rotated counterclockwise.
is moved in the anti-X direction, the permanent magnet 8 is slid obliquely downward (in the direction of arrow Y) along the inclined surface 16A due to the biasing force of the tension spring 18, that is, in the direction away from the developing sleeve 6. As a result, the magnetic force on the surface of the developing sleeve 6 is weakened.

Therefore, in the developing device having such a configuration, depending on which of the operation buttons 23 and 24 on the operation panel section 22 is pressed, a magnetic brush (in this case, By changing the standing state of the magnetic brush (of the permanent magnet part that is the main pole closest to the photosensitive drum), the amount of toner attached to the latent image on the photosensitive drum 4 is changed, and the quality of the developed image is adjusted to the user's preference. can be changed arbitrarily. That is, when the magnetic force on the surface of the developing sleeve 6 is weakened, the height and quantity of the magnetic brushes are lowered, resulting in a softer image quality (that is, the density curve is shifted to the A side as shown in FIG. 4). On the other hand, if the magnetic force on the surface of the developing sleeve is strengthened, the height and quantity of the magnetic brushes will increase, making the image quality sharper (i.e.,
As shown in FIG. 4, the concentration curve can be shifted to the B side). In addition, not only when 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, but also when the magnetic force of the permanent magnet 8 itself decreases due to age changes, etc. The magnetic force can be adjusted, and a separate standard image quality button 26 may be provided so that the standard image quality can be immediately obtained from the adjusted image quality.

In addition, in FIG. 1, the permanent magnet 8 as the main pole is disposed on the support member 9 so as to be freely displaceable, but as shown in FIG. A permanent magnet 8 may be disposed movably as a drawing pole for drawing the developer into the developing sleeve 6. In that case, when the permanent magnet 8 is moved to weaken the magnetic force on the surface of the developing sleeve 6, the amount of developer carried to the nip portion is reduced. On the other hand, if the magnetic force on the surface of the developing sleeve 6 is strengthened, the amount of developer carried to the nip increases and the image quality becomes high contrast. Furthermore, in addition to the main pole or the retracting pole, a plurality of permanent magnets 8 may be disposed movably as shown in FIG. 6, and in this case, as shown in FIG. Alternatively, a ring-shaped elastic film 28 may be placed over the magnet roller to bias the magnet roller shaft 10 side. In this embodiment, the permanently displaceable permanent magnet is driven to be displaced in multiple stages via a stepping motor and a pinion-rack mechanism, but it is also possible to drive the displacement in two stages using a solenoid or the like. Also good. Further, in this embodiment, a developing roller of the type that rotates the developing sleeve and fixes the internal magnet structure for development is described, but it is not a developing roller of the type that rotates both the developing sleeve and the internal magnet structure. It's okay. 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.

0012

As described above, according to the developing device of the present invention, the permanent magnet of the developing roller is moved in the direction toward and away from the developing sleeve by the image quality adjustment operation on the operation panel section, and the magnetic force is adjusted as desired. Since the image quality is obtained, 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 drawings]

FIG. 1 is a schematic cross-sectional view of a developing device of the present invention.

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

FIG. 3 is a diagram showing its control configuration.

FIG. 4 is a characteristic diagram showing the relationship between original density and image density.

FIG. 5 is a schematic cross-sectional view showing another embodiment.

FIG. 6 is a sectional view of a main part showing another embodiment.

FIG. 7 is a sectional view of a main part showing another embodiment.

FIG. 8 is a schematic cross-sectional view showing the configuration of a conventional developing device.

FIG. 9 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 21 Stepping motor 22 Operation panel section 25 Control section

Claims (1)

[Claims] 1. A developing device equipped with a developing roller in which a magnet structure in which a permanent magnet is arranged is fixed to a magnet roller shaft, and a developing sleeve is rotatably provided on the outside of the developing roller. A support means disposed on the magnet structure so as to be freely displaceable in a direction toward and away from the sleeve, a drive means for displacing and driving the displaceably disposed permanent magnet by the support means, and the drive means is connected to the operation panel section. 1. A developing device comprising: a control means for controlling drive according to an image quality adjustment operation.