JPS62205383A - Magnetic brush developing device - Google Patents

Abstract

PURPOSE:To simplify the constitution of each magnetic brush developing device by causing a developer to come near and off a photosensitive drum due to a change in the phase of a magnetic pole without moving an overall developing device toward the photosensitive drum. CONSTITUTION:The magnetic brush developing device adheres toner in appropriate color to a latent image formed on the photosensitive drum 11. The developing device 12 has a developing sleeve 13 and a magnet 14 located in the sleeve 13, both of which are rotatably supported at a fixed position with respect to the photosensitive drum 11 by a machine frame 5. The magnet 14 is located on the opposite side of a drive gear 17, has a magnet shaft 18 protruding out of the machine frame 15, and an interlocking disk 19 is fitted on the shaft 18. One end of the drive arm 20 is pivotally fitted at the eccentric position on the disk 19, and the other end is connected to the plunger 22 of a solenoid 21. It controls the plunger 22 at advancing and retreating positions due to its excitement and degauss, whereby the magnet 14 reciprocatingly rocks.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a magnetic brush developing device used in copying machines, printers, etc.

[Prior Art and Problems Therewith] Some so-called PPC copying machines and printers have processes for charging, exposing, developing, and transferring a photoreceptor drum, and a magnetic brush developing device is generally used for development. This magnetic brush developing device magnetically turns the developer into a brush shape by using the polarity of the magnetic carrier in the developer and the polarity of the magnet, and by bringing this into contact with the photoreceptor drum, the developer is formed into a photoreceptor tram. The latent image is developed by attaching the toner in the developer to the latent image.

On the other hand, color copying machines and printers are becoming increasingly popular, and these magnetic brush developing devices are used for each different color. In this case, the developer in the magnetic brush developing device must be brought into contact with the photoreceptor drum only when developing that color, and must be separated from the photoreceptor tram when developing other colors. In the apparatus, the entire magnetic brush developing device was movable relative to the photosensitive drum. However, it is possible to move multiple magnetic drum developing devices toward and away from the photoreceptor tram.
In addition, in order to synchronize these movements, a complicated device configuration is required, which causes an increase in the size and cost of the device.

``Object of the Invention'' The present invention is based on an awareness of the problems with the conventional magnetic brush developing device, and the present invention has been devised to apply developer to the photoconductor drum without moving the entire developing device relative to the photoconductor drum. The purpose is to obtain a device M that can be moved toward and away from each other.

"Summary of the Invention" The present invention focuses on the fact that spikes of developer containing a magnetic carrier (magnetic brush) occur near the magnetic poles of a magnet located in the developing sleeve, and the It was completed based on the idea that if the developer sleeve was changed, it would be possible to bring the spikes of developer into contact with or away from the photoreceptor drum. A marinade having a magnetic pole is provided, and a means for changing the phase of the magnetic pole is provided,
This change in the phase of the magnetic poles changes the position of the spikes of developer formed on the outer circumferential surface of the developing sleeve, so that the spikes are caused to be 'WtM' with respect to the photoreceptor drum.

"Embodiments of the Invention" The present invention will be described below with reference to illustrated embodiments. FIG. 5 shows the relationship between the photoreceptor tram 1 and the magnetic brush developing device 120. The rotationally driven photoreceptor tram 11 is exposed to light by a well-known exposure means (not shown), and an image is formed on its surface. A latent image of a correspondingly charged state is formed. The magnetic brush developing device 12 applies toner of an appropriate color to this latent image.

As shown in FIGS. 1 to 4, the magnetic brush developing device 12 includes a developing sleeve 13 and a magnet 4 located within the developing sleeve 13. It is rotatably supported by the machine frame 15 at a fixed position relative to the photoconductor tram 11 . The developing sleeve 13 has a sleeve shaft 16 protruding from the machine frame 15.
It has a driving hook 17 integrally therein, and this driving hook 17 is connected to a developing sleeve drive system (not shown).

The magnet 14 also has a magnet shaft 18 located on the opposite side of the drive carrier 17 and protruding from the machine frame 15.
An interlocking disc 19 is fixed to this magnet shaft 18. This interlocking disc 19 has a drive arm 2 at its eccentric position.
One end of the drive arm 20 is connected to the plunger 22 of the solenoid 21 . The solenoid 21 controls the plunger 22 to two positions, an advanced position and a slightly retracted position, by its excitation and demagnetization. Therefore, the magnet 14 can be reciprocated within the developing sleeve 13 by the solenoid 21 at a constant angle. This angular range is, for example, 30°.

FIGS. 1(a) and 1(b) show examples of the relationship between the polarity of the magnet 14 and the photosensitive tram 11.
On the moon's surface, different magnetic poles are formed at 90° intervals: an S pole (minor pole) and an N pole (main pole).

A developer holding agitator 24 is located on the opposite side of the visual image nose 13 with respect to the photoconductor tram 11, and within this developer holding agitator 24, two components consisting of a magnetic carrier and a toner of a predetermined color are stored. The developer 25 is still being held. This two-component developer 25 has a magnetic carrier and a magnet 14.
It adheres to the outer circumferential surface of the developing sleeve 13 due to the magnetic force, and forms spikes 26 (see FIG. 2) that are taller than the surroundings near the N and S poles.

27 is a developer height regulating plate that regulates the height of the two-component developer 25 coming out of the glare agent holding agitator 24 on the surface of the magnet 14; The developer height regulating plate 27 is always located inside the developer height regulating plate 27 to prevent the formation of spikes in this S-pole portion.

This apparatus having the above-mentioned configuration is configured such that the N pole (main pole) of the magnet 14 is placed between the rotation centers of the photoconductor tram 11 and the developing sleeve 13 as shown in FIG. Body tram] Approaching 1. In response to this, for example, by rotating the magnet 14 shown in FIG.
When the phase of the pole is changed, the spike 26 or the photoconductor tram]
It tends to deviate from 1. Therefore, by appropriately setting the distance between the photoreceptor tram 11 and the developing sleeve 13, the height of the bristles 26, etc., the bristles 26 can be moved to the photoreceptor tram 11.
It can be moved toward or away from the object. Note that FIG. 1 depicts the case where the radius of the photoreceptor tram 11 is infinite, that is, the case where the photoreceptor tram 11 is flat, as the most severe case.

The explanation will be based on the specific numerical values written in FIG. 1(b). The radius of the developing sleeve 13 + 2.5 mm, the thickness of the two-component developer 25 formed on the surface of the magnet 14 by the developer height regulating plate 27 % 2 mm, and the height of the spikes 26 formed by the N pole of 800 Gauss. @2.3mm
, the distance Mi2 between the developing sleeve 13 and the photoreceptor tram 11.
If it is 5 mm, in the state shown in Fig. 1(a), the spike 26
The height is 2.3 mm, which is sufficiently larger than the 0.5 mm gap between the surface of the two-component developer 25 and the photoreceptor drum 11.
The head stand 1526 comes into contact with the photoconductor tram 11 and sufficient development is carried out.On the other hand, when the magnet 14 is rotated by 30 degrees as shown in FIG. Photoconductor track l\11 from the center
The distance to the surface is approximately 17.3 mm, and the distance between the surface hole of the two-component developer 25 and the photoreceptor tram 11 is 4.8 m.
m, so that even if the height of the standing ears 26 is 2.3 mm, the standing ears 26 and the photoreceptor tram 11 are maintained in a non-contact state. Considering that the magnet 14 can be easily rotated by 30 degrees or more, for example, about 45 degrees, and that the photoreceptor drum 1 actually has a certain curvature, the present invention makes it possible to move the entire developing device. It is understood that it is possible to easily bring the two-component developer 25 (stand-up spikes 26) toward and away from the photoreceptor tram 11 by changing the phase of the Macnet 140 without changing the phase.

That is, in the demagnetized state of the solenoid 2], the state shown in FIG.
) and the state (b) can be obtained in the excitation state, it is possible to easily switch between the developing state and the non-developing state.

The main pole and sub-pole of the magnet 14 are determined by the relationship with the polarity of the magnetic carrier in the developer, and the S pole may be the main pole in some cases.

Further, in the above embodiment, the phase of the magnetic poles is changed by mechanically rotating the magnet 14, but this may be done electrically. Further, the present invention
Although the present invention is particularly useful for color copying machines or printers that use a plurality of developing devices, it can be similarly applied to other devices that require the developer to be brought into contact with and separated from the photoreceptor drum.

"Effects of the Invention" As described above, the magnetic brush developing device of the present invention can bring developer into contact with and away from the photoreceptor tram without moving the entire device. Therefore, the configuration of each magnetic brush developing device can be simplified, and the interlocking mechanism with other mechanisms can also be omitted or simplified, leading to a significant reduction in cost.

[Brief explanation of drawings]

1(a) and 1(b) are front views showing the developing state and non-developing state of the magnetic brush developing device according to the present invention; FIG. 2 is a front view schematically showing the state of developer spikes; Figure 3 is the first
FIG. 4 is a right side view of FIG. 3, and FIG. 5 is a front view showing the relationship between the photosensitive drum and the magnetic brush developing device. DESCRIPTION OF SYMBOLS 11... Photosensitive drum, 12... Magnetic brush developing device, 13... Developing sleeve, 14... Magnet,
DESCRIPTION OF SYMBOLS 15... Machine frame, 17... Drive carrier, ]8... Magnet shaft, 19... Interlocking disk, 2o... Drive arm, 21... Solenoid, 22... Plunger, 24
...Developer holding agitator, 25...Two-component developer, 2
6... Ear standing, 27... Developer height regulation plate. Patent applicant Asahi Optical Co., Ltd. Agent Kunio Miura Shigeru Matsui - C) Taste

Claims (2)

[Claims] (1) In a magnetic brush developing device that develops by moving a developer containing a magnetic carrier toward and away from a photoreceptor drum on which a latent image is formed by an exposure system, a developing sleeve that is driven to rotate has a periphery inside the developing sleeve. A magnet having a magnetic pole on the surface is disposed, and a means for changing the phase of the magnetic pole is provided, and by changing the phase of the magnetic pole, the position of the spikes of developer attached and formed on the outer peripheral surface of the developing sleeve is changed. A magnetic brush developing device characterized in that the spikes are brought into contact with and separated from a photoreceptor drum. (2) In claim 1, the magnet is:
A magnetic brush developing device that is rotatable around the axis of the developing sleeve, and the phase of its magnetic poles changes as it rotates.