JPS634278A - dry developing device - Google Patents

Abstract

PURPOSE:To prevent insufficient electrification due to excessive toner supply and to obtain a good picture image free from fogging by providing a magnetic pole on the upstream side of a developer layer thickness controlling member and providing a developer shielding member within the range of the magnetic field of the magnetic pole. CONSTITUTION:When magnetic particles 27 are attracted once on the surface of a sleeve 22, this state is maintained. There is only a cut magnetic pole 23a at the inside of a container 21 and there is no magnetic pole in a toner supply aperture 31. The immovable layer of magnetic particles is formed by a shielding member 26 provided above the magnetic pole 23a and within the range of its magnetic field. Thereby, the toner contents is made stable, and the creset at the position of the magnetic pole 23a is prevented. Accordingly, the excessive supply of toner from a creseting part in which the density of magnetic particles is low can be prevented. Consequently, TC becomes stable, the pressure of the magnetic particle layer in a blocked space is rised, charge giving capacity to toner is rised and a stable developer layer is obtained. Thus, a good picture image free from fogging can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a developing device that develops a latent image formed by electrophotography, electrostatic recording, or the like.

(Prior art) Devices that use powder developer as developing devices have been put into practical use, but the developer supply system uses developer that has been stored in a container in advance (cartridge-based process There are two types: a non-replenishment type (used in the unit) and a replenishment type that replenishes developer according to the amount of developer remaining in the device.

All of these are configured to generate a charge on the developer to enhance the adhesion effect to the electrostatic latent image during development, and this charge exists even in single-component developers, but is especially important in two-component developers. This is a great feature.

Since recording equipment in which a developing device is housed is forced to be smaller and improve its performance, it is inevitable that the developing device be made smaller.

In such a small developing device, it is difficult to install a complicated mechanism such as an ATR in order to give sufficient charge to the developer, and it is necessary to provide a sufficient charge to the developer with a simpler configuration. Must not be. The present applicants have disclosed Japanese Patent Application Laid-Open No. 58-143360 and Japanese Patent Application Laid-Open No. 59-101680 as these developing devices.
etc. were proposed. We are also proposing a special development method that further improves image quality.

These generate circular motion of the magnetic particle layer using magnetic force, motion, and frictional force with the developing sleeve.
This charged the developer. However, since toner is replenished by circulating the magnetic particle layer, there is a risk that excess toner will be taken into the magnetic particle layer and fog will occur due to insufficient charging.

(Objective) An object of the present invention is to provide a small-sized developing device that can prevent i-electricity shortage due to oversupply of toner and can obtain good images without fogging.

(Summary of the Invention) The present invention has a magnet fixedly provided in a developing sleeve, and a layer of magnetic particles magnetically attracted on the outer peripheral surface of the developing sleeve is provided with a toner stored in a toner storage container. A dry type developing device that prepares a magnetic developer consisting of a mixture of magnetic particles and toner by supplying toner as a developing sleeve rotates, and develops an electrostatic latent image using this magnetic developer. , where there is at least one magnetic pole located downstream of the toner supply port in the magnetic developer transport direction and upstream of the developer layer thickness regulating member, and a developer shielding member is provided within the range of the magnetic field of the magnetic pole. It is.

This prevents oversupply of toner to the magnetic particle layer, and also makes it possible to control the developer layer and sufficiently charge the developer, thereby providing a good image.

(Example) FIG. 1 is an explanatory diagram of main parts of an embodiment of the present invention.

In this figure, 1 is an electrostatic latent image carrier that carries an electrostatic latent image to be developed, and specifically, it is an endlessly movable photosensitive drum, a belt, a dielectric drum, a belt, or the like. The method of forming an electrostatic latent image thereon is not the gist of the present invention (although any known method may be used. It is a drum and is rotatable in the direction of arrow a.

The apparatus of this embodiment includes a developer container 21, a developing sleeve 22 (hereinafter simply referred to as a sleeve) that is a developer holding member, a magnet 23 that is a magnetic field generating means, and an amount of developer that is conveyed to the developing section on the sleeve 22. It has a regulation blade 24 (hereinafter simply referred to as a blade), etc., for controlling.

Each configuration will be explained below.

Container 21 contains a developer having a mixture of magnetic particles 27 and toner particles 28 . In this embodiment, the toner particles are non-magnetic toner particles having a particle size of 7 to 20 μm and are mainly formed of, for example, 10 parts of carbon and 90 parts of polystyrene. In this embodiment, the toner particles and magnetic particles are stored in the container 21 as a uniform mixture, with the concentration of the magnetic particles being high near the sleeve 22 and low in areas away from the sleeve 22. Good too. Container 21
has an opening at the lower left in FIG.

The sleeve 22 is made of a non-magnetic material such as aluminum, and is provided at the opening of the container 21, with a part of its surface exposed and the other surface protruding into the container 21. The sleeve 22 is rotatably supported around an axis perpendicular to the drawing, and is rotationally driven in the direction indicated by the arrow at approximately the same speed as the circumferential speed of the photosensitive drum.

Although the sleeve 22 is a cylindrical sleeve in this embodiment, it may be an endless belt.

The magnet 23 is fixed statically inside the sleeve 22 and remains stationary even when the sleeve 22 rotates. The magnet 23 includes an N magnetic pole 23a1 that controls the amount of developer applied onto the sleeve 22 in cooperation with a blade 24, which will be described later, and an S magnetic pole 23b1, which is a developing magnetic pole.
N magnetic pole 2 that transports the developer after passing through the developing section into the container 21
3c and an S magnetic pole 23d. The south pole and north pole may be reversed.

In this embodiment, the blade 24 has at least its tip made of a non-magnetic material such as aluminum, and the blade 24 is made of a non-magnetic material such as aluminum.
extending in the longitudinal direction of the sleeve 22 near the top of the opening;
Its base is fixed to the container 2.1, and its distal end is fixed to the sleeve 2.1.
It faces the surface of 2 with a gap. The gap between the tip of the blade 24 and the surface of the sleeve 22 is 50 to 500 μ.
m is preferably 100 to 350 μm, and in this example is 250 μm. When this gap is smaller than 50 μm, magnetic particles tend to clog the gap, and when it exceeds 500 μm, a large amount of magnetic particles and toner pass through the gap.
A developer layer of an appropriate thickness cannot be formed on the sleeve 22.

In this embodiment, an auxiliary magnetic blade 24a is provided inside the container of the non-magnetic blade 24 to further stabilize the developer layer.

Further, inside the container 21 of the auxiliary magnetic blade 24a, a magnetic particle circulation limiting member 26 is installed at a position substantially opposite to the cut magnetic pole 23a and at a position where the magnetic field extends.

Next, the operation of the developing device of this embodiment will be explained. First, magnetic particles 27 are put into the container 21 .

The charged magnetic particles are held on the sleeve 22 by the magnetic poles 23a and 23d, and adhere to each other over the entire surface of the sleeve 22 facing into the container 21, forming a magnetic particle layer. The magnetic particles 27 constitute a magnetic brush in a portion of the magnetic particle layer near the magnetic poles 23a and 23d. Thereafter, toner 28 is put into the container 21 to form a toner layer outside the magnetic particle layer. The magnetic particles 27 initially introduced have a ratio of 2 to 70% (based on the magnetic particles).
Weight) It is preferable that the toner is included, but it is also possible to include only magnetic particles. If some of the magnetic particles 27 are adsorbed and held as a magnetic particle layer on the surface of the sleeve 22, no substantial flow or inclination will occur even when the device is vibrated or tilted considerably, and the state in which the magnetic particles 27 cover the surface of the sleeve 22 will not occur. maintained.

Next, when the sleeve 22 is rotated in the direction of the arrow, the magnetic particles rise from the bottom of the container 21 in a direction along the surface of the sleeve 22 and reach the vicinity of the blade 24.

Therefore, some of the magnetic particles are transferred to the blade 24 along with the toner.
The other portion passes through the gap between the tip of the sleeve 22 and the surface of the sleeve 22, collides with the member 26, and is later conveyed as the sleeve rotates. The pressure of the magnetic particles - forms an apparently immobile immobile layer.

In other words, the magnetic particle layer formed near the surface of the sleeve 22 is blocked by a layer of magnetic particles moving as the sleeve 22 rotates near the sleeve and the circulation area limiting member 26, which is a shielding member. formed from a fixed layer.

In the toner supply opening 31, the moving layer is exposed at the lower part of the toner supply opening 31, and toner is supplied to the magnetic particle layer by the movement of the magnetic particles.
The volume of the immobile layer increases or decreases due to changes in toner content (toner content), that is, as T/C increases, the volume of the immobile layer increases, the effective opening width of the toner supply port (exposed width of the moving layer) decreases, and the amount of toner taken in increases. decreases, and conversely, when T/C decreases, the volume of the immobile layer decreases, the effective toner supply opening increases, and the amount of toner taken into the magnetic particle layer increases. /C stabilization is achieved.

In the developing device of this embodiment, there is no cut magnetic pole 23a inside the container 21, and no magnetic pole exists at the toner supply opening. Further, a shielding member 26 is provided above the cut magnetic pole 23a and within the range of the magnetic field. Shielding member 2
6, a magnetic particle immobile layer is formed, and the T/C is stabilized by the above-mentioned mechanism, and the formation of spikes at the cut magnetic pole position is prevented.Furthermore, since there is no magnetic pole at the toner supply port, the magnetic particles are Excessive supply of toner from the low-density edging part is prevented, T/C is stabilized, and the pressure of the magnetic particle layer in the closed space is further increased.
The ability to charge the toner is increased, and an extremely stable developer layer can be obtained.

As a result, it is possible to obtain high-quality images without fog or unevenness.

(Experiment example) In the developing device configured as shown in Fig. 1, the developing sleeve diameter was φ20. Omm Photosensitive drum diameter φ60. Omm Cut magnetic pole 23a 900 G development magnetic pole 23
b 950 G (on the sleeve surface) Transport magnetic pole 23c, d 800 G shielding member is placed 4 mm away from the sleeve surface at the cut magnetic pole position As the magnetic particles, ferrite particles coated with resin with an average particle size of 50 μm are used as toner. is the average particle size 1
It was installed in a PC-20 copying machine manufactured by Canon Inc. using a developer using 2 μm insulating non-magnetic toner, and the photoreceptor potential VD = 600V, Vt = 220V.

Set the process speed to 66 mm/sec,
As a developing bias, a Peah vs. Peah voltage of 1.3KVpp, a frequency of 1.6K)lz alternating electric field and a DC voltage of 1300V superimposed was used to produce an image, and a good image without fog or unevenness was obtained. It was possible. Furthermore, good quality images were obtained even after 2,000 sheets of durability.

In the above embodiment, a developing bias in which a direct current electric field is superimposed on an alternating electric field is used, but of course only a direct current bias may be used.

In the developing device of this example, the magnetic particle layer, including the passive layer, is completely restrained by the magnet in the developing sleeve, so that the magnetic particle layer will not shift due to tilting, vibration, etc. of the developing device. A stable image can be obtained without the appearance of unevenness or unevenness.

In the embodiment described above, the shielding member 26 forms a completely closed space, creates a stationary layer, and applies strong pressure to the developer layer to perform sufficient charging. When using a light pressure fixing toner, the pressure may be too high and cause deterioration of the developer, so an example in which the pressure by the shielding member 26 is weakened and the load is lightened is shown in Section 2.3.
Shown in Figure 4.

In FIG. 2, the setting positions of the regulating blade 24 and the shielding member 26 are changed to prevent the formation of an immovable layer using gravity, resulting in a light load.

The behavior of the magnetic particles in the developing device of this embodiment is such that when the sleeve 22 is rotated in the direction of the arrow, the magnetic particles rise from the bottom of the container 21 in a direction along the surface of the sleeve 22 and reach the vicinity of the blade 24. Therefore, some of the magnetic particles pass through the gap between the tip of the blade 24 and the surface of the sleeve 22 together with the toner, and the other part collides with the member 26 and is pushed by the subsequent movement of the magnetic particles and moves in the direction of arrow C. The particles move, eventually exiting the magnetic field of the magnetic pole 23a, descend by gravity on the outside of the ascending path of the magnetic particles, reach the lower part of the container 21, rise again near the sleeve 22, and repeat the above operation.

In this way, the magnetic particles that turn around and fall from the vicinity of the tip of the shielding member 26 take in toner particles from the toner layer on the outside.

By circulating in this manner with the rotation of the sleeve 22, the toner 28 is mixed with the magnetic particles 27 and the sleeve 22.
Charges up due to friction with the surface. Near the front of the blade 24, the magnetic particles 27 near the surface of the sleeve 22 are attracted to the surface of the sleeve 22 by the magnetic pole 23a, and as the sleeve 22 rotates, they pass under the blade 24 and exit the container 21. At this time, the magnetic particles 27 carry away the toner attached to their surfaces. Further, some of the charged toner particles 28 leave the container on the sleeve 22 while remaining attached to the surface of the sleeve 22 due to the reflection force. blade 24
regulates the amount of developer applied onto the sleeve 22.

In this embodiment, the shielding member 26 restricts the toner supply opening, prevents magnetic particle spikes caused by the magnetic pole 23a at the toner supply opening, prevents excessive uptake of toner from the spiked portion, and prevents the setting angle of the shielding member 26. By changing the pressure applied to the developer layer near the blade, it is possible to appropriately adjust the pressure applied to the developer layer, and it is possible to select a point that does not cause deterioration of the developer and is sufficiently charged, which is convenient.

In the developing device of this embodiment, PC-30 is used as the developer.
Developed using a light pressure fixing developer 2
There was no deterioration of the developer over 000 sheets, and images without capri mura were obtained.

In FIGS. 3 and 4, an empty chamber is provided on the downstream side of the shielding member 26 immediately before the blade to reduce the load.

FIG. 3 shows an example in which the cut magnetic pole 23a is separated from the blade portion and a shielding member 26 is provided for the cut magnetic pole 23a. The behavior of the magnetic particles in this embodiment is such that as the sleeve 22 rotates, the magnetic particles travel from the bottom of the container along the sleeve surface, take in toner, and reach the cut magnetic pole portion 23a. Near the cut magnetic pole part, the magnetic field causes the spikes to stand up and form a magnetic curtain with the shielding member. The magnetic curtain filters out excess toner taken in by the toner supply port to maintain stable toner content.

Furthermore, the developer that is not transported to the sleeve remains in the empty space, which applies a load to the developer and enables sufficient charging.

The charging load on the developer depends on the amount of the retained magnetic particle layer, and good development characteristics can be obtained by appropriately adjusting this.

In this embodiment, since a space is created between the blade 24 and the shielding member 26, the influence of the cut magnetic pole 23a is weak.
Since it is difficult to sufficiently regulate the layer thickness, it is preferable to provide an auxiliary magnetic blade 24a on the back surface of the blade 24. This stabilizes the developer coating.

In the above embodiment, the shielding member 26 was installed opposite the cut magnetic pole 23a, but it may of course be provided independently. Such an embodiment is shown in FIG.

In the developing device shown in FIG. 4, a shielding member 26 is provided opposite the magnetic pole of the magnetic pole 23e on the upstream side of the cut magnetic pole 23a.
A magnetic pole 23f is present. The magnetic pole 23f is used to improve the transportability of the developer, and may be omitted (or not present).The behavior of the magnetic particles is the same as that of the embodiment shown in FIG. 3, and detailed explanation thereof will be omitted.

In this embodiment, the shielding member 26 is used in order to strengthen the magnetic curtain formed by the magnetic pole 23e and strengthen the toner filtration effect.
It is also preferable that the opposing surface of the developing sleeve or a portion thereof be formed of a magnetic member. In this embodiment, since functions can be distributed to each magnetic pole, a more stable developer layer and image can be obtained.

Therefore, in this embodiment, as described above, a transport magnetic pole is provided at the toner supply opening to make the magnetic particles stand up at the opening, and even if excessive toner is taken in, the T/C is stable due to the toner filtration effect of the magnetic curtain. can be maintained and a good image can be maintained.

(Effects) As explained above, by providing a magnetic pole downstream of the toner supply opening and upstream of the regulating member, and by providing a developer shielding member within the range of the magnetic field, the T of the developer layer can be reduced. By maintaining /C and sufficiently charging the toner, it is possible to obtain a high-quality image without fogging or unevenness.

[Brief explanation of the drawing]

FIG. 1 is an explanatory view of a main part of one embodiment of a developing device according to the present invention, and FIGS. 2, 3, and 4 are enlarged views of main parts of other embodiments, respectively. 1 is a photosensitive drum 21 is a container 22 is a sleeve 23 is a magnet 24 is a blade 26 is a shielding member 27 is a magnetic particle 28 is a toner 29 is a magnetic seal 3゛1 is a toner supply opening 24a
is magnetic blade

Claims (1)

[Claims] 1) A developing sleeve has a magnet fixed therein, and toner stored in a toner storage container is supplied to magnetic particles magnetically attracted on the outer peripheral surface of the developing sleeve. A dry-type developing device that prepares a magnetic developer consisting of a mixture of magnetic particles and toner as the developing sleeve rotates, and develops an electrostatic latent image using this magnetic developer. A developing device characterized in that there is at least one magnetic pole on the downstream side in the magnetic developer transport direction and upstream of the developer layer thickness regulating member, and a developer shielding member is provided within the range of the magnetic field of the magnetic pole. Device. 2) The developing device according to claim 1, wherein a vacant chamber is provided between the developer shielding member and the developer layer thickness regulating member. 3) The developing device according to claim 2, wherein at least a portion of the developer layer thickness regulating member is made of a magnetic material.