JPH0777896A - Separating apparatus and image forming apparatus using this apparatus - Google Patents

Abstract

PURPOSE:To improve the reuse efficiency of developer by separating and removing only paper powder by making use of difference on the particle diameter and the polarity of the charge of toner, carrier, and the paper powder in the used developer. CONSTITUTION:The toner and the carrier in discharged developer are electrostatically charged to reverse polarity each other. The paper powder is electrostatically charged to the polarity opposite to that of the carrier, and adheres to the surface of the carrier. The toner and the paper powder in the discharged developer are carried by a carrying roller R1 incorporating a magnet roll 15, and carried to a position opposed to the carrying roller R2 while adhering to the carrier. The negatively electrostatically charged carrier is carried to the opposed position, and flies to the carrying roller R2 from the carrying roller R1. On the other hand, since the positively electrostatically charged toner and paper powder receive electric force in an opposite direction, they do not fly but are separated from the carrier; and remain on the carrying roller R1. Since the toner and the paper powder remaining on the carrying roller R1 do not have magnetism, they fall to be sifted by a mesh 22, and the paper powder having large particle diameter remains on the mesh 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separating device for removing a foreign substance from a mixture of a developer and a foreign substance, and an image forming apparatus using this device.

[0002]

2. Description of the Related Art In image forming apparatuses such as electrophotography and electrostatic recording, the amount of developer consumed is dramatically increasing with the increase in speed. Therefore, the amount of the used developer removed and collected from the surface of the photoconductor by the cleaning device is also increasing. It is extremely disadvantageous from an economical point of view to discard this used developer after collection as usual. Further, the disposal work is troublesome and is not preferable in terms of environmental hygiene. For this reason,
There is an increasing need to reuse the developer.

However, a good image cannot be obtained if the recovered developer is reused as it is after it is once supplied to the surface to be developed such as a photoreceptor. When a two-component developer is used, the recovered developer contains carrier particles and toner, as well as paper powder of transfer paper, etc., and the paper powder adheres to the carrier particles to prevent normal charging of the toner. This hinders the development efficiency. In order to separate and remove the paper powder from the developer, a method has been proposed in which the developer is sieved through a mesh having a mesh finer than the size of the paper powder to separate the paper powder.

[0004]

However, since the size of paper dust fibers is about the same as that of carrier particles, if a filter with a small mesh is used, the carrier particles are removed at the same time as the paper dust, and carrier particles in the developer are removed. There was a problem that the amount of particles decreased. If carrier particles are supplemented, the decrease can be suppressed but it is uneconomical.

[0005]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention provides a separating device for separating foreign matter from a mixture in which other foreign matter is mixed in a two-component developer having a toner and a carrier, and a separating device for the same. An image forming apparatus used,
It is characterized in that after separating the carrier from the mixture, the toner and the foreign matter are separated.

The present invention which solves this problem further provides a separating device for separating a foreign substance from a mixed substance in which other foreign substances are mixed in a two-component developer having a toner and a carrier, and an image forming apparatus using this device. Therefore, the carrier and the foreign matter are separated after the toner is separated from the mixture.

[0007]

The present invention will be specifically described below.

FIG. 4 shows a schematic structure of an example of a copying apparatus or a printer which is an image forming apparatus to which the separating apparatus according to the present invention is applied. Reference numeral 2 is a photosensitive drum having a photoconductive layer on its surface, 3 is a charger, 6 is a hopper for storing unused toner, 5 is a developing device, 10 is a transfer charger, and 11 is a cleaning device. The photosensitive drum 2 is rotatably supported in the direction of the arrow. The surface of the photosensitive drum is uniformly charged by a charger 3, and then exposed to an optical image of an original image or an exposure 4 of a light beam modulated by an image signal. Upon receipt, an electrostatic latent image is formed on the surface. Subsequently, the developer supplied from the developing device 5 adheres to the electrostatic latent image to form a visible image corresponding to the electrostatic latent image, and the visible image is carried in from outside the device by the transfer charger 10. Is transferred onto the transfer paper P. Thereafter, the transfer sheet is fixed with a visible image on the transfer sheet by a fixing device (not shown) to form a recorded image. On the other hand, the transfer residual developer remaining on the photosensitive drum in the transfer step is removed as a residue by the cleaning blade 7 of the cleaning device 11, and one cycle of image formation is completed.

The developer is a two-component developer composed of a toner and a carrier. In the developing process, the toner adheres to the image portion (characters, pictures, etc.) of the latent image, and the carrier adheres to the so-called white background portion. Further, in the transfer step, paper powder generated from the transfer paper adheres to the photosensitive drum when the photosensitive drum and the transfer paper come into close contact with each other. Therefore, in the used developer removed by the cleaning blade, toner, carrier,
Paper powder is mixed.

The used developer (hereinafter referred to as waste developer) collected by the cleaning device is sent to the developer reclaiming device (separating device) 1 by the carry-in screw 12, and paper dust is removed by the method described later. Separated into toner and carrier. The toner and the carrier are carried out from the developer regenerator 1 by the carry-out screws 18 and 19, respectively, and are again mixed and sent by the carrying screw 13 and are supplied to the developing device 5 as a reused developer.

The reused developer is sufficiently mixed with the unused developer supplied from the hopper 6 by the stirring rods 8 and 9 and used again in the developing step.

Next, the developer regenerator 1 will be described in detail.

FIG. 1 shows the structure of a developer regenerating apparatus 1. R1 and R2 are transport rollers that transport the developer. R1 is a metal sleeve 14 which is rotatably supported.
And a magnet roll 15 fixed inside thereof. Similarly, R2 also comprises a sleeve 16 and a magnet roll 17. The waste developer T0 collected by the cleaning device is carried to the carrying roller R1 by the carry-in screw 12.

The carrier and toner in the waste developer are charged with opposite polarities, and the toner particles adhere to the surface of the carrier particles. Further, according to the experiment, it was found that the paper dust was charged with the opposite polarity to the carrier and adhered to the carrier surface. The toner used in the present invention is a positively chargeable toner, and the carrier is a negatively chargeable carrier. Of course, the present invention can be applied even if the polarities of the toner and the carrier are changed according to the charging polarity of the photosensitive drum and the developing method used.

Since the carrier is made of a magnetic material, the toner and the paper powder in the waste developer remain attached to the carrier while the carrier roller R has a built-in magnet roll 15 together with the carrier.
The sheet 1 is conveyed in the direction of arrow A by 1 and is conveyed to a position facing the conveying roller R2. The gap d between the opposing positions of R1 and R2
Is held at 100 to 500 μm, the sleeve 14 of R1 is grounded, and the sleeve 16 of R2 is biased by +500 to 1500 V by the power supply 23.
Therefore, when the negatively charged carrier is carried to the facing position, it receives an electric force from R1 to R2 and flies to R2. On the other hand, the positively charged toner and paper powder do not fly because they receive an electric force from R2 to R1 and are separated from the carrier and remain on R1. The carrier T1 that has moved to R2 is transported in the direction of arrow B, scraped off from the surface of R2 by the scraper 21, and transported by the transport screw 19. R
The toner and the paper dust remaining on the sheet 1 have no magnetism and lose the restraint force on the sheet R1 and fall downward along the container wall 20 and are sifted by the mesh 22. Since the mesh size is 30 μm, the toner particle size is 10 μm, and the paper powder size is 50 μm or more, only the paper powder remains on the mesh, and the toner T2 passes through the mesh and the discharging screw 1
It is carried out by 8.

In the above, in order for the carrier to fly from R1 to R2, it is necessary that the magnetic attractive force of R1 at the facing position is not excessive. In the present invention, the magnetic flux density of the magnetic pole S1 at the facing position of R1. Was set to 600 gauss. Further, the magnetic flux density of the magnetic pole N1 at the opposing position of R2 is set to 800 Gauss, which is larger than S1, to facilitate the flight.

In this way, only the paper powder is removed from the waste developer and the toner and carrier are taken out. The toner and the carrier are carried out in a separated state, mixed by the carrying screw 13 and sent to the developing device. If paper dust on the mesh accumulates, it will be clogged, so the paper dust that has accumulated is regularly cleaned and removed.

(Embodiment 2) The developer regenerating apparatus described above uses two magnet rolls, but the second embodiment shows a developer regenerating apparatus using only one magnet roll.

The developer recycling device shown in the figure also has two transport rollers, one of which is a transport roller containing a magnet roll and the other one is a metal transport roller without a magnet roll. Is. R3 is a transport roller including a magnet roll and a sleeve, and 25 is a metal transport roller.

The carry-in screw 24 is connected to a cleaning device (not shown), and conveys the waste developer collected by the cleaning device to the developer recycling device. The conveyed waste developer adheres to the conveyance roller R3, and as the sleeve of R3 rotates (counterclockwise), the conveyance roller 2
It is carried to the position opposite to 5. The R3 and the transport roller 25 are arranged with a gap of 300 to 500 μm from each other, and a non-magnetic metal mesh 29 having a thickness of 100 μm is formed at an intermediate position of the gap in a direction perpendicular to a line connecting the centers of R3 and the transport roller 25. Is stretched. The length of the mesh 29 in the direction perpendicular to the paper surface is almost the same as the axial length of R3 and the transport roller 25, and in this example, the length is 150 mm. The mesh size is 30 μm as described above. further,
The sleeve of R3 is grounded, the conveyance roller 25 is applied with a bias 30 of -800V, and the mesh is applied with a bias of -400V. For this reason,
Of the waste developer carried to the facing position, the positively charged toner and paper powder receive an electric force from R3 toward the transport roller 25 and fly from R3 to the transport roller 25. At this time,
Since the toner can pass through the mesh, the transport roller 2
It reaches 5, but the paper dust cannot pass through the mesh, so it stops on the mesh. Therefore, the paper dust is removed and only the toner moves to the transport roller 25. The moved toner drops downward as the transport roller 25 rotates and is delivered by the delivery screw 26. On the other hand, since the carrier is negatively charged, it receives an electric force from the transport roller 25 toward R3, remains on R3, is transported to the upper right as R3 rotates, is scraped off by the scraper 28, and is unloaded by the unloading screw 27. It In this way, only the paper dust is removed from the waste developer, and the toner and the carrier are taken out in a separated state. The toner and the carrier are mixed again as described above, sent to the developing device, and reused in the developing process.

(Embodiment 3) In all of the above-mentioned developer regenerating apparatuses, toner or carrier is jetted by utilizing electric force between two facing conveying rollers to separate toner and carrier. However, in this method, it is necessary to maintain the gap between the two transport rollers at several hundreds of μm, and even if the size of the gap is about several tens of μm, the electric force changes greatly even if the gap slightly fluctuates. High mechanical precision is required because the carrier and the flying amount of the carrier are changed, and the third embodiment further solves this point, and a developer regenerating apparatus that does not require mechanical precision is shown in FIG.

Reference numeral 31 is a carry-in screw for carrying in the waste developer, 32 is the above-mentioned non-magnetic metal mesh, 36 is a rotating magnetic roller, 34 is a scraper, and 33 and 35 are carry-out screws.

The waste developer carried in by the carry-in screw 31 is discharged onto the mesh 32 stretched obliquely inside the developer recycling apparatus. This mesh 32 is vibrated in the vertical direction by a vibrating device which will be described later. The waste developer is sifted by vibration while falling down on the mesh due to its own weight, and only the toner in the waste developer is vibrated. It passes through the mesh and falls downward. The dropped toner is collected at the entrance of the carry-out screw 33 and carried out by the carry-out screw 32. On the other hand, the carrier has a particle size of 50-
Since the size is 60 μm and is about the same as the size of the paper powder, it does not pass through the mesh, and the carrier and the paper powder slide down on the mesh and contact the magnet roller 36. Magnet roller 36 is +800
A bias of V is applied and the mesh is grounded. For this reason, only the carrier that is in contact with the magnet roller and the carrier that is negatively charged among the paper powder are attached to the magnet roller by the electric attraction, are transported, are scraped by the scraper 34, and are transported by the transport screw 35. Since the paper dust is positively charged, it remains on the mesh repelled by the magnet roller. As a result, the paper powder is removed from the waste developer and the toner and carrier are taken out.

FIG. 5 shows a vibrating device for the mesh 32. Spring 3 fixed to container walls 38 and 41 of the developer recycling device
6, 39 are connected to the mesh 32 in a compressed state, and have a force to push the mesh 32 downward. On the other hand, the springs 36 and 39 with the mesh 32 sandwiched therebetween.
Cams 37 and 40 are rotatably supported on the lower part of the
It rotates at the same speed in the directions of arrows C and E. As cams 37 and 40 rotate, mesh 3
2 vibrates vertically in the D and F directions. By changing the cam diameter and rotation speed, the vibration displacement of the mesh,
The vibration speed can be adjusted, and it can be set so that the toner passes quickly.

In the above method, since the carrier and the paper dust may be brought into contact with the magnet roller, high mechanical precision is not required.

In the above embodiment, when the paper dust was removed, the physical property that the paper dust was positively charged was used.
Depending on the type of paper and the type of developer used, the paper powder may be negatively charged or may not be charged. Even in such a case, it is possible to remove the paper dust by the same method as in the above-mentioned invention by changing the polarity of the bias applied to the conveying roller or by using the vibrating mesh in combination.

[0027]

As described above, according to the present invention, in the copying machine or printer using the two-component developer, the toner, carrier and paper dust in the used developer collected from the surface of the photosensitive drum are removed. By utilizing the difference in particle size and charge polarity, only the paper powder was removed from the used developer, the toner and the carrier were collected together, and the developer generating device used again in the developing process was provided. As a result, the consumption of the carrier can be suppressed and the reuse efficiency of the developer is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a developer recycling device (Example 1).

FIG. 2 is a diagram showing a developer recycling device (Example 2).

FIG. 3 is a diagram showing a developer recycling device (Example 3).

FIG. 4 is an overall view of a copying apparatus.

FIG. 5 is a diagram showing a mesh vibrating device.

[Explanation of symbols]

 1 Developer Regenerating Device 5 Developing Device 7 Cleaning Blade 11 Cleaning Device 12 Carrying Screw 13 Carrying Screw 15, 17 Magnet Roll 18, 19 Carrying Out Screw R1, R2 Carrying Roller 21 Scraper 22 Mesh

Claims (4)

[Claims] 1. A separation device for separating foreign matter from a mixed matter in which other foreign matter is mixed in a two-component developer having a toner and a carrier, wherein the carrier and the foreign matter are separated from the mixed matter. Separation device characterized by: 2. An image forming apparatus comprising: a developing unit that forms a toner image on an image carrier using a two-component developer having a toner and a carrier; and a cleaning unit that removes residues from the image carrier. An image forming apparatus comprising: a separating unit that separates foreign matter from the removed residue, and the separating unit separates the carrier from the residue and then separates the toner and the foreign matter. 3. A separation device for separating a foreign matter from a mixed matter in which other foreign matter is mixed in a two-component developer having a toner and a carrier, wherein the toner is separated from the mixed matter.
A separating device for separating a carrier and a foreign substance. 4. An image forming apparatus comprising: a developing unit that forms a toner image on an image carrier using a two-component developer having a toner and a carrier; and a cleaning unit that removes residues from the image carrier. An image forming apparatus comprising: a separating unit that separates foreign matter from the removed residue, the separating unit separating the toner from the residue and then separating the carrier and the foreign matter.