JPH0448232B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a dry developing device used in electrophotographic copying processes and the like.

Conventional technology As a dry developing method that has already been put into practical use,
There is a one-component development method that uses a developer consisting only of magnetic toner. However, this one-component development method
Regarding toner, there is a difficult problem in that it requires contradictory conditions such as conductivity during development and insulation during transfer. Toners with high resistance are used and various measures are taken to improve development characteristics.

As one of this kind of countermeasures, the present applicant has already proposed a magnetic roller 2 inside as shown in FIG.
a developing sleeve 1 for transporting a magnetic developer made of a mixture of toner and a magnetic carrier in one direction on its outer circumferential surface; and a hot height provided on the upstream side of the developing area A in the developer transport direction [arrow b]. Regulation plate 3
Developing sleeve 1 is placed upstream of this height regulating plate 3.
A front regulating plate 4 is provided to face the outer peripheral surface of the developing sleeve 1 between the height regulating plate 3 and the front regulating plate 4.
A vacant chamber 5 formed to open toward the outer peripheral surface of the
A dry type developing device has been proposed which includes a toner replenishing section 6 installed on the upstream side of the front regulating plate 4 (see Japanese Patent Application No. 183633/1983).

In this dry type developing device, the developing sleeve 1
Based on the rotation of the magnetic roller 2 in the direction of the arrow b and/or the rotation of the magnetic roller 2 in the direction of the arrow a, toner is supplied to the magnetic carrier previously supplied on the outer peripheral surface of the developing sleeve 1 to prepare a magnetic developer, The electrostatic latent image carried on the surface of the photosensitive drum 9, which is circulated in the direction of the arrow b and rotated in the direction of the arrow c, is developed in the development area A. After development, the magnetic developer whose toner concentration has decreased passes through a perforated scraper 8 (not necessarily required), and is replenished with toner contained in a toner replenishing tank 7 at a toner replenishing section 6.

If this dry developing device is used, even if development is performed using toner that is originally a one-component developing system, the inclusion of a magnetic carrier will ensure that the toner is triboelectrically charged, and the conveyance force will be increased due to improved magnetic permeability. This prevents toner aggregation and increases the effective electric field and electric field strength in the developing area, and can be expected to greatly improve the developing characteristics. Particularly, due to the existence of the empty space 5, the magnetic developer transported to the developing area A is transported to the empty space 5.
By accumulating and mixing and stirring the magnetic carrier in the toner supply tank 7, the magnetic carrier is prevented from being diffused into the toner replenishing tank 7, and a constant toner concentration can be maintained in the development area A at all times.

Problems to be Solved by the Invention By the way, as a result of various experiments conducted by the present inventors using the above-mentioned dry type developing device, it was found that blocking toner is present in the empty chamber 5 and the magnetic developer on the developing sleeve 1. It has been confirmed that the magnetic carrier is supplied to the developer sleeve 1, and that the magnetic carrier is dissipated from the outer peripheral surface of the developing sleeve 1 into the toner replenishing tank 7 when the toner is operated for a long time. Due to this dissipation, the toner concentration of the magnetic developer prepared on the outer peripheral surface of the developing sleeve 1 increases more than necessary, and if the dissipation of the carrier is uneven in the axial direction, uneven toner concentration occurs in the axial direction. I will do it.

The former problem is caused by the fact that the toner supply section 6 is wide and does not have a blocking toner supply blocking or crushing function.

The latter problem is caused by the fact that the toner replenishing section 6 in the device is relatively long in the circumferential direction, and () the toner supplied at X ₁ is mixed and stirred with the magnetic carrier before being conveyed to X ₂ ; The magnetic carrier slightly floating above the outer peripheral surface of the developing sleeve 1 is regulated by the tip of the front regulating plate 4. () The location and direction where the toner is supplied are as shown by arrow Y ₁ , The location and direction of the dissipation are as shown by the arrow _Y2 , and this is thought to be due to the inability to effectively prevent the dissipation of the magnetic carrier. Therefore, a small amount of the magnetic carrier gradually dissipates into the toner supply tank 7.

Therefore, in view of the above-mentioned problems, the present invention has been designed to prevent the magnetic carrier in the magnetic developer conveyed in one direction on the outer circumferential surface of the developing sleeve from dissipating into the toner replenishing tank during the operation of the device and preventing blots. The purpose is to reliably prevent the supply of king toner.

Means for Solving the Problems The dry type developing device according to the present invention is based on the dry type developing device proposed by the present applicant, and extends in the axial direction of the developing sleeve, and connects the vacant space and toner supply. The toner supply tank includes a toner supply slit that communicates with the tank, and a toner supply force applying means that applies a supply force to the toner stored in the toner supply tank in the direction of the slit and the empty chamber.

In other words, the toner supply tank and the empty chamber are electrically connected only through the toner supply slit extending in the axial direction of the developing sleeve, and the toner stored in the toner supply tank is distributed as the toner in the empty chamber decreases. The toner is supplied into the cavity through the slit by the conveying force of the toner supply means, where it is mixed with the magnetic developer and agitated, and the toner is supplied to the magnetic carrier on the outer peripheral surface of the developing sleeve.

In this case, in the slit portion, the toner is applied with pressure (supply force) toward the slit and the empty chamber by the toner supply means, so that magnetic carriers that try to dissipate from the slit into the toner supply tank are suppressed. Its dissipation is prevented. In addition, the blocking toner in the toner supply tank comes into contact with the slit component and is crushed or blocked from passing through the slit, and the blocking toner is transferred to the magnetic carrier on the outer peripheral surface of the developing sleeve through the empty chamber. is prevented from being supplied to the target.

Embodiment FIGS. 1 to 4 show an embodiment of a dry developing device according to the present invention, in which a developing sleeve 10 formed in a cylindrical shape from a conductive non-magnetic material has S,
A magnetic roller 11 with N poles sequentially magnetized is housed coaxially, and this developing sleeve 10 is installed in the opening of the toner replenishing tank 20 so as to be close to the surface of the photoreceptor drum 9. Based on the rotation of the roller 11 in the direction of arrow a and/or the rotation of the developing sleeve 10 in the direction of arrow b, the developing sleeve 10 is conveyed on the outer circumferential surface of the developing sleeve 10 in the direction of arrow b.

The height regulating plate 22 is integrally formed on the inner surface of the inclined upper surface of the toner replenishing tank 20, and is installed on the upstream side of the developing area A in the developer transport direction.
Further, the toner supply tank 20 is partitioned into a developing section and a toner storage section 21 by a first partition plate 12 and a second partition plate 14. The second partition plate 14 is attached to the bottom of the toner replenishing tank 20, and its tip is close to the outer peripheral surface of the developing sleeve 10. The first partition plate 12 is attached to the ceiling of the toner supply tank 20, and its lower end is bent in the direction of the second partition plate 14, and this bent piece 12a and the second partition plate 1
4 forms a toner supply slit 13. The slit 13 extends in the axial direction of the developing sleeve 1 within a region covered by the magnetic field of the magnetic roller 11.

Further, between the height regulating plate 22 and the first partition plate 12, there is an empty space 15 in which a magnetic carrier or a mixture of a magnetic carrier and toner is loaded in advance.
is formed so as to open only toward the outer peripheral surface of the developing sleeve 10. A large number of fins 16 located in the empty chamber 15 are attached to the first partition plate 12 so as to be inclined in the axial direction of the developing sleeve 10. It has the function of stirring in the axial direction. Also,
At the lower end of the toner supply tank 20 and below the development area A, a magnetic developer spill prevention plate 17,
18 is installed, and the toner spilled from the development area A is collected by the developer spill prevention plates 17 and 1.
8 magnetically attracted.

On the other hand, the toner storage section 2 of the toner supply tank 20
1, a toner supply blade 23 and a toner empty detection plate 25 are installed. The toner supply blade 23 can be driven to rotate at a constant speed in the direction of the arrow d with the support shaft 24 as a fulcrum, and this rotation conveys the toner to the slit 13 side. The toner empty detection plate 25 is rotatable about a support shaft 26, and the toner supply blade 2 rotates in the direction of arrow d.
When the contact occurs in step 3, it moves upward, and after the contact is released, it moves downward under its own weight. This downward movement time changes depending on the amount of stored toner; that is, as the amount of toner decreases, the resistance decreases and the downward movement time becomes shorter. Therefore, the amount of toner is detected by appropriately measuring this downward movement time with a switching means, and when the toner becomes empty, it is configured to be displayed externally.

Further, a cartridge 28 for replenishing toner is detachably attached to the upper part of the toner supply tank 20. The toner stored in the cartridge 28 in advance is removed from the cartridge lid 29 by the toner replenishing tank lid 2.
By pulling it out together with 7, the container 21 is replenished.

Next, the operation of the dry developing device having the above structure will be explained.

First, a starter made of a mixture of magnetic carrier and toner is loaded into the empty chamber 15, and after the device is pre-operated, magnetic toner is loaded into the toner storage section 21. At this time, only a magnetic carrier may be loaded into the empty chamber 15 instead of the starter. In this state, the electrostatic latent image can be developed by this apparatus.

Here, the magnetic toner is indicated by the arrow a on the magnetic roller 11.
The toner is conveyed in the direction of the arrow b on the outer peripheral surface of the developing sleeve 10 based on the rotation in the direction, and is mixed and stirred with the magnetic carrier when passing through the empty chamber 15, and the toner and the magnetic carrier are each triboelectrically charged. As a result of this mixing and agitation, the toner and magnetic carrier, which are each component of the magnetic developer, are constantly integrated at a constant mixing ratio at this point, and the magnetic brush made of the magnetic developer is securely in the developing area A. is formed.
The magnetic brush formed here rubs the surface of the photoreceptor drum 9, and develops the electrostatic latent image on the surface into a visible image. After being subjected to development, the developing sleeve 10
The magnetic developer remaining on the outer peripheral surface of the toner reaches the empty chamber 15 again, where new toner is supplied, mixed and stirred, and then subjected to development again.

The toner is supplied as follows.

The magnetic toner contained in the toner storage portion 21 is conveyed to the slit 13 side by the rotation of the toner supply blade 23 in the direction of arrow d, and
1 rises along the right side of the second partition plate 14 in FIG. 1, and is supplied into the empty space 15 through the slit 13. The supply amount corresponds to the amount by which the toner in the empty chamber 15 is reduced.

Note that as the developing bias, a DC voltage is applied to the developing sleeve 10 based on a normal method, but an AC voltage may be superimposed on this, and
The developing sleeve 10 may be grounded.

By the way, when this device is used, the magnetic carrier remains in the toner storage portion 2 even after long-time operation.
It did not dissipate within 1 hour. This is because the slit 13 is the only place where the magnetic carrier is dissipated, but the slit 13 is filled with toner.
Furthermore, this toner is subjected to the action of the magnetic field of the magnetic roller 11 which also functions as a toner supply means, and pressure (supply force) is applied in the direction of the empty chamber 15 by rotation in the direction of arrow a, and the toner supply blade 23 This is because even when the magnetic carrier rotates in the direction of the arrow d, pressure (supply force) is applied in the direction of the empty chamber 15, so dissipation of the magnetic carrier is suppressed.

In this embodiment, the direction in which the magnetic carrier is dissipated is through the toner supply slit 13 in FIG.
The position is downward, and in this part the magnetic roller 1
1, the magnetic developer receives an upward conveying force, so the magnetic carrier moves into the toner storage section 2.
It can be said that the force that tries to dissipate into 1 is not very strong.

Furthermore, the toner is not immediately supplied to the magnetic developer on the developing sleeve 10, but instead enters the empty chamber 15 and is mixed and stirred there, so that the toner particles are sufficiently charged and the application of the developing bias is prevented. It works effectively and can reliably remove toner fog, etc.

Furthermore, blocking toner no longer enters the empty chamber 15 and is no longer supplied to the outer circumferential surface of the developing sleeve 10. This is because the supply passage is formed into a narrow slit 13, and the blocking toner comes into contact with the slit component and is blocked from passing and is pulverized.

On the other hand, in the empty chamber 15, the magnetic carrier and toner regulated by the brush height regulating plate 22 accumulate and are mixed and agitated.
It is also sufficiently stirred in the axial direction. And vacant room 1
If the toner concentration within 5 is constant, the toner concentration of the magnetic developer forming the magnetic brush in the development area A is constant. In the present invention, only the consumed amount of toner is supplied into the cavity 15 through the slit 13, and the amount of toner (toner concentration) within the cavity 15 is approximately constant. Therefore, automatic toner concentration control based on volume control is possible.

Here, we will show experimental data conducted by the inventors using this device. Experiments were carried out by changing the types and mixing ratios of toner and magnetic carrier, and by changing the developing conditions such as the developing gap, the height regulating gap, and the pre-regulating gap, and good results were obtained in each case.
The data shown below is an example.

Magnetic carrier: Spherical ferrite carrier (manufactured by Fuji Electrochemical Co., Ltd.) Average particle size 35 μm, resistance 1.5×10 ¹¹ Ωcm
(measured under 400V/cm electric field), saturation magnetization
50emu/g.

Toner: 100 parts by weight of styrene-acrylic copolymer (manufactured by Gutdeyer: PLIORITE AC), 80 parts by weight of magnetic fine powder (manufactured by Titan Kogyo: MAGETITE RB-BL)
Weight part, carbon black (manufactured by Mitsubishi Chemical Corporation:
Magnetic toner with an average particle diameter of 12 μm and a resistance value of 10 ¹⁴ Ωcm obtained by melting and mixing 4 parts by weight of MA#100) and 2 parts by weight of a charge control dye (manufactured by Orient Chemical Co., Ltd.: NYGROSINE), cooling, crushing, and classifying. .

Starter: A developer loaded in advance into the empty chamber 15,
200 wt% of the carrier and 100 wt% of the toner were mixed and stirred, and the toner concentration was 33 wt%.

Development conditions Developing sleeve: Diameter 24.5 mm Rotation speed 79 rpm Magnetic roller: Number of poles 8 Magnetic flux density 750 Gauss Rotation speed 900 rpm Developing gap d1: 0.45 mm Brush height regulation gap d2: 0.35 mm 2nd partition plate gap e: 1.5 mm Slit width f: 1.5mm Slit height g: 1.0mm Process speed (photosensitive drum circumferential speed): 112mm/sec Electrostatic latent image maximum potential: +500V Developing bias: DC +200V AC 600Hz (350Vrms) Toner supply blade: Rotation speed 60rpm This experiment example Although 100,000 copies were made, the magnetic carrier did not dissipate into the toner container 21, the copied images remained good until the end, and the magnetic carrier itself did not deteriorate.

Further, 64 g of the starter was previously loaded into the empty chamber 15, but in this case, the toner concentration in the development area A was 45 wt%. When a 64 g starter is loaded into the cavity 15, a slight void remains at the top of the cavity 16. When the developing device is preliminarily operated prior to development, toner is supplied into the empty chamber 15, so that the empty chamber 15 becomes, so to speak, in a full state. Development is possible from this point. The change in toner density in the developing area A due to changing the amount of starter is as shown in FIG. Therefore, the toner concentration in the development area A can be adjusted depending on the amount of magnetic carrier loaded into the empty chamber 15 in advance.

Regarding the second partition plate gap e, 1.4 to 2.5
mm range is appropriate; if it is too wide, the magnetic roller 1
The effect of the magnetic field No. 1 weakens, resulting in a shortage of toner supply, and if it is too narrow, toner supply becomes unstable and uneven toner density occurs. Regarding the slit width f, it is appropriate that it is about 1.4 to 2.5 mm; if it is too wide, uneven toner density will occur, and if it is too narrow, it will lead to insufficient supply of toner. However, the above numerical values and the toner concentration are appropriately determined depending on the magnetic force of the magnetic roller 11, the magnetic carrier, and the type of toner, and are not uniquely determined.

Although the fins 16 provided in the cavity 15 are not necessarily required in the present invention, they have the effect of improving the stirring performance of the magnetic developer in the cavity 15. Therefore, it is possible to replace the structure with a structure in which a rod-shaped body made of a magnetic material is installed in the axial direction within the empty chamber 15 as a device having a similar effect. In this case, the magnetic bar-shaped body is magnetized by the magnetic force of the magnetic roller 11, and a magnetic field for stirring is formed around it. Therefore, it is effective in a magnetic roller rotation type device like this embodiment.

Further, in order to increase the developer conveyance force by the developing sleeve 10, minute irregularities may be formed on the outer circumferential surface of the developing sleeve 10 by blasting or the like.

On the other hand, the dry type developing device shown in FIG. 1 can be used to develop electrostatic latent images using not only magnetic toner but also non-magnetic toner and magnetic carrier. In this case, since the toner is non-magnetic,
The toner cannot be supplied by the rotation of the toner due to the rotation of the magnetic roller 11, and a separate means is required to constantly apply pressure to the toner supply slit 13. By providing such a toner supply means, when a gap is created in the cavity 15 due to toner consumption, toner is supplied to the cavity 15 and the toner concentration is maintained at a constant value.

Effects of the Invention As is clear from the above explanation, according to the present invention,
A toner supply slit extending in the axial direction of the developing sleeve and communicating between the empty chamber and the toner replenishing tank, and applying a supply force to the toner stored in the toner replenishing tank in the direction of the slit and the empty chamber. Since the slit is provided with a toner supply force applying means, toner supply pressure is constantly applied to the slit.
It is possible to reliably prevent the magnetic carrier in the magnetic developer conveyed in one direction on the outer peripheral surface of the developing sleeve from dissipating into the toner supply tank during operation of the device.
Furthermore, the presence of the slit prevents the blocking toner from passing into the empty chambers and crushes it, making it possible to obtain copied images of good quality over a long period of time.

[Brief explanation of the drawing]

1 to 4 show an embodiment of the dry developing device according to the present invention, in which FIG. 1 is a cross-sectional view, FIG. 2 is a cross-sectional view taken from FIG. 1, and FIG. FIG. 4 is a graph showing toner density. FIG. 5 is a sectional view of a dry developing device disclosed as a prior art. 9...Photosensitive drum, 10...Developing sleeve,
11...Magnetic roller, 12...First partition plate, 1
3... Toner supply slit, 14... Second partition plate, 15... Vacant room, 20... Toner supply tank, 2
1... Toner storage section, 22... Hot height regulation plate, 23
...Toner supply blade, A...Development area.

Claims (1)

[Scope of Claims] 1. A dry-type developing device that develops an electrostatic latent image using a magnetic developer made of a mixture of a magnetic carrier and toner that is magnetically attracted onto the outer peripheral surface of a developing sleeve, comprising: A vacant chamber that opens toward the outer peripheral surface of the developing sleeve located upstream of the developing area in the developer conveyance direction and stores a magnetic carrier and toner, and a toner replenishment tank that stores toner to be replenished into the vacant chamber. a toner supply slit extending in the axial direction of the developing sleeve and communicating between the empty chamber and the toner supply tank; and a toner supply slit extending in the axial direction of the developing sleeve and communicating with the empty chamber and the toner supply tank; A dry developing device comprising: a toner supply force applying means for applying a toner supply force;