JP2654005B2 - Electrostatic latent image developing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrostatic latent image developing device, and more particularly, to a dry type 2 developing device.
The present invention relates to a hybrid electrostatic latent image developing device in which a component developer is used as a one-component developer.

(Prior Art) Generally, in a developing device using a dry two-component developer,
As shown in FIG. 3, a large developing tank 1 is provided with a stirring mechanism such as a stirring roller 2 and a conveying screw 3 and a stirring separator 4. After the toner replenished from the toner hopper 5 side is sufficiently mixed and stirred with the carrier by the stirring mechanism such as the stirring roller 2, the toner is supplied to the developing roller 6 as a developer carrying member. Are formed. The thickness of the attached developer layer is regulated by the doctor blade 7.

The developing roller 6 includes a plurality of magnets 9 inside a sleeve 8. By rotating at least one of the sleeve 8 and the magnet 9 in a certain direction, a magnetic brush formed on the surface of the sleeve 8 is fixed in a certain direction. Moved to Then, when the magnetic brush contacts the photosensitive drum 10 as a latent image carrier, the electrostatic latent image formed on the photosensitive drum 10 is developed and visualized. After the development, the magnetic brush is scraped into the developing tank 1 and mixed and stirred again by the stirring mechanism such as the stirring roller 2.

As described above, the two-component developer requires sufficient stirring and mixing, for the purpose of maintaining the uniformity of the toner concentration or performing good toner charging. According to the conventional developing apparatus using the two-component developer, there is an advantage that the image quality can be stabilized. However, the developer must be sufficiently stirred as described above. In order to perform sufficient stirring, various stirring mechanisms are required, and a sufficient space is provided for forming a stirring channel. further,
The carrier is required to have good fluidity in order to obtain good stirring characteristics. In particular, carriers that exhibit cohesiveness even when the magnetic field is removed due to remanence are
It cannot be applied to a developing device on the premise of the stirring mechanism. In addition, if the stirring is performed frequently, the fatigue of the carrier progresses quickly, and there is a problem in durability.

On the other hand, in order to solve the drawbacks of the developing device using the two-component developer, various developing devices which can omit the mixing and stirring of the developer have been developed. In such a developing device, toner is supplied by attaching the toner to the surface of a charging roller and then bringing the charging roller into contact with a magnetic brush. And a thin layer of toner is formed on the developing roller.

However, the former has a disadvantage that the toner density on the developing roller tends to be uneven, and the latter has a problem that the developer must still be sufficiently mixed and stirred.

(Purpose) Accordingly, the present invention is intended to reduce the size of the entire apparatus, improve the handling properties and the durability, and further reduce the dry two-component developer to a one-component developer so as to maintain good image stability. It is an object of the present invention to provide a hybrid type developing device which is designed to be used.

(Structure) In order to achieve the above object, a hybrid-type electrostatic latent image developing device according to the present invention includes a magnetic brush for supplying toner to a latent image on a latent image carrier in a toner developing area, and the magnetic brush. A toner supply means for supplying charged toner in the toner supply area to the toner supply roller, and a toner collection roller for collecting toner remaining on the magnetic brush after development in the toner collection area, and a pressure roller and a toner collection roller. A developing device for a hybrid electrostatic latent image, comprising: a toner collecting means comprising a scraped blade, wherein a bias voltage having the same polarity as that of the toner is applied to the toner supplying means; For the roller, a charging member that is frictionally charged to a different polarity from the toner due to friction with the scraping blade is used, and is collected by the toner collecting roller. The toner is scraped off from the toner collecting roller by the scraping blade, and the toner collecting roller is frictionally charged.

In such a hybrid developing device, a two-component developer is treated as a one-component developer. That is, the charged toner in the toner supply area is supplied to the magnetic brush side by the toner supply means, and development is performed. After the development, the toner remaining on the magnetic brush is recovered by a toner recovery unit in a toner recovery area, and the magnetic brush is returned to the toner supply area again after the toner concentration becomes uniform.

In particular, in the hybrid type developing device according to the present invention, the charging member used in the toner collecting means is frictionally charged to a different polarity from the toner itself by friction. Is collected. Therefore, it is not necessary to provide a bias power supply for the toner collecting means.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, a photosensitive drum 11 as a latent image carrier is rotationally driven in the direction of arrow A, that is, clockwise by a drive mechanism (not shown). The photoconductor drum 11 is made of an organic photoconductor (OPC), and the polarity of the electrostatic latent image formed on the photoconductor drum 11 is made negative (-). Therefore, the developing toner described later is charged to positive (+) with the opposite polarity.

Further, in the vicinity of the photosensitive drum 11, a non-magnetic cylindrical sleeve 12 made of aluminum or the like is arranged. The cylindrical sleeve 12 is provided with a gap of 1 mm from the photosensitive drum 11 so that a suitable developing operation can be obtained by elastically contacting the magnetic brush photosensitive drum 11 described later. Further, inside the cylindrical sleeve 12, a developing magnet roller 13 in which a plurality of magnetic poles having different polarities are alternately arranged is provided at a constant interval from the inner surface side of the cylindrical sleeve 12, A magnetic brush comprising a magnetic carrier and toner on the surface of the cylindrical sleeve 12 by the magnetic force of the developing magnet roller 13
14 are formed. This magnetic brush 14
Is moved in the direction of arrow B, ie, clockwise by rotating at least one of the cylindrical sleeve 12 and the developing magnet roller 13. As a carrier constituting the magnetic brush 14, 40 g of a resin-coated carrier having an average particle diameter of 100 μm is used.

A power supply circuit 15 applies a developing bias voltage of the same polarity to the cylindrical sleeve 12 and the photosensitive drum 11. And a magnetic brush on the cylindrical sleeve 12
A developing operation is performed by bringing the photosensitive drum 11 into contact with the photosensitive drum 11 while being moved as described above, and toner is applied to the electrostatic latent image 16 formed on the photosensitive drum 11 by the developing operation, thereby 17 can be obtained.

In this embodiment, the cylindrical sleeve 12 has an outer diameter of 20 mm.
And the developing magnet roller 13 is such that the surface magnetic force of the cylindrical sleeve 12 is about 900 gauss. Thereby, the height of the magnetic brush 14 can be set to 0.3 to 5 mm, preferably 0.7 to 2 mm.

The developing bias is applied for preventing background contamination and adjusting image density. In this embodiment, the latent image potential is set to -800 V, the background portion potential is set to -50 V, and the developing bias voltage is set to -150 V. Note that the final developing bias value is determined according to the document density or the user's desire.

Further, a toner collecting roller 18 for collecting the residual toner from the magnetic brush 14 after the development is completed is provided at a gap of 1 mm above the cylindrical sleeve 12.
The toner collecting roller 18 has a Teflon layer having a thickness of 40 μm as a charging member applied on the surface of a metal roller by coating. Since the applied Teflon is positioned at a considerably lower position in the triboelectric series, it is triboelectrically charged to the negative polarity (−) of a different polarity from the toner by frictional contact with other members. Toner (+) remaining on the magnetic brush 14 side due to such a charged state
Is moved to the toner collecting roller 18 (-) side, and the toner collecting operation is performed.

The toner collecting roller 18 is driven to rotate in the direction of arrow C, that is, clockwise by a rotation driving mechanism (not shown), and the toner collecting roller 18 is so pressed that the scraping blade 21 is pressed against the toner collecting roller 18. It is attached. The scraping blade 21 is formed of a plate-like member made of a polyurethane material which is higher in the triboelectric series than the Teflon layer of the toner collecting roller 18. Therefore, as described above, the Teflon layer is frictionally charged to the negative polarity (-) having a different polarity from the toner by the frictional contact of the toner collecting roller 18 with the Teflon layer, and the scraping blade 21 is frictionally charged to the (+) polarity. It has become.

Further, by bringing the scraping blade 21 into pressure contact with the toner collecting roller 18, the toner collected and attached to the toner collecting roller 18 is scraped off from the toner collecting roller 18. The scraped toner is
While being guided by the scraping blade 21, the toner is returned to the side of the toner hopper 23 storing the toner. When the toner collecting roller 18 is driven to rotate in the direction of arrow C, that is, clockwise as in this embodiment, it is possible to prevent the collected toner from re-adhering to the magnetic brush 14.

In this case, it is not necessary to collect all the toner contained in the magnetic brush, and it is sufficient to selectively collect the toner near the surface of the magnetic brush. That is, the minimum condition is to eliminate the difference in toner density distribution on the magnetic brush 14 caused by the development. For example, Kurobe,
The difference in toner consumption between the halftone portion and the background portion may be made even.

Generally, the toner adhesion amount of the two-component developer is 0.8 to 1.0 mg per unit area, and the photosensitive drum 11 and the magnetic brush
14 means that toner is supplied to the latent image 16 in a state where a relative speed of about 1: 3 is given. That is, the magnetic brush 14
Has only a toner supply capacity of 0.27 to 0.33 mg per unit area. Therefore, if the toner is collected so as to exceed the toner supply capacity, the magnetic brush 14
The upper toner density distribution is made uniform, and the effect of development is completely canceled.

To explain this point in more detail, from the characteristics of a general two-component developer having a bulk specific gravity of 2 and a toner concentration of 3%, the weight of the magnetic brush having a height of 1 mm is 0.2% per unit area.
g, and the toner contained therein is 6 mg,
The toner that actually contributes to development is only about 5% of the magnetic brush. In other words, it suffices to recover the toner equivalent to 5%. In the magnetic brush of the present invention, approximately 0.3 mg / cm ² of toner is unevenly distributed near the surface of the magnetic brush by the toner supply roller described later, so that the difference in toner consumption can be effectively eliminated.

Further, a toner supply roller 24 is provided at a lower portion of the cylindrical sleeve 12, that is, a downstream portion of the magnetic brush 14, so as to be in contact with the magnetic brush 14 with a gap of 1 mm with respect to the cylindrical sleeve 12. This toner supply roller 24
Is rotationally driven in the direction of arrow D, that is, in the counterclockwise direction by a rotational drive mechanism (not shown). The material of the toner supply roller 24 may be any as long as an electrical bias effect can be obtained between the toner supply roller 24 and the cylindrical sleeve 12, and metal, conductive rubber, or the like can be used. With such a toner supply roller 24, the toner 25 stored in the toner hopper 23 is sent to the magnetic brush 14 side. In this case, the toner supply roller 24 is
Will have a function to regulate the height of the spikes evenly,
This contributes to eliminating image density unevenness.

Next, a toner layer regulating blade 26 is pressed against the toner supply roller 24. By the toner layer regulating blade 26, the toner is applied on the toner supply roller 24 in a uniform thin layer, and the toner is charged by friction. Further, a charging auxiliary member 27 such as a sponge roller is provided in contact with and disposed on the toner supply roller 24 so that the function of frictionally charging the toner 25 is further exhibited, and the toner is uniformly attached to the toner supply roller 24. ing. Due to the charging effect exerted during friction of the charging auxiliary member 27, the toner is charged well.

Further, a predetermined toner supply bias voltage from a power supply circuit 28 is applied to the toner supply roller 24 and the charging auxiliary member 27, and the toner supply bias voltage causes the toner 25 to move toward the magnetic brush 14 side. And a good transfer operation is performed. That is, the bias voltage for supplying the toner is set to positive (+) having the same polarity as that of the toner.
Is set to

The power supply circuit 15 for applying the developing bias voltage is provided with an encoder that divides the output voltage into four bits and converts it into a signal, and a signal representing the output value of the developing bias voltage is supplied to a control circuit (not shown). Has been applied. The control circuit includes an arithmetic circuit that calculates an appropriate toner supply bias voltage value corresponding to the developing bias voltage value. The output signal of the control device is supplied to a power supply circuit 28 that supplies a bias voltage for toner supply, and thereby a bias voltage value for toner supply is determined.

The toner supply roller 24 has a height of the magnetic brush 14.
It is possible to arrange them so that they touch at a rate that accounts for 50% to 100%. However, the absolute value of the air gap is 1m
If it is less than m, it can be installed more than 100%.
In this case, it is necessary to use the electric bias means together. Further, the outer diameter of the rollers 18 and 24 can be arbitrarily selected. However, due to the demand for miniaturization, the outer diameter of the outer diameter of the cylindrical sleeve 12 is 80% or less, or 5 to 60 mm in absolute value, preferably 8 mm. It is good to be ~ 40mm. Since the amount of toner supply to the magnetic brush 14 is also determined by the relative speed between the magnetic brush 14 and the supply roller 24, the supply amount may be controlled by making the number of rotations of the toner supply roller 24 variable. . That is, the number of rotations of the toner supply roller 24 can be controlled by detecting the toner density by the known sensor means and detecting the number of rotations of the toner supply roller 24. As an example of the toner density detection, there is a means for detecting and calculating the reflection density of the toner on the toner collecting roller 18.

Next, an agitator 29 for preventing toner blocking is provided in the toner hopper 23. At this time,
If the toner scraped off from the toner collecting roller 18 by the scraping blade 21 is supplied as close as possible to the agitator 29, the mixing efficiency of the collected toner and the new toner can be increased.

In such a hybrid type developing device, first, the toner 25 in the toner hopper 23 is
The toner is supplied and held to the toner supply roller 24 while being frictionally charged by the rotation of the charging auxiliary member 27 and the rotation of the charging auxiliary member 27. The held toner is further thinned while being further frictionally charged by the toner layer regulating blade 26.

Then, under a predetermined toner supply bias voltage, the toner on the toner supply roller 24 is supplied and transferred to the magnetic brush 14 side in a uniform thin layer. In this case, by adjusting the toner supply bias voltage to an appropriate value, a uniform and good toner supply operation can be realized. The magnetic brush 14 to which the toner has been supplied is transferred to the photosensitive drum 11 side, and the electrostatic latent image 16 formed on the photosensitive drum 11 is developed, so that a visible image 17 is obtained.

After the development is completed, a toner density difference (unevenness) corresponding to the image is generated on the magnetic brush 14, but the residual toner on the magnetic brush 14 is transferred to the toner collecting roller 18 side.
Collected. That is, the positive (+) charged toner remaining on the magnetic brush 14 by the negative (−) friction band power charged to the toner collecting roller 18 due to the frictional contact between the toner collecting roller 18 and the scraping blade 21. Is attracted to the toner collecting roller 18 side, and the toner is collected. After the toner is collected, the magnetic brush 14 moves away from the toner collecting roller 18 in a state of a uniform toner density distribution, and proceeds to the toner supply side again. At the time of the toner collection, a uniform and good toner collection operation can be realized by appropriately adjusting the friction contact pressure between the toner collection roller 18 and the scraping blade 21 and the number of rotations of the roller.

In this embodiment, a fluorine-based resin having good releasability as a Teflon material coated on the toner collecting roller 18 is used. Therefore, although the scraping blade 21 is pressed against the toner collecting roller 18 side,
The driving torque of the toner collecting roller 18 can be reduced, and the ability to remove toner can be improved. Further, the toner collecting roller 18 may be integrally formed by a charging member that is frictionally charged as a whole.
As such a charging member, any member may be used as long as it has a lower triboelectric series and is charged to a negative (−) polarity different from that of the toner due to friction with the scraping blade 21 or the magnetic brush 14. For example, in addition to the fluorine-based resin as in the present embodiment, mention may be made of silicon-based resin, polyester-based resin, vinyl chloride / vinyl acetate copolymer, polyacrylate resin, polymethacrylate resin, polyethylene terephthalate-based resin, phenol resin, and the like. Can be.

Further, the bias voltage value for toner supply provided by the power supply circuit 28 is controlled based on the developing bias voltage value provided by the power supply circuit 15. That is, a new amount of toner is supplied to the magnetic brush 14 in an amount corresponding to the amount of toner consumed for development.
As a result, the balance between the consumption amount and the supply amount of the toner is achieved, and it is possible to eliminate the excessive supply and the insufficient supply of the toner.

Next, an example of a copier employing the above-described developing device will be functionally described with reference to FIG.

First, the optical system will be described. Light emitted from a halogen lamp 31 impinges on a document 32 and is reflected by a first mirror 33 and a second mirror 3.
4, the light passes through the third mirror 35, the lens 36, the fourth mirror 37, and the dust-proof glass 38 in this order, and is imaged on the photosensitive drum 11. The dust-proof glass 38 is provided so that suspended matter does not enter the optical system. This device has a maximum of 20
It has a zoom magnification function of 1% from 0% to a minimum of 50%. Further, an automatic density adjustment system is provided that detects an image density of the original 32 using an optical fiber and corrects a developing bias based on the detected density, thereby obtaining an image having a clear image.

Around the photosensitive drum 11, a charging unit 40, an eraser 41,
Developing device 42, neutralizing unit 43, transfer separating unit 44, cleaning unit
45 mag are arranged.

In the charging unit 40, a high voltage is applied to the charge wire in the dark to perform corona discharge, and negative charges are uniformly charged on the photosensitive drum 11. At this time, the potential of the photosensitive drum 11 is set to -800 V as described above. Air is blown in from the front surface of the charger 40a to increase the discharge efficiency. As the charge wire, a wire having a diameter of 0.08 mm is used, and the surface of the wire is coated with carbon. Also, between the charge wire and the photosensitive drum 11,
A grid for controlling the potential uniformly and uniformly is arranged. In addition, a charge cleaner for removing dirt on the charger by inserting and removing the charger 40a is provided.

The eraser 41 irradiates the charged photosensitive drum 11 with light to erase unnecessary charges, thereby facilitating cleaning. The eraser 41 is composed of a long LED, and performs side erase and tip erase. Two thermistors are attached to the erase board,
One is used for hardware and the other is used for software, and bias correction is performed.

The developing device described with reference to FIG. 1 is employed.

The charge removing section 43 has a charge remover 43a before transfer and a charge removing lamp 43b. Both are turned on at the same time as the start of the main motor 46, and are irradiated with light for eliminating residual charges on the photosensitive drum 11 while being diffused by the filter. As the pre-transfer static elimination 43a, a cold cathode tube is used.

The transfer separation unit 44 transfers the toner to the paper side by the transfer charger 44b while keeping the paper sent from the registration roller 44a in close contact with the photosensitive drum 11, and separates the paper from the photosensitive drum 11 by the separation charger 44c. It is like that. If separation cannot be performed, separation is forcibly performed by the separation claw 47. The separated paper is transported by the transport belt 44d to the fixing unit 48 side.

The cleaning unit 45 includes a fur brush 45a for scraping off residual toner on the photosensitive drum 11, and a cleaning blade 45b. The cleaning blade 45b is configured to be supported at a central point so that the right and left contact pressures are equalized. The fur brush 45a is rotated in the same direction as the photosensitive drum 11. The fur brush 45a has a function of removing foreign matter such as a piece of paper that is difficult to remove by the cleaning blade 45b. The toner scraped off by the fur brush 45a and the cleaning blade 45b is discharged to the outside by a toner collecting coil 45c and collected in a bottle.

The fixing section 48 applies a certain temperature and pressure to the paper sent from the conveying section to fuse the toner onto the paper. While the temperature is detected by the thermistor 48a, the temperature of the heater 48b (100V750W) is controlled.

In the apparatus described above, a cylindrical sleeve is used as the magnetic brush carrier, but a belt-shaped magnetic brush carrier may be employed.

(Effects) As described above, the hybrid type developing device according to the present invention is provided with the toner supply means and the toner recovery means for the magnetic brush, so that the two-component developer is agitated as in the related art. This eliminates the need for various stirring mechanisms and stirring spaces in a developing device that uses a two-component developer, greatly reducing the size of the entire device and facilitating handling similar to the one-component developing method. Can be achieved. In addition, the early agitation of the carrier can be prevented by omitting the stirring, and the image stability and flexibility of the two-component developing system can be maintained as it is.

In particular, in the present invention, since a charging member that is frictionally charged to a polarity different from that of the toner is used as the toner collecting means, a bias power supply or the like for collecting the toner remaining on the magnetic brush can be omitted. Good image quality without unevenness can be stably obtained while further reducing the overall size. Further, even if toner consumption is large, such as for color copying and printing, due to such characteristics, a large amount of toner is supplied without agitation, and a stable image with less density change and image deterioration can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a developing device according to an embodiment of the present invention, FIG. 2 is an explanatory longitudinal sectional view of a copying machine to which the developing device according to the present invention is applied, and FIG. 3 is a longitudinal sectional view of a general developing device. It is. 11 photoconductor drum, 12 cylindrical sleeve, 14 magnetic brush, 16 electrostatic latent image, 18 toner collection roller,
24: toner supply roller, 25: toner.

Claims (1)

(57) [Claims] A magnetic brush for supplying toner to a latent image on a latent image carrier in a toner developing area; toner supplying means for supplying charged toner to the magnetic brush in a toner supplying area; A hybrid electrostatic latent image including a toner collecting roller for collecting toner remaining on the magnetic brush in a toner collecting area, and toner collecting means including a scraping blade installed so as to press against the toner collecting roller. A bias voltage having the same polarity as the toner is applied to the toner supply unit, and the toner collection roller is frictionally charged to a different polarity from the toner by friction with the scraping blade. A charging member is used, and the toner collected by the toner collecting roller is scraped off from the toner collecting roller by the scraping blade. A developing device of an electrostatic latent image, characterized by triboelectric charging the toner recovery roller.