JP3447880B2 - Developing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a developing device used in a copier, a printer, a facsimile, and the like for developing and visualizing an electrostatic latent image. 2. Description of the Related Art In an image forming apparatus used in a copying machine, a printer, a facsimile machine and the like utilizing an electrophotographic method, a light image is written on a photosensitive drum by a semiconductor laser element, an LED element or the like. After forming an electrostatic latent image,
This is developed by a developing device to form a toner image, which is transferred onto recording paper. [0003] By the way, in a copying machine or the like utilizing such an electrophotographic method, a two-component developer composed of a toner and a carrier is often used. However, such a two-component developer deteriorates as it is used, and deteriorates print quality. Therefore, the developer in the developing device must be periodically replaced, which is troublesome. There was a problem that it was serious. Therefore, as a method for solving such a problem, there has been proposed a "powder developer discharging method" disclosed in Japanese Patent Application Laid-Open No. 6-230668. The method of discharging the powder developer is as follows.
As shown in FIG. 7, when discharging the developer 101 from the container 102, after opening the developer discharge port, the transfer screw 10
4 and 105 are reversed to discharge the developer 101 remaining at the bottom of the container 102, and then the developer carrier 106 is rotated forward so that the developer 1 adhering to the developer carrier 106 is removed.
01 is scraped off to the bottom of the container 102 by the peeling member 107, and then the transporting screws 104 and 105 are reversed to discharge the scraped developer 101. At this time, the permanent magnet 109 in the sleeve 108 provided below the developer carrier 106 is rotated to collect the carrier adhered on the photosensitive drum 110, and the carrier is adsorbed on the developer carrier 106. As a result, the carrier adhered on the photosensitive drum 110 is collected. Thus, the developing device 100
Then, the above-described operation is performed as needed, and the deteriorated carrier is discharged to the outside from the developer discharge port. However, in the developing device 100, when the deteriorated carrier is discharged, the transporting screws 104 and 105 are rotated in the reverse direction, or the developer carrier 106 is rotated in the normal direction.
It is necessary to open and close the developer discharge port while scraping off the 01, thereby causing a problem that the mechanism becomes complicated. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. According to the first aspect, a simple mechanism in which a scraper is provided in a sleeve for transporting the developer without periodically replacing the developer is provided. Of the developer in the developing device, a carrier having deteriorated characteristics and a carrier having specified characteristics can be efficiently separated, and only the carriers having deteriorated characteristics can be automatically discharged. It is an object of the present invention to provide a developing device capable of maintaining characteristics of a developer in the device within a specified range. In order to achieve the above object, a developing device according to the present invention, in claim 1, comprises a carrier in which a magnetic agent is dispersed in a binder resin, and an image forming agent. A hopper portion in which a two-component developer mixed with a toner is stored, and a two-component developer stored in the hopper portion, which is stored in the hopper portion and develops the electrostatic latent image on the photosensitive member. A sleeve which is conveyed and develops the electrostatic latent image on the photoreceptor into a toner image, and which is disposed so as to be vertically movable with respect to the sleeve, abuts on the sleeve at a predetermined timing, and is on the sleeve. Among the carrier particles, a first scraper for scraping carrier particles having a diameter larger than a designated diameter, and carrier particles having a diameter smaller than the designated diameter passing through the first scraper are scraped onto a transfer belt. A second scraper to be dropped. With the above arrangement, when the electrostatic latent image on the photoreceptor is developed, the carrier in which the magnetic agent is dispersed in the binder resin and the toner serving as the image forming agent are mixed. The two-component developer is transported by rotating the sleeve in the hopper portion in which the two-component developer is stored.
When the electrostatic latent image on the photoreceptor is developed into a toner image and the deteriorated carrier is collected, a first scraper, which is vertically movable with respect to the sleeve, is brought into contact with the sleeve to form a toner image. The scraper (2) scrapes carrier particles having a diameter smaller than the specified diameter out of the carrier particles on the sleeve and drops them onto the transfer belt, so that the developer is periodically replaced with a simple mechanism. Of the developer in the developing device, the carrier having the deteriorated characteristics and the carrier having the specified characteristics are efficiently separated, and only the carriers having the deteriorated characteristics are automatically discharged. Maintain the characteristics of the developer in the developing device within a specified range. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the drawings. << Description of First Reference Example >> FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus using a first reference example of a developing device according to the present invention. The image forming apparatus 1a shown in FIG. 1 takes in a recording paper (both not shown) supplied from a paper feeding device, and conveys a transfer belt 2 that conveys the recording paper.
And four image forming units 3 arranged along the transfer belt 2 to form four toner images in accordance with four image signals output from an image processing device (not shown) and the like. With the transfer belt 2 interposed, the toner images created by the respective image forming units 3 are transferred to the recording paper conveyed by the transfer belt 2 and arranged to face the respective image forming units 3. Four transfer units 4 and a belt cleaning device 5 for scraping off toner (remaining toner) remaining on the transfer belt 2
And a fixing device 6 for taking in and fixing the recording paper on which the toner image has been transferred conveyed by the transfer belt 2. When an image forming instruction is input, each image forming unit 3 creates a toner image of each color,
After each transfer unit 4 sequentially transfers the recording paper conveyed by the transfer belt 2 to form a multicolor toner image, the fixing device 6 removes the multicolor toner image formed on the recording paper. Fix the paper and discharge it outside the machine. Each of the image forming units 3 includes a photosensitive drum 7 that rotates in the direction of arrow A, a charging unit 8 that is disposed around the photosensitive drum 7 and uniformly charges the photosensitive drum 7, An optical image is written on the photosensitive drum 7 uniformly charged by the charging unit 8 to form an electrostatic latent image, and an exposure unit 9 is disposed around the photosensitive drum 7 and remains on the photosensitive drum 7. And a developing unit 11 for developing an electrostatic latent image formed on the photoconductor drum 7 with toner of a designated color. Photosensitive drum 7
Is uniformly charged, an optical image is written on the photosensitive drum 7 by the exposure unit 9 based on the image signal supplied from the image processing apparatus, and an electrostatic latent image is formed. After developing the electrostatic latent image on the body drum 7 to form a toner image of a designated color, the toner image is transferred to a recording sheet on the transfer belt 2. As shown in FIG. 2, each of the developing devices 11 includes a hopper 12 having a hollow interior,
The toner stored in the space 13 provided at the rear of the container 2 is conveyed forward (to the left in FIG. 2) while being stirred, and mixed with the carrier stored in the space 14 in front to form two components. Agitator 15 to be a developer and this space 1
4 and rotate in the normal rotation direction (arrow B direction)
The two-component developer composed of the carrier filled in the space and the toner conveyed by the agitator 15 is attracted by the plurality of permanent magnets 16 arranged inside and the plurality of grooves formed on the surface. Meanwhile, a sleeve 17 which is conveyed in the direction of arrow C to be electrostatically attracted to the photosensitive drum 7 and the two-component developer being conveyed by the sleeve 17 is moved toward the photosensitive drum 7 by a predetermined amount or more. A doctor 18 that regulates the carrier and a movable carrier in the direction of arrow D in the photosensitive drum 7 so that the carrier is not conveyed. When the deteriorated carrier is collected, the carrier is moved to a position facing the sleeve 17 and fixed. And a permanent magnet 19 to be used. When the electrostatic latent image formed on the photosensitive drum 7 is developed, the agitator 15 is rotated to remove the toner filled in the space 13 formed behind the hopper 12 into the front space. The sleeve 17 is rotated in the normal rotation direction while being transported into the space 14 and filling the space 14,
While mixing the carrier stored in the space 14 and the toner, the doctor 18 adjusts the amount to a uniform amount.
The toner of the component developer is electrostatically attracted onto the photosensitive drum 7 to develop the electrostatic latent image formed on the photosensitive drum 7. The space 14 in which the sleeve 17 is provided is filled with a predetermined amount, for example, 80 g of a carrier, mixed with the toner sent by the agitator 15 to form a two-component developer, and then moved in the normal rotation direction. Is transported by the sleeve 17 which is driven to rotate
By being regulated to a certain amount by 7, it is returned in the direction of arrow C, and when it fills the space 14, it is in a packing state, so that no more toner enters. The toner is transferred to the photosensitive drum 7 by the developing operation.
When the amount of the two-component developer is reduced by being absorbed and consumed, the toner is replenished by the agitator 15 correspondingly. In the developing device 11, as a carrier, an iron powder carrier, a ferrite carrier, a coated carrier in which ferrite is coated with a silicon resin, and a binder type carrier (hereinafter, referred to as a carrier) in which a powdery magnetic material is dispersed in resin. Is referred to as a resin carrier), but in this reference example, the saturation magnetization is mainly 20 to 5
0 [emu / g], the particle size is 50 [μm],
A conductive material is added to further adjust the resistance,
Using a resin carrier having an electric resistance of about 10 ¹¹ [Ω · cm], the developing gap (Gp) is set to “0.5”, and the doctor gap (Gd) is set to “0.4”. Therefore, when the two-component developer is transported by the sleeve 17 and electrostatically attracted to the photosensitive drum 7, the two-component developer is charged in the developer circulation path or a minute gap such as the development gap (Gp) or the doctor gap (Gd). Stress is applied to the component developer, and 2
The resin carrier in the component developer is scraped or chipped, and the resin carrier deteriorates. Thus, when a normal coat carrier is used, as a mode of deterioration, spent fine particles of toner adhere to the toner to suppress frictional charging of the uncharged toner, and the toner charge amount is defined as Unusual situations such as an inability to obtain an amount, an extremely low charge amount, and generation of a reversely charged toner occur, and the background smear becomes noticeable on the image, and the image quality is significantly reduced. However, even when the resin carrier is used as in the present embodiment, the resin carrier comes into contact with the toner and other members for a long period of time, and wears, thereby reducing the diameter. In the resin carrier,
Since the magnetic material is uniformly dispersed in the resin, the saturation magnetization decreases as the magnetic material is removed. As a result, the saturation magnetization per resin carrier becomes 50 per mass.
Even if it is [emu / g], its diameter is 50 [μm]
, The volume becomes (3/5) ³ = 0.216 times in proportion to the diameter, and the magnetic binding force by the sleeve 17 becomes weaker,
The toner carrying ability is reduced. Further, since the surface area is reduced due to the change in the diameter, the probability of contact with the toner is increased and spent is caused. As a result, background smear on the image becomes remarkable and the image quality is remarkably deteriorated. Resulting in. Further, during a normal image forming operation, the resin carrier is attracted and held on the sleeve 17 by a magnetic field formed between the resin carrier and the permanent magnet 16 in the sleeve 17. Is smaller, the sleeve 17
As a result, the resin carrier is gradually attracted to the outside of the sleeve 17 and held there, and a uniform image cannot be obtained.
In general copiers, printers, facsimile machines, etc., the amount of toner adhering to the photoreceptor drum is determined by the reflected light amount method every time development is performed for a specified number of sheets preset by the developing device. (Toner adhering amount), and when this is not a value equal to or more than a certain value, 2
Judge that it is time to replace the component developer
Promote replacement of component developer or use another method of collecting deteriorated carriers, such as returning the two-component developer to the hopper and discharging it to a specific area using a transport screw or a stirring screw. Thus, the deteriorated resin carrier is collected. However, in each of these methods, the resin carrier which has not deteriorated is also collected, so that the resin carrier is wasted and a collection container is required. Therefore, in this embodiment, as described below, the deteriorated resin carrier is recovered to prevent such a problem from occurring. First, the developing device 11
Each time the number of times the electrostatic latent image formed on the photosensitive drum 7 is developed becomes greater than or equal to a preset number, or when a preset period elapses from the previous inspection time, the developing device 11 to drive the photosensitive drum 7
When the toner in the two-component developer is electrostatically adsorbed thereon, the permanent magnet 19 having a strength satisfying the following condition is moved and fixed to a specified position provided on the back surface of the photosensitive drum 7. The deteriorated resin carrier is electrically and magnetically attracted from the sleeve 17 side of the developing device 11 to the photosensitive drum 7 side, and is collected by the cleaning unit 10. As a condition, the strength of each permanent magnet 16 arranged in the sleeve 17 is set to 0.08 [T], the developing gap (Gp) is set to “0.5”, and at this time, the saturation magnetization per resin carrier is set. Is about 50 [emu / g] and the true specific gravity is 5.6 [g / cm ³ ], the force applied to the resin carrier near the surface of the photosensitive drum 7 when calculated from the magnetic permeability and the distance is as follows: Since it is 2.6 × 10 ⁻⁸ [N], a permanent magnet having a strength of 0.04 [T] is provided on the back side of the photosensitive drum 7 so that the photosensitive drum 7 can be peeled off at substantially the same distance. 19 are arranged such that the same polarity is opposed to each other. In a normal developing operation, the sleeve 1
The permanent magnet 19 is rotated and fixed to a position not opposed to the sleeve 17 so as not to affect the two-component developer on the sleeve 7. Is omitted), the permanent magnet 19
Is rotated to a position facing the sleeve 17 and fixed at this position.
7 reduces the carrier binding force of the permanent magnets 16 disposed in the inside 7. In this state, the surface potential on the photosensitive drum 7 is reduced by-
At 100 [V] or in a normal developing state,-
By setting the developing bias set to 500 [V] to 0 [V], an electric field is formed between the sleeve 17 and the photosensitive drum 7, and the resin carrier is attracted to the photosensitive drum 7. At this time, the attraction force of the permanent magnet 16 provided in the sleeve 17 is larger than the attraction force generated by the electric field for the resin carrier that has not deteriorated. Remains and is used again, but for the deteriorated resin carrier,
Since the attraction force generated by the electric field is larger than the attraction force by the permanent magnet 16 provided in the sleeve 17, the toner is attracted to the photosensitive drum 7 and
It is scraped off by a flexible material 20 such as polyurethane provided on the cleaning unit 10 and collected, or is moved from the photosensitive drum 7 onto the transfer belt 2 and collected by the belt cleaning device 5. Or At this time, the flexible material 20 is brought into contact with the photosensitive drum 7 in the counter direction or the trailing direction so that the resin carrier on the photosensitive drum 7 can be efficiently scraped off. Is done. As described above, in the first reference example,
Each time the number of times that the electrostatic latent image formed on the photosensitive drum 7 is developed by the developing device 11 becomes equal to or greater than a preset number, or every time a preset period elapses from the previous inspection time, Then, the permanent magnet 19 disposed on the back side of the photosensitive drum 7 is moved to a position facing the sleeve 17, and the surface potential on the photosensitive drum 7 is reduced by -100.
[V], or -500
By setting the developing bias set to [V] to 0 [V], the deteriorated resin carrier is attracted to the photosensitive drum 7 side and collected by the cleaning unit 10 or the belt cleaning device 5. Because
With a simple mechanism in which only the permanent magnet 19 is arranged on the photosensitive drum 7 side, without replacing the two-component developer regularly,
Efficient separation of a resin carrier having deteriorated characteristics and a resin carrier having specified characteristics among the two-component developer in the developing device 11 and automatically discharging only the resin carrier having deteriorated characteristics. As a result, the characteristics of the two-component developer in the developing device 11 can be maintained within a specified range. << Description of First Embodiment >> FIG. 3 is a schematic configuration diagram showing an example of an image forming apparatus using a first embodiment of a developing device according to the present invention. The image forming apparatus 1b shown in this figure is different from the image forming apparatus 1a shown in FIG. 1 in that the permanent magnet 19 is removed from the back side of the photosensitive drum 7 and sleeves constituting each developing device 11 as shown in FIG. 17 is a first scraper 2 which is vertically movable on the lower surface side of
1 and the second scraper 22 are provided, and a mylar or the like provided in the opening 23 of the hopper section 12 is moved so that the opening 23 is opened while the first and second scrapers 21 and 22 degrade. The scraped resin carrier is scraped off, dropped on the transfer belt 2, and collected by the belt cleaning device 5. The first scraper 21 is formed of a member having a thickness set to 0.5 [mm], and the tip side of the
In a direction (trailing direction) toward the downstream direction of the rotation direction of the roller 7, the contact pressure is such that the contact pressure with the surface of the sleeve 17, for example, the contact pressure is 5 to 10 [g / cm]. When the resin carrier is conveyed by rotation of the sleeve 17, the diameter of the resin carrier is 30 mm.
Only the resin carrier having a particle diameter larger than [μm] is scraped off and dropped into the hopper section 12 and
Only the carrier resin carrier of [μm] or less is passed and guided to the second scraper 22 side. Second scraper 22
Is a member whose thickness is set to 1 [mm], and a direction in which the tip side is directed to the upstream direction in the rotational direction of the sleeve 17 (counter direction) with respect to the fixed point, and the surface of the sleeve 17 So that the contact pressure becomes 50 to 100 [g / cm].
When the sleeve 17 rotates and the resin carrier is conveyed, the first scraper 21
The resin carrier having a particle size of 30 [μm] or less that has passed through is scraped off, dropped from the opening 23 of the hopper section 12 onto the transfer belt 2, and collected by the belt cleaning device 5. As described above, in the first embodiment, the number of times the developing device 11 develops the electrostatic latent image formed on the photosensitive drum 7 is equal to or more than the preset number, Each time a preset period elapses from the inspection time, the first and second scrapers 21 and 22 are moved upward to abut against the sleeve 17 at a predetermined abutting pressure to remove the deteriorated resin carrier. Since the toner is scraped off and dropped on the transfer belt 2 and collected by the belt cleaning device 5, the sleeve 1 for transporting the two-component developer is used.
7, the first and second scrapers 21 and 22 are provided under the simple mechanism, and the characteristics of the two-component developer in the developing device 11 are changed without periodically changing the two-component developer. It is possible to efficiently separate the deteriorated resin carrier from the resin carrier having specified characteristics, and to automatically discharge only the resin carrier having deteriorated characteristics. Can be kept within a specified range. << Description of Second Reference Example >> FIG. 5 is a schematic configuration diagram showing an example of an image forming apparatus using a second reference example of the developing device according to the present invention. 1 is different from the image forming apparatus 1a shown in FIG. 1 in that the two-component developer containing the deteriorated resin carrier is transferred onto the photosensitive drum 7 and then normally transferred by the transfer units 4. Is formed on the transfer belt 2 by forming a reverse electric field of
The belt cleaning device 5 scrapes it off and collects it. Even in this case, similarly to the above-described first embodiment, a simple mechanism in which the permanent magnet 19 is arranged on the photosensitive drum 7 side without the need to periodically replace the two-component developer Body drum 7
Of the two-component developer in the developing device 11 without damaging the resin carrier, the resin carrier having the deteriorated characteristic and the resin carrier having the specified characteristic are efficiently separated, and only the resin carrier having the deteriorated characteristic is automatically removed. And the characteristics of the two-component developer in the developing device 11 can be maintained within a specified range. << Description of Other Embodiments >> In the first embodiment described above, when the permanent resin 19 is rotatably arranged on the back side of the photosensitive drum 7 and the deteriorated resin carrier is collected, By rotating the magnet 19 to a position facing the sleeve 17, the deteriorated resin carrier on the sleeve 17 is attracted to the photosensitive drum 7 side. When the permanent magnet 19 is fixed at the position facing the normal developing operation,
When a material having a magnetic shielding effect, for example, a metal containing lead is sandwiched between the photoconductor drum 7 and the surface of the photosensitive drum 7, when the deteriorated resin carrier is collected, the material having the magnetic shielding effect is moved downward by a driving device. For example, the magnetic field may be generated by moving the permanent magnets 16 provided in the sleeve 17 to reduce the binding force. Further, in the first embodiment described above, the carrier resin carrier of 30 [μm] or less scraped off from the sleeve 17 by the first and second scrapers 21 and 22 is dropped on the transfer belt 2 to form a belt cleaning device. 5 is collected.
As shown in (1), the carrier resin carrier of 30 [μm] or less scraped off from the sleeve 17 by the first and second scrapers 21 and 22 may be dropped into the carrier collection container 25 and collected. By doing so, the load on the belt cleaning device 5 can be reduced. Further, in each of the above-described embodiments, the conductive material of the resin carrier is added to make the electric resistance about 10 ¹¹ [Ω · cm]. When a resistance carrier is used, an edge effect (a phenomenon that the amount of toner attached to the edge portion increases) generated near the edge of the latent image is eliminated, so that the burden of image processing performed by the image processing apparatus is reduced. You may do it. In each of the above-described embodiments, the number of times the developing device 11 develops the electrostatic latent image formed on the photosensitive drum 7 is equal to or more than a preset number, or the number of times the electrostatic latent image is Every time the set period elapses, the deteriorated resin carrier is collected. However, based on the amount of reflected light, the amount of toner adhering to the photosensitive drum 7 is detected to detect a change in the development characteristic. The recovery timing of the deteriorated resin carrier may be determined according to the detection result. As described above, according to the present invention, according to the first aspect, the first and second sleeves for conveying the developer are provided.
With a simple mechanism equipped with a scraper, it is possible to efficiently separate the carrier with deteriorated characteristics and the carrier with specified characteristics among the developer in the developing device without periodically changing the developer. Only the carrier whose characteristics have deteriorated can be automatically discharged, whereby the characteristics of the developer in the developing device can be kept within a specified range.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus using a first reference example of a developing device according to the present invention. FIG. 2 is a detailed configuration diagram illustrating a detailed configuration example of a photosensitive drum and a developing device illustrated in FIG. 1; FIG. 3 is a schematic configuration diagram illustrating an example of an image forming apparatus using a first embodiment of a developing device according to the present invention. 4 is a detailed configuration diagram showing a detailed configuration example near a sleeve constituting the developing device shown in FIG. 3; FIG. 5 is a schematic configuration diagram showing an example of an image forming apparatus using a second reference example of the developing device according to the present invention. FIG. 6 is a detailed configuration diagram showing another embodiment of the developing device according to the present invention. FIG. 7 shows a conventional Japanese Patent Application Laid-Open No. 6-230668.
FIG. 1 is a schematic configuration diagram for explaining a “powder developer discharging method” described in Japanese Patent Application Laid-Open Publication No. H11-209,036. DESCRIPTION OF SYMBOLS 1a, 1b, 1c: image forming device, 2: transfer belt, 3: image forming unit, 4: transfer unit, 5: belt cleaning device, 6: fixing device, 7: photosensitive drum, 8 ... Charging unit, 9 exposure unit, 10 cleaning unit, 11 developing unit, 12 hopper unit, 13, 14 space, 15 agitator, 16 permanent magnet, 17 sleeve, 18 doctor, 19 permanent magnet (Magnet), 20: flexible material, 21: first scraper, 22: second scraper,
23 ... Opening, 25 ... Carrier collection container

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/09 G03G 15/08 501

Claims (1)

(57) Claims 1. A hopper section in which a two-component developer obtained by mixing a carrier in which a magnetic agent is dispersed in a binder resin and a toner serving as an image forming agent is stored, When developing the electrostatic latent image on the photoreceptor stored in the hopper, the two-component developer stored in the hopper is transported to develop the electrostatic latent image on the photoreceptor into a toner image. And a sleeve that is arranged to be vertically movable with respect to the sleeve, abuts the sleeve at a predetermined timing, and scrapes carrier particles having a diameter larger than a designated diameter among carrier particles on the sleeve. A first scraper and a smaller diameter than the designated diameter passed through the first scraper.
The second step is to scrape carrier particles of large diameter onto the transfer belt .
And a scraper .