JP3537644B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile.

[0002]

2. Description of the Related Art Heretofore, there has been proposed an image forming apparatus using a screw pump which moves powder in the axial direction of a rotor by rotating a rotor called a mono pump when transferring toner. .

In this transfer method, the stored toner and the collected toner can be transferred through a flexible pipe or the like. Therefore, there is no restriction on the installation of the toner storage unit and the toner collection unit, and the toner can be collected with a simple configuration . There is an advantage that the transfer can be performed reliably. In addition, the toner transfer device using the screw pump transfers the toner in a mixed state with air by the air supply means, so that stable transfer of the toner can be obtained, and unnecessary stress is not applied to the transferred toner. There is also an advantage.

[0004]

By the way, when it is attempted to transfer the collected toner by a toner transfer device using a screw pump, the amount of toner transported by the screw pump is much larger than the amount of collected toner from the cleaning device. Many. Therefore, storing the collected toner upstream of the screw pump has an effect of sealing the inlet side of the screw pump, and the amount of bite into the rotor and the stator decreases over time, and the air flows backward when the amount becomes insufficient. It is desirable that the screw pump be intermittently driven because it is possible to improve the margin of the screw pump.

[0005] However, while the screw pump is stopped, the toner that has not been completely discharged during one drive is present in the toner transport tube of the screw pump. If the state continues for a long time, a problem may occur that toner accumulates in the tube and the tube is clogged with toner.

On the other hand, the replenishment of toner for transferring the new toner to the developing device by the screw pump is performed when the toner in the developing device runs out. The frequency of driving is high. In particular, in a developing device that has been miniaturized as recently, the stirring time of the developer and the path until the toner is used for development are shortened, and the responsiveness of the toner replenishment amount to the toner replenishment signal is reduced. Good things are required. The same can be said for a developing device of a color machine in which toner density control is severe. Therefore, replenishment of the toner to the developing device by the screw pump requires good responsiveness.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional circumstances, an object of the present invention is to provide an image forming apparatus in which a transfer member is unlikely to be clogged when conveying collected toner, and good responsivity is obtained when supplying toner to a developing device. And

[0008]

In order to achieve the above object, the present invention provides a developing device for developing an electrostatic latent image formed on an image bearing member, which is disposed at a position distant from the developing device. A toner replenishing mechanism configured to replenish the toner stored in the toner storage unit, and a collected toner processing mechanism configured to transfer the collected toner from the collection unit that collects the residual toner after image formation to the collected toner storage unit for processing. Wherein the toner replenishing mechanism and the collected toner processing mechanism each include a female threaded stator having a double pitch spiral groove formed therein, and a male threaded rotor rotatably fitted in the stator. A powder pump; and an air supply means for supplying air for fluidizing the toner moved by the powder pump in a diffused state .
From the reservoir to the developing device and from the collecting unit
Transfer toner to the toner reservoir via tubes
At the same time, when the powder pump and the air supply unit are stopped, the toner supply mechanism stops the powder pump and the air supply unit at the same time, and the recovered toner processing mechanism delays the powder pump by a predetermined time after stopping the powder pump. The air supply means is stopped.

[0009]

[0010]

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a copying machine as an image forming apparatus according to the present invention.

In FIG. 1, a copying machine includes a copying machine main body A,
The copier main body A and a separate toner bank B are provided. An exposing section b, an image forming section c, and an image forming section c for forming an image by a conventionally known electrophotographic method are provided in the copying machine main body A.
It is composed of a paper feeding section a. The exposure unit b includes a light source 12 for irradiating a document placed on a contact glass 15 with light, and a plurality of mirrors 14 and a lens 13 for exposing a reflected light image from the document on a photoconductor 16. And an exposure optical system. The image forming unit c includes a drum-shaped photoconductor 16 and a charging device 1 disposed around the photoconductor 16.
7, a developing device 18, a transfer belt device 19, a photoreceptor cleaning device 20, a registration roller 23, a fixing device 21, a paper discharge roller 24, and the like.
Further, a plurality of paper feed cassettes 10 containing transfer papers as recording media of various sizes are installed in the paper feed unit a. The exposure unit b is an example of an analog exposure optical system, but a method of performing optical writing on a photoconductor in accordance with an image signal using a laser scanning optical system using a laser light source and a deflector. If it becomes, it becomes the constitution of the laser printer,
Further, if a document reading device is installed, a digital copying machine or a facsimile is obtained.

In FIG. 1, when the image forming operation is started, the photosensitive member 16 is charged by the charging device 17, and the original image from the exposure section b is exposed to form an electrostatic latent image. This electrostatic latent image is developed by a developer (two-component developer or one-component developer) of the developing device 18, and a toner image is formed on the photoconductor 16. The toner image on the photoconductor 16 is transferred to a transfer sheet fed from a paper feeding unit a and fed to a transfer position (a nip portion between the photoconductor and the transfer belt 19a) via a registration roller 23, and the toner image is transferred. The transferred transfer paper is conveyed to the fixing device 21 by the transfer belt 19a of the transfer belt device 19, and the toner image is fixed on the transfer paper by the fixing device 21. The transfer paper after fixing is discharged onto a discharge tray 25 via a discharge roller 24. On the other hand, the photoconductor 16 after the transfer of the toner image is cleaned by the photoconductor cleaning device 20 to remove and collect foreign matters such as residual toner and paper dust. Further, the transfer belt 19a after the transfer of the transfer paper is also cleaned by the cleaning means 19b in the transfer belt device 19, and foreign matters such as residual toner and paper dust are removed and collected.

In FIG. 2, a developing device 18 uses a two-component developer obtained by mixing a toner and a carrier, which is one of developers used for visible image processing. The developing device 18 includes a developing container 29 and a toner replenishing unit 28. The developing container 29 is a photosensitive drum 1 that is a latent image carrier that is movable in a direction indicated by an arrow in FIG.
6, and the toner supply unit 28 is mounted on the developing container 29.

A stirring roller 33 is provided inside the developing container 29.
A paddle wheel 34 is provided, and a two-component developer composed of toner and a magnetic carrier that are stirred and mixed by the stirring roller 33 and frictionally charged to opposite polarities is pumped up by the paddle wheel 34. I have. Further, the toner replenishing unit 28 is configured to feed the toner toward the stirring roller 33 by the rotation of the toner replenishing roller 35 when the density of the toner supplied to the photoconductor 16 decreases.

At the position where the developer is pumped up by the paddle wheel 34, a plurality of developing rollers 30 and 31 are provided in proximity to the photosensitive drum 16. The developing rollers 30 and 31 are arranged on the upstream side and the downstream side along the moving direction of the photosensitive drum 16, the one located on the upstream side is the first developing roller 30, and the one located on the downstream side This is the second developing roller 31.

The first and second developing rollers 30, 31
Has a main part including a sleeve rotatable in a counterclockwise direction in the figure by a driving unit (not shown) and a mag roller fixed inside the sleeve. The sleeve is made of a non-magnetic material such as aluminum or stainless steel, and the mag roller is a magnetic pole formed by kneading a ferrite magnet or a rubber magnet, or a mixture of nylon powder and ferrite powder, along the circumferential direction. It has a plurality of arrangements.

In the developing container 29, at a position where an arbitrary position on the peripheral surface of the first developing roller 30 reaches before facing the photosensitive drum 16, the layer thickness of the magnetic brush carried by the developing roller 30 is set. Is provided with a doctor blade 32 formed of a metal member for regulating the pressure.

In the developing container 29, the developer is pumped up by the centrifugal force generated when the paddle wheel 34 rotates, and is discharged toward the first developing roller 30. A part of the discharged developer is directly supplied to the first developing roller 30 and is carried on the surface of the first developing roller 30.
Further, when the remaining part of the discharged developer is repelled by hitting the second developing roller 31, it is carried on the surface of the first developing roller 30 by the magnetic force of the first developing roller 30 side.

In order to supply the developer to the first developing roller 30 also from the second developing roller 31 side, a paddle wheel is used to increase the amount of rebound from the second developing roller 31. It is necessary to relatively increase the rotation speed of the cylinder 34 and increase the centrifugal force.

The developer carried on the first developing roller 30 moves on the roller surface with the rotation of the developing sleeve,
The layer thickness is regulated by the doctor blade 32, and reaches the first developing region where the first developing roller 30 and the photosensitive drum 16 are opposed to each other.

When the developer that has reached the developing area moves to a position where the action of the magnetic force on the first developing roller 30 side weakens,
Due to the rotation of the developing sleeve on the side of the second developing roller 31 and the magnetic force from the mag roller, as shown by a broken line in the drawing, the second developing roller 31 and the photosensitive drum 16 are opposed to the second developing area. It is transferred to. Then, it falls to the bottom of the developing container 29 at a position where the magnetic force of the second developing roller 31 stops acting, and is again stirred by the paddle wheel 34.

The mag rollers provided on the first and second developing rollers 30 and 31 correspond to the first and second developing rollers 3.
The arrangement of magnetic poles that can form a repulsive magnetic field by the same poles is set between the closest positions of 0 and 31, and the developer transfer direction is forcibly set to the direction toward the second developing roller 31. It is supposed to be. Thus, the developer is transferred to the second developing roller 31 by the magnetic force of the magnetic pole on the second developing roller 31 side.

In the vicinity of the stirring roller 33 in the developing container 29, a toner density sensor 29a serving as a toner density detecting means for detecting a mixing ratio between the toner and the carrier is arranged. The toner density sensor 29a uses, as an example, a method of detecting a toner density from a toner content in the developer by using a change in inductance of a coil located in the developer.

In the toner supply section 28 of the developing device 18,
There is provided an agitator 36 which moves the toner to be supplied to the center thereof while stirring the toner. In FIG. 2, reference numeral 38 denotes a sensor comprising a piezoelectric element for detecting the pressure acting on the replenishing toner in the toner replenishing section 28 to detect the remaining amount of the toner based on the toner accumulation level. When the pressure from the toner stops acting, the sensor 38 outputs a toner near-end signal that determines in advance that all the toner in the toner replenishing unit 28 has been consumed a predetermined number of times or a predetermined time after that point. Output to the control unit.

As shown in FIGS. 1 and 3, the toner bank B is provided at the bottom of an outer case 42 formed in a vertically long box shape.
A caster 43 is attached and configured to be movable, and an upper cover 44 is detachably covered on the upper part. A storage case 45 capable of storing a large amount of toner is provided in the outer case 42.

As shown in FIG. 4, the toner storage case 45 has a bent plate 47 formed by bending a long plate material at a substantially center in a V-shape, and side plates 48 with seal members 50 attached to both sides thereof. 49, and a lid 51 is attached to the upper part. A round hole 51a and a long hole 51b are formed in the lid 51 side by side.
A cap 52 having a toner supply port 52a is attached to a. This cap 52 has a toner supply port 5
An opening / closing lid 52b that opens and closes 2a is provided. On the other hand,
A glass 53 for toner confirmation is attached to the elongated hole 51b.

A powder pump unit as a toner transfer means for transferring the toner toward the developing device 18 is provided at the lowest portion inside the toner storage case 45, and is stored in the toner storage case 45 above. The agitator 54 is arranged in parallel along the vertical direction in order to prevent the toner from aggregating by stirring the toner and to prevent the toner from blocking.

The powder pump unit includes a screw pump 60 called a mono pump having a well-known structure using a conveying screw and an air flow, and the screw pump 60
And an air supply means having an air pump 70 for feeding the toner under pressure.

As shown in FIG. 5, the screw pump 60 is a female screw type stator having a double pitch spiral groove formed of an elastic material such as rubber inserted into a holder 62a attached to the side plate 49. 63 and a male screw type rotor 64 rotatably fitted into the stator 63 and made of metal or the like.

The rotor 64 has one end in the axial direction and can rotate integrally with the shaft end of the transport screw 55 extending into the toner storage case 45. As shown in FIG. 4, the transport screw 55 is provided with a gear 5 attached to a shaft end opposite to the side integrated with the rotor 64.
6, the gear 56 can be rotated by meshing with a drive gear 58 provided on an output shaft of a drive motor 57. The gear 56 meshes with a gear 61 via an idle gear 59, and the agitator 54 is rotationally driven via the gear 61.

When the rotor 64 is rotated by the driving of the drive motor 57, the outer spiral portion moves in the spiral groove in the stator 63, so that the toner discharged from the shaft end of the transport screw 55 is moved in the axial direction. Can be moved to

As shown in FIG. 5, inside the stator 63, a toner discharge passage 62b communicating with the spiral groove is formed along the axial direction.
5 are connected. As the tube 65, vinyl chloride, nylon, Teflon (trade name), or the like is selected, and a tube that is relatively flexible and has durability that is less likely to be deteriorated by toner or the like is used. Thus, the toner bank B and the developing device 18 in the copying machine can be connected to each other via the flexible tube 65 regardless of the positional relationship.

The inner peripheral surface of the holder 62a and the stator 6
A very small gap d of about 1 mm is provided between the outer peripheral surface of the toner cartridge 3 and the outer peripheral surface of the cartridge 3, and the gap d communicates with the toner discharge passage 62b. Further, an air passage 66 communicates with the gap. A tube 67 shown in FIG. 4 is connected to the air passage 66. The tube 67 is connected to an air pump 70 serving as an air supply means so that air can be supplied to the gap.

The air pump 70 includes a screw pump 60
The toner in the toner storage case 45 is easily transported by the transport screw 55 toward the rotor 64 of the screw pump 60 by the negative pressure on the toner discharge side of the toner pump. Fluidization is promoted through the air, and the toner is fed from the toner storage case 45 toward the tube 65.

The toner replenishing mechanism for transferring the toner from the toner bank B to the developing device 18 by the screw pump 60 has been described. Next, the toner is collected by the photoconductor cleaning device 20 and the belt cleaning portion 19b of the transfer belt device 19. A description will be given of a toner collecting mechanism for transferring the collected toner to a waste tank (not shown) by a transfer unit.

6 and 7, in the copying machine main body A, the toner collected by the photoconductor cleaning device 20 is engaged with the toner from a collected toner discharge portion 20a provided in a part of the photoconductor cleaning device 20. The collected toner is transferred to a toner guide member 81 which is a part of the transfer unit 80. The toner guide member 81 plays a role of a toner transfer path for sending toner from the photoconductor cleaning device 20 to the toner collecting powder pump. Further, the toner collected by the belt cleaning unit 19b of the transfer belt device 19 is also part of the collected toner transfer unit 80 engaged with the collected toner discharge unit 19c provided in a part of the transfer belt device 19. Is transferred to the toner guide member 82. Reference numeral 120 in the figure denotes a main body structure (main body driving side plate) of the copying machine main body, and the photoconductor cleaning device 20, the transfer belt device 19, the photoconductor 16,
A developing device 18, other image forming members, a collected toner transfer unit 80, and the like are attached.

In FIG. 8, the recovered toner transfer unit 8
Numeral 0 uses a screw pump 83 called a mono pump, and since the configuration of the screw pump 83 itself is the same as that of the screw pump 60 described above, detailed description thereof is omitted. Also in the collected toner transfer unit 80, air is supplied by the screw pump 83 by air supply means.
Reference numeral 84 denotes an air supply port from an air pump (not shown).

In the copying machine configured as described above, when the toner collected from the photoconductor cleaning device 20 and the belt cleaning unit 19b of the transfer belt device 19 is transported,
The amount of toner transported by the screw pump 83 is much larger than the amount of collected toner.

Therefore, by storing the collected toner upstream of the screw pump 83, the screw pump 83
The screw pump 83 may be intermittently driven since there is an effect of sealing the inlet side, and over time, the amount of biting of the rotor and the stator is reduced, and the margin for the backflow of air generated when the amount becomes insufficient is improved. desirable. However, while the screw pump is stopped, the toner that has not been completely discharged during one drive is present in the toner transport tube of the screw pump. If the state continues for a long time, the toner accumulates in the tube. As described above, there is a problem that the tube is clogged with toner.

Therefore, in the present invention, the screw pump 83
After a certain period of time after the rotation of the rotor is stopped, the air supply to the discharge port of the screw pump 83 is stopped.
Air delay time is provided. By providing this air delay time, the amount of toner in the tube can be reduced, and the margin of toner clogging can be improved.

On the other hand, the screw pump 6 of the developing device 18
In the case of 0, the toner is replenished when the toner in the developing device 18 is exhausted, so that the driving is inevitably intermittent, but the driving frequency is higher than the conveyance of the collected toner. Further, in the downsized developing device, the stirring time and the path of the developer before the toner is used for development are shortened, and the responsiveness of the toner supply amount to the toner supply signal is required to be good. Is done.

[0043] Therefore, when providing the air di <br/> Ray time the screw pump 60, can be reduced the amount of toner present in the tube 65, from the start of the driving of the screw pump 60, the preceding tube 65 And the time until the toner is discharged becomes longer. At the same time, the time until the ejection of the toner is completed becomes longer.

[0044] Therefore, without providing the air de <br/> Irei time the screw pump 60, a not completely discharged toner is configured to leave the tube. As described above, if no air delay time is provided, the screw pump 6
The toner can be discharged to the developing device 18 at the same time as the operation of “0”. Further, since the discharge of the toner is stopped at the same time as the driving of the screw pump 60 is stopped, the responsiveness to the toner supply signal is improved. If the toner remains in the tube 65, the toner may be clogged in the tube. However, the toner transferred by the screw pump 60 is a new toner or a mixture of the new toner and the recycled toner. It is difficult and there is no problem at all. Further, according to the experiments conducted by the present inventors, the toner amount remaining in the tube by the air supply amount of the air pump different. Therefore, air pump for recovery air supply <br/> supply amount is set 1.0 to 2.0 liters / minute, air pump for toner replenishment the amount of air supply from 0.5 to 1.0 liters / Min. In this way, the air pump for recovery
And many air supply, air pump for toner replenishment than reducing the air <br/> supply amount, the collected toner is hardly clogged tubes, supplied toner can be improved responsiveness. The present invention is also advantageous for a developing device of a color machine in which toner density control is severe.

[0045]

According to the present invention, the recovered toner is less likely to be clogged in the transfer member, and the replenished toner can be supplied to the developing device with good responsiveness.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration example of an image forming apparatus in which the present invention is implemented.

FIG. 2 is a cross-sectional view illustrating a configuration example of a developing device provided in the image forming apparatus of FIG.

FIG. 3 is a cross-sectional view illustrating a configuration example of a toner bank.

FIG. 4 is a perspective view showing a disassembled state of the toner bank shown in FIG. 3;

FIG. 5 is a sectional view of a powder pump section of the toner transfer device.

FIG. 6 is a perspective view illustrating a configuration example of a related portion of a cleaning device and a collected toner transfer unit.

FIG. 7 is a sectional view of a relevant portion of the cleaning device and the collected toner transfer unit shown in FIG.

8 is a cross-sectional view illustrating a configuration example of the collected toner transfer unit illustrated in FIG.

[Explanation of symbols]

A Copy machine body B Toner Bank 18 Developing device 19 Transfer belt 20 Photoconductor cleaning device 60,83 screw pump 64 rotor 70 air pump

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-9-197794 (JP, A) JP-A-9-185232 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 21/00 G03G 21/10-21/12 G03G 15/08-15/08 507 G03G 15/00 303 G03G 21/00 370-540 G03G 21/14 G03G 15/01-15/01 117

Claims (1)

(57) [Claims] A developing device for developing an electrostatic latent image formed on an image bearing member; and a toner replenishing mechanism configured to replenish the toner in a toner storage portion disposed at a position away from the developing device. An image forming apparatus comprising: a collection unit that collects toner remaining after image formation; and a collection toner processing mechanism that transfers the collected toner to a collection toner storage unit for processing. The mechanism is a female screw type stator having a double pitch spiral groove, a powder pump having a male screw type rotor rotatably inserted in the stator, and a toner pumped by the powder pump. Air supply means for supplying air for fluidization in a state of being diffused, wherein the air is supplied from the toner storage section to the developing device and from the recovery section to the recovered toner storage section. The toner supply mechanism stops the powder pump and the air supply unit at the same time when the powder pump and the air supply unit are stopped, while the toner supply mechanism stops the powder pump and the air supply unit. An image forming apparatus characterized in that the air supply means is stopped after a predetermined time delay after the pump is stopped.