JPH06118791A - Image forming device - Google Patents

Abstract

PURPOSE:To provide the new image forming device where toner can be recovered to a developing device without spoiling natural particle size distribution of the toner and the recovered toner can be sufficiently agitated and recycled. CONSTITUTION:In the image forming device eliminating the toner remaining on a surface of a latent image carrier after transferring of a developed image with a cleaning device 5 and recovering the toner eliminated from the latent image carrier 7 surface by the cleaning device 5 to inside the developing device 6 by a toner recovery device, the developing device 6 is rotated inside the device to agitate and carry the developer, an agitating and carrying member 12 with more than one opening in a periphery part of its hollow rotational shaft is provided, toner carrying pipes 13a and 13b constituting the toner transporting path to transport the toner to the developing device from the cleaning device 5 and more than one toner transporting means 10 to transport the toner by air flow through these toner carrying tubes are provided in the toner recovery device and an edge part of the toner carrying pipe 13b on the developing device 6 side is connected to the hollow rotary shaft of the agitating and carrying member 12 through a bearing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art An electrostatic latent image is formed on a latent image carrier, the electrostatic latent image is dry-developed by a developing device to obtain a visible image, and the visible image is transferred and fixed on a transfer paper. Image recording devices for forming images are widely known in association with electronic copying machines, optical printers, and the like. Since the same latent image carrier is repeatedly used in such an image forming apparatus, it is necessary to remove the toner remaining on the surface of the latent image carrier after the visible image transfer by a cleaning device for each image forming process. is there.

Recently, from the viewpoint of resource saving, it has been proposed that the toner removed from the latent image bearing member by the cleaning device is not discarded, but is collected and reused in the developing device (Actual Development Sho 52). -155044, JP-A-6
0-41097, etc.).

The method of rotating the coil spring is the best known method for conveying the collected toner from the cleaning device to the developing device. In such a mechanical conveying method, the toner to be conveyed is not conveyed. It is unavoidable that the particle size distribution originally possessed by the toner is changed due to pulverization due to mechanical force, or conversely, toner particles are coagulated and coarsened. If such a toner having a changed particle size distribution is reused, it is not preferable because background dust and toner scattering due to the finely pulverized toner, or “white spots in solid portions” due to the coarsened toner occur.

Further, the toner must be sufficiently agitated together with the carrier when it is used for development. However, the recovered toner may not be sufficiently mixed with the carrier depending on the position where the recovered toner is returned into the developing device. The toner may be supplied to the developing unit without being stirred, and in this case as well, the toner is insufficiently charged due to insufficient stirring, resulting in background stains and toner scattering.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and the toner can be collected in the developing device without impairing the original particle size distribution of the toner, and the collected toner is sufficiently stirred. It is an object of the present invention to provide a new image forming apparatus that can be reused after that.

[0007]

The image forming apparatus according to the present invention includes: "A latent image bearing member is formed with an electrostatic latent image, and the electrostatic latent image is dry-developed by a developing device to obtain a visible image. The visible image is transferred and fixed on a transfer paper to form an image, and the toner remaining on the surface of the latent image carrier after the visible image transfer is removed by a cleaning device and removed from the surface of the latent image carrier by the cleaning device. An image forming apparatus in which the collected toner is collected in the developing device by a toner collecting device, which is characterized by the following points (claim 1).

The "developing device" has an agitating / conveying member which rotates inside the device to agitate / convey a developer and which has one or more openings on the peripheral surface of its hollow rotating shaft. The “toner recovery device” is a toner transfer pipe that constitutes a toner transfer path for transferring toner from the cleaning device to the developing device,
One or more toner transfer means for transferring the toner by the air flow through the toner transfer tube. The "end portion of the toner transport tube on the developing device side" is connected to the hollow rotary shaft of the stirring and transporting member via a bearing. The fact that the toner transport pipe and the hollow rotary shaft are connected “via a bearing” means that the hollow rotary shaft is rotatable regardless of the connection between the two.

As the toner transfer means for transferring the toner by the air flow, an air flow generation means such as a fan provided in the toner transfer path can be used.
As in the image forming apparatus described above, “a ventilation pipe, a check valve,
A toner transfer means having a piston chamber, a piston, and a driving means "can be used.

The "ventilation tube" has a large number of fine holes in the wall of the tube as compared with the particle diameter of the toner, and can ventilate through the tube wall, and forms a part of the toner transfer path. The "check valve" is arranged in the toner transfer passage before and after the ventilation pipe, and is configured to open only to the air flow from the cleaning device side to the developing device side. The "piston chamber" is formed by incorporating a ventilation pipe. The "piston" is provided by being fitted into the piston chamber so as to realize a pressurized state and a negative pressure state in the piston chamber, and is driven by the drive means.

In the image forming apparatus according to claim 1 or 2, "a plurality of openings of the hollow rotating shaft of the agitating / conveying member are formed in the axial direction, and the size of the opening is such that a connecting portion with the toner transfer path is formed. It can be made larger as the distance increases ”(Claim 3). In this case, the plurality of openings can be arranged in a spiral shape surrounding the rotary shaft (claim 4). It is also possible to form the opening in the form of a slit that is long in the axial direction of the hollow rotary shaft so that the slit width increases continuously or stepwise "as the distance from the connecting portion with the toner transfer path increases". Also in this case, the slit can be formed in a spiral shape.

A mesh member having a size larger than the toner particle size and smaller than the carrier particle size can be provided in the opening of the hollow rotary shaft of the stirring and conveying member (claim 5). , "Bias voltage having the same polarity as the toner" can be applied (claim 6).

Further, the image forming apparatus according to the above-mentioned claim 1 or 2 or 3 or 4 or 5 or 6 includes a toner concentration detecting means for detecting the toner concentration in the developer,
It is possible to have a control means for driving and controlling the transfer means of the toner recovery device according to the detection result of the toner concentration detection means.

[0014]

As described above, in the image forming apparatus of the present invention,
Since the collected toner is conveyed from the cleaning device to the developing device by the air flow, almost no mechanical force acts on the collected toner.

Further, the toner collected in the developing section is returned to the developer through the opening of the hollow rotary shaft of the agitating / conveying member,
The agitating / conveying member is rotated and agitated and conveyed for development.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows the main part of an image forming apparatus to which the present invention is applied. In the figure, a latent image carrier denoted by reference numeral 7 is a photoconductive photosensitive member formed in a drum shape, and is rotatable in the direction of arrow a. A charger 8, a developing device 6, a transfer / separation charger 9, and a cleaning device 5 are provided around the photoconductor 7, and image exposure (projection irradiation of an original light image is performed between the charger 8 and the developing portion by the developing device 6). And / or optical writing).

The image forming process is generally performed as follows. While the photoconductor 7 is rotated, it is uniformly charged by the charger 8, and image exposure is performed by an image exposure means (not shown) to form an electrostatic latent image. This electrostatic latent image is dry-developed by the developing device 6. That is, a so-called two-component powder developer containing toner and carrier is stored in the casing of the developing device 6, and the toner and the carrier are triboelectrically charged in opposite polarities by being stirred by the stirring and conveying member 12. While being conveyed, it is supplied to the developing roller 130.

The developing roller 130 holds the supplied developer on its peripheral surface and rotates, and supplies the developer to the electrostatic latent image in the developing section (the vicinity of the developing roller 130 and the peripheral surface of the photosensitive member 7). To visualize the electrostatic latent image. The developing device 12 is provided with a toner replenishing device 11 so that the toner stored therein is supplied into the developing device as needed.

The visible image formed on the photoconductor 7 is electrostatically transferred onto the transfer paper (not shown) conveyed in the direction of the arrow b by the transfer action of the transfer / separation charger 9. The transfer sheet onto which the visible image has been transferred is separated from the photoconductor 7 by the separating action of the transfer / separation charger 9 and conveyed to a fixing device (not shown). After the visible image is fixed on the transfer device, the transfer paper is discharged to the outside of the device. It After the transfer of the visible image, the toner remaining on the surface of the photoconductor 7 is removed from the surface of the photoconductor by the cleaning device 5.

In this image forming apparatus, the toner collecting device is composed of the toner carrying tubes 13a and 13b and the toner carrying means 1.
It is composed of 0s. The stirring / conveying member 12 arranged in the developing device for stirring / conveying the developer has fins for stirring / conveying radially formed on the outer peripheral portion of the hollow rotary shaft, and agitates and conveys the developer by rotation. Is supposed to do. Then, the toner conveying pipe 13b of the toner collecting device
The end on the developing device side is connected to the end of the hollow rotating shaft of the stirring and conveying member.

FIG. 2A schematically shows the toner transfer means 10. The ventilation pipe denoted by reference numeral 2 has a cleaning device side connected to the toner carrying pipe 13a and a developing device side connected to the toner carrying pipe 13b. The ventilation pipe 2 has a large number of holes 1 which are finer than the toner particle size on the pipe wall, and ventilation is possible through the pipe wall.

A check valve 30 is provided on the cleaning device side of the ventilation pipe 2, and the orifice 30 is weakly elastically acted by the elastic member 30a toward the cleaning device side.
The hole of b is closed. A check valve 31 is provided on the developing device side of the ventilation pipe 2, and closes the developing device side end of the ventilation pipe 2 by a weak elastic force applied to the cleaning device side by the elastic member 31a.

A piston chamber indicated by reference numeral 100 is formed so that the ventilation pipe 2 is built therein, and a piston 4 is fitted therein. When the check valves 30 and 31 are closed as shown in FIG. 2A, the piston chamber 100, the piston 4, and the check valve 3
0 and 31 form a closed space including the ventilation pipe 2. The piston 4 is driven by the driving means 50.

As shown in FIG. 2 (b), when the piston 4 is moved in the direction of arrow c, a negative pressure is generated in the sealed space, and the inside of the ventilation pipe 2 is also in a negative pressure state. Due to this negative pressure, the check valve 30 opens, and an air flow from the cleaning device side into the piston chamber 100 is generated. The toner in the cleaning device is transported in the toner transport pipe 13a by the air flow and stored inside the ventilation pipe 2. Since the fine holes 1 formed on the tube wall of the ventilation tube are finer than the toner particle size, the toner cannot pass through the tube wall of the ventilation tube 2.

In this state, the piston 4 is moved to the position shown in FIG.
When it is moved in the direction of arrow d, a positive pressure state is generated in the piston chamber 100, and the inside of the ventilation pipe 2 is also in a positive pressure state. Due to this positive pressure, the check valve 31 is opened, an air flow is generated from the piston chamber 100 toward the developing device, and the toner stored inside the ventilation pipe 2 is transferred to the developing device through the toner carrying pipe 13b. In this way, the toner can be collected from the cleaning device to the developing device.

To collect the above toner, first use the piston shown in FIG.
The toner may be moved in the direction of arrow c in (b) to store a sufficient amount of toner inside the ventilation tube 2, and thereafter, the stored toner may be collected in the developing device, if necessary. The direction of movement of the piston may be alternately changed to continuously collect the toner from the cleaning device to the developing device.

FIG. 3 shows a state in which the agitating / conveying member 12 provided in the developing device and the toner conveying pipe 13b are connected. The stirring and conveying member 12 is provided on the wall of the casing of the developing device.
A hole for fitting with the hollow rotating shaft 120 is formed, and the hollow rotating shaft 120 is supported by the bearing 14 arranged in the hole portion. A drive gear 141 is fitted and fixed to one end of the hollow rotary shaft 120, and is driven by a drive mechanism (not shown) to rotate the hollow rotary shaft 120.

In FIG. 3, a supporting member 19 is fixed to the wall portion on the right side of the casing, and the toner carrying tube 13b is fitted and fixed to a fitting portion provided on the supporting member 19. The support member 19 has a bearing portion 15, and the hollow rotary shaft 120 is fitted to the support member by the bearing portion 15. In other words,
The hollow rotary shaft 120 and the toner transport tube 13b are provided as a support member 1
9, the hollow rotary shaft 120 is rotatable regardless of the connection with the toner carrying tube 13b. Further, the mesh member 16 is provided in contact with the inner wall of the hollow rotary shaft 120.

As shown in FIG. 4, a plurality of openings 17 are formed in the hollow rotating shaft of the stirring and conveying member 12, and these openings 17 are closed by a mesh member 16.
The mesh member 16 is selected such that the particle size is larger than the particle size of the toner (maximum particle size in the particle size distribution) and smaller than the particle size of the carrier. Minute foreign matter such as powder cannot pass through the mesh member 16.

The toner transported by the air flow through the toner transport pipe 13b is mixed with the developer in the developing device through the opening 16 and is stirred by the developer by the rotation of the stirring transport member 12 while developing. It is transported toward the rollers. The opening 16 is formed in a spiral shape on the peripheral surface of the hollow rotary shaft 120, and the size of the opening is set so as to increase with the distance from the connecting portion with the toner carrying tube 13b. By doing so, the toner collected through the toner transport tube 13b can be returned to the developer substantially evenly in the length direction of the hollow rotary shaft 120.

Further, in this embodiment, the mesh member 16 is made of a conductive material such as metal, and a bias voltage having the same polarity as the toner is applied from the power source 500 as shown in FIG. After the transfer of the visible image, some of the toner remaining on the photosensitive member cannot be contributed to the development by being charged to the same polarity as the electrostatic latent image. Among them, defective toner that cannot contribute to such development is also included, but the mesh member has the same polarity as the toner (the same polarity as the normal toner charging polarity).
It is possible to prevent the defective toner from being captured and returned to the developer by applying the bias voltage of.

The mesh member 16 is the hollow rotary shaft 12
It can be attached / detached / replaced to / from 0, and can be detached from the hollow rotary shaft and replaced or cleaned as appropriate. To remove the mesh member 16, in FIG. 3, the toner carrying tube 13b is removed from the support member 19 and then the support member 1 is removed.
9 may be removed from the developing device casing, and the mesh member 16 may be extracted from the hollow rotating shaft 120.

It is necessary that the toner concentration in the developer is within a predetermined appropriate value range. Conventionally, the toner concentration in the developer is directly or indirectly detected, and the toner concentration in the developer falls below a predetermined value. The toner is replenished when

In the example of the device described, the toner concentration in the developer in the developing device is detected by the optical sensor shown in FIG. That is, after the visible image is transferred, the surface of the photoconductor toward the cleaning device 5 is irradiated with light to detect the reflection density, and the toner density in the developer is determined by the correlation between the reflection density and the toner density in the developer. To detect.

Since the toner collected by the cleaning means and the toner collecting device is only a part of the toner consumed by the development, even if the toner is continuously collected by the toner collecting device, the toner is not developed by itself. The toner concentration of the developer in the apparatus gradually decreases as the development is repeated.
Therefore, when the toner density falls below a predetermined density value, the toner replenishing device 11 is operated to replenish a predetermined amount of toner.

There is another method for replenishing toner. That is, a predetermined amount of collected toner is stored inside the ventilation pipe 2 in the piston chamber 100 without continuously collecting the toner, and normal toner supply is performed by the toner supply device 11.
Alternatively, when the amount of the replenishment toner is insufficient in the toner replenishing device 11, the recovered toner stored in the ventilation pipe 2 may be transferred and replenished into the developing device.

When the collected toner is replenished by the toner collecting device according to the output of the toner concentration detecting means, the lower limit value of the toner density when the collected toner is replenished is the difference between the toners supplied by the toner replenishing means. It may be set to the same value as the lower limit of density, or may be set to another value.

If necessary, two or more toner collecting devices as described in the embodiments may be provided in the toner transfer slag from the cleaning device to the developing device.

[0039]

As described above, according to the present invention, a novel image forming apparatus can be provided. Since the image forming apparatus is configured as described above, the toner removed from the latent image carrier by the cleaning device can be collected and contributed to the repeated development. At that time, since the collected toner is returned to the developing section by the air flow, the mechanical force hardly acts on the toner, and the toner is hardly pulverized or coarsened. Therefore, the particle size distribution of the recovered toner hardly changes during the recovery operation, and the recovered toner can be repeatedly used in a good state for a long period of time. Further, since the recovered toner is returned to the developer through the hollow rotating shaft of the stirring and conveying member in the developing device, it is sufficiently stirred in the developing device. Therefore, it is possible to effectively prevent the background stain and the toner scattering caused by the change in the particle size distribution and the insufficient stirring.

In the image forming apparatus according to claim 2,
Since the toner collected from the cleaning device can be stored inside the ventilation pipe in the toner transfer path, the toner can be collected in the developing device as needed.

According to the third aspect of the present invention, the recovered toner can be returned to the developer substantially uniformly over the longitudinal direction of the hollow rotating shaft of the stirring and conveying member. It is possible to effectively prevent the occurrence of bias.

In the apparatus according to the fourth aspect, since the openings formed in the hollow rotary shaft are arranged in a spiral shape, all the openings are not buried in the developer and the toner is transferred in the toner discharging state. Since the pressure inside the tube is kept constant, it is possible to effectively prevent backflow of the recovered toner and leakage of the recovered toner from the gap.

It is possible to prevent unnecessary foreign matter collected with the toner according to claim 5 from returning to the developer, and in the image forming apparatus according to claim 6, among the collected toner, the toner It is possible to prevent the charged toner having a polarity opposite to that of the regular counter electrode property from being returned to the developer and causing toner aggregation. According to the image forming apparatus of the seventh aspect, the toner can be properly collected in the developing device according to the toner concentration in the developer in the developing device.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing only an essential part of an example of an image forming apparatus to which the present invention is applied.

FIG. 2 is a diagram for explaining a toner recovery device in the embodiment of FIG.

FIG. 3 is a diagram for explaining the connection between the toner conveying pipe and the hollow rotating shaft of the toner collecting device of FIG.

FIG. 4 is a diagram for explaining an opening formed in a hollow rotary shaft.

[Explanation of symbols]

 5 Cleaning Device 6 Developing Device 7 Latent Image Carrier 10 Toner Transfer Means 13a, 13b Toner Conveying Pipe 12 Stirring Conveying Member

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shunji Kato 1-3-3 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd.

Claims (7)

[Claims] 1. An electrostatic latent image is formed on a latent image carrier, the electrostatic latent image is dry-developed by a developing device to obtain a visible image, and the visible image is transferred and fixed on a transfer paper. After the image formation, the toner remaining on the surface of the latent image carrier after the visible image transfer is removed by the cleaning device, and the toner removed from the surface of the latent image carrier by the cleaning device is transferred to the developing device by the toner collecting device. In the image forming apparatus configured to collect, the developing device includes an agitating / conveying member that rotates inside the device to agitate / convey the developer and to have one or more openings in the peripheral surface of the hollow rotating shaft. The toner recovery device includes a toner transport pipe that constitutes a toner transport path for transporting toner from the cleaning device to the developing device, and one or more toner transport pipes that transport the toner by an air flow through the toner transport pipe. And a over transfer means, the ends of the developing device side of the toner conveying pipe, an image forming apparatus characterized by being connected to the hollow rotating shaft of the agitation conveying member through the bearing. 2. The image forming apparatus according to claim 1, wherein the toner transfer means of the toner recovery device has a ventilation pipe, a check valve, a piston chamber, a piston, and a driving means. Has a large number of holes that are finer than the toner particle size on the tube wall and can be vented through the tube wall and forms a part of the toner transfer path. In the passage, it is arranged before and after the ventilation pipe and is configured to open only to the air flow from the cleaning device side to the developing device side, the piston chamber is formed by incorporating the ventilation pipe, and the piston is Provided in the piston chamber by fitting into the piston chamber so as to realize a pressurized state and a negative pressure state,
An image forming apparatus driven by the driving unit. 3. The image forming apparatus according to claim 1, wherein a plurality of openings of the hollow rotating shaft of the agitating / conveying member are formed in the axial direction, and the size of the opening is a connecting part with the toner transfer path. An image forming apparatus, wherein the image forming apparatus increases in size with increasing distance from. 4. The image forming apparatus according to claim 3, wherein the plurality of openings are arranged in a spiral shape surrounding the rotary shaft on a peripheral surface portion of the hollow rotary shaft. 5. The image forming apparatus according to claim 1, 2 or 3 or 4, wherein a mesh having a particle size larger than the toner particle size and smaller than the carrier particle size is provided in the opening of the hollow rotating shaft of the stirring and conveying member. An image forming apparatus comprising a member. 6. The image forming apparatus according to claim 5, wherein a bias voltage having the same polarity as that of the toner is applied to the mesh member. 7. An image forming apparatus according to claim 1, 2 or 3 or 4 or 5 or 6, according to a toner density detecting means for detecting a toner density of a developer, and a detection result of the toner density detecting means. An image forming apparatus comprising: a control unit that drives and controls a transfer unit of the toner recovery device.