JPH11258961A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease residual toner in a moving path and to eliminate the faulty carrying of recovered toner by varying a gas supply amount by a gas supply means under the control of a control part. SOLUTION: When the number of pixels counted by a pixel number detection means attains a specified number, an MPU 14 judges that the recovered toner in a toner accumulation part 21 is accumulated to some extent, and controls to actuate a toner moving device 20. As for the actuation of the device 20, an air pump 40 is actuated first. In such a case, the pump 40 is set so that air supply amount may be switched to two steps. Then, the pump 40 actuated previous to a screw pump 30 is actuated high. When one second elapses, for example, after starting the actuation, the pump 30 is actuated and simultaneously the pump 40 is switched from high to low. After two seconds, the actuation of the pump 30 is stopped, and simultaneously the pump 40 is switched from low to high again. Furthermore, after five seconds, the actuation of the pump 40 is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital copying machine,
The present invention relates to an electrophotographic image forming apparatus such as a printer, a facsimile, or a multifunction peripheral thereof.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, it is possible to collect toner remaining on an image carrier or the like after a transfer step by a cleaning means, and return the collected toner to a developing means for reuse. It has already been proposed. In an image forming apparatus provided with such a toner recycling mechanism, cleaning means removes toner that has been transferred onto a photoreceptor, but has not been transferred onto a transfer-receiving body, or toner remaining on a transfer belt. And a toner transfer device for transferring the collected toner from the cleaning means to the developing means.

As a toner transfer device, Japanese Patent Application Laid-Open No. 7-219
Japanese Unexamined Patent Publication No. 329-329 discloses a monopump having a rotor for rotating the toner of a developer in the axial direction by rotating, and a fixed stator having a passage surrounding the rotor therein and being in contact with the rotor inside the passage. A mixture of toner and air is transported through a flexible pipe using a screw pump called a pump and air supply means for supplying air for fluidizing the developer moved by the screw pump. Is disclosed.

This toner transfer device is capable of transferring stored toner and collected toner through a flexible pipe or the like. Therefore, the installation position of the toner storage unit and the toner collection unit is not restricted at all and has a simple configuration. Therefore, there is an advantage that the toner can be surely transferred. In addition, a toner transfer device using a screw pump can stably transfer the toner by transferring the mixture in a state of being mixed with air by an air supply unit in a fluidized state. Aggregation and thermal fusion of the transferred toner are less likely to occur without applying more stress.

[0005]

The above-described toner transfer device using a screw pump is extremely advantageous for transferring toner. However, when used for a long time, the collected toner adheres to the inner wall of the transport pipe, and the adhered toner is removed. The gradual build-up of water has the problem of plugging the pipe in the worst case. Further, the toner adhered to the inner wall of the transport pipe may fall due to vibration due to the movement of the machine or the like, and the toner may be concentrated on a portion where the toner is present to block the pipe.

The present invention has been made in view of the above circumstances, and provides an image forming apparatus in which toner transferred by a toner transfer unit hardly adheres to a toner transfer path and toner clogging in the transfer path can be largely suppressed. It is intended to be.

[0007]

In order to achieve the above-mentioned object, the present invention relates to a developing means which is detachable from an image forming apparatus main body and develops an electrostatic latent image formed on an image carrier. Wherein the toner replenishing toward the developing means is transferred via a transfer path as a mixture with a gas flow by the operation of a toner transfer means having a screw pump and a gas supply means. A control unit for controlling a gas supply unit of the toner transfer unit, wherein a gas supply amount by the gas supply unit is changed by control of the control unit.

It is to be noted that the present invention is directed to an image forming apparatus for transferring toner removed / recovered by a cleaning means to a toner destination as a mixture with a gas flow by operating a toner transfer means having a screw pump and an air supply means. In the above, it is effective to provide a toner reservoir for storing the collected toner upstream of the toner transport unit in the toner transport direction, and to operate the toner transport unit when the collected toner in the toner reservoir reaches a predetermined amount. is there.

Further, according to the present invention, when the control section starts the operation of the toner transfer section, the control section starts the operation of the screw pump after the operation of the gas supply section is started. It is effective to reduce the amount of gas supplied by the gas supply means.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an overall schematic diagram showing a digital copying machine as an example of an image forming apparatus according to the present invention.

In FIG. 1, a digital copying machine uses a well-known electrophotographic system, and includes a drum-shaped photosensitive member 1 as an image bearing member inside. Arrow A around photoconductor 1
A charger 2, an exposure unit 3, a developing unit 4, a transfer unit 5,
Cleaning means 6 is provided.

The exposing means 3 includes a document table 7 on the top of the copying machine.
An electrostatic latent image is formed on the photoreceptor 1 based on an image signal read by the reading means 8 from a document placed on the photosensitive member 1. The electrostatic latent image formed on the photoreceptor 1 is developed by a developing unit 4 to form a toner image, and the toner image is electrostatically transferred by a transfer unit 5 onto a transfer material fed from a paper feeding device 9. Transcribed. The transfer material on which the toner image has been transferred by the transfer is conveyed to the fixing unit 10 and after being fixed there,
Emitted outside the machine.

The toner adhered onto the photoreceptor 1 by the above-mentioned development is generally electrostatically transferred to a transfer material by the transfer means 5, but about 10% of the toner remains untransferred on the photoreceptor. This residual toner is scraped off from the photoreceptor 1 by the cleaning blade 6a and the brush roller 6b of the cleaning means 6, and the scraped-off toner is returned to the developing means 4 by a toner transfer device to be described later. Become.

On the other hand, a cleaning means 11 is also provided on the transfer belt 5a of the transfer means 5 for contacting the photosensitive member 1 in the non-transferred portion or the non-image portion and adhering toner. The toner remaining on the transfer belt 5a is scraped off by a cleaning blade 11a which is in sliding contact with the belt. The scraped toner is also transferred to the developing means 6 by a toner transfer device described later.

In the copying machine of this embodiment, the cleaning means 6 for the photosensitive member and the cleaning means 11 for the transfer belt are provided.
A toner transfer device 20 is provided for transferring the toners respectively collected to the developing means 6. As shown in FIG. 2, the toner transfer device 20 includes a screw pump 30 as a toner transfer unit and an air pump 40 as a gas supply unit.
A toner reservoir 21 is provided on the upstream side in the toner transfer direction.

Above the toner reservoir 21, there are provided discharge ports 12 and 15, which communicate with the cleaning means 6 for the photosensitive member and the cleaning means 11 for the transfer belt, respectively. The discharge port 12 of the cleaning means 6 for the photosensitive member, which is also located above, communicates with a toner reservoir 21 via a toner guide 22. In the vicinity of the bottom inside the toner reservoir 21, a conveying screw 23 as a toner conveying member is provided.
And one end of a shaft 24 of the transport screw 23 protrudes outside the toner reservoir 21, and a main motor provided inside an image forming apparatus (not shown) via a clutch 25 outside the toner reservoir 21. Drive-coupled. The transport screw 23 may be driven by a dedicated drive motor.

The screw pump 30 comprises a female screw type stator 31 having a double pitch spiral groove formed of an elastic material such as rubber, and a male screw type rotor 32 rotatably fitted in the stator 31. And the rotor 32
Are connected so that the other end of the shaft 24 of the transport screw 23 coincides with the axis. Therefore, the clutch 25
, The transport screw 23 and the screw pump 30 operate. Further, the stator 31 is inserted into a holder 33 attached outside the toner reservoir 21. The holder 33 fixes the stator 31 so as to cover the periphery of the stator 31. The holder 33 has a toner discharge port 34 formed therein.
One end of a toner transport tube 35 as a transfer path is fitted into the toner discharge port 34. As the toner transport tube 35, a flexible hose or the like can be used, and the other end can be easily connected to the developing unit 4.
A gap 37 of, for example, about 1 mm is provided between the inner peripheral surface of the holder 23 and the outer peripheral surface of the stator 21, and the gap 37 communicates with the toner discharge port 34. The holder 33 is provided with an air supply port 36 communicating with the gap 37, and the air supply port 36 is connected to the air pump 40 via an air supply tube 41. The clutch 25 and the air pump 40 are a micro processing unit (MPU) as a control unit.
14 controls its operation.

Next, the movement of the toner used in the image forming process will be described with reference to FIG. The developing means 4 is a two-component developing device and includes a developing casing 50 containing a developer composed of a carrier and a toner. When the developing unit 4 forms a toner image, the toner is consumed, so that the ratio of the toner of the developer (toner density) decreases. Therefore, in order to suppress a decrease in image density, when the toner density in the developer becomes equal to or lower than a predetermined value, the toner supply roller 53 is rotated to supply toner from the toner hopper 51 and maintain the toner density in the developer. Is done. The toner concentration in the developer is measured by a magnetic permeability sensor 52 attached to the developing casing.

The toner supplied from the toner hopper 51 is stirred and frictionally charged with the carrier by the stirring member 54 in the developing means 4. The developer including the carrier and the toner is jumped up to the developing roller 56 by the paddle wheel 55, and is attracted to the peripheral surface by the magnet in the developing roller 56. The developer is conveyed by the sleeve on the outer periphery of the developing roller, and the excess is scraped off by the developing doctor 57. The toner in the developer conveyed to the photoreceptor adheres to the electrostatic latent image due to the developing bias.

The toner adhered to the photoreceptor 1 is transferred to a transfer unit 5
Is electrostatically transferred onto a transfer material, of which about 1
0% of the toner is not transferred and remains on the photoconductor. 3 and 4, the residual toner remaining on the photoconductor 1 is scraped off from the photoconductor 1 by a cleaning blade 6a and a brush roller 6b of a cleaning unit 6, and is conveyed to an outlet 12 of a toner transfer device 20 by a coil 6c. Is done. The collected toner sent to the discharge port 12 falls in the toner guide by its own weight, and is stored in the toner storage section 21. Further, the toner remaining on the transfer belt 5a is also collected by the transfer cleaning means 11, and this toner is also stored in the toner storage section 21 through the discharge port 13, and the collected toner is operated by the toner transfer device 20 to activate the air. Is transferred to the developing means 4 via the toner transport tube 35 as an air-fuel mixture.

When the number of pixels counted by the pixel number detecting means reaches a predetermined number, for example, the MPU
14 determines that the collected toner in the toner reservoir 21 has accumulated to some extent, and controls the operation of the toner transfer device 20. Figure 5
FIG. 4 is a diagram showing a relationship between operation timings of the screw pump 30 and the air pump 40 during the operation control.

In FIG. 5, the operation of the toner transfer device 20 is performed by operating the air pump 40 first. In this example, the air pump 40 is set so that the air supply amount can be switched between two stages, for example, 2 liters / min and 1 liter / min. And screw pump 3
The air pump 40 that is operated prior to 0 is high (hi).
gh), that is, 2 liters / min with a large air supply. When the operation is started and, for example, one second has elapsed, the screw pump 30 is operated, and at the same time, the air pump 40 is changed from high to low (l).
ow). The operation of the screw pump 30 is stopped two seconds later, and at the same time, the air pump 40 is switched from low to high again. Then, the operation of the air pump 40 is stopped after 5 seconds. The operation of the toner transfer device 20 controlled by the MPU 14 has been described above.

The toner transfer device 20 controlled as described above
This is because even after the screw pump 30 is stopped, the supply amount is increased and the air is continuously supplied to the developing unit without the toner remaining in the toner conveying tube 35 or adhering to the inner wall thereof by the air from the air pump 40. Transported reliably. Therefore, the toner remaining in the toner transport tube 35 and the adhered toner can be reliably reduced, so that the risk of toner clogging in the tube is avoided. In addition, since the increased amount of air supplied from the air pump 40 is also performed before the operation of the screw pump 30 is started, there is no residual toner or adhered toner in the toner transport tube 35 in the last toner transfer. However, it can be conveyed toward the developing means. Further, since the amount of air supplied from the air pump 40 is reduced when the screw pump 30 is operated, it is possible to suppress the toner from being scattered in the developing unit 4 due to the increased amount of air being conveyed.

FIG. 6 is a diagram showing an example of the configuration of a recovered toner supply unit 60 for supplying toner to the developing means 4 and a new toner supply unit 61. The recovered toner supply unit 60 includes the toner transfer device 20 and the toner. The collected toner (T) is connected via the transport tube 35, and the recovered toner (T) is mixed with the gas (air) supplied from the air pump 40 by the screw pump 30 as described above.
The toner is transported in the toner transport tube 35. On the other hand, the new toner (NT) is supplied to the container 62 of the new toner supply unit 61.
Stored in advance. To supply toner to the toner hopper 51, first, the supply blade 6 of the new toner supply unit 61 is used.
3 and a new toner (NT) is supplied to the toner hopper 51.
When the sensor 64 detects that the toner has been replenished, the supply blade 65 of the collected toner supply unit 60 operates, and the collected toner (T) is supplied to the toner hopper 51. Then, the new toner (NT) and the collected toner (T) are transported in the direction indicated by the arrow B while being stirred by the transport screw 66, supplied to the developing casing 50 of the developing unit 4, and reused as recycled toner. A high quality image is formed.

The recovered toner supply unit 60 shown in FIG.
Is located downstream of the new toner supply unit 61 in the transport direction, and a transport screw 66 disposed immediately below both units 60 and 61 stirs the new toner (NT) and the recovered toner (T). While being transported in the direction of arrow B in FIG. The collected toner supply unit 60 is connected to the toner conveying tube 35, and the collected toner is supplied to the inside thereof. The MPU 14 adjusts the supply amount of the collected toner by using the screw pump 3
0 and / or by controlling the air pump 40. Further, the supply amount may be adjusted by rotating the supply blade 65.

The new toner supply amount in the new toner supply unit 61 is adjusted, for example, by controlling the rotation of the supply blade 63 so that the toner hopper 5
This is realized by adjusting the amount of new toner to be supplied into the printer.

Although the preferred embodiment of the present invention has been described above, the present invention should not be limited to the above embodiment. For example, in the above-described embodiment, the collected toner is returned to the developing unit. It can also be configured to send to means.

In the above embodiment, the apparatus for transferring the toner collected by the photosensitive member cleaning unit and the transfer cleaning unit together has been described.
The present invention may be configured such that only one of the photoconductor cleaning unit and the transfer cleaning unit transfers the collected toner. In particular, since the collected toner of the transfer cleaning unit contains foreign matter such as paper dust, the collected toner may be returned to the waste toner tank without being recycled.

Further, although the air supply amount by the air pump 40 is switched in two stages, the supply amount may be switched in multiple stages. In this case, the air supply amount before and after the operation of the screw pump 30 depends on the operation amount. The amount does not need to be the same if it is increased more than the time.

[0030]

According to the first aspect of the present invention, by varying the amount of gas supplied by the gas supply means, residual toner in the transfer path can be effectively reduced, and defective toner conveyance failure can be prevented. .

According to the second aspect of the present invention, when stopping the toner transfer means, the supply amount of gas by the gas supply means is increased simultaneously with the stop of the screw pump, and then the gas supply of the gas supply means is stopped. In addition, it is possible to effectively reduce the residual toner in the transfer path, and prevent the conveyance of the collected toner from being defective.

According to the third aspect of the present invention, when the operation of the toner transfer means is started, the operation of the screw pump is started after the operation of the gas supply means is started. By reducing the supply amount of the toner, it is possible to effectively reduce the residual toner in the transfer path and to prevent a defective toner conveyance failure.

Further, in the configuration of the second and third aspects, the gas supply amount is reduced when the screw pump is operated.
Scattering of toner from the developing means can also be prevented.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram illustrating an example of an image forming apparatus according to the present invention.

FIG. 2 is a cross-sectional view illustrating an example of the toner transfer device of the present invention.

FIG. 3 is a cross-sectional view illustrating an image forming unit of the present invention.

FIG. 4 is a perspective view showing an example of the toner transfer device of the present invention.

FIG. 5 is a timing chart illustrating the operation of each unit of the image forming apparatus according to the present invention.

FIG. 6 is a cross-sectional view illustrating an example of a toner supply unit according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photoconductor 4 Developing means 6, 11 Cleaning means 14 MPU 20 Toner transfer device 30 Screw pump 40 Air pump

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshihiro Sugiyama 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd.

Claims (3)

[Claims] 1. An image forming apparatus for transferring toner removed / recovered by a cleaning unit to a toner destination as a mixture with a gas flow by operating a toner transfer unit having a screw pump and an air supply unit. An image forming apparatus comprising: a control unit that controls a gas supply unit of a transfer unit; and a control unit that controls a gas supply amount of the gas supply unit. 2. The image forming apparatus according to claim 1, wherein the control unit increases a gas supply amount by the gas supply unit at the same time as stopping the screw pump when stopping the activated toner transfer unit. And then stopping the gas supply of the gas supply means. 3. The image forming apparatus according to claim 1, wherein the control unit starts operating the gas supply unit when starting the operation of the toner transfer unit, and then starts operating the screw pump. Wherein the amount of gas supplied by the gas supply unit is reduced at the same time as the start.