JPH11338327A - Toner carrying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner carrying device which securely prevents the internal pressure rising of a toner replenishment part and the leakage of a toner without providing the toner replenishment part with a filter or the like in an image forming device which carries and recycles recovered toner, as a mixture of air and it, to a developing device by using an air pump and a powder pump. SOLUTION: This toner carrying device having the screw pump 25 for carrying toner recovered by cleaners 6 and 19 and the air pump 26 for supplying air to the toner carried by the screw pump and for mixing them to fluidize the toner is provided with a separation means 36, which is situated in the toner replenishment part of the developing device and separates the air mixture into the toner and air, and circulation paths 31 and 32, which constitute paths for returning, circulating and using the air exhausted from the air recovery port 38 of the separation means 36. Here, the air pump is disposed near the toner replenishment part of the developing device, the suction part of the air pump is connected to the air recovery port 38 provided in the separation means 36, and the discharging part of the air pump 26 is connected to the screw pump 25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a toner conveying device used in a toner recycling mechanism used in an image forming apparatus such as an electrophotographic copying machine, a printer, a facsimile machine, and more particularly, to a toner recovered from an image carrier. When the toner mixture is returned to the developing device, the toner is scattered when the mixture supplied to the developing means is separated into toner and air in a toner transport device of a type that transports the toner as a mixture with air using a powder pump. The present invention relates to a toner conveying device capable of effectively preventing the toner transfer from being performed.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, a toner image obtained by developing an electrostatic latent image formed on a photoreceptor as an image carrier with toner supplied from a developing device is transferred onto transfer paper. An image is formed by transferring and fixing, and the toner remaining on the photoreceptor after the transfer is removed and collected by a cleaning device. Recently, from the viewpoint of effective use of resources, a toner recycling mechanism that reuses toner by re-supplying toner removed and recovered from an image carrier such as a photoconductor and an intermediate transfer body to a developing device without discarding the toner. Is often adopted. As such a toner recycling mechanism, instead of simply transporting the toner removed and recovered from the image carrier to the developing device using a coil screw or the like, the toner is recovered using a powder pump (screw pump, mono pump) and an air pump. A proposal has been made by the same applicant to fluidize the mixture as air and then move the mixture in a flexible tube. By the way, in such a toner recycling mechanism using a powder pump and an air pump, the air pump supplies the sucked outside air to the powder pump, so that the powder pump is mixed into the toner supply section of the developing device. When air is supplied, the internal pressure in the toner replenishing unit may increase due to the air-fuel mixture, causing toner to leak out of the developing device from the joint between the members.Therefore, a filter is provided in the toner replenishing unit to remove only air. Conventionally, a configuration in which toner is supplied to the developing device main body side while being discharged to the outside while preventing an increase in internal pressure has been adopted. As described above, in the related art, a filter is provided in the toner replenishing unit and the internal pressure is prevented from rising by discharging the filter to the outside. Cleaning and replacement are required, which increases maintenance costs. In addition, since an increase in the internal pressure induces toner leakage from a joint between members such as a joint between the toner replenishing unit and the developing device main body, measures have been taken to enhance the sealing property of the joint. Therefore, the leakage could not be completely prevented.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to recycle a toner by using an air pump and a powder pump to transport the collected toner as a mixture of air and air to a developing device. It is an object of the present invention to provide a toner conveying device capable of reliably preventing an increase in the internal pressure of the toner supply unit and preventing toner leakage without providing a filter or the like in the toner supply unit.

[0004]

In order to achieve the above object, the present invention is directed to a cleaning device for recovering toner from an image carrier, a screw pump for conveying the toner recovered by the cleaning device, and a screw. An air pump for supplying and mixing air to the toner conveyed by the pump to fluidize the toner; and a toner transfer path serving as a path for conveying a mixture of toner and air from the screw pump to the toner replenishing unit of the developing device. A separating unit provided in a toner replenishing unit of the developing device for separating toner and air from the air-fuel mixture; and a unit for returning air exhausted from an air recovery port of the separating unit to an air pump for circulating use. A circulation route that constitutes a route,
The air pump is arranged near the toner replenishing section of the developing device, the suction section of the air pump is connected to an air recovery port provided in the separating means, and the discharge section of the air pump is connected to a screw pump. According to a second aspect of the present invention, when the flow rate of the air-fuel mixture supplied from the screw pump to the separation means is A and the flow rate of the air discharged from the separation means to the air pump is B, the relationship between the two is A < B
It is characterized by having comprised so that it might become.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments shown in the drawings. FIG. 1 is a schematic diagram of a main part of an image forming apparatus provided with a toner conveying device of the present invention, FIG. 2 is an exploded view of an example of the toner conveying device, and FIG. FIG. The image forming unit of the electrophotographic image forming apparatus includes a photosensitive member 1 as an image carrier, an exposing unit 2, a developing device 3, a transfer device 4, a fixing device 5, a cleaning device 6, and the like. After the electrostatic latent image formed on the photoreceptor 1 by the exposure is developed with a toner supplied from the developing device 3 to form a toner image, the transfer fed from the paper feeding device 10 through the registration roller 11 is performed. The toner image is transferred onto the transfer paper while the paper is transported to the transfer position by the transfer device 4, and then the image is fixed by the fixing device. The cleaning device 6 has, for example, a cleaning blade 15, and the toner removed from the photoreceptor by the cleaning blade 15 is transported in a direction perpendicular to the paper by a transport screw disposed at a lower portion in the casing 16. It is conveyed to a screw pump (powder pump) 25 by the recovery pipe 17. Further, the transfer device 4 has a transfer belt 18a and a transfer corotron 18b, and discharges the transfer sheet conveyed to the transfer position by the belt 18a from the transfer corotron 18b, thereby transferring the toner image on the photoconductor 1 to the transfer paper. Transfer onto transfer paper. The toner remaining on the transfer belt is removed by a cleaning blade constituting a cleaning device 19, and is then conveyed to a screw pump 25 by a recovery pipe 21 provided at a lower portion of the casing 20.

The toner conveying device of the present invention comprises a screw pump 25, an air pump 26, and a screw pump 2
And a circulation path 31, 32 for returning the air discharged from the toner supply unit 35 of the developing device 3 to the screw pump 25 via the air pump 26. In addition, the tube constituting the toner transfer path 30 and the circulation paths 31 and 32 is formed of a flexible tube made of rubber, resin, or the like. Further, a toner replenishing section 35 is provided above the developing device main body 3, and the discharge end of the toner transfer path 30 and the suction end of the circulation path 31 are connected to the toner replenishing section, respectively. The position of the discharge end of the toner transfer path 30 is disposed below the suction end of the circulation path 31, and this arrangement constitutes separation means 36 for separating toner and air from the air-fuel mixture. The separating means 36 is provided with a gas mixture inlet 37 at a predetermined location on the inner wall of the toner replenishing section 35, for example, and the toner in the gas mixture conveyed through the conveyance path 30 is supplied to the inlet 3
7, the air supply port 38 is provided in the toner supply section 35, and an air recovery port 38 is provided on the inner wall sufficiently above the introduction port 37 to return the air to the air pump 26. The toner in the air-fuel mixture introduced from the lower inlet 37 falls down by its own weight, and only air containing no toner is returned to the air pump from the upper recovery port 38. That is, the air pump according to this embodiment does not suck the outside air and supply it to the screw pump 25 as in the conventional case, but instead circulates the air separated from the air-fuel mixture by the separation means 36 provided in the toner supply unit 35. Since the toner is sucked from the suction unit 26a via the suction unit 26 and re-supplied from the discharge unit 26b to the screw pump 25, the toner caused by the increase in the internal pressure of the toner supply unit can be provided without providing a degassing filter in the toner supply unit 36. Can be prevented from leaking.

Particularly, in the present invention, the air pump 26 is disposed near the toner replenishing section 36, and the air recovery port 38 of the toner replenishing section is directly connected to the suction section 26a via the suction pipe (circulation path) 31. Even if the air pump 36 is driven by a constant output, the amount of air sucked from the toner supply unit naturally increases. The transport path including the air pump, the screw pump, the toner supply unit, and the like is a closed loop, and theoretically, the position of the air pump 26 is
6, the amount of air recovered from the air recovery port 38 and the amount of air-fuel mixture introduced from the inlet 37 should not differ from each other. Air recovery port 3
The result that the displacement of the air from 8 was larger was obtained.
This is because air leakage and pressure loss are generated due to minute gaps between members constituting the screw pump, and the flow rate of the air-fuel mixture introduced from the inlet 37 far from the air pump is close to the air pump. It is considered that the flow rate is lower than the flow rate from the recovery port 38 where there is no room for air leakage and pressure loss.

If the position of the air pump 26 is too far from the toner replenishing section 36, the amount of air recovered from the air recovery port 38 (flow rate) is larger than the flow rate of the air-fuel mixture introduced from the inlet. If the amount is reduced, an increase in the internal pressure of the toner replenishing unit cannot be avoided, and there is a high possibility that toner leaks from the joint. However, as in the present embodiment, the toner is disposed near the toner replenishing unit of the air pump. Accordingly, the amount (flow rate) of air recovered from the air recovery port 38 can always be made larger than the flow rate of the air-fuel mixture introduced from the introduction port, and as a result, the internal pressure of the toner replenishing section 36 can be reliably increased. Can be prevented. In other words, the suction side of the air pump arranged near the toner supply unit is connected to the exhaust port of the toner supply unit to increase the suction force, while the discharge side of the air pump is connected to the screw pump located relatively far away. In addition, the flow rate of the air-fuel mixture from the inlet can be reduced.

According to experiments, for example, when the air pump is driven at a certain output, the flow rate A of the air-fuel mixture introduced into the toner replenishing section 36 from the air-fuel inlet 37 is 2. 7 Little / min. When
The flow rate B of the air discharged from the air recovery port 38 is 3.3.
Little / min. Met. Thus, the flow rate A,
By setting the position of the air pump with respect to the toner replenishing unit (developing device), the position of the screw pump, and the lengths of the tubes 30, 31, and 32 so that the relationship of B becomes A <B, the toner replenishment is performed. It is possible to effectively prevent the internal pressure in the section from rising. In the above example, the flow rate B is larger than the flow rate A by about 20%. However, this is merely an example. As long as the relation of A <B is maintained, the ratio of increasing the flow rate B is exceptional. It is not limited.

Next, a configuration of a toner conveying device used in the present invention, particularly a configuration example of a screw pump will be described with reference to FIGS. First, the recovery pipe 1 for transporting the toner recovered from each of the cleaning devices 6 and 19.
The other end of each of 7 and 21 is connected to a hollow recovery unit 40, and is once conveyed into the recovery unit 40. A casing 41 is provided below the collection unit 40, and the casing 41
Inside, a horizontal conveying screw 42 is rotatably supported. The horizontal conveying screw 42 is driven to rotate by a driving motor 44 via a driving force transmitting means 43 such as a gear and a belt. The screw pump 25 has a hollow cylindrical stator 51 made of elastic rubber or the like fixedly disposed inside a holder 50 which is a large-diameter cylindrical body, and a spiral metal rod inside the stator 51 and having one end. Is rotatably fitted with a rotor 52 fixed to one end of a lateral transport screw, and the rotor 52, which is a spiral metal rod, is inserted into the spiral inner wall of the fixed stator 51 and rotated. Accordingly, the toner is sent out to the toner transfer path 30 by the pressure generated by the relative rotation between the inner wall of the stator 51 and the rotor 52. An inner wall of the holder 50,
A minute gap is formed between the stator and the stator 51.
By connecting one end of a tube constituting the circulation path 32 to a supply port 55 provided in the holder 50, air from the air pump 26 is supplied to the minute gap, and air is supplied to the discharge port 56 through the minute gap. . As a result of this configuration, air is mixed with the toner conveyed through the space between the stator 51 and the rotor 52, and the mixed air is discharged from the discharge port 56. In the claims, the image carrier is a concept including means such as a photoreceptor, a transfer belt, and an intermediate transfer belt to which toner easily adheres and which needs to remove and collect the adhered toner by a cleaning device.

[0011]

As described above, according to the present invention, an image forming apparatus in which an air pump and a powder pump are used to convey a recovered toner as a mixture of air and air to a developing device for recycling. According to the present invention, it is possible to provide a toner conveying device capable of reliably preventing an increase in the internal pressure of the toner replenishing unit and preventing toner leakage without providing a filter or the like in the toner replenishing unit. That is, in the present invention, a means for separating toner and air from the air-fuel mixture is provided in the toner replenishing unit, the separated air is returned to the suction unit of the air pump for circulating use, and the air pump is disposed near the toner replenishing unit. Since the flow rate of the air-fuel mixture from the air-fuel mixture inlet of the toner replenishing section is made smaller than the flow rate of the air exhausted from the air recovery port, the toner replenishing section can be operated simply by driving the air pump at a constant output. Can be prevented from rising.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory diagram of an image forming unit including a toner conveying device according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of an example of a toner conveying device used in the present invention.

FIG. 3 is a cross-sectional view illustrating a configuration of an example of a screw pump.

[Explanation of symbols]

Reference Signs List 1 photoreceptor, 2 exposure unit, 3 developing device, 4 transfer device, 5 fixing device, 6 cleaning device, 10 paper feed device, 11 registration roller, 15 cleaning blade, 16 casing, 18a transfer belt, 18b
Transfer corotron, 19 cleaning device, 20 casing, 21 collection tube, 25 screw pump,
26 air pump, 26a suction unit, 26b discharge unit, 30 toner transfer path, 31, 32 circulation path, 3
5 toner replenishing section, 36 separating means, 37 mixture inlet, 38 air collecting port, 40 collecting section, 41 casing, 42 horizontal conveying screw, 43 driving force transmitting means, 4
4 drive motor, 50 holder, 51 stator, 52
Rotor.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tsutomu Kato 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (2)

[Claims] 1. A cleaning device for collecting toner from an image carrier, a screw pump for conveying the toner collected by the cleaning device, and an air pump for supplying air to the toner conveyed by the screw pump to mix and fluidize the toner. A toner transfer path that is a path for transferring a mixture of toner and air from the screw pump to the toner replenishing unit of the developing device. Separation means for separating the toner and air from the toner, and a circulation path which constitutes a path for returning the air exhausted from the air recovery port of the separation means to the air pump for circulating use. The suction unit of the air pump is arranged near the replenishing unit, and the suction unit of the air pump is connected to the air recovery port provided in the separation unit. Toner conveying device, characterized in a discharge portion that is connected to the screw pump. 2. When the flow rate of air-fuel mixture supplied from the screw pump to the separation means is A and the flow rate of air discharged from the separation means to the air pump is B, the relationship between the two is as follows: A <B A toner transport device, wherein