JP3600452B2 - Image forming device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus in an electrophotographic system such as a digital copying machine, a printer, a facsimile, or a multifunction peripheral thereof, and in particular, obtained by collecting toner remaining on an image carrier after a transfer step in the electrophotographic system. The present invention relates to an image forming apparatus provided with a toner recycling mechanism for forming an image by returning collected toner to a developing unit as a gas mixture with a gas stream without reusing the collected toner as it is and reusing it to form an image.
[0002]
[Prior art]
A toner recycling mechanism for forming an image by returning the collected toner obtained by collecting the toner remaining on the image carrier after the transfer process in the electrophotographic method to a developing unit as an air-fuel mixture with a gas flow and forming an image. In the image forming apparatus provided with the cleaning device, after the toner that has been transferred onto the photoreceptor, but has not been transferred onto the transfer-receiving member, or the toner remaining on the transfer belt is collected by the cleaning unit, Recycling development in which the toner is returned to the developing means and reused has been carried out.
[0003]
However, the recycled toner contains toner agglomerated over time and foreign matter such as paper powder attached to the photoreceptor. In addition, the toner may be agglomerated and solidified during the cleaning process and the recovery process. Sometimes. When these aggregated toners and foreign substances are reused by recycling, black spots and the like are generated on the formed image, thereby deteriorating the quality of the formed image.
[0004]
Therefore, a technology has been developed in which recycled toner is passed through a cyclone separator to remove paper dust and foreign matter with a coarse particle size, or to separate toner and other foreign matter using multiple filters with different meshes. It is known (JP-A-58-163978, JP-A-61-67074, and JP-A-7-77906).
[0005]
In addition, since properties such as chargeability and fluidity of the recycled toner are often deteriorated compared to the new toner, the recycled toner is transported to the developing means little by little and returned, and used with a large amount of the new toner. There is also known a technique in which the amount of new toner used is reduced to lower the cost per transfer sheet. For example, the toner collected by the cleaning unit is returned to the developing unit by rotating a screw conveyor in a transport pipe, and the mixing ratio with the new toner is controlled. Developing means in which defects are less likely to occur are known (JP-A-6-175488).
[0006]
Further, a toner storage means, a toner supply means, a toner transfer means and the like are respectively arranged at arbitrary positions apart from the developing means, and a rotor for moving the toner of the developer in the axial direction by rotating, and enclosing the rotor A screw pump having a passage therein and having a fixed stator in contact with the rotor inside the passage, and air supply means for supplying air for fluidizing the developer moved by the screw pump are used. A technique is also known in which a mixture of toner and air is conveyed from a toner storage unit to a developing unit through a conveying unit (a tube made of an elastic body) (Japanese Patent Laid-Open No. 7-219329). Gazette).
[0007]
Such a screw pump has advantages of downsizing and space saving of the toner conveying device, and being capable of conveying the toner in vertical and vertical directions, thereby improving the degree of freedom of machine and unit layout, assembling property, and maintenance. It can be used not only for transporting new toner because of its improved performance and low cost, but also for transporting recycled toner that is collected by the cleaning unit and returned to the developing unit for reuse. Proposed by the same applicant.
[0008]
[Problems to be solved by the invention]
However, in the image forming apparatus using the above-described screw pump, there is a possibility that the toner may be clogged in the elastic tube due to mechanical movement, vibration, or the like, and the toner may not be conveyed. At this time, if the maximum pressure of the air supply means is lower than the pressure resistance of the screw pump, the toner enters the air supply means, causing toner to scatter into the apparatus and locking of the screw pump. Conversely, when the maximum pressure of the air supply means is higher than the pressure resistance of the screw pump, the air supplied to the screw pump flows backward from the screw pump and the toner accumulates upstream of the screw pump. In this case, the toner can be detected by providing a toner remaining amount detecting means on the upstream side, but there is a problem that an abnormality is detected until a certain amount of toner is accumulated. Further, when an abnormality occurs in the gas supply unit, similarly, the toner cannot be conveyed, and the toner enters the air supply unit, which causes a problem that the toner is scattered in the apparatus and the screw pump is locked.
[0009]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus that solves the above-described conventional problems and that can reliably and early detect a conveyance abnormality of collected toner.
[Means for Solving the Problems]
[0010]
In order to achieve the above object, the present invention provides an image forming apparatus including a toner recycling mechanism that returns a collected toner collected by a cleaning unit to a developing unit as an air-fuel mixture with a gas flow and reuses the toner to form an image. At
[0011]
The toner recycling mechanism is a gas flow transfer unit that moves the collected toner collected by the cleaning unit as a mixture with a gas, a gas supply unit that supplies a gas to the gas flow transfer unit via an introduction unit, An air-fuel mixture conveyance path comprising a pipe for conveying an air-fuel mixture of the collected toner and the gas to the developing means; and a means for detecting the presence / absence of toner at the introduction section.
[0012]
The present invention is effective when, when the toner presence / absence detecting means detects the presence of toner, the toner recycle mechanism is determined to be abnormal and the machine is stopped.
Further, it is effective if the pressure resistance of the gas flow transfer means is set higher than the maximum pressure of the gas supply means.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described 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.
[0014]
In FIG. 1, the digital copying machine uses a well-known electrophotographic system, and includes a drum-shaped photosensitive member 1 as an image bearing member inside. Around the photoreceptor 1, a charger 2, an exposure unit 3, a developing unit 4, a transfer unit 5, and a cleaning unit 6 for performing an electrophotographic copying process are arranged along a rotation direction indicated by an arrow A.
[0015]
The exposure unit 3 forms an electrostatic latent image on the photoreceptor 1 based on an image signal read by a reading unit 8 from a document placed on a document table 7 on the top of the copying machine. 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 means 10, where it is fixed and then discharged out of the machine.
[0016]
Next, the movement of the toner used in the image forming process will be described with reference to FIGS.
The developing means 4 is a two-component developing means, in which a developing tank 50 contains a developer comprising a carrier and a toner. When the developing means 4 develops the latent image, the toner of the developer is consumed, and the ratio (toner density) decreases. Therefore, in order to suppress a decrease in image density, when the toner density in the developer becomes equal to or less than a predetermined value, toner is supplied from the toner hopper 51 to maintain the toner density in the developer. The toner concentration in the developer is measured by a magnetic permeability sensor 52 attached to the lower case of the developing unit 4.
[0017]
The toner supplied from the toner hopper 51 via the supply roller 53 is agitated and frictionally charged with the carrier by the agitating member 54 in the developing unit 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 onto the developing roller 56 by the magnet in the developing roller 56. The developer is transported 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 by a developing bias.
[0018]
The toner adhered onto the photoconductor 1 by the above-described development is generally electrostatically transferred to a transfer material by the transfer unit 5, and about 10% of the toner remains untransferred on the photoconductor. The 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 collected toner falls through the toner guide member 16 from the discharge port 6c by its own weight and is described later. Is returned to the developing means 4 by the means, and becomes a recycled toner. The toner guide member 16 also serves as a collected toner transfer path for sending collected toner from the cleaning means 6 to the gas flow transfer means.
[0019]
On the other hand, a cleaning unit 11 is also provided on the transfer belt 5a of the transfer unit 5 because the toner adheres to the untransferred portion or the non-image portion of the photoconductor 1 in contact therewith. The toner remaining on the transfer belt 5a is scraped off by a cleaning blade (not shown) slidingly contacting the belt. Since the scraped-off toner is highly likely to contain foreign matter such as paper dust, in this example, the toner is dropped by its own weight from the discharge port 5b without being recycled, and the collected toner container shown in FIG. Is sent to the waste toner tank 14.
[0020]
3 and 4, a powder screw pump 20 is provided as a gas flow transfer unit for transferring the toner collected by the photoconductor cleaning unit 6 to the developing unit 4. The powder screw pump 20 is also referred to as a mono pump, and conveys to the developing unit 4 as a mixture of the collected toner and a gas (air) supplied by a gas supply unit described later. The powder screw pump 20 has a stator 22 fixed to a holder 21, and a rotor 23 that moves the collected toner in the axial direction by rotating in contact with the stator 22, and the stator 22 encloses the rotor 23. So that a passage is formed. The rotor 23 is engaged with a shaft of the horizontal transport screw 24. The other end of the lateral transport screw 24 is engaged with a seal member 25, a bearing 26, and a clutch 27, and drives the image forming apparatus from a main body of the rotor 23 through a timing belt 28, a timing pulley 29, and the clutch 27. The horizontal transport screw 24 is driven to rotate. The powder screw pump 20 starts to be driven by the micro processing unit (MPU) 17 to start the operation of transferring the collected toner, and then rotates and stops for a predetermined time to stop the operation of transferring the collected toner. Is controlled so that the collected toner transfer operation is performed intermittently.
[0021]
The stator 22 is made of an elastic material such as a rubber material. The inner peripheral surface surrounds the rotor 23, and the outer peripheral surface and the inner peripheral surface of the holder 21 have a gap of about 1 mm, and communicate with the collected toner passage 30. A conveyance pipe 31 connected to the developing unit 4 is connected to the collected toner passage 30. As the transfer tube 31, an elastic tube or a somewhat hard bendable pipe or the like can be advantageously used, but an elastic tube which is easy to install and can be freely arranged is particularly advantageous.
[0022]
The holder 21 of the powder screw pump 20 is provided with an air supply port 32 through which air from an air pump 40 as a gas supply means is blown into the collected toner passage 30 from the gap. The air supply port 32 is connected to a supply pipe 41 serving as an introduction section made of a transparent elastic tube. In the middle of the supply pipe 41, there is provided a light transmission type sensor 42 as a toner presence / absence detecting means for detecting the presence / absence of toner. The maximum pressure of the air pump 40 is set lower than the withstand pressure of the mono pump even when the air pump 40 operates normally.
[0023]
In the above-described image forming apparatus, even if a toner conveyance abnormality such as a toner clogging occurs in the conveyance pipe 31 due to any cause in the toner recycling mechanism, the light transmission type sensor 42 can easily detect the abnormality. It can be detected, and a detailed description will be given next with reference to FIG.
[0024]
In FIG. 5, when toner clogging occurs in the transport pipe 31 and the toner cannot be transported, the toner extruded from the powder screw pump 20 loses its place to enter the transparent supply pipe 41. Come. That is, since the maximum pressure of the air pump 40 is lower than the pressure resistance of the powder screw pump 20, the toner enters the supply pipe 41. When the invading toner reaches the position of the light transmission type sensor 42, the light is shut off and the output of the light transmission type sensor 42 is switched from on to off, and "toner present" is detected. When this control signal is received by a control unit (not shown), the machine is stopped as a toner conveyance error, and an error is displayed.
[0025]
Thus, by detecting the presence or absence of the toner in the supply pipe 41, it is possible to reliably detect the toner conveyance abnormality.
Further, in such an abnormality detection, the toner enters the supply pipe 41 even when the air pump 40 is stopped, so that the failure of the air pump 40 can be known.
[0026]
【The invention's effect】
In the first and second aspects, the provision of the toner presence / absence detection means between the screw pump and the gas supply means makes it possible to detect toner conveyance abnormality, thereby locking the screw pump and preventing toner from scattering into the apparatus. Prevention is possible, and early detection is possible.
[0027]
In the third aspect, when the pressure resistance of the gas flow transfer means is made higher than the maximum pressure of the gas supply means, when a toner conveyance abnormality occurs, the toner is conveyed to the toner presence / absence detection means without generating a reverse flow of air. This makes it possible to reliably detect a toner conveyance abnormality.
[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 a developing unit of the image forming apparatus.
FIG. 3 is a perspective view showing a configuration of a gas flow transfer means of the present invention.
FIG. 4 is a sectional view of the gas flow transfer means of the present invention.
FIG. 5 is a perspective view showing the gas flow transfer means of the present invention when an abnormality is detected.
[Explanation of symbols]
Reference Signs List 1 photoreceptor 4 developing means 6 cleaning means 20 gas flow transfer means (powder screw pump)
40 Gas supply means (air pump)
42 Toner presence detection means (light transmission type sensor)

Claims (3)

An image forming apparatus having a toner recycling mechanism for forming an image by returning the collected toner collected by the cleaning unit to the developing unit as an air-fuel mixture with the gas flow, and forming an image,
The toner recycling mechanism is a gas flow transfer unit that moves the collected toner collected by the cleaning unit as a mixture with a gas, a gas supply unit that supplies a gas to the gas flow transfer unit via an introduction unit, An image forming apparatus comprising: a mixed gas transport path including a pipe configured to transport a mixture of the collected toner and the gas to the developing unit; and a unit configured to detect the presence or absence of the toner at the introduction unit. 2. The image forming apparatus according to claim 1, wherein when the toner presence / absence detection unit detects presence of toner, the toner recycling mechanism determines that the toner recycling mechanism is abnormal and stops the machine. 3. The image forming apparatus according to claim 1, wherein a pressure resistance of the gas flow transfer unit is set to be higher than a maximum pressure of the gas supply unit. 4.

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