JP3523149B2 - Toner transfer pump and image forming apparatus having the pump - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylindrical stator having an inner peripheral surface formed with a spiral groove, and a powdery material disposed between the stator and the inner peripheral surface of the stator. The present invention relates to a toner transfer pump including a rotor that extends spirally so as to form a toner transfer gap, and an image forming apparatus including the toner transfer pump.

[0002]

2. Description of the Related Art In an image forming apparatus configured as a copying machine, a printer, a facsimile, or a multifunction machine having at least these two functions, powdery toner is transferred to a developing device by a toner transfer pump of the above type. Then, it is conventionally known that the toner is used to form a toner image on the image carrier. The toner transfer pump transfers the powdery toner in the gap formed between the stator and the rotor by rotating the rotor. Therefore, a large compressive force acts on the toner in the voids, and a large stress is applied to the toner. Moreover, the friction between the rotating rotor and the stator causes the temperature inside the toner transfer pump to rise, so that the temperature of the toner transferred is also raised.

As described above, since a large amount of stress is applied to the toner transferred by the toner transfer pump and the temperature of the toner having a relatively low melting point rises, the toner is aggregated in the powdery toner. Yes, for example 1m
Many aggregates as small as m may be formed. Toner containing such aggregates is transferred to a developing device, a toner image is formed on the image carrier with the toner, and the toner image is transferred to a transfer material. The toner image portion and the transfer material do not adhere to each other, and a small dot-shaped toner image is formed in the toner image transferred to the transfer material.
A missing part of the image around that occurs, and the image quality deteriorates. Such a dot-shaped toner image and the image missing portion around it are also called “firefly”.

[0004]

SUMMARY OF THE INVENTION A first object of the present invention is to provide a toner transfer pump of the type described at the beginning which can effectively suppress the formation of aggregates in powdery toner. To provide.

A second object of the present invention is to provide an image forming apparatus in which the occurrence of fireflies is suppressed.

[0006]

[0007]

To achieve the first object of the present invention, in the toner transfer pump of the type described at the beginning, the rotor is a resin-molded rotor body and a surface of the rotor body. A toner transfer pump is characterized in that it has a metal coating layer coated on (1).

Further, in order to achieve the first object, the present invention is characterized in that, in the toner transfer pump of the type described at the beginning, the rotor is made of a resin containing a lubricant. A toner transfer pump is proposed (claim 2).

Advantageously, the lubricant is an oil (claim 3).

In order to achieve the second object of the present invention, the toner transfer pump according to any one of claims 1 to 3, an image carrier on which a toner image is formed, and the toner transfer pump. Image formation including a developing device that forms a toner image on the image carrier by the powdery toner transferred by the transfer device, and a transfer device that transfers the toner image formed on the image carrier to a transfer material. A device is proposed (claim 4).

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view showing a main part of an image forming apparatus having a toner transfer pump. The image forming apparatus shown here is detachably attached to an image forming apparatus main body (not shown). It has a process cartridge 18. The process cartridge 18 has a unit case 19, and a drum-shaped photoconductor 2 which is an example of an image carrier is rotatably assembled to the case 19, and the photoconductor 2 is a drive unit on the image forming apparatus main body side. Is rotated in the clockwise direction (arrow B direction). A charging roller 20, which is an example of a charging device rotatably supported by the unit case 19, abuts on the surface of the photoconductor 2 while rotating,
The charging roller 20 charges the surface of the photoconductor 2 to a predetermined polarity.

On the other hand, in the main body of the image forming apparatus, a laser writing unit (not shown) which is an example of an exposure apparatus is arranged separately from the process cartridge 18, and a laser beam L modulated by light emitted from this unit is used. ,
As shown in FIG. 1, the surface of the photoconductor after charging is exposed to form an electrostatic latent image on the surface of the photoconductor. In this example, the portion where the absolute value of the surface potential of the photoconductor is lowered by being irradiated with the laser beam L becomes an electrostatic latent image, and the surface portion of the photoconductor which is not irradiated with the laser beam becomes the background portion.

The electrostatic latent image is obtained by the process cartridge 1.
The toner image is visualized as a toner image by the developing device 22 which constitutes a part of the image forming apparatus 8. The developing device 22 includes a developing case 23 formed by a part of the unit case 19, a developing roller 24 rotatably supported by the developing case 23 and driven to rotate counterclockwise, and the developing case 23.
And a stirring roller 25 rotatably supported on the developing case 23. The developing case 23 contains a powdery two-component developer D containing toner and carrier. It is also possible to use a one-component developer having no carrier.

The developer D is agitated by the agitating roller 25 so that the toner and the carrier are triboelectrically charged with opposite polarities, and the developer D is carried on the developing roller 24 to which a bias voltage is applied. The developer whose amount is regulated by the regulation blade 26 is conveyed to the developing area between the developing roller 24 and the photoconductor 2, and the toner in the developer is electrostatic latent image formed on the surface of the photoconductor. By electrostatically transferring to the image, the electrostatic latent image is visualized as a toner image. When the toner concentration sensor 35 detects that the toner concentration of the two-component developer D contained in the developing case 23 has decreased, toner is supplied to the two-component developer D in the developing case 23 as described later. .

A paper feeding device (not shown) is arranged in the main body of the image forming apparatus below the process unit 18, and a transfer material such as a transfer paper or a resin sheet is sent out from the paper feeding device. The transfer material P is the photosensitive member 2
The transfer belt 8 that is placed opposite to and is driven to run in the direction of arrow A.
It is carried on top and conveyed to the transfer area between the photoconductor 2 and the transfer belt 8. At this time, a transfer voltage having a polarity opposite to the charging polarity of the toner on the surface of the photoconductor is applied to the transfer brush 9, which is an example of the transfer device, and thereby the toner image on the photoconductor is transferred onto the transfer material P. . Instead of the transfer brush, a transfer device such as a transfer roller, a transfer blade or a corona discharger can be used. Transfer material P on which the toner image is transferred
Is continuously conveyed in the direction of arrow A, and after being separated from the transfer belt 8, it passes through a fixing device (not shown), at which time the toner image on the transfer material is fixed. The transfer material that has passed through the fixing device is discharged outside the main body of the image forming apparatus.

The transfer residual toner adhering to the surface of the photosensitive member after the transfer of the toner image is removed by the cleaning device 27. The cleaning device 27 includes a cleaning case 28 formed by a part of the unit case 19.
And a cleaning brush 29 rotatably supported by the cleaning case 28 and driven to rotate in the arrow direction.
And a cleaning blade 30 whose base end is fixed to the cleaning case 28. The cleaning brush 29 and the cleaning blade 30 come into contact with the surface of the photoconductor 2 to scrape off the transfer residual toner on the surface. .

The transfer residual toner removed from the surface of the photoconductor is collected in the cleaning case 28, and then returned to the developing device 22 by the toner conveying device 41 and reused there. The toner carrying device 41 is provided with a toner carrying pipe 31 through which the toner returned from the cleaning case 28 of the cleaning device 27 to the developing device 22 passes, and a toner carrying device disposed inside the toner carrying pipe and rotationally driven by a driving device (not shown). And a member 32.

The transfer residual toner removed from the photoconductor 2 by the cleaning brush 29 and the cleaning blade 30 is disposed in the cleaning case 28 and is driven to rotate by the toner discharge screw 42 from the case 28. Carried to 31. At this time, the toner conveying member 32 is rotationally driven as described above,
As a result, the powdery toner carried to the toner carrying pipe 31 is carried inside the carrying pipe 31 and returned to the developing case 23 of the developing device 22 via the toner transfer pump 33 described later, and this toner is Again, the electrostatic latent image formed on the image carrier 2 is visualized.

The toner concentration sensor 35 detects that the toner concentration of the two-component developer contained in the developing case 23 of the developing device is lowered.
Then, the toner is supplied to the developing device as described below.

A toner storage container 34 shown in FIG. 2 is detachably set in a portion in the main body of the image forming apparatus which is separated from the process cartridge 18 shown in FIG. And its container body 37
And a toner sealing member 39 made of a foam attached to the opening 38 of the container, and the powdery toner T is stored in the container body 37.

On the other hand, a nozzle 43 is provided on the main body of the image forming apparatus.
The nozzle 43 shown here has a toner discharge pipe 45 having a toner discharge port 44 formed at one end side, and a nozzle pipe 46 integrally fixed to the toner discharge pipe 45. An annular air flow passage 47 is defined between 46 and the toner discharge pipe 45. The air outlet 48 on one end side of the nozzle tube 46 is opened to the inside of the container body 37, and the air supply tube 4 is provided on the other end side of the nozzle tube 46.
One end side of 9 is connected. The other end of the air supply tube 49 is connected to an air discharge port of an air pump 50 mounted on the main body of the image forming apparatus, and the other end of the toner discharge tube 45 is connected to the toner supply tube 51.
One end side of is connected.

As described above, when the toner density decrease of the developer D of the developing device 22 is detected by the toner density sensor 35 (FIG. 1), the air pump 50 shown in FIG. 2 is operated and is sent out from here. Air is sent to the nozzle pipe 46 through the air supply tube 49, and then the air passes through the air flow passage 47 and is supplied into the container body 37 from the air outlet 48 as shown by an arrow in FIG.
As a result, the powdery toner T in the container body 37 is fluidized, and the pressure in the container body 37 is increased. Therefore, as the pressure rises, the fluidized toner becomes
Also, by the cooperation with the toner transfer pump 33 shown in FIG. 3, the toner is discharged to the outside of the toner container 34 through the toner discharge port 44 of the toner discharge pipe 45. The discharged toner T is conveyed with the air through the toner discharge pipe 45 and the toner supply tube 51, and is sent to the toner transfer pump 33 side shown in FIGS. 1 and 3.

The powder transfer pump 33 is, as shown in FIG. 3 as an example, a cylindrical stator 53 in which a spiral groove is formed on the inner peripheral surface, and two spiral grooves are formed in the example in the figure, and the cylindrical stator 53. A male screw rotor (uniaxial eccentric rotor) 54 is rotatably arranged in the center hole of the stator 53, and the stator 53 is fixedly arranged in the casing 52. The stator 53 is
It is composed of an elastic body such as rubber or a rigid body. The rotor 54 arranged in the stator 53 is
And spirally extending so as to form a powdery toner transfer space R between the inner peripheral surface and the inner peripheral surface. The rotor 54 has a circular shape in any of its cross sections, and the center of the circle is eccentric with respect to the central axis of the rotor, and extends around the central axis in a spiral shape in the axial direction. As a result, a toner transfer gap R is formed between the outer peripheral surface of the rotor 54 and the inner peripheral surface of the stator 53. Stator 53
Are fixedly engaged with the rotor 54 having a spiral structure so as to wrap around the rotor 54 and fixedly. The basic structure of the toner transfer pump having such a structure is the same as that of a conventionally known pump also called a uniaxial eccentric screw pump, a screw pump, or a mono pump.

The rotor 54 is composed of the casing 52.
It is connected to a screw conveyor 55 rotatably arranged therein, and a gear 56 is connected to the conveyor 55. As shown in FIG. 3, the toner supply tube 51 shown in FIG. 2 is connected to the opening of the casing portion where the screw conveyor 55 is provided, and the toner conveying pipe 31 of the toner conveying device 41 is also the same casing portion. Is connected to the other opening.

As described above, when the toner concentration sensor 35 detects that the toner concentration of the two-component developer D in the developing device 22 has decreased, the air pump 50 (FIG. 2) starts operating and Toner transfer pump 3 shown in FIG.
The gear 56 of No. 3 is driven to rotate and the screw conveyor 55
Then, the rotor 54 starts rotating. As a result, the toner T sent to the casing 52 through the toner supply tube 51 is sent to the gap R between the rotor 54 and the stator 53. The rotation of the rotor 54 causes the gap R to move from right to left in FIG. 3, and the suction pressure generated thereby conveys the toner to the left in FIG. 3 and, as indicated by arrow C, to the casing 52. Connected discharge pipe 57 (Fig. 1
(See also), and is replenished into the developing case 23 of the developing device 22. At this time, the transfer residual toner sent to the casing 52 through the toner carrying pipe 31 is also sent to the developing case 23 of the developing device 22 together with the above-mentioned toner.

It is also possible to introduce air into the casing 52 through the air inlet 58 and supply air to the toner to further enhance its fluidity.

After the above-mentioned operation is performed for a predetermined time, the operation is stopped. Such an operation is performed every time a decrease in the toner concentration of the developer D stored in the developing device 22 is detected, whereby the toner concentration of the developer D is maintained within a certain range. Further, the developing device 22 is provided with a filter (not shown) in the developing case 23, and the air sent to the developing device 22 together with the toner is discharged to the outside of the developing device through this filter.

The toner transfer by the toner transfer pump 33 is carried out as described above. At this time, as described above, it is large for the powdery toner existing in the gap R between the rotor 54 and the stator 53. The compressive force acts, and great stress is applied to the toner. Moreover, since the rotating rotor 54 sends the toner while rubbing the inside of the stator 53, frictional heat is generated. In the conventional toner transfer pump, due to these factors, many fine agglomerates are formed in the powdery toner, which causes the transfer material P (FIG. 1).
There was a risk that firefly would be formed in the toner image transferred to and the image quality would be deteriorated.

Therefore, in the toner transfer pump 33 of this embodiment, the rotor 54 is made of a metal having a high thermal conductivity such as aluminum or stainless steel. By thus forming the rotor 54 with a material having high thermal conductivity, the frictional heat generated by the sliding friction between the rotor 54 and the stator 53 is transmitted to the outside of the toner transfer pump 33 early through the rotor 54. . For this reason,
The temperature rise of the powdery toner transferred by the toner transfer pump 33 can be suppressed, and the generation of aggregates in the toner can be prevented or effectively suppressed.
As a result, it is possible to prevent or suppress the problem of the occurrence of fireflies in the toner image transferred to the transfer material P (FIG. 1).

Conventionally, a rotor made of resin is usually used for the purpose of cost reduction, but since such a rotor has a low thermal conductivity, the heat generated by the friction between the rotor and the stator is transferred to the toner. The toner was not discharged to the outside of the pump but was accumulated inside, which increased the temperature of the toner and generated many aggregates. However, in the toner transfer pump 33 of this example, the toner transfer pump 33 is made of a metal having a high thermal conductivity. By using the rotor 54, generation of aggregates can be suppressed.

As described above, it is preferable that the rotor 54 is made of a metal having a high heat dissipation effect. However, in order to manufacture the rotor 54 made of metal, it is necessary to cut a metal material. This increases the cost of the rotor 54. To avoid this problem, the rotor may be made of a resin molded product.
The heat dissipation of the rotor is reduced, and aggregates are easily generated in the powdery toner.

Therefore, instead of forming the entire rotor 54 with a metal, the rotor body is formed with a resin molded product such as polycarbonate or ABS resin, and the surface thereof is coated with a metal having a high thermal conductivity such as nickel. Then, the rotor 54 can be configured. The rotor is configured to have a resin-molded rotor body and a metal coating layer coated on the surface of the rotor body. Since the rotor body of the rotor 54 can be molded with resin, the cost can be kept lower than that of cutting a metal material, and since the rotor body is coated with metal, its heat dissipation can be improved. The heat generated by the rubbing of the rotor 54 and the stator 53 can be quickly released to the outside of the toner transfer pump 33. As a result, the temperature rise of the powdery toner transferred by the toner transfer pump 33 is suppressed, the problem that aggregates are formed on the toner is suppressed, and the firefly is applied to the toner image transferred to the transfer material P (FIG. 1). It is possible to effectively suppress the defect that occurs and improve the image quality.

Instead of the above-mentioned two configurations, the rotor 54 may be made of a resin containing a lubricant, and an oil such as silicone oil may be used as the lubricant. By using such a rotor 54, the friction coefficient of the rotor 54 with respect to the stator 53 and toner can be reduced, and the slidability of the rotor 54 can be improved. As a result, the rotor 54 and the stator 53
Rubs smoothly, so that the amount of heat generated by these rubs can be effectively reduced. This suppresses the temperature rise of the toner transferred by the toner transfer pump 33,
It is possible to make it difficult to generate aggregates, and it is possible to effectively reduce the problem that firefly is formed in the toner image transferred onto the transfer material.

As described above, the image forming apparatus shown in FIGS. 1 to 3 has the toner transfer pump 33 having the above-mentioned constitutions.
An image carrier on which a toner image is formed, a developing device 22 for forming a toner image on the image carrier by the powdery toner transferred by the toner transfer pump 33, and an image carrier formed on the image carrier. Although it has a transfer device for transferring the toner image to the transfer material P, by adopting the toner transfer pump 33 described above in such an image forming apparatus, the image quality of the toner image transferred onto the transfer material is surely enhanced. be able to.

The present invention can be widely applied to image forming apparatuses other than the illustrated type, and the structure of the toner transfer pump should not be limited to the illustrated form. For example, the present invention can be applied to an image forming apparatus that primarily transfers a toner image formed on a photoconductor to a transfer material formed of an intermediate transfer body and secondarily transfers the toner image to a final transfer material, and a toner transfer pump thereof. The present invention can also be applied to the toner transfer pump for transferring the transfer residual toner on the photoconductor from the cleaning device to the developing device.

[0037]

[0038]

According to the first aspect of the present invention, since the metal coat layer having a high thermal conductivity is formed on the surface of the rotor body, the heat radiation effect of the metal coat layer causes the powdery powder to be transferred by the toner transfer pump. It is possible to suppress an increase in the temperature of the toner, and effectively suppress the problem that an aggregate is formed in the toner due to the aggregation of the toner. Moreover, since the rotor body is made of resin, it is possible to suppress an increase in the manufacturing cost of the rotor.

According to the second and third aspects of the invention, since the rotor is made of a resin containing a lubricant, the slidability of the rotor surface can be improved, and the rotor and stator are rubbed against each other. The amount of heat generated can be reduced. As a result, it is possible to suppress an increase in the temperature of the powdery toner transferred by the toner transfer pump and effectively suppress the problem that an aggregate is formed in the toner due to the aggregation of the toner.

According to the fourth aspect of the present invention, it is possible to suppress the generation of aggregates in the toner used for development, so that it is possible to improve the image quality of the toner image transferred to the transfer material. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of an image forming apparatus.

FIG. 2 is a sectional view of a toner storage container.

FIG. 3 is a sectional view of a toner transfer pump.

[Explanation of symbols]

22 Developing device 33 Toner transfer pump 53 Stator 54 rotor R void T toner

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhisa Sudo 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Yoshio Hattori 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Souta Fujimori 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (56) Reference JP-A-10-133462 (JP, A) JP-A-10 -153181 (JP, A) JP-A-63-109158 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 13/08-13/095 G03G 15/08-15/095

Claims (4)

(57) [Claims] 1. A cylindrical stator having a spiral groove formed on the inner peripheral surface thereof, and a powdery toner transfer gap disposed between the stator and the inner peripheral surface of the stator. A toner transfer pump comprising a rotor extending spirally so as to be formed, wherein the rotor has a rotor body of a resin molded product and a metal coating layer coated on the surface of the rotor body. Toner transfer pump. 2. A cylindrical stator having a spiral groove formed on an inner peripheral surface thereof, and a powdery toner transfer gap disposed between the stator and the inner peripheral surface of the stator. A toner transfer pump comprising a rotor extending in a spiral shape so as to be formed, wherein the rotor is made of a resin containing a lubricant. 3. The toner transfer pump according to claim 2, wherein the lubricant is oil. 4. The toner transfer pump according to claim 1, an image carrier on which a toner image is formed, and the image carrier by the powdery toner transferred by the toner transfer pump. A developing device for forming a toner image on the top,
An image forming apparatus comprising: a transfer device that transfers a toner image formed on an image carrier onto a transfer material.