JP2002132027A - Toner transfer pump and image forming device provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the extension of the long service life of a toner transfer pump for transferring the toner in a powder state, by means of rotary driving a rotor arranged in a penetrating hole of a stator. SOLUTION: As the toner T, transferred by the toner transferring pump 5, the toner composed in adding silica beyond 0.5 weight %, is used, and the stator 7 is composed by an elastic material provided with JISA hardness of 50 degrees or smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention comprises a stator and a rotor rotatably disposed in a through hole of the stator, wherein the through hole of the stator is formed by two spirally extending grooves. The rotor relates to a toner transfer pump extending spirally so that a powdery toner transfer gap is formed between the outer peripheral surface of the rotor and the inner peripheral surface of the through hole of the stator. .

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, a facsimile, or a multifunction machine having at least two of these functions, a toner transfer pump of the above-described type is used for conveying powdery toner. Is well known in the art (for example, see JP-A-11-84).
873). This toner transfer pump is also referred to as a single-shaft eccentric screw pump, or generally a Mono pump.

In the toner transfer pump of the above type, when a rotor rotates, a space defined between an outer circumferential surface of the rotor and an inner circumferential surface of a through hole of the stator moves, and the toner sealed in the space is moved. Is configured to be transported. Generally, the rotor is formed of a rigid body, the stator is formed of an elastic body, and the rotor formed of the rigid body disposed in the through hole rotates while sliding on the inner peripheral surface of the through hole. The surface wears over time due to frictional forces received from the rotor. If the amount of abrasion of the inner peripheral surface of the through hole of the stator due to the wear increases, the above-mentioned airtightness decreases, and the suction pressure (negative pressure) on the toner suction side of the toner transfer pump becomes a small value. As a result, the toner transfer capacity is reduced, and when the transfer ability becomes significant, the toner transfer pump reaches its end of life.

As can be seen from the above description, it is important to minimize the wear of the inner circumferential surface of the stator as much as possible in order to extend the life of the toner transfer pump and improve its durability. In such a toner transfer pump, such a point was not particularly taken into consideration, so that the life of the pump was short. In particular, in the toner transfer pump of the type described at the beginning, the rotor locally pressurizes the inner peripheral surface of the stator with a large pressure, and the stator portion is largely compressed and deformed. It has not been easy to improve durability.

[0005]

SUMMARY OF THE INVENTION It is a first object of the present invention to provide a toner transfer pump of the type described at the beginning, which can improve durability with a simple structure.

A second object of the present invention is to provide an image forming apparatus provided with the toner transfer pump.

[0007]

According to the present invention, in order to achieve the first object, in a toner transfer pump of the type described at the outset, the transferred toner removes silica of 0.5% by weight or more. A toner transfer pump is proposed, wherein the toner transfer pump is a powdery toner to be added, wherein the stator is made of an elastic material having a JISA hardness of 50 degrees or less.

At this time, it is advantageous that the elastic material constituting the stator is chloroprene rubber.

In the toner transfer pump according to the first or second aspect, it is particularly advantageous that the rotor is made of a material having a specific gravity of 2.5 or more.

Further, in the toner transfer pump according to the third aspect, it is further advantageous that the rotor is made of a molded product obtained by die-casting a zinc material (claim 4).

Further, in the toner transfer pump according to the present invention, it is more advantageous that the outer peripheral surface of the rotor made of the molded product is barrel-polished (claim 5).

Further, the present invention proposes an image forming apparatus comprising the toner transfer pump according to any one of claims 1 to 5 in order to achieve the second object. Item 6).

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a vertical cross-sectional view of a toner transfer pump disposed in an image forming apparatus main body (not shown). In this example, the toner transfer pump 5 includes a powdery toner T.
Is transported as described later, and the powdered toner T is supplied to the developing container 4 of the developing device 3.
The image forming apparatus is configured as a copier, a printer, a facsimile, or a multifunction peripheral having at least two of these functions.

The toner transfer pump 5 shown here includes a stator 7 made of an elastic body, and a rotor 8 made of a rigid body rotatably disposed in a through hole 6 of the stator 7. The through holes 6 of the stator 7 are spaced at a predetermined pitch,
The rotor 8 is formed by two grooves extending spirally around the center axis of the through hole 6, and the rotor 8 has a powder form between the outer peripheral surface of the rotor 8 and the inner peripheral surface of the through hole 6 of the stator 7. , So as to form a void S for toner transfer. The rotor 8 has a circular cross section in any of its cross sections, and the center of the circle is eccentric with respect to the central axis of the rotor 8 and extends spirally around the central axis. The stator 7 is wrapped around and includes a rotor 8 having a helical structure, is in contact with and engaged with the rotor 8, and is fixedly held by a case 9. The toner transfer pump having the rotor 8 and the stator 7 is a pump which is also called a uniaxial eccentric screw pump or a mono pump. The materials of the stator 7 and the rotor 8 will be described later in detail.

As will be described later, the toner is transferred from the entrance opening 20 of the through hole 6 to the exit opening 21, and the end of the rotor 8 on the entrance opening 20 side is connected to the entrance end 23.
When the end of the rotor 8 on the side of the outlet opening 21 is referred to as an outlet end 22, the connecting shaft 11 is connected to the outlet end 22 via the pin joint 10. The shaft 11 is further connected to a drive shaft 18 via another pin joint 19, and the drive shaft 18 is connected to the drive shaft 18 via a bearing 12.
The lower part is rotatably supported by the open casing 13. A gear 14 is fixed to a drive shaft portion protruding outside the casing 13, and a mating gear (not shown) is meshed with the gear 14, and the rotation of a drive motor (not shown) is also transmitted through these gears. The driving force is transmitted to the drive shaft 18 and the connection shaft 11 so that the rotor 8 is driven to rotate. The casing 13 is fixed to the case 9 described above, and a toner inlet pipe 15 is provided at an end of the case 9 opposite to the side where the connecting shaft 11 is located.
Is connected to the case 9 integrally.

The toner transfer pump 5 of the present embodiment is configured as described above.
For example, one end of a toner transfer pipe 51 made of a flexible tube is connected, and the other end of the toner transfer pipe 51 is connected to a toner outlet of a toner container (not shown).
The toner container is detachably disposed inside or outside the image forming apparatus main body, and powder toner, that is, powder toner is stored in the toner container.

The lower part of the casing 13 is connected to the developing container 4 of the developing device 3, and the inside of the casing 13 and the inside of the developing container 4 communicate with each other. As is well known per se, in the developing container 4 of the developing device 3, for example, a powdery two-component developer (not shown) having a toner and a carrier is contained, and the toner in the developer causes Similarly, a toner image is formed on the surface of an image carrier (not shown).

When the toner concentration sensor (not shown) of the developing device 3 detects a decrease in the toner concentration of the two-component developer in the developing container 4, the drive shaft 18 and the connecting shaft 11 are rotated by the drive motor described above. Driven, the rotor 8 starts rotating. Thereby, the gap S formed between the inner peripheral surface of the through hole of the stator 7 and the outer peripheral surface of the rotor 8 moves to the right in FIG. 1, whereby the side of the entrance opening 20 of the through hole 6, that is, A suction pressure is generated on the toner suction side of the toner transfer pump 5, and the toner in the toner transfer pipe 51 is sent from the entrance opening 20 of the through hole 6 into the gap S and is transferred to the right in FIG. Next, the toner is discharged into the casing 13 from the outlet opening 21 of the through hole 6. As described above, the rotation of the rotor 8 causes the powdery toner T to flow from the entrance opening 20 side of the through hole 6 to the exit opening 2.
1, and the toner T discharged from the through hole 6 of the stator 7 is supplied to the two-component developer in the developing container 4 through the casing 13. After a lapse of a predetermined time, the rotation of the rotor 8 stops. By performing such toner supply, the toner concentration of the developer in the developing container 4 is maintained within a predetermined range, and a toner image having a predetermined density can be formed on the image carrier.

As described above, in the toner transfer pump 5, the rotor 8 formed of a rigid body having higher rigidity than the stator 7 is pressed against the inner circumferential surface of the through hole of the stator 7 formed of the elastic body, and the inner circumferential surface portion is formed. The space S is elastically deformed, thereby closing each space S, and the toner T sealed therein is transferred. At that time, as described above, the stator 7
When the inner peripheral surface of the through hole is worn by the frictional force received from the rotor 8 and the shaving amount increases, the airtightness of the gap S decreases, whereby the suction pressure on the suction side of the toner transfer pump 5 decreases, and the toner As the transfer force decreases, the toner transfer pump finally reaches its end of life.

The following configuration is adopted for the toner transfer pump 5 of the present embodiment in order to extend its life and improve durability.

First, as the toner transferred by the toner transfer pump 5, a powdery toner externally added with 0.5% by weight or more of silica is used. Conventionally, fine powdered silica has been externally added to a toner used in an image forming apparatus in order to enhance its fluidity. However, the amount of the silica added is increased, and a powder containing 0.5% by weight or more of silica is added. That is, a body-shaped toner is used. Such a toner has a very high fluidity, so that the suction pressure required to transfer the toner by the toner transfer pump 5 can be greatly reduced.

A second feature of the toner transfer pump 5 of this embodiment is that the stator 7 is made of an elastic material having a JISA hardness of 50 degrees or less. As described above, in the uniaxial eccentric screw pump, the rotor 8 made of a rigid body is pressed against the inner peripheral surface of the through hole of the stator 7 with a large pressure while rotating, and the stator 7 is compressed and deformed.
Although the inner peripheral surface thereof is worn, by forming the stator 7 from an elastic material having a low hardness as described above, it is possible to reduce the repulsive force of the stator compressed and deformed by being pressed by the rotor 8. 8 and stator 7
Can be effectively made smaller than before. Thereby, abrasion of the inner peripheral surface of the through hole of the stator 7 can be suppressed, and the shaving amount can be reduced.

By employing both of the above-described structures, the suction pressure required for transferring the toner can be reduced and the amount of wear of the stator 7 can be reduced. Can be stretched much more than.

FIG. 2 is a graph in which the horizontal axis indicates the operating time of the toner transfer pump 5, that is, its use time, and the vertical axis indicates the absolute value of the suction pressure on the suction side of the toner transfer pump. The black circles, double circles, and crosses in this graph are the experimental results showing the relationship between the suction pressure of the toner transfer pump 5 having the stator 7 made of chloroprene rubber (CR) and the usage time. The diamonds indicate the results of an experiment showing the relationship between the suction pressure of the toner transfer pump 5 having the stator 7 made of EPDM and the usage time. The numerical values described after CR and EPDM are based on JIS A of each material.
It shows the magnitude of hardness.

If the suction pressure is lower than 5 KPa, the toner transfer pump 5 cannot transfer a required amount of toner, and the toner transfer pump 5 has reached the end of its life. The line indicating this pressure was taken as the durability critical line. By using a toner containing 0.5% by weight or more of silica, the durability critical pressure can be reduced. Further, if the usage time until the toner transfer pump 5 reaches the end of its life is 5 hours or more,
It is assumed that the durability of the toner transfer pump 5 is good.
Since the ratio of the operation time of the toner transfer pump 5 to the operation time of the image forming apparatus is extremely low, if the life of the toner transfer pump 5 is 5 hours or more, the toner transfer pump 5 may be operated for a considerably long time. You can continue to use.

As will be understood from a detailed examination of FIG. 2, if the hardness of the stator 7 is 50 degrees or less, the suction pressure becomes 5 KP.
The use time of the toner transfer pump 5 until the temperature becomes lower than a can be set to 5 hours or more, and the durability of the toner transfer pump 5 can be greatly improved. In particular, JIS
Use of a stator 7 made of chloroprene rubber having an A hardness of 50 degrees or less, particularly a stator 7 made of chloroprene rubber having a hardness of 40 degrees or less can greatly extend the life of the toner transfer pump 5. As described above, it is particularly advantageous that the elastic material forming the stator 7 is chloroprene rubber having a JIS A hardness of 50 degrees or less.

The cost of the stator 7 made of EPDM can be kept low. Therefore, by using the stator 7 made of EPDM having a JIS A hardness of 50 degrees or less, the cost of the toner transfer pump 5 can be reduced and the life thereof can be made relatively long.

Further, as a result of comprehensively judging the experimental results shown in FIG. 2 and the other experimental results, when the material of the stator 7 is any elastic material, its JIS A hardness is 45 degrees or less. It is also clear that the life of the toner transfer pump 5 can be prolonged. As the toner to be transferred, a powdery toner externally added with 0.5% by weight or more of silica is used, and the stator is made of an elastic material having a JIS A hardness of 45 degrees or less.

Further, from many experiments conducted by the present inventors, it has been found that the specific gravity of the rotor 8 also has a great effect on the life of the toner transfer pump 5, and the material of the rotor 8 having a specific gravity of 2.5 or more is determined. Is preferable. The reason is as follows.

If the specific gravity of the rotor 8 is lower than 2.5, it becomes lighter, so that when the rotor 8 rotates at a high speed, the center axis of the rotor 8 swings. For example, FIG.
As shown in FIG. 2, when the rotor 8 is mounted in a horizontal state, when the rotor 8 rotates, at a certain moment, the inlet-side end 23 of the rotor 8 is lowered below the normal horizontal position, and conversely. The outlet side end 22 is lifted upward,
At another moment, the inlet end 23 is lifted, and the outlet end 22 is lowered, and such movement is repeated. When the central axis of the rotor 8 swings during the rotation in this way, a so-called "one-side contact" phenomenon in which the rotor 8 is locally pressed against the inner peripheral surface of the through hole of the stator 7 with a large pressure is remarkable. And thus the stator 7
Wear of the inner peripheral surface of the substrate is promoted.

On the other hand, when the specific gravity of the rotor 8 is 2.5 or more, the total weight of the rotor 8 increases, so that the problem that the central axis swings during the rotation of the rotor can be effectively suppressed. In addition, it is possible to prevent the abrasion due to one-sided contact.

It is particularly advantageous to use a metal, particularly a zinc material, as the material having a specific gravity of 2.5 or more, and to form the rotor 8 by die casting. Here, the zinc material is a material containing zinc such as zinc or a zinc alloy. When the rotor 8 is formed of a molded product obtained by die-casting such a zinc material, the effect of increasing the dimensional accuracy of the rotor 8 and reducing the cost can be obtained. The rotor 8 has a complicated spiral shape, and if its dimensional accuracy is reduced, the toner transfer function is extremely reduced. However, by using the rotor 8 made of a die-cast product of a zinc material,
Such a problem can be avoided.

If the outer peripheral surface of the rotor 8 made of the above-mentioned molded article is barrel-polished, the outer peripheral surface can be extremely smoothed, and the surface roughness can be reduced to, for example, Ra2 or less. By smoothing the outer peripheral surface of the rotor 8 in this manner, the frictional force acting between the rotor 8 and the inner peripheral surface of the through hole of the stator 7 can be reduced, and the amount of scraping of the inner peripheral surface can be further reduced. Thus, the life of the toner transfer pump 5 can be further extended.

FIG. 3 is a graph showing the use time of the toner transfer pump 5 on the horizontal axis and the suction pressure (absolute value) on the suction side of the toner transfer pump 5 on the vertical axis as in FIG. And a solid circle (solid line) represent a stator 7 made of proloprene rubber having a JIS A hardness of 40 degrees and a rotor 8 obtained by die-casting a zinc material and barrel-polishing the outer peripheral surface thereof.
Shows the experimental results when using, and the crosses (dot-dash lines) indicate
Experimental results when the same stator 7 is used and a resin rotor 8 is used are shown. As can be seen from FIG.
When the rotor 8 made of a zinc material is used, the time required for the suction pressure to drop to a value lower than 5 KPa is greatly extended, and the durability of the toner transfer pump 5 is improved, as compared with the case where the rotor 8 made of resin is used. Can be improved.

The present invention is not limited to the configurations described above,
Various modifications can be made. Further, the image forming apparatus having the toner transfer pump of each configuration described above can be configured in various forms.

[0037]

According to the first to fifth aspects of the present invention, the life of the toner transfer pump can be extended. In particular, according to the inventions according to claims 4 and 5, in addition to the above effects, it is also possible to increase the dimensional accuracy of the rotor.

According to the sixth aspect of the present invention, it is possible to provide an image forming apparatus having the above effects.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a toner transfer pump.

FIG. 2 is a graph of an experimental example in which it has been found that the use of a stator made of a low-hardness material can extend the life of a toner transfer pump.

FIG. 3 is a graph of an experimental example in which it was found that the use of a rotor made of a zinc material can extend the life of a toner transfer pump.

[Explanation of symbols]

 5 Toner transfer pump 6 Through hole 7 Stator 8 Rotor S Air gap T Toner

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masumi Sato 1-3-6 Nakamagome, Ota-ku, Tokyo Stock inside Ricoh Company (72) Inventor Kazuhisa Sudo 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Ricoh Company (72) Inventor Yoshio Hattori 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company (72) Inventor Sota Fujimori 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company F-term (reference) 2H077 AC01 FA04 FA22

Claims (6)

[Claims] 1. A stator comprising: a stator; and a rotor rotatably disposed in a through-hole of the stator, wherein the through-hole of the stator is formed by two spirally extending grooves. In a toner transfer pump extending in a spiral shape, a toner transfer pump is formed so that a powdery toner transfer gap is formed between the outer circumferential surface of the rotor and the inner circumferential surface of the through hole of the stator. , Which is a powdery toner obtained by externally adding 0.5% by weight or more of silica.
A toner transfer pump comprising an elastic material having an A hardness of 50 degrees or less. 2. The toner transfer pump according to claim 1, wherein the elastic material forming the stator is chloroprene rubber. 3. The toner transfer pump according to claim 1, wherein the rotor is made of a material having a specific gravity of 2.5 or more. 4. The toner transfer pump according to claim 3, wherein the rotor is made of a molded product obtained by die-casting a zinc material. 5. The toner transfer pump according to claim 4, wherein an outer peripheral surface of the rotor made of the molded product is barrel-polished. 6. An image forming apparatus comprising the toner transfer pump according to claim 1.