JPH11303765A - Screw pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a rotary load and to sharply delay the abrasion of a stator by forming at least the face of the stator to be kept in contact with a rotor into a flexible low-friction face. SOLUTION: This screw pump 1 is provided with a female screw-shaped stator 2 made of an elastic body such as rubber and formed with a double-pitch spiral groove and a male screw-shaped rotor 3 rotatably inserted into the stator 2 and made of a metal. The toner inputted from the opening section 9 of an input side housing 5 is fed to the input side of the pump 1 by a conveying screw 10 in this screw pump 1. The rotor 3 is rotating at this time, the toner is filled in an advancing cavity section 15 formed in the pump 1 by the rotation of the rotor 3, and the toner is shifted. A low-friction thin film is formed on the face of the stator 2 to be kept in slide contact with the rotor 3. A diamond- like carbon thin film having an amorphous structure made of constituting elements C, H is formed by coating as the low-friction thin film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw pump suitable for transporting fluids, powders, especially powdery toner.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a printer or a facsimile machine, a female screw type stator having a double pitch spiral groove therein, and a male screw type rotor rotatably fitted in the stator. It is known to additionally provide a toner transfer device using a single-axis eccentric screw pump (commonly called a Mohno pump). In the toner transfer device using this screw pump, the stored toner or the collected toner for cleaning or the like can be transferred via a flexible pipe or the like, so there is no restriction on the installation of the toner storage unit and the toner collection unit. ,
There is an advantage that toner transfer can be reliably performed with a simple configuration. Further, the toner transfer device using the screw pump transfers the toner in a mixed state with air by the air supply means, so that stable transfer of the toner can be obtained and more unnecessary stress is not applied to the transferred toner. ,
Aggregation, thermal fusion and the like of the transferred toner are almost suppressed.

[0003] As described above, it can be seen that a toner transfer device using a screw pump is particularly superior to other toner transfer systems using other transport screws or the like.

[0004]

In a powder transfer device using a screw pump, a stator requires elasticity, and is made of a rubber material. A metal rotor slides inside the stator while sliding. As it rotates, the stator receives a high rotational load due to the high friction coefficient of the rubber material.
For this reason, the stator may undergo a dimensional change such that the inner diameter gradually increases with time, and may also undergo an elastic change with time. When the inner diameter of the stator is enlarged, there is a problem that a backflow phenomenon occurs in which air supplied after the discharge of the screw pump passes between the stator and the rotor and flows out to the input side of the pump. If a problem occurs, the screw pump has reached the end of its life and must be replaced with a new one.

The operating life of the screw pump having such a long service life is relatively short, and it has been desired to extend the life of the screw pump. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a screw pump capable of greatly extending the life.

[0006]

In order to achieve the above object, the present invention provides a female screw type stator having a double pitch spiral groove therein, and a male screw type stator rotatably inserted in the stator. In a screw pump having a rotor, at least a surface of the stator that contacts the rotor is a flexible low friction surface.

The present invention is effective when the low-friction surface is a flexible low-friction thin film coated on a surface of the stator body that contacts the rotor.

According to another aspect of the present invention, there is provided a female screw type stator having a double pitch spiral groove therein, and a male screw type rotor rotatably fitted in the stator. In the screw pump, the whole surface of the stator is coated with a flexible low-friction thin film.

Further, the present invention is effective when the flexible low friction thin film is diamond-like carbon (DLC) having an amorphous structure composed of constituent elements C and H.

Further, the present invention is effective when the flexible low friction thin film has a thickness of 3 μm or less.

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 a sectional perspective view showing the configuration of the screw pump according to the present invention.

In FIG. 1, a screw pump 1 has a female screw type stator 2 having a double pitch spiral groove made of an elastic material such as rubber, and is rotatably inserted into the stator 2 and is made of metal or the like. And a manufactured externally threaded rotor 3. The rotor 3 is provided with a horizontal conveying screw 1 on the upstream side.
A gear 13 is connected to one end of a shaft 11 of the horizontal conveying screw 10 by a coupling 12, and the other end of the shaft of the horizontal conveying screw 10 projects outside the toner input side housing 5 and is drivingly connected to a driving source (not shown). Has been fixed.

The stator 2 is supported so as to be covered by the input side housing 5 and the output side housing 4, and a gap is provided between an inner peripheral surface of the output side housing 4 and an outer peripheral surface of the stator 2. 7 are provided. This gap 7
Is a toner discharge port 6 provided on the output side of the rotor 3.
Is communicated to. The output side housing 4 is provided with an air supply port 8 communicating with the gap 7, and the air supply port 8 is fitted with an air supply tube (not shown) from an air supply source such as an air pump (not shown). Has been inserted. The air from the air pump is supplied from the air supply port 8 to the toner discharge port 6 through the gap 7, and fluidizes the toner to smoothly and reliably discharge in the direction of the arrow.

In the above-described single-shaft eccentric screw pump 1, the toner inputted from the opening 9 of the input side housing 5 is sent to the input side of the pump by the transport screw 10. At this time, the rotor 3 is also rotating, and the rotating cavity 3 formed in the pump by the rotation of the rotor 3 is filled with toner, and the toner is transferred from right to left in the drawing. Become.

By the way, the stator 2 is made of a rubber material, and the metal rotor 3 rotates while sliding in the stator 2, so that the inner diameter of the stator 2 gradually increases due to wear or the like due to wear and the like. Had reached the end of its life.

Therefore, in the screw pump 1 of the present invention, the surface of the stator 2 which is in sliding contact with the rotor 3 is a low friction thin film (not shown). As a low friction thin film of this example, diamond-like carbon (Diamond Like Carbon)
It is called LC. ) Is coated with a thin film.

Incidentally, this DLC was first synthesized in the 1970's by an ion beam evaporation method, and although carbon has a tetracoordinate bond (SP ³ bond) structurally, it has a partial SP ² bond. And a bond with hydrogen, and thus has an amorphous structure of the constituent elements C and H which does not generally have a fixed crystal structure. Therefore, it is similar in many respects to diamond in characteristics, but has a lower temperature through oxidation.
Further, it has a feature that the film surface is extremely smooth.

The characteristics of the DLC thin film include a low coefficient of friction, low abrasion, flexibility to impact, reduction of damage to a mating substrate, and high adhesion to resin and rubber. Therefore, it can be said that the DLC thin film is most suitable as a coating for the stator 2 of the screw pump for transferring powder and fluid. The coating of the DLC thin film may be applied not only to the sliding surface with the rotor 3 but also to the entire surface of the stator 2. In this case, it is possible to prevent the stator 2 from being deteriorated by powder such as toner or the environment. can do.

FIG. 2 is a graph showing the results of examining the coefficient of friction between a rubber substrate (EPT rubber (ethylene propylene rubber), silicone rubber) and a rubber substrate subjected to DLC treatment.

In FIG. 2, the experimental results are considered to differ slightly depending on the conditions such as the surface roughness of the rubber base material and the rubber hardness. In the test of an arbitrary test piece, as shown in FIG. The coefficient of friction is significantly improved compared to that of the untreated one. Especially,
In EPT rubber, about 18 untreated DLC-treated rubber
% The coefficient of friction has been reduced.

Although the DLC thin film does not affect the elastic properties of the substrate, the thickness must be set in order to have the flexibility of the thin film itself. Further, the thickness of the DLC thin film was set to be 1 μm or more and 3 μm or less in consideration of blocking of powder such as toner, abrasion life and the like.

By the way, DLC is used as the rubber base material of the stator 2.
When coating thin films, cost must also be considered. The cost of the DLC thin film greatly affects the processing time. FIG. 3 is a result of a test performed on a DLC film formed per unit time of PTFE, CR rubber, NBR rubber, and EPT rubber which can be used as a rubber base material of the stator 2, and EPT rubber is the most economical. Turned out to be.

From the above results, EPT rubber was used as the rubber base material of the stator 2 and the thickness of the DLC thin film was 3 μm.
It has been found that setting the value to m or less is useful. Incidentally, when a screw pump 1 in which a rotor 3 is made of stainless steel and a stator 2 is made of EPT rubber and coated with a 1-2 μm DLC thin film is used, the rotational load is about 1/3 or less of the conventional one, and the deformation of the stator due to friction. The transition was about 1/2 or less, and the life of the screw pump was dramatically improved.

[0024]

According to the first and second aspects of the present invention, the rotational load due to the reduction in the friction coefficient is reduced, the wear of the stator is greatly delayed, and the service life of the screw pump is prolonged.

According to the third aspect of the invention, the rotational load is reduced, the wear of the stator can be delayed, and the stator can be prevented from being degraded by powder such as toner or rubber due to the environment.

According to the fourth aspect of the present invention, the rubber base material of the stator is excellent in adhesion, has low wear, low friction coefficient, and has low opposing aggressiveness. Therefore, it is possible to provide a long-life screw pump with little influence on the fluid and powder to be transferred.

According to the fifth aspect of the present invention, the flexibility of the flexible low-friction thin film is ensured, and the cost can be reduced by shortening the film forming time.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a screw pump according to the present invention.

FIG. 2 is a graph showing test results comparing the coefficient of friction of a rubber substrate with and without a DLC film thickness.

FIG. 3 is a graph showing a DLC film forming time for each rubber substrate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Screw pump 2 Stator 3 Rotor

Claims (5)

[Claims] 1. A screw pump having a female screw type stator provided with a double pitch spiral groove therein and a male screw type rotor rotatably inserted in the stator, wherein the stator contacts at least the rotor of the stator. Side to do,
Screw pump characterized by a flexible low friction surface. 2. The screw pump according to claim 1, wherein the low friction surface is a flexible low friction thin film coated on a surface of the stator body that contacts the rotor. 3. A screw pump having a female screw type stator having a double pitch spiral groove therein and a male screw type rotor rotatably fitted in the stator, wherein the stator has a flexible low surface over its entire surface. A screw pump characterized by being coated with a friction thin film. 4. The screw pump according to claim 2, wherein the flexible low-friction thin film is diamond-like carbon (DLC) having an amorphous structure composed of constituent elements C and H. 5. The thickness of the flexible low friction thin film is 3
The screw pump according to any one of claims 1 to 3, wherein the diameter of the screw pump is not more than μm.