JPH0510791U - Uniaxial eccentric screw pump - Google Patents

Abstract

(57) [Summary] [Construction] A tubular body is provided so as to surround the stator 1 which constitutes a uniaxial eccentric screw pump, and a gap 12 formed between the tubular body and the stator 1 forms The structure is such that the parts are circulated. [Effect] Even if there is a temperature change in the pumped fluid, the rotor 2
Since the stator 1 also undergoes thermal expansion in the same manner, the rate of change in flow rate is extremely small, and excellent quantitative pressure feeding can be performed. Further, since it is covered with the cylindrical body, even if the stator 1 is made of ceramics, it is possible to prevent chipping or cracking due to external impact.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a uniaxial eccentric screw pump, which is suitable for quantitatively transporting a fluid having a large temperature change.

[0002]

[Prior Art]

 Single-axis eccentric screw pumps are capable of pumping even highly viscous fluids and have the property of being quantitative, so they are used for pumping highly viscous fluids such as oil, paint, pulp fluid, chemicals, and foods.

As shown in FIG. 2, the structure of such a uniaxial eccentric screw pump has, as shown in FIG. 2, a stator 21 having an oval cross section and an inner surface of a female thread, and a circular cross section eccentric to the rotating shaft. The male screw-shaped rotor 22 is internally provided, and a shaft 25 is connected to the rotor 22 via two universal joints 23, 23 and a connecting rod 24 and sealed by a shaft sealing portion 26. Further, the outer peripheral surface of the stator 21 is exposed to the outside, so that the stator 21 can be easily removed, disassembled, and cleaned.

Further, as the material of the stator 21 and the rotor 22, metal, rubber or the like has been used, but in recent years, ceramics having excellent corrosion resistance and heat resistance have come to be used (Japanese Patent Laid-Open No. 62-29781). (See the bulletin, etc.)

[0005]

[Problems to be solved by the device]

 However, when the high temperature fluid is pressure-fed by the conventional uniaxial eccentric screw pump as described above, the rotor 22 has a high temperature, but the stator 21 has a structure exposed to the outside, which is lower than the rotor 22. It was temperature. Therefore, the thermal expansion of the rotor 22 is larger than the thermal expansion of the stator 21, resulting in a problem that the volume of the pump chamber is decreased and the flow rate is decreased. Therefore, when the temperature of the fluid changes during pressure feeding, the flow rate is low at high temperature and high at low temperature due to the above reasons, and there is a problem that constant pressure feeding cannot be performed.

Further, when the stator 21 is made of ceramics, the structure in which the stator 21 is exposed as in the conventional case may cause chipping or cracking due to external impact.

[0007]

[Means for Solving the Problems]

 In view of the above, the present invention has a structure in which a stator that constitutes a uniaxial eccentric screw pump is surrounded by a tubular body, and a part of the pumped fluid is circulated in a gap formed between the tubular body and the stator. It was done.

[0008]

[Action]

 According to the present invention, the structure in which the pressure-fed fluid circulates around the stator allows the rotor and the stator to change the temperature in the same manner even when the temperature changes in the pressure-fed fluid, and the same thermal expansion occurs. Therefore, the volume change of the pump chamber is small, and the flow rate change due to the temperature change can be prevented.

[0009]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a male screw-shaped rotor 2 having a circular cross section eccentric with respect to a rotation axis is formed on an inner surface of a female screw having an oval cross section and a pitch twice that of the rotor 2. The rotor 1 is internally mounted in the formed stator 1, and a shaft 5 is connected to the rotor 2 via two universal joints 3 and 3 and a connecting rod 4 and is sealed by a shaft sealing portion 6. A metal end piece 9 and a stator casing 10 are arranged as a tubular body surrounding the stator 1, and the pump housing 11 covers the other parts. Further, a gap 12 is formed between the end piece 9 and the stator casing 10 and the stator 1, and passages 9a and 10a are formed in the end piece 9 and the stator casing 10 to circulate a fluid in the gap 12. I am doing it.

Then, when the rotor 2 is rotated by the shaft 5, the rotor 2 rotates about the rotation axis, and at the same time, the rotor 2 is eccentrically moved with respect to the axial center of the fixed stator 1 to cause fluid flow. Can be pumped from the suction port 7 to the discharge port 8. Further, when the fluid is pumped, a part of the pumped fluid is recirculated from the high-pressure discharge port 8 side to the suction port 7 side through the passage 9a, the gap 12, and the passage 10a. In this way, when the pumped fluid recirculates on the outer surface of the stator 1, for example, when pumping a high-temperature fluid, the stator 1 becomes a high temperature like the rotor 2 and similarly thermally expands, so that the size of the pump chamber is increased. Even if the temperature does not change, constant pressure feeding is possible.

It should be noted that when the above-mentioned reflux amount is large, the discharge amount is reduced accordingly and the performance of the pump is deteriorated. However, as a result of various experiments, if the above-mentioned reflux amount is 10% or less of the pumping amount, the pump There was no adverse effect on performance. Therefore, the sizes of the passages 9a and 10a and the gap 12 may be adjusted so that the recirculation amount is 10% or less of the pumping amount.

The stator 1 and the rotor 2 may be made of rubber, metal or the like, but in view of corrosion resistance, heat resistance, wear resistance and the like, ceramics such as alumina, silicon carbide and silicon nitride are used. Is preferably used. As described above, even when the stator 1 is made of ceramics, since it is covered by the end piece 9 and the stator casing 10, no external impact is applied to the stator 1 and cracks or cracks may occur. There is no. Further, the stator 1 and the rotor 2 are made of the same kind of ceramics or ceramics having a similar coefficient of thermal expansion, so that the quantitative pumping property can be further improved.

Further, in the above-described embodiment, the cylindrical body surrounding the stator 1 is composed of the end piece 9 and the stator casing 10. However, the cylindrical body is not necessarily limited to this structure, and it is not limited to this structure. The structure may be such that a part of the pressure-feeding fluid flows back through the formed gap 12.

Experimental Example Here, as an example of the present invention, the uniaxial eccentric screw pump shown in FIG. 1 was manufactured as a trial by forming both the stator 1 and the rotor 2 from silicon nitride ceramics. As a comparative example, the conventional one shown in FIG. 2 is formed of silicon nitride ceramics for both the stator 1 and the rotor 2 (Comparative Example 1). The stator 1 is formed of rubber and the rotor 2 is formed of stainless steel. What was done (Comparative Example 2) was prepared.

The uniaxial eccentric screw pumps of the examples of the present invention and the comparative example were subjected to a fresh water pressure feed test by rotating the shaft 5 at 200 rpm, and the temperature of the fresh water was changed from 20 ° C to 100 ° C. The decrease rate of flow rate was investigated. The results are shown in Table 1.

[0017]

[Table 1]

When used for quantitative pressure feeding for food and chemicals, the flow rate change rate is required to be ± 2% or less, depending on the application. However, as shown in Table 1, in the comparative example, the flow rate change rate when the temperature change was 20 to 100 ° C. was as large as 5% or more, and the above required characteristics were not satisfied. In particular, in the case where the stator 1 was made of rubber and the rotor 2 was made of stainless steel (Comparative Example 2), there was a difference in the coefficient of thermal expansion, so the rate of change in flow rate was large.

On the other hand, in the embodiment of the present invention, even if there is a temperature difference of 20 to 100 ° C., the flow rate change rate is 1% or less, which satisfies the above-mentioned required characteristics, and exhibits an excellent quantitative pumping property. I understand.

[0020]

[Effect of the device]

 As described above, according to the present invention, the tubular body is provided so as to surround the stator that constitutes the uniaxial eccentric screw pump, and a part of the pumped fluid is circulated in the gap formed between the tubular body and the stator. With this structure, the rotor and the stator similarly undergo thermal expansion even when the temperature of the fluid to be pumped changes, so the rate of change in the flow rate is extremely small, and excellent quantitative pumping can be performed. Further, since it is covered with the cylindrical body, it is possible to provide a uniaxial eccentric screw pump having various features such as preventing the occurrence of chipping or cracking due to external impact even when the status is made of ceramics.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a uniaxial eccentric screw pump according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view showing a conventional uniaxial eccentric screw pump.

[Explanation of symbols]

 1 ... Stator 2 ... Rotor 3 ... Universal joint 4 ... Connecting rod 5 ... Shaft 6 ... Shaft sealing part 7 ... Suction port 8 ... Discharge port 9 ... End piece 10 ... Stator casing 11 ... Pump housing 12 ... Gap

Claims (1)

[Claims for utility model registration] [Claim 1] A uniaxial eccentric screw in which a stator having a female screw inner surface is internally provided with a male screw rotor, and the rotor is connected to a shaft through a universal joint and a connecting rod. In the pump, while surrounding the stator with a tubular body so as to form a gap,
A uniaxial eccentric screw pump having a structure in which a part of the pumped fluid is circulated through this gap.