JP2006144965A - Eccentric shaft joint structure and single-shaft eccentric screw pump equipped therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an eccentric shaft joint structure for securing a service life similar to that used under normal pressure without shrinking, deforming or breaking a rubber cover or a seal member under high pressure even when air resides in a space portion inside the rubber cover or the seal member. <P>SOLUTION: A space between an end 2a of a rotor 2 and an end 11a of a coupling rod 3 and a space between an end 13a of the coupling rod 3 and and an end 4a of a driving shaft 4 are covered with the rubber cover 18 or an O-ring seal 19, including a joint pin 14. lubricating oil is filled in the space portion (s) of the rubber cover 18 or the O-ring seal 19 and a piston 17 is fitted through piston holes 11d, 13d provided in the ends 11a, 13a of the coupling rod. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention performs power transmission between two rotating shafts that are eccentric under a high pressure environment, for example, when a rotational force from an electric motor is transmitted to a rotor of a single-shaft eccentric screw pump, via a shaft joint that is eccentric under high pressure. TECHNICAL FIELD The present invention relates to an eccentric shaft joint structure and a uniaxial eccentric screw pump provided with the eccentric shaft joint structure.

  As is well known, a general uniaxial eccentric screw pump transfers a liquid to be transferred (liquid / viscous liquid) by inserting an externally threaded rotor into an internally threaded stator and rotating it eccentrically. The drive shaft that rotationally drives the rotor generally has a structure that is coupled to the rotor via a universal joint and a coupling rod (see, for example, Patent Document 1).

  That is, in the uniaxial eccentric screw pump, as shown in FIG. 8, one end of the coupling rod 33 is connected to the end of the rotor 31 via a universal joint 32 such as a cross joint, a gear joint, or a pin joint. Similarly, the other end of the coupling rod 33 is connected to the end of the drive shaft 35 via a universal joint 34. The reason why the universal joints 32 and 34 and the coupling rod 33 are used in this manner is that the rotor 31 and the drive shaft 35 cannot be directly connected because the rotor 31 rotates eccentrically with respect to the drive shaft 35.

  In addition, in the gap between the rotor end 31a and the coupling rod end 33a and the gap between the coupling rod end and the drive shaft end, as shown in FIG. In order to prevent intrusion around the pin joint) 32, a rubber cover 36 is attached, or a ring-shaped seal member (not shown) is attached. When the universal joint is a cross joint 37, for example, as shown in FIG. 9B, a bellows type rubber cover 38 is attached so as to cover the entire periphery of the cross joint 37 across the end portions 31a and 33a of the two shafts. ing. The space including the rubber covers 36 and 38 and the universal joints 32 and 37 sealed with the seal member is filled with lubricating oil or grease to reliably prevent the liquid to be transferred from entering, and the universal joint The movement is smooth.

Furthermore, not only a single-shaft eccentric screw pump, but also a rod 45 having universal joints 43 and 44 at both ends between a drive shaft 41 and a driven shaft 42 arranged at a position with a height difference as shown in FIG. In general, a power transmission structure between two eccentric shafts is used in which the rotational force of the drive shaft 41 is transmitted to the driven shaft 42 by being connected to each other.
Japanese Examined Patent Publication No. 59-04558 (3rd, 4th page and Fig.1)

However, the conventional structure in which the peripheral portion of the above-described universal joint is filled and filled with lubricating oil or grease has the following problems. That is,
1) Air remains when filling with lubricant or grease in the space sealed with a rubber cover or seal member. On the other hand, in order to completely remove the air so that it does not remain, a special assembly method, such as assembling the universal joint itself in a lubricating oil bath, must be adopted, or a structure that allows air to escape easily must be used. I must.

  2) If the lubricant is grease, it is more difficult and impossible to assemble with completely removed air.

  3) In the case of a single-shaft eccentric screw pump, the pressure inside the pump casing may become high, so if the eccentric shaft joint with air remaining is placed under high pressure, the rubber cover and seal member will be pressurized from the outside, It is easily deformed and damaged. The opportunity to place the eccentric shaft joint under high pressure is not limited to the single-shaft eccentric screw pump, but also applies to the power transmission structure shown in FIG.

  4) If the rubber cover or seal member is damaged, the internal lubricating oil or grease leaks into the liquid to be transported, and in particular, if the liquid to be transported is food, there is a problem in terms of food safety and hygiene. In addition, foreign matter may be mixed in from the outside, the lubrication state in the universal joint may be poor, and the universal joint may deteriorate early. In the case of a single-shaft eccentric screw pump, it may cause the pump to fail.

  The present invention has been made in view of the above points, and even if air remains in the space in the rubber cover or the seal member, the rubber cover or the seal member does not shrink, deform, or break under high pressure. An object of the present invention is to provide an eccentric shaft joint structure that can ensure the same life as that under normal pressure.

To achieve the above object, an eccentric shaft joint structure according to the present invention covers a universal joint for transmitting rotational force by connecting two eccentric shafts, and covering between ends of both shafts including the universal joint. An eccentric shaft joint structure provided with an elastic cover or a seal member, in which a lubricant such as lubricating oil or grease is sealed in a space in the elastic cover or seal member,
A pressure equalizing mechanism for equalizing an internal pressure of the space portion and an external pressure of the space portion is provided on the one shaft or the universal joint portion (a part of the universal joint or one of the pair). .

  According to the eccentric shaft joint structure having the above-described configuration, the coupling rod and the universal joint are placed in a high-pressure environment when the rotational force is transmitted from the drive shaft to the driven shaft, and the elastic cover and the seal member are subjected to high pressure ( For example, when several atmospheric pressures to several tens of atmospheric pressures) are applied, the outer side of the elastic cover or seal member is placed outside via a lubricant filled in the space by a pressure equalizing mechanism provided in the coupling rod or universal joint. Therefore, the elastic cover and the seal member are not deformed by being pressed inward, or even if they are deformed, there is only a slight deformation. Such pressure equalizing action is particularly effective when the lubricant in the space contains air.

A uniaxial eccentric screw pump according to the present invention is a uniaxial eccentric screw pump in which a rotor that rotates eccentrically in a stator and a drive shaft that rotationally drives the rotor are connected to each other by a coupling rod via a universal joint.
An elastic cover or a sealing member including the universal joint between at least one of the end of the rotor and the end of the coupling rod and at least one of the end of the coupling rod and the end of the drive shaft. And covering the space inside the elastic cover or seal member with a lubricant such as lubricating oil or grease,
A pressure equalizing mechanism that equalizes the internal pressure of the space and the external pressure of the space is provided in the rotor, the coupling rod, the drive shaft, or the universal joint. The elastic cover in claims 1 and 2 refers to a cover made of rubber or synthetic resin having elasticity and flexibility.

  According to the single-shaft eccentric screw pump having the eccentric shaft joint structure having the above-described configuration, the inside of the pump casing where the coupling rod (or the rotor end portion or the drive shaft end portion) or the universal joint is located becomes high pressure during operation. When a high pressure (for example, several to several tens of atmospheres) is applied to the elastic cover or seal member from the outside, the equalization provided on the coupling rod (or rotor end or drive shaft end) or universal joint is provided. Since pressure equal to the outside acts on the inside of the elastic cover and the seal member through the lubricant filled in the space by the pressure mechanism, the elastic cover and the seal member are not pressed and deformed inside, or Even if it is deformed, it is accompanied by a slight deformation. Such pressure equalizing action is particularly effective when air is contained in the lubricant in the space.

  According to a third aspect of the present invention, in the uniaxial eccentric screw pump having the eccentric shaft joint structure according to the first aspect or the eccentric shaft joint structure according to the second aspect, the pressure equalizing mechanism is connected to the one shaft end or A communication passage extending from the outside to the space portion may be formed at the end of the coupling rod, a part of the communication passage may be formed in a sliding hole of the piston, and the piston may be fitted.

  With this configuration, when high pressure acts on the outer surface of the elastic cover or seal member, the same pressure acts on the piston from the outside across the piston, reducing the volume in the space filled with the lubricant. The piston moves in the direction to go. As a result, the pressure in the space rises and becomes equal to the external pressure, so that the elastic cover and the seal member are not deformed similarly to those under normal pressure. On the other hand, when the operation of the pump is stopped and the pressure acting on the outer surface of the elastic cover and the seal member decreases and returns to normal pressure, the pressure acting on the outside of the piston also returns to normal pressure. It moves in the direction of expanding the volume in the space, and the pressure in the space drops and returns to normal pressure, so it becomes equal to the external pressure. Therefore, the elastic cover and the seal member do not deform or are slightly deformed It only involves deformation.

  As described in claim 4, in the uniaxial eccentric screw pump provided with the eccentric shaft joint structure according to claim 1 or the eccentric shaft joint mechanism according to claim 2, the pressure equalizing mechanism is connected to the one shaft end or A communicating path extending from the outside to the space can be formed at the end of the coupling rod, and a diaphragm for partitioning the communicating path from the outside can be mounted.

  With this configuration, when a high pressure acts on the outer surface of the elastic cover or seal member, the same pressure acts on the diaphragm across the diaphragm, reducing the volume in the space filled with the lubricant. The diaphragm is deformed in the direction of the movement. As a result, the pressure in the space rises and becomes equal to the external pressure, so that the elastic cover and the seal member are not deformed similarly to those under normal pressure, or even if they are deformed, there is only a slight deformation.

  Since the eccentric shaft joint structure and the uniaxial eccentric screw pump according to the present invention have the above-described configuration, the following excellent effects can be obtained.

  If high pressure acts on the outside of the elastic cover or seal member even under high pressure, the internal side of the elastic cover or seal member is maintained at the same pressure as the external side via a pressure equalizing mechanism such as a piston or diaphragm. The elastic cover and the seal member are not deformed in the same manner as under normal pressure, or even if they are deformed, they are accompanied by a slight deformation, and thus can be used stably over a long period of time.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the uniaxial eccentric screw pump provided with the eccentric shaft joint structure shown in the embodiment of the present invention ranges from low viscosity liquids such as foods / chemicals and chemical liquids / solids containing liquids / slurries / high viscosity liquids to high viscosity liquids. Single-shaft eccentric screw pump that transfers, fills, and pumps various target liquids up to (a) Transfer pump that transfers food and chemical liquids, (b) Dispenser (filling pump), (c) Discharger (pumping pump) In particular, it can be applied to those which are transferred at a high pressure.

  FIG. 1 is a sectional view showing an embodiment of an eccentric shaft joint structure in a uniaxial eccentric screw pump, which is applied to a coupling rod between a rotor and a drive shaft of the conventional uniaxial eccentric screw pump shown in FIG. And shows eccentric shaft joint structures at both ends.

  As shown in FIG. 1, a uniaxial eccentric screw pump 1 according to the present invention includes eccentric shaft coupling structures 5 and 6 in which a coupling rod 3, a rotor 2, and a drive shaft 4 are connected via joint pins 14, respectively. Yes. The coupling rod 3 is divided into three side parts 11 and 13 and an intermediate part 12. The end 2a of the rotor 2 and the end 4a of the drive shaft 4 are each formed in a cylindrical shape having an open end, while the end portions 11a and 13a of the side portions 11 and 13 are each formed in a substantially spherical shape, The end portion 11a of the one-side portion 11 is inserted into the portion 2a, and the end portion 13a of the one-side portion 13 is loosely fitted into the drive shaft end portion 4a, so that the pin holes 2c and 11c and the pin holes 4c and 13c penetrate the both. Is drilled. Joint pins 14 are inserted in series into the pin holes 2c and 11c and the pin holes 4c and 13c, respectively, and are connected so as to be able to rotate integrally and swing in all directions.

  Between the rotor end portion 2a and the coupling rod end portion 11a, a cylindrical rubber cover 18 is attached to straddle the two to seal the gap. Reference numeral 18 a denotes a retaining ring for the rubber cover 18. Further, an O-ring seal 19 is interposed and sealed in the gap between the coupling rod end portion 13a and the drive shaft end portion 4a. Further, annular grooves 2b and 4b are formed on the outer surfaces of the rotor end 2a and the drive shaft end 4a, respectively. A sleeve cover 15 is fitted in each of the annular grooves 2b and 4b via O-rings 15a and 15b to prevent the joint pin 14 from coming off.

  Both end portions 12a and 12b of the intermediate portion 12 are formed in a cylindrical shape having an outer diameter larger than that of the other end portion 11b of the one side portion 11 and the other end portion 13b of the one side portion 13 and having one end opened. Has been. Then, a female screw is processed on the inner periphery of both side end portions 12a and 12b of the intermediate portion 12, and a male screw is processed on the outer periphery of the other end portion 11b of the one side portion 11 and the other end portion 13b of the one side portion 13. 12 and the portions 11 and 13 on both sides are integrally connected by a screw fastening structure 16. In addition, the direction of each screw of the screw fastening structure 16 is set to a direction that is fastened when the pump 1 is rotated forward. Moreover, cylindrical piston holes 11d and 13d each having one end opened are formed in the other end portion 11b of the one side portion 11 and the other end portion 13b of the one side portion 13, respectively. Communication holes 11e and 13e are bored from the piston holes 11d and 13d to the pin holes 11c and 13c in the axial center portions of the respective one side portions 11 and 13, respectively.

  Further, oil supply holes 11f and 13f are formed perpendicularly to the respective communication holes 11e and 13e from the outer wall of the one side portion 11 and 13, and oil supply plugs 11g and 13g are provided in the oil supply holes 11f and 13f, respectively. Removably screwed.

  Further, atmospheric communication holes 12c and 12d are formed along the axial center from the bottom ends of the cylindrical portions (lumen portions) of both side end portions 12a and 12b of the intermediate portion 12, and the atmospheric communication holes 12c and 12d are respectively formed. It is connected to a plurality of orthogonal communication holes 12e and 12f and faces the outside. In addition, pistons 17 are slidably inserted into the cylindrical piston holes 11d and 13d via O-rings 17a. In addition, the level difference by the difference in diameter is provided in the connection part of piston hole 11d * 13d and air | atmosphere communication hole 12c * 12d, and this level | step difference functions as a stopper of piston 17. FIG. In this example, the lubricating oil j is filled and sealed in the space s from the oil supply holes 11f and 13f. In this embodiment, the piston holes 11d and 13d, the communication holes 11e and 13e, the oil supply holes 11f and 13f, the oil plugs 11g and 13g, the air communication holes 12c and 12d, the plurality of orthogonal communication holes 12e and 12f, and the piston 17 are provided. The pressure equalizing mechanism is configured by the above.

  As described above, the single-shaft eccentric screw pump 1 including the eccentric shaft joint structure 5 and 6 according to the present embodiment is configured. The operation of the single-shaft eccentric screw pump 1 is centered on the eccentric shaft joint structure 5 and 6. explain. Since the uniaxial eccentric screw pump 1 of this example has the same basic structure as that of the uniaxial eccentric screw pump of FIG. 8 except for the eccentric shaft coupling structures 5 and 6, description will be made with reference to the reference numerals in parentheses in FIG. To do.

  As shown in FIG. 8, in the installed state, the pump 1 has a pump body (8) in which the longitudinal direction of the pump 1 is horizontal and the rotor (2) rotates eccentrically in the stator (7). Have. The rotor (2) is driven to rotate through a coupling rod (3) by driving the drive shaft (4) by an electric motor with a reduction gear (not shown). An end stud (8a) is provided at one end of the pump body (8), and one end of a cylindrical pump casing (9) is connected to the other end. In the pump casing (9), the coupling rod (3) rotates integrally with the eccentric rotation of the rotor (2) via the eccentric shaft coupling structures (5) and (6). The pump casing (9) has a discharge port (9a).

The liquid to be transferred is sucked into the stator (7) from the suction port on the end stud (8a) side, and is discharged from the discharge port (9a) through the pump casing (9). In this state, the inside of the pump casing (9) is placed under high pressure, and a high pressure p acts on the left and right eccentric shaft joint structures 5 and 6 as shown in FIG. That is, the high pressure p acts on the rubber cover 18 and the O-ring seal 19, but on the other hand, the high pressure similar to that in the pump casing (9) is also applied to the piston 17 from the communication holes 12e and 12f and the atmospheric communication holes 12c and 12d. p acts, and the inside of the space s enclosed by the rubber cover 18 and the O-ring seal 19 is also maintained at the pressure p through the lubricating oil j. Therefore, since the pressure p acts on the rubber cover 18 and the O-ring seal 19 from the inside and outside and is maintained in a pressure equalized state, the rubber cover 18 and the O-ring seal 19 are not deformed. The rubber cover 18 and the O-ring seal 19 increase the rigidity of the elastic member to some extent so that the sliding resistance of the piston 17 becomes smaller when the pressure p is applied, and the sliding of the piston 17 causes the rubber cover 18 and the O-ring seal 19 to slide. The process is started before the ring seal 19 is deformed.
In addition, when discharging the liquid to be transferred from the end stud (8a) side with the rotation direction of the rotor (2) reversed, the pressure in the pump casing (9) is slightly reduced, but the rubber cover 18 Deformation of the O-ring seal 19 does not occur.

  FIG. 2 is a sectional view showing a second embodiment of the uniaxial eccentric screw pump of the present invention. In the uniaxial eccentric screw pump 1-1 of this example, outward flanges 11h and 12h are integrally formed around one end of the one side portion 11 and around one end of the intermediate portion 12, and the one side portion 11 and the intermediate portion 12 are flanged. 11h and 12h, and the bolts 20 penetrating through the holes 12i of one flange 12h are screwed into the screw holes 11i of the other flange 11h and tightened together. Although illustration is omitted, the same structure is adopted for the coupling structure of the opposite portion 13 and the intermediate portion 12. Since other configurations and operations are the same as those in the above embodiment, the description thereof is omitted, and common members are denoted by the same reference numerals.

  FIG. 3 is a sectional view showing a third embodiment of the uniaxial eccentric screw pump of the present invention. In the uniaxial eccentric screw pump 1-2 of this example, a rubber diaphragm 10 is used instead of the piston 17, and the one side portion 11 (13) and the intermediate portion 12 are abutted and sandwiched around the diaphragm 10. Yes. The structure for connecting the one side portion 11 (13) and the intermediate portion 12 is the same as that of the second embodiment, and other configurations and functions are also the same as those of the first embodiment, so that the description thereof will be omitted. These members are denoted by the same reference numerals.

  FIG. 4 is a sectional view showing a fourth embodiment of the uniaxial eccentric screw pump of the present invention. In the uniaxial eccentric screw pump 1-3 of this example, a stopper ring 26 is fitted in an annular groove 11m provided in the vicinity of the abutting portion between the one side portion 11 and the intermediate portion 12. Since other configurations and operations are the same as those in the first embodiment, description thereof is omitted, and common members are denoted by the same reference numerals.

FIGS. 5 to 7 are side views each showing a cross-section of a fifth embodiment to a seventh embodiment in which a pressure equalizing mechanism is provided in the universal joint portion. A pressure equalizing mechanism is provided on one of the joint portions. That is,
In the uniaxial eccentric screw pump 1-4 shown in FIG. 5, the rod extends from one joint portion 23 of the pair of joint portions 22, 23 constituting the cross joint 21 interposed between the rotor 2 and the coupling rod 3. The part 23a is integrally extended. Outward flanges 23 h and 3 h are provided at the end of the rod portion 23 a and the end of the coupling rod 3, respectively, and the flanges are joined together with bolts 20, and communicated with the rod portion 23 a in the cross joint 21. A communication hole 23c and a piston hole 23b are provided in series. At the end of the coupling rod 3, air communication holes 3b and 3c communicating with the piston hole 23b are provided. In addition, the code | symbol 17 is the piston slidably inserted in piston hole 23b, 24 is a rubber cover, and it is attached so that the cross joint 21 may be covered ranging between the rotor 2 and the rod part 23a, and a rubber cover 24 is filled with lubricating oil. Since other configurations and operations are the same as those in the first embodiment, description thereof is omitted, and common members are denoted by the same reference numerals.

  In the uniaxial eccentric screw pump 1-5 shown in FIG. 6, the rod portion 22a is integrally extended from one joint portion 22 of the pair of joint portions 22 and 23 constituting the cross joint 21, and the rod portion 22a Outer flanges 22h and 2h are respectively provided at the end and the end of the rotor 2, and the two flanges are integrally connected by a bolt 20, and a communication hole 22c and a piston hole 22b are connected to the rod part 22a in the cross joint 21. Are provided in a series. Further, atmospheric communication holes 2b and 2c communicating with the piston hole 22b are provided at the end of the rotor 2. Reference numeral 25 denotes a bellows type rubber cover, which is attached so as to cover the cross joint 21 between the rod portion 22a and the coupling rod 3 end portion, and the rubber cover 25 is filled with lubricating oil. Since other configurations and operations are the same as those in the fifth embodiment, description thereof is omitted, and common members are denoted by the same reference numerals.

  In the uniaxial eccentric screw pump 1-6 shown in FIG. 7, rod portions 22a and 23a are integrally extended from the pair of joint portions 22 and 23 constituting the cross joint 21, respectively, and the end of the rod portion 22a and the rotor 2 are The flanges 22h and 2h facing outward are provided at the ends, and the flanges 23h and 3h facing outward are provided at the ends of the rod 23a and the coupling rod 3, respectively. Yes. An air communication hole 22d and a piston hole 22b communicating with the inside of the cross joint 21 from the outside of the one rod portion 22a are provided in series, and the piston 17 is slidably fitted into the piston hole 22b. Since other configurations and operations are the same as those in the sixth embodiment, description thereof is omitted, and common members are denoted by the same reference numerals.

  Three embodiments of the single-shaft eccentric screw pump having the eccentric shaft joint structure have been described above. However, the eccentric shaft joint structure according to the present invention is not limited to the single-shaft eccentric screw pump. The present invention can also be applied to a rotational force transmission device between two axes (FIG. 10). In this case, a pressure equalizing mechanism is provided at the end of the drive shaft 41, the end of the driven shaft 42, or both ends of the rod 45. In addition, although not shown, a pressure equalizing mechanism may be provided on the rotor 2 side or the drive shaft 4 side. Furthermore, the eccentric shaft joint structure of the present invention can be adopted only for one of the coupling rods 3 (for example, the rotor 2 side), and the conventional general eccentric shaft joint structure can be used for the other.

It is side sectional drawing which abbreviate | omits and shows one part which shows the uniaxial eccentric screw pump provided with the eccentric shaft coupling structure which concerns on the Example of this invention. It is side sectional drawing which abbreviate | omitted and represented the 2nd Example which showed the 2nd Example of the uniaxial eccentric screw pump of this invention. It is side sectional drawing which abbreviate | omitted and represented the 3rd Example which showed the 3rd Example of the uniaxial eccentric screw pump of this invention. It is side sectional drawing which abbreviate | omitted and represented the 3rd Example which showed the 3rd Example of the uniaxial eccentric screw pump of this invention. It is the side view which represented a part in section which shows the 5th example of the present invention which provided the pressure equalization mechanism in the universal joint part. It is the side view which represented in part the cross section which shows the 6th Example of this invention which provided the pressure equalizing mechanism in the universal joint part. It is the side view which represented a part in section showing the 7th example of the present invention which provided the pressure equalization mechanism in the universal joint part. It is side view sectional drawing which shows the conventional common horizontal installation type single axis | shaft eccentric screw pump. 9A is a cross-sectional view showing a conventional general eccentric shaft joint structure using a pin joint, and FIG. 9B is a cross-sectional view showing a conventional general eccentric shaft joint structure using a cross joint. is there. It is a side view showing the conventional typical eccentric power transmission structure between two shafts.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1-1 to 1-6 Uniaxial eccentric screw pump 2 Rotor 3 Coupling rod 4 Drive shaft 5/6 Eccentric shaft coupling (7) Stator (8) Pump body (8a) End stud (9) Pump casing (9a) Discharge port 10 Diaphragm (equal pressure equalization mechanism)
11 · 13 One side portion 11d · 13d Piston hole 12 Intermediate portion 14 Joint pin 17 Piston (pressure equalizing mechanism)
18 Rubber cover 19 O-ring seal 20 Bolt 26 Stopper ring

Claims (4)

A universal joint for connecting two eccentric shafts to transmit a rotational force, and an elastic cover or a seal member covering between the ends of both shafts including the universal joint, and a space portion in the elastic cover or the seal member Is an eccentric shaft joint structure in which a lubricant such as lubricating oil or grease is sealed.
An eccentric shaft joint structure, wherein a pressure equalizing mechanism for equalizing an internal pressure of the space portion and an external pressure of the space portion is provided on the one shaft or the universal joint portion. In a uniaxial eccentric screw pump in which a rotor that rotates eccentrically in a stator and a drive shaft that rotationally drives the rotor are each connected by a coupling rod via a universal joint,
An elastic cover or a sealing member including the universal joint between at least one of the end of the rotor and the end of the coupling rod and at least one of the end of the coupling rod and the end of the drive shaft. And covering the space inside the elastic cover or seal member with a lubricant such as lubricating oil or grease,
An eccentric shaft coupling structure characterized in that a pressure equalizing mechanism for equalizing the internal pressure of the space portion and the external pressure of the space portion is provided in the rotor, the coupling rod, the drive shaft, or the universal joint portion. Single-shaft eccentric screw pump with In the single shaft eccentric screw pump provided with the eccentric shaft joint structure according to claim 1 or the eccentric shaft joint structure according to claim 2,
The pressure equalizing mechanism has a communication passage extending from the outside to the space portion at the one shaft end portion or the coupling rod end portion, and a part of this communication passage is formed in a sliding hole of the piston. It is characterized by being inserted and configured. In the single shaft eccentric screw pump provided with the eccentric shaft joint structure according to claim 1 or the eccentric shaft joint structure according to claim 2,
The pressure equalizing mechanism is configured by drilling a communication passage from the outside to the space portion at the one shaft end portion or the coupling rod end portion, and mounting a diaphragm that partitions the communication passage from the outside. Features.

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