CN113785124A

CN113785124A - Connecting shaft and uniaxial eccentric screw pump

Info

Publication number: CN113785124A
Application number: CN202080033492.8A
Authority: CN
Inventors: 榊原教晃; 森田刚志
Original assignee: Heishin Ltd
Current assignee: Heishin Ltd; Heishin Sobi KK
Priority date: 2019-06-11
Filing date: 2020-05-30
Publication date: 2021-12-10
Also published as: TW202045820A; TWI846882B; JP2024107386A; JPWO2020250720A1; WO2020250720A1; KR20220017894A; JP7568338B2; JP7514541B2

Abstract

The purpose of the present invention is to provide a connecting shaft having low bending rigidity and high torsional rigidity; the connecting shaft (10) is flexible, connects the first member and the second member, and is provided with a twisted shape portion (12) in at least one part, and the shape of the cross section of the twisted shape portion, which is orthogonal to the axial direction of the connecting shaft (10), is a shape that is continuously twisted as the cross section advances along the axial direction, or a shape that is twisted in an intermittent step-like rotation manner; the second moment of area on the cross section is different between a first direction (short side direction) orthogonal to the axial direction and having the smallest second moment of area on the cross section (13) and a second direction (long side direction) orthogonal to the first direction on the same cross section (13).

Description

Connecting shaft and uniaxial eccentric screw pump

Technical Field

The present invention relates to a connecting shaft and a uniaxial eccentric screw pump. More specifically, the present invention relates to a coupling shaft that couples a first member and a second member and transmits power therebetween, and a uniaxial eccentric screw pump using the coupling shaft.

Background

Conventionally, in order to enable eccentric rotation of a rotor of a uniaxial eccentric screw pump, a flexible coupling shaft (corresponding to a flexible drive shaft) having a round bar shape is used between a drive-side rotating portion and the rotor (for example, patent document 1).

Further, a flexible coupling shaft having a shape in which flat plate-like members with slits formed therein are orthogonal to each other is known (for example, patent document 2).

[ Prior art documents ]

[ patent document ]

Patent document 1: japanese patent laid-open No. 2012-154215

Patent document 2: japanese patent laid-open No. 2014-105827

However, the coupling shaft of patent document 1 needs to displace both ends thereof to eccentrically rotate the rotor. Therefore, the connection shaft is required to have flexibility and low bending rigidity. When the bending rigidity is high, there is a problem that the posture of the rotor is inclined in the stator by a reaction force (also referred to as a restoring force) of the coupling shaft. When the rotor is inclined in this way, the conveyance space inside the stator is deformed by forcibly pressing the rotor near the insertion port of the stator, and the discharge performance is degraded although the inside of the stator is not worn.

In order to accurately transmit the rotation angle of the drive source to the rotor when the rotation of the rotor is started or stopped, the connecting shaft is required to have high torsional rigidity. When the torsional rigidity is low, the rotational angle of the drive source cannot be accurately transmitted to the rotor at the time of starting or stopping the rotation of the rotor, and there is a problem that the responsiveness of starting and stopping the discharge of the pump is deteriorated, or a stick-slip phenomenon occurs, and abnormal sound or discharge pulsation occurs.

In general, there is a correlation that a material and a shape having high bending rigidity have high torsional rigidity, and conversely, a material and a shape having low bending rigidity have low torsional rigidity, and therefore, there is no connecting shaft that satisfies both of the high torsional rigidity and the low bending rigidity required for an ideal connecting shaft.

Therefore, a conventional connecting shaft uses a round bar made of a material such as titanium alloy or engineering plastic, which has a bending rigidity of a slight degree of bendability while securing a certain degree of torsional rigidity, and which has no problem in strength. By making the round bar long, even if the bending angle is small, only the length of the displacement amount of the eccentric rotation can be bent, and thus the reaction force is reduced. Therefore, in the uniaxial eccentric screw pump using the conventional coupling shaft, there is a problem that the length of the entire pump becomes long and the pump becomes large. Further, since the coupling shaft is long, the torsion angle of the entire shaft with respect to the torque is also large, and there is a problem that the responsiveness of discharge is not good. Further, along with this, the housing that houses the coupling shaft is also increased in size, and there are also problems that the amount of fluid remaining in the housing increases when the uniaxial eccentric screw pump is stopped, and that it is difficult to secure the installation space.

Further, the coupling shaft in patent document 2 is configured to support displacement in all directions by allowing a flat plate-like member having low bending rigidity to be orthogonal to each other only in one direction. However, the flat plate shape has a low torsional rigidity, and there is a problem that a force in a torsional direction acts on the flat plate-shaped member when a rotational torque is applied, and the flat plate-shaped member is twisted.

Further, since the force generated by the displacement acts in all directions from 360 ° at each rotational position, when a force in a direction other than the vertical direction, which is the most likely bending direction, is applied to the flat plate-shaped member, the reaction force acting on the rotor and the stator of the uniaxial eccentric screw pump greatly varies in each angle. This causes the posture of the rotor to shake in the stator, and the shape and volume of the cavity to change, thereby causing problems such as deterioration of discharge accuracy and generation of pulsation.

Disclosure of Invention

In view of the above, an object of the present invention is to provide a compact connecting shaft having high torsional rigidity in a torsional direction while allowing bending rigidity and flexibility in a bending direction, and to provide a uniaxial eccentric screw pump in which abnormal sound and discharge pulsation are not generated by the connecting shaft.

The present invention has been made to solve the above problems, and provides a connecting shaft that is flexible and connects a first member and a second member, and that is characterized by comprising a twisted shape portion in at least a part thereof, wherein a cross section of the twisted shape portion orthogonal to an axial direction of the connecting shaft has a shape that is continuously twisted as the cross section advances in the axial direction or a shape that is twisted in an intermittent stepwise rotation; the second moment of area on the cross section is different between a first direction orthogonal to the axis direction and in which the second moment of area on the cross section is smallest and a second direction orthogonal to the first direction on the same cross section.

At least a part of the connecting shaft of the present invention includes a twisted shape portion having a shape of a cross section orthogonal to an axial direction of the connecting shaft, the shape being a shape twisted continuously as it advances in the axial direction or a shape twisted so as to rotate intermittently in a stepwise manner. That is, when the coupling shaft rotates, a part of the moment in the torsional direction is converted into a force in the axial direction or the like by the shape of torsion in the initial state, and therefore, the torsional rigidity of the coupling shaft is substantially improved. Therefore, by coupling the coupling shaft of the present invention to a drive source such as a motor, the rotational angle of the drive source can be transmitted to the rotor with good responsiveness and accuracy.

The connecting shaft of the present invention has a cross-sectional shape in which a direction in which a second moment of area is smallest on the cross-section is defined as a first direction, and a length in the first direction is different from a length in a second direction intersecting the first direction on the same cross-section. That is, since the second moment of area of the coupling shaft in the first direction is the smallest, the coupling shaft is more easily displaced in the first direction than in the second direction at each position of the cross section of the coupling shaft. Further, since the shape of the cross section is a shape that twists continuously as it advances in the axial direction or a shape that twists so as to rotate intermittently in a stepwise manner, it is possible to cope with a displacement that occurs in any direction of 360 ° as it rotates eccentrically. Due to the above characteristics, it can be suitably used as an eccentric rotating shaft of various devices (for example, a pump, a compressor, a distributor, a reciprocating mechanism, etc.) requiring eccentric rotation.

The coupling shaft of the present invention is easily displaced in a first direction in which the second moment of area is smallest, and is restricted from being displaced in a second direction in which the second moment of area is larger. That is, in the coupling shaft according to the present invention, since the first direction and the second direction sequentially change in the circumferential direction as the coupling shaft rotates, it is possible to provide a coupling shaft that satisfies both requirements of having appropriate flexibility and high torsional rigidity.

Further, the coupling shaft of the present invention can allow displacement due to eccentricity. Therefore, the coupling shaft of the present invention can allow displacement due to eccentricity even if the coupling shaft is connected without using a universal joint. Therefore, when the coupling shaft of the present invention is used, the connection can be performed without providing a sliding portion on the coupling shaft, and therefore, it is possible to prevent foreign matter from being mixed due to abrasion or the like. Therefore, the connecting shaft of the present invention is suitable for use as a connecting shaft for devices for food processing, pharmaceutical, and the like, which have problems caused by foreign matter mixing.

As described above, the connecting shaft of the present invention has both the physical properties of low bending rigidity and high torsional rigidity, and therefore, can be designed to have a short length without reducing the torsional resistance against the rotational torque. Therefore, the device using the coupling shaft of the present invention can be miniaturized, and a device having high versatility and not affected by the installation space can be provided.

In the coupling shaft according to the present invention, it is preferable that a torsional axis of the coupling shaft is within the shape of the cross section when viewed from an arbitrary position in the axial direction, and the shape of the cross section is at least one of a shape that is line-symmetrical with respect to a first axis that passes through the position of the torsional axis and extends in the first direction, a shape that is line-symmetrical with respect to a second axis that passes through the position of the torsional axis and extends in the second direction, and a shape that is point-symmetrical with respect to the torsional axis.

The cross-sectional shape of the connecting shaft of the present invention may be, for example, a rectangle, an ellipse, a rounded corner, a parallelogram, a rhombus, or the like. According to the above configuration, the coupling shaft can be easily manufactured.

The coupling shaft of the present invention preferably has a total torsion angle in the torsion shape portion of ± 20 degrees which is a multiple of 180 degrees.

Since the coupling shaft according to the present invention has the above-described configuration, the first direction which is most likely to bend corresponds to the bending direction of one rotation (360 °) uniformly about the rotation axis and one half rotation (180 °), and there is no extra angle except for an error portion, and thus the variation of the reaction force is stable. Therefore, the first member or the second member coupled to both ends of the coupling shaft is stable in posture when rotated, and abnormal sound or vibration caused by unstable rotational posture of the first member or the second member can be reduced.

In order to solve the above problems, the present invention provides a uniaxial eccentric screw pump comprising: a drive-side rotating section that rotates by power of the actuator; a rotor formed of a male screw shaft body; a stator having a female screw formed on an inner peripheral surface thereof, the rotor being insertable into the stator; and a connecting shaft connecting the drive-side rotating portion and the rotor in such a manner that: the rotor can be eccentrically rotated so as to revolve along the inner circumferential surface of the stator while rotating inside the stator; as the coupling shaft, the above-described coupling shaft is used.

The uniaxial eccentric screw pump of the present invention connects the rotor and the drive-side rotating part of the uniaxial eccentric screw pump by using the connecting shaft of the present invention, and therefore, the rotational angle on the drive side can be transmitted to the rotor without a delay in response. Further, the uniaxial eccentric screw pump of the present invention can be downsized by using the connecting shaft of the present invention which can be made short in size and does not lower the response performance with respect to the rotation angle on the driving side. Thus, even in the uniaxial eccentric screw pump using the coupling shaft system, the installation space can be reduced. In addition, the volume of the casing of the uniaxial eccentric screw pump can be reduced, and the remaining amount of the fluid in the casing can be reduced. Therefore, the present invention is particularly suitable for use in fields requiring discharge of expensive fluids (for example, battery production, semiconductor production, and the like).

In the uniaxial eccentric screw pump of the present invention, it is preferable that a twisting direction of the rotor coincides with a twisting direction of the coupling shaft.

According to the above configuration, the fluid in the housing can be pushed toward the stator as the connecting shaft rotates. Therefore, even a fluid having a high viscosity can be appropriately pushed into the stator side. Thereby, the volume of the inner space of the stator is easily filled with the fluid, and thus the conveying efficiency is improved. In addition, when the pump is used in a reverse suction mode, the fluid discharged from the stator can be further assisted to be discharged to the outside of the housing.

(effect of the invention)

According to the present invention, since the coupling shaft having low bending rigidity (flexibility) and high torsional rigidity without increasing the length can be provided, various devices and mechanisms can be downsized by using the coupling shaft. Further, by using the connecting shaft of the present invention in a uniaxial eccentric screw pump, a compact pump having high versatility can be provided.

Drawings

Fig. 1 is a perspective view of a coupling shaft according to an embodiment of the present invention.

Fig. 2 (a) to (g) show modifications of the cross-sectional shape of the connecting shaft of the present invention.

Fig. 3 is a graph showing a relationship between the total torsion angle of the connecting shaft and the reaction force.

Fig. 4 is a graph showing a relationship between the total torsion angle of the connecting shaft and the reaction force.

Fig. 5 is an explanatory diagram of an evaluation method of the connecting shaft.

Fig. 6 shows the evaluation results of the coupling shaft.

Fig. 7 is an explanatory diagram comparing a conventional flexible coupling shaft and a modified example of the coupling shaft of the present invention.

Fig. 8 is a sectional view of a uniaxial eccentric screw pump according to an embodiment of the present invention.

Fig. 9 is a schematic perspective view of a part of the uniaxial eccentric screw pump of the present invention.

(symbol description)

10: connecting shaft

11: plate-like member

12: torsional shape part

13: cross section of

14: axis of symmetry

15: point of symmetry

30: single-shaft eccentric screw pump

31: pump mechanism

46: intermediate section

56: fluid transfer channel

60: rotor

73: rotating shaft (driving side rotating part)

80: driver

90: flexible connecting shaft (round bar)

Detailed Description

Hereinafter, the coupling shaft 10 according to an embodiment of the present invention will be described in detail with reference to the drawings.

The coupling shaft 10 of the present invention is used to couple a first member and a second member in various devices and mechanisms such as various pumps and compressors, and to transmit power of a power source from the first member to the second member. Therein, the connecting shaft 10 of the present invention is adapted to transfer an eccentric motion from a first component to a second component.

As shown in fig. 1, a connecting shaft 10 according to the present invention includes a twisted portion 12 formed by twisting a plate-like member 11 having a rectangular cross section 13 so as to continuously rotate as it advances in the axial direction.

The cross section 13 has a rectangular shape with a length in the short side direction a and a length in the long side direction b, and the axial length of the connecting shaft 10 is L. Here, the cross-sectional shape is formed as: the section from any position in the axial direction passes through the axial position. That is, the twisted portion 12 is formed by twisting the plate-like member in the axial direction so that the axial center of the cross section 13 is located on the axial line.

Further, the cross-sectional shape is formed such that: a direction in which the second moment of area (second moment of area) in the cross section 13 is smallest is set as a first direction, and a length in the first direction is different from a length in a second direction perpendicular to the first direction in the same cross section. In the present embodiment, a first direction in which a second moment of area in a cross section is smallest is a short side direction, and a length in the first direction is a. In the present embodiment, the short side direction in which the thickness is small corresponds to the first direction which is the direction in which the second moment of area is smallest. In addition, a second direction perpendicular to the first direction in the same cross section is a longitudinal direction, and the length in the second direction is b. That is, the length a in the first direction (short-side direction) is different from the length b in the second direction (long-side direction).

Here, the second moment of area in the first direction (short side direction) is expressed by the following equation.

(second moment of area in first direction) ba3/12

Further, the second moment of area in the second direction (longitudinal direction) is expressed by the following equation.

(second-directional second moment of area) ab3/12

As described above, by forming the cross-sectional shape so that the length in the first direction is different from the length in the second direction, the bending rigidity in the direction in which the second moment of area is smallest becomes low. That is, in the present embodiment, the bending rigidity in the short side direction in the cross section 13 becomes low. Thus, the flexibility in the short side direction in the cross section 13 becomes high. The other side is thick in the longitudinal direction, and thus has high bending rigidity. Therefore, the flexibility in the longitudinal direction is low. Thus, the characteristic of the second moment of area changes according to the ratio of the short side a to the long side b (β ═ b/a).

Further, as described above, the coupling shaft 10 has the twisted shape portion 12, and the cross-sectional shape is continuously twisted as it goes in the axial direction. Thus, each of the first direction and the second direction is continuously displaced while drawing an arc continuously. This causes the direction of low flexural rigidity and high flexibility to be continuously displaced in the circumferential direction. That is, for example, when one end of the coupling shaft 10 is connected to a power source as a first member of the uniaxial eccentric screw pump 30 and the other end is connected to the rotor 60 as a second member to rotate the coupling shaft 10, the direction in which the flexibility of the coupling shaft 10 is high and the direction in which the flexibility is low continuously rotate in the axial direction and are continuously displaced, which will be described in detail later. Therefore, the entire connecting shaft functions as a member having appropriate flexibility. Further, the degree of flexibility of the coupling shaft 10 can be appropriately adjusted according to the material used for the coupling shaft 10.

The connecting shaft 10 is configured to be continuously twisted as described above, and continuously displaced while being twisted in the axial direction in the second direction (longitudinal direction) having high bending rigidity. Accordingly, since the second moment of area is small and the bending rigidity is low in any direction of the coupling shaft 10 in the circumferential direction 360 °, a reaction force (restoring force) for restoring the coupling shaft 10 from the displaced state is also weakened. Further, when the coupling shaft 10 rotates, a part of the torque in the torsional direction applied to the torsional shape portion 12 having the torsional shape in the initial state is converted into a force in the axial direction by the torsional effect, and therefore, it is estimated that the torsional rigidity of the coupling shaft 10 is substantially improved. This suppresses torsion of the coupling shaft 10 generated when the rotational torque is applied.

As described above, the cross-sectional shape is not limited to the rectangular shape, and various cross-sectional shapes can be adopted as long as the second moment of area in the first direction is different from the second moment of area in the second direction. For example, as shown in the modification examples of (a) to (g) in fig. 2, the cross-sectional shape may be an elliptical shape, a parallelogram shape, a rounded corner shape with rounded corners, a rectangular shape with a portion rounded, a rhombus shape, or the like. In this case, as shown in the figure, the length in the first direction (short side) is represented by a, and the length in the second direction (long side) is represented by b.

In addition, when the cross-sectional shape is formed in a twisted shape that rotates continuously or in steps as it advances in the axial direction, it is preferable that the cross-sectional shape is at least one of a shape that is line-symmetrical with respect to the axis of symmetry 14 with a first axis that passes through the position of the torsional axis and extends in the first direction as the axis of symmetry 14, a shape that is line-symmetrical with respect to the axis of symmetry 16 with a second axis that passes through the position of the torsional axis and extends in the second direction as the axis of symmetry 16, and a shape that is point-symmetrical with respect to the point of symmetry 15 with the torsional axis as the point of symmetry 15, from the viewpoint of easy and accurate manufacturing. That is, the cross-sectional shape of the connecting shaft 10 may be a shape that is line-symmetric with respect to both the symmetry axes 14 and 16 and point-symmetric with respect to the symmetry point 15 as in the example of (a), (c), and (f) in fig. 2, a shape that is line-symmetric with respect to the symmetry axis 14 but asymmetric with respect to the symmetry axis 16 and the symmetry point 15 as in the example of (g) in fig. 2, a shape that is line-symmetric with respect to the symmetry axis 16 but asymmetric with respect to the symmetry axis 14 and the symmetry point 15 as in (h) in fig. 2, a shape that is point-symmetric with respect to the symmetry point 15 but asymmetric with respect to the symmetry axes 14 and 16 as in (b) and (d) in fig. 2, or the like.

Next, the structure of the twisted portion 12 of the coupling shaft 10 will be described in detail below.

In the embodiment of fig. 1, the coupling shaft 10 is formed with a twisted shape portion 12 having a total twist angle of 720 ° (the number of twists is two, hereinafter simply referred to as "two turns"). Here, the present inventors have earnestly studied and found that, when the total torsion angle is a multiple of 180 ° (0.5 turns) ± 20 °, the fluctuation of the reaction force can be reduced while allowing an appropriate displacement in the bending direction. This is presumably because: when the total torsion angle is a multiple of 180 °, the displacement in the bending direction and the torsion direction of 1 turn (360 °) can be uniformly covered (cover) with a half turn (180 °) centered on the rotation axis. Therefore, in the coupling shaft 10 of the present embodiment, since the displacement in the bending direction and the displacement in the twisting direction act while being equally dispersed over 360 °, the coupling shaft 10 has both appropriate flexibility and high rigidity in the twisting direction. Hereinafter, the case of ± 20 ° will be described.

Fig. 3 and 4 show graphs showing the evaluation results of the change in the reaction force with respect to the change in the total torsion angle and the displacement direction.

The evaluation uses a connecting shaft having the same conditions (i.e., the same material, cross-sectional shape, and overall length) except for the total torsion angle, and records the increase and decrease of the reaction force when the displacement direction is changed, with the reaction force when the other end is displaced only in the X direction with one end of the connecting shaft 10 fixed being 100%. The graph is recorded with the horizontal axis as the displacement direction and the vertical axis as the reaction force.

As is clear from fig. 3, the reaction force increases when the total torsion angle ψ is equal to or larger than 405 ° (1.125 turns), 450 ° (1.25 turns), or 495 ° (1.375 turns) which are not multiples of 180 °, as compared with 360 ° (1 turn) and 540 ° (1.5 turns) which are multiples of 180 °.

It can also be seen from fig. 4 that the reaction force decreases at 720 ° (2 turns) and 900 ° (2.5 turns) of the total torsion angle which is a multiple of 180 °, and increases in the region where the total torsion angle is not a multiple of 180 °.

As described above, when the total torsion angle is changed in stages from 360 ° (1 turn) to 900 ° (2.5 turns), the rate of change in the reaction force increases or decreases. Further, the rate of change of the reaction force decreases every time the total torsion angle is a multiple of 180 °. That is, when the total torsion angle exceeds 360 ° (1 turn), the rate of change of the reaction force increases, and as the total torsion angle approaches 540 ° (1.5 turns), the rate of change of the reaction force decreases. Thereafter, also every time the total torsion angle is a multiple of 180 °, the rate of change of the reaction force decreases, and as away from the multiple of 180 °, the rate of change of the reaction force increases. The graph shows relative values of the reaction force, and the absolute value of the reaction force tends to be lower as the total torsion angle is larger.

It is also understood that the rate of change of the reaction force decreases as the total torsion angle increases by multiples of 180 °, such as 360 ° (1 turn), 540 ° (1.5 turns), 720 ° (2 turns), and 900 ° (2.5 turns).

As described above, the coupling shaft 10 of the present invention preferably has a total torsion angle in the twisted shape portion 12 that is a multiple of 180 degrees. In consideration of an error in manufacturing the coupling shaft 10 and an error in the shape of the coupling portion when the first member and the second member are coupled in use, the error is preferably ± 20 ° in the total torsion angle. Further, when the total torsion angle is 180 ° (0.5 turns), although the effect of reducing the reaction force in the displacement direction which is most likely to bend is obtained, since the variation of the reaction force when the displacement direction is changed is large, it is preferable that the total torsion angle is 360 ° (1 turn) or more.

Next, the coupling shaft 10 of the present invention will be described below by taking as an example an embodiment that is comparable to the conventional flexible coupling shaft 90.

Fig. 6 shows the results of evaluation of six types of connection shafts 10 of the present invention having flexural rigidity equivalent to that of the conventional flexible connection shaft 90 under the precondition corresponding to the use conditions of the ordinary uniaxial eccentric screw pump, and comparing the length and torsional rigidity with the conventional flexible connection shaft 90. Fig. 7 is a schematic diagram of the coupling shafts 10a to 10f according to the comparative example and the modification of the present invention based on the table of fig. 6.

Hereinafter, an evaluation method of the above evaluation will be described with reference to fig. 5.

The preconditions for the flexible coupling shaft 90 of the comparative example and the coupling shaft 10 of the present invention are as follows. One end of the flexible coupling shaft 90 is fixed as a fixed end 90a, and the other end is displaced by 1mm in a direction perpendicular to the axial direction, thereby applying a torque of 1 Nm. At this time, the dimensions of the flexible coupling shaft 90 (comparative example) of a round bar and the coupling shaft 10 of the present invention were determined so that the reaction force to return the flexible coupling shaft 90 to the center was 1N and the stress due to bending and torsion (comparative stress) was 205MPa, and comparative evaluation was performed. In addition, the flexible coupling shaft 90 of the comparative example and the coupling shaft 10 of the present invention both used a material having a longitudinal elastic coefficient of 200GPa and a transverse elastic coefficient of 76.9 GPa.

As a comparative example, when the flexible connecting shaft 90 of a round bar was designed under the above-mentioned preconditions, the cross-section was 3.52mm and the length was 262 mm. The torsion angle of the flexible coupling shaft 90 caused by the torque at this time was 12.9 °.

In example 1, when a plate having a rectangular cross section 13 (cross-sectional dimensions: 1.6mm × 16.0mm, β ═ 10) was designed so that the total torsion angle was 360 ° (1 turn), a coupling shaft 10a having a length of 275mm was obtained. The torsion angle of the coupling shaft 10a by the torque is 6.55 °. Therefore, although the length of the coupling shaft 10a is increased by only + 5% as compared with the comparative example, the torsional angle generated by the torque is reduced by 50% as compared with the comparative example, and the torsional rigidity is greatly improved.

The connecting shaft 10 may be manufactured by twisting a plate-like member a desired number of times, or by cutting a columnar member. The coupling shaft 10 is not limited to this, and various methods can be employed.

The coupling shafts of examples 2 to 6 were designed as in example 1 under the conditions of the respective examples of fig. 5, and coupling shafts 10b to 10f were designed. The evaluation results of the respective examples are shown in fig. 5. From the evaluation results, it was found that not only the dimension was significantly reduced but also the bending rigidity was significantly improved in each example as compared with the comparative example.

The above-described embodiments are designed to facilitate comparison of the length and the bending rigidity under predetermined conditions for easy understanding, but the present invention is not limited thereto, and can be appropriately modified within the scope of the present invention. For example, a metal such as titanium or stainless steel, or a resin member such as other engineering plastic may be used as the material to be used.

Next, the uniaxial eccentric screw pump 30 according to an embodiment of the present invention will be described in detail below with reference to fig. 8 and 9. In the present embodiment, the coupling shaft 10 is used as a coupling member for coupling the rotor 60 (first member) and the power transmission mechanism 70 (second member) of the uniaxial eccentric screw pump 30.

The uniaxial eccentric screw pump 30 is a so-called rotary displacement pump configured with a pump mechanism 31 as a main part. The uniaxial eccentric screw pump 30 is constituted such that: the stator 50, the rotor 60, the power transmission mechanism 70, and the like are housed inside the case 40. The housing 40 is a metal cylindrical member, and is provided with a first opening 42 at one end side in the longitudinal direction. Further, a second opening portion 44 is provided on an outer peripheral portion of the housing 40. The second opening portion 44 communicates with the internal space of the housing 40 at an intermediate portion 46 located at a lengthwise intermediate portion of the housing 40.

The first opening 42 and the second opening 44 function as a suction port and a discharge port of the pump mechanism 31, respectively. The uniaxial eccentric screw pump 30 can function with the first opening 42 as the discharge port and the second opening 44 as the suction port by rotating the rotor 60 in the normal direction. By rotating the rotor 60 in the reverse direction, the first opening 42 can function as an intake port and the second opening 44 can function as an exhaust port.

The stator 50 is a member formed of a material mainly composed of an elastomer such as rubber or a resin, and has a substantially cylindrical outer shape. The stator 50 is a member having an inner peripheral surface 52 in a shape having n +1 female screws (n is 1 in the present embodiment). Further, the through-hole 54 of the stator 50 is formed as: the cross-sectional shape (opening shape) of the stator 50 is substantially oval when viewed from any position in the longitudinal direction.

The rotor 60 is a shaft body made of metal and having a shape with n male screws (n is 1 in the present embodiment). The rotor 60 is formed as: the cross-sectional shape of the sheet is substantially perfect circular when viewed at any position in the longitudinal direction. The rotor 60 is inserted into the through hole 54 formed in the stator 50, and is capable of freely rotating eccentrically within the through hole 54.

When the rotor 60 is inserted into the stator 50, the outer peripheral surface 62 of the rotor 60 and the inner peripheral surface 52 of the stator 50 are in contact with each other along a tangent line therebetween, and a fluid transfer passage 56 (cavity) is formed between the inner peripheral surface 52 of the stator 50 and the outer peripheral surface of the rotor 60. The fluid delivery channel 56 extends helically along the length of the stator 50 or rotor 60.

When the rotor 60 is rotated in the through hole 54 of the stator 50, the fluid delivery passage 56 advances in the longitudinal direction of the stator 50 while rotating in the stator 50. Therefore, when the rotor 60 is rotated, the fluid is sucked into the fluid transfer passage 56 from one end side of the stator 50, transferred toward the other end side of the stator 50 in a state where the fluid is confined in the fluid transfer passage 56, and discharged to the other end side of the stator 50. The pump mechanism 31 of the present embodiment can be used by rotating the rotor 60 in the forward direction, and pressurizes and conveys the viscous liquid sucked from the second opening 44 and discharges the viscous liquid from the first opening 42.

The power transmission mechanism 70 is used to transmit power from the driver 80 to the rotor 60. The power transmission mechanism 70 includes a power transmission portion 72 and an eccentric rotation portion 74. The power transmission portion 72 is provided at one end side in the longitudinal direction of the housing 40. The power transmission unit 72 includes a rotary shaft 73 that rotates by receiving power from the driver 80. The rotary shaft 73 is pivotally supported by a bearing 75 and transmits power of the driver 80 to the eccentric rotary portion 74.

The eccentric rotation portion 74 is provided on the intermediate portion 46 of the housing 40. The eccentric rotation portion 74 is a portion that connects the power transmission portion 72 and the rotor 60 so as to be able to transmit power. The eccentric rotation portion 74 is the coupling shaft 10. Thus, the eccentric rotating portion 74 can transmit the rotational power generated by operating the actuator 80 to the rotor 60, thereby eccentrically rotating the rotor 60.

The coupling shaft 10 connects the power transmission unit 72 and the rotor 60 such that the rotor 60 can eccentrically rotate while rotating inside the stator 50 and revolving around the inner circumferential surface 52 of the stator 50. The coupling shaft 10 has a characteristic of allowing flexure in a direction intersecting the axial direction and being capable of suppressing torsion in a direction around the axial direction.

The coupling shaft 10 has a coupling portion 76 on the drive side and a coupling portion 76 on the rotor side, and a twisted portion 12 is formed therebetween. Thus, the coupling shaft 10 can transmit the rotational driving force generated by operating the actuator 80 to the rotor 60, and eccentrically rotate the rotor 60.

As shown in fig. 9, the coupling shaft 10 is coupled to the rotor 60 and the rotary shaft 73 as the power transmission unit 72 via a coupling unit 76. The connection portion 76 has a short cylindrical base for connecting the rotor 60 and the rotary shaft 73. The connecting portion 76 is provided with "R" at a wire connecting portion connecting the base and the torsion shape portion 12. By providing the "R" in this manner, stress concentration on the connection portion 76 can be prevented, and breakage of the connection shaft 10 at the connection portion 76 can be prevented.

The connecting portion 76 includes screw portions (not shown) having reverse threads formed on the rotor 60 side and the rotating shaft 73 side. In addition, screw holes (not shown) having a reverse-threaded shape are provided in the base end portion of the rotor 60 and the tip end portion of the rotary shaft 73. The rotor 60 and the coupling shaft 10 are coupled by screwing the screw portion of the coupling portion 76 into the screw hole. The rotation shaft 73 and the coupling shaft 10 are coupled by screwing the screw portion of the coupling portion 76 into the screw hole. Further, when "R" is provided to connect the coupling shaft 10 to the rotor 60 or the rotary shaft 73, an error may occur in the total torsion angle. Therefore, as described above, the total torsion angle is preferably a multiple of 180 ° plus ± 20 ° obtained by adding the error and the manufacturing error.

In the uniaxial eccentric screw pump 30 of the present invention, the coupling shaft 10 is used to connect the rotary shaft 73 and the rotor 60. That is, as the coupling shaft 10, a coupling shaft is used which allows flexure in a direction intersecting the axial direction and can suppress torsion in a direction around the axial direction. Therefore, in the uniaxial eccentric screw pump 30, even when used under severe use conditions such as pressurization and conveyance of a low-viscosity fluid at a low speed, the rotor 60 can be smoothly rotated inside the stator 50 without generating stick slip or pulsation. Therefore, the uniaxial eccentric screw pump 30 of the present invention is excellent in operation stability.

In the uniaxial eccentric screw pump 30 of the present invention, since the connecting shaft 10 having appropriate flexibility and high torsional rigidity is used, the distance between the rotary shaft 73 and the rotor 60 is not increased as in the case of using the flexible connecting shaft 90 of a round bar in the related art. This makes it possible to make the uniaxial eccentric screw pump 30 compact in the longitudinal direction. Further, since the coupling shaft 10 is connected to the rotor 60 and the rotary shaft 73 by the screw portion of the connecting portion 76 as described above, foreign matter is not generated due to abrasion as compared to a universal joint. Therefore, in the uniaxial eccentric screw pump 30, the problem of mixing of foreign matter into the fluid with the wear of the connecting shaft 10 can be suppressed to the maximum.

In the uniaxial eccentric screw pump 30 of the present invention, it is preferable that the twisting direction of the rotor 60 is aligned with the twisting direction of the coupling shaft 10. As a result, the fluid in the housing 40 can be pushed toward the stator 50 as the connecting shaft 10 rotates. Therefore, even a high-viscosity fluid can be appropriately pushed into the stator 50 side from the fluid in the housing 40. This makes it easy to fill the volume of the internal space of the stator 50 with the fluid, thereby improving the conveying efficiency. In addition, when the pump is used in a reverse suction mode, the fluid discharged from the stator 50 can be further assisted in being discharged to the outside of the housing 40.

In the uniaxial eccentric screw pump 30, the example in which the shaft 10, the rotor 60, and the rotary shaft 73 of the power transmission portion 72 are connected to each other via the connection portion 76 is shown, but the connection may be performed by another method. For example, the connection may be made by providing a screw shaft at an end of the rotor 60 or an end of the rotary shaft 73, providing a screw hole on the connection shaft 10 side, and screwing the screw shaft into the screw hole. In the present embodiment, the coupling shaft 10 is connected to the rotor 60 and the rotary shaft 73 by screws, but connection by bolts, welding, or the like is not excluded, and various connection methods can be used depending on the application.

The coupling shaft 10 of the present embodiment can be used not only for the uniaxial eccentric screw pump 30 described above but also as an eccentric shaft of various devices. For example, the present invention can be suitably used in a field utilizing eccentric rotation, such as a pump, a compressor, and a reciprocating mechanism.

Further, the coupling shaft 10 of the present embodiment is formed with the twisted shape portion 12, and the shape of the cross section of the twisted shape portion 12 orthogonal to the axial direction of the coupling shaft 10 is a shape that continuously twists as it advances in the axial direction, but instead, a twisted shape portion that twists so as to rotate intermittently in a stepwise manner may be formed at least in part.

The above is an embodiment of the present invention, but the above embodiment is merely an embodiment, and the present invention is not limited to the above embodiment.

[ industrial applicability ]

The present invention can be used in a field where low bending rigidity and high torsional rigidity are required, and can be suitably applied to an eccentric shaft that requires flexibility and high torsional rigidity. Further, the uniaxial eccentric screw pump can be suitably used in a field where viscous liquid needs to be discharged.

Claims

1. A connecting shaft having flexibility and connecting a first member and a second member, the connecting shaft being characterized in that,

a twisted shape portion having a shape of a cross section orthogonal to an axial direction of the connecting shaft, the shape being a shape twisted continuously as it advances in the axial direction or a shape twisted in an intermittent stepwise rotation, is provided in at least a part of the connecting shaft;

the second moment of area on the cross section is different in a first direction and a second direction, wherein the first direction is a direction orthogonal to the axis direction and in which the second moment of area on the cross section is smallest, and the second direction is orthogonal to the first direction on the same cross section.

2. The joint shaft according to claim 1,

the torsion axis of the coupling shaft is within the shape of the cross section when viewed in cross section from any position in the axis direction, and the shape of the cross section is at least any one of a shape that is line-symmetrical with respect to a first axis that passes through the position of the torsion axis and extends in the first direction, a shape that is line-symmetrical with respect to a second axis that passes through the position of the torsion axis and extends in the second direction, and a shape that is point-symmetrical with respect to the torsion axis.

3. The connecting shaft according to claim 1 or 2,

the total twist angle in the twist profile is a multiple of 180 degrees ± 20 degrees.

4. A uniaxial eccentric screw pump, comprising:

a drive-side rotating section that rotates by power of the actuator;

a rotor formed of a male screw shaft body;

a stator having a female screw formed on an inner peripheral surface thereof, the rotor being insertable into the stator; and

a connecting shaft connecting the drive-side rotating portion and the rotor in such a manner that: the rotor can be eccentrically rotated so as to revolve along the inner circumferential surface of the stator while rotating inside the stator;

the joint shaft according to any one of claims 1 to 3.

5. The uniaxial eccentric screw pump of claim 4,

the direction of torsion of the rotor coincides with the direction of torsion of the connecting shaft.