JP7594786B2 - Electric pump shaft coupling - Google Patents

Description

This disclosure relates to a shaft coupling that is applied to a multi-stage pump.

For example, in the multi-stage pump described in Patent Document 1, a pump section with a downward suction port is combined with a pump section with an upward suction port, thereby canceling out the axial loads (also called thrust loads) and reducing the thrust load.

JP 2020-70792 A

Through prototype testing (including numerical simulations), the inventors discovered the cause of damage to multi-stage pumps caused by cavitation.

In other words, if cavitation occurs in any of the pump sections, the thrust load generated in that pump section where cavitation occurs becomes smaller, making it impossible to properly offset the thrust load, resulting in a large thrust load across the entire multi-stage pump.

When the thrust load becomes large, there is a risk that the pump main shaft will be displaced axially at the shaft coupling that connects the pump main shaft to the motor main shaft. If the pump main shaft is displaced axially, the rotating impeller and the non-rotating pump housing may come into contact, causing damage to at least one of them.

In view of the above, this disclosure discloses an example of an invention that can suppress damage to a multi-stage pump caused by the occurrence of cavitation.

A shaft coupling applied to a multi-stage pump including a first pump section (20A) having a first impeller (22A) rotated by a pump main shaft (21) and a first pump housing (23A) that houses the first impeller (22A) and has an inlet on one axial side of the pump main shaft (21), and a second impeller (22B) rotated by the pump main shaft (21) and a second pump section (20B) having a second pump housing (23B) that houses the second impeller (22B) and has an inlet on the other axial side of the pump main shaft (21), the shaft coupling transmitting the rotational force of an electric motor (10) to the pump main shaft (21) desirably has at least one of the following configurations, for example:

That is, the components are a coupling body (32) having a first cylindrical portion (32C) into which the motor shaft (11) of the electric motor (10) is inserted, and a second cylindrical portion (32D) that is positioned on the same axis as the first cylindrical portion (32C) and rotates integrally with the first cylindrical portion (32C) and into which the pump shaft (21) is inserted, a first engagement portion (33A) provided on the first cylindrical portion (32C) and transmits the rotational force of the motor shaft (11) to the first cylindrical portion (32C), a second engagement portion (34A) provided on the second cylindrical portion (32D) and transmits the rotation of the second cylindrical portion (32D) to the pump shaft (21), and a restriction portion (35) that restricts the displacement of the pump shaft (21) in one axial direction and the other axial direction relative to the motor shaft (11).

As a result, the electric pump shaft coupling restricts the pump main shaft (21) from being displaced in one axial direction or the other direction relative to the motor main shaft (11). Therefore, the pump main shaft (21) can be prevented from being displaced in the axial direction. In turn, damage to the multi-stage pump due to the occurrence of cavitation can be prevented.

Incidentally, the symbols in parentheses above are examples showing the corresponding relationship with the specific configurations etc. described in the embodiments described below, and the present disclosure is not limited to the specific configurations etc. shown by the symbols in parentheses above.

1 is an external view of an electric pump according to a first embodiment; 1 is a partial cross-sectional view of an electric pump according to a first embodiment. FIG. FIG. 1 is an external view of a shaft coupling according to a first embodiment. FIG. 2 is an exploded view of the shaft coupling according to the first embodiment. FIG. 2 shows the shaft coupling with the second coupling body removed. FIG.

The following "embodiment of the invention" shows an example of an embodiment that falls within the technical scope of this disclosure. In other words, the invention-specific matters described in the claims are not limited to the specific configurations and structures shown in the embodiment below.

Note that arrows and diagonal lines indicating directions in each figure are provided to facilitate understanding of the relationships between the figures and the shapes of each component or part. Therefore, the invention shown in this disclosure is not limited to the directions shown in each figure. Diagonal lines do not necessarily indicate cross-sectional views.

At least one of each of the components or parts described with a reference number is provided, unless otherwise specified by "one". In other words, unless otherwise specified by "one", two or more of the components may be provided. The electric pump shown in this disclosure includes at least the components or parts described with a reference number, as well as the structural parts shown in the drawings.

First Embodiment
<1. Overview of electric pump>
In this embodiment, an example of an electric pump and a shaft coupling for an electric pump (hereinafter referred to as a coupling) according to the present disclosure is applied to a water supply system that requires a high head, such as a water supply system for a building.

As shown in FIG. 1, the electric pump 1 according to this embodiment has a motor section 10 formed by an electric motor, a pump section 20, and a joint housing section 30. The motor section 10, the pump section 20, and the pump section 20 are arranged in series in this order.

<Pump section configuration>
As shown in Fig. 2, the pump section 20 is a multi-stage turbine pump. A plurality of impellers 22 are arranged in series along the longitudinal direction of a pump main shaft 21. Therefore, the plurality of impellers 22 are rotationally driven by the single pump main shaft 21.

The pump housings 23 that house each impeller 22 are provided in the same number as the impellers 22. These pump housings 23 are also stacked and arranged along the longitudinal direction of the pump main shaft 21.

In other words, in this embodiment, one turbine pump is composed of one impeller 22 and one pump housing 23, and each turbine pump is stacked along the pump main shaft 21 to form the pump section 20 (multi-stage turbine pump).

The multiple impellers 22 include an impeller belonging to a first group (hereinafter referred to as a first impeller 22A) and an impeller belonging to a second group (hereinafter referred to as a second impeller 22B).

Similarly, the multiple pump housings 23 include a pump housing that belongs to a first group (hereinafter referred to as a first pump housing 23A) and a pump housing that belongs to a second group (hereinafter referred to as a second pump housing 23B).

The first impeller 22A and the first pump housing 23A constitute the first pump section 20A. The second impeller 22B and the second pump housing 23B constitute the second pump section 20B.

In other words, the pump section 20 according to this embodiment is an eight-stage turbine pump having a four-stage first pump section 20A and a four-stage second pump section 20B. The pump section 20 according to this embodiment is used and installed with the longitudinal direction of the pump main shaft 21 aligned with the vertical direction.

Each turbine pump belonging to the first pump section 20A has a suction port on one axial side (in this embodiment, the lower side) of the pump main shaft 21. Each turbine pump belonging to the second pump section 20B has a suction port on the other axial side (in this embodiment, the upper side) of the pump main shaft 21.

As a result, when the pump main shaft 21 rotates and pump action occurs, a thrust load is generated in one axial direction in each turbine pump belonging to the first pump section 20A, and a thrust load is generated in the other axial direction in each turbine pump belonging to the second pump section 20B.

In the pump section 20 according to this embodiment, the first pump section 20A is disposed below the second pump section 20B, and water is sucked in from the first pump section 20A. A downward thrust load is generated in the first pump section 20A, and an upward thrust load is generated in the second pump section 20B.

2. Configuration of shaft coupling
1, the joint housing 30 is disposed between the motor section 10 and the pump section 20. During use, the motor section 10 is located above the pump section 20. Therefore, the motor main shaft 11 (see FIG. 2) of the motor section 10 extends vertically.

As shown in FIG. 2, the coupling 31 is housed in the coupling storage section 30. An operator who maintains and inspects the electric pump 1 can maintain and inspect the coupling 31 by removing the cover 30A provided in the coupling storage section 30. The cover 30A is provided on one horizontal side and the other horizontal side of the coupling 31.

As shown in FIG. 3, the shaft coupling 31 connects the motor main shaft 11 and the pump main shaft 21, and transmits the rotational force of the motor main shaft 11 to the pump main shaft 21. The motor section 10 and the pump section 20 are arranged so that the central axis of the motor main shaft 11 and the central axis of the pump main shaft 21 coincide with each other.

The shaft coupling 31 has a generally cylindrical coupling body 32. As shown in FIG. 4, the coupling body 32 in this embodiment is composed of a first coupling body 32A and a second coupling body 32B.

The first joint body 32A and the second joint body 32B are divided into two parts by a split surface that includes the central axis Lo and a virtual line perpendicular to the central axis Lo. The first joint body 32A and the second joint body 32B are fastened and fixed by a plurality of bolts B.

In this embodiment, a gap 32H (see FIG. 3) exists on the opposing surfaces of the first joint body 32A and the second joint body 32B at least around the area where the bolt B is inserted, even when the bolt B is tightened.

For this reason, the opposing surfaces are provided with ridges 32E and 32F (see FIG. 4) that extend parallel to the axial center line Lo. As shown in FIG. 5, the two ridges 32E are provided in close proximity to the motor main shaft 11. The two ridges 32F are provided in close proximity to the pump main shaft 21.

As shown in FIG. 3, the joint body 32 has a first cylindrical portion 32C and a second cylindrical portion 32D. The first cylindrical portion 32C is the portion into which the motor main shaft 11 is inserted. The second cylindrical portion 32D is the portion into which the pump main shaft 21 is inserted.

As shown in FIG. 5, the second cylindrical portion 32D is positioned on the same axis as the first cylindrical portion 32C and rotates integrally with the first cylindrical portion 32C. In other words, the first joint body 32A and the second joint body 32B are provided with portions that constitute the first cylindrical portion 32C and the second cylindrical portion 32D, respectively (see FIG. 4).

As shown in FIG. 4, the joint body 32 is provided with a parallel key 33A and a parallel pin 34A. The parallel key 33A is an example of a first engagement portion. The parallel pin 34A is an example of a second engagement portion.

That is, as shown in FIG. 3, the parallel key 33A transmits the rotational force of the motor main shaft 11 to the first cylindrical portion 32C. Specifically, the parallel key 33A fits into and engages with key grooves 33B, 33C provided on the first cylindrical portion 32C (in this embodiment, the second joint body 32B) and the motor main shaft 11, respectively.

The parallel pin 34A transmits the rotation of the second cylindrical portion 32D to the pump main shaft 21. Specifically, as shown in FIG. 4, the parallel pin 34A penetrates the pump main shaft 21 in a direction perpendicular to the pump main shaft 21 and fits into a recess 34B provided in the second cylindrical portion 32D.

As a result, the rotational force of the motor main shaft 11 is transmitted to the joint body 32 via the parallel key 33A. The rotational force transmitted to the joint body 32 is transmitted to the pump main shaft 21 via the parallel pin 34A.

2.1 Regulating section
4, the shaft coupling 31 includes a restricting portion 35. The restricting portion 35 restricts the pump main shaft 21 from being displaced relative to the motor main shaft 11 in one axial direction or the other direction.

The restricting portion 35 according to this embodiment is configured to have at least a parallel pin 34A, a spacer 36, and a retaining ring 37. As shown in FIG. 5, the retaining ring 37 is attached to the motor main shaft 11 and engages the first cylindrical portion 32C, i.e., the joint body 32.

The retaining ring 37 prevents the first cylindrical portion 32C, i.e., the coupling body 32, from being displaced toward the pump portion 20 (in this embodiment, downward) relative to the motor main shaft 11. The retaining ring 37 in this embodiment is a substantially C-shaped concentric retaining ring.

The spacer 36 is a block-shaped member disposed in the space 32G between the pump main shaft 21 and the motor main shaft 11. In other words, the spacer 36 is disposed between the lower end of the motor main shaft 11 and the upper end of the pump main shaft 21.

Therefore, even if the joint body 32 and the pump main shaft 21 are displaced toward the motor section 10 (upward in FIG. 5), the spacer 36 contacts the lower end of the motor main shaft 11 and the upper end of the pump main shaft 21, so that the pump main shaft 21 is restricted from being displaced in one axial direction (upward in FIG. 5) relative to the motor main shaft 11 beyond a predetermined dimension.

Even if the joint body 32 and the pump main shaft 21 are displaced toward the pump section 20 (downward in FIG. 5), the joint body 32 is locked by the retaining ring 37, and the pump main shaft 21 is connected to the joint body 32 by the parallel pin 34A, so that the pump main shaft 21 is prevented from displacing in the other axial direction (downward in FIG. 5) relative to the motor main shaft 11 beyond a predetermined dimension.

<Spacer Details (see FIG. 6)>
The spacer 36 is a substantially disk-shaped member having a central axis Lo as its center line. A rubber annular body 36A is disposed between the outer periphery of the spacer 36 and the inner circumferential surface of the joint body 32. In this embodiment, the spacer 36 is made of metal, and the annular body 36A is an O-ring made of nitrile rubber.

The spacer 36 or the joint body 32 (the spacer 36 in this embodiment) is provided with a protrusion 36B. The protrusion 36B is a portion that restricts the spacer 36 from rotating relative to the joint body 32 around the central axis Lo.

Specifically, the protrusion 36B is configured as a ridge extending in a direction perpendicular to the central axis Lo, and is sandwiched in a gap 32H (see FIG. 3) that occurs between the opposing surfaces of the first joint body 32A and the second joint body 32B.

3. Features of the electric pump (particularly, the shaft coupling) according to this embodiment
The shaft coupling 31 according to this embodiment restricts the pump main shaft 21 from being displaced in one direction or the other direction in the central axis direction Lo relative to the motor main shaft 11. This makes it possible to suppress the pump main shaft 21 from being displaced in the central axis direction Lo. As a result, damage to the multi-stage pump due to the occurrence of cavitation can be suppressed.

The spacer 36 is generally disk-shaped with the central axis Lo as its center line. This prevents the spacer 36 from becoming eccentric when the shaft coupling 31 rotates, thereby preventing adverse effects on the rotation of the motor main shaft 11 and the pump main shaft 21.

A rubber annular body 36A is disposed between the outer periphery of the spacer 36 and the joint body 32. This prevents the spacer 36 from vibrating unnecessarily due to frictional forces acting on the annular body 36A. This in turn prevents noise and the generation of wear powder, and allows the spacer 36 to rotate integrally with the joint body 32.

The protrusion 36B of the spacer 36 is sandwiched in the gap 32H that occurs on the opposing surfaces of the first joint body 32A and the second joint body 32B. This automatically determines the position of the spacer 36 relative to the joint body 32.

Other Embodiments
In the above-described embodiment, the pump main shaft 21 is formed of a single shaft material. However, the present disclosure is not limited to this. That is, the present disclosure may be configured such that, for example, a single pump main shaft 21 is formed by connecting a plurality of pump main shafts in series.

The restricting portion 35 according to the embodiment described above is configured to have at least the parallel pin 34A, the spacer 36, and the retaining ring 37. However, the present disclosure is not limited to this. In other words, the present disclosure may have, for example, any of the following configurations (1) to (4).

(1) A configuration in which the spacer 36 is eliminated, the upper end side of the first tubular portion 32A is restricted by a second retaining ring, and the retaining ring 37 and the second retaining ring restrict the joint body 32 from being displaced toward the motor portion 10, i.e., upward. (2) A configuration in which the spacer 36, the retaining ring 37, and the parallel key 33A are eliminated, and the first tubular portion 32A and the motor main shaft 11 are connected by a second parallel pin that penetrates the motor main shaft 11 in the same manner as the pump main shaft 21. (3) A configuration in which the spacer 36 is eliminated, and a groove having a groove width equal to the thickness dimension of the retaining ring 37 is provided on the inner peripheral surface of the joint body, and the outer peripheral side of the retaining ring 37 is fitted into the groove, i.e., a configuration in which the retaining ring 37 restricts both upward and downward displacement of the joint body 32. (4) A configuration in which the spacer 36 is eliminated and the gap between the lower end of the motor main shaft 11 and the upper end of the pump main shaft 21 is sufficiently small, that is, the lower end of the motor main shaft 11 and the upper end of the pump main shaft 21 come into contact with each other, thereby restricting both vertical displacement of the joint body 32. In the above-described embodiment, the pin (second engagement portion) is configured by the parallel pin 34A. However, the present disclosure is not limited to this. That is, in the present disclosure, the pin (second engagement portion) may be configured by, for example, a tapered pin.

In the above embodiment, the first engagement portion is configured with a parallel key. However, the present disclosure is not limited to this. That is, the present disclosure also allows the first engagement portion to be configured with, for example, a tapered key, splines, serrations, etc.

The electric pump 1 according to the embodiment described above is a vertical multi-stage pump in which the central axis Lo coincides with the vertical direction. However, the present disclosure is not limited to this. In other words, the present disclosure may be, for example, a multi-stage pump in which the central axis Lo coincides with the horizontal direction.

The electric pump 1 according to the embodiment described above is an eight-stage multi-stage pump in which the first pump section 20A is disposed below the second pump 20B. However, the present disclosure is not limited to this. In other words, the present disclosure may be, for example, a four-stage multi-stage pump in which the first pump section 20A is disposed above the second pump 20B.

Furthermore, the present disclosure is not limited to the above-mentioned embodiments as long as it conforms to the spirit of the disclosure described in the above-mentioned embodiments. Therefore, the present disclosure may be a configuration in which at least two of the above-mentioned embodiments are combined, or a configuration in which any of the constituent elements illustrated or the constituent elements described with reference numerals in the above-mentioned embodiments are eliminated.

REFERENCE SIGNS LIST 1... Electric pump 10... Motor section 11... Motor main shaft 20... Pump section 20A... First pump section 20B... Second pump section 21... Pump main shaft 22... Impeller 22A... First impeller 22B... Second impeller 23... Pump housing 23A... First pump housing 23B... Second pump housing 30... Coupling storage section 31... Shaft coupling 32... Coupling body 33A... Parallel key 33B... Key groove 34A... Parallel pin 35... Restricting section 36... Spacer 36A... Annular body 36B... Convex section 37... Retaining ring

Claims (7)

A shaft coupling is applied to a multi-stage pump including a first pump section having a first impeller rotated by a pump main shaft and a first pump housing that houses the first impeller and has a suction port on one axial side of the pump main shaft, and a second pump section having a second impeller rotated by the pump main shaft and a second pump housing that houses the second impeller and has a suction port on the other axial side of the pump main shaft, the shaft coupling transmitting a rotational force of an electric motor to the pump main shaft,
a coupling main body having a first cylindrical portion into which a motor main shaft of the electric motor is inserted, and a second cylindrical portion located coaxially with the first cylindrical portion, rotating integrally with the first cylindrical portion, and into which the pump main shaft is inserted, the coupling main body for transmitting rotation of the motor main shaft to the pump main shaft ;
a first engagement portion that transmits a rotational force of the motor main shaft to the first cylindrical portion;
a second engagement portion that transmits rotation of the second cylindrical portion to the pump main shaft;
a restricting portion that restricts displacement of the pump main shaft in one axial direction and the other axial direction relative to the motor main shaft, the restricting portion having at least a spacer disposed in a space between the pump main shaft and the motor main shaft, and a retaining ring that is attached to the motor main shaft and engages the first cylindrical portion, the retaining ring restricting displacement of the first cylindrical portion toward the first pump portion ,
A shaft coupling for an electric pump in which, when the spacer comes into contact with the lower end of the motor shaft, the pump shaft is restricted from being displaced in one axial direction relative to the motor shaft beyond a predetermined dimension, even if the coupling body and the pump shaft are displaced toward the electric motor section . a pin that penetrates the pump main shaft in a direction perpendicular to the pump main shaft and is fitted into the second cylindrical portion, the pin constituting the second engagement portion;
2. The electric pump shaft coupling according to claim 1 , wherein the restriction portion is constituted by the pin, the spacer, and the retaining ring. The spacer is generally disk-shaped with its axis as its center line,
3. The electric pump shaft coupling according to claim 1 , further comprising an annular rubber member disposed between an outer periphery of the spacer and the coupling body. A protrusion is provided on one of the spacer and the joint body,
4. The electric pump shaft coupling according to claim 1 , wherein the protrusion restricts rotation of the spacer relative to the coupling body about an axis line. The joint body can be divided into two parts using a virtual plane including an axis and a virtual line perpendicular to the axis as a dividing surface. When one of the divided joint bodies is a first joint body and the other is a second joint body,
5. The electric pump shaft coupling according to claim 4, wherein the convex portion is configured as a ridge extending in a direction perpendicular to the axis , and is sandwiched in a gap generated between opposing surfaces of the first coupling body and the second coupling body . a first pump section including a first impeller that is rotationally driven by a pump main shaft and a first pump housing that houses the first impeller and has a suction port provided on one axial side of the pump main shaft;
a second pump section including a second impeller that is rotationally driven by the pump main shaft and a second pump housing that houses the second impeller and has a suction port provided on the other axial side of the pump main shaft;
an electric motor that rotates the pump main shaft;
a shaft coupling that transmits a rotational force of a motor shaft of the electric motor to the pump main shaft,
The shaft coupling comprises:
a coupling body having a first cylindrical portion into which a motor main shaft of the electric motor is inserted, and a second cylindrical portion located coaxially with the first cylindrical portion, rotating integrally with the first cylindrical portion, and into which the pump main shaft is inserted, for transmitting rotation of the motor main shaft to the pump main shaft;
a first engagement portion that transmits a rotational force of the motor main shaft to the first cylindrical portion;
a second engagement portion that transmits rotation of the second cylindrical portion to the pump main shaft; and a regulating portion that regulates displacement of the pump main shaft in one axial direction and the other axial direction relative to the motor main shaft, the regulating portion having at least a spacer disposed in a space between the pump main shaft and the motor main shaft, and a retaining ring that is attached to the motor main shaft and engages the first cylindrical portion, the retaining ring restricting displacement of the first cylindrical portion toward the first pump portion ,
An electric pump in which, by the spacer coming into contact with the lower end of the motor shaft, even if the coupling body and the pump main shaft are displaced toward the electric motor section, the pump main shaft is restricted from being displaced in one axial direction relative to the motor main shaft beyond a predetermined dimension . a first pump section including a first impeller that is rotationally driven by a pump main shaft extending in a vertical direction, and a first pump housing that houses the first impeller and has a suction port provided on a lower side thereof;
a second pump section including a second impeller that is rotationally driven by the pump main shaft and a second pump housing that houses the second impeller and has an inlet port on an upper side, and that pumps out the fluid discharged from the first pump section;
an electric motor that rotates and drives the pump main shaft, the electric motor being disposed above the first pump unit and the second pump unit, the motor main shaft extending in a vertical direction;
a shaft coupling that transmits a rotational force of the motor main shaft to the pump main shaft,
The shaft coupling comprises:
a coupling body having a first cylindrical portion into which a motor main shaft of the electric motor is inserted, and a second cylindrical portion located coaxially with the first cylindrical portion, rotating integrally with the first cylindrical portion, and into which the pump main shaft is inserted, for transmitting rotation of the motor main shaft to the pump main shaft ;
a first engagement portion that transmits a rotational force of the motor main shaft to the first cylindrical portion;
a second engagement portion that transmits rotation of the second cylindrical portion to the pump main shaft; and
the pump main shaft includes a spacer disposed in a space between the pump main shaft and the motor main shaft, a pin that penetrates the pump main shaft in a direction perpendicular to the pump main shaft and is fitted into the second cylindrical portion, the pin constituting the second engagement portion, and a stop ring that is attached to the motor main shaft and engages the first cylindrical portion, the stop ring restricting displacement of the first cylindrical portion toward the first pump portion ,
Furthermore, when the spacer comes into contact with the lower end of the motor shaft, even if the coupling body and the pump main shaft are displaced toward the electric motor unit, the pump main shaft is restricted from being displaced in one axial direction relative to the motor main shaft beyond a predetermined dimension .

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