A hollow shaft for a pump and a centrifugal pump having the same

Abstract

The present invention relates to a hollow shaft for a pump and a centrifugal pump having the hollow shaft. The hollow shaft is mounted on the centrifugal pump, which includes a motor, a pump head assembly, an impeller, and a shielding tank. The motor includes a rotor assembly and a stator assembly. The hollow shaft is part of the rotor assembly. The end of the hollow shaft near the pump head assembly is a shaft head connected to a low-pressure area, and the end away from the pump head assembly is a shaft tail located within the shielding tank. The shaft head drives the impeller to rotate. The outer wall of the hollow shaft is provided with a spiral groove, and the inner area of ​​the hollow shaft is penetrated by a stepped through hole for liquid to flow from the high-pressure area to the low-pressure area, thereby achieving liquid circulation. Compared with the existing technology, the present invention has the advantages of providing an effective liquid circulation loop and alleviating the impact of scale on the operating performance of the rotating shaft.

Description

Technical Field

[0001] The present invention relates to the technical field of shaft parts, in particular to a hollow shaft for a pump and a centrifugal pump having the hollow shaft. Background Art

[0002] Centrifugal pumps used in heating and cooling systems operate in liquid environments. A typical feature of wet-running centrifugal pumps is that the rotor and bearing support system are housed within a shielded can, converting a dynamic seal into a static seal and effectively preventing liquid leakage. The bearing support of a typical centrifugal pump is mounted within the shielded can, providing support for the bearings and isolating the shielded can from the pump chamber into two relatively closed, independent chambers: the impeller chamber and the rotor chamber. The rotating shaft of the centrifugal pump is placed in the rotor, which is the transmission device of the motor rotor and impeller. When the pump is not running, due to the temperature difference and thermal expansion of the liquid, the liquid flows axially along the lubricating film between the rotating shaft and the radial bearing, which easily deposits scale between the rotating shaft and the radial bearing, causing the rotating shaft to rotate poorly, which increases the starting resistance of the pump unit; when the pump unit is working, the impeller rotates in the impeller chamber. In order to drive the liquid circulation in the pump, the liquid is required to enter the rotor chamber from the impeller chamber to cool the motor, and then return to the impeller chamber. It is necessary to design a feasible fluid channel. When considering the solution of placing the flow channel for the fluid to return from the rotor chamber to the impeller chamber in the middle of the shaft, the fluid channel inside the shaft facing the water inlet of the water pressure chamber needs to be slender. This structure is extremely difficult to process during manufacturing, and it is extremely difficult to demold even if it is compression molded.

[0003] WO 2008 / 058639 A1 discloses a centrifugal pump for an electric motor, specifically disclosing another flow path through the hollow rotor shaft to degas the rotor chamber. However, the centrifugal pump still has the above-mentioned problems.

[0004] Therefore, in order to solve the above-mentioned defects of the prior art, there is an urgent need for a hollow rotating shaft that is easy to process and form, which can provide an effective liquid circulation loop on the basis of serving as an ordinary transmission part, and alleviate the problem that when the liquid flows in the gap between the rotating shaft and the bearing, the metal ions in the liquid are deposited into scale, which affects the normal operation of the rotating shaft. Summary of the Invention

[0005] The purpose of the present invention is to provide a hollow shaft for a pump and a centrifugal pump having the hollow shaft in order to overcome the defects of the prior art.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] According to one aspect of the present invention, a hollow shaft for a pump is provided, which is installed on a centrifugal pump. The centrifugal pump includes a motor, a pump head assembly, an impeller and a shielding tank. The motor includes a rotor assembly and a stator assembly. The hollow shaft is part of the rotor assembly. The end of the hollow shaft close to the pump head assembly is a shaft head connected to a low-pressure area, and the end away from the pump head assembly is a shaft tail located in the shielding tank. The shaft head drives the impeller to rotate. The outer wall of the hollow shaft is provided with a spiral groove, and the internal area of ​​the hollow shaft is penetrated by a stepped through hole for liquid to flow from a high-pressure area to a low-pressure area, thereby realizing liquid circulation.

[0008] As a preferred technical solution, the spiral groove is a groove that passes through the shaft head and the shaft tail, or a plurality of grooves that start and end at any position on the outer wall and are arranged intermittently.

[0009] As an optimal technical solution, the stepped through hole is coaxially arranged with a shaft head countersunk hole, a center through hole and a stepped countersunk hole from the shaft head to the shaft tail. The shaft head countersunk hole is connected to the low-pressure area, and the step countersunk hole is connected to the high-pressure area.

[0010] As a preferred technical solution, a clearance space is provided between the outer wall surface of the hollow shaft and the inner wall of the front bearing of the motor.

[0011] As a preferred technical solution, the depth of the central through hole is 0.5-2.0 mm and the hole diameter is 0.4-1.0 mm.

[0012] As a preferred technical solution, the central through hole is cylindrical or conical.

[0013] As a preferred technical solution, the stepped countersink includes countersink sections with different apertures, the countersink section with the smallest aperture is directly connected to the central through hole, and the countersink section with the largest aperture passes through the shaft tail.

[0014] As a preferred technical solution, the outer wall of the shielding tank is in close contact with the inner wall of the motor stator assembly, and the heat of the stator assembly is directly transferred to the high-pressure liquid in the shielding tank through the outer wall of the shielding tank.

[0015] As a preferred technical solution, the hollow shaft is a hollow shaft made of ceramic material.

[0016] According to another aspect of the present invention, a centrifugal pump with a hollow shaft is provided, comprising a motor, a pump head assembly, an impeller and a shielding tank, wherein the motor comprises a rotor assembly and a stator assembly, and the rotor assembly comprises the hollow shaft for the pump.

[0017] Compared with the prior art, the present invention achieves the following technical effects:

[0018] 1) The present invention provides a hollow pump shaft with a spiral groove structure on its outer wall. When the pump unit is operating, the spiral groove on the outer wall and the inner wall contact surface of the front bearing have a clearance, which greatly reduces friction resistance. Therefore, the wet-running pump unit can obtain a better starting response.

[0019] 2) To address the design of a fluid circulation system for cooling the motor during pump operation, the present invention utilizes a stepped through-hole design to provide a circulation loop within the liquid shaft. Furthermore, countersunk holes are provided at the shaft head and tail, allowing the central through-hole to be directly molded, effectively resolving the difficulties in machining and demolding the elongated central through-hole.

[0020] 3) The slender central through hole of the present invention is conducive to the pressure transition of the liquid from the high-pressure area to the low-pressure area. At the same time, the depth of the central through hole ranges from 0.5 to 2 mm and the aperture ranges from 0.4 to 1.0 mm. It has a good cooling effect without significantly reducing the pump efficiency. It can also effectively avoid the blockage of large particles inside the system, which is safe and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic structural diagram of an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the spiral groove structure on the outer wall of an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the contact friction between the outer wall surface and the inner wall of the front bearing according to an embodiment of the present invention;

[0024] Figure 4 (a) is a schematic diagram of the central through hole structure of the present invention;

[0025] Figure 4(b) is a schematic structural diagram of the cylindrical central through hole in part A of Figure 4(a);

[0026] Figure 4 (c) is a schematic diagram of the conical central through-hole structure;

[0027] Figure 5 A schematic diagram of a wet-running pump unit according to an embodiment of the present invention;

[0028] Figure 6 A schematic diagram of a fluid channel according to an embodiment of the present invention;

[0029] Among them, 1 is the pump head assembly, 2 is the impeller, 3 is the impeller cover, 4 is the flat sealing ring, 5 is the shielding can, 6 is the bearing support, 7 is the front bearing, 8 is the axial stop bearing, 9 is the axial stop bearing sleeve, 10 is the rear bearing, 11 is the rear bearing support, 12 is the rotor assembly, 13 is the stator assembly, 14 is the hollow shaft, 15 is the permanent magnet, 16 is the spiral groove, 17 is the shaft head countersunk hole, 18 is the center through hole, 19 is the step countersunk hole, 20 is the first gear aperture, 21 is the second gear aperture, 22 is the outer wall, 23 is the inner wall of the front bearing, 24 is the avoidance position, 25 is the high-pressure area, 26 is the low-pressure area, S1 and S2 are fluid channels, 27 is the cylindrical center through hole, and 28 is the conical center through hole. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0031] The present invention provides a hollow shaft for a pump, which is installed on a centrifugal pump. The centrifugal pump includes a motor, a pump head assembly 1, an impeller 2 and a shielding tank 5. The motor includes a rotor assembly 12 and a stator assembly 13. The hollow shaft 14 is part of the rotor assembly. The end of the hollow shaft 14 close to the pump head assembly 1 is a shaft head connected to the low-pressure area 26, and the end away from the pump head assembly 1 is a shaft tail located in the shielding tank 5. The shaft head drives the impeller 2 to rotate. The internal area of ​​the hollow shaft 14 is penetrated by a stepped through hole for liquid to flow from the high-pressure area 25 into the low-pressure area 26, thereby realizing liquid circulation.

[0032] like Figure 1 As shown, the outer wall surface 22 of the hollow shaft 14 is provided with a spiral groove 16. The spiral groove 16 can be a groove that passes through the shaft head and the shaft tail, or a plurality of grooves that start and end at any position of the outer wall surface 22 and are intermittently arranged, such as Figure 2 The matching relationship between the hollow shaft 14, the front bearing outer wall 22 and the rotor permanent magnet 15 is shown in FIG. Figure 3As shown, there is a clearance space 24 between the outer wall surface 22 of the hollow shaft 14 and the inner wall 23 of the front bearing. The clearance space 24 effectively reduces the friction resistance between the hollow shaft 14 and the bearing, allowing the wet-running centrifugal pump unit to achieve a better starting response. The internal area of ​​the hollow shaft 14 is penetrated by a stepped through hole, which is used to provide an intra-shaft loop for fluid circulation. The stepped through hole seamlessly connects the shaft head countersunk hole 17, the center through hole 18 and the stepped through hole 19 from the shaft head to the shaft tail coaxially. The stepped through hole 19 has two sections with different apertures, namely the smaller first-stage aperture 20 and the larger second-stage aperture 21. Among them, the diameter of the central through hole 18 is the smallest, and the shape can be cylindrical (as shown in Figure 4 (b)) or conical (as shown in Figure 4 (c)). As shown in Figure 4 (a), as long as the depth range is 0.5~2mm and the aperture range is 0.4~1.0mm, it can maintain a good cooling effect without significantly reducing the operating efficiency of the pump, and can also effectively avoid clogging of large particles inside the system, which is safe and reliable.

[0033] Figure 5 This is a schematic diagram of a hollow shaft 14 used in a wet-running pump unit, which includes a pump head assembly 1, an impeller 2, an impeller cover 3, a flat seal 4, a shielding can 5, a bearing support 6, a front bearing 7, an axial stop bearing 8, a axial stop bearing rubber sleeve 9, a rear bearing 10, a rear bearing support 11, a rotor assembly 12, and a stator assembly 13. Hollow shaft 14 is mounted in rotor assembly 12 and supported at both ends by bearings. The end closest to the pump head is the shaft head, which is located in the low-pressure region 26. The end away from the pump head is the shaft tail, which passes through the high-pressure region 25 and reaches the shielding can 5. The shaft head is welded to the impeller 2 to drive the impeller 2 to rotate.

[0034] Figure 6 A liquid circulation channel is designed using the hollow shaft 14. When the pump is running, the impeller 2 rotates to form a high-pressure area 25 around it. The liquid enters the impeller 2 from the water inlet of the pump, enters the high-pressure area 25 under the action of the pump, flows to the bearing support 6, and enters the shielding tank 5 through the groove on the bearing support 6. Figure 6 S1 in the figure flows in the gap between the rotor permanent magnet 15 and the shield tank 5 in the axial direction from the shaft head to the shaft tail, achieving the effect of cooling the motor. The liquid then flows into the bottom of the shield tank 5 through the hole on the rear bearing support. When the liquid is full, it flows back to the low-pressure area 26 in the center of the impeller from the shaft tail to the shaft head through the stepped through hole inside the hollow shaft 14 in the axial direction. Figure 6 S2 in the figure achieves fluid circulation. During this process, the elongated central through-hole facilitates the pressure transition from the high-pressure area to the low-pressure area. The countersunk holes at the shaft head and tail of the stepped through-hole allow the elongated central through-hole to be directly molded, effectively solving the problems of difficult machining and demolding of the elongated central through-hole.

[0035] Example 2

[0036] like Figure 5 As shown, the present invention also provides a centrifugal pump with a hollow shaft, including a motor, a pump head assembly 1, an impeller 2 and a shielding tank 5, wherein the motor includes a rotor assembly 12 and a stator assembly 13, and the rotor assembly 12 includes the hollow shaft for the pump described in Example 1.

[0037] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A hollow shaft for a pump, wherein the hollow shaft (14) is mounted on a centrifugal pump, wherein the centrifugal pump comprises a motor, a pump head assembly (1), an impeller (2) and a shielding tank (5), wherein the motor comprises a rotor assembly (12) and a stator assembly (13), wherein the hollow shaft (14) is a part of the rotor assembly, wherein one end of the hollow shaft (14) close to the pump head assembly (1) is a shaft head communicating with a low-pressure area (26), and the other end away from the pump head assembly (1) is a shaft tail located in the shielding tank (5), wherein the shaft head drives the impeller (2) to rotate, and wherein the hollow shaft (14) is characterized in that: The outer wall surface (22) of the hollow shaft (14) is provided with a spiral groove (16), and the inner area of ​​the hollow shaft (14) is penetrated by a stepped through hole for liquid to flow from the high-pressure area (25) to the low-pressure area (26), thereby realizing liquid circulation; The spiral groove (16) is a groove that passes through the shaft head and the shaft tail, or a plurality of grooves whose starting and ending points are at any positions on the outer wall surface (22) and are arranged intermittently; The stepped through hole is coaxially arranged with a shaft head countersunk hole (17), a center through hole (18) and a stepped countersunk hole (19) from the shaft head to the shaft tail, the shaft head countersunk hole (17) is connected to the low-pressure area (26), and the stepped countersunk hole (19) is connected to the high-pressure area (25); A clearance space (24) is provided between the outer wall surface (22) of the hollow shaft (14) and the inner wall (23) of the front bearing (7) of the motor; The central through hole (18) has a depth of 0.5-2.0 mm and a hole diameter of 0.4-1.0 mm; The step countersink (19) includes countersink sections with different apertures, the countersink section with the smallest aperture is directly connected to the central through hole (18), and the countersink section with the largest aperture passes through the shaft tail.

2. A hollow shaft for a pump according to claim 1, characterized in that: The central through hole (18) is cylindrical or conical.

3. The hollow shaft for a pump according to claim 1, characterized in that: The outer wall of the shielding tank (5) is in close contact with the inner wall of the motor stator assembly (13), and the heat of the stator assembly (13) is directly transferred to the high-pressure liquid in the shielding tank (5) through the outer wall of the shielding tank (5).

4. The hollow shaft for a pump according to claim 1, characterized in that: The hollow shaft (14) is a hollow shaft made of ceramic material.

5. A centrifugal pump with a hollow shaft, comprising a motor, a pump head assembly (1), an impeller (2) and a shielding tank (5), wherein the motor comprises a rotor assembly (12) and a stator assembly (13), characterized in that: The rotor assembly (12) comprises the hollow pump shaft according to any one of claims 1 to 4.

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