Disc type shield pump

Abstract

The utility model discloses a disc type shield pump which comprises a disc type motor, the disc type motor comprises a stator, a rotor and a shaft assembly. The pump shell is provided with a liquid inlet, a liquid outlet, a flow channel and a first bearing chamber; the pump body is connected to the pump shell, the pump body is provided with a first inner cavity and a second bearing chamber, the first inner cavity is aligned and communicated with the flow channel, a stator is arranged in the first inner cavity, and the second bearing chamber is communicated with the first inner cavity; the first bearing is arranged at the first bearing chamber; the second bearing is arranged at the second bearing chamber and is connected with the shaft assembly together with the first bearing; the impeller structure is arranged in the flow channel and the first inner cavity and connected with the shaft assembly, and the impeller structure is connected with the rotor; the shielding sleeve is arranged between the pump shell and the pump body and separates the stator from the pump body, and the pump body and the stator are not in contact with a medium; therefore, the technical problems that the sealing effect is poor, the heat dissipation effect is poor, the axial force is not eliminated or balanced, the structural reliability is poor, and the service life is shortened are solved.

Description

Technical Field

[0001] The utility model relates to the technical field of centrifugal pumps, in particular to a disc canned motor pump. Background Art

[0002] Canned motor pumps are often used to transport fluid media such as flammable, explosive, volatile, and toxic substances, so as to improve the safety and reliability of the operation of petrochemical plants;

[0003] For example: The prior art with the Chinese patent application number CN02262728.6 and the patent theme name of disc centrifugal pump uses a disc motor instead of a radial motor, which reduces the volume of the pump and improves the efficiency, and is used to transport fluid media such as flammable, explosive, volatile, and toxic substances. However, there are still some deficiencies:

[0004] 1. Since a disc motor is used, the rotor is not integrally immersed in the medium. Although the phenomenon of water grinding is avoided, the price is that a dynamic seal (such as using a sealing ring and a sealing gland) must be adopted to prevent the transported medium from leaking. However, the sealing effect of the dynamic seal is not good, and the leakage problem cannot be completely solved. The sealing ring and the sealing gland must be replaced periodically, which is not convenient to use;

[0005] 2. Using heat-conducting insulating materials to dissipate heat from the motor stator and coils, this heat dissipation method has a poor heat dissipation effect. When the pump is working, the coils are often in a high-temperature state (such as a temperature of 80°-100°), which will accelerate the aging of the coils and reduce the service life of the motor;

[0006] 3. The axial force is not eliminated or balanced. During operation, this axial force will pull the rotor to axially move. Once it contacts other components on the pump shaft, it will cause component damage. Seriously, it will cause the disc canned motor pump to not work properly, and the impeller will also axially move, resulting in noise and affecting the service life. Summary of the Utility Model

[0007] Aiming at the above deficiencies in the related art, the purpose is to provide a disc canned motor pump to solve the technical problems of poor sealing effect, poor heat dissipation effect, no elimination or balance of axial force, poor structural reliability, and reduced service life in the related art.

[0008] The technical solution to achieve the purpose is: A disc canned motor pump, comprising: a disc motor; the disc motor includes: a stator, a rotor and a shaft assembly; the stator and the rotor are arranged at intervals; and further includes:

[0009] A pump casing, the pump casing is provided with a liquid inlet, a liquid outlet and a flow channel, the liquid inlet, the liquid outlet and the flow channel are communicated, and a first bearing chamber is provided in the pump casing;

[0010] The pump body is connected to the pump housing, is spaced opposite to the liquid inlet, and has a first inner cavity and a second bearing chamber on the pump body. The first inner cavity is aligned and communicated with the flow channel. The stator is arranged in the first inner cavity. The second bearing chamber is communicated with the first inner cavity, is spaced from the first bearing chamber, and the center lines of the second bearing chamber and the first bearing chamber are on the same straight line;

[0011] The first bearing is arranged at the first bearing chamber;

[0012] The second bearing is arranged at the second bearing chamber and is connected to the shaft assembly together with the first bearing;

[0013] The impeller structure is arranged in the flow channel and the first inner cavity, is connected to the shaft assembly, and the impeller structure is connected to the rotor;

[0014] And the shielding sleeve is arranged between the pump housing and the pump body, and is arranged in the first inner cavity and the second bearing chamber to separate the stator and the pump body, and the pump body and the stator do not contact the medium.

[0015] Furthermore: The shaft assembly is arranged at the middle position between the stator and the rotor, is surrounded by the stator and the rotor, is spaced from the stator and the rotor, and both ends of the shaft assembly protrude from the stator and the rotor.

[0016] Furthermore: The shaft assembly includes: a shaft connected between the first bearing and the second bearing; and a shaft sleeve sleeved on the shaft and connected to the impeller structure, and one end of the shaft sleeve contacts the first bearing and the other end contacts the second bearing.

[0017] Furthermore: There is a clearance fit between the shaft and the shaft sleeve; the material of the shaft is ceramic; the material of the shaft sleeve is graphite.

[0018] Furthermore: The liquid inlet is arranged at the middle position of the pump housing, and the center line of the liquid inlet is on the same straight line as the center line of the impeller structure.

[0019] Furthermore: There is a space between the flow channel and the impeller structure;

[0020] After the flow channel is projected onto a plane from top to bottom, starting from position A, it is arranged in an arc shape around the center line position B of the impeller structure and ends at the liquid outlet;

[0021] The straight-line distance from the center of position A to the center line position B is less than the straight-line distance from the center of the liquid outlet to the center line position B.

[0022] Further: The first inner cavity is a cylindrical inner space, and after projecting onto a plane from top to bottom, the volume dimension of the first inner cavity is smaller than the volume dimension of the flow channel.

[0023] Further: The impeller structure includes: a wheel body, a part of which is arranged in the first inner cavity and connected to the rotor, and another part is arranged in the flow channel. A through hole is provided at the middle position of the wheel body, and the shaft sleeve is sleeved at the through hole.

[0024] And an outwardly convex shaft sleeve, one end of which is connected to the wheel body, and the other end extends towards the second bearing, and the outwardly convex shaft sleeve is connected to the shaft sleeve.

[0025] Further: The through hole and the outwardly convex shaft sleeve are tightly fitted with the shaft sleeve to form an integral body.

[0026] Further: The shield includes: a first part arranged between the pump housing and the pump body; a second part, one end of which is connected to the first part, follows the pump body, is recessed in the first inner cavity, and covers the stator; and a third part connected to the other end of the second part, is recessed in the second bearing chamber, and contacts the second bearing.

[0027] A second inner cavity is formed between the second part and the impeller structure, and the second inner cavity communicates with the flow channel.

[0028] By adopting the above technical solution, the following beneficial effects are achieved: A disc-type canned motor pump, compared with the related technology, is provided with a disc-type motor, a pump housing, a pump body, a first bearing, a second bearing, an impeller structure and a shield; the disc-type motor includes: a stator, a rotor and a shaft assembly.

[0029] After the disc-type motor is powered on, the rotor and the impeller structure rotate together with the shaft assembly as the rotation center. The medium enters from the liquid inlet, and under the action of the impeller structure, the velocity potential energy of the medium is converted into pressure potential energy. The medium follows the flow channel and is discharged from the liquid outlet, realizing the transportation of the medium.

[0030] Since the shield separates the stator and the pump body, the pump body and the stator do not contact the medium, which not only protects the pump body and the stator, but also seals and blocks the medium at the first inner cavity, and the medium will not leak, and the sealing effect is relatively good. At the same time, since the medium is at the first inner cavity, it can perform liquid cooling and heat dissipation on the stator, rotor and second bearing, and the heat dissipation effect is relatively good, improving the service life of the stator coil.

[0031] Due to the provision of the first bearing and the second bearing, the first bearing and the second bearing are connected to the shaft assembly together, and the impeller structure is connected to the shaft assembly. When the impeller structure rotates around the shaft assembly as the rotation center, the axial force generated is offset and balanced by the first bearing and the second bearing, enabling the axial force to be balanced. The impeller structure and the rotor will not axially move, the structural reliability is relatively good, the noise is reduced, and the service life is extended.

[0032] Thus, it overcomes the technical problems of poor sealing effect, poor heat dissipation effect, failure to eliminate or balance axial force, poor structural reliability, and reduced service life, achieving the technical effects of relatively good sealing effect, relatively good heat dissipation effect, ability to balance axial force, relatively good structural reliability, and extended service life, and has practicality. Brief Description of the Drawings

[0033] Figure 1 is a schematic diagram of the overall assembly structure;

[0034] Figure 2 is a sectional view of the overall assembly;

[0035] Figure 3 is an exploded view of the overall assembly;

[0036] Figure 4 is a velocity contour map at the flow passage inside the pump casing;

[0037] Figure 5 is a pressure contour map at the flow passage inside the pump casing;

[0038] In the figures: 10. pump casing, 11. liquid inlet, 12. liquid outlet, 13. flow passage, 14. first bearing chamber, 20. pump body, 21. first inner cavity, 22. second bearing chamber, 30. first bearing, 40. second bearing, 50. impeller structure, 51. wheel body, 51-1. through hole, 52. outer convex shaft sleeve, 60. shielding sleeve, 61. first part, 62. second part, 63. third part, 60-1. second inner cavity, 101. stator, 102. rotor, 103. shaft assembly, 103-1. shaft, 103-2. shaft sleeve. Detailed Description of the Preferred Embodiments

[0039] To make the content easier to be clearly understood, the following further detailed description is made according to specific embodiments in conjunction with the drawings;

[0040] A disc-type canned motor pump solves the technical problems in the related art of poor sealing effect, poor heat dissipation effect, failure to eliminate or balance axial force, poor structural reliability, and reduced service life, can be manufactured and used, and achieves the positive effects of relatively good sealing effect, relatively good heat dissipation effect, ability to balance axial force, relatively good structural reliability, and extended service life. The general idea is as follows:

[0041] One embodiment:

[0042] As Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 shown; A disc shield pump, comprising: a disc motor; the disc motor includes: a stator 101, a rotor 102 and a shaft assembly 103; the stator 101 and the rotor 102 are spaced apart; further comprising:

[0043] A pump housing 10 having a liquid inlet 11, a liquid outlet 12 and a flow channel 13 thereon, the liquid inlet 11, the liquid outlet 12 and the flow channel 13 are in communication, and a first bearing chamber 14 is provided in the pump housing 10;

[0044] A pump body 20 connected to the pump housing 10, spaced apart opposite to the liquid inlet 11, and the pump body 20 has a first inner cavity 21 and a second bearing chamber 22, the first inner cavity 21 is aligned and communicated with the flow channel 13, the stator 101 is disposed in the first inner cavity 21, the second bearing chamber 22 is communicated with the first inner cavity 21, the second bearing chamber 22 and the first bearing chamber 14 are spaced apart, and the center lines of the second bearing chamber 22 and the first bearing chamber 14 are on the same straight line;

[0045] A first bearing 30 disposed at the first bearing chamber 14;

[0046] A second bearing 40 disposed at the second bearing chamber 22, connecting the shaft assembly 103 together with the first bearing 30;

[0047] An impeller structure 50 disposed in the flow channel 13 and the first inner cavity 21, connected to the shaft assembly 103, and the impeller structure 50 connects the rotor 102;

[0048] And a shield sleeve 60 disposed between the pump housing 10 and the pump body 20, and disposed in the first inner cavity 21 and the second bearing chamber 22, separating the stator 101 and the pump body 20, and the pump body 20 and the stator 101 are not in contact with the medium;

[0049] Specifically, during implementation, a disc motor, a pump housing 10, a pump body 20, a first bearing 30, a second bearing 40, an impeller structure 50 and a shield sleeve 60 are provided; the disc motor includes: a stator 101, a rotor 102 and a shaft assembly 103;

[0050] After the disc motor is powered on, the rotor 102 and the impeller structure 50 rotate together with the shaft assembly 103 as the center of rotation. The medium enters from the liquid inlet 11. Under the action of the impeller structure 50, the velocity potential energy of the medium is converted into pressure potential energy. The medium flows along the flow channel 13 and is discharged from the liquid outlet 12, realizing the transportation of the medium;

[0051] Since the shielding sleeve 60 separates the stator 101 and the pump body 20, the pump body 20 and the stator 101 do not come into contact with the medium. This not only protects the pump body 20 and the stator 101, but also seals and isolates the medium at the first inner cavity 21, preventing the medium from leaking, and the sealing effect is relatively good. At the same time, because the medium is at the first inner cavity 21, it can perform liquid cooling and heat dissipation on the stator 101, rotor 102 and the second bearing 40, and the heat dissipation effect is relatively good, improving the service life of the stator coil;

[0052] Due to the provision of the first bearing 30 and the second bearing 40, the first bearing 30 and the second bearing 40 are connected to the shaft assembly 103 together, and the impeller structure 50 is connected to the shaft assembly 103. When the impeller structure 50 rotates with the shaft assembly 103 as the center of rotation, the axial force generated is offset and balanced by the first bearing 30 and the second bearing 40, enabling the axial force to be balanced. The impeller structure 50 and the rotor 102 will not axially move, and the structural reliability is relatively good, reducing noise and improving the service life;

[0053] Another embodiment:

[0054] Such as Figure 1 、 Figure 2 、 Figure 3 shown; During implementation, the stator 101 and the rotor 102 are common structures in the prior art. After the stator 101 is powered on, it drives the rotor 102 to rotate, thereby driving the impeller structure 50 to rotate with the shaft assembly 103 as the center of rotation. A person of ordinary skill in the art can directly and unambiguously know how to set the stator 101 and the rotor 102 after seeing the disclosed content, without the need to perform creative labor or excessive experiments;

[0055] The shaft assembly 103 is arranged at the intermediate position between the stator 101 and the rotor 102, surrounded by the stator 101 and the rotor 102, and is spaced from the stator 101 and the rotor 102. Moreover, both ends of the shaft assembly 103 protrude from the stator 101 and the rotor 102, which is beneficial for connecting the impeller structure 50, and the impeller structure 50 can rotate smoothly with the shaft assembly 103 as the center of rotation;

[0056] The shaft assembly 103 includes: a shaft 103-1 connected between the first bearing 30 and the second bearing 40; and a shaft sleeve 103-2 sleeved on the shaft 103-1, connecting the impeller structure 50, and one end of the shaft sleeve 103-2 contacts the first bearing 30 and the other end contacts the second bearing 40;

[0057] There is a clearance fit between the shaft 103-1 and the shaft sleeve 103-2; the material of the shaft 103-1 is ceramic; the material of the shaft sleeve 103-2 is graphite; the control of the fit clearance and the selection of the material make the frictional resistance between the shaft sleeve 103-2 and the shaft 103-1 relatively small. When the shaft sleeve 103-2 and the impeller structure 50 rotate around the shaft 103-1 as the rotation center, it is relatively smooth. And there is an interference fit between the shaft sleeve 103-2 and the impeller structure 50. The shaft sleeve 103-2 abuts between the first bearing 30 and the second bearing 40, and the impeller structure 50 and the shaft sleeve 103-2 are positioned without axial movement. The axial force is cancelled and balanced, and the structural reliability is relatively good, reducing noise and increasing service life;

[0058] Another embodiment:

[0059] Such as Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 shown; during implementation, the liquid inlet 11 is arranged at the middle position of the pump housing 10, and the center line of the liquid inlet 11 is on the same straight line as the center line of the impeller structure 50; the setting of the position of the liquid inlet 11 is beneficial to the smooth entry of the medium into the flow channel 13;

[0060] There is a spaced arrangement between the flow channel 13 and the impeller structure 50; after the flow channel 13 is projected onto a plane from top to bottom, starting from position A, it is arranged in an arc shape around the center line position B of the impeller structure 50 and ends at the liquid outlet 12; the straight-line distance from the center of position A to the center line position B is less than the straight-line distance from the center of the liquid outlet 12 to the center line position B; the setting of the position and shape of the flow channel 13 is beneficial to the medium flowing along the flow channel 13, converting the velocity potential energy of the medium into pressure potential energy and smoothly discharging from the liquid outlet 12;

[0061] The flow channel 13 can be a volute flow channel in the prior art. From position A to the liquid outlet 12, the cross-sectional space area gradually increases, and the medium can flow smoothly along the flow channel 13 and be discharged smoothly from the liquid outlet 12;

[0062] A first bearing chamber 14 is provided, which is beneficial to accommodating and positioning the first bearing 30;

[0063] Another embodiment:

[0064] As Figure 1 , Figure 2 , Figure 3 shown; during implementation, the outer shape of the pump body 20 is a stepped structure, which is connected to the pump housing 10 through bolt parts, and is relatively convenient for installation and disassembly;

[0065] A first inner cavity 21 is provided. The first inner cavity 21 is a cylindrical inner space. After the plane projection from top to bottom, the volume size of the first inner cavity 21 is smaller than the volume size of the flow channel 13, which is beneficial to the connection and arrangement of the stator 101 and the shielding sleeve 60, and can accommodate the medium. The medium can perform liquid cooling and heat dissipation on the stator 101, the rotor 102 and the second bearing 40, and the heat dissipation effect is relatively good, improving the service life of the stator coil;

[0066] A second bearing chamber 22 is provided, which is beneficial to accommodate and position the second bearing 40;

[0067] Another implementation mode:

[0068] As Figure 1 , Figure 2 , Figure 3 shown; during implementation, the first bearing 30 or the second bearing 40 is a common structure in the prior art, such as a sliding bearing, which is beneficial to connecting and positioning the shaft 103-1 and can abut against the shaft sleeve 103-2 to balance the axial force;

[0069] Another implementation mode:

[0070] As Figure 1 , Figure 2 , Figure 3 shown; during implementation, the impeller structure 50 includes: a wheel body 51, a part of which is arranged in the first inner cavity 21 and is connected to the rotor 102, and another part is arranged in the flow channel 13. A through hole 51-1 is provided at the middle position of the wheel body 51, and the shaft sleeve 103-2 is sleeved at the through hole 51-1; and an outward convex shaft sleeve 52, one end of which is connected to the wheel body 51 and the other end extends towards the second bearing 40, and the outward convex shaft sleeve 52 is connected to the shaft sleeve 103-2;

[0071] The wheel body 51 is a closed impeller, which is integrally formed with the outward convex shaft sleeve 52. Through the through hole 51-1 and the outward convex shaft sleeve 52, it is tightly fitted with the shaft sleeve 103-2 and forms a whole with the shaft sleeve 103-2. The impeller structure 50 and the shaft sleeve 103-2 rotate together with the shaft 103-1 as the rotation center. Moreover, since the shaft sleeve 103-2 abuts between the first bearing 30 and the second bearing 40, the impeller structure 50 and the shaft sleeve 103-2 are positioned and will not axially move, and the axial force is offset and balanced, and the structural reliability is relatively good;

[0072] Another embodiment:

[0073] As shown in Figure 1 , Figure 2 , Figure 3 ; during implementation, the shielding sleeve 60 includes: a first part 61 disposed between the pump housing 10 and the pump body 20; a second part 62 having one end connected to the first part 61, following the pump body 20, recessed in the first inner cavity 21, and covering the stator 101; and a third part 63 connected to the other end of the second part 62, recessed in the second bearing chamber 22, and contacting the second bearing 40.

[0074] The first part 61, the second part 62, and the third part 63 are integrally formed by stamping, and the material is a non-magnetic corrosion-resistant material, such as stainless steel.

[0075] A second inner cavity 60-1 is formed between the second part 62 and the impeller structure 50, and the second inner cavity 60-1 communicates with the flow channel 13; the second inner cavity 60-1 is provided, and the second inner cavity 60-1 is within the first inner cavity 21 and can accommodate a medium, and the medium can perform liquid cooling and heat dissipation on the stator 101, the rotor 102, and the second bearing 40, and the heat dissipation effect is relatively good, which improves the service life of the stator coil.

[0076] The shielding sleeve 60 separates the stator 101 and the pump body 20, and the pump body 20 and the stator 101 do not contact the medium, which not only protects the pump body 20 and the stator 101, but also seals and blocks the medium at the second inner cavity 60-1, and the medium will not leak, and the sealing effect is relatively good.

[0077] Regarding the velocity contour and the pressure contour

[0078] As shown in Figure 4 , Figure 5 ; an analysis software in the prior art (such as CFD computational fluid dynamics software) is adopted. When the disc shield pump is working, the impeller structure 50 rotates, and the medium enters from the liquid inlet 11. At this time, the static pressure and flow velocity of the medium are very small. The impeller structure 50 drives the medium to flow, and the flow velocity of the medium increases. However, after entering the flow channel 13, the flow velocity of the medium decreases and the static pressure increases. When reaching the liquid outlet 12, the flow velocity of the medium is the smallest and the static pressure received is the largest. The function of the pump housing 10 is to convert the velocity potential energy of the medium into pressure potential energy. The flow velocity of the medium decreases within the pump housing 10, which can reduce the friction between the medium and the pump housing 10 and the energy loss caused by turbulence. The static pressure is the largest at the liquid outlet 12, which can also increase the head of the disc shield pump.

[0079] In the description, it should be understood that the terms "upper", "lower", "left", "right", "front", "rear", etc. indicating orientation or positional relationship are based on the positional relationship shown in the drawings, and are only for the convenience of description or simplification of the description, rather than indicating a specific orientation that must be had; the operation process described in the embodiments is not an absolute usage step, and corresponding adjustments can be made during actual use;

[0080] Unless otherwise defined individually, the technical terms or scientific terms used herein should have the ordinary meaning understood by those of ordinary skill in the art; the terms "first", "second" and similar words used in the specification and claims do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "a" or "one" do not necessarily indicate a quantity limitation, but indicate the existence of at least one, and need to be determined according to the content of the embodiments;

[0081] The above is only a preferred specific implementation manner, but the scope of protection is not limited thereto. Any person skilled in the art within the disclosed technical scope, according to the technical solutions and inventive concepts thereof, makes equivalent substitutions or changes, and should be covered within the scope of protection.

Claims

1. A disc shielded pump, comprising: Disc motor; The disc motor includes: a stator (101), a rotor (102) and a shaft assembly (103); the stator (101) is arranged at an interval from the rotor (102); It is characterized in that it further includes: A pump housing (10), which has a liquid inlet (11), a liquid outlet (12) and a flow channel (13) thereon. The liquid inlet (11), the liquid outlet (12) and the flow channel (13) are communicated with each other, and a first bearing chamber (14) is provided in the pump housing (10); A pump body (20), connected to the pump housing (10), arranged at an interval opposite to the liquid inlet (11), and the pump body (20) has a first inner cavity (21) and a second bearing chamber (22). The first inner cavity (21) is aligned and communicated with the flow channel (13). The stator (101) is arranged in the first inner cavity (21). The second bearing chamber (22) is communicated with the first inner cavity (21). The second bearing chamber (22) is arranged at an interval from the first bearing chamber (14). The center lines of the second bearing chamber (22) and the first bearing chamber (14) are on the same straight line; A first bearing (30), arranged at the first bearing chamber (14); A second bearing (40), arranged at the second bearing chamber (22), and connected to the shaft assembly (103) together with the first bearing (30); An impeller structure (50), arranged in the flow channel (13) and the first inner cavity (21), connected to the shaft assembly (103), and the impeller structure (50) is connected to the rotor (102); And a shielding sleeve (60), arranged between the pump housing (10) and the pump body (20), and arranged in the first inner cavity (21) and the second bearing chamber (22), separating the stator (101) and the pump body (20), and the pump body (20) and the stator (101) do not contact the medium.

2. The canned motor pump according to claim 1, wherein: The shaft assembly (103) is arranged at the middle position between the stator (101) and the rotor (102), surrounded by the stator (101) and the rotor (102), arranged at an interval from the stator (101) and the rotor (102), and both ends of the shaft assembly (103) protrude from the stator (101) and the rotor (102).

3. A disc shield pump according to claim 2, characterized in that: The shaft assembly (103) includes: a shaft (103-1), connected between the first bearing (30) and the second bearing (40); and a shaft sleeve (103-2), sleeved on the shaft (103-1), connected to the impeller structure (50), and one end of the shaft sleeve (103-2) contacts the first bearing (30), and the other end contacts the second bearing (40).

4. A disc shield pump according to claim 3, wherein: There is a clearance fit between the shaft (103-1) and the shaft sleeve (103-2); the material of the shaft (103-1) is ceramic; the material of the shaft sleeve (103-2) is graphite.

5. A disc shielded pump according to claim 1 or 4, characterized in that: The liquid inlet (11) is arranged at the middle position of the pump housing (10), and the center line of the liquid inlet (11) is on the same straight line as the center line of the impeller structure (50).

6. The disc shielded pump according to claim 5, characterized in that: There is a spaced arrangement between the flow channel (13) and the impeller structure (50); After the flow channel (13) is projected onto a plane from top to bottom, starting from position A, it is arranged in an arc shape around the center line position B of the impeller structure (50) and ends at the liquid outlet (12); The linear distance from the center of position A to the center line position B is less than the linear distance from the center of the liquid outlet (12) to the center line position B; 7. A disc shielded pump according to claim 6, characterized in that: The first inner cavity (21) is a cylindrical inner space, and after being projected onto a plane from top to bottom, the volume size of the first inner cavity (21) is smaller than the volume size of the flow channel (13); 8. A disc shielded pump according to claim 4, characterized in that: The impeller structure (50) includes: a wheel body (51), a part of which is arranged inside the first inner cavity (21) and connected to the rotor (102), and another part is arranged inside the flow channel (13). A through hole (51-1) is provided at the middle position of the wheel body (51), and the through hole (51-1) is sleeved on the shaft sleeve (103-2); And an outwardly convex shaft sleeve (52), one end of which is connected to the wheel body (51), and the other end extends towards the second bearing (40), and the outwardly convex shaft sleeve (52) is connected to the shaft sleeve (103-2); 9. The canned motor pump according to claim 8, wherein: The through hole (51-1) and the outwardly convex shaft sleeve (52) are tightly fitted with the shaft sleeve (103-2) to form a whole; 10. A disc shielded pump according to claim 1 or 9, characterized in that: The shielding sleeve (60) includes: a first part (61), which is arranged between the pump housing (10) and the pump body (20); a second part (62), one end of which is connected to the first part (61), follows the pump body (20), is recessed inside the first inner cavity (21), and covers the stator (101); and a third part (63), which is connected to the other end of the second part (62) and is recessed inside the second bearing chamber (22) and contacts the second bearing (40); A second inner cavity (60-1) is formed between the second part (62) and the impeller structure (50), and the second inner cavity (60-1) communicates with the flow channel (13).

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