Shielded spherical rotor pump

Abstract

The application relates to the field of pumps, in particular to a shielded spherical rotor pump, which comprises a spherical pump head coaxially arranged with a pump shell, a spherical rotor assembly in the spherical pump head is driven to rotate by a pump shaft to transport medium; a rotor assembly coaxially arranged with the pump shaft and a stator assembly arranged at the outer circle of the rotor assembly are arranged in the pump shell, the stator assembly and the rotor assembly are electromagnetically inducted to drive the pump shaft to rotate; a spherical head gap flow channel communicated with the inlet of the pump head exists between the spherical rotor assembly and the shell cavity of the spherical pump head, a pump shaft circulating flow channel penetrating through the pump shaft is axially arranged on the pump shaft, an annular flow gap flow channel exists between the rotor assembly and the stator assembly, a circulating outlet flow channel communicated with the inlet of the pump head is further arranged on the pump shell, the spherical head gap flow channel, the pump shaft circulating flow channel, the flow gap flow channel and the circulating outlet flow channel are sequentially communicated to form a medium circulating cooling channel. The spherical rotor pump can be used under high-pressure working conditions.

Description

Technical Field

[0001] This invention relates to the field of pumps, specifically a shielded spherical rotor pump. Background Technology

[0002] A spherical rotor pump is a positive displacement pump with a spherical rotor. It features a simple and compact structure, high reliability, and is widely used in fluid transport. Its structure, as described in announcement number "CN220204118U", includes a driving rotor and a driven rotor. Multiple variable displacement cavities are formed between the first mating surface of the driving rotor and the second mating surface of the driven rotor. When the driving rotor drives the driven rotor to rotate, the volume of the variable displacement cavities changes regularly between 0 and N (N is a positive number greater than 0), thus completing the function of transporting liquid.

[0003] In this process, the clearance between the rotor and the pump casing, as well as the fit between the rotor and the seals, are crucial. Under high pressure, these clearances and fits may be compressed, leading to leakage or damage, thus affecting the pump's performance and lifespan. During the pumping process, the clearance between the rotor and the pump casing, under high pressure, may be compressed, leading to leakage or damage, thus affecting the pump's performance and lifespan. Therefore, currently, spherical rotor pumps can only provide stable and continuous liquid delivery under low-pressure conditions (such as below 2.5 MPa), limiting their application environments. Summary of the Invention

[0004] To avoid and overcome the technical problems existing in the prior art, the present invention provides a shielded spherical rotor pump. The present invention enables the spherical rotor pump to be used under high-pressure conditions.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A shielded spherical rotor pump includes a spherical pump head coaxially arranged with the pump casing, a spherical rotor assembly inside the spherical pump head being driven to rotate by the pump shaft to transport the medium; a rotor assembly coaxially arranged with the pump shaft and a stator assembly arranged on the outer ring of the rotor assembly are arranged inside the pump casing, and the stator assembly and the rotor assembly are electromagnetically induced to drive the pump shaft to rotate.

[0007] There is a ball head gap flow channel between the spherical rotor assembly and the shell cavity of the spherical pump head, which communicates with the pump head inlet. A pump shaft circulation flow channel is opened along the axial direction on the pump shaft. There is an annular flow gap flow channel between the rotor assembly and the stator assembly. A circulation outlet flow channel is also opened on the pump casing, which communicates with the pump head inlet. The ball head gap flow channel, the pump shaft circulation flow channel, the flow gap flow channel and the circulation outlet flow channel are connected in sequence to form a medium circulation cooling channel.

[0008] In order to meet the continuous circulation of the circulating medium, the minimum pressure difference of the medium circulation cooling channel is ΔP, and the minimum length of the circulation outlet flow channel is calculated according to ΔP;

[0009] ΔP = ΔP1 + ΔP2 + ΔP3;

[0010]

[0011] Q L is the flow of the circulating liquid in the medium circulation cooling channel;

[0012] u1 is the flow rate of the medium in the pump shaft circulation flow channel;

[0013] u2 is the flow rate of the medium in the circulation outlet flow channel;

[0014] d1 is the diameter of the pump shaft circulation flow channel;

[0015] d2 is the diameter of the circulation outlet flow channel;

[0016] ΔP1 is the pressure difference before and after the pump shaft circulation flow channel;

[0017] ΔP2 is the pressure difference before and after the circulation outlet flow channel;

[0018] ΔP3 is the pressure difference before and after the flow gap flow channel;

[0019] λ is the flow resistance coefficient of the circulating medium;

[0020] ρ is the density of the circulating medium;

[0021] L1 is the length of the pump shaft circulation flow channel;

[0022] L2 is the length of the circulation outlet flow channel;

[0023] L3 is the length of the flow gap flow channel;

[0024] r is the gap width of the flow gap flow channel;

[0025] μ is the dynamic viscosity of the circulating medium.

[0026] As a further scheme of the present application: the pump cavity of the pump shell is provided with bearing assemblies located at both ends of the pump shaft and bidirectionally supporting the pump shaft, and the bearing inner ring of the bearing assembly is provided with a spiral liquid passage for the medium to pass through in the axial direction; the bearing of the bearing assembly adjacent to one end of the spherical pump head is the proximal bearing, and the bearing of the bearing assembly away from one end of the spherical pump head is the distal bearing; after the medium passes through the ball head gap flow channel, it is divided into two parts, one part of the medium passes through the pump shaft circulation flow channel, the liquid passage of the distal bearing, and the flow gap flow channel in sequence and then enters the circulation outlet flow channel, and the other part of the medium passes through the liquid passage of the proximal bearing and then enters the circulation outlet flow channel.

[0027] As a further scheme of the present application: a thrust disc is arranged between the shaft shoulder of the pump shaft and the bearing of the bearing assembly, the thrust disc abuts against the shaft shoulder of the pump shaft to bear the axial thrust of the pump shaft, and a recess is formed in the disc surface of the thrust disc to allow the medium in the outlet of the bearing to pass through.

[0028] As a further scheme of the present application: the pump shell is in a cylindrical structure with both ends open, a front flange and a rear flange are arranged at the openings of the two ends of the pump shell respectively, and a stator shield sleeve is arranged between the front flange and the rear flange, so as to form a ring-shaped sealing space for installing the stator.

[0029] As a further scheme of the present application: the stator and the winding assembly are coaxially arranged, and an electrical interface is arranged on the pump shell to externally connect the stator circuit.

[0030] As a further scheme of the present application: the sealing cavity of the stator assembly is filled with epoxy resin sealing.

[0031] As a further scheme of the present application: end plates are coaxially arranged at both ends of the pump shaft, a rotor shield sleeve is arranged between the two end plates, and the two end plates, the rotor shield sleeve and the pump shaft form a ring-shaped sealing space for installing the rotor; and a gap is formed between the rotor shield sleeve and the stator shield sleeve to form a flow gap channel.

[0032] As a further scheme of the present application: a hydraulic base is coaxially arranged on the front flange, the spherical pump head is fixed on the hydraulic base, a sliding sleeve is arranged in the hydraulic base, the pump shaft is coaxially fixed with the spherical rotor assembly through the sliding sleeve, and the sliding sleeve is coaxially and rotatably matched with the seat body of the spherical pump head through the bearing.

[0033] As a further scheme of the present application: diamond films are coated on the pump shaft and the sliding sleeve.

[0034] Compared with the prior art, the present application has the following advantages:

[0035] 1. The present application combines the shielded motor with the spherical rotor pump, and a medium circulation cooling channel is formed in the pump body, so that under high pressure conditions, the medium in the gap between the rotor and the pump shell can flow back to the inlet of the pump head through the medium circulation cooling channel, avoiding leakage of the medium from the gap between the rotor and the pump shell, and without affecting the performance and service life of the pump under high pressure environment, thereby expanding the application range of the spherical rotor pump.

[0036] 2. The present application calculates the length of each flow channel according to the required minimum pressure difference for establishing circulation, and selects the most suitable flow channel length according to different use conditions, so that the rotor pump meets the self-circulation cooling condition.

[0037] 3、The application introduces the medium outflowing from the pump shaft into the flow gap between the rotor assembly and the stator assembly by slotting the bearing inner ring and the thrust disc; and fills the epoxy resin glue into the sealed space through the electrical interface to seal, ensure the pressure bearing capacity of the stator assembly, and play a certain heat dissipation effect.

[0038] 4、The spherical rotor pump is realized in the form of a canned pump, the super-high lift characteristic can be applied to the fields where the traditional pump cannot be applied; the hydraulic assembly and the motor assembly of the pump are integratedly designed, and the internal circulation liquid is used for cooling and lubrication, so that the overall size of the pump is shortened; the connection mode of the assemblies is bolt connection or laser welding, and the O-shaped rubber ring static seal is used inside, so that the sealing reliability under the high pressure and high vibration working condition is improved, the integrated design makes the pump have no important components outside, the pump outer surface can be treated, and the special use environment is adapted. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 It is a structural schematic view of the application.

[0040] In the drawing:

[0041] 1, pump shell; 11, front flange; 12, rear flange; 13, bearing seat; 14, hydraulic base;

[0042] 2, stator assembly; 21, stator; 22, winding assembly;

[0043] 23, stator shield sleeve; 24, electrical interface;

[0044] 3, rotor assembly; 31, end plate; 32, rotor; 33, rotor shield sleeve;

[0045] 4, pump shaft; 41, bearing assembly; 42, thrust disc; 43, sliding sleeve;

[0046] 5, spherical pump head; 51, spherical rotor assembly; 52, pump head inlet; 53, pump head outlet;

[0047] 61, spherical head gap flow channel; 62, pump shaft circulation flow channel; 63, first bearing gap flow channel;

[0048] 64, flow gap flow channel; 65, second bearing gap flow channel; 66, circulation outlet flow channel. DETAILED DESCRIPTION

[0049] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0050] Please refer to Figure 1 In the embodiments of the present application, a shielding spherical rotor pump has a hydraulic assembly of a spherical pump head 5, and a shielding motor assembly is arranged in the pump shell 1.

[0051] The spherical pump head 5 is a prior art, and its structure is briefly described as follows. A spherical rotor assembly 51 is arranged in the mounting seat of the spherical pump head 5, and the spherical rotor assembly 51 includes an upper half-sphere and a lower half-sphere coaxially connected and arranged in the spherical cavity of the spherical pump head 5. The upper half-sphere and the lower half-sphere are connected by a pin shaft and perform periodic opening and closing movements. A boss is arranged on the upper half-sphere, and the spherical pump head 5 is provided with a groove matched with the boss, so as to provide plug-in cooperation of the upper half-sphere. The central axis of the boss is eccentric to the central axis of the lower half-sphere by a certain angle of eccentricity, and the plane of the lower half-sphere is at an angle to the plane of the upper half-sphere, so that a periodically changing working cavity is formed by the angle. The slider of the lower half-sphere is arranged in the groove of the sliding sleeve 43, and the sliding sleeve 43 is connected with the pump shaft 4, so that the lower half-sphere is driven to rotate by the pump shaft 4. When the lower half-sphere performs a circular motion with an angular velocity of ω, the angle of the working cavity of the two half-spheres periodically changes, thereby playing a role of pumping and discharging liquid. Thus, the medium is sucked into the pump head inlet 52 of the spherical pump head 5, and the medium is discharged through the pump head outlet 53 after passing through the cavity of the spherical rotor assembly 51.

[0052] The motor assembly includes a pump shell 1, a stator assembly 2 and a rotor assembly 3 arranged in the pump shell 1. The front flange 11 and the rear flange 12 are arranged at the front and rear ends of the pump shell 1 respectively, and the stator shield sleeve 23 is sealingly connected between the front flange 11 and the rear flange 12. The front flange 11, the rear flange 12, the pump shell 1 and the stator shield sleeve 23 form a sealed space and are laser-welded to each other to ensure the airtightness of the sealed space and facilitate the installation of the stator 21. The winding assembly 22 of the stator 21 is arranged in the sealed space and is fixed to the pump shell 1 by interference fit. The electrical interface 24 is arranged on the pump shell 1, the stator circuit extends to the outside of the pump shell 1 through the electrical interface 24, and the sealed space is sealed by pouring epoxy resin glue through the electrical interface 24, so as to ensure the pressure-bearing capacity of the stator assembly 2 and play a certain heat dissipation role.

[0053] The rotor assembly 3 is coaxially arranged in the inner ring of the stator assembly 2 and coaxially arranged with the pump shaft 4. The pump shaft 4 is coaxially provided with end plates 31 at the front and rear ends, and a magnetic rotor 32 is arranged between the two end plates 31. The rotor shield sleeve 33 is preferably connected between the two end plates 31 by laser welding, thereby enclosing a sealed cavity with the pump shaft 4 for installing the rotor 32. The rotor assembly 3 and the stator assembly 2 form an annular flow gap flow channel 64.

[0054] The bearing seat 13 is coaxially arranged on the rear flange 12, and the hydraulic base 14 is coaxially arranged on the front flange 11. The bearing assembly 41 is arranged in the bearing seat 13 and the hydraulic base 14. The two bearing assemblies 41 form bidirectional support for the pump shaft 4. The bearings of the two bearing assemblies 41 are in abutment with the shaft shoulder of the pump shaft 4 through the thrust disc 42, and the thrust disc 42 forms a clamping action on the pump shaft 4. After the stator assembly 2 is energized, the rotor assembly 3 is driven to rotate by electromagnetic force. The radial force during pump operation is borne by the bearings of the two bearing assemblies 41, and the thrust disc 42 is used to bear the axial force generated during the operation of the pump shaft 4. The spherical pump head 5 is connected to the hydraulic base 14 by bolts, and the sealing surface is sealed by an O-shaped rubber ring. Laser welding is used to ensure the reliability of the pump seal under high pressure and high vibration conditions.

[0055] The bearing inner ring of the bearing assembly 41 is provided with a spiral liquid passage for the medium to pass from one side of the bearing to the other side of the bearing through the liquid passage. The thrust disc 42 is also provided with a groove for the medium to pass through the liquid passage on the bearing assembly 41.

[0056] There is a gap of 0.01-0.05mm between the upper and lower hemispheres of the spherical rotor assembly 51 and the spherical cavity of the spherical pump head 5, which is the ball head gap flow channel 61. The hydraulic base 14 is provided with a sliding sleeve 43, and the spherical rotor assembly 51 is coaxially arranged with the pump shaft 4 through the sliding sleeve 43. The spherical rotor assembly 51 is clamped and positioned by the sliding sleeve 43. The pump shaft 4 is axially bored, thereby forming a pump shaft circulation flow channel 62. There is a gap between the pump shaft 4 and the bearing assembly 41 at one end of the adjacent bearing seat 13 and the bearing seat 13, for the medium to pass through. The hydraulic base 14 and the spherical pump head 5 are provided with a communication circulation outlet flow channel 66, which communicates the pump head inlet 52 with the flow gap flow channel 64.

[0057] The bearing liquid passage of the bearing assembly 41 on one side of the adjacent bearing seat 13 constitutes a first bearing gap flow channel 63, and the bearing liquid passage of the bearing assembly 41 on one side of the adjacent spherical pump head 5 constitutes a second bearing gap flow channel 65. When the spherical pump head 5 conveys medium, a part of the medium enters the ball head gap flow channel 61 to participate in the cooling work inside the pump body. The part of the medium in the ball head gap flow channel 61 successively passes through the pump shaft circulation flow channel 62, the first bearing gap flow channel 63, the through-flow gap flow channel 64, and then flows back to the pump head inlet 52 through the circulation outlet flow channel 66. Another part of the medium in the ball head gap flow channel 61 passes through the gap between the hydraulic base 14 and the sliding sleeve 43, enters the second bearing gap flow channel 65, and then flows back to the pump head inlet 52 through the circulation outlet flow channel 66 after converging with the medium flowing out of the through-flow gap flow channel 64. Through the circulating flow of high-pressure fluid, the motor is cooled and the internal components of the pump body are lubricated.

[0058] The pump shaft 4 and the sliding sleeve 43 are coated with a diamond-like film, which is beneficial to maintaining good lubrication between the internal structures and ensuring the service life of the pump; the bearings of the bearing assembly 41 are made of peek or graphite.

[0059] To meet the continuous circulation of the circulating medium, the minimum pressure difference of the medium circulation cooling channel is ΔP. Since the lengths of the pump shaft 4 and the rotor shield sleeve and the stator shield sleeve are mostly standard, the minimum length of the circulation outlet flow channel 66 can be directly calculated according to ΔP, and the circulation flow of the medium can be realized by meeting the minimum length.

[0060] Or in the circulation outlet flow channel 66, the appropriate lengths of the pump shaft and the rotor shield sleeve and the stator shield sleeve are selected by calculation.

[0061] ΔP = ΔP1 + ΔP2 + ΔP3;

[0062]

[0063]

[0064] Q L Q is the flow rate of the circulating liquid in the medium circulation cooling channel; u1 is the flow rate of the medium in the pump shaft circulation flow channel 62;

[0065] u2 is the flow rate of the medium in the circulation outlet flow channel 66;

[0066] d1 is the diameter of the pump shaft circulation flow channel 62;

[0067] d2 is the diameter of the circulation outlet flow channel 66;

[0068] ΔP1 is the pressure difference between the front and back of the pump shaft circulation flow channel 62;

[0069] ΔP2 is the pressure difference between the front and back of the circulation outlet flow channel 66;

[0070] ΔP3 is the pressure difference between the front and back of the flow gap flow passage 64;

[0071] λ is the flow resistance coefficient of the circulating medium;

[0072] ρ is the density of the circulating medium;

[0073] L1 is the length of the pump shaft circulating flow passage 62;

[0074] L2 is the length of the circulating outlet flow passage 66;

[0075] L3 is the length of the flow gap flow passage 64;

[0076] r is the gap width of the flow gap flow passage 64;

[0077] μ is the dynamic viscosity of the circulating medium;

[0078] In the medium circulation process, the following conditions need to be met,

[0079] R3 » R1 + R2;

[0080] The flow resistance of the pump shaft circulating flow passage 62 is R1;

[0081] The flow resistance of the circulating outlet flow passage 66 is R2;

[0082] The flow resistance of the flow gap flow passage 64 is R3;

[0083]

[0084] The basic principle of the present application is described above in combination with specific embodiments, but it should be pointed out that the advantages, advantages, effects and the like mentioned in the present application are only examples and not limitations, and these advantages, advantages, effects and the like cannot be considered as the must-have of each embodiment of the present application. In addition, the above-mentioned specific details are only for the purpose of example and for the purpose of understanding, and the above-mentioned details do not limit the present application to the must-use of the above-mentioned specific details.

[0085] The block diagrams of the devices, apparatuses, equipment, systems involved in the present application are only illustrative examples and are not intended to require or imply the connection, arrangement, configuration shown in the block diagram. As those skilled in the art will recognize, these devices, apparatuses, equipment, systems can be connected, arranged, configured in any manner. Words such as "include", "contain", "have" and the like are open-ended words, which mean "include but not limited to", and can be used interchangeably. The words "or" and "and" used herein mean the word "and / or", and can be used interchangeably unless the context clearly indicates otherwise. The word "such as" used herein means the phrase "such as but not limited to", and can be used interchangeably.

Claims

1. A canned spherical rotor pump characterized by, The pump comprises a pump shell (1), a spherical pump head (5) coaxially arranged in the pump shell (1), a spherical rotor assembly (51) in the spherical pump head (5) driven to rotate by a pump shaft (4) to deliver medium, a rotor assembly (3) coaxially arranged with the pump shaft (4) in the pump shell (1), and a stator assembly (2) arranged outside the rotor assembly (3), the stator assembly (2) and the rotor assembly (3) electromagnetically inductively matched to drive the pump shaft (4) to rotate. The spherical rotor assembly (51) and the shell cavity of the spherical pump head (5) are provided with a spherical head gap flow channel (61) communicated with a pump head inlet (52), the pump shaft (4) is provided with a pump shaft circulating flow channel (62) penetrating the pump shaft (4) in the axial direction, the rotor assembly (3) and the stator assembly (2) are provided with an annular flow gap flow channel (64), the pump shell (1) is further provided with a circulating outlet flow channel (66) communicated with the pump head inlet (52), and the spherical head gap flow channel (61), the pump shaft circulating flow channel (62), the flow gap flow channel (64) and the circulating outlet flow channel (66) are sequentially communicated to form a medium circulating cooling channel. In order to meet the continuous circulation of the circulating medium, the minimum pressure difference of the medium circulating cooling channel is ΔP, and the minimum length of the circulating outlet flow channel (66) is calculated according to ΔP. ΔP = ΔP1 + ΔP2 + ΔP3; Q L Q is the flow rate of the circulating liquid in the medium circulation cooling channel; u1 is the flow rate of the medium in the pump shaft circulating flow channel (62); u2 is the flow rate of the medium in the circulating outlet flow channel (66); d1 is the diameter of the pump shaft circulating flow channel (62); d2 is the diameter of the circulating outlet flow channel (66); ΔP1 is the pressure difference before and after the pump shaft circulating flow channel (62); ΔP2 is the pressure difference before and after the circulating outlet flow channel (66); ΔP3 is the pressure difference before and after the flow gap flow channel (64); λ is the flow resistance coefficient of the circulating medium; ρ is the density of the circulating medium; L1 is the length of the pump shaft circulating flow channel (62); L2 is the length of the circulating outlet flow channel (66); L3 is the length of the flow gap flow channel (64); r is the gap width of the flow gap flow channel (64); μ is the dynamic viscosity of the circulating medium.

2. A canned spherical rotor pump according to claim 1, characterized in that The pump cavity of the pump shell (1) is provided with a bearing assembly (41) located at both ends of the pump shaft (4) and bidirectionally supporting the pump shaft (4), the bearing inner ring of the bearing assembly (41) is provided with a spiral liquid passage for the medium to pass through in the axial direction; the bearing of the bearing assembly (41) at one end of the adjacent spherical pump head (5) is a proximal bearing, and the bearing of the bearing assembly (41) away from one end of the spherical pump head (5) is a distal bearing; after the medium passes through the spherical head gap flow channel (61), the medium is divided into two parts, one part of the medium sequentially passes through the pump shaft circulating flow channel (62), the liquid passage of the distal bearing, the flow gap flow channel (64) and then enters the circulating outlet flow channel (66), and the other part of the medium passes through the liquid passage of the proximal bearing and then enters the circulating outlet flow channel (66).

3. A canned motor pump according to claim 2, wherein A thrust disc (42) is arranged between the shaft shoulder of the pump shaft (4) and the bearing of the bearing assembly (41), the thrust disc (42) abuts against the shaft shoulder of the pump shaft (4) to bear the axial thrust of the pump shaft (4), and the disc surface of the thrust disc (42) is provided with a groove for the medium of the outlet of the bearing liquid passage to pass through.

4. A canned spherical rotor pump according to any one of claims 1 to 3, characterized in that The pump shell (1) is in a cylindrical structure with both ends open, and the front flange (11) and the rear flange (12) are arranged at the openings of both ends of the pump shell (1), respectively, and the stator shield sleeve (23) is arranged between the front flange (11) and the rear flange (12), and the front flange (11), the rear flange (12), the pump shell (1) and the stator shield sleeve (23) form a ring-shaped sealing space for installing the stator (21).

5. A canned spherical rotor pump according to claim 4, characterized in that The stator (21) is coaxially arranged with the winding assembly (22), and the electrical interface (24) is arranged on the pump shell (1) to connect the stator circuit.

6. A canned spherical rotor pump according to claim 4, characterized in that The sealing cavity of the stator assembly (2) is filled with epoxy resin sealant.

7. A canned motor pump according to claim 4, wherein The pump shaft (4) is coaxially arranged with the end plate (31) at both ends, and the rotor shield sleeve (33) is arranged between the two end plates (31), and the two end plates (31), the rotor shield sleeve (33) and the pump shaft (4) form a ring-shaped sealing space for installing the rotor (32); the rotor shield sleeve (33) and the stator shield sleeve (23) have a gap to form a flow gap flow channel (64).

8. A canned motor pump according to claim 4, wherein The hydraulic base (14) is coaxially arranged on the front flange (11), the spherical pump head (5) is fixed on the hydraulic base (14), the sliding sleeve (43) is arranged in the hydraulic base (14), the pump shaft (4) is coaxially fixed with the spherical rotor assembly (51) through the sliding sleeve, and the sliding sleeve (43) is coaxially rotatable with the seat body of the spherical pump head (5) through the bearing.

9. A canned spherical rotor pump according to claim 8, characterized in that The pump shaft (4) and the sliding sleeve (43) are coated with diamond film.

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