Motor sealing structure for independent cooling of rotor

Abstract

The invention belongs to a motor sealing structure for independently cooling a rotor in the technical field of motors. The inner wall, close to the motor B end (B), of the stator assembly (C) is provided with a limiting step (9), the end, close to the motor B end (B), of the sealing layer (8) abuts against the limiting step (9), the surface of the end, close to the motor B end (B), of the sealing layer (8) is attached to a B end protruding part (B1) of the motor B end (B), the surface of the end, close to the motor A end (A), of the sealing layer (8) is attached to an A end protruding part (A1) of the motor A end (A), the sealing layer (8) is of a cylindrical structure, and the outer ring of the sealing layer (8) is attached to the inner wall of the stator assembly (C). The sealing layer (8) is of a structure made of a stainless steel sheet or an aluminum alloy or copper material or a plastic material. According to the motor sealing structure for independent cooling of the rotor, sealing of the rotor area is achieved, it is ensured that independent cooling of the rotor area is achieved, cooling oil is prevented from overflowing to the stator area, and control over the working temperature of the motor is met.

Description

Technical Field

[0001] The invention belongs to the technical field of motors, and more specifically, relates to a motor sealing structure for cooling a rotor separately. Background Art

[0002] During the operation of the motor, a lot of heat will accumulate in a limited volume, which will have a serious adverse effect on the performance and life of the motor. Therefore, the motor needs to be cooled, and the motor cooling is generally achieved by the cooling medium entering the motor and taking away the heat through the circulation of the cooling medium. In the prior art, there is a technology named "Cooling structure of inner rotor motor" and published (announced) as "CN102810943A", which discloses a cooling structure of an inner rotor motor, wherein the inner rotor motor comprises a rotor shaft, a rotor part, a stator part, a front end cover and a cover; the cooling structure comprises a third cavity between the front end cover and the cover, and the third cavity serves as a part of the cooling medium channel; the rotor shaft has a heat conduction cavity, the opening of which is arranged on the side of the rotor shaft located at the front end cover, and the interior of the cavity contains a heat conduction medium; the first end of the heat conduction rod is located in the heat conduction cavity and contacts the heat conduction medium, the second end is located in the third cavity and contacts the cooling medium, and the second end is sealed with the front end cover by a static seal; the rotor shaft and the heat conduction rod are sealed by a dynamic seal; the heat of the rotor part and the rotor shaft is transferred to the second end of the heat conduction rod through the first end of the heat conduction rod in the heat conduction cavity, and the heat is dissipated through the cooling medium in the third cavity. The present application satisfies the strict requirements of insulation, sealing and volume while obtaining good heat dissipation effects of the stator and rotor. The technology does not involve the technical problems and solutions of the present application. Summary of the invention

[0003] The technical problem to be solved by the present invention is: in view of the deficiencies in the prior art, a motor sealing structure for separate rotor cooling is provided which has a simple structure and can effectively achieve isolation between the stator area and the rotor area, achieve sealing of the rotor area, ensure separate cooling of the rotor area, avoid overflow of cooling oil into the stator area, and meet the requirements of motor operating temperature control.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is:

[0005] The present invention discloses a motor sealing structure for cooling a rotor separately, comprising a stator assembly, a sealing layer arranged on the inner wall of the stator assembly, a limiting step arranged on the inner wall of the stator assembly close to the B end of the motor, one end of the sealing layer close to the B end of the motor rests on the limiting step, one end surface of the sealing layer close to the B end of the motor simultaneously fits the B end convex part of the B end of the motor, one end surface of the sealing layer close to the A end of the motor fits the A end convex part of the A end of the motor, the sealing layer is a cylindrical structure, the outer ring of the sealing layer fits the inner wall of the stator assembly, and the sealing layer is a structure made of a stainless steel sheet, an aluminum alloy, a copper material or a plastic material.

[0006] The stator assembly comprises a stator core and a stator winding.

[0007] The side of the stator winding extends to the outside of the stator core, one end of the stator winding and the B-end recess of the motor B-end are potted to form a potting resin part, and the other end of the stator winding and the A-end recess of the motor A-end are potted to form a potting resin part.

[0008] The outer ring of the B-end convex part of the motor B-end is sleeved with the B-end convex part ring, the B-end convex part ring is located in the B-end recessed step of the B-end potting resin part, and the sealing layer is sandwiched between the convex part ring and the B-end convex part.

[0009] The motor A end A is the motor end cover 5, the A end convex outer ring of the motor A end is sleeved with the A end convex ring, the A end convex ring is located in the A end recessed step of the potting resin part, and the sealing layer is sandwiched between the A end convex ring and the A end convex.

[0010] The outer ring of the B-end convex part of the B-end of the motor is provided with a B-end ring groove, and a B-end sealing ring is sleeved in the B-end ring groove.

[0011] The outer ring of the A-end convex part of the A-end of the motor is provided with an A-end ring groove, and an A-end sealing ring is sleeved in the A-end ring groove.

[0012] The sealing layer is made of high-pressure and high-temperature resistant plastic material.

[0013] The thickness of the sealing layer is ≤0.4 mm.

[0014] The stator assembly is located inside the casing, the inner ring of the stator assembly is provided with a motor rotor, and an oil-immersed cooling cavity is between the motor rotor and the sealing layer.

[0015] The technical solution of the present invention is adopted, and the working principle and beneficial effects are as follows:

[0016] The motor sealing structure for independent rotor cooling described in the present invention is that when the structure is set, the casing, stator assembly, and rotor are separately manufactured, the stator assembly is fixedly arranged on the inner wall of the casing, and the rotor is located at the inner ring of the stator assembly. According to the working characteristics of the motor, the stator needs to be cooled, and the cooling mainly relies on the heat conduction of the potted resin. Prevent the metal iron filings in the oil from damaging the stator insulation system. In addition, the stator and the rotor are separated because the oil pressure at the three-phase outlet position of the motor is too high to be sealed, and the rotor also needs to be cooled. For this reason, a sealing layer is provided on the inner wall of the stator assembly, and the sealing layer is reliably fixed on the inner wall of the stator assembly to achieve reliable support and distribution, effectively isolating the stator area and the rotor area. After the cooling oil enters, the rotor is cooled only through the rotor area, and the problem of cooling oil overflowing to the stator area will not occur, thereby ensuring the isolation and sealing reliability of the stator area and the rotor area. A limiting step is set near the inner wall of the motor B end of the stator assembly. In this way, when the sealing layer is arranged, the sealing layer is inserted into the inner ring of the stator assembly and fits the inner wall of the stator assembly to achieve radial limiting of the sealing layer. The sealing layer is close to the motor B end and abuts against the limiting step to achieve axial limiting of the sealing layer, ensuring the reliability of the arrangement. The surface of the sealing layer close to the motor B end is also fitted with the B end convex part of the motor B end, and the surface of the sealing layer close to the motor A end is fitted with the A end convex part of the motor A end. The sealing layer is a cylindrical structure. In this way, the two ends of the sealing layer are reliably supported, that is, the inner ring of the sealing layer is supported on the corresponding convex part, and the outer ring of the sealing layer is fitted with the inner wall of the stator assembly. The sealing layer is a structure made of stainless steel sheet or aluminum alloy or copper material or plastic material. The sealing layer needs to be able to bear the cavity oil pressure. Considering the influence of electromagnetic performance, it is preferred to make the sealing layer with high pressure and high temperature resistant plastic. Through the sealing layer, a sealed cavity is formed between the sealing layer and the rotor area, that is, a rotor sealing cavity. The cavity is an oil-immersed cooling cavity, which is used for cooling oil to enter and exit to cool the rotor separately. The structure of the present invention supplies cooling oil at a relatively high oil pressure, not less than 100 bar, or even higher. When the cooling oil passes through the oil-immersed cooling cavity, it exerts force on the inner wall of the sealing layer, so that the sealing layer can reliably fit the inner wall of the stator assembly. In this way, in addition to structural improvement to strengthen the seal, the high pressure during operation can also greatly improve the sealing reliability; and the overall structure is simple and compact, and the cost is low. The structure of the present invention completely limits the high-pressure cooling oil inside the rotor sealing cavity, avoiding the problem of easy failure and oil leakage of the stator outlet position seal caused by conventional overall oil immersion, and also avoiding the adverse effects of metal impurities mixed in the cooling oil on the electrical performance of the stator. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The following is a brief description of the contents and symbols in the drawings of this specification:

[0018] Figure 1 This is a schematic structural diagram of a motor sealing structure for independent rotor cooling according to the present invention;

[0019] The marks in the attached drawings are respectively: A, motor A end; A1, A end convex part; A2, A end concave part; A3, A end convex part collar; A4, A end ring groove; A5, A end sealing ring; B, motor B end; B1, B end convex part; B2, B end concave part; B3, B end convex part collar; B4, B end ring groove; B5, B end sealing ring; C, stator assembly; D, motor rotor; E, oil-immersed cooling chamber; 1, casing; 2, stator core; 3, stator winding; 4, casing mating surface; 5, cover; 6, cover mating surface; 7, potting resin part; 8, sealing layer; 9, limit step; 10, cover sealing ring. DETAILED DESCRIPTION

[0020] The following is a further detailed description of the specific implementation of the present invention, such as the shape, structure, mutual position and connection relationship between the various components involved, the function and working principle of each part, etc., through the description of the embodiments with reference to the accompanying drawings:

[0021] As attached Figure 1As shown, the present invention is a motor sealing structure for cooling the rotor separately, including a stator assembly C, a sealing layer 8 is arranged on the inner wall of the stator assembly C, a limiting step 9 is arranged on the inner wall of the stator assembly C near the motor B end B, the sealing layer 8 is close to the motor B end B and abuts on the limiting step 9, the surface of the sealing layer 8 near the motor B end B is simultaneously attached to the B end convex part B1 of the motor B end B, the surface of the sealing layer 8 near the motor A end A is attached to the A end convex part A1 of the motor A end A, the sealing layer 8 is a cylindrical structure, the outer ring of the sealing layer 8 is attached to the inner wall of the stator assembly C, and the sealing layer 8 is a structure made of stainless steel sheet or aluminum alloy or copper material or plastic material. The above structure proposes an improved technical solution to address the deficiencies in the prior art. When the structure is set, the housing 1, the stator assembly C, and the rotor are made separately, the stator assembly C is fixedly arranged on the inner wall of the housing, and the rotor is located on the inner ring of the stator assembly. According to the working characteristics of the motor, the stator needs to be cooled, and it mainly relies on the heat conduction cooling of the potted resin. Prevent metal iron filings in the oil from damaging the stator insulation system. In addition, the stator and rotor are separated because the oil pressure at the three-phase outlet position of the motor is too high to be sealed, and the rotor also needs to be cooled. For this reason, a sealing layer 8 is set on the inner wall of the stator component C. The sealing layer 8 is reliably fixed on the inner wall of the stator component C to achieve reliable support and distribution, effectively isolating the stator area and the rotor area. After the cooling oil enters, the rotor is cooled only through the rotor area, and the cooling oil will not overflow into the stator area, thereby ensuring the isolation and sealing reliability of the stator area and the rotor area. A limiting step 9 is set on the inner wall of the stator component C near the B end of the motor. In this way, when the sealing layer 8 is arranged, the sealing layer 8 is inserted into the inner ring of the stator component C and fits the inner wall of the stator component C to achieve radial limitation of the sealing layer 8. The end of the sealing layer 8 near the B end of the motor rests on the limiting step 9 to achieve axial limitation of the sealing layer 8 and ensure the reliability of the arrangement. The surface of the sealing layer 8 near the B end of the motor is in contact with the B end convex part B1 of the B end of the motor B, and the surface of the sealing layer 8 near the A end of the motor is in contact with the A end convex part A1 of the A end of the motor A. The sealing layer 8 is a cylindrical structure, so that the two ends of the sealing layer 8 can be reliably supported, that is, the inner circle of the sealing layer 8 is supported on the corresponding convex part, and the outer circle of the sealing layer 8 is in contact with the inner wall of the stator assembly C. The sealing layer 8 is a structure made of stainless steel sheet or aluminum alloy or copper material or plastic material. The sealing layer 8 needs to be able to bear the cavity oil pressure. Considering the influence of electromagnetic performance, it is preferred to make the sealing layer 8 of high-pressure and high-temperature resistant plastic, especially the material with a thermal expansion coefficient close to the stator core in the range of -40℃-120℃. Through the sealing layer 8, a sealed cavity is formed between the sealing layer 8 and the rotor area, that is, a rotor sealing cavity, which is an oil-immersed cooling cavity for cooling oil in and out to cool the rotor separately.The structure of the present invention supplies cooling oil at a relatively high oil pressure, not less than 100 bar, or even higher. When the cooling oil passes through the oil-immersed cooling chamber, it exerts force on the inner wall of the sealing layer 8, so that the sealing layer 8 can reliably fit the inner wall of the stator assembly C. In this way, in addition to the structural improvement to strengthen the seal, the high pressure during operation can also greatly improve the sealing reliability; and the overall structure is simple and compact, and the cost is relatively low. The structure of the present invention completely confines the high-pressure cooling oil to the inside of the rotor sealing cavity, avoiding the problem of easy failure and oil leakage of the stator outlet position seal caused by conventional overall oil immersion, and also avoiding the adverse effects of metal impurities mixed in the cooling oil on the electrical performance of the stator. The motor sealing structure for separate rotor cooling described in the present invention has a simple structure, can effectively achieve isolation between the stator area and the rotor area, achieve sealing of the rotor area, ensure separate cooling of the rotor area, avoid overflow of cooling oil to the stator area, and meet the motor operating temperature control.

[0022] The stator assembly C includes a stator core 2 and a stator winding 3. The side of the stator winding 3 extends to the outside of the stator core 2. One end of the stator winding C and the B-end recess B2 of the motor B end B are potted to form a potting resin part 7, and the other end of the stator winding C and the A-end recess A2 of the motor A end A are potted to form a potting resin part 7. In the above structure, the length of the sealing layer needs to be greater than the length of the stator core 2. For this purpose, the B-end recess B2 is potted to form a potting resin part 7, and the A-end recess A2 is potted to form a potting resin part 7, that is, the length of the stator core 2 and the potting resin part 7 at both ends is greater than the length of the sealing layer, and the distance between the B-end protrusion B1 and the A-end protrusion A1 is less than the length of the sealing layer. In this way, the inner circle of the sealing layer 8 can be reliably fitted to fit the B-end protrusion B1 and the A-end protrusion A1, and the outer circle of the sealing layer 8 can be reliably limited by the potting resin part 7 at both ends, so as to achieve reliable arrangement and positioning of the sealing layer, and effectively improve the isolation and sealing performance.

[0023] The outer ring of the B-end convex part B1 of the B-end B of the motor is fitted with the B-end convex part collar B3, the B-end convex part collar B3 is located in the B-end recessed step of the B-end potting resin part 7, and the sealing layer 8 is sandwiched between the collar B3 and the B-end convex part B1. The A-end A of the motor is the motor end cover 5, the outer ring of the A-end convex part A1 of the A-end A of the motor is fitted with the A-end convex part collar A3, the A-end convex part collar A3 is located in the A-end recessed step of the potting resin part 7, and the sealing layer 8 is sandwiched between the A-end convex part collar A3 and the A-end convex part A1. For the above structure, in case of high oil pressure, stainless steel collars can be added at both ends of the stator to resist the oil pressure at both ends of the sealing layer 8 to ensure the sealing reliability. In addition, the sealing layer can also be designed to be directly injected onto the inner wall of the stator, so that the design is more compact and reliable, and the sealing layer 8 is completely in contact with the stator tooth slots.

[0024] The outer ring of the B-end convex part B1 of the B-end B of the motor is provided with a B-end annular groove B4, and the B-end sealing ring B5 is set in the B-end annular groove B4. The outer ring of the A-end convex part A1 of the A-end A of the motor is provided with an A-end annular groove A4, and the A-end sealing ring A5 is set in the A-end annular groove A4. In the above structure, the annular groove is used to set the sealing ring, and the sealing ring is used to improve the sealing performance between the sealing layer 8.

[0025] The sealing layer 8 is made of high-pressure and high-temperature resistant plastic material. The above structure is based on the special performance requirements of the motor. The high-pressure and high-temperature resistant plastic meets both high-temperature requirements and high-pressure requirements, effectively ensuring the sealing performance of the sealing layer when the motor is working and improving the service life.

[0026] The thickness of the sealing layer 8 is ≤0.4 mm. In the above structure, the sealing layer is located at the air gap of the motor and the space is limited, so the thickness needs to be controlled to be very thin.

[0027] The stator assembly C is located inside the housing 1, and the motor rotor D is arranged inside the stator assembly C. The oil-immersed cooling chamber E is formed between the motor rotor D and the sealing layer 8. The above structure, through the setting of the sealing layer, forms two dry and wet separated areas inside the motor. The dry area is the stator area, and the wet area is the rotor area. The cooling oil only passes through the rotor area. In this way, the function of cooling the rotor of the motor by the high-pressure cooling oil supplied by the oil pump can be reliably realized; at the same time, the problem of oil leakage from the rotor area, especially the oil leakage at the outlet hole position, is also solved.

[0028] In the motor sealing structure described in the present invention, the sealing layer completely confines the high-pressure oil to the rotor area. A thin-walled sealing layer is designed in the very narrow stator-rotor air gap space inside the motor (usually the air gap is about 1 mm). Due to the structural setting and the oil pressure of the oil-immersed cooling chamber, the sealing layer is completely pressed against the inner wall of the stator assembly. Therefore, even if the air gap space is very small, there is no need to worry about the bulge of the thin-walled sealing layer, and the rotor will not be swept. The sealing layer can be designed as a separate thin-walled barrel-shaped component and assembled into the inner wall of the stator assembly. At this time, the structural strength of the sealing layer needs to be calculated according to the oil pressure in the inner cavity. When the pressure is high, stainless steel rings can be added at both ends of the stator to resist the oil pressure at both ends of the sealing layer to ensure the reliability of the seal.

[0029] The motor sealing structure for cooling the rotor separately described in the present invention is made of a housing 1, a stator assembly C, and a rotor. The stator assembly C is fixedly arranged on the inner wall of the housing, and the rotor is located at the inner ring of the stator assembly C. The rotor is located at the inner ring of the stator assembly. According to the working characteristics of the motor, the stator needs to be cooled, and the cooling mainly relies on the heat conduction of the potted resin. Prevent the metal iron filings in the oil from damaging the stator insulation system. In addition, the stator and the rotor are separated because the oil pressure at the three-phase outlet position of the motor is too high to be sealed, and the rotor also needs to be cooled. A sealing layer 8 is set on the inner wall of the stator assembly C, and the sealing layer 8 is reliably fixed on the inner wall of the stator assembly C to achieve reliable support and distribution, effectively isolating the stator area and the rotor area. After the cooling oil enters, the rotor is cooled only through the rotor area, and the problem of cooling oil overflowing to the stator area will not occur, thereby ensuring the isolation and sealing reliability of the stator area and the rotor area. A limiting step 9 is provided on the inner wall of the stator assembly C near the B end of the motor. In this way, when the sealing layer 8 is arranged, the sealing layer 8 is inserted into the inner ring of the stator assembly C and fits the inner wall of the stator assembly C to achieve radial limitation of the sealing layer 8. The end of the sealing layer 8 near the B end of the motor rests on the limiting step 9 to achieve axial limitation of the sealing layer 8 and ensure the reliability of the arrangement. The surface of the sealing layer 8 near the B end of the motor fits the B end convex part B1 of the B end of the motor at the same time. The surface of the sealing layer 8 near the A end of the motor fits the A end convex part A1 of the A end of the motor. The sealing layer 8 is a cylindrical structure. In this way, the two ends of the sealing layer 8 can be reliably supported, that is, the inner ring of the sealing layer 8 is supported on the corresponding convex part, and the outer ring of the sealing layer 8 fits the inner wall of the stator assembly C. The sealing layer 8 is a structure made of stainless steel sheet, aluminum alloy, copper or plastic material. The sealing layer 8 needs to be able to bear the oil pressure of the cavity. Considering the influence of electromagnetic performance, it is preferred to make the sealing layer 8 of high-pressure and high-temperature resistant plastic, especially the material with a thermal expansion coefficient close to the stator core in the range of -40℃-120℃. Through the sealing layer 8, a sealed cavity is formed between the sealing layer 8 and the rotor area, that is, a rotor sealing cavity, which is an oil-immersed cooling cavity for cooling oil to enter and exit the rotor to cool it separately. The structure of the present invention supplies cooling oil at a high oil pressure, not less than 100 bar, or even higher. When the cooling oil passes through the oil-immersed cooling cavity, it exerts force on the inner wall of the sealing layer 8, so that the sealing layer 8 can reliably fit the inner wall of the stator assembly C. In this way, in addition to structural improvements to strengthen the seal, the high pressure during operation can also greatly improve the sealing reliability; and the overall structure is simple and compact, and the cost is low. The structure of the present invention completely confines the high-pressure cooling oil to the inside of the rotor sealing cavity, avoiding the problem of easy failure and oil leakage of the stator outlet position seal caused by conventional overall oil immersion, and also avoiding the adverse effects of metal impurities mixed in the cooling oil on the electrical performance of the stator.

[0030] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A motor sealing structure for independent rotor cooling, characterized in that: The invention comprises a stator assembly (C), wherein a sealing layer (8) is arranged on the inner wall of the stator assembly (C), a limiting step (9) is arranged on the inner wall of the stator assembly (C) close to the B end (B) of the motor, one end of the sealing layer (8) close to the B end (B) of the motor abuts against the limiting step (9), one end surface of the sealing layer (8) close to the B end (B) of the motor simultaneously fits the B end convex part (B1) of the B end (B) of the motor, and one end surface of the sealing layer (8) close to the A end (A) of the motor fits the A end convex part (A1) of the A end (A) of the motor, the sealing layer (8) is a cylindrical structure, the outer ring of the sealing layer (8) fits the inner wall of the stator assembly (C), and the sealing layer (8) is a structure made of a stainless steel sheet, an aluminum alloy, a copper material or a plastic material.

2. The motor sealing structure for independent rotor cooling according to claim 1, characterized in that: The stator assembly (C) comprises a stator core (2) and a stator winding (3).

3. The motor sealing structure for independent rotor cooling according to claim 2 is characterized in that: The side surface of the stator winding (3) extends to the outside of the stator core (2), one end of the stator winding (C) and the B-end recess (B2) of the motor B-end (B) are potted to form a potting resin portion (7), and the other end of the stator winding (C) and the A-end recess (A2) of the motor A-end (A) are potted to form a potting resin portion (7).

4. The motor sealing structure for independent rotor cooling according to claim 3 is characterized in that: The outer ring of the B-end convex part (B1) of the B-end (B) of the motor is sleeved with a B-end convex part ring (B3), the B-end convex part ring (B3) is located in the B-end recessed step of the B-end potting resin part (7), and the sealing layer (8) is sandwiched between the convex part ring (B3) and the B-end convex part (B1).

5. The motor sealing structure for independent rotor cooling according to claim 2, characterized in that: The motor A end (A) is a motor end cover (5), the A end convex part (A1) of the motor A end (B) is sleeved with an A end convex part ring (A3) on its outer ring, the A end convex part ring (A3) is located in the A end recessed step of the potting resin part (7), and the sealing layer (8) is sandwiched between the A end convex part ring (A3) and the A end convex part (A1).

6. The motor sealing structure for independent rotor cooling according to claim 5, characterized in that: The outer ring of the B-end convex part (B1) of the B-end (B) of the motor is provided with a B-end ring groove (B4), and a B-end sealing ring (B5) is sleeved in the B-end ring groove (B4).

7. The motor sealing structure for independent rotor cooling according to claim 1 or 6, characterized in that: The outer ring of the A-end convex part (A1) of the A-end (A) of the motor is provided with an A-end ring groove (A4), and an A-end sealing ring (A5) is sleeved in the A-end ring groove (A4).

8. The motor sealing structure for independent rotor cooling according to claim 1 or 2, characterized in that: The sealing layer (8) is made of high pressure and high temperature resistant plastic material.

9. The motor sealing structure for independent rotor cooling according to claim 1 or 2, characterized in that: The thickness of the sealing layer (8) is ≤0.4 mm.

10. The motor sealing structure for independent rotor cooling according to claim 1 or 2, characterized in that: The stator assembly (C) is located inside the housing (1), the motor rotor (D) is arranged on the inner ring of the stator assembly (C), and an oil-immersed cooling cavity (E) is located between the motor rotor (D) and the sealing layer (8).

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