A high-rotating-speed and low-noise needle bearing for new energy vehicles

Abstract

This invention discloses a high-speed, low-noise needle roller bearing for new energy vehicles, relating to the field of bearing noise reduction technology. The high-speed, low-noise needle roller bearing for new energy vehicles includes a retaining ring connected to one side of a thrust cage, and the other side of the thrust cage connected to the bearing outer ring. An inner bearing ring is installed inside the retaining ring and the outer bearing ring, and a bearing cage is installed between the outer and inner bearing rings. A sealing cap ring is installed outside the retaining ring and the outer bearing ring. A first labyrinth seal and a second labyrinth seal, respectively installed at the gaps formed at both ends of the bearing, can seal the bearing during rotation, preventing external dust and other impurities from entering the bearing and causing wear on the needle rollers. This avoids loose needle rollers and the resulting significant noise. Furthermore, the retaining ring and the thrust cage can withstand large axial forces, ensuring good stability during high-speed rotation of the bearing.

Description

Technical Field

[0001] This invention relates to the field of bearing noise reduction technology, specifically a high-speed, low-noise needle roller bearing for new energy vehicles. Background Technology

[0002] With the rapid development of the new energy vehicle industry, extremely high demands are being placed on the performance of core components such as drive motors and reducers. As a fundamental supporting element of these core transmission systems, the performance of bearings directly affects the efficiency, noise, and reliability of the assembly. New energy vehicle drive motors typically feature high speed and low vibration and noise. Traditional needle roller bearings, under long-term high-speed operation conditions, often fail to meet the stringent standards of next-generation electric drive systems in terms of noise control and durability.

[0003] Many factors can cause abnormal noise in bearings during high-speed operation. Among them, the intrusion of external contaminants is a crucial yet often overlooked cause. During vehicle operation, especially in complex road conditions and harsh environments, fine particles such as dust, moisture, and metal shavings can easily penetrate the bearing's sealing gaps and intrude into the internal grease and raceway areas. These intruders cause multiple problems: First, hard particles cause abrasive wear between the needle rollers and raceways, damaging the precision-ground smooth surface and forming scratches and pits. This not only increases frictional torque and reduces transmission efficiency, but more importantly, at high speeds, the periodic rolling of the needle rollers over these damaged points produces significant vibration and periodic impact noise. Second, contaminants contaminate and degrade the grease, reducing its lubrication performance, exacerbating dry friction, and further leading to increased noise levels and abnormal bearing temperature rise.

[0004] Currently, most conventional needle roller bearings on the market employ either contact lip seals or non-contact clearance seals. While the former offers some dust protection, the frictional torque generated by the contact between the lip and the raceway is significant, hindering the reduction of power loss at high speeds. Furthermore, the lip is prone to wear, leading to decreased long-term sealing reliability. The latter, while exhibiting low friction, offers limited dust protection and is insufficient to effectively prevent the intrusion of fine dust particles. Therefore, there is an urgent need in this field for a high-speed needle roller bearing for new energy vehicles that can reduce dust wear on the needle rollers through a sealing structure. Summary of the Invention

[0005] The purpose of this invention is to provide a high-speed, low-noise needle roller bearing for new energy vehicles, in order to solve the problems raised in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: The high-speed, low-noise needle roller bearing for new energy vehicles includes a retaining ring, which is connected to one side of a thrust cage, and the other side of the thrust cage is connected to the outer ring of the bearing. An inner ring of the bearing is installed inside the retaining ring and the outer ring of the bearing. A bearing cage is installed between the outer ring of the bearing and the inner ring of the bearing. A sealing cap ring is installed outside the retaining ring and the outer ring of the bearing.

[0007] As a preferred technical solution, an installation groove is provided at the outermost edge of one end of the stop ring, and a plurality of screw holes are provided at the bottom surface of the installation groove. A first needle roller groove is provided at the other end face of the stop ring. A plurality of first sealing grooves are sequentially provided on the inner wall of the stop ring. The first sealing grooves are, from the outside to the inside, the outermost sealing groove, the middle sealing groove, and the innermost sealing groove. The groove depth of the first sealing groove increases sequentially from the outside to the inside, and the groove width of the first sealing groove decreases sequentially from the outside to the inside.

[0008] As a preferred technical solution, the thrust retainer is uniformly provided with a plurality of first opening slots, each of which is embedded with a first needle roller, a first oblique opening is provided on one side of the first opening slot, and an inwardly concave curved surface is provided on the side wall of the first opening slot.

[0009] As a preferred technical solution, a shoulder is provided at one end of the outer ring of the bearing, a second needle roller groove is formed on the end face of the shoulder, a receiving groove is formed on the inner wall of the outer ring of the bearing, a third needle roller groove is formed on the side wall of the receiving groove, and a second sealing groove is formed on the other end face of the outer ring of the bearing. The second sealing groove consists of an outermost sealing groove, a middle sealing groove, and an innermost sealing groove from the outside to the inside. The groove depth of the second sealing groove increases from the outermost to the innermost layer, and the groove width decreases from the outermost to the innermost layer.

[0010] As a preferred technical solution, the outer wall of the bearing inner ring is provided with a fourth needle roller groove, and the outer wall at one end of the bearing inner ring is provided with a first sealing tooth. The first sealing tooth includes an outermost sealing tooth, a middle sealing tooth and an innermost sealing tooth. The tooth height of the first sealing tooth gradually increases from the outermost to the innermost side. The tooth width of the first sealing tooth is uniform. The tooth spacing of the first sealing tooth decreases from the outermost to the innermost side. A ash storage groove is provided in the middle of the top of the first sealing tooth. Several swirling grooves are uniformly provided on the first sealing tooth. A ash storage groove is also provided in the swirling groove. A baffle is provided at the other end of the inner ring of the bearing. A second sealing tooth is provided on the side of the baffle near the fourth needle roller groove. The second sealing tooth includes an outermost sealing tooth, a middle sealing tooth, and an innermost sealing tooth. The tooth height of the second sealing tooth gradually increases from the outermost to the innermost layer. The tooth width of the second sealing tooth is uniform. The tooth spacing of the second sealing tooth decreases from the outermost to the innermost layer. A ash storage groove is provided in the middle above the second sealing tooth. Several swirl grooves are uniformly provided on the second sealing tooth.

[0011] As a preferred technical solution, the bearing cage is provided with a plurality of second opening grooves evenly arranged in a ring, each of which is embedded with a second needle roller, and a second oblique opening is provided on one side of the second opening groove.

[0012] As a preferred technical solution, the sealing cover ring has an oil inlet on its side wall, which is sealed with rubber. A plurality of mounting holes are evenly provided at one end of the sealing cover ring, and a sealing ring is provided at the bottom of the mounting hole. A screw is installed in the mounting hole.

[0013] As a preferred technical solution, the first sealing tooth of the outer wall of the bearing inner ring is embedded in the first sealing groove of the inner wall of the stop ring to form a first labyrinth seal. The gap formed when the first sealing tooth is embedded in the first sealing groove is a first labyrinth gap. The width of the first labyrinth gap decreases from the outermost to the innermost side.

[0014] As a preferred technical solution, the second sealing tooth of the bearing inner ring is embedded in the second sealing groove on the end face of the bearing outer ring to form a second labyrinth seal. The gap formed when the second sealing tooth is embedded in the second sealing groove is a second labyrinth gap. The width of the second labyrinth gap decreases sequentially from the outermost layer to the innermost layer.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. The first labyrinth seal and the second labyrinth seal installed at the gaps at both ends of the bearing can seal the bearing during rotation, preventing external dust and other impurities from entering the bearing and causing wear on the needle rollers. This avoids loosening of the needle rollers and generating significant noise. Furthermore, the retaining ring and thrust cage can withstand large axial forces, ensuring good stability of the bearing when it rotates at high speed. 2. A dust storage trough is provided at the top of the sealing teeth to store dust that enters the labyrinth sealing structure from the outside. This prevents dust from accumulating in the gaps between the labyrinths and coming into contact with the inner wall of the rotating labyrinth for a long time, which would accelerate the wear of the labyrinth. The dust storage trough ensures that the labyrinth sealing structure has a long service life. 3. The swirling grooves make the surface of the sealing teeth uneven, which can significantly reduce the circulation speed of the sealing structure and greatly improve the stability of the bearing at high speed while slightly increasing the leakage. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the main structure of the present invention; Figure 2 This is a cross-sectional structural diagram of the main body of the present invention; Figure 3 This is a schematic diagram of the thrust cage structure of the present invention; Figure 4 This is a schematic diagram of the bearing cage structure of the present invention; Figure 5 This is a cross-sectional view of the main body of the invention from another angle; Figure 6 yes Figure 2 Enlarged structural diagram at point A; Figure 7 yes Figure 2 Enlarged structural diagram at point B; Figure 8 yes Figure 5 Enlarged structural diagram at point C; Figure 9 yes Figure 5 A magnified structural diagram at point D.

[0017] In the diagram: 1. Stop ring; 2. Thrust cage; 3. Bearing outer ring; 4. Bearing inner ring; 5. Bearing cage; 6. Sealing cap ring; 7. First labyrinth seal; 8. Second labyrinth seal; 11. Mounting groove; 12. First needle roller groove; 13. First sealing groove; 21. First opening groove; 22. First needle roller; 31. Shoulder; 32. Receiving groove; 33. Second sealing groove; 41. Fourth needle roller groove; 42. First sealing tooth; 43. Ash storage groove; 44. Swirl groove; 45. Baffle; 46. Second sealing tooth; 51. Second opening groove; 52. Second needle roller; 61. Oil inlet; 62. Mounting hole; 63. Sealing ring; 64. Screw; 71. First labyrinth clearance; 81. Second labyrinth clearance; 1101, Screw hole; 1301, Outermost sealing groove; 1302, Middle sealing groove; 1303, Innermost sealing groove; 2101, First bevel; 2102, Curved surface; 3101, Second needle roller groove; 3201, Third needle roller groove; 3301, Outermost sealing groove; 3302, Middle sealing groove; 3303, Innermost sealing groove; 4201, Outermost sealing tooth; 4202, Middle sealing tooth; 4203, Innermost sealing tooth; 4601, Outermost sealing tooth; 4602, Middle sealing tooth; 4603, Innermost sealing tooth; 5101, Second bevel. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example: Figures 1-9 As shown, this invention provides a technical solution for a high-speed, low-noise needle roller bearing for new energy vehicles. This high-speed, low-noise needle roller bearing for new energy vehicles includes a retaining ring 1, which is connected to one side of a thrust cage 2. The other side of the thrust cage 2 is connected to a bearing outer ring 3. A bearing inner ring 4 is installed inside the retaining ring 1 and the bearing outer ring 3. A bearing cage 5 is installed between the bearing outer ring 3 and the bearing inner ring 4. A sealing cap ring 6 is installed outside the retaining ring 1 and the bearing outer ring 3. After the bearing is installed, since the thrust cage 2 and the bearing cage 5 have fixed the bearing inner ring 4, when the first sealing teeth 42 are sequentially embedded into the first sealing groove 13, a gap is formed between them, which is a first labyrinth gap 71. Due to the special design of the first sealing groove 13 and the first sealing teeth 42, the width of the first labyrinth gap 71 gradually decreases from the outside to the inside, while the height of the first labyrinth gap gradually decreases. The height gradually increases, so air carrying dust from the outside becomes increasingly difficult to pass through as it goes deeper into the maze. Eventually, most of the dust is collected in the dust storage tank 43, preventing dust from being in prolonged contact with the maze sidewalls during high-speed rotation, which would lead to accelerated wear of the maze structure and affect its service life. On the other hand, the high-speed rotation of the first maze seal 7 generates heat, so the air pressure inside the first maze seal 7 will be slightly higher than the outside air pressure. Under normal circumstances, it will be more difficult for outside air to enter the first maze gap 71 through the gap. In addition, due to the air pressure difference inside and outside the first maze gap 71, some of the dust trapped inside the first maze gap 71 will be blown out, playing a certain cleaning role. In summary, by setting up a maze sealing structure, most of the dust can be blocked, thereby preventing dust or metal debris from entering the bearing and causing impact noise and wear.

[0020] The outermost edge of one end of the stop ring 1 is provided with a mounting groove 11, and the bottom surface of the mounting groove 11 is provided with a plurality of screw holes 1101. The other end face of the stop ring 1 is provided with a first needle roller groove 12. The inner wall of the stop ring 1 is provided with a plurality of first sealing grooves 13 in sequence. The first sealing grooves 13 are, from the outside to the inside, the outermost sealing groove 1301, the middle sealing groove 1302 and the innermost sealing groove 1303. The groove depth of the first sealing groove 13 increases from the outside to the inside, and the groove width of the first sealing groove 13 decreases from the outside to the inside.

[0021] The thrust retainer 2 is evenly provided with a plurality of first opening slots 21, and a first needle roller 22 is embedded in each of the first opening slots 21. A first oblique opening 2101 is provided on one side of the first opening slot 21, and an inwardly concave curved surface 2102 is provided on the side wall of the first opening slot 21. By providing the first oblique opening 2101, it is easy for the first needle roller 22 to be put into the first opening slot 21. At the same time, the curvature of the curved surface 2102 is the same as that of the surface of the first needle roller 22. After the first needle roller 22 is put into the first opening slot 21, the curved surface 2102 fits tightly with the first needle roller 22, fixing the first needle roller 22 and preventing the first needle roller 22 from loosening and generating impact noise during high-speed rotation.

[0022] The bearing outer ring 3 has a shoulder 31 at one end, and a second needle roller groove 3101 is formed on the end face of the shoulder 31. The bearing outer ring 3 has a receiving groove 32 on the inner wall, and a third needle roller groove 3201 is formed on the side wall of the receiving groove 32. The bearing outer ring 3 has a second sealing groove 33 on the other end face. The second sealing groove 33 consists of an outermost sealing groove 3301, a middle sealing groove 3302, and an innermost sealing groove 3303 from the outside to the inside. The groove depth of the second sealing groove 33 increases from the outermost to the innermost layer, and the groove width of the second sealing groove 33 decreases from the outermost to the innermost layer.

[0023] The outer wall of the bearing inner ring 4 is provided with a fourth needle roller groove 41. The outer wall of one end of the bearing inner ring 4 is provided with a first sealing tooth 42. The first sealing tooth 42 includes an outermost sealing tooth 4201, a middle sealing tooth 4202 and an innermost sealing tooth 4203. The tooth height of the first sealing tooth 42 gradually increases from the outermost to the innermost. The tooth width of the first sealing tooth 42 is uniform. The tooth spacing of the first sealing tooth 42 decreases from the outermost to the innermost. A ash storage groove 43 is provided in the middle of the top of the first sealing tooth 42. Several swirling grooves 44 are evenly provided on the first sealing tooth 42. Ash storage grooves 43 are also provided in the swirling grooves 44. A baffle 45 is provided at the other end of the inner ring 4 of the bearing. A second sealing tooth 46 is provided on the side of the baffle 45 near the fourth needle roller groove 41. The second sealing tooth 46 includes an outermost sealing tooth 4601, a middle sealing tooth 4602 and an innermost sealing tooth 4603. The tooth height of the second sealing tooth 46 gradually increases from the outermost to the innermost layer. The tooth width of the second sealing tooth 46 is uniform. The tooth spacing of the second sealing tooth 46 decreases from the outermost to the innermost layer. A ash storage groove 43 is provided in the middle above the second sealing tooth 46. Several swirling grooves 44 are evenly provided on the second sealing tooth 46.

[0024] The bearing cage 5 is provided with several second opening grooves 51 evenly arranged in a ring. Each second opening groove 51 is embedded with a second needle roller 52. A second oblique opening 5101 is provided on one side of the second opening groove 51.

[0025] The sealing cover ring 6 has an oil inlet 61 on its side wall, which is sealed by rubber. A number of mounting holes 62 are evenly provided at one end of the sealing cover ring 6. A sealing ring 63 is provided at the bottom of the mounting hole 62, and a screw 64 is installed in the mounting hole 62.

[0026] The first sealing tooth 42 of the outer wall of the bearing inner ring 4 is embedded in the first sealing groove 13 of the inner wall of the stop ring 1 to form the first labyrinth seal 7. The gap formed when the first sealing tooth 42 is embedded in the first sealing groove 13 is the first labyrinth gap 71. The width of the first labyrinth gap 71 decreases from the outermost to the innermost side.

[0027] The second sealing tooth 46 of the inner ring 4 is embedded in the second sealing groove 33 on the end face of the outer ring 3 of the bearing to form a second labyrinth seal 8. The gap formed when the second sealing tooth 46 is embedded in the second sealing groove 33 is the second labyrinth gap 81. The width of the second labyrinth gap 81 decreases from the outermost layer to the innermost layer.

[0028] Working principle of the invention: After the bearing is installed, since the thrust cage 2 and bearing cage 5 have fixed the inner ring 4 of the bearing, when the first sealing teeth 42 are sequentially embedded into the first sealing groove 13, the gap formed between them is the first labyrinth gap 71. Due to the special design of the first sealing groove 13 and the first sealing teeth 42, the width of the first labyrinth gap 71 gradually decreases from the outside to the inside, while the height of the first labyrinth gap gradually increases. Therefore, when air carrying dust enters the first labyrinth gap, it becomes increasingly difficult to pass through as it goes deeper into the labyrinth, and eventually most of it is trapped inside. Dust is collected in the dust storage tank 43 to prevent dust from contacting the side walls of the maze for a long time during the high-speed rotation of the maze, which would lead to increased wear on the maze structure and affect its service life. On the other hand, heat is generated during the high-speed rotation of the first maze seal 7, so the air pressure inside the first maze seal 7 will be slightly greater than the outside air pressure. Under normal circumstances, it will be more difficult for outside air to enter the first maze gap 71 through the gap. In addition, due to the air pressure difference inside and outside the first maze gap 71, some of the dust trapped inside the first maze gap 71 will be blown out, which plays a certain role in cleaning.

[0029] The first labyrinth seal 7 and the second labyrinth seal 8, which are respectively installed in the gaps formed at both ends of the bearing, can seal the bearing during rotation, preventing external dust and other impurities from entering the bearing and causing wear on the needle rollers. This avoids the loosening of the needle rollers and the generation of large noise. In addition, the retaining ring 1 and the thrust cage 2 can withstand large axial forces, ensuring good stability of the bearing when it rotates at high speed.

[0030] The top of the sealing tooth is provided with a dust storage tank 43, which can store dust that enters the labyrinth sealing structure from the outside. This prevents dust from being trapped in the labyrinth gaps and coming into contact with the inner wall of the rotating labyrinth for a long time, thus aggravating the wear of the labyrinth sealing structure. The dust storage tank 43 can ensure that the labyrinth sealing structure has a long service life.

[0031] The swirling groove 44 makes the surface of the sealing teeth uneven, which can significantly reduce the circulation velocity of the labyrinth seal structure and greatly improve the stability of the bearing at high speed while slightly increasing the leakage.

[0032] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A high-speed, low-noise needle roller bearing for new energy vehicles, characterized in that: The high-speed, low-noise needle roller bearing for new energy vehicles includes a retaining ring (1), which is connected to one side of a thrust cage (2), and the other side of the thrust cage (2) is connected to the outer ring (3). An inner ring (4) is installed inside the retaining ring (1) and the outer ring (3). A bearing cage (5) is installed between the outer ring (3) and the inner ring (4). A sealing cover ring (6) is installed outside the retaining ring (1) and the outer ring (3). The outermost edge of one end of the stop ring (1) is provided with an installation groove (11), and the bottom surface of the installation groove (11) is provided with a plurality of screw holes (1101). The other end face of the stop ring (1) is provided with a first needle roller groove (12). The inner wall of the stop ring (1) is provided with a plurality of first sealing grooves (13). The first sealing grooves (13) are, from the outside to the inside, the outermost sealing groove (1301), the middle sealing groove (1302) and the innermost sealing groove (1303). The groove depth of the first sealing groove (13) increases from the outside to the inside, and the groove width of the first sealing groove (13) decreases from the outside to the inside. The bearing outer ring (3) has a shoulder (31) at one end, a second needle roller groove (3101) is provided on the end face of the shoulder (31), a receiving groove (32) is provided on the inner wall of the bearing outer ring (3), a third needle roller groove (3201) is provided on the side wall of the receiving groove (32), and a second sealing groove (33) is provided on the other end face of the bearing outer ring (3). The second sealing groove (33) consists of an outermost sealing groove (3301), a middle sealing groove (3302), and an innermost sealing groove (3303) from the outside to the inside. The groove depth of the second sealing groove (33) increases from the outermost layer to the innermost layer, and the groove width of the second sealing groove (33) decreases from the outermost layer to the innermost layer. The outer wall of the bearing inner ring (4) is provided with a fourth needle roller groove (41). The outer wall of one end of the bearing inner ring (4) is provided with a first sealing tooth (42). The first sealing tooth (42) includes an outermost sealing tooth (4201), a middle sealing tooth (4202) and an innermost sealing tooth (4203). The tooth height of the first sealing tooth (42) gradually increases from the outermost to the innermost. The tooth width of the first sealing tooth (42) is consistent. The tooth spacing of the first sealing tooth (42) decreases from the outermost to the innermost. A ash storage groove (43) is provided in the middle of the top of the first sealing tooth (42). Several swirling grooves (44) are evenly provided on the first sealing tooth (42). A ash storage groove (43) is also provided in the swirling groove (44). A baffle (45) is provided at the other end of the inner ring (4) of the bearing. A second sealing tooth (46) is provided on the side of the baffle (45) near the fourth needle roller groove (41). The second sealing tooth (46) includes an outermost sealing tooth (4601), a middle sealing tooth (4602), and an innermost sealing tooth (4603). The tooth height of the second sealing tooth (46) gradually increases from the outermost to the innermost layer. The tooth width of the second sealing tooth (46) is consistent. The tooth spacing of the second sealing tooth (46) decreases from the outermost to the innermost layer. A ash storage groove (43) is opened in the middle above the second sealing tooth (46). Several swirling grooves (44) are evenly opened on the second sealing tooth (46).

2. The high-speed, low-noise needle roller bearing for new energy vehicles according to claim 1, characterized in that: The thrust retainer (2) is uniformly provided with a plurality of first opening grooves (21), each of which is embedded with a first needle roller (22). A first oblique opening (2101) is provided on one side of the first opening groove (21), and an inwardly concave curved surface (2102) is provided on the side wall of the first opening groove (21).

3. A high-speed, low-noise needle roller bearing for new energy vehicles according to claim 2, characterized in that: The bearing cage (5) is provided with a plurality of second opening grooves (51) evenly arranged in a ring. Each of the second opening grooves (51) is embedded with a second needle roller (52). A second oblique opening (5101) is provided on one side of the second opening groove (51).

4. A high-speed, low-noise needle roller bearing for new energy vehicles according to claim 3, characterized in that: The sealing cover ring (6) has an oil inlet (61) on its side wall. The oil inlet (61) is sealed by rubber. A plurality of mounting holes (62) are evenly provided at one end of the sealing cover ring (6). A sealing ring (63) is provided at the bottom of the mounting hole (62). A screw (64) is installed in the mounting hole (62).

5. A high-speed, low-noise needle roller bearing for new energy vehicles according to claim 4, characterized in that: The first sealing tooth (42) of the outer wall of the bearing inner ring (4) is embedded in the first sealing groove (13) of the inner wall of the stop ring (1) to form a first labyrinth seal (7). The gap formed when the first sealing tooth (42) is embedded in the first sealing groove (13) is the first labyrinth gap (71). The width of the first labyrinth gap (71) decreases from the outermost to the innermost side.

6. A high-speed, low-noise needle roller bearing for new energy vehicles according to claim 5, characterized in that: The second sealing tooth (46) of the inner ring (4) of the bearing is embedded in the second sealing groove (33) of the bearing outer ring (3) to form a second labyrinth seal (8). The gap formed when the second sealing tooth (46) is embedded in the second sealing groove (33) is the second labyrinth gap (81). The width of the second labyrinth gap (81) decreases from the outermost layer to the innermost layer.

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