A thrust bearing with a low coefficient of friction

Abstract

A thrust bearing with a low coefficient of friction includes a lower cover, an upper cover, a middle ring, anti-friction washers, a sealing ring assembly, and a bushing. The lower cover includes a receiving groove and multiple equally spaced partitions. The middle ring includes multiple secondary middle rings, each of which has multiple oil pockets for storing lubricating grease on its side facing the upper cover. The anti-friction washers are made of metal and have a smooth, ground surface. The anti-friction washers are disposed between the middle rings and the upper cover. When the upper cover rotates relative to the lower cover, the secondary middle rings are fixed in the receiving grooves, and the anti-friction washers rotate relative to the middle rings. The lubricating grease in the oil pockets reduces the friction between the anti-friction washers and the middle rings, and the smooth surface of the anti-friction washers further reduces the coefficient of friction by rubbing against the secondary middle rings, thereby reducing the wear of the middle rings and effectively increasing the service life of the thrust bearing.

Description

Technical Field

[0001] This utility model belongs to the field of automotive parts technology, and in particular to a thrust bearing with a low coefficient of friction. Background Technology

[0002] As is well known, the hydraulic shock absorber in a strut-type suspension for the front wheels of a four-wheeled vehicle contains a strut assembly and a coil spring. During steering, the strut assembly and coil spring rotate together, and the piston rod within the strut assembly can either rotate or remain stationary. However, in any type of strut-type suspension, it is necessary to ensure that the strut assembly can rotate smoothly. Therefore, a thrust bearing is required on this strut assembly.

[0003] The friction coefficient between the various components inside the existing thrust bearing is too high, which can easily affect the service life of the thrust bearing.

[0004] As shown in the utility model patent with publication number CN222615843U, although the coefficient of friction between the friction-reducing pad and the middle ring is less than that between the middle ring and the lower cover, when the upper cover rotates relative to the lower cover, it will cause relative movement between the friction-reducing pad and the upper cover, or between the friction-reducing pad and the middle ring. Since both the middle ring and the friction-reducing pad are made of plastic, there is still a large frictional force during relative rotation. Furthermore, the middle ring will also rotate with the lower cover during relative rotation with the friction-reducing pad, which will exacerbate the wear of the middle ring. Summary of the Invention

[0005] In view of this, the present invention provides a thrust bearing with a low coefficient of friction to solve the above problems.

[0006] A thrust bearing with a low coefficient of friction includes a lower cover, an upper cover fastened to the lower cover, a middle ring sandwiched between the lower cover and the upper cover, a friction-reducing washer sandwiched between the middle ring and the upper cover, and a bushing sandwiched between the lower cover and the upper cover. The bushing is made of polytetrafluoroethylene (PTFE). The lower cover includes a lower cover base, a lower outer oil sealing ring vertically disposed on the lower cover base for sealing oil, a lower inner oil sealing ring spaced apart from the lower outer oil sealing ring and perpendicular to the lower cover base, a receiving groove located between the lower outer oil sealing ring and the lower inner oil sealing ring, and a plurality of partitions evenly formed on the receiving groove for separating the receiving groove. The middle ring includes a plurality of secondary middle rings spaced apart, the number of which is equal to the number of partitions. Each secondary middle ring includes a plurality of oil cavities disposed on the side of the secondary middle ring facing the upper cover for placing lubricating grease. The secondary ring is abutted by the lower outer oil sealing ring, the lower inner oil sealing ring, and the two adjacent partitions to restrict its horizontal movement. The height of the secondary ring is higher than the height of the receiving groove. The friction-reducing washer is made of metal and has a smooth, ground surface. When the upper cover rotates relative to the lower cover, the friction-reducing washer rotates relative to the secondary ring. Lubrication by the grease in the oil cavity reduces friction, and the smooth surface of the friction-reducing washer rubs against the secondary ring to reduce the coefficient of friction between them. The bushing is used to reduce the coefficient of friction between the lower cover and the side of the upper cover.

[0007] Furthermore, the thrust bearing with a low coefficient of friction also includes a sealing ring assembly sandwiched between the lower cover and the upper cover, the sealing ring assembly including an outer sealing ring and an inner sealing ring spaced apart from the outer sealing ring.

[0008] Furthermore, the lower cover also includes a lower outer retaining ring that extends perpendicularly to the lower cover base and a lower inner retaining ring that is spaced apart from the lower inner sealing oil ring and extends perpendicularly to the lower cover base. A lower retaining ring is also provided on the side of the lower outer retaining ring away from the lower outer sealing oil ring. The lower retaining ring is used to fix the lower cover and the upper cover relative to each other.

[0009] Furthermore, each of the partitions faces the axis of the lower cover and is evenly distributed along the circumference of the lower cover.

[0010] Furthermore, the upper cover includes an upper cover base, an upper outer retaining ring extending perpendicularly to the upper cover base, an upper outer sealing ring extending perpendicularly to the upper cover base and spaced apart from the upper outer retaining ring, an upper inner sealing ring extending perpendicularly to the upper cover base and spaced apart from the upper outer sealing ring, and an upper inner retaining ring extending perpendicularly to the upper cover base and spaced apart from the upper inner sealing ring. The outer sealing ring is sandwiched in the cavity formed between the lower outer retaining ring, the upper outer retaining ring, and the upper outer sealing ring, and abuts against the end of the lower outer retaining ring. The inner sealing ring is sandwiched in the cavity formed between the lower inner retaining ring, the upper inner retaining ring, and the upper inner sealing ring, and abuts against the end of the lower inner retaining ring.

[0011] Furthermore, the upper outer retaining ring also includes an upper snap ring disposed on the side of the upper outer retaining ring away from the upper outer sealing ring, the upper snap ring being used to fix the upper cover onto the lower cover.

[0012] Furthermore, each of the secondary rings also includes a substrate layer facing the receiving groove, and a friction layer disposed on the substrate layer facing the upper cover, wherein the oil cavity is formed on the friction layer.

[0013] Furthermore, the substrate layer is made of substrate materials such as aluminum or steel.

[0014] Furthermore, the friction layer is made of PTFE composite material.

[0015] Furthermore, the friction-reducing washer is made of stainless steel.

[0016] Compared with the prior art, the thrust bearing with a low coefficient of friction provided by this utility model uses a receiving groove on the lower cover, which is evenly divided into multiple small receiving spaces by uniformly arranged partitions, to accommodate the secondary intermediate ring. The secondary intermediate ring is fixed horizontally in conjunction with the lower outer oil seal ring and the lower inner oil seal ring, thus preventing it from rotating when the upper and lower covers rotate relative to each other. Furthermore, multiple oil pockets are provided on the side of the secondary intermediate ring facing the upper cover to hold lubricating grease, thereby reducing the friction between the anti-friction washer and the secondary intermediate ring when the upper cover rotates relative to the lower cover. The friction-reducing washer, made of stainless steel or other metal materials, has a smooth, ground surface that rubs against the secondary ring. Compared to traditional hard plastic, this reduces the coefficient of friction between the washer and the secondary ring, thereby reducing friction and wear. Furthermore, because the washer is made of metal, it is stronger than plastic and will not break, effectively increasing the lifespan of the thrust bearing. Additionally, the bushing reduces the coefficient of friction between the lower cover and the upper cover sidewalls, further decreasing friction between them. Attached Figure Description

[0017] Figure 1 An exploded view of the thrust bearing with a low coefficient of friction provided by this utility model.

[0018] Figure 2 for Figure 1 A schematic diagram of the cross-sectional structure of a thrust bearing with a low coefficient of friction.

[0019] Figure 3 for Figure 2 An enlarged structural diagram of the cross-section of a thrust bearing with a low coefficient of friction at point A.

[0020] Figure 4 for Figure 1 A schematic diagram of the secondary ring structure of a thrust bearing with a low coefficient of friction.

[0021] Figure 5 for Figure 4 A schematic diagram of the secondary ring structure in another direction. Detailed Implementation

[0022] The specific embodiments of this utility model are described in further detail below. It should be understood that the description of the embodiments of this utility model herein is not intended to limit the scope of protection of this utility model.

[0023] like Figures 1 to 5The diagram shows a structural schematic of the thrust bearing with a low coefficient of friction provided by this utility model. The thrust bearing with a low coefficient of friction includes a lower cover 10, an upper cover 20 fastened to the lower cover 10, a middle ring 30 sandwiched between the lower cover 10 and the upper cover 20, a friction-reducing washer 40 sandwiched between the middle ring 30 and the upper cover 20, a sealing ring assembly 50 sandwiched between the lower cover 10 and the upper cover 20, and a bushing 60 sandwiched between the upper cover 10 and the lower cover 20. The thrust bearing with a low coefficient of friction also includes other functional modules, such as an assembly module and a transfer module, etc., which should be known to those skilled in the art and will not be described in detail here.

[0024] like Figure 2 and Figure 3 As shown, the lower cover 10 includes a lower cover base 11, a lower outer retaining ring 12 extending perpendicularly to the lower cover base 11, a lower outer sealing ring 13 spaced apart from the lower outer retaining ring 12 and extending perpendicularly to the lower cover base 11, a lower inner sealing ring 14 spaced apart from the lower outer sealing ring 13 and extending perpendicularly to the lower cover base 11, and a lower inner retaining ring 15 spaced apart from the lower inner sealing ring 14 and extending perpendicularly to the lower cover base 11. That is, the lower cover 10 has the lower outer retaining ring 12, the lower outer sealing ring 13, the lower inner sealing ring 14, and the lower inner retaining ring 15 arranged sequentially from the outside to the inside. The lower cover 10 can be integrally molded by injection molding, and its material can be rigid plastic, such as thermoplastic plastic.

[0025] The lower outer retaining ring 12, the lower outer oil sealing ring 13, the lower inner oil sealing ring 14, and the lower inner retaining ring 15 are used to cooperate with the upper cover 20 to form a sealed receiving cavity for receiving lubricating grease. Their specific functional principles will be described below together with the upper cover 20.

[0026] A lower retaining ring 121 is also provided on the side of the lower outer retaining ring 12 away from the lower outer sealing ring 13. The lower retaining ring 121 is used to cooperate with the upper retaining ring 221 described below so that the lower cover 10 and the upper cover 20 are relatively fixed.

[0027] like Figure 2 As shown, a receiving groove 16 for accommodating the middle ring 30 is formed between the lower outer sealing ring 13 and the lower inner sealing ring 14.

[0028] The lower cover 10 also includes a plurality of partitions 17 equally spaced within the receiving groove 16 to divide the receiving groove 16. One end of each partition 17 abuts against the lower outer sealing ring 13, and the other end abuts against the lower inner sealing ring 14, dividing the receiving groove 16 into a plurality of small receiving spaces at equal intervals. The number of partitions 17 is determined by the number of secondary middle rings 31 described below. The partitions 17 are used to divide the receiving groove 16 into a plurality of small receiving spaces for placing the secondary middle rings 31. All of the partitions 17 point towards the axis of the lower cover 10 and are evenly distributed along the circumference of the lower cover 10. The heights of the partitions 17, the lower outer sealing ring 13, and the lower inner sealing ring 14 are equal.

[0029] like Figure 2 As shown, the upper cover 20 includes an upper cover base 21, an upper outer retaining ring 22 extending perpendicularly to the upper cover base 21, an upper outer sealing ring 23 extending perpendicularly to the upper cover base 21 and spaced apart from the upper outer retaining ring 22, an upper inner sealing ring 24 extending perpendicularly to the upper cover base 21 and spaced apart from the upper outer sealing ring 23, and an upper inner retaining ring 25 extending perpendicularly to the upper cover base 21 and spaced apart from the upper inner sealing ring 24. That is, the upper cover 20 has the upper outer retaining ring 22, the upper outer sealing ring 23, the upper inner sealing ring 24, and the upper inner retaining ring 25 arranged sequentially from the outside to the inside. The upper cover 20 can also be integrally molded by injection molding, and its material can be rigid plastic, such as thermoplastic plastic.

[0030] The upper outer retaining ring 22 also includes an upper snap-fit ​​ring 221 disposed on the side of the upper outer retaining ring 22 away from the upper outer sealing ring 23. The lower snap-fit ​​ring 121 can be triangular in shape in cross-section perpendicular to the arrangement direction of the lower cover 10 and the upper cover 20, with the vertex of the triangle abutting against the inner sidewall of the upper outer retaining ring 22. One side of the triangular lower snap-fit ​​ring 121 can be used as a guide side, that is, it plays a guiding role when the lower outer retaining ring 12 is inserted. This inclined side can also open up the upper outer retaining ring 22 until the lower outer retaining ring 12 is inserted into the upper outer retaining ring 22 and the upper outer sealing ring 23, at which point the other side of the lower snap-fit ​​ring 121 abuts against the inclined side of the upper snap-fit ​​ring 222, and the lower cover 10 and the upper cover 20 are assembled.

[0031] The distance between the upper outer oil sealing ring 23 and the upper inner oil sealing ring 24 is less than the distance between the lower outer oil sealing ring 13 and the lower inner oil sealing ring 14. The upper outer oil sealing ring 23 is inserted between the lower outer retaining ring 12 and the lower outer oil sealing ring 13, and the upper inner oil sealing ring 24 is inserted between the lower inner oil sealing ring 14 and the lower inner retaining ring 15, thus forming a cavity between the lower outer oil sealing ring 13 and the lower inner oil sealing ring 14 for filling with lubricating grease. Furthermore, the heights of the lower outer retaining ring 12, the upper outer oil sealing ring 23, the lower outer oil sealing ring 13, the lower inner oil sealing ring 14, the upper inner oil sealing ring 24, and the lower retaining ring 15 are inconsistent, thus forming a labyrinthine structure in a cross-section perpendicular to the arrangement direction of the lower cover 10 and the upper cover 20, to prevent lubricating grease from easily overflowing and affecting bearing life.

[0032] The upper inner retaining ring 25 and the lower inner retaining ring 15 are radially fitted together. In use, the axial side of the lower cover 11 abuts against a spring, while the axial side of the upper cover 21 abuts against a support piece mounted on the drive rod, thereby clamping the lower cover 10 and the upper cover 20 together. Therefore, only the lower retaining ring 121 and the upper retaining ring 221 are needed to fix the upper cover 20 and the lower cover 10 relative to each other, without requiring additional fixing structures.

[0033] like Figure 1 As shown, the intermediate ring 30 provides lubrication and reduces the overall friction coefficient of the thrust bearing. It comprises multiple secondary intermediate rings 31 spaced apart and evenly distributed within the receiving groove 16. Each secondary intermediate ring 31 has the same structure and function, and the number of secondary intermediate rings 31 is equal to the number of partitions 17. In this embodiment, there are six secondary intermediate rings 31 and six partitions 17.

[0034] like Figure 4 and Figure 5 As shown, each of the secondary rings 31 includes a substrate layer 32 facing the receiving groove 16, a friction layer 33 disposed on the side of the substrate layer 32 facing the upper cover 20, and a plurality of oil holes 34 disposed on the friction layer 33. The height of each secondary ring 31 is higher than the height of the receiving groove 16, so that the anti-friction washer 40 preferentially rubs against the secondary ring 31 without causing wear to the lower cover 10. Each secondary ring 31 is abutted by two adjacent partitions 17, the lower outer oil sealing ring 13, and the lower inner oil sealing ring 14 on all four sides to restrict the movement of the secondary ring 31 in the horizontal direction. That is, the secondary ring 31 is fixed in the receiving groove 16 and will not rotate with the rotation of the upper cover 20.

[0035] The substrate layer 32 is used to support the friction layer 33, and it can be made of substrate materials such as aluminum or steel.

[0036] The friction layer 33 is used to rub against the friction-reducing washer 40, and it can be made of PTFE composite material.

[0037] The oil cavity 34 is used to contain lubricating grease to reduce the frictional force when the middle ring 30 and the anti-friction washer 40 rotate.

[0038] like Figure 2 As shown, the friction-reducing washer 40 is disposed between the middle ring 30 and the upper cover 21, and is made of metal. In this embodiment, the friction-reducing washer 40 is made of stainless steel. The friction surfaces of the friction-reducing washer 40 and the middle ring 30 should be smooth surfaces formed by grinding to sufficiently reduce the coefficient of friction. Since the multiple secondary middle rings 31 are disposed in multiple cavities separated by the partition 17, the secondary middle rings do not rotate. Therefore, when the upper cover 20 rotates relative to the lower cover 10, the friction-reducing washer 40 and the middle ring 30 will move relative to each other. The coefficient of friction between the friction-reducing washer 40 and the middle ring 30 is less than the coefficient of friction between the friction-reducing washer 40 and the upper cover 21, thereby preventing frictional rotation between the upper cover 20 and the friction-reducing washer 40. By using stainless steel or other metal materials to make the anti-friction washer 40 and grinding it to make its surface smooth, the friction force between the two plastics is transformed into the friction force between the plastic and the metal when the upper cover 20 rotates relative to the lower cover 10. This further reduces the coefficient of friction between the anti-friction washer 40 and the middle ring 30 during rotation, thereby reducing the wear of the middle ring 30. Moreover, since the anti-friction washer 40 is made of metal, its strength is greater than that of plastic, and it will not break easily, thus effectively improving the service life of the thrust bearing.

[0039] like Figure 1 and Figure 5 As shown, the sealing ring assembly 50 is used to seal the gap between the lower cover 10 and the upper cover 20. It includes an outer sealing ring 51 sandwiched between the lower cover 10 and the upper cover 20, and an inner sealing ring 52 spaced apart from the outer sealing ring 51 and also sandwiched between the lower cover 10 and the upper cover 20.

[0040] The outer sealing ring 51 can be made of polytetrafluoroethylene and is sandwiched in the cavity formed between the lower outer retaining ring 12, the upper outer retaining ring 22, and the upper outer oil sealing ring 23, and abuts against the end of the lower outer retaining ring 12. The outer sealing ring 51 can not only prevent external debris from entering the area where the middle ring 30 is located, but also prevent lubricating grease from overflowing in the area where the middle ring 30 is located.

[0041] The inner sealing ring 52 can also be made of polytetrafluoroethylene and is sandwiched in the cavity formed between the lower inner retaining ring 15, the upper inner retaining ring 25, and the upper inner sealing ring 24, and abuts against the end of the lower inner retaining ring 15. The inner sealing ring 52 has the same function as the outer sealing ring 51, and will not be described in detail here.

[0042] During assembly, the secondary ring 31 can be placed on the receiving groove 16 first, and then lubricating grease can be filled into the oil cavity 34. Then, the friction-reducing washer 40 can be placed on the secondary ring 30, and then the inner sealing ring 52 and the outer sealing ring 51 can be placed on the lower cover 10 respectively. Finally, the upper cover 20 can be fastened on the lower cover 10. At this time, the upper cover 20 and the lower cover 10 are assembled.

[0043] The bushing 60 is a ring, which can be made of aluminum, steel or other materials as the base material and PTFE composite material as the wear-resistant layer. The ring is press-fitted to the inner diameter of the lower cover 20 to reduce the coefficient of friction between the sides of the lower cover 10 and the upper cover 20 when the upper cover 10 rotates relative to the lower cover 20, thereby reducing the friction between the two and improving the service life of the thrust bearing.

[0044] Compared with the prior art, the thrust bearing with a low coefficient of friction provided by this utility model uses a receiving groove 16 provided on the lower cover 10 and evenly divided into multiple small receiving spaces by evenly arranged partitions 17 to accommodate the secondary ring 31. The secondary ring 31 is fixed horizontally in conjunction with the lower outer oil sealing ring 13 and the lower inner oil sealing ring 14 to prevent it from rotating when the upper cover 20 and the lower cover 10 rotate relative to each other. Furthermore, multiple oil holes 34 are provided on the side of the secondary ring 31 facing the upper cover 20 to store lubricating grease, thereby reducing the friction-reducing washer 40 when the upper cover 20 rotates relative to the lower cover 10. The friction-reducing washer 40 has a smooth surface formed by grinding, and the friction between this smooth surface and the secondary ring 31 is reduced. By using a friction-reducing washer 40 made of stainless steel or other metal materials to rub against the secondary ring 31, the friction coefficient between the washer 40 and the secondary ring 31 is reduced compared to traditional hard plastics. This reduces the wear of the secondary ring 31. Furthermore, since the friction-reducing washer 40 is made of metal, its strength is greater than that of plastic, and it will not break, thus effectively increasing the service life of the thrust bearing. Simultaneously, the bushing 60 also reduces the friction coefficient between the sides of the lower cover 10 and the upper cover 20, thereby reducing the frictional force between them.

[0045] The above are merely preferred embodiments of the present utility model and are not intended to limit the scope of protection of the present utility model. Any modifications, equivalent substitutions or improvements within the spirit of the present utility model are covered within the scope of the claims of the present utility model.

Claims

1. A thrust bearing having a low coefficient of friction, characterized by: The thrust bearing with a low coefficient of friction includes a lower cover, an upper cover fastened to the lower cover, a middle ring sandwiched between the lower cover and the upper cover, a friction-reducing washer sandwiched between the middle ring and the upper cover, and a bushing sandwiched between the lower cover and the upper cover. The bushing is made of polytetrafluoroethylene. The lower cover includes a lower cover base, a lower outer oil sealing ring vertically disposed on the lower cover base for sealing oil, a lower inner oil sealing ring spaced apart from the lower outer oil sealing ring and perpendicular to the lower cover base, a receiving groove located between the lower outer oil sealing ring and the lower inner oil sealing ring, and a plurality of partitions evenly disposed on the receiving groove for separating the receiving groove. The middle ring includes a plurality of secondary middle rings spaced apart, the number of which is equal to the number of partitions. The number of plates is equal. Each secondary ring includes multiple oil cavities disposed on the side of the secondary ring facing the upper cover for placing lubricating grease. The secondary ring is abutted by the lower outer oil sealing ring, the lower inner oil sealing ring, and two adjacent partitions to restrict its horizontal movement. The height of the secondary ring is higher than the height of the receiving groove. The friction-reducing washer is made of metal and has a smooth surface formed by grinding. When the upper cover rotates relative to the lower cover, the friction-reducing washer rotates relative to the secondary ring. The friction is reduced by lubrication through the lubricating grease in the oil cavities, and the smooth surface of the friction-reducing washer rubs against the secondary ring to reduce the coefficient of friction between the friction-reducing washer and the secondary ring. The bushing is used to reduce the coefficient of friction between the lower cover and the side of the upper cover.

2. The thrust bearing with low coefficient of friction according to claim 1, characterized in that: The thrust bearing with a low coefficient of friction also includes a sealing ring assembly sandwiched between the lower cover and the upper cover, the sealing ring assembly including an outer sealing ring and an inner sealing ring spaced apart from the outer sealing ring.

3. The thrust bearing with low coefficient of friction according to claim 2, characterized in that: The lower cover also includes a lower outer retaining ring that extends perpendicularly to the lower cover base and a lower inner retaining ring that is spaced apart from the lower inner sealing oil ring and extends perpendicularly to the lower cover base. A lower retaining ring is also provided on the side of the lower outer retaining ring away from the lower outer sealing oil ring. The lower retaining ring is used to fix the lower cover and the upper cover relative to each other.

4. The thrust bearing with a low coefficient of friction as described in claim 1, characterized in that: Each of the partitions faces the axis of the lower cover and is evenly distributed along the circumference of the lower cover.

5. The thrust bearing having a low coefficient of friction of claim 3, wherein: The upper cover includes an upper cover base, an upper outer retaining ring extending perpendicularly to the upper cover base, an upper outer sealing ring extending perpendicularly to the upper cover base and spaced apart from the upper outer retaining ring, an upper inner sealing ring extending perpendicularly to the upper cover base and spaced apart from the upper outer sealing ring, and an upper inner retaining ring extending perpendicularly to the upper cover base and spaced apart from the upper inner sealing ring. The outer sealing ring is sandwiched in the cavity formed between the lower outer retaining ring, the upper outer retaining ring, and the upper outer sealing ring, and abuts against the end of the lower outer retaining ring. The inner sealing ring is sandwiched in the cavity formed between the lower inner retaining ring, the upper inner retaining ring, and the upper inner sealing ring, and abuts against the end of the lower inner retaining ring.

6. The thrust bearing with low coefficient of friction of claim 5, wherein: The upper outer retaining ring also includes an upper snap ring disposed on the side of the upper outer retaining ring away from the upper outer sealing ring, the upper snap ring being used to fix the upper cover onto the lower cover.

7. The thrust bearing having a low coefficient of friction of claim 1, wherein: Each of the secondary rings further includes a substrate layer facing the receiving groove, and a friction layer disposed on the substrate layer facing the upper cover, wherein the oil cavity is formed on the friction layer.

8. The thrust bearing with low coefficient of friction of claim 7, wherein: The substrate layer is made of aluminum or steel substrate materials.

9. The thrust bearing having a low coefficient of friction of claim 7, wherein: The friction layer is made of PTFE composite material.

10. The thrust bearing having a low coefficient of friction of claim 1, wherein: The friction-reducing washer is made of stainless steel.

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