JP2006312948A - Ball joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball joint capable of obtaining stable rolling frictional torque. <P>SOLUTION: A longitudinal rib portion deformed by being kept into pressure-contact with an inner chamber 21 in a state that a ball seat 4 is press-fit in the inner chamber 21, and forming a clearance between an upper side of an outer peripheral face portion 45 of the ball seat 4 and an inner peripheral face portion 31 of the inner chamber 21, is formed on an outer peripheral portion at a lower side with respect to a position corresponding to an equator of the inner chamber 21, of a socket 3 of the ball seat 4. The clearance is reduced by longitudinal deformation of the ball seat 4 in caulking deformation of the socket 3, and dimensional tolerance of the inner chamber 21 and dimensional tolerance of the ball seat 4 to an outer peripheral face portion 45 are absorbed. As a degree of pressure-contact of a sliding face 41 of the ball seat 4 to a ball portion 15 is easily set and its fluctuation is reduced, the stable rolling frictional torque of the ball joint 1 can be obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a ball joint including a bearing seat accommodated in an inner chamber of a socket.

2. Description of the Related Art Conventionally, for example, a ball joint used in a suspension device or a steering device of an automobile is a ball seat as a bearing seat in which a ball portion of a ball stud is rotatably accommodated in an inner chamber of a substantially bottomed cylindrical socket. Is held and configured. Such a ball joint is manufactured by press-fitting a ball seat holding the ball portion of the ball stud into the inner chamber of the socket and then caulking and deforming the socket (see, for example, Patent Document 1).
Japanese Utility Model Publication No. 5-42741 (page 4, FIG. 1)

  In order to give an appropriate rotational friction torque to the ball stud, the degree of pressure contact with the ball portion of the sliding surface of the ball seat is adjusted to a predetermined value. The degree of this pressure contact is set by the tightening allowance when the ball seat is press-fitted into the inner chamber of the socket and the caulking pressure of the socket.

  However, there are variations in the dimensions of the socket and the ball seat, and the tightening allowance varies depending on the variations in the dimensions. Therefore, in the ball joint as described above, it is easy to keep the variation in the rotational friction torque of the ball stud within a predetermined range. In addition, there is a problem that the rotational friction torque may become excessively high or low.

  In order to suppress the variation in the tightening allowance as described above, a configuration in which a simple groove-shaped relief portion is provided at a position corresponding to the equator of the ball portion of the sliding surface of the ball seat is also conceivable. Since it also depends on the caulking pressure of the socket, it cannot be said that the effect of suppressing variation in rotational friction torque is sufficient.

  Furthermore, if the dimensional accuracy of each part is increased in order to suppress variations in rotational friction torque, there is a problem that the manufacturing cost increases.

  This invention is made | formed in view of such a point, and it aims at providing the ball joint which can obtain the stable rotational friction torque.

  The ball joint according to claim 1 is provided with a substantially bottomed cylindrical socket having an inner chamber and an opening communicating with the inner chamber, a substantially spherical sliding surface, and a continuous sliding surface. An opening formed at one end, and is press-fitted into the inner chamber of the socket so that the opening communicates with the opening, and is deformed by caulking deformation on the opening side of the socket, and A substantially cylindrical bearing sheet held in the inner chamber; and a ball stud provided with a substantially spherical ball portion rotatably held on the sliding surface of the bearing sheet. , Projecting from the outer peripheral portion on the other end side opposite to the opening from the position corresponding to the equator of the inner chamber, the bearing seat being press-fitted into the inner chamber of the socket, Deformed by pressure on the side And an outer peripheral pressure contact portion that forms a gap reduced by deformation of the bearing seat due to caulking deformation on the opening side of the socket between the opening side of the outer peripheral portion of the bearing seat and the inner chamber. It is what.

  Then, the bearing seat is pressed into the inner chamber in a state where the bearing seat is press-fitted into the inner chamber of the socket, on the outer peripheral portion on the other end side opposite to the opening from the position corresponding to the equator of the inner chamber of the socket of the bearing seat. In addition to deformation, by projecting an outer periphery pressure contact part that forms a gap between the opening side of the outer periphery of the bearing seat and the inner chamber of the socket, this gap is reduced by deformation of the bearing seat during the caulking deformation of the socket Thus, the dimensional tolerance between the inner chamber of the socket and the outer peripheral portion of the bearing seat is absorbed, the degree of pressure contact with the ball portion of the bearing seat is easily set, and a stable rotational friction torque can be obtained.

  The ball joint according to claim 2 is the ball joint according to claim 1, wherein the bearing seat faces the side surface of the inner chamber in a state accommodated in the inner chamber of the socket and corresponds to the equator of the ball portion of the ball stud. An outer peripheral surface portion projecting from the outer peripheral pressure contact portion on the other end side from the position to be provided, and provided on a side opposite to the opening from the outer peripheral surface portion, and opposed to the bottom surface of the inner chamber while being accommodated in the inner chamber. An inclined surface portion, and a bottom surface pressure contact portion that protrudes from the inclined surface portion and deforms by being pressed against the bottom surface of the inner chamber during caulking deformation on the opening side of the socket.

  And the inclination provided on the opposite side of the opening from the outer peripheral surface portion where the outer peripheral pressure contact portion protrudes on the other end side from the position corresponding to the equator of the ball portion of the ball stud facing the side surface of the inner chamber of the socket By projecting a bottom surface pressure contact portion that is deformed by being pressed against the bottom surface during caulking deformation on the opening side of the socket on the surface portion, the respective dimensional tolerances of the inner chamber of the socket and the outer peripheral portion of the bearing seat are The deformation is more reliably absorbed and the rotational friction torque becomes more stable.

  A ball joint according to a third aspect is the ball joint according to the first or second aspect, wherein the outer peripheral pressure contact portion is divided into a plurality of quadrangular shapes and spaced apart from each other in the circumferential direction of the bearing seat.

  Then, the outer peripheral pressure contact portion is divided into a plurality of portions and separated from each other in the circumferential direction of the bearing seat, so that when the bearing seat is press-fitted into the inner chamber of the socket, there is also an extra space between the divided outer peripheral press contact portions. Relief and dimensional tolerances are more reliably absorbed, so the rotational friction torque is more stable, and the divided outer peripheral pressure contact parts are square, improving the holding force of the bearing seat in the inner chamber of the socket To do.

  According to the ball joint of the first aspect, the gap is reduced by deformation of the bearing seat when the socket is caulked and the dimensional tolerance of the inner chamber of the socket and the dimensional tolerance of the outer periphery of the bearing seat can be absorbed. The degree of pressure contact with the ball portion can be easily set, and a stable rotational friction torque can be obtained.

  According to the ball joint of the second aspect, in addition to the effect of the ball joint of the first aspect, the dimensional tolerances of the inner chamber of the socket and the outer peripheral portion of the bearing seat can be more reliably ensured by the deformation of the bottom pressure contact portion. It can absorb and rotational friction torque can be made more stable.

  According to the ball joint of the third aspect, in addition to the effect of the ball joint according to the first or second aspect, when the bearing seat is press-fitted into the inner chamber of the socket, between the divided outer peripheral pressure contact portions. The surplus material escapes and the dimensional tolerance can be absorbed more reliably, so that the rotational friction torque can be stabilized more and the divided outer peripheral pressure contact parts are formed in a square shape, so that the bearing seat in the inner chamber of the socket The holding power can be improved.

  Hereinafter, a configuration of a ball joint according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  In FIG. 1, 1 is a ball joint, and this ball joint 1 is used, for example, for a suspension device or a steering device of an automobile. The ball joint 1 includes a ball stud 2 made of steel, a substantially bottomed cylindrical socket 3 made of metal, a ball sheet 4 made of synthetic resin as a bearing sheet, and rubber or soft synthetic resin. And a dust cover 5 formed in a substantially cylindrical shape.

  Hereinafter, for convenience, the vertical direction shown in FIGS. 1 and 2 will be described as the vertical direction.

  The ball stud 2 includes a ball portion 15 rotatably held on the ball seat 4, a stud portion 16 projecting in an axial shape from the ball portion 15, and an outer peripheral portion of the stud portion 16 on the ball portion 15 side. And a flange portion 17 projecting from the head.

  The ball portion 15 is accommodated in the socket 3 while being held by the ball seat 4. The stud portion 16 protrudes from the socket 3 in the shape of a shaft.

  The socket 3 is formed by casting or forging a member such as aluminum. The socket 3 includes an inner chamber 21 in which the ball seat 4 is fitted, and is disposed in an upper end portion that is one end portion in the axial direction. An opening 22 communicating with the chamber 21 is formed, a dust cover is attached to the outer peripheral surface on one end side, and the ball seat is deformed by caulking to the outer peripheral portion on one end side in the axial direction toward the central axis side. A caulking holding part 24 for holding 4 in the inner chamber 21 is provided.

  The inner chamber 21 is provided with an inner peripheral surface portion 31 as a side surface located on the opening 22 side, and a bottom surface portion 32 as a bottom surface is provided on the opposite side to the opening 22 of the inner peripheral surface portion 31, that is, on the lower side. ing.

  The inner peripheral surface portion 31 is a portion where the outer peripheral surface of the ball seat 4 is pressed into contact, and is formed in a cylindrical inner surface shape. The inner peripheral surface portion 31 is formed including at least the equator of the inner chamber 21 of the socket 3.

  The equator of the inner chamber 21 of the socket 3 refers to the plane including the equator E of the ball portion 15 and the inner chamber 21 when the ball portion 15 held by the ball seat 4 is accommodated in the inner chamber 21 of the socket 3. The equator E of the ball portion 15 is the radius of the ball portion 15 on a plane perpendicular to the central axis of the ball stud 2 when the ball stud 2 is set upright with respect to the socket 3. The position where is the maximum.

  The bottom surface portion 32 is provided continuously with the inner peripheral surface portion 31 and is inclined to the central axis side of the socket 3, and continuously with the opposite side of the inner peripheral surface portion 31 of the inclined bottom surface portion 34, that is, the lower side. And an inner chamber bottom surface portion 35 provided.

  The inclined bottom surface portion 34 is a portion where the lower portion of the ball seat 4 is pressed into contact with the inner chamber 21 while the ball seat 4 is press-fitted.

  Further, the inner chamber bottom surface portion 35 is separated from the ball seat 4 held in the inner chamber 21.

  The ball sheet 4 is formed into a substantially cylindrical shape having a reduced diameter on the lower side corresponding to the inner chamber 21 of the socket 3 by injection molding a synthetic resin such as polyacetal having flexibility. A spherical sliding surface 41 is provided inside, and an opening 42 communicating with the sliding surface 41 is formed on one end side in the axial direction, that is, on the upper side, and the other end in the axial direction. A bottom opening 43 communicating with the sliding surface 41 is formed on the side, that is, the lower side.

  Further, an outer peripheral surface portion 45 held by the inner peripheral surface portion 31 of the socket 3 and an inclined surface portion 46 held by the bottom surface portion 32 are formed on the outer peripheral portion of the ball seat 4 when the socket 3 is caulked and deformed. Yes. Further, a plurality of, for example, four slits 48 are formed in the upper end of the ball sheet 4 in the axial direction.

  As shown in FIGS. 1 and 2, the sliding surface 41 includes an opening-side sliding surface portion 51 located on the opening 42 side, and a side opposite to the opening 42 of the opening-side sliding surface portion 51, that is, continuously below the opening 42. It has an escape portion 52 formed and a bottom opening side sliding surface portion 53 continuously formed on the opposite side of the opening side sliding surface portion 51 of the escape portion 52, that is, on the lower side, and the opening side sliding surface portion 51 And the bottom opening side sliding surface portion 53 are formed in a spherical concave shape along the outer peripheral shape of the ball portion 15 of the ball stud 2.

  The opening-side sliding surface portion 51 has an inner diameter that is smaller than the outer diameter of the ball portion 15. That is, the opening-side sliding surface portion 51 is given a tightening margin with respect to the ball portion 15. For this reason, the opening-side sliding surface portion 51 is a portion that is in pressure contact with the outer peripheral surface on the stud portion 16 side, that is, on the upper side of the equator E of the ball portion 15 when the caulking holding portion 24 is caulked.

  The relief portion 52 is formed in an annular belt shape at the portion including the equator of the sliding surface 41, and the ball seat 4 holding the ball portion 15 is held in the inner chamber 21 of the socket 3 with the ball portion 15. A slight gap 55 is formed between them. Here, the escape portion 52 is not always necessary.

  The equator of the sliding surface 41 refers to the intersecting annular portion of the sliding surface 41 and the plane including the equator E of the ball portion 15 with the ball seat 4 held in the socket 3.

  The bottom opening side sliding surface portion 53 is a portion that holds the side opposite to the stud portion 16 from the equator E of the ball portion 15, that is, the lower side. The bottom opening side sliding surface portion 53 holds a lubricant (not shown). A plurality of spherical concave dimples 57 are provided. These dimples 57 are provided, for example, spaced apart from each other in a direction parallel to the circumferential direction and the axial direction of the ball seat 4, that is, in the vertical direction.

  The dimples 57 can be formed as, for example, radial oil grooves, convex protrusions, planar protrusions, or the like.

  The opening 42 is a portion that communicates with the opening 22 and into which the stud portion 16 of the ball stud 2 is inserted.

  The bottom opening 43 faces the inner chamber bottom surface portion 35 of the socket 3 and holds a lubricant (not shown) between the bottom surface portion 32 of the socket 3 and the outer peripheral surface of the ball portion 15 of the ball stud 2.

  The outer peripheral surface portion 45 is a portion facing the inner peripheral surface portion 31 in a state where the ball seat 4 is accommodated in the inner chamber 21 of the socket 3, and has an outer diameter dimension smaller than the inner diameter dimension of the inner peripheral surface portion 31. . Further, on the lower side of the outer peripheral surface portion 45 from the position corresponding to the equator of the inner chamber 21, a vertical rib portion 61 as an outer peripheral pressure contact portion protrudes in the radial direction, and the outer diameter of the vertical rib portion 61 portion. The dimension is set larger than the inner diameter dimension of the inner peripheral surface portion 31 of the inner chamber 21 of the socket 3. Therefore, when the ball seat 4 is press-fitted into the inner chamber 21 of the socket 3, the vertical rib portion 61 is deformed by being pressed against the inner peripheral surface portion 31, as shown in FIG. 3. A gap G is formed between the peripheral surface portion 31 and the portion of the outer peripheral surface portion 45 of the ball seat 4 on the side of the opening 42 shown in FIG. When the socket 3 is caulked and deformed on the side of the opening 22 shown in FIG. 2, the gap G is reduced by deformation in the longitudinal direction, that is, the axial direction of the portion of the ball seat 4 on the side of the opening 42 shown in FIG. In this embodiment, the gap G is reduced so that almost all of the gap G is crushed. However, depending on the dimensional tolerance between the outer peripheral surface portion 41 of the ball seat 4 and the inner chamber 21 of the socket 3, the gap G may remain slightly. There is also.

  Further, the vertical rib portion 61 is divided into a plurality of long diameter portions 61a as shown in FIG. These long diameter portions 61 a are formed in a quadrangular shape having a surface along the circumferential direction of the ball sheet 4, and are separated from each other in the circumferential direction of the ball sheet 4. For this reason, a groove portion 61b is formed along the vertical direction between the long diameter portions 61a. Each vertical rib portion 61 is formed wider than the groove portion 61b in the circumferential direction of the ball seat 4.

  As shown in FIGS. 1 and 2, the inclined surface portion 46 is a portion facing the inclined bottom surface portion 34 of the bottom surface portion 32 in a state where the ball seat 4 is accommodated in the inner chamber 21 of the socket 3, and on the outer peripheral surface portion 45 side. An annular ring groove 62 is formed, and a plurality of bottom ribs 63 as bottom contact portions are protruded below the annular groove 62.

  The annular groove portion 62 has an upper end portion serving as a groove bottom portion formed in an arc shape in a sectional view, and an edge portion on the outer peripheral surface portion 45 side is a lip portion 64. The lip portion 64 has a tip end inclined toward the central axis, and the tip end portion is formed in a convex arc shape when viewed in cross section, so that the releasability from the mold during the injection molding of the ball seat 4 is improved. It has become.

  Each bottom rib portion 63 is a portion which is deformed by being pressed against the inclined bottom surface portion 34 of the inner chamber 21 in a state where the ball seat 4 is press-fitted into the inner chamber 21 of the socket 3, and in the inclined direction of the inclined surface portion 46. The ball sheets 4 are formed in a long shape along the circumferential direction of the ball sheet 4 and are separated from each other.

  Each slit 48 is formed by cutting along the vertical direction from the opening 42 to the position of the bottom opening side sliding surface portion 53, and the slits 48 are spaced apart at substantially equal intervals in the circumferential direction of the ball seat 4. Note that the number of the slits 48 can be arbitrarily set, or the slits 48 can be configured not to be provided.

  The dust cover 5 is also called a boot, and prevents dust and the like from entering the inner chamber 21 of the socket 3. The dust cover 5 includes an approximately cylindrical cover body 71 that is elastically deformable, for example, formed of rubber, soft synthetic resin, or the like. A flange contact portion 72 that contacts the ball portion 15 side of 17 is provided, and a socket contact portion 73 that contacts the outer peripheral surface of the socket 3 is provided at the other axial end of the cover body 71. .

  Next, the assembly operation of the above embodiment will be described.

  First, a lubricant is applied to the ball portion 15 of the ball stud 2, and the ball portion 15 is pressed into the ball seat 4.

  At this time, the bottom opening side sliding surface portion 53 of the ball seat 4 holds the outer peripheral surface of the ball portion 15, and the relief portion 52 of the ball seat 4 does not contact the outer peripheral surface of the ball portion 15, and the ball portion 15 A slight gap 55 is formed between the outer peripheral surface of the first and second outer surfaces.

  Then, the ball sheet 4 holding the ball portion 15 is press-fitted into the inner chamber 21 of the socket 3.

  At this time, the excess ribs of the respective long diameter portions 61a of the longitudinal rib portion 61 are deformed so as to escape in the groove portions 61b between the long diameter portions 61a or in the vertical direction, and the respective long diameter portions 61a are pressed against the inner peripheral surface portion 31 of the inner chamber 21. A gap G shown in FIG. 3 is formed between the opening 42 side portion of the outer peripheral surface portion 45 of the ball seat 4 and the inner peripheral surface portion 31 of the inner chamber 21 of the socket 3.

  In this state, the upper end portion of the outer peripheral surface of the socket 3 is caulked and deformed to the center axis side to form the caulking holding portion 24, whereby the opening 42 side portion of the ball seat 4 is deformed in the vertical direction and the gap G is reduced. For example, the entire outer peripheral surface portion 45 of the ball seat 4 is in close contact with the inner peripheral surface portion 31 of the socket 3, and the surplus of the bottom rib portions 63 of the ball seat 4 is deformed so as to escape between the bottom rib portions 63. However, each bottom rib portion 63 is pressed against the inclined bottom surface portion 34 of the bottom surface portion 32 of the inner chamber 21, and the opening 42 side portion of the sliding surface 41 preloads the ball portion 15.

  Then, the ball sheet 4 is further tightened to the center side of the ball portion 15 to hold the ball portion 15 in a retaining manner, and the ball sheet 4 and the ball stud 2 are retained to the socket 3 in a retaining manner.

  Thus, according to the above-described embodiment, the ball seat 4 is press-fitted into the inner chamber 21 at the outer peripheral portion below the position corresponding to the equator of the inner chamber 21 of the socket 3 of the ball seat 4. In addition to being deformed by being pressed against the inner chamber 21, a vertical rib portion 61 is formed to form a gap G between the upper side of the outer peripheral surface portion 45 of the ball seat 4 and the inner peripheral surface portion 31 of the inner chamber 21. The gap G is reduced by the deformation of the ball seat 4 when the socket 3 is caulked and the dimensional tolerance between the inner chamber 21 and the outer peripheral surface 45 of the ball seat 4 is absorbed, and the ball portion of the sliding surface 41 of the ball seat 4 is absorbed. The degree of pressure contact with 15 can be easily set, variation is suppressed, a stable rotational friction torque of the ball joint 1 can be obtained, and the service life of the ball joint 1 can be improved.

  In particular, in a ball joint in which the socket 3 is formed by casting aluminum or the like, variation in dimensional tolerance of the inner chamber 21 of the socket 3 is relatively large. Therefore, variation in dimensional tolerance on the ball seat 4 side as described above. By absorbing, a predetermined rotational friction torque can be reliably obtained.

  In addition, since a plurality of slits 48 are provided on the opening 42 side of the ball sheet 4, the flexibility on the opening 42 side of the ball sheet 4 is improved. The service life of the ball joint 1 can be further improved by being uniformly pressed against the portion 15.

  Further, the bottom rib portion 63 projects from the inclined surface portion 46 continuously below the outer peripheral surface portion 45 projecting the vertical rib portion 61 below the equator of the inner chamber 21, whereby the inner chamber of the socket 3 is provided. The dimensional tolerance between 21 and the outer peripheral surface portion 45 of the ball seat 4 is more reliably absorbed by the bottom rib portions 63 being deformed by being pressed against the bottom surface portion 32, and the rotational friction torque of the ball joint 1 is further stabilized. be able to.

  Moreover, the longitudinal rib portion 61 is divided into a plurality of long diameter portions 61a, and the long diameter portions 61a are separated from each other in the circumferential direction, so that when the ball seat 4 is press-fitted into the inner chamber 21 of the socket 3, the long diameter portions 61a Since extra space also escapes to the groove portion 61b between them and dimensional tolerances can be absorbed more reliably, the rotational friction torque of the ball joint 1 can be more stabilized, and each of the vertical rib portions 61 can be made rectangular. For example, as compared with the case where each long diameter portion is formed in a rib shape, a contact area between the inner peripheral surface portion 31 of the inner chamber 21 and each long diameter portion 61a is secured, and the holding force of the ball seat 4 in the inner chamber 21 is increased. It can be improved.

  Further, by providing a plurality of dimples 57 on the bottom opening side sliding surface portion 53, the slidability of the ball portion 15 can be further improved.

  In the above-described embodiment, each long diameter portion 61a of the vertical rib portion 61 may have a shape other than the above. Similarly, the bottom rib portion 63 can have various other shapes.

  Further, the shape of the stud portion 16 and the flange portion 17 of the ball stud 2 or the shape of the dust cover 5 can be arbitrarily set.

It is a longitudinal cross-sectional view which shows the ball joint of one embodiment of this invention. It is a longitudinal cross-sectional view which shows the bearing seat of a ball joint same as the above, and notched. It is a longitudinal cross-sectional view which expands and shows a part of press fit state of the bearing seat of a ball joint same as the above.

Explanation of symbols

1 Ball joint 2 Ball stud 3 Socket 4 Ball seat as bearing seat
15 Ball part
21 interior
22 opening
41 Sliding surface
42 opening
45 Outer peripheral surface
46 Inclined surface
61 Longitudinal rib as outer periphery pressure contact
63 Bottom rib part as bottom pressure contact part G Gap

Claims (3)

A substantially bottomed cylindrical socket having an inner chamber and an opening communicating with the inner chamber;
A substantially spherical sliding surface, and an opening formed at one end of the sliding surface. The opening is press-fitted into the inner chamber of the socket so as to communicate with the opening; and A substantially cylindrical bearing seat deformed by caulking deformation on the opening side of the socket and held in the inner chamber of the socket;
A ball stud having a substantially spherical ball portion rotatably held on the sliding surface of the bearing seat;
The bearing seat protrudes from the outer peripheral portion on the other end side opposite to the opening from the position corresponding to the equator of the inner chamber, and the bearing seat is press-fitted into the inner chamber of the socket. A gap which is deformed by being pressed against a side surface of the inner chamber and is reduced by deformation of the bearing seat due to caulking deformation on the opening side of the socket is formed between the opening side of the outer peripheral portion of the bearing seat and the inner chamber. A ball joint characterized by having an outer peripheral pressure contact portion formed between the two. Bearing seat
An outer peripheral surface portion facing the side surface of the inner chamber in a state accommodated in the inner chamber of the socket, and having an outer peripheral pressure contact portion projecting on the other end side from a position corresponding to the equator of the ball portion of the ball stud,
An inclined surface portion that is provided on the opposite side of the opening from the outer peripheral surface portion and faces the bottom surface of the inner chamber in a state accommodated in the inner chamber,
2. The ball joint according to claim 1, further comprising: a bottom surface pressing portion that protrudes from the inclined surface portion and is deformed by being pressed against the bottom surface of the inner chamber at the time of caulking deformation on the opening side of the socket. . 3. The ball joint according to claim 1, wherein the outer peripheral pressure contact portions are divided into a plurality of quadrangular shapes and are separated from each other in the circumferential direction of the bearing seat.

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