Dust cover and ball joint

Abstract

To provide a dust cover which enables improvement of sealability, and to provide a ball joint.SOLUTION: A dust cover is an annular dust cover which may elastically deform and is used in a ball joint including: a ball stud having a shaft part in which two flange parts, a first flange part and a second flange part, which are spaced apart from each other are provided spaced apart from a spherical part; and a socket which supports the ball stud in a rotatable and swingable manner. The dust cover includes: an annular body part having a center axis; a fixed part fixed to the socket; and a seal part. The seal part includes: an annular main seal part slidably attached to the first flange part and the second flange part; an annular lip part protruding from the main seal part along the center axis in a direction opposite to the fixed part; and an annular protruding part protruding from the main seal part along the center axis in a direction opposite to the lip part. The main seal part has, at the side opposite to the center axis of the protruding part, an annular recessed part recessed in a direction opposite to a protruding direction of the protruding part.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a dust cover and a ball joint.

Background Art

[0002] For example, ball joints are used in various devices such as automobiles. The ball joint includes, for example, a ball stud having a spherical portion provided at one end, and a socket including a bearing that supports the spherical portion. The ball joint is provided with a dust cover for preventing the attachment of dust and moisture and the outflow of grease.

[0003] The dust cover described in Patent Document 1 includes a deformable membrane-like body portion, a fixed portion provided at one end of the body portion and fixed to the socket, and a seal portion provided on the other end side of the body portion. The seal portion is slidably attached to the ball joint.

[0004] The ball joint described in Patent Document 1 includes a shaft portion and a spherical portion provided at one end of the shaft portion. The shaft portion is provided with a first flange portion and a second flange portion. A seal portion is sandwiched between the first flange portion and the second flange portion. The seal portion has a contact portion that contacts the outer peripheral surface of the first flange portion so as to improve the sealing performance.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the conventional dust cover, depending on the degree of swing of the ball stud or the like, the contact portion of the seal portion might be separated from the first flange portion. For this reason, there was a possibility that the sealing performance would deteriorate.

Means for Solving the Problems

[0007] In order to solve the above problems, a dust cover according to an aspect of the present invention is an elastically deformable annular dust cover used for a ball joint having a ball stud provided with a spherical portion at one end and having a shaft portion provided with two spaced-apart first flange portions and second flange portions spaced apart from the spherical portion, and a socket having a bearing for the spherical portion and rotatably and swingably supporting the ball stud, and includes an annular deformable body portion having a central axis, a fixed portion provided at one end of the body portion and fixed to the socket, and a seal portion provided at the other end of the body portion. The seal portion includes an annular main seal portion slidably attached to the first flange portion and the second flange portion while being sandwiched between the first flange portion and the second flange portion, an annular lip portion protruding from the main seal portion in a direction opposite to the fixed portion along the central axis, and an annular protruding portion protruding from the main seal portion in a direction opposite to the lip portion along the central axis. The main seal portion has an annular recess recessed in a direction opposite to the protruding direction of the protruding portion on the side opposite to the central axis of the protruding portion.

[0008] The ball joint according to one aspect of the present invention is a ball joint including a joint mechanism and a dust cover attached to the joint mechanism, wherein the joint mechanism includes a ball stud having a spherical portion provided at one end and a shaft portion having two spaced-apart first flange portions and second flange portions provided spaced apart from the spherical portion, and a socket having a bearing for the spherical portion and rotatably and swingably supporting the ball stud, the first flange portion being closer to the spherical portion than the second flange portion, the dust cover including an annular deformable body portion having a central axis, a fixed portion provided at one end of the body portion and fixed to the socket, and a seal portion provided at the other end of the body portion, the seal portion being slidably attached to the first flange portion and the second flange portion while being sandwiched between the first flange portion and the second flange portion, and including an annular main seal portion, an annular lip portion protruding from the main seal portion in a direction opposite to the seal portion along the central axis and having an inner peripheral surface contacting the outer peripheral surface of the second flange portion, and an annular protruding portion protruding from the main seal portion in a direction opposite to the lip portion along the central axis and having an inner peripheral surface contacting the outer peripheral surface of the first flange portion, the main seal portion having an annular recess recessed in a direction opposite to the protruding direction of the protruding portion on the side opposite to the central axis of the protruding portion.

Advantages of the Invention

[0009] According to the present invention, the sealing performance can be stably improved more than before.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

BEST MODE FOR CARRYING OUT THE INVENTION

[0011] Hereinafter, a preferred embodiment according to the present invention will be described with reference to the accompanying drawings. Note that the dimensions or scales of each part in the drawings are appropriately different from the actual ones, and there are also parts schematically shown for easy understanding. The scope of the present invention is not limited to the following embodiments unless otherwise specifically stated in the following description.

[0012] A. Embodiment 1. Ball joint FIG. 1 is a cross-sectional view illustrating the configuration of a ball joint 100 according to a preferred embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a state in which the ball stud 2 of the ball joint 100 in FIG. 1 swings with respect to the socket 3. The ball joint 100 of the present embodiment is used in various devices such as a suspension device or a steering device of an automobile, for example.

[0013] As shown in FIGS. 1 and 2, the ball joint 100 includes a joint mechanism 1 and a dust cover 5. The joint mechanism 1 includes a ball stud 2, a socket 3, and a knuckle 4. In each of FIGS. 1 and 2, the central axis A2 of the ball stud 2 and the central axis A3 of the socket 3 are illustrated.

[0014] The ball stud 2 is a rod-shaped structure. The ball stud 2 has a shaft portion 21, a spherical portion 22, and a flange group 20. The shaft portion 21 is, for example, cylindrical. The spherical portion 22 is a spherical portion provided at one end of the shaft portion 21.

[0015] The flange group 20 has a first flange portion 23, a second flange portion 24, and a third flange portion 25. The first flange portion 23, the second flange portion 24, and the third flange portion 25 are provided on the shaft portion 21. The first flange portion 23, the second flange portion 24, and the third flange portion 25 are spaced apart from the spherical portion 22 in this order. Each of the first flange portion 23, the second flange portion 24, and the third flange portion 25 is an annular protrusion along the circumferential direction of the shaft portion 21 and protrudes from the outer peripheral surface of the shaft portion 21. Also, the first flange portion 23 and the second flange portion 24 are spaced apart from each other. A portion of the outer peripheral surface of the shaft portion 21 between the first flange portion 23 and the second flange portion 24 is a seal surface 29 with which a part of the dust cover 5 comes into contact. Also, the second flange portion 24 and the third flange portion 25 are connected to each other.

[0016] The knuckle 4 is a connecting member connected to the shaft portion 21. The knuckle 4 is provided on the side of the shaft portion 21 opposite to the spherical portion 22 with the flange group 20 interposed therebetween. Also, the knuckle 4 is provided with a through hole (not shown) through which the shaft portion 21 is inserted. The opening area of the through hole is such that the tip of the shaft portion 21 can be inserted, while the third flange portion 25 cannot be inserted. With the shaft portion 21 inserted into the through hole, the knuckle 4 is fixed by a fixing member 40 between the fixing member 40 such as a nut and the third flange portion 25. Thereby, the knuckle 4 is connected to the shaft portion 21.

[0017] Socket 3 is a structure that supports ball stud 2 in a rotatable and swingable state. Socket 3 includes a housing portion 31, a bottom plate 32, and a bearing 33. The housing portion 31 is, for example, a cylindrical structure. The bottom plate 32 is a plate-like member that closes one of the two openings of the housing portion 31. The housing portion 31 constitutes the side wall of socket 3, and the bottom plate 32 constitutes the bottom of socket 3.

[0018] Bearing 33 is housed in the space formed by housing portion 31 and bottom plate 32. Bearing 33 supports spherical portion 22 of ball stud 2. Specifically, a spherical bearing surface 331 having the same diameter as the radius of curvature of spherical portion 22 is formed on bearing 33. Ball stud 2 is supported by bearing 33 with the surface of spherical portion 22 in contact with bearing surface 331. Also, grease is filled in the gap between the surface of spherical portion 22 and bearing surface 331. Therefore, ball stud 2 is rotatable about the central axis A2 of shaft portion 21 and is swingable in a state inclined with respect to the central axis A3 of socket 3 as shown in FIG. 2.

[0019] As shown in FIGS. 1 and 2, dust cover 5 is attached to joint mechanism 1. Specifically, dust cover 5 is attached to both socket 3 and ball stud 2. Dust cover 5 is provided so as to generally surround ball stud 2. Such dust cover 5 is provided to prevent the adhesion of dust or moisture to the connecting portion between spherical portion 22 and bearing 33 and the outflow of the grease applied to the connecting portion. Also, dust cover 5 is a cylindrical elastic body. For this reason, it can be deformed according to the rotation and swing of ball stud 2. Also, dust cover 5 contains an elastic material typified by rubber such as chloroprene rubber.

[0020] 2. Dust Cover FIG. 3 is a cross-sectional view of dust cover 5 in a state where it is not installed in joint mechanism 1 shown in FIG. 1. Hereinafter, the state where it is not installed in joint mechanism 1 is referred to as the "unattached state".

[0021] As shown in Fig. 3, the dust cover 5 has a body portion 51, a fixed portion 52, and a seal portion 53. The body portion 51, the fixed portion 52, and the seal portion 53 are integrally formed. The dust cover 5 is an elastic body that can be elastically deformed.

[0022] The body portion 51 is annular with a central axis A5. Note that the central axis A5 of the body portion 51 is the central axis in the non-mounted state. Also, the central axis A5 coincides with the central axis of the dust cover 5 and the central axis of the seal portion 53, respectively. The body portion 51 is, for example, circular-ring-shaped and is a deformable membrane-like shape. The body portion 51 elastically deforms in conjunction with the rotation and swing of the ball stud 2 with respect to the socket 3. The central portion of the body portion 51 is configured to bulge toward the side opposite to the central axis A5, that is, the outer side in the radial direction.

[0023] The fixed portion 52 is an annular portion provided at one end of the body portion 51. The fixed portion 52 is the portion attached to the socket 3. As shown in Fig. 1, the fixed portion 52 surrounds an annular notch 311 provided at the end of the housing portion 31 of the socket 3. An attachment groove 521 is provided on the outer side in the radial direction of the fixed portion 52. By attaching an annular tightening member 310 to the attachment groove 521, the fixed portion 52 is tightened from the outer peripheral side toward the housing portion 31. Thereby, the fixed portion 52 is fixed to the socket 3. Examples of the tightening member 310 include a circlip or a band.

[0024] As shown in Fig. 3, the seal portion 53 is an annular portion provided at the other end of the body portion 51. The seal portion 53 is provided on the side opposite to the fixed portion 52 of the body portion 51. The seal portion 53 is the portion attached to the ball stud 2. As shown in Fig. 1, the seal portion 53 surrounds the shaft portion 21 of the ball stud 2. The seal portion 53 is slidably sandwiched between the first flange portion 23 and the second flange portion 24. Also, the seal portion 53 is in close contact with the seal surface 29 of the shaft portion 21.

[0025] Figure 4 is an enlarged view of a part of the seal portion 53 of the dust cover 5 shown in Figure 3. As shown in Figure 4, the seal portion 53 has a main seal portion 531, a lip portion 532, a protrusion seal portion 533, a first seal portion 534, a second seal portion 535, and a protrusion portion 536. The seal portion 53 is, for example, annular.

[0026] The main seal portion 531 is annular and is a portion connected to the body portion 51. The thickness of the main seal portion 531 is thicker than the thickness of the body portion 51. From the main seal portion 531, the lip portion 532, the protrusion seal portion 533, the first seal portion 534, the second seal portion 535, and the protrusion portion 536 protrude.

[0027] The lip portion 532 is a side lip that protrudes from the main seal portion 531 along the central axis A5 in the direction opposite to the aforementioned fixed portion 52. The lip portion 532 is annular.

[0028] The protrusion seal portion 533 is a dust lip that protrudes from the main seal portion 531 along the central axis A5 in the direction opposite to the aforementioned fixed portion 52. The protrusion seal portion 533 is annular. The protrusion seal portion 533 is spaced apart from the lip portion 532. The protrusion seal portion 533 is closer to the central axis A5 than the lip portion 532. That is, the protrusion seal portion 533 is provided radially inside the lip portion 532. Also, the protrusion height of the protrusion seal portion 533 is lower than the protrusion height of the lip portion 532.

[0029] A first recess 537 is formed in the portion between the lip portion 532 and the protrusion seal portion 533. The first recess 537 is a depression formed in the main seal portion 531 by the lip portion 532 and the protrusion seal portion 533. The first recess 537 functions as a grease reservoir.

[0030] Each of the first seal portion 534 and the second seal portion 535 is a seal lip that protrudes from the main seal portion 531 toward the central axis A5 along a direction intersecting the central axis A5. Therefore, the protruding directions of the first seal portion 534 and the second seal portion 535 intersect the protruding directions of the lip portion 356 and the protruding seal portion 533, respectively. Each of the first seal portion 534 and the second seal portion 535 is annular. The first seal portion 534 and the second seal portion 535 are spaced apart from each other.

[0031] A second recess 538 is formed between the first seal portion 534 and the second seal portion 535. The second recess 538 is a depression formed in the main seal portion 531 by the first seal portion 534 and the second seal portion 535.

[0032] The protruding portion 536 protrudes from the main seal portion 531 along the central axis A5 in a direction opposite to the lip portion 532. In other words, the protruding portion 536 protrudes from the main seal portion 531 along the central axis A5 toward the aforementioned fixed portion 52. The protruding portion 536 is annular. The inner peripheral surface 536s of the protruding portion 536 is a stepped surface formed between the tip of the second seal portion 535 and the tip 5361 of the protruding portion 536.

[0033] In addition, an annular recess 530 is provided in the aforementioned main seal portion 531. The annular recess 530 is provided on the inner peripheral surface of the dust cover 5. The annular recess 530 is recessed in a direction opposite to the protruding direction of the protruding portion 536. The annular recess 530 is a depression that is recessed along the central axis A5 in a direction opposite to the aforementioned fixed portion 52. Also, the annular recess 530 is provided on the side opposite to the central axis A5 of the protruding portion 536. That is, the annular recess 530 is provided on the radially outer side with respect to the protruding portion 536.

[0034] FIG. 5 is an enlarged view showing a state in which the seal portion 53 is mounted between the first flange portion 23 and the second flange portion 24 of FIG. 2. Hereinafter, the state in which the seal portion 53 is mounted between the first flange portion 23 and the second flange portion 24 is referred to as the "mounted state".

[0035] As shown in FIG. 5, the main seal portion 531 is slidably attached to the first flange portion 23 and the second flange portion 24 while being sandwiched between the first flange portion 23 and the second flange portion 24.

[0036] Also, in the mounted state, a protruding seal portion 533, a first seal portion 534, and a second seal portion 535 are disposed between the first flange portion 23 and the second flange portion 24. The protruding seal portion 533 is in close contact with the surface 241 of the second flange portion 24 facing the first flange portion 23 in a slidable state. The first seal portion 534 and the second seal portion 535 are in close contact with the seal surface 29 in a slidable state.

[0037] In the mounted state, the lip portion 532 is in close contact with the outer peripheral surface 24s of the second flange portion 24 in a slidable state. The lip portion 532 does not protrude beyond the surface 242 of the second flange portion 24 facing away from the first flange portion 23. In other words, the position of the tip portion 5321 of the lip portion 532 is located between the surface 241 of the second flange portion 24 facing the first flange portion 23 and the opposite surface 242.

[0038] In the mounted state, the protruding portion 536 is in close contact with the outer peripheral surface 23s of the first flange portion 23 in a slidable state. Specifically, the inner peripheral surface 536s of the protruding portion 536 is in close contact with the outer peripheral surface 23s. Also, the protruding portion 536 does not protrude beyond the surface 232 of the first flange portion 23 facing away from the second flange portion 24. In other words, the position of the tip portion 5361 of the protruding portion 536 is located between the surface 231 of the first flange portion 23 facing the second flange portion 24 and the opposite surface 232.

[0039] As described above, the seal portion 53 has a lip portion 532 and a protruding portion 536 that protrude from the main seal portion 531 in opposite directions. Therefore, the sealing performance of the seal portion 53 can be stably exhibited. Therefore, the adhesion of dust or moisture and the outflow of grease can be stably prevented over a long period.

[0040] FIG. 6 illustrates an example of the seal portion 53x of the comparative example. The seal portion 53x of the comparative example in FIG. 6 does not have a protrusion 536. Therefore, in the comparative example, the sealing performance between the first flange portion 23 and the seal portion 53 is lower than that of the seal portion 53 of the present embodiment. Therefore, it is difficult to maintain a stable sealing state of the seal portion 53x between the first flange portion 23 and the second flange portion 24.

[0041] Furthermore, since the seal portion 53 of the present embodiment has the lip portion 532 and the protrusion 536, it is easy to incorporate the seal portion 53 between the first flange portion 23 and the second flange portion 24. Specifically, the lip portion 532 is brought into contact with the outer peripheral surface 24s of the second flange portion 24, and the protrusion 536 is brought into contact with the outer peripheral surface 23s of the first flange portion 23, and the main seal portion 531 is inserted between the first flange portion 23 and the second flange portion 24. The presence of the lip portion 532 and the protrusion 536 makes it easy to arrange the main seal portion 531 between the first flange portion 23 and the second flange portion 24 in the intended direction. Therefore, a stable sealing state of the seal portion 53 can be maintained.

[0042] Also, as described above, the seal portion 53 of the present embodiment has the annular recess 530 shown in FIG. 4. Therefore, when the ball stud 2 swings, it is possible to suppress the possibility that the seal portion 53 separates from between the first flange portion 23 and the second flange portion 24.

[0043] FIG. 7 is a diagram showing a deformed state of the dust cover 5y of the comparative example when the ball stud 2 swings. As shown in FIG. 7, the seal portion 53y of the dust cover 5y of the comparative example is not provided with the annular recess 530.

[0044] As shown in FIG. 7, consider the case where the body portion 51 of the dust cover 5y of the comparative example is deformed by the swinging of the ball stud 2. In this case, as shown by the arrow a1, the body portion 51 of the seal portion 53y is deformed so as to spring upward in the radial direction. Due to this deformation of the body portion 51, the outer peripheral surface of the body portion 51 and the outer peripheral surface of the seal portion 53y approach each other. Then, the seal portion 53y is pulled radially outward by the deformation of the body portion 51. For this reason, in the dust cover 5y of the comparative example, there is a possibility that the protruding portion 536 of the seal portion 53y is pulled in the direction of arrow a2 and separated from the outer peripheral surface 23s of the first flange portion 23.

[0045] FIG. 8 is a view showing the deformed state of the dust cover 5 of the present embodiment when the ball stud 2 swings. The dust cover 5 of the present embodiment has an annular recess 530.

[0046] In FIG. 8, as in FIG. 7, consider the case where the body portion 51 of the dust cover 5 of the present embodiment is deformed by the swinging of the ball stud 2. As shown in FIG. 8, when the body portion 51 is deformed so as to spring upward as shown by the arrow a1, the seal portion 53 is pulled radially outward by this deformation. Here, as described above, the seal portion 53 is provided with an annular recess 530. For this reason, even when a force pulling the body portion 51 radially outward is applied to the main seal portion 531, the annular recess 530 is provided, making it difficult for the force to be transmitted to the protruding portion 536. Therefore, it is possible to suppress the possibility that the protruding portion 536 is pulled in the direction of arrow a2 and separated from the outer peripheral surface 23s of the first flange portion 23.

[0047] Furthermore, as described above, since the annular recess 530 is provided, it is difficult for the deformation of the body portion 51 to be transmitted to the protruding portion 536. For this reason, when the ball stud 2 swings, the protruding portion 536 can continue to maintain a force of adhering to the first flange portion 23 as shown by the arrow a3.

[0048] In this way, by providing the annular recess 530, the sealing performance of the seal portion 53 can be enhanced. Furthermore, according to the ball joint 100 having such a dust cover 5, since the dust cover 5 has excellent sealing performance, excellent reliability can be exhibited.

[0049] Also, as described above, the seal portion 53 has the protruding seal portion 533 shown in FIG. 4. By providing the protruding seal portion 533, the sealing performance of the seal portion 53 can be enhanced as compared with the case where it is not provided.

[0050] FIG. 9 is an enlarged view showing a part of the seal portion 53z of the dust cover 5z of the modified example. As shown in FIG. 9, the protruding seal portion 533 is not provided in the seal portion 53z of the dust cover 5z of the modified example. A flat surface 539 is provided in a portion radially inside the lip portion 532 of the seal portion 53z. The flat surface 539 contacts, for example, the surface 241 facing the first flange portion 23 of the second flange portion 24 described above.

[0051] On the other hand, the seal portion 53 of the present embodiment has the protruding seal portion 533 as shown in FIG. 4. And as shown in FIG. 5, the protruding seal portion 533 is in contact with the surface 241 facing the first flange portion 23 of the second flange portion 24. For this reason, the seal portion 53 of the present embodiment in FIG. 5 can increase the surface pressure of the seal portion 53 against the surface 241 facing the first flange portion 23 of the second flange portion 24 as compared with the seal portion 53z of the modified example in FIG. 9. Therefore, by providing the protruding seal portion 533, the sealing performance of the seal portion 53 can be enhanced as compared with the case where it is not provided.

[0052] Also, as shown in FIG. 4, the inner peripheral surface 536s of the protruding portion 536 overlaps with the tip portion 5331 of the protruding seal portion 533 when viewed in the direction along the central axis A5. In other words, the inner peripheral surface 536s and the tip portion 5331 are located on a virtual annular surface L1 parallel to the central axis A5.

[0053] The portion of the seal part 53 that is radially inside the virtual toroidal surface L1 is disposed between the first flange part 23 and the second flange part 24. And, as shown in FIG. 5, the seal part 53 is supported by the base end part of the inner peripheral surface 536s and the protruding seal part 533.

[0054] When the inner peripheral surface 536s and the tip part 5331 are located on the virtual toroidal surface L1, displacement of the seal part 53 can be suppressed compared to the case where the inner peripheral surface 536s is located radially outside the virtual toroidal surface L1. Therefore, the sealing performance of the seal part 53 can be improved.

[0055] FIG. 10 is an enlarged view of a part of the seal part 53A of a modified example. In the seal part 53A of the modified example shown in FIG. 10, the inner peripheral surface 536s of the protruding part 536 is located on the central axis A3 side, that is, radially inside, of the tip part 5331 of the protruding seal part 533 when viewed in the direction along the central axis A5. In other words, the inner peripheral surface 536s is located on the central axis A5 side of the virtual toroidal surface L1. The virtual toroidal surface L1 is a plane passing through the tip part 5331 and parallel to the central axis A5.

[0056] As described above, the seal part 53A in FIG. 10 is located on the central axis A5 side of the virtual toroidal surface L1. Therefore, according to the seal part 53A, the inner peripheral surface 536s of the protruding part 536 can be more firmly brought into close contact with the outer peripheral surface 23s of the first flange part 23 compared to the case where the inner peripheral surface 536s is located radially outside the virtual toroidal surface L1. Therefore, the sealing performance of the seal part 53 can be enhanced.

[0057] Also, as shown in FIG. 4, the annular recess 530 overlaps with the first recess 537, which is the portion between the lip part 532 and the protruding seal part 533, when viewed in the direction along the central axis A5. In other words, the annular recess 530 and the first recess 537 are located on a virtual toroidal surface L2 parallel to the central axis A5.

[0058] FIG. 11 is a diagram schematically showing the dust cover 5 in FIG. 5. As shown in FIG. 11, in the seal portion 53 of the present embodiment, the annular recess 530 and the first recess 537 are located on the virtual annular surface L2. Therefore, with the seal portion 53 sandwiched between the first flange portion 23 and the second flange portion 24, the body portion 51 connected to the seal portion 53 can be deformed evenly in the vertical direction in the figure as shown by the arrow a5.

[0059] On the other hand, for example, when the annular recess 530z shown by the dashed line and the first recess 537 do not overlap when viewed in the direction along the central axis A5, the body portion 51 connected to the seal portion 53 is likely to deform upward in the figure as shown by the arrow a6.

[0060] Therefore, the annular recess 530 overlaps the first recess 537 when viewed in the direction along the central axis A5, so that compared with the case where they do not overlap, it is difficult for a difference in the ease of deformation to occur depending on the deformation direction of the body portion 51. For this reason, in the deformation of the ball stud 2 in various directions, it is difficult for a difference in the ease of deformation of the dust cover 5 to occur. Therefore, in the deformation of the ball stud 2 in various directions, the followability and the sealing performance of the dust cover 5 can be improved.

[0061] Also, the portion of the seal portion 53 located on the virtual annular surface L2 is thinner and more easily deformable than the portion of the seal portion 53 sandwiched between the first flange portion 23 and the second flange portion 24. For this reason, it is easy to absorb the deformation of the body portion 51 at the portion of the seal portion 53 located on the virtual annular surface L2. Therefore, it is possible to reduce the risk that the portion of the seal portion 53 sandwiched between the first flange portion 23 and the second flange portion 24 will come out between the first flange portion 23 and the second flange portion 24 following the deformation of the body portion 51.

[0062] Furthermore, the annular recess 530 overlaps with the first recess 537 when viewed in the direction along the central axis A5, and it is preferable that the inner peripheral surface 536s of the protruding portion 536 overlaps with the tip portion 5331 of the protruding seal portion 533 when viewed in the direction along the central axis A3, or is located on the central axis A5 side thereof. By satisfying these requirements, the seal portion 53 can exhibit a stable sealing property against deformations of the ball stud 2 in various directions as compared with the case where these requirements are not satisfied.

[0063] Also, as shown in FIG. 4, the inner peripheral surface 533s of the protruding seal portion 533 is inclined with respect to the central axis A5. Specifically, the inner peripheral surface 533s is inclined so as to face the direction opposite to the fixed portion 52. Since the inner peripheral surface 533s is inclined, it is easier to insert the protruding seal portion 533 between the first flange portion 23 and the second flange portion 24 as compared with the case where it is not inclined. Therefore, the assemblability of the seal portion 53 between the first flange portion 23 and the second flange portion 24 can be improved.

[0064] For example, the seal portion 53 is inserted between the first flange portion 23 and the second flange portion 24 by sliding the inner peripheral surface 533s against the second flange portion 24. By inserting in this way, the main seal portion 531 of the seal portion 53 can be inserted between the first flange portion 23 and the second flange portion 24 at a desired angle. Also, the protruding seal portion 533 can be surely inserted between the first flange portion 23 and the second flange portion 24.

[0065] Also, as shown in FIG. 4, no groove is provided on the outer peripheral surface of the main seal portion 531, and the outer peripheral surface of the main seal portion 531 is a flat surface.

[0066] FIG. 12 is an enlarged view of a part of the seal portion 53j of the modified example. The main seal portion 531j of the seal portion 53j of the comparative example shown in FIG. 12 has a groove 531d. The groove 531d is a depression provided on the outer peripheral surface of the main seal portion 531j. By providing the groove 531d, the ease of deformation of the seal portion 53 can be increased as compared with the case where it is not provided.

[0067] On the other hand, in the present embodiment shown in FIG. 4, the groove 531d is not provided. Therefore, the volume of the seal portion 53 can be increased as compared with the example of FIG. 12. Further, since the groove 531d is not provided, the compression rate in the direction along the central axis A5 is higher than that in the case where the groove 531d is provided. For these reasons, the sealing performance by the seal portion 53 can be enhanced.

[0068] Also, as shown in FIG. 5, the position of the tip portion 5361 of the protruding portion 536 is located between the surface 231 facing the second flange portion 24 of the first flange portion 23 and the opposite surface 232. Therefore, it is possible to suppress the possibility that the tip portion 5361 contacts an element other than the seal portion 53 such as the body portion 51. Therefore, it is possible to suppress the possibility that the protruding portion 536 is separated from the first flange portion 23 due to the contact.

[0069] Also, for example, in order to enhance the adhesion of the protruding portion 536 to the outer peripheral surface 23s of the first flange portion 23, it is preferable that the position of the tip portion 5361 is closer to the surface 232 than the surface 231.

[0070] Also, in the example shown in FIG. 4, the depth D1 of the annular recess 530 is substantially equal to the height T0 of the protruding portion 536. Therefore, the bottom of the annular recess 530 and the base end portion of the protruding portion 536 are located on the surface L3 along the radial direction. Note that the depth D1 may be larger or smaller than the height T0. However, if the depth D1 is made too large compared to the height T0, the volume of the seal portion 53 will decrease. If the depth D1 is made too small compared to the height T0, there is a possibility that the protruding portion 536 will follow the deformation of the body portion 51. It is preferable to set the depth D1 in consideration of these.

[0071] Also, in the example shown in FIG. 4, the width W1 along the radial direction of the annular recess 530 is larger than the width W0 along the radial direction of the protrusion 536, but it may also be equal to or less than the width W0. However, if the width W1 is made too large compared to the width W0, the volume of the seal portion 53 will decrease. If the width W1 is made too small compared to the width W0, there is a risk that the protrusion 536 will follow the deformation of the body portion 51. It is preferable to set the width W1 in consideration of these factors.

[0072] 2. Modification The forms exemplified above can be variously modified. For example, the protruding seal portion 533 may be located closer to the central axis A5 side than the inner peripheral surface 536s. Also, for example, the first recess 537 and the annular recess 530 may not overlap when viewed in the direction along the central axis A5. Also, for example, the protruding seal portion 533 may be omitted.

[0073] Although the present invention has been described based on the preferred embodiments, the present invention is not limited to the above-described embodiments. Also, the configuration of each part of the present invention can be replaced with any configuration that exhibits the same function as that of the above-described embodiments, and any configuration can be added.

[0074] 3. Supplementary Note From the above embodiments or modification examples, for example, the following aspects can be grasped.

[0075] The dust cover according to the first aspect, which is a preferred example of the present disclosure, is an elastically deformable annular dust cover used for a ball joint having a ball stud provided with a spherical portion at one end and having a shaft portion on which two spaced-apart first flange portions and second flange portions are provided at a distance from the spherical portion, and a socket having a bearing for the spherical portion and rotatably and swingably supporting the ball stud. The dust cover includes an annular deformable body portion having a central axis, a fixed portion provided at one end of the body portion and fixed to the socket, and a seal portion provided at the other end of the body portion. The seal portion includes an annular main seal portion slidably attached to the first flange portion and the second flange portion while being sandwiched between the first flange portion and the second flange portion, an annular lip portion protruding from the main seal portion in a direction opposite to the fixed portion along the central axis, and an annular protruding portion protruding from the main seal portion in a direction opposite to the lip portion along the central axis. The main seal portion has an annular recess recessed in a direction opposite to the protruding direction of the protruding portion on the side opposite to the central axis of the protruding portion.

[0076] According to the first aspect above, by having the lip portion and the protruding portion, the sealing performance of the seal portion can be improved. Further, by providing the annular recess, the sealing performance can be stably maintained even when the ball stud swings.

[0077] In a second aspect, which is a preferred example of the first aspect, the seal portion further includes an annular protruding seal portion protruding from the main seal portion in a direction opposite to the seal portion along the central axis. The protruding height of the protruding seal portion is lower than the protruding height of the lip portion, and the protruding seal portion is provided at a position closer to the central axis than the lip portion and spaced apart from the lip portion. By providing such a protruding seal portion, the sealing performance can be improved compared to the case where it is not provided.

[0078] In a third aspect which is a preferred example of the second aspect, the inner peripheral surface of the protruding portion overlaps with the tip of the protruding seal portion or is located on the central axis side of the tip when viewed in the direction along the central axis. Therefore, the sealing performance can be improved as compared with the case where the inner peripheral surface of the protruding portion is located on the side opposite to the central axis with respect to the tip.

[0079] In a fourth aspect which is a preferred example of the second aspect, the annular recess overlaps with a portion between the lip portion and the protruding seal portion when viewed in the direction along the central axis. Therefore, the followability and sealing performance of the dust cover can be improved.

[0080] In a fifth aspect which is a preferred example of the second aspect, the inner peripheral surface of the protruding portion overlaps with the tip of the protruding seal portion or is located on the central axis side of the tip when viewed in the direction along the central axis, and the annular recess overlaps with a portion between the lip portion and the protruding seal portion when viewed in the direction along the central axis. Therefore, the followability and sealing performance of the dust cover can be particularly effectively improved.

[0081] In a sixth aspect which is a preferred example of the second aspect, the inner peripheral surface of the protruding seal portion is inclined so as to face the direction opposite to the fixed portion with respect to the central axis. Therefore, the assemblability of the seal portion with respect to the ball joint can be enhanced. Thus, the sealing performance of the seal portion can be stably maintained.

[0082] A ball joint according to a seventh aspect, which is a preferred example of the present disclosure, is a ball joint including a joint mechanism and a dust cover attached to the joint mechanism. The joint mechanism includes a ball stud having a spherical portion provided at one end and a shaft portion having two spaced-apart first flange portions and second flange portions provided spaced apart from the spherical portion, and a socket having a bearing for the spherical portion and rotatably and swingably supporting the ball stud. The first flange portion is closer to the spherical portion than the second flange portion. The dust cover includes an annular deformable body portion having a central axis, a fixed portion provided at one end of the body portion and fixed to the socket, and a seal portion provided at the other end of the body portion. The seal portion includes an annular main seal portion slidably attached to the first flange portion and the second flange portion while being sandwiched between the first flange portion and the second flange portion, an annular lip portion protruding from the main seal portion in a direction opposite to the seal portion along the central axis and having an inner peripheral surface contacting the outer peripheral surface of the second flange portion, and an annular protruding portion protruding from the main seal portion in a direction opposite to the lip portion along the central axis and having an inner peripheral surface contacting the outer peripheral surface of the first flange portion. The main seal portion has an annular recess recessed in a direction opposite to the protruding direction of the protruding portion on the side opposite to the central axis of the protruding portion.

[0083] According to the first aspect described above, by having the lip portion and the protruding portion, the sealing performance of the seal portion can be improved. Further, by providing the annular recess, the sealing performance can be stably maintained even when the ball stud swings. For these reasons, since the ball joint includes a dust cover with excellent sealing performance, the reliability of the ball joint can be improved.

[0084] In the eighth aspect, which is a preferred example of the seventh aspect, the tip of the protruding portion is located between the surface facing the spherical portion of the second flange portion and the surface facing the first flange portion of the second flange portion. Therefore, contact between the protruding portion and other elements such as the body portion of the protruding portion can be avoided, so that the possibility of the protruding portion being separated from the first flange portion due to such contact can be suppressed.

Explanation of Reference Numerals

[0085] 1…Joint mechanism, 2…Ball stud, 3…Socket, 4…Knuckle, 5…Dust cover, 5y…Dust cover, 5z…Dust cover, 20…Flange group, 21…Shaft portion, 22…Spherical portion, 23…First flange portion, 23s…Outer peripheral surface, 24…Second flange portion, 24s…Outer peripheral surface, 25…Third flange portion, 29…Sealing surface, 31…Housing portion, 32…Bottom plate, 33…Bearing, 40…Fixing member, 51…Body portion, 52…Fixed portion, 53…Sealing portion, 53A…Sealing portion, 53j…Sealing portion, 53x…Sealing portion, 53y…Sealing portion, 53z…Sealing portion, 100…Ball joint, 231…Surface, 232…Surface, 241…Surface, 242…Surface, 310…Fastening member, 311…Notch, 331…Bearing surface, 521…Mounting groove, 530…Annular recess, 531…Main sealing portion, 531d…Groove, 531j…Main sealing portion, 532…Lip portion, 533…Protruding sealing portion, 533s…Inner peripheral surface, 534…First sealing portion, 535…Second sealing portion, 536…Protruding portion, 536s…Inner peripheral surface, 537…First recess, 538…Second recess, 539…Flat surface, 5321…Tip portion, 5331…Tip portion, 5361…Tip portion, A2…Central axis, A3…Central axis, A5…Central axis, D1…Depth, L1…Virtual annular surface, L2…Virtual annular surface, L3…Surface, T0…Height, W0…Width, W1…Width, a1…Arrow, a2…Arrow, a3…Arrow, a5…Arrow, a6…Arrow.

Claims

1. A ball stud having a spherical portion provided at one end and a shaft portion having two spaced-apart first flange portions and second flange portions provided spaced apart from the spherical portion, and a socket having a bearing for the spherical portion and rotatably and swingably supporting the ball stud, an annular dust cover that is elastically deformable and used for a ball joint, an annular deformable body portion having a central axis, a fixed portion provided at one end of the body portion and fixed to the socket, a seal portion provided at the other end of the body portion, and comprising: the seal portion, an annular main seal portion slidably attached to the first flange portion and the second flange portion while being sandwiched between the first flange portion and the second flange portion, an annular lip portion protruding from the main seal portion in a direction opposite to the fixed portion along the central axis, an annular protruding portion protruding from the main seal portion in a direction opposite to the lip portion along the central axis, and comprising: the main seal portion has an annular concave portion recessed in a direction opposite to the protruding direction of the protruding portion on the side opposite to the central axis of the protruding portion, A dust cover characterized by the above.

2. The seal portion further comprises an annular protruding seal portion protruding from the main seal portion in a direction opposite to the seal portion along the central axis, the protruding height of the protruding seal portion is lower than the protruding height of the lip portion, the protruding seal portion is provided spaced apart from the lip portion at a position closer to the central axis than the lip portion, The dust cover according to claim 1.

3. The inner peripheral surface of the protruding portion overlaps the tip of the protruding seal portion or is located on the central axis side of the tip when viewed in the direction along the central axis, The dust cover according to claim 2.

4. The annular concave portion overlaps the portion between the lip portion and the protruding seal portion when viewed in the direction along the central axis, The dust cover according to claim 2.

5. The inner peripheral surface of the protruding portion overlaps the tip of the protruding seal portion or is located on the central axis side of the tip when viewed in the direction along the central axis, The annular concave portion overlaps the portion between the lip portion and the protruding seal portion when viewed in the direction along the central axis, The dust cover according to claim 2.

6. The inner peripheral surface of the protruding seal portion is inclined so as to face the direction opposite to the fixed portion with respect to the central axis. The dust cover according to claim 2.

7. A ball joint comprising a joint mechanism and a dust cover attached to the joint mechanism, wherein the joint mechanism includes a ball stud having a spherical portion provided at one end and a shaft portion having two spaced-apart first flange portions and second flange portions provided spaced apart from the spherical portion, a socket having a bearing for the spherical portion and rotatably and swingably supporting the ball stud, wherein the first flange portion is closer to the spherical portion than the second flange portion, the dust cover includes an annular deformable body portion having a central axis, a fixed portion provided at one end of the body portion and fixed to the socket, and a seal portion provided at the other end of the body portion, wherein the seal portion includes an annular main seal portion slidably attached to the first flange portion and the second flange portion while being sandwiched between the first flange portion and the second flange portion, an annular lip portion protruding from the main seal portion in a direction opposite to the seal portion along the central axis and having an inner peripheral surface contacting the outer peripheral surface of the second flange portion, and an annular protruding portion protruding from the main seal portion in a direction opposite to the lip portion along the central axis and having an inner peripheral surface contacting the outer peripheral surface of the first flange portion, and the main seal portion has an annular recess recessed in a direction opposite to the protruding direction of the protruding portion on the side opposite to the central axis of the protruding portion, characterized in that it is a ball joint.

8. The tip of the protruding portion is located between the surface of the first flange portion facing the spherical portion and the surface of the first flange portion facing the second flange portion, The ball joint according to claim 7.

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