JPH0118886Y2 - - Google Patents

Description

[Detailed explanation of the idea]

INDUSTRIAL APPLICATION FIELD The present invention relates to a low-torque bearing for ball joints used in automobile steering systems, suspension systems, and the like. BACKGROUND ART FIG. 1 is a partial sectional view showing an example of a ball joint using a conventional bearing. Ball joints have traditionally been used in the steering and suspension systems of automobiles. Generally, the diameter of the spherical portion 7a is made slightly larger than the inner diameter of the inner wall surface 21 of the conventional bearing 20. Therefore, the spherical portion 7a is held in a preloaded state. In other words, the spherical part 7a
is held in a tightened state by the bearing 20. Problems to be Solved by the Invention For this reason, in the conventional ball joint, the sliding resistance between the ball stud 7 and the bearing 20 was large. Therefore, in order to reduce the sliding resistance, a bearing 22 shown in FIG. 2 was created. This conventional bearing 22 has a thin groove 23 formed on the equator line X and above and below the equator line X. Groove 2
3 reduces the contact area between the ball stud 7 and the bearing 22, thereby reducing sliding resistance. However, in the conventional bearing 22, since the groove 23 is formed above and below the equator line X, the load applied to the spherical part 7a is unbalanced and there is a problem in terms of durability. In addition, the conventional bearing 22
In this case, the width of the groove 23 was narrow and the sliding resistance was not sufficiently reduced. Purpose of the invention The present invention was made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a low-torque bearing that is excellent in durability, has low sliding resistance, and has low starting torque and rotational torque for a ball stud. It is an object. Summary of the Invention In order to achieve the above-mentioned object, the gist of this invention is the low-torque bearing described in claim 1 of the utility model registration. Means for Solving the Problems The low-torque bearing of the present invention has a spherical inner wall surface that has a radius equal to or slightly smaller than the radius of the spherical portion and completely surrounds the spherical portion. forming a groove so as to go around the inner wall surface above the equator line of the inner wall surface;
Moreover, the groove is formed along the equator line and has a groove width such that the contact area between the inner wall surface of the bearing and the spherical portion is approximately equal above and below the equator line, and the contact surface of the inner wall surface is formed with a groove width that is approximately equal to the contact area between the inner wall surface of the bearing and the spherical portion. The spherical part of the stud is slidably held. Embodiments Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 3 is a partial sectional view showing an example of a ball joint using the low torque bearing of the present invention. A spherical portion 7a of a ball stud 7 is fitted into the spherical inner wall surface 8 of the low torque bearing 1 of the present invention. Then, the low torque bearing 1 of the present invention is fitted into the housing 11, and the caulked portion 11
It is fixed at a. 12 holds bearing 1 with a cap. The radius r' of the spherical portion 7a is equal to or slightly larger than the basic radius r of the inner wall surface 8 of the bearing 1. Therefore, when the spherical part 7a is fitted with the inner wall surface 8, the spherical part 7a receives a preload A from the low torque bearing 1. FIG. 4 is a sectional view showing an example of the low torque bearing of the present invention. The low torque bearing 1 of the present invention is made of synthetic rubber or synthetic resin that has excellent wear resistance and low friction. The low torque bearing 1 of the present invention is composed of a bottom wall 2, a top wall 3 and a side wall 4. An inner wall surface 8 is formed on the bottom wall 2. The inner wall surface 8 is a spherical surface with a basic radius r. Inner wall surface 8
The center O of is within the low torque bearing 1. A through hole 5 is formed in the top wall 3. The top wall 3 and the inner wall surface 8 are connected by the through hole 5.
The half of the through hole 5 on the inner wall surface 8 side is wider.
The through hole 5 is formed on the center line Y. The through hole 5 serves to vent air when the spherical portion 7a of the ball stud 7 is fitted into the inner wall surface 8 and to store excess lubricant. The through hole 5 may be omitted. A rounded surface is formed on the peripheral edge 8c of the inner wall surface 8. The contact surfaces 8a, 8b slidably hold the spherical portion 7a of the ball stud 7. 8a is a contact surface below the equator line X. The side wall 4 is tapered. side wall 4
becomes slightly narrower toward the bottom wall 2. The low torque bearing 1 of the present invention is symmetrical with respect to the center line Y, and the equator line X is the center O of the inner wall surface 8.
It is a line that passes through and is parallel to the bottom wall 2. Now, a groove 9 is formed in the inner wall surface 8. The groove 9 is formed above the equator line X. Groove 9
is formed along the equator line X. The groove 9 goes around the inner wall surface 8. A plurality of recesses 10 are formed in the contact surfaces 8a and 8b. The recess 10 serves as an oil reservoir for supplying lubricant when the spherical portion 7a of the ball stud 7 slides. The recess 10 is an extremely shallow depression. The recess 10 may not be provided. The contact surfaces 8a and 8b may be smooth curved surfaces without irregularities. The starting torque and rotational torque of the ball stud 7 are determined by the contact surface 8 between the spherical portion 7a and the inner wall surface of the bearing 1.
The groove 9 can reduce the sliding resistance of the spherical portion 7a, although it is determined by the sliding resistance between the spherical portion 7a and the spherical portion 7a. In other words, the groove 9 connects the inner wall surface 8 of the low torque bearing 1 with the spherical part 7a of the ball stud 7.
This results in a decrease in the contact area. Sliding resistance means a low drag force that acts on the contact surface when the spherical part and the bearing move relative to each other. As described above, in order to reduce the sliding resistance of the spherical part 7a, the contact area between the inner wall surface 8 and the spherical part 7a may be reduced. However, the sliding resistance that strongly affects the starting torque and rotational torque is the sliding resistance near the equator line X. This will be explained below. As is clear from FIG. 10, the sliding resistance Δf applied to the minute area ΔS on the spherical portion 7a is Δf=μ·AΔS. Here, μ is the coefficient of friction, and A is the preload that the low-torque bearing 1 exerts on the spherical portion 7a.
Therefore, the torque ΔT required to rotate the minute area ΔS about the Y axis is ΔT=Δf·rcosθ. Here, θ is the angle that a line connecting the minute area ΔS and the center O makes with the equator line X. Since the torque T required to rotate the ball stud 7 about the Y axis is the total of ΔT, ΔT close to the equator line X (θ=0) greatly influences the torque T. In this way, the groove width a of the groove 9 is meaningless if it is too large. The groove width a is preferably such that the area of the contact surface 8a is equal to the area of the contact surface 8b. Furthermore, when considering the durability of the ball joint, it is necessary that the preload A acts on the spherical portion 7a in a well-balanced manner. In other words, low torque bearing 1
It is necessary that the load applied to the spherical part 7a be balanced on the left and right sides with the center line Y as a border, and that the load applied on the spherical part 7a be balanced on the top and bottom with the equator line X as a border. The projected area of the contact surface is used to consider the balance of the load applied to the spherical portion 7a. The balance in the left-right direction of the center line Y is always balanced because the low-torque bearing 1 of the present invention is symmetrical with respect to the center line Y. Therefore, it is only necessary to consider the load balance in the vertical direction with respect to the equator line X. FIG. 9 shows a projection plane of the contact surfaces 8a and 8b in the vertical direction (center line Y direction). That is, FIG. 9 shows a projection plane in the direction of arrow B. The projection surface of the contact surface 8a is 32. Further, the projection surface of the contact surface 8b is 33
becomes. In order to improve the durability of the low torque bearing 1, it is important to make the projected area of the projection surface 32 as close as possible to the projected area of the projection surface 33 to balance the load in the vertical direction. This is why the groove 9 is formed above the equator line X. If the projected area of the projection surface 32 and the projection surface of the projection surface 33 are made equal, there will be no problem in durability if the load is applied only in the longitudinal direction of the ball stud 7. However, since the projected area of the projection plane 33 in the direction perpendicular to the Y direction is narrow, if a load is applied perpendicularly to the longitudinal direction of the ball stud 7, this projected area will become extremely narrow, resulting in poor durability. A problem arises. In order to solve this problem, the contact areas of the contact surfaces 8a and 8b are made approximately equal. The recess 10 must be taken into account when considering the contact area and projected area. FIG. 11 is a partially enlarged view of the low torque bearing shown in FIG. 4. The basic radius r of the inner wall surface 8 is set to be equal to or slightly smaller than the radius r' of the stud's spherical part, and the stud's spherical part 7a is inserted. When this happens, a slight preload is applied to the entire circumference of the stud sphere, and the bottom and top peripheral edges 30, 31 (see Figure 4) come into close contact with the stud sphere, preventing the lubricant in the recess 10 from leaking to the outside. has been done. Further, R is the radius of the recess and is larger than r by several microns to several tens of microns. Contact surfaces 8a and 8b other than the recess 10 of the inner wall surface 8
comes into elastic contact with the spherical part. The boundary between the recess 10 and the contact surfaces 8a, 8b has an appropriate radius _R1 . FIG. 12 is a partially enlarged view of the ball joint assembly shown in FIG. 3, in which a preload is applied to the low-torque bearing 1, and the radius R of the inner wall surface of the bearing is expanded to the radius r' of the spherical part. . Therefore, the radius R of the bottom surface of the recess 10 is
is compressed by the housing 11 and the spherical part 7a and is reduced to R', so that the recess 10
The volume of the lubricant accumulated in the recess 10 increases the internal pressure and the surface area of the contact surface 8 is expanded.
a, 8b, a strong lubricating film surface is formed between the bottom surface of the recess 10 and the contact surfaces 8a, 8b, and the spherical part 7a, and the spherical part 7a is floated in the lubricant under high pressure. hold the state. Note that the lubricant is applied to the bottom and top peripheral parts 30,
31 to prevent leakage to the outside. The ball joint in this state always allows the stud to rotate easily, and even when the stud is suddenly rotated after a long period of rest, the starting torque is low and the stud moves smoothly. Furthermore, when an external force is applied to the spherical portion 7a, the strain on the bearing working surface further increases, the volume of the recess 10 further decreases, the internal pressure of the lubricant increases, and the lubricant is transferred to the contact surface 8.
a, 8b to further strengthen the lubricating film, and the area increases due to the compression of the contact surfaces 8a, 8b, and the center portion 18 of the bottom surface of the recess 10 also becomes a spherical portion 7.
It comes into contact with a and plays the role of increasing the contact surface, and also has the advantage of reducing stress increase due to external force. Examples of calculating the contact area are shown in FIGS. 5 to 8. Note that the following calculation example was performed for a low-torque bearing in which the recess 10 is not formed. Calculate the contact area of contact surfaces 8a and 8b. Fifth
In the embodiment shown in the figure, the groove width a of the groove 9 is 5.538 (mm). The distance j between the lower edge 9b of the groove 9 and the equator line X is
It is 0.173 (mm). Therefore, the distance k between the upper edge 9a of the groove 9 and the equator line X is 5.711 (mm). As shown in FIG. 3, a flat portion 16 is formed in the spherical portion 7a of the ball stud 7, centered on the center line Z of the ball stud 7. Therefore,
A spherical part 7a is provided on the inner wall surface 8 of the bearing 1 for low torque.
When fitted together, the spherical part 7a reaches only up to the horizontal line W (if the center line Y and the center line Z coincide). Therefore, the contact surface 8a is connected to the horizontal line W and the upper edge 9 of the groove 9.
It is between a. The contact surface 8b is between the equator line X and the bottom wall 2
It is between. The radius r' of the spherical part 7a of the ball stud 7 is 10
(mm). When the spherical portion 7a is fitted to the inner wall surface 8 of the low torque bearing 1, the basic radius r of the inner wall surface 8 becomes r'. Further, the diameter e of the flat portion 16 is 8 (mm). The diameter f of the through hole 5 is 3
(mm). The distance h between the apex 15 of the inner wall surface 8 (however, the apex 15 does not actually exist because of the through hole 5) and the upper edge 9a is h=rk=10-5.711=4.289 (mm). Therefore, the distance i between the vertex 15 and the horizontal line W is i=10-(1/2)√4×10 ² −8 ² =0.8349 (mm). Therefore, the contact area Sa of the contact surface 8a is Sa=2πrh−2πri=2πr(h−i)=217.028(mm). Also, when the ball stud 7 is swung,
The spherical portion 7a of the ball stud 7 may come into contact with the through hole 5. At this time, the contact area Sa decreases. Calculate the reduction value of this contact area Sa. FIG. 6 is an explanatory diagram showing a portion of the through hole 5. FIG. The distance m between the periphery 5a of the through hole 5 and the apex 15 is m=10−(1/2)√4×10 ² −3 ² =0.11314 (mm). Therefore, the maximum reduction value of the contact area Sa is 2πrm = 7.109 (mm). As a result of the above, the contact area Sa of the contact surface 8a is 217.028 (mm) at the maximum and 209.919 (mm) at the minimum. The contact area Sb of the contact portion 8b is as follows. The distance n between the equator line X and the bottom wall 2 is 3.5 (mm). Therefore, the lower vertex 17 of the inner wall surface 8 and the bottom wall 2
The distance b is b = r - n = 10 - 3.5 = 6.5 (mm). The peripheral edge 8c of the inner wall surface 8 is a rounded surface with a radius of 0.4 (mm). Therefore, the area Sb of the contact surface 8b is Sb={4πr ² /2−2πr(b+0.4)}+{4πr ² /2
−2πr(r−j)}=205.643(mm) The above results are summarized in a table as shown in Table 1.

[Table] When the groove 9 is formed in the position shown in FIG. 5, it is desirable that the swing angle of the ball stud 7 is 28 degrees or less. The reason is that when the swing angle becomes larger than 28 degrees, the flat part 16 of the ball stud 7
This is because, as a result, the groove 9 is scraped, the rocking rotation becomes stuck, etc. Effects of the invention As described above, in the ball joint low torque bearing according to the invention, the groove is formed above the equator line. This improves the balance of the load applied to the spherical portion. Therefore, the ball joint using the low torque bearing of the present invention exhibits excellent durability. In addition, since the low torque bearing of the present invention has a good balance of the load applied to the spherical portion, the width of the groove can be made wide. For this reason, ball joints using the low-torque bearing of this invention are
Starting torque and rotation torque can be made very low.

[Brief explanation of the drawing]

Figure 1 is a partial sectional view showing a ball joint using a conventional bearing, Figure 2 is a sectional view showing a conventional bearing, and Figure 3 is a ball joint using a low torque bearing according to the present invention. FIG. 4 is a sectional view showing an example of a low torque bearing according to the present invention; FIG.
The figure is an explanatory diagram for calculating the contact area of the low torque bearing according to the present invention, Figure 6 is an explanatory diagram showing the through hole 5 part for calculating the contact area, and Figure 7 is the contact area. Fig. 8 is an explanatory diagram showing the area above the equator line of the bearing for low torque according to the present invention in order to calculate the contact area. Figure 9 is a cross-sectional view showing the projected plane of the low torque bearing according to the present invention.
Figure 0 is an explanatory diagram showing an example of calculation of starting torque and rotating torque, Figure 11 is a partially enlarged view of the low torque bearing in Figure 4, and Figure 12 is a part of the ball joint assembly in Figure 3. This is an enlarged view. 1...Low torque bearing, 2...Bottom wall, 3
... Top wall, 4 ... Side wall, 5 ... Through hole, 7 ... Ball stud, 8 ... Inner wall surface, 9 ... Groove, 10 ...
... recess, 11 ... housing, 12 ... cap, 16 ... flat part.

Claims (1)

[Claims for Utility Model Registration] 1. A bearing for a ball joint made of elastically deformable synthetic resin or synthetic rubber that is assembled in a preloaded state between a housing and a spherical part of a ball stud, wherein the spherical part is attached to an inner wall of the bearing. forming a spherical inner wall surface having a radius equal to or slightly smaller than the radius of the spherical part, and forming a groove around the inner wall surface above the equator line of the inner wall surface; In addition, the groove is formed along the equator line and has a groove width such that the contact area between the inner wall surface of the bearing and the spherical portion is approximately equal above and below the equator line, and the contact surface of the inner wall surface is A low torque bearing characterized in that the spherical part of the ball stud is slidably held. 2. The low torque bearing according to claim 1, wherein the contact surface is a smooth curved surface with no irregularities. 3. The low torque bearing according to claim 1 or 2, wherein the contact surface is a curved surface having a plurality of oil sump recesses.