WO2019088284A1

WO2019088284A1 - Method for producing ball joint, method for producing stabilizer link, and ball joint

Info

Publication number: WO2019088284A1
Application number: PCT/JP2018/040988
Authority: WO
Inventors: 黒田　茂
Original assignee: 日本発條株式会社
Priority date: 2017-11-06
Filing date: 2018-11-05
Publication date: 2019-05-09
Also published as: JP6751068B2; JP2019086066A

Abstract

This method for producing a ball joint (10) provided with a metal ball stud (13) obtained by connecting a shaft part (11) and a ball part (12) to each other, and a housing (15) which comprises a thermoplastic resin, and has a recess portion (14) into which the ball part is inserted so as to be capable of rotating around a centre point thereof, is provided with: an assembly step in which the outer circumferential surface of the ball part and the inner surface of the recess portion are brought into close contact with each other, to join the ball stud and the housing; and a heating step in which the outer circumferential surface side of the ball part and the inner surface side of the recess portion are heated using frictional heat by moving the ball part relatively in the recess portion, and the crystallinity of the inner surface side of the recess portion is increased.

Description

Method of manufacturing ball joint, method of manufacturing stabilizer link, and ball joint

The present invention relates to a method of manufacturing a ball joint, a method of manufacturing a stabilizer link, and a ball joint.
Priority is claimed on Japanese Patent Application No. 2017-213878, filed Nov. 6, 2017, the content of which is incorporated herein by reference.

BACKGROUND ART Conventionally, a ball joint comprising a metal ball stud in which a shaft portion and a ball portion are connected to each other, and a housing made of a thermoplastic resin having a hollow portion in which the ball portion is rotatably inserted around its center point In the manufacturing method, the outer peripheral surface of the ball portion and the inner surface of the recessed portion are brought into close contact with each other to assemble the ball stud and the housing, and the outer peripheral surface side of the ball portion and the inner surface side of the recessed portion are heated. And a heating step is known. According to this method, at the time of cooling after the heating step, the ball portion is reduced to the original size, while the inner surface side of the recess is not reduced to the original size and kept larger than the original size. The close contact state between the outer peripheral surface of the ball portion and the inner surface of the recessed portion can be relaxed, and the contact state such as the gap between the outer peripheral surface of the ball portion and the inner surface of the recessed portion or the interference can be adjusted.
As the heating step, for example, a method is known in which the heat of the ball stud is transferred to the inner surface side of the recess by inductively heating the ball stud after the assembling step as shown in Patent Document 1 below.

Japanese Patent Application Laid-Open No. 2017-129223

However, in the above-described conventional ball joint manufacturing method, it may be difficult to heat the outer peripheral surface side of the ball portion and the inner surface side of the recessed portion over the entire area with little variation and accuracy during the heating step.

The present invention has been made in consideration of such circumstances, and it is possible to accurately heat the outer peripheral surface side of the ball portion and the inner surface side of the recessed portion over the entire area with little variation during the heating step. It is an object of the present invention to provide a manufacturing method, a manufacturing method of a stabilizer link, and a ball joint.

In order to solve the above problems and achieve such an object, a method of manufacturing a ball joint according to a first aspect of the present invention is a metal ball stud in which a shaft portion and a ball portion are connected to each other; And a housing made of a thermoplastic resin having a hollow portion in which the ball portion is rotatably inserted around the center point, and a manufacturing method of a ball joint, comprising: an outer peripheral surface of the ball portion; The outer surface side of the ball portion and the inner surface side of the recessed portion are brought into close contact with each other by assembling the ball stud and the housing in close contact with each other, and by relatively moving the ball portion within the recessed portion. Are heated by frictional heat to increase the degree of crystallization on the inner surface side of the depressed portion.

According to the first aspect, the outer peripheral surface of the thermally expanded ball portion is pressed against the inner surface of the softened hollow portion during the heating step, whereby the inner surface side of the hollow portion is expanded and deformed, and the inner surface side of the hollow portion While the degree of crystallinity of the hollow portion is increased, the material forming the inner surface side of the recess flows, and the ball portion shrinks to its original size at the time of subsequent cooling, while the inner surface side of the recessed portion is smaller than the original size Be kept large. Therefore, the close contact state between the outer peripheral surface of the ball portion and the inner surface of the recessed portion can be alleviated, and the contact state such as the gap between the outer peripheral surface of the ball portion and the inner surface of the recessed portion or the interference can be adjusted. .
In particular, by moving the ball relative to each other in the recess during the heating step, the outer peripheral surface side of the ball and the inner surface of the recess which are in close contact with each other are heated by frictional heat. In the ball joint, as compared with the case of using the ball joint, the shape factor of the portion other than the outer peripheral surface of the heating ball portion and the inner surface of the hollow portion and the environmental factor are the outer peripheral surface side of the ball portion and the inner surface side of the hollow portion. The influence on each heating temperature can be reduced.
Therefore, the outer peripheral surface side of the ball portion and the inner surface side of the recessed portion can be heated with less variation throughout the entire area with high accuracy, and the inner surface side of the recessed portion is raised to the desired crystallinity degree, and the outer periphery of the ball portion The aforementioned adjustment between the surface and the inner surface of the recess can be made with high accuracy. As a result, it is possible to obtain a ball joint in which the frictional force generated between the outer peripheral surface of the ball portion and the inner surface of the recessed portion is suppressed while preventing generation of rattling of the ball stud with respect to the housing, that is, abnormal noise.
In addition, since the degree of crystallization on the inner surface side of the depressed portion is increased during the heating step, the hardness on the inner surface side of the depressed portion can be improved and the surface roughness can be reduced. Therefore, even if the gap between the outer peripheral surface of the ball portion and the inner surface of the recessed portion is suppressed as much as possible to prevent generation of noise due to external force from the ball joint reliably, the ball stud and housing smooth. It is possible to ensure both relative movement and wear resistance on the inner surface side of the recess.

Here, in the first aspect, in the heating step, the ball portion and the housing may be relatively rotated around a center point of the ball portion.

In this case, since the ball portion and the housing are relatively rotated around the center point of the ball portion during the heating step, frictional heat is efficiently generated with a short moving amount on the outer peripheral surface of the ball portion and the inner surface of the hollow portion. be able to.
The relative rotation of the ball portion and the housing around the center point of the ball portion includes, for example, swinging around the center point and when the center point of the ball portion is located on the center axis of the shaft portion There is rotation etc. around the shaft.

In the first aspect, in the heating step, the ball portion and the housing may be relatively rotated around the shaft portion, and may be oscillated around a center point of the ball portion.

In this case, the ball portion and the housing are relatively rotated around the shaft portion and oscillated around the center point of the ball portion during the heating step, so the outer peripheral surface of the ball portion is sandwiched by the center point of the ball portion In the whole area including the pole part located on the opposite side of the connecting part with the shaft part, it becomes possible to heat with less variation and accuracy with certainty, and surely suppress the occurrence of temperature distribution on the inner surface of the recess. Can.

In the first aspect, in the assembling step, the housing may be injection molded using the ball portion as an insert.

In this case, since the housing is injection-molded using the ball portion as an insert during the assembling process, the above-mentioned adjustment can be performed with high accuracy since the interference of the inner surface of the recessed portion with respect to the outer peripheral surface of the ball portion is large. The possible effects are outstandingly successful.
Further, since the housing is formed by insert molding, the outer peripheral surface of the ball portion is uniformly tightened to the inner surface of the recessed portion over the entire region, and the above-described frictional heat causes the outer peripheral surface side of the ball portion It is possible to realize heating of the inner surface side of the recessed portion with less variation and accuracy with greater precision over the entire area.

In the method of manufacturing a stabilizer link according to the second aspect of the present invention, a metal ball stud in which a shaft portion and a ball portion are connected to each other, and a recess portion in which the ball portion is rotatably inserted around its center point A ball joint comprising a thermoplastic resin housing having the following: a stabilizer link in which the ball joint is separately connected to both ends of the support bar via the housing, and the ball joint is a member of the present invention. It forms by the manufacturing method of the ball joint which concerns on a 1st aspect.

According to the second aspect, it is possible to obtain a stabilizer link in which the frictional force generated between the outer peripheral surface of the ball portion and the inner surface of the recessed portion is suppressed while preventing rattling of the ball stud relative to the housing. While driving | running | working of the vehicle with which the stabilizer link was mounted | worn, while being able to prevent that noise generate | occur | produces from a stabilizer link, the stabilizer link which can be contributed to a comfortable ride can be obtained.

A ball joint according to a third aspect of the present invention is a heat having a metal ball stud in which a shaft portion and a ball portion are connected to each other, and a hollow portion in which the ball portion is rotatably inserted around its center point. And a housing made of a plastic resin, wherein the housing is formed in a cylindrical shape with a wall thickness of 2 mm or more, and the inside is a hollow portion, and the hollow portion has a center point Is formed in a spherical shape positioned on the central axis of the housing, and at least the inner surface of the hollow portion, the center of the hollow portion on the basis of a plane perpendicular to the central axis and passing through the central point of the hollow portion. The ten-point average roughness Rzjis (JIS B 0601: 2001) of a portion over a range of ± 20 ° centering on a point is set to 20 μm or less at a reference length of 0.8 mm, and the recess The hardness of the inner surface, in the housing, is equal to or greater than 110% the hardness of the portion located at a depth of 1mm from the inner surface of the recess.

According to the third aspect, the ten-point average roughness Rzjis (JIS) of the portion of the inner surface of the recess at least at least in the range of ± 20 ° centering on the center point of the recess with reference to the plane. B 0601: 2001) has a reference length of 0.8 mm and is 20 μm or less, so it is possible to reliably suppress the frictional force generated between the outer peripheral surface of the ball portion and the inner surface of the recessed portion, Smooth relative movement of the stud and the housing can be ensured.
In addition, since the hardness of the inner surface of the recessed portion is 110% or more of the hardness of the portion located at a depth of 1 mm from the inner surface of the recessed portion in the housing, the wear resistance on the inner surface side of the recessed portion is secured can do.
Moreover, since the housing is formed in a bottomed cylindrical shape having a thickness of 2 mm or more, good formability can also be ensured.

According to the method of manufacturing a ball joint and the method of manufacturing a stabilizer link according to the first and second aspects of the present invention, the outer peripheral surface side of the ball portion and the inner surface side of the recess are respectively covered over the entire area during the heating step. It is possible to heat with less variation and accuracy. Further, according to the ball joint according to the third aspect of the present invention, both of the smooth relative movement of the ball stud and the housing and the wear resistance on the inner surface side of the recessed portion can be secured.

It is a partial cross section figure of the stabilizer link shown as one embodiment concerning the present invention. It is a graph which shows the relationship of the hardness to the pressing depth in the inner surface of each hollow part obtained by the manufacturing method of the stabilizer link concerning each example of the present invention, and a comparative example. It is a graph which shows the relationship of the elastic modulus with respect to the pushing depth in the inner surface of each hollow part obtained by the manufacturing method of the stabilizer link which concerns on each of the Example and comparative example of this invention. It is a graph which shows the measurement result of the uneven | corrugated height of the inner surface of the hollow part obtained by the manufacturing method of the stabilizer link which concerns on the comparative example of this invention. It is a graph which shows the measurement result of the uneven | corrugated height of the inner surface of the hollow part obtained by the manufacturing method of the stabilizer link which concerns on the Example of this invention.

Hereinafter, one embodiment of a method of manufacturing a stabilizer link according to the present invention will be described with reference to FIG. FIG. 1 is a longitudinal cross-sectional view of the stabilizer link along a central axis O described later.
The stabilizer link 1 of the present embodiment is a housing made of a crystalline thermoplastic resin having a metal ball stud 13 in which the shaft portion 11 and the ball portion 12 are connected to each other and a hollow portion 14 in which the ball portion 12 is inserted. And 15 are connected separately to both end portions 16 a of the support bar 16 through the housing 15.
The stabilizer link 1 has one shaft portion 11 of the pair of ball joints 10 connected to the stabilizer 2 and the other shaft portion 11 connected to the suspension device 3. The other shaft 11 is connected to, for example, a cylinder or an arm member of a damper in the suspension device 3. The pair of ball joints 10 have the same size and the same shape. The pair of ball joints 10 may be formed in different shapes and in different shapes.

The housing 15 is made of, for example, polyamide 66 (PA 66), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyacetal (POM) or the like, or a thermoplastic resin material thereof, for example, carbon fiber or glass fiber Etc. are formed of a material containing a reinforcing fiber. In the present embodiment, the housing 15 is formed of PA 66 containing 30% by weight of glass fiber.
For example, the glass transition temperature of PA66 is about 50 ° C., the crystallization temperature is about 232 ° C., and the melting point is about 265 ° C.

The housing 15 is formed in a flat bottomed cylindrical shape, and the inside thereof is a recess 14. The thickness of the housing 15 is 2 mm or more. The hollow portion 14 is open on one side in the axial direction along the central axis O of the housing 15 and closed on the other side. The recess 14 is formed in a spherical shape whose center point is located on the center axis O.
Hereinafter, viewed from the axial direction, a direction intersecting the central axis O is referred to as a radial direction, and a direction circling around the central axis O is referred to as a circumferential direction.

A portion of the inner surface of the recess 14 over a range of ± 20 ° centered on the center point of the recess 14 with respect to at least a plane perpendicular to the central axis O and passing through the center point of the recess 14 The point average roughness Rzjis (JIS B 0601: 2001) is, for example, about 20 μm or less at a reference length of 0.8 mm.
The hardness of the inner surface of the recess 14 is, for example, about 110% or more of the hardness of the portion of the housing 15 located at a depth of 1 mm from the inner surface of the recess 14. This hardness can be measured based on the nanoindentation method. For example, using TriboIndenter manufactured by Hysitron, at a temperature of 23.degree. C., the force required to inflate a triangular pyramidal indenter having a tip edge radius of 50 nm or less to a certain depth, and the indented portion of the indenter. It can be measured based on the projected area.

At the peripheral edge of the opening of the recess 14 in the housing 15, a protrusion 15a that protrudes in the axial direction and extends continuously over the entire circumference is formed. The inner circumferential surface of the protruding portion 15a extends radially outward gradually as it goes to the outside of the housing 15 along the axial direction. The inclination angle of the inner peripheral surface of the protruding portion 15a with respect to the central axis O may be appropriately set according to the swing angle of the ball stud 13 around the central point S of the ball portion 12 or the like. The housing 15 is integrally formed of the same material as a whole.

The ball stud 13 is formed of, for example, a steel material, and the shaft portion 11 and the ball portion 12 are connected by welding. The entire ball stud 13 may be integrally formed. The ball portion 12 is a spherical body, and the shaft portion 11 is a cylindrical body. In the shaft portion 11, the ball portion 12 is connected to one of the end portions in the axial direction along the central axis. The center point S of the ball portion 12 is located on the center axis of the shaft portion 11.
Hereinafter, the state in which the ball stud 13 is disposed coaxially with the central axis O of the housing 15 will be described.

At an axially intermediate portion of the shaft portion 11, a flange portion 11a protruding outward in the radial direction is formed over the entire circumference. In the shaft portion 11, a male screw portion is formed in a portion located on the opposite side of the ball portion 12 with the flange portion 11a interposed in the axial direction. A circumferential groove 11b extending continuously over the entire circumference is formed at an end (an end near the flange portion 11a) on the flange portion 11a side in a portion positioned between the flange portion 11a and the ball portion 12 in the shaft portion 11 It is done.
The outer diameter of the ball portion 12 is larger than the outer diameter of the portion excluding the flange portion 11 a in the shaft portion 11.

The ball portion 12 is inserted into the recess 14 of the housing 15 so as to be rotatable about its center point S. The center point S of the ball portion 12 substantially coincides with the center point of the recess 14 of the housing 15. The diameter of the ball 12 is slightly smaller than the diameter of the recess 14. The diameter of the ball portion 12 may be equal to or larger than the diameter of the recess portion 14. The connection portion of the ball portion 12 with the shaft portion 11 protrudes outward in the axial direction from the recess portion 14. The recess portion 14 covers a portion of the outer peripheral surface of the ball portion 12 which exceeds half. The portion of the ball portion 12 that protrudes outward in the axial direction from the recess 14 is located inward in the axial direction from the protruding portion 15a, and is surrounded from the outside in the radial direction over the entire region by the protruding portion 15a. There is. A portion of the ball portion 12 protruding outward in the axial direction from the recess portion 14 may be positioned on the outer side in the axial direction from the protruding portion 15a.

In the illustrated example, the stabilizer link 1 is provided with a dust cover 17 that prevents water, dust, dust, and the like from entering between the outer peripheral surface of the ball portion 12 and the inner surface of the recessed portion 14. The dust cover 17 is formed in a cylindrical shape so as to be elastically deformable, and is disposed coaxially with the central axis O. One of both end portions in the axial direction of the dust cover 17 is mounted in the circumferential groove 11 b of the shaft portion 11, and the other is externally fitted to the protruding portion 15 a of the housing 15. The stabilizer link 1 may not have the dust cover 17.

The support bar 16 is cylindrically formed of, for example, a steel material. The central axis L of the support bar 16 passes through the central point S of the ball portion 12 and is orthogonal to the central axis O of the housing 15. Both end portions 16a of the support bar 16 are formed into a flat plate by being crushed in the axial direction (axial direction along the central axis O) by press working or the like. Both end portions 16 a of the support bar 16 are covered with a covering 18 made of a thermoplastic resin. The cover 18 is integrally formed with the housing 15.
The support bar 16 may be formed solid, and the end 16a of the support bar 16 may not be formed in a flat plate shape, and the end 16a of the support bar 16 may not be covered with the covering 18 Good. If the cover 18 does not cover the end 16 a of the support bar 16, the support bar 16 and the housing 15 may be connected.

Next, the manufacturing method of the stabilizer link 1 comprised as mentioned above is demonstrated.
The method of manufacturing the stabilizer link 1 includes an assembly process and a heating process.

In the assembling process, the ball stud 13 and the housing 15 are combined by bringing the outer peripheral surface of the ball portion 12 into close contact with the inner surface of the recess portion 14. In the present embodiment, in the assembling process, the housing 15 and the cover 18 are injection-molded using the ball portion 12 and the end portion 16a of the support bar 16 as an insert. Thereafter, the outer peripheral surface of the ball portion 12 is tightened to the inner surface of the recessed portion 14 by the molding shrinkage of the thermoplastic resin. The cover 18 may be bonded to the end 16 a of the support bar 16 by applying an adhesive to the end 16 a of the support bar 16 in advance before the assembly process.

Here, the mold temperature is, for example, about 80 ° C. or less during the assembly process. As a result, the time until the molded article obtained can be released can be kept short, and the crystallization on the outer peripheral surface side of the housing 15 can be suppressed, and the molding shrinkage of the housing 15 can be suppressed. The tightening of the inner surface of the recess 14 to the outer peripheral surface of the ball 12 can be suppressed.

In the heating step, the outer peripheral surface side of the ball portion 12 and the inner surface side of the recessed portion 14 are heated by frictional heat by relatively moving the ball portion 12 in the recessed portion 14, and the crystallization degree of the inner surface side of the recessed portion 14 Raise. In the heating process, the ball portion 12 and the housing 15 are relatively rotated around the center point S of the ball portion 12. In the present embodiment, in the heating step, the ball portion 12 and the housing 15 are relatively rotated around the shaft portion 11 (around the central axis of the shaft portion 11) and oscillated around the center point S of the ball portion 12 . At this time, the ball portion 12 is relatively moved in the recess portion 14 in a state in which no axial force is applied to the ball stud 13. Further, one of the ball portion 12 and the housing 15 is rotated around the shaft portion 11 (around the central axis of the shaft portion 11), and the other is rocked around the central point S of the ball portion 12. In this case, it is possible to perform the adjustment of the rotation and the rocking separately with high precision while suppressing the complication of the device structure.
Alternatively, only one of the ball portion 12 and the housing 15 may be rotated around the shaft portion 11 (around the central axis of the shaft portion 11) and swung around the center point S of the ball portion 12. Alternatively, the ball portion 12 may be relatively moved within the recess 14 in a state where an axial force is applied to the ball stud 13.

At the time of the heating step, the inner surface side of the recess 14 is heated to the crystallization temperature higher than the glass transition point and lower than the melting point by the above-described frictional heat or its vicinity to increase the crystallinity of the inner surface side of the recess 14.
The relative moving speed, the number of movements, and the moving time of the outer peripheral surface of the ball portion 12 and the inner surface of the recess portion 14 are the tightening force (pressing force) of the inner surface of the recess portion 14 with respect to the outer peripheral surface of the ball portion 12 The relationship with the heat generation temperature due to frictional heat may be determined in advance by experiments, and may be set based on the experimental data. The clamping force can be specified by the molding conditions.
In addition, the crystallization temperature is determined, for example, using DSC (differential scanning calorimeter) as the peak top temperature of the exothermic peak observed when the temperature is decreased from the molten state at a rate of 20 ° C./minute under a nitrogen atmosphere. Can.
The degree of crystallinity can be determined as the ratio of the measured heat of fusion to the theoretical heat of fusion at 100% crystallization. The measured heat of fusion can be determined, for example, from the difference between the heat of the endothermic peak and the heat of the exothermic peak observed when the temperature is raised to the melting point or more at a rate of 10 ° C./min under a nitrogen atmosphere using DSC. .

At the time of the heating step, the degree of crystallization on the inner surface side of the recess 14 is increased, whereby the reinforcing fibers contained in the thermoplastic resin forming the housing 15 move from the inner surface of the recess 14 toward the outer surface of the housing 15 Surface roughness of the inner surface of the recess 14 is considered to be low.
The heating process may be performed in the cavity of the molding die immediately after the assembling process without opening the mold after the assembling process, or may be performed after removing the mold after the assembling process. Good. In the former case, the time required to heat the inner surface side of the recess 14 to the crystallization temperature or its vicinity can be kept short during the heating step, and in the latter case, the molding cycle can be prevented from being lengthened.
Finally, one of both end portions in the axial direction of the dust cover 17 is mounted in the circumferential groove 11 b of the shaft portion 11, and the other is externally fitted to the protruding portion 15 a of the housing 15.

As described above, according to the method of manufacturing the stabilizer link 1 according to the present embodiment, the outer peripheral surface of the thermally expanded ball portion 12 is pressed against the inner surface of the softened recessed portion 14 during the heating step. While the inner surface side of 14 is expanded and deformed, the degree of crystallization of the inner surface side of the recess 14 is enhanced, and the material forming the inner surface of the recess 14 flows, and the ball 12 While the inner surface side of the recess 14 is kept larger than the original size. Therefore, the close contact state between the outer peripheral surface of the ball portion 12 and the inner surface of the recess portion 14 is relieved, and the contact state such as the gap between the outer peripheral surface of the ball portion 12 and the inner surface of the recess portion 14 or the interference is adjusted can do.

In particular, by relatively moving the ball portion 12 in the recess portion 14 during the heating step, the outer peripheral surface side of the ball portion 12 and the inner surface side of the recess portion 14 in close contact with each other are heated by frictional heat. The shape factor of the portion other than the outer peripheral surface of the ball portion 12 to be heated and the inner surface of the hollow portion 14 in the ball joint 10 and the environmental factor etc. The influences on the heating temperatures on the surface side and the inner surface side of the recess 14 can be reduced.

Therefore, the outer peripheral surface side of the ball portion 12 and the inner surface side of the recess portion 14 can be heated with little variation over the entire area with high accuracy, and the inner surface side of the recess portion 14 is enhanced to the desired crystallinity. The aforementioned adjustment between the outer peripheral surface of the portion 12 and the inner surface of the recess portion 14 can be performed with high accuracy. Thus, it is possible to obtain the ball joint 10 in which the frictional force generated between the outer peripheral surface of the ball portion 12 and the inner surface of the recessed portion 14 is suppressed while preventing generation of rattling of the ball stud 13 with respect to the housing 15; Be

In addition, since the degree of crystallization on the inner surface side of the recess 14 is increased during the heating step, the hardness on the inner surface side of the recess 14 can be improved and the surface roughness can be reduced. Therefore, even if the gap between the outer peripheral surface of the ball portion 12 and the inner surface of the recessed portion 14 is suppressed as much as possible to prevent generation of noise from the ball joint 10 due to external force, the ball stud 13 Both the smooth relative movement of the housing 15 and the wear resistance of the inner surface of the recess 14 can be secured.

Further, since the ball portion 12 and the housing 15 are relatively rotated around the center point S of the ball portion 12 in the heating step, the outer peripheral surface of the ball portion 12 and the inner surface of the recessed portion 14 are efficiently moved with a short movement amount. Frictional heat can be generated.
Further, in the heating process, the ball 12 and the housing 15 are relatively rotated around the shaft 11 (around the central axis of the shaft 11) and pivoted around the center point S of the ball 12, so that the ball The outer peripheral surface of the portion 12 can be heated with less variation and accuracy over the entire area including the pole portion 12a located on the opposite side of the connecting portion with the shaft portion 11 across the center point S of the ball portion 12 Thus, the occurrence of temperature distribution on the inner surface of the recess 14 can be reliably suppressed.

In addition, since the housing 15 is injection molded using the ball portion 12 as an insert during the assembly process, the interference of the inner surface of the recessed portion 14 with respect to the outer peripheral surface of the ball portion 12 is increased. The effects that can be achieved are remarkably successful.
In addition, since the housing 15 is formed by insert molding, the outer peripheral surface of the ball portion 12 is uniformly tightened to the inner surface of the recessed portion 14 over the entire area, and the above-described frictional heat of the ball portion 12 occurs during the heating process. It is possible to realize the heating on the outer peripheral surface side and the inner surface side of the recess portion 14 with less variation over the entire area with higher accuracy.

As described above, the stabilizer link 1 is obtained in which the frictional force generated between the outer peripheral surface of the ball portion 12 and the inner surface of the recessed portion 14 is suppressed while preventing the rattling of the ball stud 13 with respect to the housing 15. While traveling with the vehicle on which the stabilizer link 1 is mounted, it is possible to prevent the abnormal noise from being generated from the stabilizer link 1 and obtain the stabilizer link 1 that can contribute to a comfortable ride. .
When the heating step is performed after the assembling step and after the mold is removed, for example, air is blown to the outer peripheral surface side of the housing 15 while relatively moving the ball portion 12 in the recess portion 14 at the heating step. By cooling it, crystallization on the outer peripheral surface side of the housing 15 can be suppressed, thermal contraction of the housing 15 can be suppressed, and the above-mentioned adjustment can be performed more accurately.

Further, according to the ball joint according to the present embodiment, a ten-point average of at least a portion of the inner surface of the recess 14 over a range of ± 20 ° centering on the center point of the recess 14 with reference to the plane. Since the roughness Rzjis (JIS B 0601: 2001) is 20 μm or less with a reference length of 0.8 mm, the frictional force generated between the outer peripheral surface of the ball portion 12 and the inner surface of the recessed portion 14 can be assuredly While being able to be restrained, smooth relative movement of ball stud 13 and housing 15 can be secured.
Further, the hardness of the inner surface of the recess 14 is 110% or more of the hardness of the portion located at a depth of 1 mm from the inner surface of the recess 14 in the housing 15. Wearability can be secured.
Moreover, since the housing 15 is formed in a bottomed cylindrical shape having a thickness of 2 mm or more, good formability can also be ensured.

Next, the verification test of the effect demonstrated above is demonstrated.
As an example, the housing 15 obtained by the method of manufacturing the stabilizer link 1 of the present embodiment is adopted, and as a comparative example, among the methods of manufacturing the stabilizer link 1 of the present embodiment, it is obtained by the manufacturing method without the heating step. Adopted housing.

The hardness on the inner surface side of the recessed portion was measured based on the nanoindentation method. This measurement was performed using TriboIndenter manufactured by Hysitron, at a temperature of 23 ° C., the force required to inflate a triangular pyramidal indenter having a tip edge radius of 50 nm or less to a certain depth, and the indenter among the indenters. It measured based on the projection area of a part. This measurement was carried out with different indentation depths for each of the example and the comparative example.
As a result, as shown in FIG. 2, it was confirmed that the hardness of the inner surface side of the depression portion in the example was larger than that in the comparative example.

The elastic modulus on the inner surface side of the depressed portion was measured based on the nanoindentation method. This measurement is performed using TriboIndenter manufactured by Hysitron, and after pushing the indenter to a certain depth at a temperature of 23 ° C., the slope at the maximum load in the load-displacement curve when unloaded, the projected area, It measured based on. This measurement was carried out with different indentation depths for each of the example and the comparative example.
As a result, as shown in FIG. 3, it was confirmed that the elastic modulus on the inner surface side of the depression portion in the example was larger than that in the comparative example.
As mentioned above, the hardness and the elastic modulus of the inner surface side of a hollow part based on a nanoindentation method are larger in the direction of an example than a comparative example, and the direction of an inner surface side of a hollow portion is a direction of an example than a comparative example. It was confirmed that the hardness of the

Next, the uneven | corrugated height of the inner surface of a hollow part was measured.
The measurement length was made the same for each of the example and the comparative example. The results are shown in FIG. 4 and FIG. In FIG. 4 and FIG. 5, the order of the unevenness height on the vertical axis is the same.
As a result, it was confirmed that the surface roughness of the inner surface of the recess was smaller in the example than in the comparative example. Moreover, in the comparative example, although glass fiber was able to be visually observed on the inner surface of the hollow part, it was not able to visually observe in the Example.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention.

For example, in the above embodiment, the stabilizer joint 1 is shown in which the ball joints 10 are separately connected to the both end portions 16 a of the support bar 16 via the housing 15, but the ball joint 10 alone does not have the support bar 16. Even if there is, the present invention is applicable. The ball joint 10 alone may be applied to, for example, a robot arm or the like.
In the above embodiment, the entire housing 15 is integrally formed of the same material. However, the present invention is not limited thereto. For example, the housing main body having a recess and the recess 14 may be provided in the recess. And a ball sheet made of a crystalline thermoplastic resin constituting an inner surface. In this configuration, the housing body contains reinforcing fibers, and the ball sheet may not contain reinforcing fibers.
In the above embodiment, as the assembling process, the insert molding in which the housing 15 is injection-molded using the ball portion 12 as an insert is described. However, the invention is not limited thereto. For example, after the housing 15 having the recess 14 is injection-molded, The ball stud 12 and the housing 15 may be combined with each other by bringing the outer peripheral surface of the ball portion 12 into close contact with the inner surface of the recessed portion 14 by press-fitting the ball portion 12 into the portion 14.

In addition, it is possible to replace the component in the above-mentioned embodiment with a well-known component suitably, in the range which does not deviate from the meaning of the present invention, and may combine the above-mentioned modification suitably.

The present invention can be applied to a method of manufacturing a ball joint, a method of manufacturing a stabilizer link, and a ball joint.

Reference Signs List 1 stabilizer link 2 stabilizer 3 suspension system 10 ball joint 11 shaft 12 ball 13 ball stud 14 hollow 15 housing 16 support bar 16a end of support bar S center point

Claims

A metal ball stud with the shaft and ball connected to each other;
And a housing made of a thermoplastic resin having a hollow portion in which the ball portion is rotatably inserted about its center point, and a method of manufacturing a ball joint,
Assembling the ball stud and the housing by bringing the outer peripheral surface of the ball portion into close contact with the inner surface of the recessed portion;
A heating step of heating the outer peripheral surface side of the ball portion and the inner surface side of the recessed portion by frictional heat by relative movement of the ball portion in the recessed portion to increase the degree of crystallization of the inner surface side of the recessed portion And a method of manufacturing a ball joint.
The method for manufacturing a ball joint according to claim 1, wherein in the heating step, the ball portion and the housing are relatively rotated around a center point of the ball portion.
The method for manufacturing a ball joint according to claim 1, wherein in the heating step, the ball portion and the housing are relatively rotated around the shaft portion and oscillated around a center point of the ball portion.
The method for manufacturing a ball joint according to any one of claims 1 to 3, wherein in the assembling step, the housing is injection-molded using the ball portion as an insert.
A ball joint comprising: a metal ball stud in which a shaft portion and a ball portion are connected to each other; and a housing made of a thermoplastic resin having a hollow portion in which the ball portion is rotatably inserted around its center point. A method of manufacturing a stabilizer link separately connected to both ends of a support bar via the housing,
The manufacturing method of the stabilizer link which forms the said ball joint by the manufacturing method of the ball joint of any one of Claim 1 to 4.
A metal ball stud with the shaft and ball connected to each other;
A housing made of thermoplastic resin having a hollow portion in which the ball portion is rotatably inserted around its center point, and a ball joint comprising:
The housing is formed in a bottomed cylindrical shape having a thickness of 2 mm or more, and the inside is a hollow portion.
The recess is formed in a spherical shape whose center point is located on the center axis of the housing,
A portion of the inner surface of the recess extending over a range of ± 20 ° centered on the center point of the recess, at least on a plane perpendicular to the central axis and passing through the center point of the recess, The point average roughness Rzjis (JIS B 0601: 2001) is set to 20 μm or less at a reference length of 0.8 mm,
A ball joint having a hardness of 110% or more of a hardness of a portion positioned at a depth of 1 mm from the inner surface of the recess in the housing.