DE112012001492T5 - Method for producing a ball joint - Google Patents

Abstract

A method of manufacturing a ball joint is provided, comprising: an assembly step (17) for assembling the ball joint (J) and a heating step (18) for subsequently heating the ball joint (J) to soften a bearing seat (4), in which Heating step (18) an induction heating coil (26, 31) is arranged such that it surrounds a housing (5) of the ball joint (J), wherein the housing (5) is heated by energizing the induction heating coil (26, 31), whereby the bearing seat (4) is heated and softened by the heat conduction from an inner peripheral surface of the housing (5) to the bearing seat (4). Therefore, it is possible to provide a method of manufacturing a ball joint, which makes it possible to perform a heating step within a relatively small space on an assembly line for a ball joint, which is free from restrictions on the material of the bearing seat made of a thermoplastic resin / resin, and which enables performance-efficient electric heating to be carried out.

Description

TECHNICAL AREA

The present invention relates to an improvement of a method for producing a ball joint comprising: a housing made of a tubular metal, a ball stud made of a metal, which comprises a ball part and a pin part protruding from the ball part, and a thermoplastic resin / Resin-made bearing seat which is fitted inside the housing, wherein it surrounds and holds the ball member, so that the pin member is capable of pivoting, the method comprising: a mounting step for mounting the ball joint while applying a pre-pressure on the bearing seat and a heating step of heating the ball joint after the assembling step to soften the bearing seat so that the bearing seat adapts to an outer circumferential surface of the ball member. A ball joint produced by this manufacturing method is mainly used in a suspension device or a steering device of a vehicle.

STATE OF THE ART

In such a method for manufacturing a ball joint, applying a blank to a bearing seat in a mounting step for mounting the ball joint includes, in particular, locating the bearing seat between a ball member and a housing having a fixed engagement clearance and allowing a ball pivot to pivot without rattling when the ball joint is operated under a heavy load, thereby ensuring the longevity of the ball joint. However, when the bearing seat is interposed between the ball member and the housing with a fixed engagement clearance, irregularities such as wrinkles accompanying deformation of an inner circumferential surface of the bearing seat in pressure contact with the ball member occur, resulting in the surface pressure of the bearing seat against the ball member becomes uneven between different parts and that the pivoting torque of the ball stud varies between different products, and that the life is further deteriorated because the bearing seat easily wears at a position where the surface pressure is large. In order to eliminate such problems, performing a heating step for heating the ball joint after the mounting step proves to be effective for softening the bearing seat so that the bearing seat adapts to an outer peripheral surface of the ball member.

Such a method for manufacturing a ball joint is already known as disclosed in the following Patent Documents 1 and 2, etc.

DOCUMENTS OF THE STATE OF THE ART

PATENT DOCUMENTS

• Patent Document 1: Japanese Patent Laid-Open Publication No. 2003-130038
• Patent Document 2: Japanese Patent Laid-Open Publication No. 2008-2601

CONTENT OF THE INVENTION

TASKS TO BE SOLVED BY THE INVENTION

In the method of manufacturing a ball joint disclosed in Patent Document 1, in a heating step, a ball joint is inserted and heated in a high temperature chamber. Such a heating method requires a large high-temperature chamber, and much space is required to arrange the large high-temperature chamber on an assembly line for a ball joint. Moreover, when a high-temperature chamber can not be disposed on an assembly line for a ball joint, it is necessary to arrange the high-temperature chamber at a location different from the assembly line for a ball joint, however, requiring a ball joint between the assembly line and the high-temperature chamber are separated, to transport back and forth, whereby the production efficiency deteriorates. In addition, high electric power is required to maintain a high-temperature state in the high-temperature chamber, and moreover, temperature control is difficult.

On the other hand, in the method for producing a ball joint disclosed in Patent Document 2, in a heating step, electric current is conducted via a ball stud and a housing to a bearing seat made of a conductive resin / synthetic resin having a higher electrical resistance than the ball stud and the housing, and the bearing seat is heated in this way by Joulescher heat. Although temperature control of the bearing seat is relatively easy, since the ball stud and the housing are held by means of a terminal for introducing an electric current during heating, the held part may be damaged in such a heating method, thereby deteriorating the product quality. Moreover, when the heating method is used, there are restrictions on the material of the bearing seat because the bearing seat must be conductive.

The present invention has been accomplished in view of such circumstances and its object is to provide a method of manufacturing a ball joint which allows to carry out a heating step within a relatively small space on an assembly line for a ball joint, for which there are no limitations as to the ball joint Material of a thermoplastic resin / resin formed bearing seat exist and which allows the performance of a power-efficient electric heating.

MEANS TO SOLVE THE TASKS

In order to achieve the foregoing object, according to a first aspect of the present invention, there is provided a method of manufacturing a ball joint comprising: a housing made of a tubular metal, a ball stud made of a metal having a ball part and a ball part projecting from the ball part Spigot part, and a bearing seat made of a thermoplastic resin / resin, which is fitted inside the housing while surrounding and holding the ball part so that the spigot part is capable of pivoting, the method comprising: a mounting step for mounting of the ball joint while a pre-pressure is being transmitted to the bearing seat, and a heating step of heating the ball joint after the mounting step to soften the bearing seat so that the bearing seat adapts to an outer peripheral surface of the ball member, characterized in that the heating step comprises: disposing Induktio Heating coil such that it surrounds the housing of the ball joint, heating the housing by energizing the induction heating coil and thereby heating and softening of the bearing seat by the heat conduction from an inner peripheral surface of the housing to the bearing seat.

Moreover, according to a second aspect of the present invention, there is provided a method of manufacturing a ball joint comprising: a housing made of a tubular metal, a ball stud made of a metal including a ball part and a pin part protruding from the ball part, and a ball joint thermoplastic resin-made bearing seat which is fitted inside the housing while surrounding and holding the ball member so that the pin member is capable of pivoting, the method comprising: a mounting step for mounting the ball joint while a Form is transferred to the bearing seat, and a heating step for heating the ball joint after the mounting step to soften the bearing seat, so that the bearing seat to an outer peripheral surface of the ball part adapts, characterized in that the heating step comprises: arranging an induction heating such, d it surrounds the pin member, heating the ball stud by energizing the induction heating coil and thereby heating and softening of the bearing seat by the heat conduction from the outer peripheral surface of the ball member to the bearing seat.

Moreover, according to a third aspect of the present invention, there is provided a method of manufacturing a ball joint comprising: a housing made of a tubular metal, a ball stud made of a metal including a ball part and a pin part projecting from the ball part, and a ball joint thermoplastic resin-made bearing seat which is fitted inside the housing while surrounding and holding the ball member so that the pin member is capable of pivoting, the method comprising: a mounting step for mounting the ball joint while a Form is transferred to the bearing seat, and a heating step for heating the ball joint after the mounting step to soften the bearing seat, so that the bearing seat to an outer peripheral surface of the ball part adapts, characterized in that the heating step comprises: arranging an induction heating such, d As it surrounds the housing and the ball stud, heating the housing and the ball stud by energizing the induction heating coil and thereby heating and softening the bearing seat by the heat conduction from an inner peripheral surface of the housing to the bearing seat and the heat conduction from the outer peripheral surface of the ball portion of the ball stud to the bearing seat ,

Moreover, according to a fourth aspect of the present invention, in addition to the third aspect, in the heating step, a first induction heating coil surrounding the case and a second induction heating coil surrounding the ball pivot are arranged side by side, and the case and the ball pivot are individually energized by energizing these two induction heating coils heated.

The method further comprises, in addition to one of the first to third aspects after the heating step, a heat penetration step to allow the ball joint to stand for a fixed period of time to transfer residual heat from the housing or the ball stud to the bearing seat, according to a fifth aspect of the present invention and to compensate for the temperature distribution of the bearing seat, and after the heat penetration step, a cooling step for cooling the ball joint.

Moreover, according to a sixth aspect of the present invention, in addition to any of the first to fourth aspects in the heating step a high frequency is used as the heating frequency for the induction heating coil.

Moreover, according to a seventh aspect of the present invention, in addition to any of the first to fourth aspects in the heating step, a low frequency is used as the heating frequency for the induction heating coil.

EFFECTS OF THE INVENTION

According to the first aspect of the present invention, since, in the heating step, the housing is induction heated by the induction heating coil and the bearing seat is heated by the heat conduction from the inner peripheral surface of the housing to the bearing seat, it is possible to efficiently heat the entire bearing seat from the housing and soften, whereby the inner peripheral surface of the bearing seat is caused to conform to the outer peripheral surface of the ball member and to compensate for the residual stress of the bearing seat in its entirety. Moreover, power consumption can be lowered as compared with a case where a high-temperature chamber is used, and since an induction heater equipment has a relatively small size, it can be disposed at an assembly line or at one of these adjacent positions, thereby improving manufacturing efficiency.

In addition, since the bearing seat is heated by the heat conduction from the housing to the bearing seat, heating of the bearing seat regardless of its material is possible.

Moreover, temperature control of the bearing seat can be easily performed by adjusting the output exciting current to the induction heating coil or the energization time period. Moreover, there is no possibility of damaging the ball joint in the heating step because the induction heating coil is used without being in contact with the ball joint.

According to the second aspect of the present invention, since in the heating step, the pin member is induction-heated by the induction heating coil, and the bearing seat is heated by the heat conduction from the pin member to the ball member and the heat conduction from the outer peripheral surface of the ball member to the bearing seat to efficiently heat and soften the inner peripheral surface of the bearing seat via the pin member, thereby enabling a softening of the inner peripheral surface of the bearing seat to be effected by a relatively small electric power and to be quickly adapted to the ball member. In addition, the same effects as those of the first aspect can be obtained.

According to the third aspect of the present invention, since in the heating step, the housing and the ball stud are simultaneously heated by the induction heating coil, the bearing seat is heated from its outer peripheral surface and inner peripheral surface by means of the housing and the ball member, thereby enabling heating and soaking the entire bearing seat takes place in a short time and an adaptation of the bearing seat to the ball part is done quickly, whereby the manufacturing efficiency can be improved. In addition, the same effects as those of the first aspect are achieved.

According to the fourth aspect of the present invention, in the heating step, since the housing and the ball stud are individually heated by the first and second induction heating coils, it is possible to efficiently heat and soften the entire bearing seat in a short time by controlling the heating conditions for the first and second induction heating coils the second induction heating coil according to the heat capacity, etc. of the housing and the ball stud are selected, and it is possible that an adjustment of the bearing seat to the outer peripheral surface of the ball member and a balance of the residual stress of the bearing seat done quickly.

According to the fifth aspect of the present invention, in the heat penetration step, the residual heat of the housing can be effectively used for heating the bearing seat, whereby the energization time for the induction heating coil can be shortened in the heating step, thereby minimizing the power consumption and, moreover, the temperature distribution of the bearing seat which causes the entire inner peripheral surface of the bearing seat to reliably conform to the outer peripheral surface of the ball member, and balancing the residual stress of the bearing seat, thereby stabilizing the pivotal torque of the ball stud and thereby making it possible to provide high ball joint performance. Moreover, in the subsequent cooling step, cooling of the ball joint allows the normal hardness of the bearing seat within the ball joint to be restored.

BRIEF DESCRIPTION OF THE DRAWINGS

1 FIG. 12 is a vertical sectional view of a ball joint which is a manufacturing objective in a first embodiment of the present invention (first embodiment). FIG.

2 is an exploded view of an important part of the ball joint (first embodiment).

3 FIG. 13 is an illustration for explaining a manufacturing step for the ball joint (first embodiment). FIG.

4 FIG. 14 is an illustration for explaining a heating step for the ball joint (first embodiment). FIG.

5 Fig. 13 is a diagram for explaining a heating step for a ball joint in a second embodiment of the present invention (second embodiment).

6 Fig. 13 is a diagram for explaining a heating step for a ball joint in a third embodiment of the present invention (third embodiment).

7 FIG. 14 is a diagram for explaining a heating step for a ball joint in a fourth embodiment of the present invention (fourth embodiment). FIG.

8th FIG. 12 is a diagram for explaining a heating step for a ball joint in a fifth embodiment of the present invention (fifth embodiment). FIG.

LIST OF REFERENCE NUMBERS

J

ball joint

1

ball pin

2

spherical part

3

journal part

4

bearing seat

5

casing

17

assembly step

18

heating step

19

Wärmedurchdringungsschritt

20

cooling step

26

Induction heating coil, first induction heating coil

29

Induction heating coil, second induction heating coil

31

induction heating

EMBODIMENTS OF THE INVENTION

Embodiments of the present invention will be explained below with reference to the accompanying drawings.

FIRST EMBODIMENT

One in the 1 to 4 First embodiment of the present invention will now be explained.

First, the structure of a ball joint manufactured by a manufacturing method of the first embodiment of the present invention will be described by reference to FIGS 1 and 2 explained. A ball joint J comprises as main components a ball pin formed of metal 1 , which consists of a ball part 2 and one provided with a male thread, integral with the ball part 2 formed and to one side of this projecting pin part 3 is formed, formed of a thermoplastic resin / resin bearing seat 4 , which the ball part 2 surrounds and holds, leaving the pin part 3 is pivotable, and a cylindrical housing 5 which is the bearing seat 4 and the ball part 2 absorbs and a tightening force on the bearing seat 4 exercises. The housing 5 is made of a cylindrical housing body 6 and from a flat plate-shaped plug 7 educated.

The housing body 6 is at one end with a pin opening 10 in which the pin part 3 is arranged, and at the other end with a stepped Einpassöffnung 11 provided. An inner peripheral surface of an intermediate part serves as a support surface 12 for the bearing seat 4 , which from the fitting opening 11 is introduced.

Regarding the carrying surface 12 forms half at the side of the fitting opening 11 a cylinder and half at the side of the pin opening 10 forms a ball whose diameter is in the direction of the pin part 3 decreases, where the ball part 2 surrounding and holding this bearing seat 4 into the support surface of the fitting opening 11 is pressed with a predetermined engagement game.

After the bearing seat 4 in the support surface 12 is pressed to the fitting hole 11 to block the plug 7 in the fitting opening 11 fitted, while a flat end face 4a of the bearing seat 4 is pressed with a predetermined engagement clearance, and it is through a step portion 11a and a die section 6a of the housing body 6 held and fixed. An inner circumferential surface of the bearing seat 4 is coated in advance with grease (not shown). This is the bearing seat 4 between the housing and the ball part 2 arranged in a state in which a form is transferred to this.

A carrying arm 8th is on the case 5 mounted by interference fit or by welding and between the housing 5 and the pin part 3 is a flexible sleeve 9 customized.

In the illustrated case, the material of each part of the ball joint J is as follows:
housing body 6 S45C
plug 7 SPC
ball pin 1 SCM435
bearing seat 4 POM

The method of manufacturing the ball joint J will be described below.

As in 3 In the manufacture of the ball joint J, a component insertion step is shown 16 , an assembly step 17 , a heating step 18 , a heat penetration step 19 , a cooling step 20 , an additional component adaptation step 21 and a finished product taking step 22 consecutively on a continuous assembly line 15 executed.

First, in the component introduction step 16 Components of the ball joint J on a conveyor belt of the assembly line 15 brought and in the assembly step 17 the introduced components are mounted, whereby the ball joint J, as in 1 shown, with the exception of the support arm 8th and the sleeve 9 , is completed. In this assembly step 17 is, as described above, a form on the bearing seat 4 transfer.

At the assembly line 15 at which the subsequent heating step 18 is executed, is an adjacent conveyor belt induction heating equipment 23 provided. This induction heating equipment 23 is with an induction heating power supply 24 a plurality, in the illustrated example a pair, of the induction heating power supply 24 arranged Heizarbeitsplatten 25 and 25 and vertically above the heating worktops 25 and 25 moving induction heating coils 26 and 26 fitted. As in 4 shown is every heating countertop 25 with a workpiece positioning fixture 27 provided on which a Heizzielwerkstück, ie the ball joint J, is arranged.

In the heating step 18 become the ball joints J, which the assembly step 17 completed and which are transported one after the other by means of the conveyor belt, on the Werkstückpositionierungsmontiervorrichtungen 27 on the majority of heating worktops 25 and 25 arranged one after the other and the induction heating coils 26 and 26 are caused to descend successively.

In this case, as in 4 shown with respect to the ball joint J for each heating worksheet 25 the down-facing plug 7 on the workpiece positioning fixture 27 arranged and the induction heating coil 26 is caused to be from above the pin part 3 to lower to a fixed position, which the housing 5 in a state in which there is no contact surrounds. In this state, the induction heating power supply becomes 24 operated to the induction heating coil 26 to excite, creating the appropriate housing 5 is heated by induction. If the case 5 is heated, heat from an inner peripheral surface of the housing 5 directed to the bearing seat, the entire bearing seat 4 is heated and softened, wherein a plastic deformation can take place, so that an outer peripheral surface of the bearing seat 4 to the inner peripheral surface of the housing 5 Adjusts and an inner peripheral surface of the bearing seat 4 to an outer peripheral surface of the ball part 2 adapt; at the same time, the residual stress of the bearing seat 4 be balanced, whereby a stabilization of the pivoting torque of the ball stud 1 is possible.

In this case, the heating frequency of the induction heating coil 26 a low frequency or a high frequency between 50 Hz and 100 kHz and the softening temperature of the bearing seat 4 is about 100 ° C.

Because in this way the case 5 by means of the induction heating coil 26 is heated by induction and the bearing seat 4 by the heat conduction from the inner peripheral surface of the housing to the bearing seat 4 is heated, the entire bearing seat can 4 from the case 5 be heated efficiently; Power consumption can therefore be reduced compared to the case where a high-temperature chamber is used, and because the induction heater equipment 23 a relatively small size, it can be on the assembly line 15 or at one of these adjacent positions, thereby improving manufacturing efficiency.

In addition, since the bearing seat 4 by the heat conduction from the housing 5 to the bearing seat 4 is heated, the bearing seat 4 be heated regardless of its material.

In addition, a temperature control / control of the bearing seat 4 simply by fitting it to the induction heating coil 26 output excitation current or energization time period. In addition, since the induction heating coil 26 is used without being in contact with the ball joint J, not the possibility of the ball joint J in the heating step 18 to damage.

In general, while the workpiece is being heated by induction, the current induced in a workpiece begins to concentrate on the surface of the workpiece as the heating frequency increases. In other words, the current penetration depth in the workpiece increases as the heating frequency decreases. Therefore, as the heating frequency for the induction heating coil 26 a low frequency used when the thickness of the case 5 is relatively large, and a high frequency is used when the thickness is relatively small, thereby making it possible to have one with the bearing seat 4 in contact Section of the housing 5 is heated efficiently and therefore the heat conduction from the housing 5 to the bearing seat 4 gently done.

After the induction heating coil 26 is pulled upward, the ball joint J has the heating step 18 completed and it becomes the conveyor belt of the assembly line 15 brought back and moves to the heat penetration step 19 , The heat penetration step 19 is provided to allow the ball joint J to remain on the conveyor belt for a fixed period of time; Residual heat of the housing 5 spreads through the bearing seat 4 out and the temperature distribution in the entire bearing seat 4 is compensated. In this way, an effective use of the residual heat of the housing allows 5 when heating the bearing seat 4 a reduction in the excitation period of the induction heating coil 26 in the heating step 18 , whereby the power consumption is minimized, and also allows the temperature distribution of the bearing seat 4 is compensated, thereby reliably causing the entire inner peripheral surface of the bearing seat 4 to the outer peripheral surface of the ball part 2 adapts, and thereby reliably the residual stress of the bearing seat 4 is compensated, whereby the pivoting torque of the ball stud 1 is stabilized and contributes to the production of a ball joint J with a high performance.

The ball joint J, which is the heat penetration step 19 has completed, proceeds to the subsequent cooling step 20 Ahead. In this cooling step 20 For example, the ball joint J on the conveyor belt is forcibly air cooled to substantially room temperature by means of a cooling fan installed above the conveyor belt. Due to this forced air cooling can return the bearing seat 4 be promoted within the ball joint J to normal hardness, whereby the production time for the ball joint J is reduced.

Then it proceeds to the additional component adaptation step 21 ahead and the support arm 8th and the sleeve 9 are attached to the ball joint J on the conveyor belt, thereby producing a finished ball joint J product.

Then it proceeds to the finished product taking step 22 and the finished ball joint J product is removed from the conveyor belt.

SECOND EMBODIMENT

An in 5 The second embodiment of the present invention shown will now be explained.

In the second embodiment, in a heating step 18 an induction heating coil 29 around a pin part 3 a ball joint J arranged and the pin part 3 is thereby heated by induction, which is the only difference to the first embodiment. According to the second embodiment, in the pin part 3 Heat generated immediately to a ball part 2 and then from an outer peripheral surface thereof to a bearing seat 4 transferred, causing the bearing seat 4 is heated. If in this case a low frequency than the heating frequency of the induction heating coil 29 is used, the current penetration depth is large, with a deep inner part of the pin part 3 can be effectively heated and the heat from the deep inner part of the pin part 3 to the ball part 2 and then to an inner peripheral surface of the bearing seat 4 can be transmitted efficiently. Because the release of heat from an outer peripheral surface of the pin part 3 is low, the bearing seat can 4 to be heated to the softening temperature with a relatively low electric power. As the inner peripheral surface of the bearing seat 4 from the ball part 2 is heated, in particular a softening of the inner peripheral surface can be promoted, whereby an adaptation to the ball part 2 can be done quickly.

In addition, when a high frequency is focused as the heating frequency of the induction heating coil 29 is used, the induction current due to the skin effect on the outer peripheral surface of the pin member 3 and the area near the outer peripheral surface is effectively heated with heat quickly from the area near the outer peripheral surface of the pin part 3 to the area near the outer peripheral surface of the ball part 2 and then to the camp seat 4 can be transported and in an environment in which the release of heat from the pin part 3 is low, causing the bearing seat 4 can be heated to the softening temperature with a low electric power.

The arrangement otherwise corresponds to that of the first embodiment; Parts in 5 which correspond to those of the first embodiment are denoted by the same reference numerals, and a repetition of the explanation is therefore omitted.

THIRD EMBODIMENT

An in 6 The third embodiment of the present invention shown will now be explained.

In this third embodiment, a heating step comprises 18 in combination the heating step 18 the first embodiment and the heating step 18 the second embodiment, wherein a housing 5 and a pin part 3 simultaneously from a first induction heating 26 or a second induction heating coil 29 be heated. According to the third embodiment, since a bearing seat 4 from its outer peripheral surface and inner peripheral surface by means of the housing 5 and a ball part 2 is heated, the entire bearing seat 4 be heated and softened in a short time and an adjustment of the bearing seat 4 to the ball part 2 and compensation of a residual stress of the bearing seat can be done quickly, thereby improving the manufacturing efficiency.

In addition, it is possible because the case 5 and a ball stud 1 individually by means of the first and the second induction heating coil 26 and 29 be heated, a highly efficient heat conduction to the bearing seat 4 obtained by the heating conditions for the first and the second induction heating coil 26 and 29 according to the heat capacity, etc. of the housing 5 and the ball stud 1 to be selected.

FOURTH EMBODIMENT

An in 7 A fourth embodiment of the present invention will now be explained.

In the fourth embodiment, the structure of a ball joint J as a production target is different from each of the above embodiments. That is, in the ball joint J of the fourth embodiment, a tubular housing 5 which is both a ball part 2 as well as a ball stud 1 and a camp seat 4 absorbs and a tightening force on the bearing seat 4 has a bottomed cylindrical shape with an end face as a pin opening 10 is open and being a connecting bolt 13 integral with an outer end surface of a bottom portion 5b of the housing 5 is formed. In addition, the bottom section 5b of the housing 5 formed such that it has a thickness which is greater than the thickness of a cylindrical portion 5a of the housing 5 is, thereby increasing the connection strength between the bottom section 5b and the connecting bolt 13 is increased. On the other hand, a pin part 3 of the ball stud 1 formed as a long rod and a neck portion 3b of the pin part 3 , which with the ball part 2 is connected, has a smaller diameter than those of the previous embodiments.

In a heating step 18 The fourth embodiment becomes the connecting bolt 13 of the ball joint J in a mounting hole 28a a workpiece positioning mounting device 28 on a heating worktop 25 fitted in and the bottom section 5b of the housing 5 is held such that it comes from the workpiece positioning mounting device 28 is isolated. At the side of the case 5 is a first induction heating coil 26 around a portion of a base part of the connecting bolt 13 to the bottom section 5b of the housing 5 arranged and on the side of the ball stud 1 is a second induction heating coil 29 around a section of a main section 3a near the neck section 3b of the pin part 3 to the neck section 3b arranged. The second induction heating coil 29 is from a large diameter section 29a which is the main section 3a of the pin part 3 surrounds, and a small diameter section 29b , which has a smaller diameter than the large diameter section 29a and the neck section 3b surrounds, formed. A gap between the small diameter section 29b and the neck section 3b is set to be narrower than a gap between the large-diameter portion 29a and the main section 3a is.

When the first and the second induction heating coil 26 and 29 be energized simultaneously by an induction heating power supply 24 is operated, the bottom section 5b on the side of the case 5 , which has a particularly large thickness, through the first induction heating coil 26 heated to heat conduction from the bottom section 5b which has a large thickness and a large heat capacity, to the cylindrical portion 5a , which has a small thickness and a low heat capacity to effect and the entire housing 5 is heated at the same time without local overheating. Therefore, regardless of the thickness difference between the bottom portion 5b and the cylindrical section 5a of the housing 5 the bearing seat 4 efficient by the heat conduction from the entire inner peripheral surface of the housing 5 be heated.

On the other hand, the portion on the side of the ball stud 1 from the main section 3a to the neck section 3b of the pin part 3 by means of the second induction heating coil 29 heated, but, in particular, the gap between the neck section 3b and the second induction heating coil 29 is tight, the neck section 3b effectively heated, with the heat conduction from the neck portion 3b to the ball part 2 and moreover, from an outer peripheral surface of the ball member 2 to the bearing seat 4 takes place efficiently, reducing the bearing seat 4 efficiently heated and softened. In this process, it is possible because the main section 3a of the pin part 3 adequately through the second induction heating coil 29 is heated, the escape of heat from the neck section 3b to the main section 3a minimize heat conduction from the neck portion 3b to the ball part 2 and eventually to the bearing seat 4 is encouraged. In addition, since the bearing seat 4 is heated via its outer peripheral surface and inner peripheral surface as in the third embodiment, the entire bearing seat 4 be heated and softened in a short time and an adjustment of the bearing seat 4 to the ball part 2 and a compensation of a residual stress of the bearing seat 4 can be done quickly, thereby improving manufacturing efficiency.

FIFTH EMBODIMENT

An in 8th A fifth embodiment of the present invention will now be explained.

A ball joint J as a manufacturing target in the fifth embodiment has the same structure as that of the ball joint J of the first embodiment except that a support arm 8th integral with a side surface of a housing 5 is formed; in 8th For example, parts corresponding to those of the first embodiment are given the same reference numerals, and a repetition of the explanation will therefore be omitted.

In a heating step 18 in the fifth embodiment, the support arm 8th in a raised state by means of a carrying hole 30a a workpiece positioning mounting device 30 at a heating work platform 25 held, wherein an induction heating coil 31 is arranged to the entire ball joint J as well as a base part of the support arm 8th to surround, and the only induction heating coil 31 is energized, causing the support arm 8th , the case 5 and the ball part 3 be heated at the same time.

According to the fifth embodiment, the housing 5 and the pin part 3 efficient by means of the single induction heating coil 31 be heated while the escape of heat to the high heat capacity carrying arm 8th is minimized. Therefore, an entire bearing seat can be heated and softened in a short time, while a small size for the induction heater equipment is achieved as in the third embodiment, with an adjustment of the bearing seat 4 to a ball part 2 can be done quickly, whereby the production efficiency is improved.

Preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments and can be changed in various ways as long as the changes do not depart from the spirit and scope thereof. For example, in the cooling step 20 an air conditioning low temperature chamber on the assembly line 15 can be arranged and the ball joint J can be cooled within the chamber.

Claims (7)

A method of manufacturing a ball joint (J), comprising: a housing formed of a tubular metal (Fig. 5 ), a ball stud formed from metal ( 1 ), which a ball part ( 2 ) and one of the ball part ( 2 ) projecting pin part ( 3 ), and a bearing seat formed of a thermoplastic resin ( 4 ), which within the housing ( 5 ) while fitting the ball part ( 2 ) and this holds, so that the pin part ( 3 ) is capable of pivoting, the method comprising: an assembly step ( 17 ) for mounting the ball joint (J), while a pre-pressure on the bearing seat ( 4 ), and a heating step ( 18 ) for heating the ball joint (J) after the assembly step ( 17 ) to the bearing seat ( 4 ) soften so that the bearing seat ( 4 ) to an outer peripheral surface of the ball part ( 2 ), characterized in that the heating step ( 18 ) comprises: arranging an induction heating coil ( 26 . 31 ) such that the housing ( 5 ) of the ball joint (J) surrounds, heating the housing ( 5 ) by exciting the induction heating coil ( 26 . 31 ) and thereby heating and softening of the bearing seat ( 4 ) by the heat conduction from an inner peripheral surface of the housing ( 5 ) to the bearing seat ( 4 ). A method of manufacturing a ball joint (J), comprising: a housing formed of a tubular metal (Fig. 5 ), a ball stud formed from metal ( 1 ), which a ball part ( 2 ) and one of the ball part ( 2 ) projecting pin part ( 3 ), and one of a thermoplastic Resin / synthetic resin formed bearing seat ( 4 ), which within the housing ( 5 ) while fitting the ball part ( 2 ) and this holds, so that the pin part ( 3 ) is capable of pivoting, the method comprising: an assembly step ( 17 ) for mounting the ball joint (J), while a pre-pressure on the bearing seat ( 4 ), and a heating step ( 18 ) for heating the ball joint (J) after the assembly step ( 17 ) to the bearing seat ( 4 ) soften so that the bearing seat ( 4 ) to an outer peripheral surface of the ball part ( 2 ), characterized in that the heating step ( 18 ) comprises: arranging an induction heating coil ( 29 . 31 ) in such a way that the pin part ( 3 ), heating the ball stud ( 1 ) by exciting the induction heating coil ( 29 . 31 ) and thereby heating and softening of the bearing seat ( 4 ) by the heat conduction from the outer peripheral surface of the ball part ( 2 ) to the bearing seat ( 4 ). A method of manufacturing a ball joint (J), comprising: a housing formed of a tubular metal (Fig. 5 ), a ball stud formed from metal ( 1 ), which a ball part ( 2 ) and one of the ball part ( 2 ) projecting pin part ( 3 ), and a bearing seat formed of a thermoplastic resin ( 4 ), which within the housing ( 5 ) while fitting the ball part ( 2 ) and this holds, so that the pin part ( 3 ) is capable of pivoting, the method comprising: an assembly step ( 17 ) for mounting the ball joint (J), while a pre-pressure on the bearing seat ( 4 ), and a heating step ( 18 ) for heating the ball joint (J) after the assembly step ( 17 ) to the bearing seat ( 4 ) soften so that the bearing seat ( 4 ) to an outer peripheral surface of the ball part ( 2 ), characterized in that the heating step ( 18 ) comprises: arranging an induction heating coil ( 26 . 29 . 31 ) such that the housing ( 5 ) and the ball stud ( 1 ), heating the housing ( 5 ) and the ball stud ( 1 ) by exciting the induction heating coil ( 26 . 29 . 31 ) and thereby heating and softening of the bearing seat ( 4 ) by the heat conduction from an inner peripheral surface of the housing ( 5 ) to the bearing seat ( 4 ) and the heat conduction from the outer peripheral surface of the ball part ( 2 ) of the ball stud ( 1 ) to the bearing seat ( 4 ). A method of manufacturing a ball and socket joint according to claim 3, wherein in said heating step ( 18 ) a first, the housing ( 5 ) surrounding induction heating coil ( 26 ) and a second, the ball stud ( 1 ) surrounding induction heating coil ( 29 ) Are arranged side by side and wherein the housing ( 5 ) and the ball stud ( 1 ) individually by energizing these two induction heating coils ( 26 . 29 ) are heated. A method for producing a ball joint according to any one of claims 1 to 3, further comprising after the heating step ( 18 ) a heat penetration step ( 19 ) to allow the ball joint (J) to stand for a fixed period of time to 5 ) or the ball stud ( 1 ) to the bearing seat ( 4 ) and the temperature distribution of the bearing seat ( 4 ) and after the heat penetration step ( 19 ) a cooling step ( 20 ) for cooling the ball joint (J). A method of manufacturing a ball and socket joint according to any one of claims 1 to 4, wherein in the heating step ( 18 ) a high frequency as the heating frequency for the induction heating coil ( 26 . 29 . 31 ) is used. A method of manufacturing a ball and socket joint according to any one of claims 1 to 4, wherein in the heating step ( 18 ) a low frequency as heating frequency for the induction heating coil ( 26 . 29 . 31 ) is used.

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