JPH0115566B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of induction hardening the inner circumferential surface of a housing 7 of a ball joint 2 as shown in FIG. 1 used in an automobile suspension system, etc. The depth of the hardened layer by quenching is made uniform over the entire quenching range, including not only the conical inner surface 12 and the conical inner surface 11 connected thereto, but especially the connecting corner 13 of both inner circumferential surfaces thereof, and eliminates variations in each quench. Concerning stabilization.

It has been known to perform induction hardening on the housing 7 of the ball joint 2 in order to improve the wear resistance of the inner peripheral surface and to improve the strength of the opening periphery 9, which has been made thinner for attaching the dust cover 3. ing. Conventional housing induction hardening has been carried out using a hardening coil 30a as an inductor, which is formed by spirally winding a hollow copper pipe with a circular cross section to match the shape of the target inner peripheral surface, as shown in FIG.

According to this method, the cylindrical inner surface 12 faces the outer periphery of the ball stud head 6 in the vicinity of the equator, and the inner diameter extends toward the opening 8 which is connected above the cylindrical inner surface 12 and is prepared so that the shaft portion 5 of the ball stud protrudes. A housing 7 having a conical inner surface 11 in which the converging
, the cylindrical inner surface 12 and the conical inner surface 1
There is a problem that the depth of the hardened layer 14a at the connection corner 13 with 1 is shallower than at other parts.

Therefore, in a stud pull-out fracture strength test of the peripheral edge 9 of the shaft protruding opening of the housing as shown in FIG.
5 occurs and breaks, but there is a problem that the breaking strength in the test is low.

Therefore, in order to make the depth of the hardened layer 14a uniform, the hardened coil 30a is placed as much as possible at the connecting corner 1.
It was necessary to carry out quenching in close proximity to No. 3.
However, by placing the hardened coil 30a close to each other, the hardened coil 30a often comes into contact with the housing 7, resulting in deformation and breakage of the coil 30a. Therefore, the depth of the hardened layer 14a of the housing was not stable, and the breaking strength of the housing opening periphery 9 also varied.

Therefore, an object of the present invention is to provide a method for induction hardening a ball joint housing that solves the above-mentioned problems.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 shows an embodiment of the present invention, and symbols in the figure that correspond to those in FIG. 2 are indicated using the same numerals.

Reference numeral 41 denotes a rotary table which is rotatably driven by a drive device (not shown) to rotate the housing 7 about the housing axis. Reference numeral 40 denotes a positioning jig for mounting the housing 7 at a predetermined position on the rotary table 41, and is fixed to the rotary table 41 so that its axis coincides with the rotation axis of the rotary table 41.

Therefore, when the housing 7 is attached to the outer periphery of the positioning jig 40, the rotational axis of the rotary table 41 and the housing axis coincide, and the housing 7 can rotate around its own axis without wobbling. Further, 42 and 43 are holes formed in the axis portions of the rotary table 41 and the positioning jig 40.
1 and 32 are arranged through the hole.

The lower ends of the leg pieces 31, 32 are connected to a high frequency power supply section through electrodes (not shown).
The upper ends of the coils 2 are connected to both ends of the hardening coil 30, respectively.

The hardened coil 30 as an inductor substantially supported by the leg pieces 31 and 32 is made of a hollow copper pipe with a rectangular cross section to a diameter somewhat smaller than the diameter of the cylindrical inner surface 12 of the housing, and the inner periphery of the housing is approximately 2. It is wound in a step-like manner without spiraling around the circumference.

In forming such a hardened coil 30, the raw copper pipe is twisted so that the vicinity of the corner where the upper end surface of the coil intersects with the outer circumferential surface, that is, the outer circumferential portion 33 of the upper edge of the coil, is close to the connecting corner 13. The outer surface faces the cylindrical inner surface 12 in a substantially parallel manner, and the helical angle of the coil is not uniform over the entire circumference as in conventional coils, but is shaped like a step in an extremely narrow range on the circumference. A coil is formed in a step-like manner in a non-helical manner without providing a helical angle on the remaining circumference.

In addition, if the hardened coil 30 has at least the uppermost winding and the transition portion 34 connected thereto in a non-helical and step-like shape, the outer peripheral portion 33 of the upper edge of the coil
and the connecting corner 13 on the inner periphery of the housing can be properly brought close to each other.

Note that even when a polygonal cross-sectional material other than a rectangular cross section is used for the coil, it is formed in the same manner as the above-described coil, with the cylindrical inner surface 12 and the outer circumferential surface of the material facing approximately parallel to each other.

Further, the relative position of the hardening coil 30 with respect to the rotary table 41 is determined in advance so that the rotating housing 7 and the coil 30 do not come into contact with each other during housing hardening. That is, the axis of the coil 30 is aligned with the rotation axis of the rotary table 41, and the height of the coil 30 from the top surface of the rotary table 41 is determined by adjusting the length of the legs 31, 32 or the size and shape of the positioning jig 40. The coil is adjusted so that the upper edge outer peripheral portion 33 of the coil is close to the housing connection corner 13.

Therefore, when the housing 7 is attached to the outer periphery of the positioning jig 40, the axes of the hardened coil 30 and the housing 7 are aligned, and the outer circumferential portion 33 of the upper edge of the coil 30 has no helical angle in the uppermost winding. Therefore, it is exactly close to the connecting corner 13 of the housing 7. The hollow portions of the hardened coil 30 and the leg pieces 31, 32 are communicated with each other, so that the coolant can flow therein. Although not shown, a conduit for injecting coolant onto the heating surface opens toward the housing 7.

The housing 7, as also shown in FIG.
An opening 8 through which the shaft portion 5 of the ball stud 4 is movably protruded from the upper part, and an opening that substantially forms the opening 8 and provides an outer periphery for attaching the dust cover into which the fitting end 10 of the dust cover 3 is press-fitted. It has a peripheral edge part 9 and a crimped end part 23 for fixing the closing plate 22 at the lower part.

The housing 7 has an inner peripheral surface that accommodates an upper bearing 20 and a lower bearing 21 surrounding the spherical head 6 of the ball stud.
In particular, the conical inner surface 1 converges towards the opening 8.
1 is effective in preventing cold flow from occurring in the thin upper bearing 20 due to the load applied during use of the ball joint.

In the above configuration, when induction hardening the housing, the housing 7 is fitted into the positioning jig 40, the rotary table 41 is driven to rotate, and at the same time, a high frequency current is applied to the hardening coil 30. After that, when quenching is performed by squirting a coolant onto the heated inner peripheral surface of the housing, the hardened layer 1
4 is formed to have a substantially uniform depth as a whole, although it is slightly shallower near the connecting corner 13, as shown in FIG.

As described above, the present invention provides a method for simultaneously induction hardening the cylindrical inner surface and the conical inner surface of a ball joint housing, in which a hollow wire with a polygonal cross section is shaped in a non-helical manner to a diameter smaller than the inner diameter of the cylindrical inner surface of the housing. The inner surface of the housing is heated by high-frequency induction with the outer periphery of the upper edge of the quenched coil as an inductor wound into a shape close to the connecting joint between the cylindrical surface and the conical surface on the inner periphery of the housing. Therefore, since the uppermost winding of the coil has no helical angle and the cross section of the coil is square, the outer periphery of the upper edge of the coil can be easily and precisely brought close to the connection corner of the housing, and it is not necessary to force it as in the conventional case. Since it is not necessary to place the hardened coil close to the housing connection corner, the coil is not deformed or destroyed, and as a result, a stable hardened layer depth is always obtained. Moreover, the depth of the hardened layer at the connection corner is approximately equal to that at other portions, and the stud pull-out fracture strength at the periphery of the housing opening is also stably improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional front view of a ball joint for an automobile suspension system. FIG. 2 is an explanatory cross-sectional front view of main parts showing a conventional housing induction hardening method. FIG. 3 is an explanatory diagram of the housing strength test. FIG. 4 is an explanatory cross-sectional front view of essential parts showing an embodiment of the housing induction hardening method according to the present invention. Explanation of symbols, 2...Ball joint, 4...
Ball stud, 5...Ball stud shaft, 6
... Ball stud spherical head, 7 ... Ball joint housing, 8 ... Opening, 9 ... Opening periphery, 11 ... Conical inner surface, 12 ... Cylindrical inner surface,
13... Connection corner, 14... Hardened layer, 30... Quenched coil, 33... Upper edge outer periphery.

Claims (1)

[Claims] 1 Cylindrical inner surface 1 facing the outer periphery near the equator of the ball stud spherical head 6 of the ball joint 2
2, and a ball stud shaft portion 5 connected above it.
In a method of simultaneously induction hardening the cylindrical inner surface 12 and the conical inner surface 11 of a ball joint housing 7, which has a conical inner surface 11 whose inner diameter converges toward an opening 8 prepared to protrude, the cross-sectional A hardened coil 30 as an inductor, which is made by winding a polygonal hollow wire in a non-helical manner in a stepped manner to a diameter smaller than the inner diameter of the cylindrical inner surface 12 of the housing, is attached so that the outer circumference 33 of the upper end edge of the coil 30 is wound around the inner circumference of the housing 7. A method of induction hardening for a ball joint housing, characterized in that the inner surfaces 11 and 12 of the housing are subjected to high frequency induction heating in a state in which the inner surfaces 11 and 12 of the housing are brought close to the connecting corner 13 between the cylindrical inner surface 12 and the conical inner surface 11.