JPH0226931Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial field of application] The rack shaft of a rack and pinion type steering device for automobiles, etc. has its teeth and back surface to improve wear resistance and strength. Induction hardening is performed on the steel. The present invention relates to a rack shaft induction hardening apparatus suitable for such induction hardening.

[Conventional technology]

As shown in FIG. 1, such an induction hardening device includes an induction electrode 2 disposed close to the rack shaft 1, and a pair of induction electrodes disposed at both ends of the induction electrode and in contact with the rack shaft 1. A device having current-carrying electrodes 3 and 4 is known. The induction electrode 2 is connected to the easy shaft 1 by a high frequency current supplied from a high frequency power source 8.
At the same time, a high frequency current is passed directly to the rack shaft by the current-carrying electrodes 3 and 4, and the rack shaft is heated by both currents. The induction electrode 2 also serves as a cooling water injection device, and after heating the rack shaft for a predetermined period of time, cooling water is jetted from there to harden the rack shaft. As shown in FIG. 2, the current-carrying electrodes 3 and 4 have a contact surface with the rack shaft 1 formed into a circular arc surface 5 or the like in accordance with the shape of the contact portion of the rack shaft.

[Problems with conventional technology]

When the high-frequency current is supplied from the high-frequency power source 8 to heat the rear surface 6 of the rack shaft 1 in the state shown in FIG. 1, the rear surface rapidly heats up and thermally expands. It is greatly curved as shown in . Due to this curvature, the contact between the rack shaft 1 and the current-carrying electrodes 3, 4 changes rapidly from surface contact to line contact, and sometimes to point contact, and sparks are likely to occur at this time. The spark between the electrodes 3, 4 and the rack shaft 1 is
Since the contact surfaces of the electrodes 3 and 4 are roughened and sparks are more likely to occur, there is a problem in that the electrodes 3 and 4 are rapidly damaged. Furthermore, when the spark occurs, spark marks remain on the surface of the rack shaft 1, and these sometimes protrude beyond the surface of the rack shaft, which may impede the sliding movement between the rack shaft 1 and the bearing member.

The purpose of the present invention is to provide a rack shaft induction hardening apparatus having a current-carrying electrode that is brought into contact with the rack shaft.
The purpose is to prevent sparks between the current-carrying electrode and the rack shaft.

[Means for solving problems]

In order to achieve the above object, the present invention aims to
In a rack shaft induction hardening apparatus having an induction electrode 2 disposed close to the rack shaft 1, and a pair of current-carrying electrodes 3 and 4 disposed at both ends of the induction electrode and in contact with the rack shaft 1, the A crowning 7 in the axial direction of the rack shaft is provided on the contact arc surface 5 of the current-carrying electrodes 3, 4 with the rack shaft.

[Effect]

As mentioned above, in the present invention, the crowning 7 in the axial direction of the rack shaft is provided on the contact arc surface 5 of the current-carrying electrodes 3 and 4 with the rack shaft, so even if the rack shaft 1 is heated and curved, the rack shaft will not be damaged. 1 changes its contact position smoothly and gradually along the crowning, so no sparks are generated.

〔Example〕

In the induction hardening apparatus shown in FIG.
As shown in FIG. 3, a crowning 7 in the axial direction of the rack shaft is provided. Although the drawing shows one current-carrying electrode 4, the contact arc surface of the other current-carrying electrode 3 is also similar.

When crowning is provided on the contact arc surfaces of the current-carrying electrodes 3 and 4 in this way, even if the rack axis curves during heating, the rack axis gradually moves along the contact surface of the electrodes, as shown by the two-dot chain line in FIG. The contact position changes smoothly and does not cause sparks.

[Effect of idea]

As mentioned above, the present invention has a crowning in the axial direction of the rack shaft on the contact arc surface of the current-carrying electrode with the rack shaft, so even if the rack shaft bends during heating, sparks will not be generated and the life of the electrode will be extended. It has the effect of being able to extend the length and obtain a rack shaft with a good surface without spark marks.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway front view of the conventional example, FIG. 2 is an enlarged perspective view of the current-carrying electrode, and FIG. 3 is an enlarged partial sectional view of the embodiment of the present invention. Explanation of symbols, 1... Rack axis, 2... Induction electrode, 3, 4... Current-carrying electrode, 5... Contact arc surface, 7...
…Crowning.

Claims (1)

[Scope of utility model registration request] Induction electrode 2 placed close to rack axis 1
In a rack shaft induction hardening apparatus having a pair of current-carrying electrodes 3 and 4 disposed at both ends of the induction electrode and in contact with the rack shaft 1, the current-carrying electrodes 3 and 4 are connected to the rack shaft. A rack shaft induction hardening device characterized in that a contact arc surface 5 is provided with a crowning 7 in the axial direction of the rack shaft.