JPS6132374B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hardening apparatus for rack bars using a high frequency direct energization method, which is capable of making the hardened layer uniform.

A conventional hardening apparatus of this kind is used to harden the teeth 9 of a rack bar 8 having diagonal teeth as shown in FIG. 1, for example, and has a configuration as conceptually shown in FIG. In the figure, 1 indicates a conductor, 2 indicates the other conductor arranged below the conductor 1 in parallel with an electrical insulator 3 interposed therebetween, and the shorter conductor 1
Contact electrodes 4 and 5 are provided upwardly on the upper surface of the right end of the conductor and on the upper surface of the right end of the longer conductor, respectively. The contact electrodes 4 and 5 are spaced apart from each other so that their respective tips can contact the bottoms of the teeth at both ends of the rack bar 8.

Reference numeral 6 denotes a longitudinal proximal conductor fixed by welding to the upper surface of the conductor 2. This conductor 6 has a hollow box structure, has a large number of cooling water injection holes 7 in its upper surface, and has a cooling water introduction pipe 7' welded to its side surface, and cools the pipe 7' via a solenoid valve. It is connected to a water pump (none of which is shown). The proximal conductor 6 is made of a copper plate, and its length in the longitudinal direction corresponds to the length of the teeth 9 of the rack bar 8.

Reference numeral 10 denotes a fluid pressure cylinder that presses the rack bar 8 downward on the electrodes 4, 5 in order to bring the rack bar 8 into reliable contact with the contact electrodes 4, 5.

In the above device, when a high frequency power source 11 is connected between the base ends of the conductors 1 and 2, the high frequency current flows from the power source 11 to the conductor 1 to the contact electrode 4 to the surface of each tooth of the rack bar 8 to the contact electrode 5 to the conductor 2. →The upper surface of the adjacent conductor 6→The conductor 2→The power supply 11 flows through the path.

Here, the current output from the high frequency power supply 11 is i ₁ ,
If the current returning through the contact electrode 5 is _i2 , then the third
As shown in the enlarged view, the current i ₁ flowing through the rack bar 8 and the current i ₂ flowing through the adjacent conductor 6 are pulled together in such a manner that the generated magnetic flux is minimized (circuit impedance is minimized). They flow in a manner that approaches each other (this is called the so-called proximity effect). Therefore, the current i ₁ flows along the tooth profile of the rack bar. In this case, if the width of the adjacent conductor 6 is approximately equal to the width of the tooth portion 9, the current density in the tooth width direction will be approximately uniform.

On the other hand, since the rack bar 8, the electrodes 4 and 5, and the adjacent conductor 6 form one coil, an induced current (eddy current) i' ₁ is generated in the toothed portion 9, and this current i' ₁ is generated at the tip. Due to the effect (magnetic flux concentrates on the convex part and a large amount of eddy current flows in that part), it occurs more often at the tips of the teeth. Thus, a composite current of current i ₁ and current i' ₂ flows through the toothed portion 9 of the rack bar 8 in the manner shown in the figure.

The density of the current flowing through the tooth portion 9 has a distribution that is high at the tooth tip and low at the tooth bottom, so that the convex portion of the tooth portion 9 is heated uniformly, while the tooth bottom is heated very thinly. . However, when the tooth reaches a predetermined hardening temperature, the high frequency power source 11 is turned on.
When the heated part is rapidly cooled by injecting cooling water from the hole 7 of the adjacent conductor 6, the ideal hardening pattern is achieved in which the tooth tips are sufficiently hardened and the tooth bottoms are hardly hardened. An entry is made.

Figure 4 shows the hardening pattern when the teeth 9 of the hardened rack bar are cut in the axial direction (c-c' line) in Figure 6, and Figure 5 shows the hardening pattern along the bottom of the tooth (a -a' line) shows the same pattern when cut.

According to the above device, the tooth angle θ is θ=0 to 6.
For a rack bar of 1.5°, a substantially uniform hardening pattern of the embodiment shown in FIG. 5 can be obtained for all teeth of the tooth section. However, for a rack bar with teeth where θ>6°, the hardening pattern for one to three teeth located near the contact electrodes 4 and 5 is inclined as shown in Fig. 7, and there are parts that are not hardened. This caused the inconvenience of

In view of this, an object of the present invention is to provide a rack bar hardening device that can uniformly harden each tooth of a rack bar having teeth with a large slope θ.

Hereinafter, the present invention will be explained in detail with reference to embodiments shown in the drawings.

First, let us consider why the quenching pattern becomes uneven as shown in FIG. 7. When the angle θ of the teeth becomes θ>6°, the electric impedance of the current flowing along the tooth profile of the rack bar (this value is determined by the number of intersections between the current flowing through the tooth and the magnetic flux generated in the tooth) is minimized. like,
In other words, the current tries to flow in the direction that minimizes its area. More specifically, as shown in FIG. 6, the current tends to flow not in the axial direction (cc' direction) but in the direction perpendicular to the teeth (bb' direction).

On the other hand, the rack bar 8 and the adjacent conductor 6 shown in FIG.
The magnetic flux density in the air gap formed by the contacts 4,
It becomes uneven around 5.

Considering each tooth of the rack bar located at a location where the magnetic flux density is uniform, current in the c-c' direction flows through these teeth due to the proximity effect. On the other hand, in areas where the magnetic velocity density is non-uniform where a sufficient proximity effect cannot be obtained, that is, teeth located near the contacts 4 and 5, the b-
Current flows in the b′ direction. As a result, the current density in the portions indicated by symbols A and B in FIG. 6 becomes low, and the quench-hardened layer in those portions becomes uneven as shown in FIG. 7. In other words, the hardening pattern is inclined and some parts are not hardened.

In order to solve this problem, the hardening apparatus according to the present invention has chips 12, 13 made of steel plate as shown in FIG.
are attached to the side surfaces of the proximal conductor 6, respectively. The chips 12 and 13 are connected to the front right end and the rear left end of the adjacent conductor 6, respectively, so as to be electrically connected to the conductor 6, so that their upper surfaces are connected to parts A and B in FIG. It is located near the department.

The chips 12 and 13 have the effect of making both ends of the proximal conductor 6 protrude in the width direction of the teeth 9 of the rack bar 8 to form a large opposing area, thereby enhancing the proximity effect in these parts. Therefore, according to the device of the present invention, it is possible to flow a current in the axial direction c-c' through the teeth of the rack bar 8 located near the contacts 4 and 5, thereby causing the hardening described above. This can prevent pattern deviation. That is, a hardening pattern as shown in FIG. 5 can be obtained.

If the magnetic metal plates 14 and 15 are superimposed on the outer surfaces of the chips 12 and 13, respectively, in the manner shown by the dotted lines in the figure, the magnetic flux density in the A and B portions will be increased and the magnetic flux density in those portions will be increased. Since the generated induced eddy current can be increased, the quench-hardened layer in this portion can be made deeper.

According to experiments, a uniform hardened layer was obtained for each tooth by providing only the chips 12 and 13 with respect to a rack bar having a tooth angle of 6 DEG to 20 DEG. Further, for a rack bar with a tooth angle of 20 degrees or more, good results were obtained by using the chips 12 and 13 described above together with a magnetic metal plate.

In the above embodiment, the chips 12 and 13 are attached to the existing proximal conductor 6, but the conductor 6 itself is Of course, it is also possible to configure it in advance.

As described above, according to the present invention, even the teeth of the rack bar located near the contact electrode can be uniformly hardened, so that a highly reliable hardened product can be obtained.

[Brief explanation of the drawing]

Figure 1 shows an example of a steering rack bar, Figure 2 conceptually shows a rack bar hardening device using a conventional high-frequency direct energization method, and Figure 3 shows the direction of current flow. Partial enlarged view, 4th
The figure is a partially enlarged view showing the hardening pattern when the hardened rack bar is cut along its axis. Figure 5 is a partial enlarged view showing the hardening pattern when the hardened rack bar is cut along the tooth bottom. Figure 6 is a diagram showing the pattern, Figure 6 is a diagram showing the mode of high frequency current flowing through the teeth of the rack bar, Figure 7 is a diagram showing a state where the hardening pattern is uneven, Figure 8 is a diagram showing the hardening pattern according to the present invention. FIG. 2 is a partially enlarged view showing an embodiment of the device. 1, 2...Conductor, 3...Electric insulator, 4, 5...
... Contact electrode, 6 ... Proximity conductor, 7 ... Cooling water injection hole, 7' ... Cooling water introduction pipe, 8 ... Rack bar, 9 ... Teeth of rack bar, 10 ... Cylinder, 11 ... High frequency power supply , 12, 13... Chip, 14, 15... Magnetic metal plate.

Claims (1)

[Claims] 1. A type of firing method in which the teeth of a rack bar having teeth with a large degree of inclination and a nearby conductor are placed close to each other and face each other, electrodes are brought into contact with both ends of the teeth of the rack bar, and a high-frequency current is passed directly to the teeth. In the input device,
The upper area of both ends of the proximate conductor facing both ends of the tooth part of the rack bar is made to protrude in the tooth width direction of the tooth part to form a large opposing area, and between both ends of the tooth part of the rack bar and the proximal conductor. A rack bar hardening device characterized by increasing the proximity effect of.