JPH0583432B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a steering rack used in a rack and pinion type steering device of a vehicle such as an automobile, in which a hardened layer is formed by induction hardening on the teeth and back surface of the steering rack. and its induction hardening method.

[Prior art]

As shown in Fig. 4, the steering rack of a rack and pinion type steering device is formed with a plurality of rack teeth that mesh with the pinion, and the teeth are hardened to improve the wear resistance of the rack teeth. A hardened layer 2 is formed. Recently, in order to increase the axial strength (especially bending strength) of the steering rack, attempts have been made to form a hardened layer 3 on the back surface of the steering rack over a relatively wide area. There is. As a means for forming the quench hardened layer 3 on the back surface,
As shown in the figure, a coil formed by induction hardening using a substantially semi-cylindrical induction coil 18 was published in Japanese Patent Application Laid-Open No. 59-1999.
It is disclosed in Publication No. 9124.

[Problem that the invention seeks to solve]

However, in the above-mentioned steering rack, forming the quench-hardened layer 3 over a relatively wide area on the back surface has the disadvantage that heat treatment distortion becomes large. This made subsequent correction work difficult. As shown in FIG. 5, forming the quench-hardened layer 3 using the approximately semi-cylindrical induction coil 18 has the disadvantage that the induction coil
8 is determined by the diameter of the steering rack, there is no versatility as equipment, and the induction coil must be replaced every time the diameter of the steering rack changes, and furthermore, a hardened layer is formed over a wide area. Doing so consumes a large amount of power and is inefficient.

The present invention provides a steering rack and an induction hardening method for the steering rack, which can increase the shaft strength by forming a hardened layer on the back surface of the teeth of the steering rack, have less heat treatment distortion, and can be induction hardened with high efficiency. The purpose is to

[Means for solving problems]

As shown in FIG. 1, the steering rack of the present invention is a steering rack in which a hardened layer is formed by induction hardening on the teeth and the back surface of the steering rack, which has chord-shaped teeth on a circular cross-sectional shaft. The back surface quenched layer formed on the back surface passes through the steering rack axis O, and extends through the tooth bottom surface P.
1, approximately symmetrical to the left and right about a plane P3 that is tilted upward at an angle θ of 15° to 30° from the plane P2 perpendicular to the vehicle body, and one end thereof is the intersection of the plane P2 and the rear surface. The steering rack is formed into a substantially arcuate cross-section with a range slightly exceeding Q, and the steering rack has a circular cross-sectional shaft with chord-shaped teeth, and the rear surface of the teeth is hardened by induction hardening. In the induction hardening method for a steering rack that forms a layer, an induction coil having a substantially flat surface is aligned with the steering rack axis O.
, and is inclined at an angle θ of 15° to 30° upward from the plane P2 perpendicular to the tooth bottom surface P1 when mounted on the car body.
3, the steering rack is placed perpendicularly to the rear surface of the steering rack, and the rear surface of the steering rack is heated to a predetermined temperature by a high-frequency current flowing through an induction coil.
It is obtained by injecting a refrigerant liquid onto the back surface to form a quenched hardened layer on the back surface.

[Effect]

As shown in FIG. 1, the direction in which the maximum load F1 acts on the steering rack when the vehicle is running is the plane P2.
In addition, within or near this range, there is a direction F2 with a low section modulus, which occurs as a steering rack with a substantially circular cross section. There are two symmetrical directions in which the section modulus is low, but in one direction there is no functional problem because no strong impact force is applied during running. The maximum load F1 is most concentrated in the normal plane P2 and a range deviated by 15 degrees from it, and in the direction F with the lowest section modulus.
2 is concentrated in a range deviated from the normal plane P2 by 20° to 30°. Therefore, the most important point in terms of strength is between the most deviated angle of 15° where the maximum load F1 acts and the maximum angle of 30° in the direction where the section modulus is low. Therefore,
15° from plane P2 on the back of the steering rack.
The back surface quenched hardened layer 3 is formed to be substantially symmetrical left and right with respect to the 30° inclined surface P3, and to have a substantially arcuate cross-section in an area where one end slightly exceeds the center Q of the back surface where the section modulus is low. Therefore, the strength of the shaft in terms of its function as a steering rack is increased. Moreover, since the hardened layer is formed locally, there is little distortion due to heat treatment. Then, by hardening with an induction coil that has a substantially flat surface,
It is possible to form a hardened layer locally, there is little heat treatment distortion, and the same induction coil can be used regardless of the diameter of the steering rack, so it is highly versatile as equipment, and it is efficient because it hardens locally.

〔Example〕

The present invention has a diameter of 22 (mm), a length of 600 (mm),
Number of tooth valleys...28, rack tooth module...2, material...applied to a steering rack made of S45C material (JIS). FIGS. 2 and 3 show the hardening process of the back surface. The induction hardening device 16 used includes a high-frequency power source 4, conductors 5, 6 connected to the high-frequency power source 4, 6 and an induction coil 9 provided between the electrodes 7 and 8.
and the holding member 10 which holds the steering rack 1 between the electrodes 7 and 8, and the small hole 1 of the induction coil 9.
1 and a refrigerant supply device 12 that spouts refrigerant liquid. First, the steering rack 1, on which the hardened tooth layer 2 has been formed in advance by induction hardening, is heated to the induction coil 9, which has a substantially flat surface.
When installed on the vehicle body, an angle θ is made in the upward direction from a plane P2 that passes through the steering rack axis O and is perpendicular to the tooth bottom surface P1.
It is placed so as to face the back surface of the steering rack so as to intersect perpendicularly with the plane P3 inclined at 20 degrees, and is clamped and fixed between the electrodes 7 and 8 and the holding member 10 as shown in the drawing. is heated to a predetermined temperature. Then, a refrigerant liquid is injected into this heating part from the small hole 11 of the induction coil 9 to cool it and form a hardened layer on the back surface. As a result, as shown in Fig. 1, the end reaches the center Q of the rear surface in a substantially symmetrical manner about a plane P3 which is deviated upward by an angle θ=20° from the plane P2 of the steering rack when it is attached to the vehicle body. Steering rack 1 with hardened back layer 3
is obtained. In this steering rack 1, when the mounting angle is 17°, the angle θ at which the maximum load F1 acts = 13° (value obtained from the mounting shape and angle of the steering device) and the angle θ in the direction of the minimum section modulus = As a result of measuring the bending load resistance from a 25° direction,
This was more than 1.5 times that of a product without a hardened layer on the back surface, which was functionally sufficient as a steering rack, and the strain caused by heat treatment was also small.
Furthermore, since the induction coil 9 with a substantially flat surface is used, steering racks with different diameters can be induction hardened by simply changing the electrodes 7, 8 and the holding member 10, making the equipment highly versatile. Localized hardening results in low power consumption and high efficiency.

〔Effect of the invention〕

Since the present invention is as described above, it is possible to form a hardened layer on the back surface by induction hardening to improve the shaft strength, and to obtain a functionally sufficient steering rack even though the hardened layer is locally formed. I can do it. Since the material is locally quenched, there is less distortion due to heat treatment, and subsequent straightening work can be facilitated. In addition, by using an induction coil with a substantially flat surface, the equipment is highly versatile, and localized hardening reduces power consumption, making it possible to perform high-frequency induction hardening of steering racks. has.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a steering rack according to an embodiment of the present invention, Fig. 2 is a partially cutaway sectional view showing the hardening process of the back surface of an embodiment of the present invention, and Fig. 3 is a cross-sectional view taken from Fig. 2 A-A
4 is a sectional view showing a conventional steering rack, and FIG. 5 is a sectional view showing a hardening process of the back surface of a conventional example. Explanation of symbols, 1... Steering rack, 2...
... Quenched and hardened layer on the tooth portion, 3... Quenched and hardened layer on the back surface, 9
...Induction coil, 16...Induction hardening device.

Claims (1)

[Scope of Claims] 1. In a steering rack in which a quenched hardened layer is formed by induction hardening on the tooth portion and the back surface of the steering rack in which the tooth portion is provided in a chord shape on the circular cross-sectional shaft, The quenched hardened layer on the back side passes through the steering rack axis O, and the tooth bottom surface P.
1, approximately symmetrical to the left and right about a plane P3 that is tilted upward at an angle θ of 15° to 30° from the plane P2 perpendicular to the vehicle body, and one end thereof is the intersection of the plane P2 and the rear surface. A steering rack characterized by being formed into a substantially arcuate cross section with a range slightly exceeding Q. 2. In an induction hardening method for a steering rack in which a quenched hardened layer is formed by induction hardening on the back surface of the teeth of a steering rack having chord-like teeth on a circular cross-sectional shaft, an induction coil having a substantially flat surface is used. , the substantially flat surface passes through the steering rack axis O and is perpendicular to a surface P3 which is tilted upward at an angle θ of 15° to 30° from a surface P2 perpendicular to the tooth bottom surface P1 at an angle θ of 15° to 30° when mounted on the vehicle body. The steering rack is heated to a predetermined temperature by a high-frequency current flowing through an induction coil on the back side of the steering rack, and a refrigerant liquid is injected onto the back side to form a quenched hardened layer on the back side. Features an induction hardening method for steering racks.