JP3034524U - Steering shaft - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] When the collapse stroke of a steering shaft is shortened, the impulse to be absorbed by the shaft at the time of a vehicle collision increases, and the load received by the driver changes into a mountain shape, which exceeds the allowable limit. . SOLUTION: The steering shaft has an arcuate projection 2c formed by uniformly slightly bulging the arcuate convex surface 2a of the inner shaft 2 over the entire width in the circumferential direction, and the arcuate projection 2c having a hardness higher than that of the inner shaft. It is coaxially press-fitted into the free end of the lower outer shaft 3 to plastically deform the outer shaft during a vehicle collision,
Arc-shaped protrusion 2c for transmitting bending force between the both shafts
The surface area of the arc is significantly increased to prevent seizure, and the projection height of the arcuate projection 2c with respect to the arcuate convex surface 2a is machined to a very high degree of precision to allow fluctuations in the load received by the driver within the allowable limit. It is characterized in that it stabilizes like a hill.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to a steering shaft of a vehicle, and more particularly to a steering shaft for absorbing a shock energy applied to a steering wheel by a driver at the time of collision of the vehicle to measure the safety of the driver.

[0002]

[Prior art]

 Conventionally, such a steering shaft has a hardness member press-fitted between the hardness member holding portion of the inner shaft and the female serration valley portion of the outer shaft, as disclosed in Japanese Utility Model Publication No. 58-51096. As described in Japanese Patent Publication No. 16733, two arc-shaped convex surface portions having the same center line are arranged on the outer periphery at regular intervals, and the corresponding edge edges of the arc-shaped convex surface portions are referred to as the center line. The hardness member held on the arcuate convex surface of the inner shaft connected by parallel flat parts was press-fitted into the outer shaft to which the inner shaft slidably fits. The material is actually a steel ball with a diameter of about 3 m, and the protruding height of the steel ball is 0. It is about 3 to 0.6.

In a general automobile, when a human body collides with a steering wheel at an initial speed of 15 miles / hour (about 24 km / hour), it is required that the load on the human body does not exceed 2500 pounds (about 1135 kg). There is. This also applies to light vehicles with short vehicle lengths and small vehicles.If engine exhaust gas countermeasures, air conditioners, power steering systems, etc. are installed, the engine room will become large and the steering shaft mounting area will be limited. The effective length of the steering shaft is required to be short.

However, if the effective length of the steering shaft is shortened to about 50 to 70% of the current level, the contraction amount (collapse stroke) of the steering shaft at the time of a vehicle collision is shortened, and the impact energy is absorbed in a short stroke. Therefore, it is necessary to increase the projecting height of the steel ball described above to increase the force for pressing the steel ball against the inner wall of the outer shaft, resulting in galling (burning) on both the steel ball and the inner wall of the outer shaft. There is a problem in that the load on the human body changes into a mountain shape and the limit of 1135 kg is momentarily exceeded. This problem can be solved even if the number of steel balls held in the inner shaft is increased. Nakatsuta.

[0005]

[Problems to be solved by the device]

 The problem to be solved is that if the shrinkage of the steering shaft is shortened, the impulse to be absorbed by the steering shaft in the event of an automobile collision increases, and the load on the human body momentarily exceeds the allowable limit. This is the point at which it becomes impossible to stably absorb the impact energy.

[0006]

[Means for Solving the Problems]

 According to the present invention, each arcuate convex portion to be located in the free end portion of the outer shaft is uniformly and slightly bulged over its entire width in the circumferential direction to form an arcuate protrusion on the inner shaft. The gist of the steering shaft is that it is integrally provided, the hardness of the inner shaft is higher than that of the outer shaft, and the arcuate protrusion of the inner shaft is pressed into the free end of the outer shaft.

[0007]

[Embodiment of the invention]

 1 to 3 show an embodiment of the present invention, in which an inner shaft 2 of a steering shaft 1 is provided with two arcuate convex surface portions 2a having the same center line 0 at equal intervals on the outer periphery. , Has an oval cross section in which the corresponding edges of the arcuate convex surface portions are connected by a flat surface portion 2b parallel to the center line 0, and the right end of the inner shaft 2 in FIG. 1 has a universal joint-like joint. Via a steering gear (not shown), and a cylindrical portion 3a at the left end of the outer shaft 3 formed in a cylindrical body having an oval cross section so that the inner shaft can be slidably fitted. The outer shaft 3 of the steering shaft 1 for transmitting a rotational force, which is attached to the vehicle body in a front-back inclination state, is connected to the steering wheel shaft, and can be expanded and contracted with respect to the inner shaft 2 as before.

As shown in FIG. 2, the arcuate convex surface portion 2a of the inner shaft 2 to be located in the free end portion of the outer shaft 3 has a radial direction extending from the circular arc convex surface portion 2a over its entire circumferential width. To form a circular arc-shaped protruding portion 2c by slightly bulging evenly by δ, and the press-fitting side end portion of the protruding portion 2c into the outer shaft is chamfered 2e at an angle α equal to or greater than the static friction angle. There is.

When manufacturing the inner shaft, first, a rod-shaped body having an oval cross section having the outer diameter of the protruding portion 2c is formed by extrusion, and then the arc-shaped convex portion 2a or the like is cut and processed. . The outer shaft 3 shown in the drawing is formed by drawing the inner shaft fitting part of a tubular body into a tubular shape having an oval cross section, and by changing the hardness of the material between the two shafts 2, 3. A required hardness difference is provided.

When the protruding portion 2c of the inner shaft has been press-fitted into the free end portion of the outer shaft 3 as shown in FIG. 1, the outer shaft 3 is connected to the communicating grooves 2f and 2g formed on the outer periphery of the inner shaft. It is the same as in the prior art to prevent the unexpected relative sliding between the outer shaft and the inner shaft during use by filling the plastic through the hole 3b formed at the inner side.

According to the above configuration, when the automobile collides, the arcuate projection 2 c of the inner shaft is pressed into the outer shaft by being pressed in the axial direction while plastically deforming the outer shaft. By the force and the bending force of the steering shaft, the pressure contact force that presses the arcuate protrusion 2c or the flat surface 2b against the inner wall of the corresponding outer shaft with the contact portion of the inner shaft leading end to the inner wall of the outer shaft as a fulcrum. (It becomes maximum when the length L of the bending force transmitting portion between the two shafts is reduced), but the arc-shaped protrusion is a circular arc-shaped convex surface part of the inner shaft which should be located in the free end of the outer shaft. Are uniformly bulged over the entire width in the circumferential direction, the surface pressure acting on the arcuate protrusion is significantly lower than before, and the arcuate protrusion and the outer shear There is no risk of seizure on the inner wall of the hood.

Further, the center line 0 of the arcuate convex portion 2a or the arcuate protrusion 2c of the inner shaft is coaxial, and the machining accuracy of the arcuate protrusion 2c can be improved, and the arcuate protrusion of the arcuate convex portion can be improved. Since the radial projecting height is small, the plastic deformation amount of the outer shaft when the arcuate projecting portion 2c is press-fitted can be kept low during the collapse time. That is, even if the load received by the dummy in the steering shaft impact test to the collapse time in the time diagram is short, the load received by the dummy (human body) should be stabilized in a hill shape during the collapse time below the allowable limit. As a result, the same impact energy as in the past can be absorbed by the steering shaft.

For example, FIG. 4 shows a load-time diagram received by the dummy when an impact test is conducted with the actual size steering shaft shown in FIG. 1, and the collapse time at this time is about 0.07 seconds, and the collapse time is about 0.07 seconds. The stroke is 55 moulds, the maximum load is 790 kgf, and the load range close to the maximum load is stable for about 0.04 seconds in a hill shape within the allowable limit (1135 kgf).

The embodiment in which the inner shaft and the outer shaft are formed in an oval cross section has been described above. However, in the present invention, the vicinity of each vertex of the equilateral triangle has a constant radius whose center is the center of gravity of the equilateral triangle. It is apparent from the prior art that the present invention can also be applied to the case where the steering shaft is composed of an inner shaft and an outer shaft having a cross-sectional outer shape cut off by the arc.

[0015]

[Effect of the invention]

 The present invention remarkably increases the pressure contact area of the arcuate protrusion on the inner shaft side, which is press-fitted into the free end of the outer shaft, to reduce the surface pressure, and the arcuate protrusion on the arcuate convex portion on the inner shaft side. Even if the collapse stroke at the time of a car collision is short, the fluctuation of the load that the driver receives at that time is made into a hill shape within the allowable limit because it is combined with a coaxial structure that can process the protruding height of the part with a high degree of precision. It is possible to stabilize it, and the manufacturing and assembly of the steering shaft are easy and inexpensive.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view of a main part of an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view taken along line XX of FIG.

FIG. 3 is a sectional view taken along line YY of FIG. 2;

FIG. 4 is a load-time diagram received by a dummy in a steering shaft impact test.

[Explanation of symbols]

 1 Steering Shaft 2 Inner Shaft 2a Arc-Shaped Convex Surface 2b Flat Surface 2c Arc-Shaped Projection 3 Outer Shaft

Claims (1)

[Utility model registration claims] 1. A plurality of arcuate convex portions having the same center line are arranged at regular intervals on the outer circumference, and the corresponding end edges of adjacent arcuate convex portions are flat portions parallel to the center line. In the steering shaft composed of an inner shaft which is connected with, and a cylindrical outer shaft to which the inner shaft is slidably fitted, each arcuate convex surface part which should be located in the free end part of the outer shaft is The inner shaft is made to bulge out evenly over the entire width in the circumferential direction, and an arcuate protrusion is integrally formed on the inner shaft, and the hardness of the inner shaft is made higher than that of the outer shaft so that the inner shaft has an arc shape. A steering shaft with a protruding part press-fitted into the free end of the outer shaft.