JP4598949B2 - Steering shaft and assembly method for energy absorbing steering column - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steering shaft in an impact energy absorption type steering column and an assembling method thereof, and more particularly to fitting by a serration fitting or the like between a lower shaft and an upper shaft, which form a steering shaft that can be shrunk for absorbing impact energy. Concerning improvements at the joint.
[0002]
[Prior art]
A typical example of this type of steering shaft is disclosed in Japanese Utility Model Publication No. 58-142178.
[0003]
In this conventional structure, when the hollow shaft-like lower shaft and the solid upper shaft are serrated and fitted, an annular groove serving as a ball receiving groove is formed in advance in the middle portion of the male serration on the upper shaft side. A ball insertion hole is formed at the end of the lower shaft at a position corresponding to the valley of the female serration, and the male and female serrations are slightly fitted so that the annular groove matches the ball insertion hole. A steel ball is inserted into the annular groove from the ball insertion hole, and the lower shaft and the upper shaft are slid relative to each other by a predetermined amount in order to press-fit the steel ball to the buttock side of the female serration. .
[0004]
[Problems to be solved by the invention]
In the conventional structure as described above, it is necessary to cut the annular groove and the ball insertion hole, and since the steel ball is essential in addition to the shaft component, the cost is inevitably increased by increasing the number of processing steps and the number of parts. . Moreover, not only the workability of the ball insertion work itself is bad, but also several kinds of steel balls with different diameters are prepared in advance in order to adjust the impact energy absorption characteristic that depends on the press-fit load, that is, the steel ball. This is not preferable because the number of man-hours for managing parts is also increased.
[0005]
The present invention has been made paying attention to the above-described problems, and is an energy absorption type steering system capable of reducing the cost by reducing the number of processing steps and the number of parts and adjusting the impact energy absorption characteristics very easily. It is an object of the present invention to provide a retractable steering shaft in a column and an assembly method thereof.
[0006]
[Means for Solving the Problems]
The invention according to claim 1 is formed on the inner peripheral surface of the locking protrusion formed on the outer peripheral surface of one of the lower shaft and the upper shaft forming the steering shaft and the hollow portion of the other shaft. This is based on the assumption that the steering shaft of the energy absorption type steering column is fitted with a locking recess and can be shrunk at the time of impact energy absorption by the fitting portion based on the relative sliding motion between the two shafts.
[0007]
In addition, the area from the locking projection to the end surface on the insertion start end side adjacent to the locking projection formed on the one shaft has a smaller diameter than the maximum diameter of the locking projection. The small- diameter shaft portion is formed by a chamfered portion formed at a boundary portion with the locking convex portion and a straight portion from the chamfered portion to the end surface on the insertion start end side. while being formed, portions corresponding to the inner engagement convexed latch portion of the other shaft, pressure marks by locally locking recess the small-diameter shaft portion utilized as a mandrel consisting of the chamfered portion and the straight portion Thus, a resistance protrusion is formed that protrudes inward and press-contacts the locking protrusion.
[0008]
In the case of the serration fitting, the male concave portion and the female serration portion correspond to them, and in the case of the spline fitting, the male spline portion (shaft spline) and the female spline. The part (hole spline) corresponds to them.
[0009]
Therefore, according to the first aspect of the present invention, in the state where the lower shaft and the upper shaft forming the steering shaft that can be contracted to absorb energy at the time of collision are fitted, one of the locking recesses is formed. The resistance projection formed on the part is in strong pressure contact with the locking projection, and torque transmission from one steering shaft to the other steering shaft accompanying steering operation is via the fitting part as in the conventional case. Performed smoothly.
[0010]
When a contracting force accompanying the collision energy is applied to the steering shaft due to a secondary collision or the like of the occupant, the upper shaft and the lower shaft that form the steering shaft relatively slide.
[0011]
The invention according to claim 2 is a method of assembling the steering shaft of the energy absorption type steering column according to claim 1,
One shaft in which the locking convex portion and the small-diameter shaft portion are formed in advance and the other shaft in which the locking concave portion is formed in advance, and at least a part of the small-diameter shaft portion and the locking convex portion is the region of the locking recess And a predetermined punch while using the small-diameter shaft portion consisting of the chamfered portion and the straight portion as a mandrel in the above-mentioned fitted state in the above-mentioned fitted state. The step of forming the resistance protrusion by locally printing inward by the above and the two shafts after the formation of the printing pressure are relatively slid in the energy absorption operation direction, and the resistance protrusion protrudes from the small diameter shaft portion and And a step of setting the contraction stroke necessary for absorbing the impact energy left between the resistance projection and the mating locking projection to be a predetermined stroke.
[0012]
Therefore, in the second aspect of the present invention, the locking recess is formed in the state in which the lower shaft and the upper shaft that form a steering shaft that can be shrunk at the time of energy absorption at the time of collision are fitted. The portion of the hollow portion of the shaft that coincides with the small-diameter shaft portion adjacent to the locking convex portion is locally inside by a pressure punch or the like while using the small-diameter shaft portion consisting of a chamfered portion and a straight portion as a mandrel. The resistance protrusion is formed by applying pressure to the substrate. In this case, it is desirable to position the outer peripheral surface of the hollow portion with a pressure receiving jig having a cylindrical receiving surface so that other portions of the hollow portion are not deformed.
[0013]
The small-diameter shaft portion can be formed at the same time when cold forging one shaft itself having a locking projection, for example, without cutting. Further, the locking projection and the locking recess are processed by drawing or rolling.
[0014]
When the resistance protrusion is thus formed, the resistance protrusion and the small-diameter shaft portion are matched, but the resistance protrusion is removed until the resistance protrusion protrudes from the small-diameter shaft portion and is positioned on the locking convex portion. The lower shaft and the upper shaft are slid while being elastically deformed in the restoring direction. This sliding operation means setting the contraction stroke necessary for absorbing the impact energy left between the resistance projection and the mating locking projection to be a predetermined stroke, for example, a steering shaft The stroke may be adjusted according to the specific required characteristics.
[0015]
As a result, the steering shaft assembled by the present assembling method effectively functions as the steering shaft according to the first aspect of the present invention.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a view showing a preferred embodiment of an impact energy absorption type steering shaft according to the present invention.
[0017]
As shown in FIGS. 1A and 1B, the steering shaft 1 is formed of a hollow pipe-like lower shaft 2 and a solid upper shaft 3, and the lower shaft 2 has a female serration portion 4 as a locking recess. However, male serrations 5 are formed on the upper shaft 3 as locking projections. The lower shaft 2 and the upper shaft 3 are connected so as to be slidable relative to each other by serrations in the male and female serration portions 4 and 5, thereby forming the steering shaft 1 that can be contracted for the impact energy absorbing function. At the same time, a steering wheel is attached to the other end of the upper shaft 3 (not shown).
[0018]
The lower shaft 2 does not need to be hollow as a whole, and at least a portion that becomes the female serration portion 4 may be hollow. The male and female serrations 4 and 5 are formed by a conventionally known processing method such as drawing or rolling.
[0019]
A portion from the position where the male serration portion 5 is interrupted to the distal end surface 3a of the upper shaft 3 itself in order to form a non-serration region adjacent to the distal end side (insertion start end side) of the male serration portion 5 in the upper shaft 3 A small-diameter shaft portion 6 having a diameter smaller than the maximum diameter of the male serration portion 5 is integrally formed. The rounded chamfered portion 7 is smoothly connected to the boundary portion between the small-diameter shaft portion 6 and the male serration portion 5 with a rounded chamfering portion 7 so as not to cause a step due to the difference in diameter dimension, and toward the distal end surface 3a. A straight portion 6a is provided. As a result, the shape accuracy of the resistance protrusion 8 is stabilized, so that there is no variation in the press-fit load between the upper shaft 3 and the lower shaft 2 and the resistance projection 8 is stabilized. Here, the small diameter shaft portion 6 is formed at the same time when the upper shaft 3 itself is processed by, for example, cold forging.
[0020]
On the other hand, a portion of the lower shaft 2 corresponding to the male serration portion 5 in the normal serration coupling state is formed with a resistance protrusion 8 by inflating a part of the circumferential direction together with the female serration portion 4. ing. The resistance projection 8 has a function of locally reducing the inner diameter of the female serration 4 on the lower shaft 2 side. Therefore, when the male and male serrations 4 and 5 are serrated and fitted, The protruding portion 8 is pressed strongly against the male serration portion 5 to increase the sliding resistance between them.
[0021]
That is, as shown in FIG. 1A, when the male and female serration portions 4 and 5 are serrated and fitted, the resistance projection 8 is elastically deformed in the restoring direction while forming the raised portions 8a on both sides thereof, and the male and female portions. The distance S from the pressure contact position of the resistance projection 8 to the other end of the male serration 5 functions as an impact energy absorption stroke. The contraction stroke S required for absorbing the impact energy can be arbitrarily set according to the specifications of the steering shaft 1 or the required impact energy absorption characteristics. In addition, the sliding resistance imparted by the resistance protrusion 8 can be controlled by adjusting the amount of protrusion inward of the resistance protrusion 8 itself.
[0022]
Therefore, according to the steering shaft 1 having the above-described structure, torque transmission is performed by the coupling portion between the male and female serration portions 4 and 5 during steering operation, while the steering shaft 1 contracts due to a secondary collision of the occupant. When such impact energy is applied, the lower shaft 2 and the upper shaft 3 are slid relative to each other with the fitting portions between the male and female serration portions 4 and 5, and contract.
[0023]
As described above, according to the steering shaft 1 of the present embodiment, the contraction stroke for absorbing the required impact energy is obtained only by the lower shaft 2 formed with the resistance protrusion 8 and the upper shaft 3 formed with the small diameter shaft portion 6. In particular, it is advantageous in reducing the cost by reducing the number of parts and the number of processing steps as compared with the conventional structure.
[0024]
The same effect can be obtained by spline fitting instead of serration fitting, and the rounded chamfered portion 7 may be tapered instead of rounded. Further, male serrations may be formed for the small diameter shaft portion 6. The reason is that, for example, when the male serration portion 5 and the small diameter shaft portion 6 are simultaneously formed in one cold forging process, the small diameter shaft portion 6 and the rounded chamfered portion 7 are also formed into a male serration shape.
[0025]
Here, the following procedure is used to form the resistance protrusion 8 on the lower shaft 2.
[0026]
First, as shown in FIG. 2A, the lower shaft 2 in which the female serration portion 4 is formed in advance and the upper shaft 3 in which the male serration portion 5 and the small diameter shaft portion 6 are formed in advance are serrated. The small-diameter shaft portion 6 on the upper shaft 3 side is made to coincide with the position where the resistance projection portion 8 is to be formed in the lower shaft 2.
[0027]
And after positioning the steering shaft 1 formed by serration fitting the lower shaft 2 and the upper shaft 3 to a pressure receiving jig 10 having a cylindrical receiving surface 9 as shown in FIG. The portion corresponding to the small-diameter shaft portion 6 of the lower shaft 2 is pressurized with a predetermined pressure by the pressure punch 11 while effectively using the small-diameter shaft portion 6 itself as a mandrel, and the small-diameter shaft portion 6 and the round chamfered portion 7 is formed so as to bulge or form a printing pressure.
[0028]
Thereafter, as shown in FIG. 4D, the lower shaft 2 and the upper shaft 3 are moved relative to each other so that the resistance projection 8 comes out of the small-diameter shaft 6 and presses against the male serration 5 and presses the press. The steering shaft shown in FIG. 1 is obtained by adjusting the relative sliding amount so that the distance S from the position to the other end of the male serration portion 5 is a contraction stroke in the predetermined impact energy absorption. That is, the resistance protrusion 8 is elastically deformed in the restoring direction in the process of getting over the small-diameter shaft portion 6 and the rounded chamfered portion 7 and is strongly pressed against the male serration portion, and raised portions 8a are generated on both sides thereof due to elastic deformation. 1 is assembled.
[0029]
As shown in FIG. 1 (B), a slight gap is generated in the portion b of the serration fitting portion between the female serration portion 4 and the male serration portion 5, but there is no problem in terms of function. .
[0030]
【The invention's effect】
According to the first aspect of the present invention, since the steering shaft that can be shrunk at the time of impact energy absorption is formed with only the lower shaft and the upper shaft, the conventional ball insertion hole processing and troublesome ball insertion work can be performed. Not only is it unnecessary, but the steel ball itself is unnecessary, and it is possible to achieve a significant cost reduction by reducing the number of processing steps and parts, and the stroke amount can be adjusted according to the specific characteristics of the steering shaft. There is an effect that can be done.
[0031]
Further, according to the invention described in claim 2, there is an effect that the steering shaft described in claim 1 excellent in shrinkage at the time of energy absorption can be easily assembled with the minimum number of steps.
[Brief description of the drawings]
1A and 1B are views showing a preferred embodiment of a steering shaft according to the present invention, in which FIG. 1A is a cross-sectional explanatory view of an essential part thereof, and FIG. 1B is a cross-sectional view taken along line aa in FIG.
FIGS. 2A and 2B are diagrams illustrating an assembly procedure of the steering shaft shown in FIG. 1, wherein FIG. 2A is a cross-sectional explanatory view of a serrated connection state before forming a resistance protrusion, and FIG. Explanatory drawing, (C) is sectional explanatory drawing which follows the bb line | wire of the same figure (B), (D) is sectional explanatory drawing when a resistance projection part is press-contacted to a male serration part.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Steering shaft 2 ... Lower shaft 3 ... Upper shaft 3a ... End surface 4 ... Female serration part (locking recessed part)
5 ... Male serration part (locking convex part)
6 ... Small-diameter shaft 8 ... Resistance projection 10 ... Pressure receiving jig 11 ... Pressure punch

Claims (2)

The engagement protrusion formed on the outer peripheral surface of one of the lower shaft and the upper shaft forming the steering shaft and the engagement recess formed on the inner peripheral surface of the hollow portion of the other shaft are fitted, A steering shaft of an energy absorption type steering column that can be shrunk when absorbing impact energy by fitting based on a relative sliding operation between both the shafts,
A region from the locking projection to the end surface on the insertion start end side adjacent to the locking projection formed on the one shaft is a small-diameter shaft portion having a smaller diameter than the maximum diameter of the locking projection. The small-diameter shaft portion is formed by a chamfered portion formed at a boundary portion with the locking convex portion and a straight portion from the chamfered portion to the end surface on the insertion start end side. on the other hand,
The portion of the other shaft corresponding to the locking projection protrudes inward by locally printing the entire locking recess using the small-diameter shaft portion composed of the chamfered portion and the straight portion as a mandrel. A steering shaft for an energy absorption type steering column, wherein a resistance projection is formed in pressure contact with the locking projection. A method for assembling a steering shaft of an energy absorbing steering column according to claim 1,
One shaft in which the locking convex portion and the small-diameter shaft portion are formed in advance and the other shaft in which the locking concave portion is formed in advance, and at least a part of the small-diameter shaft portion and the locking convex portion is the region of the locking recess. Mating until it is located in
In the above-mentioned fitting state, the portion that matches the small-diameter shaft portion of the other shaft uses the small-diameter shaft portion composed of the chamfered portion and the straight portion as a mandrel, and resists by locally pressing inward with a predetermined punch. Forming a protrusion, and
The two shafts after forming the printing pressure are slid relative to each other in the energy absorbing operation direction, and the resistance projection part is pulled out from the small-diameter shaft part and is left between the resistance projection part and the mating locking projection part. A step of setting the contraction stroke necessary for absorbing shock energy to be a predetermined stroke,
A method of assembling a steering shaft in an energy absorbing steering column.

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