JPH02286468A - Steering shaft - Google Patents

Abstract

PURPOSE:To increase rigidity in a twisting direction by fitting an outer shaft with a polygon inner circumferential surface in an inner shaft with a polygon outer circumferential surface, pouring synthetic resin in a space being formed between both of them, and binding them together after solidification. CONSTITUTION:A steering shaft 20 is constituted so as to cause the full length to be contracted when an outer shaft 21 and an inner shaft 22 are combined in a telescopic form and impact force is added in the axial direction. The outer shaft 21 is formed into a circular pipe form as a whole, applying a female serration groove 23 to one end inner circumferential surface. On the other hand, the inner shaft 22 is made up into a circular rod form as a whole, forming a male serration groove 24, being engaged with the groove 23, on one end outer circumferential surface. In addition, a recess 25 is formed in two spots in the axial direction of the inner shaft 22, and a melted synthetic resin is poured into a section crescent-shaped space 26 partitioned off by each recess 25 from holes 27, 28 installed in the outer shaft 21, and it is cooled and solidified, joining both these shafts 21, 22 together.

Description

[Detailed Description of the Invention] (Industrial Application Field) The steering shaft according to the present invention is incorporated into a steering device of an automobile and used for transmitting the movement of the steering wheel to the steering gear.
In particular, the present invention relates to an improvement in a so-called collabible steering shaft that protects a driver by reducing its overall length in the event of a collision.

(Prior Art) In an automobile steering system, a mechanism as shown in FIG. 7 is used to transmit the movement of a steering wheel to a steering gear.

In this FIG. 7, 1 is a first steering shaft to which a steering wheel 2 is fixed at its upper end, and 3 is a steering wheel fixed to the lower surface of an instrument panel 6 by a bracket 4.5 between the upper and lower parts. The first steering shaft 1 is rotatably inserted through the inside of the steering column 3.

At the lower end of the first steering shaft 1, a portion protruding from the lower end opening of the steering column 3 includes:
The upper end portion of the second steering shaft 8 is connected via the first universal joint 7 . Furthermore, the lower end of the second steering shaft 8 is connected via a second universal joint 9 to a third steering shaft 10 that communicates with a steering gear (not shown).

Because it is formed in this way, the movement of the steering wheel 2 is caused by the first steering shaft 1 pushed through the steering column 3, the first universal joint 7, the second steering shaft 8, the second universal joint 9, The signal is transmitted to the steering gear via the third steering shaft 10, and a steering angle is imparted to the wheels.

By the way, in the steering mechanism configured in this way, in order to protect the driver in the event of a collision, the steering column 3 and each steering shaft 1.8 are of a so-called collabsible type, in which the overall length decreases with the impact. This is commonly done.

This type of collabible steering shaft has
The following two conditions (a) and (b) are required to be met.

(a) To ensure reliable steering, rigidity in the torsional direction must be large.

(b) In order to ensure driver protection in the event of a collision, when an impact is applied, the overall length will be reduced with a light force.

In order to satisfy these conditions, various types of steering shafts have been considered and actually used.

For example, in Japanese Unexamined Patent Publication No. 175260/1989, there are
A collapsible steering shaft as shown in FIG. 10 is disclosed.

This conventional steering shaft 19 is constructed by combining a cylindrical outer shaft 11 having two planes parallel to each other and an oval cross-sectional shape, and an inner shaft 12 also having an oval cross-section in a telescopic shape. has been done.

In this way, two wooden shafts 11.
The space between the inner circumferential surface of the outer shaft 11 and recesses 13 and 13 formed in two positions on the outer circumferential surface of the inner shaft 12 in the circumferential direction of the inner shaft 12 and the inner circumferential surface of the outer shaft 11 is made of resin. The outer shaft 11 and the inner shaft 12 are connected to each other by injecting a synthetic resin 15.15 into the resin injection space 14.14 and solidifying it.

In addition, according to Utility Model Publication No. 58-51096, etc.,
As shown in FIG. 12, the female serration grooves 16 formed on the inner circumferential surface of the outer shaft 11 and the male serration grooves 17 formed on the outer circumferential surface of the inner shaft 12 are engaged with each other, and two positions on the outer circumferential surface of the inner shaft 12 are engaged with each other. A resin injection space 14.14 exists between the recess 13.13 formed in the inner peripheral surface of the outer shaft 11.
Furthermore, a steering shaft 19 in which an outer shaft 11 and an inner shaft 12 are connected to each other by injecting and solidifying a synthetic resin 15.15 has also been known.

(Problems to be Solved by the Invention) However, in the case of these conventionally known collapsible type steering shafts 19, there are problems to be solved as described below.

That is, in order to connect the outer shaft 11 and the inner shaft 12, the resin injection space 14.1 is
A part of the synthetic resin 15 injected in a molten state into the resin injection space 14.1 is inserted between the inner peripheral surface of the outer shaft 11 and the outer peripheral surface of the inner shaft 12.
It is unavoidable that the particles enter the gap 18 (Fig. 10.11) that exists outside of the gap 4 and become solidified in the gap 18. In this way, the synthetic resin 15 enters the gap 18 and hardens due to the force required to shorten the entire length of the steering shaft 19 consisting of the outer shaft 11 and the inner shaft 12. This is not preferable because it increases the so-called collapse type.

However, in the case of the conventional steering shaft 19, since the recesses 13 for configuring the resin injection space 14 for filling the synthetic resin 15 are formed alternately around the entire circumference of the inner shaft 12, the resin injection space 14 is The synthetic resin 15 filled inside the steering shaft 19 enters the gap 18 over the entire circumference of the steering shaft 19.

The outer peripheral surface of the outer shaft 11 and the inner shaft 12
The larger the area of the part where the synthetic resin 15 has entered within the gap 18 between the inner circumferential surface of the outer shaft 11 and the inner circumferential surface of the
is undesirable because it becomes larger.

In addition, in the case of the structure shown in FIGS. 8 to 10, a rotational force in a torsional direction is applied to the steering shaft 19 based on the operation of the steering wheel 2 (FIG. 7), and the inner peripheral surface of the outer shaft 11 and the inner shaft 12 are When the synthetic resin filled between the outer circumferential surface of This results in a large surface pressure being applied to the contact area, and as the steering operation is repeated, so-called fretting wear is likely to occur in the contact area.

Such fretting wear is undesirable because it not only leads to an increase in the amount of play in the steering mechanism, but also leads to an increase in the collapse load.

Furthermore, in the case of the structure shown in FIGS. 11 and 12, since the recess 13 formed on the outer circumferential surface of the inner shaft 12 to constitute the resin injection space 14 is a mere U-shaped groove, the resin injection space 14 is formed across the resin injection space. The engagement between the synthetic resin 15 filled and solidified in the inner shaft 14 and the recess 13 cannot prevent rattling in the circumferential direction between the inner shaft 12 and the outer shaft 11.

On the other hand, there is some wobbling in the circumferential direction between the female serration grooves 16 formed on the inner circumferential surface of the outer shaft 11 and the male serration grooves 17 formed on the outer circumferential surface of the inner shaft 12. It is unavoidable to do so.

Therefore, in the case of the structure shown in FIGS. 11 and 12, the synthetic resin is prevented from entering the gap 18 existing between the inner circumferential surface of the outer shaft 11 and the outer circumferential surface of the inner shaft 12 and solidifying. , is necessary in order to prevent rattling in the circumferential direction between the two members 11 and 12, and the collapse load inevitably increases.

The steering shaft of the present invention eliminates the above-mentioned disadvantages.

(Means for Solving the Problems) A steering shaft of the present invention includes an outer shaft whose inner peripheral surface has a polygonal shape such as a female serration groove, or a shape having two mutually parallel planes, and an outer shaft whose outer peripheral surface has a polygonal shape such as a female serration groove, or a shape having two mutually parallel planes. It is constructed by combining an inner shaft having a polygonal shape such as a male serration groove that engages with the inner circumferential surface of the inner shaft, or a shape having two mutually parallel planes in a telescopic shape.

A recess is formed in a part of the outer peripheral surface of the inner shaft in the circumferential direction, and the recess defines a resin injection space between the outer peripheral surface and the inner peripheral surface.

A part of the outer shaft is formed with first and second resin injection holes, each of which communicates with the resin injection space, from which the first resin injection hole connects to the resin injection space,
Synthetic resin is injected and solidified.

(Function) In the case of the steering shaft of the present invention configured as described above, rotational force is transmitted between the outer shaft and the inner shaft through the polygonal inner peripheral surface of the outer shaft and the inner shaft, respectively. This is ensured by the engagement with the outer circumferential surface of the

At this time, the inner circumferential surface of the outer shaft and the outer circumferential surface of the inner shaft contact each other at multiple points depending on the polygonal shape of each circumferential surface, so large stress is not applied to the contact surfaces, and the contact No fretting wear occurs on the parts.

Furthermore, even when the inner circumferential surface is shaped to have two planes parallel to each other, as the synthetic resin is fed into the resin injection space, the planes located on the opposite sides of the space come into close contact with each other. Rotational force is transmitted through this close contact area, and fretting wear is prevented from occurring.

Furthermore, the resin injection space for filling the synthetic resin for coupling the outer shaft and inner shaft is
Since it is composed of a recess formed only in a part of the circumferential direction of the inner shaft, the molten synthetic resin injected into the injection space fills the gap between the inner circumferential surface of the outer shaft and the outer circumferential surface of the inner shaft. Even if it does, it will not extend all the way around the steering shaft.

Therefore, it is possible to suppress the increase in stress required for displacement between the outer shaft and the inner shaft due to the synthetic resin that has entered the gap.

Moreover, when the molten synthetic resin is fed into the resin injection space from the first resin injection hole, the necessary and sufficient amount of synthetic resin is fed into the space through the second resin injection hole. Since it is possible to prevent the amount of synthetic resin from entering the gap by feeding more synthetic resin than necessary into the space, the stress required for the displacement between the outer shaft and the inner shaft is large. The effect of preventing this from happening becomes more certain.

(Example) Next, the present invention will be explained in more detail while explaining the illustrated embodiment.

1 and 2 show a first embodiment of the present invention, in which FIG. 1 is a sectional view of a main part of a steering shaft, and FIG. 2 is a sectional view taken along line A-A in FIG.

Similar to the conventional steering shaft 19 described above, the steering shaft 20 of the present invention has an outer shaft 21 and an inner shaft 22 combined in a telescopic manner, so that the overall length is reduced when an impact force in the axial direction is applied. It is configured like this.

The outer shaft 21 has a circular tubular shape as a whole, and a female serration groove 23 is formed on the inner circumferential surface of one end, so that the inner circumferential surface has a polygonal cross-sectional shape.

The inner shaft 22 is made entirely of the same shape, and has a male serration groove 2 on the outer circumferential surface of one end that engages with a female serration groove 23 on the inner circumferential surface of the outer shaft 21.
4, the cross-sectional shape of the outer circumferential surface portion of one end of the inner shaft 22 is polygonal.

At two positions in the axial direction of the inner shaft 22, a part of the inner shaft 22 is planed to form recesses 2.
5.25, and each recess 25.25 connects the outer peripheral surface of the inner shaft 22 with the outer shaft 2.
A resin injection space 26, 26 having a crescent-shaped cross section is formed between the resin injection space 26 and the inner circumferential surface of 1.

A part of the outer shaft 21 is located at a position aligned with both ends of the resin injection space 26, 26.
First and second resin injection holes 27.2, respectively
8 is formed.

Then, the molten synthetic resin 15 is injected into the resin injection space 26 from the first resin injection hole 27.27, and the synthetic resin 15 is cooled and solidified in the resin injection space 26, thereby forming the outer shaft 21. and the inner shaft 22 are made of synthetic resin 15.
are connected via.

Steering shaft 2 of the present invention configured as described above
If 0, outer shaft 21 and inner shaft 2
The rotational force transmission in the torsional direction between the outer shaft 21 and the inner shaft 22 is transmitted between the female serration grooves 23 formed on the inner circumferential surface of the outer shaft 21 and the fiber serration grooves 24 formed on the outer circumferential surface of the inner shaft 22. This is ensured by engagement.

At this time, the number of female serration grooves 23 formed on the inner peripheral surface of the outer shaft 21 and male serration grooves 24 formed on the outer peripheral surface of the inner shaft 22 is a number corresponding to the number of teeth of each serration groove 23.24. Because they come into contact with each other at certain points, the overall contact area becomes larger, and no large stress is applied to the contact surfaces. As a result, 7
The possibility that retting wear will occur is lowered, and even if it does occur, it will be less severe.

Further, a resin injection space 26 for filling the synthetic resin 15 for coupling the outer shaft 21 and the inner shaft 22 is formed by a recess 25.25 formed only in a part of the circumferential direction on the outer peripheral surface of the inner shaft 22. Therefore, even if the molten synthetic resin 15 fed into the injection space 26 enters the gap 29 between the inner circumferential surface of the outer shaft 21 and the outer circumferential surface of the inner shaft 22, the intrusion will be caused by the steering wheel. It does not extend all the way around the shaft 20.

That is, there is a slight gap 2 between the outer peripheral surface of the inner shaft 22 in which the male serration grooves 24 are formed and the inner peripheral surface of the outer shaft 21 in which the female serration grooves 23 are formed.
9 is unavoidably formed, the resin injection space 26 faces this gap 29 only in the A range in FIG. 2, and does not face this gap 29 in the remaining B range. Therefore,
The synthetic resin 15 hardly enters into the part of the gap 29 that exists in range B, and the synthetic resin 15 that has entered the gap 29 causes the displacement between the outer shaft 21 and the inner shaft 22 to occur. It is possible to suppress the degree to which stress increases.

Moreover, the molten synthetic resin 1 is placed in the resin injection space 26.
5, the first resin injection hole 2
When the molten synthetic resin 15 is fed from step 7, it can be confirmed that the necessary and sufficient amount of synthetic resin 15 has been fed into the space 26 through the second resin injection hole 28. There is no need to feed more synthetic resin 15 than necessary. Therefore, not only can the amount of synthetic resin 15 used be reduced, but also the amount of resin injection space 2 can be reduced.
The molten synthetic resin 1.5 overflowing from 6 can be prevented from entering the gap 29. As a result, the amount of synthetic resin 15 that enters the gap 29 existing between the female serration groove 23 on the inner circumferential surface of the outer shaft 21 and the male serration groove 24 on the outer circumferential surface of the inner shaft 22 can be further suppressed. This makes it possible to more reliably prevent the stress required for displacement between the outer shaft 21 and the inner shaft 22 from increasing.

For example, according to experiments conducted by the present inventor, the 11th to 1st
In the case of the conventional steering shaft 19 as shown in Fig. 2, the relationship between the compressive load (collapse load) applied in the axial direction and the amount of axial compression (collapse amount) is as shown by the solid line a in Fig. 6. In contrast, in the case of the steering shaft 20 of the present invention described above, the relationship between the compression load and the amount of axial compression is as shown by the chain line in the figure, which indicates the role that the present invention plays in reducing the collapse load. I was able to confirm that it was large.

In the case of the steering shaft 20 of the present invention, the resin injection space 26 is located at the steering shaft 20.
Since it is provided only in a part of the circumferential direction of the outer shaft 2, even if the synthetic resin 15 does not enter into the gap 29, the outer shaft 2
The occurrence of wobbling in the circumferential direction between the inner shaft 1 and the inner shaft 22 can be reliably prevented.

Next, FIG. 3 shows a second embodiment of the present invention.

In the case of this embodiment, a part of the inner peripheral surface of the outer shaft 21 facing the resin injection space 26 has a
It forms a simple cylindrical surface 3o.

By forming the cylindrical surface 30 on a part of the inner circumferential surface of the outer shaft 21 in this way, the circumferential length of the gap 29 can be shortened, and the synthetic resin that enters the gap 29 can be reduced accordingly. By reducing the amount of 15, it is possible to further reduce the collapse load.

Furthermore, FIGS. 4 and 5 show a third embodiment of the present invention.

In the case of this embodiment, the length dimension in the axial direction of the recess 25.25 formed in a part of the outer peripheral surface of the inner shaft 22 is as follows.
It is shorter than that of the first embodiment. In accordance with this, the first and second resin injection holes 27.
28 are formed at both ends in the circumferential direction of the resin injection spaces 26.26 formed by the respective recesses 25.25.

The other configurations and operations are the same as those of the first embodiment described above, so the same parts are given the same reference numerals and redundant explanations will be omitted.

Note that the shapes of the outer circumferential surface of the inner shaft and the inner circumferential surface of the outer shaft are not limited to the serration groove shape as in the illustrated embodiment;
It is also possible to form an oval shape having two mutually parallel planes as shown in FIGS. Even when the shape of each peripheral surface is made into such an oval shape, according to the structure of the present invention, when feeding synthetic resin into the resin injection space, the planes located on the opposite side of this injection space are Since they are in close contact with each other, rotational force is transmitted over a wide area between the outer shaft and the inner shaft, and fretting wear is prevented from occurring.

(Effects of the Invention) Since the steering shaft of the present invention is configured and operates as described above, it effectively prevents the occurrence of fretting wear due to the transmission of rotational force, and improves the inner peripheral surface of the outer shaft and the outer peripheral surface of the inner shaft. It is possible to suppress the amount of synthetic resin that enters the gap between the two and to sufficiently reduce the collapse load.

Moreover, by lowering the collapse load in this way, there is no possibility of rattling in the circumferential direction between the outer shaft and the inner shaft. can be done.

[Brief explanation of the drawing]

1 and 2 show a first embodiment of the present invention, FIG. 1 is a vertical sectional side view of the main part of the steering shaft, FIG. 2 is a sectional view taken along line A-A in FIG. 1, and FIG. A sectional view similar to FIG. 2 showing a second embodiment of the invention, and FIGS. 4 and 5 showing a third embodiment of the invention, FIG. The figure is a sectional view taken along line B-B in Figure 4, Figure 6 is a line diagram showing the results of an experiment conducted to confirm the effects of the present invention, and Figure 7 is a diagram showing the results of an experiment conducted to confirm the effects of the present invention. , a side view showing an example of a steering mechanism, FIGS. 8 to 10 show an example of a conventional steering shaft, FIG.
Figure 10 is a sectional view taken along line CC in the figure, Figure 10 is a sectional view taken along line DD, and Figure 11 is a sectional view taken along line DD.
Figures 1 to 12 show a second example of a conventional steering shaft.
It is a sectional view taken along line E-E in the figure. 1z first steering shaft, 2 steering wheel, 3; steering column, 4: upper bracket, 5: lower bracket, 6; instrument panel,
7: First universal joint, 8: Second steering shaft, 9: Second universal joint, 10: Third steering shaft, 11: Outer shaft, 12: Inner shaft, 13: Recess, 14: Resin injection space,
15: Synthetic resin, 16: Acid serration groove, 17: Male serration groove,! 8: Jinma, t9.2 (1 steering shaft, 21: outer shaft, 22: inner shaft, 23: acid serration groove, 24: male serration groove, 25: recess, 26: resin injection space,
27: first resin injection hole, 28: second resin injection hole, 29: gap, 30: cylindrical surface. Patent applicant: NSK Ltd. Company representative: Koyama Structure (1 idiot)
fpeng meeting chart

Claims (3)

[Claims] (1) An outer shaft with a polygonal inner circumferential surface, an inner shaft with a polygonal outer circumferential surface that engages with the inner circumferential surface of the outer shaft, and a part formed on a part of the outer circumferential surface of the inner shaft in the circumferential direction. A resin injection space formed between the outer circumferential surface and the inner circumferential surface by the recessed portion, and a first and a second first and second resin injection space formed in a part of the outer shaft so as to communicate with the resin injection space, respectively. A steering shaft comprising a resin injection hole, and a synthetic resin injected into the resin injection space from the first resin injection hole and solidified. (2) The steering shaft according to claim 1, wherein the polygonal shape on the inner peripheral surface of the outer shaft is a female serration groove, and the polygonal shape on the outer peripheral surface of the inner shaft is a male serration groove. (3) The steering shaft according to claim 1, wherein the inner circumferential surface of the outer shaft and the outer circumferential surface of the inner shaft have two planes substantially parallel to each other, instead of being polygonal.