JPH11150U - Shock absorbing steering shaft - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To increase a collapse load with an increase in the amount of collapse. A female serration on an inner peripheral surface of an outer shaft is engaged with a male serration on an outer peripheral surface of an inner shaft. Projections 22, 22 are formed at the bottom of the valley 13b of the male serration 13, and each projection 2
2, 22 and the tops of the ridges 11a of the female serrations 11 are brought into strong contact. Further, the outer shaft 12 is normally used.
Projections 23, which are higher than the projections 22, 22, are formed in the portion located outside.

Description

[Detailed description of the invention]

[0001]

[Industrial applications]

 The shock absorbing steering shaft according to the present invention is incorporated into a steering device of an automobile, and is used to transmit the movement of a steering wheel to a steering gear.

[0002]

[Prior art]

 In an automobile steering system, a mechanism as shown in FIG. 5 is used to transmit the movement of a steering wheel to a steering gear. In FIG. 5, reference numeral 1 denotes a first steering shaft having a steering wheel 2 fixed to an upper end portion, and a steering shaft 3 fixed to the lower surface of the instrument panel 6 by upper and lower brackets 4, 5. In the column, the first steering shaft 1 is rotatably supported inside the steering column 3. The upper end of the second steering shaft 8 is connected via a first universal joint 7 to the lower end of the first steering shaft 1 and the portion protruding from the lower end opening of the steering column 3. I have. Further, the lower end of the second steering shaft 8 is connected to a third steering shaft 10 communicating with a steering gear (not shown) via a second self-joint 9. To form in this manner, the movement of the steering wheel 2 is controlled by the first steering shaft 1, the first universal joint 7, the second steering shaft 8, the second universal joint 9, The steering wheel is transmitted to the steering gear via the steering shaft 10 to impart a steering angle to the wheels.

In the steering mechanism configured as described above, in order to protect a driver in the event of a collision, the steering column 3 and each of the steering shafts 1 and 8 are provided with an impact absorbing type in which the entire length is reduced by an impact. It is common practice to do Conventionally, as such a shock-absorbing steering shaft, one described in, for example, JP-A-2-286468 is known. As shown in FIGS. 6 and 7, an impact-absorbing steering shaft as a first example of the conventional structure described in this publication includes an outer shaft 12 having a female serration 11 formed on an inner peripheral surface, and an outer shaft 12 having an outer peripheral surface formed with a female serration 11. The female serration 11 is engaged with the inner shaft 14 having the male serration 13 formed therein, and is combined with the female serration 11 in a state where the male serration 13 is inserted inside the female serration 11. Further, the synthetic resin 17 is inserted into the spaces 16, 16 between the concave portions 15, 15 formed on the outer peripheral surface of the inner shaft 14 and the inner peripheral surface of the outer shaft 12 through the through holes 19, 19 formed in the outer shaft 12. , 17 are injected and solidified to connect the outer shaft 12 and the inner shaft 14 to each other to form a shock absorbing steering shaft 18.

When a large force acts on the shock-absorbing steering shaft 18 in the axial direction following the collision, the synthetic resins 17, 17 are formed into the spaces 16, 16 and the through holes 19, 19. Is sheared in the continuous part. Then, the relative displacement between the outer shaft 12 and the inner shaft 14 is made freely, and the overall length of the shock absorbing steering shaft 18 is allowed to be reduced.

Further, Japanese Utility Model Publication No. 58-51096 discloses an impact absorbing steering shaft 18 having a structure as shown in FIGS. In the case of the conventional structure of the second example, in addition to the structure of the first example described above, a small-diameter portion 25 is formed at an intermediate portion of the inner shaft 14. Then, the steel balls 26, 26 arranged around the small diameter portion 25 are fitted to the valleys 11 b, 11 b of the female serration 11 formed on the inner peripheral surface of the outer shaft 12, and the shock absorbing steering shaft 18 is fitted. And

In the case of such a structure of the second example, when a large force acts in the axial direction of the shock absorbing steering shaft 18 due to a collision, the synthetic resin 17 causes the space 16 and the through hole 19 to communicate with each other. Sheared in a continuous section. Then, the relative displacement between the outer shaft 12 and the inner shaft 14 is made freely, and the overall length of the shock absorbing steering shaft 18 is allowed to be reduced. When the overall length of the shock-absorbing steering shaft 18 is reduced, the steel balls 26, 26 plastically deform the inner surface of the female serration 11 while the relative displacement between the outer shaft 12 and the inner shaft 14 is reduced. Tolerate.

Further, Japanese Utility Model Laid-Open Publication No. 63-147363 discloses an impact absorbing steering shaft 18 having a structure as shown in FIGS. In the third example of this conventional structure, the end of the outer shaft 12 is formed in a substantially triangular cylindrical shape with rounded corners, and the end of the inner shaft 14 is formed in a hexagonal cylindrical shape. Both ends are slidably fitted to each other, and steel balls 26, 26 are inserted into gap spaces 27, 27 between the inner peripheral surface of the outer shaft 12 and the outer peripheral surface of the inner shaft 14. The shock absorbing steering shaft 18 is press-fitted through a through hole 28 formed in the shaft 12.

In the case of such a structure of the third example, when a large force acts in the axial direction of the shock absorbing steering shaft 18 in accordance with the collision, the steel balls 26, 26 are attached to the inner peripheral surface of the outer shaft 12. And the outer peripheral surface of the inner shaft 14 are plastically deformed, while allowing the relative displacement between the outer shaft 12 and the inner shaft 14.

[0009]

[Problems to be solved by the invention]

 In the case of the conventional shock absorbing steering shaft as described above, the collapse load cannot be gradually increased with an increase in the amount of collapse. For this reason, when the collapse load is small, the shock absorbing steering shaft contracts completely (full collapse), and when the contraction is completed, the so-called bottom impact causes a large resistance. On the other hand, when the collapse load is large, a large resistance is generated at the moment when the shock absorbing steering device starts to contract, and it is difficult to enhance the protection of the driver.

In order to effectively absorb the impact energy in the event of a collision and to effectively protect the driver, it is preferable that the collapse load increases with an increase in the collapse amount. In the case of the conventional shock-absorbing steering shafts as shown in FIGS. 6 to 11, none of them can cope with such a demand, and it is difficult to design a steering apparatus for an automobile which can sufficiently enhance the protection of the driver. The shock absorbing steering shaft of the present invention has been invented in view of such circumstances.

[0011]

[Means for solving the problem]

 The shock-absorbing steering shaft of the present invention has an inner shaft having a male serration on the outer peripheral surface and a female serration on the inner peripheral surface, for example, similarly to the conventional shock-absorbing steering shaft shown in FIGS. The inner shaft and the outer shaft are engaged with each other by engaging the male serration and the female serration so that the torque can be transmitted. Between them, there is provided an impact absorbing part that allows the axial dimension to contract only when a large axial load is applied.

In particular, in the shock absorbing steering shaft of the present invention, the shock absorbing portion is a part of the valley of the male serration, and does not normally engage with the female serration in a collision accident. When the steering shaft is contracted, the projection includes a projection fixed to a portion engaged with the male serration. The projection is deformed by engagement with the female serration ridge as the shock absorbing steering shaft contracts.

[0013]

[Action]

 In the case of the shock absorbing steering shaft of the present invention configured as described above, the collapse load can be gradually increased as the amount of collapse increases. That is, when the shock absorbing steering shaft is contracted due to the occurrence of a collision accident, the protrusion engages with the peak of the female serration during the contraction. Then, after the protrusion and the mountain portion of the female serration are engaged, the collapse load increases. As described above, the collapse load increases as the amount of collapse increases, which facilitates a design for enhancing protection of a driver in a collision accident.

[0014]

【Example】

 1 to 4 show an embodiment of the present invention. The shock-absorbing steering shaft 29 of the present invention, like the conventional shock-absorbing steering shaft 18 (FIGS. 6 to 11) described above, allows the outer shaft 12 and the inner shaft 14 to be relatively displaceable in the axial direction. By combining them, the overall length is reduced when an axial impact force is applied.

The outer shaft 12 has a cylindrical shape as a whole, and a female serration 11 is formed on an inner peripheral surface at one end. The inner shaft 14 is formed in a cylindrical shape as a whole, and has a male serration 13 which is engaged with the female serration 11 on the inner peripheral surface of the outer shaft 12 on one end outer peripheral surface.

The female serrations 11 and the male serrations 13 are formed such that the tops of the peaks 11a and 13a enter the bottoms of the valleys 13b and 11b, similarly to general serrations. When the female serration 11 and the male serration 13 are engaged, gaps 20 and 21 are formed between the top and bottom.

Further, in the case of the shock-absorbing steering shaft 29 of the present embodiment, the height of the gap 21 is set at two positions axially separated from each other at the bottom of the valley 13 b of the male serration 13. Projections 22, 22 having a height H (h <H) slightly larger than the dimension (radial dimension) h are formed. When the male serrations 13 are inserted into the female serrations 11 in order to connect the outer shaft 12 and the inner shaft 14 to form a shock absorbing steering shaft 29, the respective projecting portions 22 and 22 The outer shaft 12 and the inner shaft 14 are prevented from being displaced from each other in the axial direction, and the shafts 12 and 14 are connected to each other. . In the case of this embodiment, the rear end surfaces of the protruding portions 22 and 22 (the rear end surface of the inner shaft 14 and the right end surface in FIG. 1) are inclined so that the shock absorbing steering shaft 29 is collapsed in its collapsed state. The plastic deformation of the top of the mountain portion 11a of the female serration 11 by the projections 22, 22 can be smoothly performed.

Further, at the base end (the left end in FIG. 1) of the male serration 13 on the outer peripheral surface of the inner shaft 14, a protrusion 23 having a larger height than the protrusions 22 is formed. ing. The projection 23 is normally exposed outside the outer shaft 12 (before the collision), but when the overall length of the shock absorbing steering shaft 29 is reduced due to the collision, the inner circumference of the outer shaft 12 is reduced. It engages with the crests 11a of the female serrations 11 on the surface to provide resistance to the reduction in the overall length of the shock absorbing steering shaft 29. As described above, since the male serration 13 in which the projections 22 and 23 are provided in a part of the valley 13b is formed by rolling, the manufacturing cost of the inner shaft 14 does not increase.

As described above, since the connection between the outer shaft 12 and the inner shaft 14 is performed by the protrusions 22, 22 formed integrally with the metal inner shaft 14, the joint portion has sufficient heat resistance, Depending on the operating conditions, the supporting capacity of the joint does not become insufficient. Further, since the protruding portions 22 are provided at two positions separated in the axial direction, the bending rigidity of the connecting portion between the outer shaft 12 and the inner shaft 14 is sufficiently ensured.

When a strong force is applied in the axial direction at the time of collision, each of the projections 22 and 22 plastically deforms the top of the peak 11 a of the female serration 11, and the outer shaft 12. And the inner shaft 14 is allowed to be relatively displaced, and the overall length of the shock absorbing steering shaft 29 is reduced. Further, at the time of a collapse caused by such a collision, immediately after each of the protrusions 22 starts to be displaced, the another protrusion 23 and the peak 11a engage to increase the collapse load. As a result, the impact force accompanying a collision accident can be effectively absorbed.

In the case of the shock-absorbing steering shaft 29 of the present embodiment, each of the projections 22 and 22 comes into contact with the top of the peak 11a only in a small area, so that the plastic deformation occurs. The force required to do so is relatively small. Therefore, the collapse load required to reduce the overall length of the shock absorbing steering shaft 29 is stabilized without increasing, and a large impact force is applied to the driver's body colliding with the steering wheel in the event of a collision. Can be effectively prevented. In addition, since the collapse load can be increased from the middle, it is easy to design to enhance the protection of the driver. That is, when the collapse load is increased, the maximum value (peak load) of the collapse load required to start the collapse tends to be large. In the case of the present invention, the protrusion 23 and the peak 11a are not connected to each other. However, since the engagement is performed after the start of the collapse, the peak load does not increase.

In addition, the collapse load changes the length L, and also the number (the number in the axial direction or the number in the circumferential direction), in addition to the height H of each of the protrusions 22, 22. It can be adjusted arbitrarily. In order to stabilize the collapse load, if necessary, before assembling the shock absorbing steering shaft 29 inside the steering column 3 (FIG. 5), the shock absorbing steering shaft 29 must be once suspended. The projections 22 may be moved on the top of the peak 11a by expanding and contracting.

When the collapse load is adjusted in the present embodiment, the height H, the length L, and the number of the projections 22 are changed. It can also be adjusted by changing the angle of inclination of the front end of the vehicle. The timing at which the collapse load increases after the start of the collapse is adjustable by changing the distance between the end of the female serration 11 and the front end surface of the projection 23.

[0024]

[Effect of the invention]

 Since the shock absorbing steering shaft of the present invention is constructed and operates as described above, the collapse load can be increased with an increase in the amount of collapse, and the safety of the driver in the event of a collision accident can be increased. Effectively secure.

[Brief description of the drawings]

FIG. 1 is a half vertical sectional side view showing an embodiment of the present invention.

FIG. 2 is a partially enlarged perspective view of a male serration.

FIG. 3 is a sectional view taken along line AA of FIG. 1;

FIG. 4 is a sectional view taken along the line BB in FIG.

FIG. 5 is a side view showing an example of a steering mechanism incorporating the shock absorbing steering shaft according to the present invention.

FIG. 6 is a vertical sectional side view showing a first example of a conventional structure.

FIG. 7 is a sectional view taken along line CC of FIG. 6;

FIG. 8 is a vertical sectional side view showing a second example of the conventional structure.

FIG. 9 is a sectional view taken along the line DD in FIG. 8;

FIG. 10 is a half vertical sectional side view showing a third example of the conventional structure.

FIG. 11 is a sectional view taken along line EE of FIG. 14;

[Description of Signs] 1 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 Female serration 11a Peak 11b Valley 12 Outer shaft 13 Male serration 13a Peak 13b Valley 14 Inner shaft 15 Depression 16 Space 17 Synthetic resin 18 Shock absorbing steering shaft 19 Through hole 20 Gap 21 Gap 22 Protrusion 23 Projection 24 Projection 25 Small diameter part 26 Steel ball 27 Crevice space 28 Through hole 29 Shock absorbing steering shaft

Claims (1)

[Utility model registration claims] 1. An inner shaft having a male serration formed on an outer peripheral surface thereof and an outer shaft having a female serration formed on an inner peripheral surface thereof. The inner shaft and the outer shaft are formed by engaging the male serration and the female serration. A shock absorber that combines a shaft and a shaft so as to freely transmit rotational force, and a shock absorber between the inner shaft and the outer shaft that allows the axial dimension to contract only when a large axial load is applied. In the type steering shaft, this shock absorbing part is
A part of the valley portion of the male serration, which does not normally engage with the female serration, and includes a protrusion fixed to a portion engaging with the male serration when the steering shaft contracts due to a collision accident. Wherein the projection is deformed by the engagement of the female serration with the ridge in accordance with the contraction of the shock-absorbing steering shaft. shaft.