JP4188713B2 - Shock absorbing steering shaft - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an impact absorption type steering shaft employed in an impact absorption type steering device, and more particularly to a technique for realizing effective absorption of impact energy with a relatively simple configuration.
[0002]
[Prior art]
When an automobile collides with another automobile, a building, or the like, there is a possibility that the cross member holding the steering gear moves backward and the steering shaft enters the vehicle interior. Therefore, in recent automobiles, in order to prevent such a situation, an impact absorption type steering device is widely adopted. The shock-absorbing steering system is a mechanism in which the steering shaft, etc., collapses while absorbing the impact energy. The steering shaft is divided into an outer shaft and an inner shaft, and both shafts can be slid by serration or the like. Combined ones are common. Usually, an impact absorbing mechanism that resists collapse is provided between the outer shaft and the inner shaft. When an axial load exceeding a predetermined value is applied, the steering shaft collapses and absorbs energy at that time. Impact energy is absorbed by the means.
[0003]
As an impact energy absorption method in the impact absorption type steering shaft, the outer shaft and the inner shaft are spline-engaged and the ends of both shafts are plastically deformed into an elliptical shape so that predetermined impact energy is absorbed in the initial stage of the collapse. A thing (for example, refer patent document 1) etc. which formed a part of steering shaft by the bellows of a thin steel plate, and plastically deforms this bellows at the time of collapse etc. are proposed.
[0004]
[Patent Document 1]
JP-A-8-91230 (4th and 5th pages, FIGS. 1 to 7)
[Patent Document 2]
JP-A-9-150747 (5th and 6th pages, FIGS. 1 to 11)
[0005]
[Problems to be solved by the invention]
The conventional shock absorbing steering shaft described above has the following problems. For example, in the one described in Patent Document 1, for example, a comparatively large press device is required to plastically deform an outer shaft with an outer shaft fitted on the outer shaft. However, the outer shaft and the inner after plastic deformation are required. In order to move the shaft relative to each other, the press-fitting device needs to have a high output, and there is a problem that the equipment cost increases. Moreover, in what was described in patent document 2, since a bellows is formed by carrying out a bulge or spinning process to a comparatively thin steel plate etc., an installation cost also rises and it is difficult to ensure the rigidity of a steering shaft. There was a problem such as.
[0006]
The present invention has been made in view of the above situation, and an object thereof is to provide an impact absorption type steering shaft that realizes effective absorption of impact energy with a relatively simple configuration.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, in the invention of claim 1, an outer shaft, an inner shaft fitted in the outer shaft so as to be slidable in the axial direction, an annular flange, and an inner periphery of the flange from one side to the other side. comprising a plurality of prongs that extend in the form of projecting, in the impact absorbing type steering shaft having a push nut which is fitted, press fitted to the inner shaft, the push nut, a predetermined distance in an end face of the outer shaft The other side is opposed in the axial direction by α, and the prongs extend from the inner periphery of the flange toward the inner shaft, and press contact engagement with the inner shaft at its inner edge and, and solves the engagement with the inner shaft and the prongs collide with the outer shaft the prong during collapse Proposes that the diameter of the contact portion between the prongs of the outer shaft is set smaller than the inner diameter of the flange.
[0008]
According to the invention of claim 1, when the inner shaft enters the outer shaft, the end surface of the outer shaft collides with the prong of the push nut, and the engagement between the prong and the inner shaft is released while absorbing the impact energy. . At this time, by appropriately setting the end face shape of the outer shaft, the amount of shock energy absorbed and the form of absorption change.
[0009]
According to a second aspect of the present invention, there is proposed the shock absorbing steering shaft according to the first aspect, wherein the outer shaft collides with the plurality of prongs stepwise as the collapse progresses.
[0010]
According to the invention of claim 2, when the outer shaft collides with a part of the prong of the push nut and disengages the inner shaft, the remaining prong forms an engagement mark on the surface of the inner shaft. It absorbs impact energy by moving relative to the inner shaft.
[0011]
According to a third aspect of the invention, in the shock absorbing steering shaft according to the first or second aspect, at the time of the collapse, at least one of the outer shaft and the inner shaft is at least one of friction, elastic deformation, and plastic deformation. We propose something that moves relative to each other.
[0012]
According to the invention of claim 3, impact energy is absorbed when the inner shaft enters the outer shaft with the collapse of the steering shaft.
[0013]
According to a fourth aspect of the present invention, in the shock absorbing steering shaft according to the first to third aspects, an energy absorbing means for absorbing the collapse energy by plastic deformation of a metal member is provided between the outer shaft and the inner shaft. Suggest something.
[0014]
According to the fourth aspect of the present invention, since the impact energy is absorbed by both the push nut and the energy absorbing means, it is possible to variously set the amount and form of absorption of the impact energy.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a side view showing a passenger compartment side portion of an impact absorbing electric power steering apparatus according to the present invention, and reference numeral 1 in FIG. 1 denotes a steering column. The steering column 1 is fixed to a cross member 7 that is a vehicle body structural member via a tilt mechanism 3 and a pivot pin 5. A steering upper shaft 11 serving as a first steering shaft is rotatably supported in the steering column 1 and an electric assist mechanism 13 is integrated at the tip.
[0016]
A steering wheel 15 is attached to the rear end of the steering upper shaft 11. When the driver rotates the steering wheel 15, the rotational force is increased by the electric assist mechanism 13, and then via the output shaft 17. It is transmitted to the steering intermediate shaft 19 and further transmitted to the steering gear via a steering lower shaft (not shown).
[0017]
In this steering device, when the driver rotates the steering wheel 15, the rotational force is transmitted to a steering gear (not shown) via the steering upper shaft 11, the steering intermediate shaft 19 and the like. The steering gear incorporates a rack and pinion mechanism or the like that converts rotational input into linear motion, and steering is performed by changing the steering angle of the wheel via a tie rod or the like.
[0018]
FIG. 2 is a longitudinal sectional view showing a steering intermediate shaft (hereinafter simply referred to as a steering shaft) according to the first embodiment of the present invention. The steering shaft 19 of the present embodiment is obtained by serration coupling a cylindrical outer shaft 21 and a columnar inner shaft 23. In the present embodiment, the outer shaft 21 is connected to the electric assist mechanism 13 side and the inner shaft 23 is connected to the steering lower shaft side. However, even if the positional relationship between the outer shaft 21 and the inner shaft 23 is reversed. Good.
[0019]
In the case of this embodiment, as shown in FIG. 3 (enlarged sectional view of A part in FIG. 2), a push nut 25 is externally fitted and press-fitted into the inner shaft 23. As shown in FIG. 4 (front view) and FIG. 5 (side view), the push nut 25 has an annular flange 27 and one side from the inner periphery of the flange 27 (surface: that is, the left side in FIG. 3). is formed from extending been six prongs 29. in the form of projecting, the back surface of the prongs 29 (right side in FIG. 3) is confronted with a predetermined distance α to the end 31 of the outer shaft 21 Yes. Further, the outer shaft 21 is formed in a tapered shape whose diameter decreases toward the end portion 31 side, and the end portion diameter Do is set smaller than the inner diameter Df of the flange. In the present embodiment, the number of prongs 29 is 6. However, it may be 5 or less, or 7 or more.
[0020]
The operation of the first embodiment will be described below.
When the vehicle collides with another automobile or a road structure and the cross member holding the steering gear moves backward, a large axial load acts on the steering shaft 19 via the steering lower shaft. Then, the inner shaft 23 enters the outer shaft 21 with a relatively small resistance, and the end portion 31 of the outer shaft 21 collides with the prongs 29 of the push nut 25 when the steering shaft 19 collapses by the length α. As a result, the prongs 29 of the push nut 25 are expanded by the outer shaft 21 as shown in FIG. 6, and the engagement with the inner shaft 23 is released.
[0021]
At this time, since the prong 29 is engaged with the inner shaft 23 with a predetermined engagement force, the outer shaft 21 receives a predetermined reaction force when the prong 29 is expanded, and FIG. 7 shows the relationship between the collapse stroke S and the collapse load F. As shown, the impact energy is absorbed. As shown in FIG. 8, since the fulcrum P at which the prong 29 bends is the inner peripheral surface of the flange 27, when the end diameter Do of the outer shaft 21 is close to the inner diameter Df of the flange, the collapse load F1 is large. Thus, when the end diameter Do ′ of the outer shaft 21 is significantly smaller than the inner diameter Df of the flange, the collapse load F2 becomes small.
[0022]
When the engagement between the prong 29 and the inner shaft 23 is released, the inner shaft 23 enters the outer shaft 21 with a relatively small resistance, but other energy absorbing means is provided between the outer shaft 21 and the inner shaft 23. 9, as shown in FIG. 9, the relationship between the collapse stroke S and the collapse load F, the impact energy is absorbed by combining both the push nut 25 and other energy absorbing means. Become.
[0023]
FIG. 10 is a longitudinal sectional view showing a main part of the steering shaft according to the second embodiment. The overall configuration of this embodiment is substantially the same as that of the first embodiment described above, but the shape of the end portion 31 of the outer shaft 21 is different. That is, in the second embodiment, of the end portion 31 of the outer shaft 21, the portion 31a shown in the upper part of the figure faces the half of the prongs 29 with a distance α, and the portion 31b shown in the lower part is larger than α It is facing the other half of the prongs 29 with β.
[0024]
In the case of the second embodiment, when the inner shaft 23 enters the outer shaft 21 due to the secondary collision of the driver with the steering wheel 7, the end 31 of the outer shaft 21 collides with the length α of the steering shaft 19. At the stage, it collides with half of the prongs 29 of the push nut 25 and pushes them apart, and when the steering shaft 19 collides with the length β, it collides with the other half of the prongs 29 of the push nut 25 and pushes them apart.
[0025]
In this embodiment, since the half prongs 29 are in elastic contact with the inner shaft 23 until the inner shaft 23 reaches the distance α, the sliding resistance between the prong 29 and the inner shaft 23 is very large. Become. As a result, as shown in FIG. 11, the relationship between the collapse stroke S and the collapse load F, the total absorbed amount of impact energy is larger than that of the first embodiment. Incidentally, the prongs 29 with which the end portion 31 of the outer shaft 21 collides when the steering shaft 19 is collapsed by the length α may be arranged one by one as shown by the symbol B in FIG. As shown, three adjacent sheets may be used. In the former case, the collapse load F is relatively small, and in the latter case, the collapse load F is relatively large.
[0026]
FIG. 13 is a longitudinal sectional view showing a main part of the steering shaft according to the third embodiment. The overall configuration of the present embodiment is also substantially the same as that of the first embodiment described above, but instead of making the end portion 31 of the outer shaft 21 tapered, a projecting piece that opposes the end portion 31 of the outer shaft 21 with a distance α. 33 protrudes from the prong 29. In the present embodiment, when the inner shaft 23 enters the outer shaft 21 by the distance α, the projecting piece 33 of the prong 29 collides with the end portion 31 of the outer shaft 21, and the prong 29 is expanded as in the first embodiment. The operation of this embodiment is the same as that of the first embodiment.
[0027]
FIG. 14 is a longitudinal sectional view showing a main part of the steering shaft according to the fourth embodiment. The overall configuration of the present embodiment is substantially the same as that of the third embodiment described above, but the length of the projecting piece projecting from the prong 29 is not uniform. That is, in FIG. 14, the upper protruding piece 33 faces the end portion 31 of the outer shaft 21 with a distance α, and the lower protruding piece 35 faces the end portion 31 of the outer shaft 21 with a distance β. In the case of the present embodiment, as in the second embodiment described above, the projecting piece 33 collides with the end portion 31 of the outer shaft 21 when the steering shaft 19 collapses by the length α, for example, half of the prongs 29 are pushed. When the steering shaft 19 is collapsed by the length β, the projecting piece 35 collides with the end portion 31 of the outer shaft 21 and the remaining half of the prongs 29 are expanded. The operation of this embodiment is the same as that of the second embodiment.
[0028]
FIG. 15 is a longitudinal sectional view showing a main part of a steering shaft according to the fifth embodiment. In this embodiment, the outer shaft 21 and the inner shaft 23 are in serration engagement with a predetermined engagement force. As an energy absorbing means, a bellows 41 formed by forming a steel plate or the like is fixed to the back side of the push nut 25, while a large diameter portion 43 is formed on the outer shaft 21. In the case of this embodiment, the bellows 41 faces the large diameter portion 43 with a distance α, and the end portion 31 of the outer shaft 21 faces the prong 29 with a distance β larger than α.
[0029]
In the case of the fifth embodiment, when the steering shaft 19 starts to collapse, first, the outer shaft 21 and the inner shaft 23 are frictionally slid to start absorbing impact energy. Then, when the steering shaft 19 is collapsed by the length α, the bellows 41 collides with the large diameter portion 43, and the bellows 41 absorbs impact energy while being compressed and deformed. Then, when the steering shaft 19 is collapsed by the length β, the end portion 31 of the outer shaft 21 collides with the prong 29 of the push nut 25, and the prong 29 is expanded by the outer shaft 21 to be engaged with the inner shaft 23. It will be solved. FIG. 16 is a graph showing the relationship between the collapse stroke S and the collapse load F in the fifth embodiment.
[0030]
FIG. 17 is a longitudinal sectional view showing a main part of a steering shaft according to the sixth embodiment. The overall configuration of the present embodiment is substantially the same as that of the fifth embodiment described above, but the bellows 41 is opposed to an annular protrusion 45 formed on the inner peripheral surface of the steering column 1 or the like. In the case of the present embodiment, the bellows 41 collides with the annular protrusion 45 when the steering shaft 19 is collapsed by the length α, and the bellows 41 absorbs impact energy while being compressed and deformed. When the steering shaft 19 is collapsed by the length β, the end 31 of the outer shaft 21 collides with the prong 29 of the push nut 25, and the prong 29 is expanded by the outer shaft 21 to engage with the inner shaft 23. Is solved. The operation of this embodiment is the same as that of the fifth embodiment.
[0031]
FIG. 18 is a longitudinal sectional view showing a main part of a steering shaft according to the seventh embodiment. In the present embodiment, the outer shaft 21 and the inner shaft 23 are serrated and engaged with a predetermined engaging force, and the impact energy absorbing cylinder 51 is serrated and engaged with the outer shaft 21 with a predetermined engaging force. The impact energy absorbing cylinder 51 has a diameter corresponding to the flange 27 of the push nut 25 and faces the flange 27 with a distance α. Further, the end 31 of the outer shaft 21 faces the prong 29 with a distance β larger than α.
[0032]
In the case of the seventh embodiment, when the steering shaft 19 starts to collapse, first, the outer shaft 21 and the inner shaft 23 are frictionally slid to start absorbing impact energy. Next, the impact energy absorbing cylinder 51 collides with the flange 27 of the push nut 25 when the steering shaft 19 is collapsed by the length α. In this state, since the prongs 29 of the push nut 25 are engaged with the inner shaft 23, the impact energy absorbing cylinder 51 moves relative to the outer shaft 21, and impact energy is generated by frictional sliding between the two. Is absorbed. Next, when the steering shaft 19 is collapsed by the length β, the end portion 31 of the outer shaft 21 collides with the prong 29 of the push nut 25, and the prong 29 is expanded by the outer shaft 21 to be engaged with the inner shaft 23. The match is solved. FIG. 19 is a graph showing the relationship between the collapse stroke S and the collapse load F in the seventh embodiment.
[0033]
FIG. 20 is a longitudinal sectional view showing a main part of a steering shaft according to the eighth embodiment. In the present embodiment, the outer shaft 21 and the inner shaft 23 are serrated and engaged with a predetermined engagement force, and the ironing piece 61 formed by forming a steel plate or the like on the outer periphery of the push nut 25 is fixed as energy absorbing means. Furthermore, an ironing pin 63 for ironing the ironing piece 61 on the vehicle body side member or the steering column 1 is provided. The end 31 of the outer shaft 21 faces the prong 29 with a distance α.
[0034]
In the case of the eighth embodiment, when the steering shaft 19 starts to collapse, first, the outer shaft 21 and the inner shaft 23 frictionally slide, and at the same time, the squeezing piece 61 starts to be squeezed by the squeezing pin 63, and the impact energy is thereby reduced. Absorbed. Next, when the steering shaft 19 is collapsed by the length α, the end 31 of the outer shaft 21 collides with the prong 29 of the push nut 25, and the prong 29 is expanded by the outer shaft 21 to absorb impact energy. Accordingly, the engagement between the push nut 25 and the inner shaft 23 is released. When the engagement between the push nut 25 and the inner shaft 23 is released, the ironing of the ironing piece 61 by the ironing pin 63 stops. FIG. 21 is a graph showing the relationship between the collapse stroke S and the collapse load F in the eighth embodiment.
[0035]
Although description of specific embodiment is finished above, the aspect of the present invention is not limited to the above embodiment. For example, in the first embodiment and the like, the end portion of the outer shaft is tapered, but may be stepped as shown in FIG. 22, and in this case, the same operation and effect can be obtained. Moreover, although the said embodiment applies this invention to a steering intermediate shaft, you may apply to a steering upper shaft. Further, the outer shaft, the inner shaft, and the outer shaft may be moved relative to each other with elastic deformation or plastic deformation, and energy absorbing means provided between the inner shaft and the bellows or the ironing piece is adopted. You may make it do. In addition, the specific configuration of the steering device, the specific shape of the push nut, and the like can be changed as appropriate without departing from the gist of the present invention.
[0036]
【The invention's effect】
As described above, according to the shock absorbing steering shaft of the present invention, the outer shaft, the inner shaft that is fitted in the outer shaft so as to be axially slidable, the annular flange, and the inner periphery of the flange comprising one plurality of prongs that extend in the form of protruding to the side from, in the impact absorbing type steering shaft having a push nut which is fitted, press fitted to the inner shaft, the push nut, the outer shaft The other end faces the end surface of the flange and is opposed to the other side in the axial direction. The prongs extend from the inner peripheral portion of the flange toward the inner shaft, and the inner edge pressure engaged with the shaft, and wherein with the prongs in said outer shaft upon collapse impinge upon the prongs Since the diameter of the contact portion of the outer shaft with the prong is set to be smaller than the inner diameter of the flange in order to release the engagement with the shaft, when the inner shaft enters the outer shaft, the end surface of the outer shaft Collides with the prong of the push nut, and the engagement between the prong and the inner shaft is released while absorbing the impact energy. At this time, the amount of shock energy absorbed and the form of absorption can be changed by appropriately setting the end face shape of the outer shaft.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a structure of a steering device according to the present invention on a vehicle compartment side.
FIG. 2 is a side view showing the steering shaft according to the first embodiment.
FIG. 3 is an enlarged cross-sectional view of a part A in FIG.
FIG. 4 is a front view of a push nut.
FIG. 5 is a side view of the push nut.
FIG. 6 is an explanatory diagram showing the operation of the first embodiment.
FIG. 7 is a diagram showing a relationship between a collapse stroke and a collapse load in the first embodiment.
FIG. 8 is a diagram showing a relationship between an end shaft diameter of an outer shaft and a collapse load.
FIG. 9 is a diagram showing a relationship between a collapse stroke and a collapse load in the first embodiment.
FIG. 10 is a longitudinal sectional view showing a main part of a steering shaft according to a second embodiment.
FIG. 11 is a diagram showing a relationship between a collapse stroke and a collapse load in the second embodiment.
FIG. 12 is a view showing a prong that an outer shaft collides first in the second embodiment.
FIG. 13 is a longitudinal sectional view showing a main part of a steering shaft according to a third embodiment.
FIG. 14 is a longitudinal sectional view showing a main part of a steering shaft according to a fourth embodiment.
FIG. 15 is a longitudinal sectional view showing a main part of a steering shaft according to a fifth embodiment.
FIG. 16 is a view showing a relationship between a collapse stroke and a collapse load in the fifth embodiment. FIG. 17 is a longitudinal sectional view showing a main part of the steering shaft according to the sixth embodiment.
FIG. 18 is a longitudinal sectional view showing a main part of a steering shaft according to a seventh embodiment.
FIG. 19 is a view showing the relationship between the collapse stroke and the collapse load in the seventh embodiment. FIG. 20 is a longitudinal sectional view showing the main part of the steering shaft according to the eighth embodiment.
FIG. 21 is a diagram showing a relationship between a collapse stroke and a collapse load in the eighth embodiment.
FIG. 22 is a view showing a modification of the end portion of the outer shaft.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Steering shaft 19 ... Steering intermediate shaft 21 ... Outer shaft 23 ... Inner shaft 25 ... Push nut 27 ... Flange 29 ... Prong 31 ... End part of outer shaft 33, 35 ... Projection piece 41 ... Bellows 43 ... Large diameter of outer shaft Portion 45 ... Annular projection 51 ... Impact energy absorption cylinder 61 ... Ironing piece 63 ... Ironing pin Do ... Outer shaft end diameter Df ... Flange inner diameter

Claims (4)

An outer shaft,
An inner shaft fitted in the outer shaft so as to be axially slidable;
Comprising a plurality of prongs that extend in the form projecting from the inner circumference on one side of the annular flange and the flange, in the impact absorbing type steering shaft having a push nut which is fitted, pressed into the inner shaft ,
The push nut is
The other side of the outer shaft is opposed to the end surface of the outer shaft spaced apart in the axial direction by a predetermined distance α ,
The prongs extend from the inner periphery of the flange toward the inner shaft, and press contact with the inner shaft at the inner edge;
In addition, the diameter of the abutment portion of the outer shaft with the prong is set smaller than the inner diameter of the flange so that the outer shaft collides with the prong at the time of collapse to disengage the prong from the inner shaft. A shock-absorbing steering shaft characterized by that.   The shock absorbing steering shaft according to claim 1, wherein the outer shaft collides with the plurality of prongs stepwise as the collapse progresses.   The shock absorption according to claim 1 or 2, wherein at the time of the collapse, at least one of the outer shaft and the inner shaft relatively moves with at least one of friction, elastic deformation, and plastic deformation. Type steering shaft.   The impact absorption according to any one of claims 1 to 3, further comprising energy absorbing means for absorbing collapse energy by plastic deformation of a metal member between the outer shaft and the inner shaft. Type steering shaft.

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