JP3716590B2 - Method for manufacturing shock absorbing steering shaft - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing an impact absorbing steering shaft, and more particularly to a technique for preventing serrations when an inner shaft is press-fitted into an outer shaft.
[0002]
[Prior art]
When an automobile collides with another automobile or a building, the driver may have a secondary collision with the steering wheel due to inertia, and serious damage may be caused to the head and chest. In recent passenger cars and the like, an impact absorbing steering shaft and an impact absorbing steering column are widely used to prevent such a situation. The shock-absorbing steering shaft shortens the steering shaft on the steering wheel side when the driver makes a secondary collision. The steering shaft is divided into an outer shaft and an inner shaft, which can be slid together by serrations, etc. The one engaged with is generally used. In addition, the shock absorption type steering column is one in which the steering column falls off together with the steering shaft when the driver has a secondary collision, and a synthetic resin pin or the like is used at the joint with the body (usually the dashboard). In many cases, a pin breaks due to an impact load at the time of a secondary collision and the steering column falls off.
[0003]
In the above-described shock absorbing type steering shaft, it is necessary to prevent rattling between the outer shaft and the inner shaft in order to ensure steering feeling and steering rigidity during normal operation. Therefore, Japanese Laid-Open Patent Publication No. 2-286468 proposes a loosely serrated outer shaft and an inner shaft fixed with a synthetic resin, and Japanese Utility Model Laid-Open No. 1-58373 discloses an outer shaft side. There has been proposed a method in which a female serration and a male serration on the inner shaft side are formed to be an interference fit, and then both shafts are press-fitted.
[0004]
However, in the one described in Japanese Patent Laid-Open No. 2-286468, when a steering shaft is installed in a high-temperature engine room, the synthetic resin is deformed or transformed by heat, and the steering is performed in a relatively short period of time. There was a problem that the torsional rigidity of the shaft was lowered. In addition, in the one described in Japanese Utility Model Laid-Open No. 1-58373, there is no rattling between male serrations and female serrations, so it is very difficult to match the phases of both serrations when they are fitted. It was.
[0005]
In order to solve such a problem, the present inventors have invented a completely new method of manufacturing an impact absorbing steering shaft in the past, and this is disclosed in Japanese Patent Laid-Open No. 8-91230. The present invention, as detailed in the publication, males and reduced diameter portion distal of the outer shaft female serration is formed on the inner peripheral surface of the reduced diameter portion, the outer peripheral surface of the enlarged diameter portion mesh with the female serration a step of the enlarged tip of the inner shaft serration formed fitted over a predetermined size, and nipped the site is the fitting radially from the outside, said a reduced diameter portion distal of the outer shaft inner A step of simultaneously plastically deforming the tip of the enlarged diameter portion of the shaft, and a step of relatively moving the outer shaft and the inner shaft in a direction approaching each other within a range in which the reduced diameter portion and the enlarged diameter portion are not separated from each other. Is included.
[0006]
According to the present invention, the female serration and the male serration are formed so as to be loosely engaged with each other, so that the outer diameter of the outer shaft and the inner diameter of the inner shaft can be easily fitted to each other. Since the distal end of the diameter portion and the distal end of the enlarged diameter portion can be plastically processed into an oval shape or the like at the same time, man-hours and costs required for manufacturing can be significantly reduced as compared with the conventional apparatus. In addition, the shock absorbing steering shaft manufactured by this method can transmit the rotational force of the steering shaft without any trouble because the outer shaft and the inner shaft are engaged with each other at two plastic deformation portions with a strong frictional force. When a large collapse load is applied at the time of a collision, both plastic deformation portions fall into the inner shaft or the outer shaft, and the steering shaft is immediately shortened.
[0007]
[Problems to be solved by the invention]
By the way, also in the manufacturing method of the shock absorbing steering shaft described above, the following problems may occur in the process of relatively moving the outer shaft and the inner shaft. As shown in FIG. 11, the enlarged diameter portion 29 of the inner shaft 23 is chamfered 61 by cutting or the like at the tip, and a male serration 31 is formed on the outer peripheral surface by rolling or the like. However, since the male serration 31 is pressed in the radial direction to form a plastic deformed portion 35 having an oval shape or the like, the female serration 27 on the outer shaft 21 side is fitted in the same shape (perfect circle shape). No longer. That is, when the outer shaft 21 and the inner shaft 23 are relatively moved by a press-fitting method or the like, the outer shaft 21 and the female serration 27 formed on the inner peripheral surface thereof are elastic so as to fit the plastic deformation portion 35 of the male serration 31. Will be transformed.
[0008]
At this time, the leading end of the male serration 31 becomes a sharp edge 63 and bites into the female serration 27 as shown in FIG. (Hereinafter represented by galling) 65 is generated. Since the galling 65 is normally formed on the entire circumference of the female serration 27, it becomes a large resistance when the inner shaft 23 is press-fitted into the outer shaft 21, and the sliding resistance between the two serrations 27 and 31 after assembly. There is also a possibility that the impact absorption characteristics may be affected. If no galling 65 is generated, the female serration 27 and the male serration 31 are fitted relatively loosely at portions other than the plastic deformation portions 33 and 35, and the sliding resistance between the two serrations 27 and 31. Is almost negligible.
[0009]
The present invention has been made in view of the above situation, and an object of the present invention is to provide a method of manufacturing an impact-absorbing steering shaft that prevents galling of serration in the process of relatively moving the outer shaft and the inner shaft.
[0010]
[Means for Solving the Problems]
In the present invention, to solve the above problems, the male serration meshing and reduced diameter portion distal of the outer shaft female serration is formed on the inner peripheral surface of the reduced diameter portion, the female serration on the outer peripheral surface of the enlarged diameter portion is formed a step of fitting over a predetermined size and a enlarged tip of the inner shaft is, by nipped the site is the fitting radially from the outside, expansion of the the reduced diameter portion distal of the outer shaft inner shaft A step of simultaneously plastically deforming the distal end of the diameter portion, and a step of relatively moving the outer shaft and the inner shaft in a direction approaching each other within a range in which the reduced diameter portion and the enlarged diameter portion are not separated from each other. The present invention proposes a method of manufacturing an impact-absorbing steering shaft in which the male serration is narrowed at the tip of the enlarged diameter portion.
[0011]
According to the present invention, since the male serration is constricted at the distal end of the enlarged diameter portion even after undergoing a step of plastically deforming the distal end of the enlarged diameter portion of the inner shaft by pinching the fitting portion in the radial direction from the outside, The end portion of the inner surface does not become an edge, and the female serration is not galling in the process of relatively moving the outer shaft and the inner shaft in a direction approaching each other.
[0012]
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 a steering device. In FIG. 1, reference numeral 1 denotes an impact absorption type (drop-off type) steering column. The steering column 1 is fixed to a bracket 3 on the vehicle body side with a resin pin or the like, and rotatably supports an upper steering shaft (hereinafter simply referred to as a steering shaft) 5 via a bearing (not shown). A steering wheel 7 is attached to the upper end of the steering shaft 5, while a lower steering shaft 11 is connected to the lower end via a universal joint 9. In the figure, 13 is a column cover that covers the top of the steering column 1, and 15 is a dashboard that partitions the vehicle compartment and the engine compartment.
[0013]
In this steering apparatus, when the driver rotates the steering wheel 7, the rotational force is transmitted to a steering gear (not shown) via the steering shaft 5 and the lower steering shaft 11. 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. In addition to the rack and pinion type, various types of steering gears such as a ball screw type and a worm roller type are known.
[0014]
FIG. 2 is a longitudinal sectional view showing a main part of the steering shaft 5 according to one embodiment of the present invention. The steering shaft 5 of this embodiment is obtained by serration coupling a cylindrical outer shaft 21 and a cylindrical inner shaft 23. The outer shaft 21 has a reduced diameter portion 25 having a smaller diameter at the connecting portion with the inner shaft 23 than other portions, and a female serration 27 is formed on the inner peripheral surface of the reduced diameter portion 25 by broaching. In addition, the inner shaft 23 has a large-diameter enlarged portion 29 where the coupling portion with the outer shaft 21 is larger than other portions, and a male serration 31 is formed on the outer peripheral surface of the enlarged-diameter portion 29 by rolling. ing.
[0015]
The diameter-reduced portion 25 of the outer shaft 21 is formed with an oval plastic deformation portion 33 at the tip thereof. In the plastic deformation portion 33, the inner shaft 23 is moved by the outer shaft 21 as shown in FIG. The female serration 27 and the male serration 31 are in contact with each other with a strong pressing force when pressed from the left-right direction in the figure. In addition, an elliptical plastic deformation portion 35 is formed at the tip of the enlarged diameter portion 29 of the inner shaft 23. In the plastic deformation portion 35, the outer shaft 21 is connected to the inner shaft as shown in FIG. 23, the female serration 27 and the male serration 31 are in contact with each other with a strong pressing force. Thereby, the outer shaft 21 and the inner shaft 23 are integrated by a strong frictional coupling force, and the torsional rigidity is kept high. Both serrations 27 and 31 are fitted relatively loosely at portions other than both plastic deformation portions 33 and 35.
[0016]
Since the steering shaft 5 of the present embodiment has a high coupling rigidity between the outer shaft 21 and the inner shaft 23, the feeling and rigidity when the driver steers the steering wheel 7 are substantially the same as those of the integrated type. Kept. Further, since synthetic resin or the like is not used for the connection between the outer shaft 21 and the inner shaft 23, there is no possibility that the durability of the connection portion is lowered even if high heat of the engine room is transmitted to the steering shaft 5.
[0017]
On the other hand, when the driver collides with the steering wheel 7 due to the collision of the vehicle and a predetermined collapse load acts on the steering shaft 5, the friction coupling force is overcome and the outer shaft 21 and the inner shaft 23 are overcome. The connection in both plastic deformation portions 33 and 35 is released. Then, since both serrations 27 and 31 are fitted relatively loosely at portions other than the both plastic deformation portions 33 and 35, the outer shaft 21 and the inner shaft 23 are quickly shortened, and the driver can make the head and chest. To prevent serious damage.
[0018]
Next, a method for manufacturing the steering shaft 5 will be described.
Prior to the coupling with the outer shaft 21, the male shaft 31 is formed on the outer peripheral surface of the enlarged diameter portion 29 on the inner shaft 23. In this embodiment, however, the end surface of the enlarged diameter portion 29 is not chamfered. . That is, as shown in FIG. 5, the inner shaft 23 is set in a rolling device (not shown) while the end of the enlarged diameter portion 29 is made into a complete cylindrical shape, and is brought into rolling contact with the rolling tool 41 so as to have male serrations. 31 is formed. Thereby, in the front-end | tip part of the enlarged diameter part 29, as shown in FIG. 6 (A part enlarged view in FIG. 5), it is extruded by the rolling tool 41, and a raw material is the front-end | tip direction (in FIG. 5, FIG. 6, The curled portion 45 is formed in such a manner that the straight portion 43 is smoothly constricted at the tip of the male serration 31. Thereafter, a hollow portion 47 is drilled on the tip side of the inner shaft 23.
[0019]
As shown in FIG. 7 and FIG. 8 (BB enlarged cross-sectional view in FIG. 7), the inner shaft 23 that has been molded is fitted with the distal ends of the reduced diameter portion 25 and the enlarged diameter portion 29, and is female. In a state where the serrations 27 and the male serrations 31 are engaged with each other, they are set together with the outer shaft 21 in a pressing device (not shown), and are pressed from the left and right directions in FIG. The press tools 51 and 53 are initially facing each other with a distance δ, but are opposed to each other by being pressed by a hydraulic piston or the like (not shown), and at the same time, the tips of the reduced diameter portion 25 and the enlarged diameter portion 29. Are plastically deformed into an oval shape, whereby both plastically deformed portions 33 and 35 are formed. Moreover, you may make it press with predetermined force, without making the opposing surfaces of both the press tools 51 and 53 contact | abut. At this time, in this embodiment, since the hollow portion 47 is formed on the distal end side of the inner shaft 23, the pressing force applied to the press tools 51 and 53 may be relatively small. The press tools 51 and 53 are each formed with an arcuate recess 55 for smooth positioning and plastic deformation of the outer shaft 21 during setting.
[0020]
When the plastic deformation portions 33 and 35 are formed on the outer shaft 21 and the inner shaft 23 in this way, the outer shaft 21 and the inner shaft 23 can be obtained by using a press-fitting device or the like as shown in FIG. Are moved relative to each other in a direction approaching each other. At this time, the reduced diameter portion 25 and the enlarged diameter portion 29 excluding the both plastic deformation portions 33 and 35 are elastically deformed as the plastic deformation portions 33 and 35 pass, but unlike the conventional apparatus, the reduced diameter portion 25 There is no galling in the female serration 27. That is, since the male serration 31 on the side of the enlarged diameter portion 29 is formed with a curled portion 45 that smoothly squeezes from the straight portion 43 as shown in FIG. 10 (enlarged view of C portion in FIG. 9). The female serration 27 is elastically deformed in a gradually expanded form, and no galling occurs. As a result, the resistance when the outer shaft 21 and the inner shaft 23 are moved relative to each other is reduced, and the sliding between the female serration 27 and the male serration 31 is removed at the portion excluding the both plastic deformation portions 33 and 35 after assembly. There is almost no dynamic resistance, and stable shock absorbing characteristics can be obtained.
[0021]
The relative movement between the outer shaft 21 and the inner shaft 23 is such that the distal end of the plastic deformation portion 33 on the reduced diameter portion 25 side reaches the proximal end of the enlarged diameter portion 29 and at the same time the distal end of the plastic deformation portion 35 on the enlarged diameter portion 29 side. The process is performed until the base end of the reduced diameter portion 25 is reached, whereby the state shown in FIG. 2 is obtained and the manufacture of the steering shaft 5 is completed.
[0022]
Although description of specific embodiment is finished above, the aspect of the present invention is not limited to the above embodiment. The specific configuration of the outer shaft and the inner shaft, the specific shape of the plastic deformation portion, and the like can be changed as appropriate without departing from the gist of the present invention.
[0023]
【The invention's effect】
As described above, according to the shock absorbing steering shaft manufacturing method of the present invention, the outer diameter of the outer diameter portion of the outer shaft in which the female serration is formed on the inner peripheral surface of the diameter reduction portion, and the outer circumference of the diameter expansion portion. a step of the enlarged tip of the inner shaft male serration is formed which meshes with the female serration on a surface fitted over a predetermined size, and nipped the site is the fitting radially from the outside, the outer shaft A step of simultaneously plastically deforming the distal end of the reduced diameter portion and the distal end of the enlarged diameter portion of the inner shaft, and the outer shaft and the inner shaft in a range in which the reduced diameter portion and the enlarged diameter portion are not separated from each other. The male serration is constricted at the distal end of the enlarged diameter portion, and the fitting portion is clamped in the radial direction from the outside. Even after the step of plastically deforming the tip of the enlarged diameter portion of the shaft, the end portion of the male serration does not become an edge, and the female serration is galling in the step of moving the outer shaft and the inner shaft relatively close to each other. Thus, the pressing force when the outer shaft and the inner shaft are moved relative to each other can be reduced, and a stable shock absorbing characteristic can be obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a structure of a steering device on a vehicle compartment side.
FIG. 2 is a longitudinal sectional view showing a main part of an impact absorption type steering shaft according to an embodiment of the present invention.
FIG. 3 is a longitudinal sectional view of a steering shaft at a plastic deformation portion on the outer shaft side.
FIG. 4 is a longitudinal sectional view of a steering shaft at a plastic deformation portion on the inner shaft side.
FIG. 5 is an explanatory view showing a state where male serrations are formed on the inner shaft.
6 is an enlarged view of a portion A in FIG.
FIG. 7 is an explanatory view showing a state in which a plastically deformed portion is formed on the outer shaft and the inner shaft.
8 is an enlarged cross-sectional view taken along the line BB in FIG.
FIG. 9 is a longitudinal sectional view showing a relative movement process between the outer shaft and the inner shaft in the embodiment.
10 is an enlarged view of a portion C in FIG. 9. FIG.
FIG. 11 is a longitudinal sectional view showing a relative movement process between an outer shaft and an inner shaft in a conventional apparatus.
12 is an enlarged view of a portion D in FIG.
[Explanation of symbols]
5. Steering shaft 21 ... Outer shaft 23 ... Inner shaft 25 ... Reduced diameter part 27 ... Female serration 29 ... Expanded diameter part 31 ... Male serrations 33 and 35 ... Plastic deformation part 45 ... Curled part

Claims (1)

A reduced diameter portion distal of the outer shaft female serration on the inner peripheral surface is formed of a reduced diameter portion, and a diameter tip of the inner shaft male serration is formed which meshes with the female serration on the outer peripheral surface of the enlarged diameter portion Mating over a predetermined dimension;
And nipped the site is the fitting radially from the outside, a step of simultaneously plastically deformed and enlarged tip of the reduced diameter portion tip and the inner shaft of the outer shaft,
A step of relatively moving the outer shaft and the inner shaft in a direction approaching each other within a range in which the reduced diameter portion and the enlarged diameter portion are not separated from each other, and the male serration is constricted at the distal end of the enlarged diameter portion. A method for manufacturing an impact-absorbing steering shaft, characterized by being trapped.

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