JPH11169973A - Manufacture of impact absorption type steering shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of an impact absorption type steering shaft, in which galling of a serration is prevented in the process for relatively shifting an outer shaft and an inner shaft. SOLUTION: Previous to combination with the outer shaft, in the inner shaft 23, a male serration 31 is formed on the outer peripheral surface of an enlarged diameter part 29, but at this time, a chamfer is not applied on the end surface of the enlarged diameter part 29. That is, under condition of forming the end part of the enlarged diameter part 29 to the perfect cylindrical shape, the inner shaft 23 is set in a roll forming device to form the male serration 31 while roll contacting with a roll-forming tool 41. In this way, at the tip part of the enlarged diameter part 29, a blank is shifted in the tip direction by pushed out with the roll-forming tool 41 and a curl part whose shape is smoothly shrunk, is formed at the tip part of the male serration 31. Further, in this way, the galling on a female serration at the outer shaft side is not developed and such effect that resistance is reduced at the time of relatively shifting the outer shaft and the inner shaft 23, is brought about.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a shock-absorbing steering shaft, and more particularly to a technique for preventing serration when an inner shaft is press-fitted into an outer shaft.

[0002]

2. Description of the Related Art When a vehicle collides with another vehicle, a building, or the like, the driver collides with the steering wheel due to inertia, which may cause serious damage to the head and chest. In recent years, in order to prevent such situations in passenger cars,
Shock-absorbing steering shafts and shock-absorbing steering columns are widely used. The shock-absorbing steering shaft shortens the steering shaft on the steering wheel side in the event of a secondary collision by the driver. The steering shaft is divided into an outer shaft and an inner shaft, and these can be slid mutually by serrations etc. Is generally engaged. The shock-absorbing steering column is a type in which the steering column falls off together with the steering shaft when the driver makes 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, the pins are broken due to the impact load at the time of the secondary collision and the steering column is dropped.

In the shock absorbing steering shaft of the type described above, it is necessary to prevent rattling between the outer shaft and the inner shaft in order to secure the steering feeling and the steering rigidity during normal operation. Japanese Patent Application Laid-Open No. Hei 2-286468 proposes an outer shaft and an inner shaft which are loosely serrated and fixed to each other with a synthetic resin. Japanese Utility Model Laid-Open Publication No. 1-58373 discloses an outer shaft side. A method has been proposed in which a female serration and a male serration on the inner shaft side are formed so as to be tightly fitted, and then both shafts are press-fitted.

[0004] However, according to the technique disclosed in Japanese Patent Application Laid-Open No. 2-286468, when a steering shaft is installed in an engine room where the temperature is high, synthetic resin is deformed or denatured by heat, so that a relatively short time is required. There was a problem that the torsional rigidity of the steering shaft was reduced. Further, according to Japanese Unexamined Utility Model Publication No. 1-58373, since there is no play between the male serration and the female serration, it is very difficult to match the phases of both serrations at the time of fitting. Was.

[0005] In order to solve such a problem,
The present inventors have previously invented a completely novel method of manufacturing a shock-absorbing steering shaft, which has been disclosed in Japanese Unexamined Patent Publication No. 8-91.
No. 230 is disclosed. As described in detail in the publication, the present invention relates to a male shaft that meshes with the female serration on the outer diameter surface of an outer shaft having a female serration formed on an inner peripheral surface of the reduced diameter portion and an outer peripheral surface of an enlarged diameter portion. A step of fitting the tip of the enlarged diameter portion of the inner shaft having the serration formed over a predetermined dimension, and pressing the fitted portion in the radial direction from the outside to form the tip of the reduced diameter portion of the outer shaft and the inner shaft. A step of simultaneously plastically deforming the enlarged-diameter portion tip and a step of relatively moving the outer shaft and the inner shaft in a direction in which the outer shaft and the inner shaft approach each other within a range where the reduced-diameter portion and the enlarged diameter portion are not separated. Including.

According to the present invention, the female serration and the male serration are formed so as to loosely engage with each other, so that the distal end of the outer shaft and the distal end of the inner shaft can be easily fitted to each other. In addition, since the distal end of the reduced diameter portion and the distal end of the enlarged diameter portion can be simultaneously plastically processed into an elliptical shape or the like, the man-hour and cost required for manufacturing can be greatly reduced as compared with the conventional apparatus. Further, in the shock absorbing steering shaft manufactured by this method, the outer shaft and the inner shaft are engaged with a strong frictional force at two plastically deformed portions, so that the rotational force of the steering shaft can be transmitted without loss. ,
When a large collapse load is applied during a collision, both plastically deformed portions fall into the inner shaft or the outer shaft, and the steering shaft is immediately shortened.

[0007]

By the way, the method for manufacturing the shock absorbing steering shaft described above also includes a step of relatively moving the outer shaft and the inner shaft.
The following problems may have occurred. As shown in FIG. 11, the enlarged diameter portion 29 of the inner shaft 23 has a chamfer 61 at its tip by cutting or the like, 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 plastically deformed portion 35 such as an elliptical shape, the male serration 31 is fitted with the female serration 27 on the outer shaft 21 side in the same shape (true circular 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 2
1 and the female serrations 27 formed on the inner peripheral surface thereof are elastically deformed so as to match the plastically deformed portions 35 of the male serrations 31.

At this time, the tip of the male serration 31 becomes a sharp edge 63 and bites into the female serration 27, as shown in FIG. A tear 65 (hereinafter, represented by galling) 65 is generated. This galling 65
Normally, since it is formed on the entire circumference of the female serration 27, it has a large resistance when the inner shaft 23 is press-fitted into the outer shaft 21, and also increases the sliding resistance between the serrations 27 and 31 after assembly, and There is a possibility that the absorption characteristics may be affected. When the galling 65 does not occur, the female serration 27 and the male serration 31 are relatively loosely fitted to each other at portions other than the plastic deformation portions 33 and 35, and the sliding resistance between the serrations 27 and 31 is relatively small. Is almost negligible.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a method of manufacturing a shock-absorbing steering shaft that prevents galling of serrations in a step of relatively moving an outer shaft and an inner shaft. .

[0010]

According to the present invention, in order to solve the above-mentioned problems, the outer diameter of the outer diameter of the outer diameter portion and the outer diameter of the outer diameter reduction portion of the outer shaft having female serrations formed on the inner diameter surface of the reduced diameter portion. A step of fitting the end of the inner shaft formed with the male serration meshing with the female serration with the enlarged-diameter portion tip over a predetermined dimension, and pressing the fitting portion radially from the outside to reduce the diameter of the outer shaft. A step of simultaneously plastically deforming the tip and the enlarged-diameter portion tip of the inner shaft, as long as the reduced-diameter portion and the enlarged-diameter portion are not separated,
Relatively moving the outer shaft and the inner shaft in a direction approaching each other, wherein the male serrations are narrowed at the tip of the enlarged diameter portion. is there.

According to the present invention, the male serration is constricted at the tip of the enlarged diameter portion even after the step of plastically deforming the tip of the enlarged diameter portion of the inner shaft by radially pressing the fitting portion from the outside. In addition, the end of the male serration does not become an edge, so that the female serration is not galled in the process of relatively moving the outer shaft and the inner shaft toward each other.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing a vehicle cabin side portion of a steering device, and reference numeral 1 in the figure denotes a shock absorbing (drop-off) 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 an upper end of the steering shaft 5, and a lower steering shaft 11 is connected to a lower end of the steering shaft 5 via a universal joint 9.
In the figure, reference numeral 13 denotes a column cover that covers an upper portion of the steering column 1, and reference numeral 15 denotes a dashboard that partitions a vehicle room and an engine room.

In this steering device, when the driver rotates the steering wheel 7, the driver rotates the steering wheel 7 via the steering shaft 5 and the lower steering shaft 11.
The rotational force is transmitted to a steering gear (not shown). In the steering gear, a rack and pinion mechanism etc. that converts rotation input into linear motion is built in,
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, the steering gear has a ball screw type, worm roller type, etc.
Various formats are known.

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 the present embodiment has a cylindrical outer shaft 21 and a cylindrical inner shaft 23 serrated and connected. The outer shaft 21 is
The joint portion with the inner shaft 23 is a reduced diameter portion 25 having a smaller diameter than other portions, and a female serration 27 is formed on the inner peripheral surface of the reduced diameter portion 25 by broaching.
In the inner shaft 23, the connecting portion with the outer shaft 21 is an enlarged diameter portion 29 having a larger diameter than other portions, and a male serration 31 is formed on the outer peripheral surface of the enlarged diameter portion 29 by rolling. ing.

An oval plastically deforming portion 33 is formed at the tip of the reduced diameter portion 25 of the outer shaft 21. In the plastically deforming portion 33, as shown in FIG. The female serration 27 and the male serration 3 are pressed by the shaft 21 from the left and right directions in the drawing.
1 is in contact with a strong pressing force. An oval plastic deformation portion 35 is also formed at the tip of the enlarged diameter portion 29 of the inner shaft 23. In the plastic deformation portion 35, as shown in FIG. 23, the female serration 27 and the male serration 31 are in contact with a strong pressing force. Thereby, the outer shaft 21
The inner shaft 23 and the inner shaft 23 are integrated by a strong frictional coupling force, and the torsional rigidity is also kept high.
In addition, both serrations 27 and 31 are both plastically deformed parts 33 and
Parts other than 35 are relatively loosely fitted.

The steering shaft 5 of the present embodiment is
Since the coupling rigidity between the outer shaft 21 and the inner shaft 23 is high, the feeling and rigidity when the driver steers the steering wheel 7 are maintained at substantially the same level as those of the integrated type. In addition, since the outer shaft 21 and the inner shaft 23 are not combined with a synthetic resin or the like,
Even if the high heat of the engine room is transmitted to the steering shaft 5, there is no possibility that the durability of the connecting portion is reduced.

On the other hand, when the driver makes a secondary collision with the steering wheel 7 due to the collision of the vehicle and a predetermined collapse load acts on the steering shaft 5, the outer shaft 21 and the inner shaft 21 overcome the frictional coupling force described above. The connection between the two plastic deformation portions 33 and 35 is released. Then, since the serrations 27 and 31 are relatively loosely fitted in portions other than the plastic deformation portions 33 and 35, the outer shaft 21 and the inner shaft 23 are quickly shortened, and the driver can move the head or chest. Serious damage is prevented.

Next, a method for manufacturing the steering shaft 5 will be described. Prior to coupling with the outer shaft 21, the inner shaft 23 has a male serration 31 formed on the outer peripheral surface of the enlarged diameter portion 29, but in this embodiment, 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 portion of the enlarged diameter portion 29 is in a completely cylindrical shape, and the inner shaft 23 is rolled and contacted with a rolling tool 41 to perform male serration. 31 is formed. Thereby, as shown in FIG. 6 (enlarged portion A in FIG. 5), the material is pushed out by the rolling tool 41 at the distal end of the enlarged diameter portion 29, and the material is moved in the distal direction (FIG. 5, FIG. 6). A curl portion 45 is formed at the end of the male serration 31 so as to be smoothly narrowed from the straight portion 43. Thereafter, a hollow portion 47 is formed at the tip end side of the inner shaft 23.

As shown in FIGS. 7 and 8 (enlarged sectional view taken along the line BB in FIG. 7), the tip of the reduced diameter portion 25 and the enlarged diameter portion 29 of the inner shaft 23 having been formed are fitted together. Then, in a state where the female serrations 27 and the male serrations 31 are partially engaged, the female serrations 27 and the male serrations 31 are set together with the outer shaft 21 on a pressing device (not shown), and pressed by the pair of press tools 51 and 53 from the left and right directions in FIG. . Both press tools 51,
53 are initially opposed to each other with an interval δ, but are pressed by a hydraulic piston or the like (not shown) so that the opposing surfaces come into contact with each other, and at the same time, the distal ends of the reduced diameter portion 25 and the enlarged diameter portion 29 are each formed into an oval shape. The plastically deformed portions 33 and 35 are formed. Alternatively, the pressing surfaces of the press tools 51 and 53 may be pressed with a predetermined force without being brought into contact with each other. At this time, in the present 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 can be relatively small. The press tools 51 and 53 are each formed with an arc-shaped concave portion 55 for smooth positioning and plastic deformation of the outer shaft 21 at the time of setting.

When the plastically deformed portions 33 and 35 are formed on the outer shaft 21 and the inner shaft 23 in this way, as shown in FIG. 9, the outer shaft 21 and the inner shaft 23 are formed by using a press-fitting device or the like. The shaft 23 is relatively moved in a direction to approach each other. At this time, the reduced diameter portion 25 and the enlarged diameter portion 29 except for the plastic deformation portions 33 and 35 are elastically deformed as the plastic deformation portions 33 and 35 pass. The female serration 27 is not galled. That is, as shown in FIG. 10 (enlarged view of the portion C in FIG. 9), the curl portion 45 that smoothly narrows from the straight portion 43 is formed at the end of the male serration 31 on the enlarged diameter portion 29 side. , Female serration 27
Is gradually expanded and elastically deformed,
There is no galling. Thereby, the resistance when the outer shaft 21 and the inner shaft 23 are relatively moved is reduced, and the plastic deformation portions 33,
Except for the portion 35, there is almost no sliding resistance between the female serration 27 and the male serration 31, and stable shock absorption characteristics can be obtained.

Outer shaft 21 and inner shaft 23
Relative movement of the plastic deformation portion 33 on the reduced diameter portion 25 side reaches the base 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 is the base end of the reduced diameter portion 25. 2 until the state shown in FIG. 2 is reached, and the manufacture of the steering shaft 5 is completed.

The description of the specific embodiment has been completed.
The aspects of the present invention are not limited to the above embodiment.
The specific configuration of the outer shaft and the inner shaft, the specific shape of the plastically deformed portion, and the like can also be appropriately changed without departing from the gist of the present invention.

[0023]

As described above, according to the method of manufacturing the shock absorbing steering shaft according to the present invention, the tip of the reduced diameter portion of the outer shaft in which the female serration is formed on the inner peripheral surface of the reduced diameter portion, A step of fitting over a predetermined dimension an enlarged-diameter portion tip of an inner shaft formed with a male serration that meshes with the female serration on the outer peripheral surface of the enlarged-diameter portion, and radially presses the fitting portion from the outside, A step of simultaneously plastically deforming the reduced-diameter portion tip of the outer shaft and the increased-diameter portion tip of the inner shaft, and as long as the reduced-diameter portion and the increased-diameter portion are not separated, the outer shaft and the inner shaft Relative to each other in a direction approaching each other, the male serrations are narrowed at the tip of the enlarged diameter portion, so that the fitting portion is radially pressed from outside. Even after the step of plastically deforming the tip of the enlarged portion of the inner shaft, the end of the male serration does not become an edge, and the female serration is galled in the process of relatively moving the outer shaft and the inner shaft toward each other. As a result, the pressing force when the outer shaft and the inner shaft are relatively moved can be reduced, and stable shock absorbing characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a structure of a steering device on a passenger compartment side.

FIG. 2 is a longitudinal sectional view showing a main part of the shock absorbing steering shaft according to one embodiment of the present invention.

FIG. 3 is a longitudinal sectional view of a steering shaft at a plastic deformation portion on an outer shaft side.

FIG. 4 is a longitudinal sectional view of the steering shaft at a plastic deformation portion on the inner shaft side.

FIG. 5 is an explanatory view showing a state in which male serrations are formed on an inner shaft.

FIG. 6 is an enlarged view of a portion A in FIG.

FIG. 7 is an explanatory view showing a state in which a plastic deformation portion is formed on the outer shaft and the inner shaft.

FIG. 8 is an enlarged sectional view taken along line BB in FIG. 7;

FIG. 9 is a vertical cross-sectional view showing a relative movement step between the outer shaft and the inner shaft in the embodiment.

10 is an enlarged view of a part C in FIG. 9;

FIG. 11 is a longitudinal sectional view showing a relative movement process between an outer shaft and an inner shaft in a conventional device.

FIG. 12 is an enlarged view of a portion D in FIG. 11;

[Explanation of symbols]

 5 Steering shaft 21 Outer shaft 23 Inner shaft 25 Reduced diameter part 27 Female serration 29 Extended diameter part 31 Male serration 33, 35 Plastic deformation part 45 Curl part

Claims (1)

[Claims] An inner shaft having an outer shaft having a female serration formed on an inner peripheral surface of a reduced diameter portion and an inner shaft having a male serration meshed with the female serration formed on an outer peripheral surface of the enlarged diameter portion. Fitting the distal end of the outer shaft over a predetermined dimension, and pressing the fitted portion radially from outside to simultaneously plastically deform the distal end of the outer shaft and the distal end of the inner shaft at the same time. Causing the outer shaft and the inner shaft to relatively move in a direction in which the outer shaft and the inner shaft approach each other within a range in which the reduced diameter portion and the increased diameter portion are not separated; A method of manufacturing a shock-absorbing steering shaft, characterized in that the shaft is narrowed at a tip of a portion.