JPH0679894B2 - Method of manufacturing energy absorbing steering shaft - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement in a method for manufacturing an energy absorbing steering shaft used in a vehicle such as an automobile.

[Conventional technology]

As a conventional energy absorption steering shaft, there is, for example, the one described in Japanese Utility Model Publication No. 60-100262.

In a steering device in which the main shaft is connected to a gear box through an intermediate shaft, the solid shaft having a substantially oval cross-section has a cross-sectional shape that matches the cross-sectional shape of the solid shaft. The intermediate shaft is formed by press-fitting into a hollow shaft of the shaft, and by filling a synthetic resin in a circumferential gap provided between the shafts to connect the shafts. Then, the axial force applied to the intermediate shaft is received by the shear stress of the synthetic resin and the frictional resistance force between the solid shaft and the hollow shaft, and these absorb the energy when the shafts move relative to each other. Therefore, in the case of a secondary collision, an excessive load is not applied to the driver.

Similar to a general steering shaft, such an energy absorbing steering shaft is required to have sufficient strength in the torsional direction in order to transmit the rotational force applied to the steering wheel to the steering gear side.
From the viewpoint of durability, vibration resistance, etc., it is required that there is no play in the fitting portion that allows the relative movement.

That is, it is generally required that the steering shaft has sufficient strength in the torsional direction in order to transmit the steering torque, but this is rotatably supported by the vehicle body side member and external force is applied to the steering wheel attached to the upper end. Is input, a relatively small bending force and axial force are applied to the steering shaft.
Therefore, the steering shaft is required to have both a bending strength that can withstand the bending force and an axial strength that can withstand the axial force. In particular, when the strength in the bending direction is insufficient due to the looseness in the fitting portion of the solid shaft and the hollow shaft, vibration is generated in the steering shaft, which makes it impossible to perform stable steering.

Therefore, the energy-absorbing steering shaft guarantees the normal steering torque transmission function, and at the time of a collision, it easily contracts and deforms with a small load to absorb the collision energy, so that the driver can avoid a collision even during a secondary collision. Is required to have strength characteristics so that an excessive load does not act on it.

[Problems to be solved by the invention]

However, in the above-mentioned conventional energy absorption steering shaft, since the shear pin is provided only at one position in the axial direction, if the strength of the shear pin is set so that the shear pin is cut with a relatively small axial force, the shear pin is twisted. Since the directional strength becomes too small and the transmittable steering torque decreases, the durability deteriorates and rattling easily occurs at the mating part, which causes vibration and noise. There is a point.

Therefore, in order to increase the strength in the torsional direction, the diameter of the shear pin is increased, or the shear pin is provided at two or more locations separated in the axial direction to increase the shear stress against the axial force of the entire steering shaft. Since the axial strength increases as the directional strength increases, it becomes impossible to cut the shear pin with a small load, and as a result, there is a problem that a large load may be applied to the driver during a secondary collision. .

The present invention has been made in view of such conventional problems, and a molding member is filled in at least one of fitting portions of a shaft-side shaft member and a pipe-side shaft member that form a steering shaft, After cutting the molded member,
By forming a share pin by newly filling a molding member at one location, a sufficiently large steering wheel can be obtained while minimizing the increase in the sliding resistance force when the shaft members relatively move in the axial direction at the time of a collision. The purpose is to enable transmission of torque.

[Means for solving problems]

In order to solve the above problems, the present invention is a steering shaft comprising a first shaft connected to a steering wheel and a second shaft connected in series to the first shaft, the first shaft comprising: The connecting portion of the second shaft has a non-circular cross-sectional shape and includes one shaft portion that slidably fits in the axial direction and the other pipe portion, and the shaft portion has a circumferential direction. Has an annular groove formed on the outer peripheral surface thereof, and the pipe portion has at least one through hole for communicating the annular groove of the shaft portion fitted in the pipe portion with the outside. In an energy absorbing steering shaft that connects the shafts by filling a molding material in a state of matching the groove position, the annular grooves are provided at at least two positions axially separated from each other by a predetermined distance. Out of A molding material is filled in a space formed by the annular groove and the through hole in a state where one of the through holes is aligned with one annular groove, and after the molding material is solidified, the both shafts are relatively moved in the axial direction. Cutting the shear pin formed of the molding material, and, after the step, aligning the through hole or another through hole provided with another annular groove, and in this state, the annular groove and the through hole. And a step of forming a shear pin at only one location by filling a molding material into the void formed by.

[Action]

Thus, according to the present invention, a shear pin that engages with both shafts and transmits steering torque by pressing force is provided in the fitting portion between the shaft portion of the first shaft and the pipe portion of the second shaft, and pressure contact is made with both shafts. And a molded member that transmits the steering torque by frictional force is provided, and the strength in the torsional direction is increased without increasing the strength with respect to the axial load so that the steering torque can be transmitted to some extent, When applied, both shafts are allowed to move relative to each other to prevent an excessive load from being applied to the driver during a secondary collision.

〔Example〕

An embodiment of the present invention will be described below with reference to the accompanying drawings.

1 to 5 are views showing an embodiment of the present invention. First, the structure will be described. Reference numeral 1 shown in FIG. 1 is a steering column. The steering column 1 includes a steering shaft 2 and a steering shaft 2.
And a column tube 3 which is externally fitted to and rotatably supports the steering shaft 2.

The column tube 3 is composed of an upper tube member 4 and a lower tube member 5, the lower tube member 4 has an upper end portion inserted into the lower end portion thereof, and a well-known energy absorbing mechanism provided in the inserted portion. Both tube members 4 and 5 are connected via (not shown). The column tube 3 has two column brackets 6, which are attached to the upper and lower parts in the axial direction.
It is supported by the vehicle body side member 8 via 7 so as to be detachable.

A steering wheel 9 is attached to the upper end of the steering shaft 2, and a steering gear (not shown) is connected to the lower side of the steering shaft 2 via a universal joint 10 and a center shaft 11. This steering shaft 2 has a shaft-side shaft member (first shaft) 12 having a shaft portion 12a at the upper end and a pipe side having a pipe portion 13a at the lower end, as shown in the cross-section of the main parts in FIGS. The steering wheel 9 is attached to the upper end of the tube side shaft member 13, and the universal joint 10 is attached to the lower side of the shaft side shaft member 12.

As shown in FIGS. 4 and 5, the cross-sectional shape of the shaft portion 12a of the shaft-side shaft member 12 is a substantially oval shape in which two planes extending in the axial direction are formed at the upper and lower portions of the drawing, respectively, and the outer circumference thereof. Are circumferentially continuous annular grooves 12b and 12c.
Are provided at two locations separated by a predetermined distance A in the axial direction. The tube portion 13a formed in a shape corresponding to the cross-sectional shape is fitted onto the shaft portion 12a with a slight gap provided between the tube portion 13a and the shaft portion 12a.

Through holes 13b and 13c penetrating the respective front and back surfaces of the tube portion 13a are formed in the two flat surfaces, and the annular grooves 12b, 12 at the two locations are provided.
They are provided at two locations separated by a distance B which is longer than the distance A between c. The positional relationship between the annular grooves 12b, 12c and the through holes 13b, 13c is set so that the entire length of the steering shaft 2 becomes a predetermined length depending on the position where the shear pin 15 described later is formed. Then, the voids formed by the annular grooves 12b and 12c and the through holes 13b and 13c are filled with the synthetic resin 14 as a molding member at predetermined positions.

Of the two through holes 13b and 13c, the through hole 13b provided on the lower side is formed in an inverted conical shape so that the vertical cross-sectional shape is V-shaped.
The shear pin formed by 14 is easily cut.

The energy absorbing steering shaft is manufactured through the following steps.

That is, first, the shaft portion 12a of the shaft-side shaft member 12 is inserted into the pipe portion 13a of the pipe-side shaft member 13, and as shown in FIG. 2, the shaft portion is inserted into the through hole 13b provided below the pipe portion 13a. The annular groove 12b provided on the lower side of 12a is aligned, and in this state, the synthetic resin 14 is filled in the void formed by the annular groove 12b and the through hole 13b.

Then, as shown in FIG. 3, the synthetic resin 14 is cut by further pushing the shaft portion 12a into the pipe portion 13a. At this time, since the through hole 13b is formed in an inverted conical shape and the area of the shear plane is set to be the smallest, the cutting operation of the synthetic resin 14 can be performed extremely easily, and The state of the cut can be unified to some extent. Moreover, by forming the through hole 13b as a tapered hole, it is possible to easily remove the residue 14a of the synthetic resin 14 remaining in the through hole 13b after cutting. Therefore, it is possible to prevent the occurrence of an accident such that the scrap is dropped from the through hole 13b after the assembling and is caught in the bearing or the joint portion.

Then, the shaft portion 12 is inserted into the through hole 13c provided on the upper side of the pipe portion 13a.
The annular groove 12c provided on the lower side of a is aligned, and in this state, a synthetic resin is filled in the void formed by the annular groove 12c and the through hole 13c, whereby the shear pin 15 is molded. In this way, the energy absorbing steering shaft according to the present invention is manufactured.

Thus, in the energy absorbing steering shaft according to the present invention, when a rotational force is applied to the steering wheel 9, the rotational force is applied to the pipe portion 13 of the pipe side shaft member 13.
The shaft portion 12a of the shaft-side shaft member 12 from a through the shear pin 15 in which the shaft portion fits into the through hole 13c of the pipe portion 13a and the synthetic resin 14 that frictionally contacts the inner peripheral surface of the pipe portion 13a.
Be transmitted to.

Therefore, as compared with the case where the steering torque is transmitted by the shear stress of only one shear pin provided in one place as in the conventional example, the frictional resistance force generated between the synthetic resin 14 and the pipe portion 13a in which the shaft portion is cut in advance is generated. It is possible to transmit a large steering torque by the amount of increase of. Moreover, the shaft portion 12a and the pipe portion 13a, which are fitted with each other due to the clearance fit, are fitted with the synthetic resin 14 and the shear pin 15.
Since the members are elastically connected with each other, the play between the shaft-side shaft member 12 and the tube-side shaft member 13 can be absorbed by the elasticity of both members 14 and 15. Therefore, it is possible to prevent the occurrence of vibration due to the relative fluctuation of the both shaft members 12 and 13, it is possible to prevent the generation of noise, and it is possible to secure a stable steering operation.

On the other hand, at the time of a collision, the driver is blown forward by a secondary collision, and when the driver collides with the steering wheel 9 and the collision force is applied to the steering shaft, the axial force is the same as the steering torque. Is transmitted from the pipe portion 13a of the pipe side shaft member 13 to the shaft portion 12a of the shaft side shaft member 12 via the shear pin 15 and the synthetic resin 14. At this time, when the synthetic resin 14 and the pipe portion 13a are coupled only by the frictional resistance force, and the shear pins of two share pins are used to receive the axial force due to the shear stress of both share pins as in the conventional example. Since the coupling force is smaller than that in (1), the sliding resistance force of the entire fitting portion against the axial force does not become so large.

Therefore, since the two shaft members 12 and 13 can be moved relative to each other by an axial load of a size that is not much different from the case of using the share pin at one place, an excessive load is applied to the driver during a secondary collision. Can be prevented.

When manufacturing this energy absorbing steering shaft, the sliding resistance force increased by the synthetic resin 14 is confirmed by measuring the sliding resistance force after cutting the shear pin 15 made of the synthetic resin 14. be able to. Particularly, when the shapes and sizes of the two through holes 13b and 13c are set to be equal (for example, when the through holes 13c in the embodiment are unified), not only the sliding resistance force but also the shear pin 15 Since it is possible to measure the shear load characteristics in practice, check the dimensions of the shaft portion 12a and the pipe portion 13a and the shear stress and sliding resistance force due to the injection conditions of the synthetic resin at the time of manufacture. be able to.

Further, in the above embodiment, the current groove 12b,
12c is provided, and two through holes 13b and 13c, which make a pair, are provided at two locations of the pipe portion 13, and a synthetic resin 14 is provided at one location.
After injection and cutting the same, the synthetic resin 14 was injected into the other place to form the shear pin 15. However, the present invention is not limited to the above-mentioned embodiment. It is possible to obtain various combinations, and the same effect as that of the above-mentioned embodiment can be obtained by this.

[Combination Example 1] Two annular grooves and one through hole are provided, and injection is performed at one location to cut it, and then a shear pin is formed at another location.

[Combination Example 2] Three annular grooves and two or three through holes are provided, and injection is performed at two locations to cut it, and then a shear pin is molded at another location.

[Combination Example 3] Four annular grooves and three or four through holes are provided, and after injection and cutting at three locations, a shear pin is molded at another one location.

In addition, various combinations can be adopted, but it is sufficient that they are obtained by cutting a synthetic resin injection-molded at at least one location and then injection-molding a shear pin at another location.

In addition, although the synthetic resin is used as the molding material in the above-mentioned embodiment, a metal material may be used as long as it has a shear stress similar to that.

Further, in the above embodiment, the cross-sectional shape of the shaft portion 12 is a substantially oval shape in which two planes are formed at the position displaced by 180 degrees, but the shape is not limited to this, for example, an elliptical shape. , Squares, rectangles, hexagons, and other polygons, as well as shapes with serrations or splines, other than perfect circles (non-perfect circles) that can transmit rotational force to other members on the same axis If so, various shapes can be adopted. Further, in the above embodiment, the annular grooves 12b, 12c are provided on the outer periphery of the shaft portion 12, but the present invention is not limited to this, and a groove that only extends to the middle of the circumferential direction and does not form an annular shape. It may be.

Furthermore, in the above examples, the synthetic resin after cutting
Although the scrap 14a of 14 has a shape of an inverted cone to be removed in advance and removed, if the scrap has a columnar shape, the scrap is crimped or taped to prevent the scrap from falling off. By doing so, it is possible to prevent the above-mentioned harmful effects due to dust.

〔The invention's effect〕

As described above, according to the present invention, the synthetic resin is filled in at least one of the fitting portions of the shaft portion and the pipe portion of the first shaft and the second shaft that form the steering shaft, and After cutting, the synthetic pin was newly filled in only one place to form the shear pin that connects both shafts, so that the torsional strength could be increased without significantly increasing the strength against axial load. Therefore, while a large steering torque can be transmitted, when an axial force of a certain magnitude is applied, the axial force causes the first shaft and the second shaft to move relatively easily and stably with a predetermined load. Can be made. Therefore, at the time of a collision, it is possible to prevent an excessive load due to the secondary collision from being applied to the driver.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a schematic structure of an energy absorption steering shaft according to the present invention, and FIGS. 2 and 3 are explanatory views showing an action by enlarging and cross-sectioning a main part of FIG. 1, and FIG. Is a sectional view taken along the line IV-IV in FIG. 2, and FIG.
It is a V line sectional view. 2 ... Steering shaft, 9 ... Steering wheel, 12 ... Shaft side shaft member, 12a ... Shaft part, 12
b, 12c …… annular groove (groove), 13 …… pipe side shaft member, 1
3a …… Pipe part, 13b, 13c …… Through hole, 14 …… Synthetic resin, 1
5 …… Share pin

Claims (1)

[Claims] 1. A steering shaft comprising a first shaft connected to a steering wheel and a second shaft connected in series to the first shaft, wherein a connecting portion between the first shaft and the second shaft. Has a non-circular cross-sectional shape and has one shaft portion slidably fitted in the axial direction and the other pipe portion, and the shaft portion has an annular groove formed in the circumferential direction. A state in which at least one through hole is provided on the outer peripheral surface and the pipe portion communicates the annular groove of the shaft portion fitted in the pipe portion with the outside, and the through hole is aligned with the annular groove position. In an energy-absorption steering shaft that connects both shafts by filling a molding material with, the annular grooves are provided at at least two positions axially spaced from each other, and one of the annular grooves is provided. In the through hole Formed by the molding material by filling the molding material into the void formed by the annular groove and the through hole in a state where one of them is aligned and solidifying the molding material, and then relatively moving the both shafts in the axial direction. After the step of cutting the shear pin, after the step, the through hole or the through hole provided elsewhere is aligned with another annular groove, and in this state, a molding material is formed in the void formed by the annular groove and the through hole. Filled with 1
And a step of molding the shear pin only at a portion thereof.