JP6926797B2 - Telescopic shaft - Google Patents

Description

The present invention relates to a telescopic shaft constituting a steering device for an automobile.

FIG. 10 shows a conventionally known steering device for an automobile. The steering device includes a steering wheel 1, a steering shaft 2, a steering column 3, a pair of universal joints 4a and 4b, an intermediate shaft 5, a steering gear unit 6, and a pair of tie rods 7. ..

The steering wheel 1 is attached to the rear end portion of the steering shaft 2 rotatably supported inside the steering column 3. The front end portion of the steering shaft 2 is connected to the input shaft 8 of the steering gear unit 6 via a pair of universal joints 4a and 4b and an intermediate shaft 5. Then, by converting the rotation of the input shaft 8 into a linear motion of a rack (not shown), the pair of tie rods 7 is pushed and pulled, and the steering wheel is given a steering angle according to the amount of operation of the steering wheel 1. The front-rear direction means the front-rear direction of the vehicle body to which the steering device is assembled.

By the way, when an automobile causes a collision, the front part of the vehicle body may be crushed and the steering gear unit may be pushed backward. Therefore, in order to prevent the steering wheel from being pushed up toward the driver regardless of the rearward displacement of the steering gear unit, it is considered that the intermediate shaft has a telescopic structure. FIG. 11 shows a telescopic intermediate shaft 5a described in Japanese Patent Application Laid-Open No. 2017-25964.

The intermediate shaft 5a includes an inner shaft 9 and an outer tube 10. A yoke 11 separate from the inner shaft 9 is fixed to one side of the inner shaft 9 in the axial direction, and a male spline 12 is provided on the outer peripheral surface of the other side of the inner shaft 9 in the axial direction. ing. On the other hand, a female spline 13 is provided on the inner peripheral surface of the outer tube 10 on one side in the axial direction, and a yoke 14 is integrally provided on the other side of the outer tube 10 in the axial direction with the outer tube 10. Is provided. Then, the other side portion in the axial direction of the inner shaft 9 is inserted inside the one side portion in the axial direction of the outer tube 10, and the male spline 12 and the female spline 13 are engaged with each other to form the inner shaft 9 and the outer tube 10. Are combined so that torque can be transmitted and can be expanded and contracted.

When an automobile provided with the intermediate shaft 5a as described above causes a collision accident, the inner shaft 9 and the outer tube 10 are displaced relative to each other in the axial direction, thereby shortening the total length of the intermediate shaft 5a. This absorbs the impact of a collision and prevents the steering wheel from pushing backwards.

Japanese Unexamined Patent Publication No. 2017-25964

In order to improve the collision safety performance of automobiles, there is a demand that the effects of primary collisions in which automobiles collide with obstacles are not transmitted to the steering column. Then, in order to satisfy such a requirement, it is necessary to increase the amount of contraction of the intermediate shaft.

Here, the intermediate shaft 5a having the conventional structure is in a state of being maximally contracted, and the end surface on one side in the axial direction of the outer tube 10 and the weld bead portion 15 for connecting and fixing the inner shaft 9 and the yoke 11 are in contact with each other. Get in touch. Therefore, in order to increase the amount of contraction of the intermediate shaft 5a, for example, it is conceivable to reduce the volume of the weld bead portion 15, but in this case, the coupling force between the inner shaft 9 and the yoke 11 is sufficiently strong. It becomes difficult to secure.

In view of the above circumstances, an object of the present invention is to realize a structure capable of increasing the amount of contraction of a telescopic shaft used as an intermediate shaft constituting a steering device.

The telescopic shaft of the present invention includes an inner shaft and an outer tube.
The inner shaft has a yoke portion on one side in the axial direction and a shaft portion provided integrally with the yoke portion on the other side in the axial direction of the yoke portion, and the inner shaft has a yoke portion on one side in the axial direction of the shaft portion. The outer peripheral surface of the end portion has a concave curved surface having an arcuate cross section continuous with the side surface of the yoke portion on the other side in the axial direction, and is on the other side of the shaft portion in the axial direction. An adjacent portion has a fuse portion having a diameter smaller than that of the other portion of the shaft portion and one side portion of the outer peripheral surface in the axial direction directly continuous with the concave curved surface.
In the outer tube, one side portion in the axial direction thereof is coupled to the other side portion in the axial direction of the shaft portion of the inner shaft so that torque can be transmitted and at least relative displacement in the axial direction at the time of a temporary collision is possible. There is.

In the present invention, a bellows portion can be provided in the axially intermediate portion of the outer tube.

In the present invention, the shaft portion of the inner shaft and the outer tube can be uncoupled with relative displacement in the axial direction in a steady state. In this case, the other side in the axial direction of the outer peripheral surface of the shaft portion of the inner shaft and the one side portion in the axial direction of the inner peripheral surface of the outer tube, which form the fitting portion between the inner shaft and the outer tube. Each of the plastic deformed portions having a non-circular cross section can be provided.
In other words, in the present invention, a compressive force having a magnitude greater than or equal to a predetermined value with respect to the telescopic shaft, that is, a member arranged below the inner shaft and the outer tube is pushed up in the event of a collision. Only when the accompanying compressive force is applied, a configuration can be adopted in which the relative displacement between the shaft portion of the inner shaft and the outer tube in the axial direction is possible.
Alternatively, in the present invention, the shaft portion of the inner shaft and the outer tube can be loosely engaged with each other in a steady state so as to be relatively loosely displaced in the axial direction.

Further, in the present invention, the shaft portion constituting the inner shaft may be provided with a hollow portion that opens only on the end surface on the other side in the axial direction of the shaft portion. In this case, the axial positions of the end surface (bottom surface) of the hollow portion on one side in the axial direction and the end surface portion on the other side of the fuse portion in the axial direction can be matched.

According to the telescopic shaft of the present invention, the amount of contraction in the axial direction can be increased.

FIG. 1 is a schematic view showing an example of a steering device incorporating the first telescopic shaft according to the first example of the embodiment of the present invention. FIG. 2 is a cross-sectional view of an intermediate shaft including the first telescopic shaft of the first example of the embodiment of the present invention. FIG. 3 is a cross-sectional view showing the first telescopic shaft of the first example of the embodiment of the present invention. FIG. 4 is a side view showing one side in the axial direction of the inner shaft constituting the first telescopic shaft of the first example of the embodiment of the present invention. FIG. 5 is a perspective view showing one side in the axial direction of the inner shaft constituting the first telescopic shaft of the first example of the embodiment of the present invention. FIG. 6 is a cross-sectional view showing a second telescopic shaft constituting an intermediate shaft together with the first telescopic shaft of the first example of the embodiment of the present invention. 7 (A) and 7 (B) are views for explaining that the shrinkage amount is increased by integrating the inner shaft and the yoke with respect to the first example of the embodiment of the present invention. FIG. 7A is a cross-sectional view of a telescopic shaft in which a separate yoke is welded and fixed to the inner shaft, and FIG. 7B is a cross-sectional view of the telescopic shaft in which the inner shaft and the yoke are integrally formed. .. 8 (A) to 8 (C) are views for explaining that the amount of shrinkage increases depending on the formation position of the fuse portion with respect to the first example of the embodiment of the present invention, and FIG. 8 (A) shows. , FIG. 8B is a cross-sectional view of the telescopic shaft when the fuse portion is provided at a position separated from the concave curved surface on the other side of the shaft portion in the axial direction. FIG. 8 (C) is a cross-sectional view of a telescopic shaft when a fuse portion is provided at a position adjacent to FIG. It is a figure which superimposes the contour of each inner shaft of B). 9 (A) and 9 (B) are views for explaining the shape change when the inner shaft constituting the first telescopic shaft of the second example of the embodiment is manufactured, and is shown in FIG. 9 (A). ) Is a partial cross-sectional view showing an intermediate material formed by cold forging, and FIG. 9B is a partial cross-sectional view of an inner shaft formed by machining the intermediate material. FIG. 10 is a partial cross-sectional side view showing a conventionally known steering device. FIG. 11 is a cross-sectional view showing a telescopic intermediate shaft having a conventional structure.

[First Example of Embodiment]
A first example of the embodiment will be described with reference to FIGS. 1 to 8.

[Overview of steering device]
The steering device for automobiles includes a steering wheel 1, a steering shaft 2, a steering column 3, a pair of universal joints 4c and 4d, an intermediate shaft 5b, a steering gear unit 6, and a pair of tie rods 7. I have.

The steering shaft 2 is rotatably supported inside the steering column 3 supported by the vehicle body. A driver-operated steering wheel 1 is attached to the rear end of the steering shaft 2, and the front end of the steering shaft 2 is a steering gear via a pair of universal joints 4c and 4d and an intermediate shaft 5b. It is connected to the input shaft 8 of the unit 6. Therefore, when the driver rotates the steering wheel 1, the rotation of the steering wheel 1 is transmitted to the input shaft 8 of the steering gear unit 6. The rotation of the input shaft 8 is converted into a linear motion of the rack meshed with the input shaft 8 and pushes and pulls the pair of tie rods 7. As a result, the steering wheel is provided with a steering angle corresponding to the amount of operation of the steering wheel 1.

[Composition of intermediate shaft]
As shown in FIG. 2, the intermediate shaft 5b is configured by connecting a first telescopic shaft 16 and a second telescopic shaft 17, each of which can expand and contract in the axial direction, by a joint member 18 so as to be able to transmit torque. ..

The first telescopic shaft 16 is configured so that the entire length can be contracted only when an impact load having a magnitude equal to or larger than a predetermined value is applied in the axial direction, whereas the second telescopic shaft 17 causes a collision accident. It is configured so that the entire length can be expanded and contracted in a steady state where it is not. Therefore, in the steady state, only the second telescopic shaft 17 expands and contracts to change the overall length of the intermediate shaft 5b, but when a collision accident occurs, each of the first telescopic shaft 16 and the second telescopic shaft 17 expands and contracts. By contracting, the total length is shortened. The intermediate shaft 5b of this example is used for a large vehicle, and has a longer axial dimension than that used for a general ordinary passenger car.

[Structure of the first telescopic shaft]
As shown in FIGS. 2 and 3, the first telescopic shaft 16 includes an inner shaft 9a and an outer tube 10a. The inner shaft 9a and the outer tube 10a are coupled so that torque can be transmitted and relative displacement in the axial direction is possible only at the time of a temporary collision. In other words, the inner shaft 9a and the outer tube 10a are coupled so that relative displacement in the axial direction becomes impossible in a steady state.

The inner shaft 9a is made of metal and has a yoke portion 19 on one side in the axial direction and a shaft portion 20 on the other side in the axial direction. In particular, in this example, as shown in FIGS. 4 and 5, the yoke portion 19 and the shaft portion 20 are integrally provided. That is, the yoke portion 19 and the shaft portion 20 are not connected by fitting or welding, but are integrally formed by plastically deforming the material by forging or the like.

The yoke portion 19 constitutes a universal joint 4d by another yoke 21 connected to the input shaft 8 of the steering gear unit 6 and a cross shaft (not shown), and includes a base portion 22 and a pair of arm portions 23. Have. The central portion of the other side surface of the base portion 22 in the axial direction is continuous with the end surface of one side portion in the axial direction of the shaft portion 20. The radial outer portion of the other side surface in the axial direction of the base portion 22 is a circular ring surface 24 existing on a virtual plane orthogonal to the central axis of the shaft portion 20.

The pair of arm portions 23 are formed in a substantially flat plate shape, and extend from two positions on the opposite side of the base portion 22 in the diametrical direction to one side in the axial direction. Further, the tip portion of the arm portion 23 is provided with a circular hole 25 for rotatably supporting the shaft portion constituting the cross axis so as to be coaxial with each other.

The shaft portion 20 has a substantially columnar shape, and is formed in a solid state over almost the entire length. A hollow portion 26 opened only on the end surface on the other side in the axial direction of the shaft portion 20 is provided at the other end portion in the axial direction of the shaft portion 20. A male serration 27 is provided on the outer peripheral surface of the other half of the shaft portion 20 in the axial direction. On the other hand, a concave curved surface 28 having a concave arc shape is provided on the outer peripheral surface of one end of the shaft portion 20 in the axial direction. The concave curved surface 28 is a so-called corner R portion, has a single radius of curvature r, and is smoothly and directly continuously connected to the annular surface 24 which is the other side surface in the axial direction of the base portion 22 constituting the yoke portion 19. doing. Further, a fuse portion 29 having a diameter smaller than that of the other portion of the shaft portion 20 is provided in a portion of the shaft portion 20 adjacent to the other side of the concave curved surface 28 in the axial direction. The small-diameter side portion of the concave curved surface 28 is smoothly and directly continuous with the outer peripheral surface of the one side portion in the axial direction of the fuse portion 29. Therefore, the concave curved surface 28 is directly connected to the annular surface 24 which is the other side surface in the axial direction of the base portion 22 and the outer peripheral surface of the one side portion in the axial direction of the fuse portion 29, and these annular surfaces 24 and the fuse are connected to each other. The outer peripheral surface of the portion 29 is smoothly continuous. The outer diameter dimension (diameter) of the fuse portion 29 is in the range of 13 mm to 16 mm, and the axial dimension of the fuse portion 29 is in the range of 10 mm to 30 mm. The size of the radius of curvature r of the concave curved surface 28 is in the range of 5 mm to 10 mm.

In the event of an accident such as a collision or riding on the curb of the steering wheel, the fuse portion 29 is deformed prior to other portions to absorb an impact or a load. This prevents deformation of parts other than the fuse portion 29, and even if the steering device is damaged, the accident does not occur due to the damage to the steering device, but the accident is the cause. It becomes possible to confirm that the steering device has been damaged. That is, by inspecting a vehicle in which the steering device is damaged and confirming the deformation of the fuse portion, it is possible to determine whether or not the cause of the accident is an accident such as riding on a curb.

The fuse portion 29 has a circular cross section, and the outer diameter dimension is constant in the range from the end portion on one side in the axial direction to the portion closer to the other side in the axial direction. The diameter dimension is continuously increasing. Therefore, the generatrix shape of the end of the fuse portion 29 on the other side in the axial direction is a concave arc shape. With such a configuration, stress is prevented from being concentrated between the fuse portion 29 and the portion of the outer peripheral surface of the shaft portion 20 that is detached from the fuse portion 29 on the other side in the axial direction. The outer diameter of the fuse portion 29 is regulated so that the torsional rigidity is the smallest among the intermediate shafts 5b. In particular, the torsional torque of the bellows portion 31, which will be described later, is higher than the torsional torque of the fuse portion 29. However, the outer diameter of the fuse portion 29 is deformed even if the intermediate shaft 5b is subjected to the maximum torque that can be transmitted in a steady state or a torque of a magnitude that takes into account the safety factor. However, it is regulated to be plastically deformed before other parts of the intermediate shaft 5b only when an impact load or torque is applied. The arm portion 23 of the yoke portion 19 has higher torsional rigidity than the other portions, and the fuse portion 29 is continuous from the base portion 22 of the yoke portion 19 toward the other side in the axial direction. It is possible to prevent the torsion torque of the fuse portion 29 from fluctuating due to the portion of the inner shaft 9a other than the fuse portion 29 being twisted and the torque escaping.

The outer tube 10a is made of metal and has a hollow circular tubular shape. A pair of coupling cylinder portions 30a and 30b are provided on both sides of the outer tube 10a in the axial direction, and a bellows-shaped bellows portion 31 is provided in the intermediate portion in the axial direction of the outer tube 10a.

Of the pair of coupling cylinders 30a and 30b, the first female serration 32 is provided on the inner peripheral surface of the coupling cylinder 30a on one side in the axial direction, and the inside of the coupling cylinder 30b on the other side in the axial direction. A second female serration 33 is provided on the peripheral surface.

The bellows portion 31 is a portion that absorbs the impact load due to the collision by plastically deforming so as to bend at the time of an offset collision, and the driver operates the steering wheel 1 in a steady state before the collision accident occurs. It has a torsional strength that does not deform depending on the load in the torsional direction that is applied based on the above. The bellows portion 31 is configured by arranging a plurality of mountain portions having a large diameter portion and valley portions having a small diameter portion alternately in the axial direction. Further, in this example, the top of the mountain portion and the bottom of the valley portion have an arcuate cross section. The bellows portion 31 is easily bent in the bending direction due to the action of the bending moment, but the contraction in the axial direction is difficult to shrink due to the influence of the heights of the peaks and valleys and the plate thickness.

In this example, in order to connect the inner shaft 9a and the outer tube 10a so that torque can be transmitted and the relative displacement in the axial direction at the time of a temporary collision is possible, the male serration 27 of the inner shaft 9a and the outer tube 10a are connected. The first female serration 32 is serrated engaged, and the fitting portion between the inner shaft 9a and the outer tube 10a is a so-called elliptical fitting. That is, plastic deformation having an elliptical cross-sectional shape at the end of the shaft portion 20 constituting the inner shaft 9a on the other side in the axial direction and the end of the coupling cylinder portion 30a constituting the outer tube 10 on the one side in the axial direction. Parts 34a and 34b are formed, respectively. In FIG. 3, wavy lines are provided in the formation ranges of the plastic deformation portions 34a and 34b, respectively.

In this example, with the above-described configuration, torque can be transmitted between the other side portion of the shaft portion 20 constituting the inner shaft 9a in the axial direction and the coupling cylinder portion 30a constituting the outer tube 10a in the axial direction. It is coupled so that relative displacement in the axial direction is possible only in the case of a primary collision where a large impact load is applied to. Further, since the plastic deformation portions 34a and 34b serve as resistance when the inner shaft 9a and the outer tube 10a are displaced relative to each other in the axial direction, the inner shaft 9a and the outer tube 10a are displaced relative to each other in the axial direction, and the first When the telescopic shaft 16 contracts, it absorbs energy due to collision. Further, the outer diameter of the shaft portion 20 of the inner shaft 9a is regulated to a size that allows smooth passage through the inside of the plastic deformation portion 34b.

The plastic deformed portions 34a and 34b as described above are formed, for example, as follows.
First, the axially opposite side of the shaft portion 20 is slightly inserted into the axially one side of the outer tube 10a. That is, the one side portion in the axial direction of the coupling cylinder portion 30a and the other side portion in the axial direction of the shaft portion 20 are engaged. Next, one side of the coupling cylinder 30a in the axial direction is crushed from the outside in the radial direction by a tool, and the inner peripheral surface of the one side of the coupling cylinder 30a in the axial direction and the outer peripheral surface of the other side in the axial direction of the shaft 20 are crushed. , Plastically deformed into an elliptical cross section to form plastically deformed portions 34a and 34b in the portion. After that, the inner shaft 9a and the outer tube 10a are displaced relative to each other in the axial direction so as to reduce the total length of the first telescopic shaft 16, and the total length of the first telescopic shaft 16 is set to a predetermined axial length in a steady state. .. As a result, the plastically deformed portion 34a of the inner shaft 9a and the plastically deformed portion 34b of the outer tube 10a are arranged apart from each other in the axial direction.

[Structure of the second telescopic shaft]
As shown in FIGS. 2 and 6, the second telescopic shaft 17 includes a male shaft 35, a female shaft 36, a plurality of balls 37, a plurality of rollers 38, and a plurality of leaf springs 39. ing.

The male shaft 35 is configured to be solid over the entire length, and has a first male side axial groove 40 and a second male side axial groove 41 extending in the axial direction on the outer peripheral surface of one side in the axial direction. Alternately in the circumferential direction. The first male side axial groove 40 has a substantially equilateral leg base shape in cross section, and the circumferential width of the opening is wider than the circumferential width of the bottom portion. On the other hand, the second male side axial groove 41 has a concave arc shape in cross section. Further, a ring-shaped stopper 42 is fixed to the outer peripheral surface of the end portion of the male shaft 35 on one side in the axial direction. As a result, the ball 37 arranged in the first male side axial groove 40 and the roller 38 arranged in the second male side axial groove 41 are moved to the first male side axial groove 40 and the second male side. It is prevented from coming out from the axial groove 41 to one side in the axial direction. A yoke 43 separate from the male shaft 35 is fixed to the other end of the male shaft 35 in the axial direction by welding. The yoke 43 constitutes a universal joint 4c together with another yoke 44 and a cross shaft connected to the front end portion of the steering shaft 2.

The female shaft 36 is entirely formed of a hollow circular tubular shape, and has a first female-side axial groove 45 and a second female-side axial groove 46 extending in the axial direction on the inner peripheral surface in the circumferential direction. Alternately have. The first female side axial groove 45 and the second female side axial groove 46 each have a concave arc shape in cross section.

When the male shaft 35 is inserted inside the female shaft 36, the phases of the first male side axial groove 40 and the first female side axial groove 45 are matched in the circumferential direction, and the second male side The phases of the axial groove 41 and the second female axial groove 46 in the circumferential direction are matched. Then, a plurality of balls 37 are arranged between the first male side axial groove 40 and the first female side axial groove 45. Further, a leaf spring 39 is arranged between the first male side axial groove 40 and the plurality of balls 37, and a preload is applied to the plurality of balls 37. Further, one roller 38 is arranged between the second male side axial groove 41 and the second female side axial groove 46.

In the second telescopic shaft 17 as described above, the male shaft 35 and the female shaft 36 are combined so that torque can be transmitted and the entire length can be expanded and contracted in a steady state. In particular, the second telescopic shaft 17 increases when a plurality of balls 37 and leaf springs 39 transmit torque between the male shaft 35 and the female shaft 36 during low torque transmission, and the transmitted torque increases. A plurality of rollers 38 transmit the torque of the minute. Further, when the male shaft 35 and the female shaft 36 are displaced relative to each other in the axial direction, the plurality of balls 37 roll between the first male side axial groove 40 and the first female side axial groove 45. The plurality of rollers 38 move and slide between the second male side axial groove 41 and the second female side axial groove 46. Further, in this example, since the plurality of balls 37 are pressed against the inner surface of the first female axial groove 45 by the elasticity of the leaf spring 39, the male shaft 35 and the female shaft 36 are prevented from rattling. NS.

[Structure of joint members]
In this example, the first telescopic shaft 16 and the second telescopic shaft 17 as described above are connected by the joint member 18 so as to be able to transmit torque. The joint member 18 has a female joint 47 and a male joint 48. The female joint 47 is fixed to the coupling cylinder portion 30b of the outer tube 10a constituting the first telescopic shaft 16, and the male joint 48 is fixed to the female shaft 36 constituting the second telescopic shaft 17.

The female joint 47 is formed in a substantially cylindrical shape as a whole. A male serration 49 is provided on the outer peripheral surface of one side of the female joint 47 in the axial direction, and a female serration 50 is provided on the inner peripheral surface of the other side of the female joint 47 in the axial direction. Further, a slit 51 extending in the axial direction is provided in the other half of the female joint 47 in the axial direction, and a pair of slits extending outward in the radial direction are provided on both sides of the slit 51 in the circumferential direction. A collar 52 is provided. Further, the pair of collar portions 52 are provided with screw holes 53 coaxially with each other.

Then, the male serration 49 provided on the outer peripheral surface of the female joint 47 on one side in the axial direction is serrated engaged with the second female serration 33 provided on the inner peripheral surface of the coupling cylinder portion 30b of the outer tube 10a. There is. Further, the outer peripheral surface of the female joint 47 and the end surface of the coupling cylinder portion 30 on the other side in the axial direction are welded and fixed by the weld bead portion 54. As a result, the female joint 47 and the outer tube 10a are coupled so that torque can be transmitted.

The male joint 48 has a joint shaft portion 55 on one side in the axial direction and a fitting cylinder portion 56 on the other side in the axial direction. A male serration 57 is provided on the outer peripheral surface of the joint shaft portion 55 over the entire circumference, and a notch 58 is provided in a part in the circumferential direction in a direction perpendicular to the central axis of the joint shaft portion 55. There is.

Then, the joint shaft portion 55 is inserted inside the other side portion in the axial direction of the female joint 47, and the male serration 57 and the female serration 50 are serrated engaged with each other. As a result, the female joint 47 and the male joint 48 are coupled so that torque can be transmitted. Further, a bolt (not shown) is screwed into the screw hole 53 of the pair of flange portions 52 constituting the female joint 47. Then, the intermediate portion of the bolt is arranged inside the notch 58 to prevent the joint shaft portion 55 from coming out from the female joint 47 to the other side in the axial direction. Further, the fitting cylinder portion 56 is internally fitted and fixed to the end portion of the female shaft 36 on one side in the axial direction. Further, the outer peripheral surface of the male joint 48 and the end surface of the female shaft 36 on one side in the axial direction are welded and fixed by a weld bead portion 59. As a result, the male joint 48 and the female shaft 36 are coupled so that torque can be transmitted.

In the steady state, the intermediate shaft 5b of this example as described above expands and contracts due to the relative displacement of the male shaft 35 and the female shaft 36 constituting the second telescopic shaft 17 in the axial direction. This prevents the vibration input from the tire during traveling from being transmitted to the steering wheel 1.

When a so-called full-wrap collision occurs in which the entire front surface of the vehicle body collides with another automobile or the like, the fuse portion 29 is deformed and the first telescopic shaft 16 and the second telescopic shaft 17 are contracted, respectively. As a result, the intermediate shaft 5b shortens the total length while absorbing the impact load. This prevents the steering wheel 1 from being pushed up toward the driver.

On the other hand, when a part of the front surface of the vehicle body is biased in the width direction and collides with another automobile or the like, a so-called offset collision occurs, the engine room is deformed and the intermediate shaft 5b is moved in the axial direction. It may not be able to shrink. In this case, the fuse portion 29 is deformed and the outer tube 10a is bent at the bellows portion 31 based on the impact load caused by the collision. As a result, the impact load is absorbed, and the bent intermediate shaft 5b is housed in the gap existing between the peripheral parts to prevent the intermediate shaft 5b from being displaced rearward. Therefore, even in the case of an offset collision, it is possible to prevent the steering wheel 1 from being pushed up toward the driver. Whether or not the total length of the intermediate shaft 5b contracts when an offset collision occurs depends on how an impact load is applied, how the engine room is deformed, and the like.

According to the intermediate shaft 5b of this example as described above, the amount of contraction in the axial direction can be increased.
That is, in this example, the inner shaft 9a constituting the first telescopic shaft 16 is integrated with the yoke portion 19 and the shaft portion 20, so that the amount of contraction is increased and the fuse portion 29 is included in the shaft portion 20. It is possible to increase the amount of shrinkage by providing the concave curved surface 28 at a position adjacent to the other side in the axial direction.

First, the reason why the amount of contraction of the first telescopic shaft 16 is increased by integrating the yoke portion 19 and the shaft portion 20 will be described with reference to FIG. 7.
FIG. 7A shows the structure of the telescopic shaft of Comparative Example 1 in which a separate yoke 11 is welded and fixed to the inner shaft 9 by a weld bead portion 15. On the other hand, FIG. 7B shows the structure of the telescopic shaft of Comparative Example 2 in which the inner shaft 9a is an integral structure of the yoke portion 19 and the shaft portion 20. The telescopic shaft of FIG. 7B is different from the first telescopic shaft 16 of this example in that the fuse portion 29 is not provided on the shaft portion 20 of the inner shaft 9a.

In the telescopic shaft of Comparative Example 1, the end face on one side in the axial direction of the outer tube 10a is in a state of being contracted to the maximum, as shown by a chain line showing the end on one side in the axial direction of the outer tube 10a when it is maximally contracted. , It hits the weld bead portion 15. At this time, the end surface of the outer tube 10a on one side in the axial direction is located at the X point in FIG. 7 (A).

On the other hand, the telescopic shaft of Comparative Example 2 is in a state of being fully contracted in the axial direction of the outer tube 10a as shown by a chain line at one end of the outer tube 10a in the axial direction when the outer tube 10a is contracted to the maximum. The end face on the side abuts on the inner diameter side portion of the concave curved surface 28. At this time, the end surface of the outer tube 10a on one side in the axial direction is located at the Y point in FIG. 7B.

Therefore, by integrating the yoke portion 19 and the shaft portion 20, the amount of expansion and contraction can be increased by α corresponding to the axial difference between the X point and the Y point. That is, by integrating the yoke portion 19 and the shaft portion 20, the weld bead portion 15 having a triangular cross section is provided at a position where the weld bead portion 15 is provided, instead of the weld bead portion 15, a concave curved surface having a concave arc shape in cross section. It can be changed to a structure having 28. Therefore, the amount of shrinkage can be increased based on the difference in cross-sectional shape between the weld bead portion 15 and the concave curved surface 28.

Next, refer to FIG. 8 for the reason why the amount of contraction of the first telescopic shaft 16 is increased by providing the fuse portion 29 at a position of the shaft portion 20 adjacent to the other side of the concave curved surface 28 in the axial direction. I will explain.
In FIG. 8A, the inner shaft 9a has an integral structure of the yoke portion 19 and the shaft portion 20, and the fuse is located at a position within the shaft portion 20 at a predetermined distance from the concave curved surface 28 on the other side in the axial direction. The structure of the telescopic shaft of Comparative Example 3 provided with the portion 29 is shown. On the other hand, in FIG. 8B, the inner shaft 9a has an integral structure of the yoke portion 19 and the shaft portion 20, and is located at a position of the shaft portion 20 adjacent to the other side of the concave curved surface 28 in the axial direction. The structure of the first telescopic shaft 16 of this example is shown in which a fuse portion 29 is provided and the outer peripheral surface of the fuse portion 29 is directly continuous with the concave curved surface 28.

In the telescopic shaft of Comparative Example 3, the end face on one side in the axial direction of the outer tube 10a is in a state of being contracted to the maximum, as shown by a chain line showing the end on one side in the axial direction of the outer tube 10a when it is maximally contracted. , It abuts on the inner diameter side portion of the concave curved surface 28. That is, as is clear from the structure of FIG. 7 (B), the contact position does not change even if the fuse portion 29 is provided, and the end face on one side in the axial direction of the outer tube 10a is shown in FIG. 8 (A). ) Is located at the Y point.

On the other hand, in the first telescopic shaft 16 of this example, since the fuse portion 29 is provided at a position adjacent to the other side of the concave curved surface 28 in the axial direction in the shaft portion 20, the outer is when contracted to the maximum. As shown by the chain line on one end of the tube 10a in the axial direction, the end surface of the outer tube 10a on one side in the axial direction abuts on the outer diameter side portion of the concave curved surface 28 in a state of being maximally contracted. At this time, the end surface of the outer tube 10a on one side in the axial direction is located at the Z point in FIG. 8 (B).

Therefore, by providing the fuse portion 29 at a position adjacent to the other side of the concave curved surface 28 in the axial direction in the shaft portion 20, the amount of expansion and contraction is by β corresponding to the axial difference between the Y point and the Z point. Can be increased. That is, by providing the fuse portion 29 at a position of the shaft portion 20 adjacent to the other side of the concave curved surface 28 in the axial direction, the formation position of the concave curved surface 28 can be set in FIGS. 8 (A) and 7 (B). Compared to the structure, it can be moved inward in the radial direction. In order to facilitate understanding, when the contour of the concave curved surface 28 of Comparative Example 3 and the contour of the concave curved surface 28 of this example are overlapped, as shown in FIG. 8C, Comparative Example 3 shown by a broken line is shown. The concave curved surface 28 of this example shown by a solid line is located inward in the radial direction with respect to the concave curved surface 28 of the above. Therefore, the position where the end surface of the outer tube 10a on one side in the axial direction abuts can be shifted to one side in the axial direction (left side in FIG. 8) by β, and the amount of contraction can be increased.

As described above, in this example, the increase α due to the integral structure of the yoke portion 19 and the shaft portion 20 and the fuse portion 29 are adjacent to the other side of the shaft portion 20 in the axial direction of the concave curved surface 28. The expansion / contraction amount of the first expansion / contraction shaft 16 can be increased by the sum (α + β) of the increase β provided in the portion. Therefore, according to the intermediate shaft 5b of this example, it is possible to prevent the influence at the time of the primary collision from being transmitted to the steering column 3. As a result, the collision safety performance of the automobile can be further improved.

[Second Example of Embodiment]
A second example of the embodiment of the present invention will be described with reference to FIG. The feature of this example is the structure of the inner shaft 9b constituting the first telescopic shaft 16. That is, in this example, the intermediate material 60 having the shape as shown in FIG. 9A is produced by subjecting the columnar material to cold forging. The intermediate material 60 has a bifurcated portion 61 on one side in the axial direction and a hollow shaft portion 62 on the other side in the axial direction, and these bifurcated portions 61 and the hollow shaft portion 62 are integrally formed. A hollow portion 26a opened only on the end surface on the other side in the axial direction is provided in a wide range extending from the other side portion in the axial direction to the intermediate portion of the hollow shaft portion 62. Further, a male serration 27 is provided on the outer peripheral surface of the other side portion of the hollow shaft portion 62 in the axial direction.

In this example, the inner shaft 9b of this example shown in FIG. 9B is formed by cutting the intermediate material 60 having the above-described configuration. Specifically, the yoke portion 19 is formed by cutting the bifurcated portion 61 to adjust the shape. Further, of the outer peripheral surface of the hollow shaft portion 62, the shape on one side in the axial direction from the portion provided with the male serration 27 is adjusted to form a concave curved surface 28, a fuse portion 29, and the like to form the shaft portion 20a. .. At this time, as shown in the drawing, it is preferable that the end face (bottom surface) of the fuse portion 29 on the other side in the axial direction and the end surface (bottom surface) on the one side in the axial direction of the hollow portion 26a are aligned in the axial direction. If such a configuration is adopted, the weight of the inner shaft 9b can be reduced to the maximum by providing the hollow portion 26a while ensuring the torque transmission function by the fuse portion 29. That is, when the fuse portion 29 is not deformed even if the maximum torque that can be transmitted in a steady state or a torque having a magnitude obtained by adding the safety factor to the torque is applied, and a shocking load or torque is applied. Only the function of plastic deformation is required before other parts, but if the hollow part 26a is provided inside the fuse part 29, the torque that can be transmitted without causing deformation becomes small, and the torque that can be transmitted becomes small as described above. It becomes difficult to secure the function of. Other configurations and effects are the same as in the first example of the embodiment.

In each example of the embodiment, of the first telescopic shaft and the second telescopic shaft constituting the intermediate shaft, the first telescopic shaft is arranged in the front of the vehicle and the second telescopic shaft is arranged in the rear of the vehicle. As described above, the second telescopic shaft can be arranged in front of the vehicle and the first telescopic shaft can be arranged in the rear of the vehicle.

1 Steering wheel 2 Steering shaft 3 Steering column 4a, 4b, 4c, 4d Flexible joint 5, 5a, 5b Intermediate shaft 6 Steering gear unit 7 Tie rod 8 Input shaft 9, 9a, 9b Inner shaft 10, 10a Outer tube 11 Yoke 12 Male Spline 13 Female Spline 14 Yoke 15 Welded bead part 16 First telescopic shaft 17 Second telescopic shaft 18 Joint member 19 York part 20, 20a Shaft part 21 York 22 Base part 23 Arm part 24 Circular ring surface 25 Circular hole 26, 26a Hollow part 27 Male serration 28 Concave curved surface 29 Fuse part 30a, 30b Coupling cylinder part 31 Bellows part 32 First female serration 33 Second female serration 34a, 34b Plastic deformation part 35 Male shaft 36 Female shaft 37 Ball 38 Roller 39 Leaf spring 40 First Male side axial groove 41 Second male side axial groove 42 Stopper 43 York 44 York 45 First female side axial groove 46 Second female side axial groove 47 Female joint 48 Male joint 49 Male serration 50 Female serration 51 Slit 52 Bitch 53 Screw hole 54 Weld bead 55 Joint shaft 56 Fitting cylinder 57 Male serration 58 Notch 59 Weld bead 60 Intermediate material 61 Bifurcated 62 Hollow shaft

Claims (4)

A yoke portion on one side in the axial direction and a shaft portion provided integrally with the yoke portion on the other side in the axial direction of the yoke portion are provided on the outer peripheral surface of the end portion on one side in the axial direction of the shaft portion. The shaft has a concave curved surface having an arcuate cross section continuous with the side surface on the other side in the axial direction of the yoke portion, and is adjacent to the other side of the concave curved surface in the axial direction in the shaft portion. An inner shaft having a smaller diameter than the other parts of the portion and having a fuse portion having a fuse portion whose one side portion in the axial direction of the outer peripheral surface is directly continuous with the concave curved surface.
An outer tube in which the shaft portion of the inner shaft is coupled to one side portion in the axial direction so as to be able to transmit torque and at least allow relative displacement in the axial direction at the time of a temporary collision.
Telescopic shaft with. The telescopic shaft according to claim 1, which has a bellows portion in the axially intermediate portion of the outer tube. The shaft portion of the inner shaft and the outer tube are connected in a steady state so as to be unable to perform relative displacement in the axial direction, and the inner shaft constitutes a fitting portion between the inner shaft and the outer tube. Of claims 1 and 2, the outer peripheral surface of the shaft portion is provided with a plastic deformation portion having a non-circular cross section on the other side portion in the axial direction and the inner peripheral surface of the outer tube on one side portion in the axial direction. The telescopic shaft according to any one of the above items. The shaft portion constituting the inner shaft is provided with a hollow portion that is open only on the end surface on the other side in the axial direction of the shaft portion, and the end surface on one side in the axial direction of the hollow portion and the shaft of the fuse portion. The telescopic shaft according to any one of claims 1 to 3, wherein the position in the axial direction is the same as that of the edge portion on the other side of the direction.

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