JP2008239081A - Energy absorbing shaft for steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a structure capable of absorbing impact by bending its intermediate part in a "chevron" shape at the time of collision, easily manufacturable at low cost, and having superior heat resistance. <P>SOLUTION: This energy absorbing shaft comprises a displacement limiting part allowing an inner shaft 7 and a first outer tube 6 to be axially displaced relative to each other only when a lateral strong force is applied between the inner shaft and the first outer tube. The displacement limiting part locks a stopper such as a stopper ring 17 manufactured independently of the inner shaft 7 and the first outer tube 6 to the inner shaft 7. The stopper enables the first outer tube 6 to be relatively displaced from the inner shaft 7 axially to the position where the outer tube comes off a small sectional area part 12 formed at the intermediate part of the inner shaft 7 because it is broken or axially displaced relative to the inner shaft 7 by the strong force. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an improvement of an energy absorbing shaft for a steering device that protects a driver by bending while absorbing impact energy in the event of a collision among intermediate shafts that constitute a steering device for an automobile.

  As shown in FIG. 11, the steering apparatus for automobiles moves the steering wheel 1 operated by the driver to a plurality of shafts such as a steering shaft 2 and an intermediate shaft 3, and ends of the shafts 2 and 3. Is transmitted to a steering gear (not shown) through universal joints 4a and 4b. In the vehicle steering apparatus configured as described above, in order to protect the driver in the event of a collision, the steering shaft 2 and the steering column 5 through which the steering shaft 2 is inserted, or the intermediate shaft 3 are brought into contact with the impact. In general, an energy absorption type that absorbs impact energy and shortens the entire length is used. Further, regarding the intermediate shaft 3, it has been widely practiced that the intermediate shaft 3 is bent in a “<” shape at the axial intermediate portion while absorbing the energy of the impact.

  As such an energy absorption shaft for a steering device that bends at an intermediate portion in the axial direction while absorbing impact energy, for example, those described in Patent Documents 1 to 3, for example, are known. 12-16 has shown an example of the energy absorption type shaft for steering devices described in each of these patent documents. This energy absorbing shaft for a steering device includes a first outer tube 6, an inner shaft 7, and a second outer tube 8. Each of these members 6 to 8 engages a male serration groove formed on the outer peripheral surface of the inner shaft 7 and a female serration groove formed on the inner peripheral surfaces of the first and second outer tubes 6 and 8. Thus, torque transmission and relative displacement in the axial direction are combined in a possible manner.

  However, the inner shaft 7 and the first and second outer tubes 6, 8 are small diameter portions 9 a, 9 b formed at a plurality of locations (three locations in the illustrated example) of the inner shaft 7. 9c and the synthetic resin 11a, 11b, 11c spanned between the through holes 10a, 10b, 10c formed in the outer tubes 6, 8. Therefore, the inner shaft 7 and the first and second outer tubes 6 and 8 are relatively relative to each other only in the axial direction when a strong impact is applied in the axial direction and the synthetic resins 11a, 11b, and 11c are torn. Displaceable. In addition, a small cross-sectional area portion 12 having a sufficiently small diameter compared with other portions of the inner shaft 7 is formed in a portion located on the inner diameter side of the first outer tube 6 in the middle portion of the inner shaft 7. Is provided. Further, a portion (upper right portion in FIG. 12) of one end edge of the first outer tube 6 that faces one end edge (left lower end edge in FIG. 12) of the second outer tube 8 It is made to incline in the direction which leaves | separates from the one end edge of said 2nd outer tube 8 rather than the other half part side. The one end edge of the second outer tube 8 may be inclined instead of or together with the one end edge of the first outer tube 6.

  The energy absorbing shaft for a steering device as described above is incorporated in a steering device for an automobile, and transmits the movement of the steering wheel 1 (FIG. 11) to a steering gear (not shown). Normally, the first outer tube 6 exists around the small cross-sectional area 12 based on the locking force of the synthetic resins 11b and 11c. For this reason, the inner shaft 7 is not bent at the small cross-sectional area portion 12. Further, the torque for steering is transmitted from the rear part (upper right part in FIG. 12) of the inner shaft 7 to the front part (lower left part) mainly by the first outer tube 6.

  When a strong compressive force in the axial direction is applied to the energy absorbing shaft for the steering device at the time of a collision (according to a primary collision or a secondary collision), first, the second outer tube 8 and the inner shaft 7 The synthetic resin 11a stretched between them breaks, and the locking force by the synthetic resin 11a is lost. Then, the inner shaft 7 and the second outer tube 8 are displaced in the axial direction as shown in FIGS. 12 to 13, and the upper half of one end edge of the second outer tube 8 and the first outer tube 6. The upper half of the one end edge contacts. When the inner shaft 7 further moves rearward (upper right direction in FIG. 12) with respect to the second outer tube 8 from this state, the inner shaft 7 is spanned between the first outer tube 6 and the inner shaft 7. The synthetic resins 11b and 11c are also broken, and the first outer tube 6 is pushed toward one end of the inner shaft 7 (the lower left end in FIG. 12) by the second outer tube 8. Then, as shown in FIGS. 13 to 14, the abutting surface of the first outer tube 6 and the second outer tube 8 moves in the axial direction, and this abutting surface is an intermediate portion of the small cross-sectional area portion 12. It seems to exist around. At the same time, one end surface of the first outer tube 6 abuts against a stepped surface 14 provided at one end portion of the inner shaft 7, so that it does not move in the axial direction with respect to the inner shaft 7 any more. Instead of omitting the stepped surface 14, the other end surface of the inner shaft 7 (upper right end surface in FIG. 12) is pushed to a coupling pin 16 that couples the second outer tube 8 and the universal joint yoke 15. A hitting structure can also be adopted. Although such a structure is also described in Patent Document 1, in any case, the inner shaft 7 does not move in the axial direction any more from the state shown in FIG.

  When the compression force is further applied from the state shown in FIG. 14, the inner shaft 7 that has lost the bending prevention force by the first outer tube 6 is bent. For example, as shown in the figure, in the case of a structure in which one end surface of the first outer tube 6 is abutted against the stepped surface 14, the one end edge of the inclined first outer tube 6 and the second outer tube are inclined. Based on the engagement with the one end edge of 8, a force in the direction of bending the central axes of these outer tubes 6, 8 is applied. The small cross-sectional area 12 of the inner shaft 7 is bent by plastic deformation as shown in FIGS. In this way, by plastically deforming the small cross-sectional area 12 in the direction of bending, the energy due to the collision is absorbed while the entire length of the steering shaft is reduced, and the impact applied to the driver's body is reduced. In the case of a structure in which the other end surface of the inner shaft 7 is abutted against the coupling pin 16, it is not necessary to incline the one end edge of the first outer tube 6 (it is free to incline), but in this case However, the small cross-sectional area portion 12 is bent based on the compression force.

  Regardless of the structure, the energy absorbing shaft for a steering device as described above is formed between the inner shaft 7 and the first and second outer tubes 6, 8. It is made by passing 11c. As described above, since the work of transferring the synthetic resins 11a, 11b, and 11c is troublesome, the manufacturing cost of the energy absorbing shaft for the steering device is considerably increased.

  Further, the energy absorbing shaft for a steering device as described above is often used as the intermediate shaft 3 shown in FIG. Since the intermediate shaft 3 is often installed in the engine room, it may be exposed to a high temperature during use. For this reason, the synthetic resins 11a, 11b, and 11c for preventing axial displacement between the inner shaft 7 and the first and second outer tubes 6 and 8 at normal times have sufficient heat resistance. Need to use. A synthetic resin having sufficient heat resistance is expensive, and the material cost for producing the energy absorbing shaft for a steering device is increased.

JP-A-7-309241 JP-A-8-258727 Utility Model Registration No. 2586569

  In view of the circumstances as described above, the present invention has a structure that absorbs an impact while folding an intermediate portion into a “<” shape at the time of a collision accident, and can at least easily perform a manufacturing operation. It was invented to realize a structure that can be reduced. Furthermore, it is intended to realize a structure having excellent heat resistance as required.

The energy absorbing shaft for a steering device according to the present invention includes an inner shaft, a first outer tube, a second outer tube, and a displacement limiting portion.
Of these, the inner shaft has a small cross-sectional area portion formed in the axially intermediate portion and a male serration groove formed on the outer peripheral surface.
Further, the first outer tube is provided with the small cross-sectional area part in the axial direction of the inner shaft in a state where the female serration groove formed on the inner peripheral surface and the male serration groove are serrated. The outer portion is fitted around the small cross-sectional area.
The second outer tube has a serration engagement between a female serration groove formed on an inner peripheral surface and a male serration groove around a portion of the inner shaft remaining in the axial direction and deviating from the small cross-sectional area. It is externally fitted in a combined state.
The displacement limiting portion is provided between the inner shaft and the first outer tube, and only when a strong axial force is applied between the inner shaft and the first outer tube, The inner shaft and the first outer tube can be relatively displaced in the axial direction.

In particular, in the energy absorbing shaft for a steering device according to the present invention, the displacement limiting portion is constituted by a blocking tool that is made independently of the inner shaft and the first outer tube. That is, in the state where the inner shaft and the first outer tube are combined with each other, the synthetic resin is passed between the inner shaft and the first outer tube. The inner shaft and the first outer tube are not formed by injection molding using the shaft and the first outer tube), but the inner shaft and the first outer tube are separately manufactured.
In the case of the energy absorbing shaft for a steering device of the present invention, the above-described blocking tool is locked to a part of the inner shaft. Then, by engaging the blocking tool with a part of the first outer tube, at least the first outer tube is in the axial direction with respect to the inner shaft until the first outer tube is disengaged from the small cross-sectional area. Limit relative displacement.
Further, the blocking device is relatively displaced in the axial direction up to a position where the first outer tube is disengaged from the small cross-sectional area portion by breaking or axially displacing with respect to the inner shaft based on the strong force. It makes it possible to do.

When implementing the energy absorbing shaft for a steering device of the present invention as described above, for example, as described in claim 2, the blocking tool is a blocking ring whose inner diameter can be elastically expanded and contracted. Then, the blocking ring is connected to a portion of the outer peripheral surface of the inner shaft exposed from the first outer tube on the side opposite to the second outer tube, from the second outer tube to the first outer tube. Based on the strong force applied to the tube in the axial direction, the tube is locked on the opposite side to the second outer tube so as to be axially displaceable.
When implementing such an energy absorbing shaft for a steering device according to claim 2, for example, as described in claim 3, the inner peripheral edge of the blocking ring is the first outer peripheral surface of the inner shaft. It latches in the latching groove formed in the part exposed from the 1st outer tube on the opposite side to a 2nd outer tube. And based on the strong force added to the said axial direction, the inner peripheral edge part of the said blocking ring is dropped from this latching groove.
Alternatively, as described in claim 4, the inner peripheral edge of the blocking ring is frictionally engaged with a portion of the outer peripheral surface of the inner shaft that is exposed from the first outer tube on the side opposite to the second outer tube. Let And based on the strong force added to the said axial direction, the inner peripheral part of the said prevention ring is slid with respect to the outer peripheral surface of this 1st outer tube.

  Further, when implementing the energy absorbing shaft for a steering device of the present invention as described above, for example, as described in claim 5, the blocking device is a material that can be broken based on a strong force applied in the axial direction. In this way, the blocking ring is constructed so that its diameter can be increased or decreased. Further, a portion closer to the inner diameter of the blocking ring is locked in a locking groove formed on a portion of the outer peripheral surface of the inner shaft that is exposed from the first outer tube on the side opposite to the second outer tube. To do. Then, based on the strong force applied in the axial direction, the outer diameter portion of the blocking ring is broken from the inner diameter portion, and the first outer tube is displaced to the opposite side of the second outer tube. Acceptable.

  Further, when implementing the energy absorbing shaft for a steering device of the present invention as described above, for example, as described in claim 6, the blocking device can be broken based on a strong force applied in the axial direction. A blocking pin made of material. Further, the lengthwise intermediate portion of the blocking pin penetrates the inner shaft in a radial direction in a portion of the inner shaft that is exposed from the first outer tube on the side opposite to the second outer tube. It locks in the locking hole formed in the state. Then, based on the strong force applied in the axial direction, both end portions in the length direction of the blocking pin are similarly broken from the intermediate portion, and the first outer tube is displaced to the side opposite to the second outer tube. Acceptable.

According to the energy absorbing shaft for a steering device of the present invention configured as described above, in the event of a collision, the structure can be easily manufactured with a structure that absorbs an impact while bending the intermediate portion into a "<" shape. It is possible to reduce the cost. Furthermore, if necessary, a structure having excellent heat resistance can be realized.
That is, only when a strong force is applied in the axial direction, a displacement limiting portion for enabling relative displacement in the axial direction between the inner shaft and the first outer tube is provided between the inner shaft and the first outer tube. Since it is configured by a blocking tool made independently, the displacement limiting portion can be easily configured, and the cost can be reduced.
In particular, if the blocking device is made of a heat-resistant material such as metal, a structure having excellent heat resistance can be obtained.

[First example of embodiment]
1-4 show a case where the structure of the present invention is applied to an intermediate shaft 3a as a first example of an embodiment of the present invention corresponding to claims 1 to 3. FIG. The feature of the present invention, including this example, is that the first outer tube 6 fitted on the axially intermediate portion of the inner shaft 7 is normally formed in a small cross-sectional area formed on the axially intermediate portion of the inner shaft 7. The first outer tube 6 and the inner shaft 7 are positioned so as to straddle the portion 12 and retract the first outer tube 6 from the peripheral portion of the small cross-sectional area 12 in the event of a collision. It is in the structure of the displacement limiting part provided between. Since the structure and operation of the other parts are the same as those of the conventional structure shown in FIGS. 12 to 16 described above, the same parts are denoted by the same reference numerals, and redundant description is omitted or simplified. The description will focus on the features of

  In the case of this example, the displacement limiting portion is engaged with the engaging groove 18 formed on the outer peripheral surface of the intermediate portion of the inner shaft 7 at the inner peripheral edge of the blocking ring 17 as shown in FIG. It is configured by stopping. The blocking ring 17 is formed by bending a wire having a circular cross section having elasticity, and is formed in a ring shape. A pair of locking portions 20 and 20 are respectively provided at both ends of the annular portion 19 in the radial direction. It is provided so as to protrude outward. Of these, the annular portion 19 is elastically expandable / contractible, and the inner diameter in the free state is more preferably the inner shaft 7 than the outer diameter of the inner shaft 7 (the diameter of the tip of the male serration). 7 is smaller than the outer diameter at the bottom of the locking groove 18. The locking groove 18 has a shape in which the width dimension in the axial direction gradually decreases as it goes from the opening to the bottom. As such a locking groove 18, for example, a V-shaped cross section as shown in FIG. 2B or an arc-shaped cross section as shown in FIG. 2C can be adopted. . Although not shown, the locking groove has a U-shaped cross section and the depth is sufficiently smaller than the outer diameter (height in the radial direction) of the wire constituting the blocking ring 17 (for example, less than 1/3). It is also possible to adopt a locking groove.

  Regardless of which shape is adopted, the locking groove 18 as described above is formed on the outer peripheral surface of the intermediate portion of the inner shaft 7 on the side opposite to the second outer tube 8 (the left side in FIGS. 1, 3 and 4). A portion exposed from the first outer tube 6 is formed. Further, the depth of the locking groove 18 is ½ or less of the outer diameter of the wire constituting the blocking ring 17. Therefore, in a state in which the blocking ring 17 is locked in the locking groove 18, among the annular portion 19 constituting the blocking ring 17, more than half of the radially outer half is radial from the outer peripheral surface of the inner shaft 7. It protrudes outward and opposes one axial end surface (the left end surface in FIGS. 1, 3, and 4) of the first outer tube 6.

As a result, the first outer tube 6 is sandwiched between the distal end surface of the second outer tube 8 (the left end surface in FIGS. 1, 3, and 4) and the annular portion 19 of the blocking ring 17. Thus, the amount of axial displacement with respect to the inner shaft 7 is limited. As long as the annular portion 19 does not fall off the locking groove 18, the small cross-sectional area portion 12 is not exposed from the first outer tube 6. For this reason, in the case of this example, the dimensions of each part are regulated as follows. First, as shown in FIG. 3, the axial distance between the both end edges in the axial direction of the small cross-sectional area 12 and the both end surfaces of the first outer tube 6 (the first outer tube 6 and the inner shaft 7). Are defined as L ₁ and L ₂ , respectively. Also, as shown in FIG. 3, the width in the axial direction of the gap between the both end faces of the first outer tube 6, the tip face of the second outer tube 8 and the annular portion 19 is set to δ. ₁ and δ ₂ are defined. Then, the dimensions of the respective parts are regulated so that L ₁ > δ ₁ + δ ₂ and L ₂ > δ ₁ + δ ₂ are satisfied (the overlap length is sufficiently ensured and the widths of the gaps are narrowed). . Therefore, in the normal state (when no collision accident occurs), the first outer tube 6 is present at a position across the small cross-sectional area 12 in the inner shaft 7. In this state, most of the torque for steering is transmitted by the first outer tube 6 to prevent a large stress from being generated in the small cross-sectional area portion 12 due to the steering.

  On the other hand, when an impact load in the compression direction (direction approaching each other) is applied between a pair of universal joints 4a and 4b provided at both ends of the intermediate shaft 3a due to a collision accident, the second outer tube 8 strongly presses the other axial end surface (the right end surface in FIGS. 1, 3, and 4) of the first outer tube 6. Then, the first outer tube 6 is displaced toward one end side in the axial direction, and one end surface in the axial direction of the first outer tube 6 strongly presses the annular portion 19 of the blocking ring 17 in the axial direction. As a result, the annular portion 19 is dropped from the locking groove 18 and the first outer tube 6 can be moved in the axial direction. The first outer tube 6 is connected to the second outer tube 8. It is pushed and moves in the direction of retreating from the periphery of the small cross-sectional area portion 12.

  In the illustrated example, the portion closer to the inner diameter of the annular portion 19 is locked. The locking groove 18 has a shape in which the width dimension gradually decreases from the opening portion toward the bottom portion. When 19 is pressed in the axial direction, a force in the direction of expanding the diameter is applied to the annular portion 19 based on the engagement between the inner peripheral edge of the annular portion 19 and the bottom surface of the locking groove 18. Further, since the depth of the locking groove 18 is suppressed to ½ or less of the outer diameter of the wire constituting the blocking ring 17, one end surface in the axial direction of the first outer tube 6 is formed in the annular shape. Of the one side surface in the axial direction of the portion 19, it hits the radial center position (it does not hit the portion near the outer diameter in the radial direction). Therefore, based on the abutment between the one axial end surface of the first outer tube 6 and one axial side surface of the annular portion 19, no force in the direction of reducing the diameter is applied to the annular portion 19. For this reason, when an impact load directed in the axial direction is applied from the second outer tube 8 to the first outer tube 6, the blocking ring 17 smoothly drops from the locking groove 18.

  In any case, when the first outer tube 6 moves in the direction of retreating from the periphery of the small cross-sectional area 12, the small cross-sectional area 12 is moved to the first outer tube 6 as shown in FIG. And is in a state of being present on the inner diameter side of the abutting portion between the first outer tube 6 and the second outer tube 8. If a force in the compression direction is further applied between the two universal joints 4a and 4b from this state, the small cross-sectional area is obtained in the same process as shown in FIGS. The portion 12 is bent, and while absorbing the impact energy applied between the two universal joints 4a and 4b due to a collision accident, the universal joints 4a and 4b are allowed to approach each other.

  The intermediate shaft 3a of the present example configured as described above includes a displacement limiting portion for enabling relative displacement in the axial direction between the inner shaft 7 and the first outer tube 6. The outer ring 6 is constituted by a blocking ring 17 made independently of the outer tube 6. Since the blocking ring 17 can be easily formed by bending a metal wire having elasticity, the displacement limiting portion can be easily configured, and the cost can be reduced. Further, since the blocking ring 17 made of a metal wire has sufficient heat resistance, the intermediate shaft 3a is sufficiently heat-resistant and installed in the engine room where the intermediate shaft 3a is heated. Even so, sufficient reliability and durability can be secured.

[Second Example of Embodiment]
FIG. 5 also shows a second example of the embodiment of the present invention corresponding to claims 1 to 3. In the case of this example, as the blocking ring 21 which is a blocking tool, a metal plate is formed by punching and forming a ring shape. As such a blocking ring 21, for example, what is called a C-type ring as shown in FIG. 5A or what is called an E-type ring as shown in FIG. 5B can be used. In any structure, since the inner diameter can be expanded and contracted, a portion closer to the inner diameter of the blocking ring 21 is formed on the outer circumferential surface of the intermediate portion in the axial direction of the inner shaft 7 as shown in FIG. It can be locked in the locking groove 22. However, in any structure, since the cross-sectional shape of the blocking ring 21 is rectangular, if the shape of the locking groove 22 is not devised, the blocking ring 21 is locked into the locking groove in the event of a collision. 22 is less likely to fall off. Therefore, in the case of this example, a part of the bottom surface of the locking groove 22 from which the blocking ring 21 should be separated (the left side in FIG. 5C) is the opening edge of the locking groove 22. It is set as the inclined surface 23 which inclined in the direction which becomes shallow gradually as it goes to. By providing such an inclined surface 23, the blocking ring 21 is smoothly and reliably dropped from the locking groove 22 in the event of a collision. Since the configuration and operation of the other parts are the same as in the first example of the above-described embodiment, illustration and description regarding the equivalent parts are omitted.

[Third example of embodiment]
FIG. 6 shows a third example of an embodiment of the present invention corresponding to claims 1, 2, and 4. In the case of this example, as the blocking ring 21 which is a blocking tool, a metal plate is punched and formed into an annular shape. The blocking ring 21 is formed with a plurality of tongue pieces 25, 25 protruding inward in the radial direction and inclined with respect to the axial direction on the inner diameter side of the annular portion 24. As shown in FIG. 6B, the retaining ring 21 has an outer peripheral surface of the intermediate portion of the shaft 7 in a state where the tongue pieces 25 and 25 are frictionally engaged with the outer peripheral surface of the inner shaft 7. Lock to. As a structure corresponding to claim 3, as shown in FIG. 6 (C), the same outer peripheral surface of the inner shaft 7 as that in the second example of the embodiment described above is engaged. A groove 22 may be formed, and the tongue pieces 25, 25 may be frictionally engaged with the bottom surface of the locking groove 22. In any case, in the event of a collision accident, the tip edges of the tongue pieces 25, 25 slide with respect to the outer peripheral surface of the inner shaft 7, and the first outer tube 6 (see FIG. 1, 3, 4) is allowed to be displaced. Since the configuration and operation of other parts are the same as those of the first example of the above-described embodiment, illustration and description regarding the equivalent parts are omitted.

[Fourth Example of Embodiment]
FIG. 7 shows a fourth example of an embodiment of the present invention corresponding to claims 1 and 5. In the case of this example, as the blocking ring 26 which is a blocking tool, synthetic resin, copper or a copper-based alloy, aluminum or an aluminum-based alloy, lead or a lead-based alloy or the like has a low shear resistance (compared to an iron-based material). A material that is formed in a ring shape with a material that is easy to break is used. Regardless of which material is used, the whole is rectangular in cross section and is formed in a C shape as shown in FIG. On the other hand, a locking groove 27 having a U-shaped cross section is formed on the outer peripheral surface of the intermediate portion of the inner shaft 7. The depth of the locking groove 27 is smaller than the width of the blocking ring 26 in the radial direction. Therefore, in a state where the blocking ring 26 is locked in the locking groove 27, the portion closer to the outer diameter of the blocking ring 26 is more than the outer peripheral surface of the inner shaft 7 as shown in FIG. Projects radially outward. In the event of a collision accident, a portion that protrudes radially outward from the outer peripheral surface of the inner shaft 7 near the outer diameter of the blocking ring 26 is the first outer shaft as shown in FIG. 6 to allow the first outer tube 6 to be displaced with respect to the inner shaft 7. Also in this example, if the blocking ring 26 is made of a metal material, sufficient heat resistance can be secured. Since the configuration and operation of other parts are the same as those of the first example of the above-described embodiment, illustration and description regarding the equivalent parts are omitted.

[Fifth Example of Embodiment]
FIG. 8 shows a fifth example of an embodiment of the present invention corresponding to claims 1 and 6. In the case of this example, the blocking pin 28 which is a blocking tool is formed into a hairpin shape using a material having low shear resistance, such as a synthetic resin, copper or a copper alloy, aluminum or an aluminum alloy, lead or a lead alloy. I am using something. Regardless of which material is used, by bending the intermediate portion of the wire having a rectangular cross section, it is folded back so that the width dimension increases toward the tip {upper end of FIG. A pair of locking portions 29, 29 are formed by bending to the opposite side. The length of the blocking pin 28 is larger than the outer diameter of the inner shaft 7.

  On the other hand, a locking hole 30 is formed in an intermediate portion of the inner shaft 7 so as to penetrate the inner shaft 7 in the radial direction. The inner diameter of the locking hole 30 is smaller than the diameter of the circumscribed circle in the free state of the tip of the blocking pin 28. Therefore, when the blocking pin 28 is pushed into the locking hole 30 while elastically compressing the tip thereof, both the locking portions 29, 29 are brought into contact with the outer peripheral surface of the inner shaft 7, As shown in FIG. 8B, both end portions in the length direction of the blocking pin 28 protrude outward in the radial direction from the outer peripheral surface of the inner shaft 7. In the event of a collision accident, the portions projecting radially outward from the outer peripheral surface of the inner shaft 7 at both longitudinal ends of the blocking pin 28 are the first as shown in FIG. The first outer tube 6 is allowed to be displaced with respect to the inner shaft 7 by being broken by the outer tube 6. Also in this example, if the blocking pin 28 is made of a metal material, sufficient heat resistance can be secured. Since the configuration and operation of other parts are the same as those of the first example of the above-described embodiment, illustration and description regarding the equivalent parts are omitted.

[Sixth Example of Embodiment]
FIGS. 9-10 has shown the 6th example of embodiment of this invention corresponding to Claims 1-3. In the case of this example, in addition to the blocking ring 21, which is a blocking tool for blocking the first outer tube 6 from retracting in the opposite direction to the second outer tube 8, the second blocking ring 31. Is locked between the first outer tube 6 and the second outer tube 8 on the outer peripheral surface of the intermediate portion of the inner shaft 7. In the event of a collision accident, the second blocking ring 31 has a locking groove provided on the outer peripheral surface of the inner shaft 7 before the second outer tube 8 presses the first outer tube 6. Drop off from. In the case of such a structure of this example, as shown in FIG. 10, the axial distances L ₁ , L between the axial end edges of the small cross-sectional area 12 and the end faces of the first outer tube 6 are as follows. ₂ and the widths δ ₁ and δ _{2 in} the axial direction of the gap between the both end faces of the first outer tube 6 and the blocking rings 21 and 31 are L ₁ > δ ₁ + δ ₂ , and , The dimensions of each part are regulated so that L ₂ > δ ₁ + δ ₂ . Since the configuration and operation of other parts are the same as those of the first example of the above-described embodiment, illustration and description regarding the equivalent parts are omitted.

The side view (A) and partial cutaway side view (B) of the energy absorption type shaft for steering devices which show the 1st example of embodiment of this invention in the state when the collision accident has not occurred. The front view (A) of the prevention ring incorporated in a 1st example, and the side view (B) (C) which shows two examples of the shape of the latching groove which latches this prevention ring. The figure similar to (B) of Drawing 1 for explaining the dimensional relation of each part. The figure similar to FIG. 1 which shows the 1st example of embodiment of this invention in the state at the time of the occurrence of a collision accident. The front view (A) (B) which shows two examples of the structure of the prevention ring incorporated in the 2nd example of embodiment of this invention, and the partial cutaway side view (C) which show the structure which latches this prevention ring. The front view (A) of the prevention ring integrated in the 3rd example of embodiment of this invention, and the partial cutaway side views (B) and (C) which show two examples of the structure which latches this prevention ring. A front view (A) of a blocking ring incorporated in the fourth example of the embodiment of the present invention, and a partially cut side view (B) showing this blocking ring locked to the inner shaft in a state where no collision accident has occurred. FIG. 6C is a partially cut side view (C) shown in the same state when a collision accident occurs. (A) showing a side view (a) and a front view (b) of the blocking pin incorporated in the fifth example of the embodiment of the present invention, and when this collision pin is locked to the inner shaft and no collision accident occurs The side view (B) shown in the state of (2), and the partially cutaway side view (C) shown in the state at the time of occurrence of a collision accident. The side view (A) and partial cutaway side view (B) of the energy absorption type shaft for steering devices which shows the 6th example of embodiment of this invention in the state when the collision accident has not occurred. The figure similar to (B) of Drawing 9 for explaining the dimensional relation of each part. 1 is a schematic side view showing an example of a steering apparatus for an automobile. FIG. 12 is a longitudinal side view corresponding to a portion B in FIG. 11, illustrating an example of a conventional energy absorbing shaft for a steering device. The figure equivalent to the center part of FIG. 12 which shows the state immediately after a collision start. Furthermore, the figure similar to FIG. 13 which shows the state which the collision advanced. Furthermore, the figure similar to FIG. 13 which shows the state which the collision advanced. Furthermore, the figure similar to FIG. 13 which shows the state which the collision advanced.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3, 3a Intermediate shaft 4a, 4b Universal joint 5 Steering column 6 1st outer tube 7 Inner shaft 8 2nd outer tube 9a, 9b, 9c Small diameter part 10a, 10b, 10c Through-hole 11a, 11b, 11c Synthetic resin 12 Small cross-sectional area 14 Stepped surface 15 Yoke 16 Coupling pin 17 Stop ring 18 Lock groove 19 Ring portion 20 Lock portion 21 Block ring 22 Lock groove 23 Inclined surface 24 Ring portion 25 Tongue piece 26 Blocking ring 27 Locking groove 28 Blocking pin 29 Locking portion 30 Locking hole 31 Second blocking ring

Claims (6)

  In the state where the small cross-sectional area portion is formed in the intermediate portion in the axial direction, the male serration groove is formed on the outer peripheral surface, the inner serration formed on the outer peripheral surface, the female serration groove formed on the inner peripheral surface, and the male serration groove are in serration engagement. A first outer tube that is externally fitted in a state of straddling the small cross-sectional area around the portion where the small cross-sectional area is provided in a part of the inner shaft in the axial direction, and the remaining axial portion of the inner shaft And a second outer tube that is externally fitted in a state in which the female serration groove formed on the inner peripheral surface and the male serration groove are serrated and engaged around the portion that is separated from the small cross-sectional area portion, and the inner These inner shafts are provided only when a strong axial force is applied between the inner shaft and the first outer tube, provided between the shaft and the first outer tube. In the energy absorbing shaft for a steering device, including a displacement limiting portion that enables relative displacement in the axial direction with respect to the first outer tube, the displacement limiting portion includes the inner shaft and the first outer tube. And is engaged with a part of the first outer tube while being locked to a part of the inner shaft, so that at least the first outer tube is The stopper is configured to restrict relative displacement in the axial direction with respect to the inner shaft to a position deviating from the area, and the stopper is broken in the axial direction with respect to the inner shaft. To displace the first outer tube in the axial direction to a position where it is out of the small cross-sectional area. Energy absorbing shaft steering apparatus characterized.   The blocking tool is a blocking ring capable of elastically expanding and contracting the inner diameter, and the blocking ring is formed on a part of the outer peripheral surface of the inner shaft exposed from the first outer tube on the side opposite to the second outer tube. The second outer tube is engaged with the first outer tube so as to be axially displaceable on the opposite side of the second outer tube based on a strong force applied in the axial direction. An energy absorbing shaft for a steering device as described in 1.   The inner peripheral edge of the blocking ring is locked to a locking groove formed in a portion of the outer peripheral surface of the inner shaft that is exposed from the first outer tube on the side opposite to the second outer tube, and is axially The energy absorbing shaft for a steering device according to claim 2, wherein the inner peripheral edge portion of the blocking ring is dropped from the locking groove based on a strong force applied to the steering wheel.   The inner peripheral edge of the blocking ring is frictionally engaged with the portion of the outer peripheral surface of the inner shaft that is exposed from the first outer tube on the side opposite to the second outer tube, and is based on a strong force applied in the axial direction. The energy absorbing shaft for a steering device according to claim 2, wherein the inner peripheral edge portion of the blocking ring slides on the outer peripheral surface of the first outer tube.   The blocking tool is a blocking ring made of a material that can be broken based on a strong force applied in the axial direction so that the diameter of the blocking tool can be expanded and contracted, and a portion closer to the inner diameter of the blocking ring is the second outer peripheral surface of the inner shaft. The outer ring portion of the blocking ring is fixed on the opposite side of the outer tube by a locking groove formed in the portion exposed from the first outer tube. 2. The energy absorbing shaft for a steering device according to claim 1, wherein the energy absorbing shaft for a steering device according to claim 1, wherein the first outer tube is allowed to displace to a side opposite to the second outer tube by being broken from a portion near the inner diameter.   The blocking device is a blocking pin made of a material that can be broken based on a strong force applied in the axial direction, and the longitudinal intermediate portion of the blocking pin is opposite to the second outer tube of the inner shaft. In the portion exposed from the first outer tube, it is locked in a locking hole formed so as to penetrate the inner shaft in the radial direction, and based on the strong force applied in the axial direction, 2. The energy absorption type for a steering device according to claim 1, wherein both end portions in the length direction are similarly broken from an intermediate portion, and the first outer tube is allowed to be displaced to the opposite side to the second outer tube. shaft.

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