JP2018131025A - Intermediate shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure capable of preventing torque transmission by an intermediate shaft from becoming impossible even if a restricted part formed at an inner shaft is broken.SOLUTION: A hollow cylindrical protective tube 14 is fitted on portions adjacent to both sides in the axial direction of a restricted part 7 of an inner shaft 6, straddling the restricted part 7, so that torque transmission can be executed and a relative displacement relating to the axial direction cannot be generated by fixing means 23a, 23b such as ellipse fitting under a steady state. On both sides of the restricted part 7 relating to the axial direction, there are provided a pair of snap rings 19a, 19b limiting a relative displacement relating to the axial direction of the inner shaft 6 to the protective tube 14.SELECTED DRAWING: Figure 2

Description

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

  As shown in FIG. 12, the steering apparatus for an automobile moves a steering wheel 1 operated by a driver from 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 system configured as described above, not only the steering shaft 2 but also the steering column 5 and the intermediate shaft 3 inserted through the steering shaft 2 absorb energy associated with the impact in order to protect the driver in the event of a collision. However, an energy absorption type that shortens the overall length is being performed. Further, regarding the intermediate shaft 3, it has been conventionally considered that the intermediate shaft 3 is bent in a “<” shape at the axially intermediate portion while absorbing impact energy (see, for example, Patent Document 1).

The energy absorption type intermediate shaft of the conventional structure described in Patent Document 1 is configured by serration engagement between one axial end of the outer tube and the other axial end of the inner shaft so as not to be relatively rotatable. ing. In addition, a constricted portion having a smaller cross-sectional area is formed in the intermediate portion in the axial direction of the inner shaft as compared with other portions that are fragile portions. And the protection tube is externally fitted by the axial direction intermediate part of the inner shaft in the state which straddles this narrow part. Both axial ends of the protective tube are capable of transmitting torque to the adjacent portions of the inner shaft on both sides in the axial direction of the constricted portion, and are relatively displaced in the axial direction in a steady state (no collision accident occurrence state). It is impossible to fit. Thereby, in a steady state, most of the steering torque is transmitted by the protective tube, so that a large stress is not applied to the constricted portion with the steering.
In the present specification and claims, unless otherwise specified, the axial direction and the radial direction refer to the axial direction and the radial direction with respect to the intermediate shaft.

  When a collision accident occurs, a strong compressive force acting in the axial direction acts on the intermediate shaft, and the outer tube and the inner shaft are relatively displaced in the axial direction. Based on this, a strong force directed from the outer tube toward the one end side in the axial direction acts on the protective tube, and the protective tube is retracted from the periphery of the constricted portion. And, at the position where the other end edge in the axial direction of the protective tube is present on the radially outer side of the constricted part, the one axial end of the protective tube hits the end surface of the yoke fixed to the one axial end of the inner shaft, The protective tube is prevented from further relative displacement in the axial direction. In this state, when a compressive force is further applied to the intermediate shaft, the inner shaft is bent starting from the constricted portion. Thereby, the energy based on a collision is absorbed and the impact added to a driver | operator's body is relieve | moderated.

JP 2008-239081 A JP 2007-276731 A JP 2014-84025 A

By the way, in the case of the intermediate shaft having the conventional structure as described above, both end portions in the axial direction of the protective tube can transmit torque by serration engagement or the like to the portion adjacent to both sides in the axial direction of the constricted portion of the inner shaft. In addition to being engaged, the relative displacement in the axial direction is fixed without being rattled by press fitting or the like. However, for example, due to a large torque input to the inner shaft due to an accident such as a wheel climbing on a curbstone, both ends of the protective tube in the axial direction and portions of the inner shaft adjacent to both sides in the axial direction of the constricted portion When the fitting force is reduced, a force such as a steering torque is not transmitted through the protective tube, and a large torsional torque or an axially directed force acts directly on the constricted portion. And if a use is continued in such a state, a constriction part may fracture | rupture. Then, when half of the bisected inner shaft comes out of the protective tube, torque transmission by the intermediate shaft may be disabled.
In view of such circumstances, the present invention is an invention for realizing a structure capable of preventing torque transmission by an intermediate shaft from being disabled even when a fragile portion such as a constricted portion provided on an inner shaft breaks. It is a thing.

The intermediate shaft of the present invention includes an inner shaft, an outer tube, a protective tube, and a pair of first stoppers.
Of these, the inner shaft is configured, for example, as a solid shaft as a whole, and has a weak portion such as a constricted portion in the axially intermediate portion, for example, having a sufficiently small cross-sectional area compared to other portions of the inner shaft. Has a part.
The outer tube is, for example, formed in a hollow cylindrical shape as a whole, and the other axial end portion of the inner shaft is inserted into (inserted into) the inner shaft in a relatively non-rotatable manner.
The protective tube is configured, for example, in a hollow cylindrical shape as a whole, and in a state straddling the fragile portion, a portion of the inner shaft that is adjacent to both sides in the axial direction of the fragile portion (an axis sandwiching the fragile portion) In the steady state, for example, press fitting, elliptical fitting, or the like makes the relative displacement in the axial direction impossible to rattle.
The pair of first stoppers are provided on both sides of the fragile portion with respect to the axial direction, and the inner shaft, except when a force directed to one end side in the axial direction is applied from the outer tube to the protective tube. The relative displacement in the axial direction between the protective tube and the protective tube is limited (the relative displacement amount is reduced to zero or slightly).

When carrying out the present invention, the first stopper is attached to one member (an inner shaft or a protective tube) of the inner portion of the inner shaft and a portion adjacent to both sides in the axial direction of the fragile portion and the protective tube. A structure in which the relative displacement in the axial direction between the inner shaft and the protective tube is impossible or only a slight relative displacement is allowed to be engaged with the other member (protective tube or inner shaft) in the locked state. Can be adopted.
Further, the first stopper is based on relative displacement in the axial direction between the inner shaft and the outer tube, and when a force directed from the outer tube toward the one end side in the axial direction is applied to the protective tube, at least Allowing the relative displacement of the protective tube relative to the inner shaft to one end in the axial direction by detaching from the other member or by breaking (breaking) between the inner shaft and the protective tube. Can be adopted.

Moreover, when implementing this invention, the shape of the said 1st stopper and its attachment structure are not ask | required in particular.
For example, as the first stopper, a substantially U-shaped or substantially V-shaped retaining ring or a rod-shaped (shaft-shaped) retaining pin can be employed.
When a substantially U-shaped retaining ring is used as the first stopper, the retaining ring is a portion adjacent to both sides in the axial direction of the fragile portion of the inner shaft, which is the both ends in the axial direction of the protective tube. In a state where the retaining ring is locked to a notch formed in a part fitted on the outer surface of the inner shaft, a part of the retaining ring is formed on an outer peripheral surface of a part adjacent to the both sides in the axial direction of the fragile part of the inner shaft. In addition, it is possible to employ a structure in which the relative displacement in the axial direction between the inner shaft and the protective tube is impossible to be engaged without gaps (without rattling) or loosely engaged so that slight relative displacement in the axial direction is possible. .
On the contrary, in a state where the retaining ring is engaged with a recess formed in the outer peripheral surface of the inner shaft adjacent to the both sides in the axial direction of the fragile portion, a part of the retaining ring is attached to the protective tube. A structure in which the relative displacement in the axial direction between the inner shaft and the protective tube is impossiblely engaged with the notches formed at both ends in the axial direction without a gap or loosely engaged so as to allow a slight relative displacement in the axial direction. It can also be adopted.

When the present invention is carried out, for example, the axial direction of the protective tube with respect to the inner shaft at the position where the other axial end edge of the protective tube is present on the radially outer side of the fragile portion on the inner shaft. A second stopper can be provided to prevent relative displacement toward the one end side.
Such a second stopper is, for example, separate from the inner shaft and can be fixed to the inner shaft, or can be provided integrally with the inner shaft.
When the second stopper is provided separately from the inner shaft, the shape of the second stopper, its fixing structure and fixing position are not particularly limited.
For example, it is possible to employ a structure in which an annular or semi-circular retaining ring is used as the second stopper, and relative displacement to at least one axial end side is fixed to the outer peripheral surface of the inner shaft. Alternatively, a rod-shaped (shaft-shaped) stop pin is used as the second stopper, and an axial end portion (one end portion or both end portions) of the stop pin is formed in a mounting hole formed in an open state on the outer peripheral surface of the inner shaft. ) Can be inserted in a state of protruding outward.
Further, the second stopper can be fixed to one end side in the axial direction from the protective tube in a steady state, or can be fixed to a position aligned with the protective tube in the axial direction.
Further, when the second stopper is provided integrally with the inner shaft, for example, a portion of the outer peripheral surface of the inner shaft provided with a male serration groove and a portion not provided (a portion having a lower diameter) ) Can be used as the second stopper, and a stepped surface formed by stepping the outer peripheral surface of the inner shaft can be used as the second stopper.

  Further, when the present invention is carried out, for example, in the assembled state to the vehicle body, the other axial end portion of the inner shaft is disposed below the one axial end portion of the inner shaft in the vertical direction. You can also do things. In other words, the inner shaft can be disposed on the upper side, and the outer tube can be disposed on the lower side.

Furthermore, when carrying out the present invention, for example, the axially other end side portion of the inner shaft and the axially one end side portion of the outer tube are loosened so as to allow relative displacement in the axial direction (relative to the axial direction). It can also be engaged (so that the displacement is not limited).
Alternatively, a compressive force greater than or equal to a predetermined value is applied to the intermediate shaft, that is, a compressive force associated with a member disposed below of the inner shaft and the outer tube being pushed up in the event of a collision. In such a case, it is also possible to adopt a configuration in which relative displacement in the axial direction between the other axial end portion of the inner shaft and the one axial end portion of the outer tube is possible.
In this case, for example, the inner shaft and the outer tube constituting the fitting portion of the inner shaft and the outer surface of the inner shaft and a part of the inner surface of the outer tube in the axial direction are not cross-sectioned. Circular plastic deformation portions can be provided respectively.
In order to provide such a plastically deformed portion, for example, after slightly inserting the other axial end of the inner shaft into the axial one end of the outer tube, the axial one end of the outer tube is calibrated with a tool. By crushing from the outside in the direction, the inner peripheral surface of one end portion in the axial direction of the outer tube and the outer peripheral surface of the other end portion in the axial direction of the inner shaft are plastically deformed into, for example, an elliptical cross section. Thereafter, the outer tube and the inner shaft are relatively displaced in the axial direction so as to reduce the overall length of the intermediate shaft, and the plastic deformation portion of the outer tube and the plastic deformation portion of the inner shaft are separated in the axial direction. Arrange.
Of the fitting portions between the outer tube and the inner shaft formed in this way, those in which the shape of the plastic deformation portion is an ellipse is described widely in, for example, Patent Documents 2 and 3. Generally, it is called an elliptical fitting part.

  According to the present invention having the above-described configuration, it is possible to prevent the torque transmission by the intermediate shaft from being disabled even when the fragile portion provided on the inner shaft is broken.

The side part (A) and partial cutaway side view (B) which show the intermediate shaft of a steady state regarding the 1st example of embodiment of this invention. The enlarged view corresponding to the A section of FIG. Similarly BB sectional drawing of FIG. The perspective view which similarly takes out a protection tube and shows the edge part typically. The figure (A) which shows the state immediately after a constriction part fracture | ruptures similarly, and the figure (B) and figure (C) which show the state which the lower half part of the inner shaft displaced slightly below with respect to the protection tube. The partial cutaway side view of an intermediate shaft which shows the initial state at the time of a collision accident similarly. The figure equivalent to Drawing 6 showing the middle term state at the time of a collision accident occurring similarly. FIG. 7 is a diagram corresponding to FIG. 6, showing the latter-stage state at the same time when a collision accident occurs. The partial side view of the intermediate shaft which shows the 2nd example of embodiment of this invention. The partial side view of an inner shaft which shows the 3rd example of embodiment of this invention. The partial side view of the inner shaft which shows the 4th example of embodiment of this invention. 1 is a schematic side view showing an example of a steering apparatus for an automobile.

[First example of embodiment]
A first example of the embodiment of the present invention will be described with reference to FIGS. Similar to the structure shown in FIG. 12, the intermediate shaft 3a of this example constitutes an automobile steering device and transmits the movement of the steering shaft 2 to the steering gear. It is an energy absorption type intermediate shaft that bends at an intermediate portion. Therefore, since the shape of the intermediate shaft 3a of this example changes before and after the collision accident, first, the steady state when the collision accident has not occurred will be described with reference to FIGS. The state after the occurrence will be described with reference to FIGS. The case where the constricted part 7 provided in the inner shaft 6 is broken will be described with reference to FIG.

  The intermediate shaft 3a is made of a metal-made hollow cylindrical outer tube 8 in one axial side (left side in FIGS. 1, 2 and 5-8) and a metal-made solid cylindrical inner shaft 6 in the axial direction. The other end side portion (the right side portion in FIGS. 1, 2, 5 to 8) is fitted so that relative rotation with each other is impossible and relative displacement in the axial direction is possible.

  For this purpose, a female serration groove 9 is formed on the inner peripheral surface of the outer tube 8. On the other hand, a male serration groove 10 is formed on the outer peripheral surface of the inner shaft 6. The female serration groove 9 and the male serration groove 10 are serrated and engaged by inserting the other axial end portion of the inner shaft 6 into the axial one end portion of the outer tube 8. In this example, in a state where no collision accident has occurred, that is, in a steady state before the force directed from the outer tube 8 toward the one end side in the axial direction is applied to the protective tube 14, the direction toward the axial direction acting on the intermediate shaft 3a. Based on the applied force, the female serration groove 9 and the male serration groove 10 are loosened so that the entire length of the intermediate shaft 3a can be expanded and contracted (the outer tube 8 and the inner shaft 6 can always slide in the axial direction). Engaged. In the inner shaft 6, the male serration groove 10 can be formed only on the outer peripheral surface of the other end portion in the axial direction than the second retaining ring 22 described later.

  The intermediate shaft 3a is assembled to the vehicle body in an inclined state with respect to the horizontal direction, and the other axial end portion (outer tube 8 side portion) of the inner shaft 6 is vertically above the axial end portion of the inner shaft 6. Arranged below. In other words, the inner shaft 6 is disposed on the upper side, and the outer tube 8 is disposed on the lower side. Moreover, the intermediate shaft 3a of this example is used for a large vehicle, and its axial dimension is longer than that used for a general ordinary passenger car.

  Universal joints 4a and 4b are connected to both axial ends of the intermediate shaft 3a. For this purpose, a yoke 11 constituting one universal joint 4 a is fixed to the other axial end of the outer tube 8. On the other hand, a yoke 12 constituting the other universal joint 4b is fixed to one axial end portion of the inner shaft 6. In the case of this example, a pinion shaft (not shown) constituting the steering gear unit is connected to the intermediate shaft 3a via a lower universal joint 4a, while steering is performed via an upper universal joint 4b. A steering shaft (not shown) constituting the apparatus is connected.

  A constricted portion 7 having a sufficiently small cross-sectional area as compared with other portions of the inner shaft 6 is provided in an axially intermediate portion of the inner shaft 6 and a portion exposed to the outside from the outer tube 8. . The constricted portion 7 corresponds to the fragile portion described in the claims. The constricted portion 7 has a circular cross section, and the outer diameter decreases in a curved manner as it approaches the axial center from both axial sides. The outer diameter of the portion having the smallest cross-sectional area in the constricted portion 7 varies depending on the material and outer diameter of the inner shaft 6, but in the case of the intermediate shaft 3a for a relatively large vehicle such as SUV, the inner shaft 6 is set to about 1/3 to 2/3 of the outer diameter of the other part (the part removed from the pair of engaging grooves 13a and 13b). A pair of engaging grooves 13a and 13b are formed over the entire circumference of the outer peripheral surface of the inner shaft 6 at a portion spaced from the constricted portion 7 on both sides in the axial direction by a predetermined distance. Each of the engaging grooves 13a and 13b has a concave arc shape in cross section with respect to a virtual plane including the central axis of the inner shaft 6, and the radial depth and the axial width dimension thereof are the radial depth of the constricted portion 7. Compared to the height and the axial width dimension, for example, it is sufficiently small, for example, about 1/10 to 1/2.

  In addition, a protective tube 14 is externally fitted to an intermediate portion in the axial direction of the inner shaft 6 so as to straddle (cover) the constricted portion 7 and the pair of engaging concave grooves 13a and 13b. The protection tube 14 is made of metal and is configured in a hollow cylindrical shape as a whole. The protective tube 14 has an axial dimension that is longer than the distance between the pair of engaging grooves 13a and 13b, and a female serration groove 15 is formed on the inner peripheral surface over the entire length. The female serration groove 15 is serrated and engaged with a portion of the male serration groove 10 formed on the outer peripheral surface of the inner shaft 6 adjacent to both sides in the axial direction of the constricted portion 7 so that torque can be transmitted. Further, both end portions in the axial direction of the protective tube 14 are press-fitted and caulked to both axial side portions sandwiching the constricted portion 7, which are portions adjacent to both sides in the axial direction of the constricted portion 7 on the outer peripheral surface of the inner shaft 6. The fixing means 23a, 23b, such as elliptical fitting and injection fitting, are fixed without rattling so as not to be relatively displaced in the axial direction in a steady state. That is, both ends of the protective tube 14 in the axial direction are engaged with portions of the inner shaft 6 adjacent to the both sides in the axial direction of the constricted portion 7 so that torque can be transmitted by serration engagement. The relative displacement in the axial direction is fixed by the fixing means 23a and 23b. In addition, as the fixing means 23a and 23b, since the elliptical fitting only needs to be externally fitted to the inner shaft 6 in a state in which the protective tube 14 is deformed so that its cross-sectional shape is changed from a circular shape to an elliptical shape, It can be preferably employed in terms of simple work and reduced work man-hours.

  Of the both ends of the protective tube 14 in the axial direction, locking notches 16a and 16b are formed in portions that are aligned with the engaging grooves 13a and 13b in the axial direction and open to both inner and outer peripheral surfaces of the protective tube 14. Is formed. The locking notches 16a and 16b are formed at a pair of notches 17 at both end portions (two locations on the opposite side in the radial direction of the protective tube 14) separated in the width direction of the protective tube 14 (vertical direction in FIGS. 1 to 4). , 17 are formed in a direction perpendicular to the width direction (front and back direction in FIGS. 1 and 2 and left and right direction in FIG. 3). In addition, by forming the locking notches 16a and 16b, a pair of notches 17 and 17 between the pair of notches 17 and 17 has a partial arc shape as a whole, and both sides in the width direction are concave arc surfaces. The continuous portions 18 and 18 are provided. In other words, the both ends of the protective tube 14 in the axial direction are provided with portions where the notches 17 and the continuous portions 18 are alternately arranged in the circumferential direction. Further, the interval T between the bottoms of the concave arcuate surfaces which are both side surfaces in the width direction (circumferential direction) of the continuous portions 18, 18 is the outer diameter D of the bottoms of the engaging concave grooves 13 a, 13 b formed in the inner shaft 6. Is slightly larger than.

  Further, the other axial end edge 14a of the protective tube 14 is inclined with respect to a virtual plane orthogonal to the central axis of the protective tube 14 and has an elliptical outline. On the other hand, the one axial end edge of the protective tube 14 exists on a virtual plane orthogonal to the central axis. Moreover, the axial direction one end edge part 8a of the outer tube 8 which opposes the axial direction other end edge part 14a of the protection tube 14 exists in the virtual plane orthogonal to a central axis.

  In the case of this example, the first retaining rings 19a and 19b corresponding to the first stoppers described in the claims are locked to the locking notches 16a and 16b provided in the protective tube 14, respectively. Each of the first retaining rings 19a, 19b is made of a metal wire having a circular cross section, and is configured in a substantially U shape as a whole, and a pair of arm portions 20, 20 arranged in parallel to each other, and both these arms And a semicircular arc-shaped curved portion 21 in which the base end portions of the portions 20 and 20 are continuous with each other. Further, the diameter of the metal wire constituting the first retaining rings 19a, 19b is set slightly smaller than the width dimension of the notches 17, 17 provided in the protective tube 14. The first retaining rings 19a and 19b having such a configuration are such that one continuous portion 18 is covered by the curved portion 21 from the radially outer side (the curved portion 21 is radially outward of the one continuous portion 18). In this state, the pair of arm portions 20 and 20 elastically sandwich the pair of continuous portions 18 and 18 on both side surfaces in the width direction so that the locking notches 16a and 16b do not rattle. It is locked.

  Further, in the state in which the first retaining rings 19a, 19b are locked to the locking notches 16a, 16b, the middle portion in the longitudinal direction of the pair of arm portions 20, 20 is an engagement recess formed on the inner shaft 6. It enters the inside of the grooves 13a and 13b and engages with the engaging grooves 13a and 13b. In the case of this example, in such an engaged state, a minute gap is interposed between the intermediate portion in the longitudinal direction of the arm portions 20 and 20 and the bottom surface and both axial side surfaces of the engaging grooves 13a and 13b. ing.

  In the case of this example, in a steady state, the protective tube 14 is displaced relative to the inner shaft 6 in the axial direction on one end side by fixing means 23a such as press-fitting provided between the protective tube 14 and the inner shaft 6. , 23b, and also by the first retaining rings 19a, 19b. That is, the relative displacement in the axial direction between the protective tube 14 and the inner shaft 6 is prevented double. In particular, in the case of this example, as long as the first retaining rings 19a, 19b do not fall off from the engaging grooves 13a, 13b in the axial direction (or the first retaining rings 19a, 19b break), the protective tube 14 However, the movement of the protective tube 14 is limited so that the inner tube 6 is not displaced relative to one end side in the axial direction. In this manner, in the steady state, the protective tube 14 is disposed so as to straddle the constricted portion 7, so that the inner shaft 6 is prevented from being bent at the constricted portion 7. Further, the steering torque is transmitted mainly from the rear portion of the inner shaft 6 to the front portion (from one end side to the other end side) by the protective tube 14. For this reason, it is possible to prevent a large stress from being applied to the constricted portion 7.

  Further, the first retaining rings 19a and 19b of the present example are provided on the lower side of the bisected inner shaft 6 even when the constricted portion 7 breaks due to a decrease in the fitting force (fixing force) by the fixing means 23a and 23b. The right half of FIG. 1 falls downward through the inner side of the outer tube 8 to prevent the half of the bisected inner shaft 6 from falling off the inner side of the protective tube 14. The function (role) of the first retaining rings 19a and 19b will be described in detail with reference to FIG.

  For example, when the fitting force by the fixing means 23a and 23b is reduced due to a large torque input to the inner shaft 6 due to an accident such as a wheel climbing on a curbstone, a force such as a steering torque is transmitted via the protective tube 14. The torque is not transmitted, and a large torsional torque or axially directed force acts directly on the constricted portion 7. If the use is continued in such a state, the constricted portion 7 may break as shown in FIG.

  Here, a case is considered in which the fitting force by the fixing means 23b between the portion adjacent to the other axial end side (the right side in FIG. 5) of the constricted portion 7 and the protective tube 14 is reduced. Since the inner shaft 6 and the outer tube 8 are loosely engaged so as to be relatively displaceable in the axial direction, if the inner shaft 6 breaks at the constricted portion 7, the lower half 6a of the divided inner shaft 6 Tends to fall downward by itself due to the influence of gravity. However, in this example, as shown in FIG. 5B, in this state, the first retaining ring 19b on the other end side in the axial direction is in contact with the engaging groove 13b on the other end side in the axial direction. Engage. For this reason, the movement of the lower half 6a of the inner shaft 6 with respect to the protective tube 14 is restricted (the lower half 6a is prevented from dropping), and the lower half 6a may fall off from the inside of the protective tube 14. Is prevented.

  On the other hand, the case where the fitting force by the fixing means 23a between the part adjacent to the axial direction one end side (left side of FIG. 5) of the narrow part 7 and the protective tube 14 falls is considered. In this case, the lower half 6 a of the bisected inner shaft 6 tends to drop downward together with the protective tube 14. However, in the case of this example, as shown in FIG. 5C, in this state, the first retaining ring 19a on one axial end side is engaged with the engaging groove 13a on one axial end side. Match. For this reason, the movement of the upper half 6b of the inner shaft 6 with respect to the protective tube 14 is restricted (this prevents the lower half 6a from dropping), and the upper half 6b falls off from the inside of the protective tube 14 Is prevented from doing.

  As described above, in the case of this example, even when the fitting force by the fixing means 23a, 23b provided on either the one axial end side or the other axial end side of the constricted portion 7 is reduced, 1 The retaining rings 19a and 19b can prevent the lower half 6a of the inner shaft 6 from falling, and the half of the bisected inner shaft 6 can be prevented from dropping from the inside of the protective tube 14. .

  Further, in the case of this example, a metal second retaining ring 22 corresponding to the second stopper described in the claims is provided in a portion separated by a predetermined length from the protective tube 14 toward one end in the axial direction. It has been. The second retaining ring 22 is separate from the inner shaft 6 and has an annular shape as a whole. The second retaining ring 22 has an axial relative displacement with respect to the inner shaft 6 at a portion closer to one axial end of the outer peripheral surface of the inner shaft 6. It is fixed impossible. The fixing method of the second retaining ring 22 is not particularly limited. For example, a structure in which the second retaining ring 22 is locked in a locking groove formed on the outer peripheral surface of the inner shaft 6 so as not to drop off, welding, adhesion, press fitting, caulking, screw Various conventionally known fixing structures such as stoppers can be appropriately combined as necessary.

  Further, the fixing position of the second retaining ring 22 is regulated as follows. In other words, the other end in the axial direction of the protective tube 14 in a state where the protective tube 14 abuts against the second retaining ring 22 and the protective tube 14 is prevented from being displaced relative to the inner shaft 6 toward one end in the axial direction. The fixed position of the second retaining ring 22 is regulated so that the edge portion 14a is located on the radially outer side of the constricted portion 7 and the other axial end edge portion 14a and the constricted portion 7 overlap in the radial direction. . Such a second retaining ring 22 is provided in order to keep the protective tube 14 that is relatively displaced toward one end in the axial direction with respect to the inner shaft 6 at an appropriate position (to prevent further relative displacement), In steady state, it does not perform its function.

  Although not shown, a hollow cylindrical boot may be provided so as to be bridged between one axial end portion of the outer tube 8 and the axial intermediate portion of the inner shaft 6. By providing such a boot, the male tube is formed on the outer peripheral surface of the inner shaft 6 while covering the protective tube 14 (the constricted portion 7), the first retaining rings 19a and 19b, and the second retaining ring 22, respectively. Of the groove 10, a portion exposed between one axial end of the outer tube 8 and the other axial end of the protective tube 14, and between the one axial end of the protective tube 14 and the second retaining ring 22. Each part can be covered.

  Next, a case where a collision accident occurs will be described over time with reference to FIGS. When a collision accident occurs, a compressive force is applied in a direction to bring the pair of universal joints 4a and 4b closer to each other, so that the outer tube 8 and the inner shaft 6 are axially arranged to contract the intermediate shaft 3a. Relative displacement (collapse).

  When the relative displacement between the outer tube 8 and the inner shaft 6 proceeds, as shown in FIG. 6, a part of the outer tube 8 in the circumferential direction of the axial one end edge 8 a is the other end of the protective tube 14 in the axial direction. A strong force is applied from the outer tube 8 to the protective tube 14 toward the one end side in the axial direction against the one end portion in the radial direction of the edge portion 14a. As a result, the protective tube 14 tends to be displaced relative to the inner shaft 6 toward one end in the axial direction against the resistance generated by the fixing means 23 a and 23 b provided between the protective tube 14 and the inner shaft 6. The protective tube 14 strongly presses the pair of first retaining rings 19a and 19b toward one end in the axial direction, and the width between the pair of arm portions 20 and 20 constituting the first retaining rings 19a and 19b. To spread. As a result, the first retaining rings 19a, 19b are disengaged from the engaging grooves 13a, 13b (over the engaging grooves 13a, 13b). As a result, the protective tube 14 is displaced relative to the inner shaft 6 toward the one end side in the axial direction together with the outer tube 8.

  When the relative displacement of the protective tube 14 (and the outer tube 8) toward one end in the axial direction proceeds, the protective tube 14 abuts against the second retaining ring 22 as shown in FIG. Thereby, the axial direction other end edge part 14a of the protection tube 14 exists in the radial direction outer side of the constriction part 7, and the axial direction other end edge part 14a and the constriction part 7 overlap in a radial direction. The protective tube 14 is prevented from further relative displacement in the axial direction.

  When a compressive force is further applied to the intermediate shaft 3a from such a state, the inner shaft 6 that has lost the bending prevention force by the protective tube 14 as shown in FIG. Bend at 7. Specifically, the bending is progressed in the direction after the other end edge 14a in the axial direction of the protective tube 14 and the one end edge 8a in the axial direction of the outer tube 8 are bent so as to hit the entire circumference. This allows the universal joints 4a and 4b to approach each other while absorbing the impact energy applied between the universal joints 4a and 4b due to a collision accident.

In the case of this example having the above-described configuration, it is possible to prevent torque transmission by the intermediate shaft 3a from being disabled even when the constricted portion 7 provided on the inner shaft 6 is broken.
That is, the constricted portion 7 is broken based on the fact that the fitting force by the fixing means 23b between the portion adjacent to the other axial end of the constricted portion 7 (the right side in FIG. 5) and the protective tube 14 is reduced. In this case, the lower half 6a of the bisected inner shaft 6 tends to fall downward by itself. However, in this example, as shown in FIG. 5B, in this state, the first retaining ring 19b on the other end side in the axial direction is in contact with the engaging groove 13b on the other end side in the axial direction. Therefore, the lower half 6a of the inner shaft 6 can be prevented from falling off from the inside of the protective tube 14. On the other hand, based on the fact that the fitting force by the fixing means 23a between the portion adjacent to one axial end side (left side in FIG. 5) of the constricted portion 7 and the protective tube 14 is reduced, the constricted portion 7 is broken. When it occurs, the lower half 6a of the bisected inner shaft 6 tends to fall downward together with the protective tube 14. However, in the case of this example, as shown in FIG. 5C, in this state, the first retaining ring 19a on one axial end side is engaged with the engaging groove 13a on one axial end side. Therefore, the upper half 6b of the inner shaft 6 can be prevented from falling off from the inside of the protective tube 14.

  Thus, in the case of this example, since the first retaining rings 19a and 19b are respectively provided on both side portions of the constricted portion 7 with respect to the axial direction, the axial end of the constricted portion 7 and the other axial end of the constricted portion 7 are provided. Even when the fitting force by any of the fixing means 23a and 23b provided is lowered, the lower half 6a of the inner shaft 6 can be prevented from falling, and the half of the divided inner shaft 6 is protected. It is possible to prevent the tube 14 from falling off. Therefore, it is possible to effectively prevent the torque transmission by the intermediate shaft 3a from being disabled. Further, in the case of this example, the play (rattle, gap) in the circumferential direction between the protective tube 14 and the inner shaft 6 based on the decrease in the fitting force by the fixing means 23a, 23b is driven through the steering wheel. Since the vehicle can be sensed (transmitted) to the driver, the driver can be encouraged to inspect and repair the vehicle.

[Second Example of Embodiment]
A second example of the embodiment of the present invention will be described with reference to FIG. The characteristic of the intermediate shaft 3b of this example is that the locking structure of the pair of first retaining rings 19a, 19b is different from the structure of the first example of the above embodiment. That is, in the case of this example, the depth dimension and the width dimension in the axial direction are larger at both axial ends of the protective tube 14 than the locking notches 16a and 16b of the first example of the embodiment. A pair of engagement notches 24a and 24b are formed. Further, the depth dimension and the width in the axial direction at the intermediate portion in the axial direction of the inner shaft 6 and at both side portions in the axial direction of the constricted portion 7 than the engaging grooves 13a and 13b of the first example of the embodiment. A pair of locking concave grooves 25a and 25b having reduced dimensions are formed.

  Then, in the state where the locking grooves 25a and 25b provided in the inner shaft 6 are exposed from the engagement notches 24a and 24b provided in the protective tube 14, the locking grooves 25a and 25b are 1 retaining rings 19a and 19b are respectively locked. In this state, the intermediate portions in the longitudinal direction of the pair of arm portions 20 and 20 constituting the first retaining rings 19a and 19b are connected to the engagement notches 24a and 24b via a minute gap in the axial direction. Engage.

Also in the case of this example having the above-described configuration, a pair of engagement snaps provided on the protection tube 14 and the pair of first retaining rings 19a and 19b provided on both sides of the constricted portion 7 in the axial direction. Even when the constricted portion 7 is broken due to the engagement with the notches 24 a and 24 b, it is possible to prevent the half of the bisected inner shaft 6 from dropping from the inside of the protective tube 14.
About another structure and an effect, it is the same as that of the case of the 1st example of the said embodiment.

[Third example of embodiment]
A third example of the embodiment of the present invention will be described with reference to FIG. In the case of this example, a concave portion 26 that is recessed inward in the radial direction is formed in a part in the circumferential direction of the intermediate portion of the inner shaft 6 in the axial direction. Thereby, in the axial direction intermediate portion of the inner shaft 6, a portion corresponding to the concave portion 26 in the axial direction has a smaller cross-sectional area than other portions, and corresponds to the weak portion described in the claims. A cross-sectional area 27 is provided.

Also in the case of this example having such a configuration, similarly to the case of the first example of the above embodiment, the protection tube 14 (not shown) is externally fitted to the inner shaft 6 so as to straddle the small cross-sectional area 27. To do. A pair of first retaining rings 19 a and 19 b (not shown) are provided between the protective tube 14 and the inner shaft 6. Thereby, even when the small cross-sectional area 27 is broken, it is possible to prevent the torque transmission by the intermediate shaft 3a from being disabled.
About another structure and an effect, it is the same as that of the case of the 1st example of the said embodiment.

[Fourth Example of Embodiment]
A fourth example of the embodiment of the present invention will be described with reference to FIG. In the case of this example, a plurality of (four in the illustrated example) through holes 28, 28 penetrating in the diametrical direction are formed in the axially intermediate portion of the inner shaft 6. Thereby, in the axial direction intermediate portion of the inner shaft 6, the portion provided with the through holes 28, 28 corresponds to the fragile portion described in the claims, in which the bending rigidity is lower than the other portions. A low rigidity portion 29 is provided.

Also in the case of this example having such a configuration, similarly to the case of the first example of the above-described embodiment, the protection tube 14 (not shown) is externally fitted to the inner shaft 6 so as to straddle the low-rigidity portion 29. . A pair of first retaining rings 19 a and 19 b (not shown) are provided between the protective tube 14 and the inner shaft 6. Thereby, even when the low-rigidity portion 29 is broken, it is possible to prevent the torque transmission by the intermediate shaft 3a from being disabled.
About another structure and an effect, it is the same as that of the case of the 1st example of the said embodiment.

  In carrying out the present invention, the shape of the first stopper and the second stopper and the support structure thereof are not limited to those described in each example of the above-described embodiment, and the functions of the first stopper and the second stopper are the same. As long as it can be exhibited, its shape and support structure can be changed as appropriate. For example, the first stopper (first retaining ring) can be supported with respect to the recess provided in the inner shaft and the notch provided in the protective tube without rattling. Further, for example, a rod-shaped retaining pin can be used instead of the first retaining ring. In this case, a locking through-hole can be formed in the protective tube, and a holding hole can be formed in the inner shaft, which can be tightly fitted to either. When the present invention is carried out, the other end edge in the axial direction of the protective tube may be present on the virtual plane without being inclined with respect to the virtual plane orthogonal to the central axis of the protective tube. .

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3, 3a, 3b Intermediate shaft 4a, 4b Universal joint 5 Steering column 6 Inner shaft 6a Lower side half 6b Upper side half 7 Constricted part 8 Outer tube 8a Axial one end edge 9 Female serration groove DESCRIPTION OF SYMBOLS 10 Male serration groove 11 Yoke 12 Yoke 13a, 13b Engagement ditch 14 Protection tube 14a Axial other end edge 15 Female serration groove 16a, 16b Stopping notch 17 Notch 18 Continuous part 19a, 19b 1st retaining ring 20 Arm 21 Curved portion 22 Second retaining ring 23a, 23b Fixing means 24a, 24b Engagement notch 25a, 25b Locking groove 26 Recess 27 Small cross-sectional area 28 Through hole 29 Low rigidity portion

Claims (4)

An inner shaft having a fragile portion in the middle in the axial direction;
An outer tube in which the other axial end portion of the inner shaft is inserted into the axial one end portion in a relatively non-rotatable manner;
In a state of straddling the fragile portion, the inner shaft of the inner shaft is fitted to the portion adjacent to both sides of the fragile portion in the axial direction so that torque can be transmitted and the relative displacement in the axial direction is impossible in a steady state. Protective tube,
Relative displacement in the axial direction between the inner shaft and the protective tube, except when a force directed to one end side in the axial direction is applied to the protective tube from the outer tube, provided on both sides of the fragile portion with respect to the axial direction. A pair of first stoppers that limit
Intermediate shaft with   A second displacement of the protective tube relative to the inner shaft with respect to the inner shaft is prevented at a position where the other axial end edge of the protective tube is located on the radially outer side of the weakened portion on the inner shaft. The intermediate shaft according to claim 1, wherein a stopper is provided.   The axial direction other end side part of the said inner shaft is arrange | positioned below regarding the up-down direction rather than the axial direction one end side part of this inner shaft in the assembly | attachment state to a vehicle body. The intermediate shaft described in the item.   The axial direction other end side part of the said inner shaft and the axial direction one end side part of the said outer tube are engaged loosely so that the relative displacement regarding an axial direction is possible loosely. The intermediate shaft described in 1.

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