JP2005238862A - Assembling method for intermediate shaft of steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the manufacturing cost of an intermediate shaft having an absorbing structure for impact energy in a steering device. <P>SOLUTION: The intermediate shaft of this steering device is equipped with an outer shaft 21 having a press-bonding section 25, and an inner shaft having a biting section which bites into the press-bonding section 25 under a state being inserted in the hollow section 29 of the outer shaft 21. When an impact force exceeding a set value is applied, the inner shaft and the outer shaft 21 relatively move while resisting a moving resistant force between the press-bonding section 25 and the biting section, and thus, the impact energy by the impact force is absorbed. This assembling method for the intermediate shaft 10 includes following processes. In the first process, a dummy shaft 30 is inserted in the hollow section 29 of the outer shaft 21. In the second process, a plastic deformation is applied on the peripheral wall 22a of the outer shaft 21 by utilizing the dummy shaft 30, and the press-bonding section 25 which protrudes in the hollow section 29 is formed. In the third process, the inner shaft which is inserted in the hollow section 29 is press-fitted in the press-bonding section 25 after the dummy shaft 30 is pulled out from the outer shaft 21. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an intermediate shaft for transmitting a steering operation to a steering gear in a vehicle steering apparatus, and more particularly, to an intermediate shaft assembly method having an impact absorbing structure for absorbing impact energy due to an impact force acting on the intermediate shaft. .

For example, a method disclosed in Patent Document 1 is known as an assembly method of an intermediate shaft having an impact absorbing structure that absorbs impact energy due to impact force acting upon a vehicle collision in a vehicle steering device. In this assembling method, in a state where the insertion shaft in which the circumferential groove is formed is fitted to the hollow shaft partway, a roller is applied to the outer peripheral portion of the hollow portion corresponding to the circumferential groove to pressurize the circumferential surface of the hollow portion A part of is recessed inward in the radial direction to form a recessed part. Thereafter, the insertion shaft is further inserted into the hollow shaft. At this time, a part of the male serration of the insertion shaft bites into the depression. For this reason, when an impact load acts on the intermediate shaft, the absorption of the impact is continued during the period in which the male serration of the insertion shaft passes through the depressed portion, and sufficient impact absorption is achieved.
Japanese Patent Laid-Open No. 9-272447

  By the way, in the prior art, since the insertion shaft also serves as a mold for forming the depressed portion, it is necessary to form a circumferential groove on the insertion shaft, and in order to increase the strength of the portion where the circumferential groove is formed. In this part, since it is necessary to increase the strength by heat treatment or the like, the manufacturing cost of the insertion shaft, and hence the intermediate shaft, has been difficult. Furthermore, in the insertion shaft, since the circumferential groove is formed in the middle of the male serration, it is necessary to form the male serration in a portion closer to the shaft end than the circumferential groove, and accordingly, in the axial direction of the male serration. The formation area is widened, and the manufacturing cost of the insertion shaft is also high in this respect.

  The present invention has been made in view of such circumstances, and the invention according to claims 1 and 2 aims to reduce the manufacturing cost of an intermediate shaft having an impact energy absorbing structure in a steering device. To do. Furthermore, an object of the present invention is to improve the setting accuracy of the amount of absorption of impact energy and to easily remove the dummy shaft from the outer shaft.

  The invention according to claim 1 is an intermediate shaft in which an outer shaft having a press contact portion and an inner shaft having a biting portion that bites into the press contact portion in a state of being inserted into a hollow portion of the outer shaft, When an impact force exceeding a set value is applied, the inner shaft and the outer shaft move relatively against the movement resistance force between the pressure contact portion and the biting portion, thereby causing the impact force to In the method for assembling the intermediate shaft of the steering device in which impact energy is absorbed, a step of inserting a dummy shaft into the hollow portion of the outer shaft, and a plastic deformation is applied to the outer wall of the outer shaft using the dummy shaft. And the step of forming the press contact portion protruding in the hollow portion, and the step of press-fitting the inner shaft inserted into the hollow portion into the press contact portion after the dummy shaft is removed from the outer shaft. including A method of assembling the intermediate shaft of the tearing device.

  According to this, since the pressure contact portion is formed using the dummy shaft without using the inner shaft, it is not necessary to use a heat treatment for increasing the strength of the inner shaft or a special material having high strength.

  According to a second aspect of the present invention, in the method for assembling the intermediate shaft of the steering device according to the first aspect, the dummy shaft includes a main shaft having a mold portion used for forming the press contact portion at a shaft end portion. And an auxiliary shaft that comes into contact with the main shaft at the shaft end.

  According to this, the dummy shaft is divided into a main shaft having a mold portion at the shaft end portion and an auxiliary shaft that comes into contact with the shaft end portion. Therefore, after the formation of the press contact portion is completed, the dummy shaft is connected to the auxiliary shaft. The main shaft and the auxiliary shaft can be pulled out from the outer shaft in opposite directions without contacting the press contact portion with the contact portion as a boundary.

  According to invention of Claim 1, the following effect is show | played. In other words, since the pressure contact portion for absorbing impact energy is formed using a dummy shaft different from the inner shaft, it is necessary to use a heat treatment for increasing the strength of the inner shaft or a special material having high strength. As a result, the manufacturing cost of the inner shaft, and hence the manufacturing cost of the intermediate shaft having the impact energy absorbing structure in the steering device, can be reduced.

  According to invention of Claim 2, in addition to the effect of the invention of the cited claim, there exists the following effect. That is, after the formation of the press contact portion is completed, the main shaft and the auxiliary shaft can be pulled out from the outer shaft in the opposite directions without contacting the press contact portion. The accuracy of setting the energy absorption amount can be increased, and it becomes easy to remove the dummy shaft from the outer shaft.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
Referring to FIG. 1, a steering apparatus having an intermediate shaft 10 to which the present invention is applied is mounted on a four-wheeled vehicle, and an electric power steering as a means for generating a steering assist force for assisting a driver's steering force. The steering device 1 includes a mechanism 5. The steering device 1 includes a steering wheel 2, a steering shaft 3 connected to the steering wheel 2, a cylindrical steering column 4 that houses the steering shaft 3, and a housing 5 a that is coupled to the steering column 4. 5, an intermediate shaft 10 connected to the output shaft 5c of the power steering mechanism 5 via a universal joint 6, an input shaft 8a connected to the intermediate shaft 10 via a universal joint 7, and a drive coupling to the input shaft 8a A gear box 8 having a steering gear and a link mechanism for transmitting the movement of the steering gear to the steered wheels.

  The steering column 4 rotatably supports the steering shaft 3 and is fixed to the vehicle body via a bracket 9. The steering gear is composed of a pinion provided on the input shaft 8a and a rack that meshes with the pinion. It has a rack and pinion mechanism. The power steering mechanism 5 includes a torque sensor that detects a steering torque based on a torsion amount of a torsion bar that couples the steering shaft 3 and the output shaft 5c, and a control device based on a detection signal of the torque sensor. An electric motor 5b whose rotational direction is controlled and a worm gear that transmits the rotational force of the electric motor 5b to the output shaft 5c are provided.

  When the steering wheel 2 is operated, the steering shaft 3 rotates with respect to the output shaft 5c while twisting the torsion bar based on the steering operation, and according to the steering torque detected by the torque sensor. The rotational force generated by the electric motor 5b is transmitted to the output shaft 5c via the worm gear, and the rotational force generated by the rotation of the output shaft 5c is transmitted to the steering gear via the intermediate shaft 10 as a steering assist force. Thus, the steering force of the driver is reduced.

Referring also to FIG. 2, the intermediate shaft 10 includes a solid columnar inner shaft 11 to which the universal joint 6 is connected and a cylindrical outer shaft 21 to which the universal joint 6b is connected. In both cases, the metal inner shaft 11 and the outer shaft 21 are designed to shorten the axial length of the intermediate shaft 10 when an impact force in the axial direction exceeding the set value is applied to the intermediate shaft 10 at the time of a vehicle collision. They are coupled to each other substantially coaxially so as to be movable relative to each other.
“Axial direction”, “radial direction” and “circumferential direction” mean “axial direction”, “radial direction” and “circumferential direction” with respect to the inner shaft 11 or the outer shaft 21, respectively.

  The inner shaft 11 has an inner side coupling portion 12 inserted into the hollow portion 29 of the outer shaft 21 at the shaft end portion, and the outer shaft 21 is inserted into the inner end coupling portion 12 at the shaft end portion. The outer side coupling portion 22 is coupled to the outer side coupling portion 22. The inner side coupling portion 12 has a fitting portion 13 in which a fitting structure including a serration 14 is formed on the outer peripheral surface of the inner shaft 11, and the outer side coupling portion 22 is serrated on the inner peripheral surface of the outer shaft 21. It has the fitting part 23 in which the fitting structure which consists of was formed.

  When the fitting portions 13 and 23 are fitted to each other, the serrations 14 and 24 enable the inner shaft 11 and the outer shaft 21 to rotate integrally, and the relative axial direction of the two shafts. Thus, the rotational force generated by the steering operation is transmitted from the inner shaft 11 to the outer shaft 21. In this embodiment, both the serrations 14 and 24 are sized and dimensioned so that they fit relatively loosely.

  Further, the outer side coupling portion 22 has a press-contact portion 25 that is formed in the fitting portion 23, that is, in the region where the serration 24 is formed, and to which the fitting portion 13 is pressed. A plurality of press contact portions 25 formed by plastic working are formed at intervals in the circumferential direction of the outer shaft 21, and in this embodiment, a pair of press contact portions 25 are at the same position in the axial direction and the outer shaft 21 Are formed at positions opposed to each other in the radial direction across the central axis L1. Each press contact portion 25 is configured such that a part of the peripheral wall of the outer shaft 21 is pushed inward in the radial direction from the outer peripheral surface, so that the inner peripheral surface of the peripheral wall 22a of the outer side coupling portion 22 partially protrudes at the hollow portion 29. Consists of formed protrusions.

  Referring also to FIG. 3, in the state where the inner shaft 11 is inserted into the hollow portion 29 of the outer shaft 21, each press-contact portion 25 is configured by the teeth 14a of the serration 14, that is, the protrusion or protrusion of the fitting structure. The biting portion 16 is pressed and the teeth 14a are bitten into the pressing portion 25. In this embodiment, the teeth 24a of the serration 24 in the pressing portion 25 (corresponding to the protrusions or ridges of the fitting structure) ) Is in a state of biting into the fitting portion 13. In FIG. 3, the state of the outer side coupling portion 22 before processing by plastic processing is shown by a two-dot chain line.

  When an impact force exceeding the set value acts on the intermediate shaft 10, the impact force is based on the frictional force in each press contact portion 25 or the movement resistance based on the force causing plastic deformation in the press contact portion 25 and the fitting portion 13. By moving the inner shaft 11 and the outer shaft 21 relatively against the force and performing the work of press-fitting the fitting portion 13 into each pressure contact portion 25, the impact energy of the impact force is absorbed. Is done. The shock energy is absorbed by the inner shaft 11 and the outer shaft 21 due to the impact force when the inner shaft 11 and the outer shaft 21 are assembled (the state shown in FIG. 3). The fitting portion 13 passes through the pressure contact portion 25 and the biting state of the biting portion 16 at the pressure contact portion 25 is finished. Is done.

Next, an assembling method of the intermediate shaft 10 will be described with reference to FIG.
4A and 4B, in the first insertion step, the outer shaft 21 having the fitting portion 23 in which the serration 24 is formed before the press contact portion 25 (see FIG. 2) is formed. A dummy shaft 30 is inserted into the hollow portion 29. The dummy shaft 30 includes a main shaft 31 having a mold portion 31a used for forming the press contact portion 25, and an auxiliary shaft 32 that comes into contact with the shaft end portion 31e of the main shaft 31. For the main shaft 31 and the auxiliary shaft 32, for example, a high-strength material with increased hardness is used by heat treatment or by selection of the material itself.

  The main shaft 31 has a holding portion 31b for holding the main shaft 31 in the outer shaft 21, adjacent to the mold portion 31a in the axial direction, in addition to the mold portion 31a formed at the shaft end portion 31e. The mold portion 31a is formed of a cylindrical small diameter portion having an outer diameter smaller than the valley bottom of the serration 14, that is, the smallest diameter portion of the fitting structure.

  On the other hand, the auxiliary shaft 32 is a positioning shaft for setting the position of the main shaft 31 in the axial direction so that the pressure contact portion 25 is formed at a preset position on the outer shaft 21, and the shaft end surface of the main shaft 31 A positioning portion 32c that comes into contact with the contact portion 31c, and a holding portion 32b that is formed in the shaft end portion 32e and holds the auxiliary shaft 32 in the outer shaft 21.

  Both holding portions 31b and 32b are formed with serrations 33 and 34 as fitting structures formed on the outer peripheral surfaces of the main shaft 31 and the auxiliary shaft 32, respectively. The holding portion 31b is fitted to the fitting portion 23 in both serrations 14 and 33, and the holding portions 31b and 32b are fitted to the fitting portion 23 in both serrations 24 and 34. At the time of processing, the occurrence of deformation at the outer side coupling portion 22 is prevented or suppressed.

  In the first insertion step, as shown in FIG. 4A, the auxiliary shaft 32 is inserted into the hollow portion 29 of the outer shaft 21 from the direction A2 opposite to the insertion direction A1 of the inner shaft 11, The press contact portion 25 is fixed to the outer shaft 21 at a position corresponding to the set position where the press contact portion 25 is to be formed, and then the main shaft 31 is opposed to the positioning portion 32c formed of the shaft end surface of the auxiliary shaft 32 in the axial direction. A positioning step of inserting into the hollow portion 29 from A1 is performed. This positioning process ends when the contact portion 31c of the main shaft 31 contacts the positioning portion 32c, and then the main shaft 31 is fixed so that the main shaft 31 cannot move with respect to the outer shaft 21. By this positioning step, as shown in FIG. 4B, the main shaft 31 is positioned at a predetermined position in the axial direction of the outer shaft 21 corresponding to the set position.

  In this state, the mold portion 31a is disposed between the holding portion 31b of the main shaft 31 and the positioning portion 31c in the axial direction, and is circular between the fitting portion 23 and radially outward of the mold portion 31a. An annular space 40 is formed. In the machining step for forming the pair of press contact portions 25, a part of the radially outer peripheral wall 22a of the die portion 31a is radially inward by the punch 41 that is a pressing tool with respect to the die portion 31a. Is pressed, and the peripheral wall 22a of the outer shaft 21 is plastically processed. The contact surface of the punch 41 with the peripheral wall 22a is formed, for example, as a part of a cylindrical surface, but may have a shape other than the cylindrical surface.

  In this processing step, as shown in FIG. 4C, the outer peripheral surface of the outer shaft 21 is formed into a pair of linear grooves parallel to a plane orthogonal to the central axis L1 (FIGS. 1 and 3). Also, in the hollow portion 29, a press-contact portion 25 formed at a protruding portion protruding radially inward is formed. The amount of protrusion of the pressure contact portion 25 inward in the radial direction is set so that the biting portion 16 of the inner shaft 11 bites into the pressure contact portion 25, and the maximum value is defined by the outer diameter of the die portion 31a.

  Thereafter, the main shaft 31 and the auxiliary shaft 32 are pulled out from the outer shaft 21 in the opposite directions without contacting the press contact portion 25 at the contact portion 31c of the main shaft 31 with the auxiliary shaft 32 as a boundary. A removal step is performed in which 30 is removed from the outer shaft 21.

  After the removal step, a second insertion step is performed in which the inner shaft 11 is inserted into the hollow portion 29 from the insertion direction A1. In the middle of the second insertion step, after the biting portion 16 bites into the pressure contact portion 25, the biting portion 26 of the pressure contact portion 25 and the biting portion 16 of the fitting portion 13 are mutually connected as shown in FIG. As a result, the inner shaft 11 is press-fitted into the press-contact portion 25 and consequently into the outer shaft 21. When the distance between the pressure contact portion 25 and the base end 13a (see FIG. 2) reaches the set distance, the insertion of the inner shaft 11 is completed, and the assembly of the intermediate shaft 10 is completed.

Next, operations and effects of the embodiment configured as described above will be described.
When an impact force exceeding the set value acts on the intermediate shaft 10 during a vehicle collision, the biting portion 16 constituted by the serrations 14 of the inner side coupling portion 12 bites into the pressure contact portion 25 of the outer side coupling portion 22, The inner shaft 11 and the outer shaft 21 move relatively against the movement resistance force between the press contact portion 25 and the biting portion 16 in the press-fitted state, and impact energy due to the impact force acting on the outer shaft 21 is increased. It is absorbed and the steering wheel 2 is prevented from protruding toward the driver.

  The intermediate shaft 10 includes a step in which the dummy shaft 30 is inserted into the hollow portion 29 of the outer shaft 21, and a plastic deformation is applied to the peripheral wall 22a of the outer shaft 21 by using the dummy shaft 30. Assembling by an assembling method including a step of forming a protruding pressure contact portion 25 and a step of pressing the inner shaft 11 inserted into the hollow portion 29 into the pressure contact portion 25 after the dummy shaft 30 is pulled out of the outer shaft 21. As a result, the pressure contact portion 25 is formed using the dummy shaft 30 without using the inner shaft 11, so that heat treatment for increasing the strength of the inner shaft 11 or a special material having high strength is used. Since this is not necessary, the manufacturing cost of the inner shaft 11 and, consequently, the manufacturing cost of the intermediate shaft 10 having the impact energy absorbing structure in the steering device 1 are reduced.

  The dummy shaft 30 includes a main shaft 31 having a mold portion 31a used for forming the press contact portion 25 at the shaft end portion 31e, and an auxiliary shaft that contacts the main shaft 31 at a contact portion 31c of the shaft end portion 31e. 32, the dummy shaft 30 is divided into a main shaft 31 having a mold portion 31a at the shaft end portion 31e and an auxiliary shaft 32 having a shaft end portion 32e in contact with the shaft end portion 31e. Therefore, after the formation of the press contact portion 25 using the mold portion 31a is completed, the main shaft 31 and the auxiliary shaft 32 are brought into contact with the press contact portion 25 at the contact portion 31c of the main shaft 31 with the auxiliary shaft 32 as a boundary. Without being pulled out from the outer shaft 21 in directions opposite to each other. As a result, since the press contact portion 25 is not deformed, the accuracy of setting the amount of absorption of impact energy can be increased, and the dummy shaft 30 can be easily removed from the outer shaft 21.

  In addition, since the auxiliary shaft 32 is also a positioning shaft, the positioning of the main shaft 31 is facilitated, and as a result, the formation position of the press contact portion 25 is facilitated.

Hereinafter, an embodiment in which a part of the configuration of the above-described embodiment is changed will be described with respect to the changed configuration.
A plurality of the pressure contact portions 25 are formed in the embodiment, but may be one. Further, the outer side coupling portion 22 may have a fitting portion and a pressure contact portion formed at a portion other than the fitting portion, and the pressure contact portion has a biting portion that bites into the fitting portion of the inner shaft 11. It may not be formed. In this case, the outer diameter of the mold portion 31a is smaller than the tip of the serration 14, that is, the maximum diameter portion of the fitting structure. In the above embodiment, the serrations 14 and 24 constituting the fitting parts 13 and 23 also serve as the biting parts 16 and 26. However, the fitting parts 13 and 23 and the biting parts 16 and 26 are provided separately. May be. Further, the fitting structure formed in the inner side coupling part 12 or the outer side coupling part 22 may be a structure other than serration, for example, a spline.

  The dummy shaft 30 is not divided into the main shaft 31 and the auxiliary shaft 32, and may be constituted by one shaft having a mold portion 31a. In this case, in order to facilitate the work of pulling out the dummy shaft 30 from the outer shaft 21, the portion closer to the shaft end surface than the mold portion 31a in the insertion direction A1 is made smaller than the diameter of the mold portion 31a or not provided. Also good.

  The power steering mechanism may be provided in the gear box or may be a fluid type including a power cylinder mechanism using fluid pressure. Furthermore, the steering device may not include a power steering mechanism.

1 is a schematic perspective view of a steering apparatus including an intermediate shaft to which the present invention is applied according to a first embodiment of the present invention. It is a fragmentary sectional view of the intermediate shaft of FIG. It is an expanded sectional view in the III-III arrow of FIG. FIG. 3A is a diagram illustrating a process when assembling the intermediate shaft of FIG. 2, and (A) shows a state in which the auxiliary shaft of the dummy shaft is inserted into the outer shaft before the main shaft of the dummy shaft is inserted into the outer shaft. (B) shows a state in which the main shaft and the auxiliary shaft are inserted into predetermined positions of the outer shaft, and (C) shows a state in which the press contact portion 25 is formed on the outer shaft by plastic working.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Steering device, 2 ... Steering wheel, 3 ... Steering shaft, 4 ... Steering column, 5 ... Power steering mechanism, 6, 7 ... Universal joint, 8 ... Gear box, 9 ... Bracket, 10 ... Intermediate shaft, 11 ... Inner Shaft, 12 ... Inner side coupling part, 13 ... Fitting part, 14 ... Serration, 16 ... Biting part,
21: outer shaft, 22: outer side coupling portion, 22a: peripheral wall, 23 ... fitting portion, 24 ... serration, 25 ... pressure contact portion, 26 ... biting portion, 29 ... hollow portion, 30 ... dummy shaft, 31 ... main shaft, 31a ... mold part, 31c ... contact part, 31e ... shaft end part, 32 ... auxiliary shaft, 33, 34 ... serration, 40 ... space, 41 ... punch,
L1 ... center axis, A1 ... insertion direction, A2 ... opposite direction.

Claims (2)

An intermediate shaft in which an outer shaft having a pressure contact portion and an inner shaft having a biting portion that bites into the pressure contact portion in a state of being inserted into a hollow portion of the outer shaft are coupled, and an impact force exceeding a set value acts A steering device in which impact energy due to the impact force is absorbed by the relative movement of the inner shaft and the outer shaft against the movement resistance force between the pressure contact portion and the biting portion. In the method of assembling the intermediate shaft of
A step of inserting a dummy shaft into the hollow portion of the outer shaft; and a step of forming the press-contact portion protruding in the hollow portion by plastically deforming a peripheral wall of the outer shaft using the dummy shaft. And a method of assembling the intermediate shaft of the steering device, wherein the inner shaft inserted into the hollow portion is press-fitted into the press contact portion after the dummy shaft is removed from the outer shaft.   The dummy shaft includes a main shaft having a mold portion used for forming the pressure contact portion at a shaft end portion, and an auxiliary shaft that contacts the main shaft at the shaft end portion. The method for assembling the intermediate shaft of the steering device according to claim 1.

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