JP2015182745A - Steering shaft, steering gear, and method of manufacturing steering shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering shaft which hardly causes peeling of an FRP layer and which hardly causes formation of a gap, a steering gear, and a method of manufacturing the steering shaft.SOLUTION: A steering shaft includes a rod-like rack shaft body 10 that has a recess 12 extended in an axial direction, and FRP layers 31-33 that are provided in the recess 12. A boundary surface 40 between the rack shaft body 10 and the FRP layers 31-33 in the axial direction assumes a step-wise shape with a wide radial outside.

Description

  The present invention relates to a steered shaft, a steering device, and a method for manufacturing the steered shaft.

  In order to improve fuel consumption and running performance, automobile parts are required to be lighter. Therefore, a technique is known in which a metal rack shaft (steering shaft), which is an automotive part, is partially made of FRP (Fiber Reinforced Plastic) (see Patent Documents 1 and 2). Here, a tensile or compressive load acts on the rack shaft mainly in the axial direction (vehicle width direction, left-right direction).

JP 2012-153314 A JP 2013-32047 A

  However, in Patent Documents 1 and 2, in the axial direction of the rack shaft, the boundary surface in the axial direction between the metal rack shaft main body and the FRP layer is an inclined surface (tapered surface) having a wider radial outer side. When a compressive load acts on the rack shaft in the axial direction, a shearing force is generated along the inclined surface, and there is a high possibility that the FRP layer is peeled off from the rack shaft main body.

  Further, when the FRP layer is configured by winding the prepreg around the rack shaft main body, the end surface of the prepreg is in line contact with the inclined surface on the rack shaft main body side. In addition to the gaps formed between them, the fibers may be twisted and the strength of the FRP layer may be reduced. The thicker the prepreg, the easier the gap is formed.

  Then, this invention makes it a subject to provide the manufacturing method of a turning shaft, a steering apparatus, and a turning shaft in which a FRP layer cannot peel easily and a clearance gap is hard to be formed.

  As means for solving the above-mentioned problems, the present invention comprises a rod-shaped steering shaft main body having a recess extending in the axial direction, and an FRP layer provided in the recess, and the steering shaft in the axial direction. The boundary surface between the main body and the FRP layer is a steered shaft characterized by a stepped shape having a wide radial outer side.

  According to such a configuration, the boundary surface between the steered shaft main body and the FRP layer in the axial direction has a stepped shape (stepped shape) whose outer side in the radial direction is wide. The boundary surface between the layers extends in the radial direction, that is, extends in the direction of the wheel cross-section of the steered shaft main body perpendicular to the axial direction. That is, the stepped boundary surface includes an axial boundary surface extending in the axial direction and a radial boundary surface extending in the radial direction.

  Thereby, when a compressive load is applied to the steered shaft in the axial direction, the steered shaft main body and the FRP layer are in close contact with each other via a radial boundary surface orthogonal to the axial direction. Thus, since the axial direction on which the compressive load acts and the radial boundary surface where the steered shaft main body and the FRP layer are in contact with each other are orthogonal, the steered shaft main body and the FRP layer are not easily displaced, and the FRP layer Is difficult to peel off from the steered shaft body.

  Further, since the boundary surface is stepped, it is difficult to form a gap between the rack shaft main body and the FRP layer. That is, when the FRP layer is configured by stacking prepregs, the end surface of the prepreg can be matched with the stepped boundary surface on the rack body side, and a gap is hardly formed. This increases the strength of the entire rack shaft.

  Further, since the axial boundary surface extends in the circumferential direction, the fiber extending in the FRP layer and the axial boundary surface are parallel to each other. Thus, since the fiber extending in the FRP layer and the axial boundary surface are parallel, the load can be transmitted between the FRP layer and the steered shaft main body.

  Further, in the steered shaft, the concave portion extends in the entire circumferential direction, and the FRP layer may be configured by winding and hardening a prepreg around the concave portion.

  As a means for solving the above-mentioned problems, the present invention is a steering apparatus comprising the steered shaft.

  As means for solving the above problems, the present invention comprises a rod-shaped steered shaft main body having a recess extending in the axial direction and the entire circumferential direction, and an FRP layer provided in the recess, in the axial direction. A boundary surface between the steered shaft main body and the FRP layer is a method of manufacturing a steered shaft having a stepped shape having a wide radial outer side, and a prepreg is wound around the recess to be cured, and the FRP layer is formed. It is the manufacturing method of the turning shaft characterized by forming.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the turning shaft and steering apparatus which are hard to peel an FRP layer, and a clearance gap is difficult, and a turning shaft can be provided.

It is a lineblock diagram of the steering device concerning this embodiment. It is sectional drawing in the axial direction of the rack axis | shaft which concerns on this embodiment. It is an expanded sectional view in the direction of an axis of a rack axis concerning this embodiment. It is an expanded sectional view in the direction of an axis of a rack axis concerning this embodiment, and a CFRP layer is omitted.

An embodiment of the present invention will be described with reference to FIGS.
In the following description, the axial direction means the axial direction (longitudinal direction) of the rod-shaped rack shaft 1 (steering shaft), and the radial direction means the radial direction of the rack shaft 1. The vehicle width direction outer side means the side approaching the outside of the vehicle in the vehicle width direction (left-right direction), and the vehicle width direction inner side means the side approaching the vehicle center in the vehicle width direction.

≪Steering device≫
The steering device 100 is a rack and pinion type electric power steering device, and is a pinion assist type in which an assist force generated by an electric motor is input to the pinion shaft 104. However, a column assist type or a rack assist type may be used. Also, a hydraulic power steering device that generates assist force with a hydraulic motor may be used.

  The steering device 100 includes a steering wheel 101 operated by a driver, a steering shaft 102 (steering column) that rotates integrally with the steering wheel 101, a torsion bar 103 coupled to a lower end of the steering shaft 102, and a torsion bar 103 A pinion shaft 104 connected to the lower end and a rack shaft 1 (steering shaft) extending in the vehicle width direction (left-right direction) are provided.

  The pinion teeth 104 a of the pinion shaft 104 mesh with the rack teeth 11 of the rack shaft 1. When the pinion shaft 104 rotates, the rack shaft 1 moves in the vehicle width direction, and the steered wheels 106 (wheels) connected via the tie rod 105 are steered. The rack shaft 1 is accommodated in a cylindrical housing 107 via a bush or the like.

  A worm wheel (not shown) is coaxially fixed to the pinion shaft 104. An assist force is input from an electric motor (not shown) to the worm wheel (pinion shaft 104) in accordance with the torsional torque generated by the torsion bar 103.

  A load from the road surface is input to the rack shaft via the steering wheel 106 and the tie rod 105. This load has an axial tensile or compressive component or a tensile or compressive component in a direction having an angle with respect to the axial direction. When input from a direction having a certain angle with respect to the axial direction, a force of a bending component is also applied to the rack shaft 1. An axial tensile load acts on the outside of the bending force, and an axial compressive load acts on the inside.

≪Rack shaft configuration≫
As shown in FIG. 2, the rack shaft 1 includes a rack shaft body 10, an intermediate layer 21, and a plurality of layers (here, three layers) of a first CFRP layer 31, a second CFRP layer 32, and a third CFRP layer 33 as FRP layers. And a CFRP (Carbon Fiber Reinforced Plastic) layer.

<Rack shaft body>
The rack shaft main body 10 is a rod-shaped component and extends in the left-right direction. The rack shaft main body 10 is made of metal, and is formed of, for example, carbon steel (S45C or the like) or aluminum alloy. However, the rack shaft main body 10 may be made of resin or FRP. In the case of this configuration, for example, the rack shaft body 10 can be formed by filling the cylindrical first CFRP layer 31 with resin.

  Rack teeth 11 are formed on the right side of the rack shaft body 10.

<Rack shaft body-recessed part>
On the left side of the rack shaft body 10, a recess 12 is formed that extends in the axial direction and is recessed radially inward in the entire circumferential direction (see FIG. 4). That is, the rack shaft main body 10 includes an inner cylinder portion 13 having a small diameter on the left side. A hollow portion 14 that extends in the left-right direction and opens to the outside on the left side is formed on the central axis of the inner cylinder portion 13. That is, the inner cylinder part 13 is cylindrical shape, and the thickness of a surrounding wall is 1-2 mm, for example.

  However, the structure in which the inner cylinder part 13 is solid may be sufficient. In this embodiment, the rack teeth 11 are formed on the right side and the inner cylinder portion 13 is provided on the left side. However, when the left and right sides are reversed or the rack teeth 11 are formed on both the left and right sides, the CFRP The positional relationship between the inner cylinder part in which the layer is formed and the rack teeth 11 is not limited.

  Both sides in the axial direction of the recess 12 have a stepped shape in which the outer side in the radial direction is wide, and is formed in three steps here. That is, the recess 12 includes a first step portion 15 on the radially inner side (center axis O1 side), a second step portion 16 on the radially outer side of the first step portion 15, and a radially outer side of the second step portion 16. It is comprised with the 3rd step part 17 (refer FIG. 4). The axial length L15 of the first step portion 15, the axial length L16 of the second step portion 16, and the axial length L17 of the third step portion 17 are “L15 <L16 <L17”. Note that the number of steps is not limited, and may be stepped with an arbitrary step.

  The thickness T15 of the first step portion 15, the thickness T16 of the second step portion 16, and the thickness T17 of the third step portion 17 are substantially the same (T15≈T16≈T17), for example, 0.2 to 2 mm. (See FIG. 4). And the whole thickness of the recessed part 12 is designed by 3-6 mm, for example.

<Intermediate layer>
The intermediate layer 21 is provided between the inner cylinder portion 13 and the first CFRP layer 31, but is not essential. The intermediate layer 21 is a layer that bonds the inner cylinder portion 13 and the first CFRP layer 31. Thereby, the inner cylinder part 13 and the 1st CFRP layer 31 do not shift | deviate in the circumferential direction and an axial direction. Further, the intermediate layer 21 may have a function of relaxing the difference in thermal expansion coefficient between two layers adjacent to each other via the intermediate layer 21. The intermediate layer 21 is formed of, for example, a resin layer such as a layer formed by curing an epoxy adhesive, or a double-sided tape. Further, the intermediate layer 21 may be provided between the inner cylinder portion 13 and the second CFRP layer 32 and between the inner cylinder portion 13 and the third CFRP layer 33. The intermediate layer 21 may be provided between the first CFRP layer 31 and the second CFRP layer 32 and between the second CFRP layer 32 and the third CFRP layer 33.

<CFRP layer>
The first CFRP layer 31, the second CFRP layer 32, and the third CFRP layer 33 are carbon fiber reinforced plastic layers that are lightweight and have high strength. On the radially outer side of the intermediate layer 21, the first CFRP layer 31, the second CFRP layer 32, and the third CFRP layer 33 are laminated in this order toward the radially outer side.

  The thickness T31 of the first CFRP layer 31, the thickness T32 of the second CFRP layer 32, and the thickness T33 of the third CFRP layer 33 are substantially the same (T31≈T32≈T33), and are designed to be 0.2 to 2 mm, for example. (See FIG. 3). The total thickness of the laminated first CFRP layer 31, second CFRP layer 32, and third CFRP layer 33 is designed to be, for example, 3 to 6 mm.

  The axial length L31 of the first CFRP layer 31, the axial length L32 of the second CFRP layer 32, and the axial length L33 of the third CFRP layer 33 are “L31 <L32 <L33”.

  The first CFRP layer 31, the second CFRP layer 32, and the third CFRP layer 33 are configured by arranging a plurality of reinforcing fibers in a resin matrix (base, matrix). The resin forming the matrix can be selected from, for example, a thermosetting resin such as an epoxy resin or a thermoplastic resin, but a thermosetting resin is preferable in terms of strength and moldability.

  The reinforcing fiber is made of carbon fiber, and has, for example, a strand shape formed by twisting a plurality of carbon fibers. Reinforcing fibers are contained in each CFRP layer at 40 to 90% by mass.

<Boundary surface between rack shaft body and CFRP layer>
In the axial direction, the boundary surface 40 between the rack shaft main body 10 and the first CFRP layer 31, the second CFRP layer 32, and the third CFRP layer 33 has a stepped shape having a wide radial outer side, and is configured in three steps in this embodiment. Has been. However, the number of stages is not limited to this. Further, the height of the step (thickness of each CFRP layer) and the axial width of the step (axial length of each CFRP layer) can be appropriately changed.

  The boundary surface 40 includes an axial boundary surface 41 extending in the axial direction and a radial boundary surface 42 extending in the radial direction, and the axial boundary surface 41 and the radial boundary surface 42 are alternately connected. . That is, the axial boundary surface 41 and the radial boundary surface 42 are orthogonal to each other, and the radial boundary surface 42 is also orthogonal to the axial direction.

<< Effects of rack shaft and steering device >>
The effects of the rack shaft 1 and the steering device 100 will be described.
The boundary surface 40 between the rack shaft main body 10 and the first CFRP layer 31, the second CFRP layer 32, and the third CFRP layer 33 has a stepped shape having a wide radial outer side, that is, the rack shaft main body 10 and the first CFRP layer. 31, the radial boundary surface 42 formed between the second CFRP layer 32 and the third CFRP layer 33 is orthogonal to the axial direction, so that an axial compressive load is input to the rack shaft 1. The rack shaft main body 10, the first CFRP layer 31, the second CFRP layer 32, and the third CFRP layer 33 are in close contact with each other via the radial boundary surface.

  Thus, since the axial direction in which the compressive load is input and the radial boundary surface 42 sandwiched between the rack shaft main body 10 and the first CFRP layer 31 are orthogonal, the rack shaft main body 10 and the first CFRP layer 31 etc. become difficult to shift. Therefore, the first CFRP layer 31 and the like are difficult to peel from the rack shaft main body 10.

≪Rack shaft manufacturing method≫
A method for manufacturing the rack shaft 1 by the sheet winding method will be described.
First to third prepregs corresponding to the first CFRP layer 31, the second CFRP layer 32, and the third CFRP layer 33 are prepared. However, a method of winding a single prepreg multiple times and winding it up may be used. Further, each CFRP layer may be formed using a plurality of prepregs.

  After applying an adhesive to the outer peripheral surface of the inner cylinder part 13, the first prepreg to be the first CFRP layer 31 is wound around the inner cylinder part 13 while being aligned with the first step part 15. Next, the second prepreg to be the second CFRP layer 32 is wound on the first prepreg while being aligned with the second step portion 16. Next, the third prepreg to be the third CFRP layer 33 is wound on the second prepreg while being aligned with the third step portion 17.

  Here, both sides in the axial direction of the recess 12 have a stepped shape in which the radially outer side is wide, and the axial inner wall surface 15a (see FIG. 4) of the first step portion 15 extends in the radial direction. There is no gap formed between the prepreg and the first step portion 15. Similarly, since the axial inner wall surface 16a of the second step portion 16 and the axial inner wall surface 17a of the third step portion 17 also extend in the radial direction, between the second prepreg and the second step portion 16, There is no gap formed between the third prepreg and the third step portion 17.

Next, using an appropriate pressure device and heating device, the pressure and temperature are set in accordance with the type of thermosetting resin contained in the prepreg, and the thermosetting resin is cured.
Then, the rack shaft 1 is obtained.

  Since the sheet winding method in which such a prepreg is wound around the inner cylindrical portion 13 that is a core material can be stably manufactured, the quality stability of the rack shaft 1 is increased.

<< Modification 1 >>
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to this, For example, you may change as follows.

  In the above-described embodiment, the configuration in which the reinforcing fiber is a carbon fiber has been exemplified. However, for example, a configuration in which the reinforcing fiber is an organic fiber such as glass fiber, SiC fiber, or aramid may be used. That is, the FRP may be a GFRP or the like.

<< Modification 2 >>
In the above-described embodiment, the method of forming the first CFRP layer 31 and the like by the sheet winding method is exemplified. However, for example, the first CFRP layer 31 and the like can also be formed by the filament winding method. That is, a method in which a filament (reinforced fiber) impregnated with a thermosetting resin is wound around the rack shaft main body 10 and then cured may be used.

<< Modification 3 >>
In the above-described embodiment, the steering device 100 is a rack and pinion type and the turning shaft is the rack shaft 1. However, for example, the steering device 100 is a ball nut type and the turning shaft is a nut. The structure which is a screw rod reciprocating by rotation of this may be sufficient.

1 Rack axis (steering axis)
10 Rack shaft body (steering shaft body)
12 concave portion 15 first step portion 16 second step portion 17 third step portion 31 first CFRP layer 32 second CFRP layer 33 third CFRP layer 40 boundary surface 41 axial boundary surface 42 radial boundary surface 100 steering device

Claims (4)

A rod-like steered shaft body having a recess extending in the axial direction;
An FRP layer provided in the recess;
With
A steered shaft characterized in that a boundary surface between the steered shaft main body and the FRP layer in the axial direction has a stepped shape having a wide radial outer side. The recess extends in the entire circumferential direction,
The steered shaft according to claim 1, wherein the FRP layer is obtained by winding and curing a prepreg around the concave portion. A steering apparatus comprising the steered shaft according to claim 1. A rod-shaped steered shaft main body having a recess extending in the axial direction and the entire circumferential direction, and an FRP layer provided in the concave portion, and the boundary surface between the steered shaft main body and the FRP layer in the axial direction is A method for manufacturing a steered shaft that is stepped with a radially outer side wide,
A method of manufacturing a steered shaft, wherein the FRP layer is formed by winding and curing a prepreg in the recess.

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