Shock-absorbing member and steering column

Abstract

The objective is to provide an impact-absorbing component that is a composite of metal and resin materials, possessing strength and impact absorption performance equivalent to that of a material using only metal, while also being lightweight, moldable, insulating, damping, and corrosion-resistant. [Solution] To solve the above problems, the present invention provides an impact absorbing member comprising a shaft portion 10 made of a rod-shaped metal and a hollow housing portion 20 into which at least a portion of the shaft portion 10 in the axial direction is inserted, The housing portion 20 has at least a surface made of a thermoplastic resin composition, and the thermoplastic resin composition and the metal of the shaft portion 10 are directly joined inside the housing portion 20. The device is characterized in that, upon impact, the joint between the housing portion 20 and the shaft portion 10 is broken, and thereafter the housing portion 20 and the shaft portion 10 slide against each other.

Description

Technical Field

[0001] The present invention relates to a shock absorption member including a shaft portion made of a rod-shaped metal and a hollow housing portion into which at least a part of the shaft portion in the axial direction is inserted, and a steering column using the shock absorption member.

Background Art

[0002] In a steering column provided in a vehicle such as an automobile, it is a device for absorbing an impact when a driver collides with a steering wheel following a primary collision in which the vehicle collides with another vehicle. Specifically, a structure is adopted in which a part of the steering column is detached from the vehicle body and moved in the column axial direction while absorbing an impact (energy).

[0003] For example, in Patent Document 1, a pair of locking cutouts extending parallel to the column axial direction are provided in a vehicle body side bracket fixed to the vehicle body. The column side bracket is supported via a pair of locking capsules each held by a plurality of locking pins in each locking cutout, and each locking capsule is coupled and fixed to the column side bracket via bolts passing through each locking cutout. At the time of a secondary collision, a plurality of locking pins holding each locking capsule break, so that each locking capsule detaches from the corresponding locking cutout, and the locking capsule and the column bracket move together in the column axial direction.

[0004] Further, in Patent Document 2, an inner bracket fixed to the outer peripheral surface of an inner column, and disposed outside the inner bracket in the radial direction of the inner column, and between the inner bracket and itself, extends in the axial direction of the inner column and forms a cylindrical space surrounded. A steering column device is disclosed, comprising an outer bracket, a connecting member that connects the inner bracket and the outer bracket and breaks due to the impact load applied during a secondary collision, an impact-absorbing wire arranged in a cylindrical space, and a locking member supported by the outer column that engages and disengages a second engaging portion provided on itself with a first engaging portion provided on the outer bracket. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2012-121538 [Patent Document 2] Japanese Patent Publication No. 2023-19570 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In conventional technology, as disclosed in Patent Documents 1 and 2, from the viewpoint of strength and other factors, it was common for all components except for the fracture member (locking pin, connecting member) that acts as a trigger during impacts such as primary collisions to be made of metal. However, in recent years, there has been a growing demand for parts made of hybrid materials combining metal and resin materials, due to considerations such as weight reduction, moldability, insulation, damping, and corrosion resistance. Similarly, the development of technologies using composite materials of metal and resin materials is being considered for impact components such as steering columns.

[0007] Therefore, the present invention aims to provide an impact-absorbing member and steering column that are composites of metal and resin materials, possessing strength and impact absorption performance equivalent to that of a metal material alone, while also being superior in terms of lightness, moldability, insulation, damping, corrosion resistance, etc. [Means for solving the problem]

[0008] The inventors of the present invention have conducted extensive research to solve the above-mentioned problems regarding an impact absorbing member comprising a rod-shaped metal shaft portion and a hollow housing portion into which at least a portion of the shaft portion in the axial direction is inserted. As a result, they have found that by constructing at least the surface of the housing portion into which the shaft portion is inserted from a thermoplastic resin and directly bonding it to the metal, the failure of the bond between the housing portion and the shaft portion acts as a trigger during an impact such as a primary collision. Subsequently, the frictional force generated by the sliding between the inner surface of the housing portion and the outer surface of the shaft portion after the bond has been broken enables high energy absorption. Consequently, they have found that it is possible to achieve strength and impact absorption performance equivalent to that of a metal material alone, and have completed the present invention.

[0009] This invention is based on the above findings, and its gist is as follows. (1) An impact absorbing member comprising a shaft portion made of a rod-shaped metal and a hollow housing portion into which at least a portion of the shaft portion in the axial direction is inserted, The housing portion is composed of a thermoplastic resin composition, at least on its surface. Inside the housing portion, the thermoplastic resin composition and the metal of the shaft portion are directly joined. An impact-absorbing member characterized in that, upon impact, the joint between the housing portion and the shaft portion is broken, and thereafter the housing portion and the shaft portion slide against each other. (2) The shock-absorbing member according to (1), characterized in that it absorbs the energy of the impact by the sliding motion. (3) The shock-absorbing member according to (1) or (2), characterized in that the proportion of the portion made of the thermoplastic resin composition in the entire shock-absorbing member is 2% by volume or more. (4) The shock-absorbing member according to any one of (1) to (3), characterized in that the thermoplastic resin composition contains 10 to 60% by mass of filler. (5) The shock-absorbing member according to any one of (1) to (4), characterized in that the thermoplastic resin contained in the thermoplastic resin composition is a crystalline resin and has a melting point of 150°C or higher as measured by differential scanning calorimeter (DSC) at a heating rate of 20°C / min. (6) The shock-absorbing member according to any one of (1) to (5), characterized in that the flexural modulus of the thermoplastic resin composition, as measured in accordance with ISO 178, is 3 GPa or more. (7) The impact absorbing member according to any one of (1) to (5), characterized in that the bonding strength between the thermoplastic resin composition of the housing portion and the metal of the shaft portion is such that when the metal side is placed on top and the resin side is placed on the bottom and subjected to a compression test at a test speed of 5 mm / min, the stress obtained by dividing the load at the time of failure (N) by the bonding area (mm) is 3 MPa or more. (8) The impact absorbing member according to any one of (1) to (7), characterized in that the metal of the shaft portion has irregularities on its surface. (9) The shock-absorbing member according to any one of (1) to (8), characterized in that the thermoplastic resin contained in the thermoplastic resin composition is at least one selected from the group consisting of polypropylene, polybutylene terephthalate, polyamide, and polyphenylene sulfide. A steering column characterized by using an impact-absorbing member as described in any of (10)(1) to (9). [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a shock-absorbing member and steering column that are composites of a metal material and a resin material, which have strength and shock absorption performance equivalent to that of a metal material alone, while also being lightweight, moldable, insulating, damping, corrosion-resistant, etc. [Brief explanation of the drawing]

[0011] [Figure 1] This figure schematically shows a cross-section of an example of the impact-absorbing member of this embodiment. [Figure 2]This is a diagram for explaining the flow of energy absorption during impact with respect to an example of the shock-absorbing member of the present embodiment.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. The following present embodiment is an exemplification for explaining the present invention and is not intended to limit the present invention to the following contents. The present invention can be appropriately modified and implemented within the scope of its gist.

[0013] Here, FIG. 1 is an example of the shock-absorbing member according to the present embodiment, and FIG. 2 schematically shows the flow of energy absorption during impact with respect to an example of the shock-absorbing member according to the present embodiment. Note that the dimensions and ratios of each member shown in FIGS. 1 and 2 are different from the actual ones for the sake of convenience of explanation.

[0014] <Shock-absorbing member> First, the shock-absorbing member of the present embodiment (hereinafter sometimes simply referred to as "the shock-absorbing member") will be described. As shown in FIG. 1, the shock-absorbing member of the present embodiment is a shock-absorbing member including a shaft portion 10 made of a rod-shaped metal and a hollow housing portion 20 into which at least a part of the shaft portion 10 in the axial direction is inserted.

[0015] And in the shock-absorbing member of the present embodiment, the housing portion 20 is at least composed of a thermoplastic resin composition on the surface, and as shown in FIG. 1, inside the housing portion 20, the thermoplastic resin composition and the metal of the shaft portion 10 are directly joined (forming a joining portion 30). And in the shock-absorbing member of the present embodiment, as shown in FIG. 2(a), during impact, the joining between the housing portion 20 and the shaft portion 10 is broken, and then the housing portion 20 and the shaft portion 10 slide.

[0016] Regarding the housing part 20 into which the shaft part 10 is inserted, at least the surface is made of a thermoplastic resin and is directly joined to the metal of the shaft part 10. Thus, at the time of an impact such as a primary collision (when pressure P is applied in the direction of the arrow in Fig. 2(a)), the joint part 30 between the housing part 20 and the shaft part 10 functions as a trigger and is broken. Thereafter, for example, high energy absorption becomes possible due to the frictional force of the sliding surface 31 generated by the sliding between the inner surface of the housing part 20 where the joint part 30 is broken and the outer surface of the shaft part 10. This energy absorption is not limited to being only due to the frictional force of the sliding surface 31, and it may utilize the resistance when oil or rubber enclosed in the housing part 20 or the shaft part 10 etc. sprays out from small holes, utilize the energy absorption of a member such as a wire that plastically deforms upon receiving an impact, utilize the elongation in a hook shape, etc. to realize energy absorption. Also, regarding the housing part 20, since it is mainly composed of a thermoplastic resin, improvements in lightweightness, moldability, insulation, damping, corrosion resistance, etc. are possible compared to the case of using a conventional metal material.

[0017] (Shaft part) The shaft part 10 constituting the shock absorption member of the present embodiment is a member made of a rod-shaped metal. As shown in Fig. 1, in the state of being inserted into the housing part 20 described later, it is normally fixed.

[0018] The shaft part 10 is made of metal from the viewpoint of maintaining strength during impact. The type of metal is not particularly limited and can be appropriately selected according to the type of member to be applied. For example, when the shaft part 10 is a steering shaft, high-strength steel can be used. In addition, iron, stainless steel, aluminum, aluminum alloy, magnesium, magnesium alloy, copper, copper alloy, titanium, titanium alloy, etc. can be used. Although the shaft portion 10 is made of metal, not all components constituting the shaft portion 10 necessarily need to be made of metal. It is also possible to include materials other than metal as appropriate for connecting parts to other members or other decorative parts.

[0019] Furthermore, the shaft portion 10 is rod-shaped so that it can be inserted into the housing portion 20 and, after being subjected to impact, can move (slide) inside. Regarding the rod shape, there are no particular limitations as long as it extends in one axial direction; it can also be cylindrical or polygonal. Furthermore, it can be made into a hollow tube depending on the required performance.

[0020] Furthermore, it is preferable that the metal constituting the shaft portion 10 has an uneven surface. This is because the uneven surface of the metal increases the strength of the joint surface 30 between the shaft portion 10 and the housing portion 20. The surface irregularities of the aforementioned metal can be, for example, in the range of 10 nm to 500 μm in terms of arithmetic mean height (Ra) as specified in JIS B 0601:2013. The above-mentioned range of arithmetic mean roughness is preferably 20 nm to 400 μm, more preferably 50 nm to 300 μm, even more preferably 100 nm to 200 μm, and even more preferably 1 μm to 100 μm.

[0021] (Housing Department) As shown in Figure 1, the housing portion 20 that constitutes the shock-absorbing member of this embodiment is a hollow member in which at least a portion of the shaft portion 10 in the axial direction is inserted inside.

[0022] The housing portion 20 is made of a thermoplastic resin composition at least on its surface, from the viewpoint of lightness, moldability, insulation, damping, corrosion resistance, etc. From a similar viewpoint, it is preferable that the entire housing portion 20 is made of thermoplastic resin. Furthermore, depending on the required performance, such as extremely high strength, it is also possible to use metal materials inside the housing portion 20.

[0023] Here, it is preferable that the proportion of the portion made of the thermoplastic resin composition in the entire shock-absorbing member is 2 volume% or more, more preferably 5 volume% or more, even more preferably 7 volume% or more, even more preferably 10 volume% or more, and particularly preferably 15 volume% or more. By setting the proportion of the portion made of the thermoplastic resin composition to 2 volume% or more, a sufficient bonding area can be obtained to control it as an energy absorption trigger mechanism of the present invention, and in addition, by setting it to 10 volume% or more, damping properties can be imparted to the shock-absorbing member and the steering column. Furthermore, the more resin components are used, the higher the level of weight reduction and ease of manufacturing can be achieved.

[0024] Furthermore, the thermoplastic resin used as the base resin of the thermoplastic resin composition is not particularly limited and can be appropriately selected according to the required performance. For example, from the viewpoint of good strength and manufacturing cost, the thermoplastic resin is preferably at least one selected from the group consisting of polypropylene, polybutylene terephthalate, polyamide, and polyphenylene sulfide, and more preferably contains at least one of polybutylene terephthalate, polyamide, or polyphenylene sulfide. Furthermore, from the viewpoint of impact resistance, it is particularly preferable to contain polyamide. These resins can be known resins depending on the required performance.

[0025] Furthermore, examples of the polyamides include polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 11, polyamide 12, polyamide 6 / 66, polyamide 6 / 12, polyamide 6 / 610, polyamide 6 / 66 / 12, polyamide 6 / 66 / 610, polyamide 6 / 66 / 612, polyamide 6I, polyamide 6I / 66, polyamide 6T, polyamide 6T / 6I, and polyamide 4T. The aforementioned polyamide may contain a combination of multiple types. For example, it is preferable to include crystalline polyamide from the viewpoint of component strength, while also containing different types of polyamide or amorphous polyamide to appropriately delay crystallization during molding from the viewpoint of adhesion of resin flow to uneven metal surfaces. Examples include polyamide 6 and polyamide 610, polyamide 6 and polyamide 612, polyamide 6 and polyamide 11, polyamide 6 and polyamide 12, polyamide 6 and polyamide 6I, polyamide 6 and polyamide 6T / 6I, polyamide 66 and polyamide 610, polyamide 66 and polyamide 612, polyamide 66 and polyamide 11, polyamide 66 and polyamide 12, polyamide 66 and polyamide 6I, polyamide 66 and polyamide 6T / 6I, etc.

[0026] Furthermore, the thermoplastic resin contained in the thermoplastic resin composition is preferably a crystalline resin with a melting point of 150°C or higher as measured by a differential scanning calorimeter (DSC). This is because it is possible to further improve the heat resistance, thermal fatigue resistance, and creep strength of the housing portion 20. From a similar viewpoint, the melting point of the thermoplastic resin as measured by DSC is more preferably 170°C or higher, more preferably 190°C or higher, even more preferably 200°C or higher, even more preferably 220°C or higher, even more preferably 240°C or higher, and even more preferably 250°C or higher. Setting it to 200°C or higher can particularly improve the creep strength of the part, and setting it to 240°C or higher can particularly improve the thermal fatigue resistance of the part.

[0027] Furthermore, the thermoplastic resin composition constituting the housing portion 20 preferably contains 10 to 60% by mass of filler in order to maintain high strength and durability. When the thermoplastic resin composition contains 10% by mass of filler, sufficient strength and durability can be ensured, and by limiting the filler content in the thermoplastic resin composition to 60% by mass or less, deterioration of the processability and moldability of the resin composition can be suppressed. From a similar viewpoint, the filler content is more preferably 16 to 57% by mass, even more preferably 26 to 55% by mass, even more preferably 29 to 53% by mass, and even more preferably 34 to 51% by mass. The content of the filler refers to the content of the filler in the thermoplastic resin composition.

[0028] Examples of fillers include glass fibers, carbon fibers, carbon particles, carbon black, titanium dioxide, glass particles, cellulose fibers, cellulose nanofibers, cellulose nanocrystals, clay, talc, silica, mica, and wollastonite. Among these, glass fibers or carbon fibers are more preferable from the viewpoint of balancing strength and moldability. The fillers can be used individually or in combination.

[0029] Furthermore, the thermoplastic resin composition may, in addition to the thermoplastic resin and filler described above, contain optional additives such as flame retardants, higher fatty acid-based surfactants, antioxidants such as phenol-based and phosphorus-based agents, organic heat stabilizers, ionic heat stabilizers such as copper, potassium, and iodine, ultraviolet absorbers such as benzimidazole-based, benzotriazole-based, and benzophenone-based agents, light stabilizers, lubricants, mold release agents, plasticizers, antiblocking agents, antistatic agents, antifogging agents, metal soaps such as montanic acid-based and stearic acid-based agents, pigment-based colorants such as carbon black, dye-based colorants such as nigrosine, lubricity improvers such as polytetrafluoroethylene and olefin-based block polymers, impact improvers represented by thermoplastic elastomers and particulate core-shell rubbers such as butadiene-based, acrylic-based, silicone-based, and olefin-based agents, and various compatibilizers as appropriate. There are no specific regulations regarding the formulation method, but examples include adding the additive during the polymerization of a thermoplastic resin, mixing the additive in a blender before melt-kneading after polymerization and then melt-kneading it in an extruder or Banbury mixer, or creating a high-concentration masterbatch and then kneading it.

[0030] Furthermore, from the viewpoint of more reliably improving the strength of the housing portion 20, the thermoplastic resin composition preferably has a flexural modulus of 3 GPa or higher, more preferably 5 GPa or higher, even more preferably 7 GPa or higher, even more preferably 8 GPa or higher, even more preferably 10 GPa or higher, and particularly preferably 12 GPa or higher, as measured in accordance with ISO 178. On the other hand, from the viewpoint of ensuring the flexibility of the housing portion 20, it is preferable that the flexural modulus of 20 GPa or lower, as measured in accordance with ISO 178.

[0031] As shown in Figure 1, the inner surface of the housing portion 20 is joined to the shaft portion 10, forming a joint surface 30. Regarding the joint strength between the thermoplastic resin composition of the housing portion 20 and the metal of the shaft portion 10 at the joint surface 30, when the metal side used for the shaft portion 10 is placed on top and the resin side used for the housing portion 20 is placed on the bottom and subjected to a compression test at a test speed of 5 mm / min, it is preferable that the stress obtained by dividing the load at the time of fracture (N) by the joint area (mm) is 3 MPa or more. More preferably, the stress obtained by dividing the load at the time of fracture (N) by the joint area (mm) is 5 MPa or more, even more preferably 7 MPa or more, even more preferably 9 MPa or more, and particularly preferably 11 MPa or more. This increases the strength of the joint surface 30, allowing it to adequately function as a trigger that causes the joint portion 30 between the housing portion 20 and the shaft portion 10 to break during impacts such as primary collisions. Furthermore, from the standpoint of acting as a trigger, the bonding strength between the thermoplastic resin composition of the housing portion 20 and the metal of the shaft portion 10 at the bonding surface 30 must be of an appropriate magnitude. Specifically, it is preferable that the stress obtained by dividing the load at failure (N) by the bonding area (mm) when subjected to a compression test at a test speed of 5 mm / min as described above is 100 MPa or less. More preferably it is 90 MPa or less, even more preferably 80 MPa or less, and even more preferably 70 MPa or less.

[0032] <Steering column> The steering column of this embodiment uses the impact-absorbing member of this embodiment described above. By using the shock-absorbing member of this embodiment as a steering column, it is possible to achieve strength and shock absorption performance equivalent to that of using only metal materials, while also being superior in terms of lightness, formability, insulation, damping, corrosion resistance, etc.

[0033] Furthermore, there are no particular limitations on the conditions under which the shock-absorbing member is applied to the steering column. For example, the shaft portion may be a steering shaft that constitutes a steering column, and the housing portion may be a column, bracket, or an upper or lower shaft that is different in system from the shaft portion. [Industrial applicability]

[0034] According to the present invention, it is possible to provide a shock-absorbing member and steering column that are composites of a metal material and a resin material, which have strength and shock absorption performance equivalent to that of a metal material alone, while also being lightweight, moldable, insulating, damping, corrosion-resistant, etc.

Claims

1. An impact absorbing member comprising a shaft portion made of a rod-shaped metal, and a hollow housing portion into which at least a portion of the shaft portion in the axial direction is inserted, The housing portion is composed of a thermoplastic resin composition, at least on its surface. Inside the housing portion, the thermoplastic resin composition and the metal of the shaft portion are directly joined. An impact-absorbing member characterized in that, upon impact, the joint between the housing portion and the shaft portion is broken, and thereafter the housing portion and the shaft portion slide against each other.

2. The impact absorbing member according to claim 1, characterized in that it absorbs impact energy by the aforementioned sliding motion.

3. The shock-absorbing member according to claim 1 or 2, characterized in that the proportion of the portion made of the thermoplastic resin composition in the entire shock-absorbing member is 2% by volume or more.

4. The shock-absorbing member according to claim 1 or 2, characterized in that the thermoplastic resin composition contains 10 to 60% by mass of a filler.

5. The shock-absorbing member according to claim 1 or 2, characterized in that the thermoplastic resin contained in the thermoplastic resin composition is a crystalline resin and has a melting point of 150°C or higher as measured by a differential scanning calorimeter (DSC) at a heating rate of 20°C / min.

6. The shock-absorbing member according to claim 1 or 2, characterized in that the flexural modulus of the thermoplastic resin composition, as measured in accordance with ISO 178, is 3 GPa or more.

7. The impact absorbing member according to claim 1 or 2, characterized in that the bonding strength between the thermoplastic resin composition of the housing portion and the metal of the shaft portion is such that when subjected to a compression test at a test speed of 5 mm / min with the metal side facing up and the resin side facing down, the stress obtained by dividing the load at the time of failure (N) by the bonding area (mm) is 3 MPa or more.

8. The impact absorbing member according to claim 1 or 2, characterized in that the metal of the shaft portion has irregularities on its surface.

9. The shock-absorbing member according to claim 1 or 2, characterized in that the thermoplastic resin contained in the thermoplastic resin composition is at least one selected from the group consisting of polypropylene, polybutylene terephthalate, polyamide, and polyphenylene sulfide.

10. A steering column characterized by using the shock-absorbing member described in claim 1 or 2.

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