JP2018039166A - Composite member and manufacturing method of composite member - Google Patents

Abstract

The present invention provides a composite member capable of maintaining a high bonding force between a resin coating and an aluminum material when an aluminum material is used as the metal member, and a method for manufacturing the composite member. An end portion 17 of a lower shaft 13 constituting a steering shaft 3 includes an aluminum base 41 made of aluminum or an aluminum alloy, and an oxygen-containing coating 43 formed on the surface of the aluminum base 41 and containing oxygen. And a resin bonded body 45 made of a resin bonded to the surface of the oxygen-containing film 43. The resin bonded body 45 is formed on the surface of the oxygen-containing coating 43 so as to be annularly connected over the entire circumference of the aluminum base material 41. [Selection] Figure 7

Description

  The present invention relates to a composite member and a method for manufacturing the composite member.

  Conventionally, a composite member in which the outer peripheral surface of a metal member is covered with a resin film is known (see Patent Document 1).

  The composite member described in Patent Document 1 is a shaft member that constitutes a steering shaft, and the lower end of the shaft member uses a steel material as a metal member, and the outer peripheral surface of the steel material is covered with a resin film. doing. Here, the reason why the steel material is used as the metal member is to increase the bonding force between the resin coating and the steel material.

Japanese Patent Laid-Open No. 55-24290

  However, in recent years, there is a tendency to change the steering shaft from steel to aluminum in order to reduce weight. However, the bonding force between the resin film and the aluminum material may be lower than the bonding force between the resin film and the steel material.

  The present invention has been made in view of the above problems, and its purpose is to provide a composite member capable of maintaining a high bonding force between the resin coating and the aluminum material when an aluminum material is used as the metal member, and It is providing the manufacturing method of a composite member.

  The composite member according to the present invention comprises an aluminum substrate made of aluminum or an aluminum alloy, an oxygen-containing film formed on the surface of the aluminum substrate, bonded to the surface of the oxygen-containing film, and made of a resin. And a resin joined body. The resin joined body is formed on the surface of the oxygen-containing coating so as to be annularly connected over the entire circumference in the circumferential direction of the aluminum substrate.

  The method for producing a composite member according to the present invention includes a film forming step of forming an oxygen-containing film containing oxygen on the surface of an aluminum substrate made of aluminum or an aluminum alloy, and an aluminum substrate formed on the surface of the oxygen-containing film. And a resin forming step of forming a resin joined body connected in a ring shape along the circumferential direction.

  According to the present invention, even when an aluminum material is used as the metal member, a composite member having a high bonding force between the resin coating and the aluminum material can be obtained.

FIG. 1 is a side view of a steering system including a steering shaft according to an embodiment of the present invention. FIG. 2 is a side view of the steering shaft of FIG. FIG. 3 is an exploded side view of the steering shaft of FIG. FIG. 4 is a side view showing the lower shaft of FIG. 3. FIG. 5 is a side view showing the upper shaft of FIG. 3. 6 is a cross-sectional view taken along line AA in FIG. FIG. 7 is an enlarged cross-sectional view of a portion B in FIG. 8 is a cross-sectional view taken along the line CC of FIG. FIG. 9 is a schematic view showing the aluminum resin joined body produced in the example. FIG. 10 is a schematic view showing a method for measuring the shear strength of the joint in the aluminum resin joined body. FIG. 11 is a graph showing measurement results of shear strength in the aluminum resin joined bodies of Examples 1 and 2. FIG. 12 is a photograph showing an oxygen-containing film on the aluminum substrate of Example 1. FIG. 13 is a photograph showing a cross section of the aluminum resin joined body of Example 1.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same portions are denoted by the same reference numerals, and description thereof is omitted.

  With reference to FIG. 1, the structure of the steering system provided with the steering shaft which concerns on embodiment of this invention is demonstrated.

  As shown in FIG. 1, a steering system 1 according to an embodiment of the present invention includes a steering shaft 3 extending obliquely downward, and a steering body 7 coupled to a vehicle body member 4 of an automobile via a bracket 5. A steering wheel 9 provided on the steering body 7 and rotatably held. The steering body 7 is provided with a tilt lever 11 that can be slid up and down.

  As shown in FIGS. 2 and 3, the steering shaft 3 includes a lower shaft 13 (first shaft) disposed on the lower side and an upper shaft 15 (second shaft) disposed on the upper side. In the present invention, the lower shaft 13 (first shaft) is a composite member. By inserting the upper end portion 17 of the lower shaft 13 into the insertion hole 20 (see FIG. 8) of the lower end portion 19 of the upper shaft 15, the ends 17 and 19 of the lower shaft 13 and the upper shaft 15 are connected to each other. It is slidably assembled along the direction of arrow S in FIG. As described above, in the steering shaft 3 according to the present invention, when the vehicle collides and a load is input to the steering shaft 3, the lower shaft 13 and the upper shaft 15 slide relative to each other and the entire steering shaft 3 is moved. It is a shock absorbing steering that absorbs collision energy by shortening its length.

  As shown in FIG. 4, the lower shaft 13 (first shaft) includes a joint portion 21 disposed at the lower end in the longitudinal direction, a cylindrical main body portion 23 extending obliquely upward from the joint portion 21, and a main body portion. And an end portion 17 disposed at the upper end of 23.

  The joint portion 21 is formed by forging an aluminum material, and is formed in a U shape when viewed from the side.

  The main body portion 23 is a cylindrical body formed by extrusion molding of an aluminum material, and the main body portion 23 and the end portion 17 are integrated. Moreover, the joint part 21 is joined to the main-body part 23 by friction welding, for example.

  The end portion 17 is obtained by providing an oxygen-containing film and a resin joined body on the surface of a cylindrical body formed by extrusion molding of an aluminum material, and an outer peripheral surface is formed on the first uneven portion 25 as shown in FIG. Has been. The detailed structure of the end 17 will be described later.

  As shown in FIG. 5, the upper shaft 15 (second shaft) includes a joint portion 27 disposed at the upper end in the longitudinal direction, a cylindrical main body portion 29 extending obliquely downward from the joint portion 27, and a main body portion. It is comprised integrally from the edge part 19 arrange | positioned at the lower end of 29.

  The joint portion 27 is formed by forging an aluminum material, and is formed in a U shape when viewed from the side.

  The main body 29 is a cylindrical body formed by extrusion molding of an aluminum material, and the main body 29 and the end 19 are integrated. The joint portion 27 is joined to the main body portion 29 by, for example, friction welding. The main body 29 may be formed by machining after extruding an aluminum material. Furthermore, the main body portion 29 may be formed by extruding an aluminum material and then performing a drawing process.

  The end 19 is a cylindrical body formed by extrusion molding of an aluminum material, and the inner peripheral surface 31 is formed on the second uneven portion 33 as shown in FIG. The second uneven portion 33 is formed in a shape corresponding to the first uneven portion 25 of the lower shaft 13, and the second uneven portion 33 is engaged with the first uneven portion 25. The end 19 may be formed by machining after an aluminum material is extruded. Further, the end 19 may be formed by extruding an aluminum material and then performing a drawing process.

  As shown in FIGS. 6 and 7, the upper end portion 17 of the lower shaft 13 is formed in a cylindrical shape, a hollow portion 35 is formed inward, and the outer peripheral surface 37 is formed in the first uneven portion 25. Is formed. The first concavo-convex portion 25 is provided between a convex portion 39 having an arc-shaped cross section whose radial cross section projects outward in the radial direction and convex portions 39 and 39 adjacent to each other in the circumferential direction. And a concave portion 40 having an arcuate cross section. That is, a plurality of convex portions 39 are provided at regular intervals along the circumferential direction, and a plurality of concave portions 40 are also provided at regular intervals along the circumferential direction. Hereinafter, the cross-sectional structure of the upper end portion 17 of the lower shaft 13 will be described in detail.

  The upper end portion 17 of the lower shaft 13 is formed on the surface of the aluminum base 41 made of aluminum or an aluminum alloy, the oxygen-containing coating 43 containing oxygen, and bonded to the surface of the oxygen-containing coating 43. And a resin joined body 45 made of resin. The resin bonded body 45 is formed on the surface of the oxygen-containing coating 43 so as to be annularly connected over the entire circumference of the aluminum base material 41. In this embodiment, the oxygen-containing coating 43 is continuously formed over the entire circumference of the aluminum base material 41, and the resin bonded body 45 is also oxygenated over the entire circumference of the aluminum base material 41. It is formed continuously on the surface of the containing coating 43.

  As shown in FIG. 8, the lower end portion 19 of the upper shaft 15 is formed in a cylindrical shape, and the inner peripheral surface 31 is formed in the second uneven portion 33. The second uneven portion 33 is formed in a shape that engages with the first uneven portion 25 of the lower shaft 13. Specifically, a plurality of convex portions 47 having a circular cross section projecting radially inward in the radial direction and the convex portions 47 and 47 adjacent in the circumferential direction are provided on the outer side in the radial direction. And a concave portion 49 having an arcuate cross section. Further, a plurality of convex portions 47 are provided at equal intervals along the circumferential direction, and a plurality of concave portions 49 are also provided at equal intervals along the circumferential direction. The outer peripheral surface 51 of the upper shaft 15 is formed in a circular cross section, and an insertion hole 20 is formed inward.

  Next, a method for manufacturing the upper end portion 17 of the lower shaft 13 shown in FIG. 7 (specifically, a method for forming the oxygen-containing coating 43 and the resin joined body 45) will be described.

  First, an aluminum base 41 made of aluminum or an aluminum alloy is formed into a cylindrical shape shown in FIG. 6 by extrusion molding (a step of forming the aluminum base 41).

  Next, as shown in FIG. 7, an oxygen-containing film 43 containing oxygen is formed on the surface of the aluminum base 41 by a method to be described later (film formation process).

  And the resin joined body 45 connected cyclically | annularly along the circumferential direction of the aluminum base material 41 is formed in the surface of this oxygen containing film 43 by the method mentioned later (resin formation process). Thereby, the oxygen-containing film 43 and the resin joined body 45 shown in FIG. 7 can be obtained.

<Oxygen-containing film and resin bonded body>
Next, the oxygen-containing film 43 and the resin bonded body 45 according to this embodiment will be described in detail.

  As described above, when the resin joined body 45 is provided on the surface of the upper end portion 17 of the lower shaft 13, sliding occurs between the lower end portion 19 of the upper shaft 15 which is another member. The wear can be reduced, and the frictional resistance can be reduced and adjusted. Moreover, adjustment of thermal conductivity, adjustment of electric resistance value, and adjustment of appearance color tone can also be performed. However, even if the resin bonded body 45 is directly bonded to the aluminum base material 41, it is difficult to obtain a sufficient bonding force due to the difference in material. Therefore, in this embodiment, the oxygen-containing film 43 is provided on the surface of the aluminum substrate 41, and the resin joined body 45 is bonded to the surface of the oxygen-containing film 43. With such a configuration, it is possible to increase the bonding force between the aluminum base material 41 and the resin bonded body 45 and easily obtain the above effects.

  The oxygen-containing film 43 provided on the aluminum substrate 41 is not particularly limited as long as it improves the adhesion between the aluminum substrate 41 and the resin bonded body 45. Specifically, the oxygen-containing film is obtained by a zinc film forming process using a zinc ion-containing alkaline aqueous solution, and can be a film containing zinc element.

  As the zinc film forming treatment for forming the oxygen-containing film, the surface of the aluminum substrate contains oxygen together with zinc elements such as zinc oxide (ZnO), zinc oxide iron (ZnFeO), zinc aluminum oxide (ZnAlO), etc. Any method for forming a film may be used. Thereby, it becomes possible to join strongly between an oxygen content coat and a resin joined object.

In the zinc ion-containing alkaline aqueous solution used for the zinc film forming treatment, the mass ratio (MOH / Zn ²⁺ ) of alkali metal hydroxide (MOH) and zinc ion (Zn ²⁺ ) is preferably 1 or more and 100 or less. The mass ratio is more preferably 2 or more and 20 or less, and particularly preferably 3 or more and 10 or less. And the zinc containing film | membrane containing oxygen can be formed in the surface of an aluminum base material by making the said zinc ion containing alkaline aqueous solution contact the surface of an aluminum base material at normal temperature.

  It is preferable to use at least one selected from the group consisting of sodium hydroxide, potassium hydroxide and lithium hydroxide as the alkali source (alkali metal hydroxide) in the zinc ion-containing alkaline aqueous solution. The zinc ion source in the aqueous solution containing zinc ions is preferably at least one selected from the group consisting of zinc oxide, zinc hydroxide, zinc peroxide, zinc chloride, zinc sulfate and zinc nitrate.

  In the zinc ion-containing aqueous alkali solution, the concentration of the alkali metal hydroxide is preferably 10 g / L or more and 1000 g / L or less, and more preferably 50 g / L or more and 300 g / L or less. The zinc ion concentration is preferably 1 g / L or more and 200 g / L or less, more preferably 10 g / L or more and 100 g / L or less. By setting the composition of the zinc ion-containing alkaline aqueous solution within the above range, aluminum and zinc ions cause a substitution reaction on the surface of the aluminum base, aluminum is dissolved, and zinc ions are precipitated as fine particles. As a result, an oxygen-containing film containing zinc element can be formed on the surface of the aluminum substrate. That is, aluminum dissolves to form a recess, and zinc precipitates in the recess to form an oxygen-containing film containing zinc element.

In addition, the oxygen-containing film provided on the aluminum base material is preferably a film derived from an aluminum film forming process and containing an aluminum compound. The aluminum compound is selected from the group consisting of Al (OH) ₃ , AlO (OH), Al ₂ O ₃ , Al (PO ₄ ), Al ₂ (HPO ₄ ) ₃ and Al (H ₂ PO ₄ ) _3. At least one of them.

  As the aluminum film forming process for forming such an oxygen-containing film, at least one selected from the group consisting of a hot water immersion process, a water vapor process, a phosphoric acid process, and an anodizing process can be used. The hot water immersion treatment is a treatment of immersing the aluminum substrate in warm water of 50 ° C. or higher for 60 seconds or more. The steam treatment is a treatment in which the aluminum substrate is exposed to a steam atmosphere under a pressure condition of 0.1 MPa or more for 1 minute or more. The phosphoric acid treatment is a treatment in which an aluminum substrate is immersed in a phosphoric acid aqueous solution for 30 seconds to 30 minutes and then dried with hot air at 80 to 400 ° C. for 30 seconds to 30 minutes. Examples of the phosphoric acid aqueous solution include those containing at least one selected from the group consisting of phosphate ions, monohydrogen phosphate ions and dihydrogen phosphate ions in the range of 0.1 to 100 g / L. Can do.

  The oxygen-containing film is derived from an aluminum film forming process, and includes a film containing a hydrogen bond between a hydroxyl group bonded to an aluminum element and a silanol group, and an Al—O—Si bond derived from the aluminum film forming process. A film is also preferred.

  As a treatment for forming such an oxygen-containing film, at least one of a silane coupling treatment and a silica treatment can be used. As a silane coupling treatment, an aluminum substrate is immersed in a solution containing 0.1 to 100 g / L of a silane coupling agent for 30 seconds to 30 minutes, and then heated with hot air at 80 to 400 ° C. for 30 seconds to 30 seconds. It can be set as the process dried for minutes. In addition, as the silica treatment, the aluminum base material is immersed in a solution containing 0.1 to 100 g / L colloidal silica for 30 seconds to 30 minutes, and then dried with hot air at 80 to 400 ° C. for 30 seconds to 30 minutes. Can be processed.

  The above-mentioned hot water immersion treatment, steam treatment, phosphoric acid treatment, anodizing treatment, silane coupling treatment and silica treatment are carried out by any one kind of treatment, and an oxygen-containing film is formed on the surface of the aluminum substrate. Also good. Further, these treatments may be combined to form a necessary oxygen-containing film on the surface of the aluminum substrate.

  The oxygen-containing film provided on the aluminum base material is also preferably a film formed on the surface by laser treatment.

In the laser treatment for forming such an oxygen-containing film, the vicinity of the surface of the aluminum substrate is heated to a temperature equal to or higher than the melting temperature of the aluminum substrate to be oxidized. Thus, it is possible to generate the aluminum oxide near the surface of the aluminum substrate (Al 2 _{O 3),} to form an oxygen containing coating comprising aluminum oxide. In addition, the said laser processing can be performed using a laser etching apparatus etc., for example.

  Regarding the aluminum base material on which the oxygen-containing film is formed, the oxygen content in the surface layer from the outermost surface to a depth of 3 μm is preferably 0.1% by mass or more and 20% by mass or less. The oxygen amount is more preferably 0.5% by mass or more and 15% by mass or less, and particularly preferably 1% by mass or more and 10% by mass or less. When the amount of oxygen is less than 0.1% by mass, the bonding strength between the aluminum substrate and the resin bonded body may be insufficient. In addition, an oxygen-containing film having an oxygen content exceeding 20% by mass is accompanied by manufacturing difficulties. In addition, the amount of oxygen in the surface layer from the outermost surface of the aluminum substrate to a depth of 3 μm can be measured with an electron beam microanalyzer (EPMA).

  Moreover, regarding the aluminum base material on which the oxygen-containing film is formed, when the oxygen-containing film is an anodized film, the oxygen content is 1% by mass or more and 70% by mass or less in the surface layer from the outermost surface to a depth of 3 μm. Preferably there is. Further, the oxygen content is more preferably 10% by mass or more and 60% by mass or less, and particularly preferably 25% by mass or more and 55% by mass or less. When the amount of oxygen is less than 1% by mass, the film may be too thin to form a uniform film. In addition, an oxygen-containing film having an oxygen content exceeding 70% by mass is accompanied by manufacturing difficulties.

  Regarding the aluminum base material on which the oxygen-containing film is formed, the oxygen-containing film on the surface is preferably hydrophilic. Specifically, on the surface of the oxygen-containing film, the contact angle of water droplets is preferably 70 ° or less, more preferably 10 ° or more and 50 ° or less, and particularly preferably 5 ° or more and 40 ° or less. preferable. If the contact angle of water droplets in the oxygen-containing coating exceeds 70 °, the bonding strength with the resin bonded body may be reduced due to the hydrophobicity of the surface.

  The oxygen-containing film preferably has a hydroxyl group (OH group) on the outermost layer. The presence of OH groups in the outermost layer of the oxygen-containing coating makes it possible for the thermoplastic resin and / or additive in the thermoplastic resin composition described later to hydrogen bond with the OH groups. Further, when the thermoplastic resin and / or additive has a substituent that undergoes dehydration condensation with the OH group, an ester bond is formed by a dehydration condensation reaction between the thermoplastic resin and / or additive and the OH group of the oxygen-containing film. It becomes possible.

  In the present embodiment, the resin constituting the resin joined body is preferably a thermoplastic resin composition containing at least a thermoplastic resin. The thermoplastic resin composition preferably contains an additive in addition to the thermoplastic resin. The thermoplastic resin composition contains either or both of a thermoplastic resin having an element having an unshared electron pair in the repeating unit and / or terminal and an additive containing an element having an unshared electron pair. More preferably. When the thermoplastic resin and / or additive contains an element having an unshared electron pair, the bonding force can be increased by the interaction with the oxygen-containing film.

  The element having an unshared electron pair which the thermoplastic resin and / or additive has is preferably at least one selected from the group consisting of sulfur, oxygen and nitrogen. The element having an unshared electron pair may be included in the main chain of the repeating unit of the thermoplastic resin, or may be included in the side chain.

  Examples of the thermoplastic resin contained in the thermoplastic resin composition include resins containing sulfur atoms such as polyphenylene sulfide (PPS) and sulfone-based resins. Examples thereof include polyester resins such as polybutylene terephthalate (PBT), and resins containing oxygen atoms such as liquid crystal polymers, polycarbonate resins, polyacetal resins, polyether resins, and polyphenylene ether resins. Furthermore, resin containing nitrogen atoms, such as polyamide (PA), acrylonitrile / butadiene / styrene resin (ABS), polyimide, and polyetherimide, may be used. Among these, it is preferable to use polyamide 12 as the resin bonded body.

  The additive that can be contained in the thermoplastic resin composition refers to a substance other than the thermoplastic resin that constitutes the thermoplastic resin composition. The additive having an element having an unshared electron pair is not particularly limited. That is, the additive is added for various purposes in consideration of the moldability and processability of the thermoplastic resin composition, the characteristics of the resin joined body obtained by molding the thermoplastic resin composition, and the like. Examples of such additives include antioxidants, mold release agents, plasticizers, ultraviolet absorbers, heat stabilizers, antistatic agents, dyes, pigments, lubricants, silane coupling agents, fillers, elastomers, and the like. can do.

  As the additive having an element having an unshared electron pair, the element having an unshared electron pair is preferably oxygen and having a carbon-oxygen bond, and the additive having a carbon-oxygen bond is carbonyl. More preferably, it is a compound. Specifically, the additive is preferably one or two or more compounds selected from the group consisting of carboxylic acids, esters, and amides.

  The manufacturing method of the resin joined body of the present embodiment is not particularly limited. For example, a resin joined body can be obtained by bringing a thermoplastic resin composition into contact with an aluminum base material having an oxygen-containing film by injection molding. Alternatively, first, a resin joined body may be formed by injection molding of a thermoplastic resin composition, and the obtained resin joined body may be integrally joined to the oxygen-containing film of the aluminum substrate. The resin bonded body and the oxygen-containing film can be bonded by thermocompression bonding such as laser welding, vibration welding, ultrasonic welding, hot press welding, hot plate welding, non-contact hot plate welding, or high frequency welding. .

  In the present embodiment, the oxygen-containing film and the resin joined body are provided only on the upper end portion which is a part of the lower shaft. However, the obtained aluminum is obtained by forming the oxygen-containing film on the entire surface of the aluminum substrate. You may join a resin joined body only to the required location of a base material. Alternatively, in consideration of cost, an oxygen-containing film may be formed only on a part of the surface of the aluminum base material, and the resin joined body may be joined to a necessary portion of the obtained aluminum base material. In addition, when forming the oxygen-containing film on a part of the surface of the aluminum base material, a part other than the part that forms the oxygen-containing film is masked with a masking tape or the like, and then the oxygen-containing film is formed. Finally, the masking tape or the like may be removed.

  In this embodiment, if necessary, the surface of the aluminum substrate may be pretreated before forming the oxygen-containing film. As the pretreatment, for example, at least one selected from the group consisting of a degreasing treatment, an etching treatment, a desmut treatment, a chemical polishing treatment, and an electrolytic polishing treatment can be performed.

  The degreasing treatment performed as the pretreatment can be performed using a normal degreasing bath made of sodium hydroxide, sodium carbonate, sodium phosphate, a surfactant or the like. As treatment conditions, the immersion temperature is usually 15 ° C. or higher and 55 ° C. or lower, preferably 25 ° C. or higher and 40 ° C. or lower, and the immersion time is 1 minute or longer and 10 minutes or shorter, preferably 3 minutes or longer and 6 minutes or shorter.

  As an etching treatment performed as a pretreatment, an alkaline aqueous solution such as sodium hydroxide is usually used. And when using aqueous alkali solution, the density | concentration is 20 g / L or more and 200 g / L or less, Preferably 50 g / L or more and 150 g / L or less are used. The immersion temperature is 30 ° C. or higher and 70 ° C. or lower, preferably 40 ° C. or higher and 60 ° C. or lower, and the treatment time is 0.5 minutes or longer and 5 minutes or shorter, preferably 1 minute or longer and 3 minutes or shorter. .

  In addition, an acid aqueous solution such as a sulfuric acid-phosphoric acid mixed aqueous solution can also be used for the etching treatment. When a sulfuric acid-phosphoric acid mixed aqueous solution is used, the sulfuric acid concentration is 10 g / L or more and 500 g / L or less, preferably 30 g / L or more and 300 g / L or less, and the phosphoric acid concentration is 10 g / L or more and 1200 g / L or less. Preferably, a material of 30 g / L or more and 500 g / L is used. The immersion temperature is 30 ° C. or higher and 110 ° C. or lower, preferably 55 ° C. or higher and 75 ° C. or lower, and the immersion time is 0.5 minutes or longer and 15 minutes or shorter, preferably 1 minute or longer and 6 minutes or shorter. .

  As the desmut treatment performed as the pretreatment, for example, a desmut bath made of an aqueous nitric acid solution having a concentration of 1 to 30% can be used. Then, the immersion temperature is 15 ° C. or higher and 55 ° C. or lower, preferably 25 ° C. or higher and 40 ° C. or lower, and the immersion treatment is performed under the treatment conditions of 1 minute or longer and 10 minutes or shorter, preferably 3 minutes or longer and 6 minutes or shorter.

  In addition, a conventionally well-known method can be employ | adopted about the chemical polishing process and electropolishing process performed as pre-processing.

  The joining mechanism between the aluminum base material and the resin joined body in the present embodiment is presumed from the experiment as follows. In addition, even if the aluminum base material and resin joined body of this embodiment are joined by another mechanism, the technical scope of the present invention is not affected at all.

  First, a plurality of surface-treated aluminum substrates having an oxygen-containing film on the surface of the aluminum substrate were formed. And about some surface-treated aluminum base materials, the polyamide 12 (PA12) which has a carbonyl group (C = O) on the surface was joined by injection molding.

  For the remaining surface-treated aluminum substrate, first, stearic acid was volatilized in an electric furnace maintained at 100 ° C., and the surface-treated aluminum substrate was exposed therein for 24 hours. This produced a stearic acid-treated aluminum substrate having a monomolecular film of stearic acid on the oxygen-containing coating. Furthermore, PA12 was joined to the surface of the stearic acid-treated aluminum base material by injection molding. And the difference in the joint strength by a stearic acid process was measured.

  As a result, the bonding strength of the aluminum base material subjected to the stearic acid treatment was clearly reduced as compared with the bonding strength of the aluminum base material not subjected to the stearic acid treatment.

Stearic acid has both a carboxyl group (COOH) which is a hydrophilic group and an alkyl group (C ₁₇ H ₃₅ ) which is a hydrophobic group, and has a property of forming a monomolecular film having a thickness of one molecule. When stearic acid treatment is performed, the oxygen-containing film of the aluminum base and the carboxyl group side of stearic acid are chemically bonded, and the alkyl group side comes into contact with PA12. Therefore, it is considered that the chemical bond between the aluminum base material and PA 12 is inhibited, and the bonding strength is lowered.

  Moreover, when a water droplet was dropped on the aluminum base material after the stearic acid treatment and the contact angle was measured, the contact angle was close to 120 °, and the droplet was almost spherical. This is a result confirming that the alkyl group side of stearic acid is unevenly distributed on the outermost layer side of the aluminum substrate.

  From the above, between the oxygen-containing film and the resin bonded body, a chemical bond occurs between the oxygen of the oxygen-containing film and the carbonyl group in the resin, and the action due to this chemical bond is caused by the aluminum substrate and the resin. It is considered that the bonding strength between the bonded body is increased.

<Effect>
As described above, according to the steering shaft 3 according to the embodiment of the present invention, the following operational effects can be obtained.

  (1) The end 17 of the lower shaft 13 (first shaft) serving as a composite member is formed of an aluminum base 41 made of aluminum or an aluminum alloy, and an oxygen-containing film containing oxygen formed on the surface of the aluminum base 41 43 and a resin joined body 45 made of a resin bonded to the surface of the oxygen-containing coating 43. The resin bonded body 45 is formed on the surface of the oxygen-containing coating 43 so as to be annularly connected over the entire circumference of the aluminum base material 41.

  As described above, the resin bonded body 45 is formed in an annular shape over the entire circumference of the aluminum base material 41 in the circumferential direction. Therefore, since the resin bonded body 45 clamps the aluminum base material 41 from the periphery via the oxygen-containing film 43, the adhesive force (bonding force) of the resin bonded body 45 to the aluminum base material 41 is large and reliable.

  This will be specifically described below. First, in the manufacturing process, before the resin joined body 45 is provided, the oxygen-containing film 43 is formed on the surface of the aluminum base material 41. And the aluminum base material 41 in which the oxygen containing film 43 was formed is set to a metal mold | die. Next, when molten high-temperature resin is poured into the mold, the molten resin flows into the cavity between the mold and the aluminum base 41. Then, the molten resin is filled over the entire circumference of the aluminum base material 41 through the oxygen-containing film 43. When the molten resin and the aluminum base material 41 are cooled in this state, the molten resin is cured and contracted, whereby the aluminum base material 41 is fastened from the outer periphery via the oxygen-containing film 43. As described above, the resin joined body 45 is always subjected to a physical fastening force for fastening the aluminum base material 41 from the outer periphery via the oxygen-containing film 43. Therefore, even when the aluminum base material 41 is used as a metal member for weight reduction, the adhesive force (bonding force) of the resin bonded body 45 to the aluminum base material 41 can be increased.

  In addition, since the oxygen-containing film 43 is formed on the surface of the aluminum base 41, the bonding force between the aluminum base 41 and the resin bonded body 45 can be increased.

  (2) Since the aluminum base material 41 which comprises the lower shaft 13 is formed in the cylindrical body as shown in FIG. 6, the mass of the lower shaft 13 is reduced. The lower shaft 13 may be formed in a columnar body. By using the columnar body, there is an effect that the strength of the lower shaft 13 is improved.

  (3) By inserting the end portion 17 of the lower shaft 13 (first shaft) into the insertion hole 20 of the end portion 19 of the upper shaft 15 (second shaft) formed in a cylindrical shape, the lower shaft 13 and the upper shaft The steering shaft 3 is configured such that the end portions 17 and 19 of the 15 are slidably assembled with each other. The end portion 17 of the lower shaft 13 has the oxygen-containing film 43 and the resin bonded body 45 on the surface of the aluminum base 41. Formed and configured.

  Thus, since the ends 17 and 19 of the lower shaft 13 and the upper shaft 15 slide with each other, the resin bonded body 45 can be firmly attached to a portion where wear is likely to occur due to sliding.

  (4) The first outer surface 37 of the end portion 17 of the lower shaft 13 (first shaft) undulates outward and inward in the radial direction of the end portion 17 along the circumferential direction of the end portion 17. The inner peripheral surface 31 of the end portion 19 of the upper shaft 15 (second shaft) is formed in the second uneven portion 33 that engages with the first uneven portion 25 of the lower shaft 13. .

  Since the end portion 17 of the lower shaft 13 and the end portion 19 of the upper shaft 15 are engaged with each other by the first uneven portion 25 and the second uneven portion 33, torque for rotating the upper shaft 15 is applied to the lower shaft 13. It can be transmitted reliably.

  (5) The first concavo-convex portion 25 of the lower shaft 13 (first shaft) includes a plurality of convex portions 39 having an arc-shaped cross section whose radial cross section projects outward in the radial direction, and convex portions adjacent in the circumferential direction. And a concave portion 40 having an arcuate cross section which is provided between 39 and 39 and is recessed inward in the radial direction.

  As described above, the first uneven portion 25 of the lower shaft 13 has a relatively simple cross-sectional shape. Therefore, when the first uneven portion 25 is formed by machining, the workability of machining is improved. It becomes easy.

  (6) The resin forming the resin joined body 45 is polyamide 12. Since the polyamide 12 exhibits excellent toughness, impact resistance, and flexibility due to hydrogen bonding of the amide group, wear caused by sliding between the end portion 17 of the lower shaft 13 and the end portion 19 of the upper shaft 15 is prevented. Can be suppressed.

  (7) The oxygen-containing film 43 is a film containing a zinc element obtained by a zinc film forming process using a zinc ion-containing alkaline aqueous solution. Thus, by using the oxygen-containing film 43 as a zinc-containing film, it is possible to firmly bond the oxygen-containing film and the resin bonded body.

  (8) A method of manufacturing the lower shaft 13 (first shaft) to be a composite member includes a film forming step of forming an oxygen-containing film 43 containing oxygen on the surface of an aluminum substrate 41 made of aluminum or an aluminum alloy, And a resin forming step of forming a resin joined body 45 connected in a ring shape along the circumferential direction of the aluminum base material 41 on the surface of the oxygen-containing film 43. By such a film forming process and a resin forming process, the resin bonded body 45 having a high bonding force can be easily formed on the surface of the oxygen-containing film 43.

  As described above, the embodiments of the present invention have been described. However, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art. For example, although the oxygen-containing film 43 is continuously formed over the entire circumference of the aluminum base material 41, the oxygen-containing film 43 may not be formed on a part of the entire circumference. Moreover, although the main-body part 23 and the edge part 17 of the lower shaft 13 were formed in the cylindrical body, the cylindrical body by which the inner side was formed in solid shape may be sufficient. Further, the upper end portion 17 of the lower shaft 13 and the lower end portion 19 of the upper shaft 15 only need to be engaged and slidable, and may be formed in a rectangular tube shape, for example.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.

[Example 1]
First, an aluminum base material having a length of 40 mm and a width of 40 mm was cut out from a commercially available aluminum plate (6061-T6; plate thickness 2.0 mm). Also, a zinc ion-containing sodium aqueous solution having a sodium hydroxide concentration of 100 g / L and a zinc oxide concentration of 25 g / L (20 g / L as Zn ²⁺ ) was prepared as a film forming treatment agent. Next, the above aluminum base material was immersed in this zinc ion-containing sodium aqueous solution for 3 minutes at room temperature, and then washed with water to prepare an aluminum base material having an oxygen-containing film containing zinc element formed on the surface.

  Next, a test aluminum resin joined body 200 shown in FIG. 9 was produced by injection molding using polyamide 12 (manufactured by Ube Industries, Ltd., trade name: UBESTA (registered trademark) 3014U) as a thermoplastic resin. Specifically, the aluminum base material subjected to the surface treatment as described above is set in a mold of an injection molding machine, a mold temperature of 150 ° C., a resin temperature of 320 ° C., an injection speed of 100 mm / s, a holding pressure of 50 MPa, The polyamide 12 was injection molded under injection molding conditions of a holding time of 3 seconds. Thereby, as shown in FIG. 9, a polyamide molded body 202 having a size of 5 mm × 10 mm × 30 mm was formed. Furthermore, the polyamide molded body 202 was bonded onto the zinc-containing coating of the aluminum base 201 with an area of 5 mm × 10 mm.

[Example 2]
The same aluminum plate material as in Example 1 was used as the aluminum base material. Next, the aluminum substrate was immersed in a 30 wt% nitric acid aqueous solution at room temperature for 5 minutes, and then sufficiently washed with ion-exchanged water. Further, it was immersed in a 5 wt% sodium hydroxide solution at 50 ° C. for 1 minute and then washed with water, immersed in a 30 wt% nitric acid aqueous solution at room temperature for 3 minutes and then washed with water. Next, an oxygen-containing film containing an aluminum compound (AlO (OH)) was formed on the surface of the aluminum base material by performing a hydration treatment by immersing in hot water at 91 ° C. for 5 minutes. Except this, it carried out similarly to Example 1, and produced the aluminum resin joined body 200 for a test.

[Evaluation]
Regarding the aluminum resin joined bodies obtained in Examples 1 and 2, the shear strength of the polyamide molded body was measured. Specifically, as shown in FIG. 10, the aluminum base material 201 in the aluminum resin joined body 200 obtained in Examples 1 and 2 is fixed to a jig 210, and the upper end of the polyamide molded body 202 is 1 mm / mm from above. A load 211 was applied at a speed of min. Thus, the shear strength of the joint part of an aluminum resin joined body was evaluated by the method of destroying the joint part between the aluminum base material 201 and the polyamide molded body 202.

  The measurement result of the shear strength is shown in FIG. As shown in FIG. 11, it can be seen that high shear strength can be obtained by bonding a polyamide molded body onto the oxygen-containing coating.

  In FIG. 12, the result of having observed the surface of the aluminum base material in which the oxygen containing film in Example 1 was formed with the scanning electron microscope is shown. As shown in FIG. 12, it can be seen that the particulate oxygen-containing coating 203 covers the entire surface of the aluminum substrate. In FIG. 13, the result of having observed the cross section of the aluminum resin bonded body 200 of Example 1 with the scanning electron microscope is shown. As shown in FIG. 13, it can be seen that the polyamide molded body 202 is in close contact with the oxygen-containing film 203. Further, it can be seen that a part of the polyamide molded body 202 penetrates into the oxygen-containing film 203 to form the anchor portion 204. Thus, it can be seen that by providing the oxygen-containing film 203, the bonding force increases due to physical bonding by the anchor portion 204 in addition to the above-described chemical bonding.

  Although the contents of the present invention have been described with reference to the embodiments, the present invention is not limited to these descriptions, and it is obvious to those skilled in the art that various modifications and improvements can be made.

13 Lower shaft (first shaft) (composite member)
15 Upper shaft (second shaft)
17, 19 End 20 Insertion hole 25 1st uneven part 31 Inner peripheral surface 33 2nd uneven part 37 Outer peripheral surface 39 Convex part 40 Concave part 41 Aluminum base material 43 Oxygen-containing film 45 Resin joined body

Claims (9)

An aluminum base material made of aluminum or an aluminum alloy; an oxygen-containing coating film formed on the surface of the aluminum base material and containing oxygen; and a resin joined body made of a resin bonded to the surface of the oxygen-containing coating film. ,
The composite member, wherein the resin bonded body is formed on the surface of the oxygen-containing coating so as to be annularly connected over the entire circumference of the aluminum base material. The composite member according to claim 1,
The composite member according to claim 1, wherein the aluminum substrate is formed into a cylindrical body or a columnar body. The composite member according to claim 1 or 2,
Steering structure in which the end portions of the first shaft and the second shaft are slidably assembled to each other by inserting the end portion of the first shaft into the insertion hole of the end portion of the second shaft formed in a cylindrical shape. About the shaft
An end portion of the first shaft is configured by forming the oxygen-containing film and a resin joined body on a surface of an end portion of the aluminum base material. The composite member according to claim 3,
The outer peripheral surface of the end portion of the first shaft is formed in a first concavo-convex portion that undulates outward and inward in the radial direction of the end portion along the circumferential direction of the end portion,
An inner peripheral surface of an end portion of the second shaft is formed in a second uneven portion that engages with the first uneven portion of the first shaft. The composite member according to claim 4,
The first concavo-convex portion of the first shaft is provided between a plurality of convex portions having a circular arc cross section whose radial cross section projects outward in the radial direction and the convex portions adjacent to each other in the circumferential direction. A composite member comprising: a concave portion having an arc-shaped cross-section recessed inward in the direction. The composite member according to any one of claims 1 to 5,
A composite member, wherein the resin forming the resin joined body is polyamide 12. The composite member according to any one of claims 1 to 6,
The composite member according to claim 1, wherein the oxygen-containing film is a film containing a zinc element obtained by a zinc film forming process using a zinc ion-containing alkaline aqueous solution. A film forming step of forming an oxygen-containing film containing oxygen on the surface of an aluminum substrate made of aluminum or an aluminum alloy;
On the surface of the oxygen-containing film, a resin forming step of forming a resin joined body connected in a ring shape along the circumferential direction of the aluminum base material,
A method for producing a composite member, comprising:   A composite member manufactured using the manufacturing method according to claim 8.