Patent Description:
Various methods have been suggested as a method for manufacturing a metal-resin joint by bonding a metal member made of metal and a synthetic resin member made of synthetic resin to each other (for example, refer to Patent Literatures <NUM> and <NUM> described below).

It has been suggested to increase a bonding strength of the metal member to the synthetic resin member by forming uneven anchors on the surface of the metal member by laser or chemical etching. In a method of providing the metal with uneven anchors, the bonding point is likely to be destructed due to the difference in linear expansion coefficients between the resin and metal when thermal shock testing is conducted. Intricate anchor holes are necessary to obtain firm bonding, but in addition to the difficulty in forming such anchor holes, it is difficult to completely fill the anchor holes with resin, and it is difficult to obtain stable bonding strength.

In a case of bonding the metal member and the synthetic resin member to each other by intermolecular forces due to the dipolar interaction of the metal and resin, such as friction welding, it is difficult to directly bond a resin having a small dipolar interaction, such as an olefin resin (for example, polypropylene resin (PP resin)), to a metal. By adding a compound having high dipolar interaction, such as a carboxylic anhydride, to a resin having low dipolar interaction, it is possible to increase the bonding strength, but there is a case where physical properties such as strength of the synthetic resin member itself are reduced.

The <CIT> discloses a method and apparatus for bonding two articles and in particular a metal trim strip to a thermoplastic article such as is used for automotive decorative window trim. The thermoplastic article includes a raised ridge portion which serves to provide means for accurately aligning the metal trim strip on the thermoplastic article. A plurality of holes is formed through the ridge portion at spaced locations along its length. The metal trim strip is preferably "C-shaped" in cross-section so as to define a channel having a restricted opening for receiving the raised ridge portion of the thermoplastic article. A controlled flow of hot air is directed into the holes of the thermoplastic article to plasticize a controlled portion of the thermoplastic material surrounding the holes. A stake is then projected into the plasticized material to displace the plasticized material into the channel portions of the metal strip. Upon return of the displaced thermoplastic material to a rigid state, the two articles are firmly and accurately bonded together. The resulting trim piece has a flush rear surface which facilitates proper installation of the trim piece on the vehicle body.

The <CIT> discloses a method for joining two components, the first component being provided with a surface structure in a joining region at a first component surface with the second component, the second component being made of plastic and having a lower melting temperature than the material of the first component, the material of the second component being bonded to the first component by area-by-area melting of the plastic on a second component surface in the bonding area with the surface structure of the first component and subsequent solidification of the plastic, the two components being arranged for connection in operative connection with a vibration device, the first component, before being brought into operative connection with the vibration device, being heated in the region of the first component surface to a temperature which is above the melting temperature of the material of the second component, and the plastic of the second component being melted at the second component surface by heat transfer from the previously heated first component.

The <CIT> discloses a method and an apparatus for joining a resin member and a metal member by heating, wherein the joining of the resin member and metal member is performed by heating a joining interface of the resin member and metal member to a temperature in a range of equal to or higher than a decomposition temperature of the resin member and lower than a temperature at which gas bubbles are generated in the resin member and by cooling a surface of the resin member on the opposite side from a joining surface thereof with the metal member to a temperature that is lower than the melting point of the resin member.

The <CIT> discloses a method for joining a metallic member and a resin member to each other. A polar functional group is added onto a surface of a metallic member. The resin member contains an adhesive functional group. The adhesive functional group and the polar functional group attract each other. The method for joining the metallic member and the resin member to each other includes a heating a junction between the metallic member and the resin member while pressing the metallic member and the resin member against each other with first load, maintaining temperature of the junction higher than melting temperature of a resin that structures the resin member while pressing the metallic member and the resin member with each other with second load smaller than the first load, and cooling the junction to temperature lower than the melting temperature while pressing the metallic member and the resin member against each other with third load larger than the second load.

The present disclosure is made in consideration of the above-described points, and an object of the present disclosure is to provide a method for manufacturing a metal-resin joint that can improve the bonding strength between a metal member made of metal and a synthetic resin member made of thermoplastic resin material.

The problem of the present invention is solved by a method for manufacturing a metal-resin joint according to the independent claim <NUM>, while the dependent claims refer to further advantageous developments of the present invention.

In the present disclosure, a metal-resin joint having high bonding strength between a metal member and a synthetic resin member can be obtained.

The present disclosure is not limited to the following embodiments. The following embodiments are presented as examples and are not intended to limit the scope of the invention. The new embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention.

First, a metal-resin joint <NUM> manufactured by a manufacturing method of the present embodiment will be described. As illustrated in <FIG>, the metal-resin joint <NUM> includes a synthetic resin member <NUM> made of thermoplastic resin and a metal member <NUM> made of metal, and a surface (hereinafter, there is a case where the surface is referred to as "resin bonding surface") <NUM> of the synthetic resin member <NUM> and a surface (hereinafter, there is a case where the surface is referred to as "metal bonding surface") <NUM> of the metal member <NUM> are bonded to each other.

The synthetic resin member <NUM> is a member made by molding the thermoplastic resin into a predetermined shape, such as a block, plate, or wire shape. The synthetic resin member <NUM> may be a coating film of thermoplastic resin or an adhesive layer made of thermoplastic resin adhesive. Specific examples of the thermoplastic resin that makes the synthetic resin member <NUM> include polypropylene resin (PP resin), polyacetal resin (POM resin), polyphenylene sulfide resin (PPS resin), polyetheretherketone resin (PEEK), acrylonitrile/butadiene/styrene resin (ABS resin), polyethylene resin (PE resin), polybutylene terephthalate resin (PBT resin), polyamide resin (PA resin) such as nylon <NUM> (PA66), epoxy resin, liquid crystal polymer (LCP resin), modified polyphenylene ether resin (modified PPE), and reactor type soft polypropylene resin (metallocene reactor type TPO resin). The synthetic resin member <NUM> may be made of a carbon fiber reinforced thermoplastic resin (CFRTP), in which carbon fibers are blended into the thermoplastic resin as described above, or a resin, in which a reinforcing material such as glass fiber or talc, flame retardants, degradation inhibitors, and elastomer components are blended into the above-described thermoplastic resin.

The metal member <NUM> is a member obtained by molding the metal into a predetermined shape, such as a block, plate, or wire shape. A metal that makes the metal member <NUM> is not particularly limited, and various types of metals can be used. For example, copper (Cu), iron (Fe), aluminum (Al), titanium (Ti), nickel (Ni), chromium (Cr), and the like can be used as the metal that makes the metal member <NUM>. The metal member <NUM> may be made of an alloy consisting of two or more metals, such as copper alloy, iron alloy (steel material), aluminum alloy, stainless steel, titanium alloy, nickel alloy, and chromium alloy.

The shape of the metal member <NUM> can be any desired shape depending on the application or the like. As the method for molding the metal member <NUM>, any method can be applied, and casting by pouring molten metal into a mold having a desired shape, cutting using a machine tool or the like, punching using a press machine or the like, and the like may be used.

The metal member <NUM> may also have an oxide film (metal oxide) formed on the metal bonding surface <NUM>. The oxide film may be a natural oxide film which is naturally formed on the surface of metal. The oxide film may be formed on the surface of the metal member <NUM> by surface treatment with an oxidant, electrolytic treatment with anodic oxidation, plasma oxidation treatment, or heat oxidation treatment in the oxygen-containing gas, and the like.

As a preferable aspect, the oxide film may be formed on the surface of the metal member <NUM> by rapidly heating the surface of the metal member <NUM> under an atmosphere of the oxygen-containing gas, such as in the air. It is preferable that the rising temperature of the surface of the metal member <NUM> per minute during rapid heating is equal to or higher than the melting point temperature of the metal that makes the metal member <NUM>. By rapidly heating the surface of the metal member <NUM> in this manner, a dense oxide film can be formed on the surface of the metal member <NUM>. Furthermore, by rapidly heating the surface of the metal member <NUM>, microcracks are generated on the surface of the oxide film, and a bonding area with the synthetic resin member <NUM> becomes larger.

Although the surface of the metal member <NUM> can be heated rapidly by various methods such as laser heating, induction heating, or resistor heating, the temperature raising speed at the time of heating is fast and the temperature control is easy, and thus, it is preferable to heat the surface of the metal member <NUM> by irradiating a laser beam to form the oxide film.

The metal member <NUM> may perform roughening treatment of providing an uneven shape on the metal bonding surface <NUM>. Various methods can be employed for the roughening treatment. For example, the metal bonding surface <NUM> may be roughened by irradiation of laser beam, chemical etching, or pressing.

As a preferable aspect, under an atmosphere of the oxygen-containing gas, by rapidly heating the surface of the metal member <NUM> to form the oxide film on the surface of the metal member <NUM>, and by generating microcracks on the surface of the oxide film, the metal bonding surface <NUM> may be roughened.

The metal-resin joint <NUM> is obtained by performing a first process and a second process with respect to the synthetic resin member <NUM> described in (<NUM>) above and the metal member <NUM> described in (<NUM>) above. In the present embodiment, the first process and the second process are performed using a bonding device <NUM> as illustrated in <FIG> and <FIG> to manufacture the metal-resin joint <NUM>.

The bonding device <NUM> includes: a stage <NUM> on which the metal member <NUM> is placed; a heating device <NUM> that inductively heats the metal member <NUM> placed on the stage <NUM>; and a pressing device <NUM> that pressurizes and bonds the synthetic resin member <NUM> to the metal member <NUM>.

The heating device <NUM> includes an induction heating coil connected to a power source device (not illustrated), and when a drive power source is input from the power source device, a magnetic field is generated from the induction heating coil to inductively heat the metal bonding surface <NUM> of the metal member <NUM> placed on the stage <NUM>.

The pressing device <NUM> includes: a rod <NUM> formed of insulator such as ceramics; and a pressurizing unit <NUM> that moves the rod <NUM> to press the synthetic resin member <NUM> against the metal member <NUM>. The rod <NUM> may be inserted into a hollow part of the induction heating coil of the heating device <NUM> and disposed to face the synthetic resin member <NUM>, as illustrated in <FIG>. The pressurizing unit <NUM> includes a pneumatic cylinder controlled by an electropneumatic regulator, a spring type pressurizer, or the like, and can control the speed at which the synthetic resin member <NUM> is moved together with the rod <NUM> and the pressure at which the synthetic resin member <NUM> is pressed against the metal member <NUM>.

In order to manufacture the metal-resin joint <NUM> using the bonding device <NUM>, first, the metal member <NUM> is placed on the stage <NUM> such that the metal bonding surface <NUM> faces the synthetic resin member <NUM> to be set after this in an atmosphere where gas is present. In a case where an oxide film is formed on the surface of the metal member <NUM> by heat oxidation treatment or the like, or in a case where the surface of the metal member <NUM> is roughened by roughening treatment, the metal member <NUM> is disposed such that the formed oxide film or roughened surface faces the synthetic resin member <NUM> to be set after this.

Next, the synthetic resin member <NUM> is disposed such that the resin bonding surface <NUM> faces the metal bonding surface <NUM> of the metal member <NUM> placed on the stage <NUM> with a gap therebetween. The distance between the metal bonding surface <NUM> of the metal member <NUM> and the resin bonding surface <NUM> of the synthetic resin member <NUM> is set at <NUM> to <NUM>.

Next, the heating device <NUM> is disposed to face the metal bonding surface <NUM> of the metal member <NUM> across the synthetic resin member <NUM>. In a case illustrated in <FIG>, the heating device <NUM> is disposed above the synthetic resin member <NUM>, and the synthetic resin member <NUM> is disposed between the heating device <NUM> and the metal member <NUM>.

Next, the first process of exposing the resin bonding surface <NUM> of the synthetic resin member <NUM> to a gas heated to a first temperature T1 is executed.

Specifically, the drive power source is supplied to the heating device <NUM> to generate a magnetic field from the induction heating coil provided in the heating device <NUM> and heat the metal bonding surface <NUM> of the metal member <NUM>. At this time, the drive power source supplied to the heating device <NUM>, the position of the induction heating coil provided in the heating device <NUM>, or the like are adjusted such that the metal bonding surface <NUM> of the metal member <NUM> reaches the first temperature T1. As the metal member <NUM> is heated as described above, the gas between the metal member <NUM> and the synthetic resin member <NUM> is heated to the first temperature T1. Accordingly, the resin bonding surface <NUM> of the synthetic resin member <NUM> facing the metal bonding surface <NUM> of the metal member <NUM> is exposed to the gas heated to the first temperature T1, and the resin bonding surface <NUM> of the synthetic resin member <NUM> reaches the first temperature T1. The heating device <NUM> heats the metal bonding surface <NUM> of the metal member <NUM> for a predetermined time S1 (for example, <NUM> to <NUM> seconds) to execute the first process as described above, and then completes the first process and moves to the second process.

When the first process is completed, in order to continue executing the second process, the heating device <NUM> stops heating or reduces the amount of heating of the metal member <NUM> such that the temperature of the resin bonding surface <NUM>, the metal bonding surface <NUM>, and the surrounding thereof (the gas between the metal member <NUM> and the synthetic resin member <NUM>) is lowered (cooled) until reaching a second temperature T2. The synthetic resin member <NUM> and the metal member <NUM> are bonded to each other at the second temperature T2.

In other words, in the second process, at a temperature (second temperature T2) lower than the first temperature T1, the pressing device <NUM> moves the synthetic resin member <NUM> at a predetermined speed V to make the synthetic resin member <NUM> collide with the metal member <NUM>. At this time, the synthetic resin member <NUM> is pressed strongly against the metal member <NUM> at the position corresponding to a distal end of the rod <NUM>, and is pressed against the metal member <NUM> at a predetermined pressure P for a predetermined time S2. Accordingly, the metal-resin joint <NUM> is obtained in which the resin bonding surface <NUM> of the synthetic resin member <NUM> and the metal bonding surface <NUM> of the metal member <NUM> are locally (spot-like) bonded to each other. Then, the second process is completed.

The first temperature T1 is a temperature which is equal to or higher than a deflection temperature under load Tf of the thermoplastic resin that makes the synthetic resin member <NUM> when a load of <NUM> MPa is applied. In a case where the synthetic resin member <NUM> is made of a resin in which a reinforcing material, such as carbon fiber, glass fiber, or talc, is blended into the thermoplastic resin, the deflection temperature under load Tf of the thermoplastic resin that makes the synthetic resin member <NUM> when a load of <NUM> MPa is applied is the deflection temperature under load Tf of the thermoplastic resin that does not contain the reinforcing material when a load of <NUM> MPa is applied.

An upper limit value of the first temperature T1 can be a temperature which is equal to or lower than a decomposition temperature of the thermoplastic resin that makes the synthetic resin member <NUM>, that is, can be a temperature which is lower than a temperature at which the thermoplastic resin begins to vaporize. As an example, the upper limit value of the first temperature T1 may be <NUM>. Preferably, the upper limit value of the first temperature T1 can be set to a temperature which is <NUM> higher than a melting point Tm of the thermoplastic resin that makes the synthetic resin member <NUM>.

The second temperature T2 may be a temperature lower than the first temperature T1, but is preferably equal to or higher than the deflection temperature under load Tf of the thermoplastic resin that makes the synthetic resin member <NUM> when a load of <NUM> MPa is applied. The second temperature T2 is preferably lower than the melting point Tm of the thermoplastic resin that makes the synthetic resin member <NUM>. The temperature difference between the first temperature T1 and the second temperature T2 is preferably <NUM> or higher and <NUM> or lower.

In the present specification, the melting point Tm of the thermoplastic resin is a value measured at a temperature raising speed of <NUM> per minute using a differential scanning calorimeter according to JIS K7121. The melting points of typical thermoplastic resins are <NUM> for polypropylene resin, <NUM> for nylon <NUM>, <NUM> to <NUM> for polybutylene terephthalate resin, and <NUM> for polyphenylene sulfide resin.

The deflection temperature under load Tf of the thermoplastic resin is a deflection temperature under load measured by a method according to JIS K7191 when a load of <NUM> MPa is applied. The deflection temperatures under load Tf of typical thermoplastic resins when a load of <NUM> MP is applied are <NUM> to <NUM> for polypropylene resin, <NUM> to <NUM> for nylon <NUM>, <NUM>° C for polybutylene terephthalate resin, and <NUM> for polyphenylene sulfide resin.

The first process is preferably executed in the oxygen-containing gas such as air. In other words, it is preferable to heat the metal bonding surface <NUM> and the resin bonding surface <NUM> to the first temperature T1 in an atmosphere of oxygen-containing gas, and expose the metal bonding surface <NUM> and the resin bonding surface <NUM> to the oxygen-containing gas heated to the first temperature T1.

When the first process is executed in an atmosphere of the oxygen-containing gas, the resin bonding surface <NUM> of the synthetic resin member <NUM> reacts with the oxygen contained in the oxygen-containing gas to generate functional groups that can be chemically bound by neutralization reactions with basic or amphoteric oxides, on the resin bonding surface <NUM> of the synthetic resin member <NUM>.

In general, the surface of the metal member <NUM> is oxidized and coated with an oxide film made of metal oxides, and thus, the functional groups generated on the resin bonding surface <NUM> are bonded to the metal oxides on the metal bonding surface <NUM> of the metal member <NUM> by van der Waals forces or hydrogen bonds. In addition, by bonding the synthetic resin member <NUM> and the metal member <NUM> to each other in a heated and pressurized state, the functional groups of the resin bonding surface <NUM> form covalent binding with the metal oxide of the metal member <NUM> by a neutralization reaction (dehydration condensation).

One example of the functional group generated on the resin bonding surface <NUM> includes at least one of a carboxyl group (-COOH), a carbonyl group (-CO-), or a hydroxy group (-OH) which are generated by the oxidative decomposition of the thermoplastic resin that makes the synthetic resin member <NUM>. When the thermoplastic resin that makes the synthetic resin member <NUM> is a resin that contains sulfur atoms (heteroatoms), such as polyphenylene sulfide resin (PPS), as the functional group contained in the resin bonding surface <NUM>, in addition to carboxyl groups, carbonyl groups, and hydroxy groups, the functional group containing heteroatoms such as sulfone groups (-SO<NUM>H), sulfonyl groups (-SO<NUM>-), sulfanyl groups (-SH), and disulfide groups (-SS-) may be contained.

As an example of the neutralization reaction that occurs by bonding the metal member <NUM> and the synthetic resin member <NUM> to each other, in a case where the resin bonding surface <NUM> has a carboxyl group (R-COOH) as a functional group and the metal member <NUM> is made of a divalent metal, the neutralization reaction occurs as illustrated in Equation (<NUM>) below.

<NUM>(R-COOH) + MeO = <NUM>(R-COO) - Me + H<NUM>O↑.

In Equation (<NUM>), R is the main chain of the thermoplastic resin that makes the synthetic resin member <NUM>, and Me is the metal that makes the metal member <NUM>.

In a case where the first process is executed in an atmosphere of the oxygen-containing gas, the second temperature T2 is preferably a temperature at which the functional group of the resin bonding surface <NUM> of the synthetic resin member <NUM> and the metal oxide formed on the metal bonding surface <NUM> of the metal member <NUM> can form the covalent binding by the neutralization reaction. The second temperature T2 is preferably a temperature at which the water generated by the neutralization reaction is removed from the reaction system. Since the second temperature T2 varies depending on the functional group and the type of metal oxide, it is difficult to specify the second temperature T2 in general, but the second temperature T2 is more preferable to be equal to or higher than <NUM> because the water generated by the neutralization reaction is easily removed.

In the second process, the pressure P when the synthetic resin member <NUM> is pressed against the metal member <NUM> is preferably a pressure which is equal to or higher than the compressive yield stress of the thermoplastic resin that makes the synthetic resin member <NUM>. Since the pressure P varies depending on the thermoplastic resin that makes the synthetic resin member <NUM>, it is difficult to specify the pressure P in general, but the pressure P is preferable to be <NUM> to <NUM> MPa.

In the second process, the moving speed V of the synthetic resin member <NUM> when the synthetic resin member <NUM> collides with the metal member <NUM> is not particularly limited, but may be set to <NUM> to <NUM>/sec. The time S2 for pressing the synthetic resin member <NUM> against the metal member <NUM> is not particularly limited, but may be set to <NUM> to <NUM> seconds.

In the present embodiment, a case where the pressing device <NUM> moves the synthetic resin member <NUM> toward the metal member <NUM> is described, but the metal member <NUM> may be moved toward the synthetic resin member <NUM>.

In the present embodiment, a case where the metal member <NUM> and the synthetic resin member <NUM> are bonded to each other locally is described, but the synthetic resin member <NUM> and the metal member <NUM> may be bonded to each other over a wide range. The flat surface shape of the bonding location can also be any shape, such as point, line, or surface.

In order to firmly bond the synthetic resin member <NUM> and the metal member <NUM> to each other, it is necessary to bring the thermoplastic resin that makes the synthetic resin member <NUM> and the metal material that makes the metal member <NUM> close to each other by approximately several nm, and to make the thermoplastic resin chemically react with the metal material. In the method for manufacturing the metal-resin joint <NUM> according to the present embodiment, the resin bonding surface <NUM> of the synthetic resin member <NUM> is exposed to a gas heated to the first temperature T1 which is equal to or higher than the deflection temperature under load Tf to reduce the viscosity of the thermoplastic resin positioned on the resin bonding surface <NUM>, and then the resin bonding surface <NUM> and the metal bonding surface <NUM> are bonded to each other. Therefore, in the present embodiment, even when there is a slight unevenness on the metal bonding surface <NUM>, the resin bonding surface <NUM> follows the unevenness and deforms, a chemical reaction is likely to occur between the thermoplastic resin and the metal material, and it is possible to firmly bond the synthetic resin member <NUM> and the metal member <NUM> to each other.

Moreover, in the present embodiment, it is possible to bond the synthetic resin member <NUM> and the metal member <NUM> to each other by locally heating the vicinity of the resin bonding surface <NUM> without heating the entire synthetic resin member <NUM> to a high temperature, and thus, the deformation of the synthetic resin member <NUM> can be suppressed.

In the present embodiment, after the temperature of the resin bonding surface <NUM> of the synthetic resin member <NUM> and the metal bonding surface <NUM> of the metal member <NUM> is lowered to the second temperature T2, which is lower than the first temperature T1, it is possible to bond the resin bonding surface <NUM> and the metal bonding surface <NUM> to each other. In this manner, in a case where the bonding is performed after the temperature is lowered to the second temperature T2, the deformation of the synthetic resin member <NUM> that occurs when bonding the synthetic resin member <NUM> to the metal member <NUM> can be further suppressed.

In the present embodiment, the second temperature T1 can be set to a temperature lower than the melting point Tm of the thermoplastic resin that makes the synthetic resin member <NUM>. In this manner, in a case where the second temperature T2 is a temperature, which is lower than the melting point Tm of the thermoplastic resin, the deformation of the synthetic resin member <NUM> that occurs when bonding the synthetic resin member <NUM> to the metal member <NUM> can be further suppressed.

In the present embodiment, the metal member <NUM> may be heated in a state where the synthetic resin member <NUM> and the metal member <NUM> are disposed to face each other with a gap therebetween. In such a case, it is possible to heat the gas between the synthetic resin member <NUM> and the metal member <NUM> to the first temperature T1 by the heat of the metal member <NUM>, and the resin bonding surface <NUM> can be exposed to the gas heated to the first temperature T1 by a simple configuration. In addition, it is possible to continue performing the second process of bonding the synthetic resin member <NUM> and the metal member <NUM> to each other after the first process, and it is possible to manufacture the metal-resin joint <NUM> in a short time.

In the present embodiment, the heating device <NUM> may heat the metal member <NUM> by induction heating. In such a case, it is easier to locally heat a desired position of the metal member <NUM>. In particular, by inductively heating the metal member <NUM> facing the heating device <NUM> across the synthetic resin member <NUM>, it is likely to locally heat the vicinity of the metal bonding surface <NUM> of the metal member <NUM>. Therefore, it is possible to easily control the temperature of the gas, which is in contact with the resin bonding surface <NUM> of the synthetic resin member <NUM>, and even in a case where it is difficult to perform the bonding by friction bonding or laser welding, similar to a case where the metal member <NUM> is a hollow-shaped member or a case where the volume of the metal member <NUM> is large, in the present embodiment, the firmly bonded metal-resin joint <NUM> can be obtained.

In the present embodiment, after the temperature of the resin bonding surface <NUM> and the metal bonding surface <NUM> is lowered to the second temperature T2, which is lower than the first temperature T1, the pressure P when pressing the synthetic resin member <NUM> against the metal member <NUM> may be set to a pressure which is equal to or higher than the compressive yield stress of the thermoplastic resin that makes the synthetic resin member <NUM>. In such a case, it is possible to bond the synthetic resin member <NUM> to the metal member <NUM> without using a mold, and the tact time (the time from bonding the synthetic resin member <NUM> and the metal member <NUM> to each other until practical strength is obtained) can be shortened.

In the present embodiment, the first process may be executed in the oxygen-containing gas. In such a case, the functional groups that can be chemically bound by the neutralization reaction with basic or amphoteric oxides are generated on the resin bonding surface <NUM> of the synthetic resin member <NUM>. The functional groups generated on the resin bonding surface <NUM> are bonded to the metal oxide present on the metal bonding surface <NUM> of the metal member <NUM> by dipolar interaction, and also form covalent binding with the metal oxide of the metal member <NUM> by neutralization reaction (dehydration condensation). Therefore, in a case where the first process is executed in the oxygen-containing gas, it is possible to more firmly bond the synthetic resin member <NUM> and the metal member <NUM> to each other.

In the present embodiment, a process of roughening the surface of the metal member may be executed. In such a case, by the anchor effect, it is possible to more firmly bond the synthetic resin member <NUM> and the metal member <NUM> to each other.

As described in the present embodiment, when the rod <NUM> that presses the synthetic resin member <NUM> toward the metal member <NUM> is inserted through the hollow part of the induction heating coil of the heating device <NUM> that heats the metal member <NUM>, even in a case where the bonding area between the synthetic resin member <NUM> and the metal member <NUM> is small, it is possible to accurately heat and pressurize the bonded part.

In the present embodiment, by reducing the distal end shape of the rod <NUM> of the pressing device <NUM>, it is possible to reduce the bonding area between the synthetic resin member <NUM> and the metal member <NUM>, and to simply locally bond the synthetic resin member <NUM> and the metal member <NUM> to each other. When the synthetic resin member <NUM> and the metal member <NUM> are locally bonded to each other, even when the linear expansion coefficients are different between the synthetic resin member <NUM> and the metal member <NUM>, the force generated in the metal-resin joint <NUM> during thermal expansion is unlikely to concentrate on the bonded part, and it is possible to obtain the metal-resin joint <NUM> having excellent thermal durability. In a case of deliberately peeling off the synthetic resin member <NUM> from the metal member <NUM>, such as during recycling, by concentrating the force on the local bonded part, the peeling-off can be performed relatively easily. In other words, in the manufacturing method according to the present embodiment, it is possible to simply manufacture the metal-resin joint <NUM> having excellent thermal durability and recyclability.

In order to specifically show the effects of the above-described embodiments, metal-resin joints (test specimens) of Examples <NUM> to <NUM> and Comparative Examples <NUM> to <NUM> are prepared.

In Examples <NUM> to <NUM>, the manufacturing method described in (<NUM>) above is carried out in the air to prepare the metal-resin joint. In other words, after the surface of the synthetic resin member is exposed to a gas heated to the first temperature T1, which is equal to or higher than the deflection temperature under load of the thermoplastic resin when a load of <NUM> MPa is applied, by bonding the surface of the synthetic resin member and the surface of the metal member to each other while applying a pressure of <NUM> MPa at the second temperature T2, the test specimens of Examples <NUM> to <NUM> are prepared. In Examples <NUM> to <NUM>, the types of synthetic resin member and metal member used for bonding, the first temperature T1, and the second temperature T2 are as illustrated in Table <NUM> and Table <NUM>.

In Comparative Examples <NUM> to <NUM>, after the surface of the synthetic resin member is exposed to a gas heated to a temperature ta, which is lower than the deflection temperature under load of the thermoplastic resin when a load of <NUM> MPa is applied in the air, by bonding the surface of the synthetic resin member and the surface of the metal member to each other while applying a pressure of <NUM> MPa at a temperature tb, the test specimens of Comparative Examples <NUM> to <NUM> are prepared. The metal member, the synthetic resin member, the temperature ta, and the temperature tb, which are used, are as illustrated in Table <NUM>.

The dimension of the metal member, the dimension of the synthetic resin member, and the bonding area (overlap area) between the synthetic resin member and the metal member, which are used in Examples <NUM> to <NUM> and Comparative Examples <NUM> to <NUM>, are as follows.

The details of the metal members and resin members in Tables <NUM> to <NUM> are as follows.

With respect to the metal-resin joints of Examples <NUM> to <NUM> and Comparative Examples <NUM> to <NUM>, the bonding strength and the change rate of resin thickness are evaluated. Each evaluation method is as follows.

Bonding strength: In the test method specified in JIS K <NUM>, the dimension of the metal member, the dimension of the synthetic resin member, and the bonding area between the synthetic resin member and the metal member are changed as described above, and with the other conditions set in accordance with the same standard, the measurement is performed at a tensile speed of <NUM>/min and a measurement temperature of <NUM> using a tensile tester (IMADA SEISAKUSHO CO. , NV301-NA).

Change rate of resin thickness: A thickness th1 of the synthetic resin member before bonding the metal member and a thickness th2 of the synthetic resin member after bonding the metal member are measured, and the change rate ((th1-th2)/th1) of the resin thickness is calculated by dividing the amount of decrease (th1-th2) in thickness of the synthetic resin member by the thickness th1. The thickness th2 of the synthetic resin member after bonding the metal member is a thickness of the synthetic resin member measured at the location where the pressure is applied when bonding the synthetic resin member and the metal member to each other.

The results are illustrated in Table <NUM> to Table <NUM>.

Claim 1:
A method for manufacturing a metal-resin joint (<NUM>) in which a resin bonding surface (<NUM>) of a synthetic resin member (<NUM>) made of thermoplastic resin and a metal bonding surface (<NUM>) of a metal member (<NUM>) made of metal are bonded to each other, the method comprising:
a first process of exposing the resin bonding surface (<NUM>) of the synthetic resin member (<NUM>) molded into a predetermined shape, to a gas heated to a first temperature higher than a deflection temperature under load, when a load of <NUM> MPa is applied, of the thermoplastic resin; and
a second process of bonding the resin bonding surface (<NUM>) and the metal bonding surface (<NUM>), wherein
in the first process, by heating the metal member (<NUM>) in a state where the resin bonding surface (<NUM>) and the metal bonding surface (<NUM>) are disposed to face each other with a gap of <NUM> to <NUM> in the gas, the gas between the resin bonding surface (<NUM>) and the metal bonding surface (<NUM>) is heated to the first temperature by heat of the metal member (<NUM>),
in the second process, the resin bonding surface (<NUM>) and the metal bonding surface (<NUM>) are bonded to each other at a second temperature at which a temperature of the resin bonding surface (<NUM>), a temperature of the metal bonding surface (<NUM>), and a temperature of the gas between the metal member (<NUM>) and the synthetic resin member (<NUM>) are equal to or higher than the deflection temperature under load, when the load of <NUM> MPa is applied, of the thermoplastic resin and is lower than the first temperature.