Patent Description:
A tubular member is often used for one of some structures constituting a framework of a vehicle. For example, in a vehicle structure such as an instrument panel reinforcement, a resin bracket is joined to a tubular metal member, and the tubular member is assembled to another member via the bracket to constitute a part of a vehicle framework.

There are various methods for joining a resin member such as a bracket to a tubular metal member. For example, Patent Document <NUM> discloses a method of expanding a tubular member using an elastic body to join the tubular member to a resin member by press-fitting. Specifically, an elastic body is inserted into the tubular member, and the elastic body is pressurized in the tube axis direction to expand radially outward, thereby expanding the tubular member. At this time, by arranging the resin member around the tubular member, the tubular member is joined to the resin member by press-fitting.

Patent Document <NUM> discloses a stabilizer for suspension of wheels of an axle of a motor vehicle with an essentially U-shaped design with a central part aligned transversely in the installation position and longitudinal arms adjoining the central part at an angle at each end, the stabilizer being constructed from a plurality of segments wherein at least two segments are connected to one another in a form-fitting manner by means of an hydroforming process.

Patent Document <NUM> discloses a stepped pipe member having a connecting portion in which one axial end portion of a small diameter pipe member having a smaller diameter than the large diameter pipe member is fixed to one axial end portion of the large diameter pipe member, and wherein the small diameter pipe member is expanded by electromagnetic forming into the large diameter pipe member.

Patent Document <NUM> discloses a method for joining members comprising: preparing a first tube and a second tube capable of being inserted to a tube hole of the first tube in an axial direction of the first tube; inserting the second tube into the first tube; and radially expanding the second tube toward the first tube, thereby joining the first tube and the second tube by press-fitting, wherein the first tube is made of a material having a spring back amount larger than a spring back amount of the second tube.

When the resin member and the tubular metal member are joined together by the method of Patent Document <NUM>, the joint portion (that is, the expanded tube portion) may be deformed due to the thermal influence, and the joining may be loosened. This is because the resin is more easily thermally deformed than the metal, since the linear expansion coefficient of the resin is larger than the linear expansion coefficient of the metal. That is, the resin member may be deformed more largely than the tubular metal member according to the temperature change, and the joining may be loosened.

The present invention has an object to suppress loosening of joining due to thermal influence even when a resin member and a tubular metal member are combined in a structure and a method for manufacturing the same.

A first aspect of the present invention provides a structure including: a first member made of metal having a tubular shape, and having a through-insertion hole; a second member made of resin and joined to the first member; and a third member made of metal having a tubular shape, and inserted through the through-insertion hole of the first member, in which the third member is tube-expanded toward the first member and joined to the first member by press-fitting, and wherein bulging portions are formed on both sides in a tube axis direction of the third member with respect to the first member.

According to the configuration, the third member made of metal is not directly joined to the second member made of resin by press-fitting, but the third member is joined to the first member by press-fitting. Since the first member and the third member are both made of metal, a difference in linear expansion coefficients of the first and third members is smaller than that between resin and metal. This makes it possible to suppress loosening of the joining according to the thermal influence. Here, as a method of joining the first member to the second member, a method using injection molding, an adhesive, or the like can be adopted.

The second member may be joined only to the first member. In addition, the first member and the second member may be joined together by the second member being injection-molded to the first member.

According to these configurations, the first member and the second member are firmly integrated by injection molding. In particular, since the second member is injection-molded only to the first member, the second member is not injection-molded to the third member. This makes it possible to variously design the shape of the third member. For example, when a resin member is directly injection-molded to a long member, a large injection molding apparatus is required, which is not preferable. However, in the above configuration, since the second member is not injection-molded to the third member, the third member may be a long member or can be designed in any other shape.

The first member may be provided with a joining hole for joining the first member to the second member, and injection molding may be performed such that the second member is cast into the joining hole of the first member.

According to this configuration, since the injection molding is performed such that the second member is cast into the joining hole, the first member and the second member can be firmly integrated while joining the first member to the third member by press-fitting is maintained.

In the structure described above, when linear expansion coefficients of materials are compared, a linear expansion coefficient of the second member may be largest, a linear expansion coefficient of the first member may be second largest, and a linear expansion coefficient of the third member may be smallest.

According to this configuration, in the structure, the linear expansion coefficient increases in order from the inside to the outside. In other words, between the second member disposed on the outermost side and the third member disposed on the innermost side, a first member having a linear expansion coefficient intermediate between those of the two is disposed. Therefore, as compared with the case where the second member and the third member are directly joined together, it is possible to form two pieces of joining (joining of the second member and the first member, and joining of the first member and the second member) having close linear expansion coefficients. Therefore, it is possible to further suppress loosening of the joining due to the thermal influence.

The cross-sectional shape perpendicular to the tube axis direction of the third member may be rectangular. In addition, a cross-sectional shape perpendicular to a tube axis direction of the first member may be a shape different from a rectangular shape.

According to this configuration, since the cross section of the third member is rectangular, the third member can be prevented from rotating around the tube axis. At this time, a cross-sectional shape other than a rectangle may also be adopted for the cross-sectional shape of the first member.

A second aspect of the present invention provides a method for manufacturing a structure, the method including: preparing a first member made of metal having a tubular shape, and having a through-insertion hole, a second member made of resin, a third member made of metal having a tubular shape, and an elastic body configured to be insertable into the third member; joining the second member to the first member; inserting the third member through the through-insertion hole of the first member; inserting the elastic body into the third member; and compressing the elastic body in a tube axis direction of the third member to expand the elastic body radially outward so that the third member is tube-expanded radially outward to join the third member to the first member by press-fitting, wherein bulging portions are formed on both sides in the tube axis direction of the third member with respect to the first member.

According to this method, it is possible to suppress loosening of joining due to a thermal influence as described above. In particular, in the above method, since the elastic body is used in the joining by press-fitting by tube expansion, the material and shape of the third member to be tube-expanded can be set substantially optionally. For example, electromagnetic forming can be considered as one of the methods of joining by press-fitting by similar tube expansion, but electromagnetic forming can be applied only to a member made of a highly conductive material and having a circular cross section. However, as with the above method, in the joining by press-fitting by tube expansion using the elastic body, there is no such constraint. In addition, in the joining by press-fitting by tube expansion using an elastic body, a general press machine can be used without requiring a large special facility such as electromagnetic forming.

When the second member is joined to the first member, the second member may be injection-molded only to the first member.

According to this method, the first member and the third member are firmly integrated by injection molding. In particular, since the second member is injection-molded only to the first member, the second member is not injection-molded to the third member. This makes it possible to variously design the shape of the third member. Specifically, for example, when a resin member is directly injection-molded to a long member, a large injection molding apparatus is required, which is not preferable. However, in the above configuration, since the second member is not injection-molded to the third member, the third member may be a long member or can be designed in any other shape.

In the method for manufacturing a structure, when linear expansion coefficients of materials are compared, a linear expansion coefficient of the second member may be largest, a linear expansion coefficient of the first member may be second largest, and a linear expansion coefficient of the third member may be smallest.

According to this method, in the structure to be manufactured, the linear expansion coefficient increases in order from the inside to the outside. In other words, between the second member to be disposed on the outermost side and the third member to be disposed on the innermost side, a first member having a linear expansion coefficient intermediate between those of the two is to be disposed. Therefore, it is possible to form two pieces of joining (joining of the second member and the first member, and joining of the first member and the second member) having closer linear expansion coefficients than the case where the second member and the third member are directly joined. Therefore, it is possible to further suppress loosening of the joining due to the thermal influence.

According to this configuration, since the cross section of the third member is rectangular, the third member can be prevented from rotating around the tube axis. In addition, in the joining by press-fitting by tube expansion using the elastic body, unlike electromagnetic forming, since the cross-sectional shape of the member to be tube-expanded does not matter, even when the cross-sectional shape of the third member is rectangular, joining can be easily achieved. At this time, a cross-sectional shape other than a rectangle may also be adopted for the cross-sectional shape of the first member.

According to the present invention, loosening of joining due to thermal influence can be suppressed even when a resin member and a tubular metal member are combined in a structure and a method for manufacturing the same.

In the following, embodiments of the present invention will be described with reference to the accompanying drawings.

<FIG> is a perspective view of a general instrument panel reinforcement <NUM>. The instrument panel reinforcement <NUM> is one of vehicle structural members disposed in the front portion of the vehicle interior and extending in the vehicle width direction. The instrument panel reinforcement <NUM> is formed by joining various brackets <NUM> to the tubular member <NUM>. The tubular member <NUM> has a circular tubular shape with a partially different diameter. In general, the portion 2a having a larger diameter is disposed on the driver seat side, and the portion 2b having a smaller diameter is disposed on the passenger seat side. For example, the tubular member <NUM> is made of metal. The brackets <NUM> are made of resin.

<FIG> is a perspective view of a structure <NUM> to which the joining of the present embodiment is applied at the joint portion of the tubular member <NUM> and the bracket <NUM> in the instrument panel reinforcement <NUM> as shown in <FIG>. This structure <NUM> can be adopted not only for the instrument panel reinforcement <NUM> but also for a frame of a bicycle, a hydraulic pipe of a construction machine such as a crane, a frame of another transportation machine, or the like.

The structure <NUM> includes a tubular first member <NUM> made of metal, a second member <NUM> made of resin and joined to an outer peripheral surface of the first member <NUM>, and a tubular third member <NUM> made of metal and inserted into the first member <NUM>. In the structure <NUM>, the third member <NUM> is expanded toward and joined to the first member <NUM> by press-fitting as will be described below.

The first member <NUM> is a circular tubular member with both ends opened, and has a through-insertion hole 11a (see <FIG>). The through-insertion hole 11a has a diameter through which the third member <NUM> can be inserted. For example, the first member <NUM> is made of an aluminum alloy. The first member <NUM> is an additional member not adopted in the instrument panel reinforcement <NUM> shown in <FIG>.

The third member <NUM> is a circular tubular member opened at both ends, and has an into-insertion hole 13a. The third member <NUM> is longer than the first member <NUM> and is inserted through the through-insertion hole 11a of the first member <NUM>. The third member <NUM> includes a circular tubular main body 13b and bulging portions 13c and 13c extending in the circumferential direction of the main body 13b and bulging radially outward. The bulging portions 13c and 13c are disposed on both sides of the first member <NUM> in the direction of the tube axis (central axis) C of the main body 13b. For example, the third member <NUM> is made of steel. The third member <NUM> constitutes the tubular member <NUM> in the instrument panel reinforcement <NUM> shown in <FIG>.

The second member <NUM> includes an annular holding portion 12a and an extending portion 12b extending from the holding portion 12a. The first member <NUM> is inserted through the holding portion 12a. The extending portion 12b is attached to another member (not shown). The second member <NUM> is made of resin. The second member <NUM> constitutes the bracket <NUM> in the instrument panel reinforcement <NUM> shown in <FIG>. It should be noted that the shape of the second member <NUM> is not particularly limited, and for example, the holding portion 12a does not need to be annular by cutting out a part of the holding portion 12a.

The second member <NUM> is joined to the outer peripheral surface of the first member <NUM> on the inner surface of the holding portion 12a. In the present embodiment, the second member <NUM> is joined only to the first member <NUM> by injection molding. The mode of joining is not limited to injection molding, and for example, an adhesive may be used.

Preferably, when the linear expansion coefficients of the respective materials are compared, that of the second member <NUM> is the largest, that of the first member <NUM> is the second largest, and that of the third member <NUM> is the smallest. In the present embodiment, as described above, the material of the second member <NUM> is resin, the material of the first member <NUM> is an aluminum alloy, and the material of the third member <NUM> is steel. In general, when these linear expansion coefficients are compared, that of resin is the largest, that of an aluminum alloy is the second largest, and that of steel is the smallest. Therefore, the above suitable arrangement is obtained.

As another example constituting the above suitable arrangement, the second member <NUM> may be made of resin, the first member <NUM> may be made of a magnesium alloy, and the third member <NUM> may be made of steel. In general, when these linear expansion coefficients are compared, that of resin is the largest, that of a magnesium alloy is the second largest, and that of steel is the smallest. Therefore, the above suitable arrangement is obtained.

Hereinafter, a method for manufacturing the structure <NUM> according to the present embodiment will be described.

First, referring to <FIG>, a first member <NUM>, a second member <NUM>, a third member <NUM>, and a rubber member (elastic body) <NUM> insertable into the third member <NUM> are prepared. It should be noted that in <FIG>, the shape of the second member <NUM> is clearly shown as a single body for the sake of clarity of description, but in the present embodiment, the second member <NUM> is injection-molded to the first member <NUM> and thus does not independently form its shape. That is, as shown in <FIG> described below, the second member <NUM> is joined to the first member <NUM> and is formed in its shape at the same time.

In the present embodiment, the rubber member <NUM> has a columnar shape and has dimensions that can be inserted into the third member <NUM>. It is preferable that the outer shape of the rubber member <NUM> has similarity to the inner shape of the third member <NUM> (into-insertion hole 13a) in the cross section perpendicular to the tube axis direction of the third member <NUM>, and is as large as possible as long as insertable. The material of the rubber member <NUM> is preferably any one of urethane rubber, chloroprene rubber, CNR rubber (chloroprene rubber + nitrile rubber), and silicone rubber, for example. In addition, the hardness of the rubber member <NUM> is preferably <NUM> or more in Shore A.

Next, referring to <FIG>, the second member <NUM> is injection-molded to the outer peripheral surface of the first member <NUM>. Thus, the first member <NUM> and the second member <NUM> are integrated. It should be noted that the second member <NUM> is injection-molded only to the first member <NUM>, and is not injection-molded to the third member <NUM>.

Next, referring to <FIG>, the third member <NUM> is inserted through the through-insertion hole 11a of the first member <NUM>. Thereafter, the rubber member <NUM> is inserted into the into-insertion hole 13a of the third member <NUM>. Alternatively, before the third member <NUM> is inserted through the through-insertion hole 11a of the first member <NUM>, the rubber member <NUM> may be inserted into the into-insertion hole 13a of the third member <NUM> in advance. Thus, the rubber member <NUM>, the third member <NUM>, the first member <NUM>, and the second member <NUM> are disposed in this order from the inner side to the outer side in the radial direction.

Next, referring to <FIG> again, the rubber member <NUM> is compressed in the tube axis C direction of the third member <NUM> and expanded radially outward, whereby the third member <NUM> is tube-expanded radially outward and joined to the first member <NUM> by press-fitting. That is, the bulging portions 13c and 13c of the third member <NUM> are formed. In this manner, the structure <NUM> in which the first member <NUM>, the second member <NUM>, and the third member <NUM> are joined is formed.

With reference to <FIG>, joining by press-fitting by tube expansion using the above-described rubber member <NUM> will be described in detail.

First, referring to <FIG>, before joining by press-fitting, the rubber member <NUM>, the third member <NUM>, the first member <NUM>, and the second member <NUM> are disposed in order from the inside to the outside. At this time, the positions of the rubber member <NUM>, the first member <NUM>, and the second member <NUM> are aligned in the tube axis C direction.

Next, with reference to <FIG>, the respective pushers <NUM> are inserted from both end openings in the tube axis C direction of the third member <NUM>, and the pushers <NUM> are arranged on both sides of the rubber member <NUM> in the tube axis C direction. The pusher <NUM> includes a pressing portion <NUM> for pressing the rubber member <NUM> and a rod-shaped support portion <NUM> for supporting the pressing portion <NUM>. The pressing portion <NUM> has a columnar shape and includes a flat pressing surface 31a as an end surface. The pressing portion <NUM> is attached to a press machine (not shown) or the like with interposition of the support portion <NUM>, and is driven by the press machine to sandwich the rubber member <NUM> with the pressing surfaces 31a to compress the rubber member <NUM> in the tube axis C direction of the third member <NUM> (see an arrow A in <FIG>). With this compression, the rubber member <NUM> expands radially outward of the third member <NUM>. The third member <NUM> is tube-expanded by radially outward expansion of the rubber member <NUM>. Thus, the first member <NUM> and the third member <NUM> are joined together by press-fitting. At this time, the bulging portions 13c and 13c are formed on both sides in the tube axis C direction of the third member <NUM> with respect to the first member <NUM>.

Next, referring to <FIG>, after joining the first member <NUM> to the third member <NUM> by press-fitting, a press machine (not shown) is driven to release the compression of the rubber member <NUM> by the pusher <NUM>. The rubber member <NUM> from which the compressive force by the pusher <NUM> is removed is restored to the original shape by the elasticity of the rubber member <NUM> itself. Therefore, the rubber member <NUM> can be easily removed from the third member <NUM>.

According to the present embodiment, the third member <NUM> made of metal is not directly joined to the second member <NUM> made of resin by press-fitting, but the third member <NUM> is joined to the first member <NUM> by press-fitting. Since the first member <NUM> and the third member <NUM> are both made of metal, a difference in linear expansion coefficients of the first and third members is smaller than that between resin and metal. This makes it possible to suppress loosening of the joining according to the thermal influence. In particular, in the above method, since the rubber member <NUM> is used in the joining by press-fitting by tube expansion, the material and shape of the third member <NUM> to be tube-expanded can be set substantially optionally. For example, electromagnetic forming can be considered as one of the methods of joining by press-fitting by similar tube expansion, but electromagnetic forming can be applied only to a member made of a highly conductive material and having a circular cross section. However, as in the above method, in the joining by press-fitting by tube expansion using the rubber member <NUM>, there is no such constraint. In addition, in the joining by press-fitting by tube expansion using the rubber member <NUM>, a general press machine can be used without requiring a large special facility such as electromagnetic forming.

In addition, the first member <NUM> and the second member <NUM> are firmly integrated by injection molding. In particular, since the second member <NUM> is injection-molded only to the first member <NUM>, the second member <NUM> is not injection-molded to the third member <NUM>. This makes it possible to variously design the shape of the third member <NUM>. For example, when a resin member is directly injection-molded to a long member, a large injection molding apparatus is required, which is not preferable. However, in the above configuration, since the second member <NUM> is not injection-molded to the third member <NUM>, the third member <NUM> may be a long member or can be designed in any other shape.

In addition, in the structure <NUM>, the linear expansion coefficient increases in order from the inside to the outside. In other words, between the second member <NUM> disposed on the outermost side and the third member <NUM> disposed on the innermost side, a first member <NUM> having a linear expansion coefficient intermediate between those of the two is disposed. Therefore, as compared with the case where the second member <NUM> and the third member <NUM> are directly joined together, it is possible to form two pieces of joining (joining of the second member and the first member, and joining of the first member <NUM> and the second member <NUM>) having close linear expansion coefficients. Therefore, it is possible to further suppress loosening of the joining due to the thermal influence.

In the above embodiment, the first member <NUM> and the third member <NUM> both having a circular tubular shape are exemplified, but the shapes of the first member <NUM> and the third member <NUM> are not particularly limited. For example, the cross-sectional shape perpendicular to the tube axis C direction of the third member <NUM> may be rectangular. At this time, the cross-sectional shape perpendicular to the tube axis C direction of the first member <NUM> may be different from the rectangular shape (see <FIG>).

As shown in <FIG>, even when the third member <NUM> having a rectangular cross section and the first member <NUM> having a circular cross section different from a rectangular cross section are joined, the first member <NUM> and the third member <NUM> can be easily joined together by performing joining by press-fitting by tube expansion using the rubber member <NUM>.

Alternatively, the cross-sectional shape perpendicular to the tube axis C direction of the third member <NUM> may be a polygon other than a rectangle, or an ellipse. In addition, with reference to <FIG> showing a cross section perpendicular to the tube axis C direction, a partition wall 13d may be provided to partition the inside of the third member <NUM>. The partition wall 13d extends in the tube axis direction inside the third member <NUM>. For example, only one partition wall 13d may be provided (see <FIG>), two partition walls may be provided in parallel (see <FIG>), or two partition walls may be provided in a cross shape (see <FIG>).

When the partition wall 13d is provided as shown in <FIG>, the rubber member <NUM> may be disposed in each of a plurality of chambers in the third member <NUM> partitioned by the partition wall 13d. Thus, even when the partition wall 13d is provided, the third member <NUM> can be reliably tube-expanded.

In addition, the cross-sectional shape perpendicular to the tube axis direction of the first member <NUM> may be a circle, an ellipse, a rectangle, a polygon other than a rectangle, or the like. At this time, the cross-sectional shapes of the first member <NUM> and the third member <NUM> may be different.

According to the present modification, since the cross section of the third member <NUM> is rectangular, the third member <NUM> can be prevented from rotating around the tube axis. In addition, in the joining by press-fitting by tube expansion using the rubber member <NUM>, unlike electromagnetic forming, since the cross-sectional shape of the member to be tube-expanded does not matter, even when the cross-sectional shape of the third member <NUM> is rectangular, joining can be easily achieved. At this time, a cross-sectional shape other than a rectangle may also be adopted for the cross-sectional shape of the first member <NUM>.

In the above embodiment, the second member <NUM> is joined to the outer peripheral surface of the first member <NUM> on the inner surface of the annular holding portion 12a, but this joining mode can be various. For example, as shown in <FIG>, the first member <NUM> may be provided with a flange portion 11b having a partially enlarged diameter, and the flange portion 11b may be provided with a joining hole 11c for joining to the second member <NUM>. Then, both the members <NUM> and <NUM> may be joined by injection molding such that the second member <NUM> is cast into the joining hole 11c.

In the first member <NUM> of the present modification, the joining hole 11c is a hole penetrating the first member <NUM> in the same direction as the through-insertion hole 11a. The joining hole 11c of the present modification includes two circular holes, but the shape thereof is not particularly limited.

The second member <NUM> of the present modification does not include an annular holding portion 12a (see <FIG>), and is injection-molded so that a part of the extending portion 12b covers the joining hole 11c of the first member <NUM>.

According to the present modification, it is possible to provide a structure <NUM> in which the first member <NUM> and the second member <NUM> are firmly integrated while maintaining joining the first member <NUM> to the third member <NUM> by press-fitting described above.

Claim 1:
A structure (<NUM>) comprising:
a first member (<NUM>) made of metal having a tubular shape, and having a through-insertion hole (11a);
a second member (<NUM>) made of resin, and joined to the first member (<NUM>); and
a third member (<NUM>) made of metal having a tubular shape, and inserted through the through-insertion hole (11a) of the first member (<NUM>),
wherein the third member (<NUM>) is tube-expanded toward the first member (<NUM>) and joined to the first member (<NUM>) by press-fitting,
wherein bulging portions (13c) are formed on both sides in a tube axis (C) direction of the third member (<NUM>) with respect to the first member (<NUM>).