Shock absorbing member and method of manufacturing the same

A shock absorbing member includes an outer member being hollow and made of a metal, and an inner member held in the outer member. The inner member includes a wood member and a bracket that is made of a solid resin or a metal and that is integral with the wood member. The inner member includes a holding structure configured to position and hold the bracket to the outer member.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2019-026415 filed on Feb. 18, 2019, incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The disclosure relates to a shock absorbing member including a hollow metal outer member and an inner member held in the outer member, and to a method of manufacturing the same.

2. Description of Related Art

In a vehicle, a hollow metal member corresponding to the outer member of the disclosure is often used as a vehicle exterior component or a vehicle interior component, and, for example, a bumper reinforcement at the front of the vehicle can be given as one example thereof. While it is conceivable that the load is applied to the hollow metal member from the outside, the situation where the hollow metal member is locally largely bent (the occurrence of local folding) due to this load application should be avoided as much as possible. In view of this, it may be suggested to prevent the occurrence of unintended local folding as much as possible by absorbing the load applied to the hollow metal member by the use of, for example, a wood member with excellent shock absorption performance.

A shock absorbing member disclosed in Japanese Unexamined Patent Application Publication No. 2001-153169 (JP 2001-153169 A) includes a metal strength member, a core member, and a support member. The metal strength member is a hollow metal columnar member and corresponds to the outer member of the disclosure. The core member is a member made of fiber reinforced plastic (FRP) and corresponds to the inner member of the disclosure. The core member has external dimensions smaller than those of the metal strength member and can be disposed with an appropriate gap between itself and an inner wall of the metal strength member. In JP 2001-153169 A, the support member made of foamed urethane resin is filled in the gap between the metal strength member and the core member, thereby holding the core member of short length in the metal strength member via the support member. Consequently, when the load is applied to the metal strength member, the metal strength member is first deformed and then the core member is deformed so that the applied load can be absorbed. Accordingly, it may be suggested to employ the configuration of JP 2001-153169 A to position and hold the wood member (the inner member) in the hollow metal member (the outer member).

SUMMARY

In the case where the configuration of JP 2001-153169 A is employed as referred to above, the wood member (the inner member) is held in the hollow metal member (the outer member) via the support member made of foamed urethane resin. However, the support member made of foamed urethane resin is a member that is soft and tends to degrade over time compared to the wood member, and thus is unsuitable for holding the wood member to the hollow metal member while ensuring good performance. That is, the positioning accuracy of the wood member is difficult to achieve with the configuration using the soft support member, and the support member that tends to degrade over time is not a configuration that can easily be employed, taking into account the durability and so on. The disclosure provides a shock absorbing member that can hold an inner member to an outer member while ensuring good performance, and a method of manufacturing such a shock absorbing member.

A first aspect of the disclosure relates to a shock absorbing member that can absorb the load, applied to a hollow metal outer member, by the outer member and an inner member held in the outer member. In this type of shock absorbing member, it is desirable to be able to hold the inner member to the outer member while ensuring good performance (e.g. while maintaining excellent positioning performance). Therefore, the shock absorbing member according to the first aspect of the disclosure includes an outer member being hollow and made of a metal, and an inner member held in the outer member. The inner member includes a wood member and a bracket that is made of a solid resin or a metal and that is integral with the wood member. The inner member includes a holding structure configured to position and hold the bracket to the outer member. In the inner member according to the first aspect of the disclosure, the bracket harder than a foamed resin and excellent in durability is integrated with the wood member. By positioning and holding the bracket to the outer member by the holding structure, it is possible to hold the inner member to the outer member while maintaining excellent positioning performance.

In the above-described aspect, the outer member may include a general portion extending in a predetermined direction in a state where the wood member is disposed in the general portion, and a bent-deformed portion bent and deformed in a predetermined direction with respect to the general portion, and the holding structure may be configured to position and hold a bracket portion bent and deformed to be in close contact with the bent-deformed portion. With this configuration, by providing the bent-deformed portion to the outer member, it is possible to prevent the movement of the inner member relative to the general portion as much as possible. Further, by positioning and holding the bracket in the state where the bracket is in close contact with the bent-deformed portion by the holding structure, a configuration is provided that contributes to achieving excellent positioning performance for the inner member.

In the above-described aspect, the wood member may have an outer surface portion extending in a longitudinal direction, and the bracket portion integrated with the outer surface portion may have a length equal to or greater than a length of the outer surface portion in the longitudinal direction. With this configuration, since the dimension of the bracket portion for providing the holding structures is ensured, a configuration is provided that further contributes to achieving excellent positioning performance for the inner member.

In the above-described aspect, the bracket may be provided to envelop the wood member. With this configuration, degradation of the wood member due to external stimulus can be prevented as much as possible by the bracket disposed around the wood member.

In the above-described aspect, the bracket may be made of a solid resin having flexibility. With this configuration, a configuration is provided that contributes to weight reduction of the shock absorbing member by forming the bracket of the solid resin that is lighter than a metal. The outer member may have a columnar shape or a tubular shape, and the wood member may have an elongated columnar shape or an elongated tubular shape.

A second aspect of the disclosure relates to a manufacturing method for a shock absorbing member that can absorb the load, applied to a hollow metal outer member, by the outer member and an inner member held in the outer member. According to the second aspect of the disclosure, a manufacturing method for a shock absorbing member including an outer member being hollow and made of a metal, and an inner member held in the outer member, includes forming the inner member by integrating a wood member and a bracket made of a solid resin or a metal, disposing the inner member in a base member to be the outer member, then bending and deforming at least a part of the base member along with the bracket to form a bent-deformed portion, and positioning and holding the bracket to the outer member. With this configuration, by providing the bent-deformed portion to the outer member through the bending process, it is possible to prevent the movement of the inner member relative to the outer member as much as possible. Since the bracket is bent and deformed along with the bent-deformed portion so as to be in close contact with the bent-deformed portion, it is possible to hold the inner member to the outer member while maintaining excellent positioning performance.

In the above-described aspect, the positioning and holding may be positioning and holding a bracket portion to the bent-deformed portion, the bracket portion bent and deformed along with the bent-deformed portion. With this configuration, the predetermined bracket portion is bent and deformed along with the bent-deformed portion so as to be in close contact with the bent-deformed portion and can be positioned and held more reliably by the holding structure that is provided after the bending process.

In the above-described aspect, the bracket portion bent and deformed along with the bent-deformed portion may be disposed to protrude from the wood member. With this configuration, the predetermined protruding bracket portion can be bent and deformed smoothly with as little influence from the wood member as possible and thus can be positioned and held to the outer member more appropriately.

In the above-described aspect, a general portion extending in a predetermined direction in a state where the wood member is disposed and the bent-deformed portion bent and deformed in an appropriate direction with respect to the general portion may be formed by the bending and deforming, and the bent-deformed portion may be formed on each of both end sides of the general portion in an extending direction of the general portion, along with the bracket portion bent and deformed along with the bent-deformed portion. With this configuration, the movement of the inner member relative to the general portion can be prevented more reliably by the bent-deformed portions that are respectively provided at both ends of the general portion.

According to the first aspect of the disclosure, it is possible to hold the inner member to the outer member while ensuring good performance. A configuration can be provided that contributes to achieving excellent positioning performance for the inner member. A configuration can be provided that further contributes to achieving excellent positioning performance for the inner member. It is possible to hold the inner member to the outer member while ensuring better performance. It is possible to hold the inner member to the outer member while ensuring even better performance. According to the second aspect of the disclosure, it is possible to hold the inner member to the outer member while ensuring good performance. A configuration can be provided that contributes to achieving excellent positioning performance for the inner member. A configuration can be provided that further contributes to achieving excellent positioning performance for the inner member. A configuration can be provided that even further contributes to achieving excellent positioning performance for the inner member.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, a mode for carrying out the disclosure will be described with reference toFIGS. 1 to 9. InFIG. 1, for convenience, arrows indicating the front-rear directions, the right-left directions, and the upper-lower directions of a vehicle are illustrated as appropriate. InFIGS. 2 to 9, for convenience, arrows indicating these front-rear, right-left, and upper-lower directions are illustrated as appropriate assuming a state in which a shock absorbing member and its configuration are attached to the vehicle.

A vehicle2illustrated inFIG. 1includes a vehicle body4forming the external shape of the vehicle2, a pair of right and left side members8,6extending in the front-rear direction at a lower portion of the vehicle body4, and a shock absorbing member10. The shock absorbing member10is a member that functions as a bumper reinforcement. The shock absorbing member10is supported by the right and left side members8,6and mounted on the front side of the vehicle body4. An impact load F that is applied from the front at the time of a vehicle collision or the like is absorbed by the shock absorbing member10, but, in this event, the situation where the shock absorbing member10is subjected to local folding so as to be largely bent at an unintended portion should be avoided as much as possible. In view of this, the shock absorbing member10of this embodiment is configured such that an inner member30is held in an outer member20forming the external shape of the shock absorbing member10so as to absorb the applied impact load F by the outer member20and the inner member30. In the shock absorbing member10of this type, it is desirable to hold the inner member30to the outer member20while ensuring good performance, and in particular, it is desirable to be able to maintain excellent positioning performance for the inner member30. Therefore, in this embodiment, the inner member30is held to the outer member20while ensuring good performance by a later-described configuration (holding structures40, etc.). The respective configurations will be described in detail below.

The shock absorbing member10illustrated inFIG. 1is a hollow member that is elongated in the right-left direction (vehicle-width direction), and includes the outer member20, the inner member30, and the holding structures40. As illustrated inFIGS. 1 and 3, the outer member20forming the external shape of the shock absorbing member10is a hollow columnar member that is made of a metal and is elongated in the right-left direction, and has an external shape that can be used as a bumper reinforcement. As a material of the outer member20, it is possible to use various types of metals or alloys that are plastically deformable, and the same type of metal as the vehicle body4(steel or the like) or a different type of metal may be used.

The outer member20illustrated inFIGS. 1 and 3is generally curved as a bow in plan view and has a general portion21, a right bent-deformed portion22, and a left bent-deformed portion23. The general portion21is a square prism portion extending generally straight in the right-left direction (predetermined direction) and allows a later-described wood member31of the inner member30to be disposed therein. The general portion21has an appropriate length and is provided in the middle of the outer member20in the right-left direction. The general portion21is a portion to which the impact load F is conceived to be applied. The right bent-deformed portion22is a portion that is bent and deformed rearward from the right end side of the general portion21, and is curved gradually rearward as going rightward. The left bent-deformed portion23is a portion that is bent and deformed rearward from the left end side of the general portion21, and is curved gradually rearward as going leftward. In this embodiment, through a later-described bending process, the right bent-deformed portion22and the left bent-deformed portion23are provided generally laterally symmetrical to each other. The bent-deformed portions22,23each form a part (bent structure) of the later-described holding structure40, and a part of a bracket34of the inner member30is positioned and held to each of the bent-deformed portions22,23.

As illustrated inFIGS. 2 to 4, the inner member30disposed in the outer member20is formed elongated in the right-left direction and is formed by integrating the wood member31and the bracket34(details described later). The wood member31is a member serving as a core portion of the inner member30and can absorb the impact load F, applied at the time of the vehicle collision, by being broken under pressure (crushed). The wood member31is formed in a square prism shape that can be housed in the general portion21of the outer member20. The wood member31has a right end portion31a, a left end portion31b, and four side surface portions (front side surface portion31c, rear side surface portion31d, upper side surface portion31e, lower side surface portion31f). In the state where the inner member30is disposed in the outer member20, the right end portion31ais disposed at a position facing the right bent-deformed portion22, and the left end portion31bis disposed at a position facing the left bent-deformed portion23. The side surface portions31cto31fare elongated outer surface portions extending in the right-left direction between the right end portion31aand the left end portion31b. The upper side surface portion31eand the lower side surface portion31fare disposed opposite to each other in the upper-lower direction, and the front side surface portion31cand the rear side surface portion31dare disposed opposite to each other in the front-rear direction. The front side surface portion31cforming the front outer surface of the wood member31is a portion corresponding to an outer surface portion of a wood member, extending in a longitudinal direction of the wood member, of the disclosure and can receive the impact load F applied to the outer member20.

The wood member31illustrated inFIGS. 2 to 4can be obtained from a needle-leaved tree such as a Japanese cedar, a Japanese cypress, or a pine tree, or a broad-leaved tree such as a zelkova tree or a Japanese beech. In particular, it is desirable to obtain the wood member31from the needle-leaved tree having growth rings32that are relatively clear (for convenience, symbols32are assigned to only part of the growth rings inFIG. 3). The wood member31may be disposed such that the axial direction of the growth rings32illustrated inFIG. 3extends along the extending direction of the general portion21or extends perpendicular to the extending direction of the general portion21. For example, in this embodiment, the wood member31is disposed with the axial direction of the growth rings32extending along the extending direction of the general portion21(the right-left direction) so that the processing is relatively easy. Alternatively, giving priority to the shock absorption performance, the axial direction of the growth rings32of the wood member31can be aligned with the direction perpendicular to the extending direction of the general portion21(the front-rear direction) so as to coincide with the application direction of the impact load F.

The density of the wood member31can be set taking into account the shock absorption performance, the lightness, or the like, and typically can be set in a range from 0.2 g/cm3to 1.0 g/cm3. The moisture content of the wood member31is not particularly limited as long as the wood member31has desired shock absorption performance. The moisture content of the wood member31can be adjusted typically in a range from 5% to 16% and is preferably set to about 10% and more preferably set to about 8%. As a method of making the moisture content of the wood member31about 8% to 10%, there can be cited a method of placing the wood member31in a room at a temperature of about 30° C. and a humidity of about 90% for a predetermined time. As a method of measuring the moisture content of the wood member31, there can be cited a method of measuring the moisture content from the difference between the weight of the wood member31dried by the method described above and the weight of the wood member31before the drying.

Bracket

The bracket34illustrated inFIGS. 2 to 4is a member made of a solid resin and forming the external shape of the inner member30and has a mounting portion35(a pair of right and left protruding portions36,37) (inFIGS. 3 and 4, for convenience, hatching of a portion, corresponding to the mounting portion, of the bracket differs from hatching of the other portion of the bracket). The bracket34is integrated with the outer side of the wood member31using a method such as insert molding, adhesion, or fusion bonding, and in this embodiment, the bracket34is formed in a generally square prism shape and integrated to envelop the wood member31. That is, the bracket34is provided to cover the end portions31a,31band the side surface portions31cto31fof the wood member31, and the mounting portion35(details described later) forming the front side of the bracket34is provided to cover the front side surface portion31cof the wood member31. By covering around the wood member31with the bracket34in this way, it is possible to avoid degradation of the wood member31due to light, water, or the like (external stimulus) as much as possible, thereby contributing to improvement in durability.

As illustrated inFIGS. 2 to 4, the mounting portion35forming the front side of the bracket34is elongated in the right-left direction along the front side surface portion31c. The mounting portion35is a portion that corresponds to a bracket portion integrated with the outer surface portion of the disclosure and that is held (mounted) to the outer member20. The mounting portion35has a right-left length greater than that of the front side surface portion31cand is provided with the right protruding portion36and the left protruding portion37. As illustrated inFIG. 3, the right protruding portion36is a portion, protruding rightward from the right end portion31aof the wood member31, of the mounting portion35, and is bent and deformed in the same direction as the right bent-deformed portion22of the outer member20so as to be in close contact with the right bent-deformed portion22of the outer member20. The left protruding portion37is a portion, protruding leftward from the left end portion31bof the wood member31, of the mounting portion35, and is bent and deformed in the same direction as the left bent-deformed portion23of the outer member20so as to be in close contact with the left bent-deformed portion23of the outer member20. The right protruding portion36and the left protruding portion37are provided generally laterally symmetrical to each other to each form a part (bent structure) of the later-described holding structure40, and are portions where later-described fastening structures of the holding structures40are respectively provided. In this embodiment, since the length of the mounting portion35for providing the holding structures40is ensured, a configuration is provided that contributes to achieving excellent positioning performance for the inner member30.

The length L, the height H, and the width W of the inner member30can be defined by the external dimensions of the bracket34illustrated inFIGS. 3 and 4. For example, the right-left dimension (length L) of a portion, where the wood member31is disposed, of the inner member30illustrated inFIG. 3is defined by the right-left dimension of the bracket34excluding the mounting portion35. The length L of the portion of the inner member30is set to a dimension that can be accommodated in the general portion21of the outer member20, and in this embodiment, is set to be approximately equal to that of the general portion21.

The upper-lower dimension (height H) of the inner member30illustrated inFIG. 4is defined by the upper-lower dimension of the bracket34, and the front-rear dimension (width W) of the inner member30illustrated inFIG. 4is defined by the front-rear dimension of the bracket34. The height H and the width W of the inner member30can be set as appropriate according to an internal space IS of the outer member20. For example, in this embodiment, the height H and the width W of the inner member30are adjusted so that the inner member30is housed in the outer member20in a state with substantially no gap therebetween. By disposing the inner member30in the outer member20in this way, the shock absorbing member10is in a substantially solid state so that it is possible to maintain excellent shock absorption performance. Note that “a state with substantially no gap therebetween” means to allow a slight gap (upper-lower or front-rear gap) between the outer surface of the inner member30and the inner surface of the outer member20in order to enable insertion (pushing) of the inner member30into the outer member20. That is, although the external shape of the inner member30is formed to imitate the internal space IS in a range that allows its insertion into the outer member20, there are cases where it is difficult to provide a state with no gap at all, and it is also unavoidable that a slight gap is formed due to design error. Even when a slight gap is formed between the outer member20and the inner member30due to relation to insertion work or design error, since the gap is not intentional, it can be regarded as “a state with substantially no gap therebetween”.

As the solid resin forming the bracket34, it is possible to use various types of thermoplastic resins or thermosetting resins, and it is desirable to use a resin having appropriate flexibility. As this type of thermoplastic resin, there can be cited a polyolefin resin such as polypropylene or polyethylene, a polycarbonate resin, a polyester resin such as polyethylene terephthalate, polybutylene terephthalate, poly(ethylene-2,6-naphthalate), or nylon (polyamide), a propylene-ethylene copolymer, a polystyrene resin, a copolymer of an aromatic vinyl monomer and (meth)acrylic acid alkyl ester having a lower alkyl group, a terephthalic acid-ethylene glycol-cyclohexanedimethanol copolymer, or a (meth)acrylic resin such as polymethyl methacrylate. As this type of thermosetting resin, there can be cited a phenolic resin, an epoxy resin, a melamine resin, or a urea resin. Thermoplastic resins or thermosetting resins can be used alone or can be used in combination of two or more of them.

Holding of Inner Member to Outer Member

The shock absorbing member10illustrated inFIGS. 1 to 3is mounted on the front side of the vehicle body4in the state where the inner member30is held in the outer member20. The shock absorbing member10is set in a state where an impact load F that is applied to the outer member20at the time of a vehicle collision can be absorbed by both the outer member20and the inner member30. In the shock absorbing member10of this type, it is desirable to be able to hold the inner member30to the outer member20while ensuring good performance, and in particular, it is desirable to be able to hold the inner member30to the outer member20while maintaining excellent positioning performance. Therefore, in this embodiment, the inner member30is formed by integrating the wood member31and the bracket34made of the solid resin. Further, the shock absorbing member10is provided with the later-described holding structures40that position and hold the bracket34to the outer member20.

Holding Structure

The holding structures40illustrated inFIG. 3are each a structure that positions and holds the bracket34to the outer member20. As the holding structure40, it is possible to employ the bent structure of the outer member20and the inner member30or a fixing structure that fixes the resin and the metal to each other. As this type of fixing structure, it is possible to employ various structures such as a fastening structure, a caulking structure, or an adhesive structure such as adhesion or fusion bonding. In the holding structure40of this embodiment, as will be described later, the bent structure of the outer member20and the inner member30and the fastening structure using bolt-like fasteners41and nuts42are employed in combination.

The bent structures (22and36,23and37) as the holding structures40illustrated inFIG. 3are respectively provided on the right side and the left side of the general portion21of the shock absorbing member10. That is, in this embodiment, in the state where the inner member30is disposed in the outer member20, the wood member31and the bracket34enveloping the wood member31are disposed in the general portion21. The right bent structure is composed of the right bent-deformed portion22and the right protruding portion36protruding rightward from the wood member31, and the portions22,36are bent and deformed in the same direction while being in close contact with each other. The left bent structure is composed of the left bent-deformed portion23and the left protruding portion37protruding leftward from the wood member31, and the portions23,37are bent and deformed in the same direction while being in close contact with each other. In this way, in this embodiment, the general portion21is in a state of being sandwiched between the bent structures as the holding structures40that are provided on the right side and the left side of the general portion21. In each of the bent structures as the holding structures40, the protruding portion36(37) is in close contact with the bent-deformed portion22(23) and is moderately positioned and held to the bent-deformed portion22(23). Therefore, even when the wood member31and the portion, enveloping the wood member31, of the bracket34attempts to move relative to the general portion21in the right-left direction, such movement in the right-left direction is prevented more reliably by the right and left bent structures (22and36,23and37).

Further, in this embodiment, the protruding portion36(37) is positioned and held to the bent-deformed portion22(23) by the fastening structure as the holding structure40illustrated inFIG. 3. In the shock absorbing member10, a fastening hole H1provided in the right bent-deformed portion22and a fastening hole H2provided in the right protruding portion36are arranged coaxially. The fastener41forming the fastening structure is inserted through the fastening holes H1, H2and held by the nut42. As illustrated inFIG. 1, the fastening structure (the fastener41) as the holding structure40is provided at upper and lower portions of the right bent-deformed portion22and the right protruding portion36so that the right protruding portion36can be held to the right bent-deformed portion22in a well-balanced manner in the upper-lower direction. Referring toFIGS. 1 and 3, fastening holes H1, H2are coaxially formed also in the left bent-deformed portion23and the left protruding portion37, respectively, and the fastener41forming the fastening structure is inserted through the fastening holes H1, H2and held by the nut42. In this way, with the holding structure40of this embodiment, the protruding portion36(37) of the bracket34is positioned and held to the corresponding bent-deformed portion22(23) by the bent structure and the fastening structure so that a configuration is provided that contributes to achieving excellent positioning performance for the inner member30.

Manufacturing Method for Shock Absorbing Member

The shock absorbing member10illustrated inFIGS. 1 to 3can be manufactured through a later-described manufacturing method (bending process). In the manufacturing method for the shock absorbing member10, as illustrated inFIG. 5, the inner member30formed by integrating the wood member31and the bracket34is prepared. The protruding portions36,37of the inner member30are respectively provided with the fastening holes H2at appropriate portions thereof. A base member20X formed generally straight is prepared. The base member20X is provided with the fastening holes H1at appropriate portions thereof. A forming method for the base member20X is not particularly limited, and typically the base member20X can be formed using a single metal plate or a plurality of metal plates. For example, the base member20X can be formed by preparing two metal plates each bent and deformed to a generally ]-shape and then joining the two metal plates by welding, fastening, or the like to form a hollow columnar shape. Alternatively, the base member20X can be formed by bending and deforming a single metal plate to a hollow columnar shape and then fixing it by welding or the like.

Then, as illustrated inFIG. 5, the inner member30is inserted (pushed) into the base member20X so as to be disposed at an appropriate portion of the base member20X. That is, the wood member31and the portion, enveloping the wood member31, of the bracket34are disposed at a portion to be a general portion (21) of the base member20X, and the protruding portions36,37of the bracket34are disposed at portions to be bent-deformed portions (22), (23) of the base member20X. Then, referring toFIG. 6, the outer member20is formed through a bending process in which at least a part of the base member20X is bent and deformed along with the bracket34to form a bent-deformed portion. In this event, in this embodiment, the right side and the left side of the base member20X are bent and deformed, thereby forming the general portion21, the right bent-deformed portion22, and the left bent-deformed portion23of the outer member20. In this bending process, the right protruding portion36of the bracket34is bent and deformed along with and in the same direction as the right bent-deformed portion22, and the left protruding portion37of the bracket34is bent and deformed along with and in the same direction as the left bent-deformed portion23. The right protruding portion36and the left protruding portion37correspond to a bracket portion bent and deformed along with a bent-deformed portion of the disclosure. In this embodiment, since the protruding portions36,37are made to protrude from the wood member31in the appropriate directions, it is possible to bend and deform the protruding portions36,37smoothly with as little influence from the wood member31as possible. Further, by avoiding as much as possible the occurrence of unintended stress on the wood member31that is otherwise caused by bending and deforming only the protruding portions36,37, a configuration is provided that contributes to maintaining excellent shock absorption performance of the inner member30.

In this way, in this embodiment, by providing the bent structure as the holding structure40, the protruding portion36(37) is in close contact with the bent-deformed portion22(23) and is moderately positioned and held to the bent-deformed portion22(23). Further, by providing the bent structures (22and36,23and37) respectively on both end sides of the general portion21in the right-left direction (longitudinal direction), it is possible to more reliably prevent the movement of the inner member30relative to the outer member20so that a configuration is provided that contributes to improvement in positioning performance and so on. Then, after the bending process, the protruding portion36(37) disposed in close contact with the bent-deformed portion22(23) of the outer member20as illustrated inFIG. 6is positioned and held to the bent-deformed portion22(23) via the fastening structure as the holding structure40. That is, the fastener41forming the holding structure40(fastening structure) is inserted through the fastening hole H1of the right bent-deformed portion22and the fastening hole H2of the right protruding portion36and held by the nut42. Likewise, the fastener41forming the holding structure40(fastening structure) is inserted through the fastening hole H1of the left bent-deformed portion23and the fastening hole H2of the left protruding portion37and held by the nut42. In this way, by further providing the fastening structure to the shock absorbing member10after the bending process, it is possible to more reliably position and hold the protruding portion36(37) to the bent-deformed portion22(23).

Use Example of Shock Absorbing Member

Referring toFIGS. 1 to 3, the shock absorbing member10is mounted as a bumper reinforcement on the front side of the vehicle body4. The shock absorbing member10in this state is exposed to external stimulus such as light or water, and therefore, there is a possibility that the wood member31excessively degrades due to the external stimulus. Therefore, in this embodiment, by enveloping the wood member31with the bracket34, a configuration is provided that can avoid degradation of the wood member31due to the external stimulus as much as possible, thereby contributing to maintaining excellent durability. Further, in this embodiment, a configuration is provided that contributes to weight reduction of the vehicle2by forming the bracket34of the relatively light resin.

At the time of a vehicle collision, an impact load F applied to the vehicle2is absorbed by the shock absorbing member10as the bumper reinforcement. For example, in this embodiment, a case is supposed in which the vehicle2has collided with a columnar member (not illustrated) rising from the ground. Generally, the diameter of the columnar member is smaller than the right-left dimension of the general portion21. An impact load F from the columnar member is applied to the shock absorbing member10on the general portion21of the outer member20, and this impact load F can be absorbed by moderate compression deformation of the general portion21and crushing of the wood member31in the inner member30. In this event, the large impact load F is locally applied to the general portion21, but this applied impact load F is absorbed while being dispersed in the right-left direction by the wood member31inside the general portion21. In this way, in this embodiment, the impact load F is absorbed while being dispersed by the outer member20and the inner member30so as to avoid local folding of the general portion21as much as possible, and consequently, it is possible to avoid as much as possible the situation where the shock absorbing member10is largely bent at an unintended portion.

As described above, in the inner member30of the shock absorbing member10of this embodiment, the bracket34harder than a foamed resin and excellent in durability is integrated with the wood member31. Since the bracket34is positioned and held to the outer member20by the holding structures40, it is possible to hold the inner member30to the outer member20while maintaining excellent positioning performance. In this embodiment, by providing the bent-deformed portions22,23to the outer member20, it is possible to prevent the movement of the inner member30relative to the general portion21as much as possible. Further, since the bracket34is positioned and held in the state where the bracket34is in close contact with the bent-deformed portions22,23by the holding structures40, a configuration is provided that contributes to achieving excellent positioning performance for the inner member30. In this embodiment, since the dimension of the bracket34(the mounting portion35) for providing the holding structures40is ensured, a configuration is provided that further contributes to achieving excellent positioning performance for the inner member30. In this embodiment, degradation of the wood member31due to external stimulus can be prevented as much as possible by the bracket34disposed around the wood member31. In this embodiment, a configuration is provided that contributes to weight reduction of the shock absorbing member10by forming the bracket34of the solid resin that is lighter than a metal. Therefore, according to this embodiment, it is possible to hold the inner member30to the outer member20while ensuring good performance.

In the manufacturing method for the shock absorbing member10of this embodiment, the bent-deformed portions22,23are provided to the outer member20through the bending process so that it is possible to prevent the movement of the inner member30relative to the outer member20as much as possible. Since the bracket34is bent and deformed along with the bent-deformed portions22,23so as to be in close contact with the bent-deformed portions22,23, it is possible to hold the inner member30to the outer member20while maintaining excellent positioning performance. In this embodiment, the predetermined bracket portions (the protruding portions36,37) are bent and deformed along with the bent-deformed portions22,23so as to be in close contact with the bent-deformed portions22,23and can be positioned and held more reliably by the holding structures40(fastening structures) that are provided after the bending process. In this embodiment, the predetermined protruding bracket portions (the protruding portions36,37) can be bent and deformed smoothly with as little influence from the wood member31as possible and thus can be positioned and held to the outer member20more appropriately. In this embodiment, the movement of the inner member30relative to the general portion21can be prevented more reliably by the bent-deformed portions22,23that are respectively provided at both ends of the general portion21.

Another Example of Inner Member

The inner member may have various configurations in addition to the configuration described above. For example, in a shock absorbing member10A of another example illustrated inFIG. 7, an inner member30A is formed by integrating a wood member31A and a bracket34A. In this example, the wood member31A is the same as the wood member31of the embodiment, but the bracket34A differs from the bracket34of the embodiment in that the bracket34A is a member made of a metal that is harder than a foamed resin and excellent in durability. The bracket34A has generally the same external shape as the bracket34of the embodiment and has a mounting portion35A and right and left protruding portions36A,37A. As a material of the bracket34A of this type, it is possible to use various types of metals that are plastically deformable along with the outer member20, and it is possible to use a metal of the type that is the same as or different from the outer member20. As a metal, there can be cited, in addition to a ferrous metal such as steel, a metal such as an aluminum alloy metal, a magnesium alloy metal, or a titanium alloy metal. The thickness of the metal can be set so as to allow crushing of the wood member31A.

A forming method for the bracket34A is not particularly limited. For example, the bracket34A can be formed by fixing a metal plate forming the mounting portion35A to another metal plate MP having a ]-shape in section and forming the other portion, by welding or the like. The wood member31A can be integrated with the inner surface of the bracket34A using a method such as fastening, adhesion, or fusion bonding. For example, by disposing non-illustrated bolt-like fasteners so as to pass through both the bracket34A and the wood member31A in the front-rear direction, it is possible to integrate the bracket34A and the wood member31A more firmly. In this case, it is desirable that the non-illustrated bolt-like fasteners be respectively disposed on the right-left sides of a portion to which an impact load F is conceived to be applied.

Also in the shock absorbing member10A of this example, the holding structures40that position and hold the protruding portions36A,37A of the bracket34A to the outer member20are provided. As the holding structure40of this example, it is possible to employ a bent structure of the outer member20and the inner member30A or a fixing structure that fixes the metals to each other. In the holding structure40of this example, like in the embodiment, the bent structure and a fastening structure as the fixing structure are employed in combination. As other fixing structures, it is possible to employ various structures such as a welding structure, a brazing structure such as soldering, a caulking structure, or an adhesive structure. In this way, also in this example, since the protruding portions36A,37A are positioned and held to the outer member20by the holding structures40, it is possible to hold the inner member30A to the outer member20while maintaining excellent positioning performance.

First Modification

The shock absorbing member may have various configurations in addition to the configuration described above. For example, a shock absorbing member10B of a first modification illustrated inFIG. 8includes the outer member20and an inner member30B, and the external shape of the inner member30B differs from the embodiment. That is, a bracket34B forming the external shape of the inner member30B is formed in a generally square prism shape so as to envelop a wood member, and portions corresponding to protruding portions are omitted (for convenience, illustration of the wood member is omitted inFIG. 8). The right side and the left side of the bracket34B are bent and deformed along with the corresponding bent-deformed portions22,23so that bent structures as the holding structures40are formed. Further, the right side and the left side of the bracket34B are positioned and held to the corresponding bent-deformed portions22,23by fastening structures as the holding structures40. The tips of the fasteners41forming the holding structures40pass through the fastening holes H1of the bent-deformed portions22,23and are threaded into screw holes H3provided in the bracket34B. In this way, the inner member30B of this modification is configured such that the bracket34B is elongated in the right-left direction while enveloping the wood member, and therefore, it is possible to avoid local folding of the shock absorbing member10B over a wide range as much as possible.

In the first modification, the wood member is disposed in the bent-deformed portions22,23with the right side and the left side of the wood member being slightly compressively deformed. However, it is possible to dispose only the bracket34B. In this modification, the fasteners41forming the holding structures40are disposed on the front side of the outer member20. Differently from this, the fasteners41can be disposed on the rear side of the outer member20, or can be disposed to pass through the outer member20and the inner member30B in the front-rear direction. That is, the bracket34B of this modification is configured such that both the front side and the rear side thereof are bent and deformed along with the outer member20, and therefore, the arrangement position of the fixing structure as the holding structure40can be set relatively freely. Therefore, in this modification, the degree of freedom for the arrangement position of the holding structure40is increased so that the design change or the like of the shock absorbing member10B according to the vehicle type is facilitated.

Second Modification

A shock absorbing member10C of a second modification illustrated inFIG. 9includes the outer member20and an inner member30C, and the configuration of the inner member30C differs from the embodiment. That is, in this modification, while a wood member31C that is the same as the embodiment is used, a bracket34C is provided with the front mounting portion35and a rear mounting portion351. The front mounting portion35is a portion of the same configuration as the mounting portion of the embodiment and is provided with the right protruding portion36and the left protruding portion37. In the front mounting portion35, the protruding portion36(37) can be positioned and held to the front inner surface of the corresponding bent-deformed portion22(23) by the bent structure and the fastening structure (the front holding structure40) like in the embodiment.

The rear mounting portion351is a portion forming the rear side of the bracket34C and covers the rear side surface portion31dof the wood member31C. The rear mounting portion351has a right-left length greater than that of the rear side surface portion31dand is provided with a right-rear protruding portion361and a left-rear protruding portion371like the front mounting portion35. In the rear mounting portion351, the protruding portion361(371) can be positioned and held to the rear inner surface of the corresponding bent-deformed portion22(23) by a fastening structure as a rear holding structure40X. That is, the right-rear protruding portion361is bent and deformed in the same direction as the right bent-deformed portion22so as to be in close contact with the rear inner surface of the right bent-deformed portion22. In this state, a fastener41forming the rear holding structure40X is inserted through fastening holes (symbols omitted) of the right bent-deformed portion22and the right-rear protruding portion361and held by a nut42. Likewise, the left-rear protruding portion371is bent and deformed in the same direction as the left bent-deformed portion23so as to be in close contact with the rear inner surface of the left bent-deformed portion23. In this state, a fastener41forming the rear holding structure40X is inserted through fastening holes (symbols omitted) of the left bent-deformed portion23and the left-rear protruding portion371and held by a nut42. In this way, in this modification, since the right and left sides of the bracket34C can be positioned and held to the outer member20via the holding structures40,40X in a well-balanced manner in the front-rear direction, a configuration is provided that further contributes to achieving excellent positioning performance for the inner member30C.

The shock absorbing member10and the like described above are not limited to the above-described mode and can take various other modes. In the above-described mode, the configuration (shape, dimensions, number of arrangement, arrangement position, etc.) of the outer member20is given by way of example, which is not intended to limit the configuration of the outer member in any aspect. For example, in the outer member, a single or a plurality of bent-deformed portions can be provided, and the forming positions of the general portion and the bent-deformed portions can be set as appropriate according to a use of the shock absorbing member, or the like. The general portion can be extended in a predetermined direction such as the right-left direction, the front-rear direction, the upper-lower direction, or the oblique direction. The general portion can be extended linearly or can be slightly bent after insertion of the inner member, or the like. That is, as long as the shock absorption performance of the wood member is ensured, the base member can be bent and deformed on the whole by the bending process. The bent-deformed portion can be formed by bending (curving or crooking) the outer member in an appropriate front, rear, right, left, upper, or lower direction. For example, the outer member can be bent in two directions such as rearward and upward. When providing a plurality of bent-deformed portions to the outer member, it is possible to set a bending direction per bent-deformed portion. The bent-deformed portions can be formed not only by bending and deforming the right and left sides of the outer member on the whole as illustrated inFIG. 1, but also by deforming a part of the front surface or the like of the outer member to a recessed shape. The shape of the outer member can also be changed as appropriate and can be formed into a hollow columnar shape such as a triangular prism or a square prism, or a hollow tubular shape such as a cylindrical shape or an oval cylindrical shape. The outer member may have a closed section over its entirety or may partially have an open section.

In the above-described mode, the configuration (shape, dimensions, number of arrangement, arrangement position, etc.) of the inner member30and the like is given by way of example, which is not intended to limit the configuration of the inner member in any aspect. In the above-described mode, the single inner member is disposed in the outer member, but a plurality of inner members can be disposed in the outer member. Further, it can be configured that the inner member is disposed at a portion where local folding of the general portion should be avoided (folding preventing portion) and that the inner member is not disposed intentionally (or a weak portion such as a recessed portion is provided to the wood member) at a portion where local folding of the general portion can be allowed (folding allowing portion). By intentionally weakening the folding allowing portion so as to be folded or bent in this way, it is possible to more reliably avoid unintended folding or bending of the folding preventing portion. When using a plurality of inner members, the axial direction of growth rings can be set per wood member, and, for example, the axial direction of the growth rings of the wood member can be made to coincide with the application direction of the load at the folding preventing portion. In consideration of an internal space of the outer member, the wood member can have various external shapes such as a columnar shape, for example, a prism shape or a cylindrical shape, or a plate shape. For example, it is possible to use a plurality of columnar or plate-like wood members by stacking them or placing them side by side.

The bracket can have a protruding portion according to the configuration of the outer member. When the outer member is bent at a right angle or an acute angle, it is possible to provide a hinge structure (e.g. integral hinge or the like) at a portion serving as the base point of bending of the protruding portion. As the bracket, it is possible to use a metal member and a solid-resin member in combination. It is sufficient for the bracket to be disposed to cover at least a part of the wood member in the state where the bracket can be held to the outer member. That is, instead of being disposed to envelop the wood member, the bracket can be provided integrally with a part (at least one of the end portions and the side surface portions) of the wood member. For example, the bracket can be provided only at each of the front side surface portion and the rear side surface portion (or the upper side surface portion and the lower side surface portion) of the wood member. In such a case, the brackets and the wood member can be integrated together by bolt-like fasteners or plate-like restrainers that are disposed to bridge the front side surface portion and the rear side surface portion. While it is sufficient for the mounting portion of the bracket to have a length equal to or greater than that of an outer surface portion of the corresponding wood member, it is desirable that the mounting portion have a single or a pair of protruding portions. The configurations of the inner members of the embodiment, the other example, and the modifications can be used in combination as appropriate.

In the above-described mode, the configuration (shape, dimensions, number of arrangement, arrangement position, etc.) of the holding structure40is given by way of example, which is not intended to limit the configuration of the holding structure in any aspect. For example, the holding structure can be formed only by the bent structure of the outer member and the inner member, or only by the fixing structure that fixes the metal and the resin to each other or the metals to each other. When the adhesive structure is employed as the holding structure, it is desirable to provide a projecting portion to one of the outer member and the bracket, and a recessed portion to the other one of them. For example, by performing adhesion or fusion bonding in the state where the projecting portion of the outer surface of the bracket is inserted in the recessed portion of the inner surface of the outer member, the positioning performance of them is improved, so that even when force is applied to the adhesive structure in a shear direction (e.g. the right-left direction inFIG. 3), it is possible to strongly resist this force. The configurations of the holding structures of the embodiment and the modifications can be used in combination as appropriate.

In the above-described mode, as the use of the shock absorbing member10, the bumper reinforcement that is mounted on the front side of the vehicle is given by way of example. However, the shock absorbing member can be widely used as a vehicle exterior member or a vehicle interior member. For example, the shock absorbing member can be used as a bumper reinforcement that is mounted on the rear side or the lateral side of the vehicle, or as a part of the vehicle body (pillar, side member, or the like). Further, the shock absorbing member can be used as a part of a structure in a vehicle cabin, such as a door or a ceiling.