Shock absorbing member
A shock absorbing member may include a cylindrical member that is configured to receive an impact load axially applied and to be axially collapsed, a wood member that is received in the cylindrical member while an axial direction of annual rings thereof is aligned with an axial direction of the cylindrical member, and positioning means for positioning axially both end portions of the wood member relative to axially both end portions of the cylindrical member such that a clearance can be formed between an outer surface of the wood member and an inner wall surface of the cylindrical member over an entire circumference thereof. The wood member and the cylindrical member are configured to receive the impact load in an axial direction thereof.
1. A shock absorbing member, comprising:
a cylindrical member that is configured to receive an impact load axially applied and to be axially collapsed,
a wood member that is received in the cylindrical member while an axial direction of annual rings thereof is aligned with an axial direction of the cylindrical member, and
a positioning portion positioning the wood member relative to the cylindrical member such that a clearance can be formed between an outer surface of the wood member and an inner wall surface of the cylindrical member over an entire circumference thereof,
wherein the wood member and the cylindrical member are configured to receive the impact load in an axial direction thereof.
2. The shock absorbing member as defined in claim 1 , wherein an area of the wood member in cross section perpendicular to an axis of the wood member in an axially predetermined region of the wood member is smaller than that in a region other than the predetermined region.
3. The shock absorbing member as defined in claim 2 , wherein when under the assumption that the wood member of which an area in cross section is uniform in the axial direction thereof is axially collapsed by the impact load axially applied, the impact load applied to the wood member at the start of crash is named as an initial load and the impact load applied to the wood member during the progression of crash after the start of crash is named as a successive load, a ratio of the area of the wood member in cross section in the predetermined region to the area of the wood member in cross section in the region other than the predetermined region is set to be substantially equal to a ratio of the successive load to the initial load.
4. The shock absorbing member as defined in claim 1 , wherein the positioning portion comprises a plurality of projections that are projected inwardly from the inner wall surface of the cylindrical member, the projections being positioned so as to circumferentially surround the outer surface of the wood member.
5. The shock absorbing member as defined in claim 1 , wherein the positioning portion comprises a plurality of plate-shaped members that are interleaved between the inner wall surface of the cylindrical member and the outer surface of the wood member, the plate-shaped members being positioned so as to circumferentially surround the outer surface of the wood member.
6. The shock absorbing member as defined in claim 1 , wherein the cylindrical member has a rectangular cylindrical shape, wherein the wood member has a rectangular columnar shape, and wherein the clearance has a constant size.
7. The shock absorbing member as defined in claim 1 , wherein the cylindrical member comprises an aluminum alloy molded article, and wherein the wood member comprises a cedar wood member.
8. The shock absorbing member as defined in claim 7 , wherein when a wall thickness of the cylindrical member is in a range from about 0.4 mm to about 1.1 mm, the size of the clearance is set to 0.5 mm or more.